Displacement Sensor Fringe Period Stability via Grating Reorientation
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Solution Overview
Problem
Conventional triangulation sensors experience a decrease in detection accuracy due to changes in the period of fringes detected by the light receiving part when a workpiece is displaced, caused by deviations between the period of the detection elements and the fringes generated on the light receiving surface.
Innovation Solution
The displacement sensor is configured with a radiation part, a light receiving part, and a fringe generation part arranged parallel to the displacement direction, utilizing a diffraction grating or stepped substrate to generate fringes on the light receiving surface, ensuring that the period of the fringes remains constant even when the workpiece is displaced.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a grating is irradiated with light to generate fringes for position measurement, then the position detection capability is improved, but the fringe period changes with workpiece position causing deviation between detection element period and fringe period
Solution Approach 1:
The patent transitions from a conventional arrangement where the grating plane is perpendicular to the optical axis to an arrangement where the grating plane is parallel to the optical axis. This dimensional change ensures that the fringe period remains constant regardless of workpiece position, eliminating the deviation between detection element period and fringe period.
Solution Approach 2:
The patent changes the orientation parameter of the grating from perpendicular to parallel relative to the optical axis. This parameter change maintains a constant distance relationship between the grating and light receiving surface, thereby keeping the fringe period constant across different workpiece positions.
2Device complexity
If the fringe generation part is arranged perpendicular to the displacement direction, then the structure is simpler, but the fringe period changes when the workpiece is displaced
Solution Approach 1:
The patent rotates the grating arrangement by 90 degrees from perpendicular to parallel relative to the optical axis. This dimensional reorientation causes the distance between the grating and light receiving surface to remain constant during workpiece displacement, maintaining consistent fringe period.
Solution Approach 2:
The patent creates a dynamically invariant configuration where the grating orientation is fixed parallel to the optical axis, ensuring that the geometric relationship remains unchanged during workpiece movement, thereby maintaining constant fringe period throughout the measurement range.
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 maintains accurate detection of fringes without deviation, enhancing the precision of displacement measurement by keeping the fringe period consistent with the detection elements, thus improving detection accuracy.
Implementation Method 1
light emitted from a light source of a radiation part is reflected by the workpiece. The light reflected by the workpiece is imaged on a light receiving surface
Implementation Method 2
a fringe generation part that includes a generation means for generating fringes on a light receiving surface of the light receiving part
Data Source
AI summary
A displacement sensor includes a radiation part that irradiates a workpiece displaceable in a predetermined displacement direction with light, a light receiving part that receives a reflected light generated when the light radiated by the radiation part is reflected on the workpiece, and a fringe generation part that includes a generation means for generating fringes on a light receiving surface of the light receiving part when the light receiving part receives the reflected light from the workpiece. The fringe generation part and the light receiving part are arranged such that the fringe generation part and the light receiving part are parallel to the displacement direction, or parallel to a virtual image of the displacement direction.