JP2018205527A - Large diameter wide-angle lens - Google Patents

Abstract

To provide a large diameter wide-angle lens that makes a F-number smaller to about 1.4 with the lens miniaturized, and can achieve a smooth contrast AF by causing the lens to deal with a large-sized image pick-up element, and further lightening a focus group.SOLUTION: A large diameter wide-angle lens comprises, in order from an object side,: a first lens group G1 of negative refractive power; an aperture stop S; a second lens group G2 of positive refractive power; a third lens group G3 of the positive refractive power; and a fourth lens group G4 of the negative refractive power. The first lens group G1 comprises, in order from the object side,: a 1A lens group G1A of the negative refractive power; and a 1B lens group G1B of the positive refractive power, in which a lens on a most object side of the 1B lens group G1B is a single lens or bonded lens of the positive refractive power largest in an absolute value of a lateral magnification in the first lens group G1. Upon focusing from infinity to a close distance, the third lens group G3 moves onto the object side along an optical axis, and a prescribed conditional expression is satisfied.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a large-aperture wide-angle lens suitable for a photographic lens used in a digital camera, a video camera, and the like, and having a bright F value of about 1.4 and corresponding to a large image sensor.

  In recent years, so-called mirrorless single-lens cameras, in which a quick return mirror is eliminated by providing an electronic viewfinder instead of a conventional single-lens reflex finder as a lens-interchangeable camera, are rapidly spreading. A mirrorless single-lens camera does not require a quick return mirror, its driving mechanism, a pentaprism, and the like, and is widely supported because it can be significantly reduced in size as compared with a conventional single-lens reflex camera.

  In auto-focus of a mirrorless single-lens camera, so-called contrast AF is often employed in which the focus lens is slightly driven (wobbed) in the optical axis direction to detect a contrast peak. Therefore, in order to realize high-speed and smooth contrast AF, it is required to make the focus group sufficiently light.

  In order to reduce the weight of the focus group, it is effective to adopt the inner focus or the rear focus instead of the front lens payout. Examples of the inner-focus or rear-focus wide-angle lens include the following patent documents.

  The wide-angle lens described in Patent Document 1 has a large aperture of about F1.0, and is a type in which focusing is performed with four lenses on the image plane side from the stop.

  The wide-angle lens described in Patent Document 2 uses an inner focus type with a single convex lens to reduce the weight of the focus group.

  The wide-angle lens described in Patent Document 3 is designed to reduce the weight of the focus group by adopting an inner focus type with two or less lenses while increasing the diameter to about F1.8.

JP 2014-032231 A JP 2014-035458 A International Publication WO2013 / 118466

  However, the wide-angle lens described in Patent Document 1 has a heavy focus group, and it is difficult to realize high-speed and smooth contrast AF.

  In the wide-angle lens described in Patent Document 2, only an example having an F value of about 2.8 is disclosed, and it is difficult to achieve a large aperture of F1.4 from this configuration.

  In the wide-angle lens described in Patent Document 3, when the disclosed embodiment is scaled to fit a large image sensor, the entire length of the lens system becomes long, and a small and lightweight lens system corresponding to the large image sensor can be realized. Have difficulty.

  The present invention has been made in view of such a situation, and while maintaining a small size, the F-number is brightened to about 1.4, is compatible with a large image sensor, and further, the focus group is made lighter and smoother. An object is to provide a large-aperture wide-angle lens capable of realizing contrast AF.

The first invention, which is means for solving the above-mentioned problems, is, in order from the object side, a first lens group G1 having a negative refractive power, an aperture stop S, a second lens group G2 having a positive refractive power, The lens unit includes a third lens group G3 having a positive refractive power and a fourth lens group G4 having a negative refractive power. The first lens group G1 and the first A lens group G1A having a negative refractive power in order from the object side are positive. A first lens group G1B having refractive power, and the most object side lens of the first B lens group G1B is a single lens or cemented lens having a positive refractive power having the largest absolute value of lateral magnification in the first lens group G1. The third lens group G3 is a lens and moves to the object side along the optical axis during focusing from infinity to a short distance, and satisfies the following conditional expressions (1), (2), and (3): A wide-angle lens.
(1) -2.4 <f1 / f <-0.6
(2) -0.3 <f1A / f1B <0.0
(3) 0.1 <f1A / f4 <0.5
However,
f: focal length of the entire lens system at the time of focusing on infinity f1: focal length of the first lens group G1 f1A: focal length of the first A lens group G1A f1B: focal length of the first B lens group G1B f4: fourth lens group Focal length of G4

Further, in the second invention, in order from the object side, a first lens group G1 having a negative refractive power, an aperture stop S, a second lens group G2 having a positive refractive power, and a third lens having a positive refractive power. The first lens group G1 is composed of a first lens group G1A having a negative refractive power and a first B lens group G1B having a positive refractive power in order from the object side. The most object side lens of the first B lens group G1B is a single lens or a cemented lens having a positive refractive power having the largest absolute value of lateral magnification in the first lens group G1, and the first B lens The group G1B is composed of a first Bp lens group G1Bp having a positive refractive power and a first Bm lens group G1Bm having a negative refractive power in order from the object side, and the position where the first Bp lens group G1Bp and the first Bm lens group G1Bm are separated is 1B lens group G1 In the case of focusing at infinity, the air interval is set so that the lateral magnification of the combined optical system of the lens group from the first Bm lens group G1Bm to the image plane is maximized at the time of focusing on infinity. Is a large-aperture wide-angle lens that moves to the object side along the following conditions (1), (2), and (3):
(1) -2.4 <f1 / f <-0.6
(2) -0.3 <f1A / f1B <0.0
(3) 0.1 <f1A / f4 <0.5

According to a third invention, in the first invention, the first B lens group G1B is composed of a first Bp lens group G1Bp having a positive refractive power and a first Bm lens group G1Bm having a negative refractive power in order from the object side. The position at which the first Bp lens group G1Bp and the first Bm lens group G1Bm are separated is such that the lateral magnification of the combined optical system of the lens group from the first Bm lens group G1Bm to the image plane in the first B lens group G1B when focused at infinity. 2. The large-aperture wide-angle lens according to claim 1, wherein the maximum air interval is satisfied and the following conditional expression (4) is satisfied.
(4) 0.5 <D1B / D1S <0.75
However,
D1B: Length on the optical axis from the most object side surface of the first lens group G1 to the most object side surface of the first B lens group G1B D1S: From the most object side surface of the first lens group G1 to the stop Length on the optical axis

According to a fourth invention, in the second or third invention, the first Bp lens group G1Bp further includes two or more convex lenses, and the first Bp lens group G1Bp and the first Bm lens group G1Bm are infinite. 4. The large-aperture wide-angle lens according to claim 2, wherein the lateral magnification at the time of focusing is both negative and satisfies the following conditional expressions (5) and (6): 5.
(5) −1.8 <β1Bp <−0.6
(6) 50 <ν1Bp <80
However,
β1Bp: lateral magnification of the first Bp lens group G1Bp when focused at infinity ν1Bp: average Abbe number of convex lenses in the first Bp lens group G1Bp

According to a fifth invention, in the first to fourth inventions, the third lens group G3 is composed of one convex lens, and satisfies the following conditional expressions (7) and (8): A wide-angle lens.
(7) 0.1 <f2 / f3 <0.44
(8) 0.52 <SI / f3 <1.0
However,
f2: Focal length of the second lens group G2 f3: Focal length SI of the third lens group G3: Length from the stop to the image plane when focusing on infinity

The sixth invention is a large-aperture wide-angle lens characterized by further satisfying the following conditional expression (9) in the first to fifth inventions.
(9) 2.5 <EXP / IH <4.5
However,
EXP: Length from exit pupil to image plane when focusing on infinity IH: Maximum image height

  According to the present invention, there is provided a large-aperture wide-angle lens that can realize a smooth contrast AF by making the F value as bright as about 1.4 with a small size, corresponding to a large image sensor, and further reducing the weight of the focus group. Can be provided.

It is a lens block diagram concerning Example 1 of the large aperture wide-angle lens of the present invention. FIG. 4 is a longitudinal aberration diagram of the large aperture wide angle lens according to Example 1 when focusing on infinity. FIG. 4 is a longitudinal aberration diagram of the large aperture wide angle lens of Example 1 at an imaging magnification of 40 times. 3 is a lateral aberration diagram of the large aperture wide angle lens of Example 1 when focusing on infinity. FIG. FIG. 4 is a lateral aberration diagram at a photographing magnification of 40 times in the large aperture wide angle lens according to Example 1. It is a lens block diagram which concerns on Example 2 of the large aperture wide angle lens of this invention. FIG. 6 is a longitudinal aberration diagram of the large aperture wide angle lens according to Example 2 when focusing on infinity. FIG. 6 is a longitudinal aberration diagram of the large aperture wide angle lens according to Example 2 at a shooting magnification of 40. FIG. 6 is a lateral aberration diagram of the large aperture wide angle lens according to Example 2 when focusing on infinity. FIG. 6 is a transverse aberration diagram for the large-aperture wide-angle lens of Example 2 at an imaging magnification of 40. It is a lens block diagram which concerns on Example 3 of the large aperture wide-angle lens of this invention. FIG. 6 is a longitudinal aberration diagram of the large aperture wide angle lens according to Example 3 when focusing on infinity. FIG. 6 is a longitudinal aberration diagram of the large aperture wide angle lens according to Example 3 at a shooting magnification of 40. FIG. 5 is a lateral aberration diagram of the large aperture wide angle lens according to Example 3 when focusing on infinity. FIG. 6 is a transverse aberration diagram for the large-diameter wide-angle lens of Example 3 at a shooting magnification of 40. It is a lens block diagram which concerns on Example 4 of the large aperture wide angle lens of this invention. FIG. 6 is a longitudinal aberration diagram of the large aperture wide angle lens according to Example 4 when focusing on infinity. FIG. 6 is a longitudinal aberration diagram of the large-diameter wide-angle lens of Example 4 at a shooting magnification of 40. FIG. 6 is a lateral aberration diagram of the large aperture wide angle lens according to Example 4 when focusing on infinity. FIG. 6 is a transverse aberration diagram for the large-aperture wide-angle lens of Example 4 at a shooting magnification of 40. It is a lens block diagram which concerns on Example 5 of the large aperture wide angle lens of this invention. FIG. 10 is a longitudinal aberration diagram of the large aperture wide angle lens according to Example 5 when focusing on infinity. FIG. 12 is a longitudinal aberration diagram at the shooting magnification of 40 times with the large-aperture wide-angle lens of Example 5. FIG. 10 is a transverse aberration diagram for the large-diameter wide-angle lens of Example 5 when focusing on infinity. FIG. 10 is a transverse aberration diagram for the large-aperture wide-angle lens of Example 5 at a shooting magnification of 40. It is a lens block diagram which concerns on Example 6 of the large aperture wide angle lens of this invention. FIG. 12 is a longitudinal aberration diagram of the large aperture wide angle lens according to Example 6 when focusing on infinity. FIG. 12 is a longitudinal aberration diagram at the shooting magnification of 40 times with the large-aperture wide-angle lens of Example 6. FIG. 10 is a transverse aberration diagram for the large aperture wide angle lens according to Example 6 when focusing on infinity. FIG. 10 is a transverse aberration diagram for the large-aperture wide-angle lens of Example 6 at a shooting magnification of 40.

  Hereinafter, examples of the optical system according to the present invention will be described in detail. Note that the following description of the embodiment describes an example of the optical system of the present invention, and the present invention is not limited to this embodiment without departing from the gist thereof.

  The imaging optical system of the present invention includes a first lens group having a negative refractive power in order from the object side, as can be seen from the lens configuration diagrams shown in FIGS. 1, 6, 11, 16, 21, and 26. G1, aperture stop S, second lens group G2 having a positive refractive power, third lens group G3 having a positive refractive power, and fourth lens group G4 having a negative refractive power. The third lens group G3 moves to the object side along the optical axis during focusing.

  The first lens group G1 is composed of a first A lens group G1A having a negative refractive power and a first B lens group G1B having a positive refractive power in order from the object side, and is the lens closest to the object side of the first B lens group G1B. Is a single lens or cemented lens having a positive refractive power having the largest absolute value of lateral magnification in the first lens group G1.

  In a wide-angle lens, peripheral rays are incident at a large angle with respect to the optical axis. Therefore, the incident angle of the peripheral light beam to the image sensor is reduced by making the exit angle of the peripheral light beam to the aperture stop gentle by the negative first lens unit and further relaxing by the positive second lens unit positioned on the image plane side from the stop. Can be kept small, and even with a large aperture lens with a large luminous flux, it is difficult for peripheral rays to be scattered by the light receiving portion of the image sensor. Since the on-axis light beam is converged by the positive second lens group, focusing on the third lens group closer to the image plane than the second lens group can prevent an increase in the diameter of the focus group. A large-aperture wide-angle lens capable of high-speed and smooth contrast AF can be realized by reducing the weight of the lens group.

  By constructing the first lens group G1 in order from the object side, the first A lens group G1A having a negative refractive power and the first B lens group G1B having a positive refractive power, an on-axis marginal bounced up by the first A lens group G1A The angle with respect to the optical axis of the light beam can be reduced by the first B lens group G1B to prevent an increase in the diameter of the aperture, and a small and light optical system can be realized. Further, a first lens unit G1A having a negative refractive power and a first lens group G1B having a positive refractive power are arranged in order from the object side before the stop, and a second lens having a positive refractive power in order from the object side after the stop. By arranging the group G2, the third lens group G3, and the fourth lens group G4 having negative refractive power, the symmetry of the refractive power arrangement before and after the stop increases, which is advantageous for correcting the lateral chromatic aberration and distortion. .

In order to realize a high-performance large-diameter wide-angle lens with the above configuration, it is desirable to satisfy the following conditional expressions (1), (2) and (3).
(1) -2.4 <f1 / f <-0.6
(2) -0.3 <f1A / f1B <0.0
(3) 0.1 <f1A / f4 <0.5
However,
f: focal length of the entire lens system at the time of focusing on infinity f1: focal length of the first lens group G1 f1A: focal length of the first A lens group G1A f1B: focal length of the first B lens group G1B f4: fourth lens group The focal length is G4.

  Conditional expression (1) defines a preferable range with respect to the ratio of the focal length of the entire lens system when focusing on infinity with the first lens group G1. By satisfying conditional expression (1), the focal length of the first lens group G1 can be set appropriately, and a large-aperture wide-angle lens that is compact and lightweight and has good imaging performance can be realized.

  If the lower limit of conditional expression (1) is exceeded and the negative refractive power of the first lens group G1 is weakened, it is difficult to ensure the back focus. On the other hand, if the upper limit of conditional expression (1) is exceeded and the negative refractive power of the first lens group G1 is increased, the aperture diameter is enlarged and it is difficult to realize a small and lightweight lens system. In addition, since the incident angle and the height of the on-axis marginal ray to the second lens group G2 are also increased, high-order aberrations are deteriorated, and it is difficult to ensure good imaging performance.

  Moreover, the effect of this invention can be achieved more reliably by making the lower limit of conditional expression (1) into -2.2, and making an upper limit into -0.8.

  Conditional expression (2) defines a preferable range with respect to the ratio of the focal lengths of the first A lens group G1A and the first B lens group G1B. By satisfying conditional expression (2), the refractive power arrangement in the first lens group can be set appropriately, and a compact and lightweight optical system can be realized.

  If the lower limit of conditional expression (2) is exceeded and the negative refractive power of the first A lens group G1A is weakened or the positive refractive power of the first B lens group G1B is strong, the entrance pupil moves to the image plane side. Securing the amount of peripheral light becomes difficult because the incident peripheral rays are scattered. Further, the image-side principal point of the first lens group G1 moves to the object side, and the space between the first lens group G1 and the second lens group G2 becomes narrow, so that it is difficult to secure a space for disposing the aperture unit. Become. On the other hand, if the upper limit of conditional expression (2) is exceeded and the negative refractive power of the first A lens group G1A is increased or the positive refractive power of the first B lens group G1B is weakened, the aperture diameter is enlarged and the optical system is small and lightweight. It becomes difficult to realize.

  Moreover, the effect of this invention can be achieved more reliably by making the lower limit of conditional expression (2) into -0.25.

  Conditional expression (3) defines a preferable range for the ratio of the focal lengths of the first A lens group G1A and the fourth lens group G4. By satisfying conditional expression (3), it is possible to realize a large-aperture wide-angle lens in which lateral chromatic aberration and distortion are satisfactorily corrected, and the incident angle on the image plane with respect to the light beam having the peripheral field angle is suppressed.

  When the lower limit of conditional expression (3) is exceeded and the refractive power of the fourth lens group G4 is relatively weak with respect to the first A lens group G1A, the asymmetry of the refractive power before and after the stop increases, and the lateral chromatic aberration and negative It becomes difficult to suppress distortion.

  On the other hand, when the upper limit of conditional expression (3) is exceeded and the negative refractive power of the first A lens group G1A is weakened, the effect of reducing the exit angle of the peripheral field angle with respect to the optical axis of the principal ray by the 1A lens group is weakened, The incident angle of the chief ray of the peripheral field angle on the fourth lens group G4 is increased. Further, when the negative refractive power of the fourth lens group G4 increases, the effect of jumping up the light beam by the fourth lens group increases. Therefore, the angle of incidence of the principal ray at the peripheral field angle on the image plane becomes tight. In particular, in the case of a large aperture lens with a large luminous flux, the light beam is likely to be emitted at the light receiving portion of the image sensor.

  Further, regarding the conditional expression (3) described above, it is preferable to limit the lower limit value to 0.15 and the upper limit value to 0.45 because the above-described effects can be more reliably achieved.

  In the large-aperture wide-angle lens of the present invention, it is desirable that the first B lens group G1B is composed of a first Bp lens group G1Bp having a positive refractive power and a first Bm lens group G1Bm having a negative refractive power in order from the object side. Here, the position where the first Bp lens group G1Bp and the first Bm lens group G1Bm are separated is an air interval at which the lateral magnification of the combined optical system of the lens group from the first Bm lens group G1Bm to the image plane becomes maximum when focusing on infinity. To do.

  The first B lens group G1B having a positive refractive power has an effect of preventing an increase in the aperture diameter by reducing the angle of the axial marginal ray bounced up by the first A lens group G1A with respect to the optical axis. By configuring the first B lens group G1B in order from the object side, the first Bp lens group G1Bp having a positive refractive power and the first Bm lens group G1Bm having a negative refractive power, the image side principal point of the first B lens group G1B is the object side. The axial marginal ray height on the most image-side surface of the first B lens group G1B can be lowered, which is further advantageous in reducing the aperture diameter disposed on the image side of the first B lens group G1B.

  In addition, with a general retrofocus type lens that has a negative refractive power on the object side and a positive refractive power on the image plane side from the stop, axial chromatic aberration correction can be performed with a group of positive refractive powers on the image plane side from the stop. Done. Here, by introducing the first Bp lens group G1Bp having a positive refractive power and the first Bm lens group G1Bm having a negative refractive power closer to the object side than the stop as in the present application, the effect of raising the light beam by the first A lens group G1A is achieved. As a result, the axial marginal ray height increases in the first B lens group G1B. Further, by using a low dispersion glass material for the convex lens of the first Bp lens group G1Bp, axial chromatic aberration can be corrected between the first Bp lens group G1Bp and the first Bm lens group G1Bm. Therefore, axial chromatic aberration can be corrected not only in the second lens group G2 but also in the first B lens group G1B, which is more advantageous for correcting axial chromatic aberration than a general retrofocus type.

In the large-aperture wide-angle lens of the present invention, it is desirable to satisfy the following conditional expression (4).
(4) 0.5 <D1B / D1S <0.75
However,
D1B: Length on the optical axis from the most object side surface of the first lens group G1 to the most object side surface of the first B lens group G1B D1S: From the most object side surface of the first lens group G1 to the stop The length on the optical axis.

  Conditional expression (4) defines a preferable range with respect to the position in the direction parallel to the optical axis of the first B lens group G1B in the first lens group G1. By satisfying conditional expression (4), axial chromatic aberration correction and spherical aberration correction in the first B lens group G1B can be performed in a well-balanced manner.

  When the lower limit of conditional expression (4) is exceeded and the first B lens group G1B approaches the first A lens group G1A, the on-axis marginal ray height in the first B lens group G1B decreases, so the first Bp lens group G1Bp and the first Bm lens group The effect of correcting axial chromatic aberration with G1Bm cannot be obtained sufficiently. On the other hand, if the upper limit of the conditional expression (4) is exceeded and the first B lens group G1B moves away from the first A lens group G1A, the axial marginal ray height in the first B lens group G1B increases and the diameter increases and the optical system becomes heavy. Become. Further, since the length from the most object-side surface of the first B lens group G1B to the stop is shortened, the number of lenses that can be used in the first B lens group G1B is limited, and spherical aberration correction within the first B lens group is sufficiently performed. It becomes impossible to do.

  Moreover, the effect of this invention can be achieved more reliably by making the lower limit of conditional expression (4) into 0.53, and making an upper limit into 0.72.

  Further, in the large-aperture wide-angle lens of the present invention, the first Bp lens group G1Bp has two or more convex lenses, and the lateral magnifications of the first Bp lens group G1Bp and the first Bm lens group G1Bm at infinity are both negative. It is desirable.

  If the lateral magnification at the time of focusing on infinity of the first Bp lens group G1Bp and the first Bm lens group G1Bm is negative, the axial light beam diverged by the first A lens group G1A is converged by the first Bp lens group G1Bp, and the first Bm It is diverged again by the lens group G1Bm. By adopting such a configuration, the effect of suppressing the aperture diameter by moving the image side principal point of the first B lens group G1B to the object side is strengthened, which contributes to the realization of a compact and lightweight optical system.

  Further, according to the third-order aberration theory, the field curvature is proportional to the square of the angle of view, so correction of the field curvature is an important issue in a wide-angle lens. In order to reduce the curvature of field, it is effective to suppress the Petzval sum. However, the lens configuration of the present application is a retrofocus type having a negative refractive power on the object side and a positive refractive power on the image side from the stop. Since the configuration is close to the addition of the lens group G1B, it is necessary to configure the first B lens group G1B so that the positive Petzval sum in the entire system does not increase. When the first Bp lens group G1Bp includes two or more convex lenses, the curvature of the convex lens is suppressed, which is effective in suppressing Petzval sum.

  Also, by making the lateral magnification of the first Bp lens group G1Bp negative, the axial marginal ray height in the first Bm lens group G1Bm is lowered. Therefore, in order for the first Bm lens group G1Bm to re-bounce the axial marginal ray again, it is necessary to increase the curvature of the concave lens, but the absolute value of the negative Petzval sum of the first Bm lens group G1Bm increases accordingly. The Petzval sum in the entire system can be suppressed.

In the large-aperture wide-angle lens of the present invention, it is desirable to satisfy the following conditional expressions (5) and (6).
(5) −1.8 <β1Bp <−0.6
(6) 50 <ν1Bp <80
However,
β1Bp: transverse magnification ν1Bp at the time of focusing on infinity of the first Bp lens group G1Bp: an average of Abbe numbers of convex lenses in the first Bp lens group G1Bp.

  Conditional expression (5) defines a preferable range for the lateral magnification of the first Bp lens group G1Bp when focusing on infinity. By satisfying conditional expression (5), the exit angle of the on-axis marginal ray emitted from the first Bp lens group G1Bp to the first Bm lens group G1Bm is appropriately set, which contributes to reduction of the aperture diameter and suppression of Petzval sum.

  If the lower limit of conditional expression (5) is exceeded and the absolute value of the negative lateral magnification of the first Bp lens group G1Bp increases, the height of the on-axis marginal ray incident on the first Bm lens group G1Bm will increase. Accordingly, since the curvature of the concave surface in the first Bm lens group cannot be tightened in order to suppress the effect of raising the light beam by the first Bm lens group G1Bm, it is difficult to suppress the Petzval sum. On the other hand, when the absolute value of the negative lateral magnification of the first Bp lens group G1Bp becomes smaller than the upper limit of the conditional expression (5), the curvature of the convex surface is increased in order to refract the axial marginal ray greatly in the first Bp lens group G1Bp. It becomes necessary to strengthen. Further, since the height of the on-axis marginal ray in the first Bm lens group G1Bm becomes too low, it is necessary to increase the curvature of the concave surface in order to jump up the on-axis marginal ray. Therefore, the relationship between the first Bp lens group and the first Bm lens group canceling out large aberrations generated on the surface having a strong curvature, which is not preferable because the manufacturing error sensitivity increases.

  Moreover, the effect of this invention can be achieved more reliably by making the lower limit of conditional expression (5) into -1.7, and making an upper limit into -0.7.

  Conditional expression (6) defines a preferable range for the average Abbe number of the convex lenses in the first Bp lens group G1Bp. In the first Bp lens group G1Bp, since the axial marginal ray height is high, the axial chromatic aberration can be corrected by selecting an appropriate glass material. In general, axial chromatic aberration correction is performed by using a low-dispersion glass material for a convex lens. However, a general glass material has a high refractive index when it is highly dispersed and a low refractive index when it is lowly dispersed. If a low-dispersion glass material having a low refractive index is frequently used for the convex lens to correct axial chromatic aberration, the Petzval sum will increase. Therefore, it is possible to achieve both axial chromatic aberration correction and field curvature correction by appropriately combining a low refractive index low dispersion lens and a high refractive index high dispersion lens so as to satisfy the conditional expression (6).

  If the lower limit of conditional expression (6) is exceeded and the average of the Abbe numbers of the convex lenses in the first Bp lens group G1Bp becomes small, the ability to correct axial chromatic aberration becomes insufficient. On the other hand, when the average of the Abbe numbers of the convex lenses in the first Bp lens group G1Bp is larger than the upper limit of the conditional expression (6), the refractive index of the convex lens is low due to the low refractive index property, and the Petzval sum is biased. It becomes larger and the field curvature is worsened.

  Further, by setting the lower limit value of conditional expression (6) to 55 and the upper limit value to 75, the effects of the present invention can be achieved more reliably.

  Furthermore, in the large-aperture wide-angle lens of the present invention, it is desirable that the third lens group G3, which is a focus group, is composed of a single positive lens. This reduces the weight of the focus group and enables high-speed and smooth contrast AF.

In the large-aperture wide-angle lens of the present invention, it is desirable to satisfy the following conditional expressions (7) and (8).
(7) 0.1 <f2 / f3 <0.44
(8) 0.52 <SI / f3 <1.0
However,
f2: focal length of the second lens group G2 f3: focal length SI of the third lens group G3: length from the stop to the image plane when focusing on infinity.

  Conditional expression (7) defines a preferable condition for the ratio of the focal lengths of the second lens group G2 and the third lens group G3. By satisfying conditional expression (7), it is possible to realize good imaging performance in the entire photographing distance from infinity to the closest distance with a lightweight focus group.

  If the lower limit of conditional expression (7) is exceeded and the refractive power of the third lens group G3 is weakened, the amount of focus movement increases, and it becomes difficult to reduce the size of the lens system. Further, when the refractive power of the second lens group G2 increases, the converging action of the axial light beam incident on the third lens group G3 increases, so that the third lens when the third lens group G3 moves along the optical axis during focusing. The variation in the height of the on-axis marginal ray in the group G3 increases, and the variation in spherical aberration during focusing increases, making it difficult to maintain good imaging performance over the entire shooting distance. On the other hand, if the upper limit of conditional expression (7) is exceeded and the refractive power of the second lens group G2 is weakened, the action of refracting the upper ray of the peripheral field angle passing through the second lens group G2 will be weakened, so the third lens group G3. The upper ray height at the peripheral angle of view becomes higher. On the other hand, since the refractive power of the third lens group G3 increases, the fluctuation of the flare of the upper ray at the time of focusing increases, making it difficult to maintain good imaging performance over the entire photographing distance.

  Moreover, the effect of this invention can be achieved more reliably by making the lower limit of conditional expression (7) into 0.15, and making an upper limit into 0.4.

  Conditional expression (8) defines a preferable condition for the ratio of the length from the stop to the image plane at the time of focusing on infinity and the focal length of the third lens group G3. By satisfying conditional expression (8), it is possible to realize a lens system having a small image height change rate during wobbling. Suppressing the image height change rate during wobbling is important in order to prevent the photographer from feeling uncomfortable due to a change in the magnification of the subject on the screen during moving image shooting.

  When the lower limit of conditional expression (8) is exceeded and the length from the stop to the image plane is shortened, the incident angle of the principal ray at the peripheral field angle to the third lens group G3 increases, while the refraction of the third lens group G3. When the force is weakened, the amount of focus movement increases, and the principal ray height fluctuation in the focus group during wobbling increases, making it difficult to suppress the image height change rate. Further, when the length from the stop to the image plane is shortened, the focus interval between the second lens group G2 and the fourth lens group G4 is narrowed, while the refractive power of the third lens group G3 is weakened and the focus movement amount is reduced. When becomes larger, it becomes difficult to secure a space for moving the focus group for focusing. On the other hand, if the upper limit of conditional expression (8) is exceeded and the length from the stop to the image plane is increased, the total length of the optical system is increased, making it difficult to realize a compact and lightweight optical system.

  Further, by setting the lower limit value of conditional expression (8) to 0.55 and the upper limit value to 0.9, the effects of the present invention can be achieved more reliably.

Furthermore, it is desirable that the large-aperture wide-angle lens of the present invention satisfies the following conditional expression (9).
(9) 2.5 <EXP / IH <4.5
However,
EXP: Length from the exit pupil to the image plane when focusing on infinity IH: Maximum image height.

  Conditional expression (9) defines a preferable range with respect to the ratio of the length from the exit pupil to the image plane and the maximum image height when focusing on infinity. By satisfying conditional expression (9), it is possible to realize a large-aperture wide-angle lens corresponding to a large image sensor while suppressing the diameter of the fourth lens group G4.

  When the lower limit of conditional expression (9) is exceeded and the exit pupil approaches the image plane, the light incident angle of the peripheral field angle on the image plane becomes large, and light rays are likely to be emitted by the light receiving unit of the image sensor. On the other hand, if the upper limit of conditional expression (9) is exceeded and the exit pupil moves away from the image plane, the diameter of the fourth lens group G4 increases, making it difficult to realize a compact and lightweight optical system.

  Moreover, the effect of this invention can be achieved more reliably by making the lower limit of conditional expression (9) into 3.0 and making an upper limit into 4.2.

  Next, a lens configuration of an example according to the imaging optical system of the present invention will be described. In the following description, the lens configuration is described in order from the object side to the image side. In addition, the notation of Ln in the examples indicates the nth lens from the object side.

  FIG. 1 is a lens configuration diagram of a large-aperture wide-angle lens according to Example 1 of the present invention.

  The first lens group G1 includes a first A lens group G1A and a first B lens group G1B, and has a negative refractive power as a whole.

  The first A lens group G1A includes a positive meniscus lens L11 having a convex surface facing the object side, a negative meniscus lens L12 having a convex surface facing the object side, a negative meniscus lens L13 having a convex surface facing the object side, and a biconcave shape. It is composed of a cemented lens composed of a negative lens L14 and a biconvex positive lens L15, and has a negative refractive power as a whole. The image-side surface of the negative meniscus lens L13 has a predetermined aspherical shape.

  The first B lens group G1B includes a first Bp lens group G1Bp and a first Bm lens group G1Bm, and has a positive refractive power as a whole.

  The first Bp lens group G1Bp includes a biconvex positive lens L16 and a biconvex positive lens L17, and has a positive refractive power as a whole.

  The first Bm lens group G1Bm includes a biconcave negative lens L18 and a negative meniscus lens L19 having a concave surface directed toward the object side, and has a negative refractive power as a whole.

  An aperture stop is disposed between the first lens group G1 and the second lens group G2.

  The second lens group G2 includes a cemented lens including a biconvex positive lens L21 and a negative meniscus lens L22 having a concave surface facing the object, and a biconvex positive lens L23. It has a refractive power of The image side surface of the biconvex lens L23 has a predetermined aspherical shape.

  The third lens group G3 is composed of a positive meniscus lens L31 having a convex surface directed toward the object side. The third lens group G3 has a positive refractive power as a whole, and is focused along the optical axis along the optical axis during focusing from infinity to the nearest. Move towards.

  The fourth lens group G4 includes a cemented lens including a negative meniscus lens L41 having a convex surface directed toward the object side, a biconvex positive lens L42, and a negative meniscus lens L43 having a concave surface directed toward the object side. As a whole, it has a negative refractive power.

  FIG. 6 is a lens configuration diagram of a large-aperture wide-angle lens according to Example 2 of the present invention.

  The first lens group G1 includes a first A lens group G1A and a first B lens group G1B, and has a negative refractive power as a whole.

  The first A lens group G1A includes a positive meniscus lens L11 having a convex surface facing the object side, a negative meniscus lens L12 having a convex surface facing the object side, a negative meniscus lens L13 having a convex surface facing the object side, and a biconcave shape. The lens includes a negative lens L14 and a biconvex positive lens L15, and has a negative refractive power as a whole. The image-side surface of the negative meniscus lens L13 has a predetermined aspherical shape.

  The first B lens group G1B includes a first Bp lens group G1Bp and a first Bm lens group G1Bm, and has a positive refractive power as a whole.

  The first Bp lens group G1Bp includes a biconvex positive lens L16 and a biconvex positive lens L17, and has a positive refractive power as a whole.

  The first Bm lens group G1Bm includes a negative meniscus lens L18 having a convex surface facing the object side, and a negative meniscus lens L19 having a concave surface facing the object side, and has a negative refractive power as a whole.

  An aperture stop is disposed between the first lens group G1 and the second lens group G2.

  The second lens group G2 includes a cemented lens including a biconvex positive lens L21 and a negative meniscus lens L22 having a concave surface facing the object, and a biconvex positive lens L23. It has a refractive power of The image side surface of the biconvex lens L23 has a predetermined aspherical shape.

  The third lens group G3 is composed of a positive meniscus lens L31 having a convex surface directed toward the object side. The third lens group G3 has a positive refractive power as a whole, and is focused along the optical axis along the optical axis during focusing from infinity to the nearest. Move towards.

  The fourth lens group G4 includes a cemented lens including a negative meniscus lens L41 having a convex surface directed toward the object side, a positive meniscus lens L42 having a concave surface directed toward the object side, and a negative meniscus lens L43 having a concave surface directed toward the object side. It has a negative refractive power as a whole.

  FIG. 11 is a lens configuration diagram of a large-aperture wide-angle lens according to Example 3 of the present invention.

  The first lens group G1 includes a first A lens group G1A and a first B lens group G1B, and has a negative refractive power as a whole.

  The first A lens group G1A includes a positive meniscus lens L11 having a convex surface facing the object side, a negative meniscus lens L12 having a convex surface facing the object side, a negative meniscus lens L13 having a convex surface facing the object side, and a biconcave shape. It is composed of a cemented lens composed of a negative lens L14 and a biconvex positive lens L15, and has a negative refractive power as a whole. The image-side surface of the negative meniscus lens L13 has a predetermined aspherical shape.

  The first B lens group G1B includes a first Bp lens group G1Bp and a first Bm lens group G1Bm, and has a positive refractive power as a whole.

  The first Bp lens group G1Bp includes a biconvex positive lens L16 and a biconvex positive lens L17, and has a positive refractive power as a whole.

  The first Bm lens group G1Bm includes a biconcave negative lens L18 and a negative meniscus lens L19 having a concave surface directed toward the object side, and has a negative refractive power as a whole.

  An aperture stop is disposed between the first lens group G1 and the second lens group G2.

  The second lens group G2 includes a cemented lens including a biconvex positive lens L21 and a negative meniscus lens L22 having a concave surface facing the object, and a biconvex positive lens L23. It has a refractive power of The image side surface of the biconvex lens L23 has a predetermined aspherical shape.

  The third lens group G3 is composed of a positive meniscus lens L31 having a convex surface directed toward the object side. The third lens group G3 has a positive refractive power as a whole, and is focused along the optical axis along the optical axis during focusing from infinity to the nearest. Move towards.

  The fourth lens group G4 includes a cemented lens including a negative meniscus lens L41 having a convex surface directed toward the object side, a positive meniscus lens L42 having a concave surface directed toward the object side, and a negative meniscus lens L43 having a concave surface directed toward the object side. It has a negative refractive power as a whole.

  FIG. 16 is a lens configuration diagram of a large-aperture wide-angle lens according to Example 4 of the present invention.

  The first lens group G1 includes a first A lens group G1A and a first B lens group G1B, and has a negative refractive power as a whole.

  The first A lens group G1A includes a negative meniscus lens L11 having a convex surface facing the object side, a negative meniscus lens L12 having a convex surface facing the object side, a biconcave negative lens L13, and a biconvex positive lens L14. It has a negative refractive power as a whole. The image-side surface of the negative meniscus lens L12 has a predetermined aspheric shape.

  The first B lens group G1B includes a first Bp lens group G1Bp and a first Bm lens group G1Bm, and has a positive refractive power as a whole.

  The first Bp lens group G1Bp includes a biconvex positive lens L15 and a positive meniscus lens L16 having a concave surface facing the object side, and has a positive refractive power as a whole.

  The first Bm lens group G1Bm includes a negative meniscus lens L17 having a convex surface facing the object side and a negative meniscus lens L18 having a concave surface facing the object side, and has a negative refractive power as a whole.

  An aperture stop is disposed between the first lens group G1 and the second lens group G2.

  The second lens group G2 includes a cemented lens including a biconvex positive lens L21 and a negative meniscus lens L22 having a concave surface facing the object side, and a positive meniscus lens L23 having a concave surface facing the object side. As a whole, it has a positive refractive power. The image side surface of the positive meniscus lens L23 has a predetermined aspherical shape.

  The third lens group G3 is composed of a positive meniscus lens L31 having a convex surface directed toward the object side. The third lens group G3 has a positive refractive power as a whole, and is focused along the optical axis along the optical axis during focusing from infinity to the nearest. Move towards.

  The fourth lens group G4 includes a cemented lens including a negative meniscus lens L41 having a convex surface directed toward the object side, a biconvex positive lens L42, and a negative meniscus lens L43 having a concave surface directed toward the object side. As a whole, it has a negative refractive power.

  FIG. 21 is a lens configuration diagram of a large-aperture wide-angle lens according to Example 5 of the present invention.

  The first lens group G1 includes a first A lens group G1A and a first B lens group G1B, and has a negative refractive power as a whole.

  The first A lens group G1A includes a positive meniscus lens L11 having a convex surface facing the object side, a negative meniscus lens L12 having a convex surface facing the object side, a negative meniscus lens L13 having a convex surface facing the object side, and a concave surface facing the object side And a positive meniscus lens L15 having a concave surface facing the object side, and has a negative refractive power as a whole. The image-side surface of the negative meniscus lens L13 has a predetermined aspherical shape.

  The first B lens group G1B includes a first Bp lens group G1Bp and a first Bm lens group G1Bm, and has a positive refractive power as a whole.

  The first Bp lens group G1Bp includes a cemented lens including a negative meniscus lens L16 having a convex surface directed toward the object side and a biconvex positive lens L17, and a biconvex positive lens L18, and has a positive refractive power as a whole. have.

  The first Bm lens group G1Bm includes a biconcave negative lens L19, and has a negative refractive power as a whole.

  An aperture stop is disposed between the first lens group G1 and the second lens group G2.

  The second lens group G2 includes a cemented lens including a biconvex positive lens L21 and a negative meniscus lens L22 having a concave surface facing the object, and a biconvex positive lens L23. It has a refractive power of The image side surface of the biconvex lens L23 has a predetermined aspherical shape.

  The third lens group G3 is composed of a positive meniscus lens L31 having a convex surface directed toward the object side. The third lens group G3 has a positive refractive power as a whole, and is focused along the optical axis along the optical axis during focusing from infinity to the nearest. Move towards.

  The fourth lens group G4 includes a cemented lens including a negative meniscus lens L41 having a convex surface directed toward the object side, a biconvex positive lens L42, and a negative meniscus lens L43 having a concave surface directed toward the object side. As a whole, it has a negative refractive power.

  FIG. 26 is a lens configuration diagram of a large-aperture wide-angle lens according to Example 6 of the present invention.

  The first lens group G1 includes a first A lens group G1A and a first B lens group G1B, and has a negative refractive power as a whole.

  The first A lens group G1A includes a negative meniscus lens L11 having a convex surface facing the object side, a negative meniscus lens L12 having a convex surface facing the object side, a negative meniscus lens L13 having a convex surface facing the object side, and a biconcave shape. It is composed of a cemented lens composed of a negative lens L14 and a biconvex positive lens L15, and has a negative refractive power as a whole. The image-side surface of the negative meniscus lens L12 has a predetermined aspheric shape.

  The first B lens group G1B includes a first Bp lens group G1Bp and a first Bm lens group G1Bm, and has a positive refractive power as a whole.

  The first Bp lens group G1Bp includes a positive meniscus lens L16 having a convex surface facing the object side and a positive meniscus lens L17 having a concave surface facing the object side, and has a positive refractive power as a whole.

  The first Bm lens group G1Bm includes a negative meniscus lens L18 having a convex surface facing the object side, and a negative meniscus lens L19 having a concave surface facing the object side, and has a negative refractive power as a whole.

  An aperture stop is disposed between the first lens group G1 and the second lens group G2.

  The second lens group G2 includes a cemented lens including a biconvex positive lens L21 and a negative meniscus lens L22 having a concave surface facing the object, and a biconvex positive lens L23. It has a refractive power of The image side surface of the biconvex lens L23 has a predetermined aspherical shape.

  The third lens group G3 is composed of a positive meniscus lens L31 having a convex surface directed toward the object side. The third lens group G3 has a positive refractive power as a whole, and is focused along the optical axis along the optical axis during focusing from infinity to the nearest. Move towards.

  The fourth lens group G4 includes a cemented lens including a negative meniscus lens L41 having a convex surface directed toward the object side, a biconvex positive lens L42, and a negative meniscus lens L43 having a concave surface directed toward the object side. As a whole, it has a negative refractive power.

  Next, numerical value examples and conditional expression corresponding values of the examples according to the wide angle lens system of the present invention will be described.

  In [Surface Data], the surface number is the number of the lens surface or aperture stop counted from the object side, r is the radius of curvature of each lens surface, d is the distance between the lens surfaces, and nd is for the d-line (wavelength 587.56 nm). The refractive index, vd, indicates the Abbe number with respect to the d line.

  The * (asterisk) attached to the surface number indicates that the lens surface shape is an aspherical surface.

  The (diaphragm) attached to the surface number indicates that the aperture stop is located at that position. ∞ (infinity) is entered in the radius of curvature for a plane or aperture stop.

  [Aspherical data] indicates the values of the coefficients that give the aspherical shape of the lens surface marked with * in [Surface data]. The shape of the aspherical surface is expressed by the following formula. In the following equation, y is the displacement from the optical axis in the direction perpendicular to the optical axis, z is the displacement (sag amount) in the optical axis direction from the intersection of the aspherical surface and the optical axis, and r is the radius of curvature of the reference spherical surface. The conic coefficient is represented by K. The fourth, sixth, eighth, tenth, twelfth, fourteenth and sixteenth order aspherical coefficients are represented by A4, A6, A8, A10, A12, A14 and A16, respectively.

  [Various data] shows values such as the zoom ratio and the focal length in each focal length state.

  [Variable interval data] indicates the variable interval and the value of BF in each focal length state.

  [Lens Group Data] indicates the surface number of the most object side constituting each lens group and the combined focal length of the entire group.

  In the aberration diagrams corresponding to each example, d, g, and C represent d-line, g-line, and C-line, respectively, and ΔS and ΔM represent sagittal image plane and meridional image plane, respectively. .

  In all the values of the following specifications, the focal length f, the radius of curvature r, the lens surface interval d, and other length units described are in millimeters (mm) unless otherwise specified. In the system, the same optical performance can be obtained even in proportional expansion and proportional reduction, and the present invention is not limited to this.

Numerical example 1
Unit: mm
[Surface data]
Surface number rd nd vd
Object ∞ (d0)
1 125.2460 2.9671 1.51680 64.20
2 404.5429 0.5000
3 34.3690 1.4000 2.00100 29.13
4 16.3986 5.0945
5 26.0000 1.5000 1.58913 61.25
6 * 15.5760 10.6088
7 -30.5000 1.0319 1.43700 95.10
8 170.0033 2.9642 2.00100 29.13
9 -79.7237 7.2064
10 60.8883 3.0231 1.91082 35.25
11 -300.0000 0.8578
12 85.0000 5.6577 1.43700 95.10
13 -31.8218 1.0735
14 -60.7984 0.9000 1.51742 52.15
15 40.9323 5.7178
16 -20.3273 0.9000 1.67270 32.17
17 -39.4374 1.4174
18 (Aperture) ∞ 0.9946
19 68.6066 10.3000 1.59282 68.63
20 -20.1400 0.9000 1.74950 35.33
21 -34.7714 0.1500
22 55.4013 5.5346 1.69350 53.20
23 * -69.8881 (d23)
24 25.0000 2.7637 1.59282 68.63
25 47.3486 (d25)
26 35.4444 0.9000 1.80518 25.46
27 17.8877 3.7091
28 660.0000 6.0973 1.43700 95.10
29 -17.1474 0.9000 1.90366 31.32
30 -26.4237 15.5341
31 ∞ 2.0000 1.51680 64.20
32 ∞ (BF)

[Aspherical data]
6 faces 23 faces
K -1.28713E + 00 0.00000E + 00
A4 3.03098E-05 1.05989E-05
A6 -1.10729E-07 -8.95266E-09
A8 1.95111E-09 8.67772E-12
A10 -1.86588E-11 3.47060E-14
A12 9.78438E-14 -1.61820E-16
A14 -2.62044E-16 0.00000E + 00
A16 2.69032E-19 0.00000E + 00

[Various data]
Infinity 40x distance Focal length 16.45 16.33
F number 1.46 1.46
Full angle of view 2ω 84.21 84.15
Statue height Y 14.20 14.20
Total lens length 109.00 109.00

[Variable interval data]
Infinite 40x distance
d0 ∞ 635.6343
d23 3.3044 2.8751
d25 2.0917 2.5210
BF 1.0000 1.0000

[Lens group data]
Group Start surface Focal length
G1 1 -25.91
G2 19 24.01
G3 24 85.41
G4 26 -82.42
G1A 1 -25.04
G1B 10 168.02
G1Bp 10 28.72
G1Bm 14 -25.81

Numerical example 2
Unit: mm
[Surface data]
Surface number rd nd vd
Object ∞ (d0)
1 100.6872 3.3242 1.51680 64.20
2 236.8546 0.5000
3 39.4688 1.4000 2.00100 29.13
4 16.4449 4.0477
5 22.5196 1.5000 1.58913 61.25
6 * 15.6621 10.5586
7 -26.1497 1.1604 1.43700 95.10
8 79.7110 1.2000
9 1000.0000 3.5817 1.95375 32.32
10 -52.5650 2.9643
11 42.3963 4.1580 1.90043 37.37
12 -753.9792 1.1775
13 56.0924 5.5232 1.43700 95.10
14 -43.3855 0.5000
15 181.1714 0.9000 1.51742 52.15
16 20.8110 6.6312
17 -20.3921 0.9000 1.67270 32.17
18 -55.6488 2.1057
19 (Aperture) ∞ 0.2671
20 41.4805 12.9236 1.59282 68.63
21 -17.7486 0.9000 1.74950 35.33
22 -32.8047 0.1459
23 48.8278 5.3987 1.69350 53.20
24 * -75.9402 (d24)
25 30.5407 2.7492 1.59282 68.63
26 78.1622 (d26)
27 38.6406 0.9000 1.76182 26.61
28 17.6558 4.1056
29 -73.5847 7.0542 1.43700 95.10
30 -14.0977 0.9000 1.90366 31.32
31 -19.5528 13.3839
32 ∞ 2.0000 1.51680 64.20
33 ∞ (BF)

[Aspherical data]
6 faces 24 faces
K -9.78532E-01 0.00000E + 00
A4 1.92925E-05 1.56243E-05
A6 -2.13702E-08 -1.33093E-08
A8 6.18655E-10 2.09458E-11
A10 -7.40561E-12 1.08263E-13
A12 4.56561E-14 -7.24322E-16
A14 -1.49509E-16 0.00000E + 00
A16 1.80506E-19 0.00000E + 00

[Various data]
Infinity 40x distance Focal length 16.44 16.33
F number 1.45 1.45
Full angle of view 2ω 84.91 84.91
Statue height Y 14.20 14.20
Total lens length 109.00 109.00

[Variable interval data]
Infinite 40x distance
d0 ∞ 636.7527
d24 3.3035 2.8735
d26 1.8358 2.2657
BF 1.0000 1.0000

[Lens group data]
Group Start surface Focal length
G1 1 -22.36
G2 20 21.77
G3 25 82.78
G4 27 -84.82
G1A 1 -23.15
G1B 11 130.09
G1Bp 11 26.46
G1Bm 15 -21.99

Numerical Example 3
Unit: mm
[Surface data]
Surface number rd nd vd
Object ∞ (d0)
1 95.2257 4.0453 1.51680 64.20
2 357.0935 0.5000
3 41.6162 1.4000 2.00100 29.13
4 16.3588 4.5656
5 23.9246 1.5000 1.58913 61.25
6 * 16.1531 10.4950
7 -25.6306 1.0000 1.43700 95.10
8 439.0065 3.6637 2.00100 29.13
9 -52.3922 7.3261
10 61.0026 3.5501 1.87070 40.73
11 -219.7427 0.6000
12 129.3934 5.6837 1.43700 95.10
13 -32.8059 0.5000
14 -88.4504 0.9000 1.51823 58.96
15 38.7742 5.5159
16 -21.9599 0.9000 1.73800 32.26
17 -45.6391 0.2000
18 (Aperture) ∞ 1.9831
19 48.7365 10.4963 1.59282 68.63
20 -20.6660 0.9000 1.91082 35.25
21 -31.1743 1.3706
22 52.5444 4.5915 1.69350 53.20
23 * -96.7970 (d23)
24 27.0036 2.9000 1.59282 68.63
25 63.0775 (d25)
26 44.9637 0.9000 1.80518 25.46
27 18.4018 3.4985
28 -480.5824 6.4565 1.59282 68.63
29 -15.4094 0.9000 1.72047 34.71
30 -38.2503 14.3232
31 ∞ 2.0000 1.51680 64.20
32 ∞ (BF)

[Aspherical data]
6 faces 23 faces
K -1.21506E + 00 0.00000E + 00
A4 2.48353E-05 1.34319E-05
A6 -1.44515E-08 -1.28726E-08
A8 2.60789E-10 4.59671E-11
A10 -1.78767E-12 -7.54550E-15
A12 6.09349E-15 -3.84023E-16
A14 -8.73384E-18 0.00000E + 00
A16 -1.91956E-21 0.00000E + 00

[Various data]
Infinity 40x distance Focal length 16.45 16.32
F number 1.45 1.45
Full angle of view 2ω 84.74 84.76
Statue height Y 14.20 14.20
Total lens length 109.00 109.00

[Variable interval data]
Infinite 40x distance
d0 ∞ 637.8721
d23 3.1392 2.7385
d25 2.1943 2.5950
BF 1.0000 1.0000

[Lens group data]
Group Start surface Focal length
G1 1 -26.64
G2 19 23.67
G3 24 77.33
G4 26 -72.02
G1A 1 -27.87
G1B 10 270.57
G1Bp 10 30.24
G1Bm 14 -26.21

Numerical Example 4
Unit: mm
[Surface data]
Surface number rd nd vd
Object ∞ (d0)
1 29.7068 1.4000 1.91082 35.25
2 16.3123 5.9765
3 24.4270 1.5000 1.59201 67.02
4 * 15.0446 11.2811
5 -29.5919 1.8366 1.43700 95.10
6 86.2538 4.8970 2.00100 29.13
7 -66.3583 11.3007
8 40.4099 4.3428 1.77250 49.62
9 -396.1693 1.4000
10 -200.0000 3.0776 1.43700 95.10
11 -46.0612 0.1500
12 42.0657 0.9000 1.72825 28.32
13 24.1754 6.4301
14 -21.7511 0.9000 1.80518 25.46
15 -53.2348 0.2000
16 (Aperture) ∞ 1.8007
17 37.2472 10.2599 1.59282 68.63
18 -20.0538 0.9000 1.91082 35.25
19 -28.5443 0.1537
20 -1670.3205 2.1183 1.59201 67.02
21 * -69.6590 (d21)
22 27.7533 2.8269 1.59282 68.63
23 69.6966 (d23)
24 41.4875 0.9000 1.74330 49.22
25 18.8883 2.8398
26 77.6924 4.0856 1.83481 42.72
27 -33.5741 0.9000 1.90366 31.32
28 -162.3748 15.4224
29 ∞ 2.0000 1.51680 64.20
30 ∞ (BF)

[Aspherical data]
4 sides 21 sides
K -4.20578E-01 0.00000E + 00
A4 -5.35186E-06 1.77536E-05
A6 -7.13119E-08 -7.82012E-09
A8 3.53669E-10 1.91571E-10
A10 -4.97187E-12 -1.01910E-12
A12 2.25499E-14 2.48969E-15
A14 -5.37230E-17 0.00000E + 00
A16 0.00000E + 00 0.00000E + 00

[Various data]
Infinity 40x distance Focal length 16.43 16.33
F number 1.45 1.45
Full angle of view 2ω 84.19 84.04
Statue height Y 14.20 14.20
Total lens length 108.00 108.00

[Variable interval data]
Infinite 40x distance
d0 ∞ 637.3887
d21 3.6679 3.1551
d23 3.5326 4.0454
BF 1.0000 1.0000

[Lens group data]
Group Start surface Focal length
G1 1 -29.74
G2 17 26.87
G3 22 75.89
G4 24 -167.14
G1A 1 -38.18
G1B 8 2381.82
G1Bp 8 36.58
G1Bm 12 -28.08

Numerical Example 5
Unit: mm
[Surface data]
Surface number rd nd vd
Object ∞ (d0)
1 74.7843 3.5237 1.51680 64.20
2 146.1386 0.1500
3 27.6590 1.4000 2.00100 29.13
4 14.3489 6.5548
5 29.0436 1.5000 1.58913 61.25
6 * 14.6787 8.5331
7 -25.7342 1.0000 1.43700 95.10
8 -132.5227 2.3968 2.00100 29.13
9 -54.9184 2.4217
10 47.2774 0.9000 1.80518 25.46
11 30.0000 5.3800 1.90043 37.37
12 -137.3500 2.9301
13 123.8251 4.9415 1.49700 81.61
14 -31.7350 1.7682
15 -34.8493 0.9000 1.65844 50.86
16 24.7844 4.8578
17 (Aperture) ∞ 1.6941
18 37.1933 13.1129 1.59282 68.63
19 -20.7831 0.9000 1.74950 35.33
20 -38.2911 0.1500
21 49.4051 6.2262 1.59201 67.02
22 * -42.8067 (d22)
23 24.5399 2.6000 1.59282 68.63
24 39.9642 (d24)
25 69.9507 0.9000 1.80000 29.84
26 19.4382 3.0576
27 848.9719 6.9370 1.43700 95.10
28 -12.7121 0.9000 2.00100 29.13
29 -18.4130 13.2500
30 ∞ 2.0000 1.51680 64.20
31 ∞ (BF)

[Aspherical data]
6 faces 22 faces
K -7.87255E-01 0.00000E + 00
A4 1.23060E-05 1.28481E-05
A6 -4.58967E-08 -2.34271E-08
A8 4.71467E-10 1.26978E-10
A10 -5.34441E-12 -5.47682E-13
A12 3.45392E-14 9.88849E-16
A14 -1.52463E-16 0.00000E + 00
A16 1.03760E-19 0.00000E + 00

[Various data]
Infinity 40x distance Focal length 16.44 16.32
F number 1.45 1.45
Full angle of view 2ω 83.76 83.81
Statue height Y 14.20 14.20
Total lens length 108.50 108.50

[Variable interval data]
Infinite 40x distance
d0 ∞ 636.7264
d22 3.4132 2.9539
d24 3.2010 3.6603
BF 1.0000 1.0000

[Lens group data]
Group Start surface Focal length
G1 1 -20.55
G2 18 21.50
G3 23 100.92
G4 25 -68.24
G1A 1 -19.02
G1B 10 91.87
G1Bp 10 24.02
G1Bm 15 -21.87

Numerical Example 6
Unit: mm
[Surface data]
Surface number rd nd vd
Object ∞ (d0)
1 36.3560 1.4000 1.91082 35.25
2 19.6782 2.9306
3 23.3439 1.5000 1.59201 67.02
4 * 16.4423 5.0475
5 33.5393 1.5698 1.49700 81.61
6 20.4459 9.5359
7 -34.1263 1.0002 1.43700 95.10
8 94.8850 3.9111 2.00100 29.13
9 -99.4044 6.9820
10 36.4242 4.0936 1.88300 40.80
11 211.4628 1.4000
12 -384.1715 3.7695 1.49700 81.61
13 -40.9155 1.6740
14 30.9691 0.9000 1.60342 38.01
15 20.0089 7.0945
16 -19.4954 0.9000 1.78472 25.72
17 -86.5897 1.0449
18 (Aperture) ∞ 0.9551
19 29.6354 12.4657 1.59282 68.63
20 -19.1175 0.9000 1.91082 35.25
21 -29.3199 0.7067
22 47.9016 3.5297 1.59201 67.02
23 * -100.0000 (d23)
24 28.2698 2.6610 1.59282 68.63
25 61.9503 (d25)
26 32.3972 0.9000 1.71700 47.98
27 17.8241 3.5563
28 264.0007 3.1615 1.70154 41.15
29 -45.5883 0.9000 1.90366 31.32
30 -125.2049 15.3103
31 ∞ 2.0000 1.51680 64.20
32 ∞ (BF)

[Aspherical data]
4 sides 23 sides
K -2.17940E-01 0.00000E + 00
A4 -5.51944E-06 2.40325E-05
A6 -4.85282E-08 6.31999E-09
A8 3.49561E-10 4.65758E-11
A10 -3.07066E-12 3.61472E-13
A12 1.08195E-14 -9.18950E-16
A14 -1.79912E-17 0.00000E + 00
A16 0.00000E + 00 0.00000E + 00

[Various data]
Infinity 40x distance Focal length 16.46 16.32
F number 1.45 1.45
Full angle of view 2ω 84.92 84.89
Statue height Y 14.20 14.20
Total lens length 108.50 108.50

[Variable interval data]
Infinite 40x distance
d0 ∞ 637.0828
d23 3.6349 3.1249
d25 2.0621 2.5721
BF 1.0000 1.0000

[Lens group data]
Group Start surface Focal length
G1 1 -19.63
G2 19 21.51
G3 24 85.21
G4 26 -85.00
G1A 1 -27.79
G1B 10 591.35
G1Bp 10 33.70
G1Bm 14 -23.13

  In [Conditional Expression Corresponding Values], a list of corresponding values of each embodiment corresponding to each conditional expression is shown.

[Conditional expression values]
Conditional Expression 1 Conditional Expression 2 Conditional Expression 3 Conditional Expression 4 Conditional Expression 5
Example f1 / f f1A / f1B f1A / f4 D1B / D1S β1Bp
1 -1.58 -0.15 0.30 0.63 -1.17
2 -1.36 -0.18 0.27 0.58 -1.21
3 -1.62 -0.10 0.39 0.66 -1.04
4 -1.81 -0.02 0.23 0.69 -0.81
5 -1.25 -0.21 0.28 0.56 -1.51
6 -1.19 -0.05 0.33 0.62 -1.38

Conditional Expression 6 Conditional Expression 7 Conditional Expression 8 Conditional Expression 9
Example ν1Bp f2 / f3 SI / f3 EXP / IH
1 65.18 0.28 0.66 3.56
2 66.24 0.26 0.69 3.90
3 67.92 0.31 0.73 3.69
4 72.36 0.35 0.69 3.41
5 59.49 0.21 0.59 3.96
6 61.21 0.25 0.63 3.32

G1 1st lens group G1A 1A lens group G1B 1B lens group G1Bp 1Bp lens group G1Bm 1Bm lens group G2 2nd lens group G3 3rd lens group G4 4th lens group S Aperture stop F Filter I Image surface

Claims (6)

In order from the object side, the first lens group G1 having negative refractive power, the aperture stop S, the second lens group G2 having positive refractive power, the third lens group G3 having positive refractive power, and the negative refractive power 4th lens group G4,
The first lens group G1 includes, in order from the object side, a first A lens group G1A having a negative refractive power and a first B lens group G1B having a positive refractive power, and the most object side lens of the first B lens group G1B is the above-mentioned lens. A single lens or a cemented lens having a positive refractive power having the largest absolute value of lateral magnification in the first lens group G1,
A large-aperture wide-angle lens characterized in that the third lens group G3 moves toward the object side along the optical axis during focusing from infinity to a short distance, and satisfies the following conditional expressions (1), (2), and (3).
(1) -2.4 <f1 / f <-0.6
(2) -0.3 <f1A / f1B <0.0
(3) 0.1 <f1A / f4 <0.5
However,
f: focal length of the entire lens system at the time of focusing on infinity f1: focal length of the first lens group G1 f1A: focal length of the first A lens group G1A f1B: focal length of the first B lens group G1B f4: fourth lens group Focal length of G4 In order from the object side, the first lens group G1 having negative refractive power, the aperture stop S, the second lens group G2 having positive refractive power, the third lens group G3 having positive refractive power, and the negative refractive power 4th lens group G4,
The first lens group G1 includes, in order from the object side, a first A lens group G1A having a negative refractive power and a first B lens group G1B having a positive refractive power, and the most object side lens of the first B lens group G1B is the above-mentioned lens. A single lens or a cemented lens having a positive refractive power having the largest absolute value of lateral magnification in the first lens group G1,
The first B lens group G1B is composed of a first Bp lens group G1Bp having a positive refractive power and a first Bm lens group G1Bm having a negative refractive power in order from the object side.
The position at which the first Bp lens group G1Bp and the first Bm lens group G1Bm are separated is such that the lateral magnification of the combined optical system of the lens group from the first Bm lens group G1Bm to the image plane is maximum when focusing on infinity in the first B lens group G1B. And the air spacing becomes
A large-aperture wide-angle lens characterized in that the third lens group G3 moves toward the object side along the optical axis during focusing from infinity to a short distance, and satisfies the following conditional expressions (1), (2), and (3).
(1) -2.4 <f1 / f <-0.6
(2) -0.3 <f1A / f1B <0.0
(3) 0.1 <f1A / f4 <0.5
However,
f: focal length of the entire lens system at the time of focusing on infinity f1: focal length of the first lens group G1 f1A: focal length of the first A lens group G1A f1B: focal length of the first B lens group G1B f4: fourth lens group Focal length of G4 The first B lens group G1B is composed of a first Bp lens group G1Bp having a positive refractive power and a first Bm lens group G1Bm having a negative refractive power in order from the object side.
The position at which the first Bp lens group G1Bp and the first Bm lens group G1Bm are separated is such that the lateral magnification of the combined optical system of the lens group from the first Bm lens group G1Bm to the image plane is maximum when focusing on infinity in the first B lens group G1B. The large-aperture wide-angle lens according to claim 1, wherein the following air condition is satisfied and the following conditional expression (4) is satisfied.
(4) 0.5 <D1B / D1S <0.75
However,
D1B: Length on the optical axis from the most object side surface of the first lens group G1 to the most object side surface of the first B lens group G1B D1S: From the most object side surface of the first lens group G1 to the stop Length on the optical axis The first Bp lens group G1Bp has two or more convex lenses, and the lateral magnification of the first Bp lens group G1Bp and the first Bm lens group G1Bm at the time of focusing at infinity is negative, and the following conditional expression (5) The large-aperture wide-angle lens according to claim 2 or 3, wherein (6) is satisfied.
(5) −1.8 <β1Bp <−0.6
(6) 50 <ν1Bp <80
However,
β1Bp: lateral magnification of the first Bp lens group G1Bp when focused at infinity ν1Bp: average Abbe number of convex lenses in the first Bp lens group G1Bp 5. The large-aperture wide-angle lens according to claim 1, wherein the third lens group G <b> 3 is composed of a single convex lens and satisfies the following conditional expressions (7) and (8).
(7) 0.1 <f2 / f3 <0.44
(8) 0.52 <SI / f3 <1.0
However,
f2: Focal length of the second lens group G2 f3: Focal length SI of the third lens group G3: Length from the stop to the image plane when focusing on infinity The large-aperture wide-angle lens according to claim 1, wherein the following conditional expression (9) is satisfied.
(9) 2.5 <EXP / IH <4.5
However,
EXP: Length from exit pupil to image plane when focusing on infinity IH: Maximum image height

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