In order to realize laser additive manufacturing and damage repair of complex parts with different sizes, an adjustable variable spot size laser cladding optical system is proposed. The system is an off-axis three-mirror optical system, which is composed of three aspherical reflectors. It can adjust the spot size by moving an asperical mirror with an step motor. It can eliminatesolves the problem of light energy loss fixed spot size of traditional refractive optical systems. The proposed solution is high efficient in complex parts clading process and cost effective. and lift the application limitation of high-power lasers in laser cladding. In this paper, the physical model of off-axis three-mirror optical system is established by means of Zemax software. A 4000 W fiber laser in non-sequence mode was used to simulate the intensity distribution of the spot cross-section. By defocusing, the spot diameter at the working face can change continuously from 6mm to 12mm.
In recent years, machine vision technology are widely used in the industrial production process. In this paper, We studied two straight line extraction methods. Traditional method generally use the canny algorithm and sub-pixel edge detecting algorithm to detect sub-pixel edge of the image, and then use least-squares method to fit the geometric information of the edge of the image and fulfil measurement. It was found that the image collected in the actual measurement environment is often affected by the environment and produces one or other interference information, such as dust and hair interference, which affects the extraction of image edges and the accuracy of the measurement, resulting in measurement failure. We search the sub-pixel precision edge by the caliper tool method, and then use the method of RANSAC to fit straight line and get the corresponding geometric information. Finally, the distance information of the two straight line sub-pixel edges is obtained by distance calculation, and compared with the traditional method. Through the comparison of experimental data, the caliper tool method has significantly improved the measurement accuracy and robustness of the system, and achieved a better result.
With the rapid development of computer technology, image measurement technology has been widely used because of its non-contact, high precision and other advantages. In recent years, potable consumer devices like mobile phone, VR/AR device, tablet computer etc. become more and more popular. The number of high precision small workpieces has increased exponentially. There is an urgent need for the high accuracy and high speed measurement approach for the quality control of the small workpieces. Due to the contradiction between accuracy and field of view, the existing image measuring instruments are not sufficient, and it is difficult to meet the needs of high precision and high efficiency measurement. In this paper, several aspects of high-precision image measurement system are explored, including hardware system construction, double side telecentric lens design, high-precision template matching technology, system calibration, sub-pixel feature extraction and image segmentation algorithm. According to the actual demand, a high precision detection system is integrated, a high-precision image rapid measurement system for small workpieces (size < 70mm) is designed and developed. The accuracy of 2um and speed of 7000UPH are obtained which can meet the industrial requirements.
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.
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.
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.
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.
This paper proposes a multi-attribute automatic optimization method for lens system design. The method is based on the exploitation of the multi-attribute property of lens systems. Quality attribute and sensitivity attribute of lens system are our main concerns in the proposed method. The quality attribute is considered to characterize the optical performance and the physical constraints of lens system. The sensitivity attribute is perceived as the description of feasibility and practicality in lens manufacturing. Modified coordinate-wise algorithm is employed to perform the optimization of imaging performance as well as specific constraints. The sensitivity attribute is processed to incorporate manufacturing sensitivity into the metrics to evaluate the system more comprehensively by means of minimizing incident and refracted ray angles on optical surfaces. As a result, compromise solutions between quality attribute and sensitivity attribute are obtained. Experiments on two typical lens designs demonstrate the effectiveness of the proposed method.