Camera module - lens composition principle
October 30, 2023
(1) Lens manufacturing principle
Any object is an organic combination of internal structure and external shape, both of which are indispensable. A lens also has such characteristics. First of all, from the perspective of the internal structure of the lens, the lens includes multiple lenses and apertures in a combined structure. The lens group contains different types of lenses with different thicknesses, but the imaging quality of the lens is not related to the number of internal lenses. To some extent, the image quality of a single-lens fixed-focus head is better. The aperture is a device inside the lens used to control the amount of light entering. The aperture consists of multiple blades forming a circular bayonet. The opening and closing of the aperture blades controls the amount of light received by the image sensor.
Secondly, the outside of the lens is equipped with zoom ring, focus ring, focus distance and other settings. The zoom ring is for zoom lenses. Fixed-focus lenses do not have a zoom ring. Adjusting the zoom ring can change the angle of view of the lens, and the scene can be freely changed. When the focus ring is adjusted, the internal lens moves accordingly to achieve focus. Focusing distance, lenses with different focal lengths or focal length ranges have focusing distance parameters, and these parameters will be printed on the lens. When shooting, you need to remember the minimum focusing distance of each lens. If you get too close to the subject beyond the minimum distance, you will be unable to focus.
(2) What is focal length?
Focal length, that is, focal length, is the distance from the optical center of the lens to the focus where the light is gathered when parallel light is incident. In a camera, the focal length is the distance from the center of the lens to the imaging plane such as the film or CCD.
It is necessary to note that the convex lens has two focal points, one on each side of the main optical axis. On a camera, focal length is measured in millimeters. For example, a 35mm lens means that the focal length of the lens is 35mm. The focal length of a lens determines the size of the image formed by the object captured by the lens on the imaging plane. Assuming that the same subject is photographed at the same distance, the longer the focal length of the lens, the greater the magnification of the image formed by the subject on the film or image sensor.
(3) What is the relationship between focal length and lens thickness?
The greater the focal length, the thinner the lens. The smaller the focal length, the thicker the lens. The lenses in wide angle lenses are thicker and the lenses in telephoto lenses are thinner.
(4) What is the relationship between focal length and lens angle? (qualitative)
The larger the focal length, the thinner the lens and the smaller the lens angle.
The smaller the focal length, the thicker the lens and the wider the lens angle.
The object distance is the same and the imaging range is the same. A lens with a long focal length has a small lens angle.
The object distance is the same and the imaging range is the same. A lens with a short focal length has a large lens angle.
The corresponding numerical relationship between focal length and lens angle (quantitative)
The larger the focal length, the smaller the lens angle. The smaller the focal length, the larger the lens angle.