Optical isolator and method for manufacturing same

Abstract

Provided is an optical isolator disposed between a light source and a light guide plate for propagating light received from the light source through a light incident part composed of a diffraction grating to a light emission part, the optical isolator being provided with a first plate and a second plate provided with a retarder, and the optical isolator being configured such that the first plate is provided with a plurality of linear polarizers, a region of the surface of the first plate through which light passes is divided into a plurality of sub-regions corresponding to the plurality of linear polarizers, and the directions of the linear polarizers of the respective sub-regions can be individually determined.

Description

Optical isolator and its manufacturing method

[0001] The present invention relates to an optical isolator used in a light guide plate of a glasses-type wearable device or the like.

[0002] In recent years, eyeglass-type wearable devices have been used that display an image containing additional information superimposed on an image observed by a viewer (see, for example, Patent Documents 1 to 3). In such eyeglass-type wearable devices, light from a light source is taken into the lens (glass portion) by a diffraction grating provided in the lens (glass portion) that functions as a light guide plate of the wearable device, and after the light is propagated within the lens (glass portion), an additional image is formed.

[0003] In order to improve the brightness of the formed image, it is preferable to use a reflective diffraction grating covered with a thin metal film as the diffraction grating that takes in light from the light source into the lens section. However, if a reflective diffraction grating covered with a thin metal film is used as the diffraction grating that takes in light from the light source into the lens section, the zero-order light reflected by the reflective diffraction grating may return to the light source as stray light, and a ghost image containing additional information may be formed.

[0004] Optical isolators are generally used to prevent stray light such as return light (see Patent Document 4). Therefore, even in the case of eyeglass-type wearable devices, it is conceivable to place an optical isolator between the light source and the lens portion of the wearable device. Optical isolators are generally used to target polarized laser light and suppress light returning to the light source, so they do not reduce the utilization efficiency of the light being used (light that enters from the light input portion and travels toward the light output portion). However, polarized laser light is not typically used in light guide plates for eyeglass-type wearable devices. Therefore, conventional optical isolators cannot be used as they are in light guide plates for eyeglass-type wearable devices, etc., from the perspective of light utilization efficiency.

[0005] Therefore, there is a need for an optical isolator that is placed between a light source and a lens portion of a wearable device, which prevents zero-order light reflected by the reflective diffraction grating of the lens portion from affecting the image and suppresses a decrease in light utilization efficiency.

[0006] US9791703B1US2020 / 0225498A1US2021 / 0109273A1JP2007108344

[0007] The technical object of the present invention is to provide an optical isolator that is placed between a light source and a lens portion of a wearable terminal, which prevents zero-order light reflected by the reflective diffraction grating of the lens portion from affecting an image and suppresses a decrease in light utilization efficiency.

[0008] A first aspect of the optical isolator of the present invention is an optical isolator arranged between a light source and a light guide plate that propagates light received from a light source via a light input section consisting of a diffraction grating to a light output section, and the isolator comprises a first plate and a second plate having a retarder, the first plate having a plurality of linear polarizers, the area through which light passes on the surface of the first plate being divided into a plurality of sub-regions corresponding to the plurality of linear polarizers, and the direction of the linear polarizer in each sub-region can be individually determined.

[0009] The optical isolator of this embodiment prevents the zero-order light reflected by the reflective diffraction grating of the lens section from affecting the image, and by appropriately determining the direction of the linear polarizers in each sub-region of the surface of the first plate, it is possible to suppress a decrease in light utilization efficiency.

[0010] In the optical isolator according to the first embodiment of this aspect, the first plate and the second plate are arranged in this order from the light source side.

[0011] In the optical isolator according to the second embodiment of this aspect, the second plate and the first plate are arranged in this order from the light source side.

[0012] A typical optical isolator includes a polarizer and a quarter-wave plate arranged in this order from the light source side. When polarized light is reflected by an unexpected (undesired) optical surface and travels in the opposite direction from its original direction, it passes through the quarter-wave plate twice, rotating the polarization direction by 90° and preventing the light from passing through the polarizer arranged in front of the light source. Therefore, no light returns to the light source. The optical isolator of this embodiment is characterized in that it allows the reflected light to return to the light source and then prevents it from passing through the first plate equipped with a linear polarizer.

[0013] A wearable terminal according to a second aspect of the present invention includes the optical isolator according to the first aspect.

[0014] In the wearable terminal of this embodiment, the optical isolator of the first embodiment prevents the zero-order light reflected by the reflective diffraction grating of the lens section from affecting the image, thereby suppressing a decrease in the efficiency of light utilization.

[0015] In the wearable terminal of the first embodiment of this aspect, the light source includes a collimator lens, and the optical isolator includes the plurality of sub-regions on the surface of the first plate in an area where the effective aperture of the collimator lens of the light source is projected.

[0016] According to this embodiment, the light utilization efficiency is improved because no linear grating is provided in the area of ​​the surface of the first plate through which light rays that do not return to the light source after being reflected by the diffraction grating of the light incident portion pass.

[0017] In the wearable device of the second embodiment of this aspect, the light source includes a collimator lens. When the angle that determines the numerical aperture of the collimator lens is α and the distance between the first plate and the light incident portion installed on the light guide plate is T, the width of one sub-region in a cross section including the central axis of the collimator lens is That's all.

[0018] According to this embodiment, it is possible to make it possible for a majority of the light beam traveling from the light source to the light incident portion and the light beam reflected by the light incident portion to pass through the same sub-region.

[0019] A third aspect of the present invention relates to a method for manufacturing an optical isolator, which is arranged between a light guide plate that receives light from a light source via a light entrance section made of a diffraction grating element and propagates the light to a light exit section, and which includes a first plate and a second plate that includes a retarder, and the method determines the arrangement of the light source, the first plate, and the second plate, divides the area on the surface of the first plate through which light passes into a plurality of sub-regions, and individually determines the direction of the linear polarizer in each sub-region.

[0020] In the manufacturing method of the optical isolator of this embodiment, by appropriately determining the direction of the linear polarizer in each sub-region of the area through which light passes on the surface of the first plate, it is possible to suppress a decrease in the light utilization efficiency and improve the quality of the image formed by the light exit section.

[0021] In the method for manufacturing an optical isolator according to the first embodiment of this aspect, the area through which light passes on the surface of the first plate is divided into a plurality of sub-areas according to the Cartesian coordinates of the surface, and the direction of the linear polarizer in each sub-area is individually determined according to the quality of the image formed by the light exit portion.

[0022] According to this embodiment, the area through which light passes on the surface of the first plate is divided into multiple sub-areas according to the orthogonal coordinates of the surface, and the direction of the linear polarizer in each sub-area is individually determined according to the quality of the image formed by the light emitting section, thereby easily improving the quality of images on wearable devices, etc.

[0023] 1 is a diagram showing an example of a light guide plate on which an optical isolator of the present invention is installed; FIG. 1 is a diagram showing a yz cross section of a light guide plate; FIG. 2 is a diagram showing an example of the path of a light ray within a light guide plate in the xy plane; FIG. 3 is a diagram explaining the path of a light ray P1 within a light guide plate in the yz plane; FIG. 4 is a diagram explaining the path of a light ray P2 within a light guide plate in the yz plane; FIG. 5 is a diagram showing the configuration of a reflective diffraction grating of a light incident portion; FIG. 6 is a diagram showing an example of an image formed by a light exit portion; FIG. 7 is a diagram showing an example of an optical isolator for preventing light returning to the light source from affecting an image; FIG. 8 is a diagram showing another example of an optical isolator for preventing light returning to the light source from affecting an image; FIG. 9 is a diagram showing the configuration of a system for confirming the reflection of linearly polarized light by a light incident portion by simulation; FIG. 10 is a diagram showing the relationship between the direction of linearly polarized light and the intensity of light reflected by the light incident portion; FIG. 11 is a diagram explaining angles θx and θy; FIG. 12 is a diagram showing the path of a light ray within a light guide plate in the xy plane; FIG. 13 is a diagram showing a flow chart for determining the configuration of a surface on which a linear polarizer is arranged; FIG. 14 is a diagram showing an example of a surface of a first plate divided into subregions; FIG. 15 is a diagram explaining the path of a light ray emitted from a light source and reaching a light incident portion. 1 is a diagram for explaining the path of a light ray emitted from a light source and reaching a light incident portion;

[0024] FIG. 1 is a diagram showing an example of a light guide plate for a wearable device or the like in which the optical isolator of the present invention is installed. The light guide plate corresponds to the lenses (glasses) of a glasses-type wearable device. The light guide plate includes a substrate 150, a light incident section 110, a folding section 120, and a light exit section 130. The light incident section 110, the folding section 120, and the light exit section 130 are diffraction gratings installed on the surface of the substrate 150. The x-axis is defined as the horizontal direction of the substrate 150 (the horizontal direction in FIG. 1 ), the y-axis is defined as the vertical direction of the substrate 150 (the vertical direction in FIG. 1 ), and the z-axis is defined as the direction perpendicular to the x-axis and y-axis. Figure 1 shows numerical values ​​indicating the dimensions of each part and the distance between each part. The units of length and distance are millimeters.

[0025] FIG. 2 is a diagram showing the yz cross section of the light guide plate. A light source 50 is installed facing the light incident section 110. The distance between the light source 50 and the substrate 150 is 1 millimeter, and the thickness of the substrate 150 is 1.5 millimeters. The light source 50 is configured to form an image on the light incident section 110. Light reaching the light incident section 110 is taken into the light guide plate as diffracted light and transmitted to the light folding section 120 by total reflection within the light guide plate. The light reaching the light folding section 120 is redirected by the light folding section 120 and transmitted to the light exit section 130. The light exit section 130 forms an image in the eyebox 200 using the light received from the light folding section 120. The eyebox 200 refers to the area within which the image is not lost even when the observer's pupil moves. The distance between the eyebox 200 and the substrate 150 is 18 millimeters.

[0026] 3 is a diagram showing an example of the path of light rays within the light guide plate in the xy plane. Table 1 shows the groove directions and groove spacing (grating periods) of the diffraction gratings of the light entrance section 110, the folding section 120, and the light exit section 130. The angle indicating the groove direction is a clockwise angle with respect to the y-axis.

[0027] FIG. 3 shows a light ray path P1 and a light ray path P2.

[0028] 4 is a diagram for explaining the path of a light ray P1 in the light guide plate in the yz plane. The light incident portion 110 is a reflective diffraction grating, and is disposed on the lower surface of the substrate 150.

[0029] FIG. 5 is a diagram for explaining the path of a light ray P2 in the light guide plate on the yz plane.

[0030] 4 and 5, light rays P1 and P2 that enter the light guide plate via the light incident portion 110 travel through the light guide plate while being reflected. In addition, a portion of the light rays P1 and P2 traveling through the light guide plate is diffracted at the folding portion 120 and is then changed in direction and transmitted to the light exit portion 130.

[0031] 3 to 5, when observing the paths of the light rays P1 and P2 reaching the light output unit 130, the number of reflections of the light ray P2 within the light guide plate before reaching the light output unit 130 is greater than the number of reflections of the light ray P1 within the light guide plate before reaching the light output unit 130. The symbols A and B shown in FIGS. 4 and 5 will be explained later.

[0032] 6 is a diagram showing the configuration of the reflective diffraction grating of the light incident portion 110. The reflective diffraction grating is covered with a thin metal film such as aluminum or silver to improve light utilization efficiency. Both sides of the thin metal film are covered with a protective film to prevent oxidation of the metal. The scale of the grating period direction (horizontal direction) and the scale of the grating height direction (vertical direction) in FIG. 6 are different; the length in the grating period direction is scaled larger than the length in the grating height direction.

[0033] Table 2 shows the specifications of the reflective diffraction grating.

[0034] 7 is a diagram showing an example of an image formed by the light output unit 130. In FIG. 7, a ghost of the image in the portion indicated by 1 appears in the portion indicated by 2. The ghost is thought to be caused by the zero-order light reflected by the reflective diffraction grating of the light input unit 110 returning to the light source 50 as stray light. Therefore, to prevent the occurrence of ghosts, an optical isolator is required to prevent the zero-order light reflected by the reflective diffraction grating from affecting the image.

[0035] FIG. 8 shows an example of an optical isolator for preventing light returning to a light source from affecting an image. The optical isolator includes a first plate 60 equipped with a linear polarizer and a second plate 70 equipped with a retarder such as a quarter-wave plate. Hereinafter, the first plate equipped with a linear polarizer will be referred to simply as the linear polarizer, and the second plate equipped with a retarder will be referred to simply as the retarder. The retarder 70 and the linear polarizer 60 are disposed between the light source 50 and the substrate 150 (light incident section 110) in the following order: light source 50, retarder 70, linear polarizer 60, and substrate 150. Light (1) emitted from the light source 50 passes through the retarder 70 (2), is linearly polarized by the linear polarizer 60 (3), is reflected by the light incident section 110 (4), passes again through the linear polarizer 60 to be linearly polarized (5), and passes again through the retarder 70 to be left-handed circularly polarized (6). In this state, the light is reflected by the light source 50 (7), passes through the retarder 70, and becomes linearly polarized light in a direction perpendicular to the direction of the linear polarizer 60 (8), and cannot pass through the linear polarizer 60. Therefore, the zero-order light reflected by the reflective diffraction grating is prevented from affecting the image. The reason why the direction of the linearly polarized light changes after reflection by the light incident section 110 in (4) of Figure 8 will be explained later.

[0036] FIG. 9 shows another example of an optical isolator for preventing light returning to the light source from affecting the image. The optical isolator includes a linear polarizer 60 and a retarder 75. The retarder 75 and the linear polarizer 60 are arranged between the light source 50 and the substrate 150 (light incident section 110) in the following order: light source 50, linear polarizer 60, retarder 75, and substrate 150. Light (1) emitted from the light source 50 is linearly polarized by the linear polarizer 60 (2), and after passing through the retarder 75, becomes left-handed circularly polarized light (3). After being reflected by the light incident section 110 in this state (4), it again passes through the retarder 75 and becomes linearly polarized light perpendicular to the direction of the linear polarizer 60 (5), and cannot pass through the linear polarizer 60. Therefore, the zero-order light reflected by the reflective diffraction grating is prevented from affecting the image.

[0037] Here, the reflection of the zero-order light at the linearly polarized light incident portion 110 will be described.

[0038] FIG. 10 shows the configuration of a system for simulating the reflection of linearly polarized light by the light incident section 110. The system includes a light source 50, a linear polarizer 60, and a light intensity detector 90. In the simulation, the light emitted from the light source 50 is linearly polarized. The simulation is performed so that the linearly polarized light emitted from the light source 50 passes through the linear polarizer 60, is reflected as zero-order light by the light incident section 110 of the substrate 150, and reaches the detector 90. The specifications of the reflective diffraction grating of the light incident section 110 are shown in Table 2. VirtualLab Fusion was used as the simulation app. The linear polarizer 60 is configured to be rotatable around its central axis.

[0039] FIG. 11 shows the relationship between the orientation of the linear polarizer 60 and the intensity of light reflected by the light input section 110. The horizontal axis of FIG. 11 indicates the angle between the orientation of the linear polarizer and the orientation of the linear polarizer. At an angle of 0 degrees, the orientation of the linear polarizer 60 is the same as the orientation of the linear polarized light emitted from the light source. At an angle of 90 degrees, the orientation of the linear polarizer 60 is perpendicular to the orientation of the linear polarized light emitted from the light source. The angle on the horizontal axis is changed by rotating the linear polarizer 60 around its central axis. The vertical axis of FIG. 11 indicates the relative value of the intensity of light that reaches the detector 90 after being reflected by the light input section 110. The solid and dashed lines in FIG. 11 will be explained later.

[0040] The intensity of light reaching the detector 90 is expected to be maximum at an angle of 0 degrees and zero at an angle of 90 degrees. However, according to FIG. 11 , in both the solid and dashed lines, the light intensity is maximum at an angle of approximately 10 degrees and zero at an angle of approximately 100 degrees. The simulation results shown in FIG. 11 are believed to indicate that a phase delay of approximately 10 degrees occurs due to reflection by the light input section 110. Generally, a phase delay is believed to occur due to reflection by a reflective diffraction grating such as the light input section 110. In other words, a reflective diffraction grating is believed to function as a polarization rotator that rotates the polarization direction of linearly polarized light.

[0041] In (4) of Figure 8, the reason why the direction of the linearly polarized light changes after reflection by the light incident section 110 is due to the above-mentioned phase delay. Also in (4) of Figure 9, a phase delay occurs due to reflection by the light incident section 110, so the amount of phase delay of the retarder 75 is preferably determined taking into account the phase delay due to reflection by the light incident section 110. For example, if the phase delay due to reflection by the light incident section 110 is 10 degrees, the amount of phase delay of the retarder 75 is preferably (90-10) / 2=40 degrees. A liquid crystal variable retarder may be used as the retarder 75.

[0042] FIG. 12 is a diagram illustrating angles θx and θy. θ denotes the angle between a perpendicular line drawn from the center of the light source 50 to the light-receiving surface of the light incident unit 110 and a straight line connecting the center of the light source 50 and point P on the light-receiving surface. The angle θ is the angle of incidence of the light ray from the center of the light source 50 at point P on the light-receiving surface. The x- and y-coordinates of point P are represented by xp and yp, respectively. θx denotes the angle between the perpendicular line drawn from the center of the light source 50 to the light-receiving surface of the light incident unit 110 and a straight line connecting the center of the light source 50 and point (xp, 0) on the light-receiving surface. θy denotes the angle between the perpendicular line drawn from the center of the light source 50 to the light-receiving surface of the light incident unit 110 and a straight line connecting the center of the light source 50 and point (0, yp) on the light-receiving surface. The signs of θx and θy are the same as the signs of xp and yp, respectively. In FIG. 12, θx is negative and θy is positive. In the previously described Figure 11, the solid line indicates the result of the light ray when θx = 0 (degrees), θy = 0 (degrees), and the dashed line indicates the result of the light ray when θx = 5 (degrees), θy = 5 (degrees). In this way, the position on the light receiving surface of the light incident unit 110 is determined by the angles θx and θy of the light ray emitted from the center of the light source 50 and incident on the light receiving surface. Also, in the previously described Figure 3, the paths of the light ray P1 and the light ray P2 are determined by the angles θx and θy of the light ray emitted from the center of the light source 50 and incident on the light receiving surface of the light incident unit 110.

[0043] 13 is a diagram showing the path of light rays within a light guide plate in the xy plane. For the above light rays, the angles of the incident light rays on the substrate 150 are θx = −8.07 (degrees) and θy = 9.13 (degrees). For the above light rays, when the direction of linear polarization by the linear polarizer 60 is 90 degrees clockwise from the y-axis, the light utilization efficiency of the light source 50 for light reaching the eye box 200 is 0.133 percent. When the direction of linear polarization by the linear polarizer 60 is 0 degrees clockwise from the y-axis, the light utilization efficiency of the light source 50 for light reaching the eye box 200 is 0.287 percent. Therefore, the light utilization efficiency when the clockwise angle is 0 degrees from the y-axis is 2.16 times that when the angle is 90 degrees.

[0044] The reason why the light utilization efficiency of light from light source 50 for light reaching eyebox 200 changes significantly depending on the direction of linear polarization by linear polarizer 60 is presumed to be as follows: As explained using Figure 11, the direction of linearly polarized light rotates when reflected by the reflective diffraction grating. Since the reflectance of light whose electric field vector oscillates in a direction perpendicular to the groove direction of the reflective diffraction grating (s-polarized light) differs from the reflectance of light whose electric field vector oscillates in a direction parallel to the groove direction of the reflective diffraction grating (p-polarized light), the reflectance of the reflective diffraction grating changes when the direction of linearly polarized light rotates.

[0045] 4 and 5, A indicates the location where reflection by the reflective diffraction grating occurs, and B indicates the location where reflection by the surface of the substrate 150 occurs. At A, rotation of the direction of linearly polarized light occurs, but at B, rotation of the direction of linearly polarized light does not occur. As shown in FIGS. 4 and 5, the number of reflections by the reflective diffraction grating of light reaching the eye box 200 changes depending on the path of the light ray traveling within the light guide plate, and the number of rotations of the linearly polarized light also changes. As described above, the reflectivity of the reflective diffraction grating changes when the direction of linearly polarized light rotates. Therefore, it is estimated that changing the initial direction of linear polarization of a light ray following a defined path within the light guide plate will change the utilization efficiency of the light reaching the eye box 200.

[0046] The path of the light ray traveling within the light guide plate is determined by the angles θx and θy of the light ray emitted from the center of the light source 50 and incident on the light receiving surface of the light incident unit 110. Therefore, by changing the direction of the initial linear polarization in accordance with the angles θx and θy of the light ray emitted from the center of the light source 50 and incident on the light receiving surface of the light incident unit 110, it is expected that the light utilization efficiency of the light from the light source 50 that reaches the eye box 200 will change, and the quality of the image formed by the light emitting unit 130, including the brightness, will be improved.

[0047] FIG. 14 shows a flow diagram for defining a first plate configuration comprising multiple linear polarizers.

[0048] 14, the area on the surface of the first plate through which light passes is divided into sub-areas according to the angles θx and θy of the light rays emitted from the center of the light source 50 and incident on the light-receiving surface of the light incident unit 110. The angles θx and θy correspond to the Cartesian coordinates x and y of the light-receiving surface of the light incident unit 110, respectively, so the area on the first plate through which light passes is divided into sub-areas according to the Cartesian coordinates.

[0049] FIG. 15 shows an example of the surface of the first plate divided into subregions. As an example, assume that the angle θ in FIG. 12 ranges from ±15 degrees and the aspect ratio (ratio of the length in the x-axis direction to the length in the y-axis direction) of the light incident section 110 is 4:3. Then, the range of θx is ±12.1 degrees, and the range of θy is ±9.13 degrees. Here, the subregions can be defined by, for example, equally dividing the angular range of 24.2 degrees in the x-axis direction and the angular range of 18.26 degrees in the y-axis direction. FIG. 15 shows an example in which the surface on which the linear polarizer is arranged is divided into nine sections in the x-axis direction and four sections in the y-axis direction.

[0050] In step S1020 of Fig. 14, the orientation of the linear polarizer in each sub-region is changed between 0 and 90 degrees, and the quality of the image formed in the eye box by the light output unit 130 is determined by simulation. The image quality refers to, for example, the brightness level and brightness uniformity. VirtualLab Fusion was used as the simulation application.

[0051] In step S1030 of Fig. 14, the image quality is evaluated to see if it is satisfactory. If the image quality is satisfactory, the process ends. If the image quality is not satisfactory, the process returns to step S1010, and the method of dividing the image into sub-regions is changed.

[0052] 16 and 17 are diagrams illustrating the paths of light rays emitted from the light source 50 and reaching the light incident unit 110. The light source 50 includes a light-emitting diode 51 and a collimator lens 53. The light-emitting diode may be a so-called micro LED. FIGS. 16 and 17 show cross sections including the central axis of the light source 50, i.e., the central axis of the collimator lens 53. In FIG. 16, all of the light rays emitted from the light source 50 and reflected by the light incident unit 110 return to the light source 50. In FIG. 17, some of the light rays emitted from the light source 50 and reflected by the light incident unit 110 do not return to the light source 50.

[0053] 16 and 17 , multiple subregions of a linear polarizer may be arranged in an area on the surface of the first plate 60 where the effective aperture of the collimator lens 53 of the light source 50 is projected. In order to improve the light utilization efficiency by not providing a linear grating in the area on the surface of the first plate through which the light rays that do not return to the light source 50 pass after being reflected by the diffraction grating of the light incident section 110, it is preferable that the area where the multiple subregions are arranged be the same size as the effective aperture of the collimator lens 53 of the light source 50, i.e., the spot size of the light beam, and be arranged close to the light source 50.

[0054] Furthermore, if the angle that determines the numerical aperture of the collimator lens 53 is α and the distance between the first plate 60 and the light incident portion 110 installed on the substrate 150 is T, the width of one sub-region in the cross section including the central axis of the light source 50, i.e., the central axis of the collimator lens 53, is This is preferable because the light beam traveling from the light source 50 to the light incident section 110 and the majority of the light beam reflected by the light incident section 110 pass through the same sub-region.

[0055] 18 is a diagram showing an example of an optical isolator. In this example, a linear polarizer 60 and a retarder 75 are arranged between a light source 50 and a light incident unit 110 in this order from the light source 50 side.

Claims

1. An optical isolator arranged between a light source and a light guide plate that transmits light received from a light source via a light input section consisting of a diffraction grating to a light output section, the optical isolator comprising: a first plate; and a second plate equipped with a retarder; the first plate is equipped with a plurality of linear polarizers; the area through which light passes on the surface of the first plate is divided into a plurality of sub-areas corresponding to the plurality of linear polarizers; and the direction of the linear polarizer in each sub-area can be individually determined.

2. An optical isolator according to claim 1, wherein the first plate and the second plate are arranged in this order from the light source side.

3. An optical isolator according to claim 1, wherein the second plate and the first plate are arranged in this order from the light source side.

4. A wearable terminal equipped with the optical isolator according to claim 1.

5. The wearable terminal according to claim 4, wherein the light source is provided with a collimator lens, and the optical isolator has the plurality of sub-areas on the surface of the first plate in an area where the effective aperture of the collimator lens of the light source is projected.

6. The light source is provided with a collimator lens, and the angle that determines the numerical aperture of the collimator lens is α, and the distance between the first plate and the light incident portion installed on the light guide plate is T. The width of one sub-region in the cross section including the central axis of the collimator lens is The wearable terminal according to claim 4.

7. A method for manufacturing an optical isolator that is disposed between a light source and a light guide plate that transmits light received from a light source via a light input section consisting of a diffraction grating element to a light output section, and that comprises a first plate and a second plate equipped with a retarder, the method comprising determining the arrangement of the light source, the first plate, and the second plate, dividing the area on the surface of the first plate through which light passes into a plurality of sub-areas, and individually determining the direction of the linear polarizer in each sub-area.

8. A method for manufacturing an optical isolator as described in claim 6, wherein the light passing area of ​​the surface of the first plate is divided into a plurality of sub-areas according to the Cartesian coordinates of the surface, and the direction of the linear polarizer of each sub-area is individually determined according to the quality of the image formed by the light exit portion.

Images