Holographic ROM system

1. A holographic ROM system, comprising:

a lens unit for filtering and collimating an output radiation diffracted from a holographic disk in order to produce an output data beam,

wherein the lens unit includes an objective lens for collimating the output radiation and a filtering film for filtering the output radiation, wherein the objective lens and the filtering film are formed in a single body, and

wherein the filtering film is provided with a light-impermeable region for blocking at least one cross talk beam included in the output radiation and a light-permeable region for allowing a reconstruction signal beam included in the output radiation to pass through the filtering film.

2. The holographic ROM system of claim 1 , wherein the light-permeable region is disposed on a central portion of the objective lens.

3. The holographic ROM system of claim 2 , wherein the light-permeable region has a shape of square whose width is substantially equal to or greater than that of the reconstruction signal beam and less than a distance between the reconstruction signal beam and one of the cross talk beams just beside the reconstruction signal beam.

4. The holographic ROM system of claim 3 , wherein the light-permeable region is an opening formed in the filtering film.

5. The holographic ROM system of claim 4 , wherein the filtering film is coated on the objective lens.

6. The holographic ROM system of claim 4 , wherein the filtering film is embedded in the objective lens.

7. A holographic ROM system, comprising:

a holographic disk which stores holograms;

a disk rotating device for rotating the holographic disk;

a pickup module for optically reading the holograms and producing electrical signals in response to the read holograms;

a signal processing unit for processing the electrical signals from the pickup module; and

a control unit for controlling the disk rotating device and the pickup module,

wherein the pickup module includes a laser source for generating a laser beam and a lens unit which has an objective lens for collimating an output radiation diffracted from the holographic disk, and a filtering film for preventing a cross talk beam included in the output radiation from passing through the lens unit while allowing a reconstructed signal beam included in the output radiation to pass therethrough, wherein the objective lens and the filtering film are formed in a single body, and

wherein the filtering film is provided with a light-impermeable region for blocking the cross talk beam and a light-permeable region for allowing the reconstruction signal beam to pass through the lens unit.

8. The holographic ROM system of claim 7 , wherein the light-permeable region has a width substantially equal to or greater than that of the reconstruction signal beam and less than a distance between the reconstruction signal beam and one of the cross talk beams just beside the reconstruction signal beam.

9. The holographic ROM system of claim 8 , wherein the filtering film is coated on the objective lens.

10. The holographic ROM system of claim 8 , wherein the filtering film is embedded in the objective lens.