DMD Time-Frequency Optical Imaging for Extreme Dynamic Range
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Solution Overview
Problem
Current CMOS/CCD/FPA technology is limited in delivering full spectrum, extreme dynamic range optical imaging, especially in scenarios with high contrast and varying light conditions, such as night vision and daylight, and is not cost-effective.
Innovation Solution
The CAOS camera system uses a Digital MicroMirror Device (DMD) with time-frequency coding and Walsh codes to selectively encode and decode light irradiance values from multiple spectral bands, allowing simultaneous imaging across various spectral bands with improved Signal-to-Noise Ratio (SNR) and noise reduction, utilizing a network of lenses and photo detectors for robust image processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current CMOS/CCD/FPA technology is used for optical imaging, then the system is relatively simple and cost-effective, but it cannot deliver full spectrum extreme dynamic range imaging in high contrast conditions
Solution Approach 1:
The imaging system is segmented into multiple spectral channels, each detecting a specific wavelength band. The DMD device divides the incident light into multiple beams corresponding to different spectral components, which are then detected by separate photodetectors. This segmentation enables full spectrum extreme dynamic range imaging by processing each spectral band independently while maintaining system feasibility.
Solution Approach 2:
The patent transitions from spatial imaging to spectral-dimensional imaging by using a dispersive element to separate light into wavelength components. The DMD device operates in the spectral domain, modulating different wavelength components independently. This dimensional transformation from spatial to spectral space enables extreme dynamic range measurement across the full spectrum.
2Reliability
If traditional optical cameras are used, then the structure is simpler, but they cannot achieve simultaneous multi-pixel improved signal-to-noise ratio photo-detection
Solution Approach 1:
Multiple photodetectors are merged into a single detection plane, each receiving light from specific spectral channels through the DMD device. The DMD combines the functions of multiple specialized detectors by spatially modulating the incident light to direct different wavelength components to appropriate detectors simultaneously. This merging achieves multi-pixel improved SNR photo-detection while consolidating the detection architecture.
Solution Approach 2:
The DMD device acts as an intermediary between the incident light and the photodetectors. It modulates the spatial distribution of light based on spectral content, directing different wavelength components to appropriate detectors. This intermediary function enables simultaneous multi-pixel detection with improved SNR by filtering and routing light before detection rather than requiring complex detector arrays.
3Reliability
If TDMA mode is used in CAOS camera, then optical point detector saturation is prevented, but imaging speed is reduced
Solution Approach 1:
The DMD device applies periodic temporal modulation to the light from different spatial locations using TDMA (Time Division Multiple Access). Each pixel or group of pixels is activated in sequential time slots, preventing detector saturation by ensuring that the total light energy arriving at any detector during its integration period remains within linear response limits. This periodic activation pattern enables reliable detection across extreme dynamic ranges.
Solution Approach 2:
The system dynamically adjusts the activation pattern of DMD micromirrors based on scene brightness and detector capacity. The TDMA scheduling is adaptive, allocating different time slots to different spatial regions according to their illumination levels. This dynamic time-multiplexing approach prevents saturation in bright regions while maintaining imaging capability across the entire scene, balancing reliability with effective imaging speed.
4Reliability
If FDMA and CDMA modes are engaged for simultaneous multi-pixel photo-detection, then noise reduction and DSP gain are achieved, but the system complexity increases
Solution Approach 1:
The DMD device modulates light using different frequency codes (FDMA) and orthogonal codes (CDMA) to encode spatial information. By changing the temporal and spectral parameters of the modulated light, the system enables multiple pixels to be detected simultaneously through a single photodetector. The encoded signals are then decoded using digital signal processing, achieving noise reduction through coherent integration while maintaining manageable system complexity through algorithmic rather than hardware complexity.
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 high-speed, high-resolution imaging with extreme linear dynamic range, enabling reliable image data capture in diverse lighting conditions, including simultaneous imaging of multiple spectral bands, and provides enhanced security through coded data transmission.
Implementation Method 1
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 2
images light from the pixel onto the first point Photo Detector (PD1) by means of the first lens (L3) and images encoded pixel light onto the second point Photo Detector (PD2) by means of the second lens (L2)
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
Data Source
Figure 1(a)~1(b)
Figure 2
Figure 3
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.