Optoelectronic sensor and method of measuring the distance from an object

Patent metadata

Field	Value
Publication number	US-10948575-B2
Application number	US-201816013313-A
Country	US
Kind code	B2
Filing date	Jun 20, 2018
Priority date	Jun 21, 2017
Publication date	Mar 16, 2021
Grant date	Mar 16, 2021

Abstract

An optoelectronic sensor is provided for measuring the distance from an object in a monitored zone that has a light transmitter for transmitting light signals into the monitored zone; a light receiver having at least one avalanche photodiode operated in Geiger mode for receiving the light signals reflected or remitted by the object; an individual time of flight measurement unit for determining an individual time of flight of a light signal from the sensor to the object; and an evaluation unit that is configured to generate a common measured value for the distance from a plurality of individual times of flight.

First claim

The invention claimed is:

1. An optoelectronic sensor for measuring the distance from an object in a monitored zone, the optoelectronic sensor having
a light transmitter for transmitting light signals into the monitored zone;
a light receiver having at least one avalanche photodiode operated in Geiger mode for receiving the light signals reflected or remitted by the object;
an individual time of flight measurement unit for determining an individual time of flight of a light signal from the sensor to the object; and
an evaluation unit that is configured to determine a common measured value for the distance from a plurality of individual times of flight,

wherein the evaluation unit is furthermore configured to determine a received point in time t s forming the basis of the common measured value in a predefinable time interval having a lower time boundary t 0 and an upper time boundary t 1 from a model of the number N(t) of the avalanche photodiodes still available at a respective point in time t, with an avalanche photodiode still being available as long as no avalanche has been triggered therein.

2. The sensor in accordance with claim 1 ,
wherein the evaluation unit is configured to determine the received point in time t s with the aid of a background parameter λ.

3. The sensor in accordance with claim 2 ,
wherein the evaluation unit is configured to determine the background parameter λ from a measurement of single times of flight.

4. The sensor in accordance with claim 1 ,
wherein the evaluation unit is configured to determine the received point in time with the aid of a signal strength parameter p.

5. The sensor in accordance with claim 1 ,
wherein a plurality of avalanches are triggered in the model at the received point in time t s in accordance with a Dirac pulse δ (t−t s ).

6. The sensor in accordance with claim 5 ,
wherein, in the model, the number N(t) of the avalanche photodiodes still available at a respective point in time is described in accordance with the equation N(t)=N(t 0 )e −λ(t-t 0 )-pΘ(t-t s ) by the background parameter λ and the signal strength parameter p.

7. The sensor in accordance with claim 1 ,
wherein the evaluation unit is configured to determine the signal strength parameter p from the number of still available avalanche photodiodes at the lower time boundary t 0 and at the upper time boundary t 1 .

8. The sensor in accordance with claim 1 ,
wherein the evaluation unit is configured to determine the signal strength parameter p in accordance with the equation

e

-
p

=

N
⁡

(

t
1

)

α
⁢

⁢

N
⁡

(

t
0

)

,

where α=e −λ(t 1 -t e ) with the background parameter λ.

9. The sensor in accordance with claim 1 ,
wherein the evaluation unit is configured to sequentially determine first a background parameter λ, then, with the aid of the background parameter λ, a signal strength parameter p, and then, with the aid of the background parameter λ and a signal strength parameter p, the received point in time t s .

10. The sensor in accordance with claim 1 ,
wherein the evaluation unit is configured to calculate the received point in time with the help of an analytical formula from the number of still available avalanche photodiodes N(t) at a point in time t, in particular the still available avalanche photodiodes at the point in time t=t 0 of the lower time boundary t 0 , a background parameter λ, a signal strength parameter p, and a further parameter.

11. The sensor in accordance with claim 10 ,
wherein the evaluation unit is configured to calculate the received point in time with the help of the analytical formula from the number of the still available avalanche photodiodes at the point in time t=t 0 of the lower time boundary t 0 .

12. The sensor in accordance with claim 10 ,
wherein the further parameter is a mean value μ of the individual times of flight in the predefinable time interval.

13. The sensor in accordance with claim 12 ,
wherein the evaluation unit is configured to calculate the received point in time t s as

t
s

=

(

-

1
λ

)

[

ln
(

e

λ
⁢

⁢

t

1
+
p

⁡

(

μ
⁢

⁢
λ

+

N
0

)

-

N
0

⁡

(

1
+

λ
⁢

⁢

Assignees

• Sick Ag

Inventors

• Kienzler Stefan
• Köhl Martin
• Waslowski Kai
• Zwölfer Ulrich
• Thil Christophe

Classifications

• G01S17/10 Primary

  using transmission of interrupted, pulse-modulated waves (determination of distance by phase measurements G01S17/32) · CPC title

• G01S7/497

  Means for monitoring or calibrating · CPC title

• G01S7/487

  Extracting wanted echo signals {, e.g. pulse detection} · CPC title

• G01S17/18

  wherein range gates are used · CPC title

• G01S17/894

  Three-dimensional [3D] imaging with simultaneous measurement of time-of-flight at a two-dimensional [2D] array of receiver pixels, e.g. time-of-flight cameras or flash lidar · CPC title