Variable Sensitivity Velocity Interferometer with Liquid Immersion
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Solution Overview
Problem
Conventional velocity interferometer systems for measuring high-speed projectiles have fixed sensitivity and time resolution, requiring additional hardware and alignment complexities to adjust, limiting their versatility and accuracy in dynamic compression research.
Innovation Solution
A velocity interferometer system with adjustable etalon length, utilizing optical cells with liquid immersion and piezoelectric actuators for precise control of optical reflective components, allowing continuous change in sensitivity and time resolution without additional hardware or alignment complexities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional velocity interferometer systems use fixed etalon length, then the system structure is simple, but the sensitivity and time resolution cannot be adjusted
Solution Approach 1:
The patent makes the etalon length adjustable by using motorized translation stages to move the etalon in and out of the optical path, transforming a static fixed-length etalon system into a dynamic variable-length system. This allows continuous adjustment of sensitivity and time resolution without requiring multiple discrete etalons or complex reconfiguration mechanisms.
Solution Approach 2:
The patent changes the physical parameter of etalon length to adjust the velocity measurement sensitivity and time resolution. By controlling the insertion depth of the etalon into the optical path, the system can vary the optical path difference, thereby changing the measurement parameters dynamically during operation.
2Adaptability or versatility
If multiple etalons are used to adjust sensitivity range, then the sensitivity range can be extended, but the hardware requirements and alignment complexity increase
Solution Approach 1:
The patent segments the etalon adjustment function into two independent parts: a motorized translation stage for coarse adjustment of etalon insertion depth, and a piezoelectric actuator for fine adjustment. This segmentation allows the system to achieve a wide sensitivity range through a single etalon rather than requiring multiple discrete etalons, thereby reducing hardware complexity while maintaining versatility.
Solution Approach 2:
Instead of using multiple fixed etalons with different lengths, the patent uses a single etalon whose effective length in the optical path can be dynamically adjusted. This dynamic approach replaces the need for switching between multiple hardware components, simplifying the overall system structure while providing the same functional range.
3Measurement precision
If displacement interferometer is used, then the velocity time history can be obtained through differentiation, but the Doppler shift is very large which constrains detector bandwidth
Solution Approach 1:
The patent introduces an etalon as an intermediary element in the optical path that creates a controlled time delay between the reference beam and the measurement beam. This intermediary mechanism transforms the measurement from direct Doppler shift detection (which requires high detector bandwidth) to interferometric phase detection, thereby relaxing the detector bandwidth requirements while maintaining measurement precision.
Solution Approach 2:
The patent replaces the direct Doppler shift measurement approach with an interferometric measurement approach using an etalon. This substitution changes the measurement principle from detecting frequency shifts directly (mechanical/electrical detection) to detecting optical path differences (optical interferometry), which has different bandwidth requirements and offers better precision for velocity time history measurement.
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 flexible and accurate velocity measurements with improved sensitivity and time resolution, reducing costs and complexity while maintaining high precision and versatility.
Implementation Method 1
piezoelectric actuators for precise control of optical reflective components
Implementation Method 2
optical cells with liquid immersion
Implementation Method 3
optical reflective components
Implementation Method 4
the light that undergoes a Doppler shift due to its reflection from a moving object/projectile
Data Source
AI summary
The present disclosure relates to a velocity interferometer. The interferometer described herein, comprises of two optical cells, one partially containing a liquid. The light entering the interferometer is amplitude split and made to propagate through the two cells in such a way that the apparent path lengths of the beams are equal, thereby fulfilling the condition necessary for obtaining single wide fringe in the interference pattern of the two beams. However, due to difference in the physical path traversed by the two beams, a finite delay time exists between them. The two beams, after reflection from end-mirrors or cube corner prisms in the two cells are recombined to form interference fringe patterns on active areas of multiple detectors. Doppler shifted light resulting from reflection of light from a moving projectile generate fringe shifts on the detector planes thereby producing voltage signals proportional to instantaneous velocity of fast moving projectile. The voltage signals are recorded with multi-channel digital oscilloscope and processed in a processor/controller of a computing unit to obtain velocity time history of the projectile. Controlled motion of the cube corner reflectors placed at the ends of two cells using stepper motors and piezoelectric actuators ensures that the time delay between the interfering beams is controlled accurately thereby changing the sensitivity range and time resolution of the velocity measurements.