PROCESSING TIME-SERIES MEASUREMENTS FOR LIDAR ACCURACY
An optical measurement system may include a light source and corresponding photosensor configured to emit and detect photons reflected from objects in a surrounding environment for optical measurements. An initial peak can be identified as resulting from reflections off a housing of the optical measurement system. This peak can be removed or used to calibrate measurement calculations of the system. Peaks resulting from reflections off surrounding objects can be processed using on-chip filters to identify potential peaks, and the unfiltered data can be passed to an off-chip processor for distance calculations and other measurements. A spatial filtering technique may be used to combine values from histograms for spatially adjacent pixels in a pixel array. This combination can be used to increase the confidence for distance measurements.
1 . An optical measurement system comprising:
a plurality of light sources configured to emit one or more pulse trains over one or more time intervals as part of an optical measurement;
a plurality of photosensors configured to detect reflected photons from the one or more pulse trains emitted from corresponding light sources in the plurality of light sources, wherein the plurality of photosensors comprises a first photosensor and one or more other photosensors that are spatially adjacent to the first photosensor;
a plurality of memory blocks configured to accumulate photon counts of the photons received during the one or more time intervals by corresponding photosensors in the plurality of photosensors to represent a plurality of histograms of photon counts, wherein the plurality of histograms comprises a first histogram corresponding to the first photosensor and one or more histograms corresponding to the one or more other photosensors; and
a circuit configured to combine information from the first histogram with information from the one or more other histograms to generate a distance measurement for the first photosensor.
2 . The optical measurement system of claim 1 , wherein the one or more photosensors are physically adjacent to the first photosensor in an array of photosensors.
3 . The optical measurement system of claim 2 , wherein the array of photosensors comprises a solid-state array of photosensors.
4 . The optical measurement system of claim 2 , wherein the one or more photosensors comprises eight photosensors that are orthogonally adjacent or diagonally adjacent to the first photosensor.
5 . The optical measurement system of claim 1 , wherein the one or more photosensors are not physically adjacent to the first photosensor in an array of photosensors, but wherein the one or more photosensors are positioned to receive photons from physical areas that are adjacent to a physical area from which photons are received by the first photosensor.
6 . The optical measurement system of claim 5 , wherein the plurality of photosensors are arranged in an array of photosensors that rotates around a central axis of the optical measurement system.
7 . The optical measurement system of claim 1 , wherein:
the information from the first histogram comprises a first distance measurement calculated based on the first histogram;
the information from the one or more histograms comprises one or more other distance measurements calculated based on the one or more other histograms; and
the distance measurement comprises a combination of the first distance measurement with the one or more other distance measurements.
8 . The optical measurement system of claim 7 , wherein the first distance measurement is below a detection limit of the optical measurement system before combining the first distance measurement with the plurality other of distance measurements.
9 . The optical measurement system of claim 8 , wherein the distance measurement is above the detection limit of the optical measurement system after combining the first distance measurement with the plurality of other distance measurements.
10 . The optical measurement system of claim 8 , wherein the detection limit represents a minimum number of photons received by a corresponding photosensor.
11 . The optical measurement system of claim 1 , wherein the circuit to combine the information from the first histogram with the information from the one or more histograms comprises a processor implemented on an integrated circuit that is different from an integrated circuit on which the plurality of memory blocks is implemented.
12 . The optical measurement system of claim 1 , wherein the circuit and the plurality memory blocks are implemented on a same integrated circuit.
13 . A method of using spatially adjacent pixel information in an optical measurement system, the method comprising:
transmitting one or more pulse trains over one or more first time intervals as part of an optical measurement;
detecting, using a plurality of photosensors, reflected photons from the one or more pulse trains, wherein the plurality of photosensors comprises a first photosensor and one or more photosensors that are spatially adjacent to the first photosensor;
accumulating photons counts received during the one or more time intervals by the plurality of photosensors to represent a plurality of histograms of photon counts, wherein the plurality of histograms comprises a first histogram corresponding to the first photosensor and one or more histograms corresponding to the one or more photosensors; and
combining information from the first histogram with information from the one or more histograms to generate a distance measurement for the first photosensor.
14 . The method of claim 13 , wherein the reflected photons received by the first photosensor and received by the one or more photosensors are reflected from a same object in the surrounding environment.
15 . The method of claim 13 , wherein:
the information from the first histogram comprises photon counts in the first histogram;
the information from the one or more histograms comprises photon counts in the one or more histograms; and
the distance measurement is calculated based on an aggregation of the photon counts in the first histogram with the photon counts in the one or more histograms.
16 . The method of claim 13 , wherein:
the information from the first histogram comprises first one or more peaks in the first histogram;
the information from the one or more histograms comprises second one or more peaks in the one or more histograms; and
the distance measurement is calculated based on a combination of the first one or more peaks and the second one or more peaks.
17 . The method of claim 16 , wherein the distance measurement is calculated based on a summation of the first one or more peaks and the second one or more peaks.
18 . The method of claim 16 , wherein the distance measurement is calculated based on a Gaussian combination of the first one or more peaks and the second one or more peaks.
19 . The method of claim 16 , wherein the distance measurement is calculated based on a convolution of the first one or more peaks and the second one or more peaks.
20 . The method of claim 16 , wherein the distance measurement is calculated based on a weighted combination of the first one or more peaks and the second one or more peaks.