Printing Medium Edge Sensing With Differential Optical Detection
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Solution Overview
Problem
Conventional inkjet printing apparatuses face challenges in accurately detecting the edge of a printing medium due to environmental variations, leading to issues such as staining and unintended margins, as they rely on a single light emitting and sensitive device configuration that is susceptible to environmental fluctuations.
Innovation Solution
A printing apparatus is equipped with a sensor unit comprising a light emitter, multiple light sensitive units, and an aperture member, which uses differential signal amplification to detect the edge of a printing medium, reducing the influence of environmental variations by aligning light sensitive units in the scanning direction and utilizing a shared aperture for reflected light detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single light emitting device and a single light sensitive device are used for edge detection, then the device complexity is low, but the measurement precision deteriorates due to environmental variations
Solution Approach 1:
The patent divides the single light sensitive device into multiple light sensitive devices (first light sensitive device and second light sensitive device) arranged in the scanning direction. This segmentation allows the system to detect edge positions at multiple points simultaneously, improving measurement precision while managing device complexity through systematic arrangement.
Solution Approach 2:
The patent combines multiple light sensitive devices with a shared aperture member to detect reflected light through the same opening. By merging the detection function across multiple devices while sharing common components (aperture, light emitter), the system achieves higher precision without proportionally increasing overall complexity.
2Measurement precision
If multiple light sensitive devices are used to improve detection accuracy, then the measurement precision improves, but the device complexity increases
Solution Approach 1:
Multiple light sensitive devices share a common aperture member and light emitter, merging common functions to reduce redundant components. This approach improves measurement precision through multiple detection points while controlling device complexity by eliminating duplicate structures.
Solution Approach 2:
The aperture member serves multiple functions: it limits the input of reflected light to light sensitive devices and is shared by multiple light sensitive devices simultaneously. This multi-functionality reduces the number of separate components needed, improving precision without proportionally increasing complexity.
3Power
If light sensitive devices detect reflected light independently, then the detection signal is strong, but the reliability deteriorates due to environmental variations such as staining and external light
Solution Approach 1:
The detection function is segmented across multiple light sensitive devices positioned at different locations. By detecting reflected light at multiple points and comparing results, the system maintains strong detection signals while reducing vulnerability to environmental variations affecting any single device.
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 configuration enhances the accuracy of edge detection by canceling out common disturbances among light sensitive units, stabilizing the detection process and reducing sensitivity variations, thereby improving the precision of edge detection in marginless printing.
Implementation Method 1
reflected light, which is light emitted from the light emitting device and reflected by the printing medium, is detected by the light sensitive device
Implementation Method 2
a light sensitive device that converts an optical signal into an electric signal, such as a phototransistor
Data Source
AI summary
A printing apparatus has a sensor unit including a light emitter, a plurality of light sensitive units that detect reflected light of light emitted from the light emitter, and an aperture member provided between the plurality of light sensitive units and a detection target that includes an opening for limiting input of the reflected light to a light sensitive unit. The printing apparatus causes the sensor unit to scan relative to the detection target, and, based on a differential signal of signals from a first light sensitive unit and a second light sensitive unit, detects an edge of a printing medium in the detection target. The plurality of light sensitive units are arranged to be aligned in a scanning direction, and the first and second light sensitive units detect the reflected light through the same opening of the aperture member.