3D Vision On A Chip

• US 20070091175A1
• Filed: 12/18/2006
• Published: 04/26/2007
• Est. Priority Date: 09/28/1998
• Status: Active Grant

• Current Assignee: Microsoft International Holdings BV (Microsoft Corporation)
• Original Assignee: 3DV Systems Ltd. (Microsoft Corporation)
• Inventors: Iddan, Gavriel, Yahav, Giora
• Granted Patent: US 8,102,426 B2
• Time in Patent Office: Days
• US Class Current: 348/135
• CPC Class Codes: G01S 17/08 for measuring distance only indirect measurement G01S17/46; active triangulation systems G01S17/48
• CPC Class Codes: G01S 17/14 wherein a voltage or current pulse is initiated and terminated in accordance with the pulse transmission and echo reception respectively, e.g. using counters
• CPC Class Codes: G01S 17/18 wherein range gates are used
• CPC Class Codes: G01S 17/89 for mapping or imaging
• CPC Class Codes: G01S 7/4863 Detector arrays, e.g. charge-transfer gates
• CPC Class Codes: H04N 13/207 using a single 2D image sensor
• CPC Class Codes: H04N 13/254 in combination with electromagnetic radiation sources for illuminating objects
• CPC Class Codes: H04N 23/56 provided with illuminating means
• CPC Class Codes: H04N 25/63 applied to dark current
• CPC Class Codes: H04N 25/76 Addressed sensors, e.g. MOS or CMOS sensors
• CPC Class Codes: H04N 25/77 Pixel circuitry, e.g. memories, A/D converters, pixel amplifiers, shared circuits or shared components
• CPC Class Codes: H04N 5/2226 Determination of depth image, e.g. for foreground/background separation determining depth by image analysis in general G06T7/50; segmentation by image analysis in general G06T7/10

Abstract

A 3D camera for determining distances to regions in a scene comprising: a photosurface having a plurality of pixels each of which comprises a circuit having a light sensitive element that provides a current responsive to light incident thereon, wherein the circuit comprises, at least one amplifier inside the pixel, having an input and an output; at least one feedback capacitor separate from the light sensitive element and connected between the input and output of each of the at least one amplifier; at least one controllable connection through which current flows from the light sensitive element into the input of the at least one amplifier; a light source; and, a controller that, controls the light source to illuminate the scene with light, opens and closes the at least one controllable connection to gate or modulate current from the light sensitive element of a pixel in the photosurface responsive to the time dependence of the gating or modulation of the light, controls the at least one controllable connection to provide a current for correcting biases caused by at least one of background light or dark current, and determines a distance to a region imaged on the pixel responsive to an amount of charge integrated on the feedback capacitor responsive to the gated or modulated current and the corrected biases.

Claims

1. A 3D camera for determining distances to regions in a scene comprising:

a photosurface having a plurality of pixels each of which comprises a circuit having a light sensitive element that provides a current responsive to light incident thereon, wherein the circuit comprises,

at least one amplifier inside the pixel, having an input and an output;

at least one feedback capacitor separate from the light sensitive element and connected between the input and output of each of the at least one amplifier;

at least one controllable connection through which current flows from the light sensitive element into the input of the at least one amplifier;

a light source; and

,

a controller that,

controls the light source to illuminate the scene with gated light,

opens and closes the at least one controllable connection to gate or modulate current from the light sensitive element of a pixel in the photosurface responsive to the time dependence of the gating or modulation of the light,

controls the at least one controllable connection to provide a current for correcting biases caused by at least one of background light or dark current, and

determines a distance to a region imaged on the pixel responsive to an amount of charge integrated on the feedback capacitor responsive to the gated or modulated current and the corrected biases.

2. A 3D camera according to claim 1, wherein the amplifier is an operational amplifier.

3. A 3D camera according to claim 2, wherein the circuit comprises at least one data bus and wherein the circuit comprises at least one address switch that connects a data bus of the at least one data bus to an output of one of the at least one amplifiers, either directly or via another switch.

4. A 3D camera according to claim 2, wherein the at least one controllable connection comprises at least one gate switch and the controller opens and closes the at least one gate switch to gate the pixel on and off and determines a distance to a region imaged on the pixel responsive to an amount of charge integrated on the feedback capacitor of the at least one amplifier during times at which the pixel is gated on.

5. A 3D camera according to claim 4, wherein the at least one gate switch comprises a single gate switch that connects the light sensitive element to one amplifier.

6. A 3D camera according to claim 5, wherein the capacitor is connected to the at least one amplifier by a plurality of connection switches such that:

for a first combination of open and closed connection switches a first terminal of the capacitor is connected to the input of the amplifier and a second terminal of the capacitor is connected to the output of the amplifier; and

for a second combination of open and closed connection switches the first terminal of the capacitor is connected to the output of the amplifier and the second terminal of the capacitor is connected to the input of the amplifier.

7. A 3D camera according to claim 6, wherein the controller controls the light source to illuminate the scene with a plurality of light pulses, each having a pulse width and wherein the controller gates pixels in the photosurface on or off at times responsive to times at which light pulses of the plurality of light pulses are radiated.

8. A 3D camera according to claim 7, wherein the controller gates a pixel on for a first gate period following each light pulse in the plurality of light pulses and wherein during the first gate period the controller controls the connection switches according to the first combination and current from the pixel'"'"'s light sensitive element responsive to background light and light from the radiated light pulse reflected by a region imaged by the pixel plus dark current is integrated on the capacitor and increases voltage across the capacitor.

9. A gated 3D camera according to claim 8, wherein the controller gates the pixel on for a second gate period following each light pulse in the plurality of light pulses and wherein during the second gate period light from the light pulse reflected by the region does not reach the pixel and the controller controls the connection switches according to the second combination so that dark current and current from the pixel'"'"'s light sensitive element responsive to background light is integrated on the capacitor and decreases voltage across the capacitor.

10. A 3D camera according to claim 4, wherein the at least one amplifier comprises first and second amplifiers having first and second feedback capacitors respectively and the at least one gate switch comprises first and second gate switches, the first gate switch connecting the light sensitive element to the input of the first amplifier and the second gate switch connecting the light sensitive element to the input of the second amplifier.

11. A 3D camera according to claim 10, further comprising at least one address switch comprised of first and second address switches, the first address switch connecting the output of the first amplifier to the data bus and the second address switch connecting the output of the second amplifier to the data bus.

12. A 3D camera according to claim 10, wherein the circuit additionally comprises a third amplifier having positive and negative inputs and an output, wherein the output of the first amplifier is connected to the positive input of the third amplifier, the output of the second amplifier is connected to the negative input of the third amplifier and wherein the output of the third amplifier is connected by at least one address switch to the data bus.

13. A 3D camera according to claim 10, wherein the controller controls the light source to illuminate the scene with a plurality of light pulses, each having a pulse width, and wherein the controller gates pixels in the photosurface on or off at times responsive to times at which light pulses of the plurality of light pulses are radiated.

14. A 3D camera according to claim 13, wherein the controller is operative to:

gate pixels on for a first gate period after a first time lapse following each radiated light pulse of a first plurality of radiated light pulses such that current from the light sensitive element is integrated by the first capacitor; and

gate pixels on for a second gate period after a second time lapse following each radiated light pulse of a second plurality of radiated light pulses such that current from the light sensitive element is integrated by the second capacitor.

15. A 3D camera according to claim 14, wherein the mid points of first and second gate periods are delayed with respect to the radiated light pulses that they respectively follow by the same amount of time.

16. A 3D camera according to claim 14, wherein the duration of the first gate period is substantially equal to the pulse width of the radiated light pulses.

17. A 3D camera according to claim 14, wherein the duration of the second gate is greater than or equal to three times the pulse width.

18. A 3D camera according to claim 14, wherein the first time lapse is such that light reflected by a region in the scene from the light pulse reaches a pixel on which the region is imaged during the first gate period, and current from the pixel'"'"'s light sensitive element responsive to background light, light reflected from the radiated light pulse by the region plus dark current is integrated on the first capacitor.

19. A 3D camera according to claim 14, wherein the second time lapse is such that light reflected by a region in the scene from the light pulse does not reach the light sensitive element during the second gate period and current from the pixel'"'"'s light sensitive element responsive to background light plus dark current is integrated on the second capacitor.

20. A 3D camera according to claim 9, wherein the duration of the first gate and the duration of the second gate are controlled to be substantially equal.

21. A 3D camera according to claim 9, wherein the duration of the first and second gates is substantially equal to the pulse width of the radiated light pulses.

22. A 3D camera according to claim 4, wherein the circuit comprises a reset switch connected to the light sensitive element and wherein when the reset switch is closed, voltage across the light sensitive element is set to a predetermined magnitude.

23. A 3D camera according to claim 22, wherein before the controller gates a pixel on, the controller closes and opens the reset switch of the pixel at least once so that voltage across the light sensitive element is the same each time the pixel is gated on.

24. A 3D camera according to claim 4, wherein the controller gates at least one pixel in the photosurface independently of other pixels in the photosurface.

25. A 3D camera according to claim 24, wherein pixels in the photosurface are grouped into different pixel groups and pixels in a same pixel group are gated on and off by the controller simultaneously and wherein each pixel group is controlled independently of other pixel groups.

26. A 3D camera according to claim 1, wherein the controller controls the light source to illuminate the scene with a plurality of light pulses, each having a pulse width, and wherein the controller gates pixels in the photosurface on or off at times coordinated with times at which light pulses of the plurality of light pulses are radiated.

27. A 3D camera according to claim 1, wherein the at least one controllable connection comprises at least one modulator.

28. A 3D camera according to claim 27, wherein the at least one modulator comprises one modulator that connects the light sensitive element to the input of one amplifier.

29. A 3D camera according to claim 27, wherein the controller controls the at least one modulator to modulate the current from the light sensitive element harmonically.

30. A 3D camera according to claim 27, wherein the at least one modulator is controllable to modulate the current from the light sensitive element pseudo randomly.

31. A 3D camera according to claim 29, wherein the modulated light is harmonically modulated.

32. A 3D camera according to claim 31, wherein the modulated light and the current are modulated at a same frequency of modulation.

33. A 3D camera according to claim 32, wherein the modulation of the light and the current are in phase.

34. A 3D camera according to claim 27, wherein current from the light sensitive element of at least two pixels is modulated at different frequencies.

35. A method of generating a signal responsive to light reflected by an object from a light pulse radiated by a light source, wherein the signal is corrected for effects of background light and dark current, the method comprising:

sensing the reflected light with a gated sensor that is gated on for a first gate period at a first time determined responsive to a time at which the light pulse is radiated so that at least some of the reflected light from the light pulse is incident on the sensor to generate a first signal having a first value;

gating the sensor on for a second gate period at a second time determined responsive to the time at which the light pulse is radiated so that during the second gate period light from the light source is not incident on the sensor to generate a second signal having a second value; and

subtracting the second value from the first value to form a corrected value.

36. A method according to claim 35, wherein the first gate is such that only a portion of the reflected light incident on the sensor is used to generate the signal having the first value.

37. A method according to claim 35, wherein the first gate is such that substantially all of the reflected light incident on the sensor is used to generate the signal having the first value.