Keywords: 3-d image measurement, active vision, automatic, projection pattern, controlMost of the recent 3-D image measurement methods have employed certain pattern projection techniques because of their higher reliabilities. Especially, the intensity-modulated technique can detect more stripe addresses by a single projection and therefore is very much expected for its practical use in near future. The traditional techniques of this type, however, have encountered several serious problems where 3-D measurements are difficult in sensitivity, speed and accuracy or fatally impossible for unknown objects.In order to solve the this problems, we propose an automatic control technique of angle and space frequency of projection pattern. Furthermore, for secure of measurement accuracy and measurement speed, projection pattern intensity control technique and optimal intensity-modulation projection technique are adopted in the proposal measurement system. By using proposed technique the automatic 3-D measurement intended for the geostationary objects and the swaying objects were realized in experimental results. Fig. 1 shows the outline of measurement algorithm. Firstly, the initial observation pattern image and the observed mark slit pattern image are captured. The maximum projection angle αmax, the minimum projection angle αmin and the gap between stripes γ of projection pattern are adjusted as follows,where b is a base distance between the camera and projector, Ytop, Y down are calculated maximum and minimum imagination perpendicularly axis, respectively, Ztop, Z down are calculated imagination depth axis of Ytop, Y down , respectively, using the observed mark slit image. γmin is limited stripes gap by space resolution of the projector and the camera. And the intensity of projection pattern is adjusted based on intensity analysis of initial observation pattern image. So, the ideal observation pattern image for 3-D world coordinate calculation can be obtained. Fig. 2 shows the experiment results of 3-D measurement of a swaying head, in the experiment, of a PC (CPU: Athlon TM 64 2G-HZ, 1GB-RAM), 3-LCD projector (1024 × 768 pixels, 8bit 2500lm), and a Dijital camera (1024 × 768 pixels, 8bit, Firewire) are used. Fig. 2 (a) shows the initial observation pattern image, (b) shows the mark slit pattern, (c) shows the observed mark slit pattern image, (d) shows the adjusted projection pattern image based on projection pattern control technique, (e) shows the observation pattern image the object covered ratio is 92%, (f) shows the 3-D representation based on calculated 3-D codenates the detection accuracy of stripes address is 100%. Since the proposed technique can realize the 3-D measurement automatical also to a unknown object, it is considered to be practical technique.
SUMMARYMost of the recent 3D image measurement methods have employed certain pattern projection techniques because of their higher reliabilities. Especially, the intensitymodulated technique can detect more stripe addresses by a single projection and therefore is very much expected for its practical use in the near future. The traditional techniques of this type, however, have encountered several serious problems where 3D measurements are difficult in sensitivity, speed and accuracy or fatally impossible for unknown objects. In order to solve these problems, we propose an automatic control technique of angle and space frequency of projection pattern. Furthermore, for security of measurement accuracy and measurement speed, projection pattern intensity control technique and optimal intensity-modulation projection technique are adopted in the proposal measurement system. By using the proposed technique the automatic 3D measurement intended for the geostationary objects and the swaying objects were realized in experimental results.
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