Image-Forming Apparatus Optics Without fθ Lens for Uniform Exposure
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Solution Overview
Problem
Existing image-forming apparatuses face issues with image failure due to variations in exposure amount per unit area caused by non-uniform scanning velocity of laser light spots, especially when a scanning lens without an fθ characteristic is used, leading to differences in dot formation at the end and center portions in the main scanning direction.
Innovation Solution
The image-forming apparatus employs an optical configuration using an image formation lens without an fθ characteristic, combined with partial magnification correction and brightness correction to ensure uniform pixel density and exposure, utilizing an anamorphic lens and a single image formation optical element to maintain image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a scanning lens having an fθ characteristic is used, then appropriate exposure is achieved, but the size and cost of the apparatus increase
Solution Approach 1:
The patent removes the scanning lens from the optical system entirely, replacing it with a direct reflection configuration where the polygon mirror reflects laser light directly onto the photosensitive member. This extraction of the scanning lens eliminates the need for fθ characteristic correction while maintaining acceptable exposure quality through electrical correction of dot width variations.
Solution Approach 2:
The patent applies electrical correction by dynamically adjusting the image clock frequency during scanning operations. This parameter change compensates for the non-uniform velocity of the laser spot on the photosensitive member, maintaining constant dot width without requiring an fθ characteristic scanning lens.
2Reliability
If a scanning lens having an fθ characteristic is used, then appropriate exposure is achieved, but the cost of the apparatus increases
Solution Approach 1:
The patent removes the scanning lens from the optical system entirely, replacing it with a direct reflection configuration where the polygon mirror reflects laser light directly onto the photosensitive member. This extraction of the scanning lens eliminates the need for fθ characteristic correction while maintaining acceptable exposure quality through electrical correction of dot width variations.
Solution Approach 2:
The patent applies electrical correction by dynamically adjusting the image clock frequency during scanning operations. This parameter change compensates for the non-uniform velocity of the laser spot on the photosensitive member, maintaining constant dot width without requiring an fθ characteristic scanning lens.
3Manufacturing precision
If electrical correction is performed to make dot widths constant, then dot width uniformity is achieved, but exposure amount per unit area varies causing image failure
Solution Approach 1:
The patent applies different correction strategies for different regions of the scanning area. Electrical correction is applied to maintain constant dot width, while additional exposure amount correction is applied to compensate for velocity variations at different positions (center vs. end portions), ensuring uniform exposure across the entire image area.
Solution Approach 2:
The system uses feedback control to monitor and adjust exposure parameters. By detecting the non-uniform velocity of the laser spot and responding with appropriate corrections to both dot width and exposure amount, the system maintains image quality despite the removal of the fθ characteristic scanning lens.
4Device complexity
If the spot of laser light moves at non-uniform velocity, then a scanning lens without fθ characteristic can be used, but exposure amount per unit area varies
Solution Approach 1:
The patent removes the scanning lens from the optical system entirely, replacing it with a direct reflection configuration where the polygon mirror reflects laser light directly onto the photosensitive member. This extraction of the scanning lens eliminates the need for fθ characteristic correction while maintaining acceptable exposure quality through electrical correction of dot width variations.
Solution Approach 2:
The patent applies electrical correction by dynamically adjusting the image clock frequency during scanning operations. This parameter change compensates for the non-uniform velocity of the laser spot on the photosensitive member, maintaining constant dot width without requiring an fθ characteristic scanning lens.
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 allows for a compact design while achieving uniform image quality by adjusting scanning velocity and exposure, reducing the size and cost of the apparatus without compromising image formation performance.
Implementation Method 1
causes the laser light to be reflected by a rotational polygon mirror
Implementation Method 2
causes the reflected light to be transmitted through a scanning lens, and thereby irradiates the photosensitive member with the transmitted light so that the photosensitive member is exposed
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
An image-forming apparatus includes a light irradiation unit configured to move a spot of laser light on a surface of a photosensitive member at a non-constant scanning velocity in a main scanning direction to form a latent image on the photosensitive member, an image data correcting unit (100) configured to correct a length in the main scanning direction of image data by inserting one or more image data pieces into the image data, the number of the image data pieces increasing as the scanning velocity increases, and/or extracting one or more image data pieces from the image data, the number of the image data pieces increasing as the scanning velocity decreases, and a brightness correcting unit (1) configured to correct a brightness of the laser light so that an emission brightness increases as the scanning velocity increases and/or the emission brightness decreases as the scanning velocity decreases.