I have been fascinated by the hologram scenes in Star Wars since I was a little boy. This Halloween, I decided to create the similar effect using a home made fog screen.
Fog screen is an "immaterial" projection screen that consists of air and a little humidity, and enables high-quality projected images in thin air. The image floating in thin air encourages kids to play with it.
However, most fog screen designs are either expensive or complicate to operate. We often need to control the temperature and the air flow at the same time. Some widely used ingredients such as dry ice and hot oil are also dangerous to kids. So I build a simple desktop fog screen for my daughter using a low cost ultrasonic humidifier. My humidifier costs $39.99. And it is the most expensive part. This process is also very straight forward. It took me about 2 hours. The operation of humidifier naturally creates the fog screen as a by-product. We do not need to think about adding dry ice or any fog solution. And my daughter loved it.
Another happy Halloween just past. Here is how I made it.