You need a first surface mirror a big bigger than the lens (mostly because it will be at a 45 degree angle). So, about 1.5 X the lens optic diameter.
Sometimes these can be found in such things as old overhead tranparency projectors that can be picked up for a song.
Depending on the projector's light (and IR) output, the mirror may get hot, but an overhead projector's optics should already be built to handle that.
Jon ===============================================
The diagonal mirror in a newtonian telescope is made for this job so you might check telescope suppliers, could also get a mount to adapt. Course, that's getting a bit expensive if this is just for one picture one time :-). Arizona is full of amateur astronomers and telescope builders, maybe craigslist in your area could turn one up, or find a hobby group and borrow one.
I gather that this is an SBP project. ;) If the better half is tracing it m anually, a second-surface mirror is fine, because the ghost reflection is e asy to ignore. A flat hand mirror and some duct tape will do it in a minute or two. Or just snitch the mirror from your medicine cabinet.
Alternatively, the going rate on eBay for a 4-inch square first surface mir ror is about $10.
It does. But the case is _very_ small and the back lacks vents, so I'm just avoiding the risks.
I found some cheap first-surface stuff that I can easily glue to my own plywood frame.
Then I can project out a window then down to the object. This will be probably a month long project, outdoors, mornings only to stay cool, literally a paint-by-numbers, restoring the "sand painting" of this dude...
replacing with a more colorful Navajo pattern...
I still need to add the classic corn pollen strands and some other embellishments. ...Jim Thompson
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| James E.Thompson | mens |
| Analog Innovations | et |
This is your excuse to get one of those cheap 20-40 watt CO2 cnc laser cutters from ebay. You could get really creative and use one that has a removable bottom, and laser mark directly on the stone. Better yet, look online for the closest makerspace that has one, and take your wife down to join so she can create her own stencils :-). I think it will be a real challenge to keep a projector and turning mirror sufficiently well aligned for a month, or to get it accurately realigned 30+ times. Definitely plan on fiduciary marks at your image corners that you clean off the stone at the end.
the man in the middle is a simple template to cut out and paint in five minutes
the things on the outside could quickly be done with a single template rotated around a central point, make a few cut outs to use the previously painted ones as reference to where to place next
I think he's going to need something larger than a telescope diagonal mirror. ============================================================
Yeah, I was thinking the projector would be directly above the rock so the the mirror could be centered on the rock and almost touching the projector lens; it wasn't until after I posted this that he mentioned that he wanted the projector inside the house and the rock outside, sigh. He's going to need a mirror almost as big as the rock.
Really? Geez, I'm not the greatest artist (my youngest daughter IS, she's going for her MFA) but even I (the EE, so almost the antithesis of artsy) could do this faster from a printed drawing. MONTH long project? I really think I could do this in ONE morning, if everything (paints, brushes, master drawing, etc. was all set up in advance.)
Wait a MINUTE! Rubylith suggests an idea! Print out outline patterns on transparency film, one set of transparencies for each color. These can be smaller than the stone. Set up a point light source well above the stone, with a hacked-up tripod. Place a glass plate below the light. Place the transparency patterns on the glass plate and adjust plate height to get the right image size on the stone. Align transparency to fiducials, and paint away.
This should be quick, might give brighter image (depending on what you can come up with for a point light source) and can be just left in place until the project is done. But, I really think this could be done pretty quickly, maybe one day per color. The colored rings could be done with a suction cup, string and a fine paint brush. (Jury-rigged compass.)
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