# Can I control the lighting of thousands of optical fibers?

Tags:
1. Jun 4, 2015

### Daoyang

Hi everyone!
This is my first post. I hope I am posting in the right place -- if not, please let me know.
I am also hoping my question will not sound too absurd; I am no physicist, just someone who would like to use complex technology to create an art installation, and I'm having a hard time finding the right people to speak to.

My objective is to create a dynamic (though partial) star map of the sky above the city where I live -- meaning a board, roughly 6x2 metres, on which dots of light will appear to accurately represent the real-time (at least hourly) situation of some of the stars above, reflecting differences of brightness, size, and color.

This kind of data is available online, so it seems possible to build either a database, or at least series of digital maps that a simple computer could "read" in order to produce light in the required areas of the "sky board".

My question is: would it be possible to control, very finely, the illumination of thousands of optical fibers linked to that board? In other words, can one link up some sort of optical fiber "carpet", made of hundreds of thousands of end-emitting fibers, to sources of light which could light up this or that strand selectively -- sometimes even a bunch of strands together to create a larger spot of light? Or is this completely bonkers?

I have a hunch that this might require technical means unavailable to me... But I thought I might ask, all the same.
If it seems impossible, what materials and equipment would you use?

Cheers
Dorian

2. Jun 4, 2015

### DEvens

Possibly you can use optical fibers. But why not just use a big flat panel display? Or possibly a collection of them. A 1 meter by 1 meter panel is going to be in the range of a few hundred $. Your 6x2 is therefore a few thousand$ if you construct it out of smaller panels. There are fairly standard computer graphics cards that will deal with such things. All in you can probably get an off-the-shelf system for something in the range of \$10,000. It will be very flexible. It will have standardized components so will be reparable with standard parts from standard stores. It will be serviceable by widely available technicians. And people will know how to install it using standard methods.

3. Jun 4, 2015

### bangskij

You can create a light controller using Raspberry Pi or Arduino, you may be interested in software like Cycling 74/Max and Q-light by sourceforge.

4. Jun 4, 2015

### Jeff Rosenbury

You could plug the fibers into a smaller board that covered a plasma display (i.e. computer screen). Then a computer could light up the display using a graphics program.

Home planetariums are inexpensive, though I don't know how good they are.

What sort of artistic effect are you looking for?

5. Jun 4, 2015

### Daoyang

Yes, the flat panel display option does exist, but I see it more as a backup plan for now:
First, because I'd like this installation to be specially suited to accurately imitate the night sky (flat panel displays are so versatile that they could be made to show anything, which in a way seems just too easy!); and second, because I feel optical fibers would look cooler.
However, time and money are limited, so maybe I'll fall back on this option eventually.

Thanks for the advice -- I was thinking exactly along those lines as regards the processing part of the light controller, but I wasn't sure what software to go for. I'll look into this!

I like this idea of a small screen "projecting" light onto a larger one! However, couldn't there be a risk that only the brighter pixels on the plasma display would emit enough light to travel to the end of the fibers? My understanding is that light sources have to be quite bright, thus the use of quartz halogen and xenon metal halide lights or LEDs as illuminators...?

(as a sidenote, I'll naturally have to restrict the number of stars to those above a certain apparent magnitude, but for the sake of realism I would still like to have paler, dimmer stars and planet be displayed, e.g. the multitude of stars forming the Milky Way).

The sort of effect I'd like to produce would be that of a window open on the sky: "if it weren't for all the light and air pollution in this city, this is what I'd see through this window this very minute." So, not a comprehensive planetarium, just an excuse to turn off all the lights and gaze at the ceiling, watching it move veeery slowly...

6. Jun 4, 2015

### Jeff Rosenbury

I would consider an X Y grid. Use a TTL multiplexer to power the X address. Use an open collector multiplexer for the Y address. The current from the addressed switch flows through an LED to the addressed open collector. Use diodes to power the fiberoptics. Drive one hard for a short period, then switch to another.

(Who am I kidding, I'd buy the planetarium. Why spend thousands of dollars reinventing the wheel?)

7. Jun 9, 2015

As it is the fiber is expensive as well - have you considered a regular LCD / computer projector? To get enough fibers in a panel and have it "Follow" the sky will be very difficult - depending on the fiber ends (visible end) spacing - you will see the stars jump from fiber to fiber. On the computer end, you could use a simple system like a Rasberry Pi with HDMI output - that seems almost made for that type of a project.

8. Jun 9, 2015

### Staff: Mentor

I'm skeptical that the light spots from the fibers will be bright enough when reflected from the ceiling back down to the audience. Remember that you need some orders of magnitude in brightness to represent the stars.

Here is a supplier of commercial planetarium projectors. http://www.seilerinst.com/divisions/planetarium/

You should at least study how those work, and even visit a planetarium or two before beginning your project.

Good luck.