[54] DIFFRACTIVE OPTICAL ELEMENT [75] Inventor: Tetsuya Ishii, Hachioji, Japan
[73] Assignee: Olympus Optical Company Ltd.,
Tokyo,Japan
[21] Appl. No.: 08/697,773
[22] Filed: Aug. 29, 1996
[30] Foreign Application Priority Data
Aug. 29, 1995 [JP] Japan 7-220753
May 31, 1996 [JP] Japan 8-138645
May 31, 1996 [JP] Japan 8-138646
[51] Int. CI.7 G02B 5/18; G02B 27/24
[52] U.S. CI 359/569; 359/565; 359/566;
359/574; 359/576
[58] Field of Search 359/565, 566,
359/569, 572, 574, 576
[56] References Cited
U.S. PATENT DOCUMENTS
4,426,130 1/1984 Knop 359/569
4,729,640 3/1988 Sakata 359/569
5,048,925 9/1991 Gerritsen et al 359/569
5,175,647 12/1992 Us .
FOREIGN PATENT DOCUMENTS
243503 2/1990 Japan .
A diffractive optical element including a stack of first, second and third optical regions or a stack of first, second, third and fourth optical regions, a first relief pattern formed between the first and second optical regions, and a second relief pattern formed between the second and third or between the third and fourth optical regions. The first and second relief patterns have substantially identical pitch distributions and are substantially aligned in a direction of an optical axis. Depths of the first and second relief patterns are set such that a wavelength dependency of diffraction efficiency can be decreased over a wavelength range to be used. It is possible to manufacture in a simple manner at a low cost a diffractive optical element in which undesired flares and ghosts are suppressed.
7 Claims, 20 Drawing Sheets
