Electron-beam apparatus and image forming apparatus

Abstract

Even if an output voltage from a high-voltage power source includes a ripple, this invention reduces the influence on a luminance output and suppresses the capacitances of a high-voltage power source transformer and smoothing capacitor. An electron-beam apparatus adopts line-sequential driving of allowing a plurality of electron-emitting devices to simultaneously emit electrons in an arrangement in which an accelerating potential for accelerating electrons includes a ripple. At the same time, sets of devices allowed to simultaneously emit electrons are sequentially switched. The frequency of the ripple is synchronized with the selection frequency of line-sequential driving.

Description

FIELD OF THE INVENTION

The present invention relates to an electron-beam apparatus and image forming apparatus and, more particularly, to an electron-beam apparatus and image display apparatus for accelerating, at an accelerating potential, electrons emitted by an electron-emitting device.

BACKGROUND OF THE INVENTION

Conventionally, two types of devices, namely thermionic and cold cathode devices, are known as electron-emitting devices. Known examples of the cold cathode devices are surface-conduction emission type electron-emitting devices, field emission type electron-emitting devices (to be referred to as FE type electron-emitting devices hereinafter), and metal/insulator/metal type electron-emitting devices (to be referred to as MIM type electron-emitting devices hereinafter).

A known example of the surface-conduction emission type electron-emitting devices is described in, e.g., M. I. Elinson, “Radio E-ng. Electron Phys., 10, 1290 (1965) and other examples will be described later. The surface-conduction emission type electron-emitting device utilizes the phenomenon that electrons are emitted by a small-area thin film formed on a substrate by flowing a current parallel through the film surface. The surface-conduction emission type electron-emitting device includes electron-emitting devices using an Au thin film [G. Dittmer, “Thin Solid Films”, 9,317 (1972)], an In 2 O 3 /SnO 2 thin film [M. Hartwell and C. G. Fonstad, “IEEE Trans. ED Conf.”, 519 (1975)], a carbon thin film [Hisashi Araki et al., “Vacuum”, Vol. 26, No. 1, p. 22 (1983)], and the like, in addition to an SnO 2 thin film according to Elinson mentioned above.

FIG. 17 is a plan view showing the surface-conduction emission type electron-emitting device by M. Hartwell et al. Referring to FIG. 17 , reference numeral 3001 denotes a substrate; and 3004 , a conductive thin film made of a metal oxide formed by sputtering. This conductive thin film 3004 has an H-shaped pattern, as shown in FIG. 17 . An electron-emitting portion 3005 is formed by performing electrification processing (referred to as forming processing to be described later) with respect to the conductive thin film 3004 . An interval L in FIG. 17 is set to 0.5 to 1 mm, and a width W is set to 0.1 mm. The electron-emitting portion 3005 is shown in a rectangular shape at the center of the conductive thin film 3004 for the sake of illustrative convenience.; However, this does not exactly show the actual position and shape of the electron-emitting portion. In the above surface-conduction emission type electron-emitting devices by M. Hartwell et al. and the like, typically the electron-emitting portion 3005 is formed by performing electrification processing called forming processing for the conductive thin film 3004 before electron emission. In forming processing, a constant DC voltage or a DC voltage which increases at a very low rate of, e.g., 1 V/min is applied across the conductive thin film 3004 to partially destroy or deform the conductive thin film 3004 , thereby forming the electron-emitting portion 3005 with an electrically high resistance. Note that the destroyed or deformed part of the conductive thin film 3004 has a fissure. Upon application of an appropriate voltage to the conductive thin film 3004 after forming processing, electrons are emitted near the fissure.

Known examples of the FE type electron-emitting devices are described in W. P. Dyke and W. W. Dolan, “Field emission”, Advance in Electron Physics, 8, 89 (1956) and C. A. Spindt, “Physical properties of thin-film field emission cathodes with molybdenium cones”, J. Appl. Phys., 47, 5248 (1976).

FIG. 18 is a sectional view showing the FE type device by C. A. Spindt et al. In FIG. 18 , reference numeral 3010 denotes a substrate; 3011 , an emitter wiring made of a conductive material; 3012 , an emitter cone; 3013 , an insulating layer; and 3014 , a gate electrode. In this device, a voltage is applied between the emitter cone 3012 and gate electrode 3014 to emit electrons from the distal end portion of the emitter cone 3012 . As another FE type device structure, there is an example in which an emitter and gate electrode are arranged on a substrate to be almost parallel to the surface of the substrate, in addition to the multilayered structure of FIG. 17 .

A known example of the MIM type electron-emitting devices is described in C. A. Mead, “Operation of Tunnel-Emission Devices”, J. Appl. Phys., 32,646 (1961).

FIG. 19 is a sectional view showing a typical example of the MIM type device structure. In FIG. 19 , reference numeral 3020 denotes a substrate; 3021 , a lower electrode made of a metal; 3022 , a thin insulating layer having a thickness of about 100 Å; and 3023 , an upper electrode made of a metal and having a thickness of about 80 to 300 Å. In the MIM type electron-emitting device, an appropriate voltage is applied between the upper and lower electrodes 3023 and 3021 to emit electrons from the surface of the upper electrode 3023 .

Since the above-described cold cathode devices can emit electrons at a temperature lower than that for thermionic cathode devices, they do not require any heater. The cold cathode device has a structure simpler than that of the thermionic cathode device and can shrink in feature size. Even if a large number of devices are arranged on a substrate at a high density, problems such as heat fusion of the substrate hardly arise. In addition, the response speed of the cold cathode device is high, while the response speed of the thermionic cathode device is low because thermionic cathode device operates upon heating by a heater. For this reason, applications of the cold cathode devices have enthusiastically been studied.

Of cold cathode devices, the surface-conduction emission type electron-emitting devices have a simple structure and can be easily manufactured, and thus many devices can be formed on a wide area. As disclosed in Japanese Patent Laid-Open No. 64-31332 filed by the assignee of the present applicant, a method of arranging and driving a lot of devices has been studied.

Regarding applications of the surface-conduction emission type electron-emitting devices to, e.g., image forming apparatuses such as an image display apparatus and image recording apparatus, charge beam sources, and the like have been studied. Particularly as an application to image display apparatuses, as disclosed in the U.S. Pat. No. 5,066,883 and Japanese Patent Laid-Open Nos. 2-257551 and 4-28137 filed by the assignee of the present applicant, an image display apparatus using a combination of a surface-conduction emission type electron-emitting device and a fluorescent substance which emits light upon irradiation of an electron beam has been studied. This type of image display apparatus using a combination of the surface-conduction emission type electron-emitting device and fluorescent substance is expected to exhibit more excellent characteristics than other conventional image display apparatuses. For example, compared with recent popular liquid crystal display apparatuses, the above display apparatus is superior in that it does not require any backlight because it is of a self-emission type and that it has a wide view angle.

A method of driving a plurality of FE type electron-emitting devices arranged side by side is disclosed in, e.g., U.S. Pat. No. 4,904,895 filed by the assignee of the present applicant. As a known example of an application of FE type electron-emitting devices to an image display apparatus is a flat panel display reported by R. Meyer et al. [R. Meyer: “Recent Development on Microtips Display at LETI”, Tech. Digest of 4th Int. Vacuum Microelectronics Conf., Nagahama, pp. 6-9 (1991)].

An application of a larger number of MIM type electron-emitting devices arranged side by side to an image display apparatus is disclosed in Japanese Patent Laid-Open No. 3-55738 filed by the assignee of the present applicant.

Several types of cold cathode electron sources have been described above. There is known another structure using an anode electrode for attracting an electron beam from the electron source of a cold cathode device.

Further, there is known a method of supplying, from a switching type high-voltage power source, an accelerating potential for accelerating electrons from an electron source. For example, a CRT uses a flyback type switching power source. An output potential from the switching type high-voltage power source includes an AC component (to be also referred to as a ripple hereinafter). To reduce this ripple, a smoothing circuit may be used, which increases the cost and size. Particularly, a general high-voltage power source uses a high-cost, large-volume capacitor, and the use of a satisfactory smoothing circuit increases the cost and size. Even with the use of the smoothing circuit, a ripple must be permitted to a certain degree in order to reduce the cost or suppress an increase in size.

SUMMARY OF THE INVENTION

It is an object of the present invention to realize a preferable image display apparatus and, more particularly, a preferable structure in a case in which an accelerating potential for accelerating electrons from an electron-emitting device includes an AC component.

One aspect of the present invention comprises the following arrangement.

An electron-beam apparatus comprises

an electron source having a plurality of sets each including a plurality of electron-emitting devices, each set being periodically selected, and the plurality of electron-emitting devices in each set being selected and allowed to simultaneously emit electrons,

an accelerating electrode for receiving a potential for accelerating electrons emitted by the electron-emitting device, and

a power source having an output potential including an AC component, a frequency of the AC component being controlled to be equal to a selection frequency for each set in the electron source, and the output potential being supplied to the accelerating electrode.

In this specification, “the output potential includes an AC component” means that the value periodically varies.

Another aspect of the present invention comprises the following arrangement.

An electron-beam apparatus comprises

an electron source having a plurality of sets each including a plurality of electron-emitting devices, each set being periodically selected, and the plurality of electron-emitting devices in each set being selected and allowed to simultaneously emit electrons,

an accelerating electrode for receiving a potential for accelerating electrons emitted by the electron-emitting device, and

a power source having an output potential including an AC component, a frequency of the AC component being controlled to be equal to a multiple of an integer of not less than 2 of a selection frequency for each set in the electron source, and the output potential being supplied to the accelerating electrode.

Still another aspect of the present invention comprises the following arrangement.

An electron-beam apparatus comprises

an electron source having a plurality of sets each including a plurality of electron-emitting devices, each set being periodically selected at a frequency f 2 , and the plurality of electron-emitting devices in each set being selected and allowed to simultaneously emit electrons,

an accelerating electrode for receiving a potential for accelerating electrons emitted by the electron-emitting device, and

a power source having an output potential including an AC component, letting q be at least any natural number of 1 to 10, a frequency f 1 of the AC component being controlled to satisfy equation (1), and the output potential being supplied to the accelerating electrode,

f 1 = n /( q*T )  (1)

where n is an arbitrary natural number, and T is a period from time at which any one of the electron-emitting devices is selected and allowed to emit electrons to time at which the electron-emitting devices is selected again and allowed to emit electrons.

In this case, the frequency f 1 satisfies equation (1) preferably when q is any natural number of 1 to 5, more preferably when q is any natural number of 1 to 3, and still more preferably when q is 1. The frequency f 1 preferably satisfies equation (1) when it satisfies inequality (2):

f 1 < f 2   (2)

In each aspect, it is desirable that the apparatus further comprise, in correspondence with each set, a common wiring commonly connected to the plurality of electron-emitting devices in each set, and the set be selected by applying a selection potential different from potentials of other common wirings to the common wiring of the set to be selected. In this arrangement, the electron-beam apparatus preferably further comprises, in correspondence with the plurality of electron-emitting devices in each set, a plurality of wirings for applying a potential for emitting electrons from the electron-emitting device in cooperation with the selection potential applied to the common wiring. These wirings may be shared by electron-emitting devices belonging to separate sets. This arrangement includes one known as matrix wiring. The selection potential applied to the common wiring is desirably set such that each device is not substantially driven before a potential applied to a plurality of wirings laid out in correspondence with a plurality of devices in each set reaches a value which satisfies a predetermined condition, and the device is driven when the potential applied to a plurality of wirings laid out in correspondence with a plurality of devices in each set reaches the value which satisfies the predetermined condition. Emission of electrons from the electron-emitting device is desirably controlled by controlling a potential value or an application time of a potential applied to the plurality of wirings for applying the potential for emitting electrons from the electron-emitting device in cooperation with the selection potential applied to the common wiring. The potential or a flowing current may be controlled.

Each aspect can be preferably adopted when the electron-emitting device is a cold cathode device, and can be more preferably adopted when the electron-emitting device is a surface-conduction emission type electron-emitting device.

In each aspect, the power source can preferably use a switching power source which may be a forward type switching power source, flyback type switching power source, or resonance type switching power source.

In each aspect, the set is selected based on an input horizontal sync signal, and the power source is driven based on the horizontal sync signal to generate the output potential. The power source is driven based on the horizontal sync signal at the same frequency as the frequency of the horizontal sync signal, or a frequency which is controlled based on the frequency of the horizontal sync signal and is different from the frequency of the horizontal sync signal. The frequency for driving the power source can be controlled by a phase-locked loop. The horizontal sync signal can be used as a target to be compared by the phase-locked loop.

An image forming apparatus according to the present invention comprises a fluorescent substance for emitting light upon reception of electrons emitted by the electron-emitting device in the above-described electron-beam apparatus. In this case, the power source is desirably driven based on a sync signal included in an input image signal to generate the output potential. A selection frequency for the set is preferably based on the sync signal included in the image signal.

Still another aspect of the present invention comprises the following step.

A method of driving an electron-beam apparatus having

an electron source having a plurality of sets each including a plurality of electron-emitting devices, each set being periodically selected, and the plurality of electron-emitting devices in each set being selected and allowed to simultaneously emit electrons,

an accelerating electrode for receiving a potential for accelerating electrons emitted by the electron-emitting device, and

a power source for supplying an output potential including an AC component to the accelerating electrode, comprises the step of

controlling a frequency of the AC component of the output potential to be equal to a selection frequency for each set in the electron source.

Still another aspect of the present invention comprises the following step.

A method of driving an electron-beam apparatus having

an electron source having a plurality of sets each including a plurality of electron-emitting devices, each set being periodically selected, and the plurality of electron-emitting devices in each set being selected and allowed to simultaneously emit electrons,

an accelerating electrode for receiving a potential for accelerating electrons emitted by the electron-emitting device, and

a power source for supplying an output potential including an AC component to the accelerating electrode, comprises the step of

controlling a frequency of the AC component of the output potential to be equal to a multiple of an integer of not less than 2 of a selection frequency for each set in the electron source.

Still another aspect of the present invention comprises the following step.

A method of driving an electron-beam apparatus having

an electron source having a plurality of sets each including a plurality of electron-emitting devices, each set being periodically selected at a frequency f 2 , and the plurality of electron-emitting devices in each set being selected and allowed to simultaneously emit electrons,

an accelerating electrode for receiving a potential for accelerating electrons emitted by the electron-emitting device, and

a power source for supplying an output potential including an AC component to the accelerating electrode, comprises the step of

letting q be at least any natural number of 1 to 10, controlling a frequency f 1 of the AC component of the output potential to satisfy equation (1),

f 1 = n /( q*T )  (1)

where n is an arbitrary natural number, and T is a period from time at which any one of the electron-emitting devices is selected and allowed to emit electrons to time at which the electron-emitting devices is selected again and allowed to emit electrons.

Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a waveform chart showing a pulse width modulation (PWM) pulse when the pulse width is constant;

FIG. 2 is a waveform chart showing the pulse width modulation (PWM) pulse when the pulse width changes;

FIG. 3 is a graph showing the pulse width modulation (PWM) pulse width vs. luminance characteristic;

FIG. 4 is a waveform chart showing the pulse width modulation (PWM) pulse when a high-voltage switching frequency is set to an integer multiple of a PWM horizontal frequency;

FIG. 5 is a graph showing the pulse width modulation (PWM) pulse width vs. luminance characteristic when the high-voltage switching frequency is set to an integer multiple of the PWM horizontal frequency;

FIG. 6 is a block diagram showing a display panel driving circuit;

FIG. 7 is a block diagram showing an NTSC-RGB decoder;

FIG. 8 is a block diagram showing a timing generator;

FIG. 9 is a block diagram showing an analog processor;

FIG. 10 is a timing chart for explaining the operation of the display panel driving circuit;

FIG. 11 is a circuit diagram showing a flyback type high-voltage generation means in the first embodiment;

FIG. 12 is a block diagram showing a frequency multiplication type high-voltage generation means in the second embodiment;

FIG. 13 is a block diagram showing the phase-locked loop (PLL) of the frequency multiplication type high-voltage generation means in the second embodiment;

FIG. 14 is a waveform chart showing the pulse width modulation (PWM) pulse when the pulse width is constant;

FIG. 15 is a waveform chart showing the pulse width modulation (PWM) pulse when the pulse width changes;

FIG. 16 is a graph showing the pulse width modulation (PWM) pulse width vs. luminance characteristic;

FIG. 17 is a plan view showing a Hartwell surface-conduction emission type electron-emitting device;

FIG. 19 is a sectional view showing a Spindt field emission type device;

FIG. 19 is a sectional view showing an MIM (Metal/Insulator/Metal) type device; and

FIG. 20 is a waveform chart showing the pulse width modulation (PWM) pulse when the high-voltage ripple is large.

FIG. 21 is a block diagram showing a row-direction driving means.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

The following embodiments adopt a method of allowing a plurality of electron-emitting devices on a selected row to simultaneously emit electrons in driving electron-emitting devices arranged in a matrix in order to obtain a high-quality display in an arrangement in which electrons are accelerated at an accelerating potential having an output potential including an AC component. This method of allowing a plurality of devices selected during a given selection period to simultaneously emit electrons will be called line-sequential scanning, with respect to dot-sequential scanning of scanning a screen vertically and horizontally, which is executed in the CRT.

Since a plurality of devices can simultaneously emit electrons, the influence of the AC component of the accelerating potential on the emission luminance can be suppressed compared to the structure of dot-sequentially selecting a plurality of devices.

More specifically, the following embodiments use an electron source constituted by arranging a plurality of electron-emitting devices in a matrix and connecting them to pluralities of row and column wirings. The row wirings are sequentially selected one by one at a predetermined selection frequency in a predetermined selection period. A selected row wiring receives a selection potential different from the potential of an unselected row wiring. In the selection period during which a given row wiring is selected, a potential different from one applied by the row wiring is applied from a plurality of column wirings to a plurality of electron-emitting devices connected to the selected row wiring. The electron-emitting devices connected to the selected row wiring emit electrons by the potential difference between potentials applied by the row and column wirings.

Emitted electrons are accelerated by an accelerating potential applied to an anode electrode serving as an accelerating electrode. While the electron-emitting devices connected to the selected row wiring simultaneously emit electrons, the electrons can be accelerated at the same potential to suppress the influence of a ripple even if the accelerating potential includes the ripple.

When a pulse width modulation signal is applied from the column wiring, the ripple of the accelerating potential may have an influence depending on the length of a high-level (ON) period, but can be suppressed to an allowable range. Since the deviation of an actual emission luminance from a required luminance caused by the influence of the ripple can be obtained in advance, the influence can be evaluated in advance.

The influence of the AC component of the accelerating potential on the luminance can become almost uniform between adjacent rows if the frequencies for sequentially selecting a plurality of rows are equal to each other, or the frequency of the AC component of the accelerating potential is an integer multiple of a frequency for sequentially selecting a plurality of rows. The latter is more preferable because variations in potential caused by the AC component can be suppressed because of a high frequency of the AC component of the accelerating potential.

A case in which an image is continuously displayed will be considered.

In this case, one frame period T is a period from the time at which a certain electron-emitting device is selected and allowed to emit electrons to the time at which this electron-emitting device is selected again and allows to emit electrons. The “frame” forms one screen and includes the meaning “frame” used in a general television technique.

If the accelerating potential (peak value of the AC component of the accelerating potential) is different between a case in which an electron-emitting device is allowed to emit electrons in a given frame and a case in which this electron-emitting device is allowed to emit electrons in the next frame, the luminance distribution varies between successive frames. The variations become noticeable when one period of the AC component of the accelerating potential is longer than one period of the frequency for line-sequential scanning (frequency for selecting a row wiring).

In order to suppress the variations in luminance distribution, letting t 1 be one period of the AC component of the accelerating potential, T/t 1 is set to a natural number. In practice, even if periods of the AC component of the accelerating potential do not fall within one frame period in number corresponding to a natural number, the variations can be permitted in actually looking the screen so long as periods of the AC component of the accelerating potential fall just within 10 frames, preferable 5 frames, and more preferably 3 frames. This condition is especially important when a frequency f 1 of the AC component of the accelerating potential is lower than a selection frequency f 2 of line-sequential scanning (the frequency f 2 is a row wiring selection frequency and is equal to the frequency of a horizontal sync signal). To make a natural number multiple of one period of the AC component of the accelerating potential falls just within y frames (y is a natural number), q*T/t 1 is set to an arbitrary natural number n when q takes at least any natural number of 1 to y. In q*T/t 1 , “*” means to multiply preceding and subsequent values. Accordingly, the frequency f 1 of the AC component of the accelerating potential is f 1 =1/t 1 =n/q*T. As the allowable range, y is a natural number of 10 or less, preferably a natural number of 5 or less, more preferably a natural number of 3 or less, and most preferably 1.

This will be described in more detail below.

For example, assume that one frame is formed from signals segmented by horizontal sync signals having a frequency f 2 of 15.75 kHz. In this case, the frequency of the AC component of the accelerating potential is preferably set to 15.75 kHz or a multiple of a natural number of 15.75 kHz. More specifically, the frequency of the horizontal sync signal or a frequency obtained by multiplying the frequency of the horizontal sync signal is set as a switching frequency in generating an accelerating potential. Accordingly, the frequency of the AC component of the accelerating potential can be set equal to or a multiple of a natural number of the frequency of the horizontal sync signal. A row wiring suffices to be selected at the same frequency as the frequency of the horizontal sync signal.

Considering a condition for suppressing variations in luminance distribution between successive frames, one period t 2 of the horizontal sync signal is 1/f 2 . Letting the frame period T be {fraction (1/60)} sec, a condition for setting T/t 1 to a natural number n is t 1 =1/(60*n). A condition for permitting a state in which the luminance distribution can vary up to 10 frames is t 1 =q/(60*n) where q is any natural number of 1 to 10, and n is an arbitrary natural number. This condition is preferably satisfied particularly for t 1 >t 2 .

A signal having this period can be generated based on a frame sync signal in synchronism with it. As the frame sync signal, e.g., a vertical sync signal in a CRT signal can be used. Alternatively, such signal may be generated based on a horizontal sync signal in synchronism with it. Specifically, the signal can be generated by a phase-locked loop (to be also referred to as a PLL) method. More specifically, the signal can be generated by counting, up to a count value which satisfies the above condition, the period of a reference wave having a much higher frequency than the frequency of the frame sync signal or horizontal sync signal serving as a generation source.

A luminance level control method for displaying an image such as a two-dimensional natural image includes an amplitude modulation method (to be also referred to as a PHM method) of controlling the signal amplitude (e.g., the voltage value of a voltage signal), and a method known as a pulse width modulation method (to be also referred to as a PWM method) of controlling the signal length within the selection period. The following embodiments will exemplify the PWM method superior in noise resistance and small power consumption.

The following embodiments employ a means of synchronizing the switching frequency of a high-voltage power source for supplying an accelerating voltage to be applied to an anode with the PWM horizontal frequency (row wiring selection frequency). In the first embodiment, the switching frequency of the high-voltage power source is set equal to the row wiring selection frequency. When the PWM pulse width is constant, like a waveform 4012 in FIG. 1 , the anode voltage applied during the pulse ON period is constant to obtain a constant luminance.

If the PWM pulse width changes, like a waveform 4022 in FIG. 2 , the PWM pulse width vs. luminance characteristic includes a slight gamma characteristic, like a curve 4031 in comparison with a curve 4031 for Va=constant, as shown in FIG. 3 . However, the gray level can be satisfactorily expressed.

When the switching frequency of the high-voltage power source is synchronized with an integer multiple of the PWM horizontal frequency, the voltage ripple decreases, like a ripple 4041 in FIG. 4 , because of a high frequency. Hence, the PWM pulse width vs. luminance characteristic comes very close to a curve 4050 for Va=constant, and the gray level can be satisfactorily expressed.

FIGS. 6 , 7 , 8 , and 9 are block diagrams showing an SED panel driving circuit, and FIG. 10 is a timing chart.

As shown in FIG. 6 , reference symbol P 2000 denotes a display panel. In this embodiment, the display panel P 2000 is constituted by arranging 240*720 surface-conduction emission type devices P 2001 in a matrix by 240 vertical row wirings and 720 horizontal column wirings. An electron beam emitted by each surface-conduction emission type device P 2001 is accelerated by a high voltage applied from a high-voltage power source P 30 to irradiate a fluorescent substance (not shown), thereby emitting light. The fluorescent substance (not shown) can take various color layouts in accordance with application purposes. For example, the fluorescent substance takes a vertical striped color layout of R, G, and B colors.

This embodiment will exemplify an application of displaying an NTSC television image on a display panel having pixels of 240 horizontal lines (R, G, and B trio)*240 vertical lines. Almost the same arrangement can cope with not only the NTSC image but also image signals having different resolutions and frame rates, such as a high-resolution HDTV image and computer output image.

As shown in FIG. 7 , reference symbol P 1 denotes an NTSC-RGB decoder for receiving an NTSC composite video input and outputting R, G, and B components. This decoder separates and outputs a sync signal (SYNC) superposed on an input video signal. Similarly, the decoder separates a color burst signal superposed on the input video signal, and generates and outputs a CLK signal (CLK 1 ) which synchronizes with the color burst signal.

As shown in FIG. 8 , reference symbol P 2 denotes a timing generator for generating a horizontal sync signal for synchronizing the high-voltage power source P 30 with the following timing signals necessary for converting R, G, and B analog signals decoded by P 1 into digital gray level signals for performing luminance modulation in. accordance with the SED panel. The timing generator P 2 mainly executes the following operations.

The timing generator P 2 outputs a clamp pulse for DC-regenerating R, G, and B analog signals from P 1 by analog processors P 3 .

The timing generator P 2 outputs a blanking pulse (BLK pulse) for adding blanking periods to the R, G, and B analog signals from P 1 by the analog processors P 3 .

The timing generator P 2 outputs a detection pulse for detecting the levels of the R, G, and B analog signals by video detectors P 4 .

The timing generator P 2 outputs a sample pulse (not shown) for converting the R, G, and B analog signals into digital signals by A/D converters P 6 .

The timing generator P 2 outputs a RAM controller control signal necessary for a RAM controller P 12 to control RAMs P 8 .

When the timing generator P 2 receives CLK 1 , the timing generator P 2 generates and outputs a free-running CLK signal (CLK 2 ) which synchronizes with CLK 1 from the internal PLL circuit in P 2 .

The timing generator P 2 outputs a sync signal (SYNC 2 ) generated in P 2 based on CLK 2 . (The timing generator P 2 having the free-running CLK 2 generation means can generate CLK 2 and SYNC 2 serving as reference signals even when no input video signal exists, and thus an image can be displayed by reading out image data in the RAM means P 8 .)

The timing generator P 2 outputs a horizontal sync signal for horizontally synchronizing with the high-voltage power source P 30 .

As shown in FIG. 9 , the analog processors P 3 are disposed for respective primary color signals output from P 1 . Each analog processor P 3 mainly performs the following operation.

The analog processor P 3 receives a clamp pulse from P 2 and performs DC regeneration.

The analog processor P 3 receives a BLK pulse from P 2 and adds a blanking period.

The analog processor P 3 receives a gain adjustment signal from a corresponding D/A converter P 14 serving as one of control outputs of a system controller mainly made up of a MPU P 11 , and controls the amplitudes of primary color signals input from P 1 .

The analog processor P 3 receives an offset adjustment signal from the D/A converter P 14 serving as one of control outputs of the system controller mainly made up of the MPU P 11 , and controls the black levels of primary color signals input from P 1 .

Each video detector P 4 detects an input video signal level or a video signal level after control by the analog processor P 3 . The video detector P 4 receives a detection pulse from P 2 , and the detection result is read by an A/D converter P 15 serving as one of control inputs of the system controller mainly made up of the MPU P 11 .

The detection pulse from P 2 is formed from, e.g., three, gate pulse, reset pulse, and sample & hold (to be referred to as S/H hereinafter) pulse. The video detector is comprised of, e.g., an integrator and S/H circuit.

For example, the integrator integrates a video signal in accordance with a gate pulse during the effective period of an input video signal, and the S/H circuit samples an output from the integrator in accordance with an S/H pulse generated during a vertical blanking period. The detection result is read by the A/D converter P 15 during this vertical blanking period, and then the integrator and S/H circuit are initialized by a reset pulse.

This operation enables detecting the average video level of each field.

Each LPF P 5 is a pre-filter means arranged on the input stage of a corresponding A/D converter P 6 .

The A/D converter P 6 is an A/D converter means for receiving a sample CLK from P 2 and quantizing an analog primary color signal having passed through the LPF P 5 by a necessary number of gray levels.

Each inverse γ table P 7 is a gray level characteristic conversion means adopted to convert an input video signal into the emission characteristic of the display panel. When the luminance level is expressed by pulse width modulation, like this embodiment, the emission amount often exhibits a linear characteristic almost proportional to the size of luminance data. On the other hand, a video signal applies to a TV receiver using a CRT, and thus undergoes γ processing in order to correct the nonlinear emission characteristic of the CRT. For this reason, in displaying a TV image on a panel having a linear emission characteristic, like this embodiment, the effects of γ processing must be cancelled by a gray level characteristic conversion means such as P 7 .

The emission characteristic can be properly changed by switching table data by an output from an I/O controller P 13 serving as one of control inputs/outputs of the system controller mainly made up of the MPU P 11 .

Reference symbols P 8 denote image memories which are arranged for respective R, G, and B processors and have addresses for the total number of display pixels of the panel (in this case, 240 horizontal lines*240 vertical lines*3 addresses). Each memory stores luminance data each panel pixel should emit. Luminance data are dot-sequentially read out to display an image stored in the memory on the panel.

Luminance data is output from P 8 under address control of the RAM controller P 12 .

Data is written in P 8 under the control of the system controller mainly made up of the MPU P 11 . For a simple test pattern, the RAM P 8 calculates, generates, and writes luminance data to be stored at each address in P 8 . For a natural still image pattern, an image file stored in, e.g., an external computer is loaded via a serial communication I/F P 16 serving as one of inputs/outputs of the system controller mainly made up of the MPU P 11 , and the loaded file is written in the image memory P 8 .

Reference symbols P 9 denote data selectors which determine whether image data to be output is data from the image memory P 8 or data from the A/D converter P 6 (input video signal system), on the basis of an output from the I/O controller P 13 serving as one of control inputs/outputs of the system controller mainly made up of the MPU P 11 .

In addition to the two input selection systems, a mode of generating a fixed value from P 9 is prepared. This mode can be selected by P 13 to output the fixed value. In this mode, e.g., an adjustment signal such as a whole white pattern can be displayed at a high speed without any external input.

Reference symbols P 10 denote horizontal 1-line memory means arranged for respective primary color signals. The horizontal 1-line memory means P 10 rearrange luminance data input parallel to the three, R, G, and B systems into an order corresponding to the panel color layout, converts the luminance data into a serial signal of one system, and outputs the converted signal to an X driver via a latch means P 22 .

The system controller is mainly comprised of the MPU P 11 , the serial communication I/F P 16 , the I/O controller P 13 , the D/A converter P 14 , the A/D converter P 15 , a data memory P 17 , and a user SW means P 18 .

The system controller receives a user request from the user SW means P 18 or serial communication I/F P 16 , and outputs a corresponding control signal from the I/O controller P 13 or D/A converter P 14 to meet the request.

In addition, the system controller performs optimal automatic control by receiving a system monitoring signal from the A/D converter P 15 and outputting a corresponding control signal from the I/O controller P 13 or D/A converter P 14 .

In this embodiment, the user request includes generation of a test pattern, change of the gray level, and display control such as brightness or color control. By monitoring the average video level from the video detector P 4 by the A/D converter P 15 , automatic control such as ABL can be achieved. The data memory P 17 can store the user adjustment amount.

Reference symbol P 19 denotes a Y-driver control timing generator; and P 20 , an X-driver control timing generator. Both the generators P 19 and P 20 receive signals CLK 1 , CLK 2 , and SYNC 2 to generate Y- and X-driver control signals.

Reference symbol P 21 denotes a controller for performing timing control of the line memory P 10 . The controller P 21 receives the signals CLK 1 , CLK 2 , and SYNC 2 , and generates R, G, B_WRT control signals for writing luminance data in the line memory, and R, G, B_RD control signals for reading out luminance data from the line memory in an order corresponding to the panel color layout.

Reference symbol T 104 in FIG. 10 denotes a color sample data string waveform obtained by displaying one of R, G, and B colors. The waveform T 104 is made up of 240 data strings per horizontal period. These data strings are written in the line memory P 10 during one horizontal period in accordance with a control signal. In the next horizontal period, data strings are read out from the line memory P 10 of each color at a frequency three times higher than the write frequency, thereby obtaining 720 luminance data strings per horizontal period, like a waveform T 105 .

Reference symbol P 1001 denotes an X & Y-driver timing generator which receives control signals from the Y-driver control timing generator P 19 and X-driver control timing generator P 20 , and outputs the following signals for the control of the X driver:

Shift clock

LD pulse (functioning to fetch data read in shift registers P 1101 and P 1107 in the internal memory means (not shown) of PWM generators P 1102 and D/A converters P 1103 , and functioning as a horizontal period trigger for the PWM generators P 1102 and D/A converters P 1103 )

If table ROM control signal

The X & Y-driver timing generator P 1001 outputs a horizontal period shift clock for operating the Y shift register in order to control the Y driver, and a vertical period trigger signal for applying a row scanning start trigger.

The shift register P 1101 loads the luminance data strings of 720 column wirings from the latch means P 22 every horizontal period in accordance with a shift clock such as a shift clock T 107 in FIG. 10 which synchronizes with luminance data and is output from the X & Y-driver timing generator P 1001 . Then, the shift register P 1101 transfers 720 data of one horizontal line to the PWM generators P 1102 at once in accordance with an LD pulse such as a pulse T 108 .

The shift register P 1107 loads the column wiring driving current data strings of 720 column wirings from a data selector means P 1201 every horizontal period in accordance with a shift clock, similar to luminance data. Then, the shift register P 1107 transfers 720 data of one horizontal line to the D/A converters P 1103 at once in synchronism with an LD pulse such as the pulse T 108 .

An If table ROM P 1202 is a memory means for storing data of a current amplitude value to be flowed through 720*240 surface-conduction emission type devices of the display panel P 2000 . The If table ROM P 1202 undergoes read address control in accordance with an If table ROM control signal from the X & Y-driver timing generator P 1001 , and outputs data of 720 current amplitude values for one row to be scanned, such as the data T 105 in FIG. 10 every horizontal period.

Using the If table ROM P 1202 , a current value for driving the column wiring (i.e., surface-conduction emission type electron-emitting device) is optimized for each device, thereby making the luminance uniform.

The data selector means P 1201 is adopted for a case in which the If table ROM P 1202 is not used in order to reduce the cost and the like. The data selector means P 1201 outputs, to the shift register P 1107 in accordance with a switching signal from the I/O controller P 13 , If setting data output from the I/O controller P 13 serving as one of control inputs/outputs of the system controller mainly made up of the MPU P 11 .

The PWM generator P 1102 arranged on each column wiring receives luminance data from the shift register P 1101 , and generates a pulse signal having a pulse width proportional to the data size every horizontal period, such as a waveform T 10 in FIG. 10 .

The D/A converter P 1103 arranged on each column wiring is a digital-to-analog converter for a current output. This D/A converter P 1103 receives current amplitude value data from the shift register P 1107 , and generates a driving current having a current amplitude proportional to the data size every horizontal period, such as a waveform T 111 in FIG. 10 .

Reference symbols P 1104 denote switching means each formed from a transistor and the like. Each switching means P 1104 applies a current output from the D/A converter P 1103 to a column wiring while an output from the PWM generator P 1102 is valid, and grounds the column wiring while an output from the PWM generator P 1102 is invalid. A column wiring driving waveform is represented by T 111 of FIG. 10 .

Diode means P 1105 arranged on respective column wirings are connected on the common side to a Vmax regulator P 1106 . The Vmax regulator P 1106 is a constant-voltage source capable of sucking a current, and forms together with the diode means P 1105 a protection circuit for preventing an excessive voltage from being applied to 720*204 surface-conduction emission type devices of the display panel P 2000 .

The protection voltage (potential defined by Vmax and −Vss applied upon scanning selection of a row wiring) is applied by the D/A converter P 14 serving as one of control inputs/outputs of the system controller mainly made up of the MPU P 111 . Hence, the Vmax regulator P 1106 can change the potential Vmax (or potential −Vss) in order to control the luminance control in addition to prevent application of an excessive voltage to the device.

FIG. 21 is a block diagram showing a row-direction driving means.

As shown in FIG. 21 , a Y shift register P 1002 receives a horizontal period shift clock and a vertical period trigger signal for supplying a row scanning start trigger from the X & Y-driver timing generator P 1001 , and sequentially outputs selection signals for scanning row wirings to pre-drivers P 1003 arranged on respective row wirings P 2002 . The output unit for driving each row wiring is made up of, e.g., a transistor means P 1006 , FET means P 1004 , and diode means P 1007 . The pre-driver P 1003 drives this output terminal at a high response speed. In selecting a row, the FET means P 1004 applies the potential −Vss from a constant-voltage regulator P 1005 to the row wiring via a switching means which is turned on in selection. In selecting no row, the transistor means P 1006 applies a potential Vuso from the constant-voltage regulator P 1008 to the row wiring via a switching means which is turned on in non-selection. A row wiring driving waveform is represented by T 112 of FIG. 10 .

The diode means P 1007 is used to prevent generation of an abnormal potential on the row wiring and protect the output terminal for driving each row wiring.

The constant-voltage regulator P 1005 for generating the potentials −Vss and Vuso is controlled by the D/A converter P 14 serving as one of control inputs/outputs of the system controller mainly made up of the MPU P 11 .

The high-voltage power source P 30 is also controlled by the D/A converter P 14 serving as one of control inputs/outputs of the system controller mainly made up of the MPU P 11 .

[First Embodiment]

The first embodiment concerns an example of synchronizing the horizontal sync frequency of the SED and the FBT (FlyBack Transformer; to be referred to as FBT hereinafter) type high-voltage power source.

FIG. 11 is a circuit diagram showing the arrangement of a high-voltage power source used in the first embodiment.

As shown in FIG. 11 , reference symbol IC 1 denotes an external synchronization type multivibrator capable of controlling a pulse width with a voltage. When a horizontal sync signal input from a timing generator P 2 changes to L (Low) level, the multivibrator IC 1 discharges a capacitance C 3 , and controls outputs from transistors Q 2 and Q 3 to H level. At this time, the H-level width is determined by a DC voltage applied to S 31 and the terminal voltage of C 3 .

When a MOSFET (Q 1 ) is switched by the transistors Q 2 and Q 3 , the cathode of a diode D 1 is grounded, and a voltage +B is applied to the primary side of an FBT (T 1 ) to flow a current.

When outputs from the transistors Q 2 and Q 3 change to L (Low) level after a predetermined time, Q 1 is turned off, the current flowing through the primary side of the FBT T 1 flows into a capacitance (to be also referred to as CAP hereinafter) C 1 . The inductance on the primary side of the FBT (T 1 ) and the capacitance of the CAP (C 1 ) resonate to generate across the CAP (C 1 ) a flyback voltage several to several ten times the voltage +B.

The FBT (T 1 ) outputs to the secondary side of the FBT (T 1 ) a flyback voltage corresponding to the number of turns of the transformer that is n times the flyback voltage generated on the primary side. The flyback voltage output to the secondary side is rectified into a DC voltage by a diode D 3 , and the DC voltage is applied as an anode voltage to a display panel P 2000 .

The anode voltage is divided by resistors R 3 and R 4 , amplified by an amplifier, and applied to IC 1 via S 31 to control a high-voltage output to be almost constant during the PWM ON period.

In this manner, the switching frequency of the high-voltage power source applied to the anode is synchronized with the PWM horizontal sync frequency. When an output from the high-voltage power source includes a voltage ripple such as a ripple 4002 in FIG. 20 , the voltage ripple level may be unexpectedly high or low during the ON period of a PWM pulse 4003 . Even with the same PWM pulse width, the anode voltage varies during the PWM ON period, generating a luminance difference. To the contrary, when the PWM pulse width is constant, like the waveform 4012 in FIG. 1 , the anode voltage applied during the pulse ON period is constant to obtain a constant luminance.

If the PWM pulse width changes, like the waveform 4022 in FIG. 2 , the PWM pulse width vs. luminance characteristic includes a slight gamma characteristic, like the curve 4031 in comparison with the curve 4030 for Va=constant, as shown in FIG. 3 . However, the gray level can be satisfactorily expressed.

[Second Embodiment]

The second embodiment employs a switching type high-voltage power source P 30 which synchronizes with a frequency obtained by multiplying a horizontal sync signal from a timing generator P 2 . This arrangement is shown in FIG. 12 . Detailed functions of the respective units have already been described in the first embodiment, and a description thereof will be omitted.

A horizontal sync signal input to the high-voltage power source P 30 is multiplied by a PLL (Phase-Locked Loop) S 41 to output a sync signal having a frequency nearer one which gives the highest efficiency to the high-voltage power source. For example, when the horizontal sync signal has the same frequency of 15.75 kHz as an NTSC horizontal sync signal, the PLL S 41 outputs a four-time frequency of 63 kHz.

The PLL (S 41 ) will be explained with reference to FIG. 13 .

A phase comparator S 51 compares the phase of a sync signal input in FIG. 13 with that of a signal obtained by dividing (1/integer) by a frequency divider S 55 the frequency of an oscillation output from an internal VCM (Voltage Control Multivibrator; to be referred to as VCM hereinafter) S 54 . Then, the phase comparator S 51 outputs a pulse width corresponding to the phase difference.

The pulse output from the phase comparator S 51 is outputs to an LPF (Low-Pass Filter; to be referred to as an LPF hereinafter) S 53 via a charge pump S 52 only during the pulse width period.

The LPF (S 53 ) is constituted by simple R and C filters, and integrates a pulse output from the charge pump S 52 into a DC voltage.

The VCM (S 54 ) is a square wave output oscillator capable of controlling the oscillation frequency by the DC voltage of the LPF (S 53 ). This VCM (S 54 ) allows obtaining a multiplied-output sync signal which synchronizes with an input sync signal.

The sync signal multiplied by the PLL (S 41 ) drives a transistor Q 3 . Then, a capacitance C 7 discharges every predetermined period to obtain across C 7 a sawtooth wave which synchronizes with a sync signal output from the PLL (S 41 ). This sawtooth wave is compared by a comparator S 42 with a DC voltage obtained by dividing an output from a high-voltage output S 45 by R 1 and R 2 and amplifying the divided output by an amplifier S 44 . Then, the comparator S 42 obtains a PWM output which synchronizes a sync signal output from the PLL (S 41 ).

The PWM signal obtained by the comparator S 42 drives an FET (Q 1 ) via transistors Q 2 and Q 4 . When the FET (Q 1 ) is turned on, the primary side of a transformer T 1 flows a current only during the ON period, thereby obtaining a square-wave voltage.

The square-wave voltage obtained on the primary side of the transformer T 1 is output to the secondary side as an n-time voltage in accordance with the turn count ratio (n) of the transformer T 1 .

The square-wave voltage obtained on the primary side of the transformer T 1 is output to the high-voltage output S 45 as a DC voltage output double an output voltage from a transformer T 2 via a generally used double voltage rectifying circuit S 43 .

The high voltage obtained by S 45 is divided by R 1 and R 2 , returns to the comparator S 42 via the amplifier S 44 , and acts to keep the high voltage constant. However, the ripple still remains.

In this fashion, the switching frequency of the high-voltage power source voltage applied to the anode is synchronized with a four-multiple of the PWM horizontal sync frequency. When an output from the high-voltage power source includes a voltage ripple such as the ripple 4002 in FIG. 20 , the voltage ripple level may be unexpectedly high or low during the ON period of the PWM pulse 4003 . Even with the same PWM pulse width, the anode voltage varies during the PWM ON period, generating an unexpected luminance difference. To the contrary, when the PWM pulse width is constant, like a waveform 4062 in FIG. 14 , the anode voltage applied during the pulse ON period is constant to obtain a constant luminance.

Even when the PWM pulse width changes, like a waveform 4072 in FIG. 15 , the voltage ripple decreases, like a ripple 4071 in FIG. 1 , because of a high switching frequency of the high-voltage power source. Therefore, the PWM pulse width vs. luminance characteristic comes very close to a curve 4080 for Va=constant, and the gray level can be satisfactorily expressed, like a waveform 4081 in FIG. 16 .

When the switching frequency synchronizes with a multiplied frequency, the voltage ripple decreases to reduce the influence on the luminance. It is considered that luminance variations can be reduced to an unnoticeable degree by increasing the switching frequency (two time or more) even when the switching frequency is not synchronized with a multiplied frequency. However, luminance variations cannot be completely eliminated. In practice, when the switching frequency is synchronized with a multiplied frequency, the luminance hardly varies, and the gray level can be satisfactorily expressed.

As described above, the switching frequency of the high-voltage power source is synchronized with the PWM frequency. The same effect as described above could be confirmed even if pulse width modulation was replaced with pulse height modulation in PHM.

[Third Embodiment]

The first embodiment has exemplified the arrangement in which the selection frequency of line-sequential scanning is made equal to the switching frequency of the high-voltage power source for supplying an accelerating potential. The second embodiment has exemplified the arrangement in which a natural number multiple of the selection frequency of line-sequential scanning is made equal to the switching frequency of the high-voltage power source.

In the third embodiment, letting t 1 be the switching period of the high-voltage power source and t 2 be one selection period of line-sequential scanning, t 1 >t 2 holds. The third embodiment concerns an arrangement that satisfies a condition under which the above described value q*T/t 1 becomes an arbitrary natural number n as a more preferable condition.

In the third embodiment, the selection frequency of line-sequential scanning is set to 15.75 kHz; the frame period, {fraction (1/60)} sec; q, 1; and n, 200. At this time, 262.5 signals segmented by horizontal sync signals correspond to one frame. Of these signals, 240 signals are used for display.

Then, the switching frequency of the high-voltage power source is determined to 12 kHz. The second embodiment determines the switching frequency of the high-voltage power source to be four times the horizontal sync frequency. Similarly, the third embodiment obtains 200 times the frequency by the PLL based on the frame period. The obtained frequency is set as the switching frequency of the high-voltage power source.

These numerical values are merely examples which satisfy the above condition relation. For example, another condition under which the high-voltage power source can function most efficiently can be adopted within the range of the condition relation.

As described in each embodiment, the above-mentioned arrangement can suppress or expect the influence on a luminance output when the accelerating potential for accelerating electrons includes a ripple. In addition, evaluation upon actually looking the screen can be improved. Since these effects can be attained without eliminating any ripple, the capacitances of the high-voltage power source transformer and smoothing capacitor can be suppressed, thereby reducing the apparatus cost.

The present invention can realize a preferable electron-beam apparatus and image display apparatus.

As many apparently widely different embodiments of the present invention can be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited to the specific embodiments thereof except as defined in the appended claims.

Claims

1. An electron-beam apparatus comprising:an electron source having a plurality of sets each including a plurality of electron-emitting devices, each set being periodically selected, and the plurality of electron-emitting devices in each set being selected and allowed to simultaneously emit electrons; an accelerating electrode for receiving a potential for accelerating electrons emitted by the electron-emitting devices; and a power source having an output potential including ripple, a frequency of the ripple being controlled to be equal to a selection frequency for each set in said electron source, and the output potential being supplied to said accelerating electrode.

2. The apparatus according to claim 1, wherein the apparatus further comprises, in correspondence with each set, a common wiring commonly connected to the plurality of electron-emitting devices in each set, and the set is selected by applying a selection potential different from potentials of other common wirings to the common wiring of the set to be selected.

3. The apparatus according to claim 2, further comprising, in correspondence with the plurality of electron-emitting devices in each set, a plurality of wirings for applying a potential for emitting electrons from the electron-emitting devices in cooperation with the selection potential applied to the common wiring.

4. The apparatus according to claim 3, wherein emission of electrons from the electron-emitting device is controlled by controlling a potential value or an application time of a potential applied to the plurality of wirings for applying the potential for emitting electrons from the electron-emitting devices in cooperation with the selection potential applied to the common wiring.

5. The apparatus according to claim 1, wherein at least one of the electron-emitting devices is a cold cathode device.

6. The apparatus according to claim 1, wherein at least one of the electron-emitting devices is a surface-conduction emission type electron-emitting device.

7. The apparatus according to claim 1, wherein said power source is a forward type switching power source.

8. The apparatus according to claim 1, wherein said power source is a flyback type switching power source.

9. The apparatus according to claim 1, wherein said power source is a resonance type switching power source.

10. The apparatus according to claim 1, wherein the set is selected based on an input horizontal sync signal, and said power source is driven based on the horizontal sync signal to generate the output potential.

11. The apparatus according to claim 10, wherein said power source is driven by a frequency controlled based on the horizontal sync signal to generate the output potential.

12. The apparatus according to claim 10, wherein the frequency for driving said power source is controlled by a phase-locked loop based on the horizontal sync signal.

13. The apparatus according to claim 1, wherein a frequency for driving said power source is controlled by a phase-locked loop.

14. An electron-beam apparatus comprising:an electron source having a plurality of sets each including a plurality of electron-emitting devices, each set being periodically selected, and the plurality of electron-emitting devices it each set being selected and allowed to simultaneously emit electrons; an accelerating electrode for receiving a potential for accelerating electrons emitted by the electron-emitting devices; and a power source having an output potential including ripple, a frequency of the ripple being controlled to be equal to a multiple of an integer of not less than 2 of a selection frequency for each set in said electron source, and the output potential being supplied to said accelerating electrode.

15. The apparatus according to claim 14, wherein the apparatus further comprises, in correspondence with each set, a common wiring commonly connected to the plurality of electron-emitting devices in each set, and the set is selected by applying a selection potential different from potentials of other common wirings to the common wiring of the set to be selected.

16. The apparatus according to claim 15, further comprising, in correspondence with the plurality of electron-emitting devices in each set, a plurality of wirings for applying a potential for emitting electrons from the electron-emitting devices in cooperation with the selection potential applied to the common wiring.

17. The apparatus according to claim 16, wherein emission of electrons from the electron-emitting device is controlled by controlling a potential value or an application time of a potential applied to the plurality of wirings for applying the potential for emitting electrons from the electron-emitting devices in cooperation with the selection potential applied to the common wiring.

18. The apparatus according to claim 14, wherein at least one of the electron-emitting devices is a cold cathode device.

19. The apparatus according to claim 14, wherein at least one of the electron-emitting devices is a surface-conduction emission type electron-emitting device.

20. The apparatus according to claim 14, wherein said power source is a forward type switching power source.

21. The apparatus according to claim 14, wherein said power source is a flyback type switching power source.

22. The apparatus according to claim 14, wherein said power source is a resonance type switching power source.

23. The apparatus according to claim 14, wherein the set is selected based on an input horizontal sync signal, and said power source is driven based on the horizontal sync signal to generate the output potential.

24. The apparatus according to claim 23, wherein said power source is driven by a frequency controlled based on the horizontal sync signal to generate the output potential.

25. The apparatus according to claim 23, wherein the frequency for driving said power source is controlled by a phase-locked loop based on the horizontal sync signal.

26. The apparatus according to claim 14, wherein a frequency for driving said power source is controlled by a phase-locked loop.

27. An electron-beam apparatus comprising:an electron source having a plurality of sets each including a plurality of electron-emitting devices, each set being periodically selected at a frequency f2, and the plurality of electron-emitting devices in each set being selected and allowed to simultaneously emit electrons; an accelerating electrode for receiving a potential for accelerating electrons emitted by the electron-emitting devices; and a power source having an output potential including ripple, letting q be at least any natural number of 1 to 10, a frequency f1 of the ripple being controlled to satisfy equation (1), and the output potential being supplied to said accelerating electrode, f1=n/(q*T)  (1)  where n is an arbitrary natural number, and T is a period from a time at which any one of the electron-emitting devices is selected and allowed to emit electrons to a time at which the electron-emitting device is selected again and allowed to emit electrons.

28. The apparatus according to claim 27, wherein the frequency f1 satisfies equation (1) when q is any natural number of 1 to 5.

29. The apparatus according to claim 27, wherein the frequency f1 satisfies equation (1) when q is any natural number of 1 to 3.

30. The apparatus according to claim 27, wherein the frequency f1 satisfies equation (1) when q is 1.

31. The apparatus according to claim 27, wherein the frequency f1 satisfies both equation (1) and inequality (2):f1<f2  (2).

32. The apparatus according to claim 27, wherein the apparatus further comprises, in correspondence with each set, a common wiring commonly connected to the plurality of electron-emitting devices in each set, and the set is selected by applying a selection potential different from potentials of other common wirings to the common wiring of the set to be selected.

33. The apparatus according to claim 32, further comprising, in correspondence with the plurality of electron-emitting devices in each set, a plurality of wirings for applying a potential for emitting electrons from the electron-emitting devices in cooperation with the selection potential applied to the common wiring.

34. The apparatus according to claim 33, wherein emission of electrons from the electron-emitting device is controlled by controlling a potential value or an application time of a potential applied to the plurality of wirings for applying the potential for emitting electrons from the electron-emitting devices in cooperation with the selection potential applied to the common wiring.

35. The apparatus according to claim 27, wherein at least one of the electron-emitting devices is a cold cathode device.

36. The apparatus according to claim 27, wherein at least one of the electron-emitting devices is a surface-conduction emission type electron-emitting device.

37. The apparatus according to claim 27, wherein said power source is a forward type switching power source.

38. The apparatus according to claim 27, wherein said power source is a flyback type switching power source.

39. The apparatus according to claim 27, wherein said power source is a resonance type switching power source.

40. The apparatus according to claim 27, wherein the set is selected based on an input horizontal sync signal, and said power source is driven based on the horizontal sync signal to generate the output potential.

41. The apparatus according to claim 40, wherein said power source is driven by a frequency controlled based on the horizontal sync signal to generate the output potential.

42. The apparatus according to claim 40, wherein the frequency for driving said power source is controlled by a phase-locked loop based on the horizontal sync signal.

43. The apparatus according to claim 27, wherein a frequency for driving said power source is controlled by a phase-locked loop.

44. An image forming apparatus comprising:an electron source having a plurality of sets each including a plurality of electron-emitting devices, each set being periodically selected, and the plurality of electron-emitting devices in each set being selected and allowed to simultaneously emit electrons; an accelerating electrode for receiving a potential for accelerating electrons emitted by the electron-emitting devices; a power source having an output potential including ripple, a frequency of the ripple being controlled to be equal to a selection frequency for each set in said electron source, and the output potential being supplied to said accelerating electrode; and a fluorescent substance for emitting light upon reception of electrons emitted by the electron-emitting device.

45. The apparatus according to claim 44, wherein said power source is driven based on a sync signal included in an input image signal to generate the output potential.

46. The apparatus according to claim 45, wherein a selection frequency for the set is based on the sync signal included in the image signal.

47. An image forming apparatus comprising:an electron source including a plurality of sets each including a plurality of electron-emitting devices, each set being periodically selected, and the plurality of electron-emitting devices in each set being selected and allowed to simultaneously emit electrons; an accelerating electrode for receiving a potential for accelerating electrons emitted by the electron-emitting devices; a power source having an output potential including ripple, a frequency of the ripple being controlled to be equal to a multiple of an integer of not less than 2 of a selection frequency for each set in said electron source, and the output potential being supplied to said accelerating electrode; and a fluorescent substrate for emitting light upon receipt of at least one electron.

48. The apparatus according to claim 47, wherein said power source is driven based on a sync signal included in an input image signal to generate the output potential.

49. The apparatus according to claim 48, wherein a selection frequency for the set is based on the sync signal included in the image signal.

50. An image forming apparatus comprising:an electron source having a plurality of sets each including a plurality of electron-emitting devices, each set being periodically selected at a frequency f2, and the plural of electron-emitting devices in each set being selected and allowed to simultaneously emit electrons; an accelerating electrode for receiving a potential for accelerating electrons emitted by the electron-emitting device; a power source having an output potential including ripple, letting q be at least any natural number of 1 to 10, a frequency f1 of the ripple being controlled to satisfy equation (1), and the output potential being supplied to said accelerating electrode, (1), f1=n/(q*T)  (1)  where n is an arbitrary natural number, and T is a period from a time at which any one of the electron-emitting devices is selected and allowed to emit electrons to a time at which the electron-emitting device is selected again and allowed to emit electrons; and a fluorescent substrate for emitting light upon reception of at least one electron.

51. The apparatus according to claim 50, wherein said power source is driven based on a sync signal included in an input image signal to generate the output potential.

52. The apparatus according to claim 51, wherein a selection frequency for the set is based on the sync signal included in the image signal.

53. A method of driving an electron-beam apparatus that includes (a) an electron source having a plurality of sets each including a plurality of electron-emitting devices, each set being periodically selected, and the plurality of electron-emitting devices in each set being selected and allowed to simultaneously emit electrons, (b) an accelerating electrode for receiving a potential for accelerating electrons emitted by the electron-emitting devices, (c) and a power source, the method comprising the steps of:driving the electron source; applying a potential outputted by the power source, to the accelerating electrode, wherein the potential includes ripple; and controlling a frequency of the ripple of the output potential to be equal to a selection frequency for each set in the electron source.

54. A method of driving an electron-beam apparatus that includes (a) an electron source having a plurality of sets each including a plurality of electron-emitting devices, each set being periodically selected, and the plurality of electron-emitting devices in each set being selected and allowed to simultaneously emit electrons, (b) an accelerating electrode for receiving a potential for accelerating electrons emitted by the electron-emitting devices, and (c) a power source, the method comprising the steps of:driving the electron source; applying an output potential, outputted from the power source, to the accelerating electrode, wherein the output potential includes ripple; and controlling a frequency of the ripple of the output potential to be equal to a multiple of an integer of not less than 2 of a selection frequency for each set in the electron source.

55. A method of driving an electron-beam apparatus that includes (a) an electron source having a plurality of sets each including a plurality of electron-emitting devices, each set being periodically selected at a frequency f2, and the plurality of electron-emitting devices in each set being selected and allowed to simultaneously emit electrons, (b) an accelerating electrode for receiving a potential for accelerating electrons emitted by the electron-emitting devices, and (c) a power source, the method comprising the steps of:driving the electron source; applying an output potential, outputted from the power source, to the accelerating electrode, wherein the output potential includes ripple; and letting q be at least any natural number of 1 to 10, controlling a frequency f1 of the ripple of the output potential to satisfy equation (1), f1=n/(q*T)  (1)  where n is an arbitrary natural number, and T is a period from a time at which any one of the electron-emitting devices is selected and allowed to emit electrons to a time at which the electron-emitting device is selected again and allowed to emit electrons.