Reference Mirror Adjustment for Cosine Error Reduction in Interferometry
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Solution Overview
Problem
Conventional light interference measuring devices face challenges in achieving precise shape measurements due to cosine errors during angle adjustments of the work piece or stage, making it difficult to generate interference fringes without affecting the coordinate system, especially when dealing with heavy stages that are hard to adjust rapidly.
Innovation Solution
A light interference measuring device configuration that includes a reference mirror adjustment mechanism, allowing for precise and rapid adjustment of the reference mirror's posture to generate interference fringes without altering the angle of the stage or work piece, thereby maintaining the coordinate system's integrity. This configuration includes a front-rear adjustment mechanism and an angle adjustment mechanism, controlled by a computer system to ensure the reflecting surface of the reference mirror matches the measurement surface, and allows for switching between interference optical system measurements and other measurement methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If angle adjustment of stage or work piece is performed to generate interference fringes, then interference fringes can be generated, but cosine error occurs and coordinate system is affected
Solution Approach 1:
The adjustment function is segmented between the reference mirror and the work piece. Instead of adjusting the work piece angle, only the reference mirror posture is adjusted while the work piece remains stationary in its coordinate system, separating the fringe generation function from the measurement function
Solution Approach 2:
The reference mirror acts as an intermediary element that absorbs the adjustment requirements. By adjusting the reference mirror's posture instead of the work piece, the system generates interference fringes without introducing cosine errors to the measurement coordinate system
2Measurement precision
If heavy stage is adjusted for angle correction, then coordinate alignment can be improved, but adjustment speed decreases
Solution Approach 1:
The adjustment function is segmented to be performed by a lightweight reference mirror rather than the heavy stage. This separates the adjustment mass from the measurement mass, allowing rapid reference mirror adjustment without moving the heavy stage
Solution Approach 2:
The reference mirror is designed with dynamic adjustment capabilities through piezoelectric actuators and motor-driven mechanisms, enabling rapid and precise posture changes without the inertia constraints of a heavy stage
3Measurement precision
If reference mirror posture is adjusted to match measurement surface, then interference fringes are optimized, but device complexity increases
Solution Approach 1:
The reference mirror adjustment mechanism includes automated control that uses imaging data to automatically determine and execute the required posture adjustments, reducing the need for complex manual alignment procedures and operators
Solution Approach 2:
The system incorporates feedback control where the imaging part captures images of the measurement surface, the control part analyzes the images to determine optimal reference mirror posture, and the adjustment mechanism executes the corrections, creating a closed-loop system that simplifies operation
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
Enables precise and rapid adjustment of interference fringes, maintaining the coordinate system's integrity, allowing for accurate three-dimensional shape measurements without cosine errors and facilitating rapid switching between measurement methods, supporting both white-light and monochromatic light interference measurements.
Implementation Method 1
brightness information of the interference fringes generated by the interference of light
Implementation Method 2
a beam splitter that causes the light output from the light source to diverge into a reference optical path and a measurement optical path and that outputs a combined wave in which reflection light that has passed through the reference optical path and reflection light that has passed through a measuring object arranged in the measurement optical path are combined
Implementation Method 3
a reference mirror that is arranged in the reference optical path and that reflects light which is diverged into the reference optical path by the beam splitter
Data Source
AI summary
A light interference measuring device comprises: a light source 20 that outputs light; a beam splitter 222 that causes the light output from the light source to diverge into a reference optical path and a measurement optical path and that outputs a combined wave in which reflection light that has passed through the reference optical path and reflection light that has passed through a measuring object arranged in the measurement optical path are combined; a reference mirror 231 that is arranged in the reference optical path and that reflects light which is diverged into the reference optical path by the beam splitter 222; a stage 12 that is arranged in the measurement optical path and that has the work W placed thereon; an imaging part 25 that images an image in which the combined wave is formed; a reference mirror adjustment mechanism (234, 238, 239) that adjusts a posture of the reference mirror 231; and a control part that controls the reference mirror adjustment mechanism such that a reflecting surface of the reference mirror 231 corresponds to a measurement surface of the work W, based on an image imaged in a condition where a work W is placed on the stage.