variable aperture if such an aperture is part of the system, or by dropping in an aperture plate if furnished with zoom optics.
Procedure
Access to the substage lighting requires that the glass plate be removed from the MVR stage. To remove the glass plate, perform the following steps:
1. Remove the four screws that secure the glass plate to the stage.
2. Once the screws have been removed, place two fingers in the spaces vacated by the screws and pry up one side of the glass plate. Alternatively, use a suction cup to pull up one side of the glass plate.
6.6 Mechanically Leveling the Stage Glass
Background
The glass plate can be considered level if the video image of an artifact remains in focus at high optical magnification for any stage position. MVR systems allow the glass plate to be leveled mechanically by about 1.5 mm using four screws whose head has been machined to a conical tip. Note that glass does not rest directly on the conical tips but is held by a steel frame. The glass plate is secured by screws with a spring washer.
Procedure
To mechanically level the stage glass, refer to the following figure and perform the following steps:
1. Using a 2.5 mm Allen wrench, adjust the screws as follows:
• Turn a screw clockwise to move it toward the glass plate and raise the stage.
• Turn a screw counterclockwise to move it away from the glass plate to lower it.
2. Orient the washers as shown in the following figure, keeping them barely compressed so that they have an adjustment range.
3. Four-point support will provide pivot action around two diagonal axes, make screw adjustments until the image remains in focus and the glass plate no longer tips around a diagonal axis.
Figure 23. Stage Plate with Conical Tip
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