JP6467895B2 - Optical filter - Google Patents

Description

  The invention of the embodiments relates to an optical filter.

  Solid-state imaging devices such as a CCD (Charge Coupled Device) image sensor and a CMOS (Complementary Metal Oxide Semiconductor) image sensor have higher sensitivity to infrared light than human visibility characteristics. For this reason, for example, in a digital camera or digital video, spectral correction is performed by using an optical filter such as a near infrared cut filter.

  On the other hand, in an imaging device such as a monitoring camera that continuously captures images day and night, imaging can be performed by incident light having a wavelength in the visible region during the daytime. However, since night vision is under night vision, it is necessary to capture light having a wavelength in the near-infrared region. For this reason, it is preferable to transmit light in both the visible region and the near infrared region. Therefore, it is required to perform spectral correction using an optical filter that transmits both visible and near-infrared light.

  In a conventional optical filter that transmits light in both the visible region and the near-infrared region, the angle of the light incident from the vertical direction (also referred to as normal incident light) is shifted from the vertical direction with respect to the plane of the optical filter. Insufficient consideration was given to the difference in optical characteristics with light incident from an oblique direction (also referred to as oblique incident light). In the optical filter, since the change in optical characteristics with respect to oblique incident light is larger than that with normal incident light, the amount of transmitted light having a wavelength in the near infrared region with respect to oblique incident light is significantly reduced. For this reason, when the optical filter is used in an image pickup apparatus, a problem such as deterioration in the image quality of the picked-up image tends to occur.

Japanese Patent No. 4795342 International Publication No. 2011/033984

  The problem to be solved by the invention of the embodiment is to maintain the transmitted light amount of light having a wavelength of at least the near infrared region in oblique incident light in an optical filter that transmits light in both the visible region and the near infrared region. That is.

  The optical filter according to the embodiment includes a light-transmitting substrate, a first light transmission band stacked on the substrate and provided in the visible region, and a second light transmission band provided in the near-infrared region, An optical layer having optical characteristics indicated by an optical spectrum having light transmission blocking bands provided on a shorter wavelength side and a longer wavelength side than the visible region and on a shorter wavelength side and a longer wavelength side than the near infrared region, and It has. The variation rate of the amount of transmitted light of the second light transmission band due to the difference in incident angle from 0 degree to 40 degrees with respect to the direction perpendicular to the plane of the optical layer is 7% or less.

It is a figure which shows the structural example of an optical filter. It is a figure which shows the structural example of an imaging device. 6 is a diagram for explaining a laminated structure of the optical filter of Example 1. FIG. 6 is a diagram for explaining a laminated structure of an optical filter of Example 2. FIG. 6 is a diagram for explaining a laminated structure of an optical filter of Example 3. FIG. 6 is a diagram for explaining a laminated structure of an optical filter of Comparative Example 1. FIG. 2 is a diagram showing an optical spectrum of Example 1. FIG. It is a figure which shows the optical spectrum of Example 1a. 6 is a diagram showing an optical spectrum of Example 2. FIG. 6 is a diagram showing an optical spectrum of Example 3. FIG. 6 is a diagram showing an optical spectrum of Comparative Example 1. FIG.

  Hereinafter, embodiments will be described with reference to the drawings. The drawings are schematic, and for example, the relationship between the thickness and the planar dimensions, the ratio of the thickness of each layer, and the like may be different from the actual ones. In the embodiments, substantially the same constituent elements are denoted by the same reference numerals and description thereof is omitted.

(First embodiment)
FIG. 1 is a structural example of an optical filter. An optical filter 10 shown in FIG. 1 includes a light-transmitting substrate 1 and an optical layer 2 stacked on the substrate 1. The structure of the optical layer 2 is not limited to the structure shown in FIG.

  The substrate 1 has a function as a support substrate, for example. The substrate 1 has a function of transmitting at least light having a wavelength in the visible region and light having a wavelength in the near infrared region. The visible region is preferably a region including a wavelength of 400 nm or more and less than 700 nm, for example, and the near infrared region is preferably a region including a wavelength of 700 nm or more and 1050 nm or less, for example.

  As the substrate 1, for example, at least one of a glass substrate, a plastic substrate, and a resin film substrate can be used. It is preferable that the substrate 1 does not substantially contain a light absorber such as CuO.

  The optical layer 2 has a function of transmitting light having a wavelength in the visible region and light having a wavelength in the near infrared region. The optical layer 2 includes a first light transmission band provided in the visible region, a second light transmission band provided in the near infrared region, a shorter wavelength side and a longer wavelength side than the visible region, and a near infrared region. The optical characteristic shown by the optical spectrum which has the light transmission stop band provided in the short wavelength side and long wavelength side rather than the area | region is provided. The optical spectrum is a spectrum that is measured using, for example, a spectroscopic measurement device and is represented by the relationship between the wavelength of light and the transmittance.

  The first light transmission band and the second light transmission band have a light transmittance of, for example, 70% or more, further 75% or more, and further 80% or more with respect to incident light having a corresponding wavelength. Is preferred. The light transmission blocking band preferably has a light transmittance of, for example, less than 10% with respect to incident light having a corresponding wavelength.

  In the optical filter of this embodiment, by improving the incident angle dependency, even if the incident angle of light is different in the light transmission band that transmits light having a wavelength in the near infrared region, transmission in the target wavelength range is possible. The amount of light can be maintained. As a result, the amount of received light does not change significantly due to the difference in incident angle, and a captured image in which deterioration in image quality is suppressed can be obtained.

  In recent years, with the miniaturization and thinning of digital cameras and digital videos, the wide angle of digital cameras and digital videos has been increasing. Thereby, the incident angle dependence of the wavelength region cut by the optical layer is a problem. For example, in the optical spectrum, when the rising position from the light transmission blocking band to the light transmission band is shifted (shifted) by the incident angle of light, the amount of light in a band (light transmission band) that affects image quality changes. The optical spectrum shifts to the short wavelength side with a change from normal incidence light to oblique incidence light.

  In a conventional optical filter that transmits both light having a wavelength in the visible region and light having a wavelength in the near infrared region, when the incident light changes from normal incident light to oblique incident light, particularly in the near infrared region. Since the wavelength shift of the light transmission band that transmits light having a specific wavelength and the deformation of the transmission band spectral waveform are large, the amount of light transmission in the specific wavelength range to be captured tends to decrease significantly. In addition, in order to eliminate this phenomenon, simply increasing the width of the light transmission band in the near infrared region reduces the width of the light transmission stop band in the near infrared region and the infrared region that are originally required. End up. In the optical spectrum of the optical layer 2, the shift amount of the light transmission band accompanying the change in the incident angle (change from the normal incident light to the oblique incident light) is the shift amount to the short wavelength side of the long wavelength band. Tends to be larger than the shift amount of the short band toward the short wavelength side. Therefore, when the shift amount of the light transmission band increases, the rising position from the light transmission blocking band on the longer wavelength side to the light transmission band is higher than the rising position from the light transmission blocking band on the shorter wavelength side to the light transmission band. Due to the large shift to the short wavelength side, the band width of the light transmission band tends to be narrowed.

  In the optical filter of this embodiment, when light 3 is incident as shown in FIG. 1, the second is caused by the difference in incident angle θ from 0 degrees to 40 degrees with respect to the direction perpendicular to the plane of the optical layer 2. The fluctuation rate of the amount of transmitted light in the light transmission band is controlled to 7% or less, preferably 6% or less. Thereby, it is possible to suppress the narrowing of the bandwidth of the light transmission band due to the difference in the incident angle, and it is possible to suppress the fluctuation in the amount of light taken in. Note that the variation rate of the amount of light transmitted through the light transmission band in the present invention is an integration of a transmittance of 10% or more for each wavelength of 1 nm in a band having a light transmittance of 10% or more in the second light transmission band. The value refers to the ratio of the integrated values for each incident angle.

  Further, in the second light transmission band, the shift amount of the wavelength indicating 80% light transmittance on the long wavelength side due to the difference in incident angle from 0 degree to 40 degrees is less than 60 nm and 0 degrees The width of the band having a light transmittance of 80% or more at the incident angle is preferably at least 1.2 times the shift amount. As a result, fluctuations in the light transmittance due to the difference in the incident angle can be suppressed, that is, the incident angle dependency can be improved, so that a decrease in the amount of light taken in can be suppressed. Even if the optical spectrum shifts due to the difference in the incident angle, the second light transmission band has a certain transmission band width, so that a desired amount of transmitted light can be secured. Moreover, it is preferable that the width of the band having a light transmittance of 80% or more at an incident angle of 0 degree is not more than twice the shift amount. If this shift amount is more than twice, the width of the light transmission blocking band existing on the short wavelength side and the long wavelength side of the second light transmission band is excessively reduced, which may affect the color tone of the captured image. is there. In the second light transmission band, the long wavelength side indicates a longer wavelength side than the center wavelength of the second light transmission band, and the short wavelength side indicates a wavelength shorter than the center wavelength of the second light transmission band. Indicates side.

  Here, in order to satisfy the optical characteristics, the structure of the optical layer 2 is important. For example, the optical layer 2 preferably includes a stacked unit of a stack represented by the formula [ZLHL] ^ n (where H is a high refractive index having a first optical thickness and a refractive index of 2.0 or more. Z is a symbol representing a refractive index layer, Z is a symbol representing a high refractive index layer having a second optical thickness that is twice or more the first optical thickness and a refractive index of 2.0 or more, and L is 1 Is a symbol representing a low refractive index layer having a refractive index of 0.7 or less, n is a natural number representing the number of stacks in the optical layer 2, and the order of description of H, Z, and L is the stacking order from the substrate 1 side Represents.)

  The low refractive index layer (L) in the above formula preferably has an optical thickness smaller than the optical thickness of the high refractive index layer (Z). Further, the fourth low refractive index layer (L) in the above formula may have an optical thickness different from the optical thickness of the second low refractive index layer (L). Therefore, in order to form a plurality of light transmission blocking bands, different values are more preferable.

  The optical thickness is represented by, for example, a quarter-wave optical thickness (QWOT). QWOT is an optical thickness represented by a magnification with respect to 1/4 of the wavelength of light having a specific wavelength (for example, light having a wavelength of 500 nm). At this time, you may adjust QWOT in the light which has a wavelength of 500 nm of a high refractive index layer (Z), for example to 1.30 or more and 5.00 or less. Moreover, you may adjust QWOT in the light which has a wavelength of 500 nm of a high refractive index layer (H), for example to 0.20 or more and 1.25 or less. Furthermore, QWOT in the light having a wavelength of 500 nm of the low refractive index layer (L) may be adjusted to, for example, 0.10 or more and 1.15 or less. In each layer constituting the optical layer 2, QWOT can be adjusted by adjusting the physical film thickness and the refractive index, for example.

The optical layer 2 includes, for example, a high refractive index layer (Z) 21, a low refractive index layer (L) 22 laminated on the high refractive index layer 21, and a low refractive index layer 22 as shown in FIG. the high refractive index layer (H) 23 stacked in contact with each other, as a stack having a 24 low-refractive index layer laminated on and in contact with the high refractive index layer 23 (L), the stack 20 ₁ to stack 20 _n Have. The number of units in the stack (value of n in the formula) is not particularly limited. For example, 7 units or more, 11 units or more, or 15 units or more may be stacked. In addition to the stack, at least one of another high refractive index layer and low refractive index layer may be provided.

  The stack preferably has an optical characteristic indicated by an optical spectrum having a light transmission band in both the visible region and the near infrared region. Thereby, for example, in the optical layer, compared with an optical layer in which a first optical layer having a light transmission band only in the visible region and a second optical layer having a light transmission band only in the near infrared region are laminated. A decrease in light transmittance in the light transmission band can be suppressed.

The high refractive index layers such as the high refractive index layer 21 and the high refractive index layer 23 preferably have a refractive index of 2.0 or more for light having a wavelength of 500 nm, for example. As the high refractive index layer, for example, a film containing titanium oxide (TiO ₂ ), tantalum oxide (Ta ₂ O ₅ ), niobium oxide (Nb ₂ O ₅ ), or a composite oxide thereof can be used. Moreover, if a refractive index is 2.0 or more, you may contain the additive. A higher refractive index is advantageous for suppressing the amount of wavelength shift at oblique incidence, expanding the light transmission blocking band on the ultraviolet side, and the like. For this reason, among the above three substances, titanium oxide and niobium oxide having higher refractive index are more suitable as the high refractive index layer.

The low refractive index layers such as the low refractive index layer 22 and the low refractive index layer 24 preferably have a refractive index of 1.7 or less with respect to light having a wavelength of 500 nm, for example. As the low refractive index layer, for example, a film containing silicon oxide (SiO ₂ ), magnesium fluoride (MgF ₂ ), or a composite oxide thereof can be used. Moreover, if a refractive index is 1.7 or less, you may contain the additive.

  The refractive index layers such as the high refractive index layer and the low refractive index layer are formed by using, for example, a sputtering method, a vacuum deposition method, an ion-assisted vacuum deposition method, or a CVD method. In particular, it is preferable to form the refractive index layer using a sputtering method, a vacuum deposition method, or an ion-assisted vacuum deposition method. The light transmission band is a wavelength band used for light reception by a solid-state imaging device such as a CCD image sensor or a CMOS image sensor, and the accuracy of the thickness of the optical layer is important. Sputtering, vacuum deposition, and ion-assisted vacuum deposition are excellent in controlling the thickness when forming the refractive index layer. For this reason, the precision of the thickness of each refractive index layer which comprises the optical layer 2 can be raised, As a result, a wavelength shift can be suppressed.

  The oblique incidence characteristic of the optical filter including the optical layer having one or more units of the stack is better than the oblique incidence characteristic of the optical filter not provided with the stack. Therefore, in the optical spectrum, light having a wavelength in the visible region while ensuring a wide width of a light transmission band that transmits light having a wavelength in the visible region and a width of a light transmission band that transmits light having a near-infrared region. Light transmission blocking bands can be formed at both ends of the light transmission band that transmits light and at both ends of the light transmission band that transmits light having a wavelength in the near infrared region. Further, the shift amount of the light transmission band depending on the incident angle can be reduced.

  As described above, the optical filter according to the present embodiment transmits both light having a wavelength in the visible region and light having a wavelength in the near-infrared region, and is 0 with respect to a direction perpendicular to the plane of the optical layer 2. The variation rate of the transmitted light amount of light having a wavelength in the near-infrared region due to the difference in incident angle θ from 40 degrees to 40 degrees is controlled to a low value, for example, 7% or less. Therefore, since the width of the light transmission band that transmits light having a wavelength in the near-infrared region is widened and fluctuations in the amount of light taken in can be suppressed, for example, even in imaging under night vision by an imaging device A captured image in which deterioration in image quality is suppressed can be obtained.

(Second Embodiment)
FIG. 2 is a diagram illustrating a structure example of the imaging apparatus. An imaging apparatus 100 illustrated in FIG. 2 is, for example, a digital still camera, a digital video camera, a surveillance camera, an in-vehicle camera, or a web camera, and includes a solid-state imaging device 110, a cover glass 120, a lens group 130, a diaphragm 140 And a housing 150. The solid-state image sensor 110, the cover glass 120, the lens group 130, and the stop 140 are disposed along the optical axis X.

  The solid-state image sensor 110 is, for example, a CCD image sensor or a CMOS image sensor. The solid-state imaging device 110 converts input light into an electrical signal and outputs the electrical signal to an image signal processing circuit (not shown).

  The cover glass 120 is disposed on the imaging surface side (the lens group 130 side) of the solid-state imaging device 110 and protects the solid-state imaging device 110 from the external environment.

  The lens group 130 is disposed on the imaging surface side of the solid-state imaging device 110. The lens group 130 includes a plurality of lenses L <b> 1 to L <b> 4 and guides incident light to the imaging surface of the solid-state imaging device 110.

  The diaphragm 140 is disposed between the lens L3 and the lens L4 of the lens group 130. The diaphragm 140 is configured so that the amount of light passing therethrough can be adjusted.

  The housing 150 accommodates the solid-state imaging device 110, the cover glass 120, the lens group 130, and the diaphragm 140.

  In the imaging apparatus 100, light incident from the subject side enters the solid-state imaging device 110 through the lens L 1, the lens L 2, the third lens L 3, the diaphragm 140, the lens L 4, and the cover glass 120. The incident light is converted into an electrical signal by the solid-state imaging device 110 and output as an image signal.

  The optical filter of the first embodiment is used for, for example, the cover glass 120 and the lens group 130, that is, the lens L1, the lens L2, the lens L3, or the lens L4. In other words, when the cover glass or lens group of the conventional imaging device is the substrate 1 in the optical filter of the first embodiment, the optical layer 2 in the optical filter of the first embodiment is provided on the surface of the substrate 1. .

  By applying the optical filter of the first embodiment as the imaging optical filter of the cover glass 120 or the lens group 130 of the imaging apparatus 100, the incident angle dependency can be improved, so that fluctuations in the amount of light taken in can be reduced. Can be suppressed. Therefore, it is possible to suppress deterioration of the image quality of the captured image particularly when imaging is performed by entering light having a wavelength in the near infrared region.

(Other embodiments)
The present invention is not limited to the above embodiment, and various modifications and changes can be made without departing from the scope of the present invention. The optical layer 2 may be provided only on one side of the substrate 1 or may be provided separately on both sides of the substrate 1. The optical filter of the first embodiment is used, for example, as a visibility correction filter in an imaging device such as a digital still camera, a digital video camera, a surveillance camera, an in-vehicle camera, or a web camera, or an automatic exposure meter. In an imaging apparatus such as a digital still camera, a digital video camera, a surveillance camera, an in-vehicle camera, or a web camera, for example, it is disposed between an imaging lens and a solid-state imaging device. In the automatic exposure meter, for example, it is arranged in front of the light receiving element.

  In the imaging apparatus, the optical filter of the first embodiment may be disposed at a position away from the front surface of the solid-state imaging device, or may be directly attached to the solid-state imaging device or the package of the solid-state imaging device. The cover that protects the solid-state image sensor may be the optical filter of the first embodiment. Alternatively, it may be directly attached to a low-pass filter using a crystal such as quartz or lithium niobate for suppressing moire or false color.

In this embodiment, an optical filter that transmits light having wavelengths in the visible region and the near infrared region will be described. The optical characteristics of the optical filters of Example 1, Example 1a, Example 2, Example 3, and Comparative Example 1 were evaluated using optical thin film simulation software manufactured by TFCalc and Software Spectra. Each of Example 1, Example 1a, Example 2, Example 3 and Comparative Example 1 is composed of a glass substrate, a high refractive index layer made of a TiO ₂ film, and a SiO ₂ film laminated on the glass substrate. An optical filter comprising an optical layer having a low refractive index layer.

  Details of the laminated structure of the optical layers of Example 1, Example 2, Example 3, and Comparative Example 1 will be described with reference to Tables 1 and 2 and FIGS. The layer numbers in Tables 1 and 2 and FIGS. 3 to 6 represent the stacking order of the layers on the glass substrate. Moreover, d in Table 1 and Table 2 represents the physical thickness of each layer. Further, in FIGS. 3 to 6, a portion surrounded by a dotted line represents a stack represented by the above formula [ZLHL] ^ n.

  QWOT in Tables 1 and 2 and FIGS. 3 to 6 is QWOT in light having a wavelength of 500 nm. The refractive index (n) in Tables 1 and 2 is a value calculated in consideration of wavelength dependency. The refractive index has a wavelength dependency called dispersion. For example, in the wavelength range of 300 to 1300 nm, the refractive index of a layer material or the like targeted by the present application tends to decrease as the wavelength decreases, and decrease as the wavelength increases. These wavelength-refractive index relationships are not linear, and are generally expressed using approximate equations such as Hartmann and Sellmeier. Further, the refractive index (dispersion) of the film substance varies depending on various film forming conditions. Therefore, the refractive index (n) was calculated using the dispersion data of the refractive index of each film formed by vapor deposition, ion-assisted vapor deposition, sputtering, or the like.

Example 1
As shown in Tables 1 and 2 and FIGS. 3 (A) to 3 (C), the optical filter of Example 1 has a laminated structure of a total of 50 layers including a stack represented by the formula [ZLHL] ^ 7. The optical layer which consists of comprises.

Example 1a
In addition to the configuration of the optical filter of Example 1, the optical filter of Example 1a includes a layer that cuts long-wavelength infrared light on the surface opposite to the surface on which the optical layer is formed on the glass substrate.

(Example 2)
As shown in Tables 1 and 2 and FIGS. 4 (A) to 4 (C), the optical filter according to Example 2 includes a total of 70 layers including a stack represented by the formula [ZLHL] ^ 15. An optical layer having a structure is provided.

(Example 3)
As shown in Tables 1 and 2 and FIGS. 5A to 5C, the optical filter according to Example 3 is a total of 58 layers including the stack represented by the formula [ZLHL] ^ 11. An optical layer having a structure is provided.

(Comparative Example 1)
As shown in Tables 1 and 2 and FIGS. 6A to 6C, the optical filter according to Example 1 has a total of 46 layers not including the stack represented by the above formula [ZLHL] ^ n. The optical layer which consists of these laminated structures is comprised.

  The optical characteristics of the optical filters of Example 1, Example 1a, Example 2, Example 3, and Comparative Example 1 will be described with reference to FIGS. 7 is a diagram showing an optical spectrum of the optical filter in Example 1, FIG. 8 is a diagram showing an optical spectrum of the optical filter in Example 1a, and FIG. 9 is an optical diagram of the optical filter in Example 2. FIG. 10 is a diagram showing an optical spectrum of the optical filter in Example 3, and FIG. 11 is a diagram showing an optical spectrum of the optical filter in Comparative Example 1. 7 to 11, when light having different incident angles of 0 degrees, 10 degrees, 20 degrees, 30 degrees, 35 degrees, and 40 degrees with respect to the direction perpendicular to the plane direction of the optical layer is incident. The optical spectrum is shown.

  As can be seen from FIGS. 7 to 11, the optical spectra of the optical filters of Example 1, Example 1a, Example 2, Example 3, and Comparative Example 1 are in the visible region (a region including a wavelength of 400 nm or more and less than 700 nm). 1 has a first light transmission band, and has a second light transmission band in the near-infrared region (a region including a wavelength of 700 nm to 1050 nm). Further, it can be seen that there are light transmission blocking bands on the shorter wavelength side and the longer wavelength side than the first light transmission band, and on the shorter wavelength side and the longer wavelength side than the second light transmission band. Further, it can be seen that the optical spectrum of the optical filter of Example 1a is blocked from transmitting light having a wavelength of 1050 nm or more as compared with the optical spectrum of the optical filter of Example 1.

  Further, in the optical spectra of the optical filters of Example 1, Example 1a, Example 2, Example 3, and Comparative Example 1, the position of the light transmission band as the incident angle increases from 0 degrees to 40 degrees. It can be seen that is shifted to the short wavelength side. In particular, it can be seen that the shift amount increases as the wavelength increases.

  From the optical spectrum data, in Example 1, Example 1a, Example 2, Example 3, and Comparative Example 1, the difference in incident angle from 0 degree to 40 degrees with respect to the direction perpendicular to the plane of the optical layer The shift amount of the wavelength indicating the transmittance of 80% or more on the long wavelength side and 0 due to the difference in the incident angle in the second light transmission band and the variation rate of the transmitted light amount of the light in the second transmission band. And a width of a band having a light transmittance of 80% or more at an incident angle of 50 degrees. The results are shown in Table 3.

  The rate of change was determined as follows. First, an integrated value of transmittance of 10% or more for each wavelength of 1 nm in an incident angle of 0 degree and a wavelength range of 700 nm to 1050 nm was obtained. Next, an integrated value of a transmittance of 10% or more was obtained for each wavelength of 1 nm in an incident angle of 40 degrees and a wavelength range of 700 nm to 1050 nm. Furthermore, the variation rate was determined by determining the ratio of the integrated value in the case of an incident angle of 0 degrees to the integrated value in the case of an incident angle of 40 degrees.

  The shift amount was determined as follows. First, a wavelength indicating 80% light transmittance on the long wavelength side at an incident angle of 0 degree in the second light transmission band was obtained. Next, a wavelength indicating 80% light transmittance on the long wavelength side in the case of an incident angle of 40 degrees in the second light transmission band was obtained. Then, the difference between the wavelength indicating 80% light transmittance on the long wavelength side when the incident angle is 0 degree and the wavelength indicating 80% light transmittance on the long wavelength side when the incident angle is 40 degrees. The shift amount was determined by determining.

  The bandwidth was determined as follows. First, the wavelength which shows the transmittance | permeability of 80% of the light in the short wavelength side and long wavelength side in the case of the incident angle of 0 degree in the 2nd light transmission band was calculated | required. Then, the difference between the wavelength indicating 80% light transmittance on the long wavelength side at the incident angle of 0 degree and the wavelength indicating 80% light transmittance on the short wavelength side at the incident angle of 0 degree. The bandwidth of the above band was obtained by obtaining

  As shown in Table 3, in Example 1, Example 1a, Example 2, and Example 3, the variation rate is 7% or less, whereas in Comparative Example 1, it is 15% or more. there were. Moreover, in Example 1, Example 1a, Example 2, and Example 3, the shift amount was less than 60 nm, while in Comparative Example 1, it was 70 nm or more. Furthermore, in Example 1, Example 1a, Example 2, and Example 3, the width of the band is 1.2 times or more of the shift amount, whereas in Comparative Example 1, the shift amount is It was less than 1.2 times. This shows that the oblique incidence characteristics are improved in the optical filters shown in Example 1, Example 1a, Example 2, and Example 3.

  The embodiment is presented as an example, and is not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Optical layer, 3 ... Light, 10 ... Optical filter, 20 ... Stack, 21 ... High refractive index layer, 22 ... Low refractive index layer, 23 ... High refractive index layer, 24 ... Low refractive index layer, DESCRIPTION OF SYMBOLS 100 ... Imaging device, 110 ... Solid-state image sensor, 120 ... Cover glass, 130 ... Lens group, 150 ... Housing | casing, L1-L4 ... Lens.

Claims (5)

A substrate having translucency;
A first light transmission band provided in the visible region, a second light transmission band provided in the near infrared region, a shorter wavelength side and a longer wavelength side than the visible region, An optical layer having an optical characteristic indicated by an optical spectrum having a light transmission stop band provided on a shorter wavelength side and a longer wavelength side than the near infrared region;
An optical filter comprising:
The optical layer has a multilayer film in which high refractive index layers and low refractive index layers are alternately laminated,
The high refractive index layer is a film having a refractive index of 2.0 or more with respect to light having a wavelength of 500 nm,
The low refractive index layer is a film having a refractive index of 1.7 or less with respect to light having a wavelength of 500 nm,
An optical filter, wherein a variation rate of a transmitted light amount of light in the second light transmission band is 7% or less due to a difference in incident angle from 0 degree to 40 degrees with respect to a direction perpendicular to a plane of the optical layer. A substrate having translucency;
A first light transmission band provided in the visible region, a second light transmission band provided in the near infrared region, a shorter wavelength side and a longer wavelength side than the visible region, An optical layer having an optical characteristic indicated by an optical spectrum having a light transmission stop band provided on a shorter wavelength side and a longer wavelength side than the near infrared region;
An optical filter comprising:
Wherein due to the incidence angle differences of 0 degrees with respect to the direction perpendicular to the plane of the optical layer to 40 degrees, Ri said second der fluctuation of the transmission light amount is 7% or less of the light of the light transmission band,
The optical filter includes a stack represented by a formula [ZLHL] ^ n.
(Wherein, H is a symbol representing a first high refractive index layer having a first optical thickness and a refractive index of 2.0 or more, and Z is a second larger than twice the first optical thickness. Is a symbol representing a second high refractive index layer having an optical thickness of 2.0 and a refractive index of 2.0 or more, L is a symbol representing a low refractive index layer having a refractive index of 1.7 or less, and n is (It is a natural number representing the number of the stacks in the optical layer, and the order of description of H, Z, and L represents the stacking order from the substrate side.) In the second light transmission band,
Due to the difference in incident angle from 0 degree to 40 degrees, the wavelength shift amount indicating 80% light transmittance on the long wavelength side is less than 60 nm, and 80% or more of light at an incident angle of 0 degree is less than 60 nm. The optical filter according to claim 1 or 2 , wherein a width of a band having transmittance is 1.2 times or more of the shift amount. The substrate has at least one of a glass substrate, a plastic substrate, and a resin film substrate;
The high refractive index layer, or the first high refractive index layer and the second high refractive index layer include titanium oxide,
The optical filter according to claim 1 , wherein the low refractive index layer contains silicon oxide. The optical filter according to any one of claims 1 to 4, wherein the optical filter is an optical filter for an imaging apparatus.

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