Some embodiments use several different types of networks to relay several different types of media content among several different computing devices. The ultrasound probe includes a cable, a probe head coupled to one end of the cable, and a connector coupled to the other end of the cable. 5\xb0, a second variable phase retarder with its optical axis aligned 45\xb0, a linear polarizer, a imaging sensor for sensing the intensity images of the sample, a controller and a computer. The present improved DVD or CD case has very few components which are characterized by great simplicity whereby low manufacturing and assembly cost is achieved, without sacrificing reliability and resistance to breakage or malfunctioning.