Virtual image display device and optical unit

Abstract

To prevent an optical system from being large as a whole.SOLUTION: A virtual image display device 100A is a direct virtual image type virtual image display device. The virtual image display device includes: a display element 11; a first lens 30 that has positive refractive power and on which video light ML from the display element is incident; a second lens 44 that has positive refractive power and on which the video light ML passed through the first lens is incident; a parallel flat plate-like prism light-guiding member 40 that has a first prism 41 and a second prism 42 and that causes the video light passed through the second lens to be guided; a planar polarized light separation film 45 that is provided at a bonding spot of the first prism and the second prism and that selectively reflects the video light guided in the first prism in accordance with a polarization direction; a third lens 53 having a plano-convex shape disposed facing an outer surface 41c of the first prism; a transmissive mirror 56 that is formed on a convex surface 53g of the third lens and that partially reflects the video light; and a quarter-wavelength plate 51 disposed between the outer surface and a flat surface 53f of the third lens.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a see-through type virtual image display device and an optical unit that enable viewing of a virtual image. [Background technology]

[0002] A head-mounted display comprising a display device, a projection optical member, a prism member, and a collecting reflective surface, in which image light from the projection optical member enters a first prism of the prism member, is totally reflected by the outer surface, is partially reflected by a semi-transmissive reflective surface formed at the boundary between the first and second prisms of the prism member, passes through the outer surface of the prism member and is reflected by the collecting reflective surface, is returned to the prism member, passes through the semi-transmissive reflective surface, and further passes through the inner surface facing the pupil, is known (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-08749 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned head mounted display, an intermediate image is formed in the first prism, so the optical path length is long and the overall size of the optical system becomes large. In addition, since the projection optical member is arranged in a direction inclined toward the face rather than above the prism member, the projection optical member is arranged close to the face, which makes interference more likely to occur, and there are limitations on the arrangement and size of the projection optical member. Even if a relatively small optical system that does not form an intermediate image can be realized by effectively using a light-collecting reflector, it is difficult to correct chromatic aberration in such an optical system using only the light-collecting reflector. [Means for solving the problem]

[0005] A virtual image display device according to one aspect of the present invention is a direct virtual image type virtual image display device comprising: a display element that emits image light; a first lens having positive refractive power and into which the image light from the display element is incident; a second lens having positive refractive power and into which the image light that has passed through the first lens is incident; a parallel plate-shaped prism light guide member having a first prism and a second prism and guiding the image light that has passed through the second lens; a flat polarization separation film provided at the junction between the first prism and the second prism and selectively reflecting the image light guided in the first prism in accordance with the polarization direction; a planar third lens having a planar surface arranged opposite to the outer surface of the first prism onto which the image light reflected by the polarization separation film is incident; a transmissive mirror formed on the convex surface of the third lens and partially reflecting the image light reflected by the polarization separation film toward the polarization separation film; and a quarter wave plate for image light arranged between the outer surface of the first prism and the plane of the third lens. The first prism has a higher refractive index than the first lens and the third lens. The virtual image display device suppresses chromatic aberration caused by the combination of the first lens, the second lens, the first prism, and the third lens as a whole.

[0006] According to one aspect of the present invention, an optical unit is a direct virtual image type optical unit, comprising: a first lens having a positive refractive power and on which image light from a display element that emits image light is incident; a second lens having a positive refractive power and on which the image light that has passed through the first lens is incident; a parallel flat-plate prism light guide member having a first prism and a second prism and guiding the image light that has passed through the second lens; a flat polarization separation film provided at a joint between the first prism and the second prism and selectively reflecting the image light guided in the first prism according to the polarization direction; a plano-convex third lens having a flat surface arranged opposite to an outer surface of the first prism on which the image light reflected by the polarization separation film is incident; a transmissive mirror formed on the convex surface of the third lens and partially reflecting the image light reflected by the polarization separation film toward the polarization separation film; and a quarter-wave plate for image light arranged between the outer surface of the first prism and the flat surface of the third lens. The refractive index of the first prism is higher than the refractive indexes of the first lens and the third lens. The optical unit suppresses chromatic aberration as a whole resulting from the combination of the first lens, the second lens, the first prism, and the third lens. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is an external view illustrating a state in which the virtual image display device according to a first embodiment is used. [Diagram 2] FIG. 4 is a side cross-sectional view illustrating the internal structure of one of the display devices. [Diagram 3] FIG. 2 is a perspective view illustrating the external structure of a first display unit. [Figure 4] 3A to 3C are diagrams for explaining the shapes of a first image-forming element and a first lens, etc. FIG. [Diagram 5] 4 is a perspective view for explaining an example of the structure and assembly of a first display unit. FIG. [Figure 6] 1A and 1B are diagrams illustrating chromatic aberration and suppression of chromatic aberration. [Figure 7] FIG. 11 is a side cross-sectional view illustrating the internal structure of a virtual image display device according to a second embodiment. [Figure 8] FIG. 11 is a side cross-sectional view illustrating a virtual image display device according to a third embodiment. [Figure 9] 9 is a conceptual diagram illustrating the operation of the virtual image display device shown in FIG. 8. [Figure 10] 9 is a conceptual diagram illustrating the operation of the modified example of the virtual image display device shown in FIG. 8. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] [First embodiment] Hereinafter, a first embodiment of a virtual image display device etc. according to the present invention will be described with reference to FIGS.

[0009] Fig. 1 is a diagram for explaining the wearing state of a head mounted virtual image display device (hereinafter also referred to as a head mounted display or HMD) 200, in which the observer or wearer US wearing the HMD 200 recognizes an image as a virtual image. In Fig. 1 etc., X, Y, and Z are an orthogonal coordinate system, 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 are aligned for the wearer US, and the +Z direction corresponds to the forward direction or front direction for the wearer US. The ±Y directions are parallel to the vertical axis or vertical direction.

[0010] The HMD 200 includes a first virtual image display device 100A for the right eye and a direct virtual image type, a second virtual image display device 100B for the left eye and a direct virtual image type, a pair of temple-shaped support devices 100C that support the virtual image display devices 100A and 100B, and a user terminal 90 that is an information terminal. The first virtual image display device 100A functions as an HMD alone and is composed of a first display drive unit 102a arranged at the top and a first combiner 103a that is shaped like a glasses lens and covers the front of the eyes. The second virtual image display device 100B also functions as an HMD alone and is composed of a second display drive unit 102b arranged at the top and a second combiner 103b that is shaped like a glasses lens and covers the front of the eyes. The support device 100C is a mounting member that is mounted on the head of the wearer US, and supports the upper end sides of the pair of combiners 103a and 103b via the display drive units 102a and 102b that are integrated in appearance. The first virtual image display device 100A and the second virtual image display device 100B are optically identical or are left-right inverted versions of each other, and a detailed description of the second virtual image display device 100B will be omitted.

[0011] FIG. 2 is a side cross-sectional view for explaining the internal structure 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 called 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, and is also called 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 that protects the display surface 11d of the display element 11. The first flat-plate member 40 includes a second lens 44 facing the first lens 30, and guides the image light ML emitted from the display element 11 and incident from the second lens 44 to a third lens 53 of the second flat-plate member 50. The second plate-shaped member 50 reflects the image light ML from the first plate-shaped member 40 toward the pupil position PP or the eye EY by partially returning the image light ML from the first plate-shaped member 40 back to the first plate-shaped member 40, and also allows external light to be incident on the pupil position PP via the first plate-shaped member 40. The first lens 30, the second lens 44, the first plate-shaped member 40, and the second plate-shaped member 50 each function as a lens having a positive refractive power.

[0012] Although detailed description will be 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 similar to the first image forming element 11a, the second display unit 20b is similar to the first display unit 20a, and the second circuit member 80b is similar to the first circuit member 80a.

[0013] In the first virtual image display device 100A, the first image forming element 11a is a self-luminous image light generating device. The first image forming element 11a emits the image light ML to the first flat plate-like 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, and forms a color still image or a 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 a display operation. The first image forming element 11a is not limited to an organic EL display, and can be replaced with a display device using an inorganic EL, an organic LED, an LED array, a laser array, a quantum dot light-emitting element, or the like. The first image forming element 11a is not limited to a self-luminous image light generating device, and may 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. As the first image forming element 11a, instead of an LCD, LCOS (Liquid crystal on silicon, LCoS is a registered trademark), a digital micromirror device, or the like can be used. In the first virtual image display device 100A, the optical device excluding the first circuit member 80 is called an optical unit 100. The optical unit 100 includes a direct virtual image type optical system, and can be said to be a part corresponding to the direct virtual image optical system DIS constituting the first virtual image display device 100A.

[0014] The first display unit 20a includes a first lens 30, a first flat-plate member 40, a polarization separation film 45, and a second flat-plate member 50. In the first display unit 20a, the first lens 30 has a positive refractive power, and the image light ML from the first image forming element 11a is incident on the first lens 30. The first lens 30 has a flat light entrance surface 30f that is bonded to the first image forming element 11a, and a convex light exit surface 30g. The light exit surface 30g is, for example, a spherical surface, but can be an aspheric surface having an axisymmetric shape. The first lens 30 can be considered as being divided into a parallel plate 31 and a lens portion 32. By ensuring that the thickness of the parallel plate 31 is equal to or greater than a predetermined value, foreign matter attached to the surface of the first lens 30 becomes less noticeable. The lens portion 32 is a plano-convex lens having a positive refractive power. The plano-convex lens has one surface that has a planar shape and the other surface that has a convex shape. The first lens 30 is made of, for example, fused silica and has a relatively low refractive index. As an example, the refractive index of the first lens 30 is 1.49 or less. Preferably, the first lens 30 is made of silica with a refractive index of 1.46.

[0015] The first flat-plate member 40 has a second lens 44, which is a plano-convex lens, a first prism 41 in the shape of a parallel flat plate, and a second prism 42 in the shape of a parallel flat plate. The second lens 44 and the first prism 41 are joined at the inclined surfaces 44b and 41a. The first prism 41 and the second prism 42 are joined at the inclined surfaces 41d and 42d. The second lens 44, the first prism 41, and the second prism 42 joined together are called a prism light-guiding member 48. The prism light-guiding member 48 has the appearance of a parallel flat plate. A flat polarization separation film 45 is formed on the inclined surface 41d formed on the lower side of the first prism 41. The combination of the prism light-guiding member 48 and the second flat-plate member 50 described later corresponds to the first combiner 103a in FIG. 1.

[0016] The second lens 44 is a plano-convex lens having a positive refractive index, and has an incident optical surface 44a facing the light exit surface 30g of the first lens 30, and an inclined surface 44b coupled to the first prism 41. As an example, the refractive index of the second lens 44 is 1.49 or less. Preferably, the second lens 44 is made of quartz having a refractive index of 1.46. The first prism 41 has a rectangular prism-like outer shape and a trapezoidal longitudinal section. The first prism 41 guides the image light ML, and has an inclined surface 41a coupled to the inclined surface 44b of the second lens 44, an inner surface 41b, an outer surface 41c, and an inclined surface 41d. Here, the incident optical surface 44a is inclined downward in the front as a whole, and the optical axis passing through the incident optical surface 44a extends in a direction between the +Z direction, which is the front, and the +Y direction, which is the upper direction. This makes it easier to arrange the first image forming element 11a, which is the display element 11, closer to the outside world than the inner surface 41b, and allows the angle at which the image light ML propagates in the first prism 41 (inside the first prism 41 or inside the first prism 41) to be adjusted. The incident optical surface 44a is a convex surface, and is, for example, a spherical surface, but can be an axially symmetric aspheric surface. The inner surface 41b and the outer surface 41c are parallel to each other and extend perpendicular to the optical axis AX between the pupil position PP. The inner surface 41b and the outer surface 41c internally reflect the image light ML (i.e., reflect it inside the object surface), and it is particularly preferable that they totally reflect the image light ML. The inner surface 41b can be hard-coated to increase scratch resistance or abrasion resistance. The inclined surface 41d is a flat surface. The inclined surface 41d forms an acute angle with the 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 about 20 mm. The first prism 41 is made of optical glass such as s-NBH51, and has a refractive index higher than that of the first lens 30.

[0017] The image light ML is reflected once by the inner surface 41b, once by the outer surface 41c, and once by the polarization separation film 45 described below. By making the number of internal reflections of the image light ML in the first prism 41 two, it is possible to prevent light that has been reflected a different number of times within the first prism 41 from being mixed while increasing the angle of view and pupil position PP or the aperture PPa of the image light ML. The image light ML reflected by the inner surface 41b and the outer surface 41c is less divergent than the initial divergent state emitted from the first image forming element 11a because no intermediate image is formed in the first display unit 20a or the imaging optical system IS, but it enters the inner surface 41b and the outer surface 41c in a divergent state and the divergent state is maintained.

[0018] The second prism 42, like the first prism 41, has a rectangular prism-like outer shape and a trapezoidal longitudinal section. The second prism 42 transmits the image light ML and has an inner surface 42b, an outer surface 42c, and an inclined surface 42d. Here, the inner surface 42b and the outer surface 42c are parallel to each other and extend perpendicular to the optical axis AX between the pupil position PP. The inner surface 42b can be hard-coated to improve scratch resistance or abrasion resistance. The second prism 42 is formed of optical glass such as s-NBH51, and has a refractive index equal to that of the first prism 41. As an example, the difference between the refractive index of the first lens 30 and the second lens 44 and the refractive index of the first prism 41 and the second prism 42 is 0.17 or more. As another example, the refractive index of the first prism 41 and the second prism 42 is 1.67 or more. Preferably, the first prism 41 and the second prism 42 are made of optical glass with a refractive index of 1.67.

[0019] The polarization separation film 45 is integrally formed on the inclined surface 41d of the first prism 41 and is sandwiched between the inclined surface 41d of the first prism 41 and the inclined surface 42d of the second prism 42. The space between the polarization separation film 45 and the inclined surface 42d is filled with a bonding adhesive CT. The polarization separation film 45 is formed of a dielectric multilayer film, and when the image light ML contains s-polarized light s, it efficiently reflects the s-polarized image light ML, and when the image light ML contains p-polarized light p, it efficiently transmits the p-polarized image light ML. The polarization separation film 45 may be any film that selectively reflects the image light ML according to the polarization direction, and may be, for example, a wire grid type polarizer. The polarization separation film 45 may have a flat surface that does not affect the image formation. The polarization separation film 45 may have a slightly convex or concave curved surface that does not affect the image formation. The space between the polarization separation film 45 and the inclined surface 41d may be filled with a transparent filler instead of the adhesive CT. In this case, the first prism 41 and the second prism 42 may be supported from the outside by a support member or the like to maintain the bonded state. Also, the polarization separation film 45 may be integrally formed on the slope 42d of the second prism 42, instead of on the slope 41d of the first prism 41. The scratch resistance or abrasion resistance of the polarization separation film 45 can be improved by applying a hard coat to the surface.

[0020] If the reflection angle of the image light ML on the optical axis AX in the first prism 41 is β0, the inclination angle θ of the polarization separation film 45 is 90°-β0 or more. If the maximum reflection angle of the image light ML is βmax, assuming that the polarization separation film 45 does not obstruct the path of the image light ML, it is desirable that the inclination angle θ of the polarization separation film 45 is smaller than βmax. The reflection angle β0 of the image light ML corresponds to the angle between the normal to the inner surface 41b and the optical axis AX passing through the incident optical surface 44a, and is an acute angle. In other words, the optical axis AX of the incident optical surface 44a extends in a direction less than 90° with respect to the normal to the inner surface 41b.

[0021] The second flat member 50 has a thin quarter-wave plate 51 and a cover member 52. The quarter-wave plate 51 is a crystal or the like having an optical axis between the X direction and the Y direction, and converts the s-polarized image light ML reflected by the polarization separation film 45 into circularly polarized light c, and converts the circularly polarized image light c reflected by the cover member 52 into p-polarized light p. The cover member 52 has a plano-convex third lens 53, a concave-plano compensation lens 54, a compensation plate 55 provided around the compensation lens 54, and a transmissive mirror 56.

[0022] The second flat plate member 50 is disposed at a distance of about 20 μm to 50 μm from the first flat plate member 40. The outer side surfaces 41c, 42c of the first flat plate member 40 and the inner side surface 50c of the second flat plate member 50 may be slightly curved, and a minute step may be formed at the boundary between the outer side surfaces 41c, 42c. However, by setting the distance between the outer side surfaces 41c, 42c and the inner side surface 50c to 20 μm or more, more preferably 30 μm or more, it is possible to prevent these surfaces from being excessively close to each other. Conversely, by setting the distance between the outer side surfaces 41c, 42c and the inner side surface 50c to 50 μm or less, it is possible to prevent an increase in the thickness of the first combiner 103a obtained by combining the first flat plate member 40 and the second flat plate member 50. A spacer 61 is provided between the outer surfaces 41c, 42c of the first flat plate member 40 and the 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 mutually positioned state. The spacer 61 is not provided around the entire periphery 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.

[0023] In the cover member 52, the third lens 53 is thin but has a positive refractive power, and has a flat surface 53f bonded to the quarter-wave plate 51, and a convex surface 53g facing the compensation lens 54. The convex surface 53g is, for example, a spherical surface, but can be an axially symmetric aspheric surface. The compensation lens 54 is thin but has a positive refractive power, and has a concave surface 54f facing the third lens 53, and a flat surface 54g. The compensation plate 55 is a parallel plate and has a pair of flat surfaces 55f, 55g. Here, the concave surface 54f of the compensation plate 55 has the same shape as the convex surface 53g of the third lens 53. The flat surface 54g of the compensation lens 54 and the flat surface 55g of the compensation plate 55 are on the same plane and are continuous. The transparent mirror 56 is a thin film formed on the convex surface 53g of the third lens 53, and has the same shape as the convex surface 53g. The combination of the third lens 53 and the transmissive mirror 56 is called a light-collecting reflector CR.

[0024] The third lens 53, the compensation lens 54, and the compensation plate 55 are formed of a resin material and have the same refractive index. The refractive index of the third lens 53 and the like is lower than that of the first prism 41. As an example, the refractive index of the third lens 53 is 1.49. As another example, the difference between the refractive index of the third lens 53 and the refractive index of the first prism 41 is 0.17 or more. Preferably, the third lens 53 is made of acrylic such as PMMA having a refractive index of 1.49. The compensation lens 54 and the compensation plate 55 are optical elements 58 integrally formed from the same resin material. The combination of the third lens 53, the compensation lens 54, and the compensation plate 55 functions as a parallel plate as a whole. In other words, the external light OL incident on the position of the compensation lens 54 or the compensation plate 55 passes through them without being affected by the lens action of the compensation lens 54 and the like or by the step existing on the outer edge of the compensation lens 54. The flat surfaces 54g, 55g of the compensation lens 54 and the compensation plate 55 may be coated with an anti-reflection film or a hard coat. The outside light OL that has passed through the compensation plate 55 passes above, below, left and right of the compensation lens 54, and is incident on the compensation plate 55, that is, on a peripheral area outside the incident area of ​​the image light ML corresponding to the compensation lens 54. This makes it possible to ensure a wide see-through field of view with respect to the outside world. The field of view of the outside light OL is set to, for example, about 40° upward and about 40° downward.

[0025] The diameter of the third lens 53 is set to 20 mm to 25 mm in order to ensure the angle of view. The thickness in the Z direction of the first flat plate member 40 or the prism light-guiding member 48 is 6 mm to 8 mm, and the distance from the inner sides 41b, 42b of the first flat plate member 40 to the pupil position PP is about 12 mm to 13 mm, so that the angle of view (diagonal), which is the angular range in which the image light ML is incident on the pupil position PP, can be set to about 40°.

[0026] The transmissive mirror 56 is a half mirror that partially reflects the image light ML that has passed through the third lens 53 and partially transmits the outside light OL. The transmissive mirror 56 reflects the image light ML that has been reflected by the polarization separation film 45 of the first flat plate member 40 and passed through the ¼ wavelength plate 51 and the third 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, has a concave shape toward the pupil position PP, and has 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.

[0027] The transparent mirror 56 transmits a part of the outside light OL, so that a see-through view of the outside world is possible, and a virtual image can be superimposed on an outside image. At this time, the outside light OL passes through the first flat plate-like member 40 and the second flat plate-like member 50, but the flat plate-like members 40, 50 do not act as a lens on the outside light OL. The reflectance of the transparent mirror 56 for the image light ML and the outside light OL is set to 10% or more and 50% or less in the assumed range of incidence angles of the image light ML, from the viewpoint of ensuring the brightness of the image light ML and facilitating the observation of the outside image by the see-through. The transparent mirror 56 is formed, for example, of a dielectric multilayer film made of a plurality of dielectric layers whose film thicknesses are adjusted. The transparent mirror 56 may be a single layer film or a multilayer film of a metal such as Al or Ag whose film thickness is adjusted. The transparent mirror 56 is formed, for example, by lamination using vapor deposition.

[0028] In the first virtual image display device 100A, the first lens 30, the second lens 44, the third lens 53, and the transparent mirror 56 each have a positive refractive power and tend to converge divergent light. The first lens 30, the second lens 44, the third lens 53, and the transparent mirror 56, including the main body of the first prism 41 and the second prism 42, function as an imaging optical system IS like a simple microscope type microscope that forms an erect image, or a direct virtual image optical system DIS. This makes it possible to form a virtual image by projecting a real image formed on the display surface 11d of the first image forming element 11a, for example, at infinity, or to form a virtual image by projecting a real image formed on the display surface 11d several meters ahead. At this time, by adjusting the refractive power of the first lens 30, the second lens 44, the third lens 53, and the transparent mirror 56, the focal length of the imaging optical system IS can be shortened to achieve a desired magnification ratio. In the first virtual image display device 100A, it is preferable to appropriately set the refractive indexes of the first lens 30, the second lens 44, the first prism 41, and the third lens 53 based on the dimensions and shapes of the first lens 30, the second lens 44, the first prism 41, the third lens 53, and the transmissive mirror 56 so as to suppress chromatic aberration resulting from the combination of the first lens 30, the second lens 44, the first prism 41, the third lens 53, and the transmissive mirror 56. More specifically, chromatic aberration is suppressed in the entire optical system that forms a virtual image on an optical path that passes through the first lens 30, passes through the second lens 44, is bent by the first prism 41, is reflected by the transmissive mirror 56, goes back and forth through the quarter-wave plate, goes back and forth through the third lens 53, and passes through the first and second prisms.

[0029] Referring to FIG. 3, the vertical size ay of the first flat plate member 40 or the second flat plate member 50 is, for example, 34 mm, and the horizontal size ax is, for example, 40 mm. The thickness az of the first flat plate member 40 in the front-rear direction is, for example, about 7 mm, and the combined thickness of the first flat plate member 40 and the second flat plate member 50 is suppressed to about 7.5 mm. In the first flat plate member 40, an upper flat surface 40u is provided on the left and right of the incident optical surface 44a. No light is incident on the upper flat surface 40u. In order to prevent stray light, a light shielding body (not shown) that faces and covers the upper flat surface 40u may be disposed, or a light shielding body may be applied to the upper flat surface 40u. A light shielding body or the like that covers the horizontal flat surface 40v and the lower flat surface 40w may also be provided to cover them. A light shielding body or the like that covers the periphery of the second flat plate member 50 may also be provided to cover it.

[0030] The shapes of the first image forming element 11a and the first lens 30 will be described with reference to Fig. 4. In Fig. 4, area AR1 shows the first lens 30 etc. as viewed obliquely upward from the front +Z side, area AR2 shows the first lens 30 etc. as viewed obliquely forward from the lower -Y side, and area AR3 shows the first lens 30 etc. as viewed from the side +X side. The thickness or height H of the first lens 30 is, for example, about 2 mm, the width W of the first lens 30 is, for example, about 14 mm, and the depth D of the first lens 30 is, for example, about 7 mm.

[0031] The radius of curvature of the convex light exit surface 30g of the first lens 30 is, for example, 20 mm. In addition, the radius of curvature of the incident optical surface 44a of the first prism 41 is, for example, 14 mm, and the radius of curvature of the transmissive mirror 56 is, for example, 47 mm. The surfaces of the incident optical surface 44a of the first prism 41, the transmissive mirror 56, etc. are not limited to being spherical, and may be coaxial aspheric.

[0032] Regarding the optical path, the image light ML from the first image forming element 11a passes through the first lens 30 and the second lens 44 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 second lens 44. In the optical path passing through the first prism 41, the image light ML is sequentially reflected by the inner surface 41b and the outer surface 41c of the first prism 41 without forming an intermediate image, and the s component of the image light ML is reflected by the polarization separation film 45. The s-polarized s image light ML reflected by the polarization separation film 45 passes through the outer surface 41c of the first prism 41 and passes through the ¼ wavelength plate 51 of the second flat plate-like member 50, becoming circularly polarized light c, and entering the transmissive mirror 56. The circularly polarized image light ML incident on the transmissive mirror 56 is partially reflected by the transmissive mirror 56 through the third lens 53, and passes through the quarter-wave plate 51 again in a collimated state through the third lens 53. As a result, the image light ML that has passed through the quarter-wave plate 51 becomes p-polarized p and enters the first prism 41 from the outer surface 41c, passes through the polarization separation film 45, and is emitted to the outside of the second prism 42 through the inner surface 42b. The image light ML emitted to the outside of the second prism 42 enters the pupil position PP where the eye EY or pupil of the wearer US is located. Not only the image light ML reflected by the transmissive mirror 56, but also the outside light OL that has passed through the transmissive mirror 56 and the compensation plate 55 enter the pupil position PP. In other words, the wearer US wearing the first virtual image display device 100A can observe a virtual image by the image light ML superimposed on an outside image.

[0033] An example of the structure and assembly of the first display unit 20a constituting the first virtual image display device 100A will be described with reference to FIG. 5. In FIG. 5, areas BR1 to BR5 are perspective views for explaining the assembly process of the first display unit 20a. First, as shown in area BR1, a first prism 41 and a second prism 42 are prepared. The first prism 41 and the second prism 42 are made of optical glass such as s-NBH51. The first prism 41 may have a second lens 44 bonded thereto in advance. The first prism 41 has an entrance optical surface 44a, an inner surface 41b, an outer surface 41c, and the like of the second lens 44 formed thereon. The second prism 42 has an inner surface 42b, an outer surface 42c, and the like formed thereon. On one side, a polarization separation film 45 is formed on an inclined surface 41d of the first prism 41 by vacuum deposition or other techniques. As shown in region BR2, the first prism 41 and the second prism 42 are joined at the inclined surfaces 41d, 42d to obtain the first flat plate member 40. Next, as shown in region BR3, the quarter-wave plate 51 is attached to the outer surfaces 41c, 42c of the first flat plate member 40 so as to face each other. At this time, a pair of spacers 61, which are thin adhesives, are disposed between the outer surfaces 41c, 42c of the first flat plate member 40 and the quarter-wave plate 51, and a gap is formed between the outer surfaces 41c, 42c of the first flat plate member 40 and the quarter-wave plate 51. As shown in region BR4, the third lens 53 is attached at an appropriate position on the surface of the quarter-wave plate 51. A transmissive mirror 56 is formed on the surface of the third lens 53. Next, an optical element 58 is bonded to the quarter-wave plate 51 and the like. At this time, the compensation lens 54 and the third lens 53 of the optical element 58 are positioned, fitted and bonded to each other. Also, the compensation plate 55 and the ¼ wavelength plate 51 of the optical element 58 are bonded to each other. With the above, the assembly of the first display unit 20a is completed.

[0034] In the above description, the first display unit 20a is produced by assembling the second flat plate-like member 50 on the first flat plate-like member 40, but the first flat plate-like member 40 and the second flat plate-like member 50 may be assembled separately, and then the first flat plate-like member 40 and the second flat plate-like member 50 may be joined together finally.

[0035] The virtual image display devices 100A, 100B or the optical unit 100 of the first embodiment described above is a direct virtual image type virtual image display device, and includes a display element 11 that emits image light ML, a first lens 30 having positive refractive power and on which the image light ML from the display element 11 is incident, a second lens 44 on which the image light ML that has passed through the first lens 30 is incident, a first prism 41 that is bonded to the second lens 44 and on which the image light ML that has passed through the second lens 44 is incident, a second prism 42 that is bonded to the first prism 41 to form a parallel plate-shaped prism light guide member 48, and a reflector 43 that is provided at the joint between the first prism 41 and the second prism 42 and selectively reflects the image light ML guided in the first prism 41 in accordance with the polarization direction. the third lens 53 having a flat surface 53f arranged opposite the outer surface 41c of the first prism 41 onto which the image light ML reflected by the polarization separation film 45 is incident; a transmissive mirror 56 formed on the convex surface 53g of the third lens 53 and configured to partially reflect the image light ML reflected by the polarization separation film 45 toward the polarization separation film 45; a quarter-wave plate 51 for the image light ML arranged between the outer surface 41c of the first prism 41 and the flat surface 53f of the third lens 53; and a compensation lens 54 having a concave surface 54f having a shape obtained by inverting the convex surface 53g of the third lens 53 and bonded to the convex surface 53g via the transmissive mirror 56, and a flat surface 55g parallel to the outer surface 41c of the first prism 41.

[0036] In the above-mentioned virtual image display devices 100A, 100B or optical unit 100, in order to directly form a virtual image without forming an intermediate image, refractive power is ensured by the first lens 30, the second lens 44, the third lens 53, and the transmissive mirror 56, and further, the refractive indexes of the first prism 41 and the second prism 42 are set relatively high, thereby ensuring the magnification while suppressing an increase in the optical path length, and avoiding an increase in the size of the optical system.

[0037] Moreover, the above virtual image display devices 100A, 100B or the optical unit 100 can suppress chromatic aberration. Generally speaking, the refractive index of a material that transmits and refracts light rays varies depending on the wavelength of the light. Even for the same material, the refractive index is higher for components with longer wavelengths such as red, and lower for components with shorter wavelengths such as blue. Therefore, when light containing multiple different wavelengths passes through a material and is refracted, the image formation position differs depending on the wavelength component. This phenomenon is called dispersion, and color shifts that occur due to dispersion in an image that passes through an optical system and is formed are called chromatic aberration of the optical system. An example of an index for evaluating dispersion is the Abbe number. The refractive index and Abbe number of each material generally tend to be higher for materials with lower refractive indexes, and lower for materials with higher refractive indexes. The Abbe number is defined based on the refractive index, and therefore varies depending on the wavelength. Here, as an example, the refractive index and Abbe number for light with a wavelength of 587.56 nm, called the Fraunhofer d line, are used.

[0038] 6, even if the relatively long wavelength component R0 such as red and the relatively short wavelength component B0 such as blue are observed at approximately the same position in the central portion of the image frame IF where the image light ML generated by the display element 11 is observed, the relatively long wavelength components R1, R2, R3 such as red and the shorter wavelength components B1, B2, B3 such as blue may be observed out of alignment in the peripheral portion away from the central portion. As a result, the image quality of the observed image light ML may be degraded.

[0039] As a method for suppressing such chromatic aberration, for example, there is a method called achromat. In achromat, chromatic aberration at at least two different wavelengths can be suppressed by combining and using a plurality of optical systems each having a different refractive index for the same wavelength. In this embodiment, when combining a plurality of optical elements, a combination of the difference in refractive index and Abbe number and the difference in power are appropriately set, thereby reducing chromatic aberration at at least two different wavelengths corresponding to, for example, red and blue. In this manner, in this embodiment, by utilizing a combination of a plurality of different refractive indexes, Abbe numbers, and powers between the first lens 30, the second lens 44, the third lens 53, the first prism 41, and the second prism 42, the vertical and / or horizontal chromatic aberration is at least partially canceled in the entire optical system.

[0040] More specifically, according to this embodiment, as shown in the region CR2 of FIG. 6, in the virtual image display device 100A, 100B or the optical unit 100, the refractive indexes of the first lens 30, the second lens 44, the first prism 41, and the third lens 53 are appropriately set based on the dimensions and shapes of the first lens 30, the second lens 44, the first prism 41, the third lens 53, and the transmissive mirror 56, so that the chromatic aberration resulting from the combination of the first lens 30, the second lens 44, the first prism 41, the polarization separation film 45, the third lens 53, and the transmissive mirror 56 can be suppressed as a whole. From this viewpoint, it is preferable that the refractive indexes of the first prism 41 and the second prism 42 are higher than the refractive indexes of the first lens 30, the second lens 44, and the third lens 53. In addition, it is preferable that the Abbe number of the first prism 41 and the second prism 42 is lower than the Abbe number of the first lens 30, the second lens 44, and the third lens 53. As an example, the Abbe numbers of the first lens 30, the second lens 44, and the third lens 53 may be 60 or more and 70 or less, and the Abbe numbers of the first prism 41 and the second prism 42 may be 18 or more and 28 or less.

[0041] Second Embodiment Hereinafter, the virtual image display device of the second embodiment will be described. Note that the virtual image display device of the second embodiment is a partial modification of the virtual image display device of the first embodiment, and the description of the parts common to the virtual image display of the first embodiment will be omitted.

[0042] The first virtual image display device 100A shown in FIG. 7 is obtained by replacing the first prism 41 and the second lens 44, which are bonded together in the first virtual image display device 100A shown in FIG. 2, with the first prism 410 integrated with the lens unit 440, and further changing the material of the first prism 410 and the second prism 42 to plastic. The first prism 410 in FIG. 7, except for the lens unit 440, has the same shape as the first prism 41 in FIG. 2. The lens unit 440 in FIG. 7 has the same shape as the second lens 44 in FIG. 2, but the refractive index and Abbe number of the lens unit 440 are equal to the refractive index and Abbe number of the first prism 410. The incident optical surface 440a of the lens unit 440 in FIG. 7 corresponds to the incident optical surface 44a of the second lens 44 in FIG. 2 and faces the first lens 30. The inclined surface 44b of the second lens 44 in FIG. 2 and the inclined surface 41a of the first prism 41 in FIG. 2 correspond to the imaginary boundary surfaces 440b, 410a, respectively, between the lens portion 440 and the portion other than the lens portion 440 of the first prism 410 in FIG. 7.

[0043] In the virtual image display device or the like of the second embodiment, the first prism 410 and the second prism 42, which are integrated with the lens unit 440, are made of plastic, which improves safety against breakage and reduces weight and cost compared to the case where they are made of optical glass. In addition, by selecting a plastic having an appropriate refractive index and Abbe number as the material of the first prism 410 and the second prism 42, the chromatic aberration of the combination of the first lens 30, the second lens 44, the first prism 41, the polarization separation film 45, the third lens 53, and the transmissive mirror 56 can be suppressed as a whole. As an example, the material of the first prism 410 and the second prism 42 may be a plastic such as EP9000, which has a refractive index of 1.67 and an Abbe number of 19.

[0044] Third Embodiment Hereinafter, the virtual image display device of the third embodiment will be described. Note that the virtual image display device of the third embodiment is a partially modified version of the virtual image display device of the first embodiment, and a description of the parts common to the virtual image display device of the first embodiment will be omitted.

[0045] In the case of the first virtual image display device 100A shown in FIG. 8, for example, an s-polarized light transmitting polarizing plate 12 is disposed between the first lens 30 and the first image forming element 11a in the first display unit 20a. However, the s-polarized light transmitting polarizing plate 12 is not essential in terms of function. Also, in the first display unit 20a, a third flat plate member 150 is added to the external side of the second flat plate member 50. The third flat plate member 150 is an image light blocking unit LP, and includes an outer ¼ wavelength plate 151 provided on the external side of the light collecting reflection unit, and a polarizing plate 59 provided on the external side of the outer ¼ wavelength plate 151 and selectively absorbing the image light ML transmitted through the outer ¼ wavelength plate 151 according to the polarization direction. That is, in the first display unit 20a, the inner ¼ wavelength plate 51 and the outer ¼ wavelength plate 151 are disposed between the inner polarization separation film 45 and the outer polarizing plate 59.

[0046] 9, the image light ML from the first image forming element 11a (see FIG. 8) contains only s-polarized light s, and the image light ML of s-polarized light s incident on the polarization separation film 45 is reflected by the polarization separation film 45 without loss, passes through the inner quarter-wave plate 51, becomes circularly polarized light c, and enters the transmissive mirror 56. The image light ML of circularly polarized light c incident on the transmissive mirror 56 is partially reflected by the transmissive mirror 56, and passes through the inner quarter-wave plate 51 again in the reverse direction. The image light ML that passes through the inner quarter-wave plate 51 in the reverse direction becomes p-polarized light p, passes through the polarization separation film 45, and enters the pupil position PP (see FIG. 8). On the other hand, the image light ML of circularly polarized light c that has passed through the transmissive mirror 56 passes through the outer quarter-wave plate 151, becomes p-polarized light p, enters the polarizing plate 59, and is almost completely blocked by the polarizing plate 59. That is, the image light ML is blocked by the third flat plate-shaped member 150 and does not leak out to the outside. That is, the image light ML can be prevented from being observed from the outside, so privacy can be ensured.

[0047] On the other hand, the outside light OL incident on the polarizing plate 59 becomes only s-polarized light s by passing through the polarizing plate 59, becomes circularly polarized light c by passing through the outer quarter-wave plate 151, and is partially transmitted through the transmissive mirror 56. The outside light OL of the circularly polarized light c that has partially transmitted through the transmissive mirror 56 becomes p-polarized light p by passing through the inner quarter-wave plate 51, transmits through the polarization separation film 45, and is incident on the pupil position PP (see FIG. 8).

[0048] Fig. 10 is a diagram illustrating a modified example of the first virtual image display device 100A shown in Fig. 8 and 9. In this case, it is assumed that the polarizing plate 59 constituting the third flat plate member 150 shown in Fig. 8 transmits s-polarized light s and reflects p-polarized light p.

[0049] 9, the image light ML of circularly polarized light c partially transmitted through the transmissive mirror 56 passes through the outer quarter-wave plate 151 and becomes p-polarized light p, and most of it is reflected by the polarizing plate 59 and does not leak out of the polarizing plate 59. The image light ML of p-polarized light p reflected by the polarizing plate 59 passes through the outer quarter-wave plate 151 again in the reverse direction. The image light ML of p-polarized light p that passes through the outer quarter-wave plate 51 becomes circularly polarized light c and is partially reflected by the transmissive mirror 56, but does not pass through the polarizing plate 59. The image light ML of circularly polarized light c that passes through the transmissive mirror 56 passes through the inner quarter-wave plate 51 again in the reverse direction. The image light ML that passes through the inner quarter-wave plate 51 becomes s-polarized light s and is reflected by the polarization separation film 45 and returned toward the first image forming element 11a.

[0050] On the other hand, the outside light OL incident on the polarizing plate 59 becomes only s-polarized light s by passing through the polarizing plate 59, becomes circularly polarized light c by passing through the outer quarter-wave plate 151, and is partially transmitted through the transmissive mirror 56. The outside light OL of circularly polarized light c that has partially transmitted through the transmissive mirror 56 becomes p-polarized light p by passing through the inner quarter-wave plate 51, transmits through the polarization separation film 45, and is incident on the pupil position PP (see FIG. 8). Note that, of the outside light OL, the p-polarized light p is reflected by the polarizing plate 59, but this does not cause any particular problem, and rather serves to prevent the surface of the first display unit 20a from becoming too dark.

[0051] [Variations and Others] The present invention has been described above based on the embodiments, but the present invention is not limited to the above embodiments and can be embodied in various forms without departing from the spirit of the present invention. For example, the following modifications are also possible.

[0052] In the above, the HMD 200 is described as comprising a first virtual image display device 100A and a second virtual image display device 100B, but the HMD 200 may also be configured to support a single first virtual image display device 100A or second virtual image display device 100B in front of the eyes by a support device 100C.

[0053] The compensation plate 55 may be omitted from the cover member 52. In this case, the quarter-wave plate 51 is disposed only in the range of the third lens 53, and the third lens 53 is covered by the compensation lens .

[0054] The first lens 30 is not limited to being bonded to the first image-forming element 11a, but may be disposed separately from the first image-forming element 11a.

[0055] The first image forming element 11a may be a scanning type display device having a laser light source and a scanner mirror.

[0056] In a specific embodiment, the virtual image display device is a direct virtual image type virtual image display device comprising: a display element that emits image light, a first lens having positive refractive power and into which the image light from the display element is incident, a second lens having positive refractive power and into which the image light that has passed through the first lens is incident, a parallel plate-shaped prism light guide member having a first prism and a second prism and guiding the image light that has passed through the second lens, a flat polarization separation film provided at the junction between the first prism and the second prism and selectively reflecting the image light guided in the first prism according to the polarization direction, a planar third lens having a flat surface arranged opposite the outer surface of the first prism onto which the image light reflected by the polarization separation film is incident, a transmissive mirror formed on the convex surface of the third lens and partially reflecting the image light reflected by the polarization separation film toward the polarization separation film, and a quarter-wave plate for image light arranged between the outer surface of the first prism and the flat surface of the third lens. The first prism has a higher refractive index than the first lens and the third lens. The virtual image display device suppresses chromatic aberration caused by the combination of the first lens, the second lens, the first prism, and the third lens as a whole.

[0057] In the virtual image display device, in order to directly form a virtual image without forming an intermediate image, the first lens, the second lens, and the transmissive mirror ensure refractive power, and the magnification can be ensured while suppressing an increase in the optical path length, thereby making it possible to avoid an increase in the size of the optical system. Furthermore, in the virtual image display device, the first prism having a high refractive index is combined with the first lens and the third lens having a low refractive index, thereby making it possible to suppress chromatic aberration.

[0058] In a specific embodiment of the virtual image display device, the Abbe number of the first prism is lower than the Abbe numbers of the first lens and the third lens. In the virtual image display device, the first prism is combined with the first lens and the third lens having different Abbe numbers, thereby suppressing chromatic aberration.

[0059] In a specific embodiment of the virtual image display device, the difference between the refractive index of the first prism and the second prism and the refractive index of the first lens is 0.17 or more, and the difference between the refractive index of the first prism and the second prism and the refractive index of the third lens is 0.17 or more.

[0060] In a specific embodiment of the virtual image display device, the first lens has a refractive index of 1.49 or less, the first prism and the second prism have a refractive index of 1.67 or more, and the third lens has a refractive index of 1.49 or less.

[0061] In a specific embodiment of a virtual image display device, the first lens and the second lens are made of quartz having a refractive index of 1.46, the first prism and the second prism are made of optical glass having a refractive index of 1.67, the third lens is made of acrylic having a refractive index of 1.49, and the second lens and the first prism are cemented together.

[0062] In a specific embodiment of the virtual image display device, the first lens is made of quartz with a refractive index of 1.46, the second lens, the first prism and the second prism are made of plastic with a refractive index of 1.67, the third lens is made of acrylic with a refractive index of 1.49, and the second lens and the first prism are integrated.

[0063] In a specific embodiment of the virtual image display device, the first lens, the prism light guide member, the polarization separation film, the second lens, the transmissive mirror, and the quarter-wave plate constitute a simple microscope-type imaging optical system that forms an erect image, and the first prism internally reflects the image light twice while diverging it. In this case, it is easy to shorten the distance from the display element to the transmissive mirror, and it is possible to reduce the size of the prism light guide member, and it is also easy to reduce the size of the display element and the first lens.

[0064] In a specific embodiment of the virtual image display device, the quarter-wave plate for the image light is disposed at a distance from the outer surface of the first prism, which makes it easy to ensure internal reflection of the image light at the outer surface of the first prism.

[0065] In a specific embodiment of the virtual image display device, the distance between the quarter-wave plate for image light and the outer surface of the first prism is 20 μm to 50 μm.

[0066] In a specific embodiment of the virtual image display device, the first lens has a flat light entrance surface that is bonded to the display element and a convex light exit surface. In this case, the first lens can function as a protective glass, and by ensuring that the thickness of the first lens is greater than or equal to a predetermined value, foreign matter attached to the surface of the first lens, i.e., the convex surface, becomes less noticeable.

[0067] In a specific embodiment of the virtual image display device, the polarization separation film reflects s-polarized image light and transmits image light that has been reflected by a transmissive mirror and returned through a quarter-wave plate and become p-polarized.

[0068] The optical unit in a specific embodiment is a direct virtual image type optical unit, and includes a first lens having a positive refractive power and on which image light from a display element that emits image light is incident, a second lens having a positive refractive power and on which the image light that has passed through the first lens is incident, a parallel plate-like prism light guide member having a first prism and a second prism and guiding the image light that has passed through the second lens, a flat polarization separation film provided at a joint between the first prism and the second prism and selectively reflecting the image light guided in the first prism according to the polarization direction, a planar convex third lens having a flat surface arranged opposite to the outer surface of the first prism on which the image light reflected by the polarization separation film is incident, a transmissive mirror formed on the convex surface of the third lens and partially reflecting the image light reflected by the polarization separation film toward the polarization separation film, and a quarter-wave plate for image light arranged between the outer surface of the first prism and the flat surface of the third lens. The refractive index of the first prism is higher than the refractive indexes of the first lens and the third lens. The optical unit suppresses chromatic aberration as a whole resulting from the combination of the first lens, the second lens, the first prism, and the third lens. [Explanation of symbols]

[0069] 11...display element, 30...first lens, 30f...light incident surface, 30g...light exit surface, 31...parallel plate, 32...lens portion, 40...first plate-like member, 41...first prism, 41a...inclined surface, 41b...inner surface, 41c...outer surface, 41d...inclined surface, 410a...virtual boundary surface, 42...second prism, 42b...inner surface, 42c...outer surface, 42d...inclined surface, 44...second lens, 44a...incident optical surface, 44b...inclined surface, 440...lens portion, 440a...incident optical surface, 440b...virtual boundary surface, 45...polarized light separation film, 48...prism light guide member, 50...second plate-like member, 50c...inner surface, 51...inner quarter wave plate, 151...outer quarter wave plate, 52...cover member, 53...first 2 lenses, 53f... plane, 53g... convex surface, 54... compensation lens, 54f... concave surface, 54g... plane, 55... compensation plate, 56... transmissive mirror, 58... optical element, 59... polarizing plate, 61... spacer, 71... case, 90... user terminal, 100... optical unit, 100A, 100B... virtual image display device, 100C... support device, 102a, 102b... display drive unit, 103a, 103b... combiner, AX... optical axis, B0 to B3... wavelength components, CR... light collecting and reflecting unit, CT... adhesive, EP... exit pupil, EY... eye, IF... image frame, IS... imaging optical system, LP... image light blocking unit, ML... image light, OL... outside light, PP... pupil position, R0 to R3... wavelength components, SP... gap, US... wearer

Claims

1. A direct virtual image type virtual image display device, A display element that emits image light; a first lens having a positive refractive power and on which the image light from the display element is incident; a second lens having a positive refractive power and on which the image light having passed through the first lens is incident; a parallel-plate-shaped prism light-guiding member having a first prism and a second prism, and guiding the image light that has passed through the second lens; a flat polarization separation film provided at a joint between the first prism and the second prism, the flat polarization separation film selectively reflecting the image light guided through the first prism in accordance with a polarization direction; a plano-convex third lens having a flat surface arranged to face an outer surface of the first prism onto which the image light reflected by the polarization separation film is incident; a transmissive mirror formed on a convex surface of the third lens and configured to partially reflect the image light reflected by the polarization separation film toward the polarization separation film; a quarter-wave plate for the image light disposed between the outer surface of the first prism and a plane of the third lens; Equipped with The refractive index of the first prism is higher than the refractive indexes of the first lens and the third lens, suppressing chromatic aberration of the first lens, the second lens, the first prism, and the third lens combined as a whole; Virtual image display device.

2. The Abbe number of the first prism is lower than the Abbe numbers of the first lens and the third lens. The virtual image display device according to claim 1 .

3. a difference between a refractive index of the first prism and a refractive index of the second prism and a refractive index of the first lens is 0.17 or more; a difference between a refractive index of the first prism and the second prism and a refractive index of the third lens is 0.17 or more; The virtual image display device according to claim 1 .

4. The refractive index of the first lens is 1.49 or less, The first prism and the second prism have a refractive index of 1.67 or more, The refractive index of the third lens is 1.49 or less. The virtual image display device according to claim 1 .

5. The first lens and the second lens are made of quartz having a refractive index of 1.46, the first prism and the second prism are made of optical glass having a refractive index of 1.67, The third lens is made of acrylic having a refractive index of 1.

49. The second lens and the first prism are cemented together. The virtual image display device according to claim 1 .

6. The first lens is made of quartz having a refractive index of 1.46, the second lens, the first prism, and the second prism are made of plastic having a refractive index of 1.67; The third lens is made of acrylic having a refractive index of 1.

49. The second lens and the first prism are integrated together. The virtual image display device according to claim 1 .

7. the first lens, the prism light guiding member, the polarization separation film, the third lens, the transmissive mirror, and the quarter-wave plate constitute a simple microscope-type imaging optical system that forms an erect image, The virtual image display device according to claim 1 , wherein the first prism internally reflects the image light twice while diverging the image light.

8. The virtual image display device according to claim 1 , wherein the quarter-wave plate for the image light is disposed away from the outer surface of the first prism.

9. 9. The virtual image display device according to claim 8, wherein a distance between the quarter-wave plate for image light and the outer surface of the first prism is 20 μm to 50 μm.

10. The virtual image display device according to claim 1 , wherein the first lens has a flat light entrance surface bonded to the display element and a convex light exit surface.

11. 2. The virtual image display device according to claim 1, wherein the polarization separation film reflects the image light that is s-polarized and transmits the image light that has been reflected by the transmissive mirror and passed back through the quarter-wave plate and become p-polarized.

12. A direct virtual image type optical unit, a first lens having a positive refractive power and on which image light from a display element that emits image light is incident; a second lens having a positive refractive power and on which the image light having passed through the first lens is incident; a parallel-plate-shaped prism light-guiding member having a first prism and a second prism, and guiding the image light that has passed through the second lens; a flat polarization separation film provided at a joint between the first prism and the second prism, the flat polarization separation film selectively reflecting the image light guided through the first prism in accordance with a polarization direction; a plano-convex third lens having a flat surface arranged to face an outer surface of the first prism onto which the image light reflected by the polarization separation film is incident; a transmissive mirror formed on a convex surface of the third lens and configured to partially reflect the image light reflected by the polarization separation film toward the polarization separation film; a quarter-wave plate for the image light disposed between the outer surface of the first prism and a plane of the third lens; Equipped with The refractive index of the first prism is higher than the refractive indexes of the first lens and the third lens, suppressing chromatic aberration of the first lens, the second lens, the first prism, and the third lens combined as a whole; Optical unit.

Images