Photosensor Threshold Setting for Mark Background Distinction
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Solution Overview
Problem
Existing photosensor systems require users to frequently reset determination threshold values to distinguish between mark and background colors, especially when workpieces have varying mark and background colors, which is burdensome and increases user workload.
Innovation Solution
A photosensor system that includes a light projection unit, a light receiving unit, and a threshold value setting unit that calculates contrast differences between mark and background values across multiple wavelength regions, updating the threshold value based on the maximum contrast difference to reliably distinguish between mark and background colors without requiring extensive user intervention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If users manually reset determination threshold values for different mark and background color combinations, then the sensor can accurately distinguish between mark and background colors, but the user workload and operation complexity increase significantly
Solution Approach 1:
The sensor automatically performs threshold value determination by calculating contrast differences between mark and background colors across multiple wavelength regions. The determination threshold value calculation unit computes the contrast difference for each wavelength region and sets the threshold based on the region with maximum contrast, eliminating the need for manual user adjustment and resetting of threshold values when color combinations change
Solution Approach 2:
The system changes the parameter used for threshold determination from fixed manual values to dynamically calculated contrast differences. By calculating contrast difference = |mark reflectance - background reflectance| for each wavelength region and selecting the threshold based on maximum contrast, the system adapts to different color combinations automatically without requiring user intervention
2Ease of operation
If the sensor uses a fixed determination threshold value, then the operation is simple, but the sensor cannot reliably distinguish between mark and background colors when color combinations vary
Solution Approach 1:
The determination threshold value is made dynamic rather than fixed. The calculation unit dynamically computes threshold values based on actual mark and background color characteristics by calculating contrast differences across wavelength regions. This allows the threshold to adapt automatically to different color combinations while maintaining operational simplicity, as the adaptation occurs automatically without user input
3Measurement precision
If the sensor requires manual threshold adjustment for each color combination, then accurate detection is possible, but the productivity and operational efficiency decrease due to frequent adjustments
Solution Approach 1:
The sensor performs self-adjustment of determination threshold values by automatically calculating contrast differences between mark and background colors. This eliminates the need for manual intervention when processing workpieces with different color combinations, maintaining high detection accuracy while significantly improving productivity by removing repetitive adjustment operations from the workflow
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
The system enables reliable distinction between mark and background colors, reducing the need for frequent user adjustments and minimizing workload, even when mark and background colors are similar or weak, thereby improving operational efficiency.
Implementation Method 1
a light receiving unit that receives light projected from the light projection unit and reflected from an area to which light has been projected
Data Source
AI summary
A photosensor includes a light projection unit, a light receiving unit, a determination unit that determines a magnitude relation between a received light quantity of the light receiving unit and a threshold value set for the received light quantity; and a threshold value setting unit that sets the threshold value of the received light quantity. The threshold value setting unit calculates for each of a plurality of different wavelength regions, a contrast difference that is a difference between a received light quantity obtained when projection is performed on a detection target on a surface of a workpiece and a received light quantity obtained when projection is performed on a background on the surface of the workpiece, and updates the threshold value based on the contrast difference for a wavelength region among the plurality of wavelength regions in which the contrast difference has a maximum value.