Optical device with reduced chromatic aberration and display device comprising the same

Abstract

An optical device and a display device including the same are provided. The optical device includes a first backlight configured to output first light of a first wavelength through a first output coupler; a first lens disposed to face the first output coupler and to have a focal length with respect to the first light; a second backlight including a second output coupler, the second backlight configured to output second light of a second wavelength through the second output coupler; a second lens disposed to face the second output coupler and to have different focal lengths with respect to the first light and the second light; a third backlight including a third output coupler, the third backlight configured to output third light of a third wavelength through the third output coupler; and a third lens disposed to face the third output coupler and to have different focal lengths with respect to the first light, the second light, and the third light.

Description

Technical Field

[0001] The exemplary embodiments of this disclosure relate to an optical device with reduced chromatic aberration and a display device including the optical device. Background Technology

[0002] Recently, holographic 3D image display methods have been gradually put into practical use. These methods provide full parallax and enable the brain to perceive depth in accordance with the eye's focal length.

[0003] According to this holographic display technology, when light is shone onto a holographic pattern on which an interference pattern is recorded, obtained by the interference between a reference light and object light reflected from the original object, the light is diffracted and an image of the original object is reconstructed. When using currently commercially available holographic display technology, a computer-generated hologram (CGH), rather than a holographic pattern obtained by directly exposing the original object to light, is provided as an electrical signal to a spatial light modulator. The spatial light modulator forms the holographic pattern and diffracts the reference light from the light source according to the input CGH signal, thereby generating a 3D image.

[0004] In such holographic display methods, optical elements such as field lenses or beam deflectors can be used to display a holographic image formed by a spatial light modulator at a predetermined location. Such optical elements can be implemented based on diffraction. Because diffractive elements can produce a variety of optical effects, they have recently been used in many fields, but thin optical systems may not be achievable using existing diffractive elements. Furthermore, since such optical elements exhibit different refractive indices depending on the wavelength of light, they are accompanied by chromatic aberration, especially when the size of diffraction-based elements is reduced, the performance differences according to wavelength further increase. Therefore, a method to prevent or reduce chromatic aberration is needed. Summary of the Invention

[0005] One or more example embodiments provide an optical device with reduced chromatic aberration and a display device including the optical device.

[0006] Other aspects will be set forth in part in the description which follows, and will be apparent in part from the description, or may be learned by practice of exemplary embodiments of this disclosure.

[0007] According to one aspect of an exemplary embodiment, an optical device is provided, comprising: a first backlight configured to output first light of a first wavelength through a first output coupler; a first lens configured to face the first output coupler and having a predetermined focal length with respect to the first light of the first wavelength; a second backlight including a second output coupler disposed parallel to the first output coupler, the second backlight being configured to output second light of a second wavelength through the second output coupler; a second lens configured to face the second output coupler and having different focal lengths with respect to the first light of the first wavelength and the second light of the second wavelength; a third backlight including a third output coupler disposed parallel to the second output coupler, the third backlight being configured to output third light of a third wavelength through the third output coupler; and a third lens configured to face the third output coupler and having different focal lengths with respect to the first light of the first wavelength, the second light of the second wavelength, and the third light of the third wavelength.

[0008] The first lens, the second lens, and the third lens can be geometric phase lenses.

[0009] When the focal length of the first lens about the first wavelength of the first light is f1_1, the focal lengths of the second lens about the first wavelength of the first light and the second wavelength of the second light are f2_1 and f2_2 respectively, and the focal lengths of the third lens about the first wavelength of the first light, the second wavelength of the second light and the third wavelength of the third light are f3_1, f3_2 and f3_3 respectively, the EFL(f1_1,f2_1,f3_1) as the combined focal length of f1_1, f2_1 and f3_1 can satisfy the following condition: |f3_3–EFL(f1_1,f2_1,f3_1)| / f3_3<0.0005.

[0010] The EFL(f2_2,f3_2) that is the combined focal length of f2_2 and f3_2 can satisfy the following condition: |f3_3–EFL(f2_2,f3_2)| / f3_3<0.0005.

[0011] The first lens, the second lens, and the third lens can operate with respect to light of a predetermined polarization, and the optical device may further include at least one phase retarder configured to allow light of the predetermined polarization to be incident on the first lens, the second lens, and the third lens.

[0012] According to another aspect of an exemplary embodiment, an optical device is provided, comprising: a first backlight configured to output first light of a first wavelength through a first output coupler; a first beam deflector configured to face the first output coupler and to deflect the first light of the first wavelength at a predetermined angle; a second backlight including a second output coupler disposed parallel to the first output coupler, the second backlight being configured to output second light of a second wavelength through the second output coupler; a second beam deflector configured to face the second output coupler and to deflect the first light of the first wavelength and the second light of the second wavelength at different angles; a third backlight including a third output coupler disposed parallel to the second output coupler, the third backlight being configured to output third light of a third wavelength through the third output coupler; and a third beam deflector configured to face the third output coupler and to deflect the first light of the first wavelength, the second light of the second wavelength, and the third light of the third wavelength at different angles.

[0013] The first beam deflector, the second beam deflector, and the third beam deflector can be diffraction-based deflectors.

[0014] When the first beam deflector deflects the first light of the first wavelength by an angle of a1_1, the second beam deflector deflects the first light of the first wavelength and the second light of the second wavelength by angles of a2_1 and a2_2 respectively, and the third beam deflector deflects the first light of the first wavelength, the second light of the second wavelength and the third light of the third wavelength by angles of a3_1, a3_2 and a3_3 respectively, then E3(a1_1,a2_1,a3_1), which is the combined deflection angle of a1_1, a2_1 and a3_1, can satisfy the following condition: |a3_3–EDA(a1_1,a2_1,a3_1)| / a3_3<0.0005.

[0015] The combined deflection angle of a2_2 and a3_2, EDA(a2_2,a3_2), can satisfy the following condition: |a3_3–EDA(a2_2,a3_2)| / a3_3<0.0005.

[0016] A display device may include the optical device and a spatial light modulator configured to generate a holographic image by modulating a first light output from a first backlight, a second light output from a second backlight, and a third light output from a third backlight.

[0017] A first backlight may include: a first light source configured to emit first light of a first wavelength; and a first light guide plate including a first input coupler and a first output coupler, wherein the first light from the first light source is incident on the first input coupler. A second backlight may include: a second light source configured to emit second light of a second wavelength; and a second light guide plate including a second input coupler and a second output coupler, wherein the second light from the second light source is incident on the second input coupler. A third backlight may include: a third light source configured to emit third light of a third wavelength; and a third light guide plate including a third input coupler and a third output coupler, wherein the third light from the third light source is incident on the third input coupler.

[0018] The first lens, the second lens, and the third lens can be geometric phase lenses.

[0019] When the focal length of the first lens about the first wavelength of the first light is f1_1, the focal lengths of the second lens about the first wavelength of the first light and the second wavelength of the second light are f2_1 and f2_2 respectively, and the focal lengths of the third lens about the first wavelength of the first light, the second wavelength of the second light and the third wavelength of the third light are f3_1, f3_2 and f3_3 respectively, the EFL(f1_1,f2_1,f3_1) as the combined focal length of f1_1, f2_1 and f3_1 can satisfy the following condition: |f3_3–EFL(f1_1,f2_1,f3_1)| / f3_3<0.0005.

[0020] The EFL(f2_2,f3_2) that is the combined focal length of f2_2 and f3_2 can satisfy the following condition: |f3_3–EFL(f2_2,f3_2)| / f3_3<0.0005.

[0021] The display device may further include a beam deflector configured to adjust the position of the holographic image generated by the spatial light modulator.

[0022] The display device may further include: a first beam deflector disposed between a first output coupler and a second output coupler, and configured to deflect a first light of a first wavelength at a predetermined angle; a second beam deflector disposed between a second output coupler and a third output coupler, and configured to deflect the first light of the first wavelength and the second light of the second wavelength at different angles; and a third beam deflector configured such that the first light, the second light and the third light output from the third output coupler are incident on the third beam deflector, the third beam deflector being configured to deflect the first light of the first wavelength, the second light of the second wavelength and the third light of the third wavelength at different angles.

[0023] The first beam deflector, the second beam deflector, and the third beam deflector can be diffraction-based deflectors.

[0024] When the first beam deflector deflects the first light of the first wavelength by an angle of a1_1, the second beam deflector deflects the first light of the first wavelength and the second light of the second wavelength by angles of a2_1 and a2_2 respectively, and the third beam deflector deflects the first light of the first wavelength, the second light of the second wavelength and the third light of the third wavelength by angles of a3_1, a3_2 and a3_3 respectively, the EDA(a1_1,a2_1,a3_1) as the combined deflection angle of a1_1, a2_1 and a3_1 can satisfy the following condition: |a3_3–EDA(a1_1,a2_1,a3_1)| / a3_3<0.0005.

[0025] The combined deflection angle of a2_2 and a3_2, EDA(a2_2,a3_2), can satisfy the following condition: |a3_3–EDA(a2_2,a3_2)| / a3_3<0.0005.

[0026] The first, second, and third beam deflectors can be electrically controlled to adjust the direction of incident light deflection.

[0027] The display device may further include an eye-tracking sensor, wherein the first beam deflector, the second beam deflector, and the third beam deflector may be controlled based on signals sensed by the eye-tracking sensor.

[0028] A display device may include the optical device, a spatial light modulator, and a field lens. The spatial light modulator is configured to generate a holographic image by modulating a first light of a first wavelength output from a first backlight, a second light of a second wavelength output from a second backlight, and a third light of a third wavelength output from a third backlight. The field lens is configured to focus the holographic image generated by the spatial light modulator at a predetermined position.

[0029] The first, second, and third beam deflectors can be electrically controlled to adjust the direction of incident light deflection.

[0030] The display device may further include an eye-tracking sensor, wherein the first beam deflector, the second beam deflector, and the third beam deflector may be controlled based on signals sensed by the eye-tracking sensor.

[0031] According to another aspect of the exemplary embodiment, an optical device is provided, comprising: a first backlight including a first light source and a first light guide plate, the first light source being configured to emit first light of a first wavelength, the first light guide plate including a first input coupler and a first output coupler, the first input coupler facing the first light source, and the first backlight being configured to output the first light of the first wavelength through the first output coupler; a first lens configured to face the first output coupler and having a predetermined focal length with respect to the first light of the first wavelength; and a second backlight including a second light source and a second light guide plate, the second light source being configured to emit second light of a second wavelength, the second light guide plate including a second input coupler and a second output coupler, the second input coupler facing the first light source and the first backlight being configured to output the first light of the first wavelength through the first output coupler; a first lens configured to face the first output coupler and have a predetermined focal length with respect to the first light of the first wavelength; and a second backlight including a second light source and a second light guide plate, the second light source being configured to emit second light of a second wavelength, the second light guide plate including a second input coupler and a second output coupler, the second input coupler facing the first light source and the first output ... output coupler facing the first light source and the first output coupler facing the first light source and the first output coupler facing the first light source and the first output coupler facing the first light source and the first output coupler facing the first light source and the first output coupler facing the first light source and the first output coupler facing the first light source and the For the second light source, the second backlight is configured to output second light of a second wavelength through a second output coupler; the second lens is configured to face the second output coupler and has different focal lengths with respect to the first light of a first wavelength and the second light of a second wavelength; the third backlight includes a third light source and a third light guide plate, the third light source is configured to emit third light of a third wavelength, the third light guide plate includes a third input coupler and a third output coupler, the third input coupler faces the third light source, the third backlight is configured to output third light of a third wavelength through the third output coupler; and the third lens is configured to face the third output coupler and has different focal lengths with respect to the first light of a first wavelength, the second light of a second wavelength, and the third light of a third wavelength. Attached Figure Description

[0032] The above and / or other aspects, features, and advantages of certain exemplary embodiments of the present disclosure will become more apparent from the following description taken in conjunction with the accompanying drawings, wherein:

[0033] Figure 1 A schematic configuration and optical arrangement of an optical device according to an example embodiment are shown;

[0034] Figure 2 It shows that it can be used Figure 1 The conceptual focusing operation of geometric phase lenses used in optical devices;

[0035] Figure 3 A schematic configuration and optical arrangement of an optical device according to another exemplary embodiment are shown;

[0036] Figure 4 A schematic configuration and optical arrangement of an optical device according to another exemplary embodiment are shown;

[0037] Figure 5 A schematic configuration and optical arrangement of an optical device according to another exemplary embodiment are shown;

[0038] Figure 6 It shows that it can be used Figure 5The optical operation of the diffraction-based beam deflector used in the optical device;

[0039] Figure 7 A schematic configuration and optical arrangement of a display device according to an example embodiment are shown;

[0040] Figure 8 A schematic configuration and optical arrangement of a display device according to another exemplary embodiment are shown;

[0041] Figure 9 A schematic configuration and optical arrangement of a display device according to another exemplary embodiment are shown;

[0042] Figure 10 A schematic configuration and optical arrangement of a display device according to another exemplary embodiment are shown;

[0043] Figure 11 A schematic configuration and optical arrangement of a display device according to another exemplary embodiment are shown; and

[0044] Figure 12 A schematic configuration and optical arrangement of a display device according to another exemplary embodiment are shown. Detailed Implementation

[0045] Reference will now be made in detail to the exemplary embodiments shown in the accompanying drawings, wherein the same reference numerals always denote the same elements. In this respect, the exemplary embodiments may take different forms and should not be construed as limited to the description set forth herein. Therefore, the exemplary embodiments are described below only with reference to the accompanying drawings to illustrate various aspects.

[0046] As used herein, the term “and / or” includes any and all combinations of one or more associated listed items. When a statement such as “at least one” precedes a list of elements, it modifies the entire list of elements without modifying any individual elements in that list. For example, the statement “at least one of a, b, and c” should be understood to include only a, only b, only c, both a and b, both a and c, both b and c, or all of a, b, and c.

[0047] In the following description, exemplary embodiments will be presented in detail with reference to the accompanying drawings. The embodiments described below are merely examples, and various modifications may be possible from these embodiments. The same reference numerals always refer to the same elements, and the dimensions of elements may be enlarged in the drawings for clarity and convenience of illustration.

[0048] In the following text, the expression "on top of" or "on" can include not only direct contact on it, but also non-contact on it.

[0049] Terms such as first and second can be used to describe various components, but only for the purpose of distinguishing one component from others. These terms do not limit the differences in the material or structure of the components.

[0050] Unless otherwise expressly indicated by the context, singular expressions in this disclosure include plural expressions. Furthermore, terms such as “comprising” and / or “including…” may be interpreted as indicating the presence of an element, but not as excluding the possibility of the presence or addition of other elements.

[0051] Terms used in the implementation, such as “unit” or “module”, refer to a unit for processing at least one function or operation and can be implemented in hardware, software, or a combination of hardware and software.

[0052] In the context of describing this disclosure, the terms “a” and “the”, as well as similar indicators, will be interpreted as encompassing both singular and plural.

[0053] Furthermore, all methods described herein may be performed in any suitable order unless otherwise indicated herein or obviously contradicted by the context. Unless otherwise required, any and all examples or language (such as "like") provided herein are intended only to better illustrate this disclosure and do not constitute a limitation on the scope of this disclosure.

[0054] Figure 1 A schematic configuration and optical arrangement of an optical device 100 according to an exemplary embodiment are shown. Figure 2 It shows that it can be used Figure 1 The conceptual focusing operation of the geometric phase lens (GPL) used in the optical device 100.

[0055] The optical device 100 according to the example embodiment has reduced chromatic aberration and focuses light of different wavelengths.

[0056] The optical device 100 includes a first backlight 110 that outputs light L1 of a first wavelength, a first lens 150 having a predetermined focal length with respect to the light L1 of the first wavelength emitted from the first backlight 110, a second backlight 120 that outputs light L2 of a second wavelength, a second lens 160 that exhibits different focal lengths with respect to the light L1 of the first wavelength and the light L2 of the second wavelength, a third backlight 130 that outputs light L3 of a third wavelength, and a third lens 170 that exhibits different focal lengths with respect to the light L1 of the first wavelength, the light L2 of the second wavelength, and the light L3 of the third wavelength.

[0057] The light of the first wavelength L1, the light of the second wavelength L2, and the light of the third wavelength L3 are light within the wavelength range of visible light, and can be blue light, green light, and red light respectively, but are not limited to these.

[0058] The first backlight 110, the second backlight 120, and the third backlight 130 are each provided with a first emitting surface 110a, a second emitting surface 120a, and a third emitting surface 130a that emit light toward the first lens 150, the second lens 160, and the third lens 170, respectively. The first backlight 110, the second backlight 120, and the third backlight 130 are configured such that the first emitting surface 110a, the first lens 150, the second emitting surface 120a, the second lens 160, the third emitting surface 130a, and the third lens 170 are arranged parallel to each other. An output coupler for light emission may be formed on each of the first emitting surface 110a, the second emitting surface 120a, and the third emitting surface 130a.

[0059] like Figure 2 As shown, the first lens 150, the second lens 160, and the third lens 170 can be geometrical phase lenses (GPLs). The GPL can be implemented, for example, in a liquid crystal device or a meta device, and can include a micropattern structure. The GPL is designed to have a predetermined refractive power by modulating the phase of the incident light differently according to its position. For example, when left-handed circularly polarized (LCP) light is incident, the light can be focused into right-handed circularly polarized (RCP) light through phase modulation. However, the implementation is not limited to this. For example, when the incident light is focused, right-handed circularly polarized (RCP) light can be modulated into left-handed circularly polarized (LCP) light, or the incident light can be modulated based on linear polarization. Furthermore, although a positive refractive power is shown, the GPL can be designed to exhibit negative refractive power, such as a concave lens. The GPL can have a flat plate shape and achieve the desired refractive power with a relatively small thickness.

[0060] However, because the geometric phase lens (GPL) modulates the direction of light travel through phase modulation, therefore... Figure 2 As shown, a geometrical phase lens (GPL) can exhibit different focal lengths depending on the wavelength of the incident light. For example, a GPL designed to have a first focal length f1 for light L1 of a first wavelength exhibits a second focal length f2 for light L2 of a second wavelength, which is different from the first focal length f1, and a third focal length f3 for light L3 of a third wavelength, which is different from the first focal length f1 and the second focal length f2. The focal length can be inversely proportional to the wavelength of the incident light. For example, when light with a wavelength longer than the designed wavelength is incident, the GPL exhibits a focal length shorter than the designed focal length, and when light with a wavelength shorter than the designed wavelength is incident, the GPL exhibits a focal length longer than the designed focal length. The characteristics of a GPL can be represented by chromatic aberration.

[0061] In the optical device 100 according to the example embodiment, the details and arrangement of the first lens 150, the second lens 160 and the third lens 170 are set such that light of different wavelengths L1, L2 and L3 can be focused at the same position.

[0062] Light of wavelength L1 is focused by a first lens 150, a second lens 160, and a third lens 170; light of wavelength L2 is focused by a second lens 160 and a third lens 170; and light of wavelength L3 is focused by a third lens 170. With this optical path, light of different wavelengths L1, L2, and L3 can be focused at substantially the same position, and chromatic aberration can be reduced or prevented.

[0063] The focal length of the first lens 150 with respect to the first wavelength L1 can be f1_1; the focal lengths of the second lens 160 with respect to the first wavelength L1 and the second wavelength L2 can be f2_1 and f2_2, respectively; and the focal lengths of the third lens 170 with respect to the first wavelength L1, the second wavelength L2, and the third wavelength L3 can be f3_1, f3_2, and f3_3, respectively. For example, f2_1 and f2_2 can be different values, and f3_1, f3_2, and f3_3 can also be different values.

[0064] In the optical device 100 of the example embodiment, the first lens 150, the second lens 160 and the third lens 170 can be configured such that the effective focal length EFL(f1_1,f2_1,f3_1) as the combined focal length of f1_1, f2_1 and f3_1 and the EFL(f2_2,f3_2) as the combined focal length of f2_2 and f3_2 are substantially the same as the focal length f3_3 of the third lens 170 with respect to the third wavelength light L3.

[0065] As shown in Equation 1, the combined focal length EFL of two lenses with focal lengths f1 and f2 and a center-to-center distance d can be obtained.

[0066]

[0067] As shown in Equation 2, we can obtain the focal lengths f1, f2, and f3, and the distance d between the centers of adjacent lenses. 12 and d 23 The combined focal length (EFL) of the three lenses.

[0068]

[0069] Considering the above equations and requirements, which will be described later, the details of the first lens 150, the second lens 160, and the third lens 170 can be set, namely, the focal lengths of different wavelengths of light and their arrangement space.

[0070] The first lens 150, the second lens 160, and the third lens 170 can satisfy the following conditions in Equation 3.

[0071] EFL(f1_1,f2_1,f3_1)=EFL(f2_2,f3_2)=f3_3 [Equation 3]

[0072] However, the implementation is not limited to this, and the difference between the values ​​can be set within a predetermined range so that the optical device 100 has a very small chromatic difference or a small value within the desired range.

[0073] For example, the first lens 150, the second lens 160, and the third lens 170 can satisfy the following conditions in Equations 4 and 5.

[0074] |f3_3–EFL(f1_1,f2_1,f3_1)| / f3_3<0.0005 [Equation 4]

[0075] |f3_3–EFL(f2_2,f3_2)| / f3_3<0.0005 [Equation 5]

[0076] Figure 3 A schematic configuration and optical arrangement of an optical device 101 according to another exemplary embodiment are shown.

[0077] The optical device 101 includes a first backlight 111, a first lens 150, a second backlight 121, a second lens 160, a third backlight 131, and a third lens 170.

[0078] Optical device 101 in the example embodiment and Figure 1 The optical device 100 differs in the detailed configuration of the first backlight 111, the second backlight 121, and the third backlight 131, while the configuration of the first lens 150, the second lens 160, and the third lens 170 is the same as... Figure 1 The configuration of the optical device 100 is basically the same.

[0079] The first backlight 111 includes a first light source LS1 that provides light L1 of a first wavelength and a first light guide plate WG1 that guides and emits the light L1 from the first light source LS1 in a direction toward the first lens 150. The first light guide plate WG1 includes: a first input coupler IC1 that allows the light L1 from the first light source LS1 to be incident; and a first output coupler OC1 that emits the light L1 input through the first input coupler IC1 toward the first lens 150. A collimating lens 10 is further disposed between the first light source LS1 and the first light guide plate WG1, which collimates the light from the first light source LS1 so that the light is incident parallel to the first input coupler IC1.

[0080] The first light source LS1 can be a coherent light source that emits coherent light, and can be, for example, a laser diode (LD) or a light-emitting diode (LED).

[0081] The first light guide plate WG1 serves as an optical waveguide for transmitting light and may include a material transparent to visible light, such as glass, polymethyl methacrylate (PMMA), or polydimethylsiloxane (PDMS). The first light guide plate WG1 includes two surfaces 1a and 1b facing each other, and includes a first input coupler IC1 and a first output coupler OC1. The first input coupler IC1 is used to introduce light incident from the first light source LS1 into the first light guide plate WG1, and the first output coupler OC1 is used to output light that has been totally internally reflected from the two surfaces 1a and 1b inside the first light guide plate WG1 and travels in parallel to the outside of the first light guide plate WG1. For example, the first input coupler IC1 may be disposed on one edge of surface 1a of the first light guide plate WG1, and the first output coupler OC1 may be disposed on the other edge of surface 1a of the first light guide plate WG1.

[0082] The first input coupler IC1 is configured to guide light incident on the first input coupler IC1 in an oblique direction in a direction substantially perpendicular to the surface 1a of the first light guide plate WG1. For example, the first input coupler IC1 can be configured to guide light incident on the first input coupler IC1 within a predetermined incident angle relative to the direction perpendicular to its surface into the interior of the first light guide plate WG1. The light guided into the interior of the first light guide plate WG1 is repeatedly totally internally reflected on the two opposing surfaces 1a and 1b of the first light guide plate WG1 and travels along the interior of the first light guide plate WG1. The first output coupler OC1 is configured to output light incident obliquely on the first output coupler OC1 in a direction substantially perpendicular to the surface 1a of the first light guide plate WG1. The first output coupler OC1 can be configured to guide only light incident within a predetermined incident angle range, and not light incident at other angle ranges. For example, for light incident at an angle different from the set conditions, the first output coupler OC1 can simply be used as a transparent plate.

[0083] The first input coupler IC1 and the first output coupler OC1 can be formed as a diffractive optical element (DOE) or a holographic optical element (HOE). A DOE can include multiple periodic fine grating patterns. These grating patterns of the DOE serve as diffraction gratings to diffract incident light. Specifically, depending on the size, height, period, etc., of the grating pattern, the direction of light travel can be altered by diffracting light incident within a specific angular range and generating destructive and constructive interference. Alternatively, a HOE can include periodic fine patterns of materials with different refractive indices instead of grating patterns. A HOE differs from a DOE only in its configuration and can have the same operating principle as a DOE.

[0084] In the configuration of the first light guide plate WG1, light incident on the input coupler IC1 is output to the outside of the first light guide plate WG1 through the output coupler OC1. Furthermore, the directionality and coherence of the light incident on the input coupler IC1 and output through the output coupler OC1 can be maintained within the angular range coupled by the input coupler IC1.

[0085] Similarly, the second backlight 121 includes a second light source LS2 that provides light L2 of the second wavelength, and a second light guide plate WG2 that guides and emits light L2 of the second light source LS2 in a direction toward the second lens 160, and includes a second input coupler IC2 and a second output coupler OC2. Additionally, a collimating lens 20 may be disposed between the second light source LS2 and the second light guide plate WG2. The second output coupler OC2 may function as a transparent plate with respect to light L1 of the first wavelength, and emits light L2 of the second wavelength in a direction perpendicular to the surface of the second light guide plate WG2.

[0086] Additionally, the third backlight 131 includes a third light source LS3 that provides light L3 of a third wavelength, and a third light guide plate WG3 that guides and emits light L3 of the third light source LS3 in a direction toward the third lens 170, and includes a third input coupler IC3 and a third output coupler OC3. Furthermore, a collimating lens 30 may be disposed between the third light source LS3 and the third light guide plate WG3. The third output coupler OC3 may function as a transparent plate with respect to light L1 of the first wavelength and light L2 of the second wavelength, and emits light L3 of the third wavelength in a direction perpendicular to the surface of the third light guide plate WG3.

[0087] As described above, the first wavelength light L1 forms an optical path in the order of the first output coupler OC1, the first lens 150, the second output coupler OC2, the second lens 160, the third output coupler OC3, and the third lens 170. The second wavelength light L2 forms an optical path in the order of the second output coupler OC2, the second lens 160, the third output coupler OC3, and the third lens 170. The third wavelength light L3 forms an optical path in the order of the third output coupler OC3 and the third lens 170. Based on the focal length requirements designed for each wavelength of light through the first lens 150, the second lens 160, and the third lens 170, the first wavelength light L1, the second wavelength light L2, and the third wavelength light L3 can be focused at the same position with almost no chromatic aberration or no chromatic aberration at all.

[0088] Figure 4 A schematic configuration and optical arrangement of an optical device 102 according to another exemplary embodiment are shown.

[0089] Optical device 102 in the example embodiment and Figure 3The difference between the optical device 101 and the optical device 102 is that the optical device 102 further includes additional optical elements to control the polarization of light incident on the first lens 150, the second lens 160 and the third lens 170.

[0090] As described above, the first lens 150, the second lens 160, and the third lens 170, which are geometric phase lenses, can function with respect to light with a predetermined polarization. Therefore, the optical device 102 of the example embodiment further includes one or more phase retarders that allow light with a predetermined polarization to be incident on the first lens 150, the second lens 160, and the third lens 170.

[0091] The first lens 150, the second lens 160, and the third lens 170 can focus right-hand circularly polarized (RCP) light and convert it to left-hand circularly polarized (LCP). For this operation, a quarter-wave plate 40 can be positioned between the first backlight 111 and the first lens 150. Furthermore, a quarter-wave plate 50 can be positioned between the first lens 150 and the second backlight 121. Additionally, quarter-wave plates 60, 70, and 80 can be positioned between the second backlight 121 and the second lens 160, between the second lens 160 and the third backlight 131, and between the third backlight 131 and the third lens 170, respectively.

[0092] The first backlight 111 can be configured to emit linearly polarized light, and the light L1 of a first wavelength emitted from the first backlight 111 passes through the quarter-wave plate 40 and its polarization state changes to right-hand circular polarization (RCP) before entering the first lens 150. In the first lens 150, the light L1 of the first wavelength changes to left-hand circular polarization (LCP) and is refracted according to a predetermined refractive power, then passes through the quarter-wave plate 50 again and its polarization state changes to linear polarization.

[0093] Light L1 of a first wavelength and light L2 of a second wavelength, both emitted from the second backlight 121 and in a linearly polarized state, pass through the quarter-wave plate 60 and change to a right-hand circularly polarized (RCP) state before incident on the second lens 160. Next, the first wavelength light L1 and the second wavelength light L2 pass through the second lens 160, are refracted according to a predetermined specific refractive power, and change to a left-hand circularly polarized (LCP) state. The first wavelength light L1 and the second wavelength light L2, both in a left-hand circularly polarized (LCP) state, pass through the quarter-wave plate 70 again, and their polarization state changes to linear polarization.

[0094] Light of a first wavelength L1, light of a second wavelength L2, and light of a third wavelength L3, all emitted from the third backlight 131 and in a linearly polarized state, pass through the quarter-wave plate 80 and change to a right-hand circularly polarized (RCP) state before incident on the third lens 170. Then, the first wavelength L1, the second wavelength L2, and the third wavelength L3 pass through the third lens 170 and are refracted according to a predetermined specific refractive power.

[0095] In the above description, the first lens 150, the second lens 160, and the third lens 170 operate on circular polarization, and the additional phase retarder is a quarter-wave plate; however, the implementation is not limited to this. Depending on the polarization requirements of the first lens 150, the second lens 160, and the third lens 170, other components may be used or additional components may be added.

[0096] Figure 5 A schematic configuration and optical arrangement of an optical device 200 according to another exemplary embodiment are shown. Figure 6 It shows that it can be used Figure 5 The concept optical operation of the diffraction-based beam deflector BD used in the optical device 200.

[0097] The optical device 200 in the example embodiment is a beam deflection device that exhibits reduced chromatic aberration and deflects light of different wavelengths.

[0098] The optical device 200 includes: a first backlight 111 that outputs light L1 of a first wavelength; a first beam deflector 250 that deflects light L1 of the first wavelength at a predetermined angle; a second backlight 121 that outputs light L2 of a second wavelength; a second beam deflector 260 that deflects light L1 of the first wavelength and light L2 of the second wavelength at different angles; a third backlight 131 that outputs light L3 of a third wavelength; and a third beam deflector 270 that deflects light L1 of the first wavelength, light L2 of the second wavelength, and light L3 of the third wavelength at different angles.

[0099] The first backlight 111, the second backlight 121, and the third backlight 131 have the configuration described in the above example embodiment, and the first output coupler OC1, the first beam deflector 250, the second output coupler OC2, the second beam deflector 260, the third output coupler OC3, and the third beam deflector 270 are arranged in parallel to each other in sequence.

[0100] The first beam deflector 250, the second beam deflector 260, and the third beam deflector 270 are as follows: Figure 6The diagram shows a diffraction-based beam deflector BD. The beam deflector BD can be a diffractive element including a liquid crystal or an optical element whose phase can be electrically changed. The beam deflector BD can be implemented geometrically or as a meta-element including a micropatterned structure. The beam deflector BD is designed to modulate the phase of the incident light differently depending on its position, thereby deflecting the direction of the incident light by a predetermined angle. Because this method adjusts the direction of light travel through phase modulation, as... Figure 6 As shown, light can be deflected at different angles depending on the wavelength of the incident light. For example, a first beam deflector 250, designed to have a first deflection angle with respect to a first wavelength light L1, can exhibit a second deflection angle different from the first deflection angle with respect to a second wavelength light L2, and a third deflection angle different from the first and second deflection angles with respect to a third wavelength light L3. When light with a wavelength different from the designed wavelength is incident on a diffraction-based beam deflector BD, the light can be deflected at an angle different from the designed deflection angle, which can be represented by chromatic aberration.

[0101] In the optical device 200 according to the example embodiment, the details and arrangement of the first beam deflector 250, the second beam deflector 260 and the third beam deflector 270 are set such that light of different wavelengths L1, L2 and L3 can be deflected in the same direction by the optical device 200.

[0102] Light of wavelength L1 is deflected at a predetermined angle by each of the first beam deflector 250, the second beam deflector 260, and the third beam deflector 270; light of wavelength L2 is deflected by the second beam deflector 260 and the third beam deflector 270; and light of wavelength L3 is deflected by the third beam deflector 270. According to this optical path, light of different wavelengths L1, L2, and L3 can be deflected in substantially the same direction with almost no chromatic aberration.

[0103] The first beam deflector 250 can deflect the first wavelength light L1 by an angle of a1_1. The second beam deflector 260 can deflect the first wavelength light L1 and the second wavelength light L2 by angles of a2_1 and a2_2, respectively. The third beam deflector 270 can deflect the first wavelength light L1, the second wavelength light L2, and the third wavelength light L3 by angles of a3_1, a3_2, and a3_3, respectively. For example, a2_1 and a2_2 can be different values, and a3_1, a3_2, and a3_3 can also be different values.

[0104] The first beam deflector 250, the second beam deflector 260, and the third beam deflector 270 can also be electrically controlled, and the direction of light deflection can be adjusted in detail. For example, the above values ​​can be adjusted within a predetermined range.

[0105] In the optical device 200 of the example embodiment, the first beam deflector 250, the second beam deflector 260 and the third beam deflector 270 can be configured such that the combined deflection angle EDA(a1_1,a2_1,a3_1) of a1_1, a2_1 and a3_1 and the combined deflection angle EDA(a2_2,a3_2) of a2_2 and a3_2 are substantially the same as the deflection angle a3_3 of the third beam deflector 270 with respect to the third wavelength light L3.

[0106] The first beam deflector 250, the second beam deflector 260, and the third beam deflector 270 can satisfy the following conditions in Equation 6.

[0107] EDA(a1_1,a2_1,a3_1)=EDA(a2_2,a3_2)=a3_3[Equation 6]

[0108] However, the implementation is not limited to this, and the difference between the values ​​can be set within a predetermined range so that the optical device 200 has a small directional deviation according to the wavelength, or has a small value within the desired range.

[0109] For example, the first beam deflector 250, the second beam deflector 260, and the third beam deflector 270 can satisfy the following conditions in Equations 7 and 8.

[0110] |a3_3–EDA(a1_1,a2_1,a3_1)| / a3_3<0.0005 [Equation 7]

[0111] |a3_3–EDA(a2_2,a3_2)| / a3_3<0.0005 [Equation 8]

[0112] The aforementioned deflection angle forms with the Z-axis in the XZ plane, but is not limited thereto. The first beam deflector 250, the second beam deflector 260, and the third beam deflector 270 can be configured such that the deflection angle can be defined as an angle formed with the Z-axis in the YZ plane, or it can be defined in other planes.

[0113] Figure 7 A schematic configuration and optical arrangement of a display device 1000 according to an example embodiment are shown.

[0114] The display device 1000 includes an optical device 1100 and a spatial light modulator 1800.

[0115] The optical device 1100 may have low chromatic aberration and, for example, provide light focused at a predetermined position to the spatial light modulator 1800, and may have the same characteristics as... Figure 3The optical device 101 shown has a substantially the same configuration or is derived from it. Figure 3 The optical device 101 shown has been modified.

[0116] The spatial light modulator 1800 modulates light from the first backlight 111, the second backlight 121, and the third backlight 131 of the optical device 1100 to generate a holographic image.

[0117] The spatial light modulator 1800 can form a holographic pattern based on holographic data signals (e.g., computer-generated holographic (CGH) signals) provided by a controller. After light from the first backlight 111, the second backlight 121, and the third backlight 131 is incident on the spatial light modulator 1800 and diffracted by the holographic pattern formed on the spatial light modulator 1800, a stereoscopic holographic image can be reproduced by destructive and constructive interference. The spatial light modulator 1800 can use any of the following: a phase modulator capable of performing only phase modulation, an amplitude modulator capable of performing only amplitude modulation, or a composite modulator capable of performing both phase and amplitude modulation. Liquid crystal on silicon (LCoS), a digital micromirror device (DMD), or a semiconductor modulator can be used as the spatial light modulator 1800.

[0118] exist Figure 7 In this embodiment, light passing through the first lens 150, the second lens 160, and the third lens 170 is incident on the spatial light modulator 1800, but the implementation is not limited to this. For example, the positions of the third lens 170 and the spatial light modulator 1800 can be interchanged.

[0119] In the display device 1000, light focused at a predetermined position by the optical device 1100 without chromatic aberration is provided to the spatial light modulator 1800, thereby providing the observer with a high-quality holographic image.

[0120] Figure 8 A schematic configuration and optical arrangement of a display device 1001 according to another exemplary embodiment are shown.

[0121] Display device 1001 in example implementation and Figure 7 The difference between the display device 1000 and the display device 1001 is that the display device 1001 further includes a beam deflector 1500 for adjusting the position of the holographic image.

[0122] The display device 1001 forms a holographic image at a predetermined position within the viewer's field of vision; therefore, the image may be unrecognizable when the viewer's eye position changes from the predetermined position. The beam deflector 1500 can change the position at which the optical device 1100 focuses light onto the focal plane FP. This position can be variable along the X direction on the focal plane FP, but is not limited to this. For example, the position can be variable along the Y direction, and the beam deflector 1500 can be configured to change this position in a two-dimensional direction.

[0123] The beam deflector 1500 can be a liquid crystal deflector that diffracts incident light to change its direction of travel. The beam deflector 1500 can be electrically controlled to adjust the direction in which the light is deflected.

[0124] The display device 1001 may further include an eye-tracking sensor to obtain information needed to change the focus position. The beam deflector 1500 may be controlled such that the position of the observer's eye is determined by the eye-tracking sensor and the light is focused at another position on the focal plane FP.

[0125] exist Figure 8 In this embodiment, the third lens 170, the beam deflector 1500, and the spatial light modulator 1800 are arranged sequentially, but the implementation is not limited to this, and the order of these three components can be changed. For example, the positions of the third lens 170 and the beam deflector 1500 can be interchanged, and the positions of the third lens 170 and the spatial light modulator 1800 can be interchanged.

[0126] although Figure 7 and Figure 8 Display devices 1000 and 1001 illustrate optical systems for one eye, but these optical systems can be provided for both eyes. Figure 8 The beam deflector 1500 provided in the display device 1001 can be configured to direct light toward both eyes.

[0127] Figure 9 A schematic configuration and optical arrangement of a display device 1002 according to another exemplary embodiment are shown.

[0128] The display device 1002 in the example implementation and Figure 8 The difference between the display device 1001 and the display device 1001 is that the beam deflector 1502 has a configuration in which the light is directed toward both eyes, while the rest of the configuration is basically the same.

[0129] Display device 1002 includes an optical device 1100 that provides focused light with minimal or no chromatic aberration, a beam deflector 1502, and a spatial light modulator 1800. Display device 1002 may further include an eye-tracking sensor ES that senses the position of the observer's two eyes and a controller 1900 that uses the information sensed by the eye-tracking sensor ES to control the beam deflector 1502.

[0130] The beam deflector 1502 can be a liquid crystal deflector that diffracts the incident light to produce two beams traveling at different angles. The beam deflector 1502 can simultaneously spatially direct the light toward both the left and right eyes. The beam deflector 1502 can also sequentially direct the light toward the left and right eyes. The beam deflector 1502 can also be electrically controlled and can finely adjust the two directions in which the light is directed. Detailed positional changes of the left and right eyes can be sensed by the eye-tracking sensor ES, and the beam deflector 1502, by utilizing the information sensed by the eye-tracking sensor ES, allows the position of the light divergence to be varied two-dimensionally on a parallel focal plane FP parallel to the XY plane.

[0131] Figure 10 A schematic configuration and optical arrangement of a display device 1003 according to another exemplary embodiment are shown.

[0132] The display device 1003 of the example embodiment includes wherein Figure 3 and Figure 5 The optical devices 101 and 200 shown are configured in combination with the spatial light modulator 1800.

[0133] For example, besides Figure 7 In addition to the display device 1000 shown, the display device 1003 further includes a first beam deflector 250, a second beam deflector 260, and a third beam deflector 270.

[0134] The first beam deflector 250, the second beam deflector 260, and the third beam deflector 270 can respectively adjust the focusing position of the light from the first backlight 111, the second backlight 121, and the third backlight 131 on the focusing plane FP to reduce chromatic aberration. The first beam deflector 250 is disposed between the first output coupler OC1 and the second output coupler OC2, the second beam deflector 260 is disposed between the second output coupler OC2 and the third output coupler OC3, and the third beam deflector 270 is disposed on the travel path of the light from the third output coupler OC3.

[0135] exist Figure 10In this configuration, although the first beam deflector 250 and the first lens 150 are sequentially arranged between the first output coupler OC1 and the second output coupler OC2, the first lens 150 and the first beam deflector 250 can also be sequentially arranged between the first output coupler OC1 and the second output coupler OC2. Similarly, the positions of the second beam deflector 260 and the second lens 160 can be interchanged, and the positions of the third beam deflector 270 and the third lens 170 can be interchanged. Furthermore, the position of the spatial light modulator 1800 can also be changed to be between the third beam deflector 270 and the third lens 170.

[0136] The first beam deflector 250, the second beam deflector 260, and the third beam deflector 270 can be as follows: Figure 5 The configuration described herein ensures that light L1 of the first wavelength is deflected sequentially by the first beam deflector 250, the second beam deflector 260, and the third beam deflector 270; light L2 of the second wavelength is deflected sequentially by the second beam deflector 260 and the third beam deflector 270; and light L3 of the third wavelength is deflected by the third beam deflector 270. Therefore, the deflection directions of light L1 of the first wavelength, light L2 of the second wavelength, and light L3 of the third wavelength passing through the third beam deflector 270 are substantially the same.

[0137] The first beam deflector 250, the second beam deflector 260, and the third beam deflector 270 can also be electrically controlled and the direction in which the light is deflected can be adjusted in detail.

[0138] The display device 1003 may further include an eye-tracking sensor ES, and the first beam deflector 250, the second beam deflector 260, and the third beam deflector 270 may be controlled based on signals sensed by the eye-tracking sensor ES. Depending on the operation of the first beam deflector 250, the second beam deflector 260, and the third beam deflector 270, the position of the focused light can be adjusted two-dimensionally on the focal plane FP.

[0139] Figure 11 A schematic configuration and optical arrangement of a display device 1004 according to another exemplary embodiment are shown.

[0140] The display device 1004 includes an optical device 1200, a field lens 1700, and a spatial light modulator 1800.

[0141] Optical device 1200 can provide directional light with very little or no chromatic aberration, and can have a reference... Figure 5 The optical device 200 described is substantially the same as or a modified version thereof.

[0142] Spatial light modulator 1800 modulates light from optical device 200 to generate a holographic image, and field lens 1700 focuses the generated holographic image at a predetermined position. The positions of field lens 1700 and spatial light modulator 1800 can be interchanged.

[0143] Although the display device 1004 is shown as an optical system for one eye, such an optical system can be provided for both eyes. The first beam deflector 250, the second beam deflector 260, and the third beam deflector 270 provided in the optical device 1200 can be configured to direct light toward both eyes.

[0144] Figure 12 A schematic configuration and optical arrangement of a display device 1005 according to another exemplary embodiment are shown.

[0145] Display device 1005 includes: an optical device 1205 that provides directional light with minimal or no chromatic aberration; a field lens 1700; and a spatial light modulator 1800. Display device 1004 may further include an eye-tracking sensor ES that senses the position of the observer's two eyes and a controller 1900 that controls the directionality of light from optical device 1205 using information sensed by the eye-tracking sensor ES.

[0146] The display device 1005 according to the example embodiment and Figure 11 The difference between the display device 1004 and the display device 1004 is that, Figure 12 The first beam deflector 250, the second beam deflector 260, and the third beam deflector 270 of the optical device 1205 provided in the display device 1005 include optical devices 1205 configured to direct light toward both eyes.

[0147] The light from the optical device 1205 can be directed toward both eyes, and the bifurcation direction can be adjusted according to the detailed position of the two eyes, and it is possible to adjust the direction with a small deviation from the wavelength.

[0148] Although the optical devices 100, 101, 102, and 200 described above are applied to display devices, the implementation is not limited thereto. For example, the optical devices 100, 101, 102, and 200 described above can be used in various electronic devices in which focused or directional light with a small deviation according to wavelength can be utilized.

[0149] The aforementioned display devices 1000, 1001, 1002, 1003, 1004 and 1005 can be applied to various types of wearable device displays, such as head-mounted displays (HMDs), glasses-type displays and goggle-type displays.

[0150] The aforementioned display devices 1000, 1001, 1002, 1003, 1004, and 1005 can also be combined with or connected to other electronic devices (such as smartphones) for operation. For example, the controller or processor driving the display devices 1000, 1001, 1002, 1003, 1004, and 1005 can be provided in a smartphone, and the aforementioned display devices 1000, 1001, 1002, 1003, 1004, and 1005 can be provided in a smartphone.

[0151] The aforementioned optical device can minimize wavelength-dependent deviations when controlling the direction of light of different wavelengths.

[0152] The aforementioned optical devices can be applied to lenses with very small chromatic aberration, beam deflectors, etc., and can also be applied to display devices that improve image quality.

[0153] Although an optical device and a display device including the optical device have been shown and described with reference to exemplary embodiments illustrated in the accompanying drawings, those skilled in the art will understand that various changes in form and detail may be made therein without departing from the spirit and scope defined by the claims. It should be understood that the exemplary embodiments described herein are to be considered in a descriptive sense only and not for limiting purposes. The description of features or aspects in each exemplary embodiment should generally be considered applicable to other similar features or aspects in other embodiments.

[0154] This application claims priority to Korean Patent Application No. 10-2020-0045237, filed on April 14, 2020, with the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety.

Claims

1. An optical device comprising: a first backlight configured to output first light of a first wavelength, the first backlight including a first light guide plate including a first input coupler and a first output coupler, and a first light source configured to emit the first light, the first light from the first light source being incident on the first input coupler, the first light being output through the first output coupler; a first lens disposed to face the first output coupler and having a predetermined focal length with respect to the first light of the first wavelength; a second backlight configured to output second light of a second wavelength, the second backlight including a second light guide plate including a second input coupler and a second output coupler, and a second light source configured to emit the second light, the second light from the second light source being incident on the second input coupler, the second light being output through the second output coupler, the second output coupler being disposed in parallel to the first output coupler; a second lens disposed to face the second output coupler and having different focal lengths with respect to the first light of the first wavelength and the second light of the second wavelength; a third backlight configured to output third light of a third wavelength, the third backlight including a third light guide plate including a third input coupler and a third output coupler, and a third light source configured to emit the third light, the third light from the third light source being incident on the third input coupler, the third light being output through the third output coupler, the third output coupler being disposed in parallel to the first output coupler; and a third lens disposed to face the third output coupler and having different focal lengths with respect to the first light of the first wavelength, the second light of the second wavelength, and the third light of the third wavelength. The first lens, the second lens, and the third lens are geometric phase lenses.

2. The optical device of claim 1, wherein, The first lens has a focal length f1_1 with respect to the first light of the first wavelength, the second lens has focal lengths f2_1 and f2_2 with respect to the first light of the first wavelength and the second light of the second wavelength, respectively, the third lens has focal lengths f3_1, f3_2, and f3_3 with respect to the first light of the first wavelength, the second light of the second wavelength, and the third light of the third wavelength, respectively, and 3. The optical device of claim 1, wherein, EFL(f1_1, f2_1, f3_1), which is a combined focal length of f1_1, f2_1, and f3_1, satisfies the following condition: |f3_3 - EFL(f1_1, f2_1, f3_1)| / f3_3 < 0.0005. EFL(f2_2, f3_2), which is a combined focal length of f2_2 and f3_2, satisfies the following condition:

4. The optical device of claim 3, wherein, |f3_3 - EFL(f2_2, f3_2)| / f3_3 < 0.0005. The first lens, the second lens, and the third lens operate with respect to light of a predetermined polarization, and 5. The optical device of claim 1, wherein, ​ The optical device further comprises at least one phase retarder configured to cause the light of the predetermined polarization to be incident on the first lens, the second lens and the third lens.

6. An optical device comprising: a first backlight configured to output first light of a first wavelength, the first backlight comprising a first light source configured to emit the first light and a first light guide plate comprising a first input coupler and a first output coupler, the first light from the first light source being incident on the first input coupler, the first light being output through the first output coupler; a first beam deflector disposed facing the first output coupler and configured to deflect the first light of the first wavelength at a predetermined angle; a second backlight configured to output second light of a second wavelength, the second backlight comprising a second light source configured to emit the second light and a second light guide plate comprising a second input coupler and a second output coupler, the second light from the second light source being incident on the second input coupler, the second light being output through the second output coupler, the second output coupler being disposed parallel to the first output coupler; a second beam deflector disposed facing the second output coupler, the second output coupler being configured to deflect the first light of the first wavelength and the second light of the second wavelength at different angles; a third backlight configured to output third light of a third wavelength, the third backlight comprising a third light source configured to emit the third light and a third light guide plate comprising a third input coupler and a third output coupler, the third light from the third light source being incident on the third input coupler, the third light being output through the third output coupler, the third output coupler being disposed parallel to the first output coupler; and a third beam deflector disposed facing the third output coupler, the third beam deflector being configured to deflect the first light of the first wavelength, the second light of the second wavelength and the third light of the third wavelength at different angles. The first beam deflector, the second beam deflector and the third beam deflector are diffraction-based deflectors.

7. The optical device of claim 6, wherein, The angle at which the first beam deflector deflects the first light of the first wavelength is a1_1, the angles at which the second beam deflector deflects the first light of the first wavelength and the second light of the second wavelength are a2_1 and a2_2 respectively, the angles at which the third beam deflector deflects the first light of the first wavelength, the second light of the second wavelength and the third light of the third wavelength are a3_1, a3_2 and a3_3 respectively, and 8. The optical device of claim 6, wherein, an EDA(a1_1, a2_1, a3_1) of the combined deflection angles a1_1, a2_1 and a3_1 satisfies the following condition: |a3_3 - EDA(a1_1, a2_1, a3_1)| / a3_3 < 0.0005. ​ 9. The optical device of claim 8, wherein, The EDA (a2_2, a3_2) of the combined deflection angles of a2_2 and a3_2 satisfies the following condition: |a3_3-EDA(a2_2, a3_2)| / a3_3<0.0005.

10. A display device comprising: the optical device of claim 1; and a spatial light modulator configured to generate a hologram image by modulating the first light output from the first backlight, the second light output from the second backlight, and the third light output from the third backlight.

11. The display device of claim 10, wherein, the first lens, the second lens, and the third lens are geometric phase lenses.

12. The display device of claim 10, wherein, focal lengths of the first lens with respect to the first light of the first wavelength, the second lens with respect to the first light of the first wavelength and the second light of the second wavelength are f2_1 and f2_2 respectively, and the third lens with respect to the first light of the first wavelength, the second light of the second wavelength, and the third light of the third wavelength are f3_1, f3_2, and f3_3 respectively, and EFL (f1_1, f2_1, f3_1) of the combined focal lengths of f1_1, f2_1, and f3_1 satisfies the following condition: |f3_3-EFL(f1_1, f2_1, f3_1)| / f3_3<0.0005.

13. The display device of claim 12, wherein, EFL (f2_2, f3_2) of the combined focal lengths of f2_2 and f3_2 satisfies the following condition: |f3_3-EFL(f2_2, f3_2)| / f3_3<0.0005.

14. The display device of claim 10, further comprising a beam deflector configured to adjust a position of the hologram image generated by the spatial light modulator.

15. The display device of claim 10, further comprising: a first beam deflector disposed between the first output coupler and the second output coupler, the first beam deflector configured to deflect the first light of the first wavelength at a predetermined angle; a second beam deflector disposed between the second output coupler and the third output coupler, the second beam deflector configured to deflect the first light of the first wavelength and the second light of the second wavelength at different angles; and a third beam deflector disposed such that the first light, the second light, and the third light output from the third output coupler are incident on the third beam deflector, the third beam deflector configured to deflect the first light of the first wavelength, the second light of the second wavelength, and the third light of the third wavelength at different angles. the first beam deflector, the second beam deflector, and the third beam deflector are diffraction-based deflectors.

16. The display device of claim 15, wherein, ​ 17. The display device of claim 15, wherein, the first light of the first wavelength and the second light of the second wavelength are a2_1 and a2_2, respectively, the angles at which the first light of the first wavelength, the second light of the second wavelength, and the third light of the third wavelength are deflected by the third beam deflector are a3_1, a3_2, and a3_3, respectively, and an EDA(a1_1, a2_1, a3_1) as a combined deflection angle of a1_1, a2_1, and a3_1 satisfies the following condition: |a3_3 - EDA(a1_1, a2_1, a3_1)| / a3_3 < 0.0005.

18. The display device of claim 17, wherein, an EDA(a2_2, a3_2) as a combined deflection angle of a2_2 and a3_2 satisfies the following condition: |a3_3 - EDA(a2_2, a3_2)| / a3_3 < 0.0005.

19. The display device of claim 15, wherein, the first beam deflector, the second beam deflector, and the third beam deflector are electrically controlled to adjust the directions of the deflection of incident light.

20. The display device of claim 19, further comprising an eye tracking sensor, wherein, the first beam deflector, the second beam deflector, and the third beam deflector are controlled based on a signal sensed by the eye tracking sensor.

21. A display device comprising: the optical device of claim 6; a spatial light modulator configured to generate a hologram image by modulating the first light of the first wavelength output from the first backlight, the second light of the second wavelength output from the second backlight, and the third light of the third wavelength output from the third backlight; and a field lens configured to focus the hologram image generated by the spatial light modulator at a predetermined position.

22. The display device of claim 21, wherein, the first beam deflector, the second beam deflector, and the third beam deflector are electrically controlled to adjust the directions of the deflection of incident light.

23. The display device of claim 22, further comprising an eye tracking sensor, wherein the first beam deflector, the second beam deflector, and the third beam deflector are controlled based on a signal sensed by the eye tracking sensor.

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