Industrial lens details

Industrial lenses are generally called camera lenses or photographic lenses, or lenses for short, and their role is optical imaging. The lens is an important component in the machine vision system and has a key role in imaging quality. It has several major indicators of imaging quality, including: resolution, contrast, depth of field, and various aberrations. Not only are there many types of lenses, but the quality difference is also very large. However, the general user often pays insufficient attention to the choice of the lens when designing the system, resulting in failure to obtain ideal images and even failure in system development.

Basic parameters of industrial lens

0 01, Field of View (FOV)

0 0 The range that an image acquisition device can cover. It can be the range that can be seen on a monitor, or it can make the maximum range that the digital image output by the device can cover.

0 02, Max / Min Work Distance

0 0 The range of the distance from the objective lens to the detected object is smaller than the minimum working distance and greater than the maximum working distance.

0 03, Depth Of Field

0 0 At a certain focus position, objects in the depth of field can be clearly imaged.

0 04 Distortion

0 0 Geometric distortion refers to the difference in magnification at different positions in the image range due to the lens. Geometric distortion mainly includes radial distortion and tangential distortion. Such as pincushion or barrel distortion.

0 05, lens interface

0 0 (1) C-MOUNT lens is one of the standard interfaces of the lens, the lens thread parameters:

0 0 Nominal diameter: 1

0 0 pitch: 32 teeth

0 0 (2) CS-Mount is a variant of C-Mount. The only difference is the distance between the lens positioning surface and the photosensitive surface of the image sensor.

0 0 (3) The size of the largest image sensor that C / CS can match does not exceed 1 ".

0 06, imaging surface

0 0 Object-side plane that can be clearly imaged on the image plane of the lens

0 07, Aperture and F value

0 0 aperture is a device used to control the amount of light passing through the lens, which is usually inside the lens. To express the aperture size, we use F values, such as f1, 4, f2, f2, 8etc.

0 08, Focal length

0 0 focal length is the distance from the main surface of the image side to the focal point of the image side. Such as 16mm, 25mm

Viewing angle and focal length of industrial lens

The size of the 0 0 focal length determines the size of the field of view. The value of the focal length is small, the field of view is large, and the observed range is large, but the distance of the object is not clear. The observation range is small, as long as the focal length is selected properly, even objects at a long distance can be clearly seen. Because the focal length and the field of view correspond one-to-one, a certain focal length means a certain field of view angle, so when choosing the focal length of the lens, you should fully consider whether the observation details are important or whether a large observation range is important If you want to see the details, choose a long focal length lens; if you want to see large scenes at close range, choose a wide-angle lens with a small focal length.

0 01. Calculation of focal length:

The calculation of the focal length of the lens, the size of the field of view, and the distance from the lens to the captured object are as follows:

0 0f = wL / W

0 0f: lens focal length

0 0w: image width (image width of the subject on the ccd target surface)

0 0W: Subject width

0 0L: Distance from the subject to the lens

0 0 height can be analogized.

0 02. Calculation of FOV:

0 0tg (ωH / 2) = h / 2f = W / L tg (ωV / 2) = v / 2f = H / L

0 0ωH: horizontal field of view

0 0ωV: vertical field of view

0 0f: focal length of the lens

0 0h: horizontal width of the camera's target surface

0 0v: vertical height of the camera's target surface

0 0W: half of the maximum visible object width

0 0H: half of the height of the largest visible object

0 0L: Distance from the subject to the lens

0 0 vertical viewing angle can be analogized.

Mounting dimensions and interfaces for industrial lenses

All camera lenses are threaded. There are two industry standards for CCD camera lenses, namely C mount and CS mount. The threaded part is the same, but the distance from the lens to the photosensitive surface is different.

0 0C mount: The distance from the lens mounting reference surface to the focal point is 17.526mm.

0 0C S mount: Special C mount. At this time, remove the gasket on the front of the camera before installing the lens. The distance from the lens mounting reference plane to the focal point is 12.5mm. If a C mount lens is to be mounted on a C S mount camera, a 5mm thick ferrule is required.

0 0 Lens size

The lens can be divided into 1-inch, 2 / 3-inch, 1 / 2-inch, 1 / 3-inch, 1 / 4-inch, 1-5-inch and other specifications according to the camera lens size. Below is a simple chip Size specification table:

0 0 Camera lens specifications should depend on the C C D size of the camera, and the two should correspond. probably:

0 0 ★ When the C C D target surface size of the camera is 1/2 inch, the lens should be 1/2 inch.

0 0 ★ When the C CD target surface size of the camera is 1/3 inch, the lens should be 1/3 inch.

0 0 ★ When the C C D target surface size of the camera is 1/4 inch, the lens should be 1/4 inch.

0 0 If the lens size is larger than the camera CCD target surface size, the image field of view will be smaller than the lens field of view, that is, the field of view of the lens cannot be used well; if the lens size is smaller than the camera CCD target surface size, a "tunnel" will occur "Effect", that is, the image has a round black frame, as if taken in a tunnel.

0 0 Surveillance cameras are generally relatively small, even smaller than 1/3 inch; industrial cameras are slightly larger, ranging from 1/2 inch to 1 inch; traditional 135 camera negatives are larger than current general photosensitive chips, 36mm × 24mm (1.4 inches × 0.9 inches), the diagonal length of the picture is 43mm (1.7 inches), that is, 1.7 inches, 120 medium format cameras, there are three types of photosensitive surface size: 45 × 60mm, 60 × 60mm and 90 × 60mm, visible larger format.