JP2025075128A - Virtual image display device and optical unit - Google Patents

Abstract

To address luminance unevenness in which a contrast difference with respect to a visual angle when viewing images with a virtual image display device.SOLUTION: A virtual image display device includes: a display panel that emits image light; a projection optical system that collimates the image light from the display panel; a light guide plate that guides the image light; an incident diffraction optical system that makes the image light from the projection optical system incident on the light guide plate; and an emission diffraction optical system that emits the image light from the light guide plate. The display panel includes a first partial display region and a second partial display region arranged with the center point of the display panel held therebetween. The image light emitted from the display panel includes first partial image light emitted from the first partial display region and second partial image light emitted from the second partial display region. Among incident surfaces of the incident diffraction optical system, a first incident area where the first partial image light enters is smaller than a second incident area where the second partial image light enters.SELECTED DRAWING: Figure 7

Description

The present invention relates to a virtual image display device and an optical unit that enable the observation of a virtual image.

The optical device includes a first light guide, a second light guide, a first diffractive optical element, and a second diffractive optical element, the first light guide having a first light entrance portion and a first light exit portion, the second light guide having a second light entrance portion and a second light exit portion, the first diffractive optical element is provided in the second light exit portion of the second light guide, and diffracts at least a portion of the light guided inside the second light guide to extract it to the outside of the second light guide, the second diffractive optical element is provided in the first light exit portion of the first light guide, and diffracts at least a portion of the light guided inside the first light guide and extracted by the first diffractive optical element. At least a portion of the light incident on the first light guide and the second light guide is extracted, a portion of the light incident on the first light guide enters the first light guide from the first light entrance section and is guided, and another portion enters the second light guide from the second light entrance section and is guided, the light guided inside the second light guide contains more light with longer wavelengths than the light guided inside the first light guide, the second diffractive optical element includes a portion with different diffraction efficiency between the side closer to the first light entrance section and the side farther from the first light entrance section, and the first diffractive optical element has a generally constant diffraction efficiency (Patent Document 1).

JP 2015-049376 A

In the optical device shown in Patent Document 1, the entire field angle of the image light is incident on each input grating, so the diffraction efficiency changes for each field angle. In other words, it is not possible to address the uneven brightness that occurs when viewing an image and the brightness varies with the field angle.

The virtual image display device and optical unit according to one aspect of the present invention include a display panel that emits image light, a projection optical system that collimates the image light from the display panel, a light guide plate that guides the image light, an incident diffraction optical system that causes the image light from the projection optical system to enter the light guide plate, and an exit diffraction optical system that emits the image light from the light guide plate. The display panel includes a first display area and a second partial display area that is disposed in a first direction in which the wearer's eyes are aligned as viewed from the first partial display area and has the same area and shape as the first partial display area. The image light emitted from the display panel includes a first partial image light emitted from the first display area and a second partial image light emitted from the second partial display area. Of the entrance surface of the entrance diffraction optical system, a first entrance area into which the first partial image light is incident is smaller than a second entrance area into which the second partial image light is incident.

1A and 1B are diagrams illustrating a wearing state of an HMD according to a first embodiment. FIG. 2 is a side view for explaining the arrangement of an optical system that constitutes the virtual image display device. FIG. 2 is a plan view for explaining the arrangement of an optical system that constitutes the virtual image display device. FIG. 4 is a partial perspective rear view illustrating a light-guiding optical system or a light-guiding member. FIG. 2 is a plan view illustrating an optical system. FIG. 11 is a plan view illustrating the occurrence of luminance unevenness. FIG. 2 is a plan view for explaining the arrangement of an incident diffraction layer and an optical system. FIG. 4 is a side view illustrating the emission direction of light emitted from the display panel. FIG. 11 is a side view illustrating a change in the light emission direction using a microlens. 1 is a side view illustrating light incident on an incident diffraction layer from a projection optical system. FIG. FIG. 2 is a plan view for explaining the arrangement of an incident diffraction layer and an optical system. 1 is a side view illustrating light incident on an incident diffraction layer from a projection optical system. FIG.

First Embodiment
Hereinafter, a first embodiment of virtual image display devices 100A and 100B according to the present invention will be described with reference to FIGS.

Figure 1 is a diagram for explaining the wearing state of a head-mounted 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 Figure 1 etc., X, Y, and Z are Cartesian coordinate systems, with the +X direction corresponding to the lateral direction in which the eyes EY of the observer or wearer US wearing the HMD 200 are aligned, the +Y direction corresponding to the upward direction perpendicular to the lateral direction in which the eyes EY are aligned for the wearer US, and the +Z direction corresponding to the forward or front direction for the wearer US. The ±Y directions are parallel to the vertical axis or vertical direction.

The HMD 200 includes a first virtual image display device 100A for the left eye, a second virtual image display device 100B for the right eye, 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 light guide optical system 103a that is shaped like a pair of glasses 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 light guide optical system 103b that is shaped like a pair of glasses 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 side of the pair of light guide optical systems 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 reversed from left to right, and a detailed description of the second virtual image display device 100B will be omitted.

Figure 2 is a side view specifically explaining the first display drive unit 102a and the first light guide optical system 103a of the first virtual image display device 100A. Figure 3 is a plan view specifically explaining the first display drive unit 102a and the first light guide optical system 103a. Figure 4 is a rear view mainly explaining the first light guide optical system 103a.

2 and 3, the first display drive unit 102a includes an image light generating device 10, a projection optical system 20, and a drive circuit member 88. The image light generating device 10 is an optical engine including a display panel 11a. The projection optical system 20 is a collimator including a plurality of lens elements 21. The image light ML generated by the image light generating device 10 is collimated by the projection optical system 20 and coupled to the first light guide optical system 103a, which is a light guide member 50. The drive circuit member 88 causes the display panel 11a to perform a display operation. In the first virtual image display device 100A, the optical device excluding the drive circuit member 88 is called the optical unit 100. The first virtual image display device 100A guides the image light ML to the eye EY of the wearer US, thereby allowing the wearer US to view a virtual image.

Referring to Fig. 4, the first light guide optical system 103a is a light guide member 50 that enables color display and extends approximately parallel to the XY plane. The first light guide optical system 103a has a light guide plate 51a, an incident diffraction layer 51b, a pupil enlargement grating layer 51e, and an exit diffraction layer 51c. The incident diffraction layer 51b, the exit diffraction layer 51c, and the pupil enlargement grating layer 51e diffract light in accordance with the wavelength of the image light ML. The input diffraction layer 51b guides the collimated image light ML from the first display driver 102a into the light guide plate 51a and propagates it laterally, the pupil enlargement lattice layer 51e propagates the image light ML propagating laterally in the light guide plate 51a downward while expanding the pupil size of the image light ML, and the output diffraction layer 51c expands the pupil size of the image light ML propagating downward in the light guide plate 51a while outputting the image light ML toward a pupil position PP (see FIG. 2) set inside where the eye EY (see FIG. 2) is located.

Figure 5 is a diagram explaining the optical system of the first display drive unit 102a. In the first display drive unit 102a, the image light generating device 10 includes only one display panel 11a. That is, the display panel 11a includes pixels of three colors, RGB, and the pixels of each color are arranged two-dimensionally in the display panel 11a. The projection optical system 20 includes a plurality of lens elements 21. The display panel 11a and the projection optical system 20 are fixed in a state in which they are positioned relative to each other by the lens barrel 30. As shown in Figure 2, the lens barrel 30 is supported together with the drive circuit member 88 in a state in which they are positioned relative to each other by the holder 71, which also serves as a cover, and is fixed to the first light guiding optical system 103a.

The display panel 11a is a display element or display device that emits image light ML to form an image corresponding to a virtual image. Specifically, the display panel 11a is a display of various light-emitting element arrays such as OLEDs (Organic Light Emitting Diodes), organic ELs (Organic Electro-Luminescence), inorganic ELs, and LEDs, and forms still or moving images on a two-dimensional display surface parallel to the XY plane. The display panel 11a has light-emitting elements 14a. The light-emitting elements 14a are a number of pixels arranged two-dimensionally along the XY plane on a substrate. When the display panel 11a is an OLED display, each pixel constituting the light-emitting element 14a includes, in order from the substrate side, a cathode, an electron transport layer, a light-emitting layer, a hole transport layer, and a transparent electrode layer.

The display panel 11a is 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 such as a background. Instead of an LCD, LCOS (Liquid crystal on silicon, LCoS is a registered trademark), a digital micromirror device, etc. may also be used as the display panel 11a.

The projection optical system 20 includes a first lens 21a and a second lens 21b as lens elements 21 that collimate, i.e., parallelize, the incident light. The projection optical system 20 collimates the image light ML emitted from the display surface 11d of the display panel 11a to a state having a predetermined light beam width, and emits the image light ML toward the incident diffraction layer 51b provided on the light guide member 50 in an inclination angle state according to the pixel position. The projection optical system 20 may include optical elements such as a reflecting mirror in addition to one or more lens elements made of resin or glass. The optical surfaces of the optical elements constituting the projection optical system 20 may be spherical, aspherical, or free-form. Hereinafter, the light emitted from the different light-emitting elements 14a of the image light ML may be referred to as partial image light ML0, ML1, and ML2, respectively.

Returning to FIG. 4, in the first light guide optical system 103a or the light guide member 50, the incident diffraction layer 51b is an input diffractive optical element DI, which is formed with a diffraction pattern that extends linearly in the vertical Y direction and repeats periodically in the horizontal X direction. The exit diffraction layer 51c is an output diffractive optical element DO, which is formed with a diffraction pattern that extends linearly in the horizontal X direction and repeats periodically in the vertical Y direction. The pupil enlargement grating layer 51e is a pupil enlargement diffractive optical element DE, which is provided on the -X side of the incident diffraction layer 51b and is guided into the light guide plate 51a to bend the optical path of the image light ML that travels in the -X direction as a whole, so that it travels in the -Y direction as a whole.

The light guide plate 51a is a member formed from a parallel plate and has an inner total reflection surface 51i and an outer total reflection surface 51o, which are a pair of flat surfaces extending parallel to the XY plane (see Figure 2).

The incident diffraction layer 51b, the exit diffraction layer 51c, and the pupil enlargement grating layer 51e are formed on the inner total reflection surface 51i of the light guide plate 51a.

The incident diffraction layer 51b, the exit diffraction layer 51c, and the pupil enlargement grating layer 51e diffract light according to the wavelength of the image light ML, and are formed, for example, from a surface relief type diffraction element. The surface relief type diffraction element is formed by nanoimprinting, but is not limited to this, and can also be formed by etching the surface of the light guide plate 51a, or a diffraction element can be attached.

The pupil enlargement grating layer 51e does not substantially impair the angular information of the image light ML in the left-right X direction or the vertical Y direction while switching the diffraction direction. The pupil enlargement grating layer 51e, i.e., the pupil enlargement diffractive optical element DE, guides the image light ML guided into the light guide plate 51a from the input diffractive optical element DI, which is the incident diffraction layer 51b, to the output diffractive optical element DO, which is the exit diffraction layer 51c, while enlarging the pupil of the exit diffraction layer 51c. More specifically, the pupil enlargement grating layer 51e is interposed between the incident diffraction layer 51b and the exit diffraction layer 51c, and divides the light beam while guiding the image light ML in a direction (-Y direction) intersecting the diffraction direction (-X direction) of the incident diffraction layer 51b, and has the role of expanding the width of the light beam in the horizontal direction. The pupil enlargement grating layer 51e is formed of a diffraction pattern that extends linearly in the oblique DS2 direction parallel to the XY plane and is periodically repeated in the DS1 direction parallel to the XY plane and perpendicular to the DS2 direction. The DS1 direction is rotated 45° clockwise with respect to the +Y direction, and is an intermediate direction between the -X direction and the +Y direction. The grating period or pitch in the X direction and the Y direction of the pattern formed in the pupil enlargement grating layer 51e is consistent with the grating period in the X direction of the pattern formed in the input diffraction layer 51b, and is consistent with the grating period in the Y direction of the pattern formed in the output diffraction layer 51c. The output diffraction layer 51c divides the light beam while guiding the image light ML in the -Y direction, and has a role of expanding the light beam width in the vertical direction. As a result, the light beam width in the X and Y directions of the image light ML incident on the pupil position PP shown in Figure 2 has an expansion corresponding to the exit diffraction layer 51c, and the pupil size in the vertical and horizontal directions increases through the pupil enlargement grating layer 51e, the exit diffraction layer 51c, etc. From the exit diffraction layer 51c, the image light ML is emitted, which is collimated around the exit optical axis OX (see Figure 2) perpendicular to the light guide plate 51a.

Referring to FIG. 6, the occurrence of luminance unevenness in the image light ML guided from the incident diffraction layer 51b to the exit diffraction layer 51c inside the light guide plate 51a will be described. FIG. 6 is a plan view that shows a schematic positional relationship in the XZ direction of the image light generating device 10, the lens element 21 as the projection optical system 20, the incident diffraction layer 51b, the light guide plate 51a, the exit diffraction layer 51c, the wearer's eye EY, and the image light ML. However, in FIG. 6, in order to simplify the explanation, the pupil enlargement grating layer 51e that changes the propagation direction of the image light ML on its way from the incident diffraction layer 51b to the exit diffraction layer 51c is omitted, and the dimensions of each component are exaggerated.

As shown in FIG. 6, the image light ML from the projection optical system 20 is diffracted by the input diffraction layer 51b and enters the light guide plate 51a, is guided along the light guide plate 51a while being totally reflected by the outer total reflection surface 51o and the inner total reflection surface 51i of the light guide plate 51a, is diffracted by the output diffraction layer 51c, and is emitted toward the eye EY.

Here, the image light ML includes a first partial image light ML1 and a second partial image light ML2. The first partial image light ML1 and the second partial image light ML2 are emitted from the first partial display area 111 and the second partial display area 112 shown in FIG. 5 of the display panel 11a. The first partial display area 111 is arranged in the direction of the component parallel to the first direction (±X direction) in which the wearer's both eyes EY are aligned (-X direction in the case of FIG. 6) from the center point 11c of the display panel 11a in the direction from the entrance diffraction layer 51b to the exit diffraction layer 51c. The second partial display area 112 is arranged in the opposite direction to the first partial display area 111 (+X direction in the case of FIG. 6) from the center point 11c. As shown in FIG. 5 and the region ER1 in FIG. 6, a virtual straight line AX1 that is perpendicular to the display surface 11d of the display panel 11a and passes through the center point 11c passes through the center point 510 of the incident diffraction layer 51b. The first direction (±X direction) is the direction in which the multiple convex portions included in the diffraction pattern that constitutes the incident diffraction layer 51b are periodically arranged, and is also the direction in which the image light ML that is incident on the light guide plate 51a from the incident diffraction layer 51b is guided toward the pupil enlargement grating layer 51e.

Hereinafter, in order to make it easier to compare the first partial image light ML1 and the second partial image light ML2, a case will be described in which the areas of the first partial display area 111 and the second partial display area 112 are the same, and the distances from the center point 11c to the first partial display area 111 and the second partial display area 112 are the same. Here, the center point 11c may be a point on the display surface 11d of the display panel 11a where the optical axis AX1 of the projection optical system 20 intersects, or may be a geometric center defined as the intersection of diagonal lines connecting the vertices of the display panel 11a or the center of gravity obtained based on the shape of the display panel 11a, or may be a point included in the display surface 11d of the display panel 11a and separated from the geometric center by an arbitrary distance in a direction (±Y direction) perpendicular to the first direction (±X direction).

Focusing on each of the multiple convex portions included in the incident diffraction layer 51b, when two partial image lights ML1 and ML2 emitted from two different display areas 111 and 112 included in the same display panel 11a are diffracted by the same convex portion of the diffraction pattern constituting the incident diffraction layer 51b and enter the light guide plate 51a, the angles of incidence of the partial image lights ML1 and ML2 with respect to the incident diffraction layer 51b are different. When the angles of incidence of the two partial image lights ML1 and ML2 with respect to the incident diffraction layer 51b are different from each other, the angles of incidence AI1 and AI2 at which the partial image lights ML1 and ML2 are totally reflected inside the light guide plate 51a are different from each other, and therefore the angles of reflection AR1 and AR2 are also different from each other. In other words, the angles of incidence and the angles of reflection at which the light is totally reflected inside the light guide plate 51a are different depending on the angle of view of the light included in the image light ML incident on the incident diffraction layer 51b.

Specifically, as shown in the example of FIG. 6, the first angle of incidence AI1 and the first reflection angle AR1 when the first partial image light ML1 incident on the incident diffraction layer 51b from a direction closer to the exit diffraction layer 51c is totally reflected by the outer total reflection surface 51o and the inner total reflection surface 51i are smaller than the second angle of incidence AI2 and the second reflection angle AR2 when the second partial image light ML2 incident on the incident diffraction layer 51b from a direction farther away from the exit diffraction layer 51c is totally reflected by the outer total reflection surface 51o and the inner total reflection surface 51i.

When the partial image light ML1, ML2 repeats total reflection inside the light guide plate 51a at different angles of incidence and reflection, the number of times the partial image light ML1, ML2 is totally reflected per unit length in the direction in which the light guide plate 51a extends is also different. And when the number of times the partial image light ML1, ML2 is totally reflected per unit length of the light guide plate 51a is different, the total number of convex parts that diffract the partial image light ML1, ML2 when it is emitted to the outside of the light guide plate 51a among the diffraction patterns that constitute the same exit diffraction layer 51c is also different. In other words, depending on the angle of view of the light contained in the image light ML that enters the entrance diffraction layer 51b, the angle of incidence and the angle of reflection when the light is totally reflected inside the light guide plate 51a are different, and the total number of convex parts of the exit diffraction layer 51c that diffract the image light ML when it is emitted to the outside from the light guide plate 51a is also different.

Specifically, as shown in the example of FIG. 6, the total number of convex portions in the exit diffraction layer 51c that diffract the first partial image light ML1 having the smaller first incident angle AI1 and first reflection angle AR1 when it is emitted to the outside of the light guide plate 51a is greater than the total number of convex portions that diffract the second partial image light ML2 having the larger second incident angle AI2 and second reflection angle AR2 when it is emitted to the outside of the light guide plate 51a.

When the image light ML is emitted from the light guide plate 51a, the greater the total number of convex portions in the emission diffraction layer 51c that diffract the light at a specific angle of view contained in the image light ML, the greater the amount of the emitted light and the higher the brightness of the emitted image light ML. As a result, the brightness of the image light ML has a different distribution depending on the angle of view of the light contained in the image light ML that enters the entrance diffraction layer 51b. In other words, when viewed from the eye EY of the wearer US, brightness unevenness may occur depending on the angle of view of the image light ML.

In this embodiment, as one method for reducing the brightness unevenness as described above, the positional relationship between the projection optical system 20 and the incident diffraction layer 51b is appropriately set so that when the image light ML from the projection optical system 20 is incident on the light guide plate 51a, the total number of convex parts that diffract the light contained in the image light ML in the diffraction pattern that constitutes the incident diffraction layer 51b varies for each angle of view of the light. Here, the total number of convex parts that diffract the light contained in the image light ML is proportional to the incident area of the incident surface of the incident diffraction layer 51b onto which the light is incident.

Specifically, as shown in region ER2 of FIG. 7, the position of the projection optical system 20 relative to the incident diffraction layer 51b is set so that the optical axis AX1 of the projection optical system 20 is shifted a predetermined distance D from the center of the incident diffraction layer 51b in a direction (-X direction) that is a directional component parallel to the first direction (±X direction) of the direction from the incident diffraction layer 51b to the exit diffraction layer 51c.

As a result, when the light contained in the image light ML from the projection optical system 20 is diffracted by the incident diffraction layer 51b and enters the light guide plate 51a, the total number of convex portions that diffract the light in the diffraction pattern that constitutes the incident diffraction layer 51b changes depending on the angle of view of the light in the image light ML. The more external convex portions that diffract the light, the wider the beam width of the light guided inside the light guide plate 51a. In other words, the beam widths W1 and W2 in the first direction (±X direction) of the partial image lights ML1 and ML2 contained in the image light ML from the projection optical system 20 change depending on the angle of view of the light.

Specifically, as shown in FIG. 7, when comparing the first partial image light ML1 and the second partial image light ML2 contained in the image light ML, the total number of convex portions that diffract the second partial image light ML2 is greater than the total number of convex portions that diffract the first partial image light ML1 in the diffraction pattern that constitutes the incident diffraction layer 51b. As a result, inside the light guide plate 51a, the light beam width W2 of the second partial image light ML2 is wider than the light beam width W1 of the first partial image light ML1.

Then, as described with reference to FIG. 6, when the first partial image light ML1 and the second partial image light ML2 are emitted from the light guide plate 51a, the total number of convex portions that diffract the second partial image light ML2 is greater than the total number of convex portions that diffract the first partial image light ML1 in the diffraction pattern that constitutes the emission diffraction layer 51c. In other words, the difference in brightness between the first partial image light ML1 that has a narrower light beam width W1 and is diffracted by more convex portions and is emitted, and the second partial image light ML2 that has a wider light beam width W2 and is diffracted by fewer convex portions and is emitted, is smaller compared to the configuration of FIG. 5. As a result, the brightness unevenness of the image light ML in the eye EY of the wearer US is reduced.

Second Embodiment
In the above-described first embodiment, in order to reduce the brightness unevenness of the light contained in the image light ML that occurs depending on the angle of view of the light, the positional relationship between the projection optical system 20 and the incident diffraction layer 51b is appropriately set to change the beam width of the light contained in the image light ML depending on the angle of view of the light. In the present embodiment, as another method for reducing the brightness unevenness as described above, the direction in which the projection optical system 20 emits the light contained in the image light ML is changed depending on the angle of view of the light.

Specifically, first, as shown in FIG. 8, the directions D0, D1, and D2 in which the display panel 11a emits the light contained in the image light ML are changed according to the position in the first direction (±X direction) of the partial display areas 110, 111, and 112 included in the display panel 11a. More specifically, the surface of the display panel 11a is divided and managed into a plurality of partial display areas 110, 111, and 112, and one of the partial display areas 110, 111, and 112 is set as the reference display area 110 that serves as a reference in the first direction (±X direction). The direction in which the light of the image light ML is emitted from the reference display area 110 is set as the reference emission direction D0. As an example, the reference emission direction D0 may be a direction (+Z direction) perpendicular to the display surface 11d of the display panel 11a. In a first direction (±X direction), a first partial display area 111 arranged in a first shift direction (-X direction) from the incident diffraction layer 51b to the exit diffraction layer 51c as viewed from the reference display area 110 tilts the direction D1 in which the light of the image light ML is emitted by a predetermined first tilt angle AT1 in a rotational direction approaching the reference display area 110 from the reference emission direction (+Z direction) within a virtual plane (XZ plane) including the first direction (±X direction) and the reference emission direction (+Z direction). In addition, in the first direction (±X direction), the direction in which the second partial display area 112 arranged in the second shift direction (+X direction) from the exit diffraction layer 51c toward the entrance diffraction layer 51b as viewed from the reference display area 110 emits the light of the image light ML is tilted by a predetermined second tilt angle AT2 in a rotation direction away from the reference emission direction from the reference display area 110 within a virtual plane (XZ plane) including the first direction (±X direction) and the reference emission direction (+Z direction). At this time, the first incident angle at which the first partial image light ML1 from the first lens 21a is incident on the second lens 21b is smaller than the second incident angle at which the second partial image light ML2 from the first lens 21a is incident on the second lens 21b. In FIG. 8, the intensity distributions PD0, PD1, and PD2 of the light emitted from the reference display area 110, the first partial display area 111, and the second partial display area 112 of the image light ML are shown, respectively.

At this time, the position of the microlens included in the microlens array as the first lens 21a, which is arranged corresponding to each of the reference display area 110 and the partial display areas 111 and 112, can be shifted by a predetermined distance in the first direction from the reference position, so that the direction in which each of the partial display areas 110, 111, and 112 emits the light of the image light ML can be tilted. Here, the microlens array is an optical element configured by arranging microlenses in an array so as to face each of the reference display area 110 and the partial display areas 111 and 112 as pixels or a set of pixels included in the display panel 11a. In other words, the microlens array functions as an emission direction changing optical system that changes the emission direction of light emitted from each of the multiple pixels included in the display panel 11a based on the position of each of the multiple pixels on the display panel 11a. Each microlens, together with the second lens 21b arranged behind the first lens 21a as a microlens array, is configured to collimate the light emitted from the corresponding pixel or the reference display area 110 and the partial display areas 111 and 112.

Specifically, as shown in FIG. 9, a microlens 210 corresponding to the reference display area 110 is arranged in front of the reference display area 110, a microlens 211 corresponding to the first partial display area 111 is shifted a predetermined first shift distance DS1 from the front of the first partial display area 111 in a first shift direction (-X direction), and a microlens 212 corresponding to the second partial display area 112 is shifted a predetermined shift distance DS2 from the front of the second partial display area 112 in a second shift direction (+X direction). As a result, of the image light ML, the light emitted from the reference display area 110 is emitted by the microlens 210 in the reference emission direction D0 (+Z direction) as the 0th partial image light ML0, the light emitted from the first partial display area 111 is emitted by the microlens 211 in a direction D1 tilted by the first tilt angle AT1 from the reference emission direction (+Z direction) as the first partial image light ML1, and the light emitted from the second partial display area 112 is emitted by the microlens 212 in a direction D2 tilted by the second tilt angle AT2 from the reference emission direction (+Z direction) as the second partial image light ML2.

Next, as shown in FIG. 10, the partial image light ML1, ML2 emitted from the partial display areas 111, 112 in different emission directions of the image light ML is collimated by passing through the second lens 21b of the projection optical system 20, diffracted by the incident diffraction layer 51b, and enters the light guide plate 51a. At this time, the incident angles of the partial image light ML1, ML2 when they reach the incident diffraction layer 51b are tilted by different tilt angles AT1, AT2 by the first lens 21a as a microlens array, so that the total number of convex portions that diffract the partial image light ML1, ML2 in the diffraction pattern that constitutes the incident diffraction layer 51b is different from each other. As a result, by appropriately setting the first tilt angles AT1, AT2 or the first shift distance DS1 and the second shift distance DS2, it is possible to reduce the luminance unevenness as in the embodiment, compared to the case where the partial image light ML1, ML2 is emitted in the reference emission direction.

(Variation: More partial display areas)
In the above-described second embodiment, a configuration has been described in which the display panel 11a is divided and managed into the reference display area 110, the first partial display area 111, and the second partial display area 112, and the light of the image light ML emitted from each of these three areas is emitted in a different direction. As a variation of this configuration, the display panel 11a may be divided and managed into more partial display areas, and the first lens 21a as a microlens array may be configured so that the light of the image light ML emitted from each of the partial display areas is emitted in a different direction.

(Variation: Color Filter Shift)
As a further modification of the above configuration, a color filter array may be used instead of the microlens array. The color filter array is configured by arranging color filters in an array shape to provide color information of R (red), G (green) and B (blue) components to three sub-pixels provided in each of the plurality of pixels included in the display panel 11a. That is, in this modification, the display panel 11a includes a single-plate RGB panel including a plurality of sub-pixels that individually emit light of the R, G and B components of the image light ML for each of the plurality of pixels. The plurality of sub-pixels may be arranged on a single panel, but this is merely an example and does not limit the present disclosure. In this modification, instead of arranging each color filter in front of the corresponding sub-pixel, the color filter is shifted by a predetermined shift distance in the first shift direction or the second shift direction according to the position of the sub-pixel in the display panel 11a, thereby appropriately changing the emission direction of the light emitted by each sub-pixel in the image light ML, and the luminance unevenness can be reduced as in the case of the second embodiment described above.

(Modification: Three Display Panels)
In the above second embodiment, a configuration has been described in which a microlens array is used as the first lens 21a, and a plurality of microlenses included in the microlens array are arranged corresponding to a plurality of pixels or a plurality of partial display areas 111, 112 included in the display panel 11a. As a modified example of this configuration, the display panel 11a that emits the image light ML may be replaced with three display panels that emit the three primary color components, respectively. In this case, a microlens array having the same configuration may be provided on each of the three display panels. In addition, a synthesis optical system that synthesizes the three color components that constitute the image light ML may be further provided between the three microlens arrays and the emission diffraction layer 51c.

Third Embodiment
In the above-described first embodiment, a configuration has been described in which the position of the optical axis AX1 of the projection optical system 20 relative to the center of the incident diffraction layer 51b is shifted in a first shift direction (-X direction) from the incident diffraction layer 51b to the exit diffraction layer 51c in order to reduce the luminance unevenness of the image light ML in the eye EY of the wearer US. As a modified example of this configuration, a description will be given of a case in which the position of the optical axis AX1 of the projection optical system 20 relative to the center of the incident diffraction layer 51b is shifted in a second shift direction (+X direction) from the exit diffraction layer 51c to the incident diffraction layer 51b in the opposite direction to the first embodiment, so that the luminance unevenness of the image light ML in the eye EY of the wearer US can be reduced.

11 is a diagram in which the position of the projection optical system 20 relative to the incident diffraction layer 51b is changed from that of FIG. 5 for explaining the optical system of the first display drive unit 102a according to the first embodiment. As shown in the region ER3 of FIG. 11, in this embodiment, the projection optical system 20 is shifted by an appropriate distance D in the second shift direction (+X direction) as viewed from the center of the incident diffraction layer 51b. At this time, the first partial image light ML1 is diffracted by the incident diffraction layer 51b and enters the light guide plate 51a, is totally reflected once by the outer total reflection surface 51o of the light guide plate 51a, and reaches the end of the incident diffraction layer 51b on the second shift direction side when it is totally reflected by the inner total reflection surface 51i of the light guide plate 51a. When such a condition is satisfied, the total number of convex parts that diffract the second partial image light ML2 in the diffraction pattern that constitutes the incident diffraction layer 51b is greater than the total number of convex parts that diffract the first partial image light ML1. As a result, as in the first embodiment, of the image light ML guided inside the light guide plate 51a, the luminous flux width of the second partial image light ML2 is wider than the luminous flux width of the first partial image light ML1, and the brightness unevenness of the image light ML emitted from the light guide plate 51a is reduced.

In this embodiment, as in the first embodiment, the first partial image light ML1 is emitted from the first partial display area 111 of the display panel 11a, which is located in the first shift direction (-X direction) when viewed from the center point 11c of the display panel 11a, as shown in FIG. 5 and other figures. The second partial image light ML2 is emitted from the second partial display area 112 of the display panel 11a, which is located in the second shift direction (+X direction) when viewed from the center point 11c of the display panel 11a, as shown in FIG. 5 and other figures.

Fourth Embodiment
In the above-described second embodiment, in order to reduce the luminance unevenness of the image light ML in the eye EY of the wearer US, a configuration has been described in which the direction in which the first partial image light ML1 of the image light ML emitted by the projection optical system 20 is emitted is tilted from the reference emission direction (+Z direction) in a rotational direction approaching the reference display area 110, and the direction in which the second partial image light ML2 is emitted is tilted from the reference emission direction (+Z direction) in a rotational direction moving away from the reference display area 110. As a modified example of this configuration, a description will be given of the fact that the luminance unevenness of the image light ML in the eye EY of the wearer US can be reduced even when the directions in which the first partial image light ML1 and the second partial image light ML2 are emitted are each tilted in a rotational direction opposite to that in the second embodiment.

Figure 12 is an example of Figure 10 for explaining the partial image light ML1, ML2 according to the second embodiment, in which the emission directions of the partial image light ML1, ML2 are changed. As shown in Figure 12, in this embodiment, the emission direction of the first partial image light ML1 is tilted from the reference emission direction (+Z direction) to a rotation direction away from the reference display area 110, and the emission direction of the second partial image light ML2 is tilted from the reference emission direction (+Z direction) to a rotation direction approaching the reference display area 110. At this time, the first incident angle at which the first partial image light ML1 from the first lens 21a is incident on the second lens 21b is larger than the second incident angle at which the second partial image light ML2 from the first lens 21a is incident on the second lens 21b. Here, by further changing the shape and position of the second lens 21b from the configuration shown in FIG. 10, the total number of convex portions that diffract the second partial image light ML2 in the diffraction pattern that constitutes the incident diffraction layer 51b becomes greater than the total number of convex portions that diffract the first partial image light ML1. As a result, as in the second embodiment, the light beam width of the second partial image light ML2 in the image light ML guided inside the light guide plate 51a becomes wider than the light beam width of the first partial image light ML1, and the brightness unevenness of the image light ML emitted from the light guide plate 51a is reduced.

In this embodiment, as in the second embodiment, the first partial image light ML1 is emitted from the first partial display area 111 of the display panel 11a, which is located in the first shift direction (-X direction) as viewed from the center point 11c of the display panel 11a, as shown in FIG. 5 and other figures. The second partial image light ML2 is emitted from the second partial display area 112 of the display panel 11a, which is located in the second shift direction (+X direction) as viewed from the center point 11c of the display panel 11a, as shown in FIG. 5 and other figures. However, in this embodiment, the microlenses 211 and 212 shown in FIG. 9 are shifted from the centers of the partial display areas 111 and 112 in the first shift direction (-X direction), so that the direction in which the partial image light ML1 and ML2 are emitted is opposite to the rotation direction in the second embodiment.

In the above, the virtual image display devices 100A and 100B can be used as HMDs, but the present invention is not limited to this and can be applied to various optical devices. For example, the present invention can be applied to a head-up display (HUD).

The modified examples described above can be combined with each other to the extent that there is no technical contradiction. As an example, the configurations of the first and second embodiments may be combined, or the configurations of the third and fourth embodiments may be combined.

The above describes a configuration in which the first partial display area 111 and the second partial display area 112 are disposed at the same distance from the center point 11c of the display panel 11a, but this is merely an example for ease of comparison and does not limit the present disclosure. When the positions of the display panel 11a and the projection optical system 20 are shifted in the first direction (±X direction) relative to the incident diffraction layer 51b, or the emission directions in which the partial image lights ML1 and ML2 are emitted from the partial display areas 111 and 112 are tilted at tilt angles AT1 and AT2 corresponding to the positions of the partial display areas 111 and 112 in the first direction (±X direction), respectively, if the two partial display areas 111 and 112 are at different positions in the first direction (±X direction), even if the first partial display area 111 and the second partial display area 112 have the same shape and area, the light flux widths W1 and W2 are different.

A specific embodiment of the virtual image display device includes a display panel that emits image light, a projection optical system that collimates the image light from the display panel, a light guide plate that guides the image light, an incident diffraction optical system that causes the image light from the projection optical system to enter the light guide plate, and an exit diffraction optical system that emits the image light from the light guide plate. The display panel includes a first partial display area and a second partial display area that is disposed in a first direction in which the wearer's eyes are aligned as viewed from the first partial display area and has the same area and shape as the first partial display area. The image light emitted from the display panel includes a first partial image light emitted from the first partial display area and a second partial image light emitted from the second partial display area. Of the entrance surface of the entrance diffraction optical system, a first entrance area into which the first partial image light is incident is smaller than a second entrance area into which the second partial image light is incident.

In the above virtual image display device, by providing a difference in the incident area when two partial image lights, which are emitted from two different display areas included in the display panel, enter the light guide plate, it is possible to reduce uneven brightness of the image light that is emitted from the light guide plate and observed by the wearer's eyes, which occurs due to the difference in the reflection angle when the light is guided inside the light guide plate.

In a specific embodiment of the virtual image display device, the optical axis center point where the central optical axis of the projection optical system intersects with the entrance surface of the entrance diffraction optical system is shifted from the center point of the display panel, and the second direction from the optical axis center point toward the center point includes a directional component parallel to the first direction, so that the first width in a virtual plane including the optical axis direction of the projection optical system and the first direction of the first partial image light guided inside the light guide plate is smaller than the second width in the virtual plane of the second partial image light guided inside the light guide plate.

In the above virtual image display device, the entrance area can be made different by shifting the center point of the display panel from the center point of the optical axis.

In a specific embodiment of the virtual image display device, the second direction includes a directional component of a third direction, which is a directional component parallel to the first direction, from the input diffractive optical system to the output diffractive optical system.

In a specific embodiment of the virtual image display device, the second direction includes a directional component of a fourth direction that is opposite to the third direction.

In a specific embodiment, the virtual image display device further includes an emission direction changing optical system that changes the emission direction of light emitted from each of a plurality of pixels included in the display panel based on the position of each of the plurality of pixels on the display panel.

In the above virtual image display device, the light emission direction can be changed for each pixel, allowing differences in the incident area to be created.

In a specific embodiment of the virtual image display device, the first angle of incidence at which the first partial image light from the emission direction changing optical system is incident on the projection optical system is smaller than the second angle of incidence at which the second partial image light from the emission direction changing optical system is incident on the projection optical system.

In a specific embodiment of the virtual image display device, the first angle of incidence at which the first partial image light from the emission direction changing optical system is incident on the projection optical system is greater than the second angle of incidence at which the second partial image light from the emission direction changing optical system is incident on the projection optical system.

In a specific embodiment of the virtual image display device, the emission direction changing optical system includes a microlens array in which a plurality of microlenses are arranged, each of which changes the radiation direction of light emitted from a plurality of pixels, and a predetermined distance is provided between the optical axis center point of each of the plurality of microlenses and the center point of each of the plurality of pixels, and the predetermined distance is determined based on the position of each of the plurality of pixels on the display panel.

In the virtual image display device, a difference in the incident area can be created by providing a different offset for each pixel between the center point of the pixel and the center point of the optical axis of the microlens.

In a specific embodiment of the virtual image display device, the display panel comprises a single-plate RGB panel having a plurality of sub-pixels that individually emit R (red), G (green) and B (blue) components of the image light for each of a plurality of pixels, the emission direction changing optical system comprises a color filter array in which a plurality of color filters are arranged to give color information to the light emitted from each of the plurality of sub-pixels, and a predetermined distance is provided between the center point of each of the plurality of color filters and the center point of each of the plurality of sub-pixels, and the predetermined distance is determined based on the position of each of the plurality of sub-pixels on the display panel.

In the above virtual image display device, a difference in the incident area can be created by providing a different offset for each subpixel between the center point of the subpixel and the center point of the color filter.

In a specific embodiment, the optical unit includes a display panel that emits image light, a projection optical system that collimates the image light from the display panel, a light guide plate that guides the image light, an incident diffraction optical system that causes the image light from the projection optical system to enter the light guide plate, and an exit diffraction optical system that emits the image light from the light guide plate. The display panel includes a first partial display area and a second partial display area that is disposed in a first direction in which the wearer's eyes are aligned as viewed from the first partial display area and has the same area and shape as the first partial display area. The image light that is emitted from the display panel includes a first partial image light that is emitted from the first partial display area and a second partial image light that is emitted from the second partial display area. Of the entrance surface of the entrance diffraction optical system, a first entrance area into which the first partial image light is incident is smaller than a second entrance area into which the second partial image light is incident.

10...image light generating device, 11a...display panel, 11c...center point, 11d...display surface, 14a...light emitting element, 20...projection optical system, 21a, 21b...lens, 50...light guiding member, 51a...light guiding plate, 51b...entrance diffraction layer, 51c...exit diffraction layer, 51e...pupil enlargement grating layer, 71...holder, 88...drive circuit member, 90...user terminal, 100...optical unit, 100A, 100B...virtual image display device, 100C...support device, 102a, 102b...display drive unit, 103a, 103b...light guide optical system, 110...partial display area (reference display area), 111, 112...partial display area, 200...HMD, 210, 211, 212...microlenses, 510...center point, AX1, AX2...optical axis, DE...pupil expansion diffractive optical element, DI...input diffractive optical element, DO...output diffractive optical element, EY...eye, ML...image light, ML0, ML1, ML2...partial image light, OX...exiting optical axis, PP...pupil position, US...wearer, W1, W2...light beam width

Claims (10)

A display panel that emits image light;
a projection optical system that collimates the image light from the display panel;
a light guide plate that guides the image light;
an incident diffraction optical system that causes the image light from the projection optical system to be incident on the light guide plate;
an output diffraction optical system that outputs the image light from the light guide plate;
Equipped with
The display panel includes:
A first partial display area;
A second partial display area is disposed in a first direction in which both eyes of the wearer are aligned as viewed from the first partial display area, and has the same area and shape as the first partial display area;
Including,
The image light emitted from the display panel is
a first partial image light emitted from the first partial display area;
a second partial image light emitted from the second partial display area; and
Including,
a first incident area, on an incident surface of the incident diffractive optical system, onto which the first partial image light is incident, is smaller than a second incident area, on which the second partial image light is incident. an optical axis center point where a central optical axis of the projection optical system intersects with an incident surface of the incident diffractive optical system is shifted from a center point where the central optical axis intersects with the display panel so that a first width in a virtual plane including an optical axis direction of the projection optical system and the first direction, of the first partial image light guided inside the light guide plate, is made smaller than a second width in the virtual plane of the second partial image light guided inside the light guide plate,
The virtual image display device according to claim 1 , wherein a second direction from the optical axis center point toward the center point includes a directional component parallel to the first direction. The virtual image display device according to claim 2 , wherein the second direction includes a directional component of a third direction that is a directional component parallel to the first direction among directions from the input diffractive optical system to the output diffractive optical system. The virtual image display device according to claim 2 , wherein the second direction includes a directional component of a fourth direction that is an opposite direction to a third direction that is a directional component parallel to the first direction, among directions from the input diffractive optical system to the output diffractive optical system. The virtual image display device according to claim 1 , further comprising an emission direction changing optical system that changes an emission direction of light emitted from each of a plurality of pixels included in the display panel based on a position of each of the plurality of pixels on the display panel. 6. The virtual image display device according to claim 5, wherein a first angle of incidence at which the first partial image light from the emission direction changing optical system is incident on the projection optical system is smaller than a second angle of incidence at which the second partial image light from the emission direction changing optical system is incident on the projection optical system. 6. The virtual image display device according to claim 5, wherein a first angle of incidence at which the first partial image light from the emission direction changing optical system is incident on the projection optical system is greater than a second angle of incidence at which the second partial image light from the emission direction changing optical system is incident on the projection optical system. The emission direction changing optical system includes:
a microlens array in which a plurality of microlenses are arranged, each of which changes the radiation direction of light emitted from the plurality of pixels;
a predetermined distance is provided between the optical axis center point of each of the plurality of microlenses and the center point of each of the plurality of pixels;
The virtual image display device according to claim 5 , 6 or 7 , wherein the predetermined distance is determined based on the positions of the respective pixels on the display panel. The display panel includes:
a single-plate RGB panel including a plurality of sub-pixels that individually emit light of an R (red) component, a G (green) component, and a B (blue) component of the image light for each of the plurality of pixels;
The emission direction changing optical system includes:
a color filter array in which a plurality of color filters are arranged to give color information to light emitted from each of the plurality of sub-pixels;
a predetermined distance is provided between a center point of each of the plurality of color filters and a center point of each of the plurality of sub-pixels;
The virtual image display device according to claim 5 , 6 or 7 , wherein the predetermined distance is determined based on respective positions of the plurality of sub-pixels on the display panel. A display panel that emits image light;
a projection optical system that collimates the image light from the display panel;
a light guide plate that guides the image light;
an incident diffraction optical system that causes the image light from the projection optical system to be incident on the light guide plate;
an output diffraction optical system that outputs the image light from the light guide plate;
Equipped with
The display panel includes:
A first partial display area;
A second partial display area is disposed in a first direction in which both eyes of the wearer are aligned as viewed from the first partial display area, and has the same area and shape as the first partial display area;
Including,
The image light emitted from the display panel is
a first partial image light emitted from the first partial display area;
a second partial image light emitted from the second partial display area; and
Including,
an incidence surface of the incident diffractive optical system having a first incidence area onto which the first partial image light is incident that is smaller than a second incidence area onto which the second partial image light is incident.

Images