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To acquire the instantaneous velocity outside the chamber of a high-speed bullet and its velocity distribution at different positions,this paper proposed a velocity measurement system with expanded beams based on the laser Doppler effect.The system expanded the exiting laser beam for two times and then made the two coherent beams intersect in the space to form a new probe volume with two dimensional broadening lengths.The system efficiently overcame the object deviation from the measurement region caused by the smaller probe volume in the traditional Laser Doppler Velocimiter(LDV).Therefore,it could measure the velocity of high-speed bullet that traditional LDV could not implement because of the trajectory deviation.Moreover,the system could also monitor the velocity distribution of the high-speed bullet at different positions in the trajectory by a parallel mode.Experiments for expanding different lasers were performed in different illuminating lights,and the Doppler signals were obtained from the photo-detector finally.The analysis results show that the average error of the measured velocities at 10-25 m/s can reach 1%-2%,which indicate that the proposed method is effective and feasible.

On the basis of the Michelson interferometer,a phase interference measurement system with one single arm as the measurement output port was designed to measure and analyze the thickness uniformity of a glass plate.In the system,a CCD camera was used to collect the interference pattern and the Fourier transform fringe analysis and phase unwrapping techniques were used to extracted the phase information contained in the interference pattern.For the problem that the sidelobe center of Fourier transform spectrum could not be accurately located,an applicable triangular transformation method was proposed to extract the volume of phase change directly.With this approach,the phase results could be obtained more accurately without knowing the central location of the spectral sidelobe,meanwhile,the errors induced by man-made estimation and the small carrier frequency component in vertical axis were eliminated.The thickness uniformity of a group of glass plates was measured in both of the length and width directions.The experimental results show that the theoretical accuracy is 0.93% and 0.92% in two directions,respectively,when they measured by a CCD camera with a unit size of 4.65 μm×4.65 μm.The system can measure the thickness uniformity of the glass plates,and has lower demands for the location accuracy of frequency spectral sidelobe and the direction precision of carrier frequency.

To measure the dynamic deformation and slope of an object surface,this paper proposed a shearing speckle interferometry with a spatial carrier frequency generated by double-apertures.In this method,a double-aperture mask was used to generate a spatial carrier,a rotating wedge pair was utilized to adjust the shear continuously and the sinusoidal-fitting algorithm was taken to calculate the phase distribution.This paper firstly derivated the relationship between the carrier phase and the separation of double apertures and also imaging distance.Then,the experimental condition to generate adjustable lateral shear was discussed based on the ratable wedge pair.Finally,the parameter of this measuring method was analyzed.To produce a π/2 carrier frequency,it suggested that the separation of double aperture was selected as 3.8 mm when the focus length of the imaging lens and object distance were 300 mm and 80 mm,respectively.A stress release plate after centre loading was measured,and the experimental results demonstrate that this measuring system can obtain the information of deformation in real time under the capturing rate of 15 frame/s and the measurable range of displacement peak value is from 0.11 to 1.15 μm.This approach yields simple and compact optical implementation and allows a real time detection for dynamic deformation.

Dynamic speckle correlation method was presented to measure the piezoelectric ceramic characteristic curves and scale linear intervals in this paper.Firstly,the speckle intensity cross-correlation of a projection phase diffuser in the micro-system was calculated,and influences of the resolution and magnification of the micro-system on object displacement measuring were also discussed.During the calculation of cross-correlation,a progressive correlation method was used to avoid the de-correlation caused by the object surface.A sampling system for micro speckles was designed and the hysteresis curve of displacement induced by a piezoelectric ceramic was measured.Experimental results indicate that the theory precision of the measuring system is 0.082 μm when a micro objective is with magnification of 100 and NA of 1.25.In consideration of the diffraction limit,the theory precision of the measuring system is 0.348 μm.It concludes that the method satisfies the requirements of measuring and scaling of linear intervals.Comparing with other methods,the dynamic speckle correlation can improve the calculation speed and measuring precision.