Displacement Detection Apparatus with Correcting Lens for Tilt Error Compensation
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Solution Overview
Problem
Conventional displacement detection apparatuses experience measurement errors when the diffraction grating is displaced or tilted in directions other than the intended measurement direction.
Innovation Solution
A displacement detection apparatus is designed with a light source, luminous flux-splitting section, diffraction grating, mirrors, correcting lens, and light-receiving section, where the light is split and diffracted to ensure that the diffracted light beams are superimposed and received perpendicularly to the grating plane, minimizing optical path deviations and errors due to tilting or movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional diffraction grating displacement detection apparatus is used, then displacement measurement can be performed, but measurement errors are generated when the diffraction grating is displaced or tilted in directions other than the measurement direction
Solution Approach 1:
The optical path is divided into two separate paths using a beam splitter, creating first and second luminous fluxes that travel through different routes before being combined. This segmentation allows independent control and optimization of each path to compensate for grating misalignment effects.
Solution Approach 2:
The patent employs a counterbalancing optical design where the first and second luminous fluxes experience opposite deviations when the diffraction grating is tilted. By superimposing these fluxes, the measurement errors caused by tilting in directions other than the measurement direction are compensated, effectively counterweighting the erroneous signals.
2Device complexity
If the diffraction grating is tilted or displaced in non-measurement directions, then the apparatus structure remains simple, but measurement errors occur
Solution Approach 1:
The displacement detection apparatus is designed to perform its primary measurement function while simultaneously compensating for misalignment errors through the dual luminous flux path. The beam splitter configuration enables the system to handle both normal displacement measurement and error compensation within a single integrated structure.
3Reliability
If a dual luminous flux path with beam splitter is introduced, then measurement errors due to grating tilting are reduced, but device complexity increases
Solution Approach 1:
The first and second luminous fluxes are superimposed and combined into a single interference pattern that can be detected by the light receiving element. This merging of the two separate optical paths into one combined signal allows error compensation while maintaining a relatively compact and integrated device structure.
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 significantly reduces measurement errors even when the diffraction grating is tilted or moves in directions other than the intended measurement direction, maintaining accurate displacement detection.
Implementation Method 1
a light source (2) which emits light
Implementation Method 2
a diffraction grating (4) which diffracts the first luminous flux (L1) and the second luminous flux (L2)
Implementation Method 3
the first mirror (13) reflects the first luminous flux (L1) to enter the diffraction grating (4) in a direction perpendicular to a grating plane
Implementation Method 4
a correcting lens (7) which focuses the first luminous flux (L1) and the second luminous flux (L2) diffracted by the diffraction grating (4) on one point
Implementation Method 5
The light-receiving section receives interference light beam of the first luminous flux and the second luminous flux superimposed by the luminous flux-coupling section
Data Source
AI summary
A displacement detection apparatus can reduce a measurement error even when a diffraction grating is displaced and/or tilted to a direction other than the measurement direction. A displacement detection apparatus includes a light source which emits light, a luminous flux-splitting section, a diffraction grating, a diffracted light-reflecting section, a correcting lens, a luminous flux-coupling section, and a light-receiving section. The diffracted light-reflecting section reflects a first luminous flux and a second luminous flux so as to be perpendicular to one of measuring planes of the diffraction grating and be parallel to each other. The correcting lens is arranged between the diffracted light-reflecting section and the diffraction grating.