Bi-telecentric lens used in spring quality inspection

In the automated industrial production line, there are many quality inspection items for springs. The typical ones are spring size and angle measurement, while traditional optical inspection still has some problems that cannot be solved. Wei Shi image bi-telecentric lens solves this problem with its different light path design.

Detection of size and angle

Traditional visual inspection uses high-resolution CCD industrial cameras and ordinary industrial lenses. Due to the characteristics of near-far, large-distance, and edge distortion of ordinary industrial lenses, in the actual imaging process, the imaging ratio of objects will change to varying degrees. The edges are not fixed, and the measurement results will change during the measurement process after the calibration is completed, resulting in low accuracy when measuring the angle and size.

The bi-telecentric lens has a diaphragm in the middle of the lens, so that the light entering and exiting the lens is parallel, and the remaining diffuse light sources are filtered out. This way, no matter how the object distance changes (of course, within the range that can be clearly imaged) ), The magnification will not change. This feature can solve not only the stability of the edge of the measured object, but also the impact of uncontrollable jitter on the production line on the system accuracy. It can be used for many high-precision online detection Claim.

Industrial intelligence software

The rendering of the upper and lower bottom of the spring processed by SVS intelligent software

In image processing, the presence or absence of edges is determined by the change of gray value. Due to the special structure of the spring itself, no image with the same gray value of the measured object can be obtained no matter whether it is an epi-light source or a backlight. At reflective places, gray values opposite to other areas are often obtained, resulting in final measurement results showing fractures at the corners, which results in direct failure of the inspection work.

When we use the MV-EM series of industrial digital cameras with the BTOS series of parallel light sources and bi-telecentric lenses, the image continuity is good, and it is clear at a glance whether it is detection size or defect, which meets the demand for high precision detection results. The figure below is a spring contour picture taken with a bi-telecentric lens and a parallel light source. The gray value pair is relatively obvious. The processing is very simple, and detection errors are basically impossible.

Bi-telecentric lens spring detection

Effect of BTOS bi-telecentric lens with parallel light source

Depth of field of the lens

The depth of field of ordinary industrial lenses is relatively small, and the spring itself has a certain height. It often occurs that the depth of field of the lens cannot be completely covered and the imaging cannot be clearly performed at the same time. In this case, measurement and inspection cannot be performed, and optical inspection has no solution in this field. When we use a bi-telecentric lens, due to its parallel light characteristics, the depth of field can be several times or even dozens of times compared to ordinary lenses, which can solve this problem.

iJUNCO is ready to provide you with technical services in this regard.