U.S. patent application number 10/424264 was filed with the patent office on 2004-11-04 for two-wavelength antireflection film and objective lens coated with two-wavelength antireflection film.
This patent application is currently assigned to Olympus Optical Co. , Ltd.. Invention is credited to Kohsaka, Masato, Kurata, Kiyonobu, Watanabe, Tadashi, Yamashita, Hideto, Yamauchi, Takao.
Application Number | 20040218282 10/424264 |
Document ID | / |
Family ID | 33554333 |
Filed Date | 2004-11-04 |
United States Patent
Application |
20040218282 |
Kind Code |
A1 |
Watanabe, Tadashi ; et
al. |
November 4, 2004 |
TWO-WAVELENGTH ANTIREFLECTION FILM AND OBJECTIVE LENS COATED WITH
TWO-WAVELENGTH ANTIREFLECTION FILM
Abstract
A two-wavelength antireflection film to prevent light in
two-wavelength regions of a deep-ultraviolet region and a region
from a visible region to the near-infrared region on a surface of a
substrate by coating the two-wavelength antireflection film on the
surface of the substrate which penetrates light from the
deep-ultraviolet region to the near-infrared region, comprising a
first thin film which is formed on the substrate, and has a
refractive index of 1.6 to 2.0 and optical film thickness of
0.4.lambda. to 0.7.lambda. for design main wavelength (.lambda.), a
second thin film which is formed on the first thin film, and has a
refractive index of 1.35 to 1.55 and an optical film thickness of
0.05.lambda. to 0.6.lambda. for the design main wavelength
.lambda., a third thin film which is formed on the second thin
film, and has a refractive index of 1.6 to 2.0 and an optical film
thickness of 0.1.lambda. to 0.5.lambda. for the design main
wavelength .lambda., and a fourth thin film which is formed on the
third thin film, and has a refractive index of 1.35 to 1.55 and an
optical film thickness of 0.2.lambda. to 0.35.lambda. for the
design main wavelength .lambda..
Inventors: |
Watanabe, Tadashi;
(Kamiina-gun, JP) ; Yamashita, Hideto;
(Kamiina-gun, JP) ; Kohsaka, Masato;
(Komagane-shi, JP) ; Yamauchi, Takao; (Ina-shi,
JP) ; Kurata, Kiyonobu; (Hachioji-shi, JP) |
Correspondence
Address: |
FRISHAUF, HOLTZ, GOODMAN & CHICK, PC
767 THIRD AVENUE
25TH FLOOR
NEW YORK
NY
10017-2023
US
|
Assignee: |
Olympus Optical Co. , Ltd.
Tokyo
JP
|
Family ID: |
33554333 |
Appl. No.: |
10/424264 |
Filed: |
April 28, 2003 |
Current U.S.
Class: |
359/656 |
Current CPC
Class: |
G02B 5/283 20130101;
G02B 1/115 20130101; G02B 5/281 20130101 |
Class at
Publication: |
359/656 |
International
Class: |
G02B 021/02; G02B
015/14 |
Claims
1. A two-wavelength antireflection film for antireflection in
two-wavelength regions of light between 200 nanometers and 850
nanometers wherein one of the two-wavelength regions ranges from
about 200 nanometers to 350 nanometers and includes a design main
wavelength and the other two-wavelength region extends from about
650 nanometers to 850 nanaometers comprising: a substrate which is
transparent in wavelength regions in which the substrate is to be
used; a first thin film which is formed on the substrate, and has a
refractive index of 1.6 to 2.0 and optical film thickness of
0.4.lambda. to 0.7.lambda. for the design main wavelength
(.lambda.); a second thin film which is formed on the first thin
film, and has a refractive index of 1.35 to 1.55 and an optical
film thickness of 0.05.lambda.to 0.6.lambda. for the design main
wavelength .lambda.; a third thin film which is formed on the
second thin film, and has a refractive index of 1.6 to 2.0 and an
optical film thickness of 0.1.lambda. to 0.5.lambda. for the design
main wavelength .lambda.; and a fourth thin film which is formed on
the third thin film, and has a refractive index of 1.35 to 1.55 and
optical film thickness of 0.2.lambda. to 0.35.lambda. for design
main wavelength .lambda..
2. The two-wavelength antireflection film according to claim 1,
wherein, the substrate is quartz glass or fluorite glass.
3. The two-wavelength antireflection film according to claim 1,
wherein, the first thin film and the third thin film contain
material which has a plurality of components chosen by a group of
Al.sub.2O.sub.3, LaF.sub.3, NdF.sub.3, YF.sub.3, La.sub.2O.sub.3,
and mixture or compound thereof, and the second thin film and the
fourth thin film contain material which has a plurality of
components chosen by a group of MgF.sub.2, S.sub.iO.sub.2, NaF,
LiF, and mixture or compound thereof.
4. The two-wavelength antireflection film according to claim 1,
wherein an incident angle of the light of the design main
wavelength is set within a range of 0.degree. to 70.degree..
5. The two-wavelength antireflection film according to claim 1,
wherein the design main wavelength is 248 nm.
6. The two-wavelength antireflection film according to claim 5,
wherein a wavelength which performs antireflection includes two
wavelength regions of a wavelength in vicinity of main design
wavelength and a wavelength from 650 to 800 nm, an optical film
thickness of the first thin film is 0.4.lambda. to 0.6.lambda., an
optical film thickness of the second thin film is 0.4.lambda. to
0.6.lambda., an optical film thickness of the third thin film is
0.1.lambda. to 0.3.lambda., and an optical film thickness of the
fourth thin film is from 0.35.lambda. to 0.2.lambda..
7. The two-wavelength antireflection film according to claim 5,
wherein, a wavelength which performs antireflection includes two
wavelength regions of a wavelength in vicinity of main design wave
length and a wavelength in the vicinity of 750 nm, the first thin
film and the third thin film include mixture of Al.sub.2O.sub.3 and
La.sub.2O.sub.3, and the second thin film and fourth thin film
include MgF.sub.2, an optical film thickness of the first thin film
is 0.4.lambda. to 0.6.lambda., an optical film thickness of the
second thin film is 0.4.lambda. to 0.6.lambda., an optical film
thickness of the third thin film is 0.2.lambda. to 0.3.lambda., and
an optical film thickness of the fourth thin film is 0.2.lambda. to
0.3.times..
8. The two-wavelength antireflection film according to claim 5,
wherein, a wavelength which performs antireflection includes two
wavelength regions of a wavelength in vicinity of main design
wavelength and a wavelength from 550 to 650 nm, an optical film
thickness of the first thin film is 0.5.lambda. to 0.7.lambda., an
optical film thickness of the second thin film is 0.05.lambda. to
0.2.lambda., an optical film thickness of the third thin film is
0.25.lambda. to 0.5.lambda., and an optical film thickness of the
fourth thin film is 0.2.lambda. to 0.35.lambda..
9. The two-wavelength antireflection film according to claim 5,
wherein a wavelength which performs antireflection includes two
wavelength regions of a wavelength in vicinity of main design wave
length and a wavelength in vicinity of 600 nm, the first thin film
and the third thin film include mixture of Al.sub.2O.sub.3, and
La.sub.2O.sub.3, and the second thin film and fourth thin film
include MgF.sub.2, an optical film thickness of the first thin film
is 0.6.lambda. to 0.7.lambda., an optical film thickness of the
second thin film is 0.05.lambda. to 0.1.lambda., an optical film
thickness of the third thin film is 0.25.lambda. to 0.35.lambda.,
and an optical film thickness of the second thin film is
0.25.lambda. to 0.35.lambda..
10. An objective lens used for an optical equipment, which performs
an observation by the light of the deep-ultraviolet region
wavelength of 300 nm or less and has a focusing mechanism (auto
focus) in the wavelength region from a visible region to a
near-infrared region, comprising a plurality of single lenses,
wherein each of the plurality of single lenses has a two-wavelength
antireflection film according to claim 1 on the surface
thereof.
11. The objective lens according to claim 10, further comprising a
first lens group which contains a plurality of single lenses having
positive lens and negative lens whose medium are different from
each other and has negative power as a whole; and a second lens
group which is arranged from the first lens group to the object
side, and contains a plurality of single lenses having positive
lens and negative lens whose medium are different form each other,
wherein the first and second lens groups have air intervals between
the positive lens and negative lens, respectively, and a numerical
aperture is 0.7 or more.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a two-wavelength
antireflection film which prevents reflection for two-wavelength
regions of a deep-ultraviolet region and a region from a visible
region to a near-infrared region, and relates to an objective lens
for optical device with a high numerical aperture and a high
magnification, on which the two-wavelength antireflection film is
coated.
[0003] 2. Description of the Related Art
[0004] Recently, the magnetic head used for the semiconductor such
as CPU and the hard disk drive etc. is remarkably downsized, and
extremely high resolving power is required, to accurately detect
the defect of the product etc. in the inspection apparatus used for
these inspections.
[0005] An optical microscope using a visible ray is used for the
above-mentioned inspection apparatus in general. In this case, a
resolution of the optical microscope is determined by 0.61.lambda.
(wavelength/NA) Therefore, it is necessary to enlarge an NA of the
objective lens or to shorten the wavelength of the ray in order to
obtain an enough resolution.
[0006] However, recently, enlarging NA of object lens is near
limitation. Therefore, to obtain further resolving power, a
microscope which shortens wavelength, i.e., a DUV microscope which
makes resolving power twice or more by using a deep-ultraviolet
region (Deep UV), has been put to practical use.
[0007] By the way, the DUV microscope uses the laser and/or a
general-purpose arc lamp such as the mercury lamps, as a light
source. The laser outputs light with high intensity ray at a
specific wavelength, but apparatus thereof becomes large and
expensive. On the other hand, the general-purpose arc lamp outputs
light with low intensity at a specific wavelength, but apparatus
thereof can be downsized and becomes cheap.
[0008] Then, it is noted that the general-purpose arc lamp emits
light in wideband. The general-purpose arc lamp, that an optical
amount is secured by widening the wavelength region, is considered
to be used as a light source. However, when such a general-purpose
arc lamp is used as the light source, it is necessary to compensate
the chromatic aberration. Therefore, the single lens having the
medium with different refractive index, for example, a lens which
can compensate the chromatic aberration by bonding, for instance,
fluorite glass and quartz glass with the bonding agent has been put
to practical use as the DUV objective lens used for the DUV
microscope.
[0009] However, irradiation of light in the DUV region degrades the
bonding agent to reduce the transmittance of the objective lens in
the lens in which fluorite glass and quartz glass are bonded.
[0010] Therefore, recently, as disclosed in, for example, Japanese
Patent Application KOKAI Publication No. 11-167067 and Japanese
Patent Application KOKAI Publication No. 2001-318317, the objective
lens with no bonding to correct the chromatic aberration using a
single lens of the medium with a different refractive index
(fluorite glass and quartz glass), and to prevent the reduce in
transmittance caused by the degradation of the adhesive by not
bonding between these single lenses is developed.
[0011] By the way, the objective lens of no bonding as mentioned
above is used to observe the sample image by the light of the
deep-ultraviolet region wavelength (for instance, 248 nm). In
addition, the objective lens of no bonding might be used to
correspond also to the automatic focusing by using the light of
wavelength from the visible region to the near-infrared region (for
instance, 650 to 1000 nm), so-called auto focus function
(hereafter, AF).
[0012] In this case, the objective lens should have high
transmittance simultaneously with the light of the deep-ultraviolet
region wavelength and for the light of wavelength from the visible
region to the near-infrared region.
BRIEF SUMMARY OF THE INVENTION
[0013] The two-wavelength antireflection film to prevent light in
two-wavelength regions of a deep-ultraviolet region and a region
from a visible region to the near-infrared region on a surface of a
substrate by coating the two-wavelength antireflection film on the
surface of the substrate which penetrates light from the
deep-ultraviolet region to the near-infrared region according to
one aspect of the present invention is characterized by comprising:
a first thin film which is formed on the substrate, and has a
refractive index of 1.6 to 2.0 and optical film thickness of
0.4.lambda. to 0.7.lambda. for design main wavelength (.lambda.); a
second thin film which is formed on the first thin film, and has a
refractive index of 1.35 to 1.55 and an optical film thickness of
0.05.lambda. to 0.6.lambda. for the design main wavelength
.lambda.; a third thin film which is formed on the second thin
film, and has a refractive index of 1.6 to 2.0 and an optical film
thickness of 0.1.lambda. to 0.5.lambda. for the design main
wavelength .lambda.; and a fourth thin film which is formed on the
third thin film, and has a refractive index of 1.35 to 1.55 and an
optical film thickness of 0.2.lambda. to 0.35.lambda. for the
design main wavelength .lambda..
[0014] The objective lens used for an optical equipment, which
performs an observation by the light of the deep-ultraviolet region
wavelength of 300 nm or less and has a focusing mechanism (auto
focus) in the wavelength region from a visible region to a
near-infrared region according to one aspect of the present
invention is characterized by comprising a plurality of single
lenses, wherein each of the plurality of single lenses has a
two-wavelength antireflection film according to claim 1 on the
surface thereof.
[0015] Advantages of the invention will be set forth in the
description which follows, and in part will be obvious from the
description, or may be learned by practice of the invention.
Advantages of the invention may be realized and obtained by means
of the instrumentalities and combinations particularly pointed out
hereinafter.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0016] The accompanying drawings, which are incorporated in and
constitute a part of the specification, illustrate embodiments of
the invention, and together with the general description given
above and the detailed description of the embodiments given below,
serve to explain the principles of the invention.
[0017] FIG. 1 is a figure showing a schematic configuration of the
two-wavelength antireflection film according to the first
embodiment of the present invention;
[0018] FIG. 2 is a figure showing spectral reflectance
characteristic of two-wavelength antireflection film according to
the first embodiment of the present invention;
[0019] FIG. 3 is a figure showing spectral reflectance
characteristic of two-wavelength antireflection film according to
the second embodiment of the present invention;
[0020] FIG. 4 is a figure showing spectral reflectance
characteristic of two-wavelength antireflection film according to
the third embodiment of the present invention;
[0021] FIG. 5 is a figure showing change of 246 nm reflectance
according to the incident angle in the first to third embodiments
of the present invention;
[0022] FIG. 6 is a figure showing spectral reflectance
characteristic of two-wavelength antireflection film according to
the fourth embodiment of the present invention;
[0023] FIG. 7 is a figure showing spectral reflectance
characteristic of two-wavelength antireflection film according to
the fifth embodiment of the present invention;
[0024] FIG. 8 is a figure showing spectral reflectance
characteristic of two-wavelength antireflection film according to
the sixth embodiment of the present invention;
[0025] FIG. 9 is a figure showing change of 248 nm reflectance
according to the incident angle in the fourth to seventh
embodiments of the present invention;
[0026] FIG. 10 is a figure showing spectral reflectance
characteristic of two-wavelength antireflection film according to
the seventh embodiment of the present invention;
[0027] FIG. 11 is a figure showing spectral reflectance
characteristic of two-wavelength antireflection film according to
the eighth embodiment of the present invention;
[0028] FIG. 12 is a figure showing spectral reflectance
characteristic of two-wavelength antireflection film according to
the ninth embodiment of the present invention;
[0029] FIG. 13 is a figure showing spectral reflectance
characteristic of two-wavelength antireflection film according to
the tenth embodiment of the present invention;
[0030] FIG. 14 is a figure showing change of 248 nm reflectance
according to the incident angle in the eighth to twelfth
embodiments of the present invention;
[0031] FIG. 15 is a figure showing spectral reflectance
characteristic of two-wavelength antireflection film according to
the eleventh embodiment of the present invention;
[0032] FIG. 16 is a figure showing spectral reflectance
characteristic of two-wavelength antireflection film according to
the twelfth embodiment of the present invention;
[0033] FIG. 17 is a figure showing spectral reflectance
characteristic of two-wavelength antireflection film in the first
comparison example to explain the present invention;
[0034] FIG. 18 is a figure showing spectral reflectance
characteristic of two-wavelength antireflection film in the second
comparison example to explain the present invention;
[0035] FIG. 19 is a figure showing a schematic configuration of the
objective lens used for the thirteenth embodiment of the present
invention;
[0036] FIG. 20 is a figure to explain the angle of the incident (or
output) light into (or from) the normal of the lens of the
thirteenth embodiment of the present invention;
[0037] FIG. 21 is a figure to explain an example of comparing
transmittance of the thirteenth embodiment of the present
invention;
[0038] FIG. 22 is a figure showing a schematic configuration of the
objective lens used for the fourteenth embodiment of the present
invention; and
[0039] FIG. 23 is a figure to explain an example of comparing
transmittance of the fourteenth embodiment of the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0040] Hereinafter, embodiments of the present invention will be
explained referring to the drawings.
[0041] (First Embodiment)
[0042] FIG. 1 shows a schematic configuration of the two-wavelength
antireflection film to which the first embodiment of the present
invention is applied. In FIG. 1, quartz glass, which is transparent
from the deep-ultraviolet region to the near-infrared region, is
used as a substrate material for the substrate 1. Thin films 2, 3,
4, and 5 are formed on the substrate 1 as two-wavelength
antireflection film to form a four-layer structure.
[0043] The film material and the film thickness of each of thin
films 2, 3, 4, and 5 is shown in (A) of Table 1. Table 1
collectively shows the film material and the film thickness
corresponding to the first to third embodiments ((A) to (C)) as
described later
1 TABLE 1 A B C Substrate 1 Quartz glass Quartz glass Quartz glass
Design wavelength .lambda. 248 nm 248 nm 248 nm Film Film Film Film
thickness thickness thickness material (.times..lambda.) Film
material (.times..lambda.) Film material (.times..lambda.) Thin
film 2 Al.sub.2O.sub.3 0.51 Al.sub.2O.sub.3 + La.sub.2O.sub.3 0.46
Al.sub.2O.sub.3 + La.sub.2O.sub.3 0.46 (Substance M2) (Substance
M3) Thin film 3 MgF.sub.2 0.46 MgF.sub.2 0.47 MgF.sub.2 0.50 Thin
film 4 Al.sub.2O.sub.3 0.16 Al.sub.2O.sub.3 + La.sub.2O.sub.3 0.26
Al.sub.2O.sub.3 + La.sub.2O.sub.3 0.16 (Substance M2) (Substance
M3) Thin film 5 MgF.sub.2 0.30 MgF.sub.2 0.25 MgF.sub.2 0.30
[0044] In (A) of Table 1, the film materials of thin films 2, 3, 4,
and 5, each of which forms each layer, are as follows.
Al.sub.2O.sub.3 whose refractive index in design main wavelength
(248 nm in the deep-ultraviolet region) is the middle refractive
index of about 1.7 is used to thin film 2 of the first layer and
thin film 4 of the third layer from the substrate 1. MgF.sub.2
whose refractive index in design main wavelength (248 nm in the
deep-ultraviolet region) is the low refractive index of about 1.4
is used to thin film 3 in the second layer and thin film 5 in the
fourth layer from the substrate 1. Each film thickness of these
thin films 2, 3, 4, and 5 is shown in (A) of Table 1.
[0045] FIG. 2 shows each spectral reflectance characteristic for
the two wavelength antireflection film made for trial purposes with
the configuration shown in (A) of Table 1, when changing the
incident angle of the light to 0.degree., 30.degree., 50.degree.,
and 65.degree., respectively. By changing the incident angle of the
light, the curve (a) of FIG. 5 is obtained as a result of
simulating the numerical value how the reflectance of the light of
design main wavelength (248 nm) is changed.
[0046] As is clear from FIG. 2, it becomes possible to perform
antireflection because reflectance becomes small in two-wavelength
region in the vicinity of 248 nm and within the range of 650 nm to
800 nm. It is also clear that the reflection of design main
wavelength (248 nm) is small in the range of 0.degree. to
70.degree. in incident angle of light as shown in curve (a) of FIG.
5. Therefore, by forming the two-wavelength antireflection film
configured with thin films 2, 3, 4, and 5 according to the first
embodiment on the substrate 1 of quartz glass which is transparent
from the deep-ultraviolet region to the near-infrared region, high
transmittance can be achieved for light in the deep-ultraviolet
region in the vicinity of design main wavelength (248 nm) and light
from the visible region to the near-infrared region in the vicinity
of the range of 650 nm to 800 nm, which are used for auto
focus.
[0047] (Second Embodiment)
[0048] The schematic configuration of the two-wavelength
antireflection film according to the second embodiment is similar
to that in FIG. 1, and the explanation will be described by using
FIG. 1.
[0049] The film material and the film thickness of each of thin
films 2, 3, 4, and 5 of two-wavelength antireflection films
configured as FIG. 1 is shown in (B) of Table 1.
[0050] In this case, the film materials of thin films 2, 3, 4, and
5, each of which forms each layer, are as follows The mixture of
Al.sub.2O.sub.3 and La.sub.2O.sub.3 with the middle refractive
index material is used to thin film 2 of the first layer and thin
film 4 of the third layer from the substrate 1. Specifically,
Substance M2 made by the Merck, which is the mixture of
Al.sub.2O.sub.3 and La.sub.2O.sub.3 whose refractive index is about
1.8 in design main wavelength (248 nm in the deep-ultraviolet
region) is used. MgF.sub.2 whose refractive index in design main
wavelength (248 nm in the deep-ultraviolet region) is the low
refractive index of about 1.4 is used to thin film 3 in the second
layer and thin film 5 in the fourth layer from the substrate 1
similar to the first embodiment. Each film thickness of these thin
films 2, 3, 4, and 5 is shown in (B) of Table 1.
[0051] FIG. 3 shows each spectral reflectance characteristic for
the two wavelength antireflection film made for trial purposes with
the configuration shown in (B) of Table 1, when changing the
incident angle of the light to 0.degree., 30.degree., 50.degree.,
and 65.degree., respectively. By changing the incident angle of the
light, the curve (b) of FIG. 5 is obtained as a result of
simulating the numerical value how the reflectance of the light of
design main wavelength (248 nm) is changed.
[0052] As is clear from FIG. 3, it becomes possible to perform
antireflection because reflectance becomes small in two-
two-wavelength region in the vicinity of 248 nm and within the
range of 650 nm to 800 nm. It is also clear that the reflection of
design main wavelength (248 nm) is small in the range of 0.degree.
to 70.degree. in incident angle of light as shown in curve (b) of
FIG. 5.
[0053] Therefore, high transmittance can be achieved for light in
the deep-ultraviolet region in the vicinity of design main
wavelength (248 nm) and light from the visible region to the
near-infrared region in the vicinity of the range of 650 nm to 800
nm, which are used for auto focus similar to that described in the
first embodiment.
[0054] (Third Embodiment)
[0055] The schematic configuration of the two-wavelength
antireflection film according to the third embodiment is similar to
that in FIG. 1, and the explanation will be described by using FIG.
1.
[0056] The film material and the film thickness of each of thin
films 2, 3, 4, and 5 of two-wavelength antireflection films
configured as FIG. 1 is shown in (C) of Table 1.
[0057] In this case, the film materials of thin films 2, 3, 4, and
5, each of which forms each layer, are as follows. The mixture of
Al.sub.2O.sub.3 and La.sub.2O.sub.3 with the middle refractive
index material, whose mixture ratio of Al.sub.2O.sub.3 and
La.sub.2O.sub.3 and refractive index are different from those in
the second embodiment, is used to thin film 2 of the first layer
and thin film 4 of the third layer from the substrate 1.
Specifically, Substance M3 made by the Merck, which as the mixture
of Al.sub.2O.sub.3 and La.sub.2O.sub.3 whose refractive index in
design main wavelength (248 nm in the deep-ultraviolet region) is
about 1.95, is used. MgF.sub.2 whose refractive index in design
main wavelength (248 nm in the deep-ultraviolet region) is the low
refractive index of about 1.4 is used to thin film 3 in the second
layer and thin film 5 in the fourth layer from the substrate 1
similar to the firsts embodiment. Each film thickness of these thin
films 2, 3, 4, and 5 is shown in (C) of Table 1.
[0058] FIG. 4 shows each spectral reflectance characteristic for
the two wavelength antireflection film made for trial purposes with
the configuration shown in (C) of Table 1, when changing the
incident angle of the light to 0.degree., 30.degree., 50.degree.,
and 65.degree., respectively. By changing the incident angle of the
light, the curve (c) of FIG. 5 is obtained as a result of
simulating the numerical value how the reflectance of the light of
design main wavelength (248 nm) is changed.
[0059] As is clear from FIG. 4, it becomes possible to perform
antireflection because reflectance becomes small in two-
two-wavelength region in the vicinity of 248 nm and within the
range of 650 nm to 800 nm. It is also clear that the reflection of
design main wavelength (248 nm) is small in the range of 0.degree.
to 70.degree. in incident angle of light as shown in curve (c) of
FIG. 5.
[0060] Therefore, high transmittance can be achieved for light in
the deep-ultraviolet region in the vicinity of design main
wavelength (248 nm) and light from the visible region to the
near-infrared region in the vicinity of the range of 650 nm to 800
nm, which are used for auto focus similar to that described in the
first embodiment.
[0061] (Fourth Embodiment)
[0062] The schematic configuration of the two-wavelength
antireflection film according to the fourth embodiment is similar
to that in FIG. 1, and the explanation will be described by using
FIG. 1. In this case, fluorite glass, which is transparent from the
deep-ultraviolet region to the near-infrared region, is used as a
substrate material for the substrate 1.
[0063] The film material and the film thickness of each of thin
films 2, 3, 4, and 5 of two-wavelength antireflection films
configured as FIG. 1 is shown in (A) of Table 2. Table 2
collectively shows the film material and the film thickness
corresponding to the fourth to fifth embodiments ((A) to (C)) as
described later.
2 TABLE 2 A B C Substrate 1 Fluorite glass Fluorite glass Fluorite
glass Design wavelength .lambda. 248 nm 248 nm 248 nm Film Film
Film Film thickness thickness thickness material (.times..lambda.)
Film material (.times..lambda.) Film material (.times..lambda.)
Thin film 2 Al.sub.2O.sub.3 0.47 Al.sub.2O.sub.3 + La.sub.2O.sub.3
0.48 Al.sub.2O.sub.3 + La.sub.2O.sub.3 0.49 (Substance M2)
(Substance M3) Thin film 3 MgF.sub.2 0.41 MgF.sub.2 0.44 MgF.sub.2
0.49 Thin film 4 Al.sub.2O.sub.3 0.20 Al.sub.2O.sub.3 +
La.sub.2O.sub.3 0.27 Al.sub.2O.sub.3 + La.sub.2O.sub.3 0.11
(Substance M2) (Substance M3) Thin film 5 MgF.sub.2 0.27 MgF.sub.2
0.25 MgF.sub.2 0.31
[0064] In (A) of Table 2, the film materials of thin films 2, 3, 4,
and 5, each of which forms each layer, are similar to the first
embodiment. Al.sub.2O.sub.3 whose refractive index in design main
wavelength (248 nm in the deep-ultraviolet region) is the middle
refractive index of about 1.7 is used to thin film 2 of the first
layer and thin film 4 of the third layer from the substrate 1.
MgF.sub.2 whose refractive index in design main wavelength (248 nm
in the deep-ultraviolet region) is the low refractive index of
about 1.4 is used to thin film 3 in the second layer and thin film
5 in the fourth layer from the substrate 1. Each film thickness of
these thin films 2, 3, 4, and 5 is shown in (A) of Table 2.
[0065] FIG. 6 shows spectral reflectance characteristic for the two
wavelength antireflection film made for trial purposes with the
configuration shown in (A) of Table 2, when the incident angle of
light is assumed to be 0.degree. (vertical). By changing the
incident angle of the light, the curve (a) of FIG. 9 is obtained as
a result of simulating the numerical value how the reflectance of
the light of design main wavelength (248 nm) is changed.
[0066] As is clear from FIG. 6, it becomes possible to perform
antireflection because reflectance becomes small in two-wavelength
region in the vicinity of 248 nm and within the range of 650 nm to
800 nm. It is also clear that the reflection of design main
wavelength (248 nm) is small in the range of 0.degree. to
70.degree. in incident angle of light as shown in curve (a) of FIG.
9. As a result, a similar advantage to the first embodiment can be
expected.
[0067] (Fifth Embodiment)
[0068] The schematic configuration of the two-wavelength
antireflection film according to the fifth embodiment is similar to
that in FIG. 1, and the explanation will be described by using FIG.
1. In this case, fluorite glass, which is transparent from the
deep-ultraviolet region to the near-infrared region, is used as a
substrate material for the substrate 1.
[0069] The film material and the film thickness of each of thin
film 2, 3, 4, and 5 of two-wavelength antireflection films
configured as FIG. 1 is shown in (B) of Table 2.
[0070] In this case, the film materials of thin films 2, 3, 4, and
5, each of which forms each layer, are similar to the second
embodiment. Substance M2 made by the Merck, which is the mixture of
Al.sub.2O.sub.3 and La.sub.2O.sub.3 whose refractive index is about
1.8 in design main wavelength (248 nm in the deep-ultraviolet
region) is used to thin film 2 of the first layer and thin film 4
of the third layer from the substrate 1. MgF.sub.2 whose refractive
index in design main wavelength (248 nm in the deep-ultraviolet
region) is the low refractive index of about 1.4 is used to thin
film 3 in the second layer and thin film 5 in the fourth layer from
the substrate 1. Each film thickness of these thin films 2, 3, 4,
and 5 is shown in (B) of Table 2.
[0071] FIG. 7 shows spectral reflectance characteristic for the two
wavelength antireflection film made for trial purposes with the
configuration shown in (B) of Table 2, when the incident angle of
light is assumed to be 0.degree. (vertical). By changing the
incident angle of the light, the curve (b) of FIG. 9 is obtained as
a result of simulating the numerical value how the reflectance of
the light of design main wavelength (248 nm) is changed.
[0072] As is clear from FIG. 7, it becomes possible to perform
antireflection because reflectance becomes small in two-wavelength
region in the vicinity of 248 nm and within the range of 650 nm to
800 nm. It is also clear that the reflection of design main
wavelength (248 nm) is small in the range of 0.degree. to
70.degree. in incident angle of light as shown in curve (b) of FIG.
9. As a result, a similar advantage to the second embodiment can be
expected.
[0073] (Sixth Embodiment)
[0074] The schematic configuration of the two-wavelength
antireflection film according to the sixth embodiment is similar to
that in FIG. 1, and the explanation will be described by using FIG.
1. In this case, fluorite glass, which is transparent from the
deep-ultraviolet region to the near-infrared region, is used as a
substrate material for the substrate 1.
[0075] The film material and the film thickness of each of thin
films 2, 3, 4, and 5 of two-wavelength antireflection films
configured as FIG. 1 is shown in (C) of Table 2.
[0076] In this case, the film materials of thin films 2, 3, 4, and
5, each of which forms each layer, are similar to the second
embodiment. Substance M3 made by the Merck, which is the mixture of
Al.sub.2O.sub.3 and La.sub.2O.sub.3 whose refractive index in
design main wavelength (248 nm in the deep-ultraviolet region) is
about 1.95, is used is used to thin film 2 of the first layer and
thin film 4 of the third layer from the substrate 1. MgF.sub.2
whose refractive index in design main wavelength (248 nm in the
deep-ultraviolet region) is the low refractive index of about 1.4
is used to thin film 3 in the second layer and thin film 5 in the
fourth layer from the substrate 1. Each film thickness of these
thin films 2, 3, 4, and 5 is shown in (C) of Table 2.
[0077] FIG. 8 shows spectral reflectance characteristic for the two
wavelength antireflection film made for trial purposes with the
configuration shown in (C) of Table 2, when the incident angle of
light is assumed to be 0.degree. (vertical). By changing the
incident angle of the light, the curve (c) of FIG. 9 is obtained as
a result of simulating the numerical value how the reflectance of
the light of design main wavelength (248 nm) is changed.
[0078] As is clear from FIG. 8, it becomes possible to perform
antireflection because reflectance becomes small in two-wavelength
region in the vicinity of 248 nm and within the range of 650 nm to
800 nm. It is also clear that the reflection of design main
wavelength (248 nm) is small in the range of 0.degree. to
70.degree. in incident angle of light as shown in curve (c) of FIG.
9. As a result, a similar advantage the third embodiment can be
expected.
[0079] (Seventh Embodiment)
[0080] The schematic configuration of the two-wavelength
antireflection film according to the seventh embodiment is similar
to that in FIG. 1, and the explanation will be described by using
FIG. 1.
[0081] The film material and the film thickness of each of thin
films 2, 3, 4, and 5 of two-wavelength antireflection films
configured as FIG. 1 is shown in Table 4.
3 TABLE 3 Substrate 1 Quartz glass Design wavelength .lambda. 248
nm Layer number Film (from substrate) Film material thickness
(.times..lambda.) Thin film 2 Al.sub.2O.sub.3 + La.sub.2O.sub.3
0.52 (Substance M2) Thin film 3 MgF.sub.2 0.53 Thin film 4
Al.sub.2O.sub.3 + La.sub.2O.sub.3 0.29 (Substance M2) Thin film 5
MgF.sub.2 0.28
[0082] In this case, the film materials of thin films 2, 3, 4, and
5, each of which forms each layer, are similar to the second
embodiment Substance M2 made by the Merck, which is the mixture of
Al.sub.2O.sub.3 and La.sub.2O.sub.3 whose refractive index is about
1.8 in design main wavelength (248 nm in the deep-ultraviolet
region) is used to thin film 2 of the first layer and thin film 4
of the third layer from the substrate 1. MgF.sub.2 whose refractive
index in design main wavelength (248 nm in the deep-ultraviolet
region) is the low refractive index of about 1.4 is used to thin
film 3 in the second layer and thin film 5 in the fourth layer from
the substrate 1. Each film thickness of these thin films 2, 3, 4,
and 5 is shown in Table 3.
[0083] FIG. 10 shows spectral reflectance characteristic for the
two wavelength antireflection film made for trial purposes with the
configuration shown in Table 3, when the incident angle of light is
assumed to be 0.degree. (vertical). By changing the incident angle
of the light, the curve (d) of FIG. 9 is obtained as a result of
simulating the numerical value how the reflectance of the light of
design main wavelength (248 nm) is changed.
[0084] As is clear from FIG. 10, it becomes possible to perform
antireflection because reflectance becomes small in two-wavelength
region in the vicinity of 248 nm and within the range of 650 nm to
800 nm. Especially, it becomes possible to reduce reflectance
further within the range from 30.degree. to 50.degree. in incident
angle of design main wavelength (248 nm) as shown in curve (d) of
FIG. 9. Therefore, transmittance can be further improved by using
such two-wavelength antireflection film.
[0085] (Eighth Embodiment)
[0086] The schematic configuration of the two-wavelength
antireflection film according to the eighth embodiment is similar
to that in FIG. 1, and the explanation will be described by using
FIG. 1. In this case, quartz glass, which is transparent from the
deep-ultraviolet region to the near-infrared region, is used as a
substrate material for the substrate 1.
[0087] The film material and the film thickness of each of thin
films 2, 3, 4, and 5 of two-wavelength antireflection films
configured as FIG. 1 is shown in (A) of Table 4. Table 4
collectively shows the film material and the film thickness
corresponding to the eighth to tenth embodiments ((A) to (C)) as
described later.
4 TABLE 4 A B C Substrate 1 Fluorite glass Fluorite glass Fluorite
glass Design wavelength .lambda. 248 nm 248 nm 248 nm Film Film
Film Film thickness thickness thickness material (.times..lambda.)
Film material (.times..lambda.) Film material (.times..lambda.)
Thin film 2 Al.sub.2O.sub.3 0.60 Al.sub.2O.sub.3 + La.sub.2O.sub.3
0.67 Al.sub.2O.sub.3 + La.sub.2O.sub.3 0.59 (Substance M2)
(Substance M3) Thin film 3 MgF.sub.2 0.12 MgF.sub.2 0.87 MgF.sub.2
0.98 Thin film 4 Al.sub.2O.sub.3 0.34 Al.sub.2O.sub.3 +
La.sub.2O.sub.3 0.31 Al.sub.2O.sub.3 + La.sub.2O.sub.3 0.48
(Substance M2) (Substance M3) Thin film 5 MgF.sub.2 0.26 MgF.sub.2
0.30 MgF.sub.2 0.22
[0088] In this case, the film materials of thin films 2, 3, 4, and
5, each of which forms each layer, are similar to the first
embodiment. Al.sub.2O.sub.3 whose refractive index in design main
wavelength (248 nm in the deep-ultraviolet region) is the middle
refractive index of about 1.7 is used to thin film 2 of the first
layer and thin film 4 of the third layer from the substrate 1.
MgF.sub.2 whose refractive index in design main wavelength (248 nm
in the deep-ultraviolet region) is the low refractive index of
about 1.4 is used to thin film 3 in the second layer and thin film
5 in the fourth layer from the substrate 1. Each film thickness of
these thin films 2, 3, 4, and 5 is shown in (A) of Table 4.
[0089] FIG. 11 shows spectral reflectance characteristic for the
two wavelength antireflection film made for trial purposes with the
configuration shown in (A) of Table 4, when the incident angle of
light is assumed to be 0.degree. (vertical). By changing the
incident angle of the light, the curve (a) of FIG. 14 is obtained
as a result of simulating the numerical value how the reflectance
of the light of design main wavelength (248 nm) is changed.
[0090] As is clear from FIG. 11, it becomes possible to perform
antireflection because reflectance becomes small in two-wavelength
region in the vicinity of 248 nm and within the range of 650 nm to
800 nm. It is also clear that the reflection of design main
wavelength (248 nm) is small in the range of 0.degree. to
70.degree. in incident angle of light as shown in curve (a) of FIG.
14. Therefore, if two wavelength antireflection film configured
with thin films 2, 3, 4, and 5 of the eighth embodiment is formed
on the substrate 1 of quartz glass which is transparent from the
deep-ultraviolet region to the near-infrared region, high
transmittance can be achieved for light in the deep-ultraviolet
region in the vicinity of design main wavelength (248 nm) and light
in the visible region used for auto focus within the range of 550
nm to 650 nm different from light from the visible region to the
near-infrared region used for auto focus within the range of 650 nm
to 800 nm described in the first to seventh embodiments.
[0091] (Ninth Embodiment)
[0092] The schematic configuration of the two-wavelength
antireflection film according to the ninth embodiment is similar to
that in FIG. 1, and the explanation will be described by using FIG.
1.
[0093] The film material and the film thickness of each of thin
films 2, 3, 4, and 5 of two-wavelength antireflection films
configured as FIG. 1 is shown in (B) of Table 4.
[0094] In this case, the film materials of thin films 2, 3, 4, and
5, each of which forms each layer, are as follows. The mixture of
Al.sub.2O.sub.3 and La.sub.2O.sub.3 with the middle refractive
index material is used to thin film 2 of the first layer and thin
film 4 of the third layer from the substrate 1. Specifically,
Substance M2 made by the Merck, which is the mixture of
Al.sub.2O.sub.3 and La.sub.2C.sub.3 whose refractive index is about
1.8 in design main wavelength (248 nm in the deep-ultraviolet
region) is used. MgF.sub.2 whose refractive index in design main
wavelength (248 nm in the deep-ultraviolet region) is the low
refractive index of about 1.4 is used to thin film 3 in the second
layer and thin film 5 in the fourth layer from the substrate 1
similar to the first embodiment. Each film thickness of these thin
films 2, 3, 4, and 5 is shown in (2) of Table 4.
[0095] FIG. 12 shows spectral reflectance characteristic for the
two wavelength antireflection film made for trial purposes with the
configuration shown in (B) of Table 4, when the incident angle of
light is assumed to be 0.degree. (vertical). By changing the
incident angle of the light, the curve (b) of FIG. 14 is obtained
as a result of simulating the numerical value how the reflectance
of the light of design main wavelength (248 nm) is changed.
[0096] As is clear from FIG. 12, it becomes possible to perform
antireflection because reflectance becomes small in two-wavelength
region within the range of the vicinity of 248 nm and 550 nm to 800
nm. It is also clear that the reflection of design main wavelength
(248 nm) is small in the range of 0.degree. to 70.degree. in
incident angle of light as shown in curve (b) of FIG. 14.
Therefore, high transmittance can be achieved for light in the
visible region similarly used for auto focus within the range of
light in the deep-ultraviolet region in the vicinity of design main
wavelength (248 nm) and 550 nm to 650 nm when having described in
the eighth embodiment.
[0097] (Tenth Embodiment)
[0098] The schematic configuration of the two-wavelength
antireflection film according to the tenth embodiment is similar to
that in FIG. 1, and the explanation will be described by using FIG.
1.
[0099] The film material and the film thickness of each of thin
films 2, 3, 4, and 5 of two-wavelength antireflection films
configured as FIG. 1 is shown in (C) of Table 4.
[0100] The film materials of thin films 2, 3, 4, and 5, each of
which forms each layer, are as follows. Substance M3 made by the
Merck, which is the mixture of Al.sub.2O.sub.3 and La.sub.2O.sub.3
whose refractive index in design main wavelength (248 nm in the
deep-ultraviolet region) is about 1.95, is used is used to thin
film 2 of the first layer and thin film 4 of the third layer from
the substrate 1. MgF.sub.2 whose refractive index in design main
wavelength (248 nm in the deep-ultraviolet region) is the low
refractive index of about 1.4 is used to thin film 3 in the second
layer and thin film 5 in the fourth layer from the substrate 1.
Each film thickness of these thin fills 2, 3, 4, and 5 is shown in
(C) of Table 4.
[0101] FIG. 13 shows spectral reflectance characteristic for the
two wavelength antireflection film made for trial purposes with the
configuration shown in (C) of Table 4, when the incident angle of
light is assumed to be 0.degree. (vertical). By changing the
incident angle of the light, the curve (c) of FIG. 14 is obtained
as a result of simulating the numerical value how the reflectance
of the light of design main wavelength (248 nm) is changed.
[0102] As is clear from FIG. 13, it becomes possible to perform
antireflection because reflectance becomes small in two-wavelength
region in the vicinity of 248 nm and within the range of 650 nm to
800 nm. It is also clear that the reflection of design main
wavelength (248 nm) is small in the range of 0.degree. to
70.degree. in incident angle of light as shown in curve (c) of FIG.
14. Therefore, high transmittance can be achieved for light from
the visible region used for auto focus in the vicinity of the range
of light in the deep-ultraviolet region in the vicinity of design
main wavelength (248 nm) and 550 nm to 650 nm to the near-infrared
region similar to that described in the eighth embodiment.
[0103] In the above-mentioned first to tenth embodiment, MgF.sub.2
as the low refraction material and Al.sub.2O.sub.3 or the mixture
of Al.sub.2O.sub.3 and La.sub.2O.sub.3 as the middle refractive
index material is used. It is not limited to this, even when
material having similar refractive index to these materials such as
a plurality of components selected from group of MgF.sub.2,
SiO.sub.2, NaF, LiF, and mixture thereof or compound thereof as the
low refractive index material and material one or more components
selected from group of Al.sub.2O.sub.3, LaF.sub.3, NdF.sub.3,
YF.sub.3, La.sub.2O.sub.3, and mixture thereof or compound thereof
as the middle refractive index material is used, and advantages of
above mentioned embodiments can be expected.
[0104] (Eleventh Embodiment)
[0105] The schematic configuration of the two-wavelength
antireflection film according to the eleventh embodiment is similar
to that in FIG. 1, and the explanation will be described by using
FIG. 1.
[0106] The film material and the film thickness of each of thin
films 2, 3, 4, and 5 of two-wavelength antireflection films
configured as FIG. 1 is shown in (A) of Table 5. Table 5
collectively shows the film material and the film thickness
corresponding to the fourth and fifth embodiments ((A) and (B)) as
described later.
5 TABLE 5 B C Substrate 1 Quartz glass Quartz glass Design
wavelength .lambda. 248 nm 248 nm Film Film thickness thickness
Film material (.times..lambda.) Film material (.times..lambda.)
Thin film 2 Al.sub.2O.sub.3 + La.sub.2O.sub.3 0.64 Al.sub.2O.sub.3
+ La.sub.2O.sub.3 0.50 (Substance M2) (Substance M2) Thin film 3
SiO.sub.2 0.11 SiO.sub.2 0.19 Thin film 4 Al.sub.2O.sub.3 +
La.sub.2O.sub.3 0.37 Al.sub.2O.sub.3 + La.sub.2O.sub.3 0.32
(Substance M2) (Substance M2) Thin film 5 MgF.sub.2 0.28 SiO.sub.2
0.28
[0107] The film materials of thin films 2, 3, 4, and 5, each of
which forms each layer, are as follows. Substance M2 made by the
Merck, which is the mixture of Al.sub.2O.sub.3 and La.sub.2O.sub.3
whose refractive index is about 1.8 in design main wavelength (248
nm in the deep-ultraviolet region) is used to thin film 2 of the
first layer and thin film 4 of the third layer from the substrate
1. SiO.sub.2 whose refractive index in design main wavelength (248
nm in the deep-ultraviolet region) is the low refractive index of
about 1.5, is used to thin film 3 in the second layer from the
substrate 1. MgF.sub.2 whose refractive index in design main
wavelength (248 nm in the deep-ultraviolet region) is the low
refractive index of about 1.4 is used to thin film 5 in the fourth
layer front the substrate 1. Each film thickness of these thin
films 2, 3, 4, and 5 is shown in (A) of Table 5.
[0108] FIG. 15 shows spectral reflectance characteristic for the
two wavelength antireflection film made for trial purposes with the
configuration shown in (A) of Table 5, when the incident angle of
light is assumed to be 0.degree. (vertical). By changing the
incident angle of the light, the curve (d) of FIG. 14 is obtained
as a result of simulating the numerical value how the reflectance
of the light of design main wavelength (248 nm) is changed.
[0109] As is clear from FIG. 15, it becomes possible to perform
antireflection because reflectance becomes small in two-wavelength
region in the vicinity of 248 nm and within the range of 650 nm to
800 nm. It is also clear that the reflection of design main
wavelength (248 nm) is small in the range of 0.degree. to
70.degree. in incident angle of light as shown in curve (d) of FIG.
14. As a result, a similar advantage to the first embodiment can be
expected.
[0110] (Twelfth Embodiment)
[0111] The schematic configuration of the two-wavelength
antireflection film according to the twelfth embodiment is similar
to that in FIG. 1, and the explanation will be described by using
FIG. 1.
[0112] The film material and the film thickness of each of thin
films 2, 3, 4, and 5 of two-wavelength antireflection films
configured as FIG. 1 is shown in (B) of Table 5.
[0113] The film materials of thin films 2, 3, 4, and 5, each of
which forms each layer, are as follows. Substance M2 made by the
Merck, which is the mixture of Al.sub.2O.sub.3 and La.sub.2O.sub.3
whose refractive index is about 1.8 in design main wavelength (248
nm in the deep-ultraviolet region) is used to thin film 2 of the
first layer and thin film 4 of the third layer from the substrate
1. SiO.sub.2 whose refractive index in design main wavelength (248
nm in the deep-ultraviolet region) is the low refractive index of
about 1.5, is used to thin film 3 in the second layer and thin film
5 in the fourth layer from the substrate 1. Each film thickness of
these thin films 2, 3, 4, and 5 is shown in (B) of Table 5.
[0114] FIG. 16 shows spectral reflectance characteristic for the
two wavelength antireflection film made for trial purposes with the
configuration shown in (B) of Table 5, when the incident angle of
light is assumed to be 0.degree. (vertical). By changing the
incident angle of the light, the curve (e) of FIG. 14 is obtained
as a result of simulating the numerical value how the reflectance
of the light of design main wavelength (248 nm) is changed.
[0115] As is clear from FIG. 16, it becomes possible to perform
antireflection because reflectance becomes small in two-wavelength
region in the vicinity of 248 nm and within the range of 650 nm to
800 nm. It is also clear that the reflection of design main
wavelength (248 nm) is small in the range of 0.degree. to
70.degree. in incident angle of light as shown in curve (e) of FIG.
14. As a result, a similar advantage to the first embodiment can be
expected.
FIRST COMPARISON EXAMPLE
[0116] Next, two-wavelength antireflection film of the film
configuration and the design value indicated in Table 6 as a
comparison example with two-wavelength antireflection film by each
embodiment mentioned above has been examined. The schematic
configuration of the two-wavelength antireflection film of this
case is similar to that in FIG. 1, and the explanation will be
described by using FIG. 1.
6 TABLE 6 Substrate 1 Quartz glass Design wavelength .lambda. 248
nm Layer number Film (from substrate) Film material thickness
(.times..lambda.) Thin film 2 Al.sub.2O.sub.3 + La.sub.2O.sub.3
0.96 (Substance M2) Thin film 3 MgF.sub.2 0.35 Thin film 4
Al.sub.2O.sub.3 + La.sub.2O.sub.3 0.12 (Substance M2) Thin film 5
MgF.sub.2 0.29
[0117] In the above-mentioned configuration, substance M2 made by
the Merck, which is the mixture of Al.sub.2O.sub.3 and
La.sub.2O.sub.3 whose refractive index in design main wavelength
(248 nm in the deep-ultraviolet region) is about 1.8, is used to
thin film 2 of the first layer and thin film 4 of the third layer
from the substrate 1. MgF.sub.2 whose refractive index in design
main wavelength (248 nm in the deep-ultraviolet region) is the low
refractive index of about 1.4 is used to thin film 3 in the second
layer and thin film 5 in the fourth layer from the substrate 1
similar to the second embodiment. Each film thickness of these thin
films 2, 3, 4, and 5 is shown in Table 6.
[0118] FIG. 17 shows each spectral reflectance characteristic for
the two wavelength antireflection film made for trial purposes with
the configuration shown in Table 6, when changing the incident
angle of the light to 0.degree., 30.degree., 50.degree., and
65.degree., respectively. By changing the incident angle of the
light, the curve (d) of FIG. 5 is obtained as a result of
simulating the numerical value how the reflectance of the light of
design main wavelength (248 nm) is changed.
[0119] As is clear from FIG. 17, it becomes possible to perform
antireflection because reflectance becomes small in two-wavelength
region in the vicinity of 248 nm and within the range of 650 nm to
800 nm when the incident angle of light is 00 and 30.degree..
However, reflectance in the vicinity of 248 nm becomes large as the
incident angle of light becomes large. Especially, as shown in
curve (d) of FIG. 5, when the incident angle becomes 55.degree. or
more, the function as the antireflection film is nor obtained at
all because the reflectance of 248 nm becomes larger than the
substrate on which the film is not coated as shown in curve (e) of
FIG. 5.
SECOND COMPARISON EXAMPLE
[0120] Next, two-wavelength antireflection film of the film
configuration and the design value indicated in Table 7 as other
comparison example with two-wavelength antireflection film by each
embodiment mentioned above has been examined. The schematic
configuration of the two-wavelength antireflection film of this
case is similar to that in FIG. 1, and the explanation will be
described by using FIG. 1.
7 TABLE 7 Substrate 1 Quartz glass Design wavelength .lambda. 248
nm Layer number Film (from substrate) Film material thickness
(.times..lambda.) Thin film 2 Al.sub.2O.sub.3 + La.sub.2O.sub.3
0.47 (Substance M2) Thin film 3 MgF.sub.2 0.35 Thin film 4
Al.sub.2O.sub.3 + La.sub.2O.sub.3 0.13 (Substance M2) Thin film 5
MgF.sub.2 0.29
[0121] Substance M2 made by the Merck, which is the mixture of
Al.sub.2O.sub.3 and La.sub.2o.sub.3 whose refractive index in
design main wavelength (248 nm in the deep-ultraviolet region) is
about 1.8, is used to thin film 2 of the first layer and thin film
4 of the third layer from the substrate 1. MgF.sub.2 whose
refractive index in design main wavelength (248 nm in the
deep-ultraviolet region) is the low refractive index of about 1.4
is used to thin film 3 in the second layer and thin film 5 in the
fourth layer from the substrate 1. Each film thickness of these
thin films 2, 3, 4, and 5 is shown in Table 7.
[0122] FIG. 18 shows spectral reflectance characteristic for the
two wavelength antireflection film made for trial purposes with the
configuration shown in Table 7, when the incident angle of light is
assumed to be 0.degree. (vertical). By changing the incident angle
of the light, the curve (f) of FIG. 14 is obtained as a result of
simulating the numerical value how the reflectance of the light of
design main wavelength (248 nm) is changed.
[0123] As is clear from FIG. 18, it becomes possible to perform
antireflection because reflectance becomes small in two-wavelength
region in the vicinity of 248 nm and within the range of 650 nm to
800 nm when the incident angle of light is 0.degree.. However, when
the incident angle becomes large, the reflectance of 248 nm
abruptly becomes large as shown in curve (f) of FIG. 14.
Especially, when the incident angle becomes 65.degree. or more, the
reflectance of 248 nm becomes large, and becomes larger than the
reflectance of the substrate on which the film is not coated as
shown in curve (g) of FIG. 14. The function as the antireflection
film is not obtained at all.
[0124] Next, the objective lens on which two-wavelength
antireflection film mentioned above is actually coated on the
surface of the lens will be explained.
[0125] (Thirteenth Embodiment)
[0126] FIG. 19 is a figure showing a schematic configuration of the
objective lens applied to the thirteenth embodiment of the present
invention.
[0127] The objective lens is used for an optical equipment which
observes by the light of wavelength of the ultra-violet region of
300 mm or less and has the mechanism to focus (auto focus) by the
light in the wavelength region from a visible region to the
near-infrared region. Specifically, light of 248.+-.5 nm in the
deep-ultraviolet region as wavelength used for the observation and
light of 785 nm in the near-infrared region as wavelength used for
auto focus are applied.
[0128] The objective lens has the first lens group 1G and the
second lens group G2 arranged between the first lens group 1G and
the object as shown in FIG. 19. The first lens group 1G has five
single lenses L1 to L5 which include positive lens and negative
lens with the different medium and has negative power as a whole.
The second lens group 2G has thirteen single lenses L6 to L18 which
include positive lens and negative lens with the different medium
In the first and second lens group 1G and 2G, the air interval is
provided between a positive lens and negative lens.
[0129] Tables 8 to 11 show the angle of the light which is incident
(emitted) to (from) the normal of the lens, reflectance and the
transmittance, etc. corresponding thereto, which are obtained when
two wavelength antireflection film explained in detail in the
seventh embodiment is coated to each lens surface of each single
lens L1 to L18 for each of NA=09, 0.8, 0.7, and 0.5 of such an
objective lens, and the lens data of each single lens L1 to L18
(curvature, thickness, interval, and material name).
[0130] The angle of the light which is incident (emitted) to (from)
the normal of the lens is an angle r of the light which is incident
(emitted) to (from) normal h of the objective lens L as shown in
FIG. 20.
[0131] Reflectance and transmittance are obtained from the value of
the incident angle obtained as mentioned above.
8TABLE 8 Surface Thickness and Incident number Curvature Interval
Material Angle Reflectance Transmittance L.sub.1 1 2.562 2.562
Quartz glass 40 0.476 0.995 2 2.11 0.7 23 0.421 0.996 L.sub.2 3
-2.503 0.7 Fluorite glass 31 0.329 0.997 4 3.929 5.212314 29 0.057
0.999 L.sub.3 5 INF 2.786 Fluorite glass 13 1.091 0.989 6 -4.1
0.585821 47 0.68 0.993 L.sub.4 7 -3.179 1 Quartz glass 61 10.316
0.897 8 13.25 0.205879 53 10823 0.982 L.sub.5 9 14.51 2.792
Fluorite glass 53 1.787 0.982 10 -8.069 0.135719 16 0.278 0.997
L.sub.6 11 9.175 4.016 Fluorite glass 43 0.959 0.990 12 -8.107
0.473387 59 2.554 0.974 L.sub.7 13 -6.806 1 Quartz glass 65 7.46
0.925 14 9.394 0.205775 54 1.668 0.983 L.sub.8 15 9.73 4.65
Fluorite glass 54 1.709 0.983 16 -7.998 0.105412 53 1.314 0.987
L.sub.9 17 -8.397 1 Quartz glass 50 0.958 0.990 18 13.99 0.1 40
0.611 0.994 L.sub.10 19 12.513 4.035695 Fluorite glass 43 0.968
0.990 20 -10.732 0.1 39 0.852 0.991 L.sub.11 21 35.892 1 Quartz
glass 2 0.079 0.999 22 6.835 0.201239 52 1.419 0.986 L.sub.12 23
6.916 4.203 Fluorite glass 52 1.359 0.986 24 -10.627 0.2075 51
1.626 0.984 L.sub.13 25 -10.072 0.96 Quartz glass 52 1.71 0.983 26
101.798 0.1 7 1.232 0.988 L.sub.14 27 10.53 0.9 Quartz glass 12
0.037 1.000 28 4.509 0.527319 62 9.5 0.905 L.sub.15 29 5.379 2.576
Fluorite glass 52 1.308 0.987 30 -51.505 0.1 16 0.888 0.991
L.sub.16 31 6.736 1.742 Fluorite glass 15 0.157 0.998 32 17.567 0.1
12 0.814 0.992 L.sub.17 33 4.099 1.818 Fluorite glass 15 0.656
0.993 34 9.003 0.10016 21 0.357 0.996 L.sub.18 35 1.883 1.872
Quartz glass 17 0.27 0.997 36 5.293 0.262779 58 2.765 0.972
Transmittance of the objective lens at NA = 0.9:0.537
[0132]
9TABLE 9 Surface Thickness and Incident number Curvature Interval
Material Angle Reflectance Transmittance L.sub.1 1 2.562 2.562
Quartz glass 35 0.774 0.993 2 2.11 0.7 21 0.195 0.998 L.sub.2 3
-2.503 0.7 Fluorite glass 26 0.091 0.999 4 3.929 5.212314 26 0.122
0.999 L.sub.3 5 INF 2.786 Fluorite glass 12 1.12 0.989 6 -4.1
0.585821 41 0.702 0.993 L.sub.4 7 -3.179 1 Quartz glass 53 2.825
0.972 8 13.25 0.205879 44 0.541 0.995 L.sub.5 9 14.51 2.792
Fluorite glass 43 0.435 0.996 10 -8.069 0.135719 15 0.019 1.000
L.sub.6 11 9.175 4.016 Fluorite glass 36 0.616 0.994 12 -8.107
0.473387 46 1.128 0.989 L.sub.7 13 -6.806 1 Quartz glass 51 1.157
0.988 14 9.394 0.205775 41 0.845 0.992 L.sub.8 15 9.73 4.65
Fluorite glass 41 0.82 0.992 16 -7.998 0.105412 42 0.931 0.991
L.sub.9 17 -8.397 1 Quartz glass 40 0.881 0.991 18 13.99 0.1 31
0.079 0.999 L.sub.10 19 12.513 4.035695 Fluorite glass 33 0.196
0.998 20 -10.732 0.1 31 0.329 0.997 L.sub.11 21 35.892 1 Quartz
glass 2 1.029 0.990 22 6.835 0.201239 42 0.77 0.992 L.sub.12 23
6.916 4.203 Fluorite glass 42 0.77 0.992 24 -10.627 0.2075 41 0.648
0.994 L.sub.13 25 -10.072 0.96 Quartz glass 41 0.686 0.993 26
101.798 0.1 6 1.25 0.988 L.sub.14 27 10.53 0.9 Quartz glass 10
0.178 0.998 28 4.509 0.527319 49 0.881 0.991 L.sub.15 29 5.379
2.576 Fluorite glass 42 0.77 0.992 30 -51.505 0.1 15 1.032 0.990
L.sub.16 31 6.736 1.742 Fluorite glass 12 0.021 1.000 32 17.567 0.1
12 0.912 0.991 L.sub.17 33 4.099 1.818 Fluorite glass 12 0.333
0.997 34 9.003 0.10016 20 0.465 0.995 L.sub.18 35 1.883 1.872
Quartz glass 13 0.68 0.993 36 5.293 0.262779 50 0.893 0.991
Transmittance of the objective lens at NA = 0.8:0.777
[0133]
10TABLE 10 Surface Thickness and Incident number Curvature Interval
Material Angle Reflectance Transmittance L.sub.1 1 2.562 2.562
Quartz glass 30 00.604 0.994 2 2.11 0.7 19 0.04 1.000 L.sub.2 3
-2.503 0.7 Fluorite glass 23 0.04 1.000 4 3.929 5.212314 23 0.235
0.998 L.sub.3 5 INF 2.786 Fluorite glass 11 1.15 0.989 6 -4.1
0.585821 36 0.788 0.992 L.sub.4 7 -3.179 1 Quartz glass 46 0.59
0.994 8 13.25 0.205879 37 0.155 0.998 L.sub.5 9 14.51 2.792
Fluorite glass 36 0.134 0.999 10 -8.069 0.135719 13 0.023 1.000
L.sub.6 11 9.175 4.016 Fluorite glass 30 0.151 0.998 12 -8.107
0.473387 38 0.65 0.990 L.sub.7 13 -6.806 1 Quartz glass 42 0.959
0.994 14 9.394 0.205775 33 0.227 0.990 L.sub.8 15 9.73 4.65
Fluorite glass 33 0.196 0.998 16 -7.998 0.105412 34 0.527 0.995
L.sub.9 17 -8.397 1 Quartz glass 33 0.411 0.996 18 13.99 0.1 25
0.135 0.999 L.sub.10 19 12.513 4.035695 Fluorite glass 27 0.064
0.999 20 -10.732 0.1 26 0.046 1.000 L.sub.11 21 35.892 1 Quartz
glass 1 1.189 0.988 22 6.835 0.201239 35 0.728 0.993 L.sub.12 23
6.916 4.203 Fluorite glass 35 0.709 0.993 24 -10.627 0.2075 33
0.122 0.999 L.sub.13 25 -10.072 0.96 Quartz glass 34 0.143 0.999 26
101.798 0.1 5 1.268 0.987 L.sub.14 27 10.53 0.9 Quartz glass 9
0.443 0.996 28 4.509 0.527319 40 0.725 0.993 L.sub.15 29 5.379
2.576 Fluorite glass 34 0.698 0.993 30 -51.505 0.1 13 1.091 0.989
L.sub.16 31 6.736 1.742 Fluorite glass 9 0.105 0.999 32 17.567 0.1
11 1.146 0.989 L.sub.17 33 4.099 1.818 Fluorite glass 9 0.056 0.999
34 9.003 0.10016 17 0.75 0.993 L.sub.18 35 1.883 1.872 Quartz glass
10 0.573 0.994 36 5.293 0.262779 42 0.288 0.997 Transmittance of
the objective lens at NA = 0.7:0.842
[0134]
11TABLE 11 Surface Thickness and Incident number Curvature Interval
Material Angle Reflectance Transmittance L.sub.1 1 2.562 2.562
Quartz glass 21 0.027 1.000 2 2.11 0.7 14 0.277 0.997 L.sub.2 3
-2.503 0.7 Fluorite glass 16 0.436 0.996 4 3.929 5.212314 17 0.657
0.993 L.sub.3 5 INF 2.786 Fluorite glass 8 1.215 0.988 6 -4.1
0.585821 25 0.091 0.999 L.sub.4 7 -3.179 1 Quartz glass 32 0.637
0.994 8 13.25 0.205879 25 0.433 0.996 L.sub.5 9 14.51 2.792
Fluorite glass 24 0.474 0.995 10 -8.069 0.135719 10 1.282 0.987
L.sub.6 11 9.175 4.016 Fluorite glass 20 0.255 0.997 12 -8.107
0.473387 25 0.071 0.999 L.sub.7 13 -6.806 1 Quartz glass 27 0.051
0.999 14 9.394 0.205775 21 0.231 0.998 L.sub.8 15 9.73 4.65
Fluorite glass 21 0.29 0.997 16 -7.998 0.105412 23 0.074 0.999
L.sub.9 17 -8.397 1 Quartz glass 22 0.119 0.999 18 13.99 0.1 16
0.693 0.993 L.sub.10 19 12.513 4.035695 Fluorite glass 17 0.568
0.994 20 -10.732 0.1 17 0.28 0.997 L.sub.11 21 35.892 1 Quartz
glass 1 0.189 0.998 22 6.835 0.201239 23 0.034 1.000 L.sub.12 23
6.916 4.203 Fluorite glass 23 0.034 1.000 24 -10.627 0.2075 22
0.395 0.996 L.sub.13 25 -10.072 0.96 Quartz glass 22 0.326 0.997 26
101.798 0.1 3 1.28 0.987 L.sub.14 27 10.53 0.9 Quartz glass 6 0.844
0.992 28 4.509 0.527319 26 0.144 0.999 L.sub.15 29 5.379 2.576
Fluorite glass 22 0.035 1.000 30 -51.505 0.1 9 1.197 0.988 L.sub.16
31 6.736 1.742 Fluorite glass 6 0.6 0.994 32 17.567 0.1 8 1.11
0.989 L.sub.17 33 4.099 1.818 Fluorite glass 6 0.274 0.997 34 9.003
0.10016 12 1.015 0.990 L.sub.18 35 1.883 1.872 Quartz glass 6 0.018
1.000 36 5.293 0.262779 28 0.476 0.995 Transmittance of the
objective lens at NA = 0.5:0.850
[0135] Thus, the transmittance at wavelength 248 nm and NA=0.9
shown in Table 8 becomes 53.8%. Similarly, the transmittance at
wavelength 248 nm and NA=0.8 shown in Table 9 becomes 77.7%. The
transmittance at wavelength 248 nm and NA=0.7 shown in Table 10
becomes 84.2%. The transmittance at wavelength 248 nm and NA=0.5
shown in Table 11 becomes 85%.
[0136] On the other hand, Tables 12 to 15 show the angle of the
light which is incident (emitted) to (from) the normal of the lens,
reflectance and the transmittance, etc. corresponding thereto,
which are obtained when two wavelength antireflection film
explained in detail in the first comparison example is provided to
each lens surface of each single lens L1 to L18 for each of NA=0.9,
10.8, 0.7, and 0.5 of such an objective lens, and the lens data of
each single lens L1 to L18 (curvature, thickness, interval, and
material name).
12TABLE 12 Surface Thickness and Incident number Curvature Interval
Material Angle Reflectance Transmittance L.sub.1 1 2.562 2.562
Quartz glass 40 12.006 0.880 2 2.11 0.7 23 4.17 0.958 L.sub.2 3
-2.503 0.7 Fluorite glass 31 3.548 0.965 4 3.929 5.212314 29 0.916
0.991 L.sub.3 5 INF 2.786 Fluorite glass 13 0.02 1.000 6 -4.1
0.585821 47 13.356 0.866 L.sub.4 7 -3.179 1 Quartz glass 61 12.418
0.876 8 13.25 0.205879 53 9.536 0.905 L.sub.5 9 14.51 2.792
Fluorite glass 53 9.126 0.909 10 -8.069 0.135719 16 2.994 0.970
L.sub.6 11 9.175 4.016 Fluorite glass 43 10.694 0.893 12 -8.107
0.473387 59 17.194 0.828 L.sub.7 13 -6.806 1 Quartz glass 65 17.58
0.824 14 9.394 0.205775 54 15.092 0.849 L.sub.8 15 9.73 4.65
Fluorite glass 54 14.998 0.850 16 -7.998 0.105412 53 14.768 0.852
L.sub.9 17 -8.397 1 Quartz glass 50 14.076 0.859 18 13.99 0.1 40
5.229 0.948 L.sub.10 19 12.513 4.035695 Fluorite glass 43 8.244
0.918 20 -10.732 0.1 39 8.632 0.914 L.sub.11 21 35.892 1 Quartz
glass 2 0.026 1.000 22 6.835 0.201239 52 13.928 0.861 L.sub.12 23
6.916 4.203 Fluorite glass 52 14.038 0.860 24 -10.627 0.2075 51
11.992 0.880 L.sub.13 25 -10.072 0.96 Quartz glass 52 13.038 0.870
26 101.798 0.1 7 0.032 1.000 L.sub.14 27 10.53 0.9 Quartz glass 12
0.51 0.995 28 4.509 0.527319 62 13.7 0.863 L.sub.15 29 5.379 2.576
Fluorite glass 52 14.144 0.859 30 -51.505 0.1 16 0.0085 1.000
L.sub.16 31 6.736 1.742 Fluorite glass 15 2.163 0.978 32 17.567 0.1
12 0.006 1.000 L.sub.17 33 4.099 1.818 Fluorite glass 15 6.229
0.938 34 9.003 0.10016 21 0.079 0.999 L.sub.18 35 1.883 1.872
Quartz glass 17 10.502 0.895 36 5.293 0.262779 58 10.261 0.897
Transmittance of the objective lens at NA = 0.9:0.038
[0137]
13TABLE 13 Surface Thickness and Incident number Curvature Interval
Material Angle Reflectance Transmittance L.sub.1 1 2.562 2.562
Quartz glass 35 9.479 0.905 2 2.11 0.7 21 2.506 0.975 L.sub.2 3
-2.503 0.7 Fluorite glass 26 1.75 0.983 4 3.929 5.212314 26 0.402
0.996 L.sub.3 5 INF 2.786 Fluorite glass 12 0.022 1.000 6 -4.1
0.585821 41 11.585 0.884 L.sub.4 7 -3.179 1 Quartz glass 53 12.649
0.874 8 13.25 0.205879 44 3.864 0.961 L.sub.5 9 14.51 2.792
Fluorite glass 43 3.204 0.968 10 -8.069 0.135719 15 0.886 0.991
L.sub.6 11 9.175 4.016 Fluorite glass 36 5.7 0.943 12 -8.107
0.473387 46 11.252 0.887 L.sub.7 13 -6.806 1 Quartz glass 51 14.298
0.857 14 9.394 0.205775 41 7.34 0.927 L.sub.8 15 9.73 4.65 Fluorite
glass 41 7.022 0.930 16 -7.998 0.105412 42 10.306 0.897 L.sub.9 17
-8.397 1 Quartz glass 40 8.73 0.913 18 13.99 0.1 31 1.38 0.986
L.sub.10 19 12.513 4.035695 Fluorite glass 33 2.464 0.975 20
-10.732 0.1 31 3.548 0.965 L.sub.11 21 35.892 1 Quartz glass 2
0.026 1.000 22 6.835 0.201239 42 11.607 0.884 L.sub.12 23 6.916
4.203 Fluorite glass 42 11.607 0.884 24 -10.627 0.2075 41 5.334
0.947 L.sub.13 25 -10.072 0.96 Quartz glass 41 5.678 0.943 26
101.798 0.1 6 0.034 1.000 L.sub.14 27 10.53 0.9 Quartz glass 10
0.145 0.999 28 4.509 0.527319 49 13.44 0.866 L.sub.15 29 5.379
2.576 Fluorite glass 42 11.607 0.884 30 -51.505 0.1 15 0.0148 1.000
L.sub.16 31 6.736 1.742 Fluorite glass 12 0.868 0.991 32 17.567 0.1
12 0.01 1.000 L.sub.17 33 4.099 1.818 Fluorite glass 12 3.288 0.967
34 9.003 0.10016 20 0.0315 1.000 L.sub.18 35 1.883 1.872 Quartz
glass 13 8.304 0.917 36 5.293 0.262779 50 4.377 0.956 Transmittance
of the objective lens at NA = 0.8:0.129
[0138]
14TABLE 14 Surface Thickness and Incident number Curvature Interval
Material Angle Reflectance Transmittance L.sub.1 1 2.562 2.562
Quartz glass 30 5.862 0.941 2 2.11 0.7 19 1.2252 0.988 L.sub.2 3
-2.503 0.7 Fluorite glass 23 0.717 0.993 4 3.929 5.212314 23 0.181
0.998 L.sub.3 5 INF 2.786 Fluorite glass 11 0.25 0.998 6 -4.1
0.585821 36 8.619 0.914 L.sub.4 7 -3.179 1 Quartz glass 46 13.062
0.869 8 13.25 0.205879 37 1.346 0.987 L.sub.5 9 14.51 2.792
Fluorite glass 36 1.148 0.989 10 -8.069 0.135719 13 0.662 0.993
L.sub.6 11 9.175 4.016 Fluorite glass 30 2.228 0.978 12 -8.107
0.473387 38 5.819 0.942 L.sub.7 13 -6.806 1 Quartz glass 42 9.288
0.907 14 9.394 0.205775 33 2.72 0.973 L.sub.8 15 9.73 4.65 Fluorite
glass 33 2.447 0.976 16 -7.998 0.105412 34 5.018 0.950 L.sub.9 17
-8.397 1 Quartz glass 33 4.12 0.959 18 13.99 0.1 25 0.32 0.997
L.sub.10 19 12.513 4.035695 Fluorite glass 27 0.708 0.993 20
-10.732 0.1 26 1.18 0.988 L.sub.11 21 35.892 1 Quartz glass 1 0.033
1.000 22 6.835 0.201239 35 7.157 0.928 L.sub.12 23 6.916 4.203
Fluorite glass 35 6.861 0.931 24 -10.627 0.2075 33 1.76 0.982
L.sub.13 25 -10.072 0.96 Quartz glass 34 1.95 0.981 26 101.798 0.1
5 0.0359 1.000 L.sub.14 27 10.53 0.9 Quartz glass 9 0.019 1.000 28
4.509 0.527319 40 11.156 0.888 L.sub.15 29 5.379 2.576 Fluorite
glass 34 6.839 0.932 30 -51.505 0.1 13 0.02 1.000 L.sub.16 31 6.736
1.742 Fluorite glass 9 0.25 0.998 32 17.567 0.1 11 0.019 1.000
L.sub.17 33 4.099 1.818 Fluorite glass 9 1.33 0.987 34 9.003
0.10016 17 0.006 1.000 L.sub.18 35 1.883 1.872 Quartz glass 10
5.136 0.949 36 5.293 0.262779 42 1.632 0.984 Transmittance of the
objective lens at NA = 0.7:0.316
[0139]
15TABLE 15 Surface Thickness and Incident number Curvature Interval
Material Angle Reflectance Transmittance L.sub.1 1 2.562 2.562
Quartz glass 21 0.938 0.991 2 2.11 0.7 14 0.084 0.999 L.sub.2 3
-2.503 0.7 Fluorite glass 16 0.032 1.000 4 3.929 5.212314 17 0.008
1.000 L.sub.3 5 INF 2.786 Fluorite glass 8 0.031 1.000 6 -4.1
0.585821 25 1.769 0.982 L.sub.4 7 -3.179 1 Quartz glass 32 6.208
0.938 8 13.25 0.205879 25 0.0686 0.999 L.sub.5 9 14.51 2.792
Fluorite glass 24 0.057 0.999 10 -8.069 0.135719 10 0.04 1.000
L.sub.6 11 9.175 4.016 Fluorite glass 20 0.12 0.999 12 -8.107
0.473387 25 0.503 0.995 L.sub.7 13 -6.806 1 Quartz glass 27 1.154
0.988 14 9.394 0.205775 21 0.16 0.998 L.sub.8 15 9.73 4.65 Fluorite
glass 21 0.115 0.999 16 -7.998 0.105412 23 0.483 0.995 L.sub.9 17
-8.397 1 Quartz glass 22 0.337 0.997 18 13.99 0.1 16 0.005 1.000
L.sub.10 19 12.513 4.035695 Fluorite glass 17 0.014 1.000 20
-10.732 0.1 17 0.044 1.000 L.sub.11 21 35.892 1 Quartz glass 1
0.033 1.000 22 6.835 0.201239 23 0.85 0.992 L.sub.12 23 6.916 4.203
Fluorite glass 23 0.85 0.992 24 -10.627 0.2075 22 0.074 0.999
L.sub.13 25 -10.072 0.96 Quartz glass 22 0.106 0.999 26 101.798 0.1
3 0.0371 1.000 L.sub.14 27 10.53 0.9 Quartz glass 6 0.009 1.000 28
4.509 0.527319 26 2.185 0.978 L.sub.15 29 5.379 2.576 Fluorite
glass 22 0.076 0.992 30 -51.505 0.1 9 0.029 1.000 L.sub.16 31 6.736
1.742 Fluorite glass 6 0.005 1.000 32 17.567 0.1 8 0.025 1.000
L.sub.17 33 4.099 1.818 Fluorite glass 6 0.07 0.999 34 9.003
0.10016 12 0.016 1.000 L.sub.18 35 1.883 1.872 Quartz glass 6 0.772
0.992 36 5.293 0.262779 28 0.105 0.999 Transmittance of the
objective lens at NA = 0.5:0.832
[0140] Thus, the transmittance at wavelength 248 nm and NA=0.9
shown in Table 12 becomes 3.8%. Similarly, the transmittance at
wavelength 248 nm and NA=0.8 shown in Table 13 becomes 12.9%. The
transmittance at wavelength 248 nm and NA=0.7 shown in Table 14
becomes 31.6%. The transmittance at wavelength 248 nm and NA=0.5
shown in Table 15 becomes 83.5%.
[0141] As a result, when comparing the transmittance of the
objective lens of the seventh embodiment in which two wavelength
antireflection film is coated and the objective lens of the first
comparison example in which two wavelength antireflection film is
coated with each lens surface of each single lens L1 to L18, when
two wavelength antireflection film of the seventh embodiment as
shown in FIG. 21 is coated, high transmittance can be obtained even
when NA is 0.9, 0.8, 0.7, and 0.5 as shown in curve A. In contrast,
when two-wavelength antireflection film of the first comparison
example is applied, it is apparent that transmittance reduces
rapidly as shown in curve B as NA becomes large such as 0.7, 0.8,
0.9 as shown in curve B. As a result, high transmittance in 248 nm
used for the observation and a high NA, that is, high resolutions
can be achieved by coating two-wavelength antireflection film
according to the seventh embodiment to each lens surface of each
single lens L1 to L18 which configures the objective lens.
[0142] (Fourteenth Embodiment)
[0143] FIG. 22 is a figure showing a schematic configuration of the
objective lens applied to the fourteenth embodiment of the present
invention.
[0144] In this case, the objective lens is used for an optical
equipment which observes by the light of wavelength of the
ultra-violet region of 300 nm or less and has the mechanism to
focus (auto focus) by the light in the wavelength region from a
visible region to the near-infrared region. Specifically, 248 nm in
the deep-ultraviolet region as wavelength used for the observation
and 633 nm in the visible region as wavelength used for auto focus
are applied.
[0145] The objective lens has the first lens group 1G and the
second lens group G2 arranged between the first lens group 1G and
the object side as shown in FIG. 22. The first lens group 1G has
four single lenses L21 to L24 which include positive lens and
negative lens with the different medium and has negative power as a
whole. The second lens group 2G has eight single lenses L25 to L32
which include positive lens and negative lens with the different
medium. In the first and second lens groups 1G and 2G, the air
interval is provided between a positive lens and negative lens.
[0146] Tables 16 to 19 show the angle of the light which is
incident (emitted) to (from) the normal of the lens, reflectance
and the transmittance, etc. corresponding thereto, which are
obtained when two wavelength antireflection film explained in
detail in the seventh embodiment is coated to each lens surface of
each single lens L21 to L32 for each of NA=0.9, 0.8, 0.7, and 0.5
of such an objective lens, and the lens data of each single lens
L21 to L32 (curvature, thickness, interval, and material name).
16TABLE 16 Surface Thickness and Incident number Curvature Interval
Material Angle Reflectance Transmittance L.sub.21 1 -3.543 2.15
Quartz glass 31 0.4 0.996 2 6.765 0.10358 52 1.5 0.958 L.sub.22 3
6.181 3.06 Fluorite glass 55 2.06 0.979 4 -4.042 0.153241 53 4.6
0.954 L.sub.23 5 -4.08 0.92 Quartz glass 52 4 0.960 6 8.682 0.16626
54 2 0.980 L.sub.24 7 8.883 3.11 Fluorite glass 54 2 0.980 8 -6.824
0.106344 31 0.32 0.997 L.sub.25 9 24.853 0.9 Quartz glass 9 0.03
1.000 10 6.181 0.101063 55 3.54 0.965 L.sub.26 11 5.251 3.77
Fluorite glass 66 13 0.870 12 -9.936 0.61551 45 0.96 0.990 L.sub.27
13 -6.165 0.9 Quartz glass 58 5 0.950 14 6.165 0.502246 59 5.5
0.945 L.sub.28 15 8.596 2.78 Fluorite glass 49 1.2 0.988 16 -12.005
0.197219 17 0.47 0.995 L.sub.29 17 5.353 3.51 Fluorite glass 46 2.9
0.971 18 -11.031 0.488166 54 2 0.980 L.sub.30 19 -6.791 1.35 Quartz
glass 65 7.52 0.925 20 -155.13 0.196741 14 0.01 1.000 L.sub.31 21
4.438 2.12 Quartz glass 23 0.22 0.998 22 13.067 0.095 19 0.15 0.999
L.sub.32 23 7.961 2.33 Quartz glass 30 2.58 0.974 24 10.691
0.2647.8 61 4.1 0.959 Transmittance of the objective lens at NA =
0.9:0.506
[0147]
17TABLE 17 Surface Thickness and Incident number Curvature Interval
Material Angle Reflectance Transmittance L.sub.21 1 -3.543 2.15
Quartz glass 27 0.52 0.995 2 6.765 0.10358 44 1 0.990 L.sub.22 3
6.181 3.06 fluorite glass 46 1 0.990 4 -4.042 0.153241 44 1.3 0.987
L.sub.23 5 -4.08 0.92 Quartz glass 43 1.2 0.988 6 8.682 0.16626 46
1.2 0.988 L.sub.24 7 8.883 3.11 fluorite glass 46 1.2 0.988 8
-6.824 0.106344 27 0.48 0.995 L.sub.25 9 24.853 0.9 Quartz glass 9
0.01 1.000 10 6.181 0.101063 48 1.3 0.987 L.sub.26 11 5.251 3.77
fluorite glass 56 5 0.950 12 -9.936 0.61551 36 0.8 0.992 L.sub.27
13 -6.165 0.9 Quartz glass 47 1 0.990 14 6.165 0.502246 51 1.5
0.985 L.sub.28 15 8.596 2.78 Fluorite glass 43 0.85 0.992 16
-12.005 0.197219 16 0.4 0.996 L.sub.29 17 5.353 3.51 Fluorite glass
40 1.07 0.989 18 -11.031 0.488166 45 1.16 0.988 L.sub.30 19 -6.791
1.35 Quartz glass 54 5 0.950 20 -155.13 0.196741 14 0.01 1.000
L.sub.31 21 4.438 2.12 Quartz glass 18 0.43 0.996 22 13.067 0.095
18 0.1 0.999 L.sub.32 23 7.961 2.33 Quartz glass 22 0.6 0.994 24
10.691 0.2647.8 51 1.9 0.981 Transmittance of the objective lens at
NA = 0.8:0.745
[0148]
18TABLE 18 Surface Thickness and Incident number Curvature Interval
Material Angle Reflectance Transmittance L.sub.21 1 -3.543 2.562
Quartz glass 23 0.61 0.994 2 6.765 0.10358 37 0.83 0.992 L.sub.22 3
6.181 3.06 Fluorite glass 39 0.88 0.991 4 -4.042 0.153241 37 0.4
0.996 L.sub.23 5 -4.08 0.92 Quartz glass 36 0.4 0.996 6 8.682
0.16626 39 0.9 0.991 L.sub.24 7 8.883 3.11 Fluorite glass 39 0.9
0.991 8 -6.824 0.106344 23 0.61 0.994 L.sub.25 9 24.853 0.9 Quartz
glass 8 0.01 1.000 10 6.181 0.101063 41 0.6 0.994 L.sub.26 11 5.251
3.77 Fluorite glass 47 1.2 0.988 12 -9.936 0.61551 29 0.62 0.994
L.sub.27 13 -6.165 0.9 Quartz glass 38 0.59 0.994 14 6.165 0.502246
43 0.7 0.992 L.sub.28 15 8.596 2.78 Fluorite glass 37 0.8 0.992 16
-12.005 0.197219 14 0.22 0.998 L.sub.29 17 5.353 3.51 Fluorite
glass 34 0.33 0.997 18 -11.031 0.488166 38 0.85 0.992 L.sub.30 19
-6.791 1.35 Quartz glass 45 0.96 0.990 20 -155.13 0.196741 13 0.01
1.000 L.sub.31 21 4.438 2.12 Quartz glass 15 0.58 0.994 22 13.067
0.095 16 0.07 0.999 L.sub.32 23 7.961 2.33 Quartz glass 18 0.19
0.998 24 10.691 0.2647.8 43 1.15 0.989 Transmittance of the
objective lens at NA = 0.7:0.865
[0149]
19TABLE 19 Surface Thickness and Incident number Curvature Interval
Material Angle Reflectance Transmittance L.sub.21 1 -3.543 2.15
Quartz glass 16 0.4 0.996 2 6.765 0.10358 25 0.15 0.999 L.sub.22 3
6.181 3.06 Fluorite glass 26 0.4 0.996 4 -4.042 0.153241 25 0.64
0.994 L.sub.23 5 -4.08 0.92 Quartz glass 24 0.64 0.994 6 8.682
0.16626 26 0.4 0.996 L.sub.24 7 8.883 3.11 Fluorite glass 26 0.4
0.996 8 -6.824 0.106344 16 0.42 0.996 L.sub.25 9 24.853 0.9 Quartz
glass 6 0.004 1.000 10 6.181 0.101063 28 0.65 0.994 L.sub.26 11
5.251 3.77 Fluorite glass 32 0.66 0.993 12 -9.936 0.61551 19 0.23
0.998 L.sub.27 13 -6.165 0.9 Quartz glass 26 0.6 0.994 14 6.165
0.502246 29 0.67 0.993 L.sub.28 15 8.596 2.78 Fluorite glass 25
0.46 0.995 16 -12.005 0.197219 10 0.07 0.999 L.sub.29 17 5.353 3.51
Fluorite glass 23 0.61 0.994 18 -11.031 0.488166 25 0.29 0.997
L.sub.30 19 -6.791 1.35 Quartz glass 30 0.61 0.994 20 -155.13
0.196741 9 0.01 1.000 L.sub.31 21 4.438 2.12 Quartz glass 10 0.39
0.996 22 13.067 0.095 11 0.01 1.000 L.sub.32 23 7.961 2.33 Quartz
glass 12 0.57 0.994 24 10.691 0.2647.8 29 0.3 0.997 Transmittance
of the objective lens at NA = 0.5:0.908
[0150] Thus, the transmittance at wavelength 248 nm and NA=0.9
shown in Table 16 becomes 50.6%. Similarly, the transmittance at
wavelength 248 nm and NA=0.8 shown in Table 17 becomes 74.5%. The
transmittance at wavelength 248 nm and NA=0.7 shown in Table 18
becomes 86.5%. The transmittance at wavelength 248 nm and NA=0.5
shown in Table 19 becomes 90.8%.
[0151] On the other hand, Tables 20 to 23 show the angle of the
light which is incident (emitted) to (from) the normal of the lens,
reflectance and the transmittance, etc. corresponding thereto,
which are obtained when two wavelength antireflection film
explained in detail in the first comparison example is provided to
each lens surface of each single lens L21 to L32 for each of NA
0.9, 0.8, 0.7, and 0.5 of such an objective lens, and the lens data
of each single lens L21 to L32 (curvature, thickness, interval, and
material name).
20TABLE 20 Surface Thickness and Incident number Curvature Interval
Material Angle Reflectance Transmittance L.sub.21 1 -3.543 2.15
Quartz glass 31 3.3 0.967 2 6.765 0.10358 52 7 0.930 L.sub.22 3
6.181 3.06 Fluorite glass 55 10 0.900 4 -4.042 0.153241 53 14 0.860
L.sub.23 5 -4.08 0.92 Quartz glass 52 14 0.860 6 8.682 0.16626 54 9
0.910 L.sub.24 7 8.883 3.11 Fluorite glass 54 9.3 0.907 8 -6.824
0.106344 31 3.9 0.961 L.sub.25 9 24.853 0.9 Quartz glass 9 0.01
1.000 10 6.181 0.101063 55 11.5 0.885 L.sub.26 11 5.251 3.77
Fluorite glass 66 22 0.780 12 -9.936 0.61551 45 4.2 0.958 L.sub.27
13 -6.165 0.9 Quartz glass 58 15 0.850 14 6.165 0.502246 59 16
0.840 L.sub.28 15 8.596 2.78 Fluorite glass 49 7.5 0.925 16 -12.005
0.197219 17 0.2 0.998 L.sub.29 17 5.353 3.51 Fluorite glass 46 12.5
0.975 18 -11.031 0.488166 54 7.5 0.925 L.sub.30 19 -6.791 1.35
Quartz glass 65 19.5 0.805 20 -155.13 0.196741 14 0.02 1.000
L.sub.31 21 4.438 2.12 Quartz glass 23 4 0.960 22 13.067 0.095 19
0.04 1.000 L.sub.32 23 7.961 2.33 Quartz glass 30 11 0.890 24
10.691 0.2647.8 61 9 0.910 Transmittance of the objective lens at
NA = 0.9:0.105
[0152]
21TABLE 21 Surface Thickness and Incident number Curvature Interval
Material Angle Reflectance Transmittance L.sub.21 1 -3.543 2.15
Quartz glass 27 2 0.980 2 6.765 0.10358 44 3.3 0.967 L.sub.22 3
6.181 3.06 Fluorite glass 46 4.3 0.957 4 -4.042 0.153241 44 10
0.900 L.sub.23 5 -4.08 0.92 Quartz glass 43 9 0.910 6 8.682 0.16626
46 4 0.960 L.sub.24 7 8.883 3.11 Fluorite glass 46 4 0.960 8 -6.824
0.106344 27 2 0.980 L.sub.25 9 24.853 0.9 Quartz glass 9 0.01 1.000
10 6.181 0.101063 48 9 0.910 L.sub.26 11 5.251 3.77 Fluorite glass
56 15 0.850 12 -9.936 0.61551 36 1.6 0.984 L.sub.27 13 -6.165 0.9
Quartz glass 47 8 0.920 14 6.165 0.502246 51 10 0.900 L.sub.28 15
8.596 2.78 Fluorite glass 43 4 0.960 16 -12.005 0.197219 16 0.1
0.999 L.sub.29 17 5.353 3.51 Fluorite glass 40 9 0.910 18 -11.031
0.488166 45 3 0.970 L.sub.30 19 -6.791 1.35 Quartz glass 54 10
0.900 20 -155.13 0.196741 14 0.02 1.000 L.sub.31 21 4.438 2.12
Quartz glass 18 1.9 0.981 22 13.067 0.095 18 0.03 1.000 L.sub.32 23
7.961 2.33 Quartz glass 22 7 0.930 24 10.691 0.2647.8 51 3 0.970
Transmittance of the objective lens at NA = 0.8:0.285
[0153]
22TABLE 22 Surface Thickness and Incident number Curvature Interval
Material Angle Reflectance Transmittance L.sub.21 1 -3.543 2.15
Quartz glass 23 0.9 0.991 2 6.765 0.10358 37 1.2 0.988 L.sub.22 3
6.181 3.06 Fluorite glass 39 2 0.980 4 -4.042 0.153241 37 5.5 0.945
L.sub.23 5 -4.08 0.92 Quartz glass 36 5 0.950 6 8.682 0.16626 39
1.5 0.985 L.sub.24 7 8.883 3.11 Fluorite glass 39 1.5 0.985 8
-6.824 0.106344 23 1.95 0.981 L.sub.25 9 24.853 0.9 Quartz glass 8
0.01 1.000 10 6.181 0.101063 41 5 0.950 L.sub.26 11 5.251 3.77
Fluorite glass 47 9.5 0.905 12 -9.936 0.61551 29 0.55 0.995
L.sub.27 13 -6.165 0.9 Quartz glass 38 3.6 0.964 14 6.165 0.502246
43 5.5 0.945 L.sub.28 15 8.596 2.78 Fluorite glass 37 2 0.980 16
-12.005 0.197219 14 0.05 1.000 L.sub.29 17 5.353 3.51 Fluorite
glass 34 5.3 0.947 18 -11.031 0.488166 38 1.2 0.988 L.sub.30 19
-6.791 1.35 Quartz glass 45 4.2 0.958 20 -155.13 0.196741 13 0.01
1.000 L.sub.31 21 4.438 2.12 Quartz glass 15 0.85 0.992 22 13.067
0.095 16 0.02 1.000 L.sub.32 23 7.961 2.33 Quartz glass 18 4.5
0.955 24 10.691 0.2647.8 43 1.6 0.984 Transmittance of the
objective lens at NA = 0.7:0.522
[0154]
23TABLE 23 Surface Thickness and Incident number Curvature Interval
Material Angle Reflectance Transmittance L.sub.21 1 -3.543 2.15
Quartz glass 16 0.1 0.999 2 6.765 0.10358 25 0.15 0.999 L.sub.22 3
6.181 3.06 Fluorite glass 26 0.2 0.998 4 -4.042 0.153241 25 0.85
0.992 L.sub.23 5 -4.08 0.92 Quartz glass 24 0.85 0.992 6 8.682
0.16626 26 0.2 0.998 L.sub.24 7 8.883 3.11 Fluorite glass 26 0.2
0.998 8 -6.824 0.106344 16 0.15 0.999 L.sub.25 9 24.853 0.9 Quartz
glass 6 0.01 1.000 10 6.181 0.101063 28 0.75 0.993 L.sub.26 11
5.251 3.77 Fluorite glass 32 1.8 0.982 12 -9.936 0.61551 19 0.07
0.999 L.sub.27 13 -6.165 0.9 Quartz glass 26 0.45 0.996 14 6.165
0.502246 29 0.7 0.993 L.sub.28 15 8.596 2.78 Fluorite glass 25 0.24
0.998 16 -12.005 0.197219 10 0.02 1.000 L.sub.29 17 5.353 3.51
Fluorite glass 23 0.85 0.992 18 -11.031 0.488166 25 0.13 0.999
L.sub.30 19 -6.791 1.35 Quartz glass 30 0.47 0.995 20 -155.13
0.196741 9 0.01 1.000 L.sub.31 21 4.438 2.12 Quartz glass 10 0.1
0.999 22 13.067 0.095 11 0.01 1.000 L.sub.32 23 7.961 2.33 Quartz
glass 12 0.8 0.992 24 10.691 0.2647.8 29 0.19 0.998 Transmittance
of the objective lens at NA = 0.5:0.911
[0155] Thus, the transmittance at wavelength 248 nm and NA=0.9
shown in Table 20 becomes 105%. Similarly, the transmittance at
wavelength 248 nm and NA=0.8 shown in Table 21 becomes 28.5%. The
transmittance at wavelength 248 nm and NA=0.7 shown in Table 22
becomes 52.2%. The transmittance at wavelength 248 nm and NA=0.5
shown in Table 23 becomes 91.1%.
[0156] As a result, when comparing the transmittance of the
objective lens of the seventh embodiment in which two wavelength
antireflection film is coated and the objective lens of the first
comparison example in which two wavelength antireflection film is
coated with each lens surface of each single lens L21 to L32, when
two wavelength antireflection film of the ninth embodiment as shown
in FIG. 23 is coated, high transmittance can be obtained even in a
case that NA is 0.8, and 0.9 as shown in curve A. In contrast, when
two-wavelength antireflection film of the second comparison example
is coated, it is apparent that transmittance reduces rapidly as
shown in curve B as NA becomes large such as 0.7, 0.8, 0.9 as shown
in curve B. As a result, high transmittance in 248 nm used for the
observation and a high NA, that is, high resolutions can be
achieved by coating two-wavelength antireflection film according to
the ninth embodiment to each lens surface of each single lens L21
to L32 which configures the objective lens.
[0157] As mentioned above, according to the embodiment of the
present invention, the antireflection effect can be achieved in the
vicinity of 248 nm and the wavelength region of 600 to 800 nm for
substrate (lens) material whose refractive index in the
deep-ultraviolet region is 1.4 to 1.52. Even when the incident
angle of light becomes large, the antireflection effect is never
lost in the vicinity of especially 248 nm. Therefore, high
transmittance can be achieved even when the incident angle of the
light to the surface of the lens is from vertical to about
65.degree..
[0158] A high antireflection effect can be achieved according to
the embodiment of the present invention when applying to quartz
glass and fluorite glass which are transparent material in the
deep-ultraviolet region used well, especially 248 nm
wavelength.
[0159] It is preferable the material of refractive index of 1.35 to
1.5 in the deep-ultraviolet region is used as a low refractive
index material according to the embodiment of the present
invention. Especially, a higher effect can be achieved by using one
or more component chosen by the group of MgF.sub.2, SiO.sub.2, NaF,
LiF, and mixture or compound thereof as a material with excellent
productivity and a little absorption film in the low refractive
index. Among these, MgF.sub.2 and SiO.sub.2, which have withstand
extreme environmental conditions and can be easily obtained, is
easy to use for production the effect is high. A high
antireflection characteristic can be obtained by using MgF.sub.2 to
the low refraction layer of the fourth layer (surface layer) from
the substrate caused by the low refractive index thereof.
Similarly, It is preferable the material is used as the middle
refractive index material whose the refractive index in the
deep-ultraviolet region is 1.6 to 1.9. Especially, a higher effect
can be achieved by using one or more component chosen by the group
of Al.sub.2O.sub.3, CaF.sub.3, NdF.sub.3, YF.sub.3,
La.sub.2O.sub.3, and mixture or compound thereof as a material with
excellent productivity and a little absorption film in the low
refractive index.
[0160] According to the embodiment of the present invention, when
the visible or the near-infrared wavelength (auto focus
wavelength), which performs antireflection, is within the rage of
650 to 800 nm, the above-mentioned effect can be achieved by
setting the range of the film thickness of the first layer from the
substrate to 0.4.lambda..ltoreq.nd1.ltoreq.0.6.lambda., that of the
second layer to 0.4.lambda..ltoreq.nd2.ltoreq.0.6.lambda., that of
the third layer to 0.1.lambda.<nd3.ltoreq.0.3.lambda., and that
of the fourth layer to 0.2.lambda.nd4.ltoreq.0.35.lambda., for
wavelength .lambda. (.lambda.=248 nm). In addition, when the range
of the film thickness of the first to fourth layer from the
substrate are set to 0.4.lambda..ltoreq.nd1.ltoreq.- 0.6.lambda.,
0.4.lambda..ltoreq.nd2.ltoreq.0.6.lambda.,
0.2.lambda..ltoreq.nd3.ltoreq.0.3.lambda., and
0.2.lambda..ltoreq.nd4.lto- req.0.3.lambda., respectively, two
wavelength antireflection film with high antireflection performance
can be obtained in the combination of film material with high
refractive index stability and excellent productivity (MgF.sub.2,
La.sub.2O.sub.3, and Al.sub.2O.sub.3 mixture material). When the
auto focus wavelength is selected in the vicinity of 750 nm, a
higher effect can be obtained according to such a range of the film
thickness.
[0161] Similarly, when auto focus wavelength is in 650 to 800 nm,
the above-mentioned effect can be achieved by setting the range of
the film thickness of the first layer from the substrate to
0.5.lambda..ltoreq.nd1.ltoreq.0.7.lambda., that of the second layer
to 0.05.lambda..ltoreq.nd2.ltoreq.0.2.lambda., that of the third
layer to 0.25.lambda..ltoreq.nd3.ltoreq.0.5.lambda., and that of
the fourth layer to 0.2.lambda..ltoreq.nd4.ltoreq.0.35.lambda., for
wavelength .lambda. (.lambda.=248 nm). In addition, when the range
of the film thickness of the first to fourth layer from the
substrate are set to 0.6.lambda..ltoreq.nd1.ltoreq.0.7.lambda.,
0.05.lambda..ltoreq.nd2.ltoreq- .0.1.lambda.,
0.25.lambda..ltoreq.nd3.ltoreq.0.35.lambda., and
0.25.lambda.<nd4.ltoreq.0.35.lambda., respectively, two
wavelength antireflection film with high antireflection performance
can be obtained in the combination of film material with high
refractive index stability and excellent productivity (MgF.sub.2,
La.sub.2O.sub.3, and Al.sub.2O.sub.3 mixture material). When the
auto focus wavelength is selected in the vicinity of 750 nm, a
higher effect can be obtained according to such a range of the film
thickness.
[0162] In the objective lens used for the microscope, which
observes by the light of wavelength of the ultraviolet region of
300 nm or less and has the focusing mechanism (auto focus) in the
wavelength from the visible region to the near-infrared region,
high transmittance and a high NA, that is, high resolving power can
be achieved.
[0163] The present invention is not limited to the above-described
embodiments. Various modifications can occur at its embodying stage
without departing from the scope of the invention.
[0164] In addition, for example, even if some of all the
constituent elements shown in the embodiments are deleted, in the
case where the problems described in the Brief Summary of the
Invention section can be solved, and advantageous effect described
in the Advantageous Effect of the Invention section can be
achieved, the configuration can be excerpted after these
constituent elements have been deleted.
[0165] As mentioned above, according to the present invention,
two-wavelength antireflection film in which high transmittance can
be achieved in a deep-ultraviolet region and from the visible
region to the near-infrared region, and the objective lens on which
two-wavelength antireflection film is coated can be achieved.
[0166] Additional advantages and modifications will readily occur
to those skilled in the art. Therefore, the present invention in
its broader aspects is nor limited to the specific details,
representative devices, and illustrated examples shown and
described herein. Accordingly, various modifications may be made
without departing from the spirit or scope of the general inventive
concept as defined by the appended claims and their
equivalents.
* * * * *