The invention relates to a modulation amplitude closed-loop control system and method of a photoelastic modulator based on second harmonics. The modulation amplitude closed-loop control system comprises three parts including a laser intensity sterilization module, a detection optical module and a closed-loop control module, wherein the laser intensity sterilization module is composed of a laser device, a controllable phase delayer, a polarizer, a polarization beam splitter, a first photoelectric detector and a light intensity controller and is used for stabilizing main path laser to a pre-set value; the detection optical module is composed of a sample to be detected, a quarter-wave plate, the photoelastic modulator, a polarization analyzer and a second photoelectric detector and is used for realizing conversion of main path laser photoelectric signals; and the closed-loop control module is composed of a lock phase amplifier, a signal processor and a photoelastic modulator driving circuit and is used for demodulating second harmonic signal feedback to control the modulation amplitude of the photoelastic modulator. According to the modulation amplitude closed-loop control system and method of the photoelastic modulator based on the second harmonics, modulation amplitude fluctuation of the photoelastic modulator, caused by changes of environment factors, can be effectively inhibited, so that long-period stability of a detection system is improved.

Modulation amplitude closed-loop control system and method of photoelastic modulator based on second harmonics

An optical measuring device is used for measuring a sample to be measured. The optical measuring device comprises the following components: a flat surface light source module, a first polarizer, a second polarizer, a liquid crystal box and an image sensor. The flat surface light source module is used for providing a surface light source which is used for transmitting detecting light. The first polarizer is configured in a transmission path of the detecting light. The second polarizer is also configured in the transmission path of the detecting light. The first polarizer is configured between the surface light source and the second polarizer. A sample to be measured is suitable for being configured between the first polarizer and the second polarizer. The liquid crystal box is configured in the transmission path of the detecting light and is provided between the first polarizer and the second polarizer. The image sensor is configured in the transmission path of the detecting light for sensing the detecting light. The second polarizer is configured between the liquid crystal box and the image sensor.

Optical measuring device

The invention relates to a separation method of a dynamic stress and a static stress in a dynamic photoelasticity system. According to one embodiment, the method includes the following steps that: the photoelastic image of a dynamic stress and static stress superimposed stress field and the photoelastic image of a static stress field in a transparent solid are acquired; a measuring point for separating the dynamic stress in the photoelastic images is selected, and a superimposed stress image gray value and a static stress image gray value at the measuring point are read; an included angle of the principal stress of the dynamic stress and the principal stress of the static stress is obtained; and the dynamic stress is separated out at the measuring point based on the image gray values and included angle information. According to another embodiment, the photoelastic image of a dynamic stress field is acquired; a point for separating the static stress in the photoelastic images is selected; a dynamic stress image gray value is read; and the static stress at the selected point is separated out. According to the method provided by the embodiment of the invention, the gray values of the photoelastic images area are analyzed and processed, so that the static stress near a defect in the solid can be separated out, or the dynamic stress near the defect in the solid can be separated out. The method can be also applied to the separation of a small dynamic stress and a small static stress.

Separation method of dynamic stress and static stress in dynamic photoelasticity system

The invention belongs to the field of voltage measurement and relates to a photoelastic modulation and electro-optical modulation-combined voltage sensing device and a detection method According to the photoelastic modulation and electro-optical modulation-combined voltage sensing device and detection method, based on a photoelastic modulation technology, phase difference introduced by a voltageto be measured to an electro-optical crystal is detected rapidly with high sensitivity, real-time and fast voltage sensing is realized; a single-axis electro-optic crystal is adopted as an electro-optical sensing component with an optical axis adopted as a light transmitting direction, and the temperature stability of the voltage sensing device can be improved; signal processing is realized basedon a digital phase-locked amplification technology; signal acquisition and digital phase locking are both controlled by the same FPGA, and the input signals of the LC resonant high-voltage driving circuit of a photoelastic modulator are also provided by the FPGA, and therefore, reference signals and modulated fundamental frequency signals can share the same frequency and the same source, and the precision of the signal processing is improved According to the photoelastic modulation and electro-optical modulation-combined voltage sensing device and the detection method of the invention adopted, phase-locked data processing is completed through a computer, and the voltage to be measured can be finally solved, and the voltage is stored and displayed The voltage sensing device of the invention has high measurement sensitivity and precision, has no moving parts, is low in cost, and is beneficial to industrial automation integration

Photoelastic modulation and electro-optical modulation-combined voltage sensing device and detection method

The invention makes use of a non-homogeneous light source to realise two wavelength measurement. An electrooptic modulator compensates stress-optic retardation on a measured model by using controlled electrooptic retardation.A pair of optical-rotatory devices (e.g. Faraday cells) set out of both sides of the test model so that they could rotate relatively to the linearly polarized orthogonal light field by using controlled rotative angle, and a microcomputer controlling automatically, the measuring procedure and process of experimental data. The measurement to photo-elastic stress analysis is thus improved on level of automation, experimental accuracy and period involved.

朱美栋

Papers

Automatic measuring method and apparatus