JP2022113699A - Optical element and method for manufacturing optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical element for which a Fresnel structure is used, and in which pasting (joining) together is easy and a warp is suppressed.

SOLUTION: An optical element comprises: a first optical element in which a concave lens of a Fresnel structure is formed on one principal surface, the other principal surface facing the principal surface having a planar shape; and a second optical element in which a convex lens of a Fresnel structure whose refractive index and focal distance almost equal those of the concave lens in terms of an absolute value is formed on one principal surface, the other principal surface facing the principal surface having a planar shape. The first optical element and the second optical element are joined together while the first plane of the first optical element having a planar shape and the second plane of the second optical element having a planar shape face each other.

SELECTED DRAWING: Figure 7

COPYRIGHT: (C)2022,JPO&INPIT

Description

The present invention relates to the technical field of optical elements using a Fresnel structure.

Techniques of this type are proposed in Patent Documents 1 to 3, for example. Patent Documents 1 and 2 propose a combiner in which a Fresnel lens-shaped half mirror is formed inside a flat plate. Patent Literature 3 proposes a combiner in which annular grooves made up of a plurality of Fresnel lens-like inclined surfaces are formed on both surfaces of one substrate.

Japanese Patent No. 4776669 JP 2011-191715 A JP-A-2000-249965

The combiners described in Patent Documents 1 and 2 are produced, for example, by bonding a substrate on which a Fresnel pattern is formed (Fresnel lens substrate) and a transparent cover substrate with an adhesive. However, with this method, since it is difficult for the adhesive to spread evenly on the surface on which the Fresnel pattern is formed, there are problems such as the inclusion of air bubbles in the adhesive and the uneven thickness of the adhesive. could have occurred.

On the other hand, the combiner described in Patent Literature 3 is produced, for example, by molding Fresnel patterns on both sides of one substrate (press transfer, injection molding, etc.). In this method, since no adhesion is performed, the above problems do not occur. However, there is a problem that the substrate tends to warp during pattern transfer or the like.

Examples of the problems to be solved by the present invention are as described above. SUMMARY OF THE INVENTION An object of the present invention is to provide an optical element using a Fresnel structure, which is easy to bond (bond) and suppresses warpage.

In the invention according to claim 1, the optical element comprises a first optical element in which a Fresnel structure concave lens is formed on one principal surface and the other principal surface opposite to the principal surface has a planar shape; and the concave lens. a second optical element having a convex lens with a Fresnel structure having substantially the same absolute values of refractive index and focal length on one principal surface and having a planar shape on the other principal surface opposite to the principal surface; The first optical element and the second optical element are bonded together in a state in which the first plane of the first optical element having a planar shape faces the second plane of the second optical element having a planar shape. It is characterized by

In the invention according to claim 7, the method for manufacturing an optical element includes forming a concave lens shape of a Fresnel structure by applying a mold to one of two opposing surfaces of the first substrate, Forming a convex lens shape with a Fresnel structure by forming a first optical element whose other surface has a planar shape, and applying a mold to one of the two opposing surfaces of the second substrate. and forming a second optical element having a planar surface on the other surface; , and a step of bonding.

1 is a diagram schematically showing a head-up display according to an embodiment; FIG. 2 is a schematic configuration diagram showing a combiner according to Comparative Example 1; FIG. FIG. 8 is a diagram for explaining a method for manufacturing a combiner according to Comparative Example 1; FIG. 11 is a schematic configuration diagram showing a combiner according to Comparative Example 2; It is a figure for demonstrating the manufacturing method of the combiner which concerns on the comparative example 2. FIG. It is a schematic block diagram which shows the combiner which concerns on 1st Example. It is a figure for demonstrating operation|movement of the combiner which concerns on 1st Example. It is a figure for demonstrating the manufacturing method of the combiner which concerns on 1st Example. FIG. 5 is a diagram for explaining a specific example of the characteristics of the translucent reflective film according to the first example; It is a schematic block diagram which shows the combiner which concerns on 2nd Example. It is a figure for demonstrating the manufacturing method of the combiner which concerns on 2nd Example.

In one aspect of the present invention, an optical element includes a first optical element in which a Fresnel structure concave lens is formed on one principal surface and the other principal surface opposite to the principal surface has a planar shape; a second optical element having a convex lens with a Fresnel structure having substantially the same absolute value of index and focal length on one principal surface and having a planar shape on the other principal surface opposite to the principal surface; and the first optical element. and a half mirror provided between the second optical element, wherein the first optical element and the second optical element have a planar shape with the main surface of the first optical element having a planar shape. The second optical element is joined through the half mirror while facing the main surface of the second optical element.

The optical element described above is used, for example, as a combiner for visualizing an image as a virtual image. The first optical element has a Fresnel structure concave lens formed on one principal surface and the other principal surface has a planar shape, and the second optical element has a Fresnel structure convex lens formed on one principal surface. , the other main surface has a planar shape. A concave lens and a convex lens have approximately the same absolute value of refractive index and focal length. A half mirror is provided between the first optical element and the second optical element. Furthermore, the first optical element and the second optical element are joined via a half mirror in a state in which the main surface of the first optical element having a planar shape faces the main surface of the second optical element having a planar shape. It is

In the optical element described above, since the surfaces having planar shapes are bonded together, the first optical element and the second optical element are properly bonded. In addition, since the optical element is configured by joining the first optical element and the second optical element, the optical element hardly warps. For example, even if the first optical element and the second optical element are warped, the first optical element and the second optical element are warped in the same way. be done. Thus, since the optical element is less likely to warp, it is possible to appropriately reduce the thickness of the optical element.

In the above description, the concave lens and the convex lens have substantially the same absolute values of the refractive index and the focal length, but the term "substantially equal" here means that the refractive index and the focal length are equal within the range in which the optical element exhibits the transmission function. (The same shall apply hereinafter).

In one aspect of the above optical element, the half mirror has a characteristic that the reflectance changes according to the wavelength of incident light. In a preferred example, the half mirror has characteristics such that the reflectance is high at wavelengths corresponding to red light, blue light, and green light. As a result, the brightness of the image displayed using the optical element can be improved without lowering the transmittance of the optical element.

In this specification, the term "half mirror" includes not only an optical element in which the intensity of reflected light and transmitted light is approximately the same, but also an optical element in which the intensity of reflected light and transmitted light is not the same. shall also be included. In other words, in this specification, the term "half mirror" means all optical elements that have both a reflective function and a transmissive function.

In another aspect of the present invention, the optical element includes a first optical element having a Fresnel structure concave lens formed on one principal surface and having a planar shape on the other principal surface opposite to the principal surface; A second optical element having a convex lens with a Fresnel structure having substantially equal absolute values of index and focal length formed on one principal surface and having a planar shape on the other principal surface opposite to the principal surface, and the concave lens are formed. and a half mirror provided on the main surface of the first optical element, wherein the first optical element and the second optical element have a planar shape with the principal surface of the first optical element having a planar shape. It is bonded with the main surface of the second optical element facing each other.

Also in the above optical element, since the surfaces having planar shapes are bonded together, the first optical element and the second optical element are in a state of being properly bonded. In addition, since the optical element is configured by joining the first optical element and the second optical element, the optical element hardly warps. Therefore, it is possible to appropriately reduce the thickness of the optical element. On the other hand, according to the above optical element, since the half mirror is provided on the main surface of the first optical element on which the concave lens is formed, this surface does not need to be coated with an antireflection film. Therefore, manufacturing costs can be reduced.

In another aspect of the above optical element, the concave lens and the convex lens have substantially the same lens pitch. Thereby, the transmittance of the optical element can be improved. Although the lens pitches of the concave lens and the convex lens are said to be substantially equal, the term "substantially equal" here means equal within the range in which the transmission function of the optical element is exhibited.

The optical element described above can be suitably applied to a head-up display.

According to another aspect of the present invention, a method for manufacturing an optical element includes applying a mold to one main surface of a first substrate to form a concave lens having a Fresnel structure on the main surface. A concave lens is formed in the first optical element, and the other main surface opposite to the main surface has a planar shape, and a mold is applied to one main surface of the second substrate, By forming a convex lens with a Fresnel structure whose absolute values of refractive index and focal length are substantially equal to those of the concave lens, the convex lens with the Fresnel structure is formed on the main surface, and the other main surface opposite to the main surface has a planar shape. and in a state in which the main surface of the first optical element having a planar shape and the main surface of the second optical element having a planar shape face each other, the first optical element and bonding the second optical element to the second optical element.

According to the optical element manufacturing method described above, since the first optical element and the second optical element are bonded between the surfaces having a planar shape, it is easy to appropriately bond the first optical element and the second optical element. can be done. In addition, even if the first optical element and the second optical element are warped at the time of fabrication, the first optical element and the second optical element are warped in the same way. A device is obtained.

In one aspect of the method for manufacturing an optical element described above, the step of forming a half mirror on the principal surface of the first optical element having a planar shape or the principal surface of the second optical element having a planar shape is further provided. can be

In another aspect of the method for manufacturing an optical element, the method may further include forming a half mirror on the main surface of the first optical element on which the concave lens is formed.

Preferred embodiments of the present invention will be described below with reference to the drawings.

[Configuration of head-up display]
FIG. 1 is a diagram schematically showing a head-up display according to this embodiment. In the head-up display, a screen (real image RI) to be displayed is formed, and the combiner 10 reflects light forming the real image RI, thereby allowing the driver to visually recognize the virtual image VI corresponding to the real image RI. For example, the real image RI corresponds to a screen displayed by a small liquid crystal display or an image formed on a screen by a projector (in one example, an image formed by an exit-pupil expander (EPE)). .

Here, in order to make the virtual image VI brighter and visible even in the daytime, it is sufficient to increase the light emission luminance of the real image RI, but this increases the power consumption and device price. . In order to increase the efficiency of light utilization, in a general head-up display, the light emission angle of the real image RI is limited, and the combiner 10 is configured to have a concave half surface so that the light reflected by the combiner 10 is concentrated on the observer's head. A mirror is used, and the focal length of the concave half mirror is set to an appropriate value. In one example, a half mirror using a Fresnel structure is used as the combiner 10 . Note that the area indicated by symbol EB in FIG. 1 is a virtual image observable area (eyebox) formed near the observer's head.

[Failure of Comparative Example]
Next, the deficiencies of the configurations described in Patent Documents 1 to 3 will be specifically described. Hereinafter, the configurations described in Patent Documents 1 and 2 are referred to as "Comparative Example 1", and the configuration described in Patent Document 3 is referred to as "Comparative Example 2".

FIG. 2 is a schematic configuration diagram showing an example of a combiner 10x according to Comparative Example 1. As shown in FIG. FIG. 2 shows a cross-sectional image diagram of the combiner 10x cut along a plane along the traveling direction of light. A combiner 10x according to Comparative Example 1 has a Fresnel lens substrate 10x1 on which a Fresnel lens is formed, and a transparent cover substrate 10x2. Specifically, in the combiner 10x according to Comparative Example 1, the Fresnel lens substrate 10x1 and the cover substrate 10x2 are bonded with an adhesive 10x4 such as an ultraviolet curable resin. In addition, in the combiner 10x according to Comparative Example 1, a translucent reflective film 10x3 is attached to the surface of the Fresnel lens substrate 10x1 on which the Fresnel lenses are formed.

FIG. 3 is a diagram for explaining an example of a method for manufacturing the combiner 10x according to Comparative Example 1. FIG. As shown in FIG. 3, after forming a Fresnel lens substrate 10x1 using a mold or the like, an adhesive 10x4 is placed between the Fresnel lens substrate 10x1 and the cover substrate 10x2, and pressure is applied as indicated by an arrow A1. do. As a result, the Fresnel lens substrate 10x1 and the cover substrate 10x2 are bonded together with the adhesive 10x4, whereby the combiner 10x according to Comparative Example 1 is produced. In such a manufacturing method, it is difficult for the adhesive 10x4 to spread uniformly (in other words, isotropically) on the surface on which the Fresnel lens is formed (uneven surface), so air bubbles are mixed in the adhesive 10x4. In some cases, a problem such as non-uniformity in the thickness of the adhesive 10x4 may occur.

FIG. 4 is a schematic configuration diagram showing an example of a combiner 10y according to Comparative Example 2. As shown in FIG. FIG. 4 shows a cross-sectional image diagram of the combiner 10y cut along a plane along the traveling direction of light. In the combiner 10y according to Comparative Example 2, one surface 10y1 of the two opposing surfaces is formed into a convex lens shape of a Fresnel structure (in other words, a surface shape of a Fresnel lens configured to function as a convex lens). The other surface 10y2 of the two opposing surfaces is configured in a Fresnel structure concave lens shape (in other words, a Fresnel lens surface shape configured to function as a concave lens). That is, in the combiner 10y according to Comparative Example 2, Fresnel patterns are formed on both surfaces 10y1 and 10y2 of one substrate.

FIG. 5 is a diagram for explaining a method of manufacturing a combiner 10y according to Comparative Example 2. FIG. As shown in FIG. 5, first, a plate-shaped substrate 10ya is placed between a mold 21 for forming a Fresnel structure convex lens shape and a mold 22 for forming a Fresnel structure concave lens shape. do. After that, with the substrate 10ya sandwiched between the molds 21 and 22 (assuming that the molds 21 and 22 are in a heated state), pressure is applied as indicated by an arrow A2. As a result, by removing the mold 21 and the mold 22, one surface 10y1 is molded into a Fresnel structure convex lens shape, and the other surface 10y2 is molded into a Fresnel structure concave lens shape, the combiner according to Comparative Example 2. 10y is created.

Here, in the method for manufacturing the combiner 10y according to Comparative Example 2, since there is no bonding process (specifically, because there is no bonding process), the problems described in the method for manufacturing the combiner 10x according to Comparative Example 1 does not occur. However, in the method of manufacturing the combiner 10y according to Comparative Example 2, there is a problem that the combiner 10y tends to warp during pattern transfer. Specifically, if there is even a slight difference in the stress generated when the molds 21 and 22 are removed, the combiner 10y warps. are different, the combiner 10y warps. In particular, when the thickness of the substrate 10ya is reduced, the warpage of the combiner 10y increases. If the combiner 10y warps in this way, the curvature (and thus the focal length) of the concave mirror that reflects the light from the real image RI changes, so the virtual image VI may be distorted or the position of the virtual image VI may change. do. Although the case of press transfer has been described as an example in FIG. 5, the combiner 10y is likely to warp even when injection molding is performed.

As described above, the manufacturing method according to Comparative Example 1 has a problem that it is difficult to properly bond the two members, and the manufacturing method according to Comparative Example 2 has a problem that the combiner 10y is easily warped. Therefore, in the present embodiment, a combiner that allows easy bonding and less warping is adopted.

[First embodiment]
First, the first embodiment will be described.

FIG. 6 shows a schematic configuration diagram of the combiner 10a according to the first embodiment. FIG. 6(a) shows a cross-sectional image view of the combiner 10a cut along a plane along the light traveling direction, and FIG. 6(b) is a cross-sectional view in which the broken line region R1 in FIG. 6(a) is enlarged. An image diagram is shown. The combiner 10a according to the first embodiment is applied to a head-up display instead of the combiner 10 shown in FIG.

As shown in FIG. 6A, the combiner 10a according to the first embodiment includes a concave lens (hereinafter referred to as "Fresnel concave lens") 10a1 to which the Fresnel structure is applied, and a convex lens (hereinafter referred to as "Fresnel concave lens") 10a1 to which the Fresnel structure is applied. 10a2, and a semi-transparent reflecting film 10a3 provided between the Fresnel concave lens 10a1 and the Fresnel convex lens 10a2. Further, as shown in FIG. 6B, the Fresnel concave lens 10a1 and the Fresnel convex lens 10a2 are bonded with a transparent adhesive 10a4 (for example, an ultraviolet curable resin) via a semi-transparent reflecting film 10a3. Furthermore, the Fresnel concave lens 10a1 and the Fresnel convex lens 10a2 have the same refractive index, the absolute value of the focal length, and the lens pitch (in other words, "pattern pitch"; the same shall apply hereinafter).

The combiner 10a is an example of the "optical element" in the present invention, the Fresnel concave lens 10a1 is an example of the "first optical element" in the present invention, and the Fresnel convex lens 10a2 is an example of the "second optical element" in the present invention. , and the semi-transparent reflective film 10a3 is an example of the "half mirror" in the present invention.

FIG. 7 shows a diagram for explaining the operation of the combiner 10a according to the first embodiment. As indicated by the dashed line region R2 in FIG. 7, the light from the real image RI is refracted when incident on the Fresnel convex lens 10a2, then reflected (specularly reflected) by the semi-transparent reflecting film 10a3, and then exits the Fresnel convex lens 10a2. Bend as it exits. In this case, the light from the real image RI passes through the Fresnel convex lens 10a2 twice and returns toward the real image RI in the same state as when it is reflected by the concave mirror. For example, when the combiner 10a is applied to a head-up display (FIG. 1), light from the real image RI returns to the driver's head.

On the other hand, as indicated by the dashed line area R3 in FIG. 7, the light incident on the combiner 10a from the opposite side of the real image RI (hereinafter referred to as "background light") is hardly affected by the lens action of the combiner 10a. emitted. That is, the background light passes through the combiner 10a with little lens effect. This is because the Fresnel concave lens 10a1 and the Fresnel convex lens 10a2 have the same refractive index, the absolute value of the focal length, and the lens pitch, as described above.

Although it is preferable that the Fresnel concave lens 10a1 and the Fresnel convex lens 10a2 have the same absolute values of the refractive index and the focal length, the absolute values of the refractive index and the focal length may be slightly different. This is because even if the Fresnel concave lens 10a1 and the Fresnel convex lens 10a2 have slightly different absolute values of refractive index and focal length, the transmittance of the combiner 10a can be ensured to some extent. From such a point of view, the permissible deviation of the absolute values of the refractive index and the focal length is determined based on the transmittance that the combiner 10a should have, and the Fresnel concave lens 10a1 and the Fresnel convex lens 10a2 are produced so as to be within the range of the deviation. good.

Similarly, it is preferable that the lens pitches of the Fresnel concave lens 10a1 and the Fresnel convex lens 10a2 are completely equal, but the lens pitches may deviate slightly. This is because even if the lens pitches of the Fresnel concave lens 10a1 and the Fresnel convex lens 10a2 are slightly different, the transmittance of the combiner 10a can be sufficiently ensured. From such a point of view, it is preferable to determine the permissible deviation of the lens pitch based on the transparency that the combiner 10a should have, and to produce the Fresnel concave lens 10a1 and the Fresnel convex lens 10a2 so as to be within the deviation range.

Also, the refractive index of the adhesive 10a4 is preferably equal to that of the Fresnel concave lens 10a1 and the Fresnel convex lens 10a2 (hereinafter simply referred to as "Fresnel lens" when not distinguished). By doing so, unnecessary reflection occurring at the interface between the adhesive 10a4 and the Fresnel lens can be suppressed. In addition, even if an antireflection film is not attached to the surface on which the Fresnel pattern is formed, a double image (the light reflected by the surface on which the Fresnel pattern is formed and the light reflected by the semi-transparent reflective film 10a3 may overlap). phenomenon) can be suppressed. However, the refractive index of the adhesive 10a4 and the refractive index of the Fresnel lens are not limited to the same, and the refractive index of the adhesive 10a4 and the refractive index of the Fresnel lens may be different.

FIG. 8 is a diagram for explaining the manufacturing method of the combiner 10a according to the first embodiment. First, the mold 31 for forming concave lens shapes of the Fresnel structure is applied to the substrate 10a11 having a flat plate shape, and the mold 32 for forming convex lens shapes of the Fresnel structure is applied to the substrate 10a11 having a flat plate shape. 10a21 (assuming molds 31 and 32 are in a heated state). After that, by removing the molds 31 and 32 from the substrates 10a11 and 10a21, the Fresnel concave lens 10a1 and the Fresnel convex lens 10a2 are produced. When the molds 31 and 32 are removed in this way, the molding surface of the Fresnel pattern cools and thermally shrinks, and as shown in FIG. It is in.

Next, a semi-transparent reflective film 10a3 is attached to the planar surface of the Fresnel convex lens 10a2 (that is, the surface on which the Fresnel pattern is not formed). After that, while the planar surface of the Fresnel concave lens 10a1 and the planar surface of the Fresnel convex lens 10a2 (strictly speaking, the surface to which the semi-transparent reflecting film 10a3 is attached) face each other, the concave Fresnel lens 10a1 and the Fresnel lens are An adhesive 10a4 is placed between the convex lens 10a2 and pressure is applied as indicated by an arrow A3. As a result, the Fresnel concave lens 10a1 and the Fresnel convex lens 10a2 are adhered with the adhesive 10a4, thereby producing the combiner 10a according to the first embodiment.

According to such a manufacturing method according to the first embodiment, since the adhesive surfaces of both the Fresnel concave lens 10a1 and the Fresnel convex lens 10a2 are flat, the adhesive 10a4 spreads easily. Moreover, since no pattern is formed on the adhesive surface, the adhesive 10a4 spreads uniformly (in other words, isotropically). Therefore, it is possible to appropriately suppress problems such as the inclusion of air bubbles in the adhesive 10a4 and the non-uniformity of the thickness of the adhesive 10a4, which may occur in the manufacturing method according to Comparative Example 1. Therefore, according to the manufacturing method according to the first embodiment, it is possible to easily and appropriately bond the Fresnel concave lens 10a1 and the Fresnel convex lens 10a2.

Furthermore, according to the manufacturing method according to the first example, since the Fresnel concave lens 10a1 and the Fresnel convex lens 10a2, which are similarly warped in the bowl shape, are bonded together, compared with the manufacturing method according to the comparative example 2, A combiner 10a can be made with significantly less warpage. Therefore, even if the thickness of the combiner 10a is reduced, it can be said that the combiner 10a is less likely to warp. Therefore, according to the first embodiment, it is possible to appropriately reduce the thickness of the combiner 10a.

In the above description, an example in which the semi-transparent reflecting film 10a3 is attached to the planar surface of the Fresnel convex lens 10a2 is shown (see FIG. 8). A film 10a3 may be attached.

Next, a specific example of reflectance characteristics (in other words, transmittance characteristics) of the semi-transparent reflecting film 10a3 as a half mirror will be described with reference to FIG. FIG. 9(a) shows one example of the reflectance characteristics of the semi-transparent reflective film 10a3, and FIG. 9(b) shows another example of the reflectance characteristics of the semi-transparent reflective film 10a3. In FIGS. 9A and 9B, the horizontal axis indicates the wavelength (nm) of the incident light, and the vertical axis indicates the transmittance (%) of the semi-transparent reflective film 10a3. The range of wavelengths shown on the horizontal axis roughly corresponds to the range of wavelengths for visible light. Also, the reflectance (%) of the semi-transparent reflective film 10a3 is "reflectance (%)=100-transmittance (%)".

In the example shown in FIG. 9A, the semi-transparent reflective film 10a3 has a characteristic that the reflectance is constant regardless of the wavelength. That is, in this example, the reflectance of the semi-transparent reflective film 10a3 is constant over the entire visible light.

In the example shown in FIG. 9(b), the semi-transparent reflective film 10a3 has the characteristic that the reflectance changes according to the wavelength. In this example, the reflectance of the semi-transparent reflective film 10a3 is high at a specific wavelength. Specifically, the translucent reflective film 10a3 has a property of largely reflecting light of a specific wavelength and hardly reflecting (transmitting) light of other wavelengths. The semi-transparent reflective film 10a3 having such characteristics functions as a band-pass filter (notch filter), and is realized by, for example, forming a multi-layer structure of a plurality of types of dielectric thin films. Preferably, a light source that emits red light, green light, and blue light (for example, a laser light source that emits red laser light, green laser light, and blue laser light) is used as the light source for forming the real image RI. Preferably, the semi-transparent reflective film 10a3 is configured so that the reflectance is high for each wavelength of red light, green light, and blue light. By doing so, the brightness of the image (virtual image) displayed by the combiner 10a can be improved without lowering the transmittance of the combiner 10a.

It should be noted that the semi-transparent reflective film 10a3 having the characteristics shown in FIG. 9(b) has a greater dependence on the angle of incidence than the semi-transparent reflective film 10a3 having the characteristics shown in FIG. 9(a). , Basically, it cannot be adopted for a structure using an uneven surface as a counter slope, such as a Fresnel structure. In the first embodiment, since a flat surface is used as the anti-slant surface, the semi-transparent reflective film 10a3 having the characteristics shown in FIG. 9B can be appropriately employed.

[Second embodiment]
Next, a second embodiment will be described. In the combiner 10a according to the first embodiment, the translucent reflecting film 10a3 is provided between the Fresnel concave lens 10a1 and the Fresnel convex lens 10a2, but in the combiner according to the second embodiment, the Fresnel pattern is formed in the Fresnel concave lens. A semi-transparent reflective film is provided on the surface.

In the following, the configuration different from that of the first embodiment will be mainly described, and the description of the configuration similar to that of the first embodiment will be omitted as appropriate. In other words, the configuration that is not particularly described here is the same as that of the first embodiment.

FIG. 10 shows a schematic configuration diagram of a combiner 10b according to the second embodiment. FIG. 10(a) shows a cross-sectional image view of the combiner 10b cut along a plane along the light traveling direction, and FIG. 10(b) is a cross-sectional view enlarging the broken line region R4 in FIG. 10(a). An image diagram is shown. Note that the combiner 10b according to the second embodiment is also applied to a head-up display instead of the combiner 10 shown in FIG.

As shown in FIG. 10(a), the combiner 10b according to the second embodiment includes a Fresnel concave lens 10b1, a Fresnel convex lens 10b2, and a translucent reflecting film 10b3 provided on the Fresnel pattern formed surface of the Fresnel concave lens 10b. and have Further, as shown in FIG. 10(b), the Fresnel concave lens 10b1 and the Fresnel convex lens 10b2 are bonded with a transparent adhesive 10b4 (for example, ultraviolet curable resin). Furthermore, the Fresnel concave lens 10b1 and the Fresnel convex lens 10b2 have the same refractive index, the absolute value of the focal length, and the lens pitch (pattern pitch).

The combiner 10b according to the second embodiment thus operates in the same manner as the combiner 10y according to the comparative example 2 (the configuration described in Patent Document 3). That is, the light from the real image RI is reflected by the semi-transparent reflecting film 10b3 and returns to the driver's head or the like in the same state as when it is reflected by the concave mirror. In addition, the background light passes through the combiner 10b with little lens effect.

The combiner 10b is an example of the "optical element" in the present invention, the Fresnel concave lens 10b1 is an example of the "first optical element" in the present invention, and the Fresnel convex lens 10b2 is an example of the "second optical element" in the present invention. and the semi-transparent reflecting film 10b3 is an example of the "half mirror" in the present invention.

FIG. 11 is a diagram for explaining a manufacturing method of the combiner 10b according to the second embodiment. First, a mold 41 for forming concave lenses of a Fresnel structure is applied to the substrate 10b11 having a flat plate shape, and a mold 42 for forming convex lenses of a Fresnel structure is applied to the substrate having a flat plate shape. 10b21 (assuming molds 41 and 42 are in a heated state). After that, by removing the molds 41 and 42 from the substrates 10b11 and 10b21, the Fresnel concave lens 10b1 and the Fresnel convex lens 10b2 are produced. When the molds 41 and 42 are removed in this manner, the molding surface of the Fresnel pattern cools and thermally shrinks, and as shown in FIG. It is in.

Next, a semi-transparent reflective film 10b3 is attached to the Fresnel pattern formed surface of the Fresnel concave lens 10b1. After that, with the planar surface of the Fresnel concave lens 10b1 and the planar surface of the Fresnel convex lens 10b2 facing each other, an adhesive 10b4 is placed between the Fresnel concave lens 10b1 and the Fresnel convex lens 10b2. Apply pressure as shown. As a result, the Fresnel concave lens 10b1 and the Fresnel convex lens 10b2 are adhered with the adhesive 10b4, thereby producing the combiner 10b according to the second embodiment.

According to the manufacturing method according to the second embodiment as well, since the adhesive surfaces of both the Fresnel concave lens 10b1 and the Fresnel convex lens 10b2 are flat, the adhesive 10b4 spreads easily and the adhesive 10b4 spreads evenly (in other words, etc.). directionally) spread out. Therefore, appropriate bonding between the Fresnel concave lens 10b1 and the Fresnel convex lens 10b2 can be easily performed. Also, according to the manufacturing method according to the second embodiment, since the Fresnel concave lens 10b1 and the Fresnel convex lens 10b2, which are similarly warped in a bowl shape, are bonded together, the combiner 10b with considerably less warpage can be produced. Therefore, according to the second embodiment, the thickness of the combiner 10b can be appropriately reduced.

On the other hand, according to the second embodiment, since the semi-transparent reflecting film 10b3 is attached to the surface of the Fresnel concave lens 10b on which the Fresnel pattern is formed, this surface does not need to be provided with an antireflection film, in other words, it is AR-coated. I don't have to. Therefore, in the combiner 10a according to the first embodiment, it was desirable to apply the antireflection film to both surfaces, but in the combiner 10b according to the second embodiment, it is sufficient to apply the antireflection film only to one surface. According to the second embodiment, manufacturing costs can be reduced more than the first embodiment.

In the above description, the Fresnel concave lens 10b1 and the Fresnel convex lens 10b2 are adhered after the translucent reflecting film 10b3 is attached to the Fresnel concave lens 10b (see FIG. 11). After bonding the convex lens 10b2, the translucent reflecting film 10b3 may be attached to the surface of the Fresnel concave lens 10b on which the Fresnel pattern is formed.

[Modification]
Although the embodiment in which the combiners 10a and 10b are produced by press transfer has been described above, the combiners 10a and 10b may be produced by injection molding instead of press transfer. That is, the present invention is applicable not only to press transfer but also to injection molding.

Although the embodiment in which the present invention is applied to a head-up display has been described above, the present invention can also be applied to a head-mounted display.

INDUSTRIAL APPLICABILITY The present invention can be used for display devices such as head-up displays.

10a, 10b Combiner 10a1, 10b1 Fresnel concave lens 10a2, 10b2 Fresnel convex lens 10a3, 10b3 Translucent reflecting film 10a4, 10b4 Adhesive

Claims (1)

a first optical element having a concave lens shape with a Fresnel structure formed on one of two surfaces facing each other and having a planar shape on the other surface;
a second optical element having a convex lens shape with a Fresnel structure formed on one of the two opposing surfaces and having a planar shape on the other surface;
with
The first optical element and the second optical element are bonded in a state in which the first plane of the first optical element having a planar shape faces the second plane of the second optical element having a planar shape. An optical element characterized by:

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