JP2005292763A - Zoom lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a zoom lens whose number of optical element groups to be driven is made less, whose size is reduced and whose moving mechanism is made simple by including a liquid optical element in a lens system made of a plurality of lenses. <P>SOLUTION: When a zooming operation is performed, power supply circuit 31 computes a required amount of compensation with a zooming signal (or by referring to a table) and applies a prescribed voltage to a liquid optical element QL. By controlling as above, the liquid optical element QL changes its optical power to a desired level so as to realize a compensation operation. Thus, no mechanism is required to move a first lens group G1 to an optical axis, and consequently, the composition is made simple and the size is reduced. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a small zoom lens used for a solid-state imaging device such as a CCD image sensor or a CMOS image sensor.

  In recent years, along with the improvement in performance and size of solid-state imaging devices such as CCD (Charged Coupled Device) type image sensors or CMOS (Complementary Metal Oxide Semiconductor) type image sensors, ultra-small digital cameras and imaging devices have been developed. Mobile phones equipped with the device, PDA (Personal Digital Assistance) are becoming widespread, and further, there is an increasing demand for mounting zoom lenses on these imaging devices.

By the way, in a general zoom lens, it is necessary to move all or part of the lens group constituting the imaging lens. For example, in the case of a three-group zoom lens, the variator group that changes the focal length, the compensator group that corrects the accompanying focus movement, and the focus group that corrects the focus movement that changes the object distance, or the variator group, The lens group is divided into three groups, such as a pensator and a group having a focus action, and a fixed group, and a predetermined lens group among the lens groups is moved in the coaxial direction to perform zooming and focus adjustment. . As a specific example of such a zoom optical system, a zoom lens that performs zooming and focus adjustment by moving two groups or three groups is disclosed (see Patent Document 1).
JP 2002-350726 A JP 2003-98435 A

  However, when performing zooming and focusing by moving a plurality of lens groups in the coaxial direction as in Patent Document 1, it is necessary to provide a mechanical mechanism for moving these lens groups. In addition, there is a problem that a large space is required to provide the mechanical mechanism.

  On the other hand, there is known a zoom lens in which the number of moving groups is reduced by using a refractive power variable element, and this element is loaded with a focus movement correction function associated with zooming or object distance change. As a specific example of such a zoom lens, a zoom lens using a reflective refractive power variable element is also disclosed (see Patent Document 2).

  However, astigmatism using a reflection type optical element as in Patent Document 2, aberrations that are asymmetrical with respect to the coaxial axis are generated, and it is difficult to control the reflecting surface such as a free-form surface in order to correct the aberration. I have to face it. Also, there is a problem that the refractive power cannot be finely adjusted depending on the refractive power variable element.

  The present invention has been made in view of such conventional problems. By including a liquid optical element in a lens system including a plurality of lenses, the number of optical element groups to be driven is small, and the mechanical mechanism is small. An object is to provide a simple zoom lens.

  The zoom lens according to claim 1 is a zoom lens including an optical element group that moves at the time of zooming. The second liquid that is electrically conductive or polar and the first liquid does not mix with each other. The liquid is hermetically contained in a container so that the interface has a predetermined shape, and a voltage is applied between the first liquid and the electrode provided in the container, whereby the curvature radius of the interface is increased. It has a liquid optical element that is adjusted to adjust its refractive power.

  When the liquid optical element is used as a constituent element, by adjusting the refractive power by changing the radius of curvature of the interface, the compensation action for correcting the focus movement accompanying the magnification change and the focus movement accompanying the change in the object distance are corrected. Since the focusing action can be realized, the amount of movement of the optical element group that moves for compensation and focusing can be kept small, or the optical element group that requires a mechanical drive mechanism can be only the variable power group, A zoom lens with a small number of optical elements to be driven and a simple mechanical mechanism can be obtained.

  In particular, the liquid optical element can change the refractive power in multiple steps or without a step, so that the focus can be adjusted more appropriately.

  A zoom lens according to a second aspect of the present invention is the zoom lens according to the first aspect, wherein the liquid optical element is arranged in an optical element group including a diaphragm. It can be made small, and a small zoom lens can be obtained.

  The zoom lens according to a third aspect is the zoom lens according to the first aspect, wherein when the optical element group including the liquid optical element does not include a diaphragm, the zoom lens is located at a position closest to the diaphragm in the optical system element group. Since the liquid optical element is arranged, the outer diameter of the liquid optical element can be reduced, and a small zoom lens can be obtained.

  The zoom lens according to a fourth aspect is characterized in that, in the invention according to any one of the first to third aspects, there is only one optical element group that moves at the time of zooming. A zoom lens with a small mechanical mechanism can be obtained.

  A zoom lens according to a fifth aspect of the present invention is the optical system according to any one of the first to fourth aspects, wherein an optical element group including the liquid optical element is fixed in an optical axis direction, and includes the liquid optical element. The element group has a compensatory action for correcting a focus movement caused by zooming and a focus action for correcting a focus movement caused by a change in object distance.

  The optical element group including the liquid optical element is fixed in the optical axis direction, and the liquid optical element corrects the focus movement accompanying the magnification change and the focus action corrects the focus movement accompanying the object distance change. The amount of movement of the moving optical element group can be kept small, or the optical element group requiring a mechanical drive mechanism can be limited to the zooming group. A zoom lens with a simple mechanical configuration can be obtained, and compared to a case where an optical element group including the liquid optical element moves, a wiring mechanism of a flexible cable for the liquid optical element, a mechanical mechanism, etc. Can be further simplified.

  7. The zoom lens according to claim 6, wherein the zoom lens includes an optical element group that moves at the time of zooming. The at least one optical element group that moves at the time of zooming includes a conductive or polar first liquid. And a second liquid that does not mix with the first liquid in a container so that the interface has a predetermined shape, and the first liquid and an electrode provided in the container; A liquid optical element that adjusts the refractive power by changing the radius of curvature of the interface by applying a voltage between the optical element group, and the optical element group that includes the liquid optical element has a zooming action and a distance between objects. It has a compensatory action for correcting the focus movement accompanying the change of the distance and a focus action for correcting the focus movement accompanying the change of the object distance.

  When the liquid optical element is a constituent element, the zooming action, the compensation action for correcting the focus movement accompanying the change in the distance between the object images, and the focusing action for correcting the focus movement accompanying the change in the object distance are performed. Because it can be realized, the amount of movement of the zooming group during zooming is reduced, and the amount of movement of the moving optical element group is required to correct the focus movement accompanying the zooming and object distance change, or a mechanical drive mechanism is required. Therefore, the zoom lens can be a zoom lens with a small number of optical element groups to be driven or a small and simple mechanical mechanism without driving optical element groups. Here, “having a zooming action” means that the absolute value of the refractive power of the optical element group (here, the optical element group including the liquid optical element) to be zoomed is longer than the short focal length end. It means to grow.

  According to a seventh aspect of the present invention, in the zoom lens according to the sixth aspect, the optical element group including the liquid optical element includes a stop, so that the outer diameter of the liquid optical element is reduced. Thus, a small zoom lens can be obtained.

  A zoom lens according to an eighth aspect of the present invention is the zoom lens according to any one of the first to seventh aspects, wherein the electromechanical conversion element, a driving member fixed to one end of the electromechanical conversion element, and the zoom lens move during the magnification change. A movable member connected to the optical element group that is movably held on the drive member, and the electromechanical conversion element is repeatedly expanded and contracted at different speeds in the extending direction and the contracting direction. And a driving means adapted to move the movable member.

  In the driving means, the electromechanical conversion element is deformed so as to be slightly expanded or contracted by applying a driving voltage such as a sawtooth-shaped pulse to the electromechanical conversion element for a very short time. However, the speed of expansion or contraction can be changed depending on the shape of the pulse. Here, when the electromechanical conversion element is deformed at a high speed in the extending or contracting direction, the movable member does not follow the operation of the driving member due to the inertia of the mass and remains in the same position. On the other hand, when the electromechanical conversion element is deformed in the opposite direction at a slower speed, the movable member moves following the operation of the drive member by the friction force acting therebetween. Therefore, when the electromechanical conversion element repeats expansion and contraction, the movable member can continuously move in one direction. That is, by using the driving means of the present invention having high responsiveness, the optical element group that moves at the time of zooming can be moved at a high speed and can be moved by a minute amount. Further, in the case where the optical element group moving at the time of zooming is held at a fixed position, if the power supply to the electromechanical conversion element is interrupted, it acts between the movable member and the drive member. Since it is held by frictional force, it can save energy. In addition, the structure of the driving means is advantageous in that it is simple and can be reduced in size and is low in cost.

  According to the present invention, by including a liquid optical element in a lens system composed of a plurality of lenses, it is possible to provide a zoom lens with a small number of optical element groups to be driven, a small size, and a simple mechanical mechanism.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1A and 1B are cross-sectional views of the zoom lens according to the first embodiment, in which FIG. 1A is in a short focal length end state, FIG. 1B is in an intermediate position state, and FIG. It is in the distance end state. Here, the zoom lens according to the present embodiment includes lens groups G1 to G3 in order to form a subject image on the image sensor CCD. The first lens group G1 includes a negative first lens L1 and a liquid optical element QL, and is fixed to a lens frame (not shown). The second lens group G2 includes a stop S, a positive second lens L2, a positive third lens L3, and a negative fourth lens L4, and is integrally formed in the optical axis direction by a driving source (not shown). It is movable. The third lens group G3 includes a positive fifth lens L5, and is fixed to a lens frame (not shown).

  FIG. 2 is a schematic configuration diagram of the liquid optical element QL and its driving unit. QL represents the liquid optical element according to the present embodiment. Reference numeral 40 denotes a lower container formed of a nonconductor. A first recess 41 is formed in the peripheral portion of the bottom surface (the right inner surface in the figure) of the lower container 40, and the first sealing plate 2 is disposed on the inner diameter side (center side) than this. The 2nd recessed part 42 to hold | maintain is formed. The first sealing plate (member for sealing the liquid) 2 is made of transparent acrylic or glass.

  A second electrode ring 43 is provided on the entire inner periphery of the peripheral wall of the lower container 40, and the surface of the second electrode ring 43 is made of an acrylic resin or the like that also covers the electrode end face 43a. An insulating layer 44 is formed in close contact.

  Here, the peripheral wall portion of the lower container 40 is inclined with respect to the optical axis X so that the right end side is closer to the optical axis X than the left end side in the drawing. For this reason, the first electrode ring 43 and the insulating layer 44 are both inclined with respect to the optical axis X.

  Further, the thickness of the insulating layer 44 gradually increases toward the right in the figure. Further, the water repellent layer 11 is formed by applying a water repellent treatment agent below the entire inner circumference of the insulating layer 44. Further, a hydrophilic treatment agent is applied to the left side of the entire inner circumference of the insulating layer 44 to form the hydrophilic layer 12.

  Reference numeral 50 denotes an upper container formed of a non-conductor, and holds a second sealing plate (member for sealing liquid) 6 formed of transparent acrylic or glass on the inner diameter side thereof. A sheet-like first electrode ring 51 is formed in close contact with the right end surface of the peripheral portion of the upper container 50.

  An insulating layer 52 is formed in close contact with the surface of the first electrode ring 51. The insulating layer 52 is insulated so as to have an exposed portion 51a for contacting the first liquid 21 described later and applying a voltage thereto. The layer 52 is formed so as to cover only the outer edge side of the first electrode ring 51.

  Then, the peripheral wall portion of the lower container 40 and the upper container 50 are sealed in a liquid-tight manner, thereby being surrounded by the lower container 40, the upper container 50, the first sealing plate 2, and the second sealing plate 6. A container having a predetermined volume of liquid chamber is formed.

  This container has an axisymmetric shape with respect to the optical axis X. The liquid chamber is filled with two types of liquids as follows.

  First, in the state where the optical axis X of the lower container 40 to which the first sealing plate 2 is attached is oriented in the vertical direction, the upper surface of the first sealing plate 2 that is the bottom surface of the liquid chamber and the peripheral side of the lower container 40 The second liquid 22 is dripped onto the bottom surface of these layers (which correspond to the interface-facing surfaces) by an amount so that the height of the liquid column is intermediate between the water-repellent film 11 on the peripheral wall portion.

  The second liquid 22 is a colorless and transparent silicone oil having a specific gravity of 1.06 and a refractive index of 1.45 at room temperature. Subsequently, the remaining space in the liquid chamber is filled with the first liquid 21. The first liquid 21 is an electrolyte solution (conductive or polar) having a specific gravity of 1.06 and a refractive index of 1.35 at room temperature, in which water and ethyl alcohol are mixed at a predetermined ratio and a predetermined amount of salt is added. A liquid).

  That is, as the first and second liquids 21 and 22, liquids having the same specific gravity, different refractive indexes, and incompatible with each other (insoluble) are selected. And both the liquids 21 and 22 form the interface 24, and each exists independently, without mixing.

  The shape of the interface 24 is determined by the balance of the three interfacial tensions acting on the inner surface of the liquid chamber (container), the three substances of the first liquid 21 and the second liquid 22, that is, the outer edge of the interface 24. Then, two types of liquids are sealed by attaching the upper container 50 to which the second sealing plate 6 is attached to the lower container 40.

  Reference numeral 31 denotes a power supply circuit connected to the first electrode ring 25 and the second electrode ring 3.

  Two amplifiers (not shown) of the power feeding circuit 31 are respectively connected to the first electrode ring 51 and the second electrode ring 43 along the right end surface of the upper container 50 in the direction orthogonal to the optical axis 51b, 43b.

  In the above configuration, when a voltage is applied to the first liquid 21 via the first electrode ring 51 and the second electrode ring 43, the interface 24 is deformed by a so-called electrowetting effect.

  Next, the deformation of the interface 24 in the liquid optical element QL and the optical action caused by this deformation will be described.

  First, when no voltage is applied to the first liquid 21, as shown in FIG. 2, the shape of the interface 24 is such that the interface tension between the two liquids 21 and 22, the first liquid 21 and the insulating layer 44. It is determined by the interfacial tension between the water repellent film 11 or the hydrophilic film 12, the interfacial tension between the second liquid 22 and the water repellent film 11 or the hydrophilic film 12 on the insulating layer 44, and the volume of the second liquid 22.

  On the other hand, when a voltage is applied to the first liquid 21 from the power supply circuit 31, the interfacial tension between the first liquid 21 and the hydrophilic film 12 decreases due to the electrowetting effect, and the first liquid 21 becomes the hydrophilic film 12. Over the boundary between the water repellent film 11 and the water repellent film 11. As a result, the height of the second liquid 22 on the optical axis increases.

  In this way, the application of voltage to the first liquid 21 through the first and second electrode rings 51 and 43 changes the balance of the interface tension between the two liquids, and the interface 24 between the two liquids 21 and 22 changes. The shape changes. In this way, an optical element that can freely change the shape of the interface 24 by controlling the voltage of the power feeding circuit 31 can be realized.

  Further, since the first and second liquids 21 and 22 have different refractive indexes, optical power (1 / f: f is a focal length) as an optical lens is given, that is, liquid optics. The focal length of the element QL changes due to a change in the shape of the interface 24.

  The operation of the zoom lens according to the present embodiment will be described. When zoom driving is performed from the short focal length end to the long focal length end, the second lens group G2 is moved from the position shown in FIG. It passes through the position shown in (b) and is driven in the optical axis direction to the position shown in (c). The zoom drive from the long focal length end to the short focal length end is reversed. Here, according to the conventional zoom lens, it is necessary to move the first lens group G1 in the optical axis direction in accordance with the movement of the second lens group G2 in the optical axis direction in order to perform the compensatory action. Therefore, in order to drive the first lens group G1 in the optical axis direction, it is necessary to provide a cam mechanism or the like, resulting in a complicated configuration and an increase in the size of an image pickup apparatus equipped with a zoom lens.

  On the other hand, according to the zoom lens of the present embodiment, if the zoom operation of the zoom lens in FIG. 1 is performed, the power feeding circuit 31 calculates a necessary compensation amount from the zoom signal (or refers to the table). Then, a predetermined voltage is applied to the liquid optical element QL. By controlling in this way, the liquid optical element QL can change the optical power as desired to realize a compensatory action. Therefore, a mechanism for moving the first lens group G1 in the optical axis direction is not required, and the configuration can be simplified and made compact. The change in optical power is preferably multistage, and more preferably continuous.

  According to the conventional zoom lens, the movement amount of the second lens group G2 in the optical axis direction and the movement amount of the first lens group G1 in the optical axis direction have a one-to-one correspondence depending on the cam shape. Since the object distance is variable at the time of actual imaging, for example, the third lens group G3 is displaced in the direction of the optical axis in order to focus on the light receiving surface of the imaging device CCD or the like, thereby performing a so-called focusing action. Realized. In such a case, it is necessary to provide a separate driving mechanism for the third lens group G3, which leads to a complicated configuration and an increase in size.

  On the other hand, in the present embodiment, the power feeding circuit 31 includes a signal from the image sensor CCD or a distance measurement signal from a distance measuring device (not shown) and a zoom signal (or an amount of movement in the optical axis direction of the second lens group G2). ), The shape of the liquid optical element QL can be changed so that the compensating action and the focusing action can be realized simultaneously (further, a part of the zooming action may be borne). In such a case, there is an advantage that it is not necessary to displace the third lens group G3 in the optical axis direction.

  3A and 3B are cross-sectional views of the zoom lens according to the second embodiment, in which FIG. 3A is in a short focal length end state, FIG. 3B is in an intermediate position state, and FIG. It is in the distance end state. Here, the zoom lens according to the present embodiment includes lens groups G1 to G3 in order to form a subject image on the image sensor CCD. The first lens group G1 includes a negative first lens L1 and a positive second lens L2, and is fixed to a lens frame (not shown). The second lens group G2 includes a diaphragm S, a liquid optical element QL, a positive third lens L3, and a negative fourth lens L4, and can be moved integrally in the optical axis direction by a driving source (not shown). It has become. The third lens group G3 includes a positive fifth lens L5, and is fixed to a lens frame (not shown). The basic configuration of the liquid optical element QL used in the present embodiment is the same as that shown in FIG.

  The operation of the zoom lens according to the present embodiment will be described. When zoom driving is performed from the short focal length end to the long focal length end, as shown in FIG. 2, the second lens group G2 is moved from the position shown in FIG. It passes through the position shown in (b) and is driven in the optical axis direction to the position shown in (c). The zoom drive from the long focal length end to the short focal length end is reversed.

  According to the present embodiment, if the zoom operation of the zoom lens in FIG. 1 is performed, the power feeding circuit of the liquid optical element QL calculates the necessary amount of compensation from the zoom signal (or refers to the table). Then, a predetermined voltage is applied to the liquid optical element QL. By controlling in this way, the liquid optical element QL can change the optical power as desired to realize a compensatory action. Therefore, a mechanism for moving the first lens group G1 in the optical axis direction is not required, and the configuration can be simplified and made compact. The change in optical power is preferably multistage, and more preferably continuous.

  Further, in the present embodiment, the power feeding circuit of the liquid optical element QL includes a signal from the image sensor CCD or a distance measurement signal from a distance measuring device (not shown) and a zoom signal (or movement in the optical axis direction of the second lens group G2). Based on the amount, the shape of the liquid optical element QL can be changed so that the compensating action and the focusing action can be realized simultaneously (further, a part of the zooming action may be borne). In such a case, there is an advantage that it is not necessary to displace the third lens group G3 in the optical axis direction.

  In the first and second embodiments, all the lens groups can be fixed in the optical axis direction by giving the liquid optical element QL a complete zooming action, and the lens group drive mechanism. A zoom lens without a lens can also be realized.

  FIG. 6 is a perspective view of a zoom lens unit ZU in which the zoom lens according to the above-described embodiment and its driving means are integrally stored. In FIG. 6, walls W <b> 1 and W <b> 2 extend upward from both ends of the base B. A guide shaft GS extends so as to connect the vicinity of the upper ends of the walls W1 and W2 (notched). Openings HL through which light beams pass are formed in the walls W1 and W2.

  The first lens group G1 is attached so that the outer periphery is held by the lens holder HD1 and covers the opening HL of the wall W1. When assembling the first lens group G1, it is desirable to suppress shift and tilt with respect to the reference axis as much as possible using an autocollimator or the like.

  On the other hand, the outer periphery of the second lens group G2, which is an optical element group that changes magnification, is held by a lens holder HD2. The lens holder HD2 as a movable member has an engaging portion HDa that engages with the guide shaft GS and a connecting portion HDb that receives a driving force.

  The connecting portion HDb is provided with a groove in contact with the drive shaft DS, and a leaf spring SG is attached to the upper surface. A drive shaft DS, which is a drive member, is disposed between the connecting portion HDb and the leaf spring SG, and is appropriately pressed by the urging force of the leaf spring SG. A clearance is provided on the wall W1 side of the drive shaft DS, and the other end passes through the wall W2 and is connected to a piezoelectric actuator PZ that is an electromechanical conversion element. The piezoelectric actuator PZ has a fixing portion Bh, and is fixed to the base B by adhesion or the like outside W2.

  A third lens group G3 is attached to the opening HL of the wall W2. A solid-state imaging device CCD is attached to the wall W2 adjacent to the third lens group G3. The arrangement relationship of the first lens group G1, the second lens group G2, and the third lens group G3 in the optical axis direction is as shown in FIGS.

  On the base B, an encoder (not shown) (position detecting means) that magnetically (or optically) detects the amount of movement of the connecting portion HDb, for example, magnetic information is arranged on the guide shaft GS, and the engaging portion HDa An external drive circuit (not shown) for applying a voltage via the wiring H is disposed to receive a signal from a read head or the like and drive and control the piezoelectric actuator PZ. The piezoelectric actuator PZ, the drive shaft DS, the connecting portion HDb, and the leaf spring SG constitute drive means. The drive circuit may be disposed on the base B and connected by wiring.

  The piezoelectric actuator PZ is formed by laminating piezoelectric ceramics formed of PZT (zircon / lead titanate) or the like. Piezoelectric ceramics have a property in which the center of gravity of the positive charge and the center of gravity of the negative charge in the crystal lattice do not coincide with each other, are themselves polarized, and extend when a voltage is applied in the polarization direction. However, since the distortion of the piezoelectric ceramic in this direction is very small and it is difficult to drive the driven member due to the amount of distortion, a plurality of piezoelectric ceramics PE are stacked between the electrodes as shown in FIG. A laminated piezoelectric actuator PZ having a structure in which C is connected in parallel is provided as a practical one. In the present embodiment, this stacked piezoelectric actuator PZ is used as a drive source.

  Next, a driving method of the second lens group G2 by the zoom lens unit ZU will be described. In general, the multilayer piezoelectric actuator PZ has a small amount of displacement when a voltage is applied, but has a large generated force and sharp response. Therefore, as shown in FIG. 8 (a), when a pulse voltage having a substantially sawtooth waveform with a sharp rise and a slow fall is applied, the piezoelectric actuator PZ extends rapidly at the rise of the pulse and more than that at the fall. Shrink slowly. Therefore, when the piezoelectric actuator PZ is extended, the drive shaft DS is pushed out to the back side (wall W1 side) in FIG. 6 by the impact force, but the connecting portion HDb of the lens holder HD2 holding the second lens group G2 and the leaf spring SG does not move with the drive shaft DS due to its inertia, but slips between the drive shaft DS and stays in that position (may move slightly). On the other hand, when the pulse falls, the drive shaft DS returns more slowly than when the pulse rises. Therefore, the connecting portion HDb and the leaf spring SG do not slide with respect to the drive shaft DS, and the drive shaft DS is integrated with the drive shaft DS. Move to the side (wall W2 side). That is, the lens holder HD2 can be continuously moved at a desired speed by applying a pulse whose frequency is set to several hundred to several tens of thousands of hertz. As is clear from the above, as shown in FIG. 8B, the lens holder HD2 can be moved in the opposite direction by applying a pulse in which the voltage rises slowly and sharply falls. In particular, if the guide shaft GS is straight, the lens holder HD2 moves with high accuracy in the optical axis direction, and aberration deterioration can be effectively suppressed as compared with the case where the optical axis shift occurs due to driving.

(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 imaging lens system F: F number T: Object distance R: Radius of curvature D: Axial distance Nd: Refractive index νd of lens material with respect to d-line: Abbe number of lens material

  In each embodiment, the shape of the aspheric surface is expressed by the following “Equation 1” where the vertex of the surface is the origin, the X axis is taken in the optical axis direction, and the height in the direction perpendicular to the optical axis is h.

ただし、
ｍ ：ｉ次の非球面係数
Ｒ ：曲率半径
Ｋ ：円錐定数

However,
m: i-th aspherical coefficient R: radius of curvature K: conic constant

Example 1 described below corresponds to the zoom lens according to the first embodiment. Table 1 shows data of the zoom lens according to the present example. The radius of curvature R5, the surface distances D4, D5 and Fno, f, the angle of view at the short focal length end, the intermediate focal length, and the long focal length end at the object distance T = ∞. Table 2 shows the values of 2ω, Table 3 shows the aspheric surface data, and Table 4 shows the values of the radius of curvature R5 and the surface distances D4 and D5 at the short focal length end and the long focal length end at the object distance T = 250 mm. Show. FIG. 4 shows aberration diagrams at the short focal length end (a), the intermediate focal length (b), and the long focal length end (c) at the object distance T = ∞ in the present embodiment. Here, the object distance is a distance from the object to the vertex of the zoom lens outermost object side surface. In the following (including the lens data in the table), a power of 10 (for example, 2.5 × 10 ⁻⁰³ ) is represented by using E (for example, 2.5E-03).

  As shown in Table 2, by changing the focal length from the short focal length end to the long focal length end and changing the radius of curvature of the interface of the liquid optical element QL, the compensation for correcting the focus movement accompanying the zooming is performed. Further, as shown in Table 4, since the focus can also be performed by changing the curvature radius of the interface according to the change of the object distance, the second lens group G2 which is a lens group having a zooming action. The zoom lens can be fixed to the lens frame, has a small number of drive lens groups, and has a simple mechanical mechanism. Further, the liquid optical element QL in zooming can be obtained by adopting a configuration in which the radius of curvature of the interface has an extreme value while changing the focal length from the short focal length end to the long focal length end as in this embodiment. The refractive power change of the liquid optical element QL can be reduced, and the liquid optical element QL can be easily controlled.

  Further, the zoom can be performed with reduced power consumption by providing the interface shape when no voltage is applied to the liquid optical element QL or when the applied voltage is low so that the most frequently used refractive power can be obtained during photographing. Since it can be set as a lens, it is more preferable.

  Example 2 described below corresponds to the zoom lens according to the second embodiment. Table 5 shows data of the zoom lens according to the present example. The curvature radius R7, the surface distances D6, D7 and Fno, f, the angle of view 2ω at the short focal length end, the intermediate focal length, and the focal length end at the object distance T = ∞. Table 6 shows the aspherical data, Table 7 shows the aspherical data, and Table 8 shows the values of the radius of curvature R7 and the surface distances D6 and D7 at the short focal length end and the long focal length end at the object distance T = 250 mm. . FIG. 5 shows aberration diagrams at the short focal length end (a), the intermediate focal length (b), and the long focal length end (c) at the object distance T = ∞ of the present embodiment. Here, the object distance is a distance from the object to the vertex of the zoom lens outermost object side surface.

  As shown in Table 5, by changing the focal length from the short focal length end to the long focal length end and changing the radius of curvature of the interface of the liquid optical element QL, the compensation for correcting the focus movement accompanying the zooming is performed. In addition, as shown in Table 8, since focusing can be performed by changing the radius of curvature of the interface in accordance with the change of the object distance, a lens group having a zooming function can be used. Other than the second lens group G2 can be fixed to the lens frame, and the zoom lens can be a simple mechanical mechanism with a small number of drive lens groups and a small amount of movement of the movable lens group. Further, as in this embodiment, the curvature radius of the interface of the liquid optical element QL has an extreme value while changing the focal length from the short focal length end to the long focal length end, thereby changing the magnification. The change in the refractive power of the liquid optical element can be reduced, and the control of the liquid optical element QL is simplified.

  Further, the zoom can be performed with reduced power consumption by providing the interface shape when no voltage is applied to the liquid optical element QL or when the applied voltage is low so that the most frequently used refractive power can be obtained during photographing. Since it can be set as a lens, it is more preferable.

  The present invention has been described above with reference to the embodiments. However, the present invention should not be construed as being limited to the above-described embodiments, and can be modified or improved as appropriate. The zoom lens of the present invention is preferably mounted on an imaging device such as a small digital still camera, a mobile terminal such as a mobile phone or a PDA, but is not limited thereto.

It is sectional drawing of the zoom lens concerning 1st Embodiment. It is a schematic block diagram of the liquid optical element QL and its drive part. It is sectional drawing of the zoom lens concerning 2nd Embodiment. It is an aberration diagram of the zoom lens according to the first embodiment. FIG. 6 is an aberration diagram of the zoom lens according to the second embodiment. FIG. 4 is a perspective view of a zoom lens unit ZU in which the zoom lens according to the above-described embodiment and its driving unit are housed integrally. FIG. 3 is a perspective view showing a multilayer piezoelectric actuator PZ having a structure in which a plurality of piezoelectric ceramics PE are stacked and electrodes C are connected in parallel therebetween. It is a figure which shows the waveform of the voltage pulse applied to the piezoelectric actuator PZ.

Explanation of symbols

QL Liquid optical element L1 1st lens L2 2nd lens L3 3rd lens L4 4th lens L5 5th lens S Aperture stop B Base Bh Fixed part C Electrode CCD Solid imaging device DS Drive axis GS Guide axis G1 1st lens group G2 Second lens group G3 Third lens group H Wiring HD1 Lens holder HD2 Lens holder HDa Engaging portion HDb Connecting portion HL Opening PE Piezoelectric ceramics PZ Multilayer piezoelectric actuator W1, W2 Wall ZU Zoom lens unit

Claims (8)

  In a zoom lens including an optical element group that moves at the time of zooming, a conductive or polar first liquid and a second liquid that does not mix with the first liquid have an interface of a predetermined shape. So that the refractive power is adjusted by changing the radius of curvature of the interface by applying a voltage between the first liquid and the electrode provided in the container. A zoom lens comprising the liquid optical element.   The zoom lens according to claim 1, wherein the liquid optical element is disposed in an optical element group including a diaphragm.   2. The zoom lens according to claim 1, wherein when the optical element group including the liquid optical element does not include a stop, the liquid optical element is disposed at a position closest to the stop in the optical system element group. .   The zoom lens according to claim 1, wherein only one optical element group moves during zooming.   The optical element group including the liquid optical element is fixed in the optical axis direction, and the optical element group including the liquid optical element corrects the focus movement accompanying the magnification change, and the focus movement accompanying the object distance change. The zoom lens according to claim 1, wherein the zoom lens has a focus function for correcting the zoom lens.   In a zoom lens including an optical element group that moves upon zooming, the conductive or polar first liquid and the first liquid are mixed with each other in at least one optical element group that moves upon zooming. The second liquid that is not to be sealed is contained in the container so that the interface has a predetermined shape, and a voltage is applied between the first liquid and the electrode provided in the container, A liquid optical element that adjusts the refractive power by changing the radius of curvature of the interface, and the optical element group including the liquid optical element corrects the focal movement associated with the magnification change and the change in the distance between objects. A zoom lens characterized by having a pensate action and a focus action for correcting a focus movement accompanying a change in object distance.   The zoom lens according to claim 6, wherein the optical element group including the liquid optical element includes a stop. An electromechanical conversion element, a driving member fixed to one end of the electromechanical conversion element, a movable member connected to the optical element group that moves at the time of zooming, and movably held on the driving member; The electro-mechanical conversion element is provided with driving means configured to move the movable member by repeatedly expanding and contracting the electromechanical conversion element at different speeds in an extension direction and a contraction direction. Item 8. The zoom lens according to any one of Items 1 to 7.

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