Position Code Detection Using Spectral Sensitivity and Spatial Relationships
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Solution Overview
Problem
Existing methods for recording user unit movement over a base with a position code fail when the code is obscured by other graphics, as they require different printing inks for the code and layout, making it impractical to use on forms printed with monochrome ink.
Innovation Solution
A method that determines the user unit's movement by analyzing a sequence of images, allowing absolute positions to be calculated even if the position code is not decodeable in all images, using spatial relationships between images and distributed decoding to overcome obscuration or deformation, enabling use on forms with the same ink for both code and layout.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If different printing inks are used for the position code and form layout, then the position code can be read accurately without obstruction, but the manufacturing process becomes complex and impractical
Solution Approach 1:
The patent applies color changes by using different spectral sensitivity ranges for the sensor and the printing ink. The sensor is made insensitive to the printing ink's wavelength range, allowing it to detect only the position code printed in a different color. This enables accurate position code reading while using standard monochrome printing processes, eliminating the need for complex multi-ink printing.
2Ease of manufacture
If the position code is printed with the same ink as the form layout, then the printing process is simplified, but the position code becomes obscured and unreadable in certain areas
Solution Approach 1:
The patent uses color changes by selecting a position code color that falls within a different spectral sensitivity range than the form layout printing ink. This allows both the position code and form layout to be printed with the same physical ink process while maintaining distinct detectability - the sensor tuned to the position code's wavelength range ignores the form layout ink, ensuring the position code remains readable even when printed together.
3Adaptability or versatility
If a sensor insensitive to printing ink is used, then the position code can be detected on forms printed with the same ink, but the sensor's spectral sensitivity range must be precisely controlled
Solution Approach 1:
The patent applies parameter changes by adjusting the sensor's spectral sensitivity range to be insensitive to the printing ink's wavelength while remaining sensitive to the position code's wavelength. This parameter adjustment allows the sensor to distinguish between the position code and form layout printed with the same ink, enabling compatibility with standard monochrome printed forms without requiring complex sensor modifications.
Data Source
AI summary
A position code is recorded by capturing a sequence of images while writing on the base with a user unit. The position code may be decoded to a sequence of absolute positions reflecting the movement of the user unit over the base. If the position code in any image is not sufficiently recorded, e.g. because it is obscured by other graphics on the base, the spatial relationship of the image to another image in the sequence is determined. If the position code in this other image in the image sequence is decodable to an absolute position, the absolute position of the image in which the position code is not decodable could nevertheless be determined by using the spatial relationship. In this way the movement of the user unit can be recorded even though the position code is obscured, which could be the case when the same printing ink is used for both the position code and other graphics on the base.