This paper presents a cost-effective position sensing method for 2D scanning mirrors. The method uses only one 1D PSD (position sensitive detector) located at the backside of the 2D scanning mirror plate to retrieve the 2D rotation angle about the two axes separately in real time. Any 2D scanning mirror with resonant vibration about one axis and quasi-static vibration such as sinusoidal, saw tooth, triangular oscillation about the other axis can use this method. The 2 vibration axes are orthogonal to each other to form the scanning patterns, which are most desired in scanning 3D LiDAR systems. 3D scanning LiDAR is the targeted application for this research. The method uses timing measurement to measure the resonant vibration angle and Lagrange interpolation polynomial approximation to retrieve the quasi-static vibration angle. A prototype has been built to measure the 2D rotation angle of a 2D micromirror. The measured angle using the proposed method was verified using a 2D PSD. The largest errors for the vertical/horizontal angles were 9.6% and 5.36% respectively. The position sensing mechanism is also integrated to a scanning 2D micromirror based LiDAR system to demonstrate it’s real time capability.
This paper presents a 2D FPCB (Flexible Printed Circuit Board) micromirror and a scanning 3D LIDAR based on it by integrating the 2D FPCB micromirror with a commercially available single point LIDAR. The 2D FPCB micromirror retains the benefits of previously developed 1D FPCB micromirrors, i.e., large aperture and low cost while providing rotation of the mirror plate about 2 orthogonal axes to be able to scan a laser beam about both vertical and horizontal axes to achieve 2D scanning. One 2D FPCB micromirror is integrated with a single point LIDAR to achieve a 3D scanning LIDAR, which, in comparison to the previously developed 1D FPCB micromirror based 3D LIDAR, achieved more compact structure and lower cost with no strict requirement on the alignment between two micromirrors since only one 2D micromirror rather than two 1D micromirrors used. Prototypes of the 2D FPCB micromirror and the 3D LIDAR based on it are fabricated and tested. The test results demonstrate that the 2D FPCB micromirror based 3D LIDAR achieved a volume reduction over the previous 1D FPCB micromirror based 3D LIDAR from 1042 cm3 to 754 cm3 with a FOV (Field of View) of 40°×24° at 150 Hz horizontal scanning and 2 Hz vertical scanning.
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