JP3400799B2 - Zoom lens with extended wide angle range - 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 having three or four groups, and more particularly to a zoom lens having an expanded wide-angle range.

[0002]

2. Description of the Related Art In recent years, full-automatic cameras equipped with a zoom lens having a high zoom ratio have been commercialized as new concept cameras. On the other hand, if the trend of commercialization up to now is to increase the scaling ratio, it is considered that it is a natural development process to respond to this and proceed to widening the angle in one direction. With regard to wide-angle zoom lenses, it has been proposed so far that the angle of view at the wide-angle end is a quasi-wide angle of about 63 °, or the angle of view is about 73 ° if the magnification is low. No. 284109 and the like. On the other hand, there is a demand to further widen the angle of the zoom lens.

There have been the following methods for realizing this kind of requirement. That is, it is a method of mounting the wide-angled attachment optical system on the main lens system.
The so-called rear conversion system is connected to the rear of the main lens system, and (2) the front conversion system is mounted in front of the main lens system.

However, both of these are methods of newly adding a lens system to the main lens system, and not only the total length is increased and the weight is increased, but also portability and operability are not necessarily good. .

[0005]

SUMMARY OF THE INVENTION The present invention has been made under such circumstances, and an object thereof is to add a focal length at the wide-angle end to the main lens system without adding an attachment lens system. It is to propose a method for obtaining a wide-angle focal length range.

The basic optical system of the present invention is
From the object side, the first lens group having positive refractive power and the second lens group having positive refractive power
Assume a three-group zoom lens including a lens group and a third lens group having a negative refractive power.

[0007] Further, by first considering improving the performance of the optical system in the focal range of a given optical specification, an additional function of the optical system thus constructed is to provide a focal position which should be called a super wide angle range. , Prioritizing compactness and maintaining optical performance.

Furthermore, the optical characteristics of the focal region from the expanded wide-angle end (focal length: f _WS ) to the wide-angle end (focal length: f _W ) do not necessarily need to be continuous. This is because it is extremely difficult to continuously design the wide-angle end up to the ultra-wide angle from the beginning, and an increase in size cannot be avoided. In other words, first, a compact optical system including the entire lens length is designed, and a switching function including an ultra wide angle range is provided from this state. That is, it can be said that switching to the ultra wide-angle range is an additional function configured as an auxiliary means.

By the way, in an actual shooting scene, even a slight reduction in the focal length in the wide-angle range has a large effect on the angle of view, and as a result, a large effect can be obtained. However, in terms of aberration correction,
It is well known that such reduction of the focal length is difficult, so we will study the solution and propose the result.

Further, depending on the focusing method in the focal range from the wide-angle end to the telephoto end, it may not be possible to perform focusing at the extended wide-angle end as well. Therefore, the focusing method in this case is also proposed at the same time.

Furthermore, according to the present invention, from the object side, the first lens group having the positive refractive power, the second lens group having the positive refractive power, and the third lens group having the positive refractive power are provided.
The same applies to a 4-group zoom lens including a lens group and a fourth lens group having a negative refracting power.

[0012]

A zoom lens having a wide-angle range expanded according to the present invention for achieving the above object has a first lens group having a positive refractive power, a second lens group having a positive refractive power, and a first lens group having a positive refractive power in order from the object side. The third lens group and the fourth lens group of the fourth lens group having a negative refractive power, and the distance between the first lens group and the second lens group, the distance between the second lens group and the third lens group, and Three
In order to obtain an expanded wide-angle range independent of the wide-angle end, a zoom lens that performs a zooming effect by changing the distance between the lens group and the fourth lens group satisfies the following conditional expression, and At the telephoto end, a focusing method in which the second lens group and the third lens group move is adopted, and in the extended wide-angle range, the first lens group and the second lens group are moved.
It is characterized by adopting a focusing method in which both the lens group and the third lens group move or the fourth lens group moves.

D _1W > D _1WS D _4W > D _4WS where D _1W is the actual distance between the first lens group at the wide-angle end and the second lens group, and D _1WS is the expanded first lens group at the wide-angle end. The actual spacing of the second lens group, D _4W, is the back focus of the entire lens system at the wide-angle end, and D _4WS is the back focus of the extended lens system at the wide-angle end.

[0014]

The conditions and functions of the zoom lens of the present invention with the wide angle range expanded will be described below.

The present invention relates to a focal range conversion method from a wide-angle end of a main lens system to an expanded wide-angle range. Here, the wide-angle range obtained by converting the focal length will be referred to as "ultra-wide-angle range" hereinafter.

It is generally known that in order to widen the angle, the path of the off-axis light flux passing through the lens system is largely changed, so that various problems such as optical performance degradation and light flux vignetting occur. Therefore, if the arrangement of lens groups capable of converting the focal length can be determined without the peripheral light flux of the main zoom lens system changing largely as compared with the wide-angle end, the gist of the present invention will be substantially satisfied.

From these points, it is necessary to solve the following problems in order to realize a super wide angle range. (I) The distance from the first lens surface to the entrance pupil (hereinafter referred to as the entrance pupil distance) satisfies the following condition.

EP _W −EP _WS > 0 (1) where EP _W is the entrance pupil distance at the wide-angle end, and EP _WS is
The entrance pupil distance at the ultra-wide-angle end. (Ii) The total length of the lens system satisfies the following conditions (Fig. 1).

L _W −L _WS > 0 (2) where L _W is the total lens system length at the wide-angle end, and L _WS is the total lens system length at the ultra-wide-angle end. (iii) The paraxial lateral magnification of the lens group mainly responsible for zooming from the wide-angle end to the ultra-wide-angle end is reduced. (Iv) Aberration fluctuation is small and performance deterioration is as small as possible.

In contrast to the above, (i) shortens the entrance pupil distance. Regarding (ii), vignetting of the passing light flux in the rear lens group is suppressed. For (iii), determine the relationship between the movement of the lens group that bears the variable magnification ratio and the magnification. (I
Regarding v), it depends on whether or not consideration can be given so as to compensate as much as possible for the aberration variation when converting the focal range.

In the present invention, for (i) and (ii),
The objective can be achieved as follows.

The three-group zoom lens is composed of, in order from the object side, 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. And the distance between the first lens group and the second lens group, and
In a zoom lens that performs zooming by changing the distance between the second lens unit and the third lens unit, the following conditional expression is satisfied in order to obtain an expanded wide-angle range independent of the wide-angle end. .

D _1W > D _1WS (3) D _3W > D _3WS (4) However, D _1W is the first lens group and the second lens group at the wide-angle end. The actual distance, D _1WS is the actual distance between the expanded first lens group and the second lens group at the wide-angle end, D _3W is the back focus of the entire lens system at the wide-angle end, and D _3WS is the expanded wide-angle end. The back focus of the entire lens system.

On the other hand, for the four-group zoom lens, the first lens group, the second lens group, and
The third lens group has a positive refractive power and the fourth lens group has a negative refractive power, and the distance between the first lens group and the second lens group and the distance between the second lens group and the third lens group. In a zoom lens that performs zooming by changing the distance and the distance between the third lens group and the fourth lens group, the following conditional expression is satisfied in order to obtain an expanded wide-angle range independent of the wide-angle end. To do so.

D _1W > D _1WS (5) D _4W > D _4WS (6) However, D _1W is the first lens group and the second lens group at the wide-angle end. The actual distance, D _1WS is the actual distance between the expanded first lens group and the second lens group at the wide-angle end, D _4W is the back focus of the entire lens system at the wide-angle end, and D _4WS is the expanded wide-angle end. The back focus of the entire lens system.

Now, looking at each conditional expression,
The expressions (3) and (5) have almost the same relationship and define the condition (i) of the entrance pupil distance. At this time, since there is a restriction condition that the lens configurations in each lens group are the same,
If this conditional expression is satisfied, the first
The distance between the lens group and the second lens group is reduced, and the entrance pupil distance is shortened. Therefore, if deviating from these conditional expressions, the entrance pupil distance becomes large at the time of focal length conversion, which leads to vignetting of rays and reduction in peripheral light amount, and if the lens outer diameter is increased to increase the light amount at the expense of performance, it becomes compact. It is against the situation, which is not desirable.

The expressions (4) and (6) mean almost the same contents. That is, it means the direction of shortening the back focus, and at the same time, the distance from the exit pupil position to the image plane (hereinafter referred to as the exit pupil distance) is shortened, and the outer diameter of the rear lens group is increased. It is possible to obtain the amount of peripheral light without any need. This is also clear from the image formation relationship shown below. Further, the equations (3) and (5) are
It is important from the feasibility to simultaneously satisfy the condition of (iv).

That is, for the magnification of the third lens group, the conditional expressions (3) and (5) are derived from the following relational expressions.

Β _3W = 1−D _3W φ ₃ (where φ ₃ <0, D _3W > 0) (7), D _3W > D _3WS becomes clear. However, here, β _3W is the third value at the wide-angle end.
The paraxial lateral magnification of the lens unit, φ ₃ is the refractive power of the third lens unit. The equation (5) is similarly derived for the four-group zoom lens.

Here, the present invention has a power arrangement and a movement locus as shown in FIG.
In a three-group zoom lens having positive and negative refracting power, the third lens group having negative refracting power is mainly responsible for zooming, and
It can be seen that the lens group and the second lens group form an imaging system. This is clear when the paraxial lateral magnifications of the second lens unit and the third lens unit at the wide-angle end and the telephoto end are examined in Examples 1 and 2 described later. In the table below, β
_2W and β _3W are the second lens unit at the wide-angle end, the paraxial lateral magnification of the third lens unit, and β _2T and β _3T are the second lens unit at the telephoto end and the third lens unit.
It is the paraxial lateral magnification of the lens group.

[0031] Regarding (iii) above, the movement of each zoom lens group during zooming is determined paraxially, and since this zoom lens has a power arrangement close to that of the telephoto type as a whole, back focus is required for widening the angle. In order to achieve a super wide angle, the lens outer diameter increases and flare increases due to lack of
It is desirable to use the lens group spacing that can be ensured at the wide-angle end of the main lens system to select a solution for a wider-angle lens arrangement from the vicinity of the value at the wide-angle end.

Here, by moving the third lens group to the image plane side, the magnification can be made lower than the reference wide-angle end,
In addition, it is necessary to obtain an extended wide-angle range by utilizing the aberration compensation effect between the lens groups. Here, the magnification relationship can be expressed by the following relational expression. However, the relational expressions in the parentheses are for the case of the 4-group zoom lens.

[0033] _{f 1 β 2WS β 3WS <f} 1 β 2W β 3W ······ (8) ( _{or, f 1 β 2WS β 3WS β} 4WS <f 1 β 2W β 3W β 4W) In other words, the following Magnification conditions must be met.

The _{β 2WS β 3WS <β 2W β} 3W ······ (9) ( _{or, β 2WS β 3WS β 4WS <} β 2W β 3W β 4W) where, f ₁ is the first lens group Focal length, β _2W
Is the paraxial lateral magnification of the second lens group at the wide-angle end, β _3W
Is the paraxial lateral magnification of the third lens group at the wide-angle end, β
_2WS is the paraxial lateral magnification of the second lens group at the ultra-wide-angle end, β
_3WS is the paraxial lateral magnification of the third lens group at the ultra-wide-angle end, β
_4W is the paraxial lateral magnification of the negative fourth lens group at the wide-angle end of the 4-group zoom lens, and β _4WS is the paraxial lateral magnification of the negative fourth lens group at the ultra-wide-angle end of the 4-group zoom lens. Magnification.

Now, when considering the above conditional expression and the basic properties of the zoom lens of interest here, it is clear that the negative lens group closest to the image plane greatly contributes to zooming. This will be clear when the paraxial lateral magnifications of the second lens unit to the fourth lens unit at the wide-angle end and the super-wide-angle end are examined in Examples 3 to 5 described later.

[0036] Further, this lens group basically has the following paraxial lateral magnification at the wide-angle end. That is, β _3W > 1 (or β _4W > 1: 4 group zoom lens) _··· (10) β _3W > β _3WS (or β _4W > β _4WS : 4 group zoom lens) · · ( 11) here, beta _2WS (or, beta _2WS beta _3WS) is (9), (1
It is determined so as to satisfy the expressions (0) and (11).

Therefore, if the magnification of this negative lens group at the wide-angle end is close to unity, further widening cannot be achieved. Since this negative lens group moves from the image side to the object side when zooming from the wide-angle side to the telephoto side, it is necessary to consider the above relational expression, and this paraxial lateral magnification β _3W at the wide-angle end. A value close to 1 would defeat the intent of the present invention. Outside these conditions, the back focus becomes insufficient and the peripheral light amount becomes insufficient, which is not preferable in any case.

That is, it is necessary for the third lens group of the three-group zoom lens to move toward the image plane side for demagnification when forming the super wide-angle range. In the four-group zoom lens, similarly, it is necessary to reduce the magnification by moving the fourth lens group to the image plane side.

Although the change in magnification of the second lens group is not so large, the first lens group moves to the image plane side from the wide-angle end position like the third lens group. It is desirable from the viewpoint of aberration correction that the space between the first lens group and the second lens group is reduced, together with the expressions (3) and (5).

Next, regarding the aberration of (iv), the aberration change when the zoom lens distances D _1W and D _2W are changed by Δ = + 0.01 mm with reference to the aberration correction state at the wide-angle end is shown in FIG. Shown in. Here, the amount of change in spherical aberration, astigmatism, and distortion is specified and shown. As is clear from these, the sensitivity to spherical aberration when the zoom lens interval is changed by a small amount is extremely small, and it is found that astigmatism and distortion change relatively remarkably in the same direction. Therefore, it suffices to make a correction using this property. That is, when the distance between the zoom lenses on one side changes, the distance on the other side is moved in the opposite direction, so that it is possible to suppress variation in aberration. Therefore, if expressed as a conditional expression, the following relationship is desirable.
However, since this depends on the aberration correction situation at the wide-angle end, it is important to balance each other.

Since there is a condition of D _1W > D _1WS (conditional expression (3)), the relationship of D _2W <D _2WS (12) is desirable in terms of aberration correction. However, D _2W is the actual distance between the second lens unit and the third lens unit at the wide-angle end, and
_2WS is the actual distance between the second lens group and the third lens group at the ultra wide-angle end.

Here, another condition regarding the optical system to which the present invention is applied will be described below.

0.4 <φ ₁ / φ _W <1.25 (13) 1.1 <φ _{12 W} / φ _W <3.0 (14) 1.5 <β _3T / β _3W <4.0 (15) (1.5 <β _4T / β _4W <4.0: In case of 4 group zoom lens) However, φ ₁₂ is in case of 3 group zoom lens Is the combined refractive power of the first lens group and the second lens group at the wide-angle end, and in the case of a 4-group zoom lens, the combined refractive power of the first lens group to the third lens group at the wide-angle end is 3 In the case of a group zoom lens, φ _12W = φ ₁ + φ ₂ −e ₁₂ 'φ ₁ φ ₂ , in the case of a 4 group zoom lens, instead of this, φ _12W = φ ₁ + φ ₂₃ −e ₁₃ ' φ ₁ φ ₂₃ , φ ₁ is the refractive power of the first lens group, φ ₂ is the refractive power of the second lens group, φ ₂₃ is the combined refractive power of the second and third lens groups at the wide-angle end, and φ _W is the wide-angle end. The refractive power of the whole system of, β _3T, is
The paraxial side of the negative third lens group at the telephoto end of the third group zoom lens

The magnification, β _3W, is the paraxial lateral axis of the negative third lens group at the wide-angle end of the third group zoom lens.

Magnification, e ₁₂ 'is the distance between the principal points of the first and second lens groups at the wide-angle end of the third group zoom lens, and e ₁₃ ' is the first lens group at the wide-angle end of the fourth group zoom lens. The distance between the principal points of the combined second and third lens groups, β _4T, is the paraxial horizontal axis of the negative fourth lens group at the telephoto end of the fourth group zoom lens.

The magnification, β _4W, is the paraxial lateral axis of the negative fourth lens unit at the wide-angle end of the fourth unit zoom lens.

The magnification is

Here, the equation (13) is for determining the refractive power of the first lens group, and the equation (14) is for estimating the lens size at the wide-angle end. Used for paraxial design between groups (in the case of a four-group zoom lens, used for paraxial design between the first lens group and the combined second and third lens groups). Expression (15) is a relational expression that defines the paraxial lateral magnification to be borne by the zoom lens group that should be considered as the zoom type. (13), (1
If the conditional expression (4) is deviated from the conditional expression, the paraxial arrangement, which is important for the aberration correction surface and compactness, cannot be taken. Further, in the expression (15), the condition for burdening the zoom ratio relating to the zoom type is described. If the condition is deviated from, the optical system having a particularly high zoom ratio cannot be achieved.

In consideration of the above conditions, it is important to consider the focusing system when implementing an actual lens configuration.

Next, the focusing method will be described.

The three-group zoom lens is composed of, in order from the object side, 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. And the distance between the first lens group and the second lens group, and
In a zoom lens that performs zooming by changing the distance between the second lens group and the third lens group, the lens group distance is variable so as to obtain an expanded wide-angle range independent of the wide-angle end, and focusing is performed as follows. In the extended wide-angle range, it is realized by a method different from the focusing method performed from the wide-angle end to the telephoto end.

Regarding the 4-group zoom lens, in order from the object side, the first lens group having a positive refractive power, the second lens group, the third lens group having a positive refractive power, and the fourth lens group having a negative refractive power are arranged in order.
It is composed of two lens groups, and the magnification is changed by changing the distance between the first lens group and the second lens group, the distance between the second lens group and the third lens group, and the distance between the third lens group and the fourth lens group. In the zoom lens that operates, the lens group spacing is variable so as to obtain an expanded wide-angle range independent of the wide-angle end, and in focusing, in the expanded wide-angle range, the focusing method is performed from the wide-angle end to the telephoto end. Is realized by another method.

This is because the zoom lens system according to the present invention basically realizes normal focusing by the internal focusing method. In particular, at the telephoto end from the wide-angle end, which is the normal focal range, the third lens group zoom lens moves by the second lens group,
The four-group zoom lens is realized by moving the second and third lens groups. This is because the lens group spacing that changes by moving the focusing lens group has a relationship in which aberrations are mutually compensated, and as a result, aberration variation is reduced. This is clear from the aberration correction coefficient shown in FIG.

However, in such a focusing method, when switching to the super wide-angle range, according to the conditional expressions (3) and (5) already described, the actual distance between the first lens group and the second lens becomes narrow. May mechanically interfere with each other, and focusing may not be realized.

In view of this limiting condition, it is necessary to devise a focusing method different from the normal focal range at the ultra wide-angle end. That is, specifically, focusing is usually performed by the second lens group, and at the ultra-wide-angle end, the first lens group and the second lens group are focused.
The method of moving the lens groups together is adopted. At this time, the second lens group has a focusing mechanism from the beginning,
It suffices to drive by this, and the first lens group can be moved only linearly by using the zooming cam.
It may be linked with the lens group. Further, when switching to the ultra-wide-angle end for focusing, it may be made to interlock with the second lens group. It is also possible to perform focusing by switching the focusing mechanism to the third lens group when switching to the ultra wide-angle end.

In the present invention, when switching to the ultra wide-angle end,
It can be thought of as a function that achieves only infinity shooting without focusing, but in reality it is inconvenient, and as mentioned above, we will try to realize finite distance shooting by providing a focusing mechanism different from the normal focal range. To do.

Focusing in each embodiment will be described below. Examples 1 and 2 described later are three-group zoom lenses, and Examples 3, 4, and 5 are four-group zoom lenses. Focusing from the wide-angle end to the telephoto end is realized by moving the second lens group in the three-group zoom lens, and by moving the second and third lens groups in the four-group zoom lens. On the other hand, in the ultra wide-angle range, the first and second lens groups are clogged in both cases, and the internal focus method cannot be used. Therefore, in Examples 1 and 2, by moving the first and second lens groups,
In the fifth embodiment, focusing is realized by moving the first, second and third lens groups. In this method, since the position of the entrance pupil does not change much during focusing, the situation of the light flux does not change greatly, the loss of the peripheral light amount is small, and as a result, the aberration fluctuation is small, which is the greatest advantage.

In the third and fourth embodiments, the focusing method is switched and the fourth lens group is lowered. The fourth position where the angle of the emitted light beam is large
Since the lens group is moved down, there is little variation in aberration, but it is necessary to consider a reduction in back focus and a reduction in peripheral light quantity, and to provide a separate focusing mechanism.

Next, a specific example of the focusing mechanism will be described.

FIG. 3 shows a conceptual diagram of the lens barrel structure. This figure shows the state at the wide-angle end, and the conceptual diagram of the zoom cam is shown corresponding to the upper part of the figure for explaining focusing when the zoom cam is moved to the ultra-wide-angle end. Briefly explaining the components in the drawing, 1 is a first lens group frame for holding the first lens group, and 2 is a spring for returning to an initial position (infinity position) at the time of focusing at an ultra wide angle end. is there.
Further, 3 is a boss, which is used in conjunction with the second lens group frame 5 to drive the first lens group. Reference numeral 4 is a frame for holding the second lens group. This is driven along the second lens group drive cam 20 via the cam pin 6. Further, during focusing, the second lens group is driven by the focusing spring 17, the drive rod 13, and the focus cam mechanism 16. Further, reference numeral 23 is a pin for interlocking the movable frame 10 of the first lens group for zooming movement. A frame 7 holds the third lens group, which is driven via a pin 9 during zooming. 21 is the third
It is a lens group cam. 12 is a zoom cam cylinder, and 11
Is a fixed frame, in which a linear groove is cut, and a rotation of 12 realizes a zooming drive. Here, 14 is a first lens group, 15 is a second lens group, 22 is a third lens group, and A is a fixed lens component holding frame.

By the way, the zooming drive is carried out along the zooming cam cut into 12, and when entering the super wide-angle end, the actual cam groove is further extended as shown in FIG. 3 and the frame 5 come into contact with each other, and the lens group does not retract further. Focusing is realized by moving the second lens group 15 in the normal focal range from the wide-angle end to the telephoto end. This is achieved by moving the second lens group 15 along a focus cam 16 provided in the circumferential direction. It is performed by driving toward the object by the amount of extension calculated from the distance information.

However, at the ultra-wide-angle end, the first lens group 1
4 and the second lens group 15 are in contact with each other, and the second lens group 15 is driven for focusing and moves toward the object side, and at the same time, the first lens group 14 also moves.
When the second lens group 15 returns to the infinity position by the spring 2, the first lens group 14 also returns to the original reference position.

As described above, the focusing mechanism at the wide angle end can be easily realized.

[0064]

EXAMPLES Next, Examples 1 to 5 of the zoom lens of the present invention will be described.
Will be described. Although the lens data of each example will be shown later, FIG. 4 shows lens cross sections at the ultra-wide-angle end (WS), the wide-angle end (W), and the telephoto end (T) of Example 1, and similar lenses of Examples 3 and 5 are used. Sections are shown in FIGS. 5 and 6, respectively. The lens cross section of Example 2 is the same as that of Example 1 and the lens cross section of Example 4 is similar to that of Example 3, and therefore the illustration thereof is omitted.

In the first embodiment, the focal length is 29.0-10.
This is a 5.4-group, wide-angle zoom lens. The focal length of the super wide-angle end obtained by expanding the wide-angle end according to the conditions is 26.1, and the aperture ratio is 1: 3.64.
Is. FIG. 7 shows an aberration diagram of this example. In the figure, WS
(∞), WS (2 m), W, and T are spherical aberrations at the super-wide-angle end (infinity object point state), the super-wide-angle end focusing state (object point distance 2.0 m), the wide-angle end, and the telephoto end, respectively. FIG. 6 is a diagram showing astigmatism, lateral chromatic aberration, and distortion (the same applies to the aberration diagrams of the following examples).

Now, the aberration diagrams WS (∞), WS (2
As can be seen from m), the spherical aberration hardly changes and the performance is maintained, and the astigmatism and the chromatic aberration of magnification are not extreme and are at a level that is not problematic for practical use. In this example, it is clear that the distortion aberration is displaced in a slightly negative direction. It is a barrel distortion and is not a critical issue. Therefore, it may be necessary to balance the aberrations of the main lens while paying attention to the direction of fluctuation. Further, while the focal length at the ultra wide-angle end is 26.1, the back focus is about 6 mm, which is sufficient.

The second embodiment has optical specifications close to those of the first embodiment, and the focal length at the ultra wide-angle end is 26.7. Aberration diagrams are shown in FIG. According to this aberration diagram, similarly to the above, spherical aberration is not deteriorated from the performance at the wide-angle end, the absolute amount of astigmatism and lateral chromatic aberration is slightly increased, and the fluctuation of distortion is also It is common in that it is a negative displacement. Sufficient in terms of performance.

In the third embodiment, the focal length is 38.0-17.
It is a 6.0 high-magnification zoom lens. Even if there is no significant difference in the actual angle of view, it is possible to meet the demand for setting the wide-angle end to 35. That is, in this embodiment, the wide-angle end 38.0 is changed to the ultra-wide-angle end 36.6. Aberration diagrams are shown in FIG. This optical system is a 4-group zoom lens. From the aberration diagram, it becomes clear that the aberration situation is stable regardless of which aberration.

Example 4 has a normal focal length of 36.0-1.
It is a 31.5 4-group zoom lens. The focal length at the ultra wide-angle end is 33.2, which is sufficiently satisfactory when a slightly wider angle is desired. This aberration diagram is shown in FIG. Here again, the aberration variation is at a satisfactory level.

In the fifth embodiment, the focal length is 29.5-13.
It is a high-magnification, wide-angle, four-group zoom lens with a zoom ratio of 1.0. From the beginning, the wide-angle end has a wide angle, but the ultra-wide-angle end has a focal length of 27.8. This aberration diagram is shown in FIG.

Regarding focusing at the ultra wide-angle end,
For an object point distance of 2 m, the first and second lens groups are 0.21 mm on the object side in Example 1, the first and second lens groups are 0.22 mm on the object side in Example 2, and Example 3 is The fourth lens group is moved toward the image side by 1.71 mm, the fourth example is moved toward the image side by 1.17 mm, and the fourth example is moved by the first to third lens groups toward the object side by 0.21 mm. Do it.

In the following lens data, the symbols are the above, f is the focal length of the entire system, F _NO is the F number, 2ω is the angle of view, f _B is the back focus, r ₁ and r ₂
... is the radius of curvature of each lens surface, d ₁ , d ₂ ... is the distance between the lens surfaces, n _d1 , n _d2 ... is the refractive index of the d-line of each lens, ν
_d1 and ν _d2 are the Abbe numbers of the respective lenses, and the aspherical shape is expressed by the following equation, where x is the optical axis direction and y is the direction orthogonal to the optical axis.

X = (y ² / r) / [1+ {1-P (y ² / r ² )}
^1/2 ] + A ₄ y ⁴ + A ₆ y ⁶ + A ₈ y ⁴ + A ₁₀ y ¹⁰ However, r is a paraxial radius of curvature, P is a conic coefficient, A ₄ , A ₆ ,
A ₈ and A ₁₀ are aspherical coefficients.

Example 1 f = 26.1 to 29.0 to 105.4 F _NO = 3.64 to 4.00 to 7.67 2ω = 79.2 to 73.4 to 23.2 ° f _B = 5.95 to 9.28 to 81.81 r ₁ = 123.2807 d ₁ 1.2000 n _d1 = 1.69680 ν _{d1 = 55.52 r 2 = 28.1453 d 2} = 7.0560 r 3 = 31.7325 d 3 = 5.4876 n d2 = 1.53172 ν d2 = 48.90 r 4 = 302.3165 d 4 = 1.7500 r 5 = -125.1445 d 5 = 1.0000 n d3 = 1.83400 ν d3 = 37.16 r ₆ = 33.3387 d ₆ = 0.6923 r ₇ = 40.6740 d ₇ = 3.6156 n _d4 = 1.65844 ν _d4 = 50.86 r ₈ -1157.9848 d ₈ = 0.1500 r ₉ = 32.3632 d ₉ = 5.6348 n _d5 = 1.51823 ν _d5 = 58.96 r ₁₀ = -60.9035 d ₁₀ = (Variable) r ₁₁ = -87.8043 d ₁₁ = 1.0000 n _d6 = 1.78590 ν _d6 = 44.18 r ₁₂ = 16.2024 d ₁₂ = 0.9097 r ₁₃ = 31.3832 d ₁₃ = 2.9131 n _d7 = 1.78470 ν _d7 = 26.22 r ₁₄ = -49.7711 d ₁₄ = 3.5341 r ₁₅ = -18.0019 d ₁₅ = 1.2081 n _d8 = 1.65830 ν _d8 = 53.44 r ₁₆ = -22.3951 d ₁₆ = 4.7231 r ₁₇ = (aperture) d ₁₇ = 3.4676 r ₁₈ =- _{115.0000 d 18 = 2.1300 n d9 =} 1.68893 _{d9 = 31.08 r 19 = -64.5600 d} 19 = 0.5000 r 20 = 484.4333 d 20 = 3.3939 n d10 = 1.54739 ν d10 = 53.55 r 21 = -26.1713 d 21 = 0.5903 r 22 = 146.1389 d 22 = 0.4350 n d11 = 1.78472 ν _d11 = 25.71 r ₂₃ = 17.3114 d ₂₃ = 5.4869 n _d12 = 1.58313 ν _d12 = 59.36 r ₂₄ = -25.9767 d ₂₄ = 1.2500 r ₂₅ = -19.9068 d ₂₅ = 1.4830 n _d13 = 1.74100 ν _d13 = 52.68 r ₂₆ = -20.9013 d ₂₆ = (variable) r ₂₇ = -38.0869 d ₂₇ = 2.7902 n _d14 = 1.84666 ν _d14 = 23.78 r ₂₈ = -21.4684 d ₂₈ = 2.6534 r ₂₉ = -16.2903 (aspherical) d ₂₉ = 0.3593 n _d15 = 1.52492 ν _d15 = 51.77 r ₃₀ = -17.4211 d ₃₀ = 1.3500 n _d16 = 1.77250 ν _d16 = 49.66 r ₃₁ = 82.1742 Zoom interval Aspherical surface 29th surface P = 1 A ₄ = 0.20587 × 10 ^-4 A ₆ = 0.86201 × 10 ^-7 A ₈ = -0.48242 × 10 ^-9 A ₁₀ = 0.27293 × 10 ^-11 .

[0075] Example 2 f = 26.7~ 28.9 ~ 102.0 F NO = 4.19~ 4.50 ~ 7.63 2ω = 78.0~ 73.6 ~ 24.0 ° f B = 6.58~ 9.05 ~ 80.53 r 1 = 160.7804 d 1 = 1.2000 n d1 = 1.74100 ν _d1 = 52.68 r ₂ = 34.8076 d ₂ = 6.9850 r ₃ = 38.8887 d ₃ = 3.3406 n _d2 = 1.53172 ν _d2 = 48.90 r ₄ = 142.7690 d ₄ = 1.7500 r ₅ = -194.6240 d ₅ = 1.0000 n _d3 = 1.83400 ν _d3 = 37.16 r ₆ = 38.0459 d ₆ = 0.3520 r ₇ = 43.6383 d ₇ = 3.4187 n _d4 = 1.65844 ν _d4 = 50.86 r ₈ = -730.7292 d ₈ = 0.1500 r ₉ = 32.2002 d ₉ = 5.2460 n _d5 = 1.51823 ν _d5 = 58.96 r ₁₀ = -96.2536 d ₁₀ = (variable) r ₁₁ = -498.7110 d ₁₁ = 1.0000 n _d6 = 1.78590 ν _d6 = 44.18 r ₁₂ = 15.0840 d ₁₂ = 0.8410 r ₁₃ = 24.1630 d ₁₃ = 2.7640 n _d7 = 1.78470 ν _d7 = 26.22 r ₁₄ = -102.9802 d ₁₄ = 3.9120 r ₁₅ = -14.3361 d ₁₅ = 1.1100 n _d8 = 1.65830 ν _d8 = 53.44 r ₁₆ = -16.3753 d ₁₆ = 4.9610 r ₁₇ = (aperture) d ₁₇ = 3.6000 r ₁₈ = -79.9489 d ₁₈ = 2.1300 n _d9 = 1.666 80 ν _d9 = _33.04 r ₁₉ = -51.9241 d ₁₉ = 0.5000 r ₂₀ = -555.5860 d ₂₀ = 3.0490 n _d10 = 1.51454 ν _d10 = 54.69 r ₂₁ = -26.8298 d ₂₁ = 0.1200 r ₂₂ = 103.1734 d ₂₂ = 0.6500 n _d11 = 1.80518 ν _d11 = 25.43 r ₂₃ = 17.2071 d ₂₃ = 5.4150 n _d12 = 1.60729 ν _d12 = 59.38 r ₂₄ = -26.0457 d ₂₄ = 1.2500 r ₂₅ = -21.6894 d ₂₅ = 0.8780 n _d13 = 1.77250 ν _d13 = 49.66 r ₂₆ = -22.7792 d ₂₆ = (Variable) r ₂₇ = -54.8870 d ₂₇ = 3.3170 n _d14 = 1.78472 ν _d14 = 25.71 r ₂₈ = -22.2644 d ₂₈ = 2.4970 r ₂₉ = -15.6872 (aspherical surface) d ₂₉ = 0.3600 n _d15 = 1.52492 ν _d15 = 51.77 r ₃₀ = -16.8658 d ₃₀ = 1.3200 n _d16 = 1.77250 ν _d16 = 49.66 r ₃₁ = 62.5760 Zoom interval Aspheric coefficient P = 1 A ₄ = 0.30618 × 10 ^-4 A ₆ = 0.10777 × 10 ^-6 A ₈ = -0.18514 × 10 ^-9 A ₁₀ = 0.20423 × 10 ^-11 .

Example 3 f = 36.6 to 38.0 to 176.0 F _NO = 4.62 to 4.62 to 11.20 2ω = 61.2 to 59.3 to 14.0 ° f _B = 5.91 to 6.18 to 106.06 r ₁ -8204.4298 d ₁ = 1.4500 nd ₁ = 1.83400 ν _d1 = 37.16 r ₂ = 32.1497 d ₂ = 0.8500 r ₃ = 47.5851 d ₃ = 3.2000 n _d2 = 1.61405 ν _d2 = 54.95 r ₄ -1942.9777 d ₄ = 0.2150 r ₅ = 26.3265 d ₅ = 5.0000 n _d3 = 1.53996 ν _d3 = 59.57 r ₆ = -200.2508 d ₆ = (variable) r ₇ = -39.1402 d ₇ = 1.3000 n _d4 = 1.78590 ν _d4 = 44.18 r ₈ = 20.1050 d ₈ = 0.6478 r ₉ = 33.8748 d ₉ = 2.6500 n _d5 = 1.78472 ν _d5 = 25.68 r ₁₀ = -38.3830 d ₁₀ = 1.2259 r ₁₁ = -29.0561 d ₁₁ = 1.3000 n _d6 = 1.61405 ν _d6 = 54.95 r ₁₂ = -36.4855 d ₁₂ = (variable) r ₁₃ = (aperture) d ₁₃ = 4.0000 r ₁₄ = -92.6144 d ₁₄ = 2.1000 n _d7 = 1.68893 ν _d7 = 31.08 r ₁₅ = -322.7288 d ₁₅ = 0.3250 r ₁₆ = 88.7094 d ₁₆ = 2.2000 n _d8 = 1.54739 ν _d8 = 53.55 r ₁₇ = -33.9960 d ₁₇ = 0.5862 r ₁₈ = 209.5506 d ₁₈ = 1.3000 n _d9 = 1.7 8472 ν _d9 = 25.71 r ₁₉ = 21.0222 d ₁₉ = 4.0000 n _d10 = 1.58913 ν _d10 = 61.18 r ₂₀ = -25.0062 d ₂₀ = 1.0000 r ₂₁ = -19.2691 d ₂₁ = 1.7000 n _d11 = 1.74100 ν _d11 = 52.68 r ₂₂ = -20.2562 d ₂₂ = (variable) r ₂₃ = -36.6191 d ₂₃ = 3.1500 n _d12 = 1.84666 ν _d12 = 23.78 r ₂₄ = -21.2860 d ₂₄ = 2.7816 r ₂₅ = -16.1349 (aspheric) d ₂₅ = 0.1000 n _d13 = _{1.51742 ν d13 = 52.41 r 26 =} -16.8308 d 26 = 1.5000 n d14 = 1.77250 ν d14 = 49.66 r 27 = 177.9701 zoom interval Aspherical surface 25th surface P = 1 A ₄ = 0.25779 × 10 ^-4 A ₆ = 0.78006 × 10 ^-7 A ₈ = -0.15033 × 10 ^-9 A ₁₀ = 0.17915 × 10 ^-11 .

Example 4 f = 33.2 to 36.0 to 131.5 F _NO = 4.30 to 4.62 to 9.01 2ω = 66.2 to 62.0 to 18.7 ° f _B = 6.99 to 9.78 to 83.35 r ₁ = -179.8187 d ₁ = 1.0919 n _d1 = 1.83400 ν _d1 = 37.16 r ₂ = 38.4651 d ₂ = 0.8788 r ₃ = 49.9828 d ₃ = 3.1628 n _d2 = 1.61720 ν _d2 = 54.04 r ₄ = -279.9562 d ₄ = 0.1998 r ₅ = 30.1522 d ₅ = 4.7290 n _d3 = 1.51823 ν _d3 = 58.96 r ₆ = -112.6403 d ₆ = (variable) r ₇ = -42.9353 d ₇ = 0.7101 n _d4 = 1.78590 ν _d4 = 44.18 r ₈ = 19.2434 d ₈ = 1.0696 r ₉ = 38.2064 d ₉ = 2.7010 n _d5 = 1.78472 ν _d5 = 25.71 r ₁₀ = -44.0457 d ₁₀ = 2.6789 r ₁₁ = -21.2365 d ₁₁ = 1.2931 n _d6 = 1.63854 ν _d6 = 55.38 r ₁₂ = -27.2568 d ₁₂ = (variable) r ₁₃ = (aperture) d ₁₃ = 4.0108 r ₁₄ = -402.5078 d ₁₄ = 2.1024 n _d7 = 1.68893 ν _d7 = 31.08 r ₁₅ = -97.7116 d ₁₅ = 0.3479 r ₁₆ = 107.4156 d ₁₆ = 2.6354 n _d8 = 1.54739 ν _d8 = 53.55 r ₁₇ = -33.2395 d ₁₇ = 1.5238 r ₁₈ = 193.3836 d ₁₈ = 1.2076 n _d9 = 1 .78472 ν _d9 = 25.71 r ₁₉ = 18.0304 d ₁₉ = 4.6310 n _d10 = 1.58313 ν _d10 = 59.36 r ₂₀ = -27.2813 d ₂₀ = 0.9453 r ₂₁ = -19.4411 d ₂₁ = 1.6868 n _d11 = 1.74100 ν _d11 = 52.68 r ₂₂ = -20.1265 d ₂₂ = (Variable) r ₂₃ = -47.2575 d ₂₃ = 3.0383 n _d12 = 1.84666 ν _d12 = 23.78 r ₂₄ = -23.6858 d ₂₄ = 2.4178 r ₂₅ = -17.7464 (aspherical) d ₂₅ = 0.7957 n _d13 = 1.50137 ν _d13 = 56.40 r ₂₆ = -18.0796 d ₂₆ = 0.6371 n _d14 = 1.77250 ν _d14 = 49.66 r ₂₇ = 74.5122 Zoom interval Aspherical surface 25th surface P = 1 A ₄ = 0.19070 x 10 ^-4 A ₆ = 0.49353 x 10 ^-7 A ₈ = -0.16021 x 10 ^-10 A ₁₀ = 0.58494 x 10 ^-12 .

Example 5 f = 27.8 to 29.5 to 131.0 F _NO = 4.50 to 4.50 to 8.25 2ω = 75.8 to 72.5 to 18.8 ° f _B = 7.17 to 8.92 to 87.09 r ₁ = 147.7015 d ₁ = 0.8500 nd ₁ = 1.74100 ν _d1 = 52.68 r ₂ = 39.8775 d ₂ = 6.9732 r ₃ = 34.9579 d ₃ = 4.4400 n _d2 = 1.53172 ν _d2 = 48.90 r ₄ = -509.1641 d ₄ = 1.4600 r ₅ = -55.5641 d ₅ = 0.8600 n _d3 = 1.83400 ν _d3 = 37.16 r ₆ = 38.7196 d ₆ = 0.3489 r ₇ = 45.0582 d ₇ = 3.6100 n _d4 = 1.65844 ν _d4 = 50.86 r ₈ = -134.9701 d ₈ = 0.1200 r ₉ = 36.3870 d ₉ = 4.4600 n _d5 = 1.50137 ν _d5 = 56.40 r ₁₀ = -55.5290 d ₁₀ = (variable) r ₁₁ = -74.3691 d ₁₁ = 0.5500 n _d6 = 1.78590 ν _d6 = 44.18 r ₁₂ = 15.5103 d ₁₂ = 0.7341 r ₁₃ = 24.6834 d ₁₃ = 2.6600 n _d7 = 1.78470 ν _d7 = 26.22 r ₁₄ = -63.3984 d ₁₄ = (variable) r ₁₅ = -13.9591 d ₁₅ = 0.9163 n _d8 = 1.65830 ν _d8 = 53.44 r ₁₆ = -16.2221 d ₁₆ = 4.3715 r ₁₇ = (aperture) d ₁₇ = 3.3080 r ₁₈ = -77.7267 d ₁₈ = 1.7100 n _d9 = 1.666 80 ν _d9 = _33.04 r ₁₉ = -56.3440 d ₁₉ = 0.1400 r ₂₀ = -322.6649 d ₂₀ = 2.3300 n _d10 = 1.50137 ν _d10 = 56.40 r ₂₁ = -24.8971 d ₂₁ = 0.1200 r ₂₂ = 74.2271 d ₂₂ = 0.5300 n _d11 = 1.80518 ν _d11 = 25.43 r ₂₃ = 17.1956 d ₂₃ = 5.1000 n _d12 = 1.60311 ν _d12 = 60.70 r ₂₄ = -24.4180 d ₂₄ = 1.0490 r ₂₅ = -20.8299 d ₂₅ = 0.8800 n _d13 = 1.77250 ν _d13 = 49.66 r ₂₆ = -22.2142 d ₂₆ = (variable) r ₂₇ = -50.1298 d ₂₇ = 3.2000 n _d14 = 1.78472 ν _d14 = 25.71 r ₂₈ = -21.5995 d ₂₈ = 2.3876 r ₂₉ = -14.9318 (aspheric) d ₂₉ = 0.4500 n _d15 = 1.52492 ν _d15 = 51.77 r ₃₀ = -15.1591 d ₃₀ = 1.1900 n _d16 = 1.77250 ν _d16 = 49.66 r ₃₁ = 52.7870 Zoom interval Aspherical coefficient No. 29 surface P = 1 A ₄ = 0.45142 × 10 ^-4 A ₆ = 0.15406 × 10 ^-6 A ₈ = -0.58035 × 10 ^-9 A ₁₀ = 0.42319 × 10 ^-11 .

Next, the conditional expressions (3) to
The values corresponding to (6) are shown in Table 1 below.

Table 2 below shows a comparison of the total lengths of the lens systems of Examples 1 to 5.

Further, Table 3 below shows changes in the angle of view toward the wide-angle end expanded in Examples 1 to 5.

[0082]

As described above, according to the zoom lens of the present invention with an expanded wide-angle range, the focal length at the wide-angle end is reduced in addition to the focal range designed by a normal design, resulting in a wider image. Can be achieved. Even if the aperture diameter is the same as that at the wide-angle end, a large aperture ratio can be achieved at the same time.

This expanded wide-angle range can be easily realized only by changing the lens group interval and extending the cam. Fortunately, the total length of the expanded lens system can be shortened from the wide-angle end. Also has a physical effect.

On the other hand, the connection of the cam curves as the additional mechanism does not have an inflection point, so that the cam curves are set as if they were the same cam.

Further, according to the present invention, the super wide-angle range is located closer to the image side than the wide-angle end, as can be seen from the zoom cam movement locus in the first embodiment shown in FIG. The total length will be shortened,
Moreover, the cam can be extended without causing a sudden change in the load torque of the lens that moves along the zoom cam.

[Brief description of drawings]

FIG. 1 is a diagram showing a power arrangement and a movement locus of Example 1 of a zoom lens of the present invention.

FIG. 2 is a diagram showing changes in aberration coefficients when the zoom lens interval of the zoom lens of the present invention is changed.

FIG. 3 is a conceptual diagram of an example of a lens barrel configuration for a zoom lens of the present invention.

FIG. 4 is an ultra wide-angle end (WS), a wide-angle end (W) of Example 1,
It is a lens cross-sectional view at the telephoto end (T).

FIG. 5 is a view similar to FIG. 1 of the third embodiment.

FIG. 6 is a view similar to FIG. 1 of Example 5;

FIG. 7: Ultra wide-angle end of Example 1 (infinite object state) (WS
(∞)), focusing state at ultra-wide-angle end (object point distance 2.0 m) (WS (2 m)), wide-angle end (W), telephoto end (T) spherical aberration, astigmatism, lateral chromatic aberration, and distortion. FIG. 6 is an aberration diagram showing

FIG. 8 is a view similar to FIG. 7 of the second embodiment.

FIG. 9 is a view similar to FIG. 7 of the third embodiment.

FIG. 10 is a view similar to FIG. 7 of the fourth embodiment.

FIG. 11 is a view similar to FIG. 7 of the fifth embodiment.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-4-303809 (JP, A) JP-A-63-157120 (JP, A) JP-A-63-43115 (JP, A) JP-A-2- 73211 (JP, A) JP 60-178420 (JP, A) JP 61-138227 (JP, A) JP 3-50515 (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 (6)

(57) [Claims] 1. A first lens group having a positive refracting power, a second lens group, a third lens group having a positive refracting power, and a fourth lens group having a negative refracting power, in this order from the object side. The distance between the first lens group and the second lens group, and the second lens group and the third lens group.
In order to obtain an extended wide-angle range independent of the wide-angle end in a zoom lens that performs zooming by changing the distance between the lens groups and the distance between the third lens group and the fourth lens group, the following conditions From the wide-angle end, satisfying the formula
At the telephoto end, the second lens group and the third lens group move.
Focusing method to achieve a wide-angle range.
Then, the first lens group, the second lens group, and the third lens group
Focusing system in which both move or the fourth lens unit moves
The zoom lens extends the wide angle region, characterized in that the so that the a grayed _{method: D 1W> D 1WS D 4W} > D 4WS However, D _1W, the first lens group at the wide-angle end and the second lens group Actual distance, D _1WS is the actual distance between the first lens group and the second lens group at the wide-angle end, D _4W is the back focus of the entire lens system at the wide-angle end, and D _4WS is the wide-angle end The back focus of the entire lens system. 2. The first zoom lens according to claim 1, wherein the zoom lens forms an entrance pupil, and the first lens group of the first lens group is located closest to the object side.
Zoom lens characterized in that the distance from the lens surface to the entrance pupil (incident pupil distance) satisfies the following conditional expression: EP _W −EP _WS > 0 (1) where EP _W is , The entrance pupil distance at the wide-angle end, and EP _WS is the entrance pupil distance at the super wide-angle variable power position. 3. The zoom lens according to claim 1, wherein the total length of the lens system of the zoom lens satisfies the following conditional expression: L _W −L _WS > 0 (2) where L _W is the total lens system length at the wide-angle end, and L _WS is the total lens system length at the super-wide-angle variable power position. 4. The zoom lens according to claim 1, wherein among the lens groups of the zoom lens, the lens group that contributes most to the magnification change of the discontinuous variable power from the wide-angle end to the super wide-angle variable power position is mainly used for zooming. A zoom lens characterized in that, when the lens group is assumed to be responsible, the paraxial lateral magnification of the lens group mainly responsible for the magnification change is reduced by comparing the wide-angle end and the super wide-angle variable power position. . 5. The lens group according to claim 4, which is mainly responsible for zooming to the super-wide-angle zoom position, is a negative lens group arranged closest to the image side, and satisfies the following conditional expression [b]. the zoom lens is characterized in that: [b] _{condition; β 2WS β 3WS β 4WS <} β 2W β 3W β 4W β 4W> 1 β 4W> β 4WS However, beta _2W is the second lens unit at the wide angle end Paraxial lateral magnification, β _3W , is the paraxial lateral magnification of the third lens group at the wide-angle end, β _4W is the paraxial lateral magnification, which is carried by the fourth lens group at the wide-angle end, and β _2WS is an ultra-wide-angle variable magnification The paraxial lateral magnification of the second lens group at the position, β _3WS, is the paraxial lateral magnification of the third lens group at the super wide-angle variable position, and β _4WS is the fourth lens group of the super wide-angle variable position. The paraxial lateral magnification is. 6. The zoom lens according to claim 5, wherein the negative lens group disposed closest to the image side moves to the image plane side during demagnification from the wide-angle end to the super wide-angle variable power position. .