JP2019012259A - Virtual image display apparatus - Google Patents

Abstract

To provide a virtual image display apparatus that reliably reduces color separation or lateral chromatic aberration while ensuring optical performance, even when provided with refractive surfaces inclined with respect to an optical axis at a plurality of portions.SOLUTION: A virtual image display apparatus 100 comprises: an image projection apparatus 10 that emits video light GL; and a display optical system 2 that forms a virtual image with the video light GL from a liquid crystal device (image forming apparatus) 11. The display optical system 2 is formed of at least two or more members having different refractive indices, and bends the video light GL a plurality of times between media having different refractive indices in a predetermined direction, where a cumulative value of indices for chromatic dispersion with respect to the predetermined direction on refractive surfaces at the bent portions is equal to or less than a predetermined reference value.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a head mounted display and other virtual image display devices that are used by being mounted on a head.

  2. Description of the Related Art In recent years, various types of virtual image display devices that enable formation and observation of virtual images, such as a head-mounted display, have been proposed that guide video light from a display element to an observer's pupil using a light guide plate.

  For example, an image display device including an image display element and a display optical system that forms an intermediate image that guides image light from the image display element to an observer's eye or a projection surface is known (Patent Document 1). . In the image display device of Patent Document 1, a bonded optical element in which a plurality of optical elements are bonded is disposed between the image display element and the intermediate image, and the plurality of optical elements are formed of materials having different dispersions. Correction of chromatic aberration is performed by including at least two optical elements.

  However, the optical system described in Patent Document 1 only has a cemented optical element disposed in front of the intermediate image, the inclination angle of the refractive surface is not appropriate, and correction of chromatic aberration is not sufficient. That is, for example, in order to arrange an optical system along the user's head, if it is necessary to provide a plurality of refractive surfaces inclined with respect to the optical axis in the optical system, Refractive angle dispersion of the light according to the wavelength dispersion of the medium occurs, resulting in lateral chromatic aberration. Correction conditions for complex chromatic aberration due to a plurality of inclined refracting surfaces are unclear, and aberration correction was performed through trial and error. In this case, unless the inclination angle of the refracting surface is set appropriately, the lateral chromatic aberration is not sufficiently corrected, and the desired optical performance cannot be achieved.

JP 2007-11168 A

  The present invention has been made in view of the above-described background art, and is a virtual image in which lateral chromatic aberration is reliably reduced while ensuring optical performance even when a plurality of refracting surfaces inclined with respect to the optical axis are provided. An object is to provide a display device.

ただし、

に基づいて、Ａ_０＝０から始めて色分散指標Ａ_ｋの値を順次計算したとき、最終面の番号がＫであるとして、最終面の色分散指標Ａ_Ｋが絶対値で１.０未満である。ここで、光学機能面とは、光学面や回折面を意味する。 In order to achieve the above object, a virtual image display apparatus according to the present invention includes an image forming apparatus that emits image light, and a display optical system that forms a virtual image by image light from the image forming apparatus, and the image light is viewed by an observer. The display optical system is incident on a position assumed to be an eye of the image, and the display optical system has a shape that is plane-symmetric with respect to a predetermined plane, and is emitted from an arbitrary point of the image forming apparatus for display. With respect to an image light beam that reaches the center of the observer's eye via the optical system, the image light beam and the optical function surface at the point where the optical function surface intersects the kth optical function surface of the display optical system. Α _k is the angle formed by the line that projects the normal of the functional surface onto the symmetry plane of the display optical system and the line that projects the incident light beam onto the symmetry plane, and the line and exit that project the normal of the optical functional surface onto the symmetry plane the angle formed by the line which projects a light beam to the plane of symmetry beta _k, the incident side medium The refractive index and n _k-1, the refractive index of the exit side of the medium and n _k, the refractive index dispersion of the incident side medium and V _k-1, the refractive index dispersion of the exit side medium and V _k, on the incident side Assuming that the chromatic dispersion index is A _k−1 , the emission side chromatic dispersion index is A _k , the target wavelength is λ in μm, the diffraction order is m _k, and the pitch of the diffraction grating is p _k , the following formula ( 1)

However,

When the value of the color dispersion index A _k is sequentially calculated starting from A ₀ = 0, the final surface number K is assumed to be K, and the final surface color dispersion index _AK is an absolute value of less than 1.0. is there. Here, the optical functional surface means an optical surface or a diffractive surface.

According to the virtual image display device, the absolute value of the chromatic dispersion index value A _k obtained by projection onto the plane of symmetry is equal to or less than the predetermined reference value, in the direction corresponding to the symmetry plane, inclined with respect to the optical axis Even when refracting surfaces are provided at multiple locations or diffractive surface elements are provided at multiple locations, chromatic dispersion or color separation is handled as a total imaging system while ensuring optical performance. It can be surely reduced.

で近似的に与えられる。 In a specific aspect of the present invention, in the virtual image display device, the wavelength of the F line is λ _F , the wavelength of the C line is λ _C , the refractive index of the F line is n _F in each medium, Assuming that the refractive index is n _C , the refractive index dispersion V _k is

Is given approximately.

に基づいて、Ａ_０＝０から始めて色分散指標Ａ_ｋの値を順次計算したとき、最終面の番号がＫであるとして、最終面の色分散指標Ａ_Ｋの絶対値が、０．３未満である。この場合、対称面を前提としない色分散指標値Ａ_ｋの絶対値が０．３未満であるので、光軸に対して傾斜する屈折面を複数箇所に設けたり、回折面素子を複数箇所に設けたりする場合であっても、光学性能を確保しつつ色分散又は色分離を総計的に扱って色分散を全結像系として確実に低減することができる。 In still another aspect of the present invention, the image light beam and the k-th optical functional surface of the display optical system with respect to the image light beam that originates from the center of the image forming apparatus and reaches the center of the observer's eye via the display optical system. The angle formed by the normal of the optical functional surface and the incident light at the point where the image light and the optical functional surface intersect is α _k, and the angle formed by the normal of the optical functional surface and the emitted light is β and _k, the index of refraction of the incident side of the medium and n _k-1, the refractive index of the exit side of the medium and n _k, and the refractive index dispersion of the incident side medium and V _k-1, the refractive index of the exit side medium dispersion Is V _k , the incident side chromatic dispersion index is A _k−1 , the emission side chromatic dispersion index is A _k , the target wavelength is λ in μm, the diffraction order is m _k, and the pitch of the diffraction grating is As _pk , the following formula (1)

Based on, when sequentially calculate the value of the color distribution indicator A _k starting from A 0 _{= 0,} as the number of the final surface is K, the absolute value of the chromatic dispersion index A _K of the final surface is less than 0.3 It is. In this case, since the absolute value of the chromatic dispersion index value A _k that does not assume a plane of symmetry is less than 0.3, or provided with a refracting surface inclined with respect to the optical axis at a plurality of locations, the diffractive surface elements at a plurality of locations Even if it is provided, it is possible to reliably reduce chromatic dispersion as an entire imaging system by comprehensively handling chromatic dispersion or color separation while ensuring optical performance.

In still another aspect of the present invention, the display optical system has three or more refractive surfaces whose value α _k is not zero as the optical functional surface. In this case, the occurrence of lateral chromatic aberration can be suppressed with an optical system that uses a relatively large number of non-parallel refractive surfaces.

  In still another aspect of the present invention, the display optical system has at least one non-axisymmetric free-form surface as an optical functional surface.

  In still another aspect of the present invention, the display optical system has a diffractive surface as an optical functional surface.

It is sectional drawing which shows the virtual image display apparatus which concerns on 1st Embodiment. It is a back view of the light guide device of FIG. 1A. It is an expanded sectional view explaining the state of the optical path in a light guide. It is a figure explaining the optical path of the image light in the incident side of a light guide device in an optical axis cross section. It is the elements on larger scale explaining the arrangement | positioning etc. of the mirror in the center part of a reflection unit in an optical axis cross section. It is a figure explaining the example of 1 production of a reflection unit. 1 is a cross-sectional view illustrating an optical system of Example 1. FIG. It is sectional drawing explaining the local coordinate of the optical surface shown to FIG. 6A. It is sectional drawing explaining the modification in the emission side of the optical path of image light. It is sectional drawing explaining another modification in the emission side of the optical path of image light. It is sectional drawing which shows the virtual image display apparatus which concerns on 2nd Embodiment. It is sectional drawing which shows the virtual image display apparatus which concerns on 3rd Embodiment. It is sectional drawing which shows the virtual image display apparatus which concerns on 4th Embodiment. It is a figure which shows the modification of the virtual image display apparatus shown in FIG. It is a figure which shows another modification of the virtual image display apparatus shown in FIG.

[First Embodiment]
Hereinafter, a virtual image display device incorporating the light guide device according to the first embodiment of the present invention will be described.

[1A. Structure of light guide device and virtual image display device]
With reference to FIG. 1A and 1B, the virtual image display apparatus incorporating the light guide device of 1st Embodiment is demonstrated. The virtual image display device 100 is applied to a head mounted display, and includes an image projection device 10 and a light guide device 20 as a set. 1A corresponds to the AA cross section of the light guide device 20 shown in FIG. 1B. Further, x, y, and z in the figure represent directions of three orthogonal coordinate axes.

  The virtual image display device 100 allows an observer to recognize a video image as a virtual image and allows the observer to observe an external image in a see-through manner. In the virtual image display device 100, the image projection device 10 and the light guide device 20 are normally provided one by one corresponding to the right eye and the left eye of the observer, but are symmetrical for the right eye and the left eye. Therefore, only the left eye is shown here, and the illustration for the right eye is omitted. The virtual image display device 100 as a whole has, for example, an appearance (not shown) like general glasses.

  The image projection apparatus 10 includes a liquid crystal device 11 that is an image forming apparatus, and a projection optical system 12 for optical coupling. The liquid crystal device (image forming apparatus) 11 spatially modulates illumination light from the light source 14 to form video light GL to be a moving image or other display target. The projection optical system 12 constitutes the display optical system 2 together with a light guide device 20 described later. The display optical system 2 is an optical system that is plane-symmetric with respect to a transverse section (xz section) including the optical axis AX. The projection optical system 12 functions as, for example, a collimating lens that changes the image light GL emitted from each point on the liquid crystal device 11 in the vertical y direction to a substantially parallel ray, and also includes a horizontal direction in which the asymmetry including the direction in which the eyes are lined up appears. It functions as a collimating lens in cooperation with a part of the light guide device 20 with respect to the xz section. The projection optical system 12 may function as a collimating lens in cooperation with a part of the light guide device 20 in the vertical y direction. Note that the projection optical system 12 is formed of glass or plastic, and is not limited to one, but may have a plurality of configurations. The projection optical system 12 is not limited to a spherical lens, and may include an aspheric lens, a free-form surface lens including an axisymmetric curved surface, and the like.

  As shown in an enlarged view in FIG. 2, the light guide device 20 that constitutes the display optical system 2 together with the projection optical system 12 emits the image light GL from the image projection device 10 toward the observer's eye EY as virtual image light. At the same time, the external light OL corresponding to the external image is substantially transmitted as it is. The light guide device 20 includes an incident portion 21 that captures image light, a parallel light guide 22 for guiding light, and an emission portion 23 that extracts image light. In the case of this embodiment, the incident part 21 is arrange | positioned at an observer's ear | edge side, and the injection | emission part 23 is arrange | positioned at an observer's nose side. The parallel light guide 22 and the main body of the incident portion 21 are an integral product or a single member molded from a resin material having high light transmittance. The parallel light guide 22 is disposed to be inclined with respect to the optical axis AX with respect to the eye EY of the observer, and the normal direction Z is inclined by an angle σ with respect to the optical axis AX. . In this case, the parallel light guide 22 can be arranged along the face curve, but the normal line of the parallel light guide 22 has an inclination with respect to the optical axis AX. As described above, when the normal line of the parallel light guide 22 is inclined by the angle σ with respect to the z direction parallel to the optical axis AX, the video light GL0 on and near the optical axis AX emitted from the reflection unit 30 is light The angle σ is formed with respect to the normal line of the exit surface OS.

  The incident unit 21 includes a light incident surface IS that captures the video light GL from the image projection device 10 and a reflective surface RS that reflects the captured video light GL and guides it into the parallel light guide 22. The light incident surface IS is formed as a concave curved surface 21b on the projection optical system 12 side, and the curved surface 21b also has a function of totally reflecting the image light GL reflected by the reflecting surface RS on the inner surface side. The reflection surface RS is formed of a concave curved surface 21a on the projection optical system 12 side. The reflective surface RS is formed by performing film deposition such as aluminum vapor deposition on the curved surface 21a, reflects the video light GL incident from the light incident surface IS, bends the optical path in a predetermined direction, and the curved surface 21b is formed by the reflective surface RS. The reflected image light GL is totally reflected on the inner side, and the optical path is bent in a predetermined direction. That is, the incident part 21 reliably couples the video light GL into the parallel light guide 22 by bending the video light GL incident from the light incident surface IS by two reflections. The curved surface 21b and the curved surface 21a are non-axisymmetric free-form surfaces, but are not limited thereto, and may be axi-symmetric free-form surfaces, spherical surfaces, aspheric surfaces, and the like. Moreover, when the curved surfaces 21b and 21a have refractive power in the vertical y direction, the collimating function by the projection optical system 12 can be assisted.

  The parallel light guide 22 is a flat plate portion that is parallel to the y axis and inclined with respect to the x axis or the z axis, and is also referred to as a light guide. The parallel light guide (light guide) 22 has two opposing flat surfaces 22a and 22b which are a pair of surfaces extending in parallel. Since both the planes 22a and 22b are parallel planes, no enlargement or focus shift occurs with respect to the external image. Further, the one flat surface 22a on the + z side or the Z side functions as a total reflection surface that totally reflects the image light from the incident portion 21, and has a role of guiding the image light to the emission portion 23 with a small loss. An extension plane of the back side plane 22 b is a boundary surface IF between the parallel light guide 22 and the emitting portion 23. In the parallel light guide 22, the image light GL reflected on the inner side of the reflection surface RS or the light incident surface IS of the incident portion 21 is incident on the plane 22 a which is a total reflection surface, and is totally reflected here, and is guided by the light guide device. It is led to the rear side of 20, that is, the + x side or the + X side where the injection portion 23 is provided. That is, in the parallel light guide 22, the X-axis direction is the light guide direction of the video light GL. The parallel light guide 22 has a termination surface ES as a side surface that defines an end surface on the + x side or the + X side of the outer shape of the light guide device 20. Further, the parallel light guide 22 has an upper end surface TP and a lower end surface BP as upper and lower surfaces that define an end surface on the ± y side.

  The emitting portion 23 is a member formed in a layered shape on the extension side along the back plane 22b on the back side (+ X side) of the parallel light guide 22 or in a layered shape along the boundary surface IF. is there. The emission unit 23 reflects the incident video light GL at a predetermined angle when passing the video light GL totally reflected by the predetermined surface region FR on the external surface side (total reflection surface) 22a of the parallel light guide 22. And bent to the light exit surface OS side. Here, the video light GL that first enters the emission unit 23 without passing through the emission unit 23 is the extraction target as virtual image light. That is, even if there is light reflected by the inner surface of the light exit surface OS or the boundary surface IF in the light emitting portion 23, this is not used as image light. The emission unit 23 includes a reflection unit 30 in which a plurality of transmissive mirrors and the like are arranged. A detailed structure thereof will be described in detail later with reference to FIG.

  Since the light guide device 20 has the above-described structure, the video light GL emitted from the image projection device 10 and incident on the light guide device 20 from the light incident surface IS is bent by the incident portion 21 by a plurality of reflections. The light is totally reflected in the predetermined surface region FR of the flat surface 22a of the parallel light guide 22 and travels substantially along the optical axis AX. The video light GL reflected by the predetermined surface region FR of the flat surface 22a on the + z side or the + Z side is incident on the emission unit 23. At this time, the width in the longitudinal direction of the predetermined surface region FR is narrower than the width in the longitudinal direction of the injection portion 23 in the XY plane. More specifically, the light beam bundle of the image light GL is positioned in the XZ cross section including the optical axis AX in the vicinity of the predetermined plane region FR, that is, in the vicinity of the boundary between the straight light paths P1 and P2 and straddling both straight light paths P1 and P2. As a whole, the width is narrowed and the beam width is narrowed. As a result, the incident width at which the light beam of the image light GL is incident on the emission unit 23 (or the reflection unit 30) is wider than the incident width at which the light beam of the image light GL is incident on the predetermined surface region FR. In this way, by relatively narrowing the incident width at which the light bundle of the image light GL enters the predetermined surface region FR, interference of the optical path is less likely to occur, and the boundary surface IF and the light exit surface OS are used for light guide. Instead, it becomes easy to make the image light GL from the predetermined surface area FR directly incident on the emission unit 23 or the reflection unit 30. Further, the light beam of the image light GL is narrowed in front of the emission unit 23, and it becomes easy to make the viewing angle in the horizontal direction relatively wide. The image light GL incident on the emission part 23 is in a state where it can be taken out by being bent at an appropriate angle in the emission part 23 or the reflection unit 30, and finally emitted from the light emission surface OS. The image light GL emitted from the light exit surface OS enters the observer's eye EY as virtual image light. The virtual image light forms an image on the retina of the observer, so that the observer can recognize the video light GL as a virtual image. Here, the angle at which the video light GL used for image formation is incident on the emitting portion 23 increases as the distance from the incident portion 21 on the light source side increases. That is, video light GL having a large inclination with respect to the Z direction or the optical axis AX perpendicular to the external plane 22a is incident on the back side of the emission unit 23 and is bent at a relatively large angle. On the front side, image light GL having a small inclination with respect to the Z direction or the optical axis AX is incident and bent at a relatively small angle.

[1B. (Optical path of image light)
Hereinafter, the optical path of the image light will be described in detail. As shown in FIG. 2, out of image light respectively emitted from the emission surface 11 a corresponding to the image surface of the liquid crystal device (image forming apparatus) 11, the component emitted from the center of the emission surface 11 a indicated by the broken line is imaged. A component emitted from the left side of the paper surface (−x side closer to + z) of the periphery of the emission surface 11a indicated by the alternate long and short dash line in the drawing as image light GL1, and the periphery of the emission surface 11a indicated by the two-dot chain line in the drawing. A component emitted from the right side of the drawing (+ x side closer to −z) is defined as video light GL2. Among these, the optical path of the image light GL0 is defined as an optical axis AX. When the emission point of the image light on the image forming apparatus 11 is in the symmetry plane of the optical system, the image lights GL1, GL2, and GL0 are included in the symmetry plane.

  The main components of the video lights GL0, GL1, and GL2 from the exit surface 11a of the liquid crystal device (image forming apparatus) 11 are incident on the light incident surface IS of the light guide device 20 after passing through the projection optical system 12, respectively. It passes through the parallel light guide 22 through the incident part 21 and reaches the emission part 23.

  Specifically, for example, in the symmetry plane including the optical axis AX or the xz plane, the image light GL0 emitted from the central portion of the emission surface 11a out of the image lights GL0, GL1, and GL2 is transmitted from the projection optical system 12. The lens surfaces 12a and 12b travel substantially straight. When the image light GL0 is incident substantially perpendicular to the lens surfaces 12a and 12b existing between the media having different refractive indexes, the image light GL0 is hardly bent. The video light GL0 that has passed through the lens surfaces 12a and 12b is bent at the incident portion 21 of the light guide device 20 and coupled into the parallel light guide 22, and then the predetermined surface area FR of one plane 22a at the standard reflection angle ψ0. And is totally reflected, hardly passes through the interface IF between the parallel light guide 22 and the exit portion 23 (or the reflection unit 30), passes through it, and directly enters the central portion 23k of the exit portion 23. Incident. The image light GL0 is reflected at a predetermined angle at the portion 23k, and is in the optical axis AX direction (the direction of the angle σ with respect to the Z direction) inclined from the light exit surface OS to the XY plane including the light exit surface OS. It is emitted as a parallel beam.

  On the other hand, in the xz plane including the optical axis AX, the image light GL1 emitted from one end side (−x side) of the emission surface 11a is adjusted in the state or direction of the light beam by the lens surfaces 12a and 12b of the projection optical system 12. Is done. The image light GL1 that has passed through the lens surfaces 12a and 12b is bent by the incident portion 21 and coupled into the parallel light guide 22, and then enters the predetermined surface region FR of one plane 22a at the maximum reflection angle ψ1. It is reflected and hardly reflected by the boundary surface IF between the parallel light guide 22 and the emission part 23 (or the reflection unit 30), and passes through this. A predetermined portion of the emission part 23 on the back side (+ X side) 23h The light is reflected at an angle and emitted from the light exit surface OS as a parallel light beam in a predetermined angle direction. The exit angle at this time (corresponding to the angle γ1 when the optical axis AX is used as a reference) is relatively large to be returned to the incident portion 21 side.

  The image light GL2 emitted from the other end side (+ x side) of the emission surface 11a is adjusted by the lens surfaces 12a and 12b of the projection optical system 12 in the state or direction of light rays. The image light GL1 that has passed through the lens surfaces 12a and 12b is bent by the incident portion 21 and coupled into the parallel light guide 22, and then enters the predetermined surface region FR of one plane 22a with the minimum reflection angle ψ2. Reflected and hardly reflected by the boundary surface IF between the parallel light guide 22 and the emitting part 23 (or the reflecting unit 30), and passes through this, and a predetermined portion 23m of the emitting part 23 on the entrance side (−X side) is predetermined. And is emitted from the light exit surface OS as a parallel light beam in a predetermined angle direction. The exit angle at this time (corresponding to the angle γ2 with the optical axis AX as a reference) is relatively small to the extent that it is returned to the incident portion 21 side.

  That is, the image lights GL0, GL1, and GL2 having various angles of view gather at the center EPa of the eye point EP assuming the observer's eye EY. The eye point EP means the position of the exit pupil set in the light guide device 20, and if the eye EY is placed here, a bright and clear image can be obtained. Note that the video lights GL0, GL1, and GL2 have been described on behalf of part of the entire light beam of the video light GL, but the light beam components that make up the other video light GL are similar to the video light GL0 and the like. Since these are guided and emitted from the light exit surface OS, illustration and description thereof are omitted.

When the image lights GL0, GL1, and GL2 are incident on the lens surfaces 12a and 12b existing between the media having different refractive indexes, the image lights GL0, GL1, and GL2 are refracted and bent by the light incident surface IS. To do. The boundary between the air and the lens of the projection optical system 12 at this time is the first optical surface or optical function surface (k = 1), and the refractive index before and after that, that is, the refractive index of the medium on the incident side is n _0, The refractive index of the medium on the exit side is n ₁ , the incident angle (the angle formed by the normal of the lens surfaces 12a and 12b, which are optical surfaces, and the image light, which is the incident light) is = α ₁ (°), and the exit angle Alternatively, when a refraction angle (an angle formed by the normal of the lens surfaces 12a and 12b, which are optical surfaces, and the image light, which is an emitted light) is β ₁ (°), the following relationship sin β ₁ = ( n ₀ / n ₁ ) × sin α ₁ (1-1)
Is true. Also, the boundary between the lens of the projection optical system 12 and air is the second optical surface or optical function surface (k = 2), the refractive indexes before and after that are n ₁ and n ₂ , and the incident angle is α _2. When the emission angle or the refraction angle is β ₂ , the following relationship sin β ₂ = (n ₁ / n ₂ ) × sin α ₂ (1-2) according to Snell's law.
Is true.

As shown in an enlarged view in FIG. 3, the image lights GL0, GL1, and GL2 that have passed through the projection optical system 12 are light incident surfaces IS or curved surfaces 21b (that is, normal lines NL of the tangential plane TP) that exist between media having different refractive indexes. ) With an inclination. That is, the light incident surface IS is greatly inclined with respect to the optical axis AX. For this reason, the image lights GL0, GL1, and GL2 propagating along the optical axis AX are refracted and bent by the light incident surface IS. At this time, the boundary between the air and the resin of the incident portion 21 is the third optical surface or the optical functional surface (k = 3), the refractive indexes before and after that are n ₂ and n ₃ , and the incident angle is α _3. When the emission angle or the refraction angle is β ₃ , the following relationship sin β ₃ (n ₂ / n ₃ ) × sin α ₃ (1-3) according to Snell's law.
Is true.

  Here, as an example of the value of the refractive index n of the transparent resin material used for the incident portion 21 and the parallel light guide 22, assuming that n = 1.4, the value of the critical angle ψc is ψc≈45.6 °. Become. The minimum reflection angle ψ2 of the reflection angles ψ0, ψ1, ψ2 of the respective image lights GL0, GL1, GL2 is set to a value larger than the critical angle ψc, so that necessary image light can be obtained within the parallel light guide 22. The total reflection condition on the plane 22a can be satisfied.

  The image light GL0 for the center is incident on the portion 23k of the emission part 23 at an elevation angle φ0 (= 90 ° −ψ0), and the image light GL1 for the periphery is emitted at an elevation angle φ1 (= 90 ° −ψ1). , The peripheral image light GL2 is incident on the portion 23m of the emitting portion 23 at an elevation angle φ2 (= 90 ° −ψ2). Here, a relationship of φ2> φ0> φ1 is established between the elevation angles φ0, φ1, and φ2, reflecting the magnitude relationship of the reflection angles ψ0, ψ1, and ψ2. That is, the incident angle ι (see FIG. 4 described later) of the reflection unit 30 to the mirror 31 gradually increases in the order of the portion 23m corresponding to the elevation angle φ2, the portion 23k corresponding to the elevation angle φ0, and the portion 23h corresponding to the elevation angle φ1. Get smaller. In other words, the incident angle ι to the mirror 31 or the reflection angle at the mirror 31 decreases as the distance from the incident portion 21 increases. The incident angle ι of the image lights GL0, GL1, and GL2 to the mirror 31 is set to 40 ° or more from the viewpoint of adjusting the number of passes of the mirror 31 to be small. Accordingly, when the image light GL from the incident portion 21 side enters the reflection unit 30 and enters the first mirror 31 or the adjacent mirror 31, the image light GL is reflected by the mirror 31 and the eye EY. It becomes easy to take the structure taken out to the side.

[1C. (Structure of the emission part and bending of the optical path by the emission part)
Hereinafter, the structure of the emission part 23 and the bending of the optical path of the image light by the emission part 23 will be described in detail with reference to FIGS.

  First, the structure of the injection unit 23 will be described. The emission unit 23 includes a reflection unit 30 in which a plurality of mirrors 31 that are a plurality of reflection surfaces that partially reflect the image light GL are arranged. The reflection unit 30 is a rectangular plate-like member extending along an XY plane inclined by an angle σ with respect to the optical axis AX, and has a structure in which a large number of thin strip-like mirrors (reflection surfaces) 31 are embedded in a stripe pattern. Have That is, the reflection unit 30 is configured by arranging a number of elongated mirrors 31 extending in the y direction or the Y direction in the extending direction of the parallel light guides 22, that is, in the X direction. More specifically, the mirror 31 is parallel to the planes 22a and 22b of the parallel light guide 22 shown in FIG. 2 and the like, and extends in the direction perpendicular to the X direction in which the mirrors 31 are arranged, that is, up and down. It extends linearly with the y direction or the Y direction as the longitudinal direction. Furthermore, the mirror 31 is inclined toward the incident portion 21 side toward the outside with respect to the observer side of the parallel light guide 22. More specifically, the mirror 31 is inclined so that the upper end (+ Z side) rotates counterclockwise with the longitudinal direction (Y direction) as an axis and the YZ plane orthogonal to the planes 22a and 22b as a reference. Yes. Further, all the mirrors 31 are arranged in parallel to each other.

  The reflection unit 30 has a structure in which a large number of glass members or block members 32 are joined, and the mirror (reflection surface) 31 includes a thin film sandwiched between a pair of adjacent block members (glass members) 32. It has become. Here, the refractive index of the block member 32 is different from the refractive index of the parallel light guide 22. For this reason, the angle δ for tilting the mirror 31 is adjusted or corrected in consideration of this refractive index difference.

  The reflectance of the mirror 31 with respect to the image light GL is set to be 10% or more and 50% or less in the assumed incident angle range of the image light GL from the viewpoint of facilitating observation of the external light OL by see-through. The reflectance of the mirror 31 of the specific embodiment for the video light GL is set to 20%, for example, and the transmittance for the video light GL is set to 80%, for example.

  The thickness TI of the reflection unit 30 is set to about 0.7 mm to 3.0 mm. In addition, the thickness of the parallel light guide 22 that supports the reflection unit 30 is, for example, about several mm to 10 mm, and preferably about 4 mm to 6 mm. If the thickness of the parallel light guide 22 is sufficiently larger than the thickness of the reflection unit 30, it is easy to reduce the incident angle of the image light GL to the reflection unit 30 or the boundary surface IF, and the image light GL is taken into the eye EY. It is easy to suppress the reflection at the mirror 31 at a position that is not present. On the other hand, when the thickness of the parallel light guide 22 is relatively thin, the parallel light guide 22 and the light guide device 20 can be easily reduced in weight.

  All the mirrors 31 are set to have the same inclination, and can form an inclination angle δ of, for example, about 48 ° to 70 ° in a clockwise direction with respect to the interface IF with the parallel light guide 22. The inclination angle δ is 60 °. Here, it is assumed that the elevation angle φ0 of the video light GL0 is set to, for example, 30 °, the elevation angle φ1 of the video light GL1 is set to, for example, 22 °, and the elevation angle φ2 of the video light GL2 is set to, for example, 38 °. In this case, the image light GL1 and the image light GL2 enter the observer's eye EY at an angle γ1 = γ2≈12.5 ° with the optical axis AX as a reference.

  As a result, a component having a relatively large total reflection angle (image light GL1) in the image light GL is mainly incident on the + X side portion 23h side of the reflection unit 30, which is the non-incident side, and the total reflection angle is compared. Angle when the image light GL is collected on the observer's eye EY as a whole when a relatively small component (image light GL2) is mainly incident on the −X side portion 23m side of the exit portion 23. It becomes possible to take out efficiently in a state. Since the video light GL is taken out with such an angle relationship, the light guide device 20 can pass the video light GL in the reflection unit 30 only once, as a rule, without passing it multiple times. Can be extracted as virtual image light with little loss.

  Note that the unused light that passes through the mirror 31 of the reflection unit 30 may be incident again on the external surface side plane 22a. However, if it is totally reflected here, most of the reflection light is a portion 23h on the back side of the reflection unit 30. Alternatively, it can be incident on the eyelid side and outside the effective region, and the possibility of entering the eye EY is reduced.

  In addition, in the central side and back side portions 23k and 23h of the reflection unit 30, a part of the image light GL passes through the mirror 31 a plurality of times (specifically, one reflection and one or more transmissions). Including passing). In this case, the number of times of passing through the mirror 31 is plural, but since the reflected light from the plural mirrors 31 respectively enters the observer's eye EY as the video light GL, the loss of light quantity does not become so large.

  The arrangement interval SP in the arrangement direction of the plurality of mirrors 31 or the Z direction in which the reflection unit 30 extends is set assuming the observer's eye EY from the incident side close to the incident portion 21 to the counter incident side close to the end surface ES. Further, the plurality of mirrors 31 are changed so as to be connected substantially continuously with reference to the line of sight extending from the center EPa of the eye point EP (see FIG. 2) to an arbitrary point of interest. As a result, the arrangement interval SP of the plurality of mirrors 31 in the reflection unit 30 gradually increases from the incident side close to the incident portion 21 to the non-incident side. The specific arrangement interval SP of the mirrors 31 is within a range of about 0.5 mm to 2.0 mm in each part, although there is a difference in size within the reflection unit 30.

Referring to FIG. 4, video lights GL0, GL1, and GL2 that have passed through parallel light guide 22 in the XZ plane including optical axis AX are inclined with respect to boundary surface IF existing between media having different refractive indexes. Incident. That is, the boundary surface IF is greatly inclined with respect to the optical axis AX. For this reason, the video lights GL0, GL1, and GL2 propagating along the optical axis AX are refracted and bent at the boundary surface IF. At this time, the boundary between the resin medium of the incident portion 21 and the glass or resin of the block member 32 is the fourth optical surface or optical function surface (k = 4), and the refractive indexes before and after that are n ₃ and n _4. When the incident angle is α ₄ (°) and the emission angle or the refraction angle is β ₄ (°), according to Snell's law, the following relationship sin β ₄ = (n ₃ / n ₄ ) × sin α ₄ . 1-4)
Is true.

The image light GL0 that has passed through the boundary surface IF propagates along the optical axis AX in the XZ plane including the optical axis AX, is reflected by the mirror 31, and then exists between the media having different refractive indexes. Incidently incident on the OS. That is, the light exit surface OS is not a plane perpendicular to the optical axis AX but is inclined. For this reason, the video light GL0 propagating along the optical axis AX is refracted and bent by the light exit surface OS. At this time, the boundary between the glass or resin of the block member 32 and the air is the fifth optical surface or optical function surface (k = 5), the refractive indexes before and after that are n ₄ and n ₅ , and the incident angle is α ₅ and when the emission angle or the refraction angle is β ₅ , according to Snell's law, the following relationship sin β ₅ = (n ₄ / n ₅ ) × sin α ₅ (1-5)
Is true.

  With reference to FIG. 5, an example of the manufacturing method of the reflection unit 30 is demonstrated. A large number of glass plates 91 that are parallel flat plates made of glass are prepared in advance. The thickness of each glass plate 91 is determined in consideration of the arrangement interval SP of the mirrors 31, and the thickness of the glass plate 91 corresponding to the central portion 23 k of the reflection unit 30 is used as the standard on the incident side or entrance side. The glass plate 91 corresponding to the portion 23m is relatively thin, and the glass plate 91 corresponding to the portion 23h on the counter-incident side or the back side is relatively thick. In the case of FIG. 5, the lower glass plate 91 is thin and the upper glass plate 91 is thick. After that, a large number of element plates 90 are prepared by forming a reflective film 92 that is a metal reflective film or a dielectric multilayer film on one surface of a large number of prepared glass plates 91. Thereafter, the formed many element plates 90 are stacked while being bonded with an adhesive in order of thickness, and the whole is cut obliquely along the cutting lines C1 and C2. Thus, the reflection unit 30 has a structure in which a mirror 31 made of a metal reflection film or a dielectric multilayer film is sandwiched between block members 32 which are elongated prism pieces obtained by obliquely dividing a parallel plate, and the mirror 31 is arranged on one end side. Can be obtained in which the arrangement interval of the mirror 31 is narrow and the arrangement interval of the mirrors 31 is wide on the other end side. The reflection unit 30 is attached to an appropriate position on the viewer side of the parallel light guide 22 via an adhesive, and is fixed by curing the adhesive.

  The color dispersion or color separation as the lateral chromatic aberration of the video light GL generated by the all optical system of the virtual image display device 100 such as the light guide device 20 will be described. In the entire optical system, that is, the display optical system 2, the image light GL is refracted and bent a plurality of times between media having different refractive indexes. Specifically, the image lights GL0, GL1, and GL2 are basically refracted by the lens surfaces 12a and 12b, the light incident surface IS, the boundary surface IF, and the light exit surface OS. 12b, the light incident surface IS, the boundary surface IF, and the light exit surface OS) are basically inclined or non-perpendicular with respect to the optical axis AX. Further, most of these refractive surfaces 12a, 12b, IS, IF, OS) are not parallel to each other with the optical axis AX as a reference. If the optical axis AX is not used as a reference, the two refractive surfaces IF and OS are apparently parallel.

As described above, refraction at the lens surfaces 12a and 12b of the projection optical system 12 is expressed by the relational expression (1-1) or (1-2). Further, the refraction at the light incident surface IS of the light guide device 20 is represented by the relational expression (1-3), the refraction at the boundary surface IF is represented by the relational expression (1-4), and the refraction at the light exit surface OS. Refraction is represented by the relational expression (1-5). In general, the refractive index of the k-th (k is a natural number) medium along the optical path (that is, the refractive index of the medium on the incident side) is _nk−1, and the refractive index with respect to the k + 1-th medium (that is, the emission). The refractive index of the medium on the side is _nk , the incident angle (the angle between the normal of the optical surface and the image light that is the incident light) is α _k, and the emission angle (the image that is the normal of the optical surface and the output light) When the angle formed by light is β _k , the following relational expression (2-1)
n _k-1 × sin α _k = n _k × sin β _k (2-1)
Holds. The refracting surfaces between the media are variously inclined with respect to the optical path or the optical axis. As a result, the incident angle and exit angle on a series of refractive surfaces vary greatly. 2 and 3, the video lights GL0, GL1, and GL2 are on the xz plane or the symmetry plane. However, even if the video light GL is not on the xz plane or the symmetry plane, Relational expression (2-1) is established.

  Here, on each refracting surface of the light incident surface IS, the boundary surface IF, and the light exit surface OS, chromatic dispersion or color separation as lateral chromatic aberration occurs with refraction. By sequentially calculating the chromatic dispersion index on these refractive surfaces and accumulating these values, the chromatic dispersion index (that is, the accumulated value of the chromatic dispersion index) can be evaluated as the entire optical system.

となる。この関係式（２−２）において、値Ｖ_ｋ−１及びＶ_ｋは、屈折率の波長依存性を示し、値Ａ_ｋ−１及びＡ_ｋは、色分散指標、つまり色分散又は色分離の程度を示す。なお、初期値としてのＡ_０＝ｄθ_０／ｄλは零とする。関係式（２−２）は、屈折面を順次辿れば、最終面の番号がＫであるとして、最終面の色分散指標Ａ_Ｋの絶対値（この場合、Ｋは最終面の番号であり、本実施形態では第５番目の面（つまりガラス又は樹脂と空気との境界を示す）までを見積もることができることを意味する。この際、Ｖ_ｋ−１＝ｄｎ_ｋ−１／ｄλ、Ｖｋ＝ｄｎ_ｋ／ｄλ等を用いて、一連の媒体間の屈折面を経るごとに、つまり光軸ＡＸに沿った各屈曲箇所において色分散指標Ａ_ｋ＝ｄβ_ｋ／ｄλが逐次算される。値Ｖ_ｋは、屈折面の入射側にある媒体の屈折率の波長依存性であり、例えば可視光の波長域をλｂ〜λｒ（μｍ）とし、着目媒体の屈折率域をｎｂ〜ｎｒとして、近似的には値（ｎｂ−ｎｒ）／（λｂ〜λｒ）で表すことができる。具体的には、光学媒体の屈折率特性の規格として汎用されるＦ線の波長をλ_Ｆ（μｍ）とし、Ｃ線の波長をλ_Ｃ（μｍ）とし、着目する媒体において、Ｆ線の屈折率をｎ_Ｆとし、Ｃ線の屈折率をｎ_Ｃとした場合、値Ｖ_ｋ＝ｄｎ_ｋ／ｄλは、以下の式

を利用して得ることができる。色分散指標Ａ_ｋついては、初期値Ａ_０（ｄｅｇ／μｍ）、Ｖｋ＝ｄｎｋ／ｄλ（１／μｍ）等を利用して媒体を順次辿ることで累積的に決定される。つまり、最終面の番号がＫであるとして、Ａ_０＝０から始めて色分散指標Ａ_ｋの値を順次計算したとき、最終面の色分散指標Ａ_Ｋの絶対値は、全光学系で見た最終的な色分散の指標値又は累積値を見積もるものであり、所定の基準値以下であることが望ましい。最終的色分散の角度的な大きさは、上記のようにＦ線やＣ線を利用する例では、Ｆ線及びＣ線の波長差が約１７０ｎｍ＝０．１７μｍであるとして、
０．１７×Ａ_Ｋ〔ｄｅｇ〕
で与えられる。なお、以上では、Ｆ線やＣ線を用いる例を示したが、他の波長を基準とできることは言うまでもない。 When the above relational expression (2-1) is differentiated by the wavelength λ,
sin α _k × (dn _k−1 / dλ)
+ N _k-1 cos α _k × (dα _k / dλ)
= Sin β _k × (dn _k / dλ)
+ N _k cos β _k × (dβ _k / dλ)
It becomes. Here, if V _k−1 = dn _k−1 / dλ and V _k = dn _k / dλ, and A _k−1 = dα _k / dλ and A _k = dβ _k / dλ,

It becomes. In this relational expression (2-2), the values V _k-1 and V _k indicate the wavelength dependence of the refractive index, and the values A _k-1 and A _k are chromatic dispersion indices, that is, chromatic dispersion or color separation. Indicates the degree. Note that A ₀ = dθ ₀ / dλ as an initial value is zero. Equation (2-2), if successively traced the refracting surface, as the number of the final surface is K, the absolute value of the chromatic dispersion index A _K of the final surface (in this case, K is the number of the last surface, In the present embodiment, this means that it is possible to estimate up to the fifth surface (that is, the boundary between glass or resin and air), where V _k-1 = dn _k-1 / dλ, Vk = dn. with _{k /} d [lambda], etc., each time through the refracting surfaces between successive medium, that is, the color distribution indicator a _{k =} dβ _{k / dλ} is sequentially calculated at each bending point along the optical axis AX. value V _k Is the wavelength dependency of the refractive index of the medium on the incident side of the refracting surface. For example, the wavelength range of visible light is λb to λr (μm), and the refractive index region of the target medium is approximately nb to nr. Can be expressed by the value (nb−nr) / (λb to λr). The wavelength of F-line, which is commonly used as standards rate characteristics and lambda _{F ([mu]} m), the wavelength of C-line and lambda _{C ([mu]} m), at the focus to the medium, the refractive index of the F-line and n _F, the C-line When the refractive index is n _C , the value V _k = dn _k / dλ is given by

Can be obtained using The chromatic dispersion index A _k is cumulatively determined by sequentially following the medium using the initial value A ₀ (deg / μm), Vk = dnk / dλ (1 / μm), and the like. In other words, as the number of the last surface is K, when sequentially calculate the value of the color distribution indicator A _k starting from A 0 _{= 0,} the absolute value of the chromatic dispersion index A _K of the final surface, viewed in the entire optical system The final index value or cumulative value of color dispersion is estimated, and it is desirable that it be below a predetermined reference value. As for the angular magnitude of the final chromatic dispersion, in the example using the F line and the C line as described above, the wavelength difference between the F line and the C line is about 170 nm = 0.17 μm.
0.17 × _{A K} [deg]
Given in. In addition, although the example which uses F line and C line was shown above, it cannot be overemphasized that another wavelength can be used as a reference.

If the final color distribution indicator _{A K} is 0.3, the angle difference of 0.17 × 0.3 = 0.051 (deg) = 3.06 minutes. Accordingly, in view of ensuring the sharpness of the display image, when it is desired to suppress the angular difference 3.06 (min), the absolute value of the chromatic dispersion index value A _K needs to be 0.3 or less occurs.

Limit for the absolute value of the final color distribution indicator A _K, if not satisfied even for any ray other than the main light beam (ray reaching the center of the eye EY or eye point EP from the center of the light source), the display The image is not clear. However, it is difficult to easily calculate the chromatic dispersion index A _K for any ray. Chromatic dispersion index A _K, since they represent a change in the ray angle in the plane containing the normal line of the light beam and the surface, what was the parallel plane (beam plane) including in ray and the normal to the refracting surface If the a _K of the exit side of the one surface, the incident side of the a _K of the next surface is the same, but can proceed sequentially calculated, in each case beam plane are not parallel, this is different from strict Needs to be converted.

Therefore, in the present embodiment, an optical system that is plane-symmetric with respect to one plane or symmetry plane (specifically, a transverse section (XZ section) including the optical axis AX) is assumed, and projection is performed on this plane or symmetry plane. Think about the rays and normals. Snell's law is approximately established with respect to the angle of the incident light, the outgoing light, and the normal of the surface on each refracting surface projected onto the symmetry plane. In this case, the final color distribution indicator A _K, since they represent the angular dispersion in the symmetry plane of the optical system, a color distribution indicator A _k of the exit side of a surface, the chromatic dispersion of the incident side of the next surface The index _Ak becomes the same, and it becomes easy to proceed with the calculation sequentially.

に基づいて、Ａ_０＝０（ｄｅｇ／μｍ）から始めて色分散指標Ａ_ｋ（ｄｅｇ／μｍ）の値を順次計算したとき、最終面の番号がＫであるとして、対称面への投射によって得られる最終面の色分散指標Ａ_Ｋが所定の基準値以下であることが望ましいと言える。この場合、スネルの法則は近似的に成り立つのみで、誤差を生じる可能性があるため、対称面への投射によって得られる色分散指標Ａ_Ｋの絶対値を１．０以下とすることが望ましい目標となる。 Specifically, a line obtained by projecting the normal of the surface at the point where the image light GL intersects the kth optical surface or the optical functional surface of the display optical system (that is, the display optical system 2) onto the symmetry plane of the display optical system. The angle formed by the line projected on the symmetry plane and the line projected on the symmetry plane is α _k, and the angle formed by the line projected on the symmetry plane with the normal of the optical surface or optical function surface and the line projected on the symmetry plane and beta _k, the refractive index of the incident side of the medium and n _k-1, the refractive index of the exit side of the medium and n _k, and the refractive index dispersion of the incident side medium and V _k-1, the refractive index of the exit side medium Assuming that the dispersion is V _k , the chromatic dispersion index of the incident side medium is A _k−1 , the chromatic dispersion index on the emission side obtained by projection onto the symmetry plane is A _k , and the target wavelength is λ (μm), Formula (2-4)

When the value of the chromatic dispersion index A _k (deg / μm) is calculated sequentially starting from A ₀ = 0 (deg / μm), the final surface number is K, and is obtained by projection onto a symmetric surface. Chromatic dispersion index a _K of the final surface that is it can be said that it is preferably not more than a predetermined reference value. In this case, Snell's law is only holds an approximation, since it may introduce errors, the target it is desirable to absolute value of chromatic dispersion index A _K obtained by projection onto the plane of symmetry of 1.0 or less It becomes.

Hereinafter, examples based on a specific optical system will be described. In addition, the meaning of the symbol used in each Example is as follows.
STOP: Diaphragm plane PLANE corresponding to the eye: Plane in front of the eye or in front of the image plane IMAGE: Image plane MA: Mirror array PSi: Plane (i = surface number of the same plane)
FFSj: free-form surface (j = surface number of the same kind of surface)
ASPk: spherical surface or plane (k = surface number of the same kind of surface)
T: Axial surface interval TLY: Inclination angle of optical axis (°) in cross section (XZ cross section) of specific surface
(TLY may change before and after a specific surface)
DCX: Deviation amount of the optical axis in the X-axis direction in the cross section (XZ cross section) of the specific surface

Table 1 below shows data of optical surfaces of specific optical systems common to Examples 1 to 3. For example, the symbols PS1 and FFS2 represent the planes 22a and 22b of the parallel light guide 22, and the symbols FFS1 and FFS2 represent the reflecting surface RS and the light incident surface IS of the incident portion 21. Reference numerals ASP <b> 1 to ASP <b> 6 represent lens surfaces of the projection lens 12.
[Table 1]
No Name T Medium
1 STOP 20.00 Air
2 PLANE 0.50 BK7
3 MA -0.50 Air
4 PS1 -5.00 COP
5 PS2 14.00
6 FFS1 -7.00 COP
7 FFS2 7.00
8 FFS1 7.00 Air
9 ASP1 12.00 COP
10 ASP2 1.50 Air
11 ASP3 1.00 PC
12 ASP4 2.00 Air
13 ASP5 6.00 COP
14 ASP6 5.60 Air
15 PLANE 1.10 SLICA
16 IMAGE

表中で、記号Ｆは、Ｆ線屈折率を意味し、記号ｄは、ｄ線屈折率（ｎｄ）を意味し、記号Ｃ線屈折率を意味する。また、記号Ｖは、屈折率分散を意味する。 Air, BK7, COP, PC, and SLICA in Table 1 above are medium names, and the medium data of each medium is as shown in Table 2 below.
[Table 2]

In the table, the symbol F means the F-line refractive index, the symbol d means the d-line refractive index (nd), and the symbol C-line refractive index. The symbol V means refractive index dispersion.

Table 3 below shows the optical axis tilt angle (tilt) TLY and the optical axis misalignment amount (decenter) DCX in the cross section of the optical surface in the prism constituting the specific optical system common to the first to third embodiments. Shown in
[Table 3]
No Name TLY (front) DCX (back) TLY (back)
2 PLANE 15.00 0.0 0.00
5 PS2 0.00 11.8 65.08
6 FFS1 -54.00 0.0 -54.00
7 FFS2 36.48 0.0 -36.48
8 FFS1 54.00 7.0 32.38

Table 3 below shows coefficients Akm _{, n} that are polynomial-expanded with respect to a free-form surface among optical surfaces that constitute a specific optical system common to the first to third embodiments. In Table 4, the symbols m and n mean variables or orders in the coefficient Akm _{, n} . Here, the coefficient Ak _{m, n} means a coefficient of each term X ^m · Y ⁿ constituting the polynomial representing the target k-th surface. That is, the k-th surface is represented by Z = Σ {Ak _{m, n} · (X ^m · Y ⁿ )}.
[Table 4]
mn FFS1 FFS2
2 0 4.025E-03 6.215E-03
0 2 6.136E-03 6.836E-03
3 0 2.529E-05 6.218E-05
1 2 1.150E-05 2.657E-05
4 0 2.362E-06 3.504E-06
2 2 1.238E-06 2.624E-06
0 4 4.822E-06 4.171E-06
5 0 0.000E + 00 5.012E-08
3 2 0.000E + 00 -5.990E-08
1 4 0.000E + 00 4.723E-08
6 0 0.000E + 00 7.769E-09
4 2 0.000E + 00 -2.522E-09
2 4 0.000E + 00 -6.814E-09
0 6 0.000E + 00 -4.870E-09

Table 5 below shows coefficients Bi (i = 2, 4, 6,...) Obtained by polynomial expansion of the cross-sectional shape of the aspherical surface among the optical surfaces constituting the specific optical system common to the first to third embodiments. . That is, the aspherical surface ^{as r 2 = X 2 + Y 2} , represented by Z = ΣBi · ^{r i.}
[Table 5]
ASP1 ASP2 ASP3
B2 4.088E-02 -2.844E-02 -5.546E-02
B4 4.789E-05 7.964E-05 3.746E-04
B6 1.379E-07 7.442E-08 -1.359E-06
B8 6.850E-10 -7.115E-10 2.222E-09

ASP4 ASP5 ASP6
B2 4.503E-02 6.674E-02 -1.370E-02
B4 -2.053E-04 -3.603E-06 1.003E-03
B6 1.234E-06 -2.773E-06 -1.894E-05
B8 5.199E-08 2.982E-09 1.120E-07

  FIG. 6A is a cross-sectional view of the light guide device 20 and the projection lens 12 according to the first embodiment. The projection lens 12 includes three lenses L1 to L3. The light guide device 20 includes first and second surfaces S <b> 1 and S <b> 2 as a pair of flat surfaces 22 a and 22 b of the parallel light guide 22. The plane 22a or the first surface S1 corresponds to the light emission surface OS. The light guide device 20 includes a third surface S3 that is a free-form surface and has a relatively weak negative refractive power in the cross section, and a fourth surface that is a free-form surface and has a relatively weak positive refractive power in the cross section, at the incident portion 21. S4 and a fifth surface S5 which is a transmission surface common to the third surface S3. Here, the fifth surface S5 corresponds to the light incident surface IS. As in the present embodiment, by providing a free curved surface in the incident portion 21, the burden on the projection lens can be reduced, and as a result, the optical system can be thinned.

  FIG. 6B specifically illustrates the local coordinates of the first to fifth surfaces S1 to S5 that constitute the light guide device 20.

表中で、Ａ欄は、ｋ欄に対応する色分散指標Ａ_ｋの値を示し、α欄は、ｋ欄に対応する入射角の値α_ｋを示し、β欄は、ｋ欄に対応する射出角の値β_ｋを示す。ここで、整数ｋは、画像面側からの面番号を意味し、ｋ＝０は、液晶デバイス（画像形成装置）１１の画像面に対応する射出面１１ａに対応し、ｋ＝１、２は、液晶デバイス１１のカバーガラスの面を意味する。ｋ＝３、４は、第３レンズＬ３の光学面を示し、ｋ＝５、６は、第２レンズＬ２の光学面を示し、ｋ＝７、８は、第１レンズＬ１の光学面を示す。ｋ＝９は、導光装置２０の光入射面ＩＳを示し、ｋ＝１０は、反射ユニット２０の境界面ＩＦを示し、ｋ＝１１は、光射出面ＯＳに対応する。 [Example 1]
Hereinafter, the optical data in the optical path of Example 1 will be described with reference to Table 6. The optical data of Example 1 corresponds to the light emitted from the center point (x = 0, y = 0) of the liquid crystal device 11, and the light rays and the normals of each surface are all It is included in the symmetry plane of the optical system.
[Table 6]

In the table, the A column indicates the value of the chromatic dispersion index A _k corresponding to the k column, the α column indicates the incident angle value α _k corresponding to the k column, and the β column corresponds to the k column. The emission angle value β _k is shown. Here, the integer k means the surface number from the image surface side, k = 0 corresponds to the exit surface 11a corresponding to the image surface of the liquid crystal device (image forming apparatus) 11, and k = 1, 2 is The surface of the cover glass of the liquid crystal device 11 is meant. k = 3 and 4 indicate the optical surfaces of the third lens L3, k = 5 and 6 indicate the optical surfaces of the second lens L2, and k = 7 and 8 indicate the optical surfaces of the first lens L1. . k = 9 indicates the light incident surface IS of the light guide device 20, k = 10 indicates the boundary surface IF of the reflection unit 20, and k = 11 corresponds to the light exit surface OS.

As apparent from the above table, the final cumulative value of the index value the absolute value of (lateral chromatic aberration) _{A K} is 0.075 [deg / [mu] m], 0.3 [deg / [mu] m] or less It has become.

[Example 2]
Hereinafter, the optical data in the optical path of Example 2 will be described with reference to Table 7. The optical data of Example 2 corresponds to light emitted from one of the four corners of the liquid crystal device 11 (x = 4.8, y = 2.7). The line is not included in the plane of symmetry of the optical system. The α column in the table indicates the angle α _k when the incident side ray and the surface normal are projected on the symmetry plane, and the β column indicates the angle β when the emission side ray and the surface normal are projected on the symmetry surface. _k .
[Table 7]

As apparent from the above table, the final cumulative value of the index value the absolute value of (lateral chromatic aberration) A _K is 0.274 [deg / [mu] m].

Example 3
Hereinafter, the optical data in the optical path of Example 3 will be described with reference to Table 8. The optical data of Example 3 corresponds to the light emitted from the opposite positions (x = −4.8, y = −2.7) of the four corners of the liquid crystal device 11. As in Example 2, the column α in the table indicates the angle α _k when the normal of the incident side ray and the surface is projected onto the symmetry plane, and the column β indicates the normal of the emission side ray and the surface as the symmetry plane. Shows angle β _k when projected [Table 8]

As apparent from the above table, the final cumulative value of the index value the absolute value of (lateral chromatic aberration) A _K is 0.784 [deg / [mu] m].

[1D. Summary of First Embodiment]
According to the virtual image display device 100 of the first embodiment described above, the accumulated value A _K index of the color variance for laterally a predetermined direction is a predetermined reference value 0.5 or 0.2 [deg / Μm] or less, even when a plurality of refracting surfaces inclined with respect to the optical axis AX in the lateral direction are provided, the color separation or lateral chromatic aberration is treated in total while ensuring optical performance. Dispersion can be reliably reduced for the entire imaging system.

  FIG. 7 is a diagram illustrating a modification example regarding the structure and the like of the emission unit 23 of the light guide device 20. In this case, the thickness of the reflection unit 30 is thick on the incident side close to the incident portion 21 and thin on the non-incident side far from the incident portion 21. In the light guide device 20, the elevation angle φ <b> 2 of the video light GL <b> 2 is small on the side farther from the incident portion 21, and it is possible to suppress an increase in the number of times passing through the mirror 31 by making the reflection unit 30 thin. Here, it is desirable that the observation-side light exit surface OS of the reflection unit 30 and the external light-side plane 22 a of the parallel light guide 22 are parallel to each other. That is, the part adjacent to the reflection unit 30 among the parallel light guides 22 has a slight wedge angle in principle. Also in this case, the final color dispersion index is evaluated using the relational expression (2-2) or (2-4) with respect to the light incident surface IS (not illustrated), the illustrated boundary surface IF, the light exit surface OS, and the like. Therefore, the high-performance virtual image display device 100 can be obtained while suppressing the occurrence of lateral chromatic aberration.

  FIG. 8 is a diagram for explaining another modification example regarding the structure and the like of the emission unit 23 of the light guide device 20. In this case, the reflection unit 30 provided in the emission part 23 is incorporated in an inclined state. Specifically, the reflection unit 30 is inclined so that the far side portion 23 h far from the incident portion 21 is closer to the outside than the front portion 23 m close to the incident portion 21. That is, the entrance surface 30a and the exit surface 30b of the reflection unit 30 are inclined at an appropriate angle ρ less than 90 ° counterclockwise with reference to the planes 22a and 22b of the parallel light guide 22. Here, the emission unit 23 includes a prism member 23f having a wedge-shaped cross section joined to the emission surface 30b of the reflection unit 30 on the opposite side of the parallel light guide 22 with the reflection unit 30 interposed therebetween. Thereby, the plane 22a on the outside side of the parallel light guide 22 and the light emitting surface OS or the plane 22b facing the plane 22a are parallel to each other, so that the outside light OL can be naturally observed. Even if the reflection unit 30 is arranged in an inclined state, if the angle condition is the same as in the example shown in FIGS. 2 and 4, the image light GL reflected by the plane 22 a on the external side of the parallel light guide 22 is reflected. It can be reflected by a plurality of mirrors 31 and pass through the light exit surface OS on the observation side, and a virtual image can be formed as in the case of FIG. In this case, with respect to the light incident surface IS (not shown), the surfaces 30a and 30b corresponding to the illustrated boundary surface IF, the light exit surface OS, etc., the final expression is obtained using the relational expression (2-2) or (2-4). By evaluating a chromatic dispersion index, it is possible to obtain a high-performance virtual image display device 100 while suppressing the occurrence of lateral chromatic aberration.

[Second Embodiment]
Hereinafter, a virtual image display device incorporating a light guide device according to a second embodiment of the present invention will be described. Note that the light guide device according to the second embodiment is a partial modification of the light guide device according to the first embodiment, and description of common portions is omitted.

  As shown in FIG. 9, in the case of the virtual image display device 100 of the present embodiment, in the display optical system 2, the projection optical system 12 includes an optical path bending prism 12b in addition to the collimating lens 12a. The optical path bending prism 12b has a pair of refracting surfaces PS1 and PS2, and the optical path of typical image light GL0 on the optical axis AX is bent by these refracting surfaces PS1 and PS2. In this case, with respect to the refractive surfaces PS1 and PS2, the light incident surface IS, the boundary surface IF, the light exit surface OS, etc., the final color dispersion index is evaluated using the relational expression (2-2) or (2-4). By doing so, it is possible to obtain a high-performance virtual image display device 100 while suppressing the occurrence of lateral chromatic aberration.

  Note that the collimating lens 12a and the prism 12b do not need to be separated from each other, and these optical components can be formed by integrating the lenses 12a and 12b.

[Third Embodiment]
Hereinafter, a virtual image display device incorporating a light guide device according to a third embodiment of the present invention will be described. Note that the light guide device according to the third embodiment is a partial modification of the light guide device according to the first or second embodiment, and description of common parts is omitted.

  As illustrated in FIG. 10, the virtual image display device 100 according to the present embodiment includes a light guide member 20a for light guide and see-through and a light transmissive member 20b for see-through as the light guide device 320. Among these, the light guide member 20 a includes the incident portion 21 and the parallel light guide 22, and the light transmission member 20 b is fixed to the parallel light guide 22.

  The parallel light guide 22 of the light guide member 20a has a curved optical surface 22c on the exit side. A half mirror layer 25 is attached to the surface of the optical surface 22c. The half mirror layer 25 is a light-transmitting reflective film, that is, a semi-transmissive reflective film, and is formed by forming a metal reflective film or a dielectric multilayer film, and the reflectance with respect to video light is appropriately set.

  The light transmissive member 20b has flat surfaces 122a and 122b that are disposed on an extension of a pair of flat surfaces 22a and 22b provided on the light guide member 20a, and has an optical surface 122c between the flat surfaces 122a and 122b. Yes. The optical surface 122c is a curved surface that is bonded to and integrated with the optical surface 22c of the light guide member 20a.

  In the light guide device 320, the light guide member 20 a is joined to the light transmission member 20 b via the adhesive layer CC, and the adhesive layer CC is more than the half mirror layer 25 in the image extraction area A1 where the half mirror layer 25 is located. Is also present on the light transmitting member 20b side. The image extraction area A1 is an area where image light is emitted to the user's eyes.

In this case, the occurrence of lateral chromatic aberration is suppressed by evaluating the final chromatic dispersion index using the relational expression (2-2) or (2-4) with respect to the light incident surface IS, the light exit surface OS, and the like. A high-performance virtual image display device 100 can be obtained. Incidentally, the projection optical system 12 may comprise a prism for bending an optical path folding, in this case, the accumulated value of the index, including the refractive surface of the optical path folding for the prism (lateral chromatic aberration) to evaluate the A _k.

[Fourth Embodiment]
Hereinafter, a virtual image display device incorporating a light guide device according to a fourth embodiment of the present invention will be described. Note that the light guide device according to the fourth embodiment is a partial modification of the light guide device according to the first embodiment, and a description of common portions is omitted.

  As illustrated in FIG. 11, the virtual image display device 100 according to the present embodiment includes the image projection device 10 and a light guide device 420 as a set. The image projection apparatus 10 includes an image forming apparatus 411 and a projection optical system 12. The image forming apparatus 411 includes a light modulation display element such as a liquid crystal device, and LEDs, LDs, and other light sources that generate RGB three-color light. The projection optical system 12 includes a plurality of lenses 12a having symmetry around the optical axis AX.

  The light guide device 420 that constitutes the display optical system 2 together with the projection optical system 12 includes an incident portion 21 that takes in image light, a parallel light guide 22 for guiding light, and an emission portion 23 that takes out image light. . The incident portion 21 is a sheet-shaped incident-side diffraction element fixed so as to be affixed to one end side (left side in the drawing) of the light guide plate 24 that is a parallel flat plate and the outer surface side flat surface 24 a on one end side of the light guide plate 24. 440. The parallel light guide 22 is a portion excluding both ends of the light guide plate 24. The exit portion 23 includes a sheet-like exit-side diffraction element 430 that is fixed so as to be affixed to a portion of the other end side (right side of the drawing) of the light guide plate 24 and the flat surface 24a on the outside world at the other end side of the light guide plate 24. Have

  The light guide plate 24 is made of a light-transmitting material such as glass or resin material, and has, as its main surface or surface, a flat surface 24a that is a total reflection surface on the outside and a flat surface 24b that is a total reflection surface on the back side. . The planes 24 a and 24 b are both processed into optical surfaces and have a function of maintaining the propagation angle or reflection angle of the video light GL propagating in the light guide plate 24 as light guide surfaces parallel to each other.

  The incident-side diffractive element 440 is configured to couple the image light GL collimated by the projection optical system 12 and incident on the light guide plate 24 through the plane 24b into the light guide plate 24 and propagate the image light GL in the light guide plate 24. And the incident angle is converted into a desired diffraction angle. The incident side diffraction element 440 functions as an inclined mirror equivalently.

  The incident side diffraction element 440 is a reflection type diffraction element and is one of a hologram and a surface relief diffraction grating. When the incident side diffraction element 440 is a hologram, the entire incident side diffraction element 440 functions as the diffraction surface DF. From the viewpoint of reducing color separation, the incident-side diffraction element 440 is preferably a volume hologram, particularly preferably a volume phase hologram. When the incident side diffraction element 440 is a surface relief diffraction grating, the fine diffraction structure formed in the incident side diffraction element 440 functions as the diffraction surface DF. A blazed grating is preferable from the viewpoint of light utilization efficiency. Here, a volume hologram is a hologram data recorded as a grating in a relatively thick recording medium. In particular, a volume phase hologram is a hologram obtained by recording hologram data as a refractive index grating to increase the transmittance. is there. The surface relief diffraction grating is a thin film surface with fine uneven relief corresponding to the interference pattern. Especially, the blazed grating has a fine uneven relief with a sawtooth cross-sectional shape to improve diffraction efficiency. It is. The incident side diffraction element 440 may be a diffraction element that collectively performs diffraction of each color at once, but may be a stack of diffraction elements for each color.

  The exit side diffractive element 430 extracts the image light GL that is coupled to the light guide plate 24 by the incident side diffractive element 440 and propagates through the light guide plate 24 to the outside of the light guide plate 24, and diffracts the image light GL. The propagation angle is converted into a desired diffraction angle. As a result, the image light GL incident on the exit-side diffraction element 430 from within the light guide plate 24 is restored to an exit angle equal to the incident angle before entering the original incident-side diffraction element 440. The exit side diffraction element 440 equivalently functions as a tilted mirror, emits the image light GL propagated in the light guide plate 24 to the eye EY side via the plane 24b, and the image forming apparatus 411 in front of the eye EY. It has a function of reproducing or projecting an enlarged virtual image corresponding to the image formed on the exit surface 11a. The exit side diffraction element 430 is also a reflection type diffraction element like the incident side diffraction element 440, and is either one of a hologram and a surface relief diffraction grating. In other words, the exit-side diffraction element 430 can be constituted by, for example, a volume phase hologram, a blazed grating, or the like, and has a diffraction surface DF composed of a recording layer or a fine diffraction structure.

に基づいて、Ａ_０＝０（ｄｅｇ／μｍ）から始めて色分散指標Ａ_ｋ（ｄｅｇ／μｍ）の値を順次計算したとき、最終面の番号がＫであるとして、対称面への投射によって得られる最終面の色分散指標Ａ_Ｋが所定の基準値以下であることが望ましい。具体的には、対称面への投射によって得られる色分散指標Ａ_Ｋの絶対値を０．３未満とすることが望ましい。以上の式（３−１）に関する説明で、光学機能面には、屈折面だけでなく回折面又は回折層も含まれるものとする。 In this case, the image light GL and the display optical system 2 are related to the image light beam that is emitted from the center of the exit surface 11a corresponding to the image surface of the image forming apparatus 411 and reaches the center of the observer's eye via the display optical system 2. Α _k is the angle formed by the normal of the optical functional surface and the incident ray at the point where the image light GL intersects the optical functional surface (the optical surface or the diffractive surface). the angle between the normal and the exit light beam of the optical functional surface and beta _k, the refractive index of the incident side of the medium and n _k-1, the refractive index of the exit side of the medium and n _k, the refraction of the incident side medium The index dispersion is V _k−1 , the refractive index dispersion of the exit side medium is V _k , the incident side chromatic dispersion index is A _k−1 , the exit side chromatic dispersion index is A _k , and the target wavelength is λ ( μm), the diffraction order is an integer m _k, and the pitch of the diffraction grating is p _k.

When the value of the chromatic dispersion index A _k (deg / μm) is calculated sequentially starting from A ₀ = 0 (deg / μm), the final surface number is K, and is obtained by projection onto a symmetric surface. Chromatic dispersion index a _K of the final surface that is it is preferably not more than a predetermined reference value. Specifically, the absolute value of the chromatic dispersion index A _K obtained by projection onto the plane of symmetry is preferably less than 0.3. In the description of the above formula (3-1), the optical functional surface includes not only a refractive surface but also a diffractive surface or a diffractive layer.

Expression (3-1) described above is the expression (2-1) described above in the case where the diffraction surface is not included.
n _k-1 × sin α _k = n _k × sin β _k (2-1)
N _k-1 × sin α _k = n _k × sin β _k + m _k (λ / p _k ) (2-1) ′
And rewriting, conversion processing such as differentiation is performed in the same manner. The diffraction order m _k is 0 on a normal refracting surface and an integer other than 0 on the diffractive surface. When the diffraction order m _k = 0, the above formula (3-1) is the same as the above-described formula (2-1) when the diffraction plane is not included. In the case of a diffraction grating, the pitch _pk of the diffraction grating means a repetitive interval with respect to the diffraction direction of a repetitive pattern formed in a direction along the optical function surface.

The above expression (3-1) is a generalization of the relational expression (2-2), and takes into consideration the case where not only a refracting surface but also a diffractive surface exists on the optical path. For display optical system 2 shown in FIG. 11, an incident-side diffraction element 440, to evaluate the cumulative value A _K of the index by using relationship (3-1) with respect to the exit side diffraction element 430, chromatic dispersion The high-performance virtual image display device 100 can be obtained while suppressing the occurrence of the above. For example, diffractive elements 440,430 acts on the chromatic dispersion index _{A K} as a term m / p in the formula (3-1) as a diffractive surface DF, the light incidence surface IS and the interface IF of the formula as a refractive surface ( 3-1) acting on the chromatic dispersion index _{a K} as a term _{V k-1 sinα k -V k} sinβ k in. As a result, if the pitch of the incident side diffractive element 440 and the pitch of the exit side diffractive element 430 are matched, the chromatic dispersion generated in both diffractive elements 440 and 430 cancels each other.

に基づいて、Ａ_０＝０（ｄｅｇ／μｍ）から始めて色分散指標Ａ_ｋ（ｄｅｇ／μｍ）の値を順次計算したとき、最終面の番号がＫであるとして、対称面への投射によって得られる最終面の色分散指標Ａ_Ｋが所定の基準値以下であることが望ましい。具体的には、対称面への投射によって得られる色分散指標Ａ_Ｋの絶対値を１．０以下とすることが望ましい。以上の式（３−２）に関する説明で、光学機能面には、便宜上屈折面だけでなく回折面も含まれるものとする。 As another viewpoint, when an optical path is projected onto the symmetry plane of the display optical system 2 (specifically, a cross section including the optical axis AX (XZ cross section)), an arbitrary point of the liquid crystal device (image forming apparatus) 11 is considered. The image light GL and the optical function surface of the image light GL and the k-th optical function surface of the display optical system 2 with respect to the image light beam that starts from the display optical system 2 and reaches the center of the observer's eye Α _k is the angle formed by the line projected on the plane of symmetry of the display optical system 2 and the line projected on the plane of symmetry of the optical function surface at the intersection of the the angle made by the line which is projected to the plane of symmetry of the projected line and the exit beam to the symmetry plane and beta _k, the refractive index of the incident side of the medium and n _k-1, the refractive index of the exit side of the medium n _k And the refractive index dispersion of the incident side medium is V _k−1 , the refractive index dispersion of the exit side medium is V _k , The chromatic dispersion index is A _k−1 , the emission side chromatic dispersion index obtained by projection onto the symmetry plane is A _k , the target wavelength is λ (μm), the diffraction order is m _k, and the pitch of the diffraction grating is As _pk , the following formula (3-2)

When the value of the chromatic dispersion index A _k (deg / μm) is calculated sequentially starting from A ₀ = 0 (deg / μm), the final surface number is K, and is obtained by projection onto a symmetric surface. Chromatic dispersion index a _K of the final surface that is it is preferably not more than a predetermined reference value. Specifically, the absolute value of the chromatic dispersion index A _K obtained by projection onto the plane of symmetry that is desired to be 1.0 or less. In the description of the above formula (3-2), it is assumed that the optical function surface includes not only a refractive surface but also a diffractive surface for convenience.

  The expression (3-2) is a generalization of the above-described relational expression (2-4) in the case where the diffractive surface is not included, similarly to the above expression (3-1), and the refractive surface on the optical path. In addition, the case where a diffractive surface is present is considered.

In addition, when using, for example, a volume hologram element as the diffraction elements 430 and 440, it is necessary to treat the pitch _pk as different for each portion through which the light beam passes.

  In the above description, the diffraction elements 430 and 440 are provided on the flat surface 24a on the outside, but the diffraction elements 430 and 440 may be provided on the flat surface 24b on the back side. In this case, the diffraction elements 430 and 440 are transmissive.

FIG. 12 is a diagram for explaining a modification of the virtual image display device 100 shown in FIG. In this modification, the light guide plate 24 is disposed at an angle and conforms to the shape of the face. Also in this case, based on the above formula (3-1) or (3-2), it is desirable that the final surface color dispersion index _AK is not more than a predetermined reference value, specifically, the color dispersion index _AK The absolute value is desirably less than 0.3 or 1.0 or less for each derivation method. As a result, if the pitch of the incident side diffractive element 440 and the pitch of the exit side diffractive element 430 are matched, the chromatic dispersion generated in both diffractive elements 440 and 430 cancels each other.

FIG. 13 is a diagram for explaining another modification of the virtual image display apparatus 100 shown in FIG. Even in this modification, the light guide plate 24 is tilted to follow the shape of the face, but by inserting the prism 12b into the projection optical system 12 and bending the optical path, the projection optical system 12 approaches the face side surface. It is preventing. Again, based on the above formula (3-1) or (3-2), it is desirable chromatic dispersion index A _K of the final surface is less than the predetermined reference value, in particular chromatic dispersion index A The absolute value of _K is preferably less than 0.3 or 1.0 or less for each derivation method. As a result, the chromatic dispersion index _AK is evaluated for the prism 12b, the incident side diffraction element 440, the emission side diffraction element 430, and the like. In this case, since new chromatic dispersion occurs due to the addition of the prism 12b, the pitch of the diffraction gratings 430 and 440 is adjusted to compensate for the newly generated chromatic dispersion. In this case, the pitch of the diffraction grating 430, 440 may do it set so as to be sufficiently small values of chromatic dispersion index A _K tracing calculations to.

[Others]
Although the present invention has been described based on the above embodiments, the present invention is not limited to the above embodiments, and can be implemented in various modes without departing from the gist thereof. Such modifications are also possible.

  For example, the light guide device 20 provided in the virtual image display device 100 of the first embodiment has a configuration in which the parallel light guide 22 totally reflects the video light GL only once on the plane 22a and guides it to the reflection unit 30. However, the configuration may be such that the image light GL is totally reflected a plurality of times by the opposing flat surfaces 22 a and 22 b and guided to the reflection unit 30.

  The reflectivities of a large number of mirrors 31 provided in the reflection unit 30 are matched in principle, but the reflectivities of these mirrors 31 can be gradually changed from the incident side close to the incident portion 21 to the non-incident side.

  In the above description, the transmissive liquid crystal device 11 is used as the video element. However, the video element is not limited to the transmissive liquid crystal device, and various devices can be used. For example, a configuration using a reflective liquid crystal panel is possible, and a digital micromirror device or the like can be used instead of the liquid crystal device 11. Further, a configuration using a self-luminous element typified by an organic EL or the like is also possible. Further, a configuration using a laser scanner in which a laser light source and a polygon mirror or other scanner are combined is possible.

  In the above description, the virtual image display device 100 is configured to provide one set of the image projection device 10 and the light guide device 20 corresponding to both the right eye and the left eye, but either the right eye or the left eye. Only the image projection device 10 and the light guide device 20 may be provided only for the one eye view.

  In the above description, the virtual image display device 100 of the embodiment is specifically described as a head-mounted display. However, the virtual image display device 100 of the embodiment is applied to a head-up display, a binocular handheld display, and the like. You can also.

  In the above description, the image light is totally reflected and guided by the interface with air on the flat surfaces 22a and 22b or the curved surface 21b such as the parallel light guide 22 without applying a mirror or a half mirror on the surface. The total reflection in the present invention includes reflection achieved by forming a mirror coat or a half mirror film on the whole or a part of the planes 22a and 22b. For example, a case where the incident angle of the image light GL satisfies the total reflection condition and a mirror coat or the like is applied to a part of the planes 22a and 22b to reflect substantially all the image light is included.

  The incident portion 21 and the parallel light guide 22 constituting the light guide device 20 do not need to be configured as an integral part, and the incident portion 21 and the parallel light guide 22 are configured as separate parts, and both are bonded with an adhesive. You can also

  In the above description, the parallel light guide 22 is horizontally long in the X direction or the x direction, and the light incident surface IS is positioned on the outer side in the lateral direction of the eye. However, the position of the light incident surface IS is not limited to this. For example, the light incident surface IS may be provided on the upper end surface TP or the lower end surface BP above and below the light guide device 20. In this case, the reflection unit 30 is rotated by 90 ° around the optical axis AX in front of the eyes. In this case, instead of the lateral chromatic dispersion index value, the longitudinal chromatic dispersion index value or the accumulated value (lateral chromatic aberration) is estimated.

  Further, a virtual image display device using a light guide optical element or substrate made of an array of partially reflecting surfaces as described in JP 2010-164988 A or JP 2013-210633 A as a light guide device 20 may be used. it can.

  Although not mentioned above, the upper end surface TP, the lower end surface BP, and the like of the outer peripheral portion that defines the outer shape of the parallel light guide 22 can be used as a black paint application surface or a sandblasted surface. Furthermore, you may perform black coating application | coating or sandblasting to locations other than upper end surface TP and lower end surface BP. Only a part of the upper end surface TP, the lower end surface BP, or the like may be subjected to black coating or sandblasting.

  DESCRIPTION OF SYMBOLS 10 ... Image projector, 11 ... Liquid crystal device, 11a ... Ejection surface, 12 ... Projection optical system, 12a ... Collimating lens, 12b ... Prism, 20 ... Light guide device, 21 ... Incident part, 22 ... Parallel light guide, 22a , 22b ... plane, 23 ... exit portion, 23f ... prism member, 30 ... reflection unit, 30a ... entrance surface, 30b ... exit surface, 31 ... mirror, 32 ... block member, 100 ... virtual image display device, 130 ... hologram element, AX ... optical axis, EP ... eye point, EY ... eye, GL ... video light, GL0, GL1, GL2 ... video light, IF ... boundary surface, IS ... light incident surface, IS, IF, OS ... refractive surface, OL ... External light, OS ... light exit surface, RS ... reflection surface

Claims (6)

A virtual image display apparatus comprising: an image forming apparatus that emits image light; and a display optical system that forms a virtual image by the image light from the image forming apparatus, and the image light is incident on a position assumed to be an eye of an observer Because
The display optical system has a shape symmetrical with respect to a predetermined plane,
Regarding an image light beam that originates from an arbitrary point of the image forming apparatus and reaches the center of the observer's eye via the display optical system, the image light beam and the kth optical functional surface of the display optical system An angle formed by a line projected on the symmetry plane of the display optical system and a line projected on the symmetry plane at the point where the image light beam and the optical function surface intersect was a alpha _k, and angular and beta _k formed between the projected line is a normal line and the exit light beam projected onto the plane of symmetry on the symmetry plane of the optical functional surface, the refractive index of the incident side of the medium n _k-1 The refractive index of the exit side medium is _nk , the refractive index dispersion of the incident side medium is V _k−1 , the refractive index dispersion of the exit side medium is V _k , and the incident side chromatic dispersion index is A _{k−. 1,} and the chromatic dispersion index of the exit side is a _k, and λ the wavelength of interest in μm units, the diffraction order m And then, the pitch of the diffraction grating as p _k, the following equation (1)

However,

When the value of the color dispersion index A _k is sequentially calculated starting from A ₀ = 0, the final surface number K is assumed to be K, and the final surface color dispersion index _AK is an absolute value of less than 1.0. A virtual image display device. The refractive index dispersion V _k is λ _{F as} the wavelength of the F line, λ _{C as} the wavelength of the C line, and the refractive index of the F line as n _F and the refractive index of the C line as n _C in each medium.

The virtual image display device according to claim 1, which is approximately given by: With respect to an image light beam originating from the center of the image forming apparatus and reaching the center of the observer's eye via the display optical system, the image light beam and the kth optical functional surface of the display optical system The angle formed by the normal of the optical functional surface and the incident light at the point where the image light and the optical functional surface intersect is α _k, and the angle formed by the normal of the optical functional surface and the emitted light is β _k and then, the refractive index of the incident side of the medium and n _k-1, the refractive index of the exit side of the medium and n _k, and the refractive index dispersion of the incident side medium and V _k-1, the refractive index dispersion of the exit side medium V _k , the incident-side chromatic dispersion index is A _k−1 , the emission-side chromatic dispersion index is A _k , the target wavelength is λ in μm, the diffraction order is m _k, and the pitch of the diffraction grating is p _{As k} , the following formula (1)

Based on, when sequentially calculate the value of the color distribution indicator A _k starting from A 0 _{= 0,} as the number of the final surface is K, the absolute value of the chromatic dispersion index A _K of the final surface is less than 0.3 The virtual image display device according to claim 1, wherein The virtual image display device according to claim 3, wherein the display optical system has three or more refractive surfaces where the value α _k is not zero as an optical functional surface of the display optical system.   5. The virtual image display device according to claim 1, wherein the virtual optical display device has at least one non-axisymmetric free-form surface as an optical functional surface of the display optical system.   The virtual image display device according to claim 1, which has a diffractive surface as an optical functional surface of the display optical system.

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