Proxemics is the terminology to describe spatial relationship among humans while communicating each other. It’s an interesting topic to apply proxemics theory in the domain of human computer interaction. Unlike human, it’s more difficult for computers to interpret instantly and precisely the user’s nonverbal hint, like body postures, movement, and distance, etc. In this article, we build a model which abstract the proxemic calculation based on single de-tector environment. With this model, we could easily calculate user’s position in front of the detector. And furthermore, we build a preliminary prototype of PI which applied with public screen mounted in the public area of laboratory. It serves as easy access, sharable and open platform for members of lab. We also do an experimental test with questionnaire, as well as user study to assess the usability of prototype.