Depth Sensor Module Triangulation Stray Light Immunity
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Solution Overview
Problem
Existing optical proximity sensors face challenges in detecting highly absorbing objects and suppressing stray light and reflections, which affects their reliability and accuracy, especially in the presence of dirt or dust.
Innovation Solution
A depth sensor module with a light emitting part and a light detector part spatially offset along a triangulation baseline, using at least two light sources to perform triangulation-based depth estimation, which allows for reduced requirements on light structure and increased stability against manufacturing tolerances and stray light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If intensity-measurement based proximity sensing is used, then the system is simple to implement, but it cannot reliably detect highly absorbing objects and is sensitive to stray light and reflections
Solution Approach 1:
The patent changes the measurement parameter from light intensity to depth/distance measurement using time-of-flight or phase-based methods. This allows the system to detect highly absorbing objects reliably by measuring the time or phase of reflected light rather than relying on intensity, which is sensitive to object absorption properties and stray light.
Solution Approach 2:
The patent replaces the simple intensity measurement approach with a more sophisticated depth sensing mechanism using modulated light and phase/time measurement. This substitution enables reliable detection of absorbing objects and immunity to stray light by measuring the temporal characteristics of light reflection rather than spatial intensity.
2Measurement precision
If stray light suppression measures are implemented, then measurement accuracy improves, but device complexity increases
Solution Approach 1:
The patent uses periodic modulation of the light source and synchronous detection of the reflected light. By modulating the light at a specific frequency and measuring the phase shift or time of flight of the modulated signal, the system can distinguish true depth information from stray light, achieving high measurement precision without complex physical stray light suppression structures.
3Reliability
If depth sensing is implemented to overcome stray light issues, then proximity detection reliability improves, but timing resolution requirements and system complexity increase
Solution Approach 1:
The patent offers two approaches: direct time-of-flight measurement with high timing resolution requirements, or indirect phase-based measurement with reduced timing requirements. The phase-based method measures the phase shift of modulated light instead of absolute time of flight, achieving reliable depth sensing with relaxed timing resolution requirements while maintaining immunity to stray light through synchronous detection.
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 solution enables robust and stable depth sensing with reduced susceptibility to stray light and manufacturing variations, allowing for accurate two-dimensional depth mapping and improved reliability in proximity detection.
Implementation Method 1
The light emitting part and the light detector part are spatially offset in the direction of a triangulation baseline... perform triangulation-based depth estimation
Implementation Method 2
the light detector part is configured to acquire light and to provide along the direction of the triangulation baseline an intensity distribution of the acquired light
Data Source
Figure 1a~1c
Figure 2a~2c
Figure 3a~3c
AI summary
The invention relates to a depth sensor module and depth sensing method. The depth sensor module and method is adapted to include a light detector part and emitting part with a least two light sources spatially offset in the direction of the triangulation baseline. In some of the embodiments, the pixel field of the image sensor in the light detector part consists of time-of-flight pixels. Depth measurements derived by triangulation can be used to calibrate depth maps generated by the time-of-flight measurements.