Multi-Wavelength Position Measurement for Cyclic Error Control
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Solution Overview
Problem
Existing measurement apparatuses suffer from nonlinear cyclic errors that affect measurement accuracy, and increasing measurement times to improve accuracy decreases throughput.
Innovation Solution
A measurement apparatus that uses light with multiple wavelengths to detect the position of an object, determining the target distance where the amplitude of the cyclic error falls within an allowable range to reduce measurement errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of measurement types (n) is increased to improve measurement accuracy, then measurement accuracy improves, but throughput decreases
Solution Approach 1:
The patent changes the optical path length parameter to multiple discrete values (0, λ/4, λ/2, 3λ/4) instead of using multiple measurement types. By varying the optical path length parameter and selecting measurement results where the cyclic error amplitude is within an allowable range, the patent achieves high measurement accuracy without requiring multiple measurement types, thus maintaining throughput.
2Measurement precision
If multiple measurement types are performed to reduce cyclic error, then measurement accuracy improves, but measurement time increases
Solution Approach 1:
The patent performs preliminary action by varying the optical path length before taking measurements and evaluating the cyclic error amplitude. By pre-determining which optical path length settings produce acceptable cyclic error amplitudes (within allowable range), the system avoids time-consuming multiple measurement types and directly selects measurements taken under optimal conditions, reducing total measurement time while maintaining accuracy.
3Measurement precision
If the optical path length is varied to reduce cyclic error, then measurement accuracy improves, but system complexity increases
Solution Approach 1:
The patent applies dynamics by making the optical path length variable rather than fixed. The optical path length is dynamically adjusted to multiple discrete values (0, λ/4, λ/2, 3λ/4) allowing the system to select optimal measurement conditions. This dynamic adjustment enables cyclic error reduction through simple optical path variations without requiring complex measurement systems or multiple apparatus configurations.
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
Accurately measures the position of an object while minimizing cyclic errors, maintaining throughput by optimizing the detection process.
Implementation Method 1
a measurement apparatus (interferometer) that measures the position of an object based on an interference signal generated by the interference between the detection light reflected by the object (detection surface) and the reference light reflected by a reference surface
Data Source
AI summary
The present invention provides a measurement apparatus that measures a position of an object, comprising: a detector configured to irradiate a measurement target point of the object with light having a plurality of wavelengths, and detect a position of the measurement target point based on the light reflected by the measurement target point; and a processor configured to determine the position of the object based on a detection result of the detector, wherein the detection result includes an error represented by a waveform in which an amplitude cyclically changes in accordance with a distance between the detector and the object, and wherein the processor is configured to cause the detector to detect the position of the measurement target point at the distance at which the amplitude in the waveform of the error falls within an allowable range.