WO2023193144A1

WO2023193144A1 - Display system

Info

Publication number: WO2023193144A1
Application number: PCT/CN2022/085351
Authority: WO
Inventors: Tatsuya Nakatsuji; Yoji Okazaki; Takashi Hashimoto
Original assignee: Guangdong Oppo Mobile Telecommunications Corp., Ltd.
Priority date: 2022-04-06
Filing date: 2022-04-06
Publication date: 2023-10-12

Abstract

A display system (1) includes a display device (10) and an optical system (20). The display device (10) includes a display surface (10a) and a pixel array (10b). The pixel array (10b) is arranged in a region including the display surface (10a). In the pixel array (10b), a plurality of pixels (12r, 12g, 12b) are arranged three-dimensionally. The plurality of pixels (12r, 12g,12b) correspond to a plurality of colors. The optical system (20) has a lens group (20a). The lens group (20a) includes a plurality of lenses (21-26). The optical system (20) is configured to convert light from the display device (10) into collimated light. When a distance between the display surface (10a) and an exit pupil surface is D TTL and a half of a maximum size of the display surface (10a) is W DISD, the display system (1) satisfies "D TTL/W DISD < 4".

Description

DISPLAY SYSTEM

TECHNICAL FIELD

The present invention relates to a display system.

BACKGROUND

A display system for realizing augmented reality (AR) can transmit light from the outside world toward an eyeball of a user by a light guide member. Along with that, the display system can convert light from a display device into collimated light by a collimating optical system and guide the collimated light toward the eyeball of the user by the light guide member.

SUMMARY

[Problem to be Solved by the Invention]

An AR image may be a multi-color (e.g., full-color) image. In this case, in order to correspond to a plurality of colors, when a wave synthesis prism is added between the display device and the collimating optical system to synthesize a plurality of monochromatic rays, an interval between the display device and the collimating optical system is widened due to the wave synthesis prism to increase the focal length of the collimating optical system, and thus not only an optical system including the collimating optical system grows in size but also an emission angle to be emitted from the display device as a virtual image, that is, a viewing angle of the AR image actually projected on eyes becomes small.

The present invention has been made in view of the above-described problem, and an object of the invention is to provide a display system that can easily downsize an optical system having a large viewing angle.

[Means for Solving Problem]

To solve the problem described above and achieve the object, a display system according to one aspect of the present invention includes a display device and an optical system. The display device includes a display surface and a pixel array. The pixel array is arranged in a region including the display surface. In the pixel array, a plurality of pixels are arranged three-dimensionally on the display surface. Each pixel in the plurality of pixels corresponds to a color. The optical system has a lens group. The lens group includes a plurality of lenses. The optical system is configured to convert light from the display device into collimated light. When a distance between the display surface and an exit pupil surface is D _TTL and a half of a maximum size of the display surface is W _DISD, the display system satisfies "D _TTL/W _DISD < 4" .

[Effect of the Invention]

According to one aspect of the present invention, it is possible to easily downsize the optical system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a schematic configuration of a display system according to an embodiment;

FIG. 2 is a perspective view illustrating a configuration of a display device according to the embodiment;

FIG. 3 is a cross-sectional view illustrating a configuration of a pixel group according to the embodiment;

FIG. 4 is a cross-sectional view illustrating a configuration of an optical system according to the embodiment;

FIG. 5 is a diagram illustrating sizes of the display device and a lens diaphragm according to the embodiment;

FIG. 6 is a diagram illustrating the configuration of the optical system according to the embodiment;

FIG. 7 is a diagram illustrating a lens shape of the optical system according to the embodiment;

FIG. 8 is a diagram illustrating characteristics of the optical system according to the embodiment;

FIG. 9 is a cross-sectional view illustrating a configuration of a display device according to a first modification example of the embodiment;

FIG. 10 is a cross-sectional view illustrating a configuration of an optical system according to a second modification example of the embodiment;

FIG. 11 is a diagram illustrating the configuration of the optical system according to the second modification example of the embodiment;

FIG. 12 is a diagram illustrating a lens shape of the optical system according to the second modification example of the embodiment;

FIG. 13 is a diagram illustrating characteristics of the optical system according to the second modification example of the embodiment;

FIG. 14 is a cross-sectional view illustrating a configuration of an optical system according to a third modification example of the embodiment;

FIG. 15 is a diagram illustrating the configuration of the optical system according to the third modification example of the embodiment;

FIG. 16 is a diagram illustrating a lens shape of the optical system according to the third modification example of the embodiment;

FIG. 17 is a diagram illustrating characteristics of the optical system according to the third modification example of the embodiment;

FIG. 18 is a cross-sectional view illustrating a configuration of an optical system according to a fourth modification example of the embodiment;

FIG. 19 is a diagram illustrating the configuration of the optical system according to the fourth modification example of the embodiment;

FIG. 20 is a diagram illustrating a lens shape of the optical system according to the fourth modification example of the embodiment;

FIG. 21 is a diagram illustrating characteristics of the optical system according to the fourth modification example of the embodiment;

FIG. 22 is a cross-sectional view illustrating a configuration of an optical system according to a fifth modification example of the embodiment;

FIG. 23 is a diagram illustrating the configuration of the optical system according to the fifth modification example of the embodiment;

FIG. 24 is a diagram illustrating a lens shape of the optical system according to the fifth modification example of the embodiment; and

FIG. 25 is a diagram illustrating characteristics of the optical system according to the fifth modification example of the embodiment.

DETAILED DESCRIPTION

Hereinafter, a display system according to an embodiment will be described in detail with reference to the accompanying drawings. Note that the present invention is not limited to this embodiment.

(Embodiment)

The display system according to the embodiment is, for example, a system (e.g., AR glasses) for realizing a multi-color AR image and is configured by combining a display device and an optical system, but effort to downsize the optical system is performed. For example, a display system 1 is configured as illustrated in FIG. 1. FIG. 1 is a diagram illustrating a configuration of the display system 1.

The display system 1 includes a display device 10, an optical system 20, and a light guide member 30. The display device 10 is arranged on the object side of the optical system 20. The light guide member 30 is arranged on the image side of the optical system 20. The light guide member 30 is, for example, a light guide plate 31. The optical system 20 is arranged between a side surface 31c of the light guide plate 31 and a display surface 10a of the display device 10. The side surface 31c of the light guide plate 31 substantially coincides with an exit pupil surface of the optical system 20. The side surface 31c has a wedge shape in which the side surface inclines toward a back surface 31b as the side surface heads from a front surface 31a to the back surface 31b. By employing such a wedge shape, the light collimated by the optical system 20 can be incident into the light guide plate 31 to be guided by the total reflection. Note that, instead of a wedge shape, by arranging a diffractive optical element DOE, a holographic optical element HOE, or the like on the front surface 31a or the back surface 31b, for example, the light collimated by the optical system 20 may be incident to the DOE and HOE within the light guide plate 31 and make the DOE and HOE change an angle for guide so as to guide the light within the light guide plate 31 by the total reflection.

The display system 1 can transmit light from the outside world toward an eyeball 100 of a user by using the light guide member 30. Along with that, the display system can convert the light from the display device 10 into collimated light by using the optical system 20, and guide the collimated light toward the eyeball 100 of the user by using the light guide member 30. The collimated light injected from the side surface 31c of the light guide plate 31 proceeds through the light guide plate 31 while being reflected by the front surface 31a and the back surface 31b of the light guide plate 31. The diffractive optical element DOE is formed in a region indicated by a thick line on the front surface 31a of the light guide plate 31. The diffractive optical element DOE has a diffraction grating structure such as periodic unevenness, and is configured so that light having a predetermined wavelength injected by a predetermined angle among light rays proceeding through the light guide plate 31 is reflected toward the eyeball 100. The light diffracted by the diffractive optical element DOE among the light rays proceeding through the light guide plate 31 may be guided toward the eyeball 100 of the user. As a result, the user distant from the light guide member 30 can visually recognize the AR image according to the image of the display device 10 without chipping. Moreover, the light guide plate 31 can easily expand an image to cause the user to visually recognize the image as the AR image by receiving the image of the display device 10 as the collimated light.

As illustrated in FIG. 2, the display device 10 may be configured to be able to display a multi-color (e.g., full-color) image. FIG. 2 is a perspective view illustrating a configuration of the display device 10.

The display device 10 includes the display surface 10a, a pixel array 10b, and a board 11. In FIG. 2, a direction perpendicular to the surface of the board 11 is a Z direction, and two directions orthogonal to each other on the surface perpendicular to the Z direction are X and Y directions. The display surface 10a extends in the XY direction. The image by the display device 10 is displayed on the display surface 10a. The optical system 20 is arranged on the +Z side of the display surface 10a. The display device 10 emits light according to an image from the display surface 10a to the optical system 20.

The pixel array 10b is arranged in a region that includes the display surface 10a and is arranged between the display surface 10a and the board 11. In the pixel array 10b, a plurality of pixel groups 13 (1, 1) to 13 (m, n) are arranged in the XY direction. The configuration that the pixel groups 13 (1, 1) to 13 (m, n) constituting m rows and n columns are arranged is exemplified in FIG. 2. Each of the pixel groups 13 is arranged on the +Z side of the board 11. A plurality of pixels 12 are arranged in the Z direction in each of the pixel groups 13. As a result, in the pixel array 10b, the plurality of pixels 12 are arranged three-dimensionally in the XYZ direction on the display surface 10a.

Each of the pixel groups 13 includes a plurality of

pixels

12r, 12g, and 12b. In the pixel group 13, the

pixels

12b, 12g, and 12r are arranged in the Z direction from a direction close to the optical system 20. In the plurality of

pixels

12r, 12g, and 12b, central axes passing through the centers of the light emitting surfaces and being perpendicular to the light emitting surfaces may substantially coincide with each other. An axis that roughly approximates the central axes of the plurality of

pixels

12r, 12g, and 12b may be considered as the central axis of the pixel group 13. Each pixel of the plurality of

pixels

12r, 12g, and 12b corresponds to a color. The pixel 12r corresponds to a first color, the pixel 12g corresponds to a second color, and the pixel 12b corresponds to a third color. The first color is light in the first wavelength range. The second color is light in the second wavelength range shorter than the first wavelength range. The third color is light in the third wavelength range shorter than the second wavelength range. For example, the first color is red (R) , the second color is green (G) , and the third color is blue (B) . In FIG. 2, a pixel corresponding to blue is 12b, a pixel corresponding to green is 12g, and a pixel corresponding to red is 12r. In each of the pixel groups 13, the

pixels

12r, 12g, and 12b are stacked onto the board 11 by bonding etc. A stacking order is not limited to the stacking order illustrated in FIG. 2, and an arbitrary stacking order may be employed.

The display device 10 is a micro LED (light emission diode) display, for example. As illustrated in FIG. 3, in the

pixels

12r, 12g, and 12b, P-type semiconductor films 12rp, 12gp, and 12bp extending in the XY direction and N-type semiconductor films 12rn, 12gn, and 12bn extending in the XY direction are stacked in the Z direction. The

pixels

12r, 12g, and 12b are applied with a voltage in a forward direction from a control circuit not illustrated, and thus emit light from bonded

interfaces

15r, 15g, and 15b between the P-type semiconductor films 12rp, 12gp, and 12bp and the N-type semiconductor films 12rn, 12gn, and 12bn. At this time, in each of the pixel groups 13, red light generated from the bonded outer surface 15r in the pixel 12r transmits the

pixels

12g and 12b and is emitted from the display surface 10a to the optical system 20, green light generated from the bonded outer surface 15g in the pixel 12g transmits the pixel 12b and is emitted from the display surface 10a to the optical system 20, and blue light generated from the bonded outer surface 15b in the pixel 12b is emitted from the display surface 10a to the optical system 20. The emission intensities of the

pixels

12r, 12g, and 12b may be respectively adjusted by the control circuit in accordance with colors to be displayed.

Note that reflecting

members

14R and 14L may be arranged on

side walls

13R and 13L of the pixel group 13 as illustrated in FIG. 3. The reflecting

member

14R and 14L may be formed of materials (e.g., metal) having reflectance properties or materials (e.g., silicon oxide) having a large refractive index difference from materials of the P-type semiconductor films 12rp, 12gp, and 12bp and the N-type semiconductor films 12rn, 12gn, and 12bn. As a result, the reflecting member 14R is arranged on the side wall 13R of the pixel group 13 to be able to form a reflective interface on the side wall 13R. The reflecting member 14L is arranged on the side wall 13L of the pixel group 13 to be able to form a reflective interface on the side wall 13L. As a result, in each of the pixel groups 13, light toward the

side walls

13R and 13L among light rays emitted from the bonded

interfaces

15r, 15g, and 15b in the

pixels

12r, 12g, and 12b can be reflected and be guided in a direction heading for the optical system 20.

As illustrated in FIGS. 2 and 3, in the display device 10, because the plurality of pixels 12 corresponding to the plurality of colors in the pixel array 10b are arranged three-dimensionally, the number of pixels of each color in a predetermined area can be easily improved and an image by the display device 10 can be made high definition. Alternatively, an aperture ratio of a pixel of each color in the predetermined area and the predetermined number of pixels can be easily improved, and the brightness of an image by the display device 10 can be increased.

As illustrated in FIG. 4, the optical system 20 is configured to convert the light from the display device 10 into the collimated light. FIG. 4 is a cross-sectional view illustrating a configuration of the optical system 20. In FIG. 4, the optical axis is illustrated with a dashed-dotted line.

The optical system 20 includes a lens group 20a. The lens group 20a has an incident surface 20b and an exit pupil surface 20c. The incident surface 20b faces the display surface 10a. The exit pupil surface 20c substantially coincides with the side surface 31c of the light guide member 30 (e.g., the light guide plate 31) . The optical system 20 receives light emitted from the display surface 10a of the display device 10 on the incident surface 20b, refracts the light to convert the light into collimated light substantially parallel to an optical axis PA, and emits the collimated light from the exit pupil surface 20c.

The lens group 20a includes a plurality of lenses 21 to 26 and a lens diaphragm 27 in sequence from the object side to the image side. The plurality of lenses 21 to 26 and the lens diaphragm 27 are arranged along the optical axis PA, and each of them intersects with the optical axis PA. The incident surface of the lens 21 closest to the object side among the plurality of lenses 21 to 26 forms the incident surface 20b of the optical system 20. The lens diaphragm 27 is arranged on the exit pupil surface 20c of the optical system 20.

The lenses 21 to 26 are formed of translucent material, and are formed of, for example, glass, quartz, translucent plastic, or the like. The lens diaphragm 27 may be formed of a light-shielding material, or may be formed of an arbitrary material to paint a color suitable for light shielding such as black color on its surface.

The plurality of lenses 21 to 26 are configured by combining lens having positive refractive power and lens having negative refractive power to correct an aberration of the lens group 20a. The plurality of lenses 21 to 26 may have different cross-sectional shapes including the optical axis PA. In FIG. 1, a lens configuration that the

lenses

22, 24, and 26 have positive refractive power and the

other lenses

21, 23, and 25 have negative refractive power in a paraxial region is exemplified.

It is desirable that the number of lenses included in the lens group 20a is 5 or more and 8 or less. When the number of lenses is 4 or less, it may be difficult to correct aberration characteristics so as to be within an allowable range. When the number of lenses is 9 or more, the optical system 20 may grow in size beyond an allowable range.

The lens group 20a may include a convex lens on the image side. The lens group 20a may include a meniscus lens or a concave lens on the object side. In the example illustrated in FIG. 4, the image-side lens 26 is a convex lens, and the object-side lens 21 is a meniscus lens.

In the lens group 20a, the diameter of the lens close to the incident surface 20b may be larger than the diameter of the lens close to the exit pupil surface 20c. In FIG. 4, the diameter of the lens 21 is larger than the diameter of the lens 26.

The lens diaphragm 27 is arranged between the light guide member 30 (e.g., the light guide plate 31) and the lens 26 in the Z direction. The lens diaphragm 27 has an aperture 27a. The aperture 27a is a substantially circular shape in an XY plan view.

Herein, it is assumed that a distance between the display surface 10a and the exit pupil surface 20c is D _TTL. It is assumed that a distance between the display surface 10a and a point at which the optical axis PA intersects with the incident surface 20b of the lens 21 closest to the object side among the plurality of lenses 21 to 26 is D _BL. As illustrated in (a) of FIG. 5, the display surface 10a of the display device 10 has a rectangular shape in which the X direction is a longitudinal direction in an XY plan view, and the length of the diagonal line is the maximum size. It is assumed that the half of the maximum size of the display surface 10a is W _DISD. It is assumed that the half of the size of the display surface 10a in the short direction is E _DISV. (a) of FIG. 5 is a diagram illustrating a size of the display surface 10a of the display device 10. As illustrated in (b) of FIG. 5, the aperture 27a of the lens diaphragm 27 has a substantially circular shape in an XY plan view and its diameter is an aperture diameter. It is assumed that an aperture diameter of the lens diaphragm 27 is W _EXA. (b) of FIG. 5 is a diagram illustrating a size of the aperture 27a of the lens diaphragm 27.

At this time, the optical system 20 satisfies the following Expressions (1) to (5) .

D _TTL/W _DISD < 4 (1)

D _TTL/W _DISD > 1.9 (2)

tan (θ _DFOV/2) < 0.75 (3)

D _BL < E _DISV (4)

D _EFL/W _EXA < 3.5 (5)

By satisfying Expression (1) in the optical system 20, when the display device 10 is made with a small size, because the entire length of the optical system 20 in the direction of the optical axis PA can be also reduced accordingly, the optical system 20 can be downsized in accordance with the display device 10 and a fashionable external shape can be realized for the display system 1 (e.g., AR glasses) .

By satisfying Expression (2) in the optical system 20, because the number of lenses (e.g., 5 or more and 8 or less) suitable for the aberration correction of the optical system 20 can be included, the imaging characteristic of the optical system 20 can be within an allowable range and the performance of the display system 1 can be improved.

By satisfying Expression (3) in the optical system 20, because an angle of view can be widely secured while downsizing the optical system 20, a fashionable external shape can be realized for the display system 1, and also a wide-field image can be realized and realistic sensation in use can be increased. When Expression (3) is not satisfied, because a viewing angle becomes large and thus the light guide member 30 also becomes large, it becomes difficult to fit in an appropriate size when the display system is mounted on the AR glasses having a highly fashionable glass shape, for example.

By satisfying Expression (4) in the optical system 20, when the display device 10 is made with a small size, because back focus can be shortened accordingly, the focal length of the optical system 20 can be reduced and the optical system is easy to have a wide field of view and a compact size.

By satisfying Expression (5) in the optical system 20, because effective F-number can be reduced, a combined image by the optical system 20 can easily have high brightness.

Next, a mounting configuration of the optical system 20 will be described with reference to FIGS. 4 to 7. FIG. 6 is a diagram illustrating optical configuration and characteristics of the optical system 20. FIG. 7 is a diagram illustrating surface shapes of the lenses 21 to 26 in the lens group 20a.

In FIG. 4, the configuration that the number of the lens 21 to 26 included in the lens group 20a is 6 is exemplified. In FIG. 4, the optical axis PA is illustrated with a dashed-dotted line, and passes through the substantial center of the aperture 27a of the lens diaphragm 27. Optical paths of light emitted from a center CP (see (a) of FIG. 5) of the display surface 10a of the display device 10 are illustrated with solid lines. Optical paths of light emitted from a maximum image-height position PP2 (see (a) of FIG. 5) of the display surface 10a of the display device 10 are illustrated with dotted lines. Optical paths of light emitted from a maximum image-height position PP1 (see (a) of FIG. 5) of the display surface 10a of the display device 10 are illustrated with dashed-two dotted lines.

(a) of FIG. 6 illustrates that the optical system 20 satisfies all of Expressions (1) to (5) . In other words, in (a) of FIG. 6, it is indicated that, by being configured to satisfy all of Expressions (1) to (5) , in the optical system 20, an entire length (the Z-direction length) can be set to around 8.052 mm, an angle of view can be secured to be "θ _DFOV = around 72.000 [°] " , and effective F-number can be reduced to around 1.483.

In (b) of FIG. 6 and (a) and (b) of FIG. 7, surface numbers are assigned as follows:

Surface number: 1: Exit surface of the lens diaphragm 27;

Surface number: 3: Exit surface of the lens 26;

Surface number: 4: Incident surface of the lens 26;

Surface number: 5: Exit surface of the lens 25;

Surface number: 6: Incident surface of the lens 25;

Surface number: 7: Exit surface of the lens 24;

Surface number: 8: Incident surface of the lens 24;

Surface number: 9: Exit surface of the lens 23;

Surface number: 10: Incident surface of the lens 23;

Surface number: 11: Exit surface of the lens 22;

Surface number: 12: Incident surface of the lens 22;

Surface number: 13: Exit surface of the lens 21; and

Surface number: 14: Incident surface of the lens 21.

In (b) of FIG. 6, a curvature radius R [mm] , a surface separation D [mm] , a refractive index Nd, an Abbe number Vd, and a focal length are indicated for each surface of surface numbers 1 to 14. A lens configuration is indicated with the curvature radius R. The lens group 20a is configured to include, in a paraxial region, the convex lens 26, the positive meniscus lens 25 with a convex surface facing the image side, the positive meniscus lens 24 with a convex surface facing the image side, the positive meniscus lens 23 with a convex surface facing the image side, the convex lens 22, and the positive meniscus lens 21 with a convex surface facing the image side, in order from the image side. It is possible to preferably correct a chromatic aberration by causing the lenses 21 to 26 to have the different refractive indices Nd and Abbe numbers Vd.

In (a) and (b) of FIG. 7, an aspherical shape is indicated for each surface of surface numbers 3 to 14. Assuming that the Z position (position in the direction of the optical axis PA) is z, the curvature radius is R, the XY direction distance from the optical axis PA is H, the conical constant is k, and the aspherical coefficients are A3, A4, ..., A19, and A20, the aspherical shape is expressed by the following Expression (6) .

In (a) and (b) of FIG. 7, the aspherical coefficients A3, A4, ..., A19, and A20 are indicated for each surface of surface numbers 3 to 14. Each surface of surface numbers 3 to 14 is obtained by rotating a curved line expressed by an expression obtained by substituting the aspherical coefficients A3 to A20 of (a) and (b) of FIG. 7 into Expression (6) around the optical axis PA. Note that, in (a) and (b) of FIG. 7, "E-i" is an exponential notation with a base of 10. Herein, "i" is an integer number. A spherical aberration can be preferably corrected by making each surface of surface numbers 3 to 14 an aspheric surface as illustrated in (a) and (b) of FIG. 7.

The optical system 20 configured as illustrated in FIGS. 4 to 7 exhibits aberration characteristics as illustrated in FIG. 8. FIG. 8 is a diagram illustrating aberration characteristics of the optical system 20. Note that the aberration characteristics of the optical system 20 are to present an aberration when parallel rays corresponding to an angle of view of the AR image are caused to be injected from the lens diaphragm 27 that is an exit pupil of the optical system 20 and the parallel rays are reversely traced and virtually imaged on the display surface 10a of the display device 10.

(a) of FIG. 8 illustrates an aberration diagram of astigmatism with reference to the display surface 10a (virtual image surface) . Herein, the vertical axis indicates an image height and the horizontal axis indicates the size of an aberration. In (a) of FIG. 8, the case where an angle of view θ _DFOV is 72° is exemplified. In the aberration diagram of the optical system 20 illustrated in (a) of FIG. 8, an aberration amount on a tangential surface for d-line (wavelength: 587.56 nm) is illustrated with a solid line, and an aberration amount on a sagittal surface is illustrated with a dotted line. The tangential surface is a surface including a principal ray and the optical axis PA. The sagittal surface is a surface including a principal ray and perpendicular to the tangential surface. In (a) of FIG. 8, the case where astigmatism is suppressed within an allowable range is illustrated.

(b) of FIG. 8 illustrates an aberration diagram of distortion aberration with reference to the display surface 10a (virtual image surface) . Herein, the vertical axis indicates an image height and the horizontal axis indicates the size of an aberration. In (b) of FIG. 8, the case where the angle of view θ _DFOV is 72° is exemplified. In the aberration diagram of the optical system 20 illustrated in (b) of FIG. 8, an aberration amount for d-line (wavelength: 587.56 nm) is illustrated with a solid line. In (b) of FIG. 8, the case where distortion aberration is suppressed within an allowable range is illustrated.

(c) of FIG. 8 illustrates an aberration diagram of spherical aberration with reference to the display surface 10a (virtual image surface) . Herein, the vertical axis indicates an eye image height and the horizontal axis indicates the size of an aberration. In (c) of FIG. 8, the case where the F-number Fno is 1.48 is exemplified. In the aberration diagram of the optical system 20 illustrated in (c) of FIG. 8, an aberration amount for c-line (wavelength: 656.28 nm) is illustrated with a dashed-dotted line, an aberration amount for d-line (wavelength: 587.56 nm) is illustrated with a solid line, and an aberration amount for g-line (wavelength: 435.84 nm) is illustrated with a dotted line. In (c) of FIG. 8, the case where spherical aberration is suppressed within an allowable range is illustrated.

(d) of FIG. 8 illustrates an aberration diagram of chromatic aberration of magnification with reference to the display surface 10a (virtual image surface) . Herein, the vertical axis indicates an image height and the horizontal axis indicates the size of an aberration. In (d) of FIG. 8, the case where the angle of view θ _DFOV is 72° is exemplified. In the aberration diagram of the optical system 20 illustrated in (d) of FIG. 8, an aberration amount on the sagittal surface for d-line (wavelength: 587.56 nm) is illustrated with a solid line, and an aberration amount on the tangential surface is illustrated with a dotted line. In (d) of FIG. 8, the case where chromatic aberration of magnification is suppressed within an allowable range is illustrated.

As described above, in the embodiment, the display system 1 is configured by combining the display device 10 in which the plurality of pixels 12 corresponding to the plurality of colors are arranged three-dimensionally and the optical system 20 that converts the emitted light into the collimated light. As a result, an image by the display device 10 can be made high definition or high brightness and the image with high definition and high brightness can be supplied to the light guide member 30.

Further, in the embodiment, in the optical system 20 of the display system 1, a ratio between the distance between the display surface 10a of the display device 10 and the exit pupil surface 20c of the optical system 20 and the half of the maximum size of the display surface 10a becomes smaller than 4. As a result, when the display device 10 is made with a small size, because the entire length of the optical system 20 in the direction of the optical axis PA can be also reduced accordingly, the optical system 20 can be downsized in accordance with the display device 10, and a fashionable external shape can be realized for the display system 1 (e.g., AR glasses) .

Note that the light guide member 30 can be applied with an arbitrary member that can transmit light from the outside world toward the eyeball 100 of the user and can guide light from the display device 10 toward the eyeball 100 of the user, and is not limited to the light guide plate 31 illustrated in FIG. 1. For example, instead of the diffractive optical element DOE, a holographic optical element may be provided on the light guide plate 31. The holographic optical element has an interference fringe pattern and is configured so that light having a predetermined wavelength injected by a predetermined angle among light rays proceeding through the light guide plate 31 is reflected toward the eyeball 100. Alternatively, instead of the diffractive optical element DOE, a light-guide optical element may be provided on the light guide plate 31. The light-guide optical element has a multi-stage half mirror to intersect with an optical path of light proceeding through the light guide plate 31, and is configured to reflect some of light rays incident on the multi-stage half mirror toward the eyeball 100. Alternatively, instead of the diffractive optical element DOE, a pin mirror may be provided on the light guide plate 31. The pin mirror has a multi-stage mirror with a small reflecting surface to intersect with the optical path of light proceeding through the light guide plate 31, and is configured to reflect light rays incident on the multi-stage mirror toward the eyeball 100.

Moreover, according to the first modification example of the embodiment, a display device 110 in a display system 101 may further include a plurality of micro-lenses 14 (1, 1) to 14 (m, n) , as illustrated in FIG. 9. Each micro-lens 14 (1, 1) to 14 (m, n) corresponds to a pixel group 13 (1, 1) to 13 (m, n) . Each micro-lens 14 is also referred to as an on-chip lens. FIG. 9 is a cross- sectional view illustrating a configuration of the display device 110 according to the first modification example of the embodiment. FIG. 9 also illustrates a cross section when the display device 110 is cut parallel to the Z-axis through the maximum image-height position PP2, the center CP, and the maximum image-height position PP1 (see (a) of FIG. 5) of the display surface 10a.

In each micro-lens 14, a positional relationship between the optical axis and the central axis of the corresponding pixel group 13 may correspond to an emission direction of light from the micro-lens 14 to the optical system 20.

Among the plurality of pixel groups 13 (1, 1) to 13 (m, n) , the pixel group 13 (1, 1) is a pixel group near the maximum image-height position PP1 and has a central axis AX (1, 1) . The central axis AX (1, 1) substantially coincides with axes parallel to the Z-axis through the centers of the light emitting surfaces of the pixel 12b (1, 1) , the pixel 12g (1, 1) , and the pixel 12r (1, 1) .

Among the plurality of micro-lenses 14 (1, 1) to 14 (m, n) , the micro-lens 14 (1, 1) is a micro-lens near the maximum image-height position PP1 and has an optical axis OA (1, 1) . Compared to the central axis AX (1, 1) , the optical axis OA (1, 1) shifts in the +X direction and the +Y direction so as to be closer to the center CP. The direction of the shift means that the emission direction of light from the micro-lens 14 (1, 1) to the optical system 20 is inclined from the +Z direction to the +X direction and the +Y direction.

Among the plurality of pixel groups 13 (1, 1) to 13 (m, n) , the pixel group 13 (j, k) is a pixel group near the center CP and has a central axis AX (j, k) . "j" is an integer number that is larger than 1 and smaller than m. "k" is an integer number that is larger than 1 and smaller than n. The central axis AX (j, k) substantially coincides with axes parallel to the Z-axis through the centers of the light emitting surfaces of the pixel 12b (j, k) , the pixel 12g (j, k) , and the pixel 12r (j, k) .

Among the plurality of micro-lenses 14 (1, 1) to 14 (m, n) , the micro-lens 14 (j, k) is a micro-lens near the center CP and has an optical axis OA (j, k) . The optical axis OA (j, k) substantially coincides with the central axis AX (j, k) .

Among the plurality of pixel groups 13 (1, 1) to 13 (m, n) , the pixel group 13 (m, n) is a pixel group near the maximum image-height position PP2 and has a central axis AX (m, n) . The central axis AX (m, n) substantially coincides with axes parallel to the Z-axis through the centers of the light emitting surfaces of the pixel 12b (m, n) , the pixel 12g (m, n) , and the pixel 12r (m, n) .

Among the plurality of micro-lenses 14 (1, 1) to 14 (m, n) , the micro-lens 14 (m, n) is a micro-lens near the maximum image-height position PP2 and has an optical axis OA (m, n) . Compared to the central axis AX (m, n) , the optical axis OA (m, n) shifts in the -X direction and the -Y direction so as to be closer to the center CP. The direction of the shift means that the emission direction of light from the micro-lens 14 (m, n) to the optical system 20 is inclined from the +Z direction to the -X direction and the -Y direction.

As described above, among the plurality of micro-lenses 14 in the display device 110 of the display system 101, a distance between the optical axis OA of the micro-lens 14 and the central axis AX of the pixel group 13 corresponding to the micro-lens is larger than a distance between the optical axis OA of the micro-lens 14 closer to the center CP and the central axis AX of the pixel group 13 corresponding to the closer micro-lens. As a result, the emission direction of light from the pixel group 13 can be inclined, conforming with the direction (see FIG. 4) of light proceeding to the optical system 20 in accordance with the position of the pixel group 13 on the display surface 10a, and thus the light can be efficiently emitted from the display device 110 into the optical system 20.

Moreover, according to the second modification example of the embodiment, an optical system 220 in a display system 201 may be configured as illustrated in FIGS. 10 to 12. FIG. 10 is a cross-sectional view illustrating a configuration of the optical system 220 according to the second modification example of the embodiment. FIG. 11 is a diagram illustrating optical configuration and characteristics of the optical system 220. FIG. 12 is a diagram illustrating surface shapes of lenses 221 to 226 in a lens group 220a.

The optical system 220 includes the lens group 220a instead of the lens group 20a (see FIG. 4) . The lens group 220a includes the plurality of lenses 221 to 226 and a lens diaphragm 227 corresponding to the plurality of lenses 21 to 26 and the lens diaphragm 27. The plurality of lenses 221 to 226 have cross-sectional shapes different from each other. The number of the lenses 221 to 226 included in the lens group 220a is 6. In the lens group 220a, the image-side lens 226 is a convex lens, and the object-side lens 221 is a meniscus lens. The diameter of the object-side lens 221 is larger than the diameter of the image-side lens 226.

In FIG. 10, the optical axis PA is illustrated with a dashed-dotted line and passes through the substantial center of an aperture 227a of the lens diaphragm 227. An optical path of light emitted from the center CP (see (a) of FIG. 5) of the display surface 10a of the display device 10 is illustrated with a solid line. An optical path of light emitted from the maximum image-height position PP2 (see (a) of FIG. 5) of the display surface 10a of the display device 10 is illustrated with a dotted line. An optical path of light emitted from the maximum image-height position PP1 (see (a) of FIG. 5) of the display surface 10a of the display device 10 is illustrated with a dashed-two dotted line.

(a) of FIG. 11 illustrates that the optical system 220 satisfies all of Expressions (1) to (5) . In other words, in (a) of FIG. 11, it is indicated that, by being configured to satisfy all of Expressions (1) to (5) , in the optical system 220, an entire length (the Z-direction length) can be set to around 8.492 mm, an angle of view can be secured to be "θ _DFOV = around 64.000 [°] " , and effective F-number can be reduced to around 1.588.

In (b) of FIG. 11 and (a) and (b) of FIG. 12, surface numbers are assigned as follows:

Surface number: 1: Exit surface of the lens diaphragm 227;

Surface number: 3: Exit surface of the lens 226;

Surface number: 4: Incident surface of the lens 226;

Surface number: 5: Exit surface of the lens 225;

Surface number: 6: Incident surface of the lens 225;

Surface number: 7: Exit surface of the lens 224;

Surface number: 8: Incident surface of the lens 224;

Surface number: 9: Exit surface of the lens 223;

Surface number: 10: Incident surface of the lens 223;

Surface number: 11: Exit surface of the lens 222;

Surface number: 12: Incident surface of the lens 222;

Surface number: 13: Exit surface of the lens 221; and

Surface number: 14: Incident surface of the lens 221.

In (b) of FIG. 11, the curvature radius R [mm] , the surface separation D [mm] , the refractive index Nd, the Abbe number Vd, and the focal length are indicated for each surface of surface numbers 1 to 14. A lens configuration is indicated with the curvature radius R. The lens group 220a is configured to include, in a paraxial region, the convex lens 226, the positive meniscus lens 225 with a convex surface facing the image side, the negative meniscus lens 224 with a convex surface facing the object side, the positive meniscus lens 223 with a convex surface facing the image side, the convex lens 222, and the positive meniscus lens 221 with a convex surface facing the image side, in order from the image side. It is possible to preferably correct a chromatic aberration by causing the lenses the lenses 221 to 226 to have the different refractive indices Nd and Abbe numbers Vd.

In (a) and (b) of FIG. 12, an aspherical shape is indicated for each surface of surface numbers 3 to 14. Assuming that the Z position (position in the direction of the optical axis PA) is z, the curvature radius is R, the XY direction distance from the optical axis PA is H, the conical constant is k, and the aspherical coefficients are A3, A4, ..., A19, and A20, the aspherical shape is expressed by Expression (6) .

In (a) and (b) of FIG. 12, the aspherical coefficients A3, A4, ..., A19, and A20 are indicated for each surface of surface numbers 3 to 14. Each surface of surface numbers 3 to 14 is obtained by rotating a curved line expressed by an expression obtained by substituting the aspherical coefficients A3 to A20 of (a) and (b) of FIG. 12 into Expression (6) around the optical axis PA. Note that "E-i" is an exponential notation with a base of 10 in (a) and (b) of FIG. 12. Herein, "i" is an integer number. A spherical aberration can be preferably corrected by making each surface of surface numbers 3 to 14 an aspheric surface as illustrated in (a) and (b) of FIG. 12.

The optical system 220 configured as illustrated in FIGS. 10 to 12 exhibits aberration characteristics as illustrated in FIG. 13. FIG. 13 is a diagram illustrating the aberration characteristics of the optical system 220. Note that the aberration characteristics of the optical system 220 are to present an aberration when parallel rays corresponding to an angle of view of the AR image are caused to be injected from the lens diaphragm 227 that is an exit pupil of the optical system 220 and the parallel rays are reversely traced and virtually imaged on the display surface 10a of the display device 10.

(a) of FIG. 13 illustrates an aberration diagram of astigmatism with reference to the display surface 10a (virtual image surface) . Herein, the vertical axis indicates an image height and the horizontal axis indicates the size of an aberration. In (a) of FIG. 13, the case where the angle of view θ _DFOV is 72° is exemplified. In the aberration diagram of the optical system 220 illustrated in (a) of FIG. 13, an aberration amount on a tangential surface for d-line (wavelength: 587.56 nm) is illustrated with a solid line, and an aberration amount on a sagittal surface is illustrated with a dotted line. The tangential surface is a surface including a principal ray and the optical axis PA. The sagittal surface is a surface including a principal ray and perpendicular to the tangential surface. In (a) of FIG. 13, the case where astigmatism is suppressed within an allowable range is illustrated.

(b) of FIG. 13 illustrates an aberration diagram of distortion aberration with reference to the display surface 10a (virtual image surface) . Herein, the vertical axis indicates an image height and the horizontal axis indicates the size of an aberration. In (b) of FIG. 13, the case where the angle of view θ _DFOV is 72° is exemplified. In the aberration diagram of the optical system 220 illustrated in (b) of FIG. 13, an aberration amount for d-line (wavelength: 587.56 nm) is illustrated with a solid line. In (b) of FIG. 13, the case where distortion aberration is suppressed within an allowable range is illustrated.

(c) of FIG. 13 illustrates an aberration diagram of spherical aberration with reference to the display surface 10a (virtual image surface) . Herein, the vertical axis indicates an eye image height and the horizontal axis indicates the size of an aberration. In (c) of FIG. 13, the case where the F-number Fno is 1.59 is exemplified. In the aberration diagram of the optical system 220 illustrated in (c) of FIG. 13, an aberration amount for c-line (wavelength: 656.28 nm) is illustrated with a dashed-dotted line, an aberration amount for d-line (wavelength: 587.56 nm) is illustrated with a solid line, and an aberration amount for g-line (wavelength: 435.84 nm) is illustrated with a dotted line. In (c) of FIG. 13, the case where spherical aberration is suppressed within an allowable range is illustrated.

(d) of FIG. 13 illustrates an aberration diagram of chromatic aberration of magnification with reference to the display surface 10a (virtual image surface) . Herein, the vertical axis indicates an image height and the horizontal axis indicates the size of an aberration. In (d) of FIG. 13, the case where the angle of view θ _DFOV is 72° is exemplified. In the aberration diagram of the optical system 220 illustrated in (d) of FIG. 13, an aberration amount on the sagittal surface for d-line (wavelength: 587.56 nm) is illustrated with a solid line, and an aberration amount on the tangential surface is illustrated with a dotted line. In (d) of FIG. 13, the case where chromatic aberration of magnification is suppressed within an allowable range is illustrated.

As described above, also in the optical system 220 of the display system 201, a ratio between the distance between the display surface 10a of the display device 10 and an exit pupil surface 220c of the optical system 220 and the half of the maximum size of the display surface 10a becomes smaller than 4. As a result, when the display device 10 is made with a small size, because the entire length of the optical system 220 in the direction of the optical axis PA can be also reduced accordingly, the optical system 220 can be downsized in accordance with the display device 10, and a fashionable external shape can be realized for the display system 201 (e.g., AR glasses) .

Moreover, according to the third modification example of the embodiment, an optical system 320 in a display system 301 may be configured as illustrated in FIGS. 14 to 16. FIG. 14 is a cross-sectional view illustrating a configuration of the optical system 320 according to the third modification example of the embodiment. FIG. 15 is a diagram illustrating optical configuration and characteristics of the optical system 320. FIG. 16 is a diagram illustrating surface shapes of lenses 321 to 325 in a lens group 320a.

The optical system 320 includes the lens group 320a instead of the lens group 20a (see FIG. 4) . The lens group 320a includes the plurality of lenses 321 to 325 and a lens diaphragm 327 corresponding to the plurality of lenses 21 to 26 and the lens diaphragm 27. The plurality of lenses 321 to 325 have cross-sectional shapes different from each other. The number of the lenses 321 to 325 included in the lens group 320a is 5. In the lens group 320a, the image-side lens 325 is a convex lens and the object-side lens 321 is a concave lens. The diameter of the object-side lens 321 is larger than the diameter of the image-side lens 325.

In FIG. 14, the optical axis PA is illustrated with a dashed-dotted line and passes through the substantial center of an aperture 327a of the lens diaphragm 327. An optical path of light emitted from the center CP (see (a) of FIG. 5) of the display surface 10a of the display device 10 is illustrated with a solid line. An optical path of light emitted from the maximum image-height position PP2 (see (a) of FIG. 5) of the display surface 10a of the display device 10 is illustrated with a dotted line. An optical path of light emitted from the maximum image-height position PP1 (see (a) of FIG. 5) of the display surface 10a of the display device 10 is illustrated with a dashed-two dotted line.

(a) of FIG. 15 illustrates that the optical system 320 satisfies all of Expressions (1) to (5) . In other words, in (a) of FIG. 15, it is indicated that, by being configured to satisfy all of Expressions (1) to (5) , in the optical system 320, an entire length (the Z-direction length) can be set to around 10.37 1mm, an angle of view can be secured to be "θ _DFOV = around 72.000 [°] " , and effective F-number can be reduced to around 1.451.

In (b) of FIG. 15 and (a) and (b) of FIG. 16, surface numbers are assigned as follows:

Surface number: 1: Exit surface of the lens diaphragm 327;

Surface number: 3: Exit surface of the lens 325;

Surface number: 4: Incident surface of the lens 325;

Surface number: 5: Exit surface of the lens 324;

Surface number: 6: Incident surface of the lens 324;

Surface number: 7: Exit surface of the lens 323;

Surface number: 8: Incident surface of the lens 323;

Surface number: 9: Exit surface of the lens 322;

Surface number: 10: Incident surface of the lens 322;

Surface number: 11: Exit surface of the lens 321; and

Surface number: 12: Incident surface of the lens 321.

In (b) of FIG. 15, the curvature radius R [mm] , the surface separation D [mm] , the refractive index Nd, the Abbe number Vd, and the focal length are indicated for each surface of surface numbers 1 to 12. A lens configuration is indicated with the curvature radius R. The lens group 320a is configured to include, in a paraxial region, the convex lens 325, the positive meniscus lens 324 with a convex surface facing the image side, the convex lens 323, the convex lens 322, and the negative lens 321 with concave surfaces on both sides, in order from the image side. It is possible to preferably correct a chromatic aberration by causing the lenses 321 to 325 to have the different refractive indices Nd and Abbe numbers Vd.

In (a) and (b) of FIG. 16, an aspherical shape is indicated for each surface of surface numbers 3 to 12. Assuming that the Z position (position in the direction of the optical axis PA) is z, the curvature radius is R, the XY direction distance from the optical axis PA is H, the conical constant is k, and the aspherical coefficients are A3, A4, ..., A19, and A20, the aspherical shape is expressed by Expression (6) .

In (a) and (b) of FIG. 16, the aspherical coefficients A3, A4, ..., A19, and A20 are indicated for each surface of surface numbers 3 to 12. Each surface of surface numbers 3 to 12 is obtained by rotating a curved line expressed by an expression obtained by substituting the aspherical coefficients A3 to A20 of (a) and (b) of FIG. 16 into Expression (6) around the optical axis PA. Note that "E-i" is an exponential notation with a base of 10 in (a) and (b) of FIG. 16. Herein, "i" is an integer number. A spherical aberration can be preferably corrected by making each surface of surface numbers 3 to 12 an aspheric surface as illustrated in (a) and (b) of FIG. 16.

The optical system 320 configured as illustrated in FIGS. 14 to 16 exhibits aberration characteristics as illustrated in FIG. 17. FIG. 17 is a diagram illustrating the aberration characteristics of the optical system 320. Note that the aberration characteristics of the optical system 320 are to present an aberration when parallel rays corresponding to an angle of view of the AR image are caused to be injected from the lens diaphragm 327 that is an exit pupil of the optical system 320 and the parallel rays are reversely traced and virtually imaged on the display surface 10a of the display device 10.

(a) of FIG. 17 illustrates an aberration diagram of astigmatism with reference to the display surface 10a (virtual image surface) . Herein, the vertical axis indicates an image height and the horizontal axis indicates the size of an aberration. In (a) of FIG. 17, the case where an angle of view θ _DFOV is 72° is exemplified. In the aberration diagram of the optical system 320 illustrated in (a) of FIG. 17, an aberration amount on a tangential surface for d-line (wavelength: 587.56 nm) is illustrated with a solid line, and an aberration amount on a sagittal surface is illustrated with a dotted line. The tangential surface is a surface including a principal ray and the optical axis PA. The sagittal surface is a surface including a principal ray and perpendicular to the tangential surface. In (a) of FIG. 17, the case where astigmatism is suppressed within an allowable range is illustrated.

(b) of FIG. 17 illustrates an aberration diagram of distortion aberration with reference to the display surface 10a (virtual image surface) . Herein, the vertical axis indicates an image height and the horizontal axis indicates the size of an aberration. In (b) of FIG. 17, the case where the angle of view θ _DFOV is 72° is exemplified. In the aberration diagram of the optical system 320 illustrated in (b) of FIG. 17, an aberration amount for d-line (wavelength: 587.56 nm) is illustrated with a solid line. In (b) of FIG. 17, the case where distortion aberration is suppressed within an allowable range is illustrated.

(c) of FIG. 17 illustrates an aberration diagram of spherical aberration with reference to the display surface 10a (virtual image surface) . Herein, the vertical axis indicates an eye image height and the horizontal axis indicates the size of an aberration. In (c) of FIG. 17, the case where the F-number Fno is 1.45 is exemplified. In the aberration diagram of the optical system 320 illustrated in (c) of FIG. 17, an aberration amount for c-line (wavelength: 656.28 nm) is illustrated with a dashed-dotted line, an aberration amount for d-line (wavelength: 587.56 nm) is illustrated with a solid line, and an aberration amount for g-line (wavelength: 435.84 nm) is illustrated with a dotted line. In (c) of FIG. 17, the case where spherical aberration is suppressed within an allowable range is illustrated.

(d) of FIG. 17 illustrates an aberration diagram of chromatic aberration of magnification with reference to the display surface 10a (virtual image surface) . Herein, the vertical axis indicates an image height and the horizontal axis indicates the size of an aberration. In (d) of FIG. 17, the case where the angle of view θ _DFOV is 72° is exemplified. In the aberration diagram of the optical system 320 illustrated in (d) of FIG. 17, an aberration amount on the sagittal surface for d-line (wavelength: 587.56 nm) is illustrated with a solid line, and an aberration amount on the tangential surface is illustrated with a dotted line. In (d) of FIG. 17, the case where chromatic aberration of magnification is suppressed within an allowable range is illustrated.

As described above, also in the optical system 320 of the display system 301, a ratio between the distance between the display surface 10a of the display device 10 and an exit pupil surface 320c of the optical system 320 and the half of the maximum size of the display surface 10a becomes smaller than 4. As a result, when the display device 10 is made with a small size, because the entire length of the optical system 320 in the direction of the optical axis PA can be also reduced accordingly, the optical system 320 can be downsized in accordance with the display device 10, and a fashionable external shape can be realized for the display system 301 (e.g., AR glasses) .

Moreover, according to the fourth modification example of the embodiment, an optical system 420 in a display system 401 may be configured as illustrated in FIGS. 18 to 20. FIG. 18 is a cross-sectional view illustrating a configuration of the optical system 420 according to the fourth modification example of the embodiment. FIG. 19 is a diagram illustrating optical configuration and characteristics of the optical system 420. FIG. 20 is a diagram illustrating surface shapes of lenses 421 to 425 in a lens group 420a.

The optical system 420 includes the lens group 420a instead of the lens group 20a (see FIG. 4) . The lens group 420a includes the plurality of lenses 421 to 425 and a lens diaphragm 427 corresponding to the plurality of lenses 21 to 26 and the lens diaphragm 27. The plurality of lenses 421 to 425 have cross-sectional shapes different from each other. The number of the lenses 421 to 425 included in the lens group 420a is 5. In the lens group 420a, the image-side lens 424 is a convex lens and the object-side lens 421 is a meniscus lens. The diameter of the object-side lens 421 is larger than the diameter of the image-side lens 424.

In FIG. 18, the optical axis PA is illustrated with a dashed-dotted line and passes through the substantial center of an aperture 427a of the lens diaphragm 427. An optical path of light emitted from the center CP (see (a) of FIG. 5) of the display surface 10a of the display device 10 is illustrated with a solid line. An optical path of light emitted from the maximum image-height position PP2 (see (a) of FIG. 5) of the display surface 10a of the display device 10 is illustrated with a dotted line. An optical path of light emitted from the maximum image-height position PP1 (see (a) of FIG. 5) of the display surface 10a of the display device 10 is illustrated with a dashed-two dotted line.

(a) of FIG. 19 illustrates that the optical system 420 satisfies all of Expressions (1) to (5) . In other words, in (a) of FIG. 19, it is indicated that, by being configured to satisfy all of Expressions (1) to (5) , in the optical system 420, an entire length (the Z-direction length) can be set to around 13.990 mm, an angle of view can be secured to be "θ _DFOV = 60.000 [°] " , and effective F-number can be reduced to around 1.778.

In (b) of FIG. 19 and (a) and (b) of FIG. 20, surface numbers are assigned as follows:

Surface number: 1: Exit surface of the lens diaphragm 427;

Surface number: 3: Exit surface of the lens 425;

Surface number: 4: Incident surface of the lens 425;

Surface number: 5: Exit surface of the lens 424;

Surface number: 6: Incident surface of the lens 424;

Surface number: 7: Exit surface of the lens 423;

Surface number: 8: Incident surface of the lens 423;

Surface number: 9: Exit surface of the lens 422;

Surface number: 10: Incident surface of the lens 422;

Surface number: 11: Exit surface of the lens 421; and

Surface number: 12: Incident surface of the lens 421.

In (b) of FIG. 19, the curvature radius R [mm] , the surface separation D [mm] , the refractive index Nd, the Abbe number Vd, and the focal length are indicated for each surface of surface numbers 1 to 12. A lens configuration is indicated with the curvature radius R. The lens group 420a is configured to include, in a paraxial region, the convex lens 425, the positive meniscus lens 424 with a convex surface facing the image side, the convex lens 423, the convex lens 422, and the negative lens 421 with concave surfaces on both sides, in order from the image side. It is possible to preferably correct a chromatic aberration by causing the lenses 421 to 425 to have the different refractive indices Nd and Abbe numbers Vd.

In (a) and (b) of FIG. 20, an aspherical shape is indicated for each surface of surface numbers 3 to 12. Assuming that the Z position (position in the direction of the optical axis PA) is z, the curvature radius is R, the XY direction distance from the optical axis PA is H, the conical constant is k, and the aspherical coefficients are A3, A4, ..., A19, and A20, the aspherical shape is expressed by Expression (6) .

In (a) and (b) of FIG. 20, the aspherical coefficients A3, A4, ..., A19, and A20 are indicated for each surface of surface numbers 3 to 12. Each surface of surface numbers 3 to 12 is obtained by rotating a curved line expressed by an expression obtained by substituting the aspherical coefficients A3 to A20 of (a) and (b) of FIG. 20 into Expression (6) around the optical axis PA. Note that "E-i" is an exponential notation with a base of 10 in (a) and (b) of FIG. 20. Herein, "i" is an integer number. A spherical aberration can be preferably corrected by making each surface of surface numbers 3 to 12 an aspheric surface as illustrated in (a) and (b) of FIG. 20.

The optical system 420 configured as illustrated in FIGS. 18 to 20 exhibits aberration characteristics as illustrated in FIG. 21. FIG. 21 is a diagram illustrating the aberration characteristics of the optical system 420. Note that the aberration characteristics of the optical system 420 are to present an aberration when parallel rays corresponding to an angle of view of the AR image are caused to be injected from the lens diaphragm 427 that is an exit pupil of the optical system 420 and the parallel rays are reversely traced and virtually imaged on the display surface 10a of the display device 10.

(a) of FIG. 21 illustrates an aberration diagram of astigmatism with reference to the display surface 10a (virtual image surface) . Herein, the vertical axis indicates an image height and the horizontal axis indicates the size of an aberration. In (a) of FIG. 21, the case where an angle of view θ _DFOV is 60° is exemplified. In the aberration diagram of the optical system 420 illustrated in (a) of FIG. 21, an aberration amount on a tangential surface for d-line (wavelength: 587.56 nm) is illustrated with a solid line, and an aberration amount on a sagittal surface is illustrated with a dotted line. The tangential surface is a surface including a principal ray and the optical axis PA. The sagittal surface is a surface including a principal ray and perpendicular to the tangential surface. In (a) of FIG. 21, the case where astigmatism is suppressed within an allowable range is illustrated.

(b) of FIG. 21 illustrates an aberration diagram of distortion aberration with reference to the display surface 10a (virtual image surface) . Herein, the vertical axis indicates an image height and the horizontal axis indicates the size of an aberration. In (b) of FIG. 21, the case where the angle of view θ _DFOV is 60° is exemplified. In the aberration diagram of the optical system 420 illustrated in (b) of FIG. 21, an aberration amount for d-line (wavelength: 587.56 nm) is illustrated with a solid line. In (b) of FIG. 21, the case where distortion aberration is suppressed within an allowable range is illustrated.

(c) of FIG. 21 illustrates an aberration diagram of spherical aberration with reference to the display surface 10a (virtual image surface) . Herein, the vertical axis indicates an eye image height and the horizontal axis indicates the size of an aberration. In (c) of FIG. 21, a case where the F-number Fno is 1.78 is exemplified. In the aberration diagram of the optical system 420 illustrated in (c) of FIG. 21, an aberration amount for c-line (wavelength: 656.28 nm) is illustrated with a dashed-dotted line, an aberration amount for d-line (wavelength: 587.56 nm) is illustrated with a solid line, and an aberration amount for g-line (wavelength: 435.84 nm) is illustrated with a dotted line. In (c) of FIG. 21, the case where spherical aberration is suppressed within an allowable range is illustrated.

(d) of FIG. 21 illustrates an aberration diagram of chromatic aberration of magnification with reference to the display surface 10a (virtual image surface) . Herein, the vertical axis indicates an image height and the horizontal axis indicates the size of an aberration. In (d) of FIG. 21, the case where the angle of view θ _DFOV is 60° is exemplified. In the aberration diagram of the optical system 420 illustrated in (d) of FIG. 21, an aberration amount on the sagittal surface for d-line (wavelength: 587.56 nm) is illustrated with a solid line, and an aberration amount on the tangential surface is illustrated with a dotted line. In (d) of FIG. 21, the case where chromatic aberration of magnification is suppressed within an allowable range is illustrated.

As described above, also in the optical system 420 of the display system 401, a ratio between the distance between the display surface 10a of the display device 10 and an exit pupil surface 420c of the optical system 420 and the half of the maximum size of the display surface 10a becomes smaller than 4. As a result, when the display device 10 is made with a small size, because the entire length of the optical system 420 in the direction of the optical axis PA can be also reduced accordingly, the optical system 420 can be downsized in accordance with the display device 10, and a fashionable external shape can be realized for the display system 401 (e.g., AR glasses) .

Moreover, according to the fifth modification example of the embodiment, an optical system 520 in a display system 501 may be configured as illustrated in FIGS. 22 to 24. FIG. 22 is a cross-sectional view illustrating a configuration of the optical system 520 according to the fifth modification example of the embodiment. FIG. 23 is a diagram illustrating optical configuration and characteristics of the optical system 520. FIG. 24 is a diagram illustrating surface shapes of lenses 521 to 526 in a lens group 520a.

The optical system 520 includes the lens group 520a instead of the lens group 20a (see FIG. 4) . The lens group 520a includes the plurality of lenses 521 to 526 and a lens diaphragm 527 corresponding to the plurality of lenses 21 to 26 and the lens diaphragm 27. The plurality of lenses 521 to 526 have cross-sectional shapes different from each other. The number of the lenses 521 to 526 included in the lens group 520a is 6. In the lens group 520a, the image-side lens 526 is a convex lens and the object-side lens 521 is a concave lens. The diameter of the object-side lens 521 is larger than the diameter of the image-side lens 526.

In FIG. 22, the optical axis PA is illustrated with a dashed-dotted line and passes through the substantial center of an aperture 527a of the lens diaphragm 527. An optical path of light emitted from the center CP (see (a) of FIG. 5) of the display surface 10a of the display device 10 is illustrated with a solid line. An optical path of light emitted from the maximum image-height position PP2 (see (a) of FIG. 5) of the display surface 10a of the display device 10 is illustrated with a dotted line. An optical path of light emitted from the maximum image-height position PP1 (see (a) of FIG. 5) of the display surface 10a of the display device 10 is illustrated with a dashed-two dotted line.

(a) of FIG. 23 illustrates that the optical system 520 satisfies all of Expressions (1) to (5) . In other words, in (a) of FIG. 23, it is indicated that, by being configured to satisfy all of Expressions (1) to (5) , in the optical system 520, an entire length (the Z-direction length) can be set to around 21.056 mm, an angle of view can be secured to be "θ _DFOV = 30.000 [°] " , and effective F-number can be reduced to around 3.258.

In (b) of FIG. 23 and (a) and (b) of FIG. 24, surface numbers are assigned as follows:

Surface number: 1: Exit surface of the lens diaphragm 527;

Surface number: 3: Exit surface of the lens 526;

Surface number: 4: Incident surface of the lens 526;

Surface number: 5: Exit surface of the lens 525;

Surface number: 6: Incident surface of the lens 525;

Surface number: 7: Exit surface of the lens 524;

Surface number: 8: Incident surface of the lens 524;

Surface number: 9: Exit surface of the lens 523;

Surface number: 10: Incident surface of the lens 523;

Surface number: 11: Exit surface of the lens 522;

Surface number: 12: Incident surface of the lens 522;

Surface number: 13: Exit surface of the lens 521; and

Surface number: 14: Incident surface of the lens 521.

In (b) of FIG. 23, the curvature radius R [mm] , the surface separation D [mm] , the refractive index Nd, the Abbe number Vd, and the focal length are indicated for each surface of surface numbers 1 to 14. A lens configuration is indicated with the curvature radius R. The lens group 520a is configured to include, in a paraxial region, the convex lens 526, the positive meniscus lens 525 with a convex surface facing the image side, the negative lens 524 with a convex surface facing the object side, the positive meniscus lens 523 with a convex surface facing the image side, the negative meniscus lens 522 with a convex surface facing the object side, and the negative lens 521 with concave surfaces on both sides, in order from the image side. It is possible to preferably correct a chromatic aberration by causing the lenses 521 to 526 to have the different refractive indices Nd and Abbe numbers Vd.

In (a) and (b) of FIG. 24, an aspherical shape is indicated for each surface of surface numbers 3 to 14. Assuming that the Z position (position in the direction of the optical axis PA) is z, the curvature radius is R, the XY direction distance from the optical axis PA is H, the conical constant is k, and the aspherical coefficients are A3, A4, ..., A19, and A20, the aspherical shape is expressed by Expression (6) .

In (a) and (b) of FIG. 24, the aspherical coefficients A3, A4, ..., A19, and A20 are indicated for each surface of surface numbers 3 to 14. Each surface of surface numbers 3 to 14 is obtained by rotating a curved line expressed by an expression obtained by substituting the aspherical coefficients A3 to A20 of (a) and (b) of FIG. 24 into Expression (6) around the optical axis PA. Note that "E-i" is an exponential notation with a base of 10 in (a) and (b) of FIG. 24. Herein, "i" is an integer number. A spherical aberration can be preferably corrected by making each surface of surface numbers 3 to 14 an aspheric surface as illustrated in (a) and (b) of FIG. 24.

The optical system 520 configured as illustrated in FIGS. 22 to 24 exhibits aberration characteristics as illustrated in FIG. 25. FIG. 25 is a diagram illustrating the aberration characteristics of the optical system 520. Note that the aberration characteristics of the optical system 520 are to present an aberration when parallel rays corresponding to an angle of view of the AR image are caused to be injected from the lens diaphragm 527 that is an exit pupil of the optical system 520 and the parallel rays are reversely traced and virtually imaged on the display surface 10a of the display device 10.

(a) of FIG. 25 illustrates an aberration diagram of astigmatism with reference to the display surface 10a (virtual image surface) . Herein, the vertical axis indicates an image height and the horizontal axis indicates the size of an aberration. In (a) of FIG. 25, the case where an angle of view θ _DFOV is 30° is exemplified. In the aberration diagram of the optical system 520 illustrated in (a) of FIG. 25, an aberration amount on a tangential surface for d-line (wavelength: 587.56 nm) is illustrated with a solid line, and an aberration amount on a sagittal surface is illustrated with a dotted line. The tangential surface is a surface including a principal ray and the optical axis PA. The sagittal surface is a surface including a principal ray and perpendicular to the tangential surface. In (a) of FIG. 25, the case where astigmatism is suppressed within an allowable range is illustrated.

(b) of FIG. 25 illustrates an aberration diagram of distortion aberration with reference to the display surface 10a (virtual image surface) . Herein, the vertical axis indicates an image height and the horizontal axis indicates the size of an aberration. In (b) of FIG. 25, the case where the angle of view θ _DFOV is 30° is exemplified. In the aberration diagram of the optical system 520 illustrated in (b) of FIG. 25, an aberration amount for d-line (wavelength: 587.56 nm) is illustrated with a solid line. In (b) of FIG. 25, the case where distortion aberration is suppressed within an allowable range is illustrated.

(c) of FIG. 25 illustrates an aberration diagram of spherical aberration with reference to the display surface 10a (virtual image surface) . Herein, the vertical axis indicates an eye image height and the horizontal axis indicates the size of an aberration. In (c) of FIG. 25, the case where the F-number Fno is 3.26 is exemplified. In the aberration diagram of the optical system 520 illustrated in (c) of FIG. 25, an aberration amount for c-line (wavelength: 656.28 nm) is illustrated with a dashed-dotted line, an aberration amount for d-line (wavelength: 587.56 nm) is illustrated with a solid line, and an aberration amount for g-line (wavelength: 435.84 nm) is illustrated with a dotted line. In (c) of FIG. 25, the case where spherical aberration is suppressed within an allowable range is illustrated.

(d) of FIG. 25 illustrates an aberration diagram of chromatic aberration of magnification with reference to the display surface 10a (virtual image surface) . Herein, the vertical axis indicates an image height and the horizontal axis indicates the size of an aberration. In (d) of FIG. 25, the case where the angle of view θ _DFOV is 30° is exemplified. In the aberration diagram of the optical system 520 illustrated in (d) of FIG. 25, an aberration amount on the sagittal surface for d-line (wavelength: 587.56 nm) is illustrated with a solid line, and an aberration amount on the tangential surface is illustrated with a dotted line. In (d) of FIG. 25, the case where chromatic aberration of magnification is suppressed within an allowable range is illustrated.

As described above, also in the optical system 520 of the display system 501, a ratio between the distance between the display surface 10a of the display device 10 and an exit pupil surface 520c of the optical system 520 and the half of the maximum size of the display surface 10a becomes smaller than 4. As a result, when the display device 10 is made with a small size, because the entire length of the optical system 520 in the direction of the optical axis PA can be also reduced accordingly, the optical system 520 can be downsized in accordance with the display device 10, and a fashionable external shape can be realized for the display system 501 (e.g., AR glasses) .

While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.

[Explanations of Letters or Numerals]

1, 101, 201, 301, 401, 501: display system

10, 110: display device

20, 220, 320, 420, 520: optical system

20a, 220a, 320a, 420a, 520a: lens group

21-26, 221-226, 321-325, 421-425, 521-526: lens

27, 227, 327, 427, 527: lens diaphragm

30: light guide member.

Claims

A display system comprising:

a display device that includes a display surface and a pixel array arranged in a region including the display surface, the pixel array having a plurality of pixels, each pixel in the plurality of pixels corresponding to a color, the plurality of pixels being arranged three-dimensionally on the display surface; and

an optical system having a lens group including a plurality of lenses, the optical system being configured to convert light from the display device into collimated light, wherein

when a distance between the display surface and an exit pupil surface of the optical system is D _TTL and a half of a maximum size of the display surface is W _DISD, the display system satisfies "D _TTL/W _DISD < 4" .
The display system according to claim 1, wherein

the display system further satisfies "D _TTL/W _DISD > 1.9" .
The display system according to claim 1, wherein

when a viewing angle on the exit pupil surface is θ _DFOV, the display system further satisfies "tan (θ _DFOV/2) < 0.75" .
The display system according to claim 1, wherein

the display surface has a rectangular shape in a planar view, and

when a half of a size of the display surface in a short direction is E _DISV and a distance between the display surface and a point at which an optical axis of the optical system intersects with an incident surface of a lens closest to an object side among the plurality of lenses is D _BL, the display system further satisfies "D _BL < E _DISV" .
The display system according to claim 1, wherein

the lens group further includes a lens diaphragm arranged on the exit pupil surface, and

when a focal length of the lens group is D _EFL and an aperture diameter of the lens diaphragm is W _EXA, the display system further satisfies "D _EFL/W _EXA < 3.5" .
The display system according to claim 1-5, wherein

in the pixel array, pixel groups of which each has two or more pixels arranged in a first direction along an optical axis of the optical system are arranged in a second direction perpendicular to the first direction and a third direction perpendicular to the first and second directions.
The display system according to claim 6, wherein

in each of the pixel groups, at least a first pixel and a second pixel are arranged in the first direction, the first pixel corresponding to a first color, the second pixel corresponding to a second color.
The display system according to claim 7, wherein

in each of the pixel groups, the first pixel, the second pixel, and a third pixel are arranged in the first direction, the third pixel corresponding to a third color.
The display system according to claim 8, wherein

the first color is light in a first wavelength range,

the second color is light in a second wavelength range shorter than the first wavelength range, and

the third color is light in a third wavelength range shorter than the second wavelength range.
The display system according to claim 9, wherein

the first color is red,

the second color is green, and

the third color is blue.
The display system according to claim 1, wherein

the display device further includes a reflecting member arranged on a side wall of the pixel group, the reflecting member being capable of forming a reflective interface on the side wall.
The display system according to claim 1, wherein

the display device further includes a plurality of micro-lenses arranged between a plurality of pixel groups and the optical system, and

in each of the plurality of micro-lenses, a positional relationship between an optical axis of the optical system and a central axis of a corresponding pixel group among the plurality of pixel groups corresponds to an emission direction of light from the corresponding micro-lens to the optical system.
The display system according to claim 12, wherein

each micro-lens in the plurality of micro-lenses corresponds to a pixel group in the plurality of pixel groups,

among the plurality of micro-lenses, a distance between an optical axis of a first micro-lens and a central axis of a first pixel group is larger than a distance between an optical axis of a second micro-lens and a central axis of a second pixel group, the first pixel group corresponding to the first micro-lens, the second micro-lens being closer to a center of the pixel array than the first micro-lens, the second pixel group corresponding to the second micro-lens.
The display system according to claim 1, wherein

each lens included in the lens group has a different shape from each other when seen in a cross-sectional view including an optical axis of the optical system.
The display system according to claim 14, wherein

the number of the lenses included in the lens group is 5 or more and 8 or less.
The display system according to claim 14, wherein

the lens group includes a convex lens on an image side.
The display system according to claim 14, wherein

the lens group includes a meniscus lens or a concave lens on an object side.
The display system according to claim 14, wherein

in the lens group, a diameter of an object-side lens is larger than a diameter of an image-side lens.
The display system according to claim 1, further comprising a light guide member arranged on an image side of the optical system.
The display system according to claim 19, wherein

the light guide member is able to transmit light from an outside world toward an eyeball of a user and is able to guide light from the display device toward the eyeball of the user.