Chromatic confocal point sensors are used to measure the high-precision surface distance, and it's based on the theory of chromatic dispersion and encodes the distance between the measure surface and chromatic lens. By accurately measuring the wavelength value, it indirectly calculates the distance to object surface. The accuracy of the sensor depends on the chromatic range of the lens and the resolution of the spectrograph. It is difficult to design wide measuring range chromatic lens that meanwhile satisfies the high-precision requirement. This paper proposes an optimization method to design high-precision chromatic lens for chromatic confocal point sensors. Firstly, we theoretically study the relationship of the pin-hole diameter and the sensors' performance denoted with the resolution and signal-to-noise ratio(SNR). Then, using the optimization objective FWHM(Full Width at Half Maximum), we build the mathematical model about N.A.(Numerical Aperture), PD(Pupil Diameter) and Δf. Finally, based on the optimization method, we design chromatic lens with Zemax Software, the performance gets the accuracy 2μm in the measure range 1mm.
Pipe thread plays an important role in modern industry. Traditional methods of pipe thread detection is inefficient and inexact which cannot fulfill the detection needs of modern production.Based on the actual industrial detection requirements, CCD is applied to detect outline dimension of the pipe thread and digital image processing techniques is applied to the image processing of pipe thread in this paper. According to the characteristics of the pipe thread, The filtering and edge detection algorithms in traditional image processing are optimized to realize the accurate image edge contour extraction. By calculating, the geometrical parameters of the pipe thread is obtained, the experimental results show that the improved method can improve the measurement accuracy compared with the traditional method.
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