In order to realize online, real-time, fast and automatic multiparameter measurement of complex part, the principle on encoded sequence is introduced. The sequence has an important property, named window property. The length of the window is quite small relative to the sequence. When the window slides over the whole sequence, the subsequences in the window can be seen exactly once and they may not be same entirely. So, the index of the subsequence in the whole sequence can be identified uniquely. Then, a vision inspection system based on color encoded multistripe structured light is presented. The system consists of a color encoded projector and a camera. Many structured light planes are projected into three-dimensional space. Every light plane has a kind of color and there are total four kinds of color. The combination of the color is expressed as encoded sequence. Corresponding color stripes are produced in camera when these color light planes intersect with the surface of object. Only the color of a stripe and its neighboring is needed to identify its index in the planes' group. Especially, in the case that not all the light planes are imaged in camera, the window property of encoded sequence is very important to find out the index of stripes. Furthermore, all the structured light planes can be treated as spatial planes in reference coordinate system of camera. It is well known that there exists unique correspondence between each light plane and the image plane. They can be determined uniquely by a 3/spl times/1 orientation vector and a selected spatial reference point. Afterwards, a novel method to calibrate the vision system is described. In virtue of coplanarity constraint, points on every light plane are coplanar with selected spatial points respectively. So, it is easy to set up the mathematical model on multiparameter measurement. At last, experiment is carried out to verify the validity. It shows that precise fixture is not necessary while this inspection system is working and only a single image is needed to realize multiparameter measurement.

Additional excerpts

Object recognition using a laser scanner and Fourier transform

Multi-parameter measurement of complex part based on color encoded structured light

A measurement system for moving objects using a multiple-slit projection method with random dots is introduced. In measuring moving objects, proper detection of moving objects from a single image is required considering the unique image of the slits with random dots pattern. A robust technique to extract a moving object from an image is introduced in the present paper to reduce the inappropriate influence of random dots. Generally, the cumbersome calibration required must be performed manually using a scale. Therefore, in the present paper, a semi-automatic calibration method is introduced. Using this technique, the calibration process is greatly simplified without reducing the accuracy.

3D measurement of a moving target using multiple slits with a random-dot pattern

Determination of the three-dimensional shape of objects for their recognition is an important problem. One important tool for object identification is vision. As a complement to vision laser scanner technique can be used. Differently shaped objects scatter the laser light differently. The scattered light is detected and converted to an analog voltage signal. To characterize the signals and to be able to classify the objects out of the signal we use Fourier transformation. The Fourier transformation gives a few parameters that can be used for classification. If we want to use the whole spectra for classification the statistical principal component analysis gives a good result. This method is a rather simple and inexpensive way to complement conventional object recognition systems, e.g. in robotics applications.

Object recognition using a laser scanner and Fourier transform

Citations

Multi-parameter measurement of complex part based on color encoded structured light

3D measurement of a moving target using multiple slits with a random-dot pattern

Object recognition for robot work piece identification by the use of a laser scanner combined with Fourier transform

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