Off-Axis Reflective Optical Assembly for Adjustable Focal Length
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Solution Overview
Problem
Existing optical systems with adjustable focal length suffer from low transmission, high chromatic dependence of aberrations, and physical limitations, particularly in refractive systems, which are not effectively addressed by prior reflective systems.
Innovation Solution
A reflective optical system with at least two movable mirror surfaces arranged off-axis, allowing for continuous or discrete adjustment of focal length without changing the object-side and image-side sections of the optical axis, using freeform mirror surfaces and beam deflection units to maintain constant beam position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If refractive optical systems with adjustable focal length are used, then focal length adjustment is achieved, but transmission is low and chromatic aberrations are high
Solution Approach 1:
The patent replaces refractive optical elements (lenses) with reflective optical elements (mirrors). This substitution eliminates chromatic aberrations inherent in refractive systems and significantly improves transmission by avoiding absorption and internal total reflections that occur in lens materials. The reflective system achieves focal length adjustment through mechanical movement of mirror surfaces rather than through refractive index changes.
Solution Approach 2:
The patent changes the optical path length by moving mirror surfaces along the beam path, thereby adjusting the effective focal length. By varying the position of at least one mirror surface between a first displacement position and a second displacement position, the system continuously or discretely adjusts the focal length while maintaining fixed object-side and image-side optical axis sections.
2Adaptability or versatility
If refractive optical systems with adjustable focal length are used, then focal length adjustment is achieved, but chromatic dependence of aberrations is high
Solution Approach 1:
The patent replaces refractive optical elements (lenses) with reflective optical elements (mirrors). This substitution eliminates chromatic aberrations inherent in refractive systems and significantly improves transmission by avoiding absorption and internal total reflections that occur in lens materials. The reflective system achieves focal length adjustment through mechanical movement of mirror surfaces rather than through refractive index changes.
3Adaptability or versatility
If multiple mirror surfaces are moved to adjust focal length, then focal length adjustment is achieved, but beam position changes
Solution Approach 1:
The patent employs asymmetric arrangement of mirror surfaces relative to the optical axis. At least one mirror surface is positioned off-axis, which enables independent control of beam deflection and focal length adjustment. This asymmetric configuration allows the system to change effective focal length while compensating for beam position shifts through coordinated movement of multiple mirror surfaces.
Solution Approach 2:
The patent uses dynamic movement of multiple mirror surfaces to simultaneously achieve focal length adjustment and beam position stabilization. By coordinating the displacement of at least two mirror surfaces, the system dynamically adjusts the optical path to maintain constant beam position at the input and output while varying the effective focal length.
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 provides low chromatic aberrations and flexible focal length adjustment across a wide wavelength range, applicable in illumination and imaging systems, including beam shaping and imaging multiple object fields onto a fixed image plane, with high reflectivity and robustness against external disturbances.
Implementation Method 1
a reflective optical system (1) with an adjustable effective focal length... at least two movable mirror surfaces (2, 8)... arranged off-axis and sequentially along a beam path (15)
Data Source
Figure 1a~1b
Figure 2
Figure 3
AI summary
The invention relates to a reflective optical system with adjustable effective focal length, the use of such a reflective optical system, and a method for calculating the mirror surfaces for such an optical system.