Lens assembly and display device with lens assembly

Abstract

To provide a lens assembly capable of improving display quality and a display device with the same.SOLUTION: Provided is a lens assembly OCP configured to guide light with an incident side A1 to which the light enters and an emission side A2 on the opposite side of the incident side A1. The lens assembly comprises: a first polarization layer POL1 disposed adjacent to the incident side A1; a second polarization layer POL2 disposed adjacent to the emission side A2; and a phase delay layer RTHL disposed between the first polarization layer POL1 and the second polarization layer POL2. The phase delay layer RTHL has a first phase delay index of refraction along a first direction, a second phase delay index of refraction, which is the same as the first phase delay index of refraction, along a second direction, and a third phase delay index of refraction along a third direction DR3 perpendicular to the first direction and the second direction. The first phase delay index of refraction and the second phase delay index of refraction may differ from the third phase delay index of refraction.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a lens assembly and a display device including the lens assembly. [Background technology]

[0002] As information technology develops, the importance of display devices, which are a connection medium between users and information, is increasing. Accordingly, the use of display devices such as liquid crystal display devices and organic light emitting display devices is increasing.

[0003] Recently, a head mounted display (HMD) has been developed as a type of display device. A head mounted display is a display device that is worn on a user's head to provide images, and is currently in the commercialization stage and is being widely applied in various fields such as the entertainment industry.

[0004] For example, head-mounted displays can be used for a variety of applications, such as virtual reality (VR) and augmented reality (AR).

[0005] Meanwhile, methods for improving the display quality of head-mounted display devices are being continuously sought, for example, methods for reducing ghost images are being sought in order to provide users with virtual reality and augmented reality that are close to reality. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Korean Patent Publication No. 2022-0123256 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present disclosure is to provide a lens assembly capable of improving display quality and a display device including the same. [Means for solving the problem]

[0008] A lens assembly according to an embodiment of the present disclosure is configured to guide light, and includes an input side to which the light is incident and an output side opposite the input side, the lens assembly including a first polarizing layer disposed adjacent to the input side, a second polarizing layer disposed adjacent to the output side, a phase retardation layer disposed between the first polarizing layer and the second polarizing layer, and a first quarter wave plate disposed between the second polarizing layer and the output side. the first quarter-wave plate and the second quarter-wave plate; a partially reflective mirror layer disposed between the first quarter-wave plate and the output side; a third polarizing layer disposed adjacent to the output side; the phase retardation layer has a first phase retardation refractive index along a first direction, a second phase retardation refractive index along a second direction that is the same as the first phase retardation refractive index, and a third phase retardation refractive index along a third direction perpendicular to the first direction and the second direction, and the first phase retardation refractive index and the second phase retardation refractive index can be different from the third phase retardation refractive index.

[0009] According to an embodiment, the phase retardation layer may include a material having refractive index anisotropy.

[0010] According to the embodiment, the phase retardation layer has a phase retardation value R th The phase retardation value for visible light may be 500 nm to 1500 nm. ([Formula 1]R th ={(N X +N Y ) / 2-N Z}×d, in the above formula 1, NX is the first phase retardation refractive index, N Y is the second phase retardation refractive index, N Z represents the third retardation refractive index, and d represents the thickness of the retardation layer.

[0011] According to an embodiment, the material having refractive index anisotropy may include a discotic material or a liquid crystal material.

[0012] According to an embodiment, the first phase retardation refractive index, the second phase retardation refractive index and the third phase retardation refractive index can have a range of 1.5 to 1.9.

[0013] According to an embodiment, the phase retardation layer changes the polarization state of light incident along a direction different from the third direction, and the first direction and the second direction can be directions in which a plane in which the phase retardation layer is arranged extends.

[0014] According to an embodiment, the light transmission axes of the first polarizing layer and the second polarizing layer may be the same.

[0015] According to an embodiment, the first polarizing layer may be a linear polarizing layer.

[0016] According to an embodiment, the first polarizing layer can be a film.

[0017] According to an embodiment, the first polarizing layer and the phase retardation layer may be spaced apart from each other.

[0018] According to an embodiment, a material having an isotropic refractive index may be disposed between the first polarizing layer and the phase retardation layer.

[0019] According to an embodiment, the optical fiber further includes an adhesive layer disposed between the first polarizing layer and the phase retardation layer, and the phase retardation layer can be bonded to the first polarizing layer via the adhesive layer.

[0020] According to an embodiment, the phase retardation layer and the first polarizing layer may be in contact with each other.

[0021] According to an embodiment, the phase retardation layer may be disposed on the first polarizing layer via a coating or deposition process.

[0022] A display device according to an embodiment of the present disclosure includes a display panel including a base layer arranged on a plane defined based on a first direction and a second direction different from the first direction, and a light-emitting element arranged on the base layer; and a lens assembly arranged on the display panel, configured to transmit light provided from the display panel, and including an incident side adjacent to the display panel and an exit side opposite to the incident side. The lens assembly includes a first polarizing layer arranged adjacent to the incident side, a second polarizing layer arranged adjacent to the exit side, a phase retardation layer arranged between the first polarizing layer and the second polarizing layer, and a first quarter wave plate arranged between the second polarizing layer and the exit side. the first quarter-wave plate and the second quarter-wave plate; a partially reflective mirror layer disposed between the first quarter-wave plate and the output side; a third polarizing layer disposed adjacent to the output side; the phase retardation layer has a first phase retardation refractive index along the first direction, a second phase retardation refractive index along the second direction that is the same as the first phase retardation refractive index, and a third phase retardation refractive index along a third direction perpendicular to the first direction and the second direction, and the first phase retardation refractive index and the second phase retardation refractive index can be different from the third phase retardation refractive index.

[0023] According to the embodiment, the phase retardation layer has a phase retardation value R th The phase retardation value for visible light may be 500 nm to 1500 nm. ([Formula 1]R th ={(N X +N Y ) / 2-N Z}×d, in the above formula 1, N Xis the first phase retardation refractive index, N Y is the second phase retardation refractive index, N Z represents the third retardation refractive index, and d represents the thickness of the retardation layer.

[0024] According to an embodiment, the phase retardation layer includes a material having refractive index anisotropy, and the phase retardation layer can change the polarization state of light incident in a direction different from the third direction.

[0025] According to an embodiment, the light transmission axes of the first polarizing layer, the second polarizing layer and the third polarizing layer may be the same as each other.

[0026] A lens assembly according to an embodiment of the present disclosure is configured to guide light, and includes an incident side into which the light is incident and an exit side opposite the incident side, and includes a first polarizing layer disposed adjacent to the incident side, a second polarizing layer disposed adjacent to the exit side, and a phase retardation layer disposed between the first polarizing layer and the second polarizing layer, wherein the phase retardation layer has a first phase retardation refractive index along a first direction, a second phase retardation refractive index along a second direction that is the same as the first phase retardation refractive index, and a third phase retardation refractive index along a third direction perpendicular to the first direction and the second direction, and the first phase retardation refractive index and the second phase retardation refractive index may be different from the third phase retardation refractive index.

[0027] According to the embodiment, the phase retardation layer has a phase retardation value R th The phase retardation value for visible light may be 500 nm to 1500 nm. ([Formula 1]R th ={(N X +N Y ) / 2-N Z}×d, in the above formula 1, N X is the first phase retardation refractive index, N Y is the second phase retardation refractive index, N Z represents the third retardation refractive index, and d represents the thickness of the retardation layer. Effect of the Invention

[0028] According to the embodiments of the present disclosure, it is possible to provide a lens assembly capable of improving display quality and a display device including the same. [Brief description of the drawings]

[0029] [Figure 1] FIG. 1 is a diagram illustrating a display device according to an embodiment. [Diagram 2] FIG. 2 is a schematic plan view showing a display panel according to an embodiment. [Diagram 3] 1 is a schematic cross-sectional view of a lens assembly according to a first embodiment. [Figure 4] 1 is a schematic diagram showing the optical paths of side light and front light emitted from a display panel. [Figure 5a] 13 shows the results of a simulation of the emitted light from TECH WIZ 1D with and without a phase retardation layer and with respect to the phase retardation value of the phase retardation layer. [Figure 5b] 13 shows the results of a simulation of the emitted light from TECH WIZ 1D with and without a phase retardation layer and with respect to the phase retardation value of the phase retardation layer. [Figure 5c] 13 shows the results of a simulation of the emitted light from TECH WIZ 1D with and without a phase retardation layer and with respect to the phase retardation value of the phase retardation layer. [Figure 5d] 13 shows the results of a simulation of the emitted light from TECH WIZ 1D with and without a phase retardation layer and with respect to the phase retardation value of the phase retardation layer. [Figure 5e] 13 shows the results of a simulation of the emitted light from TECH WIZ 1D with and without a phase retardation layer and with respect to the phase retardation value of the phase retardation layer. [Figure 5f] 13 shows the results of a simulation of the emitted light from TECH WIZ 1D with and without a phase retardation layer and with respect to the phase retardation value of the phase retardation layer. [Figure 6] FIG. 2 is a schematic diagram showing the way in which the optical path is folded; [Figure 7] FIG. 11 is a schematic cross-sectional view of an optical assembly according to a second embodiment. [Figure 8] FIG. 11 is a schematic cross-sectional view of an optical assembly according to a third embodiment. [Figure 9] 2 is a schematic diagram showing an example of an electronic device to which the display device of FIG. 1 can be applied. [Figure 10] 2 is a schematic diagram showing an example of an electronic device to which the display device of FIG. 1 can be applied. [Figure 11] FIG. 10 is a schematic diagram showing the head mounted display device worn by the user of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] Although the present disclosure can be modified in various ways and can be implemented in various forms, only specific embodiments are illustrated in the drawings and the present disclosure will be described based on these embodiments. However, the present disclosure is not limited to such specific embodiments, and it is to be understood that all modifications, equivalents, or alternatives within the spirit and technical scope of the present disclosure are included in the present disclosure.

[0031] Terms such as first and second are used to describe various components, but the components should not be limited by the terms. The terms are used only to distinguish one component from another. For example, a first component can be called a second component, and a second component can be called a first component, without departing from the scope of the present disclosure. A singular expression includes a plural expression unless the context clearly indicates otherwise.

[0032] In this disclosure, the terms "comprise" or "have" and the like are intended to specify the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, and are not to be understood as precluding the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof. In addition, when a layer, film, region, plate, or other part is described as being "on" another part, this includes not only the case where it is "directly on" the other part, but also the case where another part is located between them. In addition, in this specification, when a layer, film, region, plate, or other part is described as being formed on another part, the formed direction is not limited to the upper direction, but also includes the case where it is formed on the side or lower direction. Conversely, when a layer, film, region, plate, or other part is described as being "under" another part, this includes not only the case where it is "directly under" the other part, but also the case where another part is located between them.

[0033] The present disclosure relates to a lens assembly and a display device including the same. Hereinafter, a lens assembly according to an embodiment and a display device including the same will be described with reference to the accompanying drawings.

[0034] First, the configuration included in the display device DD will be briefly described with reference to FIG.

[0035] FIG. 1 is a diagram illustrating a display device according to an embodiment.

[0036] The display device DD may include a display panel DP and a lens assembly OCP.

[0037] The display panel DP is configured to emit light. According to an embodiment, the display panel DP can display moving images and still images. The display panel DP can be used as a display screen for various products such as a mobile phone, a smart phone, a tablet personal computer, a smart watch, a watch phone, a mobile communication terminal, an electronic organizer, an electronic book, a portable multimedia player (PMP), a navigation system, an Ultra Mobile PC (UMPC), etc., as well as a television, a notebook computer, a monitor, a billboard, and an Internet of Things (IOT). However, the application field of the display panel DP is not limited to a specific example.

[0038] The lens assembly OCP can transmit light provided from the display panel DP. The lens assembly OCP can guide the light provided from the display panel DP. The lens assembly OCP can guide the light provided from the display panel DP to expand an area (field of view window, eye box) in which a user can observe an image. In this way, the lens assembly OCP can provide virtual reality or augmented reality to the user.

[0039] The lens assembly OCP can be arranged on the display panel DP. According to an embodiment, the lens assembly OCP may be arranged at a certain distance from the display panel DP. According to an embodiment, the lens assembly OCP may be arranged directly on the display panel DP.

[0040] The display panel DP included in the configuration of the display device DD will be described below with reference to FIG.

[0041] FIG. 2 is a schematic plan view showing a display panel according to an embodiment.

[0042] Referring to Figure 2, the display panel DP may include a base layer BSL arranged on a plane defined based on a first direction DR1 and a second direction DR2 intersecting the first direction DR1, and a light-emitting element arranged on the base layer BSL.

[0043] The display panel DP may be formed in a rectangular plane having a short side in a first direction DR1 and a long side in a second direction DR2 different from the first direction DR1 and intersecting with the first direction DR1. A corner where the short side in the first direction DR1 and the long side in the second direction DR2 intersect may be rounded or formed at a right angle to have a predetermined curvature. The plane shape of the display panel DP is not limited to a rectangle, and may be formed in a round shape such as another polygon, a circle, or an ellipse. The display panel DP may be formed flat, but is not limited thereto. For example, the display panel DP may include curved portions formed at the ends of the left and right sides and having a constant curvature or a varying curvature. In addition, the display panel DP may be formed flexibly so that it can be bent, flexed, bent, folded, or rolled.

[0044] In the present disclosure, the first direction DR1 may be a "horizontal" direction in the row direction of the pixels PXL. The second direction DR2 may be a column direction of the pixels PXL. The first direction DR1 and the second direction DR2 may be perpendicular to each other. The third direction DR3 may be a display direction of the display panel DP or a normal direction of a plane on which the base layer BSL is arranged.

[0045] The display panel DP may include a display area DA and a non-display area NDA. The non-display area NDA may mean an area other than the display area DA. The non-display area NDA may surround at least a part of the display area DA.

[0046] The display area DA may refer to an area in which the pixels PXL are arranged, and the non-display area NDA may refer to an area in which the pixels PXL are not arranged, and the non-display area NDA may include driving circuits, wiring, and pads connected to the pixels PXL of the display area DA.

[0047] According to an embodiment, the pixel PXL (or subpixel SPX) may include a first subpixel SPX1, a second subpixel SPX2, and a third subpixel SPX3. At least one of the first subpixel SPX1, the second subpixel SPX2, and the third subpixel SPX3 may form one pixel unit PXU that can emit light of various colors. In FIG. 2, each pixel PXL is illustrated as including three subpixels SPX1, SPX2, and SPX3, i.e., the first subpixel SPX1, the second subpixel SPX2, and the third subpixel SPX3, but the embodiments of the present specification are not limited thereto.

[0048] According to an embodiment, the pixels PXL (or sub-pixels SPX) may be arranged in a stripe or PENTILE (registered trademark) array structure, etc. However, the present disclosure is not necessarily limited thereto.

[0049] The first subpixel SPX1 can emit a first light, the second subpixel SPX2 can emit a second light, and the third subpixel SPX3 can emit a third light. Here, the first light can be light in a red wavelength band, the second light can be light in a green wavelength band, and the third light can be light in a blue wavelength band. The red wavelength band can be a wavelength band of about 600 nm to 750 nm, the green wavelength band can be a wavelength band of about 480 nm to 560 nm, and the blue wavelength band can be a wavelength band of about 370 nm to 460 nm, but the examples of the present specification are not limited thereto.

[0050] Each of the first subpixel SPX1, the second subpixel SPX2, and the third subpixel SPX3 may include an inorganic light-emitting element including an inorganic semiconductor or an organic light-emitting element (OLED: Organic Light Emitting Diode) as a light-emitting element that emits light, although the embodiments of the present specification are not limited thereto.

[0051] The lens assembly OCP according to the first embodiment will be described below with reference to FIGS.

[0052] FIG. 3 is a schematic cross-sectional view of a lens assembly according to a first embodiment. FIG. 4 is a schematic diagram showing the optical paths of side light and front light emitted from a display panel. FIG. 4 is a diagram showing the S1 region of FIG. 3 and a display panel DP. FIGS. 5a to 5f are simulation results of the emitted light TECH WIZ 1D depending on the presence or absence of a phase delay layer and the phase delay value of the phase delay layer. FIG. 6 is a schematic diagram showing a path in which the optical path is folded. FIG. 6 is a diagram showing the S2 region of FIG. 3.

[0053] Incidentally, TECH WIZ is one of the optical simulation programs known in the art.

[0054] Referring to FIG. 3, the lens assembly OCP may include an incident side A1 that may be disposed adjacent to the display panel DP with respect to a third direction DR3, and an exit side A2 that is opposite to the incident side A1.

[0055] The lens assembly OCP may include a first polarizing layer POL1, a phase retardation layer RTHL, a second polarizing layer POL2, a first quarter wave plate (QWP) QWP1, a partially reflective mirror layer HFM, a second quarter wave plate QWP2, and a third polarizing layer POL3. According to an embodiment, the lens assembly OCP may have a structure in which the first polarizing layer POL1, the phase retardation layer RTHL, the second polarizing layer POL2, the first quarter wave plate (QWP) QWP1, the partially reflective mirror layer HFM, the second quarter wave plate QWP2, and the third polarizing layer POL3 are sequentially arranged.

[0056] In the figures of the present disclosure, the components of the lens assembly OCP are shown as having flat surfaces and a rectangular cross-section, but the present disclosure is not limited thereto. According to an embodiment, each of the components of the lens assembly OCP may have a concave or convex surface and a concave or convex cross-section.

[0057] The first polarizing layer POL1 may be disposed on the display panel DP with reference to the third direction DR3. The first polarizing layer POL1 may be disposed adjacent to the incident side A1. For example, the first polarizing layer POL1 may be disposed closer to the display panel DP than the second polarizing layer POL2. According to an embodiment, the first polarizing layer POL1 and the display panel DP may be physically separated. The first polarizing layer POL1 and the display panel DP may not be in contact with each other. However, the present disclosure is not limited thereto. The first polarizing layer POL1 may be disposed directly on the display panel DP so as to be in contact with the display panel DP.

[0058] The first polarizing layer POL1 may have a transmission axis (or pass axis) aligned along one direction. For example, the first polarizing layer POL1 may have a transmission axis aligned along a fourth direction DR4, which is a direction perpendicular to the third direction DR3. The fourth direction DR4 may be parallel to the first direction DR1 or the second direction DR2. The first polarizing layer POL1 may be a linear polarizing layer. The first polarizing layer POL1 may linearly polarize the unpolarized or partially polarized light emitted from the display panel DP. For example, the first polarizing layer POL1 may transmit only the light vibrating along the transmission axis of the first polarizing layer POL1 and not transmit the remaining light. Thereby, the light emitted from the display panel DP may be linearly polarized by passing through the first polarizing layer POL1, aligned with the transmission axis of the first polarizing layer POL1.

[0059] The second polarizing layer POL2 may be disposed on the first polarizing layer POL1 with respect to the third direction DR3. The second polarizing layer POL2 may be disposed between the emission side A2 and the first polarizing layer POL1. The second polarizing layer POL2 may be disposed further away from the incident side A1 than the first polarizing layer POL1. For example, the second polarizing layer POL2 may be disposed closer to the emission side A2 than the first polarizing layer POL1. The second polarizing layer POL2 may be disposed further away from the display panel DP than the first polarizing layer POL1.

[0060] The second polarizing layer POL2 may have a transmission axis (or pass axis) aligned along one direction. The second polarizing layer POL2 may have a transmission axis in the same direction as the first polarizing layer POL1. For example, the second polarizing layer POL2 may have a transmission axis aligned along a fourth direction DR4. The second polarizing layer POL2 may be a linear polarizing layer. The second polarizing layer POL2 may linearly polarize the light transmitted through the second polarizing layer POL2. For example, only the light vibrating along the transmission axis of the second polarizing layer POL2 may be transmitted, and the remaining light may not be transmitted.

[0061] The phase retardation layer RTHL may be disposed on the first polarizing layer POL1 with reference to the third direction DR3. The phase retardation layer RTHL may be disposed adjacent to the first polarizing layer POL1. The phase retardation layer RTHL may be disposed between the first polarizing layer POL1 and the second polarizing layer POL2. The phase retardation layer RTHL may be disposed between the first polarizing layer POL1 and the second polarizing layer POL2 and spaced apart from the first polarizing layer POL1 and the second polarizing layer POL2. The phase retardation layer RTHL may be in non-contact with the first polarizing layer POL1 and the second polarizing layer POL2.

[0062] A refractive index isotropic material may be filled between the phase retardation layer RTHL and the first polarizing layer POL1, and between the phase retardation layer RTHL and the second polarizing layer POL2. For example, air may be filled between the phase retardation layer RTHL and the first polarizing layer POL1, and between the phase retardation layer RTHL and the second polarizing layer POL2.

[0063] The phase retardation layer RTHL may have a phase retardation value in a certain range, which may be expressed by the following Equation 1.

[0064] [Formula 1] R th ={(N X +N Y ) / 2-N Z}×d

[0065] In the above formula 1, R th is the retardation value of the retardation layer RTHL, N X is the refractive index of the retardation layer RTHL in the first direction DR1, N Y is the refractive index of the retardation layer RTHL in the second direction DR2, N Z denotes the refractive index of the phase retardation layer RTHL in the third direction DR3, and d denotes the thickness D of the phase retardation layer RTHL.

[0066] In the present disclosure, the thickness is defined by the third direction DR3, and the first direction DR1 and the second direction DR2 are the same as the direction in which the plane in which the phase retardation layer RTHL is disposed extends.X , N Y , and N Z are defined as the first phase retardation refractive index, the second phase retardation refractive index, and the third phase retardation refractive index, respectively. The phase retardation layer RTHL has a first phase retardation refractive index N X The phase retardation layer RTHL can have a second phase retardation refractive index N Y The phase retardation layer RTHL may have a third phase retardation refractive index N Z may have the following structure:

[0067] First phase retardation index N X and the second phase retardation refractive index N Y are in-plane (e.g., the plane in which the phase retardation layer RTHL is disposed) refractive indices of the phase retardation layer RTHL and may have the same value. Z is the refractive index in the thickness direction (e.g., the third direction DR3), and the first phase retardation refractive index N X and the second phase retardation refractive index N Y The third retardation refractive index N Z is the first phase retardation refractive index N X and the second phase retardation refractive index N Y 3. The retardation layer RTHL may have an anisotropic refractive index with respect to the third direction DR3, so that light incident on the retardation layer RTHL while forming an angle with respect to the third direction DR3 (or along a direction different from the third direction DR3) may have its polarization state changed.

[0068] According to an embodiment, the first phase retardation refractive index, the second phase retardation refractive index, and the third phase retardation refractive index may have a range of 1.5 to 1.9, although the present disclosure is not limited thereto.

[0069] The phase retardation layer RTHL may have a phase retardation value of 500 nm to 1500 nm with respect to visible light (e.g., light having a wavelength of 400 nm to 700 nm). The phase retardation value may be determined according to process conditions. For example, X+N Y ) / 2-N Z When a liquid crystal having a value of 0.15 is vertically aligned and the retardation layer RTHL has a thickness of 3.5 μm, the retardation value can be 0.15×3.5 μm=525 nm.

[0070] The retardation layer RTHL may include a material having refractive index anisotropy. For example, the material having refractive index anisotropy may include a liquid crystal material. For example, the material having refractive index anisotropy may include a reactive mesogen. For example, the material having refractive index anisotropy may include a discotic material (for example, a discotic mesogen).

[0071] According to an embodiment, the phase retardation layer RTHL may be a film layer. The phase retardation layer RTHL may be a single film.

[0072] Referring to FIG. 4, a display panel DP (e.g., a light-emitting element of the display panel DP) may emit light similar to a Lambertian distribution, and the light emitted from the display panel DP may include front light FLGT and side light SLGT.

[0073] Experimentally, when the display device DD is embodied as a head-mounted display device, the front light FLGT and the side light SLGT emitted from the display panel DP can form an image for providing a user with virtual reality and augmented reality. For example, the front light FLGT and the side light SLGT emitted from the display panel DP can pass through the lens assembly OCP to form an image in front of the user's eyes.

[0074] The front light FLGT may be light emitted in a direction perpendicular to the display panel DP and parallel to the third direction DR3, and the side light SLGT may be light emitted in a direction not perpendicular to the display panel DP and at an angle to the third direction DR3.

[0075] Experimentally, when the display device DD is embodied as a head-mounted display device, the front light FLGT is light that forms a focus in front of the user's eye and may be CRA (Chief Ray Angle) light that enters the user's viewing angle (or eye box). The side light SLGT can form a ghost image to provide a virtual image to the user, and can cause the lights emitted from the light-emitting elements to mix with each other by not forming a focus properly.

[0076] The display device DD according to the present disclosure can appropriately minimize the amount of side light SLGT emitted to the outside of the lens assembly OCP while minimizing the loss of the front light FLGT, thereby improving the display quality of the display device DD.

[0077] When the front light FLGT is emitted from the display panel DP, passes through the first polarizing layer POL1, and passes through the phase retardation layer RTHL, the front light FLGT is aligned (or parallel) with the third direction DR3 and can pass through without any additional change in optical information. In other words, when the front light FLGT passes through the phase retardation layer RTHL, it can pass through the phase retardation layer RTHL without changing its polarization state. As a result, the polarization state of the front light FLGT that has passed through the phase retardation layer RTHL is not changed and it can pass through the second polarizing layer POL2. Hereinafter, the light that has passed through the second polarizing layer POL2 is defined as "light LGT passing through the second polarizing layer."

[0078] Meanwhile, when the side light SLGT is emitted from the display panel DP, passes through the first polarizing layer POL1, and passes through the phase delay layer RTHL, the side light SLGT is incident while forming an angle with respect to the third direction DR3, so that the polarization state can be changed according to the phase delay value. That is, the polarization state of the side light SLGT can be changed when passing through the phase delay layer RTHL. As a result, among the side light SLGT whose polarization state has been changed by passing through the phase delay layer RTHL, the light that does not vibrate along the transmission axis of the second polarizing layer POL2 can be blocked by the second polarizing layer POL2. That is, the polarization state of the side light SLGT can be changed by passing through the phase delay layer RTHL, and at least a part of the side light SLGT vibrating in a direction different from the transmission axis of the second polarizing layer POL2 may not be able to pass through the second polarizing layer POL2.

[0079] In this regard, the simulation results of optical information depending on the presence or absence of the phase delay layer RTHL and the phase delay value of the phase delay layer RTHL will be described with reference to Fig. 5a to Fig. 5f. Fig. 5a to Fig. 5f show the simulation results of the output light TECH WIZ 1D depending on the presence or absence of the phase delay layer RTHL and the phase delay value of the phase delay layer RTHL. Hereinafter, the simulation results shown in Fig. 5a to Fig. 5f are defined as the first to sixth images 5A to 5F, respectively.

[0080] In FIG. 5a to FIG. 5f, the first image 5A is a simulation result of the light emitted from the lens assembly OCP in which the phase retardation layer RTHL is not arranged. The second image 5B is a simulation result of the light emitted from the lens assembly OCP in which the phase retardation layer RTHL is arranged to have a phase retardation value of 300 nm. The third image 5C is a simulation result of the light emitted from the lens assembly OCP in which the phase retardation layer RTHL is arranged to have a phase retardation value of 500 nm. The fourth image 5D is a simulation result of the light emitted from the lens assembly OCP in which the phase retardation layer RTHL is arranged to have a phase retardation value of 1000 nm. The fifth image 5E is a simulation result of the light emitted from the lens assembly OCP in which the phase retardation layer RTHL is arranged to have a phase retardation value of 1500 nm. The sixth image 5F is a simulation result of the light emitted from the lens assembly OCP in which the phase retardation layer RTHL is arranged to have a phase retardation value of 1800 nm.

[0081] These images show the distribution of viewing angles for each light transmittance. The light transmittance corresponds to the Vlax shown on the right for each light and dark, and the unit of transmittance is au (arbitrary unit).

[0082] Comparing the first image 5A with the second to sixth images 5B to 5F, it can be seen that the first image 5A shows darker result values ​​(e.g., values ​​of Vlax30 to 40) in a relatively wide area corresponding to the center compared to the second to sixth images 5B to 5F. In the simulation results of TECH WIZ 1D, the fact that the relatively darker result values ​​corresponding to values ​​of Vlax30 to 40 are widely distributed in the central area means that the degree of emission of side light SLGT in the output light is large. In other words, comparing the first image 5A with the second to sixth images 5B to 5F, it can be seen that more side light SLGT can be generated in the lens assembly OCP in which the phase delay layer RTHL is not arranged.

[0083] Comparing the second image 5B and the third image 5C, it can be seen that the second image 5B shows a dark result value in a relatively wide area compared to the third image 5C. This may be because when the phase retardation value of the phase retardation layer RTHL is less than 500 nm, only a small amount of the side light SGLT in the output light is blocked. Experimentally, when only a small amount of the side light SGLT in the output light is blocked, ghost images may be frequently formed. Therefore, when the phase retardation layer RTHL is formed to have a phase retardation value of less than 500 nm, only a small amount of the side light SGLT is blocked, and ghost images may be frequently formed.

[0084] Comparing the fifth image 5E and the sixth image 5F, it can be seen that the sixth image 5F has a relatively narrow dark result value (e.g., Vlax0-5 values) in the area adjacent to the edge area in the diagonal direction compared to the fifth image 5E. Experimentally, the reduction in the dark display area (e.g., area having Vlax0-5 values) in the edge area can mean that the brightness of the emitted light is reduced. Therefore, this can indicate that if the phase retardation value of the phase retardation layer RTHL exceeds 1500 nm, the brightness of the display device DD can be excessively reduced. As a result, if the phase retardation layer RTHL is formed to have a phase retardation value exceeding 1500 nm, the brightness of the display device DD can be excessively reduced, which can deteriorate the quality of the display device DD.

[0085] Therefore, it is necessary to design the phase retardation layer RTHL by selecting a phase retardation value in an appropriate range that can adequately block the side light SLGT without excessively reducing the luminance.

[0086] 3 and 6, the first quarter-wave plate QWP1 may be disposed on the second polarizing layer POL2 with reference to the third direction DR3. The first quarter-wave plate QWP1 may be disposed adjacent to the second polarizing layer POL2. The first quarter-wave plate QWP1 may be disposed between the second polarizing layer POL2 and the output side A2. According to an embodiment, the first quarter-wave plate QWP1 may be physically separated from the second polarizing layer POL2. The first quarter-wave plate QWP1 may not be in contact with the second polarizing layer POL2.

[0087] The first quarter-wave plate QWP1 may have an optical axis aligned at 45 degrees with respect to the transmission axes of the first polarizing layer POL1 and the second polarizing layer POL2. The first quarter-wave plate QWP1 may provide a phase difference of λ / 4 to change linearly polarized light to circularly polarized light or vice versa. For example, when the second polarizing layer passing light LGT has a linear polarization of 0°, it may become a left-circularly polarized (LCP) first light L1 after passing through the first quarter-wave plate QWP1. According to an embodiment, when the second polarizing layer passing light LGT passes through the first quarter-wave plate QWP1, it may be right-circularly polarized (RCP), but for convenience, the present disclosure will be described based on an embodiment in which the second polarizing layer passing light LGT is left-circularly polarized.

[0088] A refractive index isotropic material may be filled between the first quarter-wave plate QWP1 and the second polarizing layer POL2. For example, air may be filled between the first quarter-wave plate QWP1 and the second polarizing layer POL2.

[0089] The partially reflective mirror layer HFM may be arranged on the first quarter-wave plate QWP1 with reference to the third direction DR3. The partially reflective mirror layer HFM may be arranged adjacent to the first quarter-wave plate QWP1. The partially reflective mirror layer HFM may be arranged between the first quarter-wave plate QWP1 and the output side A2. According to an embodiment, the partially reflective mirror layer HFM may be physically separated from the first quarter-wave plate QWP1. The partially reflective mirror layer HFM may not be in contact with the first quarter-wave plate QWP1.

[0090] The partially reflective mirror layer HFM may include a metallic mirror coating on the surface, or other mirror coating, such as a 50% transmissive and 50% reflective dielectric multi-layer coating.

[0091] At least a part of the first light L1 can be transmitted through the partially reflecting mirror layer HFM to become the second light L2. The polarization states of the first light L1 and the second light L2 may be the same.

[0092] A refractive index isotropic material may be filled between the partially reflective mirror layer HFM and the first quarter-wave plate QWP1. For example, air may be filled between the partially reflective mirror layer HFM and the first quarter-wave plate QWP1.

[0093] The second quarter-wave plate QWP2 may be arranged on the partially reflective mirror layer HFM with reference to the third direction DR3. The second quarter-wave plate QWP2 may be arranged adjacent to the partially reflective mirror layer HFM. The second quarter-wave plate QWP2 may be arranged between the partially reflective mirror layer HFM and the output side A2. According to an embodiment, the second quarter-wave plate QWP2 may be physically separated from the partially reflective mirror layer HFM. The second quarter-wave plate QWP2 may not be in contact with the partially reflective mirror layer HFM.

[0094] The second quarter-wave plate QWP2 can provide a phase difference of λ / 4 to vertically polarize the second polarizing layer passing light LGT. The second polarizing layer passing light LGT can be vertically polarized to become the third light L3. For example, if the second polarizing layer passing light LGT is linearly polarized at 0°, it can pass through the first and second quarter-wave plates QWP1 and QWP2 to be polarized to linearly polarized at 90°.

[0095] A refractive index isotropic material may be filled between the second quarter-wave plate QWP2 and the partially reflective mirror layer HFM. For example, air may be filled between the second quarter-wave plate QWP2 and the partially reflective mirror layer HFM.

[0096] The third polarizing layer POL3 may be disposed on the second quarter-wave plate QWP2 with respect to the third direction DR3. The third polarizing layer POL3 may be disposed adjacent to the output side A2. The third polarizing layer POL3 may be disposed adjacent to the second quarter-wave plate QWP2. According to an embodiment, the third polarizing layer POL3 may be physically separated from the second quarter-wave plate QWP2. The third polarizing layer POL3 may not be in contact with the second quarter-wave plate QWP2.

[0097] A refractive index isotropic material may be filled between the third polarizing layer POL3 and the second quarter-wave plate QWP2. For example, air may be filled between the third polarizing layer POL3 and the second quarter-wave plate QWP2.

[0098] The third polarizing layer POL3 may have a transmission axis (or pass axis) aligned along one direction. For example, the third polarizing layer POL3 may have a transmission axis aligned along a fourth direction DR4. The third polarizing layer POL3 may be a reflective polarizing layer. For example, the third polarizing layer POL3 may transmit only light that vibrates along the transmission axis of the third polarizing layer POL3 and reflect the remaining light.

[0099] As a result, when the light LGT passing through the second polarizing layer is linearly polarized at 0° and the third light L3 is linearly polarized at 90°, the third light L3 can be reflected by the third polarizing layer POL3 to become the fourth light L4.

[0100] The fourth light L4 can pass through the second quarter-wave plate QWP2 again and become right-handed circularly polarized. The right-handed circularly polarized fifth light L5 can be reflected by the partially reflective mirror layer HFM. At this time, the phase of the circularly polarized light can be changed by 180° when it is reflected, and the right-handed circularly polarized fifth light L5 can be reflected by the partially reflective mirror layer HFM and become the left-handed circularly polarized sixth light L6. The left-handed circularly polarized sixth light L6 can pass through the second quarter-wave plate QWP2 again and become the seventh light L7, which is linearly polarized at 0°.

[0101] As a result, the second polarizing layer passing light LGT and the seventh light L7 can have the same polarization value, and the seventh light L7 can transmit through the third polarizing layer POL3.

[0102] In this manner, the light path of the light emitted from the display panel DP may be folded while passing through the second polarizing layer POL2, the first quarter wave plate (QWP) QWP1, the partially reflective mirror layer HFM, the second quarter wave plate QWP2, and the third polarizing layer POL3, and the light path may be increased by the distance between the third polarizing layer POL3 and the partially reflective mirror layer HFM. As a result, the focal point may be formed closer than when the lens assembly OCP does not include the second polarizing layer POL2, the first quarter wave plate (QWP) QWP1, the partially reflective mirror layer HFM, the second quarter wave plate QWP2, and the third polarizing layer POL3, and the thickness of the display device DD may be reduced.

[0103] An optical assembly OCP' according to a second embodiment will be described below with reference to Fig. 7. Fig. 7 is a schematic cross-sectional view of the optical assembly according to the second embodiment.

[0104] The optical assembly OCP' according to the second embodiment differs from the optical assembly OCP according to the first embodiment in that the phase retardation layer RTHL' can be adhered (or bonded) onto the first polarizing layer POL1 via an adhesive layer 101. However, the position of the phase retardation layer RTHL' is not limited thereto, and according to an embodiment, the phase retardation layer RTHL' may be adhered to the lower part of the second polarizing layer POL2 via an adhesive layer 101. Content that overlaps with the above content will not be described repeatedly.

[0105] The phase retardation layer RTHL' may be adhered onto the first polarizing layer POL1 via an adhesive layer 101, and may have a form in which the phase retardation film is attached onto the first polarizing layer POL1.

[0106] The adhesive layer 101 may include a material that is optically isotropic.

[0107] The adhesive layer 101 may include a flexible material. According to an embodiment, the flexible material may include one or more of the following group: polyimide, polyethylene terephthalate, and polyethylene naphthalate.

[0108] The adhesive layer 101 may include one or more of a press sensitive adhesive (PSA) and an optical clear adhesive (OCA), although the present disclosure is not limited thereto.

[0109] Hereinafter, an optical assembly OCP″ according to a third embodiment will be described with reference to FIG. 8. FIG. 8 is a schematic cross-sectional view of the optical assembly according to the third embodiment.

[0110] The optical assembly OCP" according to the third embodiment differs from the optical assembly OCP according to the first embodiment in that the phase retardation layer RTHL" is arranged directly on the first polarizing layer POL1. However, the position of the phase retardation layer RTHL" is not limited to this, and according to the embodiment, the phase retardation layer RTHL" may be arranged directly under the second polarizing layer POL2. Content that overlaps with the above content will not be repeated.

[0111] The phase retardation layer RTHL″ can be disposed directly on the first polarizing layer POL1 via a coating or deposition process.

[0112] For example, the phase retardation layer RTHL'' may be disposed by directly coating or evaporating a material having a phase retardation value of 500 nm to 1500 nm onto the first polarizing layer POL1.

[0113] The coating or deposition process can be formed by a method commonly used in the art. For example, the coating process can be one or more of the coating processes such as spin coating, roller coating, bar coating, dip coating, gravure coating, curtain coating, die coating, spray coating, doctor coating, and kneader coating. For example, the deposition process can be one or more of the printing processes such as screen printing, spray printing, inkjet printing, letterpress printing, intaglio printing, and lithographic printing, and deposition processes such as CVD (chemical vapor deposition), PVD (physical vapor deposition), and PECVD (plasma enhanced chemical vapor deposition).

[0114] 9 and 10 are schematic diagrams showing examples of electronic devices to which the display device of FIG. 1 can be applied.

[0115] 9, the display device can be applied to a head-mounted display device. The head-mounted display device 2000 can be a wearable electronic device that can be worn on a user's head. The head-mounted display device 2000 can include a head-mounted band 2100 and a display device storage case 2200.

[0116] The head mounting band 2100 can be connected to the display device housing case 2200 to fix the display device housing case 2200. As shown in Fig. 9, the head mounting band 2100 includes a horizontal band and a vertical band to fix the head mounted display device to the user's head, and the horizontal band can be provided to surround the side of the user's head and the vertical band can be provided to surround the top of the user's head. However, the present invention is not limited thereto, and the head mounting band 2100 can be embodied in the shape of a glasses frame or a helmet.

[0117] Referring to FIG. 10, the display device may be applied to smart glasses 1000 as another form of a head-mounted display device. The smart glasses 1000 may include a frame 111 and a lens unit 112. The smart glasses 1000 may be a wearable electronic device that can be worn on a user's face, and may have a structure in which a part of the frame 111 is folded or unfolded. For example, the smart glasses 1000 may be a wearable device for augmented reality. However, the present disclosure is not limited thereto.

[0118] The frame 111 may include a housing 111b that supports a lens portion 112 and a temple portion 111a for wearing by a user. The temple portion 111a is connected to the housing 111b by a hinge and may be folded or unfolded.

[0119] The frame 111 may include a built-in battery, a touchpad, a microphone, and / or a camera. The frame 111 may also include a built-in projector that outputs light and / or a processor that controls an optical signal.

[0120] The lens portion 112 may be an optical member that transmits or reflects light, and may include glass and / or a transparent synthetic resin.

[0121] The display device DD can be applied to the lens unit 112 of the smart glasses 1000. As an example, the user can recognize an image displayed by an optical signal sent from the projector of the frame 111 through the lens unit 112. For example, the user can recognize information such as the time and date displayed on the lens unit 112.

[0122] FIG. 11 is a schematic diagram showing the head mounted display device of FIG. 9 being worn by the user.

[0123] 11, a first display panel DP1 and a second display panel DP2 are arranged in a head-mounted display device 2000. The head-mounted display device 2000 may further include one or more lenses LOCP, ROCP. The lenses LOCP, ROCP may correspond to the lens assembly OCP described above.

[0124] In the display device storage case 2200, the right eye lens ROCP can be disposed between the first display panel DP1 and the right eye of the user. In the display device storage case 2200, the left eye lens LOCP can be disposed between the second display panel DP2 and the left eye of the user.

[0125] The image output from the first display panel DP1 can be viewed by the right eye of the user through the right eye lens ROCP. The right eye lens ROCP can refract light from the first display panel DP1 toward the right eye of the user. The right eye lens ROCP can perform an optical function for adjusting the viewing distance between the first display panel DP1 and the right eye of the user.

[0126] The image output from the second display panel DP2 can be viewed by the left eye of the user through the left eye lens LOCP. The left eye lens LOCP can refract light from the second display panel DP2 toward the left eye of the user. The left eye lens LOCP can perform an optical function for adjusting the viewing distance between the second display panel DP2 and the left eye of the user.

[0127] In an embodiment, each of the right eye lens ROCP and the left eye lens LOCP can include an optical lens having a pancake-shaped cross section. The optical lens having a pancake-shaped cross section can be a second polarizing layer POL2, a first quarter wave plate (QWP) QWP1, a partially reflective mirror layer HFM, a second quarter wave plate QWP2, and a third polarizing layer POL3.

[0128] In an embodiment, each of the right-eye lens ROCP and the left-eye lens LOCP may include a multi-channel lens including sub-regions having different optical characteristics. In this case, each display panel outputs an image corresponding to each sub-region of the multi-channel lens, and the output image passes through each corresponding sub-region and can be viewed by a user.

[0129] As described above, the present disclosure has been described with reference to preferred embodiments thereof. However, it will be understood that a person skilled in the art or having ordinary knowledge in the art can modify and change the present disclosure in various ways without departing from the spirit and technical scope of the present disclosure as set forth in the claims below.

[0130] Therefore, the technical scope of the present disclosure should not be limited to the contents described in the detailed description of the specification, but should be defined by the claims. [Explanation of symbols]

[0131] DP display panel OCP Lens Assembly DD display device PXL Pixel SPX Subpixel POL1 First polarizing layer RTHL Phase retardation layer POL2 Second polarizing layer QWP1 First quarter wave plate HFM partially reflective mirror layer QWP2 Second quarter wave plate POL3 Third polarizing layer

Claims

1. 1. A lens assembly configured to guide light, the lens assembly including an input side onto which the light is incident and an output side opposite the input side, the lens assembly comprising: The lens assembly includes: A first polarizing layer disposed adjacent to the incident side; A second polarizing layer disposed adjacent to the exit side; a phase retardation layer disposed between the first polarizing layer and the second polarizing layer; a first quarter wave plate disposed between the second polarizing layer and the output side; a partially reflecting mirror layer disposed between the first quarter-wave plate and the output side; a second quarter-wave plate disposed between the partially reflecting mirror layer and the output side; a third polarizing layer disposed adjacent to the exit side; The phase retardation layer is a first retardation index along a first direction; a second phase retardation index along a second direction that is the same as the first phase retardation index; a third phase retardation index along a third direction perpendicular to the first direction and the second direction; The lens assembly, wherein the first phase retardation index and the second phase retardation index are different from the third phase retardation index.

2. The lens assembly according to claim 1 , wherein the phase retardation layer includes a material having refractive index anisotropy.

3. The phase retardation layer has a phase retardation value R ｔｈ having 3. The lens assembly according to claim 2, wherein the phase retardation value is from 500 nm to 1500 nm for visible light. [Formula 1] R ｔｈ = {(N Ｘ +N Ｙ ) / 2-N Ｚ }×d In the above formula 1, N Ｘ is the first phase retardation refractive index, N Ｙ is the second phase retardation refractive index, N Ｚ represents the third phase retardation refractive index, and d represents the thickness of the phase retardation layer.

4. The lens assembly according to claim 2 , wherein the material having refractive index anisotropy includes a discotic material or a liquid crystal material.

5. 4. The lens assembly of claim 3, wherein the first phase retardation refractive index, the second phase retardation refractive index and the third phase retardation refractive index have a range of 1.5 to 1.

9.

6. the phase retardation layer changes the polarization state of light incident along a direction different from the third direction; 4. The lens assembly of claim 3, wherein the first direction and the second direction are directions along which a plane in which the phase retardation layer is disposed extends.

7. 4. The lens assembly of claim 3, wherein the first polarizing layer and the second polarizing layer have the same light transmission axis.

8. 4. The lens assembly of claim 3, wherein the first polarizing layer is a linear polarizing layer.

9. The lens assembly of claim 3 , wherein the first polarizing layer is a film.

10. 10. The lens assembly of claim 9, wherein the first polarizing layer and the phase retardation layer are spaced apart from each other.

11. 11. The lens assembly of claim 10, wherein a material having an isotropic refractive index is disposed between the first polarizing layer and the phase retardation layer.

12. The polarizing film further includes an adhesive layer disposed between the first polarizing layer and the phase retardation layer; The lens assembly of claim 9 , wherein the phase retardation layer is coupled to the first polarizing layer via the adhesive layer.

13. 4. The lens assembly of claim 3, wherein the phase retardation layer and the first polarizing layer are in contact with each other.

14. The lens assembly of claim 13 , wherein the phase retardation layer is disposed on the first polarizing layer via a coating or deposition process.

15. a display panel including a base layer disposed on a plane defined based on a first direction and a second direction different from the first direction, and a light-emitting element disposed on the base layer; a lens assembly disposed on the display panel and configured to transmit light provided by the display panel, the lens assembly including an input side adjacent the display panel and an output side opposite the input side; The lens assembly includes: A first polarizing layer disposed adjacent to the incident side; A second polarizing layer disposed adjacent to the exit side; a phase retardation layer disposed between the first polarizing layer and the second polarizing layer; a first quarter wave plate disposed between the second polarizing layer and the output side; a partially reflecting mirror layer disposed between the first quarter-wave plate and the output side; a second quarter-wave plate disposed between the partially reflecting mirror layer and the output side; a third polarizing layer disposed adjacent to the exit side; The phase retardation layer is a first phase retarding refractive index along the first direction; a second phase retardation index along the second direction that is the same as the first phase retardation index; a third phase retardation index along a third direction perpendicular to the first direction and the second direction; A display device, wherein the first phase retardation refractive index and the second phase retardation refractive index are different from the third phase retardation refractive index.

16. The phase retardation layer has a phase retardation value R ｔｈ having 16. The display device according to claim 15, wherein the phase delay value for visible light is 500 nm to 1500 nm. [Formula 1] R ｔｈ = {(N Ｘ +N Ｙ ) / 2-N Ｚ }×d In the above formula 1, N Ｘ is the first phase retardation refractive index, N Ｙ is the second phase retardation refractive index, N Ｚ represents the third phase retardation refractive index, and d represents the thickness of the phase retardation layer.

17. The phase retardation layer includes a material having refractive index anisotropy, The display device according to claim 16 , wherein the phase retardation layer changes the polarization state of light incident in a direction different from the third direction.

18. 17. The display device according to claim 16, wherein the first polarizing layer, the second polarizing layer, and the third polarizing layer have the same light transmission axis.

19. 1. A lens assembly configured to guide light, the lens assembly including an input side onto which the light is incident and an output side opposite the input side, the lens assembly comprising: A first polarizing layer disposed adjacent to the incident side; A second polarizing layer disposed adjacent to the exit side; a phase retardation layer disposed between the first polarizing layer and the second polarizing layer; The phase retardation layer is a first retardation index along a first direction; a second phase retardation index along a second direction that is the same as the first phase retardation index; a third phase retardation index along a third direction perpendicular to the first direction and the second direction; The lens assembly, wherein the first phase retardation index and the second phase retardation index are different from the third phase retardation index.

20. The phase retardation layer has a phase retardation value R ｔｈ having 20. The lens assembly of claim 19, wherein the phase retardation value is between 500 nm and 1500 nm for visible light. [Formula 1] R ｔｈ ={(N Ｘ +N Ｙ ) / 2-N Ｚ }×d In the above formula 1, N Ｘ is the first phase retardation refractive index, N Ｙ is the second phase retardation refractive index, N Ｚ represents the third phase retardation refractive index, and d represents the thickness of the phase retardation layer.

Images