The venous indwelling needle, also known as the venous trocar, consists of a flexible catheter/cannula that can be indwelled in the blood vessel, and a stainless steel puncture guide needle core. When used, the catheter and the needle core are punctured into the blood vessel. When the catheter has fully entered the blood vessel, the needle core is withdrawn and only the soft catheter is indpended in the blood vessel for infusion therapy. Good quality needle tip can reduce the pain of children and relieve the anxiety of parents, which is the premise of successful use and promotion of indentation needle.

Due to the external catheter, the diameter of the design needle is very thin, generally about 0.45mm, its edge surface is enlarged to see the structure is more complex, there is an oval hole in the middle, and the edge surface presents a certain slope. The defects detected generally include whether the tip is sharp, dull, burr, whether the edge surface is dirty, and whether the tip is crooked.

Since the indenture needle is in a state of high-speed motion on the production line, in order to take a clear image of the needle tip in real time, in addition to ensuring a clear image of the edge surface, the edge and the background should have a clear contrast and present a clear outline.

Zhejiang Huazhou Intelligent Equipment Co., Ltd. uses its own research and development of PLS series of far-center parallel light source to provide a good solution for the tip detection. This series of parallel light source uses a telecentric lens, and its lens is specially precision cold machined to ensure that the light emitted by the lamp bead is changed into a nearly parallel beam through the telecentric lens. Because of the cylindrical shape of the needle, the edge imaging has no obvious boundary, and it is difficult to highlight the clear outline of the blade surface and the needle in the ordinary bright field or dark field lighting method. PLS parallel light source with telecentric lens can eliminate the phenomenon of edge blur caused by light source diffusion, obtain clear and sharp images, and greatly improve the measurement accuracy.