JP2005352240A - Optical system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simplify the constitution of an optical system having a camera shake correcting function by installing a function of correcting the camera shake in a finder optical system, and to reduce burdens on a driving mechanism, and also, to reduce the aberration deterioration in correcting the camera shake. <P>SOLUTION: The optical system is provided with a photographing optical system and the finder optical system, and the optical system is provided with an optical path dividing means for dividing the optical path leading to the finder optical system into the photographing optical system, and an object to be photographed is observed with the finder optical system after the object is reflected twice, and the camera shake is corrected by changing the tilt angle of one mirror. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

    The present invention relates to an optical system. In particular, the present invention relates to an optical system having a function of preventing image blur due to camera shake, for example, vibration when taking a camera by hand, and particularly relates to a finder of a photographing apparatus such as a digital camera, a film camera, and a video camera.

As a conventional example of a finder optical system having a camera shake correction function, there is an optical system described in the following document.
JP-A-9-329820 JP, 2003-91027, A Among these conventional examples, the finder optical system indicated in literature 1 is the composition as shown in FIG.

    In this optical system, an image stabilization lens L is arranged in the optical system. The camera shake correction lens L is decentered by the drive system A in parallel to the optical axis of the finder optical system. In this way, blurring of light that has entered the optical system from the subject is corrected.

    The optical system described in Document 2 has a configuration as shown in FIGS. 20 and 21, a part of the objective lens L is moved in the direction perpendicular to the optical axis. In FIG. 22, the eyepiece lens E is moved in the direction perpendicular to the optical axis. In this way, camera shake correction is performed.

    In the above-described prior art, a lens group having a function of preventing camera shake, that is, a vibration proof group is used. If this anti-vibration group is decentered, the imaging performance deteriorates due to aberrations due to decentering. Further, due to the occurrence of decentration distortion, the image becomes asymmetric with respect to the optical axis. It is necessary to prevent image formation performance degradation and image shape asymmetry due to such image stabilization.

    Further, if the weight of the vibration proof group is large, the burden on the actuator for moving the vibration proof group becomes large. Therefore, it is necessary to lighten the vibration isolation group.

    In addition, when the vibration proof sensitivity is low, the movement amount of the vibration proof group becomes large. On the other hand, if the image stabilization sensitivity is high, it is difficult to control the movement of the image stabilization group. In order to solve this problem, it is necessary to set the image stabilization sensitivity to an appropriate value.

    As described above, the image stabilization optical system needs to consider many points regarding the function for image stabilization.

    None of the optical systems described in Documents 1 and 2 discloses any study on the issues to be considered in the image stabilizing optical system. As described above, these conventional examples have not been studied sufficiently with an optimal vibration isolation method and feasibility. In particular, some of the optical paths in the optical system are not shown.

    In addition, the optical systems described in Documents 1 and 2 are both photographing devices in which the photographing optical system and the finder optical system are separate.

    The optical system of the present invention includes a photographic optical system and a finder optical system, and an optical path dividing means for dividing the optical path into the finder optical system is arranged in the photographic optical system, and the finder is reflected after the photographic object is reflected at least twice. Observed by the optical system, the viewfinder optical system has a function of preventing camera shake (camera shake correction).

    This optical system can simplify the optical system because the photographing optical system has the function of the objective lens of the finder optical system. In addition, since the viewfinder optical system has an anti-shake function, the observation image by the viewfinder optical system is stable, and in particular, there is a camera shake that becomes a problem when a user who has not been photographed when performing telephoto shooting. Can be prevented. In this case, since there are at least two reflecting mirrors including the optical path dividing means, camera shake can be prevented by one of the reflecting mirrors, and there is an advantage that the degree of freedom of layout for correcting camera shake is increased.

    In the optical system of the present invention, it is preferable to form a photographic object twice and observe the second image formed by the relay optical system as a virtual image by the eyepiece.

    Here, if the magnification of the relay optical system is made larger than 1, the finder magnification is increased and the object image observation becomes easy. In addition, the degree of freedom of the layout of the camera shake correction optical system having the camera shake correction function is increased.

    In the optical system of the present invention, it is desirable to prevent camera shake by decentering a reflecting mirror disposed in the finder optical system.

    To prevent camera shake using the reflecting mirror, there are a tilt for changing the tilt angle of the reflecting mirror and a shift for moving the lens in a plane perpendicular to the optical axis.

    Since the optical system of the present invention uses a reflecting mirror, it is possible to perform camera shake correction by the above-described method without arranging a new element such as a variable apex angle prism, and the configuration of the optical system can be simplified. .

    In addition, the amount of change in the reflection angle of the light beam by the mirror is twice (2Δ) compared to the amount of change in the tilt angle of the reflection mirror (Δ) that is performed to correct camera shake. The correction effect is greater than that.

    The finder optical system used in the optical system of the present invention has a configuration in which the primary imaging plane, relay optical system, secondary imaging plane, eyepiece, and virtual image are arranged in this order from the object side. It has a function of correcting camera shake before the next image plane.

    That is, the optical system of the present invention has a configuration in which a relay optical system and an eyepiece lens are arranged in order after the primary imaging surface, and a secondary image is formed by the relay optical system between the relay optical system and the eyepiece lens. It is preferable to form an image and observe this secondary image as a virtual image with an eyepiece.

    In the optical system configured as described above, when the field frame is disposed on the secondary imaging surface, if the camera shake correction is not performed on the secondary imaging surface, a function for preventing the field frame from being shaken is separately required. However, if camera shake correction is performed in front of the secondary imaging surface, camera shake correction for both the observation image and the field frame can be performed without separately providing a camera shake prevention function for the field frame.

    When camera shake prevention using a mirror is performed as in the present invention, a mirror for splitting the optical path from the taking lens to the viewfinder may be a camera shake prevention mirror. Further, camera shake may be prevented between the optical path splitting mirror from the photographing lens and the primary imaging plane. For example, a reflection mirror used for deflecting the optical path may be disposed between the optical path splitting mirror and the primary imaging plane, and this may be used for camera shake correction.

    As described above, a relay optical system and an eyepiece lens are arranged in order from the primary image plane, and the secondary image plane is positioned between the relay optical system and the eyepiece so that a virtual image is formed on the eye side of the eyepiece. In the finder optical system in which the image is formed, it is possible to prevent camera shake by arranging a reflecting surface between the primary imaging surface and the secondary imaging surface and decentering the reflecting surface. .

    As described above, in the optical system configured as described above, when the field frame is arranged on the secondary imaging surface, if the secondary imaging surface does not prevent camera shake, it separately corrects the field frame blur. Is required. In this case, an optical element may be disposed between the primary imaging surface and the secondary imaging surface, and the optical element may be decentered to correct camera shake. In this way, camera shake is prevented from occurring on the secondary image plane, so that it is possible to prevent camera shake of both the observation image and the field frame even without a field frame blur prevention function.

    In addition, when a mirror is arranged between the primary imaging surface and the secondary imaging surface to prevent camera shake, the diameter can be made smaller than in the case where the mirror is arranged at another location. This mirror is easy to drive and is preferable.

    In this case, it is possible to prevent camera shake by using an optical path dividing mirror from the taking lens. In addition, camera shake correction may be performed between the optical path dividing mirror from the photographing lens and the primary imaging plane.

    The relay optical system used in the optical system of the present invention described above is preferably composed of a first field lens, a relay lens, and a second field lens in order from the photographic object side.

    By configuring the relay lens system as described above, the first and second field lenses can have a role of controlling the pupil position. This is preferable because the relay optical system can be miniaturized. As a result, the size of the mirror for preventing camera shake can be reduced.

    Further, the finder optical system is arranged in the order of the virtual image formed by the first image lens, the second image formed by the relay lens, the second image formed by the relay optical system, the eyepiece, and the eyepiece. Thus, a mirror can be disposed between the first field lens and the relay lens, and camera shake correction can be performed by tilting the mirror.

    In this case, the diameter of the light beam is reduced by the first field lens. Therefore, if a reflecting mirror is arranged between the first field lens and the relay lens, the diameter can be reduced. In addition, when the field frame is arranged on the secondary imaging plane, a camera shake correction unit is required unless camera shake correction is performed on the secondary imaging plane. Therefore, if a reflection mirror is arranged between the first field lens and the relay lens to thereby perform camera shake correction, camera shake is corrected on the secondary imaging plane, and field frame shake correction is performed. It is possible to correct the camera shake of both the observation image and the field frame without performing separately.

    In the above optical system, the relay lens of the relay optical system includes at least one lens or at least one lens group.

    In the optical system of the present invention in which the relay optical system includes the first field lens, the relay lens, and the second field lens as described above, the first and second field lenses of the relay optical system satisfy the following conditions. It is preferable to satisfy (1) and (2).

(1) | t1 / f1 |> 2
(2) | t2 / f2 |> 2
Where t1 is the distance from the primary imaging plane to the entrance pupil position, t2 is the distance from the secondary imaging plane to the exit pupil, and f1 and f2 are the focal lengths of the first field lens and the second field lens, respectively. It is.

    In the optical system of the present invention, when the conditions (1) and (2) are satisfied, the field lenses have a role of controlling the pupil position, and the relay optical system can be reduced in size. Further, in the optical system of the present invention, the relay lens that mainly performs aberration correction can be made small, so that it becomes easy to provide the relay lens with an aspherical surface or a diffractive surface.

    In this case, it is preferable to provide an aspherical surface for the field lens because pupil aberration can be effectively corrected.

    In the optical system of the present invention, it is preferable that the exit pupil position of the relay lens is formed on the eye side with respect to the secondary imaging plane.

    The viewfinder optical system needs to be optimized with an optical system that combines both the relay optical system and the eyepiece optical system. If the exit pupil position of the relay optical system is formed on the eye side with respect to the secondary imaging position, the optical system combining the relay optical system and the eyepiece optical system can be reduced in size.

    In this case, in order to reduce the size of the optical system, it is preferable to satisfy the following condition (3).

(3) | t1 / f1 |> | t2 / f2 |
Furthermore, it is more preferable that the field lens satisfies the following conditions (4) and (5).

(4) s1 / f1 ≧ 0.1
(5) s2 / f2 ≧ 0.1
Here, s1 is a distance from the primary imaging surface to the first field lens, and s2 is a distance from the secondary imaging surface to the second field lens.

    A focusing screen, a field frame, and the like are arranged on the primary imaging surface and the secondary imaging surface in the finder optical system.

    If the conditions (4) and (5) are satisfied, dust attached to the focusing screen, the field frame, etc. can be prevented from being observed.

    The first and second field lenses used in the optical system of the present invention need not be field lenses in a strict sense. A lens having an action close to that of a field lens may be used.

    The optical system of the present invention performs camera shake correction by shifting a lens or a lens group having an effective diameter of 70% or less of the maximum effective diameter of the finder optical system among the lenses or lens groups constituting the finder optical system. .

    According to this optical system, a lens or a lens group that is shifted for camera shake correction is lightened, and a burden on an actuator for shifting the lens or the lens group is lightened.

    In the optical system of the present invention, the finder optical system has a relay optical system, a secondary imaging surface, an eyepiece lens, and a virtual image arranged on the eye side from the primary imaging surface, and is reflected between the secondary imaging surface and the eyepiece lens. It is desirable to correct the camera shake by changing the reflection angle of the reflection mirror.

    In this optical system, it is more desirable to dispose the reflecting mirror from the eyepiece lens at a position that is ½ of the distance between the secondary imaging plane and the eyepiece lens.

    In the optical system of the present invention, it is preferable that the relay lens of the relay optical system includes a positive lens and a negative lens. With such a configuration, there is little deterioration of chromatic aberration when the relay lens is shifted and camera shake correction is performed.

    It is further desirable to include a triplet configuration in which the relay lens is arranged in the order of a positive lens, a negative lens, and a positive lens. Such a configuration is preferable because aberration can be corrected well with a simple configuration.

    In the optical system having such a configuration, it is preferable to provide an aspherical surface in the relay optical system, in particular, a lens or lens group that performs camera shake correction, because aberration deterioration can be suppressed when camera shake correction is performed.

    In the optical system of the present invention, when camera shake is prevented by tilting the reflecting surface, it is desirable that the angle change Δ of the mirror is 0.4 ° or more and 5 ° or less. That is, it is desirable to satisfy the following condition (6).

(6) 0.4 ° <Δ <5 °
By satisfying this condition (6), the image stabilization sensitivity (image blur correction amount / change amount of image stabilization group) becomes appropriate. If the lower limit of the condition (6) is 0.4 ° or less, the image stabilization sensitivity is too high, and it becomes difficult to delicately control the mirror angle. If the upper limit is 5 ° or more, the image stabilization sensitivity is too low, and the change amount of the mirror angle becomes large, which is a burden on the actuator.

    The optical system of the present invention has a prism having a reflecting surface for deflecting the optical path between the first imaging surface and the relay optical system or between the relay optical system and the second imaging surface, and the incidence of these prisms A refracting surface such as a convex surface is used as the surface and the exit surface, and the first or second field lens is used.

    This is preferable because the number of components such as optical elements constituting the optical system is reduced, and the optical system can be simplified and quantified.

    In the optical system of the present invention, it is preferable that the magnification β of the relay optical system satisfies the following condition (7).

      (7) 1.1 ≦ β ≦ 2

    The optical system of the present invention has a reflection mirror for deflecting the optical path in the finder optical system, and the camera shake is corrected by changing the tilt angle of the reflection mirror. Therefore, it is possible to observe a good object image with less burden on the drive mechanism for changing the tilt angle of the reflection mirror and less deterioration of aberration when correcting camera shake.

    Next, examples of the optical system of the present invention will be shown.

The optical system of Example 1 of the present invention is an optical system having a lens configuration as shown in FIG. 1 and has the following data.

r ₀ = ∞ d ₀ = −0.06
r ₁ = ∞ d ₁ = 3.14
r ₂ = aspheric surface 1 d ₂ = 3.70 n ₁ = 1.4924 ν ₁ = 57.7
r ₃ = -19.66 d ₃ = 10.68
r ₄ = ∞ d ₄ = 5.00
r ₅ = 7.06 d ₅ = 3.75 n ₂ = 1.6968 ν ₂ = 55.5
r ₆ = -16.18 d ₆ = 1.80
r ₇ = -4.11 d ₇ = 0.90 n ₃ = 1.6727 ν ₃ = 32.1
r ₈ = 10.55 d ₈ = 0.75
r ₉ = 27.89 d ₉ = 4.86 n ₄ = 1.6968 ν ₄ = 55.5
r ₁₀ = -7.33 d ₁₀ = 11.05
r ₁₁ = aspheric surface 2 d ₁₁ = 4.96 n ₅ = 1.5254 ν ₅ = 55.8
r ₁₂ = -79.46 d ₁₂ = 8.15
r ₁₃ = ∞ d ₁₃ = 25.00
r ₁₄ = aspheric surface 3 d ₁₄ = 3.70 n ₆ = 1.4924 ν ₆ = 57.7
r ₁₅ = -44.85 d ₁₅ = 3.25
r ₁₆ = ∞ d ₁₆ = 1.00 n ₇ = 1.5163 ν ₇ = 64.1
r ₁₇ = ∞ d ₁₇ = 11.09
r ₁₈ = diaphragm surface d ₁₈ = -904.55
r ₁₉ = ∞ d ₁₉ = 0.00

Aspherical surface 1
Curvature radius 10.11
k = 0
A = -6.7217 × 10 ^-4 , B = 4.8326 × 10 ^-6 , C = -3.7491 × 10 ^-8

Aspherical surface 2
Curvature radius 11.84
k = 0
^{A = -1.5339 × 10 -4, B} = 1.5158 × 10 -6, C = -1.3577 × 10 -8

Aspherical surface 3
Curvature radius 17.89
k = 0
A = -3.7860 × 10 ^-5 , B = 5.2082 × 10 ^-7 , C = -5.8476 × 10 ^-9

In the above data, r ₀ , r ₁ , r ₂ ,... Are the curvature radii of each surface, d ₁ , d ₂ ,... Are the surface spacing, and n ₁ , n ₂ are the refractions of each lens with respect to the d-line. The rates, ν ₁ , ν ₂ ,... Are Abbe numbers. Here, r ₀ is the object plane, r ₁ is the primary imaging plane, r ₁₂ is the secondary imaging plane, and the units of length such as ν and d are all mm.

As shown in FIG. 1, the optical system of Example 1 includes a first field lens F1 (r _{2 to} r ₃ ) and a relay lens RL (r _{5 to} r ₃ ) in order from the primary image I1 side by the photographing optical system. _10), and a second field lens F2 (r ₁₁ ~r ₁₂₎ and become more relay optical system RLS (r ₂ ~r _12), and relayed secondary image I2 (r ₁₃₎ by a relay optical system RLS, ocular Lens E (r _{14 to} r ₁₅ ). In the optical system according to the first embodiment, the reflection mirror Ma (r ₄ ) is disposed between the first field lens F1 and the relay lens RL in the relay optical system RLS. A secondary image I2 is formed between the field lenses F2, and the virtual image is observed by the eyepiece lens E.

    The optical system of the present invention changes the angle of the reflection mirror Ma in order to correct camera shake. In the first embodiment, the inclination angle of the reflecting mirror Ma is changed by 45 ° + 0.926 ° (angle change Δ = 0.926 °), and thus correction when the primary image due to camera shake is shifted by 0.3 mm is possible. It is.

    In the optical system of the first embodiment, the aberration state when the camera shake correction is performed by the reflection mirror Ma as described above is as shown in FIGS. 4, 5, 6, 7, and 8. Of these figures, FIG. 4 shows lateral aberrations at an image height of −1.00 when the maximum image height at the virtual image position is 1.00. Similarly, FIGS. 5, 6, 7, and 8 show lateral aberrations at image heights of −0.80, 1.00, 0.80, and 0.00. Aberrations in the basic state of the optical system of Example 1 (when the tilt angle of the reflecting mirror Ma is 45 °) are as shown in FIGS. 14, 15, 16, 17, and 18. FIG. These aberration diagrams are also lateral aberrations at −1.00, −0.80, 1.00, 0.80 and 0.00. From FIGS. 4 to 8 and FIGS. 14 to 18, the optical system according to the first embodiment of the present invention has little aberration degradation when the tilt angle of the reflection mirror Ma is changed for camera shake correction.

    In the optical system according to the first embodiment, the reflection mirror Ma used for camera shake correction is arranged on the primary image side of the actual pupil of the optical system, and the tilt angle of the mirror for camera shake correction is changed. There is little deterioration of aberration. In the vicinity of the pupil, since the effective diameter of the optical system is small, the diameter of the mirror can be reduced and the burden on the actuator is reduced.

The effective diameter of the reflecting mirror Ma of this embodiment is 14.7 mm. Further, in Example 1, the effective diameter of the reflection mirror Ma when the position of the reflection mirror Ma is shifted from the data position to the 0.5 mm relay lens RL side (r ₅ side) is 14.4 mm.

The second embodiment of the present invention has the following data with the configuration shown in FIG.

r ₀ = ∞ d ₀ = −0.06
r ₁ = ∞ d ₁ = 3.14
r ₂ = aspheric surface 1 d ₂ = 3.70 n ₁ = 1.4924 ν ₁ = 57.7
r ₃ = -19.66 d ₃ = 10.68
r ₄ = 7.06 d ₄ = 3.75 n ₂ = 1.6968 ν ₂ = 55.5
r ₅ = -16.18 d ₅ = 1.80
r ₆ = -4.11 d ₆ = 0.90 n ₃ = 1.6727 ν ₃ = 32.1
r ₇ = 10.55 d ₇ = 0.75
r ₈ = 27.89 d ₈ = 4.86 n ₄ = 1.6968 ν ₄ = 55.5
r ₉ = -7.33 d ₉ = 11.05
r ₁₀ = aspheric surface 2 d ₁₀ = 4.96 n ₅ = 1.5254 ν ₅ = 55.8
r ₁₁ = -79.46 d ₁₁ = 8.15
r ₁₂ = ∞ d ₁₂ = 25.00
r ₁₃ = ∞ d ₁₃ = 7.00
r ₁₄ = aspheric surface 3 d ₁₄ = 3.70 n ₆ = 1.4924 ν ₆ = 57.7
r ₁₅ = -44.85 d ₁₅ = 3.25
r ₁₆ = ∞ d ₁₆ = 1.00 n ₇ = 1.5163 ν ₇ = 64.1
r ₁₇ = ∞ d ₁₇ = 11.09
r ₁₈ = diaphragm surface d ₁₈ = -904.55
r ₁₉ = ∞ d ₁₉ = 0.00

Aspherical surface 1
Curvature radius 10.11
k = 0
A = -6.7217 × 10 ^-4 , B = 4.8326 × 10 ^-6 , C = -3.7491 × 10 ^-8
Aspherical surface 2
Curvature radius 11.84
k = 0
^{A = -1.5339 × 10 -4, B} = 1.5158 × 10 -6, C = -1.3577 × 10 -8

Aspherical surface 3
Curvature radius 17.89
k = 0
A = -3.7860 × 10 ^-5 , B = 5.2082 × 10 ^-7 , C = -5.8476 × 10 ^-9

The optical system of Example 2 has the same configuration as that of Example 1, and includes a relay optical system RLS (r _{2 to} r ₁₁ ) and an eyepiece lens E (r _{14 to} r ₁₅ ), and includes a reflection mirror Mb ( the r _13), in which is arranged between the secondary image I2 (r ₁₂₎ and the eyepiece E formed between the relay optical system RLS and the eyepiece E. Then, camera shake correction is performed by changing the tilt angle of the reflection mirror Mb.

    In Example 2, the primary image is shifted by 0.3 mm due to camera shake by changing the reflection mirror Mb by Δ = −0.570 ° and changing the tilt angle from 45 ° to 45 ° -0.570 °. Time correction can be performed. In the second embodiment, the reflecting mirror Mb is disposed close to the eyepiece lens E so that the effective diameter of the mirror is reduced. That is, in the configuration in which the mirror Mb is disposed at the position shown in FIG. 2, the effective diameter at that time is 18.0 mm.

    In the optical system of Example 2, aberrations when the tilt angle of the reflecting mirror Mb is changed for camera shake correction are as shown in FIGS. 9, 10, 11, 12, and 13. FIG. The aberration diagrams of FIGS. 9, 10, 11, 12, and 13 show image heights of -1.00, -0.80, 1.00, 0 when the maximum image height in a virtual image is 1.00. .. Lateral aberration at 80, 0.00.

In Example 2, the reflection mirror Mb (r ₁₃ ) for correcting camera shake is separated from the secondary image (r ₁₂ ), and the change in the tilt angle of the mirror is small (Δ = −0.570 °). The camera shake can be corrected. However, in Example 2, there is a large variation in aberration when the mirror is changed for camera shake correction.

    That is, the deterioration of aberration is larger than that of the optical system of Example 1, and the effective diameter of the mirror is larger.

    In the optical systems of the first and second embodiments, a variable shape mirror may be used as the reflecting mirror. In addition, two mirrors, a variable shape mirror and a normal reflection mirror, are arranged in the optical system, and the shake angle is corrected by changing the tilt angle of the normal reflection mirror, and the deterioration of aberrations at that time is deformed. You may correct | amend by the change of the shape of.

    In these embodiments, an organic-inorganic hybrid material is used for the first field lens or the like. That is, an organic material is dispersed in an inorganic material, or an inorganic material is dispersed in an organic material. Therefore, it has a lower melting point than glass, can be molded at a low temperature, is easily mass-produced, and can be made inexpensively.

    In addition, this inorganic organic material provides an optical material having a low refractive index and a high dispersion, and is excellent in heat resistance as compared with plastic. Furthermore, it is hard to be damaged, and can be used, for example, for a front lens of an optical system.

    Therefore, it is desirable to use this organic-inorganic substance for the lens provided with the aspherical surface as described above.

    A lens provided with an aspherical surface may be made of plastic. By this. Large quantities of aspherical lenses can be produced by plastic molding. In that case, the material cost may be low, resulting in an inexpensive lens, and the optical system can also be inexpensive. In addition, since plastic is lighter than glass, the optical system can be quantified.

    In the optical system of the present invention, all the lenses can be plastic lenses. Thereby, all the lenses of the optical system can be produced by the plastic molding method, and can be easily produced in large quantities. In that case, since the material cost is low, an extremely inexpensive optical system can be obtained.

    In the optical systems of these examples, the values specified by the conditions (1) to (7) are as follows.

t1 / f1 = 14.9
t2 / f2 = 3.59
| T1 / f1 |> | t2 / f2 |
s1 / f1 = 3.2 / 14.1 = 0.23
s2 / f2 = 8.15 / 20 = 0.41
T = 0.27
Δ = 0.93 ° (Example 1)
Δ = 0.03 ° (Example 2)
β = 1.19
As in the above values, the example satisfies all of the conditions (1) to (7).

    The effective diameter of the relay lens of this embodiment is as follows.

Effective diameter of relay lens = 8.4mm
Maximum effective diameter of viewfinder optical system = 15.5 mm
Effective diameter of relay lens / maximum effective diameter of viewfinder optical system = 0.54
In this embodiment, as shown in the data, the object side surface (r ₂ ) of the first field lens F 1, the object side surface (r ₁₀ ) of the second field lens F 2, and the object side of the eyepiece E The surface (r ₁₃ ) is a rotationally symmetric aspherical surface.

    These aspheric surfaces are represented by the following equations.

z = ch ² / [1+ {1− (1 + k) c ² h ² } ^1/2 ]
+ Ah ⁴ + Bh ⁶ + Ch ⁸ + Dh ¹⁰ +...
In the above equation, h is the distance from the optical axis (h ² = x ² + y ² ), c is the curvature of the apex, k is the conic constant, A is the fourth-order aspheric coefficient, B is the sixth-order aspheric coefficient, C is an 8th-order aspheric coefficient, and D is a 10th-order aspheric coefficient.

    The aspheric coefficients and the like in the examples are shown in the data.

    FIG. 3 shows an outline of the optical system of Example 3.

    The optical system according to the first and second embodiments is an optical system including two mirrors, a mirror for dividing an optical path from a photographing optical system to a viewfinder optical system and a mirror for correcting camera shake.

    In contrast, the optical system of Example 3 is an optical system in which six reflecting mirrors are arranged as shown in FIG.

    In FIG. 3, ILS is a photographing optical system, M1 is an optical path dividing means, I1 is a primary image, P is a prism having two total reflection surfaces M2 and M3, M4 is a fourth reflecting mirror, RL is a relay lens, M5 is a reflecting mirror, F2 is a second field lens, I2 is a secondary image, M6 is a sixth mirror, and E is an eyepiece.

    In this embodiment, the first field lens F2 is formed by making the incident surface of the optical path deflecting prism P convex.

    This optical system can perform camera shake correction similar to that in the first and second embodiments by changing the tilt angle of the mirror M4 and the mirror M6.

    As described in detail above, the optical system of the present invention can achieve the object of the present invention in addition to the optical system described in the claims.

  (1) In the optical system according to claim 2 or 3, the finder optical system includes a relay optical system and an eyepiece in order from the primary imaging plane, and a secondary image by the relay optical system. Is formed between the relay optical system and the eyepiece lens, and a virtual image is formed on the eye side of the eyepiece lens, which prevents camera shake on the object side from the secondary imaging surface.

  (2) In the optical system described in the item (1), a reflection mirror is disposed between the first image forming surface and the secondary image forming surface, and the reflection mirror is decentered to prevent camera shake. Characteristic optical system.

  (3) In the optical system described in claim 2 or 3 of the claims, or in the item (1) or (2), the relay optical system is arranged in order from the photographic object side, the first field lens and the relay. An optical system comprising a lens and a second field lens.

  (4) In the optical system described in (3) above, a reflection mirror is disposed between the first field lens and the relay lens, and the tilt angle of the reflection mirror is changed to prevent camera shake. An optical system characterized by

  (5) An optical system according to the item (3) or (4), wherein the field lens satisfies the following conditions (1) and (2).

(1) | t1 / f1 |> 2
(2) | t2 / f2 |> 2
Where t1 is the distance from the primary imaging plane to the entrance pupil position, t2 is the distance from the secondary imaging plane to the exit pupil, and f1 and f2 are the focal lengths of the first field lens and the second field lens, respectively. It is.

  (6) In the optical system described in the above section (1), (2), (3), (4) or (5), the exit pupil of the relay optical system is formed on the eye side from the secondary imaging plane. An optical system.

  (7) In the optical system described in the item (3), (4), or (5), the first and second field lenses satisfy the conditions (4) and (5), respectively. Optical system.

(5) s2 / f2 ≧ 0.1
Here, s1 is a distance from the primary imaging surface to the first field lens, and s2 is a distance from the secondary imaging surface to the second field lens.

  (8) It is described in claim 1, 2 or 3 of the claims, or in the item (1), (2), (3), (4), (5), (6) or (7). An optical system that corrects camera shake by shifting a lens or a lens group having an effective diameter of 70% or less of the effective diameter of the finder optical system.

  (9) In the optical system described in (3), (4), (5), (6), or (7) above, a reflection mirror is disposed between the secondary imaging surface and the eyepiece. An optical system that corrects camera shake by changing the tilt angle of the reflecting mirror.

  (10) An optical system according to the item (9), wherein the reflecting mirror is arranged at a position closer to the eyepiece than half of the interval between the secondary imaging plane and the eyepiece.

  (11) In the optical system described in the item (3), (4), (5), (6), (7), (8), (9), or (10), the relay lens is a positive lens. And a negative lens.

(12) In the optical system described in the above item (2), (4), (5), (6) or (7), the change amount Δ of the tilt angle of the reflection mirror for camera shake correction is An optical system satisfying the condition (6).
(6) 0.4 ° <Δ <5 °

  (13) In the optical system described in the item (3), (4), (5), (6) or (7), the relay optical system has a prism for deflecting an optical path, and the prism An optical system, wherein the incident surface constitutes a first field lens or the exit surface of the prism constitutes a second field lens.

  (14) (1), (2), (3), (4), (5), (6), (7), (8), (9), (10), (11), (11) 12) or the optical system described in the item (13), wherein the magnification β of the relay optical system satisfies the following condition (7).

      (7) 1.1 ≦ β ≦ 2

    The present invention is an optical system used in a digital camera, a film camera, a video camera, and other optical devices, and the photographing optical system includes an optical path dividing means for dividing an optical path into a finder optical system. By performing the camera shake correction by changing the tilt angle of the reflection mirror for deflecting the optical path disposed in the later finder optical system, it is possible to observe a good camera-free image with little aberration deterioration.

The figure which shows the structure of the finder optical system of Example 1 of this invention. The figure which shows the structure of the finder optical system of Example 2 of this invention. Schematic which shows the structure of Example 3 of this invention. Aberration diagram at image height -1.00 of Example 1 of the present invention Aberration diagram at image height -0.80 in Example 1 of the present invention. Aberration diagram at image height 1.00 of Example 1 of the present invention Aberration diagram at image height 0.80 of Example 1 of the present invention Aberration diagram at image height 0.00 of Example 1 of the present invention Aberration diagram at image height -1.00 in Example 2 of the present invention. Aberration diagram at image height -0.80 in Example 2 of the present invention. Aberration diagram of Example 2 of the present invention at an image height of 1.00 Aberration diagram of Example 2 of the present invention at an image height of 0.80 Aberration diagram at image height 0.00 of Example 2 of the present invention Lateral aberration diagram of the reference optical system of the present invention (when there is no camera shake) at an image height of -1.00 Lateral aberration diagram of the reference optical system of the present invention (when there is no camera shake) at an image height of −0.80 Transverse aberration diagram at the image height of 1.00 of the reference optical system (when there is no camera shake) of the optical system of the present invention Transverse aberration diagram at the image height of 0.80 of the reference optical system (when there is no camera shake) 2 of the optical system of the present invention Transverse aberration diagram at an image height of 0.00 of the reference optical system (when there is no camera shake) of the optical system of the present invention The figure which shows the structure of the optical system which provided the conventional camera shake prevention function The figure which shows the structure of the optical system which provided the other conventional camera-shake prevention function The figure which shows the structure of the optical system which provided the other conventional camera-shake prevention function The figure which shows the structure of the optical system which provided the other conventional camera-shake prevention function

Claims (3)

An optical system that includes a photographic optical system and a finder optical system, and the photographic optical system includes an optical path dividing unit that divides an optical path into the finder optical system, and observes an object image after reflecting light from a photographic object twice or more. An optical system in which the viewfinder optical system has a camera shake correction function. 2. The optical system according to claim 1, wherein the finder optical system includes a relay optical system and an eyepiece optical system, and a secondary image formed by imaging the photographing object twice is observed as a virtual image by the eyepiece optical system. system. 3. The optical system according to claim 1, wherein camera shake is corrected by decentering a reflecting mirror provided in the finder optical system.

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