Lighting Lithophanes

[Tony Mac]

Many people are cutting fantastic lithophanes using PhotoVCarve that look stunning when held to the light, but then struggle to find a suitable method of back-lighting them.



PhotoVCarve customer Jeff E. has been researching this subject and came up with an excellent low cost way of back-lighting using Cold Cathode Lights. These are basically very small fluorescent tubes that have been used by computer nerds to light the inside of computer cases. They are small - less than 1/2" in diameter, come in various lengths (4 - 12 inches) and are inexpensive -- about 8 dollars for a pair of them which includes the inverter needed to drive them and generate almost no heat. Below are a couple of picture showing the tube and a litho that is back lit back by 2 12" tubes. Do an Internet search for cold cathode - you will find many suppliers.



Very useful information - Thanks Jeff.

Tony

[Geof]

I have not done lithophanes but I understand they are done with translucent plastic rather than transparent.

There is an illumination technique for engraved transparent plastic where the edges are highly polished and the light source is placed so the light enters the edge. When the plastic is untouched the light reflects around inside by total internal reflection from the surface, however, if the surface is engraved the light escapes through the 'damaged' surface. Probably everyone has seen an example of this in illuminated EXIT signs.

I wonder if a lithophane in clear acrylic illuminated from the edges this way might look quite interesting. The amount of light escaping from the engraved surfaces depends to some extent on the orientation of that surface relative to the source of the light. With high intensity colored LED illumination it would be possible to have different colors come from different edges so different proportions of different colors would escape at each part of the picture. With some experimentation it might even be possible to make 'full color' lithophanes.

[rweatherly]

It looks like the cold cathone inverter input is 12VDC. What kind of power supply would you use? Would a wall-wart work?

[turmite]

Tony is there something applied to the plastic after carving to give it that photo quality.....well near photo quality?

That example is unbelievable.

Mike

[skippy]

For anyone contemplating making a backlit lightbox as per Tony's example, it's cheaper to just buy standard small diameter fluoro tubes which come in 4, 8, 16watt. The electronic transformers are also very cheap and then you can hook it up directly to the mains power instead of having to worry about a power supply.
Geof's idea using the "Edge Lit" sign principle would also work and give stunning results. There are a few things to remember though if going in this direction. Exit signs and some others have polished edges that look nice but this lets the majority of the light escape therefore producing less effect than would otherwise be possible. For the best results, I used a chrome reflective tape around the edges. In this manner the only place the light can escape is via the engraved areas on the flat surfaces. Secondly, use a cast acrylic not an extruded acrylic as it is much higher quality. (Most of the common stuff is cast anyway) Thirdly use 5mm thickness or more. Three mm restricts the amount of light arriving in the pane (panel) Fourthly, you can add a thin backing sheet of another colour (or white in this case) behind the clear piece which also gives a good effect. Up until now the small diameter fluoro tubes have always been used but some people have been experimenting using the new generation of hi-brite LEDs (a) depending on how many you use, you can really punch out some light and (b) coloured LEDs can also give good effects. Hope this helps. I learnt these techniques from having a factory mass producing egde lit signs.

[CRFultz]

Originally Posted by turmite Tony is there something applied to the plastic after carving to give it that photo quality.....well near photo quality? That example is unbelievable. Mike

Mike what you see is the actual "straight off the cnc" picture...the results have alot of wow factor...
I usually present them without the backlight...let the pontential customer study them first then i hit the back side with a bright flashlight...I always get a wow of some sort.

Chuck

[CRFultz]

Originally Posted by rweatherly It looks like the cold cathone inverter input is 12VDC. What kind of power supply would you use? Would a wall-wart work?

works fine....12vdc at about 250 ma.for one inverter.....half a amp is more then enough for 4 bulbs...two inverters....

[Jeff E.]

I used a wall wart for the lighting you see in this example - 12v dc 500ma is plenty of power - 8-10 dollars should do the trick.

Jeff E.

[wjfiles]

Has anyone thought of mirror backing a lithophane.
Would this be an effective way.
mirroring can be done quite simply using silver nitrate, and stanous chloride and hydrozene.

[Tony Mac]

Jeff has written an excellent tutorial explaining how to build low cost
and low energy / heat light boxes and this PDF can be downloaded
from the Vectric Forum.

How to Build Litho Cold Cathode Lighting,

Tony

[wjfiles]

What is the best type and color of Corian for carving Lithophanes.Is the carving done on the back or the front of Corian.
Being translucent I would imagine that diffusion of the back lighting would not be a problem. I am trying to find a source but there seems to be many types on Ebay but I am not sure they would all be ideal.

Happy New Year To All From Down Under

[rweatherly]

sanjac1620 sells 1/4" sheets of glacier white and cameo white on eBay. I have been using the first one, but cameo is almost as white. If you use an incandescent light, the color comes from the light. sanjac's store: http://search.ebay.com/_W0QQsassZsanjac1620QQhtZ-1

You can also order samples from Corian as well as the others (Avonite, Hi-Macs), but these are almost always 1/2". I have split them with a band saw to make 2 pcs.

You look at the machined side. The image looking from the back side is not sharp.