Composite diffraction elements, instruments, and image projection systems

Abstract

The present technology aims to provide a diffraction element that functions similarly to a transmission hologram, and more specifically, to provide a diffraction element suitable for forming an image projection system. The present technology provides a composite diffraction element, which includes a stacked structure that sequentially includes a first diffraction element, a second diffraction element, and a third diffraction element. The second diffraction element diffracts and reflects light that has passed through the first diffraction element and reached the second diffraction element toward the first diffraction element. The first diffraction element diffracts and reflects light diffracted and reflected by the second diffraction element toward the third diffraction element. The third diffraction element transmits the light diffracted and reflected by the first diffraction element, and diffracts and reflects zero-order light that has passed through the first diffraction element and the second diffraction element.

Description

Technical Field

[0001] The present technology relates to a composite diffraction element, an instrument, and an image projection system. More specifically, the present technology relates to a composite diffraction element having optical properties similar to those of a transmission diffraction element, and an instrument and an image projection system including the composite diffraction element. Background Art

[0002] In recent years, technology that superimposes images on scenes from the outside world (such as scenes in the real world) has attracted attention. This technology is also known as augmented reality (AR) technology. One product that uses this technology is a head-mounted display. The head-mounted display is mounted on the user's head during use. Using the image display method of the head-mounted display, when light from the head-mounted display and light from the outside world reach the user's eyes, for example, the user perceives as if the image formed by the light from the head-mounted display is superimposed on the image of the outside world.

[0003] One example of such a head-mounted display is an image projection system that includes a projection light source that projects image display light and a diffraction element that is separated from the projection light source and guides the image display light toward the eye. For example, Patent Document 1 below discloses a diffraction element that may be used in an image projection system. Patent Document 1 below discloses an invention relating to an optical combination that includes a first optical element and a second optical element arranged so that each optical element transmits or reflects incident light depending on the angle of incidence of the light.

[0004] Reference List

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2000-28925 Summary of the Invention

[0007] Problems to be solved by the present invention

[0008] For example, in an image projection system comprising a projection light source for projecting image display light and a diffraction element that is separated from the projection light source and guides the image display light to the eye, the diffraction element can be disposed in the lens portion of the glasses. In this case, the diffraction element is designed to transmissively diffract the image display light, or it can be formed as a transmission hologram. For example, the transmission hologram preferably only selectively transmissively diffracts the image display light and transmits light from the external scene, or the transmission hologram is expected to exhibit wavelength selectivity and angle selectivity. On the other hand, in order to be disposed in the lens portion, the transmission hologram is preferably formed into a thin film. However, it is difficult for a thin transmission hologram to exhibit wavelength selectivity and angle selectivity. Therefore, it is not easy to create a transmission hologram suitable as a diffraction element for an image projection system.

[0009] In addition, due to variations in film thickness, transmission holograms have a significant influence on diffraction efficiency (see, for example, H. Kogelnik and CV Shank, “Coupled-Wave Theory of Distributed Feedback Lasers”, J. Appl. Phys., 43, 5, pp. 2327-2335 (1972)). Therefore, it is difficult to stably produce transmission holograms having the diffraction performance that a diffraction element is expected to have.

[0010] The present technology aims to provide a diffraction element that functions similarly to a transmission hologram, and more particularly, aims to provide a diffraction element suitable for forming the above-mentioned image projection system.

[0011] Solutions to the Problem

[0012] The present technology provides a composite diffraction element, comprising:

[0013] a stacked structure comprising, in sequence, a first diffraction element, a second diffraction element, and a third diffraction element,

[0014] The second diffraction element diffracts and reflects the light that has passed through the first diffraction element and reached the second diffraction element toward the first diffraction element.

[0015] The first diffraction element diffracts and reflects the light diffracted and reflected by the second diffraction element toward the third diffraction element, and

[0016] The third diffraction element transmits the light diffracted and reflected by the first diffraction element, and diffracts and reflects the zeroth-order light that has passed through the first diffraction element and the second diffraction element.

[0017] The third diffraction element may diffract and reflect the zeroth order light having passed through the first diffraction element and the second diffraction element in a direction in which the zeroth order light is transmitted by both the first diffraction element and the second diffraction element.

[0018] According to one embodiment of the present technology, the composite diffraction element as a whole may have the optical characteristics of a transmissive diffraction element.

[0019] According to a preferred embodiment of the present technology, the composite diffraction element as a whole may have the optical characteristics of a transmissive diffraction lens.

[0020] The composite diffraction element of the present technology may have a structure in which two sets of stacked structures are stacked.

[0021] One of the two stacked structures may have the optical properties of a transmissive diffraction element, while the other stacked structure may have the optical properties of a transmissive diffraction lens. Light diffracted by one stacked structure may be incident on the other stacked structure, and the other stacked structure may diffract and converge the light.

[0022] The first diffraction element, the second diffraction element, and the third diffraction element constituting the composite diffraction element of the present technology may each diffract light of a plurality of wavelengths.

[0023] At least one of the first diffraction element, the second diffraction element, and the third diffraction element constituting the composite diffraction element of the present technology may be a stack of a plurality of diffraction element layers.

[0024] According to a preferred embodiment of the present technology, a transparent plate may be inserted into the stacked structure.

[0025] According to a preferred embodiment of the present technology, the first diffraction element, the second diffraction element, and the third diffraction element may be stacked on one surface of the transparent plate.

[0026] The composite diffraction element according to the present technology can be arranged for use in front of the eye and used to diffract image display light to reach the eye.

[0027] The image display light may be emitted from an image projection device separate from the compound diffraction element.

[0028] Each of the first diffraction element, the second diffraction element, and the third diffraction element may be a reflection hologram.

[0029] The present technology may also provide an apparatus comprising:

[0030] A composite diffraction element comprising a stacked structure, wherein the stacked structure sequentially comprises a first diffraction element, a second diffraction element, and a third diffraction element,

[0031] The second diffraction element diffracts and reflects the light that has passed through the first diffraction element and reached the second diffraction element toward the first diffraction element.

[0032] The first diffraction element diffracts and reflects the light diffracted and reflected by the second diffraction element to the third diffraction element.

[0033] The third diffraction element transmits the light diffracted and reflected by the first diffraction element, and diffracts and reflects the zero-order light having passed through the first diffraction element and the second diffraction element; and

[0034] A transparent plate for placing the compound diffractive element in front of the eye.

[0035] The present technology may also provide an image projection system, comprising:

[0036] A composite diffraction element comprising a stacked structure, wherein the stacked structure sequentially comprises a first diffraction element, a second diffraction element, and a third diffraction element,

[0037] The second diffraction element diffracts and reflects the light that has passed through the first diffraction element and reached the second diffraction element toward the first diffraction element.

[0038] The first diffraction element diffracts and reflects the light diffracted and reflected by the second diffraction element to the third diffraction element.

[0039] The third diffraction element transmits the light diffracted and reflected by the first diffraction element, and diffracts and reflects the zero-order light having passed through the first diffraction element and the second diffraction element; and

[0040] An image projection device projects image display light toward the compound diffraction element. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 is a diagram showing an example of an image projection system in which the composite diffraction element according to the present technology is used.

[0042] Figure 2 is a schematic diagram of a composite diffraction element of a reference example.

[0043] Figure 3 is a schematic diagram of an example of a composite diffraction element according to the present technology.

[0044] Figure 4A This is an example of the angle design of the composite diffraction element according to the present technology.

[0045] Figure 4B A diagram for explaining an example of angle design.

[0046] Figure 5 is a schematic diagram of a composite diffraction element of a reference example.

[0047] Figure 6 is a schematic diagram of an example of a composite diffraction element according to the present technology.

[0048] Figure 7A This is an example of the angle design of the composite diffraction element according to the present technology.

[0049] Figure 7B A diagram for explaining an example of angle design.

[0050] Figure 8 is a schematic diagram of an example of a composite diffraction element according to the present technology.

[0051] Figure 9 is a diagram showing an example of an exposure optical system for producing a first diffraction element as a reflection hologram having a lens function.

[0052] Figure 10 is a diagram showing an example of an exposure optical system for producing a first diffraction element as a reflection hologram having a lens function.

[0053] Figure 11 : is a diagram showing an example of an exposure optical system for producing a second diffraction element or a third diffraction element as a reflection hologram having a grating function.

[0054] Figure 12 is an example block diagram of an image projection device forming an image projection system according to the present technology.

[0055] Figure 13 This is a diagram for explaining the magnifying optical system.

[0056] Figure 14 This is a diagram for explaining the Maxwell-view optical system.

[0057] Figure 15 is a diagram showing an example of glasses equipped with a composite diffractive element according to the present technology.

[0058] Figure 16 is a diagram showing an example shape of a composite diffraction element according to the present technology.

[0059] Figure 17 is a diagram showing an example of glasses equipped with a composite diffractive element according to the present technology.

[0060] Figure 18 An example state in which a user is using an image projection system including an image projection device as a smartphone according to the present technology is shown.

[0061] Figure 19 : is a diagram showing an example configuration of an image projection device forming the image projection system of the present technology.

[0062] Figure 20 is a diagram illustrating an example configuration of an optical detection device.

[0063] Figure 21 is a schematic diagram of an example of a composite diffraction element according to the present technology.

[0064] Figure 22A This is an example of the angle design of the composite diffraction element according to the present technology.

[0065] Figure 22B A diagram for explaining an example of angle design. DETAILED DESCRIPTION

[0066] The following is a description of preferred embodiments for carrying out the present technology. Note that the embodiments described below are typical embodiments of the present technology, and the scope of the present technology is not limited to these embodiments. Note that the present technology will be described in the following order.

[0067] 1. First embodiment (composite diffraction element)

[0068] (1) Description of the first embodiment

[0069] (2) First Example of the First Embodiment (Example of a Composite Diffraction Element Having a Structure in Which Three Diffraction Elements Are Stacked)

[0070] (2-1) Composite Diffraction Element of Reference Example

[0071] (2-2) Composite Diffraction Element According to the Present Technology

[0072] (2-3) Example of Angle Design for the Composite Diffraction Element According to the Present Technology

[0073] (3) Second Example of the First Embodiment (Example of a Composite Diffraction Element Having Two Group Structures, Each Group Structure Having Three Diffraction Elements Stacked)

[0074] (3-1) Composite Diffraction Element of Reference Example

[0075] (3-2) Composite Diffraction Element According to the Present Technology

[0076] (3-3) Example of Angle Design for the Composite Diffraction Element According to the Present Technology

[0077] (3-4) Composite diffraction element according to the present technology

[0078] (3-5) Example of Angle Design for the Composite Diffraction Element According to the Present Technology

[0079] (4) Third Example of the First Embodiment (Example of a Color-Compatible Composite Diffraction Element)

[0080] (4-1) Description of Color-Compatible Composite Diffraction Element

[0081] (4-2) Evaluation of diffraction efficiency and zero-order dimming effect

[0082] (5) Example of a method for manufacturing a composite diffraction element according to the present technology

[0083] 2. Second embodiment (apparatus)

[0084] 3. Third embodiment (image projection system)

[0085] (1) Description of the third embodiment

[0086] (2) Example Configuration of Image Projection Device

[0087] 1. First embodiment (composite diffraction element)

[0088] (1) Description of the first embodiment

[0089] Refer to the following Figure 1 An example of an image projection system in which the composite diffraction element according to the present technology is used is described. Figure 1 The illustrated image projection system 1 includes an image projection device 10 and a diffraction element 20 that is separate from the image projection device 10 .

[0090] The image projection device 10 is equipped with a projection optical system, and image display light is projected from the image projection device 10 toward the diffraction element 20 provided in front of both eyes or one eye.

[0091] The diffraction element 20 can be held in front of the user 2's eyes (both eyes or one eye) 3. To maintain this position, the diffraction element 20 can be placed on glasses 21 designed to hold the diffraction element 20 in front of the eyes and worn on the head. The diffraction element 20 diffracts the image display light projected from the image projection device 10 and brings this image display light to the eyes. As a result, the user 2 of the image projection system 10 can view the image 4 (still image or moving image) formed by the image display light. In addition, the diffraction element 20 transmits light from the space in front of the glasses 21 (in the direction of the user 2's line of sight) and guides the light to the user 2's eyes. Therefore, the image 4 is recognized by the user 2 as an image existing in this space.

[0092] As described above, considering diffraction properties (such as diffraction efficiency, wavelength selectivity, and angle selectivity), it may be difficult to use a transmission hologram as the diffraction element 20 of the image projection system 1. Therefore, it has been considered to use a reflection hologram instead of a transmission hologram because it is easier to control the diffraction properties of a reflection hologram than a transmission hologram. For example, a stack of two reflection holograms can be used as a composite diffraction element that basically behaves like a transmission hologram. However, reflection holograms have the problem of zero-order light. Therefore, not all light reaching the reflection hologram is reflected and diffracted, but rather part of the light is transmitted. The transmitted zero-order light becomes stray light and may affect the image display of the diffracted first-order light.

[0093] The two optical elements constituting the optical combination disclosed in Patent Document 1 are considered to be reflection holograms or a stack of two reflection holograms. However, Patent Document 1 does not mention any zero-order light (stray light) that passes through the reflection holograms. If the optical combination is used as the diffraction element 20 of the image projection system 1 without any modification, problems caused by zero-order light may occur.

[0094] Furthermore, to reduce the generation of zero-order light, the diffraction efficiency of the reflection hologram can be maximized. In this case, the amount of zero-order light can be reduced by increasing the diffraction efficiency, but this requires increasing the thickness of the reflection hologram, resulting in a higher reflectivity or a significantly larger Δn of the holographic material. In the former case, due to the increased thickness of the reflection hologram, the angular selectivity of the reflection hologram is very narrow and wavelength-dependent, and the angular range and wavelength width of the input light do not allow for a margin. Therefore, there is a possibility that the image projection device 10 or the diffraction element 20 may not be covered for movement or shaking, and there is also a possibility that wavelength variations caused by temperature changes in the light source of the image projection device 10 may not be covered. In particular, when the diffraction element 20 is mounted on glasses, there needs to be a margin to cover the movement of the glasses, but the problem of not being able to cover movement due to the narrow angular range of the input light becomes prominent. On the other hand, in the latter case, preparing such a holographic material is impractical due to its difficulty.

[0095] The composite diffraction element according to the present technology has a stacked structure including a first diffraction element, a second diffraction element, and a third diffraction element in sequence. The second diffraction element diffracts and reflects light that has passed through the first diffraction element and reached the second diffraction element toward the first diffraction element. The first diffraction element diffracts and reflects light diffracted and reflected by the second diffraction element toward the third diffraction element. The third diffraction element transmits the light diffracted and reflected by the first diffraction element, and diffracts and reflects zero-order light that has passed through the first diffraction element and the second diffraction element. A more specific configuration of the composite diffraction element will be described later in (2).

[0096] Using a stacked structure including three diffraction elements in sequence, the composite diffraction element according to the present technology can basically function as a transmission hologram and prevent problems due to zero-order light.

[0097] In particular, the function of a transmission hologram is provided by the combination of the first diffraction element and the second diffraction element.

[0098] Furthermore, the third diffraction element specifically addresses the issues caused by zero-order light. Furthermore, since the third diffraction element addresses these issues, there's no need to increase the film thickness to improve reflectivity, nor is there a need to significantly increase the Δn of the holographic material, as described above. Consequently, the angular range or wavelength range of the input light does not become narrower due to increased film thickness, which would complicate the use of the diffraction element. Furthermore, the diffraction element can be made of inexpensive, readily available, stable, and easy-to-use general-purpose materials. Furthermore, the thickness of the diffraction element can be adjusted to a thickness that is easily usable.

[0099] In this specification, a composite diffraction element refers to a diffraction element formed by two or more diffraction element groups. The two or more diffraction element groups may have different diffraction properties. The two or more diffraction element groups are stacked, and the stacked structure forms a composite diffraction element.

[0100] In addition, in this specification, the light diffracted by the composite diffraction element is, for example, laser light, and may preferably be laser light for presenting an image to a user. In this specification, the light for presenting an image to a user is also referred to as image display light.

[0101] According to a preferred embodiment of the present technology, the third diffraction element can diffract and reflect zero-order light that has passed through the first diffraction element and the second diffraction element in the direction in which the zero-order light is transmitted by both the first diffraction element and the second diffraction element. With this arrangement, the problem caused by zero-order light can be more reliably solved.

[0102] For example, when the diffraction element is a single-layer diffraction element, the thickness of the first diffraction element may be 1 μm to 20 μm, or preferably 3 μm to 10 μm. When the first diffraction element is a stack of multiple diffraction element layers described later in (4), the thickness of each of the multiple diffraction element layers may be, for example, 1 μm to 20 μm, or preferably 3 μm to 10 μm. These numerical ranges also apply to the second and third diffraction elements.

[0103] Each of the three diffraction elements constituting the composite diffraction element according to the present technology can be a reflection hologram, or specifically a volume phase reflection hologram. In this specification, a reflection hologram can refer to a hologram that diffracts and reflects at least a portion of the incident light incident at a predetermined angle of incidence. The remaining incident light can pass through the reflection hologram. The reflection hologram can be made thinner and its diffraction properties, such as diffraction efficiency, wavelength selectivity, and angle selectivity, can be easily controlled. Since the three diffraction elements are all reflection holograms, the desired performance can be stably imparted to the composite diffraction element, and in addition, the composite diffraction element is easy to manufacture. In addition, for example, in the image projection system 1, it is easy to improve the transmission efficiency of light (such as light from an external scene) from the space in front of the glasses (the direction of sight of the user 2).

[0104] The first, second, and third diffraction elements can selectively diffract and reflect light incident at a predetermined angle of incidence at a predetermined exit angle. Note that these diffraction elements do not necessarily diffract and reflect all light incident at the predetermined angle of incidence, or may transmit a portion of the light incident at the predetermined angle of incidence. The angles of incidence of the light diffracted and reflected by the three diffraction elements are preferably different from each other.

[0105] In addition, the first diffraction element, the second diffraction element and the third diffraction element can selectively diffract and reflect light having a predetermined wavelength. The wavelengths of the light diffracted and reflected by the three diffraction elements are preferably the same.

[0106] According to one embodiment of the present technology, the composite diffraction element as a whole can have the optical characteristics of a transmission diffraction element. In other words, the composite diffraction element according to the present technology can be used as a transmission grating.

[0107] According to a particularly preferred embodiment of the present technology, the composite diffraction element as a whole can have the optical properties of a transmissive diffraction lens. For example, the first diffraction element can diffract and reflect light diffracted and reflected by the second diffraction element to converge the light. In other words, the light propagates in a spatially converging manner on one side of the third diffraction element. With this arrangement, the composite diffraction element according to the present technology can be used as a transmissive holographic lens. Since the composite diffraction element of the present technology used as a transmissive holographic lens is used as the diffraction element 20 in the above-mentioned image projection system 10, an image can be presented to the user using, for example, a Maxwell view.

[0108] According to another embodiment of the present technology, a composite diffraction element may have a structure in which two stacked structures are stacked, each stacked structure including a first diffraction element, a second diffraction element, and a third diffraction element. That is, in the composite diffraction element, six diffraction elements are stacked. In this embodiment, one stacked structure may have the optical properties of a transmissive diffraction element, while the other stacked structure may have the optical properties of a transmissive diffraction lens.

[0109] In this embodiment, the light obtained by diffraction performed by one stacked structure can be incident on another stacked structure, and the other stacked structure can diffract the light. More preferably, the light obtained by diffraction performed by one stacked structure can be incident on another stacked structure, and the other stacked structure can diffract and converge the light.

[0110] This combination of two stacked structures makes it easy to control the angular relationship between the incident and exiting optical axes relative to the entire composite diffraction element. For example, the optical axis angles of both the incident light entering the composite diffraction element and the light exiting the composite diffraction element can be set to 0 degrees. Furthermore, the composite diffraction element can function similarly to a thick transmissive lens.

[0111] The composite diffraction element according to this embodiment can also be used as the diffraction element 20 in the above-mentioned image projection system 10 and can present an image to a user through a Maxwell view, for example.

[0112] This embodiment will be described in more detail later in (3).

[0113] At least one (e.g., one, two, or all three) of the first, second, and third diffraction elements constituting the composite diffraction element of the present technology may be a stack of multiple diffraction element layers having different wavelength selectivities. Using such a stack, high diffraction reflectivity can be independently achieved for each wavelength. This embodiment will be described in more detail later in (4).

[0114] According to one embodiment of the present technology, a transparent plate may be inserted into the stacked structure, that is, the transparent plate may be interposed between two adjacent diffraction element layers included in the stacked structure.

[0115] For example, a transparent plate may be interposed between the first diffraction element and the second diffraction element, or a transparent plate may be interposed between the second diffraction element and the third diffraction element. In the former case, the layers are stacked in the order of "first diffraction element, transparent plate, second diffraction element, and third diffraction element." In the latter case, the layers are stacked in the order of "first diffraction element, second diffraction element, transparent plate, and third diffraction element."

[0116] In addition, in the case where at least one of the first diffraction element, the second diffraction element and the third diffraction element is a stack of multiple diffraction element layers as described later in (4), a transparent plate can be inserted between each layer of the multiple diffraction element layers.

[0117] In this embodiment, the transparent plate can be, for example, a lens of eyewear (e.g., glasses), an inner visor or an outer visor of a helmet, etc., but is not limited thereto. For example, three diffractive elements can be separately arranged on two surfaces of a lens of glasses.

[0118] According to another embodiment of the present technology, a first diffraction element, a second diffraction element, and a third diffraction element may be stacked in this order on one surface of a transparent plate. That is, in this embodiment, the layers may be stacked in the order of "first diffraction element, second diffraction element, third diffraction element, and transparent plate," or "transparent plate, first diffraction element, second diffraction element, and third diffraction element." The transparent plate in this embodiment may also be made of one of the aforementioned materials. For example, a stacked structure formed by three diffraction elements may be provided on one surface of a pair of eyeglass lenses.

[0119] Since the composite diffraction element according to the present technology is provided on a transparent plate as described above, it is easy to hold the composite diffraction element in front of the eye and to use the composite diffraction element as, for example, the diffraction element 20 in the above-described image projection system 1 .

[0120] The composite diffraction element according to the present technology can be placed in front of the eye and used to diffract image display light for delivery to the eye. The image display light can be emitted from an image projection device separate from the composite diffraction element. By using the composite diffraction element in this manner, it can function as the diffraction element 20 in the aforementioned image projection system 1, for example.

[0121] The composite diffraction element according to the present technology can be used in applications other than image projection. For example, the composite diffraction element according to the present technology can be used in various applications requiring a transmissive diffraction element (particularly a transmissive diffraction lens). The composite diffraction element according to the present technology can be used in optical information reading devices such as QR code (registered trademark) or barcode readers, or can be used as an optical filter in various devices.

[0122] (2) First Example of the First Embodiment (Example of a Composite Diffraction Element Having a Structure in Which Three Diffraction Elements Are Stacked)

[0123] Figure 2 A schematic diagram of a composite diffraction element of a reference example is shown to facilitate understanding of the present technology. Figure 2 (a) is a diagram for explaining how light propagates in a composite diffraction element, and for ease of explanation, two diffraction element layers constituting the composite diffraction element are separated from each other. Figure 2 (b) shows a state where two diffraction element layers are stacked.

[0124] Figure 3 A schematic diagram showing an example of a composite diffraction element according to the present technology. Figure 3 (a) is a diagram used to illustrate how light propagates in a compound diffraction element, similar to Figure 2 (a). Figure 3 (b) shows a state where three diffraction element layers are stacked.

[0125] In the following description, reference is made to Figure 2 and Figure 3 A composite diffraction element according to the present technology is described.

[0126] (2-1) Composite Diffraction Element of Reference Example

[0127] Figure 2 (a) and Figure 2 The composite diffraction element 100 shown in (b) comprises a first diffraction element 101 and a second diffraction element 102. The two diffraction elements are as follows: Figure 2 (b) is stacked as shown. Figure 2 (a) and Figure 2As shown in (b), the composite diffraction element 100 diffracts light L1 that reaches the composite diffraction element 100 from the upper side of the paper and causes light L5 to propagate toward the lower side of the paper. Light L1 is, for example, image display light, but is not limited thereto. The composite diffraction element 100 has a diffraction function that is substantially the same as that of a transmissive holographic lens that transmissively diffracts light L1 to obtain light L5. In the following description, how light propagates in the composite diffraction element 100 is described. In the following description, the following description is first described. Figure 2 How the light indicated by the solid line in (a) propagates (how the target light propagates) is then explained, and how the light indicated by the dotted line propagates (how the unnecessary zero-order light propagates).

[0128] (How target light propagates)

[0129] The first diffraction element 101 transmits the light L1 that has been incident thereon. The light L1 that has passed through the first diffraction element 101 reaches the second diffraction element 102.

[0130] The second diffraction element 102 diffracts and reflects the light L1 that has passed through the first diffraction element 101 toward the first diffraction element 101. The diffraction reflected light L2 propagates toward the first diffraction element 101.

[0131] The first diffraction element 101 diffracts and reflects the diffracted reflected light L2 toward the second diffraction element 102. The diffracted reflected light L5 propagates toward the second diffraction element 102.

[0132] The first diffraction element 101 is capable of diffracting, reflecting and converging the light L2, preferably as Figure 2 As shown in (a).

[0133] The second diffraction element 102 transmits the light L5 diffracted and reflected by the first diffraction element 101. The transmitted light L5 can be used as desired light or image display light, for example. As described above, the light L5 can be converged and used for image presentation, for example, through a Maxwell view.

[0134] (How does unwanted zero-order light propagate?)

[0135] Not all of the light L1 is diffracted and reflected by the second diffraction element 102, but part of the light L1 may pass through the second diffraction element 102. That is, the transmitted light L3 (dashed line) is zero-order light.

[0136] Not all of the light L2 is diffracted and reflected by the first diffraction element 101, but part of the light L2 may pass through the first diffraction element 101. That is, the transmitted light L4 (dashed line) is zero-order light.

[0137] As described above, due to the combination of first diffraction element 101 and second diffraction element 102, composite diffraction element 100 has a diffraction function similar to that of a transmissive diffraction element, or more specifically, a function similar to that of a transmissive diffraction lens. However, light L3, which is zero-order light, also propagates below the paper surface where diffracted reflected light L5 propagates. Therefore, light L3 may affect the use of light L5. For example, light L3 may have an undesirable effect on the display of an image using light L5.

[0138] (2-2) Composite Diffraction Element According to the Present Technology

[0139] like Figure 3 As shown, the composite diffraction element 150 according to the present technology includes a third diffraction element 103 in addition to the first diffraction element 101 and the second diffraction element 102. The first diffraction element 101, the second diffraction element 102 and the third diffraction element 103 are stacked in the order of "the first diffraction element 101, the second diffraction element 102 and the third diffraction element 103". Figure 3 (a) and Figure 3 (b) is shown. The first diffraction element 101, the second diffraction element 102, and the third diffraction element 103 have the optical properties described below. For example, the diffraction element having the optical properties can be formed by a reflection hologram, or specifically, a volume phase reflection hologram. The diffraction element having the optical properties can be manufactured by methods well known in the art, and for example, can be manufactured by the manufacturing method described in (4) below.

[0140] and Figure 2 Like the composite diffraction element 100 shown in FIG. 1 , the composite diffraction element 150 diffracts light L1 that reaches the composite diffraction element 150 from the upper side of the paper and causes light L5 to propagate toward the lower side of the paper. Light L1 is, for example, image display light, but is not limited thereto. The composite diffraction element 150 has a diffraction function substantially the same as that of a transmissive holographic lens that transmissively diffracts light L1 to obtain light L5. The following description will explain how light propagates within the composite diffraction element 150. First, the following description will be given. Figure 3 How the light indicated by the solid line in (a) propagates (how the target light propagates) is then explained, and how the light indicated by the dotted line propagates (how the unnecessary zero-order light propagates).

[0141] (How target light propagates)

[0142] The first diffraction element 101 transmits the light L1 that has been incident thereon. The light L1 that has passed through the first diffraction element 101 reaches the second diffraction element 102.

[0143] The second diffraction element 102 diffracts and reflects the light L1 that has passed through the first diffraction element 101 toward the first diffraction element 101. The diffraction reflected light L2 propagates toward the first diffraction element 101.

[0144] The first diffraction element 101 diffracts and reflects the diffracted reflected light L2 toward the second diffraction element 102 and the third diffraction element 103. The first diffraction element 101 diffracts and reflects and converges the light L2, preferably as Figure 3 As shown in (a), the diffracted reflected light L5 propagates toward the second diffraction element 102.

[0145] The second diffraction element 102 transmits the light L5 diffracted and reflected by the first diffraction element 101 , and the transmitted light L5 reaches the third diffraction element 103 .

[0146] The third diffraction element 103 transmits the light L5 transmitted by the second diffraction element 102. The light L5 that has passed through the third diffraction element 103 is used as desired light or image display light, for example. The light L5 can be concentrated as described above and used for image presentation, for example, through a Maxwell view.

[0147] (How does unwanted zero-order light propagate?)

[0148] Not all of the light L1 is diffracted and reflected by the second diffraction element 102 , but part of the light L1 may pass through the second diffraction element 102 . That is, the transmitted light L3 is zero-order light. The transmitted zero-order light L3 propagates to the third diffraction element 103 .

[0149] Not all of the light L2 is diffracted and reflected by the first diffraction element 101, but part of the light L2 may pass through the first diffraction element 101. That is, the transmitted light L4 is zero-order light.

[0150] The third diffraction element 103 diffracts and reflects the zero-order light L3 in a direction in which the light is transmitted by both the second diffraction element 102 and the first diffraction element 101. The light L6 diffracted and reflected by the third diffraction element 103 propagates toward the second diffraction element 102.

[0151] The second diffraction element 102 transmits the light L6. The light L6 having passed through the second diffraction element 102 further propagates toward the first diffraction element 101.

[0152] The first diffraction element 101 transmits the light L6 that has passed through the second diffraction element 102 .

[0153] As described above, the third diffraction element 103 causes at least a portion of the zero-order light L3 to propagate to Figure 3 The upper side of the paper, rather than spreading to Figure 3 Therefore, the influence of the zero-order light L3 on the light L5 can be reduced, and the quality of the light L5 can be improved.

[0154] (2-3) Example of Angle Design for the Composite Diffraction Element According to the Present Technology

[0155] Now refer to Figure 4A and Figure 4B Description for composition Figure 3 An example of angle design of incident light and reflected light for each diffraction element of the composite diffraction element 150 (an example of optical path design) is shown in FIG. Figure 4A Six examples of angle designs are shown. Figure 4B 1 is a diagram for explaining Example 1 of six examples of angle design.

[0156] Described below Figure 4A The angles shown in .

[0157] The “incident-exit angle margin” is a difference between the incident angle (In) of the light L1 incident on the second diffraction element 102 and the maximum value of the exit angle (Out) of the light L5 diffracted, reflected and converged by the first diffraction element 101 .

[0158] The "connection angle offset" is the difference between the incident angle of the light L1 incident on the second diffraction element 102 and the exit angle of the light L2 diffracted and reflected by the second diffraction element 102. The connection angle offset can be, for example, 0° (which means there is no connection angle offset), but is preferably greater than 0°, more preferably 1° or greater, or even more preferably 3° or greater. The connection angle offset can be, for example, 10° or less, or preferably 8° or less. Since the diffraction performance of the second diffraction element 102 is designed to have a connection angle offset, it is possible to distinguish the reflected light formed by the second diffraction element 102 from the light L1 from the diffracted reflected light formed by the second diffraction element 102 from the light L1.

[0159] The “incident angle” of the “second diffraction element” is the incident angle of the light L1 incident on the second diffraction element 102 .

[0160] The "exit angle" of the "second diffraction element" is the exit angle of the light L2 relative to the second diffraction element 102. The "exit angle" of the "second diffraction element" is greater than the "incident angle" of the "second diffraction element" by the angle offset.

[0161] The “incident angle” of the “first diffraction element” is the incident angle of the light L2 incident on the first diffraction element 101. The “incident angle” of the “first diffraction element” may be equal to the “exit angle” of the “second diffraction element”.

[0162] The value shown in the "Effective Range" of the "First Diffraction Element" is the maximum value of the angle of incidence of light L5 diffracted, reflected, and focused by the first diffraction element 101. For example, in Example 1, "±25" is displayed, indicating that the angle of incidence of light L5 diffracted, reflected, and focused by the first diffraction element 101 ranges from -25° to +25°.

[0163] The “incident angle” of the “third diffraction element” is the incident angle of the zero-order light L3 that has passed through the second diffraction element 102 and is incident on the third diffraction element 103. The “incident angle” of the “third diffraction element” may be equal to the “incident angle” of the “second diffraction element”.

[0164] The "exit angle" of the "third diffraction element" is the minimum value of the exit angle of light L6 diffracted and reflected by the third diffraction element 103 relative to the third diffraction element 103. In other words, the diffraction performance of the third diffraction element 103 can be preferably designed to diffract and reflect light L3 at an exit angle equal to or greater than the minimum value. Therefore, it is possible to more reliably prevent light L6 from being reflected or diffracted by the second diffraction element 102 or the first diffraction element 101 and propagating toward the bottom of the paper along the propagation direction of light L5.

[0165] The "exit angle" of the "third diffraction element" is preferably, for example, 1° or greater, or preferably 3° or greater, or more preferably 5° or greater, greater than the exit angle of light L2 relative to the second diffraction element 102. Even more preferably, the "exit angle" of the "third diffraction element" is greater than the exit angle of light L2 relative to the second diffraction element 102 by an incident exit angle margin or more. This arrangement can more reliably prevent light L6 from being diffracted and reflected by the first diffraction element 101.

[0166] about Figure 4A Example 1 of the six examples of angle design shown, refer to Figure 4B Describe how to design the angles of incident and reflected light relative to each diffractive element.

[0167] In Example 1, which illustrates an example of angle design, the second diffraction element 102 diffracts and reflects light L1 incident at an angle of 35° at an exit angle of 40°. That is, the second diffraction element 102 diffracts and reflects light L1 with a connection angle offset of 5°. Light L2 diffracted and reflected by the second diffraction element 102 propagates to the first diffraction element 101 and is incident on the first diffraction element 101 at an angle of 40°.

[0168] Note that the first diffraction element 101 transmits the light L1 incident at an incident angle of 35°.

[0169] The first diffraction element 101 diffracts and reflects the light L2 incident at an incident angle of 40° at an effective angle within a range of -25° to +25°. Figure 3 As shown, the light L2 is diffracted and reflected and is converged.

[0170] The second diffraction element 102 and the third diffraction element 103 transmit the light L5 diffracted and reflected at an exit angle within the effective range of the first diffraction element 101 .

[0171] The second diffraction element 102 does not diffract and reflect all the light L1 incident at an incident angle of 35°, but transmits a portion of the light L1 to generate zero-order light. The transmitted zero-order light L3 is incident on the third diffraction element 103 at an incident angle of 35°.

[0172] The third diffraction element 103 diffracts and reflects the zero-order light L3 at an exit angle of 50° or greater. With this arrangement, it is possible to prevent the zero-order light L3 from affecting the light L5.

[0173] The diffracted reflected light L6 propagates toward the second diffraction element 102 and the first diffraction element 101 and is incident at an incident angle of 50° or greater.

[0174] The second diffraction element 102 and the first diffraction element 101 both transmit the light L6 incident at an incident angle of 50° or greater. This arrangement prevents the light L6 from being reflected or diffracted by the second diffraction element 102 and the first diffraction element 101 and affecting the light L5.

[0175] The above-mentioned angle design can achieve the effect of the present technology. In addition, in Examples 2 to 6, the effect of the present technology can be achieved as in Example 1.

[0176] As described above, the first diffraction element, the second diffraction element, and the third diffraction element constituting the composite diffraction element according to the present technology can selectively diffract and reflect light incident at a predetermined angle of incidence. Note that these diffraction elements do not need to diffract and reflect all light incident at the predetermined angle of incidence, or may transmit a portion of the light incident at the predetermined angle of incidence.

[0177] (3) Second Example of the First Embodiment (Example of a Composite Diffraction Element Having Two Group Structures, Each Group Structure Having Three Diffraction Elements Stacked)

[0178] Figure 5 A schematic diagram of a composite diffraction element of a reference example is shown to facilitate understanding of the present technology. Figure 5 (a) is a diagram for explaining how light propagates in a composite diffraction element, and for ease of explanation, four diffraction element layers constituting the composite diffraction element are separated from each other. Figure 5 (b) shows four layers of diffractive elements stacked together.

[0179] Figure 6 A schematic diagram showing an example of a composite diffraction element according to the present technology. Figure 6 (a) is a diagram used to illustrate how light propagates in a compound diffraction element, similar to Figure 5 (a). Figure 6 (b) shows six layers of diffractive elements stacked together.

[0180] In the following description, reference is made to Figure 5 and Figure 6 A composite diffraction element according to the present technology is described.

[0181] (3-1) Composite Diffraction Element of Reference Example

[0182] Figure 5 The composite diffraction element 200 shown in (a) and 5 (b) includes a first combination 210 formed by a first diffraction element 201 and a second diffraction element 202, and a second combination 220 formed by a first diffraction element 204 and a second diffraction element 205. These four diffraction elements are as follows: Figure 5 (b) is stacked as shown. Figure 5 As shown in Figures 5(a) and 5(b), the composite diffraction element 200 diffracts light L21 that reaches the composite diffraction element 200 from the upper side of the paper, and causes light L29 to propagate toward the lower side of the paper. Light L21 may be, for example, image display light, but is not limited thereto. The composite diffraction element 200 has a diffraction function substantially similar to the transmissive diffraction function of transmissively diffracting light L21 to produce light L29.

[0183] In the following description, we first explain Figure 5 How the light indicated by the solid line in (a) propagates (how the target light propagates) is then explained, and how the light indicated by the dotted line propagates (how the unnecessary zero-order light propagates).

[0184] (How target light propagates)

[0185] The first diffraction element 201 transmits the light L21. The light L21 having passed through the first diffraction element 201 reaches the second diffraction element 202.

[0186] The second diffraction element 202 diffracts and reflects the light L21 having passed through the first diffraction element 201 toward the first diffraction element 201. The diffraction reflected light L22 propagates toward the first diffraction element 201.

[0187] The first diffraction element 201 diffracts and reflects the diffracted reflected light L22 , and the diffracted reflected light L25 propagates toward the second diffraction element 202 .

[0188] The second diffraction element 202 transmits the light L25 diffracted and reflected by the first diffraction element 201 .

[0189] The light L25 that has passed through the second diffraction element 202 reaches the first diffraction element 204 forming a combination 220 .

[0190] The first diffraction element 204 forming the combination 220 transmits the transmitted light L25 , and the transmitted light L25 reaches the second diffraction element 205 .

[0191] The second diffraction element 205 forming the combination 220 diffracts and reflects the transmitted light L25 toward the first diffraction element 204. The diffracted and reflected light 26 propagates toward the first diffraction element 204.

[0192] The first diffraction element 204 diffracts and reflects the diffracted reflected light L26 , and the diffracted reflected light L29 propagates toward the second diffraction element 205 .

[0193] The second diffraction element 205 transmits the light L29 diffracted and reflected by the first diffraction element 204. The transmitted light L29 can be used as desired light, or image display light, and can be used for image presentation through a Maxwell view, for example.

[0194] (How does unwanted zero-order light propagate?)

[0195] Not all of the light L21 is diffracted and reflected by the second diffraction element 202, but part of the light L21 may pass through the second diffraction element 202. That is, the transmitted light L23 is zero-order light.

[0196] In addition, in the first diffraction element 201, not all of the light L22 is diffracted and reflected, and part of the light L22 may pass through the first diffraction element 201. That is, the transmitted light L24 is zero-order light.

[0197] Not all of the light L25 is diffracted and reflected by the second diffraction element 205, and part of the light L25 may pass through the second diffraction element 205. That is, the transmitted light L27 is zero-order light.

[0198] Not all of the light L26 is diffracted and reflected by the first diffraction element 204, and part of the light L26 may pass through the first diffraction element 204. That is, the transmitted light L28 is zero-order light.

[0199] As described above, the combination 210 of the first diffraction element 201 and the second diffraction element 202, as well as the combination 220 of the first diffraction element 204 and the second diffraction element 205, each function similarly to a transmission diffraction hologram. Furthermore, the composite diffraction element 200, formed by stacking these two combinations, also exhibits a diffraction function similar to a transmission diffraction hologram. However, zero-order light L23 and light L27 also propagate below the paper surface where diffracted reflected light L29 propagates. Therefore, light L23 and light L27 may affect the use of light L29. For example, light L23 and light L27 may have an undesirable effect on the image display utilizing light L29.

[0200] (3-2) Composite Diffraction Element According to the Present Technology

[0201] like Figure 6As shown, the composite diffraction element 250 according to the present technology includes a first combination 260 and a second combination 270. The first combination 260 includes a third diffraction element 203 in addition to the first diffraction element 201 and the second diffraction element 202. The second combination 270 includes a third diffraction element 206 in addition to the first diffraction element 204 and the second diffraction element 205. Figure 6 As shown in (a) and 6 (b), these diffraction elements 201 to 206 are stacked in this order. Figure 5 Like the composite diffraction element 200 shown in FIG. , composite diffraction element 250 diffracts light L21 that reaches composite diffraction element 250 from the upper side of the paper, causing light L29 to propagate toward the lower side of the paper. Light L21 may be, for example, image display light, but is not limited thereto. Composite diffraction element 250 has a diffraction function substantially similar to the transmissive diffraction function of transmissively diffracting light L21 to produce light L29.

[0202] In the following description, we first explain Figure 6 How the light indicated by the solid line in (a) propagates (how the target light propagates) is then explained, and how the light indicated by the dotted line propagates (how the unnecessary zero-order light propagates).

[0203] (How target light propagates)

[0204] The first diffraction element 201 transmits the light L21. The light L21 having passed through the first diffraction element 201 reaches the second diffraction element 202.

[0205] The second diffraction element 202 diffracts and reflects the light L21 having passed through the first diffraction element 201 toward the first diffraction element 201. The diffraction reflected light L22 propagates toward the first diffraction element 201.

[0206] The first diffraction element 201 diffracts and reflects the diffracted reflected light L22 toward the second diffraction element 202. The diffraction reflected light L25 propagates toward the second diffraction element 202.

[0207] The second diffraction element 202 transmits the light L25 diffracted and reflected by the first diffraction element 201. The transmitted light L25 reaches the third diffraction element 203.

[0208] The third diffraction element 203 transmits the light L25 transmitted by the second diffraction element 202. The light L25 having passed through the third diffraction element 203 reaches the first diffraction element 204 forming the second combination 270.

[0209] The light L25 is transmitted through the first diffraction element 204. The light L25 having passed through the first diffraction element 204 reaches the second diffraction element 205.

[0210] The second diffraction element 205 diffracts and reflects the light L25 that has passed through the first diffraction element 204 toward the first diffraction element 204. The diffraction reflected light L26 propagates toward the first diffraction element 204.

[0211] The first diffraction element 204 diffracts and reflects the diffracted reflected light L26 toward the second diffraction element 205. The diffracted reflected light L29 propagates toward the second diffraction element 205.

[0212] The second diffraction element 205 transmits the light L29 diffracted and reflected by the first diffraction element 204. The transmitted light L29 reaches the third diffraction element 206.

[0213] The third diffraction element 206 transmits the light L29 transmitted by the second diffraction element 205. The light L29 passing through the third diffraction element 206 can be used as desired light or image display light, and can be used for image presentation through a Maxwell view, for example.

[0214] (How does unwanted zero-order light propagate?)

[0215] Not all of the light L21 is diffracted and reflected by the second diffraction element 202, but part of the light L21 may pass through the second diffraction element 202. That is, the transmitted light L23 is zero-order light. The transmitted zero-order light L23 propagates to the third diffraction element 203.

[0216] The third diffraction element 203 diffracts and reflects the zero-order light L23 . The light L30 diffracted and reflected by the third diffraction element 203 propagates toward the second diffraction element 202 .

[0217] The light L30 is transmitted through the second diffraction element 202. The light L30 having passed through the second diffraction element 202 further propagates toward the first diffraction element 201.

[0218] In addition, the first diffraction element 201 transmits the light L30 that has passed through the second diffraction element 202 .

[0219] Not all of the light L22 is diffracted and reflected by the first diffraction element 201, and part of the light L22 may pass through the first diffraction element 201. That is, the transmitted light L24 is zero-order light.

[0220] Not all of the light L25 is diffracted and reflected by the second diffraction element 205, but part of the light L25 may pass through the second diffraction element 205. That is, the transmitted light L27 is zero-order light. The transmitted zero-order light L27 propagates to the third diffraction element 206.

[0221] The third diffraction element 206 diffracts and reflects the zero-order light L27 . The light L31 diffracted and reflected by the third diffraction element 206 propagates toward the second diffraction element 205 .

[0222] The light L31 is transmitted through the second diffraction element 205. The light L31 having passed through the second diffraction element 205 further propagates toward the first diffraction element 204.

[0223] Furthermore, the first diffraction element 204 and all the diffraction elements 203 , 202 , and 201 constituting the first combination 260 transmit the light L31 that has passed through the second diffraction element 205 .

[0224] Not all of the light L26 is diffracted and reflected by the first diffraction element 204, and part of the light L26 may pass through the first diffraction element 204. That is, the transmitted light L28 is zero-order light.

[0225] Furthermore, all of the diffraction elements 203 , 202 , and 201 constituting the first combination 260 transmit the light L28 that has passed through the first diffraction element 204 .

[0226] As described above, the third diffraction element 203 forming the first combination 260 propagates the zero-order light L23 to Figure 6 The upper side of the paper, rather than spreading to Figure 6 Therefore, the zero-order light L23 can be prevented from affecting the light L29, and the quality of the light L29 can be improved.

[0227] In addition, the third diffraction element 206 forming the second combination 270 causes the zero-order light L27 to propagate to Figure 6 The upper side of the paper, rather than spreading to Figure 6 Therefore, the zero-order light L27 can be prevented from affecting the light L29, and the quality of the light L29 can be improved.

[0228] Note that, in the case where the composite diffraction element includes the transparent plate, the transparent plate may be interposed between the first diffraction element 201 and the second diffraction element 202, between the second diffraction element 202 and the third diffraction element 203, between the third diffraction element 203 and the first diffraction element 204, between the first diffraction element 204 and the second diffraction element 205, or between the second diffraction element 205 and the third diffraction element 206. Alternatively, all six layers may be laminated on one surface of the transparent plate.

[0229] Furthermore, in the case where any of these diffraction elements 201 to 206 is a stack of a plurality of diffraction element layers described in (4) below, a transparent plate may be interposed between the plurality of diffraction element layers.

[0230] (3-3) Example of Angle Design for the Composite Diffraction Element According to the Present Technology

[0231] Now refer to Figure 7A and Figure 7B Description for the above reference Figure 6An example of designing the angles of incident light and reflected light of each diffraction element of the composite diffraction element 250 (an example of optical path design) is described. Figure 7A Six examples of angle designs are shown. Figure 7B 1 is a diagram for explaining Example 21 of six examples of angle design.

[0232] Described below Figure 7A The angles shown in .

[0233] The “incident-exit angle margin” is the difference between the incident angle (In) of the light L25 incident on the second diffraction element 205 and the maximum value of the exit angle (Out) of the light L29 diffracted, reflected and converged by the first diffraction element 204 .

[0234] The "connection angle offset" is the difference between the incident angle of the light L25 incident on the second diffraction element 205 and to be diffracted and reflected by the second diffraction element 205, and the exit angle of the light L26 diffracted and reflected by the second diffraction element 205. The connection angle offset can be, for example, 0° (which means there is no connection angle offset), but is preferably greater than 0°, more preferably 1° or greater, or even more preferably 3° or greater. The connection angle offset can be, for example, 10° or less, or preferably 8° or less. Since the diffraction performance of the second diffraction element 205 is designed to have a connection angle offset, the reflected light of the light L25 at the second diffraction element 205 can be distinguished from the diffracted and reflected light of the light L25 at the second diffraction element 205.

[0235] The “incident angle” of the “second diffraction element” in the “first combination” is the incident angle of the light L21 that is incident on the second diffraction element 202 and is to be diffracted and reflected by the second diffraction element 202 .

[0236] The “exit angle” of the “second diffraction element” in the “first combination” is the exit angle of the light L22 diffracted and reflected by the second diffraction element 202 relative to the second diffraction element 202 .

[0237] The “incident angle” of the “first diffraction element” in the “first combination” is the incident angle of the light L22 incident on the first diffraction element 201 and to be diffracted and reflected by the first diffraction element 201. The “incident angle” of the “first diffraction element” may be equal to the “exit angle” of the “second diffraction element”.

[0238] The “outgoing angle” of the “first diffraction element” in the “first combination” is the outgoing angle of the light L25 diffracted and reflected by the first diffraction element 201 .

[0239] The “incident angle” of the “third diffraction element” in the “first combination” is the incident angle of the zero-order light L23 that passes through the second diffraction element 202 and is incident on the third diffraction element 203 .

[0240] The "exit angle" of the "third diffraction element" in the "first combination" is the minimum exit angle of light L30 diffracted and reflected by the third diffraction element 203 relative to the third diffraction element 203. In other words, the diffraction performance of the third diffraction element 203 can preferably be designed to diffract and reflect light L23 at an exit angle equal to or greater than this minimum value. Therefore, light L23 can be more reliably prevented from being reflected or diffracted by the second diffraction element 202 or the first diffraction element 201 and propagating in the propagation direction of light L29.

[0241] The “incident angle” of the “second diffraction element” in the “second combination” is the incident angle of the light L25 that is incident on the second diffraction element 205 and will be diffracted and reflected by the second diffraction element 205 .

[0242] The "exit angle" of the "second diffraction element" in the "second combination" is the exit angle of the light L26 diffracted and reflected by the second diffraction element 205 relative to the second diffraction element 205. The "exit angle" of the "second diffraction element" is greater than the "incident angle" of the "second diffraction element" by the angle offset.

[0243] The “incident angle” of the “first diffraction element” in the “second combination” is the incident angle of the light L26 incident on the first diffraction element 204 and to be diffracted and reflected by the first diffraction element 204. The “incident angle” of the “first diffraction element” may be equal to the “exit angle” of the “second diffraction element”.

[0244] The "effective range" of the "first diffraction element" in the "second combination" is the maximum range of the emission angle of light L29 diffracted, reflected, and focused by the first diffraction element 204. For example, in Example 21, "±25" is displayed, indicating that the emission angle range of light L29 diffracted, reflected, and focused by the first diffraction element 204 is -25° to +25°.

[0245] The “incident angle” of the “third diffraction element” in the “second combination” is the incident angle of the zero-order light L27 that passes through the second diffraction element 205 and is incident on the third diffraction element 206. The “incident angle” of the “third diffraction element” may be equal to the “incident angle” of the “second diffraction element”.

[0246] The "exit angle" of the "third diffraction element" in the "second combination" is the minimum exit angle of light L31 diffracted and reflected by the third diffraction element 206 relative to the third diffraction element 206. In other words, the diffraction performance of the third diffraction element 206 is preferably designed to diffract and reflect light L27 at an exit angle equal to or greater than this minimum value. Therefore, light L31 can be more reliably prevented from being reflected or diffracted by other diffraction elements 201 to 205 and propagating toward the bottom of the paper along the propagation direction of light L29.

[0247] Now refer to Figure 7A Example 21 of the six examples of angle design shown in FIG and reference Figure 7B Describe how to design the angles of incident and reflected light relative to each diffractive element.

[0248] (How light propagates in the first combination)

[0249] In Example 21 of the angle design example, the second diffraction element 202 diffracts and reflects light L21 incident at an incident angle of 0° at an exit angle of 30°. The light L22 diffracted and reflected by the second diffraction element 202 propagates to the first diffraction element 201 and is incident on the first diffraction element 201 at an incident angle of 30°.

[0250] Note that the first diffraction element 201 transmits the light L21 incident at an incident angle of 0°.

[0251] The first diffraction element 201 diffracts and reflects the light L22 incident at an incident angle of 30° at an exit angle of 35°.

[0252] The second diffraction element 202 and the third diffraction element 203 transmit the light L25 incident at an incident angle of 35°. The transmitted light L25 further propagates to the first diffraction element 204 forming a second combination 270.

[0253] The second diffraction element 202 does not diffract and reflect all the light L21 incident at an incident angle of 0°, but transmits a portion of the light L21 to generate zero-order light. The transmitted zero-order light L23 is incident on the third diffraction element 203 at an incident angle of 0°.

[0254] The third diffraction element 203 diffracts and reflects the zero-order light L23 at an exit angle of 45° or greater on the right side of the paper (the side opposite to the direction in which the light L22 is diffracted and reflected by the second diffraction element 202). This arrangement prevents the zero-order light L23 from affecting the light L29.

[0255] In addition, the diffraction reflected light L30 propagates toward the second diffraction element 202 and the first diffraction element 201, and is incident at an angle of incidence of 45° or greater. The second diffraction element 202 and the first diffraction element 201 both transmit the light L30 incident at an angle of incidence of 45° or greater. With this arrangement, it is possible to prevent the light L30 from affecting the light L29.

[0256] (How light propagates in the second combination)

[0257] As described above, light L25 passing through second diffraction element 202 and third diffraction element 203 reaches first diffraction element 204 forming second combination 270. First diffraction element 204 transmits light L25 incident at an incident angle of 35°. Transmitted light L25 propagates toward second diffraction element 205.

[0258] The second diffraction element 205 diffracts and reflects the light L25 incident at an incident angle of 35° at an exit angle of 40°. The light L25 diffracted and reflected by the second diffraction element 205 propagates to the first diffraction element 204 and is incident on the first diffraction element 204 at an incident angle of 40°.

[0259] The first diffraction element 204 diffracts and reflects the light L26 incident at an incident angle of 40° at an effective angle within a range of -25° to +25°. Figure 6 As shown, light L26 is diffracted and reflected and is converged.

[0260] The second diffraction element 205 and the third diffraction element 206 transmit the light L29 diffracted and reflected at an exit angle within the effective range of the first diffraction element 204 .

[0261] The second diffraction element 205 does not diffract and reflect all the light L25 incident at an incident angle of 35°, but transmits a portion of the light L25 to generate zero-order light. The transmitted zero-order light L27 is incident on the third diffraction element 206 at an incident angle of 35°.

[0262] The third diffraction element 206 diffracts and reflects the zero-order light L27 at an emission angle of 50° or greater. With this arrangement, it is possible to prevent the zero-order light L27 from affecting the light L29.

[0263] In addition, the diffraction reflected light L31 propagates toward the second diffraction element 205 and the first diffraction element 204 and is incident at an angle of incidence of 50° or greater. The second diffraction element 205 and the first diffraction element 204 both transmit the light L31 incident at an angle of incidence of 50° or greater. In addition, the three diffraction elements constituting the first combination also transmit the incident light L31 incident at an angle of incidence of 50° or greater. With this arrangement, it is possible to prevent the light L31 from affecting the light L29.

[0264] The above-mentioned angle design can achieve the effect of the present technology. In addition, in Examples 22 to 26, the effect of the present technology can be achieved as in Example 21.

[0265] (3-4) Composite diffraction element according to the present technology

[0266] In the above reference Figure 6 In the described composite diffraction element 250, the third diffraction element 203 of the first combination 260 diffracts and reflects the zero-order light at a predetermined exit angle on the right side of the paper (the side opposite to the direction in which the light L22 is diffracted and reflected by the second diffraction element 202).

[0267] In the present technology, the third diffraction element 203 of the first combination 260 can be designed to reflect the zero-order light to the opposite side, such as Figure 21 shown.

[0268] The third diffraction element 203 designed in this way also allows the zero-order light L23 to reach Figure 21 The upper side of the paper, rather than reaching Figure 21 Therefore, it is possible to prevent the zero-order light L23 from affecting the light L23 and to improve the quality of the light L29.

[0269] Note that the description in (3-2) above applies to Figure 21 Other diffractive elements shown.

[0270] (3-5) Other Examples of Angle Design of the Composite Diffraction Element According to the Present Technology

[0271] Now refer to Figure 22A and Figure 22B Description for the above reference Figure 21 Other examples of angle designs of incident light and reflected light for each diffraction element of the composite diffraction element 250 (examples of optical path designs) are described. Figure 22A Six examples of angle designs are shown. Figure 22B 1 is a diagram for explaining Example 27 of six examples of angle design.

[0272] Figure 22A The items in the table shown are consistent with the above Figure 7A The items described in (3-3) are the same as those in (3-3), and their descriptions also apply to this example.

[0273] Now refer to Figure 22A Examples 27 and 37 of the six examples of angled designs shown in Figure 22B To describe how to design the angles of incident and reflected light relative to each diffraction element

[0274] (How light propagates in the first combination)

[0275] In Example 27 of the angle design example, the second diffraction element 202 diffracts and reflects the light L21 incident at an incident angle of 0° at an exit angle of 30°. The light L22 diffracted and reflected by the second diffraction element 202 propagates to the first diffraction element 201 and is incident on the first diffraction element 201 at an incident angle of 30°.

[0276] Note that the first diffraction element 201 transmits the light L21 incident at an incident angle of 0°.

[0277] The first diffraction element 201 diffracts and reflects the light L22 incident at an incident angle of 30° at an exit angle of 35°.

[0278] The second diffraction element 202 and the third diffraction element 203 transmit the light L25 incident at an incident angle of 35°. The transmitted light L25 further propagates to the first diffraction element 204 forming a second combination 270.

[0279] The second diffraction element 202 does not diffract and reflect all the light L21 incident at an incident angle of 0°, but transmits a portion of the light L21 to generate zero-order light. The transmitted zero-order light L23 is incident on the third diffraction element 203 at an incident angle of 0°.

[0280] The third diffraction element 203 diffracts and reflects the zero-order light L23 at an exit angle of 40° or greater on the left side of the paper (the same side as the direction in which the light L22 is diffracted and reflected by the second diffraction element 202). This arrangement prevents the zero-order light L23 from affecting the light L29.

[0281] In addition, the diffraction reflected light L30 propagates toward the second diffraction element 202 and the first diffraction element 201, and is incident at an angle of incidence of 40° or greater. The second diffraction element 202 and the first diffraction element 201 both transmit the light L30 incident at an angle of incidence of 40° or greater. With this arrangement, it is possible to prevent the light L30 from affecting the light L29.

[0282] (How light propagates in the second combination)

[0283] As described above, light L25 passing through second diffraction element 202 and third diffraction element 203 reaches first diffraction element 204 forming second combination 270. First diffraction element 204 transmits light L25 incident at an incident angle of 35°. Transmitted light L25 propagates toward second diffraction element 205.

[0284] The second diffraction element 205 diffracts and reflects the light L25 incident at an incident angle of 35° at an exit angle of 50°. The light L25 diffracted and reflected by the second diffraction element 205 propagates to the first diffraction element 204 and is incident on the first diffraction element 204 at an incident angle of 50°.

[0285] The first diffraction element 204 diffracts and reflects the light L26 incident at an incident angle of 50° at an effective angle within a range of -25° to +25°. Figure 21 As shown, light L26 is diffracted and reflected and is converged.

[0286] The second diffraction element 205 and the third diffraction element 206 transmit the light L29 diffracted and reflected at an exit angle within the effective range of the first diffraction element 204 .

[0287] The second diffraction element 205 does not diffract and reflect all the light L25 incident at an incident angle of 35°, but transmits a portion of the light L25 to generate zero-order light. The transmitted zero-order light L27 is incident on the third diffraction element 206 at an incident angle of 35°.

[0288] The third diffraction element 206 diffracts and reflects the zero-order light L27 at an exit angle of 60° or greater. With this arrangement, it is possible to prevent the zero-order light L27 from affecting the light L29.

[0289] In addition, the diffraction reflected light L31 propagates toward the second diffraction element 205 and the first diffraction element 204 and is incident at an angle of incidence of 60° or greater. The second diffraction element 205 and the first diffraction element 204 both transmit the light L31 incident at an angle of incidence of 60° or greater. In addition, the three diffraction elements constituting the first combination also transmit the incident light L31 incident at an angle of incidence of 60° or greater. With this arrangement, it is possible to prevent the light L31 from affecting the light L29.

[0290] The above-mentioned angle design can achieve the effect of the present technology. In addition, in Examples 28 to 32, the effect of the present technology can be achieved as in Example 27.

[0291] (4) Third Example of the First Embodiment (Example of a Color-Compatible Composite Diffraction Element)

[0292] (4-1) Description of Color-Compatible Composite Diffraction Element

[0293] The composite diffraction element according to the present technology can diffract light of a single wavelength or multiple wavelengths. For example, the composite diffraction element according to the present technology can diffract light of a single wavelength band or multiple wavelength bands. The single wavelength light and the multiple wavelength light are preferably visible light. As described above, the composite diffraction element according to the present technology can have wavelength selectivity, or can selectively diffract only light within a specific wavelength range or multiple wavelength ranges. For example, the composite diffraction element according to the present technology that diffracts light of multiple wavelengths can be used to display color images.

[0294] When the composite diffraction element according to the present technology diffracts light of multiple wavelengths, the number of wavelengths (i.e., the number of wavelengths) is, for example, two to five, or preferably two to four, or more preferably two or three. In this case, the first diffraction element, the second diffraction element, and the third diffraction element can all diffract light of multiple wavelengths (i.e., multiple wavelengths). The multiple wavelengths diffracted by the first diffraction element, the second diffraction element, and the third diffraction element can all be the same. In this case, each diffraction element can be manufactured through multiple exposures.

[0295] In a particularly preferred embodiment, the composite diffraction element according to the present technology can diffract three colors of light: red (R), green (G), and blue (B). That is, the composite diffraction element diffracts light in three wavelength bands. For example, the wavelength band of red light can be in the range of 610nm to 750nm, or preferably in the range of 620nm to 700nm. For example, the wavelength band of green light can be in the range of 490nm to 560nm, or preferably in the range of 500nm to 550nm. For example, the wavelength band of blue light can be in the range of 420nm to 490nm, or preferably in the range of 430nm to 480nm.

[0296] According to one embodiment of the present technology, the first, second, and third diffraction elements can each be a single-layer diffraction element, or specifically, a single-layer reflection hologram. Each of the single-layer first, second, and third diffraction elements can diffract light of multiple wavelengths. The multiple wavelengths of light diffracted by these three diffraction elements are preferably identical. That is, the wavelength bands of the multiple wavelengths of light diffracted by these three diffraction elements are preferably identical. For example, as described above, the multiple wavelengths of light can be three colors: R, G, and B.

[0297] In this embodiment, the three diffraction elements can be manufactured by methods known in the art, and for example, can be manufactured by multiple exposures using R, G, and B light.

[0298] According to another embodiment of the present technology, at least one of the first diffraction element, the second diffraction element, and the third diffraction element may be a stack of multiple diffraction element layers. The stack of multiple diffraction element layers preferably has different wavelength selectivities.

[0299] In a single-layer diffraction element manufactured by multiple exposure using the aforementioned R, G, and B light, the diffraction efficiency is distributed by R, G, and B. Consequently, the proportion of light reflected by diffraction is low, and the amount of zero-order light (light transmitted without being diffracted) may be large. In view of this, as described above, each diffraction element is formed by stacking multiple diffraction element layers, thereby increasing the proportion of light reflected by diffraction.

[0300] Refer to the following Figure 8 This embodiment is described.

[0301] Figure 8 A corresponds to the above Figure 3 (a). Figure 8 In A, the first diffraction element 301, the second diffraction element 302 and the third diffraction element 303 each form a single-layer reflection hologram that selectively diffracts light of three colors: R, G and B.

[0302] Among these three diffraction elements, any one, two or all three can be a stack of multiple diffraction element layers. For example, the stack can be a stack of a diffraction element layer that diffracts red light, a diffraction element layer that diffracts blue light and a diffraction element layer that diffracts green light.

[0303] Figure 8 B is an example of a composite diffraction element, where each of the three diffraction elements is a stack of multiple diffraction element layers. Figure 8 C is an example of a composite diffraction element, wherein, among the three diffraction elements, the first diffraction element 301 is a single-layer diffraction element layer, and the second diffraction element 302 and the third diffraction element 303 are stacked layers of multiple diffraction element layers.

[0304] Since a stack of multiple diffraction element layers is used as the first, second or third diffraction element in this manner, the diffraction efficiency can be improved.

[0305] Furthermore, a stack of multiple diffraction element layers can be manufactured by forming three diffraction element layers having different wavelength selectivities by exposing them to light of R, G, and B and stacking the three diffraction element layers. The three diffraction element layers can be exposed to have the same diffraction angle.

[0306] Note, for example, Figure 8 The first diffraction element 301 in the embodiment has a lens function. In a diffraction element having a lens function, the interference fringes are distributed in two dimensions. In order to manufacture a diffraction element having a lens function by stacking a plurality of diffraction element layers, the plurality of diffraction element layers need to overlap each other two-dimensionally with high precision. At the same time, the second diffraction element 302 and the third diffraction element 303 do not need to have a lens function. In order to manufacture the second diffraction element 302 and the third diffraction element 303 by stacking a plurality of diffraction element layers, it is only necessary that the parallelism of the interference fringes of the plurality of diffraction element layers is the same, and these diffraction elements are easier to manufacture than diffraction elements having a lens function. Therefore, compared with the diffraction element having a lens function, Figure 8 Compared with the composite diffraction element shown in B, it can be manufactured more easily Figure 8 The composite diffraction element shown in C. In addition, Figure 8 In the composite diffraction element shown in C, the diffraction reflectivity can be improved by the second and third diffraction elements, thereby achieving both ease of manufacturing and optical performance.

[0307] As described above, in the composite diffraction element according to the present technology, the first diffraction element is preferably a single layer, and the second diffraction element and the third diffraction element are preferably stacked layers of a plurality of diffraction element layers.

[0308] (4-2) Evaluation of diffraction efficiency and zero-order light reduction effect

[0309] The following (4-2-1) will describe the calculation results shown in Table 2. Figure 2 and Figure 3 The diffraction efficiency of the composite diffraction element and the zero-order light reduction effect of the third diffraction element are shown.

[0310] The following (4-2-2) will describe the calculation results shown in Table 3. Figure 5 and Figure 6 The diffraction efficiency of the composite diffraction element and the zero-order light reduction effect of the third diffraction element are shown.

[0311] Note that in these calculations, it is assumed that the diffraction efficiencies of the first diffraction element, the second diffraction element, and the third diffraction element are as shown in Table 1 below.

[0312] [Table 1]

[0313] Table 1: Assumed diffraction efficiencies

[0314]

[0315] It is assumed that each composite diffraction element is made of one of the following material groups: material 1 (low diffraction index) or material 2 (high diffraction index) as shown in Table 1. In the material group of material 1, it is assumed that the diffraction efficiency of the single-layer diffraction element subjected to monochrome exposure is 60%, the diffraction efficiency of the single-layer diffraction element subjected to RGB multiple exposure is 20%, and the diffraction efficiency of each layer in the three-layer stack formed by three diffraction element layers exposed to R, G and B colors of light is 60%. As shown in Table 1, it is assumed that the diffraction efficiency of the single-layer diffraction element subjected to RGB multiple exposure is lower than the diffraction efficiency of the three-layer stack as described above. In addition, it is believed that the three-layer stack can achieve a diffraction efficiency similar to that of the single-layer diffraction element subjected to monochrome exposure, and therefore, the diffraction efficiency of these elements is set to the same value. For the material group of material 2, a higher diffraction efficiency than that of material 1 is set, as shown in Table 1.

[0316] (4-2-1) Figure 2 and Figure 3 Comparison between the composite diffraction elements shown

[0317] Examples 3-1 to 3-6 shown in Table 2-1 below represent materials made from the material group of Material 1 or Material 2 and Figure 2 The diffraction efficiency and the ratio of zero-order light L3 in the composite diffraction element are shown in Table 2-1. In Table 2-1, "Input-Output Diffraction Efficiency" is the diffraction efficiency of the composite diffraction element, that is, the ratio of the amount of outgoing light L5 to the amount of incident light L1. In the same table, "Ratio of Stray Light to Output Side" is the ratio of the amount of zero-order light L3 to the amount of incident light L1.

[0318] [Table 2]

[0319] Table 2: Evaluation of diffraction efficiency and zero-order light reduction effect

[0320] Table 2-1: Case where the third diffraction element is not included ( Figure 2 The case of a composite diffraction element in

[0321]

[0322] Table 2-2: Case where the third diffraction element is included ( Figure 3 The case of a composite diffraction element in

[0323]

[0324] Example 3-1 is now described.

[0325] Since the composite diffraction element of Example 3-1 is a monochromatic composite diffraction element and is made of material 1, the diffraction efficiency of the first and second diffraction elements constituting the composite diffraction element is 60%, as shown in Table 1. As described in the above “(2-1) Composite diffraction element of reference example”, Figure 2 In the composite diffraction element shown, the incident light L1 is diffracted twice: once by the second diffraction element and once by the first diffraction element, and then becomes the outgoing light L5. Therefore, the diffraction efficiency of the composite diffraction element of Example 3-1 is 60% × 60% = 36%.

[0326] In addition, as described in "(2-1) Composite diffraction element of reference example", Figure 2 In the composite diffraction element shown, a portion of the incident light L1 passes through the second diffraction element, and the transmitted zero-order light L3 propagates to Figure 2 The ratio of the amount of the zero-order light L3 to the amount of the incident light L1 is 100%-60%=40%.

[0327] Likewise, in Examples 3-2 to 3-6, the diffraction efficiency and the ratio of zero-order light were calculated and shown in Table 2-1.

[0328] Examples 4-1 to 4-6 in Table 2-2 above represent materials made from the material group of material 1 or material 2 and Figure 3 The diffraction efficiency of the composite diffraction element and the ratio of the zero-order light L3 are shown in Table 2-2. In Table 2-2, "Input-Output Diffraction Efficiency" is the diffraction efficiency of the composite diffraction element, that is, the ratio of the amount of the outgoing light L5 to the amount of the incident light L1. In this table, "Ratio of stray light to the output side" is the ratio of the zero-order light L3 that passes through the third diffraction element and propagates to the Figure 3 The ratio of the amount of light on the lower side of the paper to the incident light L1.

[0329] Example 4-1 is now described.

[0330] Since the composite diffraction element of Example 4-1 is a monochromatic composite diffraction element and is made of material 1, the diffraction efficiency of the first and second diffraction elements constituting the composite diffraction element is 60%, as shown in Table 1. As described in the above “(2-2) Composite diffraction element according to the present technology”, Figure 3 In the composite diffraction element shown, the incident light L1 is diffracted twice, once by the second diffraction element and once by the first diffraction element, and then becomes the outgoing light L5. Therefore, the diffraction efficiency of the composite diffraction element of Example 4-1 is 60%×60%=36%.

[0331] Furthermore, as described in “(2-2) Composite diffraction element according to the present technology”, in Figure 3 In the composite diffraction element shown in FIG, a portion of the incident light L1 passes through the second diffraction element and is converted into zero-order light L3. The zero-order light L3 is diffracted and reflected by the third diffraction element. However, according to the diffraction efficiency of the third diffraction element, a portion of the zero-order light L3 passes through the third diffraction element and propagates to the Figure 3 In the zero-order light L3, the ratio of the amount of light passing through the third diffraction element to the amount of incident light L1 is (100%-60%)×40%=16%.

[0332] Likewise, in Examples 4-2 to 4-6, the diffraction efficiency and the ratio of zero-order light were calculated and shown in Table 2-2.

[0333] A comparison between Examples 3-1 and 4-1 shows that while the diffraction efficiency is the same, the amount of zero-order light propagating to the lower side of the paper in Example 4-1 is lower than in Example 3-1 due to the presence of the third diffraction element. This also applies to the other examples. These calculation results demonstrate that the third diffraction element can be used to reduce the amount of zero-order light that could potentially affect the output light L5 of the composite diffraction element.

[0334] In addition, Examples 4-4 to 4-6 are calculation results when a material group with a high diffraction index is used. These results show that in this case, the amount of zero-order light that may affect the output light L5 of the composite diffraction element can be reduced to a very small amount by the third diffraction element.

[0335] (4-2-2) Figure 5 and Figure 6 Comparison between the composite diffraction elements shown

[0336] Examples 5-1 to 5-3 shown in Table 3-1 below represent materials made from the material group of Material 1 or Material 2 and Figure 5The diffraction efficiency and the ratio of zero-order light L3 in the composite diffraction element are shown in Table 3-1. In Table 3-1, "Input-Output Diffraction Efficiency" is the diffraction efficiency of the composite diffraction element, that is, the ratio of the amount of outgoing light L29 to the amount of incident light L21. In the same table, "Ratio of Stray Light to Output Side" is the ratio of the amount of zero-order light L3 to the amount of incident light L21.

[0337] [Table 3]

[0338] Table 3: Evaluation of diffraction efficiency and zero-order light reduction effect

[0339] Table 3-1: Case where the third diffraction element is not included ( Figure 5 The case of a composite diffraction element in

[0340]

[0341] Table 3-2: Case where the third diffraction element is included ( Figure 6 The case of a composite diffraction element in

[0342]

[0343] Example 5-1 is now described.

[0344] Since the composite diffraction element of Example 5-1 is a monochromatic composite diffraction element and is made of Material 2, the diffraction efficiency of the first and second diffraction elements constituting the composite diffraction element is 90%, as shown in Table 1. As described in the above “(3-1) Composite diffraction element of Reference Example”, Figure 5 In the composite diffraction element shown, the incident light L1 is diffracted four times by the four diffraction elements and then becomes the outgoing light L29. Therefore, the diffraction efficiency of the composite diffraction element of Example 5-1 is 90%×90%×90%×90%=65.6%.

[0345] In addition, as described in "(3-1) Composite diffraction element of reference example", Figure 5 In the composite diffraction element shown, a portion of the incident light L21 passes through the second diffraction element, and the transmitted zero-order light L23 propagates to Figure 5 Taking into account the average transmittance of the diffraction element 204, the ratio of the amount of zero-order light L23 to the amount of incident light L21 is expressed as: (100%-90%)×(average transmittance of the diffraction element 204: assumed to be 87%)=8.7%.

[0346] Here, the average transmittance of the diffraction element 204 is a value obtained when only the light within ±10° at the center of the lens is reflected and the peripheral light within the effective range of the lens (±25°) is transmitted.

[0347] In addition, a portion of the light L25 passes through the second diffraction element 205, and the transmitted light L27 propagates to Figure 5 The ratio of the amount of the zero-order light L27 to the amount of the incident light L21 is 90%×90%×(100%-90%)=8.1%.

[0348] Considering the above facts, the spread to Figure 6 The amount of zero-order light on the lower side of the paper is 8.7%+8.1%≈17%.

[0349] Likewise, in Examples 5-2 and 5-3, the diffraction efficiency and the ratio of zero-order light were calculated and shown in Table 3-1.

[0350] Examples 6-1 to 6-3 in Table 3-2 above represent materials made from the material group 2 and Figure 6 The diffraction efficiency of the composite diffraction element and the ratio of the zero-order light L3 are shown in Table 3-2. In Table 3-2, "Input-Output Diffraction Efficiency" is the diffraction efficiency of the composite diffraction element, that is, the ratio of the amount of the outgoing light L29 to the amount of the incident light L21. In this table, "Ratio of stray light to the output side" is the ratio of the zero-order light L23 that passes through the third diffraction element and propagates to the Figure 6 The ratio of the amount of light on the lower side of the paper to the incident light L21.

[0351] Example 6-1 is now described.

[0352] Since the composite diffraction element of Example 6-1 is a monochromatic composite diffraction element and is made of Material 2, the diffraction efficiency of the first and second diffraction elements constituting the composite diffraction element is 90%, as shown in Table 1. As described in "(3-2) Composite diffraction element according to the present technology" above, Figure 6 In the composite diffraction element shown, the incident light L21 is diffracted four times by the diffraction element and then becomes the outgoing light L29. Therefore, the diffraction efficiency of the composite diffraction element of Example 6-1 is 90%×90%×90%×90%=65.6%.

[0353] Furthermore, as described in “(3-2) Composite diffraction element according to the present technology”, in Figure 6 In the composite diffraction element shown in FIG. 1 , a portion of the incident light L21 passes through the second diffraction element and is converted into zero-order light L23. The zero-order light L23 is diffracted and reflected by the third diffraction element 203. However, according to the diffraction efficiency of the third diffraction element 203, a portion of the zero-order light L23 passes through the third diffraction element 203 and propagates to the Figure 6 Considering the transmission efficiency of the first diffraction element 204 and the diffraction reflection of the third diffraction element 206, the zero-order light L23 passes through the third diffraction element and propagates to Figure 6The ratio of the amount of light on the lower side of the paper to the incident light L21 is calculated as: (100%-90%)×(100%-90%)×(average transmittance of the diffraction element 204: assumed to be about 87%)=0.87%.

[0354] In addition, the zero-order light L27 is diffracted and reflected by the third diffraction element 206, but a portion of the zero-order light L27 passes through the third diffraction element 206 and propagates to the Figure 6 The zero-order light L27 passes through the third diffraction element 206 and propagates to the lower side of the paper. Figure 6 The ratio of the amount of light on the lower side of the paper to the amount of incident light L21 is calculated to be 90%×90%×(100%−90%)×(100%−90%)=0.81%.

[0355] Considering the above facts, the spread to Figure 6 The amount of zero-order light on the lower side of the paper is 0.87%+0.81%≈1.7%.

[0356] Likewise, in Examples 6-2 to 6-3, the diffraction efficiency and the ratio of zero-order light were calculated and shown in Table 3-2.

[0357] A comparison between Examples 5-1 and 6-1 shows that while the diffraction efficiency is the same, the amount of zero-order light propagating to the lower side of the paper in Example 6-1 is lower than in Example 5-1 due to the presence of the third diffraction element. This also applies to the other examples. These calculation results show that the third diffraction element can reduce the amount of zero-order light that could potentially affect the output light L29 of the composite diffraction element.

[0358] (5) Example of a method for manufacturing a composite diffraction element according to the present technology

[0359] Each of the first, second, and third diffraction elements constituting the composite diffraction element according to the present technology is designed to have the aforementioned diffraction characteristics. Those skilled in the art can manufacture these diffraction elements using manufacturing methods known in the art. The following description illustrates an example of an exposure optical system for manufacturing these diffraction elements.

[0360] Figure 9 This is an example of an exposure optical system for manufacturing a first diffraction element as a reflection hologram having a lens function. The reflection hologram diffracts and reflects light incident at an incident angle of 30° at an exit angle of -20° to +20° to converge the light.

[0361] exist Figure 9In the exposure optical system 500 shown, laser light is incident on a beam splitter 501. The beam splitter 501 splits the laser light into a reference light (gray line) and an object light (black line). A lens 502 is arranged in the propagation direction of the object light, and the object light refracted by the lens 502 reaches a photosensitive polymer 504 attached to a glass substrate 503 as a transparent plate. The photosensitive polymer 504 can be a material known in the art and can be appropriately selected by a person skilled in the art. The lens 502 refracts the object light to form the above-mentioned exit angle. At the same time, the reference light is reflected by the mirrors 505 and 506 and reaches the photosensitive polymer 504 from the opposite side of the object light. The reference light is incident on the photosensitive polymer 504 at the above-mentioned incident angle. The above-mentioned exposure optical system produces a reflection hologram that diffracts and reflects light incident at the above-mentioned incident angle at an exit angle of -20° to +20° and then converges the light.

[0362] Figure 10 This is another example of an exposure optical system for manufacturing a first diffraction element as a reflective hologram having a lens function. The reflective hologram diffracts and reflects light incident at an incident angle of 30° at an exit angle of -20° to +20° to converge the light.

[0363] exist Figure 10 In the exposure optical system 600 shown, laser light is incident on a beam splitter 601. The beam splitter 601 splits the laser light into a reference light (gray line) and an object light (black line). A lens 602 is arranged in the propagation direction of the object light, and the object light refracted by the lens 602 is converged and then reaches the photosensitive polymer 604 attached to the glass substrate 603. The lens 602 refracts the object light to form the above-mentioned exit angle. At the same time, the reference light is reflected by the mirrors 605 and 606 and reaches the photosensitive polymer 604 from the opposite side of the object light. The reference light is incident on the photosensitive polymer 604 at the above-mentioned incident angle. The above-mentioned exposure optical system produces a reflection hologram that diffracts and reflects light incident at the incident angle of the reference light and converges the diffracted reflected light in the same manner as the light converged by the lens 602.

[0364] Figure 11 This is an example of an exposure optical system for manufacturing a second diffraction element or a third diffraction element as a reflection hologram having a grating function. The reflection hologram diffracts and reflects light incident at an incident angle of 30° at an exit angle of 40°.

[0365] exist Figure 11In the exposure optical system 700 shown, laser light is incident on a beam splitter 701. Beam splitter 701 splits the laser light into reference light (gray line) and object light (black line). A photopolymer 704 attached to a glass substrate 703 is arranged in the propagation direction of the object light, and the object light passes through the photopolymer 704 at an exit angle of 40°. At the same time, the reference light is reflected by mirrors 705 and 706 and reaches the photopolymer 704 from the opposite side of the object light. The reference light is incident on the photopolymer 704 at an incident angle of 30°. The above-described exposure optical system produces a reflection hologram that diffracts and reflects light incident at the incident angle of the reference light.

[0366] 2. Second embodiment (apparatus)

[0367] The present technology also provides an instrument comprising the composite diffraction element described in "1. First Embodiment (Compound Diffraction Element)" above and a transparent plate for placing the composite diffraction element in front of the eye. The composite diffraction element is as described in "1. First Embodiment (Compound Diffraction Element)" above, and this description also applies to this embodiment. The instrument facilitates holding the composite diffraction element in front of the eye.

[0368] As described in "(1) Description of the First Embodiment" in Section 1. above, the transparent plate may be, for example, a lens of eyewear (e.g., glasses), an inner visor or an outer visor of a helmet, etc., but is not limited thereto. That is, the device may be, for example, an eyewear device or a helmet. For example, the device is applicable to an image projection system according to the present technology.

[0369] The transparent plate and the three diffraction elements constituting the composite diffraction element may be stacked as described in "(1) Description of the first embodiment" in 1. above.

[0370] 3. Third embodiment (image projection system)

[0371] (1) Description of the third embodiment

[0372] The present technology also provides an image projection system including the composite diffraction element described in "1. First Embodiment (Compound Diffraction Element)" above and an image projection device that projects image display light onto the composite diffraction element. The composite diffraction element is as described in "1. First Embodiment (Compound Diffraction Element)" above, and this description also applies to this embodiment. The image projection device can, for example, be separate from the composite diffraction element, or more specifically, separate from the composite diffraction element and the instrument that holds the element in front of the eye.

[0373] For example, an image projection system includes a composite diffraction element disposed within the lens portion of a pair of glasses, and an image projection device, separate from the glasses and configured to project image display light onto the composite diffraction element. The composite diffraction element diffracts the image display light and directs it toward the retina of a user wearing the image projection system. The composite diffraction element also transmits light from a scene in front of the glasses and directs it toward the user's retina. As a result, the image formed by the image display light appears to float within the scene.

[0374] An example of an image projection system according to the present technology is Figure 1 The image projection system 1 shown and described in "(1) Description of the first embodiment" in 1. above. In the following description, reference is made to Figure 1 and Figure 12 The image projection system 1 is described in detail. Figure 12 FIG. 1 is a block diagram of an example of the image projection device 10 forming the image projection system 1 .

[0375] like Figure 1 As shown, the image projection device 10 includes a position information acquisition unit 11, a projection optical system 12, and a control unit 13. The control unit 13 includes an image display light adjustment unit 14. Figure 12 As shown, a compound diffraction element 20 according to the present technology is positioned in front of the eyes of a user using an image projection system 1. Compound diffraction element 20 is positioned in front of the user's eyes via an apparatus 21. For example, apparatus 21 is a pair of glasses worn on the user's head. Image projection device 10 projects image display light toward compound diffraction element 20, which diffracts the image display light so that it reaches the user's retina. The following description explains each component.

[0376] The position information acquisition unit 11 acquires three-dimensional position information about the compound diffraction element 20 placed in front of both eyes or one eye. For example, the three-dimensional position information can be three-dimensional position information of the compound diffraction element 20 relative to the image projection device 10, or preferably, can be three-dimensional position information of the compound diffraction element 20 relative to the projection optical system 12.

[0377] When a compound diffraction element is positioned in front of both eyes, the three-dimensional positional information may more preferably be positional information regarding each compound diffraction element 20 positioned in front of the right and left eyes relative to the image projection device 10 (specifically, the projection optical system 12). In other words, the three-dimensional positional information may be positional information regarding each compound diffraction element in front of the left eye and the compound diffraction element in front of the right eye. This arrangement allows for adjustment of image display light based on left-eye parallax, presenting not only a two-dimensional image but also a stereoscopic or three-dimensional image to the user.

[0378] The position information acquisition unit 11 can preferably acquire three-dimensional position information about both eyes, or more preferably, acquire three-dimensional position information about the pupils of both eyes. Using both the three-dimensional position information about the compound diffraction element and the three-dimensional position information about both eyes, the image display light adjustment unit 14 can adjust the image display light based on the three-dimensional position information about the eyes relative to the compound diffraction element. Thus, the image display light can be adjusted to better suit the user.

[0379] The three-dimensional positional information about both eyes (particularly the pupils of both eyes) may be, for example, positional information about the composite diffraction element 20. More specifically, the three-dimensional positional information about both eyes may include positional information about the left eye relative to the composite diffraction element in front of the left eye, and positional information about the right eye relative to the composite diffraction element in front of the right eye.

[0380] Furthermore, the three-dimensional positional information about both eyes (particularly the pupils of both eyes) may include information about the positional relationship between the left eye and the right eye. For example, the positional relationship information about the left eye and the right eye may include the distance between the left eye and the right eye (particularly the distance between the pupils of the left eye and the right eye) and / or positional information of the left eye and the right eye relative to each other.

[0381] In addition, the three-dimensional position information about the two eyes may include information about the pupil size of the left eye and the right eye. For example, the information may include the diameter or radius of the pupil and / or the area of ​​the pupil.

[0382] For example, the position information acquisition unit 11 may include an optical detection device 15 such as an image sensor. For example, the image sensor may be a CMOS or a CCD. Figure 20 As shown, an image of the compound diffraction element 20 positioned in front of both eyes can be acquired using the optical detection device 15. The optical detection device 15 can be provided as part of the image projection device 10. That is, in the present technology, the position information acquisition unit can include an image sensor, and based on information acquired by the image sensor, or specifically, image information acquired by the image sensor, the position information acquisition unit 11 can acquire three-dimensional position information regarding the compound diffraction element 20. Acquisition of the three-dimensional position information can be performed by the image processing unit 16 included in the position information acquisition unit 11. To acquire the three-dimensional position information, for example, some other sensor, such as a TOF sensor, can be used.

[0383] Furthermore, the image generally includes images of both eyes. Therefore, the position information acquisition unit 11 (particularly the image processing unit 16) can acquire three-dimensional position information about both eyes from the image.

[0384] exist Figure 12, the image processing unit 16 is shown as a component different from the control unit 13. However, the image processing unit 16 may be included in the control unit 13.

[0385] According to one embodiment of the present technology, the image processing unit 16 can obtain three-dimensional position information about the compound diffraction element 20 by using a marker technique. For example, a marker for the image processing unit 16 to obtain three-dimensional position information can be provided on a portion or periphery of the compound diffraction element 20. By identifying the marker in the image, the image processing unit 16 can obtain three-dimensional position information about the compound diffraction element 20.

[0386] According to another embodiment of the present technology, the image processing unit 16 may obtain three-dimensional position information about both eyes through pupil recognition technology. As the pupil recognition technology, a technology known in the art may be used.

[0387] Alternatively, the image processing unit 16 may obtain the three-dimensional position information about the compound diffraction element and / or the eyes by performing three-dimensional measurement and / or learning on the compound diffraction element and / or the eyes.

[0388] According to a preferred embodiment of the present technology, the position information acquisition unit 11 can acquire three-dimensional position information about the compound diffraction element and / or the eyes in real time. Since the three-dimensional position information acquired in real time is used, the image display light can be projected more accurately.

[0389] The image projection device 10 includes a projection optical system 12, and the projection optical system 12 can be designed to project image display light onto an area covering both eyes. In the present technology, having a projection optical system can mean that the image display light that should reach the right eye and the left eye is projected from the same projection optical system. For example, having a projection optical system can mean that there is a projection port for projecting the image display light that should reach each eye. For example, having a projection optical system can mean that the light source for projecting the image display light that should reach each eye is the same. Since the image projection device constituting the image projection system of the present technology only includes one projection optical system, the size and / or cost of the image projection device can be reduced.

[0390] Note that the image projection device 10 may include two projection optical systems.

[0391] The image display light to be projected from the projection optical system 12 may be light emitted by an LED or a CRT. For example, the image display light may be laser light.

[0392] In the present technology, it is more preferable to design the image projectable area of ​​the projection optical system so that even if the three-dimensional position of the compound diffraction element changes due to, for example, shaking of the face or hand, the optical element remains within this area. As a result, even if the three-dimensional position of the compound diffraction element changes vertically, horizontally, or in the depth direction, the image display light adjustment unit can adjust the image display light so that the image display light can be projected at the changed position.

[0393] The projection optical system 12 is designed to project the image display light adjusted by the image display light adjustment unit 14 toward the compound diffraction element 20. The type of projection optical system used in this technology can be appropriately selected by those skilled in the art, for example, based on product concepts.

[0394] According to one embodiment of the present technology, the projection optical system 12 can be designed to project image display light to both eyes using a magnifying optical system. For example, the magnifying optical system is an optical system used in microscopes, telescopes, etc. According to another embodiment of the present technology, the projection optical system 12 can be designed so that the image display light can be focused near the pupil and emitted to the retina to achieve a Maxwell view. Figure 13 and Figure 14 Describe the magnification optical system and Maxwell-view optical system respectively.

[0395] like Figure 13 As shown, in the magnifying optical system, the image display light projected from the image projection device 31 passes through the compound diffraction element 32 and reaches the pupil 33. The luminous flux of the image display light passes through the entire pupil 33 and is focused on the retina. Therefore, even if the pupil 33 or the compound diffraction element 32 moves, it is easy to ensure the field of view, and the image does not easily disappear. In addition, the virtual image 34 that appears to float in space is focused at a fixed distance, so the image that is recognized can change according to the user's vision. For example, a projection optical system that projects image display light using a magnifying optical system may include a light source unit such as an LED and an image display unit such as a liquid crystal display.

[0396] like Figure 14As shown, in a Maxwell-view optical system, image display light projected from an image projection device 41 passes through a compound diffraction element 42 and reaches the pupil 43. The image display light is focused near the pupil and emitted onto the retina. In a Maxwell-view optical system, a point in the displayed image (the smallest display unit) passes through a point on the lens, so the image of a point on the retina is not easily affected by the state of the lens. For example, even users with myopia, hyperopia, astigmatism, etc. can clearly perceive the image. In addition, the virtual image, which appears to float in space, is unfocused and remains in focus at any distance from the eye. For example, in a Maxwell-view optical system, the image display light can be focused near the pupil, on the pupil, or offset from the pupil by approximately several to tens of millimeters (e.g., 1 mm to 20 mm, or more specifically, 2 mm to 15 mm) in the direction of the optical axis. As in the latter case, a Maxwell view can be achieved even if the focus is not on the pupil. More specifically, the image display light can be focused on the pupil, in the lens, or between the corneal surface and the pupil. Since the focus moves in the direction of the optical axis, the user can be prevented from missing the image even if the image moves. Figure 14 The pupil drawn by the dashed line can be moved in front of the position where the image display light converges (toward the compound diffraction element), making it less likely for the user to miss the image. For example, a projection optical system that projects image display light using a Maxwell-view optical system may include a light source unit that outputs laser light and an optical scanning unit that two-dimensionally scans the output laser light. For example, the laser light can be output as a single luminous flux formed by red, green, and blue laser beams. For example, the optical scanning unit may include a MEMS mirror. The optical scanning unit can move the direction of the laser light at high speed to form an image on the retina.

[0397] The image display light adjustment unit 14 adjusts the image display light based on the three-dimensional position information acquired by the position information acquisition unit 11. Through this adjustment, the image display light projected onto each eye becomes suitable for presenting the desired image to the user. For example, the image display light adjustment unit 14 may adjust at least one of the wavelength, intensity, and direction of the image display light. For example, the image display light adjustment unit 14 may adjust the image display light to shift or rotate the image, or to adjust the size or distortion of the image. The image display light adjustment unit 14 may preferably adjust the image display light based on binocular parallax.

[0398] According to a preferred embodiment of the present technology, the image display light adjustment unit 14 can adjust the image display light so that a different image display light is projected onto each eye. For example, the image display light adjustment unit 14 adjusts the image display light based on binocular parallax, thereby projecting a different image display light onto each eye. Because different image display lights are projected onto each eye, the user can perceive the three-dimensional position of the presented image through binocular vision, for example. For example, the image appears to float within the scene viewed through the glasses.

[0399] like Figure 1 As shown, the composite diffraction element 20 is separated from the image projection device 10 and placed in front of the eyes. The composite diffraction element 20 is used to diffract the image display light projected from the image projection device 10 and guide the image display light to the eyes. According to one embodiment of the present technology, Figure 1 As shown, the image projection device 10 may be located below the direction of the user's line of sight. Alternatively, the image projection device 10 may be located above the direction of the user's line of sight. The propagation direction of the image display light projected from the image projection device 10 is changed by the compound diffraction element 20 and guided to the user's eyes. As a result, the user can recognize the image formed by the image display light from the image projection device 10 without the image projection device 10 being present in the user's line of sight. According to another embodiment of the present technology, the image projection device 10 may be located at a height close to that of the user's line of sight. In this case, the brightness of the image is adjusted, and / or the position of the displayed image is limited to a part of the field of view (e.g., the upper half, lower half, left half, right half, etc.) so that the user does not mind the overlap between the image projection device and the external scene. Although Figure 1 The composite diffraction element 20 allows the image display light to be incident at an incident angle greater than 0°, but the image display light in the present technology can be incident on the composite diffraction element 20 at an incident angle of 0° (or can be incident vertically). In the latter case, for example, the composite diffraction element described in (3) above can be used.

[0400] The composite diffraction element 20 preferably has optical properties such that it functions as a lens for light within the wavelength range of the image display light and transmits light having wavelengths outside this wavelength range. Due to this optical property, a user can, for example, recognize a scene in the direction of their line of sight through the composite diffraction element 20 and can recognize an image formed by the image display light.

[0401] The composite diffractive element 20 may be included in an apparatus 21 for holding the element 20 in front of the eyes. That is, the optical element 20 may be held in front of the eyes by the apparatus 21. The apparatus may be, for example, glasses, goggles, or a helmet. For example, Figure 15As shown, the composite diffraction element 53 according to the present technology can be laminated on one surface (the surface on the outside view side or the surface on the eyeball side) of each lens 52 of the glasses 51. In addition, since the composite diffraction element has the above-mentioned optical characteristics, the instrument 51 can be used for its original purpose (for example, as glasses) without image projection. The composite diffraction element 20 is attached to an instrument appropriately selected by a person skilled in the art or a person skilled in the art, thereby enabling the use of the image projection system according to the present technology. Therefore, the range of selection of instruments that can be used in the present technology is very wide.

[0402] The apparatus 21 preferably does not include a projection optical system. The apparatus 21 may more preferably not include components required to project image display light (such as a projection optical system, a power supply, and a device driven by electricity). By designing the apparatus 21 in this manner, the size and / or weight of the apparatus 21 can be reduced.

[0403] As described above, image processing unit 16 can be provided with markers on a portion of or around the compound diffraction element 20, allowing image processing unit 16 to obtain three-dimensional position information. The number of markers can be, for example, one, two, three, four, or more. The use of multiple markers allows for more accurate three-dimensional position information to be obtained. The marker positions can be selected to be inconspicuous. This arrangement improves the design of the head-mounted unit.

[0404] Examples of the shape of the composite diffraction element and the arrangement of the markings are given in Figure 16 Shown in.

[0405] like Figure 16 As shown in Figure 1(a), a composite diffraction element 62-1 according to the present technology is attached to a portion of the lens surface of a pair of glasses 61-1. Four markers 63-1 are provided around the composite diffraction element 62-1. When the image processing unit 16 recognizes these markers 63-1, three-dimensional position information about the composite diffraction element 62-1 is acquired. For example, the markers 63-1 may be formed of a hologram, a reflective film, or an infrared reflective film, or may be a predetermined pattern, etc. If the markers 63-1 are infrared reflective films, the position information acquisition unit may include an infrared projection device and an infrared detection device.

[0406] like Figure 16 As shown in (b), the composite diffraction element 62-2 according to the present technology can be attached to a portion of the lens surface of the glasses 61-2. Figure 16 In (b), marks 63-2 are provided on the four corners of the composite diffraction element 62-2.

[0407] like Figure 16As shown in (c), the composite diffraction element 62-3 according to the present technology can be attached to the entire surface of the lens of the glasses 61-3. In this case, four marks 63-3 are provided in the composite diffraction element 62-3 according to the present technology.

[0408] As described above, regarding the image processing unit 16, the three-dimensional position information about the optical element for image display light diffraction and / or the eyes can be obtained by three-dimensionally measuring and / or learning the optical element for image display light diffraction and / or the eyes. In this case, the marking is unnecessary. Therefore, as Figure 17 As shown, for example, glasses 71 to which a composite diffractive element 72 according to the present technology is simply attached can constitute a system according to the present technology.

[0409] For example, the image projection device 10 may be a portable device such as a smartphone, a mobile phone, or a wristwatch terminal. Since such a portable device is used as the image projection device in the image projection system of the present technology, image projection according to the present technology can be achieved by a small or ultra-small mobile device. Figure 18 The figure shows an example of a user using an image projection system according to the present technology, including an image projection device such as a smartphone. Glasses 850 are mounted on the user's head, and a composite diffraction element 851 according to the present technology is attached to the lenses of the glasses 850. For example, the user also holds a smartphone 810 in his / her hand.

[0410] Smartphone 810 is equipped with an image sensor (camera) 811. Image sensor 811 acquires three-dimensional positional information about a compound diffraction element 851 located in front of the user's eyes, and if necessary, acquires three-dimensional positional information about both eyes. Based on this three-dimensional positional information, a position information acquisition unit in smartphone 810 adjusts the image display light. The adjusted image display light is projected from projection port 812 of smartphone 810 toward compound diffraction element 851. The image display light is diffracted by compound diffraction element 851 and reaches both eyes of the user. As a result, the user perceives an image superimposed on the external scene.

[0411] The composite diffraction element 851 may also have optical properties such that it acts as a lens for light within the wavelength range of the image display light and transmits light having wavelengths outside of this wavelength range. As a result, the image formed by the image display light is superimposed on the external scene.

[0412] (2) Example Configuration of Image Projection Device

[0413] In the following description, reference is made to Figure 19 An example configuration of an image projection device forming the image projection system of the present technology is described. Figure 19is a diagram illustrating an example schematic configuration of an image projection device according to the present technology.

[0414] Figure 19 The image projection apparatus 1000 shown includes a central processing unit (CPU) 1002 and a RAM 1003. The CPU 1002 and the RAM 1003 are connected to each other by a bus 1005, and are also connected to other components of the image projection apparatus 1000 via the bus 1005.

[0415] The CPU 1002 controls the image projection device 1000 and performs arithmetic operations. Any suitable processor can be used as the CPU 1002, and examples thereof include processors of the Snapdragon (registered trademark) series, the Xeon (registered trademark) series, the Core (registered trademark) series, and the Atom (registered trademark) series. For example, referring to Figure 12 The functions of the control unit 13 , the image display light adjustment unit 14 , and the image processing unit 16 of the described image projection device 10 can be realized by the CPU 1002 .

[0416] The RAM 1003 includes, for example, a cache memory and a main memory, and can temporarily store programs to be used by the CPU 1002 .

[0417] The image projection apparatus 1000 may further include a magnetic disk 1004 , a communication device 1006 , a projection optical system 1007 , and a drive 1008 . Any of these components may be connected to the bus 1005 .

[0418] Disk 1004 can store an operating system (such as WINDOWS (registered trademark), UNIX (registered trademark), LINUX (registered trademark)), etc.), a program for implementing the video projection method according to the present technology, a program for performing position information acquisition processing, a program for adjusting image display light, and various other programs, as well as various data (such as image data).

[0419] The communication device 1006 connects the image projection device 1000 to the network 1010 in a wired or wireless manner. The communication device 1006 can acquire various data (e.g., image data, etc.) from the image projection device 1000 via the network 1010. For example, the acquired data can be stored in the disk 1004. Those skilled in the art can appropriately select the type of the communication device 1006. For example, the disk 1004 can be a semiconductor recording medium such as a flash memory, etc., and is not limited to any particular type.

[0420] According to the present technology, the projection optical system 1007 can project image display light toward the compound diffraction element according to the present technology.

[0421] The drive 1008 can read information recorded in the recording medium and output the information to the RAM 1003. The recording medium is, for example, a microSD memory card, an SD memory card, or a flash memory, but is not limited to these examples.

[0422] Note that the present technology can also be embodied in the configurations described below.

[0423] [1] A composite diffraction element, comprising:

[0424] A stacked structure, the stacked structure sequentially comprising a first diffraction element, a second diffraction element and a third diffraction element,

[0425] The second diffraction element diffracts and reflects the light that has passed through the first diffraction element and reached the second diffraction element toward the first diffraction element.

[0426] The first diffraction element diffracts and reflects the light diffracted and reflected by the second diffraction element toward the third diffraction element, and

[0427] The third diffraction element transmits the light diffracted and reflected by the first diffraction element, and diffracts and reflects the zeroth-order light having passed through the first diffraction element and the second diffraction element.

[0428] [2] The composite diffraction element according to [1], wherein the third diffraction element diffracts and reflects the zero-order light having passed through the first diffraction element and the second diffraction element in a direction in which the zero-order light is transmitted by both the first diffraction element and the second diffraction element.

[0429] [3] The composite diffraction element according to [1] or [2], wherein the composite diffraction element as a whole has the optical characteristics of a transmission diffraction element.

[0430] [4] The composite diffraction element according to any one of [1] to [3], wherein the composite diffraction element as a whole has the optical characteristics of a transmission diffraction lens.

[0431] [5] The composite diffraction element according to any one of [1] to [4], having a structure in which two sets of the stacked structures are stacked.

[0432] [6] The composite diffraction element according to [5], wherein

[0433] One of the two stacked structures has the optical characteristics of a transmissive diffraction element, while the other stacked structure has the optical characteristics of a transmissive diffraction lens, and

[0434] Light obtained by diffraction by the one stacked structure is incident on the other stacked structure, and the other stacked structure diffracts and converges the light.

[0435] [7] The composite diffraction element according to any one of [1] to [6], wherein the first diffraction element, the second diffraction element, and the third diffraction element each diffract light of multiple wavelengths.

[0436] [8] The composite diffraction element according to any one of [1] to [7], wherein at least one of the first diffraction element, the second diffraction element, and the third diffraction element is a stack of multiple diffraction element layers.

[0437] [9] The composite diffraction element according to any one of [1] to [8], wherein a transparent plate is inserted in the stacked structure.

[0438]

[10] The composite diffraction element according to any one of [1] to [8], wherein the first diffraction element, the second diffraction element, and the third diffraction element are stacked on one surface of a transparent plate.

[0439]

[11] A composite diffraction element according to any one of [1] to

[10] , which is placed in front of the eye for use and is used to diffract image display light to reach the eye.

[0440]

[12] The composite diffraction element according to

[11] , wherein the image display light is emitted from an image projection device separate from the composite diffraction element.

[0441]

[13] The composite diffraction element according to any one of [1] to

[12] , wherein the first diffraction element, the second diffraction element and the third diffraction element are all reflection holograms.

[0442]

[14] An apparatus comprising:

[0443] A composite diffraction element, comprising a stacked structure, wherein the stacked structure sequentially comprises a first diffraction element, a second diffraction element, and a third diffraction element,

[0444] The second diffraction element diffracts and reflects the light that has passed through the first diffraction element and reached the second diffraction element toward the first diffraction element.

[0445] The first diffraction element diffracts and reflects the light diffracted and reflected by the second diffraction element toward the third diffraction element.

[0446] the third diffraction element transmits the light diffracted and reflected by the first diffraction element, and diffracts and reflects zero-order light having passed through the first diffraction element and the second diffraction element; and

[0447] A transparent plate is used to place the composite diffractive element in front of the eye.

[0448]

[15] An image projection system comprising:

[0449] A composite diffraction element, comprising a stacked structure, wherein the stacked structure sequentially comprises a first diffraction element, a second diffraction element, and a third diffraction element,

[0450] The second diffraction element diffracts and reflects the light that has passed through the first diffraction element and reached the second diffraction element toward the first diffraction element.

[0451] The first diffraction element diffracts and reflects the light diffracted and reflected by the second diffraction element toward the third diffraction element.

[0452] the third diffraction element transmits the light diffracted and reflected by the first diffraction element, and diffracts and reflects zero-order light having passed through the first diffraction element and the second diffraction element; and

[0453] An image projection device projects image display light onto the compound diffraction element.

[0454] Reference Signs List

[0455] 150 composite diffraction element

[0456] 101 First diffraction element

[0457] 102 second diffraction element

[0458] 103 Third diffraction element

Claims

1. A composite diffraction element, comprising: A stacked structure, the stacked structure sequentially comprising a first diffraction element, a second diffraction element and a third diffraction element, The second diffraction element diffracts and reflects the light that has passed through the first diffraction element and is incident on the second diffraction element toward the first diffraction element. The first diffraction element diffracts and reflects the light diffracted and reflected by the second diffraction element toward the third diffraction element. The second diffraction element transmits the light diffracted and reflected by the first diffraction element toward the third diffraction element, and The third diffraction element transmits the light diffracted and reflected by the first diffraction element and transmitted by the second diffraction element, and diffracts and reflects the zero-order light that has passed through the first diffraction element and reached the second diffraction element and is not diffracted and reflected by the second diffraction element, wherein When the difference between the incident angle of the light passing through the first diffraction element and incident on the second diffraction element and the maximum value of the exit angle of the light diffracted and reflected by the first diffraction element is set as the incident exit angle margin, the minimum value of the exit angle of the zero-order light diffracted and reflected by the third diffraction element relative to the third diffraction element is set as the third diffraction element exit angle, and the exit angle of the light diffracted and reflected by the second diffraction element relative to the second diffraction element is set as the second diffraction element exit angle, the third diffraction element exit angle is larger than the second diffraction element exit angle by the incident exit angle margin or more.

2. The composite diffraction element according to claim 1, wherein the third diffraction element diffracts and reflects the zero-order light having passed through the first diffraction element and the second diffraction element in a direction transmitted by both the first diffraction element and the second diffraction element. 3 . The composite diffraction element according to claim 1 , wherein the composite diffraction element as a whole has the optical characteristics of a transmission diffraction element. 4 . The composite diffraction element according to claim 1 , wherein the composite diffraction element as a whole has optical properties of a transmissive diffraction lens. 5 . The composite diffraction element according to claim 1 , having a structure in which two sets of stacked structures are stacked.

6. The composite diffraction element according to claim 5, wherein One of the two stacked structures has the optical characteristics of a transmissive diffraction element, while the other stacked structure has the optical characteristics of a transmissive diffraction lens, and Light obtained by diffraction performed by the one stacked structure is incident on the other stacked structure, and the other stacked structure diffracts and converges the light.

7. The composite diffraction element according to claim 1, wherein the first diffraction element, the second diffraction element, and the third diffraction element each diffract light of multiple wavelengths. 8 . The composite diffraction element according to claim 1 , wherein at least one of the first diffraction element, the second diffraction element, and the third diffraction element is a stack of a plurality of diffraction element layers.

9. The composite diffraction element according to claim 1, wherein a transparent plate is inserted in the stacked structure.

10. The composite diffraction element according to claim 1, wherein the first diffraction element, the second diffraction element, and the third diffraction element are stacked on one surface of a transparent plate. 11 . The composite diffraction element according to claim 1 , wherein the composite diffraction element is used in a state of being placed in front of an eye and configured to diffract image display light to reach the eye.

12. The composite diffraction element according to claim 11, wherein the image display light is emitted from an image projection device separate from the composite diffraction element.

13. The composite diffraction element according to claim 1, wherein the first diffraction element, the second diffraction element, and the third diffraction element are all reflection holograms.

14. An apparatus comprising: A composite diffraction element, comprising a stacked structure, wherein the stacked structure sequentially comprises a first diffraction element, a second diffraction element, and a third diffraction element, The second diffraction element diffracts and reflects the light that has passed through the first diffraction element and reached the second diffraction element toward the first diffraction element. The first diffraction element diffracts and reflects the light diffracted and reflected by the second diffraction element toward the third diffraction element. The second diffraction element transmits the light diffracted and reflected by the first diffraction element toward the third diffraction element, The third diffraction element transmits the light diffracted and reflected by the first diffraction element and transmitted by the second diffraction element, and diffracts and reflects zero-order light that has passed through the first diffraction element and reached the second diffraction element and is not diffracted and reflected by the second diffraction element; and A transparent plate for placing the composite diffractive element in front of the eye, wherein When the difference between the incident angle of the light passing through the first diffraction element and incident on the second diffraction element and the maximum value of the exit angle of the light diffracted and reflected by the first diffraction element is set as the incident exit angle margin, the minimum value of the exit angle of the zero-order light diffracted and reflected by the third diffraction element relative to the third diffraction element is set as the third diffraction element exit angle, and the exit angle of the light diffracted and reflected by the second diffraction element relative to the second diffraction element is set as the second diffraction element exit angle, the third diffraction element exit angle is larger than the second diffraction element exit angle by the incident exit angle margin or more.

15. An image projection system comprising: A composite diffraction element, comprising a stacked structure, wherein the stacked structure sequentially comprises a first diffraction element, a second diffraction element, and a third diffraction element, The second diffraction element diffracts and reflects the light that has passed through the first diffraction element and reached the second diffraction element toward the first diffraction element. The first diffraction element diffracts and reflects the light diffracted and reflected by the second diffraction element toward the third diffraction element. The second diffraction element transmits the light diffracted and reflected by the first diffraction element toward the third diffraction element, The third diffraction element transmits the light diffracted and reflected by the first diffraction element and transmitted by the second diffraction element, and diffracts and reflects zero-order light that has passed through the first diffraction element and reached the second diffraction element and is not diffracted and reflected by the second diffraction element; and An image projection device projects image display light onto the compound diffraction element, wherein When the difference between the incident angle of the light passing through the first diffraction element and incident on the second diffraction element and the maximum value of the exit angle of the light diffracted and reflected by the first diffraction element is set as the incident exit angle margin, the minimum value of the exit angle of the zero-order light diffracted and reflected by the third diffraction element relative to the third diffraction element is set as the third diffraction element exit angle, and the exit angle of the light diffracted and reflected by the second diffraction element relative to the second diffraction element is set as the second diffraction element exit angle, the third diffraction element exit angle is larger than the second diffraction element exit angle by the incident exit angle margin or more.

Images