DMD Optical Image Detection With Walsh-Coded Dynamic Range Imaging
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Solution Overview
Problem
Current CMOS/CCD/FPA technology is limited in delivering full spectrum, extreme dynamic range, and cost-effective optical imaging, especially in scenarios with high contrast and varying light conditions, such as night vision and daylight scenarios, due to limitations in wavelength coverage and eye safety concerns.
Innovation Solution
The CAOS camera system employs a Digital MicroMirror Device (DMD) with time-frequency coding and Walsh code sequences to selectively encode and decode pixel irradiance values, using multiple access RF wireless networks and DSP for noise reduction and high SNR, enabling simultaneous imaging across multiple spectral bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If current CMOS/CCD/FPA technology is used for optical imaging, then the system is relatively simple and cost-effective, but it cannot achieve full spectrum coverage and extreme dynamic range in high contrast scenarios
Solution Approach 1:
The imaging system is segmented into multiple spectral bands, with separate detectors for different wavelength ranges (e.g., visible and NIR bands). Each detector is optimized for its specific spectral range, allowing full spectrum coverage while maintaining manageable complexity through specialized modular components.
Solution Approach 2:
The imaging system is designed to perform multiple functions within a single integrated platform, supporting both passive imaging (ambient light) and active imaging (laser illumination) modes, and capable of operating across multiple spectral bands simultaneously, thereby achieving full spectrum versatility without requiring separate dedicated systems.
2Reliability
If active imaging with laser illumination is used in high contrast scenarios, then extreme dynamic range is achieved, but eye safety concerns and wavelength coverage limitations arise
Solution Approach 1:
The laser illumination system is segmented into multiple wavelength sources, each operating in a safe spectral band (e.g., visible and NIR). By distributing the illumination across multiple safe wavelengths rather than using a single high-power wavelength, the system achieves extreme dynamic range while maintaining eye safety through lower individual wavelength intensities.
Solution Approach 2:
The system dynamically adjusts illumination parameters including wavelength selection and power levels based on scene requirements and safety constraints. By changing operational parameters to use multiple safe wavelengths with appropriate power levels, the system maintains reliable extreme dynamic range imaging while eliminating eye safety hazards.
3Measurement precision
If multiple pixels are selected for time-frequency coding in CAOS, then simultaneous multi-pixel signal-to-noise ratio photo-detection is achieved, but optical point detector saturation may occur
Solution Approach 1:
The CAOS system employs periodic time-division multiple access (TDMA) coding schemes where multiple pixels are activated in sequential time slots rather than simultaneously. Each pixel group is activated for a specific duration, allowing the detector to integrate signals periodically without saturation, while maintaining high signal-to-noise ratio through coherent integration across multiple periods.
Solution Approach 2:
The system dynamically adjusts the activation patterns and integration times for different pixel groups based on scene brightness and detector capacity. By making the coding scheme adaptive and dynamic rather than static, the system optimizes signal-to-noise ratio for each measurement while preventing detector saturation through real-time parameter adjustment.
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 CAOS camera achieves robust, cost-effective, and secure full spectrum imaging with extreme dynamic range, suitable for various applications including automotive vision, biomedical microscopy, and surveillance, by leveraging time-frequency coding and Walsh codes for enhanced signal processing and noise reduction.
Implementation Method 1
time-frequency coding by the DMD the optical irradiance values of each selected pixel using a plurality of selected bits of its associated Walsh code time sequence
Implementation Method 2
The CAOS camera operates on the principles of a multiple access Radio Frequency (RF) wireless network that relies on RF coded transmission and electronic Digital Signal Processing (DSP) based data signal recovery
Implementation Method 3
detecting the time frequency coded optical irradiance values of the selected pixels simultaneously at the first point Photo Detector and at the second point Photo Detector
Implementation Method 4
when a pixel is being encoded with a code sequence bit the +θ tilt state of a DMD micromirror associated with the pixel images light from the pixel onto the first point Photo Detector (PD1) by means of the first lens (L3) and the −θ tilt state of the DMD micromirror images encoded pixel light onto the second point Photo Detector (PD2) by means of the second lens (L2)
Implementation Method 5
The RF output signal from the optical antenna next undergoes powerful electronic DSP-based decoding that gives extreme and controllable processing gain and noise reduction for high Signal-to-Noise Ratio (SNR) pixel irradiance extraction
Data Source
AI summary
The present invention provides a method for performing optical image detection using a camera module comprising a Digital MicroMirror Device, a first point Photo Detector, a second point Photo Detector, a first lens and a second lens. The method comprises: mapping incident light onto an image plane of the DMD to form a light irradiance map; selecting N pixels on the DMD for time frequency coding; associating each selected pixel with a unique Walsh code time sequence; time frequency coding by the DMD the optical irradiance values of each selected pixel using a plurality of selected bits of its associated Walsh code time sequence; detecting the time frequency coded optical irradiance values of the selected pixels simultaneously at the first point Photo Detector and at the second point Photo Detector; and performing simultaneous signal processing on the time frequency coded optical irradiance values detected by the first point Photo Detector and by the second point Photo Detector to determine the light intensity of each of the selected pixels and produce an image of the incident light.