Basic parameters for industrial lenses

Industrial lens is equivalent to the lens of the human eye, if there is no lens, the person can not see any object, if there is no lens, then the image of the camera output, is a vast expanse of whiteness, there is no clear image output, which is consistent with the principle of our home camera and camera.
When the human eye muscles can not stretch the lens to the normal position, that is, people often say myopia, the scene becomes blurred; camera and lens coordination also has a similar phenomenon, when the image becomes unclear, you can adjust the camera's back focus, change the distance between the CCD chip and the Industrial Lens reference plane ( Equivalent to adjusting the position of the lens of the human eye, the blurred image can be made clear.

Thus, the role of the lens in the closed-circuit monitoring system is very important. Engineering and construction personnel often have to deal with the lens: the designer to calculate the lens focal length according to the object distance, the image size, the construction personnel often on-site commissioning, part of which is to adjust the lens to the best state.

A Mounting dimensions for industrial lenses, interface
All camera lenses are threaded, and the lens of the CCD camera is installed in two industrial standards, the C mounting block and the CS mount. Both threads are part of the same, but the distance from the lens to the photosensitive surface is different.
C Mounting Base: The distance from the lens mounting plane to the focus is 17. 526mm.
CS Mount: Special C installation, at this time the camera front of the washer should be removed and then installed lens. The distance from the lens mounting plane to the focus is 12. 5mm. If you want to install a C-mount lens onto a C-s mounting camera, you need to add a 5mm thick ring.

two. Dimensions of the lens
With the camera lens size shooting can be divided into 1-inch, 2/3-inch, 1/2-inch, 1/3-inch, 1/4-inch, 1/5-inch and other specifications, below is a simple chip size specification table:

format	1 inch	2/3 inches	1/2 inch	1/3 inch	1/4 inch
Height	9.6mm	6.6 mm	4.8 mm	3.6 mm	2.4 mm
width	12.8 mm	8.8 mm	6.4 mm	4.8 mm	3.2 mm

Camera lens specifications should be based on the CCD size of the video camera, the two should correspond. Probably:
★ The camera's CCD target size is 1/2 inches, the lens should be selected 1/2 inches.
★ The camera's C CD target size is 1/3 inches, the lens should be selected 1/3 inches.
★ The camera's CCD target size is 1/4 inches, the lens should be selected 1/4 inches.
If the lens size is larger than the size of the camera CCD target, it will make the image field of view smaller than the lens field of view, that is, the lens can not be well used in the field of vision, if the lens size than the camera CCD target size of the hour, there will be "tunnel effect", that is, the image has a round black frame,
Surveillance cameras are generally small, even smaller than 1/3 inches; The industrial camera is slightly larger, typically 1/2 inches to 1 inches, and the traditional 135 camera negatives are larger than the current general sensor, 36mmx24mm (1.4 inches x0.9 inches), The diagonal length of the screen is 43mm (1.7 inch), which is 1.7 inch, 120 medium camera, with a photosensitive surface of three kinds: 45x60mm, 60x60mm and 90x60mm, the visible frame is bigger.

three. Aperture of lens, F-value
The main function of the aperture is to meet the appropriate illumination required for imaging by controlling the size of the lens light. The larger the aperture, the greater the illumination of the target surface, and the higher the signal-to-noise ratio of the camera output.

It can be understood that the larger the aperture of the light, the greater the amount of light through, but we are concerned about the amount of light reaching the chip, and the longer the focal length means that the farther away the chip is from the center of the lens, the weaker the corresponding light, so the standard aperture size parameter should be related to two variables, aperture, focal length.

The aperture factor, or F value, is the parameter used to characterize the aperture size. It is equal to the lens focal length F and the aperture D ratio. The luminous flux is inversely proportional to the square of the F value, and the lower the F value, the greater the luminous flux. The law of the F-value is that the last value is exactly twice times the previous one, so the aperture is twice times less than the number of light. Common values are 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, and several others.

The general aperture can be adjusted to have a manual aperture (manual iris) and an automatic aperture (autoiris).

Manual aperture Industrial lens is the simplest industrial lens, suitable for the condition of relatively stable lighting conditions, the manual aperture is composed of several pieces of metal sheet. The luminous flux is regulated by a ring on the outer diameter of the lens. Rotate this circle to make the aperture smaller or larger. In environments where lighting conditions vary greatly or are not used to monitor a fixed target, an auto-iris industrial lens should be used, such as in places where outdoor or artificial lighting is often switched on, the action of the aperture of the automatic aperture lens is driven by the motor, and the motor is controlled by the video signal of the camera.

There are two types of auto-iris industrial lenses: One is the transmission of a video signal and a power source from the camera to the lens to control the aperture on the lens, the lens itself contains an amplifier circuit to convert the video amplitude signal from the camera to the control of the optical coil motor, which is called video-driven The other type uses the DC voltage on the camera to directly control the aperture, called the DC (DC) drive, which contains only a galvanometer-type iris motor, which requires an amplifier circuit in the camera.

For all types of auto-iris industrial lenses, there are usually two adjustable knobs, one is the ALC adjustment (metering Adjustment), with peak metering and the average light exposure according to the target of two options, generally take the average metering, and the other is the level adjustment (sensitivity), the output image can be bright or dim.