The Design Of Industrial Endoscope Based On Gradient Index Lens

Gradient Index Optics is also known as nonhomogeneous media optics, the media of gradient index is also known as nonhomogeneous media or variable refractive index media or gradients media, the refractive index of the media is changed on a rule. Therefore, the English name called the Gradient Index (Grin). Because the use of Graded-index materials, the optical system is simplified, and reduces the size, weight and the loss of optical energy. The unique properties of GRIN lens can be used to increase their depth of field of microscopy system.With the development of industrial technology, the industrial piping and equipments are increasing. Industrial pipelines often need to be tested and maintained, in order to ensure the use of industrial pipelines to be safe. while the emergence of industrial endoscopes resolved the problem that the internal detection and maintenances is hard to achieve result from the affection of environment,Industrial endoscope is a special photography system that consists of microscope and lighting system. Micro-lens can penetrate to the internal of complex object to test the clear image of object inside. The greater the magnification of microscope, the greater the accuracy of test, but the smaller the depth of field. In this paper, take advantage of the particular imaging characteristics of GRIN lens that achieve the test of industrial pipelines and solve the problem of depth of field of industrial endoscope.Aim at the requirement of industry pipeline in detection, a four times microscope objectives is designed, The geometrical depth of field of microscope objectives is for 0.018mm, and a gradient index objective lens is added in front of the objective, the geometrical depth of field becomes 1.75mm, about increase to 100 times. The physical depth of field is for 0.055mm, and becomes 5.5mm after the gradient index objective lens added, about increase to 100 times. Finally, its depth of field is about 200 times as great as the original depth of field, thus the test range of industrial endoscopes is extended, and can observe the pipeline in different parts of the inner surface accurately and precisely.