Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B13/00—Optical objectives specially designed for the purposes specified below
  • G02B13/18—Optical objectives specially designed for the purposes specified below with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B17/00—Systems with reflecting surfaces, with or without refracting elements
  • G02B17/08—Catadioptric systems
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B25/00—Eyepieces; Magnifying glasses
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
  • G02B27/02—Viewing or reading apparatus

Definitions

• the present invention relates to an eyepiece optical system with a viewing angle of 80 degrees or more, and a wide-field image display device.
• a concave surface is a surface where the edge of the lens is located further outward in the optical axis direction than the center of the lens surface
• a convex surface is a surface where the center of the lens is located further outward in the optical axis direction than the edge of the lens.
• the present invention also provides The present invention provides a wide-angle image display device comprising the above-described eyepiece optical system.
• the present invention provides an eyepiece optical system and a wide-field image display device that suppresses the occurrence of flare and ghosting and chromatic aberration.
• FIG. 1 is a cross-sectional view showing the configuration of a wide-angle image display device equipped with an eyepiece optical system according to an embodiment of the present invention.
• FIG. 2A is a perspective view showing the configuration of a wide-angle image display device equipped with an eyepiece optical system according to an embodiment of the present invention
• FIG. 2B is a perspective view showing the configuration of a third lens of the eyepiece optical system.
• Figure 3A is a cross-sectional view showing an eyepiece optical system according to an embodiment of the present invention having a fourth lens and showing how the first lens is moved in the optical axis direction
• Figure 3B is a cross-sectional view showing the fourth lens removed from the eyepiece optical system.
• FIG. 4 is a cross-sectional view of Example 1 of an eyepiece optical system according to an embodiment of the present invention.
• Figure 5A is a diagram showing the relationship between the focal movement and the absolute value of the OTF (Optical Transfer Function) in Example 1
• Figure 5B is a spot diagram in Example 1.
• FIG. 6A is a diagram showing the relationship between the field curvature and the viewing angle in Example 1
• FIG. 6B is a diagram showing the relationship between the percent distortion and the viewing angle in Example 1
• FIG. 6C is a diagram showing the chromatic aberration of magnification in Example 1.
• FIG. 7 is a cross-sectional view of Example 2 of an eyepiece optical system according to an embodiment of the present invention.
• FIG. 12A is a diagram showing the relationship between the field curvature and the viewing angle in Example 3
• FIG. 12B is a diagram showing the relationship between the percent distortion and the viewing angle in Example 3
• FIG. 12C is a diagram showing the chromatic aberration of magnification in Example 3.
• FIG. 13 is a cross-sectional view of Example 4 of an eyepiece optical system according to an embodiment of the present invention.
• FIG. 14A is a diagram showing the relationship between the focal point movement and the absolute value of the OTF in the fourth embodiment
• FIG. 14B is a spot diagram in the fourth embodiment.
• FIG. 15A is a diagram showing the relationship between the field curvature and the viewing angle in Example 4
• FIG. 15B is a diagram showing the relationship between the percent distortion and the viewing angle in Example 4
• FIG. 15C is a diagram showing the chromatic aberration of magnification in Example 4.
• FIG. 16 is a cross-sectional view of Example 5 of an eyepiece optical system according to an embodiment of the present invention.
• FIG. 17A is a diagram showing the relationship between the focal point movement and the absolute value of the OTF in the fifth embodiment
• FIG. 17B is a spot diagram in the fifth embodiment.
• FIG. 18A is a diagram showing the relationship between the field curvature and the viewing angle in Example 5
• FIG. 18B is a diagram showing the relationship between the percent distortion and the viewing angle in Example 5
• FIG. 18C is a diagram showing the chromatic aberration of magnification in Example 5.
• FIG. 19 is a cross-sectional view of Example 6 of an eyepiece optical system according to an embodiment of the present invention.
• FIG. 20A is a diagram showing the relationship between the focal point movement and the absolute value of the OTF in the sixth embodiment
• FIG. 20B is a spot diagram in the sixth embodiment
• FIG. 21A is a diagram showing the relationship between the field curvature and the viewing angle in Example 6
• FIG. 21B is a diagram showing the relationship between the percent distortion and the viewing angle in Example 6
• FIG. 21C is a diagram showing the chromatic aberration of magnification in Example 6.
• FIG. 22 is a cross-sectional view of Example 7 of an eyepiece optical system according to an embodiment of the present invention.
• FIG. 23A is a diagram showing the relationship between the focal point movement and the absolute value of the OTF in the seventh embodiment
• FIG. 23B is a spot diagram in the seventh embodiment.
• FIG. 24A is a diagram showing the relationship between the field curvature and the viewing angle in Example 7
• FIG. 24B is a diagram showing the relationship between the percent distortion and the viewing angle in Example 7
• FIG. 24C is a diagram showing the chromatic aberration of magnification in Example 7.
• the eyepiece optical system is an eyepiece optical system arranged between the eyepoint of a wide-field image display device and an image display element (display), and comprises, in order from the eyepoint side, a first lens having a convex lens surface facing the image display element and positive refractive power, a second lens having a concave lens surface facing the image display element, and a third lens having a convex lens surface facing the eyepoint side, a first film (polarization control film) that changes the polarization state of light traveling from the image display element side to the eyepoint side to a first polarization state is attached to the lens surface facing the eyepoint of the second lens, a second film is attached to the lens surface facing the eyepoint of the first lens, which reflects light in the first polarization state traveling from the image display element side to the eyepoint side and changes it to a second polarization state, and transmits light in the second polar
• a first film polarization control film
• a concave surface is a surface where the edge of the lens is located further outward in the optical axis direction than the center of the lens surface
• a convex surface is a surface where the center of the lens is located further outward in the optical axis direction than the edge of the lens.
• the "eye point” is the user's pupil.
• "Forward tracing” is tracing the light rays that travel from the image display element toward the eye point
• “reverse tracing” is tracing the light rays that travel from the eye point toward the image display element.
• a “concave surface” is a surface where the edge of the lens surface (the outer periphery of the area through which light rays pass) extends further outward in the optical axis direction than the center of the lens (the part that intersects with the optical axis).
• a “convex surface” is a surface where the center of the lens surface extends further outward in the optical axis direction than the edge of the lens surface.
• image display elements display red, green, and blue images, which are then additively mixed to create images of various colors.
• the eyepiece optical system has chromatic aberration of magnification, which is a type of chromatic aberration
• the projection magnification of the image display element onto which the eyepiece optical system projects changes according to the wavelength, resulting in a color shift of red, green, and blue in the projected image.
• this color shift can be electrically corrected by processing the image signal.
• by changing the size of the red, green, and blue images projected onto the image display element according to the chromatic aberration of magnification it is possible to create a projected image without color shift.
• magnification of the red, green, and blue light that create the red, green, and blue images changes within the range of their respective spectral widths, causing blurring that spreads in the radial direction in each of the red, green, and blue images.
• This radial blurring cannot be electrically corrected. Therefore, in order to obtain high resolution in an eyepiece optical system that enlarges and projects an image from an image display element, it is necessary to reduce chromatic aberration.
• the following describes forward tracing of light rays in the eyepiece optical system of the present invention.
• Light that leaves the image display element and enters the second lens passes through the first film, becomes in a first polarization state, and heads toward the first lens.
• the lens surface of the first lens facing the image display element is coated with a half mirror, but some of the light passes through the half mirror. It then passes through the first lens and enters the second film. Since this light (LA1) is in the first polarization state, it is reflected by the second film and changed to a second polarization state.
• This light (LA2) now in the second polarization state, travels backwards through the first lens and heads toward the half mirror coated on the image display element side of the first lens.
• the half mirror reflects a part of the light, and the reflected light (LA3) passes through the first lens again and enters the second film. Since this light (LA3) is in the second polarization state, it passes through the second polarizing film and enters the user's eye.
• the second film acts as a back-surface mirror for the light (LA1), and the half mirror acts as a back-surface mirror for the light (LA2), and furthermore, the half mirror side of these back-surface mirrors, or both the half mirror side and the second film side, act as concave mirrors. Reacting to the action of this concave mirror, the light (LA3) creates an aerial image (Ip) of the display image (Im) on the image display element (DP). The aerial image (Ip) then enters the user's eyes and is reflected.
• the eyepiece optical system in terms of reverse tracing, which is the tracing of the path of a ray from the eyepoint side to the image display element side, when light parallel to the optical axis is incident, the height of the ray basically becomes gradually lower as the ray travels, and becomes approximately zero at the image display element. In other words, the ray height is higher on the lens surface closer to the eyepoint, and the contribution of its refractive power to the refractive power of the entire system tends to be higher.
• the radius of curvature can be made larger, i.e., the curvature can be made smaller, compared to when it is arranged on the other lenses (second and third lenses).
• a back-surface concave mirror can produce refractive power with a radius of curvature that is approximately six times larger than that of a refractive convex surface, as will be explained later. Therefore, the lens surface of the first lens facing the image display element can have a smaller amount of sag, and the thickness of the first lens can be made thinner from the center to the periphery.
• the first lens acts as a concave mirror, but this concave mirror is a back-surface mirror that acts on the light traveling inside the lens.
• the refractive power of the concave surface is as follows: 2 ⁇ N1/(radius of curvature of lens surface) however, N1: Can be calculated by the refractive index of the first lens for light with a wavelength of 525 nm.
• the refractive power of a normal lens surface i.e. a refractive lens surface
• the radius of curvature can be made much larger than when a refractive lens surface, which is the lens surface of a normal lens, is used. This makes it possible to reduce the thickness of
• a so-called pancake optical system creates one and a half round trip optical paths using a first film that changes the polarization state of light traveling from the image display element side to the eye point side to a first polarization state, and a second film that reflects the light in the first polarization state traveling from the image display element side to the eye point side and changes it to a second polarization state, and transmits the light in the second polarization state traveling from the image display element side to the eye point side, and creates an image using the action of the concave mirror of the optical element placed between them.
• the optical element sandwiched between the first and second films has retardation (RT), and as a result, when the first polarization state of the light traveling from the first film to the second film is disturbed, light that is not reflected by the second film but transmits (stray light) is generated, and flare and ghosts occur in the aerial image. Therefore, the so-called pancake optical system needs to minimize the retardation of the optical element sandwiched between the first and second films.
• the only optical element sandwiched between the first and second films is the first lens. Therefore, the optical element that has retardation (RT) that causes stray light is limited to the first lens.
• the action of the first film, the second film, and the half mirror creates a round trip optical path with a concave mirror in the optical path.
• retardation occurs in the light (LA1) that passes through the first lens and enters the second film due to an element sandwiched between the first and second films, the first polarization state is disturbed, and part of the light (LA1) is transmitted without being reflected by the second film, generating stray light that superimposes flare and ghosts on the aerial image (Ip).
• stray light that superimposes flare and ghosts on the aerial image (Ip).
• Retardation occurs due to birefringence in the material that makes up the lens, and becomes larger the longer the optical path that passes through the lens. Note that, as will be described later, the allowable retardation is approximately 10 nm.
• the optical element that creates the retardation (RT) is limited to the first lens.
• the radius of curvature of the lens surface of the first lens facing the image display element is large as described above. Therefore, the thickness of the first lens can be made thin from the center to the periphery of the lens. As a result, the optical path length of the light (LA1) that passes through the first lens and enters the second film is short, and the retardation (RT) is small.
• the present invention even if a material with a relatively large birefringence is used for the first lens, flare and ghosting can be suppressed.
• the second lens and the third lens are arranged closer to the image display element than the first film, the retardation generated by these lenses does not create stray light. Therefore, a material with a large birefringence can be used for these lenses.
• plastic which has a larger birefringence than glass, for all of the first to third lenses. Plastic allows aspherical lenses to be manufactured more cheaply and lighter than glass.
• the lens surface of the third lens facing the eyepoint is convex, and positive chromatic aberration occurs similar to the chromatic aberration that occurs on the lens surface of the first lens facing the image display element.
• the lens surface of the second lens facing the image display element is concave, and negative chromatic aberration that cancels out the positive chromatic aberration occurs, and as shown in conditional formula (2), the second lens is made of a material with a smaller Abbe number than the third lens, and the amount of negative chromatic aberration is large, and is large enough to cancel out the chromatic aberration that occurs on the lens surface of the first lens facing the image display element and the lens surface of the third lens facing the eyepoint.
• the eyepiece optical system of the present invention can reduce chromatic aberration to a level that does not cause practical problems, as described below.
• the lens surface of the second lens facing the image display element and the lens surface of the third lens facing the eye point satisfy the following conditional expression (3) over the entire aperture of each lens surface.
• the aperture of a lens surface means an area on the lens surface through which light rays that create an image can pass.
• the lens surface of the second lens facing the image display element and the lens surface of the third lens facing the eye point may be cemented together.
• a light ray passing through the lens surface of the second lens on the image display element side is incident on the lens surface of the third lens on the eye point side while maintaining approximately its height, but the lens surface of the second lens on the image display element side and the lens surface of the third lens on the eye point side are constrained to have similar shapes due to conditional formula (3). Therefore, the bending angle of the light ray when passing through the lens surface of the second lens on the eye point side is opposite in sign to the bending angle of the light ray when passing through the lens surface of the third lens on the eye point side, and is approximately the same in magnitude.
• the lens surface on the eye point side of the third lens has the effect of canceling out the bending of light rays on the lens surface on the image display element side of the second lens. Therefore, as described above, the lens surface on the image display element side of the second lens and the lens surface on the eye point side of the third lens have the effect of correcting the chromatic aberration of the first lens, but have little effect on other aspects. Therefore, the lens surface on the image display element side of the second lens and the lens surface on the eye point side of the third lens can have a curvature and aspheric shape that are optimal for correcting chromatic aberration.
• the area of more than 80% of the aperture of each lens surface is the area through which light rays that create the vicinity of the edge of the image pass.
• the user's line of sight is not often directed to the vicinity of the edge of the image, so chromatic aberration is not a big problem.
• the area that exceeds 80% of the aperture means the area other than the area through which a light beam having a diameter that is 80% of the diameter of the effective light beam passes on the lens surface of the second lens facing the image display element and the lens surface of the third lens facing the eye point.
• the first and second films which are polarization control films, are preferably laminated onto a flat surface. If the polarization control film is laminated onto a curved surface, tension is applied to the film, which can cause the polarization control characteristics to be disturbed, or the film can easily peel off under high temperature and high humidity conditions.
• the eyepiece optical system of the present invention satisfies the above conditional expressions (4) and (5), when the first film and the second film are laminated to the lens surface on the eyepoint side of the second lens and the lens surface on the eyepoint side of the first lens, respectively, the shape of each film changes to fit the respective lens surface with an expansion rate of about 0.7% or less. With this expansion rate, the effect on the polarization characteristics of the first film and the second film is negligible, and the increase in the risk of peeling is also negligible.
• linear polarizers are often used as the films that make up the polarization control film, but linear polarizers are sensitive to heat. Furthermore, image display elements generate heat.
• the second and third lenses are located between the first film and the image display element, and the insulating effect of these lenses protects the first film from heat, so the first film does not deteriorate due to heat.
• the lens surface of the second lens facing the image display element has a curvature of its peripheral portion that increases in a direction in which the concave surface becomes stronger (in a negative direction) than the curvature at the center (central curvature) of the lens surface, and that, in an area of 80% or less of the opening, the lens surface of the third lens facing the eye point has a curvature of its peripheral portion that increases in a direction in which the convex surface becomes stronger (in a positive direction) than the curvature at the center of the lens surface.
• the lens surface of the second lens on the image display element side and the lens surface of the third lens on the eye point side have a large curvature in the negative direction and the lens surface of the third lens on the eye point side have a large curvature in the positive direction in an area of 80% or less of the opening of each lens surface with respect to the central curvature, so that the chromatic aberration of magnification occurring at a high image height of the image of the first lens can be sufficiently corrected.
• the rear focal position of the first lens i.e., the front focal position of the back tracking
• the rear focal position of the first lens is 9 to 15 mm due to conditional formula (6). Therefore, when a user uses an HMD to which the eyepiece optical system of the present invention is applied with a distance ER between the user's eyes and the HMD lens of 10 to 14 mm, the light ray (principal ray) passing through the center of the user's pupil becomes approximately parallel to the optical axis between the first lens and the second lens. Furthermore, when the distance ER between the eyes and the HMD lens is 20 mm, the chief ray is inclined between the first lens and the second lens so that the height of the ray decreases toward the image display element side.
• the refractive power (P3R) of the lens surface of the third lens facing the image display element has almost no effect on the refractive power P0 of the eyepiece optical system, because in the ⁇ Total system focal length calculation formula> mentioned above, the height (H i ) of the light rays on the lens surface of the third lens facing the image display element is extremely low compared to the heights of the light rays on the other lens surfaces. Due to the action of the lens surface of the third lens facing the image display element, the refractive power P0 of the eyepiece optical system remains almost unchanged, and the height of the chief ray at the image display surface of the image display element becomes lower, which means that the lens surface of the third lens facing the image display element acts to create negative distortion.
• the eye relief ER is 10 to 14 mm, and in this case the chief ray between the first lens and the second lens is approximately parallel to the optical axis. Therefore, even if the distance between these parts is changed to adjust the diopter, the height of the chief ray does not change, and the change in FOV and aberration is small.
• the FOV changes significantly with diopter adjustment
• the images reflected by the left and right eyes are different in size, creating a sense of discomfort, but this does not occur.
• the present invention allows the development of products with different diopters.
• the basic lens structure is common, making it easy to design and manufacture products with different strengths.
• the first lens is made of plastic and that the lens surface of the first lens facing the image display element is aspheric.
• the second lens and the third lens are made of plastic, and that the lens surface of the second lens facing the image display element, the lens surface of the third lens facing the eyepoint, and the lens surface of the third lens facing the image display element are aspheric.
• the first polarization state is circularly polarized light
• the second polarization state is circularly polarized light having a rotation direction opposite to that of the first polarization state.
• the first film has any azimuth angle with respect to the optical axis, and when laminated to the lens surface on the eyepoint side of the second lens, the tolerance of the azimuth angle with respect to the optical axis can be relaxed.
• the second film has any azimuth angle with respect to the optical axis, and when laminated to the lens surface on the eyepoint side of the first lens, the tolerance of the azimuth angle with respect to the optical axis can be relaxed.
• the second film is a laminated film having, in order from the eyepoint side, a reflective polarizing plate and a quarter-wave plate, the slow axis of the quarter-wave plate is inclined at 45 degrees to the transmission axis of the reflective polarizing plate when viewed from the eyepoint side
• the first film is a laminated film having, in order from the eyepoint side, a quarter-wave plate and a linear polarizing plate, the slow axis of the quarter-wave plate of the first film is inclined at 45 degrees to the transmission axis of the linear polarizing plate when viewed from the eyepoint side.
• a part of the light in this second polarization state is reflected by the half mirror of the first lens while maintaining its polarization state.
• this light is incident on the second film again and passes through the quarter-wave plate, it becomes linearly polarized parallel to the transmission axis of the reflective polarizer, passes through the reflective polarizer, and heads toward the eye point side.
• the second film further includes a polarizing plate on the eye point side of the reflective polarizing plate, the polarizing plate having a transmission axis parallel to the transmission axis of the reflective polarizing plate.
• a conventional reflective polarizer cannot sufficiently block the polarized light of the absorption axis. Therefore, even if the light in the first polarization state incident on the second film is converted into ideal linearly polarized light by a quarter-wave plate, a part of the light passes through the reflective polarizer. This light that passes through the reflective polarizer becomes stray light when it reaches the user's eye.
• a polarizer is provided on the eye point side of the reflective polarizer, and the polarizer has a transmission axis parallel to the transmission axis of the reflective polarizer, so that the polarization axis of the light that passes through the reflective polarizer and the polarizer are perpendicular to each other. Therefore, the light that passes through the reflective polarizer is absorbed by the polarizer, and stray light can be prevented.
• the first film further has a quarter-wave plate (QWP2s) on the image display element side of the linear polarizer.
• QWP2s quarter-wave plate
• the light reflected by the half mirror or the second film passes through the second linear polarizer and then the quarter-wave plate on the image display element side when passing through the first film, it becomes circularly polarized light. Then, when the circularly polarized light is reflected again by the lens surface or the image display element and enters the first film, it first passes through the quarter-wave plate and is converted into linearly polarized light whose polarization axis is perpendicular to that of the second linear polarizer. This light is then absorbed by the second linear polarizing plate, preventing stray light.
• a quarter-wave plate with this effect (a quarter-wave plate (QWP2s) provided on the image display element side of the linear polarizer of the first film) is preferably placed near the half mirror, since it can block stray light that is reflected between the half mirror and the quarter-wave plate.
• the quarter-wave plate is placed on the lens surface on the eye point side of the second lens, which is closest to the half mirror coated on the lens surface of the first lens on the image display element side, and therefore has a great effect.
• the present invention also provides a wide-field image display device that is characterized by being equipped with the above-mentioned eyepiece optical system. This makes it possible to realize a wide-field image display device that suppresses the occurrence of flare and ghosting and chromatic aberration.
• the third lens is preferably a plastic lens manufactured by injection molding, has a D-cut surface on the outer periphery, and further has a gate for injection molding on the D-cut surface, and the third lens is preferably positioned in the lens barrel so that the D-cut surface faces the nose of the user.
• the third lens is placed in the lens barrel so that the D-cut surface faces the user's nose.
• the orientation is toward the user's nose, so the user is less likely to feel uncomfortable.
• the lens surface of the second lens facing the image display element is concave, and the lens surface of the third lens facing the eyepoint is convex. If the relationship between v1 and v2 is swapped and the convex and concave surfaces are reversed, that is, the lens surface of the second lens facing the image display element is convex, and the lens surface of the third lens facing the eyepoint is concave, and chromatic aberration correction is performed, the lens that requires the D-cut surface as described above will be the second lens.
• the D-cut surface on the left eye side is located at the bottom right, and the D-cut surface on the right eye side is located at the bottom left, that is, the orientation of each D-cut surface needs to be changed so that they face toward the user's nose.
• the first film is laminated to the lens surface on the eyepoint side of the second lens.
• the first film is a film that creates a circularly polarized state, but its characteristics are incomplete and the first polarization state becomes elliptically polarized
• flare and ghosts caused by elliptically polarized light will occur differently in the images seen by the left eye and the right eye of the user. For this reason, the user will feel uncomfortable when viewing the left and right images superimposed with both eyes.
• the lens surface of the second lens facing the image display element be concave and the lens surface of the third lens facing the eyepoint be convex.
• the wide-field image display device T shown in Fig. 1 is used by a user looking into it from the left side of Fig. 1, and includes, in order from the eye point EP side, an eyepiece optical system OP and an image display element DP.
• the wide-field image display device T may be provided for each of the user's right and left eyes as shown in Fig. 2A, or may be provided for only one of the user's eyes.
• the wide-field image display device T can be applied to, for example, a VR (Virtual Reality) HMD.
• VR Virtual Reality
• the lens surface of the first lens L1 facing the eye point EP and the lens surface of the second lens L2 facing the eye point EP are flat.
• the lens surface of the first lens L1 facing the eye point EP and the lens surface of the second lens L2 facing the eye point EP are approximately flat.
• the lens surface of the second lens L2 on the side of the image display element DP and the lens surface of the third lens L3 on the side of the eye point EP are cemented together.
• the first to third lenses L1 to L3 are all made of plastic.
• the lens surface of the first lens L1 facing the image display element DP, the lens surface of the second lens L2 facing the image display element DP, and the lens surfaces of the third lens L3 facing the eye point EP and the image display element DP are aspheric.
• the lens surface of the second lens L2 facing the eye point EP (surface number 13 in the lens data below) is laminated with a first film F1 that changes the polarization state of light traveling from the image display element DP to the eye point EP to a first polarization state, more specifically, circular polarization.
• a second film F2 is laminated to the lens surface (surface numbers 4 and 10) of the first lens L1 facing the eye point EP, which reflects light in a first polarization state traveling from the image display element DP side to the eye point EP side and changes it to a second polarization state, more specifically, circular polarization having an opposite rotation direction to the circular polarization of the first polarization state, and transmits light in the second polarization state traveling from the image display element DP side to the eye point EP side.
• the lens surfaces (surface numbers 4 and 6) of the first lens L1 facing the image display element DP are coated with a half mirror HM.
• the image display element DP includes an image display surface M on which an image is displayed, a cover glass G that protects the image display surface M, and a display element substrate (not shown) that displays an image on the image display surface M.
• the image display element DP can be a display panel with a wide viewing angle, such as an OLED (Organic Light Emitting Diode) panel or a micro LED (Light Emitting Diode) panel, and in each embodiment an OLED panel is used.
• the above decision is based on the following: 1) Color shift of red and blue images relative to a green image caused by chromatic aberration of magnification of the eyepiece optical system can be canceled by adjusting the size of the red and blue images input to the OLED (Organic Light Emitting Diode). 2) The visual sensitivity of green is higher than that of blue and red. The color that has the greatest effect on resolution is the green Modulation Transfer Function (MTF) (absolute value of the Optical Transfer Function (OTF)). 3) A typical OLED has a green emission spectrum with a peak at 0.525 ⁇ m and a half-width of 0.05 ⁇ m.
• MTF Green Modulation Transfer Function
• OTF absolute value of the Optical Transfer Function
• the surface number indicates the order of the optical surface counted from the eyepoint side
• the surface spacing indicates the spacing between the mth surface (m is an integer) and the m+1th surface
• the refractive index and Abbe number indicate values for the d-line (wavelength 587.6 nm).
• Object indicates the projected image
• aperture indicates the user's pupil
• image indicates the display surface of the image display element. Note that "infinity” indicates a flat surface, and aspheric surfaces indicate the value of the paraxial radius of curvature.
• FIGS. 5A to 6C show the eyepiece optical system OP1 of Example 1 suppresses the occurrence of flare and ghosts, corrects chromatic aberration well, and has good imaging performance.
• Figures 5A to 6C all show the lens performance by back tracing of the eyepiece optical system OP1 of Example 1.
• the horizontal axis "focal movement" in Figure 5A indicates the amount of movement of the position of the surface for evaluating the OTF, and the reference is the position where an image with optimal focus is obtained.
• the vertical axis of Figure 5B indicates the field angle, and the horizontal axis indicates the focus position.
• the eyepiece optical system OP4 of Example 4 suppresses the occurrence of flare and ghosting, corrects chromatic aberration well, and has good imaging performance.
• the eyepiece optical system OP5 of Example 5 suppresses the occurrence of flare and ghosting, corrects chromatic aberration well, and has good imaging performance.
• the eyepiece optical system OP7 of Example 7 suppresses the occurrence of flare and ghosting, corrects chromatic aberration well, and has good imaging performance.
• each of the above embodiments it is possible to realize an eyepiece optical system in which the occurrence of flare and ghosting and chromatic aberration are suppressed. Furthermore, by using the eyepiece optical systems OP1 to OP7 according to the above-described embodiments in the wide-angle image display device T shown in Figures 1 and 2A, it is possible to realize a wide-angle image display device that suppresses the occurrence of flare and ghosting and chromatic aberration.

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  • 2023-12-28 JP JP2024567978A patent/JPWO2024143534A1/ja active Pending
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