Modern Light Diffusion and Model Starships by Jan Madsen part 1

Experiments in the Use of Modern Light Diffusion

Techniques as Applied to Model Starships

or

How Do We Light Them Dang Nacelles?

 by   Jan Madsen

The purpose of this article is to explain the use of surplus monitor backlight assemblies in the use of model lighting. The first part of the article explains how the technology works. It is educational and dull, but has pretty pictures. The second part describes my experiments (so far) with this technology. It is slightly less dull, and also has pretty pictures. The last part contains a summary of my findings and recommendations for using the technology. Jump down if you’re in a hurry to get useful information.

Ever since 1979 and the introduction of the refit NCC-1701 Enterprise, modelers have been faced with the problem of recreating the long even lighting effect evidenced on the engine nacelles. There have traditionally been two approaches:

1) Multiple low-voltage lighting elements (incandescent or LED lights) placed down the length of the nacelle.

2) Cold Cathode Fluorescent (CCFL) tubes or electroluminescent devices (Lightsheet or lightwire).

Both of these methods have problems. Option one results in spotty lighting. Option two requires power inverters to generate the high voltage AC power required by the devices.

In the intervening years, mundane (i.e. real world) technology has made some advances. One of these is the development of Liquid Crystal Displays (LCDs). LCD panels do not generate light, and therefor need an even, back-mounted illuminated surface to work properly. Increasing use of LCD displays (especially to replace CRT devices like TVs and computer monitors) have led to the development of thin light diffusion systems to produce a large, even lighted surface at minimal cost. These devices, generally called backlights, consist of several layers of plastic. From back to front they are:

1) A reflective layer. This is generally a piece of white plastic. It is used to reflect light that would go out the back of the panel so that it goes out the front. It looks ordinary, but probably has been tuned to do its job well. Plain white paper, aluminum foil, and other substances will also do the job.

2) A gradated dispersion element. This looks like a piece of clear plastic sheet. Close examination reveals a series of fine lines or a grid embedded in the plastic. This grid is designed to catch light entering from the edge of the plastic and direct it out the front. It is also designed to catch less light at the bottom and more at the top, producing an even vertical dispersion of the light (see the Gradated Dispersion Layer photo).

3) Three layers of diffusion filters. These are paper-thin piece of plastic, each with its own unique optical properties. Together, they take the lines of light generated by the dispersion element and create an even lighting effect.

 

The following experiments were made with a surplus 9” x 12” backlight assembly and a set of battery-powered LED Christmas lights. The LEDs are approximately .114” in diameter. The thickness of the dispersion element is .126”. This close relationship was obtained by blind luck, as the components were purchased separately without knowing those dimensions.

A photo of a dismantled backlight is shown below.

These elements are all made of plastic and are relatively easy to cut to size. LED lamps can then be attached to the edge to produce a large evenly illuminated surface using a low-voltage power source (generally 5 to 12 VDC).

Photos of my experiments with the various layers are shown below.

Gradated Dispersion Layer only.

Gradated Dispersion Layer with first diffusion layer only.

Gradated Dispersion Layer with second diffusion layer only.

Gradated Dispersion Layer with third diffusion layer only.

Gradated Dispersion Layer with all three diffusion layers (slightly offset).

The above photos demonstrate the behavior of the backlight elements when illuminated by LEDs. The Dispersion Layer generates lines of light of approximately even intensity from the bottom to the top of the panel. The diffusion layers blur the lines to create an even illuminated area. Maintaining the bottom edge of the Dispersion Layer intact, the layer can be cut to length and width for the desired lighting application, up to the entire area of the panel. The more LEDs used and the closer they are space, the more intense and even the result will be.

on to part 2

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