Optical detector having a bandpass filter in a lidar system

Patent metadata

Field	Value
Publication number	US-10121813-B2
Application number	US-201815909563-A
Country	US
Kind code	B2
Filing date	Mar 1, 2018
Priority date	Mar 28, 2017
Publication date	Nov 6, 2018
Grant date	Nov 6, 2018

Abstract

To detect light from light pulses at the operating wavelength of a light source in a lidar system, a thin-film notch filter is directly deposited on a photodetector or a lens via vacuum deposition or monolithic epoxy. The thin-film notch filter may include an anti-reflective coating such as a pattern-coated dichroic filter having an optical transmission of 90% or greater at in-band wavelengths and less than 5% at out-of-band wavelengths. To deposit the filter onto the photodetector without disrupting electronic connections between the photodetector and an application-specific integrated circuit, the area surrounding the electrodes on the photodetector is kept open using photolithography.

First claim

What is claimed is:

1. A lidar system comprising:
a light source configured to emit light pulses; and
a receiver configured to detect light from some of the light pulses scattered by one or more remote targets, the receiver including:
an application-specific integrated circuit (ASIC);
a photodetector electrically coupled to the ASIC;
a thin-film notch filter; and
a lens attached to the photodetector over the thin-film notch filter, wherein the thin-film notch filter is deposited directly on the photodetector or on a back surface of the lens.

2. The lidar system of claim 1 , wherein:
the photodetector is wire-bonded to the ASIC; and
the photodetector is configured for frontside illumination.

3. The lidar system of claim 1 , wherein the thin-film notch filter is monolithically epoxied or vacuum deposited on the photodetector or the back surface of the lens.

4. The lidar system of claim 2 , wherein the receiver further comprises electrodes attached to the photodetector which are connected to the ASIC via wire bonds and the thin-film notch filter is not deposited on areas of the photodetector occupied by the electrodes so as not to obstruct electrical connections between the photodetector and the ASIC.

5. The lidar system of claim 1 , wherein:
the photodetector is bump-bonded to the ASIC; and
the photodetector is configured for backside illumination.

6. The lidar system of claim 1 , wherein the thin-film notch filter comprises a dielectric coating that is anti-reflecting at one or more operating wavelengths of the light source and high-reflecting at one or more wavelengths away from the one or more operating wavelengths of the light source.

7. The lidar system of claim 1 , wherein the thin-film notch filter is a pattern-coated dichroic filter.

8. The lidar system of claim 1 , wherein the thin-film notch filter has a bandwidth of less than or equal to 40 nm and has a center wavelength between 350 nm and 1700 nm.

9. The lidar system of claim 8 , wherein the thin-film notch filter has an optical transmission of at least 90% at wavelengths within the bandwidth centered about the center wavelength and an optical transmission of less than or equal to 5% at other wavelengths within an operating wavelength range of the photodetector.

10. The lidar system of claim 1 , wherein the photodetector is a linear-mode avalanche photodiode (APD), a Geiger-mode APD, a single-photon avalanche diode (SPAD), or a PIN photodiode.

11. The lidar system of claim 1 , wherein the ASIC includes a pulse-detection circuit having a comparator and a time to digital converter (TDC) coupled to the comparator, and the comparators and the TDC are configured to process a received light signal to identify characteristics of the received light signal.

12. The lidar system of claim 1 , wherein the photodetector is an Indium Gallium Arsenide (InGaAs) photodetector or a Silicon (Si) photodetector.

13. A method for detecting light from light pulses having an operating wavelength in a lidar system, the method comprising:
emitting light pulses by a light source in a lidar system;
scanning, by a scanner in the lidar system, a field of regard of the lidar system, including directing the light pulses toward different points within the field of regard; and
detecting, by a receiver in the lidar system, light from one of the light pulses scattered by one or more remote targets to identify a return light pulse, the receiver including an application-specific integrated circuit (ASIC), a photodetector electrically coupled to the ASIC, a thin-film notch filter, and a lens attached to the photodetector over the thin-film notch filter, wherein the thin-film notch filter is deposited directly on the photodetector or on a back surface of the lens.

14. The method of claim 13 , wherein the light pulses are emitted at an operating wavelength and the thin-film notch filter in the receiver is configured to transmit light at the operating wavelength.

15. The method of claim 14 , wherein detecting light from one of the light pulses scattered by one or more remote targets includes transmitting a received light signal having a wavelength within a particular bandwidth centered about the operating wavelength and reflecting a received light signal having a wavelength outside of the particular bandwidth and within an operating wavelength range of the photodetector.

16. The method of claim 13 , wherein the ASIC includes a pulse-detection circuit and further comprising:
processing, by the pulse-detection circuit, a received light signal to identify characteristics of the received light signal.

17. A method for manufacturing a receiver for detecting light from light pulses having an operating wavelength in a lidar system, the method comprising:
electrically coupling a photodetector to an application-specific integrated circuit (ASIC); and
depositing a thin-film notch filter configured to transmit light at an operating wavelength directly on the photodetector or on a back surface of a lens to generate a receiver for detecting light from light pulses having the operating wavelength,
wherein a light source in a lidar system emits the light pulses having the operating wavelength and the receiver detects light having the operating wavelength from the light pulses scattered by one or more remote targets.

18. The method of claim 17 , wherein electrically coupling a photodetector to an ASIC includes wire-bonding the photodetector to the ASIC, wherein the photodetector is configured for frontside illumination.

19. The method of claim 17 , wherein depositing a thin-film notch filter on the photodetector or the back surface of the lens includes monolithically epoxying or vacuum depositing the thin-film notch filter on the photodetector or the back surface of the lens.

20. The method of claim 18 , wherein wire-bonding a photodetector to an ASIC includes attaching electrodes to the photodetector which are connected to the ASIC via wire bonds.

21. The method of claim 20 , further comprising:
applying a photoresist to the photodetector;
masking the electrodes attached to the photodetector;
developing an unmasked area of the photodetector to form an undercut;
depositing the thin-film notch filter on the unmasked area of the photodetector; and
removing the photoresist on the electrodes,
wherein the thin-film notch filter is not deposited on areas of the photodetector occupied by the electrodes so as not to obstruct electrical connections between the photodetector and the ASIC.

22. The method of claim 17 , wherein the thin-film notch filter is a pattern-coated dichroic filter.

23. The method of claim 17 , wherein electrically coupling a photodetector to an ASIC includes bump-bonding the photodetector to the ASIC, wherein the photodetector is configured for backside illumination.

Assignees

• Luminar Tech Inc

Inventors

• Eichenholz Jason M
• Campbell Scott R
• Lachapelle Joseph G

Classifications

• H10W72/884

  Die-attach connectors and bond wires · CPC title

• H10W72/877

  Bump connectors and die-attach connectors · CPC title

• H10W90/752

  between stacked chips · CPC title

• H10W72/075

  of bond wires · CPC title

• H10W72/072

  of bump connectors · CPC title