Microscope is very important in the field of biochemical science nowadays. As a optical instrument, the optical lenses in microscopes is very particular. Hanzhong Borisun Optics takes you to a simple understanding of the characteristics of optical lenses in microscopes, mainly including refractive index, lens performance, imaging laws, etc. The following is a brief explanation.
Refraction and refractive index: Light rays propagate in a straight line between two points in a uniform isotropic medium. When passing through transparent objects of different densities, refraction occurs, which is caused by the different propagation speeds of light in different media. When light rays that are not perpendicular to the surface of a transparent object (such as glass) are emitted by air, the direction of the light rays changes at its interface and forms a refraction angle with the normal. It is generally expressed in terms of refractive index, which is the ratio of the propagation speed of light in a vacuum to the propagation speed of light in the medium. The higher the refractive index of a material, the stronger its ability to refract incident light.
Performance of optical lenses: Lenses are the basic optical components that make up the optical system of microscopes, and components such as objective lenses, eyepieces, and condenser lenses are composed of a single or multiple lenses. According to their different shapes, they can be divided into two categories: convex lenses (positive lenses) and concave lenses (negative lenses). When a beam of light parallel to the optical axis intersects at a point through a convex lens, this point is called the focal point, and the plane passing through the intersection and perpendicular to the optical axis is called the focal plane. There are two focal points, the focal point in the object space is called the object focal point, and the focal plane at this point is called the object focal plane; On the contrary, the focal point in the image space is called the image focal point, and the focal plane at that point is called the image focal plane. After passing through a concave lens, light forms an upright virtual image, while a convex lens forms an upright real image. Real images can be displayed on the screen, while virtual images cannot.
Several imaging laws of convex lenses: 1 When the object is outside the focal length of the lens, a reduced inverted real image is formed within the focal length of the image and outside the focal point;
2. When the object is at the double focal length of the lens, an inverted real image of the same size is formed at the double focal length of the image;
3. When the object is within twice the focal length of the lens, but outside the focal point, an enlarged inverted real image is formed outside of the focal length of the image;
4. When the object is at the focal point of the lens, the image cannot be imaged;
5. When the object is within the focal point of the lens object, there is no image formation in the image side, and an enlarged upright virtual image is formed on the same side of the lens object side that is further away from the object.
Through the above basic introduction, we can have a better understanding of the working principle of microscopes.