How Are Polarizing Filters Made

How Does A Circular Polarizer Work

Using a Linear Polarizer and a Quarter Wave Plate to Create Circularly Polarized Light.

Linearly Polarized Light Being in the polarizer business, I like to retrieve virtually is… the polarization of calorie-free. I even search YouTube for videos about linear polarizer and circular polarizer filters. This by weekend, I looked at videos about circularly polarized concepts (please note that I really do have a life outside of polarization!), and I saw a cracking depiction of how circularly polarized light forms as it passes through a circular polarizer.

Light is a funny thing in that it is considered both a particle and a wave, and when information technology comes to a circular polarizing filter, it is easier to think about the emitted polarized light as a moving ridge. I'm sure the reader already knows this, but I would like to give a little background on light, polarization, and circular polarized filter limerick before we become to the video.

Circular Polarizer

A circular polarizer is made up of ii components: a linear polarized filter and a quarter-wave plate. The input light going into the linear polarizer filter is known equally being randomly polarized (I prefer that term over "unpolarized lite" because all light is polarized). The light exiting the linear polarizer filter is now considered linearly polarized light because the aeroplane of polarization of the output calorie-free is in one management instead of being random (or unpolarized).

The linearly polarized lite so passes through the quarter-wave plate. Hither is the critical and tricky function: the polarization axis is a vector between the electrical fields (Ex and Ey respectively).

Quarter Wave Plate Diagram

How Circular Polarizers Work The quarter-wave plate has what is called a Fast Axis and a Slow Axis. Annotation that the "Quarter Wave" designation denotes how much the Slow Axis will retard one of the electrical fields as it passes through the wave plate. To create true circularly polarized calorie-free (as opposed to elliptically polarized calorie-free), the polarizing axis must exist at 45º to the fast and boring axis. Thus the relative 45º polarizer centrality allows the electromagnetic fields to be parallel to the fast and slow axis of the moving ridge plate. With all that lined up, the polarized light and then exits the quarter-moving ridge plate, with either the Ex or Ey fields shifted by a quarter of a moving ridge.

"So what," yous say? The cyberspace effect is that concerning time, the Ex and Ey electric fields, and the polarizing axis that is a vector of the two electrical fields, the light that exits the back of the circular polarizing filter volition have a polarization state rotating. Hence the term "circular polarizer." Too, the electrical field (Ex or Ey) that is parallel to the moving ridge plate'south slow axis volition determine which field is shifted and thus which manner the polarizer axis rotates, either clockwise (right-handed) or counterclockwise (left-handed).

Merely, from a mechanical sense, how do the relationships of the electric fields actually do that equally it relates to causing the polarizer centrality to rotate? And that, my reader, leads me to this cool and informative visual representation of the of the Ex and Ey electric fields, the quarter-moving ridge shifting of one of the fields, and the rotating polarizing axis of a circular polarizer. Enjoy!

Nick Bentley