JP2009128522A - Light-absorbing antireflection structure, optical unit and lens barrel unit equipped with same and optical device equipped with them - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light-absorbing antireflection structure in which reflection is satisfactorily suppressed. <P>SOLUTION: An inner circumferential surface 10 of a lens barrel 5 is formed as a rough surface having surface roughness larger than a wavelength of incident light and on the inner circumferential surface 10, a plurality of fine rugged parts 11 arranged with a mutual average distance smaller than the wavelength of the incident light are formed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a light-absorbing antireflection structure, an optical unit and a lens barrel unit including the same, and an optical device including the same.

  For example, in Patent Document 1, a black material is applied to a substrate surface to form a coating film, and the coating film is dried while forming a Benard cell to obtain a light absorbing member having excellent light absorption. .

In addition, in the patent document 2, the present inventors have proposed a light absorbing member made of a black material in which a fine uneven structure is formed on a curved surface.
JP 2003-266580 A WO2005 / 088355

  However, the conventional light absorbing members described in Patent Document 1 and Patent Document 2 have a problem that light reflection cannot be sufficiently suppressed. In detail, the light absorbing member described in Patent Document 2 has a problem that, although high reflection suppression effect is obtained except that regular reflection occurs, generation of regular reflection cannot be sufficiently suppressed.

  This invention is made | formed in view of such a point, The place made into the objective is to provide the light absorptive antireflection structure body in which reflection was fully suppressed.

  In order to achieve the above object, a light-absorbing antireflection structure according to the present invention suppresses reflection of light having a predetermined wavelength or more and absorbs light whose reflection is suppressed. And having a rough surface having a surface roughness larger than a predetermined wavelength, and a plurality of micro uneven portions arranged so that an average distance between them is not more than the predetermined wavelength is formed on the rough surface. It is characterized by being.

  The optical unit according to the present invention is arranged so that light from the optical system and the optical system is incident thereon, and suppresses reflection of light from the optical system and absorbs light from the optical system. A light-absorbing anti-reflection structure, the surface on which light from the optical system is incident is formed on a rough surface having a surface roughness larger than the wavelength of light from the optical system, The surface is formed with a plurality of minute concavo-convex portions arranged so that the mutual average distance is equal to or less than the wavelength of light from the optical system.

  A lens barrel unit according to the present invention includes an optical system and a lens barrel that houses the optical system therein, suppresses reflection of light from the optical system, and absorbs light from the optical system, The lens barrel is formed with a rough surface whose inner peripheral surface is larger in surface roughness than the wavelength of light from the optical system, and the average distance between the inner peripheral surfaces is the wavelength of the light from the optical system. A plurality of minute concavo-convex portions arranged as follows are formed.

  An optical device according to the present invention includes the optical unit or the lens barrel unit according to the present invention.

  According to the present invention, a high reflection suppression effect can be realized.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Here, the optical device embodying the present invention will be described by taking an imaging device as an example. However, the optical device according to the present invention is not limited to the imaging device, for example, other devices such as a lighting device and a projector. It may be an optical device.

  FIG. 1 is a schematic diagram illustrating a configuration of a main part of an imaging apparatus 1 according to the present embodiment.

  The imaging device 1 includes a device body 3 and a lens barrel unit 2 as an optical unit. Although an example in which the lens barrel unit 2 is attached to the apparatus main body 3 will be described here, the lens barrel unit 2 may be configured to be detachable from the apparatus main body 3, for example.

  The lens barrel unit 2 includes a cylindrical (specifically cylindrical) lens barrel 5 and an optical system 4 housed in the lens barrel 5. On the other hand, the apparatus main body 3 includes an image sensor 6 disposed so as to be positioned on the optical axis AX of the optical system 4. The optical system 4 is for forming an optical image on the image pickup surface of the image pickup device 6, and the optical image formed on the image pickup surface by the optical system 4 is converted into an electric signal by the image pickup device 6. For example, it is stored in a memory (may be an external memory) provided in the apparatus main body 3, or is output to another apparatus via a cable connected to the apparatus main body 3. Yes. Note that the imaging device 6 can be configured by, for example, a charge coupled device (CCD), a complementary metal-oxide semiconductor (COMS), or the like.

  The optical system 4 is not particularly limited as long as it can form an optical image on the image pickup surface of the image pickup device 6. For example, as shown in FIG. 1, the first lens (group) L1 is used. The second lens (group) L2 and the third lens (group) L3 may be configured by three lenses (group). Further, at least one of the three lenses (groups) L1 to L3 may be displaceable in the direction of the optical axis AX so that focusing and / or zooming is possible.

  FIG. 2 is a front view of the lens barrel 5.

  FIG. 3 is an enlarged cross-sectional view of a part of the lens barrel 5.

  FIG. 4 is a cross-sectional view in which a part of the lens barrel 5 is further enlarged.

  The lens barrel 5 is configured to absorb light (generally visible light) incident on the optical system 4 from the image side. For this reason, the lens barrel 5 absorbs the luminous flux that is incident on the lens barrel unit 2 from the image side and that has a comprehensive angle of view or more and the reflection on the surface of the lens that constitutes the optical system 4. . Therefore, the imaging apparatus 1 according to the present embodiment has high optical performance with the occurrence of ghosts and flares being suppressed.

  Specifically, a configuration in which a light-absorbing material (for example, a dye or a pigment) is dispersed and mixed in the lens barrel 5 may be employed. Alternatively, the lens barrel 5 may be formed of a substantially light absorbing material. As a light-absorbing material that absorbs visible light, black dyes obtained by mixing a plurality of pigments such as cyan, magenta, and yellow (for example, Plato Black 8950 and 8970 manufactured by Arimoto Chemical Co., Ltd.), Carbon black etc. are mentioned. The base material in which these pigments and dyes are dispersed and mixed is, for example, a resin such as glass, an acrylic resin or a polycarbonate resin (preferably a resin having a glass transition temperature of 90 ° C. or higher and 170 ° C. or lower) or a glass fiber-containing resin. May be. Furthermore, from the viewpoint of suppressing dust and dust from adhering to the lens barrel 5, the lens barrel 5 preferably contains an antistatic material. The lens barrel 5 preferably has high light resistance (particularly light resistance to ultraviolet light).

  Furthermore, in the imaging apparatus 1 according to the present embodiment, a plurality of minute uneven portions 11 for suppressing light reflection are formed on the inner peripheral surface 10 of the lens barrel 5. Specifically, the entire length of the inner peripheral surface 10 of the lens barrel 5 is a period of a predetermined wavelength or less (here, light incident from the optical system 4, that is, a period of less than the wavelength of visible light, preferably incident from the optical system 4. The period is equal to or shorter than the shortest wavelength of the light to be transmitted, that is, the “predetermined wavelength” here means a wavelength for suppressing reflection and a wavelength for suppressing reflection. A plurality of arrayed minute uneven portions 11 are formed (hereinafter, a structure in which a plurality of minute uneven portions 11 are regularly formed may be abbreviated as “SWS”). For this reason, an abrupt refractive index change between the lens barrel 5 and the air layer is suppressed, and the refractive index gradually changes in the surface layer portion of the inner peripheral surface 10 formed by the minute irregularities 11. Therefore, as shown in FIG. 5, the surface reflection on the inner peripheral surface 10 of the lens barrel 5 is further effectively suppressed by forming the minute irregularities 11 (SWS) on the inner peripheral surface 10.

  The shape of the minute uneven portion 11 is not particularly limited as long as it has a function of gradually changing the refractive index at the interface between the inner peripheral surface 10 of the lens barrel 5 and the air layer, For example, a concave portion or convex portion having a substantially conical shape (the top portion may be chamfered or R-chamfered), a concave or convex portion having a truncated pyramid shape, a linear shape (the cross-sectional shape is a triangular shape (the top portion is R-chamfered) It may be a trapezoidal shape, a rectangular shape, or the like).

  Further, from the viewpoint of realizing a high reflection suppressing effect, the adjacent minute uneven portions 11 in a plan view from the normal direction of the reference surface of the inner peripheral surface 10 (which is formed on a rough surface) of the minute uneven portions 11 are provided. The “reference plane” refers to a plane obtained by cutting off the fine irregularities 11 and the roughness shape as a high frequency component) from the image side to the lens barrel unit 2. It is preferable that it is below the wavelength of the light which injects into. On the other hand, the height of the minute uneven portion 11 (strictly speaking, it is defined by the distance from the reference surface to the top in the normal direction of the reference surface of the inner peripheral surface 10 (formed on the rough surface)). It is preferably 0.4 or more times the wavelength of light incident on the lens barrel unit 2 from the side, more preferably 1 or more times, and even more preferably 3 or more times the wavelength. Strictly speaking, when light having a certain wavelength width is incident as in the present embodiment, the period of the minute irregularities 11 is preferably equal to or less than the shortest wavelength of incident light. Is preferably 0.4 times or more (preferably 1 time or more, more preferably 3 times or more) of the longest wavelength of incident light.

  In the design of the imaging device 1, the minute uneven portion 11 does not necessarily have to exhibit a reflection suppressing effect with respect to all incident light. For example, although the wavelength of incident light covers a wide wavelength range such as ultraviolet light, near-ultraviolet light, visible light, near-infrared light, and infrared light, the image sensor 6 detects only light in the range of 400 nm to 1000 nm. In such a case, it is not always necessary to suppress reflection of light having a wavelength of less than 400 nm and light having a wavelength of greater than 1000 nm. In this case, the period of the minute uneven portion 11 may be 400 nm or less. preferable. On the other hand, the height of the fine irregularities 11 is preferably 0.4 times or more of 1000 nm, that is, 400 nm or more.

  The minute irregularities 11 may be formed so that their heights are different from each other on each part of the inner peripheral surface 10 (for example, each part having a size of 1 mm square). Are preferably formed to be substantially the same. Further, for example, when the minute concavo-convex portion 11 is a cone-shaped concave portion or a cone-shaped convex portion, the central axes connecting the bottom center and the top portion of the cone are substantially parallel to each other. It is preferable to be formed as follows. In this case, the lens barrel 5 can be easily manufactured by injection molding. On the other hand, for the same reason, when the minute uneven portion 11 is a linear concave portion or a linear convex portion having a triangular cross section, the central axis connecting the bottom center and the top portion in the cross section is For example, it is preferable that the respective portions having a size of 1 mm square are substantially parallel to each other. The minute irregularities 11 need only be arranged so that the average distance between them is equal to or less than the predetermined wavelength, and need not be periodic.

  As described above, in the present embodiment, the lens barrel 5 absorbs light incident on the lens barrel unit 2 from the image side (strictly speaking, light having a wavelength at which reflection should be suppressed, and) Since a plurality of minute uneven portions 11 for suppressing light reflection are formed on the inner peripheral surface 10, light reflection on the inner peripheral surface 10 of the lens barrel 5 is greatly reduced. However, for example, when the inner peripheral surface 10 is a smooth surface, regular reflection on the inner peripheral surface 10 cannot be sufficiently suppressed.

  FIG. 6 is a graph showing the reflected light intensity of light incident at an incident angle of 45 degrees.

  As shown in FIG. 6, when the minute uneven portion 11 is formed on the smooth surface, reflected light having an emission angle of about 45 degrees, that is, regular reflection is observed. As described above, when the inner surface 10 on which the minute concavo-convex portion 11 is formed is a smooth surface, regular reflection of light incident on the lens barrel unit 2 from the image side cannot be sufficiently suppressed. On the other hand, as shown in FIG. 6, when SWS is formed on a rough surface having a surface roughness larger than the wavelength of incident light, regular reflection is not substantially observed. Here, in the present embodiment, as shown in FIGS. 3 and 4, the inner peripheral surface 10 of the lens barrel 5 is formed on a rough surface having a surface roughness larger than the wavelength of incident light. Specifically, the inner peripheral surface 10 is formed with a surface roughness larger than the wavelength of incident light with an average length RSm of a roughness curve element defined by ISO 4287: 1997 (corresponding to JIS B0601: 2001). Yes. Therefore, in the lens barrel 5 in the present embodiment, regular reflection on the inner peripheral surface 10 is also sufficiently suppressed. Therefore, it is possible to realize the imaging device 1 in which the occurrence of ghosts and flares is sufficiently suppressed. However, the effect of suppressing the occurrence of regular reflection tends to decrease if the surface roughness of the inner peripheral surface 10 is too large. A preferable range of the average length RSm of the roughness curve elements of the inner peripheral surface 10 is 500 μm or less. More preferably, it is 100 micrometers, More preferably, it is 50 micrometers.

  Furthermore, the reflectance with respect to incident light having a relatively large incident angle can be reduced by making the inner peripheral surface 10 forming the minute uneven portion 11 rough surface having a surface roughness larger than the wavelength of incident light. . Hereinafter, this effect will be described in detail with reference to FIGS.

  FIG. 7 is a graph showing the correlation between the incident angle and the reflectance on the surface on which the minute irregularities 11 are formed. 7 is the angle between the normal vector N2 of the tangential plane 13 of the roughness shape of the inner peripheral surface 10 and the normal vector N1 of the reference surface 12 of the inner peripheral surface 10 (FIG. 9). Reference).

  As shown in FIG. 7, when θ is 0 degrees (in other words, a smooth surface), even when the minute uneven portion 11 is formed, for example, a large incident angle exceeding 50 degrees, In the case of a large incident angle exceeding 70 degrees, the reflectance tends to increase as the incident angle increases.

  Usually, in an optical element such as a lens that transmits light, there is little need to consider such reflection of incident light having a large incident angle. However, in the case of the light-absorbing antireflection structure (so-called black body) as in the present embodiment, only light having a relatively small incident angle such as 45 degrees or less is not necessarily incident. It is preferable to have a configuration that suppresses reflection of relatively large incident light. The problem of suppressing reflection of incident light having a relatively large incident angle is unique to the light-absorbing antireflection structure.

  In this embodiment, since the inner peripheral surface 10 is formed as a rough surface, the incident angle is substantially reduced on average as compared with the case where the inner peripheral surface 10 is a smooth surface. Therefore, as shown in FIG. 5, in this embodiment, reflection of incident light having a relatively large incident angle can be effectively suppressed. On the other hand, as shown in FIG. 5, when SWS is formed on the smooth surface, incident light having a relatively large incident angle can be provided for incident light having a relatively small incident angle, although a relatively high antireflection effect can be imparted. A sufficient antireflection effect still cannot be imparted to light. That is, when the surface on which the SWS is formed is a smooth surface, it is difficult to sufficiently suppress the angle dependency of the reflectance.

  From the viewpoint of further effectively suppressing the reflection of incident light having a relatively large incident angle, as shown in FIG. 9, the tangential plane of the roughness shape of the inner peripheral surface 10 (specifically, the minute irregularities of the inner peripheral surface 10 Tangent plane of the shape (roughness shape) obtained by cutting off the minute uneven portion 11 as a high frequency component from the shape including the portion 11) and the normal vector N 1 of the reference surface 12 of the inner peripheral surface 10. It is preferable that a ratio per unit area (for example, 1 mm square) occupied by a portion having an angle (θ) of 5 degrees or less is less than 80%. In other words, the ratio per unit area occupied by the portion where θ is 5 degrees or more is preferably 20% or more. Moreover, it is preferable that the ratio per unit area which the part whose (theta) is 10 degrees or less occupies is less than 90%. In other words, it is preferable that the ratio per unit area occupied by the portion where θ is 10 degrees or more is 10% or more. In this case, the reflectance of light having an incident angle of 89 degrees can be reduced by about 30% or more as compared with the case where the minute irregularities 11 are formed on the smooth surface.

  More preferably, the ratio per unit area occupied by the portion where θ is 5 degrees or less is preferably less than 50%. In other words, the ratio per unit area occupied by the portion where θ is 5 degrees or more is preferably 50% or more. Moreover, it is preferable that the ratio per unit area which the part whose (theta) is 10 degrees or less occupies is less than 80%. In other words, the ratio per unit area occupied by the portion where θ is 10 degrees or more is preferably 20% or more. In this case, the reflectance of light having an incident angle of 89 degrees can be reduced by about 50% or more compared to the case where the minute uneven portion 11 is formed on the smooth surface.

  More preferably, the ratio per unit area occupied by the portion where θ is 5 degrees or less is preferably less than 30%. In other words, it is preferable that the ratio per unit area occupied by the portion where θ is 5 degrees or more is 70% or more. Moreover, it is preferable that the ratio per unit area which the part whose (theta) is 10 degrees or less occupies is less than 50%. In other words, the ratio per unit area occupied by the portion where θ is 10 degrees or more is preferably 50% or more. In this case, the reflectance of light having an incident angle of 89 degrees can be reduced by about 70% or more as compared with the case where the minute irregularities 11 are formed on the smooth surface.

  Next, a preferable range of the average value (θave) of θ will be described.

  FIG. 8 is a graph showing the correlation between θave and reflectance.

  As shown in FIG. 8, the incident angle dependence decreases as θave increases, and a high reflection suppression effect can be obtained even for light having a relatively large incident angle. Specifically, θave is preferably 5 degrees or more. In this case, the reflectance of light having an incident angle of 89 degrees can be reduced by about 30% or more as compared with the case where the minute irregularities 11 are formed on the smooth surface. More preferably, θave is 10 degrees or more. In this case, the reflectance of light having an incident angle of 89 degrees can be reduced by about 50% or more compared to the case where the minute uneven portion 11 is formed on the smooth surface. More preferably, θave is 15 degrees or more. In this case, the reflectance of light having an incident angle of 89 degrees can be reduced by about 30% or more as compared with the case where the minute irregularities 11 are formed on the smooth surface.

  Further, the peak of the distribution of θ (the value of θ having the highest frequency) is preferably larger than 0 degree, preferably 2 degrees or more, and more preferably 5 degrees or more.

  From the viewpoint of manufacturing, it is preferable that there is no region where θ is larger than 90 degrees as shown in FIG. In other words, it is preferable that the inner peripheral surface 10 is substantially constituted by a surface whose roughness shape is θ ≦ 90 degrees. This is because, when a region where θ is larger than 90 degrees exists as shown in FIG. 10, it becomes difficult to form the minute uneven portion 11 on the surface facing the recess 17.

The average height Rc of the roughness curve element defined in ISO 4287: 1997 (corresponding to JIS B0601: 2001) corresponds to the average amplitude of the roughness shape, while the average length RSm of the roughness curve element is This corresponds to the average period of the roughness shape. The average surface angle θave is calculated using Rc and RSm,
tan (θave) = 2Rc / RSm
It can be expressed as.

  A condition corresponding to a condition θave> 5 degrees at which a preferable reflection suppression effect is obtained is Rc / RSm> 0.175, and a more preferable condition corresponding to θave> 15 degrees is Rc / RSm> 0.536.

  Furthermore, the inner peripheral surface 10 is preferably configured so that diffracted light is not generated from incident light. Specifically, the roughness shape of the inner peripheral surface 10 is preferably aperiodic. In other words, as shown in FIG. 11, the height distribution in the normal direction of the reference surface of the inner peripheral surface 10 (including the shape of the minute uneven portion 11 formed on the inner peripheral surface 10) is Fourier-transformed. In the spectrum obtained by this, the peak width of the peak 16 derived from the roughness shape of the inner peripheral surface 10 (for example, the peak width at half the height of the peak) W2 is derived from the minute uneven portion 11. It is preferable that it is wider than the same peak width W1 of 15. For example, when the roughness shape of the inner peripheral surface 10 is periodic, diffracted light is generated from light incident on the inner peripheral surface 10, and ghosts, flares, and the like may occur due to the diffracted light. With this configuration, it is possible to effectively suppress the generation of diffracted light, and hence the generation of ghosts and flares. The roughness shape refers to a shape obtained by cutting off the minute irregularities 11 as a high frequency component from the shape including the minute irregularities 11 on the inner peripheral surface 10 (hereinafter including the minute irregularities 11 on the inner peripheral surface 10). The shape is simply referred to as “the shape of the inner peripheral surface 10”).

  From the viewpoint of effectively reducing the influence of the generated diffracted light on the optical image formed on the imaging surface of the imaging device 6, the inner peripheral surface 10 has a center period (the highest frequency ratio) of its roughness shape. It is preferable that the period distribution width normalized by (period) is 0.4 times or more the center period. When the distribution width of the period normalized by the center period of the roughness shape of the inner peripheral surface 10 is smaller than 0.4 times the center period, the diffraction angle region where the second-order diffracted light generated on the inner peripheral surface 10 exists is The region of the diffraction angle in which the third-order diffracted light exists is isolated, and there is a possibility that unevenness occurs in the generated diffracted light. On the other hand, when the distribution width of the period normalized by the central period of the roughness shape of the inner peripheral surface 10 is 0.4 times or more of the central period, the diffraction angle at which the second-order diffracted light generated on the inner peripheral surface 10 exists This region and the region of the diffraction angle where the third-order diffracted light exists partially overlap, so that unevenness of the diffracted light is reduced.

  From the viewpoint of further reducing the unevenness of the diffracted light, it is preferable that the distribution width of the period normalized by the center period of the roughness shape of the inner peripheral surface 10 is 2/3 or more times the center period. According to this configuration, the diffraction angle region where the second-order diffracted light generated on the inner peripheral surface 10 exists partially overlaps with the diffraction angle region where the third-order diffracted light exists, and at the diffraction angle where the first-order diffracted light exists. Since the region and the region of the diffraction angle where the second-order diffracted light exists partially overlap, it is possible to reduce unevenness of the diffracted light due to the absence of the region where both the first-order diffracted light and the second-order diffracted light do not exist. it can.

  Here, the example in which the SWS is directly formed on the inner peripheral surface of the lens barrel 5 has been described, but the lens mirror can be obtained by sticking or adhering a seal having the SWS formed on the inner peripheral surface of the lens barrel. The cylinder 5 may be created. In other words, the lens barrel 5 may not be integrated, and may be configured by a plurality of constituent members.

  Here, the example in which the SWS is formed over the entire inner peripheral surface 10 of the lens barrel 5 has been described. However, depending on other conditions such as the configuration of the optical system 4, the SWS may be disposed inside the lens barrel 5. It is not always necessary to provide the entire surface of the peripheral surface 10, and the SWS may be formed only at a location where necessary. In that case, not only the location where the SWS is provided, but also the other location on the inner peripheral surface 10 may be a rough surface having the same surface roughness as the location where the SWS is provided. It may be a smooth surface. Furthermore, another antireflection structure such as a multilayer film of a film having a relatively low reflectance and a film having a relatively high reflectance may be formed at a location where the SWS is not provided. That is, as long as at least a part of the light incident surface of the light-absorbing substrate is formed into a rough surface, and SWS is formed on the rough surface, the light-absorbing antireflection according to the present invention. The structure is not limited at all. In addition, even within the region where the SWS is formed, the height and period (pitch) of the SWS may be adjusted as necessary.

  Further, the SWS may be formed not only on the inner peripheral surface 10 of the lens barrel 5 but also on the surface of other members such as the lenses (groups) L1 to L3 constituting the optical system 4.

  In addition, when the lens barrel 5 absorbs light as in the present embodiment, the lens barrel 5 may generate heat when the imaging device 1 is used for a long time. Furthermore, when the heat generation becomes intense or the high temperature state continues for a long time, the lens barrel 5 may be deteriorated by heat. In order to suppress deterioration due to this heat, a space may be formed inside the lens barrel 5 and a coolant may be sealed in the space. Further, the internal space of the lens barrel 5 may be connected to a radiator or the like, and the lens barrel 5 may be sequentially cooled while circulating the internal refrigerant. In addition, as a refrigerant | coolant, the antifreezing liquid which consists of polyethyleneglycol and water, air, the liquid mixture of alcohol and water, etc. are mentioned.

  Heretofore, an imaging apparatus has been cited as an example of an optical apparatus embodying the present invention, and the light-absorbing antireflection structure (lens barrel 5) formed in a cylindrical shape has been particularly described in detail. The light-absorptive antireflection structure is not limited to such a lens barrel 5. For example, a truncated cone or a truncated pyramid having a flat hole, a sheet, and a through-hole penetrating in the height direction are formed. It may have various shapes such as a shape. Furthermore, the surface where the SWS of the light-absorbing antireflection structure is not formed may be configured as a sticking surface or an adhesive surface. Specifically, the light-absorbing anti-reflection structure is suitable for image sensors such as charge-coupled devices (CCD), power measuring devices such as power meters, energy meters, and reflectance measuring devices, micro lens arrays, photo detectors, etc. May be used.

  The light-absorptive antireflection structure according to the present invention exhibits a high antireflection effect and is useful for various optical devices such as an imaging device, an illumination device, an optical scanning device, an optical pickup device, and a display.

2 is a schematic diagram illustrating a configuration of a main part of the imaging apparatus 1. FIG. 3 is a front view of the lens barrel 5. FIG. 4 is an enlarged cross-sectional view of a part of a lens barrel 5. FIG. 3 is a cross-sectional view in which a part of the lens barrel 5 is further enlarged. FIG. It is a graph showing the correlation of an incident angle and a reflectance. It is a graph showing the reflected light intensity of the light which injects with an incident angle of 45 degree | times. It is a graph showing the correlation between the incident angle and the reflectance on the surface on which the minute irregularities 11 are formed. It is a graph showing the correlation of (theta) ave and a reflectance. FIG. 5 is a cross-sectional view illustrating a roughness shape of a portion illustrated in FIG. 4 of the inner peripheral surface 10. It is sectional drawing for demonstrating the case where (theta) is larger than 90 degree | times. It is a spectrum obtained by Fourier-transforming the height distribution in the normal direction of the reference surface of the shape of the inner peripheral surface 10.

Explanation of symbols

1 Imaging device
2 Lens barrel unit
3 Device body
4 Optical system
5 Lens barrel
6 Image sensor
10 Inner peripheral surface
11 Minute uneven parts
L1-L3 lens group

Claims (23)

A light-absorbing antireflection structure that suppresses reflection of light having a predetermined wavelength or more and absorbs light whose reflection is suppressed,
The rough surface has a rough surface having a surface roughness larger than the predetermined wavelength, and a plurality of minute uneven portions arranged so that an average distance between them is equal to or less than the predetermined wavelength is formed on the rough surface. A light-absorbing antireflection structure characterized by the above. In the light absorptive antireflection structure according to claim 1,
Each of the minute uneven portions is a substantially conical concave portion or convex portion, or a linear concave portion or a linear convex portion. In the light absorptive antireflection structure according to claim 1,
The light-absorbing antireflection structure according to claim 1, wherein the rough surface has a surface roughness larger than the predetermined wavelength by an average length RSm of roughness curve elements defined by ISO 4287: 1997. In the light absorptive antireflection structure according to claim 1,
The light-absorbing antireflection structure according to claim 1, wherein the rough surface has a surface roughness smaller than 500 μm in terms of an average length RSm of roughness curve elements defined by ISO 4287: 1997. In the light absorptive antireflection structure according to claim 1,
The light-absorbing antireflection structure, wherein the rough surface has an average length RSm of a roughness curve element defined by ISO 4287: 1997, which is smaller than 100 μm. In the light absorptive antireflection structure according to claim 1,
The light-absorbing antireflection structure according to claim 1, wherein the rough surface has a surface roughness that is less than 50 μm in terms of an average length RSm of roughness curve elements defined by ISO 4287: 1997. In the light absorptive antireflection structure according to claim 1,
The light-absorptive antireflection structure, wherein heights in a normal direction of a reference surface of the rough surface of the plurality of minute uneven portions are substantially the same. In the light absorptive antireflection structure according to claim 1,
The light-absorbing antireflection structure, wherein the rough surface has a non-periodic roughness. In the light absorptive antireflection structure according to claim 8,
The light-absorbing reflection is characterized in that the rough surface is formed such that a distribution width of a period normalized by a center period of the roughness shape has a spread of 0.4 times or more of the center period. Prevention structure. In the light absorptive antireflection structure according to claim 8,
The light-absorbing reflection is characterized in that the rough surface is formed so that a distribution width of a period normalized by a center period of the roughness shape has a spread of 2/3 times or more of the center period. Prevention structure. In the light absorptive antireflection structure according to claim 1,
The peak derived from the roughness shape of the rough surface of the spectrum obtained by Fourier transforming the height distribution in the normal direction of the reference surface of the rough surface has a width derived from the minute uneven portion of the spectrum. A light-absorbing antireflection structure characterized in that the light-absorbing anti-reflection structure is wider than the peak width. In the light absorptive antireflection structure according to claim 1,
The rough surface is configured so that the average value of the angles formed by the normal vector of the tangent plane of the roughness shape and the normal vector of the reference surface of the rough surface is 5 degrees or more. Absorptive antireflection structure. In the light absorptive antireflection structure according to claim 1,
The rough surface is configured such that the peak of the distribution of the angle between the normal vector of the tangent plane of the roughness shape and the normal vector of the reference surface of the rough surface is greater than 0 degrees. Light absorbing antireflection structure. In the light absorptive antireflection structure according to claim 1,
The rough surface has a ratio per unit area occupied by a portion whose angle between the normal vector of the tangent plane of the rough shape and the normal vector of the reference surface of the rough surface is 5 degrees or less. A light-absorbing anti-reflection structure configured to be less than%. In the light absorptive antireflection structure according to claim 1,
The rough surface has a ratio per unit area occupied by a portion whose angle between the normal vector of the rough tangent plane and the normal vector of the reference surface of the rough surface is 10 degrees or less. A light-absorbing anti-reflection structure configured to be less than%. In the light absorptive antireflection structure according to claim 1,
The rough surface is substantially composed of a surface whose angle formed by the normal vector of the tangent plane of the roughness shape and the normal vector of the reference surface of the rough surface is 90 degrees or less. Light absorbing antireflection structure. In the light absorptive antireflection structure according to claim 1,
Each of the plurality of micro concavo-convex portions is a cone-shaped concave portion or a cone-shaped convex portion. A light-absorptive antireflection structure characterized by being. In the light absorptive antireflection structure according to claim 1,
Each of the plurality of minute uneven portions has a height that is 0.4 times or more the wavelength of light at which the reflection is suppressed. In the light absorptive antireflection structure according to claim 1,
An antireflection concavo-convex structure having a cylindrical shape, wherein the plurality of minute concavo-convex portions are formed on an inner peripheral surface. An optical system and a light-absorbing antireflection structure that is arranged so that light from the optical system is incident thereon, suppresses reflection of light from the optical system, and absorbs light from the optical system. Optical unit,
In the light-absorbing antireflection structure, a surface on which light from the optical system is incident is formed in a rough surface having a surface roughness larger than the wavelength of the light from the optical system. An optical unit characterized in that a plurality of minute concavo-convex portions regularly arranged with a period equal to or shorter than the wavelength of light from the optical system are formed. A lens barrel unit including an optical system and a lens barrel that houses the optical system therein, suppresses reflection of light from the optical system, and absorbs light from the optical system;
The lens barrel has an inner peripheral surface formed on a rough surface having a surface roughness larger than the wavelength of light from the optical system, and the inner peripheral surface has a wavelength equal to or smaller than the wavelength of light from the optical system. A lens barrel unit, wherein a plurality of minute irregularities arranged regularly with a period are formed.   An optical device comprising the optical unit according to claim 20.   An optical apparatus comprising the lens barrel unit according to claim 21.

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