CDMA 3D Imaging for Focal Plane Array LIDAR
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Solution Overview
Problem
Conventional focal plane array LIDAR systems are limited by the need for large-scale arrays to achieve high imaging resolution, which increases hardware design complexity and cost, and hampers miniaturization and integration, while also limiting the ability to achieve scannerless, large field-of-view, high-accuracy, and high-resolution imaging.
Innovation Solution
A CDMA-based 3D imaging method that uses a 2N×2N encoder to divide a pulsed laser beam into encoded sections, which are then multiplexed by an M-element detector array to achieve M×22N pixel resolution, allowing for high-resolution, scannerless, and real-time 3D imaging with small-scale detectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If large-scale detector arrays are used to achieve high imaging resolution, then imaging resolution is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent divides the large-scale detection task into multiple smaller sub-tasks by using a compact detector array combined with a diffractive optical element that performs spatial segmentation of the incoming light. The DOE creates multiple virtual images or channels from different spatial regions, allowing a small physical array to effectively sample a much larger field of view with high resolution.
Solution Approach 2:
The patent introduces an additional optical dimension by using a diffractive optical element to create depth or angular encoding in the light field. This allows the system to achieve high-resolution imaging in one dimension while using a reduced array size, effectively trading physical array dimensions for optical encoding dimensions.
2Measurement precision
If large-scale detector arrays are used to achieve high imaging resolution, then imaging resolution is improved, but manufacturing cost increases
Solution Approach 1:
The patent segments the imaging function between a simple, compact detector array and a diffractive optical element that performs the complex spatial encoding. This segmentation allows the detector array to remain small and inexpensive while the DOE, which can be manufactured using standard microfabrication techniques, handles the resolution-enhancing function.
Solution Approach 2:
The diffractive optical element creates multiple virtual copies or channels of the optical field, allowing a single small detector array to capture information that would otherwise require many more detectors. This copying approach reduces the need for expensive large-scale detector arrays while maintaining high imaging resolution.
3Device complexity
If conventional algorithms are used for waveform decomposition in non-scanning LIDAR, then system simplicity is maintained, but range accuracy decreases
Solution Approach 1:
The patent replaces conventional mechanical or algorithmic waveform decomposition methods with a diffractive optical processing approach. The DOE performs spatial frequency decomposition and range encoding optically, substituting complex signal processing algorithms with an optical analog computation that achieves higher range accuracy while maintaining system simplicity.
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
This method enables high-resolution, real-time 3D imaging with small-scale detectors, achieving up to 268-million pixels per frame with a 256×64 APD array, reducing data redundancy and enhancing detector utilization while maintaining high precision and large field-of-view capabilities.
Implementation Method 1
LIDAR employs photodetectors to convert the optical signal to an electrical signal for subsequent processing
Implementation Method 2
the time-of-flight principle that the system is based on is very direct and simple
Data Source
AI summary
A focal plane array light detection and ranging 3D imaging method based on a code division multiple access technique is provided. A narrow laser pulse is shaped into a flat-top beam. The shaped beam is space-time encoded by a focal plane array-based optical encoder. The encoded beam is projected onto the target. The echo signals are obtained by a collecting lens. According to the encoding rule, the signals are grouped and multiplexed into several channels; subsequently, the multi-channel multiplexed signals are captured by a focal plane array detector and converted by a multi-channel digitizer. The multi-channel encoded full waveform signals are acquired from the digitizer by a PC terminal. The encoded full waveforms can be demodulated into the flight ranges for all subpixels via signal processing. By orthogonal range correction and pixel splicing and integrating the geographical data of all pixels, the 3D image reconstruction of the target can be accomplished.