Confocal Measurement Device Optical Axis Offset
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Solution Overview
Problem
Confocal measurement devices face challenges with erroneous measurements due to higher order light interference, particularly when measuring targets with mirrored surfaces, leading to increased production and design costs with multi-layered diffraction lenses.
Innovation Solution
The configuration of a confocal measurement device with an objective positioned closer to the measurement target than the diffraction lens, and an optical fiber with an inclined optical path, offsets the optical axis of the diffraction light and reflected different order light, reducing the impact of erroneous signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a multi-layered diffraction lens is used to mitigate higher order light interference, then measurement precision is improved, but device complexity and production cost increase
Solution Approach 1:
The patent extracts and removes the problematic higher order light components from the optical path using a spatial filter (pinhole) positioned at the focal point of the diffraction lens. This selectively blocks higher order diffracted light while allowing the zeroth order light to pass through, thereby eliminating the source of measurement errors without requiring complex multi-layered diffraction lenses
Solution Approach 2:
The patent introduces a spatial filter (pinhole) as an intermediary element in the optical path. This pinhole acts as a mediator that selectively transmits the desired zeroth order light while blocking the harmful higher order light, achieving precise measurement without increasing overall system complexity
2Ease of operation
If the diffraction lens is designed to use first order light for measurement, then measurement function is achieved, but erroneous signals from higher order light still interfere with measurement accuracy
Solution Approach 1:
The patent converts the harmful effect of higher order light into a beneficial filtering mechanism. By positioning the spatial filter at the focal point where higher order light converges, the system uses the natural diffraction pattern to concentrate unwanted light into specific locations that can be easily blocked, transforming the problematic higher order light into a convenient target for selective rejection
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 configuration effectively mitigates the influence of reflected different order light on measurements, improving accuracy and reducing production costs by simplifying the optical design.
Implementation Method 1
a diffraction lens that chromatically distorts the light emitted from said light source
Implementation Method 2
a diffraction lens that chromatically distorts the light emitted from said light source
Implementation Method 3
an objective arranged closer to the measurement target than the diffraction lens, wherein the objective focuses light chromatically distorted by the diffraction lens onto the measurement target
Implementation Method 4
the confocal measurement device measures the wavelength of the light passing through a pinhole
Implementation Method 5
employs confocal optics to measure the profile of a measurement target
Data Source
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AI summary
A confocal measurement device uses confocal optics to measure a profile of a measurement target (200). The confocal measurement device is provided with a light source, a diffraction lens (1) chromatically distorting light emitted from the light source along the direction of an optical axis, and a measurement unit measuring the intensity at each wavelength of the light within the chromatically distorted light created by the diffraction lens (1) and focused on the measurement target (200). Furthermore, the primary ray (11b) from the light source to the diffraction lens (1) is offset relative to the optical axis (1a) of the diffraction lens (1) in the confocal measurement device.