Doppler Imager Pixel Array for Speed and Direction Detection
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Solution Overview
Problem
Existing systems for detecting the speed and direction of moving objects, such as in autonomous vehicles and security cameras, are often expensive and bulky due to the combination of light detection and ranging (LIDAR) with Doppler sensing, and face challenges in distinguishing reflectivity variations and determining motion direction from a single image.
Innovation Solution
A two-dimensional array of pixels with each pixel equipped with two optical filters and detectors, generating signals proportional to the overlap between the filter pass bands and the excitation light spectrum, allowing for the determination of object speed and direction through normalized output signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If LIDAR combined with Doppler sensing is used to detect speed and direction of moving objects, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent combines multiple functions (Doppler sensing, imaging, and speed/direction detection) into a single integrated pixel array system. Each pixel contains multiple photodetectors with different spectral responses that work together to simultaneously measure intensity, Doppler shift, and determine motion direction, eliminating the need for separate LIDAR and Doppler sensing systems.
Solution Approach 2:
The pixel array serves multiple functions: it performs standard imaging, Doppler velocity measurement, and direction determination all through the same hardware structure. The multi-element pixels can operate in different modes depending on which signals are processed, making the system universally applicable for various measurement needs without requiring separate specialized devices.
2Device complexity
If a single image is used to determine motion characteristics, then device complexity is reduced, but measurement precision deteriorates due to inability to distinguish reflectivity variations and determine direction
Solution Approach 1:
Each pixel is segmented into multiple photodetector elements with different spectral characteristics. This segmentation allows the system to capture different components of the reflected light (different Doppler shifts) within the same spatial location, enabling precise measurement of both speed and direction without requiring multiple separate imaging systems.
Solution Approach 2:
The patent adds a spectral dimension to the traditional spatial imaging by incorporating multiple photodetectors with different spectral responses in each pixel. This transforms the measurement from purely spatial (2D image) to spatio-spectral (adding frequency dimension), enabling extraction of velocity and direction information from the spectral variations while maintaining the same spatial resolution.
3Measurement precision
If multiple detectors with different pass bands are used in each pixel, then measurement precision is improved, but manufacturing precision requirements increase
Solution Approach 1:
Instead of relying on precise mechanical alignment of filter pass bands, the system uses photodetectors with inherently different spectral responses (different quantum efficiency curves). The Doppler measurement is achieved by comparing the relative signals from these detectors, and the algorithm compensates for any spectral variations, making the system robust to manufacturing tolerances.
Solution Approach 2:
The system includes calibration and signal processing algorithms that measure the actual spectral response of each detector and use this information to correct measurements. The processing circuitry compensates for variations in filter characteristics and detector responses, ensuring accurate Doppler measurements even when manufacturing precision varies within normal tolerances.
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 approach reduces the cost and size of Doppler imaging systems while providing precise image-wise data on relative speeds and directions of movement, effectively addressing the limitations of previous technologies by enhancing sensitivity and direction determination.
Implementation Method 1
Each pixel includes a first optical filter having a first pass band arranged to filter excitation light reflected by a moving object and a first detector configured to detect light transmitted through the first optical filter
Implementation Method 2
The first detector generates a signal proportional to an overlap of the pass band of the first optical filter and the spectrum of the excitation light
Implementation Method 3
Doppler shift is the change in frequency of a wave in relation to an observer who is moving relative to the wave source
Data Source
AI summary
A system comprises an imaging device that includes a two dimensional array of pixels. Each pixel of the array includes a first optical filter having a first pass band arranged to filter excitation light reflected by a moving object and a first detector configured to detect light transmitted through the first optical filter and to generate a first electrical signal. Each pixel of the array also includes a second optical filter having a second pass band arranged to filter excitation light reflected by a moving object and a second detector configured to detect light transmitted through the second optical filter and to generate a second electrical signal. The imaging device further includes circuitry that generates output signals from each of the pixels based on the first electrical signal and the second electrical signal of the pixel. The output signal includes information about the speed and direction of the moving object.