JP2018189725A - Optical filter and image capturing device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical filter for thin solid-state holographic image capturing devices, which is less susceptible to ghost generation and provides good luminous sensitivity correction of silicon photodiodes, and to provide a thin solid-state holographic image capturing device having the same.SOLUTION: An optical filter 1 is introduced, comprising a substrate 10 with a plurality of shielded areas 21 formed on at least one surface of the substrate. An area outside the shielded areas has a transmittance property for vertically incident light, which is described as: (A) an average transmittance is 1% or less for light of a wavelength in a range of 300-400 nm, inclusive; (B) an average transmittance is 50% or greater for light of a wavelength in a range of 450-600 nm, inclusive; (C) an average transmittance is 5% or less for light of a wavelength of 700 nm or greater and less than 1000 nm; and (D) an average transmittance is 10% or less for light of a wavelength in a range of 1000-1200 nm, inclusive.SELECTED DRAWING: Figure 1

Description

The present invention relates to an optical filter and a solid-state imaging device. Specifically, the present invention relates to an optical filter for a holographic solid-state imaging device and a holographic solid-state imaging device using the optical filter.

In a conventional imaging device, it is necessary to construct an optical system that focuses on a subject using a lens, and the focus position cannot be converted after imaging. However, recently developed holograms such as Fresnel holograms, Fraunhofer holograms, lensless Fourier transform holograms, laser reproduction holograms such as image holograms, white light reproduction holograms such as rainbow holograms, holographic stereograms, and holographic diffraction gratings were used. In the imaging apparatus, the focal position can be changed after imaging (Non-Patent Document 1). In particular, the lensless Fourier transform hologram method is lensless, so that the imaging apparatus can be thinned (Non-patent Documents 2 and 3).

In the Fourier transform hologram method, it is necessary to calculate the object shape restoration by inverse Fourier transform from the light intensity detected by the sensor, but in the Fourier transform hologram method, in order to improve the calculation speed, it is necessary to calculate at a specific interval or pattern. Sampling is often used with a mask that blocks light. Alternatively, a filter called a Fresnel zone plate that blocks light at specific intervals may be provided (Patent Document 1).

In general, a solid-state imaging device uses a CCD or CMOS image sensor, which is a solid-state imaging device for a color image. For these solid-state imaging devices, silicon photodiodes having sensitivity in the near-infrared wavelength region that cannot be detected by the human eye in the light receiving portion are used. These solid-state image sensors are mainly composed of three types of pixels, red, blue, and green. In order to make the red, blue, and green intensities detected by individual pixels natural to the human eye It is necessary to perform visibility correction, and it is necessary to use an optical filter such as a near-infrared cut filter that selectively cuts light in a specific wavelength region that cannot be seen by human eyes.

A mask or Fresnel zone plate that blocks light at specific intervals or patterns was used when configuring an imaging device using a Fourier transform hologram method using a silicon photodiode as a solid-state imaging device and the above-described near infrared cut filter. In this case, light reflected by an optical filter, sensor, mask, or Fresnel zone plate that selectively cuts light in a specific wavelength region is incident on the solid-state imaging device again, and a ghost is generated. There was a case where it was not done normally.

International Publication No. 2006/115114 JP 2013-246424 A International Publication No. 2013/047709

Joseph W. Goodman, Yoshiharu Ozaki and Toshimitsu Asakura, “Fourier Optics”, 3rd edition, Morikita Publishing Co., Ltd., October 2012, p. 309-318 Nagaoka, Fujikawa, Matsushima, “Wide-field recording of three-dimensional images by lensless Fourier transform digital holography”, IEICE General Conference, 2005, D-11-83 Nakajo, Nagaoka, Matsushima, "Acquisition of wide-field 3D image information by phase-shift lensless Fourier digital holography", 3D Image Conference 2006, July 2006, 113-116

An object of the present invention is to provide a thin hologram type solid-state imaging device optical filter for a holographic solid-state imaging device that is less susceptible to ghosting and has good visibility correction with a silicon photodiode, and a thin holographic solid-state imaging device using the optical filter. It is in.

The optical filter according to an embodiment of the present invention has a substrate and a plurality of light shielding regions on at least one surface of the substrate, and the transmittance from the vertical direction of the region having no light shielding region is the following requirements (A) to Satisfies (D).
(A): The average transmittance of light having a wavelength of 300 nm to 400 nm is 1% or less (B): The average transmittance of light having a wavelength of 450 nm to 600 nm is 50% or more (C): a wavelength of 700 nm to less than 1000 nm The average transmittance of light of 5% or less (D): The average transmittance of light having a wavelength of 1000 nm to 1200 nm is 10% or less

According to one embodiment of the present invention, a silicon photodiode and human visibility can be corrected satisfactorily, and a thin optical filter in which the occurrence of ghost is suppressed, and correction of human visibility using the optical filter can be performed. It is possible to provide a thin hologram type solid-state imaging device that is favorable and suppresses the generation of ghosts.

It is a schematic diagram which shows an example of the optical filter which concerns on one Embodiment of this invention. It is a structural example of the conventional Fourier-transform solid-state imaging device. It is a structural example of the Fourier-transform solid-state imaging device using the optical filter which concerns on one Embodiment of this invention. It is a schematic diagram showing the distance of the conditions which satisfy | fill the Fresnel zone plate. It is a schematic diagram which shows an example of a Fresnel zone plate. It is a schematic diagram which shows the light shielding area | region which concerns on one Embodiment of this invention. It is an optical path of a ghost generated in a conventional Fourier transform solid-state imaging device. It is a figure explaining generation | occurrence | production of a ghost being suppressed in the Fourier-transform solid-state imaging device which concerns on one Embodiment of this invention. It is a schematic diagram which shows the transparent base material which concerns on one Embodiment of this invention. It is a structural example of the Fourier-transform solid-state imaging device using the optical filter which concerns on one Embodiment of this invention.

The embodiments shown in the drawings are for purposes of illustration and illustration only and are not intended to limit the invention as defined by the claims. The following detailed description of the illustrated embodiments will be understood when read in conjunction with the following drawings. In these drawings, similar structures are denoted by similar reference numerals.

Although embodiments of the present invention will be described with reference to the drawings, the drawings are provided merely for illustration, and the present invention is not limited to the drawings. It should be noted that the drawings are schematic, and the relationship between the thickness and the planar dimensions, the thickness ratio, and the like may differ from the actual ones. Furthermore, in the following description, the same reference numerals are given to configurations / uses having the same or substantially the same functions and configurations, and redundant descriptions are omitted.

FIG. 1 is a schematic cross-sectional view of an optical filter. The optical filter 1 shown in FIG. 1 includes a substrate 10 having transparency, and has a plurality of dielectric multilayer films 31 and light shielding regions 21 on at least one surface of the substrate 10. The optical filter 1 may have a dielectric layer 32 on the other surface of the substrate 10. The shape of the light shielding region 21 and the structure of the dielectric multilayer films 31 and 32 are not limited to the structure shown in FIG. For example, the light shielding region 21 may be provided on one surface of the optical filter 1, which is one surface of the substrate 10, and the dielectric multilayer film 31 may be provided on the other surface of the substrate 10.

[Characteristics of optical filter]
In the optical filter according to one embodiment of the present invention, the light transmittance from the vertical direction of the region not having the light shielding region satisfies the following requirements (A) to (D).
(A): The average transmittance of light having a wavelength of 300 nm to 400 nm is 1% or less (B): The average transmittance of light having a wavelength of 450 nm to 600 nm is 50% or more (C): a wavelength of 700 nm to less than 1000 nm The average transmittance of light of 5% or less (D): The average transmittance of light having a wavelength of 1000 nm to 1200 nm is 10% or less

The requirement (A) is more preferably an average transmittance of 0.5% or less. More preferably, the OD value which is an optical density (optical density: OD) is 3 or more. The OD value is given by the following equation.

The requirement (B) is more preferably an average transmittance of 60% or more, and further preferably 70% or more.

The requirement (C) is more preferably an average transmittance of 1% or less, and further preferably 0.4% or less. More preferably, the average OD value is 3 or more.

The requirement (D) is more preferably an average transmittance of 5% or less, further preferably 1% or less, still more preferably an average transmittance of 0.2% or less, and most preferably an average OD value of 3 or more. It is.

In the optical filter according to one embodiment of the present invention, it is preferable that the light transmittance from the vertical direction of the light shielding region satisfies the following requirement (E).
(E): Average transmittance of light having a wavelength of 400 nm or more and 600 nm or less is 5% or less

More preferably, the average OD value of light having a wavelength of 400 nm or more and 600 nm or less is 2 or more, more preferably 3 or more, and most preferably 4 or more. If it is the said range, it can fully light-shield in a light-shielding area | region.

The optical filter according to an embodiment of the present invention preferably further includes a dielectric multilayer film on at least one surface of the substrate. By having a dielectric multilayer film, it is possible to effectively shield near infrared rays detected by a silicon photodiode without being visible to human eyes while sufficiently transmitting visible light.

In the dielectric multilayer film, it is preferable that the reflectance of light incident in the vertical direction from the surface provided with the dielectric multilayer film on the substrate other than the light shielding area satisfies the following requirement (F).
(F): The average reflectance of light having a wavelength of 800 nm or more and 1000 nm or less is 80% or more

More preferably, it is 90% or more, More preferably, it is 95% or more. If it is the said range, it will fully function as a near-infrared cut function.

In the dielectric multilayer film, it is preferable that the reflectance of light incident in the vertical direction from the surface provided with the dielectric multilayer film on the substrate other than the light shielding area satisfies the following requirement (G).
(G): The average reflectance of light having a wavelength of 300 nm to 400 nm is 90% or more

More preferably, it is 95% or more, and still more preferably 98% or more. If it is the said range, it fully functions as a near-ultraviolet ray cut function.

The substrate preferably has an absorbent (A) having an absorption maximum at a wavelength of 650 nm to 900 nm. By using the absorbent (A) having the above characteristics, the obtained optical filter can suppress the occurrence of ghost at a wavelength of 650 nm to 900 nm, and a higher-quality solid-state imaging device can be obtained.

The substrate preferably has an absorbent (B) having an absorption maximum at a wavelength of 300 nm to 410 nm. By using the absorbent (B) having the above characteristics, the obtained optical filter can suppress the generation of ghost at wavelengths of 300 nm to 410 nm, and can suppress the incidence of near ultraviolet rays that degrade the sensor. A solid-state imaging device having high image quality and robustness can be obtained.

The optical filter preferably has an in-plane retardation R0 of 90 nm or less. If it is the said range, since the conjugate image in the Fourier-transform image of wavelength 360nm-800nm can be excluded, the solid-state imaging device from which a high quality image is obtained is obtained. More preferably, it is 50 nm or less, More preferably, it is 10 nm or less, More preferably, it is 1 nm or less.

[substrate]
The substrate 10 may have a function as a support substrate, for example. The substrate 10 is transparent and has a light transmission property having a wavelength of at least a visible wavelength region. The visible wavelength region is preferably a region including a wavelength of 400 nm or more and less than 700 nm, for example, and light in the visible wavelength region is visible light. The transparency of the substrate means that the transmittance of light of any wavelength exceeds 50%.

As the substrate, for example, at least one of a silicate glass substrate, a borosilicate glass substrate, a phosphate glass substrate, a fluorophosphate glass substrate, a plastic substrate, and a resin film substrate may be used. Preferably, a material having a glass transition temperature of 140 ° C. or higher is preferable, and it is more preferable to include a resin film substrate in order to make it difficult to break. Preferably, the refractive index at 500 nm is 1.40 or more and 1.7 or less. The substrate preferably contains a near-infrared absorber, such as an inorganic near-infrared absorber such as cesium tungsten oxide or copper (II) oxide, a near-infrared absorber using surface plasmons such as gold nanorods, a cyanine dye or a squarylium dye. It is preferable to contain at least one selected from organic near-infrared absorbers such as metal near-infrared absorbers such as metal dithiol complexes and metal phthalocyanine complexes. By including these near-infrared absorbers, the incidence angle dependency of red light can be reduced, and the number of laminated multilayer dielectric films can be reduced. The substrate preferably contains a near-ultraviolet absorber, and in that case, the incident angle dependency of blue light can be reduced.

The substrate is preferably composed of a plurality of layers from the viewpoint of resistance to cracking, ease of addition of a light absorber, imparting functions and effects. Functions provided to the substrate include conductivity, antistatic effect, adhesion foreign matter prevention effect, scratch prevention effect, anti-fogging property, heat resistance improvement effect, gas barrier property, high elasticity, scratch-removing effect, flatness, roughness, Examples include hygroscopicity and anti-aging effects. The number of layers of the substrate is preferably 2 to 5, and if it is 6 layers or more, there is a concern that the adhesion between the substrates is lowered or the manufacturing cost is increased. The closer the refractive index of each layer is, the better. The difference in refractive index between the layers is preferably 0.3 or less. When the substrate has a plurality of layers, the substrate may have a layer that does not have the light shielding region 21 on both sides.

The total film thickness of the substrate is preferably 30 μm or more and 200 μm or less. Within this range, it is useful for thinning the solid-state imaging device. More preferably, they are 40 micrometers or more and 150 micrometers or less, More preferably, they are 34 micrometers or more and 110 micrometers or less. If it is this range, it can be used suitably also for a thin solid-state imaging device with a total thickness of 6.5 mm or less. In the case of a film thickness of less than 30 μm, there is a concern about the ease of warping or the ease of cracking.

[Dielectric multilayer film]
An optical filter according to an embodiment of the present invention includes a multilayer in which high refractive index layers 33 and low refractive index layers 34 are alternately stacked on at least one surface of a transparent substrate, for example, as shown in FIG. Dielectric multilayer films 31 and 32 made of Although not shown, the dielectric multilayer film may have a middle refractive index layer between the high refractive index layer 33 and the low refractive index layer 34.

The dielectric multilayer film has an optical characteristic that has a light transmission band in the visible wavelength region and has a light shielding performance in the near infrared wavelength region and the near ultraviolet region. The near-infrared wavelength region is preferably a region including a wavelength of, for example, 735 nm or more and less than 1100 nm, more preferably a wavelength of 720 nm or more and 1100 nm or less, and further preferably 710 nm or more and 1100 nm or less. If the region has an optical characteristic having a light shielding performance, near infrared rays that cannot be seen by human eyes can be sufficiently shielded. The light in the near infrared wavelength region is near infrared. The near ultraviolet wavelength region is preferably a region including a wavelength of, for example, 250 nm or more and less than 400 nm, and light in the near ultraviolet wavelength region is near ultraviolet. By having an optical characteristic having a light shielding performance in the near infrared wavelength region, for example, the light transmittance in the visible wavelength region is improved as compared with the case where the light shielding performance in the near infrared wavelength region is provided only by the near infrared absorber. It becomes easy.

The high refractive index layer preferably has a refractive index of 2.0 or more, for example, where the refractive index at a wavelength of 500 nm is n _H. 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 may be used. Moreover, if a refractive index is 2.0 or more, you may contain the additive. A higher n _H is advantageous for suppressing the amount of wavelength shift at the time of 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.

When the refractive index of light having a wavelength of 500 nm is n _L , the low refractive index layer preferably has a refractive index of less than 1.6 for light having a wavelength of 500 nm, for example, and has transparency. More preferably, it is lower than the refractive index of the outermost layer of the substrate. As the low refractive index layer, for example, a film containing silicon oxide (SiO ₂ ), magnesium fluoride (MgF ₂ ), barium fluoride (BaF ₂ ), lithium fluoride (LiF), or a composite oxide thereof is used. Also good. Further, if n _L is 1.7 or less or lower than the refractive index of the outermost layer of the substrate having transparency, an additive may be contained.

The medium refractive index layer preferably has a refractive index of 1.6 or more and less than 2.0 for light having a wavelength of 500 nm, for example, where n _M is a refractive index of light having a wavelength of 500 nm, More preferably, it is lower than the refractive index of the outermost layer of the substrate having transparency. As the middle refractive index layer, for example, aluminum oxide (Ai ₂ O ₃ ), cesium fluoride (CeF ₃ ), yttrium oxide (Y ₂ O ₃ ), ytterbium oxide (Yb ₂ O ₃ ), or a composite oxide thereof is used. A containing film can be used. Moreover, if _nM is 1.6 or more and less than 2.0, you may contain the additive.

Dielectric layers such as a high refractive index layer, a medium refractive index layer, and a low refractive index layer are formed using, for example, a sputtering method, a vacuum evaporation method, an ion-assisted vacuum evaporation method, or a CVD method. In particular, it is preferable to form the dielectric 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 dielectric layer is important. Sputtering, vacuum deposition, and ion-assisted vacuum deposition are excellent in controlling the thickness when the dielectric layer is formed. For this reason, the precision of the thickness of each layer which comprises the dielectric multilayer film which consists of laminated | stacked dielectric layers can be raised, and the dielectric multilayer film of the desired optical characteristic is obtained. Among these, the ion-assisted vacuum deposition method is more preferable in order to achieve both improvement in film formation speed and film thickness control.

The dielectric multilayer film is preferably provided on both surfaces of a transparent substrate. When provided on both surfaces, an improvement in visible light transmittance can be expected by reducing reflection in the visible light region on both surfaces of the substrate, and it is suitable for reducing warpage.

Hereinafter, a holographic imaging device will be described, but description of general components will be omitted, and main components according to an embodiment of the present invention will be mainly described.

[hologram]
FIG. 2 is an example of a holographic imaging device conventionally used. An object wave 101 that has passed through the subject 100 and a reference wave 102 that has not passed through the subject 100 pass through a phase shift filter 103, a beam combining element 104, a light shielding mask 105, and an optical filter 106 having a visibility correction ability, Interference occurs on the recording surface 107, and interference fringes are formed on the sensor recording surface 107. The subject 100 and the sensor recording surface 107 are Fourier transforms of the complex amplitudes (phase and amplitude) of the object wave 101 and the reference wave 102 on the sensor recording surface 107, respectively. In order to form an image, in other words, to form a Fourier transform holographic optical system, each is arranged using the beam coupling element 104 or the like. As described above, by utilizing the interference action of the light wave, information on the complex amplitude (phase and amplitude) of the object wave 102 is recorded on the sensor recording surface 107, and the calculation is performed using the calculator 108, thereby obtaining a hologram. The object shape is restored.

FIG. 3 is a diagram schematically showing a Fourier transform holographic imaging optical system using an optical filter according to an embodiment of the present invention. It is to be noted that the shape of the subject 100 can be restored by once Fourier transforming the hologram obtained in this way by applying the Fourier transform holography method using the computer 108 of FIG.

For the calculation of the object shape restoration in the Fourier transform, a generally known method may be used. For example, JP2013-246424A (Patent Document 2), International Publication No. 2013/047709 (Patent Document 3). You may calculate using the calculation method described in these.

In a lensless Fourier transform hologram, the maximum spatial frequency is obtained from the following equation (2).

In Expression (2), w is the field of view, λ is the wavelength of the observation light, and d is the distance between the object and the sensor. If the sensor pitch is δ, it is necessary to take an image in an area where these maximum spatial frequencies satisfy 2F ≦ 1 / δ. If the region satisfies 2F ≦ 1 / δ, the shape of the subject can be restored.

The imaging apparatus according to an embodiment of the present invention preferably includes a beam splitter or beam coupling element and an optical filter between the subject and the solid-state imaging element.

As the beam coupling element, a substrate in which a dielectric multilayer film is provided on the substrate is preferable, and a polarizing beam splitter, a non-polarizing beam splitter, or the like may be used.

[Shading area]
In order to improve the calculation speed of the restoration of the subject shape by Fourier transform, it is preferable to sample the calculation to be restored from the sensor by providing a light-shielding area in order to reduce the calculation area. g (x, y) is a complex amplitude function having the phase and amplitude of the subject, and gs (x, y) is arranged with an interval of width X in the x direction and width Y in the y direction. Assuming that the complex amplitude function is sampled by an array of delta functions, gs (x, y) is sampled by the following equation (3).

In Expression (3), in order to completely restore the object shape, X and Y must satisfy the following Expression (4), respectively.

In Equation (4), 2B _x is the width in the x direction of the smallest rectangle that completely surrounds the finite region R of the frequency space that one point of the subject exerts, and 2B _x is finite in the frequency space that one point of the subject exerts. The width in the y direction of the smallest rectangle that completely surrounds the region R. As long as Expression (4) is satisfied, g (x, y) can be restored from Expression (5) below.

It is preferable that the light-shielding region is a region that allows Expression (3) within a range that satisfies Expression (4). In order to suppress the distortion of the shape of the restored subject, it is preferable that each light shielding region includes an intersection of two or more diagonal lines of the optical filter as shown in FIG. In a light-shielding region that does not include the intersection of two or more diagonal lines of the optical filter, the shape of the restored subject is likely to be distorted, making it difficult to restore the shape. As shown in FIG. 5, the intersection of two or more diagonal lines of the optical filter may be a part of the light shielding region. Each light shielding region of the optical filter may be divided into a plurality of substrates or may be provided on both surfaces of the substrate.

Regarding the number of light shielding regions, it is considered that continuous regions form one light shielding region, and having a plurality of light shielding regions means having a plurality of non-continuous light shielding regions.

Moreover, it is preferable that one light shielding area has an area of 100 μm ² or more in order to form moire fringes on the solid-state imaging device as the light shielding area. More preferably 300 [mu] m ² or more areas, more preferably 1000 .mu.m ² or more areas, and most preferably 4000 .mu.m ² or more areas.

Materials for forming the light shielding region include resin materials such as thermosetting resins, ultraviolet curable resins, and thermoplastic resins, metal materials such as chromium, molybdenum, tungsten, iron, nickel, titanium, and lower chromium oxide, graphite, and carbon nanotubes. And carbon materials such as fullerene, and absorbent materials composed of one or more kinds of pigments. An ultraviolet curable resin is preferable because of easy shape control. Further, the thickness of the light shielding region is preferably 0.1 μm or more and 10 μm or less. If it is less than 0.1 μm, it is difficult to obtain a sufficient OD value, and if it exceeds 10 μm, the influence of diffraction and reflection at the end face of the light shielding region is increased, which is not preferable. Moreover, it is preferable to provide the surface of the light-shielding region with irregularities having a height difference of about 0.1 to 2 [mu] m between the highest part and the lowest part of the light-shielding region from the viewpoint of preventing reflection.

[Fresnel zone plate]
The light shielding region preferably forms a Fresnel zone plate. As shown in FIG. 4, the Fresnel zone plate has a light shielding region (see FIG. 5) in a circle group around the point O on the light shielding region forming surface 201, and is the i th from the point P of the subject. Assume that the distance from the circumference of the circle to ra is r _a , and the distance from the circumference of the i-th circle to the point Q on the sensor recording surface 202 is r _b . Considering the optical path length from the point P to the point Q through the point on the circumference, the distance from the point P to the point O of the subject is a, the distance from the point O to the point Q is b, If the light shielding regions are drawn in a circle group so that there is an optical path difference of (m + 1/2) λ, the light shielding regions satisfy the relationship expressed by the following formula (6).

When the radius of the _nth circle is x _n , the following equation (7) is satisfied.

FIG. 5 shows an example of a light shielding region in which a Fresnel zone plate is formed.

The center corresponding to n = 0 may be either a light shielding region or a transmission region. The circle group of the Fresnel zone plate may be in a state where a part thereof is missing, and is preferably a region that allows Expression (3) within a range that satisfies Expression (4).

[Moire]
Moire is a striped pattern that is different from the original lattice that is newly generated when two regularly arranged lattice lines are overlapped. In the moire according to the present invention, it means a light and dark striped pattern formed on the solid-state imaging device according to the shape of the light shielding region.

[ghost]
FIG. 7 shows an example of a Fourier transform hologram imaging apparatus having a conventional configuration. In the Fourier transform hologram imaging apparatus having the conventional configuration, light reflected by the surface of the optical filter 106 having the visibility correction ability in addition to the normal light 109 is reflected again by the light shielding mask 106 and reenters the sensor recording surface 107. Ghost 110 is generated.

FIG. 8 shows an example of a Fourier transform hologram imaging apparatus according to an embodiment of the present invention. Since the optical filter 1 according to an embodiment of the present invention has a plurality of light shielding regions 21 on at least one surface of the substrate and also has a visibility correction ability, the light reflected from the surface of the optical filter 1 is a ghost. Therefore, a good image can be obtained.

[Evaluation method]
<Optical characteristics>
The optical characteristics of the optical filter were measured using a UV-visible-near-infrared spectrophotometer U4100 (manufactured by Hitachi High-Technologies Corporation) to measure the light-shielding area and the part other than the light-shielding area. It was.

<Warpage>
The curvature of the optical filter was measured using a digital microscope VHX-2000 (manufactured by Keyence Corporation). Those having a radius of curvature of 50 mm or more were marked with ◯, and those having a radius of curvature of less than 50 mm were marked with x.

To 100 parts by weight of norbornene resin “ARTON, refractive index 1.52, glass transition temperature 160 ° C.” manufactured by JSR Co., Ltd., 0.4% of Oxazole UV absorber “Uvitex OB” (maximum absorption wavelength 396 nm) manufactured by BASF Co., Ltd. 0.1 parts by weight of squarylium compound (maximum absorption wavelength 699 nm) represented by the following formula (8) and methylene chloride were dissolved in parts by weight to obtain a solution having a solid content of 30%.

In Formula (8), Me represents a methyl group, and Ac represents an acetyl group.

Next, the obtained solution was cast on a smooth glass plate, peeled after drying at 50 ° C. for 8 hours and further under reduced pressure at 140 ° C. for 3 hours to obtain a square transparent substrate having a side of 50 cm. By relaxing the stress at 150 ° C., the thickness was 0.05 mm and the in-plane retardation Ro was 1 nm. Subsequently, on both surfaces of the obtained transparent substrate, using an ion-assisted vacuum deposition apparatus, the dielectric multilayer film of Table 1 consisting of a dielectric multilayer film at a deposition temperature of 120 ° C. [silica (SiO ₂ : refractive index 1 of 550 nm) .45) layers and titania (TiO ₂ : 550 nm refractive index 2.45) layers are alternately laminated] to obtain an optical filter A having a thickness of 0.055 mm and a visibility correction ability. It was.

On one side of this, the light-shielding regions are not orthogonal to each other, and include the intersection of two diagonal lines of the optical filter A, the maximum diameter is 10.5 mm, the surface unevenness is 1 μm, and the thickness is 4000 μm, respectively. ^An optical filter 1 was obtained by forming a light-shielding region for forming 20 Fresnel zone plates having an area of ² or more using an ultraviolet curable resin containing chromium. The optical characteristics of the transmission region of the optical filter 1, the optical properties of the light shielding region, and the warpage were evaluated. The obtained results are shown in Table 2 (Examples 1 and 4).

A spherical wave is used as reference light, a phase shift filter with an in-plane phase difference of 150 nm is installed between the reference light and the beam combining element, and the optical filter 1 is used to set the visual field to 0.5 m and the distance to the subject to 2 m. A solid-state imaging device was configured using a color image sensor BU1203MC (4000 × 3000 [pixel], nominal sensor pitch 1.85 × 1.85 [μm], CMOS sensor) manufactured by Terry. The solid-state imaging device satisfied 2F ≦ 1 / δ in both the vertical and horizontal directions from 400 nm to 700 nm, and moire fringes were generated in the solid-state imaging device. The image of the subject restored from the obtained moire fringes was a good image with corrected visibility and no ghost.

100 parts by weight of JSR norbornene resin “ARTON, refractive index 1.52, glass transition temperature 160 ° C.”, 2 parts by weight of BASF oxazole UV absorber “Uvitex OB” (maximum absorption wavelength 396 nm) In addition, 0.5 parts by weight of squarylium compound (maximum absorption wavelength: 699 nm) represented by formula (8) and methylene chloride were added and dissolved to obtain a solution having a solid content of 30%.

Next, the obtained solution was cast on a smooth glass plate (manufactured by SCHOTT, D263, thickness 0.1 mm) and dried at 50 ° C. for 8 hours and further under reduced pressure at 140 ° C. for 3 hours. A transparent substrate composed of two layers of rectangular glass and resin was obtained. By stress relaxation at 150 ° C., the thickness was 0.11 mm and the in-plane retardation Ro was 1 nm. Subsequently, on both surfaces of the obtained transparent substrate, using an ion-assisted vacuum deposition apparatus, the dielectric multilayer film of Table 1 consisting of a dielectric multilayer film at a deposition temperature of 120 ° C. [silica (SiO ₂ : refractive index 1 of 550 nm) .45) layers and titania (TiO ₂ : 550 nm refractive index 2.45) layers are alternately laminated] to obtain an optical filter B having a thickness of 0.115 mm and a visibility correction capability. It was. On one side of this, the light shielding regions including the intersections of the two diagonal lines of the optical filter B are not perpendicular to each other, the maximum diameter is 10.5 mm, the surface irregularities are 1 μm, and the thickness is 4000 μm, respectively. ^An optical filter 2 was obtained by forming a light shielding region for forming 20 Fresnel zone plates having an area of ² or more using an ultraviolet curable resin containing chromium. The optical characteristics of the transmission area of the optical filter, the optical characteristics of the light shielding area, and the warpage were evaluated. The results obtained are shown in Table 2 (Example 2). A spherical wave is used as the reference light, a phase shift filter with an in-plane phase difference of 150 nm is installed between the reference light and the beam combining element, the optical filter 2 is used, and the field of view is 0.1 m and the distance to the subject is 2 m. A monochrome image sensor CSB4000CL-10A (2000 × 2000 [pixel], nominal sensor pitch 6.0 × 6.0 [μm], CMOS sensor) was configured. The solid-state imaging device satisfied 2F ≦ 1 / δ in both the vertical and horizontal directions, and moire fringes were generated in the solid-state imaging device. The image of the subject restored from the obtained moire fringes was a good image with corrected visibility and no ghost.

100 parts by weight of a norbornene resin “ARTON having a refractive index of 1.52 and a glass transition temperature of 160 ° C.” manufactured by JSR Co., Ltd. and 0.2 μm of an oxazole UV absorber “Uvitex OB” manufactured by BASF Co. (maximum absorption wavelength of 396 nm) are used. 0.05 parts by weight of squarylium compound (maximum absorption wavelength 699 nm) represented by formula (8) and methylene chloride were added to and dissolved in parts by weight to obtain a solution having a solid content of 30%.

Next, the obtained solution was cast on a smooth glass plate, peeled after drying at 50 ° C. for 8 hours and further under reduced pressure at 140 ° C. for 3 hours to obtain a square transparent substrate having a side of 50 cm. By relaxing the stress at 150 ° C., the thickness was 0.1 mm and the in-plane retardation Ro was 1 nm.

This transparent substrate includes the intersections of two diagonal lines, which are not orthogonal to each other, have a maximum diameter of 10.5 mm, surface irregularities of 1 μm, and a thickness of 5 μm, each having an area of 4000 μm ² or more. A light shielding region was formed using an ultraviolet curable resin containing a black absorbing material composed of a plurality of types of pigments, which forms a Fresnel zone plate.

On the surface of the transparent substrate on which the light-shielding region is formed, a methylene chloride solution having a solid content of 8% norbornene resin “ARTON having a refractive index of 1.52 and a glass transition temperature of 160 ° C.” manufactured by JSR is applied at 50 ° C. The substrate was dried for 8 hours and further under reduced pressure at 140 ° C. for 3 hours to obtain a substrate made of a two-layer resin having a light-shielding region having a thickness of 0.11 mm and having the structure shown in FIG. The dielectric multilayer film shown in Table 1 was formed on this as in Example 1 to obtain an optical filter 3 having a thickness of 0.115 mm and having a visibility correction ability.

The optical characteristics of the transmission area of the optical filter 3, the optical characteristics of the light shielding area, and the warpage were evaluated. The results obtained are shown in Table 2 (Example 3). A solid-state imaging device was configured in the same manner except that the optical filter 3 was used instead of the optical filter 1 in Example 1. Moire fringes occurred in the solid-state imaging device. The image of the subject restored from the obtained moire fringes was a good image with corrected visibility and no ghost.

An optical filter 1 was obtained in the same manner as in Example 1. Table 2 (Examples 1 and 4) shows the evaluation results of the optical characteristics of the transmission region, the optical characteristics of the light shielding region, and the warpage of the optical filter 1. In Example 4, as shown in FIG. 10, the optical filter 1 is used, and the reference light is introduced through a phase adjuster using a spherical wave, with a visual field of 0.5 m and a distance of 2 m from the subject. A solid-state imaging device was configured by using a color image sensor BU1203MC (4000 × 3000 [pixel], nominal sensor pitch 1.85 × 1.85 [μm], CMOS sensor) manufactured by the company. Moire fringes occurred in the solid-state imaging device. The image of the subject restored from the obtained moire fringes was a good image with corrected visibility and no ghost.

[Comparative Example 1]
An optical filter A was obtained in the same manner as in Example 1. This was the optical filter 3 without providing a light shielding region. The optical characteristics of the transmission area of the optical filter, the optical characteristics of the light shielding area, and the warpage were evaluated. The obtained results are shown in Table 2 (Comparative Example 1). In addition, on a separately smooth glass plate (manufactured by SCHOTT, D263, thickness 0.1 mm), the light shielding regions are not perpendicular to each other, and have a maximum diameter of 10.5 mm, surface irregularities of 1 μm and thickness of 5 μm, respectively. A light-shielding mask was produced in which a light-shielding region for forming 20 Fresnel zone plates having an area of 4000 μm ² or more was formed using an ultraviolet curable resin containing chromium. Object, beam coupling element, shading mask, optical filter 3, Toshiba Terry image sensor CSB4000CL-10A (2000 × 2000 [pixel], nominal sensor pitch 6.0 × 6.0 [μm], CMOS sensor) in this order An imaging device is installed, a spherical wave is used as reference light, a phase shift filter with an in-plane phase difference of 150 nm is installed between the reference light and the beam coupling element, a field of view is 0.5 m, and a distance from the subject is 2 m. The solid-state imaging device was configured using a color image sensor BU1203MC (4000 × 3000 [pixel], nominal sensor pitch 1.85 × 1.85 [μm], CMOS sensor). Although the visibility of the image of the subject restored from the obtained interference fringes was corrected, ghost was included and the subject could not be restored sufficiently.

[Comparative Example 2]
An optical filter C having a thickness of 0.053 mm was obtained in the same manner except that the dielectric multilayer film provided on both surfaces of the substrate in Example 1 was changed to Table 3. On one side of this, the light-shielding regions are not orthogonal to each other, and include the intersection of two diagonal lines of the optical filter C. The maximum diameter is 10.5 mm, the surface unevenness is 1 μm, and the thickness is 20 μm. The light shielding region for forming the Fresnel zone plate was formed by using an ultraviolet curable resin containing chromium, and an optical filter 4 (Table 2 “Comparative Example 2”) was obtained.

Object, beam coupling element, light shielding mask, optical filter A, Toshiba Terry image sensor CSB4000CL-10A (2000 × 2000 [pixel], nominal sensor pitch 6.0 × 6.0 [μm], CMOS sensor) in this order An imaging device is installed, a spherical wave is used as reference light, a phase shift filter with an in-plane phase difference of 150 nm is installed between the reference light and the beam coupling element, a field of view is 0.5 m, and a distance from the subject is 2 m. The solid-state imaging device was configured using a color image sensor BU1203MC (4000 × 3000 [pixel], nominal sensor pitch 1.85 × 1.85 [μm], CMOS sensor). Moire fringes occurred in the solid-state imaging device. Although the ghost image was not included in the image of the subject restored from the obtained moire fringes, the visibility correction was not sufficient and the subject could not be restored.

An optical filter according to an embodiment of the present invention is a digital still camera, a camera for a mobile phone, a digital video camera, an action camera, a drone camera, a smartphone camera, a PC camera, a surveillance camera, an automobile camera, etc. It can be suitably used for portable information terminals, personal computers, video games, medical devices, portable game machines, fingerprint authentication systems, digital music players, toy robots, toys and the like.

1: optical filter 100: subject, 101: object wave, 102: reference light, 104: beam coupling element, 105: light-shielding mask, 106: optical filter having visibility correction ability, 107: sensor recording surface, 108: computer, 109: normal light, 110: ghost light, 111: phase adjuster, 201: light shielding area forming surface, 202: sensor recording surface

Claims (12)

A substrate having a plurality of light shielding regions on at least one surface;
An optical filter characterized in that the light transmittance from the vertical direction of the region other than the light shielding region of the substrate satisfies the following (A) to (C).
(A): Average transmittance of light having a wavelength of 300 nm to 400 nm is 1% or less (B): Average transmittance of light having a wavelength of 450 nm to 600 nm is 50% or more (C): Wavelength of 700 nm to less than 1000 nm Average light transmittance of 5% or less The transmittance of light from the vertical direction of the light shielding region of the optical filter satisfies (E): the average transmittance of light having a wavelength of 400 nm or more and 600 nm or less satisfies 5% or less. Optical filter.   The optical filter according to claim 1, further comprising a dielectric multilayer film on at least one surface of the substrate.   The dielectric multilayer film has an average reflectance of 80% or more of light having a wavelength of 800 nm or more and 1000 nm or less incident in a vertical direction from a surface provided with the dielectric multilayer film in a region other than the light shielding region of the substrate. The optical filter according to claim 3, which has a near infrared cut function.   The dielectric multilayer film has an average reflectance of 90% or more of light having a wavelength of 300 nm or more and 400 nm or less incident in a vertical direction from a surface provided with the dielectric multilayer film in a region other than the light shielding region of the substrate. The optical filter according to claim 3, which has an ultraviolet cut function.   The optical filter according to any one of claims 1 to 6, wherein the substrate includes an absorbent (A) having an absorption maximum with respect to light having a wavelength of 650 nm to 900 nm.   The optical filter according to any one of claims 1 to 6, wherein the substrate includes an absorbent (B) having an absorption maximum with respect to light having a wavelength of 300 nm to 410 nm.   The optical filter according to any one of claims 1 to 7, wherein the light shielding region includes an intersection of two or more diagonal lines of the optical filter and does not intersect each other.   The optical filter according to claim 1, wherein the light shielding region is circular or elliptical.   The optical filter according to claim 1, wherein the light shielding region has a shape that forms moire fringes on the image sensor.   An image pickup apparatus comprising the optical filter according to any one of claims 1 to 10.   A lensless imaging apparatus comprising a cover material and an optical filter according to any one of claims 1 to 10 between a subject and a solid-state imaging device.