Lenses are the most basic optical components that make up the optical system of microscopes. The objective, eyepiece, and condenser components are all composed of a single or multiple lenses. Depending on their appearance, they can be divided into two types: convex lenses, also known as positive lenses and concave lenses, also known as negative lenses. What is the imaging principle of lenses?
A lens is a point where a beam of light parallel to the main optical axis intersects after passing through a convex lens, which is called the "focal point". The plane passing through the focal point 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 inverted real image. The real image can be displayed on the screen, while the virtual image cannot.
The lens is represented by a lens symbol (with two V-shaped markings at both ends of a line segment), the main optical axis is drawn, and the optical center and focal point are marked. Based on the intersection point of two refracted rays (usually those that pass through the optical center and those that are parallel to the main optical axis) from the three special rays of the lens, the characteristics of the image formed by the lens can be obtained (such as virtual reality, size, forward and backward).
When imaging with a lens, all the light emitted from each point on the object that illuminates the lens is imaged at the same position, blocking a portion and not affecting the imaging of other light rays directed towards the lens. Therefore, the complete image can still be seen. However, due to the decrease in light emitted from the image, the brightness of the screen image will decrease.