Inspection Timing Signal Control Unit for Laser Interferometer Positioning
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Solution Overview
Problem
Conventional inspection systems incur positional errors due to the non-integral multiple relationship between the distance corresponding to one pixel and the resolution of the laser interferometer, leading to accumulated errors that affect inspection accuracy.
Innovation Solution
A control unit is introduced to generate a timing signal for the imaging unit, utilizing a traveling distance determination section that detects integer count values from a laser interferometer and a timing signal generation section that adjusts thresholds to minimize positional errors, by selectively using multiple threshold values based on the detected traveling distance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the distance corresponding to one pixel is determined by rounding off the accurate count value from the laser interferometer, then the device complexity is reduced and ease of operation is improved, but measurement precision deteriorates due to accumulated positional errors
Solution Approach 1:
The patent calculates the accurate count value (including decimal parts) in advance before image capture begins. This preliminary calculation of the precise relationship between pixel distance and interferometer counts allows the system to compensate for rounding errors throughout the measurement process, thereby maintaining high measurement precision while keeping the actual operation simple.
Solution Approach 2:
The patent uses the accurately calculated count value (with decimal precision) as a reference to generate feedback for determining when one pixel distance has been traversed. This feedback mechanism allows the system to correct for the rounding error that would otherwise accumulate, maintaining measurement precision without complicating the operational process.
2Measurement precision
If the accurate count value with decimal parts is used to determine pixel distance, then measurement precision is improved, but device complexity increases due to the need for precise threshold management
Solution Approach 1:
The patent introduces an intermediary calculation process that converts the precise count value into a corrected threshold value. This intermediary step acts as a mediator between the high-precision measurement data and the practical threshold comparison operation, allowing the system to maintain measurement precision while simplifying the actual device operations by providing a pre-processed threshold value.
3Productivity
If the traveling stage moves a long distance to capture a large number of pixels, then productivity is improved, but measurement precision deteriorates due to accumulated positional errors
Solution Approach 1:
The patent performs preliminary calculation of the accurate count value corresponding to one pixel distance before the long-distance measurement begins. This advance calculation establishes a precise reference that remains valid throughout the entire measurement process, allowing the system to maintain high measurement precision even when capturing thousands of pixels over long distances, thereby enabling high productivity without sacrificing accuracy.
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 approach reduces the accumulation of positional errors, enhancing the inspection accuracy by dynamically adjusting the threshold values in response to the detected traveling distance, thereby mitigating the impact of non-integral pixel distances on the interferometer resolution.
Implementation Method 1
a laser interferometer provided in the inspection system for detecting a traveling distance of the inspection target object
Data Source
AI summary
A control unit for generating a timing signal for an imaging unit in an inspection system in which an image of an inspection target object is captured by the imaging unit while the inspection target object is caused to travel in a predetermined direction includes a traveling distance determination section configured to detect a traveling distance of the inspection target object based on a count value acquired as an integer value from a laser interferometer provided in the inspection system for detecting a traveling distance of the inspection target object, and configured to determine whether the detected traveling distance reaches a threshold, and a timing signal generation section configured to generate a timing signal when it is determined that the detected traveling distance reaches the threshold. The traveling distance determination section executes the determination by using a plurality of values selectively as the threshold.