Image Density Correction Using Rotary Phase Feedback
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Solution Overview
Problem
Existing image forming apparatuses face challenges in precisely correcting density unevenness in the sub-scanning direction due to periodic rotary members, as errors in rotation rate and variable magnification cause inaccuracies in extracting density data, leading to residual noise from other members.
Innovation Solution
The apparatus forms a pattern corresponding to multiple periods of the rotary member, with reference marks, to accurately detect the phase and calculate density data for one period, thereby isolating and correcting density unevenness caused by the rotary member while minimizing noise from other components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If density data is extracted based on theoretical period length of rotary member, then extraction process is simple, but errors due to rotation rate variations and variable magnification cause inaccurate density measurement
Solution Approach 1:
The system uses reference marks detected by the density sensor to provide feedback on the actual position and phase of the rotary member. This feedback information is used to dynamically adjust the extraction timing and calculate the actual period length, compensating for rotation rate variations and variable magnification effects.
Solution Approach 2:
The patent replaces the mechanical assumption of fixed period length with an optical detection system. Instead of relying on theoretical mechanical period calculations, the system uses a density sensor to optically detect reference marks and calculate the actual period based on detected positions, substituting mechanical precision requirements with optical measurement.
2Measurement precision
If pattern length corresponds to multiple periods of rotary member, then noise from other members is reduced through averaging, but the complexity of phase detection and data processing increases
Solution Approach 1:
The pattern is divided into multiple periods of the rotary member, with each period containing reference marks. The density data from multiple periods are separately extracted and then averaged, segmenting the measurement process to reduce noise from other members while maintaining manageable data processing through systematic segmentation.
Solution Approach 2:
The system utilizes the periodic nature of the rotary member by creating patterns that span multiple periods and detecting reference marks at regular intervals. This periodic structure allows for systematic data extraction and averaging across periods, reducing random noise while maintaining a structured approach to data processing.
3Measurement precision
If home position signal is used to synchronize phase correction with rotary member, then periodic density unevenness can be corrected, but noise from other members with different periods remains
Solution Approach 1:
The system extracts only the density data corresponding to the specific rotary member's period by using reference marks as synchronization points. By isolating and extracting data for one specific period at a time, the system separates the target rotary member's density unevenness from noise caused by other members with different periods.
Solution Approach 2:
Instead of attempting to correct all density unevenness simultaneously, the system focuses on correcting the periodic unevenness of one specific rotary member at a time. By applying correction data for individual periods separately and then combining results, the system achieves precise correction of the target member while filtering out other noise sources.
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 method allows for precise detection and correction of density unevenness in the sub-scanning direction, effectively eliminating noise from other members and ensuring high-precision image formation.
Implementation Method 1
the plate is read by a photoelectric sensor. The HP signal output by the photoelectric sensor is a rectangular wave
Implementation Method 2
the density unevenness is grasped by measuring the density of the above pattern with a density sensor
Data Source
AI summary
Disclosed is an image forming apparatus including: an image forming unit configured to form an image on a conveyed recording medium; a density detecting unit configured to detect a density of the image formed on the recording medium; a phase detecting unit configured to detect a phase of a predetermined periodic member; a control unit configured to instruct the image forming unit to form a pattern on the recording medium, and to prepare correction data for one period of the periodic member from density data obtained by detecting the density of the pattern; and a density unevenness correcting unit configured to correct image data by repeatedly applying the correction data for one period so as to match with the phase of the periodic member, and to correct the density unevenness in the conveying direction, which is caused due to the periodic member.