Imaging Optical System Temperature Compensation
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Solution Overview
Problem
Conventional imaging optical systems for surveillance and vehicle cameras face challenges in maintaining high resolution over a wide temperature range due to insufficient correction of aberrations and shallow depth of focus, leading to focus errors and poor image quality, especially at extreme temperatures.
Innovation Solution
The proposed imaging optical system includes a front group with a positive lens and a rear group with a negative lens, where the temperature-dependent variation of relative refractive indices is controlled within specific ranges to suppress focus errors and maintain high resolution, and the configuration includes aspheric lenses to correct spherical aberration, chromatic aberration, and distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional five-lens optical systems are used, then manufacturing cost is reduced, but resolution and depth of focus are insufficient, leading to focus errors at extreme temperatures
Solution Approach 1:
The patent applies parameter changes by carefully selecting glass materials with specific temperature coefficients of refractive index (θ values) and controlling the ratio |θ3/θ2| within a specific range. This allows the optical system to compensate for temperature-induced focus errors while maintaining high resolution, resolving the contradiction between manufacturing simplicity and optical precision
Solution Approach 2:
The patent uses composite material principles by combining lenses made from different glass materials with complementary thermal-optical properties. The positive lens uses glass with one temperature coefficient characteristic while the negative lens uses glass with a different characteristic, creating a composite optical system that maintains focus across temperature ranges
2Ease of manufacture
If conventional five-lens optical systems are used, then manufacturing cost is reduced, but depth of focus is shallow, making image quality sensitive to lens center shifts
Solution Approach 1:
The patent changes the thermal-optical parameters of the lens materials to achieve a deeper depth of focus. By controlling the temperature coefficients and their ratios, the system creates a more robust depth of focus that tolerates manufacturing variations in lens center positions, thereby improving reliability without increasing manufacturing complexity
3Ease of manufacture
If optical systems with large temperature coefficient of refractive index are used, then lens material selection is easier, but focus errors during extreme temperatures increase
Solution Approach 1:
The patent converts the potentially harmful effect of temperature coefficient variations into a beneficial compensation mechanism. By selecting materials where the ratio |θ3/θ2| falls within a specific range, the focus errors introduced by temperature changes in one lens are compensated by opposite errors in another lens, transforming thermal sensitivity into thermal compensation
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 configuration ensures high resolution and deep depth of focus over a wide temperature range, reducing focus errors and maintaining image quality despite temperature variations and lens shifts during manufacturing.
Implementation Method 1
where θ3 represents temperature-dependent variation of relative refractive index for d-line of the negative lens and θ2 represents temperature-dependent variation of relative refractive index for d-line of the positive lens
Implementation Method 2
the configuration includes aspheric lenses to correct spherical aberration, chromatic aberration, and distortion
Data Source
AI summary
An imaging optical system includes sequentially from an object side a front group configured to include a positive lens disposed at a position nearest a diaphragm; the diaphragm; and a rear group configured to include a negative lens disposed at a position nearest the diaphragm. The imaging optical system satisfies a conditional expression (1) 0.27≦|θ3/θ2|≦1.80, where θ3 represents temperature-dependent variation of relative refractive index for d-line of the negative lens and θ2 represents temperature-dependent variation of relative refractive index for d-line of the positive lens.