Research On High-Precision Distance Measurement Technique Of Laser Triangle Method With Sine-wave Light Intensity Modulation

As an important non-contact distance-measuring technology, the laser trianglemethod is widely applied in industrial controlling production and automationproduction. This paper is based on traditional non-contact optical triangle method asmeasuring theory, and the PSD is exploited as photoelectric converter. After specifiedcircuit processing, high precision distance-measuring of sine-wave light intensitymodulation is realized. The innovation in this paper are: the scheme of high stable sine-wave light intensitymodulation is worked out;the error compensation module based on circuit is set upand non-linear error of principle is corrected;the circuit noise module andtemperature drift is built and low noise optimization is performed. At last, theprototype has been developed. After the comparison experiment vs two-frequencylaser interferometer, the endpoint connection and transition fitting simulation isperformed base on the data before and after non-linear error correction and theexpected result is achieved. The experiment results indicated the resolution is lessthan 1um in ±10mm scaling range of the instrument, and nonlinearity, about 1.4‰, isimproved in one order after error correction. The feasibility of selected scheme isproved. The main work in this paper contains several aspects as described as follows: 1. Based on light intensity following theory, the laser is modulated by highprecision laser to develop high stable sine-wave light intensity modulationsemiconductor laser light source. In this way, the environmental interference factorsuch as background light and temperature drift is effectively depressed. The attainedlaser source is of stable light intensity, single frequency and small harmonic distortion.Compared with square-wave modulation method, this one is of concentrating usableenergy, easy to demodulate, and high signal-to-noise ratio can be achieved. 2. According to two channel output of PSD and the characteristic of AD534,mathematical compensation module is set up against nonlinearity error in principle.Then a nonlinear error correction technique based on hardware circuit is developed toget real-time character and higher controlling accuracy. 3. The circuit noise module and temperature drift module are setup up based onoperational amplifier actual module and resistance noise module, thus the low noiseoptimization is performed, the system noise is depressed, and the resolution isimproved.4. The mathematical modules of circuits are set up by part. After carefullycomputing parameters, selecting serialization values, and translation functionsimulation in Matlab, the precision and reliability are ensured.5. The mathematical module of optical design is built, the optics parameters areoptimally designed according to scaling range and accuracy requirement, the effectfrom receiving light intensity and imaging facula on system measuring error isanalyzed.6. According to EMC technology and diversity of signal and power consumption incircuit modules, the anti-interference design is performed in schematic design, PCBdrawing and module layout. As a result, the low-frequency noise is depressed in deepdegree.