JP3406958B2 - Observation device - Google Patents

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 a device called a head-up display or a glasses type display and an optical system suitable for the device.

[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
No. 969724, JP-58-78116 discloses, although slightly inferior in terms of visibility in JP-A 2-297516 JP discloses a type of the observation apparatus for observing a favorable virtual image in reducing the size .

[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 and an observation apparatus using the same.

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

For such a purpose, the observation apparatus of the present invention is a display means for forming an original image, a first surface for transmitting the light of the original image, and a light for transmitting the first surface. And a second surface that is a curved surface that totally reflects
And a third surface that reflects the light totally reflected by the surface, and has an observation optical system that forms the first to third surfaces as different surfaces of the prism, and is reflected by the third surface. An observation device that guides the emitted light to the eyeball through the second surface ,
The first surface and the third surface have azimuth angles, respectively.
It is a curved surface with different optical power, and the third surface
The paraxial radius of curvature in the cross section of the generatrix is r _y ,
When the paraxial radius of curvature is r _x , the condition is | r _x | <| r _y | .

Other characteristic matters are disclosed in the following embodiments.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION 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 means for displaying an image such as an original image of characters and pictures.
For example, it is composed of a known liquid crystal (LCD). 3a is a display
The first optical member 3b for guiding the light from the means 4 to the observer's eyes 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 2 may be considerably decentered with respect to the optical axis of the eyes. 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 different optical power to the concave mirror 2 depending on the azimuth angle greatly contributes.

Especially, the concave mirror 2 varies depending on the azimuth angle.
By applying such optical power, it becomes possible to sufficiently remove the decentering aberration caused by the decentering 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, a symmetrical power distribution is adopted, and a power layout 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, it is preferable to satisfy -15 ° ≤α≤5 °. 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, all in order to get rid of this eccentric aberration
As described above, a surface (toric surface or anamorphic surface) having a different curvature depending on the azimuth angle is adopted as the reflecting surface and the concave mirror 2 so as to suppress these decentering aberrations favorably. 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. It is advisable to satisfy | r _x | <| r _y | when the paraxial radii of curvature in the directional section and the paraxial radius of curvature in the sagittal section are r _y and r _x , respectively.

In this embodiment, the generatrix direction is the folding direction,
Since the concave mirror 2 is largely tilted (decentered) in this direction for downsizing , 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 preferable 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.

When numerical values 2 to 4 shown later are used to form a surface having different optical powers on the entrance surface 5 due to the difference in azimuth angle, 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 mirror in the generatrix direction, and the power becomes weaker when the upper limit is exceeded, so that the total 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 between the original image plane, which is the display means in the direction of the generatrix, and the incident plane is preferably set so as 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. 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) to satisfy | γ | ≦ 10 °. 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 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 an extremely thin glasses-type display of 0 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.

In the present invention, the wide viewing angle is set,
If the present invention is used with a slightly narrower field angle of view, 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 incident surface 4 Display means to form original image

Front page continued (58) Fields surveyed (Int.Cl. ⁷ , DB name) G02B 27/02 H04N 5/64

Claims (14)

(57) [Claims] 1. Display means for forming an original image,
A first surface that transmits the light of the original image, and a second surface that is a curved surface that totally reflects the light that transmits the first surface,
A third surface that reflects the light totally reflected by the second surface, and an observation optical system that forms the first to third surfaces as different surfaces of a prism, and the third surface An observation device that guides the light reflected by the eye through the second surface to the eyeball.
The first surface and the third surface are azimuths, respectively.
The curved surface having different optical power depending on the angle,
Paraxial curvature radius r _y, sagittal section in the meridional cross section of the surface
When the _{r x} paraxial radius of _{curvature, | r x | <| r} y | observation apparatus characterized by satisfying the condition that. 2. The observation device according to claim 1, wherein the second surface has a negative optical power in a sagittal section. 3. The observation device according to claim 1, wherein the third surface is a concave mirror surface, and the second surface has a negative optical power in a sagittal section. 4. The observation device according to claim 1, wherein when the observation optical system is viewed as a whole system, the paraxial focal length in each direction is almost constant. 5. The second surface is a curved surface having different optical power depending on the azimuth angle.
Observation device. 6. The observation device according to claim 1, wherein the second surface is immediately in front of the eyeball. 7. When the angle of the tangent at the surface vertex of the second surface with respect to the line perpendicular to the optical axis of the eye is α, then | α |
The observing device according to claim 1, wherein the expression ≦ 20 ° is satisfied. 8. The thickness of the observation optical system is from 10 mm to 15 mm.
The observation device according to claim 1, wherein the observation device is a spectacle type of mm. 9. The observation device according to claim 1, wherein the third surface is a light incident surface of an outside landscape. 10. The observation device according to claim 1, wherein external light is detected to illuminate the original image, and natural light illumination and backlight illumination are selectively used. 11. The observation device according to claim 1, wherein the original image and the first surface are not parallel to each other. 12. When the angle formed by the original image and the first surface in the generatrix cross section is β, 5 ° ≦ β ≦
The observation apparatus according to claim 1, wherein the expression of 30 ° is satisfied. 13. A paraxial line in a generatrix cross section of the third surface.
The observing apparatus according to claim 1, wherein the radius of curvature r _y and the paraxial radius of curvature r _x in the sagittal section satisfy the condition of | r _x / r _y | <0.85.
Place 14. A paraxial line in a cross section of a generatrix of the first surface.
The radius of curvature is r _y , and the paraxial radius of curvature in the sagittal section is r _x
When _{the, | r x |> | r} y | observation instrumentation claim 1, characterized by satisfying the following condition
Place