Print Medium Edge Sensing With Differential Optical Detection
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Solution Overview
Problem
Existing inkjet printing apparatuses face challenges in accurately detecting the edge of a print medium due to environmental changes, such as contamination, leading to inaccurate detection and unintended margins, as conventional methods are sensitive to floating conditions and ambient light.
Innovation Solution
A printing apparatus with a sensor unit comprising a light emitter, a light-receiving element array, and an aperture member, utilizing differential amplification to select specific light-receiving elements for edge detection, reducing the influence of environmental changes by using a differential signal based on the positional relation between light-receiving elements and the aperture member.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a light-emitting element and a light-receiving element are used to detect the medium edge portion, then the detection function is provided, but the detection accuracy decreases due to environmental changes such as contamination and floating conditions
Solution Approach 1:
The light-receiving element is divided into multiple elements (first light-receiving element and second light-receiving element) arranged in the sub-scanning direction. This segmentation allows the system to use differential signals between multiple elements to cancel out common environmental disturbances, thereby maintaining detection accuracy under varying conditions.
Solution Approach 2:
The system uses the positional relationship information between the light-receiving elements and the aperture member to dynamically adjust or select which light-receiving elements to use for detection. This feedback mechanism ensures that the detection system adapts to maintain accuracy despite environmental changes.
2Device complexity
If one light-emitting element and one light-receiving element are used for detection, then the device complexity is reduced, but the detection accuracy deteriorates due to sensitivity to environmental changes
Solution Approach 1:
Instead of using a single light-receiving element, the system segments the detection function across multiple light-receiving elements. This segmentation provides redundancy and enables differential measurement, improving accuracy without requiring a proportional increase in overall system complexity.
Solution Approach 2:
The system combines the signals from multiple light-receiving elements through differential amplification. By merging the detection functions of multiple elements and processing their combined output, the system achieves higher accuracy while keeping the device complexity manageable.
3Reliability
If specular reflected light is used for detection, then the detection function is provided, but the detection accuracy is affected by floating conditions of the paper
Solution Approach 1:
The system positions the light-receiving elements at specific locations relative to the aperture member to optimize their detection characteristics. By carefully selecting the local positions of the light-receiving elements, the system achieves detection that is less sensitive to paper floating conditions.
Solution Approach 2:
The use of multiple segmented light-receiving elements allows the system to detect edge portions through differential measurement, which cancels out the effects of paper floating. This segmentation approach provides robustness against variations in paper position and condition.
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 approach enhances the accuracy of detecting the edge of a print medium by canceling out common disturbances, enabling stable and precise edge detection even in varying conditions.
Implementation Method 1
a light-emitting element such as an LED and a light-receiving element such as a phototransistor that converts an optical signal into an electrical signal
Implementation Method 2
an aperture member, provided between the detection target and the light-receiving element array, having an opening portion for regulating the reflected light
Implementation Method 3
detect the edge of the print medium based on a differential signal obtained by performing differential amplification on signals from the first light-receiving unit and the second light-receiving unit
Data Source
AI summary
A printing apparatus comprises a sensor unit including a light emitter, a light-receiving element array including a plurality of light-receiving elements that receive reflected light from a detection target, and an aperture member that is provided between the detection target and the light-receiving element array and has an opening. The apparatus obtains a positional relation between each of the light-receiving elements and the opening through which the reflected light passes, selects one or more light-receiving elements to be used for detecting an edge of a print medium in the detection target, as a first light-receiving unit and a second light-receiving unit, based on the positional relation, and detects the edge of the print medium based on a differential signal of signals from the first light-receiving unit and the second light-receiving unit.