Information
-
Patent Grant
-
6456414
-
Patent Number
6,456,414
-
Date Filed
Tuesday, August 15, 200024 years ago
-
Date Issued
Tuesday, September 24, 200222 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
- Dunham; Celia C.
- Ward; James A.
- Lipovsky; Peter A.
-
CPC
-
US Classifications
Field of Search
US
- 359 204
- 358 505
- 358 518
- 347 232
- 347 235
- 347 238
- 348 196
- 348 203
- 348 210
- 348 266
- 348 268
- 348 269
- 348 750
- 348 754
- 348 755
- 348 757
-
International Classifications
-
Abstract
A sequential color scanner capable of generating both two and three dimensional moving color images has only one x- and y-deflection channel. The system includes first, second, and third optical signal generators for generating a first, second, and third optical signal, respectively. Each optical signal is characterized one of the three primary colors. The first, second, and third light signals are blue, green, and red, although not necessarily in that order. The first optical signal is generated along an optical axis. First and second beam combiners direct the second and third optical signals, respectively, along the optical axis. A first optical deflector deflects the optical signals in a first plane, and a second optical deflector for deflecting the optical signals in a second plane that is orthogonal to the first plane. First, second, and third modulators modulate the intensity of the first, second, and third optical signals, respectfully. A controller supervises each of the first, second, and third modulators so that the optical signals are generated in a pulsed, repeating sequence in accordance with an index that is counted by an index counter implemented in a controller. The controller also supervises modulation of the first and second optical deflectors so that the light signals are directed to predetermined coordinates. A time delay τ is introduced between optical signals for enhancing the sharpness of the image by assuring that the optical deflectors modulate only one light signal at a time.
Description
BACKGROUND OF THE INVENTION
The present invention generally relates to the field of optical scanning, and more particularly to an optical scanning system which generates red, blue, and green light pulses in a repetitive sequence to create two and three dimensional images.
U.S. Pat. No. 5,854,613, entitled LASER BASED 3D VOLUMETRIC DISPLAY SYSTEM, describes a system for generating three dimensional images. The system employs red, green, and blue lasers. Each laser generates a laser beam that is subdivided into multiple laser beams that are directed through a separate deflection channel along its own optical axis. Each deflection channel includes both x- and y-acousto-optic beam deflectors or modulators for directing the subdivided laser beams to appropriate coordinates of the surface of a rotating reflective structure. However, multiple deflection channels make it difficult to maintain good color convergence over an extended period of time. Moreover, separate deflection channels increase both the cost and bulk of such systems. Therefore, a need exists for a color scanner system that may be used to create two and three dimensional color images that uses only one deflection channel.
SUMMARY OF THE INVENTION
The present invention provides a sequential color scanner capable of generating both two and three dimensional, moving color images with only one x- and y-deflection channel. The system includes first, second, and third optical signal generators for generating a first, second, and third optical signal, respectively. Each optical signal is characterized by one of the three primary colors, blue, green, and red, although not necessarily in that order. The first optical signal is generated along an optical axis. First and second beam combiners direct the second and third optical signals, respectively, along the optical axis. A first optical deflector deflects the optical signals in a first plane, and a second optical deflector for deflecting the optical signals in a second plane that is orthogonal to the first plane. First, second, and third modulators modulate the intensity of the first, second, and third optical signals, respectfully, under the supervision of a controller so that the optical signals are generated in a pulsed, interlaced, and repeating sequence in accordance with an index counted by an index counter implemented in the controller. The controller also supervises modulation of the first and second optical deflectors for directing the light signals to predetermined coordinates, and generates a clock signal having a periodicity P. The repeating sequence includes a first pulse of the first optical signal having a duration of (wP-τ), a second pulse of the second optical signal having a duration of (yP-τ), and a third pulse of the third optical signal having a duration of (zP-τ), where w, y, and z are positive integers, and r represents a time delay. The time delay τ between optical signals is used to enhance the sharpness of the image by assuring that the optical deflectors modulate only one light signal at a time.
An important advantage of the invention is that it only requires one optical channel for deflecting each of the red, green, and blue pulsed optical signals. Another important advantage of the invention is that if the intensities of the first, second, and third light signals generated by the light signal generators are not equal, the invention may be configured to make the durations of the pulsed light signals different so that the light signals reflected off a reflecting structure appear to be equal.
These and other advantages of the invention will become more apparent upon review of the accompanying drawings and specification, including the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
illustrates a block diagram of a sequential color scanner embodying various features of present invention.
FIG. 2
is a block diagram of the controller shown in FIG.
1
.
FIG. 3
is a circuit diagram showing the modulator selection logic device of FIG.
2
.
FIG. 4
is a diagram illustrating the timing sequence of blue, green, and red light signal pulses emitted by system
10
of
FIG. 1
in relation to a clock signal and index counter.
FIG. 5
is an example of a circuit for controlling the acousto-optic modulator that modulates the green light signal.
FIG. 6
is an example of a circuit for controlling the diode laser driver that modulates the red light signal.
FIG. 7
is an example of a circuit for controlling the acousto-optic modulator that modulates the blue light signal.
FIG. 8
is a timing diagram of the various signals shown in FIG.
2
.
Throughout the several view, like elements are referenced using like references.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention is an optical scanning system that may be employed to create both two and three dimensional, moving color images. Referring to
FIG. 1
, optical scanning system
10
includes a red, green, and blue optical signal generators
12
,
14
, and
16
, respectively, controller
18
, wavelength selective mirrors
20
and
22
, expansion optics
24
, Y-deflector
26
, X-deflector
28
, lens
30
, red light source modulator
25
, acousto-optic modulators
27
and
29
, acousto-optic radio frequency (RF) modulator drivers
33
A and
33
B, X- and Y-digital frequency synthesizers
69
A
and
69
B
, respectively, and computer
11
. Optical signal generators
12
,
14
, and
16
generate a pulsed red, and continuous green and blue optical signals
13
,
15
A, and
17
A, respectively. Red optical signal
13
propagates through partially reflective mirrors
20
and
22
along optical axis a—a. Controller
18
provides control signals
31
,
33
, and
35
to red light source modulator
25
and acousto-optic RF modulators
33
A
and
33
B
, respectively.
Control signal
31
supervises red light source modulator
25
which generates a control signal
41
that causes red light source
12
to generate a “blanked,” or pulsed red light output signal
13
. Red modulator
25
may be implemented, for example, as a Wavelength Electronics, Inc. red laser diode driver, Model LDD200-1P (0-200 Ma). Controller
18
generates control signals
33
and
35
that supervise acousto-optic RF modulator drivers
33
A
and
33
B
, respectively. Acousto-optic RF modulator driver
33
A
generates an RF output signal MGRF that controls acousto-optic modulator
27
. Similarly, acousto-optic RF modulator driver
33
B
generates an RF output signal M
BRF
that controls acousto-optic modulator
29
. Under the supervision of RF signal M
GRF
, acousto-optic modulator
27
transforms continuous green optical signal
15
A into a pulsed and intensity modulated green optical signal
15
B. Under the supervision of RF signal M
BRF
, acousto-optic modulator
29
transforms continuous blue optical signal
17
A into a pulsed and intensity modulated blue optical signal
17
B.
The pulsed optical signals are interlaced to provide a pulse train sequence of optical signals
13
,
15
B, and
17
B, although not necessarily in that order, such that an optical signal pulse of one color only is presented at any one time along axis a—a. Also, a time delay τ is introduced between the pulses to increase image contrast. By way of example, green and blue acousto-optic modulators
27
and
29
preferably operate at 532 and 465 nm, respectively.
Pulsed green optical signal
15
B is reflected by wavelength selective mirror
20
so as to propagate along optical axis a—a. Either red optical signal
13
after passing through mirror
20
, or green optical signal
15
B after being reflected by mirror
20
is referenced as optical signal
23
A. Pulsed blue optical signal
17
B is reflected by wavelength selective mirror
22
so as to propagate along optical axis a—a. Either optical signal
23
A or blue optical signal
17
B after being reflected by mirror
22
is referenced as optical signal
23
B. Signals M
GRF
and M
BRF
are radio frequency signals. Image smearing would result if two or more excitation frequencies simultaneously propagated though the acousto-optic modulators
27
or
29
. Smearing of images generated by system
10
is avoided by inserting a blanking time delay τ between light pulses of different colors, as described more fully below.
Still referring to
FIG. 1
, expansion optical element
24
expands the width of optical signal
23
B and transforms it into optical signal
23
C. Controller
18
further generates output signals X
0xx
and Y
0xx
that supervise x- and y-digital frequency synthesizers (DFS)
69
A
and
69
B
respectively, where xx represents bit numbers. In response to receiving signals X
0xx
and Y
0xx
, DFSs
69
A
and
69
B
generate RF output signals X
RF
and Y
RF
, respectively. Signal X
RF
controls the amount by which X-deflector
28
deflects optical signal
23
D. Signal Y
RF
controls the amount by which y-deflector
26
deflects optical signal
23
C. The degree to which the X- and Y-deflectors
28
and
26
deflect optical signals
23
D and
23
C is functionally related to the frequency of signals X
RF
and Y
RF
, respectively. Optical signal
23
C may be deflected in the y-direction by Y-deflector
26
in a plane such as reference plane Y-Z, whereas optical signal
23
D may be deflected in the x-direction by X-deflector
28
in the X-Z plane which is orthogonal to reference plane X-Y. By way of example, Y- and X-deflectors
26
and
28
each may be implemented as a tellurium dioxide acousto-optic deflector that operates at wavelengths in the range of about 440 to 655 nm.
X-deflector
28
transforms optical signal
23
D into optical signal
23
E. Next, optical signal
23
is focused by lens
30
and transformed into a focused optical signal
23
F that is directed to specific coordinates of a reflective surface
43
of optically reflective structure
45
. Surface
43
may be fixed or oscillating, therefore providing system
10
with the capability of creating either two or three dimensional moving color images by scanning optical signal
23
F. An example of an oscillating surface suitable for use in the present invention is the rotating display surface described in commonly assigned U.S. Pat. No. 5,854,613, incorporated herein by reference. Optical signal
23
F is directed to x- and y-coordinates (X
R
, Y
R
) of a Cartesian coordinate system. Idealized x- and y-coordinates are represented by signals X
B
and Y
B
that are generated by computer
11
and provided to controller
18
. Controller
18
transforms signals X
B
and Y
B
into control signals X
0xx
and Y
0xx
that are used to direct optical signal
23
F to the appropriate pixel locations in plane X-Y, at for example, to exemplary coordinate (X
R
, Y
R
).
A diagram illustrating an example of the repetitive sequence
51
of the pulsed color light signals
13
,
15
B, and
17
B is shown in FIG.
4
. The sequence
51
of light pulse signals directed through lens
30
, by way of example, is, a blue pulse
17
B, green pulse
15
B, and red pulse
13
, and then the sequence repeats. In between each light pulse there is a time delay τ. The blue pulses each correspond with an index count of “0” after an initial time delay τ. The green pulses each correspond with an index count of “1” after an initial time delay τ. The red pulses each correspond with index count 2-4 after an initial time delay τ. Light pulses of all colors are timed to end on the rising edge of clock signal Dly_CLKB having a periodicity of P. However, red optical signal
13
remains “on” while signal FW is a logic high. Signal FW is a logic signal generated by computer
11
that is transformed into signal FW by memory out register
49
, as shown in FIG.
2
.
In the preferred embodiment, blue light source
16
and green light source
14
may be implemented as lasers, and red light source
12
may be implemented as a laser diode. However, the intensity of red light emitted from the laser diode is generally less than that of either blue or green light emitted from lasers. In fact, in one example of the invention, the intensity of the output of red laser diode
12
is about one third as intense as the outputs of the green and blue lasers
14
and
16
. In order to effectively normalize the perceived intensities of light signals
23
F, whether red, green, or blue, the sequence of light pulses includes one long red light pulse
13
having a width that may for example, be three clock periods less a time delay (3P-τ) and shorter green and blue pulses
15
B and
17
B, respectively, that are each one clock period wide less the time delay (P-τ), where P represents the period of the clock pulses of clock signal clock signal Dly_CLKB generated by controller
18
, and τ represents the time delay.
With reference to
FIG. 2
, controller
18
may be implemented to include a parameter register
40
, index counter
44
, multiplexer
48
, memory storage devices, such as EEProms
52
and
56
, flip-flop
60
, and modulator selection logic device
64
. In the operation of controller
18
, idealized X- and Y-coordinates, to which each light signal
23
F is to be directed, are provided as address signals X and Y to EEProms
52
and
56
. Idealized coordinates refer to the actual coordinates in a Cartesian coordinate systems to which light signal
23
F is desired to be directed. Red, blue, and green light all refract differently as they pass through refractive media, such as expansion optics
24
, X- and Y-deflectors
26
and
28
, respectively, and lens
30
. Therefore, such individual refractive behavior must be accounted for if the pulsed light signals
23
F are to be directed accurately. EEProms
52
and
56
store deflector driver data that corrects for the refractive effects of X- and Y-deflectors
26
and
28
, and lens
30
that may affect light signals
23
C,
23
D,
23
E, and
23
F.
EEProms
52
and
56
store x- and y-coordinate correction data (collectively referenced as coordinate correction data). In order for the x- and y-deflectors
28
and
26
to direct light signals
23
C and
23
D to the desired coordinates, it is necessary to incorporate coordinate correction factors into deflection control signals X
0xx
, and Y
0xx
respectively, that are output by EEProms
52
and
56
. The deflection control data is defined to work in conjunction with the specific Y- and X-deflectors
26
and
28
incorporated into system
10
. Coordinate correction data for each separate color is necessary because light signals
23
C and
23
D each include, albeit one at a time, red, green, and blue optical pulses
13
,
15
B, and
17
B that have different refractive characteristics because of their different wavelengths. EEProms
52
and
56
store deflection control data that are output as signals X
0xx
and Y
0xx
. Each defined pixel in plane AY has correction factors for each of the red, green, and blue light signals.
Coordinate correction data is determined in accordance with the following relation: θ
c
=λƒ/V
a
, where θ represents the corrected deflection angle in radians, subscript C represents a particular color, such as red, green, or blue, λ represents the wavelength of the optical signal in meters, ƒ represents the radio frequency of signal X
RF
or Y
RF
, and V
a
represents the acoustic velocity (0.651×10
3
m/s in TeO
2
, the material comprising X- and Y-deflectors
28
and
26
. Thus, θ
Red
=975.42×10
−10
s׃, where red light source
12
generates an optical output signal
13
having a wavelength of 635 nm; θ
Green
=817.20×10
−10
s׃, where green light source
14
generates an optical output signal
15
A having a wavelength of 532 nm; and θ
Blue
=714.29×10
−10
s׃, where blue light source
16
generates an optical output signal
17
A having a wavelength of 465 nm.
An example of the way coordinate correction factors are determined is provided as follows: Assume that the specific examples of the y- and x-acousto-optic deflectors
26
and
28
identified herein each have an RF range from 75 MHZ to a maximum of 125 MHZ for a bandwidth of 50 MHZ. The deflection ratio θ
blue
2/θ
Red
=0.7323. Therefore, the angular deflection of the red optical pulses
23
C must be reduced by a factor of 0.7323 compared to the angular deflection of blue optical pulse
23
C so that the red and blue optical pulses would meet at the same pixel coordinates, as for example, (X
R
,Y
R
) in the XY plane. The maximum frequency to be provided as either signal X
RF
or Y
RF
to X- and Y-deflectors
28
and
26
, respectively, to deflect red light pulses
23
C to the same coordinates that would be illuminated by the blue light pulses
23
C at the maximum desired deflection, is equal to the product of the maximum operating frequency of x- and y-deflectors
28
and
26
and the ratio θ
Blue
/θ
Red
(0.7323), i.e., 125 MHz×0.7323=91.54 MHZ, in order to obtain maximum deflection of the red optical pulses.
In another example, the deflection ratio θ
Blue
/θ
Green
=0.874. Therefore, the angular deflection of the green optical pulse
15
A must be reduced by a factor of 0.874 compared to the angular deflection of blue optical pulses
23
C so that the green optical pulses
23
C and blue optical pulses
23
C would meet at the same pixel coordinates such as (X
R
,Y
R
). The maximum frequency to be provided as either signal X
RF
or Y
RF
to X- and Y-deflectors
28
and
26
, respectively, to deflect the green pulses to the same coordinates at maximum deflection as would the blue pulses be directed, is equal to the product of the maximum blue frequency and θ
Blue
/θ
Green
(0.874), i.e., 125 Mhz×0.874=109.25 MHZ in order to obtain maximum deflection of the green optical pulses.
Based on the example, above, one would determine the minimum frequencies of X
RF
and Y
RF
to obtain the minimum deflections of the red, blue, and green optical pulses in a manner similar to that used to determine the maximum deflection for each of the primary colors. However, one would substitute the minimum operating frequency (75 MHZ) of the x- and y-deflectors
28
and
26
in place of the maximum operating frequency for the deflectors in the appropriate formulas above. The minimum and maximum operating frequencies for signals XRF and YRF for each of the red, blue, and green pulses for scaling the deflections of the different colored optical pulses are summarized in TABLE 1, below.
TABLE 1
|
|
Frequencies of Signals X
RF
and Y
RF
For Controlling X- and Y-Deflectors
|
Minimum Deflection Freq.
Maximum Deflection Freq.
|
Color
(Mhz)
(Mhz)
|
|
Red
54.92
91.54
|
Green
65.55
109.25
|
Blue
75.00
125.00
|
|
The outputs Xc and Yc of EEProms
52
and
56
are control signals that are transformed into deflector control signals X and Y, respectively, and re-timed by memory out register
49
to drive X-DFS
69
A
and Y-DFS
B
. Buffers
57
and
59
provide suitable signal conditioning to transform control signals X and Y into deflection control signals Xo and Yo. Control signals X
0
and Y
0
are used to drive X- and Y-digital frequency synthesizers (DFS)
69
A and
69
B, respectively. The output signals X
RF
and Y
RF
of DFSs
69
A
and
69
B
drive X- and Y-deflectors
28
and
26
, respectively, so that each of colored light signals
23
F may be directed to the appropriate coordinates. DFS
69
A for the X-channel deflection may be implemented as a GEC Plessey Semiconductor Model SP2001 direct digital frequency synthesizer chip. DFS
69
B
for the Y-channel deflection may be implemented as a GEC Plessey Semiconductor Model SP2002 direct digital frequency synthesizer chip.
Deflector driver look-up table data is initially loaded into EEProms
52
and
56
via data provided as signals X
b
and Y
b
, shown in FIG.
2
. The most significant bits (MSBs) for determining address locations in EEProms
52
and
56
are provided by index counter
44
and are throughput to the EEProms via 2:1 multiplexer
48
. By way of example, EEProms
52
and
56
may include eight 4K×12 EEPROM sub-blocks. The MSBs determine which one of the eight 4K×12 EEPROM sub-blocks is to be loaded. By way of example, parameter register
40
was implemented as a Texas Instruments 74ALS174 flip-flop integrated circuit. Signal Sel_Index_Rotation, generated by parameter register
40
, controls the switching function of multiplexer
48
. When signal Sel_Index_Rotation is a logical low, multiplexer
48
throughputs deflector driver information as signals Ch_Sel_LSB, Ch_Sel
—
2LSB, and Ch_Sel_MSB, as signals LSB, 2LSB and MSB, respectively, of multiplexer
48
. However, when Sel_Index_Rotation is a logical one, then multiplexer
48
provides five addresses 0-4 comprised of signals LSB, 2LSB, and MSB in a repetitive sequence to EEProms
52
and
56
. Signals LSB, 2LSB, and MSB provided by channel index counter
44
to EEProms
52
and
56
are addresses that map incoming X
b
and Y
b
data to particular X- and Y-control signal data.
Index register
60
may be implemented as a D-type flip-flop that in response to receiving a delay clock signal, DLY_CLKB from controller
18
, throughputs signals LSB, 2LSB and MSB to modulator selection logic device
64
, as signals Q
A
Q
B
, and Q
C
, respectively. The presentation of signals Q
A
, Q
B
, and Q
C
to modulator selection logic device
64
is generally synchronous with the presentation of delay clock signal DLY_CLKB generated by controller
18
, to the D input of index register
60
. Modulator selection device
64
outputs logic signals M
r
, M
g
, and M
b
to red modulator control circuit
82
, green modulator control circuit
80
, and blue modulator control circuit
84
, respectively. Logic signals M
r
, M
g
, and M
b
comprise control signals
31
,
33
, and
35
, respectively. Signals
31
,
33
, and
35
control the red, green, and blue optical modulators
25
,
27
, and
29
, respectively, so that red, green, and blue light signals
13
,
15
B, and
17
B are pulsed “on,” one-at-a-time, in a predetermined sequence. A circuit diagram of modulator selection device
64
is shown, by way of example, in FIG.
3
. TABLE 2 below is a logic table that relates the index count, Q
A
, Q
B
, Q
C
, M
r
, M
g
, and M
b
to the color of the light signal emitted from system
10
.
TABLE 2
|
|
Modulator Selection Table
|
Msb
Lsb
|
Count
Color
Q
C
Q
B
Q
A
M
b
M
g
M
r
|
|
0
blue
0
0
0
1
0
0
|
1
green
0
0
1
0
1
0
|
2
red
0
1
0
0
0
1
|
3
red
0
1
1
0
0
1
|
4
red
1
0
0
0
0
1
|
|
Still referring to
FIG. 2
, one-shot device
68
outputs a logic low signal {overscore (Q)} in response to receiving the DLY_CLKB signal from controller
18
. However, one-shot device
68
is adjusted to provide a low signal at {overscore (Q)} equal to the time delay τ when device
68
receives the rising edge of DLY_CLKB signal. When either the signal at {overscore (Q)} or signal at FW is a logic high, OR gate output signal
72
is a logic high. Thus, the {overscore (Blanking)} signal is a logic one, whereupon the selected modulator does not blank the corresponding light signal. However, when {overscore (Blanking)} is a logic low, then the corresponding light signal is blanked. Signal I
bxx
is a logic signal generated by computer
11
that is clocked into the memory out register
49
, buffered by buffer
61
, and then transformed into signal I
0
xx. Signal Io
xx
is used in conjunction with signals M
b
, M
g
, and M
r
, FW, and the {overscore (Blanking)} signal to control circuits
82
,
80
, and
84
so that red modulator
25
generates a signal
41
that causes red light source
12
to modulate and blank red optical signal
13
, and so that green modulator
27
and blue modulator
29
intensity modulate and blank green and blue light signals
15
A, and
17
A to transform them into pulsed green and blue optical signals
15
B and
17
B, respectively. Blanking signals
31
,
33
, and
35
establishes the pulse pattern of optical signals
13
,
15
B, and
17
B, respectively. Signal FW
b
(also referenced as signal “FW”) is a logic signal generated by computer
11
that is transformed into signal FW by memory out register
49
. Signal FW is amplified and transformed by buffer
63
into signal FW
0
. Memory out register
49
re-times signals X
c
, Y
c
, I
b
, and FW
b
. Signal FW
0
controls the duration of light signals
13
,
15
B, and
17
B. For example, when FW
0
is set to a logic one, the full pixel period of the light signal being emitted from system
10
is active. In other words, no blanking (τ) is deducted from the pixel period. However, blanking occurs for an initial time delay τ that precedes each optical signal pulse when FW
0
is set to 0.
Referring now to
FIG. 5
, there is shown an exemplary circuit
80
for controlling acousto-optic modulator
27
, and therefore intensity modulate and/or blank green light signal
15
A, which is thereby transformed in pulsed green light signal
15
B. When logic signal I
0xx
and logic signal Mg are presented to control circuit
80
, digital to analog converter (DAC)
81
, transforms signal I
0xx
into an analog signal that modulates the intensity of green light signal
15
A. However, if either of signals Mg and I
0xx
are not present, then acousto-optic modulator
27
blanks green optical signal
15
. The term “blanking” means that an optical signal is either completely absorbed, occluded, or not generated. If {overscore (Blanking)} is presented to analog MUX
83
as a logic low, then acousto-optic modulator
27
blanks green light signal
15
.
FIG. 6
shows an exemplary circuit
82
for controlling red light source modulator
25
. When signal I
0xx
and logic signal Mr are presented to circuit
82
, digital to analog converter (DAC)
81
of circuit
82
, transforms signal I
0xx
into an analog signal that modulates the intensity of red light signal
13
. However, if Blanking is presented to analog MUX
83
of circuit
82
as a logic low, then regardless of the values of signals I
0xx
and Mr, red light source modulator
25
blanks red light source
12
, which is preferably implemented as a red laser diode.
Referring now to
FIG. 7
, there is shown an exemplary circuit
84
for controlling acousto-optic modulator
29
, and therefore intensity modulating or blanking blue light signal
17
A, which is thereby transformed in pulsed blue light signal
17
B. When logic signals I
0xx
and logic signal Mb are presented to digital to analog converter (DAC)
81
, DAC
81
transforms signals I
0xx
into an analog signal that modulates the intensity of blue light signal
17
A. If {overscore (Blanking)} is presented to analog MUX
83
as a logic low, then acousto-optic modulator
29
blanks blue light signal
17
A regardless of the values of signals I
0xx
and M
b
.
FIG. 8
is a timing diagram showing the timing of the various signals described herein above. One shot signal {overscore (Q)} has a logic low interval τ
1
, which may be 5.4 μs. In the preferred embodiment one shot signal {overscore (Q)} may have a period of about 6.4 μs including a pulse width of about 1 μs. Interval Γ
1
is set by design to approximate the fill time τ
2
of the acousto-optic deflectors
26
and
28
so that, τ
1
≈Γ
2
, where Γ
2
=dV
A
and d represents the diameter of the light signal that is to be deflected by either of deflectors
26
and
28
, and V
A
represents the speed of sound in the crystal that comprises the deflectors. From
FIG. 8
, it may be seen that one shot signal {overscore (Q)} becomes a logic low on a rising edge of the clock pulse signal DLY_CLKB. Signal {overscore (Blanking)} has a waveform that generally corresponds to the waveform of signal {overscore (Q)}. However, when the value of logic signal FW (full width) becomes a logic high, then {overscore (Blanking)} remains at a logic high while the FW logic signal remains at a logic HI. Thus, it may be appreciated that the red signal
13
(Refer to
FIG. 1
) may have a pulse width that is generally equal to three periods of clock signal DLY_CLKB less τ (3×6.4 μs−5.4 μs=13.8 μs), where the clock signal has a period P. Green signal
15
B and blue signal
17
B each have a pulse width of one clock period less τ (6.4 μs−5.4 μs=1 μs). In this way, as far as a human observer would notice, system
10
provides pulsed red signal
13
with a brightness that appears to be about as bright as green signal
15
B and blue signal
17
B. By way of example, blanking occurs when {overscore (Blanking)} is at a logic low.
Referring again to
FIG. 2
, the values of Xc and Yc are provided by EEProms
56
and
58
, respectively, to memory out register
49
, which then outputs corresponding, re-timed values of Xc as X and Yc as Y in synchronicity with clock signal DLY_CLKB. However,
FIG. 8
shows that signals X and Y are delayed by one clock period. In general, memory out register
49
is used to re-time all values presented to it.
FIG. 8
also shows that the count, Rotation Ctr, of index counter
44
goes from 0-1-2-3-4 in a repeating cycle.
In the preferred embodiment, index counter
44
is a divide by 5 counter that repeatedly counts from a first integer value A, such as 0, to a second integer value B, such as 4. By way of example, as shown in a graph of the Rotation Ctr signal shown in
FIG. 8
, index counter
44
is a divide by 5 counter that counts from 0 to 4 to provide a count C, of 5, where C represents a positive integer. In the preferred embodiment, red, green, and blue optical signals
13
,
15
B, and
17
B may each have on “on time” equivalent to (3P-τ), (P-τ), and (P-τ), respectively. More generally in other embodiments of the invention,(wP-τ) represents the time that red light signal
13
is “on,” (yP-τ) represents the number of clock pulses that green light signal
15
A is “on,” and (zP-τ) represents the number of clock pulses that blue light signal
17
A is “on,” where x, y, and z represent positive integers.
Obviously, many modifications and variations of the present invention are possible in light of the above teachings. For example, the invention may be implemented using gas, solid state, diode lasers, or any other light source capable of generating narrow beams having the appropriate primary color. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.
Claims
- 1. An optical scanner system, comprising:optical signal generating system for generating a repeating sequence of red, green, and blue optical pulses along a common axis, where a time delay τ is interposed between each of said red, green, and blue optical pulses; a first optical deflector for deflecting said optical pulses in a first plane; a second optical deflector for deflecting said optical pulses in a second plane; a controller for directing said first and second optical deflectors to deflect said optical pulses to predetermined coordinates in response to receiving coordinate data; and a computer for providing said coordinate data to said controller.
- 2. The system of claim 1 wherein said controller includes a memory structure that stores color corrected coordinate factors for causing said first and second optical deflectors to deflect said red, green, and blue optical pulses to said predetermined coordinates.
- 3. The system of claim 1 further including a beam expander for increasing the cross-sectional areas of said optical pulses.
- 4. The system of claim 1 wherein said optical signal generating system includes:an optical signal generator for generating a red optical signal along said optical axis; a second optical signal generator for generating a green signal; a third optical signal generator for generating a blue optical signal; a first partially reflective mirror for directing said green optical signal along said optical axis; and a second partially reflective mirror for directing said blue optical signal along said optical axis.
- 5. The system of claim 4 wherein said second plane is orthogonal to said first plane.
- 6. The system of claim 5 wherein said optical signal generating system further includes:a first modulator for modulating the intensity of said red optical signal; a second modulator for modulating the intensity of said green optical signal; and a third modulator for modulating the intensity of said blue optical signal.
- 7. The system of claim 5 wherein:said computer generates coordinate data; and said controller generates deflection control signals in response to receiving said coordinate data that causes said first and second optical deflectors for deflecting said optical pulse sequence to predetermined coordinates.
- 8. The system of claim 1 wherein:said first optical signal generator is a laser diode that generates a red laser beam; said second optical generator is a first laser that generates a green laser beam; and said third optical signal generator is a second laser that generates a blue laser beam.
- 9. The system of claim 1 wherein said controller generates a clock signal having a periodicity P, and said red pulse has a duration of (wP-τ), said green pulse has a duration of (yP-τ), and said blue pulse has a duration of (zP-τ), where w, y, and z are positive integers.
- 10. The system of claim 1 wherein said optical pulses are separated by a time delay.
- 11. An optical scanning system, comprising:a first optical signal generator for generating a first optical signal characterized by a first primary color along an optical axis; a second optical signal generator for generating a second optical signal characterized by a second primary color; a third optical signal generator for generating a third optical signal characterized by a third primary color; a first beam combiner for directing said second optical signal along said optical axis; a second beam combiner for directing said third optical signal along said optical axis; a first optical deflector for deflecting said first, second, and third optical signals in a first plane; a second optical deflector for deflecting said first, second, and third optical signals in a second plane that is orthogonal to said first plane; a first modulator for modulating the intensity of said first optical signal; a second modulator for modulating the intensity of said second optical signal; a third modulator for modulating the intensity of said third optical signal; a controller for controlling said first, second, and third modulators that transform said first, second, and third optical signals into a repeating sequence of red, green, and blue optical pulses separated by a time delay τ, and for causing said first and second deflectors to deflect said optical pulse sequence to predetermined coordinates.
- 12. The system of claim 11 wherein said first, second, and third optical signal generators each generate a laser beam.
- 13. The system of claim 11 wherein said controller generates a clock signal having a periodicity P, and wherein said repeating sequence includes a first pulse of said first optical signal having a duration of (wP-τ), a second pulse of said second optical signal having a duration of (yP-τ), and a third pulse of said third optical signal having a duration of (zP-τ), where w, y, and z are positive integers.
- 14. The system of claim 11 wherein said first optical signal is red, said second optical signal is green, and said third optical signal is blue.
- 15. The system of claim 11 wherein said first optical signal is a red laser beam.
- 16. The system of claim 11 wherein said second optical signal is a green laser beam.
- 17. The system of claim 11 wherein said third optical signal is a blue laser beam.
- 18. The system of claim 11 further including:a computer for generating coordinate data; and said controller generates deflection control signals in response to receiving said coordinate data whereupon said deflection control signals cause said first and second optical deflectors to deflect said first, second, and third optical signals to said predetermined coordinates.
- 19. The system of claim 11 wherein said controller includes memory devices that store color corrected coordinate factors that are used to cause said first and second optical deflectors to deflect said red, green, and blue optical pulses to said predetermined coordinates.
- 20. The system of claim 11 further including a beam expander for increasing the cross-sectional areas of said red, green, and blue optical pulses.
- 21. The system of claim 11 further including a lens for focusing said red, green, and blue optical pulses.
US Referenced Citations (8)