JP2018060163A - Optical filter and image capturing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical filter having pass bands in the visible band and infrared band without combining multiple filters.SOLUTION: An optical filter comprises an optical multilayer film formed on a substrate, the optical multilayer film comprising a plurality of basic blocks 11 having a specific film configuration with connecting layers 12 therebetween to achieve a pass band in the visible band and a pass band in the near-infrared band without having to combine multiple filters, with a stop band having a variable bandwidth between the two pass bands.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an optical filter having a transmission band in both a visible light band and an infrared light band, and an imaging device using the same.

  As an optical filter having a transmission band in both the visible light band and the infrared light band, for example, Patent Document 1 discloses an optical filter that transmits visible light and has a transmission band in a part of the near infrared light band. Have been described.

  This optical filter is suitable for, for example, a surveillance camera that continuously shoots day and night, and in the daytime, infrared light other than the partial transmission band of the near infrared light band is blocked, so that the visible light is used. While a natural image can be taken, at night, infrared light passing through the transmission band of the near-infrared light band can be irradiated for illumination, and the reflected light can be taken.

Japanese Patent No. 4705342

  In Patent Document 1, the characteristics of the optical filter are obtained by combining the first filter and the second filter, and rise and rise in the partial transmission band of the near infrared light band. Downstream transmission characteristics are realized by a combination of the first and second filters.

  By combining the two first and second filters in this way, the transmission characteristics of the near-infrared light transmission band rise and fall are realized, so the first and second filters are manufactured. If the characteristics of the two filters vary due to variations in the two, the variations are superimposed by combining them. For this reason, variation in the characteristics of the obtained optical filter becomes large, and when the required bandwidth becomes narrow in the transmission band of the near-infrared light band, a desired transmittance may not be obtained.

  Therefore, the applicant of the present application has a transmission band in the visible light band and a transmission band in the near-infrared light band without overlapping a plurality of filters on the same day as the previous application on which the priority of the application of the present application is based. The optical filter which has is proposed.

  In the proposed optical filter, the bandwidth of the cutoff band between the long wavelength side of the transmission band of the visible light band and the short wavelength side of the transmission band of the near infrared light band cannot be varied and is required. There is a problem that some specifications cannot be satisfied depending on the specifications.

  The present invention has been made in view of the above points, and has a transmission band in the visible light band and a near-infrared light band, without overlapping a plurality of filters, and between the transmission bands. An object of the present invention is to provide an optical filter that can vary the width of the cutoff band.

  In order to achieve the above object, the present invention is configured as follows.

That is, the optical filter of the present invention is an optical filter having a transmission band in each of the visible light band and a part of the near-infrared light band, and includes a substrate and an optical multilayer film formed on the substrate, The optical multilayer film is formed by laminating a thin film made of a high refractive index material and a thin film made of a low refractive index material having a refractive index lower than that of the high refractive index material,
When H is 1/4 optical film thickness of the high refractive index material and L is 1/4 optical film thickness of the low refractive index material, the optical multilayer film has the following basic blocks as the low refractive index. It has a basic structure that includes a plurality of sandwiched layers of materials,
The tie layer includes a thin film made of the low refractive index material having an optical film thickness of about 3 L or more,
The basic block is
{(1.0 ± 0.5) H (1.0 ± 0.5) L (1.0 ± 0.5) H} A {(1.0 ± 0.5) H (1.0 ± 0 .5) L (1.0 ± 0.5) H}.

However, A is an intermediate layer included in the basic block, and when n is an integer of 1 or more,
A = (2.0 ± 1.0) L {(1.0 ± 0.5) H (2.0 ± 1.0) L} ⁽ⁿ⁻¹⁾
It is.

  “± 0.5” and “± 1.0” are tolerances.

  The tie layer including a thin film made of a low refractive material preferably has an optical film thickness of approximately 3L, approximately 5L, or approximately 7L.

  The optical multilayer film preferably includes an adjustment layer on the substrate side, and the adjustment layer preferably includes a thin film made of the high refractive index material.

In the optical filter of the present invention, the thin film made of the high refractive index material and the thin film made of the low refractive index material may be interchanged. That is, the optical filter of the present invention is an optical filter having a transmission band in each of the visible light band and a part of the near-infrared light band, and includes a substrate and an optical multilayer film formed on the substrate, The optical multilayer film is formed by laminating a thin film made of a high refractive index material and a thin film made of a low refractive index material having a refractive index lower than that of the high refractive index material,
When H is ¼ optical film thickness of the high refractive index material and L is ¼ optical film thickness of the low refractive index material, the optical multilayer film has the following basic blocks, It has a basic structure that includes a plurality of sandwiched layers of materials,
The tie layer includes a thin film made of the high refractive index material having an optical film thickness of about 3H or more,
The basic block is
(1.0 ± 0.5) L (1.0 ± 0.5) H (1.0 ± 0.5) L} A (1.0 ± 0.5) L (1.0 ± 0.5) ) H (1.0 ± 0.5) L}
It is.

However, A is an intermediate layer included in the basic block, and when n is an integer of 1 or more,
A = (2.0 ± 1.0) H {(1.0 ± 0.5) L (2.0 ± 1.0) H} ⁽ⁿ⁻¹⁾
It is.

  The tie layer including a thin film made of a highly refractive material preferably has an optical film thickness of about 3H, about 5H, or about 7H.

  Preferably, the optical multilayer film includes adjustment layers on the substrate side and the outer surface side, and the adjustment layer on the outer surface side includes a thin film made of the low refractive index material.

The tie layer including a thin film made of a low refractive index material includes three layers of a thin film made of the low refractive index material, a thin film made of the high refractive index material, and a thin film made of the low refractive index material. The optical film thickness of the layer is
(1.4 ± 0.5) L (0.1 + 0.2 / −0.09) H (1.4 ± 0.5) L
Is preferred.

The tie layer including a thin film made of a high refractive index material includes three layers of a thin film made of the high refractive index material, a thin film made of the low refractive index material, and a thin film made of the high refractive index material. The optical film thickness of the layer is
(1.4 ± 0.5) H (0.1 + 0.2 / −0.09) L (1.4 ± 0.5) H
Is preferred.

  “+0.2” and “−0.09” are tolerances.

  According to the optical filter of the present invention, the optical multilayer film includes a plurality of basic blocks having a specific film configuration via the connecting layer, thereby having a transmission band in the visible light band without combining a plurality of filters. An optical filter having a transmission band in the near-infrared light band can be realized. Thus, unlike an optical filter combining a plurality of filters, there is no inconvenience that a desired transmittance cannot be obtained in the near-infrared light transmission band due to the manufacturing variation of each filter being superimposed. This is particularly effective when the bandwidth of the near-infrared light transmission band is narrow, for example, when the half-value width of the near-infrared light transmission band is 50 nm or less.

  Further, the optical film thickness of the tie layer is set to approximately 3 L, approximately 5 L, approximately 7 L, approximately 3 H, approximately 5 H, or approximately 7 H, depending on the film configuration of the basic block. It is possible to vary the bandwidth of the cutoff band between the long wavelength side of the transmission band and the short wavelength side of the transmission band in the near infrared light band.

  Further, the tie layer is composed of three layers of a thin film made of a low refractive index material, a thin film made of a high refractive index material, and a thin film made of a low refractive index material, or a high refractive index depending on the film configuration of the basic block. Ripple in the transmission band in the visible light band can be reduced by adopting a specific three-layer film configuration of a thin film made of a material, a thin film made of a low refractive index material, and a thin film made of a high refractive index material. .

  Furthermore, by selecting n which is an integer of 1 or more in the intermediate layer A, the bandwidth of the transmission band of the near-infrared light band can be adjusted, and according to the required specifications, the transmission band Bandwidth can be selected.

  The optical filter of the present invention uses the optical multilayer film as a first optical multilayer film, and is between the long wavelength side of the transmission band of the visible light band and the short wavelength side of the transmission band of the near infrared light band. It is preferable to include a second optical multilayer film constituting a filter having a blocking characteristic.

  The first optical multilayer film has a transmission band in the visible light band and a transmission band in the near-infrared light band, and the long-wavelength side of the transmission band in the visible light band and the near-infrared light band A transmission band having a peak in which the transmittance sharply fluctuates occurs between the transmission band and the short wavelength side. Therefore, a second optical multilayer film is provided, and the peak due to the blocking characteristic of the second optical multilayer film It is preferable to remove the transmission band having

  It is preferable that the first optical multilayer film is formed on one surface of the substrate and the second optical multilayer film is formed on the other surface of the substrate.

  Since the first optical multilayer film and the second optical multilayer film are respectively formed on each surface of the substrate, a biased film stress is applied as in the case where both optical multilayer films are formed on one surface of the substrate. The deformation of the substrate can be suppressed.

  The imaging device of the present invention includes the optical filter of the present invention.

  According to the imaging device of the present invention, an optical filter having a transmission band in the visible light band and a transmission band in the near infrared light band is provided without combining a plurality of filters. There is no problem that a desired transmittance cannot be obtained in the transmission band of the near-infrared light band because the manufacturing variation of each filter is superimposed, such as a video camera, a surveillance camera, an in-vehicle camera, It is suitable for an imaging device such as an iris authentication apparatus.

  According to the optical filter of the present invention, the optical multilayer film includes a plurality of basic blocks having a specific film configuration via the connecting layer, thereby having a transmission band in the visible light band without combining a plurality of filters. An optical filter having a transmission band in the near-infrared light band can be realized. Thus, unlike an optical filter combining a plurality of filters, there is no inconvenience that a desired transmittance cannot be obtained in the near-infrared light transmission band due to the manufacturing variation of each filter being superimposed. In addition, by selecting the optical film thickness of the tie layer, the bandwidth of the cutoff band between the long wavelength side of the transmission band in the visible light band and the short wavelength side of the transmission band in the near infrared light band can be varied. .

FIG. 1 is a schematic configuration diagram of an imaging device according to an embodiment of the present invention. FIG. 2 is a schematic configuration diagram of the optical filter of FIG. FIG. 3 is a diagram showing an example of the film design of the first optical multilayer film of the optical filter of FIG. FIG. 4 is a diagram showing the transmission characteristics of the first optical multilayer film of the optical filter of FIG. FIG. 5 is a diagram showing an example of the film design of the second optical multilayer film of the optical filter of FIG. FIG. 6 is a diagram showing the transmission characteristics of the second optical multilayer film of the optical filter of FIG. FIG. 7 is a diagram showing the transmission characteristics of the optical filter of FIG. FIG. 8 is a diagram showing an example of the film design of the first optical multilayer film when the optical film thickness of the connecting layer of the first optical multilayer film is approximately 1L. FIG. 9 is a diagram showing an example of the film design of the first optical multilayer film when the optical film thickness of the connecting layer of the first optical multilayer film is about 5L. FIG. 10 is a diagram showing an example of the film design of the first optical multilayer film when the optical film thickness of the connecting layer of the first optical multilayer film is about 7L. FIG. 11 is a graph showing transmission characteristics when the optical film thickness of the connecting layer of the first optical multilayer film is approximately 1L, approximately 3L, approximately 5L, and approximately 7L. FIG. 12 is a diagram showing an example of the film design of the first optical multilayer film of another embodiment of the optical filter of FIG. FIG. 13 is a diagram showing the transmission characteristics of the first optical multilayer film of the optical filter of FIG. FIG. 14 is a diagram illustrating an example of the film design of the first optical multilayer film when the optical film thickness of the connecting layer of the first optical multilayer film is approximately 3 L and n = 1 in the intermediate layer. FIG. 15 is a diagram illustrating an example of the film design of the first optical multilayer film when the optical film thickness of the connecting layer of the first optical multilayer film is approximately 3 L and n = 3 in the intermediate layer. FIG. 16 is a diagram showing the transmission characteristics of the first optical multilayer film when the optical film thickness of the connecting layer of the first optical multilayer film is about 3 L and n = 1, 2, and 3 in the intermediate layer. FIG. 17 is a diagram showing an example of the film design of the first optical multilayer film when the optical film thickness of the connecting layer of the first optical multilayer film is approximately 1 L and n = 1 in the intermediate layer. FIG. 18 is a diagram showing an example of the film design of the first optical multilayer film when the optical film thickness of the connecting layer of the first optical multilayer film is approximately 1 L and n = 3 in the intermediate layer. FIG. 19 is a diagram showing the transmission characteristics of the first optical multilayer film when the optical film thickness of the connecting layer of the first optical multilayer film is approximately 1 L and n = 1, 2, and 3 in the intermediate layer. FIG. 20 is a diagram illustrating an example of the film design of the first optical multilayer film when the number m of basic blocks included in the first optical multilayer film is 1. FIG. FIG. 21 shows the film design of the first optical multilayer film when the optical film thickness of the connecting layer of the first optical multilayer film is approximately 3 L and the number of basic blocks included in the first optical multilayer film is m = 5. It is a figure which shows an example. FIG. 22 shows the first optical multilayer film when the optical film thickness of the connecting layer of the first optical multilayer film is approximately 3 L, and the number of basic blocks included in the first optical multilayer film is m = 1, 3, and 5. It is a figure which shows the permeation | transmission characteristic. FIG. 23 shows the film design of the first optical multilayer film when the optical film thickness of the connecting layer of the first optical multilayer film is approximately 1 L and the number of basic blocks included in the first optical multilayer film is m = 5. It is a figure which shows an example. FIG. 24 shows the first optical multilayer film when the optical film thickness of the connecting layer of the first optical multilayer film is approximately 1 L, and the number of basic blocks included in the first optical multilayer film is m = 1, 3, and 5. It is a figure which shows the permeation | transmission characteristic. FIG. 25 is a diagram showing an example of the film design of the first optical multilayer film of the optical filter according to another embodiment of the present invention. FIG. 26 is a diagram showing the transmission characteristics of the first optical multilayer film of FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of an imaging device according to an embodiment of the present invention.

  An imaging device 1 according to this embodiment includes a lens 2 constituting a coupling optical system that receives light from an external subject side, an optical filter 3 according to an embodiment of the present invention, and an imaging element 4 such as a CCD or a CMOS. I have. Further, the imaging device 1 is provided with an LED light 5 for photographing at night, and irradiates near infrared light toward the subject from the LED light 5 at night.

  The optical filter 3 of this embodiment is formed on a quartz substrate 6 that is a transparent substrate and one main surface 6a of the quartz plate 6, and in two wavelength bands, a visible light band and a near-infrared light band. A first optical multilayer film 7 having transmission characteristics and a second optical multilayer film formed on the other main surface 6b of the quartz substrate 6 and having a cutoff characteristic between the visible light band and the near-infrared light band 8 and.

  FIG. 2 is a schematic configuration diagram of the optical filter 3 of FIG.

The first optical multilayer film 7 and the second optical multilayer film 8 of the optical filter 3 of this embodiment are a high refractive index material, for example, a high refractive index film 14 made of TiO ₂ and a low refractive index material. For example, a plurality of low refractive index films 15 made of, for example, SiO ₂ are alternately stacked.

The first optical multilayer film 7 is provided with a first adjustment layer 9 on the quartz substrate 6 side serving as an interface with the optical multilayer film, while a second adjustment layer is disposed on the outer surface side serving as an interface with the outside air. 10 is provided. Between the adjustment layers 9 and 10, the basic block 11 is m (m is 2).
(Integer) In this example, three basic blocks 11 are included (m = 3), and a connecting layer 12 is interposed between the basic blocks 11.

  In this embodiment, the first adjustment layer 9 on the quartz substrate 6 side is composed of two layers in which a high refractive index film 14 and a low refractive index film 15 are laminated, and the second adjustment layer 10 on the outer surface side. Is composed of one layer of the low refractive index film 15.

  Since the adjustment layers 9 and 10 are provided on the quartz substrate 6 side and the outer surface side where the refractive index changes as described above, generation of ripples can be suppressed.

  In this embodiment, the connecting layer 12 connecting the basic blocks 11 is composed of one layer of the low refractive index film 15.

  Each basic block 11 is configured by laminating a plurality of high refractive index films 14 and low refractive index films 15 alternately, in this example, nine layers. Each basic block 11 includes an intermediate layer 13 sandwiched between three layers on both sides.

Here, when H is 1/4 optical film thickness of the high refractive index material and L is 1/4 optical film thickness of the low refractive index material, the first optical multilayer film 7 has the following basic blocks: 11 having a basic structure including a plurality of layers 11 made of the low refractive index material with a tie layer 12 interposed therebetween,
The tie layer 12 includes a thin film made of the low refractive index material having an optical film thickness of about 3 L or more,
Basic block
{(1.0 ± 0.5) H (1.0 ± 0.5) L (1.0 ± 0.5) H} A {(1.0 ± 0.5) H (1.0 ± 0 .5) L (1.0 ± 0.5) H}.

However, A is the intermediate layer 13 included in the basic block 11, and when n is an integer of 1 or more,
A = (2.0 ± 1.0) L {(1.0 ± 0.5) H (2.0 ± 1.0) L} ⁽ⁿ⁻¹⁾
It is.

  Note that n-1 is the number of repetitions and indicates that {(1.0 ± 0.5) H (2.0 ± 1.0) L} is repeatedly laminated n−1 times.

  In the above film configuration, “± 0.5” and “± 1.0” are tolerances, and the tolerance “± 0.5” is preferably “± 0.3”, more preferably “± 0”. .2 ". The tolerance “± 1.0” is preferably “± 0.6”, and more preferably “± 0.4”.

  The above-mentioned film configuration is shown by omitting these tolerances as follows.

The film configuration of the basic block 11 of the first optical multilayer film 7 is as follows:
(1.0H 1.0L 1.0H) A (1.0H 1.0L 1.0H)
And
The film configuration of A, which is the intermediate layer 13, is
A = 2.0L (1.0H 2.0L) ^(n-1)
It is.

  This A is, for example, as follows when n = 1, 2, 3.

A = 2.0L
A = 2.0L 1.0H 2.0L
A = 2.0L 1.0H 2.0L 1.0H 2.0L
From the viewpoint of manufacturing the optical filter 3, the upper limit of n is preferably about 8, for example.

  The first optical multilayer film 7 includes m (m is an integer of 2 or more) of basic blocks 11 having the above-described film configuration between the first and second adjustment layers 9 and 10 at both ends. The basic structure includes a tie layer 12 made of a low refractive index material.

  In this embodiment, the optical film thickness of the connecting layer 12 is approximately 3L. Here, approximately 3 L is 3.0 ± 0.5 L, preferably 3.0 ± 0.3 L, and more preferably 3.0 ± 0.2 L.

  In this embodiment, as shown in FIG. 2, the first optical multilayer film 7 includes three basic blocks 11 (m = 3), and the intermediate layer 13 of the basic block 11 is three layers. In the film configuration of A, which is the intermediate layer 13, n = 2. Since the first optical multilayer film 7 includes three nine basic blocks 11, the total number of the basic blocks 11 is 27, and two tie layers 12 interposed between the basic blocks 11 are provided. The first adjustment layer 9 is composed of two layers, and the second adjustment layer 10 is composed of one layer for a total of 32 layers.

  FIG. 3 is a diagram showing an example of the film design of the first optical multilayer film 7 obtained by simulation with the design wavelength (reference wavelength) λ set to 886 nm.

In FIG. 3, as described above, H is a 1/4 optical film thickness of TiO ₂ which is a high refractive index material, and L is a 1/4 optical film thickness of SiO ₂ which is a low refractive index material.

The refractive index of TiO ₂ at the design wavelength λ is 2.32, and the refractive index of SiO ₂ is 1.46.

As shown in FIG. 3, the first optical multilayer film 7 includes a first high-refractive index film (TiO ₂ ) 14 and a second low-refractive index film (SiO ₂ ) 15 on the quartz substrate 6 side. And the second adjustment layer 10 made of the 32nd low refractive index film (SiO ₂ ) 15 is provided on the outer surface side.

An optical system including three basic blocks 11 between the adjustment layers 9 and 10 (m = 3) and including a low refractive index film (SiO ₂ ) 15 on the 12th and 22nd layers between the basic blocks 11. A tie layer 12 having a thickness of about 3 L is interposed.

Each basic block 11 includes three layers of a high refractive index film (TiO ₂ ) 14, a low refractive index film (SiO ₂ ) 15 and a high refractive index film (TiO ₂ ) 14 on the side close to the quartz substrate 6, and an outer surface. close side, the high refractive index film (TiO ₂₎ 14, the low refractive index film (SiO ₂₎ 15 and a high refractive index film is provided between the three layers of (TiO ₂₎ 14, the low refractive index film (SiO ₂₎ 15, an intermediate layer 13 including three layers of a high refractive index film (TiO ₂ ) 14 and a low refractive index film (SiO ₂ ) 15 is provided.

  FIG. 4 is a diagram showing the transmission characteristics of the first optical multilayer film 7.

  The first optical multilayer film 7 of this embodiment has a transmission band (about 400 nm to about 690 nm) in the visible light band and a transmission band (about 840 nm to about 890 nm) in the near infrared light band. . The transmittance of the transmission band in the near infrared light band is 90% or more, and the half width of the transmission band is about 50 nm. Further, in the band of about 720 nm to about 760 nm between the two transmission bands, two peaks in which the transmittance sharply changes greatly are generated. In addition, there is a peak in which the transmittance sharply fluctuates around about 990 nm in the near infrared band.

  The first optical multilayer film 7 includes a plurality of basic blocks 11 having a specific film configuration as described above, thereby transmitting light in a visible light band (about 400 nm to about 690 nm) with high human visibility, and Thus, it is possible to realize the characteristic of transmitting light for night photographing out of light in the near infrared light band.

  In the conventional example, two filters are combined to form a transmission band in a part of the near-infrared light band. Therefore, when the manufacturing variation of each filter is superimposed and the transmission band of the near-infrared light band becomes narrow, a desired band is obtained. There is a drawback that the transmittance cannot be obtained.

  On the other hand, in this embodiment, only the first optical multilayer film 7 has a narrow transmission band in the near-infrared light band. Therefore, it is necessary to combine two filters as in the conventional example. In addition, the manufacturing variation of each filter is not superimposed.

  In this embodiment, the second optical multilayer film is used to remove the transmission band having two peaks in which the transmittance of about 720 nm to about 760 nm in the near-infrared band varies sharply and a peak around about 990 nm. 8 is provided.

  As shown in FIG. 2, the second optical multilayer film 8 is configured by alternately laminating a plurality of high refractive index films 14 and low refractive index films 15.

  FIG. 5 is a diagram showing an example of the film design of the second optical multilayer film 8 obtained by simulation.

The second optical multilayer film 8 of this embodiment includes a high refractive index film 14 made of, for example, TiO ₂ that is a high refractive index material, and a low refractive index film 15 made of, for example, SiO ₂ that is a low refractive index material. 28 layers are alternately laminated.

  FIG. 6 is a diagram showing the transmission characteristics of the second optical multilayer film 8.

  Similar to the first optical multilayer film 7, the second optical multilayer film 8 has a transmission band in the visible light band with high human visibility, and also in the near infrared light band. Compared to the transmission band, the transmission band has a wider bandwidth.

  The second optical multilayer film 8 has a cutoff characteristic between the long wavelength side (about 690 nm) of the visible light transmission band and the short wavelength side (about 800 nm) of the near infrared light transmission band. ing. Further, the transmittance in the near-infrared band around 990 nm is also low.

  The band blocked by the second optical multilayer film 8 includes a transmission band (about 720 nm to about 760 nm) having two peaks in which the transmittance sharply varies greatly in the first optical multilayer film 7. Yes.

  FIG. 7 is a diagram illustrating the transmission characteristics of the optical filter 3 including the first optical multilayer film 7 and the second optical multilayer film 8.

  As shown in FIG. 7, the optical filter 3 including the first optical multilayer film 7 having the transmission characteristics shown in FIG. 4 and the second optical multilayer film 8 having the transmission characteristics shown in FIG. In addition, the two peaks in the band of about 720 nm to about 760 nm, which appeared in FIG. In addition, a peak around 990 nm in the near infrared band is substantially removed.

  The optical filter 3 has a transmission band (about 400 nm to about 690 nm) in the visible light band, a transmission band (about 840 nm to about 890 nm) in the near infrared light band, and other near infrared light bands ( 700 nm to 800 nm and 900 nm to 1000 nm).

  As a result, the imaging device 1 including the optical filter 3 can perform photographing not only in daytime when natural light enters but also under night vision such as at night.

  Further, unlike the conventional example, it is not necessary to combine two filters to form a transmission band in a part of the near-infrared light band, and the manufacturing variation of each filter is superimposed to transmit the transmission band of the near-infrared light band. Therefore, there is no case where a desired transmittance cannot be obtained.

The first and second optical multilayer films 7 and 8 of this embodiment are respectively formed on the main surfaces 6a and 6b of the quartz substrate 6 using a known vacuum deposition apparatus or the like. That is, TiO ₂ and SiO ₂ are alternately deposited on one principal surface 6a of the quartz substrate 6 in a state where the other principal surface 6b side is not deposited. To adjust the film thickness, the vapor deposition operation is performed while monitoring the film thickness, and when the predetermined film thickness is reached, the deposition of the vapor deposition material (TiO ₂ , SiO ₂ ) is stopped by closing the shutter provided in the vapor deposition source. Is done. Thereafter, TiO ₂ and SiO ₂ are alternately deposited on the other main surface 6b of the quartz substrate 6 in the same manner.

  In addition, you may form into a film by not only a vacuum evaporation method but other well-known methods, such as sputtering method and an ion plating method.

  In this embodiment, since the first and second optical multilayer films 7 and 8 are formed on the principal surfaces 6a and 6b of the quartz substrate 6, respectively, both the optical multilayer films 7 and 8 are formed only on one principal surface. Compared with the case where it does, it can reduce that the biased film | membrane stress is added and can suppress that the quartz substrate 6 deform | transforms. The optical multilayer films 7 and 8 may be formed only on one main surface of the quartz substrate 6.

  According to this embodiment, as shown in FIG. 7, each of the visible light band and the near-infrared light band has a transmission band, but depending on the required specifications, the longer wavelength side of the transmission band in the visible light band There is a case where it is desired to vary the bandwidth of the cutoff band between the short wavelength side of the transmission band in the near infrared light band.

  Therefore, in this embodiment, as described above, the connecting layer 12 in the first optical multilayer film 7 includes a thin film made of a low refractive index material having an optical film thickness of about 3 L or more. By selecting the optical film thickness, the bandwidth of the cutoff band is made variable.

  The optical film thickness of the tie layer 12 is preferably about 3L, about 5L, or about 7L. About 5L is 5.0 ± 0.5L, preferably 5.0 ± 0.3L, more preferably 5.0 ± 0.2L. About 7L is 7.0 ± 0.5L, preferably 7.0 ± 0.3L, and more preferably 7.0 ± 0.2L.

  Next, the bandwidth of the cutoff band when the optical film thickness of the tie layer 12 in the first optical multilayer film 7 is set to approximately 3L, approximately 5L, or approximately 7L will be described. Here, as a reference example, the case where the optical film thickness of the connecting layer 12 is approximately 1 L will be described.

  The film design when the optical film thickness of the connecting layer 12 in the first optical multilayer film 7 is approximately 3 L is shown in FIG.

  FIG. 8 is a diagram illustrating an example of the film design of the first optical multilayer film 7 corresponding to FIG. 3 when the optical film thickness of the connecting layer 12 is approximately 1 L.

Similar to FIG. 3, the intermediate layer 13 includes three basic blocks 11 of three layers (n = 2) between the adjustment layers 9 and 10 (m = 3), and the twelfth layer between the basic blocks 11 and In the 22nd layer, a tie layer 12 composed of a low refractive index film (SiO ₂ ) 15 is interposed, and the optical film thickness of each tie layer 12 is approximately 1 L.

  FIG. 9 is a diagram showing an example of the film design of the first optical multilayer film 7 corresponding to FIG. 3 when the optical film thickness of the connecting layer 12 is about 5L.

Similar to FIG. 3, the intermediate layer 13 includes three basic blocks 11 of three layers (n = 2) between the adjustment layers 9 and 10 (m = 3), and the twelfth layer between the basic blocks 11 and In the twenty-second layer, a tie layer 12 composed of a low refractive index film (SiO ₂ ) 15 is interposed, and the optical film thickness of each tie layer 12 is approximately 5L.

  FIG. 10 is a diagram showing an example of the film design of the first optical multilayer film 7 corresponding to FIG. 3 when the optical film thickness of the connecting layer 12 is approximately 7L.

Similar to FIG. 3, the intermediate layer 13 includes three basic blocks 11 of three layers (n = 2) between the adjustment layers 9 and 10 (m = 3), and the twelfth layer between the basic blocks 11 and In the 22nd layer, a tie layer 12 composed of a low refractive index film (SiO ₂ ) 15 is interposed, and the optical film thickness of each tie layer 12 is approximately 7L.

  11 shows transmission characteristics corresponding to FIG. 4 when the optical film thickness of the tie layer 12 shown in FIGS. 3, 8, 9, and 10 is approximately 3L, approximately 1L, approximately 5L, and approximately 7L. FIG. In FIG. 11, approximately 1L is indicated by a short broken line, approximately 3L is indicated by a solid line, approximately 5L is indicated by a one-dot chain line, and approximately 7L is indicated by a long broken line. The transmission characteristic of approximately 3L indicated by the solid line is the same as that in FIG.

  In FIG. 11, the half-value on the short wavelength side of the transmission band (about 840 nm to about 890 nm) in the near-infrared light band for each of the optical film thicknesses of approximately 1 L, approximately 3 L, approximately 5 L, and approximately 7 L of the connecting layer 12. With reference to the wavelength, the bandwidths up to the half-value wavelength on the long wavelength side of the transmission band of the visible light band are indicated by BW1, BW2, BW3, and BW4, respectively.

  As shown in FIG. 11, as the optical film thickness of the tie layer 12 increases, the cutoff band between the long wavelength side of the transmission band in the visible light band and the short wavelength side of the transmission band in the near infrared light band is increased. It can be seen that the bandwidths BW1 to BW4 become smaller.

  For example, when the optical film thickness of the tie layer 12 is approximately 1 L, the bandwidth BW1 of the cutoff band is approximately 180 nm, and when the optical film thickness is approximately 7 L, the bandwidth BW4 of the cutoff band is approximately 150 nm.

  As described above, according to the present embodiment, the tie layer 12 in the first optical multilayer film 7 includes a thin film made of a low refractive index material having an optical film thickness of approximately 3 L or more. For example, by selecting any one of approximately 3L, approximately 5L, and approximately 7L, a cutoff band between the long wavelength side of the transmission band in the visible light band and the short wavelength side of the transmission band in the near infrared light band is selected. The bandwidth can be varied.

  The optical film thickness of the connecting layer 12 in the first optical multilayer film 7 may be 7 L or more, and the bandwidth of the cutoff band is variable with reference to the short wavelength side of the transmission band in the near infrared light band. However, the bandwidth of the cutoff band may be varied with reference to the longer wavelength side of the transmission band in the visible light band.

  In the first optical multilayer film 7 of the above embodiment, as shown in the transmission characteristic diagram of FIG. 4 above, ripples are generated in the transmission band (about 400 nm to about 690 nm) in the visible light band, and this ripple is reduced. It is preferable to do.

  Next, the first optical multilayer film 7 that reduces this ripple will be described.

As described above, when H is 1/4 optical film thickness of the high refractive index material and L is 1/4 optical film thickness of the low refractive index material, the first optical multilayer film 7 that reduces ripple is The basic block 11 is made of the low refractive index material, and has a basic structure including a plurality of the tie layers 12 with the tie layer 12 in between.
The tie layer 12 includes three layers of a thin film made of the low refractive index material, a thin film made of the high refractive index material, and a thin film made of the low refractive index material,
The optical thickness of the three layers is
(1.4 ± 0.5) L (0.1 + 0.2 / −0.09) H (1.4 ± 0.5) L
It is.

  In the above film configuration, “± 0.5” is the same tolerance as described above, and this tolerance “± 0.5” is preferably “± 0.3”, more preferably “± 0.2”. It is.

  “+ 0.2 / −0.09” is also a tolerance, and (0.1 + 0.2 / −0.09) H is an allowable optical film thickness range of 0.3 (= 0.1 + 0.2) H to 0. 0.001 (= 0.1-0.09) H. The tolerance “+ 0.2 / −0.09” is preferably “+ 0.1 / −0.05”, and more preferably “+ 0.05 / −0.03”.

  The above film structure is shown below with the tolerance omitted.

The film configuration of the three layers of the connecting layer 12 of the first optical multilayer film 7 is as follows:
1.4L 0.1H 1.4L
It is.

  That is, the basic block 11 and the intermediate layer 13 have the same configuration except that the configuration of the first optical multilayer film 7 and the connecting layer 12 in the above embodiment is different.

  FIG. 12 is a diagram illustrating an example of the film design of the first optical multilayer film 7 that reduces this ripple, and corresponds to FIG. 3 described above.

As shown in FIG. 12, the first optical multilayer film 7 includes a first high refractive index film (TiO ₂ ) 14 and a second low refractive index film (SiO ₂ ) 15 on the quartz substrate 6 side. And the second adjustment layer 10 made of the 36th low refractive index film (SiO ₂ ) 15 is provided on the outer surface side.

  Between both adjustment layers 9 and 10, the intermediate layer 13 includes three basic blocks 11 of three layers (n = 2) (m = 3), the 12th to 14th layers between the basic blocks 11, and In the 24th to 26th layers, the three connecting layers 12 are interposed.

Each tie layer 12 includes three layers of a low refractive index film (SiO ₂ ) 15, a high refractive index film (TiO ₂ ) 14, and a low refractive index film (SiO ₂ ) 15. 4L 0.1H 1.4L.

  FIG. 13 is a diagram showing the transmission characteristics of the optical multilayer film 7 of FIG.

  The first optical multilayer film 7 of this embodiment has a transmission band (about 400 nm to about 690 nm) in the visible light band and a transmission band in the near-infrared light band, like the optical multilayer film 7 of the above embodiment. (About 840 nm to about 890 nm).

  Furthermore, it can be seen that the ripple in the transmission band (about 400 nm to about 690 nm) in the visible light band is greatly reduced compared to the transmission characteristics of FIG.

  In this way, the linking layer 12 has a specific optical film thickness including three layers of a thin film made of a low refractive index material, a thin film made of a high refractive index material, and a thin film made of a low refractive index material. Ripple in the transmission band in the optical band can be greatly suppressed.

  Next, the number of repetitions (n−1) in A, which is the intermediate layer 13 of the basic block 11 of the first optical multilayer film 7, will be described.

  Here, the optical film thickness of the connecting layer 12 in the first optical multilayer film 7 is assumed to be approximately 3 L, and each case where n = 1, 2, 3 will be described.

  The film design in the case where the optical film thickness of the connecting layer 12 in the first optical multilayer film 7 is approximately 3L and n = 2 is shown in FIG.

  FIG. 14 is a diagram illustrating an example of a film design corresponding to FIG. 3 when the optical film thickness of the connecting layer 12 in the first optical multilayer film 7 is approximately 3 L and n = 1.

When n = 1, the above-mentioned A which is the intermediate layer 13 is shown by abbreviating the tolerance.
A = 2.0L (1.0H 2.0L) ⁰
= 2.0L
Thus, the intermediate layer 13 is a single layer.

  As shown in FIG. 14, each intermediate layer 13 of each basic block 11 is a sixth layer, a fourteenth layer, and a twenty-second layer. In this case, the first optical multilayer film 7 is composed of three basic blocks 11 (m = 3) including the first and second adjustment layers 9 and 10, the connecting layer 12, and the seven layers. The number of layers is 26.

  FIG. 15 is a diagram illustrating an example of a film design corresponding to FIG. 3 when the optical film thickness of the connecting layer 12 in the first optical multilayer film 7 is approximately 3 L and n = 3.

When n = 3, the above-mentioned A which is the intermediate layer 13 is shown by abbreviating the tolerance.
A = 2.0L (1.0H 2.0L) ²
= 2.0L 1.0H 2.0L 1.0H 2.0L
Thus, the intermediate layer 13 has five layers.

  As shown in FIG. 15, each intermediate layer 13 of each basic block 11 is the sixth layer to the tenth layer, the 18th layer to the 22nd layer, and the 30th layer to the 34th layer. In this case, the first optical multilayer film 7 is composed of three basic blocks 11 (m = 3) including the first and second adjustment layers 9 and 10, the connecting layer 12, and the eleventh layer. The number of layers is 38.

  FIG. 16 is a diagram showing the transmission characteristics corresponding to FIG. 4 in each of the cases of n = 2, n = 1, and n = 3 in FIGS. 3, 14, and 15, and the number m of basic blocks 11 is In either case, m = 3. In FIG. 16, the case where n = 1 is indicated by a broken line, the case where n = 2 is indicated by a solid line, and the case where n = 3 is indicated by a one-dot chain line.

  As shown in FIG. 16, the half-value width of the transmission band (about 800 n, m to about 900 nm) in the near-infrared light band is about 50 nm when n = 1 indicated by a broken line, When n = 3 indicated by a chain line, the thickness is about 25 nm.

  Thus, it can be seen that the bandwidth of the transmission band in the near-infrared light band becomes narrower as the value of n increases.

  Next, as a reference example, the number of repetitions (n−1) when the optical film thickness of the tie layer 12 in the first optical multilayer film 7 is approximately 1 L will be described.

  FIG. 8 shows the film design when the optical film thickness of the connecting layer 12 in the first optical multilayer film 7 is approximately 1 L and n = 2.

  FIG. 17 is a diagram illustrating an example of a film design corresponding to FIG. 8 when the optical film thickness of the connecting layer 12 in the first optical multilayer film 7 is approximately 1 L and n = 1. These are figures which show an example of the film | membrane design corresponding to FIG. 8 when the optical film thickness of the connection layer 12 in the 1st optical multilayer film 7 is about 1L, and n = 3.

  FIGS. 17 and 18 respectively correspond to FIGS. 14 and 15 in the case where the optical film thickness of the connecting layer 12 in the first optical multilayer film 7 is approximately 3L.

  FIG. 19 is a diagram showing the transmission characteristics corresponding to FIG. 4 in the case of n = 2, n = 1, and n = 3 in FIGS. 8, 17, and 18, and the number m of basic blocks 11 is In either case, m = 3. In FIG. 19, similarly to FIG. 16, the case where n = 1 is indicated by a broken line, the case where n = 2 is indicated by a solid line, and the case where n = 3 is indicated by a one-dot chain line.

  As can be seen from FIG. 19, the bandwidth of the transmission band (about 800 n, m to about 900 nm) in the near-infrared light band becomes narrower as the value of n increases.

  16 and 19 show the case where the optical film thickness of the tie layer 12 is approximately 3L and approximately 1L. However, the same applies to the case where the optical film thickness of the tie layer 12 is composed of the above three layers. The bandwidth of the transmission band in the near-infrared light band tended to become narrower as the value of n increased.

  Thus, by increasing the number of repetitions (n−1) of A, which is the intermediate layer 13 of the basic block 11, the bandwidth of the transmission band of the near infrared light band can be designed to be narrow.

  Therefore, the bandwidth of the transmission band of the near-infrared light band can be adjusted by selecting the number of repetitions (n-1) of A that is the intermediate layer 13 according to the required specifications.

  Next, the number m of basic blocks 11 included in the first optical multilayer film 7 (m is an integer of 2 or more) will be described. Here, the optical film thickness of the connecting layer 12 is approximately 3 L, and the case where m = 1 is also described.

  FIG. 3 shows the case where the optical film thickness of the connecting layer 12 in the first optical multilayer film 7 is approximately 3 L and m = 3.

  FIG. 20 is a diagram illustrating an example of a film design corresponding to FIG. 3 when m = 1.

  As shown in FIG. 20, the number of basic blocks 11 included in the first optical multilayer film 7 is one (m = 1). Therefore, the connecting layer 12 that connects the basic blocks 11 is not provided. In this case, the first optical multilayer film 7 is composed of the first and second adjustment layers 9 and 10 and one basic block 11 including nine layers, and the total number of layers is 12.

  FIG. 21 is a diagram illustrating an example of a film design corresponding to FIG. 3 when the optical film thickness of the tie layer 12 is approximately 3 L and m = 5.

  As shown in FIG. 21, the first optical multilayer film 7 includes five basic blocks 11 (m = 5), and the 12th, 22nd, and 32nd layers are provided between the basic blocks 11. The tie layers 12 are interposed in the 42nd layer. In this case, the first optical multilayer film 7 includes the first and second adjustment layers 9 and 10, the connecting layer 12, and five basic blocks 11 including nine layers, and the total number of layers is 52. Become a layer.

  Note that n in the number of repetitions (n-1) of A, which is the intermediate layer 13 in the first optical multilayer film 7 of FIGS. 3, 20, and 21, is all n = 2.

  FIG. 22 is a graph showing the transmission characteristics corresponding to FIG. 4 in the cases of m = 3, m = 1, and m = 5 in FIGS. In FIG. 22, the case where m = 1 is indicated by a broken line, the case where m = 3 is indicated by a solid line, and the case where m = 5 is indicated by a one-dot chain line.

  As shown in FIG. 22, as the number m of the basic blocks 11 included in the first optical multilayer film 7 increases, the rising and falling transmission characteristics become steep.

  Next, as a reference example, the number m of basic blocks 11 when the optical film thickness of the connecting layer 12 in the first optical multilayer film 7 is set to approximately 1 L will be described.

  FIG. 8 shows the case where the optical film thickness of the connecting layer 12 in the first optical multilayer film 7 is about 1 L and m = 3.

  When m = 1, the number of basic blocks 11 is one, the connecting layer 12 that connects the basic blocks 11 is not provided, and the film design is as shown in FIG.

  FIG. 23 is a diagram illustrating an example of a film design corresponding to FIG. 8 when the optical film thickness of the tie layer 12 is approximately 1 L and m = 5.

  Note that n in the number of repetitions (n-1) of A, which is the intermediate layer 13 in the first optical multilayer film 7 of FIGS. 8, 20, and 23, is all n = 2.

  FIG. 24 is a diagram illustrating the transmission characteristics corresponding to FIG. 4 in the cases of m = 3, m = 1, and m = 5 in FIGS. 8, 20, and 23. In FIG. 24, similarly to FIG. 22, the case where m = 1 is indicated by a broken line, the case where m = 3 is indicated by a solid line, and the case where m = 5 is indicated by a one-dot chain line.

  As shown in FIG. 24, as the number m of the basic blocks 11 included in the first optical multilayer film 7 increases, the rising and falling transmission characteristics become steep.

  22 and 24 show the case where the optical film thickness of the connecting layer 12 is approximately 3L and approximately 1L. However, the same applies to the case where the optical film thickness of the connecting layer 12 is composed of the above three layers. As the number m of the basic blocks 11 included in the first optical multilayer film 7 increases, the rising and falling transmission characteristics tend to be steep.

  In the present invention, the high refractive index film 14 and the low refractive index film 15 in the first optical multilayer film 7 of the optical filter 3 may be interchanged.

That is, in the present invention, when H is ¼ optical film thickness of the high refractive index material and L is ¼ optical film thickness of the low refractive index material as described above, the first optical multilayer film 7a is The basic block 11a has a basic structure including a plurality of tie layers 12a made of the high refractive index material, and the tie layer 12a is made of the high refractive index material having an optical film thickness of about 3H or more. Including a thin film,
The basic block is
{(1.0 ± 0.5) L (1.0 ± 0.5) H (1.0 ± 0.5) L} A {(1.0 ± 0.5) L (1.0 ± 0 .5) H (1.0 ± 0.5) L}
It is.

However, A is the intermediate layer 13a included in the basic block 11a, and when n is an integer of 1 or more,
A = (2.0 ± 1.0) H {(1.0 ± 0.5) L (2.0 ± 1.0) H} ⁽ⁿ⁻¹⁾
It is.

  When the tolerances “± 0.5” and “± 1.0” in the film configuration are abbreviated, they are as follows.

The film configuration of the basic block 11a of the first optical multilayer film 7a is
(1.0L 1.0H 1.0L) A (1.0L 1.0H 1.0L)
And
The film configuration of A, which is the intermediate layer 13a, is
A = 2.0H (1.0L 2.0H) ^(n-1)
It is.

  The first optical multilayer film 7a includes m (m is an integer of 2 or more) of basic blocks 11a having the above-described film configuration between the first and second adjustment layers 9a and 10a at both ends, and between the basic blocks 11a. The basic structure is such that a tie layer 12a made of a high refractive index material and having an optical film thickness of about 3H or more is interposed.

  FIG. 25 is a diagram showing an example of the film design of the first optical multilayer film 7a obtained by simulation with the design wavelength (reference wavelength) λ set to 886 nm, and corresponds to FIG.

The first optical multilayer film 7a includes a first adjustment layer 9a made of a first high-refractive index film (TiO ₂ ) 14 on the quartz substrate 6 side, and a 31st-layer high film on the outer surface side. A second adjustment layer 10a including a refractive index film (TiO ₂ ) 14 and a 32nd low refractive index film (SiO ₂ ) 15 is provided.

Between the adjustment layers 9a and 10a, three basic blocks 11a are included, and a connecting layer 12a made of a high refractive index film (TiO ₂ ) 14 is interposed between the 11th and 21st layers between the basic blocks 11a. . The optical film thickness of each tie layer 12a is approximately 3H.

Each basic block 11a includes three layers of a low refractive index film (SiO ₂ ) 15, a high refractive index film (TiO ₂ ) 14 and a low refractive index film (SiO ₂ ) 15 on the side close to the quartz substrate 6, and an outer surface. close side, the low refractive index film in between (SiO ₂₎ 15, a high refractive index film (TiO ₂₎ 14 and the low refractive index film (SiO ₂₎ 15 3 layers, high refractive index film (TiO ₂₎ 14, an intermediate layer 13 a including three layers of a low refractive index film (SiO ₂ ) 15 and a high refractive index film (TiO ₂ ) 14 is provided.

  FIG. 26 is a diagram showing the transmission characteristics of the first optical multilayer film 7a, and corresponds to FIG.

  The first optical multilayer film 7a of this embodiment has a visible light band (about 410 nm to about 690 nm in this embodiment) and a transmission band (about 840 nm to about 890 nm) in the near infrared light band. ing. The transmittance of the transmission band in the near infrared light band is 90% or more, and the half width of the transmission band is about 50 nm. Further, in the band of about 750 nm to about 790 nm between the two transmission bands, two peaks in which the transmittance sharply changes greatly are generated. In addition, there is a peak in which the transmittance sharply fluctuates around about 990 nm in the near infrared band.

  As described above, the first optical multilayer film 7a in which the high refractive index film 14 and the low refractive index film 15 of the above embodiment are replaced has a visible light band as in the first optical multilayer film 7 of the above embodiment. Has a transmission band (about 410 nm to about 690 nm) and a transmission band (about 840 nm to about 890 nm) in the near infrared light band.

Therefore, unlike the conventional example, it is not necessary to combine two filters to form a transmission band in a part of the near-infrared light band, and only in the visible light band and near-infrared by the first optical multilayer film 7a. Filter characteristics each having a transmission band in the optical band can be realized. Although illustration is omitted, in the first optical multilayer film 7a as well, the optical characteristics of the tie layer 12a made of a high refractive index material are the same as in the above embodiment. By selecting the film thickness from approximately 3H, approximately 5H, and approximately 7H, the band of the cutoff band between the long wavelength side of the transmission band in the visible light band and the short wavelength side of the transmission band in the near infrared light band. The width can be varied. The “substantially” of the above approximately 3H, approximately 5H, and approximately 7H is the same as in the above embodiment.

Further, the connecting layer 12a in the first optical multilayer film 7a includes three layers of a thin film made of a high refractive index material, a thin film made of a low refractive index material, and a thin film made of a high refractive index material,
The optical thickness of the three layers is
(1.4 ± 0.5) H (0.1 + 0.2 / −0.09) L (1.4 ± 0.5) H
It is good.

  As a result, as in the above embodiment, ripples in the transmission band (about 400 nm to about 690 nm) in the visible light band can be greatly reduced.

  In the first optical multilayer film 7a in which the high refractive index film 14 and the low refractive index film 15 in the first optical multilayer film 7 are interchanged, the number of repetitions of A that is the intermediate layer 13a of the basic block 11a. When the number n of the basic blocks 11a included in the first optical multilayer film 7a or the number m of the basic blocks 11a is changed, the same tendency as in the above embodiment is shown.

  In the above embodiment, the quartz substrate 6 is used. However, instead of the quartz substrate 6, a transparent glass substrate or a resin substrate may be used. Further, the substrate is not limited to a colorless and transparent substrate, and may be a colored and transparent substrate as long as light can be transmitted.

In the above embodiment, TiO ₂ is used as the high refractive index material, but ZrO ₂ , Ta ₂ O ₅ , Nb ₂ O ₅ or the like may be used instead of TiO ₂ , and SiO ₂ as the low refractive index material. instead of _2, it may be used MgF 2, AlF ₃ and the like.

DESCRIPTION OF SYMBOLS 1 Imaging device 2 Lens 3, 3a Optical filter 4 Imaging element 6 Crystal substrate 7, 7a 1st optical multilayer film 8 2nd optical multilayer film 9, 9a 1st adjustment layer 10, 10a 2nd adjustment layer 11, 11a basic block 12, 12a connecting layer 13, 13a intermediate layer 14 high refractive index film 15 low refractive index film

Claims (12)

An optical filter having a transmission band in each of a visible light band and a part of a near infrared light band,
A substrate and an optical multilayer film formed on the substrate;
The optical multilayer film is formed by laminating a thin film made of a high refractive index material and a thin film made of a low refractive index material having a refractive index lower than that of the high refractive index material,
When H is 1/4 optical film thickness of the high refractive index material and L is 1/4 optical film thickness of the low refractive index material, the optical multilayer film has the following basic blocks as the low refractive index. It has a basic structure that includes a plurality of sandwiched layers of materials,
The tie layer includes a thin film made of the low refractive index material having an optical film thickness of about 3 L or more,
The basic block is
{(1.0 ± 0.5) H (1.0 ± 0.5) L (1.0 ± 0.5) H} A {(1.0 ± 0.5) H (1.0 ± 0 .5) L (1.0 ± 0.5) H},
However, A is an intermediate layer included in the basic block, and when n is an integer of 1 or more,
A = (2.0 ± 1.0) L {(1.0 ± 0.5) H (2.0 ± 1.0) L} ⁽ⁿ⁻¹⁾
Is,
An optical filter characterized by the above. An optical filter having a transmission band in each of a visible light band and a part of a near infrared light band,
A substrate and an optical multilayer film formed on the substrate;
The optical multilayer film is formed by laminating a thin film made of a high refractive index material and a thin film made of a low refractive index material having a refractive index lower than that of the high refractive index material,
When H is ¼ optical film thickness of the high refractive index material and L is ¼ optical film thickness of the low refractive index material, the optical multilayer film has the following basic blocks, It has a basic structure that includes a plurality of sandwiched layers of materials,
The tie layer includes a thin film made of the high refractive index material having an optical film thickness of about 3H or more,
The basic block is
{(1.0 ± 0.5) L (1.0 ± 0.5) H (1.0 ± 0.5) L} A {(1.0 ± 0.5) L (1.0 ± 0 .5) H (1.0 ± 0.5) L}
Is,
However, A is an intermediate layer included in the basic block, and when n is an integer of 1 or more,
A = (2.0 ± 1.0) H {(1.0 ± 0.5) L (2.0 ± 1.0) H} ⁽ⁿ⁻¹⁾
Is,
An optical filter characterized by the above. The optical film thickness of the thin film made of the low refractive index material of the tie layer is approximately 3L, approximately 5L, or approximately 7L.
The optical filter according to claim 1. The optical film thickness of the thin film made of the high refractive index material of the tie layer is approximately 3H, approximately 5H, or approximately 7H.
The optical filter according to claim 2. An optical filter having a transmission band in each of a visible light band and a part of a near infrared light band,
A substrate and an optical multilayer film formed on the substrate;
The optical multilayer film is formed by laminating a thin film made of a high refractive index material and a thin film made of a low refractive index material having a refractive index lower than that of the high refractive index material,
When H is 1/4 optical film thickness of the high-refractive index material and L is 1/4 optical film thickness of the low-refractive index material, the optical multilayer film has the following basic blocks sandwiching a connecting layer Have a basic structure that includes multiple
The tie layer includes three layers of a thin film made of the low refractive index material, a thin film made of the high refractive index material, and a thin film made of the low refractive index material,
The optical thickness of the three layers is
(1.4 ± 0.5) L (0.1 + 0.2 / −0.09) H (1.4 ± 0.5) L
And
The basic block is
{(1.0 ± 0.5) H (1.0 ± 0.5) L (1.0 ± 0.5) H} A {(1.0 ± 0.5) H (1.0 ± 0 .5) L (1.0 ± 0.5) H},
However, A is an intermediate layer included in the basic block, and when n is an integer of 1 or more,
A = (2.0 ± 1.0) L {(1.0 ± 0.5) H (2.0 ± 1.0) L} ⁽ⁿ⁻¹⁾
Is,
An optical filter characterized by the above. An optical filter having a transmission band in each of a visible light band and a part of a near infrared light band,
A substrate and an optical multilayer film formed on the substrate;
The optical multilayer film is formed by laminating a thin film made of a high refractive index material and a thin film made of a low refractive index material having a refractive index lower than that of the high refractive index material,
When H is 1/4 optical film thickness of the high-refractive index material and L is 1/4 optical film thickness of the low-refractive index material, the optical multilayer film has the following basic blocks sandwiching a connecting layer Have a basic structure that includes multiple
The tie layer includes three layers of a thin film made of the high refractive index material, a thin film made of the low refractive index material, and a thin film made of the high refractive index material,
The optical thickness of the three layers is
(1.4 ± 0.5) H (0.1 + 0.2 / −0.09) L (1.4 ± 0.5) H
And
The basic block is
{(1.0 ± 0.5) L (1.0 ± 0.5) H (1.0 ± 0.5) L} A {(1.0 ± 0.5) L (1.0 ± 0 .5) H (1.0 ± 0.5) L}
Is,
However, A is an intermediate layer included in the basic block, and when n is an integer of 1 or more,
A = (2.0 ± 1.0) H {(1.0 ± 0.5) L (2.0 ± 1.0) H} ⁽ⁿ⁻¹⁾
Is,
An optical filter characterized by the above. A filter having a cutoff characteristic between a long wavelength side of the transmission band of the visible light band and a short wavelength side of the transmission band of the near infrared light band, wherein the optical multilayer film is a first optical multilayer film; Comprising a second optical multilayer film to constitute,
The optical filter according to claim 1. The optical multilayer film includes an adjustment layer on the substrate side,
The adjustment layer includes a thin film made of the high refractive index material,
The optical filter according to claim 1, 3 or 5. The optical multilayer film includes an adjustment layer on the substrate side and the outer surface side,
The adjustment layer on the outer surface side includes a thin film made of the low refractive index material,
The optical filter according to claim 2, 4 or 6. The first optical multilayer film is formed on one surface of the substrate, and the second optical multilayer film is formed on the other surface of the substrate.
The optical filter according to claim 7. The substrate is a transparent substrate made of at least one of quartz, glass, and resin,
The optical filter according to claim 1. The optical filter according to claim 1 is provided.
An imaging device characterized by that.

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