JP3260798B2 - Wide-angle zoom lens - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wide-angle zoom lens.

[0002]

2. Description of the Related Art In recent years, a fully automatic camera equipped with a zoom lens having a high magnification has been remarkably commercialized as a new concept camera. As described above, when the zoom lens has a high magnification, the zoom lens always moves toward a wide angle or a telephoto direction.

A conventional zoom lens has a wide angle end at 2ω = 6.
It is about 3 ° or 2ω =
The thing of about 84 degrees is known. For example, Japanese Patent Laid-Open No. 2-2
No. 84109, for example.

Further, the lens system described in Japanese Patent Application Laid-Open No. Hei 2-135312 enables a super-wide-angle zoom lens, which was conventionally only known as an interchangeable lens for a single-lens reflex camera, to be adapted to a compact camera. This is a compact zoom lens.

[0005]

Each of the above-mentioned zoom lenses is intended to widen the angle of the conventional type as it is, and it is difficult to correct aberrations. That is, although the focal length is shortened, since the zoom lens is of a telephoto type, it is insufficient in optical performance.

SUMMARY OF THE INVENTION An object of the present invention is to provide a zoom lens which is wide-angle, bright, and well corrected in aberrations by appropriately configuring the first lens group based on a conventional three-group zoom lens. To provide.

[0007]

A wide-angle zoom lens according to the present invention comprises, in order from the object side, a first lens unit having a positive refractive power;
A second lens unit having positive refractive power, and more a third lens unit having a negative refractive power, a second lens unit spread distance between the first lens group and the second lens group at the telephoto end than at the wide angle end Zooming from the wide-angle end to the telephoto end by reducing the distance between the first lens unit and the third lens unit, and the first lens unit consists of a negative lens and a positive lens in order from the object side, or only one negative lens a front group is composed of a rear group consisting of one negative lens and two positive lenses in order from the object side, the second lens group
It has a configuration having an aperture stop, and satisfies the following condition (1). (1) | φf / φ1 | <6.0 where φf is the refractive power of the front group, and φ1 is the refractive power of the first lens group. In addition, the wide-angle zoom lens of the present invention includes:
In order from the object side, a first lens group having a positive refractive power, a second lens group having a positive refractive power, a third lens group having a positive refractive power,
A fourth lens group having a negative refractive power, a distance between the first lens group and the second lens group, a distance between the second lens group and the third lens group, a distance between the third lens group and the fourth lens group, The first lens group includes at least one negative lens, at least one positive lens component, and at least one positive lens component. And a negative lens component, and satisfies the condition (1).

The present invention further develops the attempt of the applicant to propose a wide-angle lens system disclosed in Japanese Patent Application Laid-Open No. Hei 2-135312, whereby the total length of the lens system can be shortened, and the zoom lens type has an object side. The first lens group having a positive refractive power, the second lens group having a positive refractive power, and the third lens group having a negative refractive power are arranged in this order.
The basic configuration is a three-group zoom lens composed of lens groups, and the first lens group has a lens configuration suitable for widening the angle of view.

The lens system of Japanese Patent Application No. 2-1521 proposed by the applicant of the present invention can convert a negative lens component and a positive lens component constituting the first lens unit without changing the structure of the first lens unit itself. By arranging them at a certain distance or more, the angle of incidence of off-axis rays to the second lens group having a positive refractive power is made small to facilitate aberration correction and achieve a wide angle. .

On the other hand, in the present invention, the configuration itself of the first lens group is changed to one suitable for widening the angle based on the following idea.

The zoom lens of the present invention is not designed from the beginning with a wide-angle lens system as a basic specification, but is designed by setting the angle of view from the wide-angle end to the telephoto end to an easy-to-design angle of view. Is shifted to the wide-angle side to obtain a wide-angle zoom lens.

Specifically, for example, first, when the focal length f is 3
Designing an optical system of 5mm to 135mm, based on this, 28mm if a 0.8-degree wide-angle attachment is attached to it
A lens system of up to 105 mm can be obtained. Here, as long as the basic lens system has a short overall length and a small outer diameter of the lens, even if an attachment for widening the angle is added, the overall lens system does not become very large.

If the wide-angle attachment is incorporated into a basic optical system to form one optical system as a whole, it is considered that the attachment has the same configuration as that of a lens group for aberration correction. In other words, the attachment is developed from the property of an afocal converter, and is considered as a lens component for widening the angle in the lens system.

In the present invention, as shown in FIG. 43, this lens component is defined as the front group La of the first lens group, and the first lens group of the basic optical system is defined as the rear group Lb of the first lens group. The configuration was adopted. That is, the reverse telephoto type of the wide-angle lens is a lens system that starts with a first lens group of a wide-angle afocal converter (front group) and a positive lens group (rear group).
The lens system of the present invention is a retrofocus type lens system in which the actual distance between the two is reduced for compactness.

Here, in order to achieve the object of the present invention, it is necessary to satisfy the above condition (1). If this condition is not satisfied, it is difficult to achieve the object of the present invention.

According to the present invention, a wide-angle zoom lens having a field angle 2ω at the wide-angle end of about 63 ° or more is obtained by the above-described configuration. That is, in the present invention, in order to widen the lens system, the zooming was performed without changing the type or lens configuration of the zoom lens. If the angle is widened without changing the type and configuration of the lens system, the load on the third lens group increases, and it is not possible to secure a sufficient back focus at the wide angle end. Further, the magnification burden at the telephoto end becomes extremely large, and it becomes difficult to correct aberrations.

In order to solve such a problem, an aspherical surface is used, or a gradient index lens having a problem in production technology at present, particularly a radial gradient index lens, is used. These are not easy to manufacture lenses.

In general, when the angle of the lens system is widened, the path of the center light beam and the off-axis light beam passing through the lens system is greatly different, so that there is a problem in aberration correction. That is, as the angle of view increases, curvature of field, distortion, chromatic aberration of magnification, sagittal coma and the like increase. Therefore, in order to favorably correct the aberration, it is desirable to use a symmetric type or a configuration close thereto.

For the above reasons, in the present invention, as described above, the zoom lens based on the three-group zoom lens is
It is also characterized in that an aperture stop is arranged at the center of the lens group to provide a lens configuration that is close to a symmetric type, making the lens system extremely preferable for aberration correction. Also, in this lens system, the basic configuration does not change even if the aperture position is moved back and forth, only the range of use of the light beam changes.

Since it is preferable to make the lens configuration symmetrical in terms of aberration correction, the components of the lens configuration are considered so as to be suitable for widening the angle. In particular, the lens type handled in the present invention can shorten the back focus, shorten the overall length of the lens system, and reduce the outer diameter of the lens. From this point, the present invention can form a more excellent wide-angle zoom lens by using a lens system symmetrical with respect to the diaphragm and adding a lens component to widen the angle.

Here, the front group of the first lens group supplements the action of the rear group. The zoom lens having the above-described configuration includes the first lens.
Considering the luminous flux passing through the lens group and the third lens group, these lens groups have a large influence on off-axis aberration,
The lens group has a large influence mainly on axial aberration such as spherical aberration.

In order to further widen the angle of the lens system, specific aberrations such as chromatic aberration of magnification and distortion having an inflection point must be corrected. In other words, in the configuration of the zoom lens of the present invention having the above-described properties, in order to correct a specific aberration for widening the angle, it is necessary to pay attention to the configuration of the first lens group and the third lens group. . In order to increase the aperture ratio, it is necessary to pay attention to the configuration of the second lens group.

Considering the wide-angle end, it is not advisable to greatly increase the number of constituent lenses in the third lens group. Since the optical system of the present invention is an optical system having a power arrangement in which the rear principal point is located behind the lens system, it is difficult to secure a back focus before aberration correction, and conversely, the degree of freedom of aberration correction is limited. Less. Therefore, it is desirable that the third lens group is configured with a small number of lenses using an aspheric surface. As a result, residual aberration can be suppressed by the third lens group itself, and higher-order aberrations generated in the first lens group can be corrected and balanced as a whole. Also, the back focus can be ensured without difficulty, and the problem of an increase in the diameter of the rear lens and the problem of the occurrence of flare due to internal reflection from the film surface can be reduced.

In consideration of the above points, it is preferable to modify the first lens group to correct higher-order chromatic aberration and distortion unique to the wide-angle lens.

The off-axis ray height is particularly high near the wide-angle end, and it is difficult to correct residual high-order aberration by the second lens unit and the third lens unit unless aberration is sufficiently corrected in the first lens unit. is there. This can be seen from the aberration correction coefficient. In particular, it is significant to see the balance between high-order aberrations and low-order aberrations.

Tables 1 and 2 show the correction status in the first lens unit based on the aberration coefficient of Example 1 described later.

Table 1 Wide angle end K SA3 CMA3 AST3 DIS3 PTZ3 1 -0.00001 -0.00060 -0.00634 -0.68756 -0.01525 Lf 2 0.00393 -0.00302 0.00026 -0.01807 0.07043 3 -0.00388 -0.00784 -0.00176 -0.03585 -0.05142 4 0.00011 0.00380 0.01529 0.35334 0.01401 5 0.00000 0.00004 -0.01272 -0.66454 0.01346 6 0.01626 0.00255 0.00004 0.00360 0.06885 7 -0.01313 -0.01030 -0.00090 -0.01394 -0.05240 8 0.00030 0.00926 0.03159 0.29145 -0.00313 9 -0.00643 -0.01924 -0.00639 -0.06723 -0.06106 10 -0.00041 0.01420 -0.05513 0.88004 -0.02043 (1) Lf 0.00016 -0.00765 0.00744 -0.38814 0.01777 Lb -0.00341 -0.00348 -0.04350 0.42938 -0.05471 (2) -0.00568 -0.00308 0.11297 -0.99783 -0.10148 (3) 0.00164 0.00491 -0.07868 0.54632 0.13018 K SA5 CMA5 AST5 DIS5 PTZ5 SA7 1 0.00000 0.00000 0.00089 0.19925 0.00537 0.00000 Lf 2 0.00005 0.00010 -0.00019 -0.04197 -0.02465 0.00000 3 -0.00006 -0.00030 0.00309 0.05851 0.02059 0.00000 4 0.00000 0.00001 -0.00278 -0.17371 -0.00664 0.00000 5 0.00000 0.00000 0.00140 0.29779 -0.00517 0.00000 6 0.000 45 0.00065 -0.00128 -0.06874 -0.03299 0.00001 Lb 7 -0.00038 -0.00086 0.00385 0.06245 0.02784 -0.00001 8 0.00001 0.00015 -0.00667 -0.24618 -0.00634 0.00000 9 -0.00013 -0.00038 0.00605 0.10153 0.03024 0.00000 10 -0.00001 0.00027 -0.00851 -0.05951 0.00708 0.00000 ( 1) Lf -0.00001 -0.00019 0.00100 0.04207 -0.00532 0.00000 Lb -0.00006 -0.00017 -0.00516 0.08734 0.02066 0.00000 (2) 0.00215 0.00210 0.02325 0.11002 0.04238 0.00044 (3) -0.00011 -0.00182 -0.01764 -0.23535 -0.04339 -0.00001 Table 2 Telephoto end K SA3 CMA3 AST3 DIS3 PTZ3 1 -0.00012 -0.00129 -0.00153 -0.02522 -0.00533 2 0.07407 -0.15959 0.03821 -0.04511 0.02461 3 -0.07297 0.12950 -0.02554 0.02573 -0.01796 4 0.00198 0.00570 0.00182 0.00645 0.00489 5 0.00000 0.00011 -0.00449 -0.02568 0.00470 6 0.30610 -0.62100 0.13998 -0.11093 0.02405 7 -0.24715 0.48029 -0.10370 0.07903 -0.01831 8 0.00567 0.01211 0.00287 0.00127 -0.00109 9 -0.12109 0.19893 -0.03631 0.03156 -0.02133 10 -0.00765 0.05210 -0.03943 0.10570 -0.00714 (1) Lf 0.00296 -0.02568 0.01292 -0.03815 0.00621 Lb -0.06413 0.12254 -0.04108 0.08095 -0.01912 (2) -0.04759 -0.01905 0.04255 -0.06852 -0.03545 (3) 0.10867 -0.07190 -0.01371 0.05029 0.04548 K SA5 CMA5 AST5 DIS5 PTZ5 SA7 1 0.00000 0.00000 0.00003 0.00058 0.00013 0.00000 Lf 2 0.00378 -0.01177 0.00036 0.00004 -0.00079 0.00023 3 -0.00467 0.01264 -0.00018 -0.00005 0.00061 -0.00035 4 0.00003 -0.00003 0.00001 -0.00043 -0.00024 0.00000 5 0.00000 -0.00002 -0.00015 0.00139 -0.00003 0.00000 6 0.03670 -0.11819 0.00751 -0.00661 -0.00013 0.00506 Lb 7 -0.03092 0.09610 -0.00552 0.00477 0.00010 -0.00437 8 0.00066 -0.00059 -0.00011 -0.00036 -0.00021 0.00008 9 -0.01079 0.03259 -0.00184 0.00146 0.00039 -0.00114 10 -0.00095 0.00630 -0.00199 0.00210 0.00044 -0.00014 (1) Lf -0.00086 0.00083 0.00021 0.00014 -0.00028 -0.00012 Lb -0.00530 0.01618 -0.00209 0.00276 0.00056 -0.00052 (2) 0.06153 0.00426 0.00182 -0.00011 0.00112 0.03223 (3) -0.05301 -0.04412 -0.00037 0.00050 -0.00148 -0.03257 TOTAL 0.00235 -0.02284 -0.00043 0.00329 -0.00008 -0.000 97 Table 1 shows values at the wide-angle end, and Table 2 shows values at the telephoto end. In addition, the sum of the aberration correction coefficients unique to the surface is shown for the units other than the first lens unit. K (1-4) and Lf are in the front group, and K (5-
10) and Lb are the rear group, (2) and (3) are the second and third groups.
This represents a lens group.

According to these tables, the influence of spherical aberration as axial aberration is small in the first lens group. On the other hand, it can be seen that the correction situation of astigmatism and distortion, which are off-axis aberrations, has a large effect in the first lens group. That is, in the lens system of this embodiment, the front group effectively corrects the undercorrection of the rear group in the astigmatism, and the front group corrects the overcorrection of the rear group in the distortion. This is illustrated by the ray diagram shown in FIG.
Since the off-axis light beam entering the front group at an acute angle has a gentle incident angle when entering the rear group, it can be seen that the correction function is shared.

In the present invention, it is recognized that it is impossible to widen the angle of the conventional optical system based on the first lens group. As described above, a lens component having a low refractive power is added before the first lens group, and the angle of incidence on the first lens group is easily corrected for aberration. The added lens component is referred to as a front group of the first lens group, in other words, the conventional first lens group is referred to as a rear group of the first lens group. Lens system. In this case, the front group can be considered to be the simplest configuration including a single negative lens. However, in order to correct aberrations better, it is effective to add a positive lens to the negative lens.

On the other hand, in order to prevent the diameter of the front lens from being reduced and the entrance pupil from being too far away, it is desirable to regulate the diameter in accordance with the conditions described later. As described above, it is desirable that the first lens group uses at least one negative lens in the front group. On the other hand, it is desirable that the rear group includes at least one positive lens component and one negative lens component.

The condition (1) is related to the following conditions. (2) 0.1 <φ1 / φw <1.25 (3) 1.1 <φ12w / φw <3.0 (4) 1.5 <β3T / β3w <4.0 where φw is the whole system at the wide-angle end , 12w is the combined refractive power of the first and second lens groups at the wide-angle end, β3w is the magnification of the third lens group at the wide-angle end, and β3T is
This is the magnification of the third lens unit at the telephoto end . Condition (2)
Defines the refractive power of the first lens group. If the upper limit of condition (2) is exceeded, it becomes difficult to correct aberration. When the value exceeds the lower limit of the condition (2), the moving amount during zooming increases, which is not preferable in keeping the miniaturization. Condition (3) is a condition necessary for reducing the total lens length of the first lens unit and the second lens unit and determining a desirable refractive power from the viewpoint of aberration correction. If the upper limit of this condition is exceeded, it will be difficult to obtain sufficient optical performance even though miniaturization can be achieved. On the other hand, exceeding the lower limit is not preferable because the lens system becomes large. Condition (4) is a condition relating to the magnification ratio.
If the lower limit is exceeded, it becomes difficult to achieve a realistic high-magnification zoom lens even if a paraxial solution is obtained.

Further, the lens system of the present invention preferably satisfies the following conditions (5) and (6) when focusing on paraxial rays and off- axis principal rays in the first lens unit. (5) 0.5 <hB / hF <1.5 (6) 0.2 <AB / AF <2.0 where hF is the height of an on-axis marginal ray incident on the front group of the first lens unit at the wide angle end, hB is the height of an on-axis marginal ray incident on the rear group of the first lens unit at the wide-angle end, and AF is the off-axis principal light of the maximum angle of view incident on the front group of the first lens group at the wide-angle end.
The line height AB is the off-axis principal ray height at the maximum angle of view incident on the rear group of the first lens group at the wide angle end.

The condition (3) is satisfied even if the front lens unit has a function as a negative lens unit and the first lens unit is configured as an inverse telephoto type to increase the angle of view, or even if the front lens unit is a convergent system. This means that it has a weak positive refractive power. If the lower limit of the condition (5) is exceeded, the effect of correcting off-axis aberrations becomes weak at the wide-angle end. When the value exceeds the upper limit of the condition (5), the refractive power of the front unit becomes strong, the number of constituent lenses increases for aberration correction, and the lens system becomes large.

The condition (6) is also the same as the condition (5). If the lower limit of the condition (6) is exceeded, the refractive power of the front unit becomes large. If the upper limit of the condition (6) is exceeded, it becomes difficult to correct aberrations at the wide-angle end.

As described above, the conditions (5) and (6) are intended to ease the angle of the incident off-axis light beam and to make aberration correction easier. In other words, if these conditions are not satisfied, the effect on aberration correction works if the angle of view at the wide-angle end is on the telephoto side, but the effect of correcting off-axis aberrations decreases at an ultra-wide angle.

The three-group zoom has been described above.
The gist of the present invention can be applied to the group zoom. That is, as shown in FIG. 44, in order from the object side, a first lens group having a positive refractive power, a second lens group having a positive refractive power, a third lens group having a positive refractive power, and a fourth lens group having a negative refractive power. The first lens group and the second lens group, the second lens group and the third lens group, and the third lens group and the fourth lens group are changed by changing the distance between the first lens group and the second lens group. It has a doubling effect,
The first lens group is composed of a front group and a rear group for widening the angle, and satisfies the same condition (1) as in the above-described three-group zoom.

FIGS. 46, 47, 48, and 48 show the state of light rays at the paraxial and thick lenses of the first lens group, respectively.
This is shown in FIG.

[0038]

Next, embodiments of the zoom lens according to the present invention will be described. Example 1 f = 28.90 to 102.00 mm, F / 4.5 to F / 7.625, 2ω = 73.64 ° to 23.94 ° r1 = 160.7804 d1 = 1.2000 n1 = 1.74100 ν1 = 52.68 r2 = 34.8076 d2 = 6.9850 r3 = 38.883.34063 = 1.53172 v2 = 48.90 r4 = 142.7690 d4 = D1 r5 = -194.6240 d5 = 1.0000 n3 = 1.83400 v3 = 37.16 r6 = 38.00459 d6 = 0.3520 r7 = 43.6383 d7 = 3.4187 n4 = 8. = 32.2002 d9 = 5.2460 n5 = 1.51823 v5 = 58.96 r10 = -96.2536 d10 = D2 r11 = -498.7110 d11 = 1.000 n6 = 1.79090 v6 = 44.18 r12 = 15.0840 d12 = 0.8410 r13 = 24.1630 d13 = 2.76 470 = -102.9802 d14 = 3.9120 r15 = -14.3361 d15 = 1.1100 n8 = 1.65830 ν8 = 53.44 r16 = -16.3753 d16 = 4.9610 r17 = ∞ (aperture) d17 = 3.6000 r18 = -79.9489 d18 = 2.1300 n9 = 1.66680 r9 = 33.04 -51.9241 d19 = 0.5000 r20 = -555.5860 d20 = 3.0490 n10 = 1.51454 v10 = 54.69 r21 = -26.8298 d21 = 0.1200 r22 = 103.1734 d22 = 0.6500 n11 = 1.80518 v11 = 25.43 r23 = 17.2071 d23 = 5.4150 n12 = 1.60729 v12 = 59.38 r24 = -26000457 d24 = 1.2,500 25 0.8780 n13 = 1.77250 v13 = 49.66 r26 = -22.7792 d26 = D3 r27 = -54.8870 d27 = 3.3170 n14 = 1.84772 v14 = 25.71 r28 = -22.2644 d28 = 2.4970 r29 = -15.6872 (aspherical surface) d29 = 0.3600 n15 = 1.52492 v15 51.77 r30 = -16.8658 d30 = 1.3200 n16 = 1.77250 v16 = 49.66 r31 = 62.5760 Aspherical surface coefficient P = 1.0000, E = 0.30618 × 10 ^-4 , F = 0.10777 × 1
^{0 -6, G = -0.18514 × 10} -9, H = 0.20423 × 10 -11 f 28.90 54.44 102.00 D1 1.750 1.750 1.750 D2 1.500 16.298 22.421 D3 15.852 7.073 1.530 | φf / φ1 | = 0.65194, φ1 / φw = 0.246, φ12w / φw =
1.330 hB / hF = 1.1256, AB / AF = 0.8117, β3T / β3w = 3.0 Example 2 f = 28.92 to 102.02 mm, F / 4.5 to F / 7.625, 2ω = 73.6 ° to 23.94 ° r1 = -82.5283 d1 = 1.2500 n1 = 1.74100 v1 = 52.68 r2 = 8479.1527 d2 = 1.0288 r3 = 109.7348 d3 = 2.2603 n2 = 1.53172 v2 = 48.90 r4 = -234.4198 d4 = 0.7500 r5 = -104.1899 d5 = 0.83 n3 = 6,500 n3 = 6,500 r7 = 39.3253 d7 = 4.5192 n4 = 1.65844 ν4 = 50.86 r8 = -20126.4985 d8 = 0.1200 r9 = 38.2462 d9 = 5.5542 n5 = 1.65830 ν5 = 53.44 r10 = -81.9930 d10 = 1.3111 = 16. r12 = 12.1902 d12 = 0.7721 r13 = 20.1078 d13 = 3.1941 n7 = 1.78470 ν7 = 26.22 r14 = −324.9518 d14 = 2.9127 r15 = -12.2940 d15 = 0.6569 n8 = 1.65830 v8 = 53.44 r16 = −14.2480 d16 D17 = 3.4906 r18 = -39.4065 d18 = 1.9818 n9 = 1.59270 ν9 = 3 5.29 r19 = -23.5086 d19 = 1.0128 r20 = -77.1442 d20 = 2.2237 n10 = 1.50137 ν10 = 56.40 r21 = -27.3780 d21 = 0.1200 r22 = 71.2472 d22 = 0.8500 n11 = 1.84666 ν11 = 23.78 r23 = 17.8516 d12 = 14.0983 = 58.94 r24 = -19.8521 d24 = 0.8500 r25 = -20.0533 d25 = 1.5717 n13 = 1.77250 v13 = 49.66 r26 = -21.5906 d26 = D2 r27 = -49.9729 d27 = 3.4179 n14 = 1.8472 v14 = 25.71 r28 = -20.4630 d29 = 2.684 = -13.9632 (aspherical surface) d29 = 0.1000 n15 = 1.52492 ν15 = 51.77 r30 = -14.0500 d30 = 0.9444 n16 = 1.78590 ν16 = 44.18 r31 = 57.0622 Aspherical surface coefficient P = 1.0000, E = 0.46567 × 10 ^-4 , F = 0.16608 × 1
^{0 -6, G = -0.40245 × 10} -9, H = 0.76140 × 10 -11 f 28.92 54.39 102.02 D1 1.250 15.540 20.970 D2 12.853 5.873 1.207 | φf / φ1 | = 0.17379, φ1 / φw = 0.304, φ12w / φw =
1.404 hB / hF = 1.0233, AB / AF = 0.9179, β3T / β3w = 3.329 Example 3 f = 24.50-76.49 mm, F / 4.5-F / 7.5, 2ω = 82.88 ° -31.58 ° r1 = 96.5532 d1 = 1.2000 n1 = 1.69350 v1 = 53.23 r2 = 27.7448 d2 = 11.6550 r3 = -91.4665 d3 = 1.2066 n2 = 1.78470 v2 = 26.22 r4 = -303.5278 d4 = 0.1500 r5 = 39.5053 d5 = 3.0500 n3 = 1.5500 n3 = 1.5500 = 37.1151 d7 = 5.0200 n4 = 1.60311 v4 = 60.70 r8 = -206.3245 d8 = D1 r9 = 57.4357 d9 = 1.0000 n5 = 1.67790 v5 = 55.33 r10 = 16.3022 (aspherical surface) d10 = 1.5109 r11 = 61.795 = 29.24 r12 = -33.4657 d12 = 1.1015 r13 = -23.8559 d13 = 1.1100 n7 = 1.83400 v7 = 37.16 r14 = -125.8813 d14 = 4.7035 r15 = ∞ (aperture) d15 = 3.4988 r16 = -21.5971 d16 = 2.164 n8 = 1.464 65.94 r17 = -22.7796 d17 = 3.9083 r18 = -54.9728 d18 = 2.5000 n9 = 1.5182 1 ν9 = 65.04 r19 = -18.0505 d19 = 0.1200 r20 = 52.5661 d20 = 0.8500 n10 = 1.84666 ν10 = 23.78 r21 = 21.2304 d21 = 4.0000 n11 = 1.56873 ν11 = 63.16 r22 = -58.4819 d22 = 0.8250 n23 = 70.2181 n23 1.77250 v12 = 49.66 r24 = -204.8691 d24 = D2 r25 = -76.9580 d25 = 3.3170 n13 = 1.74000 v13 = 28.29 r26 = -25.1526 d26 = D2 r27 = -19.5931 (aspherical surface) d27 = 0.3600 n14 = 1.52492 v14 = 51.77 r28 -23.2468 d28 = 1.3200 n15 = 1.77250 v15 = 49.66 r29 = 35.1917 Aspheric coefficient (tenth surface) P = 1.0000, E = 0.15173 × 10 ^-4 , F = 0.
18351 × 10 ^-6 , G = -0.10833 × 10 ^-8 , H = 0.28490 × 10
^-10 (Surface 27) P = 1.0000, E = 0.22735 × 10 ^-4 , F = 0.
29706 × 10 ^-7 , G = -0.30210 × 10 ^-9 , H = 0.83428 × 10
^-12 f 24.50 45.02 76.49 D1 0.850 16.915 22.361 D2 12.830 5.031 0.510 | φf / φ1 | = 2.13856, φ1 / φw = 0.175, φ12w / φ
w = 1.365 hB / hF = 1.2347, AB / AF = 0.5986, β3T / β3w = 2.727 Example 4 f = 29.01 to 105.43 mm, F / 4 to F / 7.65, 2ω = 73.42 ° to 23.2 ° r1 = 123.2807 d1 = 1.2000 n1 = 1.69680 ν1 = 55.52 r2 = 28.1453 d2 = 7.0560 r3 = 31.7325 d3 = 5.4876 n2 = 1.53172 ν2 = 48.90 r4 = 302.3165 d4 = D1 r5 = -125.1445 d5 = 1.68 33.36 333.63 1.00.60 r7 = 40.6740 d7 = 3.6156 n4 = 1.65844 ν4 = 50.86 r8 = -1157.9848 d8 = 0.1500 r9 = 32.3632 d9 = 5.6348 n5 = 1.51823 ν5 = 58.96 r10 = -60.9035 d10 = 61.07 = 871.07 44.18 r12 = 16.2024 d12 = 0.9097 r13 = 31.3832 d13 = 2.9131 n7 = 1.78470 ν7 = 26.22 r14 = -49.7711 d14 = 3.5341 r15 = -18.0019 d15 = 1.2081 n8 = 1.65830 ν8 = 53.44 r16 = ∞23.1951 Aperture) d17 = 3.4676 r18 = -115.0000 d18 = 2.1300 n9 = 1.68893 ν9 = 31.08 r19 = -64.5600 d19 = 0.5000 r20 = 484.4333 d20 = 3.3939 n10 = 1.54739 ν10 = 53.55 r21 = -26.1713 d21 = 0.5903 r22 = 146.1389 d22 = 0.4350 n11 = 1.78472 ν11 = 25.71 r23 = 17.3114 d23 = 5.4869 n12 = 1.58313 -25.9767 d24 = 1.2500 r25 = -19.9068 d25 = 1.4830 n13 = 1.74100 ν13 = 52.68 r26 = -20.9013 d26 = D3 r27 = -38.0869 d27 = 2.7902 n14 = 1.84666 ν14 = 23.78 r28 = -21.4684 d28 = 2.6534 r29 = -1903 Aspheric surface) d29 = 0.3593 n15 = 1.52492 v15 = 51.77 r30 =-17.4211 d30 = 1.3500 n16 = 1.77250 v16 = 49.66 r31 = 82.1742 Aspheric coefficient P = 1.0000, E = 0.20587 × 10 ^-4 , F = 0.86201 × 1
0 ^-7 , G = -0.48242 x 10 ^-9 , H = 0.27293 x 10 ^-11 f 29.01 54.44 105.43 D1 1.750 1.750 1.750 D2 1.500 15.621 21.576 D3 17.439 8.661 2.636 | φf / φ1 | = 0.18545, φ1 / φw = 0.322, φ12w / φw
= 1.349 hB / hF = 1.134, AB / AF = 0.5457, β3T / β3w = 2.973 Example 5 f = 29.51 to 131.00 mm, F / 4.5 to F / 8.25, 2ω = 72.48 ° to 18.76 ° r1 = 147.7015 d1 = 0.8500 n1 = 1.74100 ν1 = 52.68 r2 = 39.8775 d2 = 6.9732 r3 = 34.9579 d3 = 4.4400 n2 = 1.53172 ν2 = 48.90 r4 = −509.1641 d4 = D1 r5 = -55.5614 d5 = 0.81.8 n3 = 0.8600 n3 = 0.8600 n3 = 0.8600 n3 = 0.8600 n3 = 0.8600 n3 = 0.8600 n3 r7 = 45.0582 d7 = 3.6100 n4 = 1.65844 ν4 = 50.86 r8 = -134.9701 d8 = 0.1200 r9 = 36.3870 d9 = 4.4600 n5 = 1.50137 ν5 = 56.40 r10 = -55.5290 d10 = 11 = 6 = 11.75 44.18 r12 = 15.5103 d12 = 0.7341 r13 = 24.6834 d13 = 2.6600 n7 = 1.78470 ν7 = 26.22 r14 = -63.3984 d14 = D3 r15 = -13.9591 d15 = 0.9163 n8 = 1.65830 ν8 = 53.44 r16 = 6.2172.1 Aperture) d17 = 3.3080 r18 = -77.7267 d18 = 1.7100 n9 = 1.66680 v9 = 33.04 19 = -56.3440 d19 = 0.1400 r20 = -322.6649 d20 = 2.3300 n10 = 1.50137 ν10 = 56.40 r21 = -24.8971 d21 = 0.1200 r22 = 74.2271 d22 = 0.5300 n11 = 1.80518 ν11 = 25.43 r23 = 17.1956 d12 = 5.1000 n12 60.70 r24 = -24.4180 d24 = 1.0490 r25 = -20.8299 d25 = 0.8800 n13 = 1.77250 v13 = 49.66 r26 = -22.2142 d26 = D4 r27 = -50.1298 d27 = 3.2000 n14 = 1.84772 v14 = 25.71 r28 = -21.599 d28 = 2.3876 -14.9318 (aspherical surface) d29 = 0.4500 n15 = 1.52492 ν15 = 51.77 r30 = -15.1591 d30 = 1.1900 n16 = 1.77250 ν16 = 49.66 r31 = 52.7870 Aspherical surface coefficient P = 1.0000, E = 0.45142 × 10 ^-4 , F = 0.15406 × 1
0 ^-6 , G = -0.58035 x 10 ^-9 , H = 0.42319 x 10 ^-11 f 29.51 62.50 131.00 D1 1.460 1.460 1.460 D2 0.766 17.061 22.292 D3 4.073 3.798 3.630 D4 15.086 6.568 1.369 │φf / φ1 │ = 0.34602, φ1 / φw = 0.360, φ12w / φw =
1.385 hB / hF = 1.0767 AB / AF = 0.9845, β3T / β3w = 3.442 Example 6 f = 29.30 to 102.00 mm, F / 4.6 to F / 7.65, 2ω = 72.88 ° to 23.94 ° r1 = -60.5111 d1 = 1.2500 n1 = 1.74100 ν1 = 52.68 r2 = -103.1603 d2 = 0.2000 r3 = 51.3114 d3 = 2.6500 n2 = 1.53172 ν2 = 48.90 r4 = 254.0371 d4 = 1.0500 r5 = -148.9276 d5 = 0.8500 n3 = 1.83400 6.75 n3 = 1.83400 = 28.5843 d7 = 4.0000 n4 = 1.65844 ν4 = 50.86 r8 = 451.3443 d8 = 0.1200 r9 = 47.3480 d9 = 4.0500 n5 = 1.65830 ν5 = 53.44 r10 = -73.2687 d10 = D1r r11 = -192.7657d6 = 11.3110 d12 = 0.6696 r13 = 21.2161 d13 = 1.9980 n7 = 1.78470 ν7 = 26.22 r14 = -75.8136 d14 = 5.3056 r15 = ∞ (aperture) d15 = 3.6513 r16 = -18.5732 d16 = 2.1356 n8 = 1.59551 ν8 = 39.100 d17 = 0.5046 r18 = -31.4506 d18 = 1.5121 n9 = 1.50137 ν9 = 56.40 r 19 = -18.2746 d19 = 0.1200 r20 = 75.5019 d20 = 0.8500 n10 = 1.84666 ν10 = 23.78 r21 = 19.0505 d21 = 3.9996 n11 = 1.60881 v11 = 58.94 r22 = -17.4005 d22 = D2 r23 = -45.2876 d23 = 3.0000 n12 = 1.7000 25.71 r24 = -18.7253 d24 = 2.6527 r25 = -12.9546 (aspherical surface) d25 = 0.1000 n13 = 1.52492 ν13 = 51.77 r26 = -14.0500 d26 = 1.0000 n14 = 1.79952 ν15 = 42.24 r27 = 119.6924 Aspherical surface coefficient P = 1.000, E = 0.37563 × 10 ^-4 , F = 0.36933 × 1
^{0 -6, G = -0.27582 × 10} -8, H = 0.24748 × 10 -10 f 29.30 54.52 102.00 D1 1.136 13.805 20.500 D2 15.118 6.870 0.998 | φf / φ1 | = 0.25624, φ1 / φw = 0.385, φ12w / φw =
1.346 hB / hF = 0.9986, AB / AF = 1.0469, β3T / β3w =
2.651 where r1, r2, ... are the radii of curvature of the respective lens surfaces, d1
, D2,... Are the thickness of each lens and the lens interval, n1
, N2, ... are the refractive indices of each lens, ν1, ν2, ...
Is the Abbe number of each lens. The first embodiment is a wide-angle zoom lens having a focal length of 29.0 to 105 mm, as shown in FIG. The lens system of this embodiment does not impose much restrictions on the overall length, and keeps a little less than 90 mm at the wide-angle end, but has stable and good optical performance over the entire zoom range. The aberration states of this embodiment are as shown in FIGS. 7 to 12, and FIGS. 7, 9, and 11 are aberration curve diagrams at the wide-angle end, an intermediate focal length, and a telephoto end for an object at infinity, and FIGS. 1
FIGS. 0 and 12 are aberration curve diagrams at the wide angle end, the intermediate focal length, and the telephoto end, respectively, for an object of 2.0 mm. Example 2
Is a wide-angle zoom lens having a focal length of 28.9 to 102 mm, and has a configuration shown in FIG. This embodiment differs from the first embodiment in that the overall length is slightly longer due to the arrangement of the lens for image plane correction in the second lens group. The aberration states of this embodiment are as shown in FIGS.
15 and 17 are aberration curve diagrams at the wide-angle end, an intermediate focal length, and a telephoto end for an object at infinity, respectively, and FIGS. 14 and 1.
6 and FIG. 18 are aberration curve diagrams at the wide-angle end, the intermediate focal length, and the telephoto end for an object distance of 2.0 m, respectively. Example 3 is a wide-angle zoom lens including a super-wide-angle lens having a focal length of 24.5 to 76.5 mm. As shown in FIG. 3, the front group in the first lens group is composed of one negative lens component.
This is an embodiment in which a lens group is provided with features. An aspheric surface is used for the second lens group in addition to the third lens group for aberration correction. The aberration states of this embodiment are as shown in FIGS. That is, FIGS. 19, 21, and 22 are aberration curve diagrams at the wide-angle end, the intermediate focal length, and the telephoto end, respectively, of an object at infinity. FIGS.
FIG. 7 is an aberration curve diagram for an object at 0 m at a wide angle end, an intermediate focal length, and a telephoto end. Example 4 has a focal length of 29.0.
It is a wide-angle zoom lens of up to 105 mm. This example is
In the lens configuration shown in FIG. 4, the overall length is relatively long. Thereby, the optical performance became better. The aberration states of the fourth embodiment are as shown in FIGS. Among these figures, FIG. 25, FIG. 27, and FIG. 29 are aberration curve diagrams of the object at infinity at the wide-angle end, the intermediate focal length, and the telephoto end, respectively, and FIGS. FIG. 7 is an aberration curve diagram at the wide angle end, an intermediate focal length, and a telephoto end with respect to FIG. In the fifth embodiment, the focal length is 2
This is a wide-angle zoom lens with a high magnification of 9.5 to 131 mm. This embodiment is a four-unit zoom lens having a configuration as shown in FIG. The overall length at the wide-angle end is reduced to 83.6, and the back focus is 8.92. The aberration states of this embodiment are as shown in FIGS.
1, FIG. 33 and FIG. 35 show the wide-angle end for an object at infinity,
FIG. 32, FIG. 34, and FIG. 36 are aberration curve diagrams at the wide-angle end, the intermediate focal length, and the telephoto end for an object of 2.0 m, respectively. In this embodiment, although there are some difficulties in the correction of the spherical aberration at the telephoto end, it is practically sufficient. In the sixth embodiment, the focal length is 2
It is a wide-angle zoom lens of 9.3 to 102 mm, and the total length is 68.25 at the wide-angle end. In this embodiment, as shown in FIG. 6, the first lens group includes a front group consisting of a negative lens and a positive lens, and a rear group consisting of one negative lens and two positive lenses. I have. Further, the third lens group uses an aspherical surface assuming that a synthetic resin material is used. The back focus is 9.52 at the wide angle end, which is sufficiently ensured. The aberration states of the sixth embodiment are as shown in FIGS. 37 to 42. FIGS. 37, 39, and 41 are aberration curve diagrams at the wide-angle end, an intermediate focal length, and a telephoto end for an object at infinity, respectively, and FIGS. 40 and 42 are aberration curve diagrams at the wide angle end, the intermediate focal length, and the telephoto end, respectively, for an object of 2.0 m. In the sixth embodiment, the total length is shortened. For this reason, the chromatic aberration of magnification at the wide-angle end cannot be sufficiently corrected at the g-line, but is in a good correction state as a whole. Also, distortion is a relatively monotonous change. Furthermore, the curvature of astigmatism in the meridional direction at the wide-angle end is affected by the aspheric surface of the third lens unit. The focusing of the lens system of the above embodiment is the second in the case of a three-unit zoom lens.
The zooming is performed by a lens group, or in the case of a four-group zoom lens, by a 2-3 lens group. Examples other than Example 6 include:
At the time of focusing, a lens component for short-range aberration correction is provided closest to the image plane in the focusing lens unit, and the lens component is fixed and the remaining lens components are moved to perform focusing and aberration correction. The shape of the aspherical surface used in the above embodiment is expressed by the following equation when the optical axis direction is the x axis and the direction perpendicular to the optical axis is the y axis. Here, r is a radius of curvature near the aspherical vertex, P is a conic constant, and E, F, G, H,... Are aspherical surface coefficients.

[0039]

According to the present invention, this type of zoom, which is conventionally considered to be disadvantageous for widening the angle of view, by giving a characteristic to the structure of the first lens group without making the overall length and outer diameter too large, is provided. The lens was able to be wide-angled while maintaining good optical performance.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a first embodiment.

FIG. 2 is a sectional view of a second embodiment.

FIG. 3 is a sectional view of a third embodiment.

FIG. 4 is a sectional view of a fourth embodiment.

FIG. 5 is a sectional view of a fifth embodiment.

FIG. 6 is a sectional view of a sixth embodiment.

FIG. 7 is an aberration curve diagram at the wide-angle end for an object at infinity according to the first embodiment.

FIG. 8 is an aberration curve diagram at the wide-angle end for a 2.0-meter object according to the first embodiment.

FIG. 9 is an aberration curve diagram at an intermediate focal length of an object at infinity according to the first embodiment.

FIG. 10 is an aberration curve diagram at an intermediate focal length of a 2.0 m object according to the first embodiment.

FIG. 11 is an aberration curve diagram at the telephoto end of an object at infinity according to the first embodiment.

FIG. 12 is an aberration curve diagram at a telephoto end of a 2.0-meter object according to the first embodiment.

FIG. 13 is an aberration curve diagram at a wide-angle end of an object at infinity according to a second embodiment.

FIG. 14 is an aberration curve diagram at the wide-angle end for a 2.0-meter object according to the second embodiment.

FIG. 15 is an aberration curve diagram at an intermediate focal length of an object at infinity according to the second embodiment.

FIG. 16 is an aberration curve diagram at an intermediate focal length for a 2.0-meter object according to the second embodiment.

FIG. 17 is an aberration curve diagram at the telephoto end for an object at infinity according to the second embodiment.

FIG. 18 is an aberration curve diagram at a telephoto end of a 2.0 m object according to the second embodiment.

FIG. 19 is an aberration curve diagram at the wide-angle end of an object at infinity according to a third embodiment.

FIG. 20 is an aberration curve diagram at the wide-angle end of a 2.0-meter object according to the third embodiment.

FIG. 21 is an aberration curve diagram at an intermediate focal length of an object at infinity according to a third embodiment.

FIG. 22 is an aberration curve diagram at an intermediate focal length of a 2.0-meter object according to the third embodiment.

FIG. 23 is an aberration curve diagram at the telephoto end of an object at infinity according to a third embodiment.

FIG. 24 is an aberration curve diagram at the telephoto end of a 2.0-meter object according to the third embodiment.

FIG. 25 is an aberration curve diagram at the wide-angle end of an object at infinity according to a fourth embodiment.

FIG. 26 is an aberration curve diagram at the wide-angle end for a 2.0-meter object in Example 4.

FIG. 27 is an aberration curve diagram at an intermediate focal length of an object at infinity according to a fourth embodiment.

FIG. 28 is an aberration curve diagram at an intermediate focal length of a 2.0 m object according to the fourth embodiment.

FIG. 29 is an aberration curve diagram at the telephoto end of an object at infinity according to a fourth embodiment.

FIG. 30 is an aberration curve diagram at the telephoto end of a 2.0-meter object in Example 4.

FIG. 31 is an aberration curve diagram at the wide-angle end of an object at infinity according to a fifth embodiment.

FIG. 32 is an aberration curve diagram at a wide-angle end of a 2.0 m object according to the fifth embodiment.

FIG. 33 is an aberration curve diagram of the fifth embodiment at an intermediate focal length with respect to an object at infinity.

FIG. 34 is an aberration curve diagram at an intermediate focal length of a 2.0 m object according to the fifth embodiment.

FIG. 35 is an aberration curve diagram at the telephoto end of an infinitely distant object according to the fifth embodiment.

FIG. 36 is an aberration curve diagram at the telephoto end of a 2.0-meter object in Example 5.

FIG. 37 is an aberration curve diagram at the wide-angle end of an object at infinity according to a sixth embodiment.

FIG. 38 is an aberration curve diagram at the wide-angle end of a 2.0-meter object according to the sixth embodiment.

FIG. 39 is an aberration curve diagram at an intermediate focal length of an object at infinity according to a sixth embodiment.

FIG. 40 is an aberration curve diagram at an intermediate focal length of a 2.0 m object according to the sixth embodiment.

FIG. 41 is an aberration curve diagram at the telephoto end of an infinitely distant object according to the sixth embodiment.

FIG. 42 is an aberration curve diagram at the telephoto end of a 2.0-meter object in Example 6.

FIG. 43 is a diagram showing a basic configuration of a third group zoom of the present invention;

FIG. 44 is a diagram showing a basic configuration of a fourth group zoom of the present invention;

FIG. 45 is a diagram showing the state of incidence of off-axis rays on the front group and the rear group of the first lens group.

FIG. 46 is a diagram showing the state of light rays on the paraxial axis at the wide angle end of the first lens unit.

FIG. 47 is a view showing the state of light rays on the paraxial line at the telephoto end of the first lens.

FIG. 48 is a diagram showing a state of light rays in a thick lens at the wide-angle end of the first lens group.

FIG. 49 is a diagram showing the state of light rays on the paraxial axis in the first lens group.

Continuation of the front page (56) References JP-A-63-148223 (JP, A) JP-A-47-33373 (JP, A) JP-A-4-362910 (JP, A) JP-A-3-50516 (JP) JP-A-3-85508 (JP, A) JP-A-2-73211 (JP, A) JP-A-3-31809 (JP, A) JP-A-2-103014 (JP, A) JP JP-A-58-137713 (JP, A) JP-A-61-52620 (JP, A) JP-A-64-93713 (JP, A) JP-A-58-224322 (JP, A) JP-A-3-17609 (JP, A A) JP-A-3-208004 (JP, A) JP-A-4-338910 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B 9/00-17/08 G02B 21 / 02-21/04 G02B 25/00-25/04

Claims (5)

(57) [Claims] A first lens group having a positive refractive power, a second lens group having a positive refractive power, and a third lens group having a negative refractive power.
More becomes lens group from the wide-angle end by the narrowed distance between the first lens group and the second lens group and the third lens group spread distance of the second lens group at the telephoto end than at the wide angle end to the telephoto end The first lens group is composed of a negative lens and a positive lens in order from the object side or a negative lens 1
A front group formed of only a sheet, is composed of a rear group consisting of one negative lens and two positive lenses in order from the object side, the second lens
A wide-angle zoom lens, wherein the lens group has an aperture stop, and satisfies the following condition (1). (1) | φf / φ1 | <6.0 where φf is the refractive power of the front lens unit, and φ1 is the refractive power of the first lens unit. 2. A first lens group having a positive refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power, in order from the object side.
A first lens group, a second lens group, a second lens group, a third lens group, a third lens group, and a fourth lens. A magnification change from the wide-angle end to the telephoto end is performed by changing the distance between the groups. The first lens group includes at least one negative lens, a front group, and at least one positive lens component. A wide-angle zoom lens, comprising: a rear group composed of at least one negative lens component and satisfying the following condition (1): (1) | φf / φ1 | <6.0 where φ1 is the refractive power of the first lens unit, and φf is the refractive power of the front unit. 3. The lens system according to claim 1, wherein the first lens group satisfies the following condition (2):
2. The wide-angle zoom lens according to claim 1, wherein the zoom lens is configured to satisfy (3) and (4). (2) 0.1 <φ1 / φw <1.25 (3) 1.1 <φ12w / φw <3.0 (4) 1.5 <β3T / β3w <4.0 where φw is the whole system at the wide-angle end Is the combined refractive power of the first and second lens groups at the wide-angle end, β3w is the magnification of the third lens group at the wide-angle end, and β3T is the magnification of the third lens group at the telephoto end. 4. A first lens group having a positive refractive power, a second lens group having a positive refractive power, and a third lens group having a negative refractive power are arranged in order from the object side.
More becomes lens group from the wide-angle end by the narrowed distance between the first lens group and the second lens group and the third lens group spread distance of the second lens group at the telephoto end than at the wide angle end to the telephoto end The first lens group includes, in order from the object side, a front group including a negative lens and a positive lens, and a rear group including one negative lens and two positive lenses .
A wide-angle zoom lens , wherein the lens group has an aperture stop and satisfies the following condition (1). (1) | φf / φ1 | <6.0 where φf is the refractive power of the front lens unit, and φ1 is the refractive power of the first lens unit. 5. A camera equipped with a wide-angle zoom lens.
The wide-angle zoom lens includes, in order from the object side, a first lens group having a positive refractive power, a second lens group having a positive refractive power,
The third lens unit has a negative refractive power. By changing the distance between the first and second lens groups and the distance between the second and third lens groups, zooming from the wide-angle end to the telephoto end is achieved. The first lens group includes, in order from the object side, a front group including a negative lens and a positive lens, and a rear group including one negative lens and two positive lenses. )
A camera characterized by satisfying (6). (1) | φf / φ1 | <6.0 (2) 0.1 <φ1 / φw <1.25 (3) 1.1 <φ12w / φw <3.0 (4) 1.5 <β3T / β3w <4.0 (5) 0.5 <hB / hF <1.5 (6) 0.2 <AB / AF <2.0 where φf is the refractive power of the front lens group, and φ1 is the refractive power of the first lens group. Refractive power, φw is the refractive power of the entire system at the wide-angle end, φ1
2w is the combined refractive power of the first and second lens groups at the wide-angle end, β3w is the magnification of the third lens group at the wide-angle end, β3T is the magnification of the third lens group at the telephoto end, hF
Is the axial circumference that enters the front group of the first lens group at the wide-angle end
Edge ray height, hB is an axial peripheral ray height incident on the rear group of the first lens group at the wide angle end, AF is an off- axis principal ray height of a maximum angle of view incident on the front group of the first lens group at the wide angle end, AB
Is the largest image incident on the rear group of the first lens group at the wide-angle end.
Off- axis chief ray height of the corner .