Patent ID: 7719947

Claim:
A reading device for holographic storage, comprising: a light source for providing a light beam; a light-directing component, disposed on a transmission path of the light beam emitted from the light source, wherein the light-directing component enables the light beam to get incidence at a holographic storage medium in a reading angle to generate a data beam; an optical sensor, located on a transmission path of the data beam for reading the data beam and reproducing a stored data; and a prism, disposed between the light source and the holographic storage medium for fine-adjusting the reading angle, wherein the prism has a light incident surface and a tight emerging surface, the light beam enters the prism from the light incident surface and emits out of the prism from the light emerging surface, the prism is rotatable about a rotation axis perpendicular to the transmission path of the light beam, the prism and the light beam satisfy the following formula: √{square root over ( n 2 −sin 2 I 1 )}×sin A −cos A sin I 1 <1 wherein I 1 is an angle of incidence of the light beam entering the prism, A is a vertex angle between the light incident surface and the light emerging surface and n is a refractive index of the prism.