Optical distance measuring device and method for optical distance measurement

Patent metadata

Field	Value
Publication number	US-9395440-B2
Application number	US-93794809-A
Country	US
Kind code	B2
Filing date	Apr 7, 2009
Priority date	Apr 14, 2008
Publication date	Jul 19, 2016
Grant date	Jul 19, 2016

Abstract

The present invention describes an optical distance measuring device having a pulsed radiation source that is implemented to transmit, in a temporally contiguous radiation pulse period, a radiation pulse having a pulse duration t p that is shorter than the radiation pulse period, and to transmit no radiation pulse in a temporally contiguous dark period. Further, the optical distance measuring device includes a detector for detecting different amounts of radiation in two overlapping detection periods during the radiation pulse period to capture reflections of the radiation pulse at an object surface and a background radiation and/or in two overlapping detection periods during the dark period to capture background radiation. The optical distance measuring device further includes an evaluator determining a signal depending on a distance of the optical distance measuring device to an object based on the detected amount of radiation. Further, the present invention provides a method for optical distance measurement and for multiple sampling.

First claim

The invention claimed is:

1. An optical distance measuring device comprising:
a pulsed radiation source implemented to transmit, in a temporally contiguous radiation pulse period, a radiation pulse with a pulse duration that is shorter than the radiation pulse period, and to transmit no radiation pulse in a temporally contiguous dark period;
a detector for detecting different amounts of radiation in, starting in, a phase-locked manner with the radiation pulse, two overlapping detection periods during the radiation pulse period to capture reflections of the radiation pulse at a surface of an object and a background radiation and in two detection periods during the dark period to capture a background radiation; and
an evaluator determining a signal depending on a distance of the optical distance measuring device to the object, based on the detected amounts of radiation by determining processed signals from the different amount of radiations detected in the two overlapping detection periods during the radiation pulse period, and from the different amount of radiations detected in the two detection periods during the dark period.

2. A method for optical distance measurement, comprising:
emitting a radiation pulse with a pulsed radiation source implemented to transmit, in a temporally contiguous radiation pulse period, a radiation pulse with a pulse duration t p that is shorter than the radiation pulse period, and to transmit no radiation pulse in a temporally contiguous dark period;
detecting different amounts of radiation with a detector that is implemented to capture reflections of the radiation pulse at a surface of an object and background radiation in two overlapping detection periods during the radiation pulse period and to capture background radiation in two overlapping detection periods during the dark period; and
determining a signal depending on a distance to be measured based on the detected amounts of radiation, wherein emitting the radiation pulse with a pulse duration t p and detecting the different amounts of radiation in two overlapping detection periods during the radiation pulse period starts phase-locked with emitting the radiation pulse, wherein a first of the two detection periods comprises the pulse duration t p and the second of the two detection periods comprises a duration t int2 that is longer than t p and wherein detecting the different amounts of radiation in two detection periods during the dark period is performed prior to or after the radiation pulse period.

3. An optical distance measuring device comprising:
a pulsed radiation source implemented to transmit, in a temporally contiguous radiation pulse period, a radiation pulse with a pulse duration that is shorter than the radiation pulse period, and to transmit no radiation pulse in a temporally contiguous dark period;
a detector for detecting different amounts of radiation in, starting in a phase-locked manner with the radiation pulse, two overlapping detection periods during the radiation pulse period to capture reflections of the radiation pulse at a surface of an object and a background radiation an amount of radiation in at least one detection period during the dark period to capture a background radiation; and
an evaluator determining a signal depending on a distance of the optical distance measuring device to the object, based on the detected amounts of radiation by determining a processed signal from the different amount of radiations detected in the two overlapping detection periods during the radiation pulse period, and using the amount of radiation detected in the at least one detection period during the dark period.

4. The optical distance measuring device according to claim 1 , wherein the detector is implemented such that the two overlapping radiation pulse detection periods during the radiation pulse period start phase-locked with the radiation pulse, wherein a first of the two radiation pulse detection periods during the radiation pulse period comprises a first duration and a second of the two radiation pulse detection periods during the radiation pulse period comprises a second duration, which is longer than a pulse duration of the radiation pulse, and such that the two overlapping dark detection periods during the dark period start phase-locked after the termination of the radiation pulse period, wherein a first of the two dark detection periods during the dark period comprises a third duration, which corresponds to the first duration, and a second of the two dark detection periods during the dark period comprises a fourth duration, which corresponds to the second duration.

5. The optical distance measuring device according to claim 1 , wherein the detector is implemented such that the two overlapping radiation pulse detection periods during the radiation pulse period start phase-locked with the radiation pulse of the pulsed radiation source, wherein a first of the two radiation pulse detection periods during the radiation pulse period comprises a first duration and a second of the two radiation pulse detection periods during the radiation pulse period comprises a second duration, which is longer than a pulse duration of the radiation pulse, and such that the two overlapping dark detection periods during the dark period start prior to or after the termination of the radiation pulse period, wherein a first of the two dark detection periods during the dark period comprises a third duration, which differs from the first duration, and a second of the two dark detection periods during the dark period comprises a fourth duration that differs from the second duration.

6. The optical distance measuring device according to claim 1 , wherein the detector is implemented such that the two overlapping detection periods during the radiation pulse period comprise a variable time offset with respect to the radiation pulse of the pulsed radiation source.

7. The optical distance measuring device according to claim 1 , wherein the evaluator is implemented such that a detected signal is a differential signal generated by subtracting temporarily stored signals describing the different amounts of radiation detected during the radiation pulse period in the two overlapping detection periods, and signals describing the different amounts of radiation detected during the dark period in the two overlapping detection periods.

8. The optical distance measuring device according to claim 1 , wherein the pulsed radiation source is a laser or an LED emitting electromagnetic radiations in the ultraviolet (UV), visible (VIS), infrared (IR) or far-infrared (FIR) spectral range.

9. The optical distance measuring device according to claim 1 , wherein the detector is a pixel sensor element providing signals at a pixel sensor element output in dependence on the detected amounts of radiation, wherein the pixel sensor element output is connected to a sample and hold circuit implemented in parallel via at least one buffer amplifier, wherein every parallel branch of the sample and hold circuit comprises a sample switch connecting the output of the at least one buffer amplifier to a sample capacitance and a transfer switch, wherein, by the transfer switch, every parallel branch of the sample and hold circuit is connectable to the evaluator, and wherein the sample switch in every parallel branch is implemented such as to be closed in two overlapping detection periods, so that after terminating the overlapping detection periods a different signal of the pixel sensor element output is temporarily stored on every sample capacitance of the parallel branch.

10. The optical distance measuring device according to claim 1 , wherein the detector is a pixel sensor element providing sign

Assignees

• Schrey Olaf
• Brockherde Werner
• Hosticka Bedrich
• Ulfig Wiebke
• Volkswagen Ag

Inventors

• Schrey Olaf
• Brockherde Werner
• Hosticka Bedrich
• Ulfig Wiebke

Classifications

• G01S7/487 Primary

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

• G01C3/08 Primary

  Use of electric radiation detectors · 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

• G01S17/107 Primary

  Physics · mapped topic