How can I make a picture frame?

How can I make a custom back-lit picture frame using led lights and a diffuser?

• The purpose is to make a solar powered night light or just a cool looking backlit picture on the wall. I have some vellum sheets with different patterns that I might test for the nightlight.  How can I get the led light to diffuse well enough while keeping the distance from the led(s) to the sheet of paper short such that it fits in a thin-ish picture frame? 

• Answer:

  The common solution for an even backlighting is to use linear LED strips mounted on the sides your frame, very much like backlighting a computer display: (Image of LED backlighting for a computer display) Here the light on edges is reflected from a light background, on the image this is marked as "reflective film" - for you, that would be the back piece of the fixture that attaches to the wall, it is quite important that this is a smooth reflector to make the backlight even, a smooth white surface is best. After reflecting from the background, the light is evenly diffused through the "light guide" (in your case, the patterned sheet). If the frame you are building is not immensely huge, you might reach even illumination even with two strips of LED, one on each side of the frame, while keeping the whole construction fairly thin. If the frame is larger, you might want to consider illumination from all sides: Another option is to mount the LEDs as an array on the back of the frame, but that usually requires more distance between the LEDs and the diffuser to create even illumination. UPDATED: added in reply to comment: Linear LEDs have many point sources next to each other. Many manufacturers produce the linear strips with a diffuser on top, so the point sources kind of blend in to each other, creating a linear source. Even without a diffuser, the LEDs are usually close enough to each other to create a reasonably uniform lighting within a couple centimetres from the strip - and if your picture frame is wide enough to cover an extra centimetre for the light to diffuse, you'll be good. Here's a picture of a LED strip with exceptionally long distance between the point sources - you see that at a little distance from the source, the lighting is already uniform. And when you have this illumination coming from many sides, you should be able to evenly illuminate the inside of your frame with no problems. This is exactly how the large street display advertisements are illuminated from the inside, here's an old snapshot of a broken display in a metro station, it's height is about 2,5 metres - see how it's actually quite large point sources on the sides: While looking for some decent image material, I stumbled upon this cool tutorial for backlit art frames, not exactly what you're looking for (LEDs on one side only, creates a gradient of light), but inspirational still: http://www.ikeahackers.net/2010/09/torked-out-ribba-backlit-frame.html Here is also an inspirational video I found about making backlit frames out of an old window and fluorescent tubes: http://blog.pegasuslighting.com/2014/04/build-light-box-video/