| 摘要 |
PROBLEM TO BE SOLVED: To provide an air gap prism which has an air spacing having higher accuracy and is more miniaturized by arranging an air spacing holding member larger than the part where opposite surfaces overlap so as to sandwich the member and removing the parts which do not correspond to the opposite surfaces. SOLUTION: The air spacing holding member 11 consists of a thin sheet-like polyimide film and is provided with holes 11a, 11b for positioning and a rectangular hole 11c through which luminous fluxes pass. After a first glass member is installed on a first positioning member, the air spacing holding member 11 is placed thereon. At this time, the positioning of the air spacing holding member 11 at the time of installation is previously executed by inserting its hole parts 11a, 11b onto the projections on the first positioning member. The air spacing holding member 11 is exactly installed to the prescribed position with the simple work by fitting of the projections and the holes 11a, 11b. Next, the air spacing holding member 11 is sandwiched by the second glass member. The parts protruding from the glass members are removed by a method, such as cutting, after temporally fixing of the glass members.
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