JP2911750B2 - Observation optical system - 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 an optical system suitable for an apparatus called a head-up display or a glasses-type display.

[0002]

2. Description of the Related Art There have been proposed some display devices in which a CRT or an LCD is arranged near the head of an observer so that an image formed by the CRT or the LCD can be observed. For example, USP4081209, USP4969
724, JP-A-58-78116, JP-A-2-
297516 and JP-A-3-101709.

Japanese Unexamined Patent Publication (Kokai) No. 3-101709 discloses a relatively easy-to-see observation device of the real image type for re-forming an original image. However, the use of an optical lens for re-imaging requires a considerable increase in size.

[0004] On the other hand, USP4081209 and USP4
969724 , JP-A-58-78116, and JP-A-2-297516 disclose an observation apparatus of a type that observes a virtual image which is slightly inferior in viewability but is advantageous for miniaturization. .

[0005]

Problems to be Solved by the Invention Observation devices of the latter type can certainly be made smaller than those of the real image type, but they are still not enough. Japanese Patent Application Laid-Open (JP-A) No. 58-78 discloses an example of the prior art in which the size is relatively reduced.
No. 116, the thickness of the eye in the optical axis direction is also increased. It also describes that an observed image has optical distortion, astigmatism, coma, and the like.

SUMMARY OF THE INVENTION In view of the foregoing, it is an object of the present invention 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 occurrence of aberration.

[0008] Under such a purpose, the present invention provides
In the observation optical system that guides the light of the original image to the eyeball,
In the road, a first curved surface that totally reflects light, and the first curved surface
A second curved surface for reflecting the reflected light;
It is characterized by having an optical path transmitting through a curved surface.

Other features are disclosed in the embodiments described below.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a display optical system which is the basis of the present invention will be described with reference to FIG. Reference numeral 4 denotes display means for displaying an image such as a character or a picture serving as an original image, and is constituted by, for example, a known liquid crystal (LCD). 3a is a first optical member for guiding the light from the display means 4 to the eyes of the observer,
3b is a second optical member. The light from the display means 4 first enters the first optical member 3a, and is then totally reflected by the total reflection surface 1 on the eye side of the first optical member, and turns to the observer concave surface constituted by a half mirror. The light is reflected by the concave mirror 2, passes through the total reflection surface 2a, and is guided to the eyes.

FIG. 1 shows this state. FIG. 1A shows an optical path diagram viewed from the head, and FIG. 1B shows an optical path diagram viewed from the temporal region.

In this way, the observer can check the image on the display means 4 by superimposing it on the outside scenery. In this embodiment, the apparatus is shown as a superimpose apparatus, but it may be an apparatus which merely looks at a video display. At this time, the concave mirror becomes a mirror.

In this embodiment, including the embodiments described later, under such a configuration, an extremely thin and small display device having an optical system thickness of about 10 mm to 15 mm is achieved. The viewing angle of view is about ± 16.8 ° in the horizontal direction and ± 11.4 ° in the vertical direction.
And a wide-angle field of view.

In the present embodiment, the surface on the observer side is used as a total reflection surface and a transmission surface, and the concave surface is used. Although the mirror 2 is considerably decentered with respect to the optical axis of the eye, in addition to this, the total reflection surface is formed as a curved surface, particularly a curved surface having a different optical power depending on the azimuth angle, as shown in numerical examples described later. That is, or each factor of giving different optical power to the concave mirror 2 depending on the azimuth angle greatly contributes.

[0015] In particular, different by the azimuth angle to the concave mirror 2
By applying a certain optical power, it becomes possible to sufficiently remove the eccentric aberration caused by the decentering of the concave mirror itself. In addition, similarly, the total reflection surface is provided with a curved surface to correct the aberration generated by the concave mirror.

Now, the direction in which light is folded 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 and an aberration occurs. On the other hand, a negative optical power is applied to the sagittal section of the total reflection surface to correct this.
In particular, 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), the negative refractive power, and the respective surfaces in that order act as follows Therefore, a symmetrical 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 with respect to the optical axis direction, it is desirable to set each element so that the optical system 3 is set up. Specifically, referring to FIG. When an angle (tilt angle) of a tangent line at the vertex with respect to a line perpendicular to the optical axis of the eye is α, | α | ≦ 20 ° may be satisfied. Exceeding this range will increase the thickness in the optical axis direction and increase the size. In addition, superimposing a video on a landscape is not preferable because the inclination of the optical member becomes large and the landscape itself is distorted.

It is more preferable that -15 ° ≦ α ≦ 5 ° is satisfied. If the lower limit is exceeded, the thickness can be reduced in the direction parallel to the optical axis of the eyeball, but the distortion increases. If the upper limit is exceeded, the thickness of the eyeball in the direction parallel to the optical axis increases, and the total weight of the prism increases, which is not preferable.

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

Next, the concave mirror 2 is considerably decentered with respect to the optical axis of the eye, and decentered aberration occurs on this surface. However, in order to eliminate this eccentric aberration, the concave mirror 2 is devised so that the concave mirror 2 has a surface (toric surface or anamorphic surface) having a different curvature depending on the azimuth angle as described above so as to suppress these eccentric aberrations well. 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 beam 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 differs depending on the difference of the azimuth angle. While being so, the focal length is almost constant in the paraxial for each direction when viewed as a whole system, i.e. the generatrix cross section and the paraxial focal length of each entire system at sagittal cross section f _y, and f _x In this case, it is desirable to satisfy the following condition: 0.9 <| f _y / f _x | <1.1.

Further, as described above, the total reflection surface (or transmission surface) or the concave mirror is set so that the optical power is different due to the difference of the azimuth angle so as to suppress the eccentric aberration. cross section, and each r _y a paraxial curvature radius 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 (eccentric) in this direction in order to reduce the size , more eccentric aberration occurs in the generatrix direction than in the sagittal direction. On the other hand, the optical power in the cross section in the meridional direction is weaker than the power in the cross section in the sagittal direction, that is, the paraxial radius of curvature in the meridional direction is made longer as shown by the conditional expression so as to suppress the occurrence of eccentric aberration in the meridional direction. I have to.

Preferably, the relationship between these curvatures is set so as to satisfy | r _x / r _y | <0.85. Beyond this range, the occurrence of decentering aberrations will increase significantly.

When a surface having a different optical power due to a difference in the azimuth angle is formed on the incident surface 5 as in Numerical Examples 2 to 4 to be described later, | r _x |> | By satisfying the condition of r _y |, it is possible to suppress the occurrence of decentering aberration.

In order to better correct aberrations, the paraxial radii of curvature of the total reflection surface (or transmission surface) 1 and the concave mirror 2 in the sagittal direction are r _x2 and 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 .

If the lower limit of the equation (a) is exceeded, the curvature (negative power) of the total reflection surface in the sagittal direction becomes tight, and 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 too steep, making it difficult to correct astigmatism. On the other hand, since the curvature of the total reflection surface in the sagittal direction exceeding the upper limit of the expression (a) becomes a direction having a positive power, it becomes difficult to satisfy the total reflection condition. on the other hand,
Exceeding the upper limit of the expression (b) is not preferable because the thickness of the concave mirror in the direction parallel to the optical axis of the eyeball increases in the direction in which the positive power of the concave mirror in the sagittal direction decreases.

Further, the total focal length in the generatrix direction is f _y ,
The radius of curvature of the total reflection surface is r _y2 , and the radius of curvature of the concave mirror is r
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).

If the lower limit of the expression (c) is exceeded, the negative power of the total reflection surface in the generatrix direction becomes strong, and it becomes difficult to correct the eccentric distortion. If the lower limit of the equation (d) is exceeded, the convex power of the concave mirror in the generatrix direction becomes strong, and the occurrence of decentered astigmatism increases. If the value exceeds the upper limit of the expression (c), the condition of total reflection in the generatrix direction is involved. If the value exceeds this value, it becomes difficult to satisfy the condition of total reflection. Equation (d) relates to the power of the concave mirror in the generatrix direction. If the power exceeds the upper limit, the power becomes weaker, so that the overall length tends to extend in the generatrix direction and increase in size.

The above description is based on the total reflection surface (or transmission surface).
1, the concave mirror 2 has been described centered on the curvature. In this embodiment, the concave mirror 2 is parallel decentered from the optical axis of the eyeball toward the original image (+) in the generatrix direction (y direction) (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,
Assuming that E is the distance in the generatrix direction to the surface vertex of the concave mirror (see FIG. 7), the eccentric distortion can be suppressed by performing parallel eccentricity so as to satisfy E ≧ 2.5 mm. In the first embodiment described later, the value of the eccentricity E is 5.2 mm. However, by increasing the amount E as in the other embodiments, it is possible to perform better aberration correction. It is more preferable that E ≧ 23 mm.

Next, focusing on the incident surface 5, FIG.
As shown in the figure, the angle β between the original image plane, which is the display means in the direction of the generatrix, and the incident plane may be set so as to satisfy 5 ° ≦ β ≦ 30 °. When the value is below the lower limit, the plane of incidence and the original image surface become nearly parallel, and the original image becomes thick in a direction parallel to the optical axis of the eyeball, which is not preferable. Conversely, if the upper limit is exceeded, the original image becomes perpendicular to the direction parallel to the optical axis of the eyeball.

In the present embodiment, although not shown in the figures for illuminating the original image, it is assumed that a backlight or direct natural light illumination is used. Here, when the original image is perpendicular to the optical axis as described above, when direct natural light illumination is considered, natural light cannot be efficiently obtained by all means, and the image of the virtual image obtained by the reflection optical system becomes dark. turn into. Therefore, in the present embodiment, natural light illumination is used in daytime when natural light is strong, and backlight illumination and outside brightness are detected in nighttime when there is no natural light, and natural light illumination and backlight illumination are selectively used.

By using a liquid crystal display device (LCD) as the display means 4 on which the original image is formed, the entire apparatus is reduced in size. Γ (see FIG. 7) preferably satisfies | γ | ≦ 10 °. This is a necessary condition when using the liquid crystal device for the original image surface. In general, the viewing angle of a liquid crystal is narrow, so that light obliquely incident on the liquid crystal and being emitted disappears. Therefore, a bright virtual image cannot be obtained unless light is made to enter and exit the liquid crystal surface as perpendicularly as possible. Therefore, by satisfying this conditional expression, a sufficiently bright image can be observed.

FIGS. 2, 3, 4, and 5 show optical sectional views of Numerical Examples 1, 2, 3, and 4, respectively. In FIG. 2, a toric aspherical surface is used for both the concave mirror and the total reflection surface. FIG. 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 is also given a curvature in order to achieve better aberration correction.

In this embodiment, acrylic is used as the optical member, but it is needless to say that glass may be used.

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

The definition expression of TAL is:

[0040]

[Outside 1] The definition formula of AAL is

[0041]

[Outside 2] It is.

Each of A _i , B _i ... Is an aspheric coefficient.

In the embodiment described below, at least a surface having a different refractive power depending on the azimuth angle is adopted as the total reflection surface. However, this surface may be constituted by 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 viewing angle ± 16.8 °, vertical viewing angle ± 11.4 °, wide viewing angle (high magnification), approx. 1 in the direction parallel to the optical axis of the eyeball
An extremely thin glasses-type display of 0 mm to 15 mm has been developed. In addition, bright and good optical performance can be obtained. Further, by making the concave mirror a semi-transmissive surface, a virtual image of a bright original image can be superimposed on the landscape without distorting the landscape.

Although the field of view of the present invention is set to be wide, the field of view is set to be slightly narrower, and if the present invention is used, the thickness can be further reduced. This is because the thickness of the present invention is determined by the width of the angle of view.

[Brief description of the 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 according to Numerical Example 2 relating to the present invention.

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

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

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

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Total reflection surface (or transmission surface) 2 Concave mirror 5 Incident surface 4 Display means for forming an original image

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G02B 27/02 H04N 5/64 511 EPAT (QUESTEL)

Claims (13)

(57) [Claims] In an observation optical system for guiding light of an original image to an eyeball, a first curved surface which totally reflects light in an optical path;
An observation optical system, comprising: a second curved surface that reflects light totally reflected by the first curved surface; and an optical path that transmits the first curved surface. 2. The observation optical system according to claim 1, wherein the first curved surface has a negative optical power in a sagittal section. 3. The first curved surface has a negative optical power in a sagittal section, and the second curved surface reflects light .
2. The observation optical system according to claim 1, wherein the observation optical system is a concave mirror surface. 4. The observation optical system according to claim 1, wherein when viewed as a whole system, the paraxial focal length in each direction is almost constant. 5. The observation optical system according to claim 1, wherein the first curved surface has a different optical power depending on an azimuth angle. 6. The observation optical system according to claim 1, wherein the second curved surface has different optical power depending on the azimuth angle. 7. The observation optical system according to claim 1, wherein the first curved surface and the second curved surface have different optical powers depending on the azimuth angle. 8. The observation optical system according to claim 1, wherein the first curved surface and the second curved surface are formed as surfaces in a prism. 9. The observation optical system according to claim 1, wherein the first curved surface is immediately before an eyeball. 10. When an angle of a tangent at a surface vertex of the first curved surface with respect to a line perpendicular to an optical axis of an eye is α, | α
The expression | ≦ 20 ° is satisfied.
Observation optical system. 11. The observation optical system has a thickness of 10 mm to 1 mm.
The observation optical system according to claim 1, which is 5 mm. 12. The observation optical system according to claim 1, wherein the second curved surface is a light incident surface of an outside scene. 13. The observation optical system according to claim 1, wherein the observation optical system is of a glasses type.