The product is composed of an outer cylinder, a telescopic cylinder, prism, slit eyepiece system, etc.. Outer cylinder, a telescopic cylinder is made of engineering plastic, the outer cylinder dimensions for φ20×60mm, wall thickness 1.5mm; The eyepiece system consists of a lens holder, an eyeglass lens seat, size φ24×13mm; slit width 1.4mm, width 7mm. Product size φ20×76mm.