Retro-reflector Optical System for Tilted Object Displacement Measurement
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Solution Overview
Problem
Conventional Michelson interferometers are unable to accurately measure the displacement of a rotating test object with a light reflective surface when it tilts over a large angle, as the light beam no longer remains perpendicular to the surface, preventing interference and accurate measurement.
Innovation Solution
The measuring device incorporates a further optical system comprising retro-reflectors and lenses that return the reflected light beam from the object to its original path, ensuring interference can occur even when the object is tilted, using elements like movable focusing lenses, corner cubes, and collimator lenses to maintain beam alignment and focus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional Michelson interferometer is used to measure displacement, then measurement precision is high when the object is perpendicular to the light beam, but measurement capability is lost when the object tilts over a large angle
Solution Approach 1:
A retro-reflector is introduced as an intermediary optical element between the beam splitter and the object. This retro-reflector redirects the light beam that has been reflected from the tilted object back into the optical system, ensuring that the beam returns to the beam splitter regardless of the object's tilt angle. This mediator component enables the measurement system to handle tilted objects while maintaining measurement precision.
Solution Approach 2:
The patent adds a spatial dimension to the optical path by positioning the retro-reflector at a specific location in the optical system. This creates an additional reflection path that compensates for the angular deviation caused by object tilt, effectively adding a dimensional correction mechanism to the interferometer.
2Adaptability or versatility
If the object tilts over a large angle, then adaptability to different object orientations is improved, but the light beam no longer remains perpendicular to the surface preventing interference
Solution Approach 1:
The retro-reflector serves as a mediator that ensures the light beam reflected from the tilted object is redirected back into the optical system at the correct angle. This guarantees that the beam returns to the beam splitter and can interfere with the reference beam, maintaining reliable interference patterns even when the object is tilted at large angles.
Solution Approach 2:
Instead of trying to keep the object perpendicular to the beam (conventional approach), the patent inverts the approach by using the retro-reflector to redirect the already-reflected beam back into the system. This inversion strategy allows the object to be tilted while still achieving reliable interference.
3Adaptability or versatility
If a further optical system with retro-reflectors and lenses is added, then measurement capability for tilted objects is improved, but device complexity increases
Solution Approach 1:
The retro-reflector is a relatively simple optical component that can be integrated into the existing interferometer without requiring complex mechanical structures or active control systems. This mediator approach adds minimal complexity while significantly improving the ability to measure tilted objects.
Solution Approach 2:
The retro-reflector performs multiple functions: it redirects the reflected beam back into the optical system, maintains beam alignment, and enables measurement of objects at various orientations. This multi-functionality reduces the need for additional specialized components, thereby limiting the increase in device complexity.
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 solution allows for precise measurement of object displacement with nanometer accuracy even when the object tilts significantly, enabling accurate interference and displacement determination by maintaining beam coincidence and path alignment.
Implementation Method 1
a beam splitter provided with a light splitting surface having a front side directed towards the light source and a rear side facing away of the light source, of which beam splitter the light splitting surface is at 45° with respect to the light beam emitted by the light source
Implementation Method 2
said further optical system is such that it returns an incoming sub light beam reflected from the light reflecting surface of the object to be measured in opposite direction and at the same place as it entered into the further optical system
Implementation Method 3
The basic idea is to return the light beam reflected on the object to be measured into itself (this is already done in known measuring devices) even when the object to be measured is tilted with respect to the light beam
Data Source
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Figure 5~6
AI summary
A measuring device of the interferometer type has an optical system 2, as well as a light source 1 and a sensor 3. The optical system has a beam splitter 4 and a reflector 9 which is under 45° with respect to light-splitting surface 5 of the beam splitter. The measuring object 21 is present in line with the beam of light emitted by the light source 6 and is located at the rear side of the beam splitter. The measuring device further comprises a further optical system 13, which is such that a reflected from the light reflecting surface 21A of the object to be measured, and in the further optical system incoming light beam in the same direction and at the same site as that in which it entered, is sent back. This may also be the case of relatively large skewness of the measurement object 21, the object of the measurement reflected light beam in itself will be sent back.