U.S. patent application number 15/871959 was filed with the patent office on 2018-09-13 for light source device and optical filtering assembly thereof.
The applicant listed for this patent is OTO PHOTONICS INC.. Invention is credited to CHIEN-HSIANG HUNG, SHENG WANG LIN.
Application Number | 20180259697 15/871959 |
Document ID | / |
Family ID | 63446460 |
Filed Date | 2018-09-13 |
United States Patent
Application |
20180259697 |
Kind Code |
A1 |
HUNG; CHIEN-HSIANG ; et
al. |
September 13, 2018 |
LIGHT SOURCE DEVICE AND OPTICAL FILTERING ASSEMBLY THEREOF
Abstract
An optical filtering assembly comprises a first interference
film and a second interference film. The first interference film
comprises multiple first film layers and multiple second film
layers. The first film layers and the second film layers are
alternately stacked. The second interference film comprises
multiple third film layers and multiple fourth film layers. The
third film layers and the fourth film layers are alternately
stacked. An optical constant of the first film layers is same as an
optical constant of the third film layers, and an optical constant
of the second film layers is same as an optical constant of the
fourth film layers, and an Optical Path Difference (OPD) produced
in the first interference film is different from an OPD produced in
the second interference film.
Inventors: |
HUNG; CHIEN-HSIANG; (Hsinchu
City, TW) ; LIN; SHENG WANG; (Hsinchu City,
TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
OTO PHOTONICS INC. |
Hsinchu City |
|
TW |
|
|
Family ID: |
63446460 |
Appl. No.: |
15/871959 |
Filed: |
January 15, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02B 5/285 20130101 |
International
Class: |
G02B 5/28 20060101
G02B005/28 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 9, 2017 |
TW |
106107793 |
Claims
1. An optical filtering assembly, comprising: a first interference
film comprising a plurality of first film layers and a plurality of
second film layers, the plurality of first film layers and the
plurality of second film layers being alternately stacked in the
first interference film; and a second interference film comprising
a plurality of third film layers and a plurality of fourth film
layers, the plurality of third film layers and the plurality of
fourth film layers being alternately stacked in the second
interference film, wherein an optical constant of the plurality of
first film layers is same as an optical constant of the plurality
of third film layers, and an optical constant of the plurality of
second film layers is same as an optical constant of the plurality
of fourth film layers, the first interference film and the second
interference film are both disposed in a transmission path of a
light beam, and an optical path difference (OPD) of the light beam
generated by travelling in the first interference film is different
from an OPD of the light beam generated by travelling in the second
interference film.
2. The optical filtering assembly as claimed in claim 1, further
comprising a first transparent substrate, wherein the first
interference film and the second interference film are respectively
formed at two opposite sides of the first transparent substrate,
and the first interference film, the first transparent substrate
and the second interference film are all disposed in the
transmission path of the light beam, a thickness of the first
interference film is different from a thickness of the second
interference film.
3. The optical filtering assembly as claimed in claim 1, further
comprising a first transparent substrate, wherein the first
interference film and the second interference film are respectively
formed at two opposite sides of the first transparent substrate,
and the first interference film, the first transparent substrate
and the second interference film are all disposed in the
transmission path of the light beam, a thickness of the first
interference film is different from a thickness of the second
interference film.
4. The optical filtering assembly as claimed in claim 1, further
comprising a first transparent substrate, wherein the first
interference film and the second interference film are respectively
formed at two opposite sides of the first transparent substrate,
and the first interference film, the first transparent substrate
and the second interference film are all disposed in the
transmission path of the light beam, a thickness of the first
interference film is different from a thickness of the second
interference film.
5. The optical filtering assembly as claimed in claim 1, further
comprising: a first transparent substrate disposed in the
transmission path of the light beam, wherein the first interference
film is formed on the first transparent substrate in order to form
a first interference filter; and a second transparent substrate
disposed in the transmission path of the light beam, wherein the
second interference film is formed on the second transparent
substrate in order to form a second interference filter.
6. The optical filtering assembly as claimed in claim 5, wherein
the first interference filter is parallel to the second
interference filter.
7. The optical filtering assembly as claimed in claim 5, wherein
the first interference filter is neither parallel to nor
perpendicular to the second interference filter.
8. The optical filtering assembly as claimed in claim 7, wherein a
thickness of the first interference filter is equal to a thickness
of the second interference filter.
9. The optical filtering assembly as claimed in claim 5, further
comprising: a third interference filter disposed in the
transmission path of the light beam, comprising: a third
transparent substrate; and a third interference film formed on the
third transparent substrate, and comprising a plurality of fifth
film layers and a plurality of sixth film layers, the plurality of
fifth film layers and the plurality of sixth film layers being
alternately stacked in the third interference film, wherein an
optical constant of the plurality of fifth film layers is same as
the optical constant of the plurality of first film layers, and an
optical constant of the plurality of sixth film layers is same as
an optical constant of the plurality of second film layers, the
third interference film is disposed in the transmission path of the
light beam, and an optical path difference (OPD) of the light beam
generated by travelling in the third interference film is different
from the OPD of the light beam generated by travelling in the first
interference film or the second interference film.
10. The optical filtering assembly as claimed in claim 1, further
comprising a first transparent substrate, wherein the first
interference film and the second interference film are respectively
formed at two opposite sides of the first transparent substrate,
and the first interference film, the first transparent substrate
and the second interference film are all disposed in the
transmission path of the light beam, a thickness of the first
interference film is different from a thickness of the second
interference film.
11. The optical filtering assembly as claimed in claim 1, further
comprising a first transparent substrate, wherein the first
interference film and the second interference film are respectively
formed at two opposite sides of the first transparent substrate,
and the first interference film, the first transparent substrate
and the second interference film are all disposed in the
transmission path of the light beam, a thickness of the first
interference film is different from a thickness of the second
interference film.
12. The optical filtering assembly as claimed in claim 1, further
comprising a first transparent substrate, wherein the first
interference film and the second interference film are respectively
formed at two opposite sides of the first transparent substrate,
and the first interference film, the first transparent substrate
and the second interference film are all disposed in the
transmission path of the light beam, a thickness of the first
interference film is different from a thickness of the second
interference film.
13. The optical filtering assembly as claimed in claim 1, further
comprising a first transparent substrate, wherein the first
interference film and the second interference film are respectively
formed at two opposite sides of the first transparent substrate,
and the first interference film, the first transparent substrate
and the second interference film are all disposed in the
transmission path of the light beam, a thickness of the first
interference film is different from a thickness of the second
interference film.
14. The optical filtering assembly as claimed in claim 1, further
comprising a first transparent substrate, wherein the first
interference film and the second interference film are respectively
formed at two opposite sides of the first transparent substrate,
and the first interference film, the first transparent substrate
and the second interference film are all disposed in the
transmission path of the light beam, a thickness of the first
interference film is different from a thickness of the second
interference film.
15. A light source device, comprising: a light source emitting a
light beam; an optical filtering assembly as claimed in claim 1,
disposed in disposed in a transmission path of the light beam
16. The light source device as claimed in claim 15, further
comprising a first transparent substrate, wherein the first
interference film and the second interference film are respectively
formed at two opposite sides of the first transparent substrate,
and the first interference film, the first transparent substrate
and the second interference film are all disposed in the
transmission path of the light beam, a thickness of the first
interference film is different from a thickness of the second
interference film.
17. The light source device as claimed in claim 15, further
comprising a first transparent substrate, wherein the first
interference film and the second interference film are respectively
formed at two opposite sides of the first transparent substrate,
and the first interference film, the first transparent substrate
and the second interference film are all disposed in the
transmission path of the light beam, a thickness of the first
interference film is different from a thickness of the second
interference film.
18. The light source device as claimed in claim 15, further
comprising a first transparent substrate, wherein the first
interference film and the second interference film are respectively
formed at two opposite sides of the first transparent substrate,
and the first interference film, the first transparent substrate
and the second interference film are all disposed in the
transmission path of the light beam, a thickness of the first
interference film is different from a thickness of the second
interference film.
19. The light source device as claimed in claim 15, further
comprising a first transparent substrate, wherein the first
interference film and the second interference film are respectively
formed at two opposite sides of the first transparent substrate,
and the first interference film, the first transparent substrate
and the second interference film are all disposed in the
transmission path of the light beam, a thickness of the first
interference film is different from a thickness of the second
interference film.
20. An optical filtering assembly, comprising: a first interference
film comprising a plurality of film layers having a first thickness
distribution; and a second interference film comprising a plurality
of film layers each of which has a second thickness, wherein an
optical constant of the plurality of first film layers is same as
an optical constant of the plurality of third film layers, and an
optical constant of the plurality of second film layers is same as
an optical constant of the plurality of fourth film layers, the
first interference film and the second interference film 120 are
both disposed in a transmission path of a light beam, and an
optical path difference (OPD) of the light beam generated by
travelling in the first interference film is different from an OPD
of the light beam generated by travelling in the second
interference film.
21. The optical filtering assembly as claimed in claim 20, further
comprising a first transparent substrate, wherein the first
interference film and the second interference film are respectively
formed at two opposite sides of the first transparent substrate,
and the first interference film, the first transparent substrate
and the second interference film are all disposed in the
transmission path of the light beam, a thickness of the first
interference film is different from a thickness of the second
interference film.
22. The optical filtering assembly as claimed in claim 20, further
comprising a first transparent substrate, wherein the first
interference film and the second interference film are respectively
formed at two opposite sides of the first transparent substrate,
and the first interference film, the first transparent substrate
and the second interference film are all disposed in the
transmission path of the light beam, a thickness of the first
interference film is different from a thickness of the second
interference film.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] The present invention is related to a light source device
and an optical filtering assembly thereof, and in particular to an
optical filtering assembly used for filtering light by means of
interference and a light source device in use of the optical
filtering assembly.
2. The Related Arts
[0002] With the development in modern optics, a kind of
interference filter has now been available. In general, the
interference filter has a multilayer film in which two kinds of
films having different optical constants are alternately stacked.
The both kind of films are transparent in appearance. Depending
upon thickness distributions and optical constants of the both kind
of films, a ray carries out constructive interference and
destructive interference while passing through the multilayer film,
so that the interference filter allows a ray of a certain
wavelength range to pass, and simultaneously blocks out a ray
outside the certain wavelength range. However, the design limit of
the multilayer film and the manufacturing tolerance of the film
thickness have negative influences on the filtering effect. In
particular, when the interference filter is applied to optical
measuring instruments such as spectrometers, monochromators or
interferometers, the measurement precision and accuracy may be
reduced.
SUMMARY OF THE INVENTION
[0003] An object of the present invention is to provide an optical
filtering assembly which utilizes different optical path
differences (OPDs) cooperatively produced by two interference
films, to improve the filtering effect.
[0004] An object of the present invention is further to provide a
light source device. The light source device comprises the above
mentioned optical filtering assembly.
[0005] An optical filtering assembly comprises a first interference
film and a second interference film. The first interference film
comprises a plurality of first film layers and a plurality of
second film layers. The plurality of first film layers and the
plurality of second film layers are alternately stacked. The second
interference film comprises plurality of third film layers and a
plurality of fourth film layers. The plurality of third film layers
and the plurality of fourth film layers are alternately stacked. An
optical constant of the first film layers is same as an optical
constant of the third film layers, and an optical constant of the
second film layers is same as an optical constant of the fourth
film layers. The first interference film and the second
interference film are arranged on a transmission path of a light
beam, and an Optical Path Difference (OPD) produced in the first
interference film is different from an OPD produced in the second
interference film.
[0006] The light source device comprises the above optical
filtering assembly and a light source, wherein the light source is
arranged near the optical filtering assembly and is used to launch
a light beam toward the optical filtering assembly.
[0007] Accordingly, the optical filtering assembly of the present
invention utilizes multiple layers of interference films whose
thickness is taken as constants to produce different OPDs and
interferences, thus to improve the light filtering effect, that is
helpful to the improvement of the precision and accuracy of optical
measuring instruments.
[0008] In order to further understand features and technology of
the present invention, please refer to detailed descriptions and
attached drawings presented as below. However, such descriptions
and drawings are simply adopted to introduce features and
technology of the present invention, and are not used to limit a
claimed scope of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1A is a schematic cross-sectional view of a light
source device in accordance with an embodiment of the present
invention.
[0010] FIG. 1B is a spectrum diagram in which the light beam of
FIG. 1A has respectively passed through a first interference film
and a second interference film.
[0011] FIG. 1C is a spectrum diagram in which the light beam of
FIG. 1A has passed through an optical filtering assembly.
[0012] FIG. 2A is a schematic cross-sectional view of a light
source device in accordance with another embodiment of the present
invention.
[0013] FIG. 2B is a schematic cross-sectional view of a light
source device in accordance with further another embodiment of the
present invention.
[0014] FIGS. 2C-2I are schematic diagrams showing optical film
designs of interference films in accordance with another
embodiments of the present invention.
[0015] FIG. 3 is a cross-sectional view of a light source device in
accordance with another embodiment of the present invention.
[0016] FIG. 4A is a cross-sectional view of a light source device
in accordance with another embodiment of the present invention.
[0017] FIG. 4B is a cross-sectional view of a light source device
in accordance with another embodiment of the present invention.
[0018] FIG. 4C is a cross-sectional view of a light source device
in accordance with another embodiment of the present invention.
[0019] FIG. 5A is a cross-sectional view of a light source device
in accordance with another embodiment of the present invention.
[0020] FIGS. 5B and 5C are spectrum diagrams in which the light
beam of FIG. 5A has passed through a first interference film and a
second interference film.
[0021] FIG. 6 is a cross-sectional view of a light source device in
accordance with another embodiment of the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
[0022] FIG. 1A is a schematic cross-sectional view of a light
source device 10a in accordance with an embodiment of the present
invention. With reference to FIG. 1A, the light source device 10a
comprises an optical filtering assembly 100 and a light source 10.
The light source 10 is disposed beside the optical filtering
assembly 100 and is used to emit a light beam L1 toward the optical
filtering assembly 100. The light beam L1 comprises a plurality of
rays. The light source 10 may be, for example, a Light Emitting
Diode (LED) or a halogen lamp. The optical filtering assembly 100
is disposed in a transmission path of the light beam L1, and
comprises two layers of interference films. The two layers of
interference films can be manufactured by existing optical film
designs. Such optical film designs are publicly disclosed in some
existing documents, such as a book titled "Thin Film Optics and
Film Coating Technology" (ISBN: 9789863940142) authored by Mr.
Cheng-Chung Lee.
[0023] In the embodiment shown in FIG. 1A, the optical filtering
assembly 100 comprises a first interference film 110 and a second
interference film 120. Both of the first interference film 110 and
the second interference film 120 are multilayer films. Taking FIG.
1A as an example, the first interference film 110 comprises a
plurality of first film layers 111 and a plurality of second film
layers 112. Each of the plurality of first film layers 111 has a
thickness T1, and each of the plurality of second film layers 112
has a thickness T2. The second interference film 120 comprises a
plurality of third film layers 123 and a plurality of fourth film
layers 124. Each of the plurality of third film layers 123 has a
thickness T3, and each of the plurality of fourth film layers 124
has a thickness T4. The plurality of first film layers 111 and the
plurality of second film layers 112 are alternately stacked, and
the plurality of third film layers 123 and the plurality of fourth
film layers 124 are alternately stacked.
[0024] The plurality of first film layers 111 and the plurality of
third film layers 123 may be made of high refractive index
material, such as tantalum pentoxide or titanium dioxide. The
plurality of second film layers 112 and the plurality of fourth
film layers 124 may be made of low refractive index material, such
as silicon dioxide. Therefore, each of the first interference film
110 and the second interference film 120 is formed by at least two
kinds of alternately stacked film layers having different optical
constants. The optical constant may be, for example, a refractive
index. In addition, the plurality of first film layers 111 and the
plurality of third film layers 123 may be made of a same material,
and the plurality of second film layers 112 and the plurality of
fourth film layers 124 may be made of another same material.
However, the material of the plurality of first film layers 111 and
the plurality of third film layers 123 is different from the
material of the plurality of second film layers 112 and the
plurality of fourth film layers 124. As a result, an optical
constant of the plurality of first film layers 111 is same as an
optical constant of the plurality of third film layers 123, and an
optical constant of the plurality of second film layers 112 is same
as an optical constant of the plurality of fourth film layers 124.
However, the optical constants of the plurality of first film
layers 111 and the plurality of third film layers 123 are different
from the optical constants of the plurality of second film layers
112 and the plurality of fourth film layers 124.
[0025] The first interference film 110 and the second interference
film 120 are both disposed in the transmission path of the light
beam L1 and are penetrated by the light beam L1. As shown in FIG.
1A, the light beam L1 firstly penetrates through the second
interference film 120, and then penetrates through the first
interference film 110. When the light beam L1 enters the first
interference film 110 and the second interference film 120, the
light beam L1 is reflected and refracted at a boundary between
every two film layers of the first interference film 110 (i.e.,
between either one of the plurality of first film layers 111 and a
corresponding one of the plurality of second film layers 112), and
a boundary between every two film layers of the second interference
film 120 (i.e., between either one of the plurality of third film
layers 123 and a corresponding one of the plurality of fourth film
layers 124) in order to generate light interference. As a result,
in the light beam L1, a part of the plurality of light rays with a
characteristic wavelength is enhanced due to constructive
interference while another part of the plurality of light rays
without the characteristic wavelength is eliminated due to
destructive interference. Hence, a function of light filtering is
achieved.
[0026] It is noted that although it is described for the above
embodiment that the plurality of first film layers 111 and the
plurality of third film layers 123 are layers of high refractive
index, and the plurality of second film layers 112 and the
plurality of fourth film layers 124 are layers of low refractive
index as an example, it is quite clear that in an alternative
embodiment, the plurality of first film layers 111 and the
plurality of third film layers 123 may be layers of low refractive
index, and the plurality of second film layers 112 and the
plurality of fourth film layers 124 may be layers of high
refractive index. Therefore, the plurality of first film layers 111
and the plurality of third film layers 123 are not limited to be
layers of high refractive index as depicted above, and the
plurality of second film layers 112 and the plurality of fourth
film layers 124 are not limited to be layers of low refractive
index as depicted above.
[0027] In the embodiment shown in FIG. 1A, the light beam L1
penetrates sequentially through the second interference film 120, a
first transparent substrate 101 and the first interference film
110. In another alternative embodiment, the light beam L1 may
penetrate sequentially through the first interference film 110, the
first transparent substrate 101 and the second interference film
120. When travelling inside the first interference film 110, the
light beam L1 penetrates sequentially through the first film layer
111, the second film layer 112, the first film layer 111, the
second film layer 112, . . . , and so on, or through the second
film layer 112, the first film layer 111, the second film layer
112, the first film layer 111, . . . , and so on. When travelling
inside the second interference film 120, the light beam L1
penetrates sequentially through the third film layer 123, the
fourth film layer 124, the third film layer 123, the fourth film
layer 124, . . . , and so on, or through the fourth film layer 124,
the third film layer 123, the fourth film layer 124, the third film
layer 123, . . . , and so on. Therefore, penetration sequence(s) of
the light beam L1 through the first film layer 111 to the fourth
film layer 124 is not limited to the above depicted embodiment as
shown in FIG. 1A.
[0028] Furthermore, in another embodiment shown in FIG. 2A, the
second interference film 120 is disposed between the first
transparent substrate 101 and a second transparent substrate 102,
and the first transparent substrate 101 is disposed between the
first interference film 110 and the second interference film 120.
However, in another embodiment, such as further another embodiment
shown in FIG. 2B, an optical filtering assembly 200b of a light
source device 20b is illustrated that the first interference film
110 and the second interference film 120 are both disposed between
the first transparent substrate 101 and second transparent
substrate 102. As a result, the light beam L1 enters the second
interference film 120 from the second transparent substrate 102,
enters the first interference film 110 from the second interference
film 120, enters the first transparent substrate 101 from the first
interference film 110, and then leaves the optical filtering
assembly 200b from the first transparent substrate 101, as shown in
FIG. 2B.
[0029] In this embodiment, a thickness ratio between each of the
plurality of first film layers 111 and either one of the plurality
of second film layer 112 adjacent thereto is same as a thickness
ratio between each of the plurality of third film layers 123 and
either one of the plurality of fourth film layer 124 adjacent
thereto. For example, a ratio between a thickness T1 of each first
film layer 111 and a thickness T2 of each second film layer 112
alternately stacked with the plurality of first film layers 111 in
the first interference film 110 is same as a ratio between a
thickness T3 of each third film layer 123 and a thickness T4 of
each fourth film layer 124 alternately stacked with the plurality
of third film layer 123 in the second interference film 120. For
another example, for every four adjacent film layers in the first
interference film 110, a thickness ratio of the first film layer
111, the second film layer 112, the first film layer 111 and the
second film layer 112 therein is 1:2:3:6, and for every four
adjacent film layers in the second interference film 120, a
thickness ratio of the third film layer 123, the fourth film layer
124, the third film layer 123 and the fourth film layer 124 therein
is 1:2:3:6. In addition, a thickness 110t of the first interference
film 110 may not be same as a thickness 120t of the second
interference film 120. Among them, the thickness T1 may not be same
as the thickness T3, and the thickness T2 may not be same as the
thickness T4.
[0030] It can be understood that both of the first interference
film 110 and the second interference film 120 have a same film
layer distribution, and an optical path length (OPL) of the light
beam L1 in the first interference film 110 is different from an OPL
of the light beam L1 in the second interference film 120. In other
words, an optical path difference (OPD) of the light beam L1
generated by travelling in the first interference film 110 is
different from an OPD of the light beam L1 generated by travelling
in the second interference film 120. Therefore, both of the first
interference film 110 and the second interference film 120 can
change a phase of a part of light rays in the light beam L1. A
phase shift of the light beam L1 caused by the first interference
film 110 is different from a phase shift of the light beam L1
caused by the second interference film 120. In other words,
interference of the light beam L1 in the first interference film
110 and interference of the light beam L1 in the second
interference film 120 (including constructive interference and
destructive interference) are different from each other.
[0031] In general, an existing interference filter piece often
generates ripples. Ripples does not only affect a filtering effect
of the interference filter piece, but also reduce accuracy and
precision of related optical measuring instruments. In details,
when the existing interference filter piece filters a light beam, a
spectrum of the filtered light beam shows as wavy curves as shown
in FIG. 1B, and the wavy curves are so-called ripples.
[0032] FIG. 1B is a spectrum diagram in which a light beam L1 has
respectively passed the first interference film 110 and the second
interference film 120. A curve C1 indicated by a solid line shows a
spectrum of the light beam L1 after the light beam L1 only passes
the first interference film 110 for the light filtering. A first
ripple effect is being produced by the first interference film 110
where light beam L1 is passing through. A curve C2 indicated by a
dashed line shows a spectrum of the light beam L1 after the light
beam L1 only passes the second interference film 120 for the light
filtering. A second ripple effect is being produced by the second
interference film 120 where the light beam L1 is passing
through.
[0033] The first interference film 110 and the second interference
film 120 have similar film structures, so the spectrums (shown as
the curves C1 and C2 in FIG. 1B) produced by the light beam L1
passing the first interference film 110 and the second interference
film 120 are similar as well. For example, the ripples of the
curves C1 and C2 roughly have a same or similar amount of peaks and
valleys, but the whereabouts and the Full Width at Half Maximum
(FWHM) of the peaks and valleys of the curves C1 and C2 are
obviously different.
[0034] In the embodiment, the thickness T1 is larger than the
thickness T3, and the thickness T2 is larger than the thickness T4.
That is, the thickness 110t of the first interference film 110 is
larger than the thickness 120t of the second interference film 120.
Therefore, the ripple (curve C1) produced by the first interference
film 110 has a wider FWHM at its peak and valley, and the ripple
(curve C2) produced by the second interference film 120 has a
narrower FWHM at its peak and valley, so that the curve C1 looks
like the curve C2 extended in a horizontal direction, and the curve
C2 looks like the curve C1 compressed in the horizontal direction.
In addition, in a certain wavelength range, e.g. in the wavelength
range from 200 nm to 350 nm as shown in FIG. 1B, the peak of the
curve C1 is aligning to the valley of the curve C2, and the valley
of the curve C1 is aligning to the peak of the curve C2, so as to
produce the destructive interference, in which the first ripple
effect and the second ripple effect can be offset, as shown in FIG.
1C.
[0035] With reference to FIG. 1B and FIG. 1C, a curve C3 shown in
FIG. 1C refers to a spectrum of the light beam L1 passing through
the second interference film 120 and the first interference film
110 in order. Because the destructive interference produced between
the curves C1 and C2 in the wavelength range from 200 nm to 350 nm
results in the offset of the first ripple effect and the second
ripple effect, the influence caused by the ripples is reduced, and
the smoother distribution curve C3 is thus produced. In particular,
the curve C3 in the wavelength range from 200 nm to 350 nm has a
shape similar to a smooth horizontal line. It can be seen that
after being filtered by the optical filtering assembly 100, the
spectrum of the light beam L1 in a certain wavelength range, (e.g.
200 nm-350 nm) appears a smoother distribution. Compared to
conventional interference filters, the optical filtering assembly
100 in accordance with the present invention has a better filtering
effect that is helpful to the improvement of the precision and
accuracy of optical measuring instruments.
[0036] With reference to FIG. 1A, in the embodiment with respect to
FIG. 1A, the first interference film 110 and the second
interference film 120 are formed on the same substrate. In this
regard, the optical filtering assembly 100 further comprises the
first transparent substrate 101. The first transparent substrate
101 may be made of glass plate or sapphire substrate. The first
interference film 110 and the second interference film 120 are
formed on the first transparent substrate 101, wherein the first
transparent substrate 101 is located between the first interference
film 110 and the second interference film 120, and on the
transmission path of the light beam L1. In other word, the first
interference film 110 and the second interference film 120 are
respectively formed on the opposite sides of the first transparent
substrate 101, and also come into contact with the first
transparent substrate 101.
[0037] The first interference film 110 and the second interference
film 120 may be formed by means of deposition. For example,
Chemical Vapor Deposition (CVD) may be adapted in the process of
forming layers from the first film layer 111 to the fourth film
layer 124, with the first interference film 110 and the second
interference film 120 both formed in situ. That is, the first
interference film 110 and the second interference film 120 are
formed in a same chamber under vacuum condition, i.e. the first
film layer 111, the second film layer 112, the third film layer 123
and the fourth film layer 124 are formed in situ.
[0038] FIG. 2A is a cross-sectional view of a light source device
in accordance with another embodiment of the present invention.
With reference to FIG. 2A, regarding a light source device 20a of
the present invention, an optical filtering assembly 200a is
similar to the optical filtering assembly 100 of the previous
embodiment. For example, the optical filtering assembly 200a
comprises the first interference film 110, the second interference
film 120 and the first transparent substrate 101. But, unlike the
optical filtering assembly 100, the optical filtering assembly 200a
comprises the second transparent substrate 102. The second
interference film 120 is formed on the second transparent substrate
102 and comes into contact with the second transparent substrate
102, instead of being formed on the first transparent substrate
101.
[0039] Specifically, the first interference film 110 is still
disposed on the first transparent substrate 101 to form a first
interference filter 201, but the second interference film 120 is
disposed on the second transparent substrate 102 to form a second
interference filter 202. Therefore, the first interference film 110
and the second interference film 120 are formed on two different
transparent substrates, i.e. on the first transparent substrate 101
and the second transparent substrate 102. The optical filtering
assembly 200a comprises at least two interference filters. i.e. the
first interference filter 201 and the second interference filter
202. In addition, a material of the second transparent substrate
102 may be same as the material of the first transparent substrate
101.
[0040] The first interference film 110, the second interference
film 120, the first transparent substrate 101 and the second
transparent substrate 102 are arranged on the transmission path of
the light beam L1. In this manner, the light beam L1 penetrates
through the 202 and the 201 in order. The second interference film
120 is disposed between the first transparent substrate 101 and the
second transparent substrate 102, and the first transparent
substrate 101 is disposed between the first interference film 110
and the second interference film 120, so that the light beam L1
enters the second interference film 120 from the second transparent
substrate 102, then enters the first interference film 110 from the
first transparent substrate 101, and then leaves the optical
filtering assembly 200a from the first interference film 110. In
addition, the first interference filter 201 may be parallel to the
second interference filter 202, so that the light beam L1 can be
transmitted along optical axes of the first interference filter 201
and the second interference filter 202.
[0041] It is noted that the "parallel to" recited in the
specification and the claims of the present invention includes
"substantially parallel to". In details, when viewing the two
filters (e.g. the first interference filter 201 and the second
interference filter 202) directly with the naked eye, without using
any measuring tools such as rulers or protractors, most viewers
believe that they must be parallel to each other. However, the
"parallel to" actually refers to "substantially parallel to".
Therefore, when viewing the first interference filter 201 and the
second interference filter 202 directly with the naked eye, most
viewers would believe that the first interference filter 201 and
the second interference filter 202 are parallel to each other.
[0042] Further, in the embodiment with respect to FIG. 2A, the
second interference film 120 is disposed between the first
transparent substrate 101 and the second transparent substrate 102,
and the first transparent substrate 101 is disposed between the
first interference film 110 and the second interference film 120.
However, in an alternative embodiment such as the optical filtering
assembly 200b of the light source device 20b shown in FIG. 2B, the
first interference film 110 and the second interference film 120
are disposed between the first transparent substrate 101 and the
second transparent substrate 102, so that the light beam L1 enters
the second interference film 120 from the second transparent
substrate 102, then enters the first transparent substrate 101 from
the first interference film 110, and then leaves the optical
filtering assembly 200b from the first transparent substrate
101.
[0043] In the embodiments with respect to FIG. 2A and FIG. 2B, each
of the first film layers 111 has same thickness T1, each of the
second film layers 112 has same thickness T2, each of the third
film layers 113 has same thickness T3, and each of the fourth film
layers 114 may have same thickness T4. However, this is just one of
multiple alternative embodiments, and the present invention is not
limited thereto. In other embodiments, the interference film may
have different thickness in each of the film layers, or may have
same thickness in parts of the film layers. For those skilled in
the art, it is possible to make a variety of modification in the
design of the film layers by requirements, without departing from
the scope and spirit of the present invention. As to the design of
the film layers, Chapter 3 of the mentioned book "Thin Film Optics
and Coating Technology" can be taken for reference as well. The
design of the film layers need not be repeated here.
[0044] FIGS. 2C-2F are schematic diagrams of the first and second
interference films as optical film designs in accordance with
another embodiments of the present invention. FIG. 2C depicts each
of odd-numbered layers of the first interference film. FIG. 2E
depicts each of even-numbered layers of the first interference
film. FIG. 2D depicts each of odd-numbered layers of the second
interference film. FIG. 2F depicts each of even-numbered layers of
the second interference film. From FIG. 2C to FIG. 2F, the vertical
axes are numbers of film layers, and the horizontal axes are
thickness of film layers. It can be seen from FIG. 2C to FIG. 2E
that the film layers numbered 1, 3, 5 . . . are alternately stacked
on the film layers numbered 2, 4, 6 . . . . In this embodiment, the
bigger the number of the film layer is, the farther away the
transparent substrate is from the film layer. On the other hand,
the smaller the number of the film layer is, the closer to the
transparent substrate the film layer is. In this embodiment, the
first interference film has 100 film layers. The odd-numbered
layers of the first interference film are made of a first material,
and the even-numbered layers of the first interference film are
made of a second material, wherein the first material is different
with the second material. The second interference film has 100 film
layers. The odd-numbered layers of the second interference film are
made of a first material, and the even-numbered layers of the
second interference film are made of a second material, wherein the
first material is different with the second material.
[0045] The first interference film includes a first continuous film
layer stack, and the second interference film includes a second
continuous film layer stack. In this embodiment, the film layers
numbered 1 to 39 in FIG. 2C and FIG. 2E are taken as an example to
illustrate the first continuous film layer stack, and the film
layers numbered 1 to 39 in FIG. 2D and FIG. 2F are taken as another
example to illustrate the second continuous film layer stack. It is
noted that the thickness of the second continuous film layer stack
(i.e. the film layers numbered 1 through 39) is 0.6 times that of
the first continuous film layer stack (i.e. the film layers
numbered 1 through 39). In this embodiment, however, there is no
common proportional relationship in thickness between the film
layers numbered 40 through 100 in the first interference film and
the film layers numbered 40 through 100 in the second interference
film. That is, the first continuous film layer stack is 39% of
total film layers in the first interference film, and the second
continuous film layer stack is 39% of total film layers in the
second interference film. Similar to the previous embodiment, this
embodiment provides the continuous film layer stack (e.g. the first
continuous film layer stack) as 39% of the interference film, which
can also improve the problem caused by ripples. The 39% is only an
example in this embodiment. Other ratio may be used in an
alternative embodiment, such as a ratio more than 30%.
[0046] Further, the first interference film may include a first
continuous film layer stack and a third continuous film layer
stack, and the second interference film may include a second
continuous film layer stack and a fourth continuous film layer
stack. Thickness of each of film layers in the first continuous
film layer stack (e.g. a first thickness distribution) is
proportional to thickness of each of film layers in the second
continuous film layer stack (e.g. a second thickness distribution)
in a first ratio. Thickness of each of film layers in the third
continuous film layer stack (e.g. a third thickness distribution)
is proportional to thickness of each of film layers in the fourth
continuous film layer stack (e.g. a fourth thickness distribution)
in a second ratio. The first ratio is different with the second
ratio. In this manner, the problem caused by ripples can be also
improved.
[0047] FIGS. 2G-2I are spectrum diagrams showing spectrums of the
optical filtering assemblies. The optical filtering assemblies with
respect to FIGS. 2G-2I are respectively shown as follows.
TABLE-US-00001 TABLE 1 Ratio of each of film layers in the first
interference film to each of film layers in the second interference
film is 0.98. (With respect to FIG. 2G) Thickness of Thickness of
each of film each of film layers in layers in Number Material the
first the second of film of film interference interference layers
layers film in nm film in nm 1.sup.st layer SiO2 94.69 92.80
2.sup.nd layer TiO2 36.45 35.72 3.sup.rd layer SiO2 100.90 98.89
4.sup.th layer TiO2 45.52 44.61 5.sup.th layer SiO2 66.78 65.45
6.sup.th layer TiO2 46.19 45.27 7.sup.th layer SiO2 66.83 65.49
8.sup.th layer TiO2 19.80 19.40 9.sup.th layer SiO2 47.00 46.06
10.sup.th layer TiO2 43.71 42.83 11.sup.th layer SiO2 67.32 65.97
12.sup.th layer TiO2 35.33 34.62 13.sup.th layer SiO2 29.16 28.57
14.sup.th layer TiO2 22.39 21.94 15.sup.th layer SiO2 67.31 65.96
16.sup.th layer TiO2 51.61 50.58 17.sup.th layer SiO2 80.37 78.77
18.sup.th layer TiO2 48.03 47.07 19.sup.th layer SiO2 73.60 72.13
20.sup.th layer TiO2 38.18 37.42 21.sup.st layer SiO2 41.40 40.58
22.sup.nd layer TiO2 31.03 30.41 23.sup.rd layer SiO2 75.24 73.74
24.sup.th layer TiO2 43.29 42.42 25.sup.th layer SiO2 86.75 85.01
26.sup.th layer TiO2 52.01 50.97 27.sup.th layer SiO2 79.30 77.72
28.sup.th layer TiO2 58.26 57.10 29.sup.th layer SiO2 73.27 71.80
30.sup.th layer TiO2 52.83 51.78 31.sup.st layer SiO2 96.49 94.56
32.sup.nd layer TiO2 46.67 45.73 33.sup.rd layer SiO2 78.76 77.18
34.sup.th layer TiO2 55.69 54.58 35.sup.th layer SiO2 90.16 88.36
36.sup.th layer TiO2 42.41 41.56 37.sup.th layer SiO2 81.29 79.67
38.sup.th layer TiO2 47.79 46.84 39.sup.th layer SiO2 160.94
157.72
TABLE-US-00002 TABLE 2 Ratio of each of film layers in the first
interference film to each of film layers in the second interference
film is 0.98, except for the 15th layer where the thicknesses in
first and second interference films are the same. (With respect to
FIG. 2H) Thickness of Thickness of each of film each of film layers
in layers in Number Material the first the second of film of film
interference interference layers layers film in nm film in nm
1.sup.st layer SiO2 94.69 92.80 2.sup.nd layer TiO2 36.45 35.72
3.sup.rd layer SiO2 100.90 98.89 4.sup.th layer TiO2 45.52 44.61
5.sup.th layer SiO2 66.78 65.45 6.sup.th layer TiO2 46.19 45.27
7.sup.th layer SiO2 66.83 65.49 8.sup.th layer TiO2 19.80 19.40
9.sup.th layer SiO2 47.00 46.06 10.sup.th layer TiO2 43.71 42.83
11.sup.th layer SiO2 67.32 65.97 12.sup.th layer TiO2 35.33 34.62
13.sup.th layer SiO2 29.16 28.57 14.sup.th layer TiO2 22.39 21.94
15.sup.th layer SiO2 67.31 67.31 16.sup.th layer TiO2 51.61 50.58
17.sup.th layer SiO2 80.37 78.77 18.sup.th layer TiO2 48.03 47.07
19.sup.th layer SiO2 73.60 72.13 20.sup.th layer TiO2 38.18 37.42
21.sup.st layer SiO2 41.40 40.58 22.sup.nd layer TiO2 31.03 30.41
23.sup.rd layer SiO2 75.24 73.74 24.sup.th layer TiO2 43.29 42.42
25.sup.th layer SiO2 86.75 85.01 26.sup.th layer TiO2 52.01 50.97
27.sup.th layer SiO2 79.30 77.72 28.sup.th layer TiO2 58.26 57.10
29.sup.th layer SiO2 73.27 71.80 30.sup.th layer TiO2 52.83 51.78
31.sup.st layer SiO2 96.49 94.56 32.sup.nd layer TiO2 46.67 45.73
33.sup.rd layer SiO2 78.76 77.18 34.sup.th layer TiO2 55.69 54.58
35.sup.th layer SiO2 90.16 88.36 36.sup.th layer TiO2 42.41 41.56
37.sup.th layer SiO2 81.29 79.67 38.sup.th layer TiO2 47.79 46.84
39.sup.th layer SiO2 160.94 157.72
TABLE-US-00003 TABLE 3 Ratio of each of film layers in the first
interference film to each of film layers in the second interference
film is 0.98, except for the 37th-39th layers where the thicknesses
in first and second interference films are the same. (With respect
to FIG. 2I) Thickness of Thickness of each of film each of film
layers in layers in Number Material the first the second of film of
film interference interference layers layers film in nm film in nm
1.sup.st layer SiO2 94.69 92.80 2.sup.nd layer TiO2 36.45 35.72
3.sup.rd layer SiO2 100.90 98.89 4.sup.th layer TiO2 45.52 44.61
5.sup.th layer SiO2 66.78 65.45 6.sup.th layer TiO2 46.19 45.27
7.sup.th layer SiO2 66.83 65.49 8.sup.th layer TiO2 19.80 19.40
9.sup.th layer SiO2 47.00 46.06 10.sup.th layer TiO2 43.71 42.83
11.sup.th layer SiO2 67.32 65.97 12.sup.th layer TiO2 35.33 34.62
13.sup.th layer SiO2 29.16 28.57 14.sup.th layer TiO2 22.39 21.94
15.sup.th layer SiO2 67.31 65.96 16.sup.th layer TiO2 51.61 50.58
17.sup.th layer SiO2 80.37 78.77 18.sup.th layer TiO2 48.03 47.07
19.sup.th layer SiO2 73.60 72.13 20.sup.th layer TiO2 38.18 37.42
21.sup.st layer SiO2 41.40 40.58 22.sup.nd layer TiO2 31.03 30.41
23.sup.rd layer SiO2 75.24 73.74 24.sup.th layer TiO2 43.29 42.42
25.sup.th layer SiO2 86.75 85.01 26.sup.th layer TiO2 52.01 50.97
27.sup.th layer SiO2 79.30 77.72 28.sup.th layer TiO2 58.26 57.10
29.sup.th layer SiO2 73.27 71.80 30.sup.th layer TiO2 52.83 51.78
31.sup.st layer SiO2 96.49 94.56 32.sup.nd layer TiO2 46.67 45.73
33.sup.rd layer SiO2 78.76 77.18 34.sup.th layer TiO2 55.69 54.58
35.sup.th layer SiO2 90.16 88.36 36.sup.th layer TiO2 42.41 41.56
37.sup.th layer SiO2 81.29 81.29 38.sup.th layer TiO2 47.79 47.79
39.sup.th layer SiO2 160.94 160.94
[0048] With reference to FIGS. 2G-2I, which shows simulating
spectrum diagrams drawn on a basis of the references listed in
above Tables, a curve C21 represents the first interference film,
and a curve C22 represents the second interference film, and a
curve C23 represents a spectrum formed along with the interference
between the curve C21 and the curve C22, as a result of
superposition of the curve C21 and the curve C22. It can be seen
from FIG. 2G to FIG. 2I that the optical filtering assembly appears
a smoother spectrum distribution after the wavelength of 580 nm
(such as curve C23). That is, the first and second ripple effects
caused by the first and second interference films can be offset to
reduce the undesirable influence caused by the ripples, and to
produce the smoother spectrum distribution of the curve C23 as
shown in FIG. 2I. As a result, the optical filtering assemblies in
accordance with the above Tables have better filtering effects as
well that is helpful to the improvement of the precision and
accuracy of optical measuring instruments.
[0049] FIG. 3 is a cross-sectional view of a light source device in
accordance with another embodiment of the present invention. With
reference to FIG. 3, the light source device 30 of this embodiment
is similar to the light source device 20a of the embodiment with
respect to FIG. 2A. For example, the optical filtering assembly 300
comprises the first interference filter 201 and the second
interference filter 202. But, unlike the optical filtering assembly
200a of FIG. 2A, the optical filtering assembly 300 further
comprises a third interference filter 203. That is, the optical
filtering assembly 300 at least comprises three interference
filters, e.g. the first interference filter 201, the second
interference filter 202 and the third interference filter 203,
wherein the three interference filters are arranged on the
transmission path of the light beam L1 and parallel to each other,
as shown in FIG. 3.
[0050] Specifically, the optical filtering assembly 300 comprises a
third transparent substrate 103 and a third interference film 130.
The third interference film 130 is disposed on the third
transparent substrate 103 to form a third interference filter 203.
That is, the third interference filter 203 comprises the third
interference film 130 and the third transparent substrate 103. The
third interference film 130 is a multilayer film comprising
multiple fifth film layers 135 and multiple sixth film layers 136.
The fifth film layers 135 and the sixth film layers 136 are
alternately stacked. In addition, an OPD produced by the light beam
L1 in the third interference film 130 is different from OPDs
produced by the light beam L1 in the first interference film 110 or
in the second interference film 120.
[0051] The fifth interference film 135 may be made of high
refractive index material, and the sixth film layers 136 may be
made of low refractive index material. The material of the fifth
interference film 135 may be same as that of the first film layer
111, and the material of the sixth film layer 136 may be same as
that of the second film layer 112. Therefore, the optical constant
of the fifth interference film 135 is same as that of the first
film layer 111, and the optical constant of the sixth film layer
136 may be same as that of the second film layer 112. In addition,
the fifth interference film 135 and the sixth film layers 136 may
be formed by means of deposition, such as Chemical Vapor Deposition
(CVD). Therefore, the third interference film 130 is formed in the
same manner that at least two kinds of film layers having different
optical constants are alternately stacked. In addition, in this
embodiment, the fifth interference film 135 is made of high
refractive index material, and the sixth film layers 136 is made of
low refractive index material. But in other embodiment, the fifth
interference film 135 may be made of low refractive index material,
and the sixth film layers 136 may be made of high refractive index
material.
[0052] In this embodiment, for the third interference film 130,
each of the fifth film layers 135 has a thickness T5, and each of
the sixth film layers 136 has a thickness T6. A ratio between the
thickness T5 of each fifth film layer 135 and the thickness T6 of
each sixth film layer 136 may be same as the ratio of thickness of
each of film layers stacked in the first interference film 110 and
in the second interference film 120. For example, for four adjacent
film layers in the first interference film 110, a thickness ratio
of the first film layer 111, the second film layer 112, the first
film layer 111, and the second film layer 112 is 1:2:3:6, and for
four adjacent film layers in the third interference film 130, a
thickness ratio of the fifth film layer 135, the sixth film layer
136, the fifth film layer 135, and sixth film layer 136 is 1:2:3:6.
In addition, a thickness 130t of the third interference film 130
may not have to be same as at least one of the thickness 110t and
the thickness 120t, wherein at least one of the thickness T1 and
the thickness T3 may not have to be same as the thickness T5, and
at least one of the thickness T2 and the thickness T4 may not have
to be same as the thickness T6.
[0053] FIG. 4A is a cross-sectional view of a light source device
in accordance with another embodiment of the present invention.
With reference to FIG. 4A, a light source device 40a is similar to
the light source device 20a described in the embodiment with
respect to FIG. 2A. For example, the optical filtering assembly
400a also comprises the first interference filter 201 and the
second interference filter 202. The difference between the optical
filtering assembly 400a and the optical filtering assembly 200a is
that the first interference filter 201 is not parallel to and not
perpendicular to the second interference filter 202. It is noted
that "not parallel to" and "not perpendicular to" recited in the
specification and the claims of the present invention means that
when viewing directly with the naked eye without using any
measuring tools such as rulers, protractors, etc., viewers would
find the two filters (e.g. the first interference filter 201 and
the second interference filter 202) not parallel to and not
perpendicular to each other.
[0054] Although it is shown in FIG. 2A and FIG. 4A that the light
beam L1 penetrates the first interference filter 201, the light
beam L1 is not incident on the first interference filter 201 along
a normal 201a of the first interference filter 201 due to the first
interference filter 201 not parallel to and not perpendicular to
the second interference filter 202. Therefore, the OPL of the light
beam L1 in the first interference film 110 of FIG. 2A is different
from that in the first interference filter 201 of FIG. 4A, so that
the OPD produced in the first interference filter 201 of FIG. 2A is
different from the OPD produced in the first interference filter
201 of FIG. 4A. So, as to the same light beam L1, the filtering
effect provided by the optical filtering assembly 400a of FIG. 4A
is different with that provided by the optical filtering assembly
200a of FIG. 2A.
[0055] An angle A1 of 30 degree between the normal 201a of the
first interference filter 201 and the transmission path of the
light beam L1 is hereby taken as an example. In other embodiments,
those in the art can modify the angle A1 by the requirement of the
improvement on the ripple range. It can be seen from FIG. 4A that
the OPL of the light beam L1 in the first interference filter 201
is related to the angle A1, so that the degree of the angle
determines the OPD of the first interference filter 201, thus to
control the optical filtering assembly 400a filtering the light
beam L1. In addition, in this embodiment, the first interference
filter 201 can rotate relative to the second interference filter
202. By the rotation of the first interference filter 201, the
filtering effect of the optical filtering assembly 400a can be
adjusted.
[0056] FIG. 4B is a cross-sectional view of a light source device
in accordance with another embodiment of the present invention.
With reference to FIG. 4B, a light source device 40b of FIG. 4B is
similar to the light source device 40a of FIG. 4A. In detail, the
optical filtering assembly 400b and the optical filtering assembly
400a comprise the same components, such as the first interference
filter 201. The difference is that the optical filtering assembly
400b comprises two same interference filters.
[0057] The optical filtering assembly 400b comprises the first
interference filter 201 and a second interference filter 402,
wherein the second interference filter 402 comprises the second
transparent substrate 102 and a second interference film 420. The
second interference film 420 is formed on the second transparent
substrate 102. The second interference film 420 is same as the
first interference film 110, which means that the second
interference film 420 is a multilayer film comprising multiple
first film layers 111 and multiple second film layers 112 (not
shown in FIG. 4B). In addition, a thickness 420t of the second
interference film 420 is same as the thickness 110t of the first
interference film 110. Therefore, the second interference film 420
is actually the first interference filter 201. That is, the optical
filtering assembly 400b substantially comprises two same
interference filters (i.e. the first interference filter 201),
wherein the second interference film 420 and the first interference
film 110 are both formed in situ. In other word, in this
embodiment, the optical filtering assembly 400b can take use of two
interference filters made in a same manufacturing process. By the
arrangement of the two interference filters (i.e. the angle set
between the two interference filters), the problem caused by
ripples can be improved.
[0058] Although the second interference filter 402 is same as the
first interference filter 201 in the optical filtering assembly
400b, the OPD produced by the first interference film 110 is
different with the OPD produced by the second interference film 420
due to the second interference filter 402 not parallel to and not
perpendicular to the first interference filter 201, wherein the
angle A1 between the normal 201a of the first interference filter
201 and the transmission path of the light beam L1 may be set equal
to or greater than 0 degree, and equal to or smaller than 70
degree. Further, it is the same as the optical filtering assembly
400a in that the first interference filter 201 can also rotate
relative to the second interference filter 402, so as to control
the filtering effect of the optical filtering assembly 400a, and
thus to remove unwanted light.
[0059] In addition, because the second interference filter 402 is
same as the first interference filter 201, and the second
interference film 420 and the first interference film 110 are
formed in situ, when the light beam is incident along the normal of
both the second interference filter 402 and the first interference
filter 201, the ripple effect produced by the second interference
filter 402 and the ripple effect produced by the first interference
filter 201 are substantially same. Nevertheless, because the second
interference filter 402 and the first interference filter 201 are
not parallel to and perpendicular to each other, which causes that
the OPD produced by the first interference film 110 is different
with the OPD produced by the second interference film 420, it is
possible to make both of the second interference filter 402 and the
first interference filter 201 produce different ripple effects
which may be offset each other by adjusting the angle A1, so as to
reduce the influence caused by the ripples.
[0060] It is noted that in the embodiments with respect to FIG. 4A
and FIG. 4B, the optical filtering assemblies 400a and 400b
comprise two interference filters, respectively. But in an
alternative embodiment, an interference filter may be additionally
added in the optical filtering assembly 400a or 400b, such as an
optical filtering assembly 400c in an embodiment with respect to
FIG. 4C. With reference to FIG. 4C, the optical filtering assembly
400c of a light source device 40c comprises at least three
interference filters such as the first interference filter 201, the
second interference filter 202 and the third interference filter
203, wherein the third interference filter 203 is parallel to the
first interference filter 201 or the second interference filter
202. An example is shown in FIG. 4C that the third interference
filter 203 is parallel to the second interference filter 202, but
is not parallel to and not perpendicular to the first interference
filter 201.
[0061] In the embodiment with respect to FIG. 4C, the first
interference filter 201, the second interference filter 202 and the
third interference filter 203 that are included in the optical
filtering assembly 400c are different interference filters. And
according to the previous embodiments, the thicknesses of the
interference films of the three interference filters are all
different. In other embodiment, the optical filtering assembly 400c
may comprise at least two same interference filters. Therefore, as
shown in FIG. 4C, at least one of the first interference filter
201, the second interference filter 202 and the third interference
filter 203 can be changed, to make the optical filtering assembly
400c comprise at least two same interference filters.
[0062] For example, the second interference filter 202 of FIG. 4C
may be changed to the second interference filter 402 of FIG. 4B to
make the optical filtering assembly 400c comprise at least two same
interference filters. Alternatively, the second interference filter
202 and the third interference filter 203 of FIG. 4C may be changed
to the first interference filter 201, to make the optical filtering
assembly 400c comprise at least three same interference filters
(i.e. the first interference filter 201).
[0063] In the embodiment with respect to FIG. 4C, the first
interference filter 201 is disposed between the second interference
filter 202 and the third interference filter 203 and is not
parallel to and perpendicular to the second interference filter 202
and the third interference filter 203. However, the arrangement of
the first interference filter 201, the second interference filter
202 and the third interference filter 203 may be changeable in
other embodiment. For example, the second interference filter 202
is disposed between the first interference filter 201 and the third
interference filter 203 and is not parallel to and perpendicular to
the first interference filter 201 and the third interference filter
203. Alternatively, the third interference filter 203 is disposed
between the first interference filter 201 and the second
interference filter 202, and the second interference filter 202 is
not parallel to and perpendicular to the first interference filter
201 and the third interference filter 203. Therefore, FIG. 4C is
taken only for an example, and the arrangement of the first
interference filter 201, the second interference filter 202 and the
third interference filter 203 is not limited thereto.
[0064] In particular, in the above embodiments, the thicknesses of
the interference films involved in the optical filtering assemblies
100-400c, such as the thickness 110t of the first interference film
110, are well-distributed, and the thickness ratios between these
film layers (e.g. the first to fourth film layers 111, 112, 123 and
124) may be the same, wherein the "well-distributed" and the "the
same" refer to "substantially well-distributed" and the
"substantially the same". In detail, in a manufacturing process of
interference films, due to the inevitable restrictions in
manufacturing equipments that cause some tolerances on thicknesses
of the film layers (e.g. the first film layer 111) of the
interference films, the thicknesses of the interference films are
found in the micron scale not well-distributed, and the thickness
ratios between the film layers are found in the micron scale not
the same. For example, the thickness ratio between the first film
layers 111 and the second film layer 112 adjacent thereto is not
the same as the thickness ratio between the third film layers 123
and the fourth film layer 124 adjacent thereto. The unintentional
consequences that the thicknesses of the interference films are not
well-distributed and the thickness ratios between the film layers
are not the same, would not affect the filtering effect of the
optical filtering assemblies 100-400c. Said "substantially
well-distributed" for the thickness covers said "not
well-distributed" for the thickness, and said "substantially the
same" for the thickness ratio covers said "not the same" for the
thickness ratio. Nevertheless, for an optical filtering assembly in
other embodiment, the interference films may have intentionally
made "not well-distributed" thicknesses, as shown in FIG. 5A.
[0065] FIG. 5A is a cross-sectional view of a light source device
in accordance with another embodiment of the present invention.
With reference to FIG. 5A, in a light source device 50, an optical
filtering assembly 500 comprises a first interference film 510, the
first transparent substrate 101 and a second interference film 520,
wherein the second interference film 520 may be the interference
film described in the previous embodiment, such as the first
interference film 110, the second interference film 120 or the
third interference film 130, and the first transparent substrate
101 is disposed between the first interference film 510 and the
second interference film 520. The difference from the previous
embodiment is that a thickness of the first interference film 510
is not well-distributed, as shown in FIG. 5A.
[0066] The first interference film 510 is a multilayer film
comprising multiple first film layers 511 and multiple second film
layers 512. The first film layers 511 and the second film layers
512 are alternately stacked. A material of the first film layers
511 and the second film layers 512 may be same as that of the first
film layer 111 and the second film layer 112. The first
interference film 510 has a first side S1 and a second side S2
opposite the first side S1. A thickness of the first interference
film 510 gradually decreases from the first side S1 toward the
second side S2, so that a top of the first interference film 510
forms an inclined surface as shown in FIG. 5A. In addition, the
first interference film 510 may be formed by means of deposition,
such as Physical Vapor Deposition (PVD). In a process of Chemical
Vapor Deposition (CVD), the first interference film 510 that is not
well distributed in thickness may be formed by inclining the first
transparent substrate 101, or by blocking out an evaporation source
in use of a shelter.
[0067] When the light beam L1 enters the first interference film
510, at least two rays in the light beam L1 have different OPLs in
the first interference film 510. FIG. 5A is an example that in the
light beam L1, an OPL near the second side S2 is smaller than an
OPL near the first side S1. Therefore, the OPLs of the light beam
L1 produced in the first interference film 510 are not consistent
with each other, so that the first interference film 510 can not
only interfere with the light beam L1 for filtering the light beam
L1, but also can compensate the light beam L1 that has gone through
the second interference film 520 to reduce the influence caused by
the ripples.
[0068] With reference to FIG. 5A, FIG. 5B and FIG. 5C, after the
light beam L1 passing through the first interference film 510,
multiple rays of the light beam L1 may produce multiple different
spectrums with respect to multiple different sections of the first
interference film 510, such as multiple different curves C5 shown
in FIG. 5B due to the thickness of the first interference film 510
gradually decreasing from the first side S1 toward the second side
S2, wherein the curves C5 respectively bring different ripple
effects that the first interference film 510 offers to the light
beam L1. As described in the previous embodiment with respect to
FIG. 1B and FIG. 1C, the different curves C5 of FIG. 5B would be
superimposed with each other to produce interference, thus to
produce a smoother distribution spectrum, such as a curve C6 shown
in FIG. 5C. Specifically, in FIG. 5C, these curves C5 in a
wavelength range from 300 nm to 500 nm would produce destructive
interference in which the ripple effects of these curves C5 are
offset, so as to reduce the influence caused by the ripples and
generate the curve C6 which in the wavelength range from 300 nm to
500 nm has a shape similar to a smooth horizontal line.
[0069] FIG. 6 is a cross-sectional view of a light source device 60
in accordance with an embodiment of the present invention,
comprising an optical filtering assembly 600. The effect of the
optical filtering assembly 600 is similar to that of the described
embodiment. The optical filtering assembly 600 comprises a first
interference filter and a second interference filter. Take FIG. 6
as an example, the first interference filter is an interference
filter 610 and the second interference filter is an interference
filter 206, wherein the interference filter 206 comprises a
transparent substrate 602 and an interference film 620 formed on
the transparent substrate 602. The interference film 620 may be any
of the first interference film 110, the second interference film
120 and the third interference film 130 described. The transparent
substrate 602 may be any of the first transparent substrate 101,
the second transparent substrate 102 and the third transparent
substrate 103 described. Therefore, the interference filter 206 may
be any of the first interference filter 201, the second
interference filter 202 and the third interference filter 203
described.
[0070] It can be seen that the interference filter 610 may be
applied to the optical filtering assemblies 200a, 200b, 300, 400a,
400b, 400c in accordance with the described embodiments. In detail,
in the embodiments with respect to FIGS. 2A-4C, any of the first
interference filter 201, the second interference filter 202, 402
and the third interference filter 203 may be replaced by the
interference filter 610. In addition, the optical filtering
assembly 100 of FIG. 1A and the optical filtering assembly 500 of
FIG. 5A may also comprise any of the first interference filter 201,
the second interference filter 202, 402, the third interference
filter 203 and the interference filter 610, so that each of the
optical filtering assembly 100 of FIG. 1A and the optical filtering
assembly 500 of FIG. 5A may comprise more than three layers of the
interference films.
[0071] In sum, the at least two interference films of the optical
filtering assembly in accordance with an embodiment of the present
invention have a similar film layer structure which is able to
produce different OPD, interference and light filtering improving
effects. For example, when filtering a light beam, the optical
filtering assembly provides the filtered light beam with a spectrum
having a smoother strength distribution to reduce the influence
caused by the ripples, which is helpful to the improvement of the
precision and accuracy in measurements. The way producing the OPD
may be achieved by making a difference of the coating film
thicknesses between the two interference films, and/or by making a
gradual change thickness between the two interference films, and/or
by inserting an angle between the two interference films.
[0072] It is understood that the invention may be embodied in other
forms within the scope of the claims. Thus the present examples and
embodiments are to be considered in all respects as illustrative,
and not restrictive, of the invention defined by the claims.
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