SEALED HOLOGRAM DISC

PURPOSE:To give a very stout structure and setting the thickness of a cover glass relatively thin because of the cover glass supported at the inside and outside circumferential parts by fixing a hologram disc and the cover glass along respective inside and outside circumferential parts with an adhesive. CONSTITUTION:A positive photoresist is coated onto the surface of the disc 1 having about a 100mm. outside diameter, about 3mm. thickness, and an about 30mm. center hole 1a diameter, and photographing is performed by a two-luminous flux interference method using an He-Cd laser, and developed to form a hologram diffraction grating 2. Meanwhile, a reflection preventing film is provided on both surfaces of the cover glass 3 having about the 100mm. outside diameter, about the 2mm. thickness, and a 30mm. transmission hole 3a. Adhesives 4a and 4b containing a pearl 5 which functions as spacer are formed with about 3mm. width on the concentric circles in the outside and the inside circumferential parts of the cover glass 3. After defoaming and prehardening, the disc 1 and the cover glass 3 are incorporated to surround the hologram diffraction grating 2, are pressurized with prescribed pressure to form them into one body.