JPH1010440A - Finder optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a real image type finder optical system by which the harmful substance of dust or the like stuck on the surface of a lens is prevented from being observed and the excellent observation of a finder image is easily performed. SOLUTION: In this finder optical system by which an object image formed by a luminous flux passing through an objective optical system OL on a primary image formation surface IP is made an erect normal image through a condenser lens FL and an image inverting means P in order and the object image being the erect normal image is observed through the eyepiece E, when distance between the primary image formation surface IP and the condenser lens FL is defined as d(mm) and the focal distance of the eyepiece is defined as f(mm), the condition of 4<1000(mm)×d/f<2> is satisfied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a finder optical system, and more particularly, to a finder image (object image) of an inverted real image formed on a primary image forming surface by an objective optical system via a condenser lens and image reversing means. The present invention relates to a viewfinder optical system which is observed through an eyepiece as a viewfinder image.

[0002]

2. Description of the Related Art Conventionally, in a finder system such as a photographic camera or a video camera, a real image formed by observing a finder image of a real image formed on a primary image forming surface through an eyepiece through an image inverting means. Various finder optical systems have been proposed. The real image type finder optical system is easily used in cameras with a zoom lens recently because the size of the entire optical system can be easily reduced as compared with the virtual image type finder optical system.

As a real image type finder optical system, for example, Japanese Patent Application Laid-Open Nos. 3-233420 and 4-2145.
17, JP-A-4-230719, JP-A-5-230719
In JP-A-164964, JP-A-6-82694, JP-A-6-289293, and the like, an object image (finder image) formed on a primary imaging surface near a condenser lens by an objective optical system having a variable magnification system is disclosed. ) Is converted into an erect finder image via an image inverting means and observed with an eyepiece. At this time, the primary image forming surface is positioned on the eyepiece side of the condenser lens, or is positioned near the condenser lens, thereby condensing the light flux from the primary image forming surface and guiding the light to the subsequent eyepiece. doing.

[0004]

In a conventional real image type finder optical system using an image inverting means such as a Porro prism for erecting an erect image, the primary image forming surface of the objective optical system is moved to the vicinity of a condenser lens or image inversion. It is provided near the entrance surface of the means. For this reason, if dust, dust, or other harmful substances adhere to the lens surface of the condenser lens or the incident surface of the image reversing means, they are observed together with the finder image through the eyepiece, and the finder image is observed. There was a problem that it became difficult.

According to the present invention, when an object image formed on a primary image forming surface by an objective optical system is observed by an eyepiece as an erect erect image using a condenser lens and image reversing means, a primary image formed by the objective optical system is used. It is an object of the present invention to provide a real image type finder optical system which enables a good finder image to be observed by appropriately setting the position of the surface so that dust, dust, and other harmful substances are not observed together with the finder image. .

[0006]

According to the present invention, there is provided a finder optical system comprising: (1-1) a light beam passing through an objective optical system;
It is characterized in that an object image formed on the next image forming plane is sequentially turned into an erect erect image via a condenser lens and an image inverting means, and the object image of the erect erect image is observed via an eyepiece.

In particular, the objective optical system comprises a variable power system having at least two lens groups of a lens group having a positive refractive power and a lens group having a negative refractive power. It is characterized in that the correction is performed by moving one lens group on the optical axis.

[0008]

1 to 4 show a first embodiment of the present invention.
It is principal part sectional drawing of 4 optical systems. In the figure, OL denotes an objective optical system, which is composed of a variable power system. G is a protective glass disposed on the object side of the objective optical system OL. IP is a primary imaging surface on which an object image (finder image) is formed by the objective optical system OL. SP is an aperture. FL denotes a condenser lens, which is located closer to the observer than the primary imaging plane IP. P denotes an image inverting member for an erect image, such as a Porro prism, and is shown as a glass block having an expanded optical path in the figure. E is an eyepiece and EP is an eye point.

In this embodiment, 1 is set by the objective optical system OL.
The finder image formed on the next image plane IP is observed as an erect image via the eyepiece E from the eye point EP via the condenser lens FL and the image reversing member P. At this time, the primary imaging plane IP is located closer to the object side than the condenser lens FL, and the distance between them is longer than a predetermined value so that the primary imaging plane IP adheres to the lens surface of the condenser lens FL, the entrance surface of the image reversing member P, and the like. Harmful substances such as dust and dust are prevented from being observed together with the viewfinder image.

In this embodiment, when the distance between the primary imaging surface and the condenser lens is d (mm) and the focal length of the eyepiece is f (mm), 4 <1000 (mm) × d / f ² (1) The following condition is satisfied.

By appropriately setting the focal length f of the eyepiece lens and the distance d between the primary imaging surface and the condenser lens so as to satisfy the conditional expression (1), dust on the lens surface of the condenser lens can be obtained. Even if harmful substances such as dust and dust are attached, these harmful substances are prevented from being observed together with the finder image, thereby facilitating observation of a good finder image.

The objective optical system OL shown in FIG.
A first lens unit L1 having a negative refractive power including two negative lenses, a second lens unit L2 having a positive refractive power including a positive lens and a negative lens, and 1
The third lens unit L3 has a positive refractive power and includes three lens units. Then, the second unit (magnifying unit) L2 is moved to the object side to perform magnification in the direction in which the finder magnification is enlarged (from the wide-angle end to the telephoto end). (Group) L1 is provided with a competition function, and is moved and corrected while having a convex locus on the image surface side. Third
The group L3 may be fixed or moved during zooming. The condenser lens FL is joined to the image reversing member P.

The objective optical system OL shown in FIG.
It has two lens groups, a first group L1 of negative refractive power composed of two negative lenses, and a second group L2 of positive refractive power composed of a positive lens and a negative lens. Then, the second unit (magnifying unit) L2 is moved to the object side to perform magnification in the direction in which the finder magnification is enlarged (from the wide-angle end to the telephoto end). (Group) L1 is provided with a competition function, and is moved and corrected while having a convex locus on the image surface side. The condenser lens FL is joined to the image reversing member P.

The objective optical system OL shown in FIG.
A first group of positive refractive power composed of two positive lenses, a second group of negative refractive power composed of one negative lens, a third group of positive refractive power composed of one positive lens, and one positive lens It has four lens groups, a fourth group of lenses having a positive refractive power. Then, the second unit (magnifying unit) L2 is moved to the image plane side to perform magnification in the direction in which the finder magnification is enlarged (from the wide-angle end to the telephoto end). Group) L4 is provided with a competition function, and is moved and corrected while having a convex locus toward the object side. The first lens unit L1 and the third lens unit L3 are fixed during zooming. In the present embodiment, the condenser lens FL and the image reversing member P are integrally formed.

The objective optical system OL shown in FIG.
A first unit L1 having a positive refractive power composed of two negative lenses and two positive lenses, a second unit L2 having a negative refractive power composed of two negative lenses, and a negative refractive power composed of one negative lens Third group L of
3, a fourth unit L4 having a positive refractive power and including one positive lens;
It has six lens groups, a fifth lens unit L5 having a positive refractive power composed of one positive lens and a sixth lens unit L6 having a negative refractive power composed of one negative lens. Then, the second lens unit (variable magnification unit) L2
Is moved to the image plane side to perform zooming in the direction in which the finder magnification is enlarged (from the wide-angle end to the telephoto end), and the third lens unit L3 and the fifth lens unit L5 are provided with a competing function for image plane fluctuations caused by zooming. As a correction group, both are moved while having a convex trajectory toward the object side for correction. First group L1, fourth group L4 and sixth group
The group L6 is fixed during zooming.

Next, numerical examples of the present invention will be described. In the numerical examples, Ri is the radius of curvature of the i-th lens surface in order from the object side, Di is the i-th lens thickness and air spacing from the object side, and Ni and νi are the i-th lens surfaces in order from the object side. The refractive index and Abbe number of glass. The aspherical shape has an X-axis in the optical axis direction, an H-axis in a direction perpendicular to the optical axis, a positive traveling direction of light, R ₀ is a paraxial radius of curvature, and A, B, C, D, and E are aspherical coefficients, respectively. And when

[0017]

(Equation 1) It is represented by the following equation. "D-0X" means "10- ^X ". (Numerical Example 1) R 1 = ∞ D 1 = 2.00 N 1 = 1.49171 ν 1 = 57.4 R 2 = ∞ D 2 = Variable R 3 = -1212.35 D 3 = 1.00 N 2 = 1.58306 ν 2 = 30.2 R 4 = 22.75 D 4 = 2.60 R 5 = -5.21 D 5 = 1.00 N 3 = 1.58306 ν 3 = 30.2 R 6 = -8.07 D 6 = Variable R 7 = Aperture D 7 = 0.1 R 8 = 6.58 D 8 = 5.30 N 4 = 1.49171 ν 4 = 57.4 R 9 = -36.90 D 9 = 0.20 R10 = 36.06 D10 = 1.00 N 5 = 1.58306 ν 5 = 30.2 R11 = 17.95 D11 = 12.55 R12 = -467.18 D12 = 2.70 N 6 = 1.49171 ν 6 = 57.4 R13 = -399.31 D13 = 2.28 R14 = Primary imaging plane D14 = 3.83 R15 = 13.00 D15 = 4.00 N 7 = 1.52540 ν 7 = 56.3 R16 = ∞ D16 = 0.00 R17 = ∞ D17 = 32.30 N 8 = 1.52540 ν 8 = 56.3 R18 = ∞ D18 = 0.50 R19 = 37.21 D19 = 2.20 N 9 = 1.49171 ν 9 = 57.4 R20 = -24.72 D20 = 15.00 R21 = Eye point Aspheric coefficient R 3 R ₀ = -1.212D + 03 A = -6.015D + 05 B = 3.489D-04 C = -1.072D-05 D = 6.002D-07 E = 1.507D-08 R 8 R ₀ = 6.587D + 00 A = -1.020D-01 B = 3.391D-05 C = -3.651D-06 D = 6.604D-08 E = 5.543D-10 R11 R ₀ = -1.795D + 01 A = -4.578D + 00 B = 1.103D-03 C = 1.474D-05 D = -6.651D -07 E = 1.352D-07 R19 R ₀ = 3.721D + 01 A = -2.516D-07 B = -2.734D-0 5 C = 2.528D-08 D = 3.646D-11 E = -1.205D-11

[0018]

[Table 1] (Numerical Example 2) R 1 = -30.00 D 1 = 1.80 N 1 = 1.58306 ν 1 = 30.2 R 2 = 54.68 D 2 = 3.00 R 3 = -8.50 D 3 = 1.80 N 2 = 1.49171 ν 2 = 57.4 R 4 = -16.24 D 4 = 17.10 R 5 = Aperture D 5 = 0.00 R 6 = 9.99 D 6 = 6.00 N 3 = 1.49171 ν 3 = 57.4 R 7 = -12.56 D 7 = 0.12 R 8 = 14.46 D 8 = 1.50 N 4 = 1.58306 ν 4 = 30.2 R 9 = 9.32 D 9 = Variable R10 = Primary imaging plane D10 = 4.87 R11 = 23.00 D11 = 5.00 N 5 = 1.57090 ν 5 = 33.8 R12 = ∞ D12 = 0.00 R13 = ∞ D13 = 26.70 N 6 = 1.57090 ν 6 = 33.8 R14 = ∞ D14 = 0.20 R15 = 21.38 D15 = 3.00 N 7 = 1.49171 ν 7 = 57.4 R16 = -31.70 D16 = 20.00 R17 = Eye point Aspheric coefficient R 1 R ₀ = -3.000D +01 A = 1.806D + 01 B = 2.505D-04 C = 2.576D-06 D = 1.794D-07 E = 0 R 4 R ₀ = -1.624D + 01 A = -5.137D + 01 B = -1.455 D-03 C = 9.163D-05 D = -2.193D-06 E = 0 R 6 R ₀ = 9.999D + 00 A = 3.582D-01 B = -1.950D-04 C = -1.407D-06 D = -3.025D-08 E = 0 R 7 R ₀ = -1.256D + 01 A = -4.596D-01 B = 7.026D-05 C = 5.778D-07 D = -3.857D-08 E = 0 R 9 R ₀ = 9.327D + 00 A = -9.026D-01 B = 3.714D-04 C = -2.253D-06 D = 3.329D-07 E = 0 R15 R ₀ = 2.138D + 01 A = -3.779D-03 B = 1.336D-04 C = -1.799D-05 D = 5.364D-07 E = -5.561D-09

[0019]

[Table 2] (Numerical Example 3) R 1 = 29.86 D 1 = 3.50 N 1 = 1.49171 ν 1 = 57.4 R 2 = -66.50 D 2 = Variable R 3 = -12.13 D 3 = 1.35 N 2 = 1.49171 ν 2 = 57.4 R 4 = 17.18 D 4 = Variable R 5 = 25.81 D 5 = 5.70 N 3 = 1.49171 ν 3 = 57.4 R 6 = -10.88 D 6 = Variable R 7 = 16.40 D 7 = 4.20 N 4 = 1.49171 ν 4 = 57.4 R 8 = -2074.80 D 8 = 10.30 R 9 = Primary imaging plane D 9 = 4.00 R10 = 11.72 D10 = 32.00 N 5 = 1.52540 ν 5 = 56.3 R11 = ∞ D11 = 0.00 R12 = ∞ D12 = 0.50 R13 = 25.31 D13 = 2.20 N 6 = 1.49171 ν 6 = 57.4 R14 = -28.17 D14 = 15.00 R15 = eye point Aspherical surface coefficient R 1 R ₀ = 2.986D + 01 A = -8.051D + 00 B = 1.829D-05 C = 3.076D-07 D = 2.076D-09 E = 0 R 3 R ₀ = -1.213D + 01 A = -1.837D + 00 B = 2.548D-04 C = -9.542D-06 D = 0 E = 0 R 4 R ₀ = 1.718D + 01 A = 3.960D + 00 B = 1.515D-05 C = -6.474D-06 D = 0 E = 0 R 6 R ₀ = -1.088D + 01 A = -1.478D + 00 B = 2.464D -05 C = -1.505D-06 D = 2.092D-08 E = -1.536D-11 R13 R ₀ = 2.531D + 01 A = -5.392D-01 B = -5.367D-05 C = 3.072D-06 D = -1.907D-07 E = 2.226D-09

[0020]

[Table 3] (Numerical Example 4) R 1 = 35.77 D 1 = 0.90 N 1 = 1.84666 ν 1 = 23.7 R 2 = 14.79 D 2 = 0.70 R 3 = 15.90 D 3 = 4.30 N 2 = 1.49171 ν 2 = 57.4 R 4 =- 59.09 D 4 = 0.20 R 5 = 13.10 D 5 = 4.20 N 3 = 1.49171 ν 3 = 57.4 R 6 = -81.43 D 6 = Variable R 7 = -33.93 D 7 = 1.00 N 4 = 1.49171 ν 4 = 57.4 R 8 = 6.10 D 8 = 1.65 R 9 = -6.26 D 9 = 1.00 N 5 = 1.49171 ν 5 = 57.4 R10 = 11.27 D10 = Variable R11 = 25.00 D11 = 1.00 N 6 = 1.49171 ν 6 = 57.4 R12 = 20.00 D12 = Variable R13 = 12.68 D13 = 2.30 N 7 = 1.49171 ν 7 = 57.4 R14 = -11.38 D14 = Variable R15 = 13.33 D15 = 2.20 N 8 = 1.49171 ν 8 = 57.4 R16 = -23.91 D16 = Variable R17 = -32.35 D17 = 1.00 N 9 = 1.58306 ν 9 = 30.2 R18 = 10.11 D18 = 11.59 R19 = Primary imaging plane D19 = 4.26 R20 = 13.00 D20 = 1.00 N10 = 1.52540 ν10 = 56.3 R21 = ∞ D21 = 0.00 N11 = 1.52540 ν11 = 56.3 R22 = ∞ D22 = 35.30 N12 = 1.52540 ν12 = 56.3 R23 = ∞ D23 = 0.10 R24 = 30.47 D24 = 2.40 N13 = 1.49171 ν13 = 57.4 R25 = -27.85 D25 = 23.00 R26 = Eye point Aspheric coefficient R 4 R ₀ = -5.909D + 01 A = 2.017D + 01 B = 2.224D-05 C = 1.317D-07 D = -4.050D-10 E = 0 R 8 R ₀ = 6.105D +00 A = -4.565D-02 B = -6.537D-04 C = -3.877D-05 D = 0 E = 0 R13 R ₀ = 1.268D + 01 A = 6.630D-01 B = -3.051D-04 C = 3.431D-06 D = -6.000D-08 E = 0 R16 R ₀ = -2.391D + 01 A = 7.462D + 00 B = 1.434D-04 C = 1.978D-05 D = -1.261D-06 E = 0 R24 R ₀ = 3.047D + 01 A = -1.107D + 00 B = -3.594D-05 C = 1.099D-06 D = -1.970D-08 E = 0

[0021]

[Table 4] (Numerical Example 4) R 1 = 0.00 D 1 = 1.00 N 1 = 1.49171 ν 1 = 57.4 R 2 = 0.00 D 2 = Variable R 3 = -21.98 D 3 = 1.10 N 2 = 1.49171 ν 2 = 57.4 R 4 = 30.21 D 4 = Variable R 5 = 7.20 D 5 = 4.50 N 3 = 1.49171 ν 3 = 57.4 R 6 = -24.48 D 6 = 0.50 R 7 = 9.81 D 7 = 1.80 N 4 = 1.49171 ν 4 = 57.4 R 8 = 5.22 D 8 = Variable R 9 = 20.63 D 9 = 3.50 N 5 = 1.49171 ν 5 = 57.4 R10 = -22.94 D10 = 6.00 R11 = 0.00 D11 = 0.70 N 6 = 1.52300 ν 6 = 58.6 R12 = 0.00 D12 = 5.30 R13 = 30.22 D13 = 37.00 N 7 = 1.52540 ν 7 = 56.3 R14 = 0.00 D14 = 1.00 R15 = 51.12 D15 = 2.40 N 8 = 1.49171 ν 8 = 57.4 R16 = -24.67 D16 = 16.00 R17 = 0.00

[0022]

[Table 5]

[0023]

According to the present invention, as described above, when an object image formed on a primary image forming surface by an objective optical system is observed as an erect image using an eyepiece lens by using a condenser lens and an image inverting means. By properly setting the position of the primary image forming plane by the objective optical system, dust, dust, and other harmful substances are prevented from being observed together with the finder image, so that a good finder image can be observed. A finder optical system can be achieved.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part when an optical path according to a first embodiment of the present invention is developed.

FIG. 2 is a sectional view of a main part when an optical path according to a second embodiment of the present invention is developed.

FIG. 3 is an essential part cross-sectional view when an optical path according to a third embodiment of the present invention is developed.

FIG. 4 is a sectional view of a main part when an optical path according to a fourth embodiment of the present invention is developed.

FIG. 5 is a sectional view of a main part when an optical path according to a fifth embodiment of the present invention is developed.

[Explanation of symbols]

 OL Objective optical system SP Aperture FL Condenser lens G Protective glass IP Primary image plane P Image reversing means E Eyepiece lens EP Eye point

Claims (6)

[Claims] An object image formed on a primary image forming plane by a light beam passing through an objective optical system is sequentially converted into an erected image via a condenser lens and an image inverting means, and an object image of the erected image is converted to an eyepiece. In the viewfinder optical system to observe through
The distance between the primary imaging plane and the condenser lens is d
(Mm), wherein a focal length of the eyepiece is f (mm), and a condition of 4 <1000 (mm) × d / f ² is satisfied. 2. The objective optical system according to claim 1, wherein said objective optical system comprises a variable power system having at least two lens groups of a lens group having a positive refractive power and a lens group having a negative refractive power. 2. The finder optical system according to claim 1, wherein the correction is performed by moving one lens group on the optical axis. 3. The finder optical system according to claim 2, wherein said condenser lens is formed integrally with said image inverting means. 4. The variable power system according to claim 1, wherein the variable power system includes a positive lens and a negative lens, and a variable power portion having a positive refractive power as a whole and two negative lenses for correcting an image plane variation caused by the variable power. 2. A power correction group.
Viewfinder optical system. 5. The zooming system according to claim 1, wherein the zooming unit includes a zooming unit including one negative lens and a correction unit including one positive lens for correcting an image plane variation caused by zooming. The finder optical system according to claim 4, wherein 6. The zooming system according to claim 1, wherein said zooming system has a zooming unit including two negative lenses and two correction groups for correcting an image plane variation caused by zooming. Viewfinder optical system.