Halftone Data Correction for Light Amount Variations in Line Head Printers
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Solution Overview
Problem
In electrophotographic image forming apparatuses using a line head as a light source, density unevenness occurs due to non-uniform light amounts across main scanning positions on a photosensitive body, which is not effectively addressed by existing correction methods, especially after halftone processing.
Innovation Solution
The apparatus includes an obtaining unit for halftone-processed image data, a generation unit for generating correction information to address light amount variations, and a correction unit that specifically corrects halftone-processed image data using this information, without altering the original printing-target image data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If correction processing is performed on image data before halftone processing, then light amount variations can be corrected, but the correction is not reflected appropriately after halftone processing and density unevenness remains
Solution Approach 1:
The patent applies correction processing after halftone processing rather than before, ensuring that the correction is applied to the final image data that will actually be used for exposure. This timing ensures that the correction profile directly affects the halftone-processed output, making the correction effective in suppressing density unevenness.
2Manufacturing precision
If correction is applied to printing-target image data, then light amount variations are corrected, but the original image quality may be degraded
Solution Approach 1:
The patent applies correction only to the halftone-processed image data, which is a local subset of the processing pipeline, rather than modifying the original printing-target image data. This allows correction to be applied where needed (in the halftone output) without altering or degrading the original image data, thus preserving original image quality while still achieving density uniformity.
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 solution effectively suppresses density unevenness in the main scanning direction by accurately correcting light amount variations in halftone-processed image data, thereby improving the quality of the formed images.
Implementation Method 1
a plurality of light-emitting elements is arranged side by side as an exposure unit
Implementation Method 2
light radiated from the plurality of light-emitting elements... on a photosensitive body
Data Source
AI summary
An electrophotographic image forming apparatus, which utilizes a line head in which a plurality of light-emitting elements is arranged as a light source, includes at least one controller having at least one processor and at least one memory. The controller is configured to obtain print data to perform printing, perform halftone processing for the obtained print data, generate a plurality of pieces of correction information for correcting variations of light amount on a photosensitive body by light radiated from the plurality of light-emitting elements, and correct the print data for which the halftone processing has been performed by using the correction information. The correction information includes various profiles for correcting the variations of light amount.