1. Field of the Invention
The present invention relates to various types of solid-state image capture apparatuses, such as CMOS image sensors, and image capture apparatuses. In particular, the present invention relates to solid-state image capture apparatuses and image capture apparatuses, each having a thinning-out readout function.
2. Description of Related Art
In recent years, development of solid-state image capture apparatuses typically represented by CMOS image sensors has been activated and the apparatuses are used in various types of camera apparatuses, mobile phones, and the like.
The CMOS image sensors are provided with an image capture region in which a plurality of pixels including photodiodes are arranged in two-dimensional directions, and a peripheral circuit region formed outside of the image capture region, both regions being disposed on an identical semiconductor substrate.
Each pixel of the image capture region has various types of pixel transistors such as a readout transistor (a transfer gate) to read out the signal charge of the photodiode onto a FD (a floating diffusion), an amplifier transistor to generate a pixel signal corresponding to the potential of the FD, a selection transistor to select a pixel for outputting the pixel signal, and a reset transistor to reset the FD. The signal charge detected by the photodiode of each pixel is converted to a pixel signal and outputted through a signal line arranged per pixel column by using the drive of each pixel transistor.
The peripheral circuit region is provided with a drive control circuit that controls pixel signal readout by supplying various types of control pulses to a pixel array section, a signal processing circuit that performs various types of signal processings to the readout pixel signal, and a power source control circuit to generate a drive power source.
Laminate films such as an insulating film, a drive electrode film for a transistor, a wiring film and a light blocking film are formed successively on the semiconductor substrate. Further, a color filter, a micro lens and the like are formed through a planarized film or the like.
In the CMOS image sensor thus configured, by using the drives of the respective pixel transistors, the signal charges accumulated in the photodiodes of the respective pixels are converted to pixel signals per each pixel, and then the signal is outputted per pixel column basis and transferred to the subsequent signal processing circuit, and the signal is subjected to noise elimination and signal processings to be outputted.
The shown solid-state image capture apparatus according to present embodiment is an example of XY address type CMOS image sensors of column parallel readout mode configured to simultaneously read out a row of pixel signals.
As shown in
The pixel array section 2 receives a color component light corresponding to the spectral characteristics of a color filter arranged above the pixel array section 2, and generates a pixel signal in accordance with the amount of light.
The vertical scan circuit 3 also controls image capture operation and pixel signal readout operation by controlling the individual pixel circuits of the pixel array section 2, based on various types of pulse signals after being subjected to level adjustment by a level shifter 8.
Each pixel is constituted of one photoelectric conversion section (a photodiode) and, for example, four MOS transistors. The signal charge detected by the photodiode is transferred from the readout transistor to the FD (floating diffusion), and the potential of the FD is detected and amplified to by the amplifier transistor to convert it to a pixel signal. Based on the operation of the selection transistor, the output pixel signal of the amplifier transistor is outputted to a vertical signal line 9 at predetermined output timing. The potential of the FD is reset to a power source potential by the reset transistor at predetermined reset timing.
In the CMOS image sensor, interless multi-row addition readout mode of a column CDS mode is employed and, besides pixel readout and reset, only the pixel reset is carried out for the necessary row so as to avoid variations in the accumulation time of the charge per row of a pixel and suppress image flicker, whereby accumulation time of pixels in all rows are unified (see for example, Japanese Unexamined Patent Application Publication No. JP 2005-191814, Patent Document 1).
Further, there has been proposed one adapted to obtain high quality images free from afterimage, in which in order to eliminate afterimage and blooming, residual charge is eliminated by turning on both a transfer gate and a reset gate after reading out the charge subjected to photoelectric conversion by a photodiode (for example, refer to Japanese Unexamined Patent Application Publication No. JP 2000-209508, Patent Document 2).
However, the former of the related art technologies disclosed in Patent Document 1 and Patent Document 2 suffer from the following problem. That is, the pixels normally not read out when the CMOS image sensor performs thinning-out readout are required to be in their reset states all the time in order to suppress the influence of blooming. At the transition from normal drive state to thinning-out readout drive, non-readout pixels (non-readout rows) are concurrently transited to their reset states. As a result, the current concurrently flows into the level shifter circuit, causing, for example, malfunction due to latch-up.
Although the latter is not intended for specifying the interless mode, similarly to the former, there is a risk that excessive current flows into a booster buffer when the transfer gates and the rest gates of all the pixels connected to the selected row during a rest period are concurrently turned on, whereby malfunction of an element may be caused.
The above-described example further suffers from the wiring problem in which the power source line is required to be thick against the excessive current.
Accordingly, it is desirable to provide a solid-state image capture apparatus and an image capture apparatus which are capable of avoiding current concurrently flowing into a level shifter circuit arranged in a scan circuit during thinning-out readout driving, and capable of preventing malfunction or the like.
The solid-state image capture apparatus of an embodiment of the present invention includes a pixel array section and pixel drive control means. The pixel array section is provided with a plurality of pixels arranged in two-dimensional directions, each having a photoelectric conversion section. The pixel drive control means performs pixel signal readout by sequentially scanning the pixel array section either in row direction or in column direction, and driving and controlling individual pixels of the pixel array section through a level shifter circuit. The pixel drive control means includes thinning-out readout control means, reset control means and gate means. The thinning-out readout control means performs pixel signal readout by selecting pixels of the pixel array section on either a per-row or per-column basis. The reset control means resets either a non-readout pixel row or a non-readout pixel column not being selected by the thinning-out readout control means. The gate means causes the pixel drive control means to perform driving control without through the level shifter circuit during thinning-out readout driving by the thinning-out readout control means. The solid-state image capture apparatus is characterized in that current concurrently flowing into the level shifter circuit during the thinning-out readout driving is avoided, thereby suppressing large current caused by the level shifter circuit.
The image capture apparatus of the present invention has an image capture section using a solid-state image capture apparatus, a controller to control the image capture section and an operation section to operate the image capture section. The solid-state image capture apparatus includes a pixel array section and pixel drive control means. The pixel array section is provided with a plurality of pixels arranged in two-dimensional directions, each having a photoelectric conversion section. The pixel drive control means performs pixel signal readout by sequentially scanning the pixel array section either in row direction or in column direction, and driving and controlling individual pixels of the pixel array section through a level shifter circuit. The pixel drive control means includes thinning-out readout control means, reset control means and gate means. The thinning-out readout control means performs pixel signal readout by selecting pixels of the pixel array section on either a per-row or per-column basis. The reset control means resets either a non-readout pixel row or a non-readout pixel column not being selected by the thinning-out readout control means. The gate means causes the pixel drive control means to perform driving control not through the level shifter circuit during thinning-out readout driving by the thinning-out readout control means. The apparatus of the present invention is characterized in that current concurrently flowing into the level shifter circuit during the thinning-out readout driving is avoided, thereby suppressing large current caused by the level shifter circuit.
According to the solid-state image capture apparatus and the image capture apparatus, owing to the gate means causing the pixel drive control means to perform driving control without through the level shifter circuit during thinning-out readout driving, it is possible to avoid current concurrently flowing into the level shifter circuit during the thinning-out readout driving. This enables suppression of large current caused by the level shifter circuit and prevention of malfunction or the like caused by the level shifter circuit.
As shown in the drawings, the CMOS image sensor of the present embodiment has a pixel array section 2, a vertical scan circuit 3, a column CDS circuit 4, horizontal scan circuits 5, an output circuit 6 and a timing generating circuit 7. The vertical scan circuit 3 includes a vertical drive circuit 31, an OR circuit 32, level shifters 33 and a V-direction decoder 36, and a logic control circuit 37 to control the components is annexed to the vertical scan circuit 3.
The present embodiment aims to avoid current concurrently flowing into the level shifters during thinning-out readout driving, by providing the OR circuit 32 and the three level shifters 33.
The horizontal scan circuits 5 are arranged on the upper and lower sides of the pixel array section 2, respectively, each having a horizontal direction drive circuit 51 and an H-direction decoder 52, to which pixel signals digitalized by a column parallel AD converter 53 at the preceding stage are inputted and processed.
The timing generating circuit 7 has a timing control circuit/communication IF 71 to control timings by inputting the instruction data and the like from the outside, and a PLL circuit 72 to perform frequency division of clock.
The vertical drive circuit 31 shown in
In the circuit, when thinning-out readout is performed, the pixels of a row to be thinned out are reset at all times. Therefore, a PVDFRSTS signal, a PVDFROGES signal and a PVDFROGOS signal shown in
In the rows whose pixels are reset, while it is surely necessary that the PVDFROGES and the PVDFROGOS are connected and operated, the signal line of the PVDFRSTS may be operated or not be operated by option. The operations of each signal lines may be simultaneously or non-simultaneously.
The pixel reset operation can be applied to an entire column of the selected columns by using the circuit configuration in which pixel signal lines 81 in a column direction and row selection lines 82 are inputted to OR circuits 83 to take the logical sum, as shown in the figure. In this case, the arrangement of the selector circuits (not shown) in the upper and lower directions enables the reset operation in a column direction corresponding to the vertical thinning-out readout.
That is, the example enables the per-pixel reset control by arranging column selection switches 84 on the respective column connecting lines of the OR circuits 83 shown in
Although details are omitted here, a programmed reset operation becomes possible by further using a memory 1 and the like, as shown in
As shown in the figure, in the example, OR circuits 92 for resetting reset transistors 90 are provided in each pixel. In the figure, vertical signal lines 91 are control signal lines for inputting the control signals supplied from a logic control circuit 37 shown in
Also in the example, by using the memory 1 shown in
As shown in the figure, in the example, NOR circuits 95 for resetting reset transistors 90 are provided in individual pixels, respectively. For example, in the configuration that the outputs of the NOR circuits 95 are connected to the gates of the reset transistors 90 in pixels, it is capable of attaining the state that a partial pixel region is not reset but the other pixel region is reset (the reset region is the reverse of that in
The foregoing examples according to the present invention may also produce the following effects.
Although description is made for certain embodiments of the solid-state image capture apparatus in the present invention, further various modifications may be made.
For example, though description is made in the above-describe embodiment about the configuration that the four transistors are provided in a pixel, the present invention may be widely applicable to various types of other solid-state image capture apparatuses, such as CMOS image sensors and CCD image sensors having other pixel configuration.
The solid-state image capture apparatuses are not limited to ones in which an image sensor or the like are arranged on a single chip. The apparatuses may be modules collectively packaging an image capture section, a signal processing section and an optical system. Alternatively, these may be apparatuses used in camera systems and mobile phones. Noted, in embodiments of the present invention, the configuration that has an image sensor function as a single unit is referred to as the solid-state image capture apparatus, and the configuration that the solid-state image capture apparatus and other elements (the control circuit, the operation section and the display section, as well as a data accumulation function, a communication function and the like) are integrated together is referred to as the image capture apparatus.
The following is a specific example of the image capture apparatus to which the present invention is applied.
In
That is, the image capture section 310 generates and outputs digital image capture signals by applying AGC (automatic gain control), OB (optical black) clamp, CDS (correlative dual sampling) and A/D conversion processings to the above-described output signals of the image sensor.
In this embodiment, the example in which the image capture section 310 converts image capture signals to digital signals and then output them to the system control section 320 is shown. Alternatively, a configuration in which analog image capture signals may be sent from the image capture section 310 to the system control section 320, and the system control section 320 may convert the signals into digital signals may be employed.
Various methods of specific control operations and signal processings within the image capture section 310 have been provided, and therefore, not to mention, no particular limitations are imposed on the image capture apparatus of the present invention.
An image capture optical system 300 includes a zoom lens 301 and an aperture mechanism 302 arranged in a lens barrel, and forms an object image on a light receiving section of the image sensor. Under the control of a drive controller 330 based on the instruction of the system control section 320, the respective components are mechanically driven to perform control, such as auto-focus or the like.
The system control section 320 includes a CPU 321, a ROM 322, a RAM 323, a DSP 324, an external interface 325 and the like.
The CPU 321 controls the entire system by sending instructions to the respective sections of the camera apparatus by use of the ROM 322 and the RAM 323.
The DSP 324 generates video signals (e.g. YUV signals) of a still image or a moving image in a predetermined format by applying various signal processings to the image capture signals from the image capture section 310.
The external interface 325 is provided with various types of encoders and a D/A converter, and exchanges various types of control signals and data with external elements connected to the system control section 320 (in this example, a display 360, a memory medium 340 and an operation panel section 350).
The display 360 is a small display device such as a liquid crystal panel assembled into the camera apparatus, and displays captured images. In addition to the small display device assembled in the camera apparatus, not to mention, a configuration in which image data may be transferred to an external large display device and displayed thereon, may be adopted.
The memory medium 340 can suitably store the captured image in various types of memory cards et al, and can exchange the memory medium with, for example, the memory medium controller 341. As the memory medium 340, disk medium using magnetism and light may also be used besides the various types of memory cards.
The operation panel section 350 is provided with input keys through which the user issues various types of instruction when performing image capture operations with the camera apparatus. The CPU 321 monitors the input signals from the operation panel section 350 and executes various types of operation controls based on the input contents.
By applying the solid-state image capture apparatus of the present invention to the camera apparatus, a high-performance image capture apparatus having an effective window cutout function can be provided. In the foregoing configuration, the combination of a unit device and a unit module which are constituent elements of the system, and scale of the set can be selected, as appropriate, based on the circumstances of product commercialization and the like. That is, the image capture apparatus of the present invention includes a wide variety of modifications.
In the solid-state image capture apparatus and the image capture apparatus according to embodiments of the present invention, a target of shooting (the object) is not limited to general video, such as people and sceneries etc. These apparatuses are also applicable to the purposes of shooting special micro image patterns, such as counterfeit bill detectors and fingerprint detectors.
As apparatus configuration of this case, the apparatus is arranged to be different from the general camera apparatus as shown in
In the case of configuring remote systems, such as remote medical care systems, security monitors and personal authentication, the apparatus configuration including a communication module connected to a network as described above may be also adopted, thereby permitting a wide range of applications thereof.
It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.
The present document contains subject matter related to Japanese Patent Application No. 2007-256768 filed in the Japanese Patent Office on Sep. 28, 2007, the entire content of which being incorporated herein by reference.
Number | Date | Country | Kind |
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2007-256789 | Sep 2007 | JP | national |