Key technologies used in industrial lenses

Key technologies used in industrial lenses

Focusing technology

For the lens, the image distance of the target imaged at different object distances is different. For the target to be observed, its imaging surface may not necessarily coincide with the photosensitive surface of the camera. In order to obtain a clear image, the position of the imaging surface needs to be adjusted to coincide with the photosensitive surface. This process is focusing.

Whole group move

This focusing method is that the entire lens moves back and forth during the adjustment process, which drives the image surface to move with it. When the image surface and the camera's photosensitive surface coincide, the imaging is the clearest. This overall focusing method does not change the optical structure of the lens, and the focal length of the lens does not change.

Single group move

Another focus adjustment method is to adjust a certain group of lenses in the lens so that it wants to move the other lenses back and forth, which can also drive the image surface to translate, and finally make the image surface and the photosensitive surface coincide to achieve clear imaging. This focusing method changes the optical structure of the lens, and the focal length of the lens changes (generally not much).

For example, the front lens group images an infinity target on the Image surface (also the position of the CCD photosensitive surface), and the rear working distance L '. Now it is necessary to image a nearby target. The image surface position is Image'. focal.

One method is to move the entire lens group forward relative to the CCD, so that the rear working distance is enlarged to L ", and the CCD photosensitive surface coincides with the image surface, and the image is clear. This method is the entire group of mobile focusing. As shown in the figure below.

There is also a focusing method: only moving a single lens (or several together) in the lens group can also achieve the purpose of focusing, as shown in the figure below. Moving the fourth lens forward from the position A to A ′, for a target at a short distance, the imaging surface also returns to a position coincident with the CCD, so that the imaging is clear. This focusing method is called single group mobile focusing.

2. Zoom Technology

The so-called zoom refers to the lens itself can be adjusted to make the focal length have a larger range of change (usually measured by the multiple of the focal length change, for example, 4x zoom refers to the maximum focal length is 4 times the minimum focal length). In the use of this lens, the imaging magnification can be changed by zooming (switching between "large scene" and "local close-up" at will), with strong adaptability and wide range of use.

The way to achieve zooming: During the zooming process, the two groups (or more) of the lenses in the optical system are moved relative to each other to change the combined focal length of the entire system (lens), and at the same time ensure that the position of the image plane does not move. Imaging is always clear.

It is different from single-group mobile focusing. Single-group mobile focusing is intended to change the position of the imaging surface (although it will also cause a small change in the focal length of the lens); while zoom is intended to change the focal length of the lens (generally several times) Change), it requires stabilization of the image plane.

3. Auto Iris

Adjusting the aperture of the lens essentially changes the aperture size of the aperture stop, thereby changing the amount of incoming light and achieving the purpose of adjusting the brightness of the imaging surface.

This process can be done manually or by motor drive. The latter method is automatic aperture adjustment.

4. Telecentric (telecentric) lens

Far away light path, generally can be divided into two kinds of object far light path and image far light path

The aperture stop is located on the focal plane of the image side of the lens (the "focal stop" is named), and the entrance pupil is located at the infinity of the object side. Such an optical path is called the object-side telecentric optical path. The characteristic of this kind of optical path: the incident main ray (shown in red) on the object side is parallel to the optical axis.

The aperture stop is located on the focal plane of the object side and the exit pupil is located at the infinite distance on the image side. Such an optical path is called the image center telecentric optical path. The characteristic of this kind of optical path is that the main ray (shown in red) emitted by the image side is parallel to the optical axis.

两种 The two optical paths are essentially interconnected, and are the forward and reverse applications of the same optical path (focal stop). They are more often found in measuring instruments, and they will show the characteristics of the grid in combination with practical applications, which requires attention. The imaging characteristics of the object-side telecentric optical path are: the size of the image is not sensitive to the object distance, but it is very sensitive to the image distance; while the imaging side of the telecentric optical path is characterized by the size of the image sensitive to the object distance, but Not sensitive.

的 The lenses made with these two telecentric optical paths are called object-side or image-side telecentric lenses, respectively