How to adjust the focal length of an image lens?

The method of adjusting the focal length of an image lens mainly depends on the specific equipment and application scenario:
Optical lens focal length adjustment
For fixed focal length convex lenses (such as optical instrument lenses), the focal length is determined by the refractive index and curvature radius of the material and cannot be directly adjusted. If you need to change the focal length, you need to replace the lens with a different focal length or change the equivalent focal length by moving the lens group (such as a zoom system). ‌
Focus adjustment of automotive dual lens
Installation positioning: Ensure that the lens is installed accurately and firmly, as any positional deviation may affect the adjustment effect. ‌
Preliminary adjustment: Turn on the car lights in a dark environment, observe the range of light projection, and make the light roughly match the expected illumination area. ‌
Fine tuning: Use tools such as illuminance meters to measure the distribution of light intensity, fine tune the lens angle and position, and optimize the focus to the optimal state. ‌
Automatic focusing system
The autofocus system automatically adjusts the distance between the lens and the imaging plane by measuring changes in object distance, ensuring clear imaging of objects at different distances. This process relies on the Gaussian formula (1/l ′ -1/l=1/f ′) to achieve dynamic focusing. ‌
If manual adjustment is required, you can refer to the camera focusing method: align the focus knob scale with the distance to the subject, and change the distance between the lens and the imaging surface by rotating the focusing ring.