Research On The Absolute Distance Measurement Technology Based On Current Tuning Semiconductor Lasers

The frequency modulated continuous wave(FMCW) laser absolute distance measurement technology has advantages of non-contact, non-rails, no cooperative targets, no manual intervention and so on. And the tschnology which has become an important way of getting 3d information about jumbo size objects has characteristics of high precision of measurement, wide measuring range and high automation level. Current tuning semiconductor lasers have gradually been perfect light sources of FMCW laser absolute distance measurement, because of their advantages of small packaging size, flexible using, high tuning speed and low costs. The paper studies the FMCW laser absolute distance measurement sysem based on a current tuning semiconductor lasers. It builds the system of optic-electronical phase locked loop(OEPLL) in order to correct the FM nonlinearity of current tuning semiconductor lasers, and builds an experimental system of FMCW laser absolute distance measurement based on tne non-linear correction semiconductor laser, which improves the precision and repeatability of measurement.Firstly, it studies theories of FMCW laser absolute distance measurement and elimination of the influence of vibration using the frequency sweep mode of symmetrical triangular FMCW(STFMCW). It analyzes FM nonlinearity influences on ranging. Secondly, it studies methods of correcting the FM nonlinearity, including iterative algorithm precorrection and closed-loop correction based on OEPLL. It analyzes the structure and mathematical model of OEPLL in detail, whose key parameters and influnces on ranging are mainly studied. It introduces an iterative algorithm precorrection based on the secant method, and gives its mathematical model and algorithm flow. Then, it introduces the concrete scheme of OEPLL and measuring methods of each module parameters of OEPLL in detail. The mathematical model of design process is given. The paper introduces the design method of OEPLL and simulates parameter calculation results. A DDS standard source is designed in order to provide OEPLL with stable and accurate reference signal. Lastly, the DDS standard source is tested and evaluated. The experiments verify nonlinearity correction effects of the iterative algorithm precorrection. The circuit of OEPLL is created and debugged. For purposes of reducing OEPLL’s initial phase errors, a new precorrection method called locked-on sampling precorrection is put forward. The paper ultimately realizes stable and accurate closed loop locking by combining the iterative algorithm precorrection, locked-on sampling precorrection and the closed-loop correction based on OEPLL, which leads to the linear frequency modulation of semiconductor lasers. The paper tests and evaluates the locking effect and realizes the frequency pulling and arbitrary chirps. An FMCW ranging experiment is carried out using the locked-on laser. The paper introduces the method of standardization and proves that the ranging system has higher measurement accuracy and nice repeatability though comparing with the dual-frequency laser interferometer. The paper also measures the vibration object, which proves vibration eliminationinhibiting ability of STFMCW. Combining the mathematical model built before, the paper analyzes sources of noises in ranging measurement system.