Patent Number: 
Section: claims

1. A focusing and shielding device for an encephalic photon knife, comprising a ray source body, a switch and an armet; said ray source body being a hemispherical shell with a certain thickness having a ray source cavity for placing a ray source and a pre-collimation hole for collimating a ray; said ray source cavity being defined on an outer surface of the hemispherical shell, and said pre-collimation hole being defined on an inner surface of the hemispherical shell and connected with said ray source cavity;said switch is defined inside the body of said ray source, and an outer surface of said switch being hemispherical shape, a middle collimation hole being set on the switch;said armet being deposited inside said switch, an inner surface of said armet is in a columnar shape, an end collimation hole being defined on said armet;a therapy path being defined when said middle collimation hole connecting said pre-collimation hole with said end collimation hole together. 2. The focusing and shielding device for an encephalic photon knife of claim 1, wherein an inner surface of said switch is in hemispherical shape, and is the same shape as an outer surface of the armet. 3. The focusing and shielding device for an encephalic photon knife of claim 2, wherein said ray source body and said switch can be turned correspondingly to each other to shut down said therapy path. 4. The focusing and shielding device for an encephalic photon knife of claim 1, wherein an inner surface of said switch is in columnar shape, and is the same shape as an outer surface of said armet. 5. The focusing and shielding device for an encephalic photon knife of claim 4, wherein said ray source body and said switch can be turned correspondingly to each other to shut down said therapy path. 6. The focusing and shielding device for an encephalic photon knife of claim 1, wherein said ray source body and said switch can be turned correspondingly to each other to shut down said therapy path.