JP2014081481A - Observation optical system and observation device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an observation optical system that has wide angle of view and high resolving power, and to provide an observation device employing the observation optical system.SOLUTION: The observation optical system comprises: a diffusion surface that is arranged in front of an observer, and diffuses light; a first optical system that is composed of an optical surface having at least three surfaces of a first surface, a second surface and a third surface, in which at least the second surface of the optical surface has a rotationally asymmetric shape, and projects a real image of a picture on an object surface onto the diffusion surface; and a second optical system that projects the real image projected onto the diffusion surface onto an eyeball of the observer as an enlarged virtual image. When a ray connecting a center of the object surface and a center of the diffusion surface is defined as an axial principal ray, the optical surface of at least the three surfaces is respectively arranged to be eccentric to the axial principal ray.

Description

  The present invention relates to an observation optical system in which an optical surface is decentered and an observation apparatus using the observation optical system.

  2. Description of the Related Art Conventionally, there are known observation apparatuses that use a small image generation apparatus and enlarge an original image of these display elements by an optical system and present it to an observer (Patent Documents 1 to 5). Since this observation apparatus is deployed around the observer's head, it is desired to reduce the size and weight of the entire apparatus. Further, in order to give a high sense of presence to an image to be presented, an optical system capable of presenting the original image of the display element as wide as possible and expressing it with a high resolution is required. As a means for satisfying such a requirement, it is effective for an optical system that guides the light flux from the display element to the observer's eyeball to form an intermediate image in the path between the display element and the observer's eyeball. For example, Patent Documents 1, 2, and 3 disclose an optical system that forms an intermediate image in an optical path. In addition, if a contact lens is used as an eyepiece optical system with a wide angle of view, the focal length can be shortened, so that a wide angle of view can be expected. For example, Patent Documents 4 and 5 disclose observation devices using contact lenses.

JP 2001-166111 A Japanese Patent Laid-Open No. 2001-255489 Japanese Patent No. 2000-212440 JP-A-10-62712 JP-A-6-347731

  In an image display device that includes a decentered optical system that forms a primary image using a relay optical system and guides the primary image to the eyeball using an eyepiece optical system, compared to an image display device that does not include a relay optical system. By enlarging a small display element to the intermediate image plane by the relay optical system, it is apparently equivalent to using a large display surface for the eyepiece optical system. Therefore, a wide viewing angle of view can be obtained even with a small display element.

  However, the conventional observation optical system using the relay optical system forms an aerial image when relaying the original image of the image generation device, and projects the aerial image that is an intermediate image onto the observer's eyeball by the eyepiece optical system. Therefore, the size of the intermediate image is limited, and it is difficult to ensure a sufficient magnification.

  Patent Documents 1 and 2 describe a two-dimensional image display element that displays an observation image, a relay optical system that projects a real image of the two-dimensional image display element in the air, an enlarged projection of the real image in the air, and a reflection bending of the optical axis. In these optical systems, the relay optical system uses a plurality of spherical or aspheric lenses, and further uses a correction optical system consisting of two decentered aspherical surfaces. As a result, the optical system becomes larger and the weight increases.

  Furthermore, Patent Document 1 includes a decentration correction optical system configured with mutually decentered surfaces between the relay optical system and the eyepiece, which is disadvantageous in terms of cost and weight. In Patent Document 2, when the angle of view becomes wider, there is a fear that the eyepiece may become so large that a prism that is eyepiece cannot be realized.

  Patent Document 3 includes an image display element that displays an observation image, a relay optical system that projects a real image of the image display element in the air, and an eyepiece that projects the real image in the air and reflects and bends the optical axis. A visual display device provided is described. In this optical system, a rotationally asymmetric concave surface mirror is used for the eyepiece optical system, so that at a wider angle of view, aberration correction such as asymmetric field curvature and distortion occurring in the relay optical system is sufficiently performed. I can't.

  On the other hand, Patent Documents 4 and 5 are disclosed as conventional techniques as a so-called contact lens type eyepiece optical system for observing in the state of being close to or in contact with an observer's eyeball.

  In the eyepiece optical system described in Patent Document 4, only the display in front of the eyes is observed using a contact lens. Therefore, when the angle of view is increased, the display becomes larger, and the apparatus becomes larger accordingly. In addition, the cost increases.

  The technique described in Patent Document 5 has a configuration in which only the vicinity of the corneal apex is used as the refractive power corresponding to the original image of the video generation apparatus, and the other portions are observed with the normal refractive power. It is known that the pupil diameter of the observer's eyeball is about 3 to 5 mm in such a state. If the area of the portion having a strong positive refractive power near the apex of the cornea is large, a bright enlarged image is obtained, but if the area is small, the image becomes dark and at the same time a strong positive power portion with respect to the pupil position is from the pupil center. There is a possibility of deviation. On the other hand, for normal external observation, if the area of the portion having strong positive refractive power near the apex of the cornea is large, the image near the center is only blurred when viewing the external image. Cannot be recognized. Even if the area is small, a blurred image always exists in the image at the center of the observation image, so that the observer feels uncomfortable.

  An object of the present invention is to provide an observation optical system having a wide angle of view and high resolution, and an observation apparatus using the observation optical system.

An observation optical system according to an embodiment of the present invention is:
A diffusing surface arranged in front of the observer and diffusing light;
The optical surface includes at least three optical surfaces having a first surface, a second surface, and a third surface, and at least two of the optical surfaces have a rotationally asymmetric shape, and a real image of an object surface image is obtained. A first optical system that projects onto the diffusing surface;
A second optical system that projects the real image projected on the diffusion surface as a virtual image enlarged on the observer's eyeball;
With
When a light ray connecting the center of the object plane and the center of the diffusion surface is an axial principal ray, the at least three optical surfaces are respectively arranged eccentric to the axial principal ray.

In the observation optical system which is an embodiment of the present invention,
The first optical system is a decentered prism surrounded by the at least three optical surfaces and filled with a medium having a refractive index of 1 or more.

In the observation optical system which is an embodiment of the present invention,
The exit pupil of the first optical system is disposed in the vicinity of the exit surface of the decentered prism.

In the observation optical system which is an embodiment of the present invention,
OP _ux , an optical path length from the exit pupil of the upper maximum field angle of the first optical system in the plane including the axial principal ray to the image plane,
OP _ix , the optical path length from the exit pupil of the lower maximum field angle of the first optical system in the plane including the axial principal ray to the image plane,
When
The following conditional expression (1) is satisfied.
1.05 ≤ OP _ux / OP _ix ≤ 1.95 (1)

In the observation optical system which is an embodiment of the present invention,
A function that defines the second surface of the first optical system in local coordinates is f (x, y),
The second-order partial differential value of x in the local coordinates (x, y) of the second surface is expressed as cx (x, y),
When the value of the local coordinates (x, y) of the second surface is (η, ζ),
The following conditional expression (2) is satisfied.
cx (η, ζa) <cx (η, ζb) (2)
However,
ζa <ζb,
η is any number,
It is.

In the observation optical system which is an embodiment of the present invention,
A function that defines the second surface of the first optical system in local coordinates is f (x, y),
The second-order partial differential value of y in the local coordinates (x, y) of the second surface is expressed as cy (x, y),
When the value of the local coordinates (x, y) of the second surface is (η, ζ),
The following conditional expression (2) is satisfied.
cy (η, ζa) <cy (η, ζb) (3)
However,
ζa <ζb,
η is any number,
It is.

In the observation optical system which is an embodiment of the present invention,
The second optical system is a contact lens disposed on the observer's eyeball.

In the observation optical system which is an embodiment of the present invention,
The diffusion surface is a curved surface.

In the observation optical system which is an embodiment of the present invention,
The diffusion surface is a spherical surface.

  The second optical system is an eyepiece optical system disposed in front of the eyeball of the observer.

In the observation optical system which is an embodiment of the present invention,
The diffusion surface is light control glass.

In the observation optical system which is an embodiment of the present invention,
A see-through lens is disposed on the opposite side of the diffusing surface from the second optical system.

In the observation optical system which is an embodiment of the present invention,
The see-through lens is a Fresnel lens.

Moreover, in the observation apparatus which is one embodiment of the present invention,
The observation optical system;
A video generation unit arranged on the object plane to display a video;
With
The image displayed on the image generation unit is transmitted through the first surface, reflected from the second surface, reflected from the first surface, and the exit pupil disposed in the third surface and the vicinity thereof. And projected onto the diffusion surface.

Moreover, in the observation apparatus which is one embodiment of the present invention,
The video generation unit displays the laser beam modulated by the video signal by reflecting it with a two-dimensional digital micromirror device.

Moreover, in the observation apparatus which is one embodiment of the present invention,
The image generation unit displays the laser beam modulated by the image signal by scanning in two dimensions.

Moreover, in the observation apparatus which is one embodiment of the present invention,
The video generation unit includes a deflection mirror that deflects the laser light,
The reflection position of the deflection mirror is disposed in the vicinity of the entrance pupil of the first optical system,
The entrance pupil position of the first optical system and the diffusion surface are tilted or shifted from each other.

Moreover, in the observation apparatus which is one embodiment of the present invention,
The image generation unit is a reflective liquid crystal or a transflective liquid crystal,
An illumination unit that illuminates the video generation unit is provided.

Moreover, in the observation apparatus which is one embodiment of the present invention,
The illumination unit has a polarization beam splitter.

Moreover, in the observation apparatus which is one embodiment of the present invention,
The illumination unit has a diffractive optical element.

Moreover, in the observation apparatus which is one embodiment of the present invention,
Equipped with glasses-type housing,
The video generation unit is disposed in a glasses-type housing.

Moreover, in the observation apparatus which is one embodiment of the present invention,
The first optical system is disposed in a glasses-type housing.

Moreover, in the observation apparatus which is one embodiment of the present invention,
Equipped with glasses-type lenses,
The diffusion surface is arranged inside a surface corresponding to a spectacle-type lens.

  According to an embodiment of the present invention, it is possible to provide an observation optical system having a wide angle of view and high resolution, and an observation apparatus using the observation optical system.

The structure of the observation optical system and observation apparatus of this embodiment is shown. FIG. 3 shows an optical path diagram of the first optical system 60 of Example 1. FIG. 6 shows a distortion map of the first optical system 60 of Example 1. FIG. FIG. 7 is an optical path diagram of a decentered prism of Modification Example 1 designed to have a vertically symmetric optical path length with the same configuration as the first optical system 60 of the present embodiment. The distortion map of the optical system of the modification 1 of FIG. 4 is shown. FIG. 10 is an optical path diagram of Modification 2 in which oblique projection is performed by moving the object position and image position of the optical system of Modification 1 of FIG. 4. It is a distortion map of the optical system of the modification 2 of FIG. FIG. 6 is a diagram illustrating a shape of a second surface 62 of the first optical system 60 of Example 1. It is a figure which shows the result of carrying out the second-order partial differentiation of the function which forms the shape of the 2nd surface 62 of the 1st optical system 60 of Example 1 by x. It is a figure which shows the result of carrying out the second-order partial differentiation of the function which forms the shape of the 2nd surface 62 of the 1st optical system 60 of Example 1 by y. FIG. 6 is a diagram illustrating an optical path diagram of a first optical system 62 of Example 2. FIG. 6 is a diagram showing a distortion map of the first optical system of Example 2. 6 is a diagram illustrating a shape of a second surface of the first optical system of Example 2. FIG. It is a figure which shows the result of having carried out the second-order partial differentiation of the function which forms the shape of the 2nd surface of the 1st optical system of Example 2 by x. It is a figure which shows the result of having carried out the second-order partial differentiation of the function which forms the shape of the 2nd surface of the 1st optical system of Example 2 by y. FIG. 11 is an optical path diagram of Example 3 in the case where the second optical system 40 of the observation optical system of the present embodiment is only the contact lens 41. Example 4 in which the diffusing surface 50 is a spherical surface is shown. The radius of curvature of the diffusion surface 50 is 50 mm. 2 is a diagram illustrating an example in which an eyepiece optical system that is the second optical system 40 of the present embodiment is arranged in front of an observer eyeball 10. FIG. FIG. 6 is a diagram showing another example in which an eyepiece optical system that is the second optical system 40 is arranged in front of an observer eyeball 10. An optical path diagram for observing an external image when a decentered prism is applied to the first optical system and a contact lens is applied to the second optical system is shown. It is a figure which shows the concept of the 1st optical system after three laser beams become one by a dichroic mirror or a dichroic prism. FIG. 3 is an optical path diagram in which a reflective display element of the present embodiment, a first optical system 60, and an illumination unit that illuminates the reflective display element are disposed therebetween.

An observation optical system according to an embodiment of the present invention is:
A diffusing surface arranged in front of the observer and diffusing light;
Consists of at least three optical surfaces having a first surface, a second surface, and a third surface, and at least two of the optical surfaces have a rotationally asymmetric shape and diffuse a real image of an object surface image. A first optical system that projects onto a surface;
A second optical system that projects a real image projected on the diffusing surface as a virtual image enlarged on the observer's eyeball;
With
When a light beam connecting the center of the object plane and the center of the diffusion surface is an axial principal ray, at least three optical surfaces are arranged eccentric to the axial principal ray.

  Hereinafter, the reason and effect | action which take the said arrangement | positioning are demonstrated.

  The first optical system includes at least three optical surfaces, of which at least two optical surfaces have surfaces having a rotationally asymmetric shape, and at least three optical surfaces are respectively object surfaces. This is a decentered optical system that is decentered with respect to an axial principal ray connecting the center and the center of the diffusion surface.

  By using such a first optical system, the first optical system for projecting the image of the image generation unit onto the diffusing surface can be provided in the vicinity of the observer's head, and the observation apparatus can be made compact. it can. Further, it is possible to correct an asymmetrical aberration with respect to the optical axis generated in the optical system arranged eccentrically.

  This will be described in detail below with reference to the drawings.

  FIG. 1 shows a configuration of an observation optical system 1 and an observation apparatus 100 according to the present embodiment.

  In this figure, the observer's eyeball is 10, the observer's pupil position is 20, the observer's visual axis is 30, the second optical system is 40, the diffusing surface is 50, the first optical system is 60, and an image display as an image generation unit Reference numeral 70 denotes an element, 61 denotes a first surface (TIR surface) of the first optical system, 62 denotes a second surface (concave reflection surface), and 63 denotes a third surface (exit surface).

  This figure shows a state in which a spectacle-type observation device 100 equipped with the observation optical system 1 of the present embodiment is attached to a cross-sectional view of the observer's head. The video generation unit 70 has an aspect ratio of 3: 4 and a display surface size of 0.24 inches. The diffusing surface 50 is a liquid crystal provided in a portion corresponding to a spectacle lens of the observation apparatus 100 that is a spectacle-type image display device. The second optical system 40 is a special contact lens. The pupil diameter at the observer eyeball position 1 is 3 mm.

  The light beam emitted from the image generation unit 70 enters the decentered prism 60 from the first surface 61 of the first optical system 60 which is the decentered prism 60 composed of three decentered surfaces. The light is reflected, is reflected internally by the first surface 61 again, is emitted from the third surface 63, and forms a real image on the diffusion surface 50 on the inner surface of the eyeglass-type observation apparatus provided on the front surface of the observer eyeball 10. On the other hand, the second optical system 40 is a special contact lens disposed on the cornea of the observer eyeball 10 so as to focus on the diffusion surface 50 in consideration of the refractive power (visual acuity) of the observer eyeball 10. The refractive power of contact lenses is determined. Therefore, the observer can observe the real image formed on the diffusing surface 50 as an enlarged virtual image.

  FIG. 2 shows an optical path diagram of the first optical system 60 of the first embodiment. FIG. 3 shows a distortion map of the first optical system 60 of the first embodiment.

  The first optical system 60 is shown by back ray tracing from the image plane Im to the display surface Ob as the object plane of the video generation unit 70 for convenience of design. Therefore, FIG. 2 shows a distortion map on the display surface.

  Here, the merit of the first optical system 60 including such a decentered optical system, in particular, the internally reflecting decentered prism 60 will be described. A refractive optical element such as a lens can be given power by adding curvature to its boundary surface. For this reason, when light rays are refracted at the boundary surface of the lens, the occurrence of chromatic aberration due to the chromatic dispersion characteristics of the refractive optical element is inevitable. As a result, another refractive optical element is generally added for the purpose of correcting chromatic aberration.

  On the other hand, reflective optical elements such as mirrors and prisms do not generate chromatic aberration in principle even if power is given to their reflecting surfaces, and it is necessary to add another optical element only for the purpose of correcting chromatic aberration. There is no. Therefore, the optical system using the reflective optical element can reduce the number of constituent elements of the optical element from the viewpoint of chromatic aberration correction, compared to the optical system using the refractive optical element.

  At the same time, since the reflection optical system using the reflection optical element folds the optical path, the optical system itself can be made smaller than the refractive optical system. In addition, since the reflecting surface has a higher decentration error sensitivity than the refracting surface, high accuracy is required for assembly adjustment.

  The first optical system 60 is an eccentric prism 60 that is surrounded by at least three optical surfaces having a first surface, a second surface, and a third surface, and is filled with a medium having a refractive index of 1 or more. .

  Among the reflective optical elements, since the relative positional relationship between the respective surfaces of the prism is fixed, it is only necessary to control the eccentricity of the prism alone, and unnecessary assembly accuracy and adjustment man-hours are unnecessary. Furthermore, the prism has an entrance surface and an exit surface, which are refracting surfaces, and a reflecting surface, and has a higher degree of freedom in correcting aberrations than a mirror having only a reflecting surface. In particular, by sharing most of the desired power to the reflecting surface and reducing the power of the entrance surface and exit surface, which are refracting surfaces, the degree of freedom of aberration correction can be kept large compared to mirrors, etc. Compared with such a refractive optical element, the occurrence of chromatic aberration can be made very small. In addition, since the inside of the prism is filled with a transparent body having a refractive index higher than that of air, the optical path length can be made longer than that of air, and the optical system is more effective than lenses and mirrors arranged in the air. Thinning and miniaturization are possible.

  Further, the observation optical system 1 is required to have good imaging performance to the periphery as well as the center performance. Therefore, in the present invention, as described above, by using one eccentric prism 60 in the optical system constituting the observation optical system 1, at least the image light emitted from the image generation unit 70 is incident on the prism, And a first surface 61 that internally reflects, a second surface 62 that internally reflects a light beam incident from the first surface 61, and a third surface 63 that emits the light. At least the reflection surface has optical power for the light beam. The rotationally asymmetric curved surface shape for correcting and correcting decentration aberrations makes it possible to correct not only the center but also off-axis aberrations.

  By adopting such a basic configuration, the number of optical elements is small compared to an optical system using a refractive optical system or a rotationally symmetric imaging optical system, and a small image display with good performance from the center to the periphery. An apparatus can be obtained. Here, when a light beam that reaches the center of the diffusion surface 50 in front of the eye from the center of the display surface of the image generation unit 70 is an axial principal ray Lc, at least one reflecting surface of the prism is in relation to the axial principal ray Lc. If it is not decentered, the incident light beam and the reflected light beam of the axial principal ray Lc take the same optical path, and the axial principal ray Lc is blocked in the optical system. As a result, an image is formed only with a light beam whose central portion is shielded from light, and the center becomes dark or no image is formed at the center. It is also possible to decenter the reflecting surface with power with respect to the axial principal ray Lc.

  As described above, in the present embodiment, the surface shape of the reflecting surface constituting the decentered prism 60 of the first optical system 60 is a rotationally asymmetric curved surface shape that gives optical power to the light flux and corrects decentration aberrations. doing. Such a surface shape is preferable for correcting decentration aberrations. The reason will be described in detail below.

  First, the coordinate system used and the rotationally asymmetric surface will be described. In the present embodiment, the intersection of the axial principal ray Lc and the image plane Im is used as the coordinate origin. The right side on the paper surface from the center of the stop S is positive, the horizontal axis is the Z axis, the axis orthogonal to the Z axis and the axis within the eccentric surface of each surface constituting the optical system is defined as the Y axis, and the Z axis An axis perpendicular to the Y axis and perpendicular to the Y axis is taken as an X axis.

  In general, in a spherical lens system composed only of spherical lenses, spherical aberration generated by the spherical surface, coma aberration, curvature of field, and other aberrations are corrected for each other on several surfaces, so that the overall aberration is reduced. It has become. On the other hand, a rotationally symmetric aspherical surface or the like is used to satisfactorily correct aberrations with a small number of surfaces. This is to reduce various aberrations that occur on the spherical surface. However, in a decentered optical system, it is impossible to correct rotationally asymmetric aberration caused by the decentration with a rotationally symmetric optical system. The rotationally asymmetric aberration generated by this decentration includes distortion, curvature of field, astigmatism generated on the axis, and coma.

  First, rotationally asymmetric field curvature will be described. For example, a light ray incident on a concave mirror decentered from an object point at infinity is reflected and imaged by hitting the concave mirror. It becomes half the radius of curvature of the part hit. Then, an image plane inclined with respect to the axial principal ray is formed. Thus, it is impossible to correct rotationally asymmetric field curvature with a rotationally symmetric optical system.

  To correct this tilted field curvature with the concave mirror itself, which is the source, the concave mirror is composed of a rotationally asymmetric surface, and in this example, the curvature is strong (refractive power is strong) with respect to the positive Y-axis direction. If the curvature is weak (refractive power is weak) with respect to the negative direction of the Y axis, the correction can be made. Further, by arranging a rotationally asymmetric surface having the same effect as the above configuration in the optical system separately from the concave mirror, a flat image surface can be obtained with a small number of components. In addition, the rotationally asymmetric surface preferably has a rotationally asymmetric surface shape that does not have a rotationally symmetric axis both in and out of the surface.

  Next, rotationally asymmetric astigmatism will be described. Similar to the above description, the astigmatism is generated for the axial ray in the concave mirror arranged eccentrically. In order to correct this astigmatism, it is possible to appropriately change the curvature in the X-axis direction and the curvature in the Y-axis direction of the rotationally asymmetric surface as in the above description.

  Further, rotationally asymmetric coma will be described. Similar to the above description, coma aberration occurs with respect to an axial ray in a concave mirror arranged eccentrically. In order to correct this coma, it is possible to change the inclination of the surface as it moves away from the origin of the X axis of the rotationally asymmetric surface and to change the inclination of the surface appropriately depending on whether the Y axis is positive or negative. In the imaging optical system of the present invention, it is possible to adopt a configuration in which at least one surface having the reflecting action described above is decentered with respect to the axial principal ray and has a rotationally asymmetric surface shape and power. By adopting such a configuration, it becomes possible to correct the decentration aberration generated by giving power to the reflecting surface by the surface itself, and by reducing the power of the refracting surface of the prism, the occurrence of chromatic aberration can be suppressed. Can be small.

  The rotationally asymmetric surface used in the present embodiment is preferably a plane-symmetric free-form surface having only one plane of symmetry. Here, the free-form surface used in the present invention is defined by the following formula (a). Note that Z in the definition formula is the Z axis of the free-form surface FFS. The coefficient term for which no data is described is zero.

Z = cr ² / [1 + √ {1- (1 + k) c ² r ² }]
₆₆
+ Σ C _j X ^m Y ⁿ (a)
^{j = 2}
Here, the first term of the equation (a) is a spherical term, and the second term is a free-form surface term.
In the spherical term,
c: curvature of vertex k: conic constant (conical constant)
r = √ (X ² + Y ² )
It is.

The free-form surface term is
₆₆
ΣC _j X ^m Y ^{n
j = 2}
= C ₂ X + C ₃ Y
+ C ₄ X ² + C ₅ XY + C ₆ Y ²
+ C ₇ X ³ + C ₈ X ² Y + C ₉ XY ² + C ₁₀ Y ³
+ C ₁₁ X ⁴ + C ₁₂ X ³ Y + C ₁₃ X ² Y ² + C ₁₄ XY ³ + C ₁₅ Y ⁴
+ C ₁₆ X ⁵ + C ₁₇ X ⁴ Y + C ₁₈ X ³ Y ² + C ₁₉ X ² Y ³ + C ₂₀ XY ⁴
+ C ₂₁ Y ⁵
+ C ₂₂ X ⁶ + C ₂₃ X ⁵ Y + C ₂₄ X ⁴ Y ² + C ₂₅ X ³ Y ³ + C ₂₆ X ² Y ⁴
+ C ₂₇ XY ⁵ + C ₂₈ Y ⁶
+ C ₂₉ X ⁷ + C ₃₀ X ⁶ Y + C ₃₁ X ⁵ Y ² + C ₃₂ X ⁴ Y ³ + C ₃₃ X ³ Y ⁴
+ C ₃₄ X ² Y ⁵ + C ₃₅ XY ⁶ + C ₃₆ Y ⁷
・ ・ ・ ・ ・ ・

However, Cj (j is an integer of 2 or more) is a coefficient. In general, the free-form surface does not have a symmetric plane in both the XZ plane and the YZ plane, but in this embodiment, by setting all odd-order terms of X to 0, the YZ plane Is a free-form surface having only one plane of symmetry parallel to the. For example, in the above defining equation _{(a), C 2, C} 5, C 7, C 9, C 12, C 14, C 16, C 18, C 20, C 23, C 25, C 27, C 29, This is possible by setting the coefficient of each term of C ₃₁ , C ₃₃ , C ₃₅ .

Further, by setting all odd-numbered terms of Y to 0, a free-form surface having only one symmetry plane parallel to the XZ plane is obtained. For example, in the above definition formula, C ₃ , C ₅ , C ₈ , C ₁₀ , C ₁₂ , C ₁₄ , C ₁₇ , C ₁₉ , C ₂₁ , C ₂₃ , C ₂₅ , C ₂₇ , C ₃₀ , C ₃₂ , This is possible by setting the coefficient of each term of C ₃₄ , C ₃₆ .

  Further, any one of the directions of the symmetry plane is set as a symmetry plane, and the eccentricity in the corresponding direction, for example, the eccentric direction of the optical system with respect to the symmetry plane parallel to the YZ plane is in the Y-axis direction, For the symmetry plane parallel to the Z plane, the decentering direction of the optical system is set to the X-axis direction, so that it is possible to improve the manufacturability while effectively correcting the rotationally asymmetric aberration caused by the decentering. It becomes.

  The definition formula (a) is shown as an example as described above, and the free-form surface of this embodiment corrects rotationally asymmetric aberration caused by decentration by using a rotationally asymmetric surface. At the same time, it is characterized by improved manufacturability, and it goes without saying that the same effect can be obtained for any other defining formula.

  Further, when the first optical system 60 is configured by an eccentric prism, the prism is configured by at least three surfaces of the first surface 61 to the third surface 63, and the first surface 61 is emitted from the image generation unit 70. The second surface 62 is configured as a reflecting surface that internally reflects the light beam incident from the first surface 61, is internally reflected again by the first surface 61, and the third surface. 63 is a transmission surface that emits the light beam reflected from the first surface 61 from the prism, and the first surface 61 to the third surface 63 both give optical power to the light beam and correct eccentric aberration. It is more desirable to correct the aberrations.

  Further, the first surface 61 of the decentered prism is a transmission surface on which the light flux from the image generation unit 70 is incident, and a reflection surface that internally reflects the reflected light of the second surface 62. With such a configuration, the first surface 61 of the decentered prism has two functions on one surface, and thus can be made small and thin. In addition, it is desirable that the angle of incidence on the first surface 61 is set to be equal to or greater than the critical angle so that the portion of the second surface 62 where the luminous flux is emitted is totally reflected. It is possible to make the angle less than the critical angle in the part that is not. In that case, it is possible to observe the entire screen by applying a reflective coating to a reflective region that does not satisfy the total reflection condition of the first surface 61.

  The exit pupil position of the first optical system 60 preferably matches or substantially matches the exit surface of the eccentric prism 60.

  By making the exit pupil position of the first optical system 60 substantially coincide with the exit surface of the decentered prism, it is possible to limit the exit light by providing a stop S near the exit surface of the decentered prism. If there is an exit pupil inside the decentered prism, or if a part of the exit pupil is in the prism, particularly the peripheral rays of off-axis rays cannot be controlled, and a light beam that has not been corrected for aberrations forms an image. On the other hand, if it moves away from the prism exit surface, a member for positioning and fixing the diaphragm S is generated, leading to an increase in cost.

Further, the optical path length from the exit pupil having the maximum upper field angle of the first optical system 60 in the plane including the axial principal ray Lc to the image plane Im is OP _ux , and the first optical in the plane including the axial principal ray Ls is used. When the optical path length from the exit pupil of the lower maximum field angle of the system 60 to the image plane Im is OP _ix , the following conditional expression (1) is preferably satisfied.
1.05 ≤ OP _ux / OP _ix ≤ 1.95 (1)

Here, the relationship in the layout of the observation optical system 1 of this embodiment and the observer's head will be described with reference to FIG. In FIG. 1, a spectacle-type head mounted display equipped with the present optical system is assumed. As described above, the first optical system 60 is disposed on the side of the observer's head, and is mounted together with the image generation unit 70 in the temple part of the glasses. Since the image is projected obliquely from the first optical system 60, the optical path length after the emission is clearly different between the outside and the inside of the glasses. That is, the outside is short and the inside is long. An optical path length OP _ux from the upper maximum field angle exit pupil to the image plane in the YZ plane of the first optical system 60; an optical path length OP _ix from the lower maximum field angle exit pupil to the image plane in the YZ plane; When satisfying the conditional expression (1), the upper and lower optical path length differences are given at an appropriate ratio, and the projection is performed obliquely. It is possible to cause interference.

  If the lower limit of conditional expression (1) is not reached, the upper and lower optical path length differences are reduced, and the merit of projecting obliquely is reduced.

  If the upper limit of conditional expression (1) is exceeded, the upper and lower optical path length differences become too large, and it becomes difficult to correct distortion by oblique projection.

Further, a function that defines the second surface 62 of the first optical system 60 with local coordinates is defined as f (x, y), and a second-order partial differential value of x in the local coordinates (x, y) of the second surface 62 is represented as cx. When the value of (x, y) and the local coordinate (x, y) of the second surface 62 is (η, ζ), it is preferable that the following conditional expression (2) is satisfied.
cx (η, ζa) <cx (η, ζb) (2)
However,
ζa <ζb,
η is any number,
It is.

Further, a function that defines the second surface 62 of the first optical system 60 in local coordinates is f (x, y), and the second-order partial differential value of y in the local coordinates (x, y) of the second surface 62 is cy. When the value of (x, y) and the local coordinate (x, y) of the second surface 62 is (η, ζ), it is preferable that the following conditional expression (2) is satisfied.
cy (η, ζa) <cy (η, ζb) (3)
However,
ζa <ζb,
η is any number,
It is.

  Normally, trapezoidal distortion occurs when oblique projection is performed as in the present embodiment. The trapezoid distortion will be described below.

  FIG. 4 is an optical path diagram of the decentered prism of Modification Example 1 designed to have a vertically symmetrical optical path length with the same configuration as the first optical system 60 of the present embodiment. FIG. 5 shows a distortion map of the optical system of Modification 1 of FIG. FIG. 6 is an optical path diagram of Modification 2 in which oblique projection is performed by moving the object position and image position of the optical system of Modification 1 of FIG. FIG. 7 is a distortion map of the optical system of Modification 2 of FIG. Since the first optical system 60 is shown by back ray tracing from the image plane Im to the display surface Ob as the object plane of the video generation unit 70 for convenience of design, FIG. 5 and FIG. Shows a distortion map.

  The distortion map of FIG. 5 is a substantially symmetric shape, and in FIG. 7, the upper side is shorter than the lower side in both the X direction and the Y direction, and has a trapezoidal shape. That is, in FIG. 6, the portion that exits from the U portion of the object plane Ob and reaches the U ′ portion of the image plane Im via the exit pupil corresponds to the upper portion in the distortion map of FIG. 7. On the other hand, the direction exiting from the L part of the object plane in FIG. 6 and reaching the L ′ part of the image plane via the pupil corresponds to the lower part in the distortion map of FIG. This is because the magnification is smaller when the object distance is longer.

  Therefore, in order to correct this trapezoidal distortion, a portion where the light beam from the U portion to the U ′ portion of the decentered prism 60 which is the projection optical system passes is more than a portion where the light beam from the L portion to the L ′ portion passes. Also, it is sufficient if there is an effect of increasing the magnification. Since the third surface 63 of the decentered prism 60 is in the vicinity of the exit pupil position, all the light beams from the on-axis to the off-axis pass through substantially the same portion, so it is difficult to make a difference in refractive power on this surface. It is.

The first surface 61 has two functions of internal reflection and incident from the object surface. The part that internally reflects and the part that exits partially overlap. Therefore, for example, it is effective to apply a strong negative power to the second surface internal reflection portion of the light flux of the UU ′ portion and a weak negative power to the internal reflection portion of the LL ′ portion. The first surface 61 has a portion that performs both internal reflection and transmission at the same time, and is a surface close to the image surface. Therefore, the refractive power necessary for off-axis aberration correction, that is, power distribution. For this reason, the shape cannot be determined simply for correcting the trapezoidal distortion.

  The second surface 62 is a surface having the main positive power of the decentered prism 60, and the power of this surface greatly affects the power of the entire optical system. Therefore, for example, the positive power of the internal reflection portion of the second surface 62 through which the light beam of the UU ′ portion passes is weaker than the positive power of the internal reflection portion of the second surface 62 of the light beam of the LL ′ portion. This is effective for correcting the trapezoidal distortion.

  That is, if the second surface 62 moves away from a position close to the third surface 63 (left side in FIG. 6), that is, as the value of Z increases, the positive power becomes stronger. Can be corrected.

The surface shape constituting the second surface 62 may be any surface, but it is desirable to have a rotationally asymmetric shape in order to satisfactorily correct aberrations. That is, it is a surface defined by the free-form surface defined in (a) above. The surface shape of any surface is defined by a function, and the curvature of the curved surface in the X direction and the Y direction can be obtained by performing second-order partial differentiation with respect to x and y, respectively.

とすると、条件式（１）を満たしていることが、第２面６２が第３面６３に近い位置から離れるにしたがって、ｘ方向の正のパワーが強くなるようになるため、ｘ方向の台形ディストーション補正に有効に作用する。 In the function f (x, y) that defines the second surface 62, the partial differential value of the second floor of x in the local coordinates (x, y) of the second surface 62 is

Then, since the positive power in the x direction becomes stronger as the second surface 62 moves away from the position close to the third surface 63, satisfying the conditional expression (1), the trapezoid in the x direction It works effectively for distortion correction.

とすると、条件式（２）を満たしていることが、第２面６２が第３面６３に近い位置から離れるにしたがって、ｙ方向の正のパワーが強くなるようになるため、Ｙ方向の台形ディストーション補正に有効に作用する。 In the function f (x, y) defining the second surface, the second-order partial differential value of y in the local coordinates (x, y) of the second surface is

Then, since the positive power in the y direction becomes stronger as the second surface 62 moves away from the position close to the third surface 63, satisfying the conditional expression (2), the trapezoid in the Y direction It works effectively for distortion correction.

  FIG. 8 is a diagram illustrating the shape of the second surface 62 of the first optical system 60 according to the first embodiment. FIG. 9 is a diagram illustrating a result of second-order partial differentiation of the function forming the shape of the second surface 62 of the first optical system 60 of Example 1 by x. FIG. 10 is a diagram illustrating a result of second-order partial differentiation of the function forming the shape of the second surface 62 of the first optical system 60 of Example 1 by y.

  Further, FIG. 11 is a diagram illustrating an optical path diagram of the first optical system 62 according to the second embodiment. FIG. 12 is a diagram illustrating a distortion map of the first optical system according to the second embodiment. FIG. 13 is a diagram illustrating the shape of the second surface of the first optical system according to the second embodiment. FIG. 14 is a diagram illustrating a result of second-order partial differentiation of the function forming the shape of the second surface of the first optical system of Example 2 by x. FIG. 15 is a diagram illustrating a result of second-order partial differentiation of the function forming the shape of the second surface of the first optical system of Example 2 by y.

  As can be seen from FIGS. 9 and 14, the second-order partial differential value of x increases as the value of y increases. As can be seen from FIGS. 10 and 15, the second-order partial differential value of y increases as the value of y increases.

  As described above, when the decentered prism 60 satisfies the conditional expressions (2) and (3) as the characteristics of the second surface, as shown in FIGS. 3 and 12 which are distortion maps of the first and second embodiments. Shows good distortion with small trapezoidal distortion.

  In the observation optical system of the present embodiment, the second optical system 40 is preferably a contact lens 41 disposed on the eyeball 10 of the observer.

  FIG. 16 is an optical path diagram of Example 3 in the case where the second optical system 40 of the observation optical system of the present embodiment is the contact lens 41 only.

In FIG. 16, the diffusing surface 5 on the inner surface of the spectacle is about 12 MM ahead by the contact lens 41 with the light beam at infinity.
It is assumed that the image is formed on 0. The contact lens 41 is designed by taking the distance from the eyeball to the diffusing surface 50, which is the inner surface of the eyeglasses, as the focal length and taking into account the visual acuity of the observer. For example, if the distance between a general eyeball and glasses is 12 MM, it is +83 diopters in terms of frequency. The visual acuity of the observer is 0.
If it is 08, the power of the contact lens 41 is -5 diopters, and in this case, the design value is +78 diopters. With such a configuration, an image projected on the diffusion surface by the first optical system 60 can be observed as an enlarged virtual image.

  In addition, when the second optical system 40 of the observation optical system of the present embodiment is a contact lens 41, the diffusing surface 50 is preferably a curved surface.

  When the second optical system 40 is a contact lens 41 provided on the observer's eyeball and an off-axis image is observed, the observer's eyeball is rotated for observation. Therefore, the diffusing surface 50 that is the object plane for the observer is focused on the object on the focal length of the contact lens 41. Therefore, it is desirable that the diffusing surface 50 is curved. Further, it is desirable that the image plane Im of the first optical system 60 is a curved image plane Im substantially coincident with the curved diffusion surface 50.

  The diffusing surface 50 is preferably a spherical surface.

  FIG. 17 shows a fourth embodiment in which the diffusing surface 50 is a spherical surface. The radius of curvature of the diffusion surface 50 is 50 mm.

  For the combination of the contact lens 41 and the eyeball of the second optical system 40, it is more preferable that the diffusing surface 50 is a spherical surface because the focus is focused on a substantially spherical surface with respect to the center of eyeball rotation. Accordingly, it is better if the curvature of field of the first optical system 60 is a spherical surface.

  Moreover, it is preferable that the 2nd optical system 40 is an eyepiece optical system arrange | positioned ahead of an observer's eyeball.

  FIG. 18 is a diagram illustrating an example in which an eyepiece optical system that is the second optical system 40 of the present embodiment is arranged in front of the observer eyeball 10. FIG. 19 is a diagram illustrating another example in which the eyepiece optical system that is the second optical system 40 is disposed in front of the observer eyeball 10.

  In the example shown in FIG. 18, a refractive lens 42 is disposed in front of the observer eyeball 10. Further, a liquid crystal element 50 as a diffusing surface 50 is disposed in front of the refractive lens 42, and a see-through lens 81 is disposed further in front of the liquid crystal element 50. Note that the eyepiece optical system as the second optical system is capable of enlarging and projecting an image formed on the liquid crystal element to form an exit pupil in the vicinity of the position of the observer's pupil, and any optical can be guided to the eyeball 10. System may be used. For example, although the refractive lens 42 is assumed in FIG. 18, the liquid crystal display surface 50 is placed downward and above the observer's eyes in the arrangement shown in FIG. 19, and is arranged below the liquid crystal display surface. A decentered prism can also be used for the eyepiece optical system 40.

  Moreover, it is preferable that the diffusion surface 50 is light control glass.

  Any surface may be used as long as it is a diffusion surface 50 that displays an image of the first optical system 60. However, if the light control glass capable of electrically adjusting the amount of light transmitted through, such as a liquid crystal element or electrochromism, the transmittance is lowered when observing the image of the image generation unit 70, and an external image is viewed. Sometimes increase the transmittance. Further, when the electronic image and the external image are superimposed and viewed, the intermediate state is set.

  In addition, it is preferable to arrange a see-through lens on the opposite side of the diffusing surface 50 from the second optical system 40.

  When a diffusing surface 50 such as a light control glass is provided in front of the observer, the power of the second optical system 40 is canceled, and a see-through lens 81 is provided so that the external image becomes an erect image. Thus, the observer can observe the external world image.

  FIG. 20 shows an optical path diagram when observing an external image when a decentered prism is applied to the first optical system 60 and a contact lens 41 is applied to the second optical system 40.

  It is assumed that a Fresnel lens 82 is attached to the back side of the liquid crystal element 50. Furthermore, when the liquid crystal element 50 has a transparent mode, light from the outside can be taken in. However, since the contact lens 41 has a strong positive power, it cannot be observed as it is.

  Therefore, as shown in FIG. 20, a Fresnel lens 82 is formed on the back side of the liquid crystal element 50, and a double-sided Fresnel lens 83 is provided outside the liquid crystal element 50, and an intermediate image is formed once and an external image is formed on the surface of the liquid crystal element 50. Try to form. With this configuration, a Kepler-type afocal optical system is configured, and an external image is formed once in the optical path and the image is relayed. Therefore, an observer can observe an external image of an erect image. .

  Further, in the configuration of the optical path in which the decentered prism is provided in the first optical system 60 and the eyepiece optical system is provided in the second optical system 40 and the liquid crystal element 50 and the negative lens are provided in the first optical system 60 shown in FIG. Since the afocal optical system is configured, an observer can observe an external image of an erect image.

  In addition, the observation apparatus 100 according to the present embodiment includes the observation optical system 1 and a video generation unit 70 that is disposed on the object plane Ob and displays a video, and the video displayed on the video generation unit 70 is the first. The light enters from the surface, is reflected by the second reflecting surface 62, is reflected by the first reflecting surface 61, exits from the third surface 63, passes through the exit pupil, and is projected onto the diffusing surface 50.

  Further, in the observation apparatus 100 of the present embodiment, if the image generation unit 70 is provided in the vicinity of the observer's head, and the display surface is reflected at least twice and projected onto the diffusion surface 50 in front of the observer, the entire apparatus is obtained. A compact configuration is possible.

  If the first optical system 60 is reflected twice, the image projected on the diffusing surface 50 is an erect image. Therefore, if the second optical system 40 is a refractive system, it can be projected as it is. Further, when a reflection type such as an eccentric prism is used for the second optical system 40, it is necessary to consider the number of reflections so that the image projected onto the eyeball becomes an erect image. On the other hand, if the first optical system 60 is reflected three times and the second optical system 40 is a refractive system, the image displayed on the video generation unit displays a reverse image.

  In addition, it is preferable that the video generation unit 70 displays the laser beam modulated by the video signal by reflecting it with a two-dimensional digital micromirror device.

  Laser light having a luminous flux larger than the size of a two-dimensional digital micromirror device (DMD) can form an image by turning on and off the two-dimensional micromirror array. To display in full color, three laser light sources of RGB (red, green, blue) are used. The first optical system 60 can project an image on the diffusing surface 50 that is the image plane by forming the light reflected by the DMD on the image plane. In this case, the first optical system 60 is preferably a decentered prism.

  Moreover, it is preferable that the video generation unit 70 displays the laser beam modulated by the video signal by two-dimensional scanning.

  FIG. 21 is a diagram illustrating a concept of the first optical system after the three laser beams are united by the dichroic mirror or the dichroic prism.

  An image can be formed by two-dimensionally scanning a diffusion surface with a laser beam modulated by a video signal input from the outside using a deflector such as a MEMS mirror. To display in full color, three laser light sources of RGB (red, green, blue) are used. The three laser beams modulated independently by the modulator are aligned with the optical axis using a dichroic mirror or dichroic prism, and apparently become one laser beam 110 that is incident on the deflecting mirror 120 and deflected in two dimensions. Is done. In this case, instead of projecting the above-described two-dimensional image, the light that is two-dimensionally scanned by the deflection mirror 120 is projected by the first optical system 60. Therefore, the light is reflected and deflected by the deflecting mirror 120 disposed at a position coincident with the entrance pupil set at a position away from the first optical system 60 and is incident on the first optical system 60. In the first optical system 60, the laser light can project the original image onto the diffusion surface 50, which is the image plane, by performing two-dimensional scanning on the image plane.

  In the observation apparatus 100 of the present embodiment, the video generation unit 70 is preferably a reflective liquid crystal or a transflective liquid crystal, and preferably includes an illumination unit 90 that illuminates the video generation unit 70.

  FIG. 22 is an optical path diagram in which the reflective display element of the present embodiment, the first optical system 60, and the illumination unit 90 that illuminates the reflective display element are disposed therebetween.

  When the image generation unit 70 is a reflective display element such as an LCOS (reflection type liquid crystal display device), an illumination unit 90 that illuminates the display element needs to be disposed between the image generation unit 70 and the first optical system 60. . The light emitted from the light source 91 becomes linearly polarized light via the polarizer 92, enters the illumination prism 93, is totally reflected at the bottom surface of the prism, is reflected by the PBS 94 on the inclined surface, and is emitted from the prism 93. The light that is circularly polarized and reflected by the reflective display element 70 becomes polarized light that is orthogonal to the polarized light incident on the quarter-wave plate again, passes through the PBS 94, and enters the first optical system 60 from the illumination prism 93. The original image is projected on the image plane.

  Moreover, in the observation apparatus 100 of this embodiment, it is preferable that the illumination part 90 has a polarization beam splitter.

  When linearly polarized light (S-polarized light) is incident on the illumination prism 93 through the optical path as shown in FIG. 22, for example, a polarization beam splitter that reflects S-polarized light and transmits P-polarized light has the above effect. Specifically, the light utilization efficiency is 100%.

  Moreover, in the observation apparatus 100 of this embodiment, it is preferable that the illumination part 90 has a diffractive optical element.

  A diffractive optical element HOE can be used instead of the above-described PBS 94. At that time, regardless of the polarization state, the light from the light source 91 is diffracted (reflected) with respect to the angle at which the light enters the HOE, and the light incident from the display element is transmitted without being diffracted. By setting so as to be, theoretically, the light utilization efficiency is 100%.

  In addition, it is preferable that the observation apparatus 100 of the present embodiment includes a glasses-type housing, and the video generation unit 70 is disposed in the glasses-type housing. In addition, it is more preferable that the first optical system 60 is disposed in a glasses-type housing. Furthermore, it is preferable that the observation apparatus 100 includes a spectacle-type lens, and the diffusing surface 50 is disposed inside a surface corresponding to the spectacle-type lens.

  It becomes possible to create a small and lightweight by using the glasses type. Moreover, it can be mounted and specified on the observer's head, and can be used with almost the same appearance as glasses.

  Next, each example according to an embodiment of the present invention will be described.

  Example 1 illustrated in FIG. 2 is an example of the first optical system 60.

  In the first optical system 60 of Example 1, it is assumed that a 0.24 inch LCD 70 with a horizontal field angle of 32 ° is disposed on the object plane Ob. In addition, a first surface 61 on which a light beam enters from the object surface side, a second surface 62 that reflects the light beam incident from the first surface 61, and a first surface 61 that reflects the light beam reflected from the second surface 62, A third surface 63 that emits the light beam reflected from the first surface 61 is provided, and the axial principal ray Lc uses a free-form surface prism 60 in which the optical paths do not intersect with each other in the prism. The first surface 61 to the third surface 63 are formed by plane-symmetric free curved surfaces. The light beam emitted from the third surface 63 forms an image on the diffusion surface 50 that is the image surface Im. The stop S, which is the exit pupil, is disposed in the vicinity of the third surface 63 at an angle that takes into account the angle of the exit beam. The angle of the axial principal ray Lc emitted to the image plane Im of Example 1 is 45 °.

  Example 2 illustrated in FIG. 11 is an example of the first optical system 60.

  In the first optical system 60 of Example 2, it is assumed that a 0.24 inch LCD 70 with a horizontal field angle of 30.5 ° is disposed on the object plane Ob. In addition, a first surface 61 on which a light beam enters from the object surface side, a second surface 62 that reflects the light beam incident from the first surface 61, and a first surface 61 that reflects the light beam reflected from the second surface 62, A third surface 63 that emits the light beam reflected from the first surface 61 is provided, and the axial principal ray Lc uses a free-form surface prism 60 in which the optical paths do not intersect with each other in the prism. The first surface 61 to the third surface 63 are formed by plane-symmetric free curved surfaces. The light beam emitted from the third surface 63 forms an image on the diffusion surface 50 that is the image surface Im. The stop S, which is the exit pupil, is disposed in the vicinity of the third surface 63 at an angle that takes into account the angle of the exit beam. The angle of the axial principal ray Lc exiting to the image plane Im of Example 1 is 31 °.

  In the first optical system 60 of Example 3, it is assumed that a 0.24 inch LCD 70 with a horizontal field angle of 34 ° is disposed on the object plane Ob. The configuration of the free-form surface prism is the same as that of the first embodiment. The angle of the axial principal ray Lc emitted to the image plane Im of the third embodiment is 31 °. The curvature radius of the image plane Im is 50 mm. The second optical system 40 is a contact lens.

  Example 4 illustrated in FIG. 16 is an example of the second optical system 40.

In the second optical system 40 of Example 4, a contact lens 41 is used. The surface on the eyeball side is a spherical surface, the outer surface is an aspherical surface, and the refractive power is +63, so that the eyeball is focused on the inner surface of the eyeglass of about 12 MM.

  Example 5 shown in FIG. 20 is an example of the second optical system 40.

  In the second optical system 40 of Example 5, a contact lens 41 is used. A Fresnel lens surface 82 is disposed on the diffusing surface 50 and the back surface of the diffusing surface 50, and a double-sided Fresnel lens 83 is disposed in front thereof.

  The configuration parameters of the above-described first to fifth embodiments are shown below. The ray tracing direction of the first to third embodiments will be described by back ray tracing from the diffusion surface 50 that is the image plane Im toward the image generation unit 70 that is the object plane Ob.

  In each embodiment, each surface is decentered in the YZ plane. Further, the only symmetric plane of each rotationally asymmetric free-form surface is the YZ plane. For the eccentric surface, from the origin of the corresponding coordinate system, the amount of eccentricity of the surface top position of the surface (X-axis direction, Y-axis direction, Z-axis direction is X, Y, Z, respectively) and the center axis of the surface ( As for the free-form surface, inclination angles (α, β, γ (°), respectively) about the X axis, the Y axis, and the Z axis of the equation (a) are given. In this case, positive α and β mean counterclockwise rotation with respect to the positive direction of each axis, and positive γ means clockwise rotation with respect to the positive direction of the Z axis.

  In addition, a surface interval is given when a specific surface (including a virtual surface) and a subsequent surface among the optical action surfaces constituting the optical system of each embodiment constitute a coaxial optical system. After the eccentricity, it returns to the origin before the eccentricity and proceeds in the Z-axis direction given by the surface interval to be the origin of the next surface.

  In addition, the refractive index and Abbe number of the medium are given according to conventional methods. Further, the shape of the surface of the free curved surface used in the present invention is defined by the equation (a), and the Z axis of the defining equation becomes the axis of the free curved surface.

The symbol “e” indicates that the subsequent numerical value is a power exponent with 10 as the base. For example, “1.0e-5” means “1.0 × 10 ⁻⁵ ”.

Example 1
Surface number Curvature radius Surface spacing Eccentricity Refractive index Abbe number image Surface ∞ 75.00 Eccentricity (1)
r1 Diaphragm surface 0.00 Eccentricity (2)
r2 FFS [1] 0.00 Eccentricity (3) 1.5254 56.2
r3 FFS [2] 0.00 Eccentricity (4) 1.5254 56.2
r4 FFS [3] 0.00 Eccentricity (5) 1.5254 56.2
r5 FFS [2] 0.00 Eccentricity (4)
Object plane ∞ 0.00 Eccentricity (6)

FFS [1]
C4 3.6893e-002 C6 6.4083e-002 C8 6.7871e-003
C10 -3.6624e-004 C11 1.3802e-004 C13 -4.2439e-004
C15 3.9371e-004 C17 5.3522e-005 C19 -2.6302e-004
C21 -1.6949e-005 C22 5.1378e-007 C24 -1.6316e-005
C26 1.1230e-005 C28 -3.9212e-007

FFS [2]
C4 6.6789e-003 C6 1.2870e-002 C8 5.9293e-003
C10 -4.2298e-004 C11 3.4687e-005 C13 -2.6633e-004
C15 1.8168e-004 C17 7.3571e-005 C19 -1.1884e-004
C21 -2.4134e-005 C22 3.5449e-005 C24 -1.6829e-005
C26 1.0632e-005 C28 1.5003e-006

FFS [3]
C4 2.8442e-002 C6 2.4977e-002 C8 4.2282e-003
C10 1.7421e-003 C11 3.4048e-005 C13 -4.7660e-004
C15 -1.3365e-004 C17 6.4510e-005 C19 2.2391e-005
C21 3.9161e-005 C22 -9.4746e-008 C24 -9.6547e-008
C26 -5.1188e-009 C28 -6.8168e-007

Eccentric [1]
X 0.00 Y 0.00 Z 0.00
α 45.00 β 0.00 γ 0.00

Eccentric [2]
X 0.00 Y 0.00 Z 0.00
α 35.58 β 0.00 γ 0.00

Eccentric [3]
X 0.00 Y 0.00 Z 0.00
α 39.00 β 0.00 γ 0.00

Eccentric [4]
X 0.00 Y 1.82 Z 6.97
α -36.31 β 0.00 γ 0.00

Eccentric [5]
X 0.00 Y 7.71 Z 7.11
α -68.46 β 0.00 γ 0.00

Eccentric [6]
X 0.00 Y 1.78 Z 11.77
α -50.00 β 0.00 γ -180.00

Example 2
Surface number Curvature radius Surface spacing Eccentricity Refractive index Abbe number image Surface ∞ 75.00 Eccentricity (1)
r1 Diaphragm surface 0.00 Eccentricity (1)
r2 FFS [1] 0.00 Eccentricity (2) 1.5254 56.2
r3 FFS [2] 0.00 Eccentricity (3) 1.5254 56.2
r4 FFS [3] 0.00 Eccentricity (4) 1.5254 56.2
r5 FFS [2] 0.00 Eccentricity (3)
Object plane ∞ 0.00 Eccentricity (5)

FFS [1]
C4 4.8978e-002 C6 6.9232e-002 C8 3.6508e-003
C10 2.6931e-004 C11 -1.5318e-004 C13 -8.6377e-004
C15 2.0572e-004 C17 2.6159e-005 C19 -3.6139e-004
C21 -4.8713e-005

FFS [2]
C4 5.9829e-003 C6 8.4123e-003 C8 3.7368e-003
C10 3.0984e-004 C11 -9.9909e-005 C13 7.8477e-006
C15 8.8455e-005 C17 6.8287e-005 C19 -5.4763e-005
C21 -3.9312e-006

FFS [3]
C4 2.5179e-002 C6 2.2687e-002 C8 3.4068e-003
C10 1.5660e-003 C11 -1.0019e-004 C13 -1.9560e-004
C15 8.4734e-006 C17 7.6240e-005 C19 -9.3229e-006
C21 2.1578e-005

Eccentric [1]
X 0.00 Y 0.00 Z 0.00
α 31.00 β 0.00 γ 0.00

Eccentric [2]
X 0.00 Y 0.37 Z 0.00
α 17.87 β 0.00 γ 0.00

Eccentric [3]
X 0.00 Y 1.05 Z 8.24
α -44.84 β 0.00 γ 0.00

Eccentric [4]
X 0.00 Y 6.46 Z 8.89
α -77.77 β 0.00 γ 0.00

Eccentric [5]
X 0.00 Y 0.18 Z 12.39
α -63.48 β 0.00 γ -180.00


Example 3
Surface number Curvature radius Surface spacing Eccentricity Refractive index Abbe number image Surface 50.00 75.00 Eccentricity (1)
r1 Diaphragm surface 0.00 Eccentricity (1)
r2 FFS [1] 0.00 Eccentricity (2) 1.5254 56.2
r3 FFS [2] 0.00 Eccentricity (3) 1.5254 56.2
r4 FFS [3] 0.00 Eccentricity (4) 1.5254 56.2
r5 FFS [2] 0.00 Eccentricity (3)
Object plane ∞ 0.00 Eccentricity (5)

FFS [1]
C4 5.0097e-002 C6 4.2610e-002 C8 3.4705e-003
C10 1.9611e-003

FFS [2]
C4 9.1122e-003 C6 -3.4810e-004 C8 2.1544e-003
C10 2.5047e-004 C11 -1.5295e-004 C13 -1.5682e-004
C15 8.2666e-007

FFS [3]
C4 2.4243e-002 C6 1.4239e-002 C8 2.3263e-003
C10 1.1413e-003 C11 -1.6864e-005 C13 -3.9474e-005
C15 7.7222e-006

Eccentric [1]
X 0.00 Y 0.00 Z 0.00
α 31.00 β 0.00 γ 0.00

Eccentric [2]
X 0.00 Y 0.64 Z 0.00
α 16.97 β 0.00 γ 0.00

Eccentric [3]
X 0.00 Y 0.86 Z 7.10
α -50.44 β 0.00 γ 0.00

Eccentric [4]
X 0.00 Y 9.21 Z 9.88
α -83.60 β 0.00 γ 0.00

Eccentric [5]
X 0.00 Y 2.01 Z 13.88
α -62.64 β 0.00 γ -180.00


Example 4
Surface number Curvature radius Surface spacing Eccentric refractive index Abbe number image
r1 (aperture) ∞ 0.40
r2 Aspherical surface [1] 12.196
Object surface 0.00 0.00

Aspherical [1]
Radius of curvature -3.49
k -0.999289
a 0.6834e-003 b -0.2089e-004

Example 5
Surface number Curvature radius Surface spacing Eccentricity Refractive index Abbe number Object surface
r1 ∞ 0.00
r2 Fresnel surface [1] 1.70 1.4918 57.4
r3 Fresnel surface [2] 1.50
r4 Fresnel surface [3] 1.70 1.4918 57.4
r5 ∞ 0.00
r6 ∞ 12.20
r7 Aspherical surface [1] 0.40 1.4918 57.4
r8 8.10 0.00
r9 (aperture) ∞ 0.00
r10 ∞ 22.00
Image plane -11.00 0.00

Fresnel surface [1]
Curvature radius 0.49734
k 0.0000e + 000

Fresnel surface [2]
Radius of curvature -0.1187
k 0.0000e + 000

Fresnel surface [3]
Radius of curvature 0.3465
k 0.0000e + 000

Aspherical [1]
Curvature radius 3.49
k -3.862634
a 7.3289e-003 b -7.6198e-004

  The values of conditional expression (1) for Examples 1 to 3 are shown below.

Example 1 Example 2 Example 3
OP _ux / OP _ix 1.66 1.35 1.50

  Although various embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and embodiments configured by appropriately combining the configurations of the respective embodiments also fall within the scope of the present invention. Is.

DESCRIPTION OF SYMBOLS 1 ... Observation optical system 10 ... Eyeball 20 ... Observer pupil position 30 ... Observer visual axis 40 ... 2nd optical system 50 ... Diffusion surface 60 ... 1st optical system (eccentric prism)
61 ... 1st surface 62 ... 2nd surface 63 ... 3rd surface 70 ... Image | video production | generation part (image display element)

Claims (23)

A diffusing surface arranged in front of the observer and diffusing light;
The optical surface includes at least three optical surfaces having a first surface, a second surface, and a third surface, and at least two of the optical surfaces have a rotationally asymmetric shape, and a real image of an object surface image is obtained. A first optical system that projects onto the diffusing surface;
A second optical system that projects the real image projected on the diffusion surface as a virtual image enlarged on the observer's eyeball;
With
When the light beam connecting the center of the object plane and the center of the diffusion surface is an axial principal ray, the at least three optical surfaces are respectively arranged eccentric to the axial principal ray. Observation optical system. The observation optical system according to claim 1, wherein the first optical system is an eccentric prism that is surrounded by the at least three optical surfaces and is filled with a medium having a refractive index of 1 or more. The observation optical system according to claim 2, wherein an exit pupil of the first optical system is disposed in the vicinity of an exit surface of the decentered prism. OP _ux , an optical path length from the exit pupil of the upper maximum field angle of the first optical system in the plane including the axial principal ray to the image plane,
OP _ix , the optical path length from the exit pupil of the lower maximum field angle of the first optical system in the plane including the axial principal ray to the image plane,
When
The observation optical system according to claim 1, wherein the following conditional expression (1) is satisfied.
1.05 ≤ OP _ux / OP _ix ≤ 1.95 (1) A function that defines the second surface of the first optical system in local coordinates is f (x, y),
The second-order partial differential value of x in the local coordinates (x, y) of the second surface is expressed as cx (x, y),
When the value of the local coordinates (x, y) of the second surface is (η, ζ),
The observation optical system according to any one of claims 1 to 4, wherein the following conditional expression (2) is satisfied.
cx (η, ζa) <cx (η, ζb) (2)
However,
ζa <ζb,
η is any number,
It is. A function that defines the second surface of the first optical system in local coordinates is f (x, y),
The second-order partial differential value of y in the local coordinates (x, y) of the second surface is expressed as cy (x, y),
When the value of the local coordinates (x, y) of the second surface is (η, ζ),
The observation optical system according to claim 1, wherein the following conditional expression (2) is satisfied.
cy (η, ζa) <cy (η, ζb) (3)
However,
ζa <ζb,
η is any number,
It is. The observation optical system according to any one of claims 1 to 6, wherein the second optical system is a contact lens disposed on an observer's eyeball. The observation optical system according to claim 7, wherein the diffusion surface is a curved surface. The observation optical system according to claim 7, wherein the diffusing surface is a spherical surface. The observation optical system according to any one of claims 1 to 6, wherein the second optical system is an eyepiece optical system disposed in front of an eyeball of an observer. The observation optical system according to claim 10, wherein the diffusion surface is a light control glass. The observation optical system according to any one of claims 7 to 11, wherein a see-through lens is disposed on a side opposite to the second optical system with respect to the diffusion surface. The observation optical system according to claim 12, wherein the see-through lens is a Fresnel lens. The observation optical system according to any one of claims 1 to 13,
A video generation unit arranged on the object plane to display a video;
With
The image displayed on the image generation unit is transmitted through the first surface, reflected from the second surface, reflected from the first surface, and the exit pupil disposed in the third surface and the vicinity thereof. The observation apparatus is characterized by being projected onto the diffusion surface. The observation apparatus according to claim 14, wherein the image generation unit displays the laser beam modulated by the image signal by reflecting the laser beam with a two-dimensional digital micromirror device. The observation apparatus according to claim 14, wherein the image generation unit displays the laser beam modulated by the image signal by two-dimensional scanning. The video generation unit includes a deflection mirror that deflects the laser light,
The reflection position of the deflection mirror is disposed in the vicinity of the entrance pupil of the first optical system,
The observation apparatus according to claim 16, wherein the entrance pupil position and the diffusion surface of the first optical system are tilted or shifted with respect to each other. The image generation unit is a reflective liquid crystal or a transflective liquid crystal,
The observation apparatus according to claim 14, further comprising an illumination unit that illuminates the video generation unit. The observation apparatus according to claim 18, wherein the illumination unit includes a polarization beam splitter. The observation apparatus according to claim 18, wherein the illumination unit includes a diffractive optical element. The observation apparatus includes a glasses-type housing.
The observation apparatus according to any one of claims 14 to 20, wherein the image generation unit is disposed in a glasses-type housing. The observation apparatus according to claim 21, wherein the first optical system is disposed in a spectacle-type housing. The observation apparatus includes a spectacle-type lens,
23. The observation apparatus according to claim 21, wherein the diffusing surface is disposed inside a surface corresponding to a spectacle-type lens.

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