JP6166562B2 - IMAGING ELEMENT, ITS DRIVING METHOD, AND IMAGING DEVICE - Google Patents

Description

  The present invention relates to an imaging element, a driving method thereof, and an imaging apparatus.

  Conventionally, in an imaging apparatus using a CMOS image sensor, a driving method (hereinafter referred to as “pixel addition driving”) is known in which signals of a plurality of pixels are added to increase a frame rate and sensitivity (hereinafter referred to as “pixel addition driving”) (FIG. 17). ).

  When performing pixel addition in a CMOS sensor, as shown in FIG. 18, a configuration is known in which a plurality of pixels share a floating diffusion (FD) portion that accumulates charges when performing charge-voltage conversion ( For example, see Patent Documents 1 and 2). Specifically, after the charges generated in the photodiodes in the plurality of pixels 181 are transferred to the FD unit 182 at the same time, an operation for charge-voltage conversion is performed. By driving in this way, charges generated in the photodiodes of the plurality of pixels 181 are added by the FD unit 182, so that sensitivity can be increased according to the number of added pixels.

JP 2009-49740 A JP 2012-23389 A

  In the above-described operation, assuming a Bayer arrangement, a single FD unit shares a plurality of same-color pixels having the same number of pixels of each color, such as a FD unit being shared by four consecutive pixels in the vertical direction. It is effective for the configuration. However, as shown in FIG. 18, in the case of a configuration in which the FD portion is shared by four pixels of two horizontal pixels and two vertical pixels, the FD is composed of one R pixel, one B pixel, and two G pixels. The part will be shared. Therefore, the charge addition operation as in the above configuration cannot be performed.

  The present invention has been made in view of the above problems, and improves sensitivity in darkness by improving sensitivity even in a configuration in which a floating diffusion portion is shared by a plurality of pixels having different numbers of pixels for each color. With the goal.

In order to achieve the above object, an image pickup device of the present invention includes a plurality of photoelectric conversion units covered with a plurality of color filters, a floating diffusion unit to which charges generated in the plurality of photoelectric conversion units are transferred, A plurality of unit pixels each including an amplifying unit that converts a charge of the floating diffusion portion into a voltage and outputs the voltage and a plurality of transfer units that transfer the charges generated in the plurality of photoelectric conversion units to the floating diffusion portion A first reading method in which the charges generated in the plurality of photoelectric conversion units and the charges generated in the plurality of photoelectric conversion units are respectively read and transferred to the floating diffusion unit; The charges of a plurality of photoelectric conversion units covered by a filter of a predetermined color are And a second read method of reading from by adding the charge is transferred to diffusion portion, a plurality of read methods have a driving means for driving said pixel portion, said drive means, said first Reading by the reading method and reading by the second reading method are alternately performed for each row of the unit pixels .

  According to the present invention, even in a configuration in which a floating diffusion portion is shared by a plurality of pixels having different numbers of pixels for each color, it is possible to improve the sensitivity in darkness and improve the followability in darkness.

1 is a block diagram showing a functional configuration of an imaging apparatus according to an embodiment of the present invention. FIG. 3 is a schematic diagram illustrating a schematic configuration of an image sensor included in the imaging device. FIG. 3 is a circuit diagram illustrating a configuration of a part of a pixel portion of an image sensor. 6 is a timing chart showing the operation of the vertical scanning circuit unit when acquiring a normal image according to the first embodiment. FIG. 3 is a schematic diagram showing a part of the circuit configuration of the output system of the image sensor according to the first embodiment. 6 is a timing chart showing the operation of the output system when acquiring a normal image according to the first embodiment. The schematic diagram showing the pixel arrangement | sequence of the normal image and pixel addition image which concern on 1st Embodiment. 6 is a timing chart showing the operation of the vertical scanning circuit unit when acquiring a charge addition image according to the first embodiment. 6 is a timing chart showing the operation of the output system when acquiring a charge addition image according to the first embodiment. FIG. 3 is a schematic diagram illustrating a pixel arrangement of a charge addition image according to the first embodiment. 9 is a timing chart showing the operation of the vertical scanning circuit when acquiring a charge addition image according to the second embodiment. The schematic diagram showing the pixel arrangement | sequence of the charge addition image which concerns on 2nd Embodiment. 9 is a timing chart showing the operation of the vertical scanning circuit unit according to the third embodiment. FIG. 9 is a schematic diagram illustrating a part of a circuit configuration of an output system of an image sensor according to a third embodiment. The timing chart which showed the operation | movement of the output type which concerns on 3rd Embodiment. FIG. 10 is a schematic diagram illustrating a pixel arrangement of two types of images according to a third embodiment. The schematic diagram of the pixel addition in conventional operation | movement. FIG. 6 is a circuit diagram illustrating a configuration example of a conventional pixel portion.

  The best mode for carrying out the present invention will be described below in detail with reference to the accompanying drawings.

<First Embodiment>
FIG. 1 is a block diagram illustrating a configuration of an imaging apparatus 100 according to the first embodiment. In the first embodiment, an example of a digital camera will be described as the imaging apparatus 100.

  The lens unit 101 condenses light from the subject onto the imaging unit 103, and includes a zoom lens, a focus lens, a shutter, and the like. The light amount adjustment unit 102 is disposed between the lens unit 101 and the imaging unit 103, and specifically, is a neutral density filter insertion mechanism or a diaphragm mechanism. The imaging unit 103 includes a pixel unit that converts light incident through the lens unit 101 and the light amount adjustment unit 102 into an analog electric signal, an AD conversion circuit that converts the analog signal into a digital signal, and the like.

  The signal processing unit 104 performs correction parameter generation and necessary image signal correction processing on the image signal input from the imaging unit 103. The imaging control unit 105 controls the imaging unit 103 and the signal processing unit 104 based on a control signal from the overall control / calculation unit 106. Specifically, a timing signal necessary for the imaging unit 103 and the signal processing unit 104, a gain setting signal for amplifying the image signal, an exposure time setting signal, a drive mode setting, and other signals necessary for control. Generate.

  The overall control / arithmetic unit 106 performs necessary processes and computations according to the operation of the imaging apparatus 100. The overall control / arithmetic unit 106 is a storage unit 107 that temporarily stores a signal from the signal processing unit 104 and the like, and a drive mode setting that switches the drive mode of the imaging unit 103 according to a signal input from the operation unit 110 Part 108. Further, the overall control / calculation unit 106 includes an exposure calculation unit 109 that determines an exposure condition for photographing the subject. Based on the calculation result, adjustment of the light amount using the light amount adjustment unit 102 and the imaging control unit 105 The exposure time used and the gain for amplifying the video signal are adjusted.

  In FIG. 1, the signal processing unit 104 and the overall control / calculation unit 106 are illustrated as independent configurations, but the signal processing unit 104 may be included in the overall control / calculation unit 106 or may be included in the imaging unit 103. It may be included. In addition, the imaging control unit 105 may be included in the imaging unit 103.

  The operation unit 110 includes a human IF such as a button or a dial, and is used by a photographer to issue an operation command for the imaging apparatus 100. The recording unit 111 records the image data generated by the overall control / calculation unit 106 on a recording medium (not shown). The display unit 112 displays image data generated by the overall control / calculation unit 106 based on a signal from the signal processing unit 104, and displays an icon corresponding to an operation input from the operation unit 110. Or

  Next, a schematic configuration of the imaging element 200 included in the imaging unit 103 is shown in FIG. The pixel unit 201 includes a light-receiving pixel unit that receives light from the lens unit 101 in FIG. 1, an OB pixel unit that is shielded to define a black level, and the like. In the present embodiment, a Bayer array color filter is arranged in each pixel. The AD conversion unit 202 performs AD conversion of the image signal output from the pixel unit 201. The horizontal scanning circuit unit 203 is a temporary storage unit that temporarily stores a signal output from the AD conversion unit 202 or a shift register that sequentially outputs a signal stored in the temporary storage unit in the horizontal direction (row direction). Etc. The output buffer unit 204 outputs a signal from the horizontal scanning circuit unit 203 to the outside. The vertical scanning circuit unit 205 includes a signal generation unit that generates a signal for driving the pixel unit 201, a decoder that determines a selected row of the pixel unit 201, and the like.

  Next, FIG. 3 shows a partial circuit configuration of the pixel portion 201 of the image sensor 200 of FIG. In the present embodiment, two horizontal pixels and two vertical pixels are taken as one unit, and FIG. 2 shows a state in which unit pixels 300 for two units are arranged in the vertical direction (column direction).

  Photodiodes (PD) 301a to 301d constituting the photoelectric conversion unit photoelectrically convert light incident from the lens unit 101 in FIG. 1 and convert it into electric charges. As described above, Bayer color filters are arranged to cover each PD. The pixel 302a includes a PD 301a and is covered with an R filter that mainly transmits red (R) light. The pixel 302b and the pixel 302c include PDs 301b and 301c, respectively, and are covered with a G filter that mainly transmits green (G) light having a higher contribution to the luminance signal. The pixel 302d includes a PD 301d and is covered with a B filter that mainly transmits blue (B) light.

  Transfer transistors (transfer Tr) 303 a to 303 d transfer charges generated in the PDs 301 a to 301 d to the subsequent floating diffusion (FD) unit 310 based on a transfer signal (TX signal) from the vertical scanning circuit unit 205. The signal amplification amplifier 304 performs an operation of converting the charge transferred from the PDs 301a to 301d to the FD unit 310 into a voltage and amplifying it when the transfer Trs 303a to 303d are turned on. A signal reset transistor (reset Tr) 305 performs a reset operation of the PDs 301 a to 301 d and the FD unit 310 based on a reset signal (RS signal) from the vertical scanning circuit unit 205. In the present embodiment, the FD unit 310, the signal amplification amplifier 304, and the reset Tr 305 are configured to be shared by the four PDs 301a to 301d. The vertical signal line 306 transmits the voltage signal output from the signal amplification amplifier 304 to the AD conversion unit 202.

  A plurality of unit pixels 300 having the above-described configuration are two-dimensionally arranged in the pixel unit 201, and the TX signal and the RS signal are commonly connected to two or more unit pixels 300 in the same row. By controlling the TX signal and the RS signal, charge accumulation and readout of the PDs 301a to 301d can be controlled.

  Next, a method (first readout method) for acquiring a normal image using the imaging apparatus 100 of FIG. 1 will be described. FIG. 4 is a timing chart showing signals generated from the vertical scanning circuit unit 205 when a normal image is acquired in the first embodiment.

  First, while the RS signal rises (from T401), the TX11 signal for transferring the charge of the PD 301a and the TX12 signal for transferring the charge of the PD 301b rise sequentially (T401 and T402). By this operation, the charges of the PD 301a and PD 301b are reset, and charge accumulation is sequentially started. Then, after a predetermined time elapses, the RS signal rises again (T405), and the TX13 signal for transferring the charge of the PD 301c and the TX14 signal for transferring the charge of the PD 301d sequentially rise (T405 and T406). By this operation, the charges of the PD 301c and PD 301d are reset, and charge accumulation is sequentially started. This operation is controlled by the imaging control unit 105 and sequentially performed in other rows according to the set conditions.

  On the other hand, after a predetermined exposure time has elapsed after the reset operation, the TX11 signal rises again (T403), and the charge of the PD 301a is transferred to the FD unit 310. The electric charge transferred to the FD unit 310 is converted into a voltage by the signal amplification amplifier 304 and amplified, read out to the vertical signal line 306 as a voltage signal, and input to the AD conversion unit 202. Next, the TX12 signal rises again (T404), and the charge of the PD 301b is transferred to the FD unit 310. The charge transferred to the FD unit 310 is also converted into a voltage by the signal amplification amplifier 304 and amplified, and is similarly read as a voltage signal to the vertical signal line 306 and input to the AD conversion unit 202. This operation is also sequentially performed in other rows according to the conditions controlled and set by the imaging control unit 105 (first transfer step).

  FIG. 5 shows a part of the circuit configuration of the AD conversion unit 202, the horizontal scanning circuit unit 203, and the output buffer unit 204 in the first embodiment.

  The AD conversion circuit 501 converts an analog signal input via the vertical signal line 306 into a digital signal. The AD conversion circuit 501 in the first embodiment can select an operation by an AD_PW signal as necessary. When it is not necessary to operate, a power saving effect can be obtained by stopping the power supply or reducing the supply power by lowering the AD_PW signal. The AD conversion circuit 501 starts AD conversion when the AD_en signal rises, ends AD conversion when the AD_en signal falls, and performs an initialization operation. The digital memories 502a and 502b can store information of a plurality of bits, and temporarily store a signal from the AD conversion circuit 501. Which of the digital memories 502a and 502b is stored can be selected by a memory selection signal (M1_sel or M2_sel). In the first embodiment, a configuration in which two digital memories are provided for one AD conversion circuit is used, but three or more digital memories may be used. The output buffer 503 sequentially reads the digital signals stored in the digital memories 502 a and 502 b and outputs the digital signals to the outside of the image sensor 200. The arithmetic circuit 504 performs an operation of adding pixel signals of a plurality of rows or a plurality of columns stored in the digital memories 502a and 502b. The shift register 505 performs an operation of outputting a signal (SW signal) for selecting a signal to be transmitted to the output buffer 503.

  FIG. 6 is a timing chart showing an operation when the normal image of the output system shown in FIG. 5 is acquired. The AD_PW signal of the AD conversion circuit 501 rises at the timing when the analog signal from the pixel is read to the vertical signal line 306, and the power supply to the AD conversion circuit 501 is started (T601). Then, the AD_en signal rises and AD conversion is performed on the signal of each pixel (T602 and T604). The digital data after AD conversion of each pixel is stored in each of the digital memories 502a and 502b while the M1_sel or M2_sel signal is H (the period from T602 to T603 or the period from T604 to T605). The stored digital data receives the SW signal from the shift register 505, is sequentially read while the SW1 or SW2 signal is H (period starting from T606 or T607), and is output to the output buffer 503.

  Here, the operation shown in FIG. 4 and FIG. 6 is repeated, and the read operation is performed by adding the read data of a plurality of rows or columns by the arithmetic circuit 504 to perform the operation of averaging or averaging. An addition operation can be realized. FIG. 7A is a diagram illustrating a pixel array when a normal image is acquired, and FIG. 7B is a diagram illustrating a pixel array of an image subjected to a normal pixel addition operation. In the pixel covered with the filter having the same action (same color) as the R filter covering the pixel 302a, the vertical m-th pixel and horizontal n-th pixel are denoted as R_mn. Similarly, a G1 filter that covers the pixel 302b has the same action (same color) as G1_mn, a G2 filter that covers the pixel 302c has the same action (same color) as G2_mn, and a B filter that covers the pixel 302d (same color). The filter is represented as B_mn.

  As shown in FIG. 7B, in this embodiment, the same color pixels for two horizontal pixels and two vertical pixels are added, but the same effect can be obtained by changing the number of horizontal or vertical additions. can get. Further, the same effect can be obtained when the position of the center of gravity after the addition is changed by multiplying a part of a plurality of pixels to be added by a predetermined gain.

  Here, the image pickup device 200 mounted on the image pickup apparatus 100 according to the present embodiment is a CMOS image pickup device. For this reason, the setting of the vertical scanning circuit unit 205 can select which row of the transfer Tr 303 is driven in what order, and can repeatedly select the same row and read the signal. Further, by setting the horizontal scanning circuit unit 203, it is possible to select which column signal is output from the same row signal depending on which column SW is operated. Thereby, it is possible to specify in what order from which pixel in the screen the data is read out. The read signal is subjected to necessary correction processing in the signal processing unit 104. Thereafter, a final image is created by the overall control / calculation unit 106.

  In the present embodiment, each AD conversion circuit 501 has two digital memories 502, but two or more digital memories may be used. Further, although one AD conversion circuit is provided for the vertical signal line 306, two or more AD conversion circuits may be provided. In addition, although the example in which the AD conversion timing and the digital data output timing are performed in time series is shown as the operation of FIG. 6, an operation that overlaps with the AD conversion timing or the digital output timing of the immediately preceding or immediately following row may be performed.

  Next, a method for acquiring a charge addition image according to the first embodiment using the imaging apparatus 100 of FIG. 1 will be described. FIG. 8 is a timing chart showing signals generated by the vertical scanning circuit unit 205 when acquiring the charge addition image in the first embodiment. 7, the R_11 pixel corresponds to the pixel 302a in FIG. 3, the G1_11 pixel corresponds to the pixel 302b, the G2_11 pixel corresponds to the pixel 302c, and the B_11 pixel corresponds to the pixel 302d.

  After resetting the charges of the PDs 301a to 301d, the TX signal rises after a predetermined exposure time elapses and transfers the charges to the FD unit 310. The electric charge transferred to the FD unit 310 is converted into a voltage by the signal amplification amplifier 304 and amplified, read out as a voltage signal to the vertical signal line 306, and converted into a digital signal. These operations are the same as those for obtaining a normal image. The difference from the normal operation is that the TX signals TX12 and TX13 corresponding to the transfer Trs 303b and 303c connected to G1_11 and G2_11 respectively rise at the time of the reset operation and the charge read operation (T802 and T804). Since the TX signals TX12 and TX13 rise simultaneously, the reset timing, exposure time, and readout time of the two pixels are the same. Since the amount of charge transferred to the FD unit 310 is for two pixels, the voltage signal value output from the signal amplification amplifier 304 is also a value for two pixels.

  FIG. 9 is a timing chart showing the operation of the output system shown in FIG. 5 when acquiring the charge addition image in the first embodiment. The AD_PW signal rises at the timing when the analog signal from the pixel is read out to the vertical signal line 306, and power supply to the AD conversion circuit 501 is started (T901). Then, the AD_en signal rises and AD conversion is performed on the signal of each pixel (T902 and T904). The digital data after AD conversion of each pixel is stored in each digital memory 502a or 502b while the M1_sel or M2_sel signal is H (period T902 to T903, period T904 to T905, period T911 to T912). The point of this operation is that the timing of TX13 is advanced to the same timing as TX12, so that the power supply to the AD conversion circuit 501 is stopped during a period (T908 to T910) corresponding to TX13 in normal driving. In addition, at the above timing (T908 to T909), the SW3 signal is received and the data in the digital memory 502b is copied to the digital memory 502a. Then, in a period (T911 to T912) corresponding to TX14, a new digital AD conversion result is stored in the digital memory 502b. Finally, the SW data (SW1 or SW2 signal) from the shift register 505 rises (T906, T907, T913, T914) and the digital data is sequentially output to the output buffer 503.

  By repeating the above operation for each row, an image of one surface can be acquired. FIG. 10 is a diagram illustrating a pixel arrangement of a charge addition image obtained by performing the charge addition operation in the first embodiment. Further, the output order in this charge addition operation is the same as in normal driving. Therefore, by repeating the operations shown in FIGS. 8 and 9, it is possible to combine the read data of a plurality of rows with a normal addition operation (FIG. 7B) performed by the arithmetic circuit 504 or the like with the same configuration. It can be carried out.

  By performing this operation, the normal read operation and the charge addition operation can be realized in the same output order without adding a large circuit. This charge addition operation can obtain a luminance signal whose luminance level is twice as high as that of the conventional pixel addition based on voltage averaging, and can improve dark follow-up performance. When the color ratio is different, the white balance coefficient and the like may be adjusted.

  In addition, although the normal addition operation in 1st Embodiment showed the example which performs the digital data after AD conversion in the arithmetic circuit 504 in a horizontal circuit, you may add at the time of the analog signal before AD conversion. The AD converter may add the values.

  Further, in the first embodiment, the image pickup element in which the color filters of the Bayer array are arranged is illustrated, but the operation of the above-described first embodiment is performed even when a plurality of color filters other than the Bayer array are used. By doing so, the same effect can be obtained.

  Moreover, although the example which adds the electric charge of two pixels in which the G filter which mainly permeate | transmits green light is arrange | positioned was shown, even if the electric charge of the pixel in which the filter of the same color other than green is arranged is added Good. In addition to the normal addition operation, the charge addition operation of this embodiment is also effective in the operation of thinning out a part of vertical or horizontal pixels.

  Further, since the output value is different for a pixel to which no charge is added, a gain corresponding to the output difference may be multiplied before output.

<Second Embodiment>
Next, a second embodiment of the present invention will be described. The configuration of the imaging device, the pixel and the peripheral circuit configuration, etc. in the second embodiment are the same as those described with reference to FIGS. 1 to 3 and 5 in the first embodiment. The description is omitted here.

  In the first embodiment, the imaging apparatus that realizes the normal reading operation and the charge addition operation in the same output order without adding a large circuit is illustrated. Further, by combining the charge addition operation and the normal pixel addition operation, it is possible to improve the dark followability.

  When the number of pixels of the image sensor 200 increases, the time required to output an image on one surface increases, and it may be a problem to maintain a predetermined frame rate during moving image shooting. Therefore, it may be preferable not to read out all the pixels but to read out some pixels. Hereinafter, a driving method (second reading method) of the image sensor 200 in a case where some pixels are read by thinning out according to the second embodiment will be described.

  FIG. 11 is a timing chart showing signals generated by the vertical scanning circuit unit 205 when a part of pixels are read out using the imaging apparatus 100 in the second embodiment. After resetting the charges of the PDs 301a to 301d, the TX signal rises after a predetermined exposure time elapses and transfers the charges to the FD unit 310. The electric charge transferred to the FD unit 310 is converted into a voltage by the signal amplification amplifier 304 and amplified, read out as a voltage signal to the vertical signal line 306, and converted into a digital signal. These operations are the same as in the case of acquiring a normal image of the first embodiment. The following points are different from the normal operation. The first point is that the TX12 signal and the TX13 signal rise simultaneously (T1102), the charges of G1_11 and G2_11 are reset, and exposure is started. The second point is that the TX22 signal and the TX23 signal rise simultaneously (T1105), the charges of G1_21 and G2_21 are reset, and exposure is started. The third point is that since the TX14 signal and the TX21 signal do not rise, the reset of B_11 and R_21 (the filter of the color other than one color) is not selectively performed. These operations are sequentially performed in a predetermined order from each pixel under the conditions set by the imaging control unit 105. After the reset, after a predetermined exposure time has elapsed, the TX signal rises again and transfers the charge of the PD 301 to the FD unit 310. Also in this case, TX12 and TX13, and TX22 and TX23 rise simultaneously (T1104 and T1107), and the TX14 signal and TX21 signal do not rise.

  Since TX12 and TX13 and TX22 and TX23 rise at the same time as described above, the reset timing, exposure time, and readout time of the two PDs 301 are the same. Since the amount of charge transferred to the FD unit 310 is for two pixels, the voltage signal value output from the signal amplification amplifier 304 is also a value for two pixels. Furthermore, by not starting up TX14 and TX21, it is possible to acquire images for four rows with a readout time for two rows, so that the frame rate can be improved. In addition, by performing horizontal addition in the arithmetic circuit 504, the frame rate can be further improved.

  FIG. 12 shows an example of pixel addition in the case where the signals of two pixels are added in the horizontal direction (row direction) after being read out in half in the vertical direction (column direction) in the second embodiment. Note that the pixel array of the image sensor 200 is shown in FIG. In the second embodiment, two horizontal pixels are added and the vertical pixels are subtracted for half a minute, but the same effect can be obtained even if the horizontal or vertical addition number or thinning number is changed. it can.

  By performing this operation, the normal read operation and the charge addition operation can be realized in the same output order without adding a large circuit. Then, by combining this charge addition operation and the normal pixel addition operation, it is possible to improve the dark followability.

<Third Embodiment>
Next, a third embodiment of the present invention will be described. Note that the configuration of the imaging device and the schematic circuit configuration of the pixels and the peripheral portion in the third embodiment are the same as those described with reference to FIGS. 1 to 3 in the first embodiment. Omitted. Detailed circuit configurations of the AD conversion unit 202, the horizontal scanning circuit unit 203, and the output buffer unit 204 are different from those shown in FIG.

  In the second embodiment described above, the operation of thinning out some pixels has been described in order to improve the frame rate. However, when only a part of the pixels is subjected to charge addition, the signal level of the pixel subjected to charge addition is approximately twice that of the pixel not subjected to charge addition, which may not be preferable as the final image quality. On the other hand, it is not always necessary to have high image quality when performing focus adjustment or when dimming during flash operation.

  Therefore, in the third embodiment, by performing the following operation, two types of images, that is, an image in which the luminance signal is enhanced and an image that is not enhanced are acquired by one imaging operation. According to the method of the third embodiment described below, it is possible to improve the measurement accuracy of various photographing auxiliary functions without adding a large-scale circuit and without reducing the image quality. Here, the photographing assistance function includes a function for measuring the degree of focus of the subject, a function for calculating the luminance of the subject, a framing function for adjusting the angle of view, and the like.

  FIG. 13 is a timing chart showing signals generated by the vertical scanning circuit unit 205 when an image is acquired in the third embodiment. After resetting the charges of the PDs 301a to 301d, the TX signal rises after a predetermined exposure time elapses and transfers the charges to the FD unit 310. Then, the electric charge transferred to the FD unit 310 is converted into a voltage by the signal amplification amplifier 304 and amplified, read out to the vertical signal line 306 as a voltage signal, and converted into a digital signal. These operations are the same as in the case of acquiring a normal image of the first embodiment.

  In the third embodiment, an operation in which charge addition is performed for each unit pixel 300 or not is performed alternately for each row of the unit pixels 300. Specifically, TX12 and TX13 rise simultaneously (T1303), the charges of G1_11 and G2_11 are reset, and charge accumulation is started. However, the TX22 signal and the TX23 signal do not rise at the same time (T1304 and T1310), the charges of G1_21 and G2_21 are sequentially reset, and charge accumulation is started. This sequential reset operation is sequentially performed in a predetermined order from each pixel under the conditions set by the imaging control unit 105. Thereafter, after a predetermined time elapses, each TX signal rises again and transfers the charge of the PD 301 to the FD unit 310. Also in this case, TX12 and TX13 are simultaneously (T1307) (second transfer step), and the TX22 signal and TX23 signal are sequentially raised (first transfer step) (T1308, T1313).

  FIG. 14 shows a part of the circuit configuration of the AD conversion unit 202, the horizontal scanning circuit unit 203, and the output buffer unit 204 in the third embodiment.

  The AD conversion circuit 131 converts an analog signal input via the vertical signal line 306 into a digital signal. The digital memories 132a to 132d can store information of a plurality of bits and temporarily store a signal from the AD conversion circuit 131. In the third embodiment, one AD converter circuit 131 has four digital memories. The output buffers 133a and 133b sequentially read out the digital signals stored in the digital memories 132a to 132d and output them to the outside of the image sensor 200. In the third embodiment, two output buffers 133a and 133b are provided, and independent signals can be output. The arithmetic circuit and output buffer switching circuit 134 performs an operation of adding signals of a plurality of rows or columns stored in the digital memories 132a to 132d, an operation of selecting which output buffer to output, and the like. The shift register 135 performs an operation of outputting a SW signal for selecting a signal to be transmitted to the output buffer 133.

  FIG. 15 is a timing chart showing the operation of the output system shown in FIG. The AD_PW signal of the AD conversion circuit 131 rises at the timing when the analog signal from the pixel is read out to the vertical signal line 306, and power supply to the AD conversion circuit 501 is started (T1501 or T1516). Then, the AD_en signal rises and AD conversion is performed on the signal of each pixel (T1502, T1504, etc.). The digital data after AD conversion of each pixel is stored in each of the digital memories 132a to 132d while the M1_sel to M4_sel signals are H (period T1502 to T1503, period T1504 to T1505, etc.). The SW signal (SW1, SW2, SW3, or SW4 signal) from the shift register 135 rises, and the stored digital data is sequentially output to the output buffer 133a or 133b. The point of this operation is that the timing of TX13 is advanced to the same timing as TX12, and therefore, the power supply of the AD conversion circuit 131 is stopped during the period corresponding to TX13 in the normal drive (the period from T1514 to T1516). In addition, at the above timing, in response to SW5, the operation of copying the data in the digital memory 132b to the digital memory 132a is performed (T1514). Then, in the period corresponding to TX14, a new digital AD conversion result is stored in the digital memory 132b (period T1519 to T1520). On the other hand, the timing of TX23 is the same as that in the case of performing normal reading (period from T1517 to T1518). The digital data stored in the digital memories 132a and 132b is output from the output buffer 133a, and the digital data stored in the digital memories 132c and 132d is output from the output buffer 133b.

  Here, the operations shown in FIG. 13 and FIG. 15 are repeated, and the read data of a plurality of rows are added in the horizontal direction by the arithmetic circuit 134 or the like, thereby realizing a normal pixel addition operation. FIG. 16 shows a pixel arrangement diagram 16a of the pixels output from the output buffer 133a when the charge addition image is acquired, and the pixels output from the output buffer 133b when the image of the normal pixel addition operation is acquired. FIG. 16B shows a pixel array of FIG. In both cases, the normal horizontal two addition is performed by the arithmetic circuit 134.

  By performing this operation, an image read without performing the charge addition operation and an image read by performing the charge addition operation can be output at the same timing without adding a large-scale circuit. In applications where image quality is required, the image shown in FIG. 16 (b) is used, and in applications where the image quality is not necessarily required, such as when measuring the degree of focus of the subject or when dimming during flash operation. The image shown in FIG. 16A is used. By doing so, it is possible to improve the dark followability without deterioration of the image quality.

  In the third embodiment, two output buffers are provided, but the same effect can be obtained even if three or more output buffers are provided. In the third embodiment, two types of images are output at the same time. However, two types may be read out in time division, or two or more types may be read out. In addition, pixel addition or thinning operation may be further performed in the vertical direction.

Claims (12)

A plurality of photoelectric conversion units covered with filters of a plurality of colors, a floating diffusion unit to which charges generated in the plurality of photoelectric conversion units are transferred, and an amplifying unit that converts the charges of the floating diffusion units into a voltage and outputs the voltage A plurality of unit pixels each including a plurality of transfer means for transferring charges generated in the plurality of photoelectric conversion units to the floating diffusion unit,
A first reading method for reading out the charges generated in the plurality of photoelectric conversion units by transferring them to the floating diffusion unit, and a filter of a predetermined color among the charges generated in the plurality of photoelectric conversion units. Driving the pixel unit by a plurality of readout methods, including a second readout method of transferring the charges of the plurality of photoelectric conversion units transferred to the floating diffusion unit for each unit pixel and adding the charges. Means ,
The image pickup device , wherein the driving unit alternately performs reading by the first reading method and reading by the second reading method for each row of the unit pixels .   The signal read out by adding the charges in the second readout method is used as a signal of each of the plurality of photoelectric conversion units covered by the filter of the predetermined color of the corresponding unit pixel. The imaging device according to claim 1.   In the second readout method, the driving unit transfers the charges converted by the photoelectric conversion unit covered with the filter of a color other than the predetermined color independently to the floating diffusion unit. The imaging device according to claim 1 or 2.   In the second readout method, the driving unit is configured to obtain a signal in the same color arrangement order as the filter color arrangement order from the pixel unit. The image pickup device according to claim 1, wherein the image pickup device is driven so as to selectively read out charges converted by a photoelectric conversion unit covered with a filter of a predetermined color and a filter of another color. AD conversion means for converting the voltage signal output from the amplification means into a digital signal, and addition means for adding the digital signal of the same color output from the AD conversion means in at least one of the column direction and the row direction. imaging device according to any one of claims 1 to 4, further comprising. The color of the filter which is determined in advance, according to any one of claims 1 to 5, wherein the contribution to the luminance signal is a color filter which more transmit higher color light Image sensor. The plurality of photoelectric conversion units included in the unit pixel are two-dimensionally arranged, and one photoelectric conversion unit is covered with the predetermined color filter in each row of the unit pixel. The imaging device according to any one of claims 1 to 6 . In each unit pixel, two photoelectric conversion units are arranged in each of the row direction and the column direction, and are covered with a Bayer array filter. The predetermined color filter mainly transmits green light. The imaging device according to claim 7 , wherein the imaging device is a filter. An AD converter for converting a voltage signal output from said amplifying means to digital signals, according to claim 1 to 8, further comprising a memory for temporarily storing the digital signal converted by said AD conversion means The imaging device according to any one of the above. The imaging device according to any one of claims 1 to 9 ,
Setting means for setting a drive mode for the image sensor;
An image pickup apparatus comprising: a control unit that controls the driving unit to drive the pixel unit by the second reading method when a predetermined driving mode is set. The imaging apparatus according to claim 10 , wherein the predetermined drive mode includes at least a mode for determining focus adjustment or exposure conditions. A plurality of photoelectric conversion units covered by a plurality of color filters, a floating diffusion unit to which charges generated in the plurality of photoelectric conversion units are transferred, an amplifying unit, and a charge generated in the plurality of photoelectric conversion units A driving method of an imaging device having a plurality of unit pixels each including a plurality of transfer means for transferring to a floating diffusion portion and a pixel portion arranged two-dimensionally,
A first transfer step in which the transfer unit transfers charges generated in the plurality of photoelectric conversion units to the floating diffusion unit, respectively.
The transfer means transfers the charges of a plurality of photoelectric conversion units covered by a predetermined color filter among the charges generated in the plurality of photoelectric conversion units to the floating diffusion unit for each unit pixel, A second transfer step of transferring the charge of the photoelectric conversion unit covered by the filter other than the predetermined color among the charges generated in the plurality of photoelectric conversion units to the floating diffusion unit, respectively;
A drive means for controlling the transfer means to alternately perform the first transfer step and the second transfer step for each row of the unit pixels;
Each time the charge is transferred to the floating diffusion part, the amplification means converts the charge of the floating diffusion part into a voltage and outputs the voltage; and
A method for driving an imaging device, comprising:

Images