The refractive index is an intrinsic optical property of seawater and it is one of the essential parameters in ocean observation. The traditional method of detecting the refractive index of seawater is calculated by measuring the temperature, conductivity, and pressure of seawater using CTD (Conductivity-Temperature-Depth) device. However, CTD can only detect the conductive ions in seawater, but not the non-electrolytic solutes in seawater, which leads to errors in salinity detection, and the accuracy of current seawater refractive index detection methods cannot meet the requirements. In this paper, based on the requirements of seawater refractive index measurement, the Zemax optical simulation analysis of the seawater refractive index measurement system was carried out. The influence of the angle between the two pass lenses in the detection area, the focal length of the focusing lens, and the size of the photo sensitive surface of the detector on the measurement system are analyzed. When the angle between the two pass lenses is 30°, the focal length of the focusing lens is 300 mm and the size of the photosensitive surface of the detector is determined to 4×4 mm2, the optimal refractive index measurement sensitivity of the optical system is obtained. it is calculated that when the detector accuracy is 1μm, the refractive index detection sensitivity of the optical system is 10-6 RIU.
Laser Doppler technology is widely used in precision vibration measurement such as voice acquisition. The fundamental of voice acquisition is to detect the vibration of targets induced by sound wave using a Laser Doppler voice acquisition system, and then demodulate the voice signal from interference signal. Therefore the target’s vibration characteristics will be the principal factor influencing the effect of voice acquisition. In this paper, we focus on the plane structure’s vibration characteristics caused by voice. There are mainly two parts in this paper, simulation and experimental verify. In simulation, the finite element method is used. The Finite Element Analysis method is widely used in material properties analysis, dynamic analysis, and acoustic analysis. Through finite element analysis method, the plane structure models of thick smooth aluminum are established by ANSYS. Then the frequency responses of different constraints are compared. The Laser Doppler voice acquisition system is applied to test and verify the simulation results. The response characteristics of aluminum board under different excitation frequency are measured. The experimental results and simulation results are compared to verify the correctness and reasonableness of simulation. At the same time, this provides theoretical guidance for Laser Doppler voice acquisition system to choose targets and improve voice acquisition performance.
A novel acoustical-vibration signal detection system based on laser Doppler is proposed. The system is based on the
M - Z interferometer optical system, and used more adaptive piezoelectric ceramics modulation and demodulation
system to restore signal. The whole system satisfies the requirements of non-contact, remote, high sensitivity and
anti-interference. It has the advantages of strong stability, compact light path, low cost and easy miniaturization
compared with heterodyne interferometer based on Acoustical Optical Modulator (AOM). At last the influence of the
laser power fluctuations (frequency instability and amplitude instability) on the system is analyzed theoretically.
Through the studying on the M-Z interferometer optical system, the authors give a strict contrast analysis of
influence on the steadiness of optical system about optical power, polarization state of laser and optical feedback caused
by different types of beam splitters was made. After adjusting and optimizing the optical system, the authors built a high
a precision vibration measurement of optical system. The system is advantage at the nano-level vibration measurement,
low energy loss and far measuring distance.
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