Stereo Camera Polarization Combiner Thermal Stability
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Solution Overview
Problem
Conventional stereo cameras face challenges in accurately measuring distance due to temperature-induced distortions in optical members and mounting position shifts, leading to position errors in pixel correspondence, which are costly to correct.
Innovation Solution
A stereo camera design that combines the optical paths of left and right light using a polarization combiner, focusing the combined light onto a single imager through a shared optical member, ensuring that both images are affected equally by temperature changes, thus minimizing the impact on distance measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate optical members are used for left and right imaging systems, then the stereo camera can capture images with disparity, but temperature changes cause different distortions in each optical member leading to position errors of several pixels
Solution Approach 1:
The patent merges the optical paths of left and right imaging systems into a single shared optical member (lens). By using one common lens for both imaging paths instead of separate lenses, the system ensures that temperature-induced distortions affect both images equally, eliminating differential distortion and the resulting position errors between corresponding pixels.
Solution Approach 2:
The single optical member serves multiple functions by simultaneously forming both the left image and the right image with disparity. This universal optical component replaces the traditional separate optical members, providing thermal stability while maintaining the stereo imaging capability needed for distance measurement.
2Strength
If metal mounting members are used to fix positions between left and right imagers, then the structure is mechanically strong, but the large linear expansion coefficient causes mounting position shifts with temperature changes
Solution Approach 1:
The patent changes the material parameter (linear expansion coefficient) of the mounting structure by replacing metal with resin. Although resin has lower mechanical strength, it provides superior thermal stability with minimal expansion/contraction, preventing position shifts between imagers during temperature changes. This parameter change prioritizes dimensional stability over mechanical strength.
Solution Approach 2:
The patent employs composite material construction in the housing, using resin materials that combine adequate mechanical strength with low thermal expansion properties. This composite approach allows the mounting structure to maintain both structural integrity and thermal stability, avoiding the position shifts that occur with pure metal constructions.
3Measurement precision
If calibration is performed to correct distortion and mounting position errors, then distance measurement accuracy improves, but the apparatus becomes expensive
Solution Approach 1:
The patent implements preliminary design actions that prevent distortion and position errors from occurring in the first place. By using a shared optical member and thermally stable resin mounting structure from the outset, the system eliminates the need for complex post-manufacturing calibration procedures, thereby reducing manufacturing costs while maintaining measurement accuracy.
Solution Approach 2:
The patent converts the potential harm of temperature changes into a benefit by designing a system where temperature-induced effects are uniform across both imaging paths. The shared optical member ensures that any thermal distortion affects both images equally, which actually simplifies the system by eliminating differential distortion, thereby reducing calibration needs and manufacturing costs.
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 design reduces the need for costly calibration corrections, providing a cost-effective and environmentally resistant stereo camera that maintains accurate distance measurements despite temperature-induced changes.
Implementation Method 1
a polarization combiner that combines optical paths of left light and right light, directions of polarization of which are different in a perpendicular direction
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3~5
AI summary
A stereo camera that obtains an image having disparity with respect to a photographic subject, includes: a polarization combiner that combines optical paths of left light and right light, directions of polarization of which are different in a perpendicular direction and which form two images having disparity, into one; an imager that captures an image having at least two polarized components; and an optical member that focuses the combined left light and right light onto the imager.