| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a preform from which a high precision optical element can be obtained. <P>SOLUTION: The preform for precision press forming is made of glass and a rotary body having one rotary symmetric axis and has a first face including a first intersecting point of two intersecting points where the rotary symmetric axis intersects with the surfaces and having an outwardly projected shape, and a second face including a second intersecting point of the two intersecting points and having an outwardly projected shape. When the minimum curvature radius of the inner part of a circle having the first intersecting point of the first face as the center and a diameter of 2/3 of the outer diameter is defined as R<SB>1(min)</SB>, the minimum curvature radius and the maximum curvature radius of the inner part of a circle having the second intersecting point of the second face as the center and a diameter of 1/3 of the outer diameter are defined as R<SB>2(min)</SB>and R<SB>2(max)</SB>, respectively, the maximum curvature radius of the outer part of a circle having the second intersecting point of the second face as the center and a diameter of 2/3 of the outer diameter is defined as R<SB>3(max)</SB>, the distance between the first intersecting point and the gravity center is defined as H<SB>1</SB>, and the distance between the second intersecting point and the gravity center is defined as H<SB>2</SB>, the they have following relations: ¾R<SB>3(max)</SB>¾<¾R<SB>2(min)</SB>¾<¾R<SB>2(max)</SB>¾<¾R<SB>1(min)</SB>¾ and H<SB>1</SB><¾R<SB>1(min)</SB>¾. <P>COPYRIGHT: (C)2007,JPO&INPIT</p> |
