LiDAR scanning mirror with a patterned Freznel zone plate profile

Patent metadata

Field	Value
Publication number	US-11835730-B2
Application number	US-202017136976-A
Country	US
Kind code	B2
Filing date	Dec 29, 2020
Priority date	Dec 29, 2020
Publication date	Dec 5, 2023
Grant date	Dec 5, 2023

Abstract

Embodiments of the disclosure provide a collimating scanner for an optical sensing system, a method for fabricating the collimating scanner, and a transmitter that includes the collimating scanner. An exemplary collimating scanner may include a scanning mirror configured to steer a light beam towards an object. The collimating scanner may also include a Fresnel zone plate profile patterned on the scanning mirror configured to collimate the light beam. The disclosed collimating scanner eliminates the use a separate collimating lens and thus improves the form factor of the optical sensing system.

First claim

What is claimed is:

1. A collimating scanner for an optical sensing system, comprising:
a scanning mirror configured to steer a light beam towards an object; and
a Fresnel zone plate profile patterned on the scanning mirror configured to collimate the light beam
wherein the scanning mirror is driven by a MEMS actuator, wherein the MEMS actuator and the scanning mirror with the Fresnel zone plate are self-aligned.

2. The collimating scanner of claim 1 , wherein a shape of the Fresnel zone plate profile is selected based at least in part on an incident angle of the light beam.

3. The collimating scanner of claim 2 , wherein the shape of the Fresnel zone plate profile is elliptical when the incident angle is non-zero.

4. The collimating scanner of claim 2 , wherein the shape of the Fresnel zone plate profile is circular when the incident angle is zero.

5. The collimating scanner of claim 1 , wherein one or more of a pitch, a step height, or a shape of the Fresnel zone plate profile is predetermined according to one or more of a divergence angle, an operation wavelength, or a diameter of the light beam.

6. The collimating scanner of claim 1 , wherein the Fresnel zone plate profile includes concentric rings of at least two height steps.

7. The collimating scanner of claim 1 , further comprising the MEMS actuator configured to drive the collimating scanner to steer the light beam towards the object at a plurality of scanning angles, wherein the MEMS actuator and the scanning mirror with the Fresnel zone plate profile are formed using a self-alignment process.

8. The collimating scanner of claim 7 , wherein the MEMS actuator includes a plurality of staggered vertical comb drives formed in a first wafer and the scanning mirror with the Fresnel zone plate profile is formed in a second wafer bonded to the first wafer.

9. The collimating scanner of claim 8 , wherein the first wafer and the second wafer are Silicon on Insulator (SOI) wafers.

10. A method of forming a scanning mirror with a Fresnel zone plate profile patterned thereon, the method comprising:
forming a first wafer with a first set of actuator features;
bonding a second wafer to the first wafer;
forming a scanning mirror surface on the second wafer;
patterning a Fresnel zone plate profile on the scanning mirror surface; and
etching the second wafer to form a second set of actuator features aligned with the first set of actuator features.

11. The method of claim 10 , further comprising:
etching a backside substrate of the first wafer to release the scanning mirror including the Fresnel zone plate profile.

12. The method of claim 10 , wherein forming the first wafer comprises:
forming a substrate layer;
forming an insulating layer on the substrate layer; and
forming a device layer on the insulating layer.

13. The method of claim 10 , wherein the first wafer and the second wafer are Silicon on Insulator (SOI) wafers.

14. The method of claim 10 , wherein the forming the scanning mirror surface on the second wafer comprises:
grinding a surface roughness onto the second wafer.

15. The method of claim 10 , wherein the patterning the Fresnel zone plate profile on the scanning mirror surface comprises:
patterning the Fresnel zone plate profile to a quarter-wavelength depth on the scanning mirror surface; and
etching the Fresnel zone plate profile after patterning.

16. The method of claim 10 , wherein the etching the scanning mirror surface with the Fresnel zone plate profile patterned thereon to form the second set of actuator features comprises:
performing a first etching process and a second etching process to form the second set of actuator features aligned with the first set of actuator features.

17. The method of claim 10 , wherein the first set of actuator features are stator actuator features and the second set of actuator features are moveable actuator features.

18. The method of claim 10 , wherein the first set of actuator features and the second set of actuator features form a MEMS actuator including a plurality of staggered vertical comb drives configured to drive the scanning mirror to steer rotate to a plurality of scanning angles.

19. The method of claim 10 , wherein at least one of a pitch, step height, or shape of the Fresnel zone plate profile is designed based at least in part on information associated with a laser source.

20. A transmitter for an optical sensing system, comprising:
a light source configured to emit a light beam towards an object; and
a collimating scanner that comprises:
a scanning mirror configured to steer the light beam towards the object; and
a Fresnel zone plate profile patterned on the scanning mirror configured to collimate the light beam
wherein the scanning mirror is driven by a MEMS actuator, wherein the MEMS actuator and the scanning mirror with the Fresnel zone plate are self-aligned.

Assignees

• Beijing Voyager Tech Co Ltd

Inventors

• Wang Youmin
• Lu Yue

Classifications

• G02B27/30 Primary

  Collimators · CPC title

• G01S7/4817

  relating to scanning · CPC title

• G02B5/189

  Structurally combined with optical elements not having diffractive power · CPC title

• G02B26/0833

  the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD (G02B26/0825 takes precedence; micromechanical devices in general B81B) · CPC title

• G02B26/10

  Scanning systems · CPC title