Anamorphic Collimator Lens with Diffraction Grating for Optical Scanning
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Solution Overview
Problem
Optical scanning apparatuses face challenges in achieving satisfactory field curvature correction and distortion correction while reducing costs, particularly in the sub-scanning section where aberrations are difficult to correct due to stronger refractive power, and the use of toric lenses manufactured by plastic injection molding leads to deterioration in optical performance when lens length is reduced.
Innovation Solution
The optical scanning apparatus employs a single fθ lens with specific conditional expressions to balance the fθ coefficient and focal length, and incorporates an anamorphic collimator lens with a diffraction grating surface to correct aberrations and reduce manufacturing costs by minimizing the number of lenses and optimizing the lens's size and thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the lens length is reduced to increase the number of lenses obtained in one injection molding cycle, then manufacturing cost is reduced, but field curvature, distortion, and optical performance deteriorate
Solution Approach 1:
The patent applies parameter changes by precisely controlling the lens length within a specific range (0.03L ≤ d ≤ 0.07L where L is the distance from the deflection unit to the lens) and adjusting the aspherical coefficients (E2, E4, E6) to compensate for the reduced lens length. This allows maintaining good field curvature correction and optical performance while enabling multiple lenses per injection molding cycle, thus reducing manufacturing cost
2Productivity
If the lens length is reduced to increase productivity, then the number of lenses per injection molding cycle increases, but distortion correction and fθ characteristics worsen
Solution Approach 1:
The patent changes the aspherical parameters (E2, E4, E6 coefficients) to compensate for the reduced lens length, maintaining distortion correction and fθ characteristics while enabling shorter lens lengths that allow multiple lenses per injection molding cycle, thereby improving productivity
3Device complexity
If a single lens is used to reduce device complexity and cost, then the number of parts is reduced, but aberration correction becomes more difficult due to stronger refractive power requirements
Solution Approach 1:
The patent uses an aspherical lens design with specific aspherical coefficients (E2, E4, E6) to correct aberrations. The aspherical surfaces allow a single lens to achieve the refractive power needed for aberration correction without requiring multiple lenses, thus reducing device complexity while maintaining good aberration correction
Solution Approach 2:
The patent adjusts the aspherical parameters and lens geometry to compensate for the stronger refractive power required in a single-lens system, enabling effective aberration correction while maintaining a simple one-lens structure that reduces cost and complexity
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 approach effectively corrects field curvature and distortion, enhances optical performance, and reduces manufacturing costs by allowing for a more compact design while maintaining high-definition imaging capabilities.
Implementation Method 1
an incident optical system has a diffraction optical surface
Data Source
AI summary
Provided is an optical scanning apparatus, including: a deflection unit; and an imaging optical element (IOE) guiding a light flux deflected by deflection unit onto a scanned surface, in which, an fθ coefficient of IOE, a focal length of IOE, and when an intersection between deflection unit and an optical axis of IOE is set as an origin, a coordinate in an optical axis direction (OAD) of an intersection between a principal ray of an outermost off-axis light flux and an incident surface of IOE, a coordinate in OAD of an intersection between principal ray of outermost off-axis light flux and an exit surface of IOE, a coordinate in OAD of an intersection between a principal ray of an on-axis light flux and the incident surface, and a coordinate in OAD of an intersection between principal ray of on-axis light flux and the exit surface are appropriately set.