JPH07333551A - Observation optical system - Google Patents

Abstract

PURPOSE:To miniaturize and thin an observation optical system leading a beam of an original image to an eye ball of an observer through a reflection optical system by providing a curved surface having total reflection action in the reflection optical system. CONSTITUTION:An original image, a picture, or the like is displayed on a display means 4. A beam from the display means 4 is made incident on a first optical member 3a first of all, and is totally reflected by the total reflection surface 1 of the eye side of the first optical member 3a, and is reflected by a concave mirror 2 constituted of a half mirror facing a concave surface to the observer to be led to the eye after transmitting through the total reflection surface 1. Thus, the observer confirms the video of the display means 4 while superimposing on an outer scene. At this time, by imparting optical power to the concave mirror 2 by an azimuth angle in particular, eccentric aberration occurring due to the fact that the concave mirror 2 itself is eccentric is removed sufficiently. Further, the aberration occurring in the concave mirror 2 is also corrected by imparting the curved surface to the total reflection surface 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an observation optical system, and more particularly to an optical system suitable for a device called a head-up display or a glasses type display.

[0002]

2. Description of the Related Art Conventionally, some proposals have been made for a display device in which a CRT or LCD is placed near the head of an observer and an image formed by the CRT and LCD can be observed. For example, USP4081209 and USP4969
No. 724, JP-A-58-78116, JP-A-2-
There are 297516 and JP-A-3-101709.

Japanese Unexamined Patent Publication (Kokai) No. 3-101709 discloses a real image type comparatively easy-to-see observation device for re-imaging an original image. However, since the optical lens for re-imaging is used, it is inevitably made large in size.

On the other hand, USP4081209 and USP4
In Japanese Patent Publication No. 96972, Japanese Patent Laid-Open No. 58-78116, and Japanese Patent Laid-Open No. 2-297516, there is disclosed an observing device of a type for observing a virtual image which is slightly inferior in viewability but is advantageous for downsizing. .

[0005]

The latter type of observing device can certainly be downsized as compared with the real image type, but it is still not sufficient. Japanese Patent Laid-Open No. 58-78 discloses an example of the prior art which is relatively small.
No. 116 is cited, but the thickness of the eye in the direction of the optical axis is still thick. Moreover, it is described that optical distortion, astigmatism, coma, etc. occur in an observed image.

In view of the above points, the present invention has an object to provide a small and thin observation optical system.

It is another object of the present invention to provide an observation optical system with less aberration.

With respect to such an object, the feature of the present invention resides in that in the observation optical system for guiding the original image to the eyeball of the observer through the reflection optical system, in the reflection optical system, the whole image is provided. In a viewing optical system that has a curved surface that acts as a reflection, or in the observation optical system that guides the light of the original image to the eyeball, the light is totally reflected in the direction away from the eyeball by the curved surface, and the totally reflected light is reflected by the eyeball. In the observation optical system that reflects the light to the side and transmits the curved surface to guide the light to the eyeball, or in the observation optical system that guides the light of the original image to the eyeball, the total reflection surface that totally reflects the light and the optical angle azimuth The feature is that the light is guided to the eyeball through the reflecting surfaces having different powers.

Other characteristic matters are disclosed in the following embodiments.

[0010]

EXAMPLE First, a display optical system which is the basis of the present invention will be described with reference to FIG. Reference numeral 4 is a display unit for displaying an image such as characters and pictures as an original image, and is composed of, for example, a known liquid crystal (LCD). 3a is a first optical member for guiding the light from the display means 1 to the observer's eyes,
Reference numeral 3b is a second optical member. The light from the display means 4 first enters the first optical member 3a, and then is totally reflected by the total reflection surface 1 on the eye side of the first optical member, and the concave surface of the observer composed of a half mirror is directed. The light is reflected by the concave mirror 2 and transmitted through the total reflection surface 2a to be guided to the eye.

This state is shown in FIG. FIG. 1A shows an optical path as seen from the head, and FIG.

In this way, the observer can confirm the image on the display means 4 by superimposing it on the outside scenery. In the present embodiment, the device is shown as a superimposing device, but it may be a device that merely sees a video display. At this time, the concave mirror becomes a mirror.

In the present embodiment, including the embodiments described later, an extremely thin compact display device having an optical system thickness of about 10 mm to 15 mm is achieved under such a structure. In addition, the field of view angle is ± 16.8 ° in the horizontal direction and ± 11.4 ° in the vertical direction.
It has achieved a wide field of view.

As a factor of such miniaturization, wide angle, and good optical performance, in this embodiment, the surface on the observer side was used as a total reflection surface and a transmission surface, and a concave surface was used. The mirror 2b may be considerably decentered with respect to the optical axis of the eye. In addition to this, the total reflection surface is a curved surface, particularly a curved surface having different optical power depending on the azimuth angle, as shown in a numerical example described later. That is, or each element of giving optical power to the concave mirror 2 by the azimuth angle greatly contributes.

In particular, the optical power is given to the concave mirror 2 by the azimuth angle, so that it is possible to sufficiently remove the eccentric aberration caused by the eccentricity of the concave mirror itself. Similarly, the total reflection surface is also given a curved surface to correct the aberration generated by the concave mirror.

Now, hereinafter, the folding direction of light will be referred to as the generatrix direction, and the direction orthogonal thereto will be referred to as the sagittal direction.
In this embodiment, the angle of view in the sagittal direction is set to be wide, but the concave mirror has a relatively strong positive refractive power, which causes aberration. However, the aberration generated by this positive power On the contrary, in the sagittal cross section of the total reflection surface, negative optical power is given to the contrary to correct it.
Especially when viewed from the sagittal section, when the optical path is traced from the display element side or the observer's eye side, the negative refractive power, the positive refractive power (concave mirror), and the negative refractive power and the respective surfaces act in order. As a result, the target type refractive power arrangement is adopted, and a power arrangement that easily removes various aberrations is adopted.

In order to reduce the thickness of the eye in the optical axis direction, it is desirable to set each element so that the optical system 3 stands up. Specifically, referring to FIG. When the angle (tilt angle) of the tangent line at the apex to the line perpendicular to the optical axis of the eye is α, it is preferable to satisfy | α | ≦ 20 °. If it exceeds this range, the thickness in the optical axis direction becomes thick and the size becomes large. Further, when the image is superimposed on the landscape, the inclination of the optical member becomes large and the landscape itself is distorted, which is not preferable.

More preferably, -15 ° ≤α≤5 ° is satisfied. Beyond the lower limit, the thickness can be reduced in the direction parallel to the optical axis of the eyeball, but the distortion becomes large. If the upper limit is exceeded, the thickness of the eyeball in the direction parallel to the optical axis becomes large, and the total weight of the prism becomes heavy, which is not preferable.

In this embodiment, since the total reflection surface is a concave surface facing the eyeball side, the outer light incident surface 6 is also provided with a curved surface having substantially the same shape so that the landscape is not distorted. .

Next, the concave mirror 2 is considerably decentered with respect to the optical axis of the eye, and decentering aberration occurs on this surface. However, in order to eliminate this eccentric aberration, a surface (a toric surface or an anamorphic surface) having a different curvature depending on the azimuth angle is adopted as the concave mirror 2 as described above, and the decentering aberration is effectively suppressed. is doing. Desirably, an aspherical surface (a toric aspherical surface or an anamorphic aspherical surface) is used for these surfaces to obtain extremely good optical performance.

When the folding direction of the light rays is the generatrix direction (y direction) and the direction perpendicular thereto is the sagittal direction (x direction), each surface is set so that the optical power is made different due to the difference in azimuth angle. However, the paraxial focal lengths in each direction are almost constant when viewed as an entire system, that is, the paraxial focal lengths in each system in the generatrix section and the sagittal section are f _y and f _x , respectively. It is desirable to satisfy 0.9 <| f _y / f _x | <1.1 at that time.

Further, the total reflection surface (or the transmission surface) or the concave mirror is set to have different optical powers due to the difference of the azimuth angle as described above to suppress the decentering aberration. cross section, and each r _y paraxial radius of curvature in the sagittal cross section, when the r _x | r _x | <| better to satisfy the | r _y.

In this embodiment, the generatrix direction is the folding direction,
Since the concave mirror 2 is largely tilted (decentered) in this direction in order to reduce the size, more decentering aberration occurs in this generatrix direction than in the sagittal direction. On the other hand, the optical power in the cross section in the generatrix direction is weaker than the power in the cross section in the sagittal direction, that is, the paraxial radius of curvature in the generatrix direction is increased as shown in the conditional expression to suppress the occurrence of eccentric aberration in the generatrix direction. I have to.

It is desirable to set the relationship of these curvatures so as to satisfy | r _x / r _y | <0.85. If this range is exceeded, decentration aberrations will be noticeably increased.

As in Numerical Examples 2 to 4 described later, when a surface having different optical power due to the difference in azimuth angle is formed on the entrance surface 5, the condition | r _x |> | By satisfying the conditional expression r _y |, it becomes possible to suppress the occurrence of decentration aberrations.

In order to satisfactorily correct the aberration, the paraxial radius of curvature of each of the total reflection surface (or transmission surface) 1 and the concave mirror 2 in the sagittal direction is r _x2 , r _x3.
When a, it may be set in a range of _{-2.0 <2f x / r x2 <} -0.1 ... (a) -2.5 <2f x / r x3 <-0.5 ... (b) The condition .

When the value goes below the lower limit of the expression (a), the curvature (negative power) of the total reflection surface in the sagittal direction becomes so tight that it becomes difficult to correct distortion. If the lower limit of the expression (b) is exceeded, the curvature (positive power) of the concave mirror in the sagittal direction becomes so tight that it becomes difficult to correct astigmatism. On the other hand, since the curvature of the total reflection surface in the sagittal direction that exceeds the upper limit of the expression (a) has a positive power, it becomes difficult to satisfy the total reflection condition. on the other hand,
If the value exceeds the upper limit of the expression (b), the positive power of the concave mirror in the sagittal direction becomes weak, and the thickness in the direction parallel to the optical axis of the eyeball becomes large, which is not preferable.

Further, the focal length of the entire system in the direction of the generatrix is f _y ,
Let r _{y2 be} the radius of curvature of the total reflection surface, and r be the radius of curvature of the concave mirror.
when the _{y3 -1.0 <2f y / r y2} <0 ... (c) -2.5 <2f y / r y3 < may be set so as to satisfy the -0.2 ... (d).

When the value goes below the lower limit of the equation (c), the negative power of the total reflection surface in the generatrix direction becomes strong, and it becomes difficult to correct the eccentric distortion. When the value goes below the lower limit of the equation (d), the convex power of the concave mirror in the generatrix direction becomes strong, and the decentering astigmatism increases. If the upper limit of the expression (c) is exceeded, the condition of total reflection in the generatrix direction is involved, and if it exceeds this, it becomes difficult to satisfy the condition of total reflection. The formula (d) relates to the power of the concave-convex mirror in the generatrix direction. When the upper limit is exceeded, the power becomes weak, so that the overall length tends to increase in the generatrix direction and the size tends to increase.

The above explanation is for a total reflection surface (or a transmission surface).
1 and the concave mirror 2 was described centering on the curvature, but in the present embodiment, the concave mirror 2 is decentered parallel to the original image side (+) in the generatrix direction (y direction) from the optical axis of the eyeball (see FIG. 7). By doing so, the eccentric distortion in the generatrix direction is also suppressed to a small level.

The shift amount of the parallel eccentricity (from the optical axis of the eyeball,
If the distance in the generatrix direction to the surface apex of the concave mirror is E (see FIG. 7), it is possible to suppress the eccentric distortion by performing parallel eccentricity so as to satisfy E ≧ 2.5 mm. In Example 1 to be described later, the value of the eccentricity amount E is 5.2 mm, but it is possible to perform better aberration correction by increasing the amount E as in other examples. Therefore, it is more preferable that E ≧ 23 mm.

Next, focusing on the incident surface 5, the description will be made with reference to FIG.
As shown in, the angle β formed by the original image plane, which is the display means in the direction of the generatrix, and the incident plane is preferably set to satisfy 5 ° ≦ β ≦ 30 °. When the value goes below the lower limit, the plane of incidence and the original image surface become nearly parallel, which is not preferable because the original image becomes thick in the direction parallel to the optical axis of the eyeball. On the contrary, if the upper limit is exceeded, the original image becomes perpendicular to the direction parallel to the optical axis of the eyeball.

In this embodiment, although not shown in the figure for illuminating the original image, it is assumed that a backlight or direct natural light illumination is used. Here, if the original image is perpendicular to the optical axis as described above, it becomes difficult to efficiently obtain natural light when considering direct natural light illumination, and the image of the virtual image obtained by the reflection optical system becomes dark. turn into. Therefore, in this embodiment, natural light illumination is used during daytime when natural light is strong, and backlight illumination and outside brightness are detected at night when there is no natural light to selectively use natural light illumination and backlight illumination.

By the way, the liquid crystal display element (LCD) is used for the display means 4 on which the original image is formed, so that the size of the entire apparatus is reduced. At this time, the optical axis of the image center of the original image and the original image are used. It is preferable that the angle γ (see FIG. 7) formed by the principal ray of the emitted light (the central light flux when the eyeball is used as the diaphragm) that satisfies | γ | ≦ 10 ° is satisfied. This is a necessary condition when using the liquid crystal device for the original image plane. Since liquid crystal generally has a narrow viewing angle, light that obliquely enters and exits the liquid crystal disappears. Therefore, a bright virtual image cannot be obtained unless the light is incident and emitted perpendicularly to the liquid crystal surface. Therefore, a sufficiently bright image can be observed by satisfying this conditional expression.

2, FIG. 3, FIG. 4, and FIG. 5 are optical sectional views of Numerical Examples 1, 2, 3, and 4 shown below, respectively. In FIG. 2, a toric aspherical surface is used for both the concave mirror and the total reflection surface. 3 shows a concave mirror, a total reflection surface,
Anamorphic aspherical surfaces are used for all light incident surfaces.
4 and 5, anamorphic aspherical surfaces are used for all surfaces.

Numerical examples 2 to 2 corresponding to FIGS.
In No. 4, the entrance surface 5 also has a curvature in order to achieve better aberration correction.

Although acrylic is used as the optical member in this embodiment, it goes without saying that a glass material may be used.

Next, the numerical values of the examples of the present invention are shown below. TAL is a toric aspherical surface, and AAL is an anamorphic aspherical surface.

The definition formula of TAL is

[0040]

[Outer 1] The definition formula of AAL is

[0041]

[Outside 2] Is.

Each A _i , B _i ... Is an aspherical surface coefficient.

In the embodiments described below, at least a total reflection surface has a surface having a different refractive power depending on the azimuth angle. However, this surface may be formed as a rotationally symmetric spherical surface or an aspherical surface.

[0044]

[Outside 3]

[0045]

[Outside 4]

[0046]

[Outside 5]

[0047]

[Outside 6]

[0048]

As described above, according to the present invention,
Horizontal angle of view ± 16.8 °, vertical angle of view ± 11.4 ° and wide field of view (high magnification), approximately 1 in the direction parallel to the optical axis of the eyeball.
We were able to develop a very thin glasses-type display of 0 mm to 15 mm. Moreover, bright and good optical performance can be obtained. Further, by using the concave mirror as a semi-transmissive surface, it is possible to superimpose a virtual image of a bright original image on the landscape without distorting the landscape.

Further, although the wide viewing angle of view of the present invention is set, if the narrow viewing angle of view is set a little and the present invention is used, the thickness can be made thinner. This is because the thickness of the present invention is determined by the wide angle of view.

[Brief description of drawings]

FIG. 1 is a diagram showing an optical path in an observation optical system according to the present invention.

FIG. 2 is a diagram showing a cross section and an optical path in an observation optical system of Numerical Example 1 according to the present invention.

FIG. 3 is a diagram showing a cross section and an optical path in an observation optical system of Numerical Example 2 according to the present invention.

FIG. 4 is a diagram showing a cross section and an optical path in an observation optical system of Numerical Example 3 according to the present invention.

FIG. 5 is a diagram showing a cross section and an optical path in an observation optical system of Numerical Example 4 according to the present invention.

FIG. 6 is an optical sectional view which is a basis of an observation optical system according to the present invention.

FIG. 7 is an optical sectional view which is a basis of an observation optical system according to the present invention.

[Explanation of symbols]

 1 total reflection surface (or transmission surface) 2 concave mirror 5 incidence surface 4 display means for forming an original image

Claims (13)

[Claims] 1. An observation optical system for guiding light to an eyeball of an observer through a reflection optical system, wherein the reflection optical system has a curved surface for total reflection. 2. The observation device according to claim 1, wherein the curved surface is located immediately in front of the eyeball. 3. The observation apparatus according to claim 1, wherein the curved surface has a negative refractive power in a sagittal section. 4. The observation apparatus according to claim 1, wherein the curved surface is a surface having different optical power depending on the azimuth angle. 5. An observation optical system for guiding light of an original image to an eyeball, wherein the light is totally reflected by a curved surface in a direction away from the eyeball, and the totally reflected light is reflected by an reflecting surface toward the eyeball side. An observation optical system that guides light to the eyeball through a curved surface. 6. The observing optical system according to claim 5, wherein an expression of | α | ≦ 20 ° is satisfied, where α is an angle of a tangent line at the apex of the curved surface with respect to a line perpendicular to the optical axis of the eye. system. 7. The observation optical system according to claim 5, wherein the curved surface has a negative refractive power. 8. The observation optical system according to claim 5, wherein the curved surface has a different optical power depending on the azimuth angle. 9. The observation optical system according to claim 5, wherein the reflecting surface has a different optical power depending on the azimuth angle. 10. An observation optical system for guiding light of an original image to an eyeball, wherein light is guided to the eyeball through a total reflection surface for totally reflecting the light and a reflection surface having different optical power depending on an azimuth angle. Observing optical system. 11. The expression: αα ≦ 20 ° is satisfied, where α is an angle of a tangent line at the apex of the total reflection surface with respect to a line perpendicular to the optical axis of the eye. Observation optics. 12. The observation optical system according to claim 10, wherein the total reflection surface has a negative refractive power in a sagittal section. 13. The reflection surface is a curved surface having different optical power depending on the azimuth angle.
0 observation optical system.