Large aperture surface-micromachined rotating micromirror with the majority of dimples removed

Zuo, Haoyi; He, Siyuan

doi:10.1088/1361-6439/ab3e8d

“…However, a low unit cost can be achieved through a batch production. MEMS micromirrors normally have an aperture size of 10s µm ~ 1 mm [57]- [62] such as to obtain the low unit cost. When the aperture size becomes very large, e.g., ≥ 10 mm, the low unit cost benefit disappears because the unit cost is inversely proportional to the square of aperture size.…”

Section: Mems Mircomirror-lorentz Force Moving Coils Basedmentioning

confidence: 99%

Development of FPCB (Flexible Printed Circuit Board) Mirror Technology

Zuo¹

2023

Preprint

0

View full text Add to dashboard Cite

A low cost and large aperture scanning mirror with high surface quality is always highly desired. This is especially true for scanning LiDARs for autonomous vehicles. Polygon, galvanometer or MEMS mirrors can have a large aperture, but they are bulky, high power consumption and costly. This dissertation proposes a novel mirror technology for laser scanning, i.e., FPCB (flexible printed circuit board) masked one-step etching large aperture mirror, which simply etches a silicon wafer with a FPCB structure as the etching mask and the other side coated with a metal film as the etching stop layer and reflective surface. Meanwhile the FPCB structure embeds copper coils to generate Lorentz force to oscillate the mirror. The FPCB structure is fabricated using mature and commercially available FPCB process, which is 0.1 mm-resolution based photolithography, instead of 1 μm based photolithography micromachining used in traditional MEMS mirrors. In addition, only one-step DRIE etching is needed without requiring any critical alignment. Such that a low cost can be achieved, e.g., a few dollars per mirror. Moreover, the mirror plate is as thick as the silicon wafer (100~200 μm), which leads to a good flatness (ROC of 10~20 m). Prototypes are fabricated and tested. Achieved performances are: aperture of 12 x 12 mm and 24 x 24 mm, oscillation frequency from 160 Hz ~1 kHz, FOV (field of view) of 30o, 20o and 15o. A 2D and 3D scanning LiDARs based on this novel mirror technology are constructed. This dissertation also develops two electrostatic parallel plate based FPCB micromirrors with performance improved than the previously developed deigns in our group, e.g., FPCB ring-square electrode sandwiched micromirror and double-stage FPCB electrostatic micromirror. The improvements include: the rotation angle increased by 90%, the resonant frequency increased by 40-70%, and the performance variation reduced from 40% to 12%. A large aperture FPCB mirror and a 2D LiDAR based on it are developed with the following performances: aperture 25 x 50 mm, FOV of 60o, measurement distance 50 m, 500 points per frame.

show abstract

“…However, a low unit cost can be achieved through a batch production. MEMS micromirrors normally have an aperture size of 10s µm ~ 1 mm [57]- [62] such as to obtain the low unit cost. When the aperture size becomes very large, e.g., ≥ 10 mm, the low unit cost benefit disappears because the unit cost is inversely proportional to the square of aperture size.…”

Section: Mems Mircomirror-lorentz Force Moving Coils Basedmentioning

confidence: 99%

Development of FPCB (Flexible Printed Circuit Board) Mirror Technology

Zuo¹

2023

Preprint

0

View full text Add to dashboard Cite

A low cost and large aperture scanning mirror with high surface quality is always highly desired. This is especially true for scanning LiDARs for autonomous vehicles. Polygon, galvanometer or MEMS mirrors can have a large aperture, but they are bulky, high power consumption and costly. This dissertation proposes a novel mirror technology for laser scanning, i.e., FPCB (flexible printed circuit board) masked one-step etching large aperture mirror, which simply etches a silicon wafer with a FPCB structure as the etching mask and the other side coated with a metal film as the etching stop layer and reflective surface. Meanwhile the FPCB structure embeds copper coils to generate Lorentz force to oscillate the mirror. The FPCB structure is fabricated using mature and commercially available FPCB process, which is 0.1 mm-resolution based photolithography, instead of 1 μm based photolithography micromachining used in traditional MEMS mirrors. In addition, only one-step DRIE etching is needed without requiring any critical alignment. Such that a low cost can be achieved, e.g., a few dollars per mirror. Moreover, the mirror plate is as thick as the silicon wafer (100~200 μm), which leads to a good flatness (ROC of 10~20 m). Prototypes are fabricated and tested. Achieved performances are: aperture of 12 x 12 mm and 24 x 24 mm, oscillation frequency from 160 Hz ~1 kHz, FOV (field of view) of 30o, 20o and 15o. A 2D and 3D scanning LiDARs based on this novel mirror technology are constructed. This dissertation also develops two electrostatic parallel plate based FPCB micromirrors with performance improved than the previously developed deigns in our group, e.g., FPCB ring-square electrode sandwiched micromirror and double-stage FPCB electrostatic micromirror. The improvements include: the rotation angle increased by 90%, the resonant frequency increased by 40-70%, and the performance variation reduced from 40% to 12%. A large aperture FPCB mirror and a 2D LiDAR based on it are developed with the following performances: aperture 25 x 50 mm, FOV of 60o, measurement distance 50 m, 500 points per frame.

show abstract

“…Since the dimple cuts with depth of 0.75 µm is used in this design, the actual vertical gap between the electrodes of the electrostatic parallel plate actuator would become 1.25 µm which is more than three times the maximum vertical stroke limit (0.4 µm) and thus the pull in effect can be avoided. This also helps to reduce stiction between the two surfaces [31]. ANCHOR1 is used to cut through the first oxide layer to anchor the pillar structures made of the POLY1 layer to the substrate.…”

Section: Microfabrication Of Optical Phased Array Devicementioning

confidence: 99%

Conventional surface micromachining process for the fabrication of a linear optical phased array based on piston micromirrors

Mohammad

¹

,

He

²

,

Mrad

³

2021

J. Micromech. Microeng.

Self Cite

View full text Add to dashboard Cite

Micro electromechanical system (MEMS) based optical phased array (OPA) technology generally demands narrow and tightly spaced suspended microstructures with high-aspect-ratio in the lateral dimensions. This paper presents an one dimensional OPA system which is fabricated using the standard PolyMUMPs process, leading to a low-cost, simplified and commercially accessible surface micromachining technique for the OPA technology. The proposed OPA device utilizes an array of metal-coated silicon micromirrors with high-aspect-ratio structures which act as optical phase shifters. Each micromirror along the array is individually actuated by an electrostatic parallel plate micro-actuator made of a micro-cantilever beam positioned above a fixed electrode. The field of view obtained by the device is measured as 4.76° which is comparable to those by the previous MEMS based OPA devices fabricated using custom-run and complex surface micromachining processes. The OPA device has a response time of 6.5 µs and an out of plane actuation stroke of 0.16 µm at a bias voltage of 55 V. The magnitude of the out of plane displacement by the phase shifters is equal to one-quarter of the laser wavelength (650 nm) used which leads to the desired optical phase shift of π radian.

show abstract

Large aperture surface-micromachined rotating micromirror with the majority of dimples removed

Cited by 3 publications

References 27 publications

Development of FPCB (Flexible Printed Circuit Board) Mirror Technology

Development of FPCB (Flexible Printed Circuit Board) Mirror Technology

Development of FPCB (Flexible Printed Circuit Board) Mirror Technology

Conventional surface micromachining process for the fabrication of a linear optical phased array based on piston micromirrors

Contact Info

Product

Resources

About