Freeform Surface Reflective Scanning System Design
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Solution Overview
Problem
Designing a freeform surface reflective scanning system with a simple structure while maintaining superior imaging effect is challenging due to the complexity of freeform surfaces and the need to consider volume, weight, and number of lenses in conventional reflective scanning systems.
Innovation Solution
A freeform surface reflective scanning system is designed using two freeform surface mirrors with specific polynomial surface equations, optimizing the light path and aperture placement to achieve a compact structure and improved imaging quality, with each field scanning error controlled to less than ±1 μm and modulation transfer function close to the diffraction limit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If freeform surfaces are used in reflective scanning systems, then imaging quality and design freedom are improved, but system complexity and manufacturing difficulty increase
Solution Approach 1:
The freeform reflective scanning system is divided into multiple independent freeform mirrors (first freeform mirror, second freeform mirror, etc.), each with specific polynomial surface equations. This segmentation allows complex imaging functions to be distributed across simpler individual components, reducing overall system complexity while maintaining high imaging quality through optimized light path control at each stage.
Solution Approach 2:
The patent employs asymmetric freeform surfaces defined by polynomial equations (e.g., z = c + kx² + ky² + A₂x²y + A₃xy² + A₄y³) instead of conventional rotationally symmetric surfaces. This asymmetry provides additional design freedom to correct aberrations and optimize imaging performance, directly improving manufacturing precision while the mathematical definition keeps the surfaces manufacturable.
2Adaptability or versatility
If freeform surfaces with multiple variables are used, then design freedom increases, but structure simplification becomes more difficult
Solution Approach 1:
Each freeform mirror is designed with specific local surface properties defined by polynomial equations tailored to its position in the optical path. The first freeform mirror, second freeform mirror, and subsequent mirrors have different polynomial coefficients optimized for their specific functions, allowing localized optimization of light control while maintaining overall system simplicity.
Solution Approach 2:
The patent transitions from conventional 2D rotationally symmetric surface design to 3D freeform surfaces with polynomial definitions, adding a dimensional aspect to surface control. This enables independent manipulation of x and y coordinates through polynomial terms, providing enhanced design freedom for correcting aberrations and optimizing the optical path without increasing structural complexity.
3Ease of manufacture
If conventional rotationally symmetric surfaces are used, then manufacturing is easier, but aberrations increase and design freedom is limited
Solution Approach 1:
The patent replaces conventional rotationally symmetric surfaces with asymmetric freeform surfaces defined by polynomial equations. This asymmetry introduces additional design parameters (polynomial coefficients A₂, A₃, A₄, etc.) that enable precise control over wavefront aberrations while maintaining manufacturability through well-defined mathematical surfaces that can be fabricated using modern precision machining and polishing techniques.
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 achieves a simple structure with superior imaging quality, effective scanning range, and good linearity, suitable for applications like laser printers and scanners, with scanning errors minimized and imaging quality comparable to diffraction limits.
Implementation Method 1
a first freeform surface mirror 14, and a second freeform surface mirror 16
Data Source
AI summary
A freeform surface reflective scanning system includes a light source, an aperture, a first freeform surface mirror, and a second freeform surface mirror. The light source is configured to provide a laser. The first freeform surface mirror is located on an aperture side that is away from the light source. The first freeform surface mirror is configured to reflect the laser to form a first reflected light. The second freeform surface mirror is located on a first reflected light path. The second freeform surface mirror is configured to reflect the first reflected light to form a second reflected light. Both the first freeform surface mirror and the second freeform surface mirror are a fourth XY polynomial surface.