Negative-Positive Lens Pair for Thermal Focus Stability
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Solution Overview
Problem
Existing optical systems face challenges in controlling focal position variation due to environmental temperature changes while maintaining aberration correction, as they often require lenses with large refractive index and Abbe number differences, limiting material selection freedom.
Innovation Solution
An optical system comprising a negative lens and a positive lens adjacent to each other, with specific inequalities defining their distance, curvature radii, refractive indices, Abbe numbers, and temperature coefficients, allowing for temperature compensation and aberration correction regardless of the sign of the coefficient β.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pair of positive lens and negative lens having large differences in refractive index and Abbe number is employed to control focal position variation, then temperature compensation is achieved, but material selection freedom is limited
Solution Approach 1:
The invention changes the approach from requiring large differences in refractive index and Abbe number to using specific relationships between temperature coefficients of refractive index. By defining conditions on dnA/dt and dnB/dt (where either has a negative sign) and their relationship to curvature radii and spacing, the patent enables material selection based on temperature coefficient characteristics rather than traditional refractive index differences, thus resolving the contradiction between temperature compensation and material selection freedom
Solution Approach 2:
The invention applies different material properties to different lenses in the pair. Specifically, it requires that one lens (either positive or negative) has a negative temperature coefficient of refractive index while the other has a positive coefficient, creating a localized differentiation in thermal-optical properties that enables temperature compensation without requiring extreme differences in overall refractive index or Abbe number
2Reliability
If lenses with large refractive index and Abbe number differences are used, then focal position variation control is improved, but aberration correction becomes difficult
Solution Approach 1:
The invention changes the controlling parameters from refractive index and Abbe number differences to temperature coefficients of refractive index and their relationship to curvature radii. This parameter transformation allows for better aberration correction because it provides more flexibility in selecting lens materials and designs that can simultaneously achieve focal position stability and aberration control through the defined relationships between dnA/dt, dnB/dt, RA, and RB
3Reliability
If material selection is restricted to achieve temperature compensation, then focal position control is maintained, but optical system design flexibility is reduced
Solution Approach 1:
The invention transforms the design criteria from fixed requirements on refractive index and Abbe number to flexible relationships involving temperature coefficients. By specifying that either dnA/dt or dnB/dt has a negative sign and defining their relationship to curvature radii and spacing, the patent creates a more flexible design space that maintains temperature compensation while allowing greater design freedom in selecting specific lens combinations and configurations
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 controls focal position variation and corrects various aberrations across temperature changes, enhancing material selection freedom and maintaining high optical performance.
Implementation Method 1
where NA and NB denote refractive indices of the negative lens and the positive lens, respectively, with respect to a d-line, νA and νB denote Abbe numbers of the negative lens and the positive lens, respectively, with respect to the d-line, and dnA/dt [10-6/° C.] and dnB/dt [10-6/° C.] denote temperature coefficients of refractive indices of the negative lens and the positive lens, respectively, with respect to the d-line at 20° C. to 40° C., and either dnA/dt or dnB/dt has a negative sign
Implementation Method 2
RA and RB denote curvature radii of facing lens surfaces of the negative lens and the positive lens, respectively
Data Source
AI summary
An optical system includes a negative lens and a positive lens adjacent to each other, wherein the following inequalities are satisfied: 0.00≤DAB≤1.00, and 0.80≤RA/RB≤1.20, where DAB[mm] denotes a distance on an optical axis between the negative lens and the positive lens, and RA and RB denote curvature radii of facing lens surfaces of the negative lens and the positive lens, respectively, and wherein specific inequalities are satisfied.