Patent ID: 8562144
Filing Date: 2013-10-22
Classification: B01D,G03B

Abstract:
1. An image projection device comprising: a replaceable air filter disposed near an opening of a housing of the image projection device; a switcher for switching over a present working area of the replaceable air filter to a fresh working area of the replaceable air filter in a step by step manner; a pollution level detector for detecting a pollution level of the replaceable air filter; and a controller for controlling the switcher, wherein when the pollution level detected by the pollution level detector reaches a given threshold value, the controller temporarily switches the present working area to the fresh working area, and compares a pollution level difference between the present working area and the fresh working area, and the controller determines whether or not sent working area needs to be switched to the fresh working area based on the pollution level difference between the present working area and the fresh working area.