Patent Application
20150276990
This application claims the benefit of Japanese Priority Patent Application JP2014-074950 filed Mar. 31, 2014, the entire contents of which are incorporated herein by reference.
The present technology relates to an optical device having a plurality of structures on the front surface thereof, an original plate for manufacturing the optical device, a method of manufacturing the original plate, and an imaging apparatus having the optical device.
Up until now, various technologies for reducing the reflection of light on front surfaces have been used in the technical field of optical devices. As such, a technology for forming sub-wavelength structures on the front surface of an optical device has been known (see, for example, Japanese Patent No. 4539657).
Generally, when passing through a concavo-convex shape periodically provided on the front surface of an optical device, light is diffracted with the straight advancing component thereof greatly reduced. However, if the concavo-convex shape has a pitch shorter than that of the wavelength of the passing light, the diffraction is not caused and an antireflection effect may be satisfactorily obtained.
It is desirable to provide an optical device having excellent antireflection characteristics on the curved surface thereof, an original plate for manufacturing the optical device, a method of manufacturing the original plate, and an imaging apparatus having the optical device.
According to an embodiment of the present technology, there is provided an optical device including a curved surface and a plurality of structures spirally provided on the curved surface at an interval of less than or equal to a wavelength of light for which reflection is to be reduced.
Each of the plurality of structures includes one of a convex portion protruding in a light-axis direction and a concave portion recessed in the light-axis direction. The curved surface has a region, in which the plurality of structures are not provided, at a center thereof.
According to another embodiment of the present technology, there is provided an original plate including a curved surface and a plurality of structures spirally provided on the curved surface at an interval of less than or equal to a wavelength of light for which reflection is to be reduced. Each of the plurality of structures includes one of a convex portion protruding in a central-axis direction of the curved surface and a concave portion recessed in the central-axis direction thereof. The curved surface has a region, in which the plurality of structures are not provided, at a center thereof.
According to still another embodiment of the present technology, there is provided an imaging apparatus including an optical device having a curved surface and a plurality of structures spirally provided on the curved surface at an interval of less than or equal to a wavelength of light for which reflection is to be reduced. Each of the plurality of structures includes one of a convex portion protruding in a light-axis direction of the optical device and a concave portion recessed in the light-axis direction thereof. The curved surface has a region, in which the plurality of structures are not provided, at a center thereof.
According to yet another embodiment of the present technology, there is provided a method of manufacturing an original plate including: perpendicularly applying light onto a curved surface of the original plate to form spiral exposure portions on a resist provided on the curved surface of the original plate at an interval of less than or equal to a wavelength of light for which reflection is to be reduced; developing a resist layer having the plurality of exposure portions to form a resist pattern; and etching the original plate in a central-axis direction of the curved surface using the resist pattern as a mask to form a plurality of structures on the curved surface.
As described above, it is possible to provide an optical device having excellent antireflection characteristics on the curved surface thereof according to the present technology.
These and other objects, features and advantages of the present disclosure will become more apparent in light of the following detailed description of best mode embodiments thereof, as illustrated in the accompanying drawings.
An optical device is desirably a lens such as a concave lens having a concave curved surface and a convex lens having a convex curved surface. As the convex lens, a biconvex lens, a plano-convex lens, a convex meniscus lens, or the like is desirable. As the concave lens, a bioconcave lens, a plano-concave lens, a concave meniscus lens, or the like is desirable.
The optical device desirably has an incident surface on which light is incident and an emission surface from which the light is emitted, and a plurality of structures are desirably provided on at least one of the surfaces and more desirably provided on both the surfaces.
Examples of the optical device include, but not limited to, a lens, a film, a glass plate (such as a glass plate for an imaging device package), a polymeric resin plate, a filter, a semi-transmission mirror, a dimmer device, a prism, a polarization device, and a front-surface plate for display.
The optical device is desirably applied to an optical system, an imaging apparatus, an imaging device package, an imaging module, an optical appliance, an electronic apparatus, or the like. Examples of the imaging apparatus include, but not limited to, a digital camera and a digital video camera. Examples of the optical appliance include, but not limited to, a telescope, a microscope, an exposure apparatus, a measurement apparatus, an inspection apparatus, and an analysis appliance. Examples of the electronic apparatus include, but not limited to, a personal computer, a mobile phone, a tablet computer, a display apparatus, and a drive for an optical recording medium. Examples of the optical system include, but not limited to, an optical system such as the imaging apparatus, the optical appliance, and the electronic apparatus described above.
Embodiments of the present technology will be described in the following order. Note that in all the figures of the following embodiments, the same or corresponding components will be denoted by the same symbols.
Hereinafter, a description will be given, with reference to
The device main body 1 and the plurality of structures 2 are separately or integrally molded. When the device main body 1 and the plurality of structures 2 are separately molded, the optical device may further have, if necessary, an intermediate layer 3 between the device main body 1 and the plurality of structures 2 as shown in
As shown in
Hereinafter, the device main body 1 and the plurality of structures 2 of the optical device will be described sequentially.
(Device Main Body)
As shown in
The curved surface is formed, for example, when a curved line in a YZ plane represented by the following formula (1) is rotated about a Z-axis.
(where 1/R represents a center curvature, K represents a conic constant, and A, B, C, and D represent prescribed constants.)
Note that the relationships between the conic constant K and the types of the curved surface are shown below.
K<−1: hyperboloidal surface
K=−1: paraboloidal surface
−1<K<0: ellipsoidal surface (ellipsoidal surface about long axis)
K=0: spherical surface
K>0: ellipsoidal surface (ellipsoidal surface about short axis)
The device main body 1 has transparency. As a material of the device main body 1, any of an organic material and an inorganic material may be used so long as it has transparency. Examples of the inorganic material include quartz, sapphire, and glass. As the organic material, a common polymeric material in, for example, the technical field of an optical device may be used. Specifically, examples of the common polymeric material include a thermoplastic resin such as an acrylic resin (PMMA), a polycarbonate resin (PC), and a cycloolefin polymer resin (COP).
When an organic material is used as the material of the device main body 1, an undercoating layer may be provided as font-surface treatment in order to improve front-surface energy, coating performance, slipping performance, flatness, or the like on the front surface of the device main body 1. Examples of the material of the undercoating layer include an organoalkoxymetal compound, polyester, acrylic-modified polyester, and polyurethane. In addition, front-surface treatment such as corona discharge and UV application treatment may be applied to the front surface of the device main body 1 in order to obtain the same effect as that of the undercoating layer.
(Structures)
As shown in
When the entirety of the curved surface of the device main body 1 is seen in the light-axis direction DL, the plurality of structures 2 are spirally arranged, as shown in
As shown in
The region RL0 has desirably a diameter of greater than or equal to 0.07 nm in consideration of the resolution of next-generation laser scales. In addition, the region RL0 has desirably a diameter of greater than or equal to 10 nm in consideration of the resolution of existing laser scales.
Moreover, the region RL0 has desirably a diameter of greater than or equal to 50 nm in consideration of the precision limits of existing rotation apparatus systems.
The region RL0 has desirably a diameter of less than or equal to 20 mm in consideration of the sizes of the unprocessed regions of CDs (Compact Discs) or the like. In addition, the region RL0 has desirably a diameter of less than or equal to 1 mm in consideration of the fact that the optical device 1 is hardly used if it has an opening. Moreover, the region RL0 has desirably a diameter of less than or equal to 0.1 mm in consideration of a size with which the region RL0 is visually recognizable.
When a part of the curved surface of the device main body 1 is seen in the light-axis direction DL, the plurality of structures 2 are regularly arranged on the curved surface of the device main body 1 as shown in
Hereinafter, a description will be given, with reference to
As shown in
Note that the central axis M of the original plate 11 passes through the center of the curved surface.
The curved surface of the original plate 11 desirably has a region RM0, in which the plurality of structures 12 are not provided, at the central portion thereof. This is because the curved surface of the device main body 1 has the region RL0 at the central portion thereof. The arrangement and the shape of the structures 12 of the original plate 11 are the same as those of the structures 2 of the optical device described above. As a material of the original plate 11, glass, silicon, or the like may be, for example, used. However, the material of the original plate 11 is not particularly limited to such materials.
Hereinafter, a description will be given, with reference to
A laser light source 21 is a light source used to expose a resist layer 13 deposited on the front surface of the original plate 11 serving as a recording medium and oscillates recording laser light 14 having a wavelength X of, for example, 266 nm. The laser light 14 emitted from the laser light source 21 goes straight as a parallel beam and is incident on an EOM (Electro Optical Modulator) 22. The laser light 14 passing through the EOM 22 is reflected by a mirror 23 and introduced into a modulation optical system 25.
The mirror 23 is constituted by a polarization beam splitter and has the function of reflecting one polarization component while causing the other polarization component to pass through. The polarization component passing through the mirror 23 is received by a photodiode 24, and the electro optical modulator 22 is controlled based on the receiving signal to modulate the phase of the laser light 14.
In the modulation optical system 25, the laser light 14 is condensed by a condenser lens 26 on an AOM (Acousto-Optic Modulator) 27 made of glass (SiO2) or the like. The laser light 14 is intensity-modulated and diffused by the AOM 27 and then formed into a parallel beam by a lens 28. The laser light 14 emitted from the modulation optical system 25 is reflected by a mirror 31 and horizontally and parallelly introduced onto a movement optical table 32.
The movement optical table 32 has a beam expander 33, a mirror 34, and an objective lens 35. The laser light 14 introduced onto the movement optical table 32 is formed into a desired beam shape by the beam expander 33 and then applied onto the resist layer 13 of the original plate 11 via the mirror 34 and the objective lens 35. The original plate 11 is mounted on a turn table 37 connected to a spindle motor 36. Further, the laser light 14 is moved in the height direction of the original plate 11 and intermittently applied onto the resist layer 13 while the original plate 11 is rotated, whereby an exposure process is performed on the resist layer 13. The movement of the spot of the laser light 14 on the resist layer 13 coincides with the horizontal movement of the movement optical table 32 in a direction indicated by an arrow R.
The exposure apparatus has a control mechanism 38 used to form a latent image corresponding to a two-dimensional lattice pattern such as a (quasi)-hexagonal lattice and a (quasi)-tetragonal lattice on the resist layer 13. The control mechanism 38 has a formatter 29 and a driver 30. The formatter 29 has a polarity inversion portion, and the polarity inversion portion controls timing for applying the laser light 14 onto the resist layer 13. The driver 30 controls the acousto-optic modulator 27 with the reception of an output from the polarity inversion portion.
In the exposure apparatus, a polarity inversion formatter signal and a rotation controller are synchronized with each other for every spiral cycle so as to allow the spatial linkage of a two-dimensional pattern when a signal is generated, and then the signal is intensity-modulated by acousto-optic modulator 27. For example, by patterning with an appropriate rotation number, an appropriate modulation frequency, and an appropriate feeding pitch as well as with a constant angular velocity (CAV), a lattice pattern such as a (quasi)-hexagonal lattice and a (quasi)-tetragonal lattice may be recorded on the resist layer 13.
In the exposure apparatus having the configuration described above, the laser optical system is entirely tilted to allow the laser light 14 to be perpendicularly applied onto the curved surface of the original plate 11 as shown in
Hereinafter, a description will be given of an example of the operation of the exposure apparatus having the configuration described above. Here, a description will be given of an example of position control by the laser optical system of the exposure apparatus when the original plate 11 having an aspheric surface represented by the following formula (2) is exposed.
Hereinafter, a description will be given, with reference to
(Resist Deposition Process)
First, as shown in
(Exposure Process)
Then, as shown in
By the exposure, a plurality of latent images 13a are formed on the resist layer 13. Specifically, the plurality of latent images 13a are spirally formed when the entirety of the curved surface of the original plate 11 is seen in the central-axis direction DM. In addition, the plurality of latent images 13a are formed with a regular pattern such as a lattice pattern when a part of the curved surface of the original plate 11 is seen in an enlarged fashion in the central-axis direction DM.
For example, the start position of the exposure is the central position of the curved surface of the original plate 11 and desirably a position slightly deviating from the center of the curved surface of the original plate 11. Thus, the curved surface of the original plate 11 may have a non-exposure region RN0, in which the resist layer 13 is not exposed, at the central portion thereof. That is, in an etching process that will be described later, the curved surface of the original plate 11 may have the region RM0, in which the plurality of structures 12 are not provided, at the central portion thereof. The latent images 13a have, for example, a substantially circular shape, a substantially elliptical shape, or the like.
(Development Process)
Next, for example, a developing solution is dropped onto the resist layer 13 while the original plate 11 is rotated, whereby the resist layer 13 is developed. Thus, as shown in
(Etching Process)
Then, the curved surface of the original plate 11 is etched using the pattern (resist pattern) of the resist layer 13 formed on the curved surface of the original plate 11 as a mask. On this occasion, as shown in
Hereinafter, a description will be given, with reference to
First, front-surface treatment such as corona treatment may be applied to the convex curved surface of the device main body 1 if necessary. Next, as shown in
As the energy ray source 16, a source capable of discharging an energy ray such as an electron beam, ultraviolet light, infrared light, laser light, visible light, ionizing radiation (X-ray, α-ray, β-ray, γ-ray, or the like), a microwave, and a high-frequency wave may be used. However, the energy ray source 16 is not particularly limited.
As the transfer material 15, an energy ray curable resin composition may be desirably used. As the energy ray curable resin composition, an ultraviolet curable resin composition may be desirably used. The energy ray curable resin composition may include a filler, a functional additive, or the like if necessary.
The ultraviolet curable resin composition includes, for example, acrylate and an initiator. The ultraviolet curable resin composition includes, for example, a mono-functional monomer, a bi-functional monomer, a multi-functional monomer, or the like and specifically includes a composition in which any of the following materials is singly used or the materials are mixed together.
Examples of the mono-functional monomer may include carboxylic acid types (acrylic acid), hydroxy types (2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate), alkyl, alicyclic types (isobutyl acrylate, t-butyl acrylate, isooctyl acrylate, lauryl acrylate, stearyl acrylate, isobornyl acrylate, cyclohexyl acrylate), and other functional monomers (2-methoxyethyl acrylate, methoxyethylene glycol acrylate, 2-ethoxyethyl acrylate, tetrahydrofurfuryl acrylate, benzyl acrylate, ethylcarbitol acrylate, phenoxyethyl acrylate, N,N-dimethylaminoethyl acrylate, N,N-dimethylaminopropyl acrylic amid, N,N-dimethyl acrylic amid, acryloyl morpholine, N-isopropyl acrylic amid, N,N-dimethyl acrylic amid, N-vinyl pyrrolidone, 2-(perfluorooctyl)ethyl acrylate, 3-perfluorohexyl-2-hydroxypropyl acrylate, 3-perfluorooctyl-2-hydroxypropyl acrylate, 2-(perfluorodecyl)ethyl acrylate, 2-(perfluoro-3-methylbutyl)ethyl acrylate, 2,4,6-tribromophenol acrylate, 2,4,6-tribromophenol methacrylate, 2-(2,4,6-tribromophenoxyl)ethyl acrylate, and 2-ethylhexyl acrylate).
Examples of the bi-functional monomer may include tri(propylene glycol)diacrylate, trimethylol propane diallyl ether, and urethane acrylate.
Examples of the multi-functional monomer may include trimethylol propane triacrylate, dipenta erythritol penta and hexaacrylate, and ditrimethylol propane tetraacrylate.
Examples of the initiator may include 2,2-dimethoxy-1,2-diphenylethane-1-on, 1-hydroxy-cyclohexyl phenyl ketone, and 2-hydroxy-2-methyl-1-phenyl propane-1-on.
As the filler, both inorganic fine particles and organic fine particles may be used. As the inorganic fine particles, fine particles containing metal oxides may be, for example, used. As the metal oxides, one or more types selected from a group including silicon oxide (SiO2), titanium oxide (TiO2), zirconium oxide (ZrO2), tin oxide (SnO2), aluminum oxide (Al2O3), or the like may be, for example, used.
Examples of the functional additive may include an ultraviolet absorbent, a catalyzer, a colorant, an antistat, a lubricant, a leveling agent, a front-surface regulator, an antifoam, an antioxidant, a fire retardant, an infrared absorbent, a surfactant, a front-surface modifier, a thixotropic agent, and a plasticizer.
From the viewpoint of improving the separation of the original plate 11, it is desirable to further add an additive such as a fluorine-based additive and a silicone-based additive to the transfer material 15.
Next, as shown in
Since the optical device according to the first embodiment has the plurality of structures 2 spirally provided on the curved surface thereof at an interval of less than or equal to the wavelength of light for which reflection is to be reduced, it is possible to provide the curved surface with excellent antireflection characteristics.
In the optical device according to the first embodiment, the curved surface of the device main body 1 has the region RL0, in which the plurality of structures 2 are not provided, at the central portion thereof. Accordingly, when the optical device is applied to an optical system such as an imaging apparatus, it is possible to align the light axis of the optical system and the light axis L of the optical device with each other using the region RL0.
In the method of manufacturing the original plate according to the first embodiment, the original plate 11 is rotated and the laser light 14 is intermittently applied onto the resist layer 13 while being moved from the center to the peripheral direction of the original plate 11, whereby a spiral exposure pattern is formed. Thus, it is possible to expose the resist layer 13 accurately and with a short period of time. Accordingly, it is possible to improve the productivity of the original plate 11. In addition, since the spiral exposure pattern is employed, it is possible to reduce the fluctuation of a feeding pitch in a radius direction compared with a case in which a concentric exposure pattern is employed. That is, it is possible to reduce the fluctuation of the distance between the structures 12 in the radius direction. Thus, it is possible to reduce the occurrence of diffraction light or the like.
In the method of manufacturing the original plate according to the first embodiment, it is possible to form the structures 12 such as moth-eye structures on a curved surface such as an aspherical surface. In addition, it is possible to set the position, the size, the shape, the depth, the slant-surface shape, or the like of the plurality of structures 12 with the numeric control of the irradiation time, the irradiation energy amount, and the irradiation interval of laser light for use in exposure. Accordingly, it is possible to control the reflectivity characteristics of the optical device molded using the original plate 11.
In the method of manufacturing the optical device according to the first embodiment, it is possible to provide an optical device such as an aspherical lens, a spherical lens, and an imager cover glass with antireflection characteristics through a shape transfer using the original plate 11. Accordingly, it is possible to improve the productivity of an optical device having antireflection characteristics.
The first embodiment described above exemplifies the configuration in which the device main body 1 has the convex curved surface and the plurality of structures 2 are provided on the curved surface. However, the front surface on which the plurality of structures 2 are provided may have any shape. For example, as shown in
The first embodiment described above exemplifies the configuration in which the structures 2 are the convex portions protruding in the light-axis direction DL on the curved surface of the device main body 1. However, the structures 2 may have any configuration. For example, as shown in
(Exposure Apparatus)
As shown in
The focus control portion 61 has lenses 62 and 63 and a photo detector 64.
A collimator lens 42, beam shaping prisms 43 and 44, and a ½ wavelength plate 45 are provided between the laser diode 41 and the beam splitter 46. ½ wavelength plates 47 to 49 and a ¼ wavelength plate 50 are provided between the beam splitters 46 and 51. A collimator lens 52 and a condenser lens 53 are provided between the beam splitter 51 and an original plate 71.
Lenses 57 and 58 are provided between the beam splitters 51 and 59. A noise reduction portion 61 is provided between the beam splitter 59 and the focus control portion 61. An aperture 65 and a collimator lens 66 are provided between the laser diode 67 and the beam splitter 59.
Blue laser light (having a wavelength of 405 nm) emitted from the laser diode 41 is converted from diffused light to parallel light by the collimator lens 42. Then, with the spot shape thereof shaped by the beam shaping prisms 43 and 44, the converted light is incident on the beam splitter 46 via the ½ wavelength plate 45.
The beam splitter 46 causes the blue laser light incident from the laser diode 41 to pass through while reflecting the blue laser light reflected by a resist layer 13 of the original plate 71. Thus, the light path of the blue laser light traveling to the resist layer 13 is separated from the light path of the blue laser light returning from the resist layer 13.
The blue laser light reflected by the beam splitter 46 is condensed by the condenser lens 55 and received by the photo detector 56.
The blue laser light passing through the beam splitter 46 is incident on the beam splitter 51 via the ½ wavelength plates 47 to 49 and the ¼ wavelength plate 50.
The beam splitter 51 causes the blue laser light incident from the laser diode 41 to pass through while causing the blue laser light reflected by the resist layer 13 of the original plate 71 to pass through.
The blue laser light passing through the beam splitter 51 is incident on the resist layer 13 of the original plate 71 via the collimator lens 52 and the condenser lens 53. The blue laser light reflected by the resist layer 13 is converted from diffused light to parallel light by the condenser lens 53 and incident on the beam splitter 51 via the collimator lens 52.
Red laser light (having a wavelength of 650 nm) emitted from the laser diode 67 is converted from diffused light to parallel light by the collimator lens 66 and then incident on the beam splitter 59 via the aperture 65. The beam splitter 59 reflects the red laser light incident from the laser diode 67. The reflected light is incident on the beam splitter 51 via the lenses 58 and 57.
The beam splitter 51 reflects the red laser light incident from the laser diode 67 toward the resist layer 13 of the original plate 71 while reflecting the red laser light reflected by the resist layer 13 of the original plate 71 toward the beam splitter 59.
The red laser light reflected by the beam splitter 51 is incident on the beam splitter 59 via the lenses 57 and 58. The beam splitter 59 causes the red laser light incident from the beam splitter 51 to pass through. The light passing through the beam splitter 59 is received by the photo detector 56 via the noise reduction portion 60 and the lenses 62 and 63.
In the exposure apparatus having the configuration described above, it is possible to perform exposure with the adjustment of differences from the tracks shown in
A second embodiment will describe a method of manufacturing an optical device. Specifically, a first duplicate original plate (hereinafter referred to as a “master original plate”) is manufactured based on an original plate, and then a second duplicate original plate (hereinafter referred to as a “mother original plate”) is manufactured based on the master original plate. The optical device is manufactured using the mother original plate. In the following example, an optical device having a concave curved surface shown in
Hereinafter, a description will be given, with reference to
(Method of Manufacturing Original Plate)
First, as shown in
Then, as shown in
Next, for example, a developing solution is dropped onto the resist layer 13 while the original plate 71 is rotated, whereby the resist layer 13 is developed. Thus, as shown in
Then, the curved surface of the original plate 71 is etched using the pattern (resist pattern) of the resist layer 13 formed on the curved surface of the original plate 11 as a mask. On this occasion, the etching process is controlled such that the original plate 71 is etched in a central-axis direction DM. Thus, as shown in
(Method of Manufacturing Master Original Plate)
First, as shown in
(Method of Manufacturing Mother Original Plate)
Next, as shown in
(Method of Manufacturing Optical Device)
Next, as shown in
A third embodiment will describe a method of manufacturing the optical device by injection molding.
Hereinafter, a description will be given, with reference to
Next, a melted resin material 84 is filled in the cavity 83. As the resin material, a thermoplastic resin such as an acrylic resin (PMMA), a polycarbonate resin (PC), and a cycloolefin polymer resin (COP) may be, for example, used. The resin material is heated and melted in a material supply apparatus (not shown) and supplied to the cavity 83 via a runner 85 that serves as a supply path.
Then, the melted resin material 84 filled in the cavity 83 is cooled, solidified, and clamped. Note that when the resin material 84 is clamped, the movable die 81 is moved so as to be much closer to the fixed die 82. Thus, the resin material 84 filled in the cavity 83 is pressed, whereby the fine concave and convex shape of the molding surface 81s of the movable die 81 is reliably transferred.
Next, after the resin material 84 is sufficiently cooled and solidified, the movable die 81 is moved so as to be distant from the fixed die 82 while the solidified resin material 84 is released from the movable die 81 and the fixed die 82. Through the steps described above, the optical device is obtained as desired.
A fourth embodiment will describe a method of manufacturing the optical device in which a fine structure pattern is transferred onto the front surface of a glass member by thermal pressure.
Hereinafter, a description will be given, with reference to
Then, as shown in
As shown in
The imaging device 113 is fixed at the prescribed position of the package 112 by a die bonding agent 115.
The imaging device 113 is electrically connected to the package 112 by a wire 116. The peripheral portions of the antireflection cover glass 114 and the package 112 are bonded together by an adhesive 117 such as an epoxy-based seal resin.
As the imaging device 113, a CCD (Charge Coupled Device) imaging sensor device, a CMOS (Complementary Metal-Oxide Semiconductor) imaging sensor device, or the like may be, for example, used.
The antireflection cover glass 114 is an example of the optical device and has a cover glass main body 114a, a plurality of structures 114b, and an AR (AntiReflection) coat 114c. The plurality of structures 114b are provided on one of the principal surfaces of the cover glass main body 114a on a side opposite to the imaging device 113. The AR coat 114c is provided on the other of the principal surfaces of the cover glass main body 114a on a side on which light from a subject is incident. The plurality of structures 114b are the same as the plurality of structures 2 of the first embodiment. Note that instead of the AR coat 114c, the plurality of structures 114b may be provided on the front surface on the side on which light from a subject is incident.
The antireflection cover glass 114 may further have an optical low-pass filter and an infrared reduction filter (IR reduction filter) between the cover glass main body 114a and the AR coat 114c.
In the device package 111 according to the fifth embodiment, the plurality of structures 114b are provided on one of the principal surfaces of the cover glass main body 114a on the side opposite to the imaging device 113. Accordingly, it is possible to obtain an excellent antireflection effect not only for light reflected by the front surface of the imaging device 113 but for light reflected by the front surface of a structure such as the wire 116.
As shown in
The imaging device 134 is mounted at a prescribed position on the front surface of the circuit substrate 136.
The housing 135 is fixed to the front surface of the circuit substrate 136 so as to accommodate the imaging device 134. The lens 132 and the IR reduction filter 133 are accommodated in the housing 135. The lens 132 and the IR reduction filter 133 are provided in this order from a subject to the imaging device 134 with a prescribed interval therebetween. Light from a subject is condensed by the lens 132 and formed into an image on the imaging surface of the imaging device 134 via the IR reduction filter 133. The lens 132 and the IR reduction filter 133 have the plurality of structures 2 of the first embodiment on the front surfaces thereof. Here, the front surfaces represent at least one of incident surfaces on which light from a subject is incident and emission surfaces from which the light incident from the incident surfaces is emitted.
As shown in
The imaging optical system 203 has a lens 211, a light-amount adjuster 212, a semi-transmission mirror 213, a device package 214a, and an auto focus sensor 215. The lens 211, the light-amount adjuster 212, and the semi-transmission mirror 213 are provided in this order from the tip end of the lens barrel 202 to the device package 214a. At least one type selected from a group including the lens 211, the light-amount adjuster 212, the semi-transmission mirror 213, and the device package 214a has an antireflection function. The auto focus sensor 215 is provided at a position at which light LI reflected by the semi-transmission mirror 213 is receivable. The imaging apparatus 200 may further have a filter 216 if necessary. When the imaging apparatus 200 has the filter 216, the filter 216 may have an antireflection function. Hereinafter, the respective constituents and the antireflection function will be described sequentially.
(Lens)
The lens 211 condenses the light LI from a subject toward the device package 214a.
(Light-Amount Adjuster)
The light-amount adjuster 212 is an aperture unit that adjusts a size of an aperture opening about the light axis of the imaging optical system 203. The light-amount adjuster 212 has, for example, a pair of aperture blades and an ND (Neutral Density) filter that reduces a transmission amount of light. As the driving system of the light-amount adjuster 212, a system in which the pair of aperture blades and the ND filter are driven by one actuator and a system in which the pair of aperture blades and the ND filter are driven by two separate actuators may be used. However, the driving system is not particularly limited to such systems. As the ND filter, a filter whose transmittance or density is constant or a filter whose transmittance or density changes gradually may be used. In addition, the number of the ND filters is not limited to one, but a plurality of laminated ND filters may be used.
(Semi-Transmission Mirror)
The semi-transmission mirror 213 is a mirror that causes a part of incident light to pass through and reflects the rest of the light. Specifically, the semi-transmission mirror 213 reflects a part of the light LI condensed by the lens 211 toward the auto focus sensor 215 while causing the rest of the light LI to pass through toward the device package 214a. Examples of the shape of the semi-transmission mirror 213 may include, but not particularly limited to, a sheet shape and a plate shape. Here, it is defined that a sheet includes a film.
(Device Package)
The device package 214a receives light passing through the semi-transmission mirror 213, converts the received light into an electric signal, and outputs the signal to a signal processing circuit (not shown). As the device package 214a, the device package 111 according to the fifth embodiment may be used.
(Auto Focus Sensor)
The auto focus sensor 215 receives light reflected by the semi-transmission mirror 213, converts the received light into an electric signal, and outputs the signal to a control circuit (not shown).
(Filter)
The filter 216 is provided at the tip end of the lens barrel 202 or provided in the imaging optical system 203. Note that
As the filter 216, a filter generally provided at the tip end of the lens barrel 202 or provided in the imaging optical system 203 is used and not particularly limited. Examples of the filter include a polarization (PL) filter, a sharp cut (SC) filter, a color emphasizing-and-effecting filter, a neutral density (ND) filter, a light balancing (LB) filter, a color correction (CC) filter, a white balance acquisition filter, and a lens protection filter.
(Antireflection Function)
In the imaging apparatus 200, the light LI from a subject passes through the plurality of optical devices (i.e., the lens 211, the light-amount adjuster 212, the semi-transmission mirror 213, and the cover glass of the device package 214a) before reaching the imaging device in the device package 214a via the tip end of the lens barrel 202. In the following description, the optical devices through which the light LI from a subject passes before reaching the imaging device after being taken in the imaging apparatus 200 will be referred to as “transmission optical devices.” When the imaging apparatus 200 further has the filter 216, the filter 216 is also identified as one of the transmission optical devices.
At least one of the plurality of transmission optical devices has the plurality of structures 2 of the first embodiment at the front surface thereof. Here, the front surface of the transmission optical devices represents at least one of an incident surface on which the light LI from a subject is incident and an emission surface from which the light LI incident from the incident surface is emitted.
Specifically, the device package 111 according to the fifth embodiment may be, for example, used as the device package 214a. The transmission optical devices may desirably have a region RL0, in which the plurality of structures 2 are not provided, at the central portions of the curved surfaces or the plane surfaces thereof. The region RL0 is desirably provided on the optical axis of the imaging optical system 203.
The seventh embodiment described above exemplifies a case in which the present technology is applied to a digital camera (digital still camera) that serves as an imaging apparatus. However, the present technology may be applied to any other cases. An eighth embodiment of the present technology will describe an example in which the present technology is applied to a digital video camera.
As shown in
(Lens Groups)
The first lens group L1 and the third lens group L3 are fixed lenses. The second lens group L2 is a zoom lens. The fourth lens group L4 is a focus lens.
(Device Package)
The device package 302 converts incident light into an electric signal and supplies the signal to a signal processing unit (not shown). As the device package 302, the device package 111 according to the fifth embodiment may be used.
(Low-Pass Filter)
The low-pass filter 303 is provided on the front-surface side of the device package 302, i.e., on the light incident surface of the cover glass of the device package 302. The low-pass filter 303 is used to reduce a false signal (moire) generated when a striped image or the like having a pitch close to a pixel pitch is taken, and is made of, for example, artificial crystal.
The filter 304 is, for example, used to reduce the infrared region of light incident on the device package 302, prevent spectral floating in a near-infrared region (630 nm to 700 nm), and make light intensity in a visible region (400 nm to 700 nm) even. The filter 304 is constituted by, for example, an infrared reduction filter (hereinafter referred to as an “IR reduction filter”) 304a and an IR reduction coat layer 304b, i.e., an IR reduction coat laminated on the IR reduction filter 304a. Here, the IR reduction coat layer 304b is formed on, for example, at least one of the surface of the IR reduction filter 304a on the side of a subject and the surface of the IR reduction filter 304a on the side of the device package 302.
The motor 305 moves the fourth lens group L4 based on a control signal supplied from a control unit (not shown). The iris blade 306 is used to adjust an amount of light incident on the device package 302 and driven by a motor (not shown).
The electric dimmer device 307 is used to adjust the amount of light incident on the device package 302. The electric dimmer device 307 is an electric dimmer device made of a liquid crystal containing at least a dye-based pigment, e.g., an electric dimmer device made of a dichroic GH liquid crystal.
(Antireflection Function)
In the imaging apparatus 301, light from a subject passes through the plurality of optical devices (the first lens group L1, the second lens group L2, the electric dimmer device 307, the third lens group L3, the fourth lens group L4, the filter 304, and the cover glass with the low-pass filter 303) before reaching the imaging device in the device package 302. In the following description, the optical devices through which light LI from a subject passes before reaching the imaging device will be referred to as “transmission optical devices.” At least one of the plurality of transmission optical devices has the plurality of structures 2 of the first embodiment on the front surface thereof. Specifically, the device package 111 according to the fifth embodiment may be, for example, used as the device package 302. The transmission optical devices may desirably have a region RL0, in which the plurality of structures 2 are not provided, at the central portions of the curved surfaces or the plane surfaces thereof. The region RL0 is desirably provided on the optical axis of the imaging optical system.
A ninth embodiment will describe an example of an electronic apparatus having the camera module 131 according to the sixth embodiment.
As shown in
Hereinafter, the present technology will be specifically described based on Examples but is not limited only to the Examples.
First, a glass original plate having a convex aspherical surface was prepared. Next, an inorganic resist layer was evenly formed on the aspherical surface of the glass original plate.
(Exposure Process)
Then, the glass original plate was rotated and laser light was intermittently applied while being moved from the center to the peripheral direction (radius direction) of the aspherical surface of the glass original plate, whereby the inorganic resist layer formed on the aspherical surface of the glass original plate was exposed. On this occasion, a laser optical system was controlled such that the laser light was kept perpendicularly incident on the aspherical surface of the glass original plate. In addition, the laser optical system was controlled such that a plurality of latent images were spirally formed as a whole and that a substantially hexagonal lattice pattern was locally formed when the aspherical surface of the glass original plate was seen in the central-axis direction thereof. Note that the laser light was applied at a feeding pitch of 200 nm in the radius direction of the glass original plate and applied at a feeding pitch of 230 nm in the rotation direction thereof.
(Development Process)
Next, for example, a developing solution was dropped onto the inorganic resist layer while the glass original plate was rotated, whereby the inorganic resist layer was developed in a direction perpendicular to the aspherical surface of the glass original plate. Thus, a plurality of opening portions corresponding to the latent images were formed on the inorganic resist layer.
(Etching Process)
Then, the aspherical surface of the glass original plate was etched using the inorganic resist layer having the plurality of opening portions as a mask. On this occasion, the etching process was controlled such that glass original plate was etched in the central-axis direction thereof. Thus, a plurality of structures were formed on the aspherical surface of the glass original plate. Next, the inorganic resist layer remaining on the aspherical surface of the glass original plate was removed by ashing.
(Transfer Process)
Then, an ultraviolet curable resin composition was interposed between the concave aspherical surface of a plano-concave lens and the convex aspherical surface (molding surface) of the glass original plate, brought into intimate contact with both the aspherical surfaces, and cured by the application of ultraviolet light. Next, the plano-concave lens integrated with the cured ultraviolet curable resin was separated from the aspherical surface of the glass original plate. Thus, a plurality of structures were spirally formed on the concave aspherical surface of the plano-concave lens. Note that the column pitch of the structures between the adjacent portions of the spiral was 200 nm and the pitch of the structures in the peripheral direction of the spiral was 230 nm. In addition, the diameter of the bottom surfaces of the structures was 200 nm, and the height of the structures was 200 nm. In the way described above, an antireflection plano-concave lens was obtained as desired.
A four-layer AR coat was formed on the concave aspherical surface of a plano-concave lens, whereby an antireflection plano-concave lens was obtained.
(Evaluation of Reflection Spectrums)
Each of the reflection spectrums of the antireflection plano-concave lenses of Example 1 and Comparative Example 1 was evaluated as follows. First, a black tape was adhered to the plane side of the antireflection plano-concave lens.
Next, light was incident at an incident angle of 5° or 45° on a concave aspherical surface on a side opposite to the side where the black tape is adhered to evaluate the reflection spectrum (wavelength band: 400 nm to 700 nm).
Reflection Spectrum at Incident Angle of 5°
As for Example 1 in which the plurality of structures are provided on the concave aspherical surface, the reflection spectrum hardly depends on wavelengths and is almost flat. On the other hand, as for Comparative Example 1 in which the four-layer AR coat is provided on the concave aspherical surface, the reflection spectrum is almost flat but tends to slightly increase near a wavelength of 400 nm.
Reflection Spectrum at Incident Angle of 45°
As for Example 1 in which the plurality of structures are provided on the concave aspherical surface, it appears that the reflection spectrum tends to increase in a range of 500 nm to 700 nm. On the other hand, as for Comparative Example 1 in which the four-layer AR coat is provided on the concave aspherical surface, it appears that the reflection spectrum tends to increase in a range of 400 nm to 700 nm. The increasing degree of the reflection spectrum of Comparative Example 1 is greater than that of Example 1.
The embodiments of the present technology are described above. However, the present technology is not limited to the embodiments described above but may be modified in various ways based on the technical ideas of the present technology.
For example, the configurations, the methods, the processes, the shapes, the materials, the numerical values, or the like of the embodiments described above are only for illustration. If necessary, different configurations, methods, processes, shapes, materials, numerical values, or the like may be used.
In addition, the configurations, the methods, the processes, the shapes, the materials, the numerical values, or the like of the embodiments described above may be combined together so as not to depart from the spirit of the present technology.
In addition, the present technology may employ the following configurations.
(1-1) An optical device, including:
a curved surface; and
a plurality of structures spirally provided on the curved surface at an interval of less than or equal to a wavelength of light for which reflection is to be reduced,
(1-2) The optical device according to (1-1), in which
a spiral formed by the plurality of structures and the center of the curved surface correspond to or substantially correspond to each other.
(1-3) The optical device according to (1-1) or (1-2), in which
the curved surface has a shape symmetrical with respect to a light axis, and
the center of the curved surface includes one of an apex portion and a bottom portion of the curved surface.
(1-4) The optical device according to any one of (1-1) to (1-3), in which
the curved surface includes one of a spherical surface and an aspherical surface.
(1-5) The optical device according to any one of (1-1) to (1-4), in which
the curved surface includes one of a convex shape and a concave shape.
(1-6) The optical device according to any one of (1-1) to (1-5), in which
the plurality of structures contain an ultraviolet curable resin.
(1-7) The optical device according to any one of (1-1) to (1-6), in which
the light includes visible light.
(1-8) The optical device according to any one of (1-1) to (1-7), in which
the plurality of structures are arranged in a lattice pattern on the curved surface.
(1-9) An original plate, including:
a curved surface; and
a plurality of structures spirally provided on the curved surface at an interval of less than or equal to a wavelength of light for which reflection is to be reduced,
(1-10) An imaging apparatus, including:
the optical device according to any one of (1-1) to (1-9).
(1-11) The imaging apparatus according to (1-10), further including:
an optical system having the optical device, in which
the region is provided on a light axis of the optical system.
(1-12) A method of manufacturing an original plate, including:
perpendicularly applying light onto a curved surface of the original plate to form spiral exposure portions on a resist provided on the curved surface of the original plate at an interval of less than or equal to a wavelength of light for which reflection is to be reduced;
developing a resist layer having the plurality of exposure portions to form a resist pattern; and
etching the original plate in a central-axis direction of the curved surface using the resist pattern as a mask to form a plurality of structures on the curved surface.
Moreover, the present technology may employ the following configurations.
(2-1) A method of manufacturing an original plate, including:
exposing a resist layer formed on one of a curved surface and a plane surface of the original plate in a prescribed pattern;
developing the resist layer to form a mask having a plurality of opening portions; and
etching one of the curved surface and the plane surface of the original plate in a central-axis direction of the original plate based on a difference in an etching rate between the plurality of opening portions and a remaining portion of the mask to form a plurality of structures on one of the curved surface and the plane surface of the original plate.
(2-2) The method of manufacturing the original plate according to (2-1), in which
the exposure is controlled such that an incident direction of light corresponds to a normal-line direction of one of the curved surface and the plane surface when the original plate is rotated about a central axis thereof and a focal position of the light for use in the exposure is moved from a center to a peripheral direction of the original plate.
(2-3) The method of manufacturing the original plate according to (2-1) or (2-2), in which,
in the exposure, an application time, an application energy amount, and an application interval of the light for use in the exposure are numerically controlled.
(2-4) The method of manufacturing the original plate according to any one of (2-1) to (2-3), in which,
in the exposure, the application time, the application energy amount, and the application interval are changed for each exposure point to appropriately adjust a position, a size, a shape, a depth, and a slant-surface shape of the plurality of structures obtained by the etching.
(2-5) The method of manufacturing the original plate according to any one of (2-1) to (2-4), further including
manufacturing a duplicate original plate based on the original plate.
(2-6) The method of manufacturing the original plate according to (2-5), in which
the duplicate original plate is manufactured in such a way that a conductive layer is deposited on one of the curved surface and the plane surface of the original plate by one of sputtering and deposition and then a metal layer is formed on the conductive layer by electroforming.
(2-7) The method of manufacturing the original plate according to any one of (2-1) to (2-6), in which
the curved surface of the original plate includes a spherical surface.
(2-8) The method of manufacturing the original plate according to any one of (2-1) to (2-7), in which
the plurality of structures are provided at an interval of less than or equal to a wavelength of light for which reflection is to be reduced.
(2-9) The method of manufacturing the original plate according to any one of (2-1) to (2-8), in which
the structures include moth-eye structures.
(2-10) The method of manufacturing the original plate according to any one of (2-1) to (2-9), in which
the resist layer contains an incomplete oxide of transition metal.
(2-11) A method of manufacturing an optical device, including:
exposing a resist layer formed on one of a curved surface and a plane surface of the original plate in a prescribed pattern;
developing the resist layer to form a mask having a plurality of opening portions;
etching one of the curved surface and the plane surface of the original plate in a central-axis direction of the original plate based on a difference in an etching rate between the plurality of opening portions and a remaining portion of the mask to form a plurality of structures on one of the curved surface and the plane surface of the original plate; and
forming the optical device having a plurality of structures using one of the original plate and a duplicate original plate of the original plate.
(2-12) The method of manufacturing the optical device according to (2-11), in which
the optical device having the plurality of structures is formed in such a way that a shape-transfer is performed on an ultraviolet curable resin using one of the original plate and the duplicate original plate.
(2-13) The method of manufacturing the optical device according to (2-11) or (2-12), in which
the optical device includes a lens having an aspherical shape, and
the plurality of structures are formed on the aspherical surface.
(2-14) An imaging device package, including:
an imaging device; and
a package accommodating the imaging device,
the package having a light transmission unit in which a plurality of structures are spirally provided at an interval of less than or equal to a wavelength of light for which reflection is to be reduced.
(2-15) The imaging device package according to (2-14), in which
the light transmission unit includes a glass plate.
(2-16) The imaging device package according to (2-14) or (2-15), in which
a spiral formed by the plurality of structures has a region, in which the plurality of structures are not provided, at a central portion thereof.
(2-17) The imaging device package according to any one of (2-14) to (2-16), in which
the plurality of structures are provided on one surface of the glass plate, and a multi-layer antireflection film is provided on the other surface thereof.
(2-18) The imaging device package according to (2-17), in which
the surface on which the plurality of structures are provided opposes the imaging device.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2014-074950 | Mar 2014 | JP | national |
