Increasing tolerance of sensor-scanner misalignment of the 3D camera with epipolar line laser point scanning
First Claim
1. A method comprising:
- performing a one-dimensional (1D) point scan of a three-dimensional (3D) object along a scanning line using a light source, wherein the point scan projects a sequence of light spots on a surface of the 3D object;
selecting a plurality of rows of pixels in an image sensor, wherein the image sensor has a plurality of pixels arranged in a two-dimensional (2D) array forming an image plane, and wherein at least one of the plurality of the selected rows forms a portion of an epipolar line of the scanning line on the image plane;
for pixels in the selected row of pixels, sensing a pixel-specific detection of a corresponding light spot in the sequence of light spots;
for a group of pixels detecting a common light spot, generating a pixel-specific timestamp value for each pixel in the group substantially simultaneously; and
determining a distance to the common light spot on the surface of the 3D object based at least on the generated pixel-specific timestamp values and on a scan angle used by the light source for projecting the common light spot.
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Abstract
Using the same image sensor to capture a two-dimensional (2D) image and three-dimensional (3D) depth measurements for a 3D object. A laser point-scans the surface of the object with light spots, which are detected by a pixel array in the image sensor to generate the 3D depth profile of the object using triangulation. Each row of pixels in the pixel array forms an epipolar line of the corresponding laser scan line. Timestamping provides a correspondence between the pixel location of a captured light spot and the respective scan angle of the laser to remove any ambiguity in triangulation. An Analog-to-Digital Converter (ADC) in the image sensor operates as a Time-to-Digital Converter (TDC) to generate timestamps. When the epipolar line is misaligned or curved, multiple TDC arrays acquire timestamps of multiple pixels (in multiple rows) substantially simultaneously. Multiple timestamp values are reconciled to obtain a single timestamp value for a light spot.
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Citations
20 Claims
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1. A method comprising:
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performing a one-dimensional (1D) point scan of a three-dimensional (3D) object along a scanning line using a light source, wherein the point scan projects a sequence of light spots on a surface of the 3D object; selecting a plurality of rows of pixels in an image sensor, wherein the image sensor has a plurality of pixels arranged in a two-dimensional (2D) array forming an image plane, and wherein at least one of the plurality of the selected rows forms a portion of an epipolar line of the scanning line on the image plane; for pixels in the selected row of pixels, sensing a pixel-specific detection of a corresponding light spot in the sequence of light spots; for a group of pixels detecting a common light spot, generating a pixel-specific timestamp value for each pixel in the group substantially simultaneously; and determining a distance to the common light spot on the surface of the 3D object based at least on the generated pixel-specific timestamp values and on a scan angle used by the light source for projecting the common light spot. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. An imaging unit comprising:
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a light source operative to perform a one-dimensional (1D) point scan of a three-dimensional (3D) object along a scanning line, wherein the point scan projects a sequence of light spots on a surface of the 3D object; and an image sensor unit that includes; a plurality of pixels arranged in a two-dimensional (2D) pixel array forming an image plane, wherein each pixel in a column of pixels in the 2D pixel array is associated with a respective row of pixels in the 2D pixel array, and wherein each pixel in the column of pixels is operative to detect a corresponding light spot in the sequence of light spots, a plurality of Analog-to-Digital Converter (ADC) units per column of pixels in the 2D pixel array, wherein at least two adjacent pixels in a column of pixels are connected to different ADC units, and wherein each ADC unit is operative to generate a pixel-specific timestamp value for a respective pixel connected thereto in response to a pixel-specific detection of the corresponding light spot by the respective pixel, and a processing unit coupled to the plurality of ADC units, wherein the processing unit is operative to perform the following; select a plurality of rows of pixels in the 2D pixel array associated with a group of pixels detecting a common light spot in the sequence of light spots, wherein at least one of the plurality of the selected rows forms a portion of an epipolar line of the scanning line on the image plane, for pixels in the selected rows of pixels, sense a pixel-specific detection of the common light spot, trigger the ADC units associated with the pixels in the group of pixels so as to substantially simultaneously generate a pixel-specific timestamp value for each pixel in the group of pixels, and determine a distance to the common light spot on the surface of the 3D object based at least on the generated pixel-specific timestamp values and on a scan angle used by the light source for projecting the common light spot. - View Dependent Claims (12, 13)
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14. A system comprising:
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a light source operative to perform a one-dimensional (1D) point scan of a three-dimensional (3D) object along a scanning line, wherein the point scan projects a sequence of light spots on a surface of the 3D object; a plurality of pixels arranged in a two-dimensional (2D) pixel array forming an image plane, wherein each pixel in a column of pixels in the 2D pixel array is associated with a respective row of pixels in the 2D pixel array, and wherein each pixel in the column of pixels is operative to detect a corresponding light spot in the sequence of light spots; a plurality of Analog-to-Digital Converter (ADC) units per column of pixels in the 2D pixel array, wherein at least two adjacent pixels in a column of pixels are connected to different ADC units, and wherein each ADC unit is operative to generate a pixel-specific timestamp value for a respective pixel connected thereto in response to a pixel-specific detection of the corresponding light spot by the respective pixel; a memory for storing program instructions; and a processor coupled to the memory and to the plurality of ADC units, wherein the processor is configured to execute the program instructions, whereby the processor is operative to perform the following; select a plurality of rows of pixels in the 2D pixel array associated with a group of pixels detecting a common light spot in the sequence of light spots, wherein at least one of the plurality of the selected rows forms a portion of an epipolar line of the scanning line on the image plane, for pixels in the selected rows of pixels, sense a pixel-specific detection of the common light spot, trigger the ADC units associated with the pixels in the group of pixels so as to substantially simultaneously generate a pixel-specific timestamp value for each pixel in the group of pixels, and determine a distance to the common light spot on the surface of the 3D object based at least on the generated pixel-specific timestamp values and on a scan angle used by the light source for projecting the common light spot. - View Dependent Claims (15, 16, 17, 18, 19, 20)
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Specification