Imaging device and camera system including sense circuits to make binary decision
An imaging device includes: a pixel array section having an array of pixels, each of which has a photoelectric converting device and outputs an electric signal according to an input photon; a sense circuit section having a plurality of sensor circuits each of which makes binary decision on whether there is a photon input to a pixel in a predetermined period upon reception of the electric signal therefrom; and a decision result IC section which integrates decision results from the sense circuits, pixel by pixel or for each group of pixels, multiple times to generate imaged data with a gradation, the decision result IC section including a count circuit which performs a count process to integrate the decision results from the sense circuits, and a memory for storing a counting result for each pixel from the count circuit, the sense circuits sharing the count circuit for integrating the decision results.
1. An imaging device comprising:
a pixel array having an array of pixels in a first semiconductor substrate, each of the pixels having a photoelectric converting device and outputting an electric signal according to an input photon;
a plurality of sense circuits in a second semiconductor substrate, each of the sense circuits making a binary decision on whether there is a photon input to a pixel in a predetermined period upon reception of the electric signal therefrom; and
a decision result IC in the second semiconductor substrate including
a count circuit which performs a count process to integrate the decision results from the sense circuits, and
a memory which stores a counting result for each pixel from the count circuit.
2. The imaging device according to claim 1 , wherein the pixel array has a plurality of pixel blocks formed therein each including a plurality of pixels to be selected by selection circuitry, and
the sense circuit has independent sense circuits arranged therein in association with the pixel blocks.
3. The imaging device according to claim 2 , wherein the selection circuitry, in the sense circuit section, cyclically selects each pixel in the pixel block, and outputs a signal of the selected pixel to the sense circuit, and
the sense circuit makes a decision on whether a photon is input to each pixel in a given period from previous selection to current selection.
4. The imaging device according to claim 3 , wherein the imaging device includes a reset function of resetting each of the pixels to a state where a photon is not input, and
an adjustment function of adjusting an exposure period by inserting a reset process to set the exposure period constant for the individual pixels between selective outputting of each pixel and next selective outputting in the pixel block.
5. The imaging device according to claim 1 , wherein the imaging device includes a reset function of resetting each of the pixels to a state where a photon is not input, wherein each of the sense circuits carries out the binary decision by reading a signal in a reset state and a read signal after exposure, and comparing the signals one of which is added with an offset with each other.
6. The imaging device according to claim 1 , wherein the decision result IC has a function of adding count values for a plurality of pixels via the count circuit shared by the pixels.
7. The imaging device according to claim 1 , wherein the first semiconductor substrate and the second semiconductor substrate are connected together by adhesion of polished junction surfaces thereof, and
output signals from the pixels or the pixel blocks are transferred to the respective sense circuits via capacitors formed at the junction surfaces.
8. The imaging device according to claim 1 , wherein the plurality of sense circuits have a function of repeatedly executing binary decision in a unit frame period multiple times, and integrating the decision results to derive an amount of photons input to a light receiving surface, and
a function of variably setting a cycle period of the decision within a range of a plurality of cycle periods according to N times a unit cycle period (N being an integer).
9. The imaging device according to claim 8 , wherein the imaging device includes a mode of carrying out derivation of the amount of photons input in a same unit frame period in a small number of decisions over a long cycle period, and a mode of carrying out the derivation of the amount of photons input in a large number of decisions over a short cycle period.
10. The imaging device according to claim 9 , wherein a plurality of decisions including a decision in a short cycle period and a decision in a long cycle period are further cyclically made in the unit frame period, results of the decisions are combined and integrated to derive an amount of photons input to the light receiving surface.
11. The imaging device according to claim 8 , wherein a small number of decisions are made over a long cycle period in imaging at low illuminance, and a large number of decisions are made over a short cycle period in imaging at high illuminance.
12. The imaging device according to claim 1 , wherein two or more pixels share each of the count circuits.