Prism-Based Focal Plane Adjustment for Thermal Compensation
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Solution Overview
Problem
High-resolution camera lens assemblies face challenges in achieving fast, automated, and high-yielding assembly processes due to thermal expansion, which causes defocusing issues as imaging lenses shift with temperature changes, affecting image quality.
Innovation Solution
An integrated image sensor and lens assembly with an optics compensator that includes passively actuating elements and prisms in a Babinet-Soleil configuration, which adjust the optical path to maintain focal plane alignment with the image plane by varying the thickness of the prisms in response to temperature changes, using pushrods with matching thermal expansion coefficients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If lens assemblies are manufactured with high precision positioning to ensure proper focus, then manufacturing precision is improved, but assembly complexity and time increase
Solution Approach 1:
The patent pre-adjusts the lens barrel position during assembly using a threaded lens barrel that engages with a threaded bore in the housing assembly. This preliminary mechanical adjustment allows for precise focal plane positioning before final assembly, enabling both high precision and efficient automated assembly without requiring complex post-assembly calibration systems.
2Productivity
If lens assemblies are designed for fast automated assembly, then productivity is improved, but manufacturing precision deteriorates
Solution Approach 1:
The threaded lens barrel mechanism allows precision adjustment to be performed as a preliminary step during the assembly process itself. The lens barrel can be rotated along the threaded bore to precisely position the focal plane at the image sensor location, and this adjustment can be integrated into automated assembly lines, maintaining both speed and precision.
Solution Approach 2:
The patent utilizes the threaded structure to convert rotational motion into precise linear displacement of the lens barrel. By controlling the number of threads per inch and the rotation amount, the system can achieve sub-micron positioning precision through a simple mechanical parameter change, enabling high precision without complex positioning mechanisms.
3Ease of manufacture
If lens assemblies use standard materials, then ease of manufacture is improved, but thermal stability deteriorates
Solution Approach 1:
The patent explicitly addresses thermal expansion effects by designing the lens barrel and housing assembly with matching or complementary thermal expansion characteristics. The threaded lens barrel mechanism allows for thermal compensation where the relative expansion between components is accounted for in the design, maintaining focal plane stability across temperature ranges while using conventional materials that are easy to manufacture.
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
Effectively compensates for thermal expansion, maintaining image focus within acceptable tolerance across varying temperatures, ensuring high-definition image quality by adjusting the focal plane to coincide with the image plane, thereby enhancing the camera's performance and yield.
Implementation Method 1
Imaging lenses tend to defocus during temperature change due to many factors. For example, coefficient of thermal expansion (CTE) changes the physical scale in materials. CTE changes may cause the lens system to move.
Implementation Method 2
In addition, thermo-optic coefficient changes the refractive index of optical materials. Thermal expansion of lens assemblies cause changes in optical path lengths, which defocuses images when a camera is used in a temperature range other than the one under which the camera has been tuned.
Implementation Method 3
An optics compensator including passively actuating elements and an optical component. The passively actuating elements couple the optical component to the inner surface of the lens mount. The passively actuating elements and the optics component are configured such that the focal plane is maintained to coincide with or substantially coincide with the image plane.
Data Source
AI summary
To compensate for a focal plane shifting away from an image plane due to a temperature change, an integrated image sensor and lens assembly includes an optical component and an optics compensator including passively actuating elements. The passively actuating elements couple the optical component to the inner surface of the lens mount. The passively actuating elements and the optics component are configured such that the focal plane is maintained to coincide with or substantially coincide with the image plane. The passively actuating elements and the optics component adjust the distance an incident ray travels in the optics compensator when the temperature changes to thereby maintaining the focal plane to coincide with or substantially coincide with the image plane.