JP2006259476A - Finder optical system and single-lens reflex camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact relay finder optical system coping with a single-lens reflex camera using a comparatively small imaging element, and to provide the single-lens reflex camera. <P>SOLUTION: The finder optical system comprises a relay optical system for re-imaging an object image formed at a primary imaging position 12 by an objective optical system 2 at a secondary imaging position 17, and ocular optical systems 27-29 for observing the image. The relay optical system includes a positive refracting power FP lens group, a negative refracting power N lens group and a positive refracting power RP lens group. The FP lens group is composed of the first lens 21 with positive refracting power and the second lens 22 with positive refracting power. The N lens group is composed of the third lens 23 with negative refracting power. The RP lens group is composed of the fourth lens with negative refracting power and the fifth lens with positive refracting power. When a composed focal length of the FP lens group, the N lens group and the RP lens group is f1r and the primary imaging position and a distance on an optical axis of the primary imaging position side of a first lens is d1, 0.3<d1/f1r<3 is satisfied. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a finder optical system and a single-lens reflex camera, and more particularly to a relay type finder optical system and a single-lens reflex camera using the same.

A single-lens reflex camera having an imaging surface smaller than a conventional Leica size has been proposed and commercialized. In particular, those using electronic image sensors such as CCDs and C-MOSs are expanding the market. Since the imaging surface has become smaller, there is a demand for a finder system with a large magnification. In order to increase the finder magnification, it is necessary to shorten the focal length of the entire finder system, but this makes it difficult to construct a finder system with a widely used pentaprism type. As another method, a relay type finder optical system is known in Patent Document 1, Patent Document 2, etc., but it is used for a relay type finder optical system having good performance, suitable for a small imaging surface, and capable of compact layout. No relay optical system has been proposed.
JP-A-4-337705 JP-A-1-101530

  The present invention has been made in view of such problems of the prior art, and the object thereof is to be compatible with a single-lens reflex camera using a relatively small image sensor, and to provide a compact relay-type finder optical system. It is to provide a single-lens reflex camera used.

A first finder optical system according to the present invention includes a relay optical system for re-imaging a subject image as a primary image formed at a primary image formation position by an objective optical system at a secondary image formation position, and the relay In a finder optical system having an eyepiece optical system for observing an image re-formed by the optical system,
The relay optical system includes a positive refractive power FP lens group, a negative refractive power N lens group, and a positive refractive power RP lens group,
The FP lens group having positive refractive power is composed of a first lens having positive refractive power and a second lens having positive refractive power arranged on the eyepiece optical system side thereof.
The negative lens N lens group is disposed on the eyepiece optical system side of the FP lens group, and includes a third lens having negative refractive power,
The RP lens group having positive refractive power is disposed closer to the eyepiece optical system than the N lens group, and has a fourth lens having negative refractive power and a positive refractive power arranged on the eyepiece optical system side. Consists of 5 lenses,
When the combined focal length of the FP lens group, the N lens group, and the RP lens group is f1r, and the distance on the optical axis on the primary imaging position side of the primary imaging position and the primary lens position is d1, The following conditional expression is satisfied.

0.3 <d1 / f1r <3 (1)
The reason why the first finder optical system adopts the above configuration and the operation and effect will be described below.

  In the relay lens of the present invention, a positive FP lens group, a negative N lens group, and a positive RP lens group are arranged in this order to perform a re-imaging function and aberration correction. By arranging this lens group, the symmetry of refractive power is improved, which is advantageous for aberration correction.

  Furthermore, the positive refracting power of the positive FP lens group is shared by the two positive lenses, and a favorable aberration correction is performed by configuring so as to obtain a necessary power with a lens surface having a gentle curvature.

  The positive RP lens group is composed of two lenses, a negative lens and a positive lens, from the primary imaging plane side, and performs chromatic aberration correction.

  If the lower limit of 0.3 of the conditional expression (1) is exceeded, the first lens will be too close to the primary imaging plane, and the contribution of the power of the first lens to reimaging will be small. Accordingly, the load for re-imaging of the second lens and the fifth lens is increased, and spherical aberration and the like are likely to occur, which is not preferable. When the upper limit of 3 to conditional expression (1) is exceeded, the total length of the relay optical system tends to be long. If the relay optical system is configured while keeping the overall length small, it is difficult to correct aberrations with a small number of sheets, and the number of components increases, which is not preferable in terms of securing compactness and paraxial arrangement.

  In the conditional expression (1), the lower limit value is preferably 0.8, and more preferably 1.2.

  Further, the upper limit is preferably set to 2.4, and more preferably 1.8.

A second finder optical system according to the present invention includes a relay optical system that re-images a subject image as a primary image formed at a primary imaging position by an objective optical system at a secondary imaging position, and the relay In a finder optical system having an eyepiece optical system for observing an image re-formed by the optical system,
The relay optical system includes a positive refractive power FP lens group, an N lens group having a negative refractive power disposed on the eyepiece optical system side, and an RP lens having a positive refractive power disposed on the eyepiece optical system side. Have a group,
The RP lens group is composed of a negative lens and a positive lens in order from the primary imaging position side, to the most secondary imaging position side surface of the FP lens group and the secondary imaging position side surface of the N lens group. The distance on the optical axis is drf, and the distance on the optical axis from the surface on the secondary imaging position side of the N lens group to the surface on the most primary imaging position side of the RP lens group is drr. The following conditional expression (2) is satisfied.

0.2 <drf / drr <0.8 (2)
In the following, the reason why the second finder optical system is configured as described above and the function and effect will be described.

  In the relay lens of the present invention, a positive FP lens group, a negative N lens group, and a positive RP lens group are arranged in this order to perform a re-imaging function and aberration correction. By arranging this lens group, the symmetry of refractive power is improved, which is advantageous for aberration correction.

  Furthermore, it is preferable that the distance between the negative component of the N lens group and the negative lens of the RP lens group is appropriately determined by configuring the RP lens with a negative lens and a positive lens and satisfying the conditional expression (2). Thereby, axial chromatic aberration and off-axis chromatic aberration can be favorably corrected.

  If the lower limit of 0.2 of conditional expression (2) is exceeded, the N lens group and the RP lens group will be too far apart, resulting in an increase in the total length of the relay optical system and an increase in the number of components. It is not preferable in terms of shaft arrangement. If the upper limit of 0.8 is exceeded, the negative lens will be too close, and it will be difficult to balance the correction of axial chromatic aberration and off-axis chromatic aberration.

  Preferably, the N lens group is composed of one negative lens. By doing so, the relay optical system can be made compact. Preferably, the FP lens group is composed of two positive lenses. By configuring so as to obtain a necessary power with a lens surface having a gentle curvature in this way, it is possible to perform a good aberration correction.

  With respect to the conditional expression (2), the lower limit value is preferably set to 0.3, more preferably 0.4.

  Further, the upper limit value is preferably 0.65, more preferably 0.55.

A third finder optical system according to the present invention includes a relay optical system that re-images a subject image as a primary image formed at a primary imaging position by an objective optical system at a secondary imaging position, and the relay In a finder optical system having an eyepiece optical system for observing an image re-formed by the optical system,
The relay optical system includes a positive refractive power FP lens group, a negative refractive power N lens group, and a positive refractive power RP lens group,
The FP lens group having positive refractive power is composed of a first lens having positive refractive power and a second lens having positive refractive power arranged on the eyepiece optical system side thereof.
The negative lens N lens group is disposed on the eyepiece optical system side of the FP lens group, and includes a third lens having negative refractive power,
The positive refractive power RP lens group is disposed closer to the eyepiece optical system than the N lens group,
The combined focal length of the FP lens group, the N lens group, and the RP lens group is f1r, and the distance on the optical axis on the primary imaging position side of the primary imaging position and the primary imaging position is d1, and the RP The following conditional expressions (1) and (3) are satisfied, where ds is the distance on the optical axis from the surface on the secondary image forming position side of the lens group to the secondary image forming position: It is.

0.3 <d1 / f1r <3 (1)
0.5 <ds / f1r <2 (3)
The reason why the above configuration is adopted in the third finder optical system and the effects thereof will be described below.

  In the relay lens of the present invention, a positive FP lens group, a negative N lens group, and a positive RP lens group are arranged in this order to perform a re-imaging function and aberration correction. By arranging this lens group, the symmetry of refractive power is improved, which is advantageous for aberration correction.

  Furthermore, the positive refracting power of the positive FP lens group is shared by the two positive lenses, and a favorable aberration correction is performed by configuring so as to obtain a necessary power with a lens surface having a gentle curvature.

  If the lower limit of 0.3 of the conditional expression (1) is exceeded, the first lens will be too close to the primary imaging plane, and the contribution of the power of the first lens to reimaging will be small. Accordingly, the load for re-imaging of the second lens and the positive lens of the RP lens group is increased, and spherical aberration and the like are likely to occur, which is not preferable. When the upper limit of 3 to conditional expression (1) is exceeded, the total length of the relay optical system tends to be long. If the relay optical system is configured while keeping the overall length small, it is difficult to correct aberrations with a small number of sheets, and the number of components increases, which is not preferable in terms of securing compactness and paraxial arrangement.

  If the lower limit of 0.5 of conditional expression (3) is exceeded, the RP lens group will be too close to the secondary imaging plane, and the contribution of the power of the RP lens group to reimaging will be small. Accordingly, the load on the first lens and the second lens is increased, and spherical aberration is likely to occur. If the upper limit of 2 is exceeded, the total length of the relay optical system becomes long or the number of components increases, which is not preferable in terms of ensuring compactness and paraxial arrangement.

  In the conditional expression (1), the lower limit value is preferably 0.8, and more preferably 1.2.

  Further, the upper limit is preferably set to 2.4, and more preferably 1.8.

  With respect to the conditional expression (3), it is more preferable that the lower limit value is 0.7, further 1.0.

  Further, it is more preferable that the upper limit value is 1.7, further 1.5.

  In the present invention, any one of the configuration of the first finder optical system, the configuration of the second finder optical system, and the configuration of the third finder optical system may be satisfied simultaneously.

For example, a fourth finder optical system of the present invention includes a relay optical system that re-images a subject image as a primary image formed at a primary image forming position by an objective optical system at a secondary image forming position; In a finder optical system comprising an eyepiece optical system for observing an image re-imaged by the relay optical system,
The relay optical system includes a positive refractive power FP lens group, a negative refractive power N lens group, and a positive refractive power RP lens group,
The FP lens group having positive refractive power is composed of a first lens having positive refractive power and a second lens having positive refractive power arranged on the eyepiece optical system side thereof.
The negative lens N lens group is disposed on the eyepiece optical system side of the FP lens group, and includes a third lens having negative refractive power,
The RP lens group having positive refractive power is disposed closer to the eyepiece optical system than the N lens group, and has a fourth lens having negative refractive power and a positive refractive power arranged on the eyepiece optical system side. Consists of 5 lenses,
The combined focal length of the FP lens group, the N lens group, and the RP lens group is f1r, the distance on the optical axis on the primary imaging position side of the primary imaging position and the first lens is d1, and the FP lens. The distance on the optical axis between the surface closest to the secondary imaging position of the lens group and the surface of the N lens group on the secondary imaging position side is drf, and the distance from the surface on the secondary imaging position side of the N lens group to the surface The distance on the optical axis to the surface closest to the primary imaging position of the RP lens group is drr, and the distance on the optical axis from the surface on the secondary imaging position side of the RP lens group to the secondary imaging position is finder optical system characterized by satisfying the following conditional expressions (1), (2), and (3) when ds:
0.3 <d1 / f1r <3 (1)
0.2 <drf / drr <0.8 (2)
0.5 <ds / f1r <2 (3)
Can be configured.

  According to a fifth finder optical system of the present invention, in the first to fourth finder optical systems, the conditional expression (4) is provided between the secondary imaging position side surface and the secondary imaging position of the positive RP lens group. The relay optical system auxiliary lens is arranged so as to satisfy the above.

0.25 <dh / ds <0.75 (4)
Where dh is the distance on the optical axis of the secondary imaging position side of the RP lens group and the RP lens group side of the relay optical system auxiliary lens,
ds: distance on the optical axis from the surface on the secondary imaging position side of the RP lens group to the secondary imaging position;
It is.

  The reason why the above configuration is adopted and the function and effect of the fifth finder optical system will be described below.

  By placing a certain distance between the RP lens group and the relay optical system auxiliary lens, the on-axis light beam and the off-axis light beam are separated, and the off-axis aberration correction effect is enhanced. Further, it is possible to supplement the condenser function and pupil aberration correction function in the secondary imaging operation. If the lower limit of 0.25 in the conditional expression (4) is exceeded, the separation of the on-axis light beam and the off-axis light beam is not sufficient, and if the upper limit of 0.75 is exceeded, the image forming position is too close. It becomes difficult to produce an effect on aberration correction. Preferably, the relay optical system auxiliary lens is a positive lens.

  For conditional expression (4), the lower limit is preferably set to 0.3, and more preferably to 0.4.

  Moreover, it is preferable to make the upper limit into 0.6, further 0.5.

  The sixth finder optical system of the present invention is characterized in that in the fifth finder optical system, an aspherical surface is used for at least one surface of the relay optical system auxiliary lens.

  The reason why the above configuration is adopted in the sixth finder optical system and the effects thereof will be described below.

  By using an aspherical surface for the relay optical system auxiliary lens, it is possible to effectively control off-axis light beams having high separability and enhance off-axis aberration correction effects.

  According to a seventh finder optical system of the present invention, in the first to sixth finder optical systems, the RP lens group is a cemented lens in which a negative lens and a positive lens are bonded together.

  The reason why the above configuration is adopted in the seventh finder optical system and the effects thereof will be described below.

  By using a cemented lens as the RP lens group, decentration sensitivity is lowered, which is advantageous for correcting chromatic aberration. In addition, it is possible to easily control the lens thickness by suppressing the occurrence of high-order aberrations.

  A single-lens reflex camera including the finder optical system according to any one of the first to seventh aspects described above and a focusing screen arranged at one image forming position can be used when a small image sensor is used. Even in such a case, the camera can observe a good subject.

  According to the present invention described above, it is possible to realize a compact relay-type finder optical system with good refractive power symmetry and good aberration correction, and also for a single-lens reflex camera using a relatively small image sensor. It is possible to provide a compact relay type finder optical system and a single-lens reflex camera using the same.

  Hereinafter, a finder optical system and a single-lens reflex camera of the present invention will be described based on examples.

  FIG. 1 shows a cross-sectional view taken along the optical axis by developing the finder optical system of Example 1 of the present invention.

In FIG. 1, this finder optical system includes a first lens having positive refractive power indicated by surfaces r _{7 to} r ₈ , a second lens having positive refractive power indicated by surfaces r _{9 to} r ₁₀ , and surfaces r _{12 to} r _13. A lens group having a positive refractive power, a surface r, which is composed of a third lens having a negative refractive power represented by the lens, a cemented lens of a fourth lens having a negative refractive power represented by the surfaces r _{14 to} r ₁₆ and a fifth lens having a positive refractive power. ₁₈ ~r ₁₉ positive refractive power of the relay optical system auxiliary lens shown in, and, and a positive refractive power of the condenser lens shown in terms r ₂₁ ~r _22, formed on the primary image position indicated by surface r ₁ It is intended to be re-imaged secondary imaging position shown an object image as a primary image that is a plane r _23, an aperture stop which is indicated by surface r ₁₁ between the second lens and the third lens I have. In this embodiment, the secondary image formation position of the surface r ₂₃ coincides with the surface r ₂₂ opposite to the primary image formation side of the condenser lens 26.

Reimaged been image to secondary image position r _23, a cemented lens of a biconcave negative lens and a biconvex positive lens indicated by surface r ₂₆ ~r _28, biconvex represented in terms r ₂₉ ~r ₃₀ Through an eyepiece optical system including a positive lens and a convex flat positive lens indicated by surfaces r _{31 to} r ₃₂ , an enlarged observation is performed via an observer's pupil located on the surface r ₃₃ , that is, an eye point EP.

In the configuration of FIG. 1, the surfaces r _{2 to} r ₅ between the primary imaging position and the first lens are prisms 13 to be described later for bending the optical axis, and the surface r ₆ is a mirror 14 to be described later for bending the optical axis. The surface r ₁₇ between the fifth lens and the relay optical system auxiliary lens, and the surface r ₂₀ between the relay optical system auxiliary lens and the condenser lens are assumed to be mirrors 15 and 16 described later that bend the optical axis, respectively. is doing. Further, the parallel flat plate indicated by the surfaces r _{24 to} r ₂₅ between the secondary imaging position and the eyepiece optical system is assumed to be a dustproof glass 32 described later.

  Although the numerical data of this embodiment will be described later, the first lens constituting the finder optical system is a positive meniscus lens having a convex surface facing the primary imaging position side, and the second lens is a convex surface facing the primary imaging position side. The third lens is composed of a biconcave negative lens, the fourth lens is composed of a negative meniscus lens having a convex surface toward the primary imaging position side, and the fifth lens is composed of a biconvex positive lens. Thus, the relay optical system auxiliary lens is composed of a positive meniscus lens having a convex surface directed toward the primary image forming position, and the condenser lens is composed of a convex positive lens.

An aspherical surface is used for the surface r ₇ on the primary imaging position side of the first lens, both surfaces r ₁₈ and r _{19 of} the auxiliary auxiliary optical system lens, and the surface r ₂₁ on the primary imaging position side of the condenser lens. ing.

In the numerical data to be described later, the relationship between the distances d ₂₅ and d _{30 for} adjusting the diopter and the diopter is shown.

FIG. 2 is a cross-sectional view taken along the optical axis by developing the finder optical system according to the second embodiment of the present invention. Basically, it is substantially the same as the embodiment of FIG. 1 except that the relay optical system auxiliary lens is a biconvex positive lens, and the eye point side lens of the eyepiece optical system is a biconvex positive lens. And aspherical surfaces are used for the three surfaces r ₁₈ and r _{19 of} the relay optical system auxiliary lens, and the surface r ₂₁ on the primary imaging position side of the condenser lens. It is the same.

Numerical data of Examples 1 and 2 are shown below, where r ₁ , r _2, ... Are the curvature radii of the lens surfaces (optical surfaces), and d ₁ , d _2, are the intervals between the lens surfaces (optical surfaces). , N _d1 , n _d2 ... _Are the refractive index of the d-line of each lens (optical medium), and ν _d1 , ν _d2 ... Are the Abbe numbers of each lens (optical medium). The aspherical shape is represented by the following formula, where x is an optical axis with the light traveling direction being positive, and y is a direction orthogonal to the optical axis.

x = (y ² / r) / [1+ {1- (K + 1) (y / r) ² } ^1/2 ]
+ A ₄ y ⁴ + A ₆ y ⁶
Here, r is a paraxial radius of curvature, K is a conical coefficient, and A ₄ and A ₆ are fourth-order and sixth-order aspheric coefficients, respectively.

Example 1 (-1 diopter)
r ₁ = ∞ (primary imaging plane) d ₁ = 7.00
r ₂ = ∞ d ₂ = 10.00 n _d1 = 1.51633 ν _d1 = 64.14
r ₃ = ∞ d ₃ = 22.80 n _d2 = 1.51633 ν _d2 = 64.14
r ₄ = ∞ d ₄ = 10.80 n _d3 = 1.51633 ν _d3 = 64.14
r ₅ = ∞ d ₅ = 8.92
r ₆ = ∞ d ₆ = 7.88
r ₇ = 14.94 (aspherical surface) d ₇ = 4.72 n _d4 = 1.69350 ν _d4 = 53.21
r ₈ = 200.43 d ₈ = 0.44
r ₉ = 14.06 d ₉ = 4.81 n _d5 = 1.80400 ν _d5 = 46.57
r ₁₀ = 25.38 d ₁₀ = 2.09
r ₁₁ = ∞ (aperture) d ₁₁ = 0.75
r ₁₂ = -14.50 d ₁₂ = 1.10 n _d6 = 1.84666 ν _d6 = 23.78
r ₁₃ = 10.42 d ₁₃ = 8.92
r ₁₄ = 300.05 d ₁₄ = 1.60 n _d7 = 1.71736 ν _d7 = 29.52
r ₁₅ = 26.50 d ₁₅ = 5.46 n _d8 = 1.80400 ν _d8 = 46.57
r ₁₆ = -22.88 d ₁₆ = 10.71
r ₁₇ = ∞ d ₁₇ = 11.22
r ₁₈ = 30.04 (aspherical surface) d ₁₈ = 5.55 n _d9 = 1.52542 ν _d9 = 55.78
r ₁₉ = 276.45 (aspherical surface) d ₁₉ = 10.67
r ₂₀ = ∞ d ₂₀ = 11.00
r ₂₁ = 56.07 (aspherical surface) d ₂₁ = 3.05 n _d10 = 1.52542 ν _d10 = 55.78
r ₂₂ = ∞ d ₂₂ = 0.00
r ₂₃ = ∞ (secondary imaging plane) d ₂₃ = 4.14
r ₂₄ = ∞ d ₂₄ = 1.00 n _d11 = 1.51633 ν _d11 = 64.14
r ₂₅ = ∞ d ₂₅ = 7.68
r ₂₆ = -14.71 d ₂₆ = 1.37 n _d12 = 1.84666 ν _d12 = 23.78
r ₂₇ = 66.77 d ₂₇ = 6.56 n _d13 = 1.60311 ν _d13 = 60.64
r ₂₈ = -20.00 d ₂₈ = 0.50
r ₂₉ = 244.69 d ₂₉ = 3.62 n _d14 = 1.78590 ν _d14 = 44.20
r ₃₀ = -39.79 d ₃₀ = 3.36
r ₃₁ = 37.55 d ₃₁ = 3.30 n _d15 = 1.83400 ν _d15 = 37.16
r ₃₂ = ∞ d ₃₂ = 23.00
r ₃₃ = ∞ (observer's pupil)
Aspherical coefficient 7th surface K = 0.1155
A ₄ = 6.48 × 10 ^-6
18th surface K = -0.8404
A ₄ = 1.39 × 10 ^-5
19th face K = 84.0521
A ₄ = 1.29 × 10 ^-5
21st surface K = -0.6627
A ₄ = 3.05 × 10 ^-5
Diopter adjustment amount -1diopter -3diopter + 1diopter
d ₂₅ 7.68 5.50 9.84
d ₃₀ 3.36 5.54 1.20.

Example 2 (-1 diopter)
r ₁ = ∞ (primary imaging plane) d ₁ = 7.00
r ₂ = ∞ d ₂ = 10.00 n _d1 = 1.51633 ν _d1 = 64.14
r ₃ = ∞ d ₃ = 22.80 n _d2 = 1.51633 ν _d2 = 64.14
r ₄ = ∞ d ₄ = 10.80 n _d3 = 1.51633 ν _d3 = 64.14
r ₅ = ∞ d ₅ = 8.92
r ₆ = ∞ d ₆ = 7.88
r ₇ = 14.32 d ₇ = 4.64 n _d4 = 1.71300 ν _d4 = 53.87
r ₈ = 484.25 d ₈ = 0.41
r ₉ = 15.50 d ₉ = 4.78 n _d5 = 1.80400 ν _d5 = 46.57
r ₁₀ = 23.20 d ₁₀ = 2.07
r ₁₁ = ∞ (aperture) d ₁₁ = 0.75
r ₁₂ = -15.23 d ₁₂ = 1.33 n _d6 = 1.84666 ν _d6 = 23.78
r ₁₃ = 10.30 d ₁₃ = 8.86
r ₁₄ = 312.27 d ₁₄ = 1.49 n _d7 = 1.71736 ν _d7 = 29.52
r ₁₅ = 27.57 d ₁₅ = 5.55 n _d8 = 1.80400 ν _d8 = 46.57
r ₁₆ = -22.16 d ₁₆ = 10.71
r ₁₇ = ∞ d ₁₇ = 11.24
r ₁₈ = 31.04 (aspherical surface) d ₁₈ = 5.53 n _d9 = 1.52542 ν _d9 = 55.78
r ₁₉ = -291.42 (aspherical surface) d ₁₉ = 10.67
r ₂₀ = ∞ d ₂₀ = 11.00
r ₂₁ = 52.58 (aspherical surface) d ₂₁ = 3.05 n _d10 = 1.49236 ν _d10 = 57.86
r ₂₂ = ∞ d ₂₂ = 0.00
r ₂₃ = ∞ (secondary imaging plane) d ₂₃ = 4.14
r ₂₄ = ∞ d ₂₄ = 1.00 n _d11 = 1.51633 ν _d11 = 64.14
r ₂₅ = ∞ d ₂₅ = 7.66
r ₂₆ = -14.33 d ₂₆ = 1.34 n _d12 = 1.84666 ν _d12 = 23.78
r ₂₇ = 75.22 d ₂₇ = 6.54 n _d13 = 1.60311 ν _d13 = 60.64
r ₂₈ = -20.34 d ₂₈ = 0.50
r ₂₉ = 238.56 d ₂₉ = 3.80 n _d14 = 1.78590 ν _d14 = 44.20
r ₃₀ = -37.80 d ₃₀ = 3.31
r ₃₁ = 40.09 d ₃₁ = 3.23 n _d15 = 1.83400 ν _d15 = 37.16
r ₃₂ = -797.23 d ₃₂ = 23.00
r ₃₃ = ∞ (observer's pupil)
Aspheric coefficient 18th surface K = -0.8405
A ₄ = 1.73 × 10 ^-5
19th face K = 84.0517
A ₄ = 1.64 × 10 ^-5
21st surface K = -0.6627
A ₄ = 4.50 × 10 ^-5
A ₆ = -1.81 × 10 ^-7
Diopter adjustment amount -1diopter -3diopter + 1diopter
d ₂₅ 7.66 5.48 9.81
d ₃₀ 3.31 5.49 1.16.

  Aberration diagrams of Examples 1 and 2 are shown in FIGS. 3 and 4, respectively. In these aberration diagrams, (a) is for +1 diopter, (b) is for -1 diopter, (c) is for spherical aberration (SA), astigmatism (AS), distortion (DT), and lateral chromatic aberration at -3 diopter. (CC) is shown. In the figure, “φ” represents the pupil diameter, and “ω” represents the exit angle. The aberration states in these aberration diagrams show the aberration states of the finder optical system after the primary imaging surface.

  The values of conditional expressions (1) to (4) in Examples 1 and 2 are as follows.

Conditional Expression (1) Conditional Expression (2) Conditional Expression (3) Conditional Expression (4)
d1 / f1r drf / drr ds / f1r dh / ds
Example 1 1.66 0.44 1.29 0.42
Example 2 1.65 0.47 1.28 0.42.

  Next, an example of a single-lens reflex camera of the present invention to which the finder optical system as in the above embodiment is applied will be described. FIG. 5 is a cross-sectional view showing a configuration of a single-lens reflex camera equipped with a finder optical system according to Embodiment 1 of the present invention. In the figure, reference numeral 1 denotes a single-lens reflex camera equipped with a finder optical system according to one embodiment of the present invention. Reference numeral 2 denotes an interchangeable photographic lens. The taking lens 2 may be configured integrally with the camera body.

  Below, it demonstrates according to the order which the light beam which emitted from the to-be-photographed object and inject | emitted from the photographic lens 2 progresses.

  The light beam emitted from the photographing lens 2 is reflected by the quick return mirror 11. In this example, the light is reflected at a reflection angle of 90 °. Note that the light beam transmitted through the quick return mirror 11 as a half mirror may be guided to a focus detection means (not shown).

  Thereafter, the direction in which the optical axis is reflected by the quick return mirror 11 is perpendicular to the optical axis emitted from the photographing lens 2 with reference to the position where the optical axis emitted from the photographing lens 2 is reflected by the quick return mirror 11. The direction in which the photographic lens 2 is arranged parallel to the optical axis of the photographic lens 2 is referred to as a subject direction, and the direction opposite to the direction in which the photographic lens 2 is arranged is referred to as an observer direction.

  The light beam reflected by the quick return mirror 11 is incident on a focusing screen 12 disposed at a position (primary imaging position) that is optically equivalent (conjugate) to an imaging device 103 described later. In FIG. 6 to be described later, when the subject image is formed on the image sensor 103, the image is also formed on the focusing screen 12. The focusing screen 12 may have a condenser lens function.

  The light beam emitted from the focusing screen 12 enters the prism 13. The prism 13 has an incident surface 13a, a reflecting surface 13b, a reflecting surface 13c, and an exit surface 13d. The incident surface 13a is desirably perpendicular to the incident optical axis. The light beam incident on the incident surface 13a is reflected toward the subject by the reflecting surface 13b. At this time, the loss of light quantity is reduced by satisfying the total reflection condition. Further, the light beam is reflected upward so that the optical axis has a subject direction and an upward direction component on the reflecting surface 13c (that is, the optical axis direction at this time is between the subject direction and the upward direction). . At this time, the loss of light quantity is reduced by satisfying the total reflection condition. Further, the light beam exits the prism 13 at the exit surface 13d. At this time, the exit surface 13d is desirably perpendicular to the optical axis.

  The light beam emitted from the prism 13 is further reflected by the mirror 14 toward the observer, and the optical axis is approximately parallel to the optical axis of the photographing lens 2.

  Next, the lens 21, the lens 22, the lens 23, and the lens 24 that form the relay optical system are transmitted and subjected to the lens action. In the embodiment of FIG. 5, the lens 21 is a positive meniscus lens having a strong convex surface facing the subject side, and is the first lens of Embodiment 1, and the lens 22 is a positive meniscus lens having a strong convex surface facing the subject side. This is the second lens of Example 1, and these two lenses correspond to the FP lens group. The lens 23 is a biconcave negative lens, which is the third lens of Example 1, and corresponds to the N lens group. The lens 24 is a cemented lens of a negative meniscus lens and a biconvex positive lens having a convex surface facing the subject having a positive composite power. The negative meniscus lens of the cemented lens 24 is the fourth lens of Example 1, and the biconvex positive lens is the fifth lens. The cemented lens 24 corresponds to an RP lens group. The combined power of the lens group disposed here is configured to be positive, and plays a main part of the relay optical system.

  Note that an aperture stop 31 may be disposed in the vicinity of the negative lens 23 to perform efficient pupil transmission.

  Next, the light beam is reflected by the mirror 15, and the optical axis is bent toward the subject and downward. Further, although the optical axis is reflected by the mirror 16 toward the observer, the positive lens 25 is disposed between the mirror 15 and the mirror 16 to improve the imaging performance and the pupil transmission performance of the relay optical system. I am trying. The positive lens 25 corresponds to a relay system auxiliary lens.

  The light beam reflected by the mirror 16 is incident on a condenser lens 26 disposed in the vicinity of the secondary imaging position 17. In the embodiment of FIG. 5, the condenser lens 26 is a convex flat lens having a convex surface on the object side, and the plane side and the secondary image forming position 17 are substantially matched.

  Further, the light beam passes through the dustproof glass 32. The dust-proof glass 32 prevents dust and the like from adhering to the lens surface in the vicinity of the secondary imaging position 17 together with other frames.

  Further, the light beam is subjected to a lens action by the lens 27, the lens 28, and the lens 29 constituting the eyepiece optical system, and is emitted from the camera body. Then, the light beam is guided to the observer's eyes.

  In FIGS. 1 and 2, reference numerals corresponding to the components corresponding to the components in FIG. 5 are given.

  FIG. 6 is a diagram illustrating a situation at the time of photographing with the single-lens reflex camera of FIG. 5. However, the frame line indicating the camera body is omitted.

  At the time of photographing, the quick return mirror 11 is retracted from the optical path, and the light beam emitted from the photographing lens 2 sequentially passes through the filter 101 and the filter 102 and enters the image sensor 103. The filer 101 and the filter 102 have functions such as an infrared cut filter, a low-pass filter, and a dust filter, and are not limited to two. The image sensor 103 is composed of an electronic image sensor such as a CCD or C-MOS, or a silver salt film.

  In the embodiment using the finder optical system of the present invention, the deviation of the conjugate relationship between the primary image forming position and the secondary image forming position due to errors or the like at the time of manufacturing such as assembling is determined as one of the relay optical systems or You may make it correct | amend by adjusting two space | intervals.

  In this case, when adjustment is performed using two intervals, adjustment may be performed by moving a part of the relay optical system in the optical axis direction so that the sum of the adjustment amounts becomes zero.

Specifically, it is desirable to adjust any of the following parts. That is, in Numerical Examples 1 and 2, the adjustment of the distance d ₆ between the primary imaging position r ₁ and the lens (first lens) 21 and the distance d between the lens 22 (second lens) and the lens 23 (third lens). adjustment of ₁₀ + d _11, movement of only the lens 23 (third lens), the lens 24 spacing (fourth lens + fifth lens) only the movement of the lens 25 (relay optical system auxiliary lens) and the lens 26 (condenser lens) Any adjustment or the like may be performed.

  Further, in order to make the optical axis of the photographing lens 2 and the optical axis of the eyepiece optical system of the lenses 27 to 29 have a predetermined relationship, the positions of the mirrors 14 to 16 arranged in the relay optical system are adjusted and corrected. May be.

  In the present invention, a lens action surface may be provided in the vicinity of the primary imaging surface or between the primary imaging surface and the FP lens group (first lens + second lens) to provide a condenser function or the like. A lens working surface may be provided between the RP lens group (fourth lens + fifth lens) and the eyepiece lens group (lenses 27 to 29) to provide a condenser function or the like.

It is sectional drawing which developed the finder optical system of Example 1 of this invention, and took it along the optical axis. It is sectional drawing which developed the finder optical system of Example 2 of this invention, and took it along the optical axis. FIG. 6 is an aberration diagram of Example 1. FIG. 6 is an aberration diagram of Example 2. It is sectional drawing which shows the structure of the single-lens reflex camera carrying the finder optical system of Example 1 of this invention. It is a figure which shows the condition at the time of imaging | photography with the single-lens reflex camera of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Single-lens reflex camera 2 ... Shooting lens 11 ... Quick return mirror 12 ... Focus plate 13 ... Prism 13a ... Incident surface 13b, 13c ... Reflective surface 13d ... Ejection surface 14, 15, 16 ... Mirror 17 ... Secondary image formation position 21 , 22, 23, 24 ... lens 25 ... positive lens 26 ... condenser lens 27, 28, 29 ... lens (eyepiece optical system)
31 ... Aperture 32 ... Dust-proof glass

Claims (8)

A relay optical system for re-imaging a subject image as a primary image formed at a primary image formation position by an objective optical system at a secondary image formation position, and an image re-imaged by the relay optical system A viewfinder optical system with an eyepiece optical system
The relay optical system includes a positive refractive power FP lens group, a negative refractive power N lens group, and a positive refractive power RP lens group,
The FP lens group having positive refractive power is composed of a first lens having positive refractive power and a second lens having positive refractive power arranged on the eyepiece optical system side thereof.
The negative lens N lens group is disposed on the eyepiece optical system side of the FP lens group, and includes a third lens having negative refractive power,
The RP lens group having positive refractive power is disposed closer to the eyepiece optical system than the N lens group, and has a fourth lens having negative refractive power and a positive refractive power arranged on the eyepiece optical system side. Consists of 5 lenses,
When the combined focal length of the FP lens group, the N lens group, and the RP lens group is f1r, and the distance on the optical axis on the primary imaging position side of the primary imaging position and the primary lens position is d1, A viewfinder optical system satisfying the following conditional expression.
0.3 <d1 / f1r <3 (1) A relay optical system for re-imaging a subject image as a primary image formed at a primary image formation position by an objective optical system at a secondary image formation position, and an image re-imaged by the relay optical system A viewfinder optical system with an eyepiece optical system
The relay optical system includes a positive refractive power FP lens group, an N lens group having a negative refractive power disposed on the eyepiece optical system side, and an RP lens having a positive refractive power disposed on the eyepiece optical system side. Have a group,
The RP lens group is composed of a negative lens and a positive lens in order from the primary imaging position side, to the most secondary imaging position side surface of the FP lens group and the secondary imaging position side surface of the N lens group. The distance on the optical axis is drf, and the distance on the optical axis from the surface on the secondary imaging position side of the N lens group to the surface on the most primary imaging position side of the RP lens group is drr. A finder optical system characterized by satisfying the following conditional expression (2).
0.2 <drf / drr <0.8 (2) A relay optical system for re-imaging a subject image as a primary image formed at a primary image formation position by an objective optical system at a secondary image formation position, and an image re-imaged by the relay optical system A viewfinder optical system with an eyepiece optical system
The relay optical system includes a positive refractive power FP lens group, a negative refractive power N lens group, and a positive refractive power RP lens group,
The FP lens group having positive refractive power is composed of a first lens having positive refractive power and a second lens having positive refractive power arranged on the eyepiece optical system side thereof.
The negative lens N lens group is disposed on the eyepiece optical system side of the FP lens group, and includes a third lens having negative refractive power,
The positive refractive power RP lens group is disposed closer to the eyepiece optical system than the N lens group,
The combined focal length of the FP lens group, the N lens group, and the RP lens group is f1r, and the distance on the optical axis on the primary imaging position side of the primary imaging position and the primary imaging position is d1, and the RP A finder that satisfies the following conditional expressions (1) and (3) when the distance on the optical axis from the surface on the secondary image forming position side of the lens group to the secondary image forming position is ds: Optical system.
0.3 <d1 / f1r <3 (1)
0.5 <ds / f1r <2 (3) A relay optical system for re-imaging a subject image as a primary image formed at a primary image formation position by an objective optical system at a secondary image formation position, and an image re-imaged by the relay optical system A viewfinder optical system with an eyepiece optical system
The relay optical system includes a positive refractive power FP lens group, a negative refractive power N lens group, and a positive refractive power RP lens group,
The FP lens group having positive refractive power is composed of a first lens having positive refractive power and a second lens having positive refractive power arranged on the eyepiece optical system side thereof.
The negative lens N lens group is disposed on the eyepiece optical system side of the FP lens group, and includes a third lens having negative refractive power,
The RP lens group having positive refractive power is disposed closer to the eyepiece optical system than the N lens group, and has a fourth lens having negative refractive power and a positive refractive power arranged on the eyepiece optical system side. Consists of 5 lenses,
The combined focal length of the FP lens group, the N lens group, and the RP lens group is f1r, the distance on the optical axis on the primary imaging position side of the primary imaging position and the first lens is d1, and the FP lens. The distance on the optical axis between the surface closest to the secondary imaging position of the lens group and the surface of the N lens group on the secondary imaging position side is drf, and the distance from the surface on the secondary imaging position side of the N lens group to the surface The distance on the optical axis to the surface closest to the primary imaging position of the RP lens group is drr, and the distance on the optical axis from the surface on the secondary imaging position side of the RP lens group to the secondary imaging position is A finder optical system characterized by satisfying the following conditional expressions (1), (2), and (3) when ds.
0.3 <d1 / f1r <3 (1)
0.2 <drf / drr <0.8 (2)
0.5 <ds / f1r <2 (3) 2. A relay optical system auxiliary lens is arranged between the side surface of the secondary imaging position of the positive RP lens group and the secondary imaging position so as to satisfy the conditional expression (4). The finder optical system according to any one of 4.
0.25 <dh / ds <0.75 (4)
Where dh is the distance on the optical axis of the secondary imaging position side of the RP lens group and the RP lens group side of the relay optical system auxiliary lens,
ds: distance on the optical axis from the surface on the secondary imaging position side of the RP lens group to the secondary imaging position;
It is. 6. The finder optical system according to claim 5, wherein an aspherical surface is used for at least one surface of the relay optical system auxiliary lens. The viewfinder optical system according to any one of claims 1 to 6, wherein the RP lens group is a cemented lens in which a negative lens and a positive lens are bonded together. 8. A single-lens reflex camera comprising: the finder optical system according to claim 1; and a focusing screen disposed at the one image forming position.

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