Difference between 6mm eyepiece and 20mm eyepiece

The focal length of eyepiece is different, and the visual field of 20mm eyepiece is less than that of 6mm eyepiece. In astronomical telescope, magnification = objective focal length ÷ eyepiece focal length, so under the same objective focal length, the shorter the eyepiece focal length, the smaller the field of view of the telescope. The eyepiece is mainly composed of two groups of lenses. Facing the main mirror, the lens that receives the beam of the main mirror is called a field mirror, and the lens close to the eyes is called glasses.

eyepiece

The eyepiece is also the main part of the microscope, and its main function is to enlarge the real image enlarged by the objective lens again, thus forming a clear virtual image at the apparent distance; So its quality will eventually affect the quality of the object image. In photomicrography, the real image is formed on ground glass. Some eyepieces (such as compensation eyepieces) can not only enlarge, but also correct the residual aberration produced in the imaging process of the objective lens.

There are several types of eyepieces:

1, Fogen eyepiece: eyepiece can be divided into positive eyepiece system and negative eyepiece system.

2. Reston eyepiece: It consists of two plano-convex lenses, and its main focus is outside the lower lens (field lens), so it is called a positive lens.

3. Compensating eyepiece: Flat-field achromatic objective lens and flat-field semi-achromatic objective lens with vertical chromatic aberration of 1.5%~2% are all objective lenses with insufficient vertical chromatic aberration correction.

4. Micrometer eyepiece: Add a graduated glass piece to the eyepiece for quantitative measurement or micro-indentation length measurement.

5. Photographic eyepiece: This eyepiece is specially used for photography or close-range projection, and cannot be used for microscopic observation or individual amplification.

6. Wide-angle eyepiece: Generally, the field of view of eyepiece is about 30.