Large Lens

A brief introduction to the concept of lens

The lens can be widely used in security, car wear, digital cameras, lasers, optical instruments, and other fields. With the continuous development of the market, lens technology is also more and more widely used.

The lens is made according to the refraction law of light. A lens is an optical element made of transparent materials (such as glass, crystal, etc.). A lens is a refractor whose refracting surface is a transparent body with two spheres (part of the sphere) or one sphere (part of the sphere) and one plane. The image it forms has both real and virtual images.

Convex lens: thick in the middle and thin at the edge, including biconvex, Plano-convex and concave-convex;

Concave lens: thin in the middle and thick at the edge, including double concave, flat-concave, and convex-concave.

A thin lens is a kind of lens whose thickness of the central part is large compared with the radius of curvature of both sides. In the beginning, the camera was only equipped with a convex lens, so it was called a "single lens". With the development of science and technology, modern lenses have several convex and concave lenses with different forms and functions to form a convergent lens, which is called a "compound lens". The concave lens in the compound lens is used to correct various aberrations.

Optical glass has high transparency, purity, colorless, uniform texture, and good refractive ability, so it is the main raw material for lens production. 

Due to different chemical compositions and refractive index, optical glasses include:

1. Flint glass -- add lead oxide to the glass composition to increase the refractive index (1.8804)

2. Coronal glass -- it is made by adding sodium oxide and calcium oxide to the glass composition to reduce its refractive index (the refractive index of barium coronal glass is 1.7055)

3. Lanthanum crown glass -- it is the discovered variety. It has the excellent characteristics of high refractive index and low dispersion index, which provides conditions for creating large aperture advanced lenses.

The lens is the most basic optical element of the microscope optical system. The objective lens, eyepiece, condenser, and other components are composed of single and multiple lenses. 

According to their different shapes, they can be divided into the convex lens (positive lens) and concave lens (negative lens).

When a beam of light parallel to the main optical axis passes through the convex lens and intersects at a point, this point is called the "focus", and the plane passing through the focus and perpendicular to the optical axis is called the "focal plane". There are two focuses. The focus in the object space is called "object focus", and the focal plane there is called "object focal plane"; On the contrary, the focus in the image space is called "image focus", and the focal plane there is called "image focal plane".

After the light passes through the concave lens, it becomes an upright virtual image, and the convex lens becomes an inverted real image. The real image can be displayed on the screen, but the virtual image cannot.