JAI TM-6740GE, Operation Manual

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Page 36
Installation
TM-6740GE Hardware
7.2.5 Adjustable Back-Focus
Before cameras are shipped,back focus is carefully set using a collimator, oscilliscope and other
specialized equipment. While the factory-set focus serves well in most cases, an adjustable back focus
makes it possible to improve image sharpness when using lower-cost zoom lenses, custom optics, or in
unusual parameters.
There should be an obvious need to refocus the lens before attempting to change the back focus. This is
a very exacting task. Some cameras have been returned to the factory to reset the back focus after failed
attempts to change the focus by customers. It might be wise to label cameras whose back focus was
adjusted
1.
The camera must be connected to a monitor before attempting to adjust the back focus.
2.
To back focus the camera, first attach a C-mount lens in the mount. Be certain that the lens is prop-
erly seated.
3.
Next set the lens focus to infinity (if the lens is a manual iris, set the iris to a high f number while
still retaining a well illuminated image).
4.
Loosen the three miniature hex set-screws (use a 0.9 mm hex wrench) that lock the focus ring in
place (two screws for a CS-mount). Slowly turn the lens and focus ring assembly back and forth
until you obtain the best image of the desired object. This sets the back focus. Once the best image
is obtained, tighten the focus ring set-screws until they are snug. Do not over-tighten the screws.
Note: Mini-bayonet cameras adapted to C-mount do not have the back focus feature.
Figure 27. Back-Focus Set-Screw Locations
(two 2mm screws for a
attempt to adjust this
focus.
Loosen the three
2mm screws around
the perimeter of the
C-mount lens collar
CS-mount) to adjust the
back focus. Unless you
absolutely must, do not