JP2020194129A - Optical filter, spectrometer, and spectroscopic camera - Google Patents

Abstract

To expand the wavelength region of transmission light in an optical filter.SOLUTION: Provided is an optical filter equipped with a Fabry-Perot resonator comprising including a cavity layer and a pair of reflection layers facing each other across the cavity layer. The optical filter is a band-pass filter having such an in-plane characteristic distribution that the center wavelength of a transmission passband changes along at least one direction of the principle plane, the absorptance of light of (n+1)th resonance wavelength of the resonator at a position in the principle plane where the center wavelength of the transmission passband corresponds to the n-th resonance wavelength of the resonator in at least one reflection layer of the pair of reflection layers being larger than the absorptance of light of the n-th resonance wavelength of the resonator.SELECTED DRAWING: Figure 1

Description

The present invention relates to optical filters, spectroscopic detectors and spectroscopic cameras.

Conventionally, an interference filter in which the film thickness of the interference film is formed in a wedge shape in order to continuously change the transmission wavelength has been known (for example, Patent Document 1). However, it is necessary to use another filter together to eliminate the influence of unnecessary interference light.

Japanese Unexamined Patent Publication No. 3-126024

According to the first aspect, the optical filter is an optical filter including a fabric perot type resonator including a cavity layer and a pair of reflection layers facing each other with the cavity layer interposed therebetween. A bandpass filter having an in-plane characteristic distribution in which the central wavelength of the transmission band changes along at least one direction of the main surface, and the center wavelength of the transmission band in the main surface is the nth order of the resonator. At the position corresponding to the resonance wavelength of the above, the absorption rate of light of the n + 1th order resonance wavelength of the resonator in at least one reflection layer of the pair of reflection layers is the light of the nth order resonance wavelength of the resonator. Is greater than the absorption rate of.

It is a figure which schematically exemplifies an example of the structure of the optical filter by one Embodiment. It is a figure which shows typically the structure of the optical filter in an Example. It is a figure which shows the film thickness of each layer of the optical filter in an Example. It is a graph which shows the spectral transmission characteristic of the optical filter of an Example and a comparative example. It is a block diagram which shows typically the main part structure of the sputtering apparatus in embodiment. It is a figure which shows typically the positional relationship between the mask and the substrate which the sputtering apparatus has in Embodiment. It is a block diagram which shows typically the structure of another example of the sputtering apparatus of embodiment. It is a block diagram which shows typically the main part structure of another example of the sputtering apparatus of embodiment. It is a block diagram which shows typically the main part structure of the spectroscopic measurement apparatus of embodiment. It is a block diagram which shows typically the main part structure of the image pickup apparatus of an embodiment.

The optical filter according to the embodiment of the present invention is a Fabry-Perot type cavity including a cavity layer and a pair of reflective layers facing each other with the cavity layer interposed therebetween, and a transmission band along at least one direction of the main surface of the optical filter. It functions as a bandpass filter having an in-plane characteristic distribution in which the center wavelength of is changed. At a position in the main surface of the optical filter where the central wavelength of the transmission band corresponds to the nth-order resonance wavelength of the resonator, the n + 1th-order resonance wavelength of the resonator in at least one reflection layer of the pair of reflection layers. The light absorption rate is larger than the light absorption rate of the nth-order resonance wavelength of the resonator. As a result, the optical filter suppresses the transmission of light having an n + 1th-order resonance wavelength and makes it possible to transmit light having an nth-order resonance wavelength in a wide wavelength region. The details will be described below.

An optical filter according to an embodiment will be described with reference to the drawings. It should be noted that the present embodiment is specifically described for understanding the gist of the invention, and is not limited to the present invention unless otherwise specified.

FIG. 1 is a diagram schematically illustrating an example of the structure of the optical filter 1 according to the present embodiment. FIG. 1A is a plan view showing the appearance of the optical filter 1, and FIG. 1B is a diagram showing a cross-sectional structure of the optical filter 1. In the following description, the Cartesian coordinate system including the X-axis, the Y-axis, and the Z-axis is set as shown in FIG. Further, FIG. 1B shows the scale magnification enlarged in the film thickness direction (Z direction) in order to make it easier to understand the structure of the thin film. The optical filter 1 of the present embodiment has a structure for functioning as a bandpass filter for light traveling in the Z direction. In the present specification, an optical filter 1 which is a bandpass filter in which the central wavelength of the transmission band changes in the range of 380 nm or more and 950 nm or less depending on the position in the X direction will be described as an example.

The optical filter 1 has a substrate 10, a first reflective layer 11, a second reflective layer 12, and a cavity layer 13. The first reflective layer 11, the second reflective layer 12, and the cavity layer 13 are formed on the substrate 10 in the order of the first reflective layer 11, the cavity layer 13, and the second reflective layer 12 from the Z-axis − side. Be filmed. The first reflective layer 11 and the second reflective layer 12 are a pair of reflective layers facing each other with the cavity layer 13 interposed therebetween, and form a Fabry-Perot type resonator.

The substrate 10 is, for example, a plate-shaped member using optical glass such as synthetic silica glass or BK-7 (borosilicate crown glass) or optical crystals such as sapphire or fluorite. In FIG. 1, the planar shape of the substrate 10 is shown as an example of a rectangular shape having a long side along the X direction and a short side along the Y direction, but the planar shape of the substrate 10 is rectangular. It is not limited, and can have various shapes such as a circle, an ellipse, a ring, a triangle, and a polygon having a pentagon or more.

The cavity layer 13 is constructed by using a dielectric material such as Al ₂ O ₃ , SiO ₂ , Ta ₂ O ₅ , Nb ₂ O ₅ , MgF ₂ , or CaF ₂ .
In general, a Fabry-Perot type optical filter has a maximum transmittance for light at the center wavelength (nth-order resonance wavelength) and resonates, ignoring absorption by the reflective layer (and its wavelength dispersion). It is a transmission filter having a bandpass characteristic such that the transmittance decreases as the wavelength deviates from the wavelength.
The optical filter 1 having a Fabry-Perot type resonator according to the present embodiment is a bandpass filter having an in-plane characteristic distribution. Here, the in-plane characteristic distribution is a characteristic in which the central wavelength of the transmission band of transmitted light changes along at least one direction of the main surface. In the present embodiment, the case where one of the above directions is the X direction will be described as an example.

In order to have the above-mentioned in-plane characteristic distribution, the cavity layer 13 is formed so that its film thickness (magnitude in the Z direction) differs along the X direction. The cavity layer 13 may be formed so that its film thickness is continuously different along the X direction, or may be formed so as to be stepwise (stepwise) different. The film thickness of the cavity layer 13 at each position is set based on the central wavelength of the light to be transmitted at each position. FIG. 1 shows, as an example, a case where the film thickness of the cavity layer 13 increases toward the + side in the X direction. In the optical filter 1, the central wavelength of the light transmission band transmitted toward the + side in the X direction is longer. The film thickness of the cavity layer 13 may be increased toward the X direction. In this case, the central wavelength of the transmission band of the light transmitted through the optical filter 1 is longer toward the X direction − side.
When the substrate 10 of the optical filter 1 has a circular shape or a ring shape, the in-plane characteristic distribution is, for example, the central wavelength of the transmission band of the transmitted light transmitted along the direction (circumferential direction) along the arc. The cavity layer 13 is formed so that That is, the cavity layer 13 is formed so that its film thickness is continuously or stepwise different along the direction along the circumference.

The first reflective layer 11 and the second reflective layer 12 are metal layers. The first reflective layer 11 and the second reflective layer 12 are formed with a constant film thickness (that is, the size in the Z direction) along the X direction. The first reflective layer 11 and the second reflective layer 12 are semi-transmissive films that transmit a part of the light incident on the optical filter 1 and reflect a part of the light.
The metal used for the first reflective layer 11 and the second reflective layer 12 has a higher energy (high frequency) side than the frequency (plasma frequency) of the collective vibration (plasma oscillation) of free electrons in the metal. Greater light absorption. At least one of the first reflective layer 11 and the second reflective layer 12 has an absorption rate of light having an nth-order resonance wavelength at a position in the X direction in which the central wavelength of the transmitted light corresponds to the nth-order resonance wavelength. Also has the characteristic that the absorption rate of light having an n + 1th order resonance wavelength (that is, light having a higher frequency than light having an nth order resonance wavelength) is larger. Therefore, at least one of the first reflective layer 11 and the second reflective layer 12 transmits light having an nth-order resonance wavelength, but light having an n + 1th-order resonance wavelength is further reduced. For example, at least one of the first reflective layer 11 and the second reflective layer 12 is of light having a secondary resonance wavelength at a position in the X direction corresponding to the central wavelength (first resonance wavelength) of the transmitted light. The absorption rate is larger than the absorption rate of the center wavelength (first-order resonance wavelength). Therefore, in at least one of the first reflective layer 11 and the second reflective layer 12, the transmission of light having a secondary resonance wavelength is further reduced.
There are metals used in the first reflective layer 11 and the second reflective layer 12 so that light of the primary resonant wavelength is transmitted and transmission of light of the secondary resonant wavelength is further reduced. It is preferable that the absorptivity increases sharply with the wavelength as a boundary. Examples of the metal used for the first reflective layer 11 and the second reflective layer 12 include precious metals (for example, copper (Cu), silver (Ag), gold (Au), etc.). In precious metals, the absorption rate sharply increases on the higher energy side than the plasma frequency due to the effect of the dielectric constant due to the interband transition and the dielectric constant of free electrons. Since copper (Cu) has a sharply large absorption rate for light having a wavelength shorter than around 600 nm, when a Cu layer is used as the metal layer, transmission of light having a secondary resonance wavelength shorter than 600 nm is suppressed. .. Since the absorption rate of silver (Ag) rapidly increases with respect to light having a wavelength shorter than the vicinity of 380 nm, the transmission of light having a secondary resonance wavelength shorter than 380 nm is suppressed when the Ag layer is used as the metal layer. ..

Each of the first reflective layer 11 and the second reflective layer 12 is composed of a metal layer in which a copper (Cu) layer and a silver (Ag) layer are laminated at least in a part of the plane. Gold (Au) may be used instead of Cu. One of the first reflective layer 11 and the second reflective layer 12 may be configured by laminating a Cu layer and an Ag layer. In the X direction, the longer the central wavelength of the light transmitted through the optical filter 1 (+ side in the X direction), the larger the ratio of Cu to Ag in the first reflective layer 11 and / or the second reflective layer 12. The reason will be explained later. In the example shown in FIG. 1, the Cu layer is thicker in the first reflective layer 11 and the second reflective layer 12 toward the + side in the X direction, and the Ag layer is thicker toward the − side in the X direction.
At the position where the Ag layer is formed among the first reflective layer 11 and the second reflective layer 12, light having a wavelength of 800 nm or less, and in the present embodiment, light having a wavelength of 380 nm to 800 nm is selected according to the position in the X direction. Is transparent. Further, at the position where the Cu layer is formed among the first reflective layer 11 and the second reflective layer 12, light having a wavelength of 600 nm or more, and in the present embodiment, light having a wavelength of 700 nm to 950 nm is selectively transmitted. At the position where the Cu layer and the Ag layer are laminated among the first reflective layer 11 and the second reflective layer 12, light of 700 nm to 800 nm is selectively transmitted.

In the following description, of the first reflective layer 11, the region where the Cu layer is formed is referred to as the first region 11-1, and the region where the Ag layer is formed is referred to as the second region 11-2. The region where the laminated film of the Cu layer and the Ag layer is formed is called the third region 11-3. Similarly, in the second reflective layer 12, the region where the Cu layer is formed is called the first region 12-1, and the region where the Ag layer is formed is called the second region 12-2, which is called the Cu layer. The region where the laminated film with the Ag layer is formed is called the third region 12-3.
In the optical filter 1, the portion including the first region 11-1 of the first reflective layer 11 and the first region 12-1 of the second reflective layer 12 (the portion surrounded by the alternate long and short dash line in FIG. 1) is the first portion. Called 1-1. In the optical filter 1, the portion including the second region 11-2 of the first reflective layer 11 and the second region 12-2 of the second reflective film 12 (the portion surrounded by the broken line in FIG. 1) is the second portion 1. Call it -2. In the optical filter 1, the portion including the third region 11-3 of the first reflective layer 11 and the third region 12-3 of the second reflective film 12 (the portion surrounded by the alternate long and short dash line in FIG. 1) is the third. Called part 1-3. In the present embodiment, the optical filter 1 has a first portion 1-1, a third portion 1-3, and a second portion 1-2 from the + side in the X direction.

In the following description, it is assumed that white light is incident from the Z direction + side of the optical filter 1. In addition, light having a predetermined wavelength component may be incident instead of white light, and in that case, the spectrum of the emitted light at each position of the optical filter 1 changes according to the intensity of each wavelength component of the incident light. Needless to say.
In the first portion 1-1, the light incident on the optical filter 1 resonates in the cavity layer 13 depending on the incident position, and as a result, is emitted as light having a center wavelength in the range of 800 nm to 950 nm. .. That is, the first portion 1-1 of the optical filter 1 functions as a bandpass filter having a center wavelength of 800 nm to 950 nm depending on the incident position of light. When light having a wavelength of 800 nm to 950 nm resonates in the cavity layer 13 as primary light, the wavelength of the secondary light is 400 nm to 475 nm. The absorption rate of at least one of the first reflection layer 11 and the second reflection layer 12 in the first portion 1-1 for these secondary lights is larger than the absorption rate for the primary light. As a result, the transmission of secondary light is reduced compared to the transmission of primary light. Similarly, for the light after the third light, the transmission of the first portion 1-1 is reduced as compared with the transmission of the primary light.

In the second portion 1-2, the incident light resonates in the cavity layer 13 depending on the incident position, and as a result, is emitted as light having a center wavelength in the range of 380 nm to 700 nm. That is, the second portion 1-2 of the optical filter 1 functions as a bandpass filter having a center wavelength of 380 nm to 700 nm depending on the incident position of light. When light having a wavelength of 380 nm to 700 nm resonates in the cavity layer 13 as primary light, the wavelength of the secondary light is 190 nm to 350 nm. The absorption rate of at least one of the first reflection layer 11 and the second reflection layer 12 in the second portion 1-2 for these secondary lights is larger than the absorption rate for the primary light. As a result, the transmission of secondary light is reduced compared to the transmission of primary light. Similarly, for the light after the third light, the transmission of the second portion 1-2 is reduced as compared with the transmission of the primary light.

In the third regions 11-3 and 12-3, Cu and Ag are laminated. In the third regions 11-3 and 12-3, the Cu layer is thicker and the Ag layer is thinner toward the + side in the X direction. FIG. 1B shows, as an example, the case where the Cu layer is thicker and the Ag layer is thinner toward the + side in the X direction in the third regions 11-3 and 12-3. FIG. 1B illustrates a case where the ratio of the film thicknesses of the Cu layer and the Ag layer changes linearly. That is, the boundary between the Cu layer and the Ag layer has a linear slope. However, it is not limited to the case where the boundary between the film thicknesses of the Cu layer and the Ag layer changes linearly as shown in FIG. 1 (b). For example, as shown in FIG. 1 (c), it may be curved. FIG. 1 (c) is an enlarged view showing the vicinity of the third region 11-3 of the first reflective layer 1. Further, the third region 11-3 is not limited to the case where the Cu layer and the Ag layer are laminated, and the layer may be formed in a state where the Cu particles and the Ag particles are mixed, or the Cu and Ag may be formed. Layers may be formed by alloying with. When such a layer is formed, the film may be formed in the third region 11-3 so that the ratio of the Cu content and the Ag content changes along the X direction.
The same shape can be applied to the third region 12-3 of the second reflective layer 12.

In the third portion 1-3, the incident light resonates in the cavity layer 13 depending on the incident position, and as a result, is emitted as light having a center wavelength in the range of 700 nm to 800 nm. That is, the third portion 1-3 of the optical filter 1 functions as a bandpass filter having a center wavelength of 700 nm to 800 nm depending on the incident position of light. When light having a wavelength of 700 nm to 800 nm resonates in the cavity layer 13 as primary light, the wavelength of the secondary light is 350 nm to 400 nm. The absorption rate of at least one of the first reflection layer 11 and the second reflection layer 12 in the third portion 1-3 for these secondary lights is larger than the absorption rate for the primary light. As a result, the transmission of secondary light is reduced compared to the transmission of primary light. Similarly, for the light after the third light, the transmission of the third portion 1-3 is reduced as compared with the transmission of the primary light.

As described above, in each of the first portion 1-1, the second portion 1-2, and the third portion 1-3, the transmission of the transmitted light (primary light) after the secondary is suppressed. Will be done. Therefore, the optical filter 1 functions as a bandpass filter in which the influence of the second and subsequent light is suppressed over a wide central wavelength range of 380 nm to 950 nm.

When the substrate 10 of the optical filter 1 has a circular shape or a ring shape, the cavity layer 13 is formed so that the in-plane characteristic distribution is in the direction along the arc as described above. In this case, the first region 11-1, 12-1, the second region 11-2, 12-2, and the third region 11-3, 12-3 are arcs in the direction along the in-plane characteristic distribution. The film is formed in the direction along.

[Example]
An embodiment of the optical filter 1 in this embodiment will be described.
2A and 2B are views schematically showing the structure of the optical filter 1 in the embodiment, FIG. 2A shows the appearance of the optical filter 1, and FIG. 2B shows the cross-sectional structure of the optical filter 1. In FIG. 2, the Cartesian coordinate system is set in the same manner as in the case shown in FIG.

The substrate 10 is a flat plate member manufactured using synthetic silica glass and having a long side of 112 mm, a short side of 22 mm, and a thickness of 0.3 mm. The first reflective layer 11, the second reflective layer 12, the cavity layer 13, and the first dielectric are located in a 110 mm × 20 mm region 1 mm inside from the outer edge of the surface (plane parallel to the XY plane) of the substrate 10. The body layer 14 and the second dielectric layer 15 are formed into a film. Each layer is formed on the substrate 10 in the order of the first dielectric layer 14, the first reflective layer 11, the cavity layer 13, the second reflective layer 12, and the second dielectric layer 15 from the Z direction − side. To. The cavity layer 13, the first dielectric layer 14, and the second dielectric layer 15 are each composed of an Al ₂ O ₃ layer. In this embodiment, the case where the optical filter 1 has the first dielectric layer 14 and the second dielectric layer 15 is shown for the purpose of improving the transmittance of the optical filter 1, but the first dielectric layer is shown. The body layer 14 and the second dielectric layer 15 may not be provided. The first dielectric layer 14 is formed on the substrate 10 so that the thickness increases toward the + side in the X direction.

FIG. 3 shows the first at X = 0 mm (X direction-side end), 4 mm, 10 mm, 20 mm, 30 mm, 40 mm, 50 mm, 60 mm, 70 mm, 80 mm, 90 mm, 100 mm, 110 mm (X direction + side end). The physical film thicknesses of the first reflective layer 11, the second reflective layer 12, the cavity layer 13, the first dielectric layer 14, and the second dielectric layer 15 are shown. The physical film thickness of the first dielectric layer 14 is 45 nm at the position of X = 0 mm (X direction-side end), and increases linearly as the value of X increases. At the position of X = 110 mm (X direction + side end), the physical film thickness is 125 nm. The film thickness of the first dielectric layer 14 is determined by a commonly used thin film optimization calculation so that the transmittance of light of a desired wavelength (or wavelength band) is maximized at each position in the X direction. The film thickness at both ends of the first dielectric layer 14 is determined by optimization based on the wavelength of the light transmitted at both ends of the optical filter 1 (that is, X = 0 mm and X = 110 mm), and 0 mm <X < The film thickness of the first dielectric layer 14 in the range of 110 mm may be determined by linear interpolation based on the film thickness at the positions at both ends.

A first reflective layer 11 is formed on the first dielectric layer 14. As shown in FIG. 3, the physical film thickness of the first reflective layer 11 is constant and is 38 nm. As described above, the Ag layer is formed in the range of the first reflective layer 11 in which the value of X is 0 mm or more and 50 mm or less (that is, the second region 11-2). As described above, the Cu layer is formed in the range of the first reflective layer 11 in which the X value is 80 mm or more and 110 mm (that is, the first region 11-1).
In the first reflective layer 11, in the range where the X value is 50 mm to 80 mm (that is, the third region 11-3), the Ag layer and the Cu layer are laminated as described above. As shown in FIG. 3, at the position of X = 60 mm in the third region 11-3, a Cu layer having a thickness of 13 nm is laminated on the − side in the Z direction and an Ag layer having a thickness of 25 nm is laminated on the + side in the Z direction. To. At the position of X = 70 mm in the third region 11-3, a Cu layer having a thickness of 25 nm is laminated on the − side in the Z direction and an Ag layer having a thickness of 13 nm is laminated on the + side in the Z direction.

A cavity layer 13 is formed on the first reflective layer 11. The physical film thickness of the cavity layer 13 is 67 nm at the position of X = 0 mm (X direction-side end), and increases linearly as the position in the X direction increases. At the position of X = 110 mm (X direction + side end), the physical film thickness is 236 nm. In this embodiment, the cavity layer 13 has a film thickness larger than the film thickness of the first dielectric layer 14 and the film thickness of the second dielectric layer 15 described later.

A second reflective layer 12 is formed on the cavity layer 13. Like the first reflective layer 11, the second reflective layer 12 has a constant physical film thickness of 38 nm (see FIG. 3). As described above, the Ag layer is formed in the range of the second reflective layer 12 in which the value of X is 0 mm or more and 50 mm or less (that is, the second region 12-2). A Cu layer is formed in the range of the second reflective layer 12 in which the value of X is 80 mm or more and 110 mm (that is, the first region 12-1) as described above.
In the range where X is 50 mm or more and less than 80 mm (that is, the third region 12-3) of the second reflective layer 12, the Ag layer and the Cu layer are laminated as described above. As shown in FIG. 3, at the position of X = 60 mm in the third region 12-3, a Cu layer having a thickness of 13 nm is laminated on the − side in the Z direction and an Ag layer having a thickness of 25 nm is laminated on the + side in the Z direction. To. At the position of X = 70 mm in the third region 11-3, a Cu layer having a thickness of 25 nm is laminated on the − side in the Z direction and an Ag layer having a thickness of 13 nm is laminated on the + side in the Z direction.

A second dielectric layer 15 is formed on the second reflective layer 12. The physical film thickness of the second dielectric layer 15 is 45 nm at the position of X = 0 mm (X direction-side end), and the value of X is the same as the physical film thickness of the first dielectric layer 14. Increases linearly as At the position of X = 110 mm (X direction + side end), the thickness is 125 nm. The film thickness of the second dielectric layer 15 may be determined by a commonly used thin film optimization calculation in the same manner as when the film thickness of the first dielectric layer 14 is determined, or both ends of the optical filter 1. It may be determined by linear interpolation based on the value of the film thickness optimized in.
The second dielectric layer 15 has an effect as a protective film for the second reflective layer 12 by forming a film on the surface (Z direction + side) of the optical filter 1.

FIG. 4A shows the spectral transmittance of the optical filter 1 of the embodiment having the above structure. The optical filter 1 functions as a bandpass filter having a center wavelength corresponding to the incident position in the X direction with respect to light having a continuous wavelength component, but in FIG. 4A, some of them are discrete. It shows the transmittance of light with the wavelength of. As shown in FIG. 4A, the optical filter 1 functions as a bandpass filter having a central wavelength of transmitted light of 380 nm to 950 nm depending on the position in the X direction. In FIG. 4A, several peaks are observed on the shorter wavelength side than the wavelength of 350 nm. These peaks indicate the peaks of secondary light corresponding to the light transmission band of 700 nm or less. However, in the wavelength range longer than 350 nm, the peak corresponding to the secondary light is negligibly small. That is, the peak of the secondary light of the light in the wavelength range exceeding 800 nm is so small that it can be ignored, and the transmission of the secondary light can be reduced in the bandpass filter region having the center wavelength in these wavelength ranges. I understand. That is, it can be seen that the optical filter 1 functions as a bandpass filter having an in-plane characteristic distribution that suppresses the influence of the peak of the secondary light over a wide central wavelength range of 380 nm to 950 nm.

[Comparison example]
The comparative example with respect to the optical filter 1 of the above embodiment has the same configuration as the optical filter 1 of the embodiment except that the first reflective layer 11 and the second reflective layer 12 are both composed of an Ag layer. .. That is, in the comparative example, both the first reflective layer 11 and the second reflective layer 12 do not contain Cu. FIG. 4B shows the spectral transmittance spectrum of the portion of the first region of the optical filter of the comparative example where the center wavelength is about 850 nm. As shown in FIG. 4B, it can be seen that the peak of the secondary light is observed as a peak having a central wavelength longer than the wavelength of 400 nm. That is, it can be seen that the optical filter of the comparative example does not function as a bandpass filter for light in a short wavelength region having a wavelength of less than 500 nm.

Next, a method of manufacturing the optical filter 1 of the above-described embodiment or example will be described with reference to FIG. In the present embodiment, the optical filter 1 is manufactured by using a sputtering apparatus.
FIG. 5 is a block diagram schematically showing an example of the main configuration of the sputtering apparatus 3. The sputtering device 3 includes a first cathode 31, a second cathode 32, a third cathode 33, a stage 34, a mask 35, and a control device 36. Note that FIG. 5A shows an outline of the configuration of the sputtering apparatus 3 on the XY plane, and FIG. 5B shows an outline of the configuration on the ZX plane.

The first cathode 31 has an alumina (Al ₂ O ₃ ) target, and the sputtering apparatus 3 uses the first cathode 31 to perform sputtering on a substrate 10 provided on a stage 34, which will be described later, on a cavity layer 13. , The first dielectric layer 14 and the second dielectric layer 15 are formed. The second cathode 32 has a silver (Ag) target and the third cathode 33 has a copper (Cu) target. The sputtering apparatus 3 forms a first reflective layer 11 and a second reflective layer 12 on the substrate 10 by sputtering using the second cathode 32 and the third cathode 33.

The substrate 10 is placed on the upper surface (Z direction + side) of the stage 34. The substrate 10 on the stage 34 is fixed by a holder (not shown). The substrate 10 is placed and fixed on the stage 34 so that the long side is in the X direction. The stage 34 has a moving mechanism such as a guide rail or a motor provided along the X direction, so that the stage 34 is located below the first cathode 31, the second cathode 32, and the third cathode 33 (-side in the Z direction) along the X direction. To move. In addition, in FIG. 5, the stage 34 shows the case where three substrates 10 can be mounted as an example. However, the stage 34 may be capable of mounting one substrate 10, two substrates 10, or three or more substrates 10. May be good.
In the following description, the position of the center of the substrate 10 is referred to as the center position C.

The mask 35 is provided on the holder of the stage 34 and limits the area where the substrate 10 placed on the stage 34 is formed. The mask 35 has a rectangular opening 351 and within the range of the opening 351, the first reflective layer 11, the second reflective layer 12, the cavity layer 13, the first dielectric layer 14 and the second dielectric are on the substrate 10. The body layer 15 is formed. The mask 35 moves along the X direction by, for example, a mask moving mechanism such as a guide rail or a motor along the X direction.
The mask 35 is provided at a position separated from the surface of the substrate 10 (the surface on the + side in the Z direction) by a predetermined distance (for example, 3 mm). The above-mentioned predetermined distance is not limited to 3 mm. The larger the distance (gap), the easier it is for the particles generated by sputtering to pass through (wrap around) the gap, so that the film thickness change of the layer to be formed is gentle at the boundary of the opening portion of the mask 35. Become.

FIG. 6 schematically shows the positional relationship between the mask 35 and the substrate 10 on the XY plane. FIG. 6A shows a case where the position of the mask 35 in the X direction is set so that the entire region of the substrate 10 is included inside the opening 351 of the mask 35. FIG. 6B shows a case where the mask 35 is moved in the X direction − side by the mask moving mechanism from the state shown in FIG. 6A. The region of the substrate 10 on the + side in the X direction from the center of the substrate 10 is covered with the mask 35, and the region on the − side in the X direction from the center position C of the substrate 10 is included inside the opening 351 of the mask 35. In this case, the film can be formed in the region on the X direction − side from the center position C of the substrate 10. FIG. 6C shows a case where the mask 35 is moved to the + side in the X direction by the mask moving mechanism from the state shown in FIG. 6A. The region on the X direction − side from the center of the substrate 10 is covered with the mask 35, and the region on the X direction + side from the center position C of the substrate 10 is included inside the opening 351 of the mask 35. In this case, the film can be formed in the region on the + side in the X direction from the center of the substrate 10.

The control device 36 of FIG. 5 includes a microprocessor and its peripheral circuits, and is a sputtering device by reading and executing a control program stored in advance in a storage medium (for example, a flash memory) (not shown). It is a processor that controls each part of 3. The control device 36 controls the moving mechanism to control the moving speed of the stage 34. The control device 36 controls the mask moving mechanism to move the mask 35 and control the range of the film-formed region on the substrate 10.

The optical filter 1 is manufactured as follows by the sputtering apparatus 3 having the above-described configuration. In the following description, a case where the optical filter 1 having the first dielectric layer 14 and the second dielectric layer 15 is manufactured will be described as an example. In the case of manufacturing the optical filter 1 which does not have the first dielectric layer 14 and the second dielectric layer 15, the sputtering apparatus 3 includes the first dielectric layer 14 and the second dielectric layer in the following description. The process for forming the layer 15 may not be performed.
First, the sputtering apparatus 3 forms a first dielectric layer 14 on the substrate 10. The substrate 10 is placed on the stage 34 and fixed by a holder. The control device 36 controls the mask moving mechanism so that the entire region of the substrate 10 is included inside the opening 351 of the mask 35 (that is, the positional relationship shown in FIG. 6A can be obtained). The position of the mask 35 in the X direction is controlled.

When the position of the mask 35 is determined, the control device 36 controls the moving mechanism to move the stage 34 in the X direction + side at a constant speed. As the stage 34 passes through the lower part (Z direction − side) of the first cathode 31, the first dielectric layer 14 is formed on the substrate 10. When the stage 34, which has been moving at a constant speed, reaches a predetermined position, the control device 36 controls the moving mechanism to increase the moving speed of the stage 34 in the X direction + side. In this case, the predetermined position is, for example, a position where the center position C of the substrate 10 on the stage 34 is aligned with the center point of the first cathode 34 in the X direction. The position of the stage 34 in the X direction is detected by an encoder (not shown).

Since the moving speed of the stage 34 is controlled as described above, as described above, the first dielectric layer 14 is formed so that the film thickness becomes thicker toward the + side in the X direction. That is, while the stage 34 is moving at a constant speed, the film formation region is gradually exposed from the X-direction + side end of the substrate 10, so that the center position C of the substrate 10 is set to the above-mentioned predetermined position. At the time of reaching, the film forming time of the end portion on the X direction + side of the substrate 10 is the longest, and the film forming time of the end portion on the X direction − side of the substrate 10 is the shortest. Therefore, the film thickness of the substrate 10 on the X direction + side is thicker than the film thickness of the substrate 10 on the X direction − side.

As the speed of the stage 34 increases, the time during which the region on the X direction − side from the center position C of the substrate 10 is exposed to the film formation region after the speed of the stage 34 increases is before the speed of the stage 34 increases. The region on the + side in the X direction from the center position C of the substrate 10 is shorter than the time exposed to the film formation region. That is, on the substrate 10, the film thickness formed in the region on the X direction − side from the center position C of the substrate 10 after the speed of the stage 34 increases is the center of the substrate 10 when the speed of the stage 34 is constant. It is thinner than the film thickness formed in the region on the + side in the X direction from the position C. As a result, the first dielectric layer 14 is formed on the substrate 10 so that the film thickness becomes thicker toward the + side in the X direction.
The control device 36 sets the moving speed of the stage 34 based on the film thickness formed on the substrate 10. The relationship between the film thickness and the moving speed is stored in a predetermined storage device (not shown) of the control device 36 as data associated with the results obtained in advance by various tests, simulations, etc., and when the film is formed. The control device 36 may refer to this data to determine the moving speed.

Next, the sputtering apparatus 3 forms a first reflective layer 11 on the upper portion of the first dielectric layer 14. That is, the control device 36 controls the mask moving mechanism so that the region on the X direction − side from the center position C of the substrate 10 is included inside the opening 351 of the mask 35 (that is, in FIG. 6B). The mask 35 is moved in the X direction − side so as to have the positional relationship shown. When the positional relationship between the mask 35 and the substrate 10 is set as shown in FIG. 6B, the control device 36 moves the stage 34 in the X direction + side at a constant speed. As the stage 34 passes through the lower part (Z direction − side) of the second cathode 32, the Ag layer is formed on the half region of the substrate 10 on the X direction − side. Since the moving speed of the stage 34 is constant, the film thickness of the Ag layer to be formed is constant. Since the surface of the substrate 10 and the mask 35 are separated by a predetermined distance in the Z direction, Ag particles wrap around a part of the region on the + side in the X direction from the center position C of the substrate 10 through this distance. ..

When the film formation of the Ag layer is completed, the control device 36 controls the mask moving mechanism so that the region on the + side in the X direction from the center position C of the substrate 10 is included inside the opening 351 of the mask 35 (that is,). , The mask 35 is moved in the X direction + side so as to have the positional relationship shown in FIG. 6 (c). When the positional relationship between the mask 35 and the substrate 10 is set as shown in FIG. 6C, the control device 36 moves the stage 34 in the X direction + side at a constant speed. As the stage 34 passes through the lower part (Z direction − side) of the third cathode 33, a Cu layer is formed on the region of the substrate 10 on the X direction + side from the center position C. Since the moving speed of the stage 34 is constant, the film thickness of the Cu layer to be formed is constant. Since the surface of the substrate 10 and the mask 35 are separated by a predetermined distance in the Z direction, Cu particles wrap around a part of the region on the X direction − side from the center position C of the substrate 10 through this distance. .. As a result, a laminated film of the Ag layer and the Cu layer is formed in the region where the Ag particles and the Cu particles wrap around.

By controlling the position of the mask 35 as described above, the first region 11-1 on which the Cu layer is formed, the second region 11-2 on which the Ag layer is formed, and Ag are formed on the substrate 10. The first reflective layer 11 having the third region 11-3 on which the layer and the Cu layer are laminated is formed. As described above, since the moving speed of the stage 34 passing through the lower parts of the second cathode 32 and the third cathode 33 is constant, the film thickness of the first reflective layer 11 is constant. The Ag particles wrap around in the X direction + side to form an Ag layer, and the Cu particles wrap around in the X direction − side to form a Cu layer. Therefore, in the third region 11-3, the Ag layer is thinner toward the + side in the X direction, and conversely, the Cu layer is thinner toward the − side in the X direction.

When the film formation of the first reflective layer 11 is completed, the cavity layer 13 is formed by passing the stage 34 through the lower part of the first cathode 31 again. When the cavity layer 13 is formed, the control device 36 controls the moving speed of the stage 34 in the same manner as in the case of forming the first dielectric layer 14, and the cavity whose film thickness is thicker in the X direction + side. The layer 13 is formed. After that, the control device 36 passes the stage 34 through the lower parts of the second cathode 32 and the third cathode 33, and forms the second reflective layer 12 on the cavity layer 13. At this time, the control device 36 controls the position of the mask 35 in the same manner as when the first reflective layer 11 is formed, so that the second reflective layer 12 is the first region 12 on which the Cu layer is formed. -1, a second region 12-2 on which the Ag layer is formed, and a third region 12-3 on which the Ag layer and the Cu layer are laminated are formed. Also in the second reflective layer 12, the Ag particles wrapping around in the X direction + side and the Cu particles wrapping around in the X direction − side make the Ag layer thinner toward the X direction + side in the third region 12-3, and the X direction − side. The Cu layer is so thin.
When the film formation of the second reflective layer 12 is completed, the second dielectric layer 15 is formed by passing the stage 34 through the lower part of the first cathode 31 again. When the second dielectric layer 15 is formed, the control device 36 controls the moving speed of the stage 34 in the same manner as when the first dielectric layer 14 is formed, and the film thickness is on the + side in the X direction. A moderately thick second dielectric layer 15 is formed.

In the above description, as shown in FIG. 5, the sputtering apparatus 3 has a first cathode 31, a second cathode 32, and a third cathode 33 arranged in a straight line along the X direction as an example. However, it is not limited to this example. For example, as shown in FIG. 7, the sputtering apparatus 3 may have a first cathode 31, a second cathode 32, and a third cathode 33 arranged along the circumference. In this case, the control device 36 can form a film on the substrate 10 by moving the stage 34 along the circumference (for example, the arrow A1 shown in FIG. 7).
Further, in the above description, the sputtering apparatus 3 forms a film while moving the substrate 10 at the lower part (Z direction − side) of the first cathode 31, the second cathode 32, and the third cathode 33, that is, so-called sputtering down. It has the structure of. However, the sputtering apparatus 3 may have a sputtering-up configuration in which the substrate 10 is formed by moving the substrate 10 on the upper part (Z direction + side) of the first cathode 31, the second cathode 32, and the third cathode 33. Alternatively, it may have a side sputtering configuration in which a film is formed on the substrate 10 from the lateral direction.

Although the above-mentioned sputtering apparatus 3 is an example of a magnetron sputtering apparatus provided with a magnetron cathode, an ion beam sputtering apparatus may also be used.
A method of manufacturing the optical filter 1 by the ion beam sputtering apparatus 300 will be described with reference to FIG. FIG. 8A is a schematic configuration diagram schematically showing an example of the configuration of the ion beam sputtering apparatus 300. The ion beam sputtering apparatus 300 includes a stage 310 on which the substrate 10 is placed, a region limiting mask 308, a film thickness adjusting mask 309, a target portion 313, a beam emitting portion 314, and a control device 315. ..
Note that FIG. 8A shows an example in which the film thickness adjusting mask 309 is arranged closer to the target portion 313 with respect to the arrangement of the area limiting mask 308 and the film thickness adjusting mask 309 in the Z direction. However, the area limiting mask 308 may be arranged on the side closer to the target portion 313.

The beam emitting unit 314 emits an ion beam toward the target unit 313 (direction indicated by arrow A2 in FIG. 8A).
The target unit 313 has a first target 313-1, a second target 313-2, and a third target 313-3 rotatably. The first target 313-1 is composed of alumina (Al ₂ O ₃ ), the second target 313-2 is composed of silver (Ag), and the third target 313-3 is composed of copper (Cu). The target unit 313 uses the first target 313-1 (alumina), the second target 313-2 (Ag), and the third target 313-3 (3rd target 313-3) to irradiate the ion beam from the beam emitting unit 314 for sputtering. It has a configuration that can be selected from Cu). Specifically, the target unit 313 switches the target to which the beam emitting unit 314 is irradiated by rotating around the rotation axis Ar parallel to the X axis by a drive mechanism (not shown) such as a motor.

The particles emitted from the target portion 313 after being irradiated by the ion beam proceed in the Z direction − side (arrow A3 in FIG. 8A), and are formed on the surface of the substrate 10 mounted on the stage 310. To.
FIG. 8B schematically shows the stage 310 viewed from the + side in the Z direction and the substrate 10 mounted on the stage 310. In the stage 310, the substrate 10 is placed on the surface on the target portion 313 side (Z direction + side in the example shown in FIGS. 8A and 8B). The substrate 10 is fixed to the stage 310 by a holder (not shown). The stage 310 has a rotation axis Az parallel to the Z axis, and is rotated by a rotation mechanism (not shown) such as a motor. The substrate 10 mounted on the stage 310 rotates with the rotation of the stage 310. In the present embodiment, the substrate 10 is placed so that the longitudinal direction of the substrate 10 is along the radial direction (diameter direction) from the rotation axis Az of the stage 310. In the example shown in FIG. 8B, the case where two substrates 10 are mounted on the stage 310 is shown, but three or more substrates 10 may be mounted on the stage 310. The rotation of the stage 310 is performed when the sputtered particles from the target portion 313 are formed.

The area limiting mask 308 has a first area limiting mask 308A and a second area limiting mask 308B (see FIG. 8C), and is detachably provided on the holder of the stage 310. The region limiting mask 308 is attached when the first reflective layer 11 and the second reflective layer 12 are formed on the substrate 10. The center of the region limiting mask 308 is arranged so as to coincide with the rotation axis Az of the stage 310, and rotates together with the stage 310. The area limiting mask 308 may be attached by a drive mechanism such as a guide rail or a motor, or may be manually attached by the user.
The area limiting mask 308 is provided at a position separated from the surface of the substrate 10 by a predetermined distance, similarly to the mask 35 included in the sputtering apparatus described with reference to FIG.

FIG. 8C shows the appearance of the first region limiting mask 308A and the second region limiting mask 308B when viewed from the + side in the Z direction, the stage 310, and the substrate 10. The first region limiting mask 308A is, for example, a rectangular member, and shields a region of the substrate 10 mounted on the stage 310 on the side closer to the rotation axis Az from the center of the substrate 10. The second region limiting mask 308B has, for example, a rectangular opening 308B1 in a region close to the rotation axis Az from the center of the substrate 10 mounted on the stage 310 among the disk-shaped members, and the substrate 10 Of the above, the region opposite to the rotation axis Az is shielded from the center of the substrate 10.

The film thickness adjusting mask 309 has a first mask 311 and a second mask 312 (see FIG. 8D), is detachably provided between the stage 310 and the target portion 313, and is mounted on the stage 310. The film thickness of each layer formed on the placed substrate 10 is adjusted. Both the centers of the first mask 311 and the second mask 312 are arranged so as to coincide with the rotation axis Az of the stage 310. The first mask 311 and the second mask 312 may be attached by a drive mechanism such as a guide rail or a motor, or may be manually attached by the user.
In the above description, instead of rotating the stage 310, the first mask 311 and the second mask 312 may have a rotatable configuration, or the stage 310, the first mask 311 and the second mask may be rotatable. The 312 may have a rotatable configuration.

Next, the first mask 311 and the second mask 312 will be described in detail. The density of the particles emitted from the target unit 313 after being irradiated by the ion beam tends to increase as it approaches the rotation axis Az on the stage 310. Therefore, when the first mask 311 or the second mask 312 is not used, the film thickness formed on the surface of the substrate 10 tends to be inclined so as to be thicker toward the side closer to the rotation axis Az of the stage 310. .. In the following description, this tendency will be referred to as a gradient tendency.

FIG. 8D schematically shows an example of the appearance shapes of the first mask 311 and the second mask 312. The first mask 311 and the second mask 312 are produced, for example, in a shape in which a part of a region of a disk-shaped member is cut out. The first mask 311 and the second mask 312 have shielding portions 311a1, 311a2, 312a1, 312a2 and openings 311b1, 311b2, 312b1, 312b2, respectively. In the first mask 311 the boundary 311c between the shielding portion 311a1 and the opening 311b1 is formed linearly in the radial direction from the center of the first mask 311. The boundary 311d between the light-shielding portion 311a1 and the opening 311b2 is formed in a radial direction from the center of the first mask 311. As for the shape of the boundary 311d, as compared with the case where the shielding portion 311a1 has a fan-shaped shape 311e (shown by a broken line in FIG. 8D), the region closer to the center of the first mask 311 has a viewing angle in the circumferential direction. It is made to be small. The boundary between the light-shielding portion 311a2 and the openings 311b1 and 311b2 has a similar shape. That is, the closer to the center of the first mask 311 (that is, the vicinity of the rotation axis Az of the stage 310), the more the openings 311b1 and 311b2 have a viewing angle in the circumferential direction as compared with the case where the openings are fan-shaped. large. Therefore, the closer to the center of the first mask 311 is, the longer the time of exposure to the sputtered particles from the target portion 313 becomes longer, and the above-mentioned inclination tendency is further promoted, and the substrate 10 placed on the rotating stage 310 is further promoted. Of these, the closer the region is to the rotation axis Az, the thicker the film thickness is. This makes it possible to obtain a desired film thickness inclination.

In the second mask 312, the boundary 312c between the shielding portion 312a1 and the opening portion 312b1 is formed in a straight line extending along the radial direction from the center of the second mask 312. The boundary 312d between the light-shielding portion 312a1 and the opening 312b2 is formed in a curved shape from the center to the circumference of the second mask 312. As for the shape of the boundary 312d, as compared with the case where the shielding portion 312a1 has a fan-shaped shape 312e (shown by a broken line in FIG. 8D), the region closer to the center of the second mask 312 has a viewing angle in the circumferential direction. It is made to be large. The boundary between the light-shielding portion 312a2 and the openings 312b1 and 312b2 has a similar shape. That is, the closer to the center of the second mask 312 (that is, the vicinity of the rotation axis Az of the stage 310), the more the openings 312b1 and 312b2 have a viewing angle in the circumferential direction as compared with the case where the openings are fan-shaped. small. Therefore, the closer to the center of the second mask 312, the shorter the time of exposure to the sputtered particles from the target portion 313, the above-mentioned inclination tendency is canceled, and the substrate 10 placed on the rotating stage 310 The film thickness formed over the entire area is almost the same.

The control device 315 has a microprocessor and its peripheral circuits, and the ion beam sputtering device 300 by reading and executing a control program stored in advance in a storage medium (for example, a flash memory) (not shown). It is a processor that controls each part of. The control device 315 controls the rotation mechanism to control the rotation of the stage 310. The control device 315 controls the drive mechanism to switch the target facing the beam emitting unit 314.

The optical filter 1 is manufactured by the ion beam sputtering apparatus 300 having the above configuration as follows.
First, when the first dielectric layer 14 is formed, the control device 315 rotates the target unit 313 so that the first target 313-1 faces the beam emitting unit 314. The control device 315 controls the rotation mechanism to rotate the stage 310. With the area limiting mask 308 removed, the first mask 311 attached, and the second mask 312 removed, the control device 315 emits an ion beam to the beam emitting unit 314. Sputtered particles emitted from the first target 313 by irradiation with an ion beam pass through the opening 311b of the first mask 311 and are formed on the substrate 10 of the rotating stage 310. As described above, when the first mask 311 is used, the first dielectric layer 14 having a desired film thickness inclination is thicker in the region closer to the rotation axis Az among the substrates 10 mounted on the rotating stage 310. Is formed.

Next, when the first reflective layer 11 is formed, the control device 315 rotates the target portion 313 so that the second target 313-2 faces the beam emitting portion 314, and the film is formed by Ag. To be done. With the first area limiting mask 308A attached, the second area limiting mask 308B removed, the first mask 311 removed, and the second mask 312 attached, the control device 315 uses the beam emitting unit 314. Ion beam is emitted. Sputtered particles from the second target 313-2 by irradiation with an ion beam pass through the opening 312b of the second mask 312 and the outside of the first region limiting mask 308A, and the first of the substrate 10 of the rotating stage 310 is rotated. A film is formed on the dielectric layer 14. As described above, when the second mask 312 is used, the film thickness formed over the entire area of the substrate 10 placed on the rotating stage 310 is substantially equal. Therefore, on the substrate 10, an Ag layer having a film thickness substantially equal to that of the region opposite to the rotation axis Az is formed from the center position C of the substrate 10.
Since the surface of the substrate 10 and the area limiting mask 308 are separated by a predetermined distance in the Z direction, the Ag particles are one of the regions on the rotation axis Az side from the center position C of the substrate 10 through this distance. Go around to the club.

When the Ag layer is formed, the control device 315 rotates the target unit 313 so that the third target 313-3 faces the beam emitting unit 314 so that the film is formed by Cu. When forming a film with Cu, the first region limiting mask 308A is removed, the second region limiting mask 308B is attached, the first mask 311 is removed, and the second mask 312 is attached. Film formation is performed. As a result, the sputtered particles from the third target 313-3 due to the irradiation of the ion beam pass through the opening 312b of the second mask 312 and the opening 308B1 of the second region limiting mask 308B to rotate the stage 310. A film is formed on the first dielectric layer 14 of the substrate 10 placed on the substrate 10. As a result, a Cu layer having a film thickness substantially equal to that of the region of the substrate 10 on the side closer to the rotation axis Az from the center position C of the substrate 10 is formed.
Since the surface of the substrate 10 and the area limiting mask 308 are separated by a predetermined distance in the Z direction, Cu particles are separated from the center position C of the substrate 10 on the side opposite to the rotation axis Az through this distance. Go around a part of the area. As a result, a laminated film of the Ag layer and the Cu layer is formed in the region where the Ag particles and the Cu particles wrap around.
In this way, the first reflective layer 11 is formed by switching between the first region limiting mask 308A and the second region limiting mask 308B.
The cavity layer 13 and the second dielectric layer 15 are formed in the same manner as when the first dielectric layer 14 is formed. The second reflective layer 12 is formed in the same manner as when the first reflective layer 11 is formed.

In the above-mentioned example, the case where sputtering is performed as a film forming method has been described. However, in the present embodiment, the film thickness method is not limited to the one in which sputtering is performed, and a film for each layer (first reflective layer 11, second reflective layer 12, cavity layer 13, etc.) with required accuracy. If a method capable of controlling the thickness distribution can be applied, a film forming method other than sputtering may be adopted. For example, thin film deposition or the like can be applied to the film formation of the first reflective layer 11 and the second reflective layer 12.

Next, a spectroscopic detector having the optical filter 1 manufactured as described above will be described.
FIG. 9 is a schematic configuration diagram schematically showing an example of a spectroscopic measuring device 40 as a spectroscopic detector. The spectroscopic measurement device 40 shown in FIG. 9A includes a detector 41, an optical filter 1, a drive mechanism 42 for changing the relative positions of the optical filter 1 and the detector 41, and a control device 43. In the spectroscopic measuring apparatus 40 of the present embodiment, the sample 9 is irradiated with the light beam L (white light) from the light source (not shown), and the transmitted light transmitted through the sample 9 among the irradiated light beams is the optical filter 1. It is incident on the detector 41 via. In the present embodiment, a cut filter (not shown) that cuts light having a wavelength shorter than 420 nm is provided on the upstream side (Z direction + side) of the sample 9.
In FIG. 9, the X-axis and the Y-axis are set so that the surface parallel to the detection surface of the detector 41 and the substrate 10 of the optical filter 1 is an XY plane, and the X-axis and the Y-axis are set along the traveling direction of the light beam L. The Z axis is set and the explanation will be given. The X-axis is set along the longitudinal direction of the optical filter 1.

The detector 41 is, for example, a silicon detector such as a PIN photodiode or a Si avalanche photodiode (SiAPD), and receives a light beam transmitted through the sample 9 and the optical filter 1.
The drive mechanism 42 includes a stage on which the optical filter 1 is placed, a guide rail for moving the stage along the X direction, a motor, and the like. The drive mechanism 42 moves the optical filter 1 in the X direction by moving the stage along the X direction. As a result, the drive mechanism 42 changes the relative position of the optical filter 1 with respect to the detector 41 in the X direction.

The control device 43 includes a microprocessor and peripheral circuits thereof, and by reading and executing a control program stored in advance in a storage medium (for example, a flash memory) (not shown), the drive mechanism 42 described above. It is a processor that controls the movement amount of the optical filter 1 by. By moving the optical filter 1 in the X direction, the incident position of the light beam transmitted through the sample 9 on the optical filter 1 changes along the longitudinal direction (X direction) of the optical filter 1. As described above, the optical filter 1 has an in-plane characteristic distribution in which the central wavelength of the transmission band changes along the X direction, and has an n + 1th-order resonance wavelength in the first reflection layer 11 and the second reflection layer 12. It has the characteristic that the absorption rate of light (for example, secondary light) is larger than the absorption rate of light of nth-order resonance wavelength (for example, primary light) (that is, light of higher-order resonance wavelength is difficult to transmit). Therefore, each time the position of the optical filter 1 in the X direction is changed, for example, a light beam having a central wavelength with a different transmission band is transmitted in a state where the generation of secondary light is suppressed, and the transmitted light beam is detected. It is incident on the vessel 41. This makes it possible to acquire the transmittance information of the sample 9 in the range of 420 nm to 950 nm without being affected by the secondary light.

In addition to the above configuration, the spectroscopic measurement device 40 may have a configuration for monitoring the intensity of the light source. FIG. 9B is a schematic configuration diagram schematically showing an example of the spectroscopic measuring device 40 in this case.
The spectroscopic measurement device 40 includes a detector 41 shown in FIG. 9A, an optical filter 1, a drive mechanism 42, a control device 43, an intensity detection detector 44, and an intensity detection optical filter 45. It has an intensity detection drive mechanism 46 and an optical branching portion 47. The spectroscopic measurement device 40 in this case is also provided with a cut filter (not shown) on the upstream side (Z direction + side) of the optical branching portion 47 to cut light having a wavelength shorter than 420 nm.

The optical branching portion 47 is, for example, a half mirror, and is arranged on the upstream side (Z direction + side) of the sample 9. The optical branching portion 47 branches the laser beam L from the light source into the + side in the X direction and the − side in the Z direction. The intensity detection detector 44 is a silicon detector similar to the detector 41, and is arranged so that the light receiving surface is parallel to the YZ plane. An intensity detection optical filter 45 similar to the optical filter 1 is arranged in the front stage (X direction − side) of the intensity detection detector 44. The intensity detection optical filter 45 is provided along the Z direction by an intensity detection drive mechanism 46 having a stage on which the intensity detection optical filter 45 is placed and a guide rail, a motor, or the like for moving the stage along the Z direction. And move. With the above configuration, the light beam reflected by the optical branching portion 47 in the X direction + side is incident on the intensity detection detector 44 through the intensity detection optical filter 45 without passing through the sample 9.

The control device 43 also controls the amount of movement of the intensity detection optical filter 45 by the intensity detection drive mechanism 46. By moving the intensity detection optical filter 45 in the Z direction, the incident position of the light beam branched at the optical branching portion 47 on the intensity detection optical filter 45 is the longitudinal direction (Z direction) of the intensity detection optical filter 45. ) Changes. The control device 43 controls the movement amount of the optical filter 1 and the movement amount of the intensity detection optical filter 45, and controls the central wavelength of the transmission band of the light beam transmitted through the optical filter 1 and the intensity detection optical filter 45. Align with the center wavelength of the transmission band of the light beam that passes through. As a result, the intensity detection detector 44 detects the light beam having the same center wavelength as the center wavelength of the transmission band of the light beam detected by the detector 41. As a result, the intensity information of the light beam transmitted through the sample 9 can be acquired based on the output of the intensity detection detector 44.

The spectroscopic detector having the optical filter 1 described above can be applied to an imaging device.
FIG. 10 is a schematic configuration diagram schematically showing an example of a spectroscopic camera 50 as an imaging device. The spectroscopic camera 50 shown in FIG. 10A includes an imaging optical system 51, an optical filter 1, an image sensor 52, a drive mechanism 53 that changes the relative positions of the optical filter 1 and the image sensor 52, and a control device. It has 54 and. In the spectroscopic camera 50 of the present embodiment, the light from the subject (not shown) passes through the imaging optical system 51 and enters the image sensor 52 via the optical filter 1.
In FIG. 10, the X-axis and the Y-axis are set so that the plane parallel to the image pickup surface of the image pickup element 52 and the substrate 10 of the optical filter 1 is an XY plane, and the light from the subject (not shown) is measured. The Z-axis is set along the traveling direction for explanation. The X-axis is set along the longitudinal direction of the optical filter 1.

The imaging optical system 51 forms an image of light from the subject on the imaging surface of the image pickup device 52. The image sensor 52 is composed of, for example, CCD or CMOS. The image sensor 52 has a plurality of pixels arranged two-dimensionally on the XY plane, and outputs an electric signal generated by photoelectric conversion of light from a subject by each pixel.
The drive mechanism 53 has the same configuration as the drive mechanism 42 of the spectroscopic measurement device 40 described above, and moves the optical filter 1 arranged in the front stage (Z direction + side) of the image pickup device 52 in the X direction. As a result, the drive mechanism 53 changes the relative position of the optical filter 1 with respect to the image pickup device 52 in the X direction. The control device 54 includes a microprocessor and peripheral circuits thereof, and by reading and executing a control program stored in advance in a storage medium (for example, a flash memory) (not shown), the drive mechanism 53 described above. The amount of movement of the optical filter 1 is controlled by.

In the example shown in FIG. 10A, the luminous flux L1 transmitted through the position X1 along the X direction of the optical filter 1 is a plurality of pixels arranged in a predetermined pixel row C1 along the Y direction of the image sensor 52. Incident in. Similarly, the luminous fluxes L2 and L3 transmitted through the positions X2 and X3 of the optical filter 1 are incident on the pixels arranged in the pixel rows C2 and C3, respectively. As described above, since the optical filter 1 has an in-plane characteristic distribution in which the central wavelength of the transmission band changes along the X direction, the luminous fluxes L1, L2, which are incident on the pixel rows C1, C2, and C3, respectively, L3 has a different central wavelength in the transmission band. That is, the image sensor 52 receives a light flux in a wavelength region different for each pixel row. In this case as well, the influence of the secondary light is reduced by the optical filter 1.
The image sensor 52 photoelectrically converts the light received as described above and outputs an electric signal.

In the spectroscopic camera 50, since the positional relationship between the optical filter 1 and the image pickup element 52 in the X direction is known, the positional relationship between the pixel rows C1, C2, C3 and the positions X1, X2, X3 on the optical filter 1 is also known. It is known. From these relationships, the wavelength regions of the luminous fluxes L1, L2, and L3 can be discriminated. The control device 54 acquires information indicating the position of the optical filter 1 detected by, for example, an encoder (not shown), and transmits the position X1 of the optical filter 1 to the wavelength region of the luminous flux L1 incident on the pixel row C1. The determination is made based on the position X1 of the optical filter 1. Similarly, the control device 54 determines the wavelength region of the luminous flux incident on the other pixel rows based on the position of the optical filter 1 corresponding to each pixel row. The control device 54 generates transmission wavelength information by associating the determined wavelength region of the luminous flux with the pixel row on which the luminous flux is incident. The generated transmission wavelength information is associated with the electrical signal output from the image sensor 52 and is temporarily stored in a storage medium (not shown) such as a memory.

When the optical filter 1 is moved in the X direction by the drive mechanism 53, the luminous flux L1 incident on the pixel row C1 of the image sensor 52 is the position X1 shown in FIG. 10A among the positions of the optical filter 1 in the X direction. Is transparent to different positions. The luminous fluxes L2 and L3 incident on the pixel rows C2 and C3 of the image sensor 52 also pass through positions different from the positions X2 and X3 shown in FIG. 10A. As a result, the luminous fluxes L1, L2, and L3 transmitted through the optical filter 1 and incident on the pixel rows C1, C2, and C3 are the luminous fluxes in a wavelength region different from the wavelength region when transmitted before the movement of the optical filter 1 is performed. Is. That is, due to the movement of the optical filter 1 in the X direction, each pixel of the image sensor 52 receives a light flux in a central wavelength region different from that before the movement of the optical filter 1. The image sensor 52 receives light fluxes in different wavelength regions for each pixel row, performs photoelectric conversion, and outputs an electric signal.

The control device 54 acquires information indicating the position of the optical filter 1 after movement based on the output from the encoder or the like, and determines the wavelength region of the luminous flux incident on each pixel row of the image sensor 52 based on this information. To do. The control device 54 generates transmission wavelength information by associating the determined wavelength region of the luminous flux with the pixel row on which the luminous flux is incident. It is temporarily stored in a storage medium (not shown) such as a memory in association with the electric signal output from the image sensor 52.

Image data of the subject in a certain wavelength region is generated based on the electric signal generated each time the position of the optical filter 1 is changed. In this case, based on the transmitted wavelength information, an electric signal output from the pixels of the pixel row that has received the luminous flux in the selected wavelength region is extracted, and image data of the subject is generated from the extracted electric signal. As a result, image data based only on the luminous flux transmitted through the position X1 of the optical filter 1, image data based only on the luminous flux transmitted through the position X2, and image data based only on the luminous flux transmitted through the position X3 are generated. The above processing may be performed by an image processing unit (not shown) included in the spectroscopic camera 50, or may be performed by an image processing unit included in an external device different from the spectroscopic camera 50.

In the spectroscopic camera 50 described above, the case where the optical filter 1 is arranged in the vicinity of the image sensor 52 has been given as an example, but the present invention is not limited to this example. For example, as shown in the schematic configuration diagram of the spectroscopic camera 50 of FIG. 10B, it has a first imaging optical system 51-1 and a second imaging optical system 51-2, and has a first imaging optical system. The optical filter 1 may be arranged between the 51-1 and the second imaging optical system 51-2. In this case, the optical filter 1 is arranged at the position of the imaging surface of the first imaging optical system 51-1. The second imaging optical system 51-2 forms an image on the image pickup device 52 at the position of the imaging surface of the first imaging optical system 51-1. Other configurations of the spectroscopic camera 50 are the same as those shown in FIG. 10 (a).

According to the above-described embodiment, the following effects can be obtained.
(1) The optical filter 1 is a Fabry-Perot type resonator including a cavity layer 13 and a pair of first reflection layer 11 and second reflection layer 12 facing each other with the cavity layer 13 interposed therebetween. The optical filter 1 is a bandpass filter having an in-plane characteristic distribution in which the central wavelength of the transmission band changes along at least one direction of the main surface. The optical filter 1 has at least one of a pair of first reflective layer 11 and second reflective layer 12 at a position in the main surface where the central wavelength of the transmission band corresponds to the nth resonance wavelength of the resonator. The absorption rate of light at the n + 1th-order resonance wavelength of the resonator is larger than the absorption rate of light at the n-th order resonance wavelength of the resonator. As a result, since the optical filter 1 absorbs more light after the second order, it is possible to prevent the wavelength region that can be transmitted from being limited to a narrow range due to the influence of the light after the second order. That is, the optical filter 1 can function as a bandpass filter that transmits light in a wide wavelength region while suppressing the transmission of light from the second order onward.

(2) At least one of the first reflective layer 11 and the second reflective layer 12 contains copper (Cu). As a result, the optical filter 1 can transmit light having a long center wavelength.

(3) At least one of the first reflective layer 11 and the second reflective layer 12 contains copper (Cu) and silver (Ag), and the position where light having a longer central wavelength of the transmission band is transmitted has a higher Cu Ag with respect to Ag. The ratio is high. Therefore, the optical filter 1 can make the position where the light having a long center wavelength is transmitted and the position where the light having a short center wavelength is transmitted different from each other along the X direction. By making the position of transmitting light different along the X direction according to the central wavelength of the transmitted light, one optical filter 1 is quadratic from light in a short wavelength region to light in a long wavelength region. It can function as a bandpass filter that suppresses the influence of subsequent light.

(4) The Cu layer and the Ag layer are laminated. As a result, the optical filter 1 can transmit light in a wavelength region resonating with Cu and light in a wavelength region resonating with Ag, and thus functions as a bandpass filter that transmits light in a wide wavelength region. Can be done.

(5) The film thickness of at least one of the Cu layer and the Ag layer is inclined along one direction (X direction) of the main surface 2. As a result, in the first reflective film 11 and the second reflective film 12, the first regions 11-1 and 12-1 on which the Cu layer is formed and the second regions 11-2 on which the Ag layer is formed are formed. Also in the third regions 11-3 and 12-3, which are boundaries with 12-2, the central wavelength of the transmission band can be continuously changed along the X direction.

(6) The spectroscopic measurement device 40 includes an optical filter 1 and a detector 41 that detects light transmitted through the optical filter 1. As a result, wavelength measurement in a wide range from the visible light region to the near infrared region can be performed in a state where the influence of the second and subsequent light is suppressed. Further, as compared with a conventional spectroscopic measuring device using a diffraction grating or the like, spectroscopic measurement can be performed with a simple configuration.

(7) The spectroscopic measurement device 40 includes a drive mechanism 42 that changes the relative position of the optical filter 1 with respect to the detector 41 along one direction. By moving the position of the optical filter 1, spectroscopic measurement can be performed at fine wavelength intervals while the influence of the second and subsequent light is suppressed.

(8) The spectroscopic camera 50 includes an imaging optical system 51, an image sensor 52 having pixels arranged in two dimensions, and an optical filter 1. As a result, it is possible to perform imaging in a state in which the influence of the secondary and subsequent light is suppressed on the light having a wavelength in a wide range from the visible light region to the near infrared region.

The present invention is not limited to the above-described embodiment as long as the features of the present invention are not impaired, and other embodiments considered within the scope of the technical idea of the present invention are also included within the scope of the present invention. ..

1 ... Optical filter 10 ... Substrate 11 ... First reflective layer 12 ... Second reflective layer 13 ... Cavity layer 40 ... Spectral measuring device 41 ... Detector 42 ... Drive mechanism 50 ... Spectral camera 51 ... Imaging optical system 52 ... Image sensor 53 ... Drive mechanism

Claims (14)

An optical filter including a Fabry-Perot type resonator including a cavity layer and a pair of reflective layers facing each other across the cavity layer.
The optical filter is a bandpass filter having an in-plane characteristic distribution in which the central wavelength of the transmission band changes along at least one direction of the main surface.
At a position in the main surface where the central wavelength of the transmission band corresponds to the nth-order resonance wavelength of the resonator.
An optical filter in which the absorption rate of light having an n + 1th-order resonance wavelength of the resonator in at least one of the pair of reflection layers is larger than the absorption rate of light having an n-th order resonance wavelength of the resonator. .. In the optical filter according to claim 1,
An optical filter in which at least one of the reflective layers contains Cu. In the optical filter according to claim 2,
An optical filter in which the at least one reflective layer contains Cu and Ag, and the ratio of the Cu to the Ag is higher in the at least one reflective layer at a position where the central wavelength of the transmission band is longer. In the optical filter according to claim 3,
An optical filter in which the Cu and the Ag are laminated. In the optical filter according to claim 4,
An optical filter in which the film thickness of at least one of the Cu and the Ag is inclined along the one direction. In the optical filter according to any one of claims 1 to 5,
The cavity layer is an optical filter that is a dielectric material. The optical filter according to any one of claims 1 to 6.
An optical filter having a center wavelength of 380 nm or more in the transmission band. In the optical filter according to any one of claims 1 to 7.
An optical filter having a center wavelength of the transmission band of 950 nm or less. In the optical filter according to any one of claims 1 to 8.
An optical filter in which the one direction is a direction along a straight line on the main surface. In the optical filter according to any one of claims 1 to 8.
An optical filter in which the one direction is along one arc on the main surface. The optical filter according to any one of claims 1 to 10.
A spectroscopic detector comprising a detector for detecting light transmitted through the optical filter. In the spectroscopic detector according to claim 11,
A spectroscopic detector comprising a driving mechanism that changes the relative position of the optical filter with respect to the detector along the one direction. In the spectroscopic detector according to claim 11 or 12.
A spectroscopic detector in which the detector is a two-dimensional image sensor. The spectroscopic detector according to claim 13,
A spectroscopic camera equipped with an imaging optical system.

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