Angle measurement is widely used in various fields as an important part of geometric metrology. Optical angle measurement methods stands out from many angle measurement methods because of its high measurement accuracy. Due to the limitation of grating line density, it is difficult to further improve the measurement accuracy of grating angle measurement method which was widely used in industrial field. The creatively new angle measurement method combined the regular pyramid with the right-angle reflector is proposed in this paper. The rotation angle of the measured object is transformed into a rotating laser through the regular pyramid, the variation of the rotating laser is geometrically amplified through the right angle mirror to realize the amplification of the variation of the angle and laser displacement is measured by position sensitive detector (PSD). The measured angle is divided into several equal parts by the pyramid, which reduces the angle measurement range of each PSD. Through the alternating measurement of several PSDs, the large range of continuous angle measurement can be achieved. The measurement principle of angle sensor based on optical arm amplification is researched in this paper, the mathematical model is established, and the correctness of the principle is verified through simulation analysis and actual measurement experiment by the prototype of angle sensor. The experimental results showed that the measurement error is ± 2 “in the range of 0.78°.
In order to realize precise displacement measurement with low cost, a precise displacement sensor composed of right-angle reflectors is proposed in this paper. The sensor was designed as a reading head composed of a laser source and a position sensitive detector. The geometric optical amplification principle is proposed in this paper, when the relative displacement of the laser relative to the right angle mirror occurs, the relative displacement of the outgoing laser reflected by the right angle mirror will be multiplied. The displacement sensor with even magnification effect can be constructed only by the optical characteristics of right-angle mirror. The displacement measurement principle based on geometric optical amplification proposed in this paper, and the sensor prototype with double amplification is constructed, and relevant experiments are carried out. The experimental results showed that the sensor could achieve twofold amplification, the displacement measurement accuracy was ±500 nm, and measurement resolution was better than 100 nm. High-precision displacement measurement and a wide range can be achieved by using multiple reading heads. The measurement system does not require high precision of optical devices, so it is especially suitable for constructing a displacement measurement system with small range and high precision, through the multiple amplification structure, more than 10 times geometric optical amplification can be realized.
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