Vicon IX 2000 L Información técnica descargar pdf (Pagina 42)

MX Cameras

3-6 Vicon MX Hardware System Reference

Another characteristic of the camera sensor is the image circle. This

is the sharp circular image that the camera lens casts onto the sensor,

as shown in Figure 3-4.

Figure 3-4: Image circle

The diameter of this image circle is the maximum area of usable

quality image that the lens can produce. Most lenses produce their

best image at the center of the lens, dropping off in performance

towards the outer extremes of the lens. This results in a gradual

darkening of the image towards the corners of the image, known as

vignetting. Theoretically, vignetting gets worse for wider angle lenses

and for wider open apertures, but the area at which vignetting starts

to occur depends on the lens.

Thus for optimum performance, the image circle projected should be

larger than the sensor area used by the camera. This ensures that the

entire sensor is utilized and eliminates the fall-off of light that occurs

towards the edge of the image circle. If the image circle of a lens is

too small for the sensor size, then the camera image around the edges

and corners is lost. MX Cameras are fitted with lenses that have an

appropriately sized image circle for the sensor.

If you wish to change the supplied lens, you must consider the sensor

size of the new lens. Even if the focal length of the new lens is the

same, a different sensor size will produce a different field of view. For

example, the sensor sizes of C-Mount lenses are specified in formats

of 1”, 2/3”, 1/2”, 1/3”, and 1/4”, which reflect a ratio of

1:0.69:0.5:0.38:0.25. Thus, a 1/2” format is 50% of a 1" format, a

1/3” format is 75% of a 1/2” format, and so on. For guidance on the

necessary image circle diameter for a specific sensor format, see

MXhardware_Reference.book Page 6 Monday, April 30, 2007 1:56 PM

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Vicon IX 2000 L Información técnica Pagina 42