Image display device

Abstract

An image display device is disclosed. An image display device includes an image display element; and an eyepiece optical system configured to guide 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 region and a peripheral region different from the central region. When first light is light emitted from a central portion of the image display element, and second light is light emitted from an outermost peripheral portion of the image display element, the characteristics of the at least one correction element are set so that the color shift of the second light after passing through the peripheral region relative to the first light after passing through the central region is less than the color shift of the second light before passing through the peripheral region relative to the first light before passing through the central region.

Description

Technical Field

[0001] This disclosure relates to image display devices such as head-mounted displays, which are suitable for magnifying and observing images on an image display element via an eyepiece optical system. Background Technology

[0002] In order to realize a thin and lightweight image display device with a wide viewing angle, Japanese Patent Publication No. (“JP”) 2021-71602 discloses a configuration that uses polarization to fold the optical path.

[0003] However, in the configuration disclosed in JP 2021-71602, the emission angle of the light emitted from the peripheral portion of the image display element is too large, causing color drift (or displacement) in the peripheral portion of the image display element relative to the center portion of the image display element, and the peripheral portion of the image cannot be viewed with the correct color. Summary of the Invention

[0004] This disclosure provides an image display apparatus that facilitates reducing color drift of the peripheral portion of an image display element relative to the central portion of the image display element.

[0005] An image display device according to one aspect of this disclosure includes: an image display element; and an eyepiece optical system configured to guide 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 region and a peripheral region different from the central region. When a first light is emitted from the central portion of the image display element and a second light is emitted from the outermost peripheral portion of the image display element, the characteristics of the at least one correction element are set such that the color shift of the second light after passing through the peripheral region relative to the first light after passing through the central region is less than the color shift of the second light before passing through the peripheral region relative to the first light before passing through the central region.

[0006] An image display device according to another aspect of this disclosure includes: an image display element; and an eyepiece optical system configured to guide light from the image display element to an exit pupil. In the eyepiece optical system, the white balance is different between the central portion of the image display element and regions of the image display element different from the central portion, such that after first light emitted from the central portion of the image display element and second light emitted from the outermost peripheral portion of the image display element pass through the eyepiece optical system, the color shift of the second light relative to the first light is less than the color shift of the second light relative to the first light before the first and second lights pass through the eyepiece optical system.

[0007] Other features of this disclosure will become clear from the following description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0008] Figure 1 A head-mounted display, as an example of an image display device according to the first embodiment, is described.

[0009] Figure 2 The optical system for the right eyepiece according to the first embodiment is described.

[0010] Figure 3 This is an external view of the head-mounted display according to the first embodiment.

[0011] Figure 4 The optical system for the right eyepiece according to the first embodiment is described.

[0012] Figure 5 The emission angle of light emitted from the image display element according to the first embodiment is explained.

[0013] Figure 6 The color drift of the image display element in the first embodiment is explained.

[0014] Figures 7A to 7C The characteristics of the polarizer and polarization beam splitter in the first embodiment are explained.

[0015] Figure 8 The color drift of the eyepiece optical system according to the first embodiment is explained.

[0016] Figure 9 A head-mounted display, as an example of an image display device according to the second embodiment, is described.

[0017] Figure 10 The optical system for the right eyepiece according to the second embodiment is described.

[0018] Figure 11 The emission angle of light emitted from the image display element according to the second embodiment is explained.

[0019] Figure 12 The color drift of the image display element according to the second embodiment is explained.

[0020] Figure 13A and Figure 13B The characteristics of the polarizing plate according to the second embodiment are explained.

[0021] Figure 14 The color drift of the eyepiece optical system according to the second embodiment is explained.

[0022] Figure 15A and 15B An example of the characteristics of a polarizing plate according to the second embodiment is illustrated.

[0023] Figure 16 A head-mounted display, as an example of an image display device according to the third embodiment, is described.

[0024] Figure 17 The optical system for the right eyepiece according to the third embodiment is described.

[0025] Figure 18 The characteristics of the polarizing plate according to the third embodiment are explained.

[0026] Figure 19 A head-mounted display, as an example of an image display device according to the fourth embodiment, is described.

[0027] Figure 20 A head-mounted display according to the fourth embodiment is described as another example of an image display device.

[0028] Figure 21 A head-mounted display, as an example of an image display device according to the fifth embodiment, is described.

[0029] Figure 22 The illustration shows a head-mounted display according to a fifth embodiment connected to a PC.

[0030] Figure 23 The optical system for the right eyepiece according to the sixth embodiment is described.

[0031] Figure 24 The characteristics of the negative filter according to the sixth embodiment are explained.

[0032] Figure 25 The characteristics of the negative filter according to the sixth embodiment are explained.

[0033] Figure 26 The emission spectrum of the image display element according to the sixth embodiment is described.

[0034] Figure 27 The emission spectrum of the image display element according to the sixth embodiment is described.

[0035] Figure 28 The emission spectrum of the image display element according to the sixth embodiment is described.

[0036] Figure 29 The right eyepiece optical system according to the seventh embodiment is described.

[0037] Figure 30 The characteristics of the infrared (IR) (cut-off) filter according to the seventh embodiment are explained.

[0038] Figure 31 The characteristics of the IR cutoff filter according to the seventh embodiment are explained.

[0039] Figure 32 The emission spectrum of the image display element according to the seventh embodiment is described.

[0040] Figure 33 The emission spectrum of the image display element according to the seventh embodiment is described.

[0041] Figure 34 The emission spectrum of the image display element according to the seventh embodiment is described. Detailed Implementation

[0042] A detailed description of embodiments according to the present disclosure will now be given with reference to the accompanying drawings. Corresponding elements in the various figures will be designated by the same reference numerals, and repeated descriptions thereof will be omitted.

[0043] First Embodiment

[0044] Figure 1 A head-mounted display (hereinafter, HMD) 101, as an example of an image display device according to a first embodiment, is described. HMD 101 includes lenses 104, 105, 106, and 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. Each of the right-eye image display element 108 and the left-eye image display element 109 is an organic electroluminescent (“EL”) display.

[0045] The right eyepiece optical system magnifies and projects the original image displayed on the right eye image display element 108 into a virtual image, guiding it to the observer's right eye 102. The left eyepiece optical system magnifies and projects the original image displayed on the left eye image display element 109 into a virtual image, guiding it to the observer's left eye 103. Each of the right and left eyepiece optical systems has a focal length of 12mm, a horizontal viewing angle of 45°, a vertical viewing angle of 34°, and a diagonal viewing angle of 54°. The distance (visual distance) between the HMD 101 and each of the observer's eyeballs is 18mm.

[0046] The eyepiece optical system according to this embodiment has a configuration that uses polarization to fold the optical path. The optical path of the eyepiece optical system will be described with reference to the right eyepiece optical system. Figure 2The optical system of the right eyepiece according to this embodiment is described. The right eyepiece optical system, starting from one side of the right eye image display element 108, sequentially includes a polarizing plate (first polarizing plate) 110, a phase plate (first phase plate) 111, lenses 105 and 104, a phase plate (second phase plate) 113, and a polarizing beam splitter (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 vapor-deposited serves as a semi-transmissive reflective surface (semi-transmissive reflective film). Each of the phase plate 113 and PBS 114 has a planar shape. Each of the phase plates 111 and 113 is a quarter-wave plate with a phase difference of λ / 4.

[0047] In this embodiment, the slow axis of phase plate 111 is tilted at 45° relative to the polarization direction of the transmitted polarizer 110, and the slow axis of phase plate 113 is tilted at -45° relative to the polarization direction of the transmitted polarizer 110. Furthermore, the polarization direction of the transmitted polarizer 110 is orthogonal to the polarization direction of the transmitted PBS 114. In this configuration, light emitted from the right-eye image display element 108 passes through polarizer 110, becoming linearly polarized light, and then passes through phase plate 111, becoming circularly polarized light. Subsequently, the polarized light passes through semi-transparent mirror 112, then through phase plate 113, and becomes linearly polarized light again. Since the polarization direction of the linearly polarized light is orthogonal to the polarization direction of the transmitted PBS 114, the linearly polarized light is reflected by PBS 114, passes through phase plate 113, and becomes circularly polarized light. This light is then reflected by semi-transparent mirror 112, then passes through phase plate 113, and becomes linearly polarized light again. Since the polarization direction of the linearly polarized light is the same as that of the light transmitted through the PBS 114, the linearly polarized light is guided to the observer's right eye 102 through the PBS 114. A similar optical path is formed in the left eyepiece optical system.

[0048] The eyepiece optics system configured in this embodiment, which uses polarization to fold the optical path, can make the HMD101 thinner and reduce the focal length of the eyepiece optics system, thus enabling the observation of images with a wide viewing angle.

[0049] Figure 3 This is an external view of HMD 101. HMD 101 is a head-mounted image display device, therefore it needs to be lightweight. Therefore, each lens in the eyepiece optics system can be made of resin, which has a lower specific gravity than glass. This embodiment uses lenses 104 and 106, each made of resin and configured as plano-convex aspherical lenses, to improve aberration correction. Each of lenses 105 and 107 is made of resin and configured as a double-sided aspherical lens.

[0050] Figure 4The right eyepiece optical system according to this embodiment is described. In the right eyepiece optical system according to this embodiment, the position of the exit pupil is set to 28mm, which is formed by adding the viewing distance (=18mm) and the rotation radius of the eyeball (=10mm), and the diameter of the exit pupil is set to 6mm. Therefore, even when the eyeball rotates to view the image up, down, left, and right, light enters the eyeball in this direction. The viewing distance can be 15mm or longer, allowing an observer wearing glasses to wear HMD 101. As the viewing distance increases, the outer diameter of each lens increases and the HMD 101 becomes larger. Therefore, the viewing distance can be 25mm or less.

[0051] Because the eyepiece optical system according to this embodiment has a short focal length and is thin, therefore, as from Figure 4 As understood, the emission angle of light emitted from the peripheral portion of the image display element to the exit pupil of the eyepiece optics system is large. The peripheral portion is the area outside the central portion of the right eye image display element 108. Figure 5 The emission angle of light emitted from the image display element according to this embodiment is explained, and the relationship between the display viewing angle and the emission angle of light emitted from the image display element to the exit pupil is illustrated. The emission angle of light emitted from the image display element is the emission angle of the principal ray guided to the center of the exit pupil. Figure 5 As illustrated in the diagram, the emission angle increases with the increase in display viewing angle. The emission angle of light emitted from the horizontal end of the image display element is 37 degrees, and the emission angle of light emitted from the vertical end is 29 degrees. In order to shorten the focal length of the eyepiece optics system and make the HMD 101 thinner, the emission angle of light emitted from the peripheral portion of the image display element toward the center of the exit pupil can be 30 degrees or greater.

[0052] As the emission angle of light emitted from the image display element increases, color shift occurs due to interference from the light-emitting layer of the organic EL and the color mixing effect of the color filter. In this embodiment, as the emission angle of light emitted from the image display element increases, such as Figure 6 As illustrated in the diagram, the chromaticity shifts towards red, resulting in a color shift. Therefore, when an observer views a white image, red is observed in the peripheral areas of the image, making the image appear unnatural.

[0053] Therefore, this embodiment uses at least one of polarizer 110 and PBS 114 as a correction element with different characteristics between the central portion and a region different from the central portion (peripheral portion). When polarizer 110 is used as the correction element, polarizer 110 has the characteristic that the spectral transmittance differs between the central and peripheral portions. When PBS 114 is used as the correction element, PBS 114 has the characteristic that at least one of spectral transmittance and spectral reflectance differs between the central and peripheral portions. Thus, after the first light emitted from the central portion of the right-eye image display element 108 and the second light emitted from the outermost peripheral portion pass through the right-eye eyepiece optics system, the color shift of the second light relative to the first light can be made smaller than the color shift of the second light relative to the first light before the first and second lights pass through the right-eye eyepiece optics system. That is, the color shift in the peripheral portion of the right-eye image display element 108 can be eliminated. Figures 7A to 7C The characteristics of polarizer 110 and PBS 114 are explained. Figure 7A The figure shows the transmittance (spectral transmittance) of polarizer 110 for light at a 0-degree incident angle for each wavelength. Figure 7B The figure shows the reflectance (spectral reflectance) of PBS 114 for light at a 0-degree incident angle for each wavelength. Figure 7C The figure illustrates the transmittance (spectral transmittance) of PBS 114 for light at a 0-degree incident angle for each wavelength. The image shows the dominant wavelength of the element as blue (450 nm), green (525 nm), and red (610 nm). Figures 7A to 7C The diagram illustrates the transmittance and reflectance at each wavelength. The blue wavelength (first wavelength) can be included in the range from 430 nm to 480 nm. The green wavelength (second wavelength) can be included in the range from 520 nm to 570 nm. The red wavelength (third wavelength) can be included in the range from 600 nm to 650 nm. When differentiating spectral transmittance between the central and peripheral portions, the variation can be subtle and gradual.

[0054] like Figure 7A As illustrated in the diagram, even with increasing incident angle, the transmittance of polarizer 110 for blue and green light remains almost unchanged, but the transmittance of polarizer 110 for red light decreases with increasing incident angle. The reflectance and transmittance of PBS 114 exhibit a similar trend. Light emitted from the peripheral portion of the right-eye image display element 108 has a large emission angle and a large incident angle on polarizer 110 and PBS 114. Therefore, when red-shifted light emitted from the peripheral portion of the right-eye image display element 108 passes through polarizer 110, is reflected, and transmits through PBS 114, its red intensity and color shift can be reduced.

[0055] Figure 8 The color shift of the eyepiece optics system is explained, and the relationship between the emission angle and chromaticity after light passes through the eyepiece optics system is illustrated. In the case of a standalone image display element, as the emission angle increases, as... Figure 6 As shown in the diagram, the chromaticity changes towards red, but when light passes through the eyepiece optical system, such as Figure 8 As illustrated in the diagram, the chromaticity change is reduced, and the color shift can be decreased. In this embodiment, in a single image display element, as the emission angle increases, the chromaticity difference x on the chromaticity coordinate system (chromaticity diagram) is 0.1 and the chromaticity difference y is 0.055. However, after the light passes through the eyepiece optics system, the chromaticity difference x can be reduced to 0.04 and the chromaticity difference y can be reduced to 0.015. To make the color shift less noticeable to the observer and to allow for a natural viewing experience, the chromaticity difference x on the chromaticity coordinate system can be 0.05 or less, and the chromaticity difference y can be 0.05 or less.

[0056] In this embodiment, the ratio of the intensity of light emitted from the peripheral portion of the image display element to the intensity of light emitted from the central portion of the image display element to the exit pupil becomes a maximum wavelength of 610 nm, i.e., the dominant red wavelength, and a red shift occurs as the emission angle increases. Therefore, by setting the wavelength with the lowest transmittance of polarizer 110 and PBS 114 among red, green, and blue wavelengths to red, the color shift of the image display element can be eliminated. Thus, due to the characteristic that the spectral transmittance of polarizer 110 and PBS 114, which are color correction elements, differs between each central and peripheral portion of polarizer 110 and PBS 114, the color shift of the peripheral portion of the right-eye image display element 108 relative to the central portion of the right-eye image display element 108 is reduced, and the observer can thus observe a more natural image.

[0057] According to this embodiment, the right-eye image display element 108 has an emission angle of 37 degrees and a semi-horizontal display viewing angle of 22.5 degrees for light emitted from its horizontal end, and the incident angle on the polarizer 110 is greater than the incident angle on the PBS 114. Therefore, the emission angle characteristics of the right-eye image display element 108 can be eliminated by the characteristics of the polarizer 110, which are close to the characteristics of the right-eye image display element 108.

[0058] In the optical path of the right eyepiece optical system, the PBS 114 acts twice, through reflection and transmission. Therefore, if the emission angle characteristics of the right eye image display element 108 are eliminated by the characteristics of the PBS 114, the effect of reducing color shift is high. When the color shift direction differs between the horizontal and vertical directions due to the arrangement of the color filters in the right eye image display element 108, the characteristics of the polarizer 110 and the PBS 114 may be altered in both the horizontal and vertical directions. In the case where a large emission angle of light emitted from the right eye image display element 108 causes red shift in the horizontal direction and blue shift in the vertical direction, the characteristics of the polarizer 110 in the horizontal direction can be set to minimize red transmittance, and the characteristics of the polarizer 110 in the vertical direction can be set to minimize blue transmittance.

[0059] This embodiment reduces chromatic aberration in cases of large emission angles of light emitted from the right-eye image display element 108, but can also reduce the chromatic aberration ΔE*. In this case, the chromatic aberration ΔE* can be 15 or less.

[0060] In this embodiment, the surface of the translucent mirror 112 on which the lens 104 is deposited is a convex surface that protrudes towards the right eye image display element 108. Depositing the translucent mirror 112 on the convex surface can achieve a wide viewing angle while making the HMD 101 thinner. Forming the convex surface on which the vapor-deposited translucent mirror 112 is deposited into an aspherical shape can enhance the aberration correction effect.

[0061] In this embodiment, lenses 105 and 107 are resin lenses, but because of their small size and minimal impact on weight, they can be glass lenses. The very low birefringence of glass lenses can provide high-quality image viewing.

[0062] To reduce ghosting from external light and increase the contrast of the observed image, polarizing plates can be deployed between the PBS 114 and each of the observer's eyeballs.

[0063] Because this embodiment strikes a trade-off between a longer viewing distance and a thinner HMD 101, the surface on the observer's right eye 102 side, where the PBS 114 and phase plate 113 with lens 104 are deployed, is set to a flat surface. With the surface of lens 104 on the observer side recessed towards the observer, lens 104 becomes thicker to ensure viewing distance in the peripheral portion. Additionally, the convex surface makes lens 104 thicker to ensure thickness in the lens edge portion.

[0064] In this embodiment, each of phase plates 111 and 113 is a quarter-wave plate with a phase difference of λ / 4, but the phase difference can be offset from λ / 4 to eliminate birefringence of lenses 104 and 105. In this case, the sum of the phase differences of lens 104 and phase plate 113 can be 3λ / 20 or greater and 7λ / 20 or less. Similarly, the sum of the phase differences of lens 105 and phase plate 111 can be 3λ / 20 or greater and 7λ / 20 or less. If each value is outside these ranges, the intensity of the ghosting light will increase, and a more natural image cannot be observed.

[0065] In this embodiment, the right-eye image display element 108 emits unpolarized light as an organic EL, but can emit linearly polarized light as a liquid crystal display. In this case, the polarizing plate 110 becomes unnecessary, and the HMD 101 can be thinner and the number of components can be reduced.

[0066] In this embodiment, the eyepiece optics system uses a PBS114 that switches transmission and reflection in the direction of linearly polarized light, but a PBS that switches reflection and transmission in the direction of circularly polarized light can be used. In this case, the phase plate 113 becomes unnecessary, and the HMD 101 can be thinner and the number of components can be reduced.

[0067] Second Embodiment

[0068] Figure 9 A head-mounted display (HMD) 201, as an example of an image display device according to this embodiment, is described. HMD 201 includes lenses 204, 205, 206, and 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 and 205, as well as lenses 206 and 207, are cemented lenses and can be easily held in place. Each of the right-eye image display element 208 and the left-eye image display element 209 is an organic EL display.

[0069] The right eyepiece optical system magnifies and projects the original image displayed on the right eye image display element 208 into a virtual image, guiding it to the observer's right eye 202. The left eyepiece optical system magnifies and projects the original image displayed on the left eye image display element 209 into a virtual image, guiding it to the observer's left eye 203. Each of the right and left eyepiece optical systems has a focal length of 13mm, a horizontal viewing angle of 60°, a vertical viewing angle of 60°, and a diagonal viewing angle of 78°. The distance (visual distance) between the HMD 201 and each of the observer's eyeballs is 20mm.

[0070] The eyepiece optical system according to this embodiment has a configuration that uses polarization to fold the optical path. The optical path of the eyepiece optical system will be described with reference to the right eyepiece optical system. Figure 10 The optical system of the right eyepiece according to this embodiment is described. The right eyepiece optical system, starting from the right eye image display element 208 side, sequentially includes a polarizing plate (first polarizing plate) 210, a phase plate (first phase plate) 211, lenses 205 and 204, a phase plate (second phase plate) 213, a polarizing beam splitter (hereinafter referred to as PBS) 214, and a polarizing plate (second polarizing plate) 215. A semi-transparent mirror 212 is deposited on the surface of lens 204 on the lens 205 side. The surface on which the semi-transparent mirror 212 is deposited serves as a semi-transparent reflective surface. Each of the phase plate 213, PBS 214, and polarizing plate 215 has a planar shape. Each of the phase plates 211 and 213 is a quarter-wave plate with a phase difference of λ / 4.

[0071] In this embodiment, the slow axis of phase plate 211 is tilted at 45° relative to the polarization direction of the transmitted polarizer 210, and the slow axis of phase plate 213 is tilted at -45° relative to the polarization direction of the transmitted polarizer 210. The polarization direction of the transmitted polarizer 210 is orthogonal to the polarization direction of the transmitted PBS 214. The polarization direction of the transmitted PBS 214 is equal to the polarization direction of the transmitted polarizer 215. In this configuration, light emitted from the right-eye image display element 208 passes through polarizer 210, becoming linearly polarized light, and then passes through phase plate 211, becoming circularly polarized light. Subsequently, the polarized light passes through semi-transparent mirror 212, then through phase plate 213, and becomes linearly polarized light again. Since the polarization direction of the linearly polarized light is orthogonal to the polarization direction of the transmitted PBS 214, the linearly polarized light is reflected by PBS 214, passes through phase plate 213, and becomes circularly polarized light. Subsequently, this light is reflected by semi-transparent mirror 212, then passes through phase plate 213, and becomes linearly polarized light again. Since the polarization direction is the same as that of the light transmitted through PBS 214, the linearly polarized light is guided to the observer's right eye 202 through PBS 214 and polarizing plate 215. A similar optical path is formed in the left eyepiece optical system.

[0072] In this embodiment, a polarizing plate 215 is deployed between the PBS 214 and the observer's right eye 202 to reduce ghosting of external light and increase the contrast of the observed image.

[0073] The eyepiece optics system configured in this embodiment, which uses polarization to fold the optical path, can make the HMD201 thinner and reduce the focal length of the eyepiece optics system, thus enabling the observation of images with a wide viewing angle.

[0074] HMD 201 is a head-mounted image display device, and therefore needs to be lightweight. Therefore, each lens in the eyepiece optics system can be made of resin with a smaller specific gravity than glass. This embodiment uses lenses 204, 205, 206, and 207, each made of resin and configured as aspherical lenses, to improve aberration correction.

[0075] In the eyepiece optical system according to this embodiment, the exit pupil is positioned at 30mm, which is formed by adding the viewing distance (=20mm) and the rotation radius of the eyeball (=10mm), and the diameter of the exit pupil is set to 6mm. Therefore, even when the eyeball rotates to view the image up, down, left, and right, light enters the eyeball in this direction. The viewing distance can be 15mm or longer, allowing an observer wearing glasses to wear the HMD 201. As the viewing distance increases, the outer diameter of each lens increases, and the HMD 201 becomes larger. Therefore, the viewing distance can be 25mm or less.

[0076] Because the eyepiece optical system according to this embodiment has a short focal length and is thin, the emission angle of the light emitted from the peripheral portion of the image display element to the exit pupil of the eyepiece optical system is large. Figure 11 The emission angle of light emitted from the image display element according to this embodiment is explained, and the relationship between the display viewing angle and the emission angle of light emitted from the image display element to the exit pupil is illustrated. The emission angle of light emitted from the image display element is the emission angle of the principal ray guided to the center of the exit pupil. Figure 11 As illustrated in the diagram, the emission angle increases with the increase in display viewing angle, and the emission angles of light emitted from both the horizontal and vertical ends of the image display element are 47 degrees. In order to shorten the focal length of the eyepiece optics system and make the HMD201 thinner, the emission angle of light emitted from the image display element toward the center of the exit pupil can be 30 degrees or greater.

[0077] As the emission angle of light emitted from the image display element increases, color shift occurs due to interference from the light-emitting layer of the organic EL and the color mixing effect of the color filter. In this embodiment, as the emission angle of light emitted from the image display element increases, such as Figure 12 As shown in the diagram, the chromaticity shifts towards blue, resulting in a color shift. Therefore, when an observer views a white image, blue is observed in the peripheral areas of the image, making the image unnatural to view.

[0078] Therefore, this embodiment uses at least one of polarizers 210 and 215 as a correction element with different characteristics between the central portion and a region different from the central portion (the peripheral portion). More specifically, at least one of polarizers 210 and 215 has the characteristic that the spectral transmittance differs between the central portion and the peripheral portion. Thus, after the first light emitted from the central portion of the right-eye image display element 208 and the second light emitted from the outermost peripheral portion of the right-eye image display element 208 pass through the right-eye eyepiece optics system, the color shift of the second light relative to the first light can be made smaller than the color shift of the second light relative to the first light before the first and second lights pass through the right-eye eyepiece optics system. That is, the color shift in the peripheral portion of the right-eye image display element 208 can be eliminated. Figure 13A and Figure 13B The characteristics of polarizers 210 and 215 are explained. Figure 13A and Figure 13B The images illustrate the transmittance (spectral transmittance) of polarizers 210 and 215 for light at a 0-degree angle of incidence for each wavelength. The dominant wavelengths of the blue polarizers are 470 nm, 545 nm, and 605 nm, respectively. Figure 13A and Figure 13B The diagram illustrates the transmittance at each wavelength. The blue wavelength (first wavelength) can be included in the range from 430 nm to 480 nm. The green wavelength (second wavelength) can be included in the range from 520 nm to 570 nm. The red wavelength (third wavelength) can be included in the range from 600 nm to 650 nm.

[0079] like Figure 13A As illustrated in the diagram, even with an increasing incident angle, the transmittance of polarizer 210 for green and red light remains almost unchanged, but the transmittance for blue light decreases with increasing incident angle. The transmittance of polarizer 215 exhibits a similar trend. Light emitted from the peripheral portion of the right-eye image display element 208 has a large emission angle and a large incident angle at polarizers 210 and 215. Therefore, when blue-drifted light emitted from the peripheral portion of the right-eye image display element 208 passes through polarizers 210 and 215, the intensity of the blue light and its color drift can be reduced.

[0080] Figure 14 The color shift of the eyepiece optics system is explained, and the relationship between the emission angle and chromaticity after light passes through the eyepiece optics system is illustrated. In the case of a standalone image display element, as the emission angle increases, as... Figure 12 As shown in the diagram, the chromaticity shifts towards blue, but when light passes through the eyepiece optical system, as... Figure 14As illustrated in the diagram, the chromaticity variation decreases, and the color shift can be reduced. In this embodiment, in a single image display element, as the emission angle increases, the chromaticity difference x in the chromaticity coordinate system is 0.055 and the chromaticity difference y is 0.07. However, after the light passes through the eyepiece optics system, the chromaticity difference x can be reduced to 0.015 and the chromaticity difference y can be reduced to 0.02. To make the color shift less noticeable to the observer and to allow for a natural viewing experience, the chromaticity difference x in the chromaticity coordinate system can be 0.05 or less, and the chromaticity difference y can be 0.05 or less.

[0081] In this embodiment, the ratio of the intensity of light emitted from the peripheral portion of the image display element to the intensity of light emitted from the central portion of the image display element to the exit pupil becomes a maximum wavelength of 470 nm, i.e., the dominant blue wavelength, and a blue 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 can be eliminated. Thus, due to the characteristic that the spectral transmittance of polarizers 210 and 215, which are color correction elements, differs between each central portion and each peripheral portion, the color shift of the peripheral portion of the image display element relative to the central portion of the image display element is reduced, thereby allowing the observer to view a more natural image.

[0082] The right eyepiece optical system according to this embodiment has an emission angle of 47 degrees and a half-horizontal display viewing angle of 30 degrees for light emitted from the horizontal end of the right eye image display element 208, and the angle of incidence on polarizer 210 is greater than the angle of incidence on polarizer 215. Therefore, the emission angle characteristic of the image display element can be eliminated by the characteristics of polarizer 210, which is close to the right eye image display element 208. Half of the display viewing angle 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 on polarizer 215 can be greater than the angle of incidence on polarizer 210. In this case, the emission angle characteristic of the right eye image display element 208 can be eliminated by the characteristics of polarizer 215.

[0083] In this embodiment, the color shift caused by the emission angle of light emitted from the image display element is eliminated by the characteristics of the polarizer, but can be eliminated by the characteristics of the phase plate. In this case, in order to change the transmittance and reflectance when the polarizer or PBS is combined, the transmittance (spectral transmittance) of each wavelength of the phase plate can be changed, or the phase amount of each wavelength of the phase plate can be changed.

[0084] Color shift caused by the emission angle of light emitted from the image display element can be eliminated by the fact that at least one of the spectral transmittance and spectral reflectance differs between the central portion of the semi-transparent mirror and a region different from the central portion of the semi-transparent mirror. In this case, such as Figure 9 As illustrated in the diagram, the difference in the angle of incidence between light emitted from the center of the image display element and light emitted from the peripheral portion of the image display element during transmission through the semi-transparent mirror is large, but the difference in the angle of incidence during light reflection on the semi-transparent mirror is small. Therefore, color shift can be eliminated by observing the characteristics of light transmission through the semi-transparent mirror.

[0085] In this embodiment, the large emission angle of the light emitted from the image display element causes a color shift towards blue, regardless of the emission direction. Since the color to be shifted is the same, there is no need to change the characteristics of the polarizer according to the incident direction. Because the color to be shifted is blue, which has low human optical visibility, the color shift perceived by the observer is small even if the intensity of the light emitted from the image display element increases.

[0086] When the polarizer 210 has different characteristics in the horizontal and vertical directions, the human field of vision in the horizontal direction is wider than that in the vertical direction, and the observer may notice color shift in the horizontal direction. Therefore, characteristics that minimize color shift in the horizontal direction can be used. For example, the characteristics in the horizontal direction could be as follows: Figure 15A The map shown in the image is configured to have a high blue elimination effect, and its vertical properties can be as follows: Figure 15B The polarizer 215 is configured as shown in the diagram. When the polarizer 215 has different characteristics in the horizontal and vertical directions, the characteristics can be set to minimize color shift in the horizontal direction.

[0087] This embodiment reduces chromatic aberration in cases of large emission angles of light emitted from the right-eye image display element 208, but the characteristics of polarizers 210 and 215 can be configured to reduce the chromatic aberration ΔE*. In this case, the absolute values ​​of the transmittance and reflectance for each color can be changed.

[0088] In this embodiment, the surface of the translucent mirror 112 on which the lens 204 is deposited is a convex surface that protrudes towards the right-eye image display element 208. Depositing the translucent mirror 212 on the convex surface can achieve a wide viewing angle while making the HMD 201 thinner. Forming the convex surface on which the vapor-deposited translucent mirror 212 is deposited into an aspherical shape can enhance the aberration correction effect.

[0089] In this embodiment, since lenses 204 and 205 are cemented together, the surface on which the vapor-deposited semi-transparent mirror 212 is deposited can be the surface of lens 205 on the observer's right eye 202 side. Even in this case, the surface on which the vapor-deposited semi-transparent mirror 212 is deposited is a convex surface protruding toward the right eye image display element 208.

[0090] Because this embodiment compromises between a longer viewing distance and a thinner HMD 201, the surface on the observer's right eye 202 side, where the PBS 214 with lens 204 and phase plate 213 are formed, is set to be flat.

[0091] In this embodiment, each of phase plates 211 and 213 is a quarter-wave plate with a phase difference of λ / 4, but the phase difference can be offset from λ / 4 to eliminate birefringence of lenses 204 and 205. In this case, the sum of the phase differences of lens 204 and phase plate 213 can be 3λ / 20 or greater and 7λ / 20 or less. Similarly, the sum of the phase differences of lens 205 and phase plate 211 can be 3λ / 20 or greater and 7λ / 20 or less. If each value is outside these ranges, the intensity of the ghosting light will increase, and a more natural image cannot be observed.

[0092] Third Embodiment

[0093] Figure 16 A head-mounted display (HMD) 301, as an example of an image display device according to this embodiment, is described. The HMD 301 includes lenses 304, 305, 306, and 307, a right-eye image display element 308, and a left-eye image display element 309. Lenses 304 and 305 constitute the right-eye eyepiece optical system, and lenses 306 and 307 constitute the left-eye eyepiece optical system. Lenses 304 and 305, as well as lenses 306 and 307, are cemented lenses and can be easily held in place. Each of the right-eye image display element 308 and the left-eye image display element 309 is an organic EL display.

[0094] The right eyepiece optical system magnifies and projects the original image displayed on the right eye image display element 308 into a virtual image, guiding it to the observer's right eye 302. The left eyepiece optical system magnifies and projects the original image displayed on the left eye image display element 309 into a virtual image, guiding it to the observer's left eye 303. Each of the right and left eyepiece optical systems has a focal length of 13mm, a horizontal viewing angle of 60°, a vertical viewing angle of 60°, and a diagonal viewing angle of 78°. The distance (viewing distance) between the HMD 301 and the observer's eyeball is 20mm.

[0095] The eyepiece optical system according to this embodiment has a configuration that uses polarization to fold the optical path. The optical path of the eyepiece optical system will be described with reference to the right eyepiece optical system. Figure 17The right eyepiece optical system according to this embodiment is described. The right eyepiece optical system, starting from the right eye image display element 308 side, sequentially includes a polarizing plate (first polarizing plate) 310, a phase plate (first phase plate) 311, lenses 305 and 304, a phase plate (second phase plate) 313, a polarizing beam splitter (hereinafter referred to as PBS) 314, and a polarizing plate (second polarizing plate) 315. A semi-transparent mirror 312 is deposited on the surface of lens 304 on the lens 305 side. The surface on which the semi-transparent mirror 312 is deposited serves as a semi-transparent reflective surface. Each of the phase plate 313, PBS 314, and polarizing plate 315 has a planar shape. Each of the phase plates 311 and 313 is a quarter-wave plate with a phase difference of λ / 4. Since the optical path of the eyepiece optical system is similar to that of the first or second embodiment, its description will be omitted.

[0096] Because the eyepiece optical system according to this embodiment has a short focal length and is thin, the emission angle of light emitted from the peripheral portion of the image display element to the exit pupil of the eyepiece optical system is large, and the emission angles of light emitted from both the horizontal and vertical ends of the image display element are 47 degrees. To shorten the focal length of the eyepiece optical system and make the HMD 301 thinner, the emission angle of light emitted from the peripheral portion of the image display element to the center of the exit pupil can be 30 degrees or greater.

[0097] As the emission angle of light emitted from the image display element increases, color shift occurs due to interference from the light-emitting layer of the organic EL and the color mixing effect of the color filter. In this embodiment, as the emission angle of light emitted from the image display element increases, a blue shift appears at the right end of the displayed image and a red shift appears at the left end due to color mixing by the color filter. Therefore, when an observer views a white image, red or blue is observed in the peripheral areas of the image, making it difficult to observe the image naturally.

[0098] Therefore, this embodiment uses the polarizer 310 as a correction element with different characteristics between the central portion and a region different from the central portion (the peripheral portion). More specifically, the polarizer 310 has characteristics that cause the spectral transmittance to differ between the central portion, the right end of the peripheral portion, and the left end of the peripheral portion. Thus, after the first light emitted from the central portion of the right-eye image display element 308 and the second light emitted from the outermost peripheral portion of the right-eye image display element 308 pass through the right-eye eyepiece optics system, the color shift of the second light relative to the first light can be made smaller than the color shift of the second light relative to the first light before the first and second lights pass through the right-eye eyepiece optics system. That is, the blue shift at the right end of the peripheral portion of the right-eye image display element 308 and the red shift at the left end of the peripheral portion of the right-eye image display element 308 can be eliminated. Figure 18The characteristics of polarizer 310 are explained, and the spectral transmittance of the central portion, the spectral transmittance at the right end of the peripheral portion, and the spectral transmittance at the left end of the peripheral portion of polarizer 310 are illustrated. Figure 18 As illustrated in the diagram, compared to the transmittance at the center of polarizer 310, the transmittance of the blue-side wavelengths is lower at the right end, and the transmittance of the red-side wavelengths is lower at the left end. Therefore, when blue-drifted light emitted from the right end of the image display element passes through the right end of polarizer 310, its blue intensity and blue drift can be reduced. Similarly, when red-drifted light emitted from the left end of the right-eye image display element 308 passes through the left end of polarizer 310, its red intensity and red drift can be reduced. The dominant blue wavelength of the right-eye image display element 308 is 470 nm, the dominant green wavelength is 545 nm, and the dominant red wavelength is 605 nm. The blue wavelength (first wavelength) can be included in the range from 430 nm to 480 nm. The green wavelength (second wavelength) can be included in the range from 520 nm to 570 nm. The red wavelength (third wavelength) can be included in the range from 600 nm to 650 nm.

[0099] As described above, the color drift of the peripheral portion of the right eye image display element 308 relative to the central portion can be reduced by changing the spectral transmittance between the central and peripheral portions of the polarizing plate 310, which serves as a color correction element, so that the observer can see a more natural image.

[0100] In this embodiment, such as Figure 16 As shown in the diagram, the beam width of the polarizer 310 near the right eye image display element 308 is very small, making it easy to separate each viewing angle. Therefore, the emission angle characteristics of the right eye image display element 308 can be eliminated by the characteristics of each position of the polarizer 310.

[0101] In this embodiment, the color shift caused by the emission angle of light emitted from the image display element is eliminated by the characteristics of the polarizer, but can be eliminated by the characteristics of the phase plate. In this case, to change the transmittance and reflectance when the polarizer or PBS is combined, the transmittance (spectral transmittance) of each wavelength of the phase plate can be changed, or the phase amount of each wavelength of the phase plate can be changed.

[0102] Color shift caused by the emission angle of light emitted from the image display element can be eliminated by the difference in at least one of the spectral transmittance and spectral reflectance between the central portion of the semi-transparent mirror and a region different from the central portion of the semi-transparent mirror. In this case, such as Figure 16 As illustrated in the diagram, the beam width of the light from the image display element is very small, making it easy to separate each viewing angle. Therefore, color drift can be eliminated by utilizing the characteristics of each position of the semi-transparent mirror.

[0103] Fourth embodiment

[0104] Figure 19 A head-mounted display (HMD) 401, as an example of an image display device according to this embodiment, is described. HMD 401 includes 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. Each of the right-eye image display element 408 and the left-eye image display element 409 is an organic EL display.

[0105] The right eyepiece optical system magnifies and projects the original image displayed on the right eye image display element 408 into a virtual image, guiding it to the observer's right eye 402. The left eyepiece optical system magnifies and projects the original image displayed on the left eye image display element 409 into a virtual image, guiding it to the observer's left eye 403. Each of the right and left eyepiece optical systems has a focal length of 10mm, a horizontal viewing angle of 90°, a vertical viewing angle of 90°, and a diagonal viewing angle of 110°. The distance (viewing distance) between the HMD 401 and the observer's eyeball is 12mm.

[0106] The eyepiece optical system according to this embodiment has a configuration that folds the optical path by using polarization. Since the configuration is similar to that of the first embodiment, its detailed description will be omitted.

[0107] Because the eyepiece optical system according to this embodiment has a short focal length and is thin, the emission angle of light emitted from the peripheral portion of the image display element to the exit pupil of the eyepiece optical system is large, and the emission angles of light emitted from both the horizontal and vertical ends of the image display element are 60 degrees. To shorten the focal length of the eyepiece optical system and make the HMD 401 thinner, the emission angle of light emitted from the peripheral portion of the image display element to the center of the exit pupil can be 30 degrees or greater.

[0108] As the emission angle of light emitted from the image display element increases, color shift occurs due to interference from the light-emitting layer of the organic EL and the color mixing effect of the color filter. In this embodiment, as the emission angle of light emitted from the image display element increases, a blue shift appears in the peripheral portion of the displayed image due to color mixing by the color filter. Therefore, when an observer views a white image, blue is observed in the peripheral portion of the image, making it impossible to observe the image naturally.

[0109] Therefore, this embodiment uses at least one of lenses 405 and 407 as a correction element with different characteristics between the central portion and a region different from the central portion (the peripheral portion). More specifically, the anti-reflective film deposited on the curved surface of the image display element side of each of lenses 405 and 407 has the characteristic that the spectral transmittance differs between the central portion and the peripheral portion. Thus, after the first light emitted from the central portion of the right-eye image display element and the second light emitted from the outermost peripheral portion of the right-eye image display element pass through the right-eye eyepiece optics system, the color shift of the second light relative to the first light can be made smaller than the color shift of the second light relative to the first light before the first and second lights pass through the right-eye eyepiece optics system. That is, the color shift in the peripheral portion of the image display element can be eliminated.

[0110] As described above, the color drift of the peripheral portion of the image display element relative to the central portion can be reduced by changing the spectral transmittance between the central and peripheral portions of the antireflective film of each of the lenses 405 and 407, which are color correction elements, so that the observer can view the image more naturally.

[0111] Because the curved surfaces of each of lenses 405 and 407 exhibit a large difference in the angle of incidence of light emitted from the central portion of the image display element compared to the angle of incidence of light emitted from the peripheral portion of the image display element, color shift can be eliminated by utilizing the properties of the anti-reflective film deposited on the curved surfaces of each of lenses 405 and 407 on the image display element side. Anti-reflective films with similar properties can be deposited on both sides of each of lenses 404 and 406 and on the observer-side surface of each of lenses 405 and 407. In this case, the effect of reducing color shift can be enhanced.

[0112] In addition, since there is a large difference between the incident angle of light emitted from the center part of the image display element and the incident angle of light emitted from the peripheral part of the protective glass of the image display element, an anti-reflective film can be deposited on the protective glass so that the transmittance of blue wavelength can be reduced as the incident angle increases.

[0113] like Figure 20 As illustrated, color correction elements 410 and 411 are positioned between the right-eye image display element 408 and lens 405, and between the left-eye image display element 409 and lens 407, so that color shift in the peripheral portion can be eliminated by utilizing the characteristics of correction elements 410 and 411. At this time, color correction elements 410 and 411 have the characteristic of reducing the transmittance of the blue wavelength as the incident angle increases.

[0114] In the case where, as in the third embodiment, the color to be shifted varies depending on the position of the displayed image, resulting in a blue shift at the right end and a red shift at the left end, the characteristics of the antireflective coating of each of lenses 405 and 407 can vary between the central portion, the right end of the peripheral portion, and the left end of the peripheral portion. More specifically, the transmittance of the blue wavelength is lower at the right end compared to the transmittance at the center of the antireflective coating, and the transmittance of the red wavelength is lower at the left end. Therefore, when blue-shifted light emitted from the right end of the image display element passes through the right end of each of lenses 405 and 407, its blue intensity and blue shift can be reduced. Similarly, when red-shifted light emitted from the left end of the image display element passes through the left end of each of lenses 405 and 407, its red intensity and red shift can be reduced. Even in this case, color drift can be reduced by changing the spectral transmittance of the antireflective coating of each of lenses 404 and 406, the transmittance of the antireflective coating of the protective glass, or the transmittance of the color correction elements 410 and 411 between the right and left ends relative to the center.

[0115] Fifth Embodiment

[0116] Figure 21 A head-mounted display (hereinafter, HMD) 501, which is an example of an image display device according to this embodiment, is described. Figure 22 The diagram shows the HMD 501 connected to the PC 510.

[0117] HMD 501 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 and 505, as well as lenses 506 and 507, are cemented lenses and can be easily held in place. Each of the right-eye image display element 508 and the left-eye image display element 509 is an organic EL display.

[0118] The right eyepiece optical system magnifies and projects the original image displayed on the right eye image display element 508 into a virtual image, guiding it to the observer's right eye 502. The left eyepiece optical system magnifies and projects the original image displayed on the left eye image display element 509 into a virtual image, guiding it to the observer's left eye 503. Each of the right and left eyepiece optical systems has a focal length of 13mm, a horizontal viewing angle of 60°, a vertical viewing angle of 60°, and a diagonal viewing angle of 78°. The distance (viewing distance) between the HMD 501 and the observer's eyeball is 20mm.

[0119] The eyepiece optical system according to this embodiment has a configuration that uses polarization to fold the optical path. Since the configuration is similar to that of the second embodiment, its detailed description will be omitted.

[0120] Because the eyepiece optical system according to this embodiment has a short focal length and is thin, the emission angle of light emitted from the peripheral portion of the image display element to the exit pupil of the eyepiece optical system is large, and the emission angles of light emitted from both the horizontal and vertical ends of the image display element are 47 degrees. To shorten the focal length of the eyepiece optical system and make the HMD 501 thinner, the emission angle of light emitted from the peripheral portion of the image display element to the center of the exit pupil can be 30 degrees or greater.

[0121] As the emission angle of light emitted from the image display element increases, color shift occurs due to interference from the light-emitting layer of the organic EL and the color mixing effect of the color filter. In this embodiment, as the emission angle of light emitted from the image display element increases, a blue shift appears in the peripheral portion of the displayed image due to color mixing by the color filter. Therefore, when an observer views a white image, blue is observed in the peripheral portion of the image, making it difficult to observe the image naturally.

[0122] Therefore, this embodiment eliminates color shift in the peripheral portion of the image displayed on the image display element by changing the characteristics between the central and peripheral portions. The image displayed on the image display element has a white balance based on the spectral transmittance of the eyepiece optical system. Typically, the white balance is uniform across the entire surface of the image display element. In this embodiment, color shift occurs in the peripheral portion relative to the central portion; therefore, color shift in the peripheral portion is reduced by changing the white balance between the central and peripheral portions by the image processing unit 511. Taking into account the blue shift in the peripheral portion of the image, this embodiment adjusts the white balance in the peripheral portion so that the gain of red and green is greater than the gain of blue, and the image in the peripheral portion is yellower than the image in the center. Thus, the white balance of the image displayed in the peripheral portion of the image display element is yellower than the image displayed in the central portion, and since the blue shift is caused by a large emission angle, the emitted image becomes an image with reduced color shift in the central portion.

[0123] Here, the dominant blue wavelength of the image display element is 470 nm, the dominant green wavelength is 545 nm, and the dominant red wavelength is 605 nm. The blue wavelength (first wavelength) can be included in the range from 430 nm to 480 nm. The green wavelength (second wavelength) can be included in the range from 520 nm to 570 nm. The red wavelength (third wavelength) can be included in the range from 600 nm to 650 nm.

[0124] In this embodiment, the wavelength at which the ratio of the intensity of light emitted from the peripheral portion of the image display element to the intensity of light emitted from the center portion of the image display element to the exit pupil becomes the largest is 470 nm, which is the dominant blue wavelength, and a blue shift occurs as the emission angle increases. Therefore, by setting the wavelength at which the ratio of the peripheral gain to the center gain of the image display element becomes the smallest among red, green, and blue wavelengths to blue, the color shift of the image display element can be eliminated. Thus, by changing the white balance between the center and peripheral portions, the color shift of the peripheral portion of the image display element relative to the center portion is reduced, and the observer can observe a more natural image. The white balance of the peripheral portion relative to the center portion can be gradually changed from the center portion to the peripheral portion, or it can be changed only in the outermost peripheral portion. In the case where the color shift of the peripheral portion is blue regardless of position, as in this embodiment, the gain value of each color to be changed from the center portion to the peripheral portion can be stored as a function of the distance from the center portion. In this case, the required storage capacity can be smaller compared to the case of storing a data image.

[0125] In this embodiment, the image processing unit 511 changes the white balance, but the PC 510 that generates the display image of the HMD 501 can also change the white balance. In this case, since the processing inside the HMD 501 is reduced, the power consumption of the image processing unit 511 can be reduced.

[0126] If the image display element is a liquid crystal display (LCD) and color shift in the peripheral portion depends on position, resulting in a blue shift at the right end and a red shift at the left end, then the color shift can be reduced by altering the characteristics between the right and left ends. In this case, because the image at the right end shifts towards blue, the white balance at the right end is adjusted to make the gain of red and green greater than the gain of blue, making the image at the right end more yellow than the image at the center. Because the image at the left end shifts towards red, the white balance at the left end is adjusted to make the gain of green and blue greater than the gain of red, making the image at the left end more blue-green (cyan) than the image at the center. Thus, the white balance of the image displayed at the right end of the image display element is more yellow than at the center, and the blue shift caused by the large emission angle reduces the color shift at the right end of the emitted image compared to the center. Similarly, the white balance of the image displayed at the left end of the image display element is more blue-green than at the center, and the red shift caused by the large emission angle reduces the color shift at the left end of the emitted image compared to the center.

[0127] Sixth Embodiment

[0128] Figure 23A right eyepiece optical system according to this embodiment is described. The right eyepiece optical system according to this embodiment differs from the right eyepiece optical system according to the first embodiment in that it includes a dielectric multilayer film (negative filter) 601 as a correction element disposed between the right eye image display element 108 and the polarizing plate 110. In this embodiment, descriptions of configurations similar to those in the first embodiment will be omitted. In this embodiment, the aforementioned color shift is reduced by the negative filter 601. Now, a method for reducing color shift using a dielectric multilayer film will be described.

[0129] First, dielectric multilayer films are typically used as filters, which reduce transmittance within a specific wavelength range by alternately stacking dielectric films with high refractive indices and those with low refractive indices. In this specification, the wavelength range with lower transmittance than the surrounding wavelength range will be referred to as the stopband, and other wavelength ranges with high transmittance will be referred to as the passband. The stopband has a relatively narrow width and, as... Figure 24 The filter shown in the diagram has the property of locally reducing transmittance and is called a negative filter. Figure 24 The negative filter has a stopband in the low transmittance region around 500 nm and a passband in the remaining high transmittance region. The structure and materials of the filter's multilayer film are appropriately designed according to the desired characteristics. Filters using such dielectric multilayer films are essentially designed to obtain the desired transmission characteristics based on interference effects; therefore, such as... Figure 25 As shown in the diagram, the transmission characteristics of the filter are known to shift towards the shorter wavelength side during oblique incidence compared to the transmission characteristics during 0-degree incident incidence. This embodiment... Figure 23 A negative filter is formed on the surface of the organic EL side, and the layered structure is illustrated in Table 1 below. The substrate is made of BK7 glass, Ta2O5 is used as the high refractive index material, and SiO2 is used as the low refractive index material, and they are stacked in 60 layers.

[0130] Table 1

[0131]

[0132] Figure 26 The illustration shows the emission spectrum 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. Figure 27 The figure illustrates the emission spectrum 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 28The diagram illustrates the emission spectral distribution of the organic EL panel at a 50-degree emission direction and the transmittance distribution of the negative filter 601 at a 50-degree incident direction. First, without the negative filter 601, the chromatic difference ΔE*ab of light at a 30-degree emission direction relative to the 0-degree emission direction is 15.6, the absolute value of the chromatic difference Δx is 0.0024, and the absolute value of the chromatic difference Δy is 0.0227. Without the negative filter 601, the chromatic difference ΔE*ab of light at a 50-degree emission direction relative to the 0-degree emission direction is 27.0, the absolute value of the chromatic difference Δx is 0.0009, and the absolute value of the chromatic difference Δy is 0.03608.

[0133] from Figure 26 , Figure 27 and Figure 28 The emission spectrum is understood to show that as the emission angle increases, the intensity of blue increases and chromatic aberration and color difference become more pronounced. For example... Figure 26 As illustrated in the diagram, the negative filter provided in this embodiment is designed to have a stopband around 500 nm during 0-degree incident light. Figure 27 and Figure 28 As illustrated in the diagram, the negative filter's function is to shift the stopband towards the shorter wavelength side during oblique incidence, gradually reducing the transmittance in the blue wavelength range. As a result, when light passes through the negative filter 601 in this embodiment, the color difference ΔE*ab of light emitted at 30 degrees relative to the 0-degree emission direction becomes 6.5, the absolute value of the color difference Δx becomes 0.007, and the absolute value of the color difference Δy becomes 0.004. The color difference ΔE*ab of light emitted at 50 degrees relative to the 0-degree emission direction becomes 10.2, the absolute value of the color difference Δx becomes 0.018, and the absolute value of the color difference Δy becomes 0.013.

[0134] Therefore, by shifting the stopband of the negative filter towards the shorter wavelength side during oblique transmission, the color shift characteristic that intensifies the blue color due to the oblique emission of the organic EL display is reduced. In cases where the blue component of the display tends to be stronger, as in this embodiment, the stopband of the dielectric filter during 0-degree incidence is designed to exist between the common blue wavelength band of 430nm to 480nm and the green wavelength band of 520nm to 570nm. Thus, there is almost no color change during vertical incidence, and the blue component can be reduced during oblique incidence. Therefore, if the stopband exists on a wavelength side longer than the color component that needs to be reduced relative to the emission angle, chromatic aberration or color difference can be reduced by shifting the stopband in the visible light range during oblique incidence. This is similarly applied to the green component (520nm to 570nm) and the red component (600nm to 650nm). Filters with multiple stopbands are also suitable when correcting multiple color components.

[0135] Using a separate image display element according to this embodiment, at an emission angle of 50 degrees, the absolute value of chromaticity difference x is 0.0009 and the absolute value of chromaticity difference y is 0.03608. After light passes through the eyepiece optics, the absolute value of chromaticity difference x increases to 0.018, but the absolute value of chromaticity difference y decreases to 0.013. To allow the observer to view a more natural image without noticing color shift, the absolute values ​​of chromaticity differences x and y can be 0.03 or less. In this embodiment, it should be understood that the chromaticity difference is corrected to a level that allows the observer to view a more natural image.

[0136] The color difference ΔE*ab can be reduced from 27.0 to 10.2. To allow the observer to see a more natural image without noticing color shift, the color difference ΔE*ab on the chromaticity coordinate system can be 15 or less. In this embodiment, it should be understood that the color difference is corrected to a level that allows the observer to see a more natural image.

[0137] In this embodiment, the filter is deployed as a separate component, but it can be placed on the surface of the protective glass of the organic EL panel to save space and reduce the number of components. The filter can also be formed on the surface of any optical element. In these cases, the required multilayer film configuration can be appropriately designed based on the refractive index of the substrate material, etc. The configuration of the dielectric multilayer film can be appropriately designed based on the emission spectrum of the organic EL panel, the display optical system, the color shift characteristics at the emission angle in the tilt direction, etc.

[0138] In the above description, the image viewing device according to this embodiment includes a dielectric multilayer film on a surface between the light-emitting portion of the image display element and the exit pupil. Due to the incident angle characteristics of the dielectric multilayer film, when light passes through the dielectric multilayer film, the color difference or chromaticity difference between the light emitted from the peripheral portion of the image display element toward the exit pupil and the light emitted from the central portion of the image display element toward the exit pupil decreases.

[0139] Seventh Embodiment

[0140] Figure 29 The right eyepiece optical system according to this embodiment is described. The right eyepiece optical system according to this embodiment differs from the right eyepiece optical system according to the second embodiment in that the right eyepiece optical system according to this embodiment includes a dielectric multilayer film (IR cutoff filter) 602 as a correction element disposed between the right eye image display element 208 and the polarizing plate 210. In this embodiment, descriptions of configurations similar to those in the second embodiment will be omitted. In this embodiment, the IR cutoff filter 602 reduces the aforementioned color shift. Now, a method for reducing color shift using this dielectric multilayer film will be described.

[0141] like Figure 30 The dielectric multilayer film filter shown in the diagram, which has the property of reducing transmittance in the infrared region, is called an IR cutoff filter. Figure 30 The IR cutoff filter has a passband in the high transmittance range below 690 nm and a stopband in the low transmittance range on its longer wavelength side. The structure, materials, etc., of the filter's multilayer film are appropriately designed according to the desired characteristics. Filters using dielectric multilayer films are basically designed to obtain the desired transmission characteristics based on interference effects, and such... Figure 31 As illustrated in the diagram, it is known that the transmission characteristics shift towards the shorter wavelength side during oblique incidence compared to the transmission characteristics during 0-degree incident incidence. In this embodiment, in Figure 29 An IR cutoff filter is formed on the surface of the polarizer 210 on the organic EL (right eye image display element 208) side, and the layered structure is illustrated in Table 2 below. The substrate is made of BK7 glass, TiO2 is used as the high refractive index material, and SiO2 is used as the low refractive index material, and they are stacked in 35 layers.

[0142] Table 2

[0143]

[0144] Figure 32 The illustration shows the emission spectrum distribution of the organic EL panel in the 0-degree emission direction and the transmission distribution of the IR cut-off filter in the 0-degree incident direction in this embodiment. Figure 33 The illustration shows the emission spectrum distribution of the organic EL panel in the 30-degree emission direction and the transmission distribution of the IR cut-off filter in the 30-degree incident direction. Figure 34 The diagram illustrates the emission spectral distribution of an organic EL panel at a 50-degree emission direction and the transmission distribution of an IR cutoff filter at a 50-degree incident direction. First, without the IR cutoff filter, the chromatic difference ΔE*ab of light at a 30-degree emission direction relative to the 0-degree emission direction is 17.4, the absolute value of the chromatic difference Δx is 0.0015, and the absolute value of the chromatic difference Δy is 0.0212. The chromatic difference ΔE*ab of light at a 50-degree emission direction relative to the 0-degree emission direction is 21.7, the absolute value of the chromatic difference Δx is 0.0083, and the absolute value of the chromatic difference Δy is 0.0208.

[0145] from Figure 32 , Figure 33 and Figure 34 The emission spectrum and chromaticity difference in [the text] can be understood as follows: as the emission angle increases, the intensity of red increases and the chromatic difference becomes more pronounced. For example... Figure 32 As illustrated in the diagram, the IR cutoff filter provided in this embodiment is designed to have a stopband in the wavelength range of 730 nm or higher (i.e., the infrared wavelength range) during 0-degree incident light. Figure 33and Figure 34 As illustrated in the diagram, the function of the IR cutoff filter is to shift the stopband towards the shorter wavelength side during oblique incidence, gradually reducing the transmittance in the red wavelength range. As a result, when light passes through the IR cutoff filter 602 in this embodiment, the color difference ΔE*ab of light in the 30-degree emission direction relative to the 0-degree emission direction becomes 13.1, the chromaticity difference Δx becomes 0.0023, and the chromaticity difference Δy becomes 0.0166. The color difference ΔE*ab of light in the 50-degree emission direction relative to the 0-degree emission direction becomes 11.4, the chromaticity difference Δx becomes 0.0108, and the chromaticity difference Δy becomes 0.0173. Therefore, by shifting the stopband of the IR cutoff filter towards the shorter wavelength side during oblique transmission, the color shift characteristic of increased red intensity due to oblique emission of the organic EL display is reduced.

[0146] In cases where the display exhibits a strong red component, as in this embodiment, the stopband of the dielectric filter during 0-degree incidence is designed to exist at 640 nm or higher (i.e., the common red wavelength). Consequently, there is almost no color change during vertical incidence, and the red component can be reduced during oblique incidence. Therefore, if a dielectric multilayer filter with a stopband located on a wavelength side longer than the color component to be reduced relative to the emission angle is used, as in the first embodiment, chromatic aberration or color difference can be reduced by shifting the stopband in the visible light range during oblique incidence.

[0147] When reducing the red component as in this embodiment, it is not necessary to use a filter with a local stopband like a negative filter, and this embodiment can use an IR cutoff filter with a wide range of stopbands in the invisible range on the long wavelength side.

[0148] Using a separate image display element according to this embodiment, at an emission angle of 50 degrees, the absolute value of the chromaticity difference x is 0.0083 and the absolute value of the chromaticity difference y is 0.0208. After the light passes through the eyepiece optics, the absolute value of the chromaticity difference x increases to 0.0108, but the absolute value of the chromaticity difference y decreases to 0.0173. To allow the observer to view a more natural image without noticing color shift, the absolute values ​​of the chromaticity differences x and y on the chromaticity coordinate system can be 0.03 or less, or 0.018 or less. In this embodiment, it should be understood that the chromaticity difference is corrected to a level that allows the observer to view a more natural image.

[0149] The color difference ΔE*ab can be reduced from 21.7 to 11.4. To allow the observer to see a more natural image without noticing color shift, the color difference ΔE*ab on the chromaticity coordinate system can be 15 or less. In this embodiment, it should be understood that the color difference is corrected to a level that allows the observer to see a more natural image.

[0150] In this embodiment, the filter is deployed as a separate component, but it can be placed on the surface of the protective glass of the organic EL panel to save space and reduce the number of components. The filter can also be formed on the surface of any other optical element. In these cases, the required multilayer film configuration can be appropriately designed based on the refractive index of the substrate material, etc. The configuration of the dielectric multilayer film can be appropriately designed based on the emission spectrum of the organic EL panel, the display optical system, the color shift characteristics at the emission angle in the tilt direction, etc.

[0151] Each embodiment can provide an image display device that helps reduce color drift of the peripheral portion of the image display element relative to the central portion of the image display element.

[0152] While this disclosure has been described with reference to exemplary embodiments, it is to be understood that this disclosure is not limited to the disclosed exemplary embodiments. The scope of the appended claims should be given the broadest interpretation to include all such modifications and equivalent structures and functions.

Claims

1. An image display device, comprising: Image display elements; as well as An eyepiece optical system configured to direct light from the image display element to the exit pupil. The eyepiece optical system is characterized by comprising at least one correction element, wherein the at least one correction element has different characteristics between a central region and a peripheral region different from the central region. Wherein, when the first light is emitted from the central portion of the image display element and the second light is emitted from the outermost peripheral portion of the image display element, the characteristic of the at least one correction element is configured such that the color shift of the second light after passing through the peripheral region relative to the first light after passing through the central region is less than the color shift of the second light before passing through the peripheral region relative to the first light before passing through the central region.

2. The image display device according to claim 1, characterized in that, The at least one correction element includes a phase plate. Specifically, for each wavelength, at least one of the spectral transmittance and phase quantity is different between the central portion of the phase plate and a region of the phase plate that is different from the central portion.

3. The image display device according to claim 1, characterized in that, The at least one correction element includes a polarization beam splitter. Wherein, at least one of the spectral transmittance and spectral reflectance is different between the central portion of the polarization beamsplitter and a region of the polarization beamsplitter that is different from the central portion.

4. The image display device according to claim 3, characterized in that, The polarization beam splitter reflects the first linearly polarized light and allows the second linearly polarized light to pass through, the second linearly polarized light having a polarization direction orthogonal to the polarization direction of the first linearly polarized light.

5. The image display device according to claim 1, characterized in that, The at least one correction element includes a polarizing plate. The spectral transmittance is different between the central portion of the polarizer and a region of the polarizer that is different from the central portion.

6. The image display device according to claim 1, characterized in that, The at least one correction element includes a phase plate, a polarization beam splitter, and a polarization plate. Specifically, among the first wavelength included in the range of 430 nm to 480 nm, the second wavelength included in the range of 520 nm to 570 nm, and the 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 becomes the largest is equal to the wavelength at which at least one of the transmittance of the polarizer, the transmittance of the phase plate, the reflectance of the polarizing beam splitter, and the transmittance of the polarizing beam splitter becomes the smallest in the optical path from the outermost peripheral portion to the exit pupil.

7. The image display device according to claim 1, characterized in that, The at least one correction element includes a semi-transparent reflective film. Wherein, at least one of the spectral transmittance and spectral reflectance is different between the central portion of the semitransmissive reflective film and a region of the semitransmissive reflective film that is different from the central portion.

8. The image display device according to claim 1, characterized in that, The at least one correction element includes an anti-reflective film. The spectral transmittance is different between the central portion of the antireflective film and a region of the antireflective film that is different from the central portion.

9. The image display device according to claim 8, characterized in that, Among a first wavelength ranging from 430 nm to 480 nm, a second wavelength ranging from 520 nm to 570 nm, and a third wavelength ranging from 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 becomes the largest is equal to the wavelength at which the transmittance of the antireflective film becomes the smallest in the optical path from the outermost peripheral portion to the exit pupil.

10. The image display device according to claim 1, characterized in that, The at least one correction element comprises a dielectric multilayer film. Wherein, at least one of the spectral transmittance and spectral reflectance is different between the central portion of the dielectric multilayer film and a region of the dielectric multilayer film that is different from the central portion.

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

12. The image display device according to claim 11, characterized in that, in, The first wavelength is in the range of 430 nm to 480 nm, the second wavelength is in the range of 520 nm to 570 nm, and the third wavelength is in the range of 600 nm to 650 nm. The stopband of the dielectric multilayer film exists in each of the following: the band between the first wavelength and the second wavelength, the band between the second wavelength and the third wavelength, and the band having a wavelength longer than the third wavelength.

13. The image display device according to claim 10, characterized in that, The dielectric multilayer film is a negative filter or an IR cutoff filter.

14. The image display device according to claim 1, characterized in that, The eyepiece optical system, starting from the image display element side, includes, in sequence, a first polarizing plate, a first phase plate, a lens, a second phase plate, and a polarizing beam splitter.

15. The image display device according to claim 1, characterized in that, The eyepiece optical system, starting from the image display element side, includes, in sequence, a first polarizing plate, a first phase plate, a lens, a second phase plate, a polarizing beam splitter, and a second polarizing plate.

16. The image display device according to claim 14, characterized in that, The emission angle of the second light is greater than half the display angle of the eyepiece optical system. In this embodiment, at least one of the first polarizing plate and the first phase plate is used as the correction element.

17. The image display device according to claim 15, characterized in that, The emission angle of the second light is greater than half the display angle of the eyepiece optical system. In this embodiment, at least one of the second phase plate, the polarization beam splitter, and the second polarization plate serves as the correction element.

18. The image display device according to claim 1, characterized in that, After the first light and the second light pass through the eyepiece optical system, the chromatic difference ΔE* of the second light relative to the first light is 15 or less.

19. The image display device according to claim 1, characterized in that, After the first light and the second light pass through the eyepiece optical system, on the chromaticity diagram, the chromaticity difference x of the second light relative to the first light is 0.05 or less, and the chromaticity difference y of the second light relative to the first light is 0.05 or less.

20. The image display device according to claim 1, characterized in that, The emission angle of the second light is 30 degrees or greater.

21. The image display device according to claim 1, characterized in that, The ratio of the intensity of the second light to the intensity of the first light becomes the wavelength that is most significant, which is included in the range from 430 nm to 480 nm.

22. The image display device according to claim 1, characterized in that, In a first wavelength ranging from 430 nm to 480 nm, a second wavelength ranging from 520 nm to 570 nm, and a third wavelength ranging from 600 nm to 650 nm, the ratio of the intensity of the second light to the intensity of the first light becomes equal to the wavelength at which the intensity of the second light is maximized, regardless of the emission direction of the light emitted from the image display element.

23. The image display device according to claim 1, characterized in that, After the first light and the second light pass through the eyepiece optical system, the color shift of the second light in the horizontal direction relative to the first light is less than the color shift of the second light in the vertical direction relative to the first light.

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

25. The image display device according to claim 24, characterized in that, Among the first wavelength, which includes the range of 430 nm to 480 nm, the second wavelength, which includes the range of 520 nm to 570 nm, and the third wavelength, which includes 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 becomes the largest is equal to the wavelength at which the ratio of the gain of the outermost peripheral portion of the image display element to the gain of the central portion of the image display element becomes the smallest.

Images