Image display device

Abstract

To provide an image display apparatus advantageous for reducing color drift to a central area of a peripheral area of an image display element.SOLUTION: An image display apparatus includes: an image display element; and an eyepiece optical system which guides light from the image display element to an exit pupil. The eyepiece optical system includes at least one correction element having different characteristics between a central area and an area different from the central area. The characteristics of at least one correction element are set such that color drift of second light to first light becomes smaller after the first light emitted from the central area of the image display element and the second light emitted from an outermost peripheral area of the image display element pass through the eyepiece optical system than before the first light and the second light pass through the eyepiece optical system.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an image display device suitable for a head-mounted display or the like that enlarges and observes an image on an image display element through an eyepiece optical system.

Background Art

[0002] In order to realize a thin and lightweight image display device with a wide viewing angle, Patent Document 1 discloses a configuration that folds an optical path using polarization.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the configuration of Patent Document 1, the emission angle of light emitted from the peripheral portion of the image display element is large, and color deviation occurs with respect to the central portion of the peripheral portion of the image display element. Therefore, the peripheral portion of the image cannot be observed in the correct color.

[0005] An object of the present invention is to provide an image display device that is advantageous in reducing color deviation with respect to the central portion of the peripheral portion of an image display element.

Means for Solving the Problems

[0006] An image display device as one aspect of the present invention comprises an image display element and an eyepiece optical system that guides light from the image display element to an exit pupil, wherein the eyepiece optical system includes at least one correction element with different characteristics in the central region and in a region other than the central region, and the characteristics of at least one correction element are set such that the color shift of the second light relative to the first light is smaller after the first light emitted from the central part of the image display element and the second light emitted from the outermost part of the image display element have passed through the eyepiece optical system than before they have passed through it. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an image display device that is advantageous in reducing color shift in the peripheral part of an image display element relative to the center. [Brief explanation of the drawing]

[0008] [Figure 1] This is an explanatory diagram of a head-mounted display, which is an example of an image display device according to the first embodiment. [Figure 2] This is an explanatory diagram of the eyepiece optical system for the right eye of the first embodiment. [Figure 3] This is an external view of the head-mounted display according to the first embodiment. [Figure 4] This is an explanatory diagram of the eyepiece optical system for the right eye of the first embodiment. [Figure 5] This is an explanatory diagram of the emission angle of light emitted from the image display element of the first embodiment. [Figure 6] This is an explanatory diagram of the color shift of the image display element according to the first embodiment. [Figure 7] This is an explanatory diagram illustrating the characteristics of the polarizing plate and PBS in the first embodiment. [Figure 8] This is an explanatory diagram of the chromatic aberration in the eyepiece optical system of the first embodiment. [Figure 9] This is an explanatory diagram of a head-mounted display, which is an example of an image display device according to the second embodiment. [Figure 10] This is an explanatory diagram of the right eyepiece optical system of the second embodiment. [Figure 11]Explanatory diagram of the emission angle of light emitted from the image display element of the second embodiment. [Figure 12] Explanatory diagram of the color shift of the image display element of the second embodiment. [Figure 13] Explanatory diagram of the characteristics of the polarizing plate of the second embodiment. [Figure 14] Explanatory diagram of the color shift of the ocular optical system of the second embodiment. [Figure 15] Diagram showing an example of the characteristics of the polarizing plate of the second embodiment. [Figure 16] Explanatory diagram of a head-mounted display which is an example of an image display device according to the third embodiment. [Figure 17] Explanatory diagram of the ocular optical system for the right eye of the third embodiment. [Figure 18] Explanatory diagram of the characteristics of the polarizing plate of the third embodiment. [Figure 19] Explanatory diagram of a head-mounted display which is an example of an image display device according to the fourth embodiment. [Figure 20] Explanatory diagram of a head-mounted display which is another example of an image display device according to the fourth embodiment. [Figure 21] Explanatory diagram of a head-mounted display which is an example of an image display device according to the fifth embodiment. [Figure 22] Diagram showing a state where the head-mounted display of the fifth embodiment is connected to a PC. [Figure 23] Explanatory diagram of the ocular optical system for the right eye of the sixth embodiment. [Figure 24] Explanatory diagram of the characteristics of the minus filter of the sixth embodiment. [Figure 25] Explanatory diagram of the characteristics of the minus filter of the sixth embodiment. [Figure 26] Explanatory diagram of the emission spectrum of the image display element of the sixth embodiment. [Figure 27] Explanatory diagram of the emission spectrum of the image display element of the sixth embodiment. [Figure 28] Explanatory diagram of the emission spectrum of the image display element of the sixth embodiment. [Figure 29] This is an explanatory diagram of the eyepiece optical system for the right eye according to the seventh embodiment. [Figure 30] This is an explanatory diagram of the characteristics of the IR cut filter according to the seventh embodiment. [Figure 31] This is an explanatory diagram of the characteristics of the IR cut filter according to the seventh embodiment. [Figure 32] This is an explanatory diagram of the emission spectrum of the image display element of the seventh embodiment. [Figure 33] This is an explanatory diagram of the emission spectrum of the image display element of the seventh embodiment. [Figure 34] This is an explanatory diagram of the emission spectrum of the image display element of the seventh embodiment. [Modes for carrying out the invention]

[0009] The embodiments of the present invention will be described in detail below with reference to the drawings. In each figure, the same reference numeral is used for identical components, and redundant explanations are omitted.

[0010] In this embodiment, we will mainly describe the eyepiece optical system for the right eye, but the same applies to the eyepiece optical system for the left eye. [First Embodiment] Figure 1 is an explanatory diagram of a head-mounted display (hereinafter referred to as HMD) 101, which is an example of an image display device according to this embodiment. The HMD 101 has lenses 104, 105, 106, 107, a right-eye image display element 108, and a left-eye image display element 109. Lenses 104 and 105 constitute the right-eye eyepiece optical system, and lenses 106 and 107 constitute the left-eye eyepiece optical system. The right-eye image display element 108 and the left-eye image display element 109 are organic EL displays.

[0011] The right eyepiece optical system projects the original image displayed on the right eye image display element 108 as a magnified virtual image and guides it to the observer's right eye 102. The left eyepiece optical system projects the original image displayed on the left eye image display element 109 as a magnified virtual image and guides it to the observer's left eye 103. The focal length of the right and left eyepiece optical systems is 12 mm, the horizontal display field of view is 45°, the vertical display field of view is 34°, and the diagonal display field of view is 54°. The distance between the HMD 101 and the observer's eyeball (eye relief) is 18 mm.

[0012] The eyepiece optical system of this embodiment has a configuration that folds the optical path using polarization. The optical path of the eyepiece optical system will be explained using the right-eye eyepiece optical system. Figure 2 is an explanatory diagram of the right-eye eyepiece optical system of this embodiment. The right-eye eyepiece optical system includes, in order from the right-eye image display element 108 side, a polarizer (first polarizer) 110, a phase plate (first phase plate) 111, lenses 105, 104, a phase plate (second phase plate) 113, and a polarization separation element (hereinafter referred to as PBS) 114. A half mirror 112 is deposited on the surface of lens 104 on the lens 105 side. The surface on which the half mirror 112 is deposited acts as a semi-transparent reflective surface (semi-transparent reflective film). The phase plate 113 and PBS 114 are planar in shape. The phase plates 111 and 113 are waveplates with a phase difference of λ / 4.

[0013] In this embodiment, the slow axis of the phase plate 111 is tilted at 45° with respect to the polarization direction transmitted by the polarizing plate 110, the slow axis of the phase plate 113 is tilted at -45° with respect to the polarization direction transmitted by the polarizing plate 110, and the polarization direction transmitted by the polarizing plate 110 and the polarization direction transmitted by the PBS 114 are orthogonal. In this configuration, light emitted from the right eye image display element 108 passes through the polarizing plate 110 to become linearly polarized, passes through the phase plate 111 to become circularly polarized. After that, it passes through the half mirror 112 and then through the phase plate 113 to become linearly polarized. Since the polarization direction of this linearly polarized light is orthogonal to the polarization direction transmitted by the PBS 114, it is reflected by the PBS 114 and passes through the phase plate 113 to become circularly polarized. After that, it is reflected by the half mirror 112 and then passes through the phase plate 113 to become linearly polarized. The linearly polarized light passes through PBS114 and is guided to the observer's right eye 102 because its polarization direction coincides with the polarization direction transmitted through PBS114. The same optical path applies to the left eyepiece optical system.

[0014] As in this embodiment, by having an eyepiece optical system that folds the optical path using polarization, the HMD101 can be made thinner, and the focal length of the eyepiece optical system can be shortened, thereby enabling wide-angle image observation.

[0015] Figure 3 is an external view of the HMD101. Since the HMD101 is a head-mounted image display device, it is desirable that it be lightweight. Therefore, it is desirable that the lenses constituting the eyepiece optical system be made of resin, which has a lower specific gravity than glass. In this embodiment, the aberration correction effect is enhanced by making lenses 104 and 106 aspherical lenses with a plano-convex shape made of resin. Lenses 105 and 107 are double-sided aspherical lenses made of resin.

[0016] Figure 4 is an explanatory diagram of the right eyepiece optical system of this embodiment. In the right eyepiece optical system of this embodiment, the exit pupil is positioned at 28 mm, which is the sum of the eye relief (=18 mm) and the radius of rotation of the eyeball (=10 mm), and the exit pupil diameter is 6 mm. This ensures that even when the eyeball rotates to observe images in all directions (up, down, left, or right), light from that direction enters the eyeball. It is desirable that the eye relief be 15 mm or more so that observers wearing glasses can also wear the HMD101. Furthermore, since a longer eye relief increases the outer diameter of the lens and makes the HMD101 larger, it is desirable that the eye relief be 25 mm or less.

[0017] Because the eyepiece optical system in this embodiment has a short focal length and is thin, the emission angle of light emitted from the periphery of the image display element toward the exit pupil of the eyepiece optical system is large, as can be seen from Figure 4. The periphery refers to the area outside the center of the right eye image display element 108. Figure 5 is an explanatory diagram of the emission angle of light emitted from the image display element in this embodiment, showing the relationship between the display field of view and the emission angle of light emitted from the image display element toward the exit pupil. The emission angle of light emitted from the image display element is defined as the emission angle of the principal ray guided to the center of the exit pupil. As shown in Figure 5, the emission angle increases as the display field of view increases, with the emission angle of light emitted from the horizontal end of the image display element being 37 degrees and the emission angle of light emitted from the vertical end being 29 degrees. In order to shorten the focal length of the eyepiece optical system and achieve a thinner HMD101, it is desirable that the emission angle of light emitted from the periphery of the image display element toward the center of the exit pupil be 30 degrees or more.

[0018] When the emission angle of light emitted from the image display element increases, color shift occurs due to interference of the organic EL light-emitting layer and the mixing of colors in the color filter. In this embodiment, when the emission angle of light emitted from the image display element increases, the chromaticity shifts towards red, as shown in Figure 6, causing color shift. Therefore, when an observer views a white image, red is observed when viewing the peripheral areas of the image, making natural image viewing impossible.

[0019] Therefore, in this embodiment, at least one of the polarizer 110 and the PBS 114 is made to function as a corrective element with different characteristics in the central part and a region different from the central part (periphery). When the polarizer 110 functions as a corrective element, the polarizer 110 has the characteristic of having different spectral transmittance in the central part and the peripheral part. Also, when the PBS 114 functions as a corrective element, the PBS 114 has the characteristic of having different spectral transmittance and spectral reflectance in the central part and the peripheral part. As a result, the color shift of the second light relative to the first light emitted from the central part of the right eye image display element 108 and the second light emitted from the outermost peripheral part can be reduced after they have passed through the right eye eyepiece optical system compared to before they have passed through. In other words, the color shift in the peripheral part of the right eye image display element 108 can be canceled out. Figure 7 is an explanatory diagram of the characteristics of the polarizer 110 and the PBS 114. Figure 7(a) shows the transmittance (spectral transmittance) of the polarizer 110 for light at an incident angle of 0 degrees for each wavelength. Figure 7(b) shows the reflectance (spectral reflectance) of PBS114 for light at an incident angle of 0 degrees at each wavelength. Figure 7(c) shows the transmittance (spectral transmittance) of PBS114 for light at an incident angle of 0 degrees at each wavelength. The primary wavelength of blue in the image display element is 450 nm, the primary wavelength of green is 525 nm, and the primary wavelength of red is 610 nm. Figure 7 shows the transmittance and reflectance at each wavelength. The wavelength of blue (first wavelength) should be within the range of 430 nm to 480 nm. The wavelength of green (second wavelength) should be within the range of 520 nm to 570 nm. The wavelength of red (third wavelength) should be within the range of 600 nm to 650 nm. When the spectral transmittance differs between the central and peripheral areas, it is desirable to change it gradually so that the change is not noticeable.

[0020] As shown in Figure 7(a), the blue and green transmittance of the polarizer 110 does not change much even when the angle of incidence is large, but the red transmittance decreases as the angle of incidence increases. The reflectance and transmittance of the PBS 114 show a similar trend. The light emitted from the periphery of the right eye image display element 108 has a large exit angle, and the angle of incidence to the polarizer 110 and PBS 114 is also large. Therefore, the red color-shifted light emitted from the periphery of the right eye image display element 108 passes through the polarizer 110 and is reflected and transmitted by the PBS 114, reducing the intensity of the red color and thus reducing the color shift.

[0021] Figure 8 is an explanatory diagram of the chromatic shift in the eyepiece optical system, showing the relationship between the emission angle and chromaticity after passing through the eyepiece optical system. With the image display element alone, as the emission angle increases, the chromaticity shifts towards red, as shown in Figure 6. However, after passing through the eyepiece optical system, the change in chromaticity becomes smaller, as shown in Figure 8, thus reducing chromatic shift. In this embodiment, with the image display element alone, as the emission angle increases, the chromaticity difference x on the chromaticity coordinate is 0.1 and the chromaticity difference y is 0.055. However, after passing through the eyepiece optical system, the chromaticity difference x can be reduced to 0.04 and the chromaticity difference y to 0.015. For the observer to be less likely to notice the chromatic shift and to observe a natural image, it is desirable that the chromaticity difference x on the chromaticity coordinate is 0.05 or less and the chromaticity difference y is 0.05 or less.

[0022] In this embodiment, the wavelength at which the ratio between the intensity of light emitted from the periphery of the image display element to the exit pupil and the intensity of light emitted from the center of the image display element to the exit pupil is greatest is 610 nm, the dominant wavelength of red light, and a red color shift occurs as the emission angle increases. Therefore, by setting the wavelength with the lowest transmittance of the polarizer 110 and the lowest transmittance and reflectance of the PBS 114 among the red, green, and blue wavelengths to red, the color shift of the image display element is canceled. In this way, the color shift of the periphery relative to the center of the right eye image display element 108 is reduced by the characteristic that the spectral transmittance differs between the center and periphery of the polarizer 110 and PBS 114, which are color correction elements, allowing the observer to observe a more natural image.

[0023] In the right-eye eyepiece optical system of this embodiment, the emission angle of light emitted from the horizontal end of the right-eye image display element 108 is 37 degrees, and the horizontal display half-angle of view is 22.5 degrees. The angle of incidence to the polarizer plate 110 is greater than the angle of incidence to the PBS 114. Therefore, it is desirable to cancel out the emission angle characteristics of the right-eye image display element 108 with the characteristics of the polarizer plate 110 that are close to those of the right-eye image display element 108.

[0024] Furthermore, in the optical path of the right eye eyepiece optical system, the PBS 114 acts twice, once for reflection and once for transmission. Therefore, canceling the emission angle characteristics of the right eye image display element 108 with the characteristics of the PBS 114 is highly effective in reducing color shift. If the direction of color shift differs between the horizontal and vertical directions due to the arrangement of the color filters of the right eye image display element 108, the characteristics of the polarizer 110 and PBS 114 may be changed for the horizontal and vertical directions. When the emission angle of light emitted from the right eye image display element 108 is large, if the color shift is red in the horizontal direction and blue in the vertical direction, the characteristics of the polarizer 110 may be set so that the horizontal transmittance is low and the vertical transmittance is low.

[0025] In this embodiment, the chromaticity shift is reduced when the emission angle of light emitted from the right eye image display element 108 is large, but the color difference ΔE * You may also set it to reduce the deviation. In that case, the color difference ΔE * It is preferable that the value be 15 or less.

[0026] In this embodiment, the surface of the lens 104 on which the half-mirror 112 is deposited is a convex surface that is convex toward the right-eye image display element 108. By depositing the half-mirror 112 on the convex surface, a wide field of view can be achieved while making the HMD 101 thinner. Furthermore, by making the convex surface on which the half-mirror 112 is deposited aspherical, the aberration correction effect can be enhanced.

[0027] In this embodiment, lenses 105 and 107 are resin lenses, but they may also be glass lenses because their small external size and minimal weight increase would have little effect. Since the birefringence of glass lenses is very small, high-quality image observation becomes possible.

[0028] Furthermore, a polarizing plate may be placed between the PBS114 and the observer's eyeball to reduce ghosting from ambient light and improve the contrast of the observed image.

[0029] In this embodiment, in order to achieve both an increased eye relief and a thinner HMD 101, the surface of the lens 104 on the side of the observer's right eye 202, where the phase plate 113 and PBS 114 are located, is made flat. If the surface of the lens 104 on the observer side is a concave surface that is concave toward the observer, the lens 104 becomes thicker in order to ensure eye relief in the peripheral area. Conversely, if it is a convex surface, the lens 104 becomes thicker in order to ensure the thickness of the lens edge.

[0030] In this embodiment, the phase plates 111 and 113 are waveplates with a phase difference of λ / 4, but the phase difference may be shifted from λ / 4 to cancel out the birefringence of the lenses 104 and 105. In this case, it is desirable that the sum of the phase differences between lens 104 and phase plate 113 is 3λ / 20 or more and 7λ / 20 or less. It is also desirable that the sum of the phase differences between lens 105 and phase plate 111 is 3λ / 20 or more and 7λ / 20 or less. If it falls outside the above range, the intensity of ghost light will increase, making it impossible to observe a natural image.

[0031] In this embodiment, the right-eye image display element 108 emits unpolarized light as an organic EL, but it may also emit linearly polarized light as a liquid crystal display. In this case, the polarizing plate 110 becomes unnecessary, allowing for a thinner HMD 101 and a reduction in the number of components.

[0032] In this embodiment, the eyepiece optical system uses a PBS114 that switches between transmission and reflection based on the direction of linear polarization. However, a polarization separation element that switches between transmission and reflection based on the direction of circular polarization may also be used. In this case, the phase plate 113 becomes unnecessary, allowing for a thinner HMD101 and a reduction in the number of components. [Second Embodiment] Figure 9 is an explanatory diagram of a head-mounted display (hereinafter referred to as HMD) 201, which is an example of an image display device according to this embodiment. The HMD 201 has lenses 204, 205, 206, 207, a right-eye image display element 208, and a left-eye image display element 209. Lenses 204 and 205 constitute the right-eye eyepiece optical system, and lenses 206 and 207 constitute the left-eye eyepiece optical system. Lenses 204, 205 and lenses 206, 207 are cemented lenses, which can be easily held. The right-eye image display element 208 and the left-eye image display element 209 are organic EL displays.

[0033] The right-eye eyepiece optical system projects the original image displayed on the right-eye image display element 208 as a magnified virtual image and guides it to the observer's right eye 202. The left-eye eyepiece optical system projects the original image displayed on the left-eye image display element 209 as a magnified virtual image and guides it to the observer's left eye 203. The focal length of the right-eye and left-eye eyepiece optical systems is 13 mm, the horizontal display field of view is 60°, the vertical display field of view is 60°, and the diagonal display field of view is 78°. The distance between the HMD 201 and the observer's eyeball (eye relief) is 20 mm.

[0034] The eyepiece optical system of this embodiment has a configuration that folds the optical path using polarization. The optical path of the eyepiece optical system will be explained using the right-eye eyepiece optical system. Figure 10 is an explanatory diagram of the right-eye eyepiece optical system of this embodiment. The right-eye eyepiece optical system includes, in order from the right-eye image display element 208 side, a polarizer (first polarizer) 210, a phase plate (first phase plate) 211, lenses 205, 204, a phase plate (second phase plate) 213, a polarization separation element (hereinafter referred to as PBS) 214, and a polarizer (second polarizer) 215. A half mirror 212 is deposited on the surface of lens 204 on the lens 205 side. The surface on which the half mirror 212 is deposited acts as a semi-transparent reflective surface. The phase plate 213, PBS 214, and polarizer 215 are planar in shape. The phase plates 211 and 213 are waveplates with a phase difference of λ / 4.

[0035] In this embodiment, the slow axis of the phase plate 211 is tilted at 45° with respect to the polarization direction transmitted by the polarizing plate 210, the slow axis of the phase plate 213 is tilted at -45° with respect to the polarization direction transmitted by the polarizing plate 210, and the polarization direction transmitted by the polarizing plate 210 and the polarization direction transmitted by the PBS 214 are orthogonal. Also, the polarization direction transmitted by the PBS 214 and the polarization direction transmitted by the polarizing plate 215 are the same. In this configuration, light emitted from the right eye image display element 208 passes through the polarizing plate 210 to become linearly polarized, passes through the phase plate 211 to become circularly polarized. After that, it passes through the half mirror 212 and then through the phase plate 213 to become linearly polarized. Since the polarization direction of this linearly polarized light is orthogonal to the polarization direction transmitted by the PBS 214, it is reflected by the PBS 214 and passes through the phase plate 213 to become circularly polarized. After that, it is reflected by the half mirror 212 and then passes through the phase plate 213 to become linearly polarized. The linearly polarized light, whose polarization direction coincides with the polarization direction transmitted through PBS214, passes through PBS214 and the polarizer 215 and is guided to the observer's right eye 202. The same optical path is used for the left eyepiece optical system.

[0036] In this embodiment, a polarizing plate 215 is placed between the PBS 214 and the observer's right eye 202 to reduce ghosting from ambient light and enhance the contrast of the observed image.

[0037] As in this embodiment, by providing an eyepiece optical system that folds the optical path using polarization, the HMD201 can be made thinner, and the focal length of the eyepiece optical system can be shortened, thereby enabling wide-angle image observation.

[0038] Since the HMD201 is a head-mounted image display device, it is desirable that it be lightweight. Therefore, it is desirable that the lenses constituting the eyepiece optical system be made of resin, which has a lower specific gravity than glass. In this embodiment, the aberration correction effect is enhanced by making lenses 204, 205, 206, and 207 aspherical lenses made of resin.

[0039] In the eyepiece optical system of this embodiment, the exit pupil is positioned at 30 mm, which is the sum of the eye relief (=20 mm) and the radius of rotation of the eyeball (=10 mm), and the exit pupil diameter is 6 mm. This ensures that even when the eyeball rotates to observe images in all directions (up, down, left, and right), light from that direction enters the eyeball. It is desirable that the eye relief be 15 mm or more so that observers wearing glasses can also wear the HMD201. Furthermore, since a longer eye relief increases the outer diameter of the lens and makes the HMD201 larger, it is desirable that the eye relief be 25 mm or less.

[0040] In this embodiment, the eyepiece optical system has a short focal length and is thin, so the emission angle of light emitted from the periphery of the image display element to the exit pupil of the eyepiece optical system is large. Figure 11 is an explanatory diagram of the emission angle of light emitted from the image display element in this embodiment, showing the relationship between the display field of view and the emission angle of light emitted from the image display element to the exit pupil. The emission angle of light emitted from the image display element is defined as the emission angle of the principal ray guided to the center of the exit pupil. As shown in Figure 11, the emission angle increases as the display field of view increases, and the emission angle of light emitted from the horizontal and vertical ends of the image display element is 47 degrees. In order to shorten the focal length of the eyepiece optical system and achieve a thinner HMD201, it is desirable that the emission angle of light emitted from the image display element to the center of the exit pupil be 30 degrees or more.

[0041] When the emission angle of light emitted from the image display element increases, color shift occurs due to interference of the organic EL light-emitting layer and the mixing of colors in the color filter. In this embodiment, when the emission angle of light emitted from the image display element increases, the chromaticity shifts towards blue, as shown in Figure 12, causing color shift. Therefore, when an observer views a white image, blue is observed when viewing the peripheral areas of the image, making natural image viewing impossible.

[0042] Therefore, in this embodiment, at least one of the polarizers 210 and 215 functions as a correction element with different characteristics in the central part and a region different from the central part (periphery). Specifically, at least one of the polarizers 210 and 215 has the characteristic of having different spectral transmittance in the central part and the peripheral part. As a result, the color shift of the second light relative to the first light emitted from the central part of the right eye image display element 208 and the second light emitted from the outermost peripheral part can be reduced after they have passed through the right eye eyepiece optical system compared to before they have passed through. In other words, the color shift in the peripheral part of the right eye image display element 208 can be canceled out. Figure 13 is an explanatory diagram of the characteristics of the polarizers 210 and 215. Figures 13(a) and 13(b) show the transmittance (spectral transmittance) of the polarizers 210 and 215 for light at an incident angle of 0 degrees for each wavelength. The primary wavelengths for blue, green, and red in the image display element are 470 nm, 545 nm, and 605 nm, respectively. Figure 13 shows the transmittance at each wavelength. Note that the blue wavelength (first wavelength) should be within the range of 430 nm to 480 nm. The green wavelength (second wavelength) should be within the range of 520 nm to 570 nm. The red wavelength (third wavelength) should be within the range of 600 nm to 650 nm.

[0043] As shown in Figure 13(a), the transmittance of green and red light through polarizer 210 does not change much even when the angle of incidence increases, but the transmittance of blue light decreases as the angle of incidence increases. The transmittance of polarizer 215 shows a similar trend. Light emitted from the periphery of the right eye image display element 208 has a large exit angle and a large angle of incidence to polarizers 210 and 215. Therefore, the blue-color-shifted light emitted from the periphery of the right eye image display element 208 passes through polarizers 210 and 215, reducing the intensity of the blue light and thus reducing the color shift.

[0044] Figure 14 is an explanatory diagram of the chromatic shift in the eyepiece optical system, showing the relationship between the emission angle and chromaticity after passing through the eyepiece optical system. With the image display element alone, as the emission angle increases, the chromaticity shifts towards blue, as shown in Figure 12. However, after passing through the eyepiece optical system, the change in chromaticity becomes smaller, as shown in Figure 14, thus reducing chromatic shift. In this embodiment, with the image display element alone, as the emission angle increases, the chromaticity difference x on the chromaticity coordinate is 0.055 and the chromaticity difference y is 0.07. However, after passing through the eyepiece optical system, the chromaticity difference x can be reduced to 0.015 and the chromaticity difference y to 0.02. Here, in order for the observer to not notice the chromatic shift and to observe a natural image, it is desirable that the chromaticity difference x on the chromaticity coordinate is 0.05 or less and the chromaticity difference y is 0.05 or less.

[0045] In this embodiment, the wavelength at which the ratio of the intensity of light emitted from the periphery of the image display element to the intensity of light emitted from the center of the image display element to the intensity of light emitted from the periphery to the exit pupil is greatest is 470 nm, the dominant wavelength of blue light, and a blue color shift occurs as the emission angle increases. Therefore, by setting the wavelength with the lowest transmittance of polarizers 210 and 215 among red, green, and blue wavelengths to blue, the color shift of the image display element is canceled out. In this way, the color shift of the periphery relative to the center of the image display element is reduced by the characteristic that the spectral transmittance differs between the center and periphery of the polarizers 210 and 215, which are color correction elements, allowing the observer to observe a more natural image.

[0046] In the right-eye eyepiece optical system of this embodiment, the emission angle of light emitted from the horizontal end of the right-eye image display element 208 is 47 degrees, and the horizontal display half-angle of view is 30 degrees. The angle of incidence to the polarizer 210 is greater than the angle of incidence to the polarizer 215. Therefore, it is desirable to cancel the emission angle characteristics of the image display element with the characteristics of the polarizer 210, which is closer to the right-eye image display element 208. In addition, there are cases where the horizontal display half-angle of view is greater than the emission angle of light emitted from the horizontal end of the right-eye image display element 208, and the angle of incidence to the polarizer 215 is greater than the angle of incidence to the polarizer 215. In this case, it is desirable to cancel the emission angle characteristics of the right-eye image display element 208 with the characteristics of the polarizer 215.

[0047] In this embodiment, the color shift caused by the emission angle of light emitted from the image display element is canceled by the properties of the polarizing plate, but it may also be canceled by the properties of the phase plate. In that case, the transmittance and reflectance when combined with the polarizing plate and PBS may be changed, or the phase amount of the phase plate may be changed for each wavelength.

[0048] Alternatively, the color shift caused by the emission angle of light emitted from the image display element may be canceled by having at least one of the spectral transmittance and spectral reflectance characteristics differ between the center of the half mirror and a region outside the center. In that case, as shown in Figure 9, the difference in the incident angle when light emitted from the center of the image display element and light emitted from the periphery is large when transmitted through the half mirror, but the difference in the incident angle when reflected from the half mirror is small. Therefore, it is desirable to cancel the color shift using the characteristics when light is transmitted through the half mirror.

[0049] In this embodiment, when the emission angle of light emitted from the image display element is large, the color shift is blue regardless of the direction of light emission. Since the shifted color is the same, there is no need to change the characteristics of the polarizer according to the direction of incidence. Furthermore, since the shifted color is blue, which is a color for which humans have low relative luminous sensitivity, the color shift perceived by the observer is small even when the intensity of light emitted from the image display element is high.

[0050] If the characteristics of the polarizing plate 210 differ in the horizontal and vertical directions, it is desirable to have characteristics that reduce horizontal color shift, as the human field of view is wider horizontally than vertically, and observers are more likely to notice horizontal color shift. For example, the horizontal characteristics could be as shown in Figure 15(a) for high blue cancellation effect, and the vertical characteristics as shown in Figure 15(b). Also, if the characteristics of the polarizing plate 215 differ in the horizontal and vertical directions, it is desirable to have characteristics that reduce horizontal color shift.

[0051] In this embodiment, the color shift is reduced when the emission angle of light emitted from the right eye image display element 208 is large, but the characteristics of the polarizers 210 and 215 are used to reduce the color difference ΔE *You may also adjust the settings to reduce the discrepancy. In that case, you may change the absolute values ​​of the transmittance and reflectance for each color.

[0052] In this embodiment, the surface of the lens 204 on which the half-mirror 112 is deposited is a convex surface that is convex toward the right-eye image display element 208. By depositing the half-mirror 212 on the convex surface, a wide field of view can be achieved while making the HMD 201 thinner. Furthermore, by making the convex surface on which the half-mirror 212 is deposited an aspherical shape, the aberration correction effect can be enhanced.

[0053] In this embodiment, since lenses 204 and 205 are joined together, the surface on which the half-mirror 212 is deposited may be the surface of lens 205 facing the observer's right eye 202. Even in that case, the surface on which the half-mirror 212 is deposited is a convex surface that is convex toward the right-eye image display element 208.

[0054] In this embodiment, in order to achieve both an increased eye relief and a thinner HMD201, the surface on the side of the observer's right eye 202, where the phase plate 213 and PBS214 of the lens 204 are formed, is made flat.

[0055] In this embodiment, the phase plates 211 and 213 are waveplates with a phase difference of λ / 4, but the phase difference may be shifted from λ / 4 to cancel out the birefringence of the lenses 204 and 205. In this case, it is desirable that the sum of the phase differences of lens 204 and phase plate 213 be 3λ / 20 or more and 7λ / 20 or less. It is also desirable that the sum of the phase differences of lens 205 and phase plate 211 be 3λ / 20 or more and 7λ / 20 or less. If it falls outside the above range, the intensity of ghost light will increase, making it impossible to observe a natural image. [Third Embodiment] Figure 16 is an explanatory diagram of a head-mounted display (hereinafter referred to as HMD) 301, which is an example of an image display device according to this embodiment. The HMD 301 has lenses 304, 305, 306, and 307, a right-eye image display element 308, and a left-eye image display element 309. The right-eye eyepiece optical system is formed by lenses 304 and 305, and the left-eye eyepiece optical system is formed by lenses 306 and 307. Lenses 304, 305 and lenses 306 and 307 are cemented lenses, which can be easily held. The right-eye image display element 308 and the left-eye image display element 309 are organic EL displays.

[0056] The right eyepiece optical system projects the original image displayed on the right eye image display element 308 as a magnified virtual image and guides it to the observer's right eye 302. The left eyepiece optical system projects the original image displayed on the left eye image display element 309 as a magnified virtual image and guides it to the observer's left eye 303. The focal length of the right and left eyepiece optical systems is 13 mm, the horizontal display field of view is 60°, the vertical display field of view is 60°, and the diagonal display field of view is 78°. The distance between the HMD201 and the observer's eyeball (eye relief) is 20 mm.

[0057] The eyepiece optical system of this embodiment has a configuration that folds the optical path using polarization. The optical path of the eyepiece optical system will be explained using the right eyepiece optical system. Figure 17 is an explanatory diagram of the right eyepiece optical system of this embodiment. The right eyepiece optical system includes, in order from the right eye image display element 308 side, a polarizer (first polarizer) 310, a phase plate (first phase plate) 311, lenses 305, 304, a phase plate (second phase plate) 313, a polarization separation element (hereinafter referred to as PBS) 314, and a polarizer (second polarizer) 315. A half mirror 312 is deposited on the surface of lens 304 on the lens 305 side. The surface on which the half mirror 312 is deposited acts as a semi-transparent reflective surface. The phase plate 313, PBS 314, and polarizer 315 are planar in shape. The phase plates 311 and 313 are waveplates with a phase difference of λ / 4. The optical path of the eyepiece optical system is the same as in the first or second embodiment, so a description will be omitted.

[0058] In this embodiment, the eyepiece optical system has a short focal length and is thin, so the emission angle of light emitted from the periphery of the image display element toward the exit pupil of the eyepiece optical system is large, and the emission angle of light emitted from the horizontal and vertical ends of the image display element is 47 degrees. In order to shorten the focal length of the eyepiece optical system and achieve a thinner HMD101, it is desirable that the emission angle of light emitted from the periphery of the image display element toward the center of the exit pupil be 30 degrees or more.

[0059] When the emission angle of light emitted from the image display element increases, color shift occurs due to interference of the organic EL light-emitting layer and the mixing of colors in the color filter. In this embodiment, when the emission angle of light emitted from the image display element increases, the mixing of colors in the color filter causes a color shift, with the right edge of the display screen shifting towards blue and the left edge shifting towards red. Therefore, when an observer views a white image, they will see red or blue in the peripheral areas, making natural image viewing impossible.

[0060] Therefore, in this embodiment, the polarizer 310 functions as a correction element with different characteristics in the central part and the region other than the central part (periphery). Specifically, the polarizer 310 has different spectral transmittances in the central part, the right edge of the peripheral part, and the left edge of the peripheral part. This makes it possible to reduce the color shift of the second light relative to the first light after it has passed through the right eyepiece optical system, compared to before it has passed through the right eye image display element 308. In other words, it is possible to cancel out the color shift of the blue light at the right edge and the red light at the left edge of the peripheral part of the right eye image display element 308. Figure 18 is an explanatory diagram of the characteristics of the polarizer 310, showing the spectral transmittances of the central part, the right edge of the peripheral part, and the left edge of the peripheral part of the polarizer 310. As shown in Figure 18, compared to the transmittance of the center of the polarizer 310, the transmittance of blue wavelengths is reduced at the right edge, and the transmittance of red wavelengths is reduced at the left edge. Therefore, the blue-color-shifted light emitted from the right edge of the image display element is reduced in intensity by passing through the right edge of the polarizing plate 310, thereby reducing the blue color shift. Similarly, the red-color-shifted light emitted from the left edge of the right-eye image display element 308 is reduced in intensity by passing through the left edge of the polarizing plate 310, thereby reducing the red color shift. The dominant wavelength for blue in the right-eye image display element 308 is 470 nm, the dominant wavelength for green is 545 nm, and the dominant wavelength for red is 605 nm. The wavelength for blue (first wavelength) should be within the range of 430 nm to 480 nm. The wavelength for green (second wavelength) should be within the range of 520 nm to 570 nm. The wavelength for red (third wavelength) should be within the range of 600 nm to 650 nm.

[0061] As explained above, the color shift in the peripheral area relative to the central area of ​​the right eye image display element 308 can be reduced by changing the spectral transmittance of the central and peripheral areas of the polarizing plate 310, which is a color correction element. This allows the observer to observe a more natural image.

[0062] In this embodiment, as shown in Figure 16, the light beam width of the polarizing plate 310 near the right eye image display element 308 is small and easily separated for each field of view. Therefore, it is desirable to cancel out the emission angle characteristics of the right eye image display element 308 using the characteristics of each location on the polarizing plate 310.

[0063] In this embodiment, the color shift caused by the emission angle of light emitted from the image display element is canceled by the properties of the polarizing plate, but it may also be canceled by the properties of the phase plate. In that case, the transmittance and reflectance when combined with the polarizing plate and PBS may be changed, or the phase amount of the phase plate may be changed for each wavelength.

[0064] Alternatively, the color shift caused by the emission angle of light emitted from the image display element may be canceled by having at least one of the spectral transmittance and spectral reflectance differ between the central part of the half mirror and a region other than the central part. In that case, as shown in Figure 16, since the light beam width of the light from the image display element is small and easily separated for each field of view, it is desirable to cancel the color shift using the characteristics of each location of the half mirror. [Fourth Embodiment] Figure 19 is an explanatory diagram of a head-mounted display (hereinafter referred to as HMD) 401, which is an example of an image display device according to this embodiment. The HMD 401 has lenses 404, 405, 406, and 407, a right-eye image display element 408, and a left-eye image display element 409. Lenses 404 and 405 constitute the right-eye eyepiece optical system, and lenses 406 and 407 constitute the left-eye eyepiece optical system. The right-eye image display element 408 and the left-eye image display element 409 are organic EL displays.

[0065] The right eyepiece optical system projects the original image displayed on the right eye image display element 408 as a magnified virtual image and guides it to the observer's right eye 402. The left eyepiece optical system projects the original image displayed on the left eye image display element 409 as a magnified virtual image and guides it to the observer's left eye 403. The focal length of the right and left eyepiece optical systems is 10 mm, the horizontal display field of view is 90°, the vertical display field of view is 90°, and the diagonal display field of view is 110°. The distance between the HMD201 and the observer's eyeball (eye relief) is 12 mm.

[0066] The eyepiece optical system of this embodiment includes a configuration that folds the optical path using polarization. Since this configuration is the same as in Embodiment 1, a detailed explanation will be omitted.

[0067] In this embodiment, the eyepiece optical system has a short focal length and is thin, so the emission angle of light emitted from the periphery of the image display element toward the exit pupil of the eyepiece optical system is large, and the emission angles of light emitted from the horizontal and vertical ends of the image display element are 60 degrees. In order to shorten the focal length of the eyepiece optical system and achieve a thinner HMD101, it is desirable that the emission angle of light emitted from the periphery of the image display element toward the center of the exit pupil be 30 degrees or more.

[0068] When the emission angle of light emitted from the image display element increases, color shift occurs due to interference of the organic EL light-emitting layer and the mixing of colors in the color filter. In this embodiment, when the emission angle of light emitted from the image display element increases, a blue color shift occurs in the peripheral areas of the display screen due to the mixing of colors in the color filter. Therefore, when an observer views a white image, a blue color is observed when viewing the peripheral areas of the image, making natural image viewing impossible.

[0069] Therefore, in this embodiment, at least one of the lenses 405 and 407 functions as a corrective element with different characteristics in the central part and in a region different from the central part (periphery). Specifically, the anti-reflective film deposited on the curved surface of the lens 405 and 407 on the side of the image display element has different spectral transmittance in the central part and the peripheral part. As a result, the color shift of the second light relative to the first light emitted from the central part of the image display element and the second light emitted from the outermost peripheral part can be reduced after they have passed through the eyepiece optical system compared to before they have passed through. In other words, the color shift in the peripheral part of the image display element can be canceled out.

[0070] As explained above, the color shift in the peripheral areas relative to the center of the image display element can be reduced by changing the spectral transmittance of the anti-reflective coating on the center and peripheral areas of the color correction elements, lenses 405 and 407. This allows the observer to observe a more natural image.

[0071] Because the curved surface of lenses 405 and 407 on the image display element side has a large difference between the angle of incidence of light from the center of the image display element and the angle of incidence of light from the periphery, it is desirable to reduce color shift by the properties of the anti-reflective coating deposited on the curved surface of lenses 405 and 407 on the image display element side. Alternatively, an anti-reflective coating with similar properties may be deposited on both sides of lenses 404 and 406, or on the observer-side surface of lenses 405 and 407. In that case, the effect of reducing color shift can be greatly enhanced.

[0072] Furthermore, because the difference between the angle of incidence of light from the center and the angle of incidence of light from the periphery of the image display element is large, an anti-reflective coating may be deposited on the cover glass of the image display element, and its properties may be such that the transmittance of blue wavelengths decreases as the angle of incidence increases.

[0073] Furthermore, as shown in Figure 20, color correction elements 410 and 411 may be placed between the right eye image display element 408 and the lens 405, and between the left eye image display element 409 and the lens 407, to cancel out peripheral color shifts using the characteristics of the color correction elements 410 and 411. In this case, the characteristics of the color correction elements 410 and 411 are such that the transmittance of blue wavelengths decreases as the angle of incidence increases.

[0074] Furthermore, in the case where the shifted color differs depending on the location on the display screen, such as blue at the right edge and red at the left edge, as in the third embodiment, the characteristics of the anti-reflective coating on lenses 405 and 407 can be changed at the center and at the right and left edges of the periphery. Specifically, the transmittance of the blue wavelength should be reduced at the right edge and the transmittance of the red wavelength should be reduced at the left edge relative to the transmittance at the center of the anti-reflective coating. As a result, the blue-color-shifted light emitted from the right edge of the image display element will pass through the right edge of lenses 405 and 407, reducing its intensity and thus reducing the blue color shift. Similarly, the red-color-shifted light emitted from the left edge of the image display element will pass through the left edge of lenses 405 and 407, reducing its intensity and thus reducing the red color shift. In this case as well, the color shift may be reduced by changing the spectral transmittance of the anti-reflective coating on lenses 404 and 406, the anti-reflective coating on the cover glass, or the color correction elements 410 and 411 relative to the center at the right and left edges. [Fifth Embodiment] Figure 21 is an explanatory diagram of a head-mounted display (hereinafter referred to as HMD) 501, which is an example of an image display device according to this embodiment. Figure 22 is a diagram showing the HMD 501 connected to the PC 510.

[0075] The HMD501 includes lenses 504, 505, 506, and 507, a right-eye image display element 508, a left-eye image display element 509, and an image processing unit 511. Lenses 504 and 505 constitute the right-eye eyepiece optical system, and lenses 506 and 507 constitute the left-eye eyepiece optical system. Lenses 504, 505 and lenses 506 and 507 are cemented lenses, which can be easily held. The right-eye image display element 508 and the left-eye image display element 509 are organic EL displays.

[0076] The right eyepiece optical system projects the original image displayed on the right eye image display element 508 as a magnified virtual image and guides it to the observer's right eye 502. The left eyepiece optical system projects the original image displayed on the left eye image display element 509 as a magnified virtual image and guides it to the observer's left eye 503. The focal length of the right and left eyepiece optical systems is 13 mm, the horizontal display field of view is 60°, the vertical display field of view is 60°, and the diagonal display field of view is 78°. The distance between the HMD201 and the observer's eyeball (eye relief) is 20 mm.

[0077] The eyepiece optical system of this embodiment includes a configuration that folds the optical path using polarization. Since this configuration is the same as in Embodiment 2, a detailed explanation will be omitted.

[0078] In this embodiment, the eyepiece optical system has a short focal length and is thin, so the emission angle of light emitted from the periphery of the image display element toward the exit pupil of the eyepiece optical system is large, and the emission angle of light emitted from the horizontal and vertical ends of the image display element is 47 degrees. In order to shorten the focal length of the eyepiece optical system and achieve a thinner HMD101, it is desirable that the emission angle of light emitted from the periphery of the image display element toward the center of the exit pupil be 30 degrees or more.

[0079] When the emission angle of light emitted from the image display element increases, color shift occurs due to interference of the organic EL light-emitting layer and the mixing of colors in the color filter. In this embodiment, when the emission angle of light emitted from the image display element increases, a blue color shift occurs in the peripheral areas of the display screen due to the mixing of colors in the color filter. Therefore, when an observer views a white image, a blue color is observed when viewing the peripheral areas of the image, making natural image viewing impossible.

[0080] Therefore, in this embodiment, the color shift in the peripheral area is canceled by changing the characteristics of the central and peripheral parts of the image displayed on the image display element. The image displayed on the image display element has a white balance that takes into account the spectral transmittance of the eyepiece optical system, and normally the same white balance is applied to the entire surface of the image display element. In this embodiment, a color shift occurs in the peripheral area relative to the central area, so the image processing unit 511 reduces the color shift in the peripheral area by changing the white balance between the central and peripheral areas. In this embodiment, the image in the peripheral area has a blue color shift, so the white balance of the peripheral area is adjusted so that it becomes yellow relative to the center by increasing the gain of red and green relative to blue. As a result, the image displayed in the peripheral area of ​​the image display element has a white balance that is yellow relative to the center, and because the emission angle is large, it has a blue color shift, so the emitted image is an image with reduced color shift relative to the center.

[0081] Here, the dominant wavelength for blue in the image display element is 470 nm, the dominant wavelength for green is 545 nm, and the dominant wavelength for red is 605 nm. The wavelength for blue (first wavelength) should be within the range of 430 nm to 480 nm. The wavelength for green (second wavelength) should be within the range of 520 nm to 570 nm. The wavelength for red (third wavelength) should be within the range of 600 nm to 650 nm.

[0082] In this embodiment, the wavelength at which the ratio of the intensity of light emitted from the periphery of the image display element to the intensity of light emitted from the center of the image display element to the exit pupil is largest is 470 nm, the dominant wavelength of blue light, and a blue color shift occurs as the emission angle increases. Therefore, the color shift of the image display element is canceled by setting the wavelength at which the ratio of the gain at the periphery to the gain at the center of the image display element is smallest among the red, green, and blue wavelengths to be the wavelength of blue light. In this way, by changing the white balance of the center and periphery, the color shift of the periphery relative to the center of the image display element can be reduced, allowing the observer to observe a more natural image. When changing the white balance of the periphery relative to the center, it may be changed gradually from the center to the periphery, or only the outermost periphery may be changed. Also, if the color shift of the periphery is blue regardless of location, as in this embodiment, the gain values ​​for each color that are changed from the center to the periphery may be stored as a function of the distance from the center. In that case, the amount of memory required can be reduced compared to storing it as a map.

[0083] In this embodiment, the image processing unit 511 changes the white balance, but it may also be changed by the PC 510 that generates the display image for the HMD 501. In this case, the processing inside the HMD 501 is reduced, which makes it possible to reduce the power consumption of the image processing unit 511.

[0084] If the image display element is a liquid crystal display and the color shift at the edges differs depending on the location, with the right edge appearing blue and the left edge red, the color shift can be reduced by changing the characteristics of the right and left edges. In this case, since the image at the right edge is shifted to blue, the white balance at the right edge is adjusted by increasing the gain of red and green relative to blue, so that it appears yellow relative to the center. Similarly, since the image at the left edge is shifted to red, the white balance at the left edge is adjusted by increasing the gain of green and blue relative to red, so that it appears blue-green (cyan) relative to the center. As a result, the image displayed at the right edge of the image display element has a white balance that is yellow relative to the center, and because the emission angle is large, it shifts to blue, thus reducing the color shift of the emitted image relative to the center. Similarly, the image displayed at the left edge of the image display element has a white balance that is blue-green relative to the center, and because the emission angle is large, it shifts to red, thus reducing the color shift of the emitted image relative to the center. [Sixth Embodiment] Figure 23 is an explanatory diagram of the right eyepiece optical system of this embodiment. The right eyepiece optical system of this embodiment differs from the right eyepiece optical system of the first embodiment in that it has a dielectric multilayer film (negative filter) 601 installed between the right eye image display element 108 and the polarizer plate 110 as a correction element. In this embodiment, the same configuration as in the first embodiment will not be described. In this embodiment, the aforementioned color shift is reduced by the negative filter 601. The method for reducing color shift with this dielectric multilayer film will be described below.

[0085] Generally, dielectric multilayer films are used as optical filters that can reduce transmittance in a specific wavelength range by alternately stacking dielectric films with high refractive indices and dielectric films with low refractive indices. In this specification, the wavelength range in which transmittance is lower than the surrounding wavelength range is called the stopband, and the other high transmittance wavelength range is called the transmitband. Filters with a relatively narrow stopband width and characteristics in which transmittance is locally reduced, as shown in Figure 24, are known as negative filters. In the negative filter in Figure 24, the low transmittance region around 500 nm is the stopband, and the other high transmittance region is the transmitband. The configuration and materials of the filter's multilayer film are designed as appropriate according to the required characteristics. Optical filters using such dielectric multilayer films are basically designed to obtain the desired transmission characteristics through the effect of interference, and as shown in Figure 25, it is known that the transmission characteristics shift to the shorter wavelength side when obliquely incident compared to the characteristics when incident at 0 degrees. In this embodiment, a negative filter is formed on the organic EL side in Figure 23, and the layer configuration is shown in the table below. The substrate is BK7 glass, and it is constructed by stacking 60 layers of Ta2O5 as the high refractive index material and SiO2 as the low refractive index material.

[0086] [Table 1]

[0087] Figure 26 shows the emission spectral distribution of the organic EL panel in the 0-degree emission direction and the transmittance distribution of the negative filter 601 in the 0-degree incident direction in this embodiment. Figure 27 shows the emission spectral distribution of the organic EL panel in the 30-degree emission direction and the transmittance distribution of the negative filter 601 in the 30-degree incident direction. Figure 28 shows the emission spectral distribution of the organic EL panel in the 50-degree emission direction and the transmittance distribution of the negative filter 601 in the 50-degree incident direction. First, without the negative filter 601, the color difference ΔE*ab of light in the 30-degree emission direction relative to the 0-degree emission direction is 15.6, the absolute value of the chromaticity difference Δx is 0.0024, and the absolute value of the chromaticity difference Δy is 0.0227. Also, without the negative filter 601, the color difference ΔE*ab of light in the 50-degree emission direction relative to the 0-degree emission direction is 27.0, the absolute value of the chromaticity difference Δx is 0.0009, and the absolute value of the chromaticity difference Δy is 0.03608.

[0088] From the emission spectra in Figures 26, 27, and 28, it can be seen that as the emission angle increases, the intensity of blue increases, resulting in color difference and chromaticity difference. The negative filter arranged in this embodiment is designed to have a stopband around 500 nm when incident at 0 degrees, as shown in Figure 26. Furthermore, as shown in Figures 27 and 28, the negative filter's stopband shifts to shorter wavelengths with oblique incidence, gradually reducing the transmittance of light in the blue wavelength region. As a result, in this embodiment, after passing through the negative filter 601, the color difference ΔE*ab of light emitted at 30 degrees relative to the 0-degree emission direction is 6.5, the absolute value of the chromaticity difference Δx is 0.007, and the absolute value of the chromaticity difference Δy is 0.004. Also, the color difference ΔE*ab of light emitted at 50 degrees relative to the 0-degree emission direction is 10.2, the absolute value of the chromaticity difference Δx is 0.018, and the absolute value of the chromaticity difference Δy is 0.013.

[0089] In this way, the color shift characteristic of organic EL displays, where blue becomes stronger when emitted at an oblique angle, is reduced by utilizing the shift of the stopband of the negative filter to the shorter wavelength side during oblique transmission. In cases where the blue component of the display tends to be stronger, as in this embodiment, the stopband of the dielectric filter at 0-degree incidence is designed to be between the wavelengths of 430-480 nm (typical for blue) and 520-570 nm (for green). This minimizes color change during perpendicular incidence and reduces the blue component during oblique incidence. Thus, if the stopband exists at a wavelength longer than the color component to be reduced relative to the emission angle, the color difference or chromaticity difference can be reduced by shifting the stopband within the visible light range during oblique incidence. The same applies to the green (520-570 nm) and red (600-650 nm) components. Furthermore, when correcting multiple color components, it is possible to use filters with multiple stopbands.

[0090] In this embodiment, the image display element alone has an absolute chromaticity difference of 0.0009 for x and 0.03608 for y at an emission angle of 50 degrees. After passing through the eyepiece optical system, the absolute chromaticity difference increased to 0.018 for x, but was reduced to 0.013 for y. Here, in order for the observer to not notice the color shift and to observe naturally, it is desirable that the absolute chromaticity difference of both x and y be 0.03 or less. In this embodiment, it can be seen that the chromaticity difference is corrected to a level that allows for natural observation.

[0091] Furthermore, the color difference ΔE*ab has been reduced from 27.0 to 10.2. Here, in order for the observer to not notice the color shift and to observe naturally, it is desirable that the chromaticity difference ΔE*ab on the chromaticity coordinate system be 15 or less. In this embodiment, it can be seen that the color difference has been corrected to a level that allows for natural observation.

[0092] In this embodiment, the filter is arranged as a separate component, but it is preferable to install it on the cover glass surface of the organic EL panel to reduce the number of components and save space. It is also possible to form it on the surface of any optical surface. In those cases, the necessary multilayer film configuration can be designed appropriately according to the refractive index of the substrate, etc. Furthermore, the configuration of the dielectric multilayer film can be appropriately designed according to the emission spectrum of the organic EL panel, the display optical system, the color shift characteristics at oblique emission angles, etc.

[0093] As described above, the image observation device of this embodiment has a dielectric multilayer film on one surface between the light-emitting portion and the exit pupil of the image display element. Due to the incident angle characteristics of the dielectric multilayer film, it can be seen that the color difference or chromaticity difference between the light emitted from the peripheral portion of the image display element to the exit pupil of the image display element becomes smaller as it passes through the dielectric multilayer film. [Seventh Embodiment] Figure 29 is an explanatory diagram of the right eyepiece optical system of this embodiment. The right eyepiece optical system of this embodiment differs from the right eyepiece optical system of the second embodiment in that it has a dielectric multilayer film (IR cut filter) 602 installed between the right eye image display element 208 and the polarizing plate 210 as a correction element. In this embodiment, the same configuration as in the second embodiment will not be described. In this embodiment, the aforementioned color shift is reduced by the IR cut filter 602. The method for reducing color shift with this dielectric multilayer film will be described below.

[0094] As shown in Figure 30, dielectric multilayer filters that exhibit a decrease in transmittance in the infrared region are known as IR cut filters. In the IR cut filter shown in Figure 30, the high transmittance region below 690 nm is the transmission band, and the low transmittance region on the longer wavelength side is the stopband. The configuration and materials of the filter's multilayer film are designed as appropriate according to the required characteristics. Optical filters utilizing these dielectric multilayer films are basically designed to obtain the desired transmission characteristics through the effect of interference, and as shown in Figure 31, it is known that the transmission characteristics shift to the shorter wavelength side when incident at an oblique angle compared to the characteristics when incident at 0 degrees. In this embodiment, an IR cut filter is formed on the organic EL side of 302 in Figure 29, and the layer configuration is shown in the table below. The substrate is BK7 glass, with TiO2 as the high refractive index material and SiO2 as the low refractive index material, and these are stacked in a 35-layer configuration.

[0095] [Table 2]

[0096] Figure 32 shows the emission spectral distribution of the organic EL panel in the 0-degree emission direction and the transmittance distribution of the IR cut filter in the 0-degree incident direction in this embodiment. Figure 33 shows the emission spectral distribution of the organic EL panel in the 30-degree emission direction and the transmittance distribution of the IR cut filter in the 30-degree incident direction. Figure 34 shows the emission spectral distribution of the organic EL panel in the 50-degree emission direction and the transmittance distribution of the IR cut filter in the 50-degree incident direction. First, without an IR cut filter, the color difference ΔE*ab of light in the 30-degree emission direction relative to the 0-degree emission direction is 17.4, the absolute value of the chromaticity difference Δx is 0.0015, and the absolute value of the chromaticity difference Δy is 0.0212. Also, the color difference ΔE*ab of light in the 50-degree emission direction relative to the 0-degree emission direction is 21.7, the absolute value of the chromaticity difference Δx is 0.0083, and the absolute value of the chromaticity difference Δy is 0.0208.

[0097] From the emission spectra and chromaticity differences in Figures 32, 33, and 34, it can be seen that as the emission angle increases, the intensity of red increases, resulting in a color difference. The negative filter arranged in this embodiment is designed to have a stopband in the infrared wavelength range of 730 nm or higher when incident at 0 degrees, as shown in Figure 32. Furthermore, as shown in Figures 33 and 34, the negative filter's stopband shifts to shorter wavelengths with oblique incidence, gradually reducing the transmittance of light in the red wavelength range. As a result, in this embodiment, after passing through the IR cut filter 602, the color difference ΔE*ab of light emitted at 30 degrees relative to the 0-degree emission direction is 13.1, the chromaticity difference Δx is 0.0023, and the chromaticity difference Δy is 0.0166. Also, the color difference ΔE*ab of light emitted at 50 degrees relative to the 0-degree emission direction is 11.4, the chromaticity difference Δx is 0.0108, and the chromaticity difference Δy is 0.0173. In this way, the color unevenness characteristic of organic EL displays, where red becomes stronger when emitted at an oblique angle, is reduced by shifting the stopband of the IR cut filter to the shorter wavelength side when transmitted at an oblique angle.

[0098] In this embodiment, when the red component of the display tends to be strong, the dielectric filter is designed so that its stopband at 0-degree incidence is above 640 nm, which is the typical wavelength of red. This minimizes color change during perpendicular incidence and reduces the red component during oblique incidence. Thus, as in the first embodiment, by using a dielectric multilayer filter whose stopband exists at a wavelength longer than the color component to be reduced with respect to the emission angle, the color difference or chromaticity difference can be reduced by shifting the stopband within the visible light range during oblique incidence.

[0099] Furthermore, when reducing the red component as in this embodiment, it is not necessary to use a filter with a locally occurring stopband, such as a negative filter; an IR cut filter with a wide stopband over the non-visible light region on the longer wavelength side can be used.

[0100] In this embodiment, the image display element alone has an absolute chromaticity difference of 0.0083 for x and 0.0208 for y at an emission angle of 50 degrees. After passing through the eyepiece optical system, the absolute chromaticity difference increases to 0.0108 for x, but is reduced to 0.0173 for y. Here, in order for the observer to not notice the color shift and to observe naturally, it is desirable that the absolute chromaticity difference on the chromaticity coordinate system be 0.03 or less for both x and y, and more preferably 0.018 or less. In this embodiment, it can be seen that the chromaticity difference is corrected to a level that allows for natural observation.

[0101] Furthermore, the color difference ΔE*ab has been reduced from 21.7 to 11.4. Here, for the observer to be less likely to notice the color shift and to be able to observe naturally, it is desirable that the color difference ΔE*ab be 15 or less. In this embodiment, it can be seen that the color difference has been corrected to a level that allows for natural observation.

[0102] In this embodiment, the filter is arranged as a separate component, but it is preferable to install it on the cover glass surface of the organic EL panel to reduce the number of components and save space. It is also possible to form it on the surface of any other optical surface. In those cases, the necessary multilayer film configuration can be designed appropriately according to the refractive index of the substrate, etc. Furthermore, the configuration of the dielectric multilayer film can be appropriately designed according to the emission spectrum of the organic EL panel, the display optical system, the color shift characteristics at oblique emission angles, etc.

[0103] Although preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of its gist. [Explanation of symbols]

[0104] 101, 201, 301, 401, 501 HMD (Head-Mounted Display) 108,208,308,408,508 Image display elements for the right eye 109, 209, 309, 409, 509 Left eye image display element

Claims

1. The image display button and, It has an eyepiece optical system that guides light from the image display element to the exit pupil, The eyepiece optical system includes at least one correcting element whose characteristics differ between the central region and a region different from the central region. The characteristics of at least one correction element are set such that the color shift of the second light relative to the first light is smaller after the first light emitted from the center of the image display element and the second light emitted from the outermost part of the image display element have passed through the eyepiece optical system than before they have passed through the eyepiece optical system.

2. The at least one correction element includes a phase plate, The image display device according to claim 1, characterized in that at least one of the spectral transmittance and the phase amount for each wavelength is different in the central part of the phase plate and in a region other than the central part.

3. The at least one correction element includes a polarization separation element, The image display device according to claim 1 or 2, characterized in that at least one of the spectral transmittance and spectral reflectance differs between the central part of the polarization separation element and a region other than the central part.

4. The image display device according to claim 3, characterized in that the polarization separation element reflects a first linearly polarized light and transmits a second linearly polarized light in a polarization direction perpendicular to the polarization direction of the first linearly polarized light.

5. The at least one correction element includes a polarizing plate, The image display device according to any one of claims 1 to 4, characterized in that the spectral transmittance differs between the central part of the polarizing plate and a region other than the central part.

6. The at least one correction element includes a phase plate, a polarization separation element, and a polarizer. An image display device according to any one of claims 1 to 5, characterized in that, among a first wavelength included in the range of 430 nm to 480 nm, a second wavelength included in the range of 520 nm to 570 nm, and a third wavelength included in the range of 600 nm to 650 nm, the wavelength with the largest ratio of the intensity of the second light to the intensity of the first light is the same as the wavelength in which at least one of the transmittance of the polarizing plate, the transmittance of the phase plate, the reflectance of the polarization separation element, and the transmittance of the polarization separation element is smallest in the optical path from the outermost part to the exit pupil.

7. The at least one correction element is a semi-transparent reflective film, The image display device according to any one of claims 1 to 6, characterized in that at least one of the spectral transmittance and spectral reflectance differs between the central part of the semi-transparent reflective film and a region other than the central part.

8. The at least one corrective element is an anti-reflective coating, The image display device according to any one of claims 1 to 7, characterized in that the spectral transmittance differs between the central part of the anti-reflective film and a region other than the central part.

9. The image display device according to claim 8, characterized in that, among a first wavelength included in the range of 430 nm to 480 nm, a second wavelength included in the range of 520 nm to 570 nm, and a third wavelength included in the range of 600 nm to 650 nm, the wavelength at which the ratio of the intensity of the second light to the intensity of the first light is largest is the same as the wavelength at which the transmittance of the anti-reflective film is smallest in the optical path from the outermost part to the exit pupil.

10. The at least one correction element is a dielectric multilayer film, The image display device according to any one of claims 1 to 9, characterized in that at least one of the spectral transmittance and spectral reflectance differs between the central part of the dielectric multilayer film and a region other than the central part.

11. The image display device according to claim 10, characterized in that the dielectric multilayer film is provided on the image display element.

12. The image display device according to claim 11, characterized in that, when a wavelength included in the range of 430 nm to 480 nm is defined as the first wavelength, a wavelength included in the range of 520 nm to 570 nm is defined as the second wavelength, and a wavelength included in the range of 600 nm to 650 nm is defined as the third wavelength, the dielectric multilayer film has a stopband in any of the following: the band between the first wavelength and the second wavelength, the band between the second wavelength and the third wavelength, or the band with wavelengths longer than the third wavelength.

13. The image display device according to any one of claims 10 to 12, characterized in that the dielectric multilayer film is a negative filter or an IR cut filter.

14. The image display device according to any one of claims 1 to 13, characterized in that the eyepiece optical system includes, in order from the side of the image display element, a first polarizing plate, a first phase plate, a lens, a second phase plate, and a polarization separation element.

15. The image display device according to any one of claims 1 to 13, characterized in that the eyepiece optical system includes, in order from the side of the image display element, a first polarizing plate, a first phase plate, a lens, a second phase plate, a polarization separation element, and a second polarizing plate.

16. The second light emission angle is greater than the half-angle of view displayed by the eyepiece optical system. The image display device according to claim 14 or 15, characterized in that at least one of the first polarizing plate and the first phase plate functions as the correction element.

17. The second light emission angle is greater than the half-angle of view displayed by the eyepiece optical system. The image display device according to claim 15, characterized in that at least one of the second phase plate, the polarization separation element, and the second polarizer plate functions as the correction element.

18. After the first and second lights pass through the eyepiece optical system, the color difference ΔE of the second light relative to the first light is determined. ＊ The image display device according to any one of claims 1 to 17, characterized in that the value is 15 or less.

19. The image display device according to any one of claims 1 to 18, characterized in that, after the first light and the second light have passed through the eyepiece optical system, the chromaticity difference x of the second light with respect to the first light is 0.05 or less, and the chromaticity difference y is 0.05 or less.

20. The image display device according to any one of claims 1 to 19, characterized in that the emission angle of the second light is 30 degrees or more.

21. The image display device according to any one of claims 1 to 20, characterized in that the wavelength at which the ratio of the intensity of the second light to the intensity of the first light is greatest is included in the range of 430 nm to 480 nm.

22. An image display device according to any one of claims 1 to 21, characterized in that, among a first wavelength included in the range of 430 nm to 480 nm, a second wavelength included in the range of 520 nm to 570 nm, and a third wavelength included in the range of 600 nm to 650 nm, the wavelength with the largest ratio of the intensity of the second light to the intensity of the first light is the same regardless of the direction of emission of the light emitted from the image display element.

23. The image display device according to any one of claims 1 to 22, characterized in that, after the first light and the second light have passed through the eyepiece optical system, the horizontal color shift of the second light relative to the first light is smaller than the vertical color shift.

24. The image display device according to any one of claims 1 to 23, characterized in that the white balance differs between the central part of the image display element and a region other than the central part.

25. The image display device according to claim 24, characterized in that, among a first wavelength included in the range of 430 nm to 480 nm, a second wavelength included in the range of 520 nm to 570 nm, and a third wavelength included in the range of 600 nm to 650 nm, the wavelength at which the ratio of the intensity of the second light to the intensity of the first light is largest is the same as the wavelength at which the ratio of the gain of the outermost part of the image display element to the gain of the central part of the image display element is smallest.

Images