Permutation of measuring capacitors in a time-of-flight sensor

Patent metadata

Field	Value
Publication number	US-11002836-B2
Application number	US-201815978679-A
Country	US
Kind code	B2
Filing date	May 14, 2018
Priority date	May 14, 2018
Publication date	May 11, 2021
Grant date	May 11, 2021

Abstract

A time of flight sensor device is capable of generating accurate propagation time information for emitted light pulses using a small number of measurement cycles by using multiple measuring capacitors to capture more return pulse information per pulse period. To mitigate the effects of mismatched measuring capacitors and reading paths, embodiments of the time of flight sensor device perform multiple measuring sequences per measurement operation, permutating the roles of the measuring capacitors for each of the measuring sequences. The data collected by the measuring capacitors for the multiple measuring sequences is then aggregated and used to compute the propagation time and corresponding distance. This technique mitigate yields accurate measurements despite mismatches between reading paths and measuring capacitors without the need to implement pixel-level calibration and compensation, thereby saving calibration time, memory space, and computing time.

First claim

What is claimed is:

1. A time of flight sensor device, comprising:
an emitter component configured to emit a light pulse at a first time during each measuring sequence of multiple measuring sequences of a distance measurement operation;
a photo-sensor component comprising a photo-detector, the photo-detector comprising
a photo device configured to generate electrical energy in proportion to a quantity of received light, and
multiple measuring capacitors comprising at least
a first measuring capacitor connected to the photo device via a first control line switch controlled by a first gating signal, and
a second measuring capacitor connected to the photo device via a second control line switch controlled by a second gating signal,

wherein the photo-sensor component is configured to, for each measuring sequence,
designate the first gating signal to be one of a first signal or a second signal,
designate the second gating signal to be another of the first signal or the second signal,
set the first signal at a second time during the measuring sequence defined relative to the first time, and reset the first signal at a third time during the measuring sequence defined relative to the first time, wherein setting the first signal at the second time and resetting the first signal at the third time causes a first portion of the electrical energy to be stored in a corresponding first capacitor of the first measuring capacitor or the second measuring capacitor, and
set the second signal at the third time and reset the second signal at a fourth time during the measuring sequence defined relative to the first time, wherein setting the second signal at the third time and resetting the second signal at the fourth time causes a second portion of the electrical energy to be stored in a corresponding second capacitor of the first measuring capacitor or the second measuring capacitor, and

wherein the photo-sensor component is further configured to perform at least two of the multiple measuring sequences using respective different designations for the first signal and the second signal; and
a distance determination component configured to determine a propagation time for the light pulse based on first measured values of the first portion of the electrical energy measured on the first capacitor for the multiple measuring sequences and second measured values of the second portion of the electrical energy measured on the second capacitor for the multiple measuring sequences.

2. The time of flight sensor device of claim 1 , wherein the distance determination component is configured to determine the propagation time based on a first sum of the first measured values and a second sum of the second measured values.

3. The time of flight sensor device of claim 1 , wherein
the multiple measuring capacitors further comprise at least a third measuring capacitor connected to the photo device via a third control line switch controlled by a third gating signal,
the photo-sensor component is further configured to, for each measuring sequence,
designate the first gating signal to be one of the first signal, the second signal, or a third signal,
designate the second gating signal to be another of the first signal, the second signal, or the third signal,
designate the third gating signal to be a remaining one of the first signal, the second signal, or the third signal,
set the first signal at the second time and reset the first signal at the third time causing the first portion of the electrical energy to be stored in the corresponding first capacitor of the first measuring capacitor, the second measuring capacitor, or the third measuring capacitor,
set the second signal at the third time and reset the second signal at the fourth time causing the second portion of the electrical energy to be stored in the corresponding second capacitor of the first measuring capacitor, the second measuring capacitor, and the third measuring capacitor, and
set the third signal at the fourth time and reset the third signal at a fifth time during the measuring sequence defined relative to the first time, wherein setting the third signal at the fourth time and resetting the third signal at the fifth time causes a third portion of the electrical energy to be stored in a corresponding third capacitor of the first measuring capacitor, the second measuring capacitor, or the third measuring capacitor,

the photo-sensor component is further configured to perform at least three of the multiple measuring sequences using respective different designations for the first signal, the second signal, and the third signal, and
the distance determination component is configured to determine the propagation time based on the first measured values, the second measured values, and third measured values of the third portion of the electrical energy measured on the third capacitor for the multiple measuring sequences.

4. The time of flight sensor device of claim 3 , wherein the distance determination component is configured to, in response to a determination that the first measured values represent a leading edge portion of a reflected light pulse,
subtract a third sum of the third measured values from the first sum of the first measured values to yield a leading edge value,
subtract the third sum of the third measured values from the second sum of the second measured values to yield a trailing edge value, and
determine the propagation time based on a ratio of the trailing edge value to a total of the leading edge value and the trailing edge value.

5. The time of flight sensor of claim 4 , wherein the distance determination component is configured to determine that the first measured values represent the leading edge portion of the reflected light pulse based on a determination that the first sum of the first measured values and the second sum of the second measured values are greater than the third sum of the third measured values.

6. The time of flight sensor device of claim 3 , wherein the distance determination component is configured to, in response to a determination that the second measured values represent a leading edge portion of a reflected light pulse,
subtract the first sum of the first measured values from the second sum of the second measured values to yield a leading edge value,
subtract the first sum of the first measured values from a third sum of the third measured values to yield a trailing edge value, and
determine the propagation time based on a ratio of the trailing edge value to a total of the leading edge value and the trailing edge value.

7. The time of flight sensor device of claim 3 , wherein the distance determination component is configured to determine the propagation time based on
t p =( V 2a +V 0b +V 1c )−( V 0a +V 1b +V 2c )/( V 1a +V 2b +V 0c )+( V 2a +V 0b +V 1c )−2·( V 0a +V 1b +V 2c ) T 0 +T s

where
t p is the propagation time,
T 0 is a duration of the light pulse,
V 0a is one of the first measured values measured on the first measuring capacitor for a first measuring sequence of the multiple measuring sequences,
V 1a is one of the second measured values measured on the second measuring capacitor for the first measuring sequence,
V 2a is one of the third measured values measured on the third measuring capacitor for the first measuring sequence,
V 0b is one of the third measured values measured on the first measuring capacitor for a second measuring sequence of the multiple measuring sequences,
V 1b is one of the first measured values measured on the second measuring capacitor for the second measuring sequence,
V 2b is one of the second measured values measured on the third measuring capacitor for the se

Assignees

• Rockwell Automation Tech Inc

Inventors

• Boutaud Frederic

Classifications

• G01S17/42

  Simultaneous measurement of distance and other co-ordinates (indirect measurement G01S17/46) · CPC title

• G01S7/4865 Primary

  Time delay measurement, e.g. time-of-flight measurement, time of arrival measurement or determining the exact position of a peak (peak detection in noise, signal conditioning G01S7/487) · CPC title

• G01S17/18

  wherein range gates are used · CPC title

• G01S7/4863 Primary

  Detector arrays, e.g. charge-transfer gates · CPC title