Printer Media Alignment Using RGB Sensor and IR Filter
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Solution Overview
Problem
Existing printing devices face challenges in accurately aligning pre-printed forms and labels due to limitations with traditional infrared reflective photoelectric sensors, which are sensitive to sunlight and require complex sensor sorting and matching, often resulting in inaccurate media detection.
Innovation Solution
A printer mechanism utilizing a red-green-blue (RGB) light sensor with an infrared light filter, coupled to a programmed processor, to detect and align pre-printed elements on the print medium by filtering out infrared light and using an I2C interface for precise alignment and media detection, eliminating the need for backside reflective sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional infrared reflective photoelectric sensors are used for media alignment detection, then the printer can detect media position, but the system becomes sensitive to direct sunlight and requires costly sensor sorting and matching operations
Solution Approach 1:
The patent changes the operating wavelength parameter from infrared to visible light spectrum, specifically using blue LED (430-480nm) and corresponding blue-sensitive photodetector. This parameter change makes the system immune to infrared sunlight interference while maintaining detection capability for media alignment
Solution Approach 2:
The patent replaces expensive infrared sensors requiring sorting and matching with inexpensive visible light LEDs and photodetectors that do not require costly calibration procedures. The simpler technology allows direct use without expensive quality control processes
2Measurement precision
If a pre-printed black mark is placed on the front side of the media for alignment, then media alignment can be detected, but it introduces an undesired element to the print canvas or creates large inter-form/label gaps
Solution Approach 1:
The patent replaces the mechanical/optical marker system (black mark on media) with an optical sensing system using visible light. The alignment detection is achieved through sensing pre-printed elements like barcodes or color variations without requiring physical marks that interfere with the print area
Solution Approach 2:
The patent moves the detection mechanism from the back side of the media to the front side, using a different spatial dimension (visible light spectrum vs infrared). This allows detection without adding physical elements to the media surface that would interfere with printing
3Measurement precision
If an infrared light source and reflective sensor are installed on the back side of the printer door, then media alignment can be detected, but the device complexity increases and the system is limited to sensing infrared light reflection
Solution Approach 1:
The patent inverts the traditional approach by placing the light source and sensor on the front side of the media path rather than the back side of the printer door. This reversal simplifies the mechanical design and allows direct sensing of media elements during the printing process
Solution Approach 2:
The patent uses a multi-color LED (emitting multiple wavelengths including blue) and a photodetector that can sense various pre-printed elements. This universal sensing approach can detect different types of media markers (barcodes, color bars, alignment marks) without requiring separate sensing systems for each type
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 enables accurate alignment and detection of pre-printed elements without the need for black marks or backside sensors, improving media registration and reducing complexity in printer design, while being robust against sunlight interference and variations in material quality.
Implementation Method 1
An infrared light filter is situated between the RGB light sensor and the paper so as to filter out infrared light entering the RGB light sensor
Implementation Method 2
A red-green-blue (RGB) light sensor is positioned to receive light from the light source that is reflected by the print medium
Data Source
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AI summary
A printer has a light source (20) that directs light toward a print medium path. An RGB sensor (28) is positioned to receive light from the light source (20) that is reflected by the print medium (24). An infrared light filter (32) is situated between the RGB sensor (28) and the paper to filter out infrared light. A programmed processor (40) is coupled to an output of the RGB sensor (28) in order to detect form elements in the output from the RGB light sensor, retrieve a stored electronic representation of a form, match the form elements to the stored electronic representation of the form to identify locations on the form, and control printing to the form.