Chromatic Confocal Measurement Diffractive Lens Spherical Aberration
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Solution Overview
Problem
Existing confocal measurement apparatuses face challenges in achieving high measurement accuracy due to factors such as varying product shapes and materials, which affect displacement measurement performance.
Innovation Solution
A confocal measurement apparatus is designed with a diffractive lens that generates chromatic aberration and includes a light shielding film on its plane, allowing only focused light to pass through, enhancing measurement accuracy by reducing spherical aberration and improving angle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a diffractive lens is used to generate chromatic aberration for displacement measurement, then measurement capability is enabled, but spherical aberration occurs degrading measurement accuracy
Solution Approach 1:
The patent extracts and removes the harmful central portion of light that causes spherical aberration by introducing a pinhole aperture. This aperture blocks the central light rays that would otherwise pass through the diffractive lens and contribute to spherical aberration, while allowing peripheral rays to pass through and maintain the chromatic aberration effect needed for measurement.
Solution Approach 2:
The patent applies different quality requirements to different portions of the light beam. The central portion is blocked to eliminate spherical aberration, while the peripheral portion is allowed to pass to maintain chromatic aberration for measurement. This local differentiation of light path treatment resolves the contradiction between enabling measurement and eliminating aberration.
2Measurement precision
If light is allowed to pass through the entire diffractive lens area, then sufficient light intensity is achieved, but angle characteristics deteriorate reducing measurement accuracy
Solution Approach 1:
The pinhole aperture extracts and removes the central light portion that causes angle characteristic deterioration. By blocking this central portion and allowing only peripheral light to pass, the patent improves angle characteristics while maintaining sufficient light intensity through the optimized aperture size.
Solution Approach 2:
The patent optimizes the pinhole aperture size as a critical parameter. By carefully selecting the aperture diameter, the system achieves the optimal balance between blocking harmful central light (improving angle characteristics) and allowing sufficient peripheral light to pass (maintaining light intensity for measurement).
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 apparatus achieves enhanced measurement accuracy by ensuring consistent focal distance across the measurement target, regardless of shape or material variations, thereby improving displacement measurement precision.
Implementation Method 1
a diffractive lens that includes a diffraction surface and a plane to generate a chromatic aberration along an optical axis direction in light emitted from the light source
Implementation Method 2
an objective lens that is disposed on a measurement target side with respect to the diffractive lens to collect the light
Implementation Method 3
a pin hole that allows passage of that part of the light collected by the objective lens that is in focus on the measurement target
Data Source
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AI summary
PROBLEM: Providing a confocal measurement apparatus that can achieve high measurement accuracy. MEANS FOR SOLVING PROBLEM: A confocal measurement apparatus includes 101 a light source 21 that emits light having a plurality of wavelengths; a diffractive lens 1 that generates a chromatic aberration in the light emitted from the light source 21; an objective lens 2 that collects the light, in which the chromatic aberration is generated, on a measurement target 200; a pin hole (optical fiber 11) that allows passage of the focused light; and a measurement part (spectroscope 23 and imaging element 24) that measures a light intensity in each wavelength. The diffractive lens 1 includes a diffraction surface 1 a in which a diffraction pattern is formed in order to generate the chromatic aberration; and a plane 1 b that is located on an opposite side to the diffraction surface 1 a. In the plane 1 b of the diffractive lens a, a circular light shielding film 4 is disposed around an optical axis X of the diffractive lens 1.