JPH06324266A - Real image type variable power finder - Google Patents

Abstract

PURPOSE:To provide a new real image type power variable finder capable of realizing a high variable power without causing the extension of a folding total length and excellently correcting the aberrations by mutually switching objective systems having variable focal length to be combined with a common eyepiece system. CONSTITUTION:This finder is provided with a first objective system having variable focal length (objective system 1), a second objective system having variable focal length (objective system 2), a prism P1, an eyepiece lens L6 of an eyepiece system and a prism P2. The prism P1 and the prism P2 constitutes an image inverting system and the prism P1 constitutes one of the reflection member of an optical axis changeover means. In the objective systems 1, 2, the focal length is varied while keeping an image plane on a fixed position by the movement of a second group as a variator and a fourth group as a compensator. When photographing is performed in a zoom area from a wide angle end to an intermediate focal length in a zoom photographing system, the objective system 1 is combined with the eyepiece system, and when photographing is performed in a zoom area from the intermediate focal length to the telescopic end, the objective system 2 is combined with the eyepiece system.

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 variable power viewfinder. INDUSTRIAL APPLICABILITY The real image type variable magnification viewfinder of the present invention can be suitably used for a lens shutter camera capable of zoom photographing, particularly a lens shutter camera having a high zoom magnification ratio. The real image type variable power viewfinder of the present invention can also be suitably used as a viewfinder for a video camera or an electronic still camera.

[0002]

2. Description of the Related Art In recent years, not only electronic still cameras, video cameras, etc., but also lens shutter cameras have become capable of zoom photography, and the zoom ratio in zoom photography tends to increase. In response to this, zooming finder used in these cameras is also required to have a high zooming ratio.

In order to realize a high zoom ratio in the real image type zoom finder, it is necessary to increase the amount of movement of the variator in the variable focal length objective system or to increase the refracting power of the group constituting the objective system. is there. In order to increase the variator moving amount to increase the zoom ratio, it is necessary to secure a long moving space for the variator on a straight line, and the so-called "bending total length" from the objective system to the eyepiece system is likely to be large,
It becomes difficult to mount it on a compact camera. If the refractive power of the group is increased to increase the zoom ratio, it becomes extremely difficult to correct aberration.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is possible to realize a high zoom ratio without causing an increase in the total bending length and to correct aberrations satisfactorily. The objective is to provide a real image type variable magnification viewfinder.

[0005]

The real image type variable power finder of the present invention is a real image type variable power finder which "inverts a real image by an objective system having a variable focal length and observes it as an erected image by an eyepiece system". The following points are characteristic (claim 1).

The "objective system" is composed of N (≧ 2) variable-focal-length objective systems having different focal length changing regions. The "eyepiece system" is a single lens system provided so as to be selectively combined with any one of the N variable focal length objective systems. The optical axis of the desired one of the N variable focal length objective systems is joined to the optical axis on the eyepiece system side by the "optical axis switching means".

The focal length variable regions of the N variable focal length objectives have, for example, the longest focal length in one focal length variable objective equal to the shortest focal length in another focal length variable objective. It is possible to form a "continuous focal length variable region as a whole" without overlapping with each other, or the focal length variable regions overlap each other,
A desired focal length variable region may be formed.

In the variable magnification viewfinder of the real image type according to claim 1, the "N focal length variable objective systems" can have a long back focus in the order of the longest maximum focal length, and the optical axes of the objective lenses can be mutually different. The arrangement can be performed in parallel and so that the arrangement order in space is the order of the length of the back focus (claim 2).

In this case, the optical axes are switched by disposing N focal length variable objective systems, for example, on a turret in a ring shape.
The optical axis junction may be switched by rotating the turret, or the N focal length variable objective systems may be arranged in parallel to form a unit and the entire unit may be moved in parallel to switch the optical axis junction. May be.

In the variable magnification finder of the real image type according to the second aspect, N variable focal length objectives are fixed in the apparatus space and are arranged in parallel with each other, and the optical axis switching means is set to "each focal length". N reflecting means which are provided corresponding to the individual variable objective systems and which join the optical axes of the corresponding variable focal length objective systems to the optical axis on the eyepiece system side confluently, and the longest of these reflecting means. And (N-1) reflecting means other than those for the variable focal length objective system having a back focus, and a state switching means for switching between the optical axis bonding state and the retracted state ". (Claim 3) In this case, "(N-1) reflection means capable of switching between the optical axis bonding state and the retracted state are used as mirrors, and the state switching is performed in a swinging manner." It is possible (Claim 4).

In the real image type variable power viewfinder according to the second, third or fourth aspect, "when the optical axis is switched, two focal length variable objective systems involved in the optical axis switching, that is, before and after the optical axis switching. The focal lengths of the two variable-focal-length objectives that are combined with the eyepiece side can be made the same ”.

[0012]

As described above, according to the present invention, by using N (≧ 2) variable focal length objective systems having different focal length changing regions, as a whole, the focal length corresponding to the desired zoom ratio is obtained. A variable region is formed, and a variable focal length objective system according to the zoom ratio of zoom photographing is selected and combined with the eyepiece system.

[0013]

EXAMPLES Specific examples will be given below.

FIG. 1 shows two variable-focal-length objective systems and an eyepiece system in an embodiment in which the real-image variable-magnification finder of the present invention is implemented with the number of variable-focal-length objective systems constituting the objective system: N. A lens structure is shown. An "image inversion system" is provided between the eyepiece system and the variable focal length objective system combined with the eyepiece system.

FIG. 1A shows a first variable focal length objective system (hereinafter referred to as objective system 1), and FIG. 1B shows a second objective system.
1) shows a variable focal length objective system (hereinafter referred to as objective system 2) and a prism P ₁ , and FIG. 1C shows an eyepiece lens L ₆ which is an eyepiece system and a prism P ₂ . The prisms P ₁ and P ₂ form an “image inversion system”. The prism P ₁ also constitutes one of the reflecting members of the optical axis switching means, as will be described later. The portion shown in FIG. 1C is the “eyepiece side”. The objective system 1 is composed of lenses L _{1 to} L ₅ , and the objective system 2 is L ₁ ′ to
It is composed of L ₅ '.

The paraxial refractive power arrangement of the objective systems 1 and 2 is shown in FIG. The objective systems 1 and 2 both have a positive / negative / positive / positive four-group configuration in order from the object side to the image side.
Has a focal length change region of F = 8.0 to 20.9 mm, and the objective system 2 has a focal length change region of F ′ = 20.9 to 45.6 mm. Therefore, the maximum focal length of the objective system 2 is larger than that of the objective system 1.

In both the objective systems 1 and 2, the second group moves as a variator and the fourth group moves as a compensator to change the focal length while keeping the image plane at a constant position. Figure 2
As shown in, the wide-angle end (WID
E, F _W = 8.0) to the intermediate focal length (MEAN, F _M =
When photographing is performed in the zoom range of 20.9), the objective system 1 is combined with the eyepiece system, and the intermediate focal length (MEAN, F
_M '= 20.9) to the telephoto end (TELE, F _T ' = 45.
When photographing is performed in the zoom range of 6), the objective system 2 is combined with the eyepiece system.

Objective system 1 has a back focus: BF = 1
Objective lens 2 has a back focus of B: 1.3 mm
It has F ′ = 24.3 (> BF).

FIG. 3 is a block diagram for explaining the optical axis switching in this embodiment. As shown in FIGS. 3A and 3B, the objective systems 1 and 2 are arranged such that their optical axes are parallel to each other and their optical axis positions are fixed. The optical axis of the objective system 2 is bent at a right angle by the prism P ₁ described above,
The optical axis of the objective system 1 is bent at a right angle by a mirror m as a reflecting member.

These bent optical axes are joined "jointly" with the optical axes on the eyepiece system side (prism ₂ ).
That is, the optical axis of the objective system 2 bent by the prism P _{1 and} the optical axis of the objective system 1 bent by the mirror m coincide with the optical axis on the eyepiece system side. In addition, the objective systems 1 and 2
In consideration of the length of the back focus, the objective system 1 having a short back focus is arranged closer to the eyepiece system side than the objective system 2.

FIG. 3A shows a state in which the optical axis of the objective system 1 is joined to the optical axis on the eyepiece system side. The mirror m is disposed on the object side of the prism P ₂ which is the image reversing system on the eyepiece side, with its reflecting surface inclined at 45 degrees with respect to the optical axis of the objective system 1. The optical axis of the objective system 2 bent by the prism P ₁ is blocked by the mirror m and is not joined to the optical axis on the eyepiece system side.

In the state of FIG. 3A, the focal length from the wide-angle end (WIDE, F _W = 8.0) to the intermediate focal length (MEAN, F _M = 20.9) due to the magnification change of the objective system 1. The finder image of the range can be observed.

FIG. 3B shows a state in which the optical axis of the objective system 2 is joined to the optical axis on the eyepiece system side. The mirror m is rotated 45 degrees clockwise by a drive system (which constitutes an optical axis switching means together with the prism P ₁ and the mirror m) to retract the reflecting surface from the object side of the eyepiece system. Therefore, the optical axis of the objective system 2 bent by the prism P ₁ is joined to the optical axis on the eyepiece system side.

In the state of FIG. 3 (b), the objective system 2 is scaled so that the intermediate focal length (MEAN, F _M '= 20.
The finder image in the focal length range from 9) to the telephoto end (TELE, F _T '= 45.6) can be observed.

When the optical axes are switched, if the objective systems 1 and 2 have a common focal length of 20.9 mm, a discontinuous change in the magnification of the finder image due to the switching of the optical axes can be avoided. Therefore, the magnification of the finder image can be continuously changed regardless of switching between the objective systems 1 and 2.

The specific elements of the optical elements shown in FIGS. 1 (a), 1 (b) and 1 (c) will be described below. As shown in FIG. 1 (a), in a state of being bonded to the optical axis of the objective 1 and the ocular system, the radius of curvature of the i-th view from the object side (including the prism surface) R _i (i = 1 to 14), the surface distance on the optical axis between the i-th surface and the (i + 1) -th surface is D _i (i = 1 to 14), and the j-th optical element (lens and prism) counted from the object side. The refractive index and Abbe number for the d-line of the material of) are N _j and ν _j (j = 1 to 7), respectively. However, regarding D ₁₀ , D _10F is the distance on the optical axis between the image side surface of the fourth group (lens L ₅ ) of the objective system 1 and the position where the optical axis is bent by the retractable reflecting member, and D 10 _10R represents the distance on the optical axis between the position where the optical axis is bent and the object side surface of the prism P ₂ on the eyepiece system side.

As shown in FIG. 1B, regarding the objective system 2 and the prism P ₁ on the image side thereof, the i-th object is counted from the object side.
The radius of curvature of the surface in the figure (including the prism surface) is R _i '(i =
1 to 12), the surface distance on the optical axis between the i-th surface and the (i + 1) -th surface is D _i '(i = 1 to 12), and the j-th optical element (lens and prism) counted from the object side. The refractive index and Abbe number of the material of () for the d-line are N _j ′ and ν _j ′ (j = 1 to 6), respectively. Regarding D ₁₂ ', D
_12F 'is the distance on the optical axis between the image side surface of the prism P ₁ and the position where the optical axis is joined when the reflecting member is retracted, D'
_12R represents the distance on the optical axis between the position where the optical axes are joined when the reflecting member is retracted and the object side surface of the prism P ₂ on the eyepiece side. Note that D _10R = D ′ _12R .

In FIG. 1 (c), the reference numerals with dashes in parentheses indicate the surfaces, surface spacings, and levels of the optical element from the object side when the objective system 2 is optically bonded to the eyepiece system side. Is represented.

In this embodiment, aspherical surfaces are used for both the objective systems 1 and 2 and the eyepiece system side. In this specification, an "aspherical surface" is a radius of curvature on the optical axis, a height from the optical axis is H, coordinates in the optical axis direction corresponding to H are X, K is a conic constant, quaternary, 6 The aspherical coefficients of the 8th and 8th orders are A, B, and
When C, X = [(H ² / R) / {1 + √ (Y)}] + A · H ⁴ + B
^{· H 6 + C · H 8} , Y = a 1- (1 + K) · ( H 2 / R 2) becomes curved surface formula. The shape of each aspherical surface is specified by giving a conical constant: K and a higher-order aspherical surface coefficient: A, B, C. In addition, [E
-Number] represents a power. For example, if the [E-10], which means the 1/10 ^10], this number is multiplied to the number in front thereof.

Objective System 1 i R _i D _i j N _j ν _j 1 20.063 2.69 1 1.49154 57.82 2 -27.373 Variable 3 14.004 1.04 2 1.49154 57.82 4 4.418 2.82 5 -4.938 1.03 3 1.49154 57.82 6 -9.7726 Variable 7 10.101 2.13 4 1.49154 57.82 8 -29.529 Variable 9917 .798 2.52 5 1.49154 57.82 10 -13.587 variable (D _10F).

Aspherical first surface K = -2.049, A = -7.25E-5, B = -9.
19E-7, C = 7.03E-10 Fourth surface K = -0.180, A = -7.21E-5, B = 4.
01E-6, C = 1.91E-6 Fifth surface K = -0.518, A = -6.29E-5, B = 9.
17E-5, C = 8.11E-7 Tenth surface K = 2.328, A = 6.13E-4, B = 7.
96E-6, C = 0
.

Variable amount (WIDE) magnification: 0.367 D ₂ = 0.263, D ₆ = 8.287, D ₈ = 3.58,
D _10F = 5.586 (WIDE-MEAN) Magnification: 0.595 D ₂ = 4.405, D ₆ = 4.145, D ₈ = 2.95
1, D _10F = 6.215 (MEAN) Magnification: 0.963 D ₂ = 8.287, D ₆ = 0.263, D ₈ = 3.58,
D _10F = 5.586.

Objective System 2 i R _i 'D _i ' j N _j 'ν _j ' 1 11.289 2.60 1 1.49154 57.82 2 18.013 Variable 3 10.651 2.80 2 1.58500 29.30 4 7.117 2.30 5 -11.973 1.10 3 1.58500 29.30 6 -7.173 Variable 7 26.354 2.10 4 1.49154 57.82 8 -37.162 Variable 9 36.559 2.50 5 1.51680 64.20 10 −27.894 Variable 11 ∞ 12.00 6 1.56883 56.04 12 ∞ 9.976 (D _12F ′).

Aspherical First surface K = -0.315, A = -1.336E-7, B =-
4.2816E-7, C = 1.1102E-8 Fourth surface K = -0.0272, A = -3.84E-5, B =-
1.0542E-6, C = 3.7908E-7 Fifth surface K = 0.16, A = 2.3668E-5, B =-
2.5555E-6, C = 4.5146E-7 Eighth surface K = -1.124, A = 5.0595E-5, B =-
3.3288E-7, C = 1.1535E-8
.

Variable amount (MEAN) magnification: 0.963 D ₂ '= 0.898, D ₆ ' = 14.063, D ₈ '=
_{3.021, D 10 '= 0.979 (} MEAN-TELE) _{magnification: 1.394 D 2' = 7.31,} D 6 '= 7.651, D 8' = 1.9
42, D ₁₀ '= 2.058 (TELE) Magnification: 2.098 D ₂ ' = 14.684, D ₆ '= 0.277, D ₈ ' =
2.485, D ₁₀ '= 1.515
.

Eyepiece system side i R _i D _i j N _j ν _j 10 10.13 (D _10R = D ′ _12R ) 11 17.069 27.500 5 1.52580 52.10 12 ∞ 0.300 13 36. 904 2.200 6 1.49154 57.82 14-19.251 15.000 eyepoints.

Aspheric surface 11th surface K = -38.343, A = 2.45E-4, B =-
3.88E-6, C = 0.0
.

In the above embodiment, the above-mentioned WIDE, WIDE-ME when the objective system 1 is optical-axis joined to the eyepiece system side.
Aberration diagrams in each state of AN and MEAN are shown in FIGS.
Are shown in sequence. FIGS. 7 to 9 sequentially show aberration diagrams in each of the states of MEAN, MEAN-TELE, and TELE when the objective system 2 is optical axis joined to the eyepiece system side. In these aberration diagrams, C, D, and F indicate that they are related to the C line, D line, and F line, the broken line in the spherical aberration diagram indicates the "sinusoidal condition", and the solid line in the astigmatism diagram indicates the tangential. The broken line indicates each direction of meridional.

In each state of the optical axis cementing between the objective systems 1 and 2 and the eyepiece system side, the aberration is well corrected and the performance is good. A very high zoom ratio of 5.27 times is realized in total.

Although the case where there are two types of variable focal length objective systems is shown above, it is also possible to use three or more types of variable focal length objective systems having different focal length change regions. It will be readily understood from the above description.

[0041]

As described above, according to the present invention, it is possible to provide a new real image type variable magnification finder. In the present invention, as described above, an extremely high zoom ratio can be realized by switching the variable focal length objective system combined with the common eyepiece system. Since each focal length variable objective system itself does not need to have a very large focal length change region, the total bending ratio is extremely high, but the total bending length is small, and good aberration correction is possible. is there.

In the second and third aspects of the invention, the optical arrangement is easy, and in the fourth aspect of the invention, the optical axis switching means is simple. According to the invention of claim 5, the magnification of the finder image can be continuously changed before and after the switching of the objective system.

[Brief description of drawings]

FIG. 1 is a diagram showing a specific lens configuration of a variable focal length objective system and an eyepiece system side (image inverting prism and eyepiece system) in one embodiment of a real image type variable magnification finder of the present invention.

FIG. 2 is a diagram showing a refractive power arrangement of each objective system in an example.

FIG. 3 is a diagram for explaining optical axis switching in the embodiment.

FIG. 4 is an aberration diagram in a WIDE state when the objective system 1 is optically bonded to the eyepiece system side in Example.

FIG. 5 is an aberration diagram in a WIDE-MEAN state when the objective system 1 is optical axis joined to the eyepiece system side in Example.

FIG. 6 is an aberration diagram in the MEAN state when the objective system 1 is optical axis joined to the eyepiece system side in the example.

FIG. 7 is an aberration diagram in a NEAN state when the objective system 2 is optical axis joined to the eyepiece system side in Example.

FIG. 8 is an aberration diagram in a MEAN-TELE state when the objective system 2 is optically bonded to the eyepiece system side in the example.

FIG. 9 is an aberration diagram in a TELE state when the objective system 2 is optical axis joined to the eyepiece system side in Example.

[Explanation of symbols]

L _{1 to} L ₅ objective system 1 (first focal length variable objective system)
Lenses L ₁ 'to L ₅ ' Each lens of the objective system 2 (second focal length variable objective system) P ₁ Prism which is a constituent element of the optical axis switching means P ₂ Image inversion system L ₆ Eyepiece which is an eyepiece system lens

Claims (5)

[Claims] 1. A real image type variable magnification finder for observing a real image by an objective system having a variable focal length by an image inverting system and observing it as an erect image by an eyepiece system, wherein the objective system has different focal length changing regions. (≧
2) is composed of a variable focal length objective system, and the eyepiece system is a single lens system provided so as to be selectively combined with any of the N variable focal length objective systems, 2. A real image type variable power viewfinder having an optical axis switching means for joining the optical axis of a desired one of the variable focal length objective systems to the optical axis on the side of the eyepiece system. 2. The variable-magnification real-image finder according to claim 1, wherein the N variable focal length objectives have a long back focus in order of increasing maximum focal length, and are arranged with their optical axes parallel to each other. A real-image variable-magnification viewfinder characterized in that the order of arrangement in space is the order of the length of the back focus. 3. The real image variable magnification finder according to claim 2, wherein the N focal length variable objective systems are fixed in the apparatus space and arranged in parallel with each other, and the optical axis switching means is each focal length variable objective. N reflecting means provided corresponding to each of the systems, which join the optical axes of the corresponding variable focal length objective systems to the optical axis on the eyepiece system side, and the longest back focus among these reflecting means. (N- other than for variable focal length objectives with
1) A real image type variable power viewfinder having a position switching means for switching the individual reflecting means between an optical axis bonding state and a retracted state. 4. The variable magnification finder of the real image type according to claim 3, wherein the optical axis bonding state and the retracted state are switchable (N-1).
A real image type variable power viewfinder in which each of the reflecting means is a mirror, and the postures are switched in a swinging manner. 5. The real image variable magnification finder according to claim 2, 3 or 4, wherein, when the optical axes are switched, two focal length variable objective systems involved in the optical axis switching have the same focal length. A real image type zoom finder.