DMD Diffractive Lidar FOV Expansion
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Solution Overview
Problem
Current lidar systems face challenges in achieving a wide field of view (FOV) with high angular resolution and fast scan rates while maintaining a large aperture, due to limitations in photon detection efficiency and scanning modalities.
Innovation Solution
A MEMS-based all-solid-state lidar system employing a Digital Micromirror Device (DMD) as a programmable blazed grating and a 2-dimensional sensor array, which uses nanosecond pulsed laser illumination to diffractively steer laser pulses and expand the FOV by a factor of seven without sacrificing angular resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a 2D MPPC sensor array is used for flash lidar system, then the device area is reduced to 1-2 mm, but the total FOV is limited to 1-2 degrees
Solution Approach 1:
The patent introduces temporal dimension by using sequential scanning of multiple sub-FOVs over time. The DMD device dynamically redirects light from different angular ranges to different regions of the compact MPPC array, effectively expanding the total FOV beyond the array's physical angular coverage while maintaining compact form factor.
Solution Approach 2:
The system employs a dynamically controllable DMD device that can rapidly switch between different sub-FOV configurations. This dynamic beam steering capability allows the compact sensor array to sequentially capture light from a much wider angular range, achieving expanded total FOV without increasing device area.
2Area of moving object
If mechanical scanning modalities such as scanning mirrors are employed, then the FOV can be expanded, but the scan speed is limited
Solution Approach 1:
The patent replaces traditional mechanical scanning mirrors with a DMD-based electrostatic micromirror array. The DMD can rapidly switch between different sub-FOV configurations using electrical actuation, achieving much faster switching speeds compared to mechanical scanning systems while maintaining expanded FOV capability.
Solution Approach 2:
The system uses dynamically controllable DMD micromirrors that can rapidly reconfigure beam steering angles without mechanical moving parts. This dynamic electrostatic actuation enables fast switching between sub-FOVs, significantly improving scan speed compared to traditional mechanical scanning modalities.
3Speed
If MEMS resonant mirrors are used, then the scanning angle and scanning speed are increased, but the aperture size is limited to mm scale
Solution Approach 1:
The patent combines a DMD device with a compact MPPC sensor array to create a hybrid system. The DMD provides fast beam steering capability while the MPPC array provides compact detection, achieving both fast scanning speed and reasonable aperture size by merging the strengths of these two components.
Solution Approach 2:
The system uses temporal multiplexing to scan through multiple sub-FOVs sequentially, allowing the aperture to be optimized for each sub-FOV while achieving a much larger total effective aperture through time-sequential operation. This dimensional approach allows fast scanning with effective aperture size larger than the physical component dimensions.
4Area of moving object
If the number of pixel counts of MPPC sensor array is increased, then the FOV can be expanded, but the device area increases significantly
Solution Approach 1:
The patent introduces temporal dimension by sequentially scanning multiple sub-FOVs over time. Instead of using a large 2D array to capture all FOV simultaneously, the system uses a compact array that sequentially samples different angular regions, achieving expanded total FOV without proportionally increasing device area.
Solution Approach 2:
The total FOV is divided into multiple sub-FOVs that are scanned sequentially. Each sub-FOV is captured by a small portion of the MPPC array at a time, allowing the use of a compact sensor array to achieve a much larger total FOV through time-sequential sampling of segmented angular regions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system achieves a seven times improvement in FOV while maintaining angular resolution, enabling real-time horizontal expansion of the lidar detection area to 44°, enhancing the maximum detection range and power density of laser pulses.
Implementation Method 1
A MEMS-based all-solid-state lidar system employs a Digital Micromirror Device (DMD) as a programmable blazed grating and a 2-dimensional sensor array, which uses nanosecond pulsed laser illumination to diffractively steer laser pulses
Implementation Method 2
The micromirror element tilts along its rotation axis in +12° between the on-state and off-state. The on-state micromirrors redirect the light to the pupil of a projection lens, while the off-state micromirrors redirect the light outside of the pupil.
Implementation Method 3
While the mirrors are in motion, a nanosecond pulse illuminates the micromirrors. Due to the three orders of magnitude difference in the time scale between the transitional period of the DMD from the off- to the on-state (several μs) and ns pulse, the dynamic movement of the micromirrors between the off-state and on-state is effectively 'frozen' so that the transitional states of micromirrors satisfies the blazed grating condition.
Data Source
AI summary
A LIDAR system includes a laser source configured to generate laser light pulses, a first DMD, a second DMD and a two-dimensional (2D) sensor array. The first DMD is configured to receive the laser light pulses and diffractively steer the light pulses to sequentially illuminate different sub-regions within the extended region. The second DMD is configured to receive reflected light pulses from the different sub-regions in a sequential manner as each of the different sub-regions is illuminated by the light pulses. The 2D sensor array configured to receive reflected light pulses from the second DMD and form an image of the different sub-regions as the reflected light pulses from each of the different sub-regions is sequentially received from the second DMD.