JPH04235514A - Super-wide angle zoom lens - Google Patents

Abstract

PURPOSE:To provide excellent image forming performance over a range from an infinitely distant objective point to a short distance objective point in every variable power domain by relatively compactly forming a super-wide angle zoom lens of a less number of composition lenses though an image angle at the wide angle end exceeds 100 deg.. CONSTITUTION:The first group of lenses G1 has the first lens component G11 having negative refracting power, the second lens component G12 having negative refracting power, and the third lens component G13 having positive refracting power in order from the side of a body, and has an aspheric surface on at least one lens face. In varying a power from the wide-angle end to the telescopic end, an air space between the first group of lenses G1 and the second group of lenses G2 is reduced, and that between the second group of lenses G2 and the third group of lenses G3 is enlarged, and that between the third group of lenses G3 and the forth group of lenses G4 is reduced, and in focusing from an infinitely distant objective point to an extremely short distance objective point, at least the third group of lenses G3 is moved toward an optical axis.

Description

Detailed Description of the Invention [0001] [Industrial Application Field] The present invention is suitable for 35 mm Leica single-lens reflex cameras, electronic still cameras, TV cameras, etc., and has an angle of view of 100° or more at the wide-angle end. This invention relates to an ultra-wide-angle zoom lens that uses an internal focusing method (inner focus method or rear focus method) and has a sufficient back focus. 2. Description of the Related Art Conventionally, many wide-angle zoom lenses having four or more lens groups (negative, positive, negative, positive) have been proposed. However, in the various conventional wide-angle zoom lenses described above, the angle of view at the wide-angle end is 95° or less, and very few ultra-wide-angle zoom lenses have been proposed that exceed 100°. [0003] For example, Japanese Patent Application Laid-open No. 2-201310,
In Japanese Patent Application Laid-Open No. 60-87312, etc., there are four
A wide-angle zoom lens consisting of a group structure is disclosed, and the former has an angle of view of about 93° at the wide-angle end, and the latter has an angle of view of 85° at the wide-angle end, as disclosed in Japanese Patent Laid-Open No. 60-87312. It has a certain degree. Further, as for a focusing method for an ultra-wide-angle zoom lens, an internal focusing method has been proposed in the above-mentioned Japanese Patent Laid-Open No. 2-201310. [0004] Problem to be Solved by the Invention: The above-mentioned Japanese Patent Application Laid-Open No. 2-201
In JP-A No. 310 and JP-A-60-87312, the first lens group has a relatively complicated structure and is thick. Since the second positive lens from the object side in the first lens group largely refracts oblique rays with a large angle of view in the direction of the optical axis, it is difficult to widen the angle any further with the same configuration as the first lens group. Very difficult. If we were to increase the angle of view with the same configuration as the first lens group,
In addition to the negative lens closest to the object in the lens group and the positive lens second from the object side becoming large, the entire first lens group becomes thick. Furthermore, based on the lens configuration of the first lens group, if we proceed with the development of an ultra-wide-angle zoom lens that exceeds 100 degrees, the second lens in the first lens group will be The refraction effect of the positive lens on the oblique rays increases, and the angle of incidence of the oblique rays on the lens located on the image side increases dramatically, until eventually even the rays no longer pass through. This problem is the first
The greater the refractive power of the second positive lens from the object side in the lens group, and the greater the air gap between that positive lens and the lens immediately following it, the more pronounced this becomes. On the other hand, when looking at the wide-angle zoom lenses disclosed in JP-A-2-201310 and JP-A-60-87312 in terms of aberrations, the curvature of field increases as the angle of view becomes wider. As the aberration becomes larger, astigmatism and distortion aberration increase, and coma aberration at a large angle of view also worsens. In particular, the zoom lens disclosed in JP-A-60-87312 has an angle of view of about 85°, but has large distortion, astigmatism, and field curvature at the wide-angle end, and has large upper coma. Aberrations were not sufficiently corrected, with a large amount occurring in the positive direction, and comatic aberrations fluctuated greatly during zooming, so the aberrations were not sufficient. Therefore, it is difficult to achieve a wider angle due to aberrations. As described above, the wide-angle zoom lenses disclosed in JP-A-2-201310 and JP-A-60-87312 have a 100° angle view in terms of lens construction and aberration structure. In order to achieve an ultra-wide angle that exceeds
It was extremely difficult. By the way, when looking at aberrations, the conventional focusing method for ultra-wide-angle zoom lenses in which the first lens group is extended has large fluctuations in coma aberration and field curvature that occur during focusing, and especially in the image. This becomes even more noticeable with ultra-wide-angle zooms where the angle exceeds 100 degrees. Moreover, according to the focusing method in which the first lens group is extended, the principal ray passes through a position significantly away from the optical axis at short distances, which increases the diameter of the front lens, leading to an increase in the size of the entire system. As a result, the amount of peripheral light is drastically reduced, which is not preferable. In particular, this problem becomes more pronounced as the angle of view becomes larger. Therefore, as a focusing method different from the focusing method in which the first lens group is extended, the above-mentioned Japanese Patent Application Laid-Open No. 2-2013
No. 10 proposes a method of focusing using a lens group inside the first lens group as a focusing group. However, with the proposed focusing method, it is necessary to secure air space to move the focusing group inside the first lens group, so it is necessary to increase the size of the first lens group and the diameter of the front lens. I don't like it. Furthermore, since a relatively large lens is used for focusing, the movable group (focusing group) becomes heavy, and rapid focusing cannot be achieved when focusing by autofocus (AF). Furthermore, in terms of aberrations, as the focusing group moves, the incident height of the principal ray at the maximum angle of view that enters the focusing group set inside the first lens group changes significantly. Variations in field curvature and chromatic aberration of magnification are large, which is undesirable. Furthermore, if the angle of view is further increased as in the present invention, these aberrations will worsen significantly, which is undesirable. Therefore, the present invention aims to provide an ultra-wide-angle zoom lens with an angle of view exceeding 100 degrees at the wide-angle end, which uses a so-called internal focusing method ( (inner focus method or rear focus method) guarantees excellent imaging performance from an object point at infinity to a close object point in each magnification state, achieving quick focusing, and is relatively compact, with a small number of lens components. The aim is to provide a high-performance ultra-wide-angle zoom lens. Means for Solving the Problems In order to achieve the above object, the present invention, as shown in FIG. The first lens group G1 has a second lens group G2 having a refractive power of , a third lens group G3 having a negative refractive power, and a fourth lens group G4 having a positive refractive power. In order, a first lens component G11 with negative refractive power, a second lens component G12 with negative refractive power, and a third lens component G13 with positive refractive power.
and having an aspherical surface on at least one lens surface, reducing the air gap between the first lens group G1 and the second lens group G2 when changing power from a wide-angle end to a telephoto end; The air distance between the second lens group G2 and the third lens group G3 is increased, and the air distance between the third lens group G3 and the fourth lens group G4 is decreased, so that the distance from an object point at infinity to a close object point is increased. When focusing on a distance object point, at least the third lens group G3 is moved in the optical axis direction. Based on the above basic configuration, it is more desirable to satisfy the following conditional expression. (1) 0.12≦d23/fW≦2.0 (2)
300 /fW ≦｜f1 | ≦680 /fW
(3) 0.01≦|AS-S|/fW≦0.
5 However, fW: focal length of the entire system at the wide-angle end, f1: focal length of the first lens group G1, d23: the closest image side of the negative second lens component G12 and the positive third lens component in the first lens group G1 The axial air distance between the lens component G13 and the closest object side surface, AS-S: the difference in the optical axis direction between the aspheric surface at the outermost periphery of the effective diameter and a reference spherical surface having a predetermined apex radius of curvature. [Operation] In general, when designing an ultra-wide-angle zoom lens with a large angle of view at the wide-angle end, it is especially important to suppress increases in astigmatism and negative distortion, as well as to suppress lateral chromatic aberration, The problem is how to reduce the image curvature aberration caused by the difference in the angle of view, and at the same time how to properly correct aberrations such as sagittal coma flare. Regarding ultra-wide-angle zoom lenses that have such problems, what is important in the design is the appropriate refractive power arrangement of each lens group, especially the first lens with negative refractive power that greatly contributes to off-axis aberrations. This is the refractive power and configuration of group G1. Generally, when correcting aberrations of an ultra-wide-angle lens, a larger burden is placed on correcting aberrations for off-axis rays than for aberrations for axial rays. In particular, the distortion aberration is 3
Since the distortion aberration increases in proportion to the power of the distortion aberration, correction of distortion becomes an extremely important issue in an ultra-wide-angle lens having a large angle of view. Originally, ultra-wide-angle lenses for single-lens reflex cameras need to have sufficient back focus, so they have no choice but to use retrofocus lenses, which consist of negative and positive lens groups, which are highly asymmetrical in terms of refractive power arrangement. I don't get it. Therefore,
This retrofocus type lens basically has a tendency to increase negative distortion. Therefore, it is necessary to sufficiently correct negative distortion using the object-side diverging group in the retrofocus lens. However, if only the distortion is corrected by the divergent group, the curvature of field will be extremely deteriorated, so generally a plurality of meniscus-shaped negative or positive lenses are used in the divergent group to correct off-axis aberrations. It refracted light rays gently and balanced the correction for off-axis aberrations. Therefore, when trying to achieve an ultra-wide-angle lens with an angle of view of more than 100° using such conventional methods, the diverging group becomes increasingly complex due to the large angle of view, and the number of lenses increases.
Become thicker. Therefore, the chief ray passes through a position further away from the optical axis, making it difficult to secure a sufficient amount of peripheral light. Originally, ultra-wide-angle lenses with an angle of view exceeding 100° have a significantly large angle of view, so the cosine fourth power law (cos4θ
(rule), the amount of peripheral light decreases significantly. Therefore, it is necessary to ensure the amount of peripheral light to a practical level by making the aperture efficiency extremely high. However, trying to secure the amount of peripheral light will further increase the diameter of the front lens of the lens system and increase the thickness of the lens system. This makes it even more difficult to correct coma aberration and sagittal coma flare that occur at As described above, in order to achieve an ultra-wide-angle zoom lens like the present invention, it is necessary to overcome all of the above-mentioned problems and also to overcome the fundamental problems that ordinary zoom lenses have. In other words, spherical aberration, astigmatism, field curvature, distortion aberration, chromatic aberration due to changes in magnification, coma aberration due to changes in magnification and image height are fully corrected, and at the same time, the overall optical system It is also necessary to keep the size to a practical level. For the above reasons, very few ultra-wide-angle zoom lenses having a large angle of view exceeding 100 degrees have been proposed. In the present invention, based on a configuration having four groups (negative, positive, negative, and positive), the first lens group having negative refractive power is optimized so as to be able to sufficiently cope with ultra-wide angles of view exceeding 100°. In order to set a lens configuration and refractive power that are suitable for use, and also to make it possible to use a zoom lens with an ultra-wide angle,
By appropriately distributing the refractive power of each lens group and appropriately changing the air spacing between each lens group, it is possible to realize an ultra-wide-angle zoom lens. In particular, the configuration and refractive power of the first lens group in the ultra-wide-angle zoom lens according to the present invention is such that, like the aforementioned retrofocus lens, the divergent group closest to the object is free from distortion, field curvature, As well as playing an important role in the correction of astigmatism and chromatic aberration of magnification, the angle of view 10
This is extremely important in achieving ultra-wide angles exceeding 0°. Therefore, in the present invention, first, the first lens component G11 closest to the object in the first lens group is replaced with a negative lens component (a negative single lens, a cemented negative lens of a negative lens and a positive lens, or a negative lens and a positive lens). It is a so-called concave leading type, which is a separated negative lens that is slightly separated and has a negative composite refractive power. The reason for this will be shown below. As shown in FIG. 50, there are basically two types of divergent groups closest to the object in retrofocus ultra-wide-angle lenses and ultra-wide-angle zoom lenses. One type is (a
), and the other type is the convex leading type shown in (b) in FIG.
) is a concave leading type. There is almost no decisive difference in the aberration structure between the two types up to an angle of view of about 90°, but when the angle of view is greater than that, the following problem occurs. Although the addition of a positive lens in the first lens group has the effect of correcting negative distortion, it has the paradox of increasing the refractive power of the negative lens and increasing the occurrence of negative distortion. It is originally desirable that the positive refractive power be small. Therefore, the product of the incident height of the principal ray at the maximum angle of view on the positive lens and the refractive power of the positive lens is an index indicating the ability to correct distortion aberration. Now, in both types shown in FIGS. 50(a) and 50(b), if the product of the incident height of the principal ray at the maximum angle of view on the positive lens and the refractive power of the positive lens is the same value. , the higher the incident height of the principal ray at the maximum angle of view in the positive lens,
It becomes possible to reduce the refractive power of the positive lens. Therefore, as shown in FIG. 50, it is possible to make the refractive power of the positive lens smaller in the type (a) configuration than in the type (b) configuration, and for a wide-angle lens with an angle of view of about 90°, ( a)
type has a slight advantage. However, when an ultra-wide-angle lens has a maximum angle of view of about 90° or more, the effect of correcting negative distortion is accelerated, and distortion becomes extremely overcorrected at the maximum angle of view. For this reason, for example, the distortion becomes largely negative at an intermediate angle of view, and changes greatly in the positive direction at the maximum angle of view, sometimes becoming positive, resulting in a strong distortion exhibiting a so-called cylindrical shape. Moreover, this effect also appears in the chromatic aberration of magnification, and the change in the chromatic aberration of magnification depending on the angle of view increases, resulting in large curvature. Furthermore, in terms of the structure of the lens, the positive lens becomes larger and thicker, which is unfavorable in terms of manufacturing. On the other hand, in the case of a concave leading type as shown in the type shown in FIG. 50(b), the principal ray at the maximum angle of view is subjected to a diverging effect by the negative lens, compared to the type shown in FIG. 50(a). Therefore, the angle of incidence of the chief ray at the maximum angle of view on the positive lens becomes small. Therefore, the adverse effects on distortion and chromatic aberration of magnification that the type shown in FIG. Therefore, it can be understood that in order to achieve a wide-angle lens with a maximum angle of view of about 90° or more, a concave leading type lens like the type (b) is desirable. This is explained in detail, for example, in "Lens Design Engineering" by Jihei Nakagawa (Tokai University Press), pages 113 to 123. However, in the case of an ultra-wide-angle lens with a maximum angle of view of about 100 degrees or more, even the positive lens of type (b) shown in Figure 50 increases distortion and curvature of chromatic aberration of magnification, similar to type (a). . Therefore, in order to correct distortion, etc. without worsening astigmatism and curvature of field, in both types shown in FIG. 50, the negative lens and positive lens are usually divided into multiple lenses, and It is necessary to take a shape that gently refracts the light rays. As a result, a problem arises in that the number of lens components increases, leading to an increase in the size of the lens system. If we were to further develop both types shown in FIG. 50 to create a zoom lens while accepting the above-mentioned problem of increasing the size due to the ultra-wide angle, we would be able to create a zoom lens with a negative first lens group and a positive lens group It became extremely difficult to secure the principal point distance between the first and second lens groups for zooming.
It is not possible to change the air distance between the lens group and the lens group. Therefore, with both types shown in FIG. 50, it is difficult to make an ultra-wide-angle zoom lens, so both types cannot be easily adopted. [0024] Therefore, as a configuration of the first lens group of a conventional zoom lens that allows the principal point of the negative first lens group to be brought out to the image side and can be made into a zoom lens, as shown in Fig. 51(b). Examples include negative, positive, and negative lens types. When this type of lens is applied as the first lens group of an ultra-wide-angle zoom lens, as mentioned above, the second positive lens from the object side (left side of the figure) will greatly reduce distortion and chromatic aberration of magnification. Moreover, oblique light rays entering or exiting this positive lens are largely refracted in the optical axis direction, which worsens astigmatism and curvature of field, and furthermore worsens coma aberration. If you further widen the angle in this state, the refraction effect of the second positive lens on oblique rays will increase,
From this point on, the angle of incidence of the oblique rays that enter the lens on the image side increases dramatically, until the rays no longer pass through. [0025] In summary, in the present invention, in order to achieve an ultra-wide-angle zoom lens with a maximum angle of view exceeding 100°, as described in FIG. 50(b), first,
The first lens component G11 closest to the object side of the first lens group G1
is a negative lens component, that is, a concave leading type, which is advantageous for angles of view exceeding 90°. Next, as described in FIG. 51(b), in order to eliminate the negative effect of the second positive lens from the object side when achieving an ultra-wide angle, the second lens component G12, the second lens from the object side, is added. As a negative lens component,
By gently refracting oblique light rays, the lens is configured to suppress the occurrence of astigmatism and field curvature. In addition to this configuration, by arranging the third lens component G13 having a positive refractive power third from the object side, it can sufficiently contribute to the correction of mainly downward coma aberration and furthermore, chromatic aberration of magnification. Finally, by introducing an aspherical surface in the first lens group G1, it becomes possible to effectively correct negative distortion generated in the first and second lens components having negative refractive power. That is, in the present invention, as shown in FIG. 51(a), at least three lens components, negative and negative,
By configuring the lens group G1, the configuration is advantageous for making an ultra-wide-angle zoom lens, and furthermore, in this configuration, due to the ultra-wide angle, it is possible to correct the distortion generated by the two negative lens components from the object side. By introducing an aspheric surface that is the main contributing factor, it has become theoretically possible to realize an ultra-wide-angle zoom lens with a maximum angle of view of more than 100 degrees. Furthermore, according to the configuration of the present invention, the principal ray with the maximum angle of view that passes through the negative first lens group G1 passes through a position closer to the optical axis than in conventional lens types. A new effect can be obtained in that it becomes possible to increase the amount of peripheral light. The present invention is an ultra-wide-angle zoom lens that employs an internal focusing method (inner focus method or rear focus method) based on the above-mentioned fundamental structure. The reason why the internal focusing method is adopted in the present invention is based on the two reasons mentioned above. Firstly, in the method in which the first lens group G1 is extended during focusing, the first
Since the lens group G1 moves significantly, the first lens group G1
The incident height of oblique rays incident on the object changes significantly. As a result, not only astigmatism and curvature of field vary significantly, but coma aberration also varies significantly accordingly. In particular, in an ultra-wide-angle zoom lens with an angle of view exceeding 100 degrees, fluctuations in off-axis aberrations such as astigmatism, field curvature, and coma become noticeable. Second, during focusing, the first lens group G1
In addition to the above-mentioned problem of fluctuations in off-axis aberrations, when focusing on an object at a short distance compared to focusing on an object at infinity, the principal ray that enters the lens system tends to be located farther from the optical axis. The diameter of the front lens increases. This results in an increase in the lens diameter and thickness of the first lens group G1, resulting in an increase in the size of the entire lens system. As a result, if an attempt is made to keep the lens system to a practical size, the amount of peripheral light will be insufficient, which is undesirable. For the above reasons, it is difficult to realize the focusing method of the ultra-wide-angle zoom lens according to the present invention by extending the first lens group G1, both from the viewpoint of the aberration structure and the lens configuration. , it is desirable to use a lens group closer to the image side than the positive second lens group G2 as a focusing group. However, in the case of an ultra-wide-angle zoom lens like the present invention, since the first lens group G1 has a strong negative refractive power, the first lens group G1
The emitted light beam diverges greatly. For this reason, the second
When the lens group G2 is used as a focusing group and is moved along the optical axis during focusing, the field curvature worsens, and accordingly, only comatic aberration, spherical aberration, and axial chromatic aberration worsen. Therefore, in the internal focusing method of the present invention, when focusing, the third lens group G3 or the third lens group G
3. By moving the lens group closer to the image side in the optical axis direction, even when creating an ultra-wide-angle zoom lens, the lens system can be made compact and aberration fluctuations during focusing can be kept to a minimum. It became possible. In particular, if an aperture stop is placed inside or near the third lens group G3, and this third lens group G3 is used as a focusing group,
The degree of convergence of the axial light beam (light beam from an axial object point at infinity) entering the third lens group G3 is smaller than that of the other lens groups, and becomes close to afocal (parallel). Therefore, during focusing, it has become possible to significantly suppress fluctuations in axial aberrations, especially spherical aberrations. At the same time, since the third lens group G3, which is located near the aperture stop or includes the aperture stop, is moved during focusing, off-axis aberrations, especially field curvature, are reduced. It has also become possible to minimize fluctuations in focus time. However, when the amount of movement of the third lens group G3 during focusing is large due to the imaging magnification of the third lens group G3, or when the degree of freedom in correcting aberrations of the entire system during focusing is increased. In this case, it is desirable to use another lens group closer to the image side than the third lens group G3 for focusing together with the third lens group, and to move these independently during focusing. By utilizing effects such as floating, which are obtained by the movement of each lens group during focusing, to correct for fluctuations in field curvature due to focusing, it is possible to bring out even better close-range performance. Become. Based on the configuration employing the internal focusing method as described above, it is desirable that the following conditional expression be satisfied. (1) 0.12≦d23/fW≦2.0 (2)
300 /fW ≦｜f1 | ≦680 /fW
(3) 0.01≦|AS-S|/fW≦0.
5 However, fW: Focal length of the entire system at the wide-angle end (mm), f1:
Focal length (mm) of the first lens group G1, d23: On-axis air distance between the most image side surface of the negative second lens component G12 and the most object side surface of the positive third lens component G13 in the first lens group G1 ( mm), AS-S: Difference in the optical axis direction between the aspheric surface at the outermost periphery of the effective diameter and a reference spherical surface having a predetermined radius of apex curvature (mm)
), is. Conditional expression (1) expresses the axial air distance d23 between the most image side surface of the negative second lens component G12 and the most object side surface of the positive third lens component G13 in the first lens group G1. It specifies appropriate values for . This air distance d23 is extremely effective for correcting lower coma aberration and for correcting fluctuations in lower coma aberration due to zooming in a well-balanced manner.
It functions effectively to reduce the incident height of the chief ray at the maximum angle of view that enters the lens. Therefore, by setting the air gap d23 to an appropriate value, the diameter of the lens components constituting the first lens group G1 can be kept small, the amount of peripheral light can be increased, and the desired variable power ratio can be secured. under 10
Good aberration correction can be achieved in all magnification ranges, including the wide-angle end exceeding the 0° angle of view. When the lower limit of conditional expression (1) is exceeded, the air distance d23 between the second lens component G12 and the third lens component G13 becomes too small, resulting in lower coma aberration, especially due to fluctuations due to zooming and image height differences. Variability increases. Furthermore, the principal ray is significantly separated from the optical axis, which not only reduces the amount of light at the periphery, but also increases the diameter of the front lens, making the first lens group G1 thicker as a whole. On the other hand, if the upper limit of conditional expression (1) is exceeded, the second lens component G12 and the third lens component G13
This increases the air distance d23 between the first lens group G1 and the second lens group G2, which is advantageous for correcting coma aberration, but when the air distance between the first lens group G1 and the second lens group G2 decreases significantly and the zoom is changed to the telephoto end, physical This is not desirable as it interferes with the target. In addition, in order to more fully correct aberrations and make the first lens group G1 more compact, the lower limit of conditional expression (1) is set to 0.25, and the conditional value is set to 1.4, and this range must be satisfied. More preferred. Conditional expression (2) defines an appropriate focal length of the first lens group G1. When the lower limit of conditional expression (2) is exceeded, the negative refractive power of the first lens group G1 becomes significantly strong, and therefore negative distortion increases. Furthermore, since the value of the Petzval sum moves significantly in the negative direction, astigmatism and field curvature also worsen. Further, fluctuations in chromatic aberration of magnification due to the angle of view and fluctuations in lower coma aberration due to zooming increase, which is undesirable. On the other hand, when the upper limit of conditional expression (2) is exceeded, the negative refractive power of the first lens group G1 becomes significantly weaker, and the oblique rays enter the first lens group G1 at a position further away from the optical axis. Therefore, the first lens group G1 becomes larger and thicker. As a result, the amount of peripheral light decreases, which is not preferable. In addition, in terms of aberrations, if the refractive power of the first lens group becomes significantly smaller, the balance of refractive power distribution in each group will be greatly disrupted, and even if aberration fluctuations due to zooming are reduced, the result will be , which worsens off-axis aberrations, especially downward coma aberration and field curvature. Therefore, this range is practically desirable. Now, the first lens group G1 of the present invention is provided with an aspherical surface mainly for correcting distortion in a well-balanced manner. It also functions effectively to correct aberrations such as lower coma, astigmatism, and field curvature. Therefore, in order to maximize the effect of this aspherical surface, it is preferable to satisfy conditional expression (3). Conditional expression (3) is a condition regarding the effect of the aspheric surface provided in the first lens group G1, and at the position of the effective diameter determined by the ray passing farthest from the optical axis,
This is a condition in which the strength of the aspherical surface is appropriately set, that is, the difference in the optical axis direction between the reference spherical surface and the aspherical surface created by the apex radius of curvature of a predetermined standard. If the lower limit of conditional expression (3) is exceeded, the effect as an aspheric surface will be drastically reduced, making it difficult to correct distortion aberration, and if forced correction with other lenses will result in axial distortion such as field curvature and coma aberration. External aberrations are significantly worsened, which is undesirable. On the other hand, when the upper limit of conditional expression (3) is exceeded, there is a tendency for the lower coma aberration to have a rapid displacement from the middle part to the extreme periphery due to the influence of higher-order aberrations. Furthermore, it is difficult to manufacture an aspherical surface in this case, which is not preferable. Note that in order to more effectively obtain the effect of the aspheric surface provided in the first lens group, the lower limit of conditional expression (3) should be set to 0.
．． 095, and it is more desirable to satisfy this range. Furthermore, the effect of the aspherical surface as described above can basically be obtained no matter where the aspherical surface is provided in the first lens group G1.
If it is provided on a lens relatively close to the object side, the oblique rays will pass further away from the optical axis, so it can function more effectively in correcting off-axis aberrations. Therefore, in order to maximize the effect of the aspheric surface, it is more preferable to introduce it into the first lens component G12. Furthermore, in order to maximize the effects of the internal focusing method of the present invention, it is more desirable to satisfy the following conditional expression (4). (4) βW ≦−1.1, βW ≧−0.9, where βW is the composite imaging magnification of the lens group having a focusing function at the wide-angle end. As described above, in the present invention, during focusing, the third lens group G3, or this third lens group G3 and a lens group on the image side of this group, are moved in the optical axis direction as a focusing group. In this case, it is more desirable to perform focusing under the optimum imaging magnification in the focusing group, as defined in condition (4). Condition (4) defines the optimal composite imaging magnification at the wide-angle end of the lens groups that have a focusing function.In other words, the combination of all lens groups used for focusing at the wide-angle end The imaging magnification of -1.
A value range of more than 1 and less than -0.9 means that it is not desirable. This is because, under the imaging magnification of the focusing group in this range, the amount of movement of the focusing group during focusing increases significantly, and aberration fluctuations become large, especially fluctuations in field curvature. That's because there isn't. Further, as the amount of movement of the focusing group increases, it is necessary to secure a large air gap for focusing, which is not preferable because the entire lens system becomes larger and furthermore, it becomes impossible to secure a sufficient back focus. Note that in the present invention, the third lens group G3
Alternatively, although the third lens group G3 and the lens group on the image side thereof are used as focusing groups, the third lens group G3 may be divided at the time of focusing, and these divided groups may be moved independently. Now, in order to achieve more sufficient aberration correction in all zoom ranges in the ultra-wide-angle zoom lens of the present invention, it is preferable that the following conditions be satisfied. (5) 1≦f2 /fW≦5 (6) 1.1≦|f3 |/fW ≦3.5,
f3 <0 (7) 1.4 ≦f4 /fW ≦
4(8) 0.16≦d23/L≦0.6 However, f2: Focal length of the second lens group G2, f3: Focal length of the third lens group G3, f4: Focal length of the fourth lens group G4, d23: The third lens component G that is closest to the image side of the negative second lens component G12 in the first lens group G1
13, L: From the lens vertex of the object side of the lens closest to the object in the first lens group G1 to the lens vertex of the image side of the most image side lens of the first lens group G1 distance (first lens group G
axial thickness of 1). Conditional expression (5) defines the optimum ratio between the focal length of the second lens group G2 and the focal length of the entire system at the wide-angle end. When the lower limit of conditional expression (5) is exceeded, the positive refractive power of the second lens group G2 becomes extremely strong, the fluctuations in field curvature and astigmatism due to zooming increase, and spherical aberration at the telephoto side worsens. I don't like it. On the other hand, when the upper limit of conditional expression (5) is exceeded, the positive refractive power becomes significantly weaker, and the value of the Petzval sum changes in the negative direction. Therefore, the curvature of field worsens, especially on the wide-angle side, and the astigmatism becomes significant, which is not preferable. Note that, in order to achieve more sufficient aberration correction, it is more preferable to set the lower limit of conditional expression (5) to 1.45 and the upper limit to 3, and to configure the system so that these ranges are satisfied. Conditional expression (6) defines the optimum ratio between the focal length of the third lens group G3 and the focal length of the entire system at the wide-angle end. If the lower limit of conditional expression (6) is exceeded, the third
The negative refractive power of the lens group G3 becomes extremely strong, which worsens the spherical aberration, especially on the telephoto side, which not only becomes difficult to correct, but also increases fluctuations in the spherical aberration due to zooming. Furthermore, it becomes difficult to correct upper coma aberration, and fluctuations in upper coma aberration due to zooming also increase, which is undesirable. Conversely, conditional expression (6)
If the upper limit of
The balance of aberrations in the lens group is greatly disrupted, and as a result,
Not only does the upper coma aberration worsen, but also the longitudinal chromatic aberration worsens, and the variation of the longitudinal chromatic aberration due to zooming becomes enormous. In addition,
In order to sufficiently suppress aberration fluctuations due to zooming while achieving more sufficient aberration correction, the lower limit of conditional expression (6) should be set to 1.
5, it is more preferable to set the upper limit to 3.2 and configure the structure to satisfy this range. Conditional expression (7) defines the optimum ratio between the focal length of the fourth lens group G4 and the focal length of the entire system at the wide-angle end. If the lower limit of conditional expression (7) is exceeded, the fourth
The positive refractive power of the lens group G4 becomes extremely strong, the upper coma aberration worsens, and the fluctuation of the upper coma aberration due to zooming becomes significant. Furthermore, fluctuations in chromatic aberration of magnification due to zooming also increase, which is not preferable. On the other hand, if the upper limit of conditional expression (7) is exceeded, the positive refractive power of the fourth lens group G4 becomes significantly weaker, and the aberrational balance with the third lens group G3 is greatly disrupted. As a result, upper coma aberration becomes extremely worse, and it becomes difficult to correct coma aberration, especially on the wide-angle side. In addition, in order to achieve better aberration balance, the lower limit of conditional expression (7) should be set to 1.7.
, it is more preferable to set the upper limit to 3.0 and configure the structure to satisfy this range. Conditional expression (8) is based on the air distance d between the negative second lens component G12 and the positive third lens component G13 with respect to the total thickness (axial thickness) of the first lens group G1.
It defines the appropriate ratio of 23. As stated in conditional expression (1), the air distance d23 between the negative second lens component G12 and the positive third lens component G13 is determined in order to properly correct lower coma, astigmatism, and field curvature. have an important role. Increasing this air gap d23 within an appropriate range is extremely important in ensuring the degree of freedom in correcting off-axis aberrations such as coma, astigmatism, and field curvature. In other words, by increasing the air gap d23, the oblique rays incident on the positive lens component G13 located closest to the image side in the first lens group G1 will be incident on a position further away from the optical axis. The off-axis rays and on-axis rays in the lens component G13 are well separated. As a result, off-axis aberrations can be corrected extremely well without significantly affecting the axial aberrations in the positive lens component G13. However, increasing the air gap d23 also leads to thickening of the entire first lens group G1, and unless a certain limit is defined for the value of the air gap d23, the entire system may become large. This results in disadvantages such as a decrease in the amount of peripheral light. Therefore, in conditional expression (8), the second lens component G is negative with respect to the total thickness (axial thickness) of the first lens group G1.
12 and the positive third lens component G13 d2
It stipulates the appropriate ratio range for 3. If the lower limit of conditional expression (8) is exceeded, not only will it be difficult to correct the lower coma aberration, but also the third lens component G1
This is not preferable because the principal ray passing through the lens 3 passes through a position further away from the optical axis, resulting in an insufficient amount of light at the periphery. On the other hand, if the upper limit of conditional expression (8) is exceeded, the first lens group G1 becomes thicker and larger, and the first lens group G1 becomes larger during zooming.
It is also not preferable when moving. In addition, in order to achieve more balanced and sufficient aberration correction in the ultra-wide-angle zoom lens of the present invention,
The third lens group G3 with negative refractive power has a cemented negative lens component made up of a positive lens and a negative lens, and the positive fourth lens group G4 has a cemented negative lens component made up of a positive lens and a negative lens closest to the image side. It is desirable to have a configuration including a cemented positive lens component. At this time, it is more desirable to satisfy the following conditions. (9) 60/fW≦d4p≦185
/fW (10) |n3n-n3p|≦0.13
(11) −50≦ν3p−ν3n≦−20 (1
2) 0.1 ≦n4n-n4p≦0.4 (13)
25≦ν4p−ν4n However, d4p: Center thickness of the positive lens in the cemented positive lens component located closest to the image side in the fourth lens group G4, n3n: Center thickness of the negative lens in the cemented negative lens component in the third lens group G3. refractive index for the d-line (587.6 nm), n3p: refractive index for the d-line (587.6 nm) of the positive lens in the cemented negative lens component in the third lens group G3, ν3n: cemented negative lens in the third lens group G3 Abbe number of the negative lens in the component, ν3p: Abbe number of the positive lens in the cemented negative lens component in the third lens group G3, n4n: Negative in the cemented positive lens component located closest to the image side in the fourth lens group G4 Lens d-line (587.6nm
), n4p: d-line (587.6 nm) of the positive lens in the cemented positive lens component located closest to the image side in the fourth lens group G4
), ν4n: Abbe number of the negative lens in the cemented positive lens component located closest to the image side in the fourth lens group G4, ν4p: refractive index in the cemented positive lens component located closest to the image side in the fourth lens group G4 is the Abbe number of the positive lens. Conditional expression (9) is a condition regarding the cemented positive lens component located closest to the image side in the positive fourth lens group G4. If the lower limit of conditional expression (9) is exceeded, the positive lens in the cemented positive lens component becomes thin and has no edge thickness, which not only makes manufacturing difficult, but also reduces the effect of correcting aberrations for oblique rays and chromatic aberration of magnification. So I don't like it. On the other hand, if the upper limit of conditional expression (9) is exceeded, the radius of curvature of the cemented surface becomes small, and the edge thickness of the positive lens in the cemented positive lens component also disappears, making it difficult to manufacture. In addition, this is not preferable because it generates extremely large high-order aberrations and worsens aberrations for oblique rays, especially upper coma, astigmatism, and field curvature. Note that this cemented positive lens component is preferably a positive and negative cemented lens in order from the object side. In other words, this configuration prevents the cemented surface from having an extremely large refractive power with respect to the incidence of oblique light rays. Conditional expression (10) defines the optimum refractive index difference between the positive lens and the negative lens constituting the cemented negative lens component in the third lens group G3, and conditional expression (11) This defines the optimum Abbe number difference between the positive lens and the negative lens constituting the cemented negative lens component in the three lens group G3. In the present invention, it is necessary to arrange the aperture stop in the second lens group G2, between the second lens group G2 and the third lens group G3, in the third lens group G3, or immediately after the third lens group G3. In particular, it is desirable for this aperture stop to be placed in front of or in the third lens group G3 in terms of aberration correction. Therefore, when the aperture stop is placed in or near the third lens group G3, the function of aberration correction in the third lens group G3 is to correct on-axis aberrations rather than to correct off-axis aberrations caused by oblique rays. The main focus is on correction. The cemented negative lens disposed in the third lens group G3 in this case has a function of mainly correcting axial chromatic aberration, color-based aberration such as spherical aberration, and the like. Therefore, in order to effectively correct these aberrations, it is necessary to set a large difference in Abbe number without making much of a difference in refractive index between the positive lens and the negative lens that constitute the cemented negative lens in the third lens group G3. It is desirable to do so. Therefore, conditional expressions (10) and (11) are intended to satisfactorily correct chromatic aberrations such as axial chromatic aberration and spherical aberration. If the upper limit of conditional expression (10) is exceeded, not only will the spherical aberration be adversely affected, but the value of the Petzval sum will also change significantly. In addition, due to the limitations of existing glass materials, it is difficult to obtain a sufficient difference in Abbe number, resulting in axial chromatic aberration,
It is not possible to satisfactorily correct aberrations due to color of spherical aberration, etc. Note that in order to correct axial aberrations in a more balanced manner, it is desirable to set the upper limit of conditional expression (10) to 0.07 and to satisfy this range. When the upper limit of conditional expression (11) is exceeded, the effect on chromatic aberration correction decreases, and fluctuations in axial chromatic aberration due to zooming increase. On the other hand, if the lower limit of conditional expression (11) is exceeded, an expensive and special glass material must be used, which is undesirable as it causes manufacturing problems and increases costs. Conditional expression (12) defines the difference in refractive index between the positive lens and negative lens that constitute the cemented positive lens component disposed closest to the image side of the fourth lens group G4, and conditional expression (13) This defines the difference in Abbe numbers between the positive lens and the negative lens that constitute the cemented positive lens component disposed closest to the image side of the four lens group G4. If the lower limit of conditional expression (12) is exceeded, the value of the Petzval sum changes in the negative direction, resulting in worsening of field curvature and astigmatism, which is not preferable. On the other hand, if the upper limit of conditional expression (12) is exceeded, the value of the Petzval sum can be maintained appropriately, but the refractive index of the positive lens in the cemented positive lens component becomes significantly small. As a result, the radius of curvature of the cemented surface becomes small and the edge thickness of the positive lens in the cemented positive lens component disappears, making it difficult to manufacture. Moreover,
High-order aberrations occur significantly, leading to aggravation of aberrations for oblique rays, especially upper coma, astigmatism, and field curvature. When the lower limit of conditional expression (13) is exceeded, it becomes difficult to correct chromatic aberration of magnification. Note that, as shown in each embodiment of the present invention to be described later, the first lens group G1 having a negative refractive power is
A negative first lens component G11 consisting of a negative single lens including an aspherical surface, a negative second lens component G12 consisting of a negative single lens or a cementation of a negative lens and a positive lens, and a positive single lens or a positive lens. If the configuration has a positive third lens component G13 made of a cemented lens and a negative lens,
This is advantageous for reducing the thickness and cost of the first lens group G1. [Embodiments] Next, embodiments according to the present invention will be described. In each embodiment according to the present invention, the angle of view at the wide-angle end is 10
This is an ultra-wide-angle zoom lens that has an angle of more than 0°. In each embodiment, basically, as shown in FIG. 1, in order from the object side, a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, and a second lens group G2 having a negative refractive power. The third lens group G3 has a positive refractive power, and the fourth lens group G4 has a positive refractive power. When zooming from the wide-angle end to the telephoto end, the first lens group G1 moves toward the image side in a curved (nonlinear) manner, and the second lens group G2, third lens group G3, and fourth lens group G4 move toward the object in a nearly straight line (linear shape) with different amounts of movement. Due to the movement of each lens group due to zooming from the wide-angle end to the telephoto end, the first lens group G
1 and the second lens group G2 decreases, the air distance between the second lens group G2 and the third lens group G3 increases, and the air distance between the third lens group G3 and the fourth lens group G4 increases. Decrease. Furthermore, when focusing from an object point at infinity to an object point at a short distance, in Examples 1, 2, 3, 4, 5, and 7, the third lens group G3 and the fourth lens group G4 are independently operated. In the sixth embodiment, only the third lens group G3 moves toward the image side. In addition, in each example, the aspherical surface is formed at the closest object side of the negative meniscus lens (first lens component) G11, which is provided closest to the object side of the first lens group G1 and has a convex surface facing the object side. The aperture stop S is arranged on the object side of the third lens group G3. Next, each embodiment will be explained. The ultra-wide-angle zoom lens of Example 1 according to the present invention has a focal length f=15
．． 5 ~ 27.3, angle of view 2ω = 111.2 ° ~ 76.4
°, with an F number of 4.1. As can be seen from FIG. 1, the specific lens configuration of Example 1 is such that the negative first lens group G1 includes a negative meniscus lens (first lens component) G11 with a convex surface facing the object side, and a biconcave negative lens group G11. Lens (2nd
The positive second lens group G2 is composed of a negative meniscus lens with a convex surface facing the object side, and a positive lens (third lens component) G13 with a surface with a stronger curvature facing the object side. , a cemented positive lens (component of cemented positive lens), which is cemented to a positive lens with a surface of stronger curvature facing the object side, and a biconvex positive lens. The negative third lens group G3 consists of a positive meniscus lens with a convex surface facing the image side, and a negative lens cemented to this with a surface with a stronger curvature facing the object side. The positive fourth lens group G4 consists of a positive meniscus lens with a convex surface facing the object side, a negative meniscus lens with a convex surface facing the object side, and a positive meniscus lens with a convex surface facing the image side. , a cemented positive lens (a cemented positive lens component) consisting of a positive lens with a surface of stronger curvature facing the image side, and a negative meniscus lens cemented to the positive lens with a convex surface facing the image side. Next, the ultra-wide-angle zoom lens of Example 2 according to the present invention has a focal length f=16.4 to 27.3 and an angle of view of 2.
ω=108.2°~76.4°, F number 4.1
has. As shown in FIG. 8, the specific lens configuration of Example 2 is basically the same as that of the zoom lens of Example 1, except that in the first lens group G1, a negative second lens The component G12 is composed of a negative meniscus lens with a convex surface facing the object side, and the positive third lens component G13 is composed of a positive meniscus lens with a convex surface facing the object side. Further, the positive lens closest to the object side of the fourth positive lens group G4 is a biconvex positive lens. The ultra-wide-angle zoom lens according to the third embodiment of the present invention has a focal length f=18.4 to 27.3 and an angle of view 2ω=1.
01.2° to 76.4°, and has an F number of 4.1. As shown in FIG. 15, the specific lens configuration of Example 3 is basically the same as the zoom lens of Example 1, except that the positive third lens in the first lens group G1 The component G13 is composed of a positive meniscus lens with a convex surface facing the object side. Moreover, in the second lens group G2,
The positive lens in the cemented positive lens has a biconvex shape, and the positive lens on the image side of the cemented positive lens has a meniscus lens shape. Next, the ultra-wide-angle zoom lens of Example 4 according to the present invention has a focal length of f=18.4 to 27.3 and an angle of view of 2.
ω=101.5°~76.4°, F number 4.1
~4.6. As shown in FIG. 22, the specific lens configuration of Example 4 has basically the same configuration as the zoom lens of Example 3 regarding the second lens group.
The configurations of the first, third, and fourth lens groups are different. In other words,
The negative second lens component G12 in the first lens group G1 is
The third lens group G consists of a biconcave negative lens and a positive meniscus lens cemented to this with a convex surface facing the object side.
3 is composed of a negative cemented lens in which a negative lens and a positive lens are cemented in this order. The fourth lens group G4 includes a meniscus lens with a convex surface facing the object side and an extremely weak negative refractive power, and a positive meniscus lens with a convex surface facing the image side.
It consists of four lenses: a positive lens with a surface of stronger curvature facing the image side, and a cemented positive lens consisting of a negative meniscus lens with a convex surface facing the image side. The ultra-wide-angle zoom lens of Example 5 according to the present invention has a focal length f=18.4 to 27.3 and an angle of view 2ω=1.
01.3° to 76.4°, and has an F number of 4.6. The specific lens configuration of Example 5 is basically the same as Example 1 regarding the third and fourth lens groups, as shown in FIG.
This zoom lens has a similar configuration to that of the above zoom lens, but the configurations of the first and second lens groups are different. In other words, the first lens group G
1, the negative second lens component G12 is composed of a negative lens with a surface of stronger curvature facing the object side, and the third lens component G13 is composed of a biconvex positive lens and a positive lens cemented to this to face the object side. It is composed of a cemented lens with a negative lens facing the surface of stronger curvature. The positive lens in the cemented positive lens component in the second lens group G2 has a biconvex shape. The ultra-wide-angle zoom lens of Example 6 according to the present invention has a focal length f=18.4 to 27.3 and an angle of view 2ω=1.
01.4° to 76.4°, with an F number of 4.1. As shown in FIG. 36, the specific lens configuration of Example 6 is basically the same as the zoom lens of Example 1, except that in the second lens group G2, The positive lens in the cemented positive lens component inside has a biconvex shape. The ultra-wide-angle zoom lens of Example 7 according to the present invention has a focal length f=18.4 to 27.3 and an angle of view 2ω=1.
01.4° to 76.4°, with an F number of 4.1. The specific lens configuration of Example 7, as shown in FIG. 43, is basically the same as the zoom lens of Example 1, but in the second lens group G2, the cemented positive lens The positive lens has a biconvex shape, and the positive lens on the image side of the cemented positive lens has a meniscus lens shape. Now, below, the values of specifications and numerical values corresponding to conditions of each embodiment of the present invention are listed in order. However, the number on the left side represents the order from the object side, r is the radius of curvature of the lens surface, d is the distance between lens surfaces, ν is Abbe's number, n
is the refractive index at the d-line (λ = 587.6 nm), f is the focal length of the entire system, FNO is the F number, φ is the effective diameter of the aspherical lens, and D0 is the distance from the object to be photographed to the first surface of the lens. , β represents the close-range photographing magnification. In addition, for the aspheric surfaces shown in the specification values, the distance along the optical axis direction from the tangential plane of the apex of each aspheric surface at the height y in the vertical direction from the optical axis is defined as X (h), and the reference paraxial When the radius of curvature is r, the conic coefficient is k, and the nth-order aspherical coefficient is Cn, then
/r2 )1/2 ]+C2 h2
+
C4 h4 +C6 h6 +C8 h8 +C10h
It is expressed in 10. Further, E-n at the left end of the conic coefficient k and the n-th-order aspherical coefficient Cn indicates 10-n. [Example 1] Aspherical surface (first surface) Standard paraxial radius of curvature: r = 69.600 Conic coefficient:
k = 1 aspheric coefficient c2 = 0.0, c4 = 0.79789E-
05,c6=-0.39445E-08,c8=0
．． 24046E-11 c10=0.315
60E-14 [Example 2] Aspherical surface (first surface) Standard paraxial radius of curvature: r = 56.830 Conic coefficient:
k= 1 Aspheric coefficient c2=0.0, c4=0.41777E-
05, c6=0.36563E-09, c8=-0.
98160E-12 c10=0.21972
E-14 [Example 3] Aspherical surface (first surface) Standard paraxial radius of curvature: r = 49.794 Conic coefficient:
k = 1 aspheric coefficient c2 = 0.0, c4 = 0.89224E-
05, c6=-0.47558E-08, c8=0.
82136E-11 c10=0.33662
E-14 [Example 4] Aspherical surface (first surface) Standard paraxial radius of curvature: r = 90.937 Conic coefficient:
k = 1 aspheric coefficient c2 = 0.0, c4 = 0.41120E-
05,c6=-0.10463E-08,c8=
0.26766E-12 c10=0.948
21E-15 [Example 5] Aspheric surface (first surface) Standard paraxial radius of curvature: r = 48.498 Conic coefficient:
k = 1 aspheric coefficient c2 = 0.0, c4 = 0.15694E-
04, c6 = -0.11607E-07, c8
= 0.18735E-10 c10=
0.28146E-13 [Example 6] Aspheric surface (first surface) Standard paraxial radius of curvature: r = 43.716 Conic coefficient:
k = 1 aspheric coefficient c2 = 0.0, c4 = 0.56396E-
05, c6=0.31551E-08, c8=-0.6
9514E-11 c10=0.1470
9E-13 [Example 7] Aspheric surface (first surface) Standard paraxial radius of curvature: r = 66.171 Conic coefficient:
k= 1 Aspheric coefficient c2=0.0, c4=0.98928E-
05, c6=-0.63815E-08, c8=0.
86133E-11 c10=0.98912
E-16 As can be seen from the values of the specifications of each example, the zoom lens of each example has a compact structure with as few lens elements as possible in each lens group, yet it can achieve a maximum angle of 100 degrees at the wide-angle end. An internal focusing ultra-wide-angle zoom lens that achieves a wide angle exceeding 110 degrees has been realized, and in particular, in Example 1, an internal focusing ultra wide-angle zoom lens with a wide angle exceeding 110 degrees has been realized. FIGS. 2, 9, 16, 23, 30, 37, and 44 show the zoom lenses of Examples 1 to 7 of the present invention at the wide-angle end (shortest focal length state), respectively. It shows various aberration diagrams in a focused state at infinity. 3, FIG. 10, FIG. 17, FIG. 24, FIG. 31, FIG. 38, and FIG. It shows an aberration diagram. FIG. 4, FIG. 11, FIG. 18, FIG. 25, FIG. 32,
39 and 46 respectively show various aberration diagrams of the zoom lenses of Examples 1 to 7 of the present invention in the infinity focus state at the telephoto end (longest focal length state). Figure 5,
12, FIG. 19, FIG. 26, FIG. 33, FIG. 40, and FIG. 47 respectively show close-range focusing states ( β
=-1/30). FIG. 6, FIG. 13, FIG. 20, FIG. 27, FIG. 34,
FIGS. 41 and 48 respectively show various aberration diagrams of the zoom lenses of Examples 1 to 7 of the present invention in a close focus state (β=-1/30) at an intermediate focal length state. Figure 7, Figure 14, Figure 21, Figure 28, Figure 35, Figure 42,
FIG. 49 shows various aberration diagrams of the zoom lenses of Examples 1 to 7 of the present invention in a close focus state (β=-1/30) at the telephoto end (longest focal length state). . Here, in each aberration diagram, d is the d-line (λ
= 587.6 nm), g indicates the aberration curve due to g (435.8 nm), and for astigmatism in each aberration diagram, the dotted line is the meridional image plane, and the solid line is the spherical It shows the image plane (sagittal image plane). In addition,
In the various aberration diagrams, H indicates the incident height of the axial ray, and Y indicates the image height. Comparison of the aberration diagrams shows that in each example, despite achieving a wide angle of over 100 degrees at the wide-angle end, It can be seen that various aberrations are very well corrected over the distance object point, and that the lens has excellent imaging performance. In each of the embodiments according to the present invention, the third lens group G3 is moved as a movable group to contribute to the power change. It may be fixed to In addition, the second lens group G2
, the third lens group G3, and the fourth lens group G4, or by introducing an aspheric surface into a plurality of lens groups, a larger aperture ratio and higher performance can be achieved. Furthermore, the negative first lens component G11, the negative second lens component G12, and the positive third lens component G13 in the first lens group G1 can all be composed of a single lens or a cemented lens. However, it goes without saying that in this case, the cemented lens may be composed of separate lens components, each consisting of a positive lens and a negative lens. Furthermore, in the present invention, it is theoretically possible to configure the first lens group G1 with three lens components, negative, negative, and positive, but even if lens components are added based on this configuration, the essence of the present invention is It's not something to deviate from. Furthermore, although the ultra-wide-angle zoom lens of the present invention basically has a four-group configuration, the present invention can be applied even if each lens group is divided or additional lens groups are added based on the configuration of the present invention. It does not deviate from its essence. As described above, according to the present invention, each lens group is compactly constructed with as few lenses as possible, yet a wide-angle of more than 100 degrees at the wide-angle end is achieved. Despite this, various aberrations are corrected in an extremely well-balanced manner, and it has excellent imaging performance, even when focusing from an object point at infinity to a close object point in the entire magnification range from the wide-angle end to the telephoto end. I know what you're doing.

[Brief explanation of the drawing]

FIG. 1 is a lens configuration diagram at a wide-angle end (minimum focal length state), an intermediate focal length state, and a telephoto end (minimum focal length state) in Example 1 of the present invention.

FIG. 2 is a diagram of various aberrations in the infinity focus state at the wide-angle end (minimum focal length state) of Example 1 of the present invention.

FIG. 3 is a diagram of various aberrations in the infinity focus state in the intermediate focal length state of Example 1 of the present invention.

FIG. 4 is a diagram of various aberrations in the infinity focused state at the telephoto end (longest focal length state) of Example 1 of the present invention.

FIG. 5 is a diagram of various aberrations in a short-distance focused state at the wide-angle end (shortest focal length state) of Example 1 of the present invention.

FIG. 6 is a diagram of various aberrations in a short-distance focusing state in an intermediate focal length state in Example 1 of the present invention.

FIG. 7 is a diagram of various aberrations in a close focus state at the telephoto end (longest focal length state) of Example 1 of the present invention.

FIG. 8 is a lens configuration diagram at a wide-angle end (minimum focal length state), an intermediate focal length state, and a telephoto end (minimum focal length state) in Example 2 of the present invention.

FIG. 9 is a diagram of various aberrations in the infinity focus state at the wide-angle end (minimum focal length state) of Example 2 of the present invention.

FIG. 10 is a diagram of various aberrations in the infinity focus state in the intermediate focal length state of Example 2 of the present invention.

FIG. 11 is a diagram of various aberrations in the infinity focused state at the telephoto end (longest focal length state) of Example 2 of the present invention.

FIG. 12 is a diagram of various aberrations in a short-distance focusing state at the wide-angle end (minimum focal length state) of Example 2 of the present invention.

FIG. 13 is a diagram of various aberrations in a short-distance focused state in an intermediate focal length state in Example 2 of the present invention.

FIG. 14 is a diagram of various aberrations in a close focus state at the telephoto end (longest focal length state) of Example 2 of the present invention.

FIG. 15 is a lens configuration diagram at a wide-angle end (minimum focal length state), an intermediate focal length state, and a telephoto end (minimum focal length state) in Example 3 of the present invention.

FIG. 16 is a diagram of various aberrations in the infinity focus state at the wide-angle end (minimum focal length state) of Example 3 of the present invention.

FIG. 17 is a diagram of various aberrations in the infinity focused state in the intermediate focal length state of Example 3 of the present invention.

FIG. 18 is a diagram of various aberrations in the infinity focused state at the telephoto end (longest focal length state) of Example 3 of the present invention.

FIG. 19 is a diagram of various aberrations in a close focus state at the wide-angle end (shortest focal length state) of Example 3 of the present invention.

FIG. 20 is a diagram of various aberrations in a short-distance focused state in an intermediate focal length state in Example 3 of the present invention.

FIG. 21 is a diagram of various aberrations in a close focus state at the telephoto end (longest focal length state) of Example 3 of the present invention.

FIG. 22 is a lens configuration diagram at a wide-angle end (minimum focal length state), an intermediate focal length state, and a telephoto end (minimum focal length state) in Example 4 of the present invention.

FIG. 23 is a diagram of various aberrations in the infinity focus state at the wide-angle end (minimum focal length state) of Example 4 of the present invention.

FIG. 24 is a diagram of various aberrations in the infinity focused state in the intermediate focal length state of Example 4 of the present invention.

FIG. 25 is a diagram of various aberrations in the infinity focus state at the telephoto end (longest focal length state) of Example 4 of the present invention.

FIG. 26 is a diagram of various aberrations in a close focus state at the wide-angle end (minimum focal length state) of Example 4 of the present invention.

FIG. 27 is a diagram of various aberrations in a short-distance focusing state in an intermediate focal length state in Example 4 of the present invention.

FIG. 28 is a diagram of various aberrations in a close focus state at the telephoto end (longest focal length state) of Example 4 of the present invention.

FIG. 29 is a lens configuration diagram at a wide-angle end (minimum focal length state), an intermediate focal length state, and a telephoto end (minimum focal length state) in Example 5 of the present invention.

FIG. 30 is a diagram of various aberrations in the infinity focus state at the wide-angle end (minimum focal length state) of Example 5 of the present invention.

FIG. 31 is a diagram of various aberrations in the infinity focused state in the intermediate focal length state of Example 5 of the present invention.

FIG. 32 is a diagram of various aberrations in the infinity focused state at the telephoto end (longest focal length state) of Example 5 of the present invention.

FIG. 33 is a diagram of various aberrations in a short-distance focusing state at the wide-angle end (minimum focal length state) of Example 5 of the present invention.

FIG. 34 is a diagram of various aberrations in a short-distance focusing state in an intermediate focal length state of Example 5 of the present invention.

FIG. 35 is a diagram of various aberrations in a close focus state at the telephoto end (longest focal length state) of Example 5 of the present invention.

FIG. 36 is a lens configuration diagram at a wide-angle end (minimum focal length state), an intermediate focal length state, and a telephoto end (minimum focal length state) in Example 6 of the present invention.

FIG. 37 is a diagram of various aberrations in the infinity focus state at the wide-angle end (minimum focal length state) of Example 6 of the present invention.

FIG. 38 is a diagram of various aberrations in an infinity focus state in an intermediate focal length state of Example 6 of the present invention.

FIG. 39 is a diagram of various aberrations in the infinity focused state at the telephoto end (longest focal length state) of Example 6 of the present invention.

FIG. 40 is a diagram of various aberrations in a close focus state at the wide-angle end (shortest focal length state) of Example 6 of the present invention.

FIG. 41 is a diagram of various aberrations in a close focus state in an intermediate focal length state in Example 6 of the present invention.

FIG. 42 is a diagram of various aberrations in a close focus state at the telephoto end (longest focal length state) of Example 6 of the present invention.

FIG. 43 is a lens configuration diagram at a wide-angle end (minimum focal length state), an intermediate focal length state, and a telephoto end (minimum focal length state) in Example 7 of the present invention.

FIG. 44 is a diagram of various aberrations in the infinity focus state at the wide-angle end (minimum focal length state) of Example 7 of the present invention.

FIG. 45 is a diagram of various aberrations in an infinity focused state in an intermediate focal length state according to Example 7 of the present invention.

FIG. 46 is a diagram of various aberrations in the infinity focused state at the telephoto end (longest focal length state) of Example 7 of the present invention.

FIG. 47 is a diagram of various aberrations in a short-distance focused state at the wide-angle end (shortest focal length state) of Example 7 of the present invention.

FIG. 48 is a diagram of various aberrations in a short-distance focusing state in an intermediate focal length state in Example 7 of the present invention.

FIG. 49 is a diagram of various aberrations in a close focus state at the telephoto end (longest focal length state) of Example 7 of the present invention.

FIG. 50 is a diagram showing lens types of a divergent group closest to the object side of an ultra-wide-angle lens or an ultra-wide-angle zoom lens.

FIG. 51 is a diagram showing the lens type of the divergent group closest to the object side of the ultra-wide-angle zoom lens.

[Explanation of symbols of main parts]

G1...First lens group G2...Second lens group G3...Third lens group G4...4th lens group G11... Negative first lens component G12... Negative second lens component G13...Positive third lens component

Claims (7)

[Claims] Claim 1: In order from the object side, the first lens has a negative refractive power.
a lens group G1, a second lens group G2 having positive refractive power;
The first lens group G1 includes a third lens group G3 having a negative refractive power and a fourth lens group G4 having a positive refractive power.
are, in order from the object side, the first lens component G1 with negative refractive power;
1. It has a second lens component G12 with negative refractive power and a third lens component G13 with positive refractive power, and has an aspherical surface on at least one lens surface, and when changing the magnification from the wide-angle end to the telephoto end. , reducing the air gap between the first lens group G1 and the second lens group G2, and increasing the air gap between the second lens group G2 and the third lens group G3;
reducing the air gap between the third lens group G3 and the fourth lens group G4, and moving at least the third lens group G3 in the optical axis direction when focusing from an object point at infinity to a close object point; An ultra-wide-angle zoom lens that is characterized by the ability to 2. The super wide-angle zoom lens according to claim 1, wherein the super wide-angle zoom lens satisfies the following conditional expression. (1) 0.12≦d23/fW≦2.0 (2)
300 /fW ≦｜f1 | ≦680 /fW
(3) 0.01≦|AS-S|/fW≦0.
5 However, fW: focal length of the entire system at the wide-angle end, f1: focal length of the first lens group G1, d23: the closest image side of the negative second lens component G12 and the positive third lens component in the first lens group G1 The axial air distance between the lens component G13 and the closest object side surface, AS-S: the difference in the optical axis direction between the aspheric surface at the outermost periphery of the effective diameter and a reference spherical surface having a predetermined apex radius of curvature. 3. The ultra-wide-angle zoom lens according to claim 1 or 2, wherein the ultra-wide-angle zoom lens satisfies the following conditional expression. (4) βW ≦−1.1, βW ≧−0.9, where βW is the combined imaging magnification of the lens group having a focusing function at the wide-angle end. 4. The ultra-wide-angle zoom lens according to claim 1, wherein only the third lens group G3 is moved in the optical axis direction when focusing from an object point at infinity to an object point at a close distance. An ultra-wide-angle zoom lens featuring 5. The super wide-angle zoom lens according to claim 1, wherein the third lens group G3 and the fourth lens group are independently operated when focusing from an object point at infinity to an object point at a close distance. An ultra-wide-angle zoom lens that moves in the optical axis direction. 6. The super wide-angle zoom lens according to claim 1, wherein the super wide-angle zoom lens satisfies the following conditional expression. (5) 1≦f2 /fW≦5 (6) 1.1≦|f3 |/fW ≦3.5,
f3 <0 (7) 1.4 ≦f4 /fW ≦
4(8) 0.16≦d23/L≦0.6 However, fW: Focal length of the entire system at the wide-angle end, f2: Focal length of the second lens group G2, f3: Focal length of the third lens group G3 , f4: focal length of the fourth lens group G4, d23: third lens component G that is closest to the image side of the negative second lens component G12 in the first lens group G1
13, L: From the lens vertex of the object side of the lens closest to the object in the first lens group G1 to the lens vertex of the image side of the most image side lens of the first lens group G1 distance (first lens group G
axial thickness of 1). 7. In the super wide-angle zoom lens according to any one of claims 1 to 6, when changing the magnification from the wide-angle end to the telephoto end,
An ultra-wide-angle zoom lens characterized in that the first lens group G1, the second lens group G2, and the fourth lens group G4 are moved at least in the optical axis direction.