The industrial parts' dimensions are the important characteristics for their eligibility evaluation; typically, the multiple
cameras system is the preferred technology that fitting the inspection, especially for on-line testing, but the cameras
calibration, images matching, etc. are necessary when put in practice, also, multiple cameras system is either too costly
or impractical sometimes. A novel dimensions inspection technology based on single-image for planar industrial parts is
presented. The technology described here uses single-image taken by a camera in arbitrary pose, and requires four
scale-bars with known distances sticking on the planar industrial part, the four known distances are used to correct the
single-image to normal, and the part's dimensions are obtained by triangulation comparability from the normal image.
The utilities of this method are its low-cost, simplicity, ease of implementation and camera calibration needless. The
technology is being used in the real-time inspection of precision machining for the evaporator tubes plate of nuclear
boiler, applications show that the method is effective, and the typical dimensions accuracy is 0.05 mms if the testing
range is about 0.5ms by 0.5ms per-time.