Phosphorescent Belt Edge Detection for Printing Devices
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Solution Overview
Problem
Optical sensors in printing devices often fail to accurately detect the leading and trailing edges of sheets, especially when the contrast between colored media and a black vacuum belt is insufficient, leading to improper alignment and marking.
Innovation Solution
A phosphorescent belt, such as one made with zinc sulfide or strontium aluminate, is used in conjunction with a light source and optical sensor, where the belt emits light after being charged, allowing for precise edge detection by measuring changes in light irradiance, even with colored media.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical sensors are used to detect sheet edges, then edge detection is enabled, but detection accuracy deteriorates when contrast between colored media and black belt is insufficient
Solution Approach 1:
The patent applies color changes by using a phosphorescent belt that emits light in a specific wavelength range (e.g., ultraviolet, visible, or infrared) to create contrast with the media sheets. The belt's phosphorescent material absorbs light and re-emits it, allowing optical sensors to detect sheet edges even when the media color closely matches the black belt appearance, thereby resolving the contrast insufficiency problem.
Solution Approach 2:
The patent introduces a phosphorescent belt as an intermediary between the light source and the optical sensor. The belt absorbs light from the source and re-emits it with different characteristics, creating a detectable signal that enhances the contrast between the belt and the media sheets, thus enabling accurate edge detection despite poor inherent contrast.
2Reliability
If conventional optical sensors are used, then edge detection is possible, but reliability deteriorates with colored media lacking sufficient contrast
Solution Approach 1:
The phosphorescent belt changes the optical characteristics by absorbing light and re-emitting it at different wavelengths. This color transformation creates a reliable contrast signal that is independent of the media sheet's original color, thereby improving detection reliability even when colored media are used.
Solution Approach 2:
The patent changes the optical parameters by using a phosphorescent material that converts absorbed light into emitted light with different intensity, wavelength, or temporal characteristics. This parameter change enables the optical sensor to reliably distinguish the belt from the media sheets regardless of the media's color properties.
3Measurement precision
If light source continuously illuminates the belt, then edge detection is enabled, but energy consumption increases
Solution Approach 1:
The patent implements periodic action by activating the light source only during specific intervals or in a pulsed manner rather than continuously. The phosphorescent belt stores energy during illumination periods and continues to emit light during dark periods, maintaining detection capability while significantly reducing overall energy consumption of the light source.
Solution Approach 2:
The phosphorescent belt performs preliminary action by absorbing and storing light energy in advance during illumination periods. This stored energy is then released as emitted light during subsequent detection periods, allowing the system to maintain edge detection capability without requiring continuous light source activation.
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 solution provides accurate and rapid edge detection with improved sensitivity and response time, maintaining accuracy even at higher process speeds and with thicker or colored media, reducing errors in printing alignment.
Implementation Method 1
The phosphorescent belt accumulates energy from the primary light and produces belt-emitted light after absorbing the energy from the primary light
Data Source
AI summary
Printing devices include a media supply storing print media, a luminescent belt positioned adjacent the media supply in a location to move sheets of the print media from the media supply, a print engine positioned adjacent the luminescent belt in a location to receive the sheets from the luminescent belt, an optical sensor positioned adjacent the belt in a location to receive belt-emitted light from the luminescent belt, and a processor electrically connected to the optical sensor. The processor receives the image from the optical sensor and identifies locations of the sheets on the belt based on where the sheets block the belt-emitted light from the luminescent belt.