Optical system and image display device

Abstract

The purpose of the present invention is to provide an optical system and an image display device that improve visibility.　The present invention provides an optical system comprising a luminous flux diameter control unit that controls the diameter of a luminous flux from a light source, and a relay optical system that guides the luminous flux to the pupil of an observer, the luminous flux diameter control unit enlarging or reducing the diameter of the luminous flux. The relay optical system may have an optical element for expanding the diameter of the luminous flux. The optical element may be disposed in the vicinity of the position of a focal point of the luminous flux formed in the relay optical system.

Description

Optical system and image display device

[0001] The technology according to the present disclosure (hereinafter also referred to as "the technology") relates to an optical system and an image display device.

[0002] Conventionally, direct retinal imaging image display devices have been used, which project images directly onto the retina of the eyeball, allowing even those with impaired eyesight to view images without adjusting the crystalline lens.

[0003] As an example of this type of image display device, for example, Patent Document 1 discloses technology relating to "an image projection device having a drive control unit that controls a drive unit to move a reflecting unit so that the position at which multiple image light rays enter an optical element changes depending on the direction in which the pupil moves as detected by a detection unit."

[0004] Japanese Patent Application Laid-Open No. 2023-76137

[0005] However, when a configuration is adopted in which the reflecting portion is moved, as in the technology disclosed in Patent Document 1, for example, the device may become larger and heavier, and power consumption may increase.

[0006] Furthermore, not only in the technology disclosed in Patent Document 1, but also in other direct retinal imaging image display devices, the light beam emitted is very thin and therefore difficult to make incident on the observer's pupil, and therefore the observer cannot see the image unless the light beam is emitted at an accurate position.

[0007] Therefore, a main object of the present technology is to provide an optical system and an image display device that improve visibility.

[0008] The present technology provides an optical system including: a beam diameter control unit that controls a diameter of a beam from a light source; and a relay optical system that guides the beam to a pupil of an observer, wherein the beam diameter control unit expands or reduces the diameter of the beam. The relay optical system may have a function of expanding the beam diameter. The optical system may further include an optical element that expands the diameter of the beam from the beam diameter control unit. The optical system may further include an optical element that expands the diameter of the beam from the beam diameter control unit, wherein the relay optical system may have a function of expanding the beam diameter. The relay optical system may include an optical element that expands the beam diameter. The optical element may be arranged near a position of a focal point of the beam formed in the relay optical system. The optical system may further include a scanning unit that scans the beam from the light source, wherein the beam diameter control unit is arranged between the light source and the scanning unit. The beam diameter control unit may be arranged at an arbitrary position between the light source and the scanning unit. When the light beam is projected onto the pupil, the light beam diameter control unit may reduce the diameter of the light beam. The image display device may further include a pupil detection unit that detects the position of the pupil. The position of the optical element may be configured to be changeable according to the position of the pupil. The position of the light beam diameter control unit may be configured to be changeable according to the position of the pupil. The image display device may further include a gaze detection unit that detects whether the observer is gazing or not. When the observer is gazing, the light beam diameter control unit may increase the diameter of the light beam. The optical element may include a diffraction element. The optical element may include a spatial light modulator. The light beam diameter control unit may include at least one of an aperture and a spatial light modulator. The light from the light source may be laser light. The present technology also provides an image display device including: a light source; a light beam diameter control unit that controls the diameter of the light beam from the light source; and a relay optical system that guides the light beam to the observer's pupil, wherein the light beam diameter control unit increases or decreases the diameter of the light beam. The image display device may be worn on the viewer's head.

[0009] According to the present technology, it is possible to provide an optical system and an image display device that improve visibility. Note that the effects described herein are not necessarily limited to those described herein, and may be any of the effects described in the present disclosure.

[0010] FIG. 1 is a schematic diagram showing a configuration example of an image display device 100 according to an embodiment of the present technology. FIG. 2 is a schematic diagram showing a configuration example of an image display device 100 according to an embodiment of the present technology. FIG. 3 is a schematic diagram showing a configuration example of an image display device 100 according to an embodiment of the present technology. FIG. 4 is a flowchart showing an example of processing of the image display device 100 according to an embodiment of the present technology. FIG. 5 is a schematic diagram showing an example of the configuration of the image display device 100 according to an embodiment of the present technology. FIG. 6 is a flowchart showing an example of processing of the image display device 100 according to an embodiment of the present technology.

[0011] Hereinafter, preferred embodiments for implementing the present technology will be described with reference to the drawings. Note that the embodiment described below shows an example of a typical embodiment of the present technology, and does not limit the scope of the present technology. In addition, the present technology can be combined with any of the following examples and their modifications.

[0012] In the following description of the embodiments, configurations may be described using terms including "approximately," such as "approximately parallel" and "approximately perpendicular." For example, "approximately parallel" does not only mean completely parallel, but also means substantially parallel, i.e., including a state where the orientation is deviated from the completely parallel state by, for example, a few percent. The same applies to other terms including "approximately." Furthermore, each figure is a schematic diagram and is not necessarily an accurate depiction. The scale of the drawings has been exaggerated to make the features of the technology easier to understand. Therefore, it should be noted that the scale of the drawings and the scale of the actual device are not necessarily the same.

[0013] Unless otherwise specified, in the drawings, "top" means the top or upper side in the drawing, "bottom" means the bottom or lower side in the drawing, "left" means the left or left side in the drawing, and "right" means the right or right side in the drawing. Furthermore, in the drawings, the same or equivalent elements or members are given the same reference numerals, and redundant explanations will be omitted.

[0014] The description will be given in the following order: 1. First embodiment of the present technology (optical system example 1) (1) Overall configuration (2) Optical element (3) Light beam diameter control unit 2. Second embodiment of the present technology (optical system example 2) 3. Third embodiment of the present technology (optical system example 3) 4. Fourth embodiment of the present technology (optical system example 4) 5. Fifth embodiment of the present technology (optical system example 5) 6. Sixth embodiment of the present technology (optical system example 6) 7. Seventh embodiment of the present technology (example of image display device)

[0015] [1. First Embodiment of the Present Technology (First Example of Optical System)] [(1) Overall Configuration] The present technology provides an optical system including a light beam diameter control unit that controls the diameter of a light beam from a light source, and a relay optical system that guides the light beam to a pupil of an observer, wherein the light beam diameter control unit enlarges or reduces the diameter of the light beam.

[0016] An example of the configuration of an optical system according to an embodiment of the present technology will be described with reference to Fig. 1 and Fig. 2. Fig. 1 and Fig. 2 are schematic diagrams showing an example of the configuration of an image display device 100 according to an embodiment of the present technology.

[0017] 1 , an optical system 10 according to an embodiment of the present technology includes a light beam diameter control unit 2, a scanning unit 4, and a relay optical system 3. The light beam diameter control unit 2 controls the diameter of a light beam from a light source 1. The scanning unit 4 scans the light beam from the light source 1. The relay optical system 3 guides the light beam to a viewer's pupil.

[0018] The light from the light source 1 is preferably laser light. That is, the image display device 100 is preferably a laser scanning type (LBS: Laser Beam Scanning) device. The laser scanning type image display device 100 displays an image by scanning laser light. Because laser light has high coherency and a narrow wavelength width, an optical system can be realized that narrows the spot on the retina. This allows high resolution to be maintained. Furthermore, because laser light is less likely to diffuse, it is possible to display clear images with less image distortion. Furthermore, because laser light has high light brightness and consistent wavelength characteristics, it is suitable for projecting clear, bright images onto the retina. Features of laser light include a high contrast ratio, a wide color gamut, and high resolution.

[0019] The scanning unit 4 scans the light from the light source 1. For example, a MEMS (Micro Electro Mechanical Systems) mirror or a digital micromirror device (DMD) can be used as the scanning unit 4. The MEMS mirror scans the light from the light source 1 by changing the angle of the mirror using an electric signal. The digital mirror device is a MEMS device in which many tiny movable mirrors are arranged on an integrated circuit substrate.

[0020] The relay optical system 3 guides the light beam to the pupil of the observer. The relay optical system 3 includes, for example, at least two lenses 31 and 33.

[0021] This optical system 10 can be mounted on an image display device 100. In this configuration example, a head-mounted display (HMD), which is an example of the image display device 100, includes the optical system 10. A housing 101 of the HMD is worn on the head H of an observer.

[0022] When worn by a viewer, the image display device 100 can realize cross reality (XR) such as virtual reality (VR), augmented reality (AR), and mixed reality (MR).

[0023] Virtual reality (VR) is a technology that blocks out the real world and allows a viewer to fully experience a virtual world. By wearing the image display device 100, the viewer can immerse their senses, such as sight and hearing, in the virtual world. For example, in the medical field, virtual reality can be used for patient rehabilitation and surgical training.

[0024] Augmented reality (AR) is a technology that overlays virtual information on the real world. For example, the image display device 100 may be configured so that the observer can observe the real world without an optical system 10 or the like being placed in front of the observer's eyes. Augmented reality can realize a new gaming experience in entertainment, for example, by introducing virtual characters and items into the real world.

[0025] Mixed reality (MR) is a technology that blends the real world and the virtual world and allows them to interact with each other. Mixed reality allows virtual objects and information to be displayed in the real world, and virtual objects to be brought into the real world. For example, in entertainment, mixed reality can realize an experience in which users can freely move between the real world and the virtual world.

[0026] The image display device 100 may be a retinal direct imaging type image display device based on Maxwellian vision. A retinal direct imaging type image display device projects an image directly onto the retina of the eye. With this image display device, even a person with reduced eyesight can observe an image without adjusting the crystalline lens.

[0027] To achieve free focus characteristics that are not dependent on an individual's visual acuity or focal position, it is necessary to make the diameter of the light beam projected onto the eyeball E extremely small. Specifically, for example, the diameter of the light beam needs to be 1 mm or less.

[0028] However, because the pupil position is constantly changing, if the diameter of the light beam is made very small, it becomes difficult for it to enter the observer's pupil. If the light beam is not emitted to the correct position, the observer will not be able to see the image.

[0029] One possible solution to this problem is to change the position of the scanning unit 4, which is optically conjugate with the eyeball E, according to the position of the eyeball E. However, changing the position of the scanning unit 4 requires a mechanism for changing this position. This may result in the image display device 100 becoming larger and heavier, and increasing power consumption. In particular, if the image display device 100 is an HMD, difficulties may arise when wearing it.

[0030] Therefore, in the optical system 10 according to an embodiment of the present technology, the relay optical system 3 has a function of expanding the diameter of the light beam. This is realized by optimizing the lens configuration within the relay optical system 3, and the system can be naturally expanded while effectively guiding the light beam to the observer's pupil. For example, by adjusting the design magnification of the relay optical system 3, the diameter of the light beam after passing through the relay optical system 3 can be expanded. Specifically, for example, by adjusting the focal lengths of the respective lenses 31 and 33, the diameter of the light beam after passing through the relay optical system 3 can be expanded.

[0031] Specifically, when the focal length of lens 33 is longer than the focal length of lens 31, the diameter of the light beam passing through lens 33 expands. This expansion increases the diameter of the light beam reaching the observer's pupil, resulting in a pupil expansion effect.

[0032] On the other hand, if the focal length of lens 33 is shorter than the focal length of lens 31, the diameter of the light beam passing through lens 33 will be reduced. When the light beam diameter is reduced, the diameter of the light beam reaching the observer's pupil will also be reduced, resulting in a pupil reduction effect.

[0033] The beam diameter control unit 2 controls the diameter of the beam from the light source 1. Specifically, the beam diameter control unit 2 enlarges or reduces the diameter of the beam from the light source 1. As shown in Fig. 1, when the beam diameter control unit 2 reduces the beam diameter, the image display device 100 functions as a retinal direct imaging type image display device. On the other hand, as shown in Fig. 2, when the beam diameter control unit 2 enlarges the beam diameter, the image display device 100 functions as a general image display device that is not a retinal direct imaging type.

[0034] When it is difficult to make a light beam with a very small diameter incident on the pupil, the image display device 100 can function as a general image display device that is not a direct retinal imaging type. When it is possible to make a light beam with a very small diameter incident on the pupil, the image display device 100 can function as a direct retinal imaging type image display device. With this configuration, visibility can be improved.

[0035] For example, if an image display device 100 such as an HMD is not placed in the correct position immediately after wearing it, the extremely thin beam of light is unlikely to enter the pupil. As a result, the observer cannot see the image, making it difficult to place the device in the correct position. Furthermore, because head shapes and pupil positions vary from person to person, the exact position also varies from person to person. It is difficult for an individual to grasp this exact position.

[0036] On the other hand, according to the present technology, the beam diameter control unit 2 increases the beam diameter, so the observer can easily view the image, and therefore the observer can wear the HMD in an appropriate position.

[0037] Furthermore, according to the present technology, a mechanism for changing the position of the scanning unit 4 is not required, which not only improves visibility but also enables the device to be made smaller.

[0038] Furthermore, according to the present technology, there is no need to increase the size of the scanning unit 4, and therefore restrictions on the performance of the scanning unit 4 are alleviated.

[0039] At least one of these effects also occurs in other embodiments described below, and therefore, repeated description of the effects may be omitted in the description of the other embodiments.

[0040] It should be noted that the image display device according to the present technology does not have to be worn on the head of the observer. For example, a light beam from the image display device 100 disposed at a position away from the head may be deflected by an eyepiece device disposed in front of the observer's eye and projected onto the retina. This eyepiece device may be, for example, a glasses-type device or a contact lens-type device.

[0041] The relay optical system 3 can also reduce the diameter of the light beam, thereby achieving free focus characteristics that are independent of the individual's eyesight or the focal position, for example.

[0042] [(2) Optical Element] The optical system 10 may further include an optical element 32 that expands the diameter of the light beam from the light beam diameter control unit 2. This optical element 32 may be disposed inside the relay optical system 3, or may be disposed separately from the relay optical system 3. By further including the optical element 32, it becomes possible to expand the diameter of the light beam and appropriately guide it to the observer's pupil, even if, for example, the design of the relay optical system 3 does not directly provide a pupil expansion function.

[0043] Alternatively, the optical system 10 may further include an optical element 32 that expands the diameter of the light beam from the light beam diameter controller 2, and the relay optical system 3 may have the function of expanding the diameter of the light beam. In this configuration, the optical system 10 includes the optical element 32 that expands the diameter of the light beam from the light beam diameter controller 2, and the relay optical system 3 has the function of expanding the diameter of the light beam. In this configuration, the expansion of the diameter by the relay optical system 3 itself and the further expansion of the diameter by the added optical element 32 are combined to maximize the effect of expanding the light beam.

[0044] Alternatively, in order to enlarge the diameter of the light beam, for example, the relay optical system 3 may include an optical element 32 that enlarges the diameter of the light beam.

[0045] In a direct retinal imaging image display device, the scanning unit 4 and the eyeball E are in an optically conjugate relationship. Therefore, a condensing point is formed inside the relay optical system 3. In this case, as shown in Fig. 1, the optical element 32 is preferably disposed near the position of the condensing point of the light beam formed in the relay optical system 3. The optical element 32 can increase the divergence angle of light from this condensing point or decenter the optical axis, thereby increasing the diameter of the light beam.

[0046] The optical element 32 may be disposed at a position that is displaced from the position of the light-converging point, as long as it is disposed at a position that can enlarge the diameter of the light beam.

[0047] Furthermore, the optical element 32 may have any configuration as long as it can expand the diameter of the light beam. For example, the optical element 32 may have a diffraction element. The diffraction element diffracts incident light, thereby expanding the diameter of the light beam. In particular, it is preferable that the optical element 32 has a diffraction element array in which a plurality of diffraction elements are arranged in an array.

[0048] Alternatively, the optical element 32 may include a diffusion plate (including a film-shaped or sheet-shaped one). The diffusion plate diffuses light, thereby increasing the diameter of the light beam.

[0049] Alternatively, the optical element 32 may include a holographic optical element. Of the light beams of each wavelength incident on the holographic optical element, only light beams of a specific wavelength coming from a specific direction interfere with each other due to interference fringes formed on the holographic optical element, and are diffracted in a specific direction. In particular, the optical element 32 may include a holographic optical element array in which a plurality of holographic optical elements are arranged in an array.

[0050] Alternatively, the optical element 32 may have a pinhole. A pinhole is a narrow hole with a diameter of about several microns to several millimeters. Light that passes through a pinhole spreads in various directions due to the phenomenon of diffraction. In particular, the optical element 32 may have a pinhole array in which a plurality of pinholes are arranged in an array.

[0051] Alternatively, the optical element 32 may include a spatial light modulator (SLM). A spatial light modulator is a device that modulates the phase, amplitude, polarization, etc. of light by utilizing the birefringence of liquid crystals.

[0052] A spatial light modulator is composed of a liquid crystal layer and a transparent conductive film laminated together. When a voltage is applied to the transparent conductive film, the light beam passing through the liquid crystal is modulated by the liquid crystal. This allows the spatial light modulator to expand the diameter of the light beam passing through the liquid crystal.

[0053] The optical element 32 may be configured by combining two or more of the above-mentioned diffraction element, diffusion plate, holographic optical element, pinhole, and spatial light modulator.

[0054] (3) Beam diameter control unit The beam diameter control unit 2 is disposed between the light source 1 and the scanning unit 4. This arrangement allows the beam diameter control unit 2 to control the diameter of the beam from the light source 1. When the beam is projected onto the pupil, the beam diameter control unit 2 reduces the beam diameter. When the beam is not projected onto the pupil, the beam diameter control unit 2 increases the beam diameter.

[0055] When the image display device 100 functions as a general image display device that is not a direct retinal imaging type, the diameter of the light beam from the light source 1 can be, for example, about 1.0 mm. When the diameter of the scanning unit 4 is about 1.0 mm, the diameter of the light beam projected onto the pupil can be about 5.0 mm.

[0056] When the image display device 100 functions as a direct retinal imaging type image display device, the diameter of the light beam from the light source 1 can be, for example, about 0.2 mm. When the diameter of the scanning unit 4 is about 1.0 mm, the diameter of the light beam projected onto the pupil can be about 1.0 mm.

[0057] The light beam diameter control unit 2 may have any configuration as long as it can control the diameter of the light beam, and its configuration is not particularly limited. For example, the light beam diameter control unit 2 may have an aperture. The aperture is a thin plate with an opening through which the light beam from the light source 1 passes. By changing the size of this opening, the aperture can reduce or expand the diameter of the light beam. The aperture has a simple configuration and does not require a mechanism for changing the position of the scanning unit 4, which enables the image display device 100 to be made smaller.

[0058] As described above, it is preferable that the light from the light source 1 is laser light. Laser light has high coherency, and therefore, even if laser light in a substantially parallel state passes through an opening in an aperture, it is more likely to maintain its straightness compared to light with low coherency.

[0059] The light beam diameter control unit 2 can be placed at any position between the light source 1 and the scanning unit 4. Since the space inside the device can be used effectively, the image display device 100 can be made smaller.

[0060] Furthermore, the light beam diameter control unit 2 may be movable to any position between the light source 1 and the scanning unit 4. This will be described with reference to Fig. 3. Fig. 3 is a schematic diagram showing a configuration example of an image display device 100 according to an embodiment of the present technology.

[0061] 3, the beam diameter control unit 2 is configured to be movable to the left in the drawing. With this configuration, for example, the beam diameter control unit 2 can change the direction of the beam from the light source 1 according to the position of the pupil.

[0062] Known techniques can be used to change the position of the beam diameter control portion 2. For example, the position of the beam diameter control portion 2 can be changed using a drive unit such as an electric motor.

[0063] The above description of the optical system according to the first embodiment of the present technology can be applied to other embodiments of the present technology unless there is a particular technical contradiction.

[0064] 2. Second Embodiment of the Present Technology (Example 2 of Optical System) A state in which the image display device 100 functions as a general image display device that is not a direct retinal imaging type is defined as a first state. A state in which the image display device 100 functions as a direct retinal imaging type image display device is defined as a second state. The first state and the second state may be switched instantaneously or gradually. For example, when the first state and the second state are switched gradually, the beam diameter control unit 2 gradually reduces the beam diameter as the proportion of the beam projected onto the pupil increases.

[0065] This will be described with reference to Fig. 4. Fig. 4 is a flowchart showing an example of processing by the image display device 100 according to an embodiment of the present technology.

[0066] 4, first, in step S11, the beam diameter control unit 2 sets the beam diameter to the initial state, thereby placing the image display device in the first state.

[0067] Next, in step S12, the pupil detection unit 5 detects the position of the pupil. The pupil detection unit 5 will be described later.

[0068] Next, in step S13, the calculation unit included in the image display device detects whether or not the light beam is projected onto the pupil.

[0069] Next, when the light beam is projected onto the pupil (step S13: Yes), in step S14, a calculation unit included in the image display device calculates the proportion of the light beam projected onto the pupil. When the light beam is not projected onto the pupil (step S13: No), the process ends. Note that when the light beam is not projected onto the pupil (step S13: No), step S11 may be executed.

[0070] Next, in step S15, the beam diameter control unit 2 changes the diameter of the beam from the light source 1 in accordance with the proportion of the beam projected onto the pupil. By repeating steps S12 to S15, the beam diameter control unit 2 gradually reduces the beam diameter as the proportion of the beam projected onto the pupil increases. In other words, the state is gradually switched from the first state to the second state. Since the image gradually changes as the viewer approaches the appropriate wearing position, it becomes easier for the viewer to wear the image display device 100 in an appropriate position.

[0071] In addition to the pupil detection unit 5, a contact sensor or a sensor that detects the amount of light leakage may be used as a technique for detecting the appropriate wearing position.

[0072] The above description of the optical system according to the second embodiment of the present technology can be applied to other embodiments of the present technology unless there is a particular technical contradiction.

[0073] 3. Third Embodiment of the Present Technology (Third Optical System Example) The light beam diameter control unit 2 shown in Fig. 1 may include a spatial light modulator (SLM). The spatial light modulator is a device that modulates the phase, amplitude, polarization, etc. of light by utilizing the birefringence of liquid crystal.

[0074] A spatial light modulator is composed of a liquid crystal layer and a transparent conductive film laminated together. When a voltage is applied to the transparent conductive film, the liquid crystal layer modulates the light beam passing through the liquid crystal. This allows the spatial light modulator to reduce or increase the diameter of the light beam passing through the liquid crystal.

[0075] The beam diameter control unit 2 may include at least one of an aperture and a spatial light modulator, that is, the beam diameter control unit 2 may include one or both of an aperture and a spatial light modulator.

[0076] The above description of the optical system according to the third embodiment of the present technology can be applied to other embodiments of the present technology unless there is a particular technical contradiction.

[0077] 1 , the optical system 10 may further include a pupil detection unit 5 that detects the position of the pupil. By including the pupil detection unit 5, it is possible to detect that a light beam is projected onto the pupil. When the light beam is projected onto the pupil, the light beam diameter control unit 2 reduces the diameter of the light beam.

[0078] The pupil detection unit 5 may detect the position of the pupil using a known eye tracking technique, such as the scleral reflex method or the corneal reflex method.

[0079] The scleral reflex method utilizes the difference in reflectance of light (e.g., near-infrared light) between the cornea and the sclera, and detects the position of the pupil based on the change in the amount of light reflected from the eyeball.

[0080] The corneal reflex method involves irradiating the cornea with light (for example, near-infrared light) and capturing the reflected image of the cornea with a camera, etc. Since the shape of the cornea varies from person to person, the position of the pupil can be detected from the reflected image of the cornea.

[0081] The position of the beam diameter control unit 2 may be configured to be changeable in accordance with the position of the pupil detected by the pupil detection unit 5. Based on the position of the pupil detected by the pupil detection unit 5, the beam diameter control unit 2 can change the direction of the beam from the light source 1.

[0082] Furthermore, the pupil detection unit 5 can also detect the diameter of the pupil. The position of the beam diameter control unit 2 can be changed according to the pupil diameter detected by the pupil detection unit 5. Furthermore, the beam diameter control unit 2 can reduce or increase the diameter of the beam from the light source 1 according to the pupil diameter detected by the pupil detection unit 5.

[0083] With this configuration, even if the position or diameter of the pupil changes, the image display device 100 can direct the light beam to enter the pupil.

[0084] The above description of the optical system according to the fourth embodiment of the present technology can be applied to other embodiments of the present technology unless there is a particular technical contradiction.

[0085] 1 may be configured so that its position can be changed according to the position of the pupil. With this configuration, for example, the optical element 32 can change the direction of the light beam guided to the pupil according to the position of the pupil.

[0086] A known technique can be used to change the position of the optical element 32. For example, the position of the optical element 32 can be changed using a driving unit such as an electric motor.

[0087] The above description of the optical system according to the fifth embodiment of the present technology can be applied to other embodiments of the present technology unless there is a particular technical contradiction.

[0088] [6. Sixth Embodiment of the Present Technology (Sixth Example of Optical System)] As described above, in order to realize free focus characteristics that are not dependent on an individual's visual acuity or a focus position, it is necessary to make the diameter of the light beam projected onto the pupil (exit pupil) very small. On the other hand, if the exit pupil is made small while the light beam is projected onto the pupil, the size of the spot on the retina increases, which may result in a decrease in image resolution.

[0089] Therefore, when the light beam is projected onto the pupil, it is preferable to increase the diameter of the light beam to increase the resolution of the image. In order to detect that the light beam is projected onto the pupil, it is preferable to detect, for example, whether the viewer is gazing at the image.

[0090] An example configuration of an optical system 10 that detects whether or not a viewer is gazing at an image will be described with reference to Fig. 5. Fig. 5 is a schematic diagram showing an example configuration of an image display device 100 according to an embodiment of the present technology.

[0091] As shown in Figure 5, the optical system 10 may further include a gaze detection unit 6 that detects whether or not the observer is gazing. The gaze detection unit 6 can use known technology. For example, by detecting convergence, which is the function of aligning the lines of sight of both eyes at the same point, it is possible to estimate what point the observer is gazing at. By displaying a specific object in the image and detecting whether the line of sight follows the movement of this object, it is possible to detect whether or not the observer is gazing.

[0092] When the observer is gazing, the beam diameter control unit 2 can enlarge the diameter of the beam from the light source 1. In the direct retinal imaging type image display device 100, the larger the diameter of the beam entering the pupil, the smaller the size of the spot on the retina, allowing the observer to view an image with higher resolution.

[0093] That is, it is preferable that the light beam diameter control unit 2 reduces the diameter of the light beam when the light beam is projected onto the pupil, and that the light beam diameter control unit 2 increases the diameter of the light beam when the observer is gazing at the light beam. This will be described with reference to Fig. 6. Fig. 6 is a flowchart showing an example of processing of the image display device 100 according to an embodiment of the present technology.

[0094] 6, first, in step S21, the beam diameter control unit 2 sets the beam diameter to an initial state, whereby the image display device functions as a general image display device that is not of the direct retinal type.

[0095] Next, in step S22, the pupil detection unit 5 detects the position of the pupil.

[0096] Next, in step S23, a calculation unit included in the image display device detects whether or not the light beam is projected onto the pupil. If the light beam is projected onto the pupil (step S23: Yes), in step S24, the light beam diameter control unit 2 reduces the diameter of the light beam. This allows the image display device to function as a direct retinal imaging type image display device. If the light beam is not projected onto the pupil (step S23: No), the processing ends. Note that if the light beam is not projected onto the pupil (step S23: No), step S21 may be executed.

[0097] Next, in step S25, the gaze detection unit 6 detects whether the observer is gazing. If the observer is gazing (step S25: Yes), in step S26, the beam diameter control unit 2 enlarges the beam diameter. This allows the image display device to display a high-resolution image. If the observer is not gazing (step S25: No), step S22 may be executed.

[0098] The above description of the optical system according to the sixth embodiment of the present technology can be applied to other embodiments of the present technology unless there is a particular technical contradiction.

[0099] 7. Seventh Embodiment of the Present Technology (Example of Image Display Device) The present technology provides an image display device including a light source, a light flux diameter control unit that controls a diameter of a light flux from the light source, and a relay optical system that guides the light flux to a pupil of an observer, wherein the light flux diameter control unit enlarges or reduces the diameter of the light flux.

[0100] An example of the configuration of this image display device will be described with reference to Fig. 1 again. The image display device according to an embodiment of the present technology includes a light source 1, a light beam diameter control unit 2, and a relay optical system 3.

[0101] The beam diameter control unit 2 controls the diameter of the beam from the light source 1. The beam diameter control unit 2 increases or decreases the diameter of the beam from the light source 1.

[0102] The relay optical system 3 guides the light beam to the pupil of the observer. The relay optical system 3 may include an optical element 32 that expands the diameter of the light beam.

[0103] This image display device 100 can be worn on the head H of an observer, for example.

[0104] The above description of the image display device according to the seventh embodiment of the present technology can be applied to other embodiments of the present technology unless there is a particular technical contradiction.

[0105] It should be noted that the embodiments of the present technology are not limited to the above-described embodiments, and various modifications are possible within the scope of the present technology. The specific numerical values, shapes, materials (including compositions), etc. described in each embodiment are merely examples, and the present technology is not limited to these.

[0106] The present technology may also have the following configurations. [1] An optical system including: a beam diameter control unit that controls a diameter of a beam from a light source; and a relay optical system that guides the beam to a pupil of an observer, wherein the beam diameter control unit expands or reduces the diameter of the beam. [2] The optical system according to [1], wherein the relay optical system has a function of expanding the diameter of the beam. [3] The optical system according to [1] or [2], further including an optical element that expands the diameter of the beam from the beam diameter control unit. [4] The optical system according to [1], further including an optical element that expands the diameter of the beam from the beam diameter control unit, wherein the relay optical system has a function of expanding the diameter of the beam. [5] The optical system according to [1], wherein the relay optical system has an optical element that expands the diameter of the beam. [6] The optical system according to [3], wherein the optical element is arranged near a position of a focal point of the beam formed in the relay optical system. [7] The optical system according to any one of [1] to [6], further comprising a scanning unit that scans the light beam from the light source, and the light beam diameter control unit is disposed between the light source and the scanning unit. [8] The optical system according to [7], wherein the light beam diameter control unit can be disposed at any position between the light source and the scanning unit. [9] The optical system according to any one of [1] to [8], wherein the light beam diameter control unit reduces the diameter of the light beam when the light beam is projected onto the pupil.

[10] The optical system according to [9], wherein the light beam diameter control unit gradually reduces the diameter of the light beam as the proportion of the light beam projected onto the pupil increases.

[11] The optical system according to any one of [1] to

[10] , further comprising a pupil detection unit that detects the position of the pupil.

[12] The optical system according to any one of [3] to

[11] , wherein the position of the optical element is configured to be changeable depending on the position of the pupil.

[13] The optical system according to any one of [1] to

[12] , further comprising a gaze detection unit that detects whether the viewer is gazing at the object.

[15] The optical system according to any one of [1] to

[14] , wherein the beam diameter control section increases the diameter of the beam when the observer is gazing at the object.

[16] The optical system according to any one of [1] to

[15] , wherein the beam diameter control section reduces the diameter of the beam when the beam is projected onto the pupil, and increases the diameter of the beam when the observer is gazing at the object.

[17] The optical system according to any one of [3] to

[13] , wherein the optical element includes a diffraction element.

[18] The optical system according to any one of [3] to

[17] , wherein the optical element includes a spatial light modulator.

[19] The optical system according to any one of [1] to

[18] , wherein the beam diameter control section includes an aperture.

[20] The optical system according to any one of [1] to

[19] , wherein the beam diameter control section includes a spatial light modulator.

[21] The optical system according to any one of [1] to

[20] , wherein the beam diameter control section has at least one of an aperture and a spatial light modulator.

[22] The optical system according to any one of [1] to

[21] , wherein the light from the light source is laser light.

[23] An image display device comprising: a light source; a beam diameter control section that controls the diameter of the beam from the light source; and a relay optical system that directs the beam to a viewer's pupil, wherein the beam diameter control section enlarges or reduces the diameter of the beam.

[24] The image display device according to

[23] , which is worn on the head of the viewer.

[0107] REFERENCE SIGNS LIST 1 Light source 2 Light beam diameter control unit 3 Relay optical system 31, 33 Lens 32 Optical element 4 Scanning unit 5 Pupil detection unit 6 Gaze detection unit 10 Optical system 100 Image display device

Claims

1. An optical system comprising: a beam diameter control unit that controls the diameter of a beam of light from a light source; and a relay optical system that directs the beam of light to an observer's pupil, wherein the beam diameter control unit expands or reduces the diameter of the beam of light.

2. The optical system according to claim 1, wherein the relay optical system has a function of expanding the diameter of the light beam.

3. The optical system according to claim 1, further comprising an optical element that expands the diameter of the light beam from the light beam diameter control section.

4. The optical system according to claim 1, further comprising an optical element that expands the diameter of the light beam from the light beam diameter control section, wherein the relay optical system has the function of expanding the diameter of the light beam.

5. The optical system according to claim 1, wherein the relay optical system has an optical element that expands the diameter of the light beam.

6. The optical system according to claim 3, wherein the optical element is disposed near the position of the focal point of the light beam formed in the relay optical system.

7. The optical system according to claim 1, further comprising a scanning unit that scans the light beam from the light source, and the light beam diameter control unit is disposed between the light source and the scanning unit.

8. The optical system according to claim 7, wherein the light beam diameter control unit can be arranged at any position between the light source and the scanning unit.

9. The optical system according to claim 1, wherein the beam diameter control unit reduces the diameter of the beam when the beam is projected onto the pupil.

10. The optical system according to claim 1, further comprising a pupil detection unit that detects the position of the pupil.

11. The optical system according to claim 3, wherein the position of the optical element is changeable according to the position of the pupil.

12. The optical system according to claim 1, wherein the position of the light beam diameter control section is changeable in accordance with the position of the pupil.

13. The optical system according to claim 1, further comprising a gaze detection unit that detects whether the viewer is gazing or not.

14. The optical system according to claim 1, wherein the light beam diameter control section increases the diameter of the light beam when the observer is gazing at the light beam.

15. The optical system of claim 3, wherein the optical element comprises a diffractive element.

16. The optical system of claim 3, wherein the optical element comprises a spatial light modulator.

17. The optical system according to claim 1, wherein the beam diameter control section has at least one of an aperture and a spatial light modulator.

18. The optical system according to claim 1, wherein the light from the light source is laser light.

19. An image display device comprising: a light source; a light beam diameter control unit that controls the diameter of a light beam from the light source; and a relay optical system that directs the light beam to an observer's pupil, wherein the light beam diameter control unit enlarges or reduces the diameter of the light beam.

20. The image display device according to claim 19, which is worn on the viewer's head.

Images