Position Detection Apparatus Using Three-Grating Optical Path
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Solution Overview
Problem
Existing position detection methods, such as those using diffraction gratings, face challenges in achieving high accuracy due to errors caused by the inclination of the reflection surface, leading to unreliable gap detection.
Innovation Solution
A position detection apparatus is designed with a configuration that includes a light source unit, a first grating between the light source and the object, a second grating between the object and the light receiver, and a third grating between the second grating and the light receiver, which forms periodic images to detect phase variations and accurately determine the object's position, minimizing the impact of surface inclination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional gap detection methods using diffraction gratings are used, then position detection can be performed, but detection accuracy deteriorates due to errors caused by reflection surface inclination
Solution Approach 1:
The patent introduces a third grating in the optical path to create a multi-dimensional measurement system. By adding this additional grating element, the system can detect and compensate for surface inclination errors that conventional two-grating systems cannot handle, thereby maintaining high measurement precision even when the reflection surface is inclined.
Solution Approach 2:
The third grating acts as an intermediary element that mediates the measurement process by providing reference information about surface inclination. This intermediary component enables the system to separate the effects of actual position changes from those caused by surface inclination, improving detection reliability.
2Measurement precision
If multiple gratings are introduced to improve measurement accuracy, then position detection precision improves, but device complexity increases
Solution Approach 1:
The patent merges the functions of multiple gratings into a coordinated optical system where the first, second, and third gratings work together as an integrated unit. This combining approach allows the system to achieve high measurement precision while managing complexity through functional integration rather than separate independent components.
Solution Approach 2:
The third grating serves multiple functions: it provides reference information for inclination detection, enables compensation for surface errors, and maintains the measurement signal path. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in device complexity while improving precision.
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 high-accuracy position detection with reduced influence from surface warpage or inclination, providing stable and precise gap detection without wavelength dependence, unlike conventional methods.
Implementation Method 1
a first grating in an optical path between the light source unit and the object, the light from the light source unit transmits through the first grating to form a first periodic image
Implementation Method 2
light corresponding to the first periodic image transmits through the second grating to form a second periodic image on the third grating
Implementation Method 3
receives reflected light from the object on a light receiver to detect position information of the object
Data Source
AI summary
A position detection apparatus that illuminates light from a light source unit onto an object and that receives reflected light from the object on a light receiver to detect position information of the object, includes a detector (10) and a signal processor (102), the detector includes a first grating (15) in an optical path between the light source unit and the object, a second grating (16) in an optical path between the object and the light receiver, and a third grating (17) in an optical path between the second grating and the light receiver, the signal processor acquires the position information of the object based on a phase variation of the second periodic image detected by the light receiver, and the position information of the object is information related to a distance from the detector to the object.