Image Sharpness Recovery Using Frequency-Segmented Filters
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Solution Overview
Problem
Existing image sharpness recovery processing techniques for image forming apparatuses, such as inkjet printers, face challenges in maintaining brightness while compensating for sharpness degradation due to frequency characteristic changes, often resulting in overcorrection or insufficient correction, especially in higher-frequency regions.
Innovation Solution
The proposed solution involves using a combination of lower-frequency recovery filters and all-frequency recovery filters, along with dot arrangement control in halftone processing, to compensate for sharpness degradation. Specifically, lower-frequency components are addressed using a 11 × 11-sized lower-frequency recovery filter, while higher-frequency components are handled through dot arrangement, generating a recovery amount image to adjust dot priorities, thereby preventing brightness decreases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If sharpness recovery processing is performed using a filter having reverse characteristics, then sharpness degradation is compensated, but brightness decreases in higher-frequency regions
Solution Approach 1:
The patent segments the sharpness recovery processing into two distinct frequency regions: lower-frequency components are processed using a lower-frequency recovery filter, while higher-frequency components are processed using an all-frequency recovery filter. This segmentation allows different filtering strategies to be applied to different frequency bands, enabling sharpness recovery while controlling brightness degradation in the higher-frequency region.
Solution Approach 2:
The patent changes the filter characteristics based on frequency parameters by selecting different filters (lower-frequency recovery filter vs. all-frequency recovery filter) for different frequency regions. Additionally, the dot arrangement control adjusts the priority of dots based on frequency characteristics, effectively changing the processing parameters to balance sharpness recovery and brightness maintenance.
2Manufacturing precision
If correction amount is increased to compensate for frequency characteristic degradation, then sharpness is improved, but overcorrection or insufficient correction occurs
Solution Approach 1:
The patent applies local quality by using dot arrangement control that assigns different priorities to different dots based on their frequency characteristics and local image features. This allows the correction amount to be locally optimized for each region, preventing both overcorrection and insufficient correction by adapting the correction strength to the specific local requirements of each image region.
3Manufacturing precision
If conventional sharpness recovery processing is applied, then frequency characteristic degradation is compensated, but arithmetic operation load increases
Solution Approach 1:
The patent segments the frequency spectrum into lower-frequency and higher-frequency regions, allowing each region to be processed with an optimized filter. This segmentation enables the use of simpler, more efficient filtering strategies for each band, reducing the overall arithmetic operation load compared to applying a single complex all-frequency filter to the entire image.
Data Source
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AI summary
To implement sharpness recovery processing suitable for an image, an image processing apparatus (1) for generating, based on an input image, a halftone image to be provided to an image forming unit (2) which forms an image on a printing medium, comprises: recovery processing means (102) for performing, on the input image, recovery processing for compensating for sharpness degradation in an image formed by the image forming unit; generating means (112) for generating a recovery amount of each pixel by using the input image having undergone the recovery processing; and halftone processing means (108) for generating, based on the recovery amount, the halftone image by performing halftone processing on the input image having undergone the recovery processing.