Optical system and observation apparatus

Abstract

To provide an optical system that is compact and also is capable of appropriately detecting the line of sight of a user.SOLUTION: An optical system 1 for forming an enlarged image of a display surface PNL at an exit pupil EP and forming a reduced image of the exit pupil EP at an imaging surface IM guides first polarization in a first direction in a first optical path RY1 from the display surface PNL to the exit pupil EP, guides first polarization and second polarization in a second direction different from the first direction in a second optical path RY2, RY2a from the exit pupil EP to the imaging surface IM, and has first polarization control means disposed in the second optical path for suppressing transmission of the first polarization.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical system and an observation device. [Background technology]

[0002] Observation devices such as head-mounted displays that are worn on the head of an observer (user) and allow the user to view an image are known. Observation devices that have a function of detecting the user's line of sight by providing the observation device with an optical system (imaging optical system) that captures an image of the user's pupil are also known. Patent Document 1 discloses an optical system having an optical path that passes through an optical system that allows the user to view an image and guides an image of the user's pupil or an image reflected by the user's pupil to an imaging element. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-86613 Summary of the Invention [Problem to be solved by the invention]

[0004] In the optical system disclosed in Patent Document 1, an optical path that passes through the transmissive-reflective surface and an optical path that passes through after being reflected twice are simultaneously formed. When the imaging surface is moved closer to the display surface for further miniaturization, the optical path that guides the image displayed on the display surface to the user's eye as an enlarged image overlaps with the optical path that passes through the transmissive-reflective surface and the optical path that passes through after being reflected twice is guided to the imaging surface. As a result, ghosts and flares caused by the multiple optical paths occur, reducing detection accuracy and making it difficult to properly detect the user's gaze direction.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an optical system that is compact yet capable of appropriately detecting the direction of a user's line of sight. [Means for solving the problem]

[0006] An optical system according to one aspect of the present invention is an optical system that forms an enlarged image of a display surface at an exit pupil and forms a reduced image of the exit pupil at an imaging surface, and has a first polarization control means that guides a first polarized light in a first direction in a first optical path from the display surface to the exit pupil, and guides a second polarized light in a second direction different from the first polarized light and the first direction in a second optical path from the exit pupil to the imaging surface, and is arranged in the second optical path to suppress the passage of the first polarized light.

[0007] Other objects and features of the present invention will be described in the following embodiments. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide an optical system that is compact yet capable of appropriately detecting the direction of the user's line of sight. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is a diagram illustrating the configuration of an optical system according to the present embodiment. [Figure 2] FIG. 3 is an explanatory diagram of a first optical path in the present embodiment. [Figure 3] FIG. 10 is a diagram illustrating the configuration of an optical system according to a modified example of the present embodiment. [Figure 4] 10A and 10B are explanatory diagrams of the mechanism related to the occurrence of ghosts or flares that occur in the second and third optical paths. [Figure 5] FIG. 4 is an explanatory diagram of a second optical path in the present embodiment. [Figure 6] 2 is an example of a first polarization control means in this embodiment. [Figure 7] FIG. 4 is an explanatory diagram of a third optical path in this embodiment. [Figure 8] 10 is an example of a second polarization control means in this embodiment. [Figure 9] FIG. 2 is a detailed diagram of a second lens unit and a third lens unit in the present embodiment. [Figure 10] FIG. 2 is a schematic diagram of an observation device according to the present embodiment. [Figure 11] FIG. 2 is an explanatory diagram of a display unit of the observation device in this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the drawings may be drawn at a scale different from the actual scale for convenience. In addition, the same reference numerals are used to designate the same components in the drawings, and redundant explanations will be omitted.

[0011] First, an optical system 1 according to this embodiment will be described with reference to FIG. 1. FIG. 1 is a configuration diagram of the optical system 1. The optical system 1 has a first lens unit (first optical system) LU1 and a second lens unit (second optical system) LU2, and forms an enlarged image of the display surface PNL at the exit pupil EP and a reduced image of the exit pupil on the imaging surface IM. The first lens unit LU1 forms an enlarged image of the image displayed on the display surface PNL at the exit pupil EP of the user's eye EYE (forms an enlarged image of the display surface PNL). The second lens unit LU2 forms an image of the cornea, etc. of the user's eye EYE through the first lens unit LU1 and onto the imaging surface IM. An optical path RY1 from the display surface PNL to the exit pupil EP is referred to as a first optical path, and an optical path RY2 from the eye EYE to the imaging surface IM is referred to as a second optical path. A polarizing unit (circular polarization conversion element) FL is disposed on the optical path RY1 between the display surface PNL and the first lens unit LU1 (on the display surface PNL side of the first transmission-reflection surface HM1). The first lens unit LU1 is rotationally symmetric with respect to the optical axis of the optical path RY1.

[0012] The display surface PNL is the display surface of a display element (spatial modulation element), such as an LCD (Liquid Crystal Display) or an LED (Light Emitting Diode) display. The polarization state can be controlled by the orientation of liquid crystals in a display such as an LCD; in other words, the function of the polarizer FL may be formed within the display element. In this case, the polarizer FL does not need to be provided between the display surface PNL and the first lens unit LU1.

[0013] The imaging surface IM is the light receiving surface of the imaging element. The imaging element is a photoelectric conversion element such as a CCD (Charge Coupled Device) sensor or a CMOS (Complementary Metal Oxide Semiconductor) sensor. However, this embodiment is not limited to this, and other photoelectric conversion elements such as a SPAD (Single Photon Avalanche Diode) sensor may also be used.

[0014] In the optical system 1, the first lens unit LU1 has a first lens G1 and a second lens G2. The first lens G1 has a first transmission-reflection surface HM1. The second lens G2 has a second transmission-reflection surface HM2. The first lens unit LU1 may include additional lenses as needed to correct various aberrations.

[0015] Next, the optical path (first optical path) RY1 will be described with reference to FIG. 2. FIG. 2 is an explanatory diagram of the optical path RY1. The polarizing unit FL has a first polarizing element (linear polarizer) PL1 and a first quarter-wave plate QWP1. Light having an axis perpendicular to the transmission axis of the first polarizing element PL1 is preferably absorbed by the first polarizing element PL1. The second transflective surface HM2 has a second quarter-wave plate QWP2 and a polarization-selective reflective polarizing element PBS. The polarization-selective reflective polarizing element PBS is preferably a wire-grid polarizing element. A wire-grid polarizing element is an optical element that has a fine metal grid (slits) and transmits or reflects light depending on its polarization state. The optical path RY1 passes through the first polarizing element PL1 of the polarizing unit FL, and light polarized in one direction (first direction, first polarization direction) is formed. In this embodiment, the first direction is the vertical direction in the plane of FIG. 2.

[0016] After passing through the first polarizing element PL1, the light is circularly polarized by the first quarter-wave plate QWP1 and then transmitted through the first transmission-reflection surface HM1. In FIG. 2, the circularly polarized light is formed to be clockwise circularly polarized relative to the direction of propagation. The light (not shown) reflected by the first transmission-reflection surface HM1 is formed to be counter-circularly polarized relative to the direction of propagation, and is absorbed by the first polarizing element PL1 after passing through the first quarter-wave plate QWP1. The light transmitted through the first transmission-reflection surface HM1 is converted to linearly polarized light by the second quarter-wave plate QWP2 and then enters the polarization-selective reflective polarizing element PBS.

[0017] The polarization-selective reflective polarizing element PBS reflects the linearly polarized light converted by the second quarter-wave plate QWP2 in one direction and transmits the light in the other direction. Therefore, the light that has passed through the first transmission-reflection surface HM1 is reflected once by the polarization-selective reflective polarizing element PBS. The reflected light passes through the second quarter-wave plate QWP2 again, where it is converted into circularly polarized light and reflected by the first transmission-reflection surface HM1.

[0018] The direction of rotation of the circularly polarized light relative to the direction of propagation when it enters the first transmissive-reflective surface HM1 is perpendicular to the direction of propagation after it is reflected. Therefore, the polarization state when the light passes through the second quarter-wave plate QWP2 again is perpendicular to the polarization state when it passed through the first time. As a result, the light passes through the polarization-selective reflective polarizing element PBS and reaches the exit pupil EP of the user's eye EYE. Therefore, the optical path RY1 follows an optical path that involves two reflections. This makes it possible to widen the field of view and effectively correct various aberrations while minimizing the thickness of the first lens unit LU1 in the optical axis direction.

[0019] On the other hand, as shown in Figure 1, optical path RY2 passes from the exit pupil EP through the second transmissive-reflective surface HM2 and the first transmissive-reflective surface HM1, and then is imaged on the imaging plane IM by the second lens unit LU2. By not using an optical path that reflects off the first transmissive-reflective surface HM1 and the second transmissive-reflective surface HM2, the number of times the light passes through the transmissive-reflective surfaces can be reduced, making it possible to suppress a decrease in the amount of light incident on the imaging plane IM. Furthermore, by passing the light through the first lens unit LU1, it is possible to restrict the imaging angle of the user's eye EYE and suppress vignetting of the pupil and iris caused by the eyelids, eyeball rotation, etc.

[0020] As shown in FIG. 1, light passes through the peripheral portions of the first lens G1 and the second lens G2 that make up the first lens unit LU1 and enters the second lens unit LU2. Therefore, it is desirable for the second lens unit LU2 to include an asymmetric optical surface to correct decentration aberrations caused by the first lens G1 and the second lens G2. It is also desirable for the imaging surface IM to be parallel to or substantially coplanar with the display surface PNL. This allows the imaging element and display element that make up the imaging surface IM and the display surface, respectively, to be integrated, thereby enabling the overall device to be miniaturized.

[0021] 1, the first transmission-reflection surface HM1 and the second transmission-reflection surface HM2 are formed on the refractive surfaces of the first lens G1 and the second lens G2, respectively, but this embodiment is not limited to this. For example, the first transmission-reflection surface HM1 and the second transmission-reflection surface HM2 may be disposed on both surfaces of the first lens G1. Alternatively, a cover glass or the like may be disposed, and the transmission-reflection surfaces may be formed on the cover glass or the like.

[0022] Furthermore, the optical path is not limited to that shown in FIG. 2 , and the transmission axis of the polarizing element and the slow axis of the quarter-wave plate may be changed as appropriate. Furthermore, the polarization-selective reflective polarizing element PBS shown in FIG. 2 transmits or reflects linearly polarized light, but is not limited thereto. It may also be an element that transmits or reflects circularly polarized light depending on the direction of rotation. The transmission-reflection surface may also be an element that transmits or reflects linearly or circularly polarized light depending on the direction. In this case, the quarter-wave plate must be appropriately positioned, but appropriate modifications or changes can be made within the scope of the present embodiment. Here, the polarization-selective reflective polarizing element and the polarizing element transmit 80% or more of incident light polarized parallel to the transmission axis. They transmit 5% or less of incident light polarized perpendicular to the transmission axis.

[0023] Next, an optical system 1a as a modified example of this embodiment will be described with reference to Fig. 3. Fig. 3 is a configuration diagram of the optical system 1a. In addition to a first lens unit LU1 and a second lens unit LU2, the optical system 1a has a third lens unit (third optical system) LU3 that forms an optical path (third optical path) RY3 for guiding light emitted by a light-emitting surface LS of a light-emitting element (light source) to the user's eye EYE.

[0024] In the optical path RY3, the light from the light-emitting surface LS passes through the third lens unit LU3, and then passes through the first transmission-reflection surface HM1 of the first lens G1 and the second transmission-reflection surface HM2 of the second lens G2, illuminating the user's eye EYE. By passing the light through the third lens unit LU3, it is possible to make the unit size more compact than when the light-emitting surface is located outside the outer diameter of the lens (for example, the first lens unit LU1).

[0025] The light-emitting surface LS illuminates the user's eye EYE, and the light diffused by the eye EYE or the light reflected by the cornea is guided (directed) to the imaging plane IM by the first lens unit LU1 and the second lens unit LU2. Although only one light-emitting surface LS is shown in FIG. 3, light-emitting surfaces LS (multiple light sources) may be arranged at multiple positions to prevent vignetting of light reflected by the cornea of ​​the eye EYE due to factors such as the eyelid or eyeball rotation. In this case, it is desirable to arrange the third lens unit LU3 so that it corresponds to the multiple light-emitting surfaces LS. Furthermore, it is desirable that the light emitted by the light-emitting surface LS or the light guided to the imaging plane IM be near-infrared light (wavelength 750 to 1000 nm).

[0026] The third lens unit LU3 preferably includes an asymmetric optical surface to properly illuminate the eye EYE, which allows the orientation angle of the light-emitting surface LS to be constant regardless of the first lens unit LU1, thereby reducing manufacturing costs, etc.

[0027] Next, the mechanism of occurrence of ghosts or flares caused by the optical paths RY2 and RY3 of the optical system 1a will be described with reference to Fig. 4. Fig. 4 is an explanatory diagram of the mechanism of occurrence of ghosts or flares.

[0028] The optical system 1a has an optical path RY2a that is guided to the imaging plane IM and is different from the optical path RY2, and an optical path RY3a that is guided from the light-emitting surface LS to the eye EYE and is different from the optical path RY3. That is, the second optical path includes the optical path (single-path optical path) RY2 and the optical path (triple-path optical path) RY2a, and the third optical path includes the optical path RY3 and the optical path RY3a. The light along the optical path RY2a is reflected by the first transmission-reflection surface HM1 and the second transmission-reflection surface HM2, and then passes through the first transmission-reflection surface HM1 to be guided to the second lens unit LU2. The light along the optical path RY3a is reflected by the first transmission-reflection surface HM1 and the second transmission-reflection surface HM2, and then passes through the second transmission-reflection surface HM2 to be guided to the exit pupil EP.

[0029] Next, the optical path RY2 and the optical path RY2a will be described with reference to Fig. 5. Fig. 5 is an explanatory diagram of the optical path RY2 and the optical path RY2a. Light from the eye EYE passes through the polarization-selective reflective polarizing element PBS and the second quarter-wave plate QWP2 that constitute the second transmissive-reflective surface HM2, and is incident on the first transmissive-reflective surface HM1 as circularly polarized light. One light is transmitted by the first transmissive-reflective surface HM1, and the other light is reflected and separated. The optical path of the transmitted light is the optical path RY2, and the optical path of the reflected light is the optical path RY2a.

[0030] The light that passes through the first transflective surface HM1 is guided directly to the imaging surface IM. The light that reflects off the second transflective surface HM2 is polarized in the opposite direction to the direction of propagation, different from the polarization state at the time of incidence, and passes through the second quarter-wave plate QWP2 again. The light that is reflected by the polarization-selective reflective polarizing element PBS, passes through the second quarter-wave plate QWP2, and passes through the first transflective surface HM1 is guided to the imaging surface IM. The polarization state (polarization direction, second direction) RP11 of the optical path RY2 guided to the imaging surface IM is orthogonal to the polarization state (polarization direction, first direction) RP12 of the optical path RY2a. Furthermore, the polarization state RP11 after passing through the polarizing unit FL in FIG. 2 is orthogonal to the polarization state RP11. In other words, the polarization states for forming the optical paths that reflect off the first transflective surface HM1 and the second transflective surface HM2 are orthogonal to the polarization state RP11.

[0031] Therefore, a first polarization control means is disposed between the first transmission-reflection surface HM1 and the imaging surface IM so as to prevent light in polarization state RP12 (first polarization) from reaching the imaging surface IM (so as to reduce the amount of light in polarization state RP12 passing through the optical path RY2a). This prevents the optical paths RY2 and RY2a from mixing, and makes it possible to guide the light in optical path RY2 (second polarization) to the imaging surface IM (preventing the light in optical path RY2a from reaching the imaging surface IM). Preferably, the amount of light in optical path RY2a that reaches the imaging surface IM is 5% or less of the light in optical path RY2. More preferably, only the light in optical path RY2 reaches the imaging surface IM.

[0032] Next, an example of the first polarization control means in the optical path RY2 will be described with reference to Fig. 6. Fig. 6 shows an example of the first polarization control means in the optical path RY2. In this embodiment, the first polarization control means has a third quarter-wave plate QWP3 and a second polarizing element PL2.

[0033] As in FIG. 5, the light along optical paths RY2 and RY2a that passes through the first transmission-reflection surface HM1 enters the third quarter-wave plate QWP3 and second polarizing element PL2, which constitute the first polarization control means. The third quarter-wave plate QWP3 in FIG. 6 and the first quarter-wave plate QWP1 in FIG. 2 have the same slow axis. The transmission axis of the second polarizing element PL2 and the transmission axis of the first polarizing element PL1 in FIG. 2 are orthogonal to each other. The polarization states of the light along optical path RY2 and the light along optical path RY2a are orthogonal to each other. Therefore, the second polarizing element PL2 guides only the light along optical path RY2 to the imaging plane IM.

[0034] 6, the second polarizing element PL2 is configured to allow only light of optical path RY2 to pass through, but this is not limiting. The transmission axes of the first polarizing element PL1 and the second polarizing element PL2 may be aligned with each other, and the slow axis of the first quarter-wave plate QWP1 and the slow axis of the third quarter-wave plate QWP3 may be perpendicular to each other.

[0035] Although the polarization states RP11 and RP12 are orthogonal to each other, the polarization states may not be strictly orthogonal due to manufacturing errors, etc. In this case, it is preferable to set the transmission axis or slow axis of the first polarization control means to be in the range of 70° to 110° with respect to the transmission axis or slow axis of the polarizing unit FL in FIG. 2. By setting it within this range, ghosts and flares can be suppressed, and the accuracy of detecting the user's gaze direction by the imaging surface IM can be improved. More preferably, the transmission axis or slow axis of the first polarization control means to be in the range of 75° to 105° with respect to the transmission axis or slow axis of the polarizing unit FL.

[0036] Next, the optical paths RY3 and RY3a will be described with reference to Figure 7. Figure 7 is an explanatory diagram of the optical paths RY3 and RY3a. Light from the light-emitting surface LS passes through the first transmission-reflection surface HM1 and the second quarter-wave plate QWP2 and enters the polarization-selective reflective polarizing element PBS. The polarization-selective reflective polarizing element PBS separates the light into transmitted light and reflected light. The transmitted light enters the eye EYE as is, while the reflected light passes through the quarter-wave plate QWP2 again to become circularly polarized light and is reflected by the first transmission-reflection surface HM1. The reflected light passes through the quarter-wave plate QWP2 and the polarization-selective reflective polarizing element PBS and enters the eye EYE.

[0037] As shown in Figure 4, optical path RY3 and optical path RY3a pass through the peripheral portion of first lens unit LU1 before reaching the eye EYE, and therefore optical path RY3 and optical path RY3a reach different points on the cornea of ​​the eye EYE. Therefore, two reflected images of the cornea captured by imaging surface IM are formed, reducing detection accuracy and making it difficult to properly detect the user's gaze direction. Furthermore, by using optical path RY3 instead of optical path RY3a, it is possible to suppress the reduction in light intensity caused by first transmissive-reflective surface HM1.

[0038] Next, an example of the second polarization control means on the optical path RY3 will be described with reference to Fig. 8. Fig. 8 shows an example of the second polarization control means. The second polarization control means has a third polarizing element PL3 ​​and a fourth quarter-wave plate QWP4. The second polarization control means transmits only the polarized light that is transmitted by the polarization-selective reflective polarizing element PBS from the light emitting surface LS.

[0039] 8, light from the light-emitting surface LS passes through the third polarizing element PL3, which is the second polarization control means, and the fourth quarter-wave plate QWP4, and then passes through the first transmission-reflection surface HM1 and the second quarter-wave plate QWP2 in a circularly polarized state, and enters the polarization-selective reflective polarizing element PBS. Because the polarization state is selected by the third polarizing element PL3, the light is only transmitted through the polarization-selective reflective polarizing element PBS and is irradiated onto the eye EYE.

[0040] The transmission axis of the third polarizing element PL3 ​​in Fig. 8 is perpendicular to the transmission axis of the first polarizing element PL1 in Fig. 2 and parallel to the transmission axis of the second polarizing element PL2 in Fig. 6. This allows light emitted from the light-emitting surface LS to be guided to the eye EYE without being reflected by the polarization-selective reflective polarizing element PBS, thereby achieving high detection accuracy and enabling the user's gaze direction to be detected appropriately. The transmission axes of the first to third polarizing elements PL1, PL2, and PL3 may be aligned with each other, and the slow axis of the fourth quarter-wave plate QWP4 and the slow axis of the first quarter-wave plate QWP1 may be perpendicular to each other and parallel to the slow axis of the third quarter-wave plate QWP3.

[0041] As with the first polarization control means described with reference to Fig. 6, the transmission axis or slow axis of the second polarization control means is preferably set within a range of 70° to 110° relative to the transmission axis or slow axis of the polarizing unit FL in Fig. 2. More preferably, the transmission axis or slow axis of the second polarization control means is set within a range of 75° to 105° relative to the transmission axis or slow axis of the polarizing unit FL.

[0042] Next, the second lens unit LU2 and the third lens unit LU3 will be described in detail with reference to FIG. 9. FIG. 9 is a detailed diagram of the second lens unit LU2 and the third lens unit LU3. The second lens unit LU2 includes optical elements G21 and G22, an aperture stop (aperture stop) AP21, a third quarter-wave plate QWP3, a near-infrared transmission filter IRF, and a second polarizing element PL2. The third lens unit LU3 includes an optical element G31, an aperture stop (aperture stop) AP31, a fourth quarter-wave plate QWP4, and a third polarizing element PL3. The optical elements G21, G22, and G31 have functions such as refraction, reflection, and diffraction. The second lens unit LU2 preferably has at least a diffractive surface. At least one of the optical elements G21, G22, and G31 may be configured as a lens (metalens) with a metasurface. In this case, polarization control means such as a quarter-wave plate and a polarizing element may be included in the metasurface. That is, the metasurface may constitute at least one of the first polarization control means or the second polarization control means.

[0043] The first, third, and fourth quarter-wave plates QWP1, QWP3, and QWP4 and the first, second, and third polarizing elements PL1, PL2, and PL3 are each composed of separate members. However, this embodiment is not limited to this, and they may be composed of the same member if their slow axes or transmission axes are aligned. Furthermore, the number of optical elements, the position of the aperture, and the like are not limited to the configuration in FIG. 9, and may be modified or changed as appropriate.

[0044] Next, an observation device 100 including the optical system 1 of this embodiment will be described with reference to Fig. 10 and Fig. 11. Fig. 10 is a schematic diagram of the observation device 100. Fig. 11 is an explanatory diagram of the display units 102, 202 of the observation device 100.

[0045] As shown in Fig. 10, the observation device 100 has optical systems 101, 201 and display units 102, 202. As shown in Fig. 11, the display units 102, 202 each include a display element PE, an imaging element SE, and a light-emitting element LE. The display element PE, the imaging element SE, and the light-emitting element LE may be formed on a single panel surface, or may be configured as separate members.

[0046] 10, the observation device 100 allows an image displayed by the display unit 102 to be viewed as an enlarged image by the user's right eye through the optical system 101, and allows an image displayed by the display unit 202 to be viewed as an enlarged image by the user's left eye through the optical system 201. The display unit or optical system may be different for each of the left and right sides depending on the user's eyesight, etc. As shown in FIG. 11, one image sensor SE and four light-emitting elements LE are disposed, but this embodiment is not limited to this, and the positions, numbers, or sizes of the image sensor SE and light-emitting elements LE can be modified or changed as appropriate.

[0047] The image of the user's pupil or the image reflected from the cornea acquired by the image sensor SE is converted into a line of sight direction by a calculation unit 301 built into the observation device 100 or provided in an external device connected to the observation device 100. Depending on the line of sight direction, the resolution of the image displayed on the display unit 102, 202 can be changed, or a user interface on the display (not shown) can be processed. Alternatively, it can be used as an authentication means for identifying a user by the user's iris image. Furthermore, the image of the pupil or the image reflected from the cornea or the iris image may be acquired from only one eye.

[0048] The optical system of this embodiment has an optical path (first optical path) RY1 and optical paths (second optical paths) RY2 and RY2a. In the optical path RY1, polarized light in a first direction (first polarized light) is guided from the display surface PNL toward the exit pupil EP. In the optical paths RY2 and RY2a, polarized light in the first direction and polarized light in a second direction (second polarized light) different from the first direction are guided from the exit pupil EP toward the imaging surface IM. The optical system has a first polarization control means that suppresses passage of polarized light in the first direction in the second optical path (suppresses polarized light in the first direction from reaching the imaging surface IM). Note that the polarized light in the first direction and the polarized light in the second direction are the polarization directions (polarization axis direction, vibration direction) of light, not the traveling direction of light.

[0049] Preferably, the optical system has a first transmission-reflection surface HM1 and a second transmission-reflection surface HM2, and a polarization-selective reflective polarizing element PBS is provided on at least one of the first transmission-reflection surface HM1 or the second transmission-reflection surface HM2. The first polarization control means is disposed between the first transmission-reflection surface HM1 and the imaging surface IM. Preferably, the first polarization control means has a second polarizing element PL2.

[0050] In the above-described embodiment, in order to prevent triple-path light from reaching the imaging plane IM, the second lens unit LU2, which has the function of preventing triple-path light from reaching the imaging plane IM, is disposed between the first lens unit LU1 and the imaging plane IM. That is, in the above-described embodiment, a configuration in which the second lens unit LU2 is provided with a first polarization control means has been described. However, this embodiment is not limited to this.

[0051] Instead of providing the second lens unit LU2, the first lens unit LU1 may be configured to have the same function as described above. That is, the first lens unit LU1 may be provided with a first polarization control means. For example, the first polarization control means may include an optical filter (optical element) inside the first lens unit LU1 that prevents triple-pass light from exiting the first lens unit LU1 (from entering the second lens unit LU2). Such an optical filter controls the polarization state of light in a specific wavelength range. For example, an optical filter that functions with near-infrared light (wavelengths 750 to 1550 nm) as light in the specific wavelength range (an optical filter that controls the polarization state of near-infrared light) may be used. This allows the filter function to be exerted on the light in the second optical path (near-infrared light) that is guided from the exit pupil EP to the imaging surface IM without affecting the light in the first optical path (visible light) that is guided from the display surface PNL to the exit pupil EP. Using such an optical filter can prevent light in the triple-pass polarization direction (second direction) in the second optical path from exiting the first lens unit LU1. The optical filter is disposed, for example, closer to the exit pupil EP than the first transmission-reflection surface HM1. The optical filter is disposed on the surface of at least one lens (optical element) constituting the first lens unit LU1, or disposed as an independent optical element.

[0052] Alternatively, instead of providing the second lens unit LU2, the image sensor SE may be configured to have the same functionality as described above. That is, the image sensor SE may be provided with a first polarization control means. As the first polarization control means, for example, a polarizing element that passes only light of a desired polarization state (polarization direction) (and does not pass light of the triple-pass polarization direction) can be provided at a position corresponding to each color filter of the image sensor SE. By using an image sensor SE (polarized image sensor) equipped with such a polarizing element, it is possible to prevent light of the triple-pass polarization direction (second direction) that has exited from the first lens unit LU1 from entering the imaging plane IM.

[0053] The optical system of this embodiment can suppress ghosts or flares caused by different optical paths and improve the accuracy of detecting the user's gaze direction. Therefore, this embodiment can provide an optical system and observation device that are compact yet capable of appropriately detecting the user's gaze direction.

[0054] The disclosure of each embodiment includes the following configuration. (Configuration 1) An optical system that forms an enlarged image of a display surface at an exit pupil and forms a reduced image of the exit pupil on an imaging surface, guide a first polarized light in a first direction along a first optical path from the display surface to the exit pupil; guide the first polarized light and the second polarized light in a second direction different from the first direction in a second optical path from the exit pupil to the imaging surface; An optical system comprising a first polarization control means disposed in the second optical path and configured to suppress passage of the first polarized light. (Configuration 2) the optical system has a first transmissive-reflective surface and a second transmissive-reflective surface, a polarization-selective reflective polarizing element is provided on at least one of the first transmission-reflection surface and the second transmission-reflection surface; 2. The optical system according to configuration 1, wherein the first polarization control means is disposed between the first transmission-reflection surface and the imaging surface. (Configuration 3) 3. The optical system according to configuration 2, wherein the first polarization control means has a polarizing element. (Configuration 4) the optical system has a first transmissive-reflective surface and a second transmissive-reflective surface, a polarization-selective reflective polarizing element is provided on at least one of the first transmission-reflection surface and the second transmission-reflection surface; 2. The optical system according to configuration 1, wherein the first polarization control means is disposed closer to the exit pupil than the first transmission-reflection surface. (Configuration 5) 5. The optical system according to configuration 4, wherein the first polarization control means is an optical filter that controls the polarization state of near-infrared light. (Configuration 6) 6. The optical system according to any one of configurations 2 to 5, wherein the light on the first optical path travels from the display surface, passes through the first transmissive-reflective surface, reflects off the second transmissive-reflective surface, reflects off the first transmissive-reflective surface, passes through the second transmissive-reflective surface, and is guided to the exit pupil. (Configuration 7) 7. The optical system according to any one of configurations 2 to 6, wherein the light in the second optical path passes from the exit pupil, passes through the second transmissive-reflective surface, passes through the first transmissive-reflective surface, and is guided to the imaging surface. (Configuration 8) 8. The optical system according to any one of configurations 2 to 7, wherein the second transmission-reflection surface is provided on the polarization-selective reflection-type polarizing element. (Configuration 9) 9. The optical system according to any one of configurations 2 to 8, wherein the optical system includes a circular polarization conversion element disposed closer to the display surface than the first transmission-reflection surface. (Configuration 10) 10. The optical system according to configuration 9, wherein the circular polarization conversion element has a linear polarizer and a quarter-wave plate. (Configuration 11) 11. The optical system according to any one of configurations 2 to 10, wherein the polarization-selective reflective polarizing element is a wire-grid polarizing element. (Configuration 12) 12. The optical system described in any one of configurations 1 to 11, wherein the first polarization control means transmits light having a polarization direction within a range of 70° to 110° with respect to the polarization direction of light incident on the first optical path from the display surface to the optical system. (Configuration 13) the optical system includes a first optical system that forms the first optical path, 13. The optical system according to any one of configurations 1 to 12, wherein the first optical system is rotationally symmetric with respect to the optical axis of the first optical path. (Configuration 14) the optical system includes a second optical system that forms the second optical path together with the first optical system, 14. The optical system according to configuration 13, wherein the second optical system is disposed between the first optical system and the imaging surface. (Configuration 15) the optical system has a third optical path that passes from the light emitting surface through the optical system and is guided to the exit pupil, the optical system includes a third optical system that forms the third optical path together with the first optical system, The optical system according to configuration 13 or 14, wherein the third optical system is disposed between the light emitting surface and the first optical system, and has a second polarization control means. (Configuration 16) the optical system has a first transmissive-reflective surface and a second transmissive-reflective surface, a polarization-selective reflective polarizing element is provided on at least one of the first transmission-reflection surface and the second transmission-reflection surface; 16. The optical system according to configuration 15, wherein the light in the third optical path is transmitted through the first transmissive-reflective surface, transmitted through the second transmissive-reflective surface, and guided to the exit pupil. (Configuration 17) 17. The optical system according to configuration 16, wherein the second polarization control means transmits polarized light that is transmitted by the polarization-selective reflective polarizing element, out of the light from the light-emitting surface. (Configuration 18) 18. The optical system according to any one of configurations 15 to 17, wherein the transmission axis of the first polarization control means and the transmission axis of the second polarization control means are parallel to each other. (Configuration 19) 15. The optical system according to configuration 14, wherein the second optical system has a diffractive surface. (Configuration 20) The optical system of configuration 14, wherein the second optical system has a metasurface. (Configuration 21) The optical system described in configuration 20, characterized in that the metasurface functions as the first polarization control means. (Configuration 22) 22. An observation device comprising: the optical system according to any one of configurations 1 to 21; a display element having the display surface; and an imaging element having the imaging surface. (Configuration 23) 23. The observation device according to claim 22, further comprising a plurality of light sources each having a light-emitting surface. (Configuration 24) An observation device having an optical system that forms an enlarged image of a display surface at an exit pupil and forms a reduced image of the exit pupil on an imaging surface, and an imaging element that has the imaging surface, guide a first polarized light in a first direction along a first optical path from the display surface to the exit pupil; guide the first polarized light and the second polarized light in a second direction different from the first direction in a second optical path from the exit pupil to the imaging surface; The imaging device is characterized in that it has a first polarization control means disposed in the second optical path and suppressing passage of the first polarized light. (Configuration 25) 25. The optical system according to configuration 24, wherein the first polarization control means has a polarizing element.

[0055] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist of the present invention. [Explanation of symbols]

[0056] 1, 1a Optical system EP exit pupil IM imaging plane PNL display surface RY1 optical path (first optical path) RY2, RY2a optical paths (second optical path)

Claims

1. An optical system that forms an enlarged image of a display surface at an exit pupil and forms a reduced image of the exit pupil on an imaging surface, guide a first polarized light in a first direction along a first optical path from the display surface to the exit pupil; guide the first polarized light and the second polarized light having a second direction different from the first direction in a second optical path from the exit pupil to the imaging surface; an optical system comprising a first polarization control means disposed in the second optical path and configured to suppress passage of the first polarized light;

2. the optical system has a first transmissive-reflective surface and a second transmissive-reflective surface, a polarization-selective reflective polarizing element is provided on at least one of the first transmission-reflection surface and the second transmission-reflection surface; 2. The optical system according to claim 1, wherein the first polarization control means is disposed between the first transmission / reflection surface and the imaging surface.

3. 3. The optical system according to claim 2, wherein the first polarization control means comprises a polarizing element.

4. the optical system has a first transmissive-reflective surface and a second transmissive-reflective surface, a polarization-selective reflective polarizing element is provided on at least one of the first transmission-reflection surface and the second transmission-reflection surface; 2. The optical system according to claim 1, wherein the first polarization control means is disposed closer to the exit pupil than the first transmission-reflection surface.

5. 5. The optical system according to claim 4, wherein the first polarization control means is an optical filter that controls the polarization state of near-infrared light.

6. 6. The optical system according to claim 2, wherein light on the first optical path passes from the display surface, passes through the first transmissive-reflective surface, reflects off the second transmissive-reflective surface, reflects off the first transmissive-reflective surface, passes through the second transmissive-reflective surface, and is guided to the exit pupil.

7. 6. The optical system according to claim 2, wherein light in the second optical path passes from the exit pupil, passes through the second transmissive-reflective surface, passes through the first transmissive-reflective surface, and is guided to the imaging surface.

8. 6. The optical system according to claim 2, wherein the second transmissive-reflective surface is provided on the polarization-selective reflective polarizing element.

9. 6. The optical system according to claim 2, further comprising a circular polarization conversion element disposed closer to the display surface than the first transmission-reflection surface.

10. 10. The optical system according to claim 9, wherein the circular polarization conversion element comprises a linear polarizer and a quarter-wave plate.

11. 6. The optical system according to claim 2, wherein the polarization-selective reflective polarizing element is a wire grid polarizing element.

12. 6. The optical system according to claim 1, wherein the first polarization control means transmits light having a polarization direction within a range of 70° to 110° with respect to the polarization direction of light incident on the first optical path from the display surface to the optical system.

13. the optical system includes a first optical system that forms the first optical path, 6. The optical system according to claim 1, wherein the first optical system is rotationally symmetric with respect to the optical axis of the first optical path.

14. the optical system includes a second optical system that forms the second optical path together with the first optical system, The optical system according to claim 13 , wherein the second optical system is disposed between the first optical system and the imaging surface.

15. the optical system has a third optical path that passes from the light emitting surface through the optical system and is guided to the exit pupil, the optical system includes a third optical system that forms the third optical path together with the first optical system, 14. The optical system according to claim 13, wherein the third optical system is disposed between the light emitting surface and the first optical system, and includes a second polarization control means.

16. the optical system has a first transmissive-reflective surface and a second transmissive-reflective surface, a polarization-selective reflective polarizing element is provided on at least one of the first transmission-reflection surface and the second transmission-reflection surface; 16. The optical system according to claim 15, wherein the light in the third optical path is transmitted through the first transmissive-reflective surface, transmitted through the second transmissive-reflective surface, and guided to the exit pupil.

17. 17. The optical system according to claim 16, wherein the second polarization control means transmits polarized light that is transmitted by the polarization-selective reflective polarizing element, out of the light from the light-emitting surface.

18. 16. The optical system according to claim 15, wherein the transmission axis of the first polarization control means and the transmission axis of the second polarization control means are parallel to each other.

19. The optical system according to claim 14 , wherein the second optical system has a diffractive surface.

20. The optical system of claim 14 , wherein the second optical system comprises a metasurface.

21. The optical system of claim 20 , wherein the metasurface functions as the first polarization control means.

22. An observation device comprising: the optical system according to claim 1 ; a display element having the display surface; and an imaging element having the imaging surface.

23. 23. The observation device of claim 22, further comprising a plurality of light sources each having a light-emitting surface.

24. An observation device having an optical system that forms an enlarged image of a display surface at an exit pupil and forms a reduced image of the exit pupil on an imaging surface, and an imaging element that has the imaging surface, guide a first polarized light in a first direction along a first optical path from the display surface to the exit pupil; guide the first polarized light and the second polarized light having a second direction different from the first direction in a second optical path from the exit pupil to the imaging surface; The imaging device is characterized in that it has a first polarization control means disposed in the second optical path and suppressing passage of the first polarized light.

25. 25. The optical system of claim 24, wherein the first polarization control means comprises a polarizing element.

Images