There are different lenses with special performance for machine vision. Today we are going to introduce the typical ones. Zoom!
High resolution lens, mega-pixel lens
A «high resolution lens» is a lens manufactured for «high definition cameras» with a fine pixel pitch. It is also called a «megapixel lens» because it is used for high-resolution cameras with over 1 million pixels.
For a camera with an image size of 1/2 inch (diagonal 8 mm), the corresponding pixel pitch is as follows. 2
- VGA lens: Approximately 10 μm
- 1.3M compatible lens: Approximately 4.9 μm
- 2M compatible lens: Approximately 3.9 μm
- 5M compatible lens: Approximately 2.5 μm
- 10M compatible lens: Approximately 1.8 μm
The state in which the light ray (main ray) passing through the center of the aperture of the lens is parallel to the optical axis is called telecentric. A telecentric lens is a lens in which the main light beam incident on or emitted from the lens is telecentric (hereinafter referred to as «telecentric» in this section). There are telecentric lenses on both sides. The «object-side» and «both-side» lenses are special lenses with an «angle of view of 0 °» and have characteristics suitable for measurement applications such as «the optical magnification does not change even if the distance to the subject changes». I have it (beyond the depth of field, it causes out-of-focus). Since the angle of view is 0 °, the optical magnification cannot be changed according to the shooting distance like a general shooting lens. In principle, the effective diameter of the lens must be larger than the size of the subject, so if the optical magnification is small, such as when shooting a wide range, the lens barrel and front lens will inevitably become large, and as a result, the price will be relatively high. It will be expensive.
When using «coaxial epi-illumination» that illuminates through a lens, a telesen lens on the object side or both sides is generally required.
Coaxial epi-illumination compatible lens (in-line illumination lens)
Coaxial epi-illumination is an illumination method in which illumination is built into the optical path of the photographing lens, the subject is illuminated through the front lens of the lens, and the subject is photographed with the same lens. Telecentric lenses on the object side or both sides» are used as lenses, and the structure is generally such that a light guide (optical fiber) for lighting or an LED is inserted into a lens barrel with a half mirror.
3CCD camera lens (3-CCD lens)
The «3CCD camera lens» uses a color separation prism (thick glass block for color separation) to divide the subject color into red, green, and blue (RGB) colors, and uses three imaging sensors to achieve high definition. It is a lens with optimized optical performance for a «three-plate camera» (also called a «3 CCD camera») that can shoot.
If you use a general single-plate lens for a 3-plate camera, you will not be able to take full advantage of the high-definition image quality that is a feature of 3-plate cameras.
Day & night lens, day & night lens
Since a normal lens is optically designed to handle only the «visible light» range, when infrared light (infrared light) is photographed, the image formation position becomes longer than in visible light, causing defocus.
«Day / night lens» and «day / night lens» are mainly for surveillance cameras, and are designed so that the focus position does not shift between visible light for daytime lighting (including natural light) and infrared light for nighttime lighting. ..
«Built-in lens» is an integrated camera lens mainly used for surveillance.
Various controls can be customized according to the application of the camera.
Image stabilized lens
«Anti-vibration lens» is a lens with anti-vibration function due to shaking of the installation location.
It is mainly used for surveillance purposes, and is especially effective for telephoto lenses with long focal lengths.
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