Continuous Zoom LWIR Lens

(1)The focal length can be changed uniformly as well as continuously. 

    With the increasing improvement of processing and assembling technology, the application of the zoom structure is becoming more and more common, and its function is becoming more and more convenient. In the continuous zoom system, the focal length can be uniformly changed between the maximum and the minimum focal length, and can also take any focal length value within the range.

(2)The image plane remains stable during continuous zooming. 

    The so-called image plane remains stable, usually in two aspects: first, the stability of the position of the phase plane during zooming; second, during zooming, the size of the image formed by the system remains unchanged.

(3)The image quality meets the requirements. 

    The requirement of the continuous zoom system on the imaging quality is not only good imaging quality for some unique focal length positions, but also requires the imaging quality to be as consistent as possible in the entire zoom range. Thus, it requires that the motion of the zoom group and the compensation group be well connected. The motion curve should be smooth, and unnecessary inflection points should be avoided as much as possible.

    Both are variable lenses with variable focal length and adjustable sharpness. But there is several fundamental differences:

    A. Structurally, a continuous zoom lens has two sets of adjustable lenses, which are used to adjust the focus and sharpness respectively. The dual-field lens has only one set of adjustable lenses, which is used to switch focal length and adjusts the sharpness of the picture.

    B. In General, continuous zoom lenses require two sets of motors to control. Dual-field lenses require only one set of motors to switch the focal length and adjust sharpness.

    C. The focal length of continuous zoom lenses can be any value within the design range. Whereas the focal length of dual-field lenses can only be switched between the two fixed focal length.

    A. In the continuous zoom process, the distance between each lenses has been strictly determined. At the structural design step, there are strict requirements on the size of the lens group and the lens barrel, and it is not easy to adjust

    B. Increasing the axial length of the guide rail can make the lens group more stable during the movement, but due to the limitation of the infrared optical design, the lens group has a limited range of movement. Once the range is too small, it will cause transmission problems

    C. Under special circumstances, it is necessary to use a zoom lens with nested motion, which increases the complexity of the structure and increases various costs.

    The shortcomings listed above are only individual phenomena, which can be improved from the source, that is, when carrying out the optical design of the continuous zoom lens, these problems should be taken into account, and the optical design can be carried out on the basis of avoiding these shortcomings. solve these problems.