What Is an Eyepiece?

The eyepiece is used to observe the image formed by the optical system in front. The eyepiece is a component of visual optical instruments such as telescopes and microscopes. Its main function is to magnify the real image obtained by the objective lens again. In order to eliminate aberrations, eyepieces are usually composed of several lenses, which have a large field of view and viewing angle magnification.

The eyepiece is also the main component of the microscope. Its main function is to magnify the real image obtained by magnifying the objective lens again.

According to the structure, the eyepieces have the following types:

1. Fugen Eyepiece: Separate Eyepiece

1. Eyepiece mark The eyepiece is engraved with the following marks: eyepiece category,

Some properties of eyepieces are very important to the function of optical products, and comparisons are needed to determine the eyepiece that best suits the needs.

Distance design of entrance pupil

The entrance pupil of the eyepiece is always designed outside the optical system of the eyepiece. They must be designed to have excellent performance at a specific distance (that is, minimal distortion at this distance). Refraction

Huygens eyepieces

Designed by Dutch scientist Huygens in 1703, it consists of two plano-convex lenses. The front is a field lens and the rear is an eyepiece. Their convex surfaces are facing one end of the objective lens. The focal length of the field lens is generally 2-3 times that of the eyepiece. Is half the sum of their focal lengths. The field of view of Huygens eyepieces is approximately 25-40 degrees. In the past, Huygens eyepieces were the first choice for small refraction lenses. However, with the increase of the telescope's optical power, its short field of view, low contrast, chromatic aberration, and obvious shortcomings of spherical aberration are gradually exposed, so the current structure is generally It is adopted for the eyepiece of the microscope. ^[2]

Ransden Eyepieces

Successfully designed in 1783, it also has two sets of two structures, consisting of two plano-convex lenses with opposite convex surfaces and the same focal length. The pitch is 2 / 3-3 / 4 of the sum of the focal lengths of the two. The chromatic aberration is slightly larger, and the field curvature is significantly reduced. The field of view is about 30-45 degrees, which is rarely used at present. ^[2]

Kellner Eyepiece

It was developed on the basis of the Ransted eyepieces and appeared in 1849. The main improvement is to change the single-piece eyepieces to double cemented achromatic lenses, which greatly improves the improvement of chromatic aberration and edge image quality. 40-50 degrees, sometimes at low magnification

eyepiece

With a comfortable exit pupil distance, it is currently widely used in some low and medium magnification telescopes, but it does not perform well at high magnifications. In addition, the field lens of the Kellner eyepiece is close to the focal plane, so that the dust on the field lens can easily form an image and affect the observation, so special attention should be paid to cleaning. Based on Kellner eyepieces, a company in the United States further improved and developed RKE eyepieces, whose edge image quality is better than the classic structure. ^[2]

Abbe's distortion-free eyepieces

Designed by Abbe, one of the founders of the German Zeiss company in 1880, it has four two-group structures. The field lens is a triple cemented lens and the eyepiece is a plano-convex lens. This eyepiece successfully controls the chromatic aberration and spherical aberration. The image and field curvature have been reduced to a level that is difficult to perceive. It also has a flat field of view of 40-50 degrees and a sufficient exit pupil distance. It has good performance at various magnifications and has been widely used. ^[2]

Eller Wide Eyepiece

Successfully developed in 1917, it was specially designed for military telescopes that require a large field of view. It is the originator of all subsequent wide-angle eyepieces. The structure is five pieces in three groups and the field of view is as high as 60-75 degrees. It is very suitable for observing deep-sky objects. Because there is astigmatism at the edges, it is not suitable for high-power design. Its performance at low power is very good. ^[2]

Prosser eyepiece

Also called symmetrical eyepiece. It consists of two identical sets of double cemented achromatic lenses. Its parameter performance is equivalent to that of OL eyepieces, but it has a larger exit pupil distance and field of view, lower cost, and is applicable to all magnifications. The eyepieces have derived a variety of improved types. ^[2]

Nagler eyepieces

A high-end eyepiece designed by Americans in 1979, with an amazing field of view of 82 degrees, excellent edge image quality and comfortable exit pupil distance, complex structure and high price, and a weight of more than one kilogram. ^[2]