3D Vision On A Chip

Abstract

A 3D camera for determining distances to regions in a scene wherein gating or modulating apparatus for the 3D camera is incorporated on a photosurface of the camera on which light detectors of the camera are also situated. Each pixel in the photosurface may include its own pixel circuit for gating the pixel on or off or for modulating the sensitivity of the pixel to incident light. The circuit may comprise at least one amplifier inside the pixel, 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, and at least one controllable connection through which current flows from the light sensitive element into the input of the at least one amplifier. The 3D camera may further include a light source and a controller.

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 each pixel, having an input and an output; 
 at least one feedback capacitor separate from the light sensitive element and 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; 
 at least one controllable connection inside each pixel through which the 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, 
 gates or modulates the current from the light sensitive element of each pixel in the photosurface through the at least one controllable connection by opening or closing the at least one controllable connection of each pixel in the photosurface to gate the pixel on and off responsive to the time dependence of the gating or modulation of the light, 
 controls the at least one controllable connection to correct for biases caused by at least one of background light or dark current, and 
 determines a distance to a region imaged on a pixel responsive to an amount of charge integrated on the at least one feedback capacitor responsive to the gated or modulated current and the corrected biases; 
   the at least one controllable connection including at least one gate switch that connects the light sensitive element to one amplifier 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.   
     
     
         2 . 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 responsive to times at which light pulses of the plurality of light pulses are radiated. 
     
     
         3 . A 3D camera according to  claim 2 , 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. 
     
     
         4 . A gated 3D camera according to  claim 3 , 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. 
     
     
         5 . A 3D camera according to  claim 4 , wherein the duration of the first gate and the duration of the second gate are controlled to be substantially equal. 
     
     
         6 . A 3D camera according to  claim 4 , wherein the duration of the first and second gates is substantially equal to the pulse width of the radiated light pulses. 
     
     
         7 . A 3D camera according to  claim 1 , wherein the at least one controllable connection includes at least one modulator that connects the light sensitive element to the input of the at least one amplifier, the controller controlling the at least one modulator to modulate the current from the light sensitive element, the modulation of the light and the current being in phase. 
     
     
         8 . 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 for each pixel comprises,
 at least one amplifier inside each pixel, having an input and an output, the at least one amplifier being an operational amplifier; 
 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 inside each pixel through which the 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, 
 gates or modulates the current from the light sensitive element of each pixel in the photosurface through the at least one controllable connection responsive to the time dependence of the gating or modulation of the light, 
 controls the at least one controllable connection to correct for biases caused by at least one of background light or dark current, and 
 determines a distance to a region imaged on a pixel responsive to an amount of charge integrated on the at least one feedback capacitor responsive to the gated or modulated current and the corrected biases; 
   the at least one controllable connection including 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 the distance to the region imaged on the pixel responsive to an amount of charge integrated on the at least one feedback capacitor of the at least one amplifier during times at which the pixel is gated on;   the at least one amplifier including 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.   
     
     
         9 . A 3D camera according to  claim 8 , 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. 
     
     
         10 . A 3D camera according to  claim 8 , 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. 
     
     
         11 . A 3D camera according to  claim 8 , 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. 
     
     
         12 . A 3D camera according to  claim 11 , 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.   
     
     
         13 . A 3D camera according to  claim 12 , 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. 
     
     
         14 . A 3D camera according to  claim 12 , wherein the duration of the first gate period is substantially equal to the pulse width of the radiated light pulses. 
     
     
         15 . A 3D camera according to  claim 12 , wherein the duration of the second gate is greater than or equal to three times the pulse width. 
     
     
         16 . A 3D camera according to  claim 12 , 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. 
     
     
         17 . A 3D camera according to  claim 12 , 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. 
     
     
         18 . 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.   
     
     
         19 . A method according to  claim 18 , 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. 
     
     
         20 . A method according to  claim 18 , 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.