Dual Refractive Element Passive Temperature Compensation
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Solution Overview
Problem
Optical devices with refractive elements experience thermally induced changes in refractive index and surface shape, leading to unfavorable temperature-dependent performance, particularly affecting wavefront transmission and focal power.
Innovation Solution
A dual refractive element system where the refractive indices and surface shapes of the first and second refractive elements are carefully selected and designed to maintain temperature independence of the transmitted wavefront within a defined temperature range, using materials with different thermal expansion coefficients and refractive index dependencies on temperature and wavelength, and incorporating a deformable liquid lens with a tunable radius.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single refractive element is used, then the device structure is simple, but the wavefront transmission is temperature-dependent and unstable
Solution Approach 1:
The patent divides the single refractive element into two separate refractive elements with different materials. Each element has specific refractive indices (n1 and n2) and surface curvatures (R1, R2, R3) that are independently designed. This segmentation allows each element to compensate for thermal effects differently, achieving temperature-independent wavefront transmission while maintaining reasonable structural complexity.
Solution Approach 2:
The patent employs composite material design by combining two different transparent materials with distinct thermal and optical properties. The first material has refractive index n1 and the second material has refractive index n2, where both materials are selected to have complementary thermal expansion coefficients and refractive index temperature dependencies. This composite approach enables the system to achieve thermal compensation that neither material could achieve alone.
2Manufacturing precision
If refractive indices and surface shapes are optimized for a specific temperature, then the wavefront is temperature-independent at that temperature, but the device becomes sensitive to temperature variations
Solution Approach 1:
The patent systematically varies multiple parameters including refractive indices (n1, n2), surface curvatures (R1, R2, R3), and thicknesses (d1, d2) to achieve temperature compensation. The design equations incorporate temperature-dependent terms for thermal expansion coefficients (α1, α2) and refractive index temperature dependencies (dn1/dT, dn2/dT). By optimizing these parameters simultaneously, the system achieves wavefront independence across a temperature range from -40°C to 85°C.
Solution Approach 2:
The patent introduces intermediate compensation mechanisms through the second refractive element that acts as a mediator between the first refractive element and the outgoing wavefront. The second element with its specific refractive index n2 and surface curvatures R2, R3 provides compensating optical path length changes that counteract the thermal effects in the first element, enabling temperature-independent performance across a broad range.
3Reliability
If two refractive elements with different materials are used, then temperature compensation is achieved, but the device complexity increases
Solution Approach 1:
The patent segments the optical system into two distinct refractive elements with specific functions. The first element (with material having refractive index n1) handles primary refraction, while the second element (with material having refractive index n2) provides thermal compensation. This segmentation is achieved through separate manufacturing and assembly of two elements with controlled interfaces, achieving temperature independence with manageable complexity.
Solution Approach 2:
The patent uses composite material construction by combining two transparent materials with complementary properties. The first material is selected with refractive index n1 and thermal expansion coefficient α1, while the second material has refractive index n2 and thermal expansion coefficient α2. These materials are chosen such that their combined thermal and optical effects cancel out, achieving temperature compensation through material composition rather than complex mechanical structures.
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 solution ensures that the wavefront of transmitted light remains independent of temperature, reducing chromatic aberration and allowing for adjustable focal length without thermal fluctuations, effectively compensating for temperature-induced changes.
Implementation Method 1
a first refractive element configured to refract incoming light, wherein the first refractive element comprises a first refractive index and a first surface for receiving a wavefront of said incoming light
Implementation Method 2
a second refractive element configured to refract light coming from the first refractive element, wherein the second refractive element comprises a second refractive index and a third surface for transmitting light coming from the first refractive element
Implementation Method 3
the first refractive index and the shape of the first surface depend on the temperature due to the thermal expansion of the optical device
Data Source
AI summary
An optical device (1), comprising: a first refractive element (10) configured to refract incoming light (L), wherein the first refractive element (10) comprises a first refractive index (n1(T)) and a first surface S1(T) for receiving a wavefront (W) of said incoming light, a second refractive element (11) configured to refract light coming from the first refractive element (10), wherein the second refractive element (11) is arranged adjacent the first refractive element (10) such that a second surface (S2(T)) is formed between the first refractive element (10) and the second refractive element (11), via which second surface (S2(T)) light can pass from the first refractive element (10) to the second refractive element (11), and wherein the second refractive element (11) comprises a second refractive index (n2(T)) and a third surface (S3(T)) for transmitting light coming from the first refractive element (10) and passing through the second refractive element (11), and wherein the refractive indices (n1(T), n2(T)) and the shapes of the surfaces (S1(T), S2(T), S3(T)) are adapted such that a shape of a wavefront (W′) of the transmitted light is independent of a temperature of the optical device, when said temperature (T) lies within a pre-defined temperature range.