This article designed an embedded smart camera based on the ZYNQ-7000 development board, which has an ARM+FPGA architecture. The system functions are divided into three parts: image acquisit ion, image processing and image display, each of them adopting a modular design. The image acquisition part adopts OV7725 camera. The image processing section uses the VIVADO HLS development kit to design hardware IP-based image processing algorithms. Compared with the traditional HDL-based IP core design method, HLS method that use C/C++ to design IP reduces the development difficulty and shortens the development cycle. Hardware IP implemented through HLS includes image preprocessing, spot-based centroid positioning algorithm, edge detection and corner detection. For complex image processing algorithms, it is still used software to implement, while preprocessing are accomplished through hardware IP. The VDMA channel realizes high-speed data interaction between hardware and software. The image display part is based on the embedded Linux system, OpenCV, and cross -platform C++ graphical user interface development framework QT to implement the GUI interface. The entire embedded smart camera system finally achieves accelerat ion processing based on hardware IP, such as spot location, sobel edge detection, and corner detection.
Autocollimators are mainly based on computers or the electronic devices that can be connected to the internet, and its precision, measurement range and resolution are all defective, and external displays are needed to display images in real time. What's more, there is no real-time calibration for autocollimator in the market. In this paper, we propose a biaxial autocollimator based on the ZYNQ embedded platform to solve the above problems. Firstly, the traditional optical system is improved and a light path is added for real-time calibration. Then, in order to improve measurement speed, the embedded platform based on ZYNQ that combines Linux operating system with autocollimator is designed. In this part, image acquisition, image processing, image display and the man-machine interaction interface based on Qt are achieved. Finally, the system realizes two-dimensional small angle measurement. Experimental results showed that the proposed method can improve the angle measurement accuracy. The standard deviation of the close distance (1.5m) is 0.15" in horizontal direction of image and 0.24"in vertical direction, the repeatability of measurement of the long distance (10m) is improved by 0.12 in horizontal direction of image and 0.3 in vertical direction.
Interferometry is one of the most suitable method for microsphere profile inspection, and the eccentricity errors during measurement is always allowed to exit and corrected by Zernike polynomials fitting method for better dynamic response ability and higher efficiency. The common usage of coordinates on CCD instead of these on wave-front in fitting process may lead to factors errors when effective aperture is bigger than 0.25. In order to correct the eccentricity errors during microsphere interferometry precisely, the impact of normalized polar radius approximating on Zernike polynomials fitting is analyzed. An accurate correction method based on coordinates transformation is proposed, and the calibration method of NA is also given, which will be necessary in the transformation. The experiment results indicate that the PV and RMS value of corrected profile data are 0.1628λ and 0.0326λ separately, and is much more similar to the standard data where the microsphere is placed at the zero-fringe position with the PV and RMS value of 0.1636λ and 0.0332λ separately. So, it can be seen that the correction method is feasible and effective.
In order to get the precise whole surface feature of micro-ball efficiently without missing points, a laser interfering measurement system and method is developed. Based on the principle of phase-shifting diffraction interference with short- coherence light source, a wave-separation interfering light path is designed, which contains single mode fiber for filtration and pin-hole reflector for diffraction. An accessory system is also projected to complete the whole micro-ball surface scanning, including negative pressure adsorption stage-group with five degree of freedom moving for micro-ball support, overturning stages, and vision monitoring mechanism. A technological process for whole surface measurement is also given. The experiment result shows that, in the case of testing light focusing on the centre of sphere, surface topographic characteristics of micro-ball can be shown clearly and directly by the distribution of interference pattern.
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