Precise 2D optical measurements in back illumination

OPAS technology combines principles of measurement with the image processing to analyze and measure sizes and positions of planar 2-D shapes. Though originally designed for evaluation and adjustment of milling cutters, it can be used for measuring shapes of any nontransparent objects and it is ideal for upgrading manual back-light measurement projectors to automatic measurement.

OPAS hardware OPAS screenshot
Camera and illumination unit OPAS user interface

OPAS consists of a light source, custom optics, a camera, PCI digitizer, a Pentium based PC computer, and an image processing and shape analysis software running under MS Windows 95 or NT.

OPAS image processing
Image of a back illuminated part is processed and its shape is measured

An object illuminated by a telecentric back-light is projected to a digital camera where the image is captured. Discrete image is converted to a video-signal which is digitized in the computer by a PCI digitizer assuring exact line synchronization and minimal pixel jitter. The contour of the object is extracted from the digital image with the resolution about 0.2 pixels (i.e. 0.001 mm for the field of view 4.5 x 3.5 mm).

Measurements are done directly at each point of the contour or on the curves, e.g. lines and circular segments, automatically extracted from the image. Radii, distances from defined lines, and angles can be measured with high precision reaching 0.05 pixel (i.e. 0.0003 mm for 4.5 x 3.5 mm f.o.v.) if larger portions of the curves are seen.

Windows'95/NT GUI displays results overlaid on live images with the frequency more than from 15 frames per second (90MHz Pentium) for simple piecewise linear shapes and dropping to 10 frames for more complex parts containing both lines and circular segments. Client server architecture based on DDE standard allows to select from about 10 different measurement modes. OPAS technology can easily be adapted to the needs of each customer.

To get more information about OPAS technology, check our facts sheets page.