High dynamic range for sensing systems and methods

Patent metadata

Field	Value
Publication number	US-10969476-B2
Application number	US-201816031084-A
Country	US
Kind code	B2
Filing date	Jul 10, 2018
Priority date	Jul 10, 2018
Publication date	Apr 6, 2021
Grant date	Apr 6, 2021

Abstract

A time of flight (TOF) sensor device employs a measuring sequence that facilitates accurate distance measurement across a high dynamic range. In one or more embodiments, for a given measuring sequence in which a distance of an object or surface corresponding to a pixel is to be determined, the TOF sensor device performs multiple iterations of a measuring cycle, whereby for each successive iteration the number of emitted and measured pulses that are accumulated for the iteration is increased relative to the previous iteration of the measuring cycle. In this way, multiple values of increasing resolution are measured for the same physical entity over a corresponding number of measuring cycles. The sensor then selects a value from the multiple measured values that yields the highest resolution without saturating the pixel, and this value is used to determine the pulse propagation time and object distance.

First claim

What is claimed is:

1. A time of flight sensor device, comprising:
an emitter component configured to emit, for each pulse period of each measuring cycle of a distance measuring sequence, a light pulse having a falling e at a first time, wherein the distance measuring sequence comprises multiple measuring cycles and each measuring cycle comprises multiple pulse periods;
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
a measuring capacitor connected to the photo device via a control line switch controlled by a gating signal,

wherein
the photo-sensor component is configured to, for each pulse period of each measuring cycle, set the gating signal of the control line switch at a second time during the pulse period defined relative to the first time, and reset the control signal at a third time, wherein setting the gating signal at the second time and resetting the gating signal at the third time causes a portion of the electrical energy to be stored in the measuring capacitor,
the portion of the electrical energy is proportional to one of ambient light, a leading edge portion of a received light pulse plus the ambient light, or a trailing edge portion of the received light pulse plus the ambient light,
the emitter component and the photo-sensor component are configured to, for each measuring cycle of the multiple measuring cycles after a first of the measuring cycles, increase the number of pulse periods executed in the measuring cycle relative to an immediately preceding measuring cycle of the multiple measuring cycles,
the photo-sensor component is configured to measure a voltage value on the measuring capacitor and store the voltage value in response to completion of each of the multiple measuring cycles to yield multiple values of a pulse characteristic, and
the time of flight sensor device further comprises a distance determination component configured to, in response to completion of all of the multiple measuring cycles of the distance measuring sequence, select a pulse characteristic value of the multiple values of the pulse characteristic and determine a propagation time of the light pulse based on the pulse characteristic value.

2. The time of flight sensor device of claim 1 , wherein the distance determination component is configured to select, as the pulse characteristic value, a highest value of the multiple values that does not exceed a threshold value.

3. The time of flight sensor of claim 1 , wherein the distance determination component is configured to select, as the pulse characteristic value, a lowest value of the multiple values that exceeds a threshold value.

4. The time of flight sensor device of claim 1 , wherein
the measuring capacitor is a first measuring capacitor, the control line switch is a first control line switch, the gating signal is a first gating signal, the portion of the electrical energy is a first portion of the electrical energy, the voltage value is a first voltage value, and the multiple values of the pulse characteristic are multiple first values of a first pulse characteristic,
the photo-sensor component further comprises
a second measuring capacitor connected to the photo device via a second control line switch controlled by a second gating signal, and
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 pulse period of the measuring cycle:
set the second gating signal of the second control line switch at or approximately at the third time and reset the second gating signal at a fourth time during the pulse period defined relative to the first time, wherein setting the second gating signal at or approximately at the third time and resetting the second gating signal at the fourth time causes a second portion of the electrical energy to be stored in the second measuring capacitor, and
set the third gating signal of the third control line switch at or approximately at the fourth time and reset the third gating signal at a fifth time during the pulse period defined relative to the first time, wherein setting the third gating signal at or approximately at the fourth time and resetting the third gating signal at the fifth time causes a third portion of the electrical energy to be stored in the third measuring capacitor, and
the photo-sensor component is further configured to:
measure a second voltage value on the second measuring capacitor and store the second voltage value in response to completion of each of the multiple measuring cycles to yield multiple second values of a second pulse characteristic, and
measuring a third voltage value on the third measuring capacitor and store the third voltage value in response to completion of each of the multiple measuring cycles to yield multiple third values of a third pulse characteristic.

5. The time of flight sensor device of claim 4 , wherein the distance determination component is further configured to, in response to completion of the multiple measuring cycles of the distance measuring sequence,
select a second pulse characteristic value of the multiple second values,
select a third pulse characteristic value of the multiple third values, and determine the propagation time of the light pulse based on the first pulse characteristic value, the second pulse characteristic value, and the third pulse characteristic value.

6. The time of flight sensor device of claim 5 , wherein the distance determination component is configured to determine the propagation time of the light pulse based on

t
p

=

V
2

-

V
0

V
1

+

V
2

-

2
·

V
0

⁢

T
0

+

T

s
⁢

⁢
12

where
tp is the propagation time,
T 0 is a duration of the light pulse,
T s12 is the fourth time,
V 0 is the first pulse characteristic value indicative of ambient light,
V 1 is the second pulse characteristic value indicative of the leading edge portion of the received light pulse plus the ambient light, and
V 2 is the third pulse characteristic value indicative of the trailing edge portion of the received light pulse plus the ambient light.

7. The time of flight sensor device of claim 5 , wherein the

Assignees

• Rockwell Automation Tech Inc

Inventors

• Boutaud Frederic

Classifications

• G01S7/4863

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

• G06T2207/20208

  High dynamic range [HDR] image processing · CPC title

• G01S7/4873

  by deriving and controlling a threshold value · CPC title

• G06T2207/10028

  Range image; Depth image; 3D point clouds · CPC title

• G01S7/489

  Gain of receiver varied automatically during pulse-recurrence period · CPC title