Countertop Video Projector?

bcorrigan78 asks: "After reading the recent Slashdot post regarding Microsoft's perfect home, I got to wondering if there was a way to build or buy a counter-top projector like the one pictured in the article here. It looks like it might be some kind of laser scanning low-res projector? Anyone seen anything like this?"

Comments

Projection

[amigaluvr]

This would use a projector in the roof.

An image is created on a CRT or perhaps LCD, then sent through mirrors, lenses and the like, and projected downwards.

What happens is the CRT has to be backwards though, so you can't build one yourself.

Once it's projected downwards however you have to deal with shadows and the like

However I believe it can be done

Would probably be fairly easy to build...

[cr0sh]

Actually, by far the best way to do a "countertop video display" is a recessed LCD - get an old laptop, extend the wires to the LCD, mount the CPU out of the way somewhere (in the cabinet, or on the rear wall - just make sure you can get to it), and put the LCD in a hole cut in the countertop. Rabbet the edge of the hole with a router so you can recess a piece of glass or similar material over the LCD. Add gasket material to seal out moisture (clear or custom-colored silicone would probably be best). Want to make it truely sweet? Add "pointer" capability - put pressure sensitive resistive strain gauges at the corners of the recess, and in the middle of the edges, prior to gluing the glass down. Run wires from these to the computer (think voltage divider connected to A/D converter - you could probably hack something up that connects to the serial port). Now, when you press on the glass, resistance of the strain gauges change, indicating where your finger is (because each has a different pressure registered). Custom software would have to be written to convert these eight values into X/Y coordinates (probably some simple averaging routine, along with a noise reduction algorithm). Finally, add code to detect single and double taps for selection use, then interface all of that with your GUI or text display.

But, if what you *really* want is a projector...

First, think about the color of the surface you are projecting on - notice that in the image you provided, the surface was dark, and the image was *very* bright. In fact, just from the picture I think it was too bright, it would probably dazzle you to actually use it in real life. A projector may or may not work well on such a surface, unless the image it was projecting had mostly light colors (whitish). Otherwise, you would want your surface to be something lighter (like a tan or grey color) - which may mean changing your countertop.

Once that issue is out of the way, all you have to do is build the projector (easier said than done, BTW). A simple projector is nothing more than an image source, and a convex (magnifying) lens. Simple "project-a-picture" projectors found at arts/crafts supply stores use this system. It works OK, but isn't the best (see numerous examples online and on ebay about 100 inch TV plans) - but may work well for your application. If you really want to do this right, look up information and discussion about "triplet projection lenses" - these are lens systems that are designed for projection, and tend to have everything set up to make the image projected clear and undistorted. Unfortunately, you will tend to find new triplet assemblies to be rather pricey - which is where surplus comes in. There are people out there building such projectors (for TV projection mainly) - the projectors thus built tend to be big, but in a theater-type setting, it doesn't matter as much (other than asthetics). But this is because the builders are trying to get a huge picture, and so need a lens with a large focal length, which increases the size of the projector (unless you are adept with mirrors and folding the light path - which is outside the scope of most builders). However, since you would be projecting a much shorter distance, you can get away with a smaller lens, and hence a smaller enclosure for the projector you build.

Here are a couple of sites to get you started:

Alan's DIY Projector

Apogee, Inc.

The first one is a guy who sells triplet lenses on eBay, but provides the plans and such for free. The second is a source I found for surplus lenses, and they have a few low focal length lenses that might fit the bill for what you are wanting to do. It also might be possible to build your own custom triplet assembly from lenses picked out of an Edmund Scientific catalog, but it will be pricey.

For an LCD, to keep the size down, use something like a smaller 5 or 6 inch LCD - these can be found surplus, or you can use something like that used for "in-dash" auto video systems. You will have to disassemble the LCD in order to add a bright backlight system (which is a whole discussion in and of itself - look at the sites off of Alan's links and you will see what has been tried, and how well it works - don't forget about heat issues and the LCD, too!). Hook up a VGA to TV converter, stick to a low-res display with larger fonts, and you are set.

Mouse pointer issues can be a problem here, but I would suggest a variation on what I described first, except instead of a clear glass inset in the counter, get a white or light color porcelain (ok, I I think I mangled that word) cutting "board", make the rabbets wider to hold the board better, and install a stainless steel "splash guard" around the seam, and seal it. Project down onto this. It can act as a "screen", and serve as a useful cutting board for cooking (ok, I am thinking "kitchen computer" here - where it seems the picture you provided was aimed at). Otherwise, inset a light panel of similar countertop or desk material instead.

I hope this helps - sometimes I wonder why I am not paid for this...

Re:It can be done very cheaply.

[merlin_jim]

I've used a fresnel lens. A couple notes:

Use a small CRT. 13" or so. Not only are these cheap (used), they're what the fresnel is designed for. The bigger the screen is compared to the fresnel, the less distinct it'll be.

Turn brightness all the way up, right up to the edge of getting pixel bleed

Don't project more than a couple feet... beyond that it's too dim to be daylight readable...

I use this in my MAME arcade machine... 13" lcd projecting onto smoked glass. It works pretty good, especially with the arcade machine not having any direct light on it (it's in a corner of my living room, approximately 5 feet away from the sliding glass doors along the same wall) For the smoked glass, I started with snow frosting you can find in art stores around christmas time, but moved to acrylic sanded with 240 grit sandpaper. The higher the grit the better resolution you get...