Eyepiece optical system and wide-field image display device

Abstract

The invention provides an eyepiece optical system and the like capable of suppressing generation of light spots, ghosting and chromatic aberration. An eyepiece optical system for a wide-field image display device has, in order from an eye point (EP) side, a positive first lens (L1) having a convex surface facing an image display element (DP) side, a second lens (L2) having a concave surface facing the image display element (DP) side, and a third lens (L3) having a convex surface facing the eye point (EP) side. A first film (F1) for changing the light traveling toward the eyespot (EP) side to a first polarization state is attached to the eyespot (EP) side of the second lens (L2), and a second film (F2) for reflecting the light traveling toward the eyespot (EP) side and changing the light traveling toward the eyespot (EP) side to a second polarization state is attached to the eyespot (EP) side of the first lens (L1). A half mirror (HM) is coated on the side surface of the image display element (DP) of the first lens (L1), and a predetermined conditional expression is satisfied.

Description

Technical Field

[0001] The present invention relates to an eyepiece optical system with a viewing angle of 80 degrees or more and a wide-viewing-field image display device. Background Art

[0002] Conventionally, eyepiece optical systems used in wide-field-of-view image display devices such as HMDs (Head Mounted Displays) have been proposed (for example, see Patent Documents 1 and 2).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2022-88582

[0006] Patent Document 2: International Publication No. 2022 / 038777 Summary of the Invention

[0007] Problems to be solved by the invention

[0008] The conventional eyepiece optical system such as the one disclosed in Patent Document 1 has the problem of easily generating flare and ghosting. In addition, the conventional eyepiece optical system such as the one disclosed in Patent Document 2 has the problem of generating large chromatic aberration.

[0009] Therefore, the present invention has been made in view of the above-mentioned problems, and an object thereof is to provide an eyepiece optical system and a wide-viewing-field image display device in which the generation of flare and ghosting, as well as chromatic aberration, is suppressed.

[0010] Means for solving problems

[0011] To solve the above-mentioned problems, the present invention provides an eyepiece optical system disposed between an eyepoint and an image display element of a wide-field image display device, characterized in that the eyepiece optical system comprises, in order from the eyepoint side: a first lens having a convex lens surface facing the image display element and having 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 is attached to the lens surface facing the eyepoint side of the second lens, the first film changing the polarization state of light traveling from the image display element side toward the eyepoint side to a first polarization state; a second film is attached to the lens surface facing the eyepoint side of the first lens, the second film reflecting light in the first polarization state traveling from the image display element side toward the eyepoint side and changing it to a second polarization state, and transmitting light in the second polarization state traveling from the image display element side toward the eyepoint side; and a half mirror is coated on the lens surface facing the image display element side of the first lens, satisfying the following conditional expression.

[0012] 0.8×P0<(2×N1 / L1e)+(2×N1 / L1r)<1.

[0013] 2×P0

[0014] v2<v3

[0015] Wherein, P0: the refractive power of the eyepiece optical system (unit: mm -1 ),

[0016] N1: the refractive index of the first lens for light with a wavelength of 525 nm,

[0017] L1e: the radius of curvature of the lens surface on the eye point side of the first lens (unit: mm),

[0018] L1r: the radius of curvature of the lens surface of the first lens on the image display element side (unit: mm),

[0019] ν2: Abbe number of the second lens for d-line (wavelength 587.6nm),

[0020] ν3: Abbe number of the third lens for d-line (wavelength 587.6 nm),

[0021] The curvature radii L1e and L1r have positive values ​​for convex surfaces. A concave surface is a surface where the edge of the lens protrudes outward from the center of the lens surface in the optical axis direction, and a convex surface is a surface where the center of the lens surface protrudes outward from the edge of the lens in the optical axis direction.

[0022] In addition, the present invention provides a wide-field image display device, characterized in that it has the above-mentioned eyepiece optical system.

[0023] Effects of the Invention

[0024] According to the present invention, it is possible to provide an eyepiece optical system and a wide-viewing-field image display device in which the occurrence of flare, ghosting, and chromatic aberration is suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a cross-sectional view showing the structure of a wide-viewing-field image display device including an eyepiece optical system according to an embodiment of the present invention.

[0026] Figure 2A is a perspective view showing the structure of a wide-viewing-field image display device having an eyepiece optical system according to an embodiment of the present invention. Figure 2B It is a perspective view showing the structure of the third lens of the eyepiece optical system.

[0027] Figure 3A 1 is a cross-sectional view showing a case where the eyepiece optical system according to an embodiment of the present invention includes a fourth lens and moves the first lens in the optical axis direction. Figure 3B It is a cross-sectional view showing a state in which the fourth lens is removed from the eyepiece optical system.

[0028] Figure 4 This is a cross-sectional view of Example 1 of the eyepiece optical system according to an embodiment of the present invention.

[0029] Figure 5A : is a graph showing the relationship between the focus movement and the absolute value of OTF (Optical Transfer Function) in Example 1, Figure 5B This is the spot diagram of Example 1.

[0030] Figure 6A : is a diagram showing the relationship between field curvature and viewing angle in Example 1, Figure 6B is a graph showing the relationship between the percentage distortion and the viewing angle of Example 1, Figure 6C This is a graph showing the chromatic aberration due to magnification in Example 1.

[0031] Figure 7 It is a cross-sectional view of Example 2 of the eyepiece optical system according to the embodiment of the present invention.

[0032] Figure 8A : is a diagram showing the relationship between the focus movement and the absolute value of OTF in Example 2, Figure 8B This is the spot diagram of Example 2.

[0033] Figure 9A : is a diagram showing the relationship between field curvature and viewing angle in Example 2. Figure 9BThis is a graph showing the relationship between the percentage distortion and the viewing angle in Example 2. Figure 9C This is a graph showing the chromatic aberration due to magnification in Example 2.

[0034] Figure 10 This is a cross-sectional view of Example 3 of the eyepiece optical system according to the embodiment of the present invention.

[0035] Figure 11A : is a diagram showing the relationship between the focus movement and the absolute value of OTF in Example 3, Figure 11B This is the spot diagram of Example 3.

[0036] Figure 12A : is a diagram showing the relationship between field curvature and viewing angle in Example 3. Figure 12B : is a graph showing the relationship between the percentage distortion and the viewing angle of Example 3, Figure 12C This is a graph showing the chromatic aberration due to magnification in Example 3.

[0037] Figure 13 It is a cross-sectional view of Example 4 of the eyepiece optical system according to an embodiment of the present invention.

[0038] Figure 14A : is a diagram showing the relationship between the focus movement and the absolute value of OTF in Example 4, Figure 14B This is the spot diagram of Example 4.

[0039] Figure 15A : is a diagram showing the relationship between field curvature and viewing angle in Example 4. Figure 15B is a graph showing the relationship between the percentage distortion and the viewing angle of Example 4, Figure 15C This is a graph showing the chromatic aberration due to magnification in Example 4.

[0040] Figure 16 It is a cross-sectional view of Example 5 of the eyepiece optical system according to the embodiment of the present invention.

[0041] Figure 17A : is a diagram showing the relationship between the focus movement and the absolute value of OTF in Example 5, Figure 17B This is the spot diagram of Example 5.

[0042] Figure 18A : is a diagram showing the relationship between field curvature and viewing angle of Example 5, Figure 18B is a graph showing the relationship between the percentage distortion and the viewing angle of Example 5, Figure 18C This is a graph showing the chromatic aberration due to magnification in Example 5.

[0043] Figure 19 It is a cross-sectional view of Example 6 of the eyepiece optical system according to the embodiment of the present invention.

[0044] Figure 20A: is a diagram showing the relationship between the focus movement and the absolute value of OTF in Example 6, Figure 20B This is the spot diagram of Example 6.

[0045] Figure 21A : is a diagram showing the relationship between field curvature and viewing angle in Example 6, Figure 21B : is a graph showing the relationship between the percentage distortion and the viewing angle of Example 6, Figure 21C This is a graph showing the chromatic aberration due to magnification in Example 6.

[0046] Figure 22 It is a cross-sectional view of Example 7 of the eyepiece optical system according to the embodiment of the present invention.

[0047] Figure 23A : is a diagram showing the relationship between the focus movement and the absolute value of OTF in Example 7, Figure 23B This is the spot diagram of Example 7.

[0048] Figure 24A : is a diagram showing the relationship between field curvature and viewing angle in Example 7. Figure 24B : is a graph showing the relationship between the percentage distortion and the viewing angle of Example 7, Figure 24C Graphs showing chromatic aberration due to magnification in Example 7. DETAILED DESCRIPTION

[0049] Hereinafter, an eyepiece optical system and a wide-field image display device according to embodiments of the present invention will be described.

[0050] The eyepiece optical system of this embodiment is arranged between the eyepoint of a wide-field image display device and an image display element (display). The eyepiece optical system comprises, in order from the eyepoint side, a first lens having a convex lens surface facing the image display element and having 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, with a first film (polarization control film) attached to the lens surface of the second lens facing the eyepoint side. The first film changes the polarization state of light traveling from the image display element side to the eye point side into a first polarization state, and a second film is attached to the lens surface on the eye point side of the first lens. The second film reflects the light in the first polarization state traveling from the image display element side to the eye point side and changes it into 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. A half-mirror is coated on the lens surface on the image display element side of the first lens, satisfying the following conditional expressions (1) and (2).

[0051] (1)0.8×P0<(2×N1 / L1e)+(2×N1 / L1r)<1.

[0052] 2×P0

[0053] (2) v2<v3

[0054] Wherein, P0: the refractive power of the eyepiece optical system (unit: mm -1 ),

[0055] N1: the refractive index of the first lens for light with a wavelength of 525 nm,

[0056] L1e: the radius of curvature of the lens surface on the eye point side of the first lens (unit: mm),

[0057] L1r: the radius of curvature of the lens surface of the first lens on the image display element side (unit: mm),

[0058] ν2: Abbe number of the second lens for d-line (wavelength 587.6nm),

[0059] ν3: Abbe number of the third lens for d-line (wavelength 587.6 nm),

[0060] The curvature radii L1e and L1r have positive values ​​for convex surfaces. A concave surface is a surface where the edge of the lens protrudes outward from the center of the lens surface in the optical axis direction, and a convex surface is a surface where the center of the lens surface protrudes outward from the edge of the lens in the optical axis direction.

[0061] (Effect)

[0062] This configuration makes it possible to realize a so-called flat optical system with less flare and ghosting and reduced chromatic aberration.

[0063] The "eyepoint" is the user's pupil. "Forward tracking" is the tracking of light rays from the image display element toward the eyepoint, and "reverse tracking" is the tracking of light rays from the eyepoint toward the image display element. A "concave surface" is a surface where the edge of the lens surface (the outer periphery of the area where light rays pass) protrudes outward from the center of the lens (the area intersecting the optical axis) in the direction of the optical axis. A "convex surface" is a surface where the center of the lens surface protrudes outward from the edge of the lens surface in the direction of the optical axis.

[0064] Most image display elements display red, green, and blue images, mixing these colors additively to create images of various colors. When chromatic aberration, a type of chromatic aberration, occurs in the eyepiece optical system, the projection magnification of the image display element projected by the eyepiece optical system varies depending on the wavelength, resulting in color deviations in the red, green, and blue colors of the projected image. However, this color deviation can be electrically corrected through image signal processing. Specifically, by varying the size of the red, green, and blue images projected by the image display element based on the chromatic aberration of magnification, a projected image without color deviation can be created.

[0065] However, if the eyepiece optical system has chromatic aberration of magnification, the red, green, and blue light that form the red, green, and blue images will experience variations in magnification within the width of their respective spectra, causing radially extending blur in the red, green, and blue images. Furthermore, this radial blur cannot be electrically corrected.

[0066] Therefore, in order to obtain high resolution in the eyepiece optical system that magnifies and projects the image of the image display element, it is necessary to reduce chromatic aberration.

[0067] The forward tracking of light in the eyepiece optical system of the present invention is described. Light emitted from the image display element and incident on the second lens passes through the first film, becomes a first polarization state, and is directed toward the first lens. The lens surface on the image display element side of the first lens is coated with a half-reflecting mirror, but a portion passes through the half-reflecting mirror. Then, it passes through the inside of the first lens and is incident on the second film. This light (LA1) is in the first polarization state, so it is reflected by the second film and becomes a second polarization state. This light (LA2) that has become the second polarization state travels back inside the first lens and is directed toward the half-reflecting mirror coated on the image display element side of the first lens.

[0068] The half mirror reflects part of the light, and the reflected light (LA3) passes through the first lens again and enters the second film. The light (LA3) is in the second polarization state, and thus passes through the second polarizing film and enters the user's eyes.

[0069] The second film functions as a back mirror for light (LA1), and the half-mirror functions as a back mirror for light (LA2). Furthermore, the half-mirror side, or both the half-mirror side and the second film side, of these back mirrors function as concave mirrors. Light (LA3) is affected by the concave mirrors and forms an aerial image (Ip) of the display image (Im) of the image display element (DP). The light then enters the user's eyes, reflecting the aerial image (Ip).

[0070] Generally, the refractive power of the entire optical system can be calculated using the following formula.

[0071] Refractive power of the entire optical system = (1 / H1) × (H1 × Φ1 + H2 × Φ2 + ... + H n ×Φ n )

[0072] Among them, H i : The height of a ray of light incident on the optical system parallel to the optical axis at the i-th lens surface from the incident side (i is an integer)

[0073] Φ i : The refractive power of the i-th lens surface

[0074] n: the number of the final lens surface of the optical system

[0075] The eyepiece optical system will be described in reverse tracing the path of light rays from the eyepoint side to the image display element side. When light is incident parallel to the optical axis, the ray height generally decreases as the light travels, reaching approximately zero at the image display element. Specifically, the closer the lens surface is to the eyepoint, the higher the ray height, and the higher the contribution of its refractive power to the overall system's refractive power tends to be.

[0076] In view of this, the eyepiece optical system of the present invention is constructed such that the refractive power of the eyepiece optical system required for producing a wide field of view image is generated by the first lens, the lens on the eyepoint side, while the second and third lenses function to correct chromatic aberration caused by the first lens. Furthermore, the refractive power of the first lens is generated by the action of a concave mirror on the back surface of the first lens. Since a concave mirror does not generate chromatic aberration, chromatic aberration of the first lens is significantly reduced compared to a case where the same refractive power is generated by conventional lenses, making chromatic aberration correction in the second and third lenses easier.

[0077] Furthermore, by placing a surface that functions as a back-type concave mirror on the first lens, its radius of curvature can be increased, or in other words, reduced, compared to when it is placed on the other lenses (the second and third lenses). Furthermore, as described below, the back-type concave mirror can generate refractive power with a radius of curvature approximately six times greater than that of a refractive-type convex surface. Consequently, the lens surface on the image display element side of the first lens can have a reduced amount of sag, allowing the thickness of the first lens to decrease from the center to the periphery.

[0078] The first lens acts as a concave mirror, but this concave mirror is a back mirror type that acts on the light traveling through the lens. The refractive power of its concave surface is 2×N1 / (radius of curvature of the lens surface).

[0079] Wherein, N1 can be calculated by the refractive index of the first lens for light with a wavelength of 525 nm.

[0080] The refractive power of a normal lens surface, i.e., a refractive lens surface, is (refractive index of the lens material - 1) / (radius of curvature of the lens surface). The refractive power of a concave mirror is (2 × refractive index of the lens material) / (radius of curvature of the lens surface). Therefore, assuming that both have the same refractive power and the same refractive index, and assuming the refractive index is 1.5 to compare the curvature radius, then (radius of curvature of the concave mirror) / (radius of curvature of the normal lens) = (2 × 1.5) / (1.5 - 1) = 6

[0081] In the present invention, a back-type concave mirror is used to meet the required refractive power, thereby making it possible to make the curvature radius significantly larger than when using a lens surface of a normal lens, that is, a refractive lens surface.

[0082] This allows the thickness of the first lens to be reduced. Specifically, as will be described later, the center thickness can be reduced to 10 mm or less.

[0083] Here, similar to the eyepiece optical system of the present invention, a so-called flattening optical system uses a first film that changes the polarization state of light traveling from the image display element side toward the eyepoint side to a first polarization state, and a second film that reflects and changes the first polarization state of light traveling from the image display element side toward the eyepoint side to a second polarization state, while transmitting the second polarization state of light traveling from the image display element side toward the eyepoint side. This creates an image using the action of a concave mirror in an optical element interposed between the first and second films. However, the optical element sandwiched between the first and second films exhibits retardation (RT). Consequently, when the first polarization state of light traveling from the first film toward the second film is disturbed, light (stray light) is generated that is not reflected by the second film but is transmitted, resulting in flare and ghosting in the image. Therefore, a so-called flattening optical system requires minimizing the retardation of the optical element sandwiched between the first and second films.

[0084] In the present invention, the optical element sandwiched between the first film and the second film is only the first lens. Therefore, the optical element having retardation (RT) that causes stray light is limited to the first lens.

[0085] As described above, in the eyepiece optical system of the present invention, the first film, the second film, and the half-reflecting mirror form a round-trip optical path with a concave mirror in the optical path. Here, when a retardation (RT) is generated in the light (LA1) passing through the first lens and incident on the second film due to an element sandwiched between the first and second films, the first polarization state is disturbed, and a portion of the light (LA1) is not reflected by the second film but passes through, generating stray light that overlaps the aerial image (Ip) with a light spot or ghost. Furthermore, the greater the retardation, the stronger the stray light. Furthermore, the retardation is caused by the birefringence of the material constituting the lens, but the longer the optical path through the lens, the greater the retardation. Furthermore, as will be described later, the permissible retardation is based on 10 nm.

[0086] In the present invention, the optical element that forms the retardation (RT) is limited to the first lens. Furthermore, the radius of curvature of the lens surface on the image display element side of the first lens is large as described above. Therefore, the first lens can be made thinner throughout the entire range from the center to the periphery. Consequently, the optical path length of light (LA1) passing through the first lens and incident on the second film is shortened, reducing the retardation (RT).

[0087] Therefore, in the present invention, even if the first lens is made of a material with relatively high birefringence, flare and ghosting can be suppressed. Furthermore, because the second and third lenses are positioned closer to the image display element than the first film, the retardation generated by these lenses does not generate stray light. Therefore, these lenses can be made of materials with high birefringence. In other words, the first through third lenses can all be made of plastic, which has a higher birefringence than glass. Compared to glass, plastic allows for the manufacture of aspheric lenses at a lower cost and is more lightweight.

[0088] (1)0.8×P0<(2×N1 / L1e)+(2×N1 / L1r)<1.2×P0

[0089] According to the optical formula, 2×N1 / L1e represents the refractive power of the lens surface on the eye point side of the first lens due to the back mirror effect, and 2×N1 / L1r represents the refractive power of the lens surface on the display side of the first lens due to the back mirror effect.

[0090] Therefore, as described above, in the eyepiece optical system according to the present invention, the first lens generates the refractive power P0 of the eyepiece optical system required to produce a wide-field image. Furthermore, conditional expression (1) indicates that the refractive power of the first lens is generated by the action of a concave mirror on either or both of the lens surface on the eyepoint side and the lens surface on the image display element side of the first lens.

[0091] Because concave mirrors lack chromatic aberration, the chromatic aberration produced by the first lens is much smaller than that produced by a conventional lens of the same refractive power. This chromatic aberration primarily arises from the bending of light by the convex lens as it passes through the image display element-side surface of the first lens. Therefore, the chromatic aberration produced by the first lens has the same direction as that produced by a conventional convex lens surface, and is referred to as positive chromatic aberration.

[0092] In the eyepiece optical system of the present invention, the lens surface on the eyepoint side of the third lens is convex, producing positive chromatic aberration similar to the chromatic aberration produced on the lens surface on the image display element side of the first lens. However, the lens surface on the image display element side of the second lens is concave, producing negative chromatic aberration that offsets the positive chromatic aberration. As shown in conditional equation (2), the second lens is made of a material with a smaller Abbe number than the third lens, and its negative chromatic aberration is large, which offsets the chromatic aberration produced on the lens surface on the image display element side of the first lens and the lens surface on the eyepoint side of the third lens. Therefore, as described later, the eyepiece optical system of the present invention can reduce chromatic aberration to a level that is practically acceptable.

[0093] As described above, the chromatic aberration of the first lens is very small compared to a typical lens of the same refractive power. Therefore, the curvature of 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, which correct for this chromatic aberration, does not need to be very strong. As will be described later, they can be designed so as not to affect the size of aberrations other than chromatic aberration.

[0094] Furthermore, in the present invention, it is preferable that 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 satisfy the following conditional expression (3) throughout the entire aperture of each lens surface.

[0095] (3)DD<OL / 10

[0096] Wherein, DD is the maximum value (in mm) of the distance between 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 measured in the optical axis direction.

[0097] OL: the opening diameter of the lens surface of the second lens on the image display element side (unit: mm),

[0098] The opening of the lens surface refers to a region on the lens surface through which light rays forming an image can pass.

[0099] Furthermore, in the present invention, the lens surface of the second lens on the image display element side may be cemented to the lens surface of the third lens on the eye point side.

[0100] (Effect)

[0101] Light rays passing through the image display element-side lens surface of the second lens enter the eyepoint-side lens surface of the third lens while maintaining substantially its height. However, according to conditional expression (3), the image display element-side lens surface of the second lens and the eyepoint-side lens surface of the third lens are constrained to have similar shapes. Therefore, the bending angle of the light rays passing through the eyepoint-side lens surface of the second lens and the bending angle of the light rays passing through the eyepoint-side lens surface of the third lens have opposite signs and are substantially the same in magnitude.

[0102] Specifically, the eyepoint-side lens surface of the third lens acts to eliminate the bending of light rays on the image display element-side lens surface of the second lens. Therefore, as described above, the image display element-side lens surface of the second lens and the eyepoint-side lens surface of the third lens act to correct the chromatic aberration of the first lens, but the effect on the other lenses is minimized. Consequently, the image display element-side lens surface of the second lens and the eyepoint-side lens surface of the third lens can have a curvature or aspherical shape optimal for correcting chromatic aberration.

[0103] In addition, as described later, the area exceeding 80% of the opening of each lens surface (the lens surface on the image display element side of the second lens or the lens surface on the eye point side of the third lens) is the area through which light rays near the edge of the image pass. In particular, in a wide-field eyepiece optical system, the frequency of the user's line of sight toward the edge of the image is also low, so chromatic aberration does not become a problem. On the other hand, the first lens that generates refractive power under the action of a concave mirror produces fewer aberrations overall than a conventional refractive lens with the same refractive power, but near the edge of the image, the generation of off-axis aberrations such as coma, astigmatism, and field curvature increases. Therefore, in the area exceeding 80% of the opening of 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 through which light rays in this area pass, it is not necessary to satisfy conditional formula (3), and it is preferred to use the aspherical effect of these lens surfaces to correct the off-axis aberrations. Here, the area exceeding 80% of the aperture refers to the area other than the area through which a light beam having a diameter of 80% of the diameter of the effective light beam passes, with respect to 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.

[0104] Furthermore, the present invention preferably satisfies the following conditional expressions (4) and (5).

[0105] (4)|SAG1(h1)|<0.05×h1

[0106] (5)|SAG2(h2)|<0.05×h2

[0107] Wherein, SAG1(h1): the sag amount (in mm) of the lens surface on the eye point side of the first lens at a position at a height h1 (in mm) within the aperture diameter from the optical axis,

[0108] SAG2(h2): the sag amount (in mm) of the lens surface on the eye point side of the second lens at a height h2 (in mm) within the aperture diameter from the optical axis,

[0109] The sag amount refers to the coordinates of the lens surface in the optical axis direction, and the reference is the position where the lens surface intersects the optical axis.

[0110] (Effect)

[0111] The first and second films as polarization control films are preferably laminated in a flat surface. If the polarization control film is laminated in a curved surface, tension is applied to the film, causing deviations in polarization control properties, or the film is easily peeled under high temperature and high humidity conditions.

[0112] However, in the eyepiece optical system of the present invention, when the above-mentioned conditional expressions (4) and (5) are satisfied, when the first film and the second film are laminated on the lens surface on the eyepoint side of the second lens and the lens surface on the eyepoint side of the first lens, respectively, each film changes shape along each lens surface at a rate of expansion or contraction of approximately 0.7% or less. At this rate of expansion or contraction, the polarization characteristics of the first and second films are minimally affected, and the risk of delamination is also minimally increased.

[0113] Furthermore, linear polarizers are often used as films constituting polarization control films. However, these films are not heat-resistant and, in turn, generate heat in the image display element. In the eyepiece optical system of the present invention, the second and third lenses are positioned between the first film and the image display element. These second and third lenses provide a heat-insulating effect that protects the first film from heat, thereby preventing thermal degradation of the first film.

[0114] Furthermore, in the present invention, it is preferred that the lens surface on the image display element side of the second lens has a peripheral curvature that increases in a direction in which the concavity becomes stronger (negative direction) compared to the curvature at the center of the lens surface (central curvature) in an area less than 80% of the aperture, and the lens surface on the eyepoint side of the third lens has a peripheral curvature that increases in a direction in which the convexity becomes stronger (positive direction) compared to the curvature at the center of the lens surface in an area less than 80% of the aperture.

[0115] The image display element-side lens surface of the second lens and the eyepoint-side lens surface of the third lens function to correct chromatic aberration produced by the first lens. As the image height increases, the lateral chromatic aberration, one type of chromatic aberration produced by the first lens, increases. While correction is necessary, it is less necessary in the center of the image. Furthermore, light rays forming high-image-height images pass through the areas of the second lens' image display element-side lens surface and the third lens' eyepoint-side lens surface that are distal to the optical axis.

[0116] Therefore, regarding the curvature of the second lens's image display element-side lens surface and the third lens's eyepoint-side lens surface, relative to their central curvature, within an area less than 80% of the aperture of each lens surface, the second lens's image display element-side lens surface has a greater curvature in the negative direction, while the third lens's eyepoint-side lens surface has a greater curvature in the positive direction. This effectively corrects lateral chromatic aberration arising in areas with higher image heights of the first lens's image. Furthermore, to achieve equivalent chromatic aberration correction, the amount of droop in the edges of the second lens's image display element-side lens surface and the third lens's eyepoint-side lens surface can be reduced compared to a case where the second lens's image display element-side lens surface and the third lens's eyepoint-side lens surface are spherical surfaces. Consequently, the thickness of the second lens and the third lens, including the edges, can be reduced, shortening the distance between the first and third lenses. This has the effect of moving the rear focus position of the eyepiece optical system away from the image display element during reverse tracking.

[0117] When the refractive power P0 of the eyepiece optical system of the present invention is increased, the rear focal position of the eyepiece optical system during reverse tracking shifts toward the eyepoint, ultimately sinking into the third lens. The display surface of the image display element must be positioned at or near this rear focal position, resulting in mechanical interference between the third lens and the image display element.

[0118] The curvatures of the lens surface of the second lens on the image display element side and the lens surface of the third lens on the eyepoint side relative to their central curvatures are such that, within an area less than 80% of the aperture of each lens surface, the lens surface of the second lens on the image display element side has a greater curvature in the negative direction, while the lens surface of the third lens on the eyepoint side has a greater curvature in the positive direction. This prevents the aforementioned interference and increases the refractive power P0 of the eyepiece optical system. Furthermore, increasing the refractive power P0 of the eyepiece optical system increases the image display field of view angle FOV of the eyepiece optical system.

[0119] Furthermore, the area exceeding 80% of the aperture of each lens surface is where light rays near the edge of the image pass. In particular, in wide-field eyepiece optical systems, the user's line of sight is less likely to be directed toward the edge of the image, so chromatic aberration is less of a problem. Therefore, the need for chromatic aberration correction for light rays passing through an area exceeding 80% of the aperture of each lens surface is minimal. Therefore, the curvature of the lens surface on the image display element side of the second lens and the lens surface on the eyepoint side of the third lens relative to their central curvature increases in the positive direction for the lens surface on the image display element side of the second lens and in the negative direction for the lens surface on the eyepoint side of the third lens in the area exceeding 80% of the aperture, thereby reducing the amount of droop on each surface.

[0120] In addition, in the eyepiece optical system of the present invention, the lens surface of the second lens on the image display element side is concave, and the lens surface of the third lens on the eye point side is convex. However, in a structure where ν2 is not less than ν3, but ν2>ν3, and the convex and concave surfaces are opposite, that is, when the lens surface of the second lens on the image display element side is convex and the lens surface of the third lens on the eye point side is concave to correct chromatic aberration, it is preferable that the lens surface of the third lens on the image display element side is convex as described later, so that the third lens becomes a meniscus lens. Therefore, it is difficult to fully impart negative refractive power to the third lens, and chromatic aberration cannot be fully corrected. Therefore, in the eyepiece optical system of the present invention, it is preferable that the lens surface of the second lens on the image display element side is concave, and the lens surface of the third lens on the eye point side is convex, as described above.

[0121] In the present invention, it is preferable that the rear focal position of the first lens, that is, the front focal position of the reverse tracking, is located closer to the eye point than the second film and satisfies the following conditional expression (6).

[0122] (6)9<FF<15

[0123] Wherein, FF: the distance from the second film to the rear focal position of the first lens (unit: mm)

[0124] (Effect)

[0125] Typically, glasses are sold with the distance between the lens and the user's eye adjusted to approximately 12 mm when worn. If this distance is shorter than 12 mm, eyelashes can easily come into contact with the lens, staining it, or tear droplets can adhere to the lens, staining it. For similar reasons, the distance between the user's eye and the HMD lens (exit pupil distance) when using an HMD is likely to be around 12 mm.

[0126] On the other hand, the required aperture diameter (DF) for the lens surface closest to the eye point of the HMD, which in this invention is the lens surface on the eye point side of the second film, can be calculated using the following formula. That is, it increases roughly in proportion to the exit pupil distance (ER). DF = 2 × ER × tan(FOV / 2) + α (mm)

[0127] Among them, FOV: the image display field of view angle of the eyepiece optical system (unit: degree),

[0128] α: margin of opening diameter (unit: mm, 0 to 5 mm in the present invention),

[0129] DF: The opening diameter of the lens surface on the eye point side with the margin added (unit: mm, in the present invention, the opening diameter on the eye point side of the second film),

[0130] ER: The distance between the eye point and the lens surface of the HMD closest to the eye point (unit: mm).

[0131] Here, as the aperture of the lenses that make up the eyepiece optical system increases, the overall weight of the HMD increases, making it less user-friendly. In particular, when the FOV exceeds 90 degrees, the overall weight of the HMD increases significantly as the distance ER between the eye and the HMD lens increases. Therefore, it is undesirable to assume and design an excessively large value for the distance ER between the eye and the HMD lens. Therefore, when designing an HMD for use without glasses, the preferred assumed value for the distance ER between the eye and the HMD lens is 10 mm or greater and 14 mm or less.

[0132] On the other hand, HMDs are sometimes designed so that users can use them while wearing glasses. In this case, the distance ER between the eye and the HMD lens can be designed to be approximately 20 mm. However, in this case, it is preferable to set the FOV to 100 degrees or less to avoid increasing the lens opening diameter and the weight of the HMD.

[0133] According to conditional expression (6), the rear focal position of the first lens, i.e., the front focal position for back tracking, is 9 to 15 mm in the eyepiece optical system of the present invention. Therefore, when a user uses an HMD employing the eyepiece optical system of the present invention with a distance ER between the user's eye and the HMD lens of 10 to 14 mm, a ray (principal ray) passing through the center of the user's pupil is substantially parallel to the optical axis between the first lens and the second lens.

[0134] Furthermore, when the distance ER between the eye and the lens of the HMD is 20 mm, the principal ray is inclined between the first lens and the second lens so that the ray height becomes lower toward the image display element side.

[0135] The following is an explanation of tracing (reverse tracing) the light (principal ray) passing through the center of the user's pupil from the eye point side toward the image display element side. As described above, the first lens is thin-walled and the lens surface of the first lens on the image display element side is convex, so the wall thickness of the edge of the first lens is thinner. That is, the lens surface on the eye point side of the first lens and the lens surface on the image display element side are close to each other along the optical axis near the edge. Therefore, the principal ray at the edge of the field of view travels back and forth between the lens surface on the eye point side of the first lens and the lens surface on the image display element side once and a half, but maintains approximately the same height (ray height) and moves toward the second lens. Moreover, as described above, the principal ray moves from the first lens toward the second lens, approximately parallel to the optical axis or at a lowered ray height.

[0136] As described above, the droop of the lens surface on the eyepoint side of the second lens is preferably |SAG2(h2)| < 0.05×h2, and is flat or substantially flat. Therefore, after passing through the lens surface on the eyepoint side of the second lens, the principal ray remains approximately parallel to the optical axis, or at a lower ray height, and proceeds toward the lens surface on the image display element side of the second lens. Furthermore, the edge thickness of the third lens is small. As described above, the lens surface on the eyepoint side of the third lens offsets the curvature of the ray on the lens surface on the image display element side of the second lens. Therefore, the principal ray passing through the lens surface on the eyepoint side of the second lens reaches the lens surface on the image display element side of the third lens without significantly changing its inclination relative to the optical axis. In this way, the principal ray at the edge of the field of view passes through each lens surface at a ray height that is approximately the same as or lower than the ray height on the lens surface on the eyepoint side of the first lens.

[0137] Furthermore, the opening of each lens surface only needs to be large enough to allow the principal ray at the edge of the field of view to pass through.

[0138] The eyepiece optical system of the present invention satisfies the above-mentioned conditional expression (6) "9 < FF < 15", thereby enabling the aperture diameter of each lens surface of the entire optical system to be equal to or smaller than the aperture diameter on the eyepoint side of the second film. Furthermore, as can be seen from the above-mentioned "DF = 2 × ER × tan(FOV / 2) + α (mm)", the aperture diameter DF of the lens surface on the eyepoint side of the first lens is a value determined by the lens specifications and cannot be reduced by design methods. Therefore, conditional expression (6) can be said to be a conditional expression for reducing the thickness of the lens to the limit determined by the specifications in the eyepiece optical system of the present invention.

[0139] In order to ensure the effect of the present invention, it is preferable to set the lower limit of conditional expression (6) to 10. In order to reliably obtain the effect of the present invention, it is preferable to set the upper limit of conditional expression (6) to 14.

[0140] In addition, the present invention preferably satisfies the following conditional formula (7).

[0141] (7)DN<1.2×DF

[0142] Wherein, DF: the opening diameter of the second film on the eye point side (unit: mm),

[0143] DN: The aperture diameter (unit: mm) of the lens surface with the largest aperture diameter among the lens surfaces other than the lens surface on the eye point side of the first lens.

[0144] (Effect)

[0145] The aperture diameter of each lens surface should be at least large enough to allow the principal ray at the edge of the field of view to pass through, but it is preferable to have a certain degree of margin in the aperture diameter. This margin in the aperture diameter can prevent or reduce vignetting, for example, when the user's pupil deviates from the optical axis of the optical system. However, if the margin in the aperture diameter of the lens surface on the eyepoint side of the first lens is larger than the margin in the aperture diameters of the other lens surfaces, while the edge of the opening on the eyepoint side of the first lens is naturally visible when the user observes the HMD, the edges of the opening on the lens surface on the eyepoint side of the first lens will also be easily visible. This is undesirable because light is easily scattered at the edges of the opening, resulting in stray light. Therefore, by making the margin in the aperture diameter of the other lens surfaces larger than the margin in the aperture diameter of the lens surface on the eyepoint side of the first lens, the edges of the opening on the lens surface on the eyepoint side of the first lens are blocked by the opening on the lens surface on the eyepoint side of the first lens, thereby preventing stray light.

[0146] This method of providing a margin for the aperture diameter allows the aperture diameter DN of the lens surface with the largest aperture diameter among the lens surfaces other than the eyepoint-side lens surface of the first lens to be larger than the aperture diameter DF of the second lens on the eyepoint side, thereby increasing the outer diameter of the second or third lens. However, when providing a margin for the aperture diameter, it is preferable to limit it to a range that achieves sufficient results. Specifically, even if a margin is provided for the aperture diameter DN, as long as it is limited to a range not exceeding 1.2×DF, stray light can be prevented, and the increase in the outer diameter of the lens is minimal.

[0147] In addition, as described above, the opening diameter DF can be calculated by the following formula.

[0148] DF = 2 × ER × tan(FOV / 2) + α (unit: mm)

[0149] Here, α is assumed to be 0 mm to the average pupil diameter of 4 mm, ER is 10 to 14 mm when glasses are not used when the FOV is greater than 90 degrees, and 20 mm when glasses are used when the FOV is less than 100 degrees. DF is calculated as follows using the five combinations.

[0150]

[0151] According to the results, the optimal value of DF based on the implementation of the present invention can be said to be 24 mm to 38 mm.

[0152] In the present invention, it is preferable that the lens surface on the eye point side of the first lens is a flat surface or a substantially flat surface and satisfies the following conditional expressions (8) to (10).

[0153] Furthermore, these conditional expressions (8) to (10) do not contradict the above-mentioned conditional expression (6) "9 < FF < 15".

[0154] (8)44 <L1r<65

[0155] (9)0<L1d<5

[0156] (10)1.45<N1<1.55

[0157] Wherein, L1r: the curvature radius of the lens surface of the first lens on the image display element side (unit: mm),

[0158] L1d: thickness of the edge of the first lens in the optical axis direction (unit: mm),

[0159] N1: the refractive index of the first lens for light with a wavelength of 525 nm.

[0160] In the present invention, in order to suppress the retardation (RT) of the first lens, the first lens is preferably thin, and it is not preferable to excessively increase the edge of the first lens. Therefore, it is preferable that the thickness of the edge of the first lens satisfies the above-mentioned conditional expression (9).

[0161] Furthermore, when the first lens satisfies the above-mentioned conditional expression (8), as shown in the following expression regarding droop, the droop of the edge of the lens surface on the image display element side of the first lens is less than 5 mm. If the center wall thickness is made thicker than 5 mm, 0 < L1d can be achieved. In other words, the center wall thickness of the first lens can be made 10 mm or less.

[0162] Droop = |L1r| - {(L1r) 2 -(DF / 2) 2} 1 / 2 <5mm

[0163] However, in order to simplify the calculation formula, the lens surface of the first lens on the image display element side is considered to be a spherical surface. In addition, DF is based on the above calculation example, and L1r is based on conditional formula (8) as follows.

[0164] DF<40mm

[0165] 44 <L1r

[0166] Furthermore, if the center wall thickness of the first lens is 10 mm or less, the birefringence can be 1×10 -6 The first lens is manufactured from a material of about 100 Å. In addition, there are many plastic materials that satisfy the above-mentioned conditional expression (10), and since the first lens can be manufactured using these materials, it is preferable.

[0167] Furthermore, as described below, the above conditional expressions (8) to (10) do not contradict the above conditional expression (6) "9 < FF < 15".

[0168] The refractive power of the lens surface on the image display element side of the first lens when it functions as a concave mirror is 2×N1 / L1r, and the focal length is the reciprocal of this power. Substituting the above conditional expression (8) into the reciprocal expression, the focal length (RF) of the lens surface on the image display element side of the first lens becomes

[0169] 14mm <RF<21mm。

[0170] If the center thickness of the first lens is set to 5 mm to 10 mm based on the above, the optical path length of the center thickness of the first lens is < (5 to 10 mm) / (1.45 to 1.55) ≈ 3.2 to 6.9 mm.

[0171] The front focal position (FF) of the first lens can be estimated by subtracting the optical path length from the aforementioned focal length RF.

[0172]

[0173] This does not contradict the above conditional expression (6).

[0174] In order to ensure the effect of the present invention, it is preferable to set the upper limit of conditional expression (8) to 60.

[0175] In order to reliably obtain the effects of the present invention, the upper limit of conditional expression (9) is preferably set to 3.5. In order to more reliably obtain the effects of the present invention, the upper limit of conditional expression (9) is preferably set to 2.

[0176] In addition, the present invention preferably satisfies the following conditional formula (11).

[0177] (11) ID<0.9×DF

[0178] Wherein, ID: the size (in mm) of the image displayed on the image display surface of the image display element projected by the eyepiece optical system when the image (all or part) displayed on the image display surface of the image display element is magnified and projected into space by the eyepiece optical system,

[0179] DF: opening diameter of the second film on the eye point side (unit: mm).

[0180] (Effect)

[0181] To achieve a slender eyepiece optical system, i.e., a small diameter, it is necessary to reduce the diameter of the lenses that comprise the eyepiece optical system, and also to reduce the mechanical dimensions of the image display element. The mechanical dimensions of the image display element are larger than the dimensions of the image display surface. Considering this, the dimensions of the image display surface of the image display element are preferably smaller than the opening diameter DF of the second film on the eyepoint side, which serves as a reference for the lens opening diameter. This is expressed by the above-mentioned conditional equation (11).

[0182] In the present invention, it is preferred that the lens surface of the third lens on the image display element side is an aspherical surface whose center protrudes outward in the optical axis direction relative to the edge (the peripheral portion of the region where light passes through the lens surface). Thus, the present invention can more effectively satisfy the above-mentioned conditional expression (11).

[0183] (Effect)

[0184] According to this structure, the lens surface on the image display element side of the third lens of the eyepiece optical system of the present invention is convex at least in the edge portion toward the eye point side. When the main light ray passing through the edge portion of the field of view edge is traced in reverse, due to the refraction effect of the lens surface on the image display element side of the third lens, the main light ray bends in a direction in which its light height becomes lower toward the image display element after passing through the lens surface on the image display element side. The main light ray height at the field of view edge on the display surface of the image display element represents the size of the image that must be displayed on the display surface of the image display element. By making the lens surface on the image display element side of the third lens convex, the effect of reducing the size of the image based on the image display element is produced. As a result, the size of the image display surface of the image display element can be smaller than the opening diameter DF on the eye point side of the second membrane, which serves as a reference for the opening diameter of the lens.

[0185] Furthermore, in order to reduce the height of the chief ray at the edge of the field of view by a specified amount, if the lens surface on the image display element side of the third lens is set to an aspheric surface having a curvature greater than the curvature of the central portion in the direction of forming a convex surface from the center toward the periphery, the drooping amount of the edge portion can be reduced compared to setting the lens surface to a spherical surface. If the drooping amount is large, in order to ensure that the edge of the third lens can be manufactured, the center thickness of the third lens becomes thicker, and the rear focus position of the entire eyepiece optical system in reverse tracking is embedded in the third lens. In this case, the image display surface of the image display element needs to be placed near the rear focus position, so the image display element cannot be configured. In order to avoid this situation, it is preferred that the lens surface on the image display element side of the third lens is an aspheric surface with an increasing curvature in the direction of forming a convex surface toward the periphery.

[0186] In addition, the refractive power (P3R) of the lens surface on the image display element side of the third lens has almost no effect on the refractive power P0 of the eyepiece optical system. This is because, in the above-mentioned <Complete System Focal Length Calculation Formula>, the height of the light ray on the lens surface on the image display element side of the third lens (H i ) is extremely low compared to the height of light rays from other lens surfaces.

[0187] Due to the action of the lens surface on the image display element side of the third lens, the refractive power P0 of the eyepiece optical system remains almost unchanged, and the height of the main light on the image display surface of the image display element becomes lower. This can be said to be the effect of the lens surface on the image display element side of the third lens producing negative distortion.

[0188] In addition, the present invention preferably satisfies the following conditional expressions (12) to (14).

[0189] (12)80 <FOV

[0190] (13)0.045<(2×N1 / L1e)+(2×N / 1L1r)<0.065

[0191] (14)DIS<-20

[0192] Wherein, FOV is the image display field of view angle of the eyepiece optical system (in degrees),

[0193] N1: the refractive index of the first lens for light with a wavelength of 525 nm,

[0194] L1e: the radius of curvature of the lens surface on the eye point side of the first lens (unit: mm),

[0195] L1r: radius of curvature of the lens surface of the first lens on the image display element side (unit: mm), DIS: back tracking distortion (unit: %),

[0196] In addition, the curvature radii L1e and L1r have positive values ​​for convex surfaces.

[0197] In addition, the distortion of backtracking is defined as follows.

[0198] II=(1 / P0)×tanβ

[0199] DIS (%) = {(RI-II) / II} 100%

[0200] Where, II: the height of the main ray on the display surface without distortion (unit: mm),

[0201] P0: refractive power of the eyepiece optical system (unit: mm -1 ),

[0202] β: the angle of the principal ray incident on the first lens (in degrees),

[0203] RI: Height of the principal ray on the image display surface of the image display element (distance from the optical axis) (unit: mm),

[0204] In addition, it is assumed that the image display position is located sufficiently far away from the eyepiece optical system.

[0205] (Effect)

[0206] Conditional expression (12) is the FOV achieved by the present invention, and conditional expressions (13) and (14) represent the preferred conditions of satisfying conditional expression (12) and conditional expression (11) "ID < 0.9 × DF". This is confirmed for the following two cases.

[0207] In order to simplify the calculation, the inequality of conditional expression (13) uses the central value, which is set as

[0208] (2×N1 / L1e)+(2×N1 / L1r)=(0.045+0.065) / 2=0.055.

[0209] Therefore, when P0 is calculated according to the conditional expression (1) "0.8×P0<(2×N1 / L1e)+(2×N1 / L1r)<1.2×P0", it becomes

[0210] 0055 / 1.2<P0<0.055 / 0.8(mm -1 )

[0211] 0.046 <P0<0.069(mm -1 ).

[0212] [Setting conditions for the first case]

[0213] FOV = 100 degrees (i.e. the inclination angle of the main light incident on the first lens is 50 degrees)

[0214] ER=12mm

[0215] Distortion = -35%

[0216] P0=0.065mm -1 : A value close to the calculated upper limit of P0 above

[0217] [Setting conditions for the second case]

[0218] FOV = 80 degrees (i.e. the inclination angle of the main light incident on the first lens is 40 degrees)

[0219] ER=20mm

[0220] Distortion = -20%

[0221] P0=0.045mm -1 : A value close to the calculated lower limit of P0 above

[0222] [Calculate the first case:]

[0223] DF=2×ER×tan(FOV / 2)+α

[0224] If α=0, then DF=28.6mm,

[0225] According to the conditional expression (11) "ID<0.9×DF", ID<25.7 mm must be satisfied.

[0226] On the other hand, according to II=(1 / P0)×tanβ

[0227] So II = 18.3 mm

[0228] Therefore, when the distortion is 0%, RI=18.3mm,

[0229] When the distortion is -35%, RI = (1-0.35) × II = 11.9 mm

[0230] ID is twice RI, so when the distortion is 0%, ID = 36.6 mm, which does not satisfy the ID < 25.7 mm calculated in equation (11). However, when the distortion is -35%, ID = 23.8 mm, which satisfies the ID < 25.7 mm calculated in equation (11).

[0231] [Calculate the second case:]

[0232] DF=2×ER×tan(FOV / 2)+α

[0233] If α = 0, then DF = 33.6 mm

[0234] Therefore, according to the conditional expression (12) "ID<0.9×DF", ID<30.2 mm.

[0235] On the other hand, according to II=(1 / P0)×tanβ,

[0236] II=18.6mm

[0237] Therefore, when the distortion is 0%, RI=18.6mm,

[0238] When the distortion is -20%, RI = (1-0.2) × II = 14.8mm

[0239] ID is twice RI, so when the distortion is 0%, ID = 36.2 mm, which does not satisfy the ID < 30.2 mm calculated in equation (11). However, when the distortion is -20%, ID = 29.6 mm, which satisfies the ID < 30.2 mm calculated in equation (11).

[0240] In order to reliably obtain the effects of the present invention, it is preferable to set the lower limit of conditional expression (12) to 82 and the upper limit of conditional expression (14) to -22.

[0241] Furthermore, in the present invention, it is preferable that the diopter adjustment is performed by changing the air space between the first lens and the second lens.

[0242] (Effect)

[0243] The present invention can adjust the diopter with little change in FOV and aberration. Since the refractive power of the first lens is large, the adjustment amount of the interval required for adjusting the diopter can be very small.

[0244] The adjustment amount per diopter is 1 / (1000×P0 2 )mm.

[0245] Refractive power of the first lens ≒ (2×N1 / L1e) + (2×N1 / L1r)

[0246] 0.045<(2×N1 / L1e)+(2×N1 / L1r)<0.065

[0247] Even in the case of P0=0.05, the adjustment amount per diopter is small, which is 1 / (1000×0.05 2 )=0.4mm.

[0248] Furthermore, assuming the user's exit pupil distance ER is 10-14 mm when not wearing glasses, the principal ray between the first and second lenses is roughly parallel to the optical axis. Therefore, even if the distance between these locations is changed to adjust the diopter, the height of the principal ray remains largely unchanged, resulting in minimal changes in FOV and aberrations.

[0249] If a user with different diopters for the left and right eyes uses an eyepiece optical system with a large change in FOV due to diopter adjustment, the size of the images projected in the left and right eyes will be different, causing discomfort. However, this is not the case.

[0250] Furthermore, in the present invention, it is preferable that a fourth lens for diopter correction is further provided on the eye point side of the first lens. The fourth lens for diopter correction has positive or negative refractive power and functions as a spectacle lens.

[0251] (Effect)

[0252] The present invention can develop products with different refractive powers.

[0253] The basic lens structure is the same, making it easy to design and manufacture products with different powers.

[0254] Furthermore, in the present invention, it is preferable that the fourth lens be insertable and removable between the eye point and the first lens.

[0255] (Effect)

[0256] In the present invention, the user can change the diopter.

[0257] The user can adjust the eyepiece optical system of the present invention to a power that suits his or her eyes.

[0258] When the diopter is adjusted by changing the air gap between the first lens and the second lens, the adjustment range is limited. Users with diopter exceeding this adjustment range can also use the eyepiece optical system of the present invention.

[0259] In the present invention, it is preferable that the first lens is made of plastic, and the lens surface of the first lens on the image display element side is an aspherical surface.

[0260] (Effect)

[0261] Experiments have shown that the retardation that causes flare and ghosting can be tolerated to a minimum of 10 nm. According to the present invention, the retardation that causes flare and ghosting is solely the retardation caused in the first lens relative to the light (LA1) that passes through the first lens and enters the second film. Furthermore, according to the present invention, since the first lens can be formed thin, the material of the first lens can also have relatively high birefringence.

[0262] In view of this, the present invention uses plastic to form the first lens. Plastic is lighter than glass. Furthermore, plastic allows for the inexpensive manufacture of aspherical lenses, which offer higher aberration correction capabilities than spherical lenses. The lens surface on the eyepoint side of the first lens is preferably flat or substantially flat. However, in this case, aberrations can also be substantially reduced by making the lens surface on the image display element side of the first lens aspherical.

[0263] Furthermore, according to the present invention, the thickness of the first lens can be reduced to 10 mm or less, and the retardation can be reduced to 10 nm. Therefore, the birefringence of the material used for the first lens can be such that it satisfies the following conditions.

[0264] Δn<1×10 -6

[0265] Wherein, Δn: the difference between the maximum and minimum refractive index of linearly polarized light in any orientation,

[0266] There are many plastics that meet this condition and can be used to manufacture the first lens. For example, AZP (registered trademark) from Asahi Kasei Corporation, Optimas (registered trademark) from Mitsubishi Gas Chemical Corporation, and APEL (registered trademark) from Mitsui Chemicals, Inc. can be used to manufacture the first lens.

[0267] Furthermore, in the present invention, it is preferred that the second lens and the third lens are made of plastic, and the lens surface of the second lens on the image display element side, the lens surface of the third lens on the eye point side, and the lens surface of the third lens on the image display element side are aspherical surfaces.

[0268] (Effect)

[0269] Wide-field eyepiece optical systems generally have difficulty correcting aberrations, and when constructed from spherical lenses, a large number of lenses are required. However, according to the present invention, chromatic aberration can be corrected using only two lenses: the second and third lenses. Furthermore, by making the lens surfaces of the second and third lenses aspherical, aberrations other than chromatic aberration can also be corrected. Therefore, the eyepiece optical system can be constructed from a total of three lenses. Furthermore, the delay generated by the second and third lenses does not cause flare or ghosting, thereby providing a wider range of plastic material options.

[0270] In addition, in the present invention, preferably, the first polarization state is circularly polarized light, and the second polarization state is circularly polarized light having a rotation direction opposite to that of the circularly polarized light in the first polarization state.

[0271] (Effect)

[0272] These polarization states can be easily formed using existing polarization control films.

[0273] Furthermore, unlike linearly polarized or elliptically polarized light, circularly polarized light does not have a specific azimuth axis. Therefore, the first film can have any azimuth angle relative to the optical axis, and when laminated to the eyepoint-side lens surface of the second lens, the tolerance of the azimuth angle relative to the optical axis can be mitigated. Similarly, the second film can have any azimuth angle relative to the optical axis, and when laminated to the eyepoint-side lens surface of the first lens, the tolerance of the azimuth angle relative to the optical axis can be mitigated.

[0274] In addition, the present invention preferably has the second film being a laminated film having a reflective polarizer and a quarter-wave plate in sequence from the eye point side, and when viewed from the eye point side, the low-speed axis of the quarter-wave plate is tilted 45 degrees relative to the transmission axis of the reflective polarizer, and the first film being a laminated film having a quarter-wave plate and a linear polarizer in sequence from the eye point side, and when viewed from the eye point side, the low-speed axis of the quarter-wave plate of the first film is tilted 45 degrees relative to the transmission axis of the linear polarizer.

[0275] (Effect)

[0276] According to this structure, when light emitted from the image display element enters the first film, it passes through the linear polarizer and becomes linearly polarized light. It then passes through the quarter-wave plate and becomes circularly polarized light, which is in the first polarization state. If this light further enters the second film, it passes through the quarter-wave plate and becomes linearly polarized light, traveling toward the reflective polarizer. The reflective polarizer has a transmission axis perpendicular to the polarization axis of the incident linearly polarized light and reflects the incident linearly polarized light. This reflected light passes through the quarter-wave plate of the first film again, becoming circularly polarized light in the opposite direction to the first polarization state. This represents the second polarization state. Light in this second polarization state is partially reflected by the half-mirror of the first lens while maintaining its polarization state. This light enters the second film again, passes through the quarter-wave plate, and becomes linearly polarized light parallel to the transmission axis of the reflective polarizer. It then passes through the reflective polarizer and travels toward the eye point.

[0277] In the present invention, it is preferable that the second film further includes a polarizer having a transmission axis parallel to the transmission axis of the reflective polarizer on the eye point side of the reflective polarizer.

[0278] (Effect)

[0279] Existing reflective polarizers cannot adequately block polarized light with an absorption axis. Therefore, even if light in the first polarization state incident on the second film is converted to ideal linear polarization by the quarter-wave plate, some of this light will pass through the reflective polarizer. This light that passes through the reflective polarizer becomes stray light when it reaches the user's eye. However, a polarizer is located on the eyepoint side of the reflective polarizer, and this polarizer has a transmission axis parallel to the transmission axis of the reflective polarizer. As a result, the light that passes through the reflective polarizer is perpendicular to the polarization axis of the polarizer. Therefore, the light that passes through the reflective polarizer is absorbed by the polarizer, preventing stray light.

[0280] Furthermore, in the present invention, it is preferred that the first film further include a quarter wavelength plate (QWP2s) on the image display element side of the linear polarizing plate.

[0281] (Effect)

[0282] When the light emitted from the image display element is incident on the half-mirror of the first lens, a portion of it is transmitted, and the remaining portion is reflected and directed toward the image display element. This reflected light is relatively strong because it is reflected by the half-mirror. In addition, when the light emitted from the image display element is incident on the second film, a portion of it is transmitted, and the remaining portion is reflected and directed toward the image display element. When this reflected light is reflected by the second lens, the third lens, and the image display element and returns to the eye point side, a portion of it becomes stray light. The eyepiece optical system of the present invention is capable of blocking this stray light by having a 1 / 4 wavelength plate on the image display element side of the linear polarizer of the first film. In detail, the light reflected by the half-mirror and the second film passes through the linear polarizer of the second layer and the 1 / 4 wavelength plate on the image display element side when passing through the first film, thereby becoming circularly polarized light. Then, when the light that has become circularly polarized light is reflected again by the lens surface and the image display element and is incident on the first film, it initially passes through the 1 / 4 wavelength plate, thereby becoming linearly polarized light with a polarization axis perpendicular to the second linear polarizer. Furthermore, this light is absorbed by the linear polarizing plate of the second layer, thereby preventing stray light.

[0283] The quarter-wave plate (QWP2s) exhibiting this effect, located on the image display element side of the linear polarizer of the first film, is preferably placed near the half-mirror because it can block stray light generated by reflection between the half-mirror and the quarter-wave plate. In the present invention, the quarter-wave plate is placed on the eyepoint-side lens surface of the second lens, which is closest to the lens surface coated on the image display element side of the first lens, achieving a greater effect.

[0284] The present invention also provides a wide-view image display device, characterized by including the above-mentioned eyepiece optical system, thereby realizing a wide-view image display device that suppresses the generation of flare, ghosting, and chromatic aberration.

[0285] In addition, in the present invention, it is preferred that the third lens is a plastic lens manufactured by injection molding, has a D-cut surface on the outer periphery, and has a gate for injection molding on the D-cut surface, and the third lens is arranged in the lens barrel with the D-cut surface facing the user's nose.

[0286] (Effect)

[0287] In order to achieve achromatic aberration through the combination of the second lens and the third lens, it is necessary to increase the absolute value of the refractive power of the second lens and the third lens. Therefore, the convex surface of the third lens on the image display element side becomes sharper and the edge thickness becomes smaller. In this third lens, it is difficult to fully ensure the optical axis dimension of the gate used for injection molding (the longitudinal dimension of the gate). Therefore, by cutting a portion of the outer periphery of the third lens into a plane to form a D-cut surface, and arranging a gate on this D-cut surface, it is possible to ensure a sufficient longitudinal dimension of the gate. Then, the third lens is arranged in the lens barrel with the D-cut surface facing the user's nose. Thus, even if a portion of the light forming the image is haloed due to the D-cut portion of the third lens, and a portion of the image is missing, its orientation is also the user's nose, so the user is less likely to feel discomfort.

[0288] Furthermore, in the eyepiece optical system of the present invention, to correct chromatic aberration, the lens surface of the second lens on the image display element side is concave, and the lens surface of the third lens on the eyepoint side is convex. Reversing the relationship between ν1 and ν2 to achieve a configuration where the convex and concave surfaces are reversed, that is, the lens surface of the second lens on the image display element side is convex and the lens surface of the third lens on the eyepoint side is concave, requires the second lens to have a D-cut surface as described above. Furthermore, when the eyepiece optical system of the present invention is assembled into a binocular housing, the D-cut surface on the left eye side is located at the lower right, and the D-cut surface on the right eye side is located at the lower left. In other words, the orientation of the D-cut surfaces must be reversed so that they face the user's nose.

[0289] However, the first film is laminated on the eyepoint-side lens surface of the second lens. For example, if the first film's properties as a film that forms a circular polarization state are incomplete, resulting in the first polarization state being elliptically polarized light, when the eyepiece optical system of the present invention is assembled into a binocular housing, as described above, when the orientation of the second lens is changed left and right, different flare and ghosting due to elliptically polarized light will occur in the image seen by the user's left eye and right eye, respectively. Consequently, the user experiences discomfort when viewing the left and right images with both eyes overlapping. For the reasons described above, it is also preferable that the image display element-side lens surface of the second lens be concave, and the eyepoint-side lens surface of the third lens be convex.

[0290] <Regarding International Publication No. 2022 / 038777>

[0291] International Publication No. 2022 / 038777 has large chromatic aberration, resulting in reduced resolution in the periphery of the image. The eye-side surface of the lens on the image display element side is convex, and light passes through it three times. Chromatic aberration occurs at this point, but it is not corrected. As a result, the eyepiece optical system has large magnification chromatic aberration. In most image display elements used in HMDs, the spectrum of the image light emitted from them has a certain width. Therefore, when using these image display elements, due to magnification chromatic aberration, the point image becomes increasingly blurred in the radial direction toward the periphery of the image. In addition, the tangential MTF is reduced.

[0292] <About Japanese Patent Application Laid-Open No. 2022-88582>

[0293] Although Japanese Patent Application Laid-Open No. 2022-88582 corrects chromatic aberration, it is prone to produce light spots and ghosting. The film is laminated into a curved surface, and the polarization characteristics of the film are destroyed, which easily produces light spots and ghosting. Furthermore, there are two lenses sandwiched between the films, and the center wall thickness is relatively thick. Therefore, due to the birefringence of the lens material, the delay generated in the light path of one and a half times of round trip in the lens tends to become larger. This delay causes light spots and ghosting. As an effective countermeasure, these lenses are made of glass with low birefringence instead of resin. However, if glass is used, it becomes difficult to make the lens aspheric, and it is difficult to correct aberrations with a small number of lenses.

[0294] [about Figure 1 and Figure 2]

[0295] Figure 1 The wide field of view image display device T shown is used by the user to Figure 1 The device used for looking from the left includes an eyepiece optical system OP and an image display element DP in order from the eye point EP side. Figure 2A As shown, the wide-field image display device T can be provided for the user's right eye and left eye, or for only one eye. The wide-field image display device T can be used, for example, in a VR (Virtual Reality) head-mounted display device (HMD). The eyepiece optical system OP preferably uses the eyepiece optical systems OP1 to OP7 of the embodiments of the present invention described below.

[0296] Hereinafter, examples of eyepiece optical systems according to embodiments of the present invention will be described with reference to the accompanying drawings.

[0297] Figure 4 、 Figure 7 、 Figure 10 、 Figure 13 、 Figure 16 、 Figure 19 、 Figure 22The eyepiece optical systems OP1 to OP7 of the illustrated embodiments 1 to 7 include, in order from the eye point EP side: a first lens L1 having a plano-convex or biconvex shape with a positive refractive power and a convex surface toward the image display element DP side; a second lens L2 having a plano-concave or biconcave shape with a negative refractive power and a concave surface toward the image display element DP side; and a third lens L3 having a biconvex shape with a positive refractive power and a convex surface toward the eye point EP side.

[0298] In the eyepiece optical systems OP1 to OP6 of Examples 1 to 6, the lens surface of the first lens L1 on the eyepoint EP side and the lens surface of the second lens L2 on the eyepoint EP side are flat surfaces. In the eyepiece optical system OP7 according to Example 7, the lens surface of the first lens L1 on the eyepoint EP side and the lens surface of the second lens L2 on the eyepoint EP side are substantially flat surfaces.

[0299] In the eyepiece optical system OP4 of Example 4, the lens surface of the second lens L2 on the image display device DP side and the lens surface of the third lens L3 on the eye point EP side are cemented to each other.

[0300] The first to third lenses L1 to L3 are all made of plastic.

[0301] The lens surface of the first lens L1 on the image display device DP side, the lens surface of the second lens L2 on the image display device DP side, and the lens surface of the third lens L3 on the eye point EP side and the lens surface on the image display device DP side are aspherical surfaces.

[0302] A first film F1 is laminated on the lens surface on the eye point EP side of the second lens L2 (surface number 13 in the lens data described below) for changing the polarization state of light traveling from the image display element DP side toward the eye point EP side to the first polarization state, specifically, to circularly polarized light.

[0303] A second film F2 is laminated on the lens surface (surface numbers 4 and 10) on the eye point EP side of the first lens L1. The second film F2 reflects light in the first polarization state traveling from the image display element DP side to the eye point EP side and changes it into a second polarization state, specifically, into circularly polarized light having a rotation direction opposite to that of the circularly polarized light in 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.

[0304] The lens surface (surface numbers 4 and 6 ) of the first lens L1 on the image display device DP side is coated with a half mirror HM.

[0305] The first film F1 (surface numbers 12 to 13) is a laminated film comprising a quarter-wave plate and a linear polarizer in this order from the eye point EP side. The slow axis of the quarter-wave plate is tilted 45 degrees relative to the transmission axis of the linear polarizer as viewed from the eye point EP side. The first film F1 also comprises a quarter-wave plate on the image display element DP side of the linear polarizer.

[0306] The second film F2 is a laminated film comprising, in order from the eye point EP side, a reflective polarizer (surface numbers 2-3) and a quarter-wave plate (surface numbers 3-4, surface numbers 7-8, and surface numbers 9-10). The slow-speed axis of the quarter-wave plate is tilted 45 degrees relative to the transmission axis of the reflective polarizer as viewed from the eye point EP side. The second film F2 also includes a linear polarizer (surface number 2) with a transmission axis parallel to the transmission axis of the reflective polarizer on the eye point EP side of the reflective polarizer.

[0307] like Figure 3A As shown, by moving the first lens L1 in the optical axis direction, the air gap between the first lens L1 and the second lens L2 can be changed to adjust the diopter.

[0308] like Figure 3A As shown in FIG. 1 , a fourth lens L4 for diopter correction is further provided on the eye point EP side of the first lens L1. Figure 3B As shown, the fourth lens L4 can be at the eye point EP ( Figure 3B (not shown) and inserted and removed between the first lens L1.

[0309] The image display device DP includes an image display surface M for displaying images, a cover glass G for protecting the image display surface M, and a display device substrate (not shown) for displaying images on the image display surface M. The image display device DP can use 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. In each embodiment, an OLED panel is used.

[0310] The image light emitted from the image display element DP goes along Figure 1 The illustrated regular optical path (including the return optical path) enters the user's eye (pupil).

[0311] In detail, Figure 1 As shown in the example, image light emitted from the image display surface M of the image display element DP via the cover glass G passes through the third lens L3 and the second lens L2, and then passes through the first film F1 of the second lens L2, thereby becoming circularly polarized, which is the first polarization state. The image light in the first polarization state passes through the half mirror HM of the first lens L1. At this time, a portion of the image light in the first polarization state is reflected by the half mirror HM, but this becomes useless light that does not contribute to the formation of the projected image.

[0312] The image light that has passed through the half-mirror HM of the first lens L1 is reflected by the second film F2 of the first lens L1 and becomes a second polarization state, or circular polarization state, with a rotational direction opposite to the first polarization state, and is then reflected by the half-mirror HM of the first lens L1. At this time, a portion of the image light in the second polarization state passes through the half-mirror HM, but becomes useless light that does not contribute to the formation of the projected image. Furthermore, the lens surface of the image display element DP of the first lens L1 coated with the half-mirror HM functions as a concave mirror. Therefore, the image light reflected by the half-mirror HM passes through the second film F2 again and forms a magnified image of the image displayed by the image display element DP in space. This allows the user to view a magnified image of the image displayed on the image display surface of the image display element DP.

[0313] <Ray Tracing>

[0314] Each embodiment is presented using back-tracing data.

[0315] <Wavelength>

[0316]

[0317] The above contents are determined based on the following contents.

[0318] 1) The color deviation of the red and blue images relative to the green image caused by the chromatic aberration of magnification in the eyepiece optical system can be eliminated by adjusting the size of the red and blue images input to the OLED (Organic Light Emitting Diode).

[0319] 2) Regarding visibility, green has higher visibility than blue and red. The green MTF (Modulation Transfer Function) (absolute value of OTF (Optical Transfer Function)) has the greatest impact on resolution.

[0320] 3) The green emission spectrum of a typical OLED has a peak at 0.525 μm and a half-value width of 0.05 μm.

[0321] <mtf>

[0322] MTF with a spatial frequency of 20 cycles / mm and a focus range of ±0.5mm

[0323] Determine the wavelength based on the following information.

[0324] 1) The maximum contrast sensitivity of the human eye is 5cyle / mm.

[0325] If this is converted into an image on the image display element, it becomes 1 / {focal length of the eyepiece optical system×tan(1 / 5)}≒20cycle / mm.

[0326] However, the focal length of the eyepiece optical system of the embodiment is approximately 15 mm.

[0327] 2) Since the human eye has the ability to adjust focus, the MTF is calculated taking this into account.

[0328] Assuming that the focus adjustment capability of the human eye is 4D (±2D), the amount of movement of the focus on the image display element side that the eye can adjust the focus can be calculated by the following formula.

[0329] Focus shift = ±2D × {focal length of eyepiece optical system (mm)} 2 / 1000

[0330] ≒±0.5(mm)

[0331] Therefore, if the MTF of 20 cycles / mm is a good value within the focus shift of ±0.5 (mm), it can be said that the resolution performance is good.

[0332] <Aspherical Surface>

[0333] In the "Aspherical Surface Data" in each table described later in Examples 1 to 6, the aspherical surface coefficient when the shape of each aspherical surface is expressed by the following formula is shown.

[0334] SAG(h)=(h 2 / R) / [1+[1-(1+K)·(h / R) 2 ] 1 / 2 ]+A·h 2 +B·h 4 +C·h 6 +D·h 8 +E·h 10 +F*h 12 +G·h 14 +H·h 16

[0335] Where, h (unit: mm): distance from the optical axis (height in the direction perpendicular to the optical axis),

[0336] R (unit: mm): Curvature radius (paraxial curvature radius). When viewed from the center of the lens surface, the value of the lens surface with the curvature center on the image display element side is positive, and the value of the lens surface with the curvature center on the eye point side is negative.

[0337] SAG(h) (unit: mm): The distance in the optical axis direction with the optical axis center of the aspheric surface at height h as the origin (sag)

[0338] K: cone constant

[0339] A~H: Aspheric coefficient

[0340] In addition, the cone constant K is 0 in each embodiment.

[0341] "em" (m is an integer) means "×10 -m ”.

[0342] For example, "1.234e-05" means "1.234×10 -5 ”.

[0343] In [Surface Data], the surface number indicates the order of the optical surfaces, starting from the eyepoint. The surface interval indicates the distance between the mth surface (m is an integer) and the m+1th surface. The refractive index and Abbe number are their values ​​relative to the d-line (wavelength 587.6 nm). "Object" represents the projected image, "Aperture" represents the user's pupil, and "Image" represents the display surface of the image display element. "Infinity" represents a flat surface, and aspherical surfaces represent the paraxial radius of curvature.

[0344] <Structure and face number>

[0345]

[0346] Note that the above description is common to the tables of Examples 1 to 6.

[0347] (Table 1) Example 1 [surface data]

[0348]

[0349] [Aspherical surface data]

[0350]

[0351] [General lens data]

[0352] Aperture surface:

[0353] Aperture Radius: 2

[0354] Effective focal length: 15.62819 (image space) Rear focal length: 0.2809868 Field of view type: Angular (degrees) Maximum circular field of view: 50

[0355] Dominant wavelength: 0.525 μm

[0356] [Conditional value]

[0357] Distortion (%) -37.7

[0358] N1 1.5053

[0359] P0 0.06399

[0360] v2 21.4

[0361] v3 55.7

[0362] DD 2.58

[0363] LL 19.1

[0364] OL 31.22

[0365] SAG1(h1) 0

[0366] SAG2(h2) 0

[0367] FF 12.0

[0368] DN 32

[0369] DF 32

[0370] L1e Unlimited

[0371] L1r -51.14821

[0372] 1d 1.1

[0373] ID 23.2

[0374] FOV 100

[0375] 2×N1 / L1e 0

[0376] 2×N1 / L1r 0.05886

[0377] (1)0.8×P0<(2×N1 / L1e)+(2×N1 / L1r)<1.2×PO→0.051<0.059<0.076

[0378] (2)ν2<v3→21.4<55.7

[0379] (3)DD <OL / 10→2.58<3.12

[0380] (4)|SAG1(h1)|<0.05×h1→|SAG1(h1)|=0

[0381] (5)|SAG2(h2)|<0.05×h2→|SAG2(h2)|=0

[0382] (6)9 <FF<15→9.0<12.0<15.0

[0383] (7)DN<1.2×DF→32.0<38.4

[0384] (8)44 <L1r<65→44.0<51.1<65.0

[0385] (9)0<L1d<5→0<1.1<5

[0386] (10)1.45<N1<1.55→1.45<1.5053<1.55

[0387] (11)ID<0.9×DF→23.2<28.8

[0388] (12) 80<FOV→80<100

[0389] (13)0.045<(2×N1 / L1e)+(2×N1 / L1r)<0.065→0.045<0.05886<0.065

[0390] (14) DIS (%) → -37.7

[0391] according to Figures 5A to 6C It can be seen that the eyepiece optical system OP1 of Example 1 suppresses the generation of flare and ghosting, satisfactorily corrects chromatic aberration, and has excellent imaging performance.

[0392] in addition, Figures 5A to 6C Both show the lens performance of the eyepiece optical system OP1 according to Example 1 based on back tracking. Figure 5A The horizontal axis "focus movement" represents the amount of movement of the position of the surface for evaluating the OTF, with the reference being the position of the image at which the optimal focus is obtained. Figure 5B The vertical axis represents the viewing angle, and the horizontal axis represents the focus position. Figure 6C The difference in image height between light having a wavelength of 0.50 μm and light having a wavelength of 0.55 μm, that is, chromatic aberration of magnification, is shown. The above also applies to the respective figures of Examples 2 to 7 described later.

[0393] (Table 2) Example 2

[0394] [Surface data]

[0395]

[0396] [Aspherical surface data]

[0397]

[0398] [General lens data]

[0399] Aperture surface: 2

[0400] Aperture Radius: 2

[0401] Effective focal length: 15.16928 (image space)

[0402] Rear focal length: 0.2417917

[0403] Field of view type: Angle (degrees)

[0404] Maximum circular field of view: 50

[0405] Dominant wavelength: 0.525 μm

[0406] [Conditional expression Corresponding value ]

[0407] Distortion (%) -37.2

[0408] N1 1.5053

[0409] P0 0.06592

[0410] v2 23.9

[0411] v3 55.6

[0412] DD 3.98

[0413] LL 18.6

[0414] OL 30.04

[0415] SAG1(h1) 0

[0416] SAG2(h2) 0

[0417] FF 11.9

[0418] DN 31.4

[0419] DF 31.4

[0420] L1e Unlimited

[0421] L1r -51.67

[0422] 1d 1.67

[0423] ID 22.8

[0424] FOV 100

[0425] 2×N1 / L1e 0

[0426] 2×N1 / L1r 0.05827

[0427] (1)0.8×P0<(2×N1 / L1e)+(2×N1 / L1r)<1.2×P0→0.053<0.058<0.079

[0428] (2) v2<ν3→23.9<55.6

[0429] (4)|SAG1(h1)|<0.05×h1→|SAG1(h1)|=0

[0430] (5)|SAG2(h2)|<0.05×h2→|SAG2(h2)|=0

[0431] (6)9 <FF<15→9.0<11.9<15.0

[0432] (7)DN<1.2×DF→31.4<37.68

[0433] (8)44<L1r<65→44.0<51.7<65.0

[0434] (9)0 <L1d<5→0<1.7<5

[0435] (10)1.45<N1<1.55→1.45<1.5053<1.55

[0436] (11)ID<0.9×DF→22.8<28.3

[0437] (12) 80 < FOV → 80 < 100

[0438] (13)0.045<(2×N1 / L1e)+(2×N1 / L1r)<0.065→0.045<0.05827<0.065

[0439] (14) DIS (%) → -37.2

[0440] according to Figures 8A to 9C It can be seen that the eyepiece optical system OP2 of Example 2 suppresses the generation of flare and ghosting, satisfactorily corrects chromatic aberration, and has excellent imaging performance.

[0441] (Table 3) Example 3

[0442] [Surface data]

[0443]

[0444] [Aspherical surface data]

[0445]

[0446] [General lens data]

[0447] Aperture surface: 1

[0448] Aperture Radius: 2

[0449] Effective focal length: 15.7838 (image space)

[0450] Rear focal length: 0.2610584

[0451] Field of view type: Angle (degrees)

[0452] Maximum circular field of view: 50

[0453] Dominant wavelength: 0.525 μm

[0454] [Conditional expression Corresponding value ]

[0455] Distortion (%) -37.5

[0456] N1 1.5053

[0457] P0 0.06336

[0458] v2 23.9

[0459] v3 55.6

[0460] DD 1.32

[0461] LL 18.8

[0462] OL 28.89

[0463] SAG1(h1) 0

[0464] SAG2(h2) 0

[0465] FF 11.5

[0466] DN 31.4

[0467] DF 31.4

[0468] L1e Unlimited

[0469] L1r -49.333

[0470] L1d 1.1

[0471] ID 23.4

[0472] FOV 100

[0473] 2×N1 / L1e 0

[0474] 2×N1 / L1r 0.06103

[0475] (1)0.8×P0<(2×N1 / L1e)+(2×N1 / L1r)<1.2×P0→0.051<0.061<0.076

[0476] (2)ν2<ν3→23.9<55.6

[0477] (3)DD <OL / 10→1.32<2.89

[0478] (4)|SAG1(h1)|<0.05×h1→|SAG1(h1)|=0

[0479] (5)|SAG2(h2)|<0.05×h2→|SAG2(h2)|=0

[0480] (6)9 <FF<15→9.0<11.5<15.0

[0481] (7)DN<1.2×DF→31.4<37.68

[0482] (8)44<L1r<65→44.0<49.3<65.0

[0483] (9)0<L1d<5→0<1.1<5

[0484] (10)1.45<N1<1.55→1.45<1.5053<1.55

[0485] (11)ID<0.9×DF→23.4<28.3

[0486] (12)80 <FOV→80<100

[0487] (13)0.045<(2×N1 / L1e)+(2×N1 / L1r)<0.065→0.045<0.06103<0.065

[0488] (14) DIS (%) → -37.5

[0489] according to Figures 11A to 12C It can be seen that the eyepiece optical system OP3 of Example 3 suppresses the generation of flare and ghosting, satisfactorily corrects chromatic aberration, and has excellent imaging performance.

[0490] (Table 4) Example 4

[0491] [Surface data]

[0492]

[0493] [Aspherical surface data]

[0494]

[0495] [General lens data]

[0496] Aperture surface: 1

[0497] Aperture Radius: 2

[0498] Effective focal length: 13.4741 (image space)

[0499] Rear focal length: 0.1946818

[0500] Field of view type: Angle (degrees)

[0501] Maximum circular field of view: 50

[0502] Dominant wavelength: 0.525 μm

[0503] [Conditional expression Corresponding value ]

[0504] Distortion (%) -35.4

[0505] N1 1.5053

[0506] P0 0.07422

[0507] v2 23.9

[0508] v3 55.6

[0509] DD 0.00 (joint)

[0510] LL 15.9

[0511] OL 28.75

[0512] SAG1(h1) 0

[0513] SAG2(h2) 0

[0514] FF 9.3

[0515] DN 31

[0516] DF 31

[0517] l1e unlimited

[0518] L1r -43.743

[0519] L1d 1.6.

[0520] D 23.2

[0521] FOV 100

[0522] 2×N1 / L1e 0

[0523] 2×N1 / L1r 0.06882

[0524] (1)0.8×P0<(2×N1 / L1e)+(2×N1 / L1r)<1.2×P0→0.059<0.069<0.089

[0525] (2)ν2<v3→23.9<55.6

[0526] (3)DD <OL / 10)→0.00<2.87

[0527] (4)|SAG1(h1)|<0.05×h1→|SAG1(h1)|=0

[0528] (5)|SAG2(h2)|<0.05×h2→|SAG2(h2)|=0

[0529] (6)9<FF<15→9.0<9.3<15.0

[0530] (7)DN<1.2×DF→31.0<37.2

[0531] (8)44 <L1r<65→44.0<43.7<65.0

[0532] (9)0 <L1d<5→0<1.6<5

[0533] (10)1.45 <N1<1.55→1.45<1.5053<1.55

[0534] (11)ID<0.9×DF→23.2<27.9

[0535] (12)80 <FOV→80<100

[0536] (14) DIS (%) → -35.4

[0537] according to Figures 14A to 15C It can be seen that the eyepiece optical system OP4 of Example 4 suppresses the generation of flare and ghosting, satisfactorily corrects chromatic aberration, and has excellent imaging performance.

[0538] (Table 5) Example 5

[0539] [Surface data]

[0540]

[0541] [Aspherical surface data]

[0542]

[0543] [General lens data]

[0544] Aperture surface: 1

[0545] Aperture Radius: 2

[0546] Effective focal length: 17.17824 (image space)

[0547] Rear focal length: 0.305454

[0548] Field of view type: Angle (degrees)

[0549] Maximum circular field of view: 41.5

[0550] Dominant wavelength: 0.525 μm

[0551] [Conditional expression Corresponding value ]

[0552] Distortion (%) -25.7

[0553] N1 1.5053

[0554] P0 0.05821

[0555] v2 21.1

[0556] v3 55.6

[0557] DD 1.63

[0558] LL 21.1

[0559] OL 30.64

[0560] SAG1(h1) 0

[0561] SAG2(h2) 0

[0562] FF 13.4

[0563] DN 35.6

[0564] DF 35.6

[0565] L1e Unlimited

[0566] L1r -57.344

[0567] L1d 1.4

[0568] ID 22.8

[0569] FOV 83

[0570] 2×N1 / L1e 0

[0571] 2×N1 / L1r 0.05250

[0572] (1)0.8×P0<(2×N1 / L1e)+(2×N1 / L1r)<1.2×P0→0.047<0.053<0.070

[0573] (2)ν2<ν3→21.1<55.6

[0574] (3)DD<OL / 10→1.63<3.06

[0575] (4)|SAG1(h1)|<0.05×h1→|SAG1(h1)|=0

[0576] (5)|SAG2(h2)|<0.05×h2→|SAG2(h2)|=0

[0577] (6)9 <FF<15→9.0<13.4<15.0

[0578] (7)DN<1.2×DF→35.6<42.72

[0579] (8)44 <L1r<65→44.0<57.3<65.0

[0580] (9)0 <L1d<5→0<1.4<5

[0581] (10)1.45<N1<1.55→1.45<1.5053<1.55

[0582] (11)ID<0.9×DF→22.8<28.8

[0583] (12)80 <FOV→80<83

[0584] (13)0.045<(2×N1 / L1e)+(2×N1 / L1r)<0.065→0.045<0.05250<0.065

[0585] (14) DIS (%) → -25.7

[0586] according to Figures 17A to 18C It can be seen that the eyepiece optical system OP5 of Example 5 suppresses the generation of flare and ghosting, satisfactorily corrects chromatic aberration, and has excellent imaging performance.

[0587] (Table 6) Example 6

[0588] [Surface data]

[0589]

[0590] [Aspherical surface data]

[0591]

[0592] [General lens data]

[0593] Aperture surface: 1

[0594] Aperture Radius: 2

[0595] Effective focal length: 16.7546 (image space)

[0596] Rear focal length: 0.2913612

[0597] Field of view type: Angle (degrees)

[0598] Maximum circular field of view: 41.5

[0599] Dominant wavelength: 0.525 μm

[0600] [Conditional expression Corresponding value ]

[0601] Distortion (% -23.3

[0602] N1 1.5053

[0603] P0 0.05969

[0604] ν2 21.4

[0605] ν3 55.6

[0606] DD 2.43

[0607] L1 21.1

[0608] OL 34.50

[0609] SAG1(h1) 0

[0610] SAG2(h2) 0

[0611] FF 13.7

[0612] DN 35.6

[0613] DF 35.6

[0614] L1e Unlimited

[0615] L1r -58.599

[0616] L1d 1.4

[0617] ID 22.8

[0618] FOV 83

[0619] 2×N1 / L1e 0

[0620] 2×N1 / L1r 0.05138

[0621] (1) 0.8×P0 < (2×N1 / L1e) + (2×N1 / L1r) < 1.2×P0 → 0.048 < 0.051 < 0.071

[0622] (2) v2 < ν3 → 21.4 < 55.6

[0623] (3) DD < OL / 10 → 2.43 < 3.45

[0624] (4) |SAG1(h1)| < 0.05×h1 → |SAG1(h1)| = 0

[0625] (5) |SAG2(h2)| < 0.05×h2 → |SAG2(h2)| = 0

[0626] (6) 9 < FF < 15 → 9.0 < 13.7 < 15.0

[0627] (7) DN < 1.2×DF → 34.9 < 42.72

[0628] (8) 44 < L1r < 65 → 44.0 < 58.6 < 65.0

[0629] (9) 0 < L1d < 5 → 0 < 1.4 < 5

[0630] ​​​​​​​​​​​​​​​​​It can be seen that the eyepiece optical system OP6 of Example 6 suppresses the generation of flare and ghosting, satisfactorily corrects chromatic aberration, and has excellent imaging performance.

[0636] (Table 7) Example 7

[0637] [Surface data]

[0638]

[0639] [Aspherical surface data]

[0640]

[0641] [General lens data]

[0642] Aperture surface: 1

[0643] Aperture Radius: 2

[0644] Effective focal length: 14.68561 (image space)

[0645] Rear focal length: 0.254127

[0646] Field of view type: Angle (degrees)

[0647] Maximum circular field of view: 45

[0648] Dominant wavelength: 0.525 μm

[0649] [Conditional expression Corresponding value ]

[0650] Distortion (%) -26.4

[0651] N1 1.502

[0652] P0 0.068094

[0653] v2 21.5

[0654] v3 55.7

[0655] DD 1.08

[0656] OL 29.3

[0657] SAG1(h1) 0.67

[0658] SAG2(h2) 0.65

[0659] FF 11.7

[0660] DN 29.7

[0661] DF 30.2

[0662] L1e 170

[0663] L1r 71.662

[0664] L1d 1.4

[0665] ID 21.7

[0666] FOV 90

[0667] 2×N1 / L1e 0.0177

[0668] 2×N1 / L1r 0.042

[0669] (1)0.8×P0 < (2×N1 / L1e) + (2×N1 / Lr) < 1.2×P0 → 0.054 < 0.060 < 0.081

[0670] (2)v2 < ν3 → 21.5 < 55.7

[0671] (3)DD < OL / 10 → 1.08 < 2.93

[0672] (4)|SAG1(h1)| < 0.05×h1 → 0.67 < 0.76 (h = 15.1)

[0673] (5)|SAG2(h2)| < 0.05×h2 → 0.65 < 0.72 (h = 14.8)

[0674] (6)9 < FF < 15 → 9.0 < 11.7 < 15.0

[0675] (7)DN < 1.2×DF → 29.7 < 36.2

[0676] (9)0 < L1d < 5 → 0 < 1.4 < 5

[0677] (10)1.45 < N1 < 1.55 → 1.45 < 1.502 < 1.55

[0678] (11)ID < 0.9×DF → 21.7 < 27.2

[0679] (12)80 < FOV → 80 < 90

[0680] (13)0.045 < (2×N1 / L1e) + (2×N1 / L1r) < 0.065 → 0.045 < 0.060 < 0.065

[0681] (14)DIS(%) → -26.4%

[0682] According to Figures 23A to 24C It can be seen that the eyepiece optical system OP7 of Example 7 suppresses the generation of flare and ghosting, satisfactorily corrects chromatic aberration, and has excellent imaging performance.

[0683] According to the above-described embodiments, it is possible to realize an eyepiece optical system in which the occurrence of flare, ghosting, and chromatic aberration is suppressed.

[0684] In addition, by using the eyepiece optical systems OP1 to OP7 of the above-mentioned embodiments Figure 1 、 Figure 2A The wide-viewing-angle image display device T shown can realize a wide-viewing-angle image display device that suppresses the occurrence of flare, ghosting, and chromatic aberration.

[0685] Description of labels

[0686] OP1~OP7: eyepiece optical system; L1: first lens; L2: second lens; L3: third lens; L4: fourth lens; F1: first film; F2: second film; HM: half mirror; EP: eye point; DP: image display element; M: image display surface of image display element; G: cover glass of image display element.< / mtf>

Claims

1. An eyepiece optical system disposed between an eye point and an image display element of a wide-field image display device, characterized in that: The eyepiece optical system has, in order from the eye point side: a first lens having a convex lens surface on the image display element side and having positive refractive power; a second lens having a concave lens surface on the image display element side; as well as The third lens has a convex lens surface on the eye point side. A first film is attached to the lens surface of the second lens on the eye point side, and the first film changes the polarization state of light traveling from the image display element side to the eye point side to a first polarization state. A second film is attached to the lens surface of the first lens on the eyepoint side. The second film reflects light of the first polarization state traveling from the image display element side toward the eyepoint side and changes the light into the second polarization state, while transmitting light of the second polarization state traveling from the image display element side toward the eyepoint side. A half mirror is coated on the lens surface of the first lens on the image display element side. The following conditions are met: 0.8×P0<(2×N1 / L1e)+(2×N1 / L1r)<1. 2×P0 v2<v3 Wherein, P0: the refractive power of the eyepiece optical system (unit: mm -1 ), N1: the refractive index of the first lens for light with a wavelength of 525 nm, L1e: the radius of curvature of the lens surface on the eye point side of the first lens (unit: mm), L1r: the radius of curvature of the lens surface of the first lens on the image display element side (unit: mm), ν2: Abbe number of the second lens for d-line (wavelength 587.6nm), ν3: Abbe number of the third lens for d-line (wavelength 587.6 nm).

2. The eyepiece optical system according to claim 1, wherein: The second lens has negative refractive power, The third lens has positive refractive power.

3. The eyepiece optical system according to claim 1, wherein: 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 satisfy the following conditional expression over the entire range of each lens surface: DD<OL / 10 Wherein, DD is the maximum value (in mm) of the distance between 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 measured in the optical axis direction. OL: The opening diameter of the lens surface of the second lens on the image display element side (unit: mm).

4. The eyepiece optical system according to claim 1, wherein: The lens surface of the second lens on the image display element side is cemented to the lens surface of the third lens on the eye point side.

5. The eyepiece optical system according to claim 1, wherein: The following conditions are met, |SAG1(h1)|<0.05×h1 |SAG2(h2)|<0.05×h2 Wherein, SAG1(h1): the sag amount (in mm) of the lens surface on the eye point side of the first lens at a position at a height h1 (in mm) within the aperture diameter from the optical axis, SAG2(h2): The sag amount (in mm) of the lens surface on the eye point side of the second lens at a position at a height h2 (in mm) within the aperture diameter from the optical axis.

6. The eyepiece optical system according to claim 1, wherein: The rear focal position of the first lens is located closer to the eye point than the second lens. The following conditions are met, 9 <FF<15 Wherein, FF is the distance from the second film to the rear focal position of the first lens (unit: mm).

7. The eyepiece optical system according to claim 1, wherein: The following conditions are met, DN<1.2×DF Wherein, DF: the opening diameter of the second film on the eye point side (unit: mm), DN: The opening diameter (unit: mm) of the lens surface having the largest opening diameter among the lens surfaces other than the lens surface on the eye point side of the first lens.

8. The eyepiece optical system according to claim 1, wherein: The following conditions are met, 44＜L1r＜65 0<L1d<5 1.45＜N1＜1.55 Wherein, L1d is the thickness of the edge portion of the first lens in the optical axis direction (unit: mm).

9. The eyepiece optical system according to claim 1, wherein: The following conditions are met, ID<0.9×DF Wherein, ID: the size (in mm) of the image displayed on the image display surface of the image display element projected by the eyepiece optical system when the image displayed on the image display surface of the image display element is magnified and projected into the air by the eyepiece optical system, DF: opening diameter of the second film on the eye point side (unit: mm).

10. The eyepiece optical system according to claim 1, wherein: The lens surface of the third lens on the image display element side is an aspherical surface whose center protrudes outward in the optical axis direction relative to the edge.

11. The eyepiece optical system according to claim 1, wherein: The following conditions are met, 80<FOV 0.045<(2×N1 / L1e)+(2×N1 / L1r)<0.065 DIS<-20 Wherein, FOV is the image display field of view angle of the eyepiece optical system (in degrees), DIS: Distortion of reverse tracking (in %).

12. The eyepiece optical system according to claim 1, wherein: The diopter adjustment is performed by changing the air space between the first lens and the second lens.

13. The eyepiece optical system according to claim 1, wherein: A fourth lens for diopter correction is further provided on the eye point side of the first lens.

14. The eyepiece optical system according to claim 13, wherein: The fourth lens is insertable and removable between the eye point and the first lens.

15. The eyepiece optical system according to claim 1, wherein: The first lens is made of plastic. The lens surface of the first lens on the image display element side is an aspherical surface.

16. The eyepiece optical system according to claim 1, wherein: The second lens and the third lens are made of plastic. The lens surface of the second lens on the image display element side, the lens surface of the third lens on the eye point side, and the lens surface of the third lens on the image display element side are aspherical surfaces.

17. The eyepiece optical system according to claim 1, wherein: The first polarization state is circularly polarized light, The second polarization state is circularly polarized light that is opposite to the circularly polarized light in the first polarization state.

18. The eyepiece optical system according to claim 17, wherein: The second film is a laminated film having a reflective polarizer and a quarter-wave plate in this order from the eye point side. The slow axis of the quarter-wave plate is tilted 45 degrees relative to the transmission axis of the reflective polarizer when viewed from the eye point. The first film is a laminated film having a quarter-wave plate and a linear polarizer in this order from the eye point side. The slow axis of the quarter-wave plate of the first film is tilted by 45 degrees with respect to the transmission axis of the linear polarizing plate when viewed from the eye point side.

19. The eyepiece optical system according to claim 18, wherein: The second film further includes a polarizer having a transmission axis parallel to the transmission axis of the reflective polarizer on the eye point side of the reflective polarizer.

20. The eyepiece optical system according to claim 18, wherein: The first film further includes a quarter-wave plate on the image display element side of the linear polarizing plate.

21. The eyepiece optical system according to claim 1, wherein: The lens surface of the second lens on the image display element side has a larger curvature in the negative direction relative to the center curvature in an area less than 80% of the opening, or the lens surface of the third lens on the eye point side has a larger curvature in the positive direction relative to the center curvature in an area less than 80% of the opening.

22. The eyepiece optical system according to claim 21, wherein: The lens surface of the second lens on the image display element side has a peripheral curvature that increases in a direction toward a more concave surface relative to the central curvature in an area less than 80% of the aperture. The lens surface of the third lens on the eye point side has a peripheral curvature that increases in a direction in which the convex surface becomes stronger relative to the central curvature in a region of 80% or less of the aperture.

23. A wide-viewing-field image display device, characterized in that: The wide-view image display device includes the eyepiece optical system according to any one of claims 1 to 22.

24. The wide-viewing-field image display device according to claim 23, wherein: The third lens is a plastic lens manufactured by injection molding, has a D-cut surface on its outer periphery, and has a gate for injection molding on the D-cut surface. The third lens is arranged in the lens barrel with the D-cut surface facing the nose side of the user.

Images