JPH10221638A - Image observation optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image observation optical system suitable for a device such as a head mounted display and a glass type display and small in the size of whole device. SOLUTION: In this image observation optical system for guiding luminous flux from a display means displaying image information to an observer side through an optical means 3 provided with three or more optical surfaces including the surface having an eccentric curvature and consisting of a prism body of a single medium and observing the image information displayed on the display means, the optical means 3 is provided with two or above of optical surfaces with different diffractive force according to an azimuth angle around a surface vertex, and when the diffractive index and the Abbe's number of the medium of the prism body are defined respectively as Nd, νd, the optical means 3 satisfies the relations of 1.52<Nd, νd<57.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image observation optical system, and is particularly suitable for use in an image observation apparatus such as a viewfinder of a camera, a so-called head mounted display or a glasses type display, and an imaging apparatus such as a camera. .

[0002]

2. Description of the Related Art Conventionally, in an image observation apparatus such as a head-mounted display (HMD) and a glasses-type display, a reduction in the size of the entire apparatus has been demanded, and various optical systems for achieving this have been proposed. Have been.

The present applicant has disclosed in Japanese Patent Application Laid-Open No. 7-333551 an LCD as display means for displaying image information.
An image observation device using a (liquid crystal) and a small prism as an observation optical system is proposed to reduce the size of the entire device.

In this publication, light emitted from an LCD displaying image information is incident on a small prism, and the light is folded between a refracting surface, a total reflection surface, and a reflection surface having a curvature formed on the small prism. Then, a small prism is emitted to guide the light to the observer. Thereby, a virtual image of the image information displayed on the display means (LCD) is formed, and the virtual image is observed by an observer.

[0005]

In an image observation apparatus such as an HMD, it is important to reduce the size and weight of the entire apparatus in order to mount the apparatus on the observer's head. In addition, it is important to widen the observation angle of view in order to enhance the observation of the image information displayed on the display means.

According to the present invention, when observing image information displayed on a display means such as a liquid crystal display in a wide viewing field, a prism having a refraction function for guiding a light beam from the display means to an observer's eyeball. An object of the present invention is to provide an image observation optical system capable of observing the image information with a good image quality in a wide observation field of view by appropriately setting the configuration of the optical means.

[0007]

According to the present invention, there is provided an image observation optical system comprising: (1-1) three or more optical surfaces including a decentered curved surface of a light beam from a display means for displaying image information; In an image observation optical system for guiding image information displayed on the display means by guiding light to the observer side through an optical means composed of one medium, the optical means has a different refractive power depending on an azimuth angle around a surface vertex. It has two or more optical surfaces, and satisfies the following condition: 1.52 <Nd vd <57 when the refractive index and Abbe number of the medium are Nd and vd, respectively.

(1-2) It has three or more optical surfaces including a reflection curved surface decentering a light beam from a display means for displaying image information, and is directed to an observer side through an optical means composed of a single medium. In an image observation optical system which guides light and observes image information displayed on the display means, a local refractive power on a local meridional section of the reflecting surface is weaker than a local refractive power on a local spherical section, and Refractive index and Abbe number are each N
When d and vd, the condition 1.52 <Nd vd <57 is satisfied.

In particular, in the constitution (1-1) or (1-2), (1-2-1) the optical means has a plurality of reflection curved surfaces.

(1-2-2) One optical surface of the optical means has both a transmitting action and a total reflecting action and has a curvature. And so on.

(1-3) A light beam from a display means for displaying image information is transmitted to an observer through an optical means having three or more optical surfaces including two or more reflection curved surfaces and comprising a single medium. In an image observation optical system that guides light to the side and observes image information displayed on the display means, when the refractive index and Abbe number of the medium are Nd and νd, respectively, the condition 1.52 <Ndνd <57 is satisfied. It is characterized by satisfaction.

(1-4) An optical system having three or more optical surfaces including curved surfaces having both a transmitting function and a total reflecting function for transmitting a light beam from a display means displaying image information and comprising a single medium. 1.52 <Nd in an image observation optical system for guiding image information displayed on the display means by guiding light to the observer side through the means, where the refractive index and Abbe number of the medium are Nd and νd, respectively. νd <57 is satisfied.

In particular, in the configurations (1-1) to (1-4), (1-4-
1) The refractive index Nd of the medium is set to 1.54 <Nd.

The optical element of the present invention has: (2-1) three or more optical surfaces including an eccentric curved surface,
An optical element composed of a single medium, comprising two or more optical surfaces having different refractive powers depending on the azimuth angle around the surface apex of the optical surface, wherein the refractive power and Abbe number of the medium are respectively Nd,
When νd is satisfied, the condition 1.52 <Nd νd <57 is satisfied.

(2-2) An optical element having three or more optical surfaces including an eccentric reflection curved surface and comprising a single medium, wherein the local refractive power of the reflection surface on a local meridional section is It is weaker than the local refractive power on the local spherical section, and satisfies the condition 1.52 <Ndνd <57 when the refractive power and Abbe number of the medium are Nd and νd, respectively.

(2-3) An optical element having three or more optical surfaces including two or more reflection curved surfaces and constituted by a single medium, wherein the refractive power and Abbe number of the medium are determined. Nd,
When νd is satisfied, the condition 1.52 <Nd νd <57 is satisfied.

(2-4) An optical element having three or more optical surfaces including a curved surface having both a transmitting action and a total reflecting action and comprising a single medium, When the refractive power and the Abbe number are Nd and νd, respectively, the condition 1.52 <Nd νd <57 is satisfied.

[0018]

1 to 5 are sectional views (main meridional sectional view, azimuth angle of 0 degree, suffix y) of main parts of Numerical Examples 1 to 5 to be described later of the present invention. When the surface vertex coordinate system of the first surface is taken as shown in the figure, the YZ section represents a meridional section. The spherical section (the azimuth angle is 90 degrees and the suffix is x) is the xz section in the surface vertex coordinate system (based on the first surface vertex coordinate system) of each surface. Note that these are conventionally defined on the paraxial axis, and the local meridional section and the local spherical section on the local paraxial axis are as described below.

In FIG. 1, reference numeral 4 denotes display means for displaying image information such as characters and pictures as an original image, which is constituted by a known liquid crystal (LCD), for example. 3 is an optical means,
It is composed of a prism having a refractive power for guiding the light from the display means 4 toward the eyes 6 of the observer. Light from the display means 4 is incident on the incident surface 5 of the prism body 3, then is incident on the surface (total reflection surface) 1 at an angle equal to or greater than the critical angle, is totally reflected on the surface 1, and is reflected on the concave mirror 2. This time, the light enters the surface 1 at an angle equal to or smaller than the critical angle and passes through the surface 1. Thus, the light from the display means 4 that has entered the prism body 3 undergoes a refraction effect, exits the prism body 3, and is guided to the eye 6.

In this embodiment, the entrance surface 5 of the prism body 3
A free-form surface described later is used for the three surfaces of the total reflection surface 1 and the concave mirror 2, and the eccentric aberration is suppressed to be small. Also, by increasing the refractive index Nd of the material of the prism body 3, the critical angle condition of the total reflection surface 1 is relaxed, and the aberration correction is favorably performed. Further, the curvature of the total reflection surface is set so that the total reflection condition on the total reflection surface is satisfied with respect to the total effective light flux, thereby achieving an image observation apparatus having no light amount loss in principle. G is a field lens.

In this embodiment, the optical surfaces (5, 1, 2) of the optical means 3 are constituted by an eccentric system, and the radius of curvature, surface spacing, focal length, refractive power, etc. of each optical surface are appropriately defined, By deciding, the image information displayed on the display means 4 is favorably observed.

Next, before describing the structural features of the present embodiment, local curvature radius, local surface spacing, local focal length, local refractive power, etc., corresponding to the eccentric system applied to the optical system of the image observation apparatus. Is explained.

In the present invention, a central ray emitted from the center of the image of the display means 4 and incident on the center of the observation plane is used as a reference ray.
So-called local radius of curvature, local surface spacing, based on the hit point (incident point) of each surface of the reference light beam, instead of the conventional radius of curvature, surface spacing, focal length, and refractive power of each surface based on the vertex of each surface. The local focal length and local refractive power are used.

Here, the local radius of curvature refers to a local radius of curvature on the hit point point of the optical surface (a radius of curvature on a local meridional section, a radius of curvature on a local spherical section). The local plane interval refers to a value of a distance (distance on a reference ray) between two hit points between the current plane and the next plane. The local focal length is a value calculated by a conventional focal length calculation method (paraxial tracking) from the local radius of curvature, the refractive index before and after the surface, and the local surface interval. The local refractive power is a reciprocal value of the local focal length.

With such a definition, an effective numerical value corresponding to any eccentric system can be obtained. In each embodiment of the present invention, the conventional curvature radius, surface spacing, eccentricity, refractive index, Abbe number and local curvature radius, surface refractive index, local surface spacing, local focal length, etc. are shown for reference. I have. In addition, the surface including the incident light beam and the outgoing light beam on each surface in the reference light beam is a local meridional section of each surface (azimuth angle 0 degree, suffix is y), and the surface vertex coordinates including a hit point and perpendicular to the local meridian section A plane parallel to the xz section of the system is defined as a local sphere section of each plane (azimuth angle 90 degrees, suffix x).

Next, the configuration of the prism body 3 in the present embodiment will be described. The prism body 3 according to the present invention has a reduced focal length of the prism body in order to reduce the size. However, by increasing the refractive index of the material of the prism body, the shortage of the optical path length in the prism body is solved, The size of the prism body is reduced while the physical quantities such as the angle of view and the pupil diameter are sufficiently secured without the surface 4 entering the prism body 3.

[0027] For example, Japanese Patent Application Laid-Open No.
The volume is about 60% of that of the prism body disclosed in Japanese Patent No. 333551.

As one specific example of the present invention, a display means 4 for forming image information, an optical means 3 for guiding light from the display means 4 to the eye, and the optical means 3 are provided with an eccentric surface having a curvature. A prism body of a single medium including three or more different optical surfaces, wherein the prism body has two or more surfaces having different refractive powers depending on the azimuth angle around the surface vertex; The material is characterized in that the refractive index Nd (d line) and Abbe number νd (d line) satisfy Nd> 1.52 ‥‥‥ (1) νd <57 ‥‥‥ (2).

In the present invention, eccentric aberration occurs on a surface which is decentered and has a curvature, but decentering aberration is suppressed by a surface having different refractive power depending on the azimuth angle around the surface apex (hereinafter referred to as a "free-form surface").

However, if this free-form surface is one surface, the focal length of the meridional section of the optical system and the focal length of the spherical section are different from each other. Absent.

Therefore, by using two or more free-form surfaces, the magnification in the vertical and horizontal directions is set to be the same.
As for the conditional expression (1), if the value exceeds the expression (1), when the focal length of the prism body is to be shortened, the liquid crystal surface 4 enters the prism body 3 because the refractive index is too low.
Exceeding both formulas (1) and (2) is not preferable because the cost of the prism body increases because there is no appropriate plastic molding material.

In this embodiment, conditional expressions (1) and (2)
The optical means 3 is manufactured by molding a plastic material having a high refractive index satisfying the following.

As another specific example of the present invention, a display means 4 for forming image information, an optical means 3 for guiding light from the display means 4 to an eye, and the optical means 3 are eccentric and have a curvature. A single-medium prism including a reflecting surface and composed of three or more different optical surfaces, wherein the local refractive power of the reflecting surface on the local meridional section is weaker than the local refractive power on the local spherical section. , The refractive index Nd of the material of the prism body
(D line) and Abbe number νd (d line) satisfy Nd> 1.52 ‥‥‥ (3) νd <57 ‥‥‥ (4).

The conditional expressions (3) and (4) are the same as the conditional expressions (1) and (2). The decentered and curved reflecting surface is a free-form surface, and the local refractive power on the local meridional section is weaker than the local refractive power on the local spherical section. This is because the occurrence of eccentric aberration is greater in the local meridional section than in the local spherical section, so that the local refractive power on the local meridional section is weakened to suppress the occurrence of eccentric aberration in the local meridional section.

Further, as another specific example of the present invention, a display means 4 for forming image information, an optical means 3 for guiding light from the display means 4 to an eye, and the optical means 3 may be provided from three or more different optical surfaces. The prism body has a plurality of reflecting surfaces having a curvature, and the refractive index Nd (d-line) and Abbe number νd (d-line) of the material of the prism body are provided. Nd> 1.52 ‥‥‥ (5) νd <57 ‥‥‥ (6)

By providing the prism body with a reflecting surface having two or more curvatures, as shown in each embodiment of FIGS. 1 to 5, the light beam is folded so that the prism body 3 is made thinner and the prism body itself is made thin. Has the function of a lens so that unnecessary lenses can be removed. Conditional expression (5),
The condition (6) is the same as the conditional expressions (1) and (2).

Further, as another specific example of the present invention, a display means 4 for forming image information, an optical means 3 for guiding light from the display means 4 to the eye, and the optical means 3 is a single medium prism The prism body has a surface having a curvature having both a transmission action and a total reflection action, and the refractive index Nd (d-line) and Abbe number νd (d-line) of the material of the prism body are Nd> 1.52 ‥‥‥ (7) νd <57 ‥‥‥ (8)

In this method, a curved surface that satisfies the condition of total reflection or total reflection or transmission depending on the incident angle of the light beam is set for all the effective light beams. In this type, there is no see-through function to superimpose the image, and the outside world is not visible), there is no light amount loss in principle, and a bright LCD virtual image is obtained. Unnecessary lenses were removed by the curved surface, and unnecessary surfaces were removed by setting one surface having both transmission and total reflection. The conditional expressions (7) and (8) are the same as the conditional expressions (1) and (2).

The above-mentioned conditional expressions (1), (3), (5),
In (7), it is particularly desirable that Nd> 1.54 (9) is satisfied. In this case, the above-described effect becomes more remarkable.

Further, the Abbe number of the material of the prism body is ν
When d is satisfied, it is preferable that νd <35 ‥‥‥ (10). In this case, a more inexpensive mold material having a higher refractive index can be used for the prism body.

It is desirable that the light from the display means is incident on and transmitted through the prism body, reflected, and then travels in the order of reflection.
In this way, the light from the display means 4 can be immediately folded by the two reflecting surfaces 1 and 2, which is effective for making the prism body thin.

It is preferable that the reflecting surface having two curvatures have different sign powers such that one of them has a positive power and the other has a negative power. This cancels out aberrations and provides good optical performance. In particular, when the two reflecting surfaces are free-form surfaces, good optical performance can be obtained if the local refractive power on the spherical section has a different sign.

Next, other numerical conditional expressions will be described. When the local radius of curvature of the local meridional section is local-ry-m and the local radius of curvature of the local spherical section is local-rx-m on the reflecting surface of the free-form surface with the eccentricity of the prism body, | local-rx- m / local-ry-m | <0.9 ‥‥‥ (11)

If it exceeds this range, the occurrence of eccentric aberration becomes noticeable. Further, when the reflecting surface having the strongest local refractive power among the optical means for guiding the light of the display means to the eye is set so as to satisfy the above conditional expression, the occurrence of eccentric aberration is further suppressed.

On the local meridional section, the local focal length of the reflection surface having the strongest local refractive power among the optical means for guiding the light of the display means to the eye is defined as local-fy-s, and the local focus of the entire optical means is defined as local-fy-s. When the distance is set to local-fy-all, it is preferable to satisfy 0.4 <local-fy-s / local-fy-all <1.5 (12). If the lower limit of the expression (9) is exceeded, the power of the local meridional section of the reflecting surface becomes strong, and the occurrence of decentered astigmatism increases. If the upper limit is exceeded, the power will be loosened and the overall length will increase in the meridian direction and the size will increase.

On the local sphere lacking section, the local focal length of the reflecting surface having the strongest local refractive power among the optical means for guiding the light of the display means to the eye is defined as local-fx-s, When the focal length is set to local-fx-all, it is preferable to satisfy 0.2 <local-fx-s / local-fx-all <1.0 (13). When the value exceeds the lower limit of the expression (10), the power of the local spherical section of the reflecting surface becomes strong, and it becomes difficult to correct astigmatism. If the value exceeds the upper limit, the power becomes loose, and the optical system expands in the direction of the sphere lacking section, which is not good.

Next, Tables 1 to 5 show numerical data of Numerical Examples 1 to 5 of the present invention. In the conventional paraxial axes shown in Tables 1 to 5, the meridional section curvature radius ry, the spherical section curvature radius rx, and the surface interval d
(Parallel to the surface vertex coordinate system of the first surface) eccentricity (in the meridional section, the parallel eccentricity of the surface vertex of each surface with respect to the surface vertex coordinate system of the first surface is shifted, and the tilt eccentricity is tilt degrees) The d-line refractive index Nd and Abbe number νd · ZAL are free-form surface coefficients, AL
Indicates an aspheric coefficient. The surface with M is a reflection surface, and the refractive index Nd of the d-line has the opposite sign. AL
The definition of (aspheric) is

[0048]

(Equation 1) It is. Each of b _i and c _i非 is an aspheric coefficient. ZAL
The definition of (free-form surface) is

[0049]

(Equation 2) It is.

Each of c _1i and c _5iで is a free-form surface coefficient. (Note: In the case of a free-form surface, among free-form surface coefficients, there are coefficients related to the paraxial axis. The radius of curvature r y of the ry-sphere section cross section does not coincide with the radius of curvature r y of the meridional section at the vertex of the surface, and the point (0,0), ie, the radius of curvature r y of the meridional section at the vertex of the plane, The radius of curvature rx of the cross section is also shown.)

On the local paraxial side, the local curvature radius lo
cal-ry, local-rx, local surface interval local-d (reflection surface has reverse sign), local focal length local-fy, local-fx, surface refractive index nd (reflection surface has reverse sign). Also, the hit point coordinates (0,0 at the surface vertex) and the local focal length, F-number, and angle of view of each system are shown.

[0052]

[Table 1]

[0053]

[Table 2]

[0054]

[Table 3]

[0055]

[Table 4]

[0056]

[Table 5]

[0057]

According to the present invention, as described above, when observing the image information displayed on the display means such as a liquid crystal display in a wide observation visual field, the light flux from the display means is guided to the observer's eyeball. By appropriately setting the configuration of the optical means composed of a prism body having a refraction function, it is possible to reduce the size of the entire apparatus and observe the image information with a good image quality in a wide observation field. A system can be achieved.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of a first numerical embodiment of the present invention.

FIG. 2 is a sectional view of a main part of a second numerical embodiment of the present invention;

FIG. 3 is a sectional view of a main part of a third numerical embodiment of the present invention;

FIG. 4 is a sectional view of a main part of a numerical example 4 of the present invention.

FIG. 5 is a sectional view of a main part of a numerical example 5 of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Total reflection surface 2 Concave mirror 3 Optical means 4 Display means 5 Incident surface 6 eyes

Claims (11)

[Claims] 1. A light flux from a display means for displaying image information, which has three or more optical surfaces including a decentered curved surface, and is guided to the observer side through an optical means made of a single medium. In an image observation optical system for observing image information displayed on the display means, the optical means has two or more optical surfaces having different refractive powers depending on an azimuth angle around a surface vertex, and determines a refractive index and an Abbe number of the medium. An image observation optical system characterized by satisfying the following condition: Nd and νd, respectively. 2. A light beam from a display means for displaying image information, which has three or more optical surfaces including decentered reflection curved surfaces and is guided to the observer side through an optical means made of a single medium. In the image observation optical system for observing the image information displayed on the display means, the local refractive power on the local meridional section of the reflecting surface is weaker than the local refractive power on the local spherical section, and the refractive index of the medium and Abbe numbers are Nd,
An image observation optical system, which satisfies the following condition: νd: 1.52 <Nd νd <57. 3. An image observation optical system according to claim 1, wherein said optical means has a plurality of reflection curved surfaces. 4. An image observation optical system according to claim 3, wherein one optical surface of said optical means has both a transmitting action and a total reflecting action and has a curvature. 5. A light beam from a display means for displaying image information is guided to an observer via an optical means having three or more optical surfaces including two or more reflection curved surfaces and comprising a single medium. In an image observation optical system that observes image information displayed on the display means by light, when the refractive index and Abbe number of the medium are Nd and νd, respectively, the condition 1.52 <Nd νd <57 is satisfied. An image observation optical system characterized by the following. 6. A curved surface including a curved surface having both of a transmitting action and a total reflecting action for a light beam from a display means for displaying image information.
An image observation optical system that has at least one optical surface and guides the image information displayed on the display unit by guiding the light to the observer side through an optical unit composed of a single medium. An image observation optical system which satisfies a condition of 1.52 <Nd vd <57 when Abbe numbers are Nd and vd, respectively. 7. An image observation optical system according to claim 1, wherein said medium has a refractive index Nd of 1.54 <Nd. 8. An optical element having three or more optical surfaces including an eccentric curved surface and comprising a single medium, wherein an optical surface having a different refractive power depending on an azimuth angle around a surface vertex of the optical surface. An optical element, wherein when the refractive power and Abbe number of the medium are Nd and νd, respectively, the following condition is satisfied: 1.52 <Nd νd <57. 9. An optical element comprising three or more optical surfaces including an eccentric reflection curved surface and comprising a single medium, wherein the local refractive power on the local meridional section of the reflection surface is a local spherical aberration. An optical element which is weaker than a local refractive power on a cross section and satisfies a condition of 1.52 <Ndνd <57 when the refractive power and Abbe number of the medium are Nd and νd, respectively. 10. An optical element having three or more optical surfaces including two or more reflection curved surfaces and configured by a single medium, wherein the refractive power and Abbe number of the medium are Nd and Nd, respectively. ν
An optical element which satisfies a condition of 1.52 <Nd vd <57 when d is satisfied. 11. An optical element comprising three or more optical surfaces including a curved surface having both a transmitting action and a total reflecting action and comprising a single medium, wherein the refractive power of the medium is provided. An optical element satisfying the following condition: 1.52 <Nd vd <57, where Nb and Abd number are Nd and vd, respectively.