Optical Scanning Aperture Offset for Uniform Beam Spacing
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Solution Overview
Problem
Existing optical scanning apparatuses suffer from image defects due to angular misalignment of the polygon mirror, causing uneven intervals between imaged light beams and color displacement, which increases manufacturing complexity and cost.
Innovation Solution
The optical scanning apparatus includes a light source with multiple light-emitting portions, a cylindrical lens, a restricting portion with movable apertures, and scanning lenses, which adjust the optical path width and beam pitch to maintain consistent beam intervals despite polygon mirror misalignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the polygon mirror rotation axis tilts and angular misalignment occurs, then the light beams are reflected and imaged on the scanned surface, but the angles of incidence change causing displacement of light beams along the sub scanning direction and uneven intervals between imaged light beams
Solution Approach 1:
The patent applies preliminary action by pre-adjusting the positions of the first apertures in the restricting portion before the polygon mirror rotation occurs. The centers of the first openings are deliberately displaced along the sub scanning direction to compensate for the angular misalignment that will occur during rotation. This pre-positioning ensures that even when the polygon mirror tilts, the light beams pass through the correct aperture positions to maintain uniform beam intervals on the scanned surface, preventing color displacement and image defects.
2Device complexity
If conventional optical scanning apparatus is used with fixed apertures, then the structure is simple, but angular misalignment causes color displacement and image defects
Solution Approach 1:
The patent applies the dynamics principle by making the first apertures movable along the sub scanning direction. The restricting portion can be positioned at different locations to adjust the optical path width of light beams. This dynamic adjustment capability allows the system to compensate for angular misalignment of the polygon mirror rotation axis, ensuring uniform beam intervals and preventing color displacement while maintaining a relatively simple overall structure.
3Manufacturing precision
If the restricting portion adjusts optical path width with movable apertures, then beam pitch can be adjusted to maintain uniform intervals, but the device complexity increases
Solution Approach 1:
The patent applies parameter changes by adjusting the position of the first apertures along the sub scanning direction to change the optical path width of the light beams. By displacing the centers of the first openings and making them movable, the system can modify the beam pitch parameter to compensate for angular misalignment. This parameter adjustment approach maintains uniform beam intervals on the scanned surface without requiring fundamentally new structural components, thus limiting the increase in device 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 configuration prevents image defects by ensuring uniform beam spacing, reducing manufacturing costs through component reduction, and improving image quality.
Implementation Method 1
The cylindrical lens converges the light beams emitted from the light-emitting portions respectively
Implementation Method 2
The polygon mirror has a deflecting surface that reflects the light beams having passed through the cylindrical lens
Data Source
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AI summary
An optical scanning apparatus (5) includes a light source (26) having five or more light-emitting portions (LD1 to LD8) arrayed in a row, a cylindrical lens (42), a restricting portion (47), a polygon mirror (45), and a plurality of scanning lenses (49a, 49b). A plurality of such light sources (26) are provided and each emit light beams. The restricting portion (47) has a plurality of first apertures (43) that restrict the optical path width of the light beams along the sub scanning direction. The first apertures have first openings (43a) respectively that penetrate them along the optical axis direction and let the light beams pass through them. The centers of the first openings along the sub scanning direction are disposed displaced along the sub scanning direction (Z1-Z2).