Interference Measuring Device Movable Aperture Stop
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Solution Overview
Problem
Interference measuring devices with lower magnification objective lenses can only receive reflected beams within a limited tilt angle, restricting their ability to measure objects with surfaces not perpendicular to the optical axis, especially those with convex or concave profiles.
Innovation Solution
The device employs a movable aperture stop and adjustable reference mirrors to control the path of light rays, allowing the objective lens to receive light reflected from surfaces at angles closer to perpendicular, thereby easing restrictions on curvature radius and tilt angle limitations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If lower magnification objective lenses are used to measure wider fields, then the measurement field of view is improved, but the maximum tilt angle that can be received decreases
Solution Approach 1:
The aperture stop is made movable along the optical axis rather than being fixed, allowing dynamic adjustment of the light reception angle. This enables the system to adapt to different measurement scenarios - using lower magnification for wide-field measurement while compensating for reduced tilt angle reception by adjusting the aperture stop position.
Solution Approach 2:
The system changes the parameter of aperture stop position along the optical axis to control the light reception characteristics. By adjusting this parameter, the system can compensate for the reduced maximum tilt angle reception that occurs when using lower magnification objective lenses, thus maintaining adaptability while achieving wide-field measurement.
2Measurement precision
If the aperture stop is fixed at the focal point for telecentric measurement, then measurement precision is improved, but the ability to measure convex or concave surfaces is restricted
Solution Approach 1:
The aperture stop is designed to be movable rather than fixed at the focal point. This dynamic configuration allows the system to maintain telecentric measurement precision when measuring flat surfaces by positioning the aperture stop at the focal point, while also enabling measurement of convex or concave surfaces by adjusting the aperture stop to appropriate positions that account for surface curvature.
Solution Approach 2:
The movable aperture stop mechanism provides multi-functionality, enabling the same optical system to handle both telecentric measurements of flat surfaces and non-telecentric measurements of curved surfaces. This single mechanism serves multiple measurement purposes, making the system universal rather than requiring separate configurations for different surface types.
3Device complexity
If the objective lens receives reflected beams at limited tilt angles, then optical system simplicity is maintained, but measurement capability for angled surfaces is restricted
Solution Approach 1:
Rather than complicating the optical system with additional lenses or mirrors, the invention uses a simple movable aperture stop mechanism. This dynamic adjustment of the aperture stop position allows the objective lens to receive reflected beams at varied tilt angles corresponding to convex or concave surfaces, maintaining optical system simplicity while enhancing measurement capability.
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 enables the device to efficiently measure objects with convex or concave surfaces by adjusting the aperture stop and using appropriate reference mirrors, enhancing light reception and measurement precision beyond the conventional tilt angle limitations.
Implementation Method 1
information on the brightness of interference fringes generated by optical interference
Implementation Method 2
the beam reflected off the reference mirror with the beam reflected off a measurement object
Data Source
AI summary
The present invention provides an interference measuring device with an optical system that can receive light reflected from a measurement object of a surface profile that is not perpendicular to an optical axis. An interference measuring device includes a light source for emitting light and an interferometric objective lens. The interferometric objective lens includes a reference mirror disposed in a reference beam path and a beam splitter that splits the incident light into a beam traveling along the reference beam path and a beam traveling along a measurement beam path. The beam splitter also combines the beam reflected off the reference mirror with the beam reflected off a measurement object disposed in the measurement beam path before emitting the combined beams. The interference measuring device further includes an imaging unit for taking an image of the combined beams forming on the unit and an aperture stop disposed in an optical path linking the interferometric objective lens, the light source, and the imaging unit together. The aperture stop is movable along an optical axis of the interferometric objective lens.