JP2015201793A - Imaging device and imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging device which can add a pixel signal in arbitrary pixels whose reduction of an opening rate of a photodiode is suppressed and reading time can be shortened.SOLUTION: An imaging apparatus includes: a light receiving circuit where pixels having photoelectric conversion elements, FD capacities for holding electric charges from the photoelectric conversion elements and light receiving circuit connection sections connected to the FD capacities are two-dimensionally arranged; and an addition circuit having a plurality of first direction wiring, a plurality of second direction wiring which extend in a direction different from that of the first direction wiring and are connected to the first direction wiring at a cross section and an addition circuit connection section connected to the light receiving circuit connection section. Connection points with the second direction wiring adjacent on the first direction wiring are connected via a column connection switch. Connection points with the first direction wiring adjacent on the second direction wiring are connected via a row connection switch. The connection points of the first direction wiring and the second direction wiring are connected with the addition circuit connection section via an FD connection switch, and the FD capacities are coupled in arbitrary combination.

Description

  The present invention relates to an imaging element and an imaging apparatus having the imaging element.

  The image sensor (image sensor) can add and average the pixel outputs in the horizontal direction and the vertical direction by connecting the capacitance in the image sensor and the floating diffusion (FD) capacitance of the pixel at the time of reading. For example, Patent Document 1 discloses a means for integrating charges obtained by exposure with adjacent pixels for each color with respect to a Bayer array type image sensor.

  In addition, a technique relating to a semiconductor module including an image sensor chip and a signal processing chip has been proposed (see, for example, Patent Document 2). Patent Document 2 discloses a semiconductor module in which an image sensor chip and a signal processing chip are connected by micro bumps, and a pixel signal obtained by analog-digital conversion on the image sensor chip side is stored in a memory on the signal processing chip side via the micro bumps. Is described.

JP 2003-189316 A JP 2009-170944 A

  The image obtained by the Bayer array type image sensor generates interference fringes (moire) due to the relationship between the pixel pitch for each color and the high frequency component of the subject. The occurrence of moiré degrades the image quality. For this reason, in many imaging apparatuses using Bayer array type imaging devices, an optical low-pass filter is disposed in front of the imaging device so that high frequency components that cause moire do not enter the imaging device.

  There are also imaging devices such as compact digital cameras and digital single-lens reflex cameras that can shoot still images and moving images. In these products, the pixel pitch and low-pass filter characteristics are designed in accordance with a still image that requires resolution, and are often not optimized for thinning readout or addition readout during moving image shooting. It is known that pixel signal addition (pixel addition) is effective in suppressing moire during moving image shooting with such a product.

  In order to add pixel signals in the technique described in Patent Document 1, a light receiving pixel, pixel addition wiring, and a selection switch are required, and the pixel aperture ratio and pixel signal of the pixel are added by wiring and transistor installation. The degree of freedom in selecting pixels to be traded off. In the technique described in Patent Document 2, it is possible to add pixel signals while maintaining the aperture ratio of the photodiode by adding and averaging digital data stored in the memory by digital processing. However, since it is necessary to read out a pixel signal by performing charge-voltage conversion for each pixel used for addition, the readout time increases.

  An object of the present invention is to provide an imaging device capable of adding a pixel signal between arbitrary pixels that suppresses a decrease in the aperture ratio of a photodiode of a pixel and shortens a readout time.

  The image pickup device according to the present invention includes a plurality of the pixels, each pixel including a photoelectric conversion element, a capacitor that holds a charge from the photoelectric conversion element, and a first connection portion that is electrically connected to the capacitor. Is a two-dimensionally arranged light receiving circuit, an adder circuit having a second connecting portion corresponding to the first connecting portion of the light receiving circuit, and the first connecting portion and the adding circuit of the light receiving circuit. Connecting means for electrically connecting the second connection portion, and the adder circuit includes a plurality of first direction wirings extending in a first direction and a direction different from the first direction. A plurality of second direction wirings that extend and electrically connect to the first direction wiring at intersections with the first direction wiring; and the first of the connection points of the first direction wiring and the second direction wiring. A first connection switch disposed between adjacent connection points on the one-way wiring; A second connection switch disposed between adjacent connection points on the second direction wiring among the connection points of the first direction wiring and the second direction wiring; the first direction wiring; It has 3rd connection switch each arrange | positioned between the connection point of direction wiring, and the said 2nd connection part, It is characterized by the above-mentioned.

  According to the present invention, the capacitance can be coupled between arbitrary pixels by controlling the connection switch, and the pixel signal can be transmitted between arbitrary pixels without affecting the aperture ratio or readout time of the photoelectric conversion element. Addition can be performed.

It is a figure showing an example of composition of an image sensor concerning a 1st embodiment. It is a figure showing an example of composition of an image sensor concerning a 1st embodiment. It is a schematic diagram which shows arrangement | positioning of the switch of the image pick-up element which concerns on 1st Embodiment. It is a figure which shows the drive example of the non-addition read of the image pick-up element which concerns on 1st Embodiment. It is a figure for demonstrating the addition method of the pixel signal in 1st Embodiment. It is a figure which shows the example of addition of the pixel signal (G pixel) in 1st Embodiment. It is a figure which shows the example of addition of the pixel signal (R pixel) in 1st Embodiment. It is a figure which shows the example of addition of the pixel signal (B pixel) in 1st Embodiment. It is a schematic diagram which shows the structural example of the imaging device which concerns on this embodiment. It is a figure which shows the example of a drive of addition reading of the image pick-up element which concerns on 1st Embodiment. It is a figure for demonstrating the addition method of the pixel signal in 2nd Embodiment. It is a figure which shows the addition example of the pixel signal in 2nd Embodiment. It is a figure which shows the addition example of the pixel signal in 2nd Embodiment. It is a figure which shows the drive example of the addition reading in the moving image mode of the image pick-up element which concerns on 2nd Embodiment. It is a figure which shows the other structural example of the addition circuit in embodiment of this invention. It is a figure which shows the other structural example of the image pick-up element in embodiment of this invention. It is a figure which shows the structural example of the mobile telephone as embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
A first embodiment of the present invention will be described. 1 and 2 are diagrams illustrating a configuration example of the image sensor 100 according to the first embodiment. Here, a case where the image sensor 100 according to the first embodiment is realized by a back-illuminated image sensor (image sensor) is shown as an example.

  The image sensor 100 according to the present embodiment includes a light receiving circuit 200 and an adding circuit 300. As shown in FIG. 2, the light receiving circuit 200 and the adding circuit 300 are formed on one semiconductor chip, and the adding circuit 300 is formed on the back side of the light receiving circuit 200 (on the opposite side of the light receiving surface). The light receiving circuit connecting portion 208 included in the light receiving circuit 200 and the adding circuit connecting portion 306 included in the adding circuit 300 are electrically connected by connecting means 400 such as a through via. The light receiving circuit connection unit 208 and the addition circuit connection unit 306 are, for example, electrical contacts exposed to the outside for electrical connection to the outside of the circuit, such as metal pads. Note that an appropriate connection unit 400 may be selected according to the configuration of the image sensor 100 or the like.

  Further, as shown in FIG. 2, the image sensor 100 includes an on-chip microlens 101 that increases the light collection efficiency to the photoelectric conversion element (photodiode) in the light receiving circuit 200, and a color filter 102 for color separation. . In the color filter 102, for example, color filters of a plurality of colors of R (red), G (green), and B (blue) are arranged in a Bayer array. Specifically, in a Bayer array type image sensor, R, Gr, Gb, and B color filters are arranged with 2 × 2 pixels as a basic unit.

  The light receiving circuit 200 includes a plurality of pixels arranged two-dimensionally (row direction and column direction), a column circuit 211 provided for each column, a capacitor 212, a column selection switch 213, and a main amplifier 214. . Each pixel includes a photoelectric conversion element 201, a transfer switch 202, a floating diffusion (FD) capacitor 203, a reset switch 204, an amplification transistor 205, a row selection switch 206, and a light receiving circuit connection unit 208. Here, each switch is composed of, for example, a transistor and is controlled by a signal supplied to its gate (the same applies to each switch in the following description).

  Hereinafter, the pixels will be described by taking the pixels arranged in i rows and j columns as an example. The photoelectric conversion element 201 is a photodiode, and accumulates photoelectric charges corresponding to incident light by photoelectric conversion. The transfer switch 202 controls transfer of the photocharge accumulated in the photoelectric conversion element 201 to the FD capacitor 203. The transfer switch 202 is controlled to be conductive / non-conductive (ON / OFF) by a signal φTX (i). The FD capacitor 203 holds the photocharge from the photoelectric conversion element 201.

  The reset switch 204 controls resetting of charges accumulated in the photoelectric conversion element 201 and the FD capacitor 203. The reset switch 204 is controlled to be conductive / non-conductive (ON / OFF) by a signal φR (i). The amplification transistor 205 amplifies the charge held in the FD capacitor 203 and converts it into a voltage. The row selection switch 206 controls connection between the output of the amplification transistor 205 and the column output line. The row selection switch 206 is controlled to be conductive / non-conductive (ON / OFF) by a signal φSEL (i). The light receiving circuit connection unit 208 is connected to the FD capacitor 203.

  The column circuit 211 is commonly connected to a plurality of pixels in the corresponding column via a column output line, and amplifies and outputs a signal from the pixel. The capacitor 212 stores the output of the corresponding column circuit 211. The column selection switch 213 controls connection between the capacitor 212 and the main amplifier 214. The column selection switch 213 is controlled to be conductive / non-conductive (ON / OFF) by a signal φPH (j).

  Here, as shown in FIG. 1, in each pixel, a connection in which conduction / non-conduction (on / off) is controlled by a signal φADDSEL (i, j) between the FD capacitor 203 and the light receiving circuit connection unit 208. A capacity cut switch 207 may be arranged. In this way, the connection capacitance cut switch 207 is arranged, and when the pixel signal is not added, the capacitance component can be reduced by turning off the connection.

  The adder circuit 300 connects the pixels arranged in the first direction of the light receiving circuit 200, and the first direction wiring 301 extending in the first direction, and the pixels arranged in the second direction orthogonal to the first direction. And a second direction wiring 302 extending in the second direction. The first directional wiring 301 and the second directional wiring 302 are electrically connected at the intersection thereof, and form a mesh wiring (additional wiring).

  An adder circuit connection unit 306 corresponding to each pixel of the light receiving circuit 200 described above is located at an electrically equivalent position to each node (connection point) connecting the first direction wiring 301 and the second direction wiring 302. 305 is connected. In other words, the FD connection switch 305 is disposed between the connection point between the first direction wiring 301 and the second direction wiring 302 and the addition circuit connection unit 306. The FD connection switch 305 is controlled to be conductive / non-conductive (on / off) by a signal φFADD (i, j) for controlling addition of pixel signals.

  Further, in each of the first direction wiring 301 and the second direction wiring 302 in the mesh wiring, a connection switch for separating adjacent nodes on the same wiring is arranged. By controlling this connection switch, adjacent nodes on the same wiring can be electrically separated or connected.

  Here, in the present embodiment, between the connection points adjacent to each other on the first direction wiring among the connection points of the first direction wiring 301 and the second direction wiring 302 that are arranged with respect to the first direction wiring 301. The connection switch arranged in is called a column connection switch 303. Further, the connection arranged between the connection points adjacent to each other on the second direction wiring among the connection points between the first direction wiring 301 and the second direction wiring 302. The switch is called a row connection switch 304. The column connection switch 303 is controlled to be conductive / non-conductive (ON / OFF) by a signal φRADD (i, j) for controlling addition of pixel signals. The row connection switch 304 is controlled to be conductive / non-conductive (ON / OFF) by a signal φCADD (i, j) for controlling addition of pixel signals.

  FIG. 3 is a schematic diagram showing the arrangement of the connection capacity cut switch 207, the column connection switch 303, the row connection switch 304, and the FD connection switch 305 described above. In FIG. 3, some components are not shown for easy understanding of the drawing. Adjacent nodes in the same first direction wiring 301 can be connected via the column connection switch 303, and adjacent nodes in the same second direction wiring 302 can be connected via the row connection switch 304. It has become. Further, a node connecting the first direction wiring 301 and the second direction wiring 302 is connected to the corresponding pixel via the connection capacitance cut switch 207, the light receiving circuit connection unit 208, the addition circuit connection unit 306, and the FD connection switch 305. Connection to the FD capacitor 203 is possible.

  In the imaging device 100 according to the first embodiment described above, as shown in an example in FIG. 4, for example, non-addition readout of pixel signals can be performed by driving and controlling the signals φTX, φR, φSEL, φADDSEL, and φPH. . FIG. 4 is a diagram illustrating a driving example of non-addition reading of the image sensor 100 according to the first embodiment. In FIG. 4, it is assumed that each signal is at a high level when asserted and is at a low level when negated.

  First, the signal φR (φR (1) to φR (n)) and the signal φTX (φTX (1) to φTX (n) of all the pixel rows in the image pickup device 100 in a state where the image pickup device 100 with the shutter closed is shielded from light. ). Thereby, the electric charges of the photoelectric conversion element 201 and the FD capacitor 203 included in each pixel of the imaging element 100 are reset. After negating the signals φR and φTX of all the pixel rows, the shutter is opened, light from the subject is incident on the pixels of the image sensor 100, and photoelectric charges are accumulated in the photoelectric conversion element 201. After that, the shutter is closed and the image sensor 100 is shielded from light, whereby the accumulation of photocharges in the photoelectric conversion element 201 is stopped.

  After stopping the accumulation of photoelectric charge in the photoelectric conversion element 201, the signal φTX corresponding to each pixel row in the image sensor 100 is temporarily asserted, and then the signal φPH is changed for each column during the period in which the signal φSEL is asserted. Assert to. By repeating this for each pixel row, a signal corresponding to the photocharge accumulated in each pixel can be read from the image sensor 100. In non-addition reading, the signal φADDSEL is always negated, that is, the connection capacitor cut switch 207 is always in a non-conductive (off) state.

  Next, addition of pixel signals in the image sensor 100 according to the first embodiment will be described. FIG. 5 is a diagram for explaining a pixel signal adding method according to the first embodiment. Among the pixels on the image sensor 100, the light receiving circuit 200 and the adding circuit 300 corresponding to the vicinity of the coordinates (i, j). The structure of is schematically shown. In the present embodiment, pixel signal addition can be controlled by opening / closing control of the column connection switch 303, the row connection switch 304, the FD connection switch 305, and the connection capacitance cut switch 207.

  For example, a method for adding pixel signals of G pixels in the configuration shown in FIG. 5 will be described. In the following example, coordinates (i, j + 1), (i, j + 3), (i + 1, j), (i + 1, j + 2), (i + 2, j + 1), (i + 2, j + 3), (i + 3, j), (i + 3) , J + 2), an example of adding pixel signals of eight G pixels will be described.

  The connection capacitance cut switch 207 and the FD connection switch 305 of the pixels at the coordinates (i, j + 1), (i, j + 3), (i + 1, j), (i + 1, j + 2) are turned on, and the G pixels The FD capacitor 203 is connected to the addition wiring of the addition circuit 300. Further, the connection capacitance cut switch 207 and the FD connection switch 305 of the pixel at the coordinates (i + 2, j + 1), (i + 2, j + 3), (i + 3, j), (i + 3, j + 2) are turned on (on), and these G The FD capacitor 203 of the pixel is connected to the addition wiring of the addition circuit 300. In FIG. 5, at least one of the connection capacitance cut switch 207 and the FD connection switch 305 of the pixel at other coordinates is in a non-conductive (off) state.

  Further, the row connection switch 304 at coordinates (i, j + 1), (i + 1, j + 1), (i + 2, j + 1) is turned on. Also, coordinates (i, j + 2), (i, j + 3), (i + 1, j + 1), (i + 1, j + 2), (i + 2, j + 2), (i + 2, j + 3), (i + 3, j + 1), (i + 3, j + 2) The column connection switch 303 is turned on. In FIG. 5, the row connection switch 304 and the column connection switch 303 of other coordinates are in a non-conduction (off) state.

  In this way, by controlling the column connection switch 303, the row connection switch 304, the FD connection switch 305, and the connection capacitance cut switch 207, the FD capacitance of eight G pixels in the 4 × 4 pixels shown in FIG. Can be connected. The connection status at this time is shown in FIG.

At this time, the charge accumulated in the FD capacitor 203 of the pixel at the coordinates (p, q ₎ is expressed as Q _{(p, q),} and the total charge of the FD capacitor 203 of each pixel is
Q _total = Q _{(i, j + 1)} + Q _{(i, j + 3)} + Q _{(i + 1, j)} + Q _{(i + 1, j + 2)} + Q _{(i + 2, j + 1)} + Q _{(i + 2, j + 3)} + Q _{(i + 3, j)} + Q _{(i + 3, j + 2)}
If Q _total [C] is held, the charge is distributed to the FD capacitors 203 of the eight connected G pixels.

  Here, since it takes time for the charge distribution to be determined by the time constant determined by the impedance of the adder circuit 300, it is desirable to maintain a sufficient connection state. Actually, there are various manufacturing variations in the capacitance components present in each switch (transistor) and wiring. If these variations are negligible, the charge is the FD capacitance of each connected pixel. 203 evenly distributed.

When all the switches that are turned on (on) when the FD capacitor 203 is connected to the addition wiring after charge distribution are turned off (off), the accumulated charge of the pixel at the coordinate (i, j + 1) is ideal. Is Q _total / 8 [C]. However, the above-described manufacturing variations are ignored, and the loss of signal charges due to stray capacitance components other than the FD capacitor 203 is also ignored. Therefore, although it actually deviates from the ideal value, the deviation amount appears as a ratio of capacitance components, so it is desirable to compensate the gain for the loss.

  Next, a method for adding pixel signals of R pixels in the configuration shown in FIG. 5 will be described. In the following example, an example in which pixel signals of four R pixels at coordinates (i, j), (i, j + 2), (i + 2, j), and (i + 2, j + 2) are added will be described.

  The connection capacitance cut switch 207 and the FD connection switch 305 of the pixel at the coordinates (i, j), (i, j + 2), (i + 2, j), (i + 2, j + 2) are turned on, and the R pixels The FD capacitor 203 is connected to the addition wiring of the addition circuit 300. In FIG. 5, at least one of the connection capacitance cut switch 207 and the FD connection switch 305 of the pixel at other coordinates is in a non-conductive (off) state.

  Further, the row connection switch 304 at the coordinates (i, j + 1), (i + 1, j + 1) is turned on, and the coordinates (i, j + 1), (i, j + 2), (i + 2, j + 1), (i + 2, j + 2) are set. ) Column connection switch 303 is turned on. In FIG. 5, the row connection switch 304 and the column connection switch 303 of other coordinates are in a non-conduction (off) state.

  In this way, by controlling the column connection switch 303, the row connection switch 304, the FD connection switch 305, and the connection capacitance cut switch 207, the FD capacitances of the four R pixels in the 4 × 4 pixels shown in FIG. Can be connected. The connection status at this time is shown in FIG.

  Next, a method for adding the pixel signals of the B pixel in the configuration shown in FIG. 5 will be described. In the following example, an example will be described in which pixel signals of four B pixels at coordinates (i + 1, j + 1), (i + 1, j + 3), (i + 3, j + 1), and (i + 3, j + 3) are added.

  The connection capacity cut switch 207 and the FD connection switch 305 of the pixels at the coordinates (i + 1, j + 1), (i + 1, j + 3), (i + 3, j + 1), (i + 3, j + 3) are turned on, and the B pixels The FD capacitor 203 is connected to the addition wiring of the addition circuit 300. In FIG. 5, at least one of the connection capacitance cut switch 207 and the FD connection switch 305 of the pixel at other coordinates is in a non-conductive (off) state.

  Further, the row connection switch 304 at the coordinates (i + 1, j + 1), (i + 2, j + 1) is turned on, and the coordinates (i + 1, j + 2), (i + 1, j + 3), (i + 3, j + 2), (i + 3, j + 3) are set. ) Column connection switch 303 is turned on. In FIG. 5, the row connection switch 304 and the column connection switch 303 of other coordinates are in a non-conduction (off) state.

  In this way, by controlling the column connection switch 303, the row connection switch 304, the FD connection switch 305, and the connection capacitance cut switch 207, the FD capacitances of the four B pixels in the 4 × 4 pixels shown in FIG. Can be connected. The connection status at this time is shown in FIG.

  As described above, the pixel signals are added, and a signal corresponding to the charge amount of the FD capacitor 203 after charge distribution is read out. By doing in this way, compared with the case where the signal according to the charge amount of the FD capacitor 203 is thinned and read without charge distribution, the generation of moire can be suppressed because the high frequency components are averaged. The above-described addition average filter using pixels in the vicinity of the surroundings is known as a filter having a low-pass characteristic of spatial frequency, and an equivalent effect can be obtained by addition reading.

  Here, an example has been described in which pixel signals of the same color pixels are added to the R pixel, G pixel, and B pixel in the same 4 × 4 pixel region, but the combination of pixels to be added is not limited. What is necessary is just to set suitably the combination of the pixel which adds a pixel signal.

  Hereinafter, an image capturing apparatus 500 using the image sensor 100 according to the present embodiment will be described with reference to FIG. The imaging apparatus 500 is assumed to be a digital still camera. The imaging device 500 includes an imaging device 100 according to the present embodiment, a lens 503 for condensing light on the pixels of the imaging device 100, an optical low-pass filter 501 disposed between the imaging device 100 and the lens 503, and the imaging device. A shutter 502 for shielding 100 is provided. In addition, the imaging apparatus 500 includes a control unit 505 that controls each component included in the imaging apparatus 500 including them, a shooting button 504, a recording medium 506, and the like.

  The optical low-pass filter 501 is used for the purpose of suppressing interference fringes called moire generated by a component having a high spatial frequency in an image obtained by a Bayer array type image sensor. The pass band of the optical low-pass filter 501 is preferably one that passes a wavelength up to twice the pixel pitch so as to be optimal for the shortest pixel pitch in the image sensor 100. However, since the design philosophy varies depending on various conditions, the pass band characteristics of the optical low-pass filter 501 are not limited to those that allow wavelengths up to twice the pixel pitch to pass.

  The imaging apparatus 500 has a plurality of imaging modes that can be set, and the control unit 505 can switch the control method of the imaging apparatus 500 according to the set imaging mode. As a method for selecting the shooting mode, various methods such as a touch panel liquid crystal and a control button (not shown) can be applied.

  For example, in the high-resolution still image shooting mode, the control unit 505 controls each functional unit of the imaging apparatus 500 so that a high-resolution image can be acquired. As an example of control in the high-resolution still image shooting mode, when the control unit 505 detects a pressing signal of the shooting button 504, the control unit 505 drives the image sensor 100 as illustrated in FIG. An image output is obtained by reading the pixel signal of the pixel by non-addition. The acquired image can be displayed on a display device such as a liquid crystal display, or can be recorded on a recording medium.

  For example, in the reduced still image shooting mode, the control unit 505 controls each functional unit of the imaging apparatus 500 so that a reduced-size image can be acquired by adding and reading out pixel signals. An example of control in the reduced still image shooting mode will be described with reference to FIG. In FIG. 10, each signal is at a high level when asserted and is at a low level when negated.

  When the control unit 505 detects a pressing signal of the shooting button 504 in the reduced still image shooting mode, the control unit 505 asserts the signal φR and the signal φTX of all the pixel rows in the image sensor 100 during the reset period. Thereby, the electric charges of the photoelectric conversion element 201 and the FD capacitor 203 included in each pixel of the imaging element 100 are reset. At this time, the signal φADDSEL, the signal φRADD, the signal φCADD, and the signal φFADD for adding desired pixel signals are appropriately asserted to reset the signal including the adder circuit 300. The connection switches may be turned on as shown in FIGS. 6, 7, and 8 with different timings for each combination of pixels to which pixel signals are added.

  All signals asserted in the reset period are negated before the transition to the accumulation period in which the shutter 502 is opened. Photoelectric charges are accumulated in the photoelectric conversion element 201 of the light receiving circuit 200 after the shutter 502 is opened and light from the subject is incident on the imaging element 100 until the shutter 502 is closed and the imaging element 100 is shielded. The The charge transfer period starts after the shutter 502 is closed. In the charge transfer period, the signal φTX is asserted for all the pixel rows in the image sensor 100, and the charge in the photoelectric conversion element 201 is transferred to the FD capacitor 203. The assertion period of the signal φTX is ensured only for a time necessary for charge transfer to the FD capacitor 203.

  In the addition ON period, the signal φADDSEL, the signal φRADD, the signal φCADD, and the signal φFADD are reasserted similarly to the reset period. That is, the signal φADDSEL, the signal φRADD, the signal φADDSEL, the signal φRADD, and the connection switches are turned on as illustrated in FIGS. 6, 7, and 8 at different timings for each combination of pixels to which pixel signals are added. The signal φCADD and the signal φFADD are asserted. As a result, the FD capacitor 203 of the target pixel is connected via the adder circuit 300, and the pixel signals are added to perform charge distribution in the capacitor. After the addition ON period is continued until the charge distribution is completed, each signal is negated in the addition OFF period.

  In the read period, the signal φPH is asserted for each thinning column during the period in which the signal φSEL is asserted. By repeating this operation for each thinning row, an output signal obtained by averaging the photoelectric charges of the pixels can be read from the image sensor 100. For example, when 4 × 4 pixels described in FIGS. 6, 7, and 8 are used as unit patterns and the photoelectric charges are averaged in the pixels for each color, the signal φPH is asserted by thinning out 4 rows and 4 columns. do it.

  By reading out the pixel signal by thinning out in this way, the time required for reading out the pixel signal can be shortened. However, by performing decimation readout with 4 rows and 4 columns, the apparent pixel pitch widens. As a result, moiré occurs even with a component having a lower spatial frequency than the high-resolution still image described in the non-addition readout, but the occurrence of moiré can be suppressed due to the low-pass filter characteristics by addition readout as described above. In order to exhibit the low-pass filter characteristics by the addition of pixel signals without depending on the direction, the photocharges may be added and averaged in pixels adjacent in the vertical, horizontal, and diagonal directions. In addition, it is possible to use a farther pixel to make the passband lower. The pixel combination illustrated in the present embodiment is not limited to the combination of pixels, and which pixel's photocharge is to be averaged may be appropriately set according to the required filter characteristics.

  In the present embodiment, the addition circuit 300 is installed on the back side of the photoelectric conversion element (photodiode) 201 with respect to the light incident direction of the light receiving circuit 200. Thereby, the influence on the aperture ratio of the photoelectric conversion element (photodiode) 201 is small, and a combination of pixels that add and average photocharges can be arbitrarily selected by the connection switch. In addition, pixel signals can be added and averaged without increasing the pixel signal read time by thinning and reading out the pixel signals at the time of averaging the photocharges.

  In the above description, the non-addition control method at the time of high-resolution still image shooting and the pixel addition control method at the time of reduced still image shooting have been described. However, the present invention is not limited thereto, and can be appropriately used depending on the application. is there. In addition, as an embodiment of the image sensor 100, various processes as exemplified below can be considered as manufacturing processes of the light receiving circuit 200 and the adding circuit 300 and other examples of the light receiving circuit 200 and the adding circuit 300.

(Second Embodiment)
A second embodiment of the present invention will be described. Hereinafter, differences from the first embodiment described above will be described, and description of the same points as in the first embodiment will be omitted. Another example of the adding circuit 300 will be described with reference to FIG. FIG. 11 is a diagram for explaining a pixel output addition method according to the second embodiment. As illustrated in FIG. 11, the adder circuit 300 of the image sensor 100 according to the second embodiment includes the first direction wiring A 301 a and the first direction for each pixel array in the first direction in which the first direction wiring 301 extends. There are two types of first direction wirings of the direction wiring B301b.

  In the Bayer array type image sensor, R (red), Gr (green in the same row as the R pixel), Gb (green in the same row as the B pixel), and B (blue) color filters are basically 2 × 2 pixels. Arranged as a unit. In order to add pixel outputs of the same color pixel for each color, it is necessary to electrically connect the first direction wiring A301a, the first direction wiring B301b, and the second direction wiring 302 in accordance with the basic unit of the color filter. is there.

  Here, for description, the row connection switch arranged for the first direction wiring A301a is referred to as a row connection switch A303a, and the row connection switch arranged for the first direction wiring B301b is referred to as a row connection switch B303b. Further, among the second direction wirings 302, those belonging to the even-numbered columns are distinguished from the second direction wiring A302a, and those belonging to the odd-numbered columns are distinguished from the second direction wiring B302b. The column connection switch arranged for the second direction wiring A302a is called a column connection switch A304a, and the column connection switch arranged for the second direction wiring B302b is called a column connection switch B304b.

  The second direction wiring A302a is electrically connected to the first direction wiring A301a in the even-numbered row and the first direction wiring B301b in the odd numbered row at nodes (connection points) intersecting each other. The second direction wiring B302b is electrically connected to the odd-numbered first direction wiring A301a and the even-numbered first direction wiring B301b at nodes intersecting each other. With the connection as described above, the pixel output for each color can be added to the basic unit of the color filter of 2 × 2 pixels.

  For example, the pixel signal addition method in the second embodiment will be described with reference to FIG. 12 taking R pixels and G pixels as examples. In the description of FIG. 12, except for the switch shown to be in the conductive (on) state, the switch is in the non-conductive (off) state (note that at least one of the connection capacitance cut switch 207 and the FD connection switch 305 is at least one of them. Any non-conducting (off) state is acceptable.

  The connection capacitance cut switch 207 and the FD connection switch 305 of the pixels at the coordinates (i, j + 1), (i, j + 3), (i + 1, j), (i + 1, j + 2) are turned on, and the G pixels The FD capacitor 203 is connected to the addition wiring of the addition circuit 300. Further, the connection capacitance cut switch 207 and the FD connection switch 305 of the pixel at the coordinates (i + 2, j + 1), (i + 2, j + 3), (i + 3, j), (i + 3, j + 2) are turned on (on), and these G The FD capacitor 203 of the pixel is connected to the addition wiring of the addition circuit 300.

  Further, the row connection switch A303a of the first direction wiring A301a at the coordinates (i, j + 2), (i, j + 3), (i + 2, j + 2), and (i + 2, j + 3) is turned on. Further, the row connection switch B303b of the first direction wiring B301b at the coordinates (i + 1, j + 1), (i + 1, j + 2), (i + 3, j + 1), (i + 3, j + 2) is turned on (ON). Further, the column connection switch B304b of the second direction wiring B302b at the coordinates (i, j + 2), (i + 1, j + 2), (i + 2, j + 2) is turned on. In this way, by controlling each switch, pixel outputs of 8 G pixels in 4 × 4 pixels can be added.

  Further, the connection capacitance cut switch 207 and the FD connection switch 305 of the pixel at the coordinates (i, j), (i, j + 2), (i + 2, j), (i + 2, j + 2) are turned on (on), and these R The FD capacitor 203 of the pixel is connected to the addition wiring of the addition circuit 300. Further, the row connection switch 303b of the first direction wiring B301b at the coordinates (i, j + 1), (i, j + 2), (i + 2, j + 1), (i + 2, j + 2) is turned on. In addition, the column connection switch 304a of the second direction wiring A302a at the coordinates (i, j + 1) and (i + 1, j + 1) is turned on. In this way, by controlling each switch, the pixel outputs of four R pixels in 4 × 4 pixels can be added.

  Next, a pixel output addition method according to the second embodiment will be described with reference to FIG. 13 taking B pixels and G pixels as examples. In the description according to FIG. 13, except for the switch shown to be in the conductive (on) state, the non-conductive (off) state is set (note that at least one of the connection capacitance cut switch 207 and the FD connection switch 305 is at least one of them. Any non-conducting (off) state is acceptable. The addition of pixel outputs of 8 G pixels in 4 × 4 pixels is the same as that shown in FIG.

  The connection capacity cut switch 207 and the FD connection switch 305 of the pixels at the coordinates (i + 1, j + 1), (i + 1, j + 3), (i + 3, j + 1), (i + 3, j + 3) are turned on, and the B pixels The FD capacitor 203 is connected to the addition wiring of the addition circuit 300. Further, the row connection switch 303a of the first direction wiring A301a at the coordinates (i + 1, j + 2), (i + 1, j + 3), (i + 3, j + 2), (i + 3, j + 3) is turned on. Further, the column connection switch 304a of the second direction wiring A302a at the coordinates (i + 1, j + 1) and (i + 2, j + 1) is turned on (on). In this way, by controlling each switch, pixel outputs of four B pixels in 4 × 4 pixels can be added.

  In the present embodiment, it is assumed that pixel signals are read out for each row, and in particular, the row direction is defined as the first direction. In this case, since the addition operation for each row can be temporally separated, pixel output can be added even in moving image shooting in which a slit rolling operation is performed.

  In the above description, the case where the color filter is arranged with 2 × 2 pixels as a basic unit and the first direction is defined as the row direction has been described, but the present embodiment is not limited to this. For example, when m × n pixels are used as a basic unit and m × n types are added separately, m first direction wirings may be provided. At that time, the second-direction wirings are classified into m types, and the first-direction wirings may be electrically connected to the different first-direction wirings at nodes intersecting with each other every (n−1) rows. Further, it does not limit which one of the first direction wiring and the second direction wiring is formed for each pixel arrangement, and may be appropriately determined according to various design conditions. A plurality of first direction wirings may be provided for each pixel array in the first direction, and a plurality of second direction wirings may be provided for each pixel array in the second direction. Alternatively, a plurality of first direction wirings and second direction wirings may be provided.

  In general, in a moving image shooting mode of an imaging apparatus, a resolution and a frame rate that match a known moving image format such as HD (High Definition) and FHD (Full HD) are required. Usually, in a digital still camera, in order to read an image signal with a resolution lower than that of a still image in moving image shooting, thinning readout or addition readout is performed on the pixel output of the image sensor. Further, in some cases, an image output corresponding to each moving image format may be obtained by performing an image expansion / contraction process.

  As an example of control in the moving image shooting mode, the shutter is opened when the operation mode is changed to the moving image shooting mode, and shooting is started by pressing the shooting button. During moving image shooting, for example, each signal is controlled as in the driving example shown in FIG. 14, and the image sensor is driven for each frame to perform addition reading of pixel signals to obtain an image output. As shown in FIG. 14, the operation in each frame can be defined by the frame synchronization signal.

  In the case of a CMOS type image sensor, moving image shooting is performed by slit rolling driving that performs reset and accumulation for each row. Here, the read operation of the 4 × i, 4 × i + 1, 4 × i + 2, 4 × i + 3 row will be described. The reset period starts at the timing of the row readout synchronization signal, and the signals φR and φTX corresponding to the pixels in the 4 × i, 4 × i + 1, 4 × i + 2, 4 × i + 3 rows are simultaneously asserted, and the pixels in the target row are reset. I do.

  In the next addition ON period, for example, the signal φADDSEL, the signal φRADD, the signal φCADD, and the signal φFADD of the addition wiring as described with reference to FIGS. 12 and 13 are asserted, so that the FD capacitor 203 of the target pixel is electrically Connect to. At this time, the potential in the adder circuit 300 can be reset by asserting the signal φR.

  Then, when the signal φR and the signal φTX are negated, the accumulation period is started, and the photoelectric conversion element 201 of the light receiving circuit 200 starts accumulating photoelectric charges. In the addition OFF period, the signal φADDSEL, the signal φRADD, the signal φCADD, and the signal φFADD are negated. In the read period, the signal φPH is asserted for each thinning column during the period in which the signal φSEL is asserted. By repeating this operation for each thinning-out row, an output signal obtained by averaging the photoelectric charges of the pixels can be read from the image sensor. For example, when pixel outputs are added using the 4 × 4 pixels described in FIGS. 12 and 13 as a unit pattern, the signal φPH may be asserted by thinning out 4 rows and 4 columns.

  In the present embodiment, the same effects as those of the first embodiment described above can be obtained, and pixel outputs of arbitrary pixels can be added by the connection switch of the addition circuit even in slit rolling reading.

  The adder circuit 300 is not limited to the configuration described above, and may include an analog memory as a memory unit that holds charges in the adder circuit 300 as shown in FIG. FIG. 15 is a diagram illustrating another configuration example of the adder circuit 300. In the addition circuit 300 shown in FIG. 15, an analog memory 307 and a memory connection switch 308 are connected to each node of the mesh-like wiring (addition wiring). In this manner, by providing the analog memory 307 connected to the addition wiring via the memory connection switch 308, the charge (pixel signal) acquired at another time can be held. Pixel signals can be added between frames.

  In the above-described embodiments, the imaging device according to the present embodiment is realized by a back-illuminated imaging device in which the light receiving circuit 200 and the adding circuit 300 are formed on one semiconductor chip. However, the present invention is not limited thereto. Is not to be done. For example, as shown in FIG. 16, an image sensor may be configured by the light receiving circuit 200 and the adding circuit 300 formed on different semiconductor chips. That is, the light receiving circuit chip 250 in which the light receiving circuit 200 is formed and the adding circuit chip 350 in which the adding circuit 300 is formed may be electrically connected by the connecting means 410 such as a micro bump. In this manner, the FD capacitor 203 of the light receiving circuit 300 and the addition wiring of the addition circuit 300 may be connected.

(Other embodiments)
FIG. 17 is a block diagram illustrating a configuration example of a mobile phone 600 as an embodiment of the present invention. The mobile phone 600 according to the present embodiment has an electronic mail function, an Internet connection function, an image shooting and playback function, etc. in addition to a voice call function.

  In FIG. 17, a communication unit 601 communicates audio data and image data with other telephones by a communication method according to a communication carrier contracted by a user. The voice processing unit 602 converts voice data from the microphone 603 into a format suitable for transmission and sends it to the communication unit 601 during a voice call. Also, the voice processing unit 602 decodes voice data from the communication partner sent from the communication unit 601 and sends it to the speaker 604. The image capturing unit 605 includes the image sensor 100 according to the above-described embodiment, and captures an image of a subject or outputs image data. The image processing unit 606 processes the image data captured by the imaging unit 605 at the time of capturing an image, converts it into a format suitable for recording, and outputs it. In addition, when the recorded image is reproduced, the image processing unit 606 processes the reproduced image and sends it to the display unit 607. The display unit 607 includes a liquid crystal display panel of about several inches, and displays various screens in accordance with instructions from the control unit 609. The nonvolatile memory 608 stores data such as address book information, e-mail data, and image data captured by the imaging unit 605.

  The control unit 609 includes a CPU, a memory, and the like, and controls each unit of the telephone 600 according to a control program stored in a memory (not shown). The operation unit 610 includes a power button, number keys, and other various operation keys for a user to input data. A card IF (interface) 611 records and reproduces various data with respect to the memory card 612. The external IF 613 transmits data stored in the nonvolatile memory 608 and the memory card 612 to an external device, and receives data transmitted from the external device. The external IF (interface) 613 performs communication by a known communication method such as a wired communication method such as USB (Universal Serial Bus) or wireless communication.

  Next, a voice call function in the telephone 600 will be described. When making a call to the other party, the user operates the number key of the operation unit 610 to input the number of the other party, or the address book stored in the nonvolatile memory 608 is displayed on the display unit 607 to call the other party. Select and instruct to make a call. When the transmission is instructed, the control unit 609 transmits the communication unit 601 to the other party. When an incoming call is received, the communication unit 601 outputs the other party's voice data to the voice processing unit 602 and transmits the user's voice data to the other party.

  When transmitting an e-mail, the user uses the operation unit 610 to instruct mail creation. When mail creation is instructed, the control unit 609 displays a mail creation screen on the display unit 607. The user inputs a transmission destination address and text using the operation unit 610 and instructs transmission. When mail transmission is instructed, the control unit 609 sends address information and mail text data to the communication unit 601. The communication unit 601 converts mail data into a format suitable for communication and sends the data to a transmission destination. When the communication unit 601 receives an electronic mail, the communication unit 601 converts the received mail data into a format suitable for display and displays the data on the display unit 607.

  Next, the photographing function in the telephone 600 will be described. When the user operates the operation unit 610 to set the shooting mode and then instructs to shoot a still image or a moving image, the imaging unit 605 shoots the still image data or the moving image data and sends it to the image processing unit 606. The image processing unit 606 processes captured still image data and moving image data, and stores them in the nonvolatile memory 608. Also, the image processing unit 606 sends the captured still image data and moving image data to the card IF 611. The card IF 611 stores still image data and moving image data in the memory card 612.

  In addition, the telephone 600 can transmit a file including still image data and moving image data shot in this way as an attached file of an e-mail. Specifically, when an e-mail is transmitted, an image file stored in the nonvolatile memory 608 or the memory card 612 is selected, and transmission is instructed as an attached file.

  The phone 600 can also transmit a file including captured still image data and moving image data to an external device such as a PC (computer) or another telephone using the external IF 613. The user operates the operation unit 610 to select an image file stored in the nonvolatile memory 608 or the memory card 612 and instruct transmission. The control unit 609 controls the external IF 613 so that the selected image file is read from the nonvolatile memory 608 or the memory card 612 and transmitted to the external device.

  The above-described embodiments are merely examples of implementation in carrying out the present invention, and the technical scope of the present invention should not be construed as being limited thereto. That is, the present invention can be implemented in various forms without departing from the technical idea or the main features thereof.

DESCRIPTION OF SYMBOLS 100: Image pick-up element 200: Light receiving circuit 201: Photoelectric conversion element (photodiode) 203: Floating diffusion (FD) capacity | capacitance 207: Connection capacity cut switch 208: Light receiving circuit connection part 300: Adder circuit 301: 1st direction wiring 302: 1st Two-way wiring 303: Column connection switch 304: Row connection switch 305: FD connection switch 306: Adder circuit connection unit 307: Analog memory 308: Memory connection switch 400, 410: Connection means 500: Imaging device 503: Lens 505: Control unit

Claims (7)

Each pixel has a photoelectric conversion element, a capacitor for holding charges from the photoelectric conversion element, and a first connection portion electrically connected to the capacitor, and the plurality of pixels are arranged two-dimensionally. A light receiving circuit;
An adder circuit having a second connection corresponding to the first connection of the light receiving circuit;
Connection means for electrically connecting the first connection part of the light receiving circuit and the second connection part of the adding circuit;
The adder circuit
A plurality of first direction wirings extending in a first direction;
A plurality of second direction wirings extending in a direction different from the first direction and electrically connected to the first direction wiring at an intersection with the first direction wiring;
A first connection switch disposed between connection points adjacent to each other on the first direction wiring among connection points of the first direction wiring and the second direction wiring;
A second connection switch disposed between connection points adjacent to each other on the second direction wiring among connection points of the first direction wiring and the second direction wiring;
An image pickup device comprising: a third connection switch disposed between a connection point of the first direction wiring and the second direction wiring and the second connection portion.   The imaging device according to claim 1, wherein at least one of the first direction wiring and the second direction wiring includes a plurality of wirings for each pixel array in a direction in which the wiring extends.   The imaging device according to claim 1, wherein the light receiving circuit includes a connection capacitance cut switch disposed between the capacitor and the first connection portion.   The adder circuit includes a memory unit that is connected to a connection point between the first direction wiring and the second direction wiring via a fourth connection switch and holds electric charges at the connection point. Item 4. The imaging device according to any one of Items 1 to 3. The addition circuit is disposed on the back side of the photoelectric conversion element with respect to the light incident direction in the light receiving circuit,
The imaging device according to claim 1, wherein the light receiving circuit and the adding circuit are formed on a single semiconductor chip.   The image sensor according to claim 1, wherein the light receiving circuit and the adding circuit are formed on different semiconductor chips. The image sensor according to any one of claims 1 to 6,
A lens that collects light on the pixels of the image sensor;
An imaging apparatus comprising: a control unit that controls the imaging element and the lens.

Images