On the cadge ..

[ZeroID (Brent)]

For another project.

I have acquired a rather unusual optical element. I pulled apart an old vid projector to see what if anything was salvageable inside. At the heart of the beast was a cube of glass which turns out to be an prism cube ( my description). It takes the inputs from the three screens that compose the vid output and combines them for the lens. Effectively it is a beam splitter.

Looking through it from any face gives images from each of the other optical faces with varying amounts of transmission at each. Straight through gives about 70-80% while the two opposing side faces seem to share the rest. I have the idea that it could be made into a Camera, EP, Guide setup. It may also work as a Herschel Wedge for solar viewing although that will be a very careful test process if I ever decide to go that far.

Anyway here comes the 'cadge ' part. To try and put this together I need two old diagonal assemblies to mount it into to give me the housing and optical ports necessary. I want to make up a square box with a 1.25" front end to the scope and 3 x 1.25" exits. If anyone feels so inclined to offer any bits up at reasonable prices or whatever it would be much appreciated. I don't need the mirrors working etc, just the diagonal bodies and if possible the ports. I don't feel like coughing up a $100 or so for a project that may just be a waste of time.

It's a cool piece of glass to play with. Antireflective coatings and some filter elements bonded. Seems a shame to not try and use it somehow.

[brian nordstrom (As avatar)]

Cant help you here Brent , but I hope you keep us informed as to how this progresses , sounds like a cool project , good luck.
Brian.

[LewisM]

I have 2 diagonals from the old 0.965" system if you want them? Probably WAY too small though?

[ZeroID (Brent)]

It's not very big actually, 32mm on an edge I think ( I'll check ).
Here's a pic of the beast. If you look carefully at the top surface you can just see the diag join lines. It's certainly an interesting piece of glass and throws all sorts of colours and effects if you twist it through various angles. It needs to be in a dark place to stop view through the block interfering with the incoming light from the front face ( Left facing in the pic ).

[mswhin63 (Malcolm)]

Looks like an RGB fliter allowing 3 mons signals to shoot through and combine to produce full colour. Maybe it could be reversed. Could telescope inside and split into 3 colours and simultaneous image the three colours at the same time. Not really necessary but would need 3 cameras to image. I think this would be better for planetary mainly RGB shooting maybe cross with sky quality.

[ZeroID (Brent)]

I think your description is right Malcolm. Three cameras, LRGB, hadn't thought of that one. I liked the possibility of see, guide & shoot through it. So another possible idea. I'll just have to load it onto a scope and see what happens.

Excellent .. this is gonna keep me amused for a while.

And my new super PC has arrived. M92 with i7 processors, 32 gig Ram, 2 terabytes of HD and some super graphics card I can't remember the specs of. It's going to be a busy weekend.

[ZeroID (Brent)]

Lewis,

Ok the 'cube' is not quite a cube. The Optical faces are 32mm wide but the 'height' of the prism edge face is only 30mm so if the body of your two diags will be close to or wider than 30mm apart internally then I'll be interested in acquiring them.
Let me know ...

cheers
Brent

[Barrykgerdes]

That is an interesting item.

If it is part of a prjector it will be an early colour TV projector. It would have used three projection tubes (R, G and B)and combined the output to give a full colour picture on the screen.

However these cubes were also used in early colour TV cameras and in this case the cube actually did the colour splitting to have the separated colours focused onto monochrome vidicons or plumbicons. Back in 1969 I was looking for one of these devices to make a three vidicon colour TV camera but could not justify the expense.

If your cube displays all sorts of colour effects it is possibly a filter type and used three high intensity monochrome projection tubes that combined the output in the same way from R,G and B signals on the monochrome projectors to give a colour picture.

Barry

PS Its usefulness against modern components would be rather low as the type of result obtained were mediocre compared to hi-res digital imaging like we use today.

[ZeroID (Brent)]

Hi Barry, the projector was not all that old. I pulled it apart. One quartz halogen bulb at the back and a mirror assembly which split it into three paths through various filters and lenses. Three tiny translucent lcd screens were arranged around the cube, one for each colour, CMY to make up the full colour composite.

No tubes were harmed in the deconstruction of this projector ...