The following factors must be considered when choosing a suitable industrial lens for a specific application:
• Field of view-the size of the imaged area.
• Working distance (WD)-the distance between the camera lens and the object or area being observed.
• CCD – The size of the camera imaging sensor device.
• These factors must be treated in a consistent manner. If you are measuring the width of an object, you need to use the horizontal CCD specification, and so on. If the measurement is in inches, it is calculated in feet and then converted to millimeters.
Refer to the following example: There is a 1/3” C-mount CDD camera (4.8 mm horizontally). The distance from the object to the front of the lens is 12” (305 mm). The size of the field of view or object is 2.5” (64 mm). The conversion factor is 1” = 25.4 mm (rounded).
FL = 4.8 Mm x 305 Mm / 64 Mm
FL = 1464 Mm / 64 Mm
FL = According to the requirements of 23 mm lens
FL = 0.19” x 12” / 2.5”
FL = 2.28” / 2.5”
FL = 0.912” x 25.4 Mm/inch
FL = According to the requirements of 23 mm lens
Note: Do not confuse the working distance with the distance from the object to the image. The working distance is the distance from the front of the lens to the object being observed. The distance from the object to the image is the distance between the CCD sensor and the object. When calculating the required focal length of the lens, the working distance must be used.
