JP4431962B2 - Zoom lens and imaging device - Google Patents

Description

  The present invention relates to a novel zoom lens and an imaging apparatus. Specifically, the present invention relates to a zoom lens having a four-group configuration that can be configured in a small size with a short overall length, and an imaging apparatus using the zoom lens.

  Conventionally, as zoom lenses mainly used for consumer video cameras and still image video cameras, first to fourth lens groups having positive, negative, positive, and positive refractive powers are arranged in order from the object side. In general, a four-group inner focus zoom lens in which the positions of the second lens group and the fourth lens group are movable is employed.

  Further, in the four-group inner focus type that is the zoom lens system described above, the third lens group has a convex, concave or convex, convex, concave lens configuration in order from the object side. Some have a strong concave surface facing the image side.

  In addition, the third lens group is composed of a combination of single lenses, and no cemented lens is used. In order to make the principal point of the third lens group closer to the front (object side), the convex lens has a strong positive refractive power on the surface located on the object side, and the concave lens has a strong negative surface on the image side. Therefore, the configuration has to have a refractive power of 5. However, spherical aberration, coma aberration, and astigmatism have a strong canceling force between the convex surface and concave surface with strong refractive power, and also due to manufacturing errors of parts during mass production and lens eccentricity during assembly. There was a drawback that performance variations were likely to occur.

  However, in order to avoid the problem caused by the eccentricity of the lens, there is a method called alignment assembly, that is, a method of fixing to the lens barrel by bonding or the like while aligning the optical axes of a plurality of lenses. However, this requires labor and cost. Therefore, as the number of lenses constituting the third lens group increases, it becomes difficult to obtain stable mass productivity.

  The present applicant in Example 3 and Example 4 of Patent Document 1 is composed of a three-piece cemented lens of a high refractive index convex lens, a low refractive index convex lens, and a high refractive index concave lens in which the third lens group is arranged in order from the object side. As a result, the object side principal point of the third lens group is moved forward to reduce the overall length, and the decentering sensitivity is reduced by joining the three lenses, and the three lenses can be easily joined in the joining process. A lens configuration that can adjust the optical axis of the lens is presented.

JP 2001-305427 A

  By the way, in the zoom lens disclosed in Patent Document 1 described above, one aspheric glass mold lens is used for each of the third lens group and the fourth lens group. An aspheric glass mold lens has a disadvantage that its manufacturing cost is higher than that of a spherical polished lens. The production volume of consumer video cameras is increasing rapidly, and price competition is intensifying, so reducing manufacturing costs is a major issue. In view of the above problems, the present invention reduces the overall length of the zoom lens to a smaller size, makes it less likely to cause performance variations due to manufacturing errors, and further reduces the cost compared to the prior art. It is another object of the present invention to provide an imaging device using the zoom lens.

In order to solve the above-described problem, the zoom lens of the present invention includes a first lens group having a positive refractive power and a fixed position arranged in order from the object side, a negative refractive power and a variable magnification. Therefore, the second lens group of the variable magnification system whose position is movable, the third lens group having a positive refractive power and a fixed position, and a focus having a positive refractive power at the time of zooming and focusing. The fourth lens group whose position is movable in order to adjust the position, and the first lens group is a cemented lens of the first lens of the concave lens and the second lens of the convex lens arranged in order from the object side And a third lens of a convex meniscus lens having a convex surface facing the object side, and the second lens group is arranged in order from the object side, the fourth lens of the concave lens, the fifth lens of the biconcave lens, and the fifth lens of the convex lens. 6 lenses and a third lens. The lens group is composed of a seventh lens of a biconvex lens, an eighth lens of a convex meniscus lens having a convex surface facing the image side, and a ninth lens of a concave lens having a strong concave surface facing the object side, arranged in order from the object side. The fourth lens group is constituted by a tenth lens of a biconvex lens, the seventh lens to the ninth lens in the third lens group are spherical lenses, and H3 is a third lens. The distance between the object-side principal point of the lens group and the most object-side surface of the third lens group, f3 the focal length of the third lens group, and n31 the lens closest to the object side of the third lens group (seventh lens) The refractive index at the d-line, n32 is the refractive index at the d-line of the convex lens (eighth lens) sandwiched between the third lens groups, and n33 is the most image side lens (the ninth lens) of the third lens group. Refractive index at d-line, D 2 is the thickness of the convex lens (eighth lens) sandwiched between the third lens groups, D3 is the thickness of the three-piece cemented lens constituting the third lens group, and r31 is the lens closest to the object side of the third lens group ( As the radius of curvature of the object side surface of the seventh lens), the following conditional expressions (1) -0.2 <H3 / f3 <0, (2) 0.31 <n31-n32, (3) 0.35 <N33-n32, (4) 0.45 <D32 / D3 <0.65, (5) 0.667 ≦ r31 / f3 <0.75 are satisfied.

In order to solve the above-described problem, the imaging apparatus of the present invention includes a zoom lens and an imaging unit that captures an optical image formed by the zoom lens, and the zoom lens is arranged in order from the object side. A first lens group having a positive refractive power and a fixed position; a second lens group having a negative refracting power; and a variable power second lens group whose position is movable for zooming; and positive refraction. A third lens group having a fixed force and a position, and a fourth lens group having a positive refractive power and a movable position for adjusting the focal position at the time of zooming and focusing. The first lens group includes a cemented lens of a first lens of a concave lens and a second lens of a convex lens and a third lens of a convex meniscus lens having a convex surface facing the object side, which are arranged in order from the object side. The two lens groups are concave lenses arranged in order from the object side. The third lens group includes a fourth lens and a fifth lens of a biconcave lens and a sixth lens of a convex lens, and the third lens group has a convex surface on the image side and a seventh lens of the biconvex lens arranged in order from the object side. The fourth lens group includes a tenth lens of a biconvex lens. The fourth lens group includes an eighth lens of the convex convex meniscus lens and a ninth concave lens having a strong concave surface facing the object side. The seventh to ninth lenses in the third lens group are spherical lenses, and H3 is the distance between the object side principal point of the third lens group and the most object side surface of the third lens group, f3 Is the focal length of the third lens group, n31 is the refractive index at the d-line of the most object side lens (seventh lens) of the third lens group, and n32 is a convex lens (eighth lens) sandwiched between the third lens groups. The refractive index at the d-line, n33 is the refractive index at the d-line of the most image side lens (9th lens) of the third lens group, and D32 is the convex lens (eighth lens) sandwiched between the third lens groups. The following conditional expressions are used, where thickness, D3 is the thickness of the three-piece cemented lens constituting the third lens group, and r31 is the radius of curvature of the object-side surface of the third lens group closest to the object side (seventh lens). (1) -0.2 <H3 / f3 <0, (2) 0.31 <n31-n32, (3) 0.35 <n33-n32, (4) 0.45 <D32 / D3 <0.65 (5) 0.667 ≦ r31 / f3 <0.75 is satisfied.

  Therefore, in the present invention, it is possible to achieve downsizing, particularly downsizing in the optical axis direction and cost reduction, while correcting aberrations well.

  The zoom lens of the present invention includes a first lens group having a positive refractive power and a fixed position arranged in order from the object side, and a variable lens having a negative refractive power and movable for zooming. Second lens group of magnification system, third lens group having positive refractive power and fixed position, and movable position to adjust the focal position at the time of zooming and focusing with positive refractive power In the zoom lens comprising the fourth lens group, the first lens group has a convex lens on the object side and a cemented lens of the first lens of the concave lens and the second lens of the convex lens arranged in order from the object side. The second lens group includes a fourth lens of a concave lens, a fifth lens of a biconcave lens, and a sixth lens of a convex lens, which are arranged in order from the object side. And the third lens group is A three-piece cemented lens composed of a seventh lens of a biconvex lens, an eighth lens of a convex meniscus lens having a convex surface facing the image side, and a ninth lens of a concave lens having a strong concave surface facing the object side, arranged in order from the body side The fourth lens group is configured by a tenth lens of a biconvex lens, and the seventh to ninth lenses in the third lens group are spherical lenses, and the following conditional expressions (1), ( 2. A zoom lens characterized by satisfying each of 2), (3), (4) and (5).

(1) -0.2 <H3 / f3 <0
(2) 0.31 <n31-n32
(3) 0.35 <n33-n32
(4) 0.45 <D32 / D3 <0.65
(5) 0.667 ≦ r31 / f3 <0.75
However,
H3: distance between the object side principal point of the third lens group and the most object side surface of the third lens group f3: focal length of the third lens group n31: lens closest to the object side of the third lens group (first lens 7 lens) d-line refractive index n32: convex lens (eighth lens) sandwiched between third lens groups d-line refractive index n33: third lens group most image side lens (9th lens) Refractive index D32 at the d-line: Thickness of convex lens (eighth lens) sandwiched between the third lens group D3: Thickness of three-piece cemented lens constituting the third lens group r31: Most object of the third lens group The radius of curvature of the object side surface of the side lens (seventh lens) is used.

  The imaging apparatus of the present invention is an imaging apparatus including a zoom lens and an imaging unit that captures an optical image formed by the zoom lens, and the zoom lens is arranged in order from the object side. A first lens unit having a refractive power of λ and a fixed position, a second lens unit having a negative refracting power and a variable power second lens unit whose position is movable for zooming, and a positive refractive power. And a third lens group having a fixed refractive position and a fourth lens group having a positive refractive power and movable in order to adjust the focal position at the time of zooming and focusing. The group is composed of a cemented lens of a first lens of a concave lens and a second lens of a convex lens and a third lens of a convex meniscus lens having a convex surface facing the object side, arranged in order from the object side. Is a fourth lens and a concave lens arranged in order from the object side. The third lens group is composed of a cemented lens of a fifth lens of a biconcave lens and a sixth lens of a convex lens, and the third lens group is arranged in order from the object side, and is convex with the convex surface facing the seventh lens of the biconvex lens and the image side. The fourth lens group includes a tenth lens of a biconvex lens, and includes a cemented three-lens lens including an eighth lens of a meniscus lens and a ninth lens of a concave lens having a strong concave surface facing the object side. The seventh to ninth lenses in the three lens groups are spherical lenses, and satisfy the following conditional expressions (1), (2), (3), (4), and (5). An imaging apparatus characterized by that.

(1) -0.2 <H3 / f3 <0
(2) 0.31 <n31-n32
(3) 0.35 <n33-n32
(4) 0.45 <D32 / D3 <0.65
(5) 0.667 ≦ r31 / f3 <0.75
However,
H3: distance between the object side principal point of the third lens group and the most object side surface of the third lens group f3: focal length of the third lens group n31: lens closest to the object side of the third lens group (first lens 7 lens) d-line refractive index n32: convex lens (eighth lens) sandwiched between third lens groups d-line refractive index n33: third lens group most image side lens (9th lens) Refractive index D32 at the d-line: Thickness of convex lens (eighth lens) sandwiched between the third lens group D3: Thickness of three-piece cemented lens constituting the third lens group r31: Most object of the third lens group The radius of curvature of the object side surface of the side lens (seventh lens) is used.

  Therefore, in the zoom lens according to the present invention, the main point of the third lens group is moved to the front side, and the back focal length is shortened by shortening the focal length of the fourth lens group, so that the overall length can be shortened. Play. In addition, the third lens group is composed of three cemented lenses to reduce the sensitivity of aberration deterioration due to decentration and to facilitate the assembly of alignment in the joining process. Can be solved. Further, by configuring the difference in refractive index before and after the cemented surface of the third lens group to be sufficiently large, the aspherical surface can be eliminated from the third lens group, and a great cost reduction effect can be obtained.

  In the second and fifth aspects of the invention, since at least one surface of the tenth lens constituting the fourth lens group is an aspherical surface, aberration correction can be performed satisfactorily.

  In the invention described in claims 3 and 6, the tenth lens constituting the fourth lens group is a plastic lens having at least one aspherical surface and an Abbe number of 50 or more. Further cost reduction can be achieved by eliminating the expensive glass molded aspherical lens from the fourth lens group.

  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 accompanying drawings. In the following embodiment, the present invention is applied to a zoom lens 1 (see FIG. 1) or 2 (see FIG. 5) for a video camera or a still image video camera.

  The zoom lenses 1 and 2 are so-called four-group inner focus type zoom lenses, and as shown in FIGS. A lens group G1, a variable power second lens group G2 having a negative refractive power and movable for zooming, and a third lens group G3 having a positive refractive power and a fixed position. And a fourth lens group G4 having positive refractive power and movable in order to adjust the focal position at the time of zooming and focusing.

  The first lens group G1 includes, in order from the object side, a cemented lens of a first lens L1 that is a concave lens and a second lens L2 that is a convex lens, and a third lens L3 that is a convex meniscus lens having a convex surface facing the object side. Has been.

  The second lens group G2 includes, in order from the object side, a cemented lens including a fourth lens L4 that is a concave lens, a fifth lens L5 that is a biconcave lens, and a sixth lens L6 that is a convex lens.

  The third lens group G3 includes a seventh lens L7 of a biconvex lens, an eighth lens L8 of a convex meniscus lens having a convex surface facing the image side, and a concave lens having a strong concave surface facing the object side, arranged in order from the object side. It is constituted by a three-piece cemented lens including nine lenses L9. The seventh lens L7 to the ninth lens L9 are spherical lenses.

  The fourth lens group G4 includes a tenth lens L10 that is a biconvex lens having an aspheric object-side surface.

  The feature of the configuration of the present invention is particularly the third lens group G3, which will be described in detail below.

  As a means for reducing the size of the zoom lenses 1 and 2, as in the above-mentioned Patent Document 3, between the seventh lens L 7 having a positive refractive power and the ninth lens L 9 having a negative refractive power. By disposing them at a distance, the object side principal point of the third lens group G3 can be moved forward, the focal length of the fourth lens group G4 can be shortened, and the back focus is shortened. The total length is shortened.

  Further, in the zoom lenses 1 and 2, H3 is the distance between the object side principal point of the third lens group and the most object side surface of the third lens group, f3 is the focal length of the third lens group, and n31 is the first distance. The refractive index at the d-line of the most object side lens (seventh lens) of the three lens groups, n32 is the refractive index at the d-line of the convex lens (eighth lens) sandwiched between the third lens groups, and n33 is the third. The refractive index of the lens closest to the image side (9th lens) in the d-line, D32 is the thickness of the convex lens (eighth lens) sandwiched between the third lens groups, and D3 is the third lens group. The following conditional expressions (1), (2), and (3) are used, where the thickness of the three-lens cemented lens, r31 is the radius of curvature of the object side surface of the third lens group, the most object side lens (the seventh lens) , (4) and (5) are satisfied.

(1) -0.2 <H3 / f3 <0
(2) 0.31 <n31-n32
(3) 0.35 <n33-n32
(4) 0.45 <D32 / D3 <0.65
(5) 0.667 ≦ r31 / f3 <0.75
Next, each conditional expression will be described. Conditional expression (1) is a condition necessary for achieving downsizing, and the most object-side principal point of the third lens group of the third lens group G3 and the most of the third lens group. The refractive power arrangement of the three-piece cemented lens must be determined so that the distance H3 between the object side surface does not exceed the upper limit and the object side principal point is in front. By configuring the third lens group G3 to satisfy this condition, the focal length of the fourth lens group G4 can be set short, and the back focus can be shortened to achieve miniaturization. The seventh lens L7 having a positive refractive power and the ninth lens L9 having a negative refractive power are necessary for miniaturization and at the same time play an important role in correcting spherical aberration, coma aberration, and astigmatism. Plays. If the refractive power arrangement is such that the object side principal point jumps out to the object side below the lower limit of the conditional expression (1), the force that cancels each aberration generated by the seventh lens L7 and each aberration by the ninth lens L9 is obtained. It becomes stronger and it becomes difficult to correct aberration with good balance.

  Conditional expressions (2), (3), and (5) are necessary conditions for using a spherical lens for the seventh lens L7, and are sandwiched between the seventh lens L7 and the ninth lens L9. In order for the eighth lens L8 to function as a substitute for air, it is necessary to increase the difference in refractive index. A spherical polished lens using a relatively inexpensive glass material is used for the seventh lens L7 by satisfying the conditional expressions (2) and (3) and by making the curvature of the r31 surface gentler than the lower limit of the conditional expression (5). I can do it. However, if the upper limit of conditional expression (5) is exceeded, conditional expression (1) cannot be satisfied and miniaturization cannot be achieved.

  Conditional expression (4) is for balancing the good aberration correction without using an aspherical surface and miniaturization. When the lower limit is exceeded, the object side principal point of the third lens group G3 is moved forward. The refractive power of each of the seventh lens L7 and the ninth lens L9 is increased in order to make it closer, and the object side surface of the seventh lens L7 is made aspherical in order to correct spherical aberration generated from the seventh lens L7. Will have to. If the upper limit is exceeded, the refractive powers of the seventh lens L7 and the ninth lens L9 can be weakened, which is advantageous for aberration correction. However, the total thickness of the third lens group G3 is increased to achieve downsizing. I can't do that.

  By configuring the third lens group G3 so as to satisfy the above conditional expressions (1) to (5), it becomes possible to make the seventh lens L7 spherical, which was not possible with the zoom lens disclosed in Patent Document 3, and is desired. The cost can be reduced while maintaining the performance.

  By using a low-dispersion plastic material for the tenth lens L10 of the fourth lens group G4, the tenth lens L10 of the fourth lens group G4 can be constituted by a low-cost aspheric lens by injection molding, and further Cost can be reduced.

  Next, each numerical example embodying the zoom lenses 1 and 2 of the present invention will be described.

  In the following description, “ri” is the radius of curvature of the i-th surface counted from the object side, “di” is the surface interval between the i-th surface and the i + 1-th surface counted from the object side, “ “dFL” is the surface spacing of the filter FL, “ni” is the refractive index at the d-line of the material constituting the i-th lens, “nFL” is the refractive index at the d-line of the material constituting the filter FL, and “νi” is the i-th The Abbe number of the material composing the lens, “νFL” represents the Abbe number of the material composing the filter FL, and (ASP) represents that the surface is aspheric.

  Further, the aspherical shape is defined by Equation 1 where “xi” is the depth of the aspherical surface and “H” is the height from the optical axis.

  Table 1 shows “ri”, “di”, “dFL”, “ni”, “nFL”, “νi”, and “νFL” in Numerical Example 1 in which the zoom lens 1 is embodied.

  In the zoom lens 1, the surface distance d5 between the first lens group G1 and the second lens group G2, the surface distance d10 between the second lens group G2 and the stop, the third lens group G3 and the fourth lens group G4. And the surface distance d17 between the fourth lens group G4 and the filter FL are variable. Therefore, Table 2 shows the values at the wide-angle end, the intermediate focal position, and the telephoto end of the spacing between these surfaces together with the focal length, F-number, and angle of view (2ω (degrees)).

In the zoom lens 1, the object-side surface s16 of the tenth lens L10 constituting the fourth lens group G4 is formed of an aspherical surface. Table 3 shows the fourth-order, sixth-order, eighth-order, and tenth-order aspheric coefficients A4, A6, A8, and A10 of the surface s16. Note that “ei” in the aspheric coefficient indicates “× 10 ⁻ⁱ ”.

  Table 4 shows numerical values of the conditional expressions (1) to (5) in Numerical Example 1.

  2 to 4 show spherical aberration, astigmatism, and distortion at the wide angle end, the intermediate focal position, and the telephoto end in the first numerical embodiment.

  In the spherical aberration diagram, the solid line shows the respective aberration curves for the d-line (wavelength 587.6 nm), the broken line shows the g-line (wavelength 435.8 nm), and the alternate long and short dash line shows the respective aberration curves for the C-line (wavelength 656.3 nm). In the aberration diagrams, the solid line indicates the sagittal image plane, and the broken line indicates the meridional image plane.

  As shown in Tables 1 to 4 and FIGS. 2 to 4, it can be seen that in the numerical value example 1, each aberration is satisfactorily corrected and miniaturization is achieved.

  Next, Table 5 shows “ri”, “di”, “dFL”, “ni”, “nFL”, “νi”, and “νFL” in Numerical Example 2 in which the zoom lens 2 is embodied.

  In the zoom lens 2, the surface distance d5 between the first lens group G1 and the second lens group G2, the surface distance d10 between the second lens group G2 and the stop, the third lens group G3 and the fourth lens group G4. And the surface distance d17 between the fourth lens group G4 and the filter FL are variable. Therefore, Table 6 shows the values of these surface intervals at the wide-angle end, the intermediate focal position, and the telephoto end together with the focal length, F-number, and angle of view (2ω (degrees)).

In the zoom lens 2, the object-side surface s16 of the tenth lens L10 constituting the fourth lens group G4 is formed of an aspherical surface. Accordingly, Table 4 shows the fourth-order, sixth-order, eighth-order and tenth-order aspheric coefficients A4, A6, A8 and A10 of the surface s16. Note that “ei” in the aspheric coefficient indicates “× 10 ⁻ⁱ ”.

  Table 8 shows the numerical values of the conditional expressions (1) to (5) in Numerical Example 2.

  6 to 8 show spherical aberration, astigmatism, and distortion at the wide-angle end, the intermediate focal position, and the telephoto end in the second numerical embodiment.

  In the spherical aberration diagram, the solid line shows the respective aberration curves for the d-line (wavelength 587.6 nm), the broken line shows the g-line (wavelength 435.8 nm), and the alternate long and short dash line shows the respective aberration curves for the C-line (wavelength 656.3 nm). In the aberration diagrams, the solid line indicates the sagittal image plane, and the broken line indicates the meridional image plane.

  As shown in Tables 5 to 8 and FIGS. 6 to 8, it can be seen that in the numerical value example 2, each aberration is satisfactorily corrected and miniaturization is achieved.

  FIG. 9 shows an embodiment of the imaging apparatus of the present invention. FIG. 9 shows an embodiment in which the imaging apparatus of the present invention is applied to a still image video camera capable of taking still images in addition to moving images.

  The video camera 10 includes a zoom lens 20 and an image pickup device 30 such as a CCD or CMOS as an image pickup means for picking up an optical image formed by the zoom lens 20. The zoom lenses 1 and 2 described above can be applied as the zoom lens 20. Then, the image sensor 30 converts the optical image formed by the zoom lens 20 into an electrical signal and sends it to the image processing unit 40.

  The video camera 10 includes a central processing unit (CPU) 50 for controlling the entire system. The central processing unit 50 controls each unit in accordance with the operation of the operation unit 60.

  The operation unit 60 is provided with a recording mode changeover switch 61, a start / stop button 62, a shutter button 63, a zoom switch 64, a playback button 65, and the like, and signals obtained by operating these switches and buttons are input to the central processing unit 50. Is done. When the moving image shooting mode and the still image shooting mode are selected by operating the recording mode changeover switch 61 and the moving image shooting mode is selected, if the start / stop button 62 is pressed, the moving image shooting start and shooting are performed each time the button is pressed. Stops are realized alternately. Further, when the still image shooting mode is selected, when the shutter button 63 is pressed, a still image is shot. When the zoom switch 64 is operated, zooming up or down is performed according to the direction of the operation. When the play button 65 is pressed, a moving image or a still image is played according to the selected mode.

  When the zoom switch 64 is operated, a driving signal is sent from the central processing unit 50 to the motor drive 70 in accordance with the operation, and the movable lens group (which corresponds to the zoom lenses 1 and 2) is responded to the driving signal. Then, the second lens group G2 and the fourth lens group G4) are moved to adjust zooming and image position based on zooming.

  The electrical signal sent from the image pickup device 30 is processed by the image processing unit 40 and sent to the monitor unit 80 and the recording unit 90, displayed on the monitor unit 80, and recorded by the recording unit 90. Further, the processing status in the image processing unit 40 is sent to the central processing unit 50. The image processing unit 40 includes a moving image processing unit 41 and a still image processing unit 42, and performs processing according to the selected mode. That is, when the moving image shooting mode is selected, it is processed by the moving image processing unit 41 of the image processing unit 40, and the moving image information generated thereby is sent to the moving image recording unit 91 and the monitor unit 80, and still image shooting is performed. When the mode is selected, it is processed by the still image processing unit 42 of the image processing unit 40 and the still image information generated thereby is sent to the still image recording unit 92 and the monitor unit 80. In the recording unit 90, the moving image information is recorded by the moving image recording unit 91, and the still image information is recorded by the still image recording unit 92. The recording units 91 and 92 of the recording unit 90 record the respective image information on a desired recording medium. For example, the moving image recording unit 91 records moving image information on a recording medium such as a magnetic tape or a DVD (Digital Versatile Disk), and the still image recording unit 92 records it on a solid memory such as a memory stick.

  When the playback button 65 is operated, a signal is sent from the moving image recording unit 91 or the still image recording unit 92 to the monitor unit 80 according to the selected mode, and the moving image or still image is reproduced.

  It should be noted that the specific shapes, structures, and numerical values of the respective parts shown in the above embodiments and numerical examples are merely examples of specific embodiments in carrying out the present invention. Therefore, the technical scope of the present invention should not be limitedly interpreted.

  The present invention can be applied to a video camera, a still image video camera, a still camera, etc., and various aberrations can be corrected satisfactorily, and a small and inexpensive configuration can be achieved.

2 to 4 show a first embodiment of a zoom lens according to the present invention, and this figure is a schematic diagram showing a lens configuration. FIG. It is a figure which shows the spherical aberration, astigmatism, and distortion aberration in a wide angle end. It is a figure which shows the spherical aberration, astigmatism, and a distortion aberration in the intermediate focus position of a wide angle end and a telephoto end. It is a figure which shows the spherical aberration, astigmatism, and distortion aberration in a telephoto end. 6 to 8 show a second embodiment of the zoom lens of the present invention, and this figure is a schematic diagram showing the lens configuration. FIG. It is a figure which shows the spherical aberration, astigmatism, and distortion aberration in a wide angle end. It is a figure which shows the spherical aberration, astigmatism, and a distortion aberration in the intermediate focus position of a wide angle end and a telephoto end. It is a figure which shows the spherical aberration, astigmatism, and distortion aberration in a telephoto end. It is a schematic block diagram which shows embodiment of this invention imaging device.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Zoom lens, G1 ... 1st lens group, G2 ... 2nd lens group, G3 ... 3rd lens group, G4 ... 4th lens group, L1 ... 1st lens, L2 ... 2nd lens, L3 ... 3rd lens L4 ... fourth lens, L5 ... fifth lens, L6 ... sixth lens, L7 ... seventh lens, L8 ... eighth lens, L9 ... ninth lens, L10 ... tenth lens, 2 ... zoom lens, 10 ... Still image video camera (imaging device), 20 ... zoom lens, 30 ... imaging device (imaging means)

Claims (6)

A first lens group having a positive refractive power and a fixed position arranged in order from the object side, and a second zooming system lens having a negative refractive power and a movable position for zooming Group, a third lens group having a positive refractive power and a fixed position, and a fourth lens having a positive refractive power and movable in order to adjust the focal position at the time of zooming and focusing In a zoom lens consisting of
The first lens group is composed of a cemented lens of a first lens of a concave lens and a second lens of a convex lens and a third lens of a convex meniscus lens having a convex surface facing the object side, which are arranged in order from the object side.
The second lens group is composed of a cemented lens of a fourth lens of a concave lens and a fifth lens of a biconcave lens and a sixth lens of a convex lens, which are arranged in order from the object side.
The third lens group includes a seventh lens of a biconvex lens, an eighth lens of a convex meniscus lens having a convex surface facing the image side, and a ninth lens of a concave lens having a strong concave surface facing the object side, which are arranged in order from the object side. Is composed of a three-piece cemented lens consisting of
The fourth lens group includes a tenth lens that is a biconvex lens,
The seventh to ninth lenses in the third lens group are spherical lenses, and satisfy the following conditional expressions (1), (2), (3), (4) and (5), respectively. A zoom lens characterized by that.
(1) -0.2 <H3 / f3 <0
(2) 0.31 <n31-n32
(3) 0.35 <n33-n32
(4) 0.45 <D32 / D3 <0.65
(5) 0.667 ≦ r31 / f3 <0.75
However,
H3: distance between the object side principal point of the third lens group and the most object side surface of the third lens group f3: focal length of the third lens group n31: lens closest to the object side of the third lens group (first lens 7 lens) d-line refractive index n32: convex lens (eighth lens) sandwiched between third lens groups d-line refractive index n33: third lens group most image side lens (9th lens) Refractive index D32 at the d-line: Thickness of convex lens (eighth lens) sandwiched between the third lens group D3: Thickness of three-piece cemented lens constituting the third lens group r31: Most object of the third lens group The radius of curvature of the object side surface of the side lens (seventh lens) is used. The zoom lens according to claim 1, wherein at least one surface of the tenth lens constituting the fourth lens group is an aspherical surface. The zoom lens according to claim 1, wherein the tenth lens constituting the fourth lens group is a plastic lens having at least one aspheric surface and an Abbe number of 50 or more. An image pickup apparatus comprising a zoom lens and an image pickup means for picking up an optical image formed by the zoom lens,
The zoom lens includes a first lens group having a positive refractive power and a fixed position arranged in order from the object side, and a zooming power having a negative refractive power and a movable position for zooming. A second lens group of the system, a third lens group having a positive refractive power and a fixed position, and a movable position to adjust the focal position at the time of zooming and focusing with a positive refractive power A fourth lens group,
The first lens group is composed of a cemented lens of a first lens of a concave lens and a second lens of a convex lens and a third lens of a convex meniscus lens having a convex surface facing the object side, which are arranged in order from the object side.
The second lens group is composed of a cemented lens of a fourth lens of a concave lens and a fifth lens of a biconcave lens and a sixth lens of a convex lens, which are arranged in order from the object side.
The third lens group includes a seventh lens of a biconvex lens, an eighth lens of a convex meniscus lens having a convex surface facing the image side, and a ninth lens of a concave lens having a strong concave surface facing the object side, which are arranged in order from the object side. Is composed of a three-piece cemented lens consisting of
The fourth lens group includes a tenth lens that is a biconvex lens,
The seventh to ninth lenses in the third lens group are spherical lenses, and satisfy the following conditional expressions (1), (2), (3), (4) and (5), respectively. An imaging apparatus characterized by the above.
(1) -0.2 <H3 / f3 <0
(2) 0.31 <n31-n32
(3) 0.35 <n33-n32
(4) 0.45 <D32 / D3 <0.65
(5) 0.667 ≦ r31 / f3 <0.75
However,
H3: distance between the object side principal point of the third lens group and the most object side surface of the third lens group f3: focal length of the third lens group n31: lens closest to the object side of the third lens group (first lens 7 lens) d-line refractive index n32: convex lens (eighth lens) sandwiched between third lens groups d-line refractive index n33: third lens group most image side lens (9th lens) Refractive index D32 at the d-line: Thickness of convex lens (eighth lens) sandwiched between the third lens group D3: Thickness of three-piece cemented lens constituting the third lens group r31: Most object of the third lens group The radius of curvature of the object side surface of the side lens (seventh lens) is used. The imaging apparatus according to claim 4, wherein at least one surface of the tenth lens constituting the fourth lens group is an aspherical surface. The imaging device according to claim 4, wherein the tenth lens constituting the fourth lens group is a plastic lens having at least one aspheric surface and an Abbe number of 50 or more.

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