What is retroreflection?

The secret to retroreflection is glass beads

How do reflection and retroreflection differ? You have likely heard about fluorescent paint and luminous paint (phosphorescent), but the following will describe “retroreflection,” which is less talked about.
Normally, when light reflects, diffuse reflection occurs when it reflects off of a rough surface, and when it reflects off of glass or metal, specular reflection occurs in which the light reflects away at an angle opposite the incident angle.

With retroreflection, by changing the reflection mechanism, the light is always reflected back in the same direction as the source, regardless of whether the reflecting surface is distorted or curved.
The secret to this mechanism is the microscopic glass beads contained in the paint. When a reflective material is placed behind the glass beads, as a result of refraction due to the glass beads and specular reflection from the reflective material, the light is reflected back in the same direction as the source.This phenomenon is called retroreflection.

Difference compared to luminous paint

Fluorescent paints give off fluorescent colors when sunlight shines on them, but they do not reflect when light is shined on them at night. Also, fluorescent materials are weak against UV rays, and they change color and lose intensity over time. Luminous paints (phosphorescent) store the light energy from UV radiation and emit light, but the light emitted weakens over time.

Mechanism of retroreflection

Komatsu Process has continued development of retroreflective agents that can be used on a variety of materials and shapes that have previously been incompatible with existing retroreflective sheets.
Also, traditional retroreflective inks have been limited to the single color silver, but by changing the reflection mechanism, Komatsu Process has succeeded in developing a wide spectrum of reflective ink colors.

※Komatsu Process’s retroreflective paints can be used on any material and shape.

Method of confirming retroreflection

Retroreflection reflects light back in the same direction as the source. Therefore, as the reflection angle α shown in the illustration on the left decreases, the intensity of the reflected light increases. Retroreflection reflects light back in the same direction as the source. Therefore, as the reflection angle α shown in the illustration on the left decreases, the intensity of the reflected light increases.

Possible to paint a variety of materials and shapes

In the pictures below, retroreflective paint has been sprayed on the tires and part of the frame. Both the tires and frame are curved surfaces, but the entire area of the surface sprayed can reflect light.
As described here, retroreflection is a completely different way of illuminating objects than normal reflection, fluorescent paint and luminous paint (phosphorescent).

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