KR101955333B1 - Light Deflector and Display Device - Google Patents

Abstract

The optical deflector according to the present disclosure includes a first optical deflector having a refractive index that changes according to the magnitude of an applied electric field disposed on a transparent substrate and a different electric field for each region or time of the first optical deflector, For an adjustable optical deflector. Such an optical deflector is smaller in volume than the optical deflector made of an optical element, and the refractive index can be controlled freely.

Description

[0001] Optical deflector and display device [0002]

The present disclosure relates to an optical deflector and a display device.

As the information society develops, the demand for the display field is increasing in various forms. A light deflector for changing the traveling direction of light has been mainly manufactured by using an optical element such as a lens or a mirror. In this case, however, there is a limit in that the volume is large and the speed of angle conversion is limited. Accordingly, studies are being made on an optical deflector using an optical deflection panel that changes the traveling direction of light with an electrical signal. Such an optical deflector can be used in a display device capable of displaying a 2D image, a 3D image, and a holographic image.

The present disclosure is directed to an optical deflector and a display device.

A display device according to the present disclosure includes a light source that provides light of a plurality of wavelength components, a first light deflection portion having a light path conversion surface that deflects incident light from the light source and outputs the deflected light, A control unit including an electric wiring structure for controlling the first light deflecting unit such that light of a plurality of wavelength components included in the incident light is deflected in the same direction; and a control unit provided on the first light deflecting unit, And a transparent passivation layer capable of protecting the first optical deflector from the optical deflector, wherein the electrical wiring structure is formed of a transparent material; A beam expander including a first exit pattern for emitting light incident from the optical deflector; A light guide plate including a second exit pattern for totally reflecting light emitted from the beam expander in two dimensions; And a display for displaying an image using light emitted from the light guide plate; .

Wherein the first light deflecting portion includes: an optical deflecting layer on which the light path changing surface is formed; And a first electrode layer and a second electrode layer spaced apart from each other with the light deflecting layer interposed therebetween.

The first electrode layer may include a plurality of first sub-electrodes arranged to be spaced apart from each other.

The second electrode layer may be a common electrode for applying a voltage to each of the plurality of first sub-electrodes.

The control unit may adjust the optical path conversion surface by applying a separate voltage to each of the plurality of first sub-electrodes.

A refractive index distribution of the optical deflecting layer is formed in accordance with a voltage distribution applied between each of the plurality of first sub-electrodes and the second electrode layer, and an interface forming a boundary having a different refractive index in the optical deflecting layer, .

The first electrode layer and the second electrode layer may be made of a transparent conductive material.

The light deflecting layer may include a liquid crystal.

The control unit may control the light source and the first light deflecting unit so that light of a plurality of wavelength components is transmitted through the first light deflecting unit in a time-division manner.

Wherein the control unit divides the time of one frame into a plurality of subframes and controls the light source to cause light of different wavelengths to be incident on the first light deflecting unit at the same incident angle in the plurality of subframes, It is possible to control the first optical deflecting unit so that angles incident on the different optical path changing surfaces are different from each other.

The time lengths of the plurality of subframes may be equal to each other.

And a second light deflecting unit having a light path changing surface that is variable so that the deflection direction of the incident light is adjusted.

The light source may provide light of different wavelengths to the first and second light deflecting units.

The control unit may control the first and second light deflecting units so that the lights having different wavelengths are incident on the light path conversion surfaces of the first and second light deflecting units at different angles.

And at least one light path changing member for changing an optical path such that light of different wavelengths emitted from the first and second light deflecting units form the same light path.

The light path changing member may include a dichroic mirror.

The second optical deflecting unit may have an optical path changing surface that is located on an optical path passing the light passing through the first optical deflecting unit and varies to adjust a deflecting direction of the light passing through the first optical deflecting unit.

The axis on which the optical path changing surface of the first optical deflecting unit is varied and the axis on which the optical path changing surface of the second optical deflecting unit is variable may be orthogonal to each other.

The incidence direction of the light incident on the beam expander and the emergence direction of the light emitted from the second exit pattern may be opposite directions.

The display and the beam expander may be disposed in the same direction with respect to the light guide plate.

The first emission pattern and the second emission pattern may be disposed in the same direction with respect to the light guide plate.

The optical deflector and the display according to the present disclosure have a variable optical path changing layer, and can emit a plurality of incident lights having different wavelengths at the same angle. Therefore, the optical deflector and the display described above can prevent the scattering phenomenon at the time of optical deflection, and can have a high deflection efficiency. Also, the above-described optical deflector may be driven by a time division method or a space division method.

1 is a cross-sectional view schematically showing an optical deflector according to an embodiment.
2 is a plan view schematically showing a sub-electrode pattern.
3A and 3B are schematic views when light is applied to the light deflector.
FIGS. 4 and 5 are diagrams showing the operation of the optical deflector of FIG. 1 in a time division manner.
6 is a cross-sectional view schematically showing an optical deflector according to another embodiment.
7 is a cross-sectional view schematically showing a light deflector according to yet another embodiment.
8 and 9 are views showing the operation of the space division method of the optical deflector according to FIG.
10 is a cross-sectional view schematically showing a light deflector according to yet another embodiment.
11 and 12 schematically show a display device including a light deflector.

Hereinafter, the optical deflector and the display device will be described in detail with reference to the accompanying drawings. The size of each component in the drawings may be exaggerated for clarity and convenience of explanation. Furthermore, the embodiments described below are merely illustrative, and various modifications are possible from these embodiments. In the following, what is referred to as "upper" or "upper"

1 is a cross-sectional view schematically showing an optical deflector 100 according to an embodiment. 1, the optical deflector 100 includes a first optical deflecting unit 120 including a light deflecting layer 121, a first electrode layer 122, a second electrode layer 123, And a control unit 110 for controlling the display unit 120. The first light deflecting unit 120 may have an optical path changing surface 125 that deflects incident light and outputs the deflected light so that the deflection direction of the incident light is varied. The light path conversion surface 125 may be formed such that light of a plurality of wavelength components included in the incident light is deflected at the same angle. The control unit 110 may adjust the voltage distribution to adjust the light path conversion surface 125. FIG.

The optical deflector 100 according to the present embodiment can deflect light of a plurality of wavelength components incident at a predetermined angle in the same direction to prevent scattering. The light is maintained in the same direction within the region having the same refractive index, and is refracted at a certain angle when it meets another refractive index interface. Since the refraction angle depends on the wavelength of the light, the mixed light including the light having the plurality of wavelengths has different refractive indices depending on the respective wavelengths at the refractive index interface, and dispersion occurs. For example, red light, green light, when the blue light passes through the refractive index interface of mixed white light, the angle at which the θ _R, the green light in the angle at which the red light is refracted refraction θ _G, the angle of θ _B is the blue light refraction is different from each other Do. This causes a problem that each light emitted from the optical deflector 100 is not focused. Accordingly, the control unit 110 can prevent scattering phenomenon by controlling the optical path changing surface 125 so that the refraction angles are the same for each light of each of the plurality of wavelengths.

In order for an optical deflector to be utilized in various display devices such as a 3D display and a holographic display, it is necessary to minimize scattering of light. If the focusing device due to the scattering phenomenon is separately provided, the volume of the display may be increased and the cost may be increased. Accordingly, the optical deflector 100 according to the present embodiment can prevent scattering of light by time multiplexing or space multiplexing.

The first light deflecting unit 120 may include a first electrode layer 122 and a second electrode layer 123 spaced apart from each other with the light deflecting layer 121 and the light deflecting layer 121 interposed therebetween.

The light deflecting layer 121 may have a light path conversion surface that deflects the light of the incident light according to the magnitude of the applied voltage. For example, the light deflecting layer 121 may comprise liquid crystal. When the voltage is not applied to the light deflecting layer 121, the deflection function is turned off and can function as an isotropic plate. In this case, the incident light can pass through the optical deflecting layer 121 at a predetermined angle. When a voltage is applied to the light deflecting layer 121, it may have an index gradient according to the arrangement of the directors of the internal liquid crystal. Various types of optical path changing surfaces can be formed by adjusting the voltage distribution applied to the optical deflecting layer 121. [ For example, the director of the liquid crystal may be arranged in the direction of the electric field if the dielectric anisotropy is positive and perpendicular to the direction of the electric field if the dielectric anisotropy is negative. By using this principle, the distribution of the liquid crystal director can be adjusted according to the voltage distribution applied to the light deflecting layer 121, and it is possible to form the light path conversion surface using the refractive index gradient. The deflection angle of the incident light can be adjusted according to the slope of the light path conversion surface. The refractive index distribution of the optical deflecting layer 121 is formed in accordance with the voltage distribution applied between each of the plurality of first sub-electrodes and the second electrode layer 123, and the boundary surface of the optical deflecting layer 121, It can be a light path conversion surface.

The light source 130 may provide light of a plurality of wavelength components. The light source 130 may emit light of a plurality of wavelength components to the first light deflector 120 at the same incident angle. The operation of the light source 130, the incident angle, and the like can be controlled by the control unit 110.

The first electrode layer 122 can apply a voltage to the light deflecting layer 121 under the control of the control unit. The first electrode layer 122 may include a plurality of first sub-electrodes spaced apart from each other. Referring to FIG. 2, the first electrode layer 122 may include a plurality of first sub-electrodes spaced apart from each other along one direction. One direction in which the first sub-electrode is disposed may coincide with the axial direction in which the optical path changing surface of the above-described optical deflecting layer 121 is varied. The first electrode layer 122 may be formed of a transparent conductive material such as indium-tin-oxide (ITO), indium-zinc-oxide (IZO), or indium-tin-zinc-oxide (ITZO).

The second electrode layer 123 can apply a voltage to the first electrode layer 122. The second electrode layer 123 may be made of a transparent conductive material such as ITO, IZO, or ITZO. The second electrode layer 123 can function as a common electrode to which a constant voltage is applied. For example, the second electrode layer 123 may be integrally formed over the entire surface of the transparent substrate SUB. However, the second electrode layer 123 may include a plurality of second sub-electrodes corresponding to the first sub-electrodes of the first electrode layer 122. In this case, the plurality of second sub-electrodes may function as a common electrode to which a constant voltage is applied, or a voltage distribution may be applied to the second sub-electrode, and the first sub-electrode may function as a common electrode. In other words, it is preferable that one of the first electrode layer 122 and the second electrode layer 123 should be applied with a driving voltage for adjusting the optical path changing surface of the light deflecting layer 121 and the other electrode functions as a common electrode can do. In this embodiment, a case in which the second electrode layer 123 is integrally formed over the entire surface of the substrate is taken as an example.

The control unit 110 may include a device unit for applying a voltage to the first electrode layer 122 and the second electrode layer 123 to adjust the variable optical path conversion surface formed in the optical deflection layer 121 have. For example, the control unit 110 may include an electrical addressing structure for controlling the first sub-electrodes of the first electrode layer 122, respectively. The electrical wiring structure may have a transistor structure. The electrical wiring structure may also have transparency. The controller 110 may apply a constant voltage to make the second electrode layer 120 function as a common electrode.

The transparent substrate SUB is a substrate on which the first light deflecting unit 120 can be formed, and has transparency to allow incident light to pass therethrough.

A passivation layer (PV) is provided on the light deflecting portion to protect the light deflector from external shocks and stimuli. The passivation layer (PV) may have transparency.

2 is a cross-sectional view schematically showing a sub-electrode pattern. The first electrode layer 122 may include a plurality of first sub-electrodes as described above. Referring to FIG. 2, the first sub-electrodes may be arranged to be periodically spaced along a predetermined direction, for example, along a first direction. The first direction may coincide with the axial direction of the light path conversion surface 125. [

FIGS. 3A to 5 are diagrams showing a time division operation of the optical deflector 100 according to FIG. 1) and the optical deflecting unit 120 (see FIG. 1) so that the light of a plurality of wavelength components is transmitted through the light deflecting unit 120 in a time-division manner, Can be controlled.

FIG. 3A is a schematic cross-sectional view showing the operation of the optical deflector 100 according to the time division manner according to FIG. Referring to FIG. 3A, the variable optical path changing surface 170 can deflect the incident light corresponding to each time interval at the same angle. The light path changing surface 170 may show a deflecting surface formed by changing the refractive index gradient of the light deflecting layer 121 described above. The optical path changing surface 170 is formed in a plane such that the refractive index interface has the same function as the prism, and the incident light can be refracted at a certain angle according to the wavelength. However, the light path conversion surface 170 is not necessarily formed in a plane, but may be formed into a curved surface according to the intended purpose.

The light source 130 may cause white light W mixed with red light R, green light G and blue light to enter the optical deflector 100 at the same angle. The white light W according to the present embodiment may be mixed light of red light R, green light G, and blue light B, which are sequentially incident on a predetermined time interval. The control unit 110 may vary the light path conversion surface 170 corresponding to each of the red light R, green light G and blue light incident thereto. 3B, red light R, green light G, and blue light B may be deflected at different angles when the light path conversion surface 170 is not variable. Referring to FIG. 4, a time interval may be divided into each frame, and each frame may be further subdivided into a plurality of sub-primes. The control unit 110 may control the light source 130 such that light of different wavelengths enters the optical deflecting unit 120 at the same incident angle in the plurality of subframes. Also, the controller 110 may control the optical deflector 120 such that angles incident on different optical path changing surfaces 170 are different from each other in the plurality of sub-frames according to lights of different wavelengths. The time lengths of the sub-frames may be equal to each other. For example, each frame can be equally distributed to 1/3 of a sub-frame corresponding to red light (R), green light (G), and blue light (B) which are incident light. The red light R, the green light G and the blue light B can be sequentially irradiated to the light deflecting unit 120 according to a time period corresponding to each subframe. The control unit 110 applies V (R) to the optical deflecting unit 120 to form the optical path changing surface 170 in which the red light _R is deflected at the angle? _R in the sub frame to which the red light R is irradiated can do. The controller 110 may then apply V (G) to the optical deflector 120 to form a light path conversion surface 170 in which the green light _G is deflected at an angle? _G. The controller 110 may then apply V (B) to the optical deflector 120 to form a light path conversion surface 170 where the blue light _B is deflected at an angle &thetas; _B.

 As described above, the angle of deflection for each wavelength can satisfy the relationship expressed by the following equation (1).

It is also possible to continuously irradiate the white light W including the red light R, green light G and blue light B according to the time period corresponding to each subframe, but the scattering prevention efficiency can be reduced .

When the time-division-type optical deflector 100 is utilized in a display, a screen formed on the display may be as shown in FIG. In order to express one screen, the pixels of each of red light R, green light G and blue light B are represented in time according to the flow of time in the first frame of the time interval, and these pixels can be combined and viewed as an image. Since the human body can recognize a set of discrete pictures having a frequency of 60 Hz or more as an image, the time interval frame 1 may be, for example, 1/60 second, and each of the red light R, green light G, The time interval may be 1/180 second, which is one-third thereof. Each subframe may have the same length of time.

6 to 9 are views showing the operation of the space division method of the optical deflector. 6 is a cross-sectional view schematically showing an optical deflector 200 according to another embodiment. The optical deflector 200 according to the present embodiment may further include a second optical deflector P2 having a light path conversion surface that is variable such that a deflection direction of incident light is adjusted. The light source 230 may provide light of different wavelengths to the first light deflecting unit P1 and the second light deflecting unit P2. In this embodiment, the first deflecting portion P1, the second deflecting portion P2 and further the third deflecting portion P3 include the light deflecting layer 221, the first electrode 222, and the second electrode 223, May be referred to as a separate region where different light path changing surfaces are formed in the light deflecting portion. Unlike the above-described time division method, the spatial light splitter 200 divides an area and controls the first electrode 222 and the second electrode 223 for each area, . The controller 210 controls the first optical deflector P1 and the second optical deflector P2 so that light of different wavelengths enters the optical path changing surfaces 251 and 252 of the first optical deflecting unit P1 and the second optical deflecting unit P2 at different angles, It is possible to control the portion P1 and the second optical deflecting portion P2.

Referring to FIG. 6, the light source 230 includes a red light R, a green light G, and a blue light R, respectively, to the first light deflecting unit P1, the second light deflecting unit P2 and the third light deflecting unit P3. (B) can be incident at the same angle. The control unit 210 may apply V (R) to the first light deflecting unit P1 to form the light path changing surface 251 in which the red light _R is deflected at the angle? _R. The control unit 210 can apply V (G) to the second optical deflecting unit P2 to form the optical path changing surface 252 in which the green light _G is deflected at the angle? _G. The control unit 210 may apply V (B) to the third light deflecting unit P3 to form the light path changing surface 253 in which the blue light _B is deflected at the angle? _B. As described above, the light refraction angles? _R ,? _{B, and} ? _G can be matched with each other to prevent scattering of light.

7 is a cross-sectional view schematically showing an optical deflector 200 according to yet another embodiment. Referring to FIG. 7, the optical path changing member 280 may further include at least one optical path changing member 280 that converts an optical path such that light of different wavelengths emitted from the optical deflecting unit forms the same optical path. The light path changing member 280 may include a dichroic mirror. A dichroic mirror is a kind of optical member that selectively transmits and reflects light according to wavelength. Since the third light path changing member 283 only needs to reflect the blue light B, the normal light path changing member 280 is sufficient. For example, the light path changing member 283 may comprise a mirror or a metal. The second optical path changing member 282 may be a dichroic mirror that reflects the green light G since the blue light B is transmitted and the optical path of the green light G is changed. The first optical path changing member 281 may be a dichroic mirror that reflects the red light R since the first optical path changing member 281 transmits the red light G and changes the optical path of the green light G and the blue light B,

Referring to FIG. 8, in the space division type optical deflector 200, the light source 230 is disposed in the first light deflecting portion P1, the second light deflecting portion P2, and the third light deflecting portion P3 Light of different wavelengths can be provided in the same time frame. A screen formed on a display including an optical deflector operating in a space division manner may be as shown in FIG. The red light R, the green light G and the blue light B can be simultaneously displayed on the pixel in the same time frame to express one screen. Unlike the time division method, since the pixels for the red light R, the green light G, and the blue light B are separately required, the total area of the display can be increased. For example, one pixel may be composed of R, G, G, and B as a Bayer filter.

10 is a view schematically showing a light deflector according to yet another embodiment. Referring to FIG. 10, the second optical deflecting unit 340 is located on the optical path passing the light passing through the first optical deflecting unit 320, and the deflecting direction of the light passing through the first optical deflecting unit 320 The light path changing surface 345 can be changed so as to be adjusted. In other words, the second light deflecting unit 340 according to the present embodiment may be positioned on the first light deflecting unit 320.

The second light deflecting unit 340 has a light path changing surface 345 that is variable to adjust the deflection direction of the incident light and is formed in a direction different from the inclination of the variable light path changing surface 325 of the first light deflecting unit . The optical deflector 300 according to the present embodiment can separately adjust the variable optical path changing surfaces 325 and 345 having different inclination directions so that the deflection direction of the light can be two-dimensionally adjusted. For example, the variable axis of the optical path changing surface 325 of the first optical deflecting portion and the variable axis of the optical path changing surface 345 of the second optical deflecting portion may be orthogonal to each other. In this case, if the first optical deflecting unit 325 adjusts the change of the optical path with the x axis as a variable axis, the second optical deflecting unit 345 can adjust the change of the optical path with the y axis as a variable axis. Such an optical deflector 300 can be utilized in a 3-dimensional device including a TOF camera (Time of Flight Camera).

11 and 12 schematically show a display device 400 including an optical deflector. Referring to FIG. 11, the display device 400 may include the light deflector described above as the light source 410. The white light W emitted from the light source 410 may be incident on the beam expander 430 through the optical path changing member 420. The white light W entering the beam expander 430 may be totally reflected along the beam expander 430. The white light W may be incident on the light guide plate 450 from the beam expander 430 due to the first emission pattern 440 formed on the beam expander 430. [ The white light W may be totally reflected two-dimensionally along the light guide plate 450. The white light W may be incident on the display 470 from the light guide plate 450 due to the second emission pattern 460 formed on the light guide plate 450. The display 470 can display various images from the transmitted white light W. The display 470 may include various types of flat plates such as a liquid crystal display panel, a field emission display panel, a plasma display panel, and an electrophoresis display panel. A display panel can be used.

The optical deflector according to the present embodiment can be utilized as a deflection element on the display 470 described above. For example, an optical deflector may be disposed on the display 470 to deflect the image generated on the display 470 in various forms according to the display method. For example, by using the refractive index gradient of the optical deflector, the optical deflector is operated to have an optical deflection function like a lenticular lens, so that a 3D image of a non-eyeglass system can be realized.

The optical deflector may also be utilized in 3D display devices. With at least one optical deflector, it is possible to project light in the same time interval in which the angles are the same in both sides of the observer and the directions are opposite to each other. Conventional 3D displays require a driving speed of substantially 120 Hz, for example, when driven at 60 Hz, by alternately irradiating light to the left and right eyes of an observer. However, a plurality of optical deflectors according to the present embodiment or a separate variable optical path changing surface is formed for each area, and a 3D image is implemented at a driving speed of 60 Hz by irradiating lights of opposite angles to the left and right eyes in the same time interval .

Up to now, exemplary embodiments of an optical deflector and a display device have been described and shown in the accompanying drawings to facilitate understanding of the present invention. It should be understood, however, that such embodiments are merely illustrative of the present invention and not limiting thereof. And it is to be understood that the invention is not limited to the details shown and described. Since various other modifications may occur to those of ordinary skill in the art.

100: optical deflector
110:
120: first optical deflection part
121: Optical deflection layer
122: first electrode layer
123: second electrode layer
125: light path conversion surface
130: Light source
340: second optical deflection part
SUB: Transparent substrate
PV: passivation layer

Claims (21)

A first optical deflector having a light path conversion surface that changes the deflection direction of the incident light so as to deflect incident light from the light source to provide a light having a plurality of wavelength components, And an electric wiring structure for controlling the first light deflecting unit so that the light of the wavelength component of the first light deflecting unit is deflected in the same direction and a second light deflecting unit provided on the first light deflecting unit, An optical deflector including a transparent passivation layer that can be protected, the electrical wiring structure being formed of a transparent material;
A beam expander including a first exit pattern for emitting light incident from the optical deflector;
A light guide plate including a second exit pattern for totally reflecting light emitted from the beam expander in two dimensions; And
A display for displaying an image using light emitted from the light guide plate; . The method according to claim 1,
Wherein the first light deflecting unit comprises:
An optical deflection layer on which the optical path changing surface is formed;
And a first electrode layer and a second electrode layer spaced apart from each other with the light deflecting layer interposed therebetween. 3. The method of claim 2,
Wherein the first electrode layer comprises a first electrode layer,
And a plurality of first sub-electrodes arranged to be spaced apart from each other. The method of claim 3,
And the second electrode layer
And a common electrode for applying a voltage between each of the plurality of first sub-electrodes and each of the plurality of first sub-electrodes. The method of claim 3,
Wherein the control unit adjusts the light path conversion surface by applying a separate voltage to each of the plurality of first sub-electrodes. The method of claim 3,
A refractive index distribution of the optical deflecting layer is formed in accordance with a voltage distribution applied between each of the plurality of first sub-electrodes and the second electrode layer, and an interface forming a boundary having a different refractive index in the optical deflecting layer, Lt; / RTI > 3. The method of claim 2,
Wherein the first electrode layer and the second electrode layer comprise a transparent conductive material. 3. The method of claim 2,
Wherein the light deflecting layer comprises a liquid crystal. The method according to claim 1,
Wherein the control unit controls the light source and the first light deflecting unit so that light of a plurality of wavelength components is transmitted through the first light deflecting unit in a time-division manner. 10. The method of claim 9,
Wherein,
The time of one frame is divided into a plurality of subframes,
The light source is controlled so that light of different wavelengths enters the plurality of subframes at the same incident angle to the first light deflecting unit,
And controls the first optical deflecting unit so that the angles of incidence on the different optical path changing surfaces are different from each other according to the lights of the different wavelengths. 11. The method of claim 10,
Wherein the time lengths of the plurality of sub-frames are equal to each other. The method according to claim 1,
Wherein the optical deflector further comprises a second optical deflector having a light path changing surface that is variable such that a deflecting direction of the incident light is adjusted. 13. The method of claim 12,
Wherein the light source provides light of different wavelengths to the first and second light deflecting portions. 14. The method of claim 13,
The control unit
And controls the first and second optical deflecting units so that the lights having different wavelengths enter the optical path changing surfaces of the first and second optical deflecting units at different angles. 15. The method of claim 14,
Wherein the optical deflector further comprises at least one optical path changing member for converting an optical path such that light of different wavelengths emitted from the first and second light deflecting units form the same optical path. 16. The method of claim 15,
Wherein the light path changing member includes a dichroic mirror. 13. The method of claim 12,
Wherein the second light deflecting unit is located on an optical path passing light passing through the first light deflecting unit. 18. The method of claim 17,
Wherein an axis at which the optical path changing surface of the first optical deflecting unit is varied and an axis at which the optical path changing surface of the second optical deflecting unit is varied are orthogonal to each other. The method according to claim 1,
Wherein an incidence direction of the light incident on the beam expander and an emerging direction of light emitted from the second exit pattern are opposite directions. The method according to claim 1,
Wherein the display and the beam expander are disposed in the same direction with respect to the light guide plate. The method according to claim 1,
Wherein the first emission pattern and the second emission pattern are arranged in the same direction with respect to the light guide plate.

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