JPH08160518A - Display optics - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a display optical system that is compact and capable of obtaining an optical image of a field frame or the like in a good diopter state. According to the present invention, in a display optical system for introducing an optical image formed by a display member into an observation optical system and displaying the optical image by superimposing the optical image on a visual field image formed by the observation optical system, At least one of optical members constituting the system
At least two surfaces having different radii of curvature
It is formed from two spherical surfaces.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display optical system, and more particularly to a display optical system for displaying information such as a field frame in a viewing optical system such as a finder by superposing it on a field image of the viewing optical system.

[0002]

2. Description of the Related Art In a conventional optical image frame lighting type finder,
The optical image frame, which is a display member, is illuminated by external light or the like, and the optical image for displaying the visual field frame or the like is displayed by being superposed on the visual field image of the finder by a half mirror or the like. When superimposing information such as the shooting range formed as an optical image on the visual field image of the observation optical system such as a finder, the diopter of the visual field image and the diopter of the optical image are matched, and observation with a visual field magnification is performed. The display optical system has a target lens in order to match the field of view with the shooting range indicated by the optical image frame. In recent years, with downsizing of observation optical systems such as viewfinders, downsizing of display optical systems has also been required. Particularly, downsizing of the display member such as the optical image frame and simplification of the target lens are effective for downsizing of the display optical system.

[0003]

However, in order to simplify the target lens while reducing the size of the optical image frame of the display optical system, it is necessary to further enlarge the optical image. As a result, the target lens needs a large refractive power, and it becomes difficult to sufficiently correct the aberration when enlarging the optical image. That is, the fluctuation of the diopter of the optical image becomes large between the central portion and the peripheral portion.

As described above, the conventional display optical system has a disadvantage that it is not possible to obtain an optical image of a field frame or the like in a good diopter state while achieving miniaturization. The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a display optical system that is compact and capable of obtaining an optical image of a field frame or the like in a good diopter state.

[0005]

In order to solve the above problems, in the present invention, an optical image formed by a display member is introduced into an observation optical system, and the optical image is formed in a visual field image formed by the observation optical system. In the display optical system for overlapping and displaying, at least one surface of an optical member forming the display optical system is formed of at least two spherical surfaces having different radii of curvature. I will provide a.

According to a preferred aspect of the present invention, the at least one surface is formed of a spherical surface having a radius of curvature different from each other in a central portion and a peripheral portion around the optical axis. In this case, it is preferable that the radius of curvature of the spherical surface of the peripheral portion is larger than the radius of curvature of the spherical surface of the central portion.

[0007]

As described above, it is effective to downsize the display member such as the optical image frame in order to downsize the display optical system for forming a light image. Therefore, it is necessary to magnify and observe the optical image with the target lens and the eyepiece lens, and the target lens and the eyepiece lens need a large refractive power. Further, if the target lens and the eyepiece lens are also simplified for downsizing and each is composed of a single lens or the like, aberration is likely to occur and it becomes impossible to maintain a good aberration state when magnifying and observing the optical image.

In particular, when both the target lens and the eyepiece lens are composed of a single lens having a positive refractive power, or when the target lens is omitted and the optical image is magnified and observed only by the eyepiece lens, an optical system for observing the optical image is used. It will consist of only positive refractive power. For this reason, it becomes extremely difficult to correct aberrations satisfactorily, and it is particularly difficult to correct aberrations of field curvature.
When a large field curvature occurs, the diopter varies greatly between the center of the optical image frame and its periphery, making it difficult to observe the optical image.

Therefore, in the display optical system of the present invention, at least one surface of the constituent optical member is formed by at least two spherical surfaces having different radii of curvature. In this way, it is possible to correct the field curvature of the light flux that enters the eyepoint from each portion of the optical image frame, and observe the optical image in a good diopter state. Specifically, for example, in at least one of the above-mentioned surfaces, it is desirable that the central portion centered on the optical axis of the display optical system and the peripheral portion thereof be formed of spherical surfaces having different radii of curvature. In this way, it is possible to satisfactorily correct the field curvature of the central portion and the peripheral portion of the optical image, and it is possible to observe the optical image on the eyepoint from the center to the periphery in a good diopter state.

Further, in order to correct the field curvature of the optical image more satisfactorily, in the surface where the central part and the peripheral part have different radii of curvature, the size of the radius of curvature of the spherical surface of the peripheral part is the central part. It is desirable that the radius of curvature of the spherical surface is larger than that of the spherical surface. Further, by forming the peripheral portion and the central portion of the above-mentioned at least one surface by so-called aspherical surfaces instead of perfect spherical surfaces, it is possible to further satisfactorily correct the field curvature.

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a diagram showing a configuration of an optical image frame lighting type finder optical system to which the display optical system of the present invention is applied. The finder optical system shown in the drawing is an inverse lens composed of an objective lens 1 having a negative refractive power, a half prism 2 for introducing an optical image of a later-described lighting frame optical system (display optical system) into the finder optical system, and an eyepiece lens 3. It is equipped with a Galileo observation optical system. The illustrated finder optical system further includes a display optical system including a target lens 4, a mirror 5 for folding the optical path, an optical image frame 6, and a daylighting window 7 having a diffusion characteristic.

In the optical image frame 6, for example, a distance measuring range display portion is formed in the center portion and a visual field frame display portion is formed in the peripheral portion so as to transmit light. Therefore, the optical image frame 6 is illuminated by the light from the outside through the daylighting window 7 having the diffusion characteristic, and the light transmitted through the distance measuring range display section and the field frame display section is incident on the mirror 5. The light reflected by the mirror 5 enters the half prism 2 through the target lens 4. The light reflected to the right side in the figure by the reflecting surface of the half prism 2 enters the eyepoint 8 via the eyepiece lens 3. In this way, the optical image having the information of the range-finding range display and the field-of-view frame display frame is superimposed and displayed on the field-of-view image observed at the eye point 8 through the objective lens 1, the half prism 2 and the eyepiece lens 3.

[Examples and Comparative Examples] FIG. 2 is a diagram showing a configuration of a display optical system taken out from the finder optical system of FIG. In the display optical system of FIG. 2, the optical path is expanded to show its configuration, the half prism 2 is represented by a glass block, and the mirror 5 is omitted. Further, the display optical system of FIG. 2 is a comparative example, and the target lens 4 and the eyepiece lens 3 are each formed of a spherical lens according to the conventional technique.

FIG. 3 is a diagram showing the structure of a display optical system according to an embodiment of the present invention. The display optical system of the present example has the same configuration as that of the comparative example, but in the lens surface of the target lens 4 on the half prism 2 side, the central portion and the peripheral portion are formed of spherical surfaces having different radii of curvature. The only difference is that FIG. 4 is a diagram showing the configuration of the target lens 4 of this embodiment. As shown in FIG. 4, on the lens surface of the target lens 4 on the side of the half prism 2, a central portion up to a radius of 2.4 mm with respect to the optical axis is formed by a spherical surface having a radius of curvature of 32 mm.
Further, the outer peripheral portion is formed by a spherical surface having a radius of curvature of 36 mm.

On the other hand, the lens surface of the target lens 4 on the optical image frame 6 side is formed as a spherical surface having a radius of curvature of 120.028 mm. A lens having a shape as shown in FIG. 4 can be easily manufactured by using a resin such as plastic. It can also be manufactured by joining a central spherical surface portion formed of an optical material such as plastic to a spherical glass lens having a radius of curvature of 36 mm. Needless to say, in any case, the effects of the present invention can be obtained.

The following table (1) lists the values of the specifications of the comparative example and this example. In Table (1), the numbers on the left end indicate the order of each lens surface from the optical image frame, r the radius of curvature of each lens surface, d the distance between each lens surface, and n and ν respectively the d line (λ = (587.6 nm) and the Abbe number. The surface number of the optical image frame is 1.
(E.P.) indicates an eye point.

[0017]

[Table 1] r d n ν 1 15.40 1.0 2 120.028 2.60 1.49 108 57.5 3 -32.000 0.70 1.0 (Comparative example) 3 -32.000 (center part) 0.70 1.0 (this example) -36.000 (peripheral part) 4 ∞ 17.50 1.51680 64.1 5 ∞ 1.00 1.0 6 38.300 3.40 1.49108 57.5 7 -38.300 15.00 1.0 8 (EP)

FIGS. 5 and 6 are spot diagram diagrams of the display optical systems of the comparative example and the present example, respectively. In the spot diagram, the eye point has a diameter of 4
Assuming that the circular area is mm, the circular area is equally divided into 120, and the degree of light condensing on the light image frame when the light ray is traced on the light image frame from each divided portion is shown. Therefore,
If the influence of the curvature of field of the display optical system is properly corrected at each angle of view, each light beam is concentrated on one point on the optical image frame.
In each spot diagram, D is a d-line (λ = 582.6 nm), θ is an emission angle of each light ray emitted from an eye point, and y is an optical image frame of a principal ray of a light beam having each emission angle. The heights from the optical axis are shown above.

As is apparent from FIG. 5, in the display optical system of the comparative example, the light beam of the light beam having a large angle of view θ (in particular, the angle of view of 100% and 70% of the maximum angle of view) is condensed on the optical image frame. Not
It can be seen that the influence of field curvature is large. On the contrary,
Referring to FIGS. 5 and 6, in the display optical system of the present embodiment in which the central portion and the peripheral portion of the target lens are formed of spherical surfaces having different radii of curvature, the optical image frame of the light beam at each angle of view is obtained. It can be seen that the converging degree above is remarkably improved and the influence of the field curvature is well corrected. The diopter of the display optical system at the eye point is set to 0 diopter in both the comparative example and the present embodiment.

In the above embodiment, the lens surface on the half prism side of the target lens has the central portion and the peripheral portion formed of spherical surfaces having different radii of curvature. However, at least one surface of the optical member that constitutes the display optical system, such as the lens surface of the target lens on the field frame side or the lens surface of the eyepiece lens, is formed of at least two spherical surfaces having different radii of curvature. Then, the same effect can be obtained. Further, although the present invention has been described with respect to the reverse Galilean type finder optical system in the above-described embodiments, it is obvious that the present invention can be applied to a real image type finder optical system using an optical image frame.

[0021]

As described above, according to the display optical system of the present invention, an optical image can be observed in a good diopter state while being downsized.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an optical image frame lighting type finder optical system to which a display optical system of the present invention is applied.

FIG. 2 is a diagram showing a configuration of a display optical system of a comparative example of the present invention.

FIG. 3 is a diagram showing a configuration of a display optical system according to an example of the present invention.

FIG. 4 is a diagram showing a configuration of a target lens of the embodiment of FIG.

5 is a spot diagram of the display optical system of the comparative example of FIG.

FIG. 6 is a spot diagram of the display optical system of the embodiment of FIG.

[Explanation of symbols]

 1 Objective Lens 2 Half Prism 3 Eyepiece 4 Target Lens 5 Mirror 6 Optical Image Frame 7 Daylighting Window 8 Eyepoint

Claims (3)

[Claims] 1. A display optical system in which an optical image formed by a display member is introduced into an observation optical system, and the optical image is superimposed on a visual field image formed by the observation optical system for display. At least one surface of the optical member to be formed is formed of at least two spherical surfaces having different radii of curvature, the display optical system. 2. The display according to claim 1, wherein the at least one surface is formed as a spherical surface having a radius of curvature different from each other in a central portion and a peripheral portion around the optical axis. Optical system. 3. The display optical system according to claim 2, wherein the radius of curvature of the spherical surface of the peripheral portion is larger than the radius of curvature of the spherical surface of the central portion.