JP2001078209A - Solid-state image pickup device and signal read method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid-state image pickup device where the image quality of an image obtained by a main image pickup can be enhanced even with a higher number of pixels and low power consumption and to provide a signal read method. SOLUTION: A digital camera 10 uses a timing signal supply section 22 to generate a drive signal driving photodetectors PD of an image pickup section 30 for reading signal charges of an odd number column and an even number column of the light receiving elements alternately while reading is executed twice, this drive signal is fed to the image pickup section 30 in response to an instruction of this image from a system control section 18, a horizontal transfer register HR reads the signal charges of only the odd number column or the even number column of the light receiving section 30a so as to generate an empty packet between the packets of the signal charges, thereby making defective transfer between pixels not conspicuous. Then the signal charges of only an even number column or an odd number column of the light receiving section 30a are conversely read in a succeeding field.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state imaging device and a signal readout method, and is suitably applied to, for example, a digital camera or an image input device having a large number of pixels.

[0002]

2. Description of the Related Art In recent years, various techniques for further increasing the number of pixels of a digital camera for electrically photographing an image of a subject have been proposed aiming at image quality of a silver halide camera. For example, Japanese Patent Application Laid-Open No. 10-136391 discloses a solid-state imaging device that optimizes spatial sampling of an image, displaces pixels so as to improve light receiving efficiency, and suppresses false signals such as moiré. Proposed.

Incidentally, in a digital camera or the like using a pixel array having a high pixel count in an image pickup section for the purpose of high image quality, before performing a main image pickup (that is, still image pickup),
AE / AF (Automatic Exposur
e / Automatic Focusing) and movie drive to display images on the LCD screen. Here, the high pixel indicates, for example, a pixel number of one million pixels or more, that is, a so-called megapixel. The imaging unit having a higher number of pixels for the control reads the driving for the preliminary imaging and the driving for the main imaging of the still image with the same driving.

[0004]

However, as described above, in the preliminary imaging, the reading of the signal charges from the imaging unit having the pixel array with the increased number of pixels has not been taken into consideration. When the horizontal transfer path is driven at a low voltage / high speed, a transfer failure of signal charges occurs in the image area of low illuminance due to the drive frequency, drive voltage, and the like of the horizontal transfer path. The transfer failure causes color mixture between pixels in this area, and for example, when a movie is displayed on a liquid crystal monitor, correct color reproduction cannot be performed. As the number of pixels in an image sensor increases and the life of a battery in consideration of portability increases, power consumption decreases. Color mixing in a low-illuminance area is likely to occur.

The present invention solves such disadvantages of the prior art, and provides a solid-state imaging device and a signal reading method capable of achieving high image quality of an image obtained by main imaging even if the number of pixels and power consumption are reduced. The purpose is to do.

[0006]

According to the present invention, in order to solve the above-mentioned problems, light receiving elements for photoelectric conversion are two-dimensionally arranged.
For each light-receiving element, the signal was obtained by preliminary photographing before the main imaging, in which all signal charges were read out from imaging means in which color separation means for color-separating the incident light was arranged on the incident light side from the object field. The main imaging is performed based on the information, the signal charges are read, and the signal charges are sequentially transferred to a vertical transfer path and a horizontal transfer path formed so as to output the signal charges. The obtained signals are subjected to digital signal processing and output. In a solid-state imaging device, when a signal is read from a light receiving element in a normal manner, the conditions under which color mixing appears in an image due to the number of light receiving elements, a driving voltage for signal reading, and driving of a signal charge in a horizontal transfer path are set. Control means for switching control of readout of signal charges from the imaging means in preliminary imaging and main imaging, respectively,
A signal for supplying a drive signal to the image pickup means for use in driving to read the signal charges alternately in the odd rows and the even rows of the light receiving elements of the image pickup means in a plurality of times in response to an instruction of the main image pickup from the control means. Supply means.

Here, it is preferable that the signal supply means sets the driving frequency of the horizontal driving signal to a lower driving frequency than in the preliminary imaging.

In the solid-state imaging device according to the present invention, the signal supply means generates a drive signal used for driving the odd-numbered rows and the even-numbered rows of the light receiving elements of the imaging means alternately to read out the signal charges a plurality of times. By supplying a driving signal generated in response to a main imaging instruction from the control unit to the imaging unit,
The signal charges of only the odd columns or even columns are read out to the horizontal transfer path. Focusing on the horizontal transfer path between the packets having signal charges, an empty packet is generated between the packets having the signal charges. By generating this empty packet, one packet when driving is performed in the same manner as normal signal reading is performed.
Transfer failure between pixels can be ignored.

According to the present invention, in order to solve the above-mentioned problems, the positions of the light receiving elements for photoelectric conversion are two-dimensionally shifted from each other with respect to the adjacent light receiving elements, and each light receiving element is incident from the object field. The main imaging is performed based on information obtained by preliminary imaging performed before the main imaging, in which all signal charges are read out from imaging means in which color separation means for performing color separation of the incident light is disposed on the light side. In a solid-state imaging device that reads out and sequentially transfers the signal charges to a vertical transfer path and a horizontal transfer path formed so as to output the signal charges, performs digital signal processing on the obtained signals, and outputs the signals, the signal reading from the light receiving element is performed. In the case of performing the normal method, if the condition that the color mixture appears in the image due to the number of light receiving elements, the driving voltage for signal reading, and the driving of the signal charge in the horizontal transfer path satisfies the condition, the preliminary photographing and the actual photographing are performed. A control means for switching control of signal charge readout from the means, and a signal charge for one line of a light-receiving element of the imaging means reaching a horizontal transfer path in response to an instruction for main imaging from the control means. Signal supply means for supplying a drive signal for performing the one-line signal charge read-out drive every time.

Here, the signal supply means may set the driving frequency of the horizontal driving signal to a lower driving frequency than at the time of preliminary imaging.

The solid-state imaging device of the present invention reads out signal charges from a light-receiving element shifted in pixels, which is a so-called honeycomb arrangement, according to a shift signal, and vertically transfers these signal charges toward a horizontal transfer path. Is in the horizontal transfer path
When the data is transferred by the number of lines, empty packets can be generated between packets having signal charges even if all of the signal charges for one line are read. This makes it possible to ignore transfer failures between one pixel when driven in the same manner as in normal signal reading.

According to the present invention, in order to solve the above-mentioned problems, a plurality of light receiving elements prepared are arranged in a two-dimensional arrangement. The main imaging is performed based on information obtained by preliminary imaging performed before the main imaging, in which each light is subjected to photoelectric conversion by each light receiving element and all signal charges are read out. In the signal reading method of reading out charges, sequentially transferring the signal charges in the vertical direction and the horizontal direction, and outputting the signal charges, when signal reading from the light receiving elements is performed in a normal manner, the number of light receiving elements and the driving of signal reading are performed. When satisfying the condition that the color mixture appears in the image by driving the voltage and the signal charge in the horizontal direction, the control is switched to either one of the imaging of the signal charge readout from the imaging unit according to the preliminary imaging and the main imaging. A switching control step, and generating a shift signal at a timing of reading signal charges from the two-dimensionally arranged odd-numbered or even-numbered light receiving elements in accordance with the control at the time of performing the main imaging in the switching control step; A signal generation step of generating a drive signal for transferring the signal charges in the vertical and horizontal directions, and one of the odd-numbered or even-numbered signal charges photoelectrically converted by the light receiving element by supplying the shift signal generated in the signal generation step A first signal shift step of reading only the column, a first column image reading step of sequentially reading the signal charges read in the first signal shift step in a vertical direction and a horizontal direction according to a supplied drive signal; Only one column of the even-numbered or odd-numbered signal charges, which is photoelectrically converted by the light receiving element by the supply of the shift signal generated in the generation process and is opposite to the first signal shift process A second signal shift step of reading, and a second column image reading step of sequentially reading the signal charges read in the second signal shift step in a vertical direction and a horizontal direction according to a drive signal supplied thereto. And

Here, in the signal generation step, it is desirable to set the horizontal drive frequency of the drive signal to a lower drive frequency than during preliminary imaging.

According to the signal reading method of the present invention, a signal to be supplied at the time of imaging is generated in accordance with the switching control, and signal charges are read out from either the odd-numbered column or the even-numbered column in accordance with the generated signal. Transfer in the horizontal and vertical directions, read the even columns when the read column is an odd column, read the odd columns when the read column is an even column, and similarly transfer in the vertical and horizontal directions, and output the read signal charges I do. In particular, when performing horizontal transfer, signal charges are read out from only one of the columns. Therefore, even if an empty packet is generated between packets and driving is performed in the same manner as normal signal reading, transfer failure between one pixel is performed. Can be ignored.

In order to solve the above-mentioned problem, the present invention arranges a plurality of two-dimensionally arranged light-receiving elements in a positional relationship in which the light-receiving elements are shifted from adjacent light-receiving elements. In response to the above, the color is separated into each color on the incident light side from the object scene, and this color-separated light is photoelectrically converted by each light receiving element and all signal charges are read out. Based on the obtained information, the main imaging is performed to read out the signal charges, and the signal charges are read in the vertical direction,
In the signal reading method of sequentially transferring and outputting in the horizontal direction, when the signal reading from the light receiving element is performed in a normal manner, the number of light receiving elements, the driving voltage for signal reading, and the driving of the signal charge in the horizontal direction In the case where the condition for causing color mixture to appear in the image is satisfied, a switching control step of switching the control of reading out the signal charge from the imaging means to one of the imaging modes according to the preliminary imaging and the main imaging, and the main imaging in this switching control step Generating a shift signal at the timing of reading signal charges from the two-dimensionally arranged light receiving elements in accordance with the control at the time of performing the operation, and generating a drive signal for transferring the read signal charges of the column in the vertical and horizontal directions. A signal shifting step of reading out signal charges photoelectrically converted by the light receiving element by supplying the shift signal generated in the signal generating step; A vertical transfer step of transferring the read signal charges in the vertical direction according to the supplied drive signal; and supplying the signal charges according to the drive signal when the signal charges are transferred in the horizontal direction perpendicular to the vertical direction by the vertical transfer step. Done 1
And a horizontal transfer step of reading out all the lines, wherein the signal charge is read out by repeating the vertical transfer step and the horizontal transfer step.

Here, in the signal generation step, it is preferable to set the horizontal drive frequency of the drive signal to a lower drive frequency than in the preliminary imaging.

In the color separation, a color G is arranged at a position of a square lattice corresponding to the light receiving element, and a color R or a color B is alternately arranged at the center position of the square lattice of the color G to completely check the color. Is desirably performed with an arrangement pattern that forms By using the pixel shift, that is, the so-called honeycomb arrangement, the time required for each line to reach the horizontal transfer path is different, so that all pixels are simultaneously read out without using a mechanical shutter and signal charges are output without color mixing.

According to the signal reading method of the present invention, for example, various signals such as shift signals, vertical and horizontal drive signals are generated, and signal charges obtained by the shift signals are read from the light receiving elements and transferred in the vertical direction. Then, since empty packets are formed between the signal charges of a predetermined color read when performing the horizontal transfer and the arrangement relationship of the pixel shift, color mixing is prevented, and the signal charges of the next line are transferred. Before reading, all of the data for one line is read out to realize simultaneous reading of all pixels.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the solid-state imaging device according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows the configuration of a digital still camera 10 according to an embodiment to which the present invention is applied. The digital still camera 10 of FIG. 1 includes an optical lens system 12, an operation unit 14, a system control unit 18, a signal generation unit 20, a timing signal supply unit 22, an aperture adjustment mechanism 24, an optical low-pass filter 26, a color separation unit 28,
Imaging unit 30, pre-processing unit 32, A / D conversion unit 34, signal processing unit 36,
A compression / expansion unit 38, a recording / reproducing unit 40, and a monitor 42 are provided. These components will be described sequentially. Optical lens system
12, for example, is configured by combining a plurality of optical lenses. Although not shown, the optical lens system 12 has a zoom mechanism that adjusts the position of these optical lenses and adjusts the angle of view of the screen according to an operation signal from the operation unit 14, and the distance between the subject and the camera 10 AF that adjusts the focus accordingly
(Automatic Focus) adjustment mechanism is included. The adjustment of these mechanisms is performed based on information obtained by performing preliminary imaging of the object scene when the release shutter forming a part of the operation unit 14 is half-pressed, for example. The operation signal is supplied to the system control unit 18 via the system bus 16. A drive signal is supplied to the optical lens system 12 via a signal generation unit 20, a timing signal generation unit 22a of a timing signal supply unit 22, and a driver unit 22b described later. In the case of actual imaging, the imaging timing is supplied to the system control unit 18 by fully pressing the release shutter in a state set according to the obtained information, and imaging control is performed.

The operation unit 14 has a release shutter (not shown) and a function of selecting an item displayed on a monitor screen, for example. In particular, the release shutter outputs an operation signal to the system controller 18 via the system bus 16 so as to operate the camera 10 in each of a plurality of stages. In the present embodiment, the operation unit 14 performs various operations and
The user also operates the pointing device displayed on the monitor so that the user can select a mode for processing.
The operation of the operation unit 14 in this case is also supplied to the system control unit 18 as an operation signal.

The system control unit 18 includes, for example, a CPU (Cent
ral Processing Unit). The system control unit 18 has a ROM (Read Only Memory) in which the operation procedure of the digital still camera 10 is written. The system control unit 18, for example,
A control signal for controlling the operation of each unit is generated using the information supplied from the operation unit 14 in accordance with the operation of the user and the information of the ROM. The system control unit 18 transmits the generated control signal to the signal generation unit 20, although not explicitly showing the supply of the control signal, in addition to the timing signal supply unit 22, the preprocessing unit 32, and the A / D conversion unit 34, the system bus The signal is also supplied to a signal processing unit 36, a compression / expansion unit 38, a recording / reproducing unit 40, and a monitor 42 via 16. In particular, the system control unit 18 controls the timing signal supply unit 22, which will be described later, so that the timing signal and the like generated in the preliminary imaging and the main imaging are different. In addition, the system control unit 18 performs various controls having characteristics also on a signal processing unit 36 described later.

The signal generator 20 generates a system clock by an oscillator under the control of the system controller 18. The signal generator 20 supplies the system clock to the timing signal supplier 22 and the signal processor. Also,
The system clock is also supplied via the system bus 16 as a reference for the operation timing of the system control unit 18, for example.

The timing signal supply section 22 includes a timing signal generation section 22a and a driver section 22b. The timing signal supply unit 22 generates different timing signals by switching control between preliminary imaging and main imaging under the control of the system control unit 18. The timing signal generating section 22a includes a circuit for generating a timing signal for operating each section based on the supplied system clock based on the control signal. The timing signal generator 22a basically generates a timing signal according to the imaging mode under the control of the system controller 18, outputs the generated timing signal to each unit as shown in FIG. Also supply. The driver unit 22b also supplies drive signals to the aperture adjustment mechanism 24 and the imaging unit 30 in addition to the zoom adjustment mechanism and the AF adjustment mechanism of the optical lens system 12 described above. The driver unit 22b may also be directly controlled by the system control unit 18. The present embodiment is characterized in that the supply of the signal used for reading out the signal charge at the time of the main imaging is controlled. In response to the switching control, the system control section supplies the generated field shift pulse to the timing signal generating section 22a to only one of the columns, that is, the column, that is, the odd-numbered column and the even-numbered column. Supply control is performed. In addition, the system control unit 18 includes a driver unit 22
For b, for example, the superposition of the field shift pulse of the column not desired to be read on the drive signal may be prohibited. In the horizontal driving, the driving frequency is reduced so that signal charges are read out at a lower rate by preliminary imaging.

The aperture adjusting mechanism 24 is a mechanism for adjusting the cross-sectional area of the incident light beam (that is, the aperture opening area) so that the optimum light beam of the incident light is supplied to the image pickup section 30 in photographing the subject. A drive signal is also supplied from the driver 22b to the aperture adjustment mechanism 24. This drive signal is a signal for operating according to the control from the system control unit 18 described above.
In this case, although not shown, the system control unit 18
AE (Automatic Exposu) based on the signal charge photoelectrically converted in 30
re: Automatic exposure) The aperture and exposure time are calculated as processing. A drive signal corresponding to the signal from the timing signal generator 22a to which the control signal corresponding to the calculated value has been supplied to the aperture adjustment mechanism 24 from the driver 22b.

The image pickup section 30 arranges the image pickup element for photoelectric conversion so that a plane perpendicular to the optical axis of the optical lens system 12 is formed. Also, on the incident light side of the image sensor, a color filter CF of a color separation unit 28 that performs color separation integrally with an optical low-pass filter 26 that limits the spatial frequency of an optical image to a Nyquist frequency or lower corresponding to each image sensor. Are provided integrally. In this embodiment, imaging is performed using a single-plate type color filter. The type of the color filter CF will be described in more detail later.
The image sensor includes a CCD (Charge Coupled Device) and a MOS (Metal Oxide Semiconductor) type. The imaging unit 30 reads out the signal charges obtained by the photoelectric conversion in accordance with the supplied drive signal in accordance with the preliminary imaging and the main imaging.

In this embodiment, a so-called honeycomb arrangement in which pixels are shifted, that is, a color filter G is arranged in a square lattice pattern in a color filter pattern, and a color R or a color B is arranged in the center of the square lattice pattern. Since the complete checkerboard pattern is formed by the color RB, the signal readout in other embodiments is all pixel readout (progressive scan) as shown in the later stage.
Can also be done. The color filter arrangement pattern used is called a G square (lattice) RB perfect checkerboard pattern.

Although not shown, the pre-processing unit 32 includes a CDS (Corr
elated Double Sampling: Correlated double sampling; below
CDS) section. The CDS unit includes, for example, a clamp circuit that uses a CCD type imaging device and basically clamps various noises generated by the device with a timing signal from the timing signal generation unit 22a.
It has a sample-and-hold circuit that holds a signal charge by a timing signal. The CDS section removes the noise component and sends it to the A / D conversion section 34. The A / D converter 34 quantizes a signal level of the supplied analog signal, which is an analog signal, by a predetermined quantization level and converts the signal level into a digital signal.
It has a converter. The A / D converter outputs a digital signal converted by a timing signal such as a conversion clock supplied from the timing signal generator 22a to the signal processor.

Although not shown, the signal processing unit 36 includes a data correction unit, a luminance data generation function unit, a luminance data interpolation function unit, a high resolution plane interpolation function unit, and a data correction unit (not shown) for further improving the quality of the obtained image. A matrix processing unit is included. The data correction unit includes a gamma correction circuit that performs color correction and AWB (Automat
ic White Balance) circuit. In particular, the gamma correction circuit uses a look-up table, which is a set of a plurality of data sets in which a digital signal supplied to a ROM (Read Only Memory) and correction data output corresponding to the digital signal are combined. The data correction unit is not limited to this arrangement, and may be provided at a subsequent stage. However, by arranging at this position, the number of lookup tables can be minimized. In these series of data corrections as well, the data is supplied according to the timing signal from the timing signal generator 22a. The data correction unit outputs the processed correction data to the luminance data generation function unit.

The luminance data generating function unit is a system control unit 18.
It operates under the control of. The luminance data generation function unit generates the luminance data Y at the pixel where the light receiving element is located by the arithmetic processing as described above, and outputs the luminance data Y to the luminance data interpolation function unit.
The luminance data interpolation function unit is an arithmetic function unit that performs interpolation generation of luminance data at a position of a virtual pixel between supplied luminance data Y. Luminance data interpolation function unit generates the luminance data Y _h plane is supplied to the high-resolution plane interpolation function unit. High-resolution plane interpolation function unit, the luminance data Y _h and data corrected three primary colors R plane, G, B
Is an arithmetic function unit that receives the pixel data of the above and generates R plane data, G plane data and B plane data using these data. The high resolution plane interpolation function unit outputs the generated three primary color RGB plane data to the matrix processing unit. The high-resolution plane interpolation function unit stores the image data obtained by performing the signal processing, and includes a nondestructive readable memory. The high-resolution plane interpolation function unit reads out pixel data used for plane interpolation and calculates pixel data. The matrix processing unit uses the supplied R-plane data, G-plane data, and B-plane data of each of the three primary colors RGB to convert into a format used for image display, that is, luminance data Y, color difference data (RY), (BY). .
The data in these output formats is obtained by multiplying each color by a determined mixing ratio and calculating. As a coefficient for determining the mixing ratio, a conventional value is used. An anti-aliasing process is performed by setting the three converted data to a cutoff frequency that includes each band and does not cause aliasing distortion. this house,
The luminance data Y is sent to the aperture adjustment unit,
Raise the high frequency range of Y. Thereby, the outline of the image is emphasized. In this way, the matrix processing unit
Compression / decompression unit for luminance data Y and color difference data (RY), (BY)
38 and the monitor 42. The matrix processing unit supplies the captured image to the monitor 42 via the system bus 16.

With this configuration, the signal processing unit 36 uses the pixel data of the light receiving element to generate, for example, luminance data Y and chrominance data from the pixel data having the larger correlation, and then performs compression / expansion. Output to the unit 38 and the monitor 42.

The compression / decompression unit 38 has, for example, a circuit for performing compression according to the JPEG (Joint Photographic Experts Group) standard using orthogonal transformation, and a circuit for decompressing this compressed image to original data again. The compression / decompression unit 38 supplies the compressed data to the recording / reproduction unit 40 via the system bus 16 during recording under the control of the system control unit 18. Further, the compression / decompression unit 38 includes the system control unit 18 as described above.
Through the data from the signal processing unit 36,
The data may be supplied to the monitor 42 via the system bus 16.
When the compression / expansion unit 38 performs the expansion process,
The data read from 40 is taken into the compression / decompression unit 38 via the system bus 16 and processed. Here, the processed data is also supplied to the monitor 42 for display.

The recording / reproducing section 40 includes a recording processing section for recording on a recording medium, and a reproducing processing section for reading image data recorded from the recording medium (both not shown). The recording medium includes, for example, a semiconductor memory such as a so-called smart media, a magnetic disk, and an optical disk. When a magnetic disk or an optical disk is used, there is a head for writing the image data together with a modulator for modulating the image data. The monitor 42 has a function of considering the size of the screen and displaying the luminance data and the color difference data or the data of the three primary colors RGB supplied via the system bus 16 under the control of the system control unit 18 while adjusting the timing. Have. When a movie is displayed using a monitor such as a liquid crystal display, for example, in a preliminary image pickup, the light receiving elements, that is, the pixels are displayed while thinning out the pixels.

The digital camera 10 shown in FIG. 1 is configured as described above and has an image pickup section 30 with a high number of pixels. Imaging is performed. In particular, signal reading is performed in an image area of low illuminance to prevent the occurrence of color mixture due to a decrease in transfer efficiency, thereby improving the image quality of the entire image regardless of the illuminance.

Next, the color filter CF used in the image pickup section 30 and the color separation section 28 will be described. FIG. 2 shows vertical transfer drive signals V1 to V8 from the image pickup surface of the image pickup section 30 and the driver section 22b.
Is applied. As described above, the imaging unit 30 includes, as described above, a light receiving unit 30a in which light receiving elements PD adjacent to the light receiving element PD that photoelectrically converts incident light are vertically and horizontally shifted and two-dimensionally arranged. Light receiving section
An electrode EL arranged to bypass the opening AP formed on the front surface of the light-receiving element 30a and for extracting a signal from the light-receiving element PD;
A vertical transfer register VR for sequentially transferring a signal supplied through the electrode EL in the vertical direction of the light receiving section 30a, and a horizontal transfer register HR for transferring a signal in a direction orthogonal to the vertical transfer register VR, that is, in a horizontal direction. And

The vertical transfer register VR transfers signals according to the supplied vertical transfer drive signals V1 to V8. That is, the vertical transfer register has a four-electrode structure per light receiving portion. Further, a horizontally adjacent region of one light receiving portion region has a two-electrode structure, and is shifted by pixels as described above. Correspondingly, the horizontal transfer register HR also has a two-electrode structure.
The opening AP formed in the imaging unit 30 of the present embodiment is formed in a hexagonal honeycomb shape. The opening shape is generally a square lattice, but this shape may satisfy the conditions for improving the sensitivity and keeping the width of the vertical transfer register the same so as not to lower the transfer efficiency. As can be seen from this, the shape may be a polygon, and as another example, an opening shape obtained by rotating a square lattice by 45 ° is, for example, a rhombus, and may be an octagon.

As shown in FIG. 2, each of the openings AP
When the interval between the light receiving elements PD arranged directly below the color filters CF covering the pixels is a pixel pitch PP in each direction, the arrangement of the apertures AP is vertical in each column or horizontal in each row. The two-dimensional arrangement is shifted in the direction by the pixel pitch PP. When using a polygon that is more than a rectangle,
The openings AP may be arranged in a dense arrangement with no gap between the openings AP in accordance with the shape of the openings. In such a case, the pixel pitch PP for arrangement may be shifted by a half pitch. In the case of a hexagon as shown in FIG. 2, a dense arrangement can be formed by an arrangement (| PP | / 2) shifted by half the above-described pixel pitch PP in both the horizontal and vertical directions. Obtaining such a dense arrangement depends on the shape of the opening AP.

The image pickup section 30 shown in FIG. 2 is located on the leftmost side, and the light receiving elements of the colors R and B are arranged in odd columns in the vertical direction. Also,
As is clear from FIG. 2, the vertical drive signal including the field shift pulse corresponding to the position where the electrode EL is provided is
V1, V3, V5, and V7. Then, in the preliminary imaging (at the time of half-pressing the release shutter) in this embodiment, high-speed reading is performed in the same manner as in the previous operation.

The operation of the digital camera 10 to which the imaging unit 30 having the above configuration is applied at the time of actual imaging will be described. Each mechanism for performing the AE / AF adjustment based on information obtained in the preliminary imaging performed before the main imaging is set. Also, according to this preliminary imaging, the state shown in FIG.
The mechanical shutter, which is a part of the AE adjustment mechanism, is in an open state from the half-pressed state of the release shutter to the end of exposure through the imaging timing of the main imaging, for example.
Thereafter, the mechanical shutter is closed.

In the digital camera 10, the image pickup unit 30
Is supplied with a vertical synchronizing signal VS as a predetermined timing signal (see FIG. 3B). The imaging unit 30 has a vertical synchronization signal VS
The electronic shutter is operated in synchronization with. Normally, the electronic shutter performs an unnecessary charge sweep-out process in synchronization with the vertical synchronization signal VS. This processing applies a sweep pulse to the substrate voltage of the imaging unit 30 during the horizontal retrace period, and during the vertical synchronization period,
The signal charge accumulated so far during the period from time T1 to time T2 is swept to the substrate side (see FIG. 3 (c)). Actually, a period during which the electronic shutter is turned on is an exposure time based on information obtained by preliminary imaging (see FIG. 3D). In this case, the electronic shutter is a period from the end of the electric charge discharge at the time T2 of the vertical synchronization period VD to the time when the mechanical shutter of FIG. 3A is closed.

The reading of the signal charges stored in the light receiving element PD is started in synchronization with the next vertical synchronizing signal after the exposure (see FIG. 3D). Here, the signal charge to be read is
The timing signal generator 22a generates a field shift pulse in accordance with the control from the system controller 18 so as to read from the odd column 30a, and supplies it to the driver 22b. With this supply, the driver unit 22b applies the drive signals V1 and V5 including the field shift pulse to the electrode EL.
The electrode EL performs a gate opening / closing switch function in accordance with a signal applied to the gate for storing signal charges. By supplying a drive signal only to these electrodes EL, the color BR is read from the odd-numbered columns, that is, from the imaging unit 30 in FIG.

The state shown in FIG. 2 is a state in which the obtained signal charges are read out to the vertical transfer register VR, vertical transfer is performed, and the signal charges are transferred to the horizontal transfer register HR. At this time, as indicated by the horizontal transfer register HR in FIG. 2, there is an empty packet between the signal charges in the positional relationship of the signal charges in the horizontal transfer register. This is a packet in which the signal charges of the even-numbered columns enter, but are consequently cleared by reading out only the odd-numbered columns. By forming this empty packet between the light receiving elements, a transfer failure between one pixel can be ignored. For this reason, it is possible to largely prevent the color from being mixed with the individual pixel data. The signal charge read out to the horizontal transfer register HR is output until the next signal charge is transferred, similarly to the normal readout. However, since it is only necessary to read out half of the signal charge during the period of one field,
The transfer rate of the horizontal transfer can be reduced to about half of the conventional rate.

In the previous field, signal charges were read from only odd columns. In the next field, although not shown, a field shift pulse is generated and applied so as to read out signal charges of only even-numbered columns. That is, by supplying the vertical drive signals V3 and V7, the signal charges of only the color G are read out to the vertical transfer register VR. As described above, the signal charges are sequentially transferred in the direction of the horizontal transfer register. Horizontal transfer register HR
, Empty packets (for odd-numbered signal charges) are generated between signal charges read from the light receiving elements. Thereby, even in this field, the transfer failure between one pixel can be ignored. Even in this field, if the signal charge readout from the horizontal transfer register HR is reliably output for each line, the signal charges can be read out while largely preventing color mixing of pixels. As described above, the signal charges obtained by the exposure in the light receiving section 30a of the imaging section 30 are read out for each column, and the signal charges obtained in both fields in the subsequent signal processing are converted into the signals obtained by simultaneous reading of two lines at this stage. By generating images by rearranging them into charge relationships, it is possible to generate a single high-quality image in which color mixing does not occur even when a low-illuminance region is in the field.

The operation performed so far in FIG. 3E will be described as a comparative example. The settings and operations in FIGS. 3A to 3C are the same as those in the above-described embodiment. Exposure is performed with the same exposure time. However, the reading of the signal charge is performed in the time of one field. In order to read out the signal charges, two lines are read out simultaneously in order to extract the three primary colors RGB without distinguishing between odd and even columns as in the embodiment of the present invention. In this case, since the light receiving elements are arranged with pixels shifted, the read signal charges are transferred to the horizontal transfer register.
Even if transferred to the HR, the color data does not mix theoretically. As a result, the horizontal transfer register HR contains "G_B_G_R_G_
B_G_R_... "Are arranged in this order. here,"_
"" Indicates one register area of the two-electrode structure register in the horizontal transfer register HR.

When the two lines are read simultaneously,
Although the three primary colors RGB can be obtained from the line, transfer in a low illuminance region tends to cause transfer failure due to an increase in the horizontal drive frequency and a decrease in the drive voltage as described in the subject. As a result, color mixing occurs in this area, and the color reproducibility of the image is poor. This deterioration in image quality tends to become more severe as the number of pixels increases and the power consumption decreases.

As described above, by specifying the column from which the pixels are to be read and reading out the data in two steps, reading is performed at a reading rate lower than the conventional reading rate as a result.
Conventionally, the horizontal drive frequency is read out the same between the preliminary imaging and the main imaging. Therefore, it can be said that the driving is performed at a driving frequency lower than the horizontal driving frequency at the time of the preliminary imaging. In imaging in which a higher number of pixels is required, switching between the high-speed readout of the signal charge of the preliminary image pickup and the signal charge readout with priority on the image quality of the main image is controlled and read, so that the transfer failure between pixels in the main image can be prevented. Disregarding, it is possible to provide a high quality image with good color reproducibility even in a low illuminance region.

The present embodiment is applied to a so-called honeycomb arrangement image pickup section. However, this signal readout method is low even if an image pickup section in which pixels are not shifted is similarly specified and read out slowly. Color mixing in the illuminance range can likewise be avoided.

Next, another embodiment of the digital camera 10 to which the solid-state imaging device of the present invention is applied will be described. This embodiment has an effect peculiar to the so-called pixel honeycomb arrangement of the pixel shift arrangement. Digital camera 10
Is almost the same as the previous embodiment. The difference in configuration is that no mechanical shutter is used. When reading out the signal charges from the light receiving element PD, even if the signal charges are read out at the same time and the signal charges are transferred in the vertical direction at the same time due to the feature of the pixel shift arrangement, the signal charges are supplied to the horizontal transfer register HR for each line.

At this time, the signal charges in the horizontal transfer register HR are transferred via the empty packets to the same positional relationship of the signal charges in the odd columns as in the above-described embodiment. When the next line is transferred to the horizontal transfer register HR, the signal charges are supplied in the same arrangement as that of the signal charges in the even columns. From this, it can be seen that the information of each line should be controlled to read out signal charges before the next line is supplied. As a result, the same transfer effect as in the above embodiment can be obtained. That is, when performing normal reading,
As in the above-described embodiment, when reading is performed over a plurality of fields, the horizontal drive frequency can be reduced, and there is a great effect in that all pixels can be read. Further, it is clear that color deterioration can be significantly prevented because image quality deterioration due to color mixing is handled as an empty packet and signal charges are read.

With the above configuration, the image pickup is performed by switching between the preliminary image pickup and the main image pickup, and the signal charges are read out by different signal charge readouts. In particular, in the signal charge readout in the main image pickup, only a specific column is read out. Is read, and an empty packet is formed between signal charges (that is, pixel data) at the time of horizontal transfer, so that transfer failure between one pixel is negligible. Even if there is a region, the image quality degradation that has occurred in this region can be significantly improved. In forming this empty packet, the horizontal transfer of the main imaging should be read out more slowly than in the preliminary imaging.

In a so-called honeycomb arrangement with pixel shift, two imagings are switched and controlled. In the main imaging, signal charges are read out from all pixels, sequentially transferred vertically, and supplied to a horizontal transfer register. Therefore, even if the horizontal transfer of the signal charges is performed until all the signal charges in the horizontal transfer register are read out until the next line is transferred to the horizontal transfer register, the high pixel of the device is further increased. Higher image quality can be achieved in response to higher power consumption and lower power consumption.

[0052]

As described above, according to the solid-state imaging device of the present invention, the control unit switches and controls the preliminary imaging and the main imaging, and supplies the signal generated by the signal supply unit to the imaging unit in accordance with each imaging. Then, the signal charges are read out by different signal charge readouts. In particular, in the signal charge readout in the main image pickup, only a specific column is read out, and an empty packet is formed between the signal charges at the time of the horizontal transfer, thereby forming one packet. By improving the transfer failure so as to be negligible, even if there is a low illuminance region when the imaging unit with a high pixel count is used, it is possible to greatly improve the image quality degradation that has occurred in this region until now. Also,
In a so-called honeycomb arrangement of pixel shifting, switching between two imagings is controlled, and in the main imaging, signal charges are read out from all pixels, sequentially vertically transferred, and supplied to a horizontal transfer register.
Since an empty packet is formed due to the pixel shift, horizontal transfer of the signal charge is performed by reading all the signal charges in the horizontal transfer register until the next line is transferred to the horizontal transfer register. It is also possible to achieve higher image quality in response to higher pixel and lower power of the device.

According to the signal reading method of the present invention,
Generate a signal to be supplied when capturing an image according to the switching control,
The signal charges are read out from either the odd-numbered column or the even-numbered column in accordance with the generated signal, and the transfer is performed in the vertical and horizontal directions. When the read-out column is an odd-numbered column, the even-numbered column is read. When the odd columns are read and similarly transferred in the vertical and horizontal directions to output the read signal charges, signal charges are read from only one of the columns, so that empty packets are generated between packets. Even when driving is performed in the same manner as in normal signal reading, transfer failure between one pixel is inconspicuous, so that image quality deterioration can be improved. When all pixels are read out in a so-called honeycomb arrangement, signal charges can be read out while maintaining the relation of formed empty packets by horizontally transferring and outputting all the lines one by one, and the image quality degradation is also improved. Can be.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a schematic configuration of a digital camera to which a solid-state imaging device according to the present invention is applied.

FIG. 2 is a schematic diagram showing an imaging plane of the digital camera in FIG. 1 as viewed from an incident light side and showing a positional relationship of signal charges of horizontal transfer in imaging.

FIG. 3 is a timing chart illustrating an operation in imaging in the digital camera of FIG. 1;

FIG. 4 is a schematic diagram showing a positional relationship between signal charges of horizontal transfer in imaging by a conventional digital camera.

FIG. 5 is a schematic diagram showing an imaging plane of an imaging unit in the digital camera of FIG. 1 as viewed from an incident light side and showing a positional relationship of signal charges when all pixels are read.

[Explanation of symbols]

 10 Digital camera 12 Optical lens 14 Operation unit 18 System control unit 22 Timing signal supply unit 30 Imaging unit 32 Preprocessing unit 34 A / D conversion unit 36 Signal processing unit 38 Compression / expansion unit 42 Monitor 22a Timing signal generation unit

Claims (9)

[Claims] 1. A light receiving element for photoelectric conversion is two-dimensionally arranged.
It was obtained by a preliminary photographing performed before the main imaging, in which all the signal charges were read out from the imaging means in which color separation means for performing color separation of the incident light was arranged on the side of the incident light from the object field for each light receiving element. The main imaging is performed based on the information, the signal charges are read out, the signal charges are sequentially transferred to a vertical transfer path and a horizontal transfer path formed so as to output the signal charges, and the obtained signals are subjected to digital signal processing and output. In the solid-state imaging device, when the signal reading from the light receiving element is performed in a normal manner, the number of the light receiving elements, the driving voltage for signal reading, and the signal charge in the horizontal transfer path. A control unit that controls switching of signal charge readout from the imaging unit between the preliminary imaging and the main imaging when a condition that a color mixture appears in the image due to the driving; and a control of the main imaging from the control unit. Signal supply means for supplying to the image pickup means a drive signal used for driving to read out the signal charges alternately in odd and even rows of the light receiving elements of the image pickup means in a plurality of times as indicated. A solid-state imaging device characterized by the above-mentioned. 2. The solid-state imaging device according to claim 1, wherein the signal supply unit sets the driving frequency of the horizontal driving signal to a lower driving frequency than at the time of the preliminary imaging. 3. A light-receiving element for photoelectric conversion is two-dimensionally displaced from an adjacent light-receiving element with respect to each other, and color-separated for each light-receiving element on an incident light side from an object field. The main imaging is performed based on information obtained by preliminary imaging performed before the main imaging in which all the signal charges are read out from the imaging unit in which the color separation unit is arranged, and the signal charges are read out, and the signal charges are output. In a solid-state imaging device that sequentially transfers a vertical transfer path and a horizontal transfer path formed on the solid-state imaging device, performs digital signal processing on the obtained signal, and outputs the processed signal, the signal is read from the light-receiving element in a normal method. When performed, the number of light receiving elements, the drive voltage for signal reading, and the condition that color mixing appears in the image due to the driving of the signal charges in the horizontal transfer path, the preliminary shooting and the main shooting Previous Control means for switching control of signal charge readout from the image pickup means; and signal charges for one line of the light receiving element of the image pickup means arrived at the horizontal transfer path in response to the instruction for the main image pickup from the control means. And a signal supply unit for supplying a drive signal for performing the signal charge readout driving for one line each time. 4. The solid-state imaging device according to claim 3, wherein the signal supply unit sets a driving frequency of the horizontal driving signal to a driving frequency lower than that in the preliminary imaging. 5. A plurality of prepared light receiving elements are arranged in a two-dimensional arrangement, and each of the plurality of light receiving elements is color-separated into each color on the side of incident light from the object scene corresponding to each of the plurality of light-receiving elements. The main imaging is performed to read out the signal charges based on information obtained by preliminary imaging performed before the main imaging that performs photoelectric conversion by each light receiving element and reads out all the signal charges, and reads the signal charges in the vertical direction. In a signal reading method for sequentially transferring and outputting in the horizontal direction, the method comprises the steps of: when the signal reading from the light receiving element is performed by a normal method, the number of the light receiving elements, the driving voltage for signal reading, and the horizontal direction. Switching control for switching the signal charge readout from the imaging unit to one of the imaging modes according to the preliminary imaging and the main imaging, when a condition that a color mixture appears in the image by driving the signal charges to the imager is satisfied. And generating a shift signal at a timing for reading signal charges from the two-dimensionally arranged odd-numbered or even-numbered light receiving elements in accordance with the control at the time of performing the main imaging in the switching control step. A signal generating step of generating a drive signal for transferring the signal charges in the vertical and horizontal directions; and supplying one of the odd-numbered or even-numbered signal charges photoelectrically converted by the light receiving element by supplying the shift signal generated in the signal generating step. A first signal shift step of reading only the columns of the first column, a first column image reading step of sequentially reading the signal charges read in the first signal shift step in the vertical and horizontal directions according to the supplied drive signal, One of signal charges in an even-numbered column or an odd-numbered column, which is photoelectrically converted by the light receiving element by supplying the shift signal generated in the signal generation step and is reverse to that of the first signal shift step A second signal shift step of reading only the column, and a second column image reading step of sequentially reading the signal charges read in the second signal shift step in the vertical and horizontal directions according to the supplied drive signal. A signal reading method characterized by the above-mentioned. 6. The method according to claim 5, wherein in the signal generating step, the horizontal driving frequency of the driving signal is set to a lower driving frequency than that in the preliminary imaging. 7. A plurality of two-dimensionally arranged light receiving elements are arranged in a positional relationship deviated from adjacent light receiving elements, and incident light from an object field corresponds to each of the plurality of light receiving elements. On the light side, color separation is performed on each color, and the color-separated light is photoelectrically converted by the respective light receiving elements to read out all signal charges. A signal readout method, sequentially transferring the signal charges in a vertical direction and a horizontal direction, and outputting the signal charge.In the signal readout method, when the signal readout from the light receiving element is performed in a normal manner, The signal from the imaging unit according to the preliminary imaging and the main imaging when the condition that a color mixture appears in the image by the driving of the number of light receiving elements, the driving voltage for signal reading, and the signal charge in the horizontal direction is satisfied. Charge reading A switching control step of switching control to either one of the imaging operations, and generating a shift signal at a timing for reading signal charges from the two-dimensionally arranged light receiving elements in accordance with the control at the time of performing the main imaging in the switching control step. And a signal generation step of generating a drive signal for transferring the read signal charges of the column in the vertical and horizontal directions; and supplying the shift signal generated in the signal generation step to convert the signal charges photoelectrically converted by the light receiving element. A signal shift step for reading, a vertical transfer step for transferring the signal charges read in the signal shift step in a vertical direction according to a supplied drive signal, and a horizontal direction in which the signal charges are orthogonal to the vertical direction by the vertical transfer step. A horizontal transfer step of reading out all one line supplied in response to the drive signal when transferring to the Signal reading wherein the reading out the signal charges by repeating the transfer process. 8. The method according to claim 7, wherein in the signal generating step, the horizontal drive frequency of the drive signal is set to a lower drive frequency than during the preliminary imaging. 9. The method according to claim 7, wherein the color separation is performed at a position in a square lattice corresponding to the light receiving element.
G, and place a color R or color at the center of the square lattice of the color G.
A signal readout method, wherein B is alternately arranged to form a complete checkered pattern.