Image sensor and image capturing apparatus
An image sensor of a photon counting type that suppresses a reduction in the efficiency of photon detection dependent on a pixel position, is disclosed. The image sensor comprising a pixel region in which a plurality of pixels are arrayed in a matrix, each pixel including a photoelectric conversion region and an avalanche breakdown region. In a plan view of a pixel, a size of the avalanche breakdown region is smaller than a size of the photoelectric conversion region. In addition, at least some of pixels arranged in a peripheral region of the pixel region, the avalanche breakdown region is formed such that a position thereof is shifted with respect to a position of the avalanche breakdown region in pixels arranged in a central region of the pixel region.
1. An image sensor comprising:
a pixel region in which a plurality of pixels are arrayed in a matrix, each pixel including a photoelectric conversion region that generates charges through photoelectric conversion of incident light, and an avalanche breakdown region in which avalanche breakdown occurs due to the charges generated by the photoelectric conversion,
wherein
in a plan view of each pixel arrayed in the pixel region, a size of the avalanche breakdown region is smaller than a size of the photoelectric conversion region, and
in at least some of pixels that are arranged in a peripheral region of the pixel region among the pixels arrayed in the pixel region, the avalanche breakdown region is formed in such a manner that a position thereof is shifted with respect to a position of the avalanche breakdown region in pixels arranged in a central region of the pixel region.
2. The image sensor according to claim 1 , wherein
in a predetermined pixel among the pixels arrayed in the pixel region, the avalanche breakdown region is formed in such a manner that a position thereof is shifted in a direction away from a reference position of the pixel region compared to a position of the avalanche breakdown region in other pixels.
3. The image sensor according to claim 2 , wherein
each pixel further includes a first conductive type region to which a first voltage is applied, and a second conductive type region which forms a junction surface together with the first conductive type region and to which a second voltage is applied, and
a position where the avalanche breakdown region is formed is controlled in accordance with a position where the first conductive type region or the second conductive type region is formed.
4. The image sensor according to claim 3 , wherein
in the predetermined pixel, the position where the first conductive type region or the second conductive type region is formed is based on an average position where photoelectric conversion occurs in the photoelectric conversion region.
5. The image sensor according to claim 4 , wherein
the average position is based on a penetration depth of light of a wavelength corresponding to a color of a color filter provided in each pixel.
6. The image sensor according to claim 2 , wherein
a magnitude of a positional shift of the avalanche breakdown region is based on a distance between the predetermined pixel and the reference position.
7. The image sensor according to claim 2 , wherein
the predetermined pixel is a pixel that is at a distance of a threshold or more from the reference position.
8. The image sensor according to claim 2 , wherein
each pixel further includes a microlens, and
in the predetermined pixel, the microlens is formed in such a manner that a center thereof is at a position that is shifted in a direction toward the reference position.
9. The image sensor according to claim 2 , wherein
each pixel further includes a microlens,
the predetermined pixel is a pixel that is at a distance of a threshold or more from the reference position, and
in the predetermined pixel and one or more pixels that are at a shorter distance from the reference position than the predetermined pixel, the microlens is formed in such a manner that a center thereof is at a position that is shifted in a direction toward the reference position.
10. The image sensor according to claim 8 , wherein
a magnitude of the positional shift of the microlens is based on a distance between the predetermined pixel and the reference position.
11. The image sensor according to claim 9 , wherein
a magnitude of the positional shift of the microlens is based on a distance between the predetermined pixel and the reference position.
12. The image sensor according to claim 2 , wherein
the predetermined pixel includes a plurality of avalanche breakdown regions, and each of the plurality of avalanche breakdown regions is formed at a position that is shifted in a direction away from the reference position compared to a position of the avalanche breakdown region.
13. The image sensor according to claim 2 , wherein
the predetermined pixel is a pixel including a light-shielding film that blocks light from entering a part of a light-receiving region, and
a magnitude of the positional shift of the avalanche breakdown region is based on a position of an aperture area included in the light-shielding film.
14. The image sensor according to claim 2 , wherein
the reference position is an optical axis center at which an optical axis of an imaging optical system and the pixel region intersect with each other.
15. The image sensor according to claim 2 , wherein
the reference position is a center of the pixel region.
16. An image sensor comprising:
a pixel region in which a plurality of pixels are arrayed, each pixel including an avalanche breakdown region in which avalanche breakdown occurs due to charges generated by photoelectric conversion, and an electrode for applying a voltage for the avalanche breakdown,
wherein
in a pixel that is arranged in a first position of the pixel region among the pixels arrayed in the pixel region, the electrode is formed in such a manner that a position thereof is shifted in a direction away from a reference position of the pixel region compared to a position of the electrode in a pixel that is arranged in a second position that is different from the first position.
17. An image sensor comprising:
a pixel region in which a plurality of pixels are arrayed, each pixel including an avalanche breakdown region in which avalanche breakdown occurs due to charges generated by photoelectric conversion,
wherein
in a pixel that is arranged in a first position of the pixel region among the pixels arrayed in the pixel region, the avalanche breakdown region is formed in such a manner that a position thereof is shifted in a direction away from a reference position of the pixel region compared to a position of the avalanche breakdown region in a pixel that is arranged in a second position that is different from the first position.
18. An image capturing apparatus, comprising:
an image sensor; and
a processor for controlling a readout mode of the image sensor,
wherein the image sensor comprises:
a pixel region in which a plurality of pixels are arrayed in a matrix, each pixel including a photoelectric conversion region that generates charges through photoelectric conversion of incident light, and an avalanche breakdown region in which avalanche breakdown occurs due to the charges generated by the photoelectric conversion,
wherein
in a plan view of each pixel arrayed in the pixel region, a size of the avalanche breakdown region is smaller than a size of the photoelectric conversion region, and
in at least some of pixels that are arranged in a peripheral region of the pixel region among the pixels arrayed in the pixel region, the avalanche breakdown region is formed in such a manner that a position thereof is shifted with respect to a position of the avalanche breakdown region in pixels arranged in a central region of the pixel region.