Optical sensor and signal readout method thereof, optical area sensor and signal readout method thereof

Patent metadata

Field	Value
Publication number	US-2021217801-A1
Application number	US-201817267980-A
Country	US
Kind code	A1
Filing date	Aug 23, 2018
Priority date	Aug 23, 2018
Publication date	Jul 15, 2021
Grant date	—

Abstract

[Problem] To provide an optical sensor which can read out faster and requires lower power consumption than conventional optical sensors while maintaining advantages and superiorities of conventional optical sensors in which a transfer switch is provided between a light receiving element (PD) and a floating diffusion (CFD).
[Solution] A semiconductor junction of a light-receiving element is fully depleted and a potential curve of electrons has a negative slope toward the floating diffusion and connected to an uppermost position of an electronic potential well of the floating diffusion keeping its negative slope state.

First claim

1 . A signal readout method of an optical sensor, comprising performing light-receiving by a light-receiving element which has a semiconductor junction fully depleted and a potential curve of electrons having a negative slope toward a floating diffusion and connected to an uppermost position of an electronic potential well of the floating diffusion while keeping its negative slope state; and performing at least twice during each frame period provided in a period of the light-receiving, a step of transferring electrons generated in the light-receiving element in response to the light-receiving to the potential well according to the potential curve, and accumulating the electrons in the potential well.

2 . The signal readout method of an optical sensor according to claim 1 , wherein the accumulation period in the accumulating step is 1 μs or less.

3 . An optical sensor comprising:
a light-receiving element; a floating diffusion that is electrically directly connected to the light-receiving element and accumulates electric charges generated by light input to the light-receiving element; and a pixel signal line, wherein a signal readout path is connected to the pixel signal output line; a capacitance of the light-receiving element (CPD) and a capacitance of the floating diffusion (CFD) have the following relationship:
0.0008≤( CPD )/( CFD )≤0.8   (1)

4.0×10−18 F ≤( CPD )≤4.0×10−16 F   (2)

5.0×10−16 F ≤( CFD )≤5.0×10−15 F   (3); and

the light-receiving element has a semiconductor junction that is fully depleted and a potential curve of electrons that has a negative slope toward the floating diffusion direction and is connected to an uppermost position of an electronic potential well of the floating diffusion while keeping its negative slope state.

4 . An optical area sensor comprising:
(1) An optical sensor pixel circuit unit including: an optical sensor pixel circuit which has two output systems alternatively used on a time axis, a light-receiving element and a floating diffusion that is electrically directly connected to the light-receiving element and accumulates electric charges generated by light input to the light-receiving element; the light-receiving element having a semiconductor junction that is completely depleted and a potential curve of electrons that has a negative slope toward the floating diffusion and connected to an uppermost position of an electronic potential well of the floating diffusion while keeping its negative slope state; and an intra-pixel correlated double sampling circuit which outputs a signal (ab 1 ) produced by noise cancellation based on a first output (a 1 ) and a second output (b 1 ) based on an amount of light-electric charges generated in the light-receiving element by light-irradiation, which is output from one the output systems; and (2) An analog memory circuit unit including: an analog memory array in which a plurality of memory cells holding one of the signal (ab 1 ), the first output (a 2 ) and the second output (b 2 ) output from the other output system are arranged in rows and columns; a memory cell row selection switch array for selecting any of the rows of the memory cells; and a memory readout circuit for reading out a signal held in any of the memory cells.

5 . The optical area sensor according to claim 4 , wherein a capacitance (C PD ) of the light-receiving element and a capacitance (CFD) of the floating diffusion have the following relationship:
0.0008≤( C PD )/( C FD )≤0.8   (1)
4.0×10−18 F ≤( CPD )≤4.0×10−16 F   (2)
5.0×10−16 F ≤( CFD )≤5.0×10−15 F   (3).

6 . The optical area sensor according to claim 4 , wherein the optical sensor pixel circuit unit and the analog memory circuit unit are disposed adjacently to each other on a same planar.

7 . The optical area sensor according to claim 4 , wherein the optical sensor pixel circuit unit and the analog memory circuit unit are stacked adjacently to each other.

Assignees

• Univ Tohoku

Inventors

• Sugawa Shigetoshi
• Kuroda Rihito

Classifications

• H04N25/76

  Addressed sensors, e.g. MOS or CMOS sensors · CPC title

• H04N25/77

  Pixel circuitry, e.g. memories, A/D converters, pixel amplifiers, shared circuits or shared components · CPC title

• H04N25/53

  Control of the integration time · CPC title

• H04N25/78

  Readout circuits for addressed sensors, e.g. output amplifiers or A/D converters · CPC title

• H10F39/18 Primary

  Complementary metal-oxide-semiconductor [CMOS] image sensors; Photodiode array image sensors · CPC title