C Mount

A C mount is a type of lens mount that is commonly found on 16 mm movie cameras, CCTV, machine vision cameras and microscope phototubes.

A c mount adapter for a microscope without a lens in it, is merely a connector for a camera. What is seen is a ‘direct image’ on the monitor screen, which is more magnification than what is seen in the eyepieces due to the inherent magnification with image sensors and microscopes. While this type of arrangement is good for many users, others require an image on the monitor that looks more like the FOV (field of view) that is seen in the microscope phototubes.

C MountTo compensate for too much magnification, or to match more closely the microscopes FOV, a C mount with reduction lenses can be used to adjust the field of view seen on the monitor. The reduction lenses required will depend on the chip size of the camera. For example, if the camera being used has a ½” image sensor, the c-mount required would be 0.45X.

C mount lenses provide a male thread, which mates with a female thread on the camera. The thread is nominally 1.000 inch (25.4 mm) in diameter, with 32 threads per inch, designated as “1-32 UN 2A” in the ANSI B1.1 standard for unified screw threads. The flange focal distance is 17.526 mm (0.6900 in) for a C mount.

Depending on the format, the design of the lens and its performance will differ considerably. For example, for the 4/3 format, a 12 mm lens is a wide-angle lens and will have a retrofocus design. For the 2/3-inch format, a 12 mm lens is “normal” and can have a simple and fast double Gauss layout. For the 1/3-inch format, a 12 mm lens is long and can have a telephoto design.  Universe Optics will ensure you are getting correct the precision lens for your application.

To say that a lens is “C mount” does not indicate the intended use of the lens. C mount lenses have been made for many different formats. They are built for the 8 mm and 16 mm film formats, and the 1/3” ½”, 2/3”, 1” and 4/3” video formats, all which correspond to a range of image circles that range from approximately 5 to 22 mm in diameter.

A C mount lens is still the most common type in industrial image processing, especially in factory automation. They are mostly used with digital cameras like USB, Fire_Wire, Gig-E and Smart Cameras.

Universe Kogaku designs and manufactures optical lenses for automated agricultural equipment, security, high tech and electronic applications. We stock 1000’s of standard lens assemblies and can custom design a solution for scanners, CCTV, CCD/CMOS, medical imaging, surveillance systems, machine vision and night vision systems.

Posted in C Mount Lens, Lens Mounts, Technical News.