Display optical system and display device

Abstract

To suppress a magnification fluctuation of a display image in a focus adjustment.SOLUTION: A display optical system 1000 introduces display light from a display surface of a display element 1400 to a pupil surface SP. The display optical system includes, sequentially arranged from a pupil surface side to a display surface side, a first transmission reflection surface A and a second transmission reflection surface C. The display device changes an interval between the first transmission reflection surface and the second transmission reflection surface, so as to perform a focus adjustment within a range from a first diopter to a second diopter as a diopter on the pupil surface. If a focal distance of the display optical system including the first diopter and a focal distance of the display optical system including the second diopter are ft[D1] and ft[D2], respectively, a condition 0.97≤ft[D2] / ft[D1]≤1.03 is satisfied.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a display optical system suitable for a display device such as a head-mounted display (HMD). [Background technology]

[0002] As an example of such a display optical system, Patent Document 1 discloses one in which focus adjustment is performed by shifting a lens or a display element. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6494752 Summary of the Invention [Problem to be solved by the invention]

[0004] In the display optical system disclosed in Patent Document 1, the magnification of the displayed image changes when the focus is adjusted. [Means for solving the problem]

[0005] A display optical system according to one aspect of the present invention guides display light from a display surface of a display element to a pupil plane. The display optical system includes a first transmissive-reflective surface and a second transmissive-reflective surface, arranged in this order from the pupil plane side to the display surface side. By changing the distance between the first transmissive-reflective surface and the second transmissive-reflective surface, focus adjustment can be performed within a range of diopters on the pupil plane from the first diopter to the second diopter. When focus adjustment is performed, the focal lengths of the display optical system including the first diopter and the second diopter are defined as ft[D1] and ft[D2], respectively. 0.97≦ft[D2] / ft[D1]≦1.03 The display device having the above-described display optical system also constitutes another aspect of the present invention. [Effects of the Invention]

[0006] According to the present invention, it is possible to suppress fluctuations in the magnification of a displayed image during focus adjustment. [Brief explanation of the drawings]

[0007] [Figure 1] 3A and 3B are a cross-sectional view and an aberration diagram of the display optical system of the first embodiment when not adjusted. [Figure 2] 1A and 1B are partial enlarged views of Example 1, and are diagrams showing the relationship between the light-emitting position on a display element and the output angle, and the optical path. [Figure 3] 4A and 4B are a cross-sectional view and aberration diagrams of the display optical system of Example 1 during −4D adjustment. [Figure 4] 4A and 4B are a cross-sectional view and aberration diagrams of the display optical system of Example 1 during −5D adjustment. [Figure 5] 10A and 10B are a cross-sectional view, an aberration diagram, and an explanatory diagram of a main part of the display optical system of Example 2 when not adjusted. [Figure 6] FIG. 10 is a diagram showing an optical path of a display optical system according to a second embodiment. [Figure 7] 10A and 10B are a cross-sectional view and aberration diagrams of the display optical system of Example 2 during −4D adjustment. [Figure 8] 10A and 10B are cross-sectional views and aberration diagrams of the display optical system of Example 2 when adjusted to −5D. [Figure 9] FIG. 1 is a perspective view of an HMD equipped with the display optical systems of the first and second embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, before describing the first and second embodiments in detail, matters common to the first and second embodiments will be described.

[0009] The display optical system in each embodiment is provided for the right eye and the left eye in the HMD as a display device, and guides display light from the display surface of the display element to the pupil plane, thereby enlarging the original image displayed on the display surface and displaying the enlarged image.

[0010] Among the display optical systems in each embodiment, the first-class optical system has two transmissive-reflective surfaces (a first transmissive-reflective surface and a second transmissive-reflective surface) that function as both transmissive and reflective surfaces, arranged in this order from the pupil plane side to the display surface side. The second-class optical system has a first optical system (pupil plane-side optical system), a second optical system (transmissive-reflective optical system), and a third optical system (panel-side optical system), arranged in this order from the pupil plane side to the display surface side. The second optical system includes two transmissive-reflective surfaces (a first transmissive-reflective surface and a second transmissive-reflective surface) and is an optical system sandwiched between them. The first optical system is an optical system sandwiched between the pupil plane and the first transmissive-reflective surface. The third optical system is an optical system sandwiched between the second transmissive-reflective surface and the display element. The first optical system and the third optical system may not exist.

[0011] In such a display optical system, focus adjustment (convergence adjustment: hereinafter also referred to as VAC adjustment) is required to resolve a vergence-accommodation conflict, which is a mismatch between the convergence position of both eyes and the focus position. However, if the magnification of the displayed image fluctuates due to VAC adjustment, which is performed frequently in response to changes in the displayed image or the observer's point of gaze, the observer will feel uncomfortable. In this case, it is possible to suppress the fluctuating magnification of the displayed image by performing image processing on the displayed image (original image). However, performing image processing frequently increases the load of calculation processing. Furthermore, if the load of calculation processing increases, defects will appear in the displayed image and the resolution of the displayed image will deteriorate. The display optical system of each embodiment solves this problem.

[0012] The display optical systems of the first and second embodiments will be specifically described below. [Example]

[0013] 1A shows the configuration of a display optical system 1000 for one eye used in an HMD, which is a display optical system according to Example 1. The display optical system 1000 has a pupil plane side optical system (first optical system) 1100 and a transmission / reflection optical system (second optical system) 1200.

[0014] The pupil plane side optical system 1100 has a first lens 1101 as a first optical element, and the transmission / reflection optical system 1200 has a second lens 1201 as a second optical element. In this way, the pupil plane side optical system 1100 and the transmission / reflection optical system 1200 each have one optical element (1101, 1201) that refracts, reflects, or diffracts light rays.

[0015] 2(A) shows an enlarged view of a portion of the display optical system 1000. The first lens 1101 has three optical surfaces, and the second lens 1201 has two optical surfaces. The optical surfaces of the first lens 1101 are referred to as the R1 surface, the R2 surface, and the R3 surface from the pupil plane side. The optical surfaces of the second lens 1201 are referred to as the R1 surface and the R2 surface from the pupil plane side.

[0016] The R2 surface of the first lens 1101 is a diffractive surface formed on a flat base surface, and the R3 surface is a curved surface. The R1 surface is a flat surface formed by applying a resin material to the R2 surface. The R1 and R2 surfaces of the second lens 1201 are both curved surfaces.

[0017] Display light from the panel unit 1400 including the display element is reflected once each by the first transmission-reflection surface and the second transmission-reflection surface of the transmission-reflection optical system 1200, passes through the transmission-reflection optical system 1200, and then passes through the pupil-plane-side optical system 1100 toward the pupil plane SP. This allows the viewer to view a virtual image (display image) of the original image displayed on the display element through their eye, which is located at the pupil plane SP where the exit pupil of the display optical system 1000 is located. At this time, light that follows the optical path for forming the display image is referred to as display light, and the rest is referred to as unwanted light. Furthermore, in this embodiment (and other embodiments described below), the pupil plane SP is the position of the entrance pupil of the viewer's eye, not the vertex of the cornea of ​​the eye.

[0018] FIG. 1B shows the longitudinal aberrations (spherical aberration, astigmatism, distortion, and chromatic aberration) of the display optical system 1000 in this embodiment when the eye relief is 12 mm and a virtual image is displayed at infinity from the pupil plane SP. The eye relief is the distance on the optical axis (hereinafter simply referred to as on-axis) from the pupil plane SP to the lens surface of the pupil-plane-side optical system 1100 closest to the pupil plane. The longitudinal aberrations shown here are those observed by an eye with 0 D (diopters) of visual acuity. The maximum half angle of view is assumed to be 50°. Furthermore, FIG. 1B shows the longitudinal aberrations when the panel unit 1400 is used as the image plane in the reverse optical path (reverse tracing) from the pupil plane SP to the panel unit 1400, rather than the forward optical path (forward tracing) from the panel unit 1400 to the pupil plane SP. The longitudinal aberrations in the reverse tracing correspond to the longitudinal aberrations in the forward tracing.

[0019] In the spherical aberration diagrams, Fno indicates the F-number, the solid line indicates the spherical aberration at the reference wavelength, the d-line (wavelength 587.6 nm), the two-dot chain line indicates the spherical aberration at the g-line (wavelength 435.8 nm), and the one-dot chain line indicates the spherical aberration at the C-line (wavelength 656.3 nm). In the astigmatism diagrams, the solid line S indicates the astigmatism at the sagittal image plane, and the dashed line M indicates the astigmatism at the meridional image plane. The distortion aberration diagrams show the distortion aberration at the d-line. The chromatic aberration diagrams show the chromatic aberration of magnification at the g-line and C-line. These aberration diagrams show that the display optical system 1000 of this embodiment has good imaging performance.

[0020] Furthermore, the specifications of the polarizing elements, such as the polarizing plate, quarter-wave plate, and polarization-selective transmission / reflection element, which will be described later, are uniformly set to a thickness of 0.5 mm, a refractive index at the d-line of 1.52, and an Abbe number based on the d-line of 64, but the actual specifications may differ from these.

[0021] 2(C) shows the direction and polarization state of display light passing through each surface in the display optical system 1000. The panel unit 1400 has a display element (light modulation element) such as a liquid crystal display element or an organic EL element, a polarizing plate E, and a second quarter-wave plate D. The shape of the display element is a square with a diagonal of 1.6 inches (each side is 28.7 mm). The display element, polarizing plate E, and second quarter-wave plate D are arranged close to each other in this order toward the pupil plane.

[0022] The display light emitted from the display element as unpolarized light is converted into linearly polarized light by the polarizing plate E. This linearly polarized light is then converted into circularly polarized light by the second quarter-wave plate D, and the circularly polarized light is directed toward the transmission / reflection optical system 1200. The polarizing plate E may be configured integrally with the display element. For example, many liquid crystal display elements include a polarizing plate in their configuration, and polarizing plates are sometimes used in organic EL elements for the purpose of anti-reflection. In this case, the light emitted from the display element becomes linearly polarized. In this case, there is no need to provide a separate polarizing plate E.

[0023] The transmission-reflection optical system 1200 has a transmission-reflection film (half mirror) C as a second transmission-reflection member having a second transmission-reflection surface, a first quarter-wave plate B, a second lens 1201, and a polarization-selective transmission-reflection element A as a first transmission-reflection member having a first transmission-reflection surface.

[0024] The transflective film C is formed of a dielectric multilayer film or a metal film, and is vapor-deposited on the R2 surface of the second lens 1201. The first quarter-wave plate B is arranged so that its slow axis is inclined at 90° with respect to the slow axis of the second quarter-wave plate D, and is also inclined at 45° with respect to the polarization transmission axis of the polarizing plate E. The first quarter-wave plate B is adhered to the R1 surface of the second lens 1201.

[0025] The polarization-selective transmission-reflection element A is an element that reflects linearly polarized light in the same polarization direction as when it passed through the polarizing plate E and transmits linearly polarized light in a polarization direction perpendicular to the polarized light, and is configured, for example, by a wire grid polarizer or a laminated birefringent film polarizer. An example of a wire grid polarizer is the "WGF" manufactured by Asahi Kasei Corporation, and the wire grid-formed surface functions as the transmission-reflection surface. In this example, the polarization-selective transmission-reflection element A is bonded to the R2 surface of the first lens 1101 of the pupil plane-side optical system 1100.

[0026] Each transmissive-reflective member includes a transmissive-reflective surface, is an integral member with the transmissive-reflective surface, has almost no refractive power, and is primarily responsible for optical functions other than refraction (such as absorption according to the polarization state, change in the polarization state, and anti-reflection) and mechanical functions (such as adhesion and protection). In this embodiment, the polarization-selective transmissive-reflective element A corresponds to the first transmissive-reflective member, and the transmissive-reflective film C corresponds to the second transmissive-reflective member. Each transmissive-reflective member may be composed of a series of members with multiple functions. The thickness of the transmissive-reflective member is 0.5 mm or less or 1 mm or less. Because the transmissive-reflective film C is a thin film, it is omitted from the figures and from the numerical examples described below.

[0027] The display light incident on the transflective film C passes through it and is converted by the first quarter-wave plate B into linearly polarized light with the same polarization direction as when it passed through the polarizer E, and then incident on the polarization-selective transflective element A. This linearly polarized light is reflected by the polarization selectivity of the polarization-selective transflective element A. The display light reflected by the polarization-selective transflective element A is converted by the first quarter-wave plate B into circularly polarized light with the same rotation as when it was first converted into circularly polarized light by the second quarter-wave plate D, and then incident on the transflective film C, where it is reflected.

[0028] The display light reflected by the transflective film C becomes circularly polarized light in the opposite direction to the light before reflection, enters the first quarter-wave plate B again, and is converted into linearly polarized light with a polarization direction perpendicular to the polarization direction when the light first passed through the polarizer E, and then enters the polarization-selective transflective element A. This linearly polarized light is transmitted by the polarization-selective transflective element A and directed to the pupil plane SP. In this way, the display optical system 1000 employs a triple-path design that folds the optical path twice, thereby enabling it to display a sufficiently enlarged display image despite its compact configuration.

[0029] [VAC Adjustment (Congestion Adjustment)] By providing parallax to the displayed image observed through display optical systems provided for each of the observer's left and right eyes, the observer can experience a sense of three-dimensionality. The gaze points of both eyes (the convergence position of the line of sight) differ depending on whether the observer directs their gaze in front of or behind the displayed image, but if the display optical system does not have a focus adjustment mechanism, the focus positions of both eyes will remain unchanged. If the convergence position and the focus positions of each eye do not match, this is undesirable as it causes fatigue and discomfort to the observer. For this reason, it is desirable to be able to perform VAC adjustment, which is a focus adjustment that matches the displayed image and the convergence position.

[0030] In VAC adjustment, the amount by which the focus position is corrected (focus adjustment amount) changes depending on the displayed image and the observer's point of gaze, which can change rapidly, so automatic adjustment is necessary.The adjustment range of VAC adjustment, from infinity (equivalent to 0D) to the 250mm position (equivalent to -4D), is sufficient for VAC adjustment in response to changes in the normal displayed image and the observer's point of gaze.

[0031] When a focus adjustment mechanism that drives an optical element is employed, it is preferable to reduce the drive amount of the optical element in order to perform focus adjustment at high speed. To this end, the VAC adjustment mechanism changes the distance (first distance) between the two transmissive-reflective surfaces. This makes it possible to utilize the return of the optical path and obtain a large focus adjustment amount with a small drive amount. A focus adjustment mechanism that does not change the distance between the two transmissive-reflective surfaces requires a large drive amount to obtain the same focus adjustment amount. As a result, in order to perform focus adjustment at high speed, the VAC adjustment mechanism needs to be enlarged, which undesirably leads to increased weight and power consumption.

[0032] [Configuration of this Example] In this embodiment, a VAC adjustment mechanism is provided as an automatic adjustment mechanism that automatically drives the second lens 1201 having a second transmissive-reflective surface (transmissive-reflective film C) to adjust the focus, and it is possible to perform VAC adjustment in response to changes in the displayed image or the observer's point of gaze.

[0033] Figure 3(A) shows the optical path of the display optical system 1000 when VAC adjustment is performed at the 250 mm position (equivalent to -4D) (when adjusted to -84), and Figure 3(B) shows the aberration diagram at that time. These figures show that even when VAC adjustment is performed, sufficiently good imaging performance is obtained.

[0034] In this way, by providing a VAC adjustment mechanism that adjusts the distance between the first transmission-reflection surface and the second transmission-reflection surface, it is possible to perform VAC adjustment.

[0035] As shown in Figure 2(A), the light-emitting position y on the display element of the display light with a half angle of view θ toward the pupil plane SP changes during focus adjustment. That is, the magnification of the displayed image fluctuates during focus adjustment. To prevent the displayed image from appearing unnatural without performing the aforementioned calculation processing, it is advisable to limit the fluctuating magnification of the displayed image to within ±3%, preferably ±2%. The light-emitting position y is approximately proportional to the focal length ft of the entire display optical system 1000, including the diopter on the pupil plane.

[0036] The focal lengths ft of the entire display optical system 1000 including the diopters when not adjusted (in the case of the first diopter D1) and when adjusted to -4D (in the case of the second diopter D2) are respectively ft[0D] (= ft[D1]) and ft[-4D] (= ft[D2]). 0.97≦ft[-4D] / ft[0D]≦1.03 It is preferable that the following conditions are satisfied: 0.98≦ft[-4D] / ft[0D]≦1.02 It is desirable to satisfy the following conditions:

[0037] Furthermore, it is more desirable to suppress the fluctuation in the magnification of the displayed image to within ±1.0%. 0.99≦ft[-4D] / ft[0D]≦1.01 It is more desirable to satisfy the conditions below.

[0038] In this embodiment, ft[0D]=19.026mm ft[-4D]=18.959mm Therefore, ft[-4D] / ft[0D]=0.996 and the above conditions are satisfied.

[0039] The first diopter D1 and the second diopter D2 may be diopters other than 0D and -4D, respectively.

[0040] [Expanded adjustment range] To further reduce fatigue due to convergence conflict, it is desirable to set the VAC adjustment range from infinity (equivalent to 0D) to the 200 mm position (equivalent to -5D).

[0041] Figure 4(A) shows the optical path of the display optical system 1000 when VAC adjustment is performed at the 200 mm position (equivalent to -5D) (at -5D adjustment), and Figure 4(B) shows the longitudinal aberration at that time. These figures show that even when VAC adjustment is performed over a wide adjustment range, sufficiently good imaging performance is obtained.

[0042] In this case, if the focal length ft of the entire system including the diopter when adjusted to -5D is ft[-5D], then, just like ft[-4D] / ft[0D], 0.98≦ft[-5D] / ft[0D]≦1.02 or 0.99≦ft[-5D] / ft[0D]≦1.01 It is preferable to satisfy the following conditions.

[0043] In this embodiment, ft[0D]=19.026mm ft[-5D]=18.924mm Therefore, ft[-5D] / ft[0D]=0.995 and the above conditions are satisfied.

[0044] In this embodiment, the nominal maximum half angle of view is assumed to be 50°. Specifically, the maximum angle of the chief ray of the display light passing through the pupil plane SP (the ray passing through the center of the pupil plane SP) is set to 50°.

[0045] Generally, if the maximum half angle of the display light's chief ray is 30° or more, it can be said to have a wide field of view, the range of stereoscopic vision is wide, and the effect of VAC adjustment is easy to realize. Conversely, if the maximum half angle of view is less than 30°, the range of stereoscopic vision is narrow, and it is difficult to obtain the effect of VAC adjustment.

[0046] Furthermore, the larger the maximum half angle of view, the more noticeable the fluctuation in magnification of the displayed image becomes. If the maximum half angle of view is less than 30°, the displayed image is unlikely to look unnatural even if the above conditions are not met. If the maximum half angle of view is 30° or more, the displayed image is likely to look unnatural unless the above conditions are met.

[0047] [Optical definition of focus adjustment] From the perspective of optical performance, a focused state refers to a state in which the meridional and sagittal image planes are within ±1 mm in the range from the on-axis angle of view to an angle of view equivalent to 70% of the maximum half angle of view in the reverse optical path (reverse tracing) described above. For this reason, the larger the focus adjustment range and the wider the field of view, the more difficult it becomes to achieve a focused state.

[0048] [Definition of focus adjustable] A focus adjustable state refers to a state in which there is the ability to adjust focus from perspectives other than optical performance, such as whether there is enough room for driving for focus adjustment within the focus adjustment range, whether it can be driven with appropriate precision and speed without interference with other components, etc. In other words, simply being able to change the optical design values ​​does not mean that focus is adjustable.

[0049] Table 1 below shows the spacing between each optical element (the i-th surface and the (i+1)-th surface) in the display optical system 1000 when no VAC adjustment is performed, when -4D adjustment is performed, and when -5D adjustment is performed, along with the surface number i. d5, d10, and d13 indicate the spacing between the polarization-selective transflective element A and the first quarter-wave plate B, and d16 indicates the spacing between the transflective film C and the second quarter-wave plate D. Changing these parameters changes the first spacing between the first transflective surface and the second transflective surface. The spacing for changing the first spacing is defined as the internal spacing, and the spacing on the pupil plane side of the two internal spacings (i.e., d5, d10, and d13) is defined as the first internal spacing on the pupil plane side.

[0050] The focal length ft of the entire display optical system 1000, including diopter (visual acuity), is also shown. Furthermore, the focal length fe2 of the transmitted light path from the first internal spacing on the pupil plane side to the pupil plane SP on the pupil plane side (downstream), the focal length fe1 of the transmitted light path from the first transmissive reflector to the pupil plane SP on the pupil plane side (downstream), and the focal length fr1 at the time of reflection by the first transmissive reflector are also shown. In other words, the focal length fe2 is the focal length of the transmitted light path up to just before the first internal spacing on the pupil plane side when traced back from the pupil plane, and the focal length fe1 is the focal length of the transmitted light path up to just before the first transmissive reflector when traced back from the pupil plane.

[0051] [Table 1]

[0052] If the ray angle α (see FIG. 2A) between the transmissive-reflective surfaces of the principal ray of the maximum half angle of view toward the pupil plane SP is large, the position where the ray passes on the transmissive-reflective surface during VAC adjustment will change significantly, which is undesirable because it increases the size of the transmissive-reflective surface required and increases the fluctuation of optical performance. Ray angle α<maximum half angle of view θmax Specifically, when the focal length fe2 of the transmitted light path from the first internal spacing on the pupil plane side to the pupil plane SP on the pupil plane side without adjustment is fe2[0D], 1.0≦fe2[0D] / ft[0D]≦10.0 It is preferable to satisfy the following condition. The upper limit of this condition means that the optical path from the first internal spacing on the pupil plane side to the pupil plane SP on the pupil plane side has a positive power equivalent to 10% or more of the power of the entire display optical system 1000. The lower limit of this condition means that the optical path from the first internal spacing on the pupil plane side to the pupil plane SP on the pupil plane side has a positive power equivalent to the power of the entire system. If the lower limit is not satisfied, the power balance will be poor, which is undesirable in terms of optical performance (optical aberration).

[0053] It is more preferable that the transmission optical path from the first internal spacing on the pupil plane side to the pupil plane SP on the pupil plane side has a positive power equivalent to 15% or more of the power of the entire system. 1.0≦fe2[0D] / ft[0D]≦6.6 It is more preferable that the following conditions be satisfied:

[0054] In this example, from Table 1, ft[0D]=19.026mm fe2[0D]=110.401mm Therefore, fe2[0D] / ft[0D]=5.803 and the above conditions are satisfied.

[0055] The power of the transmitted light path from the first internal spacing on the pupil plane side to the pupil surface SP on the pupil plane side is divided into the power due to the optical surfaces included in the transmission-reflection optical system and the power due to the optical surfaces included in the pupil-plane-side optical system. The optical surfaces included in the transmission-reflection optical system are likely to affect the optical performance (optical aberrations) because they are surfaces through which light rays pass three times due to the folding back of the optical path, or they may also function as transmission-reflection surfaces. Therefore, in terms of optical performance (optical aberrations), it is preferable to utilize the flexibility of the optical surfaces included in the pupil-plane-side optical system and allocate a certain amount of power or more.

[0056] Specifically, when the focal length fe1 of the transmitted light path from the first transmitting-reflecting surface to the pupil surface SP on the pupil surface side without adjustment is fe1[0D], 1.0≦fe1[0D] / fe2[0D]≦10.0 It is preferable to satisfy the following condition. The upper limit of this condition means that the transmitted optical path from the first transmitting-reflecting surface to the pupil surface SP on the pupil surface side has positive power equivalent to 10% or more of the power of the transmitted optical path from the first internal spacing on the pupil surface side to the pupil surface SP on the pupil surface side. The lower limit means that the transmitted optical path from the first transmitting-reflecting surface to the pupil surface SP on the pupil surface side has positive power equivalent to the power of the transmitted optical path from the first internal spacing on the pupil surface side to the pupil surface SP on the pupil surface side. If the lower limit is not satisfied, the power balance will be poor, which is undesirable in terms of optical performance (optical aberration).

[0057] Furthermore, it is more preferable that the transmitted optical path from the first transmitting-reflecting surface to the pupil plane SP on the pupil plane side has a positive power equivalent to 15% or more of the power of the transmitted optical path from the first internal spacing on the pupil plane side to the pupil plane SP on the pupil plane side. 1.0≦fe1[0D] / fe2[0D]≦6.6 It is more preferable that the following conditions be satisfied:

[0058] In this example, from Table 1, fe2[0D]=110.401mm fe1[0D]=343.038 mm Therefore, fe1[0D] / fe2[0D]=3.107 and the above conditions are satisfied.

[0059] The following describes the exit angle β of the chief ray emitted from the light-emitting position y on the display surface shown in Figure 2(A) with respect to the normal to the display surface. The exit angle β is negative (-) in the direction away from the optical axis and positive (+) in the direction toward the optical axis. If the exit angle β at the maximum half angle of view is negative without adjustment, the magnification fluctuation of the displayed image during -4D adjustment can be reduced. This also allows for a reduction in the size of the display element, which is preferable from the perspective of weight.

[0060] 2B shows the relationship between the light-emitting position y on the display element and the emission angle β when there is no adjustment of the display optical system 1000. It can be seen that the emission angle β at the maximum half angle of view is −25.2°, which is negative.

[0061] Up to this point, we have explained that the light-emitting position y is proportional to the focal length ft of the entire system, including the diopter. This is based on paraxial theory, and while it is correct in most cases, it is not strictly accurate. In particular, if there are many optical surfaces within the effective beam diameter where the positive and negative of the local power (the second-order differential value with respect to the optical axis direction of the infinity shape) is reversed, the error can become large. Specifically, if there are three or more optical surfaces where the positive and negative of the local power is reversed, it is advisable to evaluate the amount of error and check whether fluctuations in the magnification of the displayed image are being suppressed.

[0062] The effective beam diameter is the diameter of the range through which display light from the display element can pass. Within this effective beam diameter, high-precision processing of the pupil-facing surface is required to ensure optical performance.

[0063] In this embodiment, there is no optical surface in which the positive and negative powers are locally reversed within the effective beam diameter. In this way, by adopting a configuration in which there are no more than three optical surfaces in which the positive and negative powers are locally reversed (i.e., there are two or fewer optical surfaces), it is easier to obtain results based on the paraxial theory, and there is an advantage in that it is easier to design an optical system that can suppress fluctuations in the magnification of a displayed image.

[0064] In addition, in this embodiment, the change in magnification of the displayed image that occurs during VAC adjustment is sufficiently small that correction by image processing is not necessary, thereby reducing the load on the calculation process. However, image processing for other correction targets such as magnification (distortion) when no adjustment is performed may be required.

[0065] As mentioned above, VAC adjustment is performed in response to changes in the displayed image and the viewer's gaze point, and therefore requires high-speed driving. To make the VAC adjustment mechanism as small as possible, it is preferable that the weight of the driven components be small. Specifically, it is preferable that the display element, which is generally heavy, is not driven, and that the optical elements to be driven are two or less refractive elements made of resin. In this embodiment, the VAC adjustment does not drive the panel unit 1400, but drives a single refractive element made of resin, the second lens 1201, and therefore satisfies the above conditions.

[0066] Furthermore, in this embodiment, the first lens 1101 having the pupil-facing surface (surface R1) is not driven during VAC adjustment. Driving the pupil-facing surface during VAC adjustment is not preferable because the resulting air fluctuations may be transmitted to the viewer, causing discomfort.

[0067] As mentioned above, it is preferable that the drive amount in VAC adjustment is small, but it is not preferable that the drive amount is too small and that the focus adjustment error becomes large. Specifically, when the amount of change in the distance between the two transmissive-reflective surfaces in focus adjustment from infinity (equivalent to 0D) to 250 mm (equivalent to -4D) is dG (the maximum amount of change in convergence adjustment), 0.5mm≦|dG|≦7.0mm It is preferable to satisfy the following conditions.

[0068] In addition, 0.5mm≦|dG|≦4.0mm It is more preferable that the following conditions be satisfied:

[0069] In this example, from Table 1, |dG|=|1.983mm-2.980mm|=0.997mm and the above conditions are satisfied.

[0070] In particular, to make it easier to satisfy |dG|≦7.0 mm, it is advisable to increase the amount of focus adjustment when changing the distance between the two transmissive-reflective surfaces. One method for doing so is to increase the absolute value of the power of the first transmissive-reflective surface and the second transmissive-reflective surface. To achieve this, it is preferable to configure the first transmissive-reflective surface to have a negative power as its power during reflection. In this case, the focal length of the entire display optical system 1000 is roughly maintained due to requirements for optical performance, so the positive power of the second transmissive-reflective surface also increases. Specifically, when the focal length fr1 during reflection of the first transmissive-reflective surface without adjustment is fr1[0D], -10.0≦fr1[0D] / ft[0D]≦0 It is preferable that the following condition be satisfied: This means that the first transmission-reflection surface has a negative power equivalent to 10% or more of the power of the entire system.

[0071] Furthermore, in order to make it easier to satisfy 0.5 mm≦|dG|, it is sufficient to prevent the negative power given to the first transmitting-reflecting surface from being too large. -10.0≦fr1[0D] / ft[0D]≦-0.5 It is preferable to satisfy the following condition: This means that the absolute value of the negative power of the first transmitting-reflecting surface is equal to or less than two times the absolute value of the power of the entire system.

[0072] It is preferable that the absolute value of the negative power of the first transmission-reflection surface corresponds to 15% or more of the absolute value of the power of the entire system. -6.6≦fr1[0D] / ft[0D]≦-0.5 It is preferable to satisfy the following conditions.

[0073] In this example, from Table 1, ft[0D]=19.026mm fr1[0D] = -31.316mm Therefore, fr1[0D] / ft[0D]=-1.646 and the above conditions are satisfied.

[0074] As explained above, from the perspective of weight, a smaller display element is preferable. However, when considering fluctuations in optical performance (optical aberration) when performing VAC adjustment, a somewhat larger display element is preferable.

[0075] Specifically, assuming a maximum half angle of view of 30° or more, the shape of the display surface is preferably such that the diagonal length of the square circumscribing the display surface is 1.3 inches or more (each side of the circumscribing square is 23.3 mm).

[0076] Next, we will explain the fluctuation of chromatic aberration of magnification during focus adjustment (magnification fluctuation for each color of the displayed image). VAC adjustment is performed frequently, so performing image processing to correct the magnification fluctuation for each color increases the load of calculation processing, which is undesirable. Therefore, it is preferable to reduce chromatic aberration of magnification as an optical performance. Specifically, it is preferable to configure the optical elements to be driven as one or two refractive elements with an Abbe number of 50 or more based on the d-line, or two refractive elements with a difference in Abbe number of 20 or more.

[0077] In this embodiment, the second lens 1201, which is a single resin refractive element with an Abbe number of 56, is driven to satisfy the above conditions.

[0078] Here, the optical element refers to an optical element having a power that causes fluctuations in lateral chromatic aberration due to driving. Optical elements with little or no power are not included in the optical element, but may be associated with the optical element.

[0079] Furthermore, when an organic EL display, LCD, or the like is used as the display element, electrical processing to correct the distortion and lateral chromatic aberration of the display optical system may be added to the original image depending on the amount of distortion and lateral chromatic aberration. However, even after image processing to correct lateral chromatic aberration, residual correction errors may remain. Furthermore, it is difficult to correct axial chromatic aberration using image processing. For this reason, it is preferable that the optical performance of the display optical system 1000 be such that both lateral chromatic aberration and axial chromatic aberration are reduced. One method for achieving this is to provide a diffractive surface. However, because the diffraction efficiency varies depending on the angle of incidence of the light beam, the diffractive surface must be provided on an optical element that is not driven by VAC adjustment.

[0080] In this embodiment, a diffractive surface is provided on the R2 surface of the first lens 1101, which is not driven by VAC adjustment, and the above conditions are satisfied. [Example]

[0081] Next, a description will be given of a display optical system 2000 according to a second embodiment. In this embodiment, the description common to the first embodiment will be omitted.

[0082] 5A shows the configuration of a display optical system 2000. The display optical system 2000 has a pupil plane side optical system (first optical system) 2100, a transmission / reflection optical system (second optical system) 2200, and a panel side optical system (third optical system) 2300.

[0083] The pupil plane-side optical system 2100 has a first lens 2101 as a first optical element. The transmission-reflection optical system 2200 has a second lens 2201 as a second optical element and a third lens 2202 as a third optical element. The panel-side optical system 2300 has a fourth lens 2301 as a fourth optical element. Thus, the pupil plane-side optical system 2100 has one optical element (2101, 2201, 2202, 2301) that refracts, reflects, or diffracts light rays, the transmission-reflection optical system 2200 has two optical elements (2101, 2201, 2202, 2301) that refract, reflect, or diffract light rays, and the transmission-reflection optical system 2200 has two optical elements (2101, 2201, 2202, 2301) that refract, reflect, or diffract light rays from the pupil plane side. Each optical element has two optical surfaces, R1 and R2, from the pupil plane side, and all of these optical surfaces are curved.

[0084] Display light from the panel unit 2400 including a display element passes through the panel-side optical system 2300, is reflected once each by the first transmission-reflection surface and the second transmission-reflection surface of the transmission-reflection optical system 2200, passes through the transmission-reflection optical system 2200, and then passes through the pupil-plane-side optical system 2100 toward the pupil plane SP. This allows the viewer to view a virtual image (display image) of the original image displayed on the display element through their eye located on the pupil plane SP where the exit pupil of the display optical system 2000 is located. The light that follows the optical path for forming the display image at this time is called display light, and the rest is called unwanted light.

[0085] FIG. 5B shows the longitudinal aberration of the display optical system 2000 in this embodiment when the eye relief (the distance on the optical axis from the pupil plane SP to the lens surface of the pupil-plane-side optical system 2100 closest to the pupil plane) is 12 mm and a virtual image is displayed at infinity from the pupil plane SP. Again, the longitudinal aberration is shown when observed by an eye with 0D visual acuity, assuming a maximum half angle of view of 50°. Furthermore, FIG. 5B shows the longitudinal aberration in the reverse optical path (reverse tracing) from the pupil plane SP to the panel unit 2400, when the panel unit 2400 is the image plane. The explanations for the other aberration diagrams are the same as those for Example 1 (FIG. 1B, etc.). It can be seen from FIG. 5B that the display optical system 2000 of this embodiment has good imaging performance.

[0086] The configuration of the panel unit 2400 is the same as that of the panel unit 1400 of Example 1. However, the shape of the display element is a square with a diagonal of 2.2 inches (each side is 39.5 mm).

[0087] A transflective film (half mirror) C is deposited on the R2 surface of the third lens 2202 and is bonded to the R1 surface of the fourth lens 2301. A first quarter-wave plate B is bonded to the R2 surface of the first lens 2201 and the R1 surface of the third lens 2202.

[0088] The polarization-selective transmission-reflection element A is bonded to the R2 surface of the first lens 2101 of the pupil plane side optical system 2100. The transmission-reflection film C and the polarization-selective transmission-reflection element A are included in the transmission-reflection optical system 2200. In this embodiment, the transmission-reflection film C and the first quarter-wave plate B correspond to the second transmission-reflection member, and the polarization-selective transmission-reflection element A corresponds to the first transmission-reflection member.

[0089] 6 shows the direction and polarization state of the display light passing through each surface in the display optical system 2000. The direction and polarization state of the display light are the same as those in the first embodiment (FIG. 2(C)).

[0090] [Configuration of this Example] This embodiment has a VAC adjustment mechanism as an automatic adjustment mechanism that adjusts focus by automatically driving an optical element that integrates a third lens 2202 having a second transmissive-reflective surface (transmissive-reflective film C), a first lens 2201, and a fourth lens 2301. This makes it possible to perform VAC adjustment in response to changes in the displayed image and the observer's point of gaze.

[0091] Figure 7(A) shows the optical path of the display optical system 2000 when VAC adjustment is performed at the 250 mm position (equivalent to -4D) (when adjusted to -84), and Figure 7(B) shows the longitudinal aberration at that time. These figures show that even when VAC adjustment is performed, sufficiently good imaging performance is obtained.

[0092] In this way, by providing a VAC adjustment mechanism that adjusts the distance between the first transmission-reflection surface and the second transmission-reflection surface, it is possible to perform VAC adjustment.

[0093] As in the first embodiment, in order to prevent the display image from appearing unnatural even without performing the above-mentioned calculation processing, it is generally preferable to limit the variation in the magnification of the display image to within ±2%. 0.98≦ft[-4D] / ft[0D]≦1.02 It is preferable to satisfy the following conditions.

[0094] In this embodiment, from Table 2 shown later, ft[0D]=24.901mm ft[-4D]=25.271mm Therefore, ft[-4D] / ft[0D]=1.015 and the above conditions are satisfied.

[0095] however, 0.99≦ft[-4D] / ft[0D]≦1.01 is not satisfied.

[0096] [Expanded adjustment range] As in the first embodiment, in order to further reduce fatigue due to convergence conflict, it is desirable to set the VAC adjustment range from infinity (equivalent to 0D) to the 200 mm position (equivalent to -5D).

[0097] Fig. 8(A) shows the optical path of the display optical system 2000 when VAC adjustment is performed at the 200 mm position (equivalent to -5D) (at -5D adjustment), and Fig. 8(B) shows the longitudinal aberration at that time. These figures show that even when VAC adjustment is performed over a wide adjustment range, sufficiently good imaging performance is obtained.

[0098] At this time, 0.98≦ft[-5D] / ft[0D]≦1.02 It is preferable to satisfy the following conditions.

[0099] In this example, from Table 2, ft[0D]=24.901mm ft[-5D]=25.339mm Therefore, ft[-5D] / ft[0D]=1.018 and the above conditions are satisfied.

[0100] In this embodiment, too, a maximum half angle of 50° is assumed in the design nominal design. Specifically, the maximum angle of the chief ray of the display light passing through the pupil plane SP is set to 50°. This makes it easier to obtain the effect of the VAC adjustment and reduces the likelihood of discomfort caused by fluctuations in the magnification of the display image due to the VAC adjustment.

[0101] Table 2 below shows the spacing between each optical element (the i-th surface and the (i+1)-th surface) in the display optical system 2000 when no VAC adjustment is performed, when -4D adjustment is performed, and when -5D adjustment is performed, along with the surface number i. d4, d11, and d14 indicate the spacing between the polarization-selective transflective element A and the first lens 2201, and d19 indicates the spacing between the fourth lens 2301 and the second quarter-wave plate D. Changing these parameters changes the first spacing between the first transflective surface and the second transflective surface. The spacing for changing the first spacing is defined as the internal spacing, and the spacing on the pupil plane side of the two internal spacings (i.e., d4, d11, and d14) is defined as the first internal spacing on the pupil plane side.

[0102] Also shown is the focal length ft of the entire display optical system 2000, including diopter (visual acuity). Also shown are the focal length fe2 of the transmitted light path from the first internal spacing on the pupil plane side to the pupil plane SP on the pupil plane side (downstream), the focal length fe1 of the transmitted light path from the first transmissive reflecting member to the pupil plane SP on the pupil plane side (downstream), and the focal length fr1 upon reflection at the first transmissive reflecting surface.

[0103] [Table 2]

[0104] In this embodiment, similarly to the first embodiment, in order to reduce the increase in the magnification fluctuation of the displayed image and the increase in the size of the necessary transmissive-reflective surface, 1.0≦fe2[0D] / ft[0D]≦10.0 It is preferable to satisfy the following conditions.

[0105] moreover, 1.0≦fe2[0D] / ft[0D]≦6.6 It is more preferable to satisfy the following.

[0106] In this example, from Table 2, ft[0D]=24.901mm fe2[0D] =96.355mm Therefore, fe2[0D] / ft[0D]=3.869 and the above conditions are satisfied.

[0107] Also in this embodiment, similarly to the first embodiment, from the viewpoint of optical performance (optical aberration), 1.0≦fe1[0D] / fe2[0D]≦10.0 It is preferable to satisfy the following conditions.

[0108] moreover, 1.0≦fe1[0D] / fe2[0D]≦6.6 It is more preferable that the following conditions be satisfied:

[0109] However, in this example, from Table 2, fe2[0D]=96.355mm fe1[0D]=∞ mm (non-power) Therefore, fe1[0D] / fe2[0D]=∞ So the above condition is not satisfied.

[0110] Note that this embodiment does not have an optical surface in which the positive and negative powers are reversed at the effective beam diameter, as in Example 1. This has the advantage that it is easier to obtain results based on the paraxial theory and to design an optical system that can suppress fluctuations in the magnification of a displayed image.

[0111] Here, in this embodiment, in order to satisfy the above-mentioned condition 1.0≦fe1[0D] / fe2[0D]≦10.0, it is sufficient to have one or two optical surfaces whose power is reversed in terms of balance of optical performance (optical aberration). In other words, since there are no more than three optical surfaces whose power is reversed in terms of positive and negative, it is clear that the effect of suppressing fluctuations in the magnification of the displayed image is obtained. However, in this embodiment, for ease of understanding, it is decided not to satisfy the above condition and not to have any optical surfaces whose power is reversed in terms of positive and negative.

[0112] FIG. 5C shows the relationship between the light-emitting position y on the display element and the output angle β when the display optical system 2000 is not adjusted. The sign of the output angle β is the same as in Example 1 (FIG. 2B). At the maximum half angle of view, the output angle β is -4.9°, which is negative. This allows for a reduction in the magnification fluctuation of the displayed image and a reduction in the size of the display element.

[0113] Furthermore, the amount of light emitted from the display element is basically greatest when the emission angle β is 0°, and the amount of light decreases as the absolute value of the emission angle β at the maximum half angle of view increases. Therefore, from the viewpoint of the amount of light, it is important that the emission angle β is 20° or less, i.e., |Output angle β|≦15° It is preferable to satisfy the following conditions.

[0114] moreover, |Output angle β|≦15° It is more preferable that the following conditions be satisfied:

[0115] In this embodiment, as shown in FIG. Maximum value of |Output angle β| = 5.0° and the above conditions are satisfied.

[0116] Also in this embodiment, as in the first embodiment, the change in magnification of the observed image that occurs during VAC adjustment is small, so correction by image processing is not necessary, and the load of calculation processing can be reduced.

[0117] Furthermore, in this embodiment, the first lens 2101 having the pupil-facing surface (R1 surface) is not driven during VAC adjustment, as in embodiment 1. This reduces discomfort felt by the observer during VAC adjustment and the sense of pressure felt when wearing the HMD, as described above.

[0118] Furthermore, in this embodiment, as in the first embodiment, 0.5mm≦|dG|≦7.0mm It is preferable that the following conditions are satisfied: 0.5mm≦|dG|≦4.0mm It is more preferable that the following conditions be satisfied:

[0119] In this example, from Table 2, |dG|=|2.021mm-3.028mm|=1.007mm and the above conditions are satisfied.

[0120] In addition, similar to Example 1, in order to easily satisfy |dG|≦7.0 mm, -10.0≦fr1[0D] / ft[0D]≦0 It is preferable to satisfy the following condition. To make it easier to satisfy 0.5 mm ≦ |dG|, -10.0≦fr1[0D] / ft[0D]≦-0.5 It is preferable to satisfy the following conditions.

[0121] moreover, -6.6≦fr1[0D] / ft[0D]≦-0.5 It is preferable to satisfy the following conditions.

[0122] In this example, from Table 2, ft[0D]=24.901mm fr1[0D] = -17.237mm Therefore, fr1[0D] / ft[0D]=-0.692 and the above conditions are satisfied.

[0123] Also in this embodiment, as in Example 1, the shape of the display element is such that the diagonal length of the square circumscribing the display surface is 1.3 inch or more (one side of the circumscribing square is 23.3 mm), which makes it possible to reduce fluctuations in optical performance (optical aberration) when performing VAC adjustment.

[0124] Furthermore, apart from the method of providing a diffractive surface shown in Example 1, another method of reducing lateral chromatic aberration and axial chromatic aberration is to provide, between two transmissive-reflective surfaces, a plurality of (for example, two) refractive elements that are bonded together and whose difference in Abbe number relative to the d-line is 20 or more. This allows the display light to pass through the bonded surface of the two refractive elements three times, thereby enhancing the effect of reducing lateral chromatic aberration and axial chromatic aberration.

[0125] In addition, when the optical path between the two transmissive-reflective surfaces changes during VAC adjustment, a configuration in which two refractive elements are bonded together has the advantage that deterioration of optical performance (optical aberrations) other than lateral chromatic aberration and axial chromatic aberration is less likely to occur than a configuration in which the refractive elements are spaced apart. Furthermore, a refractive element may be bonded to an optical element that is driven by VAC adjustment, or a refractive element may be bonded to an optical element that is not driven.

[0126] In this embodiment, a second lens 2201 and a third lens 2202 are cemented together between two transmissive-reflective surfaces. If the Abbe number of the second lens 2201 based on the d-line is v1 and the Abbe number of the third lens 2202 based on the d-line is v2, then v1 = 22.4, v2 = 56.0, and |v1 - v2| = 33.6, which satisfies the above condition.

[0127] To be precise, the first quarter-wave plate B is sandwiched between the second lens 2201 and the third lens 2202, but because the first quarter-wave plate B has no power and is sufficiently thin, it does not affect the lateral chromatic aberration or axial chromatic aberration. In this way, when a polarizing plate, a quarter-wave plate, a polarization-selective transmission / reflection element, or the like is sandwiched between optical elements, it may be treated as if it does not exist.

[0128] Numerical Examples 1 and 2 corresponding to Examples 1 and 2, respectively, are shown below. In the surface data, surface number i indicates the ith surface when counted from the pupil surface side. r is the radius of curvature (mm) of the ith surface, and d is the lens thickness or air gap (mm) between the ith and (i+1)th surfaces. d is a value without adjustment. nd is the refractive index at the d-line of the material of the ith optical element. νd is the Abbe number based on the d-line of the material of the ith optical element. The Abbe number based on the d-line, νd, is given by: νd=(Nd-1) / (NF-NC) It is expressed as:

[0129] An asterisk (*) next to a surface number indicates that the surface has an aspherical shape. The aspherical shape is expressed by the following equation, where x is the displacement in the optical axis direction at a position of height h from the optical axis relative to the vertex of the surface, R is the paraxial radius of curvature, k is the conic constant, and Ai (i = 4, 6, 8, 10, ...) are the aspherical coefficients of each order.

[0130]

number

[0131] In addition, "e±XX" in the conic constant and aspherical coefficient is "×10± XX " means.

[0132] Furthermore, the phase shape F(h, m) of the diffractive optical element at a height h in the radial direction from the optical axis is expressed as follows, where m is the diffraction order, λ is the reference wavelength, and C (i is a natural number) is the phase coefficient of the 2i-th order term: F(h,m)=(2π / mλ0)(C1h2+C2h4+C3h6+…) In this case, the refractive power φ of the diffractive surface of the diffractive optical element for an arbitrary wavelength λ and an arbitrary diffraction order m is expressed by the following equation using a phase coefficient C1.

[0133] φ(λ,m)=-2C1mλ / λ0 In the diffractive optical element of this numerical example, the diffraction order m of the diffracted light is 1, and the design wavelength λ0 is the d-line (587.6 nm). [Numerical Example 1] Unit: mm Surface Data Surface number rd nd νd 1 (Aperture) ∞ (Variable) 2 ∞ 0.10 1.64270 40.2 3(diffraction) ∞ 2.40 1.58800 28.3 4* -95.200 0.50 1.52000 64.0 5* -95.200 (variable) 6 -400.000 0.50 1.52000 64.0 7 -400.000 6.00 1.54390 56.0 8* -52.400 -6.00 9 -400.000 -0.50 -1.52000 64.0 10 -400.000 (variable) 11* -95.200 -0.50 -1.52000 64.0 12* -95.200 0.50 13* -95.200 (variable) 14 -400.000 0.50 1.52000 64.0 15 -400.000 6.00 1.54390 56.0 16* -52.400 (variable) 17 ∞ 0.50 1.52000 64.0 Image plane ∞ Aspheric data Surface 3 (diffractive surface) C 2=-1.45757e-03 C 4=-8.94091e-07 C 6= 5.15514e-10 C 8= 1.21057e-11 C10= 6.73893e-15 Side 4 K = 0.00000e+00 A 4= 4.11683e-06 A 6= 7.69779e-09 A 8=-8.21078e-12 5th page K = 0.00000e+00 A 4= 4.11683e-06 A 6= 7.69779e-09 A 8=-8.21078e-12 Side 8 K =-1.14035e+00 Page 11 K = 0.00000e+00 A 4= 4.11683e-06 A 6= 7.69779e-09 A 8=-8.21078e-12 Side 12 K = 0.00000e+00 A 4= 4.11683e-06 A 6= 7.69779e-09 A 8=-8.21078e-12 Page 13 K = 0.00000e+00 A 4= 4.11683e-06 A 6= 7.69779e-09 A 8=-8.21078e-12 Page 16 K =-1.14035e+00 Focal length 19.03 d 1 12.00 d5 2.98 d10 -2.98 d13 2.98 d16 1.02 [Numerical Example 2] Unit: mm Surface Data Surface number rd nd νd 1* ∞ (variable) 2* ∞ 8.60 1.54390 56.0 3* -52.400 0.50 1.52000 64.0 4* -52.400 (variable) 5* -52.400 1.50 1.64220 22.4 6 -112.000 0.50 1.52000 64.0 7 -112.000 5.50 1.54390 56.0 8* -44.200 -5.50 9 -112.000 -0.50 -1.52000 64.0 10 -112.000 -1.50 1.64220 22.4 11* -52.400 (variable) 12* -52.400 -0.50 -1.52000 64.0 13* -52.400 0.50 14* -52.400 (variable) 15* -52.400 1.50 1.64220 22.4 16 -112.000 0.50 1.52000 64.0 17 -112.000 5.50 1.54390 56.0 18* -44.200 2.30 1.54390 56.0 19* -48.400 (variable) 20 ∞ 0.50 1.52000 64.0 21 ∞ (variable) Image plane ∞ Aspheric data 2nd side K = 0.00000e+00 A 4= 6.42067e-06 A 6=-1.25684e-08 A 8= 9.14810e-12 3rd page K = 0.00000e+00 A 4= 5.36133e-06 A 6=-8.24463e-09 A 8= 3.33122e-12 Side 4 K = 0.00000e+00 A 4= 5.36133e-06 A 6=-8.24463e-09 A 8= 3.33122e-12 5th page K = 0.00000e+00 A 4= 5.36133e-06 A 6=-8.24463e-09 A 8= 3.33122e-12 Page 8 K = 0.00000e+00 A 4= 1.50921e-06 A 6=-5.12708e-10 A 8= 1.31884e-13 Page 11 K = 0.00000e+00 A 4= 5.36133e-06 A 6=-8.24463e-09 A 8= 3.33122e-12 Page 12 K = 0.00000e+00 A 4= 5.36133e-06 A 6=-8.24463e-09 A 8= 3.33122e-12 Page 13 K = 0.00000e+00 A 4= 5.36133e-06 A 6=-8.24463e-09 A 8= 3.33122e-12 Page 14 K = 0.00000e+00 A 4= 5.36133e-06 A 6=-8.24463e-09 A 8= 3.33122e-12 Page 15 K = 0.00000e+00 A 4= 5.36133e-06 A 6=-8.24463e-09 A 8= 3.33122e-12 Page 18 K = 0.00000e+00 A 4= 1.50921e-06 A 6=-5.12708e-10 A 8= 1.31884e-13 Page 19 K = 0.00000e+00 A 4= 1.37816e-05 A 6=-6.96093e-08 A 8= 5.96919e-11 Focal distance 24.90 d 1 12.00 d 4 3.03 d11 -3.03 d14 3.03 d19 0.97 d21 0.04 [Representation device] 9 shows a head mounted display (HMD) 1 as a display device using the display optical systems of Examples 1 and 2. The HMD 1 is worn on the head (in front of the eyes) of a viewer by means of a wearing gear (not shown).

[0134] The HMD1 has display elements RID and LID for the right and left eyes, a right-eye display optical system ROS that guides display light from the right-eye display element RID to the observer's right eye, and a left-eye display optical system LOS that guides display light from the left-eye display element LID to the observer's left eye.

[0135] By using the display optical systems shown in the first and second embodiments as the right-eye and left-eye display optical systems ROS and LOS, it is possible to realize an HMD that allows the viewer to view good images.

[0136] The above embodiment includes the following configurations.

[0137] (Configuration 1) A display optical system that guides display light from a display surface of a display element to a pupil plane, the display optical system includes a first transmissive-reflective surface and a second transmissive-reflective surface arranged in this order from a pupil plane side to a display surface side, a first distance between the first transmission-reflection surface and the second transmission-reflection surface can be changed to perform focus adjustment within a range of a first diopter to a second diopter on the pupil plane, When the focal length of the display optical system including the first diopter and the focal length of the display optical system including the second diopter are respectively ft[D1] and ft[D2], 0.97≦ft[D2] / ft[D1]≦1.03 A display optical system characterized by satisfying the following conditions: (Configuration 2) 0.98≦ft[D2] / ft[D1]≦1.02 2. The display optical system according to configuration 1, wherein the following condition is satisfied: (Configuration 3) When the first diopter is 0 diopter, the second diopter is −4 diopter, and ft[D1] at 0 diopter is ft[0D], and ft[D2] at −4 diopter is ft[−4D], 0.98≦ft[-4D] / ft[0D]≦1.02 3. The display optical system according to configuration 2, wherein the following condition is satisfied: (Configuration 4) 2. The display optical system according to configuration 1, wherein a maximum half angle of view formed by a chief ray of the display light passing through the pupil plane is 30° or more. (Configuration 5) When the diopter on the pupil plane when the focus adjustment is performed is 0 diopter as the first diopter, the focal length of the display optical system including the diopter is defined as ft[0D], and when the diopter on the pupil plane is 0 diopter, the focal length of the transmitted light path to the pupil plane on the pupil plane side of the first internal spacing, which is the spacing on the pupil plane side, that causes a change in the first spacing when the diopter on the pupil plane is 0 diopter is defined as fe2[0D], 1.0≦fe2[0D] / ft[0D]≦10.0 5. The display optical system according to any one of configurations 1 to 4, wherein the following condition is satisfied: (Configuration 6) When the diopter on the pupil plane after the focus adjustment is 0 diopter, the focal length of the transmitted light path from the first transmitting-reflecting surface to the pupil plane on the pupil plane side is fe1[0D], 1.0≦fe1[0D] / fe2[0D]≦10.0 6. The display optical system according to configuration 5, wherein the following condition is satisfied: (Configuration 7) The display optical system according to any one of configurations 1 to 6, wherein an exit angle of a chief ray of the display light at a maximum half angle of view among the chief rays of the display light passing through the pupil plane is an angle directed away from the optical axis of the display optical system. (Configuration 8) 8. The display optical system according to configuration 7, wherein the exit angle is 20° or less. (Configuration 9) 9. The display optical system according to any one of configurations 1 to 8, wherein the number of optical surfaces whose power changes from positive to negative within the effective beam diameter is two or less. (Configuration 10) 10. The display optical system according to any one of configurations 1 to 9, wherein, in the focus adjustment, the display element is not driven, but two or less refractive elements made of resin are driven. (Configuration 11) 11. The display optical system according to any one of configurations 1 to 10, wherein an optical element having an optical surface facing the pupil plane is not driven during the focus adjustment. (Configuration 12) When the maximum change amount of the distance between the first transmissive-reflective surface and the second transmissive-reflective surface during the focus adjustment within the adjustment range is dG, 0.5mm≦|dG|≦7.0mm 12. The display optical system according to any one of configurations 1 to 11, wherein the following condition is satisfied: (Configuration 13) When the diopter on the pupil plane after the focus adjustment is 0 diopter as the first diopter, the focal length of the display optical system including the diopter is ft[0D], and when the diopter on the pupil plane is 0 diopter, the focal length upon reflection on the first transmissive-reflective surface is fr1[0D], -10.0≦fr1[0D] / ft[0D]≦-0.5 13. The display optical system according to any one of configurations 1 to 12, wherein the following condition is satisfied: (Configuration 14) 14. The display optical system according to any one of configurations 1 to 13, wherein the diagonal length of a square circumscribing the display surface is 1.3 inches or more. (Configuration 15) 15. The display optical system according to any one of configurations 1 to 14, wherein the optical element driven in the focus adjustment is composed of one or two refractive elements having an Abbe number based on the d-line of 50 or more, or two refractive elements having an Abbe number difference based on the d-line of 20 or more. (Configuration 16) the display optical system includes an optical element that is not driven by the adjustment mechanism, 16. The display optical system according to any one of configurations 1 to 15, wherein the optical element has a diffractive surface. (Configuration 17) 17. The display optical system according to any one of configurations 1 to 16, characterized in that a plurality of refractive elements are bonded together between the first transmitting-reflecting surface and the second transmitting-reflecting surface, the difference between their Abbe numbers based on the d-line being 20 or more. (Configuration 18) 18. The display optical system according to any one of configurations 1 to 17, wherein the display light is guided to the pupil plane after being transmitted through the second transmissive-reflective surface, reflected at the first transmissive-reflective surface, reflected at the second transmissive-reflective surface, and transmitted through the first transmissive-reflective surface. (Configuration 19) 19. A display device comprising the display optical system according to any one of configurations 1 to 18. (Configuration 20) the display optical systems are provided for the right and left eyes, 20. The display device according to configuration 19, further comprising an automatic adjustment mechanism that performs convergence adjustment as the focus adjustment in accordance with the image displayed on the display surface. (Configuration 21) The display optical system according to configuration 19 or 20, characterized in that no image processing is performed on the image displayed on the display element to reduce fluctuations in magnification of the image displayed by the display light when the focus adjustment is performed.

[0138] The embodiments described above are merely representative examples, and various modifications and alterations are possible to each embodiment when implementing the present invention. [Explanation of symbols]

[0139] 1000,2000 Display optical system 1400,2400 Panel section (display element) A. Polarization-selective transmission / reflection element (first transmission / reflection member) C. Transmissive reflective film (second transmissive reflective member) SP pupil

Claims

1. A display optical system that guides display light from a display surface of a display element to a pupil plane, the display optical system includes a first transmissive-reflective surface and a second transmissive-reflective surface arranged in this order from a pupil plane side to a display surface side, a first distance between the first transmission-reflection surface and the second transmission-reflection surface can be changed to perform focus adjustment within a range of a first diopter to a second diopter on the pupil plane, When the focal length of the display optical system including the first diopter and the focal length of the display optical system including the second diopter are respectively ft[D1] and ft[D2], 0.97≦ft[D2] / ft[D1]≦1.03 A display optical system characterized by satisfying the following conditions:

2. 0.98≦ft[D2] / ft[D1]≦1.02 2. The display optical system according to claim 1, wherein the following condition is satisfied:

3. When the first diopter is 0 diopter, the second diopter is −4 diopter, and ft[D1] at 0 diopter is ft[0D], and ft[D2] at −4 diopter is ft[−4D], 0.98≦ft[-4D] / ft[0D]≦1.02 3. The display optical system according to claim 2, wherein the following condition is satisfied:

4. 2. The display optical system according to claim 1, wherein a maximum half angle of view formed by a chief ray of the display light passing through the pupil plane is 30[deg.] or more.

5. When the diopter on the pupil plane when the focus adjustment is performed is 0 diopter as the first diopter, the focal length of the display optical system including the diopter is defined as ft[0D], and when the diopter on the pupil plane is 0 diopter, the focal length of the transmitted light path to the pupil plane on the pupil plane side of the first internal spacing, which is the spacing on the pupil plane side, that causes a change in the first spacing when the diopter on the pupil plane is 0 diopter is defined as fe2[0D], 1.0≦fe2[0D] / ft[0D]≦10.0 2. The display optical system according to claim 1, wherein the following condition is satisfied:

6. When the diopter on the pupil plane when the focus adjustment is performed is 0 diopter, the focal length of the transmitted light path from the first transmitting-reflecting surface to the pupil plane on the pupil plane side is fe1[0D], 1.0≦fe1[0D] / fe2[0D]≦10.0 6. The display optical system according to claim 5, wherein the following condition is satisfied:

7. 2. The display optical system according to claim 1, wherein an exit angle of a chief ray of the display light passing through the pupil plane at a maximum half angle of view from the display surface is an angle directed away from the optical axis of the display optical system.

8. 8. The display optical system according to claim 7, wherein the exit angle is 20 degrees or less.

9. 2. The display optical system according to claim 1, wherein the number of optical surfaces whose power changes from positive to negative within the effective beam diameter is two or less.

10. 2. The display system according to claim 1, wherein, in the focus adjustment, the display element is not driven, but two or less refractive elements made of resin are driven.

11. 2. The display optical system according to claim 1, wherein an optical element having an optical surface facing the pupil plane is not driven during the focus adjustment.

12. When the maximum change amount of the distance between the first transmissive-reflective surface and the second transmissive-reflective surface during the focus adjustment within the adjustment range is dG, 0.5mm≦|dG|≦7.0mm 2. The display optical system according to claim 1, wherein the following condition is satisfied:

13. When the diopter on the pupil plane after the focus adjustment is 0 diopter as the first diopter, the focal length of the display optical system including the diopter is ft[0D], and when the diopter on the pupil plane is 0 diopter, the focal length upon reflection by the first transmissive-reflective surface is fr1[0D], -10.0≦fr1[0D] / ft[0D]≦-0.5 2. The display optical system according to claim 1, wherein the following condition is satisfied:

14. 2. The display optical system according to claim 1, wherein the diagonal length of the square circumscribing the display surface is 1.3 inches or more.

15. 2. The display optical system according to claim 1, wherein the optical element driven in the focus adjustment is composed of one or two refractive elements having an Abbe number of 50 or more based on the d-line, or two refractive elements having an Abbe number difference of 20 or more based on the d-line.

16. the display optical system includes an optical element that is not driven by the adjustment mechanism, 2. The display optical system according to claim 1, wherein the optical element has a diffractive surface.

17. 2. The display optical system according to claim 1, further comprising a plurality of refractive elements bonded together between the first and second transmissive-reflective surfaces, the difference between their Abbe numbers based on the d-line being 20 or more.

18. 2. The display optical system according to claim 1, wherein the display light is guided to the pupil plane via transmission at the second transmission-reflection surface, reflection at the first transmission-reflection surface, reflection at the second transmission-reflection surface, and transmission at the first transmission-reflection surface.

19. A display device comprising the display optical system according to any one of claims 1 to 18.

20. the display optical systems are provided for the right and left eyes, 20. The display device according to claim 19, further comprising an automatic adjustment mechanism that performs convergence adjustment as the focus adjustment in accordance with an image displayed on the display surface.

21. 20. The display optical system according to claim 19, wherein image processing is not performed on the image displayed on the display element to reduce fluctuations in magnification of the image displayed by the display light when the focus adjustment is performed.

Images