Optical detector having a bandpass filter in a lidar system

• US 10,121,813 B2
• Filed: 03/01/2018
• Issued: 11/06/2018
• Est. Priority Date: 03/28/2017
• Status: Active Grant

• Current Assignee: Luminar Technologies, Inc.
• Original Assignee: Luminar Technologies, Inc.
• Inventors: Eichenholz, Jason M., Campbell, Scott R., LaChapelle, Joseph G.
• Primary Examiner(s): Bolda, Eric L
• Application Number:
  US15/909,563
• Publication Number:
  US 20180286909A1
• Time in Patent Office: 250 Days
• CPC Class Codes: G01S 17/10 using transmission of interrupted, pulse-modulated waves determination of distance by phase measurements G01S17/32
• CPC Class Codes: G01S 17/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S17/46
• CPC Class Codes: G01S 17/87 Combinations of systems using electromagnetic waves other than radio waves
• CPC Class Codes: G01S 17/89 for mapping or imaging
• CPC Class Codes: G01S 17/931 of land vehicles
• CPC Class Codes: G01S 7/4812 transmitted and received beams following a coaxial path
• CPC Class Codes: G01S 7/4816 of receivers alone
• CPC Class Codes: G01S 7/4817 relating to scanning
• CPC Class Codes: G01S 7/4861 Circuits for detection, sampling, integration or read-out
• CPC Class Codes: H01L 2224/32145 the bodies being stacked
• CPC Class Codes: H01L 2224/45099 Material
• CPC Class Codes: H01L 2224/48145 the bodies being stacked
• CPC Class Codes: H01L 2224/73253 Bump and layer connectors
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• CPC Class Codes: H01L 24/16 of an individual bump connector
• CPC Class Codes: H01L 24/32 of an individual layer connector
• CPC Class Codes: H01L 24/48 of an individual wire connector
• CPC Class Codes: H01L 24/49 of a plurality of wire connectors
• CPC Class Codes: H01L 24/73 Means for bonding being of different types provided for in two or more of groups H01L24/10, H01L24/18, H01L24/26, H01L24/34, H01L24/42, H01L24/50, H01L24/63, H01L24/71
• CPC Class Codes: H01L 24/81 using a bump connector
• CPC Class Codes: H01L 24/85 : using a wire connector wire bonding in general B23K20/004
• CPC Class Codes: H01L 27/14634 : Assemblies, i.e. Hybrid structures
• CPC Class Codes: H01L 2924/00 : Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/00014 : the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/10253 : Silicon [Si]
• CPC Class Codes: H01L 2924/10337 : Indium gallium arsenide [InGaAs]
• CPC Class Codes: H01L 2924/12043 : Photo diode
• CPC Class Codes: H01L 2924/1433 : Application-specific integrated circuit [ASIC]

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.

Claims

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.