Recording Medium Edge Detection Using Differential Light Signals
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Solution Overview
Problem
Conventional methods for detecting the edge of a recording medium in an ink-jet type image recording apparatus suffer from poor accuracy due to environmental variations, leading to issues like staining and margin occurrence during borderless printing.
Innovation Solution
An image forming apparatus with a detection unit comprising a light-emitting unit and multiple light receiving units, including a first and second light receiving unit, uses differential signal processing to accurately detect the edge of the recording medium by switching input signals based on scanning direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single light-sensitive device is used for edge detection, then the device complexity is reduced, but the measurement precision degrades due to environmental variations
Solution Approach 1:
The detection device is segmented into multiple light-sensitive devices (first and second light-sensitive devices) arranged in the scanning direction. Each device independently detects light reflected from the recording medium, and their outputs are processed separately to determine edge positions, thereby improving measurement precision while maintaining relatively simple device structure
Solution Approach 2:
The patent introduces a new dimension of detection by arranging light-sensitive devices not just in the scanning direction but also positioning them at different locations. The edge detection leverages the positional information of these devices in the scanning direction to calculate more accurate edge positions through coordinate comparison
2Device complexity
If conventional light-sensitive devices are used without differential processing, then the device complexity is lower, but the reliability deteriorates due to voltage threshold variations caused by environmental factors
Solution Approach 1:
The patent implements a feedback mechanism where the output signals from the first and second light-sensitive devices are continuously monitored and processed by a determination unit. The system uses the relative positions and signal characteristics to dynamically determine edge locations, providing feedback that compensates for environmental variations and maintains reliable detection
Solution Approach 2:
A determination unit acts as an intermediary between the light-sensitive devices and the final edge detection result. This intermediary processes the signals from multiple light-sensitive devices, comparing their positions and outputs to calculate accurate edge positions, thereby filtering out environmental noise and improving reliability
3Ease of operation
If the detection unit scans in only one direction, then the operation is simpler, but the measurement precision degrades due to inability to compensate for bidirectional scanning variations
Solution Approach 1:
The detection system is designed to handle dynamic scanning operations in both forward and backward directions. The controller is configured to determine edge positions based on the scanning direction, dynamically adjusting the detection methodology. This allows the system to maintain high measurement precision regardless of whether the scanning unit moves in the positive or negative direction
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
Enhances edge detection accuracy by compensating for environmental variations, reducing staining and margin issues, and enabling precise borderless printing on various recording mediums.
Implementation Method 1
a light-emitting unit configured to emit light towards a recording medium and a plurality of light receiving units configured to detect reflected light of the light
Data Source
AI summary
An image forming apparatus has a detection unit having a light-emitting unit and a plurality of light receiving units that detect reflected light of light emitted from the light-emitting unit. The plurality of light receiving units include a first light receiving unit and a second light receiving unit which are arranged to be aligned in a scanning direction of the detection unit, and the apparatus detects an edge of the recording medium based on a first coordinate of position information obtained when a differential signal between a first light reception signal outputted from the first light receiving unit and a second light reception signal outputted from the second light receiving unit becomes greater than or equal to a threshold and a second coordinate of position information obtained when the differential signal becomes less than or equal to the threshold.