Welcome, Albert of Munich! Good to have you on board. You have a most interesting background. Thanks too goes to Harry in Australia for his ever-present interest and enthusiasm.
albertMunich wrote:And one of the most interesting collections there was the television department, where they had all the mechanical devices from the first crude Nipkow disk to the sophisticated scanner that had the disc running in a vacuum chamber to get rid of the wind and friction problems.
I wonder if there also you saw the early 1930s TeKaDe 180-line mirror screw! If this indeed originally gave good results, the mind boggles at the engineering precision required!
albertMunich wrote: I have more than 30 years of experience in 3D stereoscopic photography, projection and adjacent fields like 3d video.
Fascinating! In my humble way, some years ago I did demonstrate 3D NBTV at a Convention. It used beam splitters and left-right shutters (at both camera and monitor), switching 30-line views at half frame speed... 6¼ Hz!... involved no glasses, and televised a vertical pencil in front of a more remote background. You had to lie on the floor with your head exactly in the right position to see the effect. It wasn't very convincing.
albertMunich wrote:You describe the various effects when approaching the screw or changing the viewing angle. This makes me wonder what would happen if one used two light lines at a slight distance from each other to illuminate the screw? Would you see two different images at different angles? could these be made to be 2 cones of light with just the right interocular distance so that each would be seen by just one eye? Would there be crosstalk?
I have also been wondering about this. The last time I had the mirror screw running (it's a pain: it takes half an hour to set up and means a mess of trailing leads all over the living room) I considered this question briefly and it seemed that the effect of switching between eyes was the
opposite of that required for stereo.
I'm due to set it all up again though for the photographs that will accompany my article in a future club magazine. I'll then consider the question more carefully. As you say, crosstalk is likely to be a problem. Because the mirror screw demands viewing at the correct distance to get the aspect ratio right and fill the 'screen' with only one picture, we don't have the luxury of adjusting the viewing distance to get the reflected parallax right for stereoscopic television (even assuming the parallax has the correct polarity, which as I have said, I don't think it has).
albertMunich wrote:The other idea I had when reading about all the synchronization problems inherent in these mechanical devices- has anybody used model aircraft brushless motors? These are basically steppers without the noise and when run by a dedicated controller from the same timing pulse, they would be automatically in synch. ??
This sounds a great idea if the motor has sufficient power for the application. I'll defer comment to the motor synch experts here. As you know, my mirror screw used a simpler (for me) arrangement, synching the source to the screw rather than the other way round.
albertMunich wrote:Please continue to publish your work, its a great inspiration.
Your comment is most kind and helps morale greatly, because often I wonder what is the point of it all... what a strange and eccentric waste of time this is in an age of otherwise advanced technology, etc...
albertMunich wrote:My last thought is that a nipkow disk is hard to 3d print, but I believe the slats for a mirror screw could be 3d printed if there could be a way to make them reflective...? Some kind of electro plating process?
This might be possible. It certainly was possible to plate fibreglass for example, as was done in the "Retrovisor Imperial" I made in 1993 (shown below). A conductive coating was plated first with copper, then nickle. Nickle has a slightly 'warmer' tone than chrome and the overall effect was a television set made of silver!
Harry Dalek wrote:I wonder if it would work viewing off a curved screen ? i see your thinking of using a same sort of idea water lens.
Probably a curved screen would give more even focus. Whether this (or the curve) would be noticeable at a practical viewing distance is a moot point though.
Harry Dalek wrote:You seem to need a fair distance for it to work can you adjust it for a closer focus ? adjusting the mirror slats or lenses ? Screen perhaps plastic that would curve.
We are talking close-in, off angle, lens positioning using standard LED-based lines-of-light, which of course produce diverging 'fans' of light. I no longer think line-pattern lasers would work because there would be no 'fan' pattern to fill the horizontal travel of the reflected spot. The cylindrical lens would have to be larger than the screw and close by, to capture all the light.
Harry Dalek wrote:I wonder if also you could out of interest if you had 2 or more light strips pointed at the mirror screw would it project the 2 rasters as is or mix them ? i think due to the angles you would get 2 rasters
Well Harry, I am using three displaced (red, green and blue) rasters at present and they are being successfully converged by having different delays applied by Karen's Timing Corrector. Once we interpose a screen though, this might change, or even remove this effect. I shall have to think carefully about this.
All the above comes with a health warning. I still don't really understand the optics of mirror screws!
Steve O