Virtual Image Display

Abstract

To provide a virtual image display device that prevents the occurrence of a difference in refractive index characteristics and reduces color irregularity even when a difference in film thickness occurs in a reflection coating to allow satisfactory image formation.SOLUTION: A virtual image display device comprises: video light emission devices 102a, 102b that emit video light ML; and a see-through mirror 23 as an optical member that has a reflection coating 23m reflecting the video light ML. The see-through mirror 23 has a first area D1 on which a light beam MLc at a central angle of view of the video light ML is incident, and second areas D2 on which light beams MLp1, MLp2 of the video light ML are incident, the light beams being different from the light beam MLc at the central angle of view. A film thickness d in the first area D1 of the reflection coating 23m is larger than a film thickness d' in the second areas D2. The first area D1 of the reflection coating 23m has refractive index characteristics corresponding to a wavelength band wider on a long-wavelength side than the wavelength band of the video light ML emitted from video light emission devices 102a, 102b.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a virtual image display device that enables observation of a virtual image and is used, for example, as a head-mounted display. [Background technology]

[0002] A known image display device has a curved combiner that is composed of a semi-transparent concave mirror and transmits part of the incident light beam and reflects the rest, and the light beam of the image is reflected by the curved combiner, allowing the user to observe a virtual image (see Patent Document 1). In this case, part of the light incident from the outside world is transmitted through the curved combiner. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-159038 A Summary of the Invention [Problem to be solved by the invention]

[0004] In order to manufacture something like the curved surface combiner in the image display device of Patent Document 1, for example, if an attempt is made to form a film on a curved surface that has the property of transmitting part of the incident light beam and reflecting the remainder, a difference in film thickness will occur between the center and peripheral sides of the curved surface during film formation, making it impossible to obtain the desired reflection / transmission characteristics, and as a result, it may not be possible to form a good image. [Means for solving the problem]

[0005] A virtual image display device according to one aspect of the present invention comprises an image light emission device that emits image light, and an optical element having a reflective film that reflects the image light, the optical element having a first region into which light rays that form a central angle of view of the image light are incident, and a second region into which light rays other than the light rays that form the central angle of view of the image light are incident, the film thickness of the reflective film in the first region being thicker than the film thickness in the second region, and the first region of the reflective film having reflectance characteristics corresponding to a wavelength band that is wider on the longer wavelength side than the wavelength band of the image light emitted from the image light emission device. [Brief description of the drawings]

[0006] [Figure 1] FIG. 1 is an external perspective view illustrating an example of an image display device according to a first embodiment. [Diagram 2] 1 is a conceptual side cross-sectional view illustrating an internal optical system of an image display device. [Diagram 3] FIG. 2 is an external perspective view illustrating an example of a combiner (see-through mirror). [Figure 4] FIG. 13 is a conceptual diagram illustrating an example of the formation of a reflective film in a combiner. [Diagram 5] 11 is a graph for explaining an example of the reflectance characteristics of the reflective film in a first region. [Figure 6] 10 is a graph for explaining an example of the reflectance characteristics of the reflective film in a second region. [Figure 7] 11 is a graph for explaining the reflectance characteristics of a reflective film in a conventional example. [Figure 8] 11 is a conceptual graph for comparing the reflectance characteristics of a reflective film of a conventional example with the reflectance characteristics of the reflective film of the first embodiment. [Figure 9] 13 is a graph for explaining an example of the reflectance characteristics of a reflective film in a second region as an example of an image display device according to a second embodiment. [Figure 10] 13 is a graph for explaining another example of the reflectance characteristics of the reflective film in the second region. [Figure 11] 11 is a graph for explaining an example of the reflectance characteristics of the reflective film in a first region. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] [First embodiment] Hereinafter, with reference to FIG. 1 etc., a structure, operation, etc. of an image display device as a virtual image display device according to the present invention will be described.

[0008] FIG. 1 is a diagram for explaining a wearing state of the image display device 100. The image display device 100 is a head-mounted display, and allows an observer or wearer US wearing the image display device to recognize an image as a virtual image. In FIG. 1 and the like, X, Y, and Z are an orthogonal coordinate system, and the +X direction corresponds to the lateral direction in which the eyes EY of the observer or wearer US wearing the image display device 100 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.

[0009] The image display device 100 includes a main body 200a arranged to cover the front of the eyes of the wearer US, and a pair of temple-shaped support devices 200b that support the main body 200a. From a functional perspective, the main body 200a includes a first display device 100A for the right eye and a second display device 100B for the left eye. The first display device 100A is composed of an image light emitting device 102a arranged at the top and a combiner 103a in the shape of a glasses lens that covers the front of the eyes. Similarly, the second display device 100B is composed of an image light emitting device 102b arranged at the top and a combiner 103b in the shape of a glasses lens that covers the front of the eyes.

[0010] With reference to Fig. 2, among the components of the image display device 100, particularly those having optical functions will be described. Of the left-right symmetric first display device 100A and second display device 100B (see Fig. 1) that constitute the image display device 100, the example of Fig. 2 shows the first display device 100A as a representative. Here, with reference to the side cross-sectional view shown in Fig. 2, the optical structure of the first display device 100A will be described. Note that the second display device 100B (see Fig. 1) for the left eye is similar to the first display device 100A, so a detailed description thereof will be omitted.

[0011] As shown in FIG. 2, the first display device 100A for the right eye includes a display element 11a and an imaging optical system 20 as a part having an optical function (optical unit).

[0012] The imaging optical system 20 is also called a light guide optical device. The imaging optical system 20 includes a projection lens 21, a prism mirror 22, a plate-shaped optical element 28, and a see-through mirror 23, which are projection optical systems. For example, the display element 11a, the projection lens 21, the prism mirror 22, and the plate-shaped optical element 28 correspond to the image light emitting device 102a in FIG. 1, and the see-through mirror 23 corresponds to the first combiner 103a in FIG. 1. That is, the image light emitting device 102a emits image light ML, which is image light, to the first combiner 103a. The first combiner 103a also reflects a part of the image light ML emitted from the image light emitting device 102a and incident thereon to form an exit pupil.

[0013] The display element 11a is, for example, an OLED (Organic Light Emitting Diode) display, that is, an organic EL (Organic Electro-Luminescence) display. Here, as an example, the display element 11a is configured with an OLED display, and emits unpolarized light as image light ML from the display surface 11d, that is, the display element 11a forms a color still image or moving image on the two-dimensional display surface 11d. The display element 11a is arranged along an xy plane that is rotated around the X axis and tilted with respect to the XY plane. The display element 11a performs a display operation by being driven by a control device (not shown) provided on a circuit board. The display element 11a is not limited to an OLED display (organic EL display), and can be replaced with a micro LED display, or a display device using an inorganic EL, a laser array, a quantum dot light-emitting element, or the like.

[0014] The display element 11a and the projection lens 21 and prism mirror 22 of the imaging optical system 20 are fixed to the first frame 61a in a state where they are mutually aligned by a frame body (not shown), and are housed in a space SP1 sandwiched between the first cover member 71a and the first frame 61a. The plate-shaped optical element 28 is disposed so as to be fitted into a step formed in the optical opening of the first frame 61a, and the periphery of the optical opening is kept in an airtight state.

[0015] The projection lens 21 passes the image light ML emitted from the display element 11a and makes it enter the prism mirror 22. The projection lens 21 condenses the image light ML emitted from the display element 11a into a state close to a parallel light beam. The projection lens 21 includes a first lens 21p and a second lens 21q. The prism mirror 22 has an internal reflection surface 22b, and makes the image light ML emitted from the projection lens 21 enter the inside from the entrance surface 22a, totally reflects it at the internal reflection surface 22b, and emits it to the outside from the exit surface 22c. At this time, the prism mirror 22 emits the image light ML incident from the front so as to be folded back in a direction inclined with respect to a direction in which the incident direction is reversed (the direction of the light source as seen from the prism mirror 22). The plate-shaped optical element 28 refracts and passes the image light ML emitted from the exit surface 22c of the prism mirror 22, and the see-through mirror 23 reflects the image light ML emitted from the prism mirror 22 toward a pupil position PP (the position of the exit pupil). The pupil position PP is a position where the image light ML from each point on the display surface 11d is incident in a predetermined divergent or parallel state so as to be superimposed from an angular direction corresponding to the position of each point on the display surface 11d.

[0016] The see-through mirror 23 is a reflective optical member having a curved surface shape, and has a reflective film 23m that reflects the image light ML. More specifically, the see-through mirror 23 is a curved plate-like optical member that functions as a concave surface mirror, and reflects the image light ML incident from the prism mirror 22 through the plate-like optical element 28 toward the pupil position PP by the reflective film 23m. The see-through mirror 23 covers the pupil position PP where the exit pupil position, i.e., the eye EY or the pupil, is located, and has a concave shape toward the pupil position PP and a convex shape toward the outside world. The see-through mirror 23 is a mirror plate having a structure in which the reflective film 23m is formed on the surface of the plate-like body 23b. The reflective film 23m that forms the reflective surface 23a of the see-through mirror 23 has transparency. Outside light OL that has passed through the see-through mirror 23 is also incident on the pupil position PP. As described above, the reflective film 23m has partial transparency, and the see-through mirror 23, which is an optical member, is a combiner 103a that folds back part of the image light ML emitted from the image light emitting device 102 at the reflective film 23m and transmits part of the outside light OL, thereby enabling so-called see-through viewing. In other words, the wearer US wearing the image display device 100 can observe a virtual image produced by the image light ML superimposed on an outside world image.

[0017] In the above, the optical surfaces constituting the projection lens 21, the prism mirror 22, the plate-like optical element 28, and the see-through mirror 23 include free-form surfaces, and at least some of the optical surfaces can be replaced with aspherical or spherical surfaces.

[0018] The imaging optical system 20 is an off-axis optical system OS due to the see-through mirror 23 being a concave mirror, etc. In the present embodiment, the projection lens 21, the prism mirror 22, the plate-shaped optical element 28, and the see-through mirror 23 are arranged non-axisymmetrically and have a non-axisymmetric optical surface. In this imaging optical system 20, that is, the off-axis optical system OS, the optical axis AX is bent so that the optical axis AX extends along an off-axis plane (a plane parallel to the YZ plane) corresponding to the paper surface. In this imaging optical system 20, the optical axis AX is bent within the off-axis plane parallel to the YZ plane, so that the optical elements 21, 22, and 23 are arranged along the off-axis plane. The imaging optical system 20 includes optical axis portions AX1, AX2, and AX3 that are arranged along an off-axis plane (a plane parallel to the YZ plane) that is a reference plane extending in the vertical direction and are inclined to each other before and after the reflecting surface. The optical axis AX as a whole extends along the optical path of the chief ray emitted from the center of the display element 11a and passes through the eye ring ER corresponding to the eye point or the center of the pupil. When viewed in a cross section parallel to the YZ plane, the optical axis AX is arranged in a Z-shape with multiple optical axis portions AX1, AX2, and AX3. In other words, on an off-axis plane parallel to the YZ plane, the optical path P1 from the projection lens 21 to the internal reflection surface 22b, the optical path P2 from the internal reflection surface 22b to the see-through mirror 23, and the optical path P3 from the see-through mirror 23 to the pupil position PP are folded back in two stages in a Z-shape.

[0019] In the above configuration, the light ray (central light ray) of the image light ML that forms the central angle of view is defined as light ray MLc, the light ray (peripheral light ray) different from the light ray that forms the central angle of view that forms an upper side of the angle of view is defined as light ray MLp1, and the light ray (peripheral light ray) different from the light ray that forms the central angle of view that forms a lower side of the angle of view is defined as light ray MLp2. That is, the component emitted from a point that is a central position or a point that is approximately a central position of the display surface 11d of the display element 11a is defined as light ray MLc, and the optical axis corresponding to light ray MLc is defined as optical axis portion AXc. The component emitted from a peripheral point above the central position of the display surface 11d is defined as light ray MLp1, and the optical axis corresponding to light ray MLp1 is defined as optical axis portion AXp1. Also, the component emitted from a peripheral point below the central position is defined as light ray MLp2, and the optical axis corresponding to light ray MLp2 is defined as optical axis portion AXp2. In the figure, the principal rays are shown as rays MLc, MLp1, and MLp2 to represent the respective components. Therefore, the optical axis portions AXc, AXp1, and AXp2 coincide (or nearly coincide) with the rays MLc, MLp1, and MLp2 in the figure.

[0020] 2 and 3, in the see-through mirror 23, which is an optical member, the range into which the light MLc is incident is defined as the first region D1, and the range into which the light MLp1 and MLp2 are incident is defined as the second region D2. That is, in the image (virtual image) to be viewed, the range through which the component light corresponding to the central angle of view passes is the optical axis AX and its vicinity shown in FIG. 2, i.e., the first region D1 on the central side, and the peripheral side of the first region D1 is the second region D2. That is, the see-through mirror 23 having a curved surface shape forms an exit pupil at the pupil position PP by the component reflected in the first region D1 and the component reflected in the second region D2.

[0021] 2, the film thickness d in the first region D1 of the reflective film 23m is thicker than the film thickness d' in the second region D2. In other words, there is a relationship of d>d'. Such a difference in film thickness is due to the shape of the see-through mirror 23, i.e., the combiner 103a, and the deposition of the reflective film 23m.

[0022] As a method for forming the reflective film 23m, that is, a method for manufacturing the see-through mirror 23 (combiner 103a), various techniques are conceivable. For example, a dielectric multilayer film can be formed by vacuum deposition.

[0023] 4, an example of the formation of the reflective film 23m in the see-through mirror 23 will be described below. As shown in the figure, first, the substrate MM (corresponding to the plate-shaped body 23b) to become the see-through mirror 23 is fixed in a vacuum chamber CC by a jig or the like (not shown), and a film-forming material (evaporation source) DS is evaporated in the vacuum chamber CC and adhered to the surface (interface) SS of the substrate MM to form a thin film, thereby providing the reflective film 23m and forming the see-through mirror 23.

[0024] When the see-through mirror 23 is manufactured as described above, the thickness of the reflective film 23m is likely to vary between the center and periphery of the portion that is to become the reflective film 23m due to the relationship of the angle between the deposition source DS and the surface SS of the substrate MM. Specifically, in the central portion CP facing the deposition source DS that evaporates in the direction indicated by the arrow DD1, and the peripheral portion EP that is angled with respect to the arrow DD1 compared to the central portion CP, as shown in a partially enlarged view in the figure, the thickness of the deposit SE that is to become the reflective film 23m is thicker in the central portion CP than in the peripheral portion EP (the peripheral portion EP is thinner than the central portion CP). Here, it is assumed that the attitude of the substrate MM is adjusted so that the central portion CP corresponds to the first region D1 and the peripheral portion EP corresponds to the second region D2. In this case, with respect to the central portion CP (corresponding to the first region D1), the directional axis LL that is normal to the central portion CP indicated by the dashed line is parallel to the direction indicated by the arrow DD1. Here, when the central portion CP faces the deposition source DS and is not inclined, if the angle between the normal to the peripheral portion EP (corresponding to the second region D2) and the directional axis LL that is the normal to the central portion CP is defined as angle θ, a film thickness difference according to the angle θ occurs between the central portion CP and the peripheral portion EP. Expressed numerically, after the deposition of the reflective film 23m, in the see-through mirror 23 that is produced, if the film thickness of the reflective film 23m in the first region D1 is d, the film thickness of the reflective film 23m in the second region D2 is d', and the inclination angle of the second region D2 with respect to the first region D1 is angle θ as described above, then the following relational expression (1) d' = dcosθ…(1) It is designed to satisfy the following requirements.

[0025] Here, if the thickness of the reflective film 23m becomes thinner than expected, the reflectance characteristics of the reflective film 23m at that location will shift to the shorter wavelength side than the expected wavelength band according to the amount of the thinner film. Therefore, for example, if the thickness d of the reflective film 23m formed as described above in the first region D1 is as expected, while the thickness d' in the second region D2 is thinner than expected, the reflectance characteristics in the second region D2 will shift to the shorter wavelength side than expected. As a result, there is a risk that the reflectance characteristics in the second region D2 will not be the desired reflectance characteristics on the long wavelength side of the wavelength band of the image light ML. To avoid such a situation, in the image display device 100 according to the present embodiment, the reflective film 23m is formed in the see-through mirror 23 so as to have reflectance characteristics corresponding to longer wavelengths than the wavelength band of the image light ML, so that even if a portion of the reflective film 23m that is thinner than expected occurs and the reflectance characteristics at that portion shift to the shorter wavelength side than expected, the desired reflectance characteristics can be obtained for the wavelength band of the image light ML even at that portion. That is, even if a difference (film thickness difference) occurs between the film thickness d in the first region D1 and the film thickness d' in the second region D2 in the reflective film 23m, the occurrence of a difference in the reflectance characteristics due to the film thickness difference is suppressed, and color unevenness in the reflection of the image light ML by the reflective film 23m is reduced, enabling good image formation.

[0026] 4, if the angle between the normal of the peripheral portion EP corresponding to the second region D2 and the directional axis LL that is the normal of the central portion CP is about θ=30° (tilt angle θ=0°), the difference in film thickness with respect to the central portion CP corresponding to the first region D1 is assumed to be about 0.87 times the film thickness d from the above formula (1). In this case, by previously setting the wavelength band in which the reflectance characteristics are maintained when the assumed film thickness is formed to be about 13% wider on the long wavelength side than the wavelength band of the image light ML, it is possible to obtain the desired reflectance characteristics not only in the first region D1 but also in the second region D2.

[0027] In the above, in the figures, the inclination angle θ is the angle at the surface (interface) SS of the substrate MM, i.e., the deposition surface, but this is not limited to the above. For example, if the substrate MM (plate-like body 23b) has a substantially uniform thickness, it is also possible to use the angle θ' at the surface SSa of the substrate MM (plate-like body 23b) facing the outside world as the basis for measuring the angle, as shown in the figures.

[0028] The following Table 1 is a data table showing a specific example of the reflective film 23m made of a dielectric multilayer film. [Table 1]

[0029] As shown in Table 1, in this example, the reflective film 23m is formed of a dielectric multilayer film having an 11-layer structure composed of a combination of SiO2-TiO2.

[0030] A specific example according to this embodiment will be described below with reference to Fig. 5 and other figures. Fig. 5 is a graph for explaining an example of the reflectance characteristics of the reflective film 23m in the first region D1. That is, Fig. 5 shows the reflectance characteristics when the reflective film 23m is formed to have a film thickness shown in Table 1. In the figure, the horizontal axis indicates the wavelength band of light (unit: nm), and the vertical axis indicates the reflectance of light (unit: %).

[0031] First, the curve RR1 indicates the wavelength characteristic (spectrum of the light source) of the light source (here, an OLED is used). That is, the curve RR1 corresponds to the wavelength band of the image light ML emitted from the image light emitting device 102a. In this case, the long wavelength side of the wavelength band of the image light ML is used up to about 650 nm. That is, in this case, it is required that the reflectance characteristic of the reflective film 23m is maintained in a desired state up to about 650 nm.

[0032] In contrast to the above, the curves Q1 to Q5 in the figure show the reflection characteristics for each incident angle of light to the reflective film 23m. Specifically, for example, the curve Q1 is a curve showing the reflectance for each wavelength of a component incident on the first region D1 of the reflective film 23m at an incident angle of 20°. Similarly, the curve Q2 shows the reflection characteristics at an incident angle of 25°, the curve Q3 shows the reflection characteristics at an incident angle of 30°, the curve Q4 shows the reflection characteristics at an incident angle of 35°, and the curve Q5 shows the reflection characteristics at an incident angle of 40°. That is, the entire WW1 of the curves Q1 to Q5 shows the reflection characteristics (reflectance characteristics) of the reflective film 23m for light incident at an incident angle range of 20° to 40°. Note that, assuming that the image light ML is incident on the first region D1 at a certain angle range, the curves are made to correspond to light having the above-mentioned angle range. In addition, here, it is assumed that the reflectance of the reflective film 23m is maintained at about 50% so that the see-through mirror 23 functions as a half mirror.

[0033] In the above case, the curves Q1 to Q5 satisfy the necessary requirements if they have a reflectance of about 50% up to about 650 nm on the long wavelength side of the wavelength band of the image light ML. However, as will be described later with reference to FIG. 6, taking into consideration that the film thickness of the reflective film 23m in the second region D2 is not necessarily as shown in Table 1 above, the curves Q1 to Q5 maintain a reflectance of about 50% in a wide range (for example, up to about 780 nm) on the long wavelength side from 650 nm. As described above, the reflectance characteristics in the first region D1 of the reflective film 23m correspond to a wavelength band (up to 780 nm or more) that is 1.2 times wider on the long wavelength side than the usage wavelength band of the image light ML emitted from the image light emission device 102a (up to about 650 nm).

[0034] Fig. 6 is a graph for explaining an example of the reflectance characteristics of the reflective film 23m in the second region D2. That is, Fig. 6 shows the reflectance characteristics of the reflective film 23m whose thickness is thinner than that shown in Table 1 when the reflective film 23m is formed. More specifically, this example shows the reflectance characteristics when the thickness of the reflective film 23m is 20% thinner than that shown in Table 1 or Fig. 5. In the figure, the horizontal axis indicates the wavelength band of light (unit: nm), and the vertical axis indicates the reflectance of light (unit: %).

[0035] Curves S1 to S5 in the figure indicate the reflection characteristics for each angle of incidence of light on the reflective film 23m. Specifically, for example, curve S1 is a curve that indicates the reflectance for each wavelength of a component that is incident on the second region D2 of the reflective film 23m at an incident angle of 20°. Similarly, curve S2 indicates the reflection characteristics at an incident angle of 25°, curve S3 at an incident angle of 30°, curve S4 at an incident angle of 35°, and curve S5 at an incident angle of 40°. That is, the entire WW2 of curves S1 to S5 indicates the reflection characteristics (reflectance characteristics) of the reflective film 23m for light that is incident at an incident angle range of 20° to 40°.

[0036] In this case, the curves S1 to S5 satisfy the necessary requirements up to about 650 nm on the long wavelength side of the wavelength band of the image light ML. That is, the reflectance of the reflective film 23m is maintained at about 50%, and the see-through mirror 23 can function as a half mirror. In the case shown in FIG. 6, since the film thickness of the reflective film 23m is thinner than expected (film thickness shown in Table 1), it can be seen that the range in which the reflectance of 50% is maintained, that is, the range in which the reflectance characteristics are maintained, is shifted overall to the short wavelength side when the entire WW2 of the curves S1 to S5 is compared with the entire WW1 of the curves Q1 to Q5 in FIG. 5. However, as described above, the reflectance characteristics (reflectance characteristics) at the film thicknesses shown in Table 1 are set to correspond to a wavelength band wider than the wavelength band of the image light ML emitted from the image light emitting device 102a (for example, 650 nm on the long wavelength side) (for example, the reflectance is maintained up to about 750 nm). As a result, even if there is a region such as the second region D2 in which the thickness of the reflective film 23m is thin and the reflective characteristics (reflectance characteristics) are shifted to the short wavelength side, the reflective characteristics (reflectance characteristics) in the wavelength band required for reflecting the image light ML (for example, 650 nm on the long wavelength side) can be maintained, and image degradation can be suppressed and maintained in a good condition.

[0037] Hereinafter, a conventional example of this embodiment will be considered with reference to FIG. 7 and the like. In the reflective film 23m having the characteristics illustrated in the graph of FIG. 7 as a conventional example, there is a possibility that color unevenness will occur when a film thickness difference occurs. Specifically, in the graph of FIG. 7, the entire WW1 of the curves Q1 to Q5 and the entire WW2 of the curves S1 to S5 indicate the reflection characteristics for each angle of incidence of light to the reflective film 23m, similar to the cases of FIG. 5 and FIG. 6. That is, in the figure, the horizontal axis indicates the wavelength band of light (unit: nm), the vertical axis indicates the reflectance (unit: %) as the spectral characteristic (reflection characteristic) of light, the entire WW1 indicates the reflection characteristics (reflectance characteristics) at an assumed film thickness, and the entire WW2 indicates the reflection characteristics (reflectance characteristics) when the film thickness is 20% thinner than the assumed film thickness.

[0038] In the above case, in the whole WW1, for example, the reflectance is maintained at about 50% up to about 650 nm, but in the whole WW2, a shift occurs to the short wavelength side, and the reflectance is maintained only up to about 600 nm. In this case, there is a risk that the reflection will decrease on the long wavelength side, i.e., in the red wavelength band, causing color unevenness and ultimately causing image degradation.

[0039] Fig. 8 is a conceptual graph for comparing the reflectance characteristics of the reflective film of the conventional example shown in Fig. 7 with the reflectance characteristics of the reflective film of this embodiment. In the figure, the horizontal axis indicates the wavelength band of light (unit: nm), and the vertical axis indicates the reflectance (unit: %) as the spectral characteristic (reflection characteristic) of light. For example, this corresponds to something like an average value of those exemplified in Figs. 5 to 7.

[0040] In FIG. 8, the graph of the region AR1 shows the reflectance characteristics of the reflective film of the conventional example, and the graph of the region AR2 shows the reflectance characteristics of the reflective film 23m of this embodiment. The curve C1 shown by the solid line in the figure shows the spectral characteristics of light in the assumed film thickness as in the first region D1, and the curve C2 shown by the dashed line in the figure shows the spectral characteristics of light in the film thickness thinner than the assumed film thickness as in the second region D2. In addition, the wavelength band used as the image light ML is shown as the hatched range XX. As shown in the region AR1 and as described with reference to FIG. 7, in the conventional example, the curve C1 maintains the desired spectral characteristics (reflection characteristics) in the range XX, but does not maintain them in a wider range. Therefore, the curve C2, which shifts the spectral characteristics (reflection characteristics) to the short wavelength side, cannot be maintained on the long wavelength side of the range XX. In contrast to this, in this embodiment, as shown in area AR2, by maintaining the desired spectral characteristics (reflection characteristics) in a wider range on the longer wavelength side than the range XX, even if a shift occurs, the desired spectral characteristics (reflection characteristics) are maintained in the range XX in both the curve C1 and the curve C2.

[0041] As described above, the image display device 100 as a virtual image display device in this embodiment includes an image light emission device 102a (image light emission device 102b) that emits image light ML, and a see-through mirror 23 (combiners 103a, 103b) as an optical element having a reflective film 23m that reflects the image light ML, and the see-through mirror 23 has a first region D1 into which a light ray MLc that forms the central angle of view of the image light ML is incident, and a second region D2 into which light rays MLp1, MLp2 different from the light ray MLc that forms the central angle of view of the image light ML are incident, and the film thickness d of the reflective film 23m in the first region D1 is thicker than the film thickness d' in the second region D2, and the reflective film 23m has reflectance characteristics corresponding to a wavelength band wider than the wavelength band of the image light ML emitted from the image light emission device 102a. In this case, the first region D1 of the reflective film 23m has reflectance characteristics corresponding to a wavelength band that is wider on the longer wavelength side than the wavelength band of the image light ML emitted from the image light emission device 102a, so that even if there is a difference (film thickness difference) between the film thickness d in the first region D1 and the film thickness d' in the second region D2, the difference in reflectance characteristics caused by the film thickness difference can be suppressed, and color unevenness in the reflection of the image light ML by the reflective film 23m can be reduced, making it possible to form a good image.

[0042] Second Embodiment Hereinafter, an image display device as a virtual image display device according to the second embodiment will be described with reference to Fig. 9 etc. Note that the image display device as an example of the image display device according to this embodiment is a partially modified version of the image display device 100 of the first embodiment, and other configurations are similar except for the configuration of the dielectric multilayer film constituting the reflective film 23m. Therefore, detailed illustrations and explanations will be omitted for components with the same reference numerals as in other drawings in the overall configuration, and matters explained with reference to other drawings will be used as necessary.

[0043] The following Table 2 is a data table showing an example of the reflective film 23m formed of a dielectric multilayer film in this embodiment. [Table 2]

[0044] As shown in Table 2, in this example, the reflective film 23m is formed of a 13-layer dielectric multilayer film made of a combination of SiO2-TiO2.

[0045] 9 and 10 are graphs for explaining an example of the reflectance characteristics of the reflective film 23m in the second region D2 of the see-through mirror 23 in the image display device 100 according to this embodiment, and correspond to FIG. 6. FIG. 9 shows the reflectance characteristics in the case where the film thickness of the reflective film 23m is 30% thinner than that shown in Table 2 as an example of the second region D2, and FIG. 10 shows the reflectance characteristics in the case where the film thickness of the reflective film 23m is 20% thinner as another example of the second region D2. That is, FIG. 9 shows a portion of the second region D2 where the angle θ (see FIG. 4) with respect to the first region D1 is larger, while FIG. 10 shows a portion of the second region D2 where the angle θ (see FIG. 4) is smaller than that in FIG. 9.

[0046] 11 is a graph for explaining an example of the reflectance characteristics of the reflective film 23m in the first region D1 of the see-through mirror 23, and corresponds to FIG. 5. That is, it shows the reflectance characteristics when the film has the thickness shown in Table 2 above.

[0047] In each figure, the horizontal axis indicates the wavelength band of light (unit: nm), and the vertical axis indicates the reflectance of light (unit: %).

[0048] In Fig. 9, the curves R1 to R5 are the same as those in the other figures. That is, the curve R1 is a curve showing the reflectance for each wavelength of the component incident on the second region D2 of the reflective film 23m at an incident angle of 20°, and similarly, the curve R2 shows the reflection characteristic at an incident angle of 25°, the curve R3 shows the reflection characteristic at an incident angle of 30°, the curve R4 shows the reflection characteristic at an incident angle of 35°, and the curve R5 shows the reflection characteristic at an incident angle of 40° as the whole WW3, showing the reflection characteristic (reflectance characteristic) in the reflective film 23m for the light incident at an incident angle range of 20° to 40°. Note that the curves S1 to S5 in Fig. 10 and the curves Q1 to Q5 in Fig. 11 are the same as those in Figs. 6 and 5, and therefore the description thereof will be omitted.

[0049] In this embodiment, as shown in FIG. 9, even if the thickness of the reflective film 23m becomes thinner and an area in which the reflective characteristics (reflectance characteristics) are shifted to the shorter wavelength side occurs, the reflective characteristics (reflectance characteristics) can be maintained in a wavelength band (for example, 650 nm on the long wavelength side) required for reflection of the image light ML, and thus image degradation can be suppressed and maintained favorably. In addition, in this embodiment, as shown in FIG. 10, even if the thickness of the reflective film 23m becomes thinner to some extent and an area in which the reflective characteristics (reflectance characteristics) are shifted to the shorter wavelength side to some extent occurs, the reflective characteristics (reflectance characteristics) are maintained. In the example shown in FIG. 10, the reflective characteristics (reflectance characteristics) are maintained in a range wider than 650 nm on the long wavelength side (for example, up to about 750 nm). Furthermore, as shown in FIG. 11, the reflective film 23m maintains the reflective characteristics (reflectance characteristics) up to about 900 nm in the first area D1. That is, the reflective film 23m has reflectance characteristics corresponding to wavelength components up to 900 nm in the first region D1.

[0050] In the present embodiment, the reflective film 23m has reflectance characteristics corresponding to a wavelength band wider than the wavelength band of the image light ML emitted from the image light emission devices 102a and 102b, thereby suppressing differences in reflectance characteristics caused by film thickness differences in the reflective film 23m and reducing color unevenness in the reflection of the image light ML by the reflective film 23m, thereby enabling good image formation. In particular, in the present embodiment, the first region D1 has reflectance characteristics corresponding to wavelength components up to 900 nm, so that good image formation is maintained even if the film thickness of the reflective film 23m is 30% thinner than expected (for example, the angle θ is about 50°).

[0051] [Variations and Others] The present invention has been described above with reference to each embodiment, 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 invention. For example, the following modifications are also possible.

[0052] In the above, the shape of the see-through mirror 23 (combiners 103a, 103b) which is an optical member having a reflective film 23m is an off-axis optical system, and the optical surface may include a free curved surface, or at least a part of the optical surface may be replaced with an aspheric surface or a spherical surface. Therefore, various shapes, i.e., angles θ, of the first region D1 and the second region D2 are possible. In this case, the film thickness difference that occurs is not uniform, but differs from place to place according to the curved surface shape. However, the present invention is not limited to such a mode, and can be applied to an optical member whose overall shape is spherical, for example.

[0053] In addition, in the above, a vacuum deposition method was shown as an example of forming the reflective film 23m, but the present invention can also be applied to various methods such as sputtering, depending on the resulting film thickness difference.

[0054] In addition, in the above, the reflective film 23m is formed of a dielectric multilayer film, but the present invention is not limited to this, and it is also possible to form the reflective film 23m by, for example, interposing a metal film between the dielectric multilayer film. Depending on the expected range of angles of incident light, the dielectric multilayer film may be formed of materials other than those mentioned above, and the number of layers may be other than those mentioned above.

[0055] In the above, the reflective film 23m is configured on the assumption that a thickness difference of, for example, about 20% or more (about 30%) occurs, but the present invention is not limited to this, and it is also conceivable to apply the present invention to a case where the maximum thickness difference is, for example, about 10%. In this case, the shift to the short wavelength side is also considered not to be so large compared to the cases of Figures 6 and 9, and it is conceivable to configure the reflective film 23m to have a reflective film characteristic that corresponds to a wavelength band about 1.1 times wider than the wavelength band of the image light ML in the first region D1, for example.

[0056] In addition, in the above, the long wavelength side usage region for the image light ML is set to approximately 650 nm, and this value is used as one of the indicators for determining the wavelength band to be widened, but it is possible to use various values ​​as the indicator rather than being limited to approximately 650 nm, depending on the wavelength characteristics (spectrum of the light source) of the light source used, etc.

[0057] In addition, the display element 11a may be, in addition to the above-mentioned OLED display (organic EL display), not limited to a self-luminous image light generating device, but 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 (light emitting portion) such as a backlight. Instead of an LCD, it is also possible to use LCOS (Liquid crystal on silicon, LCoS is a registered trademark), a digital micromirror device, or the like as the display element 11a.

[0058] In the above, the image display device 100 is configured as a see-through type that allows a user to recognize an image as a virtual image and to visually recognize or observe an outside world image, but it is also possible to apply the present invention to a configuration that does not involve visual recognition of an outside world image (a so-called closed type).

[0059] Although the above describes the image display device 100 as being for both eyes, it is possible to omit one of the parts for the right eye or the left eye of the image display device 100, in which case it becomes a monocular head-mounted display.

[0060] In a specific embodiment, a virtual image display device includes an image light emission device that emits image light, and an optical element having a reflective film that reflects the image light, the optical element having a first region into which light rays that form a central angle of view of the image light are incident, and a second region into which light rays other than the light rays that form the central angle of view of the image light are incident, the film thickness of the reflective film in the first region being thicker than the film thickness in the second region, and the first region of the reflective film having reflectance characteristics corresponding to a wavelength band that is wider on the long wavelength side than the wavelength band of the image light emitted from the image light emission device.

[0061] In the above virtual image display device, the reflective film in the first region has reflectance characteristics corresponding to a wide wavelength band on the longer wavelength side than the wavelength band of the image light emitted from the image light emitting device, so that even if there is a difference (film thickness difference) between the film thickness in the first region and the film thickness in the second region, the difference in reflectance characteristics caused by the film thickness difference can be suppressed, and color unevenness in the reflection of the image light by the reflective film can be reduced, thereby enabling good image formation.

[0062] In a specific aspect, the optical member has a curved shape, and an exit pupil is formed by a component reflected by the first region and a component reflected by the second region. In this case, a virtual image can be visually recognized by the component reflected by the optical member.

[0063] In a specific aspect, the thickness of the reflective film in the first region and the thickness of the reflective film in the second region are expressed by the following relational expression, where d is the thickness of the reflective film in the first region, d' is the thickness of the reflective film in the second region, and θ is the inclination angle of the second region with respect to the first region. d'=dcosθ In this case, by providing a reflective film having reflectance characteristics that correspond to the difference in film thickness that occurs according to the difference in the inclination angle between the first region and the second region, it becomes possible to form a good image.

[0064] In a specific aspect, the reflectance characteristics in the first region of the reflective film correspond to a wavelength band that is 1.2 times or more wider than the wavelength band of the image light emitted from the image light emitting device. In this case, even if the reflectance characteristics in the second region are different from those in the first region, the necessary reflectance characteristics can be ensured.

[0065] In a specific aspect, the reflective film has reflectance characteristics corresponding to wavelength components up to 900 nm in the first region. In this case, even if the optical member has a shape in which the angle of the second region with respect to the first region is about 30°, the necessary reflectance characteristics can be maintained.

[0066] In a specific aspect, the reflective film has partial transparency, and the optical member is a combiner that folds back a part of the image light emitted from the image light emitting device and transmits a part of the outside light at the reflective film. In this case, so-called see-through visibility is possible.

[0067] In a specific aspect, the reflective film is a dielectric multilayer film formed by a vacuum deposition method. In this case, the vacuum deposition method makes it possible to form a film having a required density, and the dielectric multilayer film can be used to form a reflective film according to various characteristics such as angular characteristics.

[0068] In a specific aspect, the image light emitting device emits a non-polarized component as the image light. In this case, the reflecting film can be manufactured without being affected by the polarization separation characteristics. [Explanation of symbols]

[0069] 11a...display element, 11d...display surface, 20...imaging optical system, 21...projection lens, 21p...first lens, 21q...second lens, 22...prism mirror, 22a...entrance surface, 22b...internal reflection surface, 22c...exit surface, 23...see-through mirror (optical member), 23a...reflection surface, 23b...plate-shaped body, 23m...reflection film, 28...plate-shaped optical element, 100...image display device, 100A...first display device, 100B...second display device, 102...image light emission device, 102a, 102b...image light emission device, 103a, 103b...combiner, 200a...main body, 200b...support device, AR1, AR2...area, AX...optical axis, AX1, AX2, AX3...Optical axis part, C1, C2...Curve, CC...Vacuum chamber, CP...Central part, D1...First region, D2...Second region, DD1...Arrow, DS...Deposition material (evaporation source), EP...Peripheral part, ER...Eye ring, EY...Eye, LL...Direction axis, ML...Image light, MLc, MLp1, MLp2...Light beam, MM...Substrate, OL ...External light, OS...Optical system, P1-P3...Optical path, PP...Pupil position, Q1-Q5,R1-R5,S1-S5,RR1...Curve, SE...Deposit, SP1...Space, SS...Surface (interface), SSa...Surface, US...Wearer, WW1-WW3...Overall, XX...Range, d...Film thickness, d'...Film thickness, θ...Angle (tilt angle), θ'...Angle

Claims

1. an image light emitting device that emits image light; an optical member having a reflective film that reflects the image light; Equipped with the optical member has a first region onto which a light ray of the image light having a central angle of view is incident, and a second region onto which a light ray of the image light different from the light ray having the central angle of view is incident, The thickness of the reflective film in the first region is greater than the thickness of the reflective film in the second region, the first region of the reflective film has a reflectance characteristic in which the reflectance is equal in a wide wavelength band on the long wavelength side up to a wavelength 1.2 times the long wavelength end of the wavelength band of the image light, including the wavelength band of the image light covering all colors emitted from the image light emitting device; The thickness of the reflective film in the first region and the thickness of the reflective film in the second region are expressed by the following relational expression, where d is the thickness of the reflective film in the first region, d' is the thickness of the reflective film in the second region, and θ is the inclination angle of the second region with respect to the first region. d'=d cos θ Meet the needs of virtual image display devices.

2. The virtual image display device according to claim 1 , wherein the optical member has a curved surface shape, and an exit pupil is formed by a component reflected by the first region and a component reflected by the second region.

3. 3 . The virtual image display device according to claim 1 , wherein the reflective film has equal reflectances corresponding to wavelength components from the wavelength band of the image light to 900 nm in the first region.

4. The reflective film has partial transparency, The optical element is a combiner that folds back a portion of the image light emitted from the image light emitting device at the reflective film and transmits a portion of outside light. The virtual image display device according to any one of claims 1 to 3.

5. 5. The virtual image display device according to claim 1, wherein the reflective film is a dielectric multilayer film.

6. 6. The virtual image display device according to claim 1, wherein the image light emitting device emits a non-polarized component as the image light.

Images