Variable-Focus Lens Optical Scanning System for Compact Laser Printers
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Solution Overview
Problem
Conventional optical scanning systems for laser printers require large, expensive long-length imaging lenses to maintain a constant beam spot diameter along the scanning line, leading to a complex and costly structure, and fail to provide a compact solution for maintaining consistent spot diameter across the entire scanning line.
Innovation Solution
An optical scanning system utilizing a variable-focus element, an imaging lens, and a deflector, where the reciprocal of the focal length of the variable-focus element is adjusted to balance numerical apertures at the center and ends of the scanning line, ensuring a constant spot diameter through specific distance relationships and focal length variations, allowing for a compact design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a long-length imaging lens is used to maintain constant spot diameter, then spot diameter consistency is improved, but device size and cost increase
Solution Approach 1:
The patent employs a variable-focus lens that dynamically adjusts its focal length during scanning operations. The focal length is varied to compensate for the cosine effect, maintaining constant spot diameter without requiring a long fixed focal length lens. This dynamic adjustment allows compact apparatus size while achieving the required spot diameter consistency across the scanning line.
Solution Approach 2:
The patent changes the focal length parameter of the imaging lens based on the scanning angle. By adjusting the focal length according to the deflection angle, the system compensates for the oblique incidence effect and maintains constant spot diameter. This parameter change approach replaces the need for a physically long lens with a controllable optical parameter variation.
2Volume of moving object
If a variable-focus element is used to reduce apparatus size, then device complexity is reduced, but spot diameter variation increases
Solution Approach 1:
The variable-focus lens dynamically adjusts its focal length in real-time during scanning, with the focal length being shorter for off-axis positions and longer for on-axis positions. This dynamic adjustment compensates for the cosine effect that would otherwise cause spot diameter variation, thereby maintaining spot diameter consistency while using a compact optical system.
Solution Approach 2:
The system preemptively adjusts the focal length of the variable-focus lens before the beam reaches the image plane, counteracting the expected spot diameter increase at oblique angles. By pre-adjusting the focal length based on the scanning angle, the system prevents spot diameter variation rather than correcting it after the fact.
3Manufacturing precision
If multiple fixed-focus lenses and variable-focus lenses are combined to maintain spot diameter, then spot diameter consistency is improved, but device complexity and cost increase
Solution Approach 1:
The patent combines the imaging function and the cosine effect compensation function into a single variable-focus lens. Instead of using separate fixed-focus lenses for imaging and additional variable-focus lenses for compensation, the invention merges these functions, reducing the number of optical elements and simplifying the overall optical system structure while maintaining spot diameter consistency.
Solution Approach 2:
The variable-focus lens serves multiple functions simultaneously: it acts as the primary imaging lens and also provides cosine effect compensation through its variable focal length capability. This multi-functionality eliminates the need for separate compensation optics, reducing system complexity and component count.
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 compact and cost-effective solution by balancing numerical apertures and maintaining spot diameter consistency across the scanning line, reducing the apparatus size and variation in spot diameter to less than 5%, while maintaining image quality.
Implementation Method 1
an optical scanning system which uses a variable-focus element
Implementation Method 2
deflects the beam by a deflector such as a polygon mirror or a swing mirror
Data Source
AI summary
An optical scanning system includes a variable-focus element, an imaging lens and a deflector, wherein the reciprocal of the focal length f of the variable-focus element is changed from 1/fMIN to 1/fMAX, and for the case that the equation1/f={(1/fMAX)+(1/fMIN)}/2holds, a beam which has passed through the variable-focus element is a divergent beam, andx2+x22x1>x3(1)is satisfied, where x1 represents a distance from a virtual image point of the divergent beam to the principal point on the entry side of the variable-focus element, x2 represents a distance from the principal point on the exit side of the variable-focus element to the principal point on the entry side of the imaging lens, and x3 represents a distance from the principal point on the exit side of the imaging lens to an image point.