Multi-Beam Image-Forming Apparatus: Reciprocity-Failure Density Smoothing
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Solution Overview
Problem
Existing image-forming apparatuses suffer from density level differences due to reciprocity failure, which occurs when the relationship between light amount and exposure time varies, leading to image density unevenness, especially in multi-beam scanning systems, and current solutions are complex, costly, or ineffective in synchronizing density and bow corrections.
Innovation Solution
The image-forming apparatus employs a configuration with a bow corrector, density smoothing processor, and density correction processor to perform electronic bow correction and density smoothing processes, along with a light emitting element driver controller to control light emission, thereby smoothing density level differences caused by reciprocity failure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple exposure is performed using a VCSEL with a large number of light emitting points arranged in main and sub-scanning directions, then density differences become invisible, but the driving system becomes complicated and cost increases
Solution Approach 1:
The patent segments the light emitting elements into a manageable array (e.g., 2x2 or similar configuration) rather than using an enormous number of beams. This segmentation approach maintains the ability to perform multi-exposure while significantly reducing the complexity of the driving system compared to using 32 or more beams.
Solution Approach 2:
The patent implements periodic multi-exposure operations at a certain scanning frequency to make density differences invisible. By performing exposure operations in periodic cycles with multiple light beams at controlled intervals, the system achieves uniform image density without requiring an excessively complex driving system.
2Measurement precision
If electronic bow correction is performed in a multi-beam scanning optical system, then image position accuracy improves, but density unevenness occurs due to reciprocity failure caused by surface-crossing by end semiconductor laser devices
Solution Approach 1:
The patent applies preliminary anti-action by pre-correcting the light amount of end light emitting elements before the surface-crossing exposure occurs. By reducing the light amount of end elements in advance, the system prevents reciprocity failure from causing density unevenness, thereby maintaining both position accuracy and density uniformity during electronic bow correction.
Solution Approach 2:
The patent applies local quality by differentiating the light amount control between end light emitting elements and intermediate elements. Specifically, the light amount of end elements is reduced while intermediate elements maintain normal light output, allowing bow correction to proceed without causing density unevenness at the boundaries where surface-crossing occurs.
3Manufacturing precision
If light amount of end light emitting elements is reduced to prevent surface-crossing reciprocity failure, then density unevenness is suppressed, but overall exposure efficiency decreases
Solution Approach 1:
The patent applies local quality by selectively reducing light amount only for end light emitting elements while maintaining normal light output for intermediate elements. This localized adjustment suppresses density unevenness caused by surface-crossing reciprocity failure at boundaries, while preserving overall exposure efficiency by keeping the majority of light beams operating at full intensity.
Solution Approach 2:
The patent applies partial action by reducing the light amount of only the end light emitting elements rather than reducing all beams. This partial adjustment is sufficient to prevent density unevenness at the critical surface-crossing regions while maintaining high exposure efficiency for the overall image formation process.
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 effectively suppresses density level differences in halftone images by synchronizing density and bow corrections, reducing streaks and unevenness, and simplifies the circuit configuration while maintaining accurate density correction.
Implementation Method 1
a light beam emitted from a light source, such as a laser diode, is focused on a photoconductor drum (image carrier) by a scanning optical system to form an electrostatic latent image on a surface of the photoconductor drum
Implementation Method 2
a vertical cavity surface emitting laser (VCSEL) in which a large number of light emitting points are arranged in a main scanning direction and a sub-scanning direction is used as a light source
Data Source
AI summary
An image-forming apparatus employing an electrophotographic method that scans a surface of an image carrier with multi-beams emitted from a plurality of light emitting elements based on image data includes a density smoothing processor that performs a density smoothing process to smooth a density level difference of an image subjected to electronic bow correction, a density correction processor that performs density correction on the image subjected to the bow correction by light amount correction of a surface-crossing exposure segment, and a light emitting element driver controller that controls light emission of a plurality of light emitting elements of a light beam emitter based on the image data subjected to the density smoothing process and a control signal subjected to the density correction.