Configurable memory blocks for LIDAR measurements
An optical measurement system may include a plurality of light sources and a plurality of photosensors, where the photosensors are configured to receive photons from the light sources that are reflected off objects in the surrounding environment. Photons may be stored in memory blocks corresponding to the photosensors to form histograms of the receive photons. A select circuit may be used to share memory blocks between photosensors, such that a plurality of photosensors may write to a single memory block, or a single photosensor may write to a plurality of memory blocks. Sampling clock cycles for the photosensors may be adjusted relative to the clock cycles for the memory blocks based on the select circuit output.
1 . An optical measurement system comprising:
a light source configured to transmit one or more pulse trains over one or more time intervals as part of an optical measurement, wherein each of the one or more time intervals includes one of the one or more pulse trains, and wherein each of the one or more time intervals is subdivided into a plurality of time bins;
a photosensor configured to detect photons from the light source;
one or more memory blocks, wherein each of the one or more memory blocks comprises a plurality of registers configured to store accumulated photon counts from the photosensor, and wherein each of the plurality of registers is associated with a corresponding one of the plurality of time bins to represent a histogram; and
a select circuit configured to:
receive accumulated photon counts from the photosensor during the one or more time intervals;
provide a select signal that adds or removes memory blocks from the one or more memory blocks that accumulate photon counts from the photosensor; and
change a clock signal associated with the photosensor in response to the adding or removing of memory blocks from the one or more memory blocks.
2 . The optical measurement system of claim 1 , further comprising one or more buffers coupled to the select circuit and the one or more memory blocks and configured to receive the accumulated photon counts from the photosensor.
3 . The optical measurement system of claim 2 , wherein the one or more buffers are configured to receive the accumulated photon counts incrementally from the photosensor as they are provided by the photosensor.
4 . The optical measurement system of claim 2 , wherein the one or more buffers are configured to provide the accumulated photon counts to the one or more memory blocks when each of the one or more buffers are filled.
5 . The optical measurement system of claim 2 , wherein each of the one or more buffers are divided into a plurality of sections.
6 . The optical measurement system of claim 5 , wherein each of the plurality of sections are populated with accumulated photon counts from different time bins in the plurality of time bins.
7 . The optical measurement system of claim 5 , wherein each of the plurality of sections are populated with accumulated photon counts from the photosensor.
8 . The optical measurement system of claim 2 , wherein a bit-width of a memory block is the same as a bit-width of a buffer.
9 . The optical measurement system of claim 1 , wherein the select circuit comprises a plurality of multiplexers that route outputs from the photosensor to the one or more memory blocks.
10 . The optical measurement system of claim 1 , further comprising a clock multiplier that increases a frequency of a clock used for the photosensor.
11 . A method of using an optical measurement system, the method comprising:
transmitting one or more pulse trains from a light source over one or more time intervals as part of an optical measurement, wherein each of the one or more time intervals includes one of the one or more pulse trains, and wherein each of the one or more time intervals is subdivided into a plurality of time bins;
detecting photons from the one or more pulse trains using a photosensor;
selecting one or more memory blocks from a plurality of memory blocks to store accumulated photon counts from the photosensor; and
accumulating photon counts from the photosensor received during the one or more time intervals into the one or more memory blocks, wherein each of the one or more memory blocks comprises a plurality of registers, and each of the plurality of registers is associated with a corresponding one of the plurality of time bins for the photosensors to represent a histogram;
changing the number of memory blocks in the one or more memory blocks; and
changing a clock signal associated with the photosensor based on the changed number of memory blocks in the one or more memory blocks.
12 . The method of claim 11 , wherein selecting the one or more memory blocks from the plurality of memory blocks comprises:
receiving a signal from an on-chip processor.
13 . The method of claim 11 , wherein selecting the one or more memory blocks from the plurality of memory blocks comprises:
receiving a signal from an off-chip processor as the optical measurement system is operating.
14 . The method of claim 11 , wherein increasing the number of memory blocks in the one or more memory blocks increases a frequency of the clock signal associated with the photosensor.
15 . The method of claim 11 , wherein decreasing the number of memory blocks in the one or more memory blocks decreases a frequency of the clock signal associated with the photosensor.
16 . The method of claim 11 , further comprising causing one or more photosensors to remain idle, wherein the one or more photosensors are associated with the one or more memory blocks.
17 . The method of claim 11 , wherein clock signals associated with the one or more memory blocks are phase-shifted 90° relative to each other.
18 . The method of claim 11 , wherein clock signals associated with the one or more memory blocks are phase-shifted 180° relative to each other.
19 . A method of using an optical measurement system, the method comprising:
transmitting one or more pulse trains from a light source over one or more time intervals as part of an optical measurement, wherein each of the one or more time intervals includes one of the one or more pulse trains, and wherein each of the one or more time intervals is subdivided into a plurality of time bins;
detecting photons from the one or more pulse trains using a photosensor;
selecting one or more memory blocks from a plurality of memory blocks to store accumulated photon counts from the photosensor; and
accumulating photon counts from the photosensor received during the one or more time intervals into the one or more memory blocks, wherein each of the one or more memory blocks comprises a plurality of registers, and each of the plurality of registers is associated with a corresponding one of the plurality of time bins for the photosensors to represent a histogram;
receiving a select signal that adds or removes memory blocks from the one or more memory blocks that accumulate photon counts from the photosensor; and
changing a clock signal associated with the photosensor in response to the adding or removing of memory blocks from the one or more memory blocks.