System and methods for depth imaging using conventional CCD image sensors

1. A method for depth imaging using a CCD image sensor, comprising:

providing an optical lens for collecting light from a scene having objects in front of the lens;

providing a CCD image sensor device arranged to receive light from the optical lens and having an array of pixels and having corresponding pixel charge storage elements;

providing a light source for transmitting light pulses towards the scene responsive to a pulse control signal;

providing timing signals to configure the CCD image sensor to collect and store charge from pixels including a VSUB control signal that clears the pixel charge storage elements, a first readout control signal that enables a transfer cell corresponding to a pixel in a first sub-array of pixels to store charge, and a second readout control signal that enables a transfer cell corresponding to a pixel in a second sub-array of pixels to store charge;

in a background frame period, collecting a background charge A corresponding to light incident on the CCD sensor that is reflected ambient light from objects in front of the lens into a transfer cell in the first sub-array, and for a portion of the background frame period, collecting a background charge B corresponding to light incident on the CCD sensor that is reflected ambient light from objects in front of the lens into a transfer cell in the second sub-array;

in a depth frame period, outputting a pulse from the light source, and collecting a depth charge A corresponding to light that is reflected from objects due to the ambient light and due to a portion of the reflected light from the pulse from the light source into a transfer cell in the first sub-array, and in a portion of the depth frame period, collecting a depth charge B corresponding to light that is reflected from objects due to the ambient light and due to a portion of the reflected light from the pulse from the light source into a transfer cell in the second sub-array; and

performing a depth calculation using the background charge A and the background charge B and the depth charge A and the depth charge B, for each pixel in the array of pixels in the CCD image sensor.

2. The method of claim 1 , and further comprising, in the background frame period:

configuring the VSUB control signal to enable pixels to collect charge;

during an entire background frame period, activating the first readout control signal to enable the collection of background charge A into the transfer cell in the first sub-array; and

during a portion of the background frame period, activating the second readout control signal to enable the collection of background charge B into the transfer cell in the second sub-array.

3. The method of claim 1 , and further comprising, in the depth frame period:

configuring the VSUB control signal to enable pixels to collect charge;

during a portion of the depth frame period, activating the pulse control signal to cause a light pulse from the light source;

during an entire depth frame period, activating the first readout control signal to enable the collection of depth charge A into the transfer cell in the first sub-array; and

during a portion of the depth period that corresponds to the light pulse, activating the second readout control signal to enable the collection of depth charge B into the transfer cell in the second sub-array.

4. The method of claim 1 , wherein performing the calculation further comprises:

subtracting the background charge B from the depth charge B, and dividing a difference obtained by a sum of: the depth charge B with the background charge B subtracted from it, and the depth charge A with the background charge A subtracted from it.

5. The method of claim 1 , wherein collecting background charge A comprises collecting charge corresponding to a 2D color image of the objects.