CNBackground:
Focal length is closely related to depth of field. As a key factor affecting the range of image clarity, precise focal length adjustment can enable the target object to be clearly imaged on the image sensor.Depth of field refers to the object distance range corresponding to the clear imaging on a fixed image plane. Due to factors such as the improvement of the imaging system’s resolution and the increase of the magnification, the depth of field range will be limited. The limitation of the depth of field makes it impossible for traditional imaging systems to achieve clear imaging of objects with large depth differences under fixed focus.
In the use of medical endoscopes, it is often necessary to change the imaging magnification flexibly. Low magnification is used to observe images within a larger range of the human body to avoid missing the diseased part. After determining the observation or treatment position, magnification is required to observe the details of the affected part.Traditional endoscopes are mostly fixed-focus lenses or require manual adjustment of optical interfaces. Doctors have to frequently switch between different focal lengths (such as 18mm, 22mm, 28mm, etc.) based on the actual observation needs of different endoscopes, which is complicated and inconvenient to use. The VF technology solves this problem ingeniously. While adjusting the magnification through the zoom system, it can also make the image focus clear synchronously, making surgical treatment more convenient.
VF Technology Principle:
The key to realizing the automatic zoom and focusing function lies in the internal structure design of the endoscope, in which the key components mainly include the lens group, drive mechanism, aperture, and spectral element.The lens group includes two types: a movable lens group and a fixed lens group. They are arranged in sequence along the optical axis from the object side to the image side. The movable lens group includes a zoom lens group and a focus lens group. The driving mechanism is connected to the movable lens group driving motor through a controller, thereby driving at least one movable lens group to reciprocate along the optical axis direction, thereby realizing variable focusing.
The aperture is located on the image side of the lens group close to the object side and moves synchronously with the lens group. Since the aperture determines the diameter of the light beam entering the optical system, and the function of the lens group is to refract and image the light, when the relative positions of the two remain unchanged, the angle and range of the light beam limited by the aperture entering the lens group will not change. Therefore, the entrance pupil diameter can be kept unchanged, and the entrance pupil distance changes very little. This feature can improve the imaging quality of the optical system and present a stable and clear image to the doctor, helping him to accurately diagnose the disease. The spectral element is located on the image side of the lens group close to the image side. With the help of the spectral element, the application of fluorescence or special spectrum can be realized, which expands the function and application range of endoscopes in medical detection.
The above is the structural principle of the automatic zoom function.
The variable focus function allows doctors to adjust the focus according to the actual observation needs of different endoscopes without having to replace adapters with different focal lengths, greatly improving the convenience and simplicity of operation.
