Photoelectric conversion device, camera module, endoscope, endoscope system, and apparatus
A photoelectric conversion device is provided. The device includes a pixel array in which pixels are arranged, a drive controller configured to drive the pixel array, a horizontal transfer unit configured to sequentially output analog signals respectively output from columns of the pixel array, an AD converter configured to convert an analog signal output from the horizontal transfer unit into a digital signal, a first clock generator configured to generate a clock signal used to control an operation of the drive controller, and a second clock generator configured to generate a clock signal used to control the horizontal transfer unit and the AD converter. A clock tree in which a clock signal is distributed from the first clock generator and a clock tree in which a clock signal is distributed from the second clock generator form clock trees different from each other.
1. A photoelectric conversion device comprising:
a pixel array in which a plurality of pixels are arranged so as to form a plurality of rows and a plurality of columns;
a drive controller configured to drive the pixel array;
a horizontal transfer unit configured to sequentially output analog signals respectively output from a plurality of columns of the pixel array;
an AD converter configured to convert an analog signal output from the horizontal transfer unit into a digital signal;
a first clock generator configured to generate a clock signal used to control an operation of the drive controller; and
a second clock generator configured to generate a clock signal used to control the horizontal transfer unit and the AD converter, wherein
a clock tree in which a clock signal is distributed from the first clock generator and a clock tree in which a clock signal is distributed from the second clock generator form clock trees different from each other.
2. The photoelectric conversion device according to claim 1 , wherein
the drive controller 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 an analog signal from the pixel array, and
the horizontal transfer unit starts to output, to the AD converter, an analog signal output from the pixel array in accordance with the horizontal transfer control signal and in synchronization with a clock signal supplied from the second clock generator.
3. The photoelectric conversion device according to claim 1 , wherein
the drive controller transfers, to the second clock generator, an image capturing control signal indicating an image capturing period for performing image capturing in the pixel array, and
in accordance with the image capturing control signal, the second clock generator starts to generate a clock signal used to control the AD converter.
4. The photoelectric conversion device according to claim 3 , wherein
based on the image capturing control signal, the AD converter starts an operation of converting an analog signal into a digital signal.
5. The photoelectric conversion device according to claim 1 , wherein
the AD converter samples an analog signal, which has been output from the horizontal transfer unit in synchronization with a clock signal supplied from the second clock generator, after a predetermined time has elapsed from an edge of the clock signal which has triggered output of the analog signal.
6. The photoelectric conversion device according to claim 1 , wherein
the horizontal transfer unit comprises a shift register in which a plurality of registers are connected in series, and an output of a last-stage register of the plurality of registers is connected to an input of a first-stage register of the plurality of registers, and
in the shift register, a pulse makes one cycle from the first-stage register to the last-stage register in one horizontal transfer period for transferring signals corresponding to one row of the pixel array.
7. The photoelectric conversion device according to claim 6 , wherein
number of the plurality of registers is defined by number of pixels, among the plurality of pixels, from which signals are transferred in the one horizontal transfer period, and a horizontal synchronization period.
8. The photoelectric conversion device according to claim 1 , wherein
each of the plurality of pixels comprises a photoelectric conversion element, and
not less than two photoelectric conversion elements share a floating diffusion.
9. The photoelectric conversion device according to claim 6 , wherein
each of the plurality of pixels comprises a photoelectric conversion element,
not less than two photoelectric conversion elements share a floating diffusion, and
number of the plurality of registers is defined by number of pixels, among the plurality of pixels, from which signals are transferred in the one horizontal transfer period, a horizontal synchronization period, and number of photoelectric conversion elements arranged in a row direction among the not less than two photoelectric conversion elements sharing the floating diffusion.
10. The photoelectric conversion device according to claim 1 , further comprising an oscillator,
wherein each of the first clock generator and the second clock generator generates a clock signal based on an output of the oscillator.
11. The photoelectric conversion device according to claim 1 , wherein
each of the first clock generator and the second clock generator comprises an oscillator configured to generate a clock signal.
12. The photoelectric conversion device according to claim 1 , wherein
the second clock generator supplies clock signals of different frequencies to the horizontal transfer unit and the AD converter, respectively, based on a reference clock signal in the second clock generator.
13. The photoelectric conversion device according to claim 12 , wherein
a frequency of a clock signal supplied from the second clock generator to the AD converter is higher than a frequency of a clock signal supplied from the second clock generator to the horizontal transfer unit.
14. The photoelectric conversion device according to claim 12 , wherein
the second clock generator supplies the reference clock signal to the AD converter, and supplies a clock signal obtained by dividing the reference clock signal to the horizontal transfer unit.
15. The photoelectric conversion device according to claim 1 , wherein
a frequency of a clock signal supplied to the AD converter by the second clock generator is higher than a frequency of a clock signal supplied to the drive controller by the first clock generator.
16. The photoelectric conversion device according to claim 1 , wherein
a frequency of a clock signal supplied to the horizontal transfer unit by the second clock generator is higher than a frequency of a clock signal supplied to the drive controller by the first clock generator.
17. The photoelectric conversion device according to claim 1 , wherein
the AD converter is a successive-approximation type AD converter.
18. The photoelectric conversion device according to claim 1 , further comprising a digital signal processor configured to perform digital signal processing on a digital signal output from the AD converter,
wherein the digital signal processor is supplied with a clock signal from the second clock generator via the AD converter.
19. A camera module comprising:
the photoelectric conversion device according to claim 1 ; and
an optical system configured to allow light to enter the photoelectric conversion device.
20. An endoscope comprising:
the camera module according to claim 19 ; and
a cable configured to transmit a signal output from the camera module.
21. An endoscope system comprising:
the endoscope according to claim 20 ; and
a signal processor connected to the cable, and configured to process a signal output from the camera module.
22. An apparatus comprising:
the photoelectric conversion device according to claim 1 ; and
a signal processor configured to process a signal output from the photoelectric conversion device.