Virtual image display device and optical unit

Abstract

To prevent unwanted light from reaching the eyes. [Solution] The virtual image display device comprises a display element, a first prism into which image light from the display element is incident, a second prism joined to the first prism, an oblique mirror portion provided at the joint between the first and second prisms and reflecting at least a portion of the image light guided in the first prism, a second lens having positive power and positioned opposite the first outer surface of the first prism, and a transmissive mirror formed on the external side of the second lens and partially reflecting the image light reflected by the oblique mirror portion toward the oblique mirror portion, wherein the oblique mirror portion is formed corresponding to a partial region excluding the periphery of the inclined surfaces of the first and second prisms.

Description

Technical Field

[0001] The present invention relates to a direct virtual image type virtual image display device and an optical unit that enable observation of a virtual image.

Background Art

[0002] As a head-mounted display device, there is a known device including a liquid crystal image display panel, a first lens, a beam splitter, a concave mirror, a quarter-wave plate, and a second lens, in which image light from the liquid crystal image display panel is incident on the beam splitter and reflected by a beam splitting surface that reflects polarized light in a first direction, passes through the quarter-wave plate back and forth when reflected by the concave mirror, and passes through the beam splitter as polarized light in a second direction (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The above-described head-mounted display device has a configuration in which an intermediate image is not generated and there is no aperture stop. Therefore, unnecessary light is trapped in the light guide plate, and there is a problem that unnecessary light reaches the eyes.

Means for Solving the Problems

[0005] A virtual image display device in one aspect of the present invention comprises a display element that emits image light, a first prism into which the image light from the display element is incident, a second prism joined to the first prism to form a parallel plate-shaped prism light guide member, an oblique mirror portion provided at the joint between the first prism and the second prism and reflecting at least a portion of the image light guided in the first prism, a positive-power lens positioned opposite the outer surface of the first prism into which the image light reflected by the oblique mirror portion is incident, and a transmissive mirror formed on the external side of the lens and partially reflecting the image light reflected by the oblique mirror portion toward the oblique mirror portion, wherein the oblique mirror portion is formed corresponding to a partial region excluding the periphery of the inclined surfaces of the first and second prisms.

[0006] An optical unit in one aspect of the present invention comprises a display element that emits image light, a first prism into which the image light from the display element is incident, a second prism joined to the first prism to form a parallel plate-shaped prism light guide member, an oblique mirror portion provided at the joint between the first prism and the second prism and reflecting at least a portion of the image light guided in the first prism, a positive-power lens positioned opposite the outer surface of the first prism into which the image light reflected by the oblique mirror portion is incident, and a transmissive mirror formed on the external side of the lens and partially reflecting the image light reflected by the oblique mirror portion toward the oblique mirror portion, wherein the oblique mirror portion is formed corresponding to a partial region excluding the periphery of the inclined surfaces of the first and second prisms. [Brief explanation of the drawing]

[0007] [Figure 1] This is an external view illustrating the usage state of the virtual image display device of the first embodiment. [Figure 2] This is a lateral cross-sectional view illustrating the internal structure of one of the virtual image display devices. [Figure 3] This is a perspective view of a virtual image display device. [Figure 4] This is an exploded view of the first flat plate-shaped member. [Figure 5] This is a conceptual perspective view illustrating the formation area of ​​the oblique mirror section. [Figure 6] This is a side cross-sectional view of the prism light guide member. [Figure 7] This is a magnified cross-sectional view illustrating the reflective polarizing element before it is attached to the prism. [Figure 8] Figure 2 and other diagrams illustrate the optical path and other aspects of the virtual image display device shown. [Figure 9] This is a conceptual diagram illustrating, in detail, the unwanted light incident on the upper part of the first prism. [Figure 10] This is a conceptual diagram illustrating the optical path of unwanted light entering the first prism. [Figure 11] This is a conceptual diagram illustrating a specific optical path for other unwanted light entering the first prism. [Figure 12] This figure illustrates the projection state of unwanted light in a conventional or embodiment of the apparatus. [Figure 13] This is a side cross-sectional view illustrating the virtual image display device of the third embodiment. [Figure 14] This is a lateral cross-sectional view illustrating a modified virtual image display device. [Modes for carrying out the invention]

[0008] [First Embodiment] A first embodiment of the virtual image display device, etc., according to the present invention will be described below with reference to Figures 1 and 2, etc.

[0009] Figure 1 illustrates the wearing state of a head-mounted virtual image display device (hereinafter also referred to as a head-mounted display or HMD) 200. The HMD 200 causes the observer or wearer US to perceive an image as a virtual image. In Figure 1, etc., X, Y, and Z are Cartesian coordinate systems. The +X direction corresponds to the lateral direction in which the eyes (EY) of the observer or wearer US wearing the HMD 200 are aligned. The +Y direction corresponds to the upward direction perpendicular to the lateral direction in which the eyes (EY) of the wearer US are aligned. The +Z direction corresponds to the forward or frontal direction in which the wearer US is positioned. The ±Y directions are parallel to the vertical axis or the vertical direction.

[0010] The HMD200 comprises a first virtual image display device 100A for the right eye, which is of the direct virtual image type; a second virtual image display device 100B for the left eye, which is also of the direct virtual image type; a pair of temple-shaped support devices 100C that support these virtual image display devices 100A and 100B; and a user terminal 90, which is an information terminal. The first virtual image display device 100A functions as an HMD on its own and consists of a first display drive unit 102a located at the top and a first combiner 103a that is spectacle-lens-shaped and covers the area in front of the eyes. Similarly, the second virtual image display device 100B also functions as an HMD on its own and consists of a second display drive unit 102b located at the top and a second combiner 103b that is spectacle-lens-shaped and covers the area in front of the eyes. The support devices 100C are mounting members that are attached to the head of the wearer US. The support device 100C supports the upper ends of the pair of combiners 103a and 103b via display drive units 102a and 102b, which are integrated externally. The first virtual image display device 100A and the second virtual image display device 100B are optically identical or horizontally inverted versions thereof.

[0011] Figure 2 is a side cross-sectional view illustrating the internal structure of the first virtual image display device 100A. Figure 3 is a perspective view of the first virtual image display device 100A. The first virtual image display device 100A comprises a first image forming element 11a, a first display unit 20a, and a first circuit member 80a. The first image forming element 11a is also called the display element 11. The first display unit 20a is an imaging optical system IS that directly forms a virtual image without forming an intermediate image. The first display unit 20a is also called the direct virtual image optical system DIS. The imaging optical system IS includes a first lens 30, a first flat plate member 40, and a second flat plate member 50. The first lens 30 functions as protective glass to protect the display surface 11d of the display element 11. A cover glass may be provided between the display element 11 and the first lens 30. The first flat plate member 40 guides the image light ML emitted from the display element 11 to the second lens 53 of the second flat plate member 50. The second flat plate-shaped member 50 reflects the image light ML from the first flat plate-shaped member 40 toward the pupil position PP or eye EY so as to partially return it to the first flat plate-shaped member 40, and also causes the ambient light OL to enter the pupil position PP via the first flat plate-shaped member 40. The first lens 30, the first flat plate-shaped member 40, and the second flat plate-shaped member 50 each function as lenses having positive refractive power.

[0012] Although a detailed explanation is omitted, the second virtual image display device 100B comprises a second image forming element 11b, a second display unit 20b, and a second circuit member 80b. The second image forming element 11b is the same as the first image forming element 11a. The second display unit 20b is the same as the first display unit 20a. The second circuit member 80b is the same as the first circuit member 80a.

[0013] In the first virtual image display device 100A, the first image forming element 11a is a self-emitting type image light generation device. The first image forming element 11a emits image light ML to the first flat plate member 40 through the first lens 30. The first image forming element 11a is housed and supported in the case 71. The first image forming element 11a is, for example, an organic EL (organic electroluminescence) display. The first image forming element 11a forms a color still image or moving image on the two-dimensional display surface 11d. The first image forming element 11a is driven by the first circuit member 80a to perform a display operation. The first image forming element 11a can be replaced not only with an organic EL display but also with a display device using inorganic EL, organic LED, LED array, laser array, quantum dot light emitting type element, etc. The first image forming element 11a is not limited to a self-emitting type image light generation device, and may be composed of an LCD or other light modulation element, and an image may be formed by illuminating the light modulation element with a light source such as a backlight. As the first image forming element 11a, LCOS (Liquid crystal on silicon, LCoS is a registered trademark) or the like can also be used instead of the LCD. In the first virtual image display device 100A, the optical device excluding the first circuit member 80a is called the optical unit 100. The optical unit 100 includes a direct virtual image type optical system and can also be said to be a part corresponding to the direct virtual image optical system DIS that constitutes the first virtual image display device 100A.

[0014] The first display unit 20a comprises a first lens 30, a first flat plate member 40, an oblique mirror portion IM, and a second flat plate member 50. In the first display unit 20a, the first lens 30 has a positive refractive power, and image light ML from the first image forming element 11a is incident on it. The first lens 30 has a planar light incident surface 30f joined to the first image forming element 11a, and a convex light emission surface 30g. The light emission surface 30g is, for example, spherical, but can be an aspherical surface having an axially symmetric shape. The first lens 30 can be considered separately as a parallel plate 31 and a lens portion 32. By ensuring that the thickness of the parallel plate 31 is greater than a predetermined amount, foreign matter adhering to the surface of the first lens 30 becomes less noticeable. The parallel plate 31 functions as a cover glass. The lens portion 32 is a plano-convex lens with a positive refractive power. A plano-convex lens has one flat surface and the other convex surface. The parallel plate 31 and the lens portion 32 may be bonded together or separated. The lens portion 32 does not have to be a plano-convex lens; for example, it may be a biconvex lens. The first lens 30 is made of, for example, fused silica and has a relatively low refractive index.

[0015] The first flat plate member 40 has a parallel flat plate-shaped first prism 41 and a parallel flat plate-shaped second prism 42. The first prism 41 and the second prism 42 are joined at the inclined surfaces 41d and 42d with the oblique mirror portion IM in between. The joined first prism 41 and the second prism 42 are called the prism light guide member 48. The prism light guide member 48 has the appearance of a parallel plate. The combination of the prism light guide member 48 and the second flat plate-shaped member 50, which will be described later, corresponds to the first combiner 103a.

[0016] Figure 4 is an exploded view of the first flat plate member 40. As shown in FIGS. 2 to 4, the first prism 41 has a quadrangular prism-shaped outer shape and a trapezoidal longitudinal cross section. The first prism 41 guides the video light ML. The first prism 41 has an incident optical surface 41a, a first inner surface 41b, a first outer surface 41c, and a first inclined surface 41d. The first prism 41 also has an upper plane 40u and a first lateral surface 41e. Here, the incident optical surface 41a is inclined downward and forward as a whole, and the optical axis passing through the incident optical surface 41a extends in a direction between the forward +Z direction and the upward +Y direction. Thereby, it becomes easier to arrange the first image forming element 11a, which is the display element 11, on the outside of the first inner surface 41b with respect to the outside world, and the angle for propagating the video light ML in the first prism 41 (inside the first prism 41 or within the first prism 41) can be adjusted. The incident optical surface 41a is a convex surface, for example, a spherical surface, but can be an axially symmetric aspherical surface. The first prism 41 can be considered to include a lens portion 44 including the incident optical surface 41a. The lens portion 44 is a convex plano lens having a positive refractive power. The lens portion 44 may be directly formed on the first prism 41 or adhered to the first prism 41. The first inner surface 41b and the first outer surface 41c are parallel to each other and extend perpendicular to the optical axis AX between them and the pupil position PP. The first inner surface 41b and the first outer surface 41c internally reflect the video light ML (that is, reflect inside the object surface), and it is particularly desirable that they are total reflection surfaces. The first inner surface 41b can be enhanced in scratch resistance or abrasion resistance by applying a hard coat. The first lateral surface 41e is disposed opposite in the lateral direction, that is, the X direction, which intersects the Y direction in which the first prism 41 and the second prism 42 are arranged, between the first outer surface 41c and the first inner surface 41b. The first inclined surface 41d is a flat surface. The first inclined surface 41d forms an acute angle with the first outer surface 41c, specifically, an angle of 25° to 32°. The distance between the optical axis AX passing through the pupil position PP and the upper end of the first lens 30 is about 20 mm. The first prism 41 is formed of a resin material.

[0017] The number of reflections of the image light ML in the first prism 41 is once at the first inner surface 41b, once at the first outer surface 41c, and once at the oblique mirror section IM, which will be described later. By making the number of internal reflections of the image light ML in the first prism 41 two, it is possible to increase the field of view of the image light ML, the pupil position PP, or its aperture PPa while efficiently avoiding the mixing of light with different reflection counts within the first prism 41. Furthermore, it becomes easier to shorten the distance from the display element 11 to the transmissive mirror 56 of the cover member 52, which will be described later, allowing for miniaturization of the prism light guide member 48, and also making it easier to miniaturize the display element 11 and the first lens 30.

[0018] The second prism 42, like the first prism 41, has a rectangular prism shape and a trapezoidal longitudinal cross-section. The second prism 42 transmits the image light ML. The second prism 42 has a second inner surface 42b, a second outer surface 42c, a second bevel surface 42d, and a bottom surface 42f. The bottom surface 42f is the surface of the prism light guide member 48 or the first flat plate member 40 that is opposite to the incident optical surface 41a. Also, the bottom surface 42f is the surface of the second prism 42 that is opposite to the second bevel surface 42d. The second prism 42 also has a second transverse surface 42e. Here, the second inner surface 42b and the second outer surface 42c are parallel to each other and extend perpendicular to the optical axis AX between them and the pupil position PP. The second inner surface 42b can be hard-coated to improve scratch resistance or abrasion resistance. The second prism 42 is made of a resin material. The second lateral surface 42e is positioned between the second outer surface 42c and the second inner surface 42b, and is positioned in a lateral direction, i.e., the X direction, which intersects with the Y direction, the direction in which the first prism 41 and the second prism 42 are aligned.

[0019] The beveled portion ST, which is the joint JS between the first prism 41 and the second prism 42, has flat portions FL on the first and second outer surfaces 41c and 42c. Both flat portions FL are formed continuously from the lower ends of the first bevel 41d and the second bevel 42d. Both flat portions FL are obtuse to the first bevel 41d and the second bevel 42d and extend substantially parallel to the XZ plane. The flat portions FL are positioning structures AS provided around the bevels 41d and 42d of the first prism 41 and the second prism 42. When joining the first prism 41 and the second prism 42, by facing and bringing these bevels 41d and 42d close together, the pair of flat portions FL provided adjacent to the bevels 41d and 42d also come into contact with each other as contact surfaces AF extending parallel to each other, and are tightly attached. This allows the first prism 41 and the second prism 42 to be positioned with respect to the inclination direction of their inclined surfaces 41d and 42d, that is, the intermediate direction between the Z and Y directions, and also with respect to an axis perpendicular to the inclined surfaces 41d and 42d. As a result, the flat section FL positions the first prism 41 and the second prism 42 with respect to the +Z direction or the depth direction, and sets their relative rotational orientations as designed. By using the flat section FL as a contact surface AF, not only is the assembly of joining the first prism 41 and the second prism 42 made easier, but it can also function as a misalignment prevention section. This improves the joining accuracy of the first prism 41 and the second prism 42. In the area between the first prism 41 and the second prism 42 where the oblique mirror section IM is not provided, gaps PN1 and PN2 are formed (see Figure 2 and Figure 6 described later). The distance from the lower end of the oblique mirror section IM to the outer surfaces 41c and 42c can be made relatively wide, making it easy to provide a flat section FL, i.e., a positioning structure AS. Furthermore, if a sufficient area that does not reflect light can be secured, the joint JS between the first prism 41 and the second prism 42 may have a flat section as a positioning structure AS on the first and second inner surfaces 41b and 42b.

[0020] The oblique mirror section IM reflects at least a portion of the image light ML guided in the first prism 41. The oblique mirror section IM is provided at the joint JS between the first prism 41 and the second prism 42 via an adhesive member AD. In other words, the oblique mirror section IM is attached to the first bevel surface 41d of the first prism 41 and the second bevel surface 42d of the second prism 42 by the adhesive member AD. As will be described in detail later, the oblique mirror section IM is formed in a slightly narrower area excluding the outer edges of the bevel surfaces 41d and 42d of the first prism 41 and the second prism 42.

[0021] In this embodiment, the oblique mirror portion IM is a polarization separation film 45. The reflective polarizing element 45 is, for example, a polarizing beam splitter having s-polarization reflection characteristics. When the image light ML contains s-polarized PLs, the reflective polarizing element 45 efficiently reflects the s-polarized PLs of the image light ML, and when the image light ML contains p-polarized PLp, it efficiently transmits the p-polarized PLp of the image light ML. The reflective polarizing element 45 only needs to selectively reflect the image light ML according to its polarization direction. The reflective polarizing element 45 may also transmit s-polarized PLs and reflect p-polarized PLp.

[0022] Examples of the reflective polarizing element 45 include multilayer films, wire grid type polarizers such as wire grid films, and reflective polarizing elements utilizing film stretching.

[0023] The oblique mirror portion IM only needs to have a flat surface that does not affect image formation. Alternatively, the oblique mirror portion IM may have a slightly curved surface that is convex or concave, as long as it does not affect image formation. The scratch resistance or abrasion resistance of the oblique mirror portion IM can be improved by applying a hard coat to its surface.

[0024] Details regarding the formation range and structure of the oblique mirror portion IM will be described later.

[0025] As shown in Figure 2, the second flat plate member 50 has a thin quarter-wave plate 51 and a cover member 52. The quarter-wave plate 51 is made of a crystal, liquid crystal material, etc., having an optical axis between the X direction and the Y direction. The quarter-wave plate 51 converts the image light ML of s-polarized PLs reflected by the oblique mirror portion IM, which is the reflection polarizing element 45, into circularly polarized PLc, and converts the image light ML of circularly polarized PLc reflected by the cover member 52 into p-polarized PLp. The cover member 52 has a plano-convex second lens 53 having positive power, a concave-flat compensating lens 54, a compensating plate 55 provided around the compensating lens 54 and extending parallel to the prism light guide member 48, and a transmissive mirror 56.

[0026] The second flat plate-shaped member 50 is positioned approximately 20 μm to 100 μm away from the first flat plate-shaped member 40. The first and second outer surfaces 41c, 42c of the first flat plate-shaped member 40 and the third inner surface 50c of the second flat plate-shaped member 50 may be slightly curved, and a minute step may be formed at the boundary between the first and second outer surfaces 41c, 42c. However, by setting the distance between the first and second outer surfaces 41c, 42c and the third inner surface 50c to 20 μm or more, more preferably 30 μm or more, it is possible to avoid these surfaces being excessively close together. Conversely, by setting the distance between the first and second outer surfaces 41c, 42c and the third inner surface 50c to 100 μm or less, it is possible to avoid an increase in the thickness of the first combiner 103a, which is the first flat plate-shaped member 40 and the second flat plate-shaped member 50 combined. A spacer 61 is provided between the first and second outer surfaces 41c, 42c of the first flat plate member 40 and the third inner surface 50c of the second flat plate member 50 to adjust the distance between the first flat plate member 40 and the second flat plate member 50 and fix them in a relative position. The spacer 61 is not provided around the entire circumference of the second flat plate member 50. In other words, the gap SP between the first flat plate member 40 and the second flat plate member 50 is not sealed and is in communication with the outside world.

[0027] In the cover member 52, the second lens 53 is positioned opposite the first outer surface 41c of the first prism 41 or the quarter-wave plate 51. The second lens 53 focuses the image light ML. The second lens 53 is a thin but positively refractive plano-convex lens. A plano-convex lens has one surface that is planar and the other surface that is convex outward. The second lens 53 has a plane 53f joined to the quarter-wave plate 51 and a convex surface 53g opposite the compensating lens 54. The convex surface 53g is, for example, a sphere, but can be an axially symmetric aspherical surface. The compensating lens 54 is thin but has positive refractive power. The compensating lens 54 has a concave surface 54f opposite the second lens 53 and a plane 54g. The compensating plate 55 is a parallel plate. The compensating plate 55 has a pair of planes 55f, 55g. Here, the concave surface 54f of the compensating lens 54 has the same shape as the convex surface 53g of the second lens 53. The plane 54g of the compensating lens 54 and the plane 55g of the compensating plate 55 are on the same plane and are continuous. The transmissive mirror 56 is a thin film formed on the convex surface 53g on the external side of the second lens 53, and has the same shape as the convex surface 53g. The combination of the second lens 53 and the transmissive mirror 56 is called the light-gathering and reflecting section CR.

[0028] The second lens 53, the compensating lens 54, and the compensating plate 55 are made of resin material and have the same refractive index. The refractive index of the second lens 53, etc., is lower than that of the first prism 41. The compensating lens 54 and the compensating plate 55 are optical elements 58 integrally formed from the same resin material.

[0029] The combination of the second lens 53, the compensating lens 54, and the compensating plate 55 functions as a parallel plate as a whole. In other words, ambient light OL incident at the positions of the compensating lens 54 and the compensating plate 55 passes through them without being affected by the lensing effect of the compensating lens 54, etc., or by the step present on the outer edge of the compensating lens 54. In this way, the compensating lens 54 optically compensates for the effect of the second lens 53 on ambient light OL. In this sense, the plane 53f of the second lens 53, the plane 54g of the compensating lens 54, and the planes 55f, 55g of the compensating plate 55 are not necessarily limited to strictly flat planes, but may be, for example, approximately flat, or may include curved surfaces partially or entirely. Furthermore, the plane 53f of the second lens 53, the plane 54g of the compensating lens 54, and the planes 55f, 55g of the compensating plate 55 may include curved surfaces for correcting the wearer's vision, or curved surfaces as a design element, such as sunglasses or fashion glasses, to the extent that it does not cause any inconvenience in terms of optical performance. The flat surfaces 54g and 55g of the compensating lens 54 and compensating plate 55 can be coated with an anti-reflective film or a hard coating. The ambient light OL passing through the compensating plate 55 passes above, below, to the left and right of the compensating lens 54. This ambient light OL is incident from the peripheral region outside the incident region of the image light ML corresponding to the compensating lens 54, i.e., from the compensating plate 55. This ensures a wide see-through field of view with respect to the outside world. The field of view range of the ambient light OL is set, for example, to about 40° upwards and about 40° downwards.

[0030] The transmissive mirror 56 is a half-mirror. The transmissive mirror 56 partially reflects the image light ML that has passed through the second lens 53 and partially transmits the ambient light OL. The transmissive mirror 56 reflects the image light ML that has been reflected by the oblique mirror portion IM of the first flat plate member 40 or the reflective polarizing element 45 and passed through the quarter-wave plate 51 and the second lens 53 toward the pupil position PP. The transmissive mirror 56 is a concave mirror that covers the pupil position PP where the eye EY or pupil is located and has a concave shape toward the pupil position PP and a convex shape toward the outside world. The pupil position PP or its opening PPa is called the eye point or eye box and corresponds to the exit pupil EP of the first display unit 20a.

[0031] The transmissive mirror 56 transmits some of the ambient light OL, enabling see-through viewing of the outside world and allowing a virtual image to be superimposed on the image of the outside world. In this case, the ambient light OL passes through the first flat plate member 40 and the second flat plate member 50, but the flat plate members 40 and 50 do not produce a lens effect on the ambient light OL. The reflectivity of the transmissive mirror 56 with respect to the image light ML and ambient light OL is set to 10% to 50% within the assumed incident angle range of the image light ML, from the viewpoint of ensuring the brightness of the image light ML and facilitating observation of the outside world image through see-through. The transmissive mirror 56 is formed, for example, from a dielectric multilayer film consisting of multiple dielectric layers with adjusted film thicknesses. The transmissive mirror 56 may also be a single-layer or multilayer film of a metal such as Al or Ag with adjusted film thickness. The transmissive mirror 56 is formed, for example, by lamination using vapor deposition.

[0032] In the first virtual image display device 100A, the first lens 30, lens section 44, second lens 53, and transmissive mirror 56 each have positive refractive power and tend to converge divergent light. The first lens 30, lens section 44, second lens 53, and transmissive mirror 56, along with the body of the first prism 41, the second prism 42, etc., function as an imaging optical system IS or a direct virtual image optical system DIS, similar to a single-lens microscope, that forms an erect image. This makes it possible to form a virtual image by projecting, for example, the real image formed on the display surface 11d of the first image forming element 11a to infinity, or to form a virtual image by projecting the real image formed on the display surface 11d to a distance of several meters. In this case, by adjusting the refractive power of the first lens 30, lens section 44, second lens 53, and transmissive mirror 56, the focal length of the imaging optical system IS can be shortened to achieve a desired magnification.

[0033] The vertical dimensions of the first flat plate member 40 or the second flat plate member 50 are, for example, 34 mm, and the horizontal dimensions are, for example, 40 mm. The front-to-back thickness of the first flat plate member 40 is, for example, about 7 mm to 8 mm, and the combined thickness of the first flat plate member 40 and the second flat plate member 50 is kept to about 7.5 mm to 8.5 mm.

[0034] In the first prism 41 of the first flat plate member 40, the incident optical surface 41a, the first inner surface 41b, and the first outer surface 41c can be sources of stray light caused by the image light ML. That is, since the first virtual image display device 100A or optical unit 100 is a direct virtual image optical system DIS, an aperture diaphragm cannot be provided, and there is a relatively high possibility that the image light ML will bend into an unintended optical path, reach the pupil position PP, and be observed as a ghost. In the prerequisite technology prior to the improvements of this invention, the above-mentioned ghosting is suppressed by providing a light-absorbing layer AL in appropriate places on the first flat plate member 40 or the prism light guide member 48 (see Figure 3).

[0035] Specifically, in the first prism 41, a light-absorbing layer AL is provided on the upper plane 40u. The upper plane 40u corresponds to the peripheral region of the incident optical surface 41a, which is the incident surface 40i of the first prism 41. The light-absorbing layer AL has a contour corresponding to the upper plane 40u, but is not limited to this; for example, it may cover the vicinity of the incident optical surface 41a, while exposing the upper plane 40u in a region close to the lateral surfaces 41e and 42e.

[0036] Furthermore, a light-absorbing layer AL is also provided on the bottom surface 42f of the prism light guide member 48 or the second prism 42. This light-absorbing layer AL also prevents the image light ML that has passed through the oblique mirror portion IM or the reflective polarizing element 45 from becoming stray light. The second prism 42 has a curved surface 42g at the boundary between the bottom surface 42f and the second lateral surface 42e. It is preferable that the light-absorbing layer AL extends from the bottom surface 42f to the curved surface 42g. In other words, the light-absorbing layer AL extends to the R-shaped portion at the boundary between the bottom surface 42f and the second lateral surface 42e of the second prism 42.

[0037] Furthermore, a light-absorbing layer AL is also provided on the upper part of the first prism 41, more specifically, on the upper end region 41u of the first outer surface 41c of the first prism 41. The light-absorbing layer AL provided on the upper end region 41u is formed as a long, band-shaped region in the lateral X direction at the upper end of the first outer surface 41c.

[0038] As described above, even if a light-absorbing layer AL is provided in the appropriate location on the prism light guide member 48, image light ML that bends into unintended optical paths may remain, leaving a lot of unwanted light outside the image area and potentially causing ghosting. In this embodiment, in order to suppress the above-mentioned ghosting, the formation range of the oblique mirror portion IM or the reflective polarizing element 45 is adjusted so as to efficiently reflect image light ML in the normal optical path and suppress the reflection of components of image light ML that cause ghosting by passing through unintended optical paths.

[0039] Figure 5 is a conceptual perspective view illustrating the formation range of the oblique mirror portion IM. The oblique mirror portion IM is formed in a partial region AA excluding the periphery or outer edge of the inclined surfaces 41d and 42d of the first prism 41 and the second prism 42. In other words, the oblique mirror portion IM is formed to cover the main region AI excluding the end regions of the inclined surfaces 41d and 42d. More specifically, a hypothetical rectangular plane RP is considered to extend along the central portion 48i of the inclined surfaces 41d and 42d of the first prism 41 and the second prism 42 between the inner surfaces 41b and 42b and the outer surfaces 41c and 42c, and the portion IM is formed in correspondence with the partial region AA excluding the outer edge of this rectangular plane RP. Specifically, the partial region AA is the region of the rectangular plane RP excluding the outer end region Z1 close to the outer surfaces 41c and 42c, the inner end region Z2 close to the inner surfaces 41b and 42b, and the lateral end regions Z3 and Z4 close to the lateral surfaces 41e and 42e. The outer end region Z1, the inner end region Z2, and the lateral end regions Z3, Z4 are the sloped surface exposed region RA, and these regions Z1, Z2, Z3, Z4 together are called the end regions of the slopes 41d, 42d. If the image light ML were to enter the outer end region Z1, the inner end region Z2, and the lateral end regions Z3, Z4 via an unintended optical path and be reflected, it would be reflected by the first outer surface 41c and the transmissive mirror 56, and then enter the pupil position PP as stray light, causing ghosting. In other words, by forming a slanted mirror section IM in the partial region AA excluding the outer end region Z1, the inner end region Z2, and the lateral end regions Z3, Z4, and providing the sloped surface exposed region RA, the occurrence of ghosting can be suppressed.

[0040] In the above configuration, the width W1 in the inclination direction of the outer end region Z1 is wider than the width W2 in the inclination direction of the inner end region Z2. Furthermore, the width W1 in the inclination direction of the outer end region Z1 is wider than the widths W3 and W4 in the lateral or X-direction of the lateral end regions Z3 and Z4. In a normal optical path, the image light ML is more significantly affected by being blocked in the inner end region Z2 than in the outer end region Z1. Therefore, by making the width W1 in the inclination direction of the outer end region Z1 wider than the width W2 in the inclination direction of the inner end region Z2, it becomes easier to prevent deterioration of the display state of the virtual image. Moreover, from the viewpoint of making the prism light guide member 48 thinner, it is desirable that the lower end position of the effective image light ML incident on the first inner surface 41b be as close as possible to the upper end of the oblique mirror portion IM, and that the image light ML not pass through the gap between the first inner surface 41b and the upper end of the oblique mirror portion IM. For this reason, it is desirable that the inner end region Z2 be narrow.

[0041] In this embodiment, a flat portion FL, which is a positioning structure AS, is provided near the outer end region Z1. Since an oblique mirror portion IM cannot be provided on the flat portion FL, the outer end region Z1 needs to be wider above the upper end of the flat portion FL.

[0042] Figure 6 is a lateral cross-sectional view of the prism light guide member 48. The structure of the oblique mirror portion IM and its surrounding portion will be explained with reference to Figure 6.

[0043] The oblique mirror section IM has adhesive members AD on the surface facing the first prism 41 and the surface facing the second prism 42. As a result, the first prism 41 and the second prism 42 are joined by the adhesive members AD provided on the oblique mirror section IM, eliminating the need for a separate adhesive.

[0044] Figure 7 is an enlarged cross-sectional view illustrating the oblique mirror portion IM before it is attached to the first prism 41 and the second prism 42. As shown in Figure 7, the main body of the oblique mirror portion IM is specifically a reflective polarizing element 45. Adhesive members AD are provided on both sides 45j and 45k of the reflective polarizing plate 45a, which is the main body of the reflective polarizing element 45. The reflective polarizing element 45 is a reflective polarizing plate with an adhesive film, composed of a combination of a flat plate or film-shaped reflective polarizing plate 45a and the adhesive member AD. The overall thickness d1 of the reflective polarizing element 45 is, for example, 78 μm to 80 μm. The thickness d2 of the reflective polarizing plate 45a of the reflective polarizing element 45 is, for example, 70 μm to 75 μm. The thickness d3 of the adhesive member AD is, for example, 2 μm to 5 μm.

[0045] The adhesive component AD is, for example, OCA (Optical Clear Adhesive). OCA is a film-like adhesive sheet. OCA has a refractive index close to that of the first prism 41 or second prism 42 to which it is bonded. OCA has a uniform or nearly uniform thickness and low product variation. Also, unlike adhesives, OCA does not overflow with excess adhesive.

[0046] Before the reflective polarizing element 45 is attached, both sides 45m and 45n of the reflective polarizing element 45 are protected by a protective film PF. The reflective polarizing element 45 before molding, protected by the protective film PF, is called a blank member 45x. The reflective polarizing element 45 is formed by cutting out the blank member 45x using a die-cutting die (not shown).

[0047] As shown in Figure 4, the size of the reflective polarizing element 45 is smaller than the size of the inclined surfaces 41d and 42d of the first prism 41 and the second prism 42 in the direction of inclination of the inclined surfaces 41d and 42d. In other words, the reflective polarizing element 45 is not provided at the upper and lower ends of the inclined surfaces 41d and 42d. As a result, as shown in Figure 6, when the reflective polarizing element 45 is sandwiched between the first and second prisms 41 and 42, a gap PN1 is formed on the outside side and a gap PN2 is formed on the pupil position PP side. Due to these gaps PN1 and PN2, an inclined surface exposure region RA exists at the joint JS of the prism light guide member 48. The inclined surface exposure region RA limits the reflection area of ​​the image light ML at the reflective polarizing element 45 in the inclined surface ST, allowing unintended image light ML to pass through in the allowable region around the reflective polarizing element 45. In other words, it prevents unwanted light that causes ghosting from entering the reflective polarizing element 45 and reduces the reflection of unwanted light at the reflective polarizing element 45.

[0048] The oblique mirror section IM is positioned, for example, about 3 mm away from the lower end of the first inclined surface 41d of the first prism 41 or the second inclined surface 42d of the second prism 42. The oblique mirror section IM is positioned, for example, about 1 mm away from the upper end of the first inclined surface 41d of the first prism 41 or the second inclined surface 42d of the second prism 42. Alternatively, the oblique mirror section IM may be positioned from the lower end of the inclined surfaces 41d and 42d by adjusting the length of the flat section FL. The oblique mirror section IM is positioned, for example, about 1 mm away from the lateral surfaces 41e and 42e of the first prism 41 or the second prism 42.

[0049] Figure 8 is a diagram illustrating the optical path of the first virtual image display device 100A. As shown in Figure 8, the image light ML from the first image forming element 11a passes through the first lens 30 and enters the first prism 41. At this time, the degree of divergence of the image light ML is suppressed by the positive refractive power of the first lens 30 and the lens portion 44. In the optical path passing through the first prism 41, the image light ML is sequentially reflected by the first inner surface 41b and the first outer surface 41c of the first prism 41 without forming an intermediate image (see Figure 2), and the s-polarized PLs of the image light ML are reflected by the reflective polarizing element 45, which acts as an oblique mirror portion IM. The image light ML of the s-polarized PLs reflected by the reflective polarizing element 45 passes through the first outer surface 41c of the first prism 41 and through the quarter-wave plate 51 of the second flat plate member 50, becoming circularly polarized PLc, and enters the second lens 53 and the transmissive mirror 56. A portion of the circularly polarized PLc image light ML incident on the transmissive mirror 56 is reflected by the transmissive mirror 56 after passing through the second lens 53, and then passes through the quarter-wave plate 51 again in a collimated state after passing through the second lens 53. As a result, the image light ML that has passed through the quarter-wave plate 51 becomes p-polarized PLp and is incident on the first prism 41 from the first outer surface 41c, passes through the reflective polarizing element 45, and is emitted outside the second prism 42 via the second inner surface 42b. The image light ML emitted outside the second prism 42 is incident on the pupil position PP where the wearer's eye EY or pupil is located (see Figure 2). Not only the image light ML reflected by the transmissive mirror 56, but also the ambient light OL that has passed through the transmissive mirror 56 and the ambient light OL that has passed through the compensating plate 55 are incident on the pupil position PP. In other words, the wearer US wearing the first virtual image display device 100A can observe a virtual image of the image light ML superimposed on the ambient image. In this embodiment, the observation of ghosting is suppressed by limiting unwanted light GL1 to GL3, as described below, by the inclined exposed region RA around the reflective polarizing element 45.

[0050] Figure 9 is a conceptual diagram illustrating unwanted light GL1 caused by image light ML incident on the upper part UP of the first prism 41 from an unintended optical path. In this case, the unwanted light GL1 is sequentially reflected by the first inner surface 41b and the first outer surface 41c at unexpected locations on the upper part UP of the first prism 41. As a result, the unwanted light GL1 is reflected twice each by the first inner surface 41b and the first outer surface 41c within the first prism 41, passes through the oblique mirror section IM and the transmissive mirror 56, and incident on the pupil position PP (see Figure 2) from a downward oblique direction at an angle of approximately 17° along with the image light ML from the normal optical path. This unwanted light GL1 is outside the image region of the virtual image and forms a ghost image below the image region. However, the passage of such unwanted light GL1 is restricted by the light-absorbing layer AL provided on the upper end region 41u and the upper plane 40u as shown in Figure 3, etc., and the observation of ghosts is suppressed.

[0051] Figure 10 illustrates the optical path of unwanted light GL2 caused by another image light ML that enters the incident optical surface 41a of the first prism 41 from an unintended optical path. In this case, the unwanted light GL2 is reflected at the upper end of the oblique mirror section IM at the boundary between the first prism 41 and the second prism 42, deviates from the optical path, passes through the transmissive mirror 56, etc., and enters the pupil position PP (see Figure 2) from an oblique upward direction at an angle of about 20°. This unwanted light GL2 is outside the image region of the virtual image and forms a ghost image on the upper side of the image region. However, the passage of such unwanted light GL2 is restricted by the presence of the oblique surface exposure region RA (see Figure 4, etc.), that is, by limiting the size of the oblique mirror section IM on the pupil position PP side, and the observation of ghosting is suppressed.

[0052] Figure 11 illustrates the optical path of unwanted light GL3 caused by another image light ML that enters the incident optical surface 41a of the first prism 41 from an unintended optical path. In this case, the unwanted light GL3 is sequentially reflected by the first inner surface 41b and the first outer surface 41c, and is reflected by the first outer surface 41c without entering the transmissive mirror 56 via the oblique mirror section IM, and enters the pupil position PP (see Figure 2) from a downward oblique direction at an angle of about 13°. This unwanted light GL3 is outside the image region of the virtual image and forms a ghost image below the image region. However, the passage of such unwanted light GL3 is restricted by the presence of the oblique surface exposure region RA (see Figure 4, etc.), that is, by limiting the size of the outer side of the oblique mirror section IM on the outer side or by the second lens 53, and the observation of ghosting is suppressed.

[0053] Figure 12 is a diagram illustrating the projection state of unwanted light in a virtual image display device. Region AR1 in Figure 12 illustrates the projection state of unwanted light in a comparative example virtual image display device, and region AR2 in Figure 12 illustrates the projection state of unwanted light in a virtual image display device 100A according to an embodiment of this example. In the comparative example device, the reflective polarizing element 45 is formed over the entire rectangular plane RP or the inclined surfaces 41d, 42d. On the other hand, in the embodiment device, the reflective polarizing element 45 is formed in the region excluding the outer periphery of the inclined surfaces 41d, 42d.

[0054] In Figure 12, in area AR1, the chart group C1 on the left assumes that the eye EY is positioned above the pupil position PP in the comparative example apparatus, the chart group C2 in the center assumes that the eye EY is positioned in the center of the pupil position PP, and the chart group C3 on the right assumes that the eye EY is positioned below the pupil position PP. Similarly, in Figure 12, in area AR2, the chart group C1 on the left assumes that the eye EY is positioned above the pupil position PP in the example apparatus, the chart group C2 in the center assumes that the eye EY is positioned in the center of the pupil position PP, and the chart group C3 on the right assumes that the eye EY is positioned below the pupil position PP. In this way, chart group C1 corresponds to the state in Figure 11 where unwanted light GL3 is observed, and chart group C3 corresponds to the state in Figure 10 where unwanted light GL2 is observed.

[0055] In each chart group C1, C2, and C3, the left region shows a simulation image illustrating the detection state by angle receivers positioned above and below the pupil position PP when a full-white image is displayed on the display element 11. To the right of this simulation image, a logarithmic graph of the luminance distribution on the central vertical axis, which is 0° on the H-axis (horizontal axis), is shown. As a premise of the simulation, the angle receivers evaluate the observed image in areas with a diameter of 3 mm set at the top, middle, and bottom of the eye box set at the pupil position PP. The values ​​shown in the H-axis luminance distribution represent the percentage of unwanted light when the luminance of the video area IA visible in the center of the screen of the simulation image is set to 100%.

[0056] As shown in area AR1 of Figure 12, in the comparative example's virtual image display device, a ghost GH1 is formed above the image area IA, separated by approximately half a vertical angle. The ghost GH1 has a brightness of about 10% compared to the central image area IA.

[0057] As shown in area AR2 of Figure 12, in the virtual image display device of the embodiment, the reflective polarizing element 45 formed in the region excluding the outer edges of the inclined surfaces 41d and 42d of the first prism 41 and the second prism 42 reduces the brightness of the ghost GH1 to 2.7%.

[0058] An example of the structure and assembly of the first display unit 20a constituting the first virtual image display device 100A will be described. A first prism 41 and a second prism 42 are prepared. A reflective polarizing element 45 is attached between the first prism 41 and the second prism 42 via an adhesive member AD. As a result, the first prism 41 and the second prism 42 are joined at the inclined surfaces 41d and 42d, and a prism light guide member 48 or a first flat plate member 40 is obtained. In parallel with this, a quarter-wave plate 51, a second lens 53 with a transmissive mirror 56 formed thereon, and an optical element 58 are joined together and integrated, and this is attached to the outer surfaces 41c and 42c of the first flat plate member 40 facing each other. In this case, a pair of thin adhesive spacers 61 are placed between the outer surfaces 41c, 42c of the first flat plate member 40 and the quarter-wave plate 51, forming a gap SP between the outer surfaces 41c, 42c of the first flat plate member 40 and the quarter-wave plate 51.

[0059] The light-absorbing layer AL can be provided as appropriate during or after the assembly of the first display unit 20a.

[0060] The virtual image display device 100A, 100B, or optical unit 100 of the first embodiment described above comprises a display element 11 that emits image light ML, a first prism 41 into which the image light ML from the display element 11 is incident, a second prism 42 joined to the first prism 41 to form a parallel plate-shaped prism light guide member 48, and an oblique mirror provided at the joint JS between the first prism 41 and the second prism 42 to reflect at least a portion of the image light ML guided in the first prism 41. The system comprises a section IM, a second lens 53 having positive power positioned opposite the first outer surface 41c of the first prism 41 into which the image light ML reflected by the oblique mirror section IM enters, and a transmissive mirror 56 formed on the external side of the second lens 53 to partially reflect the image light ML reflected by the oblique mirror section IM toward the oblique mirror section IM. The oblique mirror section IM is formed in a partial region AA excluding the periphery of the inclined surfaces 41d and 42d of the first prism 41 and the second prism 42. Specifically, the oblique mirror section IM is formed in a partial region AA of a rectangular plane RP extending between the inner surfaces 41b and 42b facing the outer surfaces 41c and 42c along the central portion 48i of the inclined surfaces 41d and 42d of the first prism 41 and the second prism 42.

[0061] In the above virtual image display device, the oblique mirror section IM is formed in accordance with a portion region AA of the rectangular plane RP that extends between the inner surface facing the outer surface and along the central portion 48i of the inclined surfaces of the first prism 41 and the second prism 42. Therefore, even if an unintended component of the image light ML is incident on the upper part of the first prism 41, this unwanted light is prevented from being incident on the oblique mirror section IM and can be diverted from the optical path toward the eye. As a result, unwanted light that causes ghosting that degrades image quality can be reduced. This makes it possible to suppress the observation of ghosting around the virtual image that is the object of observation.

[0062] [Second Embodiment] The virtual image display device of the second embodiment will now be described. The virtual image display device of the second embodiment is a modified version of the virtual image display device of the first embodiment, and the parts common to the virtual image display device of the first embodiment will not be described.

[0063] Figure 13 is a side cross-sectional view illustrating the virtual image display device 100A of the second embodiment. As shown in Figure 13, the virtual image display device 100A of the second embodiment does not have the flat portion FL shown in Figure 2, etc., on the first inclined surface 41d of the first prism 41 and the second inclined surface 42d of the second prism 42.

[0064] [Variations and other variations] Although the present invention has been described in reference to the embodiments described above, the present invention is not limited to the embodiments described above, and can be implemented in various forms without departing from the spirit thereof, for example, the following modifications are also possible.

[0065] In the above description, the HMD200 is assumed to include a first virtual image display device 100A and a second virtual image display device 100B. However, the HMD200 may also be configured to support a single first virtual image display device 100A or a second display device 100B in front of the eyes by a support device 100C.

[0066] The display element 11 may emit linearly polarized image light ML, or a polarizing filter may be provided after the display element 11. This allows s-polarized image light ML to be incident on the reflective polarizing element 45.

[0067] The partial region AA forming the oblique mirror portion IM does not necessarily have to exclude all of the outer end region Z1, the inner end region Z2, and the lateral end regions Z3 and Z4. For example, the oblique mirror portion IM may be formed in the region corresponding to the lateral end regions Z3 and Z4 or the inner end region Z2. In the case of the structure shown in Figure 13, referring to Figure 5, the oblique mirror portion IM may be formed in the partial region AA excluding the inner end region Z2 and the lateral end regions Z3 and Z4.

[0068] The positioning structure AS is not limited to consisting only of a flat section FL, but may also have a shape that includes, for example, a step that enables positioning. The flat section FL can be provided away from the inclined surfaces 41d and 42d, in which case a connecting surface consisting of a plane or a curved surface, or a step consisting of multiple surfaces, can be provided between the flat section FL and the inclined surfaces 41d and 42d. The flat section FL may be provided in two or more locations, for example, in the lateral X direction.

[0069] In the cover member 52, the compensating plate 55 can be omitted. In this case, the quarter-wave plate 51 is placed only within the range of the second lens 53, and the second lens 53 is covered by the compensating lens 54.

[0070] In the second flat plate-shaped member 50, the cover member 52 may be omitted.

[0071] The reflective polarizing element 45 may be bonded on one side with an adhesive material AD such as OCA, and on the other side with adhesive, provided that the adhesive does not spread.

[0072] The first lens 30 is not essential and can be omitted. In the first prism 41 of the first flat plate member 40, the incident optical surface 41a can also be omitted. In this case, the optical system will be one in which the lens portion 44 is omitted.

[0073] The first lens 30 is not limited to being bonded to the first image forming element 11a, but may also be arranged separately from the first image forming element 11a.

[0074] The second lens 53 is not limited to a plano-convex lens with positive power, but can be replaced with a diffractive lens, holographic lens, or the like, also with positive power. In this case, the compensating lens 54 can be, for example, a diffractive lens, holographic lens, or liquid crystal lens with an inverted shape. In this case, the optical element such as the diffractive lens, holographic lens, or liquid crystal lens used as the second lens 53 can be given the function of partially reflecting the image light ML, but a planar transmissive mirror may be placed on the external side of such an optical element.

[0075] The light-absorbing layer AL may be omitted.

[0076] The gaps PN1 and PN2 formed between the first prism 41 and the second prism 42 may or may not be filled with adhesive.

[0077] As shown in Figure 14, the first virtual image display device 100A may have an s-polarized light transmitting polarizer 12 placed between the first lens 30 and the display element 11 in the first display unit 20a. In addition, a third flat plate member 150 is added to the outer side of the second flat plate member 50 in the first display unit 20a. The third flat plate member 150 is an image light blocking unit LP. The third flat plate member 150 comprises an outer quarter-wave plate 151 provided on the outer side of the transmissive mirror 56 or the light-gathering reflective unit CR, and a polarizer 59 provided on the outer side of the outer quarter-wave plate 151. In other words, in the first display unit 20a, the inner quarter-wave plate 51 and the outer quarter-wave plate 151 are arranged between the inner reflective polarizing element 45 and the outer polarizer 59. The polarizer 59 selectively absorbs the image light ML transmitted through the outer quarter-wave plate 151 according to the polarization direction.

[0078] The circularly polarized image light ML that passes through the transmissive mirror 56 becomes p-polarized after passing through the outer quarter-wave plate 151, and is incident on the polarizing plate 59, where it is almost completely blocked. In other words, the image light ML is shielded by the third flat plate member 150 and does not leak out to the outside. This prevents the image light ML from being observed from the outside, thus ensuring privacy. On the other hand, the ambient light OL incident on the polarizing plate 59 becomes only s-polarized after passing through the polarizing plate 59, becomes circularly polarized after passing through the outer quarter-wave plate 151, and partially passes through the transmissive mirror 56. The circularly polarized ambient light OL that partially passes through the transmissive mirror 56 becomes p-polarized after passing through the inner quarter-wave plate 51, passes through the reflective polarizing element 45, and is incident on the pupil position PP.

[0079] In a specific embodiment, the virtual image display device includes a display element that emits image light, a first prism into which the image light from the display element is incident, a second prism joined to the first prism to form a parallel plate-shaped prism light guide member, an oblique mirror portion provided at the joint between the first prism and the second prism and reflecting at least a portion of the image light guided in the first prism, a positive-power lens positioned opposite the outer surface of the first prism into which the image light reflected by the oblique mirror portion is incident, and a transmissive mirror formed on the external side of the lens and partially reflecting the image light reflected by the oblique mirror portion toward the oblique mirror portion, wherein the oblique mirror portion is formed corresponding to a partial region excluding the periphery of the inclined surfaces of the first prism and the second prism.

[0080] In the above-described virtual image display device, the oblique mirror portion is formed in accordance with a rectangular plane subregion extending between the inner surface facing the outer surface, along the central portion of the inclined surfaces of the first and second prisms. Therefore, even if unintended components of the image light are incident on the upper part of the first prism, this unwanted light is prevented from being incident on the oblique mirror portion and can be diverted from the optical path toward the eye. This reduces unwanted light that causes ghosting, which degrades image quality. As a result, it is possible to suppress the observation of ghosting around the virtual image being observed.

[0081] In a specific embodiment of the virtual image display device, a positioning structure is provided around the inclined surfaces of the first and second prisms to position the first and second prisms with respect to the inclination direction of the inclined surfaces. This facilitates the assembly of the first and second prisms.

[0082] In a specific embodiment of the virtual image display device, the oblique mirror portion is formed in the region of the rectangular plane excluding the outer edge region near the outer surface. This makes it possible to suppress the generation of ghosting caused by unwanted light reflected from the outer edge region.

[0083] In a specific embodiment of a virtual image display device, the oblique mirror portion is formed in the region of the rectangular plane excluding the inner edge region near the inner surface. Since unwanted light reflected from the inner edge region is relatively likely to be directed towards the pupil position, forming the oblique mirror portion in the region excluding the inner edge region enhances the effect of suppressing ghosting.

[0084] In a specific embodiment of a virtual image display device, the oblique mirror portion is formed in the area of ​​the rectangular plane excluding the outer edge region near the outer surface, and the width in the inclination direction of the outer edge region is wider than the width in the inclination direction of the inner edge region. Since the image light in a normal optical path is more affected by being blocked in the inner edge region than in the outer edge region, making the width in the inclination direction of the outer edge region wider than the width in the inclination direction of the inner edge region makes it easier to prevent deterioration of the virtual image display state.

[0085] In a specific embodiment of the virtual image display device, the first prism has a pair of lateral surfaces positioned between its outer surface and its opposing inner surface, in a direction intersecting the direction in which the first and second prisms are aligned. The oblique mirror portion is formed in the rectangular plane, excluding the lateral edge regions close to the pair of lateral surfaces. This makes it possible to suppress the generation of ghosting caused by unwanted light reflected in the lateral edge regions.

[0086] In a specific embodiment of the virtual image display device, a positioning structure is provided near the outer edge region for positioning the first prism and the second prism with respect to the inclination direction of the slope. The outer edge region can be made relatively wide, making it easy to provide the positioning structure.

[0087] In a specific embodiment of the virtual image display device, the positioning structure is a flat portion provided on the outer surface at the joint between the first prism and the second prism, forming an obtuse angle with respect to a rectangular plane. Such a flat portion is easy to form and can improve the accuracy of the joint between the first prism and the second prism.

[0088] In a specific embodiment of a virtual image display device, a quarter-wave plate is further provided between the outer surface of the first prism and the plane of the second lens, and the oblique mirror portion has a polarization separation film that selectively reflects the image light according to its polarization direction. In this case, the image light from the first prism is efficiently reflected by the polarization separation film, and when reflected by the transmissive mirror, it travels back and forth across the quarter-wave plate and is transmitted through the polarization separation film with little loss.

[0089] In a specific embodiment, the optical unit comprises a display element that emits image light, a first prism into which the image light from the display element is incident, a second prism joined to the first prism to form a parallel plate-shaped prism light guide member, an oblique mirror portion provided at the joint between the first prism and the second prism and reflecting at least a portion of the image light guided in the first prism, a second lens having positive power positioned opposite the outer surface of the first prism into which the image light reflected by the oblique mirror portion is incident, and a transmissive mirror formed on the external side of the second lens and partially reflecting the image light reflected by the oblique mirror portion toward the oblique mirror portion, wherein the oblique mirror portion is formed corresponding to a partial region excluding the periphery of the inclined surfaces of the first and second prisms. [Explanation of Symbols]

[0090] 11…Display element, 30…First lens, 40…First flat plate member, 41…First prism, 41a…Incident optical surface, 41b…Inner surface, 41c…Outer surface, 41d…Inclined surface, 41e…Side surface, 42…Second prism, 42b…Inner surface, 42c…Outer surface, 42d…Inclined surface, 42e…Side surface, 42f…Bottom surface, 42g…Curved surface, 44…Lens part, 45…Reflective polarizing element, 45 a...Reflective polarizer, 48...Prism light guide member, 48i...Central part, 50...Second flat plate member, 50c...Inner surface, 51, 151...Quarter wave plate, 52...Cover member, 53...Second lens, 54...Compensating lens, 55...Compensating plate, 56...Transmitting mirror, 58...Optical element, 59...Polarizer, 61...Spacer, 71...Case, 90...User terminal, 100...Optics Unit, 100A, 100B… Virtual image display device, 100C… Support device, 102a, 102b… Display drive unit, 103a, 103b… Combiner, IM… Oblique mirror part, RP… Rectangular plane, AA… Partial area, AS… Positioning structure, AD… Adhesive member, AL… Light absorption layer, AX… Optical axis, CR… Light concentrating and reflecting part, DIS… Direct virtual image optical system, EP… Exit pupil, EY… Eye, FL… Flat part, GH1… Ghost, GL1~GL3… Unwanted light, IA… Image area, IS… Imaging optical system, JS… Joint location, LP… Image light blocking part, ML… Image light, OL… External light, PF… Protective film, PLc… Circular polarization, PLp… p polarization, PLs… s polarization, PN1, PN2… Gap, PP… Pupil position, RA… Slanted surface exposure area, ST… Slanted surface part, US… Wearer

Claims

1. A display element that emits image light, A first prism into which the image light from the display element is incident, A second prism is joined to the first prism to form a parallel plate-shaped prism light guide member, An oblique mirror portion is provided at the junction of the first prism and the second prism, and reflects at least a portion of the image light guided in the first prism, A positive-power lens is positioned opposite the outer surface of the first prism into which the image light reflected by the oblique mirror portion is incident, A transmissive mirror formed on the external side of the lens, which partially reflects the image light reflected by the oblique mirror portion toward the oblique mirror portion, Equipped with, The oblique mirror portion is formed in a manner corresponding to a partial region excluding the areas around the inclined surfaces of the first and second prisms. Virtual image display device.

2. The aforementioned partial region corresponds to a part of a rectangular plane extending along the central portion of the slope between the outer surface and the inner surface facing it. The virtual image display device according to claim 1.

3. The first prism and the second prism have a positioning structure around the inclined surface of the inclined surface, which positions the first prism and the second prism with respect to the inclination direction of the inclined surface. The virtual image display device according to claim 1.

4. The oblique mirror portion is formed in the region of the rectangular plane excluding the outer edge region close to the outer surface. The virtual image display device according to claim 2.

5. The oblique mirror portion is formed in the region of the rectangular plane excluding the inner end region near the inner surface. The virtual image display device according to claim 2.

6. The oblique mirror portion is formed in the area of ​​the rectangular plane excluding the outer edge region close to the outer surface, The width in the inclination direction of the outer end region is wider than the width in the inclination direction of the inner end region. The virtual image display device according to claim 5.

7. The first prism has a pair of lateral surfaces that are positioned between the outer surface and the inner surface facing it, and in a direction that intersects with the direction in which the first prism and the second prism are aligned. The oblique mirror portion is formed in the region of the rectangular plane excluding the lateral edge region close to the pair of lateral sides. The virtual image display device according to claim 2.

8. Near the outer end region, there is a positioning structure that positions the first prism and the second prism with respect to the inclination direction of the slope, The virtual image display device according to claim 4.

9. The positioning structure is provided on the outer surface side at the joint between the first prism and the second prism, and is a flat portion that forms an obtuse angle with respect to the rectangular plane. The virtual image display device according to claim 8.

10. The first prism further comprises a quarter-wave plate positioned between the outer surface of the first prism and the plane of the lens, The oblique mirror portion has a polarization separation film that selectively reflects the image light according to its polarization direction. The virtual image display device according to claim 1.

11. A display element that emits image light, A first prism into which the image light from the display element is incident, A second prism is joined to the first prism to form a parallel plate-shaped prism light guide member, An oblique mirror portion is provided at the junction of the first prism and the second prism, and reflects at least a portion of the image light guided in the first prism, A positive-power lens is positioned opposite the outer surface of the first prism into which the image light reflected by the oblique mirror portion is incident, A transmissive mirror formed on the external side of the lens, which partially reflects the image light reflected by the oblique mirror portion toward the oblique mirror portion, Equipped with, The oblique mirror portion is formed in a manner corresponding to a partial region excluding the areas around the inclined surfaces of the first and second prisms. Optical unit.

Images