Dual Line Sensor Inspection for Image Positioning Deviation
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Solution Overview
Problem
Existing image forming apparatuses face inefficiencies in inspecting large sheets due to the need for line sensors with lengths equal to or greater than the sheet width, which are costly and result in reduced working efficiency when front and back surfaces are reversed for inspection.
Innovation Solution
An image forming apparatus with a conveyor, image forming section, and dual line sensors on each surface, where the sensors' detection ranges partially overlap and extend in different directions, allowing for efficient inspection without reversing the sheet, using a controller to calculate and adjust positional deviations based on marks on both surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a line sensor with length equal to or larger than the sheet width is used to inspect the entire sheet, then the inspection coverage is sufficient, but the production cost increases significantly
Solution Approach 1:
The patent divides the inspection task into two segments: one line sensor inspects the front surface of the sheet, and another line sensor inspects the back surface of the sheet. Each sensor only needs to cover half the sheet width, allowing the use of shorter, less expensive sensors while achieving complete inspection coverage of the entire sheet.
Solution Approach 2:
Instead of using a single long sensor to scan the entire sheet width in one direction, the patent inverts the approach by scanning the front and back surfaces separately with shorter sensors. The back surface sensor reads marks that are visually aligned with the front surface marks, enabling complete inspection without requiring a sensor as long as the full sheet width.
2Ease of manufacture
If the front and back surfaces of the sheet are reversed for inspection to use shorter line sensors, then the sensor cost is reduced, but the working efficiency deteriorates due to longer reading time
Solution Approach 1:
The patent applies preliminary action by forming position detection marks on both the front and back surfaces of the sheet during the image formation process itself. These marks are pre-positioned so that when the sheet passes through the inspection section, the marks on both surfaces are visually aligned, allowing simultaneous reading by both line sensors without requiring sheet reversal or additional positioning time.
3Speed
If a single line sensor reads only the front surface, then the inspection speed is maintained, but the positional deviation between front and back surface images cannot be detected
Solution Approach 1:
The patent merges the inspection functions by combining two line sensors that simultaneously read marks on both the front and back surfaces of the sheet. Since the marks on both surfaces are visually aligned during image formation, both sensors can operate at full speed without slowing down the process, while the controller compares the read positions to detect any positional deviations between the front and back surface images.
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 efficient inspection and accurate image positioning on large sheets using shorter, less expensive line sensors, maintaining high working efficiency without the need to reverse the sheet, thus reducing production costs and improving inspection speed.
Implementation Method 1
a first line sensor located on a first surface side midway in the transportation path to read the front surface of the sheet on which the image forming section has formed an image
Implementation Method 2
a second line sensor located on a second surface side opposite to the first surface side, midway in the transportation path to read the back surface of the sheet on which the image forming apparatus has formed an image
Data Source
AI summary
An image forming apparatus includes: a conveyor that transports a sheet; an image former that forms an image on front and back surfaces of the sheet being transported in a transportation path and forms marks on the front and back surfaces; a reader that comprises a first line sensor that is disposed on a front surface side and reads the front surface; and a second line sensor that is disposed on a back surface side and reads the back surface; and a controller that: calculates a positional deviation between the images formed on the front and back surfaces based on positions of the marks on the front surface read by the first line sensor and positions of the marks on the back surface read by the second line sensor, and controls the image former to adjust positions of the images formed on the front and back surfaces.