Coating processes – Optical element produced
Reexamination Certificate
1999-08-26
2002-11-05
Chen, Bret (Department: 1762)
Coating processes
Optical element produced
C427S282000, C427S571000, C427S585000, C204S192110, C204S192260
Reexamination Certificate
active
06475557
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for manufacturing an optical filter having a single layer or multiple layers of dielectric material deposited on a substrate.
2. Description of the Background Art
Conventionally, a dielectric single layer film filter or dielectric multi-layer film filter formed by depositing dielectric materials on a glass substrate has been used as an optical filter for wavelength selection purpose. In such an optical filter, the transmission wavelength is made variable by varying the thickness of deposition of the dielectric material in a planar direction of the filter. Such an optical filter is manufactured by depositing the dielectric material while giving a planar distribution in the dielectric material deposition thickness at a time of depositing a dielectric film
2
on a disk shaped substrate
1
as shown in Fig. In this way, it is possible to realize an optical filter with the transmission wavelength varying with respect to an angle &thgr; (=0 to 2&pgr;) along the direction of rotation of the substrate
1
. See U.S. patent application Ser. No. 09/174,724, now U.S. Pat. No. 6,157,025, for further detail.
Such an optical filter should preferably have a characteristic that the transmission wavelength varies linearly with respect to the rotation angle &thgr; of the substrate
1
. In this regard, the conventional manufacturing method has employed a film formation method in which the deposition time of the dielectric material is varied linearly with respect to the angle &thgr;, i.e., in the spiral shape, by using a shutter
3
that can be opened or closed like fans as shown in FIG.
2
.
However, this method using the fan shaped shutter
3
of
FIG. 2
inevitably leaves a region of the angle &thgr; on which no dielectric material is deposited on the substrate
1
. Namely, even when the shutter
3
is fully opened, there remains a region which is continually covered by the shutter
3
as shown in
FIG. 3
, so that this region cannot be utilized as the optical filter. Also, in this method, it is difficult to smoothly move the shutter
3
up to a fully opened state, so that it has been impossible to deposit the dielectric material at sufficient precision. For this reason, it has been impossible to realize an optical filter in which almost the entire range of the angle &thgr; is utilizable as the optical filter.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a method for manufacturing an optical filter capable of manufacturing an optical filter in such a manner that the transmission wavelength varies linearly with respect to the angle &thgr; in the rotation direction of the substrate and that almost the entire range of the angle &thgr; is utilizable as the optical filter.
According to one aspect of the present invention there is provided a method for manufacturing a disk shaped optical filter, comprising the steps of: providing a mask over a substrate, the mask being capable of being rotated relatively with respect to the substrate coaxially on a plane parallel to the substrate and the mask having an aperture extending along a radius direction with an aperture angle &phgr;; and depositing a dielectric material in a single layer or multiple layers on the substrate from the mask side within a deposition chamber, while relatively rotating the mask with respect to the substrate at least once at a non-constant angular speed during a formation of the single layer or the multiple layers on the substrate.
According to another aspect of the present invention there is provided a method for manufacturing a disk shaped optical filter, comprising the steps of: providing a mask over a substrate, the mask being capable of being rotated relatively with respect to the substrate coaxially on a plane parallel to the substrate and the mask extending along a radius direction to cover an angle &phgr;; and depositing a dielectric material in a single layer or multiple layers on the substrate from the mask side within a deposition chamber, while relatively rotating the mask with respect to the substrate at least once at a non-constant angular speed during a formation of the single layer or the multiple layers on the substrate.
Other features and advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 3530824 (1970-09-01), Illsley et al.
patent: 3859131 (1975-01-01), Miles
patent: 4022928 (1977-05-01), Piwczyk
patent: 4543910 (1985-10-01), Dobrowolski
patent: 5032461 (1991-07-01), Shaw et al.
patent: 5731898 (1998-03-01), Orzi et al.
patent: 5866204 (1999-02-01), Robbie et al.
patent: 5872655 (1999-02-01), Seddon et al.
patent: 5214426 (1977-12-01), None
patent: 3-2802 (1991-01-01), None
patent: 3-002802 (1991-01-01), None
patent: 8 86914 (1996-04-01), None
patent: 9-243822 (1997-09-01), None
patent: 9-324267 (1997-12-01), None
patent: 10-110259 (1998-04-01), None
“Synchro-Scanned Rotating Tunable Optical Disk Filter for Wavelength Discrimination”, Katagiri,IEEE Photonics Technology Letters,vol. 10, No. 1, Mar. 1998 pp 400-402.
“Circularly Wedged Optical Coatings”, Thelen,Applied Optics,vol. 4, No. 8, Aug. 1965 pp 977-985.
Katagiri Yoshitada
Mori Kunihiko
Chen Bret
Kilpatrick & Stockton LLP
Nippon Telegraph and Telephone Corporation
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