JP2007003625A - Attachment optical system for finder, and waterproof camera case using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-versatility attachment optical system for a finder, with which displacement of exit pupil can be carried out moderately, and satisfactory observation images can be obtained, and to provide a waterproof camera case. <P>SOLUTION: The attachment optical system for the finder, which is disposed on the emission side of a finder optical system, includes, in the order starting from the finder optical system side: a negative lens both faces of which are concave and a positive lens the emission side face of which is convex. The attachment optical system for the finder satisfies conditional equations: (1) 0.6<¾f1/f2¾<1.0, and (2) 0.045<HF1/(d1+d2+d3)<0.091, where f1 is the focal distance of the negative lens, f2 is the focal distance of the positive lens, d1 is the thickness of the negative lens on an optical axis, d2 is the distance between the negative lens and positive lens on the optical axis, d3 is the thickness of the positive lens on the optical axis, and HF1 is the distance from the top of the incident side lens face of the negative lens to the front-side principal point of the negative lens. By the "front side" is meant the side on which light rays are made incident. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is a finder attachment optical system suitable for a still camera, a video camera, etc., and in particular, by displacing the exit pupil position away from the final surface of the finder optical system, it is possible to observe a good object image. The present invention relates to a finder attachment optical system and a waterproof camera case using the same.

  Conventionally, in a single-lens reflex camera or the like, by attaching to the exit side of the eyepiece of the viewfinder optical system, an attachment optical for viewfinder that enables an observer to observe an object image at a predetermined position away from the exit direction. The system is known.

  Further, a waterproof camera case provided with such a finder attachment optical system is also known. Here, the waterproof camera case refers to a case in which the camera is built in so that the camera can be used underwater and can be completely prevented from entering even under water pressure. In general, such a waterproof camera case is optically connected to the operation means that is installed in the case body and can operate the camera from the outside of the case body, and the finder optical system of the built-in camera that is installed in the rear part of the case body. And a finder attachment optical system.

As such an attachment optical system for a finder, for example, as in the optical system described in Patent Document 1, it can be attached to and detached from the camera, and the finder optical system side is connected to the exit side of the finder optical system of the camera. There is an attachment optical system for a finder in which a biconcave negative lens and a positive lens having a convex surface on the exit side are arranged in order to displace the exit pupil of the finder optical system of the camera to the exit side. Moreover, as a waterproof camera case as described above, there is a waterproof camera case provided with a finder attachment optical system, like the waterproof camera case described in Patent Document 2.
JP-A-7-72381 Japanese Patent Laid-Open No. 9-80623

  However, the finder attachment optical system described in Patent Document 1 has a principal point position (distance from the incident side surface of the negative lens to the front principal point) on the front side of the negative lens (the side on which the light beam enters the optical system). Is shallow. For this reason, the thickness of the negative lens on the optical axis is thin and it is difficult to sufficiently displace the exit pupil to the exit side, or the refractive power of the entrance side of the negative lens is too strong, so off-axis aberrations It is difficult to correct.

  In addition, when shooting underwater with such a finder attachment optical system built into the waterproof camera case, there must be a space for the operation keys of the waterproof camera case or between the underwater mask and the photographer's eyes. Since there is a predetermined distance, the projection position of the exit pupil assumed in the finder attachment optical system is unlikely to be the eyeball position (eye point) of the photographer. Point is located.

  Furthermore, since the attachment optical system for the finder provided in the camera case described in Patent Document 2 is too far away from the negative lens and the positive lens, the negative lens is attached to the eyepiece portion of the camera, The positive lens is attached to the waterproof camera case. Therefore, it takes time to prepare for shooting.

  Further, when the distance between the negative lens and the positive lens is large, the distance between the principal points of the negative lens and the positive lens becomes long, and the magnification tends to be small. In order to increase the magnification, the focal length of both lenses must be increased. In this case, the negative lens has a weak influence on the off-axis light beam, and the incident height of the off-axis light beam on the positive lens is low. Therefore, the distance from the exit surface to the observation position is shortened.

  The present invention has been made in view of such problems, and it is possible to appropriately displace the position of the exit pupil while maintaining the magnification, and to reduce off-axis aberrations and to use a lens. To provide a versatile finder attachment optical system capable of obtaining a good observation image while suppressing the influence of decentering, and a waterproof camera case using the same.

In order to achieve the above object, a finder attachment optical system according to the present invention is a finder attachment optical system for observing an object image formed on the exit side of the finder optical system and formed by the finder optical system. The finder attachment optical system has, in order from the finder optical system side, a biconcave negative lens and a positive lens whose exit side is convex, and the following conditional expressions (1), (2 ) Is satisfied.
0.6 <| f1 / f2 | <1.0 (1)
0.045 <HF1 / (d1 + d2 + d3) <0.091 (2)
However,
f1: Focal length of the negative lens f2: Focal length of the positive lens d1: Thickness on the optical axis of the negative lens d2: Distance on the optical axis between the negative lens and the positive lens d3: On the optical axis of the positive lens Thickness HF1: A distance from the surface vertex of the entrance lens surface of the negative lens to the front principal point of the negative lens. The front side means the side on which the light beam enters.

The finder attachment optical system is preferably configured to satisfy the following conditional expression (3).
0.4 <(d1 + d2 + d3) / f2 <1.00 (3)

The finder attachment optical system is preferably configured so that the negative lens satisfies the following conditional expression (4).
-0.15 <(R1 + R2) / (R1-R2) <0.70 (4)
However,
R1: Paraxial radius of curvature of the entrance lens surface of the negative lens R2: Paraxial radius of curvature of the exit lens surface of the negative lens.

In the finder attachment optical system, it is preferable that the positive lens has a biconvex shape and satisfies the following conditional expression (5).
-0.15 <(R3 + R4) / (R3-R4) <0.75 (5)
However,
R3: Paraxial radius of curvature of the entrance lens surface of the positive lens R4: Paraxial radius of curvature of the exit lens surface of the positive lens.

The finder attachment optical system is preferably configured to satisfy the following conditional expressions (6) and (7).
12.00 (mm) <d1 + d2 + d3 <23.00 (mm) (6)
0.41 (mm) <HF1 <2.00 (mm) (7)

The finder attachment optical system is preferably configured to satisfy the following conditional expression (8).
0.08 <d1 / (d1 + d2 + d3) <0.30 (8)

Furthermore, it is more preferable that the finder attachment optical system satisfies the following conditional expression (9).
0.05 <d2 / (d1 + d2 + d3) <0.50 (9)

  In order to achieve the above object, a waterproof camera case according to the present invention includes a case body that incorporates a camera and prevents water from entering under water pressure, and is installed in the case body. A waterproof camera case comprising: operating means capable of operating a camera; and a finder attachment optical system optically connected to a finder optical system of the camera and disposed on an exit side of the finder optical system, The finder attachment optical system is configured using any of the finder attachment optical systems described above.

  According to the present invention, the position of the exit pupil is appropriately displaced, the off-axis aberration is reduced, the magnification is maintained, and an excellent observation image can be obtained while suppressing the influence of decentering by the lens. A finder attachment optical system and a waterproof camera case using the same can be obtained.

  The focal length of the finder attachment optical system is almost infinite. At this time, when the finder attachment optical system is configured to have a negative lens and a positive lens in order from the light incident side, the refractive power of the negative lens inevitably increases. Therefore, by forming the negative lens on which the light beam emitted from the finder is incident into a biconcave shape, it is possible to divide the refractive power between the incident side lens surface and the exit side lens surface of the negative lens and reduce the occurrence of aberrations. Furthermore, if the front principal point of the negative lens is set to an appropriately deep position, the exit pupil can be displaced to the exit side. Further, if the exit side lens surface of the subsequent positive lens is a convex surface having positive refracting power, both lenses are brought close to each other while maintaining a proper distance between the principal points of the negative lens and the positive lens, which is necessary for the positive lens. Eye relief can be secured while maintaining refractive power.

Accordingly, the finder attachment optical system according to the present invention is a finder attachment optical system that is disposed on the exit side of the finder optical system and for observing an object image formed by the finder optical system, the finder attachment optical system. The optical system has, in order from the finder optical system side, a biconcave negative lens and a positive lens whose exit side surface is convex, and satisfies the following conditional expressions (1) and (2). .
0.6 <| f1 / f2 | <1.0 (1)
0.045 <HF1 / (d1 + d2 + d3) <0.091 (2)
However,
f1: Focal length of the negative lens f2: Focal length of the positive lens d1: Thickness on the optical axis of the negative lens d2: Distance on the optical axis between the negative lens and the positive lens d3: On the optical axis of the positive lens Thickness HF1: A distance from the surface vertex of the entrance lens surface of the negative lens to the front principal point of the negative lens. The front side means the side on which the light beam enters.

  Conditional expression (1) defines the ratio of the focal lengths of the negative lens and the positive lens, and means the magnification of the finder attachment optical system. If the lower limit of conditional expression (1) is not reached, the absolute value of the viewfinder magnification becomes too small, and the observation viewing angle becomes small. Note that the upper limit of the conditional expression (1) is not exceeded in the lens configuration as a premise in the present invention.

  Here, in the conditional expression (1), in order to ensure the observation viewing angle, it is more preferable that the lower limit value is 0.63, and further 0.65. In order to displace the exit pupil to a position away from the finder optical system, it is more preferable that the upper limit value is 0.78, and further 0.73.

  Conditional expression (2) uses the distance from the entrance lens surface of the negative lens to the exit lens surface of the positive lens as the denominator, and the front principal point position of the negative lens (from the entrance side vertex of the negative lens to the front principal point) Length). If the lower limit of the condition (2) is not reached, the thickness of the negative lens becomes too thin, and it becomes difficult to displace the exit pupil to a position away from the finder optical system such as a camera. Or, since the refractive power of the exit lens surface of the negative lens becomes smaller due to the shallow principal point position, or the refractive power of the entrance lens surface of the negative lens becomes larger, it is difficult to correct field curvature and the like. Become. If the upper limit of conditional expression (2) is exceeded, the thickness of the negative lens becomes too thick, or the refractive power of the exit lens surface of the negative lens becomes too strong, making it difficult to correct aberrations in the entire observation field. Or, since the length from the entrance lens surface of the negative lens to the exit lens surface of the positive lens is shortened, when trying to secure a long eye relief, the curvature of the exit lens surface of the positive lens becomes too large and mutual eccentricity etc. The effect on the aberration due to is increased.

  Here, in the conditional expression (2), it is more preferable that the lower limit value is 0.048, and further 0.050. Further, the upper limit is more preferably 0.087, and further preferably 0.085.

Moreover, it is preferable that the attachment optical system for viewfinders of this invention satisfies the following conditional expressions (3).
0.4 <(d1 + d2 + d3) / f2 <1.00 (3)

  Conditional expression (3) defines the distance from the entrance lens surface of the negative lens to the exit lens surface of the positive lens with respect to the focal length of the positive lens. If the lower limit of conditional expression (3) is not reached, each lens becomes thin, and it becomes difficult to displace the observation position to a position away from the viewfinder optical system. If the upper limit of conditional expression (3) is exceeded, each lens becomes thick, the rear principal point of the positive lens tends to be deep, and it is difficult to ensure a long eye relief.

  Here, in the conditional expression (3), it is more preferable that the lower limit value is 0.44, further 0.50. Further, it is more preferable that the upper limit value is 0.70, further 0.60.

  The present invention makes it easy to secure the thickness of the negative lens by appropriately deepening the principal point position of the negative lens, and makes it easy to displace the exit pupil position away from the finder optical system such as a camera. . In this case, it is preferable to correct the off-axis aberration generated in the negative lens itself by appropriately adjusting the curvature radius of the entrance lens surface and the exit radius of the negative lens.

Therefore, in the finder attachment optical system of the present invention, it is preferable that the negative lens satisfies the following conditional expression (4).
-0.15 <(R1 + R2) / (R1-R2) <0.70 (4)
However,
R1: Paraxial radius of curvature of the entrance lens surface of the negative lens R2: Paraxial radius of curvature of the exit lens surface of the negative lens.

  Conditional expression (4) defines the shape of the negative lens. If the lower limit of conditional expression (4) is not reached, the curvature of the incident-side lens surface becomes large. On the other hand, if the upper limit of conditional expression (4) is exceeded, the negative refractive power of the exit-side lens surface becomes large. In either case, the incident angle of the off-axis light beam is increased on one surface, and aberration is likely to occur.

  Here, in the conditional expression (4), it is more preferable that the lower limit value is set to -0.08, further 0.01. Further, it is more preferable that the upper limit value is 0.60, further 0.50.

Moreover, it is preferable that the attachment optical system for finder of this invention satisfies the following conditional expressions (5).
-0.15 <(R3 + R4) / (R3-R4) <0.75 (5)
However,
R3: Paraxial radius of curvature of the entrance lens surface of the positive lens R4: Paraxial radius of curvature of the exit lens surface of the positive lens.

  If the lower limit of conditional expression (5) is not reached, the curvature of the entrance-side lens surface of the positive lens will increase, making it difficult to ensure eye relief. If the upper limit of conditional expression (5) is exceeded, the curvature of the exit-side lens surface of the positive lens will increase, and aberration will tend to occur on the exit-side lens surface.

  Here, in the conditional expression (5), it is more preferable that the lower limit value is −0.01, and further 0.10. Further, it is more preferable that the upper limit value is 0.72, and further 0.69.

  When the finder attachment optical system lens is provided in a waterproof camera case for underwater photography, the exit surface of the finder attachment optical system, i.e., the exit lens surface of the positive lens, is appropriately close to the observer. It is desirable that the distance from the exit surface of the finder optical system provided in the main body to the exit side lens surface of the positive lens has a certain length.

Therefore, the finder attachment optical system of the present invention preferably satisfies the following conditional expressions (6) and (7).
12.00 (mm) <d1 + d2 + d3 <23.00 (mm) (6)
0.41 (mm) <HF1 <2.00 (mm) (7)
However,
d1: Thickness on the optical axis of the negative lens d2: Distance on the optical axis between the negative lens and the positive lens d3: Thickness on the optical axis of the positive lens HF1: Surface vertex of the incident-side lens surface of the negative lens To the front principal point of the negative lens. The front side means the side on which the light beam enters.

  If the lower limit of conditional expression (6) is not reached, the exit-side lens surface of the positive lens will be close to the viewfinder optical system, and the position of the exit pupil cannot be displaced much toward the exit side. In addition, when the attachment optical system of the present invention is used for a waterproof camera case or the like, the position of the displaced exit pupil becomes close to the camera, and the camera operation member provided in the waterproof camera case becomes an obstacle. It becomes difficult to observe. If the upper limit of conditional expression (6) is exceeded, the exit-side lens surface of the positive lens will be too far from the camera, and the observation viewing angle will tend to be small.

  Here, in the conditional expression (6), it is more preferable that the lower limit value is 13.50 mm, more preferably 15.00 mm. Further, it is more preferable that the upper limit value is 20.0 mm, more preferably 18.0 mm.

  Conditional expression (7) defines the distance from the surface apex of the incident lens surface of the negative lens to the front principal point of the negative lens. If the lower limit of conditional expression (7) is not reached, the negative lens becomes thin, and it becomes difficult to lengthen the overall length of the finder attachment optical system. Further, the refractive power of the incident lens surface of the negative lens becomes too strong, making it difficult to correct off-axis aberrations. When the upper limit of conditional expression (7) is exceeded, the negative lens becomes too thick, and it becomes difficult to obtain the effect of correcting off-axis aberrations on the incident lens surface of the positive lens.

  Here, in conditional expression (7), it is more preferable that the lower limit value is 0.50 mm, and further 0.65 mm. Further, it is more preferable that the upper limit value is 1.70 mm, further 1.50 mm.

Further, the finder attachment optical system of the present invention is more preferable when the following conditional expression (8) is satisfied.
0.08 <d1 / (d1 + d2 + d3) <0.30 (8)
However,
d1: thickness on the optical axis of the negative lens d2: distance on the optical axis between the negative lens and the positive lens d3: thickness on the optical axis of the positive lens

  Conditional expression (8) defines the thickness of the negative lens on the optical axis. In order to make it easy to maintain the magnification while keeping the total length of the finder attachment optical system to an appropriate length, it is preferable to satisfy the conditional expression (8) so that the principal point interval of the negative lens becomes an appropriate length. . If the lower limit of conditional expression (8) is not reached, it is difficult to deepen the front principal point position of the negative lens. If the upper limit of conditional expression (8) is exceeded, the negative lens becomes thick, that is, the distance from the entrance-side lens surface to the exit-side lens surface of the negative lens becomes long, making it difficult to correct aberrations.

  Here, in conditional expression (8), it is more preferable that the lower limit value is 0.10, and further 0.12. Further, it is more preferable that the upper limit value is 0.21, and further 0.18.

  In order to secure the magnification of the finder attachment optical system and maintain the overall length, it is preferable to increase the ratio of the lens medium to the distance from the entrance lens surface of the negative lens to the exit lens surface of the positive lens. Therefore, it is preferable that the distance on the optical axis between the negative lens and the positive lens is reasonably short.

Therefore, it is preferable that the finder attachment optical system of the present invention satisfies the following conditional expression (9).
0.05 <d2 / (d1 + d2 + d3) <0.50 (9)
However,
d1: thickness on the optical axis of the negative lens d2: distance on the optical axis between the negative lens and the positive lens d3: thickness on the optical axis of the positive lens

  If the lower limit of conditional expression (9) is not reached, the distance between the negative lens and the positive lens becomes too short, making it difficult to correct coma. If the upper limit of conditional expression (9) is exceeded, the distance between the negative lens and the positive lens becomes too long, and it becomes difficult to ensure an appropriate magnification and maintain the overall length.

  Here, in conditional expression (9), it is more preferable that the lower limit value is 0.08, and further 0.10. Further, it is more preferable that the upper limit value is 0.45, further 0.40.

  Further, the waterproof camera case according to the present invention includes a case body that incorporates a camera and prevents entry of water under water pressure, an operating means that is installed in the case body and that can operate the camera from the outside of the case body, A waterproof camera case optically connected to the finder optical system of the camera and provided with a finder attachment optical system disposed on the exit side of the finder optical system, wherein the finder attachment optical system is any of the above The finder attachment optical system was used.

  The above-described finder attachment optical system displaces the exit pupil from the camera to the exit side, obtains an appropriate magnification, and can satisfactorily correct off-axis aberrations. Therefore, by using it for a waterproof camera case, it is possible to observe the subject satisfactorily during underwater photography.

  It should be noted that it is more preferable to satisfy a plurality of characteristic items of the present invention at the same time because the respective effects can be obtained simultaneously.

  Hereinafter, the present invention will be described in detail based on illustrated embodiments.

In the numerical data of the lenses in the following examples, r is the radius of curvature of each lens surface, D is the thickness or spacing of each lens, Nd is the refractive index of each lens at the d-line, and Vd is the d-line of each lens. Abbe number in k, k is a conical coefficient, and A ₄ , A ₆ and A ₈ are aspherical coefficients, respectively.
Further, the aspheric shape is expressed by the following equation using the aspheric coefficient. However, the coordinate in the optical axis direction is Z, and the coordinate in the direction perpendicular to the optical axis is Y.
Z = (Y ² / r) / [1+ {1− (1 + k) · (Y / r) ² } ^1/2 ]
+ A ₄ Y ⁴ + A ₆ Y ⁶ + A ₈ Y ⁸

  FIG. 1 is a diagram illustrating a configuration of a finder optical system and a finder attachment optical system according to the present embodiment. FIG. 2 is an aberration diagram showing spherical aberration, astigmatism, distortion, and lateral chromatic aberration of the finder optical system at the assumed exit pupil position. FIG. 3 is an aberration diagram showing spherical aberration, astigmatism, distortion, and lateral chromatic aberration of the finder attachment optical system according to the present example at an assumed eye point.

First, the finder optical system L _f will be described. The finder optical system L _f, as shown in FIG. 1, in order from the image plane side obtained by other optical systems such as a camera having the finder optical system L _f, positive having a convex surface directed toward the image plane side A meniscus lens L _f1 , a biconvex positive lens L _f2 having an aspherical imaging surface side, a biconcave negative lens L _f3 , and a cover glass CG.

Next, numerical data of lenses constituting the finder optical system L _f will be shown.

Diopter -1 (1 / m)
Pupil diameter (diameter) 8 (mm)
Injection half angle of view 12.79 (°)

Surface r D Nd Vd
1 (imaging plane) ∞ 72.13
2 20.932 7.80 1.51633 64.14
3 1012.061 1.8464
4 * 21.015 5.22 1.52542 55.78
5 -782.022 3.6568
6 -68.933 1.80 1.58423 30.49
7 13.879 2.5
8 ∞ 1.0 1.51633 64.14
9 ∞
In addition, * mark represents the aspherical surface. Further, the surface number 8 is a surface on the incident side of the cover glass CG, and the surface number 9 is a surface on the emission side of the cover glass CG.

Aspherical coefficient surface rk A ₄ A ₆ A ₈
4 21.015 0.000 -1.47489 × 10 ^-5 -3.77827 × 10 ^-8 -2.49840 × 10 ^-10

Note that the exit pupil contemplated by the finder optical system L _f from the plane of the exit side of the cover glass CG, is located a distance of about 20mm in the direction of the finder attachment optical system L _a (19.8023mm). The aberration diagram shown in FIG. 2 shows the aberration at that position.

Next, a description will be given attachment optical system L _a finder. Finder attachment optical system L _a of this embodiment, in order from the finder optical system L _f side, a biconcave negative lens L _a1, is composed of a biconvex positive lens L _a2. In addition, since any lens surface is spherical, it is possible to reduce the manufacturing cost compared to a lens having an aspherical surface.

Subsequently, numerical data of lenses constituting the attachment optical system L _a finder.

Surface r D Nd Vd
1 -45.003 2.10 1.51633 64.14
2 20.878 8.14
3 39.062 7.00 1.51633 64.14
4 -39.062

The data related to the above conditional expressions is
Conditional expression (1): | f1 / f2 | = 0.70
Conditional expression (2): HF1 / (d1 + d2 + d3) = 0.054
Conditional expression (3): (d1 + d2 + d3) /f2=0.442
Conditional expression (4): (R1 + R2) / (R1-R2) = 0.37
Conditional expression (5): (R3 + R4) / (R3-R4) = 0.00
Conditional expression (6): d1 + d2 + d3 = 17.24 (mm)
Conditional expression (7): HF1 = 0.94 (mm)
Conditional expression (8): d1 / (d1 + d2 + d3) = 0.218
Conditional expression (9): d2 / (d1 + d2 + d3) = 0.472
It is. In addition,
f1 = −27.3246 (mm)
f2 = 39.017 (mm)
It is.

The distance on the optical axis Lc from the exit-side glass surface of the cover glass CG of the finder optical system L _f to the entrance-side lens surface vertex of the negative lens L _a1 is 7.68 mm. Distance on the optical axis Lc from the vertex of the exit-side lens surface of the positive lens L _a2 to the exit pupil to be projected is 12.28mm in length in air. Distance on the optical axis Lc from the exit-side lens surface of the positive lens L _a2 to the eye point E on the assumption is 28.00mm in length in air. The aberration diagram shown in FIG. 3 shows the aberration at the position of the eye point E (photographer's eyeball).

  FIG. 4 is a diagram illustrating a configuration of a finder optical system and a finder attachment optical system according to the present embodiment. FIG. 5 is an aberration diagram showing spherical aberration, astigmatism, distortion, and lateral chromatic aberration of the finder attachment optical system according to the present example at an assumed eye point.

On the exit side of the similarly finder optical system L _f this embodiment is also as in Example 1, has a configuration that connects the attachment optical system L _a finder. Since this finder optical system L _f is the same as that of the first embodiment, its description is omitted.

Finder attachment optical system L _a of this embodiment, in the same manner as in Example 1, in order from the finder optical system L _f side, a biconcave negative lens L _a1, is composed of a biconvex positive lens L _a2. In addition, since any lens surface is spherical, it is possible to reduce the manufacturing cost compared to a lens having an aspherical surface.

Subsequently, numerical data of lenses constituting the attachment optical system L _a finder.

Surface r D Nd Vd
1 -31.4876 2.4221 1.51633 64.14
2 22.2548 5.5833
3 57.5968 9.1945 1.51633 64.14
4 -26.002

The data related to the above conditional expressions is
Conditional expression (1): | f1 / f2 | = 0.69
Conditional expression (2): HF1 / (d1 + d2 + d3) = 0.054
Conditional expression (3): (d1 + d2 + d3) /f2=0.477
Conditional expression (4): (R1 + R2) / (R1-R2) = 0.17
Conditional expression (5): (R3 + R4) / (R3-R4) = 0.38
Conditional expression (6): d1 + d2 + d3 = 17.20 (mm)
Conditional expression (7): HF1 = 0.9217 (mm)
Conditional expression (8): d1 / (d1 + d2 + d3) = 0.1408
Conditional expression (9): d2 / (d1 + d2 + d3) = 0.325
It is. In addition,
f1 = −24.8717 (mm)
f2 = 36.0458 (mm)
It is.

The distance on the optical axis Lc from the exit-side glass surface of the cover glass CG of the finder optical system L _f to the entrance-side lens surface vertex of the negative lens L _a1 is 5.83Mm. Distance on the optical axis Lc from the vertex of the exit-side lens surface of the positive lens L _a2 to the exit pupil to be projected is 11.48mm in length in air. Distance on the optical axis Lc from the exit-side lens surface of the positive lens L _a2 to the eye point E on the assumption is 28.86mm in length in air. The aberration diagram shown in FIG. 5 shows the aberration at the position of the eye point E.

  FIG. 6 is a diagram illustrating a configuration of a finder optical system and a finder attachment optical system according to the present embodiment. FIG. 7 is an aberration diagram showing spherical aberration, astigmatism, distortion, and lateral chromatic aberration of the finder attachment optical system according to the present example at an assumed eye point.

This embodiment also Example 1, on the exit side of the similarly finder optical system L _f of Example 2 has a structure that connects the attachment optical system L _a finder. Since this finder optical system L _f is the same as that in the first and second embodiments, the description thereof is omitted.

Finder attachment optical system L _a of this embodiment, in the same manner as in Example 1, Example 2, in order from the finder optical system L _f side, a biconcave negative lens L _a1, a biconvex positive lens L _a2, is composed of ing. In addition, since any lens surface is spherical, it is possible to reduce the manufacturing cost compared to a lens having an aspherical surface.

Subsequently, numerical data of lenses constituting the attachment optical system L _a finder.

Surface r D Nd Vd
1 -38.3925 2.05 1.51633 64.14
2 19.7235 7.51
3 42.211 7.89 1.51633 64.14
4 -32.1496

The data related to the above conditional expressions is
Conditional expression (1): | f1 / f2 | = 0.68
Conditional expression (2): HF1 / (d1 + d2 + d3) = 0.051
Conditional expression (3): (d1 + d2 + d3) /f2=0.476
Conditional expression (4): (R1 + R2) / (R1-R2) = 0.32.
Conditional expression (5): (R3 + R4) / (R3-R4) = 0.14
Conditional expression (6): d1 + d2 + d3 = 17.44 (mm)
Conditional expression (7): HF1 = 0.88 (mm)
Conditional expression (8): d1 / (d1 + d2 + d3) = 0.174
Conditional expression (9): d2 / (d1 + d2 + d3) = 0.430
It is. In addition,
f1 = −24.9359 (mm)
f2 = 36.67 (mm)
It is.

The distance on the optical axis Lc from the exit-side glass surface of the cover glass CG of the finder optical system L _f to the entrance-side lens surface vertex of the negative lens L _a1 is 7.81Mm. Distance on the optical axis Lc from the vertex of the exit-side lens surface of the positive lens L _a2 to the exit pupil to be projected is 17.48mm in length in air. Distance on the optical axis Lc from the exit-side lens surface of the positive lens L _a2 to the eye point E on the assumption is 33.27mm in length in air. The aberration diagram shown in FIG. 7 shows the aberration at the position of the eye point E.

  FIG. 8 is a diagram illustrating a configuration of a finder optical system and a finder attachment optical system according to the present embodiment. FIG. 9 is an aberration diagram showing spherical aberration, astigmatism, distortion, and lateral chromatic aberration of the finder attachment optical system according to the present example at an assumed eye point.

On the exit side of the similarly finder optical system L _f this embodiment is also as in Example 1 to Example 3 has a configuration for connecting the attachment optical system L _a finder. Since this finder optical system L _f is the same as that in the first to third embodiments, the description thereof is omitted.

Finder attachment optical system L _a of this embodiment, in the same manner as in Example 1, Example 2, in order from the finder optical system L _f side, a biconcave negative lens L _a1, a biconvex positive lens L _a2, is composed of ing. In addition, since any lens surface is spherical, it is possible to reduce the manufacturing cost compared to a lens having an aspherical surface.

Subsequently, numerical data of lenses constituting the attachment optical system L _a finder.

Surface r D Nd Vd
1 -21.3319 4.86 1.51633 64.14
2 24.5299 3.00
3 96.1279 9.54 1.51633 64.14
4 -19.1563

The data related to the above conditional expressions is
Conditional expression (1): | f1 / f2 | = 0.67
Conditional expression (2): HF1 / (d1 + d2 + d3) = 0.083
Conditional expression (3): (d1 + d2 + d3) /f2=0.547
Conditional expression (4): (R1 + R2) / (R1-R2) = − 0.07
Conditional expression (5): (R3 + R4) / (R3-R4) = 0.67
Conditional expression (6): d1 + d2 + d3 = 17.40 (mm)
Conditional expression (7): HF1 = 1.4384 (mm)
Conditional expression (8): d1 / (d1 + d2 + d3) = 0.2792
Conditional expression (9): d2 / (d1 + d2 + d3) = 0.172
It is. In addition,
f1 = -21.3283 (mm)
f2 = 31.8333 (mm)
It is.

The distance on the optical axis Lc from the exit-side glass surface of the cover glass CG of the finder optical system L _f to the entrance-side lens surface vertex of the negative lens L _a1 is 5.83Mm. Distance on the optical axis Lc from the vertex of the exit-side lens surface of the positive lens L _a2 to the exit pupil to be projected is 14.35mm in length in air. Distance on the optical axis Lc from the exit-side lens surface of the positive lens L _a2 to the eye point E on the assumption is 35.55mm in length in air. The aberration diagram shown in FIG. 9 shows the aberration at the position of the eye point E.

  FIG. 10 is a diagram illustrating a configuration of a finder optical system and a finder attachment optical system according to the present embodiment. FIG. 11 is an aberration diagram showing spherical aberration, astigmatism, distortion, and lateral chromatic aberration of the finder attachment optical system according to the present example at an assumed eye point.

On the exit side of the similarly finder optical system L _f the present embodiment also as Examples 1 to 4 are configured to connect the attachment optical system L _a finder. Since this finder optical system L _f is the same as that in the first to fourth embodiments, the description thereof is omitted.

Finder attachment optical system L _a of this embodiment, in the same manner as in Example 1, Example 2, in order from the finder optical system L _f side, a biconcave negative lens L _a1, a biconvex positive lens L _a2, is composed of ing. In addition, since any lens surface is spherical, it is possible to reduce the manufacturing cost compared to a lens having an aspherical surface.

Subsequently, numerical data of lenses constituting the attachment optical system L _a finder.

Surface r D Nd Vd
1 -21.5409 2.98 1.51633 64.14
2 23.2754 2.86
3 97.4803 11.56 1.51633 64.14
4 -19.1652

The data related to the above conditional expressions is
Conditional expression (1): | f1 / f2 | = 0.66
Conditional expression (2): HF1 / (d1 + d2 + d3) = 0.053
Conditional expression (3): (d1 + d2 + d3) /f2=0.542
Conditional expression (4): (R1 + R2) / (R1-R2) = − 0.04
Conditional expression (5): (R3 + R4) / (R3-R4) = 0.67
Conditional expression (6): d1 + d2 + d3 = 17.40 (mm)
Conditional expression (7): HF1 = 0.9223 (mm)
Conditional expression (8): d1 / (d1 + d2 + d3) = 0.710
Conditional expression (9): d2 / (d1 + d2 + d3) = 0.165
It is. In addition,
f1 = -21.188 (mm)
f2 = 32.1029 (mm)
It is.

The distance on the optical axis Lc from the exit-side glass surface of the cover glass CG of the finder optical system L _f to the entrance-side lens surface vertex of the negative lens L _a1 is 6.31Mm. Distance on the optical axis Lc from the vertex of the exit-side lens surface of the positive lens L _a2 to the exit pupil to be projected is 13.14mm in length in air. Distance on the optical axis Lc from the exit-side lens surface of the positive lens L _a2 to the eye point E on the assumption is 33.93mm in length in air. The aberration diagram shown in FIG. 11 shows the aberration at the position of the eye point E.

  FIG. 12 is a diagram illustrating a configuration of a finder optical system and a finder attachment optical system according to the present embodiment. FIG. 13 is an aberration diagram showing spherical aberration, astigmatism, distortion, and lateral chromatic aberration of the finder attachment optical system according to the present example at an assumed eye point.

On the exit side of the similarly finder optical system L _f this embodiment is also as in Example 1 to Example 5 has a structure that connects the attachment optical system L _a finder. Since the finder optical system L _f is the same as that in the first to fifth embodiments, the description thereof is omitted.

Finder attachment optical system L _a of this embodiment, in the same manner as in Example 1, Example 2, in order from the finder optical system L _f side, a biconcave negative lens L _a1, a biconvex positive lens L _a2, is composed of ing. In addition, since any lens surface is a spherical surface, it is possible to reduce the manufacturing cost as compared with a lens having an aspherical surface.

Subsequently, numerical data of lenses constituting the attachment optical system L _a finder.

Surface r D Nd Vd
1 -20.8065 3.55 1.51633 64.14
2 23.0857 3.62
3 99.1722 10.24 1.51633 64.14
4 -18.9333

The data related to the above conditional expressions is
Conditional expression (1): | f1 / f2 | = 0.65
Conditional expression (2): HF1 / (d1 + d2 + d3) = 0.062
Conditional expression (3): (d1 + d2 + d3) /f2=0.548
Conditional expression (4): (R1 + R2) / (R1-R2) = − 0.05
Conditional expression (5): (R3 + R4) / (R3-R4) = 0.68
Conditional expression (6): d1 + d2 + d3 = 17.40 (mm)
Conditional expression (7): HF1 = 1.08 (mm)
Conditional expression (8): d1 / (d1 + d2 + d3) = 0.2038
Conditional expression (9): d2 / (d1 + d2 + d3) = 0.208
It is. In addition,
f1 = -20.6272 (mm)
f2 = 31.7272 (mm)
It is.

The distance on the optical axis Lc from the exit-side glass surface of the cover glass CG of the finder optical system L _f to the entrance-side lens surface vertex of the negative lens L _a1 is 6.26Mm. Distance on the optical axis Lc from the vertex of the exit-side lens surface of the positive lens L _a2 to the exit pupil to be projected is 13.77mm in length in air. Distance on the optical axis Lc from the exit-side lens surface of the positive lens L _a2 to the eye point E on the assumption is 41.27mm in length in air. The aberration diagram shown in FIG. 13 shows the aberration at the position of the eye point E.

  Next, an example of a waterproof camera case using the above finder attachment optical system of the present invention will be described.

As shown in FIG. 14, the waterproof camera case 1 includes a case body 11 that includes a camera 2 and prevents entry of water under water pressure, an operating means 3 installed in the case body 11, and a viewfinder optical system of the camera 2. A finder attachment optical system L _a (here, the one in Example 6) optically connected to L _f and disposed on the exit side thereof.

First, the finder optical system L _f provided in the camera 2 will be described. The finder optical system L _f folds the light beam incident from the photographic lens 21 side of the camera 2 in the lateral direction (perpendicular to the paper surface) of the camera to form a finder optical path, and retracts the light beam from the photographic lens by a retraction device such as a CCD It has a quick return mirror (not shown) that leads to the image sensor CCD. A focus surface (not shown) having a fine prism surface having a ground glass surface and a pattern structure is disposed at the tip of the light beam reflected by the quick return mirror. Note that this focus surface is a surface corresponding to the imaging surface. The light beam that has passed through the focus surface is reflected by the three reflecting surfaces. That is, the light path is reflected in a polo mirror shape by the quick return mirror and its three reflecting surfaces, and the light beam is guided to the eyepiece lens of the camera 2. In this way, the finder optical system _Lf is configured to enlarge the image on the focus surface and observe the object image as a virtual image.

  Next, each member constituting the waterproof camera case will be described. The case body 1 includes a case body front half part 11, a case body rear half part 12, and a lens port 13.

  The case body front half part 11 is formed with grooves for placing synthetic rubber O-rings 41 and 42 in the attachment part with the case body rear half part 12 and the attachment part with the lens port 13. The O-rings 41 and 42 are disposed in the groove and then deformed to attach the case body rear portion 12 and the lens port 13 to effectively prevent water from entering even under water pressure. .

  The case body front half part 11 and the case body rear half part 12 are attached by a buckle or the like (not shown) provided in each case, and the case body front half part 11 and the lens port 13 are attached by a plurality of screws 5. Has been done by. However, how to attach them is not limited to these methods. In addition, the O-rings 41 and 42 are not only arranged one by one, but a plurality of O-rings 41 and 42 may be arranged by providing a plurality of grooves in each mounting portion, and by doing so, The waterproof effect of the waterproof camera case 1 can be further enhanced.

Casing half portion 12 has, on its rear portion (rear portion of the case body 1), the attachment optical system L _a finder, as its optical axis coincides with the optical axis of the camera 2 body of the finder optical system L _f It is installed. Further, as the exit side lens surface and the air contact surface of the positive lens L _a2 of the finder attachment optical system L _a, and substantially comprises a transparent cover glass CG1 parallel plate. Note that a transparent member formed of a resin may be used instead of the cover glass CG1.

  With the configuration of the rear half 12 of the case body, the photographer observes a good subject image having an appropriate viewing angle when looking through the viewfinder even when the underwater mask 6 is worn. be able to.

  The lens port 13 is attached to the subject side of the front half 11 of the case body, and this lens port 13 has a transparent cover glass CG2 so as not to irradiate light incident on the photographing lens 21 of the camera 2 body. Yes. Although the cover glass CG2 is a parallel plate here, it may be a dome shape having a concentric spherical entrance surface and an exit surface, or a shape advantageous for wide-angle shooting. Moreover, you may use the transparent member formed with resin instead of this cover glass CG2. Further, the lens port 13 may be variously changed according to the type of the photographing lens 21 attached to the camera 2 body.

  Next, each member which comprises the operation means 3 is demonstrated. The operation means 3 is attached to the case body rear half part 12, and is comprised by the operation key 31 which has the press part 31a and the latching | locking part 31b, and the coil spring 32. FIG.

  The operation key 31 penetrates the rear half 12 of the case body, and the pressing operation of the operation key 31 is applied to the operation member 22 such as a release button of the camera 2 body or a button for setting shooting conditions via the pressing portion 31a. It has a structure that is transmitted. In addition, the coil spring 32 urges the operation key 31 to return until the locking portion 31b provided integrally with the operation key 31 contacts the inner surface of the rear half portion 12 of the case after the pressing operation. ing.

  Note that the operation means 3 is not limited to the above-mentioned pressing type, but may be a dial type. Moreover, it is good also as a structure which transmits an electrical signal to the camera 2 and controls imaging | photography conditions.

Thus, the waterproof camera case, by the case body 1 is provided with attachment optical system L _a finder, since the eye point E is displaced in position, a state wearing the underwater mask 6 However, the operation keys do not get in the way when observing the subject, and underwater shooting can be performed satisfactorily. Further, by providing the operation means 3, it is possible to operate the camera 2 even in water.

It is a figure which shows the structure of the attachment optical system for finder which concerns on Example 1 of this invention, and a finder optical system. FIG. 4 is an aberration curve diagram of the finder optical system according to Example 1 of the present invention. It is an aberration curve figure of the attachment optical system for finder which concerns on Example 1 of this invention. It is a figure which shows the structure of the attachment optical system for finder which concerns on Example 2 of this invention, and a finder optical system. It is an aberration curve figure of the attachment optical system for finder which concerns on Example 2 of this invention. It is a figure which shows the structure of the attachment optical system for finder which concerns on Example 3 of this invention, and a finder optical system. It is an aberration curve figure of the attachment optical system for finder which concerns on Example 3 of this invention. It is a figure which shows the structure of the attachment optical system for finder which concerns on Example 4 of this invention, and a finder optical system. It is an aberration curve figure of the attachment optical system for finder which concerns on Example 4 of this invention. It is a figure which shows the structure of the attachment optical system for finder which concerns on Example 5 of this invention, and a finder optical system. It is an aberration curve figure of the attachment optical system for finder which concerns on Example 5 of this invention. It is a figure which shows the structure of the attachment optical system for finder which concerns on Example 6 of this invention, and a finder optical system. It is an aberration curve figure of the attachment optical system for finder which concerns on Example 6 of this invention. It is a figure which shows the structure of the waterproof camera case containing the attachment optical system for finder which concerns on this invention.

Explanation of symbols

CCD Image sensor CG1, CG2 Cover glass E Eyepoint Lc Optical axis L _a Attachment optical system for viewfinder L _a1 negative lens L _a2 positive lens L _f finder optical system L _f1 positive meniscus lens L _f2 biconvex positive lens L _f3 biconcave negative lens 1 Case body 11 Case front half 12 Case body rear half 13 Lens port 2 Camera 21 Shooting lens 22 Operation member 3 Operating means 31 Operation key 31a Press part 31b Locking part 32 Coil spring 41, 42 O-ring 5 Screw 6 Underwater mask

Claims (8)

An attachment optical system for a finder disposed on the exit side of the finder optical system for observing an object image formed by the finder optical system,
The finder attachment optical system has, in order from the finder optical system side, a biconcave negative lens and a positive lens whose exit side is convex,
A finder attachment optical system characterized by satisfying the following conditional expressions (1) and (2).
0.6 <| f1 / f2 | <1.0 (1)
0.045 <HF1 / (d1 + d2 + d3) <0.091 (2)
However,
f1: Focal length of the negative lens f2: Focal length of the positive lens d1: Thickness on the optical axis of the negative lens d2: Distance on the optical axis between the negative lens and the positive lens d3: On the optical axis of the positive lens Thickness HF1: A distance from the surface vertex of the entrance lens surface of the negative lens to the front principal point of the negative lens. The front side means the side on which the light beam enters. The attachment optical system for a finder according to claim 1, wherein the following conditional expression (3) is satisfied.
0.4 <(d1 + d2 + d3) / f2 <1.00 (3) The finder attachment optical system according to claim 1 or 2, wherein the negative lens satisfies the following conditional expression (4).
-0.15 <(R1 + R2) / (R1-R2) <0.70 (4)
However,
R1: Paraxial radius of curvature of the entrance lens surface of the negative lens R2: Paraxial radius of curvature of the exit lens surface of the negative lens. The finder attachment optical system according to any one of claims 1 to 3, wherein the positive lens has a biconvex shape and satisfies the following conditional expression (5).
-0.15 <(R3 + R4) / (R3-R4) <0.75 (5)
However,
R3: Paraxial radius of curvature of the entrance lens surface of the positive lens R4: Paraxial radius of curvature of the exit lens surface of the positive lens. The finder attachment optical system according to any one of claims 1 to 4, wherein the following conditional expressions (6) and (7) are satisfied.
12.00 (mm) <d1 + d2 + d3 <23.00 (mm) (6)
0.41 (mm) <HF1 <2.00 (mm) (7) The finder attachment optical system according to any one of claims 1 to 5, wherein the following conditional expression (8) is satisfied.
0.08 <d1 / (d1 + d2 + d3) <0.30 (8) The finder attachment optical system according to any one of claims 1 to 6, wherein the following conditional expression (9) is satisfied.
0.05 <d2 / (d1 + d2 + d3) <0.50 (9) A case body with a built-in camera that prevents water from entering under water pressure,
An operating means installed on the case body and capable of operating the shooting conditions of the camera from the outside of the case body,
A waterproof camera case optically connected to the finder optical system of the camera and provided with a finder attachment optical system disposed on the exit side of the finder optical system,
A waterproof camera case, wherein the finder attachment optical system is the finder attachment optical system according to any one of claims 1 to 7.