1. Optical compensation zoom system: When several sets of lenses are used for zooming and compensating in the zoom objective lens, the movement of each lens group is performed at the same direction, so that it is only necessary to connect the lens groups together in a simple mechanical structure for linear operation. Since the optical compensation zoom system cannot completely compensate for the image plane displacement, the moving group must be moved to a certain special position to obtain a stable and clear image surface, and the focal length is difficult to achieve continuous change, but several discrete values, so the usage is limited. However, it simplifies the mechanical structure and is beneficial to control the accuracy of the optical axis; and only uses a set of electromechanical control systems to achieve zooming and focusing, thereby reducing the cost and weight of the system, but the design difficulty is relatively large.
2. Mechanical compensation zoom system: It means that each movement component is relatively complex and different corresponding movement according to different motion laws, and finally achieves the purpose of preventing image surface movement. Mechanically compensated zoom lens: one set of lenses makes a linear movement (known as a zoom group) to change the focal length, and the other set of lenses (commonly called the compensation set) makes a small amount of nonlinear motion to compensate for the image plane displacement to achieve optical system zooming. The image position is stable. The variable magnification group is generally a negative lens group, and the compensation group has a positive lens group and a negative lens group. The movement of the compensating lens group is different from the moving direction of the variator lens group and is not constant speed, but their relative motions have a strict correspondence relationship, and each lens group realizes relative motion by a complicated cam mechanism. The focal length of such a zoom lens continuously changes within a certain range.
The mechanical compensation zoom lens has an optical structure consisting of a front fixed group, a zoom group, a compensation group, and a rear fixed group.
Front fixed group: its role is to provide a fixed image to the system;
Zoom group: It is responsible for the zooming effect of the system, and linear movement to change the focal length;
Compensation group: non-linear motion according to a certain curve trajectory to compensate the image plane movement generated by the variable magnification group during the zooming process;
Rear fixed group: used to convert the image of the compensation group into the final real image of the system, and adjust the synthetic focal length value of the system and the device aperture stop to ensure that the relative aperture of the system does not change during the zooming motion.
The cam is adjusted.
Focusing with a linear motor.
Screw nut adjustment.