原创 Create a mind-boggling infinity mirror (Part 1)

Step back. Put on your safety goggles. I'm in the throes of a creative urge, and my juices are in full flood.

I recently assembled a 4x4x4 tri-colour LED cube kit. Since then I've been happily programming it to achieve some rather cool effects; I will be blogging about them in more detail in the not-so-distant future.

4x4x4 RGB LED cube.

The thing is that, once you have a 4x4x4 cube, your mind starts to ponder the even more amazing effects you could achieve if you were fortunate enough to have an 8x8x8 LED cube, as demonstrated in this video.

But why stop there? Just imagine how much fun you could have with a 16x16x16 LED cube, such as this one.

In addition to its 4,096 tri-coloured LEDs, this beauty boasts 4,000 feet of wire and is powered by 16 Arduino Megas. You can purchase something equivalent commercially on the web. I found a site that proclaimed "SALE... Normal Price ?5950; Now ONLY ?4165." Sad to relate, even the sale price is $6,741 in US dollars, which is a tad too expensive for my wallet.

The problem is that, by the time I discovered just how much these beauties cost, I was in the mood to build something involving flashing LEDs. (Is there ever a time when one isn't in the mood for this?) So I decided to console myself by building an infinity mirror.

Just to make sure we're all tap-dancing to the same drum beat, an infinity mirror involves a relatively thin enclosure (frame) with a full mirror at the back and a partial mirror (or a half-mirror or one-way mirror) at the front. This is illustrated by the following cross-sectional diagram I just threw together.

Cross-sectional view of an infinity mirror.

Sandwiched between the full and partial mirrors is a ring of LEDs mounted around the periphery of the frame. The light from the LEDs is reflected back and forth recursively. The lights appear to recede into infinity, thereby creating the appearance of a tunnel of lights of great depth. As an example of a simple rectangular infinity mirror, take a peek at this video.

Of course, you aren't limited to rectangular infinity mirrors. You can play with all sorts of shapes. As you can see in this interesting example, these can look rather tasty, and they're not all that expensive or difficult to build. The strange thing is that, though there are lots of how-to videos and articles available on the web, they all say things like "You can make the partial mirror using regular glass covered with the film used to tint car windows," but this film comes in all sorts of shades, and they don't tell you which is best.

One thing I'm going to do is experiment with different films to see which I like the best. Also, if you look at the cross-sectional diagram above, I'm going to experiment with different H_T values and H₁:H₂ ratios to see which combinations offer the best effects. I shall, of course, report back in a future blog.
Now, I know infinity mirrors have been around for yonks (an indeterminate amount of time), but I've never actually built one of these rascals myself. And, even though the concept is not exactly new, the really cool LED strip technologies and controllers—like the Arduinos and chipKITs I'm currently playing with—mean you can achieve all sorts of mega-cool effects that would have been prohibitively complex and/or expensive in the not-so-distant past.

As a starting point, I've ordered a 1m NeoPixel Digital RGB strip from Adafruit. I really wanted the strip with the black backing, but that's on back order, so I requested the version with the white backing to give me something to play with while I'm waiting. This beauty boasts 60 RGB pixels, which should allow me to create some amazing effects.

NeoPixel strip from Adafruit (60 tri-colour LEDs per metre).

As you will see from the Adafruit website, these LEDs are all daisy-chained together and can be controlled individually. Each LED contains its own tiny controller, and each controller boasts three PWMs giving you full 24bit colour. Even better, the entire string can be controlled using a single pin from your Arduino.

I have all sorts of ideas buzzing around in my head, but I'll save these for future blogs. In the meantime, have you ever experimented with infinity mirrors? Do you have any pictures or videos to share with the rest of us? Do you think you might be tempted to build one of these little beauties based on this column? What do you have in mind? A wall-mounted display? A table-top presentation? Interesting shapes?