Folks,
I'm slowly gearing up to produce some Nipkow wheels to experiment with. I've gathered the materials, and collected/fabricated the tools I'll need to lay out the hole patterns.
As I prepare to drill holes, I can't help but wonder about the reasoning behind aspect ratios, both those chosen by Baird, and the standard chosen by the club. My thoughts are as follows:
The 30-line standard applied to a Nipkow wheel results in pie-shaped scanning segments with an apex angle of only 12 degrees. The 32 line standard results in even slimmer pie slices, with apex angles of 11.25 degrees. There isn't a whole lot of area within those triangular slices to which a rectangular frame aperature can be applied. The most efficient application of frame to the narrow triangular scanning segment is a rectangle that is comparatively long in one dimension (corresponding to the scanning segment's radial dimension) and short in the other dimension (corresponding to the scanning segment's chord dimension.)
If the requirement is to scan images from a position to the right of the wheel's axis (the 3 o'clock position), it follows that the best aspect ratio of the frame should be of the "landscape" variety, that is, wider than tall. This makes most efficient use of the limited area within the scanning "pie slice." Yet, for some reason, the Baird standard was the opposite...3(wide) to 7(tall). Even the club standard seems counter-intuitive at 2(wide) to 3(tall).
Stated another way, if the goal was to produce "portrait" images, it seems to me it would have been far better to place the frame aperature and optics at the 12 o'clock position on the Nipkow wheel.
Any ideas as to the reasoning/logic behind the existing standards? Am I misunderstanding/overlooking something here?
Pete
AC7ZL