6.Filters and Lenses
© 2023 China Daheng Group, Inc. Beijing Image Vision Technology Branch 40
6.2.
Lens Selection Reference
DAHENG IMAGING is a professional supplier for images and machine vision devices in China. In addition
to industrial cameras, it also provides high-resolution, high-optical machine vision lenses for a wide range
of industrial cameras on the market.
In order to meet the requirements of machine vision for high resolution and low distortion, DAHENG
IMAGING released nine series of industrial lenses, resolution from 2 megapixels to 25 megapixels, with
small size, light weight, high resolution and low distortion rate, etc.
When choosing a lens, there are several factors to consider:
1)
Lens mount
According to the connection methods of the lens and the camera, the commonly used mounts are C,
CS, F, V, Leica, M42, M58, M72, M90, and so on
The MARS series digital camera is equipped with a standard C-Mount, M58-Mount or F-Mount. When
selecting a lens, select the lens of the same mount as the camera
2)
Max. Image Circle
The maximum sensor size that the lens image can cover. There are mainly 1/2", 2/3", 1/1.2", 1", 1.1",
4/3", and so on
When selecting a lens, make sure that the lens max. image circle is not smaller than the sensor size
of the digital camera
3)
Resolution
The resolution represents the ability of the lens to record the details of the object, usually in units of
line pairs that can be resolved per millimeter: line pair/mm (lp/mm). The higher the resolution of the
lens, the sharper the image
When selecting a lens, make sure that the accuracy required by the system is less than the resolution
of the lens
4)
Working distance
The distance from the first working surface of the lens to the object being measured
When selecting a lens, make sure that the working distance is larger than the lens parameter
"minimum object distance"
5)
Focal length
The focal length is the distance from the center point of the lens to the clear image formed on the focal
plane. The smaller the focal length value, the larger the field of view of the digital camera
For focal length calculation, we need to confirm three parameters: the field of view, the sensor size of
the digital camera and the working distance. The focal length (f) of the expected lens can be calculated
