Photo detecting apparatus for detecting reflected light from an object and excluding an external light componet from the reflected light

• US 5,705,807 A
• Filed: 10/24/1995
• Issued: 01/06/1998
• Est. Priority Date: 10/24/1994
• Status: Expired due to Term

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Throngnumchai, Kraisorn, Nousou, Kazunori
• Primary Examiner(s): LE, QUE TAN
• Application Number:
  US08/547,230
• Time in Patent Office: 805 Days
• Field of Search: 250/214 P, 250/214 A, 250/214.1, 250/214 R, 250/214 B, 356/221, 356/225, 356/226, 327/509, 327/514, 327/517, 330/308, 330/59, 330/9, 330/51, 396/80, 396/111, 396/120
• US Class Current: 250/214.00P
• CPC Class Codes: G01J 1/4228 arrangements with two or more detectors, e.g. for sensitivity compensation
• CPC Class Codes: H01L 27/14609 Pixel-elements with integrated switching, control, storage or amplification elements scanning details of imagers (circuitry of solid-state image sensors H04N25/00); circuitry of imagers H04N25/70
• CPC Class Codes: H01L 27/14643 Photodiode arrays; MOS imagers
• CPC Class Codes: H03F 3/005 using switched capacitors, e.g. dynamic amplifiers; using switched capacitors as resistors in differential amplifiers H03F3/45 takes precedence
• CPC Class Codes: H03F 3/087 with IC amplifier blocks H03F3/085 takes precedence

Abstract

There is provided a photosensor having a photoelectric converter for converting incident light into a photoelectric current, and a function of removing noise light from imaging light including noise light and reflected from an object to be photographed. A plurality of photosensors each having the arrangement are used as an image sensor. A single photosensor having the arrangement or a plurality of photosensors each having the arrangement are used as a distance sensor. There is provided a photosensor in which a storage unit stores electric quantity corresponding to fixed light, and electric quantity corresponding to reflected light in the state wherein electric quantity stored in the storage unit is reproduced by a reproduction unit is introduced, and the difference therebetween is reproduced as an electric signal. A single photosensor having the arrangement or a plurality of photosensors each having the arrangement are used as a distance sensor. The plurality of photosensors are used as an image or distance image sensor.

Claims

1. A photo detecting apparatus for detecting reflected light from an object and excluding an external light component from the reflected light comprising:

a light-emitting unit for emitting light; and

a photo detecting unit, having a plurality of pixels, for detecting light reflected from an object;

the photo detecting unit, for each pixel, having photoelectric conversion means for converting incident light into a photoelectric current; and

differential electric quantity generation means for calculating a difference between an electric quantity based on a photoelectric current obtained by said photoelectric conversion means in a first period and an electric quantity based on a photoelectric current obtained by said photoelectric conversion means in a second period;

wherein the first period is a period in which the light-emitting unit is emitting light, and the second period is a period in which the light-emitting unit is not emitting light.

2. The photodetecting apparatus to claim 1, wherein:

said differential electric quantity generation means comprises;

a first storing electrostatic capacitor in which charges serving as electric quantity corresponding to the first period are stored;

a second storing electrostatic capacitor in which charges serving as electric quantity corresponding to the second period are stored;

transfer means for subtracting the charges stored in the second storing electrostatic capacitor from the charges stored in the first storing electrostatic capacitor and transferring resultant charges; and

a holding electrostatic capacitor in which the charges transferred by said transfer means are stored.

3. The photodetecting apparatus according to claim 1, wherein:

said differential electric quantity generation means comprises;

a storing electrostatic capacitor in which charges serving as electric quantity corresponding to the first or second period are stored;

transfer means for transferring charges serving as electric quantity corresponding to the second or first period converted by said photoelectric conversion means and the charges stored in said storing electrostatic capacitor in characteristics opposite to each other; and

a holding electrostatic capacitor in which the charges transferred by said transfer means are stored.

4. The photodetecting apparatus according to claim 1, wherein:

said differential electric quantity generation means comprises;

transfer means for transferring charges serving as electric quantity corresponding to the first period converted by said photoelectric conversion means and charges serving as electric quantity corresponding to the second period in characteristics opposite to each other; and

a holding electrostatic capacitor in which the charges transferred by said transfer means are stored.

5. The photodetecting apparatus according to claim 1, wherein:

said differential electric quantity generation means comprises;

a storing electrostatic capacitor in which, after charges serving as electric quantity corresponding to the first period converted by said photoelectric conversion means are stored, charges serving as electric quantity corresponding to the second period are stored in opposite characteristics;

transfer means for transferring the charges stored in said storing electrostatic capacitor; and

a holding electrostatic capacitor in which the charges transferred by said transfer means are stored.

6. The photodetecting apparatus according to claim 1, wherein:

said differential electric quantity generation means comprises;

a storing electrostatic capacitor for storing charges serving as electric quantity corresponding to the first period converted by said photoelectric conversion means and charges serving as electric quantity corresponding to the second period in characteristics opposite to each other;

transfer means for transferring the charges serving as electric quantity corresponding to the first period stored in said storing electrostatic capacitor, and after that, transferring the charges serving as electric quantity corresponding to the second period stored in said storing electrostatic capacitor; and

a holding electrostatic capacitor for storing the charges transferred by said transfer means.

7. The photodetecting apparatus according to claim 2, wherein:

said differential electric quantity generation means further comprises;

storing time change means for amplifying a current stored as charges in said first storing electrostatic capacitor by a predetermined plural number, and storing, in said second storing electrostatic capacitor, charges in a period which is the predetermined plural number times as long as a predetermined period stored in said first storing electrostatic capacitor.

8. The photodetecting apparatus according to claim 2, wherein:

said differential electric quantity generation means further comprises;

storing time change means for amplifying a voltage based on charges stored in said first storing electrostatic capacitor in a predetermined period by a predetermined plural number, and storing, in said second storing electrostatic capacitor, charges in a period which is the predetermined plural number times as long as the predetermined period.

9. The photodetecting apparatus according to claim 2, wherein:

said differential electric quantity generation means further comprises;

storing time change means for setting a capacitance of said first storing electrostatic capacitor to be 1/(a predetermined number) times as large as a capacitance of said second storing electrostatic capacitor.

10. The photodetecting apparatus according to claim 2, wherein:

said differential electric quantity generation means further comprises;

storing time change means for holding charges stored in said first storing electrostatic capacitor in a predetermined period in a period which is a predetermined plural number times as long as the predetermined period, and storing charges in said second storing electrostatic capacitor every predetermined period.

11. The photodetecting apparatus according to claim 2, wherein:

said differential electric quantity generation means further comprises;

storing time changing means for storing, in said first storing electrostatic capacitor, charges obtained by detection for a time which is a predetermined plural number times as long as a predetermined time, for the predetermined time, or storing, in said first storing electrostatic capacitor, 1/(the predetermined plural number) charges obtained by detection for a time which is a predetermined plural times as long as a predetermined time,

for storing charges in said second storing electrostatic capacitor for the predetermined time, and subtracting the charges stored for the predetermined time or the 1/(the predetermined plural number) charges from the charges stored in said second storing electrostatic capacitor, and

for transferring resultant charges to said holding electrostatic capacitor.

12. The photodetecting apparatus according to claim 3, wherein:

said differential electric quantity generation means further comprises;

storing time change means for amplifying a current stored as charges in said storing electrostatic capacitor by a predetermined plural number, and storing, in said holding electrostatic capacitor, charges in a period which is the predetermined plural number times as long as a predetermined period stored in said storing electrostatic capacitor.

13. The photodetecting apparatus according to claim 3, wherein:

said differential electric quantity generation means further comprises;

storing time change means for amplifying a voltage based on charges stored in said storing electrostatic capacitor in a predetermined period by a predetermined plural number, and storing, in said holding electrostatic capacitor, charges in a period which is the predetermined plural number times as long as the predetermined period.

14. The photodetecting apparatus according to claim 3, wherein:

said differential electric quantity generation means further comprises;

storing time change means for setting a capacitance of said storing electrostatic capacitor to be 1/(a predetermined number) times as large as a capacitance of said holding electrostatic capacitor.

15. The photodetecting apparatus according to claim 3, wherein:

said differential electric quantity generation means further comprises;

storing time change means for holding charges stored in said storing electrostatic capacitor in a predetermined period in a period which is a predetermined plural number times as long as the predetermined period, and storing charges in said holding electrostatic capacitor every predetermined period.

16. The photodetecting apparatus according to claim 6, wherein:

said differential electric quantity generation means further comprises;

storing time change means for amplifying a current which corresponds to the first period and is stored as charges in said storing electrostatic capacitor in a predetermined period by a predetermined plural number, and storing, in said storing electrostatic capacitor, charges corresponding to the second period in a period which is the predetermined plural number times as long as the predetermined period.

17. The photodetecting apparatus according to claim 6, wherein:

said differential electric quantity generation means further comprises;

storing time change means for amplifying a voltage based on charges which correspond to the first period and are stored in said storing electrostatic capacitor in a predetermined period by a predetermined plural number, and storing, in said holding electrostatic capacitor, charges corresponding to the second period in a period which is the predetermined plural number times as long as the predetermined period.

18. The photodetecting apparatus according to claim 2, wherein:

said transfer means comprises, an electric switch comprising an arithmetic amplifier and a MOSFET, an electric switch comprising a unit gain buffer comprising a voltage follower and a MOSFET, or an electric switch including a source follower type MOSFET and a MOSFET.

19. The photodetecting apparatus according to claim 2, wherein:

at least part of said storing electrostatic capacitor, said first storing electric capacitor, or said second storing electric capacitor is formed by a junction capacitor of said photoelectric conversion means or a parasitic capacitor of a wiring.

20. The photodetecting apparatus according to claim 2, wherein:

at least part of said holding electrostatic capacitor is formed by an input capacitor of said arithmetic amplifier or said unit gain buffer or a parasitic capacitor of a wire.

21. A photosensor group, comprising:

a plurality of photosensors, each photosensor comprising,

photoelectric conversion means for converting incident light into a photoelectric current, and

differential electric quantity generation means for calculating a difference between an electric quantity based on a photoelectric current obtained by said photoelectric conversion means in a first period and an electric quantity based on a photoelectric current obtained by said photoelectric conversion means in a second period, said first period being a period in which a light emitting unit is emitting light, and said second period being a period in which the light emitting unit is not emitting light;

said differential electric quantity generation means including,

a first storing electrostatic capacitor in which charges serving as electric quantity corresponding to the first period are stored,

a second storing electrostatic capacitor in which charges serving as electric quantity corresponding to the second period are stored,

transfer means for subtracting the charges stored in the second storing electrostatic capacitor from the charges stored in the first storing electrostatic capacitor and transferring resultant charges, and

a holding electrostatic capacitor in which the charges transferred by said transfer means are stored;

a wire for one- or two-dimensionally connecting said plurality of photosensors to each other; and

a plurality of scanning switches for selecting said plurality of photosensors, respectively.

22. A photosensor, comprising:

photoelectric conversion means for converting incident light into a photoelectric current, and

differential electric quantity generation means for calculating a difference between an electric quantity based on a photoelectric current obtained by said photoelectric conversion means in a first period and an electric quantity based on a photoelectric current obtained by said photoelectric conversion means in a second period, said first period being a period in which a light emitting unit is emitting light, and said second period being a period in which the light emitting unit is not emitting light;

wherein, said differential electric quantity generation means comprises;

storage means for storing electric quantity based on a photoelectric current in the first period;

reproduction means for reproducing, in the second period, the electric quantity stored in said storage means; and

generation means for performing addition or subtraction of electric quantity based on a photoelectric current in the second period and the electric quantity reproduced by said reproduction means to generate a difference therebetween as electric quantity.

23. A photosensor according to claim 22, wherein:

said reproduction means comprises a MOSFET, and said storage means comprises a gate capacitor of said MOSFET.

24. The photosensor group, comprising:

a plurality of photosensors, each photosensor comprising a photosensor according to claim 22,

a wire for one- or two-dimensionally connecting said plurality of photosensors to each other; and

a plurality of scanning switches for selecting said plurality of photosensors, respectively.

25. The photosensor group of claim 24, wherein

the reproduction means of each said photosensor comprises a MOSFET, and the corresponding storage means of each said photosensor comprises a gate capacitor of said MOSFET.

26. A photo detecting apparatus for detecting reflected light from an object and excluding external light component from the reflected light, comprising:

a light-emitting unit for emitting light; and

a photo detecting unit, having a plurality of pixels, for detecting light reflected from an object;

the photo detecting unit, for each pixel, having a photoelectric conversion device for converting the detected light into current;

a high-pass filter or a bandpass filter for passing a time frequency component, having a frequency higher than a predetermined frequency, of an output from said photoelectric conversion means under a state that said light-emitting unit is emitting light on the object; and

a holding electrostatic capacitor in which the charged having passed through the filter are stored.

27. The photo detecting apparatus according to claim 26 wherein:

a holding electrostatic capacitor which is at least part of an integrator is arranged, an output terminal of said high-pass filter or said bandpass filter is connected to said integrator constituted by said holding electrostatic capacitor, and said high-pass filter or said bandpass filter has an order of not less than 2.

28. The photodetecting apparatus according to claim 26, wherein:

said high-pass filter or said bandpass filter is constituted by a switched capacitor type circuit.

29. A method of sensing distance using a light-emitting unit and a photosensor, said photosensor comprising photoelectric conversion means for converting incident light into a photoelectric current and differential electric quantity generation means for calculating a difference between an electric quantity based on a photoelectric current obtained by said photoelectric conversion means in a first period and an electric quantity based on a photoelectric current obtained by said photoelectric conversion means in a second period, said first period being a period in which the light emitting unit is emitting light, and said second period being a period in which the light emitting unit is not emitting light and wherein the incident light related to the first period is regarded as fixed light and the incident light related to the second period is regarded as reflected light related to light emitted from said light-emitting means, wherein said differential electric quantity generation means comprises, storage means for storing electric quantity based on a photoelectric current in the first period, reproduction means for reproducing, in the second period, the electric quantity stored in said storage means, and generation means for performing addition or subtraction of electric quantity based on a photoelectric current in the second period and the electric quantity reproduced by said reproduction means to generate a difference therebetween as electric quantity, said method comprising:

emitting light from said light emitting unit;

detecting light reflecting from an object; and

measuring a time from light emission of said light emitting unit to generation of an electric quantity by said generation means.

30. The method of claim 29, wherein

said reproduction means comprises a MOSFET, and said storage means comprises a gate capacitor of said MOSFET.

31. In a photosensor group including

a plurality of photosensors, each photosensor comprising

photoelectric conversion means for converting incident light into a photoelectric current, and

differential electric quantity generation means for calculating a difference between an electric quantity based on a photoelectric current obtained by said photoelectric conversion means in a first period and an electric quantity based on a photoelectric current obtained by said photoelectric conversion means in a second period, said first period being a period in which a light emitting unit is emitting light, and said second period being a period in which the light emitting unit is not emitting light, wherein said differential electric quantity generation means comprises.

storage means for storing electric quantity based on a photoelectric current in the first period,

reproduction means for reproducing, in the second period, the electric quantity stored in said storage means, and

generation means for performing addition or subtraction of electric quantity based on a photoelectric current in the second period and the electric quantity reproduced by said reproduction means to generate a difference therebetween as electric quantity;

a wire for one- or two-dimensionally connecting said plurality of photosensors to each other; and

a plurality of scanning switches for selecting said plurality of photosensors, respectively;

a method for sensing an image, comprising;

sensing the incident light with said plurality of photosensors;

processing the incident light related to the first period as noise light; and

processing the incident light related to the second period as imaging light including the noise light and reflected light from an object to be photographed.