Starting at the beginning with Mirror Screws
Posted: Thu Sep 01, 2011 8:00 am
I'd really like to have a go at a "high" definition mirror screw for my next project. I'd get one of Darryl's 'universal' converters for the source and get in a position to use a mirror screw set as my main household colour tv. A handsome mirror screw set in the corner of the room would make quite a talking point.
Another thing... I could actually carry a mirror screw in to the NBTV Convention! I've stopped coming to conventions the past few years because my mechanical colour camera and monitor are just too heavy and bulky to shift... they really need a fork lift truck!
Trouble is... I'm still trying to get my head round the optical concepts of mirror screws - which should be simple. But alas, not for a brain like mine.
Starting right at the beginning....
Mirror screws all have this 'three section' corkscrew appearance. I guess that's how it always turns out when you have a complete single turn built in to the stack of mirrors - yes?
I'm trying to work out whether, for example, it would be possible to make a 90-line mirror screw to give a 4:3 12-inch horizontally scanned picture. Doesn't this mean the mirror screw would have to also be 12 inches in diameter? But if 90 lines meant a mere 4 degrees of rotation per line, wouldn't this also mean a tall thin picture resulted? Or by placing the line of light - and the viewer - far away, can this be overcome?
Is there a formula (or something) to work out the dimensions and aspect ratio of the picture vis-a-vis the number of lines and the mirror screw dimensions?
So far, I've been experimenting with a single polished aluminium bar on a pivot, and an LED bar (car maintenance) light, to try to get the hang of what happens.
To make the mirror screw's slats, I propose to design some sort of interlocking plate that automatically locks to other similar plates at the right 'stagger' angle. These would be laser cut from stainless steel. I have a good laser cutters nearby - they produced the 20-inch discs for my last NBTV rig.
Any help appreciated. Thanks!
Steve O
Another thing... I could actually carry a mirror screw in to the NBTV Convention! I've stopped coming to conventions the past few years because my mechanical colour camera and monitor are just too heavy and bulky to shift... they really need a fork lift truck!
Trouble is... I'm still trying to get my head round the optical concepts of mirror screws - which should be simple. But alas, not for a brain like mine.
Starting right at the beginning....
Mirror screws all have this 'three section' corkscrew appearance. I guess that's how it always turns out when you have a complete single turn built in to the stack of mirrors - yes?
I'm trying to work out whether, for example, it would be possible to make a 90-line mirror screw to give a 4:3 12-inch horizontally scanned picture. Doesn't this mean the mirror screw would have to also be 12 inches in diameter? But if 90 lines meant a mere 4 degrees of rotation per line, wouldn't this also mean a tall thin picture resulted? Or by placing the line of light - and the viewer - far away, can this be overcome?
Is there a formula (or something) to work out the dimensions and aspect ratio of the picture vis-a-vis the number of lines and the mirror screw dimensions?
So far, I've been experimenting with a single polished aluminium bar on a pivot, and an LED bar (car maintenance) light, to try to get the hang of what happens.
To make the mirror screw's slats, I propose to design some sort of interlocking plate that automatically locks to other similar plates at the right 'stagger' angle. These would be laser cut from stainless steel. I have a good laser cutters nearby - they produced the 20-inch discs for my last NBTV rig.
Any help appreciated. Thanks!
Steve O