JP7554073B2 - Lens, optical device, mold, and manufacturing method - Google Patents

Description

The present invention relates to a lens, an optical device equipped with the lens, a mold for press-molding the lens, and a method for manufacturing the lens.

In recent years, the range of applications of optical devices has expanded beyond imaging to include distance measurement and shape measurement. Lenses made of translucent materials such as glass and plastic as the base material are widely used in optical devices. One effective way to improve the performance of a lens is to suppress the reflection on the optically effective surface, and a surface treatment in which an anti-reflection film is provided on one or both of a pair of optically effective surfaces is widely known.

This anti-reflection film is composed of a single layer film made of a material with a lower refractive index than the lens substrate, or a multi-layer film in which low-refractive index materials and high-refractive index materials are alternately laminated. Such anti-reflection films often require highly accurate processes, such as precise control of film thickness, which increases manufacturing costs. In addition, since the principle is to improve transmission efficiency by utilizing the interference of reflected light, the anti-reflection performance tends to be highly wavelength-dependent. Therefore, such anti-reflection films have the problem that it is difficult to broaden the wavelength range of use. In addition, due to the adhesion of the film, the difference between the linear expansion coefficient of the substrate and the linear expansion coefficient of the film, the heat resistance of the film material itself, etc., such anti-reflection films are not suitable for use in high-temperature environments or environments where sudden temperature changes occur.

As a result, a method of providing a fine uneven structure with a size equal to or smaller than the wavelength of the incident light on the surface of the optically effective surface is becoming popular as an alternative to anti-reflection coatings. The principle of this method is to use a fine uneven structure to suppress the sudden change in refractive index at the interface between the optically effective surface and the atmosphere. Therefore, with such an uneven structure, it is expected that the usable wavelength range will be wider than with the anti-reflection coatings described above.

Furthermore, if a fine uneven structure is simultaneously processed on the element surface when processing the lens shape, manufacturing costs can be reduced and heat resistance can be improved compared to the above-mentioned anti-reflection film. For example, it has been proposed to combine this with a press molding method to form an uneven structure on an optically effective surface. Patent Document 1 discloses a method of press molding chalcogenide glass using a mold with a fine uneven structure. Figure 9 of Patent Document 1 shows a press molding device for performing this press molding.

Furthermore, lenses are used by being attached to the frame of an optical device (such as a lens barrel or a housing). At this time, if the assembly precision to the frame is low, the optical performance of the lens will be significantly reduced, no matter how high the anti-reflection performance of the lens. Therefore, it is preferable that this assembly precision be as high as possible.

However, for lenses with an uneven structure on the surface of the optically effective surface, it is difficult to process the mounting surface again after press molding (so-called post-processing). This is because bell clamps used in post-processing cannot be used on lenses with an uneven structure on the optically effective surface. Bell clamps adopt a method of adjusting the position of the lens by holding the optically effective surface. If a bell clamp is used on a lens with an uneven structure on the optically effective surface, the surface of the optically effective surface does not slide due to the uneven structure, and the uneven structure is easily damaged, which is a problem. Patent Document 2 discloses a method of simultaneously forming a fine uneven structure and an mounting surface by press molding.

JP 2010-72484 A JP 2020-71361 A JP 2013-35713 A

However, in press molding, the higher the temperature of the lens material, the lower the viscosity of the molding material becomes, making it easier to deform, and the pressure applied to the mold tends to decrease.

Also, as shown in the left diagram of FIG. 10, the normal force FN exerted on the material by the convex surface 1211, which is the part that transfers the optically effective surface of the mold 121, is directed in a direction away from the press axis that passes through the center of the convex surface 1211. Also, as shown in the right diagram of FIG. 10, the normal force FN exerted on the material by the convex surface 1221, which is the part that transfers the optically effective surface of the mold 122, is directed in a direction toward the press axis that passes through the center of the concave surface 1221.

When a lens whose optically effective surface is concave is press molded using a mold 121 including a convex surface 1211, the normal force FN faces in a direction away from the press axis passing through the center of the convex surface 1211. Therefore, during pressing, the material is likely to deform in the radially outward direction, which is the direction from the center of the optically effective surface toward the outer periphery of the optically effective surface.

On the other hand, when a lens whose optically effective surface is a convex surface is press molded using a mold 122 including a concave surface 1221, the normal force FN faces in a direction approaching the press axis passing through the center of the concave surface 1221. Therefore, the above-mentioned radially outward deformation of the material is easily suppressed.

Many people with experience in lens press molding intuitively understand that the above-mentioned radially outward deformation of the material is more likely to occur when a die such as die 121 is used to press mold an optically effective surface composed of a concave surface, compared to when a die such as die 122 is used to press mold an optically effective surface composed of a convex surface. In Patent Document 3, the cases where the normal force FN faces in a direction toward the press axis and where the normal force FN faces in a direction away from the press axis are expressed as aggregation and divergence of the deformation stress, respectively. Patent Document 3 describes a method for predicting the difficulty of molding an aspheric glass molded lens. This method is based on the assumption that molding is easy if the deformation stress is aggregation, whereas molding is difficult if it is divergence.

The inventors of the present application have found that the degree to which the shape of the concave-convex structure in a lens after press molding can be made to resemble the shape of the concave-convex structure determined at the time of design is heavily dependent on the following two points. The first point is the cumulative pressure applied to the concave-convex structure portion on the mold side during the deformation process of press molding, and the second point is the viscosity (i.e., temperature) of the material. In other words, the higher the cumulative pressure is, and the lower the viscosity of the material is (i.e., the higher the temperature is), the easier it is to make the shape of the concave-convex structure in a lens after press molding resemble the shape of the concave-convex structure determined at the time of design. One example of a parameter that indicates the shape of the concave-convex structure is the amount of protrusion of the convex parts that make up the concave-convex structure. This amount of protrusion is an important factor that affects the anti-reflection performance exhibited by the concave-convex structure.

The technology described in Patent Document 2 is a technology that can simultaneously form a concave-convex structure and an assembly surface for a frame body using press molding. However, the inventors of the present application have found that in lenses press molded using this technology, when the optically effective surface is composed of a concave surface, the amount of protrusion of the convex portion tends to be smaller than the amount of protrusion determined at the time of design. This is because, as described above, the normal force FN is directed in a direction away from the press axis. Even if the viscosity of the material is reduced, the integrated pressure applied to the mold decreases, and the material is more likely to deform in the radially outward direction. Therefore, it is difficult to bring the amount of protrusion of the convex portion close to the amount of protrusion determined at the time of design.

It is possible to increase the cumulative pressure applied to the mold by reducing the thickness of the annular plate portion described in Patent Document 2, but since the annular plate portion is used as an assembly surface for the frame and therefore requires mechanical strength, it is difficult to make it thin. Furthermore, if the annular plate portion is set too thin, a large amount of internal stress accumulates in the molding material, causing the problem that a good optically effective surface shape cannot be obtained. Furthermore, since the relationship with other lenses to be assembled to the frame is determined at the time of design, it is difficult to adjust the thickness according to the degree of transfer of the uneven structure produced by press molding.

The present invention has been made in consideration of the above-mentioned problems, and its purpose is to make the shape of the concave-convex structure of a lens that includes an optically effective surface that is composed of a concave surface and has a concave-convex structure that reduces reflection closer to the shape determined at the time of design.

In order to solve the above problems, a lens according to one aspect of the present invention comprises a first optically effective surface that is formed of a concave surface and has an uneven structure that reduces reflection, a second optically effective surface that faces the first optically effective surface, a main portion that includes a concentric side surface that is interposed between the first optically effective surface and the second optically effective surface, and a ring-shaped gripping portion that is provided around the entire circumference of the side surface and protrudes from the side surface, and a first region that is part of the outer circumferential surface is a free surface.

In order to solve the above problem, a mold according to one aspect of the present invention is a mold for press-molding a lens having a first optically effective surface formed of a concave surface and provided with an uneven structure that reduces reflection, a second optically effective surface facing the first optically effective surface, and a main portion including a concentric side surface interposed between the first optically effective surface and the second optically effective surface, and an annular gripping portion provided around the entire circumference of the side surface and protruding from the side surface, the mold including a first portion that transfers the shape of the first optically effective surface, the first portion including a convex surface corresponding to the concave surface, a second portion that transfers the shape of the second optically effective surface, the second portion facing the first portion, and a third portion that transfers the shape of the side surface and the gripping portion, the transfer surface being concentric, and a gap being formed in an area corresponding to a part of the outer circumferential surface of the gripping portion.

In order to solve the above problem, a manufacturing method according to one aspect of the present invention is a manufacturing method for manufacturing a lens by press molding using a mold, the lens having a first optically effective surface that is formed of a concave surface and has an uneven structure that reduces reflection, a second optically effective surface that faces the first optically effective surface, a main portion that includes a concentric side surface interposed between the first optically effective surface and the second optically effective surface, and an annular gripping portion that is provided around the entire circumference of the side surface and protruding from the side surface, the manufacturing method including a heating process for heating a material set in the mold, and a pressing process for press molding the material into the lens by applying weight to the mold, the press molding being performed while releasing the pressure applied to a first region that is a part of the outer circumferential surface of the gripping portion.

According to one aspect of the present invention, in a lens that includes an optically effective surface that is composed of a concave surface and has a concave-convex structure that reduces reflection, the shape of the concave-convex structure can be made to approximate a shape determined at the time of design.

1A and 1B are a cross-sectional view and a pair of plan views of a lens according to a first embodiment of the present invention. 2 is an enlarged cross-sectional view of a concave-convex structure provided on a first optically effective surface of the lens shown in FIG. 1 . 2 is an enlarged plan view of a concave-convex structure provided on a first optically effective surface of the lens shown in Fig. 1. The left side shows a concave-convex structure in which columnar protrusions are arranged in a hexagonal fashion, and the right side shows a concave-convex structure in which columnar protrusions are arranged in a square fashion. FIG. 2 is an enlarged cross-sectional view of a gripping portion of the lens shown in FIG. 1 . FIG. 4 is a cross-sectional view of a mold according to a second embodiment of the present invention. 10 is a flowchart of a manufacturing method according to a third embodiment of the present invention. FIG. 2 is a cross-sectional view of a modified example of the lens shown in FIG. 1 . FIG. 6 is a cross-sectional view of a modified example of the mold shown in FIG. 5 . FIG. 13 is a schematic cross-sectional view of an imaging device according to a fourth embodiment of the present invention. 1A and 1B are cross-sectional views of a mold in which a portion for transferring an optically effective surface is constituted by a convex surface, and a mold in which a portion for transferring an optically effective surface is constituted by a concave surface.

First Embodiment
A lens 10 according to a first embodiment of the present invention will be described with reference to FIGS.

Figure 1 shows a cross-sectional view and a pair of plan views of lens 10. Of the pair of plan views, the plan view located at the top of the cross-sectional view is a plan view obtained when lens 10 is viewed from the side of first optically effective surface 111, of the pair of optically effective surfaces that constitute lens 10, that is, first optically effective surface 111 and second optically effective surface 112. Of the pair of plan views, the plan view located at the bottom of the cross-sectional view is a plan view obtained when lens 10 is viewed from the side of second optically effective surface 112.

Figure 2 is an enlarged cross-sectional view of the uneven structure 1111 provided on the first optically effective surface 111. In Figure 2, of the multiple convex portions 1113 that make up the uneven structure 1111, the convex portion 1113 that is closest to the central axis of the first optically effective surface 111 (in this embodiment, the convex portion 1113 located at the center of the first optically effective surface 111) is shown on the left side, and the other convex portions 1113 are shown in the center and on the right side.

Figure 3 is an enlarged plan view of the uneven structure 1111. The left side shows the uneven structure 1111 in which the protrusions 1113 are arranged in a hexagonal fashion, and the right side shows the uneven structure 1111 in which the protrusions 1113 are arranged in a square fashion.

Figure 4 is an enlarged cross-sectional view of the grip portion 12 of the lens 10.

<Lens material and wavelength range>
The lens 10 is one aspect of an optical element made of a light-transmitting material. In this embodiment, chalcogenide glass IRG206 is used as the light-transmitting material constituting the lens 10. However, the light-transmitting material constituting the lens 10 can be appropriately selected from materials that have translucency for light belonging to a predetermined wavelength range, have a glass transition point, and can be molded by press molding using a mold. The typical glass transition point of the chalcogenide glass IRG206 is 180°C.
Examples of such light-transmitting materials include glass and plastic. In the following, the wavelength range in which the light transmittance of the light-transmitting material constituting the lens 10 is 85% or more is referred to as the wavelength range of use of the lens 10. The wavelength range of use in a typical example of the chalcogenide glass IRG206 is about 7 μm or more and 14 μm or less. The lens 10 is designed on the assumption that it will be used in the vicinity of 10 μm in this wavelength range of use. 10 μm is an example of a wavelength λ, which is a predetermined wavelength belonging to the wavelength range of use, and the predetermined wavelength can be arbitrarily selected from 7 μm to 14 μm. In the case of the visible light range, the wavelength range of use is about 0.4 μm to 0.7 μm or less, and the predetermined wavelength can be arbitrarily selected within this range. In the case of the near-infrared range, the wavelength range of use is about 0.7 μm to 2.0 μm or less, and the predetermined wavelength can be arbitrarily selected within this range.

<Lens construction>
1, the lens 10 includes a main portion 11 and a grip portion 12. The lens 10 is made of a single material (in this embodiment, chalcogenide glass IRG206).
(Main part)
1, the main portion 11 includes a pair of optically effective surfaces, that is, a first optically effective surface 111 and a second optically effective surface 112, and a side surface 113. When the lens 10 is viewed in a plan view, the contours of the first optically effective surface 111 and the second optically effective surface 112 are circular (circular in this embodiment).

As shown in FIG. 2, the first optically effective surface 111 has a concave-convex structure 1111. The base shape of the first optically effective surface 111 is formed by a concave surface 1112. The concave surface 1112 may be a spherical surface or an aspherical surface.

As shown in Fig. 3, the uneven structure 1111 is formed by regularly arranging a plurality of convex portions 1113 on the surface of the concave surface 1112. In this embodiment, the convex portions 1113 are columnar protrusions formed in a truncated cone shape including a pair of bottom surfaces. Hereinafter, the bottom surface of the pair of bottom surfaces constituting the convex portion 1113 that is farther from the concave surface 1112 and corresponds to the tip of the convex portion 1113 will be referred to as the upper bottom surface, and the bottom surface of the pair of bottom surfaces constituting the convex portion 1113 that is closer to the concave surface 1112 and corresponds to the base of the convex portion 1113 will be referred to as the lower bottom surface.
In this embodiment, the convex portion 1113 has a substantially circular cross section, a diameter of the upper bottom surface is smaller than a diameter d of the lower bottom surface, and a tapered shape in which the diameter in the cross section decreases from the base to the tip. Note that the cross section of the convex portion 1113 is a cross section obtained when the convex portion 1113 is viewed along a plane perpendicular to the optical axis _AL .

In addition, in each convex portion 1113, when viewed along a direction substantially parallel to the optical axis _AL , the point that protrudes most from the concave surface 1112 (in other words, the point that is furthest away) is defined as point A, and the intersection point between a straight line that passes through point A and is parallel to the optical axis _AL and the lower bottom surface is defined as point B. In addition, in each convex portion 1113, the distance between point A and point B is defined as the protrusion amount h.

The central axis of the convex portion 1113 located near the center of the first optically effective surface 111 shown on the left side of Fig. 2 does not coincide with the optical axis A _L. However, the central axis of the convex portion 1113 located near the center of the first optically effective surface 111 may coincide with the optical axis A _L. Note that in the convex portion 1113 closest to the optical axis A _L (in this embodiment, the convex portion 1113 located near the center of the first optically effective surface 111), the distance between point A and point B is set as a protrusion amount _h0 , and is distinguished from the protrusion amounts h of the other convex portions 1113.

In this embodiment, the upper bottom surface is configured with a gentle convex surface. However, the shape of the upper bottom surface is not limited to a convex surface. The upper bottom surface may be configured with, for example, a flat surface. Also, in this embodiment, a hem portion is formed near the base of the convex portion 1113, which gently connects between the side surface of the convex portion 1113 and the concave surface 1112. However, the manner in which the side surface and the concave surface 1112 are connected is not limited to this. For example, the side surface of the convex portion 1113 and the concave surface 1112 may be directly connected without a hem portion.

Examples of regular arrangements of multiple protrusions 1113 include a hexagonal arrangement (see the left side of FIG. 3) and a square arrangement (see the right side of FIG. 3). In a hexagonal arrangement, a protrusion 1113 is arranged at each vertex of a regular hexagon (regular hexagon on the left side of FIG. 3) and approximately at the center of the regular hexagon (center on the left side of FIG. 3). In a square arrangement, a protrusion 1113 is arranged at each vertex of a square shape (square on the right side of FIG. 3).

In each of the hexagonal arrangement and square arrangement, of the adjacent convex portions 1113, the distance between points A of two convex portions 1113 arranged along the x-axis direction is referred to as pitch Pa, and the distance between points A of two convex portions 1113 arranged along a direction intersecting the x-axis is referred to as pitch Pb. In this embodiment, pitch Pa and pitch Pb are equal. Therefore, unless there is a need to particularly distinguish between the two, pitch Pa and pitch Pb are collectively referred to as pitch P.

In the uneven structure 1111 configured in this manner, the pitch P preferably satisfies 0.2×λ≦Pa≦λ, and in this embodiment, it is 4 μm. Note that the wavelength λ is a predetermined wavelength that belongs to the wavelength range used as described above, and in this embodiment, it is 10 μm.

In addition, it is preferable that the protrusion amount h of the convex portion 1113 satisfies 0.25×λ≦h. Note that, like the protrusion amount h, the protrusion amount _h0 of the convex portion 1113 closest to the optical axis of the first optically effective surface 111 also satisfies 0.25×λ≦ _h0 .

Furthermore, it is preferable that the protrusion amount h and the protrusion amount _h0 satisfy 0.75× _h0 ≦h≦1.25× _h0 .

The diameter d at the base of the convex portion 1113 preferably satisfies 0.2×λ≦d≦0.6×λ, and is 3.5 μm in this embodiment. Note that the wavelength λ is a predetermined wavelength that belongs to the wavelength range used as described above, and is 10 μm in this embodiment.

The lens 10 is preferably made of a single material that has a glass transition point.
As shown in FIG. 1, the second optically effective surface 112 faces the first optically effective surface 111. In this embodiment, the shape of the second optically effective surface 112 is a convex surface. However, the shape of the second optically effective surface 112 is not limited to a convex surface, and may be a flat surface or a concave surface. A lens 10A which is a modified example of the lens 10 and in which the shape of the second optically effective surface 112A corresponding to the second optically effective surface 112 is a concave surface will be described later with reference to FIG. 7. In addition, the second optically effective surface 112 may be a spherical surface or an aspherical surface.

In this embodiment, the second optically effective surface 112 is provided with a concave-convex structure similar to the concave-convex structure 1111 provided on the first optically effective surface 111. However, the concave-convex structure provided on the second optically effective surface 112 may be omitted.

The side surface 113 is an outer surface of a columnar member interposed between the first optically effective surface 111 and the second optically effective surface 112. In the lens 10, the side surface 113 constitutes a part of an assembly surface when the lens 10 is assembled to a frame (e.g., the housing 2 shown in FIG. 9 ) of an optical device (e.g., the image pickup device 1 shown in FIG. 9 ). In this embodiment, the columnar member has a cylindrical shape. Therefore, a cross section of the side surface 113 that is perpendicular to the optical axis _AL is concentric when viewed from any position in the z-axis direction.
The lens 10 configured as above is an example of a meniscus lens.

(Grip portion)
As shown in Fig. 1, the grip portion 12 is an annular member provided around the entire circumference of the side surface 113 and protruding from the side surface 113. As shown in Fig. 4, an outer peripheral surface 121 constituting the outer edge of the grip portion 12 is composed of a first region 1211 and a second region 1212. A pair of bottom surfaces, which are the regions of the surface of the grip portion 12 other than the outer peripheral surface 121, are composed of flat surfaces. In the lens 10, the pair of bottom surfaces, together with the above-mentioned side surface 113, constitute an assembly surface when the lens 10 is assembled to a frame (e.g., the housing 2 shown in Fig. 9) of an optical device (e.g., the imaging device 1 shown in Fig. 9).

As described later with reference to Figures 5 and 6, lens 10 is formed by press molding using a mold. In this press molding process, first region 1211 is a region whose surface shape has not been transferred using the mold, and is a region formed by excess material escaping into gap P33 in the mold. Therefore, the surface of first region 1211 is a free surface (see Figure 4).
In the present embodiment, the first region 1211 is formed in an annular shape over the entire circumference of the outer circumferential surface 121. However, it is sufficient that the first region 1211 is formed over at least a portion of the entire circumference of the outer circumferential surface 121.
If the thickness of the gripping portion 12 is t ₁ and the thickness of the thickest portion of the lens is T, it is preferable that t ₁ and T satisfy 1 mm≦t ₁ ≦T−0.5 mm.
Furthermore, when the thickness of the first region is _t2 , it is preferable that _t2 ≦0.9× _t1 is satisfied.
The second region 1212 is a region of the outer circumferential surface 121 other than the first region 1211. The shape of the second region 1212 is transferred to the surface of the second region 1212 by a mold in a press molding process. As shown in FIG. 2 , the second region 1212 is provided on the negative z-axis direction side of the first region 1211 and is adjacent to the first region 1211.

4, the second region 1212 is composed of a reverse taper region R _1T adjacent to the first region 1211, and a straight region R _1S . The reverse taper region R _1T is provided on the negative z-axis direction side of the first region 1211 and is adjacent to the first region 1211. The straight region R _1S is provided on the negative z-axis direction side of the reverse taper region R _1T and is adjacent to the reverse taper region R _1T .
The inverse taper region _RT has a concentric shape with the optical axis _AL as the center axis, and in this embodiment, has a truncated cone shape. The inverse taper region _RT is configured such that the diameter of the cross section perpendicular to the optical axis _AL increases as it approaches the first region 1211 from the straight region _RS side.
The straight region R _S has a concentric circular shape with the optical axis A _L as the central axis, and is cylindrical in this embodiment. The straight region R _S is configured so that the diameter of a cross section perpendicular to the optical axis A _L is substantially constant (constant in this embodiment) regardless of the distance from the first region 1211.

In the cross section of the lens 10 shown in Fig. 4, the angle θ between the surface of the reverse taper region _RT and a plane perpendicular to the optical axis _AL is θ = 45° in this embodiment. However, the angle θ is not limited to 45° and can be appropriately set within the range of 0° ≦ θ < 90°, and it is preferable that 0° ≦ θ ≦ 60°. By setting θ ≦ 60°, it is possible to prevent deterioration of the surface shape and damage due to internal stress.
When θ=90°, the reverse taper region R _T cannot be defined, and the outer circumferential surface 121 is composed only of the straight region R _S. In this manner, in one modified example of the lens 10, the reverse taper region R _T can be omitted. Also, in one modified example of the lens 10, the straight region R _S can be omitted.

As described above, the first optically effective surface 111 has a circular shape (circular in this embodiment) when the lens 10 is viewed in a plan view. It is preferable that the protrusion amount f from the side surface 113 of the gripping portion 12 and the diameter _D1 of the first optically effective surface 111 satisfy 0.5 mm≦f≦ _D1 . In this embodiment, since the shape of the gripping portion 12 and the shape of the first optically effective surface 111 are both circular when viewed in a plan view, the protrusion amount f is defined as ½ of the difference between the diameter of the gripping portion 12 and the diameter _D1 .

In this embodiment, the second region 1212 consisting of the inverse tapered region R _1T and the straight region R _1S is provided only on one side (the side close to the second optical effective surface 112) of the first region 1211. However, the second region 1212 may be provided only on the other side (the side close to the first optical effective surface 111) of the first region 1211, or may be provided on both sides of the first region 1211 (the side close to the first optical effective surface 111 and the side close to the second optical effective surface 112).

In this embodiment, the surface of the inverse tapered region _RT is configured with a side surface of a truncated cone, which is a smoothly curved surface. With this configuration, it is possible to suppress the generation of unnecessary internal stress.

In this embodiment, the inverse taper region R 1 _T and the straight region R 2 _S are connected in a discontinuous, bent state (see FIG. 4 ). However, the inverse taper region R 1 _T and the straight region R 2 _S may be connected in a continuous state forming a smooth curved surface. By connecting the inverse taper region R 1 _T and the straight region R 2 _S with a smooth curved surface, it is possible to suppress the generation of unnecessary internal stress.

Second Embodiment
A mold 20 according to a second embodiment of the present invention will be described with reference to FIGS. 1 to 4 and 5. FIG.

As described above, FIG. 1 is a cross-sectional view and a pair of plan views of lens 10, FIG. 2 and FIG. 3 are, respectively, an enlarged cross-sectional view and an enlarged plan view of the uneven structure 1111 provided on the first optically effective surface 111, and FIG. 4 is an enlarged cross-sectional view of the grip portion 12 of lens 10.

Figure 5 is a cross-sectional view of the mold 20. In Figure 5, part of the contour of the lens 10 is shown by a virtual line (two-dot chain line), and the reference numerals indicating each part of the lens 10 and the hatching applied to the cross section of the lens 10 are omitted.

The die 20 can press-mold the lens 10 by applying a load FL (see FIG. 5) in a direction along the load axis while heating the chalcogenide glass IRG206 set in its internal space. The lens 10 has been described with reference to FIGS. 1 to 4, so a description of the lens 10 will be omitted here.

<Mold configuration>
5, the mold 20 includes a first optically effective surface transfer mold 21, a second optically effective surface transfer mold 22, a side surface transfer mold 23, a second area transfer mold 24, a shim 25, a first positioning mold 26, a second positioning mold 27, and a sliding sleeve mold 28. All of these members are made of metal.

(First optically effective surface transfer mold)
The first optically effective surface transfer mold 21 is a cylindrical member including the first portion P1 and having a convex surface P11 at one end. A flange portion having an enlarged outer diameter is provided at the end of the first optically effective surface transfer mold 21 opposite the convex surface P11.

The first part P1 is a part of the first optically effective surface transfer mold 21. The first part P1 transfers the shape of the first optically effective surface 111. The first part P1 includes a convex surface P11 corresponding to the concave surface 1112. The convex surface P11 is provided with an uneven structure for transferring the uneven structure 1111 (see Figures 2 and 3) provided on the concave surface 1112 of the lens 10.

(Second optically effective surface transfer mold)
The second optically effective surface transfer mold 22 is a cylindrical member including the second portion P2 and having a concave surface P21 at one end. A flange portion with an enlarged outer diameter is provided at the end of the second optically effective surface transfer mold 22 opposite the concave surface P21.

The second part P2 is a part of the second optically effective surface transfer mold 22. The second part P2 includes a concave surface P21 that transfers the shape of the second optically effective surface 112. The second part P2 faces the first part P1. The concave surface P21 is provided with an uneven structure similar to the uneven structure provided on the convex surface P11. However, this uneven structure may be omitted.

(Side transfer mold)
The side surface transfer mold 23 is a cylindrical member. One end of the side surface transfer mold 23 forms a gap P33 together with a second area transfer mold 24 described later. A flange portion with an enlarged outer diameter is provided at the end of the side surface transfer mold 23 opposite the gap P33. The side surface transfer mold 23 accommodates the portion of the first optically effective surface transfer mold 21 other than the flange portion in its inner space.

The transfer surface P31, which is the inner surface of the side transfer mold 23 that protrudes from the first optically effective surface transfer mold 21, transfers the side surface 113 of the lens 10. In addition, the bottom surface that constitutes one end of the side transfer mold 23 transfers one bottom surface of the gripping portion 12 of the lens 10.

The second area transfer mold 24 is a cylindrical member. One end of the second area transfer mold 24 forms a gap P33 together with the side transfer mold 23. The second area transfer mold 24 accommodates the portion of the second optically effective surface transfer mold 22 other than the flange portion in its inner space.

A transfer surface P32, which is an inner surface protruding from the second optically effective surface transfer mold 22 among the inner surfaces of the second area transfer mold 24, transfers the second area 1212 of the outer circumferential surface 121 of the lens 10. The inner diameter of the transfer surface P32 is determined so as to correspond to the shapes of the straight region R _S and the reverse tapered region R _T shown in FIG.

(Part 3)
The third portion P3 is mainly composed of a part of the side transfer mold 23 and a part of the second region transfer mold 24, and includes a part of the first positioning mold 26, a part of the second positioning mold 27, and a part of the sliding sleeve mold 28. The third portion P3 transfers the shape of the side surface 113 and the gripping portion 12. The third portion P3 has a concentric transfer surface, and a gap P33 is formed in a region corresponding to the first region 1211, which is a part of the outer circumferential surface of the gripping portion 12. By forming the gap P33 in a part of the third portion P3, the mold 20 can release the internal stress PI applied to the chalcogenide glass IRG206 during press molding. In addition, by forming the gap P33 in a part of the third portion P3, the surface of the first region 1211 of the lens 10 is not transferred with the shape by the mold 20, and as a result, it becomes a free surface.

In this embodiment, the gap P33 is formed in an annular shape around the entire circumference of the transfer surface of the third portion P3. Therefore, in this embodiment, the gap P33 is isotropic in a cross section perpendicular to the load axis. However, the gap P33 is not limited to this configuration. For example, the gap P33 may be formed in a part of the transfer surface of the third portion P3, or may be formed anisotropically in a cross section perpendicular to the load axis.

(SIM)
The shim 25 is a circular plate-like member. The shape of the shim 25 in plan view is almost the same as the shape of the bottom surface constituting the other end of the second area transfer mold 24. As shown in FIG. 5, the shim 25 is interposed between the flange portion of the second optical effective surface transfer mold 22 and the second area transfer mold 24, so that the amount of protrusion of the second area transfer mold 24 protruding from one end of the second optical effective surface transfer mold 22 can be adjusted, and as a result, the interval ΔG of the gap P33 can be adjusted. In the mold 20, it is preferable that a plurality of shims 25 with different thicknesses are prepared in advance. The manufacturer of the lens 10 can adjust the internal stress PI applied to the chalcogenide glass IRG206 during press molding by appropriately selecting the thickness of the shim 25.

The shim 25 configured in this manner is an example of an adjustment mechanism that adjusts the gap ΔG. However, the type of adjustment mechanism is not limited to a replaceable type like the shim 25, and may be any type that can adjust the amount of protrusion of the second area transfer die 24 that protrudes from one end of the second optically effective surface transfer die 22. Another type of adjustment mechanism is a screw type.

(Positioning die and sliding sleeve die)
The first positioning die 26 is a cylindrical member whose inner diameter changes in two stages. The first positioning die 26 accommodates the first optical effective surface transfer die 21 and the side surface transfer die 23 in an integrated state in the inner space.

The second positioning die 27 is a cylindrical member whose inner diameter changes in two stages, similar to the first positioning die 26. The second positioning die 27 accommodates the second optical effective surface transfer die 22, the second area transfer die 24, and the shim 25 in an integrated state in its inner space.

The sliding sleeve mold 28 is a cylindrical member. The sliding sleeve mold 28 accommodates in its inner space the first optically effective surface transfer mold 21 and the side transfer mold 23 integrated by the first positioning mold 26, and the second optically effective surface transfer mold 22, the second area transfer mold 24, and the shim 25 integrated by the second positioning mold 27, in an integrated state. The sliding sleeve mold 28 limits the directions in which the first optically effective surface transfer mold 21, the side transfer mold 23, and the first positioning mold 26 can move, and the directions in which the second optically effective surface transfer mold 22, the second area transfer mold 24, the shim 25, and the second positioning mold 27 can move to directions along the central axis of the sliding sleeve mold 28 (up and down in the mold 20 shown in FIG. 5). Hereinafter, the central axis of the sliding sleeve mold 28 is referred to as the load axis.

(Heating mechanism and cooling mechanism)
5, the mold 20 further includes a heating mechanism for heating the chalcogenide glass IRG 206 set in the mold 20 and a cooling mechanism for cooling the same.

Third Embodiment
A manufacturing method M1 according to a third embodiment of the present invention will be described with reference to Fig. 1, Fig. 5, and Fig. 6. As described above, Fig. 1 is a cross-sectional view and a pair of plan views of a lens 10, and Fig. 5 is a cross-sectional view of a mold 20. Fig. 6 is a flowchart of manufacturing method M1.

Manufacturing method M1 can be used to manufacture the lens 10 shown in FIG. 1 by press molding using the mold 20 shown in FIG. 5. The lens 10 has been described with reference to FIGS. 1 to 4, and the mold 20 has been described with reference to FIG. 5, so descriptions of the lens 10 and the mold 20 are omitted here.

<Production Method>
As shown in FIG. 6, the manufacturing method M1 includes a heating step S11 and a pressing step S12.

(Heating process)
The heating step S11 is a step of heating the material set in the internal space of the mold 20 by using a heating mechanism provided in the mold 20. In this embodiment, the material used in the heating step S11 is chalcogenide glass IRG206. However, as described in the description of the lens 10, this material can be appropriately selected from among materials that are translucent to light belonging to a predetermined wavelength range, have a glass transition point, and can be molded by press molding using a mold.

In the heating step S11, the material is preferably heated to a temperature equal to or higher than the glass deformation point -15°C. When the material is chalcogenide glass IRG206, the typical deformation point is 216°C, and the typical glass deformation point -15°C is 201°C. In this embodiment, a heating temperature of 225°C is used.

(Pressing process)
The pressing step S12 is a step of press-molding the material into the lens 10 by applying a load FL (see FIG. 5 ) to the die 20. In the pressing step S12, the material is press-molded into the lens 10 while releasing the pressure applied to the first region 1211, which is a part of the outer circumferential surface 121 of the gripping portion 12.

As in the case of the heating step S11, during the pressing step S12, it is preferable that the material is heated to a temperature equal to or higher than the glass yield point -15°C. In this embodiment, the heating step S11 is performed in parallel with the pressing step S12, and a heating temperature of 225°C is used.

The load FL applied to the die 20 in the pressing step S12 and the period for performing the pressing step S12 can each be determined appropriately. In this embodiment, a load FL of 500 N was applied to the die 20, and the heating temperature was maintained at 225°C for 4 minutes. Then, with a load FL of 500 N still applied to the die 20, the heating temperature was cooled to 180°C at a rate of -10°C/min.

(Slow cooling process)
6, the manufacturing method M1 may further include a slow cooling step in addition to the heating step S11 and the pressing step S12. The slow cooling step is performed after the pressing step S12. The slow cooling step is a step of gradually lowering the temperature of the mold 20 from the heating temperature at the end of the pressing step S12 to room temperature in a state where the load FL is not applied to the mold 20.

[Modifications of Lens and Mold]
A lens 10A which is a modified example of the lens 10 and a die 20A which is a modified example of the die 20 will be described with reference to Fig. 7 and Fig. 8. Fig. 7 is a cross-sectional view of the lens 10A. Fig. 8 is a cross-sectional view of the die 20A.

<Lens construction>
7, the lens 10A includes a main portion 11A and a grip portion 12A. The main portion 11A corresponds to the main portion 11 of the lens 10, and the grip portion 12A corresponds to the grip portion 12 of the lens 10.

(Main part)
The main portion 11A has a pair of optically effective surfaces, a first optically effective surface 111A and a second optically effective surface 112A, and a side surface 113A. When the lens 10A is viewed in a plan view, the contours of the first optically effective surface 111A and the second optically effective surface 112A are circular (circular in this embodiment). The first optically effective surface 111A, the second optically effective surface 112A, and the side surface 113A correspond to the first optically effective surface 111, the second optically effective surface 112, and the side surface 113 of the lens 10, respectively.

The first optically effective surface 111A, like the first optically effective surface 111, has a base shape formed of a concave surface, and an uneven structure similar to the uneven structure 1111 (see Figures 3 and 4) is provided on the surface of the concave surface.

The second optically effective surface 112A, like the first optically effective surface 111A, has a base shape formed of a concave surface, and the concave surface has an uneven structure similar to the uneven structure 1111 (see Figures 3 and 4).

As described above, the main portion 11 of lens 10 and the main portion 11A of lens 10A differ in the following respects. That is, the main portion 11 is a lens in which each of a pair of optically effective surfaces is composed of a concave surface and a convex surface, whereas the main portion 11A is a lens in which both of the pair of optically effective surfaces are composed of concave surfaces. Apart from this point, the main portion 11A is configured in the same way as the main portion 11. Therefore, in this modified example, a detailed description of the main portion 11A will be omitted.

(Grip portion)
Similar to the gripping portion 12 of the lens 10 shown in Fig. 1, the gripping portion 12A is an annular member provided around the entire circumference of the side surface 113A and protruding from the side surface 113A. As shown in Fig. 7, the outer peripheral surface 121A constituting the outer edge of the gripping portion 12A is composed of a first region 1211A and a second region 1212A. The outer peripheral surface 121A, the first region 1211A, and the second region 1212A of the gripping portion 12A correspond to the outer peripheral surface 121, the first region 1211, and the second region 1212 of the gripping portion 12, respectively.

The surface of the first region 1211A is a free surface, similar to the surface of the first region 1211.

In this embodiment, the first region 1211 is formed in an annular shape around the entire circumference of the outer circumferential surface 121. However, it is sufficient that the first region 1211 is formed around at least a portion of the entire circumference of the outer circumferential surface 121.

In lens 10A, the thickness of gripping portion 12A is _t1 , the thickness of first region 1211A is _t2 , and the thickness of the thickest part of lens 10A is T, and the conditions that thickness _t1 , thickness _t2 , and thickness T preferably satisfy are the same as in the case of lens 10.

The second region 1212A is the area of the outer circumferential surface 121A other than the first region 1211A. The shape of the surface of the second region 1212A is transferred by the mold 20A during the press molding process.

7, the second region 1212A is configured with a reverse tapered region R _1212T adjacent to the first region 1211. That is, the straight region _{R 1212} provided in the second region 1212 is omitted in the second region 1212A.

In addition, in the cross section of lens 10A shown in FIG. 7, the angle θ between the surface of reverse tapered region _RT and a plane perpendicular to the optical axis of lens 10A is θ=45°, similar to the case of lens 10.

As described above, the gripping portion 12 of the lens 10 and the gripping portion 12A of the lens 10A differ in the following respects. That is, while the second region 1212 of the gripping portion 12 is composed of a reverse taper region R _1T and a straight region R _1S , the gripping portion 12A is different in that it is composed of a reverse taper region. Apart from this point, the gripping portion 12A is configured in the same way as the gripping portion 12. Therefore, in this modified example, a detailed description of the gripping portion 12A will be omitted.

<Mold configuration>
8, the mold 20A includes a first optically effective surface transfer mold 21A, a second optically effective surface transfer mold 22A, a side surface transfer mold 23A, a second area transfer mold 24A, a shim 25A, a first positioning mold 26A, a second positioning mold 27A, and a sliding sleeve mold 28A. The first optically effective surface transfer mold 21A, the second optically effective surface transfer mold 22A, the side surface transfer mold 23A, the second area transfer mold 24A, the shim 25A, the first positioning mold 26A, the second positioning mold 27A, and the sliding sleeve mold 28A correspond to the first optically effective surface transfer mold 21, the second optically effective surface transfer mold 22, the side surface transfer mold 23, the second area transfer mold 24, the shim 25, the first positioning mold 26, the second positioning mold 27, and the sliding sleeve mold 28 of the mold 20, respectively.

As described above, lens 10A differs from lens 10 in that the pair of optically effective surfaces, the first optically effective surface 111A and the second optically effective surface 112A, are concave lenses, and the second region 1212A of the gripping portion 12A is configured as an inverse tapered region. Therefore, in this modified example, the second optically effective surface transfer mold 22A and the second region transfer mold 24A related to these points will be described, and descriptions of the other members will be omitted.

(Second optically effective surface transfer mold)
The second optically effective surface transfer mold 22A is a cylindrical member including a second portion P2A. While one end of the second optically effective surface transfer mold 22 is formed of a concave surface P21, one end of the second optically effective surface transfer mold 22A is formed of a convex surface P21A (see FIG. 8).

(Side transfer mold)
The side surface transfer mold 23A is a cylindrical member. One end of the side surface transfer mold 23A forms a gap P33A, which is a distance ΔG, with a second area transfer mold 24A, which will be described later.

The transfer surface P31A, which is the inner surface of the side transfer mold 23A that protrudes from the first optically effective surface transfer mold 21A, transfers a part of the side surface 113A of the lens 10A. In addition, the bottom surface that constitutes one end of the side transfer mold 23A transfers the bottom surface of the gripping portion 12 of the lens 10.

The second area transfer mold 24A is a cylindrical member. One end of the second area transfer mold 24A forms a gap P33, which is the distance ΔG, with the side transfer mold 23A.

The transfer surface P32, which is the inner surface of the second area transfer mold 24A that protrudes from the second optically effective surface transfer mold 22, transfers a portion of the side surface 113A of the lens 10A and the reverse taper area, which is the second area 1212A of the outer peripheral surface 121A. The inner diameter of the transfer surface P32 is determined to correspond to the shape of the reverse taper area shown in FIG. 7.

Fourth embodiment
<Optical device>
An image pickup device 1, which is one aspect of an optical device according to a fourth embodiment of the present invention, will be described with reference to Fig. 9. Fig. 9 is a schematic cross-sectional view of the image pickup device 1.

As shown in FIG. 9, the imaging device 1 includes a housing 2, an optical system 3, a filter 4, and an imaging element 5.

The housing 2 houses the optical system 3, the filter 4, and the image sensor 5.

The optical system 3 is made up of six lenses in three groups, lenses 31 to 36. Of the lenses 31 to 36, lens 33 has the same structure as lens 10 shown in FIG. 1.

In this embodiment, among lenses 31 to 36, only lens 33 is a lens that is an aspect of the present invention. However, the lens that is an aspect of the present invention can be used in any of lenses 31, 35, and 36, one of which has an optically effective surface that is formed as a concave surface.

Filter 4 is a bandpass filter that transmits light that belongs to a specific wavelength range that includes the wavelength range used by lens 33, and does not transmit other light.

The image sensor 5 converts the light transmitted through the optical system 3 and the filter 4 into an electrical signal to generate image information representing an image. The image may be a still image or a moving image.

Although not shown, one aspect of the optical device according to the fourth embodiment of the present invention is not limited to an imaging device, and may be a measuring device that senses (measures) information related to distance. Examples of measuring devices include a TOF (Time-of-Flight) camera and LiDAR (Light Detection and Ranging or Laser Imaging Detection and Ranging). Such measuring devices include a light projection optical system that projects light used for sensing, and a light receiving optical system that receives the light used for sensing. In the measuring device, a lens (e.g., lens 10 shown in FIG. 1 and lens 10A shown in FIG. 7) which is one aspect of the present invention can be used in either or both of the light projection optical system and the light receiving optical system.

[First embodiment]
A first embodiment of the present invention will be described below. The first embodiment is an embodiment of a lens 10 shown in Fig. 1. The lens 10 is an example of a meniscus lens.

In this embodiment, the lens 10 was designed assuming use at around 10 μm. The material constituting the lens 10 was chalcogenide glass IRG206, which has a glass transition point of 180° C. The wavelength range in which the chalcogenide glass IRG206 is used is approximately 7 μm or more and 14 μm or less. In addition, the mold 20 shown in FIG. 5 was used as the mold for press-molding the lens 10, and the manufacturing method M1 shown in FIG. 6 was used as the manufacturing method.

In manufacturing method M1, a heating temperature of 225°C was used in heating step S11, and the chalcogenide glass IRG206 set in the internal space of the mold 20 was heated for 4 minutes before carrying out the pressing step S12.

Next, in parallel with the pressing process S12 in which a load FL of 500 N is applied to the die 20, the heating temperature is maintained at 225°C for 4 minutes, and then, with a load FL of 500 N applied to the die 20, the heating temperature is cooled to 180°C at a rate of -10°C/min.

After that, the load FL was not applied to the die 20 (FL = 0 N), and the temperature of the die 20 was gradually lowered from the heating temperature at the end of the pressing process S12 to room temperature.

In the lens 10 of this embodiment, the thickness T is T = 5.3 mm, the thickness t ₁ is t ₁ = 2 mm, and the thickness t ₂ is t ₂ = 0.8 mm. The diameter D ₁ is D ₁ = 9.2 mm, and the diameter D ₂ is D ₂ = 14.2 mm. The angle θ between the surface of the reverse taper region R _T and the surface perpendicular to the optical axis A _L of the lens 10 is θ = 45 °. The arrangement pitch P is P = 3.3 μm (= 0.33 λ), and the diameter d is approximately d = 3 μm (~ 0.33 λ). The arrangement of the multiple convex portions 1113 in the concave-convex structure 1111 is a hexagonal arrangement. The protrusion amount h and the protrusion amount h ₀ at the time of designing the multiple convex portions 1113 are set to 3.2 μm.

In the lens 10 manufactured using the mold 20 and the manufacturing method M1, the protrusion amounts h and _h0 of the multiple convex portions 1113 were measured and the average was calculated, which was 3.2 μm.

On the other hand, in a lens produced using a conventional mold in which no gap P33 was provided in the third portion P3 (i.e., a lens that is a comparative example of lens 10), the average value of the protrusion amount h and the protrusion amount _h0 of the multiple convex portions 1113 was 2.8 μm.

Therefore, it was found that the shape of the uneven structure of lens 10 can be made closer to the shape determined at the time of design.

Second Example
A second embodiment of the present invention will be described below. The second embodiment is an embodiment of the lens 10A shown in Fig. 7. The lens 10A is an example of a lens in which the first optically effective surface 111A and the second optically effective surface 112A are each formed of a concave surface.

In this example, lens 10A was designed assuming use at around 1.3 μm. Chalcogenide glass K-PG375, which has a glass transition point of 344° C., was used as the material constituting lens 10A. In addition, die 20A shown in FIG. 8 was used as the die for press-molding lens 10A, and manufacturing method M1 shown in FIG. 6 was used as the manufacturing method.

In manufacturing method M1, a heating temperature of 373°C was used in heating step S11, and the chalcogenide glass K-PG375 placed in the internal space of mold 20A was heated for 4 minutes before pressing step S12 was performed.

Next, in parallel with the pressing process S12 in which a load FL of 2KN is applied to the die 20A, the heating temperature is maintained at 373°C for 5 minutes, and then, with a load FL of 2KN applied to the die 20, the heating temperature is cooled to 352°C at a rate of -10°C/min.

After that, the load FL was not applied to the die 20A (FL = 0N), and the temperature of the die 20A was gradually lowered from the heating temperature at the end of the pressing process S12 to room temperature.

In the lens 10 of this embodiment, the thickness T is T = 8.5 mm, the thickness _t1 is _t1 = 2.5 mm, and the thickness _t2 is _t2 = 2.0 mm. In addition, the diameter _D1 is _D1 = 34.2 mm, and the diameter _D2 is _D2 = 34.0 mm. In addition, the angle θ between the surface of the reverse taper region _RT and the surface perpendicular to the optical axis of the lens 10A is θ = 45 °. In addition, the arrangement pitch P is P = 0.52 μm (= 0.4 λ), and the diameter d is approximately d = 0.48 μm (= 0.4 λ). In addition, a hexagonal arrangement is adopted as the arrangement of the multiple convex portions 1113A in the concave-convex structure 1111A. In addition, the protrusion amount h and the protrusion amount _h0 at the time of designing the multiple convex portions 1113A are set to 0.48 μm.

In the lens 10A manufactured using the mold 20A and the manufacturing method M1, the protrusion amounts h and _h0 of the multiple convex portions 1113A were measured and the average was calculated, and the average value was 0.48 μm.

On the other hand, in a lens produced using a conventional mold in which no gap P33A was provided in the third portion P3A (i.e., a lens that is a comparative example of lens 10A), the average value of the protrusion amount h and the protrusion amount _h0 of the multiple convex portions 1113 was 0.41 μm.

Therefore, it was found that the shape of the uneven structure of lens 10 can be made closer to the shape determined at the time of design.

〔summary〕
A lens according to a first aspect of the present invention comprises: a main portion including a first optically effective surface constituted by a concave surface and provided with an uneven structure that reduces reflection; a second optically effective surface opposed to the first optically effective surface; and a concentric side surface interposed between the first optically effective surface and the second optically effective surface; and a circular gripping portion provided around the entire circumference of the side surface and protruding from the side surface, the gripping portion having a first region that is a part of the outer circumferential surface and consisting of a free surface.

The fact that the first region, which is part of the outer peripheral surface, is made of a free surface means that the first region is not transferred by a mold in the press process for press-molding the lens. This means that the internal stress that occurs when a load is applied to the material in the press process of the lens is suppressed compared to the internal stress that occurs when a load is applied to the material in the press process of a conventional lens. Therefore, the lens is a lens that includes an optically effective surface that is composed of a concave surface and has an uneven structure that reduces reflection, and the shape of the optically effective surface can be made closer to the shape determined at the time of design than in the past.

The lens according to the second aspect of the present invention has the same configuration as the lens according to the first aspect described above, but in addition, the first region is formed in an annular shape around the entire circumference of the outer circumferential surface.

According to the above configuration, the first region is isotropically arranged when the first optically effective surface is viewed in a plan view. Therefore, the lens can have a higher symmetry in shape compared to a lens in which the first region is formed on a part of the outer circumferential surface.

The lens according to the third aspect of the present invention has, in addition to the configuration of the lens according to the first or second aspect described above, a configuration in which the thickness _t1 of the gripping portion and the thickness T of the thickest part of the lens satisfy 1 mm≦ _t1 ≦T−0.5 mm.

The lens according to the fourth aspect of the present invention has, in addition to the configuration of the lens according to any one of the first to third aspects described above, a configuration in which the thickness _t1 of the gripping portion and the thickness _t2 of the first region satisfy _t2 ≦0.9× _t1 .

With these configurations, when the lens is used as part of an optical device such as an imaging device or measuring device, it is possible to maintain a mechanical strength sufficient for practical use, and it is also possible to easily improve the precision when assembling the lens to the housing or frame of the optical device.

The lens according to the fifth aspect of the present invention has the same configuration as the lens according to any one of the first to fourth aspects described above, and further has a configuration in which the region of the outer circumferential surface other than the first region is defined as a second region, and the second region is adjacent to the first region and includes an inverse tapered region whose diameter increases as it approaches the first region.

The above configuration reduces discontinuities, preventing damage caused by stress concentration at corners. In addition, fluidity is ensured, preventing deterioration of the surface shape due to excessive internal stress.

The lens according to the sixth aspect of the present invention has the same configuration as the lens according to the fifth aspect described above, but in addition, the second region is configured with the reverse taper region and a straight region whose diameter is approximately constant regardless of the distance from the first region.

With the above configuration, the thickness of the gripping portion can be increased compared to when the second region is composed only of an inverted taper region, thereby increasing the mechanical strength of the gripping portion.

A lens according to a seventh aspect of the present invention employs, in addition to the configuration of the lens according to any one of the first to sixth aspects described above, a configuration in which the first optically effective surface is circular in a plan view, and an amount of protrusion f from the side surface of the gripping portion and a diameter _D1 of the first optically effective surface satisfy 0.5 mm≦f≦ _D1 .

The above configuration makes it possible to easily assemble the lens to the housing or frame of the optical device, while preventing the lens from becoming unnecessarily large, when the lens is used as part of an optical device such as an imaging device or a measuring device.

The lens according to the eighth aspect of the present invention has the same configuration as the lens according to any one of the first to seventh aspects described above, and further has a configuration in which the uneven structure is formed by regularly arranging a plurality of columnar protrusions, and the arrangement pitch P of the plurality of columnar protrusions satisfies 0.2×λ≦P≦λ, where λ is a predetermined wavelength that belongs to the wavelength range used.

The lens according to the ninth aspect of the present invention has the same configuration as the lens according to the eighth aspect described above, and further has a configuration in which the protrusion amount h of the multiple columnar protrusions satisfies 0.25×λ≦h.

A lens according to a tenth aspect of the present invention has the configuration of the lens according to the eighth or ninth aspect described above, and further has a configuration in which the first optically effective surface is circular in a plan view, and a protrusion amount h of the plurality of columnar protrusions satisfies 0.75× _h0 ≦h≦1.25× _h0 , where _h0 is the protrusion amount of the columnar protrusion that is closest to the optical axis of the first optically effective surface.

The lens according to the eleventh aspect of the present invention has the same configuration as the lens according to any one of the eighth to tenth aspects described above, and further has a configuration in which the plurality of columnar projections have a circular cross section and a tapered shape in which the diameter decreases from the base to the tip, and the diameter d of the plurality of columnar projections at the base satisfies 0.2×λ≦d≦0.6×λ.

These configurations are ideal for enhancing the reflection reduction performance of the uneven structure.

The lens according to the twelfth aspect of the present invention has the same configuration as the lens according to any one of the first to eleventh aspects described above, but is made of a single material that has a glass transition point.

The above configuration makes it easy to manufacture the lens using press molding.

The scope of the present invention also includes lenses according to any one of the first to twelfth aspects described above.

The mold according to the fourteenth aspect of the present invention is a mold for press-molding a lens having a first optically effective surface formed of a concave surface and provided with an uneven structure for reducing reflection, a second optically effective surface facing the first optically effective surface, and a main part including a concentric side surface interposed between the first optically effective surface and the second optically effective surface, and an annular gripping part provided around the entire circumference of the side surface and protruding from the side surface, and the mold is provided with a first part that transfers the shape of the first optically effective surface, the first part including a convex surface corresponding to the concave surface, a second part that transfers the shape of the second optically effective surface and facing the first part, and a third part that transfers the shape of the side surface and the gripping part, the transfer surface being concentric, and a gap being formed in an area corresponding to a part of the outer circumferential surface of the gripping part.

By using this mold, the lens according to the first aspect described above can be press molded.

The mold according to the fifteenth aspect of the present invention has the same configuration as the mold according to the fourteenth aspect described above, but in addition, the gap is formed in a circular ring shape around the entire circumference of the transfer surface of the third portion.

The above configuration can improve the symmetry of the press-molded lens shape.

The mold according to the sixteenth aspect of the present invention has the same configuration as the mold according to the fifteenth aspect described above, but also includes an adjustment mechanism for adjusting the spacing of the gap.

According to the above configuration, the spacing of the gap can be adjusted, so the magnitude of the internal stress that may occur when the lens is press molded can be adjusted. Therefore, the shape of the concave-convex structure in the lens after press molding can be fine-tuned without changing the mold.

The manufacturing method according to the seventeenth aspect of the present invention is a manufacturing method for manufacturing a lens by press molding using a mold, the lens having a first optically effective surface that is formed of a concave surface and has an uneven structure that reduces reflection, a second optically effective surface that faces the first optically effective surface, a main portion that includes a concentric side surface interposed between the first optically effective surface and the second optically effective surface, and an annular gripping portion that is provided around the entire circumference of the side surface and protruding from the side surface, the manufacturing method including a heating process for heating a material set in the mold, and a pressing process for press molding the material into the lens by applying weight to the mold, the pressing process performing press molding while releasing the pressure applied to a first region that is a part of the outer circumferential surface of the gripping portion.

By using this manufacturing method, the lens according to the first aspect described above can be press molded.

The manufacturing method according to the eighteenth aspect of the present invention has the same configuration as the manufacturing method according to the seventeenth aspect described above, but in addition, the heating step heats the material so that the temperature of the material is at least 15°C below the glass deformation point, and the pressing step presses the material into the lens in a state where the temperature is at least 15°C below the glass deformation point.

The above configuration allows the shape of the uneven structure to be closer to the shape determined at the time of design.

[Additional Notes]
The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

10, 10A Lens 11, 11A Main part 111, 111A First optically effective surface 1111, 1111A Uneven structure 1112, 1112A Circumscribed surface (concave surface)
1113, 1113A convex portion 112, 112A second optically effective surface 113, 113A side surface 12, 12A gripping portion 121, 121A outer peripheral surface 1211, 1211A first region 1212, 1212A second region R _S straight region R _T reverse tapered region 20, 20A mold 21, 21A first optically effective surface transfer mold 22, 22A second optically effective surface transfer mold 23, 23A side surface transfer mold 24, 24A second area transfer mold 25, 25A shim 26, 26A first Positioning die 27, 27A Second positioning die 28, 28A Sliding sleeve die

Claims (17)

a main portion including a first optically effective surface that is formed of a concave surface and that is provided with an uneven structure that reduces reflection, a second optically effective surface that faces the first optically effective surface, and a concentric side surface that is interposed between the first optically effective surface and the second optically effective surface;
and a circular grip portion provided around the entire periphery of the side surface and protruding from the side surface,
A lens characterized in that the outer peripheral surface of the gripping portion is composed of a first region consisting of a free surface and a second region consisting of a surface different from the free surface . The first region is formed in an annular shape around the entire outer circumferential surface.
The lens of claim 1 . The thickness _t1 of the gripping portion and the thickness T of the thickest portion of the lens satisfy 1 mm≦ _t1 ≦T−0.5 mm.
3. A lens according to claim 1 or 2. 4. The lens according to claim 1, wherein a thickness _t1 of the gripping portion and a thickness _t2 of the first region satisfy _t2 ≦0.9× _t1 . The second region is adjacent to the first region and includes a reverse tapered region whose diameter increases toward the first region.
The lens according to any one of claims 1 to 4. The second region is composed of the reverse tapered region and a straight region having a substantially constant diameter regardless of the distance from the first region.
6. The lens of claim 5. the first optically effective surface is circular in a plan view,
A protrusion amount f of the grip portion from the side surface and a diameter _D1 of the first optically effective surface satisfy 0.5 mm≦f≦ _D1 .
The lens according to any one of claims 1 to 6. the concave-convex structure is formed by regularly arranging a plurality of columnar projections,
The arrangement pitch P of the plurality of columnar protrusions satisfies 0.2×λ≦P≦λ, where λ is a predetermined wavelength that belongs to the wavelength range of use.
The lens according to any one of claims 1 to 7. a protrusion amount h of the plurality of columnar protrusions satisfies 0.25×λ≦h;
9. The lens of claim 8. the first optically effective surface is circular in a plan view,
a protrusion amount h of the plurality of columnar protrusions satisfies 0.75×h ₀ ≦h≦1.25×h ₀ , where h ₀ is a protrusion amount of a columnar protrusion that is closest to the optical axis of the first optically effective surface;
10. A lens according to claim 8 or 9. The plurality of columnar projections have a circular cross section and a tapered shape in which the diameter decreases from the base to the tip,
a diameter d of the plurality of columnar projections at the base satisfies 0.2×λ≦d≦0.6×λ;
The lens according to any one of claims 8 to 10. Consisting of a single material having a glass transition point;
The lens according to any one of claims 1 to 11. The lens according to any one of claims 1 to 12 is provided.
1. An optical device comprising: A mold for press-molding a lens, the mold comprising: a first optically effective surface formed of a concave surface and provided with an uneven structure for reducing reflection; a second optically effective surface opposed to the first optically effective surface; a main portion including a concentric side surface interposed between the first optically effective surface and the second optically effective surface; and an annular gripping portion provided around an entire periphery of the side surface and protruding from the side surface,
a first portion for transferring a shape of the first optically effective surface, the first portion including a convex surface corresponding to the concave surface;
a second portion that transfers a shape of the second optically effective surface and faces the first portion;
a third portion for transferring the shape of the side surface and the grip portion, the third portion having a concentric transfer surface and a gap formed in an area corresponding to an outer peripheral surface of the grip portion;
A mold characterized by: The gap is formed in an annular shape around the entire circumference of the transfer surface of the third portion.
15. The mold according to claim 14. Further comprising an adjustment mechanism for adjusting the gap.
16. The mold according to claim 15. A manufacturing method for manufacturing a lens by press molding using a mold, the lens comprising: a first optically effective surface that is formed of a concave surface and that is provided with an uneven structure that reduces reflection; a second optically effective surface that faces the first optically effective surface; a main portion that includes a concentric side surface that is interposed between the first optically effective surface and the second optically effective surface; and an annular gripping portion that is provided around an entire circumference of the side surface and protrudes from the side surface, the method comprising the steps of:
a heating step of heating the material set in the mold;
a pressing step of press-molding the material into the lens by applying a load to a die, the press molding being performed while releasing pressure applied to a first region that is a part of the outer circumferential surface of the gripping part and applying pressure to a second region that is a region of the outer circumferential surface other than the first region,
A manufacturing method comprising the steps of:

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