| 摘要 |
A device or planoscope for determining a certain plane through the use of a change in an angle of bands of a moire interference pattern. The device may have several sets of screens of opaque lines separated by transparent lines. Each set of screens has a rearward screen of lines and two forward screens of lines. The first forward screen is angled relative to the length of the rearward screen and the second forward screen is parallel to the rearward screen and is located adjacent a side of the first forward screen. The lines of all three screens are parallel to each other and to the length of the rearward screen. The number of lines per unit width of the rearward screen is different than the number of lines per unit width of the forward screens. When the rearward screen is viewed through the forward screens in the certain plane, the bands of the moire interference pattern which arises are parallel to the screen lines. When the rearward screen is viewed through the forward screens outside of the certain plane, the bands of the interference pattern formed by the rearward screen and the second forward screen are parallel to the screen lines, while the bands of the interference pattern formed by the rearward screen and the first forward screen are angled relative to the screen lines.
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