Method and apparatus for signal processing in a laser radar receiver
First Claim
1. An apparatus for processing signals received from a photodetector in a laser radar device, comprising:
- a) a plurality of comparators, each comparator comprising;
1) first comparative input for receiving an output from the photodetector,2) a second comparative input, and3) a comparator output;
b) a plurality of shift registers connected to the comparator outputs;
c) a threshold controller for providing a threshold level at each second comparative inputs, wherein the threshold controller can independently adjust the threshold level at each second comparative input.
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Abstract
An apparatus for receiving signals from a photodetector in a photodetector array. The apparatus has a number of comparators (e.g. 5) connected to the photodetector. each photodetector in the array has a similar circuit connected. Each comparator compares the output of the photodetector with an adjustable threshold level. Each threshold level is controlled by a threshold controller. Each threshold level corresponds with a light intensity value. Outputs of the comparators are each connected to a shift register. Each shift register is triggered to sample the output of its associated comparator at a certain speed (e.g. 800 Mhz). In operation, the shift registers each store a bit sequence representative of the comparator output. The data acquired is used to adjust the threshold levels applied to the comparators. In this way, adjustable intensity resolution is provided at desired ranges of intensity. The present invention includes a method for combining data from multiple laser pulses and fitting the data to a best fit statistical distribution so that an intensity value is obtained for each voxel in a 3-D laser radar image. Also, the present invention includes embodiments where different photodetectors in the array have different set threshold levels.
93 Citations
28 Claims
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1. An apparatus for processing signals received from a photodetector in a laser radar device, comprising:
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a) a plurality of comparators, each comparator comprising; 1) first comparative input for receiving an output from the photodetector, 2) a second comparative input, and 3) a comparator output; b) a plurality of shift registers connected to the comparator outputs; c) a threshold controller for providing a threshold level at each second comparative inputs, wherein the threshold controller can independently adjust the threshold level at each second comparative input. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method for processing signals received from a photodetector, comprising the steps of:
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a) illuminating a scene comprising voxels with a light pulse having a duration less than 5 nanoseconds; b) detecting backscattered light from the scene using a photodetector, wherein the photodetector has a time response less than 5 nanoseconds; c) comparing an output from the photodetector with a plurality of threshold levels; d) generating a bit sequence for each threshold level, wherein each bit sequence indicates when the photodetector output exceeds the corresponding threshold level, whereby each bit sequence is associated with a threshold level. - View Dependent Claims (10, 11, 12, 13)
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14. An apparatus for processing signals received from a photodetector array in a laser radar device, comprising:
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a) a plurality of comparators associated with each photodetector in the array, each comparator comprising; 1) first comparative input for receiving an output from the associated photodetector, 2) a second comparative input, and 3) a comparator output; b) a plurality of shift registers connected to the comparator outputs; c) a threshold controller for providing a threshold level at each second comparative inputs, wherein the threshold controller can independently adjust the threshold level at each second comparative input. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21)
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22. A method for laser radar imaging of a scene comprising voxels, comprising the steps of:
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a) illuminating the scene with a light pulse having a duration less than 5 nanoseconds; b) detecting backscattered light from the scene using a photodetector array, wherein each photodetector in the array has a time response less than 5 nanoseconds; c) comparing an output from each photodetector with a plurality of threshold levels; d) for each photodetector, generating a bit sequence for each threshold level, wherein each bit sequence indicates when the photodetector output exceeds the corresponding threshold level, whereby each bit sequence is associated with a threshold level. - View Dependent Claims (23, 24, 25, 26, 27, 28)
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Specification