Photoelectric conversion device, camera module, endoscope, endoscope system, and device

Abstract

To provide a technique to prevent an increase in circuit scale and power consumption due to clock control, thereby advantageous for reducing the size of a photoelectric conversion device.SOLUTION: A photoelectric conversion device includes: a pixel array in which a plurality of pixels are arranged to form a plurality of rows and a plurality of columns; a drive control unit for driving the pixel array; a horizontal transfer unit that sequentially outputs analog signals output from the plurality of columns of the pixel array; an AD conversion unit that converts the analog signals output from the horizontal transfer unit into digital signals; a first clock generation unit that generates clock signals for controlling the operation of the drive control unit; and a second clock generation unit that generates clock signals for controlling the horizontal transfer unit and the AD conversion unit. A clock tree to which the clock signals are distributed from the first clock generation unit and a clock tree to which the clock signals are distributed from the second clock generation unit form clock trees different from each other.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a photoelectric conversion device, a camera module, an endoscope, an endoscope system, and an instrument. [Background technology]

[0002] In recent years, ultra-compact photoelectric conversion devices have been developed for applications such as endoscopy. Patent Document 1 discloses an endoscope system that outputs analog image signals via a signal cable and performs AD conversion outside the photoelectric conversion device, thereby reducing the circuit scale of the photoelectric conversion device. In the configuration of Patent Document 1, analog signals are output using a long transmission path, making the output image susceptible to noise. Meanwhile, Non-Patent Document 1 discloses an ultra-compact digital image sensor that includes a successive approximation AD converter within the photoelectric conversion device and outputs a digital signal. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-192328 [Non-patent literature]

[0004] [Non-Patent Document 1] M. Waeny et al., "Ultra small digital image sensor for endoscopic applications," Proceedings of the 2009 International Image Sensor Workshop, (Norway), March 26, 2009. Summary of the Invention [Problem to be solved by the invention]

[0005] In the configuration of Non-Patent Document 1, the readout controller controls the imaging operation and the horizontal transfer operation, and the AD conversion controller controls the AD converter, each using a clock output by the ring oscillator. AD conversion must be performed in synchronization with the horizontal transfer operation, and maintaining a synchronous relationship between the control of the readout controller and the AD conversion controller requires an increased number of clock buffers for timing control within the circuit, which can increase the circuit size. Furthermore, increasing the number of clock buffers increases power consumption.

[0006] An object of the present invention is to provide a technique that is advantageous for miniaturizing a photoelectric conversion device by suppressing increases in circuit size and power consumption due to clock control. [Means for solving the problem]

[0007] In view of the above-described problems, a photoelectric conversion device according to an embodiment of the present invention is a photoelectric conversion device including: a pixel array in which a plurality of pixels are arranged to form a plurality of rows and a plurality of columns; a drive control unit for driving the pixel array; a horizontal transfer unit that sequentially outputs analog signals output from each of the plurality of columns of the pixel array; an AD conversion unit that converts the analog signals output from the horizontal transfer unit into digital signals; a first clock generation unit that generates a clock signal that controls an operation of the drive control unit; and a second clock generation unit that generates a clock signal that controls the horizontal transfer unit and the AD conversion unit, wherein a clock tree to which a clock signal is distributed from the first clock generation unit and a clock tree to which a clock signal is distributed from the second clock generation unit constitute different clock trees. the drive control unit causes the pixel array to output an analog signal, and transfers to the horizontal transfer unit a horizontal transfer control signal indicating a period for outputting the analog signal from the pixel array, and the horizontal transfer unit starts outputting the analog signal output from the pixel array to the AD conversion unit in synchronization with a clock signal supplied from the second clock generation unit in response to the horizontal transfer control signal. It is characterized by: [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a technique that is advantageous for miniaturizing a photoelectric conversion device by suppressing increases in circuit size and power consumption due to clock control. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing an example of the configuration of a photoelectric conversion device according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing an example of the configuration of a pixel of the photoelectric conversion device of FIG. 1. [Figure 3] 2 is a diagram showing an example of the configuration of a horizontal transfer unit of the photoelectric conversion device of FIG. 1; [Figure 4] 2 is a diagram showing an example of output data in one horizontal transfer period of the photoelectric conversion device of FIG. 1; [Figure 5] FIG. 2 is a timing diagram of horizontal transfer in the photoelectric conversion device of FIG. 1. [Figure 6] FIG. 2 is a diagram showing an example of the configuration of an AFE of the photoelectric conversion device of FIG. 1. [Figure 7] 2 is a diagram showing an example of the configuration of an AD conversion unit of the photoelectric conversion device of FIG. 1; [Figure 8] FIG. 2 is a timing diagram of the AFE of the photoelectric conversion device of FIG. 1. [Figure 9] FIG. 2 is a diagram showing an example of the layout of the photoelectric conversion device of FIG. 1. [Figure 10] FIG. 3 is a diagram showing a modified example of the pixel in FIG. 2. [Figure 11] FIG. 4 is a diagram showing a modification of the horizontal transfer section of FIG. 3. [Figure 12] 1. FIG. 3 is a diagram showing a modification and a layout example of the photoelectric conversion device of FIG. [Figure 13] 2A and 2B are diagrams showing configuration examples of a camera module including the photoelectric conversion device of FIG. 1, an endoscope using the camera module, and an endoscope system. [Figure 14] FIG. 2 is a diagram showing an example of the configuration of an apparatus including the photoelectric conversion device of FIG. 1. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the scope of the invention claimed. Although multiple features are described in the embodiments, not all of these multiple features are necessarily essential to the invention, and multiple features may be combined arbitrarily. Furthermore, in the accompanying drawings, the same reference numerals are used to designate the same or similar components, and redundant explanations will be omitted.

[0011] A photoelectric conversion device according to an embodiment of the present disclosure will be described with reference to Figures 1 to 14. Figure 1 is a block diagram showing a schematic configuration of a photoelectric conversion device 100 according to this embodiment. As shown in Figure 1, the photoelectric conversion device 100 includes a pixel array 101, a drive control unit 102, a horizontal transfer unit 104, an analog front end (AFE) 105, a digital signal processing unit (DSP) 107, and an output unit 108.

[0012] The pixel array 101 has a plurality of pixels 201 arranged to form a plurality of rows and a plurality of columns. The drive control unit 102 drives the pixel array 101. The horizontal transfer unit 104 sequentially outputs analog signals output from the plurality of columns of the pixel array 101 via vertical signal lines 202 to the AFE 105. The AFE 105 includes an analog amplifier and an AD conversion unit, and converts the analog signals output from the horizontal transfer unit into digital signals. The DSP 107 performs digital signal processing on the digital signals output from the AFE 105. The output unit 108 is an interface for outputting the digital data output from the DSP 107 to the outside of the photoelectric conversion device 100.

[0013] The photoelectric conversion device 100 further includes a first clock generation unit 103 that generates a clock signal that controls the operation of the drive control unit 102, and a second clock generation unit 106 that generates a clock signal that controls the horizontal transfer unit 104 and the AFE 105. The first clock generation unit 103 controls the drive control unit 102 using the first clock signal. The second clock generation unit 106 controls the horizontal transfer unit 104 and the AFE 105 using the second clock signal and a third clock signal. The first clock generation unit 103, the second clock generation unit 106, and their respective clock signals will be described later.

[0014] 2 shows an example of the configuration of a pixel 201 arranged in the pixel array 101. An output node of the pixel 201 is connected to a vertical signal line 202. The vertical signal line 202 is connected to a constant current source (not shown) and the horizontal transfer unit 104.

[0015] The pixel 201 includes a photoelectric conversion element 311, a charge transfer switch 312, a floating diffusion FD, a reset switch 313, a signal amplification switch 314, and a row selection switch 315. The photoelectric conversion element 311 can be, for example, an element such as a photodiode PD that generates charges according to the amount of light incident on the photoelectric conversion element 311.

[0016] The charge transfer switch 312 is disposed between the photoelectric conversion element 311 and the floating diffusion FD. The charge transfer switch 312 can be a transfer transistor for reading out the charge accumulated in the photoelectric conversion element 311. The charge transfer switch 312 is controlled to be in a conductive (ON) state or a non-conductive (OFF) state by a control signal PTX.

[0017] The reset switch 313 is disposed between the power supply voltage VDD and the floating diffusion FD. The reset switch 313 may be a reset transistor that supplies the power supply voltage VDD to the floating diffusion FD and resets the circuit. The reset switch 313 is controlled between a conductive (ON) state and a non-conductive (OFF) state by a control signal PRES.

[0018] The signal amplification switch 314 may be a source follower transistor that converts the charge accumulated in the floating diffusion FD into a voltage, amplifies the voltage, and outputs the voltage signal to the vertical signal line 202. A control terminal of the signal amplification switch 314 is connected to the floating diffusion FD. Two main terminals of the signal amplification switch 314 are connected to a power supply voltage VDD and the row selection switch 315, respectively.

[0019] The row selection switch 315 is disposed between the output of the signal amplification switch 314 and the vertical signal line 202. The row selection switch 315 may be a transistor for selecting a row for outputting a pixel signal. The row selection switch 315 is controlled to be in a conductive (on) state or a non-conductive (off) state by a control signal PSEL.

[0020] In each pixel 201, for example, a noise signal (N signal) is read out, and then a signal signal (S signal) is read out. The charge of the floating diffusion FD after the reset of the floating diffusion FD is released is read out as an N signal via the signal amplification switch 314. Next, the charge of the photoelectric conversion element 311 is transferred to the floating diffusion FD via the charge transfer switch 312, and the charge transferred from the photoelectric conversion element 311 to the floating diffusion is read out as an S signal via the signal amplification switch 314. The reset noise of the floating diffusion FD is removed by performing correlated double sampling processing on the S signal and N signal output from the pixel 201 in the AFE 105.

[0021] The drive control unit 102 controls the photoelectric conversion device 100 under control of an external control device (not shown). The drive control unit 102 controls an internal state machine in accordance with serial communication with the external control device, and transitions from a stopped state to an imaging state. When the drive control unit 102 enters the imaging state, it generates control signals PTX, PRES, and PSEL for the pixel array 101 according to, for example, the values ​​of a horizontal counter and a vertical counter arranged within the drive control unit 102, and controls the exposure and readout operations of the pixels 201. The control signals PTX, PRES, and PSEL may be generated for each row of the pixel array 101, and a slit rolling operation may be performed by controlling reset row scanning and readout row scanning for the pixels 201 in parallel.

[0022] The drive control unit 102 also generates a horizontal transfer control signal for the horizontal transfer unit 104, a readout control signal, and an imaging control signal for the AFE 105 and second clock generation unit 106 in accordance with a horizontal counter, a vertical counter, and a state machine. The horizontal transfer control signal is asserted when imaging of the top row of the pixel array 101 is complete and readout preparation is complete, and is deasserted when the readout operation of the last row is complete. The horizontal transfer control signal can be considered a signal indicating a period during which analog signals are output from each pixel 201 of the pixel array 101. The readout control signal is a signal that controls the output of N signals and S signals from the pixels 201 via the vertical signal lines 202. The imaging control signal is a signal that indicates an imaging period during which imaging is performed by the pixel array 101, and is asserted when the state machine of the drive control unit 102 is in an imaging state. The imaging control signal is a signal that controls the operation of the AFE 105 and second clock generation unit 106.

[0023] The control of the horizontal counter and vertical counter by the drive control unit 102 may be, for example, an external synchronization system in which the horizontal counter and vertical counter operate in accordance with a synchronization signal input from outside the photoelectric conversion device 100, or an internal synchronization system in which the horizontal counter and vertical counter operate in accordance with a synchronization signal generated internally. When considering ultra-compactness of the photoelectric conversion device 100 for use in an endoscope or the like, the internal synchronization system allows for a reduction in the number of input terminals. Furthermore, although the present embodiment uses a system in which pixels are driven by a slit rolling operation, if the pixel structure is compatible with a global shutter, a configuration in which shutter scanning is performed simultaneously on all pixels may also be used.

[0024] The horizontal transfer unit 104 has a function of outputting analog signals of the pixels 201 output from the pixel array 101 to the AFE 105 in synchronization with a second clock signal supplied from the second clock generation unit 106 in response to a horizontal transfer control signal transferred from the drive control unit 102. The horizontal transfer unit 104 also has a function of generating a horizontal synchronization signal indicating one horizontal period and outputting the horizontal synchronization signal to the AFE 105.

[0025] 3 is a block diagram showing an example of the configuration of the horizontal transfer unit 104. The horizontal transfer unit 104 includes an edge detection circuit 1041, a horizontal transfer control unit 1042, two sets of vertical signal line selection units 1043, and an output control unit 1044.

[0026] The edge detection circuit 1041 detects the edge of the horizontal transfer control signal that the drive control unit 102 outputs to the horizontal transfer unit 104 when it causes each pixel 201 in the pixel array 101 to output an analog signal. When the edge detection circuit 1041 detects the edge of the horizontal transfer control signal, it outputs a pulse with a one-clock width to the horizontal transfer control unit 1042.

[0027] The horizontal transfer control unit 1042 includes a shift register that transfers a pulse every clock. The shift register may have a ring-type circuit configuration in which a plurality of registers FFs are connected in series, and the output of the final register among the plurality of registers FFs is connected to the input of the first register among the plurality of registers FFs. A logical OR signal of the output pulse of the edge detection circuit 1041 and the signal of the final register of the shift register is input to the first register of the shift register.

[0028] The shift register of the horizontal transfer control unit 1042 is configured so that a pulse makes one cycle from the first register to the last register during one horizontal transfer period for transferring a signal corresponding to one row of the pixel array 101. For example, as shown in FIG. 4 , consider a case where one horizontal transfer period includes two horizontal synchronization periods Hblk, including a period for outputting a horizontal synchronization signal and a horizontal blanking period, and where a signal is output from one pixel 201 during one period and signals are output from m pixels 201. The horizontal synchronization period Hblk is a period during which no signal is output from a pixel 201. In this case, the shift register of the horizontal transfer control unit 1042 can be configured as a shift register that makes one cycle in m periods plus the horizontal synchronization period Hblk (two periods in this embodiment). In other words, the number of registers FF in the shift register of the horizontal transfer control unit 1042 can be determined by the number of pixels 201 to which signals are transferred during one horizontal transfer period among the multiple pixels 201 and the horizontal synchronization period. The horizontal transfer control unit 1042 is connected to the switch SWT of the vertical signal line selection unit 1043 so as to control the readout operation of the vertical signal line selection unit 1043 according to the pulse position of the shift register.

[0029] The vertical signal line selection unit 1043 has a memory function for holding the S signals and N signals of the pixels 201 input via the vertical signal lines 202. For example, the wiring capacitance between the switch SWT and the switches SWS and SWN can function as the memory. The vertical signal line selection unit 1043 has a function for outputting the S signals and N signals of each column of the pixel array 101 to the AFE 105 during one horizontal transfer period in response to a control signal input from the horizontal transfer control unit 1042.

[0030] The vertical signal line selection unit 1043 transfers analog signals output from the pixels 201 arranged in one row of the pixel array 101 to the AFE 105, for example, using two horizontal transfer periods. FIG. 5 shows a timing chart of horizontal transfer. First, during the first horizontal transfer period, N signals and S signals in the first row are output from the pixels 201 to the vertical signal lines 202 in sequence in accordance with a readout control signal P_TN1 for N signals and a readout control signal P_TS1 for S signals input from the drive control unit 102. The vertical signal line selection unit 1043 holds the N signals and the S signals. Here, it is shown that the N signals and the S signals are held in the memory N and memory S of the vertical signal line selection unit 1043, respectively. Next, during the second horizontal transfer period, the held N signals and S signals are output in sequence to the AFE 105 in accordance with a control signal output from the shift register of the horizontal transfer control unit 1042. The shift register of the horizontal transfer control unit 1042 makes one cycle of a pulse during one horizontal transfer period, and therefore, signals output from one row of pixels 201 during one horizontal transfer period are output to the AFE 105. During a horizontal synchronization period Hblk during which no pixel signals are output within the horizontal transfer period, the vertical signal line selection unit 1043 selects a predetermined fixed potential instead of the vertical signal line 202, and the fixed potential is output to the AFE 105. In addition, the output of the first-stage register of the horizontal transfer control unit 1042 is output to the AFE 105 as a horizontal synchronization signal HS.

[0031] In this way, two horizontal transfer periods are used to output signals from the pixels 201 of one row arranged in the pixel array 101 and to horizontally transfer the signals to the AFE 105. In each horizontal transfer period, the horizontal transfer unit 104 may include at least two sets of vertical signal line selection units 1043 to transfer analog signals output from the pixels 201 to the AFE 105. The two sets of vertical signal line selection units 1043 are controlled by the output control unit 1044 to alternately read out signals from the pixels 201 and horizontally transfer the signals every horizontal transfer period. Figure 5 shows the horizontal transfer operations for the first and second rows.

[0032] The horizontal transfer unit 104 repeats the above operation until readout scanning of all areas of the pixel array 101 is completed and the horizontal transfer control signal input from the drive control unit 102 is deasserted. In this way, signals for one frame of image are transferred from the pixel array 101 to the AFE 105. The horizontal transfer unit 104 can be reset until the horizontal transfer control signal is asserted and transfer of the next frame begins.

[0033] The AFE 105 performs gain adjustment processing, correlated double sampling processing, and AD conversion processing to convert the analog signals into digital signals on the analog S and N signals output from the horizontal transfer unit 104. An example of the configuration of the AFE 105 in this embodiment is shown in Fig. 6. The AFE 105 includes an AMP unit 1051, an AD conversion unit 1052, and a horizontal synchronization signal delay circuit 1053.

[0034] The AMP unit 1051 performs correlated double sampling and gain adjustment on the S and N signals transferred from the horizontal transfer unit 104. The gain adjustment may be performed using a programmable gain amplifier (PGA) that can adjust the gain for each set value from a register (not shown). Upon receiving an imaging control signal transferred from the drive control unit 102 indicating an imaging period during which imaging is performed by the pixel array 101, the AMP unit 1051 outputs to the AD conversion unit 1052 the processing results of the analog signals from the horizontal transfer unit 104 that are input in synchronization with the second clock signal supplied from the second clock generation unit 106.

[0035] The AD conversion unit 1052 performs AD conversion to convert the analog signal transferred from the AMP unit 1051 into a digital signal. In this embodiment, a configuration example and an operation example are shown assuming that the AD conversion unit 1052 is a successive approximation type AD conversion unit. As shown in FIG. 7 , the AD conversion unit 1052 includes an AD conversion control unit 10521, a sample-and-hold unit 10522, a successive approximation register 10524, a DAC 10525, and a comparator 10523. The AD conversion control unit 10521 controls the AD conversion operation in the AD conversion unit 1052. The sample-and-hold unit 10522 holds the voltage of the analog signal transferred from the AMP unit 1051. The DAC 10525 performs DA conversion based on the output value of the successive approximation register 10524 and a reference voltage. The comparator 10523 compares the output voltage of the DAC 10525 with the voltage of the sample-and-hold unit 10522.

[0036] 8 is a timing diagram showing an example of the operation of the AD conversion unit 1052. The AD conversion unit 1052 starts converting an analog signal into a digital signal based on an imaging control signal transferred from the drive control unit 102. More specifically, upon receiving the imaging control signal, the AD conversion control unit 10521 generates control signals for the sample hold unit 10522, comparator 10523, and successive approximation register 10524 in synchronization with a third clock signal supplied from the second clock generation unit 106. This starts the AD conversion process. Below, the operation of AD converting an analog signal output from one pixel 201 will be described.

[0037] The sample-and-hold unit 10522 captures a voltage in accordance with a sampling signal from the AD conversion control unit 10521 during a stable period of the analog signal V_IN input from the AMP unit 1051. As described above, the horizontal transfer unit 104 (and the AMP unit 1051) outputs an analog signal in synchronization with the second clock signal supplied from the second clock generation unit 106. Here, the time from the edge of the clock signal that triggers the output of the analog signal in the horizontal transfer unit 104 to the stabilization of the analog signal V_IN output after processing by the AMP unit 1051 is defined as time T_STBL. In this case, the sample-and-hold unit 10522 needs to capture the analog signal V_IN after a period equal to or greater than time T_STBL has elapsed since the rising edge of the second clock signal. In other words, the AD conversion unit 1052 needs to sample the analog signal output from the horizontal transfer unit 104 in synchronization with the second clock signal supplied from the second clock generation unit 106 after a predetermined time has elapsed since the edge of the clock signal that triggered the output of the analog signal. For this reason, the AD conversion control unit 10521 asserts the sampling signal at a timing when the time T_STBL or more has elapsed since the rising edge of the second clock. The assertion timing of the sampling signal may be configured to be set, for example, by the above-mentioned external control device. When sampling of the analog signal V_IN is completed, the sample-and-hold unit 10522 outputs the voltage V_SMPL to the comparator 10523.

[0038] The successive approximation register 10524 has a function of controlling the voltage that the DAC 10525 outputs to the comparator 10523 in accordance with an SAR control signal supplied from the AD conversion control unit 10521, and a function of outputting the AD conversion result. The successive approximation register 10524 can have a number of control bits that is equal to or greater than the output precision of the AD conversion unit 1052. Here, the explanation will be given assuming that the number of output bits of the AD conversion unit 1052 is 10 bits, and that the number of bits of the successive approximation register 10524 is also 10 bits.

[0039] At time T_SAR1, the successive approximation register 10524 outputs an initial value for AD conversion of an analog signal output from each pixel 201 to the DAC 10525, with 1 for the MSB and 0 for the remaining bits, i.e., the median value of the maximum output value. The DAC 10525 outputs a voltage V_DAC1 of the median value to the comparator 10523 in accordance with the output value of the successive approximation register 10524. At time T_COMP1, the comparator 10523 compares the voltage V_SMPL output by the sample-and-hold unit 10522 with the voltage V_DAC1 output by the DAC 10525 in accordance with a comparator control signal output by the AD conversion control unit 10521. If the comparison shows that the voltage V_SMPL is greater than the voltage V_DAC1, the comparator 10523 outputs 1, and the successive approximation register 10524 determines the MSB to be 1. If the voltage V_SMPL is smaller than the voltage V_DAC1, the comparator 10523 outputs 0, and the successive approximation register 10524 determines the MSB as 0.

[0040] At time T_SAR2, which is the next cycle, the successive approximation register 10524 sets the MSB to the above-mentioned determined value, the value of the bit one bit lower than the MSB to 1, and the values ​​of the other bits to 0, and causes the DAC 10525 to generate a voltage V_DAC2. The comparator 10523 compares the sampling voltage V_SMPL with the voltage V_DAC2.

[0041] By repeating the above-described operation up to the bit precision (LSB) of the AD conversion, the value of each bit is determined and the AD conversion is completed. The digital signal (digital data) output from the AD conversion unit 1052 may be serial data synchronized with the third clock signal, or may be parallel data synchronized with the second clock signal. Here, the digital signal output from the AD conversion unit 1052 is described as serial data synchronized with the third clock signal. In this case, the comparison result output by the comparator 10523 is output from the successive approximation register 10524. A clock signal (the third clock signal in this embodiment) synchronized with the output digital signal is output from the AFE 105 to the DSP 107. The horizontal synchronization signal delay circuit 1053 of the AFE 105 delays the horizontal synchronization signal transferred from the horizontal transfer unit 104 by an internal delay of the AFE 105, and supplies the delayed signal to the DSP 107.

[0042] In this embodiment, an example in which AD conversion is performed by a single AD conversion unit 1052 has been described. However, this is not limiting. To improve the accuracy of AD conversion, for example, AD conversion may be divided into upper and lower bits, and an amplifier that increases the input voltage gain during AD conversion of the lower bit may be provided to improve the accuracy of the lower bit. Various AD conversion methods may be used, such as flash AD conversion, which sets multiple reference voltages and compares the output signal of the AMP unit 1051 in parallel using parallel comparators, pipeline AD conversion, or ΔΣ AD conversion. To reduce the size of the photoelectric conversion device 100, a method with a small circuit scale may be appropriately selected for the AD conversion unit 1052. Furthermore, during the horizontal synchronization period Hblk, during which no signal is output from the pixel 201, a digital signal corresponding to a predetermined fixed potential may be output, as described above, or, for example, appropriate additional information may be output.

[0043] The DSP 107 performs various digital processes such as digital gain processing and shading correction processing on the digital signal output from the AD conversion unit 1052 of the AFE 105. A third clock signal is supplied to the DSP 107 from the second clock generation unit 106 via the AFE 105 including the AD conversion unit 1052, and digital processing is performed on the digital signal in synchronization with the third clock signal. The DSP 107 outputs the processed digital signal to the output unit 108.

[0044] The output unit 108 is an interface for outputting a digital signal to the outside of the photoelectric conversion device 100, and may use, for example, a differential output such as LVDS. By using a clock-embedded protocol that requires a small number of pins for the output unit 108, the circuit scale of the photoelectric conversion device 100 can be reduced, but this is not limitative. For example, communication standards such as MIPI and HDMI (registered trademark) may be used for the output unit 108. In this embodiment, the horizontal transfer period is the same cycle for each row, and as shown in FIG. 4, after signals for two horizontal synchronization periods are output, digital signals for m pixels are output.

[0045] Next, the first clock generating unit 103, the second clock generating unit 106, and the clock tree to which the clock signal is distributed from the first clock generating unit 103 and the clock tree to which the clock signal is distributed from the second clock generating unit 106 will be described.

[0046] The first clock generation unit 103 generates a first clock signal that controls the operation of the drive control unit 102. The resolution of the horizontal transfer control signal and readout control signal that the drive control unit 102 transfers to the horizontal transfer unit 104 is lower than the resolution of the drive pulses used by the drive control unit 102 to drive the pixel array 101. Similarly, the resolution of the imaging control signal that the drive control unit 102 transfers to the second clock generation unit 106 and the AFE 105 is lower than the resolution of the drive pulses used by the drive control unit 102 to drive the pixel array 101. Therefore, the operating frequency of the drive control unit 102 is determined by the frequency of the first clock signal depending on the resolution of the drive pulses used to drive the pixel array 101. In this embodiment, the frequency of the first clock signal that the first clock generation unit 103 supplies to the drive control unit 102 so that the drive control unit 102 drives each pixel 201 arranged in the pixel array 101 is set to 5 MHz.

[0047] The second clock generation unit 106 generates a second clock signal and a third clock signal that control the operation of the horizontal transfer unit 104 and the AFE 105. More specifically, as described above, the second clock generation unit 106 generates the second clock signal and supplies it to the horizontal transfer unit 104 and the AFE 105. The second clock generation unit 106 also generates a third clock signal and supplies it to the AFE 105. As shown in FIG. 8 , the AD conversion unit 1052, which operates in synchronization with the third clock signal, needs to operate at a higher speed than the AMP unit 1051, which operates in synchronization with the second clock signal. In other words, the frequency of the third clock signal supplied from the second clock generation unit 106 to the AD conversion unit 1052 is higher than the frequency of the second clock signal supplied from the second clock generation unit 106 to the horizontal transfer unit 104 and the AMP unit 1051. For example, the frequency of the second clock signal may be 10 MHz, and the frequency of the third clock signal may be 120 MHz.

[0048] In this way, the second clock generating unit 106 supplies clock signals of different frequencies to the horizontal transfer unit 104 and the AD conversion unit 1052 based on the reference clock signal in the second clock generating unit 106. For example, the second clock generating unit may supply a 120 MHz reference clock signal as the third clock signal to the AD conversion unit 1052, and supply a clock signal obtained by dividing the reference clock signal by 12 as the second clock signal to the horizontal transfer unit 104 and the AMP unit 1051. Alternatively, for example, the second clock generating unit may supply a 10 MHz reference clock signal as the second clock signal to the horizontal transfer unit 104 and the AMP unit 1051, and supply a clock signal obtained by multiplying the reference clock signal by 12 as the third clock to the AD conversion unit 1052. Alternatively, the reference clock signal in the second clock generating unit 106 may have a higher frequency than the second clock signal and the third clock signal, and each may be divided to a desired frequency.

[0049] The reference clock signals in first clock generating unit 103 and second clock generating unit 106 may be configured to be input from the outside. Also, for example, first clock generating unit 103 and second clock generating unit 106 may each include an oscillator for generating a reference clock signal for supplying the first to third clock signals.

[0050] In the present embodiment, as described above, the frequency of the third clock signal is higher than the frequencies of the first clock signal and the second clock signal. That is, the frequency of the third clock signal that the second clock generation unit 106 supplies to the AD conversion unit 1052 is higher than the frequency of the clock signal that the first clock generation unit 103 supplies to the drive control unit 102. Furthermore, the frequency of the second clock signal is higher than the frequency of the first clock signal. That is, the frequency of the second clock signal that the second clock generation unit 106 supplies to the horizontal transfer unit 104 and the AMP unit 1051 is higher than the frequency of the clock signal that the first clock generation unit 103 supplies to the drive control unit 102. However, this is not limiting. For example, the frequency of the first clock signal may be the same as the frequency of the second clock signal or the frequency of the third clock signal.

[0051] As described above, the AD conversion unit 1052 needs to synchronize the sampling timing of the sample-and-hold unit 10522 with the analog signal output by the AMP unit 1051. For this reason, the AD conversion unit 1052 and the second clock generation unit 106 start operating in response to the imaging control signal transferred from the drive control unit 102. Furthermore, they operate so that the phase relationships among the second clock signal, the third clock signal, the sampling signal, the comparator control signal, and the SAR control signal are aligned to the relationships shown in FIG.

[0052] In this way, the horizontal transfer unit 104 and the AFE 105 (the AMP unit 1051 and the AD conversion unit 1052) operate without receiving the first clock signal directly from the first clock generation unit 103 or via the drive control unit 102. That is, in this embodiment, the clock tree to which the clock signal is distributed from the first clock generation unit 103 and the clock tree to which the clock signal is distributed from the second clock generation unit 106 constitute mutually separate clock trees.

[0053] FIG. 9 shows the block layout of the photoelectric conversion device 100 and the clock signals supplied thereto. In this embodiment, the pixel array 101 is driven by a first clock signal supplied from a first clock generation unit 103, and the horizontal transfer unit 104 and the AFE 105 are driven by a second clock signal and a third clock signal supplied from a second clock generation unit 106. The horizontal transfer unit 104 and the AFE 105 are started to operate by a horizontal transfer control signal, a readout control signal, and an imaging control signal, which have low resolution and are transferred from the drive control unit 102. Therefore, there is no need to provide many clock buffers for timing control between the clock tree to which the clock signal is distributed from the first clock generation unit 103 and the clock tree to which the clock signal is distributed from the second clock generation unit 106. As shown in FIG. 9, the horizontal transfer unit 104 and the AFE 105, which operate on the clock tree to which the clock signal is supplied from the second clock generation unit 106, can be arranged relatively close to each other, thereby reducing the number of clock buffers required. As a result, increases in the circuit size and power consumption of the photoelectric conversion device 100 due to clock control can be suppressed, and the photoelectric conversion device 100 can be made smaller.

[0054] 10 and 11, a case will be described in which two or more adjacent pixels (photoelectric conversion elements 311) share a floating diffusion FD in the pixel array 101 in order to further reduce the size of the photoelectric conversion device 100. Fig. 10 shows an example configuration of a pixel group 901 in which two or more adjacent pixels (photoelectric conversion elements 311) share a floating diffusion FD, and Fig. 11 shows an example configuration of a horizontal transfer unit 1004 corresponding to the pixel array 101 including the pixel group 901.

[0055] In this embodiment, the pixel array 101 includes pixels (photoelectric conversion elements 311) arranged in a matrix of n rows and m columns. In this case, as shown in FIG. 10 , K photoelectric conversion elements 311 arranged along vertical signal lines 202 and L photoelectric conversion elements 311 arranged along the row direction form a pixel group 901 in which one floating diffusion FD is shared. In other words, output nodes of the K×L photoelectric conversion elements 311 are connected to one vertical signal line 202. Here, as shown in FIG. 10 , it is assumed that K=4 and L=2, and a total of eight photoelectric conversion elements 311a to 311h share one floating diffusion FD and are connected to one vertical signal line 202.

[0056] In the above-described embodiment, an analog signal can be output in one horizontal transfer period from the pixels 201 arranged in one row of the pixel array 101. On the other hand, if the pixel array 101 has a configuration in which two photoelectric conversion elements 311 in the row direction share a floating diffusion FD, as shown in Fig. 10, the signals of the pixels (photoelectric conversion elements 311) arranged in odd-numbered columns and the signals of the pixels (photoelectric conversion elements 311) arranged in even-numbered columns need to be output in different horizontal transfer periods.

[0057] For this reason, the horizontal transfer unit 1004 corresponding to the pixel array 101 having the pixel group 901 shown in FIG. 10 is configured to be connected to m / L vertical signal lines 202, as shown in FIG. 11. As described above, one horizontal transfer period is the horizontal synchronization period Hblk plus the period during which signals are output from the pixels. Therefore, the shift register of the horizontal transfer control unit 1042 of the horizontal transfer unit 1004 is configured so that a pulse makes one cycle from the first register to the last register during m / L periods plus the horizontal synchronization period Hblk (e.g., two periods as described above). In this case, the number of registers FF in the shift register can be m / L+2. In this way, it can be said that the number of registers FF in the shift register of the horizontal transfer control unit 1042 is determined by the number of pixels 201 to which signals are transferred in one horizontal transfer period among the multiple pixels 201, the horizontal synchronization period, and the number of photoelectric conversion elements 311 arranged in the row direction among the photoelectric conversion elements 311a to 311h that share the floating diffusion FD.

[0058] The drive control unit 102 reads out a signal from one photoelectric conversion element 311 in the pixel group 901 every horizontal transfer period. The drive control unit 102 controls the transfer control signals to the pixel group 901 and the horizontal transfer unit 1004 so that signals are read out in the order of, for example, photoelectric conversion elements 311a, 311b, ..., 311h over eight horizontal transfer periods. When outputting signals from the photoelectric conversion elements 311a, 311c, 311e, and 311g, the drive control unit 102 sets N signal readout control signal 1 and S signal readout control signal 1 to a connected state, transfers the signals to the vertical signal line selection unit 1043, and outputs the signals to the AFE 105 during the next horizontal transfer period. Furthermore, when signals are to be output from the photoelectric conversion elements 311b, 311d, 311f, and 311h, the N signal readout control signal 2 and the S signal readout control signal 2 are set to a connected state, the signals are transferred to the vertical signal line selection unit 1043, and the signals are output to the AFE 105 during the next horizontal transfer period.

[0059] In this way, when two or more pixels (photoelectric conversion elements 311) arranged in the row direction share a floating diffusion FD, the number of stages of the registers FF of the shift register is configured so that the pulse makes one cycle in the m / L period plus the horizontal synchronization period Hblk. This makes it possible to configure a horizontal transfer unit 1004 that operates in the same way as the above-mentioned horizontal transfer unit 104. By using the configurations shown in Figures 10 and 11, the circuit scale of the pixel array 101 can be reduced, and further miniaturization of the photoelectric conversion device 100 can be achieved.

[0060] 1 shows an example in which the first clock generating unit 103 and the second clock generating unit 106 generate the first to third clock signals separately. However, the generation of clock signals is not limited to the configuration shown in FIG. 1. The photoelectric conversion device 100 may include an oscillator 109, and the first clock generating unit 103 and the second clock generating unit 106 may generate clock signals based on the output of the oscillator 109.

[0061] FIG. 12(a) illustrates a configuration example of a photoelectric conversion device 100 including an oscillator 109, and FIG. 12(b) illustrates a block layout of the photoelectric conversion device 100 and the clock signals supplied thereto. As illustrated in FIG. 12(a), the first clock generation unit 103 and the second clock generation unit 106 receive a clock signal output by the oscillator 109. The first clock generation unit 103 generates a first clock signal, and the second clock generation unit 106 generates a second clock signal and a third clock signal. Because the clock tree through which the first clock signal is distributed is different from the clock tree through which the second clock signal and the third clock signal are distributed, the phases of the clock signals supplied from the oscillator 109 do not need to be aligned between the first clock generation unit 103 and the second clock generation unit 106. The frequency of the oscillator 109 may be adjustable, for example, by a voltage supplied from an external power source (not shown). Alternatively, the frequency of the oscillator 109 may be adjustable via communication from the external control device described above.

[0062] Here, the description will be given assuming that oscillator 109 generates a 120 MHz clock signal. In this case, first clock generating unit 103 may divide the 120 MHz clock signal supplied from oscillator 109 by 12 and output the 10 MHz clock signal as the first clock signal. Second clock generating unit 106 may divide the 120 MHz clock signal by 12 and output the 10 MHz clock signal as the second clock signal. Furthermore, second clock generating unit 106 may output the 120 MHz clock signal supplied from oscillator 109 as a 120 MHz third clock signal without any change.

[0063] As shown in FIGS. 12(a) and 12(b), when the oscillator 109 is included in the photoelectric conversion device 100, the first clock signal, the second clock signal, and the third clock signal for controlling each component in the photoelectric conversion device 100 are generated from a clock signal output from the single oscillator 109, making it difficult for deviations due to clock deviations to occur. Furthermore, even in the configurations shown in FIGS. 12(a) and 12(b), there is no need to place many clock buffers for timing control between the clock tree to which the clock signal is distributed from the first clock generating unit 103 and the clock tree to which the clock signal is distributed from the second clock generating unit 106. Furthermore, as shown in FIG. 9, the horizontal transfer unit 104 and the AFE 105, which operate on the clock tree to which the clock signal is supplied from the second clock generating unit 106, can be arranged relatively close to each other, thereby reducing the number of clock buffers required. As a result, increases in the circuit size and power consumption of the photoelectric conversion device 100 due to clock control can be suppressed, and the photoelectric conversion device 100 can be made more compact.

[0064] Next, as application examples of the above-described photoelectric conversion device 100, a camera module including the photoelectric conversion device 100, and an endoscope and an endoscope system using the camera module including the photoelectric conversion device 100 will be described. FIG. 13 is a block diagram showing a configuration example of an endoscope system 1300 including an endoscope 1320 using a camera module 1310 including the above-described photoelectric conversion device 100. The endoscope system 1300 includes an endoscope 1320 including the camera module 1310 including the photoelectric conversion device 100 and a cable 1321 that transmits a signal output from the camera module 1310. The endoscope system 1300 also includes a control device 1330 that is connected to the cable 1321 and includes a signal processing unit 1331 that processes the signal output from the camera module 1310. The endoscope system 1300 may further include a display device 1340 that displays an image corresponding to the signal output from the camera module 1310, and a light source device 1350 that supplies light when the camera module 1310 captures an image.

[0065] In the endoscope system 1300, at least a portion of an endoscope 1320 including a camera module 1310 and a cable 1321 is inserted into a body cavity and used to observe an object. The camera module 1310 is disposed at an end 1324 of the endoscope 1320 that is inserted into the body cavity. The camera module 1310 includes the above-described photoelectric conversion device 100 and an optical system 1311 that directs light into the photoelectric conversion device 100. The optical system 1311 is configured to include one or more lenses.

[0066] An illumination optical system 1352 for irradiating the observation object with light emitted from a light source device 1350 is disposed at an end 1324 of the endoscope 1320 where the camera module 1310 is disposed. The illumination optical system 1352 is configured to include one or more lenses. The light emitted from the light source device 1350 is supplied to the illumination optical system 1352 via an optical path 1351 such as a flexible optical fiber, and illuminates the observation object.

[0067] The cable 1321 of the endoscope 1320 may be flexible. The cable 1321 can be deformed in any direction and angle by the user operating the operation unit 1322 of the endoscope 1320. This makes it possible to point the camera module 1310 in a desired direction depending on the object to be observed. A signal transmission line 1323 is arranged in the cable 1321, and transmits a signal output from the camera module 1310 to a signal processing unit 1331 of the control device 1330. The above-mentioned optical path 1351 may also pass through the cable 1321.

[0068] The end 1324 of the endoscope 1320 and the cable 1321 may be provided with insertion holes for inserting forceps, wires, syringe needles, etc. for collecting biological tissue of the observation target, as well as storage holes for storing electric scalpels for similarly collecting biological tissue. The end 1324 of the endoscope 1320 and the cable 1321 may be provided with fluid passages for supplying air or water to the observation target site or for suctioning liquid.

[0069] The control device 1330 includes a control unit 1335 for controlling each component of the endoscope system 1300. The control unit 1335 may be an electronic circuit including a processor (e.g., a CPU, an MPU, an ASIC, etc.) that executes software (programs) to perform processing. The programs may be stored, for example, in a memory 1332 of the control device 1330, and may be read out and executed by the control unit 1335 when a user operates a user interface 1333 of the control device 1330. The programs may be supplied to the control unit 1335 via a network or various storage media such as an external memory. The user interface 1333 may be, for example, a personal computer attached to the endoscope system 1300, or a touch panel. Furthermore, the display device 1340 may function as a part of the user interface 1333.

[0070] The control unit 1335 transfers setting data of imaging conditions such as exposure conditions in the photoelectric conversion device 100 to the photoelectric conversion device 100 via a signal transmission line 1323 in accordance with a user's operation. The control unit 1335 can also function as a signal processing unit 1331 that processes an image signal obtained by the photoelectric conversion device 100 to convert the signal into data that can be displayed as an image on a display device 1340, for example. In the configuration shown in FIG. 13 , a part of the control unit 1335 processes a signal output from the camera module 1310, but the control unit 1335 and the signal processing unit 1331 may be arranged independently. Data for image display processed by the signal processing unit 1331 may be stored in a memory 1332 of the control device 1330.

[0071] The display device 1340 may be, for example, a liquid crystal display. The control device 1330 and the display device 1340 may be connected by wire or wirelessly. The display device 1340 may be used to display an image of an observation target corresponding to a signal obtained by the photoelectric conversion device 100. Furthermore, when observing a subject using the endoscope system 1300, the display device 1340 may display, for example, imaging conditions of the photoelectric conversion device 100, and setting information of each component included in the endoscope system 1300.

[0072] The light source device 1350 may be, for example, a light source that emits white light. The light source device 1350 may also be a light source that emits red or blue light other than white. The light emitted by the light source device 1350 is not limited to visible light, as long as the light is a color to which the photoelectric conversion elements 311 of the photoelectric conversion device 100 are sensitive. The light source device 1350 is configured to emit light of an appropriate wavelength depending on the object of observation. The light source device 1350 emits light of a set color under the control of the control unit 1335 of the control device 1330, and simultaneously, the photoelectric conversion device 100 captures an image under the control of the control unit 1335 of the control device 1330, thereby obtaining an image of the object of observation.

[0073] The circuit scale of the photoelectric conversion device 100 is suppressed as described above, and the photoelectric conversion device 100 is miniaturized, which enables the camera module 1310 to be miniaturized. This allows the end 1324 of the endoscope 1320 that is inserted into a body cavity to be miniaturized, thereby reducing the burden on the subject. Furthermore, if the size of the end 1324 of the endoscope 1320 does not need to be changed, miniaturizing the camera module 1310 creates more space that can be used for the above-mentioned insertion hole, storage hole, fluid passage, etc., and allows the endoscope 1320 to have more functions.

[0074] Application examples of the photoelectric conversion device 100 are not limited to the camera module 1310, endoscope 1320, and endoscope system 1300 shown in FIG. 13. FIG. 14 is a schematic diagram illustrating an apparatus 1400 including the photoelectric conversion device 100 of this embodiment. The photoelectric conversion device 100 can be housed in a package 1420 and mounted on the apparatus 1400. The package 1420 can include a base to which the photoelectric conversion device 100 is fixed and a cover such as glass that faces the pixel array 101 of the photoelectric conversion device 100. The package 1420 can further include bonding members such as bonding wires and bumps that connect terminals provided on the base to output terminals provided on the output section 108 of the photoelectric conversion device 100.

[0075] The device 1400 can include at least one of an optical device 1440, a control device 1450, a processing device 1460, a display device 1470, a storage device 1480, and a mechanical device 1490. The optical device 1440 is, for example, a lens, a shutter, or a mirror. The control device 1450 controls the photoelectric conversion device 100. The control device 1450 is, for example, a semiconductor device such as an ASIC.

[0076] The processing device 1460 functions as a signal processing unit that processes signals output from the photoelectric conversion device 100. The processing device 1460 is a semiconductor device such as a CPU or ASIC for configuring an analog front end (AFE) or a digital front end (DFE). The display device 1470 is an EL display device or a liquid crystal display device that displays information (images) obtained by the photoelectric conversion device 100. The storage device 1480 is a magnetic device or a semiconductor device that stores information (images) obtained by the photoelectric conversion device 100. The storage device 1480 is a volatile memory such as an SRAM or a DRAM, or a non-volatile memory such as a flash memory or a hard disk drive.

[0077] The mechanical device 1490 has a moving part or a propulsion part such as a motor or an engine. In the device 1400, the signal output from the photoelectric conversion device 100 is displayed on a display device 1470, or transmitted to the outside by a communication device (not shown) provided in the device 1400. For this purpose, the device 1400 may further include a storage device 1480 and a processing device 1460 in addition to the storage circuit and arithmetic circuit provided in the photoelectric conversion device 100. The mechanical device 1490 may be controlled based on the signal output from the photoelectric conversion device 100.

[0078] The device 1400 is also suitable for electronic devices such as information terminals with a photographing function (e.g., smartphones and wearable devices) and cameras (e.g., interchangeable lens cameras, compact cameras, video cameras, and surveillance cameras). The mechanical device 1490 in the camera can drive components of the optical device 1440 for zooming, focusing, and shutter operation. Alternatively, the mechanical device 1490 in the camera can move the photoelectric conversion device 100 for vibration isolation.

[0079] Furthermore, the device 1400 may be transportation equipment such as a vehicle, a ship, or an aircraft. The mechanical device 1490 in transportation equipment may be used as a moving device. The device 1400 as transportation equipment is suitable for transporting the photoelectric conversion device 100 or for assisting and / or automating driving (piloting) using an imaging function. The processing device 1460 for assisting and / or automating driving (piloting) can perform processing for operating the mechanical device 1490 as a moving device based on information obtained by the photoelectric conversion device 100. Alternatively, the device 1400 may be a medical device such as an endoscope, a measuring device such as a distance measuring sensor, an analytical device such as an electron microscope, an office machine such as a copier, or an industrial device such as a robot.

[0080] According to the above-described embodiment, a photoelectric conversion device 100 is realized that has a small circuit scale and reduced power consumption. Therefore, the value of the equipment 1400 that includes the photoelectric conversion device 100 can be increased. In this case, increasing the value corresponds to at least one of adding functions, improving performance, improving characteristics, improving reliability, improving manufacturing yield, reducing environmental impact, reducing costs, reducing size, and reducing weight.

[0081] Therefore, if the photoelectric conversion device 100 according to this embodiment is used in the equipment 1400, the value of the equipment can also be improved. For example, by installing the photoelectric conversion device 100 in transportation equipment, excellent performance can be obtained when photographing the exterior of the transportation equipment or measuring the external environment. Therefore, when manufacturing and selling transportation equipment, deciding to install the semiconductor device according to this embodiment in the transportation equipment is advantageous in terms of improving the performance of the transportation equipment itself. In particular, the photoelectric conversion device 100 is suitable for transportation equipment that performs driving assistance and / or automatic driving of the transportation equipment using information obtained by the photoelectric conversion device 100.

[0082] The disclosure of this specification includes the complement of the concepts described in this specification. In other words, if this specification states, for example, that "A is B" (A=B), then even if the statement that "A is not B" (A≠B) is omitted, this specification is deemed to disclose or suggest that "A is not B." This is because when "A is B," it is assumed that the case where "A is not B" is taken into consideration.

[0083] The invention is not limited to the above-described embodiments, and various changes and modifications can be made without departing from the spirit and scope of the invention. Accordingly, the following claims are appended to apprise the public of the scope of the invention. [Explanation of symbols]

[0084] 100: Photoelectric conversion device, 101: Pixel array, 102: Drive control unit, 103: First clock generation unit, 104: Horizontal transfer unit, 106: Second clock generation unit, 201: Pixel, 1052: AD conversion unit

Claims

1. a pixel array in which a plurality of pixels are arranged to form a plurality of rows and a plurality of columns; a drive control unit for driving the pixel array; a horizontal transfer unit that sequentially outputs analog signals output from each of a plurality of columns of the pixel array; an AD conversion unit that converts an analog signal output from the horizontal transfer unit into a digital signal; a first clock generating unit that generates a clock signal that controls the operation of the drive control unit; a second clock generating unit that generates a clock signal that controls the horizontal transfer unit and the AD conversion unit, a clock tree to which a clock signal is distributed from the first clock generating unit and a clock tree to which a clock signal is distributed from the second clock generating unit constitute different clock trees from each other, the drive control unit causes the pixel array to output an analog signal, and transfers to the horizontal transfer unit a horizontal transfer control signal indicating a period during which the pixel array is to output the analog signal; a horizontal transfer unit that starts outputting the analog signal output from the pixel array to the AD conversion unit in synchronization with the clock signal supplied from the second clock generation unit in response to the horizontal transfer control signal.

2. the drive control unit transfers an imaging control signal indicating an imaging period during which imaging is performed by the pixel array to the second clock generation unit; 2. The photoelectric conversion device according to claim 1, wherein the second clock generation unit starts generating a clock signal for controlling the AD conversion unit in response to the imaging control signal.

3. A pixel array in which a plurality of pixels are arranged to form a plurality of rows and a plurality of columns; a drive control unit for driving the pixel array; a horizontal transfer unit that sequentially outputs analog signals output from each of a plurality of columns of the pixel array; an AD conversion unit that converts an analog signal output from the horizontal transfer unit into a digital signal; a first clock generating unit that generates a clock signal that controls the operation of the drive control unit; a second clock generating unit that generates a clock signal that controls the horizontal transfer unit and the AD conversion unit, a clock tree to which a clock signal is distributed from the first clock generating unit and a clock tree to which a clock signal is distributed from the second clock generating unit constitute different clock trees from each other, the drive control unit transfers an imaging control signal indicating an imaging period during which imaging is performed by the pixel array to the second clock generation unit; The photoelectric conversion device, wherein the second clock generation unit starts generating a clock signal that controls the AD conversion unit in response to the imaging control signal.

4. 4. The photoelectric conversion device according to claim 2, wherein the AD conversion unit starts an operation of converting an analog signal into a digital signal based on the imaging control signal.

5. A photoelectric conversion device as described in any one of claims 1 to 4, characterized in that the AD conversion unit samples the analog signal output from the horizontal transfer unit in synchronization with the clock signal supplied from the second clock generation unit after a predetermined time has elapsed from the edge of the clock signal that triggered the output of the analog signal.

6. the horizontal transfer unit includes a shift register in which a plurality of registers are connected in series, and an output of a final stage register among the plurality of registers is connected to an input of a first stage register among the plurality of registers, The photoelectric conversion device according to any one of claims 1 to 5, characterized in that in one horizontal transfer period in which a signal corresponding to one row of the pixel array is transferred, a pulse travels around the shift register from the first stage register to the last stage register.

7. 7. The photoelectric conversion device according to claim 6, wherein the number of the plurality of registers is determined by the number of pixels among the plurality of pixels to which signals are transferred in one horizontal transfer period and a horizontal synchronization period.

8. Each of the plurality of pixels includes a photoelectric conversion element, 8. The photoelectric conversion device according to claim 1, wherein two or more photoelectric conversion elements share a floating diffusion.

9. Each of the plurality of pixels includes a photoelectric conversion element, Two or more photoelectric conversion elements share a floating diffusion; 7. The photoelectric conversion device according to claim 6, wherein the number of the plurality of registers is determined by the number of pixels among the plurality of pixels to which signals are transferred during one horizontal transfer period, the horizontal synchronization period, and the number of photoelectric conversion elements arranged in the row direction among the two or more photoelectric conversion elements that share the floating diffusion.

10. further comprising an oscillator; 10. The photoelectric conversion device according to claim 1, wherein the first clock generating section and the second clock generating section each generate a clock signal based on an output of the oscillator.

11. 10. The photoelectric conversion device according to claim 1, wherein the first clock generating unit and the second clock generating unit each include an oscillator for generating a clock signal.

12. The photoelectric conversion device according to any one of claims 1 to 11, characterized in that the second clock generation unit supplies clock signals of different frequencies to the horizontal transfer unit and the AD conversion unit based on a reference clock signal in the second clock generation unit.

13. 13. The photoelectric conversion device according to claim 12, wherein the frequency of the clock signal supplied from the second clock generation unit to the AD conversion unit is higher than the frequency of the clock signal supplied from the second clock generation unit to the horizontal transfer unit.

14. 14. The photoelectric conversion device according to claim 12, wherein the second clock generation unit supplies the reference clock signal to the AD conversion unit, and supplies a clock signal obtained by dividing the reference clock signal to the horizontal transfer unit.

15. A photoelectric conversion device according to any one of claims 1 to 14, characterized in that the frequency of the clock signal supplied by the second clock generating unit to the AD conversion unit is higher than the frequency of the clock signal supplied by the first clock generating unit to the drive control unit.

16. A photoelectric conversion device according to any one of claims 1 to 15, characterized in that the frequency of the clock signal supplied by the second clock generating unit to the horizontal transfer unit is higher than the frequency of the clock signal supplied by the first clock generating unit to the drive control unit.

17. 17. The photoelectric conversion device according to claim 1, wherein the AD conversion section is a successive approximation type AD conversion section.

18. further comprising a digital signal processing unit that performs digital signal processing on the digital signal output from the AD conversion unit; 18. The photoelectric conversion device according to claim 1, wherein a clock signal is supplied to the digital signal processing unit from the second clock generating unit via the AD conversion unit.

19. The photoelectric conversion device according to any one of claims 1 to 18, an optical system that causes light to be incident on the photoelectric conversion device; A camera module comprising:

20. a camera module according to claim 19; a cable for transmitting a signal output from the camera module; An endoscope comprising:

21. The endoscope according to claim 20; a signal processing unit connected to the cable and configured to process a signal output from the camera module; An endoscope system comprising:

22. The photoelectric conversion device according to any one of claims 1 to 18, a signal processing unit that processes a signal output from the photoelectric conversion device; An apparatus characterized by comprising:

Images