I need to project simple lines in a bright environment

November 8, 2017 4:19 AM

How can I project very visible guide lines on a work table in a reasonably lit room without breaking the bank?

Upon a work table, I'd like to project guide lines to place materials by. A simple ceiling mounted downward pointing regular projector seems like it might work, but the room is quite bright (to be able to work there!), the table surface darkish and the lines are difficult to make out. I know that there are super-bright projectors, but those are very expensive. Is there such a thing as an inexpensive laser persistence-of-vision projector? For my purposes a single colour would suffice. I found a few hobby projects online but couldn't find a commercial offering.

Or do you have any other suggestions?

posted by Harald74 to Technology (9 answers total)

Home improvement stores will have laser levels that use a prism to split the laser into a plane, to project a line. Discount models can be <$20. How many lines do you need to project? Could you temporarily dim the room lights while positioning materials?
posted by jon1270 at 4:46 AM on November 8, 2017 [1 favorite]

Response by poster: Laser levels are a good, low-cost solution, jon, except that I need the lines to be programmable to point out different positions on the table. That's why I mentioned the projector first, although I probably should have been clearer.
posted by Harald74 at 5:51 AM on November 8, 2017

Does the table need to be the present table? An acrylic tabletop with the projection from below might work or indeed layered over an old flatscreen tv on its back if that might work.
posted by Iteki at 6:17 AM on November 8, 2017

Given your requirements, a projector is probably your best bet. Spitballing other ideas, from least to most fantastical:
- Make a custom jig to hold laser levels in the right sequence of positions along your work table
- Make a set of cardboard gobos (basically, stencil cutouts) such that you can slide each of them in turn in front of a very bright LED worklight mounted above a table.
- Rig up a large sheet of clear acrylic over your worktable to serve as your work surface. Put LED strips under the acrylic and connect them up to an Arduino or similar to program the necessary guide lights in the correct sequence. Optional: put some kind of diffuser fabric or wax paper between the LED strips and the underside of the acrylic.

If you're down for a cheap, reliable, lo-fi solution, you could mark the table itself (or a large cutting mat) with different colors of spike tape to indicate different steps and placements, and write yourself a guide to using it. For instance:
- Step 1: align four doohickeys with pink lines
- Step 2: center a thingamijig on each yellow X
- Step 3: lay the whatchamacallits along the green lines and attach
posted by ourobouros at 6:17 AM on November 8, 2017

Re contrast between room lights and projector light, could you dim the lights in the room somewhat anyway, since that would be offset by the light from the projector itself?
posted by solotoro at 9:05 AM on November 8, 2017

The only drawback I could see with an overhead projector is someone blocking the projection if they leaned over the table to do the work.
posted by Thorzdad at 10:08 AM on November 8, 2017

How big and heavy are the projects? Because you can use a light table, which is a thick glass over an opening with light underneath. Then you can tape down a schematic, and use that over and over. You can use artist's tape, it comes up when you are finished and does not take the finish with it. You could just make a pattern for your schematics, in tape lengths, and crossings. Put down a tape pattern for one project, take it up, put it down for another. Or you can use colored tape, they make electrician's tape in a lot of colors now, so you could put down green for one thing, white for another or red, etc.
posted by Oyéah at 10:14 AM on November 8, 2017

Response by poster: Some good suggestions here guys, but the table top is a steel vacuum holddown table, so it's not feasible to project anything from the back.

I was hoping that someone would point me to some commercial offering along these lines, but it seems like maybe there's no such thing.
posted by Harald74 at 12:25 AM on November 9, 2017

Response by poster: Aaaaand, I apparently suck at googling because I just stumbled across the correct combination of words to bring me to the laser projector article. It didn't help that including "vector" in the searches mostly brought me to a manufacturer of projectors under that name.
posted by Harald74 at 12:32 AM on November 9, 2017