JP2008270832A - Solid-state imaging element and imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid-state imaging element in which a ratio of sensitivity of high-sensitivity pixels to that of low-sensitivity pixels can be changed. <P>SOLUTION: In this solid-state imaging element, first photoelectric conversion elements 350 and second photoelectric conversion elements 360 are arranged in a square lattice shape, respectively, and disposed in positions shifted from each other in a row direction X and a column direction Y by 1/2 of an array pitch. The detection charges of the photoelectric conversion elements 350, 360 are transferred to an output portion 340 through a plurality of vertical transfer parts 310 and horizontal transfer parts 320. A color filter is provided on the upper part of the photoelectric conversion elements 350, 360, and arranged in a Bayer array, respectively. The charge read area of the first photoelectric conversion element 350 and the charge read area of the second photoelectric conversion element 360 are formed at positions corresponding to vertical transfer electrodes having a different positional relationship, respectively. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a solid-state imaging device including a plurality of photoelectric conversion elements arranged on a semiconductor substrate surface in a row direction and a column direction orthogonal thereto, and an imaging apparatus including such a solid-state imaging device.

  Since a solid-state imaging device used for a digital camera detects charges corresponding to an image signal by a photoelectric conversion device, it is generally difficult to widen the dynamic range. Therefore, in order to obtain an image with a wide dynamic range, a relatively high-sensitivity photoelectric conversion element (hereinafter sometimes referred to as “high-sensitivity pixel”) and a relatively low-sensitivity photoelectric conversion element (hereinafter referred to as “high-sensitivity pixel”). It has been proposed to use a solid-state imaging device having “low-sensitivity pixels” (see Patent Documents 1 to 3).

  Photoelectric conversion signals having different sensitivities change the aperture area of the photoelectric conversion element (see, for example, Patent Document 3), or change the light transmittance of a filter provided above the photoelectric conversion element (for example, Patent Document 1, Patent Document). 2), and can be obtained by changing the shape of the microlens provided above the photoelectric conversion element (see, for example, Patent Document 3).

  However, the sensitivity ratio between the high-sensitivity pixel and the low-sensitivity pixel of the solid-state image sensor disclosed in Patent Documents 1-3 depends on the structure of the solid-state image sensor and cannot be changed. Therefore, it is difficult to shoot with an optimal dynamic range according to the scene.

JP 2000-69491 A JP 2000-316163 A JP 2001-8104 A

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a solid-state imaging device capable of changing the sensitivity ratio between a high-sensitivity pixel and a low-sensitivity pixel. It is another object of the present invention to provide an imaging apparatus capable of changing the dynamic range according to the shooting scene.

  A solid-state imaging device according to the present invention is a solid-state imaging device including a plurality of photoelectric conversion elements arranged on a semiconductor substrate surface in a row direction and a column direction orthogonal thereto, and is arranged above the photoelectric conversion elements. The color filter, a vertical transfer unit that transfers charges from the photoelectric conversion element in the column direction, a horizontal transfer unit that transfers charges from the vertical transfer unit in the row direction, and the horizontal transfer unit. The photoelectric conversion element includes a plurality of first photoelectric conversion elements arranged in a square lattice pattern in a row direction and a column direction perpendicular thereto, and a row. A plurality of second photoelectric conversion elements arranged in a square lattice pattern in a direction perpendicular to the direction, the first photoelectric conversion elements and the second photoelectric conversion elements at the same arrangement pitch, In addition, the row direction and the half of the arrangement pitch with each other. The color filter arranged above the first photoelectric conversion element and the color filter arranged above the second photoelectric conversion element are arranged at positions shifted in the column direction, respectively. The vertical transfer unit includes a plurality of vertical transfer channels formed on the semiconductor substrate corresponding to the plurality of photoelectric conversion elements arranged in a column direction, and each of the vertical transfer channels. A plurality of vertical transfer electrodes formed so as to intersect with each other in plan view, and a charge read region for reading out the charge of the photoelectric conversion element to the vertical transfer channel, the vertical transfer channel of the photoelectric conversion element It has a meandering shape extending in the column direction as a whole, and a plurality of the vertical transfer electrodes are provided corresponding to the photoelectric conversion elements, and between the electric conversion elements As a whole, it has a meandering shape extending in the row direction, and the charge readout region corresponding to the first photoelectric conversion element and the charge readout region corresponding to the second photoelectric conversion element have different positional relationships. Are provided at positions corresponding to the vertical transfer electrodes.

  According to the present invention, for a solid-state imaging device in which the photoelectric conversion element is a so-called honeycomb arrangement, the charge readout timing from the first photoelectric conversion element to the vertical transfer channel and the charge from the second photoelectric conversion element to the vertical transfer channel The read timing can be controlled independently. Therefore, by controlling the driving pulse of the solid-state imaging device, at least one of the charge accumulation time in the first photoelectric conversion element and the charge accumulation time in the second photoelectric conversion element can be changed. The sensitivity ratio between the sensitivity image signal and the low sensitivity image signal can be changed.

  The solid-state imaging device of the present invention includes one in which the first photoelectric conversion element has a relatively high photoelectric conversion sensitivity and the second photoelectric conversion element has a relatively low photoelectric conversion sensitivity.

  In the solid-state imaging device of the present invention, the readout pulse instructing readout of charges in the electrical charge readout region changes in the readout pulse applied to the first photoelectric conversion element and the second photoelectric conversion element according to the imaging scene. Including an exposure time control pulse.

  The solid-state imaging device according to the present invention is such that the exposure time control pulse sweeps out charges accumulated in the photoelectric conversion device before the exposure time control pulse to the outside through the vertical transfer channel. including. According to the present invention, since the charge accumulation start time of at least one of the first photoelectric conversion element and the second photoelectric conversion element can be controlled, the sensitivity ratio between the two image signals can be controlled.

  In the solid-state imaging device of the present invention, the exposure time control pulse is used for reading out the charge accumulated in the photoelectric conversion element before the exposure time control pulse as the signal charge to the vertical transfer channel. including. According to the present invention, since the charge accumulation end time of at least one of the first photoelectric conversion element and the second photoelectric conversion element can be controlled, the sensitivity ratio between the two image signals can be controlled.

  The solid-state imaging device of the present invention includes one in which the first photoelectric conversion device and the second photoelectric conversion device which are adjacent to each other in the same positional relationship have the same relative spectral sensitivity characteristics.

  The imaging device of the present invention is an imaging device including the above-described solid-state imaging element, and an exposure time control unit that changes an exposure time of the first photoelectric conversion element and an exposure time of the second photoelectric conversion element; and the solid state A signal processing unit configured to perform signal processing based on an imaging signal output from the imaging device, wherein the signal processing performed by the signal processing unit includes a high-sensitivity image signal based on a signal from the first photoelectric conversion device and the second photoelectric signal; The exposure time control unit discriminates the type of the shooting scene, and determines the type of the first photoelectric according to the determined type of the scene, including a synthesis process for generating a synthesized signal with the low-sensitivity imaging signal based on the signal from the conversion element. By changing the charge readout timing from the conversion element and the second photoelectric conversion element to the vertical transfer channel, the exposure time of the first photoelectric conversion element and the exposure time of the second photoelectric conversion element are changed. Is intended to further.

  According to the present invention, since the sensitivity ratio between the high-sensitivity image signal and the low-sensitivity image signal can be changed according to the shooting scene, it is possible to obtain an image with a wide wide dynamic range.

  The image pickup apparatus of the present invention includes one in which the exposure time control unit obtains a luminance distribution of a photographic scene and determines the type of the photographic scene based on the obtained luminance distribution.

  As is clear from the above description, according to the present invention, it is possible to provide a solid-state imaging device capable of changing the sensitivity ratio between a high-sensitivity pixel and a low-sensitivity pixel. In addition, it is possible to provide an imaging apparatus capable of changing the dynamic range according to the shooting scene.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 shows a schematic configuration of the solid-state imaging device according to the first embodiment of the present invention. 1 includes a plurality of photoelectric conversion elements arranged in a square lattice pattern in a row direction (X direction in FIG. 1) and a column direction (Y direction in FIG. 1) perpendicular to the row direction on the surface of a semiconductor substrate. 150 and 160 (in FIG. 1, only a part of the reference numerals are attached. Hereinafter, the pixel may be described as “pixel”), the light intensity is converted into a charge signal and accumulated. A vertical transfer unit 110 that transfers charges from the elements 150 and 160 in the column direction (in FIG. 1, only a part thereof is labeled), and a horizontal transfer unit that transfers charges from the vertical transfer unit 110 in the row direction. A transfer unit 120 and an output unit 140 that outputs a signal 141 corresponding to the charges transferred by the horizontal transfer unit 120 are included.

  The first photoelectric conversion element 150 accumulates signal charges for obtaining a relatively high sensitivity image signal, and is arranged in a checkered pattern. The second photoelectric conversion element 160 accumulates signal charges for obtaining a relatively low-sensitivity image signal, and is arranged in a checkered pattern at a position where the first photoelectric conversion element 150 is not arranged. . The first photoelectric conversion element 150 has a higher photoelectric conversion sensitivity than the second photoelectric conversion element 160. In order to change the photoelectric conversion sensitivity, the area of the light receiving surface of the photoelectric conversion element may be changed, or the condensing area may be changed by a microlens provided above the photoelectric conversion element. Since these methods are all well-known, description is abbreviate | omitted. In the example of FIG. 1, a difference is provided in photoelectric conversion sensitivity between the first photoelectric conversion element 150 and the second photoelectric conversion element 160 in consideration of the area efficiency of the element. Also good. If the photoelectric conversion sensitivity is the same, the design and manufacture are simplified.

  1 has a color filter (not shown) above the first photoelectric conversion element 150 and the second photoelectric conversion element 160 in order to detect a color image signal. The arrangement method of the color filters is arbitrary, but the first photoelectric conversion element 150 and the second photoelectric conversion element 160 that are adjacent to each other in the same positional relationship have the same color. In FIG. 1, three color filters of R (red), G (green), and B (blue) are provided, and charges corresponding to red light, green light, and blue light are accumulated.

  The vertical transfer unit 110 transfers charges from the first photoelectric conversion element 150 and the second photoelectric conversion element 160 in the column direction, and includes a plurality of vertical transfer channels (not shown) formed on the semiconductor substrate. A first charge readout region 151 and a second charge readout for reading out the charges of the plurality of vertical transfer electrodes 111 to 113, the first photoelectric conversion element 150 and the second photoelectric conversion element 160 formed in the upper layer of the transfer channel to the vertical transfer channel. A region 161 (shown schematically by an arrow in FIG. 1) is included.

  The vertical transfer channel is a linear region having a constant width extending in the column direction to the side of the first photoelectric conversion element 150 and the second photoelectric conversion element 160, and is formed by vertical transfer electrodes 111 to 113 formed thereon. The area where charges are accumulated and transferred is divided. Three vertical transfer electrodes 111 to 113 are provided corresponding to each of the first photoelectric conversion element 150 and the second photoelectric conversion element 160 (in FIG. 1, only those corresponding to one row of photoelectric conversion elements are matched. The vertical transfer electrodes having the same positional relationship between the photoelectric conversion elements in the same row are only connected to the electrode wirings 121 to 123 (in FIG. 1, corresponding to the photoelectric conversion elements for one row). Are electrically connected. The vertical transfer electrodes 111 to 113 are made of polycrystalline silicon or the like.

  Three-phase vertical transfer pulses are applied to the vertical transfer electrodes 111 to 113 via the terminals 131 to 133, and charges in the vertical transfer channel are transferred in the column direction. The vertical transfer pulse is also applied to the transfer electrodes 114 to 116 between the vertical transfer unit 110 and the horizontal transfer unit 120, and for each period of the vertical transfer pulse, the first photoelectric conversion element 150 and the second photoelectric transfer for one row. The charges detected by the conversion element 160 are sent to the horizontal transfer unit 120.

  The first charge readout region 151 is provided at a position corresponding to the vertical transfer electrode 111, and charge readout from the first photoelectric conversion element 150 to the vertical transfer channel is performed by a first-phase vertical transfer pulse applied to the terminal 131. This is done by superimposing the readout pulse. The second charge readout region 161 is provided at a position corresponding to the vertical transfer electrode 112, and charge readout from the second photoelectric conversion element 160 to the vertical transfer channel is performed by the second phase vertical transfer applied to the terminal 132. This is done by superimposing a readout pulse on the pulse. Therefore, the charge read timing from the first photoelectric conversion element 150 to the vertical transfer channel and the charge read timing from the second photoelectric conversion element 160 to the vertical transfer channel can be controlled independently.

  The horizontal transfer unit 120 transfers charges from the vertical transfer unit 110 in the row direction, and includes a horizontal transfer channel and a horizontal transfer electrode (both not shown). Two-phase horizontal transfer pulses are applied to the horizontal transfer electrodes via the terminals 134 and 135, and the signal charges of the photoelectric conversion elements 150 and 160 for one row transferred from the vertical transfer unit 110 are output to the output unit 140. Forwarded to The output unit 140 has a floating diffusion amplifier configuration, and a voltage signal 141 corresponding to the transferred charge is output.

  1 has an overflow drain region (not shown) that sweeps out the electric charges accumulated in the photoelectric conversion elements 150 and 160. When a sweep pulse is applied to the overflow drain electrode terminal 136, the solid-state imaging device 100 in FIG. The charges accumulated in the photoelectric conversion elements 150 and 160 are swept out to the semiconductor substrate. A pulse is applied to overflow drain electrode terminal 136 at a predetermined timing in response to the operation of the release button, and the charge accumulation time of photoelectric conversion elements 150 and 160 is controlled.

  Although not shown in FIG. 1, channel stops are formed between the vertical transfer channels. In FIG. 1, the vertical transfer electrodes 111 to 113 are shown larger than the first photoelectric conversion element 150 and the second photoelectric conversion element 160, but are actually smaller.

  FIG. 2 is a diagram showing a schematic configuration of the digital camera according to the embodiment of the present invention. The digital camera in FIG. 2 includes an imaging unit 1, an analog signal processing unit 2, an A / D conversion unit 3, a driving unit 4, a strobe 5, a digital signal processing unit 6, a compression / expansion processing unit 7, a display unit 8, and system control. A unit 9, an internal memory 10, a media interface 11, a recording medium 12, and an operation unit 13. The digital signal processing unit 6, compression / decompression processing unit 7, display unit 8, system control unit 9, internal memory 10, and media interface 11 are connected to a system bus 20.

  The imaging unit 1 includes an optical system such as a photographic lens 1a and the solid-state imaging device 100 shown in FIG. 1, and shoots a subject, and outputs an analog imaging signal. An imaging signal obtained by the imaging unit 1 is sent to the analog signal processing unit 2, subjected to predetermined analog signal processing, converted into a digital signal by the A / D conversion unit 3, and then digitally converted as so-called RAW image data. It is sent to the signal processing unit 6. The RAW image data is digital image data that has been digitized in the form of the imaging signal from the imaging unit 1.

  When shooting, the imaging unit 1 is controlled via the drive unit 4. The solid-state imaging device 100 outputs an analog voltage signal generated in response to incident light and based on the accumulated signal charge. The solid-state imaging device 100 has a timing generator (not shown) included in the drive unit 4 at a predetermined timing when a release switch (not shown) is turned on by operating a release button (not shown) that is a part of the operation unit 13. 2 is driven by a drive signal from TG). The drive unit 4 outputs a predetermined drive signal based on the control of the system control unit 9, and also outputs a drive signal for the mechanical shutter 1b, a drive signal for the analog signal processing unit 2 and the A / D conversion unit 3. .

  The strobe 5 operates when the brightness of the subject is equal to or lower than a predetermined value, and is controlled by the system control unit 9.

  The digital signal processing unit 6 performs digital signal processing on the digital image data from the A / D conversion unit 3 according to the operation mode set by the operation unit 13. The processing performed by the digital signal processing unit 6 includes black level correction processing (OB processing), linear matrix correction processing (correction that removes the color mixture component caused by the photoelectric conversion characteristics of the imaging element with respect to the primary color signal from the imaging unit. And a white balance adjustment process (gain adjustment), a gamma correction process, an image composition process, a synchronization process, a Y / C conversion process, and the like. The image composition processing of the digital signal processing unit 6 will be described later.

  The digital signal processing unit 6 is configured by a DSP, for example. The compression / decompression processing unit 7 performs compression processing on the Y / C data obtained by the digital signal processing unit 6 and also performs decompression processing on the compressed image data obtained from the recording medium 12. .

  The display unit 8 includes, for example, an LCD display device, and displays an image based on image data that has been shot and has undergone digital signal processing. An image is also displayed based on the image data obtained by decompressing the compressed image data recorded on the recording medium. It is also possible to display a through image at the time of shooting, various states of the digital camera, information on operations, and the like.

  The internal memory 10 is, for example, a DRAM and is used as a work memory for the digital signal processing unit 6 and the system processing unit 9, as well as a buffer memory that temporarily stores captured image data recorded on the recording medium 12, and a display It is also used as a buffer memory for display image data to the unit 8. The media interface 11 inputs / outputs data to / from a recording medium 12 such as a memory card.

  The system control unit 9 controls the entire digital camera including shooting operations. Specifically, the system control unit 9 is mainly configured by a processor that operates according to a predetermined program. The processing performed by the system control unit 9 includes scene discrimination processing for discriminating the type of shooting scene, and charge readout timing from the first photoelectric conversion element or the second photoelectric conversion element to the vertical transfer channel according to the determined scene type. The exposure time control process which changes and changes the exposure time of a 1st photoelectric conversion element or the exposure time of a 2nd photoelectric conversion element is contained.

  The operation unit 13 performs various operations when using the digital camera, and performs an operation mode (shooting mode, playback mode, etc.) of the digital camera, a shooting method at the time of shooting, shooting conditions, settings, and the like. The operation unit 13 may be provided with an operation member corresponding to each function, but may share the operation member in conjunction with the display of the display unit 8. The operation unit 13 also includes a release button for starting a shooting operation.

Next, driving of the solid-state imaging device 100 will be described. FIG. 3 shows a timing chart for explaining the driving of the solid-state imaging device 100. In FIG. 3, the vertical synchronization signal VD, the overflow drain pulse (hereinafter referred to as “OFD pulse”) _φOFD applied to the terminal 136, the drive pulse φ _V1 applied to the terminal 131, and the terminal 132 are applied. The driving pulse φ _V2 , the driving pulse φ _V3 applied to the terminal 133, the output signal V _OUT , and the open / close state of the mechanical shutter are shown. In this example, the photoelectric conversion sensitivities of the first photoelectric conversion element 150 and the second photoelectric conversion element 160 are formed at 4: 1, and the high sensitivity image signal and the low sensitivity image signal are obtained by the scene determination process of the system control unit 9. In this case, the sensitivity ratio is set to 16: 1 so as to acquire an image signal.

When a release button (not shown) of the operation unit 13 is pressed, an exposure value is set and autofocus control is performed. Then, at time t1, an OFD pulse φ _OFD is applied to the terminal 136, and the first photoelectric conversion element 150 is applied. In addition, the charges accumulated in the second photoelectric conversion element 160 are swept out. Then, charge accumulation according to the incident light is started. During this time, the first to third phase vertical transfer pulses are periodically applied to the terminals 131 to 133, but at time t2, the second phase vertical transfer pulse is transferred to the vertical transfer channel from the second photoelectric conversion element 160. A readout pulse 161b for instructing charge readout is superimposed. The readout pulse 161b is an exposure time control pulse for changing the exposure time of the second photoelectric conversion element 160 with respect to the exposure time of the first photoelectric conversion element 150, and is accumulated in the second photoelectric conversion element 160 at time t2. The charge is swept out again. Therefore, the second photoelectric conversion element 160 starts to accumulate charges again from time t2.

  In this example, if the exposure times of the first photoelectric conversion element 150 and the second photoelectric conversion element 160 are the same, the sensitivity ratio of the high-sensitivity image signal and the low-sensitivity image signal becomes 4: 1. In order to set the sensitivity ratio of the low-sensitivity image signal to 16: 1, the exposure time of the second photoelectric conversion element is set to ¼ of the exposure time of the first photoelectric conversion element 150. That is, since the exposure time of the first photoelectric conversion element 150 is the time from time t1 to time t3 when the mechanical shutter is closed, the time from time t2 to time t3 is the time from time t2 to time t3. It is determined to be 1/4 of the time until.

  When the mechanical shutter is closed at time t3, the charge accumulation of the first photoelectric conversion element 150 and the second photoelectric conversion element 160 is stopped. At this time, 16: 1 signal charges are accumulated in the first photoelectric conversion element 150 and the second photoelectric conversion element 160. However, this value is a case where the saturation accumulation amount of the first photoelectric conversion element 150 and the second photoelectric conversion element 160 is not exceeded, and actually, the case where the saturation accumulation charge amount is exceeded for the first photoelectric conversion element 150. Therefore, the actual charge accumulation amount is different.

  After that, at time t4, in order to sweep out the charge remaining in the vertical transfer channel, application of a vertical transfer pulse having a frequency sufficiently higher than that in the normal operation is started. When the high-speed vertical transfer pulse is applied until time t5, there is almost no charge in the vertical transfer channel.

  After stopping the application of the high-speed vertical transfer pulse, at time t6, the first-phase read pulse 151a is superimposed on the first-phase vertical transfer pulse, and the second-phase read pulse 161a is superimposed on the second-phase vertical transfer pulse. To do. Note that the first phase readout pulse 151a and the second phase readout pulse 161a are superimposed on the vertical transfer pulse having the same cycle, and are not strictly the same time.

When the first phase readout pulse 151a and the second phase readout pulse 161a are applied, the signal charges accumulated in the first photoelectric conversion element 150 and the second photoelectric conversion element 160 are read out to the vertical transfer channel. When the signal charge for one row is transferred to the horizontal transfer unit 120 by the vertical transfer pulse of the normal frequency, it is transferred horizontally by the horizontal transfer pulse (not shown) and sent to the output unit 140. The output signal V _OUT is sent to the analog signal processing unit 2. Such transfer is repeated until all the signal charges read out to the vertical transfer channel are sent to the output unit 140.

The output signal V _OUT is an unnecessary signal until the time t7 when the signal charge read out to the vertical transfer channel at time t6 is output, so the signal charge read out to the vertical transfer channel at time t6. The horizontal transfer pulse until the signal is transferred to the horizontal transfer unit may be stopped and swept out from the drain unit provided in the horizontal transfer unit 120.

  Next, the image composition processing of the digital signal processing unit 6 will be described. The digital signal processing unit 6 separately performs OB processing and linear matrix correction processing on high-sensitivity image data based on the accumulated charge of the first photoelectric conversion element 150 and low-sensitivity image data on the accumulated charge of the second photoelectric conversion element 160. After the white balance adjustment process and the gamma correction process, the image data of the first photoelectric conversion element 150 and the second photoelectric conversion element 160 that have the same relative spectral sensitivity characteristics and are adjacent in the same positional relationship are synthesized. . An example of the synthesis method is shown in equation (1).

  Sc = αSH + (1−α) SL (1)

  Here, Sc is a composite signal, and SH and SL are high-sensitivity image data and low-sensitivity image data. In the case of a color image, it is obtained for each of red, green, and blue. α is a coefficient for determining the synthesis ratio, and is set to 0 <α <1. The α value is determined according to the shooting scene.

  In the above description, the photoelectric conversion sensitivity of the first photoelectric conversion element 150 and the second photoelectric conversion element 160 is assumed to be 4: 1. However, the photoelectric conversion sensitivity is not limited to 4: 1 and is the same photoelectric conversion. Sensitivity may be used. Regardless of the photoelectric conversion sensitivity ratio, the sensitivity ratio between the high-sensitivity image data and the low-sensitivity image data can be controlled by controlling the timing at which the readout pulse 161b that is the exposure time control pulse is superimposed.

  Further, the exposure time of the first photoelectric conversion element 150 may be changed by superimposing the exposure time control pulse on the first-phase vertical transfer pulse. In this case, it is preferable that the ratio of the photoelectric conversion sensitivities of the first photoelectric conversion element 150 and the second photoelectric conversion element 160 is sufficiently large (it is necessary to be equal to or greater than the maximum sensitivity ratio of the required image signal). .

The driving of the solid-state imaging device 100 when the exposure time control pulse is superimposed on the first-phase vertical transfer pulse will be described. FIG. 4 shows a timing chart for explaining the driving of the solid-state imaging device 100 in that case. 4, as in FIG. 3, the vertical synchronization signal VD, the OFD pulse φ _OFD applied to the terminal 136, the drive pulse φ _V1 applied to the terminal 131, the drive pulse φ _V2 applied to the terminal 132, and the terminal 133. The driving pulse φ _V3 applied to the output signal V _OUT , the open / close state of the mechanical shutter are shown.

  The times t11 and t13 to t17 in FIG. 4 are the same timings as the times t1 and t3 to t7 in FIG. Time t12 is the timing at which the readout pulse 151b is superimposed on the first-phase vertical transfer pulse, and the charge accumulated in the first photoelectric conversion element 150 is swept out again at time t12. Therefore, the first photoelectric conversion element 150 starts to accumulate charges again from time t12. In this case, the readout pulse 151 b is an exposure time control pulse for changing the exposure time of the first photoelectric conversion element 150 with respect to the exposure time of the second photoelectric conversion element 160.

  When the readout pulse 151b is not superimposed, an image signal having a sensitivity ratio that matches the photoelectric conversion sensitivity of the first photoelectric conversion element 150 and the second photoelectric conversion element 160 is obtained, but the readout pulse 151b is superimposed and the superposition time is set. As the delay is made, the sensitivity ratio of the obtained image signal can be reduced.

In driving the solid-state imaging device 100 as shown in FIGS. 3 and 4, it is necessary to drive the mechanical shutter, but control when the mechanical shutter is not driven or when the mechanical shutter is not driven as in moving image shooting or the like. Will be described. FIG. 5 shows a timing chart for explaining the driving of the solid-state imaging device 100 in that case. In FIG. 4, the vertical synchronization signal VD, the OFD pulse φ _OFD applied to the terminal 136, the drive pulse φ _V1 applied to the terminal 131, the drive pulse φ _V2 applied to the terminal 132, and the drive applied to the terminal 133. A pulse φ _V3 and an output signal V _OUT are shown.

In this example, an OFD pulse φ _OFD is applied in synchronization with the vertical synchronization signal, the charges of the first photoelectric conversion element 150 and the second photoelectric conversion element 160 are swept out, and charge accumulation corresponding to the amount of incident light is started. .

The readout pulses 152b and 152c of the first photoelectric conversion element 150 are superimposed on the first-phase vertical transfer pulse in synchronization with the vertical synchronization signal, and when the OFD pulse φ _{OFD is} applied (time t23, t26, etc.) and the readout pulse 152b, During the period when 152c is superimposed (t22, t25, etc.), the charge accumulated in the first photoelectric conversion element 150 is read out to the vertical transfer channel. The signals are sequentially transferred to the horizontal transfer unit 120 and output from the output unit 140 during the period until the next readout pulses 152b and 152c are superimposed.

The readout pulses 162b and 162c of the second photoelectric conversion element 160 are superimposed on the vertical transfer pulse of the second phase at a set time (in this example, times t21 and t24) between the vertical synchronization signals VD, and the OFD pulse φ _The charge accumulated in the second photoelectric conversion element 160 is read out to the vertical transfer channel during the period of time when the _{OFD is} applied (time t23, t26, etc.) and when the readout pulses 162b and 162c are superimposed. The signals are sequentially transferred to the horizontal transfer unit 120 and output from the output unit 140 during the period until the next readout pulses 162b and 162c are superimposed. The read pulses 162b and 162c control the exposure time of the second photoelectric conversion element 160.

In the example of FIG. 5, an image signal corresponding to the electric charge accumulated in the first photoelectric conversion element 150 until the readout pulse 152b is superimposed (time t22) is output during a period from time t22b to time t25b, and the OFD pulse φ _The output signal _VOUT corresponding to the charge accumulated in the second photoelectric conversion element 160 from the time of applying the _OFD (time t23) to the time of superimposing the readout pulse 152b (time t24) is from time t24c to time t27c (not shown). (Time corresponding to the read pulse 162d not to be output).

  As apparent from FIG. 5, the accumulated charge of the second photoelectric conversion element 160 is output earlier than the accumulated charge of the first photoelectric conversion element 150 by a certain time, so that high-sensitivity image data based on each charge and low The combination with the sensitivity image data is performed on data that are shifted by a predetermined time. The time that is output earlier is the time from the time when the readout pulses 162b and 162c are superimposed to the time when the readout pulses 152b and 152c are superimposed. Since this time is determined according to the sensitivity ratio between the high-sensitivity image data and the low-sensitivity image data determined according to the scene described later, the digital signal processing unit 6 receives data to be shifted from the system control unit 9. Is obtained and the composition process is performed.

  Next, the charge read timing from the first photoelectric conversion element 150 or the second photoelectric conversion element 160 to the vertical transfer channel is changed according to the scene determination process performed by the system control unit 9 and the type of the determined scene, An exposure time control process for changing the exposure time of the photoelectric conversion element 150 or the exposure time of the second photoelectric conversion element 160 will be described.

  The scene determination process is performed using the luminance distribution of the captured image data used for exposure control and autofocus control during shooting. In order to know the luminance distribution, imaging data based on the signal charge from the second photoelectric conversion element 160 is used. Then, a histogram is generated by the system control unit 9 and the digital signal processing unit 3. The imaging data based on the signal charge from the second photoelectric conversion element 160 is used to acquire a wide range of luminance values.

  Next, from the generated histogram, a peak on the low luminance side and a peak on the high luminance side are discriminated, and respective peak luminance values are acquired. Shooting scenes that require shooting with a wide dynamic range often have luminance distributions that have peaks on the low and high luminance sides, such as scenes that include indoor subjects and subjects outside the window. The sensitivity ratio between the high-sensitivity image data and the low-sensitivity image data is set so that the luminance range on the high luminance side in such a scene becomes the imaging range.

  Specifically, assuming that the peak value on the low luminance side is the center of the luminance range that can be imaged by the first photoelectric conversion element 150, the peak value on the high luminance side is the center of the imageable range of the second photoelectric conversion element 160. The required imaging range of the second photoelectric conversion element 160 is obtained so that Then, the sensitivity ratio between the high-sensitivity image data and the low-sensitivity image data is determined based on the ratio between the luminance range that is twice the peak value on the low-luminance side and the required imaging range of the second photoelectric conversion element 160.

  If the generated histogram does not have a clear peak, the default sensitivity ratio is set to 4: 1, for example. In this case, as assumed in the description of FIG. 3, if the photoelectric conversion sensitivities of the first photoelectric conversion element 150 and the second photoelectric conversion element 160 are 4: 1, it is not necessary to change the exposure time.

  Note that the sensitivity ratio between the high-sensitivity image data and the low-sensitivity image data does not need to be set finely, and it is sufficient if the sensitivity ratio can be switched to about 4: 1, 8: 1, 16: 1, and 32:14.

(Second Embodiment)
As described above, as the solid-state imaging device 100, the first photoelectric conversion device 150 and the second photoelectric conversion device 160 that are driven by three-phase vertical transfer pulses and can read all pixels are used. An interlace type that reads out the stored charge of the conversion element in two frames may be used.

  FIG. 6 shows a schematic configuration of a solid-state imaging device according to the second embodiment of the present invention. The solid-state imaging device 200 of FIG. 6 is in the form of a square lattice in the row direction (X direction of FIG. 6) and the column direction (Y direction of FIG. 6) orthogonal to the surface of the semiconductor substrate, like the solid-state imaging device 100 of FIG. The vertical transfer unit 210 converts the light intensity into a charge signal and stores it by a plurality of photoelectric conversion elements 250 and 260 disposed in the vertical direction, and transfers the charge from the photoelectric conversion elements in the column direction, and the vertical transfer unit A horizontal transfer unit 220 that transfers charges from 210 in the row direction and an output unit 240 that outputs a signal 241 corresponding to the charges transferred by the horizontal transfer unit 220 are included.

  The first photoelectric conversion element 250 and the second photoelectric conversion element 260 accumulate signal charges for obtaining a relatively high sensitivity image signal and signal charges for obtaining a relatively high sensitivity image signal. It is arranged in a checkered pattern. The specific configuration is the same as that of the first photoelectric conversion element 150 and the second photoelectric conversion element 160 of the solid-state imaging device 100 in FIG.

  The vertical transfer unit 210 transfers charges from the first photoelectric conversion element 250 and the second photoelectric conversion element 260 in the column direction. The vertical transfer unit 210 includes a plurality of vertical transfer channels (not shown) formed on the semiconductor substrate. A first charge readout region 251 and a second charge readout for reading out the charges of the plurality of vertical transfer electrodes 211 to 214, the first photoelectric conversion element 250 and the second photoelectric conversion element 260 formed in the upper layer of the transfer channel to the vertical transfer channel. A region 261 (represented schematically by an arrow in FIG. 6) is included.

  The vertical transfer unit 210 has substantially the same configuration as the vertical transfer unit 110 of the solid-state imaging device 100 in FIG. 1, but the number and arrangement of the vertical transfer electrodes 211 to 214 are different. Four vertical transfer electrodes 211 to 214 are provided corresponding to the first photoelectric conversion element 250 and the second photoelectric conversion element 260 for two rows. Four-phase vertical transfer pulses are applied to the vertical transfer electrodes 211 to 214 via the terminals 231 to 234, and charges in the vertical transfer channel are transferred in the column direction. The vertical transfer pulse is also applied to the transfer electrodes 215 to 218 between the vertical transfer unit 210 and the horizontal transfer unit 220, and for each period of the vertical transfer pulse, the first photoelectric conversion element 250 and the second photoelectric sensor for one row. The charges detected by the conversion element 260 are sent to the horizontal transfer unit 220.

  The first charge readout region 251 is provided at a position corresponding to the vertical transfer electrodes 211 and 213, and charge readout from the first photoelectric conversion element 250 to the vertical transfer channel is performed by first-phase vertical transfer applied to the terminal 231. The readout pulse is superimposed on the pulse and the third-phase vertical transfer pulse applied to the terminal 233. The second charge readout region 261 is provided at a position corresponding to the vertical transfer electrodes 212 and 214, and charge readout from the second photoelectric conversion element 260 to the vertical transfer channel is performed in the second phase applied to the terminal 232. This is performed by superimposing the readout pulse on the vertical transfer pulse and the fourth-phase vertical transfer pulse applied to the terminal 234. Therefore, the charge read timing from the first photoelectric conversion element 250 to the vertical transfer channel and the charge read timing from the second photoelectric conversion element 260 to the vertical transfer channel can be controlled independently.

  The horizontal transfer unit 220 has the same configuration as the horizontal transfer unit 120 of the solid-state imaging device 100 of FIG. 1, and a horizontal transfer electrode (not shown) to which a two-phase horizontal transfer pulse is applied via terminals 235 and 236. ). The output unit 240 has a floating diffusion amplifier configuration, and has an overflow drain region (not shown). When a sweep pulse is applied to the overflow drain electrode terminal 237, the photoelectric conversion elements 250 and 260 are Similar to the solid-state imaging device 100 of FIG. 1, the accumulated charge is swept out to the semiconductor substrate.

  The solid-state imaging device 200 of FIG. 6 is accumulated by being divided into first photoelectric conversion elements 250 and second photoelectric conversion elements 260 in odd rows and first photoelectric conversion elements 250 and second photoelectric conversion elements 260 in even rows. Read the signal charge. When reading the signal charges of the first photoelectric conversion element 250 and the second photoelectric conversion element 260 in the odd-numbered rows, the read pulse is superimposed on the first-phase vertical transfer pulse and the second-phase vertical transfer pulse. Then, after the read signal charges are output via the horizontal transfer unit 220, the third-phase vertical transfer pulse and the read signal charges of the first photoelectric conversion elements 250 and the second photoelectric conversion elements 260 in the even-numbered rows are read out. The readout pulse is superimposed on the fourth phase vertical transfer pulse. Similarly, the read signal charges are output via the horizontal transfer unit 220.

However, in order to control the exposure time of the first photoelectric conversion element 250 or the second photoelectric conversion element 260, the readout pulse superimposed during the OFD pulse φ _OFD mechanical shutter closing is the first photoelectric conversion element of all rows. 250 and the second photoelectric conversion element 260 are superimposed at the same timing (precisely, with respect to the transfer pulse having the same cycle). In addition, the solid-state imaging device 200 in FIG. 6 can also read the signal charges accumulated in the first photoelectric conversion element 250 and the second photoelectric conversion element 260. When reading the signal charge of the first photoelectric conversion element 250, when the read pulse is superimposed on the first-phase vertical transfer pulse and the third-phase vertical transfer pulse and reading the signal charge of the second photoelectric conversion element 260, The readout pulse may be superimposed on the second-phase vertical transfer pulse and the fourth-phase vertical transfer pulse.

(Third embodiment)
The solid-state imaging device in which the photoelectric conversion elements are arranged in a square lattice shape has been described above, but is not limited to a square lattice arrangement. FIG. 7 shows a schematic configuration of a solid-state imaging device according to the third embodiment of the present invention. A solid-state image sensor 300 in FIG. 7 is a so-called honeycomb-structured solid-state image sensor.

  7 includes a plurality of photoelectric conversion elements 350 and 360 (see FIG. 7) arranged on the surface of a semiconductor substrate in a row direction (X direction in FIG. 7) and a column direction (Y direction in FIG. 7) perpendicular thereto. 7, the light intensity is converted into a charge signal and accumulated, and the photoelectric conversion elements 350 and 360 are used. A vertical transfer unit 310 (in FIG. 7, only a part is given a reference numeral), a horizontal transfer unit 320 that transfers charges from the vertical transfer unit 310 in the row direction, An output unit 340 that outputs a signal 341 corresponding to the charge transferred by the horizontal transfer unit 320 is included.

  The first photoelectric conversion element 350 and the second photoelectric conversion element 360 are respectively arranged in a square lattice pattern in the row direction and the column direction orthogonal thereto. The arrangement pitch of the first photoelectric conversion element 350 and the arrangement pitch of the second photoelectric conversion element 360 are the same, and the first photoelectric conversion element 350 and the second photoelectric conversion element 360 are ½ of the arrangement pitch. They are disposed at positions shifted only in the row direction and the column direction. In order to change the photoelectric conversion sensitivity of the first photoelectric conversion element 350 and the second photoelectric conversion element 360, the area of the light receiving surface of the photoelectric conversion element may be changed, or the light is collected by a microlens provided above the photoelectric conversion element. The light area may be changed. Since these methods are all well-known, description is abbreviate | omitted.

  7 has a color filter (not shown) above the first photoelectric conversion element 350 and the second photoelectric conversion element 360 in order to detect a color image signal. The arrangement method of the color filters is arbitrary, but the first photoelectric conversion element 350 and the second photoelectric conversion element 360 that are adjacent to each other in the same positional relationship have the same color. In FIG. 7, the color filter has a Bayer arrangement for each of the first photoelectric conversion element 350 and the second photoelectric conversion element 360, and the corresponding photoelectric conversion elements respectively correspond to red light, green light, and blue light. Detect charge.

  The vertical transfer unit 310 transfers charges from the first photoelectric conversion element 350 and the second photoelectric conversion element 360 in the column direction, and a plurality of vertical transfer channels (not shown) formed on the semiconductor substrate, A charge readout region for reading out the charges of the plurality of vertical transfer electrodes 311 to 314, the first photoelectric conversion element 350, and the second photoelectric conversion element 360, which are formed so as to intersect each of the vertical transfer channels in plan view, to the vertical transfer channel 351 and 361 (represented schematically by arrows in FIG. 7).

  The vertical transfer channel has a meandering shape extending in the column direction between the first photoelectric conversion element 350 and the second photoelectric conversion element 360 as a whole, and is formed by vertical transfer electrodes 311 to 314 formed thereabove. A region where charges are accumulated and transferred is divided. Four vertical transfer electrodes 311 to 314 are provided corresponding to each of the first photoelectric conversion element 350 and the second photoelectric conversion element 360 (in the figure, only those corresponding to one row of high-sensitivity pixels are denoted by reference numerals). In other words, a meandering shape extending in the row direction between the first photoelectric conversion element 350 and the second photoelectric conversion element 360 as a whole is exhibited. In FIG. 7, the shape of the region sections where charges are stored and transferred is described as being connected, but in reality, they are formed of conductors having substantially the same width.

  Four-phase vertical transfer pulses are applied to the vertical transfer electrodes 311 to 314 via the terminals 331 to 334, and charges in the vertical transfer channel are transferred in the column direction. The vertical transfer pulse is also applied to the transfer electrodes 315 and 316 between the vertical transfer unit 310 and the horizontal transfer unit 320, and for each period of the vertical transfer pulse, the first photoelectric conversion element 350 and the second photoelectric transfer for one row. The charges detected by the conversion element 360 are sent to the horizontal transfer unit 320.

  The first charge readout region 351 is provided at a position corresponding to the vertical transfer electrode 311, and charge readout from the first photoelectric conversion element 350 to the vertical transfer channel is performed by a first-phase vertical transfer pulse applied to the terminal 331. This is done by superimposing the readout pulse. The second charge readout region 361 is provided at a position corresponding to the vertical transfer electrode 313, and charge readout from the second photoelectric conversion element 160 to the vertical transfer channel is performed by a third-phase vertical transfer applied to the terminal 333. This is done by superimposing a readout pulse on the pulse. Therefore, the charge read timing from the first photoelectric conversion element 350 to the vertical transfer channel and the charge read timing from the second photoelectric conversion element 360 to the vertical transfer channel can be controlled independently.

  The horizontal transfer unit 320 transfers charges from the vertical transfer unit 310 in the row direction, and includes a horizontal transfer channel and a horizontal transfer electrode (both not shown). Two-phase horizontal transfer pulses are applied to the horizontal transfer electrodes via the terminals 335 and 336, and the signal charges of the first photoelectric conversion elements 350 for one row transferred from the vertical transfer unit 310 and for one row are transferred. The signal charge of the second photoelectric conversion element 360 is transferred to the output unit 340. The output unit 340 has a floating diffusion amplifier configuration, and outputs a voltage signal 341 corresponding to the transferred charge.

  7 has an overflow drain region (not shown) that sweeps out charges accumulated in the photoelectric conversion elements 350 and 360. When a sweep pulse is applied to the overflow drain electrode terminal 337, the solid-state imaging device 300 in FIG. The charges accumulated in the photoelectric conversion elements 350 and 360 are swept out to the semiconductor substrate. A pulse is applied to overflow drain electrode terminal 337 at a predetermined timing in response to the operation of the release button, and the charge accumulation time of photoelectric conversion elements 350 and 360 is controlled.

  Although not shown in FIG. 7, channel stops are formed between the vertical transfer channels. In FIG. 7, the vertical transfer electrodes 331 to 334 are shown larger than the first photoelectric conversion element 350 and the second photoelectric conversion element 360, but are actually smaller.

  The solid-state imaging device 300 of FIG. 7 can perform the same operation as the operation of the solid-state imaging device 100 described with reference to FIGS. For example, when the operation as shown in FIG. 3 is performed, the third-phase vertical applied to the terminal 333 is assumed to correspond to the readout pulse 161b superimposed on the second-phase vertical transfer pulse for exposure time control. The readout pulse is superimposed on the transfer pulse. Further, as a signal corresponding to the signal charge read pulse 151 a of the first photoelectric conversion element 150, the read pulse is superimposed on the first-phase vertical transfer pulse applied to the terminal 331, and the signal charge of the second photoelectric conversion element 160 is The readout pulse is superimposed on the third-phase vertical transfer pulse applied to the terminal 333 as the one corresponding to the readout pulse 161a.

The figure which shows schematic structure of the solid-state image sensor of the 1st Embodiment of this invention. The figure which shows schematic structure of the digital camera of embodiment of this invention The figure which shows the timing chart for demonstrating an example of the drive of the solid-state image sensor of this invention The figure which shows the timing chart for demonstrating the other example of the drive of the solid-state image sensor of this invention The figure which shows the timing chart for demonstrating the further another example of the drive of the solid-state image sensor of this invention The figure which shows schematic structure of the solid-state image sensor of the 2nd Embodiment of this invention. The figure which shows schematic structure of the solid-state image sensor of the 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Imaging part 1a ... Shooting lens 1b ... Mechanical shutter 2 ... Analog signal processing part 3 ... A / D conversion part 4 ... Drive part 5 ... Strobe 6 ... Digital signal processing unit 7: Compression / decompression processing unit 8 ... Display unit 9 ... System control unit 10 ... Internal memory 11 ... Media interface 12 ... Recording medium 13 ... Operation unit 20 ... System bus 100, 200, 300 ... Solid-state image sensor 110, 210, 310 ... Vertical transfer unit 120, 220, 320 ... Horizontal transfer unit 140, 240, 340 ... Output unit 150 , 250, 350... First photoelectric conversion elements 151, 251, 351... First charge readout region 160, 260, 360... Second photoelectric conversion elements 161, 261, 361. 2 charge read-out region 111～113,211～214,311～314 ... vertical transfer electrodes 136,237,337 ... overflow drain electrode terminal

Claims (8)

A solid-state imaging device including a plurality of photoelectric conversion elements arranged on a semiconductor substrate surface in a row direction and a column direction orthogonal thereto,
A color filter arranged above the photoelectric conversion element;
A vertical transfer unit for transferring charges from the photoelectric conversion elements in the column direction;
A horizontal transfer unit that transfers charges from the vertical transfer unit in the row direction;
An output unit that outputs a signal corresponding to the charge transferred by the horizontal transfer unit,
The photoelectric conversion elements are arranged in a square lattice pattern in a row direction and a column direction orthogonal to the first photoelectric conversion elements disposed in a square lattice pattern in the row direction and the column direction orthogonal to the first photoelectric conversion element. A plurality of second photoelectric conversion elements,
The first photoelectric conversion element and the second photoelectric conversion element are arranged at the same arrangement pitch and at positions shifted by a half of the arrangement pitch in the row direction and the column direction.
The color filter arranged above the first photoelectric conversion element and the color filter arranged above the second photoelectric conversion element are each Bayer array,
The vertical transfer unit intersects each of the plurality of vertical transfer channels formed in the semiconductor substrate corresponding to the plurality of photoelectric conversion elements arranged in the column direction and the vertical transfer channels in plan view. A plurality of vertical transfer electrodes formed as described above, and a charge readout region for reading out the charge of the photoelectric conversion element to the vertical transfer channel,
The vertical transfer channel has a meandering shape extending in the column direction between the photoelectric conversion elements as a whole,
A plurality of the vertical transfer electrodes are provided corresponding to the photoelectric conversion elements, respectively, and exhibit a meandering shape extending in the row direction between the electric conversion elements as a whole,
The charge readout region corresponding to the first photoelectric conversion element and the charge readout region corresponding to the second photoelectric conversion element are respectively provided at positions corresponding to the vertical transfer electrodes having different positional relationships. . The solid-state imaging device according to claim 1,
The first photoelectric conversion element has a relatively high photoelectric conversion sensitivity, and the second photoelectric conversion element has a relatively low photoelectric conversion sensitivity. The solid-state imaging device according to claim 1 or 2,
The readout pulse for instructing the readout of charges in the charge readout region includes an exposure time control pulse in which the readout pulse applied to the first photoelectric conversion element and the second photoelectric conversion element changes according to the imaging scene. Image sensor. A solid-state imaging device according to claim 3,
The exposure time control pulse is a solid-state imaging device for sweeping out charges accumulated in the photoelectric conversion device before the exposure time control pulse to the outside through the vertical transfer channel. The solid-state imaging device according to claim 3,
The exposure time control pulse is a solid-state imaging device for reading out the charge accumulated in the photoelectric conversion device before the exposure time control pulse as the signal charge to the vertical transfer channel. The solid-state imaging device according to any one of claims 1 to 5,
The first photoelectric conversion element and the second photoelectric conversion element that are adjacent to each other in the same positional relationship have the same relative spectral sensitivity characteristics. An imaging apparatus comprising the solid-state imaging device according to any one of claims 1 to 6,
An exposure time control unit for changing an exposure time of the first photoelectric conversion element and an exposure time of the second photoelectric conversion element;
A signal processing unit that performs signal processing based on an imaging signal output from the solid-state imaging device;
The signal processing performed by the signal processing unit is a combining process for generating a combined signal of a high-sensitivity image signal based on the signal from the first photoelectric conversion element and a low-sensitivity imaging signal based on the signal from the second photoelectric conversion element. The exposure time control unit discriminates the type of the shooting scene and changes the charge readout timing from the first photoelectric conversion element and the second photoelectric conversion element to the vertical transfer channel according to the determined scene type. By doing so, the imaging apparatus which changes the exposure time of the said 1st photoelectric conversion element, and the exposure time of the said 2nd photoelectric conversion element. The imaging apparatus according to claim 7,
The said exposure time control part calculates | requires the luminance distribution of a photography scene, and discriminate | determines the classification of a photography scene based on the calculated | required luminance distribution.

Images