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Optical Lenses in Microscopes

Mar. 05, 2022

A microscope is a sophisticated optical instrument used to observe small objects at close range, such as viruses, molecules and atoms. Optical microscopes can achieve a magnification of 1000-1500 times by improving the quality and quantity of optical lenses, using oil immersion lenses or strengthening light sources.

The optical system of a microscope includes an eyepiece, an objective lens, and an illumination device consisting of a condenser and a reflector. The eyepiece and objective lens magnify the observed object for observation. The eyepiece is used to observe the image formed by the objective lens. Eyepieces have an exit pupil, generally outside the focal point of the eyepiece and very close to the focal point. When observing, the pupil of the human eye must coincide with the exit pupil, so that the formed image can be observed correctly. The objective lens directly determines the optical quality and optical performance of the microscope. The structure of the objective lens is generally very complex. The larger the numerical aperture, the more complex the structure.

The eyepiece is an optical component used to observe the object imaged by the objective lens, which is an integral part of the visual optical instrument. It is located above the microscope barrel and is generally composed of two convex lenses. In addition to further expanding the real image formed by the objective lens, it also limits the field of view observed by eyes. According to the magnification, the commonly used eyepieces are 5 times, 10 times and 15 times. Generally, the image of the objective lens is located on the focal plane of the object side of eyepieces, so the light beam emitted from eyepieces is a parallel light beam. The image is imaged at infinity (or photopic distance). Because the pupil of the eye coincides with the exit pupil, the lens distance should not be too short, generally not less than 6mm or 8mm, and about 10mm is the most suitable. In military instruments, the eye clearance is usually required to be longer, requiring more than 20mm.

The microscope objective lens is generally located below the microscope barrel. It is close to the object to be observed and consists of 8-10 lenses. Its function is to enlarge (to create an enlarged real image of the object), to ensure the quality of the image, and to improve the resolution. Commonly used objective lenses can be divided into low magnification, medium magnification, high magnification and oil immersion objective lenses according to the magnification. Its aperture stop is near the lens group or at the back focal plane. Short focal length, large aperture, and small field of view are the characteristics of microscope objectives. When selecting or designing, optical properties to be considered include magnification, numerical aperture, and linear field of view.

The basic types of microscope objective structures include achromatic objectives, plan objectives, apochromatic objectives and catadioptric microscope objectives. The structure of achromatic objective lens includes an achromatic objective lens, a hemispherical lens and a meniscus positive lens. The microscope illumination system refers to an illumination device composed of a light source, a condensing mirror, a condensing mirror and an auxiliary lens. Not only for microscope systems, but also for photography or projection projection systems.

CLZ Optical Co., Ltd. specializes in the production of spherical lenses, achromatic lenses and meniscus lenses for objective lenses and eyepieces, like BK7 biconvex lenses, BK7 planoconcave lenses, fused silica biconvex lenses and fused silica planoconcave lenses. Our company precisely processes the optical glass according to the design drawings, so that the optical components can be adapted to the structure of your microscopes. If you need more information, please contact