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Steve Ostler

At the Conventions Steve Ostler is always present with his left handed optics Nipkow type colour camera and monitor. In the past this was a two colour camera matrixed to obtain RGB signals for the RGB monitor. But Steve wanted more perfection, so he started work to make an RGB camera. From this work he reported us frequently.

From Steve Ostler

Now I have installed the disks laser-cut from Denis Asseman's file, here are some examples of results, taken from the screen of my mechanical colour monitor.



The signal source for most of them was Grant's eprom generator, though one picture shows Mickey Mouse as seen through my mechanical colour NBTV camera. I could do with a willing model! In reality the pictures look much better - some degradation has been caused by the digital photography.
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Enjoyed meeting everybody at Loughborough.

I'm thinking of how I can improve things next year so the monitor can work in brighter light, and the camera in dimmer light, making things more practical in the environment we have.

How about this?

Strip out the 'colour' capability from my camera and use the then-unobstructed photomultiplier to make a very sensitive b/w camera that
I could use in even dim light. A Luxeon to replace the colour mosaic in the monitor would give brilliant b/w pictures. I'd then have a very sensitive b/w system giving bright pictures. It would then be simple to modify the current 3D shutter disks for frame-sequential RGB colour. No electronic work necessary at all! Stereoscopy could be included too.

But to do this I need one thing. I haven't got: a panchromatic photomultiplier. I've heard they exist. Anyone know where I could get one?

Thanks, Steve Ostler

New photomultipliers

I've now installed the three new photomultipliers (with colour filters) and new signal chains into my mechanical colour camera. I'm getting NBTV pictures in full colour (ie. with all the three primaries correctly
rendered). Thanks to using a panchromatic R446 PMT on the red channel (with 931A's on the rest), red sensitivity is fine. However the old problem is back - getting all the light evenly spread across the field into all the three colour channels (R,G,B) at once. The result on the picture is a 'purity error' with a pronounced yellow cast toward the left.

To pass the light to the PMTs, I'm currently using a single condenser lens and simple light diffusers. I found this arrangement works the best but it's also inefficient. It means the camera is insensitive and will only work in daylight. You'll recall I was having trouble getting adequate sensitivity and matching evenness of the colour fields with my new 3-photomultiplier camera, which had replaced my earlier '2½ colour' arrangement seen at the convention; this used one PMT (blue) and one club cell (red).

Colour splitters!!

I'm pleased to report I've now been offered no less than two dichroic RGB splitters (ex broadcast tv cameras) from different people, both for free. Aren't people kind?
I now look forward to mechanically generating really high quality NBTV in full colour and in quite dim light.

The three colour camera at work

Here are some off-screen photos taken with my new 'improved' (what - again...? :) NBTV camera and displayed on the separate monitor. Needless to say, trying to capture the results to do them justice with a digital camera is difficult...



Unlike at the convention, pictures are now in full RGB colour, and (as before) are using laser-cut 30-line discs with square holes. DC restoration has now been added (as it should have been long ago!).



The colour separations in the camera are achieved using a dichroic block (taken from a defunct broadcast tv camera).The three parallel colour channels are all photomultiplier-driven, including the red channel. The R446 I am using for the red is physically identical to the 931A's used in the green and blue, but is red-sensitive. 3D-stereo colour pictures are still possible using plug-in adapters I made for both camera and monitor.

Thanks to the efficient dichroic splitter and the use of PMTs, the camera is very sensitive and indeed gives its best results in subdued room light, meaning it's now easy to be televised and view the results on the monitor at the same time. For use in very dark locations, the camera includes its own auxiliary lighting, mainly consisting of little fluorescent tubes, as can be seen in the photo.



I hope I can now lay this NBTV obsession to rest - at least until the next convention ! ;-)

Steve

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