JP3288740B2 - Real image finder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a real image type viewfinder used for a compact camera or the like, and more particularly to an eyepiece lens system located on the pupil side in the viewfinder.

[0002]

2. Description of the Related Art A real image type viewfinder generally comprises an objective lens system, an erecting optical system such as a prism for inverting an image, and an eyepiece lens system. A conventional real image type viewfinder provided in a compact camera generally has an eyepiece system including only one positive lens.

[0003]

However, as in the above-described conventional real image type viewfinder, one eyepiece lens system is required.
If only the positive lens is used, it is necessary to set the focal length of the eyepiece lens large in order to secure the space for the erecting optical system. Especially in the case of a wide-angle system, the angular magnification of the entire finder becomes small. easy.

Further, if the focal length of the eyepiece lens system is reduced to increase the angular magnification, there is not enough room between the object image formed by the objective lens system and the erecting optical system. It is not possible to provide a mechanism for taking in and out the field of view corresponding to photographing.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems in the prior art, and can secure a large space for installing an erecting optical system without reducing the angular magnification of the entire finder. It is an object of the present invention to provide a real image type finder having a sufficient space between an object image formed by an objective lens system and an erecting optical system.

[0006]

In order to achieve the above object, a real image type finder according to the present invention comprises, in order from the object side, an objective lens system, and a condenser lens for guiding an object image by the objective lens system to the eyepiece side. the erecting optical system for the object image is inverted orientation, is constructed from the object side positive, a lens group arranged in the negative order, said eyepiece lens system for guiding the inverted image to the eye, the condenser lens and the erecting Optics and
Panorama shooting that can be put in and out in addition to the normal field frame during
The eyepiece lens system has a concave surface, the focal length of the eyepiece lens system is concave, the focal length of the eyepiece lens system is fE, the focal length of the negative lens on the pupil side of the eyepiece lens is fEN, and the eyepiece lens system is The condition of Formula 1 is satisfied, where rE is the radius of curvature of the concave surface closest to the pupil, LE is the distance between the condenser lens and the erecting optical system, and fBE is the air-converted distance from the condenser lens to the eyepiece lens system.

(Equation 1) -0.7 <fE / fEN <00.5 <fE / rE <3.5 0.15 <LE / fE < 0.50.9 <fBE / fE <1.3

[0008]

Embodiments of the present invention will be described below.

As shown in FIG. 1, for example, the real image type viewfinder of the embodiment is represented by an objective lens system shown by a first surface to a twelfth surface and a thirteenth surface and a fourteenth surface in order from the object side. A condenser lens for guiding the object image by the objective lens system to the eyepiece side; a prism system as an erecting optical system for reversing the object image developed and shown on the fifteenth and sixteenth surfaces; To the twentieth surface, and an eyepiece system for guiding the inverted image to the eye.

The distance from the condenser lens to the eyepiece system can be increased without increasing the focal length of the eyepiece lens by arranging the eyepiece lens system in the order of the positive lens group and the negative lens group from the object side. And a large angle magnification of the entire viewfinder system can be secured.

Further, the real image type viewfinder of the embodiment satisfies the condition of Expression 2 where the focal length of the eyepiece lens system is fE and the focal length of the negative lens on the pupil side of the eyepiece lens system is fEN.

[0012]

Equation 2 -0.7 <fE / fEN <0 (1)

The condition (1) defines the power distribution between the positive lens unit and the negative lens unit of the eyepiece lens system. When the value exceeds the upper limit of the condition (1), the eyepiece lens system does not form a positive or negative arrangement from the object side. When the value falls below the lower limit, a large angular magnification can be secured, but the power of the positive and negative lens units is excessive. Becomes
It becomes difficult to see the field frame, and it becomes difficult to correct aberrations in the eyepiece lens system and the entire finder system.

Further, the positive lens group of the eyepiece lens system is a single positive lens, the negative lens group is a negative meniscus lens having a concave surface facing the pupil side, and the radius of curvature of the concave surface of the negative meniscus lens is rE. , Equation 3 is desirably satisfied.

[0015]

[Formula 3] 0.5 <fE / rE <3.5 (2)

By using a negative meniscus lens for the negative lens group of the eyepiece lens system, the power of the eyepiece lens system is increased and the angular magnification of the entire finder system is increased while ensuring a large distance between the condenser lens and the eyepiece lens system. It can be secured large.

Condition (2) defines the shape of the negative lens on the pupil side of the eyepiece lens system. If the upper limit is exceeded, it becomes difficult to correct astigmatism. If the lower limit is exceeded, the radius of curvature of the concave surface will be too small. As a result, the distance from the eyepiece to the pupil decreases. Since the distance from the eyepiece system to the pupil changes depending on the use condition, it is necessary to ensure a large distance.

Further, by moving the positive lens group in the eyepiece lens system, the diopter can be adjusted without changing the distance between the eyepiece and the pupil.

Recently, some compact cameras can use a wider-angle photographing lens and perform panoramic photographing by cutting the upper 1/4 and lower 1/4 of the screen. In order to match the field of view of the viewfinder with the shooting range, the camera has a field frame inserted into the optical path of the viewfinder according to the shooting range of panoramic shooting. Since the panorama frame is inserted into a space between the condenser lens and the erecting optical system, it is necessary to secure a large space for panoramic imaging.

Therefore, in order to insert a field frame or the like for panoramic photography, the distance between the condenser lens and the erecting optical system is LE, and the air conversion distance from the condenser lens to the eyepiece lens system is fBE. It is desirable to satisfy the conditions.

[0021]

[Equation 4] 0.15 <LE / fE <0.5 (3) 0.9 <fBE / fE <1.3 (4)

Condition (3) defines the distance between the condenser lens and the erecting optical system. If the distance is less than the lower limit, sufficient space cannot be secured. If the upper limit is exceeded, the total length of the eyepiece lens system is excessive. Become.

The condition (4) defines the distance from the condenser lens to the eyepiece system. If the distance is less than the lower limit, the space for the erecting optical system is insufficient to satisfy the condition (3) at the same time. If it exceeds, the total length of the eyepiece system becomes large, and it becomes difficult to correct the aberration of the eyepiece system.

In the embodiment, a prism system is used as the erecting optical system, but a plurality of mirrors may be used in combination.

[0025]

Embodiment 1 FIG. 1 is a lens diagram of a real image type viewfinder of Embodiment 1 at a high magnification, and FIG. 2 is a chromatic aberration, a chromatic aberration of magnification, and an astigmatism at d-line, g-line, e-line, and C-line thereof (S: Sagittal, M: meridional) and distortion. FIGS. 3 and 4 are a lens diagram and various aberration diagrams of the first embodiment at a low magnification.

Specific numerical configurations of the first embodiment are as shown in Tables 1 to 3. The symbol in the table and figures is EP
Is the distance from the pole of the final lens to the eye point (eye relief), r is the radius of curvature of each lens surface, d is the lens thickness or lens interval (the unit is mm), n is the d-line refractive index of each lens, ν is the Abbe number of the d-line of each lens; R
Is Eyring.

The lens of the first embodiment has a third, fourth, fifth, sixth
The 7, 10, 11, 13, and 18 surfaces are aspherical. The aspheric surface has a distance X from the tangent plane of the aspherical vertex of a coordinate point on the aspherical surface whose height from the optical axis is Y, and a curvature of the aspherical vertex (1).
/ R) is C, the conic coefficient is K, and the fourth, sixth, and eighth order aspherical coefficients are A4, A6, and A8.

[0028]

(Equation 5)

The conic coefficient and aspheric coefficient of each aspheric surface are shown in Table 2 below.
It is as shown in. Note that the radius of curvature of the aspheric surface in Table 1 is the radius of curvature of the apex of the aspheric surface. Also, the magnification M,
Table 3 shows the half angle of view ω and the distances d2, d6 and d10 according to the magnification.
Changes as shown in FIG.

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

[Table 3]

[0033]

Embodiment 2 FIG. 5 is a lens diagram of the real image type finder of Embodiment 2 at a high magnification, and FIG. 6 is a diagram of various aberrations. Also,
7 and 8 are a lens diagram and various aberration diagrams at the time of low magnification of the second embodiment.

Specific numerical configurations of the second embodiment are as shown in Tables 4 to 6. The lens of Example 2 is
The 4, 5, 6, 7, 10, 11, 13, and 18 surfaces are aspherical. The conic coefficient and aspheric coefficient of each aspheric surface are as shown in Table 5. Magnification M, half angle of view ω, intervals d2, d6, d1
0 changes as shown in Table 6 with magnification.

[0035]

[Table 4]

[0036]

[Table 5]

[0037]

[Table 6]

[0038]

Third Embodiment FIG. 9 is a lens diagram of the real image type finder of the third embodiment at a high magnification, and FIG. 10 is a diagram of various aberrations. FIGS. 11 and 12 are a lens diagram and various aberration diagrams at the time of low magnification of the third embodiment.

Specific numerical configurations of the second embodiment are as shown in Tables 7 to 9. The lens of Example 3 is
The 4,8,9,12,13,15,20 surfaces are aspherical. The conic coefficient and aspheric coefficient of each aspheric surface are as shown in Table 8. Magnification M, half angle of view ω, intervals d2, d8, d12
Changes as shown in Table 9 with magnification.

[0040]

[Table 7]

[0041]

[Table 8]

[0042]

[Table 9]

Table 10 shows the relationship between each embodiment and the conditional expressions described above.

[0044]

[Table 10]

[0045]

As described above, according to the present invention, it is easy to correct the aberration of the eyepiece lens system, and a large space for the erecting optical system is secured without reducing the angular magnification of the entire viewfinder. In addition to this, it is possible to secure a large space between the object image by the objective lens system and the erecting optical system, and to insert a field frame or the like that supports panoramic imaging.

[Brief description of the drawings]

FIG. 1 is a lens diagram of a real image type viewfinder of Example 1 at a high magnification.

FIG. 2 is a diagram illustrating various aberrations of the finder according to the first embodiment at a high magnification.

FIG. 3 is a lens diagram of the real image type viewfinder of Example 1 at a low magnification.

FIG. 4 is a diagram illustrating various aberrations of the finder according to the first embodiment at a low magnification.

FIG. 5 is a lens diagram of a real image type viewfinder of Example 2 at a high magnification.

FIG. 6 is a diagram illustrating various aberrations of the finder according to the second embodiment at a high magnification.

FIG. 7 is a lens diagram of a real image type viewfinder of Example 2 at a low magnification.

FIG. 8 is a diagram illustrating various aberrations of the finder according to the second embodiment at a low magnification.

FIG. 9 is a lens diagram of a real image type viewfinder of Example 3 at a high magnification.

FIG. 10 is a diagram illustrating various aberrations of the finder according to the third embodiment at a high magnification.

FIG. 11 is a lens diagram of a real image type viewfinder of Example 3 at a low magnification.

FIG. 12 is a diagram illustrating various aberrations of the finder according to the third embodiment at a low magnification.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-1-309020 (JP, A) JP-A-1-319723 (JP, A) JP-A-1-129225 (JP, A) JP-A-3-309 46608 (JP, A) JP-A-4-26815 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03B 13/00-13/28 G02B 9/00-17/08 G02B 21/02-21/04 G02B 25/00-25/04

Claims (3)

(57) [Claims] 1. An object lens system, a condenser lens for guiding an object image by the objective lens system to an eyepiece, an erecting optical system for reversing the direction of the object image, and a positive and a negative lens from the object side. It consists of lens groups arranged in this order, and eyepiece lens system for guiding the inverted image to the eye, the capacitor Len
Between the camera and the upright optical system in addition to the normal field frame.
A real image type viewfinder comprising: a viewable frame for panoramic photography; a surface closest to the pupil of the eyepiece lens system being concave, and satisfying the following conditions. −0.7 <fE / fEN <00.5 <fE / rE <3.5 0.15 <LE / fE <0.50.9 <fBE / fE <1.3 fE: Focus of the eyepiece system Distance fEN: Focal length of the negative lens on the pupil side of the eyepiece lens system rE: Radius of curvature of the concave surface closest to the pupil of the eyepiece lens system LE: Distance between the condenser lens and the erecting optical system fBE: From the condenser lens to the eyepiece lens system Air equivalent distance 2. The eyepiece lens system according to claim 1, wherein two lenses, a positive lens and a negative meniscus lens having a concave surface facing the pupil side, are arranged in order from the object side. 2. The real image type viewfinder according to 1. 3. The real image type viewfinder according to claim 1, wherein the eyepiece lens system adjusts a diopter by moving the positive lens group in the eyepiece lens system.