<P> In the fourth photo, the inside of the optics package can be seen . Note that since this is a CD - ROM drive, there is only one laser, which is the black component mounted to the bottom left of the assembly . Just above the laser are the first focusing lens and prism that direct the beam at the disc . The tall, thin object in the center is a half - silvered mirror that splits the laser beam in multiple directions . To the bottom right of the mirror is the main photodiode that senses the beam reflected off the disc . Above the main photodiode is a second photodiode that is used to sense and regulate the power of the laser . </P> <P> The irregular orange material is flexible etched copper foil supported by thin sheet plastic; these are "flexible printed circuits" that connect everything to the electronics (which is not shown). </P> <P> Most optical drives are backward compatible with their ancestors up to CD, although this is not required by standards . </P> <P> Compared to a CD's 1.2 mm layer of polycarbonate, a DVD's laser beam only has to penetrate 0.6 mm in order to reach the recording surface . This allows a DVD drive to focus the beam on a smaller spot size and to read smaller pits . DVD lens supports a different focus for CD or DVD media with same laser . With the newer Blu - ray disc drives, the laser only has to penetrate 0.1 mm of material . Thus the optical assembly would normally have to have an even greater focus range . In practice, the Blu - ray optical system is separate from the DVD / CD system . </P>

Windows can natively play dvds in which of the following operating systems