JP5558255B2 - Optical device - Google Patents

Description

  The present invention relates to an optical device.

  In recent years, a molded lens having a highly accurate surface shape is produced by softening a preform lens (original) at a high temperature and press-molding it with a mold. For example, molten glass or plastic resin is poured into a mold having an aspherical shape, and then cooled and hardened to produce a lens.

In particular, resin-based plastic molded lenses are popular because they are inexpensive. Here, the plastic mold lens has a large temperature characteristic.
For this reason, the focal position of the plastic mold lens also changes due to a change in the environmental temperature.
In addition, the air spacing of the optical system may change from a predetermined design value due to a change in environmental temperature.
In either case, the optical characteristics change, so some correction is required.

As an apparatus for correcting such a change in optical characteristics or an apparatus for driving a lens, apparatuses disclosed in the following Patent Documents 1, 2, 3, and 4 are known.
Patent Document 1 discloses a projection display device that can change the aspect ratio and trapezoidal distortion of a projected image.
Patent Document 2 discloses a compact imaging device having a focusing mechanism. Patent Document 3 discloses a spacer for adjusting the distance between lenses with high accuracy.
Patent Document 4 discloses a photographing apparatus that adjusts a lens using a polymer actuator.

Japanese Patent Laid-Open No. 11-211979 JP 2007-86158 A JP 07-119366 A JP 2009-94237 A

  However, none of Patent Documents 1, 2, 3, and 4 proposes a configuration for reducing deterioration of optical characteristics due to the influence of environmental temperature. For this reason, when the environmental temperature changes, there is a problem that the optical characteristics deteriorate (for example, the imaging position and the image plane shift).

  The present invention has been made in view of the above, and an object of the present invention is to provide an optical device that can always obtain stable optical characteristics even when the environmental temperature changes.

In order to solve the above-described problems and achieve the object, the optical device of the present invention includes:
An imaging optical system having a plurality of lens groups and forming an image of an object;
A holding frame for movably holding the lens of the imaging optical system;
A temperature correction interval adjusting unit whose length changes in a direction along the optical axis direction;
One end of the temperature correction interval adjusting unit contacts the holding frame, the other end in the direction in which the length changes, contacts other than the effective area of the movable lens,
Further, an elastic member that is disposed on the opposite side of the temperature correction interval adjustment unit with respect to the movable lens and that applies an external force to the movable lens in a direction in which the length of the temperature correction interval adjustment unit changes;
A temperature detector for detecting the temperature of the imaging optical system;
A table storing the correspondence between the amount of change in the image plane of the imaging optical system due to a change in temperature and the temperature;
A control unit that controls the length of the temperature adjustment interval adjustment unit to be a target value based on the temperature from the temperature detection unit and the correspondence relationship stored in the table;
It is characterized by having.

  Moreover, according to a preferable aspect of the present invention, it is desirable to further include an imaging element having an imaging surface for converting an image formed by the imaging optical system into an electrical signal.

  According to a preferred aspect of the present invention, it is desirable that the plurality of lens groups are zoom lenses in which the distance between the lens groups changes during zooming from the wide-angle end to the telephoto end.

  According to a preferred aspect of the present invention, it is desirable that the imaging optical system has a lens made of resin and having an aspherical surface.

  According to a preferred aspect of the present invention, it is desirable that the temperature detection unit is disposed in the vicinity of a lens made of resin.

  According to a preferred aspect of the present invention, the control unit sets the length of the temperature correction interval adjusting unit so as to cancel out the amount of movement in the optical axis direction of the image plane of the imaging optical system due to a change in environmental temperature. It is desirable to control and move the movable lens.

  The movable lens is desirably at least one of a lens and a lens group.

  According to a preferred aspect of the present invention, it is desirable that the temperature correction interval adjusting unit is provided in a plurality of lens groups.

Furthermore, it is desirable that the following conditional expressions (1), (2), (3), and (4) are satisfied.
0.50 <| fm / fw | <10.00 (1)
0.01 <| fm / ft | <3.00 (2)
0.50 <| fc / fw | <10.00 (3)
0.01 <| fc / ft | <3.00 (4)
here,
fw is the focal length at the wide-angle end of the entire zoom lens system,
ft is the focal length at the telephoto end of the entire zoom lens system,
fm is a focal length of a lens made of resin and having an aspheric surface,
fc is the focal length of the movable lens or lens group,
It is.

According to a preferred aspect of the present invention, the imaging optical system includes at least the order from the object side,
A first lens unit having positive refractive power;
A second lens unit having negative refractive power;
A third lens unit having positive refractive power;
A fourth lens unit having positive refractive power;
It is desirable to have

  According to a preferred aspect of the present invention, it is desirable that the first lens group has a reflecting member having a reflecting surface that bends the optical path.

According to a preferred aspect of the present invention, the imaging optical system includes at least the order from the object side,
A first lens unit having negative refractive power;
A second lens group having positive refractive power;
A third lens unit having positive refractive power;
A fourth lens unit having positive refractive power;
It is desirable to have

According to a preferred aspect of the present invention, the temperature correction interval adjusting portion is formed of a shape memory alloy,
The control unit desirably controls the length of the temperature correction interval adjusting unit by controlling the current applied to the shape memory alloy.

  According to the present invention, there is an effect that it is possible to provide an optical device that can always obtain stable optical characteristics even when the environmental temperature changes.

It is a front perspective view which shows the external appearance of a digital camera. 1 is a rear front view showing the appearance of a digital camera. It is typical sectional drawing which shows the structure of a digital camera. (A) is an external view which shows the other attachment position of temperature sensor TS. (B) is an external view showing still another attachment position of the temperature sensor TS. (C) is a diagram showing a cross-sectional configuration example of the imaging optical system. It is a figure which shows the cross-sectional structure of the junction lens vicinity of the lens L4 and the lens L5. It is a figure which shows the functional block regarding the drive of a lens. It is a flowchart which shows a procedure when a functional block is used. It is a flowchart which shows the content of the space | interval adjustment subroutine. FIG. 3 is a lens cross-sectional view of the zoom lens of Example 1 at a wide-angle end (a), an intermediate focal length state (b), and a telephoto end (c) when focusing on an object point at infinity. FIG. 6 is a lens cross-sectional view of the zoom lens of Example 2 at a wide angle end (a), an intermediate focal length state (b), and a telephoto end (c) when focusing on an object point at infinity. FIG. 6 is a lens cross-sectional view of the zoom lens of Example 3 at a wide-angle end (a), an intermediate focal length state (b), and a telephoto end (c) when focusing on an object point at infinity. FIG. 6 is a lens cross-sectional view of the zoom lens of Example 4 at a wide-angle end (a), an intermediate focal length state (b), and a telephoto end (c) when focusing on an object point at infinity. FIG. 10 is a lens cross-sectional view of the zoom lens of Example 5 at a wide-angle end (a), an intermediate focal length state (b), and a telephoto end (c) when focusing on an object point at infinity. The figure which shows the relationship between the variation | change_quantity of the image plane position with respect to the change of environmental temperature in the telephoto end state of the zoom lens which concerns on Numerical Example 1, and the variation | change_quantity of the image plane position with respect to the temperature change of an adjustment member (shape memory alloy). It is. The figure which shows the relationship between the variation | change_quantity of the image plane position with respect to the change of environmental temperature in the telephoto end state of the zoom lens which concerns on Numerical Example 2, and the variation | change_quantity of the image plane position with respect to the temperature change of an adjustment member (shape memory alloy). It is. The figure which shows the relationship between the variation | change_quantity of the image surface position with respect to the change of environmental temperature in the telephoto end state of the zoom lens which concerns on Numerical Example 3, and the variation | change_quantity of the image plane position with respect to the temperature change of an adjustment member (shape memory alloy). It is. The figure which shows the relationship between the variation | change_quantity of the image plane position with respect to the change of environmental temperature in the telephoto end state of the zoom lens which concerns on Numerical Example 4, and the variation | change_quantity of the image plane position with respect to the temperature change of an adjustment member (shape memory alloy). It is. The figure which shows the relationship between the variation | change_quantity of the image plane position with respect to the change of environmental temperature in the telephoto end state of the zoom lens which concerns on numerical Example 5, and the variation | change_quantity of the image plane position with respect to the temperature change of an adjustment member (shape memory alloy). It is.

  Embodiments of an optical device according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Digital camera)
1 to 3 are conceptual diagrams of a configuration of a digital camera 100 in which a later-described zoom lens is incorporated in a photographing optical system 101. FIG. FIG. 1 is a front perspective view showing the appearance of the digital camera 100, and FIG. 2 is a rear front view of the same. FIG. 3 is a schematic cross-sectional view showing the configuration of the digital camera 100. However, in FIGS. 1 and 3, the photographing optical system 101 is not retracted.

  In this example, the digital camera 100 includes a photographing optical system 101 having a photographing optical path 102, a finder optical system 103 having a finder optical path 104, a shutter button 105, a flash 106, a liquid crystal display monitor 109, a focal length change button 108, When the photographing optical system 101 is retracted, including the setting change switch 118 and the like, the photographing optical system 101, the finder optical system 103, and the flash 106 are covered with the cover 107 by sliding the cover 107. Then, when the cover 107 is opened and the camera 100 is set to the photographing state, the photographing optical system 101 enters the non-collapsed state of FIG. When the shutter button 105 disposed on the upper part of the camera 100 is pressed, photographing is performed through the photographing optical system 101, for example, a zoom lens of Example 1 described later in conjunction therewith. An object image formed by the photographic optical system 101 is formed on the imaging surface of the CCD 110 through a low-pass filter F and a cover glass C that are provided with a wavelength band limiting coat. The object image received by the CCD 110 is displayed as an electronic image on the liquid crystal display monitor 109 provided on the back of the camera via the processing means 112. Further, a storage means 113 is connected to the processing means 112, and a photographed electronic image can be recorded. The storage means 113 may be provided separately from the processing means 112, or may be configured to perform recording / writing electronically using a flexible disk, a memory card, an MO, or the like. Further, instead of the CCD 110, it may be configured as a silver salt camera in which a silver salt film is arranged.

  Further, a finder objective optical system 114 is disposed on the finder optical path 104. The finder objective optical system 114, a plurality of lens groups (four groups in the figure) and two prisms, and a zoom optical system in which the focal length changes in conjunction with the zoom lens of the photographing optical system 101, this finder The object image formed by the objective optical system 114 is formed on the field frame 116 of the erecting prism 115 which is an image erecting member. Behind the erecting prism 115 is an eyepiece optical system 117 that guides the erect image to the observer eyeball E. A cover member 111 is disposed on the exit side of the eyepiece optical system 117.

  The digital camera 100 configured as described above has the zoom lens of the present invention as the photographing optical system 101. For this reason, stable optical characteristics can always be obtained even when the ambient temperature changes.

  The temperature sensor TS is provided in the vicinity of the plastic mold lens. Furthermore, the temperature correction interval adjusting unit 120 is provided to drive an adjusting lens described later.

(Explanation of temperature sensor)
Next, the position where the temperature sensor TS is provided will be described.
As shown in the external configuration diagram of the digital camera 100 in FIG. 1, the temperature sensor TS is preferably installed as close to the lens of the photographing optical system 101 as possible in order to minimize the error from the temperature in the lens frame LB. Thereby, compared with installing the temperature sensor TS in the lens frame exterior / mirror frame, the layout is easy to perform.

  Further, if the temperature sensor TS is installed on the grip side of the body of the digital camera 100, there is a possibility that accurate temperature measurement cannot be performed due to the influence of body temperature. For this reason, it is preferable to install temperature sensor TS on the opposite side to a grip.

  FIG. 4A is an external view showing another mounting position of the temperature sensor TS. A temperature sensor TS is provided outside the lens barrel LB of the digital camera 100. Thereby, compared with installing temperature sensor TS in the lens frame LB, layout is easy to perform. Further, the temperature error can be reduced by bringing the temperature sensor TS closer to the lens to be measured for temperature. Which lens or lens group among the plurality of lenses or lens groups constituting the optical system is to be subjected to temperature measurement will be described later using a specific example of the imaging optical system.

Furthermore, by arranging the temperature sensor TS below the lens frame LB, a temperature error due to direct sunlight can be reduced.
The lens frame LB is desirably a straight-ahead system during zooming.

FIG. 4B is an external view showing still another attachment position of the temperature sensor TS. A temperature sensor TS is provided inside the lens barrel LB of the digital camera 100.
Thereby, compared with installing the temperature sensor TS in the lens frame LB, layout is easy to perform.
Further, the temperature sensor TS is not installed in the drive part of the lens frame LB. For this reason, compared with the installation location shown in FIG.

FIG. 4C shows a cross-sectional configuration example of the imaging optical system. Here, the lens L3 is a plastic mold lens. Further, the cemented lens of the lenses L4 and L5 is held so as to be movable in the optical axis direction.
A temperature sensor TS is installed in the lens frame LB. Thereby, an error with the temperature in the lens frame LB can be reduced.
In order to detect a temperature change of the movable lens group, it is desirable to place the temperature sensor TS at an intermediate point of the lens movable range.

Next, a mechanism for holding the lens movably will be described.
FIG. 5 is a diagram showing a cross-sectional configuration in the vicinity of the cemented lens of the lens L4 and the lens L5. The lens L3 is a plastic mold lens.
The holding frame 124 holds the lenses L4 and L5 of the imaging optical system so as to be movable. The length of the temperature correction interval adjusting unit 120 changes in a direction along the direction of the optical axis 102 (see FIG. 1).

  One end of the temperature correction interval adjusting unit 120 is in contact with the holding frame 124. The other end in the direction in which the length changes is in contact with an area other than the effective area of the movable lens L4. Further, the movable lenses L4 and L5 are arranged on the side opposite to the temperature correction interval adjusting unit 120, and an external force is applied to the movable lens in the direction in which the length of the temperature correction interval adjusting unit 120 changes. An elastic member 121 is provided.

  One end of the elastic member 121 is in contact with the holding frame 123. The other end of the elastic member 121 is in contact with a region other than the effective area of the movable lens L4.

The lens L3 is a plastic mold lens that is highly sensitive to temperature changes. Then, a temperature sensor TS is installed near the lens L3. Thereby, the error between the temperature of the lens L3 itself and the environmental temperature around the lens L3 can be reduced.
Further, the temperature correction interval adjusting unit 120 is specifically made of a shape memory alloy material. The elastic member 121 can be a ring or a compression coil spring.

FIG. 6 shows functional blocks related to driving of the lens of this embodiment. For example, the user inputs the following information from the adjustment mode selection unit 201. The adjustment mode selection unit 201 can use a jog dial or the like.
The adjustment mode selection unit 201 selects, for example, “correction mode”.

Information on the adjustment mode is sent to the CPU 204. A temperature sensor 202 and a RAM 203 are connected to the CPU 204.
The RAM 203 corresponds to the table TB. The table TB stores the correspondence between the amount of change in the image plane of the imaging optical system due to the change in temperature and the temperature.
Further, the CPU 204 corresponding to the control unit sets the length of the temperature correction interval adjusting unit 120 to the target value based on the temperature from the temperature sensor TS as the temperature detecting unit and the correspondence stored in the table TB. The applied current to the shape memory alloy is controlled so that
A specific example of the “correspondence” stored in the table TB will be described later.

  Further, the CPU 204 calculates a driving amount of the lens, for example, a zoom driving amount, a focusing driving amount, and an adjustment amount of the movable lens.

  Control signals from the CPU 204 are output to the drivers 206a, 206b, and 206c via the analog switches 205a, 205b, and 205c, respectively.

  The driver 206a drives the zoom motor 207. The driver 206b drives the focus motor 208. The driver 206c applies current to the shape memory alloy member 209 constituting the temperature correction interval adjusting unit and drives it.

FIG. 7 is a flowchart showing a procedure when the above-described functional blocks are used.
In step S301, the user turns on the camera and then selects a shooting mode. Next, the adjustment mode is selected using the adjustment mode selection unit 201.

In step S302, first, the zoom lens is driven to a desired focal length state.
In step S303, the CPU 204 determines whether or not the zoom lens is in the telephoto end state.

  When the determination result in step S303 is true (Yes), an interval adjustment subroutine described later is executed in step S304. As a result, the movable lens or lens group is moved (referred to as “lens adjustment” as appropriate).

  When the determination result in step S303 is false (No), the process returns to step S302, and the driving of the zoom lens is repeated. This flowchart shows a procedure for performing lens adjustment when the zoom lens is in the telephoto end state. However, the present invention is not limited to this, and lens adjustment may be performed when the zoom lens is in the wide-angle end state or the intermediate focal length state. In this case, in the determination in step S303, it may be determined whether the state is the wide-angle end state or the intermediate focal length state.

  In step S305, lens driving for focusing is performed. In step S306, the process waits until the user takes a picture. In step S307, shooting is performed under shooting conditions desired by the user.

  FIG. 8 is a flowchart showing the contents of the interval adjustment subroutine. In step S401, the CPU 204 measures the temperature in the vicinity of the adjustment lens using the temperature sensor TS.

  In step S402, the CPU 204 calculates a difference, that is, a difference between the measured temperature and a predetermined design temperature. Here, the “design temperature” refers to a temperature at which the optical system is in a state of exhibiting optical characteristics as designed. If the ambient temperature is equal to the design temperature, no lens adjustment is necessary.

  In step S403, the CPU 204 calculates control amounts of the drivers 206a, 206b, and 206c so as to obtain a desired lens adjustment value.

  In step S404, the drivers 206a, 206b, and 206c are driven to perform lens adjustment and the like.

  Further, when the temperature range that can be adjusted by the lens is exceeded, an alarm may be displayed to the user.

  Next, a specific example of the imaging optical system included in the optical device according to the present invention will be described.

  In the following imaging optical system, the plurality of lens groups are zoom lenses in which the distance between the lens groups changes during zooming from the wide-angle end to the telephoto end. Thereby, the user can select a desired photographing magnification.

  The imaging optical system includes a lens made of resin (plastic) and having an aspheric surface. Thereby, an inexpensive and highly accurate aspherical lens can be obtained. As a result, various aberrations can be corrected satisfactorily.

  Furthermore, the temperature sensor TS is disposed in the vicinity of a lens made of resin.

  The CPU, which is a control unit, controls the length of the temperature correction interval adjusting unit 120 so as to cancel out the amount of movement in the optical axis direction of the image plane of the imaging optical system due to a change in environmental temperature. Move the lens. As a result, as will be described in detail later in the numerical examples, the amount of change in image plane movement can be offset. For this reason, stable optical characteristics can be obtained.

  Here, when heating the shape memory alloy which is the temperature correction adjusting unit 120, it is desirable that only the shape memory alloy is efficiently heated and the plastic mold lens is insulated. Thereby, it can reduce that a mold lens deform | transforms by heating a shape memory alloy.

  The movable lens is at least one of a lens and a lens group.

  The temperature correction interval adjusting unit 120 may be provided in a plurality of lens groups. Thereby, it is possible to adjust a lens group effective for adjusting the image plane position.

Furthermore, it is desirable that the following embodiments satisfy the following conditional expressions (1), (2), (3), and (4).
0.50 <| fm / fw | <10.00 (1)
0.01 <| fm / ft | <3.00 (2)
0.50 <| fc / fw | <10.00 (3)
0.01 <| fc / ft | <3.00 (4)
here,
fw is the focal length at the wide-angle end of the entire zoom lens system,
ft is the focal length at the telephoto end of the entire zoom lens system,
fm is a focal length of a lens made of resin and having an aspheric surface,
fc is the focal length of the movable lens or lens group,
It is.

  Conditional expression (1) defines an appropriate range of the ratio between the focal length of the mold lens and the focal length at the wide-angle end of the zoom lens.

  Conditional expression (2) defines an appropriate range of the ratio of the focal length of the mold lens to the focal length of the telephoto end of the zoom lens.

  Conditional expression (3) defines an appropriate range of the ratio between the focal length of the adjustment lens and the focal length at the wide-angle end of the zoom lens.

Conditional expression (4) defines an appropriate range of the ratio of the focal length of the adjustment lens to the focal length of the telephoto end of the zoom lens.
When conditional expressions (1), (2), (3), and (4) are combined, if the lens power is too low, the sensitivity is too high if the lens power is too strong, and fine adjustment of image plane matching becomes difficult.
When the upper limit is exceeded, if the lens power is too weak, the sensitivity is too low, and the image plane cannot be adjusted by changing the adjustment member.

Examples 1 to 5 of the zoom lens according to the present invention will be described below. FIGS. 9 to 13 are lens cross-sectional views of the wide-angle end (a), the intermediate focal length state (b), and the telephoto end (c) when focusing on an object point at infinity in Examples 1 to 5, respectively. 9 to 13, the first lens group is G1, the second lens group is G2, the brightness (aperture) stop is S, the third lens group is G3, the fourth lens group is G4, and infrared light is limited. The parallel flat plate constituting the low-pass filter to which the wavelength band limiting coat is applied is indicated by F, the parallel flat plate of the cover glass of the electronic image sensor is indicated by C, and the image plane is indicated by I. In addition, you may give the multilayer film for a wavelength range restriction | limiting to the surface of the cover glass C. FIG. Further, the cover glass C may have a low-pass filter action.
In each embodiment, the adjustment lens moves in the direction of the arrow described in each figure (a).

  In each embodiment, the aperture stop S moves integrally with the third lens group G3. All of the numerical data is data in a state where an object at infinity is focused. The unit of length of each numerical value is mm, and the unit of angle is ° (degree). In any of the embodiments, focusing is performed by moving the lens group closest to the image side.

Example 1
As shown in FIG. 9, the zoom lens of Example 1 includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, an aperture stop S, A third lens group G3 having a positive refractive power and a fourth lens group G4 having a positive refractive power are disposed.

  During zooming from the wide-angle end to the telephoto end, the first lens group G1 moves to the object side, the second lens group G2 moves to the object side, the third lens group G3 moves to the object side, and the fourth lens Group G4 moves to the image side.

In order from the object side, the first lens group G1 includes a cemented lens formed by a negative meniscus lens L1 having a convex surface directed toward the object side and a biconvex positive lens L2.
The second lens group G2 includes a biconcave negative lens L3 and a cemented lens of a biconcave negative lens L4 and a biconvex positive lens L5.
The third lens group G3 includes a biconvex positive lens L6 and a negative meniscus lens L7 having a convex surface directed toward the object side.
The fourth lens group G4 is composed of a biconvex positive lens L8.

  The aspheric surface is used for six surfaces including the image side surface of the biconvex positive lens L2, both surfaces of the biconcave negative lens L3, both surfaces of the biconvex positive lens L6, and the object side surface of the biconvex positive lens L8. ing.

  In Example 1, the biconcave negative lens L3 is a plastic mold lens. The cemented lens of the biconcave negative lens L4 and the biconvex positive lens L5 is an adjustment lens.

(Example 2)
As shown in FIG. 10, the zoom lens of the second embodiment has the same specification values as the zoom lens of the first embodiment, and thus a duplicate description is omitted.
In Example 2, the biconcave negative lens L3 is a plastic mold lens. The negative meniscus lens L7 is an adjustment lens.

In addition, as the adjustment lens group, both the second lens group G2 and the third lens group G3 may be moved.
For example, when the environmental temperature is high, the second lens group G2 is moved as an adjustment lens group. When the environmental temperature is low, the third lens group G3 is moved as an adjustment lens group. Thereby, since the position of the image plane can be adjusted efficiently, power consumption can be reduced.

(Example 3)
As shown in FIG. 11, the zoom lens according to the third embodiment includes, in order from the object side, a first lens group G1 having a negative refractive power, an aperture stop S, a second lens group G2 having a positive refractive power, A third lens group G3 having a positive refractive power and a fourth lens group G4 having a positive refractive power are disposed.

  At the time of zooming from the wide-angle end to the telephoto end, the first lens group G1 moves to the image side, then reverses and moves to the object side, the second lens group G2 moves to the object side, and the third lens group G3 The fourth lens group G4 is substantially fixed.

In order from the object side, the first lens group G1 includes a biconcave negative lens L1 and a positive meniscus lens L2 having a convex surface directed toward the object side.
The second lens group G2 includes a biconvex positive lens L3 and a cemented lens of a biconvex positive L4 and a biconcave negative lens L5.
The third lens group G3 includes a positive meniscus lens L6 having a convex surface directed toward the image side.
The fourth lens group G4 includes a positive meniscus lens L7 having a convex surface directed toward the image side.

  The aspheric surfaces are the image side surface of the biconcave negative lens L1, the both surfaces of the positive meniscus lens L2, the both surfaces of the biconvex positive lens L3, the image side surface of the positive meniscus lens L6, and the object of the positive meniscus lens L7. It is used for 7 surfaces with the side surface.

  In Example 3, the biconcave negative lens L1 is a plastic mold lens. The positive meniscus lens L2 is an adjustment lens.

(Example 4)
As shown in FIG. 12, the zoom lens of the fourth embodiment has the same specification values as the zoom lens of the third embodiment, and thus a duplicate description is omitted.
In Example 4, the biconcave negative lens L1 is a plastic mold lens. A cemented lens formed by a cemented lens of the biconvex positive L4 and the biconcave negative lens L5 is an adjustment lens.

(Example 5)
As shown in FIG. 13, the zoom lens of Example 5 includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a first lens group having a positive refractive power. A three-lens group G3, an aperture stop S, a fourth lens group G4 having a positive refractive power, and a fifth lens group G5 having a negative refractive power are arranged.

  At the time of zooming from the wide-angle end to the telephoto end, the first lens group G1 is fixed, the second lens group G2 is moved to the image plane side, the third lens group G3 is substantially fixed, and the fourth lens group G4 is an object. The fifth lens group G5 moves to the object side.

In order from the object side, the first lens group G1 includes a planoconcave negative lens L1, a prism L2, a planoconvex positive lens L3, and a biconvex positive lens L4.
The second lens group G2 includes a negative meniscus lens L5 having a convex surface directed toward the object side, and a cemented lens of a biconcave negative lens L6 and a biconvex positive lens L7.
The third lens group G3 includes a positive meniscus lens L8 having a convex surface directed toward the object side.
The fourth lens group G4 includes a cemented lens of a biconvex positive lens L9 and a negative meniscus lens L10 having a convex surface facing the image surface, and a positive meniscus lens L11 having a convex surface facing the image surface.
The fifth lens group includes a biconcave negative lens L12.

  The aspherical surface includes both surfaces of the biconvex positive lens L4, both surfaces of the negative meniscus lens L5, both surfaces of the positive meniscus lens L8, both surfaces of the positive meniscus lens L11, and the image side surface of the biconcave negative lens L12. It is provided on 9 sides.

  The positive meniscus lens L8 is a plastic mold lens, and the cemented lens of the biconvex positive lens L9 and the negative meniscus lens L10 is an adjustment lens.

Below, the numerical data of each said Example are shown. Symbols are the above, f is the focal length of the entire system, BF is the back focus, f1, f2... Are the focal lengths of the lens groups, _FNO is the F number, ω is the half angle of view, WE is the wide angle end, ST is the middle Focal length state, TE is a telephoto end, r is a radius of curvature of each lens surface, d is a distance between the lens surfaces, nd is a refractive index of d-line of each lens, and νd is an Abbe number of each lens. The total lens length described later is obtained by adding back focus to the distance from the lens front surface to the lens final surface. BF (back focus) represents the distance from the last lens surface to the paraxial image plane in terms of air.

  The aspherical shape is represented by the following formula, where x is an optical axis with the light traveling direction being positive, and y is a direction orthogonal to the optical axis.

x = (y ² / r) / [1+ {1- (K + 1) (y / r) ² } ^1/2 ]
+ A4 y ⁴ + A6 y ⁶ + A8 y ⁸ + A10y ¹⁰ + A12y ¹²
Where r is the paraxial radius of curvature, K is the conic coefficient, and A ₄ , A ₆ , A ₈ , A ₁₀ , and A ₁₂ are the fourth, sixth, eighth, tenth, and twelfth aspheric coefficients, respectively. . In the aspheric coefficient, “e−n” (n is an integer) indicates “10 ⁻ⁿ ”.

Numerical example 1
Numerical Example 1 is common to Numerical Example 2.

Unit mm

Surface data surface number rd nd νd
Object ∞ ∞
1 19.348 0.80 1.84666 23.78
2 13.468 3.06 1.58233 59.30
3 * -46.885 variable
4 * -14.693 0.70 1.52542 55.78
5 * 8.596 2.36
6 -7.064 0.41 1.61772 49.81
7 32.985 1.20 1.92286 18.90
8 -32.985 Variable
9 (Aperture) ∞ -0.10
10 * 5.318 2.41 1.58233 59.30
11 * -9.464 0.34
12 6.861 1.48 1.92286 18.90
13 3.451 Variable
14 * 19.426 2.47 1.52542 55.78
15 -16.727 Variable
16 ∞ 0.50 1.51633 64.14
17 ∞ 0.50
18 ∞ 0.50 1.51633 64.14
19 ∞ 0.59
Image plane ∞

Aspheric data 3rd surface
K = -8.273
A4 = 1.02528e-05, A6 = 2.23537e-07, A8 = -6.92546e-09, A10 = 6.31578e-11
4th page
K = -71.439
A4 = 3.06012e-04, A6 = 2.11113e-05, A8 = -1.01947e-06, A10 = 1.38358e-08
5th page
K = 0.975
A4 = 2.34067e-03, A6 = -1.70768e-04, A8 = 1.65358e-05, A10 = -5.19352e-07
10th page
K = -4.225
A4 = 1.73712e-03, A6 = -2.15108e-04, A8 = 7.54343e-07, A10 = 6.66853e-09
11th page
K = 5.493
A4 = 7.36536e-04, A6 = -8.38739e-05, A8 = 5.33716e-07, A10 = 5.34934e-10
14th page
K = -80.176
A4 = 1.25061e-03, A6 = -5.40302e-05, A8 = 1.77633e-06, A10 = -2.69508e-08

Zoom data
WE ST TE
Focal length 6.46 14.08 31.22
FNO. 3.70 5.04 5.88
Angle of view 2ω 64.77 30.28 13.89
BF 5.89 5.67 5.12
Total length 32.97 39.60 45.51

d3 0.41 5.13 11.16
d8 8.59 4.68 1.40
d13 2.94 8.98 12.70
d15 4.12 3.94 3.37

Group focal length
f1 = 27.70 f2 = -6.44 f3 = 8.94 f4 = 17.52

Numerical Example 3
Numerical Example 3 is common to Numerical Example 4.

Unit mm

Surface data surface number rd nd νd
Object ∞ ∞
1 * -22.854 0.97 1.52542 55.78
2 * 4.743 1.54
3 * 7.433 1.40 1.63493 23.90
4 * 13.330 variable
5 (Aperture) ∞ 0.70
6 * 4.289 1.33 1.53110 55.91
7 * -11.463 0.10
8 6.223 1.37 1.58913 61.14
9 -9.415 0.45 1.64769 33.79
10 2.994 Variable
11 -116.218 1.70 1.53110 55.91
12 * -7.587 variable
13 * -20.000 0.60 1.53110 55.91
14 -20.000 0.80
15 ∞ 0.50 1.51633 64.14
16 ∞ 0.37
Image plane ∞

Aspheric data first surface
K = 0.000
A4 = 5.52404e-04, A6 = -1.20527e-05, A8 = 8.62813e-08
Second side
K = -0.451
A4 = 1.40911e-04, A6 = 3.80259e-05, A8 = -7.75971e-07
Third side
K = 0.000
A4 = -9.62631e-04
4th page
K = 0.000
A4 = -1.04008e-03, A6 = -4.97126e-06, A8 = -2.42870e-08, A10 = -6.79084e-09
6th page
K = -0.278
A4 = -1.23389e-03, A6 = -3.87694e-06, A8 = -9.45601e-06
7th page
K = 0.000
A4 = 5.56121e-04, A6 = -7.58513e-06, A8 = -8.46415e-06
12th page
K = 0.000
A4 = 9.95377e-04, A6 = -3.47152e-05, A8 = 1.07919e-06, A10 = -1.02230e-08
13th page
K = 0.000
A4 = 1.80111e-04, A6 = -6.34866e-05, A8 = 1.91836e-06

Zoom data
WE ST TE
Focal length 4.66 8.85 17.77
FNO. 3.01 4.23 6.67
Angle of view 2ω 0.00 0.00 0.00
BF 1.53 1.48 1.44
Total length 28.36 26.47 32.07

d4 11.30 4.71 0.70
d10 2.59 7.71 17.24
d12 2.78 2.41 2.53

Group focal length
f1 = -11.06 f2 = 8.68 f3 = 15.20 f4 = 3618.76

Numerical Example 5
Unit mm

Surface data surface number rd nd νd
Object ∞ ∞
1 ∞ 0.60 2.00069 25.46
2 10.749 1.80
3 ∞ 7.60 1.84666 23.78
4 ∞ 0.10
5 ∞ 1.70 1.49700 81.54
6 -15.842 0.10
7 * 9.753 2.40 1.52542 55.78
8 * -19.574 variable
9 * 240.547 0.52 1.88300 40.76
10 * 5.445 1.38
11 -14.864 0.53 1.88300 40.76
12 7.876 1.36 1.92286 18.90
13 -72.851 Variable
14 * 5.150 1.20 1.52542 55.78
15 * 12.101 1.10
16 (Aperture) ∞ Variable
17 5.402 3.30 1.48749 70.23
18 -13.198 0.55 1.92286 18.90
19 -42.412 0.23
20 * -27.005 1.91 1.52542 55.78
21 * -9.658 variable
22 -14.851 0.55 1.90 200 25.10
23 * 58.076 Variable
24 ∞ 0.50 1.51680 64.20
25 ∞ 0.30
Image plane ∞

Aspheric data 7th surface
K = 0.000
A4 = -1.27897e-04, A6 = -2.18156e-06, A8 = 1.40894e-08
8th page
K = 0.000
A4 = 7.08593e-06, A6 = -5.67775e-07, A8 = 1.59153e-08
9th page
K = 0.000
A4 = 6.05989e-04, A6 = -6.55770e-05, A8 = 1.43802e-06
10th page
K = 0.000
A4 = 3.74970e-04, A6 = -5.84130e-05, A8 = -2.87829e-06
14th page
K = -0.596
A4 = 1.03399e-03, A6 = 5.12399e-05, A8 = 1.40482e-05
15th page
K = -10.847
A4 = 2.37614e-03, A6 = 1.89488e-05, A8 = 2.35259e-05
20th page
K = 0.000
A4 = -1.16900e-03, A6 = 8.62117e-05
21st page
K = 0.000
A4 = 8.11807e-04, A6 = 1.25389e-04
23rd page
K = 0.000
A4 = 1.71086e-04, A6 = -6.09997e-06, A8 = 2.12654e-06

Zoom data
WE ST TE
Focal length 4.46 9.56 22.66
FNO. 3.91 4.40 5.71
Angle of view 2ω 90.38 43.16 18.96
BF 9.34 11.13 15.31
Total length 52.33 52.34 52.33

d8 0.31 4.66 7.96
d13 8.62 4.28 0.97
d16 6.44 3.95 0.37
d21 0.68 1.40 0.79
d23 8.71 10.49 14.67

Group focal length
f1 = 10.88 f2 = -4.86 f3 = 16.11 f4 = 9.71 f5 = -13.06

  FIG. 14 shows the amount of change in image plane position with respect to the change in environmental temperature and the amount of change in image plane position with respect to the change in temperature of the adjustment member (shape memory alloy) in the telephoto end state of the zoom lens according to Numerical Example 1. It is a figure which shows the relationship. In the figure, the change amount of the image plane position with respect to the change of the environmental temperature is indicated by a black square, and the change amount of the image plane position with respect to the temperature change of the adjusting member (shape memory alloy) is indicated by a white circle. Hereinafter, the same description will be given in FIGS. The unit of length is mm, and the unit of temperature is ° C. (degrees).

Table 1 shows the amount of change in image plane position with respect to the change in environmental temperature and the image with respect to the change in temperature of the adjustment member (shape memory alloy) in the telephoto end state of the zoom lens according to Numerical Example 1 in Numerical Example 1. List specific numerical values for the change in surface position.
In all the following Tables 1 to 5, the width of the shape memory alloy is 4 mm, which is a value when assuming a case where the width changes constant with the outside air temperature.

  As is apparent from FIG. 14 and Table 1, by controlling the temperature of the adjustment member (shape memory alloy) to the target value, it is possible to substantially cancel the change in the image plane position due to the change in the environmental temperature. Thereby, stable optical characteristics can be obtained at all times.

(Table 1)
Example 1

Environmental temperature Environmental temperature Adjusting member adjusting member temperature Image plane change Image plane change
-0.211 50.0 0.220 76.3
-0.150 40.0 0.148 64.2
-0.100 30.0 0.101 52.1
-0.001 20.0 0.000 40.0
0.081 10.0 -0.080 27.5
0.158 0.0 -0.157 15.4
0.237 -10.0 -0.239 2.9
0.316 -20.0 -0.314 -9.2
0.394 -30.0 -0.390 -21.3
0.477 -40.0 -0.478 -33.8
0.556 -50.0 -0.560 -45.8
0.638 -60.0 -0.640 -58.3

  FIG. 15 shows the amount of change in image plane position with respect to the change in environmental temperature and the amount of change in image plane position with respect to the change in temperature of the adjustment member (shape memory alloy) in the telephoto end state of the zoom lens according to Numerical Example 2. It is a figure which shows the relationship.

  Table 2 shows the amount of change in the image plane position with respect to the change in environmental temperature and the image with respect to the change in temperature of the adjustment member (shape memory alloy) in the telephoto end state of the zoom lens according to Numerical Example 1 in Numerical Example 2. List specific numerical values for the change in surface position.

  As is apparent from FIG. 15 and Table 2, the change in the image plane position due to the change in the environmental temperature can be offset by controlling the temperature of the adjustment member (shape memory alloy) to the target value. Thereby, stable optical characteristics can be obtained at all times.

(Table 2)
Example 2

Environmental temperature Environmental temperature Adjusting member adjusting member temperature Image plane change Image plane change
-0.045 50.0 0.044 55.1
-0.030 40.0 0.031 45.8
-0.015 30.0 0.015 36.4
0.000 20.0 0.000 27.0
0.013 10.0 -0.011 17.5
0.028 0.0 -0.026 8.2
0.050 -10.0 -0.050 -0.9
0.070 -20.0 -0.069 -10.1
0.085 -30.0 -0.086 -19.5
0.105 -40.0 -0.104 -28.6
0.125 -50.0 -0.124 -37.8
0.138 -60.0 -0.140 -47.3

  FIG. 16 shows the amount of change in image plane position with respect to a change in environmental temperature and the amount of change in image plane position with respect to a change in temperature of the adjustment member (shape memory alloy) in the telephoto end state of the zoom lens according to Numerical Example 3. It is a figure which shows the relationship.

  Table 3 shows the amount of change in the image plane position with respect to the change in environmental temperature and the image with respect to the change in temperature of the adjusting member (shape memory alloy) in the telephoto end state of the zoom lens according to Numerical Example 1 in Numerical Example 3. List specific numerical values for the change in surface position.

As apparent from FIG. 16 and Table 3, the change in the image plane position due to the change in the environmental temperature can be offset by controlling the temperature of the adjustment member (shape memory alloy) to the target value. Thereby, stable optical characteristics can be obtained at all times.

(Table 3)
Example 3

Environmental temperature Environmental temperature Adjusting member adjusting member temperature Image plane change Image plane change
-0.350 50.0 0.349 50.3
-0.232 40.0 0.233 41.5
-0.111 30.0 0.111 32.8
0.000 20.0 0.000 24.0
0.139 10.0 -0.140 15.5
0.268 0.0 -0.267 6.9
0.399 -10.0 -0.398 -1.6
0.532 -20.0 -0.533 -10.6
0.665 -30.0 -0.665 -18.9
0.798 -40.0 -0.799 -27.5
0.929 -50.0 -0.929 -35.8
1.058 -60.0 -1.055 -44.3

  FIG. 17 shows the amount of change in image plane position with respect to a change in environmental temperature and the amount of change in image plane position with respect to a change in temperature of the adjustment member (shape memory alloy) in the telephoto end state of the zoom lens according to Numerical Example 4. It is a figure which shows the relationship.

  Table 4 shows the amount of change in the image plane position with respect to the environmental temperature change and the image with respect to the temperature change of the adjusting member (shape memory alloy) in the telephoto end state of the zoom lens according to Numerical Example 1 in Numerical Example 4. List specific numerical values for the change in surface position.

As is apparent from FIG. 17 and Table 4, the change in the image plane position due to the change in the environmental temperature can be offset by controlling the temperature of the adjustment member (shape memory alloy) to the target value. Thereby, stable optical characteristics can be obtained at all times.

(Table 4)
Example 4

Environmental temperature Environmental temperature Adjusting member adjusting member temperature Image plane change Image plane change
-0.350 50.0 0.348 50.8
-0.232 40.0 0.230 41.5
-0.111 30.0 0.116 32.3
0.000 20.0 0.000 23.0
0.139 10.0 -0.140 13.9
0.268 0.0 -0.268 4.7
0.399 -10.0 -0.400 -4.5
0.532 -20.0 -0.533 -13.6
0.665 -30.0 -0.661 -22.7
0.798 -40.0 -0.790 -31.8
0.929 -50.0 -0.922 -40.9
1.058 -60.0 -1.060 -50.0

  FIG. 18 shows the amount of change in image plane position with respect to a change in environmental temperature and the amount of change in image plane position with respect to a change in temperature of the adjusting member (shape memory alloy) in the telephoto end state of the zoom lens according to Numerical Example 5. It is a figure which shows the relationship.

  Table 5 shows the amount of change in the image plane position with respect to the change in environmental temperature and the image with respect to the change in temperature of the adjustment member (shape memory alloy) in the telephoto end state of the zoom lens according to Numerical Example 1 in Numerical Example 5. List specific numerical values for the change in surface position.

As apparent from FIG. 18 and Table 5, the change in the image plane position due to the change in the environmental temperature can be offset by controlling the temperature of the adjustment member (shape memory alloy) to the target value. Thereby, stable optical characteristics can be obtained at all times.

(Table 5)
Example 5

Environmental temperature Environmental temperature Adjusting member adjusting member temperature Image plane change Image plane change
0.296 50.0 -0.296 50.6
0.196 40.0 -0.196 41.4
0.094 30.0 -0.093 32.2
0.000 20.0 0.000 23.0
-0.115 10.0 0.115 14.0
-0.223 0.0 0.223 4.8
-0.332 -10.0 0.332 -4.3
-0.444 -20.0 0.444 -13.3
-0.556 -30.0 0.556 -22.4
-0.670 -40.0 0.670 -31.4
-0.780 -50.0 0.780 -40.3
-0.886 -60.0 0.880 -49.4

The values corresponding to the conditional expressions in each example are listed below.

Conditional expression (1) 0.50 <| fm / fw | <10.00
(2) 0.01 <| fm / ft | <3.00
(3) 0.50 <fc / fw | <10.00
(4) 0.01 <fc / ft | <3.00

fw: Focal length at the wide-angle end of the zoom lens
ft: Focal length at the telephoto end of the zoom lens
fm: Focal length of plastic mold lens
fc: Focal length of adjusting lens or adjusting lens group

Example 1 Example 2 Example 3 Example 4 Example 5
Conditional formula for mold lens (1) | fm / fw | 1.58 1.58 1.59 1.59 3.61
(2) | fm / ft | 0.33 0.33 0.42 0.42 0.71

Conditional expression for adjusting lens (3) | fc / fw | 4.290 1.471 5.204 2.057 2.175
(4) | fc / ft | 0.887 0.304 1.364 0.539 0.428

  The optical device described above is not limited to a digital camera, but is suitable for a projector, a mobile phone, a notebook PC, an in-vehicle camera, and a surveillance camera.

  As described above, the optical device according to the present invention is suitable for a device having stable optical characteristics regardless of changes in environmental temperature.

G1 ... 1st lens group G2 ... 2nd lens group G3 ... 3rd lens group G4 ... 4th lens group S ... Brightness stop F ... Low pass filter C ... Cover glass I ... Image surface 100 ... Digital camera 101 ... Shooting optical system DESCRIPTION OF SYMBOLS 102 ... Optical path for imaging | photography 103 ... Finder optical system 104 ... Optical path for finder 105 ... Shutter button 106 ... Flash 107 ... Cover member 108 ... Focal length change button 109 ... Liquid crystal display monitor 110 ... CCD
112 ... Processing means 113 ... Storage means 114 ... Finder objective optical system 115 ... Field frame 116 ... Erecting prism 117 ... Eyepiece optical system 118 ... Setting change switch 120 ... Temperature correction interval adjusting member TS ... Temperature sensor TB ... Table

Claims (13)

An imaging optical system having a plurality of lens groups and forming an image of an object;
A holding frame for movably holding the lens of the imaging optical system;
A temperature correction interval adjusting unit whose length changes in a direction along the optical axis direction;
One end of the temperature correction interval adjusting unit is in contact with the holding frame, and the other end in the direction in which the length is changed is in contact with a region other than the effective area of the movable lens,
Further, the movable lens is arranged on the side opposite to the temperature correction interval adjusting unit, and elastically applies an external force to the movable lens in a direction in which the length of the temperature correction interval adjusting unit changes. Members,
A temperature detector for detecting the temperature of the imaging optical system;
A table storing the correspondence between the amount of change in the image plane of the imaging optical system due to a change in temperature and the temperature;
A control unit that controls the length of the temperature correction interval adjustment unit to be a target value based on the temperature from the temperature detection unit and the correspondence stored in the table;
An optical device comprising:   The optical apparatus according to claim 1, further comprising an imaging element having an imaging surface that converts an image formed by the imaging optical system into an electrical signal.   3. The optical device according to claim 1, wherein the plurality of lens groups are zoom lenses in which distances between the lens groups change during zooming from the wide-angle end to the telephoto end.   The optical apparatus according to claim 1, wherein the imaging optical system includes a lens made of resin and having an aspheric surface.   The optical device according to claim 4, wherein the temperature detection unit is disposed in the vicinity of the lens made of resin.   The control unit controls the length of the temperature correction interval adjusting unit so as to cancel the amount of movement of the image plane of the imaging optical system in the optical axis direction due to a change in environmental temperature, and the movable lens The optical device according to claim 1, wherein the optical device is moved.   The optical device according to claim 1, wherein the movable lens is at least one of a lens and a lens group.   The optical apparatus according to claim 7, wherein the temperature correction interval adjusting unit is provided in the plurality of lens groups. Furthermore, the following conditional expression (1), (2), (3), (4) is satisfied, The optical apparatus as described in any one of Claims 3-8 characterized by the above-mentioned.
0.50 <| fm / fw | <10.00 (1)
0.01 <| fm / ft | <3.00 (2)
0.50 <| fc / fw | <10.00 (3)
0.01 <| fc / ft | <3.00 (4)
here,
fw is the focal length at the wide angle end of the entire zoom lens system,
ft is the focal length at the telephoto end of the entire zoom lens system;
fm is the focal length of the lens made of resin and having an aspheric surface,
fc is the focal length of the movable lens or lens group,
It is. The imaging optical system, at least in order from the object side,
A first lens unit having positive refractive power;
A second lens unit having negative refractive power;
A third lens unit having positive refractive power;
A fourth lens unit having positive refractive power;
The optical device according to claim 1, comprising:   The optical device according to claim 10, wherein the first lens group includes a reflecting member having a reflecting surface that bends the optical path. The imaging optical system, at least in order from the object side,
A first lens unit having negative refractive power;
A second lens group having positive refractive power;
A third lens unit having positive refractive power;
A fourth lens unit having positive refractive power;
The optical device according to claim 1, comprising: The temperature correction interval adjuster is formed of a shape memory alloy,
The said control part controls the length of the said space | interval adjustment part for temperature correction by controlling the electric current applied to the said shape memory alloy, It is characterized by the above-mentioned. Optical device.

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