Research Of The Photoelectric Detection Technology For Inner Diameter Of Deep Hole

The system of photoelectric detection for inner diameter of deep hole based on reflective intensity modulated fiber optic sensor is presented in this paper, which is involved in fiber optic sensing technology, weak signal detecting technology and digtal signal processing technology, etc. This system can accomplish the aperture measurement of small deep blind hole, which has the advantages of simplicity, strong anti-interference ability, wide measurement range and online continuously detecting ability, etc. In theory, the measurement range is 1mm and the precision can reach 10μm.The main research work of this paper would be introduced as below.Firstly, the intensity modulated mathematical function of optic fiber pair based on qusi-Gaussian beam model of light emitted from the multimode transmitting fiber is established. Then, the numerical simulation is fulfilled, along with a series of rules of the influence on intensity modulation property caused by fiber parameters and the curvature radius of the reflectors, which will provide theoretical fundamentals for designing this type of optical fiber sensors in practical application.Secondly, on the basis of the established intensity modulated function of optic fiber pair, the intensity modulated function of several common fiber bundles is established and simulated as well. Through the analysis of simulation curves of intensity modulated characteristics, the coaxial random-type fiber bundles with the structure of light intensity compensation is selected, which is used to eliminate the influence arising from lamp-house's wave, photoelectric cell's excursion, the to-be-measured surface's glisten coefficient, etc.Again, suitable light source and photoelectric conversion device are selected. The weak signal processing circuit composed of several functional modules, such as preamplification, band-pass filter, phase sensitive detection, low pass filter etc is designed, which accomplished the task of amplification and extraction of analog signals. The two processed signals are inputted to ADuC812 and then processed through software approach, including functions of signal division, linearization and compensation etc.Finally, kinds of error factors which have effects on the accuracy of this detection system are analyzed systematically, and several methods are introduced to realize high accuracy measurement.