JPH1184241A - Zoom lens - Google Patents

Abstract

(57) [Problem] To provide a zoom lens having high optical performance over the entire object distance by performing focusing by moving at least two lens groups independently. SOLUTION: In a zoom lens having a plurality of lens groups that move by zooming and at least two focus lens groups that move during focusing, one of the two focus lens groups A
Denotes a lens group that moves during zooming, and the lens group A
Is different in the amount of movement when focusing on the same distance object depending on the zoom position, the other focus lens group B is such that the amount of movement when focusing on the same distance object is constant regardless of the zoom position, and the focus lens group A is Moving along a curve set using two different curves.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens, and more particularly, to a zoom lens suitable for an imaging system of a still camera or a video camera using a so-called floating focus that moves two lens groups independently during focusing. is there.

[0002]

2. Description of the Related Art Conventionally, among single-lens reflex camera photographing lenses, a single focus lens, particularly a wide-angle lens or a macro lens, has two lenses during focusing for the purpose of preventing deterioration of optical performance in short-range photographing. Many proposals have been made using a method of independently moving a group, that is, a focus method called a so-called floating focus.

[0003] Conventionally, a so-called front lens focusing method in which focusing is performed by a first lens unit on the object side is generally used as a focusing method of a zoom lens in a video camera, a still camera, or the like. This method has an advantage that the lens barrel structure can be simplified since the amount of extension of the focus lens for the same object distance is constant regardless of the zoom position. However, when the front lens focus method is used for a high-magnification zoom lens, it is necessary to increase the outer diameter of the front lens in order to secure the peripheral light amount at the time of close-up shooting, and the entire lens system becomes larger. There was a tendency to come.

[0004] As other focus methods, various types of photographing lenses of a rear focus method and an inner focus method have been proposed.

[0005] These methods have the advantage that the focusing lens can be made relatively small and lightweight, so that when used in an autofocus camera, quick focusing becomes possible, and that the entire lens system can be miniaturized. There are advantages. However, this focusing method has a problem in that even when focusing on a specific object, if zooming is performed in many cases, the focus lens may be out of focus because the position on the optical axis of a focus lens that is in focus differs at each zoom position. there were. Therefore, it is necessary to adjust the focus by moving the position of the focus lens in accordance with zooming.

On the other hand, in Japanese Patent Application Laid-Open No. 58-202416, a paraxial refractive power arrangement is set so that the amount of movement of the focus lens is optically constant over the entire zoom range, and the focus movement accompanying zooming is reduced. A corrected zoom lens is proposed.

[0007]

In this method, the arrangement of paraxial refractive power is strictly restricted, so that the entire lens system tends to be enlarged. Japanese Patent Application Laid-Open No. Hei 3-235908 discloses that a focus cam and a correction cam
When performing zooming from a state in which an object at an arbitrary distance is in focus by preparing two cams, moving the lens on a curve set using the focus cam and the correction cam causes a practical problem of occurrence of focus movement. There has been proposed a focus method capable of suppressing the size of the focus. This method mechanically corrects the focus movement due to zooming, so optically, the degree of freedom of the paraxial refractive power arrangement was increased and the lens system could be downsized. Depending on the paraxial refractive power arrangement and the lens type, the optical performance may deteriorate during close-up photography.

According to the present invention, when two lenses among a plurality of lens groups constituting a zoom lens are independently moved and a floating operation for focusing is used, by appropriately setting each element, an object at infinity can be obtained. It is an object of the present invention to provide a zoom lens that achieves good optical performance from a short distance to an object at a close distance, and that performs zooming and focusing with a simple lens barrel structure.

[0009]

According to the present invention, there is provided a zoom lens comprising: (1-1) a zoom lens having a plurality of lens groups moved by zooming and at least two focus lens groups moved during focusing. One focus lens group A of the two focus lens groups is
The lens group A moves during zooming. The lens group A has a moving amount at the time of focusing on the same distance object depending on the zoom position, and the other focus lens group B has a moving amount at the time of focusing on the same distance object. Are constant irrespective of the zoom position, and the focus lens group A moves along a curve set using two different curves.

In particular, (1-1-1) the movement of the focus lens A for focusing on photographing from an object at infinity to an object at a close distance uses one curve defined by a predetermined function g over the entire zoom range. At this time, the moving amount Δ of the focus lens A at an arbitrary zoom position
When the entire object distance is represented by the focus parameter x and the entire zoom range is represented by the zoom parameter z, the following equation is obtained by using the following formula: Δ = g (z + x) -g (z). When a function of a curve used to move the focus lens group A at the time of zooming in a state where the object is focused on an arbitrary object distance is defined as F (z), It is characterized in that the function F (z) is represented by the following formula: F (z) = g (z + x) -gz (z).

[0011]

FIG. 1 is a sectional view of a lens at a wide-angle end in a numerical example 1 of the present invention described later, and FIG. 2 is a diagram showing a paraxial refractive power arrangement of the numerical example 1 in FIG. 9 and 1
Numeral 0 is a lens cross-sectional view at a wide-angle end in Numerical Examples 2 and 3 described later of the present invention.

In the drawing, L1 to L6 are first to sixth groups, respectively. S is an aperture. 2, 9, and 10, the solid lines indicate the movement trajectories of the respective lens groups when zooming from the wide-angle end to the telephoto end, and the dotted lines indicate the lens groups that are fixed during zooming.

In the first and second numerical embodiments, the first lens unit L1, the third lens unit L3, the fifth lens unit L5, and the sixth lens unit L6 move toward the object side during zooming from the wide-angle end to the telephoto end. L2,
The fourth lens unit L4 is fixed. In FIG. 10, the first lens unit L1 to the fifth lens unit L5 are all moved to the object side during zooming.

The zoom lens according to the present embodiment, which includes a plurality of lens groups, is a zoom lens that performs focusing for photographing from an object at infinity to an object at a close distance by moving at least two lens groups independently. Preferably, the at least one lens group moves along a curve represented by a formed locus using two different curves during zooming or focusing.

The other lens groups are characterized in that the amount of extension when focusing on the same object distance is constant regardless of the zoom position.

In FIGS. 1 and 9, focusing from an object at infinity to an object at a close distance uses floating, which is performed by separately moving the sixth unit L6 and the fourth unit L4. At this time, the amount of movement for focusing to the same object distance is constant regardless of the zoom position of the focus lens unit B in the fourth lens unit L4, and is constant depending on the zoom position of the focus lens unit A in the sixth lens unit L6. The moving amount changes.

In the present embodiment, each element (refractive power of each lens group, paraxial refractive power arrangement, zoom locus, etc.) is set so as to perform such floating.

In the drawing, A is assigned to the element relating to the focus lens group A, and B is assigned to the element relating to the focus lens group B.
Is attached.

FIG. 3 is an explanatory diagram showing the extension amount Δ6 of the sixth lens unit L6 for focusing at each zoom position. The horizontal axis is the focus parameter (equivalent to the object distance) O
D, the vertical axis is the feed amount Δ6 of the sixth lens group.

In this embodiment, in the sixth lens unit, the extension amount Δ6 to the same object distance increases from the wide (wide-angle end) W to the tele (telephoto end) T.

Here, the focus parameter is a numerical value corresponding to the object distance. In this embodiment, 0 is infinity and 0.5 is 1.5 meters in the vicinity. In the present embodiment, the zoom parameter uses a value proportional to the amount of rotation of the focus key.

FIG. 4 is an explanatory diagram showing the extension amount x4 of the fourth lens unit L4 for focusing at each zoom position. The horizontal axis is the focus parameter, and the vertical axis is the feed amount Δ4 of the fourth lens unit. As is clear from the graph, the extension amount Δ4 of the fourth lens unit to the same object distance is constant depending on the zoom position. Thus, the focus movement of the fourth lens unit can be realized by a simple mechanism such as a focus cam as in the case of the front lens focus.

Next, a specific method of moving the focus and zoom of the sixth lens group in the embodiment will be described.
FIG. 5 is an explanatory diagram of the focus cam curve of the sixth lens unit L6. The horizontal axis is obtained by adding the zoom parameter and the focus parameter. The vertical axis is the feeding amount Δ6. The curve g in FIG. 5 is realized by shifting the payout curve shown in FIG. 3 in the focus parameter direction and the payout direction for each zoom position, superimposing them, and then approximating with one curve.

More specifically, the movement trajectory relating to focusing of the sixth lens unit L6 as a focus lens unit for photographing from an object at infinity to an object at a close distance is determined by a predetermined function g (see FIG. 5) over the entire zoom range. This is performed using one defined curve (the focus cam 77 in FIG. 8). At this time, the amount of movement Δ6 of the sixth unit L6 at an arbitrary zoom position is represented by the following formula: Δ = g (z + x) −g (z) where the entire object distance is represented by the focus parameter x and the entire zoom range is represented by the zoom parameter z. I use it. Then, a curve function gz (correction cam 79 in FIG. 8) is defined for the function g so as to correspond to the entire zoom range, and when zooming is performed in a state where an arbitrary object distance is focused, When the function of the curve used to move the sixth unit L6 is F (z), the function F (z) is set using two curves g and gz. For example, F (z) = g (z + x) -gz (z).

In the present embodiment, the fourth lens unit other than the sixth lens unit has a constant extension amount when focusing on the same object distance regardless of the zoom position.

When focusing with the sixth lens group, the lens is moved by approximation by one curve. To reduce the error of this approximation, the relationship between the focus parameter and the object distance, and the relationship between the zoom parameter and the focal length are determined. Is changing. Here, the zoom parameter is a numerical value corresponding to each focal length from the wide-angle end to the telephoto end. In the present embodiment, 0 is the wide-angle end and 1 is the telephoto end.

FIG. 5 shows a curve g. In FIG. 5, the range Z1 is the range of use of the focus cam from the object at infinity to the closest object at the wide-angle end, and the range Z2 is the object from the object at infinity at the intermediate focal length. The range of use of the focus cam to the object, range Z3, indicates the range of use of the focus cam from the object at infinity to the closest object at the telephoto end. By changing the range of use of the focus cam depending on the zoom position in this way, the amount of extension is changed for the same object distance in accordance with the zoom position.

FIG. 6 is an explanatory diagram showing a curve of the correction cam (the correction cam 79 in FIG. 8). The horizontal axis is the zoom parameter,
The vertical axis is the correction movement amount. Explanation of the correction movement is shown in FIGS.
In the description.

FIG. 7 is a sectional view schematically showing a lens barrel structure for realizing the focus system of the present invention. FIG. 8 is an explanatory view schematically showing a development view of a lens barrel for realizing the focus method of the present invention. In FIG. 7, L6 is the sixth lens group, and L4 is the fourth lens group.

First, the movement of the fourth lens unit L4 will be described. The fourth lens unit L4 is fixed to the image plane during zooming. The fourth lens unit L4 moves in the optical axis direction indicated by the arrow Fa along the focus cam 74 of the focus cam barrel 73 in FIG.

Next, the movement of the sixth lens unit L6 will be described.
When focusing is performed at an arbitrary zoom position, the focus key 82 is rotated along with a focus cam (function g) 77 shown in FIG.
Moves in the optical axis direction, the sixth unit L6 connected to the focus pin 78 moves in the optical axis direction. At this time, the focus cam cylinder 76 is fixed.

Next, a case in which zooming is performed from a state in which an object at an arbitrary distance is focused will be described step by step. By rotating the zoom cam barrel 71 in FIG. 8, the focus cam barrel 76 connected by the connecting pin 72 implanted in the zoom cam barrel 71 is rotated, and the focus cam barrel 76 is formed along the correction cam (function gz) 79 in the optical axis direction. At this time, the connecting pin 72 is fixed to the focus cam barrel 76, and the fixing pin 80 is fixed to the fixed barrel 81.
It is fixed to. The sixth lens unit L connected to the focus pin 78 with the movement of the focus cam barrel 76
6 is the curve (function g) of the focus cam 77 and the correction cam 7
9 (function gz), a curve (function Fz)
(Z)) Move on the optical axis direction. At this time, the focus key 82 is fixed.

The focus cam 77 is moved so that the focus movement due to the zooming becomes practically acceptable.
Curve (function g) and the curve of the correction cam 79 (function g)
z) has been calculated.

Table 1 is a table in which the focus extension amount from an object at infinity at each zoom position and each object distance is calculated. DX is the extension amount by paraxial calculation, and DXC is the extension amount approximated by the focus cam A. is there.

[0035]

[Table 1] In the zoom lens including five units according to Numerical Example 3 shown in FIG. 10, the first unit L1 and the second unit L2 are used to perform floating.

The first unit L1 corresponds to the fourth unit in FIGS. 1 and 9 in which the amount of movement is constant regardless of the zoom position when focusing on an object at the same distance, and the second unit L2 is the same. This corresponds to a sixth group in FIGS. 1 and 9 in which the amount of movement changes depending on the zoom position when focusing on a distance object.

The basic structure of the lens barrel is the same as in the first and second numerical embodiments.

In the numerical examples, ri is the i-th from the object side.
The radius of curvature of the i-th lens surface, di is the i-th lens thickness or air gap from the object side, and ni and vi are the refractive index and Abbe number of the i-th lens. The coefficients of each group movement coefficient, the focus cam A, the correction cam, and the focus cam B are a1 to a6 of the movement curve coefficient, the movement amount is m, and the parameter is p (zoom parameter or zoom parameter + focus parameter). Then, m = a1 * p + a2 * p ＾ 2 + a3 * p ＾ 3 + a4 * p
＾ 4 + a5 * p ＾ 5 + a6 * p ＾ 6

Numerical Example 1 pat9512-1 (100300 / flo003) f = 76.9 to 292.3 FNO = 1: 4.1 to 5.8 2ω = 31.4 ° to 8.5 ° r 1 = 71.015 d 1 = 2.60 n 1 = 1.80518 ν 1 = 25.4 r 2 = 54.945 d 2 = 0.20 r 3 = 55.164 d 3 = 7.60 n 2 = 1.43387 ν 2 = 95.1 r 4 = -1179.789 d 4 = 0.20 r 5 = 100.052 d 5 = 3.00 n 3 = 1.51633 ν 3 = 64.2 r 6 = 244.081 d 6 = Variable r 7 = -106.208 d 7 = 1.40 n 4 = 1.69680 ν 4 = 55.5 r 8 = 44.478 d 8 = 3.60 r 9 = -53.864 d 9 = 1.40 n 5 = 1.69680 ν 5 = 55.5 r10 = 48.790 d10 = 2.60 n 6 = 1.84666 ν 6 = 23.9 r11 = -3532.252 d11 = Variable r12 = 72.920 d12 = 4.20 n 7 = 1.58144 ν 7 = 40.8 r13 = -56.775 d13 = 0.20 r14 = 76.263 d14 = 4.50 n 8 = 1.49700 ν 8 = 81.6 r15 = -51.103 d15 = 1.50 n 9 = 1.80518 ν 9 = 25.4 r16 = -196.239 d16 = 2.00 r17 = 0.000 (aperture) d17 = variable r18 = -50.373 d18 = 2.50 n10 = 1.78590 ν10 = 44.2 r19 = -82.865 d19 = variable r20 = 624.128 d20 = 1.50 n11 = 1.83400 ν11 = 37.2 r21 = 36.443 d21 = 5.50 n12 = 1.48749 ν12 = 70.2 r22 = -69.388 d22 = 0.15 r23 = 48.563 d23 = 4.00 n13 = 1.69680 ν13 = 55.5 r24 = -190.311 d24 = variable r25 = 163.858 d25 = 1.50 n14 = 1.80518 14 = 25.4 r26 = 41.354 d26 = 4.30 r27 = -46.745 d27 = 1.50 n15 = 1.62299 ν15 = 58.1 r28 = 81.338 d28 = 1.00 r29 = 87.277 d29 = 4.20 n16 = 1.84666 ν16 = 23.9 r30 = -89.583 d30 = Variable r31 = 0.000 Focal length 76.86 115.92 292.27 pat9512-1 (= 100300 ・ flo033) Variable interval f FNO 2ω ω d 6 4.00 26.00 59.00 76.9 4.1 31.4 15.7 d11 18.91 15.37 2.17 115.9 4.6 21.1 10.6 d17 6.00 9.54 22.74 292.3 5.8 8.5 4.2 d19 30.43 21.24 1.98 d24 20.12 15.28 1.95 d30 5.00 19.02 51.61 Transfer coefficient 1st 2nd 3rd 4th 5th 6th 1st group -55.000000 3rd group -12.457685 17.871664 -22.157247 5th group -17.022055 -17.122830 5.697627 6th group -22.08044 -44.95663 41.13380 -34.09481 30.29348 -16.90904 Focus cam A 2.981990 2.481774 -0.006598 0.572113 0.789188 0.001177 Correction cam -25.062430 -47.438404 41.140398 -34.666923 29.504292 -16.910217 Focus cam B-2.093877 -1.5917591 -1.6145029 0.74705801 Numerical example 2 = 76.9 ~ 292.2 FNO = 1: 4.1 ~ 5.8 2ω = 31.4 ° ~ 8.5 ° r 1 = 67.046 d 1 = 2.60 n 1 = 1.80 518 ν 1 = 25.4 r 2 = 51.913 d 2 = 0.20 r 3 = 52.121 d 3 = 7.60 n 2 = 1.43387 ν 2 = 95.1 r 4 = -1704.255 d 4 = 0.20 r 5 = 98.919 d 5 = 3.00 n 3 = 1.51633 ν 3 = 64.2 r 6 = 228.238 d 6 = Variable r 7 = -87.155 d 7 = 1.40 n 4 = 1.69680 ν 4 = 55.5 r 8 = 44.888 d 8 = 3.60 r 9 = -67.511 d 9 = 1.40 n 5 = 1.69680 ν 5 = 55.5 r10 = 42.689 d10 = 2.60 n 6 = 1.84666 ν 6 = 23.9 r11 = 557.831 d11 = Variable r12 = 64.223 d12 = 4.20 n 7 = 1.58144 ν 7 = 40.8 r13 = -54.750 d13 = 0.20 r14 = 76.906 d14 = 4.50 n 8 = 1.49700 ν 8 = 81.6 r15 = -49.490 d15 = 1.50 n 9 = 1.80518 ν 9 = 25.4 r16 = -206.348 d16 = 2.00 r17 = 0.000 (aperture) d17 = Variable r18 = -45.590 d18 = 2.50 n10 = 1.78590 ν10 = 44.2 r19 = -88.224 d19 = variable r20 = 748.136 d20 = 1.50 n11 = 1.83400 ν11 = 37.2 r21 = 36.288 d21 = 5.50 n12 = 1.48749 ν12 = 70.2 r22 = -58.720 d22 = 0.15 r23 = 50.716 d23 = 4.00 n13 = 1.69680 ν13 = 55.5 r24 = -135.813 d24 = Variable r25 = 149.478 d25 = 1.50 n14 = 1.80518 ν14 = 25.4 r26 = 39.952 d26 = 4.30 r27 = -45.328 d27 = 1.50 n15 = 1.62299 ν15 = 58.1 r28 = 68.450 d28 = 1.00 r29 = 75.081 d29 = 4.20 n16 = 1.84666 ν16 = 23.9 r30 = -101.668 d30 = Variable r31 = 0.000 Focal length 76.87 115.15 292.24 pat9512-2 (= 100300 ・ flo004) Variable interval f FNO 2ω ω d 6 4.00 26.00 59.00 76.9 4.1 31.4 15.7 d11 17.42 14.38 1.92 115.2 4.5 21.3 10.6 d17 6.00 9.04 21.50 292.2 5.8 8.5 4.2 d19 22.78 15.74 1.96 d24 20.29 15.80 1.79 d30 5.00 16.52 44.32 Transfer coefficient 1st 2nd 3rd 4th 5th 6th 1st group -55.000000 3rd group -11.209468 17.871664 -22.157247 5th group -12.078194 -17.137606 8.392095 6th group -16.62320 -43.21068 42.84715 -38.73292 36.35755 -19.95350 Focus cam A 2.996485 2.204997 -0.006569 0.943506 0.564269 0.001169 Correction cam -19.61968 -45.41568 42.85372 -39.67643 35.79328 -19.95467 Focus cam B-2.65110 -1.98568 -1.186.81 -1.186.81.1 pat9512-3 (= lxy / e-3) f = 29.2 ~ 131.0 fno = 1: 3.5 ~ 4.7 2ω = 73.1 ° ~ 18.8 ° r 1 = 105.578 d 1 = 2.00 n 1 = 1.84666 ν 1 = 23.8 r 2 = 50.919 d 2 = 7.00 n 2 = 1.69680 ν 2 = 55.5 r 3 = 537.137 d 3 = 0.12 r 4 = 44.506 d 4 = 6.00 n 3 = 1.71300 ν 3 = 53.8 r 5 = 128.427 d 5 = Variable r 6 = 80.225 d 6 = 1.20 n 4 = 1.83400 ν 4 = 37.2 r 7 = 12.326 d 7 = 4.34 r 8 = -57.043 d 8 = 1.10 n 5 = 1.80400 ν 5 = 46.6 r 9 = 31.364 d 9 = 0.10 r10 = 21.783 d10 = 4.40 n 6 = 1.84666 ν 6 = 23.9 r11 = -44.112 d11 = 0.59 r12 = -28.266 d12 = 1.10 n 7 = 1.83481 ν 7 = 42.7 r13 = 282.648 d13 = Variable r14 = 0.000 (aperture) d14 = 0.00 r15 = 21.782 d15 = 1.20 n 8 = 1.84666 ν 8 = 23.8 r16 = 13.048 d16 = 5.83 n 9 = 1.60311 ν 9 = 60.7 r17 = -57.777 d17 = 0.12 r18 = 29.602 d18 = 2.10 n10 = 1.77250 ν10 = 49.6 r19 = 65.791 d19 = Variable r20 = -45.911 d20 = 3.35 n11 = 1.77520 ν11 = 27.5 r21 = -12.172 d21 = 1.10 n12 = 1.80400 ν12 = 46.6 r22 = 132.338 d22 = Variable r23 = 69.726 d23 = 5.45 n13 = 1.48749 ν13 = 70.2 r24 = -19.071 d24 = 0.12 r25 = 68.541 d25 = 2.58 n14 = 1.69680 ν14 = 55.5 r26 = -97.906 d26 = 3.05 r27 = -18.296 d27 = 1.40 n15 = 1.84666 ν15 = 23.8 r28 = -52.561 d28 = Variable r29 = 0.000 Moving coefficient Focal length 29.17 47.98 130.95 pat9512-3 (= lxy / e-3) Variable interval f FNO 2ω ω d 5 1.91 13.16 31.57 29.2 3.5 73.1 36.6 d13 13.88 9.72 1.74 48.0 4.0 48.5 24.3 d19 2.18 4.75 8.53 131.0 4.7 18.8 9.4 d22 7.48 4.90 1.12 d28 0.00 5.38 11.49 Transfer coefficient 1st 2nd 3rd 4th 5th 6th 1st group -29.006062 2nd group -5.046110 14.73034 -60.53437 145.4351 -158.3628 64.42849 3rd group -16.409394 12.186120 -7.264314 4th Group -10.988949 13.803568 -7.946752 Group 5 -16.409394 12.186120 -7.264314

[0040]

As described above, according to the present invention,
When using floating for focusing by moving two lens groups independently of a plurality of lens groups constituting a zoom lens, by setting each element appropriately, it is possible to obtain a good object from an object at infinity to an object at a close distance. It is possible to achieve a zoom lens that achieves optical performance, and performs zooming and focusing well with a simple lens barrel structure.

In addition, according to the present invention, it is possible to realize a floating focus method in a zoom lens with a simple lens barrel structure. By using a floating method as a focus method, it is possible to obtain an excellent object from an object at infinity to an object at a close distance. A zoom lens having optical performance can be realized.

[Brief description of the drawings]

FIG. 1 is a sectional view of a lens at a wide angle end according to Numerical Embodiment 1 of the present invention.

FIG. 2 is a diagram illustrating a paraxial arrangement according to Numerical Embodiment 1 of the present invention.

FIG. 3 is an explanatory diagram showing a focus extension amount of a sixth group at each zoom position according to the present invention.

FIG. 4 is an explanatory diagram showing a focus extension amount of a fourth lens unit according to the present invention.

FIG. 5 is an explanatory diagram of a curve of a focus cam of a sixth group according to the present invention.

FIG. 6 is an explanatory diagram of a curve of a fourth group of focus cams according to the present invention.

FIG. 7 is a cross-sectional view schematically showing a lens barrel structure for realizing a focus method according to the present invention.

FIG. 8 is a view schematically showing a development view of a lens barrel for realizing the focus method of the present invention.

FIG. 9 is a sectional view of a lens at a wide angle end according to Numerical Example 2 of the present invention.

FIG. 10 is a sectional view of a lens at a wide angle end according to Numerical Embodiment 3 of the present invention.

[Explanation of symbols]

 L1 First group L2 Second group L3 Third group L4 Fourth group L5 Fifth group L6 Sixth group SP Aperture 71 Zoom cam cylinder 72 Connecting pin 74, 77 Focus cam 73 Focus cam cylinder 76 Focus cam cylinder 79 Correction cam 80 Fixed Pin 82 Focus key

Claims (2)

[Claims] 1. A zoom lens having a plurality of lens groups that move by zooming and at least two focus lens groups that move at the time of focusing, wherein one of the two focus lens groups is a focus lens group A.
Denotes a lens group that moves during zooming, and the lens group A
Is different in the amount of movement when focusing on the same distance object depending on the zoom position, the other focus lens group B is such that the amount of movement when focusing on the same distance object is constant regardless of the zoom position, and the focus lens group A is A zoom lens, which moves along a curve set using two different curves. 2. The movement of the focus lens A related to focusing from photographing an object at infinity to an object at a close distance is defined by a predetermined function g over the entire zoom range.
The movement amount Δ of the focus lens A at an arbitrary zoom position is represented by a focus parameter x and a zoom parameter z representing the entire object distance, and Δ = g (z + x). -G (z) is used to define a function gz of a curve corresponding to the entire zoom range for the function g, and perform zooming while focusing on an arbitrary object distance. When a function of a curve used to move the focus lens group A is F (z), the function F (z) is expressed by the following equation: F (z) = g (z + x) −gz (z) The zoom lens according to claim 1, wherein: