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Section VI Paragraphs 6- 16 to 6- 17
Model 196A
RO
Figure 6-4. Image-to-Object Change Detail
Turn on the oscilloscope graticule to full brilliance and either reduce room lighting o r place a black cloth over both your head and the camera. Adjust the oscilloscope brilliance until the trace can be easily seen on the frosted plate. NOTE
1) Due to the separation between the graticule and the oscilloscope phosphor, the square wave will now appear shorter horizontally than the graticule. This is caused by parallax (paragraph 5-5).
2) Note that the graticule will not be in focus. This is because of the poor depth of focus
j.
should be exactly 1 cm apart. I they are closer tof gether than that, more lens gaskets must be added to correct the ratio. I the lines are wider than that, f then one or more gaskets will have to be removed. In either case, steps a through k will have to be repeated until the desired ratio has been attained. n. Working through the lens access door and using
the stubby screwdriver, loosen the lens mounting
screws just enough to allow a hindered movement of
the lens- jamnut assembly. p. Move the lens until the center of the graticule lines up with the cross hairs on the plexiglass plate.
with the large lens opening (paragraph 5-8). This will have no effect on the accuracy of the following adjustment. k. Since, due to parallax, the oscilloscope presentation and the graticule as seen on theplexiglass plate will be a different horizontal size, you will have to decide whether you want the graticule o r the oscilloscope presentation to be a perfect 1-to -1 ratio. m. Measure the desired presentation with a centimeter scale. I a 1-to-1 ratio is desired, the lines f 6-4
q. Tighten the lens mounting screw evenly, working around the lens several times. 6-16. REFOCUSING. 6-17. GENERAL. The 196A Oscilloscope Camera is prefocused at the factory on a plane 3/8 inch from the camera nose, which is the standard combined thickness of the graticule, filter and cathode ray tube glass. Unless the camera has been dropped, o r a non-standard lens-to-object distance is desired, the camera should never need refocusing. An alternate 01038- 1
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