Study of the influence of various reflectors and scatterers on the shape of a light beam
I am a cyclist. When you drive on public roads, you understand that there isn’t much light, and once again I sat down to read forums and articles in order to buy something else good on my steering wheel and helmet. Among other things, I came across an article by a friend known in bicycle circles, in which he recommended simple and cheap Chinese flashlights as a universal tool - equipped with various types of mounts, they can be used independently, as a bicycle headlight, and even in a bunch of different situations. One thing is bad - for different purposes, a different shape of the light beam is needed.
This model of flashlights is a kind of designer, to which the manufacturer supplies various types of reflectors and diffusers, so I ordered everything that was available, waited for delivery, and started testing.
So I had:
- 4 identical flashlights. The package included smooth parabolic reflectors and plain flat glass as a diffuser.
- Reflectors of the type orange peel (orange peel) are parabolic, but not smooth, but equipped with small, 0.5 - 1 mm, irregularities over the entire inner surface.
- Diffusers in stock:
- Smooth (not pictured)
- Small (0.5 mm) hexagonal cells
- Parallel ribs of a triangular profile
- Large (1 mm) hexagonal cells
- Also large cells, as the previous paragraph. At first I decided that they put two of the same - but it turned out that they give completely different light spots. after careful consideration, it became clear that they have different forms of internal recesses in the emitter:
So, it turned out 12 options for combinations of reflectors and diffusers. I photographed the light beam that is formed from each combination and formed a summary table:
Based on these images, we can draw the following conclusions:
- The best point source (as a search lamp) - is formed with a combination of a smooth parabolic reflector and without a diffuser.
- Paradoxically, the use of an “orange peel” type reflector has almost no effect on the light beam. Compared to the type of diffuser, its effect is minimal.
- The use of an orange peel reflector without a diffuser increases the angular size of the central beam by about 1.5 times.
- The smoothest-growing beam (with intensity growing toward the center, approximately according to the Gaussian law) is obtained by combining an orange peel reflector and a coarse-diffused diffuser. The reflector makes the distribution a little smoother. Such a bundle is suitable, for example, for mounting on a helmet during night riding in the woods.
- A wide beam of uniform intensity did not work out under any combination, but closest to it was a smooth diffuser with a smooth reflector. In the center, with this combination, artifacts similar to the shape of the emitting crystal are observed.
- And finally, the most interesting result is obtained by combining an orange peel reflector and a ribbed diffuser. This combination allows you to get a beam expanded in one plane. Such a light is ideally suited as a bicycle headlight, as it will allow you to illuminate a fairly wide angle and not blind oncoming pedestrians and drivers of other vehicles, which, given the very serious power of this flashlight, is an urgent problem.