A polymeric coating composition chemically grafts to cellulose or synthetics, and the resulting product serves as a filter in a filtration system which keeps the filtered liquid or gas clean by removing soot, solids, liquids and other contaminants, thus maximizing the life of equipment or engines. Accordingly, a plurality of broadband microphones that can be used as general microphones provided to an electronic device are used in a case where information is input by using an ultrasonic generating device. Each of the right-eye display device 20R and the left-eye display device 20L is for displaying a predetermined image and is provided in such a manner that it is not very clearly visible for a user when the user wearing the main body 10 on his or her head looks straight ahead and that it becomes clearly visible for the user only when the user moves his or her forward-looking eyes away.