Richard's Light box photo

[Greg Erker <erker@xxxxxxxxxxxxxx>]

See it at:
http://www.angelfire.com/ca/erker/images/backlight.jpg

Regards - Greg E.


>Rather than buy a commercial light panel, then cut
>it apart, I made my own Saturn viewer backlight from raw components (Cold
>Cathode Fluorescent Light and inverter - available from Digi-Key
>[www.digikey.com] at $10 for the bulb and $15 for the inverter).
>
>The particular CCFL I used is manufactured by JKL (model BF5118 – 5.6mm dia
>x 118mm long, 5000K color temperature).  I used tab-and-slot mahogany
>construction to match the viewer which the backlight slips onto between the
>existing semicircle "wings" (essentially adding no real bulk to the original
>viewer).
>
>Very uniform illumination is produced by cutting an acrylic mirror to form a
>trapezoidal reflector/diffuser arrangement with a narrow apex mirror
>parallel to the diffuser and in contact with the rear surface of the bulb.
>The (top-to-bottom) middle of the diffuser sees just the front surface of
>the bulb, while moving toward the top or bottom sees more of the reflected
>rear bulb surface (kind of a modified dipole radiation pattern with more
>light coming out the sides than the ends due to the bulb itself being
>opaque.  The approximately compensates for the increasing distance of the
>bulb from the center of the diffuser (also, the light should fall off as 1/r
>instead of 1/r^2 since it is closer to a line than point source).  A piece
>of matte vellum is added to the existing acrylic diffuser to increase the
>light integration within this chamber.  A piece of UV-absorbing acrylic was
>also added for eye safety.
>
>The backlight weighs just over 200 grams (with four internal AA batteries –
>or an AC adapter can be plugged in), added to the 300 gram viewer makes a
>very hand-holdable package (just under 18 oz.).  The lamp/reflector assembly
>lifts out to change batteries (which last 5-6 hrs.).  If you don't mind
>spending a little time tinkering, a relatively cheap (compared to commercial
>light panels) backlight can be made that matches the viewer cosmetically,
>and produces bright, uniform illumination.
>Richard Rylander