Image Scanning Apparatus Anomaly Pixel Correction
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Solution Overview
Problem
Image scanning apparatuses using gray reference members face challenges in obtaining accurate gradation values without elongating the scanning time, particularly due to dust or blot on the reflection surface affecting neighboring pixel density values.
Innovation Solution
An image scanning apparatus with a gray reference member having a lower reflection coefficient than white, equipped with a scanning unit, photoelectric conversion elements, and a controller that sets target pixel numbers, determines reference gradation values, corrects anomaly pixels by adjusting light source intensity and illuminating period, and applies shading corrections based on digital signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the light quantity of the light source is adjusted to obtain a predetermined reflection density value from the gray reference member, then accurate shading correction can be performed, but determination of anomaly pixels for all pixels elongates the scanning period
Solution Approach 1:
The patent applies partial action by determining anomaly pixels only for a partial region (e.g., a specific number of pixels or a representative subset) rather than all pixels across the entire gray reference member. This reduces the computational burden and scanning time while still capturing sufficient information to identify dust or blot contamination patterns, thereby resolving the contradiction between measurement precision and time loss.
2Reliability
If dust or blot is adhered on the reflection surface of the reference member, then density values of affected pixels differ largely from neighboring pixels, but identifying and correcting all anomaly pixels increases processing time
Solution Approach 1:
The patent extracts only the necessary information for anomaly detection by focusing on a subset of pixels or a representative region rather than processing all pixels. This extraction approach identifies dust or blot contamination sufficient for reliable shading correction while maintaining scanning efficiency, thus resolving the contradiction between reliability and productivity.
3Measurement precision
If a gray reference member with lower reflection coefficient is used to reduce show-through phenomenon, then image scanning accuracy is improved, but the system becomes more sensitive to dust and blot on the reference member surface
Solution Approach 1:
The patent implements feedback by detecting anomaly pixels in the gray reference member and using this information to adjust or correct the shading correction process. The system monitors for dust or blot contamination and compensates for its effects, thereby maintaining the advantages of using a gray reference member (reduced show-through) while mitigating its increased sensitivity to surface contamination.
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
Enables accurate gradation value determination and correction of anomaly pixels due to dust or blot, maintaining efficient scanning time by adjusting light source parameters and applying shading corrections effectively.
Implementation Method 1
a scanning unit configured to scan an image on the original sheet on a line basis, the scanning unit including a light source configured to illuminate the original sheet when passing the gray reference member and a plurality of photoelectric conversion elements aligned in a scanning direction
Data Source
AI summary
A controller is configured to set a reference gradation value when a gray reference member is illuminated. When the number of pixels, of which the gradation values is equal to or greater than the reference gradation value, is a target number of pixels, both are stored in association with each other. A correction target number which is a minimum target number of pixels from among a plurality of target numbers of pixels respectively providing differences, which is less than a predetermined value, between the reference gradation values stored in association with an M-th target number and an (M+1)-th target number. The controller further determines an anomaly pixel number which is the number of anomaly pixels having gradation values which are equal to or greater than a base gradation value. The gradation values of the determined number of anomaly pixels are corrected.