Structured Light Projector Thermal Reference Correction for Depth Mapping
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Solution Overview
Problem
Existing depth mapping devices using structured light projectors with diffractive optical elements (MOEs) suffer from systematic errors due to temperature-dependent variations in wavelength and optical behavior, leading to inaccuracies in depth coordinate conversion.
Innovation Solution
A method and device that includes a thermal sensor to measure projector temperature, using an optical and thermal model to compute and store multiple reference images for different temperatures, and select the most relevant reference image for depth map computation, correcting for variations in focal length, tilt angle, and wavelength changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single reference image is used for depth mapping, then the device complexity is low, but the measurement precision deteriorates due to temperature-dependent optical variations
Solution Approach 1:
Multiple reference images are pre-computed for different projector temperatures before actual depth mapping operations. The system captures reference images at various known temperatures and stores them for later selection, eliminating the need for real-time thermal compensation calculations during depth mapping.
Solution Approach 2:
The reference images are generated with varying thermal parameters (temperature) to match different operating conditions. By changing the temperature parameter of the reference images to match the current projector temperature, the system maintains accurate depth mapping across varying thermal conditions.
2Adaptability or versatility
If the projector operates at varying temperatures, then the adaptability to different environmental conditions is improved, but the measurement precision deteriorates due to systematic errors in depth coordinate conversion
Solution Approach 1:
The system measures the actual projector temperature during operation and uses this feedback to select the appropriate pre-computed reference image. This closed-loop approach ensures that the depth mapping always uses reference data corresponding to the current thermal state of the projector, maintaining precision across varying environmental conditions.
3Measurement precision
If multiple reference images are computed for different temperatures, then the measurement precision is improved, but the loss of information increases due to the need to store and manage multiple reference datasets
Solution Approach 1:
The reference image data is segmented into discrete temperature-specific datasets rather than storing a continuous range. Each reference image corresponds to a specific temperature point, allowing efficient storage and quick retrieval without managing large continuous datasets.
Data Source
AI summary
A method for depth mapping includes operating a projector at a first temperature to project a pattern of optical radiation onto a reference plane, capturing a first image of the projected pattern on the reference plane, using the first image and an optical and thermal model of the projector to compute multiple reference images associated with different respective temperatures of the projector. Using the projector, the pattern is projected onto a scene, and a temperature of the projector is measured while projecting the pattern. The method further includes capturing a second image of the projected pattern on the scene, selecting one of the reference images responsively to the measured temperature; and computing a depth map of the scene by comparing the pattern in the second image to the selected one of the reference images.