Image Forming Apparatus Secondary Transfer Voltage Edge Detection
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Solution Overview
Problem
Existing image forming apparatuses face difficulties in accurately determining the positions of test images for adjusting secondary transfer voltage, especially when using color sheets, due to erroneous edge detection of the sheet edges as patch edges.
Innovation Solution
The apparatus includes a control unit that outputs a test chart with a reference image and applies various test voltages, allowing the reader to scan from a position within the recording material boundary to outside the test images, enabling precise detection of edges and adjustment of the secondary transfer voltage based on the scanned results.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the edge detection threshold is set to be less severe to detect halftone image patches, then the detection sensitivity is improved, but the sheet edges are erroneously detected as patch edges
Solution Approach 1:
The patent divides the test chart into distinct regions: a margin region (first region) and a test image region (second region). By segmenting the scanning area and excluding the margin region from patch detection, the system can use a less severe detection threshold for halftone patches without erroneously detecting sheet edges, thus resolving the contradiction between detection sensitivity and detection accuracy.
2Measurement precision
If the reader scans from the boundary of the recording material to accurately detect test image positions, then the detection accuracy is improved, but the scanning time is increased
Solution Approach 1:
The patent performs preliminary action by defining the scanning range in advance to start from the boundary of the recording material. The control unit is configured to control the reader to read the test chart by scanning from a first position (within the boundary) to a second position (within the test images). This preliminary setup of scanning parameters ensures accurate position detection without requiring excessive scanning time.
3Adaptability or versatility
If a color sheet is used for adjustment, then the adaptability to different recording materials is improved, but the edge detection accuracy deteriorates due to erroneous detection of sheet edges
Solution Approach 1:
The patent applies local quality by setting different detection criteria for different regions of the test chart. The margin region (first region) is excluded from patch detection, while the test image region (second region) undergoes normal detection. This regional differentiation allows the system to maintain high adaptability for color sheets while preventing erroneous edge detection in areas where sheet edges might be confused with test image edges.
Data Source
AI summary
An image forming apparatus includes an image forming portion, a transfer unit, a power supply, and a reader. A test chart is formed by transferring test images to a recording material while applying test voltages from the power supply to the transfer unit. A transfer voltage to be applied to the transfer unit during transfer is set based on the read test images. A reference image is formed on the test chart. The reader reads the test chart by scanning the test chart from a first position to a second position that falls within the test images. The first position falls within a boundary of the recording material on which the test chart is formed and falls outside the test images. Based on the reference image, the result of the reader reading the test chart is obtained by scanning the test chart from the first position to the second position.