Image display device and image display method

Abstract

The purpose of the present invention is to achieve both enlargement of a free focus range and enhancement of image resolution.　An image display device (100) according to the present invention comprises: a plurality of light source units (11); a scanning unit (12) that scans each of the emitted light beams emitted from the light source units (11); a relay optical system (13) that relays the beams scanned by the scanning unit (12) so as to cause an observer to view an image by forming the image on the retina of the observer; and a control unit (14) that controls the driving of each of the light source units (11). The divergence angles of the emitted light beams are each different from each other.

Description

Image display device and image display method

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

[0002] Retinal projection displays have been developed that allow an observer to view an image by projecting it onto the observer's retina. Because the image is projected onto the observer's retina, the observer can clearly view a high-resolution image even if the observer moves their lens to change the focus to some extent. The range in which a high-resolution image can be clearly viewed even if the observer changes the focus is called the free focus range.

[0003] Various technologies have been developed as light sources for generating these images. For example, Patent Document 1 describes a "light-emitting device that can be miniaturized and realizes a light-emitting point pitch and light-emitting position that cannot be achieved with a laser diode alone."

[0004] Japanese Patent Application Laid-Open No. 2022-169006

[0005] When viewing an image using a retinal projection display, it is preferable to be able to view a high-resolution image with a wide free focus range.

[0006] However, conventional retinal projection displays have room for improvement in terms of both expanding the free focus range and improving the image resolution.

[0007] Therefore, a main object of the present technology is to provide an image display device and an image display method that can achieve both an expansion of the free focus range and an improvement in image resolution.

[0008] The present technology provides an image display device including: a plurality of light source units; a scanning unit that scans each of the emitted light beams emitted from the light source units; a relay optical system that relays the light beams scanned by the scanning units and forms an image on a viewer's retina to allow the viewer to view the image; and a control unit that controls driving of each of the light source units, wherein the emitted light beams have different divergence angles. The control unit may switch the free focus range by controlling driving of each of the light source units based on a display position of the image. The plurality of light source units may include at least a first light source unit, a second light source unit, and a third light source unit, and when a first free focus range determined by the first light source unit and a second free focus range determined by the second light source unit are switched at a predetermined threshold, the third free focus range determined by the third light source unit may include the predetermined threshold. The light source units may be arranged at different positions. The light source units may be arranged at different positions in the optical axis direction of the emitted light. The optical system may further include an adjustment unit that adjusts the divergence angle of the emitted light and emits it to the relay optical system. The exit pupils of the respective lights incident on the observer's pupil may be substantially the same. The optical system may include a plurality of optical waveguides that guide the light emitted from each of the light source units. The positions of the light output ends of each of the optical waveguides may be different in the optical axis direction of the emitted light. The plurality of optical waveguides may be formed in a planar lightwave circuit, the planar lightwave circuit having a light output surface including the light output end, the light output surface being formed in a direction substantially perpendicular to the optical axis direction of the emitted light, and the light output ends may be formed on different planes. The plurality of light source units may include a first light source unit that emits output light in a first wavelength band, a second light source unit that emits output light in a second wavelength band, and a third light source unit that emits output light in a third wavelength band. The first wavelength band may be a wavelength band corresponding to red, the second wavelength band may be a wavelength band corresponding to green, and the third wavelength band may be a wavelength band corresponding to blue. The divergence angles of the emitted lights may differ depending on the wavelength bands of the emitted lights.The image display device may further include a multiplexing unit that multiplexes the emitted light beams emitted from the light source units and outputs the multiplexed light to the relay optical system. The relay optical system may have an adjustment element that adjusts the divergence angle of the emitted light beams, and the adjustment element may be configured to be movable based on the display position of the image. The image display device may further include an optical element that is placed in front of the viewer's eye, and the optical element may transmit a portion of light incident on the optical element and reflect a portion of the light beam to output the light toward the viewer's pupil. The optical element may be a diffraction element. The optical element may be worn on the viewer's head. The present technology also provides an image display method for an image display device that includes: a plurality of light source units; a scanning unit that scans the emitted light beams emitted from the light source units; a relay optical system that relays the light scanned by the scanning unit to form an image on the viewer's retina, allowing the viewer to view the image; and a control unit that controls driving of the light source units, wherein the emitted light beams have different divergence angles.

[0009] According to the present technology, it is possible to achieve both an expansion of the free focus range and an improvement in image resolution. Note that the effects described here are not necessarily limited to those described herein, and may be any of the effects described in this disclosure.

[0010] FIG. 1 is a schematic diagram showing an example of a configuration of an image display device 100 according to an embodiment of the present technology. FIG. 2 is a graph showing the correlation between the size of a retinal spot and the free focus range. FIG. 3 is a schematic diagram showing an example of a configuration of a light source unit 11 according to an embodiment of the present technology. FIG. 4 is a schematic diagram showing an example of a configuration of a light source unit 11 according to an embodiment of the present technology. FIG. 5 is a graph showing the correlation between the size of a retinal spot and the free focus range. FIG. 6 is a schematic diagram showing an example of a configuration of a light source unit 11 according to an embodiment of the present technology. FIG. 7 is a schematic diagram showing an example of a configuration of a light source unit 11 according to an embodiment of the present technology. FIG. 8 is a schematic diagram showing a state in which an image is formed on the retina of an observer. FIG. 9 is a schematic diagram showing an example of a configuration of an image display device 100 according to an embodiment of the present technology. FIG. 10 is a schematic diagram showing an example of a configuration of an image display device 100 according to an embodiment of the present technology. FIG. 11 is a schematic diagram showing an example of a configuration of an 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 (example 1 of image display device) (1) Overview (2) Configuration of image display device (3) Arrangement position of light source unit 2. Second embodiment of the present technology (example 2 of image display device) 3. Third embodiment of the present technology (example 3 of image display device) 4. Fourth embodiment of the present technology (example 4 of image display device) 5. Fifth embodiment of the present technology (example 5 of image display device) 6. Sixth embodiment of the present technology (example 6 of image display device) 7. Seventh embodiment of the present technology (example 7 of image display device) 8. Eighth embodiment of the present technology (example 8 of image display device) 9. Ninth embodiment of the present technology (example of image display method)

[0015] [1. First embodiment of the present technology (example 1 of image display device)] [(1) Overview] When light incident on the pupil reaches the retina, photoreceptor cells inside the retina detect the light and convert it into neural signals. These neural signals are sent to the brain via the optic nerve, and the brain interprets the signals to enable us to recognize the scenery and objects we see.

[0016] In order to allow a viewer to view an image, a retinal projection display projects the image onto the viewer's retina and forms an image on the retina. The area on the retina where the image is formed is called an epiretinal spot. The smaller the size of this epiretinal spot, the higher the resolution of the image the viewer can view.

[0017] However, the smaller the size of the retinal spot, the narrower the free focus range. This will be explained with reference to Figure 13. Figure 13 is a graph showing the correlation between the size of the retinal spot and the free focus range. The vertical axis represents the size of the retinal spot. The horizontal axis represents diopters (D), which are values ​​corresponding to the accommodation distance of the eye.

[0018] The free focus range is the range in which the size of the spot on the retina remains constant even when the diopter value changes. In this free focus range, the observer can view a high-resolution image even if the focus is changed by accommodating the eyeball. In this figure, the range approximately parallel to the horizontal axis is the free focus range.

[0019] When a light beam that allows an observer to view an image is projected onto the observer's pupil, the diameter of this light beam is called the exit pupil. The exit pupil can be, for example, 0.5 mm, 1.0 mm, or 1.5 mm. Each line (L11 to L17) in this graph has a different exit pupil value. The light beam is light that has an arbitrary object point (e.g., the light beam's emitting point) and an arbitrary exit pupil (e.g., L11 to L17) on the pupil. The relationship between the free focus range and the retinal spot size, such as narrow or wide, relative to the exit pupil does not depend on the position of the object point. The light beam indicated by line L11 has the smallest exit pupil, and the light beam indicated by line L17 has the largest exit pupil. The larger the exit pupil, the smaller the retinal spot size, allowing the observer to view an image with higher resolution.

[0020] On the other hand, as shown in this graph, the larger the exit pupil, the narrower the free focus range. For example, the free focus range when the light beam indicated by line L17 is projected onto the retina is narrower than the free focus range when the light beam indicated by line L11, which has a smaller exit pupil, is projected onto the retina.

[0021] Thus, the larger the exit pupil, the smaller the spot size on the retina, allowing the observer to see a higher resolution image.However, the larger the exit pupil, the narrower the free focus range, and even slight changes in focus caused by the observer's eye accommodation will result in the image appearing out of focus and blurred.

[0022] Therefore, with conventional technologies, it is difficult to achieve both an expansion of the free focus range and an improvement in image resolution. Therefore, the present technology provides an image display device that can achieve both. Specifically, the present technology provides an image display device that includes a plurality of light source units, a scanning unit that scans each of the light beams emitted from the light source units, a relay optical system that relays the light beams scanned by the scanning unit and forms an image on the retina of a viewer to visually recognize the image, and a control unit that controls the driving of each of the light source units, and the divergence angles of the emitted light beams are different.

[0023] [(2) Configuration of Image Display Device] A configuration example of an image display device according to an embodiment of the present technology will be described with reference to Fig. 1. Fig. 1 is a schematic diagram showing a configuration example of an image display device 100 according to an embodiment of the present technology. As shown in Fig. 1, the image display device 100 includes at least a plurality of light source units 11, a scanning unit 12, a relay optical system 13, and a control unit 14.

[0024] For example, a laser light source can be used as the light source unit 11. Lasers have high light brightness and consistent wavelength characteristics, making them suitable for projecting clear, bright images onto the retina. Lasers have advantages such as a high contrast ratio, a wide color gamut, and high resolution.

[0025] Alternatively, for example, an LED (Light Emitting Diode) may be applied as the light source unit 11. An LED has low power consumption and can provide a wide range of color expression and high brightness.

[0026] The scanning unit 12 scans the light emitted from each light source unit 11 to form an image. For example, a MEMS (Micro-Electro-Mechanical Systems) mirror can be used as the scanning unit 12. The MEMS mirror is a mirror with a fine mechanical structure, and can be minutely vibrated and rotated using an electric signal. This allows the emitted light to be scanned to form an image.

[0027] The elements constituting the scanning unit 12 are not limited to MEMS mirrors, but may also be, for example, galvanometers. A galvanometer is a device that scans emitted light by minutely vibrating a mirror using an electrical signal. By controlling the position of the mirror, the direction of the light can be changed, allowing the emitted light to be scanned.

[0028] The relay optical system 13 relays the light scanned by the scanning unit 12 and forms an image on the observer's retina, allowing the observer to view the image. The relay optical system 13 has a plurality of optical elements. Each of these optical elements relays the light scanned by the scanning unit 12 and forms an image on the observer's retina, allowing the observer to view the image.

[0029] The control unit 14 controls the driving of each light source unit 11. Specifically, the control unit 14 controls the turning on and off of each light source unit 11. Alternatively, the control unit controls the driving of the scanning unit 12. As the control unit 14, for example, a microcontroller, a driver integrated circuit (IC), a signal generating circuit, etc. can be used.

[0030] In this case, it is preferable that the divergence angles of the emitted light beams emitted from the respective light source units 11 are different. The divergence angle is an angle that indicates how much the emitted light beams emitted from the light source units 11 spread as they travel through space. The emitted light beams emitted from the light source units 11 spread at a certain angle as they travel. The divergence angle is used as an index that quantifies how much the emitted light beams spread as they travel.

[0031] Because the divergence angles of the emitted light beams are different, the image display device 100 can set a plurality of free focus ranges. This will be explained with reference to FIG. 2. FIG. 2 is a graph showing the correlation between the size of the retinal spot and the free focus range. The vertical axis represents the size of the retinal spot. The horizontal axis represents diopters (D), which are values ​​corresponding to the accommodation distance of the eyeball.

[0032] When the image display device 100 includes a plurality of light source units 11 including a first light source unit and a second light source unit, the first line L1 in this graph shows the characteristics of the light emitted from the first light source unit, and the second line L2 shows the characteristics of the light emitted from the second light source unit.

[0033] The divergence angle of the light emitted from the first light source unit shown by the first line L1 is different from the divergence angle of the light emitted from the second light source unit shown by the second line L2. Therefore, the free focus range (0 to 2D) determined by the first light source unit shown by the first line L1 is different from the free focus range (2 to 4D) determined by the second light source unit shown by the second line L2. Note that the exit pupils of the respective lights incident on the observer's pupil are substantially the same.

[0034] The control unit 14 (see FIG. 1 ) controls the driving of each light source unit 11. For example, when the control unit 14 turns on the first light source unit, the free focus range indicated by the first line L1 is achieved. When the control unit 14 turns on the second light source unit, the free focus range indicated by the second line L2 is achieved. By switching the free focus range in this way, it is possible to project light with a wide free focus range and a large exit pupil (small spot size on the retina) onto the observer's retina. In other words, it is possible to achieve both an expansion of the free focus range and an improvement in image resolution. Note that this effect also occurs in other embodiments described below. Therefore, repeated description may be omitted in the description of other embodiments.

[0035] It is preferable that the exit pupils of the respective light beams incident on the observer's pupils are substantially the same, which can suppress changes in resolution due to switching of the free focus range, thereby reducing the sense of discomfort felt by the observer.

[0036] The criteria for switching the free focus range are not particularly limited. For example, the control unit 14 can switch the free focus range by controlling the drive of each light source unit based on the display position of the image. Using this graph as an example, the first light source unit indicated by the first line L1 emits light so that the observer can observe an object point located at a diopter value of 1.4D on the horizontal axis. The second light source unit indicated by the second line L2 emits light so that the observer can observe an object point located at a diopter value of 3.4D on the horizontal axis. In other words, 1.4D and 3.4D are each the display positions of the image. The control unit 14 can switch the free focus range by controlling the drive of each light source unit based on the display position of the image. This makes it possible to achieve both an expansion of the free focus range and an improvement in image resolution.

[0037] 1 , the image display device 100 may further include an adjustment unit 15. The adjustment unit 15 can adjust the divergence angle of each light beam emitted from each light source unit 11 and emit the light beam to the relay optical system 13.

[0038] The adjustment unit 15 may have, for example, a collimating optical system. The collimating optical system can adjust the divergence angle by converting the light emitted from the light source unit 11 into approximately parallel light. More specifically, the collimating optical system may have a collimator lens, a fiber collimator, a prism, a mirror, etc.

[0039] Although not shown in the drawings, for example, the relay optical system 13 may have an adjustment unit 15. In this case, the relay optical system 13 can adjust the divergence angle of the light scanned by the scanning unit 12 while relaying the light.

[0040] (3) Position of Light Source Units There is no particular limitation on the means for varying the divergence angles of the light emitted from each light source unit 11. An example of the means for varying the divergence angles will be described with reference to FIG. 3. FIG. 3 is a schematic diagram showing an example configuration of the light source unit 11 according to an embodiment of the present technology. As shown in FIG. 3, since the light source units 11 are disposed at different positions, an optical path difference occurs between the light emitted from each light source unit 11. Therefore, the divergence angles of the light emitted can be varied.

[0041] In this case, the direction in which the light source units 11 are arranged at different positions is not particularly limited, but it is preferable that the light source units 11 are arranged at different positions in the optical axis direction of the emitted light (left and right direction in the figure). This allows the space within the image display device 100 to be used effectively, which contributes to the miniaturization of the image display device 100.

[0042] Furthermore, the number of light source units 11 is not particularly limited. In this configuration example, the number of light source units 11 is two, but it may be three or more. Increasing the number of light source units 11 may increase costs, but may further expand the free focus range and result in a clearer image. As described above, the larger the exit pupil, the higher the resolution of the image, but the narrower the free focus range. By increasing the number of light source units 11, it is possible to expand the free focus range while allowing the observer to view a high-resolution image.

[0043] The above description of the image display device 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.

[0044] 2. Second Embodiment of the Present Technology (Example 2 of Image Display Device) As described above, the free focus range can be switched by the control unit 14 controlling the driving of each light source unit 11. At this time, there is a risk that necessary switching will not occur or unnecessary switching will occur due to an event such as a sudden change in the display position of the image or a malfunction in eyeball sensing.

[0045] Therefore, for example, when a first light source unit and a second light source unit are configured, it is preferable to further include a third light source unit for smoothly switching the free focus range. This will be described with reference to Fig. 4 and Fig. 5. Fig. 4 is a schematic diagram showing an example configuration of the light source unit 11 according to an embodiment of the present technology. Fig. 5 is a graph showing the correlation between the size of the retinal spot and the free focus range.

[0046] As shown in Fig. 4, in this configuration example, the multiple light source units include at least a first light source unit 111, a second light source unit 112, and a third light source unit 113. The first light source unit 111, the second light source unit 112, and the third light source unit 113 are arranged at different positions, which causes an optical path difference in the emitted light. This allows the divergence angles of the emitted light to be different. It is preferable that the first light source unit 111, the second light source unit 112, and the third light source unit 113 are arranged at different positions in the optical axis direction of the emitted light (the left-right direction in the figure).

[0047] 5, the first free focus range determined by first light source unit 111 shown by first line L1, the second free focus range determined by second light source unit 112 shown by second line L2, and the third free focus range determined by third light source unit 113 shown by third line L3 are all different. In this graph, the first free focus range is a range of 0 to 2D, the second free focus range is a range of 2 to 4D, and the third free focus range is a range of 1 to 3D.

[0048] The control unit 14 (see FIG. 1 ) switches between a first free focus range determined by the first light source unit 111 and a second free focus range determined by the second light source unit 112 using a predetermined threshold. In this graph, the threshold is set to 2D. When the diopter value is 2D or greater, the control unit 14 turns on the first light source unit 111. When the diopter value is less than 2D, the control unit 14 turns on the second light source unit 112. In this manner, the free focus range can be switched. Note that this threshold is not limited to 2D and can be set to an appropriate value depending on the situation.

[0049] In this case, it is preferable that the third free focus range determined by the third light source unit 113, which is indicated by the third line L3, includes this predetermined threshold value. In this graph, the threshold value is 2D, so the third free focus range (1D to 3D) includes this threshold value.

[0050] This allows the free focus range to be switched stably. For example, when the diopter value on the horizontal axis is near 0D, the first light source unit 111 shown on the first line L1 is turned on. As the diopter value gradually increases and approaches the threshold value of 2D, the third light source unit 113 shown on the third line L3 is turned on. Even if the diopter value increases further and becomes slightly larger than the threshold value, the third light source unit 113 remains turned on. When the diopter value becomes significantly larger than the threshold value, the second light source unit 112 shown on the second line L2 is turned on. In this way, the free focus range does not switch even if the diopter value slightly rises or falls above or below the threshold value. This improves the robustness of the image display device 100.

[0051] The above description of the image display device 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.

[0052] 3. Third Embodiment of the Present Technology (Example 3 of Image Display Device) In order to reduce the size of the image display device, it is preferable to arrange the light source units 11 in close proximity to each other. However, since each light source unit 11 has a finite size, there is a limit to how close the light source units 11 can be arranged. Furthermore, if the light source units 11 are arranged too close to each other, there is a risk of interference between the light beams emitted from the light source units 11.

[0053] Therefore, it is preferable that the image display device 100 has a plurality of optical waveguides that guide the light emitted from each light source unit 11. This will be described with reference to Fig. 6. Fig. 6 is a schematic diagram showing an example of the configuration of the light source unit 11 according to an embodiment of the present technology.

[0054] 6 , the image display device 100 has a plurality of optical waveguides 1611 and 1612 that guide the light emitted from the respective light source units 111 and 112. This allows the respective light source units 111 and 112 to be located as close as possible to each other, which contributes to miniaturization of the image display device 100.

[0055] The optical waveguides 1611 and 1612 may be formed in any suitable form, but may be formed in a planar lightwave circuit (PLC) 16. The planar lightwave circuit 16 is easier to miniaturize and integrate than optical fibers and has the advantage of providing high reliability and functionality. Furthermore, the planar lightwave circuit 16 can be mass-produced using mask optical technology, enabling low-cost mass production.

[0056] The light beams emitted from the light source units 111 and 112 are emitted via the optical waveguides 1611 and 1612, respectively. Since the positions of the light emitting ends 1621 and 1622 of the optical waveguides 1611 and 1612 are different, an optical path difference occurs between the light beams emitted from the light emitting ends 1621 and 1622, respectively. This makes it possible to make the divergence angles of the light beams different.

[0057] In this case, the direction in which the positions of the light emitting ends 1621, 1622 of the respective optical waveguides 1611, 1612 are made different is not particularly limited, but it is preferable that the positions of the light emitting ends 1621, 1622 of the respective optical waveguides 1611, 1612 are made different in the optical axis direction of the emitted light (the left-right direction in the figure). This allows the space within the image display device 100 to be used effectively, which can contribute to the miniaturization of the image display device 100.

[0058] Note that Patent Document 1 (JP 2022-169006 A) discloses that the normal direction N1 of the light exit surface 240 is inclined with respect to the optical axis direction 32 of the lens 30. This inclination causes the distance (optical path length) from each light exit end to the surface of the lens 30 to differ. It explains that by adjusting the angle of this inclination, the distance from each light exit end to the surface of the lens 30 can be matched to a focal length that matches the wavelength of light.

[0059] However, when the light exit surface is tilted, depending on the angle, light may be reflected rather than refracted, resulting in light being emitted in an unintended direction, which may reduce the light utilization efficiency.

[0060] On the other hand, in the present technology, the planar lightwave circuit 16 has light exit surfaces 1631 and 1632 including light exit ends 1621 and 1622 of the respective optical waveguides 1611 and 1612. The light exit surfaces 1631 and 1632 are formed in a direction substantially perpendicular to the optical axis direction of the emitted light. This reduces the possibility of the emitted light traveling in an unintended direction, thereby improving the light utilization efficiency.

[0061] Furthermore, the respective light emitting ends are formed on different planes. In this configuration example, the first light emitting end 1621 of the first light waveguide 1611 and the second light emitting end 1622 of the second light waveguide 1612 are formed on different planes. A first light emitting surface 1631 including the first light emitting end 1621 of the first light waveguide 1611 is higher than a second light emitting surface 1632 including the second light emitting end 1622 of the second light waveguide 1612. This causes an optical path difference between the light beams emitted from the first light source unit 111 and the second light source unit 112. This makes it possible to make the divergence angles of the emitted light beams different.

[0062] In this configuration example, the light emitting surfaces 1631 and 1632 are formed in a stepped shape, but the shape is not limited to this. The first light emitting surface 1631 and the second light emitting surface 1632 may be connected by, for example, an inclined surface. In addition, in this configuration example, there is one step, but there may be multiple steps.

[0063] The above description of the image display device 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.

[0064] 4. Fourth Embodiment of the Present Technology (Example 4 of Image Display Device)] The wavelength bands of the light emitted from each of the plurality of light source units 11 may be the same or different. A configuration example in which the wavelength bands are different will be described with reference to Fig. 7. Fig. 7 is a schematic diagram showing a configuration example of the light source unit 11 according to an embodiment of the present technology.

[0065] 7 , the plurality of light source units include a first light source unit 111 that emits output light in a first wavelength band, a second light source unit 112 that emits output light in a second wavelength band, and a third light source unit 113 that emits output light in a third wavelength band. By appropriately adjusting each of the first wavelength band, the second wavelength band, and the third wavelength band, it is possible to allow the viewer to view an image that has high saturation, a wide dynamic range, and appropriate white balance.

[0066] More specifically, the first wavelength band may be a wavelength band corresponding to red, the second wavelength band may be a wavelength band corresponding to green, and the third wavelength band may be a wavelength band corresponding to blue. This allows the image display device 100 to allow the viewer to view a full-color image. The wavelength band corresponding to red may be, for example, approximately 620 to 750 nm. The wavelength band corresponding to green may be, for example, approximately 500 to 550 nm. The wavelength band corresponding to blue may be, for example, approximately 430 to 500 nm.

[0067] Furthermore, it is preferable that the divergence angles of the emitted light beams differ depending on the wavelength bands of the emitted light beams. This will be explained with reference to Fig. 8. Fig. 8 is a schematic diagram showing how an image is formed on the retina of the observer.

[0068] As shown in Figure 8, the position of the focus on the retina depends on the focal length of the crystalline lens E1 and the wavelength of light. For example, blue light BL has a short wavelength, so it is refracted more strongly by the crystalline lens E1 and forms a focus in front of the retina. Red light RL has a long wavelength, so it is refracted less strongly by the crystalline lens E1 and forms a focus behind the retina. Green light GL forms a focus somewhere in between.

[0069] Therefore, in order to form an image at an appropriate position on the retina, it is preferable that the divergence angle of each emitted light differs depending on the wavelength band of the emitted light. Referring again to FIG. 7 , it is preferable that the divergence angle of the emitted light from the first light source unit 111 is adjusted depending on the wavelength band of the emitted light. Similarly, it is preferable that the divergence angle of the emitted light from the second light source unit 112 is adjusted depending on the wavelength band of the emitted light. It is preferable that the divergence angle of the emitted light from the third light source unit 113 is adjusted depending on the wavelength band of the emitted light. This makes it possible to expand the free focus range while allowing the viewer to view an image with the highest possible resolution.

[0070] The above description of the image display device 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.

[0071] 5. Fifth Embodiment of the Present Technology (Fifth Example of Image Display Device) In order to increase the degree of freedom in designing the image display device 100, the image display device 100 may further include a multiplexing unit that multiplexes the respective emitted light beams. This will be described with reference to Fig. 9. Fig. 9 is a schematic diagram showing a configuration example of the image display device 100 according to an embodiment of the present technology.

[0072] 9, the image display device 100 further includes a multiplexing unit 17. The multiplexing unit 17 multiplexes the light beams emitted from the light source units 11, and outputs the multiplexed light beams to the relay optical system 13.

[0073] This increases the degree of freedom in designing the image display device 100. For example, as shown in Fig. 3, if the light source units 11 are arranged at different positions in the optical axis direction of the emitted light, there is a risk of interference between the emitted light beams if the distance between the light source units 11 is long. On the other hand, in the configuration example shown in Fig. 9, the positions of the light source units 11 can be freely arranged, thereby generating an optical path difference between the emitted light beams.

[0074] Examples of the multiplexer 17 include a polarizing beam splitter (PBS), a polarization beam combiner (PBC), a half mirror, and an interference filter.

[0075] In this embodiment, there is no particular limitation on the number of light source units 11. In this configuration example, the multiplexing unit 17 multiplexes the light emitted from one light source unit 11 and the light emitted from another light source unit 11, but the number of each light source unit may be two or more.

[0076] The above description of the image display device 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.

[0077] 6. Sixth Embodiment of the Present Technology (Example 6 of Image Display Device)] Instead of or in addition to the adjustment unit 15 shown in Fig. 1 , for example, a relay optical system 13 may adjust the divergence angle. This will be described with reference to Fig. 10. Fig. 10 is a schematic diagram showing a configuration example of an image display device 100 according to an embodiment of the present technology.

[0078] 10 , in this configuration example, the relay optical system 13 has an adjustment element 131 that adjusts the divergence angle of the emitted light. This adjustment element 131 is configured to be movable based on the display position of the image. The movement direction of the adjustment element 131 is not particularly limited, but for example, the adjustment element 131 may be configured to be movable in the direction of the arrow in the figure.

[0079] The adjusting element 131 may be, for example, a convex lens that has the property of converging light. When the adjusting element 131 is a convex lens, the divergence angle increases as the adjusting element 131 moves away from the light source unit 11. Conversely, the divergence angle decreases as the adjusting element 131 moves closer to the light source unit 11.

[0080] The adjustment element 131 may be, for example, a concave lens that has the property of diffusing light. When the adjustment element 131 is a concave lens, the divergence angle decreases as the adjustment element 131 moves away from the light source unit 11. Conversely, the divergence angle increases as the adjustment element 131 moves closer to the light source unit 11.

[0081] The above description of the image display device 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.

[0082] [7. Seventh Embodiment of the Present Technology (Example 7 of Image Display Device)] An image display device according to the present technology can be used, for example, in XR (Extended Reality) including Augmented Reality (AR) and Virtual Reality (VR). A configuration example of an image display device 100 that realizes AR, which is a technology for overlaying digital information on a real environment, will be described with reference to FIG. 11 . FIG. 11 is a schematic diagram showing a configuration example of an image display device 100 according to an embodiment of the present technology.

[0083] 11 , the image display device 100 further includes an optical element 18 disposed in front of the viewer's eye. This optical element 18 transmits a portion of the light incident on the optical element 18 and reflects a portion of the light to be emitted toward the viewer's pupil. Because the optical element 18 is transparent, the viewer can view the image generated by the image display device 100 while viewing the real environment that exists beyond the optical element 18.

[0084] Examples of the optical element 18 include a half mirror, a prism, a lens, an optical fiber, a diffraction element, etc. In particular, the optical element 18 may be a diffraction element such as a holographic optical element, a Fresnel lens, a reflection type diffraction grating, or a transmission type diffraction grating. A diffraction element can diffuse or converge light by utilizing the diffraction effect of light.

[0085] The optical element 18 being a diffractive element can, for example, simplify the image display device 100. Compared to other optical elements such as lens arrays that have complex optical configurations, the diffractive element can realize a simple and compact device design.

[0086] Furthermore, a diffraction element generally has a thin and lightweight structure, which makes it suitable for the eyeglass-type image display device 100, for which fit and comfort are important factors.

[0087] Furthermore, the diffractive element can provide high optical quality and resolution, so that the image display device 100 can display images clearly.

[0088] 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.

[0089] 8. Eighth Embodiment of the Present Technology (Eighth Example of Image Display Device) An image display device 100 according to the present technology can be worn on the head of a viewer. This configuration example will be described with reference to Fig. 12. Fig. 12 is a schematic diagram of a viewer wearing the image display device 100 according to an embodiment of the present technology on their head, viewed from the front.

[0090] 12 , the image display device 100 can be attached to the viewer's head by, for example, a frame 20. The frame 20 is composed of a front section 21 placed in front of the viewer's eyes, two temple sections 23 rotatably attached to both ends of the front section 21 via hinges 22, and end sections (also called tip cells, earmuffs, or ear pads) 24 attached to the tip of each temple section 23. The frame 20 may be made of metal or plastic.

[0091] The image display device 100 is disposed in a part of the front section 21. The optical element 18 according to the seventh embodiment is disposed in front of the viewer's eyes by the front section 21. Although not shown, the front section 21 may include nose pads. In other words, the assembly of the frame 20 and nose pads can basically have substantially the same structure as ordinary eyeglasses.

[0092] The above description of the image display device according to the eighth embodiment of the present technology can be applied to other embodiments of the present technology unless there is a particular technical contradiction.

[0093] [9. Ninth Embodiment of the Present Technology (Example of Image Display Method)] The present technology provides an image display method for an image display device including a plurality of light source units, a scanning unit that scans each of the light source units with light emitted therefrom, a relay optical system that relays the light scanned by the scanning unit to form an image on the retina of a viewer, thereby allowing the viewer to view the image, and a control unit that controls driving of each of the light source units, wherein the divergence angles of the emitted light are different. Image display devices according to other embodiments can be applied to this image display device.

[0094] The above description of the image display method according to the ninth embodiment of the present technology can be applied to other embodiments of the present technology unless there is a particular technical contradiction.

[0095] 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.

[0096] The present technology may also be configured as follows. [1] An image display device including: a plurality of light source units; a scanning unit that scans each of the light source units; a relay optical system that relays the light scanned by the scanning units to form an image on a viewer's retina so that the viewer can view the image; and a control unit that controls driving of each of the light source units, wherein the divergence angles of the emitted light are different. [2] The image display device according to [1], wherein the control unit switches the free focus range by controlling driving of each of the light source units based on a display position of the image. [3] The image display device according to [2], wherein the plurality of light source units include at least a first light source unit, a second light source unit, and a third light source unit, and wherein, when a first free focus range determined by the first light source unit and a second free focus range determined by the second light source unit are switched at a predetermined threshold, the third free focus range determined by the third light source unit includes the predetermined threshold. [4] The image display device according to any one of [1] to [3], wherein the light source units are arranged at different positions. [5] The image display device according to [4], wherein the light source units are arranged at different positions in the optical axis direction of the emitted light. [6] The image display device according to any one of [1] to [5], further comprising an adjustment unit that adjusts the divergence angle of the emitted light and emits it to the relay optical system. [7] The image display device according to any one of [1] to [6], wherein the exit pupils of the lights incident on the pupil of the observer are substantially the same. [8] The image display device according to any one of [1] to [7], wherein the image display device has a plurality of optical waveguides that guide the light emitted from the light source units. [9] The image display device according to [8], wherein the positions of the light emission ends of the optical waveguides are different in the optical axis direction of the emitted light.

[10] The image display device according to [9], wherein the plurality of optical waveguides are formed in a planar lightwave circuit, the planar lightwave circuit has a light exit surface including the light exit end, the light exit surface is formed in a direction substantially perpendicular to the optical axis direction of the emitted light, and each of the light exit ends is formed on a different plane.

[11] The image display device according to any one of [1] to

[10] , wherein the plurality of light source units include a first light source unit that emits output light in a first wavelength band, a second light source unit that emits output light in a second wavelength band, and a third light source unit that emits output light in a third wavelength band.

[12] The image display device according to

[11] , wherein the first wavelength band is a wavelength band corresponding to red, the second wavelength band is a wavelength band corresponding to green, and the third wavelength band is a wavelength band corresponding to blue.

[13] The image display device according to any one of [1] to

[12] , wherein the divergence angles of the output lights differ depending on the wavelength bands of the output lights.

[14] The image display device according to any one of [1] to

[13] , further comprising a multiplexer that multiplexes the output lights emitted from the light source units and outputs the multiplexed light to the relay optical system.

[15] The image display device according to any one of [1] to

[14] , wherein the relay optical system has an adjustment element that adjusts the divergence angle of the emitted light, and the adjustment element is configured to be movable based on the display position of the image.

[16] The image display device according to any one of [1] to

[15] , further comprising an optical element that is placed in front of the eye of the observer, and the optical element transmits a portion of light incident on the optical element and reflects a portion of the light to be emitted to the pupil of the observer.

[17] The image display device according to

[16] , wherein the optical element is a diffraction element.

[18] The image display device according to any one of [1] to

[17] , which is worn on the head of the observer.

[19] An image display method for an image display device comprising: a plurality of light source units; a scanning unit that scans each of the emitted light beams emitted from the light source units; a relay optical system that relays the light beams scanned by the scanning unit and forms an image on the retina of a viewer to allow the viewer to view the image; and a control unit that controls driving of each of the light source units, wherein the divergence angles of the emitted light beams are different.

[0097] REFERENCE SIGNS LIST 100 Image display device 11 Light source unit 12 Scanning unit 13 Relay optical system 131 Adjusting element 14 Control unit 15 Adjusting unit 16 Planar lightwave circuit 161 Optical waveguide 162 Light emitting end 163 Light emitting surface 17 Wave-combining unit 18 Optical element 20 Frame 21 Front unit 22 Hinge 23 Temple unit 24 End piece

Claims

1. An image display device comprising: a plurality of light source units; a scanning unit that scans each of the outgoing lights emitted from each of the light source units; a relay optical system that relays the light scanned by the scanning unit and focuses the image on the observer's retina to allow the observer to view the image; and a control unit that controls the operation of each of the light source units, wherein the divergence angles of each of the outgoing lights are different.

2. The image display device according to claim 1, wherein the control unit switches the free focus range by controlling the driving of each of the light source units based on the display position of the image.

3. The image display device according to claim 2, wherein the plurality of light source units include at least a first light source unit, a second light source unit, and a third light source unit, and when a first free focus range determined by the first light source unit and a second free focus range determined by the second light source unit are switched at a predetermined threshold value, a third free focus range determined by the third light source unit includes the predetermined threshold value.

4. The image display device according to claim 1, wherein the light source sections are arranged at different positions.

5. The image display device according to claim 4, wherein the light source sections are arranged at different positions in the direction of the optical axis of the emitted light.

6. The image display device according to claim 1, further comprising an adjustment section that adjusts the divergence angle of the emitted light and emits it to the relay optical system.

7. The image display device according to claim 1, wherein the exit pupils of the respective lights incident on the pupils of the observer are substantially the same.

8. The image display device according to claim 1, further comprising a plurality of optical waveguides for guiding the light emitted from each of said light source sections.

9. The image display device according to claim 8, wherein the positions of the light exit ends of the optical waveguides are different in the direction of the optical axis of the emitted light.

10. An image display device as described in claim 9, wherein the plurality of optical waveguides are formed in a planar lightwave circuit, the planar lightwave circuit has a light output surface including the light output end, the light output surface is formed in a direction approximately perpendicular to the optical axis direction of the output light, and each of the light output ends is formed on a different plane.

11. The image display device according to claim 1, wherein the plurality of light source units include a first light source unit that emits light in a first wavelength band, a second light source unit that emits light in a second wavelength band, and a third light source unit that emits light in a third wavelength band.

12. An image display device as described in claim 11, wherein the first wavelength band is a wavelength band corresponding to red, the second wavelength band is a wavelength band corresponding to green, and the third wavelength band is a wavelength band corresponding to blue.

13. The image display device according to claim 1, wherein the divergence angles of the emitted lights are different depending on the wavelength bands of the emitted lights.

14. The image display device according to claim 1, further comprising a multiplexing section which multiplexes the light beams emitted from the light source sections and outputs the multiplexed light beams to the relay optical system.

15. The image display device according to claim 1, wherein the relay optical system has an adjustment element that adjusts the divergence angle of the emitted light, and the adjustment element is configured to be movable based on the display position of the image.

16. An image display device according to claim 1, further comprising an optical element arranged in front of the eye of the observer, the optical element transmitting a portion of light incident on the optical element and reflecting a portion of the light toward the pupil of the observer.

17. The image display device according to claim 16, wherein the optical element is a diffraction element.

18. The image display device according to claim 1, which is worn on the viewer's head.

19. An image display method for an image display device comprising: a plurality of light source units; a scanning unit which scans each of the outgoing lights emitted from each of the light source units; a relay optical system which relays the light scanned by the scanning unit and focuses the image on the observer's retina to allow the observer to view the image; and a control unit which controls the driving of each of the light source units, wherein the divergence angles of each of the outgoing lights are different.