Title:
RING-LIKE ND FILTER HAVING RECESSED SURFACE
Document Type and Number:
Japanese Patent JP3131828
Kind Code:
B2
Abstract:
PROBLEM TO BE SOLVED: To remove the occurrence of focal movement at the time of releasing and minimally stopping a mechanical diaphragm by providing a recessed surface in the direction for canceling the lens action by a laminated circular ND filter film on the opposite surface of the lamination forming surface of the circular ND filter film on a transparent substrate.
SOLUTION: A recessed surface 15 is formed on the surface opposite to the lamination forming surface of ND filter films (light absorbing films) 12-14 on a transparent substrate 1. The curvature of the recessed surface 15 is determined so as to cancel the convex lens action by the ND filter films 12-14. The magnitude (magnitude of refractive index) of convex lens action by the ND filter films 12-14 is calculated by performing light ray tracing based on the refractive indices, diameters and thicknesses of the ND filter films 12-14. The curvature of the recessed surface 15 is determined so as to cancel the convex lens action by the ND filter films 12-14. The recessed surface 15 is formed by subjecting the transparent substrate made of a glass material to grinding.
Inventors:
Masayuki Arai
Toru Shikano
Takayasu Shishido
Toru Shikano
Takayasu Shishido
Application Number:
JP17951597A
Publication Date:
February 05, 2001
Filing Date:
July 04, 1997
Export Citation:
Assignee:
Asahi Precision Co., Ltd.
International Classes:
G02B5/00; G03B9/02; G03B11/00; (IPC1-7): G02B5/00; G03B9/02; G03B11/00
Domestic Patent References:
| JP273201A |
Attorney, Agent or Firm:
Kunio Miura
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