This item is a device from Snellius Minerals LLC designed to project interference figures, as well as operate similar to an Optical Ring Sight (ORS).  This particular device consists of two oriented cleavage sheets of muscovite mica at 45 and 135 degrees to extinction sandwiched between two crossed linear polarizers.  These are held together in a magnetic baseball card holder that can be opened and rearranged to have the muscovite plates interfere destructively or constructively.  The first photo shows this device projecting an interference figure in a darkened room by shining a flashlight through the device with the muscovite plates destructively interfering.  The second photo shows this device projecting an interference figure in a darkened room by shining a flashlight through the device with the muscovite plates constructively interfering. The video demonstrates a variety of viewing options for using the card interference figure projector.  The video starts with the device backlit by an LED light board causing the mica to generate interference colors.  Bringing in a converging lens (marble) allows us to observe interference figures.  Changing our viewing angle allows us to shift the interference colors as well.  By bringing the camera lens close to the device we can also generate an interference figure.  We then lift the device to the camera allowing a view through the card interference figure projector.  This view through the device is similar in concept to how an Optical Ring Sight (ORS) works.  The third photo shows an example device itself in ambient lighting and the fourth shows all the components of the device.  This listing is for a representative device, actual interference figures will vary a bit with muscovite thickness.   

The interference figure projection is dependent in part on the geometry of the flashlight used.  Flashlights with converging lenses work particularly well, as do cell phone flashlights.  Because this device does not have a light diffuser the interference figure produced is not as good as similar devices with a light diffuser, and flashlight geometry is more important.  

A more detailed description of the large interference figure projector can be found in the educational Youtube video "Snellius Minerals LLC Large Interference Figure Projectors"

https://youtu.be/izCR9kRiabs


If you'd like to learn more about the optical properties of muscovite mica, check out the educational Youtube video "Snellius Minerals LLC Oriented Muscovite Mica Sheet v2"

https://youtu.be/mgUdbzP3tBM


There are a wide variety of large interference figure projectors that can be made using these techniques and many more styles that we have in stock.  Feel free to reach out with any custom orders!