With the table now square to the focus travel, optical comparator lens and projected image check the image horizon in relation to the screen vernier 0. To do this place a pointy object (like the corner of a razor blade) on the center of the stage. Have it stick straight up from the stage. Bring the object into focus in the center of the optical comparator screen. Turn the screen until the 0 protractor mark on the glass screen is lined up with the 0 mark on the vernier under the screen. Now (without moving the screen) move the point of the image on the screen to just touch the bottom of the horizontal (horizon) line. Now without moving the screen move the X axis left and right the pointer (image) should stay just touching the bottom of the optical comparator screen horizon line as it is moved. If the image moves diagonally on the screen the image horizon is off. This can be corrected two ways. Adjusting the vernier on the chart ring to match the image horizon (for a slight adjustment) or by adjusting the mirrors (for a gross adjustment). Twisting one mirror left or right will dramatically affect the horizon. The lower mirror has more affect on this than the upper one. The idea is to keep an eye on the horizon while you are adjusting the optical comparator magnification this way the horizon is good when the magnification is finished.

If the magnification is not correct adjust the optical comparator mirrors as needed to optimize the magnification. If when you are done with the magnification the horizon is slightly off you can correct it by loosening the three chart ring screws and rotating the ring slightly. Zeros on the calibration sheet indicate the magnification in that quadrant of the screen is within the acceptable limit listed on the sheet. Once the magnification is set for one lens, other lenses can be easily checked for proper magnification.

This can be done by placing another lens in the comparator and looking at the image from the Acu-Rite Measurement Master on the screen. For instance the one inch scale on the master should measure ten inches on the screen if you are using a 10X lens. If it does not measure exactly ten inches loosen the three screws on the back side of the lens and screw the back part of the lens in or out until the correct magnification is achieved. Use this technique for any additional lenses. The optical comparator mirrors only need to be adjusted for one lens. The remaining lenses are adjusted to set their magnification. The circle around the lens magnification on the inspection sheet indicates the final inspection was performed using that lens.

Related posts:

1. Optical comparator mirror replacement
2. Optical comparator calibration
3. The basic elements found in every optical comparator