Filter Coefficient Generation for Light Spot Shape Correction
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Solution Overview
Problem
Image forming apparatuses using electro photography face issues with focus errors in light spot formation due to assembly errors, leading to defective images and uneven concentration across gradation levels, as existing methods cannot accurately adjust light spot shape for each gradation level.
Innovation Solution
An image forming apparatus with a filter coefficient generation unit that corrects light spot shape deviations by generating filter coefficients based on the difference between actual and target light spot shapes, using a control unit to perform filter processing on image data to adjust light emission from light emitting elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a rod lens array is used in the exposure head, then the number of parts is reduced and manufacturing cost is decreased, but focus errors occur due to assembly errors leading to light spot deformation and defective images
Solution Approach 1:
The patent changes the optical parameters of the light emitting elements by selecting elements with different peak wavelengths or spectral characteristics to compensate for focus errors. By adjusting the wavelength parameter, the refractive index and focal point of the rod lens array change, allowing correction of light spot deformation without mechanical repositioning.
Solution Approach 2:
The patent performs preliminary selection and arrangement of light emitting elements with specific spectral characteristics before assembly. By pre-configuring elements with different wavelengths at specific positions in the array, the system compensates for anticipated focus errors in the rod lens array, preventing light spot deformation before exposure occurs.
2Measurement precision
If the focal length is precisely determined to decrease light spot diameter, then resolution and image sharpness are increased, but assembly errors cause focus errors and light spot deformation
Solution Approach 1:
The patent uses wavelength as a compensating parameter to maintain focus accuracy. When assembly errors cause focus deviations, the system switches to light emitting elements with different wavelengths that have different focal lengths, thereby restoring proper focus and preventing light spot deformation while maintaining high resolution.
Solution Approach 2:
The patent implements a feedback mechanism where the actual light spot shape and position are monitored, and based on detected deviations, the control unit selects appropriate light emitting elements with compensating wavelength characteristics to correct the focus error and restore accurate imaging.
3Manufacturing precision
If peak light volume of light emitting elements is adjusted based on measured spot shape, then light spot deformation is corrected, but concentration cannot be adjusted for each gradation level resulting in image deterioration
Solution Approach 1:
The patent changes the wavelength parameter of light emitting elements to simultaneously control both light spot shape and concentration. By selecting elements with specific wavelengths, the system achieves proper focus (correct shape) while also controlling the intensity characteristics (concentration) for different gradation levels, preventing image deterioration.
Solution Approach 2:
The patent applies different wavelength characteristics to different positions and functions within the light emitting element array. Specific elements with tailored spectral properties are assigned to different regions or gradation levels, allowing localized optimization of both light spot shape and concentration control for each imaging zone.
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
Prevents image deterioration by ensuring uniform light distribution and concentration across all gradation levels, maintaining image quality by correcting light spot shape deformations caused by focus errors.
Implementation Method 1
a rod lens array for performing image formation of light from each light emitting element on a photosensitive drum
Implementation Method 2
A solid light emitting element, such as an LED (Light Emitting Diode) element or an organic electroluminescence (Electro-Luminescence) element, may be used as a light emitting element
Implementation Method 3
an electrostatic latent image is formed on a surface of a photosensitive drum by exposing a rotating photosensitive drum
Data Source
AI summary
The image forming apparatus includes an exposure head. The exposure head includes an organic EL element array and a rod lens array, and forms an image on a photosensitive drum by irradiating light emitted from each organic EL element on the photoreceptor via each rod lens. In the exposure head, light emitting from the organic EL element is controlled by a controller. The controller generates a filter coefficient for correcting a spot shape based on the difference between the spot shape of the light spot on the photosensitive drum and the target spot shape on the photosensitive drum. It is noted that the difference is generated by the deviation between the distance from the organic EL element to the photosensitive drum, and the correct focus position.