Structured Light Sensing Module With Multi-Axis Polarizing Units
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Solution Overview
Problem
3D depth sensing technologies using structured light are sensitive to optical interference from ambient light, leading to reduced signal-to-noise ratio (SNR) and inaccurate depth information, especially in outdoor conditions where the object is moving.
Innovation Solution
A structured light sensing module with a structured light source and a sensing device equipped with polarizing units, each having different absorption axis orientations, to distinguish between structured light and ambient light, thereby optimizing SNR and improving depth accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If structured light is projected for 3D depth sensing, then depth information can be acquired with high spatial resolution, but the reflected patterns become sensitive to optical interference from ambient light, reducing signal-to-noise ratio
Solution Approach 1:
A polarizing filter is introduced as an intermediary component between the imaging sensor and the incoming light. This polarizing filter selectively transmits light with specific polarization orientations while blocking other orientations, thereby separating the structured light signal from ambient light interference and improving signal-to-noise ratio in outdoor conditions
2Object-affected harmful factors
If image capture is performed without structured light projection to reduce ambient light influence, then SNR may be improved, but the ability to distinguish structured light patterns is lost
Solution Approach 1:
The system changes the polarization parameter of the projected structured light. By projecting light with specific polarization orientations and using a polarizing filter to detect these orientations, the system can distinguish structured light from ambient light based on polarization differences, maintaining depth sensing accuracy while reducing ambient light interference
3Object-affected harmful factors
If multiple polarizing patterns are overlapped on each sensing unit, then the module can distinguish structured light from ambient light, but device complexity increases
Solution Approach 1:
The polarizing filter is segmented into multiple polarizing patterns (e.g., first, second, third, and fourth patterns with different transmission axes) that are overlapped on each sensing unit. Each pattern transmits light with specific polarization orientations, allowing the system to distinguish structured light from ambient light through differential transmission while maintaining a relatively compact structure
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 module effectively eliminates the impact of ambient light, enhancing the SNR and providing more accurate depth information by separating structured light from ambient light.
Implementation Method 1
Each polarizing unit includes at least four polarizing patterns. Each of the at least four polarizing patterns has an absorption axis. The axial directions of the absorption axes of the at least four polarizing patterns are different from each other.
Implementation Method 2
Each polarizing pattern has an absorption axis, and the axial directions of the absorption axes of the at least four polarizing patterns are different from each other
Data Source
AI summary
A structured light sensing module including a structured light source, a sensing device and a plurality of polarizing units is provided. The structured light source is configured to emit structured light having a polarization toward a sensing target. The sensing device is configured to receive the structured light reflected from the sensing target and has a plurality of sensing units. The polarizing units are disposed on a side of a light-receiving surface of the sensing device, and respectively overlap the plurality of sensing units. Each polarizing unit includes at least four polarizing patterns. Each of the at least four polarizing patterns has an absorption axis. The axial directions of the absorption axes of the at least four polarizing patterns are different from each other.