Adjustable Back-Focus; Figure 6. Back Focus Set-Screw Locations - JAI TM-9730CL User Manual

TM/TMC/RM/RMC-9730CL
2.2.7

Adjustable Back-Focus

Before cameras are shipped, back focus is carefully set using a collimator, oscilloscope 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 an 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 is wise to label cameras whose back focus
was adjusted.
4. The camera must be connected to a monitor before attempting to adjust the back focus.
5. To back focus the camera, first attach a C-mount lens in the mount. Be certain that the lens is
properly seated.
6. 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).
7. Loosen the three miniature hex set-screws (use a 0.9 mm hex wrench) that lock the focus ring in
place. 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.
Figure 6. Back Focus Set-Screw Locations
Installation 9