WO2008102894A1 - Variable magnification afocal optical system - Google Patents

Variable magnification afocal optical system Download PDF

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Publication number
WO2008102894A1
WO2008102894A1 PCT/JP2008/053114 JP2008053114W WO2008102894A1 WO 2008102894 A1 WO2008102894 A1 WO 2008102894A1 JP 2008053114 W JP2008053114 W JP 2008053114W WO 2008102894 A1 WO2008102894 A1 WO 2008102894A1
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WO
WIPO (PCT)
Prior art keywords
liquid material
lens group
focal length
optical system
variable
Prior art date
Application number
PCT/JP2008/053114
Other languages
French (fr)
Japanese (ja)
Inventor
Akihiko Obama
Original Assignee
Nikon Corporation
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Filing date
Publication date
Priority to JP2007041141A priority Critical patent/JP2008203650A/en
Priority to JP2007-041141 priority
Priority to JP2007041132A priority patent/JP2008203648A/en
Priority to JP2007-041132 priority
Application filed by Nikon Corporation filed Critical Nikon Corporation
Publication of WO2008102894A1 publication Critical patent/WO2008102894A1/en

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    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS, OR APPARATUS
    • G02B15/00Optical objectives with means for varying the magnification
    • G02B15/14Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective
    • G02B15/16Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective with interdependent non-linearly related movements between one lens or lens group, and another lens or lens group
    • G02B15/177Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective with interdependent non-linearly related movements between one lens or lens group, and another lens or lens group having a negative front lens or group of lenses

Abstract

It is an object to provide a variable magnification afocal optical system that uses a variable focal distance element, outputs a substantially afocal projection light ray from the optical system, satisfactorily corrects an aberration, and has high optical performance. The variable magnification afocal optical system is provided with a first lens group (G1) of a variable focal distance element (L1V) and a second lens group (G2), wherein a variable magnification from a low magnification state (L) to a high magnification state (H) is carried out by changing a focal distance of the first lens group (G1), one of the focal distances of the first lens group (G1) and the second lens group (G2) is positive and another is negative, and the variable focal distance element (L1V) changes a boundary shape between a first liquid material (LQ1) and a second liquid material (LQ2) which are enclosed in a container, and are different in refractive index from, and are not mixed with, each other.

Description

 MEMO BOOK ZOOM FOCAL OPTICAL SYSTEM TECHNICAL FIELD

 The present invention relates to a variable magnification focal optical system having a variable focal length element. BACKGROUND ART Conventionally, many optical systems using variable focal length elements have been proposed, and among them, several optical systems in which the light emitted from the optical system is almost afocal have been proposed. For example, a variable magnification optical system that uses an elastic lens made of silicon rubber as a variable focal length element and enables the variable magnification only with a simple movable mechanism is known (for example, see Japanese Patent Laid-Open No. Sho-A-55).

6 1-8 7 1 1 6).

 However, the conventional variable power optical system does not disclose any aberration correction and cannot be said to have high optical performance. Disclosure of the invention

In order to solve the above-described problem, a first aspect of the present invention includes a first lens group having a variable focal length element and a second lens group, from a low magnification end state to a high magnification end state. The focal length of the first lens unit is changed by changing the focal length of the first lens unit, and the focal length of the first lens unit and the focal length of the second lens unit are positive for one and the focal length for the other. The variable focal length element includes a first liquid material and a second liquid material that has a refractive index different from that of the first liquid material and is not mixed in a container, and the first liquid material and the first liquid material By changing the physical quantity applied to the second liquid material, the focal length is changed by changing the shape of the interface between the first liquid material and the second liquid material, The refractive index of the first liquid material at the reference wavelength is n 1, the refractive index of the second liquid material at the reference wavelength is n 2, and the optical system light having the first lens group and the second lens group The tangent of the angle formed by the axis and the outgoing light beam corresponding to the maximum angle of view of the optical system is tan 0, the refractive power of the variable focal length element in the low magnification end state of the optical system is Φ L, Provided is a variable power focal optical system characterized by satisfying the following conditional expression (1) when the refractive power of the variable focal length element in the magnification end state is defined as:

(1) 0. 005 <| φΗ— (i> L | X t an 2 e / (nl Xn 2) <20 (Unit: 1 / m)

 According to the first aspect of the present invention, the physical quantity is preferably a voltage. According to the first aspect of the present invention, the distance between the first lens group and the second lens group is changed in accordance with the change in the focal length of the first lens group. It is desirable to change the magnification.

 According to the first aspect of the present invention, along the optical axis, the first lens group is closer to the object side than the second lens group, and with the change in the focal length of the first lens group, the first lens group It is desirable to change the magnification of the entire optical system by moving only one lens group along the optical axis.

 According to the first aspect of the present invention, along the optical axis, the second lens group is closer to the object side than the first lens group. It is desirable to change the magnification of the entire optical system by moving only the two lens groups along the optical axis.

 According to the first aspect of the present invention, it is desirable that the second lens group is composed of only one or more fixed focal length elements.

 According to the first aspect of the present invention, it is desirable that the surface of the variable focal length element that contacts the air is a curved surface.

According to the first aspect of the present invention, the first lens group has one or more fixed focal lengths. 2. The variable magnification focal optical system according to claim 1, further comprising a separating element.

 According to the first aspect of the present invention, when the refractive index at the reference wavelength of the first liquid material is n 1 and the refractive index at the reference wavelength of the second liquid material is n 2, the following conditional expression It is desirable to satisfy (2).

 (2) 0. 030 <| n l-n2 | <0. 600

 According to the first aspect of the present invention, it is desirable that the first liquid material and the second liquid material have substantially the same density.

 According to the first aspect of the present invention, it is desirable that at least one of the first liquid material and the second liquid material contains an antifreeze material component.

 Further, according to the first aspect of the present invention, the variable focal length element has a first optical window that contacts the first liquid material, and a second optical window that contacts the second liquid material, DL 1 L is the distance on the optical axis from the surface where the first liquid material and the first optical window are in contact to the boundary surface in the double edge state, and the surface where the second liquid material and the second optical window are in contact The distance on the optical axis from the interface to the boundary surface is DL 2 L. In the high magnification end state, the distance on the optical axis from the surface where the first liquid material and the first optical window are in contact to the boundary surface is DL 1 When the distance on the optical axis from the surface where the second liquid material and the second optical window are in contact to the boundary surface is DL 2 H, the following conditional expressions (3), (4), (5) It is desirable to satisfy (6).

 (3) DL 1 L> 0.005 (Unit: mm)

 (4) DL 2 L> 0.005 (Unit: mm)

 (5) DL 1 H> 0.005 (Unit: mm)

 (6) DL 2H> 0.005 (Unit: mm)

Further, according to the first aspect of the present invention, the variable focal length element has a first optical window that contacts the first liquid material, and a second optical window that contacts the second liquid material, From the magnification end state to the high magnification end state, the distance from the surface where the first liquid material and the first optical window are in contact to the boundary surface, and the second liquid material and the second optical window are in contact It is desirable that the sum of the distances from the surface to the boundary surface is unchanged.

 The second aspect of the present invention is composed of a first lens group having a first variable focal length element and a second lens group having a second variable focal length element, from a low magnification end state to a high magnification end state. The zooming is performed by changing at least one of the refractive power of the first lens group and the refractive power of the second lens group. In the low magnification end state or the high magnification end state, The refractive power and the refractive power of the second lens group are such that one of the bending powers is positive and the other refractive power is negative. The first variable focal length element includes the first liquid material, the first liquid, A material and a second liquid material having a different refractive index and not mixed are enclosed in a container, and the physical quantity applied to the first liquid material and the second liquid material is changed, thereby changing the first liquid material and the second liquid material. By changing the shape of the first interface with the liquid material to change the refractive power, The second variable focal length element encloses a third liquid material and a fourth liquid material that has a refractive index different from that of the third liquid material and does not mix in a container, and the third liquid material and the fourth liquid By changing the physical quantity applied to the material, the refractive power is changed by changing the shape of the second interface between the third liquid material and the fourth liquid material, and the refractive index at the reference wavelength of the first liquid material is changed to n 1. Refractive index at the reference wavelength of the second liquid material is n2, Refractive index at the reference wavelength of the third liquid material is n3, Refractive index at the reference wavelength of the fourth liquid material is n4, The angle tangent between the optical axis of the optical system composed of the first lens group and the second lens group and the outgoing light beam corresponding to the maximum field angle of the optical system is ta ta 0, The refractive power of the first variable focal length element in the magnification end state is φ 1 L, the refractive power of the second variable focal length element in the low magnification end state of the optical system is φ 2 L, and the refractive power of the first variable focal length element in the high magnification end state of the optical system is φ 1 H A variable power afocal optical system satisfying the following conditional expression (7), where ψ 2 H is the refractive power of the second variable focal length element in the high magnification end state of the optical system.

(7) 0. 00005 <(tan 0) x | (1H- φ 1L) I (nlxn2) + (2Η-2 L) I (η3χη4) I 10 (Unit: 1 Zm) 8053114

 Five

According to the second aspect of the present invention, zooming from the low magnification end state to the high magnification end state is performed by changing the refractive power of the first lens group and the refractive power of the second lens group. It is desirable to do this.

 Further, according to the second aspect of the present invention, the direction of change in the refractive power of the first lens group and the refractive power of the second lens group during zooming from the low magnification end state to the high magnification end state. It is desirable that the directions of change are opposite to each other.

 Further, according to the second aspect of the present invention, it is desirable that the air gap between the first lens group and the second lens group is fixed when zooming from the low magnification end state to the high magnification end state. Yes.

 According to the second aspect of the present invention, it is desirable that the following conditional expressions (8) and (9) are satisfied.

 (8) 0. 020 <I n 1 -n 2 I <0. 600

 (9) 0. 020 <I n 3 -n 4 I <0. 600

 According to the second aspect of the present invention, it is desirable that the optical system has one or more fixed focal length elements.

 According to the second aspect of the present invention, it is desirable that at least one of the surfaces of the first variable focal length element and the second variable focal length element in contact with air is a curved surface.

According to the second aspect of the present invention, the first variable focal length element has a first optical window in contact with the first liquid material and a second optical window in contact with the second liquid material. In the low magnification end state, the distance on the optical axis from the surface where the first liquid material and the first optical window are in contact to the first boundary surface is DL 1 L, the second liquid material and the second optical window The distance on the optical axis from the surface in contact with the first boundary surface is DL 2 L, in the high magnification end state, from the surface in contact with the first liquid material and the first optical window to the first boundary surface Where DL 1H is the distance on the optical axis, and DL 2 H is the distance on the optical axis from the surface where the second liquid material and the second optical window are in contact with the first boundary surface, 3), T / JP2008 / 053114

 6

It is desirable to satisfy (4), (5) and (6).

 (3) DL 1 L> 0.005 (Unit: mm)

 (4) DL 2 L> 0.005 (Unit: mm)

 (5) DL 1 H> 0.005 (Unit: mm)

 (6) DL 2H> 0.005 (Unit: mm)

 According to the second aspect of the present invention, the second variable focal length element has a third optical window in contact with the third liquid material, and a fourth optical window in contact with the fourth liquid material. In the low magnification end state, the distance on the optical axis from the surface where the third liquid material and the third optical window are in contact to the second boundary surface is DL 3 L, the fourth liquid material and the fourth optical window The distance on the optical axis from the surface in contact with the second boundary surface is DL 4 L, in the high magnification end state, from the surface in contact with the third liquid material and the third optical window to the second boundary surface When the distance on the optical axis is DL 3H, and the S separation on the optical axis from the surface where the fourth liquid material and the fourth optical window are in contact to the second boundary surface is DL 4 H, the following conditions are satisfied: Formula (10),

It is desirable to satisfy (1 1), (1 2) and (1 3).

 (10) DL 3 L> 0.005 (Single: mm;

 (1 1) DL 4 L> 0.005 (Single: mm)

 (1 2) DL 3H> 0.005 (Unit: mm)

 (13) DL 4H> 0.005 (Single 1: mm)

The third aspect of the present invention includes a first lens group having a variable focal length element, and a second lens group, and the focal length of the first lens group and the focal length of the second lens group are equal to one focal point. In the variable magnification afocal optical system zooming method in which the distance is positive, the other focal length is negative, and the following conditional expression (1) is satisfied, the variable focal length element includes the first liquid material, the first liquid material, (1) A liquid material and a second liquid material having a different refractive index and not mixed are sealed in a container, and the physical quantity applied to the first liquid material and the second liquid material is changed, thereby changing the first liquid material and the second liquid material. Low magnification by changing the focal length by changing the shape of the interface with the second liquid material and changing the focal length of the first lens group A zooming method for a zooming / focal optical system characterized by zooming from an end state to a high magnification end state is provided.

(1) 0. 005 <| <ί) Η— (i L | X t an 2 0Z (nl Xn 2) <20 (Unit: 1 Zm)

here,

n 1: refractive index at a reference wavelength of the first liquid material

n 2: refractive index of the second liquid material at the reference wavelength, the first lens group and t an Θ: an outgoing light beam corresponding to the optical axis of the optical system having the second lens group and the maximum field angle of the optical system Tangent of the angle between

<i) L: refractive power of the variable focal length element in the low magnification end state of the optical system Φ H: refractive power of the variable focal length element in the high magnification end state of the optical system A first lens group having a first variable focal length element and a second lens group having a second variable focal length element, the refractive power of the first lens group in a low magnification end state or a high magnification end state And the refractive power of the second lens group is a zooming method of a zooming focal lens optical system satisfying the following conditional expression (7), in which one refractive power is positive and the other refractive power is negative: The first variable focal length element encloses a first liquid material and a second liquid material that has a refractive index different from that of the first liquid material and does not mix in a container, and supplies the first liquid material and the second liquid material to the first liquid material. By changing the physical quantity to be added, the first liquid material The second variable focal length element has a refractive index different from that of the third liquid material and does not mix. A second boundary surface between the third liquid material and the fourth liquid material is obtained by enclosing the fourth liquid material in a container and changing a physical quantity applied to the third liquid material and the fourth liquid material. By changing the refractive power by changing the shape, at least one of the refractive power of the first lens group and the refractive power of the second lens group is changed to change the magnification from the low magnification end state to the high magnification end state. The present invention provides a zooming method for a zooming / focal optical system characterized in that (7) 0.00005 <(tan 2 (φΙΗ-1L) / (nlxn) + (2H-2L) / (n3xn4) I 10 (Unit: 1 / m) n 1: Refractive index at the reference wavelength of the first liquid material

n 2: refractive index at the reference wavelength of the second liquid material

n 3: refractive index at the reference wavelength of the third liquid material

n 4: refractive index of the fourth liquid material at the reference wavelength

t ειηθ Tangent of the angle formed by the optical axis of the optical system composed of the first lens group and the second lens group and the outgoing light beam corresponding to the maximum field angle of the optical system

 1 L: refractive power of the first variable focal length element in the low magnification end state of the optical system

 2L: Refracting power of the second variable focal length element in the low magnification end state of the optical system

 Φ 1H: refractive power of the first variable focal length element in the high magnification end state of the optical system

 2Η: The refractive power of the second variable focal length element in the high magnification end state of the optical system

 According to the present invention, there is provided a variable magnification afocal optical system that uses a variable focal length element, the emitted light from the optical system is substantially focal, corrects aberrations satisfactorily, and has high optical performance. be able to. Brief Description of Drawings

 FIG. 1 is a lens configuration diagram of a variable power afocal optical system according to a first example of the first embodiment.

Fig. 2 Α 2 C 2C are graphs showing various aberrations of the variable magnification afocal optical system according to the first example of the first embodiment. Fig. 2A is a low magnification end state, Fig. 2B is an intermediate magnification state, and Fig. 2 JP2008 / 053114

 9

C shows various aberration diagrams in the high magnification end state.

 FIG. 3 is a lens configuration diagram of a variable magnification afocal optical system according to a second example of the first embodiment.

 4A, 4B, and 4C are graphs showing various aberrations of the variable magnification optical system according to the second example of the first embodiment. FIG. 4A is a low magnification end state, and FIG. 4B is an intermediate diagram. FIG. 4C shows various aberration diagrams in the high magnification end state.

 FIG. 5 is a lens configuration diagram of a variable focal optical system according to a third example of the second embodiment.

 6A, 6B, and 6C are graphs showing various aberrations of the variable magnification focal optical system according to the third example of the second embodiment. FIG. 6A is a low magnification end state, and FIG. 6B is an intermediate magnification. Fig. 6C shows aberration diagrams in the high magnification end state.

 FIG. 7 is a lens configuration diagram of a variable magnification afocal optical system according to a fourth example of the second embodiment.

 8A, 8B, and 8C are graphs showing various aberrations of the variable magnification focal optical system according to Example 4 of Embodiment 2. FIG. 8A shows a low magnification end state, and FIG. 8B shows an intermediate magnification. Fig. 8C shows aberration diagrams in the high magnification end state. BEST MODE FOR CARRYING OUT THE INVENTION

The variable power focal system according to each embodiment of the present invention will be described below. As is generally known, at least two lens groups are required to form an optical system in which the light emitted from the optical system is almost afocal. For an optical system composed of two lens groups, the object-side lens group is the objective lens group O and its focal length is ί o [mm], the pupil-side lens group is the eyepiece lens group E and its focal length is; fe When [mm] is used, in order to form an almost afocal lens group, when the principal point interval between the objective lens group O and the eyepiece lens group E is d [mm], the following conditional expression (A) is approximately It is necessary to satisfy. (A) d = fo + fe

Further, the magnification m in this afocal optical system is given by the following equation (B).

(B) m = — f o Z f e

 Here, as can be seen from equation (B), at least one of the focal length fo of the objective lens group O and the focal length fe of the eyepiece lens group E must be changed in order to change the magnification of the afocal optical system. It is.

 (First embodiment)

 Therefore, in the first embodiment, the first lens group having the variable focal length element and the second lens group are configured, and the high magnification is changed from the low magnification end state by changing the focal length of the first lens group. A variable power focal system is realized by zooming to the end state.

 In addition, the erecting afocal optical system means that the magnification m is set to a positive value. Therefore, the focal length fo of the objective lens group 0 and the focal length fe of the eyepiece lens group E are obtained from the equation (B). Must have one focal length positive and the other focal length negative.

 Therefore, in the first embodiment, the focal length of the first lens group and the focal length of the second lens group are such that one focal length is positive and the other focal length is negative. A focal optical system is realized.

 Next, the variable focal length element is described.

 In the variable focal length optical system according to the first embodiment, the variable focal length element encloses a first liquid material and a second liquid material that has a refractive index different from that of the first liquid material and does not mix in the container, By changing the physical quantity applied to the first liquid material and the second liquid material, the focal length can be changed by changing the shape of the boundary surface between the first liquid material and the second liquid material.

In the first embodiment, the refractive index at the reference wavelength of the first liquid material is n 1, the refractive index at the reference wavelength of the second liquid material is n 2, and the first lens group and the second lens group are provided. The tangent of the angle between the optical axis of the optical system and the output ray corresponding to the maximum angle of view of the optical system is tan 0, and the refractive power of the variable focal length element in the low magnification end state of the optical system is * L, optical When the refractive power of the variable focal length element in the high magnification end state of the system is ΦΗ, the following conditional expression (1) is satisfied.

(1) 0. 005 Ι ΦΗ— (i> L lxt an 2 0 / (nlXn2) 20 20

 (Unit: lZm) Note that the exit beam is the light that exits this optical system in use, whether the first lens group is on the object side or the second lens group is on the object side. That is.

 Conditional expression (1) reduces the diopter change due to aberration variation over the entire field of view when zooming from the low magnification end state to the high magnification end state, and is a highly variable optical system. This is a conditional expression for obtaining academic performance.

 If the lower limit value of conditional expression (1) is not reached, the exit angle from the optical system becomes excessively small, so that a sufficient field of view cannot be obtained, and the change in diopter over the entire field of view is suppressed. High optical performance cannot be obtained as a variable magnification focal optical system. Or, since the difference in refractive power of the variable focal length element between the low magnification end state and the high magnification end state becomes excessively small, a sufficient zooming range cannot be secured, and the zooming optical optical system Cannot achieve itself.

 When the upper limit of conditional expression (1) is exceeded, the refractive power difference of the variable focal length element becomes excessively large between the low-magnification end state and the high-magnification end state, and the Petzval sum in the entire variable-afocal optical system The fluctuation of the will become excessively large. As a result, the change in the diopter due to curvature of field at the periphery of the field of view becomes excessively large between the low magnification end state and the high magnification end state, and extends from the low magnification end state to the high magnification end state. High optical performance cannot be obtained.

In order to secure the effect of the present embodiment, it is preferable to set the lower limit value of conditional expression (1) to 0.01. In order to further ensure the effect of this embodiment, More preferably, the lower limit value of the formula (1) is set to 0.04. In order to ensure the effect of the present embodiment, it is preferable to set the upper limit value of conditional expression (1) to 8. In order to further secure the effect of the present embodiment, it is more preferable to set the upper limit of conditional expression (1) to 6.

 In the variable power afocal optical system according to the first embodiment, the physical quantity is preferably a voltage.

 Various variable focal length elements have been proposed using various means, and recently, variable focal length elements using a phenomenon called electron capillary phenomenon or electrowetting phenomenon have been proposed.

 For the two types of liquid materials used for the variable focal length element, a conductive liquid material and an insulating liquid material are selected. As the conductive liquid material, an aqueous solution of a salt such as sodium chloride, or a polar liquid material such as a liquid material added with conductivity by adding a conductive component or an ionic component can be used. Non-polar liquid materials such as oils such as silicone oil, liquid hydrocarbons, liquid hydrocarbon mixtures, nonpolar halides, or insulating liquid materials that do not mix with conductive liquid materials are used as insulating liquid materials. be able to. By using the physical quantity applied to the variable focal length element as a voltage, a variable focal length element with a simple configuration using the electrowetting phenomenon can be realized, and a variable magnification afocal optical system with a simple configuration can be easily obtained. .

 As a means for preventing the first liquid material and the second liquid material from mixing, a thin film is disposed between the first liquid material and the second liquid material, and added to the first liquid material and the second liquid material as a physical quantity and added to the thin film. A similar variable focal length element can be realized by controlling the tension or controlling the force or heat applied to one or both of the liquids.

In addition, the variable power afocal optical system according to the first embodiment changes the distance between the first lens group and the second lens group in accordance with the change in the focal length of the first lens group. It is desirable to change the magnification. With this configuration, the variable power afocal optical system changes the diopter change caused by the change in the focal length of the variable focal length element in the variable magnification from the low magnification end state to the high magnification end state with the first lens group. It can be corrected by changing the interval of the second lens group, and high optical performance can be obtained.

 In the variable power afocal optical system according to the first embodiment, the first lens unit is located on the object side with respect to the second lens unit along the optical axis. It is desirable to change the magnification of the entire optical system by moving only one lens group along the optical axis.

 With this configuration, the variable power afocal optical system allows the first lens group to function as the objective lens group 0 and the second lens group as the eyepiece lens group E. It is possible to obtain high optical performance by correcting the diopter change caused by the change in the focal length of the variable focal length element by changing the focal length of the variable focal length element by moving the first lens group, that is, the objective lens group 0. Further, since only the first lens group needs to be moved, a variable power afocal optical system having a simple configuration can be obtained with a simple movable mechanism. In the variable power afocal optical system according to the first embodiment, along the optical axis, the second lens group is closer to the object side than the first lens group. As the focal length of the first lens group changes, It is desirable to change the magnification of the entire optical system by moving only the two lens units along the optical axis.

With this configuration, the variable power afocal optical system has the function of the objective lens group 0 in the second lens group and the eyepiece group E in the first lens group. A change in the diopter caused by a change in the focal length of the variable focal length element during zooming to the end state is corrected by moving the second lens group, that is, the objective lens group 0, and high optical performance can be obtained. Further, since only the second lens group needs to be moved, a variable power afocal optical system with a simple configuration can be obtained with a simple movable mechanism. In the variable power focal optical system according to the first embodiment, it is desirable that the second lens group is composed of only one or more fixed focal length elements. 14

With this configuration, since the configuration within the lens group can be simplified, a variable power afocal optical system with a simple configuration can be realized. In addition, since there is no aberration fluctuation in the second lens group during zooming from the low magnification end state to the high magnification end state, it is possible to efficiently suppress the aberration fluctuation of the entire zooming focal optical system. High optical performance can be obtained in the double range.

 In the variable power focal system according to the first embodiment, it is desirable that the surface of the variable focal length element that contacts the air is a curved surface.

 In the variable power afocal optical system according to the first embodiment, the boundary surface between the two liquids of the variable focal length element is variable in focal length only within a specific finite range. On the other hand, in order to realize a variable magnification focal optical system, an optimum refractive power arrangement of each lens group is required. In other words, it is necessary to optimize the focal length variable range of the first lens group. Therefore, by making the surface of the variable focal length element in the first lens group in contact with air a curved surface, the focal length variable range of the first lens group is changed to the focal length variable range of the boundary surface between the two liquids of the focal length variable element. Therefore, an optimum refractive power arrangement can be achieved, and a variable power afocal optical system with a simple configuration can be realized.

 In the variable power afocal optical system according to the first embodiment, it is desirable that the first lens group has one or more fixed focal length elements.

 In the variable power afocal optical system according to the first embodiment, the boundary surface between the two liquids of the variable focal length element is variable in focal length only within a specific finite range. On the other hand, in order to realize a variable magnification focal optical system, an optimum refractive power arrangement of each lens group is required. In other words, it is necessary to optimize the focal length variable range of the first lens group. Therefore, the first lens group has one or more fixed focal length elements, so that the focal length variable range of the first lens group is shifted from the focal length variable range of the boundary surface between the two liquids of the focal length variable element. Therefore, the optimum refractive power arrangement is possible, and a variable power afocal optical system with a simple configuration can be realized.

In the variable power focal system according to the first embodiment, the base of the first liquid material is used. When the refractive index at the quasi-wavelength is n 1 and the refractive index at the reference wavelength of the second liquid material is n 2, it is desirable that the following conditional expression (2) is satisfied.

 (2) 0. 0 3 0 <I n 1-n 2 I <0. 6 0 0

 Conditional expression (2) is a conditional expression for obtaining high optical performance by suppressing the aberration variation of the variable magnification focal optical system when zooming from the low magnification end state to the high magnification end state.

 If the lower limit of conditional expression (2) is not reached, the refractive index difference at the boundary surface between the first liquid material and the second liquid material of the variable focal length element becomes excessively low. Then, since the refractive power at the interface is weakened, the change in the shape of the interface between the first liquid material and the second liquid material becomes excessively large when zooming from the low magnification end state to the high magnification end state. It becomes difficult to suppress fluctuations in field curvature, and it becomes impossible to obtain a variable-afocal optical system with high optical performance.

 When the upper limit value of conditional expression (2) is exceeded, the refractive index difference at the boundary surface between the first liquid material and the second liquid material of the variable focal length element becomes excessively high. Then, it becomes easy to be influenced by the surface accuracy error of the boundary surface, and it becomes difficult to suppress the fluctuation of the decentration coma aberration due to the surface accuracy error of the boundary surface, and the variable magnification afocal optical system with high optical performance. You will not be able to get

 In order to secure the effect of the present embodiment, it is preferable to set the lower limit value of conditional expression (2) to 0.05 0. In order to further secure the effect of the present embodiment, it is more preferable to set the lower limit of conditional expression (2) to 0.080. In order to ensure the effect of the present embodiment, it is preferable to set the upper limit value of conditional expression (2) to 0.550. In order to further secure the effect of the present embodiment, it is more preferable to set the upper limit value of the conditional expression (2) to 0.5 00.

 It goes without saying that the reference wavelength is preferably within the range of the wavelength used in the present optical system.

In the variable power afocal optical system according to the first embodiment, it is desirable that the first liquid material and the second liquid material have substantially the same density. 8053114

 16

With this configuration, it is possible to avoid the influence of the direction of gravity on the boundary surface between the two liquids and mixing due to vibration. As a result, it is possible to avoid the occurrence of decentration coma caused by the boundary shape distortion of two liquids caused by the influence of the direction of gravity and mixing due to vibration, ensuring high optical performance that is not affected by gravity or acceleration. can do.

 In the variable power afocal optical system according to the first embodiment, it is desirable that at least one of the first liquid material and the second liquid material contains an antifreeze material component.

 In the variable magnification optical system according to the first embodiment, the first liquid material or the second liquid material may freeze and solidify depending on the operating temperature. Then, not only the optical characteristics change, but also the interface shape cannot be changed, and a variable magnification focal optical system cannot be realized. Therefore, at least one of the first liquid material and the second liquid material contains an antifreeze material component such as ethylene glycol to prevent solidification due to freezing, and the variable magnification over a wide temperature range. A focal optical system can be realized. It is desirable that the antifreeze material component is contained in the liquid having the higher freezing point of the first liquid material and the second liquid material, or in the conductive liquid.

 Further, in the variable power afocal optical system according to the first embodiment, the variable focal length element has a first optical window in contact with the first liquid material and a second optical window in contact with the second liquid material. In the magnification end state, the distance on the optical axis from the surface where the first liquid material and the first optical window are in contact to the boundary surface is DL 1 L, and the light from the surface where the second liquid material and the second optical window are in contact to the boundary surface is The distance on the axis is DL 2 L, and in the high magnification end state, the distance on the optical axis from the surface where the first liquid material and the first optical window are in contact to the boundary surface is DL 1H, the second liquid material and the second optical window When DL 2H is the distance on the optical axis from the contact surface to the boundary surface, the following conditional expression should be satisfied.

 (3) DL 1 L> 0.005 (Unit: mm)

 (4) DL 2L> 0.005 (Unit: mm)

(5) DL 1 H> 0.005 (Unit: mm) (6) DL 2 H> 0. 0 0 5 (Unit: mm)

 Conditional expression (3) is a conditional expression for maintaining the boundary surface shape accuracy of the variable focal length element and realizing high optical performance in the low magnification end state.

 Below the lower limit of conditional expression (3), the boundary surface is too close to the first optical window. In this case, since tension is generated between the first optical window and the boundary surface, the accuracy of the boundary surface shape deteriorates, and aberrations such as spherical aberration and curvature of field occur and high optical performance cannot be maintained.

 Conditional expression (4) is a conditional expression for maintaining the boundary surface shape accuracy of the variable focal length element and realizing high optical performance in the low magnification end state.

 Below the lower limit of conditional expression (4), the boundary surface is too close to the second optical window. In this case, since tension is generated between the second optical window and the boundary surface, the shape accuracy of the boundary surface deteriorates, and aberrations such as spherical aberration and curvature of field occur and high optical performance cannot be maintained.

 Conditional expression (5) is a conditional expression for maintaining the boundary surface shape accuracy of the variable focal length element and realizing high optical performance in the high magnification end state.

 Below the lower limit of conditional expression (5), the boundary surface is too close to the first optical window. Then, since tension is generated between the first optical window and the boundary surface, the boundary surface shape accuracy is deteriorated, and aberrations such as spherical aberration and field curvature are generated, and high optical performance cannot be maintained.

 Conditional expression (6) is a conditional expression for maintaining the boundary surface shape accuracy of the variable focal length element and realizing high optical performance in the high magnification end state.

 Below the lower limit of conditional expression (6), the boundary surface is too close to the second optical window. In this case, since tension is generated between the second optical window and the boundary surface, the shape accuracy of the boundary surface deteriorates, and aberrations such as spherical aberration and curvature of field occur and high optical performance cannot be maintained.

In the variable magnification focal optical system according to the first embodiment, the variable focal length element has a first optical window in contact with the first liquid material and a second optical window in contact with the second liquid material, From the low magnification end state to the high magnification end state, the distance from the surface where the first liquid material and the first optical window are in contact to the boundary surface, and the distance from the surface where the second liquid material and the second optical window are in contact to the boundary surface It is desirable that the sum of By adopting such a configuration, it is not necessary to change the thickness of the entire variable focal length element in the optical axis direction, and a variable focal length device having a simple configuration can be obtained. Therefore, a variable power afocal optical system with a simple configuration can be realized.

 Needless to say, the variable power afocal optical system according to the first embodiment is not limited to the observation optical system, but can be applied to a focal front converter, a relay optical system, and the like of the photographing optical system.

 In addition, the distance between the first lens group and the second lens group is changed minutely, or the focal length of the first lens group G1 is changed minutely, so that the emitted light from the optical system is shifted from the focal so-called view. It is also possible to adjust the degree.

 〔Example〕

 Examples of the variable power afocal optical system according to the first embodiment will be described below with reference to the drawings.

 [First Example]

 FIG. 1 is a lens configuration diagram of the variable focal lens optical system according to the first example of the first embodiment. L is a low magnification end state, M is an intermediate magnification state, and H is a high magnification end state. It represents.

 The first lens group G 1 is disposed closer to the object side than the second lens group G 2. The first lens group G 1 serves as an objective lens group, and the second lens group G 2 serves as an eyepiece group. The first lens group G 1 includes a negative meniscus lens L 1 S having a convex surface directed toward the object side and a variable focal length element L 1 V. The variable focal length element L 1 V includes the first liquid material LQ 1 and the first liquid material LQ 1 in which the refractive index is different from that of the first liquid material LQ 1 and is not mixed. And the second liquid material LQ 2 by changing the voltage, which is a physical quantity applied to the first liquid material LQ 1 and the second liquid material LQ 2. The focal length of the entire lens group G1 can be changed in a negative range.

The variable focal length element L 1 V is a parallel plate glass that is part of the container in order from the object side. PT / JP2008 / 053114

 19

L ll (first optical window), lens part L 1 2 made of the first liquid material LQ 1, lens part L 1 3 made of the second liquid material LQ 2, and plano-concave lens L which is part of the container 1 4 (second optical window). The plano-concave lens L 1 4 has a concave surface on the pupil EP side. That is, the surface in contact with air is a curved surface. The first liquid material is a mixture of sodium chloride aqueous solution, which is a conductive liquid material, and ethylene glycol, which is an antifreeze liquid, and the second liquid material is silicon oil, which is an insulating liquid material, and has the same density. .

 The second lens group G 2 is arranged at a fixed position on the pupil EP side of the first lens group G 1 and is composed of only a biconvex positive lens L 2 S that is a fixed focal length element.

 To change the magnification from the low magnification end state L to the high magnification end state H, the refractive power of the variable focal length element LIV in the first lens group G 1 is changed in the direction in which the negative refractive power becomes weaker, and the first By moving only the lens group G1 to the pupil EP side, a variable power lens optical system is realized with a simple configuration.

Table 1 below lists the values of the specifications of the variable magnification focal optical system according to the first example. In the table, m is the magnification of the entire optical system (unit: dimensionless), ω is the maximum half angle of view (unit: degree), and 0 is the maximum light emission half angle (unit: degree). Note that the corresponding value in the table is the value for the chief ray, that is, the ray passing through the center of the exit pupil. In the lens data, nd is the refractive index at the d-line (λ = 587. 6 nm) which is the reference wavelength, and the air refractive index nd = l. 0 0 0 0 0 0 is omitted. Yes. Here, since the optical system is assumed to be used for visible light, it is clear that the reference wavelength is within the range of the used wavelength. The RLQ in the lens design and variable data represents the radius of curvature of the boundary surface LB between the first liquid material LQ 1 and the second liquid material LQ 2. The same reference numerals are used in Table 2 of the second embodiment, which will be described later, and the subsequent description is omitted. As can be seen from Table 1, from the low magnification end state L to the high magnification end state H, the distance from the surface where the first liquid material and the first optical window are in contact to the boundary surface, the second liquid material and the second optical window The sum of the distance from the surface that touches the boundary surface is unchanged. In the first embodiment, “mm” is used as the unit for the radius of curvature and the surface interval, but the optical system can obtain the same optical performance even when proportionally enlarged or reduced. Other suitable units can also be used without limitation. The same applies to each embodiment described later.

 (table 1)

 [Overall specifications]

 L M H

m 0. 3 6 0. 6 0 0. 8 0

ω 2 5-7 0 1 7. 5 5 1 2. 40

θ 9. 0 0 9. 0 0 9. 0 0

 [Lensra = Overnight]

Surface number Curvature radius Surface spacing n d

 1) 250.000 1.000 1.491080

 2) 12.475 3.500

 3) οο 1.000 1.516800

 4) οο DL1 1.378000 (LQ1)

 5) RLQ DL2 1.715000 (LQ2)

 6) ∞ 1.000 1.516800

 7) 20.000 D1

 8) 30.000 3.500 1.491080

 9) -28.000 15.000

 10> οο (EP)

 [Variable data-evening]

 L M H

RLQ -17. 770 90.000 17.600

DL1 1. 700 1.200 0.500 Four

 twenty one

DL2 0.800 1.300 2.000

 Dl 15.200 9.810 2.800

 [Values for conditional expressions]

(1) Ι ΦΗ— (i> L lxt an 2 e / (nl Xn 2) = 0. 42

 (2) I n 1 -n 2 I = 0. 337

 (3) DL 1 L = 1. 700

 (4) DL 2 L = 0. 800

 (5) DL 1H = 0. 500

 (6) DL2H = 2. 000

 2A, 2B, and 2C show various aberration diagrams for the reference wavelength d-line (λ = 587.6 nm) of the variable magnification afocal optical system according to the first example of the first embodiment, and FIG. Magnification end state L, Fig. 2B shows various aberration diagrams in intermediate magnification state M, and Fig. 2C shows high magnification end state H, respectively.

The unit of the spherical aberration diagram is m- 1 (diopter D), and h is the incident height. The incident height h is the height at which the land light passes through the lens surface closest to the object, and the land light is the light ray farthest from the optical axis among the light rays having a field angle of zero. Astigmatism The solid line in the figure shows the sagittal image plane, and the broken line shows the meridional image plane (unit: m- 1 ; diop evening D). A indicates the light incident angle (unit: degree). The vertical axis of the coma aberration diagram represents the coma aberration (unit: minutes) at each incident angle. Note that the same reference numerals are used in the various aberration diagrams of the following examples, and the following description is omitted.

 Figures 2A, 2B, 2. According to the above, it is clear that the aberration is corrected well, the aberration fluctuation between the low magnification end state and the high magnification end state H is suppressed, and the optical performance is high.

 [Second Example]

FIG. 3 is a lens configuration diagram of the variable focal lens optical system according to the second example of the first embodiment. L is a low magnification end state, M is an intermediate magnification state, and H is a high magnification end state. Represents each.

 The first lens group G 1 is disposed closer to the pupil EP than the second lens group G 2. The first lens group G 1 serves as an eyepiece lens group, and the second lens group G 2 serves as an objective lens group. The second lens group G 2 is a fixed focal length element and is composed only of a biconvex positive lens L 2 S having a strong refractive power on the object side surface.

 The first lens group G 1 is arranged on the pupil EP side of the second lens group G 2, and in order from the object side, a biconcave lens L 1 S having a strong refractive power on the pupil EP side and a variable focal length element It consists of LIV. The variable focal length element LIV encloses the first liquid material LQ 1 and the first liquid material LQ 1 with the first liquid material LQ 1 and the second liquid material LQ 2 that have different refractive indexes and does not mix. 2Liquid material LQ 2 is an element that changes the focal length by changing the boundary LB shape of the first liquid material LQ 1 and the second liquid material LQ 2 by changing the voltage, which is the physical quantity applied to the LQ 2. The focal length of the entire group G 1 can be changed in the negative range.

 The variable focal length element LIV includes, in order from the object side, a parallel plate glass L 1 1 (first optical window) which is a part of the container, a lens portion L 1 2 made of the first liquid material LQ 1, and a second It is composed of a lens portion L 1 3 made of the liquid material LQ 2 and a parallel flat glass L 1 4 (second optical window) which is a part of the container. The first liquid material is a sodium chloride aqueous solution, which is a conductive liquid material, and the second liquid material is silicon oil, which is an insulating liquid material.

 To change the magnification from the low magnification end state to the high magnification end state H, the refractive power of the variable focal length element LIV in the first lens group G1 is changed in the direction in which the negative refractive power increases, and the second lens By moving only the lens group G2 to the object side, a variable power optical system is realized with a simple configuration.

Table 2 below lists the specifications of the variable power focal system according to the second example. As can be seen from Table 2, from the low magnification end state L to the high magnification end state H, the distance from the contact surface between the first liquid material and the first optical window to the boundary surface, the second liquid material and the second optical 8053114

 twenty three

The sum of the distance from the surface where the window touches to the boundary is unchanged.

 (Table 2)

 [Overall specifications]

 L Μ H

m 1.19 1.44 1.88

ω 6.80 5. 59 4. 14

θ 8 .00 8. 00 8. 00

 [Lensra Overnight]

Surface number Curvature radius Surface spacing n d

 1) 26.000 5.000 1.589130

 2) -260.000 D1

 3) -30.000 1.000 1.516800

 4) 24.000

 5) οο 1.000 1.516800

 6) οο DL1 1.383000 (LQ1)

 7) RLQ DL 1.635000 (LQ2)

 8) οο 1.000 1.516800

 9) ∞ 15.000

 10> οο (EP)

 [Variable de-evening]

 L M H

RLQ 30. 000 90.000 -37. 500

 DL1 0. 900 1.200 1. 500

 DL2 1. 600 1.300 1. 000

 D1 4.220 9.500 15. 200

[Values for conditional expressions] (1) 1 ΦΗ— (i LIX t an 2 0 / (n 1 Xn 2) = 0.13

 (2) I n 1-n 21 = 0. 252

 (3) DL 1 L = 0. 900

 (4) DL 2L = 1. 600

 (5) DL 1H = 1. 500

 (6) DL 2H = 1. 000

 4A, 4B, and 4C show various aberration diagrams for the reference wavelength d-line (λ = 587.6 nm) of the variable power focal system according to the second example of the first embodiment, and FIG. 4A shows a low magnification. End state L, Fig. 4B shows various aberrations in intermediate magnification state M, and Fig. 4C shows high magnification end state H, respectively.

 According to Figs. 4A, 4B, and 4C, it is clear that aberrations are corrected well, and aberration variation between the low magnification end state and the high magnification end state H is suppressed, and the optical performance is high. It is.

 As described above, according to the first embodiment, the variable focal length element is used, the emitted light from the optical system is almost afocal, the aberration is corrected well, and the camera finder is a camera converter. It can be used for a lens, a telescope, etc., and a variable magnification focal optical system having high optical performance can be provided.

 In the variable power optical system of each example, the air distance D1 between the first lens group G1 and the second lens group G2 is slightly changed, or the focal length of the first lens group G1 is changed. By making slight changes, it is possible to perform so-called diopter adjustment that slightly shifts the emitted light from the optical system from the focal.

In each example, a two-group lens system is shown. However, it goes without saying that a three-group including the two groups and an optical system having a group structure of two or more groups are also effective lens systems. Absent. In addition, in the configuration within each lens group, it goes without saying that a lens group obtained by adding a lens to the configuration of the embodiment is a lens group having the same effect. 8 053114

 twenty five

In each embodiment, only the example in which the second lens group is composed of a fixed focal length element is shown, but a variable focal length element may be included.

 (Second embodiment)

 Hereinafter, a variable power afocal optical system according to a second embodiment of the present invention will be described. In the second embodiment, the first lens group having the first variable focal length element and the second lens group having the second variable focal length element are used, and the refractive power of the first lens group, that is, the reciprocal of the focal length. By changing at least one of the refractive power of the second lens group, that is, the reciprocal of the focal length, the magnification is changed from the low magnification end state to the high magnification end state, thereby realizing a variable magnification afocal optical system. is doing.

 In addition, an erecting optical system means that the magnification m is set to a positive value. Therefore, the focal length fo of the objective lens group O and the eyepiece lens group E are obtained from the above equation (B). It is necessary to reverse the signs of the focal length fe.

 Therefore, in the second embodiment, in the low magnification end state or the high magnification end state, the refractive power of the first lens group and the refractive power of the second lens group are positive, and the other refractive power is negative. By doing so, an erecting variable magnification focal system is realized.

 In order to maintain erectness, the refractive power of the first lens group and the refractive power of the second lens group are positive when one refractive power is positive and the other refractive power is not negative. Needless to say, this is the case where the vertical variable afocal optical system is approximately equal in magnification, and only when the emitted light is slightly deviated from the full afocal force.

 Next, the variable focal length element is described.

In the variable magnification optical system according to the second embodiment, the first variable focal length element includes a first liquid material and a second liquid material that has a refractive index different from that of the first liquid material and does not mix in the container. By enclosing and changing the physical quantity applied to the first liquid material and the second liquid material, the first boundary surface shape between the first liquid material and the second liquid material is changed to change the refractive power. The variable focal length element encloses a third liquid material and a fourth liquid material that has a refractive index different from that of the third liquid material and does not mix in the container. 053114

 26 By changing the physical quantity applied to the fourth liquid material, the second interface shape between the third liquid material and the fourth liquid material is changed to change the refractive power.

 In the second embodiment, the refractive index at the reference wavelength of the first liquid material is n 1, the refractive index at the reference wavelength of the second liquid material is n 2, and the refractive index at the reference wavelength of the third liquid material is n 3, The refractive index at the reference wavelength of the fourth liquid material is n 4, and the tangent of the angle between the optical axis of the optical system composed of the first lens group and the second lens group and the outgoing light beam corresponding to the maximum field angle of the optical system Ta ηΘ, the refractive power of the first variable focal length element in the low magnification end state of the optical system is φ 1 L, the refractive power of the second variable focal length element in the low magnification end state of the optical system is Φ 2 L, When the bending power of the first variable focal length element in the high magnification end state of the optical system is Φ 1 H and the refractive power of the second variable focal length element in the high magnification end state of the optical system is Φ 2 以下, Conditional expression (7) is satisfied.

(7) O. OOOO5 <(t an 2 0) x | (Φ 1H- φ 1L) / (nlxn2) + (2Η-Φ 2L) / (η3χη4) I <10 (Unit: 1 / m)

 Conditional expression (7) reduces the diopter change due to aberration fluctuation (curvature of field) over the entire field when zooming from the low magnification end state to the high magnification end state. This is a conditional expression for obtaining high optical performance as a system.

If the lower limit value of conditional expression (7) is not reached, the exit angle from the optical system becomes excessively small, so that a sufficient range of field of view cannot be secured, and high optical performance as a variable power afocal optical system. Can't get. Or, since the refractive power difference of the variable focal length element between the low magnification end state and the high magnification end state becomes excessively small, a sufficient zooming range cannot be secured, and the zooming focal lens optical system itself Cannot be achieved. When the upper limit of conditional expression (7) is exceeded, the refractive power difference of the variable focal length element becomes excessively large between the low magnification end state and the high magnification end state, and the Petzval sum of the entire variable magnification focal optical system The fluctuation will become excessively large. Then, the diopter change due to curvature of field at the periphery of the field of view becomes excessively large between the low magnification end state and the high magnification end state, and high optical performance is observed from the low magnification end state to all the high magnification end states. Get performance 2008/053114

 27

I can't do that.

 In order to secure the effect of this embodiment, it is preferable to set the lower limit value of conditional expression (7) to 0.0 0 0 0 8. In order to further secure the effect of the present embodiment, it is more preferable to set the lower limit value of conditional expression (7) to 0.0 0 0 1. In order to ensure the effect of this embodiment, it is preferable to set the upper limit value of conditional expression (7) to 5. In order to further secure the effect of the present embodiment, it is more preferable to set the upper limit value of conditional expression (7) to 1.

 In the variable power afocal optical system according to the second embodiment, the physical quantity is preferably a voltage.

 Various variable focal length elements have been proposed using various means, and recently, variable focal length elements using a phenomenon called electron capillary phenomenon or electrowetting phenomenon have been proposed.

 For the two liquid materials used for the first and second variable focal length elements, a conductive liquid material and an insulating liquid material are selected. As the conductive liquid material, a polar liquid material such as an aqueous solution of a salt such as sodium chloride sodium salt, a liquid material to which conductivity is imparted by adding a conductive component or an ionic component can be used. For the insulating liquid material, use non-polar liquid materials such as silicon oils, liquid hydrocarbons, liquid hydrocarbon mixtures, nonpolar halides, or insulating liquid materials that do not mix with conductive liquid materials. Can be. The liquid material of the first variable focal length element and the liquid material of the second variable focal length element may be the same substance or different. .

 By using the physical quantity applied to the variable focal length element as a voltage, a variable focal length element with a simple configuration using the electrowetting phenomenon can be realized, and a variable magnification focal optical system with a simple configuration can be easily obtained. it can.

As a means for preventing the first liquid material and the second liquid material from mixing, a thin film is disposed between the first liquid material and the second liquid material, and added to the first liquid material and the second liquid material as a physical quantity and added to the thin film. Control tension and apply to one or both fluids It is also possible to realize a similar variable focal length element by controlling the force and heat. The same applies to the third liquid material and the fourth liquid material.

 In addition, the variable power optical system according to the second embodiment changes the refractive power of the first lens group and the refractive power of the second lens group by changing the magnification from the low magnification end state to the high magnification end state. It is desirable to do so.

 If the refractive power of one variable focal length element is changed during zooming from the low magnification end state to the high magnification end state, diopter change is caused accordingly. Therefore, by changing the refractive power of the other variable focal length element, diopter change can be corrected, and high optical performance can be obtained.

 In the variable power afocal optical system according to the second embodiment, the direction of change in the refractive power of the first lens group and the refractive power of the second lens group during zooming from the low magnification end state to the high magnification end state. The direction of force change should be opposite to each other.

 If the refractive power of one of the variable focal length elements is changed at the time of zooming from the low magnification end state to the high magnification end state, diopter change is caused accordingly. Therefore, by changing the refractive power of the other variable focal length element, the direction of change of the refractive power of the first lens group and the direction of change of the refractive power of the second lens group are opposite to each other. Correction is possible, and high optical performance can be obtained.

 Further, in the zooming optical system according to the second embodiment, the air gap between the first lens unit and the second lens unit is fixed when zooming from the low magnification end state to the high magnification end state. Is desirable.

 With this configuration, the movable mechanism for zooming of the first lens group and the second lens group is not necessary, and a zooming focal optical system having a simple configuration can be obtained.

 In the variable power afocal optical system according to the second embodiment, it is preferable that the following conditional expressions (8) and (9) are satisfied.

 (8) 0. 020 <| n l-n2 | <0. 600

(9) 0. 020 <I n 3 -n 4 I <0. 600 Conditional expression (8) is a conditional expression for obtaining high optical performance while suppressing the aberration variation of the variable magnification focal optical system when zooming from the low magnification end state to the high magnification end state.

 When the lower limit value of conditional expression (8) is not reached, the refractive index difference at the first boundary surface between the first liquid material and the second liquid material of the first variable focal length element becomes excessively low. Then, since the refractive power at the interface is weakened, the change in the shape of the first interface between the first liquid material and the second liquid material is excessive when zooming from the low magnification end state to the high magnification end state. When this is increased, it becomes difficult to suppress fluctuations in the image plane curve, and it becomes impossible to obtain a variable-afocal optical system with high optical performance.

 When the upper limit value of conditional expression (8) is exceeded, the refractive index difference at the first boundary surface between the first liquid material and the second liquid material of the first variable focal length element becomes excessively high. Then, it becomes easy to be affected by the surface accuracy error of the boundary surface, and it becomes difficult to suppress the fluctuation of the decentration coma aberration due to the surface accuracy error of the boundary surface. I can't get it.

 In order to secure the effect of the present embodiment, it is preferable to set the lower limit value of conditional expression (8) to 0.05 0. In order to further secure the effect of this embodiment, it is more preferable to set the lower limit value of conditional expression (8) to 0.080. In order to ensure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (8) to 0.550. In order to further secure the effect of this embodiment, it is more preferable to set the upper limit value of conditional expression (8) to 0.5 00.

 Conditional expression (9) is a conditional expression for obtaining high optical performance while suppressing the aberration variation of the variable magnification focal optical system when zooming from the low magnification end state to the high magnification end state.

When the lower limit value of conditional expression (9) is not reached, the refractive index difference at the second boundary surface between the third liquid material and the fourth liquid material of the second variable focal length element becomes excessively low. Then, since the refractive power at the interface is weakened, the change in the shape of the second interface between the third liquid material and the fourth liquid material is excessive when zooming from the low magnification end state to the high magnification end state. As it becomes larger, it becomes difficult to suppress fluctuations in the image plane curve, and a variable optical focal system with high optical performance is required. I can't get it.

 If the upper limit value of conditional expression (9) is exceeded, the refractive index difference at the second boundary surface between the third liquid material and the fourth liquid material of the second variable focal length element becomes excessively high. Then, it becomes easy to be affected by the surface accuracy error of the boundary surface, and it becomes difficult to suppress the fluctuation of the decentration coma aberration due to the surface accuracy error of the boundary surface, and the zoom optical system with high optical performance. You will not be able to get.

 In order to secure the effect of the present embodiment, it is preferable to set the lower limit value of conditional expression (9) to 0.05 0. In order to further secure the effect of the present embodiment, it is more preferable to set the lower limit value of conditional expression (9) to 0.080. In order to ensure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (9) to 0.550. In order to further secure the effect of this embodiment, it is more preferable to set the upper limit value of conditional expression (9) to 0.5 00.

 It goes without saying that the reference wavelength is preferably within the range of the wavelength used in the present optical system.

 In addition, it is desirable that the variable power afocal optical system according to the second embodiment has one or more fixed focal length elements.

In the variable power afocal optical system according to the second embodiment, the boundary surface of each of the two liquids of the first variable focal length element or the second variable focal length element is variable in refractive power only within a specific finite range. is there. On the other hand, in order to realize a variable power focal system, an optimum refractive power arrangement for each lens group is required. In other words, it is necessary to optimize the refractive power variable range of the first lens group and the refractive power variable range of the second lens group. Therefore, by setting the variable magnification optical system to have one or more fixed focal length elements, the refractive power variable range of the first lens group is shifted from the focal length variable range of the first boundary surface, or The variable range of refractive power of the second lens group can be shifted from the variable range of focal length of the second boundary surface, making it possible to arrange the optimal refractive power and to realize a variable power afocal optical system with a simple configuration . Further, in the variable power afocal optical system according to the second embodiment, it is desirable that at least one of the surfaces of the first variable focal length element and the second variable focal length element in contact with air is a curved surface.

 In the variable magnification focal optical system according to the second embodiment, the boundary surface between the two liquids of the variable focal length element is variable in focal length only within a specific finite range. On the other hand, in order to realize a variable magnification focal optical system, an optimum refractive power arrangement of each lens group is required. That is, it is necessary to optimize the focal length variable range of the first lens group and the focal length variable range of the second lens group. Therefore, by making at least one of the surfaces of the first variable focal length element and the second variable focal length element in contact with air into a curved surface, the refractive power variable range of the first lens group is changed to the first boundary surface. It is possible to shift from the focal length variable range of the second lens group, or the refractive power variable range of the second lens group can be shifted from the focal length variable range of the second boundary surface, which makes it possible to arrange the optimum refractive power and to make a simple configuration It is possible to realize a focal optical system.

 In the variable magnification optical system according to the second embodiment, it is desirable that the first liquid material and the second liquid material have substantially the same density.

 With this configuration, it is possible to avoid mixing due to the influence of the direction of gravity and vibration on the first boundary surface. As a result, it is possible to avoid the occurrence of decentration coma due to the distortion of the first interface shape caused by the influence of the direction of gravity and mixing due to vibration, ensuring high optical performance that is not affected by gravity or acceleration. be able to. In the variable power afocal optical system according to the second embodiment, it is desirable that the third liquid material and the fourth liquid material have substantially the same density.

With this configuration, it is possible to avoid mixing due to the influence of the direction of gravity and vibration on the second boundary surface. As a result, it is possible to avoid the occurrence of decentration coma due to the distortion of the second interface shape caused by the influence of the direction of gravity and mixing due to vibration, ensuring high optical performance that is not affected by gravity or acceleration. be able to. In the variable power afocal optical system according to the second embodiment, the first liquid material and the first liquid material It is desirable that at least one of the two liquid material, the third liquid material, and the fourth liquid material includes an antifreeze material component.

 In the variable magnification optical system according to the second embodiment, the first liquid material, the second liquid material, the third liquid material, or the fourth liquid material may freeze and solidify depending on the operating temperature. As a result, not only the optical characteristics change, but also the interface shape cannot be changed, and a variable magnification focal optical system cannot be realized. Therefore, at least one of the first liquid material, the second liquid material, the third liquid material, and the fourth liquid material contains an antifreeze material component such as ethylene glycol to prevent solidification due to freezing. A variable power focal system can be realized over a wide temperature range. It is desirable that the antifreeze material component is contained in a liquid having a high freezing point or a conductive liquid among the first liquid material, the second liquid material, the third liquid material, and the fourth liquid material.

 Further, in the variable power afocal optical system according to the second embodiment, the first variable focal length element has a first optical window in contact with the first liquid material and a second optical window in contact with the second liquid material. In the low magnification end state, the distance on the optical axis from the surface where the first liquid material and the first optical window are in contact to the first boundary surface is DL 1L, the surface force where the second liquid material and the second optical window are in contact The distance on the optical axis to the boundary surface is DL 2 L. In the high magnification end state, the distance on the optical axis from the surface where the first liquid material and the first optical window are in contact to the first boundary surface is DL 1 H, When the distance on the optical axis from the surface where the second liquid material and the second optical window are in contact to the first boundary surface is D L2H, it is desirable that the following conditional expression is satisfied.

 (3) DL 1 L> 0.005 (Unit: mm)

 (4) DL 2L> 0.005 (Unit: mm)

 (5) DL 1H> 0.005 (Unit: mm)

 (6) DL2H> 0.005 (Unit: mm)

 Conditional expression (3) is a conditional expression for maintaining the first boundary surface shape accuracy of the first variable focal length element and realizing high optical performance in the low magnification end state.

Below the lower limit of conditional expression (3), the first boundary surface is too close to the first optical window. Then, since tension is generated between the first optical window and the first boundary surface, the boundary surface shape accuracy is deteriorated, and aberrations such as spherical aberration and field curvature are generated, and high optical performance cannot be maintained. Conditional expression (4) is a conditional expression for maintaining the first boundary surface shape accuracy of the first variable focal length element and realizing high optical performance in the low magnification end state.

 If the lower limit of conditional expression (4) is not reached, the first boundary surface is too close to the second optical window. Then, since tension is generated between the second optical window and the first boundary surface, the boundary surface shape accuracy deteriorates, and aberrations such as spherical aberration and curvature of field occur and high optical performance cannot be maintained. Conditional expression (5) is a conditional expression for maintaining the first boundary surface shape accuracy of the first variable focal length element and realizing high optical performance in the high magnification end state.

 If the lower limit value of conditional expression (5) is not reached, the first boundary surface is too close to the first optical window. Then, since tension is generated between the first optical window and the first boundary surface, the accuracy of the boundary surface deteriorates, and aberrations such as spherical aberration and curvature of field occur and high optical performance cannot be maintained. Conditional expression (6) is a conditional expression for maintaining the first boundary surface shape accuracy of the first variable focal length element and realizing high optical performance in the high magnification end state.

 Below the lower limit of conditional expression (6), the first boundary surface is too close to the second optical window. Then, since tension is generated between the second optical window and the first boundary surface, the boundary surface shape accuracy deteriorates, and aberrations such as spherical aberration and curvature of field occur and high optical performance cannot be maintained. In the variable power focal system according to the second embodiment, the second variable focal length element has a third optical window in contact with the third liquid material and a fourth optical window in contact with the fourth liquid material. In the low magnification end state, the distance on the optical axis from the surface where the third liquid material and the third optical window are in contact to the second boundary surface is DL 3 L, and the distance from the surface where the fourth liquid material and the fourth optical window are in contact is 2 The distance on the optical axis to the boundary surface is DL 4 L. In the high magnification end state, the distance on the optical axis from the surface where the third liquid material contacts the third optical window to the second boundary surface is DL 3 H. When the distance on the optical axis from the surface where the fourth liquid material and the fourth optical window are in contact to the second boundary surface is DL 4 H, it is desirable that the following conditional expression is satisfied.

(1 0) DL 3 L> 0. 0 0 5 (Unit: mm) (11) DL4L> 0.005 (Unit: mm)

 (12) DL 3H> 0.005 (Unit: mm)

 (13) DL4H> 0.005 (Unit: mm)

 Conditional expression (10) is a conditional expression for maintaining the second boundary surface shape accuracy of the second variable focal length element and realizing high optical performance in the low magnification end state.

 Below the lower limit of conditional expression (10), the second boundary surface is too close to the third optical window. Then, since tension is generated between the third optical window and the second boundary surface, the boundary surface shape accuracy deteriorates, and aberrations such as spherical aberration and curvature of field occur and high optical performance cannot be maintained.

 Conditional expression (11) is a conditional expression for maintaining the second boundary surface shape accuracy of the second variable focal length element and realizing high optical performance in the low magnification end state.

 Below the lower limit of conditional expression (1 1), the second boundary surface is too close to the fourth optical window. Then, since tension is generated between the fourth optical window and the second boundary surface, the boundary surface shape accuracy deteriorates, and aberrations such as spherical aberration and curvature of field occur and high optical performance cannot be maintained.

 Conditional expression (12) is a conditional expression for maintaining the second boundary surface shape accuracy of the second variable focal length element and realizing high optical performance in the high magnification end state.

 Below the lower limit of conditional expression (12), the second boundary surface is too close to the third optical window. Then, since tension is generated between the third optical window and the second boundary surface, the boundary surface shape accuracy deteriorates, and aberrations such as spherical aberration and curvature of field occur and high optical performance cannot be maintained.

 Conditional expression (13) is a conditional expression for maintaining the second boundary surface shape accuracy of the second variable focal length element and realizing high optical performance in the high magnification end state.

Below the lower limit of conditional expression (13), the second boundary surface is too close to the fourth optical window. As a result, tension is generated between the fourth optical window and the second boundary surface, resulting in poor boundary shape accuracy and high aberrations such as spherical aberration and field curvature. Absent.

 Further, in the variable power afocal optical system according to the second embodiment, the first variable focal length element has a first optical window in contact with the first liquid material and a second optical window in contact with the second liquid material. In the low magnification end state to the high magnification end state, the distance from the surface where the first liquid material and the first optical window are in contact to the first boundary surface, and the surface where the second liquid material and the second optical window are in contact with the first boundary It is desirable that the sum of the distances to the surface is unchanged.

 With this configuration, it is not necessary to change the thickness of the entire first variable focal length element in the optical axis direction, and a variable focal length element with a simple configuration can be obtained. Therefore, a variable power afocal optical system with a simple configuration can be realized.

 In the variable power focal system according to the second embodiment, the second variable focal length element has a third optical window in contact with the third liquid material and a fourth optical window in contact with the fourth liquid material. In the low magnification end state to the high magnification end state, the distance from the surface contacting the third liquid material to the third optical window to the second boundary surface, and the second boundary from the surface contacting the fourth liquid material to the fourth optical window It is desirable that the sum of the distances to the surface is unchanged.

 With this configuration, there is no need to change the thickness of the entire second variable focal length element in the optical axis direction, and a variable focal length element with a simple configuration can be obtained. Therefore, a variable power afocal optical system with a simple configuration can be realized.

 Needless to say, the variable power afocal optical system according to the second embodiment is not limited to the observation optical system, but can also be applied to an optical front converter of the photographing optical system, such as a rear optical system.

 In addition, by changing the distance between the first lens group and the second lens group, or by changing the refractive power of the first lens group or the second lens group, It is also possible to perform so-called diopter adjustment.

Even if the first lens group is considered as objective lens group 0, the second lens group as eyepiece lens group E, the first lens group as eyepiece lens group E, and the second lens group as objective lens group 〇 It is clear that either can realize a variable focal optical system. 〔Example〕

 Examples of the variable power afocal optical system according to the second embodiment will be described below with reference to the drawings.

 [Third embodiment]

 FIG. 5 is a lens configuration diagram of a variable focal lens optical system according to the third example of the second embodiment. L is a low magnification end state, M is an intermediate magnification state, and H is a high magnification end state. It represents.

 The first lens group G 1 is disposed closer to the object side than the second lens group G 2. The first lens group G 1 serves as an objective lens group, and the second lens group G 2 serves as an eyepiece group. The first lens group G 1 includes a negative meniscus lens L 1 S having a convex surface facing the object side and a first variable focal length element L I V. The first variable focal length element L 1 V includes a first liquid material LQ 1 and a second liquid material LQ 2 that has a refractive index different from that of the first liquid material LQ 1 and is not mixed. By changing the voltage, which is a physical quantity applied to LQ 1 and the second liquid material LQ 2, the first boundary surface LB 1 between the first liquid material LQ 1 and the second liquid material LQ 2 is changed to change the focal length. The refractive power of the entire first lens group G1 can be changed in a negative range.

 The first variable focal length element LIV includes, in order from the object side, a parallel plate glass L 1 1 (first optical window) that is a part of the container, a lens portion L 1 2 made of the first liquid material LQ 1, 2 Consists of a lens part L 1 3 made of liquid material LQ 2 and a plano-concave lens L 1 4 (second optical window) which is a part of the container. The plano-concave lens L 14 has a concave surface on the pupil EP side. That is, the surface in contact with air is a curved surface. The first liquid material is a mixed liquid of sodium chloride aqueous solution, which is a conductive liquid material, and ethylene glycol, which is an antifreeze liquid, and the second liquid material is silicon oil, which is an insulating liquid material, and has the same density.

The second lens group G 2 consists of a biconvex lens L 2 S and a second variable focal length element L 2 V 53114

 37

It consists of and. The second variable focal length element L 2 V includes a third liquid material LQ 3 and a fourth liquid material LQ 4 that has a refractive index different from that of the third liquid material LQ 3 and is not mixed in the container. By changing the voltage, which is a physical quantity applied to LQ 3 and the fourth liquid material LQ 4, the second interface LB 2 shape between the third liquid material LQ 3 and the fourth liquid material LQ 4 can be changed to make the focal length variable. The refractive power of the entire second lens group G2 can be changed in the positive range.

 The second variable focal length element L 2 V includes, in order from the object side, a parallel plate glass L 2 1 (third optical window) that is a part of the container, and a lens portion L 2 2 made of the third liquid material LQ 3 The lens portion L 2 3 made of the fourth liquid material LQ 4 and the parallel plate glass L 2 4 (fourth optical window) which is a part of the container. The third liquid material is a mixed liquid of sodium chloride aqueous solution, which is a conductive liquid material, and ethylene glycol, which is an antifreeze, and the fourth liquid material is silicon oil, which is an insulating liquid material, and has the same density. Yes. The first liquid material L Q 1 and the third liquid material L Q 3 are different in the sodium chloride concentration and the ethylene glycol mixing ratio. The second liquid material L Q 2 and the fourth liquid material L Q 4 are silicon oils but have different substances.

 When zooming from the low magnification end state L to the high magnification end state H, the refractive power of the first variable focal length element LIV in the first lens group G 1 is changed from negative to positive, The refractive power of the second variable focal length element L 2 V in the lens group G 2 is changed in the direction from positive to negative. That is, the refractive power of the first variable focal length element LIV in the first lens group G1 and the refractive power of the second variable focal length element L2V in the second lens group G2 are opposite to each other. By changing to, the diopter change is suppressed and high optical performance is secured. Also, at the time of zooming, the air gap between the first lens group G1 and the second lens group G2 is fixed, and a zooming power optical system is realized with a simple configuration.

Table 3 below lists the values of the specifications of the variable magnification afocal optical system according to the third example. In the table, m is the magnification of the entire optical system (unit: dimensionless), ω is the maximum half field angle (unit: degree), and Θ is the maximum light emission half angle (unit: degree). The corresponding value of 0 in the table is the chief ray That is, it is a value for a light ray passing through the center of the payout pupil. In the lens data, nd is the refractive index at the d-line (λ = 587.6 nm), which is the reference wavelength, and the air refractive index nd = 1.000000 is omitted. Here, since it is assumed that the optical system is used for visible light, it is clear that the reference wavelength is within the range of wavelengths used. In the lens data and variable data, RLQ 1 represents the radius of curvature of the first interface LB 1 between the first liquid material LQ 1 and the second liquid material LQ2, and RLQ2 represents the third liquid material LQ 3 and the fourth liquid material. This represents the radius of curvature of the second interface LB 2 with LQ 4. The same reference numerals are used in Table 2 of the second embodiment, which will be described later, and description thereof is omitted.

 The second surface is an aspheric surface (AS) and is expressed by the following equation.

= cy {1 + (1 _ κ c 2 y 2 ) 1/2 }

y is the height from the optical axis, X is the amount of sag, c is the standard curvature and the reciprocal of the radius of curvature, and κ is the conic constant. The constants are shown in [Aspheric data] in the table.

 As can be seen from Table 3, from the low magnification end state L to the high magnification end state H, the distance from the surface where the first liquid material and the first optical window are in contact to the first interface, the second liquid material and the second The sum of the distance from the surface where the optical window contacts to the first boundary is unchanged. In addition, from the low magnification end state L to the high magnification end state H, the distance from the surface where the third liquid material and the third optical window are in contact to the second boundary surface, and the fourth liquid material and the fourth optical window are in contact. The sum of the distance from the surface to the second boundary is unchanged.

 In the third embodiment, “mm” is used as the unit for the radius of curvature and the surface spacing. However, since the optical system can obtain the same optical performance even when proportionally enlarged or reduced, the “mm” is used. Other suitable units can also be used without limitation. The same applies to the fourth embodiment to be described later.

 (Table 3)

 [Overall specifications]

LMH Four

 39

m 0. 32 0. 42 0.

ω 39. 8 28. 7 1 8.

θ 12. 0 12. 0 1 2.

 [Lens de overnight]

Surface number Curvature radius Surface spacing n d

 1) 250.000 1.000 1.491080

 2) 12.000 4.000 (AS)

 3) οο 1.000 1.516800

 4) οο DL1 1.378000 (LQ1)

 5) RLQ1 DL2 1.821000 (LQ2)

 6) οο 1.000 1.516800

 7) 25.000 D1

 8) 47.000 3.000 1.491080

 9) -47.000 1.000

 10) οο 1.000 1.516800

 11) οο DL3 1.372000 (LQ3)

 12) RLQ2 DL4 1.707000 (LQ4)

 13) ∞ 1.000 1.516800

 14) οο 15.000

 15> ∞ (EP)

 [Aspherical surface]

 Surface number: 2nd surface

 κ = 0 ... 800

 [Variable de-evening]

 L M H

RLQ1-15. 100 oo 14.000 RLQ2 25.000 46.300 -72.000

 DL1 2.500 1.500 0.400

 DL2 0.500 1.500 2.600

 DL3 0.600 0.800 1.100

 DL4 1.400 1.200 0.900

 Dl 15.000 15.000 15.000

 [Values for conditional expressions]

 (3) DL 1 L = 2. 500

 (4) DL 2 L = 0. 500

 (5) DL 1 H = 0. 400

 (6) DL 2H = 2. 600

(t an 2 x I (φ 1H— φ 1L) / (nlxn2) + (φ 2H— Φ 2L) I (n3xn4) I = 0.00078

(8) 1 n 1-n 2 1 0. 443

 (9) 1 n 3— n 4 I 0. 335

 (10) DL 3 L = 0. 600

 (11) DL 4 L = 1. 400

 (12) DL 3H = 1. 100

 (13) DL 4H = 0. 900

 6A, 6B, and 6C are graphs showing various aberrations with respect to the reference wavelength d-line (e = 58 7.6 nm) of the variable magnification afocal optical system according to the third example of the second embodiment. Low magnification end state L, Fig. 6B shows various aberration diagrams in intermediate magnification state M, and Fig. 6C shows high magnification end state H, respectively.

The unit of the spherical aberration diagram is m- 1 (diopter D), and h is the incident height. The incident height h is the height at which the land light passes through the lens surface closest to the object, and the land light is the light ray farthest from the optical axis among the light rays having a field angle of zero. Astigmatism The solid line in the figure is the sagittal image plane, the broken line is the meridional image plane (unit: m—diops) Evening D) is shown. A indicates the light incident angle (unit: degree). The vertical axis of the coma aberration diagram represents the coma aberration (unit: minutes) at each incident angle. Note that the same reference numerals are used in the various aberration diagrams of the following fourth embodiment, and description thereof is omitted.

 According to Figs. 6A, 6B, and 6C, the aberration is corrected well, and the fluctuation in aberration between the low magnification end state L and the high magnification end state t H is suppressed, and the optical performance is high. It is clear that

 [Fourth embodiment]

 FIG. 7 is a lens configuration diagram of a variable focal lens optical system according to the fourth example of the second embodiment. L is a low magnification end state, M is an intermediate magnification state, and H is a high magnification end state. It represents.

 The first lens group G 1 is disposed closer to the object side than the second lens group G 2. The first lens group G 1 serves as an objective lens group, and the second lens group G 2 serves as an eyepiece group.

 The first lens group G 1 includes a biconvex lens L 1 S having a strong refracting surface on the object side and a first variable focal length element L I V. The first variable focal length element LIV includes a first liquid material LQ 1 and a second liquid material LQ 2 that has a refractive index different from that of the first liquid material LQ 1 and is mixed in the container. By changing the voltage, which is a physical quantity applied to the 1st and 2nd liquid material LQ2, the shape of the first interface LB1 between the 1st liquid material LQ1 and the 2nd liquid material LQ2 was changed to make the focal length variable. It is an element and can change the refractive power of the entire first lens group G1.

The first variable focal length element L 1 V includes, in order from the object side, a parallel plate glass L 1 1 (first optical window) that is a part of the container, and a lens portion L 1 2 made of the first liquid material LQ 1 The second liquid material LQ 2 is composed of a lens portion L 1 3 and a parallel plate glass L 14 (second optical window) which is a part of the container. The first liquid material is a mixture of a sodium chloride aqueous solution, which is a conductive liquid material, and ethylene glycol, which is an antifreeze liquid, and the second liquid material is silicon oil, which is an insulating liquid material, and has the same density. Yes. The second lens group G2 is composed of a second variable focal length element L2V. The second variable focal length element L 2 V contains the third liquid material LQ 3 and the fourth liquid material LQ 4 which has a refractive index different from that of the third liquid material LQ 3 and is mixed in the container. By changing the voltage, which is a physical quantity applied to the material LQ 3 and the fourth liquid material LQ 4, the shape of the second interface LB 2 between the third liquid material LQ 3 and the fourth liquid material LQ 4 is changed. This element has a variable focal length and can change the refractive power of the entire second lens group G2.

 The second variable focal length element L 2 V is composed of, in order from the object side, a plano-concave lens L 2 1 (third optical window) that is a part of the container and has a concave surface facing the object side, and a third liquid material LQ 3 It consists of a lens part L 2 2 consisting of a lens part L 2 3 consisting of a fourth liquid material LQ 4, and a parallel flat glass L 2 4 (fourth optical window) that is part of the container. The surface in contact with the air is curved. The third liquid material is a mixture of a sodium chloride aqueous solution, which is a conductive liquid material, and ethylene glycol, which is an antifreeze liquid. The fourth liquid material is silicon oil, which is an insulating liquid material, and is composed of the same density. . The first liquid material L Q 1 and the third liquid material L Q 3 have different sodium chloride concentrations. The second liquid material L Q 2 and the fourth liquid material L Q 4 are silicon oils but have different substances.

 When zooming from the low magnification end state L to the high magnification end state H, the refractive power of the first variable focal length element LIV in the first lens group G 1 is changed from negative to positive, and the second lens. The refractive power of the second variable focal length element L 2 V in group G 2 is changed in the direction from positive to negative. That is, the refractive power of the first variable focal length element LIV in the first lens group G1 and the refractive power of the second variable focal length element L2V in the second lens group G2 are opposite to each other. By changing to, the diopter change is suppressed and high optical performance is secured. Also, during zooming, the air gap between the first lens group G1 and the second lens group G2 is fixed, and a zooming focal optical system is realized with a simple configuration.

Table 4 below shows the variable power focal optical system according to the fourth example of the second embodiment. List the values of the specifications.

 As can be seen from Table 4, from the low magnification end state L to the high magnification end state H, the distance from the surface where the first liquid material and the first optical window are in contact to the first interface, the second liquid material and the second The sum of the distance from the surface where the optical window contacts to the first boundary is unchanged. Further, from the low magnification end state to the high magnification end state H, the distance from the surface where the third liquid material and the third optical window are in contact to the second boundary surface, and the fourth liquid material and the fourth optical window are in contact. The sum of the distance from the surface to the second boundary is unchanged.

 (Table 4)

 [Overall specifications]

 L M H

m 0. 94 1. 46 1. 96

ω 1 2. 1 7. 5 5. 5

 θ 1 1. 0 11. 0 1 1. 0

 [Lens de overnight]

Surface number Curvature radius Surface spacing n d

 1) 185.000 4.500 1, .516800

 2) -500.000 2.000

 3) οο 1.000 1 .516800

 4) οο DL1 1 .386000 (LQ1)

 5) RLQ1 DL2 1.794000 (LQ2)

 6) οο 1.000 1 .516800

 7) οο D1

 8) -63.000 1.500 1 .516800

 9) οο DL3 1.405000 (LQ3)

 10) RLQ2 DL4 1.670000 (LQ4)

11) οο 1.000 1 .516800 12) CO 15.000

 13> co (EP)

 [Variable data]

 L M H LQ1 -75.000 222.000 80.500

 RLQ2 28.000 CO -30.000

 DL1 3.000 1.800 1.000

 DL2 1.000 2.200 3.000

 DL3 0.800 1.000

 DL4 1.200 1.000 0.800

 Dl 50.000 50.000 50.000

 [Values for conditional expressions]

 (3) DL 1 L = 3 000

 (4) DL 2 L = 000

 (5) DL 1H-000

 (6) DL 2H = 3 000

(7) (t an 2 x I (φ 1H- φ 1L) / (nlxn2) Ι (2Η-2L) I (n3xn4) 1 = 0.00014 (8) n 1 ― n 2 1 0. 408

 (9) n 3 1 n 4 1 = 0.265

 (1 0) DL 3 L = 0 800

 (1 1) DL 4 L 1 200

 (1 2) DL 3H 1 200

 (1 3) DL 4H — 0 800

8A, 8B, and 8C are graphs showing various aberrations with respect to the reference wavelength d-line (E = 587.6 nm) of the variable magnification afocal optical system according to the fourth example of the second embodiment, and FIG. Magnification end state L, Fig. 8 B is intermediate magnification state M, Fig. 8 C is high magnification end state H 3114

 45

Each aberration diagram is shown.

 According to Figs. 8A, 8B, and 8C, aberrations are corrected well, aberration fluctuations between the low magnification end state and the high magnification end state H are suppressed, and high optical performance is achieved. Is clear.

 As described above, according to the second embodiment, the variable focal length element is used, the light beam emitted from the optical system is almost afocal, the aberration is corrected well, and the camera finder is a camera converter. A variable power afocal optical system that can be used for lenses, telescopes, etc. and has high optical performance can be provided.

 In the variable power afocal optical system of each example, the air gap D 1 between the first lens group G 1 and the second lens group G 2 is slightly changed, or the first lens group G 1 or the second lens By changing the refractive index of the group G 2 slightly, it is also possible to perform so-called diopter adjustment that slightly shifts the emitted light from the optical system from the focal point.

 In each example, a two-group lens system is shown. However, it goes without saying that a three-group including the two groups and an optical system having a group structure of two or more groups are also effective lens systems. Absent. In addition, in the configuration within each lens group, it goes without saying that a lens group obtained by adding a lens to the configuration of the embodiment is a lens group having the same effect.

 Further, the above-described embodiments and examples are merely examples, and are not limited to the above-described configuration, shape, and liquid material, and are within the scope of the present invention, such as enlargement, reduction, and movement of a zoom range. Can be modified or changed as appropriate.

Claims

46 Scope of request
1. By having a first lens group having a variable focal length element and a second lens group, changing the focal length of the first lens group by changing the magnification from the low magnification end state to the high magnification end state Done
 The focal length of the first lens group and the focal length of the second lens group are such that one focal length is positive and the other focal length is negative.
 The variable focal length element encloses in a container a first liquid material and a second liquid material that has a refractive index different from that of the first liquid material and is not mixed, to the first liquid material and the second liquid material. By changing the physical quantity to be applied, the focal length is changed by changing the interface shape between the first liquid material and the second liquid material,
A refractive index at a reference wavelength of the first liquid material is n 1, a refractive index at the reference wavelength of the second liquid material is n 2, and an optical axis of an optical system having the first lens group and the second lens group; The tangent of the angle formed by the outgoing light beam corresponding to the maximum field angle of the optical system is tan S, the refractive power of the variable focal length element in the low magnification end state of the optical system is Φ L, and the high magnification end of the optical system A variable power focal optical system characterized by satisfying the following condition when the refractive power of the variable focal length element in a state is Φ Η. 0. 0 0 5 <I Φ Η-Φ LIX tan 2 (/ (n 1 X n 2) 2 0
 (Unit: l Zm)
2. The variable magnification focal optical system according to claim 1, wherein the physical quantity is a voltage.
3. The magnification of the entire optical system is changed by changing an interval between the first lens group and the second lens group in accordance with a change in focal length of the first lens group. 1. A variable magnification focal optical system according to 1.
4. Along the optical axis, the first lens group is closer to the object side than the second lens group, and only the first lens group follows the optical axis as the focal length of the first lens group changes. 2. The variable magnification focal optical system according to claim 1, wherein the magnification of the entire optical system is changed by moving the optical system.
5. Along the optical axis, the second lens group is closer to the object side than the first lens group, and only the second lens group follows the optical axis as the focal length of the first lens group changes. 2. The variable magnification afocal optical system according to claim 1, wherein the magnification of the entire optical system is changed by moving the optical system.
6. The variable magnification afocal optical system according to claim 1, wherein the second lens group includes only one or more fixed focal length elements.
7. The variable power optical system according to claim 1, wherein a surface of the variable focal length element that comes into contact with air is a curved surface.
8. The variable power afocal optical system according to claim 1, wherein the first lens group includes one or more fixed focal length elements.
9. The following condition is satisfied, where n 1 is a refractive index of the first liquid material at a reference wavelength and n 2 is a refractive index of the second liquid material at the reference wavelength. Variable magnification focal optical system.
 0. 0 3 0 <I n 1-n 2 I <0. 6 0 0
1 0. The first liquid material and the second liquid material have substantially the same density. The variable power afocal optical system according to claim 1.
1. The variable power afocal optical system according to claim 1, wherein at least one of the first liquid material and the second liquid material includes an antifreeze material component.
12. The variable focal length element has a first optical window in contact with the first liquid material, and a second optical window in contact with the second liquid material,
 In the low magnification end state, the distance on the optical axis from the surface where the first liquid material and the first optical window are in contact to the boundary surface is DL 1 L, and the second liquid material and the second optical window are in contact with each other. DL 2 L, the distance on the optical axis from the surface to the boundary surface
 In the high magnification end state, the distance on the optical axis from the surface where the first liquid material and the first optical window are in contact to the boundary surface is DL 1H, and the surface where the second liquid material and the second optical window are in contact 2. The variable power afocal optical system according to claim 1, wherein the following conditional expression is satisfied, where DL 2 H is a distance on the optical axis from the surface to the boundary surface.
 DL 1 L> 0. 005 (Unit: mm)
 DL 2L> 0. 005 (Unit: mm)
 DL 1H> 0.005 (Unit: mm)
 DL 2H> 0.005 (Unit: mm)
13. The variable focal length element has a first optical window in contact with the first liquid material, and a second optical window in contact with the second liquid material,
In the low magnification end state to the high magnification end state, the distance from the surface where the first liquid material and the first optical window are in contact to the boundary surface, and the surface where the second liquid material and the second optical window are in contact with each other 2. The variable magnification focal optical system according to claim 1, wherein a sum of distances to the boundary surface is invariant.
1 4. Consists of a first lens group having a first variable focal length element and a second lens group having a second variable focal length element,
 The zooming from the low magnification end state to the high magnification end state is performed by changing at least one of the refractive power of the first lens group and the refractive power of the second lens group,
 In the low magnification end state or the high magnification end state, the refractive power of the first lens group and the refractive power of the second lens group are such that one refractive power is positive and the other refractive power is negative. 1 The variable focal length element encloses a first liquid material and a second liquid material that has a refractive index different from that of the first liquid material and does not mix in a container, and supplies the first liquid material and the second liquid material. By changing the physical quantity to be applied, the refractive power is changed by changing the first interface shape between the first liquid material and the second liquid material,
 The second variable focal length element encloses a third liquid material and a fourth liquid material that has a refractive index different from that of the third liquid material and does not mix in a container, and the third liquid material and the fourth liquid By changing the physical quantity applied to the material, the refractive power is changed by changing the second interface shape of the third liquid material and the fourth liquid material,
Wherein n 1 the refractive index at the reference wavelength of the first liquid material, the refractive index in the reference wavelength of the second liquid material n 2, the refractive index in the reference wavelength of the third liquid material n 3, the fourth The refractive index of the liquid material at the reference wavelength is n 4, and the optical axis of the optical system composed of the first lens group and the second lens group is defined as the emission light beam corresponding to the maximum field angle of the optical system. The tangent of the angle is tan θ, the refractive power of the first variable focal length element in the low magnification end state of the optical system is Φ 1 L, and the refraction of the second variable focal length element in the low magnification end state of the optical system is Φ 2 L, the refractive power of the first variable focal length element in the high magnification end state of the optical system is Φ 1 H, and the refractive power of the second variable focal length element in the high magnification end state of the optical system is When Φ 2 H, the variable is characterized by satisfying the following conditional expression: Double-focal optical system.
0. 00005 <(tan 2 θ) χ | (1H-1L) bar nlxn2) + (φ 2Η- φ 2L) / (n3 X η4) I 10 (unit: l Zm)
15. The zooming from the low magnification end state to the high magnification end state is performed by changing the refractive power of the first lens group and the refractive power of the second lens group. Variable magnification optical system.
16. When zooming from the low magnification end state to the high magnification end state, the direction of change in the refractive power of the first lens group and the direction of change in the refractive power of the second lens group should be opposite to each other. 16. The variable magnification afocal optical system according to claim 15, wherein:
17. The zooming focal of claim 14, wherein the air space between the first lens unit and the second lens unit is fixed when zooming from the low magnification end state to the high magnification end state. Optical system.
18. The variable magnification focal optical system according to claim 14, wherein the following conditional expression is satisfied.
 0. 020 <I n 1 -n 2 I <0. 600
 0. 020 I n 3-n 4 I <0. 600
19. The variable power afocal optical system according to claim 14, wherein the optical system includes one or more fixed focal length elements.
20. The zooming focal plane according to claim 14, wherein at least one of the surfaces of the first variable focal length element and the second variable focal length element that are in contact with air is a curved surface. Optical system.
21. The first variable focal length element includes a first optical window in contact with the first liquid material; A second optical window in contact with the second liquid material,
 In the low magnification end state, the distance on the optical axis from the surface where the first liquid material and the first optical window are in contact to the first boundary surface is DL 1 L, and the second liquid material and the second optical window are DL 2 L, the distance on the optical axis from the surface where the
 In the high magnification end state, DL 1H is the distance on the optical axis from the surface where the first liquid material and the first optical window are in contact to the first boundary surface, and the second liquid material and the second optical window are 15. The variable magnification afocal optical system according to claim 14, wherein the following conditional expression is satisfied, where DL 2H is a distance on the optical axis from the contacting surface to the first boundary surface.
 DL 1 L> 0. 005 (Unit: mm)
 DL 2 L> 0. 005 (Unit: mm)
 DL 1 H> 0.005 (Unit: mm)
 DL 2H> 0.005 (Unit: mm)
22. The second variable focal length element has a third optical window in contact with the third liquid material, and a fourth optical window in contact with the fourth liquid material,
 In the low magnification end state, the distance on the optical axis from the surface where the third liquid material and the third optical window are in contact to the second boundary surface is DL 3 L, and the fourth liquid material and the fourth optical window are DL 4 L, the distance on the optical axis from the surface where the
 In a high magnification end state, the distance on the optical axis from the surface where the third liquid material and the third optical window are in contact to the second boundary surface is DL 3 H, and the fourth liquid material and the fourth optical window are 15. The variable magnification afocal optical system according to claim 14, wherein a distance on the optical axis from a surface in contact with the second boundary surface is defined as DL4H, and the following condition is satisfied.
 DL 3L> 0.005 (Unit: mm)
 DL4L> 0.005 (Unit: mm)
DL 3H> 0.005 (Unit: mm) 52
DL4H> 0. 005 (Unit: mm)
23. A first lens group having a variable focal length element, a second lens group, and the focal length of the first lens group and the focal length of the second lens group are positive in one focal length, On the other hand, the focal length of the zoom optical system, which has a negative focal length and satisfies the following conditions,
 The variable focal length element encloses in a container a first liquid material and a second liquid material that has a refractive index different from that of the first liquid material and is not mixed, to the first liquid material and the second liquid material. By changing the physical quantity to be applied, the focal length is changed by changing the shape of the boundary surface between the first liquid material and the second liquid material, and the focal length of the first lens group is changed. A zooming method for a zooming focal optical system, characterized in that zooming from an end state to a high magnification end state is performed.
0. 005 <Ι ΦΗ— d L | X t an 2 0Z (nl Xn 2) <20
 (Unit: 1 Zm) where
n 1: refractive index at a reference wavelength of the first liquid material
n 2: refractive index at the reference wavelength of the second liquid material
 t a n 0: Tangent of the angle formed by the optical axis of the optical system having the first lens group and the second lens group and the outgoing ray corresponding to the maximum field angle of the optical system
 ΦΙ ^: refractive power of the variable focal length element in the low magnification end state of the optical system ΦΗ refractive power of the variable focal length element in the high magnification end state of the optical system
24. A first lens group having a first variable focal length element and a second lens group having a second variable focal length element,
In the low magnification end state or the high magnification end state, the refractive power of the first lens group and the refractive power of the second lens group are positive in one power and negative in the other power. In the zooming method of the zooming / focal optical system that satisfies the following conditions,
 The first variable focal length element encloses a first liquid material and a second liquid material that has a refractive index different from that of the first liquid material and does not mix in a container, and the first liquid material and the second liquid By changing the physical quantity applied to the material, the refractive power is changed by changing the first interface shape between the first liquid material and the second liquid material,
 The second variable focal length element encloses a third liquid material and a fourth liquid material that has a refractive index different from that of the third liquid material and does not mix in a container, and the third liquid material and the fourth liquid By changing the physical quantity applied to the material, the refractive power is changed by changing the second interface shape of the third liquid material and the fourth liquid material,
 Magnifying power optical system characterized in that at least one of the refractive power of the first lens group and the refractive power of the second lens group is changed to perform zooming from a low magnification end state to a high magnification end state. System scaling method.
0. 00005 <(tan 2 9) X | (φ 1H— φ 1L) Z (nl X η2) + (φ 2Η- (!) 2L) / (η3 X η4) I
10 (Unit: 1 / m) where
n 1: refractive index at a reference wavelength of the first liquid material
n 2: refractive index at the reference wavelength of the second liquid material
n 3: refractive index at the reference wavelength of the third liquid material
n 4: refractive index of the fourth liquid material at the reference wavelength
 t a n Θ: Tangent of the angle formed by the optical axis of the optical system composed of the first lens group and the second lens group and the outgoing ray corresponding to the maximum field angle of the optical system
 1 L: refractive power of the first variable focal length element in the low magnification end state of the optical system
 2 L: Refracting power of the second variable focal length element in the low magnification end state of the optical system
Φ 1 H: Refraction of the first variable focal length element in the high magnification end state of the optical system Refraction of the second variable focal length element in the high magnification end state of the optical system
PCT/JP2008/053114 2007-02-21 2008-02-18 Variable magnification afocal optical system WO2008102894A1 (en)

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JP2007041141A JP2008203650A (en) 2007-02-21 2007-02-21 Variable power afocal optical system
JP2007-041141 2007-02-21
JP2007041132A JP2008203648A (en) 2007-02-21 2007-02-21 Variable power afocal optical system
JP2007-041132 2007-02-21

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US8520313B2 (en) 2009-10-19 2013-08-27 Canon Kabushiki Kaisha Zoom lens and image pickup device including the same
WO2013157606A1 (en) * 2012-04-20 2013-10-24 浜松ホトニクス株式会社 Beam expander

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WO2013157606A1 (en) * 2012-04-20 2013-10-24 浜松ホトニクス株式会社 Beam expander
JPWO2013157606A1 (en) * 2012-04-20 2015-12-21 浜松ホトニクス株式会社 Beam expander
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