Virtual image display device and optical unit

Abstract

To prevent unwanted light from reaching the eyes. [Solution] The virtual image display device or 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 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 first prism has a ghosting prevention structure on one of its inner surfaces opposite to its outer surface at its upper part to suppress the propagation of image light.

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 first prism has a ghosting prevention structure on one of its inner surfaces opposite to its outer surface at its upper part to suppress the propagation of image light.

[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 first prism has a ghosting prevention structure on one of its inner surfaces opposite to its outer surface at its upper part to suppress the propagation of image light. [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] Figure 2 and other diagrams illustrate the optical path and other aspects of the virtual image display device shown. [Figure 5]This is a conceptual diagram illustrating, in detail, the unwanted light incident on the upper part of the first prism. [Figure 6] This illustrates the optical path of unwanted light entering the upper part of the first prism. [Figure 7] This illustrates the optical path of other unwanted light entering the upper part of the first prism. [Figure 8] This is a perspective view illustrating a modified example of the virtual image display device shown in Figure 3, etc. [Figure 9] This figure illustrates the projection state of unwanted light in a comparative example virtual image display device. [Figure 10] This figure illustrates the projection state of unwanted light in the virtual image display device of the embodiment. [Figure 11] This is a perspective view illustrating a virtual image display device of a second embodiment. [Figure 12] This figure illustrates the projection state of unwanted light in the virtual image display device of the embodiment. [Figure 13] This is a perspective view illustrating a virtual image display device of the third embodiment. [Figure 14] This figure illustrates the projection state of unwanted light in the virtual image display device of the embodiment. [Figure 15] This is a perspective view illustrating the virtual image display device of the fourth embodiment. [Figure 16] This is a perspective view illustrating the virtual image display device of the fifth embodiment. [Figure 17] 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] FIG. 2 is a side sectional view for explaining the internal structure of the first virtual image display device 100A. FIG. 3 is a perspective view of the first virtual image display device 100A. The first virtual image display device 100A includes 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 referred to as a 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 referred to as a 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 a protective glass for protecting the display surface 11d of the display element 11. Note that a cover glass may be provided between the display element 11 and the first lens 30. The first flat plate member 40 guides the video light ML emitted from the display element 11 to the second lens 53 of the second flat plate member 50. The second flat plate member 50 reflects the video light ML from the first flat plate member 40 toward the pupil position PP or the eye EY so as to partially return it to the first flat plate member 40, and allows the external light OL to enter the pupil position PP through the first flat plate member 40. The first lens 30, the first flat plate member 40, and the second flat plate member 50 each function as a lens having a positive refractive power.

[0012] Although detailed description is omitted, the second virtual image display device 100B includes 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-emissive image light generation device. The first image forming element 11a emits image light ML onto the first flat plate member 40 via 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 electroluminescent (OLED) display. The first image forming element 11a forms a color still image or moving image on a two-dimensional display surface 11d. The first image forming element 11a is driven by the first circuit member 80a to perform display operations. The first image forming element 11a is not limited to an OLED display, but can be replaced with a display device using inorganic EL, organic LED, LED array, laser array, quantum dot light-emitting element, etc. The first image forming element 11a is not limited to a self-emissive image light generation device, but may also be composed of an LCD or other light modulation element, and may form an image by illuminating the light modulation element with a light source such as a backlight. Instead of an LCD, an LCOS (Liquid crystal on silicon, LCoS is a registered trademark) or the like can be used as the first image forming element 11a. 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 optical system and can be said to be the 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 includes a first lens 30, a first flat plate member 40, an inclined mirror unit IM, and a second flat plate member 50. In the first display unit 20a, the first lens 30 has a positive refractive power, and the video light ML from the first image forming element 11a is incident thereon. The first lens 30 has a light incident surface 30f on the plane joined to the first image forming element 11a and a convex light emitting surface 30g. The light emitting surface 30g is, for example, a spherical surface, but can be an aspherical surface having an axially symmetric shape. The first lens 30 can be considered as being divided into a parallel flat plate 31 and a lens unit 32. By ensuring that the thickness of the parallel flat plate 31 is a predetermined value or more, foreign matter adhering to the surface of the first lens 30 becomes less conspicuous. The parallel flat plate 31 has a function as a cover glass. The lens unit 32 is a plano-convex lens having a positive refractive power. The plano-convex lens has one surface having a planar shape and the other surface having a convex shape. Note that the parallel flat plate 31 and the lens unit 32 may be adhered or separated. The lens unit 32 does not have to be a plano-convex lens, and for example, a biconvex lens may be used. Also, the first lens 30 is made of, for example, fused quartz 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 by inclined surfaces 41d and 42d. The combination of the first prism 41 and the second prism 42 joined together is called a prism light guide member 48. The prism light guide member 48 has the appearance of a parallel flat plate. An inclined mirror unit IM having a planar shape is formed on a first inclined surface 41d formed on the lower side of the first prism 41. The combination of the prism light guide member 48 and a second flat plate member 50 described later corresponds to a first combiner 103a.

[0016] The first prism 41 has a rectangular prism shape and a trapezoidal longitudinal cross-section. The first prism 41 guides the image 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 (see Figure 3). Here, the incident optical surface 41a as a whole is inclined forward and downward, 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. This makes it easier to position the first image forming element 11a, which is the display element 11, on the outside side of the first inner surface 41b, and allows adjustment of the angle at which the image light ML propagates within the first prism 41 (inside the first prism 41 or inside the first prism 41). The incident optical surface 41a is a convex surface, for example a sphere, but can be an axially symmetric aspherical surface. The first prism 41 can be considered to include a lens portion 44 that includes the incident optical surface 41a. The lens portion 44 is a convex-flat lens having positive refractive power. The lens portion 44 may be formed directly on the first prism 41 or bonded 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 image light ML (i.e., reflect it on the inside of the object surface), and it is particularly desirable that they perform total internal reflection. The first inner surface 41b can be hard-coated to improve scratch resistance or abrasion resistance. The first bevel surface 41d is a plane. The first inclined surface 41d forms an acute angle with respect to the first outer surface 41c, specifically an angle of 25° to 32°. The distance between the optical axis AX, which passes through the pupil position PP, and the upper end of the first lens 30 is approximately 20 mm. The first prism 41 is made of 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 first bottom surface 42f. The first 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 first 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 (see Figure 3). 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 made scratch-resistant by applying a hard coat. The second prism 42 is made of a resin material.

[0019] 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 potentially cause stray light due to 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 this embodiment, as will be described in detail later, in the upper part UP of the first prism 41, a light-absorbing type ghost prevention structure GPQ, specifically a light-absorbing layer 41i, is provided on the first outer surface 41c as a ghost prevention structure GP, which blocks the image light ML that causes stray light by absorption. The ghost prevention structure GP can be called an image light ghost prevention structure from the viewpoint of restricting the passage of stray light caused by the image light ML, and can be called an in-light guide ghost prevention structure from the viewpoint of restricting the passage of stray light propagating in the prism light guide member 48.

[0020] The light-absorbing layer 41i, which is a light-absorbing ghost prevention structure GPQ, is formed as a long, band-shaped region in the lateral X direction at the upper part UP of the first prism 41, more specifically at the upper end region of the first outer surface 41c of the first prism 41. The light-absorbing layer 41i is formed from the upper end position P1 to the lower end position P2 of the first outer surface 41c of the first prism 41. In the illustrated example, the lower end position P2 is higher than the upper end position P3 of the second lens 53. The illustrated light-absorbing layer 41i is merely an example, and the vertical width of the light-absorbing layer 41i is determined by estimating the optical path or effective region of unintended image light ML incident on the upper part UP of the first prism 41 through simulation or the like. The shape of the lower end of the light-absorbing layer 41i is not limited to a straight line, but may also be curved.

[0021] The light-absorbing layer 41i is a matte black coating used in optical applications. The light-absorbing layer 41i is formed by applying a liquid material, such as a mixture of black pigment, resin, solvent, etc., to a desired area on the first outer surface 41c, thereby providing light absorption, and then drying it. The light-absorbing layer 41i efficiently absorbs the incident image light ML and suppresses the scattering of the image light ML.

[0022] The light-absorbing layer 41i is not limited to completely absorbing the image light ML, but may also partially transmit the image light ML. Furthermore, the light-absorbing layer 41i may be a black dot pattern consisting of dots of the absorbing material. However, it is desirable that it can cut at least half, preferably 80%, of the image light ML. The light-absorbing layer 41i may be achieved by an absorbing or reflective polarizer, preferably an absorbing polarizer. In this case, it is desirable that the polarization direction of the polarizer be perpendicular to the polarization direction of the polarization separation film 45, described later, and is set, for example, to block s-polarization.

[0023] As shown in Figure 2, a light-absorbing layer 41i is also provided on the first bottom surface 42f of the prism light guide member 48 as a ghosting prevention structure GP0. This light-absorbing layer 41i also prevents stray light from being caused by image light ML passing through the oblique mirror section IM and external light OL entering the interior from the second prism 42.

[0024] In the prism light guide member 48, a light-absorbing layer 41i is provided as a ghosting prevention structure GPa in a narrow region at the upper end of the inclined surface 41d of the first prism 41. The light-absorbing layer 41i of the ghosting prevention structure GPa is formed in an extremely narrow linear region in the vertical or Y direction, so as not to obstruct the view. This light-absorbing layer 41i also prevents the image light ML incident on the upper end of the polarization separation film 45 from becoming stray light.

[0025] The oblique mirror portion IM reflects at least a portion of the image light ML guided in the first prism 41. The oblique mirror portion IM is integrally formed on the first bevel surface 41d of the first prism 41 and sandwiched between the first bevel surface 41d of the first prism 41 and the second bevel surface 42d of the second prism 42. The space between the oblique mirror portion IM and the second bevel surface 42d is filled with bonding adhesive CT. The oblique mirror portion IM and the second bevel surface 42d may be bonded not only with adhesive CT, but also with an adhesive film or the like. In this embodiment, the oblique mirror portion IM is a polarization separation film 45. The polarization separation film 45 is, for example, a polarization beam splitter having s-polarization reflection characteristics. The polarization separation film 45 is, for example, formed of a dielectric multilayer film, and when the image light ML includes s-polarized PLs, it efficiently reflects the image light ML of s-polarized PLs, and when the image light ML includes p-polarized PLp, it efficiently transmits the image light ML of p-polarized PLp. The polarization separation film 45 can be any film that selectively reflects the image light ML according to its polarization direction, and may be a multilayer film, a wire grid type polarizer such as a wire grid film, or a reflective polarizing element utilizing film stretching.

[0026] The polarization separation film 45 may also transmit s-polarized light PLs and reflect p-polarized light PLp.

[0027] 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, to the extent that it does not affect image formation. The space between the oblique mirror portion IM and the first inclined surface 41d may be filled with a light-transmitting filler instead of adhesive CT. In this case, the joint between the first prism 41 and the second prism 42 may be maintained by supporting them from the outside with a support member or the like. The oblique mirror portion IM may also be integrally formed on the second inclined surface 42d of the second prism 42 instead of the first inclined surface 41d of the first prism 41. The scratch resistance or abrasion resistance of the oblique mirror portion IM can be improved by applying a hard coat to its surface.

[0028] 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 and Y directions. The quarter-wave plate 51 converts the s-polarized PLs image light ML reflected by the oblique mirror portion IM, which is the polarization separation film 45, into circularly polarized PLc, and converts the circularly polarized PLc image light ML reflected by the cover member 52 into p-polarized PLp. The cover member 52 has a plano-convex second lens 53 with 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. In the illustrated example, the second flat plate member 50 is formed in a narrower area than the first flat plate member 40, but it may be formed in an area of ​​about the same size as the first flat plate member 40.

[0029] The second flat plate-shaped member 50 is positioned approximately 20 μm to 50 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 50 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.

[0030] In the cover member 52, the second lens 53 is positioned opposite the first outer surface 41c and 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 plate 55 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 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 reflective section CR.

[0031] 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.

[0032] 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.

[0033] 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 polarization separation film 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] Figure 4 is a diagram illustrating the optical path of the first virtual image display device 100A. As shown in Figure 4, 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 polarization separation film 45. The image light ML of s-polarized PLs reflected by the polarization separation film 45 passes through the first outer surface 41c of the first prism 41 and passes through the quarter-wave plate 51 of the second flat plate member 50 to become 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, passes through the second lens 53, and then passes through the quarter-wave plate 51 again in a collimated state. 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 polarization separation film 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.

[0038] In this embodiment, unwanted light GL, which is ghost light caused by the image light ML, enters the upper part UP of the first prism 41 via an unintended optical path and enters the first outer surface 41c at an unexpected location. If the ghost prevention structure GP is not provided on the first outer surface 41c, the unwanted light GL1 that enters the first outer surface 41c is reflected by the first outer surface 41c, guided within the prism light guide member 48, and reaches the wearer's eye EY. As a result, ghosting caused by unwanted light GL1 is projected into the field of view, meaning that the ghost image is projected adjacent to or superimposed on the virtual image that should be observed, hindering the observation of the virtual image. On the other hand, if the ghost prevention structure GP is provided on the first outer surface 41c, the unwanted light GL that enters the first outer surface 41c is efficiently absorbed by the light absorption layer 41i of the ghost prevention structure GP, does not reach the wearer's eye EY, and does not become ghosting. As a result, the wearer can observe the virtual image without ghosting in the field of view.

[0039] Figure 5 is a conceptual diagram illustrating a specific example of 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, unwanted light GL1a, a specific component of unwanted light GL1, is sequentially reflected by the first inner surface 41b and the first outer surface 41c at an unexpected location on the upper part UP of the first prism 41. As a result, unwanted light GL1a 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 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 on the lower side of the image region. Unwanted light GL1b, another component of unwanted light GL1, is sequentially reflected by the first inner surface 41b and the first outer surface 41c at an unexpected location on the upper part UP of the first prism 41. This unwanted light GL1b passes through the oblique mirror section IM and the transmissive mirror 56, and together with the image light ML from the normal optical path, it enters the pupil position PP from an oblique upward direction at an angle of approximately 20°. This unwanted light GL1b is outside the image region of the virtual image and forms a ghost image on the lower side of the image region. However, the passage of such unwanted light GL1, i.e., unwanted light GL1a and GL1b, is restricted by the ghost prevention structure GP shown in Figure 3, and the observation of ghosts is suppressed.

[0040] Figure 6 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 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 ghost prevention structure GPa shown in Figure 2, and the observation of ghosts is suppressed.

[0041] Figure 7 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 from a downward oblique direction at an angle of approximately 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 ghost prevention structure GPa shown in Figure 2, and the observation of ghosts is suppressed.

[0042] Figure 8 is a perspective view illustrating a modified example of the first virtual image display device 100A or optical unit 100 shown in Figure 3, etc. In this case, a light-absorbing layer 41i is provided on the upper plane 40u of the first prism 41 as a ghosting prevention structure GP1. This ghosting prevention structure GP1 suppresses the image light ML from bending into an unintended optical path, reaching the pupil position PP, and being observed as a ghost. The upper plane 40u of the first prism 41 corresponds to the peripheral region of the incident optical surface 41a, which is the incident surface 40i of the first prism 41.

[0043] The light-absorbing layer 41i 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 and expose the upper plane 40u in a region close to the lateral surfaces 41e and 42e.

[0044] A light-absorbing layer 50i may be provided, although it is not essential, on the surface of the left and right outer peripheral portions 51f of the quarter-wave plate 51 or on the back surface 55f of the compensating plate 55 corresponding to the outer peripheral portion 51f. This light-absorbing layer 50i targets, for example, the image light ML and ambient light OL that are emitted from the prism light guide member 48 via the oblique mirror portion IM and incident near the outside of the second lens 53, thereby preventing such unwanted light from causing ghosting.

[0045] Referring to Figure 2, a light-absorbing layer 41i is also provided on the first bottom surface 42f of the prism light guide member 48 as a ghosting prevention structure GP0.

[0046] Figure 9 illustrates the projection state of unwanted light in a comparative example of a virtual image display device, and Figure 10 illustrates the projection state of unwanted light in a virtual image display device according to an embodiment of the first embodiment. Figure 9 shows the case where the main ghost prevention structure GP, i.e., the light-absorbing type ghost prevention structure GPQ, is removed from the first virtual image display device 100A or optical unit 100 shown in Figure 8, and Figure 10 shows the case where the ghost prevention structure GP, i.e., the light-absorbing type ghost prevention structure GPQ, is retained while maintaining the configuration shown in Figure 8.

[0047] In Figures 9 and 10, the upper left region shows a simulated image illustrating the detection state by an angle light receiver positioned at pupil position PP when a full-white image is displayed on the display element 11. To the right of this simulated image, a logarithmic graph of the luminance distribution along the central vertical axis, which is 0° on the H-axis (horizontal axis), is shown. Below the simulated image, a logarithmic graph of the luminance distribution along the central horizontal axis, which is 0° on the V-axis (vertical axis), is shown. The angle light receiver assumed in the simulation evaluates the observed image using the entire eye box set at pupil position PP. The numerical values ​​shown in the luminance distribution of the H-axis and V-axis represent the percentage of unwanted light when the luminance of the image area visible in the center of the screen of the simulated image is set to 100%.

[0048] As shown in Figure 9, in the conventional virtual image display device, a lot of unwanted light causes ghosting outside the image area, making it unsuitable for applications such as video viewing. Five types of ghosts, GH1, GH2, GH3, GH4, and GH5, are formed above and below the image area. The first type of ghost, GH1, is formed above the image area, separated by about half a vertical angle. The second type of ghost, GH2, is formed near the bottom of the first type of ghost, GH1. The third type of ghost, GH3, is formed near the bottom of the second type of ghost, GH2. In other words, the second type of ghost, GH2, is formed between the first type of ghost, GH1, and the third type of ghost, GH3. The fourth type of ghost, GH4, is formed below the image area, separated by a gap. The fifth type of ghost, GH5, is formed near the bottom of the fourth type of ghost, GH4. The first type of ghosting, GH1, has a brightness of approximately 0.1% compared to the central image area; the second type of ghosting, GH2, has a brightness of approximately 5.5% compared to the central image area; the third type of ghosting, GH3, has a brightness of approximately 7.7% compared to the central image area; the fourth type of ghosting, GH4, has a brightness of approximately 0.8% compared to the central image area; and the fifth type of ghosting, GH5, has a brightness of approximately 5.9% compared to the central image area.

[0049] As shown in Figure 10, in the virtual image display device of the embodiment, the brightness of the third type ghost GH3, the fourth type ghost GH4, and the fifth type ghost GH5 is reduced by the light-absorbing layer 41i, which is the ghost prevention structure GP. The brightness of the third type ghost GH3 is reduced from 7.7% in the comparative example to approximately 0%. The brightness of the fourth type ghost GH4 is reduced from 0.8% in the comparative example to approximately 0%. The brightness of the fifth type ghost GH5 is also reduced from 5.9% in the comparative example to approximately 0%.

[0050] 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 light-absorbing layer 41i is formed on the upper end region of the first inner surface 41b of the first prism 41 by applying and drying a light-absorbing liquid material. A polarization separation film 45 as an oblique mirror portion IM is formed on the first inclined surface 41d of the first prism 41 by various methods such as attaching a sheet-like reflective polarizing film or wire grid polarizing film made of a resin multilayer film, or forming a dielectric multilayer film by vacuum deposition. After that, the first prism 41 and the second prism 42 are joined at the inclined surfaces 41d and 42d to obtain a prism light guide member 48 or a first flat plate-shaped member 40. In parallel with this, a quarter-wave plate 51, a second lens 53 on which a transmissive mirror 56 is formed, and an optical element 58 are joined together to form an integrated structure, which is then attached to the outer surfaces 41c and 42c of the first flat plate member 40 so as to face each other. At this time, a pair of thin adhesive spacers 61 are placed between the outer surfaces 41c and 42c of the first flat plate member 40 and the quarter-wave plate 51, forming a gap SP between the outer surfaces 41c and 42c of the first flat plate member 40 and the quarter-wave plate 51.

[0051] The oblique mirror portion IM is not limited to the polarization separation film 45, but may also be a transparent mirror. In this case, the quarter-wave plate 51 can be omitted.

[0052] The first embodiment of the virtual image display device 100A, 100B, or optical unit 100 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 and constituting a parallel plate-shaped prism light guide member 48, and an oblique mirror portion IM provided at the joint between the first prism 41 and the second prism 42, which reflects at least a portion of the image light ML guided in the first prism 41. The first prism 41 comprises a plano-convex second lens 53 positioned opposite the first outer surface 41c of the first prism into which the image light ML reflected by the mirror section IM enters, and a transmissive mirror 56 formed on the convex surface 53g of the second lens 53 which partially reflects the image light ML reflected by the oblique mirror section IM toward the oblique mirror section IM. The first prism 41 has a ghosting prevention structure GP on one of its upper parts UP, the first outer surface 41c and the first inner surface 41b opposite to it, which suppresses the propagation of the image light ML.

[0053] In the above-mentioned virtual image display devices 100A, 100B, or optical unit 100, the first prism 41 has a ghosting prevention structure GP on one of its upper surfaces UP, either the first outer surface 41c or the first inner surface 41b, which suppresses the propagation of image light ML. Therefore, even if unwanted light GL1 or other unintended components of the image light ML are incident on the upper surface UP of the first prism 41, their passage is restricted by the ghosting prevention structure GP, thereby suppressing the observation of ghosting around the virtual image being observed.

[0054] [Second Embodiment] The virtual image display device of the second embodiment will be described below. 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.

[0055] Figure 11 is a perspective view illustrating the first virtual image display device 100A or optical unit 100 of the second embodiment. In this embodiment, the ghosting prevention structure GP2 is formed as an elongated strip-shaped region in the lateral X direction at the upper part UP of the first prism 41, more specifically at the upper end region of the first inner surface 41b of the first prism 41. Specifically, the ghosting prevention structure GP2 is a light-absorbing layer 41i, which is a black matte coating used in optical applications. The ghosting prevention structure GP includes a central portion RA1, a right portion RA2, and a left portion RA3. The central portion RA1 is adjacent to the incident optical surface 41a and its vertical width changes. The right portion RA2 and the left portion RA3 are adjacent to the upper plane 40u and their vertical widths do not change. Although not shown in the illustration, similar to Figure 8, a light-absorbing layer 41i, which is a ghost-preventing structure GP1, is formed on the upper surface 40u of the first prism 41, and a light-absorbing layer 41i is also provided on the first bottom surface 42f of the prism light guide member 48.

[0056] The ghosting prevention structure GP2 of this embodiment restricts the passage of unwanted light GL1, as shown in Figure 5, by absorbing it when it is incident on the upper end of the first inner surface 41b, thereby suppressing the observation of ghosting.

[0057] In the ghosting prevention structure GP2, the central portion RA1 is more effective than the right portion RA2 and left portion RA3 in restricting the passage of unwanted light GL1 and suppressing ghost formation. In other words, the ghosting prevention structure GP2 may consist only of the central portion RA1, and the ghosting suppression effect can be achieved even if the right portion RA2 and left portion RA3 are omitted.

[0058] Figure 12 is a diagram illustrating the projection state of unwanted light in a virtual image display device according to an embodiment of the second embodiment. In the virtual image display device of the embodiment, it can be seen that the brightness of the third type ghost GH3, the fourth type ghost GH4, and the fifth type ghost GH5 is reduced by the light-absorbing layer 41i, which is the ghost prevention structure GP2. The brightness of the third type ghost GH3 is reduced from 7.7% in the comparative example to approximately 0%. The brightness of the fourth type ghost GH4 is reduced from 0.8% in the comparative example to approximately 0%. The brightness of the fifth type ghost GH5 is also reduced from 5.9% in the comparative example to approximately 4.3%.

[0059] [Third Embodiment] The following describes the virtual image display device of the third embodiment. Note that the virtual image display device of the third embodiment is a partial modification of the virtual image display device of the first embodiment.

[0060] Figure 13 is a perspective view illustrating the first virtual image display device 100A or optical unit 100 of the third embodiment. In this embodiment, a ghosting prevention structure GP is provided on the first outer surface 41c of the upper part UP of the first prism 41, and a ghosting prevention structure GP2 is provided on the first inner surface 41b. The ghosting prevention structure GP is the same as the ghosting prevention structure GP of the first embodiment shown in Figures 2 and 3, and the ghosting prevention structure GP2 is the same as the ghosting prevention structure GP2 of the second embodiment shown in Figure 11. Although not shown, similar to Figure 8, a light absorbing layer 41i, which is the ghosting prevention structure GP1, is formed on the upper plane 40u of the first prism 41, and a light absorbing layer 41i is also provided on the first bottom surface 42f of the prism light guide member 48.

[0061] Figure 14 is a diagram illustrating the projection state of unwanted light in a virtual image display device according to an embodiment of the third embodiment. In the virtual image display device of the embodiment, it can be seen that the brightness of the third type ghost GH3, the fourth type ghost GH4, and the fifth type ghost GH5 is reduced by the light-absorbing layer 41i, which is the ghost prevention structure GP, GP1, GP2. The brightness of the third type ghost GH3 is reduced from 7.7% in the comparative example to approximately 0%. The brightness of the fourth type ghost GH4 is reduced from 0.8% in the comparative example to approximately 0%. The brightness of the fifth type ghost GH5 is also reduced from 5.9% in the comparative example to approximately 0%.

[0062] [Fourth Embodiment] The following describes the virtual image display device of the fourth embodiment. Note that the virtual image display device of the fourth embodiment is a partial modification of the virtual image display device of the first or second embodiment.

[0063] Figure 15 is a perspective view illustrating the first virtual image display device 100A or optical unit 100 of the fourth embodiment. The first virtual image display device 100A is provided with a refractive ghost prevention structure GP22 as a ghost prevention structure GP20 attached to the first inner surface 41b at the upper part UP of the first prism 41. The refractive ghost prevention structure GP22 suppresses the guidance of unintended image light ML by the prism light guide member 48 in the direct projection type first virtual image display device 100A. The refractive ghost prevention structure GP22 is an optical film or optical element that shifts the image light ML by refraction, and is a refractive element RS. The refractive element RS is, for example, a Fresnel refractive surface 41j, which causes the image light ML to diverge or scatter by a number of minute band-shaped refractive surfaces and be emitted outside the prism light guide member 48. In addition, in the ghost prevention structure GP22, a Fresnel refractive surface 41j or a light-absorbing layer 41i may be provided in the central portion RA1 corresponding to the lens portion 44, but this can be omitted.

[0064] The Fresnel refractive surface 41j can be formed collectively during the molding of the first prism 41, but it may also be formed by attaching a sheet-like member having a Fresnel surface to the first inner surface 41b. Instead of the Fresnel refractive surface 41j, a continuous curved surface may be used as the refractive element RS.

[0065] [Fifth Embodiment] The following describes the virtual image display device of the fifth embodiment. Note that the virtual image display device of the fifth embodiment is a partial modification of the virtual image display device of the first or fourth embodiment.

[0066] Figure 16 is a perspective view illustrating the first virtual image display device 100A or optical unit 100 of the fifth embodiment. The first virtual image display device 100A is provided with a diffraction-type ghosting prevention structure GP23 as a ghosting prevention structure GP20 attached to the first inner surface 41b at the upper part UP of the first prism 41. The diffraction-type ghosting prevention structure GP23 suppresses the guidance of unintended image light ML by the prism light guide member 48 in the direct projection type first virtual image display device 100A. The refractive-type ghosting prevention structure GP23 is an optical film or optical element that shifts the image light ML by a minute step that gives a phase difference, and is a diffraction element DS. The diffraction element DS is, for example, a blazed diffraction grating 41k, which causes the image light ML to diverge or scatter by diffraction and be emitted outside the prism light guide member 48. In addition, in the central portion RA1 of the ghost prevention structure GP23, a blazed diffraction grating 41k or a light-absorbing layer 41i may be provided in the region corresponding to the lens portion 44, but this can be omitted. The diffraction element DS is formed, for example, by nanoimprint. The diffraction element DS may be formed as a volume hologram or as a structure such as a metalens.

[0067] The ghost prevention structure GP23 is not limited to the diffraction element DS; it may also be something like a random scattering surface after grinding. [Variations and other variations]

[0068] 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.

[0069] 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.

[0070] 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.

[0071] In the second flat plate-shaped member 50, the cover member 52 may be omitted. In that case, the transparent mirror 56 can be replaced with one that does not transmit light.

[0072] The boundary between the first inner surface 41b of the first prism 41 and the upper plane 40u is not limited to a precise edge shape, but may have a slight radius. In this case, the ghosting prevention structure GP2 can be formed on the radiused surface.

[0073] The first lens 30 of the first prism 41 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.

[0074] 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.

[0075] 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, liquid crystal lens, etc., that also has positive power. In this case, the compensating lens 54 can be, for example, a diffractive lens or holographic 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.

[0076] As shown in Figure 17, 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 reflecting 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 polarization separation film 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.

[0077] 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 polarization separation film 45, and is incident on the pupil position PP.

[0078] 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 first prism has a ghosting prevention structure on one of its inner surfaces opposite its outer surface at its upper part to suppress the propagation of image light.

[0079] In the above-described virtual image display device, the first prism has a ghosting prevention structure on one of its outer or inner surfaces at the top to suppress the propagation of image light. Therefore, even if unintended components of the image light are incident on the top of the first prism, their passage is restricted by the ghosting prevention structure, and the observation of ghosts around the virtual image being observed can be suppressed.

[0080] In a specific embodiment of the virtual image display device, the ghosting prevention structure is provided on the inner surface of the upper end of the first prism. The inner surface of the upper end of the first prism is one of the main causes of ghosting formed around the virtual image being observed, and by providing the ghosting prevention structure here, the ghosting suppression effect can be enhanced.

[0081] In a specific embodiment of the virtual image display device, the ghosting prevention structure is provided on the outer surface of the upper end of the first prism. The outer surface of the upper end of the first prism is one of the causes of ghosting formed around the virtual image being observed, and by providing the ghosting prevention structure here, the ghosting suppression effect can be enhanced.

[0082] In a specific embodiment of the virtual image display device, the ghosting prevention structure is provided on the inner surface and the outer surface of the upper end.

[0083] In a specific embodiment of a virtual image display device, the ghost prevention structure is provided in the peripheral region of the incident surface of the first prism. The peripheral region of the incident surface of the first prism is where unintended image light from the image light emitted from the display element is incident, and by preventing the passage of such unintended image light, the occurrence of ghosting can be further reduced.

[0084] In a specific embodiment of a virtual image display device, the ghost prevention structure is a light-absorbing type ghost prevention structure formed by a light-absorbing layer. The light-absorbing layer blocks unintended image light by absorbing it.

[0085] In a specific embodiment of a virtual image display device, the ghost prevention structure is an optical film or optical element that shifts the path of the image light as it passes through. Here, shifting means changing the path of the image light from the normal optical path of the image light, such as transmission, refraction, or reflection.

[0086] In a specific embodiment of a virtual image display device, the ghosting prevention structure is a refractive element that shifts the image light by refraction. The refractive structure is, for example, a Fresnel lens, which can divert unintended image light from the light path leading to the pupil.

[0087] In a specific embodiment of a virtual image display device, the ghosting prevention structure is a diffraction element that shifts the image light by diffraction. The diffraction structure can divert unintended image light from the optical path leading to the pupil.

[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 lens, and the oblique mirror portion has a polarization separation film that selectively reflects the image light according to the 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 direct 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 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 first prism has a ghosting prevention structure on one of its inner surfaces opposite its outer surface at its upper part to suppress the propagation of image light. [Explanation of Symbols]

[0090] 11…Display element, 11d…Display surface, 31…Parallel plate, 32…Lens part, 40…First flat plate-shaped member, 40i…Incident surface, 40u…Upper plane, 41a…Incident optical surface, 41c,42c…Outer surface, 41d,42d…Inclined surface, 41i…Light absorption layer, 41j…Fresnel refractive surface, 41k…Blazed diffraction grating, 44…Lens part, 45…Polarization separation film, 48…Prism light guide member, 50… Second flat plate member, 51f...outer periphery, 52...cover member, 53f...flat surface, 53g...convex surface, 54...compensating lens, 54f...concave surface, 54g, 55g...flat surface, 55...compensating plate, 56...transmissive mirror, 58...optical element, 59...polarizing plate, 61...spacer, 100...optical unit, 100A, 100B...virtual image display device, 100C...support device, 102a, 102b...display drive 103a,103b…Combiner, AX…Optical axis, CR…Light-gathering and reflecting section, CT…Adhesive, DIS…Direct virtual image optical system, DS…Diffractive element, EP…Exit pupil, EY…Eye, GH1,GH2,GH3,GH4,GH5…Ghost, GL1,GL2,GL3…Unwanted light, GP,GP0,GP1,GP2,GP20…Ghost prevention structure, GPQ…Light-absorbing ghost prevention structure, GP22…Refractive ghost prevention structure, GP23…Diffractive ghost prevention structure, IM…Angular mirror section, IS…Imaging optical system, LP…Image light blocking section, ML…Image light, OL…Outside light, P1,P3…Upper end position, P2…Lower end position, PLc…Circular polarization, PLp…p-polarization, PLs…s-polarization, PP…Pupil position, PPa…Aperture, RS…Refractive element, SP…Gap, UP…Upper 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 first prism has, at its upper end, a ghosting prevention structure on one of its inner surfaces facing the outer surface, which suppresses the propagation of the image light. Virtual image display device.

2. The ghost prevention structure is provided on the inner surface of the upper end of the first prism. The virtual image display device according to claim 1.

3. The ghost prevention structure is provided on the outer surface of the upper end of the first prism. The virtual image display device according to claim 1.

4. The ghosting prevention structure is provided on the inner surface and the outer surface of the upper end. The virtual image display device according to claim 2.

5. The ghost prevention structure is provided in the peripheral region of the incident surface of the first prism. The virtual image display device according to claim 1.

6. The ghosting prevention structure is a light-absorbing type ghosting prevention structure formed by a light-absorbing layer. The virtual image display device according to claim 1.

7. The ghost prevention structure is an optical film or optical element that causes the image light to shift as it passes through. The virtual image display device according to claim 1.

8. The ghost prevention structure is a refractive element that shifts the image light by refraction. The virtual image display device according to claim 7.

9. The ghost prevention structure is a diffraction element that shifts the image light by diffraction. The virtual image display device according to claim 7.

10. The first prism further comprises a quarter-wave plate disposed 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 first prism has, at its upper end, a ghosting prevention structure on one of its inner surfaces facing the outer surface, which suppresses the propagation of the image light. Optical unit.

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