HOLOGRAPHIC ROM SYSTEM, PARTICULARLY CONCERNED WITH REDUCING INTENSITY DISTRIBUTION DIFFERENCES BETWEEN A REFERENCE LIGHT AND A SIGNAL LIGHT BY SUPPLYING THE REFERENCE LIGHT HAVING UNIFORM INTENSITY DISTRIBUTIONS TO AN OPTICAL RECORDING MEDIUM

摘要

PURPOSE: A holographic ROM system is provided to make reference lights having uniform intensity distributions incident on an optical recording medium by using a conical mirror having reflecting surfaces with different reflectivity distributions, thereby recording data having uniform diffraction efficiency on the medium. CONSTITUTION: A light source(10) generates a laser beam requested for holography. A PBS(Polarizer Beam Splitter)(16) transmits signal lights among laser lights emitted from the light source(10), and reflects reference lights. The first reflective mirror(20) reflects the transmitted signal lights to the first optical path. A mask(34) modulates the reflected signal lights into predetermined data patterns, and radiates the patterns on a holographic medium(32). The second reflective mirror(28) radiates the reflected reference lights via the second and third optical paths. A conical mirror(50) has reflecting surfaces with different reflectivity distributions, reflects the reference lights to the reflecting surfaces, and radiates the reference lights having uniform intensity distributions on the holographic medium(32).