ToF Camera Polarizer Layout for Stray Light Filtering
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Solution Overview
Problem
Existing time-of-flight cameras suffer from errors in depth images due to stray light from ambient sources, which are not effectively distinguished from detection light.
Innovation Solution
A time-of-flight camera system with dual receivers and orthogonal polarizers filters stray light by comparing images with different polarization states, enhancing depth image accuracy through stereo vision and image synthesis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If detection light of fixed frequency is emitted to calculate depth information, then depth measurement capability is achieved, but stray light from ambient sources causes errors in depth images
Solution Approach 1:
The patent changes the polarization state parameter of the detection light by using a polarizer. The detection light is converted to polarized light with a specific polarization direction, allowing the system to distinguish between polarized detection light and non-polarized or differently polarized ambient stray light, thereby improving depth measurement accuracy in the presence of ambient light
Solution Approach 2:
The patent introduces polarized light as an intermediary carrier for the detection signal. By encoding the detection light with a specific polarization state, the system creates a distinguishable signal that can be separated from ambient light interference through polarization filtering, effectively using polarization state as a mediator to resolve the interference problem
2Measurement precision
If dual receivers with orthogonal polarizers are used to filter stray light, then depth image accuracy is improved, but device complexity increases
Solution Approach 1:
The patent segments the light reception function into two separate receivers, each equipped with a polarizer oriented at orthogonal polarization directions (e.g., 0 degrees and 90 degrees). This segmentation allows the system to capture light components with different polarization states separately, enabling effective stray light filtering through comparison and synthesis of the two received signals
Solution Approach 2:
The dual receiver system with orthogonal polarizers serves multiple functions: it captures the detection light signal, filters ambient stray light through polarization differentiation, and provides redundant information for error correction. The same receiver structure can be used for different polarization angles to adapt to various lighting conditions, demonstrating multi-functionality
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 system effectively filters out stray light, improving depth image accuracy and reliability by distinguishing and reducing the impact of ambient light interference.
Implementation Method 1
a first polarizer 35 and a second polarizer 37, the first polarizer 35 is arranged on a side of the first receiver 31 for receiving the reflected light L2... the second polarizer 37 is arranged on a side of the second receiver 33 for receiving the reflected light L2... Polarization directions of the first polarizer 35 and the second polarizer 37 are orthogonal to each other
Data Source
AI summary
A depth information detector includes a light receiving module and a processor. The light receiving module includes a first receiver and a second receiver set at intervals. The first receiver and the second receiver receive a reflected light reflected by an object to be detected at different positions respectively. The processor electrically connects to the light receiving module. The processor is configured for synthesizing the reflected light received by the first receiver and the second receiver into a depth image. The light receiving module also includes a first polarizer and a second polarizer, the first polarizer is on one side of the first receiver, the second polarizer is on one side of the second receiver, a polarization direction of the first polarizer and a polarization direction of the second polarizer are orthogonal to each other. A time-of-flight camera and a depth image acquisition method are further disclosed.