This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2015-039261, filed Feb. 27, 2015, the entire contents of which. are incorporated herein by this reference.
1. Field of the Invention
The present invention relates to a reflector and a microscope including the reflector, in particular, a reflector having a high reflectance in a wide wavelength band and a microscope including the reflector.
2. Description of the Related Art
In the field of microscopes, an aluminum mirror is conventionally used for a reflector. The aluminum mirror has a high reflectance in a visible wavelength region, and has a lower reflectance in an infrared wavelength region than in the visible wavelength region. Accordingly, in recent years, in which multi-photon excitation microscopes and the like have spread, a reflector in which an Ag (silver) film having a high reflectance in the infrared wavelength region in addition to the visible wavelength region is formed has also been used. The reflector in which the Ag film is formed is described, for example, in Japanese Laid-Open Patent Publication No. 8-234004, Japanese Laid-Open Patent Publication No. 11-149005, and the like.
It is known that the reflector in which the Ag film is formed can realize a high reflectance in a wide wavelength band including the infrared wavelength region, but has a low durability against temperature and humidity. Therefore, a protective film is usually formed on the Ag film in order to maintain the performance of the reflector.
In a first aspect of the present invention, a reflector is provided that includes: an Au film formed over a board; and a dielectric multilayer formed over the Au film, the dielectric multilayer having a reflectance higher than that of the Au film in a visible wavelength region.
In another aspect of the present invention, a microscope including the reflector in the first aspect is provided.
The present invention will be more apparent from the following detailed description when the accompanying drawings are referenced.
In order to sufficiently exhibit the performance of a reflector in which an Ag film is formed, it is preferable that a protective film have a high transmittance over a wide wavelength band. However, it is difficult to design a protective film having a high transmittance over a wide band. In particular, it is very difficult to form a protective film having a high durability against temperature and humidity under such a design limitation in a transmittance characteristic,
Embodiments of the present invention are described below in detail.
In this specification, the visible wavelength region is a wavelength region from about 400 nm to about 700 nm. The infrared wavelength region is a wavelength region from about 700 nm to about 2500 nm. An ultraviolet wavelength region is a wavelength region less than 400 nm.
A material (a base material) of the board 11 is not particularly limited, but it is, for example, optical glass S-BSL7 from Ohara Inc.
The Au film 12 is a thin film composed of Au (gold) , and is formed over the board 11. Au has a higher durability against temperature and humidity than Ag (silver) used in a conventional wide-wavelength-band mirror, and also has a high reflectance in the infrared wavelength region, similarly to Ag. The Au film 12 may be formed so as to interpose a layer between the Au film 12 and the board 11. Namely, the phrase “over the board 11” includes “on the board 11” and “above the board 11”, and the Au film 12 does not always need to be formed on the board 11 so as to be in contact with the board 11, as illustrated in
As the thickness of the Au film 12 increases up to about 80 nm, the reflectance is further improved, as illustrated in
The dielectric multilayer 15 is an optical thin-film laminate formed by alternately laminating a high-refractive-index layer 13 and a low-refractive-index layer 14 having a refractive index lower than the refractive index of the high-refractive-index layer 13. The dielectric multilayer 15 is formed over the Au film 12. The high-refractive-index layer 13 and the low-refractive-index layer 14 are composed of materials having different refractive indices. The high-refractive-index layer 13 is composed, for example, of TiO2 or Ta2O5. The low-refractive-index layer 14 is composed, for example, of SiO2 or MgF2. It is preferable that the thicknesses of the high-refractive-index layer 13 and the low-refractive-index layer 14 that are alternately laminated do not greatly differ from each other from the viewpoint of ease of film formation. The dielectric multilayer 15 may be formed so as to interpose a layer between the dielectric multilayer 15 and the Au film 12. Namely, the phrase “over the Au film 12” includes “on the Au film 12” and “above the Au film 12”, and the dielectric multilayer 15 does not always need to be formed on the Au film 12 so as to be in contact with the Au film 12, as illustrated in
Au and the Au film 12 have a high reflectance in the infrared wavelength region, as illustrated in FIG, 2, but have a relatively low reflectance in the visible wavelength region. Specifically, an Au film 12 having a thickness of 80 nm or more has a particularly high reflectance that exceeds 95% in a wavelength region of 700 nm or more under the condition of an incident angle of 45°. On the other hand, the reflectance gradually decreases in a wavelength region of about 650 nm, and the reflectance decreases up to about 90% at a wavelength of about 600 nm, and decreases up to about 40% at a wavelength of about 400 nm. The dielectric multilayer 15 compensates for a reflectance in the visible wavelength region in which the Au film 12 has a relatively low reflectance. The dielectric multilayer 15 is a dichroic mirror that has been designed so as to have a reflectance higher than the reflectance of the Au film 12 in the visible wavelength region. The dielectric multilayer 15 does not need to have a reflectance higher than that of the Au film 12 in the entirety of the visible wavelength region, and may have a reflectance higher than that of the Au film 12 in at least a portion of the visible wavelength region.
It is preferable that the dielectric multilayer 15 be a dichroic mirror that has been designed so as to have a reflectance higher than that of the Au film 12, for example, at least in a wavelength region of 400 nm to 600 nm. This is because the reflectance of the Au film 12 is low, in particular in the wavelength region of 400 nm to 600 nm in the visible wavelength region.
It is further preferable that the dielectric multilayer 15 be a dichroic mirror that has been designed so as to have a reflectance higher than that of the Au film 12 in a wavelength region of 350 nm to 650 nm including the ultraviolet wavelength region. The dielectric multilayer 15 may have a rising edge wavelength of short-wavelength reflection and long-wavelength transmission in a band of 600 nm to 700 nm, such as about 650 nm, and may have a rising edge wavelength of long-wavelength reflection and short-wavelength transmission in a band of 400 nm or less.
In the reflector 10 with the configuration above, principally the Au film 12 can realize a high reflectance in the infrared wavelength region and principally the dielectric multilayer 15 can realize a high reflectance in the visible wavelength region (and the ultraviolet wavelength region) Therefore, a high reflectance can be realized in a wide wavelength band from the visible wavelength region or the ultraviolet wavelength region to the infrared wavelength region. The dielectric multilayer 15 generally has a high durability against temperature and humidity. The Au film 12 also has a high durability against temperature and humidity, compared with an Ag film. Accordingly, the reflector 10 can achieve a higher durability against temperature and humidity than a conventional wide-wavelength-band mirror in which a protective film is formed on the Ag film. Thus, the reflector 10 enables both a high reflectance and a high durability against temperature and humidity in a wide wavelength band from the visible wavelength region or the ultraviolet wavelength region to the infrared wavelength region.
The reflector 10 can be widely used in the field of optical apparatuses including microscopes, and it is particularly preferable that the reflector 10 be used in optical apparatuses in which both infrared light and visible light (or the ultraviolet wavelength region) are used, such as infrared microscopes, Raman microscopes, or multiphoton excitation microscopes (for example, two-photon excitation microscopes). An example of a microscope including the reflector 10 is described below.
As illustrated in
The gold mirror 106 is a mirror that is arranged in a position where only infrared light from the laser 102 enters. The gold mirror 106 has a high reflectance in the infrared wavelength region, and therefore the gold mirror 106 can efficiently reflect the infrared light from the laser 102.
The reflectors 10a and 10b are reflecting mirrors similar to the reflector 10 described above, and are reflecting mirrors in which the dielectric multilayer 15 having a reflectance higher than that of the Au film 12 in the visible wavelength region is formed over the Au film 12. The reflectors 10a and 10b are arranged in positions where visible light from the laser 101, fluorescence (visible light) emitted from a sample S excited by the visible light from the laser 101, and infrared light from the laser 102 enter. The reflectors 10a and 10b have a high reflectance in a wide wavelength band from the visible wavelength region to the infrared wavelength region, and therefore the reflectors 10a and 10b can efficiently reflect the visible light (including the fluorescence) and the infrared light.
The reflector 10a is a mirror that configures a scanner such as a galvano-scanner. The reflector 10b is a mirror that is removably arranged in an optical path. In a case in which a sample S illuminated, for example, by a transmission illumination means not illustrated is visually observed, the reflector 10b is removed from the light path.
The microscope 100 having the configuration above enables light to be efficiently reflected by using the reflectors 10a and 10b in both one-photon excitation imaging and two-photon excitation imaging. As a result, a bright fluorescent image can be obtained. In particular, in two-photon excitation imaging, a luminous efficiency of fluorescence is proportional to the square of an average power of excitation light, and consequently, deterioration in the luminous efficiency of fluorescence is also proportional to the square of an amount of deterioration in reflectance. Accordingly, the reflectors 10a and 10b having a high reflectance are extremely useful. Further, the reflectors 10a and 10b have a high durability compared with a conventional wide-wavelength-band mirror in which an Ag film is formed, and this allows the frequency of exchanging reflectors to be reduced.
Specific examples of the reflector 10 described above are described below.
A reflector according to this example is a reflecting mirror, and includes a board 11, an Au film 12 formed over the board 11, and a dielectric multilayer 15 that is a dichroic mirror formed over the Au film 12, as illustrated in
The dielectric multilayer 15 is an optical thin-film laminate formed by alternately laminating a high-refractive-index layer 13 that is a vapor-deposited film composed of TiO2, and a low-refractive-index layer 14 that is a vapor-deposited film composed of SiO2. Refractive indices and absorption coefficients of the vapor-deposited film composed of TiO2 and the vapor-deposited film composed of SiO2 are illustrated in
When a design wavelength λ0 is 600 nm, a film structure of the dielectric multilayer 15 in a direction from the side of the board 11 to the air side is as described below. Here, H represents the high-refractive-index layer 13, L represents the low-refractive-index layer 14, and a numerical value before H or L represents the thickness of each of the layers that is calculated under the assumption that design wavelength λ0×1/4−1. The 0 before the decimal point is omitted.
Dielectric Multilayer 15 .3933H .72682L .61295H .50916L .57695H .65639L .58225H .683 94L .53476H .70861L .62952H .64346L .5804H .67874L .5537H .71281 .56974H .58891L .59547H .69449L .62499H .6801L .61114H .718381 .65609H .73035L .60771H .63278L .63942H .75466L .63918H .70997L .62651H .719221 .71487H .83822L .74725H .800 55L .66412H .90132L .79718H .82424L .76094H .828991 .7995H .856871 .82086H .86419L .83028H .87225L .83317H .87523L .82 739H .85338L .79906H .84531L .78325H .79256L .6926H 1.03062L .91033H 1.11103L .94956H 1.03235L .89546H 1.11273L 1.0212411 1.09312L .89429H 1.08402L .94595H 1.14538L .8992H 1.10017L .95718H 1.11426L .91803H 1.05893L .91007H 1.12409L 1.03133H 1.89058L
By using the reflector according to this example, a high reflectance can be achieved in a wide wavelength band from the visible wavelength region to the infrared wavelength region, as represented by a line L12 in
A reflector according to this example is a reflecting mirror, and is different from the reflector according to Example 1 in that a film structure of a dielectric multilayer is different from the film structure of the dielectric multilayer 15. In the other respects, the reflector according to this example is similar to the reflector according to Example 1.
A dielectric multilayer according to this example is an optical thin-film laminate formed by alternately laminating a high-refractive-index layer that is an IAD (Ion assisted deposition) film composed of Ta2O5, and a low-refractive-index layer that is an IAD film composed of SiO2. Refractive indices and absorption coefficients of the IAD film composed of Ta2O5 and the IAD film composed of SiO2 are illustrated in
When a design wavelength λ0 is 600 nm, a film structure of the dielectric multilayer according to this example in a direction from the side of the board 11 to the air side is as described below. Here, H represents the high-refractive-index layer, L represents the low-refractive-index layer, and a numerical value before H or L represents the thickness of each of the layers that is calculated under the assumption that design wavelength λ0×1/4=1. The 0 before the decimal point is omitted. A numerical value after ( ) represents the number of repetitions of a structure described in ( ).
By using the reflector according to this example, a high reflectance can be achieved in a wide wavelength band from the visible wavelength region to the infrared wavelength region, as represented by a line L22 in
A reflector according to this example is a reflecting mirror, and is different from the reflector according to Example 1 in that a film structure of a dielectric multilayer is different from the film structure of the dielectric multilayer 15. In the other respects, the reflector according to this example is similar to the reflector according to Example 1.
A dielectric multilayer according to this example is an optical thin-film laminate formed by alternately laminating a high-refractive-index layer that is an IAD (Ion assisted deposition) film composed of Ta2O5, and a low-refractive-index layer that is an IAD film composed of SiO2, similarly to the dielectric multilayer according to Example 2. Refractive indices and absorption coefficients of the IAD film composed of Ta2O5 and the IAD film composed of SiO2 are illustrated in
When a design wavelength AO is 600 nm, a film structure of the dielectric multilayer according to this example in a direction from the side of the board 11 to the air side is as described below. Here, H represents the high-refractive-index layer, L represents the low-refractive-index layer, and a numerical value before H or L represents the thickness of each of the layers that is calculated under the assumption that design wavelength λ0×1/4=1. The 0 before the decimal point is omitted. A numerical value after ( ) represents the number of repetitions of a structure described in ( ).
By using the reflector according to this example, a high reflectance can be achieved in a wide wavelength band from the visible wavelength region to the infrared wavelength region, as represented by a line L32 in
A reflector according to this example is a reflecting mirror, and is different from the reflector according to Example 1 in that a film structure of a dielectric multilayer is different from the film structure of the dielectric multilayer 15. In the other respects, the reflector according to this embodiment is similar to the reflector according to Example 1.
A dielectric multilayer according to this example is an optical thin-film laminate formed by alternately laminating a high-refractive-index layer that is an IAD (Ion assisted deposition) film composed of Ta2O5, and a low-refractive-index layer that is an IAD film composed of SiO2, similarly to the dielectric multilayers according to Examples 2 and 3. Refractive indices and absorption coefficients of the IAD film composed of Ta2O5 and the IAD film composed of SiO2 are illustrated in
When a design wavelength λ0 is 600 nm, a film structure of the dielectric multilayer according to this example in a direction from the side of the board 11 to the air side is as described below. Here, H represents the high-refractive-index layer, L represents the low-refractive-index layer, and a numerical value before H or L represents the thickness of each of the layers, calculated under the assumption that design wavelength λ0×1/4=1. The 0 before the decimal point is omitted.
Dielectric Multilayer .5896H .79954L .67841H .5902L .61871H .7864L .7018H .81667L .6655H .70363L .67981H .81294L .64345H .63555L .65188H .87 178L .83445H .96228L .85763H .78846L .84448H .85255L .82139 H 98332L .91949H 1.01704L .89139H .77987L .71475H .82288L .94151H 1.02223L .92208H 1.09584L 1.05267H 1.08257L 1.03665H 1.16557L 1.0454H 1.06684L 1.05624H 1.16198L 1.07658H 1.0496L 1.01611H 1.0963L 1.06231H 1.07625L 1.06196H 2.05828L
By using the reflector according to this example, a high reflectance can be achieved in a wide wavelength band from the visible wavelength region to the infrared wavelength region, as represented by a line L42 in
A reflector according to this example is a reflecting mirror, and is different from the reflector according to Example 1 in that a film structure of a dielectric multilayer is different from the film structure of the dielectric multilayer 15. In the other respects, the reflector according to this embodiment is similar to the reflector according to Example 1.
The dielectric multilayer according to this example is an optical thin-film laminate formed by alternately laminating a high-refractive-index layer that is a vapor-deposited film composed of TiO2, and a low-refractive-index layer that is a vapor-deposited film composed of MgF2. Refractive indices and absorption coefficients of the vapor-deposited film composed of TiO2 and the vapor-deposited film composed of MgF2 are illustrated in
When a design wavelength λ0 is 600 nm, a film structure of the dielectric multilayer according to this example in a direction from the side of the board 11 to the air side is as described below. Here, H represents the high-refractive-index layer, L represents the low-refractive-index layer, and a numerical value before H or L represents the thickness of each of the layers that is calculated under the assumption that design wavelength λ0×1/4=1. The 0 before the decimal point is omitted. A numerical value after ( )represents the number of repetitions of a structure described in ( ).
By using the reflector according to this example, a high reflectance can be achieved in a wide wavelength band from the visible wavelength region to the infrared wavelength region, as represented by a line L52 in
The embodiments described above give specific examples in order that the invention can be easily understood, and the present invention is not limited to the embodiments described above. Various modifications or variations of a reflector and a microscope can be made without departing from the present invention specified in the claims. A single example can be implemented by combining some features in the contexts of respective examples described in the specification.
In
It is preferable that the reflector have an average reflectance of 90% or more in a wavelength region from 400 nm to 1500 nm. It is further preferable that the reflector have an average reflectance of 90% or more in a band from 350 nm to 2000 nm.
Number | Date | Country | Kind |
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2015-039261 | Feb 2015 | JP | national |