Patent Application
20240032406
The present invention relates to an image observation apparatus in which an image displayed on a display element can be observed through an ocular optical system.
A head-mounted display (HMD), which is worn on the head of an observer, is known as an image observation apparatus in which an image displayed on a display element can be observed through an ocular optical system. In such an HMD, an ocular optical system that bends the optical path is sometimes used to achieve both miniaturization and a wide view angle. A polarizing optical system that uses polarized light, a freeform prism having a reflective surface inside the lens, and the like can be given as examples of such an ocular optical system.
Such ocular optical systems are characterized by a shorter focal length, which increases the light emission angle from the display element at peripheral view angles and tends to degrade the viewing angle characteristics (causes shifts in the luminance and chromaticity) of the display element. Such systems are also prone to producing what is known as “ghost light”, which is light that passes through an optical path not intended by design. For example, when a plastic lens is used as part of a polarizing optical system to reduce weight, birefringence within the plastic lens may disrupt the polarization state of the light and produce ghosting.
PTL 1 and PTL 2 disclose HMDs having ocular optical systems that use polarized light to provide a wide view angle. Furthermore, PTL 2 discloses that increasing the size of a color filter provided on the display element with distance from the center to the periphery improves the viewing angle characteristics at peripheral view angles.
However, in the HMD disclosed in PTL 2, the light source and the center of the color filter are aligned such that the viewing angle characteristics in the normal direction of the display element are good, and thus ghosting caused by lens birefringence cannot be reduced.
Having been made in view of the above-described problem, the present invention provides an image observation apparatus that can reduce ghosting while improving the viewing angle characteristics at peripheral view angles of an ocular optical system configured to bend an optical path.
An image observation apparatus according to the present invention includes: a display element including a plurality of light-emitting elements disposed two-dimensionally on a plane and a plurality of microlenses provided for corresponding ones of the plurality of light-emitting elements; and an ocular optical system, containing at least one reflective surface therein, that guides light from a display surface of the display element to an exit pupil. In a peripheral part of the display element, a center position of the light emission region of each light-emitting element and a center of the microlens corresponding to the light-emitting element are shifted from each other in a direction parallel to the plane.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain principles of the invention.
Hereinafter, embodiments will be described in detail with reference to the attached drawings. Note, the following embodiments are not intended to limit the scope of the claimed invention. Multiple features are described in the embodiments, but limitation is not made to an invention that requires all such features, and multiple such features may be combined as appropriate. Furthermore, in the attached drawings, the same reference numerals are given to the same or similar configurations, and redundant description thereof is omitted.
In embodiments of the present invention, ghosting can be reduced while improving the viewing angle characteristics at peripheral view angles of an ocular optical system that bends an optical path by shifting the center position of a microlens provided on a light-emitting element with respect to the light emission center position of the light-emitting element.
First, an embodiment of a display element that improves viewing angle characteristics and reduces ghosting will be described. Then, as examples of combinations of display elements and ocular optical systems that bend an optical path, a first embodiment and a second embodiment will describe embodiments of a polarizing optical system that uses polarized light, and a third embodiment will describe an embodiment that uses a freeform prism. Preferred forms of the ocular optical system that bends the optical path will be described in the embodiments.
Embodiments of the display element of the present invention will be described hereinafter with reference to the drawings. Note that for parts not specifically illustrated or described in the present specification, well-known or publicly-known techniques in the corresponding technical field are applied. Furthermore, the present invention is not intended to be limited to the embodiments described below.
The light-emitting element 10 on the substrate 8 has a first electrode 11 disposed on the main surface of the substrate 8, an organic layer 12 including a light-emitting layer, and a second electrode 13 disposed on the first electrode 11 with the organic layer 12 interposed therebetween. Additionally, to maintain the characteristics of the light-emitting element 10 at the outermost periphery of the display region 1, dummy pixels 10′ are disposed outside the range indicated by the line between points A and A′, which is the edge of the display region 1. The dummy pixels 10′ may be formed in a plurality of columns and a plurality of rows.
The organic layer 12 may be configured with a light-emitting layer emitting a single light emission color deposited as a common layer between the light-emitting elements 10, such that the display element 100 can display a single light emission color. The organic layer 12 may also be configured by patterning a light-emitting layer that emits a different color for each light-emitting element 10 such that the display element 100 can display at least two colors. Each pixel of the display element 100 covers the edge of the first electrode 11 and has an opening above the first electrode 11, and has an insulating layer 16 that functions as a bank, a protective layer 14 disposed on the second electrode 13, and the microlens 15. The light emitted from the light-emitting element 10 enters the microlens 15.
In the present embodiment, the microlens 15 is disposed offset from the light emission region 17 of the light-emitting element 10 in the direction indicated by the arrow B. The direction indicated by the arrow B is the direction in which the main light rays of an ocular optical system that bends the optical path are projected onto the main surface when the display element 100 is seen in plan view. By using such a configuration, the luminous intensity of light that reaches the pupil of an observer through the ocular optical system is greater than when the microlenses are not provided, the microlenses and the light emission regions are arranged so as to overlap in plan view, and the like, which improves the utilization efficiency of the light emitted by the light-emitting layer. In addition, the luminous intensity of light that passes through unintended optical paths and is perceived as ghosting by the observer is reduced. The effects will be described in greater detail later. It is desirable that a relationship between a refractive index n1 of the microlens and a refractive index n0 of the medium above the microlens in the present embodiment, illustrated in
In each light-emitting element 10, the microlens 15 and the light emission region 17 being shifted means that a center position 19 of the microlens 15 and the center position 18 of the light emission region 17 do not overlap in plan view, and are instead separated by a given distance. The center of the microlens 15 is the center of gravity of a shape (outline) formed from lines connecting the edges in plan view. The edges of the microlens 15 are the positions where the height in the Z direction of the microlens 15, in a cross-sectional view thereof, is the lowest. In
In the present embodiment, the microlens 15 is disposed so as to be shifted with respect to the light emission region 17 of the light-emitting element 10. In other words, the center 19 of the microlens 15 and the center position 18 of the light emission region 17 are separated by a given distance apart (not coincident) in a plan view of the surface of the substrate 8 on which the light-emitting elements 10 are disposed. Here, the cross-sectional shape of the microlens 15 is spherical, and thus the apex of the microlens 15 and the center of the light emission region 17 are also separated by a given distance.
In the present embodiment, the pitch of the microlenses 15 (the distance between the centers of adjacent microlenses in the plan view of the surface on which the light-emitting elements 10 of the substrate 8 are disposed) is constant. The pitch of the light-emitting elements 10 (the distance between the centers of the light emission regions of adjacent light-emitting elements 10 in the plan view of the surface on which the light-emitting elements 10 are disposed on the substrate 8) is also constant, and coincides with the pitch of the microlenses 15. Accordingly, the microlenses 15 and light emission regions 17 are shifted by a certain distance (a shift amount). In other words, the present embodiment describes an example in which the distance between the center of microlens 15 and the center of the light emission region 17 in plan view (a microlens shift amount) is constant for each pixel.
When the organic layer 12 is constituted by a layer that emits white light, a color filter 20 may be provided between the light-emitting element 10 and the microlens 15, as illustrated in
The substrate 8 may be any material that can support the first electrode 11, the organic layer 12, and the second electrode 13. Glass, plastic, silicon, or the like can be used, for example. Switching elements such as transistors, interconnects, and interlayer insulating films, and the like (not shown) may be disposed in the substrate 8.
The first electrode 11 may be transparent or opaque. If opaque, a metal material having a reflectance of at least 70% at the light emission wavelength is desirable. Metals such as Al and Ag, alloys having Si, Cu, Ni, Nd, or the like added thereto, as well as ITO, IZO, AZO, or IGZO can be used. Here, light emission wavelength refers to the spectral range emitted from the organic layer 12. The first electrode 11 may be a layered electrode having a barrier electrode formed from a metal such as Ti, W, Mo, Au, or an alloy thereof, or a layered electrode including a transparent oxide film electrode such as ITO or IZO, as long as the reflectance is higher than desired.
On the other hand, if the first electrode 11 is a transparent electrode, the configuration may be such that a reflective layer is further provided below the first electrode 11. ITO, IZO, AZO, and IGZO can be used as the transparent electrode, for example. For the purpose of optimizing the optical distance, another insulating film may further be provided between the reflective layer and the transparent electrode.
The second electrode 13 is disposed on the organic layer 12, and is light-transmissive. The second electrode 13 may be a semi-transparent material that has a property of transmitting some of the light reaching the surface thereof and reflecting the rest (i.e., semi-transmissive reflectivity). A transparent material, such as a transparent conductive oxide, can be used as the material of the second electrode 13, for example. A semi-transparent material formed from a single metal such as aluminum, silver, and gold, an alkali metal such as lithium and cesium, an alkali-earth metal such as magnesium, calcium, and barium, and alloy materials containing these metal materials can be used. Alloys based on magnesium or silver are particularly preferable as the primary component of the semi-transparent material. The second electrode 13 may have a layered configuration including layers of the above materials as long as the preferred transmittance is achieved. The second electrode 13 may be shared by a plurality of light-emitting elements 10.
One of the first electrode 11 or the second electrode 13 functions as the anode, and the other as the cathode. In other words, the first electrode 11 may be the anode and the second electrode 13 the cathode, or vice versa. The organic layer 12 is disposed on the first electrode 11 and can be formed through publicly-known techniques such as vapor deposition and spin coating.
The organic layer 12 may be constituted by a plurality of layers. When the organic layer 12 is an organic compound layer, any one or a combination of the following can be given as the plurality of layers: a hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting layer, a hole blocking layer, an electron transport layer, and an electron injection layer.
The light-emitting layer emits light when holes injected from the anode and electrons injected from the cathode recombine in the organic compound layer. The light-emitting layer may be constituted by a single layer or a plurality of layers. Each light-emitting layer can have a red light-emitting material, a green light-emitting material, and a blue light-emitting material, and it is also possible to obtain white light by mixing the light emission colors. Each of the light-emitting layers may also contain light-emitting materials in complementary color relationships, such as a blue light-emitting material and a yellow-light emitting material. The light-emitting materials may be fluorescent materials, phosphorescent materials, delayed fluorescent materials, or the like, or may be quantum dots such as CdS or perovskite. Different colors may also be emitted by changing the materials and composition of the light-emitting layers in each pixel. Light-emitting layers may also be provided one-to-one for the light-emitting elements 10. In this case, the light-emitting layer may be patterned for each of the light-emitting elements 10.
The protective layer 14 is an insulating layer and preferably contains an inorganic material that is light-transmissive and has low permeability to oxygen and moisture from the outside. For example, the protective layer 14 can be formed using an inorganic material such as silicon nitride (SiN), silicon oxynitride (SiON), silicon oxide (SiOx), aluminum oxide (Al2O3), titanium oxide (TiO2), or the like. Inorganic materials such as SiN, SiON, and Al2O3 are particularly preferable in terms of protective performance. Chemical vapor deposition (CVD), atomic layer deposition (ALD), or sputtering is preferable to use to form the protective layer 14.
The protective layer 14 may have a single-layer structure or a layered structure combining the above materials and formation techniques, as long as the layer has sufficient moisture blocking performance. For example, a layer of silicon nitride, and a high-density layer formed by atomic deposition, may be used. Furthermore, the protective layer 14 may have an organic layer, as long as the moisture blocking performance is maintained. Organic layers include, for example, polyacrylate, polyimide, polyester, epoxy, and the like. Furthermore, the protective layer 14 may be disposed across a plurality of the light-emitting elements 10. A planarization layer may be formed between the protective layer 14 and the microlenses 15 for the purpose of eliminating unevenness in the protective layer 14. A color filter may be disposed between microlens 15 and the protective layer 14 or between the microlens 15 and the planarization layer.
The microlenses 15 can be formed by an exposure and development process. Specifically, a film (a photoresist film) is formed from the material used to form the microlenses, and the photoresist film is exposed and developed using a mask in which the gradation changes continuously. A gray mask, or an area gradation mask that allow continuous gradation of light exposure on the image forming surface by varying the density distribution of dots formed from a light shielding film at a resolution less than or equal to that of the exposure device, can be used as the mask.
The lens shape can be adjusted by etching back the microlenses formed by the exposure and development process. The shape of the microlens may be spherical, or asymmetric in terms of the cross-sectional shape, as long as the shape is capable of refracting radiated light.
Effects of the present embodiment will be described next using the example of a light-emitting element having convex microlenses on the side opposite from the substrate. The effects of the present embodiment are independent of the direction of the convex shape of the microlenses. In other words, microlenses having a convex shape in the downward direction in the drawing, as illustrated in
In
On the other hand, ghost light is light that is emitted from a light-emitting element and passes through an optical path not intended by the design, and is observed as ghosting by the observer. In general, the optical path of ghost light is roughly determined by the positional relationship between the light-emitting elements of the display region 1 and the observer's pupil, as illustrated in
By disposing the microlens 15 and the light emission region 17 shifted by a given distance, it is possible not only to increase the luminous intensity of the normal light at the edges of the display region 1, but also to reduce ghost light at the same time.
Light is emitted from the light emission region 17 at an angle θ1 and is bent in the direction of an angle θ2 at a point A on the microlens 15. Here, the tilt of the normal line of the microlens surface at the point A relative to the normal line of the substrate 8 at this time is an angle α. Assuming that α+θ1 is β, the following Formula (1) is established, according to Snell's law.
1×sin(θ2+α)=n×sin β=n×sin(θ1+α) (1)
By solving Formula (1) for θ1, θ1 is expressed by Formula (2).
θ1=sin−1{sin(θ2+α)/n}−α (2)
As illustrated in
In order to effectively use the microlens 15 to the edge thereof, it is desirable that α<θ2 in the entire region of the microlens 15 with respect to the radiation angle θ2 of the main light rays of normal light.
Here, assume that AML is the amount of shift of the apex of the microlens 15 from the center of the light emission region 17. To increase the emission intensity at the desired emission angle θ2, θ1 and β satisfying the above Formula (2) may be calculated for a at each of points on the microlens 15, and ΔML may be set such that a light emission region X is present in either β direction. In other words, as the ratio of the light emission region X to the light emission region 17 illustrated in
On the other hand,
θ′1=sin−1{sin(θ2′+α′)/n}−α′ (3)
θ″1=sin−1{sin(θ2′+α″)/n}−α″ (4)
To reduce the emission intensity of the light at the emission angle θ2′, which is ghost light, it is desirable that light emission regions Y1 and Y2 do not overlap with the light emission region 17. Specifically, θ1′ and θ1″ obtained from Formulas (3) and (4) may be increased. This is because increasing θ1′ and θ1″ reduces the optical intensity of light emitted from the light-emitting element. When a given critical angle is exceeded, total reflection occurs internally and light does not reach the microlens.
In this manner, the shift amount ΔML may be determined such that the light emission region X from which normal light is emitted is large with respect to the light emission region 17, and the light emission regions Y1 and Y2 in which light is emitted in the direction that produces ghost light are small. In the present embodiment, the shape of the opening may be optimized as appropriate, and the shape may be circular, hexagonal, elliptical, or the like. For example, the shape of the opening in the light-emitting pixel may be formed such that X is larger and Y1 and Y2 are smaller.
As illustrated in
6.0°≤φ1≤37.5° (5)
A shift amount ΔCF of the color filter will be described next. When the organic layer 12 is constituted by a layer that emits white light, the color filter 20 may be provided between the light-emitting element 10 and the microlens 15, as illustrated in
0≤A≤0.85 (6)
On the other hand,
However, when a color filter is disposed above a microlens having a convex shape in the downward direction in the drawing, as illustrated in
In the present embodiment, the shift amount ΔML at each position in the display region 1 is adjusted as appropriate in accordance with the design of the ocular optical system.
As illustrated in
In an image observation apparatus having an ocular optical system, the value of the shift amount ΔML is designed such that the viewing angle characteristics at a horizontal edge 38 or a vertical edge 39 in
If light-emitting elements are not disposed in all the diagonal regions, the display region becomes an octagon (an n-polygon), as indicated by a region 44. If light-emitting elements are not disposed only in the diagonal regions 40 and 42, the display region becomes a hexagon constituted by regions 41, 43, and 44. As in
Alternatively, the shift amount ΔML of the microlens in the diagonal regions 40, 41, 42, and 43 (or 45, 46, 47, and 48) may be kept constant, and kept consistent with the shift amount at the edge 38 or the edge 39, so as not to exceed the shift amount ΔML of the microlens at the horizontal edge 38 and the vertical edge 39.
As described above, by shifting the light emission region 17 and the microlens 15 in the direction parallel to the main surface of the substrate 8 at the edge of the display region 1, the luminous intensity of the normal light of the ocular optical system, which bends the optical path, can be increased, and ghosting can be reduced.
Several embodiments illustrating that the above-described display element is effective in various ocular optical systems that bend the optical path will be described next. The first embodiment and a second embodiment describe examples of application in a polarizing optical system which uses polarized light. A third embodiment will describe an example of application in a freeform prism. In addition, desirable configurations of the ocular optical system that bends the optical path will also be described in each embodiment. Each of the embodiments described here is only a representative example, and many variations and changes can be made to each of the embodiments when carrying out the present invention.
The configuration of a display device according to the present embodiment will be described here.
The display device according to the present embodiment may have color filters with red, green, and blue colors. The color filters may be disposed with the red, green, and blue colors arranged in a delta array.
The display device according to the present embodiment may be used in a display unit of a mobile terminal. In this case, both a display function and an operation function may be provided. A mobile telephone such as a smartphone, a tablet, a head-mounted display, and the like can be given as examples of mobile terminals.
The display device according to the present embodiment may be used as a display unit in an image capturing device including an optical unit having a plurality of lenses and an image sensor that receives light passing through the optical unit. The image capturing device may have a display unit that displays information obtained by the image sensor. The display unit may be a display unit that is exposed to the exterior of the image capturing device, or a display unit disposed within a viewfinder. The image capturing device may be a digital camera or a digital video camera.
Because the optimal timing for capturing an image is very short, it is better to display the information as quickly as possible. It is therefore preferable to use a display device that uses the organic light-emitting element of the present invention. This is because organic light-emitting elements have a high response speed. In such devices which require high display speeds, a display device using an organic light-emitting element can be used more favorably than a liquid crystal display device.
The image capturing device 1100 includes an optical unit, which is not shown. The optical unit has a plurality of lenses, and an image is formed on the image sensor, which is contained within the housing 1104. The focal point can be adjusted by adjusting the relative positions of the plurality of lenses. This operation can also be performed automatically. The image capturing device may be called a photoelectric conversion device. Rather than sequentially capturing images, the photoelectric conversion device can include image capturing methods such as a method that detects a difference from a previous image, a method that cuts out from an image that is continuously recorded, and the like.
The frame 1301, as well as a base 1303 that supports the display unit 1302, are provided. The base 1303 is not limited to the form illustrated in
The frame 1301 and the display unit 1302 may also be curved. The curvature radius thereof may be at least 5000 mm and at most 6000 mm.
The lighting device is, for example, a device that illuminates a room. The lighting device may emit light which is white, daylight color, or any other color from blue to red. A dimming circuit that dims the light may be provided as well. The lighting device may have the organic light-emitting element of the present invention and a power supply circuit connected thereto. The power supply circuit is a circuit that converts AC voltage into DC voltage. White has a color temperature of 4200 K, and daylight color has a color temperature of 5000 K. The lighting device may have a color filter.
The lighting device according to the present embodiment may also have a heat dissipation unit. The heat dissipation unit dissipates heat from inside the device to outside the device, and a metal having a high specific heat, liquid silicon, and the like can be given as examples thereof.
The tail lamp 1501 may have the organic light-emitting element according to the present embodiment. The tail lamp may have a protective member that protects the organic EL element. The protective member may be formed from any material which has a certain degree of strength and is transparent, but is preferably formed from polycarbonate or the like. The polycarbonate may be mixed with a furandicarboxylic acid derivative, an acrylonitrile derivative, or the like.
The automobile 1500 may have a vehicle body 1503 and a window 1502 attached thereto. The window may be a transparent display, as long as that window is not used to check the front and rear of the automobile. The transparent display may have the organic light-emitting element according to the present embodiment. In this case, the materials constituting the electrodes and the like of the organic light-emitting element are constituted by transparent members.
The moving body according to the present embodiment may be a ship, an aircraft, a drone, or the like. The moving body may have a fuselage and a lighting fixture provided in the fuselage. The lighting fixture may emit light for indicating the position of the fuselage. The lighting fixture has the organic light-emitting element according to the present embodiment.
The eyeglasses 1600 are further provided with a control device 1603. The control device 1603 functions as a power supply that supplies power to the image capturing device 1602 and the display device according to the embodiments. The control device 1603 also controls the operations of the image capturing device 1602 and the display device. An optical system for focusing light onto the image capturing device 1602 is formed in the lens 1601.
The user's gaze with respect to the displayed image is detected from the captured image of the eyeball obtained from capturing the image of infrared light. Any publicly-known method can be used for the gaze detection using a captured image of the eyeball. For example, a gaze detection method based on a Purkinje image produced by the reflection of irradiation light at the cornea can be used.
More specifically, gaze detection processing is performed based on a pupil-corneal reflection method. Using the pupil-corneal reflection method, the user's gaze is detected by calculating a gaze vector, which represents the orientation (rotation angle) of the eyeball, based on an image of the pupil and a Purkinje image in the captured image of the eyeball.
A display device according to one embodiment of the present invention may have an image capturing device having a light-receiving element, and may control images displayed by the display device based on gaze information of the user from the image capturing device.
Specifically, based on the gaze information, a first visual field region at which the user gazes and a second visual field region outside the first visual field region are determined in the display device. The first visual field region and the second visual field region may be determined by the control device of the display device, or regions determined by an external control device may be received. In the display region of the display device, the display resolution of the first visual field region may be controlled to be higher than the display resolution of the second visual field region. In other words, the resolution of the second visual field region may be lower than that of the first visual field region.
Additionally, the display region has a first display region and a second display region that is different from the first display region, and a region having a higher priority is determined from the first display region and the second display region based on the gaze information. The first visual field region and the second visual field region may be determined by the control device of the display device, or regions determined by an external control device may be received. The resolution of the higher-priority region may be controlled to be higher than the resolution of regions aside from the higher-priority region. In other words, the resolution may be lowered for regions of relatively low priority.
Note that AI may be used to determine the first visual field region, the higher-priority region, and the like. The AI may be a model configured to estimate the angle of the gaze and a distance to an object being gazed upon from an image of an eyeball, using images of eyeballs and the directions in which the eyeballs in those images are actually gazing as supervisory data. An AI program may be held in the display device, in the image capturing device, or in an external device. If held in an external device, the program may be provided to the display device through communication.
When controlling the display based on gaze detection, the present invention can be preferably applied in smart glasses that further included an image capturing device that captures images of the exterior. The smart glasses can display the captured outside information in real time.
As described thus far, using a device which uses the organic light-emitting element according to the present embodiment makes it possible to achieve a stable display over long periods of time with good image quality.
An example in which the display element of the present embodiment is combined with an ocular optical system that bends the optical path will be described next.
Reference sign 108 indicates a right eye display element, and reference sign 109 indicates a left eye display element. Each of the display elements 108 and 109 are flat, plate-type display elements, and in the present embodiment, organic EL elements are used.
The ocular optical systems OR1 and OL1 project enlarged virtual images of the display image onto the right eye 102 and the left eye 103 of the observer by guiding light from the display elements 108 and 109 to the exit pupils ER1 and EL1, respectively. As a result, the observer can observe (a virtual image of) the display image displayed by the display elements 108 and 109 through the ocular optical systems OR1 and OL1.
In the present embodiment, the focal length of each ocular optical system is 12 mm, the horizontal display angle is 45°, the vertical display angle is 34°, and the diagonal display angle is 54°. An eye relief E1, which is a distance between the surface of each ocular optical system closest to the exit pupil side (the exit pupil-side surface of a polarization separation element 114, described later) and the exit pupil of the corresponding ocular optical system, is 18 mm.
The right eye and left eye ocular optical systems OR1 and OL1 in the present embodiment are optical systems which bend the optical path using polarized light, and the configurations thereof will be described using the right eye ocular optical system OR1. The same applies to the left eye ocular optical system OL1, and thus descriptions thereof will not be given.
As illustrated in
The polarizing plate 110, the first phase plate 111, the second phase plate 113, and the PBS 114 are all formed as flat plates. The polarization direction of first linearly-polarized light passing through the polarizing plate 110 is inclined by 45° with respect to the slow axis of the first phase plate 111, and the polarization direction of the first linearly-polarized light passing through the polarizing plate 110 is inclined by −45° with respect to the slow axis of the second phase plate 113 (i.e., by the same angle, but in the opposite direction from the slow axis of the first phase plate 111 with respect to the polarization direction of the first linearly-polarized light). The polarization direction of the first linearly-polarized light passing through the polarizing plate 110 and the polarization direction of second linearly-polarized light passing through the PBS 114 are orthogonal to each other.
Unpolarized light emitted from the right eye display element 108 passes through the polarizing plate 110 and becomes linearly-polarized light, which then passes through the first phase plate 111 to become circular polarized light, and then passes through the display lens 105. The circular polarized light then passes through the half mirror 112, the display lens 104, and the second phase plate 113, and becomes first linearly-polarized light as a result. This first linearly-polarized light has a polarization direction orthogonal to the polarization direction when passing through the PBS 114, and is therefore reflected by the PBS 114 and passes through the second phase plate 113 to become circular polarized light. This circular polarized light passes through the display lens 104 and is reflected by the half mirror 112, passes through the display lens 104 again, and then passes through the second phase plate 113 to become the second linearly-polarized light. The second linearly-polarized light has a polarization direction which matches the polarization direction when passing through the PBS 114, and thus passes through the PBS 114 and is guided to the exit pupil ER1 (the right eye 102). The light emitted from the left eye display element 109 is similarly guided to the exit pupil EL1 (the left eye 103) by the left eye ocular optical system OL1.
By configuring each ocular optical system to bend the optical path using polarized light in this manner, each ocular optical system can be made thinner in the optical axis direction, and the focal length of each ocular optical system can be shortened to enable the observation of images having a wide view angle.
It is desirable that the HMD is lightweight from the standpoint of being worn on the observer's head. As such, it is desirable that the display lenses constituting the ocular optical systems, an image capturing lens constituting an imaging optical system, and the like be made of a resin, which has a lower relative density than glass. Accordingly, in the present embodiment too, the display lenses 104 to 107 are resin lenses. The display lenses 104 and 106 furthest on the exit pupil side are plano-convex lenses having convex surfaces toward the display element side, and providing the half mirror 112 on the convex surfaces achieves a wide view angle while making the ocular optical systems thinner. Furthermore, the convex surfaces of the display lenses 104 and 106 are given an aspheric shape to increase an aberration correction effect. The display lenses 105 and 107 are double-sided aspheric lenses made of resin to increase the aberration correction effect.
However, the display lenses 105 and 107 have small outer diameters and little effect on the weight, and may therefore be glass lenses. The display lenses 104 and 106 may also be glass lenses as long as the weight of the HMD 101 as a whole is within a permissible range.
In the HMD 101 of the present embodiment, it is desirable that the eye relief E1 be at least 15 mm so as to be wearable even by an observer who is wearing glasses. However, if the eye relief is too long, the outer shape of the display lenses will become larger and increase the size of the HMD, and it is thus desirable that the eye relief be no greater than 25 mm. In other words, it is preferable that the eye relief E1 satisfies the following condition:
15 mm≤E1≤25 mm (7)
In the HMD 101 of the present embodiment, as illustrated in
In an ocular optical system having a long eye relief, a short focal length, and which is thin, as with the ocular optical system of the present embodiment, the light emission angle from the display element (display surface) is large at peripheral view angles among the display view angles. If the light emission angle from the display surface is large, viewing angle characteristics such as the display luminance and display chromaticity are reduced, and the observed image becomes darker, an image having the correct color cannot be observed, or the like.
In the right eye ocular optical system OR1, the light rays emitted from the right eye display element (display surface) 108 and passing through the center of the exit pupil ER1 (ER1′) of the ocular optical system OR1 are the main light rays. In this case, in the present embodiment, when the eyeball is facing the center of the display surface as illustrated in
The emission angle from the display surface is the normal direction (0°) of the substrate 8 at the center of the display element, and increases roughly linearly with respect to the display view angle (the position of the display element). The radiation direction is a direction tilted in the outward direction of the display element. Accordingly, it is desirable that the microlenses of the display element be disposed such that the shift amount ΔML of the microlenses at the center of the display element is 0, with ΔML increasing with proximity to the edges, as illustrated in
The occurrence of ghost light, which is unwanted light, in the ocular optical systems OR1 and OL1 of the present embodiment will be described next with reference to
In the ocular optical system OR1 which uses polarized light, as in the present embodiment, birefringence within the display lenses 104 and 105, the polarization characteristics of the polarizing plate 110, the phase plates 111 and 113, and the PBS 114, and the like result in the light emitted from the display element 108 being guided not long the normal optical path illustrated in
In the ghost light illustrated in
Birefringence in a lens generally increases from the center of the lens to the peripheral parts thereof, and thus the intensity of ghost light caused by birefringence in the lens also increases from the center of the lens to the peripheral part thereof. Reducing the brightness of light from the peripheral parts of the display surface is therefore effective for reducing ghost light passing through the peripheral parts of the lens. In the present embodiment, when the main light ray angle of the normal light in the forward viewing state at the edge of the display element is represented by Om and the radiation angle of the ghost light is represented by θg, it is desirable that the ocular optical system satisfies the following Formula (8).
|θm−θg|≥15° (8)
Effects achieved by combining the display element and the ocular optical system of the present embodiment will be described next. In the present embodiment, the organic EL element illustrated in
On the other hand, the results of the first working example show that the luminous intensity increases as the radiation angle relative to the normal light radiation direction increases, increasing to 0.85 at the radiation angle of 37° of normal light in the right edge viewing state. On the other hand, at the radiation angle of −11° of the ghost light in the forward viewing state, the value is significantly lower, at 0.32. In this manner, the luminous intensity of the normal light can be make higher than the luminous intensity in the direction of the ghosting. The increase in the luminous intensity of the normal light emission is due to the refraction of the light 27 incident on the surface 28, as indicated in
The effect of the numerical aperture of the light-emitting element will be described next. Table 3 shows the luminous intensity ΔL of normal light and ghost light for the first working example, a second working example, and a third working example, which are examples having varying numerical apertures. The normal light at a numerical aperture of 40% was 0.82, but was 0.85 at a numerical aperture of 30% and 0.91 at a numerical aperture of 20%. In this manner, reducing the numerical aperture increases the luminous intensity of the normal light. This is due to an increase in the ratio of the region X to the light emission region 17, as indicated in
The effect of the shift amount ΔCF for the color filters will be described next based on Table 4. Table 4 shows the color shift ΔE of the normal light and the luminous intensity ΔL of the ghost light when φ1 is fixed and φ2 is varied (when A is varied). Table 4 also shows the first comparative example as reference values.
The definition of the color shift ΔE is indicated by Formal (9), below and is the change in hue in an a*b* space. The references a0 and b0 here are the values at 0° in the first comparative example.
ΔE=√((a−a0)2+(b−b0)2) (9)
The color shift ΔE of normal light at A=0.84 was 20, but was 18 at A=0.43 and 17 at A=0 (no color filter shift). In other words, reducing the shift amount for the color filters reduces the color shift ΔE of the normal light. This drop in the color shift is due to light 33 radiated to the wide-angle side being blocked by the adjacent color filter, as illustrated in
The effects in the polarizing optical system illustrated in
In this manner, in the present embodiment, shifting the microlens with respect to the pixel makes it possible to reduce ghost light while improving viewing angle characteristics such as luminance and color shift at the peripheral parts of the observed image.
Birefringence in the lens is more likely to occur when the lens is manufactured by molding a resin material, with the difference in cooling between the thin parts and the thick parts of the lens during cooling after the molding increasing as the uneven thickness ratio of the lens increases, which in turn leads to an increase in birefringence.
The uneven thickness ratio of the display lens 104 having a reflective surface (half mirror 112) having the highest optical power increases in the ocular optical system OR1 having a wide view angle and a thin profile, as in the present embodiment. The uneven thickness ratio in the optically effective region of the display lens 104 is 2.0, and it is desirable that the uneven thickness ratio be at least 1.5 and at most 4. If the uneven thickness ratio is less than 1.5, the optical power of the display lens 104 will decrease, and the curvature radius or the thickness of the display lens 104 will increase. If the optical power of the display lens 104 decreases, it becomes impossible to achieve a wide view angle, or it becomes necessary to add a lens having a high optical power, which in turn makes it impossible to make the ocular optical system OR1 thinner. If the thickness of the display lens 104 increases, the ocular optical system OR1 cannot be made thinner. On the other hand, if the uneven thickness ratio is greater than 4, the birefringence of the display lens 104 will become too great, which increases the intensity of the ghost light. Note that the optical path of the normal light and the optical path of the ghost light in the ocular optical system differ in terms of the number of reflections within the ocular optical system.
If a thickness L1 of the ocular optical system OR1 is defined as the distance from the surface of the PBS 114 on the exit pupil side to the display element 108, the thickness L1 is 13 mm, and the ratio L1/E1 between the thickness L1 and eye relief E1, which is 18 mm, is 0.72. It is desirable that this value satisfies the condition
0.60≤L1/E1≤1.00 (10)
in order to achieve both an appropriate length for the eye relief and a thinner ocular optical system. If L1/E1 is lower than 0.60, the eye relief becomes too long, the outer diameter of the display lens becomes larger, and the HMD 101 also becomes larger, which is undesirable. Moreover, the birefringence of the display lens 104 increases with the outer diameter, which increases the intensity of ghost light. On the other hand, if L1/E1 is greater than 1.00, the ocular optical system becomes thicker, making the HMD 101 larger; furthermore, the eye relief becomes too short, giving the observer a sense of oppression or making it impossible for an observer wearing glasses to wear the HMD, which is undesirable.
In the present embodiment, a maximum diagonal half-view angle θ1 of the ocular optical system OR1 is 27°. In this case, E1×tan θ1=9.2 mm. It is desirable that this value satisfies the condition
8 mm≤E1×tan θ1≤20 mm (11)
in order to achieve both an appropriate length for the eye relief and a wider view angle in the ocular optical system. If E1×tan θ1 is lower than 8 mm, the eye relief becomes too short, giving the observer a sense of oppression or making it impossible for an observer wearing glasses to wear the HMD, which is undesirable. The display view angle of the ocular optical system also becomes too narrow, and thus natural images having a sense of presence cannot be observed. On the other hand, if E1×tan θ1 is higher than 20 mm, the eye relief becomes too long, the outer diameter of the display lens 104 becomes larger, and the HMD 101 also becomes larger, which is undesirable. Moreover, the birefringence of the display lens 104 increases with the outer diameter, which increases the intensity of ghost light. Furthermore, the display view angle becomes too wide, causing the emission angle of the main light rays from the display surface to increase at peripheral view angles, which worsens the viewing angle characteristics.
A polarizing plate may be disposed between the PBS 114 and the exit pupil of each ocular optical system to reduce ghost light caused by ambient light and increase the contrast of the image being observed.
Furthermore, in the present embodiment, as illustrated in
The first and second phase plates 111 and 113 in the present embodiment are waveplates having a phase difference of λ/4, but the phase difference may be shifted from λ/4 to cancel out the birefringence of the lens 104 and lens 105. In this case, it is desirable that the sum of the phase difference between the lens 104 and the phase plate 113 be at least 3λ/20 and at most 7λ/20. Additionally, it is desirable that the sum of the phase difference between the lens 105 and the first phase plate 111 be at least 3λ/20 and at most 7λ/20. Outside this range, the intensity of ghost light increases, making natural observation impossible. The conditions indicated by Formulas (5) to (7), (10) and (11) described in the present embodiment are the same in the second embodiment described below.
At least one additional one of a second half mirror, a third phase plate, a second PBS, and a fourth phase plate may be disposed between the first phase plate 111 and the half mirror 112. When disposing a second half mirror, an additional convex surface may be formed in the direction of the display element side, and the second half mirror may be provided on that convex surface.
The third phase plate or the fourth phase plate may be used as a variable phase plate by applying an electrical signal. For example, the phase difference of the phase plate may be switched so that when on, the half mirror 112 is in a polarization state where normal light is reflected by the half mirror 112, and when off, the phase plate is in a polarization state where normal light is reflected by the second half mirror. The phase plate may also be used as a foveated display that time-division multiplexes high-resolution video for the center of the field of view and low-resolution video for the peripheral field of view by switching in this manner.
A variable focus lens may be disposed inside or outside the half mirror 112 and the PBS 114. Variable focus lenses can be glass lenses, polymer lenses, liquid crystal lenses, or a combination thereof. The liquid crystal lens may be a Fresnel liquid crystal lens having a segmented parabolic phase shape, a Pancharatnum-Berry phase lens, or a combination thereof. Multiple Pancharatnum-Berry phase lenses may be layered. An additional phase plate that can be switched on and off by applying an electrical signal may be disposed on the Pancharatnum-Berry Phase lens, and multiple alternating layers of Pancharatnum-Berry phase lenses and phase plates may be used.
The preferred lens materials, shapes, and the like described in the present embodiment also apply to the second embodiment.
Reference sign 208 indicates a right eye display element, and reference sign 209 indicates a left eye display element. Each of the display elements is flat, plate-type display elements, and in the present embodiment, organic EL elements are used.
The ocular optical systems OR2 and OL2 project enlarged virtual images of a display image displayed by the display elements 208 and 209 (an original image) onto the right eye 202 and the left eye 203 of the observer by guiding light from the display elements 208 and 209 to the exit pupils ER2 and EL2, respectively. As a result, the observer can observe (a virtual image of) the display image displayed by the display elements 208 and 209 through the ocular optical systems OR2 and OL2.
In the present embodiment, the focal length of each ocular optical system is 13 mm, the horizontal display angle is 60°, the vertical display angle is 60°, and the diagonal display angle is 78°. An eye relief E2, which is a distance between the surface of each ocular optical system closest to the exit pupil side (the exit pupil-side surface of a polarization separation element 214, described later) and the exit pupil of the corresponding ocular optical system, is 20 mm.
As in the first embodiment, the right eye and left eye ocular optical systems OR2 and OL2 in the present embodiment are optical systems which bend the optical path using polarized light, and the configurations thereof will be described using the right eye ocular optical system OR2. As illustrated in
The polarizing plate 210, the first phase plate 211, the second phase plate 213, and the PBS 214 are all formed as flat plates. The polarization direction of first linearly-polarized light passing through the polarizing plate 210 is inclined by 45° with respect to the slow axis of the first phase plate 211, and the polarization direction of the first linearly-polarized light passing through the polarizing plate 210 is inclined by −45° with respect to the slow axis of the second phase plate 213. The polarization direction of the first linearly-polarized light passing through the polarizing plate 210 and the polarization direction of second linearly-polarized light passing through the PBS 214 are orthogonal to each other.
Unpolarized light emitted from the right eye display element 208 passes through the polarizing plate 210 and becomes linearly-polarized light, which then passes through the first phase plate 211 to become circular polarized light, and then passes through the display lens 205. The circular polarized light then passes through the half mirror 212, the display lens 204, and the second phase plate 213, and becomes first linearly-polarized light as a result. This first linearly-polarized light has a polarization direction orthogonal to the polarization direction when passing through the PBS 214, and is therefore reflected by the PBS 214 and passes through the second phase plate 213 to become circular polarized light. This circular polarized light passes through the display lens 204 and is reflected by the half mirror 212, passes through the display lens 204 again, and then passes through the second phase plate 213 to become the second linearly-polarized light. The second linearly-polarized light has a polarization direction which matches the polarization direction when passing through the PBS 214, and thus passes through the PBS 214 and is guided to the exit pupil ER2 (the right eye 202). The light emitted from the left eye display element 209 is similarly guided to the exit pupil EL2 (the left eye 203) by the left eye ocular optical system OL2.
In the present embodiment, as in the first embodiment, by configuring each ocular optical system to bend the optical path using polarized light, each ocular optical system can be made thinner, and the focal length of each ocular optical system can be shortened to enable the observation of images having a wide view angle.
In the present embodiment, two display lenses are joined in each ocular optical system to reduce the thickness thereof in the optical axis direction to 13.5 mm. Furthermore, as mentioned above, 20 mm is ensured as the eye relief E2 of the ocular optical system. Joining the two display lenses into a joined lens makes it easier for the body of the HMD 201 to hold the display lenses.
In the present embodiment too, the display lenses 204 to 207 are resin lenses, and furthermore, the display lenses 204 to 207 are aspherical lenses to enhance the aberration correction effect.
Additionally, because the display lenses 204 and 205 are joined lenses, the half mirror 212 may be provided on the surface of the display lens 205 on the exit pupil side thereof. Even in this case, the surface on which the half mirror is provided is convex in the direction of the display element 208.
In the HMD 201 of the present embodiment, as illustrated in
In the right eye ocular optical system OR2, the light rays emitted from the right eye display element (display surface) 208 and passing through the center of the exit pupil ER2 (ER2′) of the ocular optical system OR2 are the main light rays. In this case, in the present embodiment, as illustrated in
The emission angle from the display surface is the normal direction (0°) of the substrate at the center of the display element, and increases roughly linearly with respect to the display view angle. The radiation direction is a direction tilted in the outward direction of the display element 208. Accordingly, it is desirable that the microlenses of the display element of the present embodiment be disposed such that the shift amount ΔML of the microlenses at the center of the display element is 0, with ΔML increasing with proximity to the edges, as illustrated in
In the ocular optical systems OR2 and OL2 of the present embodiment, ghost light is produced for the same reason as in the first embodiment. As illustrated in
Effects achieved by combining the display element and the ocular optical system of the present embodiment will be described next. The characteristics in the right edge viewing state at the horizontal edge position of the display element will be described, as mentioned above. Here, as in the first embodiment, the organic EL element illustrated in
Table 5 shows the radiation angle dependence of a relative luminance ΔL in a first comparative example and a sixth working example. The first comparative example is a configuration in which the shift amount for the microlenses is 0. The sixth working example is a configuration in which the microlenses are shifted, and the values of the numerical aperture, φ1, φ2, and A are shown in Table 5. Referring to
This is because, as illustrated in
On the other hand, the results of the sixth working example show that the luminous intensity increases with progress toward the radiation direction of normal light, increasing to 0.65 at the radiation angle of 47° of normal light in the right edge viewing state. On the other hand, at the radiation angle of −15° of the ghost light in the forward viewing state, the value is significantly lower, at 0.23. In this manner, the luminous intensity of the normal light can be made higher than the luminous intensity in the direction of the ghosting. The increase in the luminous intensity of the normal light emission is due to the refraction of the light 27 incident on the surface 28, as indicated in
The effect of the numerical aperture of the light-emitting element will be described next. Table 6 shows the luminous intensity ΔL of normal light and ghost light for sixth to eighth working examples, which are examples having varying numerical apertures. The normal light at a numerical aperture of 40% was 0.71, but was 0.75 at a numerical aperture of 30% and 0.94 at a numerical aperture of 20%. In this manner, reducing the numerical aperture increases the luminous intensity of the normal light. This is due to an increase in the ratio of the region X to the light emission region 17, as indicated in
Table 7 shows the effect of the color filter shift amount ΔCF. Table 7 shows the color shift ΔE of the normal light and the luminous intensity ΔL of the ghost light when φ1 is fixed and φ2 is varied (when A is varied). Table 7 also shows the first comparative example as reference values.
The color shift ΔE of normal light at A=0.64 was 31, but was 28 at A=0.33 and 25 at A=0 (no color filter shift). In other words, reducing the shift amount for the color filters reduces the color shift ΔE of the normal light. In addition, the sixth, ninth, and tenth working examples satisfy Formula (6) and therefore have a lower color shift ΔE than in the first comparative example. This drop in the color shift is due to light 33 radiated to the wide-angle side being blocked by the adjacent color filter, as illustrated in
When the maximum display view angle is greater than 60°, the wide view angle makes it difficult for the observer to recognize the peripheral parts of the image when in the forward viewing state. Accordingly, it is preferable to determine the shift amount of the color filter by assuming the emission angle of the main light rays from the display surface in the direction the viewer is looking when looking at the peripheral parts of the image, rather than when in the forward viewing state. However, depending on the lens design, light may be vignetted at the edges of the display element, and it is therefore not absolutely necessary to align with the edges.
In the present embodiment too, the uneven thickness ratio of the display lens 204 having a reflective surface (half mirror 212) having the highest optical power increases in the right eye ocular optical system OR2 having a wide view angle and a thin profile. The display lenses 204 and 205 are joined, and thus the curvature radius of the joined surface of the display lens 205 with the display lens 204 is short, and the uneven thickness ratio of the display lens 205 is also large. In the present embodiment, the uneven thickness ratio in the optically effective region of the display lens 204 is 3.6, and the uneven thickness ratio in the optically effective region of the display lens 205 is 2.8. As described in the first embodiment, it is desirable that the uneven thickness ratio be at least 1.5 and at most 4.
If a thickness L2 of the right eye ocular optical system OR2 is defined as the distance from the surface of the PBS 214 on the observer's right eye 202 side to the right eye display element 208, the thickness L2 is 13.5 mm, and the ratio L2/E2 between the thickness L2 and the eye relief E2 is 0.68. It is desirable that this value be at least 0.6 and at most 1 to achieve both an appropriate eye relief length and a thinner ocular optical system.
In the present embodiment, the eye relief E2 of the right eye ocular optical system OR2 is 20 mm, and a maximum diagonal half-view angle θ2 is 39°. In this case, E2×tan θ2=16.2 mm, which satisfies the condition of Formula (11). The uneven thickness ratio, L2/E2, and E2×tan θ2 are the same for the left eye ocular optical system OL2.
In the present embodiment too, a polarizing plate may be disposed between the PBS 214 and the exit pupil of each ocular optical system to reduce ghost light caused by ambient light and increase the contrast of the image being observed.
The configuration of an HMD 301 according to a third embodiment will be described next.
The right eye ocular optical system 304 magnifies and projects an original image displayed by the right eye image display element 306 and guides the image to the observer's right eye 302, while the left eye ocular optical system 305 magnifies and projects an original image displayed by the left eye image display element 307 and guides the image to the observer's left eye 303. The horizontal display angle for the right eye ocular optical system 304 and the left eye ocular optical system 305 is 40°, the vertical display angle is 30°, and the diagonal display angle is 50°.
As illustrated in
The light rays from the right eye image display element 306 are reflected twice in the right eye ocular optical system 304, and are guided to the right eye 302. The emission surface to the eye in the right eye ocular optical system 304 is an optical surface having reflection and transmission effects, and it is therefore desirable that the reflection be total internal reflection to eliminate light intensity loss. In addition, by making the surface constituting the right eye ocular optical system 304 a freeform surface shape, the degree of freedom for eccentric aberration correction is increased, which enables image display with good image quality. The same applies to the left eye ocular optical system 305.
Similar to the first embodiment and the second embodiment, the ocular optical system of the present embodiment has a large emission angle from the image display element at peripheral view angles, and there is thus a risk that the viewing angle characteristics will deteriorate at the peripheral parts, resulting in reduced luminance and making it impossible to observe images with correct colors.
In the ocular optical system of the present embodiment, the emission angle of the main light rays from the image display element is 20° at a maximum peripheral view angle of 20° in the horizontal direction when the observer is looking forward, as illustrated in
The radiation direction is a direction tilted in the outward direction of the display element. Accordingly, it is desirable that the microlenses of the display element of the present embodiment be disposed such that the shift amount ΔML of the microlenses at the center of the display element is 0, with ΔML increasing with proximity to the edges, as illustrated in
In the case the ocular optical system of the present embodiment, ghost light is produced in optical paths such as those illustrated in
Effects achieved by combining the display element and the ocular optical system of the present embodiment will be described next. The characteristics in the lower edge viewing state at the vertical position of the display element will be described, as mentioned above. Here, as in the first embodiment, the organic EL element illustrated in
Table 8 shows the radiation angle dependence of a relative luminance ΔL in a first comparative example and an 11th working example. The first comparative example is a configuration in which the shift amount for the microlenses is 0. The 11th working example is a configuration in which the microlenses are shifted, and the values of the numerical aperture, φ1, φ2, and A are shown in Table 8. Referring to
On the other hand, the results of the 11th working example show that the luminous intensity increases with progress toward the radiation direction of normal light, increasing to 1.0 at the radiation angle of 22.5° of normal light in the right edge viewing state. On the other hand, at the radiation angle of −34° of the ghost light in the forward viewing state, the value is significantly lower, at 0.23. In this manner, the luminous intensity of the normal light can be make higher than the luminous intensity in the direction of the ghosting. The increase in the luminous intensity of the normal light emission is due to the refraction of the light 27 incident on the surface 28, as indicated in
The effect of the numerical aperture of the light-emitting element will be described next. Table 9 shows the luminous intensity ΔL of normal light and ghost light for 11th to 13th working examples, which are examples having varying numerical apertures. The normal light at a numerical aperture of 40% was 0.93, but was 0.94 at a numerical aperture of 30% and 1.00 at a numerical aperture of 20%. In this manner, reducing the numerical aperture increases the luminous intensity of the normal light. This is due to an increase in the ratio of the region X to the light emission region 17, as indicated in
Table 10 shows the effect of the color filter shift amount ΔCF. Table 10 shows the color shift ΔE of the normal light and the luminous intensity ΔL of the ghost light when φ1 is fixed and φ2 is varied (when A is varied). Table 10 also shows the first comparative example as reference values.
The color shift ΔE of normal light at A=0.63 is 7, but is 6 for A=0.00 (without shifting the color filters). In other words, reducing the shift amount for the color filters reduces the color shift ΔE of the normal light. In addition, the 11th working example and the 14th working example satisfy Formula (6), and thus the color shift ΔE is smaller than that in the first comparative example. This drop in the color shift is due to light 33 radiated to the wide-angle side being blocked by the adjacent color filter, as illustrated in
In this manner, in the present embodiment, shifting the microlens with respect to the pixel makes it possible to reduce ghost light while improving viewing angle characteristics such as luminance and color shift at the peripheral parts of an image observed with an ocular optical system using a freeform prism.
Although the freeform prism of the ocular optical system in the above-described embodiment is an optical system which does not have an intermediate image forming surface, an optical system having an intermediate image forming surface may be used as well. Additionally, a freeform prism may also be used as an optical element that couples the display surface of the display element to a waveguide combiner.
According to the present invention, ghosting can be reduced while improving the viewing angle characteristics at peripheral view angles of an ocular optical system configured to bend an optical path.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-069268 | Apr 2021 | JP | national |
This application is a Continuation of International Patent Application No. PCT/JP2022/014130, filed Mar. 24, 2022, which claims the benefit of Japanese Patent Application No. 2021-069268, filed Apr. 15, 2021, both of which are hereby incorporated by reference herein in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2022/014130 | Mar 2022 | US |
| Child | 18477623 | US |
