In order to see the tiny objects or the details of the objects clearly, you need to move the objects closer to the eye position, so that you can increase the viewing angle and form a larger real image on the retina. But when the object is too close to the eye, it is impossible to see clearly.
In other words, to be aware of the details, not only should the object have a large enough opening angle to the eye, but also the appropriate distance should be taken. Obviously for the eye, however, these two requirements are mutually restricted. If a convex lens is arranged in front of the eye, this problem can be solved. Convex lens is one of the simplest magnifying glasses, a simple optical instrument used to help the eyes observe tiny objects or details.
Now take a convex lens as an example to calculate its magnification power. Place the objective lens body PQ between the object focal point of the lens L and the lens and make it close to the focal point, as shown in Figure 2-20(a), and the object passes through the lens into a magnified virtual image P'Q'.
If the image-side focal length of the convex lens is 10cm, the magnifying power of the magnifying glass should be 2.5 times, written as 2.5×. If only considering the magnification power, the focal length should be shorter, and it seems that arbitrarily large magnification power can be obtained in this way. However, due to the existence of aberrations, the magnification power generally used is about 3×. If a double magnifying glass (such as eyepieces) is used, aberrations can be reduced and the magnification power can reach 20×.
Obviously, for the eyes, these two requirements always restrict each other. If an optical lens and a convex lens are arranged in front of the eyes, this problem can be solved. Convex lens is one of the simplest magnifying glass lenses, a simple optical instrument that can help the eye observe tiny objects or details.
A magnifying glass lens with no chromatic aberration, which can clearly observe the picture and the identification of gemstones, generally equipped It has a handle and a packing box for easy carrying. Professionals can also be used for jewelry certification testing, substrate surface quality, color correction and other inspections.
The mold materials used for glass lens molding are generally hard and brittle materials. If you want to precisely process these mold materials into molds, you must use high rigidity and resolution performance. The high-resolution ultra-precision computer digital control processing machine tool with a high-resolution ultra-precision computer digital control of less than 0.01μm uses a diamond grinding wheel for grinding and focusing mirror work. Grinding can obtain the desired shape accuracy, but then it needs to be polished and finished into an optical mirror surface.
In the high-precision aspheric surface processing, the aspheric surface shape test and evaluation technology is very important. For the processing of micro-lens pressing molds, the requirements are more stringent, and it is necessary to further improve the accuracy and reduce the traces of grinding.
Application of glass molding technology
At present, optical glass lens molding technology has been used to mass produce precision Spherical and aspheric lenses. In normal times, in addition to the general production of lenses with a diameter of about 15mm, it can also produce large-diameter lenses and micro-lens arrays with a diameter of 50mm. Now it is possible to manufacture aspheric lens micro lens arrays with a diameter of 100 μm for each lens.
①Manufacture of spherical and aspherical optical parts used in military and civilian optical instruments, such as lenses and prisms , And filters, etc.;
②Manufacturing aspheric lenses for optical fiber couplers for optical communications;
③Manufacturing Condensing aspheric lens for optical discs. A single aspheric lens manufactured by the compression molding method can replace the three spherical lenses used in the optical lens of the optical disc reader.
Because of the high precision of the molded aspheric lens, it can not only control and correct the axial aberration of the large numerical aperture, but also reduce the weight of the original optical lens. The cost is reduced by 30-50%.
④ Manufacturing aspheric lenses for camera viewfinders, aspheric lenses for movie projectors and camera lenses, etc.