Image Forming Apparatus Density Correction via Exposure Amount Adjustment
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Solution Overview
Problem
Existing methods for correcting density irregularities in image forming apparatuses, such as those using two test print images with different exposure amounts, suffer from reduced interpolation accuracy and increased time requirements due to nonlinear relationships between exposure amounts and densities, leading to significant errors and prolonged printing times.
Innovation Solution
An image forming apparatus that forms first and second test print images with adjusted exposure amounts based on density readings, using linear interpolation to correct exposure settings, thereby reducing errors and shortening the printing time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two test print images with different exposure amounts are printed for density correction, then density correction can be performed, but interpolation accuracy is reduced and significant errors occur due to the nonlinear relationship between exposure amount and density
Solution Approach 1:
The patent changes the exposure amount parameter in a stepped manner across multiple test print images, creating discrete exposure levels that sample the nonlinear exposure-density relationship. This allows the system to capture actual density values at different exposure points and use these empirical measurements to determine the optimal exposure amount, rather than relying on inaccurate linear interpolation between just two points.
Solution Approach 2:
The patent uses multiple disposable test print images with different exposure amounts to gather density data. These test prints are temporary objects created solely for measurement purposes, allowing the system to obtain multiple data points across the exposure range without permanent commitment to a single correction approach. The test prints serve as inexpensive means to map the nonlinear relationship.
2Measurement precision
If multiple test print images are printed to improve correction accuracy, then density correction precision is improved, but the time required for printing test images increases
Solution Approach 1:
The patent prints multiple test images with exposure amounts that extend beyond what would be minimally required (excessive action), creating a range of exposure levels that covers the nonlinear relationship more thoroughly. This partial oversampling ensures that at least some of the test prints will provide accurate density measurements for correction, compensating for the fact that not all exposure levels will be equally useful.
Solution Approach 2:
The system performs preliminary testing with multiple exposure levels to map the exposure-density relationship before final correction is applied. By gathering density data from multiple test prints in advance, the system can identify the optimal exposure amount and establish accurate correction values, preventing the need for repeated testing and adjustment.
3Productivity
If test print images are printed with exposure amounts away from target density, then fewer test prints are needed, but large errors occur in the corrected exposure amounts
Solution Approach 1:
The patent systematically varies the exposure amount parameter across multiple test prints to map the nonlinear exposure-density relationship. By measuring actual density values at different exposure levels, the system can identify the exposure amount that corresponds to target density, even when initial test prints are taken at exposure levels away from the target. This empirical approach compensates for the nonlinear relationship.
Solution Approach 2:
The system uses density measurements from test print images as feedback to determine the optimal exposure amount. By reading the actual density values and comparing them to target density, the system can adjust and refine the exposure amount setting. This feedback loop allows the system to converge on the correct exposure amount despite starting from exposure levels that produce large initial errors.
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 approach enhances density correction precision and reduces the time needed for printing test images by accurately adjusting exposure amounts to achieve target densities in the main scanning direction.
Implementation Method 1
an exposure device exposes a surface of a photoreceptor to form an electrostatic latent image
Implementation Method 2
an image reading device reads densities of the formed test print images
Data Source
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AI summary
To acquire a density of a test print image at each position in the main scanning direction, which is read by the image reading unit after a first test print image is formed by an image forming unit (step S5), to correct a setting value of an exposure amount of an exposure device to a first light amount, which is higher than a reference light amount that is an exposure amount when the first test print image is formed, in an area where the acquired density is lower than a target density, to correct the exposure amount of the exposure device to a second light amount, which is lower than the reference light amount, in an area where the acquired density is higher than the target density, and to form a second test print image. On the basis of a reading result of a density of the second test print image by the image reading unit, density correction is performed (step S9).