JP2014122941A - Optical element and observation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical element having both projection optical function and imaging optical function.SOLUTION: The optical element having a projection optical function for projecting an original image displayed on an image display surface onto eye balls of an observer includes: at least four optical surfaces arranged eccentrically to each other, at least two of the four surfaces having rotationally asymmetric faces; and an imaging optical function for emitting light reflected on the optical surfaces from the optical element and forming an image on an imaging surface, the optical surfaces from among the four surfaces, opposite to the image display surface, and having two actions of transmission and reflection.

Description

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

  2. Description of the Related Art Conventionally, an observation apparatus that uses small image display elements and enlarges an original image of these display elements with an observation optical system and presents it to an observer is known. In order to observe an image with such an observation apparatus, it is necessary to overlap the exit pupil of the observation optical system and the pupil of the observer's eyeball. Further, when the distance from the exit pupil center is reached, an image that is distorted due to pupil aberration and is difficult to view is also presented. There is a demand for an optical system capable of presenting with high resolution that the pupil position of the observer and the exit pupil center of the observation optical system match as much as possible even if the observer's head moves slightly.

  As a means for satisfying such a requirement, a method of enlarging the exit pupil of the optical system to be projected with a diffusion plate (Patent Document 1), photographing the vicinity of the observer's eyeball and following the observer's line of sight, the observation optical system An optical system (Patent Documents 2 to 6) that projects onto an exit pupil is disclosed.

Japanese Patent Laid-Open No. 2004-301876 JP 2006-53321 A Japanese Patent Laid-Open No. 10-179521 JP 2008-46253 A JP 2008-241822 A Japanese Patent No. 4040730

  Although Patent Document 1 uses a diffusion hologram to enlarge the pupil, a large optical element is required, leading to high costs. In Patent Documents 2 to 5, in addition to the optical system for displaying an image, means for imaging the observer's pupil must be prepared, and the entire apparatus becomes large. In Patent Document 6, the imaging optical system is formed in the see-through optical member. However, the transmittance of the see-through image may partially change, or a part that cannot be partially seen may occur.

  An object of the present invention is to provide an optical element capable of projecting an image of an image display element as a virtual image onto an observer's eyeball while simultaneously imaging the vicinity of the eyeball of the observer, even though the number of optical elements is one. The purpose is that. Furthermore, the surface facing the image display element is a semi-transmissive surface, and the reflected light is imaged on the image sensor, so that the vicinity of the observer's eyeball can be photographed. The present invention provides an optical element that presents a stable observation image with high resolving power by tracking the captured image so that it always enters the exit pupil formed by the optical element in the pupil of the observer. .

In order to solve the above problems, the optical element according to the present invention is:
In an optical element having a projection optical function of projecting an original image displayed on an image display surface onto an observer's eyeball,
The optical element has at least four optical surfaces, the at least four optical surfaces are arranged eccentric to each other, and at least two surfaces have a rotationally asymmetric shape,
Of the at least four optical surfaces, the optical surface facing the image display surface has two functions of transmission and reflection, and the light reflected by the optical surface is emitted from the optical element and imaged. An imaging optical function for forming an image on a surface is provided.

  According to the present invention, while having a single optical element, it has a projection optical function for projecting the image of the image display element as a virtual image onto the observer's eyeball, and at the same time, an imaging optical function for imaging the vicinity of the eyeball of the observer It is possible to provide an optical element having

The figure which shows the structure of the observation apparatus which concerns on embodiment of this invention. The figure which shows the structure of the observation apparatus (projection optical function) which concerns on embodiment of this invention. The figure which shows the structure of the observation apparatus (imaging optical function) which concerns on embodiment of this invention. The figure for demonstrating the curvature of field which generate | occur | produces with the concave mirror of eccentric arrangement | positioning Diagram for explaining astigmatism generated by a decentered concave mirror Diagram for explaining on-axis coma generated by a decentered concave mirror The figure which shows the spot diagram of the optical element (projection optical function) which concerns on embodiment of this invention. The figure which shows the spot diagram of the optical element (imaging optical function) which concerns on embodiment of this invention The figure which shows the distortion map of the optical element (projection optical function) which concerns on embodiment of this invention. The figure which shows the distortion map of the optical element (imaging optical function) which concerns on embodiment of this invention.

  The optical element according to the present invention has at least four optical surfaces, the at least four optical surfaces are arranged eccentric to each other, and at least two surfaces have a rotationally asymmetric shape, Of the at least four optical surfaces, the optical surface facing the image display element has two functions of transmission and reflection, and the light reflected by the optical surface is emitted from the optical element and forms an image on the imaging surface. It is characterized by doing.

  By using such an optical element, it is possible to present an enlarged virtual image (projection optical function) by projecting the image of the image display element onto the observer's eyeball. Furthermore, not only the projection but also the vicinity of the observer's eyeball can be imaged (imaging optical function) from the aperture stop located below the surface on which the original image of the image display element is emitted.

  In this way, by using optical elements in which the optical surfaces are decentered, it is possible to correct asymmetrical aberrations with respect to the generated optical axis. This will be described in detail below with reference to the drawings. FIG. 1 shows a configuration of an observation apparatus configured to include an image display element and an imaging element for the optical element 2 according to the present invention.

  In FIG. 1, the observer eyeball is 1, the observer visual axis is 1a, the optical element is 2, the exit pupil of the optical element 2 is 3, the entrance pupil of the optical element 2 is 4, the imaging element is 5, and the image display element is 6 The first surface (transmission and internal reflection surface) of the optical element 2 is 21, the second surface (projection reflection surface) is 22, the third surface (imaging reflection surface) is 23, and the fourth surface (reflection / transmission surface). 24, and the fifth surface (imaging exit surface) is 25. The optical element 2 is formed of an eccentric prism in which the optical surfaces of the first surface 21 to the fifth surface 25 are filled with a transparent medium having a refractive index greater than 1. In addition, although the optical element 2 of a present Example is a form formed with 5 surfaces, the optical element 2 is formed with 4 surfaces by forming the 2nd surface 22 and the 3rd surface 23 by one continuous surface. It is also possible to adopt a form.

  The optical element 2 shown in FIG. 1 has a projection optical function for projecting an original image from the image display element 6 through the optical element 2 to the observer's eyeball 1 and the light reflected by the observer's eyeball 1 through the optical element 2 and the imaging element. 5 also has an imaging optical function to form an image.

  The image display element 6 has an aspect ratio of 3: 4, a display surface size of 1.2 inches, and a pupil diameter at the position of the observer eyeball 1 is 6 mm. The image pickup device is assumed to be 2/3 inch, and is a diagram showing an aperture stop 3 mm ray.

  First, the projection optical function of virtual image observation in the optical element 2 will be described. Light emitted from the image display element 6 enters the decentered prism constituting the optical element 2 from the fourth surface 24 of the optical element 2, and is internally reflected by the first surface 21 toward the second surface 22. When the incident light with respect to the first surface 21 has an incident angle greater than the critical angle, the total reflection condition is satisfied, and therefore the first surface 21 does not need to be provided with a reflective coating. Moreover, since it is also a surface which inject | emits to an observer's eyeball, it is desirable not to carry out reflective coating. The second surface 22 is provided with a metal coating such as aluminum so as to be a back reflecting surface. After internal reflection at the second surface 22, the light travels toward the first surface 21 again, passes through the first surface 21, exits from the optical element 2, and enters the observer's eyeball 1. The exit pupil 3 of the optical element 2 is formed in the vicinity of the observer pupil position, and almost all the light emitted from the screen of the image display element 6 is guided into the observer eyeball 1, so that the entire screen is enlarged. It can be observed as a virtual image.

  Here, the merit of configuring the optical element 2 with such a decentered optical system, in particular, an internally reflecting decentered prism will be described. A refractive optical element such as a lens can be given power only by giving a 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. Moreover, since the reflecting surface has a higher eccentricity error sensitivity than the refracting surface, high accuracy is required for assembly adjustment.

  However, among the reflective optical elements, since the relative positional relationship between the prisms 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 greater degree of freedom in aberration correction 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. Thinning and miniaturization are possible. Further, the observation optical system is required to have good imaging performance to the periphery as well as the center performance.

Therefore, in the present invention, as described above, the optical element 2 uses one decentered prism, and at least the fourth surface 24 on which the image light emitted from the image display element 6 enters the prism, the fourth surface 24 thereof. A first surface 21 that internally reflects and emits a light beam incident from the surface 24, and a second surface 22 that internally reflects a light beam reflected by the first surface 21, and includes at least two of the optical surfaces. Is configured to have a rotationally asymmetric curved surface shape that gives optical power to the light flux and corrects decentration aberrations, so that not only the center but also off-axis aberrations can be corrected well.

  By adopting such a basic configuration of the optical element 2, the number of optical elements is less than that of an optical system using a refractive optical system or a rotationally symmetric imaging optical system, and the performance is good from the center to the periphery. A small image display device can be obtained. Here, when a light ray that reaches the center of the diffusion surface in front of the eye from the center of the display surface of the image display element 6 is an axial principal ray, at least one reflecting surface of the prism is not decentered with respect to the axial principal ray. Then, the incident light of the axial chief ray and the reflected light take the same optical path, and the axial chief ray 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.

  As described above, in this embodiment, the surface shape of the reflecting surface constituting the decentered prism as the optical element 2 (projection optical function) is a rotationally asymmetric curved surface that gives optical power to the light beam and corrects decentration aberrations. It has a shape. 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. The center of the aperture position of the optical system is the coordinate origin. The right side of the drawing from the center of the aperture is positive, the horizontal axis is the Z axis, the axis is orthogonal to the Z axis, and the axis within the eccentric surface of each surface constituting the imaging optical system is defined as the Y axis. In addition, an axis orthogonal to the Y axis is taken as an X axis. The ray tracing direction will be described by back ray tracing from a diffusion surface as an image plane to an image display element as an object plane.

  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, as shown in FIG. 4, an image plane tilted 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. As in the above description, in the concave mirror arranged eccentrically, astigmatism as shown in FIG. 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, in the concave mirror arranged eccentrically, coma aberration as shown in FIG. 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 invention 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 the Z axis of the defining formula is the axis of the free-form surface.
Z = cr ² / [1 + √ {1- (1 + k) c ² r ² }]
66
+ Σ Cj X ^m Y ⁿ
j = 2
... (a)
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
Σ Cj X ^m Y ⁿ
j = 2
= C1
+ C2 X + C3 Y
^{+ C4 X 2 + C5 XY +} C6 Y 2
^{+ C7 X 3 + C8 X 2} Y + C9 XY 2 + C10Y 3
^{+ C11X 4 + C12X 3 Y +} C13X 2 Y 2 + C14XY 3 + C15Y 4
+ C16X ⁵ + C17X ⁴ Y + C18X ³ Y ² + C19X ² Y ³ + C20XY ⁴
+ C21Y ⁵
+ C22X ⁶ + C23X ⁵ Y + C24X ⁴ Y ² + C25X ³ Y ³ + C26X ² Y ⁴
+ C27XY ⁵ + C28Y <sup>6
+ C29X 7 + C30X 6 Y +</sup> C31X 5 Y 2 + C32X 4 Y 3 + C33X 3 Y 4
+ C34X ² Y ⁵ + C35XY ⁶ + C36Y ⁷
(1)
However, Cj (j is an integer of 2 or more) is a coefficient.

In general, the free-form surface does not have a symmetric surface in both the XZ plane and the YZ plane. However, in the present invention, by setting all odd-order terms of X to 0, the free-form surface is parallel to the YZ plane. This is a free-form surface with only one symmetrical plane. For example, in the above definition (a), the coefficients of the terms C2, C5, C7, C9, C12, C14, C16, C18, C20, C23, C25, C27, C29, C31, C33, C35. It is possible by setting 0 to 0. 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, the coefficient of each term of C3, C5, C8, C10, C12, C14, C17, C19, C21, C23, C25, C27, C30, C32, C34, C36. Is possible.

  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, XZ By making the decentering direction of the optical system parallel to the plane parallel to the X-axis direction, it is possible to improve the manufacturability at the same time while effectively correcting the rotationally asymmetric aberration caused by the decentering. Become.

  The definition formula (a) is shown as an example as described above, and the present invention uses a rotationally asymmetric aberration caused by decentering by using a rotationally asymmetric surface having only one symmetric surface. It is a feature that the manufacturing efficiency is improved at the same time, and it goes without saying that the same effect can be obtained for any other defining formula.

  The first surface 21 of the optical element 2 is a transmission surface that emits a light beam from the image display element, and a reflection surface that internally reflects the light beam incident from the fourth surface 24. With such a configuration, the first surface 21 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 21 is set to be greater than the critical angle so that the first surface 21 is totally reflected at the portion where the light beam is emitted. 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 the reflective region that does not satisfy the total reflection condition of the first surface 21.

  Next, an imaging optical function for photographing the vicinity of the observer's eyeball with the optical element 2 will be described. The vicinity of the eyeball is illuminated brightly by illumination means (not shown) for illuminating the vicinity of the observer's eyeball. In the present embodiment, infrared light (including near infrared light) having a wavelength longer than that in the visible range is used. The light emitted from the vicinity of the observer's eyeball enters the decentered prism constituting the optical element 2 from the first surface 21 of the optical element 2. At that time, it is desirable that the exit pupil in the projection optical function of the optical element 2 and the aperture stop of the optical element 2 (imaging optical function) do not overlap with each other. Therefore, it is desirable that the axial principal ray incident on the optical element 2 (imaging optical function) is set to be inclined with respect to the axial principal ray in the projection optical function of the optical element 2. In this embodiment, it is set to be inclined by 25 degrees.

  Thereafter, the light is internally reflected by the third surface 23 adjacent to the second surface 22 used in the projection optical function of the optical element 2 and returns to the first surface 21 again. At this time, since the incident angle on the first surface 21 is set to be equal to or larger than the critical angle, the internal reflection is caused by the total reflection even if the reflective coating is not applied.

  Thereafter, the fourth surface 24 performs internal reflection. The fourth surface 24 may be a transmission surface when acting as an optical surface of the projection optical function, and may be a reflection surface when acting as an optical surface of the imaging optical function. Therefore, it is possible to satisfy the requirements even with half mirrors, but if dichroic mirror coating that has reflectivity only for infrared light is applied, only the object light in the part illuminated with infrared light Is reflected by the fourth surface 24. Therefore, since it does not reflect the wavelength of light used in the projection optical function, in principle, 100% of the action of the transmission surface can be used.

Thereafter, the light passes through the fifth surface 25 and reaches the imaging device 5 (imaging surface), so that the vicinity of the observer's eyeball can be photographed. In this embodiment, since infrared light (including near infrared light) is used as the illumination means, the imaging element 5 is a two-dimensional image sensor having a susceptibility to infrared light. With such a configuration, it is possible to suppress the influence on the original image observed by the observer.

  The pupil position of the observer eyeball 1 can be detected from an image in the vicinity of the observer eyeball 1 photographed by such an optical element 2 (imaging optical function). By providing a tracking mechanism for tracking the exit pupil 3 of the optical element 2 (projection optical function) so that the observer pupil position and the exit pupil 3 of the optical element 2 (projection optical function) overlap, the head of the observer When the camera moves or when the observer moves the eyeball, the exit pupil of the optical element 2 (projection optical function) follows the pupil of the observer's eyeball 1, so that an enlarged image can be always presented. It becomes.

  The tracking mechanism is controlled so that the angle of the light beam emitted from the optical element 2 (projection optical function) is changed by the stepping motor or the gimbal stage. Or by controlling to change the position of the light beam emitted from the optical element 2 (projection optical function), the observer's pupil is tracked and the exit pupil always overlaps the observer's pupil. Will do.

  Further, in the projection optical function of the optical element 2, it is preferable to provide a moving means that can move the position of the image display element 6 back and forth along the axial principal ray. By moving the position of the image display element back and forth by the visual acuity of the observer, the diopter can be changed and observation can be performed in a suitable focus state.

  Also in the imaging optical function of the optical element 2, it is preferable to provide a moving means that can move along the axial principal ray. With such a moving means, the photographing position by the imaging optical function can be adjusted to an appropriate position, and the pupil position of the observer eyeball 1 can be accurately supplemented.

  Now, specific numerical examples of the present invention will be described. In the configuration parameters of the examples described later, as shown in the drawing, the projection optical function of the optical element 2 is the reverse ray tracing, and the observer visual axis 1a (axial principal ray) is set to the optical element 2 (projection optical function). It is defined by a light ray that passes through the center of the exit pupil 3 and reaches the center of the image plane (image display element 6). Moreover, the imaging optical function of the optical element 2 is forward ray tracing, and is defined by light rays that pass through the center of the entrance pupil 4 and reach the center of the imaging element 5 that is the image plane.

  An axial principal ray (line segment connecting the center of the object (corresponding to the pupil center position of the observer's eyeball 1) to the center of the entrance pupil 4) in the imaging optical function is the observer's visual axis 1a (axial principal ray of the projection optical function). In this way, the exit pupil 3 in the projection optical function and the entrance pupil 4 in the imaging optical function are not actively overlapped. In the present embodiment, the axial principal ray in the imaging optical function is tilted 25 degrees in the clockwise direction with respect to the axial principal ray in the projection optical function.

  In this embodiment, the direction along the traveling direction of the axial principal ray 1a is the Z-axis positive direction, the plane including the Z-axis and the center of the image plane is the YZ plane, and passes through the origin to the YZ plane. A direction perpendicular to the paper surface and extending from the front side to the back side is defined as an X-axis positive direction, and an X-axis, a Z-axis, and an axis constituting a right-handed orthogonal coordinate system are defined as a Y-axis. A coordinate system is illustrated in FIGS.

In this embodiment, each surface is decentered in this YZ plane, and the only symmetric surface 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 addition,
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.

  Further, among optical action surfaces constituting the optical element 2 of the embodiment, when a specific surface (including a virtual surface) and a subsequent surface constitute a coaxial optical system, a surface interval is given, 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. In addition, the term regarding the free-form surface for which no data is described is zero. The refractive index is shown for d-line (wavelength 587.56 nm). The unit of length is mm.

The optical element 2 (projection optical function) of the present embodiment shown in FIG. 2 assumes an image display element 6 having a horizontal angle of view of 1.2 inches and a fourth surface on the image display element side 6. 24, the first surface 21 that reflects the light beam incident from the fourth surface 24, the third surface 23 that reflects the light beam reflected from the first surface 21, and the light beam reflected from the third surface 23 are emitted. The decentered prism 2 that includes the first surface 21 and in which the axial principal ray does not intersect in the prism in the optical path from the fourth surface 24 to the first surface 21 is used, and faces the first surface 21 to the fourth surface 24. A symmetric free-form surface is used. The focal length in the X direction of the optical element 2 (projection optical function) is mm, the focal length in the Y direction is mm, and the pupil diameter is φ6.0 mm.

  The optical element 2 (imaging optical function) of the present embodiment shown in FIG. 3 assumes an image sensor 5 having a horizontal field angle of 10 ° and a 2/3 inch, and a first surface 21 that is an incident surface on the object side, A second surface 22 that is an internal reflection surface, a first surface 21 that is internally reflected again, a fourth surface 24 that is an internal reflection surface, and a fifth surface 25 that emits reflected light from the fourth surface 24 to the imaging device, In the optical path from the first surface 21 to the fifth surface 25, a decentered prism in which the axial principal ray intersects at two points in the prism is used, and the first surface 21, the second surface 22, and the fourth surface 24 are surfaced. A rotationally symmetric aspherical surface is used for the symmetric free-form surface and the fifth surface 25.

  FIG. 1 is an optical path diagram in which the optical functions of FIG. 2 and FIG. As can be seen from FIG. 1, it can be seen that one optical element 2 realizes the projection optical function and the photographing optical function.

  The decentered prism constituting the optical element 2 is composed of five optical surfaces, the first surface 21 to the fifth surface 25, and is filled with a transparent medium having a refractive index larger than 1 between the five surfaces. The pupil diameter of the optical element 2 (imaging optical function) is φ3.0 mm.

  The configuration parameters of the above embodiment are shown below. “FFS” in these tables indicates a free-form surface.

(Numerical example: projection optical function)
Surface number Curvature radius Surface spacing Eccentricity Refractive index Abbe number Object surface ∞ -1000.00
1 ∞
2 ∞ (diaphragm surface) 30.00
3 FFS [1] Eccentricity (1) 1.6340 23.9
4 FFS [2] Eccentricity (2) 1.6340 23.9
5 FFS [1] Eccentricity (1) 1.6340 23.9
6 FFS [3] Eccentricity (3)
Image plane ∞ Eccentricity (4)

FFS [1]
C4 3.7479e-004 C6 -1.8072e-003 C8 -1.2789e-004
C10 1.6397e-005 C11 -3.5404e-006 C13 2.7427e-006
C15 -1.6060e-006 C17 1.5350e-007 C19 -1.5019e-009
C21 3.1921e-008 C67 2.0000e + 001

FFS [2]
C4 -2.1659e-003 C6 -4.2599e-003 C8 -6.0672e-005
C10 2.5676e-005 C11 -1.4447e-006 C13 1.7139e-006
C15 -2.4349e-007 C17 7.4164e-008 C19 -2.7166e-008
C21 -1.2440e-008 C22 2.5230e-010 C24 -6.8156e-010
C26 7.1352e-010 C28 5.7736e-010

FFS [3]
C4 -4.3367e-003 C6 -6.1642e-003 C8 -3.2267e-005
C10 1.3495e-005 C11 -6.2912e-007 C13 6.8871e-008
C15 -1.2948e-007 C17 5.8792e-008 C19 3.0210e-008
C21 1.2406e-008 C22 1.4285e-010

Eccentric [1]
X 0.00 Y 8.00 Z -2.00
α 13.00 β 0.00 γ 0.00

Eccentric [2]
X 0.00 Y -8.02 Z 26.00
α -18.23 β 0.00 γ 0.00

Eccentric [3]
X 0.00 Y 36.62 Z 20.00
α 73.46 β 0.00 γ 0.00

Eccentric [4]
X 0.00 Y 51.95 Z 12.38
α 61.90 β 0.00 γ 0.00

(Numerical example: imaging optical function)
Surface number Curvature radius Surface spacing Eccentricity Refractive index Abbe number Object surface ∞ 30.00 Eccentricity (1)
1 ∞
2 ∞ (diaphragm surface) Eccentricity (2)
3 FFS [1] Eccentricity (3) 1.6340 23.9
4 FFS [2] Eccentricity (4) 1.6340 23.9
5 FFS [1] Eccentricity (3) 1.6340 23.9
6 FFS [3] Eccentricity (5) 1.6340 23.9
7 Aspherical surface [1] Eccentricity (6)
Image plane ∞ Eccentricity (7)

Aspherical [1]
Radius of curvature ∞
k 0.0000e + 000
a 2.6246e-004 b -1.3466e-006

FFS [1]
C4 3.7479e-004 C6 -1.8072e-003 C8 -1.2789e-004
C10 1.6397e-005 C11 -3.5404e-006 C13 2.7427e-006
C15 -1.6060e-006 C17 1.5350e-007 C19 -1.5019e-009
C21 3.1921e-008 C67 2.0000e + 001

FFS [2]
C4 -3.2019e-003 C6 -6.0721e-003 C8 -1.4334e-004
C10 -6.8888e-005 C11 6.5127e-006 C13 1.3428e-005
C15 2.9181e-006 C17 3.4497e-006 C19 8.1277e-007
C21 3.3928e-007 C22 3.1380e-008 C24 2.2118e-007
C26 1.3816e-008 C28 5.4467e-009

FFS [3]
C4 -4.3367e-003 C6 -6.1642e-003 C8 -3.2267e-005
C10 1.3495e-005 C11 -6.2912e-007 C13 6.8871e-008
C15 -1.2948e-007 C17 5.8792e-008 C19 3.0210e-008
C21 1.2406e-008 C22 1.4285e-010

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

Eccentric [2]
X 0.00 Y -14.00 Z 0.00
α 0.00 β 0.00 γ 0.00

Eccentric [3]
X 0.00 Y 8.00 Z -2.00
α 13.00 β 0.00 γ 0.00

Eccentric [4]
X 0.00 Y -8.00 Z 24.74
α -22.32 β 0.00 γ 0.00

Eccentric [5]
X 0.00 Y 36.62 Z 20.00
α 73.46 β 0.00 γ 0.00

Eccentric [6]
X 0.00 Y -25.29 Z 13.00
α 80.00 β 0.00 γ 0.00

Eccentric [7]
X 0.00 Y -28.69 Z 11.97
α 101.27 β 0.00 γ 0.00

FIG. 7 shows a spot diagram of the optical element 2 (projection optical function), and FIG. 8 shows a spot diagram of the optical element 2 (imaging optical function). The RMS number in each figure indicates the value of the root mean square of the spot diagram at each angle of view of X and Y on the left side. FIG. 7 shows the result of calculation by distributing five wavelengths of C line (656.28), d line (587.56), e line (546.07), f line (486.13), and g line (435.84). It is the result calculated about monochromatic light of 830 nm.

  FIG. 9 shows a distortion map of the optical element 2 (projection optical function), and FIG. 10 shows a distortion map of the optical element 2 (imaging optical function). The maximum value in FIG. 9 is 6.9%. The maximum value in FIG. 10 is 10.8%.

  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 ... Observer eyeball 1a ... Observer visual axis 2 ... Optical element 21 ... 1st surface 22 ... 2nd surface 23 ... 3rd surface 24 ... 4th surface 25 ... 5th surface 3 ... Exit pupil 4 ... Entrance pupil 5 ... Image sensor 6 ... Image display element

Claims (17)

In an optical element having a projection optical function of projecting an original image displayed on an image display surface onto an observer's eyeball,
The optical element has at least four optical surfaces, the at least four optical surfaces are arranged eccentric to each other, and at least two surfaces have a rotationally asymmetric shape,
Of the at least four optical surfaces, the optical surface facing the image display surface has two functions of transmission and reflection, and the light reflected by the optical surface is emitted from the optical element and imaged. An optical element having an imaging optical function for forming an image on a surface. The optical element according to claim 1, wherein an exit pupil in the projection optical function and an entrance pupil in the imaging optical function do not overlap. The axial principal ray from the optical surface facing the observer's eyeball to the exit pupil center in the projection optical function and the axial principal ray from the object center to the entrance pupil center in the imaging optical function are not parallel. The optical element according to claim 1 or 2. The optical element according to any one of claims 1 to 3, wherein the optical surface facing the image display surface is a semi-transmissive surface coated with a half mirror. The optical element according to any one of claims 1 to 3, wherein the optical surface facing the image display surface is a semi-transmissive surface coated with a dichroic mirror. The optical surface facing the observer eyeball is the first surface,
An optical surface facing the observer's eyeball across the first surface is a second surface,
The optical surface facing the observer eyeball across the first surface is a third surface,
The optical surface facing the image display surface is a fourth surface,
The optical element according to any one of claims 1 to 5, wherein an optical surface facing the imaging surface is provided as a fifth surface. The light emitted from the image display surface is transmitted through the fourth surface, reflected by the first surface, reflected by the second surface, transmitted through the first surface, and projected onto the observer eyeball. The optical element according to claim 6. The light incident on the first surface is reflected by the third surface, reflected by the first surface, reflected by the fourth surface, and passes through the fifth surface to form an image on the imaging surface. The optical element according to claim 6 or 7. The optical element according to any one of claims 6 to 8, wherein the second surface and the third surface are formed as one continuous surface. The optical element according to any one of claims 1 to 9,
An image display element forming the image display surface;
An observation device comprising: an imaging element that forms the imaging surface. The observation apparatus according to claim 10, further comprising an illumination unit that illuminates the vicinity of the observer's eyeball. The observation apparatus according to claim 11, wherein the illuminating unit illuminates with infrared light. The tracking mechanism that moves the exit pupil of the optical element so that the pupil position of the observer's eyeball and the exit pupil of the optical element overlap each other is provided. The observation apparatus described in 1. The observation device according to claim 13, wherein the tracking mechanism is controlled to change an angle of a light beam emitted from the optical element. The observation apparatus according to claim 13, wherein the tracking mechanism is controlled to change a position of a light beam emitted from the projection optical element. The observation device according to any one of claims 10 to 15, wherein the image display element is movable along an axial principal ray in the projection optical function. The observation apparatus according to any one of claims 10 to 16, wherein the position of the imaging element is movable along an axial principal ray in the imaging optical function.

Images