I know this will seem controversial, and many who believe in lens discs or bead-discs will scoff at this analysis. However, for efficiency figures of lens discs viz a viz simple aperture scanning discs, first log in to this forum, and then look up this section of the "Patents and Articles" section of the forum:
http://www.taswegian.com/NBTV/forum/viewtopic.php?t=575
The discussion of lens disc scanners commences on page 208 of L M Myers' book "Television Optics" (viewable on the page above), and continues for about five pages of maths. The author examines real-image lens disc scanners and virtual-image lens disc scanners (like the bead disc).
His conclusion, after deriving an optical efficiency equation for apertured discs (p.170) and the lens disc (p.210) - to quote from page 210-211:
"...this will at once be recognised as
identical with that of the aperture disc in the same circumstances. This being the case, the aperture disc would be used in preference on economic grounds alone..."
Hard to believe? Maybe so, but the figures are there. Of course, this is comparing the lens disc system to an ideal apertured disc scanner where the objective lens, condensor lenses and photodetector/light source are all properly matched to the image area of the apertured disc. I have rarely seen this successfully done by NBTVA members.
I bet this starts a raging debate! It seems extremely contra-intuitive, but the maths are provided, with the necessary explanatory diagrams.
Best wishes,
Chris Long VK3AML.