JP4844809B2 - Zoom lens and imaging device - Google Patents

Description

  The present invention relates to a novel zoom lens and an imaging apparatus. More specifically, in a rear focus type zoom lens, in addition to the first variable magnification which is a normal variable magnification, a variable magnification range (focal length range) different from the first variable magnification by a simple operation, particularly super telephoto The present invention relates to a technique for obtaining a second variable magnification having a variable magnification range up to.

  A video camera having an inner focus lens is known. For example, in the inner focus lens LNS as shown in FIG. 1, the first lens group 101 is disposed closest to the object side, and the second lens group 102, the third lens group 103, and the fourth lens are arranged on the image side. Groups 104 are arranged in order. The first lens group 101 and the third lens group 103 are fixed lenses, the second lens group 102 is a variator, and the fourth lens group 104 is a compensator and a focus lens. An iris 105 for exposure control is provided between the second lens group 102 and the third lens group 103. The light that has passed through the inner focus lens LNS forms an image on the light receiving surface 107 of the image sensor.

  As the image pickup element 107, for general consumer use, a so-called 1/4 inch size having a diagonal length of about 4 mm or a 1/6 inch size having a diagonal length of about 3 mm is often used. In addition, the number of pixels of these image pickup devices is increasing year by year, and those having 800 to 3 million pixels are common.

  As described above, the image size of the image pickup apparatus is small compared to the diagonal 43 mm of the so-called 135 film silver salt camera, so that a lens having the same angle of view can be significantly reduced in size as compared with the lens of the film camera. At the same time, it is generally possible to increase the zoom ratio, and those having a zoom ratio of 10 to 30 times are known.

  Further, as described above, it is desired to respond to the user's demand for use on the telephoto side as well as being capable of high magnification.

  Conventionally, various methods for displacing the zoom lens zoom range have been proposed. For example, a so-called rear converter system that displaces the focal length range of the entire system by inserting a rear converter lens group or an extender lens group having positive or negative refractive power between the final lens surface and the image plane of the zoom lens, There has been proposed an afocal converter system in which an afocal converter lens group having an infinite focal length is mounted in front of a zoom lens to expand or reduce the focal length range of the entire system. In addition, there is a method of simply enlarging the zooming range by changing the zooming magnification of the zoom lens. For example, there is a method of increasing the amount of movement of the zoom lens unit, increasing the refractive power of the zoom lens unit, or increasing the number of zoom lens units.

  Among the methods of displacing the zoom range of the zoom lens, the rear converter method can make the tele ratio relatively small, but it is necessary to correct various aberrations with the rear converter lens group alone. The configuration becomes complicated and large.

  On the other hand, the afocal converter system can relatively easily widen the angle and telephoto of the entire zoom lens system, but the lens group tends to become larger because the lens group is mounted in front of the lens. .

  In any of the converter systems described above, a converter lens group must be provided in addition to the zoom lens main body, and the converter lens is inserted between the normal lens and the main body. It takes time and effort to attach it in front of a regular lens, and is not suitable for portability and rapid shooting.

  If it is configured such that the zoom lens shown in Patent Document 1 or Patent Document 2 is switched to or inserted into a converter lens inside the camera, it will be suitable for at least rapid shooting characteristics, and the number of loads when carrying it. However, the lens structure becomes complicated and large, and the portability is not improved so much.

  In addition, the method of changing the zooming magnification of the zoom lens increases the total lens length, increases the amount of aberration generated over the entire zooming range, makes it difficult to correct aberration fluctuations at zooming, etc. There is a problem.

  As these solutions, there is one that achieves the object by moving the third lens group by a predetermined amount on the optical axis as in the zoom lens disclosed in Patent Document 3. If it is such, both portability and quickness can be improved.

JP-A-6-324267 JP 2003-338982 A Japanese Patent Laid-Open No. 6-102456

  By the way, since the third lens group is usually in the vicinity of the iris, there is a possibility that the moving mechanism for moving the third lens group and the iris mechanism may interfere with each other, so that the lens barrel structure is expected to be complicated and enlarged. The

  In view of the above-described problems, the present invention provides a zooming lens of a rear focus type that has a zooming range (focal length range) different from the first zooming by a simple operation in addition to the normal zooming. It is an object to obtain a second variable magnification having a variable magnification range up to super telephoto.

  In order to solve the above-described problem, the zoom lens according to the present invention includes a first lens group having a positive refractive power and a second lens group having a negative refractive power, which are arranged in order from the object side. And a third lens group having a positive refractive power as a fixed lens and a fourth lens group having a positive refractive power for focusing, and having an iris for reducing the amount of light from the imaging target to an appropriate amount. And correcting the image plane variation due to the zooming caused by the movement of the second lens group by moving the fourth lens group, and moving the fourth lens group to perform focusing, After moving the first lens group by a predetermined amount in the optical axis direction, the fourth lens group is corrected by moving the fourth lens group to correct the image plane variation due to zooming caused by the movement of the second lens group, and the fourth lens group is moved. And have a second zooming to focus .

  Therefore, in the zoom lens according to the present invention, the second variable having a variable magnification range (focal length range) different from the first variable magnification is obtained by moving the first lens group from the position in the first variable magnification. Displaced twice.

  The imaging device of the present invention includes the zoom lens of the present invention.

  The zoom lens according to the present invention has a first lens group having a positive refractive power, a second lens group having a negative refractive power by a variable power lens, and a positive refractive power by a fixed lens, which are arranged in order from the object side. And a third lens group having a positive refracting power for focusing, and an iris for reducing the amount of light from the imaging object to an appropriate amount, and moving the second lens group The first lens unit that corrects the image plane variation caused by the zooming by moving the fourth lens unit and moves the fourth lens unit to focus, and the first lens unit in the optical axis direction. Then, after the predetermined amount of movement, the second lens group is corrected by moving the fourth lens group to correct the image plane variation due to the magnification change due to the movement of the second lens group, and at the same time, the second lens group is moved for focusing. It is characterized by having a double.

  Accordingly, in the zoom lens of the present invention, the second lens having a variable magnification range (focal length range) different from the first variable magnification is obtained by moving the first lens group from the position in the first variable magnification. Transition to magnification can be made. Therefore, the same zooming range as when the converter lens is mounted can be obtained by a simple operation of moving the first lens unit from the first zooming position without carrying the retrofitted converter lens. In addition, both portability and quickness can be improved. Furthermore, a zoom lens designed as a normal zoom lens having no second variable magnification is simply changed so that the first lens group can be moved, and a second image having an image quality equivalent to or higher than that of the converter lens is mounted. It is possible to use a scaling factor of 2.

  The imaging apparatus of the present invention is an imaging apparatus that includes a zoom lens and an imaging element that converts an object image formed by the zoom lens into an electric signal, and the zoom lens is arranged in order from the object side. A first lens group having a negative refractive power, a second lens group having a negative refractive power by a variable power lens, a third lens group having a positive refractive power by a fixed lens, and a positive refractive power for focusing. A fourth lens group, and an iris for reducing the amount of light from the object to be imaged to an appropriate amount, and the fourth lens group is subject to image plane fluctuations due to zooming caused by movement of the second lens group. The first zooming is performed by moving and correcting the fourth lens group, and the first lens group is moved by a predetermined amount in the optical axis direction, and then the second lens group is moved. 4th image field fluctuation Is corrected by moving the's group, characterized in that it has a second zooming by moving the fourth lens group performs focusing.

  Therefore, in the imaging apparatus of the present invention, the zoom lens has a zooming range (focal length range) different from the first zooming by moving the first lens group of the zoom lens from the position in the first zooming. Transition to the second magnification can be made. Therefore, even if the converter lens attached later is not carried, shooting is performed in the same zooming range where the converter lens is mounted by a simple operation of moving the first lens unit from the position of the first zooming. It is possible to improve both portability and quickness. In addition, it is possible to use the second variable magnification having the same or higher image quality as that provided with the converter lens.

  In the invention described in claim 2 and claim 5, the second zooming is switched by moving the first lens unit to the object side from the telephoto end state in the first zooming. When photographing at a long focal length is required during photographing at the telephoto end in the first variable magnification, the object can be achieved without requiring a troublesome work of mounting a teleconverter lens. In addition, since only the first lens unit is moved to the object side from the telephoto end in the first variable magnification, no compensating or focusing is required in the intermediate focal range, and the control mechanism and control method are simplified. As a result, an inexpensive zoom lens can be obtained.

According to a third aspect of the present invention, the amount of movement of the first lens group is as follows: ft is the focal length of the telephoto end at the first variable magnification, ftt is the focal length of the telephoto end at the second variable magnification, f1 is the combined focal length of the first lens unit, f123 is the combined focal length from the first lens unit to the third lens unit at the telephoto end at the first variable magnification, and d4 is the first variable to the second variable. As the amount of displacement of the fourth lens group at the time of switching to the magnification, the following conditional expression (1) 0.1 <(1-ft ² / f123 ² ) / (ft / f1) ² · d4 · ft / ftt <0.4
Therefore, the focal length at the telephoto end in the second variable magnification can be 1.2 times or more of the focal length at the telephoto end in the first variable magnification, and the fourth lens group is moved. The distance can be kept in an appropriate range.

  The best mode for carrying out the zoom lens and the imaging apparatus of the present invention will be described below with reference to the drawings.

  The outline of the zoom lens of the present invention will be described with reference to FIG. The zoom lens ZL shown in FIG. 2 is a four-group inner focus type zoom lens, and shows the telephoto end state at the first variable magnification above the center line (optical axis) xx. On the side, a second zoom is shown in which the first lens group G1 is moved d1 from the position of the first lens group G1 to the object side at the telephoto end of the first zoom. In the second variable magnification, the fourth lens group G4 which is a focus group for compensating for the fluctuation of the image plane position accompanying the movement of d1 of the first lens group G1 toward the object side and focusing on the image plane IMG. Is displaced by d4 toward the image plane side.

When the first lens group G1 is displaced toward the object side by d1, the focal position P1t of the first lens group G1 is displaced by the same amount as d1, and becomes the position of P1tt. If the fourth lens group G4, which is the focus group, remains in its original position, the in-focus position becomes (1-β1 ² ) · β234 ² according to the combination magnification from the second lens group G2 to the fourth lens group G4. -Only d1 is on the object side. Similarly, when the focus lens group G4 is displaced by d4, the movement of the in-focus position is (1-β4 ² ) · βFL ² · d4. Therefore, when the first lens group G1 is displaced by d1, the original position is moved. The moving amount d4 of the focus lens group G4 for focusing on the focal position IMG is given by
d4 = (1-β1 ² ) ・ β234 ² / (1-β4 ² ) ・ βFL ²・ d1 ・ K
^{= (Ft / f1) 2 /} (1-ft 2 / f123 2) · d1 · K
It becomes.

Note that K is an aberration balance in an actual lens, and is a coefficient determined from a change in magnification accompanying displacement of the first lens group G1 and the fourth lens group G4. Also, f4 is the combined focal length of the fourth lens group G4, f234 is the combined focal length of the second, third, and fourth lens groups G2, G3, and G4 at the telephoto end before the first lens group is shifted (first variable magnification). The distance, fFL is the combined focal length of the optical filter FL, β1 is the combined magnification of the first lens group G1, β4 is the combined magnification of the fourth lens group G4, and β123 is before the shift of the first lens group G1 (first variable magnification). ) Is the combined magnification of the first, second, and third lens groups G1, G2, and G3 at the telephoto end, and β234 is the second, third, and fourth lenses at the telephoto end before the first lens group G1 is shifted (first variable magnification). Synthesis magnification of groups G2, G3, G4,
βFL is a composite magnification of the optical filter FL.

  The first lens group G1 is formed by a physical space (including a case where a control range, a control error, and a mechanical error are taken into consideration) between the fourth lens group G4 and an optical member (here, the optical filter FL) on the image plane side. The maximum amount of displacement is self-evident. As a matter of course, the displaceable amount has an allowable limit from the aberration balance caused by the displacement of the first lens group G1 and the fourth lens group G4. As a standard, an image quality equivalent to or better than an image quality deteriorated by an electronic zoom or the like that can obtain the same angle of view can be considered. In this way, when the first lens group G1 and the fourth lens group G4 are displaced, as shown in FIG. 2, the focal length becomes longer from the original ft, and a telephoto lens can be obtained. I understand.

  In the zoom lens ZL described above, the timing at which the first lens group G1 is moved toward the object side is determined depending on what convenience is desired. Regardless of the position of the second lens group G2 in the first zooming, if the first lens group G1 is displaced toward the object side and transitioned to the second zooming, the first zooming Zooming in the zooming region including the focal length in the zooming region is also possible, and taking only zooming allows shooting with a wide range of field angles, which is convenient. When shooting in a wider zooming range than image quality is necessary, it is convenient to start shooting by moving the first lens group G1 to the second zooming position from the beginning. .

  When the first lens group G1 is moved to the second zoom position, the first lens group G4 is corrected only by moving the fourth lens group G4 (compensation for variations in image plane position). It is difficult to obtain an image quality that is the same as the image quality at the zoom ratio. In order to secure a larger zoom magnification, the first lens group is advanced toward the object side as it is displaced toward the telephoto side, and accordingly, all the lens groups subsequent to the second lens group are moved to increase the magnification ratio. There is a zoom lens that ensures high image quality, but it must be expensive due to factors such as the large number of movable lens groups.

  However, normal shooting does not require a very large zoom ratio, but rather high image quality is desired, but in extreme cases, shooting at a higher magnification than the normal telephoto end may be required. For users who want to move, the lens group to be moved can be reduced by considering the fact that, while eliminating the hassle of wearing a converter lens, it is possible to obtain at least the same image quality as when using a converter lens, By limiting to two groups, the zoom lens has a simple structure, and therefore does not become so expensive. As a zoom lens, the zoom lens is shifted from the point at which the telephoto end is reached by the first zooming to the second zooming. Is practical. With this configuration, a higher image quality can be obtained in the zooming range in the first zooming, and in an emergency, it can be instantly displaced to a magnification that cannot be obtained by the first zooming, and the converter lens can be carried. And you are freed from the hassle of wearing it.

In the zoom lens of the present invention, ft is the focal length of the telephoto end at the first zooming, ftt is the focal length of the telephoto end at the second zooming, f1 is the combined focal length of the first lens group, and f123 is the first focal length. The combined focal length from the first lens group to the third lens group at the telephoto end in zooming, and d4 as the amount of displacement of the fourth lens group at the time of switching from the first zooming to the second zooming, It is preferable that the movement amount of one lens group satisfies the following conditional expression (1).
(1) 0.1 <(1-ft ² / f123 ² ) / (ft / f1) ² · d4 · ft / ftt <0.4
If the upper limit value of conditional expression (1) is exceeded, the amount of movement of the fourth lens group G4 increases, and there is no space between the optical filter on the image plane side, and spherical aberration and field curvature are considered due to aberration balance. Becomes under and image performance deteriorates. On the other hand, if the lower limit value is not reached, the magnification (ftt / ft) on the super telescopic side at the second variable magnification becomes 1.2 or less, and the effect of applying the present invention is reduced.

  As a structure for moving the first lens group G1, those shown in FIGS. 3 and 4 are conceivable.

  A rotating frame 20 is rotatably attached to the front end of the fixed barrel 10. The first lens group G1 is held by a lens holding frame 30 supported by the fixed barrel 10 so as to rotate together with the rotary frame 20. The connecting projections 31, 31, 31 projecting forward at three locations that are spaced at substantially equal intervals in the circumferential direction of the portion near the periphery of the lens holding frame 30 (in FIG. 3, this connecting projection 31 and the members and parts related thereto are (Only one is shown). The connecting projections 31, 31, 31 are inserted through mounting holes 22, 22, 22 formed in the flange portion 21 of the rotating frame 20 so as to be slidable in the front-rear direction, and the lens 21 and the lens holding portion of the rotating frame 20 are held. Between the frame 30, compression coil springs 32, 32, 32 are inserted into the connection protrusions 31, 31, 31 in an outer fitting manner. Further, sliding pins 33, 33, 33 (only one is shown in FIG. 3) project from the outer peripheral portion of the lens holding frame 30 at positions spaced at substantially equal intervals in the circumferential direction. The distal ends of the moving pins 33, 33, 33 are slidably engaged with cam grooves 11, 11, 11 formed on the inner peripheral surface of the front end of the fixed barrel 10. As shown in FIG. 4, the cam groove 11 includes a first portion 11a extending in the circumferential direction, a position forward (object side) from the first portion 11a, and spaced apart from the first portion 11a in the circumferential direction. The second portion 11b extending in the circumferential direction at the only position and the inclined portion 11c connecting the first portion 11a and the second portion 11b are connected in series. An introduction portion 11d extends forward from an end portion of the cam groove 11 opposite to the end portion connected to the inclined portion 11c of the first portion 11a, and the introduction portion 11d is fixed to the fixed barrel 10. The front end 12 is open. When the lens holding frame 30 is supported on the front end portion of the fixed barrel 10, the sliding pins 33, 33, 33 of the lens holding frame 30 are moved from the front ends of the introduction portions 11 d, 11 d, 11 d of the cam grooves 11, 11, 11. In this state, the lens holding frame 30 is moved rearward, and the sliding pins 33, 33, 33 collide with the rear ends of the introduction portions 11d, 11d, 11d. By the way, when the lens holding frame 30 is slightly rotated in the clockwise direction (the direction indicated by the arrow CW in FIG. 4), the sliding pins 33, 33, 33 become the first portions 11 a of the cam grooves 11, 11, 11, It will be in the state engaged with 11a and 11a.

  FIG. 3 shows a state in which the sliding pins 33, 33, 33 of the lens holding frame 30 are engaged with the first portions 11a, 11a, 11a of the cam groove 11, and in this state, the lens holding frame 30 moves within the moving range. In this state, the first lens group G1 held by the lens holding frame 30 is in the first zooming position. When the rotating frame 20 is rotated in the clockwise direction from the state indicated by the solid line in FIGS. 3 and 4 toward the object side, the lens holding unit connected to the rotating frame 20 by the connecting protrusions 31, 31, 31 is retained. The frame 30 is also rotated in the same direction, and the sliding pins 33, 33, 33 of the lens holding frame 30 are moved from the first portions 11a, 11a, 11a of the cam grooves 11, 11, 11 to the inclined portions 11c, 11c, 11c. After entering, it will be in the state engaged with 2nd part 11b, 11b, 11b (refer the dashed-two dotted line of FIG. 4). The compression coil springs 32, 32, 32 are further compressed while the sliding pins 33, 33, 33 advance through the inclined portions 11 c, 11 c, 11 c, and the sliding pins 33, 33, 33, and thus the lens holding frame 30. Is displaced forward and the sliding pins 33, 33, 33 are positioned at the second portions 11b, 11b, 11b, the first lens group G1 held by the lens holding frame 30 is moved to the second change. Reach position in double. Then, when changing from the second magnification to the first magnification, the sliding pin 33 can be obtained by rotating the rotary frame 20 in the direction opposite to the above, that is, in the direction opposite to the arrow CW in FIG. , 33 and 33 slide on the cam grooves 11, 11, and 11 in the opposite direction to reach the position at the first magnification.

  Furthermore, as a structure for moving the first lens group G1, the structure shown in FIG. 5 is also conceivable.

  Two guide shafts 41 and 41 (only one is shown in FIG. 4) and one front end portion of the fixed barrel 40, that is, an end portion on the object side, are spaced at substantially equal intervals in the circumferential direction. The lead screw 42 is disposed so as to extend in the optical axis direction. The lead screw 42 is rotated by a motor 50 supported by the fixed barrel 40.

  The lens holding frame 60 holding the first lens group G1 is screwed with the lead screw 42 and is slidably supported by the two guide shafts 41 and 41.

  Therefore, when the motor 50 is rotated, the lead screw 42 is rotated, and the lens holding frame 60 screwed with the lead screw 42 is sent by the lead screw 42 and moves forward or backward.

  FIG. 6 shows an embodiment in which the imaging apparatus of the present invention is applied to a video camera.

  The imaging apparatus 100 includes a zoom lens 110. The zoom lens 110 has a configuration similar to that of the zoom lens ZL shown in FIG. 2, and is configured to be able to switch between the first zooming and the second zooming. The image sensor 110 is arranged such that its light receiving surface is positioned on the image forming surface of the zoom lens 110, and an image formed by the zoom lens 110 is output as electrical image data. As the imaging device 120, a device using a photoelectric conversion device such as a charge coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS) is applicable.

  Image data output from the image sensor 120 is temporarily stored in the frame memory 131 via the signal processing circuit 130.

  Then, an analog image signal to be supplied to the image reproduction unit 132 is formed from the image data after the camera signal processing, and the analog image signal is supplied to the image reproduction unit 132, whereby the subject image is transmitted from the LCD or the like through the image reproduction unit 132. Is displayed on the screen display unit 133.

  Further, the signal processing circuit 130 compresses the image data on which the camera signal processing has been performed by a predetermined compression method, and records this in the image recording unit 134 in accordance with control from the system control circuit 140. Here, the image recording unit 134 records on a hard disk, a disk drive for recording on a removable disk type recording medium such as a DVD (Digital Versatile Disc) -RAM, DVD-RW / R, or a magnetic tape housed in a cassette. It can take various forms such as a tape drive and a card slot in which a memory card containing a solid memory is detachably mounted. Alternatively, a plurality of recording means having different forms, for example, a disk drive and a card slot may be provided.

  The system control circuit 140 controls the entire imaging apparatus 100. For example, although not shown in detail, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), an EEPROM (Electrical Erasable and Programmable ROM) is configured as a microcomputer connected through a system bus. The system control circuit 140 receives operation signals from a release switch 141, a zoom switch 142 for instructing zooming and its direction, and a mode switch 143 for selecting various shooting modes.

  The system control circuit 140 is connected to a zoom information memory 144 in which various information related to the zoom operation is stored.

  When the release switch 141 is operated, an image formed on the image sensor 120 is captured as a still image, and recorded as still image data, for example, in a memory card mounted in a card slot.

  The second lens group G2 of the zoom lens 110 is, for example, by a zoom drive unit 151 using a stepping motor as a drive source, and the fourth lens group G4 is, for example, by a focus drive unit 152 using a stepping motor as a drive source. Moved. The position of the second lens group G2 is detected by the zoom position detection unit 161, and the position of the fourth lens group G4 is detected by the focus position detection unit 162. Each detection value is system controlled as focal length information. Returned to circuit 140. For example, when a stepping motor is used as the drive source of the drive units 151 and 152, a counter that counts the number of feed steps from the initial position is driven by the DC motor in each of the detection units 161 and 162. In the case of a source, an MR sensor is used when the encoder uses a linear motor as a drive source. Then, the system control circuit 140 refers to the positions of the second lens group G2 and the fourth lens group G4 based on the signals from the zoom position detection unit 161 and the focus position detection unit 162, and the zoom drive unit 151 and the focus drive unit 152. To move the second lens group G2 and the fourth lens group G4 to predetermined positions.

  The aperture diameter of the iris S that adjusts the amount of light reaching the image sensor 120 from the subject is changed by the iris drive unit 153, and the aperture diameter of the iris S is detected by the iris position detection unit 163, and the detection signal is Referenced by the system control circuit 140. Then, the system control circuit 140 controls the iris driving unit 153 to change the opening diameter of the iris S while referring to the opening diameter of the iris by the detection signal of the iris position detecting unit 163.

  In the imaging apparatus 100, the zooming drive unit 154 for moving the first lens group G1 to change the zooming range between the first zooming and the second zooming is provided. Prepare. For example, the zoom driving unit 154 includes the first lens group moving mechanism shown in FIG. Then, the magnification position detecting unit 164 detects whether the current magnification mode is the first magnification or the second magnification. The zoom position detection unit 164 includes various switches such as a limit switch operated by the lens holding frame 60, a proximity switch configured by a magnet supported by the lens holding frame 60 and a Hall element supported by the fixed barrel 40, and the like. Can take form. For example, when a command for changing to the second magnification is input from the state at the telephoto end of the first magnification by the mode switch 143, for example, the command is sent from the system control circuit 140 to the magnification driving unit 154. When the first lens group G1 is moved to the second zoom position and this is detected by the zoom position detector 164, the system control circuit 140 stores the zoom memory information memory 144 in the zoom memory information memory 144. Referring to the focus position detector 162, a signal is sent to the focus driver 152 so that the position of the fourth lens group G4 is a predetermined position (for example, to move the distance d4 in FIG. 2). As a result, the zoom lens 110 enters the second variable power state. Such a change between the first magnification and the second magnification is performed by the system control circuit 140 that has received a command by operating the mode switch 143, for example.

  There are several methods for changing the magnification range between the first magnification and the second magnification described above, and these will be described with reference to FIGS.

  The method shown in FIG. 7 is a method in which the position of the first lens group G1 is switched manually, for example, by the mechanism shown in FIGS. 3 and 4, and the zoom operation is not performed in the second zooming.

  First, as a result of determining whether or not the zoom operation has been performed in the normal zoom range (first variable magnification) (step AS1), if the zoom operation has been performed (YES), the process proceeds to the next step AS2. If the zoom operation is not performed (NO), the process returns to step AS1.

  In step AS2, the zoom position is detected, and the process proceeds to the next step AS3.

  In step AS3, it is determined whether or not the position of the first lens group G1 has been switched. If NO (NO), the process returns to step AS1 (that is, normal zoom shooting is performed), and switching is performed. If yes (YES), the process proceeds to the next step AS4.

  In step AS4, it is determined whether or not the zoom position is at the telephoto end. If not (NO), a warning is displayed (AS5), the process returns to step AS1, and if it is in the telephoto end (YES), Proceed to next step AS6. The reason why the warning is displayed in step AS5 is to allow the displacement to the second magnification only from the telephoto end state of the first magnification.

  In step AS6, the process proceeds to the second variable power state. That is, the fourth lens group G4 is moved to a predetermined position so as to be the focal length at the telephoto end in the second zooming. That is, in the example of FIG. 2, the fourth lens group G4 is moved to the image plane side by d1 from the telephoto end position in the first zooming. Then, the process proceeds to the next step AS7.

  In step AS7, it is determined whether or not the zoom operation to the wide angle side has been performed. If NO (NO), the process returns to step AS7, and if the zoom operation to the wide angle side has been performed (YES), Proceed to step AS8.

  In step AS8, it is determined whether or not the switching operation of the first lens group G1 has been performed. If NO (NO), a warning is displayed (step AS9) and the process returns to step AS7 to return to the first lens group G1. When the switching operation is performed (YES), the process proceeds to the next step AS10.

  In step AS10, the process proceeds to the first variable power state. That is, the fourth lens group G4 is moved to a predetermined position so as to be the focal length at the telephoto end in the first zooming. That is, in the example of FIG. 2, the fourth lens group G4 is moved to the object side by d1 from the telephoto end position in the second variable power. Then, the process returns to step AS1.

  In the method shown in FIG. 7, the teleconverter lens is attached when it is necessary to shoot at a longer focal length urgently at the telephoto end of normal shooting (shooting at the first variable magnification). Without moving the first lens group G1 to the second variable magnification position manually, the focal length is the same as when the teleconverter lens is mounted, for example, the focal point at the telephoto end of the first variable magnification. This enables photographing at a focal length with a magnification of about 1.5 times or more than the distance. Moreover, it is freed from the hassle of purchasing a teleconverter lens, carrying it, and removing it.

  The method shown in FIG. 8 is a method in which the position of the first lens group G1 is automatically switched by the mechanism shown in FIG. 5, for example, and the zoom operation is not performed in the second zooming.

  First, it is determined whether or not the zoom operation has been performed in the normal shooting state, that is, when shooting in the zoom range of the first variable magnification (step BS1), whether or not (NO). If the zoom operation is performed (YES), the process proceeds to the next step BS2.

  In step BS2, the zoom position is detected, and the process proceeds to step BS3.

  In step BS3, it is determined whether or not the zoom position is the telephoto end of the first variable magnification. If NO (NO), the process returns to step BS1 (that is, normal zoom shooting is performed). If it is the telephoto end with a variable magnification of 1 (YES), the process proceeds to the next step BS4.

  In step BS4, it is determined whether or not the zoom operation is to the further telephoto side. If NO (NO), the process returns to step BS1 (that is, normal zoom shooting is performed), and further to the telephoto side. If the zoom operation has been performed (YES), the process proceeds to the next step BS5.

  In step BS5, the process proceeds to the second variable power state. That is, the first lens group G1 and the fourth lens group G4 are moved to predetermined positions so as to be the focal length at the telephoto end in the second zooming. That is, in the example of FIG. 2, the first lens group G1 is moved to the object side by d1 from the position at the first zooming, and the fourth lens group G4 is d4 from the position at the telephoto end at the first zooming. Move only to the image plane side. Then, the process proceeds to the next step AS6.

  In step BS6, it is determined whether or not a zoom operation to the wide angle side has been performed. If NO (NO), the process returns to step BS6 and a zoom operation to the wide angle side has been performed (YES). Advances to the next step BS7.

  In step BS7, the process proceeds to the first variable power state. That is, the first lens group G1 and the fourth lens group G4 are moved to predetermined positions so as to be the focal length at the telephoto end in the first zooming. That is, in the example of FIG. 2, the fourth lens group G4 is moved to the object side by d1 from the telephoto end position in the second variable power. Then, the process returns to step AS1.

  In the method shown in FIG. 8 described above, a teleconverter lens is attached when it is necessary to shoot at a longer focal length urgently at the telephoto end of normal shooting (shooting at the first variable magnification). Without any further zooming to the telephoto side, the focal length is the same as the teleconverter lens, for example, about 1.5 times or more than the focal length at the telephoto end of the first variable magnification. It is possible to shoot at a focal length of a magnification of. Moreover, it is freed from the hassle of purchasing a teleconverter lens, carrying it, and removing it. Further, when returning to shooting in the normal zoom range, if the zoom operation to the wide angle side is performed in the second zooming, the zooming is automatically switched to the first zooming.

  The method shown in FIG. 9 is a method in which the position of the first lens group G1 is switched manually, for example, by the mechanism shown in FIGS. 3 and 4, and a zoom operation can be further performed in the second zooming.

  First, it is determined whether or not a zoom operation has been performed (step CS1). If NO (NO), the process returns to step CS1, and if a zoom operation has been performed (YES), the process proceeds to the next step CS2.

  In step CS2, the zoom position is detected, and the process proceeds to the next step CS3.

  In step CS3, it is determined whether or not the position of the first lens group G1 has been switched. If NO (NO), the process returns to step CS1 and the position of the first lens group G1 is switched. In (YES), it progresses to following step CS4.

  In step CS4, it is determined whether or not the zoom position is the first zooming telephoto end. If NO (NO), a warning is displayed (step CS5), and the process returns to step CS1. The reason why the warning is displayed is that switching to the second magnification is performed at the telephoto end of the first magnification. If the zoom position is at the first variable magnification telephoto end (YES), the process proceeds to the next step CS6.

  In step CS6, the shift to the second magnification is performed. That is, the second lens group G2 and the fourth lens group G4 are moved to predetermined positions so as to have the same focal length as that of the first zooming telephoto end. That is, from this point, zoom photographing in a zooming range that can be called super telephoto is possible. Then, the process proceeds to the next step CS7.

  In step CS7, it is determined whether or not a zoom operation has been performed. If NO (NO), the process returns to step CS7. If a zoom operation has been performed (YES), the process proceeds to the next step CS8.

  In step CS8, the zoom position is detected, and the process proceeds to the next step CS9.

  In step CS9, it is determined whether or not the focal length is the same as the focal length at the telephoto end of the first variable magnification. If NO (NO), the process returns to step CS7, where the focal length is equal to the first variable magnification. When it is the same as the focal length at the telephoto end (YES), the process proceeds to the next step CS10.

  In step CS10, it is determined whether or not the zoom operation is to the wide angle side. If NO (NO), the process returns to step CS7. If the zoom operation is to the wide angle side (YES), the process proceeds to the next step CS11. .

  In step CS11, it is determined whether or not the first lens group G1 has been switched to the first zooming position. If not (NO), a warning is displayed (step CS12) to step CS7. Returning to step CS13 when the first lens group G1 is switched to the first zoom position (YES).

  In step CS13, the shift to the first scaling is performed. That is, the second lens group G2 and the fourth lens group G4 are moved to predetermined positions so as to have the same focal length as that of the first zooming telephoto end. Then, the process returns to step CS1.

  According to the method shown in FIG. 9, the focal length can be changed even in the second zooming. That is, it is possible to take an image with an arbitrary focal length from the wide angle end of the first variable magnification to the telephoto end of the second variable magnification.

  The method shown in FIG. 10 is a method in which the position of the first lens group G1 is automatically switched by, for example, the mechanism shown in FIG.

  First, it is determined whether or not a zoom operation has been performed (step DS1). If NO (NO), the process returns to step DS1, and if a zoom operation has been performed (YES), the process proceeds to the next step DS2.

  In step DS2, the zoom position is detected, and the process proceeds to the next step DS3.

  In step DS3, it is determined whether or not the zoom position is at the first zooming telephoto end. If NO (NO), the process returns to step DS1, and the zoom position is at the first zooming telephoto end. If there is (YES), the process proceeds to the next step DS4.

  In step DS4, it is determined whether or not the zoom operation is to the telephoto end side. If NO (NO), the process returns to step DS1, and if the zoom operation is to the telephoto end side (YES), the next step is performed. Proceed to DS5.

  In step DS5, a shift to the second magnification is performed. That is, the first lens group G1, the second lens group G2, and the fourth lens group G4 are moved to predetermined positions so as to have the same focal length as that of the first zooming telephoto end. That is, from this point, zoom photographing in a zooming range that can be called super telephoto is possible. Then, the process proceeds to next Step DS6.

  In step DS6, it is determined whether or not a zoom operation has been performed. If NO (NO), the process returns to step DS6. If a zoom operation has been performed (YES), the process proceeds to the next step DS7.

  In step DS7, the zoom position is detected, and the process proceeds to the next step DS8.

  In Step DS8, it is determined whether or not the focal length is the same as the focal length at the telephoto end of the first variable magnification. If NO (NO), the process returns to Step DS6 and the focal length is equal to the first variable magnification. When it is the same as the focal length at the telephoto end (YES), the process proceeds to the next step DS9.

  In step DS9, it is determined whether or not the zoom operation is to the wide angle side. If NO (NO), the process returns to step DS6. If the zoom operation is to the wide angle side (YES), the process proceeds to the next step DS10. .

  In step DS10, the shift to the first zooming is performed. That is, the first lens group G1, the second lens group G2, and the fourth lens group G4 are moved to predetermined positions so as to have the same focal length as that of the first zooming telephoto end. Then, the process returns to step DS1.

  According to the method shown in FIG. 10, the focal length can be changed even in the second zooming. That is, it is possible to take an image with an arbitrary focal length from the wide angle end of the first variable magnification to the telephoto end of the second variable magnification. In addition, switching between the first magnification and the second magnification can be performed by simply performing a zoom operation.

  In the method shown in FIG. 11, when the position of the first lens group is switched, the zooming area is changed immediately, and zooming cannot be performed with the second zooming.

  First, it is determined whether or not the position of the first lens group G1 has been switched from the position at the first magnification to the position at the second magnification (step ES1). If NO (NO), the process returns to step ES1, and if the first lens group G1 is switched to the second zoom position (YES), the process proceeds to the next step ES2.

  In step ES2, a shift to the second zooming is performed. That is, the second lens group G2 and the fourth lens group G4 are moved to predetermined positions so as to have the same focal length as that of the second zooming telephoto end. Then, the process proceeds to next Step ES3.

  In step ES3, it is determined whether or not the position of the first lens group G1 has been switched from the position at the second magnification to the position at the first magnification. If NO (NO), the process returns to step ES3, and if the first lens group G1 is switched to the first zoom position (YES), the process proceeds to the next step ES4.

  In step ES4, the shift to the first zooming is performed. That is, the fourth lens group G4 is moved to a predetermined position so as to have the same focal length as that of the first zooming telephoto end. Then, the process returns to step ES1.

  In the method shown in FIG. 11, when the position of the first lens group G1 is switched to the position in the second zooming, regardless of the focal length at the first zooming, the second zooming is immediately performed. Can be switched to the telephoto end. The zoom operation cannot be performed in the second zooming, and when the first lens group G1 is switched to the position in the first zooming in the second zooming, the zooming is switched to the telephoto end of the first zooming.

  In the method shown in FIG. 12, the zooming area is changed immediately when the position of the first lens group is switched, and the zoom operation can be performed even with the second zooming.

  First, it is determined whether or not the position of the first lens group G1 has been switched from the position at the first zooming to the position at the second zooming (step FS1). If NO (NO), the process returns to step FS1, and if the first lens group G1 is switched to the second zoom position (YES), the process proceeds to the next step FS2.

  In step FS2, the shift to the second magnification is performed. That is, the second lens group G2 and the fourth lens group G4 are moved to predetermined positions so as to have the same focal length as that of the first zooming telephoto end. That is, from this point, zoom photographing in a zooming range that can be called super telephoto is possible. Then, the process proceeds to the next step FS3.

  In step FS3, it is determined whether or not a zoom operation has been performed. If NO (NO), the process returns to step FS3. If a zoom operation has been performed (YES), the process proceeds to the next step FS4.

  In step FS4, the zoom position is detected, and the process proceeds to next step FS5.

  In step FS5, it is determined whether or not the position of the first lens group G1 has been switched from the position at the second magnification to the position at the first magnification. If NO (NO), the process returns to step FS3, and if the first lens group G1 is switched to the first zoom position (YES), the process proceeds to the next step FS6.

  In step FS6, the shift to the first zooming is performed. That is, the second lens group G2 and the fourth lens group G4 are moved to predetermined positions so as to have the same focal length as that of the first zooming telephoto end. Then, the process returns to step FS1.

  In the method shown in FIG. 12, when the position of the first lens group G1 is switched to the position in the second zooming, regardless of the focal length at the first zooming, the second zooming is immediately performed. Can be switched to. Then, the zoom operation can be performed within the range of the second variable magnification range. Then, when the first lens group G1 is switched to the first zoom position in the second zooming, the first zooming is switched to the telephoto end.

  Embodiments of the zoom lens according to the present invention will be described below with reference to the drawings and tables.

  First, items common to the embodiments will be described.

  In the following description, “ri” is the radius of curvature of the i-th lens surface from the object side, “di” is the surface spacing on the optical axis between the i-th surface and the i + 1-th surface from the object side, “Ni” is the refractive index for the d-line (wavelength 587.6 nm) on the i-th surface from the object side, “ν i” is the Abbe number for the d-line on the i-th surface from the object side, and “f” is the entire lens system It is assumed that the focal length, “Fno” is an open F value, and “ω” is a half angle of view.

  In addition, the lenses of the embodiments include those in which the lens surface is an aspherical surface. The aspheric shape is defined by the following equation (1).

Here, “Z” is the distance in the optical axis direction when the height from the optical axis between the tangential plane and the spherical surface at the apex of the aspheric surface is “H” (= √ (X ² + Y ² )), and “C” is non- It is assumed that the curvature of the spherical vertex (1 / r), “K” represents the conic constant, and “A2i” represents the second i-th aspherical coefficient.

  As shown in FIGS. 13, 22, and 31, the zoom lenses 1, 2, and 3 in each embodiment are arranged in order from the object side, the first lens group G1, the second lens group G2, and the third lens group. This is a so-called rear focus type zoom lens that includes four lens groups, G3 and a fourth lens group G4, and has an optical filter FL disposed between the fourth lens group G4 and the image plane IMG.

  As shown in FIGS. 13, 22, and 31, the first lens group G1 has a positive refractive power as a whole, and the second lens group G2 has a negative refractive power as a whole. The position is made movable. The third lens group G3 has a positive refractive power and its position is fixed. The fourth lens group G4 has a positive refractive power as a whole, and its position is movable.

  Zooming in the zoom lenses 1, 2, and 3 is performed between the first lens group G1 and the third lens group G3 as shown in FIGS. 13 to 15, FIGS. 22 to 24, and FIGS. This is done by moving the second lens group G2 closer to the first lens group G1 or closer to the third lens group G3 in the optical axis direction. In addition, the fourth lens group G4 is arranged between the third lens group G3 and the optical filter FL in the optical axis direction in order to correct the change in the position of the image plane due to the zooming and to perform focusing. It moves closer to the lens group G3 or closer to the optical filter FL.

  As a method of displacing the first lens group G1, mechanical means or electrical means are used in combination.

  In the second zooming, the first lens group G1 is displaced toward the object side within the range of the conditional expression (1) with the configuration of each lens group.

  Next, items unique to each embodiment of the zoom lens of the present invention will be described.

  13 to 21 show the first embodiment 1 of the zoom lens according to the present invention.

  Table 1 shows each value of the zoom lens 1.

  In Table 1 above, the values of d5, d10, d15 and d17 vary with zooming and focusing. Therefore, in the first zooming, d5, d10, d15 and d17 when zooming is performed from the wide angle end to the telephoto end and the focal length f (magnification) is changed to 1.00, 3.16 and 10.00. Values are shown in Table 2.

  In the second scaling, the values of d5, d10, d15 and d17 are as shown in Table 3 below.

Moreover, r11, r12, r16, and r17 are comprised by the aspherical surface. Therefore, Table 4 shows the fourth, sixth, eighth and tenth aspherical coefficients A4, A6, A8 and A10 of r11, r12, r16 and r17. In Table 4 and the following tables showing aspheric coefficients, “E-i” represents an exponential expression with a base of 10, that is, “10- ⁱ ”. For example, “0.26029E-05” represents “ 0.26029 × 10 ⁻⁵ ”.

  Table 5 shows values of f and Fno of the zoom lens 1 at the first variable magnification. Similarly, Table 6 shows each value at the second magnification.

  Further, the values corresponding to the conditional expression (1) when switching from the first magnification to the second magnification are as shown in Table 7.

  FIGS. 16 to 18 show respective aberration diagrams of spherical aberration, astigmatism, and distortion at the wide-angle end, the standard end, and the telephoto end of the zoom lens 1. Each shows a value at the wavelength d line (wavelength 587.6 nm), and in the astigmatism diagram, the solid line shows the value on the sagittal image plane, and the broken line shows the value on the meridional image plane (FIGS. 19 to 21 shown below). The same applies to FIGS. 25 to 30 and FIGS. 34 to 39.)

  Similarly, FIGS. 19 to 21 show aberration diagrams in the second variable magnification.

  22 to 30 show a second embodiment 2 of the zoom lens according to the present invention.

  Table 8 shows each value of the zoom lens 2.

  In Table 8 above, the values of d5, d10, d15 and d17 vary with zooming and focusing. Therefore, in the first zooming, d5, d10, d15, and d17 when zooming is performed from the wide-angle end to the telephoto end and the focal length f (magnification) is changed to 1.00, 3.46, and 12.00. Table 9 shows the values.

  In the second scaling, the values of d5, d10, d15, and d17 are as shown in Table 10 below.

  r12 and r16 are constituted by aspheric surfaces. Therefore, Table 11 shows the fourth, sixth, eighth and tenth aspherical coefficients A4, A6, A8 and A10 of r12 and r16.

  Table 12 shows each value of f and Fno of the zoom lens 2 at the first variable magnification. Similarly, Table 13 shows each value at the second magnification.

  Furthermore, the values corresponding to the conditional expression (1) when switching from the first magnification to the second magnification are as shown in Table 14.

  FIG. 25 to FIG. 27 show respective aberration diagrams of spherical aberration, astigmatism, and distortion at the wide-angle end, the standard end, and the telephoto end of the zoom lens 2.

  Similarly, FIGS. 28 to 30 show aberration diagrams in the second variable magnification.

  31 to 39 show a third embodiment 3 of the zoom lens according to the present invention.

  Table 15 shows each value of the zoom lens 3.

  In Table 15 above, the values of d5, d10, d12, and d16 change with zooming and focusing. Therefore, when zooming is performed from the wide-angle end to the telephoto end in the first zooming and the focal length f (magnification) is changed to 1.00, 4.47, and 20.00, d5, d10, d12, and d16 Values are shown in Table 16.

  In the second variable magnification, values of d5, d10, d12, and d16 are as shown in Table 17 below.

  R11 and r13 are aspherical surfaces. Table 18 shows the fourth, sixth, eighth and tenth aspherical coefficients A4, A6, A8 and A10 of r11 and r13.

  Table 19 shows values of f and Fno of the zoom lens 3 at the first variable magnification. Similarly, Table 20 shows each value at the second magnification.

  Furthermore, the values corresponding to the conditional expression (1) when switching from the first magnification to the second magnification are as shown in Table 21.

  FIGS. 34 to 36 show respective aberration diagrams of spherical aberration, astigmatism, and distortion at the wide angle end, the standard end, and the telephoto end of the zoom lens 3.

  Similarly, FIGS. 37 to 39 show aberration diagrams in the second variable magnification.

  According to the zoom lens and the image pickup apparatus of the present invention described above, the first variable magnification and the second variable magnification that changes the magnification after the first lens group is moved to a predetermined position on the optical axis. By appropriately selecting the doubling operation, it is possible to perform photographing at a focal length that should be a super telephoto having a longer focal length than the focal length at the telephoto end at the zoom position at the telephoto end.

  Furthermore, since it is possible to perform super-telephoto shooting with the second zooming, the camera system can be simplified by limiting the zoom position at which the first zooming is switched to the second zooming.

  Further, by limiting the amount of displacement of the first lens group and the fourth lens group by the second zooming, the image performance is better than super telephoto shooting using an electronic zoom or the like, and super high using a converter lens or the like. The lens configuration can be simplified and reduced in size compared to telephoto shooting.

  According to the present invention, even when the lens design is optimal for the first zooming, it is possible to perform shooting at a super telephoto having a longer focal length by slightly shifting the first lens group.

  It should be noted that the specific shapes and numerical values of the respective parts shown in the respective embodiments and examples described above are merely examples of the implementation performed in carrying out the present invention, and the present invention is thereby limited. This technical scope should not be interpreted in a limited way.

It is a figure which shows the concept of a 4 group inner focus type zoom lens. It is a figure for demonstrating the concept of this invention zoom lens. FIG. 4 shows an example of a mechanism for moving the first lens group together with FIG. It is a figure which expands and shows the cam groove formation part of a fixed barrel in a plane. It is a longitudinal cross-sectional view of the lens barrel front end portion showing another example of a mechanism for moving the first lens group. It is a block diagram which shows an example of implementation of this invention imaging device. It is a flowchart figure which shows the 1st example of the control method of the 1st magnification and the 2nd magnification in this invention. It is a flowchart figure which shows the 2nd example of the control method of the 1st magnification and the 2nd magnification in this invention. It is a flowchart figure which shows the 3rd example of the control method of the 1st magnification and the 2nd magnification in this invention. It is a flowchart figure which shows the 4th example of the control method of the 1st magnification and the 2nd magnification in this invention. It is a flowchart figure which shows the 5th example of the control method of the 1st magnification and the 2nd magnification in this invention. It is a flowchart figure which shows the 6th example of the control method of the 1st magnification and the 2nd magnification in this invention. FIG. 14 to FIG. 21 show a first embodiment of a zoom lens according to the present invention, which is a diagram showing a lens configuration at the wide angle end. It is a figure which shows the lens structure in standard time. It is a figure which shows the lens structure in a telephoto end. FIG. 22 is a diagram illustrating each aberration together with FIGS. 17 to 21, and this diagram is a diagram illustrating spherical aberration, astigmatism, and distortion at the wide angle end at the first zooming. It is a figure which shows the spherical aberration, astigmatism, and distortion aberration in the standard time in the 1st variable magnification. It is a figure which shows the spherical aberration, astigmatism, and distortion aberration in the telephoto end in the 1st variable magnification. It is a figure which shows the spherical aberration, the astigmatism, and the distortion aberration in the wide angle end in the 2nd magnification. It is a figure which shows the spherical aberration, astigmatism, and distortion aberration in the standard time in the 2nd magnification. It is a figure which shows the spherical aberration, the astigmatism, and the distortion aberration in the telephoto end in the 2nd magnification. FIG. 23 to FIG. 30 show a second embodiment of the zoom lens according to the present invention, and this figure shows a lens configuration at the wide angle end. It is a figure which shows the lens structure in standard time. It is a figure which shows the lens structure in a telephoto end. FIG. 26 is a diagram illustrating each aberration together with FIG. 26 to FIG. 30, and this diagram is a diagram illustrating spherical aberration, astigmatism, and distortion at the wide angle end at the first variable magnification. It is a figure which shows the spherical aberration, astigmatism, and distortion aberration in the standard time in the 1st variable magnification. It is a figure which shows the spherical aberration, astigmatism, and distortion aberration in the telephoto end in the 1st variable magnification. It is a figure which shows the spherical aberration, the astigmatism, and the distortion aberration in the wide angle end in the 2nd magnification. It is a figure which shows the spherical aberration, astigmatism, and distortion aberration in the standard time in the 2nd magnification. It is a figure which shows the spherical aberration, the astigmatism, and the distortion aberration in the telephoto end in the 2nd magnification. FIG. 32 to FIG. 39 show a third embodiment of the zoom lens according to the present invention, and this figure shows a lens configuration at the wide angle end. It is a figure which shows the lens structure in standard time. It is a figure which shows the lens structure in a telephoto end. It is a figure which shows each aberration with FIG. 35 thru | or 39, and this figure is a figure which shows the spherical aberration, the astigmatism, and the distortion aberration in the wide angle end in the 1st magnification. It is a figure which shows the spherical aberration, astigmatism, and distortion aberration in the standard time in the 1st variable magnification. It is a figure which shows the spherical aberration, astigmatism, and distortion aberration in the telephoto end in the 1st variable magnification. It is a figure which shows the spherical aberration, the astigmatism, and the distortion aberration in the wide angle end in the 2nd magnification. It is a figure which shows the spherical aberration, astigmatism, and distortion aberration in the standard time in the 2nd magnification. It is a figure which shows the spherical aberration, the astigmatism, and the distortion aberration in the telephoto end in the 2nd magnification.

Explanation of symbols

  ZL ... zoom lens, 1 ... zoom lens, 2 ... zoom lens, 3 ... zoom lens, G1 ... first lens group, G2 ... second lens group, G3 ... third lens group, G4 ... fourth lens group, S ... Iris, 100 ... imaging device, 110 ... zoom lens, 120 ... imaging device

Claims (5)

A first lens group having a positive refractive power, a second lens group having a negative refractive power as a variable power lens, and a third lens group having a positive refractive power as a fixed lens, arranged in order from the object side; A fourth lens group having a positive refractive power for focusing, and an iris for reducing the amount of light from the imaging object to an appropriate amount,
A first zooming for performing focusing by moving the fourth lens group and correcting the image plane variation due to the zooming due to the movement of the second lens group, and moving the fourth lens group; After moving one lens group by a predetermined amount in the optical axis direction, the image plane variation due to zooming due to movement of the second lens group is corrected by moving the fourth lens group, and the fourth lens group is moved. A zoom lens comprising: a second variable power for focusing. 2. The zoom lens according to claim 1, wherein the second zooming is switched by moving the first lens unit toward the object side from a telephoto end state in the first zooming. The zoom lens according to claim 1 or 2, wherein the moving amount of the first lens group satisfies the following conditional expression (1).
(1) 0.1 <(1-ft ² / f123 ² ) / (ft / f1) ² · d4 · ft / ftt <0.4
However,
ft: Focal length at the telephoto end at the first variable magnification
ftt: Focal length at the telephoto end in the second variable magnification
f1: Composite focal length of the first lens group
f123: Composite focal length from the first lens unit to the third lens unit at the telephoto end in the first variable magnification
d4: The amount of displacement of the fourth lens group at the time of switching from the first variable magnification to the second variable magnification. An imaging apparatus comprising a zoom lens and an image sensor that converts a subject image formed by the zoom lens into an electrical signal,
The zoom lens has a first lens group having a positive refractive power, a second lens group having a negative refractive power by a variable power lens, and a positive lens having a positive refractive power, which are arranged in order from the object side. A third lens group and a fourth lens group having positive refractive power for focusing, and an iris for reducing the amount of light from the imaging object to an appropriate amount,
A first zooming for performing focusing by moving the fourth lens group and correcting the image plane variation due to the zooming due to the movement of the second lens group, and moving the fourth lens group; After moving one lens group by a predetermined amount in the optical axis direction, the image plane variation due to zooming due to movement of the second lens group is corrected by moving the fourth lens group, and the fourth lens group is moved. An image pickup apparatus comprising: a second zooming unit that performs focusing. The imaging apparatus according to claim 4, wherein the second zooming is switched by moving the first lens unit toward the object side from a telephoto end state in the first zooming.

Images