Optical lock-in vibration detecting using photorefractive four-wave mixing
Many important applications for photorefractive crystals (PRCs) have been found recently by various investigators. These applications range from volumetric information storage in optical computing to adaptive, remote detection of ultrasonic vibration in optical nondestructive evaluation. In this paper, we propose the use of PRCs for lock-in detection of continuously vibrating structures. A method for achieving lock-in detection using the photorefractive effect was presented by Khoury et al of Rome Laboratory in 1991. They described a technique for the purpose of extracting a small signal phase modulation embedded in a large noise environment. This was carried out by mixing two optical beams, a signal and a reference, with different phase modulation in a photorefractive medium. They presented a first-step analytical model that described the temporal behavior of a photorefractive lock-in device, along with experimental verification of this behavior. The effects of varying different mixing parameters were described qualitatively. Here, we explore the optical lock-in technique for application in vibration detection and, in particular, its potential for narrowband vibration mode spectral analysis. In addition, we have performed a shot-noise limited signal-to-noise ratio analysis of this device to determine its minimum detectable displacement sensitivity, and simulated the lock-in spectrum analysis method.
- Research Organization:
- EG and G Idaho, Inc., Idaho Falls, ID (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC07-94ID13223
- OSTI ID:
- 135049
- Report Number(s):
- INEL--95/00069; CONF-950785--5; ON: DE96002511
- Country of Publication:
- United States
- Language:
- English
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