We will now model a rainbow. First, in order to model a raindrop, we use a spherical object with a radius of 0.1 mm and water as the material.
Because there are no reflected rays between the angles of the primary and the secondary rainbows, the dark band is created. Although there are reflected rays under the primary and above the secondary rainbows, all colors are mixed so that no individual colors can be observed. There is a caustic line in the angle of the primary and secondary rainbows and hence the rainbows are in vivid color.
Because both of the reflections are Fresnel reflections, the secondary rainbow only has 2% of energy in comparison to the primary. The reflected rays exit the drop on the upper part, as drawn in the purple and create the secondary rainbow and the brighter section above it. In addition, there are some rays entering at the bottom part of the raindrop which reflect twice at the back of the drop. This makes the primary rainbow and the brighter section under it. As you can see, most of the rays directly emerge from the raindrop as displayed in red lines. However, some rays entering the upper part of the raindrop reflect at the back of the drop with a Fresnel reflection of 2%, as drawn in brown lines, and they leave the drop close to the bottom, as shown in the yellow line which refracts at the exit. The parallel incidents rays are drawn in blue lines, which represent the light from the sun, and the rays refract as they enter the sphere, which represents the spherical raindrop rays traveling inside of the raindrop are plotted with green lines. It is set to color rays by segments. In other words, the rays are a different color after each refraction and reflection. The displayed field angle is ☑6 degrees horizontally and ☙ degrees vertically. The darkness between these two bows is the so called the “dark Alexander’s Band”.Īs you can see, the secondary rainbow is dark and its color order from red to purple is in the inverse order. In the detector image above, you can see a “primary rainbow” which is the brighter rainbow on the bottom, and a “secondary rainbow”, the dimmer rainbow on the top.
Here is the simulated image of a rainbow. The files we use are attached to this article.
#Zemax 16 gaussian source how to#
By generating a black body source used in conjunction with user-defined coating, we will show how to model a rainbow in this article. In OpticStudio's Non-Sequential Mode, a rainbow can be simulated in a few steps. Non-Sequential Mode has the ability to model true color sources using several source color models.Īuthored By Shinichi Nagata, Lensya Limited Downloads This article describes how to model a rainbow using the non-sequential capabilities of OpticStudio.