In photogrammetry, an approach of automatic detection and recognition on reference points have been proposed to meet the requirements on detection and matching of reference points. The reference points used here are the CCT(circular coded target), which compose of two parts: the round target point in central region and the circular encoding band in surrounding region. Firstly, the contours of image are extracted, after that noises and disturbances of the image are filtered out by means of a series of criteria, such as the area of the contours, the correlation coefficient between two regions of contours etc. Secondly, the cubic spline interpolation is adopted to process the central contour region of the CCT. The contours of the interpolated image are extracted again, then the least square ellipse fitting is performed to calculate the center coordinates of the CCT. Finally, the encoded value is obtained by the angle information from the circular encoding band of the CCT. From the experiment results, the location precision of the CCT can be achieved to sub-pixel level of the algorithm presented. Meanwhile the recognition accuracy is pretty high, even if the background of the image is complex and full of disturbances. In addition, the property of the algorithm is robust. Furthermore, the runtime of the algorithm is fast.
Aiming at these problems in real-time measurement about multiple targets in large scale, we propose a vision measuring method with CCD Rotation Ranging System (CRRS) to achieve the dynamic measurement with high-accuracy. CRRS is composed of mechanical rotating platform and Area scan CCD camera. The CCD camera is fixed on a mechanical rotating platform which is droved by motor. Firstly, we calibrate the CCD camera before the measurement. Secondly, the two CCD cameras is revolved and pitched by the rotating platform to measure a fixed field of the large area with high precision. The two CCD cameras composed of a Binocular stereo vision system to measure the local coordinates of the target. Thirdly, the poses of two CCD cameras are got from the rotating platform, so we can translate the local coordinates of target to the global coordinates. The experiment results show that, the measurement device can measure the targets precisely and efficiently, with non-contact the rotation CCD probe.
During the experimental process of the spatial point's position detection, we analyze the advantages
and disadvantages of the classical method, and propose an improved method. First, we interpolate the
point's data to increase the size of the image. Then use the Zernike moment to detect the edge of the
point. Finally, we obtain a coordinate of the center of the point by using the ellipse fitting algorithm,
and take this coordinate as the position of the spatial point. Experimental results in laboratory show
that, the proposed detection method on sub-pixel level is realized to detect the spatial point's position
with high-accuracy. And experimental results of relative measurement with 100 meters outdoor show
that, the repeatable accuracy of this method can reach 0.12 pixel during the day and 0.05 pixel at night.
The method of 3D reconstruction from multi-view of the object with single camera is proposed in this paper. The images
of the planar pattern from different views are captured by the single camera. The internal and external parameters of the
camera are calculated precisely with Two-stage camera calibration method. On this basis, the image points of calibration
pattern can be matched and reconstructed. Experimental results show that: the flatness of reconstructed planar pattern is
about 0.006mm; the position error of sign is about 0.012mm. The proposed method is high-accuracy, simple, flexible and
A new method of attitude measurement of the calibration target based on machine vision is proposed in this paper.
Firstly, the internal parameters and external parameters of the CCD camera are calibrated by using the feature points on
the calibration target. Secondly, shoot the calibration target in different positions and gather any different image
information. Finally, measure the calibration target's attitude through reconstructing the positions of those feature points
which on the calibration target. Experiment results show that the standard deviation of the attitude measurement errors is
less than 10 arc-second. This method is an effective high-precision space attitude measurement algorithm which can
meet the engineering requirements.
The focal plate is one of the most important components of the LAMOST, whose shape precision to be centripetal and
spherical structure of multi-hole. The hole drilling distortion duing to residual stress becomes one of the striking
problems. Studying on the distortion prediction, this paper adopts the finite element simulation based on the metal
cutting principles. The distribution to the surface residual stress is achieved by building the FEM model using
ANSYS .The influence of cutting depths on the distortion of the focal plate was investigated. With the confirmation of
the final CMM test result, the deviation which compared the measuring point with the theoretical sphere is less than
0.066mm. The result showed that the FEM analysis is an effective method which predicts the machining distortion of the
Camera calibration is the important step for the stereo vision measurement system. The accuracy of the calibration
affects the accuracy of the vision measurement system. The calibration is realized with a planar pattern. The pattern
has some spot array with high precision. Stereo vision measurement system captures the images of the calibration
pattern at several different orientations. The parameter model is modified as the polynomial model to describe the
lens distortion. The calibration experiment demonstrates that the error of 3-D reconstruction is 0.020mm.
This paper discusses an extension of image mosaics technology of the 2D coordinates measurement technique.
Fourier-Mellin Transform (FMT) is widely used as an image mosaics method. Based on analyses of frequency
spectrum, FMT automatically stitches images with relationships of translation, rotation, scaling. The course of FMT is
simulated and optimized, and the character of FMT for shifted images is educed. Furthermore, the particular rules for
polar coordinate transform of rotated and zoomed images are advanced, making noise depressed and the feasibility of
the algorithm greatly increased. Moreover, The proposed method that adopt filter technique aiming at finite discrete
images can eliminate efficiently the artifact in the Fourier-Mellin space, and obtain significant correlated peak values
and resist the influence of noise interference. Finally, making use of the separation pattern technology based on
difference calibrations to evaluate the precision of registration image. Experimental results demonstrate this method is
At present, the LAMOST project is in a crucial period. The machining progressing of LAMOST Focal Plane Plate has
completed. The inspection of the machining quality for the Focal Plane Plate in the machining process is a pivotal work.
In all of the design requirements, the most crucial standards of accuracy are the profile tolerance and the unit-holes
dimensional angle. Theirs precision will influence the observation efficiency of the LAMOST. But there are more than
4000 unit-holes on the 1.75m diameter Focal Plane Plate, it is impossible to measure all unit-holes and the whole area of
the Focal Plane Plate. How to measure the minimal unit-hole and get the most accurate results about the machining
process, judge whether the final machining Focal Plane Plate satisfy the design requirements. The measurement scheme
optimization is discussed in the paper. There are two different ways to measure the Focal Plane Plate, one is the
traditional way whish use specially designed implements for the every individual parameter, the other way used the
CMM to measure the pivotal design requirements such as unit-hole dimensional angle and the profile tolerance of the
Focal Plane Plate. The advantage of this is saving the time and cost on the CMM, improving the efficiency for the whole
measurement work, and acquires the direct vision results before measuring the Focal Plane Plate on CMM. Whereas the
implement which used in the measurement need to design and machine precisely for the credible measurement results.
And all the measuring work is calibrated by the CMM sampling detection. The sampling detection based on the
processing technology and some implements are mentioned in the paper.