JP2014238469A - Zoom lens and imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a zoom lens that is compactified in a thickness direction and has appropriately corrected aberration, and an imaging apparatus with the same.SOLUTION: A zoom lens comprises, in order from an object side, at least a first lens group Gr1 having negative refractive power and a second lens group Gr2 having positive refractive power, and performs zooming by changing distances between individual lens groups Gr1, Gr2, .... The first lens group Gr1 includes a reflection optical element PRM that is disposed closest to the object and bends an optical path by reflecting light beams. The reflection optical element PRM has a concave object-side surface 12a. The first lens group Gr1 includes at least two lenses L11, L12, ... that have negative refractive power on an image side of the reflection optical element PRM.

Description

  The present invention relates to a zoom lens that includes a plurality of lens groups and performs zooming by changing the distance between the lens groups in the optical axis direction, and an imaging apparatus including such a zoom lens, and in particular, the optical axis is bent by a reflective optical element. The present invention relates to a type of zoom lens and an imaging apparatus.

  In recent years, with the improvement in performance and miniaturization of imaging devices using solid-state imaging devices such as CCD (Charged Coupled Device) type image sensors or CMOS (Complementary Metal Oxide Semiconductor) type image sensors, Portable information terminals are becoming widespread. Since these devices are very limited in size and cost, they have a single focal point consisting of a small solid-state image sensor with a small number of pixels and about 1 to 4 plastic lenses compared to a normal digital still camera. An imaging device including an optical system is generally used. On the other hand, imaging devices mounted on personal digital assistants can cope with high-pixel imaging elements and can capture subjects away from the photographer as the number of pixels and functionality is rapidly increasing. In addition, there is a demand for a small zoom lens that can be mounted on a mobile phone or the like, such that shooting is possible even when the distance from the subject cannot be sufficiently separated as in indoor shooting.

In order to mount a zoom lens on a cellular phone or a portable information terminal, it is particularly required to reduce the thickness direction among the miniaturization.
In a zoom lens of a thin type, a bending optical system that bends the optical axis by 90 degrees using a reflective optical element such as a prism is often used. In the variable magnification optical systems disclosed in Patent Documents 1 to 4, the first lens is used. There is disclosed a variable magnification optical system in which the reflective optical element is used for a group to reduce the size in the thickness direction.

  In general, in a variable magnification optical system using a reflective optical element as in Patent Documents 1 and 2, a lens having a negative refractive power on the object side of the reflective optical element in order to reduce the optical usage range of the first lens group. However, in this zoom optical system as disclosed in Patent Documents 3 and 4, the object side of the reflective optical element is used instead of the lens. The concave surface is used to reduce the thickness.

  However, if the concave surface on the object side of the reflective optical element becomes strong, the incident angle with respect to the off-axis light beam becomes large and the concentric lens shape is not obtained, so that various aberrations are likely to occur. Therefore, there is a limit to suppressing the optical usage range of the first lens group only by the concave surface on the object side.

From the above situation, in the optical system of Patent Document 3, the negative refractive power of the entire first lens group becomes weak, and the optical usage range of the first lens group becomes large. It is enough.
In Patent Document 4, the image side surface of the reflective optical element is also made concave to compensate for negative refractive power. However, in the case of a reflective optical element having an action of bending the optical path, the object side surface and the image side surface are bent 90 degrees. Therefore, it is difficult to align the axis of the object side surface with the axis of the image side surface, which often causes deterioration of optical performance. In addition, by molding with a mold such as a glass mold lens or plastic lens, it becomes relatively easy to align the axis of the object side and the axis of the image side, but the flatness of the reflecting surface is deteriorated and the reflection is reduced. Since this causes waviness on the surface, a problem that similarly causes deterioration of optical performance occurs.

JP 2007-93955 PR JP 2008-65347 PR Japanese Laid-Open Patent Publication No. 2004-151552 Japanese Patent No. 4869522

  The present invention has been made in view of the above-described background art, and by solving the problem when the reflective optical element has refractive power, various aberrations are achieved while achieving compactness in the thickness direction in particular. It is an object of the present invention to provide a zoom lens that is well corrected and an imaging apparatus using the zoom lens.

  In order to achieve the above object, a zoom lens according to the present invention includes, in order from the object side, at least a first lens group having a negative refractive power and a second lens group having a positive refractive power, and each lens group. The first lens unit has a reflective optical element that bends the optical path by reflecting the light beam closest to the object side, and the object side surface of the reflective optical element is: The first lens group is concave and has at least two lenses having negative refractive power on the image side of the reflective optical element.

The zoom lens according to the present invention has a negative refracting power in order from the object side and bends the optical path by reflecting light rays in order from the object side as a basic configuration for obtaining a zoom lens that is small and has good aberration correction. And a second lens group having a positive refractive power. By making the first lens group in a negative configuration, it is possible to quickly relax light rays that are incident at a large angle from the object side, and it is advantageous in reducing the thickness by suppressing the optical usage range of the first lens group. In addition, by including the reflective optical element in the first lens group, the size of the imaging device in the depth direction can be reduced. Furthermore, by arranging the reflective optical element closest to the object side and making the object side surface concave, compared to the case where a negative lens is arranged on the object side of the reflective optical element while suppressing the optical usage range of the first lens group, In addition, it is possible to reduce the size of the imaging device in the thickness direction.
However, if the concave surface on the object side of the reflective optical element becomes strong, the incident angle with respect to the off-axis light beam becomes large and the concentric lens shape is not obtained, so that various aberrations are likely to occur. Therefore, there is a limit to suppressing the optical usage range of the first lens group only by the concave surface on the object side.
For this reason, it is desirable to compensate for the negative refractive power of the first lens group by disposing a lens having negative refractive power on the image side of the reflective optical element. However, for example, spherical aberration and chromatic aberration at the telephoto end are corrected. In order to achieve this, an element that weakens the negative refractive power of the first lens unit is often incorporated, such as a lens having a positive refractive power. For this reason, in order to increase the negative refractive power of the first lens group, a method of increasing the refractive power of a lens having a negative refractive power can be used. There is a possibility that aberrations such as coma aberration may occur due to the lens.
Accordingly, in the zoom lens according to the present invention, since at least two lenses having negative refractive power are provided on the image side of the reflective optical element, the refractive power can be shared. The optical usage range of one lens group can be suppressed to some extent, and the zoom lens can be further reduced in thickness.

  In a specific aspect of the present invention, in the zoom lens, the first lens group includes a lens having a negative refractive power closest to the object side on the image side of the reflective optical element. In this way, by arranging a lens having negative refractive power, the light emitted from the reflective optical element can be quickly relaxed, so that the optical usage range of the first lens group can be suppressed, and the zoom lens is thin. Can be performed.

In another aspect of the present invention, the following conditions are satisfied.
1.7 <n1n1 <2.1 (1)
n1n1: Refractive index of the lens closest to the object side among the lenses on the image side of the reflective optical element The conditional expression (1) indicates the refractive index of the lens closest to the object side among the lenses on the image side of the reflective optical element. The preferable range is defined. By exceeding the lower limit of the conditional expression (1), it is possible to increase the negative refractive power while suppressing an increase in the curvature of the lens, and thus optical use of the first lens group while suppressing the occurrence of aberrations. The range can be suppressed, and the zoom lens can be thinned. On the other hand, it can comprise with the easily available glass material by being less than the upper limit of conditional expression (1). Further, glass materials that exceed the upper limit of conditional expression (1) generally have high dispersion. Therefore, it is possible to suppress the occurrence of chromatic aberration at the telephoto end by falling below the upper limit of conditional expression (1). .

  In still another aspect of the invention, the first lens group includes a single lens having negative refractive power, a lens having negative refractive power, and a lens having positive refractive power on the image side of the reflective optical element. It consists of a cemented lens combined. By arranging two lenses having negative refractive power on the image side of the reflective optical element, it becomes possible to quickly relax the light emitted from the reflective optical element while sharing the negative refractive power as described above. Therefore, it is possible to suppress the optical usage range of the first lens group while suppressing the occurrence of aberration. Further, by disposing a lens having a positive refractive power on the image side of these negative lenses, it is possible to effectively correct the lateral chromatic aberration at the wide-angle end and the axial chromatic aberration at the telephoto end. In addition, the air space between the second lens having negative refractive power and the lens having positive refractive power is often very narrow, and is easily affected by optical performance due to lens manufacturing errors. It is desirable to join these lenses.

In still another aspect of the present invention, the following conditions are satisfied.
30 <ν1n2-ν1p1 <65 (2)
However,
ν1n2: Abbe number of a lens having negative refractive power among cemented lenses of the first lens group ν1p1: Abbe number of lens having positive refractive power among cemented lenses of the first lens group Conditional expression (2) is The difference between the Abbe numbers of the cemented lenses in the first lens group is defined. By exceeding the lower limit of the conditional expression (2), it becomes a combination of a negative lens having a relatively small dispersion and a positive lens having a relatively large dispersion, and the entire first lens group has a negative refractive power. It becomes possible to correct chromatic aberration efficiently. On the other hand, when the lower limit value of conditional expression (2) is not reached, a cemented lens can be configured with a readily available glass material.

In still another aspect of the present invention, the following conditions are satisfied.
0.4 <d11 / fW <0.9 (3)
However,
d11: Distance from the vertex of the object side surface of the reflecting optical element (the surface closest to the object side of the first lens group) to the intersection of the reflecting surface of the reflecting optical element and the optical axis fW: Focal length of the entire system at the wide angle end Conditional expression (3) defines the distance from the apex of the most object side surface of the first lens group to the intersection of the reflecting surface of the reflecting optical element and the optical axis as a ratio to the focal length of the entire system at the wide angle end. By falling below the upper limit of conditional expression (3), it is possible to reduce the thickness in the vicinity of the reflective optical element that often determines the thickness of the imaging device, so that the imaging device can be made thinner. On the other hand, exceeding the lower limit of conditional expression (3) prevents excessive thinning of the reflective optical element and prevents a sudden decrease in the amount of peripheral light due to cutting of the peripheral luminous flux in order to maintain the feasibility of optical path bending. Is possible.

In still another aspect of the present invention, the following conditions are satisfied.
-4.0 <r1 / d1 <-2.0 (4)
However,
r1: Paraxial radius of curvature of the object side surface of the reflecting optical element d1: Distance on the optical axis from the object side surface of the reflecting optical element to the image side surface Conditional expression (4) shows the paraxial curvature radius of the reflecting optical element on the object side. The ratio is defined as the ratio to the distance on the optical axis from the object side surface to the image side surface of the reflective optical element. By exceeding the lower limit of conditional expression (4), the object side of the reflective optical element can have an appropriate negative refractive power, and the optical usage range of the first lens group can be suppressed. Can be realized. On the other hand, by falling below the upper limit of conditional expression (4), the curvature on the object side is prevented from becoming excessively large with respect to the thickness of the reflecting optical element, and the light beam is incident on the object surface again after being reflected by the reflecting surface. By doing so, it is possible to suppress the generation of unnecessary ghosts.

  In still another aspect of the present invention, the image side surface of the reflective optical element is a plane. In this case, it is relatively easy to align the axes of the reflective optical element object side surface and the image side surface, and optical performance is hardly deteriorated. Further, even when the reflective optical element is molded by a mold, the flatness of the reflecting surface can be increased, and deterioration of optical performance due to the reflective optical element can be suppressed. Regarding the reflective optical element, in addition to the image side surface being a flat surface, it is more desirable that the object side surface be a spherical surface generated by polishing.

In still another aspect of the present invention, the following conditional expression is satisfied.
1.80 <nprm <2.20 (5)
However,
nprm: Refractive index of the reflective optical element Conditional expression (5) defines a preferable range of the refractive index of the reflective optical element. By exceeding the lower limit of the conditional expression (5), the refraction angle of the light beam incident on the reflective optical element becomes small and passes through a position closer to the optical axis, so the effective diameter of the first lens group becomes small. This is advantageous for downsizing. On the other hand, by falling below the upper limit of the conditional expression (5), it is possible to produce a reflective optical element with an easily available glass material.

In still another aspect of the present invention, the following conditional expression is satisfied.
23 <νprm <50 (6)
However,
νprm: Abbe number of the reflective optical element Conditional expression (6) defines a preferable range of the Abbe number of the reflective optical element. By exceeding the lower limit of the conditional expression (6), it is possible to suppress the occurrence of chromatic aberration at the telephoto end that occurs on the object side surface. On the other hand, it can comprise with the easily available glass material by being less than the upper limit of conditional expression (6).

  In still another aspect of the present invention, the zoom lens has, in order from the object side, the first lens group having a negative refractive power, the second lens group having a positive refractive power, and a negative refractive power. It consists of a third lens group and a fourth lens group having a positive refractive power. As described above, since the third lens group has negative refractive power, the power arrangement of the combined positive refractive power of the first lens group and the second lens group and the negative refractive power of the third lens is “ "Positive / negative" and telephoto placement. In such a zoom lens, it is possible to suppress the total optical length while ensuring a relatively long focal length. Further, since the fourth lens group has a positive refractive power, the principal ray incident angle (angle formed by the principal ray and the optical axis) of the ray bundle formed on the periphery of the imaging surface of the solid-state imaging device can be suppressed small. And so-called telecentric characteristics can be ensured.

  In still another aspect of the present invention, the zoom lens has, in order from the object side, the first lens group having a negative refractive power, the second lens group having a positive refractive power, and a positive refractive power. The third lens group. In this way, by arranging the third lens group having a positive refractive power on the image side of the second lens group, the zooming burden of the lens group having a positive refractive power at the time of zooming is different from that of the second lens group. Since it can be shared by the third lens group, it is possible to suppress the amount of movement of the second lens group at the time of zooming, and the optical total length can be suppressed.

  In order to achieve the above object, in yet another aspect of the present invention, the third lens group moves in the optical axis direction during focusing. As described above, by focusing with the third lens group, it is possible to obtain a clear image up to a short distance object without causing an increase in the total optical length or an increase in the front lens diameter due to the extension.

  In still another aspect of the present invention, the fourth lens group does not move in the optical axis direction during zooming and focusing. The fourth lens group is the lens group closest to the solid-state image sensor. If the fourth lens group is moved during zooming or focusing, the distance from the solid-state image sensor will be closer, and the final lens will be affected by dust and scratches. May be easier to receive. In particular, in a miniaturized zoom lens, since the distance between the final lens and the solid-state image sensor is closer, the tendency is prominent. On the other hand, by adopting a configuration in which the fourth lens group is not moved, the distance between the final lens and the solid-state imaging device is fixed, so that the influence of dust and scratches can be suppressed. In addition, since the solid-state imaging device can be sealed, it is possible to prevent dust and other dust from entering the solid-state imaging device.

  In still another aspect of the present invention, the lens further includes a lens having substantially no power.

  An imaging apparatus according to the present invention includes the zoom lens described above and an imaging element that photoelectrically converts an image formed on an imaging surface by the zoom lens. By using the zoom lens of the present invention, it is possible to obtain an image pickup apparatus that achieves compactness mainly in the thickness direction and further suppresses various aberrations.

It is a figure explaining an imaging device or an imaging module provided with the zoom lens of one embodiment concerning the present invention. (A) is a conceptual diagram explaining the object side surface of a reflective optical element, (B) is a conceptual diagram explaining the lens shape of a 4th lens group. It is a block diagram explaining a portable communication terminal provided with the imaging device of FIG. (A) And (B) is a perspective view of the surface side and back surface side of a portable communication terminal. 3 is a cross-sectional view of the zoom lens of Example 1. FIG. (A) is sectional drawing in the wide angle end of Example 1, (B) is sectional drawing in the middle, (C) is sectional drawing in a telephoto end. (A) is an aberration diagram at the wide-angle end of Example 1, (B) is an aberration diagram at the middle, and (C) is an aberration diagram at the telephoto end. (A) is sectional drawing in the wide angle end of Example 2, (B) is sectional drawing in the middle, (C) is sectional drawing in a telephoto end. (A) is an aberration diagram at the wide-angle end of Example 2, (B) is an aberration diagram at the middle, and (C) is an aberration diagram at the telephoto end. (A) is sectional drawing in the wide angle end of Example 3, (B) is sectional drawing in the middle, (C) is sectional drawing in a telephoto end. (A) is an aberration diagram at the wide-angle end of Example 3, (B) is an aberration diagram at the middle, and (C) is an aberration diagram at the telephoto end.

[First Embodiment]
FIG. 1 is a cross-sectional view illustrating a camera module as an imaging apparatus including a zoom lens according to an embodiment of the present invention.

  The camera module (imaging device) 50 includes a zoom lens 10 that forms a subject image, an image sensor 51 that photoelectrically converts the subject image formed by the zoom lens 10, and holds the image sensor 51 from behind and wiring and the like. A wiring board 52 having a zoom lens 10 and the like, and a lens barrel portion 54 having an opening OP for allowing light rays from the object side to enter the zoom lens 10 are provided. The zoom lens 10 has a function of forming a subject image on the imaging surface (or projection surface) I of the image sensor 51. This camera module 50 is used by being incorporated in a portable terminal described later.

  The zoom lens 10 includes, in order from the object side, a first lens group Gr1, a second lens group Gr2, a third lens group Gr3 (including an aperture stop S), and a fourth lens group Gr4. Among these, the lens group Gr1 includes a plurality of negative lenses, and each of the lens groups Gr2 to Gr4 can include a single lens or a plurality of lenses. The first lens group Gr1 incorporates a triangular prismatic reflective optical element (prism mirror) PRM that bends the optical path by reflection, and reflects the light beam directed in the -Z direction by the inclined inner surface (or reflecting surface) 12b. To bend 90 ° and point in the + Y direction. That is, the optical axis AX extends orthogonally across the reflecting surface 12b, and has an axis AX1 parallel to the Y axis and an axis AX2 parallel to the Z axis. In the first lens group Gr1, the object side surface 12a of the reflective optical element PRM is a concave surface, and the image side surface 12c of the reflective optical element PRM is a flat surface. The zoom lens 10 illustrated in FIG. 1 has the same configuration as the zoom lens 11 of Example 1 described later.

  The image sensor 51 is a sensor chip made of a solid-state image sensor. The photoelectric conversion unit 51a of the image sensor 51 is composed of a CCD (charge coupled device) or a CMOS (complementary metal oxide semiconductor), photoelectrically converts incident light for each pixel of RGB, and outputs an analog signal thereof. The surface of the photoelectric conversion unit 51a as the light receiving unit is an imaging surface (projected surface) I.

  The wiring substrate 52 has a role of aligning and fixing the image sensor 51 to other members (for example, the lens barrel portion 54) via a support. The wiring board 52 receives supply of voltages and signals for driving the image sensor 51 and the first and second drive mechanisms 55a and 55b from an external circuit, and outputs a detection signal to the external circuit. Is possible.

  On the zoom lens 10 side of the image pickup device 51, a parallel plate F made of, for example, an IR cut filter, an optical low-pass filter, or the like is disposed and fixed by a holder member (not shown) so as to cover the image pickup device 51 and the like. .

  The lens barrel 54 houses and holds the zoom lens 10. The lens barrel portion 54 moves the second and third lens groups Gr2 and Gr3 of the lens groups Gr1 to Gr4 constituting the zoom lens 10 along the optical axis AX, thereby changing the magnification and focusing of the zoom lens 10. In order to enable this operation, the first and second drive mechanisms 55a and 55b are provided. Both drive mechanisms 55a and 55b can operate independently. One first drive mechanism 55a reciprocates the second lens group Gr2 along the optical axis AX, and the other second drive mechanism 55b The three lens groups Gr3 are reciprocated along the optical axis AX. The first drive mechanism 55a includes, for example, a stepping motor, a tangent screw type power transmission member, and a slide guide. The second drive mechanism 55b includes a voice coil motor and a guide, for example. The drive mechanism is not limited to the above, and the first drive mechanism 55a is an actuator using a piezoelectric element instead of a stepping motor (for example, see US Pat. No. 5,589,723), a voice coil motor, or the like. Alternatively, the second drive mechanism 55b may be configured by an actuator using a piezoelectric element, a stepping motor, or the like instead of the voice coil motor.

  Hereinafter, the zoom lens 10 will be described in detail. The zoom lens 10 in FIG. 1 forms a subject image on the imaging surface I of the image sensor 51, and in order from the object side, the first lens group Gr1 having a negative refractive power and a positive refractive power. The second lens group Gr2 includes a third lens group Gr3 having negative refractive power, and a fourth lens group Gr4 having positive refractive power. Here, the first lens group Gr1 includes, for example, a reflective optical element PRM whose object side surface 12a is concave and whose image side surface 12c is flat, a biconcave negative first lens L11, and a biconcave negative second lens L12. , And a biconvex positive third lens L13. Here, the third lens L13 is cemented to the second lens L12 to form a cemented lens L1b. The second lens group Gr2 includes, for example, an aperture stop S, a biconvex positive fourth lens L21, a negative meniscus fifth lens L22 convex toward the object side, and a biconvex positive sixth lens L23. . Here, the sixth lens L23 is cemented to the fifth lens L32 to form a cemented lens L2b. The third lens group Gr3 includes a seventh lens L31 that is substantially plano-concave and negative, for example. The fourth lens group Gr4 includes, for example, an eighth lens L41 that is convex on the image side and has a positive meniscus. The fourth lens L21, the seventh lens L31, the eighth lens L41, and the like can be aspherical lenses.

  The zoom lens 10 of FIG. 1 changes the positions of the second lens group Gr2 and the third lens group Gr3 among the first to fourth lens groups Gr1 to Gr4 when zooming from the wide-angle end to the telephoto end. Specifically, at the time of zooming from the wide angle end to the telephoto end, the first and fourth lens groups Gr1 and Gr4 are fixed with respect to the imaging surface I and the like and do not move, and the second lens group Gr2 is moved to the object side. The third lens group Gr3 also moves to the object side.

  As shown in FIG. 2A, the reflective optical element PRM has a substantially circular concave surface as the object side surface 12a, and a flat surface 12f is formed outside the effective area around the object side surface 12a. As shown in FIG. 2B, the eighth lens L41 has an oval or oval outline, that is, an oval or oval object side surface 13a. That is, in the eighth lens L41, both sides on the long side are cut to provide a straight portion (cutting portion) C corresponding to the imaging surface I of the photoelectric conversion portion 51a. Thereby, the thickness of the zoom lens 10 in the Z direction can be reduced as much as possible.

  In the above description, the zoom lens 10 includes the first lens group Gr1, the second lens group Gr2, the third lens group Gr3, and the fourth lens group Gr4 in this order from the object side. However, the first lens group Gr1, the second lens group Gr2, and the third lens group Gr3 can be sequentially formed from the object side. In this case, the first lens group Gr1 has negative refracting power and the second lens group Gr2 has positive refracting power. The third lens group Gr3 includes the third lens group Gr3 shown in FIG. Although different, it is assumed to have a positive refractive power as in the fourth lens group Gr4 shown in FIG. Such a zoom lens 10 changes the positions of the second and third lens groups Gr2 and Gr3 upon zooming from the wide-angle end to the telephoto end. Specifically, at the time of zooming from the wide-angle end to the telephoto end, the first lens group Gr1 is fixed and not moved with reference to the imaging surface I or the like, but the second lens group Gr2 is moved to the object side, and the third lens group Gr2 is moved to the object side. The lens group Gr3 is once moved to the image side and then moved to the object side. A case where the zoom lens 10 includes the first to third lens groups Gr1 to Gr3 corresponds to Example 2 described later.

  Next, an example of a mobile communication terminal 300 that is a mobile terminal equipped with the camera module 50 illustrated in FIG. 1 will be described with reference to FIGS. 3, 4A, and 4B.

  The mobile communication terminal 300 is a smartphone-type mobile communication terminal, and includes an imaging function unit 200 having a camera module 50 that is an imaging device, and a control unit that comprehensively controls each unit and executes a program corresponding to each process ( CPU) 310, display operation unit 320 that is a touch panel that displays data related to communication, captured images and videos, and receives user operations, an operation unit 330 including a power switch, and the like, via antenna 341 A wireless communication unit 340 for realizing various types of information communication with an external server and the like, and a storage unit (ROM that stores necessary data such as a system program, various processing programs, and a terminal ID of the mobile communication terminal 300 360, various processing programs and data executed by the control unit 310, processing data, Temporary storage unit used as a work area for temporarily storing the imaging data and the like by the imaging function unit 200 and a (RAM) 370 or the like.

  In addition to the camera module 50 described above, the imaging function unit 200 includes a control device 74, an optical system driving circuit unit 105a, an imaging element driving device 77, an image storage device 78, and the like.

  The control device 74 controls each unit of the imaging function unit 200. The control device 74 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and the like, and various programs are read out from the ROM and expanded in the RAM in cooperation with the CPU. Execute the process. The control unit 310 is communicably connected to the control device 74 of the imaging function unit 200, and can exchange control signals and image data.

  The optical system drive circuit unit 105a operates the first and second drive mechanisms 55a and 55b of the zoom lens 10 to change the state of the zoom lens 10 when performing zooming, focusing, exposure, and the like under the control of the control device 74. To control. The optical system drive circuit unit 105a operates the first drive mechanism 55a to appropriately move the second lens group Gr2 along the optical axis AX, and operates the second drive mechanism 55b to light the third lens group Gr3. By appropriately moving along the axis AX, the zoom lens 10 is caused to perform a zoom operation. That is, during the zoom operation, the first and fourth lens groups Gr1 and Gr4 are fixed. When zooming from the wide-angle end to the telephoto end, the second lens group Gr2 moves to the object side (-Y side in FIG. 1) in the case of the zoom lens 10 corresponding to FIG. 1, and the third lens group Gr3 also Move to the object side (-Y side in FIG. 1). On the other hand, the zoom lens 10 can be focused. That is, the optical system drive circuit unit 105a operates the second drive mechanism 55b to appropriately move the third lens group Gr3 along the optical axis AX, thereby causing the zoom lens 10 to perform a focusing operation. During the focusing operation, the first, second, and fourth lens groups Gr1, Gr2, and Gr4 are fixed. When the zoom lens 10 has a three-group configuration, the optical system drive circuit unit 105a moves the second and third lens groups along the optical axis AX by, for example, the drive mechanisms 55a and 55b and performs a zoom operation. Then, the second lens driving mechanism 55b moves the third lens group Gr3 along the optical axis AX to cause the zoom lens 10 to perform a focusing operation.

  The image sensor driving device 77 controls the operation of the image sensor 51 when performing exposure or the like under the control of the control device 74. Specifically, the image sensor driving device 77 scans and controls the image sensor 51 based on the timing signal. Further, the image sensor driving device 77 can perform various image processing such as distortion correction, color correction, and compression on an image signal sent from the image sensor 51 or a circuit attached to the image sensor 51.

  The image storage device 78 receives the digitized image signal from the image sensor driving device 77 and stores it as readable and writable image data.

  Here, the photographing operation of the mobile communication terminal 300 including the imaging function unit 200 will be described. When the camera mode in which the mobile communication terminal 300 is operated as a camera is set, subject monitoring (through image display) and image shooting execution are performed. In monitoring, an image of the subject obtained through the zoom lens 10 is formed on the imaging surface I (see FIG. 1 and the like) of the imaging element 51. The image sensor 51 is scanned and driven by the image sensor driving device 77, and outputs an analog signal for one screen as a photoelectric conversion output corresponding to a light image formed at regular intervals.

  This analog signal is converted into digital data after gain adjustment is appropriately performed for each primary color component of RGB in a circuit attached to the image sensor 51. The digital data is subjected to color process processing including pixel interpolation processing and Y correction processing in the image sensor driving device 77 to generate a digital luminance signal Y and color difference signals Cb, Cr (image data). And stored in the image storage device 78. The stored digital data is periodically read out from the image storage device 78 to generate a video signal thereof, and is output to the display operation unit 320 via the control device 74 and the control unit 310.

  The display operation unit 320 functions as an electronic viewfinder in monitoring and displays captured images in real time. In this state, zooming, focusing, exposure, and the like of the zoom lens 10 are set by driving the optical system driving circuit unit 105a based on an operation input performed by the user via the display operation unit 320 as needed.

  In such a monitoring state, when the user appropriately operates the display operation unit 320, still image data is captured. One frame of image data stored in the image storage device 78 is read in accordance with the operation content of the display operation unit 320 and compressed by the image sensor driving device 77. The compressed image data is recorded in, for example, a flash memory or other auxiliary storage unit (not shown) via the control device 74 and the control unit 310.

  The above-described imaging function unit 200 is an example of a configuration suitable for the present invention, and the present invention is not limited to this.

  In other words, the camera module 50 that is an imaging device equipped with the zoom lens 10 is not limited to being built in the smartphone-type mobile communication terminal 300, but is built in a mobile phone, a PHS (Personal Handyphone System), or the like. Alternatively, it may be incorporated in a PDA (Personal Digital Assistant), a tablet personal computer, a mobile personal computer, a digital still camera, a video camera, or the like.

Hereinafter, numerical conditions satisfied by the zoom lens 10 of the embodiment shown in FIG. 1 will be described. The zoom lens 10 of FIG. 1 has the conditional expression (1) already described.
1.7 <n1n1 <2.1 (1)
Satisfied. Here, the value n1n1 indicates the refractive index of the lens L11 closest to the object side among the lenses on the image side of the reflective optical element PRM.

In the zoom lens 10 of the embodiment, in addition to the conditional expression (1), the conditional expression (2) already described.
30 <ν1n2-ν1p1 <65 (2)
Satisfied. However, the value ν1n2 indicates the Abbe number of the lens L12 having negative refractive power among the cemented lenses L1b of the first lens group Gr1, and the value ν1p1 is a positive value among the cemented lenses L1b of the first lens group Gr1. The Abbe number of a lens having a refractive power L13 is shown.

In the zoom lens 10 according to the embodiment, in addition to the conditional expression (1) and the like, the conditional expression (3) already described.
0.4 <d11 / fW <0.9 (3)
Satisfied. However, the value d11 is the distance from the vertex 12m of the object side surface 12a of the reflective optical element PRM (the surface closest to the object side of the first lens group Gr1) to the intersection 12n between the reflective surface 12b of the reflective optical element and the optical axis AX. The value fW indicates the focal length of the entire zoom lens 10 system at the wide angle end.

In the zoom lens 10 according to the embodiment, in addition to the conditional expression (1) and the like, the conditional expression (4) already described.
-4.0 <r1 / d1 <-2.0 (4)
Satisfied. However, the value r1 indicates the paraxial radius of curvature of the object side surface 12a of the reflective optical element PRM, and the value d1 indicates the distance d11 + d12 on the optical axis AX from the object side surface 12a of the reflective optical element PRM to the image side surface 12c.

In the zoom lens 10 of the embodiment, in addition to the conditional expression (1) and the like, the conditional expression (5) already described.
1.80 <nprm <2.20 (5)
Satisfied. However, the value nprm indicates the refractive index of the reflective optical element PRM.

In the zoom lens 10 according to the embodiment, in addition to the conditional expression (1) and the like, the conditional expression (6) already described.
23 <νprm <50 (6)
Satisfied. However, the value nprm indicates the Abbe number of the main body material (refractive medium that internally reflects the reflective optical element PRM).

〔Example〕
Examples of the zoom lens according to the present invention will be described below. Symbols used in each example are as follows.
f: Focal length of the entire zoom lens system Fno: F number 2Y: Diagonal length of the imaging surface of the solid-state imaging device R: Paraxial radius of curvature D: Spacing on the axial surface Nd: Refractive index νd of lens material with respect to d-line: Abbe of lens material Number d11: distance from the vertex of the object side surface of the reflecting optical element to the intersection of the reflecting surface of the reflecting optical element and the optical axis

ただし、
Ａｉ：ｉ次の非球面係数
Ｒ ：曲率半径
Ｋ ：円錐定数 In each embodiment, the surface described with “*” after each surface number (Surf.N) is a surface having an aspherical shape, and the aspherical shape has the apex of the surface as the origin and the optical axis direction. Is expressed by the following “Equation 1” where the height in the direction perpendicular to the optical axis is h. In addition, the symbol inf. Means infinity or ∞, and the symbol stop means aperture.
[Equation 1]

However,
Ai: i-order aspheric coefficient R: radius of curvature K: conic constant

  Specific examples of the zoom lens according to the present invention will be described below.

[Example 1]
The basic features of the zoom lens of Example 1 are as follows.
Zoom ratio = 2.85
Total lens length = 26.597
d11 = 2.48

Table 1 shows lens data of Example 1. In the following (including the lens data in the table), a power of 10 (for example, 2.5 × 10 ⁻⁰² ) is expressed using E (for example, 2.5E-02).
[Table 1]
[Curvature radius, surface spacing, etc.]
Surf.NR (mm) D (mm) Nd νd Effective radius (mm)
1 -14.220 5.380 2.00100 29.1 2.86
2 inf. 0.289 2.01
3 -11.007 0.400 1.88300 40.8 1.98
4 50.279 0.272 1.96
5 -14.495 0.400 1.49700 81.6 1.96
6 21.909 0.010 1.51400 42.8 1.99
7 21.909 0.835 1.92290 20.9 1.99
8 -20.134 gd1 2.00
9 (stop) inf. 0.250 2.01
10 * 5.898 1.830 1.72900 54.0 2.18
11 * -20.136 0.332 2.18
12 10.525 0.600 2.00070 25.5 2.13
13 4.307 0.010 1.51400 42.8 2.00
14 4.307 1.766 1.49710 81.6 2.00
15 * -10.055 0.150 1.98
16 inf.gd2 1.94
17 * 108.890 0.527 1.54470 56.2 1.85
18 * 4.002 gd3 1.82
19 * -15.701 1.706 1.54470 56.2 2.96
20 * -4.479 2.391 3.11
21 inf. 0.210 1.51680 64.2 2.98
22 inf. 0.640 2.97

[Aspheric coefficient]
10th page
K = 0.00000E + 00, A4 = -0.76329E-03, A6 = 0.12221E-03,
A8 = -0.87163E-04, A10 = 0.17294E-04, A12 = -0.13459E-05
11th page
K = 0.00000E + 00, A4 = 0.62456E-03, A6 = 0.79378E-04,
A8 = -0.10405E-03, A10 = 0.22536E-04, A12 = -0.18276E-05
15th page
K = 0.00000E + 00, A4 = 0.56987E-03, A6 = -0.17855E-03,
A8 = 0.20075E-03, A10 = -0.56274E-04, A12 = 0.55828E-05,
17th page
K = 0.00000E + 00, A4 = -0.18863E-02, A6 = 0.21678E-02,
A8 = -0.10897E-02, A10 = 0.13615E-03, A12 = 0.24439E-04,
A14 = -0.52397E-05
18th page
K = 0.00000E + 00, A4 = -0.27319E-02, A6 = 0.34476E-02,
A8 = -0.21257E-02, A10 = 0.53285E-03, A12 = -0.49042E-04,
A14 = -0.97401E-07
19th page
K = 0.00000E + 00, A4 = -0.91837E-03, A6 = 0.22291E-03,
A8 = 0.13428E-07, A10 = -0.15372E-05, A12 = 0.10398E-06
20th page
K = 0.00000E + 00, A4 = 0.15697E-02, A6 = 0.28684E-04,
A8 = 0.24545E-04, A10 = -0.28292E-05, A12 = 0.12938E-06

The focal length (f) of the entire system at each position (Po) 1 to 3 of the zoom lens according to the first embodiment, the F number (Fno), the angle of view, the diagonal length of the imaging surface (2Y), and the group interval (gd1 to gd3). ) Is shown in Table 2 below. Note that Po = 1 is the wide-angle end, Po = 2 is the middle, and Po = 3 is the telephoto end.
[Table 2]
Po f Fno angle of view 2Y
1 4.76 2.88 63.4 5.002
2 7.94 3.86 40.7 5.742
3 13.58 5.02 23.9 5.888

Po gd1 gd2 gd3
1 6.856 1.812 1.932
2 3.458 2.161 4.981
3 0.150 4.085 6.365

Data of each lens group of the zoom lens of Example 1 is shown in Table 3 below.
[Table 3]
Lens group Start surface Focal length (mm)
1 1 -7.10
2 9 5.75
3 17 -7.64
4 19 10.92

  FIG. 5 is a sectional view of the zoom lens of Example 1. FIG. The zoom lens 11 according to the first exemplary embodiment includes, in order from the object side, a first lens group Gr1, a second lens group Gr2, a third lens group Gr3, and a fourth lens group Gr4. Here, the first lens group Gr1 includes a reflective optical element PRM that is a right-angle prism having a concave surface on the object side, a negative first lens L11 that is biconcave, and a second negative lens L12 that is biconcave and negative. A biconvex positive third lens L13. Among these, the reflective optical element PRM is a right-angled prism that can bend a light beam incident on the object side surface 12a from the object side at a right angle. The second lens L12 and the third lens L13 are cemented lenses. The second lens group Gr2 includes an aperture stop S, a biconvex positive fourth lens L21, a negative meniscus fifth lens L22 convex toward the object side, and a biconvex positive sixth lens L23. Among these, the fifth lens L22 and the sixth lens L23 are cemented lenses. The third lens group Gr3 includes a seventh lens L31 that is close to plano-concave but convex to the object side and has a negative meniscus. The fourth lens group Gr4 includes a positive meniscus eighth lens L41 that is convex on the image side. In addition, the code | symbol F shows the parallel plate which assumed the optical low-pass filter, IR cut filter, the sealing glass of a solid-state image sensor, etc. Reference numeral I denotes an imaging surface that is a projection surface of the imaging device 51. These parallel plate F and imaging surface I are the same in the second and third embodiments described below, and will not be described in the future.

  6A to 6C respectively show the positions of the zoom lens 11 of the first embodiment during the zoom operation. 6A is a cross-sectional view at the wide-angle end of the zoom lens 11, FIG. 6B is a cross-sectional view at the middle, and FIG. 6C is a cross-sectional view at the telephoto end. In Example 1 and the following examples, the reflective optical element PRM is represented as a concave single lens having a rotationally symmetric shape equivalent to the optical path length.

  FIG. 7A is an aberration diagram (spherical aberration, astigmatism, and distortion aberration) at the wide-angle end of the zoom lens 11, and FIG. 7B is an intermediate aberration diagram (spherical aberration, astigmatism, and distortion aberration). FIG. 7C is an aberration diagram (spherical aberration, astigmatism, and distortion aberration) at the telephoto end. In the aberration diagrams and the subsequent aberration diagrams, in the spherical aberration diagram, the solid line represents the d line and the dotted line represents the g line, and in the astigmatism diagram, the solid line represents the sagittal image plane and the dotted line represents the meridional. It shall represent the image plane.

  In the zoom lens 11 of Example 1, the second lens group Gr2 moves to the object side along the optical axis AX direction during zooming from the wide-angle end to the telephoto end, and the third lens group Gr3 moves to the optical axis AX. Move to the object side along the direction. The other lens groups Gr1 and Gr4 are fixed during zooming, and zooming can be performed by changing the interval between the lens groups Gr1 to Gr4. Further, focusing from infinity to a finite distance can be performed by moving the third lens group Gr3. The fourth and sixth lenses L21 and L23 are assumed to be glass mold lenses, the seventh and eighth lenses L31 and L41 are assumed to be plastic lenses, and the other lenses are assumed to be polished lenses made of a glass material.

[Example 2]
The basic features of the zoom lens of Example 2 are as follows.
Zoom ratio = 2.86
Total lens length = 25.722
d11 = 2.573

Table 4 shows lens data of Example 2.
[Table 4]
[Curvature radius, surface spacing, etc.]
surf.NR (mm) D (mm) Nd νd Effective radius (mm)
1 -15.964 5.573 2.00100 29.1 3.08
2 inf. 0.248 2.17
3 -15.428 0.400 1.92290 20.9 2.14
4 22.433 0.405 2.08
5 -13.249 0.445 1.59350 67.0 2.07
6 10.956 0.010 1.51400 42.8 2.07
7 10.956 1.011 1.92290 20.9 2.07
8 * -19.241 gd1 2.05
9 (stop) inf. 0.000 1.91
10 * 3.448 1.826 1.55330 71.7 2.05
11 * -5.644 1.096 2.01
12 27.513 0.600 2.00100 29.1 1.59
13 2.130 0.010 1.51400 42.8 1.41
14 2.130 2.000 1.88200 37.2 1.41
15 * 3.452 gd2 1.20
16 * 8.487 1.200 1.90270 31.0 2.95
17 * 17.319 gd3 2.92
18 inf. 0.210 1.51680 64.2 2.86
19 inf.0.100 2.87

[Aspheric coefficient]
8th page
K = 0.00000E + 00, A4 = -0.41440E-03, A6 = 0.27136E-03,
A8 = -0.75125E-04, A10 = 0.87893E-05, A12 = -0.17903E-06
10th page
K = 0.00000E + 00, A4 = -0.36785E-02, A6 = -0.61427E-04,
A8 = -0.20845E-04, A10 = -0.66845E-05
11th page
K = 0.00000E + 00, A4 = 0.38619E-02, A6 = -0.27218E-03,
A8 = -0.31015E-05, A10 = -0.46493E-05
15th page
K = 0.00000E + 00, A4 = -0.84124E-03, A6 = 0.40339E-02,
A8 = -0.41822E-02, A10 = 0.28159E-02, A12 = -0.68662E-03
16th page
K = 0.00000E + 00, A4 = -0.13295E-02, A6 = -0.13300E-02,
A8 = 0.35712E-03, A10 = -0.32673E-04, A12 = 0.10650E-05
17th page
K = 0.00000E + 00, A4 = -0.22083E-02, A6 = -0.15464E-02,
A8 = 0.38031E-03, A10 = -0.32553E-04, A12 = 0.96962E-06

The focal length (f) of the entire system at each position (Po) 1 to 3 of the zoom lens according to the second embodiment, the F number (Fno), the angle of view, the diagonal length of the imaging surface (2Y), the group interval, and the like (gd1 to gd3) is shown in Table 5 below. Note that Po = 1 is the wide-angle end, Po = 2 is the middle, and Po = 3 is the telephoto end.
[Table 5]
Po f Fno angle of view 2Y
1 4.74 2.88 63.6 5.010
2 8.04 4.09 40.2 5.642
3 13.58 5.38 24.5 5.719

Po gd1 gd2 gd3
1 6.52 2.45 1.62
2 3.63 6.01 0.95
3 0.30 1.71 8.58

Data for each lens group of the zoom lens of Example 2 is shown in Table 6 below.
[Table 6]
Lens group Start surface Focal length (mm)
1 1 -7.66
2 9 5.65
3 16 17.32

  8A to 8C are cross-sectional views of the zoom lens according to the second embodiment, and illustrate positions during the zoom operation of the zoom lens 12 according to the second embodiment. 8A is a cross-sectional view at the wide-angle end of the zoom lens 12, FIG. 8B is a cross-sectional view at the middle, and FIG. 8C is a cross-sectional view at the telephoto end.

  The zoom lens 12 according to the second exemplary embodiment includes, in order from the object side, a first lens group Gr1, a second lens group Gr2, and a third lens group Gr3. Here, the first lens group Gr1 includes a reflective optical element PRM that is a right-angle prism having a concave surface on the object side, a negative first lens L11 that is biconcave, and a second negative lens L12 that is biconcave and negative. A biconvex positive third lens L13. Among these, the reflective optical element PRM is a right-angled prism that can bend a light beam incident on the object side surface 12a from the object side at a right angle. The second lens L12 and the third lens L13 are cemented lenses. The second lens group Gr2 includes an aperture stop S, a biconvex positive fourth lens L21, a negative meniscus fifth lens L22 convex toward the object side, and a positive meniscus sixth lens L23 convex toward the object side. including. Among these, the fifth lens L22 and the sixth lens L23 are cemented lenses. The third lens group Gr3 includes a seventh lens L31 that is close to a convex flat surface but is convex toward the object side and has a negative meniscus. In addition, the zoom lens 12 includes a parallel plate F that is a filter or the like.

  9A is an aberration diagram (spherical aberration, astigmatism, and distortion aberration) at the wide-angle end of the zoom lens 12, and FIG. 9B is an intermediate aberration diagram (spherical aberration, astigmatism, and distortion aberration). FIG. 9C is an aberration diagram (spherical aberration, astigmatism, and distortion aberration) at the telephoto end.

  In the zoom lens 12 of Example 2, the second lens group Gr2 moves toward the object side along the direction of the optical axis AX and the third lens group Gr3 moves to the optical axis AX when zooming from the wide-angle end to the telephoto end. After moving slightly to the image side along the direction, it moves to the object side. The other lens group Gr1 is fixed at the time of zooming, and zooming can be performed by changing the interval between the lens groups Gr1 to Gr3. Further, focusing from infinity to a finite distance can be performed by moving the third lens group Gr3. The first, third, fourth, sixth, and seventh lenses L11, L13, L21, L23, and L31 are assumed to be glass mold lenses, and the other lenses are assumed to be polished lenses made of a glass material.

Example 3
The basic features of the zoom lens of Example 3 are as follows.
Zoom ratio = 2.85
Total lens length = 29.799
d11 = 2.810

Table 7 shows lens data of Example 3.
[Table 7]
[Curvature radius, surface spacing, etc.]
Surf.NR (mm) D (mm) Nd νd Effective radius (mm)
1 -19.922 6.022 1.88100 40.1 3.39
2 inf. 0.329 2.18
3 -10.797 0.400 1.91082 35.3 2.13
4 32.208 0.383 2.08
5 -18.139 0.600 1.49700 81.6 2.06
6 18.207 0.010 1.51400 42.8 2.03
7 18.207 0.828 1.92286 20.9 2.03
8 -29.659 gd1 2.00
9 (stop) inf. 0.000 1.99
10 * 6.317 1.797 1.72903 54.0 2.08
11 * -25.113 0.459 2.09
12 12.357 0.400 1.84666 23.8 2.05
13 4.816 0.010 1.51400 42.8 1.98
14 4.816 1.685 1.49710 81.6 1.98
15 * -9.436 0.150 1.96
16 inf.gd2 1.92
17 * 867.545 0.600 1.54470 56.2 1.83
18 * 4.125 gd3 1.81
19 * -19.559 1.679 1.54470 56.2 2.99
20 * -4.794 2.577 3.13
21 inf. 0.210 1.51680 64.2 2.98
22 inf. 0.640 2.97

[Aspheric coefficient]
10th page
K = 0.00000E + 00, A4 = -0.55874E-03, A6 = 0.11736E-03,
A8 = -0.86892E-04, A10 = 0.17973E-04, A12 = -0.14760E-05
11th page
K = 0.00000E + 00, A4 = 0.62200E-03, A6 = 0.60228E-04,
A8 = -0.97981E-04, A10 = 0.21680E-04, A12 = -0.18463E-05
15th page
K = 0.00000E + 00, A4 = 0.74033E-03, A6 = -0.83221E-04,
A8 = 0.14025E-03, A10 = -0.38797E-04, A12 = 0.38536E-05
17th page
K = 0.00000E + 00, A4 = -0.20482E-02, A6 = 0.20319E-02,
A8 = -0.99136E-03, A10 = 0.13594E-03, A12 = 0.21331E-04,
A14 = -0.52397E-05
18th page
K = 0.00000E + 00, A4 = -0.26571E-02, A6 = 0.29448E-02,
A8 = -0.18182E-02, A10 = 0.47887E-03, A12 = -0.47099E-04,
A14 = -0.97401E-07
19th page
K = 0.00000E + 00, A4 = -0.51998E-03, A6 = 0.17546E-03,
A8 = -0.98627E-06, A10 = -0.13045E-05, A12 = 0.80632E-07
20th page
K = 0.00000E + 00, A4 = 0.15930E-02, A6 = 0.94073E-05,
A8 = 0.22080E-04, A10 = -0.25856E-05, A12 = 0.10389E-06

The focal length (f) of the entire system at each position (Po) 1 to 3 of the zoom lens according to the third embodiment, the F number (Fno), the angle of view, the diagonal length of the imaging surface (2Y), and the group interval (gd1 to gd3). ) Is shown in Table 2 below. Note that Po = 1 is the wide-angle end, Po = 2 is the middle, and Po = 3 is the telephoto end.
[Table 8]
Po f Fno angle of view 2Y
1 4.76 2.88 63.4 5.001
2 7.94 3.86 40.7 5.748
3 13.58 5.04 23.9 5.888

Po gd1 gd2 gd3
1 7.334 1.820 1.868
2 3.817 2.100 5.105
3 0.400 3.800 6.822

Data for each lens group of the zoom lens of Example 3 is shown in Table 9 below.
[Table 9]
Lens group Start surface Focal length (mm)
1 1 -7.45
2 9 5.78
3 17 -7.61
4 19 11.21

  10A to 10C are cross-sectional views of the zoom lens 13 according to the embodiment, and illustrate positions during the zoom operation of the zoom lens 13 according to the third embodiment. 10A is a cross-sectional view at the wide-angle end of the zoom lens 13, FIG. 10B is a cross-sectional view at the middle, and FIG. 10C is a cross-sectional view at the telephoto end.

  The zoom lens 13 of Example 3 includes, in order from the object side, a first lens group Gr1, a second lens group Gr2, a third lens group Gr3, and a fourth lens group Gr4. Here, the first lens group Gr1 includes a reflective optical element PRM that is a right-angle prism having a concave surface on the object side, a negative first lens L11 that is biconcave, and a second negative lens L12 that is biconcave and negative. A biconvex positive third lens L13. Among these, the reflective optical element PRM is a right-angled prism that can bend a light beam incident on the object side surface 12a from the object side at a right angle. The second lens L12 and the third lens L13 are cemented lenses. The second lens group Gr2 includes an aperture stop S, a biconvex positive fourth lens L21, a negative meniscus fifth lens L22 convex toward the object side, and a biconvex positive sixth lens L23. Among these, the fifth lens L22 and the sixth lens L23 are cemented lenses. The third lens group Gr3 includes a seventh lens L31 that is close to plano-concave but convex to the object side and has a negative meniscus. The fourth lens group Gr4 includes a positive meniscus eighth lens L41 that is convex on the image side. In addition, the zoom lens 13 includes a parallel plate F that is a filter or the like.

  FIG. 11A is an aberration diagram (spherical aberration, astigmatism, and distortion aberration) at the wide-angle end of the zoom lens 13, and FIG. 11B is an intermediate aberration diagram (spherical aberration, astigmatism, and distortion aberration). FIG. 11C is an aberration diagram (spherical aberration, astigmatism, and distortion aberration) at the telephoto end.

  In the zoom lens 13 according to the third exemplary embodiment, the second lens group Gr2 moves toward the object side along the optical axis AX during zooming from the wide-angle end to the telephoto end, and the third lens group Gr3 moves to the optical axis AX. Move to the object side along the direction. The other lens groups Gr1 and Gr4 are fixed during zooming, and zooming can be performed by changing the interval between the lens groups Gr1 to Gr4. Further, focusing from infinity to a finite distance can be performed by moving the third lens group Gr3. The fourth and sixth lenses L21 and L23 are assumed to be glass mold lenses, the seventh and eighth lenses L31 and L41 are assumed to be plastic lenses, and the other lenses are assumed to be polished lenses made of a glass material.

以上では、実施形態や実施例に即して本発明を説明したが、本発明は、上記実施形態等に限定されるものではない。 Table 10 below summarizes the values of Examples 1 to 3 corresponding to the conditional expressions (1) to (6) for reference.
[Table 10]

In the above, the present invention has been described based on the embodiments and examples, but the present invention is not limited to the above-described embodiments and the like.

  For example, in the first and third embodiments, the plastic lens in which the inorganic particles are dispersed is used for the production of plastic lenses such as the seventh and eighth lenses L31 and L41 of the lens groups Gr3 and Gr4. It is possible to further suppress the image point position fluctuation when the system temperature changes.

  Recently, it has been found that by mixing inorganic fine particles in a plastic material, the temperature change of the plastic material can be reduced. In detail, when fine particles are mixed with a transparent plastic material in general, light scattering occurs and the transmittance decreases, so that it was difficult to use as an optical material. By making it smaller than the wavelength, it is possible to substantially prevent scattering. The refractive index of the plastic material decreases with increasing temperature, but the refractive index of inorganic particles increases with increasing temperature. Therefore, it is possible to make almost no change in the refractive index by using these temperature dependencies so as to cancel each other. Specifically, by dispersing inorganic particles having a maximum length of 20 nanometers or less in a plastic material as a base material, a plastic material with extremely low temperature dependency of the refractive index is obtained. For example, by dispersing fine particles of niobium oxide (Nb2O5) in acrylic, the refractive index change due to temperature change can be reduced. In the present invention, by using a plastic material in which such inorganic particles are dispersed in a plastic lens such as the lenses L31 and L41 in the first and third embodiments, the image point position fluctuation at the time of temperature change of the entire zoom lens system. Can be kept smaller.

  In Examples 1 and 3, an energy curable resin may be used for manufacturing plastic lenses such as the seventh and eighth lenses L31 and L41 of the lens groups Gr3 and Gr4.

  In recent years, as a method for mounting an image pickup apparatus at a low cost and in large quantities, a reflow process (heating process) is performed on a substrate on which solder is previously potted while an IC chip or other electronic component and an optical element are placed on the substrate. A technique has been proposed in which an electronic component and an optical element are simultaneously mounted on a substrate by melting the substrate. In order to perform mounting using such a reflow process, it is necessary to heat the optical element to about 200 to 260 ° C. together with the electronic component. At such a high temperature, a lens using a thermoplastic resin is not suitable. There is a problem that the optical performance deteriorates due to thermal deformation or discoloration. As one of the methods for solving such a problem, a technology has been proposed that uses a glass mold lens having excellent heat resistance and achieves both miniaturization and optical performance in a high temperature environment. The cost is generally higher than the lens used. Therefore, by using an energy curable resin as the material of the zoom lens (specifically, for example, the seventh and eighth lenses L31 and L41), compared to a lens using a thermoplastic resin such as polycarbonate or polyolefin. Because the optical performance degradation when exposed to high temperatures is small, it is effective for reflow processing, is easier to manufacture than glass mold lenses, is inexpensive, and the low cost and mass productivity of an imaging device incorporating a zoom lens can be achieved. Can be compatible. The energy curable resin refers to both a thermosetting resin and an ultraviolet curable resin.

  It should be noted that the present invention is not limited to the examples described in the specification, and that other examples and modifications are included in the art based on the examples and ideas described in the present specification. It is obvious to For example, even when a dummy lens having substantially no power is further provided, it is within the scope of the present invention.

  AX: Optical axis, F: Parallel plate, Gr1 to Gr4: Lens group, I: Imaging surface, L11, L12, L13: First group lens, L21, L12, L23: Second group lens, L31: Third Group lens, L41 ... Fourth lens group, OP ... Aperture, PRM ... Reflective optical element, Zoom lenses 11, 12, 13, 50 ... Camera module, 51 ... Imaging element, 51a ... Photoelectric conversion unit, 54 ... Mirror Tube unit, 55a, 55b ... drive mechanism, 74 ... control device, 77 ... image sensor drive device, 78 ... image storage device, 105a ... optical system drive circuit unit, 200 ... imaging function unit, 300 ... mobile communication terminal

Claims (16)

In order from the object side, at least a first lens group having a negative refractive power and a second lens group having a positive refractive power are provided,
A zoom lens that performs zooming by changing the interval between each lens group,
The first lens group includes a reflective optical element that bends the optical path by reflecting a light beam closest to the object side;
The object side surface of the reflective optical element is a concave surface,
The zoom lens, wherein the first lens group includes at least two lenses having negative refractive power on the image side of the reflective optical element.   2. The zoom lens according to claim 1, wherein the first lens group includes a lens having a negative refractive power closest to the object side on the image side of the reflective optical element. The zoom lens according to claim 1, wherein the zoom lens satisfies the following condition.
1.7 <n1n1 <2.1 (1)
n1n1: Of the lenses on the image side of the reflective optical element, the refractive index of the lens closest to the object side   The first lens group includes, on the image side of the reflective optical element, a single lens having negative refractive power, and a cemented lens in which a lens having negative refractive power and a lens having positive refractive power are combined. The zoom lens according to any one of claims 1 to 3. The zoom lens according to claim 4, wherein the zoom lens satisfies the following condition.
30 <ν1n2-ν1p1 <65 (2)
However,
ν1n2: Abbe number of the lens having negative refractive power among the cemented lenses of the first lens group ν1p1: Abbe number of the lens having positive refractive power among the cemented lenses of the first lens group The zoom lens according to claim 1, wherein the zoom lens satisfies the following condition.
0.4 <d11 / fW <0.9 (3)
However,
d11: distance from the vertex of the object side surface of the reflecting optical element to the intersection of the reflecting surface of the reflecting optical element and the optical axis fW: focal length of the entire system at the wide angle end The zoom lens according to claim 1, wherein the zoom lens satisfies the following condition.
-4.0 <r1 / d1 <-2.0 (4)
However,
r1: Paraxial radius of curvature of the object side surface of the reflective optical element d1: Distance on the optical axis from the object side surface of the reflective optical element to the image side surface   The zoom lens according to claim 1, wherein an image side surface of the reflective optical element is a flat surface. The zoom lens according to any one of claims 1 to 8, wherein the following conditional expression is satisfied.
1.80 <nprm <2.20 (5)
However,
nprm: refractive index of the reflective optical element The zoom lens according to any one of claims 1 to 9, wherein the following conditional expression is satisfied.
23 <νprm <50 (6)
However,
νprm: Abbe number of the reflecting optical element   The zoom lens includes, in order from the object side, the first lens group having a negative refractive power, the second lens group having a positive refractive power, a third lens group having a negative refractive power, and a positive lens The zoom lens according to claim 1, comprising a fourth lens group having a refractive power.   The zoom lens includes, in order from the object side, the first lens group having a negative refractive power, the second lens group having a positive refractive power, and a third lens group having a positive refractive power. The zoom lens according to any one of claims 1 to 10.   The zoom lens according to claim 11, wherein the third lens group moves in the optical axis direction when focused.   The zoom lens according to claim 11, wherein the fourth lens group does not move in the optical axis direction at the time of zooming and focusing.   The zoom lens according to claim 1, further comprising a lens having substantially no power. The zoom lens according to any one of claims 1 to 15,
An image sensor that photoelectrically converts an image formed on the imaging surface by the zoom lens;
An imaging apparatus comprising:

Images