Optical Scanning Layout for Beam Shaping in Compact Laser Scanners
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional optical scanning devices face challenges in achieving both miniaturization of the condensing lens and maintaining the necessary beam size due to the reduction in the distance between the polygon mirror and the condensing lens, leading to issues with beam size and spot diameter on the image plane.
Innovation Solution
The optical scanning device employs a light condensing and diffusing member that aligns the direction of the light beam's divergent angle with the sub-scanning direction and uses a single lens with both cylindrical and expander lens functions to manage beam size and diffusion, allowing for miniaturization of the condensing lens while maintaining required beam dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the distance between the polygon mirror and the condensing lens is shortened to miniaturize the condensing lens, then the device size is reduced, but the beam size on the image plane becomes excessively large
Solution Approach 1:
The optical system is divided into distinct functional sections: a light condensing section (cylindrical lens) that condenses the light beam in the sub-scanning direction, and a light diffusing section (expander lens) that diffuses the beam in the main scanning direction. This segmentation allows independent optimization of beam dimensions in different directions, enabling the condensing lens to be miniaturized while maintaining proper beam size on the image plane.
Solution Approach 2:
The patent changes the parameters of the light beam by introducing optical elements that modify its dimensional characteristics. The cylindrical lens changes the beam width in the sub-scanning direction by condensing it, while the expander lens changes the beam width in the main scanning direction by diffusing it. These parameter changes enable the system to achieve the necessary beam dimensions despite the shortened PGM-FL distance.
2Length of moving object
If the distance between the polygon mirror and the condensing lens is shortened, then the optical path length is reduced, but the linewidth of the light beam entering the condensing lens decreases, causing the spot diameter to increase
Solution Approach 1:
The patent applies preliminary actions to the light beam before it reaches the condensing lens. The cylindrical lens performs preliminary condensing in the sub-scanning direction, and the expander lens performs preliminary diffusion in the main scanning direction. These preliminary actions prepare the beam with appropriate dimensions and characteristics before condensation, ensuring that even with a shortened optical path, the final spot diameter on the image plane remains within the necessary range.
3Ease of manufacture
If conventional optical systems align the major axis of the elliptical light beam with the main scanning direction, then the beam configuration matches traditional designs, but the condensing lens cannot be miniaturized without compromising beam quality
Solution Approach 1:
The patent introduces asymmetry into the beam configuration by using a cylindrical lens that creates different beam widths in the main scanning and sub-scanning directions. The beam width in the sub-scanning direction is made larger than in the main scanning direction, which is opposite to the conventional alignment. This asymmetric configuration, combined with the expander lens, enables the condensing lens to be miniaturized while maintaining proper beam quality on the image plane.
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 configuration ensures the desired beam size is achieved on the image plane, enabling the optical scanning device to be miniaturized by shortening the distance between the deflector and the condensing lens, reducing the number of lenses, and enhancing optical path length and transmittance.
Implementation Method 1
a collimator lens disposed between the light emitting element and the deflector and converting the light beam emitted from the light emitting element into parallel light
Implementation Method 2
a condensing lens disposed on a downstream side of the light beam with respect to the deflector and condensing the light beam deflected by the deflector toward an object to be scanned
Implementation Method 3
a light condensing and diffusing member disposed between the aperture and the deflector and having a first function to condense a beam in a sub-scanning direction and a second function to diffuse a beam in the main scanning direction
Data Source
AI summary
An optical scanning unit steers a light beam emitted from a laser diode in the main scanning direction by a polygon mirror. The laser diode, a collimator lens, an aperture, a first lens, the polygon mirror, and a condensing lens are sequentially placed in the optical system of the optical scanning unit. The laser diode emits a light beam in which divergent angles in intersecting two directions are different from each other. The direction in which the light beam divergent angle is large is aligned with the sub-scanning direction, and the direction in which the light beam divergent angle is small is aligned with the main scanning direction. The first lens has a first function to condense a beam in the sub-scanning direction and a second function to diffuse a beam in the main scanning direction.