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.
The traditional Canny algorithm has the problem of edge loss in the process of smoothing the image and needs to set up the high and low threshold, an improved adaptive edge detection algorithm based on Canny is proposed in this paper. Firstly, the improved anisotropic diffusion filter is used to smooth the image, and the edge is protected when de-noising. Then, 4 gradient templates in horizontal direction, vertical direction, 45° direction, and 135° direction are used to calculate gradient amplitude. Finally, the threshold is adaptively determined according to the gray histogram of image. Experimental results indicate that the proposed algorithm has better anti-noise performance while detecting more edge details.
Solder ball detection in full-field ball grid array (BGA) images has a broad range of applications, such as height extraction of solder ball, inspection of substrate coplanarity, and defective detection. Existing methods usually have poor performance due to the diversity of defects, image noise, and the disturbances of background. In this paper, we propose a coarse-to-fine process for solder ball detection by combing the strength of the threshold method and the active contour method. In the coarse process, the solder ball is roughly segmented by a simple threshold method. In the fine process, the region information and shape prior are integrated into the energy function of the active contour method to better segment the solder ball. The initial shape used in the fine process can be given by the simple threshold method in the coarse process. Experiments on full-field BGA images demonstrate the robustness and accuracy of our method.
In recent years, with the increasing demand of intelligent transportation system for large-scale field monitoring, it is a pretty much necessity for the continuous zoom system with large scale ratio and large field angle. Therefore, based on the characteristic of its optical system with 30 times variable ratio and large field angle, the mechanical structure of continuous zoom lens has been designed in detail, and finally two kinds of cam mechanism are described in this paper in order to realize the zoom and focusing process. Furthermore, in order to meet the work environment requirements of video monitoring system for the zoom system, the static simulation and thermal deformation simulation of the key component zoom cam has been analyzed in this paper. The static analysis results show that the deformation of the force of the zoom cam is 0.0015 mm, which can be ignored. Thermal deformation analysis results show that the zoom cam at - 15 °C to 50 °C under the temperature load of maximum deformation is 0.007 mm, which has meet the requirements of the system of working temperature, and all of the above results have verified the rationality of the design of zoom cam mechanism. On the basis of the selective zoom mechanism, a reasonable focusing mechanism is carried out to ensure the focus stability of the focusing mechanism, which can provide the stability of the whole continuous zoom lens system.
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