JP2014052503A - Fish-eye lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact fish-eye lens which includes an inner focus function and an image position correction function which are capable of excellently photographing a moving image and is excellent in optical performance.SOLUTION: The fish-eye lens comprises, in order from an object side, a first lens group Ghaving positive refractive power, a second lens group Ghaving negative refractive power, and a third lens group Ghaving positive refractive power. A positive lens Lincluded in the first lens group Gis arranged in the vicinity of an aperture diaphragm S and has the function of an image position correction optical system. The second lens group Gcomprises a negative lens Larranged in the vicinity of the aperture diaphragm S and has a focus function. Then, by satisfying a predetermined condition, the compact fish-eye lens which is excellent in optical performance can be achieved.

Description

  The present invention relates to a fisheye lens, and more particularly to a small fisheye lens suitable for a digital camera, particularly a digital single lens reflex camera.

  Most conventional general fish-eye lenses are focused by the entire pay-out system, and most of them do not have an image position correcting optical system. In focusing by the entire payout method, it takes time to drive the lens during focusing. However, in the case of still image shooting, even if it takes some time to drive the lens during focusing, there was no problem. In addition, since the fisheye lens has a relatively short focal length, there is little risk of blurring of the captured image in still image shooting, and a camera shake correction function is not particularly required.

  However, in recent years, an increasing number of digital cameras including a digital single-lens reflex camera have a moving image shooting function. In moving image shooting, focusing time reduction and a camera shake correction function are required compared to still image shooting. Therefore, a fisheye lens mounted on a camera having a moving image shooting function is desired to have a function for performing rapid focusing and a function for correcting camera shake.

  However, there is no fisheye lens having such two functions in the past, and a fisheye lens that emphasizes only the focus function (see, for example, Patent Document 1) is used, or another type that has an image position correction function that performs camera shake correction. There was no method other than substituting an optical system (for example, see Patent Document 2).

JP2012-22109A Japanese Patent No. 3412964

  The fish-eye lens described in Patent Document 1 can perform quick focusing by providing the inner focus function, but has a problem that the optical system itself cannot perform camera shake correction because it does not have an image position correction function.

  The optical system described in Patent Document 2 is an inner focus optical system that has an image position correction function and prevents a decrease in optical performance when an image position correction effect is exhibited. However, since this optical system is intended for use as a telephoto lens with a relatively long focal length, if it is used in place of a wide-angle or fish-eye lens, the image position correction angle is insufficient, and good video shooting is possible. Have difficulty. There is a limit in using the optical system described in Patent Document 2 as a substitute for a fisheye lens in a camera having a moving image shooting function.

  The present invention is to provide a small-sized fisheye lens having an excellent optical performance, which has an inner focus function and an image position correction function that enable good moving image shooting in order to solve the above-described problems caused by the conventional technology. Objective.

In order to solve the above-described problems and achieve the object, a fisheye lens according to the present invention includes a first lens group having a positive refractive power and a second lens having a positive or negative refractive power, which are sequentially arranged from the object side. A first lens group, and a third lens group having a positive refractive power, the second lens group is moved along the optical axis to perform focusing from an object at infinity to a near object, and the first lens At least a part of the group or at least a part of the third lens group has a function as an image position correction optical system for correcting an image position by moving in a direction orthogonal to the optical axis, and the second lens group An aperture stop is disposed in the vicinity of the image position correcting optical system and satisfies the following conditional expression.
(1) 1.0 ≦ | fv | /f≦5.0
(2) 1.0 ≦ | f2 | /f≦10.0
Here, fv is a focal length of the image position correcting optical system, f is a focal length of the whole fisheye lens system at the time of photographing an object at infinity, and f2 is a focal length of the second lens group.

  According to the present invention, it is possible to provide a small-sized fisheye lens having an excellent optical performance, which is provided with an inner focus function and an image position correction function that enable good moving image shooting.

The fisheye lens according to the present invention is characterized in that, in the above invention, the first lens group includes a negative lens component and satisfies the following conditional expression.
(3) 0.5 ≦ ff / Gn1B ≦ 5.0
However, ff represents the focal length of the lens system disposed on the object side of the aperture stop, and Gn1B represents the air space from the negative lens component disposed on the most object side of the first lens group to the next lens component. .

  According to the present invention, it is possible to reduce the size of the second lens group that performs focusing and the image position correction optical system that corrects the image position, thereby providing a smaller fisheye lens.

The fisheye lens according to the present invention is characterized in that, in the above invention, the following conditional expression is satisfied.
(4) 100 ≦ f / tan θv ≦ 6000
Here, θv represents an image position correction angle by the image position correction optical system.

  According to the present invention, better image position correction can be realized.

The fisheye lens according to the present invention is characterized in that, in the above invention, the following conditional expression is satisfied.
(5) ff ′ ≦ 0
Here, f ′ represents the focal length of the entire fish-eye lens system when shooting a short-distance object (shooting magnification is 1/40).

  According to the present invention, an appropriate angle of view is ensured at the time of photographing a short distance object with a fisheye lens, and a good image can be obtained.

  According to the present invention, there is an effect that it is possible to provide a small-sized fisheye lens having an excellent optical performance, which is provided with an inner focus function and an image position correction function that enable good moving image shooting. In particular, a large image position correction angle can be ensured, and deterioration of optical performance can be prevented while sufficiently exhibiting the image position correction effect. The fisheye lens of the present invention is suitable for a small digital camera, particularly a digital single lens reflex camera.

1 is a cross-sectional view along the optical axis showing the configuration of a fisheye lens according to Example 1. FIG. FIG. 6 is a diagram illustrating various aberrations with respect to d-line when an object at infinity is photographed by the fisheye lens according to Example 1; FIG. 6 is a cross-sectional view along the optical axis showing the configuration of a fisheye lens according to Example 2. FIG. 10 is a diagram illustrating various aberrations with respect to the d-line when an object at infinity is photographed by the fisheye lens according to Example 2; FIG. 6 is a cross-sectional view along the optical axis showing the configuration of a fisheye lens according to Example 3; FIG. 10 is a diagram illustrating various aberrations with respect to d-line when an object at infinity is photographed by a fisheye lens according to Example 3; FIG. 6 is a cross-sectional view along the optical axis showing the configuration of a fisheye lens according to Example 4; FIG. 12 is a diagram illustrating various aberrations with respect to d-line when an object at infinity is photographed by a fisheye lens according to Example 4;

  Hereinafter, a preferred embodiment of a fisheye lens according to the present invention will be described in detail.

  The fisheye lens according to the present invention includes a first lens group having a positive refractive power, a second lens group having a positive or negative refractive power, and a third lens having a positive refractive power, which are arranged in order from the object side. And a group.

  It is an object of the present invention to provide a small-sized fisheye lens suitable for a small-sized digital camera having a moving image shooting function that is becoming popular in recent years, particularly a digital single-lens reflex camera. In order to achieve this object, the fish-eye lens is required to have high optical performance in addition to an inner focus function and an image position correction function that enable good moving image shooting. Therefore, in the present invention, various conditions as shown below are set in order to meet such a requirement.

  The fisheye lens according to the present invention performs focusing from an infinitely distant object to a close object by moving the second lens group along the optical axis. Further, at least a part of the first lens group or at least a part of the third lens group has a function as an image position correcting optical system for correcting the image position. That is, the image position correction optical system is moved in a direction orthogonal to the optical axis to correct the image position due to camera shake during photographing.

  In the fisheye lens according to the present invention, an aperture stop is disposed in the vicinity of the second lens group and the image position correcting optical system. The aperture of the second lens group and the image position correcting optical system is arranged by arranging the second lens group as the focus group and the image position correcting optical system as the image stabilizing group in the vicinity of the aperture stop having the smallest beam diameter in the optical system. Can be reduced. By doing so, the second lens group and the image position correcting optical system can be reduced in size and weight. As a result, it is possible to reduce the weight load on the driving mechanism of the second lens group and the image position correcting optical system.

In addition, in the fisheye lens according to the present invention, in order to obtain excellent optical performance, the focal length of the image position correcting optical system is fv, the focal length of the entire fisheye lens system at the time of photographing an infinite object is f, and the focal point of the second lens group When the distance is f2, it is preferable that the following conditional expression is satisfied.
(1) 1.0 ≦ | fv | /f≦5.0
(2) 1.0 ≦ | f2 | /f≦10.0

  Conditional expression (1) shows the relationship between the focal length of the whole fisheye lens system and the focal length of the image position correcting optical system when photographing an object at infinity. By satisfying conditional expression (1), the focal length of the image position correcting optical system becomes relatively long, and its power can be weakened. As the power becomes weaker, various aberrations generated in the lens group including the image position correcting optical system can be suppressed. As a result, it is possible to suppress the occurrence of various aberrations while ensuring a large image position correction angle.

  If the lower limit value of conditional expression (1) is not reached, the focal length of the image position correcting optical system becomes too short and the power becomes too strong. For this reason, in order to perform quick image position correction, it is difficult to suppress the occurrence of various aberrations in the image position correction optical system in which the weight is reduced and the number of lenses is reduced as much as possible, and the image position correction angle is increased. I can't. On the other hand, if the upper limit value in conditional expression (1) is exceeded, the focal length of the image position correcting optical system becomes too long and the power becomes too weak. For this reason, unless the amount of movement in the direction orthogonal to the optical axis of the position correction optical system is increased, good image position correction cannot be performed. As a result, the fisheye lens is increased in size in the radial direction.

  Conditional expression (2) shows the relationship between the focal length of the whole fisheye lens system at the time of photographing an object at infinity and the focal length of the second lens group which is a focus group. By satisfying conditional expression (2), the focal length of the second lens group becomes relatively long, and its power can be weakened. For this reason, it becomes possible to suppress various aberrations generated in the second lens group, and good optical performance can be maintained.

  If the lower limit value of conditional expression (2) is not reached, the focal length of the second lens group, which is the focus group, becomes too short and its power becomes too strong. For this reason, it is difficult to suppress the occurrence of various aberrations in the second lens group in which the weight is reduced and the number of lenses is minimized. On the other hand, if the upper limit value is exceeded in the conditional expression (2), the focal length of the second lens group becomes too long and the power becomes too weak. For this reason, unless the amount of movement of the second lens group is increased, good focusing cannot be achieved. As a result, the entire length of the fisheye lens is extended.

In addition, if the conditional expressions (1) and (2) satisfy the following ranges, more favorable effects can be expected.
(1a) 1.5 ≦ | fv | /f≦4.4
(2a) 2.0 ≦ | f2 | /f≦9.0
If the range defined by the conditional expressions (1a) and (2a) is satisfied, a small fisheye lens having a more excellent image position correction function and aberration correction function can be realized.

Furthermore, when the conditional expressions (1a) and (2a) satisfy the following ranges, further preferable effects can be expected.
(1b) 2.0 ≦ | fv | /f≦3.8
(2b) 2.8 ≦ | f2 | /f≦8.0
If the range defined by the conditional expressions (1b) and (2b) is satisfied, a small fisheye lens having an extremely excellent image position correction function and aberration correction function can be realized.

Furthermore, in the fisheye lens according to the present invention, the first lens group includes a negative lens component, and the focal length of the lens system disposed on the object side relative to the aperture stop is ff, and is disposed on the most object side of the first lens group. When the air interval from the negative lens component to the next lens component is Gn1B, it is preferable that the following conditional expression is satisfied.
(3) 0.5 ≦ ff / Gn1B ≦ 5.0

  Conditional expression (3) is the relationship between the focal length of the lens system arranged on the object side from the aperture stop and the air interval from the negative lens component arranged closest to the object side of the first lens group to the next lens component. Is shown. If the absolute value of the value of ff is reduced, the aperture stop diameter and the aperture of the surrounding optical system are reduced, and the on-axis light beam and off-axis light beam can be collected. However, due to the nature of a fish-eye lens in which a negative lens component is disposed on the most object side, correction of various aberrations becomes difficult if the absolute value of ff is small. Therefore, in the present invention, the negative lens component is utilized by setting the air interval from the negative lens component disposed on the most object side to the next lens component within an appropriate range that satisfies the conditional expression (3). Fully correct the various aberrations.

  Further, when the conditional expression (3) is satisfied, the apertures of the image position correction optical system and the second lens group can be reduced to reduce the weight, and the weight applied to the driving mechanism of the second lens group and the image position correction optical system. The load can also be reduced. As a result, these drive controls become easy and can be driven quickly. In particular, with a fish-eye lens, if the image position correction angle is not taken large, the effect of image position correction is diminished. Therefore, it is particularly important to reduce the size and weight of the image position correction optical system.

  If the lower limit value of conditional expression (3) is not reached, a fish-eye lens in which many negative lens components are arranged on the object side has a shorter positive focal length of the lens system on the object side than the aperture stop, and the power is strong. Thus, it becomes difficult to correct various aberrations. On the other hand, if the upper limit is exceeded in conditional expression (3), the aperture stop, the surrounding image position correcting optical system, and the aperture of the second lens group cannot be reduced. As a result, the image position correcting optical system and the second lens group are increased in weight, and the weight load applied to the driving mechanism of the second lens group and the image position correcting optical system cannot be reduced. It becomes difficult and becomes a lens unsuitable for moving image shooting.

In addition, if the said conditional expression (3) satisfies the range shown next, a more preferable effect can be anticipated.
(3a) 0.55 ≦ ff / Gn1B ≦ 4.0
If the range defined by the conditional expression (3a) is satisfied, it is possible to provide a better aberration correction function while reducing the diameters of the image position correction optical system and the second lens group.

Furthermore, if the said conditional expression (3a) satisfies the range shown next, the further preferable effect can be anticipated.
(3b) 0.6 ≦ ff / Gn1B ≦ 3.5
If the range defined by this conditional expression (3b) is satisfied, an extremely good aberration correction function can be provided while reducing the apertures of the image position correction optical system and the second lens group.

Furthermore, in the fisheye lens according to the present invention, it is preferable that the following conditional expression is satisfied when the focal length of the entire fisheye lens system at the time of photographing an object at infinity is f and the image position correction angle by the image position correction optical system is θv. .
(4) 100 ≦ f / tan θv ≦ 6000

  Conditional expression (4) shows the relationship between the focal length of the whole fisheye lens system and the image position correction angle by the image position correction optical system when photographing an object at infinity. In general, when performing wide-angle shooting with a fisheye lens, if the image position correction angle by the image position correction optical system is small, the image position correction effect cannot be exhibited sufficiently. In order to avoid this inconvenience, in the present invention, satisfactory image position correction can be performed by satisfying conditional expression (4).

  If the lower limit value of conditional expression (4) is not reached, the image position correction angle by the image position correction optical system becomes too large, and it becomes difficult to correct various aberrations by the image position correction optical system. On the other hand, if the upper limit value in conditional expression (4) is exceeded, the image position correction effect by the image position correction optical system becomes thin, and it becomes difficult to reduce image blur especially during moving image shooting.

In addition, if the said conditional expression (4) satisfies the range shown next, a more preferable effect can be anticipated.
(4a) 150 ≦ f / tan θv ≦ 1000
If the range defined by the conditional expression (4a) is satisfied, a better image position correction function can be provided.

Furthermore, when the conditional expression (4a) satisfies the following range, a further preferable effect can be expected.
(4b) 170 ≦ f / tan θv ≦ 300
If the range defined by the conditional expression (4b) is satisfied, an extremely good image position correcting function can be provided.

Further, in the fisheye lens according to the present invention, the focal length of the whole fisheye lens system when photographing an object at infinity is f, and the focal length of the whole fisheye lens system when photographing a short distance object (imaging magnification is 1/40 times) is f ′. It is preferable that the following conditional expression is satisfied.
(5) ff ′ ≦ 0

  Conditional expression (5) shows the relationship between the focal length of the entire fish-eye lens system when shooting an object at infinity and the focal length of the entire fish-eye lens system when shooting a short-distance object (imaging magnification is 1/40). In the fish-eye lens of the present invention, when the object distance becomes a short distance, the second lens group, which is a focus group, is moved along the optical axis to be focused. If the focal length of the entire lens system is shortened due to the movement of the second lens group, the angle of view becomes large, and there is a possibility that the periphery of the photographing screen may be vignetted or the photographing equipment or the photographer himself may be reflected. In order to avoid this inconvenience, it is necessary to set the focal length so that the angle of view at the time of shooting an object at close distance does not exceed the angle of view at the time of shooting an object at infinity. In the fisheye lens according to the present invention, when the conditional expression (5) is satisfied, it is possible to set an appropriate focal length at the time of photographing a short-distance object.

  As described above, the fish-eye lens according to the present invention is small and excellent with the above-described configuration and the inner focus function and the image position correction function that enable satisfactory moving image shooting by satisfying the above conditional expressions. It becomes a fisheye lens having optical performance. In particular, a large image position correction angle can be ensured, and deterioration of optical performance can be prevented while sufficiently exhibiting the image position correction effect. The fisheye lens of the present invention is suitable for a small digital camera, particularly a digital single lens reflex camera.

  Embodiments of a fisheye lens according to the present invention will be described below in detail with reference to the drawings. In addition, this invention is not limited by the following examples.

FIG. 1 is a cross-sectional view along the optical axis showing the configuration of the fisheye lens according to the first embodiment. This fish-eye lens includes a first lens group G ₁₁ having a positive refractive power, a second lens group G ₁₂ having a negative refractive power, and a third lens group G having a positive refractive power in order from the object side (not shown). ₁₃ are arranged.

A first lens group G ₁₁ is provided between the second lens group G _12, an aperture stop S is disposed to define a predetermined diameter. Between the third lens group G ₁₃ and an image plane IMG, filter group F such infrared cut filter is disposed. Note that the light receiving surface of the image sensor is disposed on the image plane IMG.

The first lens group G ₁₁ includes, in order from the object side, a negative lens L _111, a negative lens L _112, a positive lens L _113, a positive lens L _114, is formed are disposed. The positive lens L ₁₁₄ is disposed in the vicinity of the aperture stop S, and an aspheric surface is formed on both surfaces thereof. The positive lens L ₁₁₄ has the function of the image position correcting optical system. That is, image position correction is performed by moving the positive lens L ₁₁₄ in a direction orthogonal to the optical axis.

The second lens group G ₁₂ includes, is composed of a negative lens L _121. The negative lens L ₁₂₁ is disposed in the vicinity of the aperture stop S, and an aspheric surface is formed on both surfaces thereof. The second lens group G _12, and thereby play a function as a focus group. That is, by moving from the object side to the image side along the second lens group G ₁₂ to the optical axis to perform focusing from an infinity object to a close object.

The third lens group G ₁₃ is constituted in order from the object side, a negative lens L _131, a positive lens L _132, a positive lens L _133, a negative lens L _134, a positive lens L _135, is the placement . The negative lens L ₁₃₁ and the positive lens L ₁₃₂ are cemented. The positive lens L ₁₃₃ and the negative lens L ₁₃₄ are also cemented.

  Various numerical data relating to the fisheye lens according to Example 1 will be described below.

f (focal length of the whole fisheye lens system when shooting an object at infinity) = 9.707
Fno. (F number) = 2.87
ω (half angle of view) = 90.50

(Lens data)
r ₁ = 40.820
d ₁ = 2.000 nd ₁ = 1.883 νd ₁ = 40.81
r ₂ = 12.969
d ₂ = 12.306
r ₃ = -36.811
d ₃ = 1.500 nd ₂ = 1.883 νd ₂ = 40.81
r ₄ = 22.349
d ₄ = 4.408
r ₅ = 90.887
d ₅ = 4.119 nd ₃ = 2.001 νd ₃ = 25.46
r ₆ = -37.463
d ₆ = 10.671
r ₇ = 19.865 (aspherical surface)
d ₇ = 4.906 nd ₄ = 1.497 νd ₄ = 81.56
r ₈ = -19.386 (aspherical surface)
d ₈ = 5.000
r ₉ = ∞ (aperture stop)
d ₉ = 1.100
r ₁₀ = 67.768 (aspherical surface)
d ₁₀ = 1.000 nd ₅ = 1.821 νd ₅ = 24.06
r ₁₁ = 17.746 (aspherical surface)
d ₁₁ = 3.083
r ₁₂ = 22.334
d ₁₂ = 1.000 nd ₆ = 2.001 νd ₆ = 25.46
r ₁₃ = 17.027
_{d 13 = 2.141 nd 7 = 1.497} νd 7 = 81.61
r ₁₄ = 31.952
d ₁₄ = 0.671
r ₁₅ = 43.402
d ₁₅ = 4.088 nd ₈ = 1.497 νd ₈ = 81.61
r ₁₆ = -21.820
d ₁₆ = 1.000 nd ₉ = 2.003 νd ₉ = 19.32
r ₁₇ = -29.680
d ₁₇ = 0.300
r ₁₈ = 31.251
d ₁₈ = 2.707 nd ₁₀ = 1.883 νd ₁₀ = 40.81
r ₁₉ = 76.213
d ₁₉ = 1.000
r ₂₀ = ∞
d ₂₀ = 3.000 nd ₁₁ = 1.517 νd ₁₁ = 64.20
r ₂₁ = ∞
d ₂₁ = 14.000
r ₂₂ = ∞ (image plane)

Cone coefficient (k) and aspheric coefficient (A, B, C, D)
(Seventh side)
k = 0,
A = -1.5313 × 10 ^-5 , B = 9.4893 × 10 ^-8 ,
C = -1.8128 × 10 ^-9 , D = 8.7528 × 10 ^-12
(8th page)
k = 0,
A = 9.4784 × 10 ⁻⁵ , B = −5.6706 × 10 ⁻⁷ ,
C = 3.1435 × 10 ⁻⁹ , D = −5.8172 × 10 ⁻¹²
(Tenth aspect)
k = 0,
A = 3.9901 × 10 ⁻⁴ , B = -1.4077 × 10 ⁻⁵ ,
C = 2.7313 × 10 ⁻⁷ , D = −2.6707 × 10 ⁻⁹
(11th page)
k = 0,
A = 3.8524 × 10 ⁻⁴ , B = −1.3527 × 10 ⁻⁵ ,
C = 2.3317 × 10 ⁻⁷ , D = −1.7242 × 10 ⁻⁹

(Numerical values related to conditional expression (1))
fv (focal length of the positive lens L ₁₁₄ ) = 20.592
| Fv | /f=2.121

(Numerical value related to conditional expression (2))
f2 (the focal length of the second lens group G ₁₂₎ = - 29.544
| F2 | /f=3.044

(Numerical values related to conditional expression (3))
ff (focal length of the lens system disposed on the object side of the aperture stop S) = 10.103
Gn1B (air distance from the negative lens L ₁₁₁ to the negative lens L ₁₁₂ ) = 12.306
ff / Gn1B = 0.817

(Numerical values related to conditional expression (4))
θv (image position correction angle by positive lens L ₁₁₄ ) = 3.057
f / tan θv = 181.779

(Numerical values related to conditional expression (5))
f ′ (focal length of the whole fisheye lens system when shooting a short-distance object (shooting magnification is 1/40 ×)) = 9.718
ff '=-0.011

  FIG. 2 is a diagram illustrating various aberrations with respect to the d-line (λ = 587.56 nm) when the fisheye lens according to Example 1 is used to photograph an object at infinity. In the astigmatism diagrams, S and M represent aberrations with respect to the sagittal image surface and the meridional image surface, respectively. Further, in the distortion diagram, the shift amount by the equidistant projection method (Y = fθ) is displayed (Y: image height, f: focal length of the entire optical system, θ: half angle of view).

FIG. 3 is a cross-sectional view along the optical axis showing the configuration of the fisheye lens according to the second embodiment. The fish-eye lens includes a first lens group G ₂₁ having a positive refractive power, a second lens group G ₂₂ having a positive refractive power, and a third lens group G having a positive refractive power in order from an object side (not shown). _{And 23} are arranged.

An aperture stop S that defines a predetermined aperture is disposed between the second lens group G ₂₂ and the third lens group G ₂₃ . Between the third lens group G ₂₃ and an image plane IMG, filter group F such infrared cut filter is disposed. Note that the light receiving surface of the image sensor is disposed on the image plane IMG.

The first lens group G ₂₁ includes a negative lens L ₂₁₁ , a negative lens L _212, and a positive lens L ₂₁₃ arranged in order from the object side.

The second lens group G ₂₂ includes, a positive lens L _221. The positive lens L ₂₂₁ is disposed in the vicinity of the aperture stop S. Further, the second lens group G _22, and thereby play a function as a focus group. That is, by moving from the image side to the object side along the second lens group G ₂₂ to the optical axis to perform focusing from an infinity object to a close object.

The third lens group G ₂₃ includes, in order from the object side, a negative lens L _231, a negative lens L _232, a positive lens L _233, a positive lens L _234, a negative lens L _235, a positive lens L _236, but Arranged and configured. The negative lens L ₂₃₂ and the positive lens L ₂₃₃ are cemented. The positive lens L ₂₃₄ and the negative lens L ₂₃₅ are also cemented. The negative lens L ₂₃₁ is disposed in the vicinity of the aperture stop S, and an aspheric surface is formed on both surfaces thereof. Further, the negative lens L ₂₃₁ has a function of an image position correcting optical system. That is, image position correction is performed by moving the negative lens L ₂₃₁ in a direction orthogonal to the optical axis.

  Various numerical data related to the fisheye lens according to Example 2 are shown below.

f (focal length of the whole fisheye lens system when shooting an object at infinity) = 9.712
Fno. (F number) = 2.85
ω (half angle of view) = 90.00

(Lens data)
r ₁ = 54.753
d ₁ = 2.000 nd ₁ = 1.883 νd ₁ = 40.81
r ₂ = 17.826
d ₂ = 16.368
r ₃ = −54.112
d ₃ = 2.000 nd ₂ = 1.497 νd ₂ = 81.61
r ₄ = 20.495
d ₄ = 13.865
r ₅ = 39.300
d ₅ = 4.500 nd ₃ = 1.904 νd ₃ = 31.32
r ₆ = -117.735
d ₆ = 11.294
r ₇ = 18.962
d ₇ = 2.096 nd ₄ = 1.883 νd ₄ = 40.81
r ₈ = 70.614
d ₈ = 2.521
r ₉ = ∞ (aperture stop)
d ₉ = 1.237
r ₁₀ = -24.333 (aspherical surface)
d ₁₀ = 1.000 nd ₅ = 1.517 νd ₅ = 64.20
r ₁₁ = 42.193 (aspherical surface)
d ₁₁ = 0.677
r ₁₂ = 75.518
d ₁₂ = 1.000 nd ₆ = 1.946 νd ₆ = 17.98
r ₁₃ = 10.764
d ₁₃ = 2.769 nd ₇ = 1.786 νd ₇ = 43.93
r ₁₄ = -66.665
d ₁₄ = 0.200
r ₁₅ = 31.929
d ₁₅ = 4.742 nd ₈ = 1.497 νd ₈ = 81.61
r ₁₆ = -9.593
d ₁₆ = 1.000 nd ₉ = 1.723 νd ₉ = 37.99
r ₁₇ = 172.213
d ₁₇ = 0.429
r ₁₈ = 55.304
d ₁₈ = 3.665 nd ₁₀ = 1.923 νd ₁₀ = 20.88
r ₁₉ = -34.254
d ₁₉ = 1.000
r ₂₀ = ∞
d ₂₀ = 3.000 nd ₁₁ = 1.517 νd ₁₁ = 64.20
r ₂₁ = ∞
d ₂₁ = 14.637
r ₂₂ = ∞ (image plane)

Cone coefficient (k) and aspheric coefficient (A, B, C, D)
(Tenth aspect)
k = 0,
A = 6.2842 × 10 ⁻⁴ , B = −2.2904 × 10 ⁻⁵ ,
C = 5.9425 × 10 ⁻⁷ , D = −7.1578 × 10 ⁻⁹
(11th page)
k = 0,
A = 6.0112 × 10 ⁻⁴ , B = −2.1167 × 10 ⁻⁵ ,
C = 4.7960 × 10 ⁻⁷ , D = −4.8289 × 10 ⁻⁹

(Numerical values related to conditional expression (1))
fv (focal length of the negative lens L ₂₃₁ ) = − 29.711
| Fv | /f=3.059

(Numerical value related to conditional expression (2))
f2 (the focal length of the second lens group G ₂₂₎ = 28.810
| F2 | /f=2.966

(Numerical values related to conditional expression (3))
ff (focal length of the lens system disposed on the object side of the aperture stop S) = 10.271
Gn1B (air distance from the negative lens L ₂₁₁ to the negative lens L ₂₁₂ ) = 16.368
ff / Gn1B = 0.627

(Numerical values related to conditional expression (4))
θv (image position correction angle by the negative lens L ₂₃₁ ) = 3.061
f / tan θv = 181.641

(Numerical values related to conditional expression (5))
f ′ (focal length of the entire fish-eye lens system when shooting a short-distance object (shooting magnification is 1/40)) = 9.743
ff ′ = − 0.031

  FIG. 4 is a diagram illustrating various aberrations with respect to the d-line (λ = 587.56 nm) at the time of photographing an object at infinity of the fish-eye lens according to the second example. In the astigmatism diagrams, S and M represent aberrations with respect to the sagittal image surface and the meridional image surface, respectively. Further, in the distortion diagram, the shift amount by the equidistant projection method (Y = fθ) is displayed (Y: image height, f: focal length of the entire optical system, θ: half angle of view).

FIG. 5 is a cross-sectional view along the optical axis showing the configuration of the fisheye lens according to the third embodiment. The fish-eye lens includes a first lens group G ₃₁ having a positive refractive power, a second lens group G ₃₂ having a negative refractive power, and a third lens group G having a positive refractive power in order from an object side (not shown). ₃₃ is arranged.

An aperture stop S that defines a predetermined aperture is disposed between the second lens group G ₃₂ and the third lens group G ₃₃ . Between the third lens group G ₃₃ and an image plane IMG, filter group F such infrared cut filter is disposed. Note that the light receiving surface of the image sensor is disposed on the image plane IMG.

The first lens group G ₃₁ includes a negative lens L ₃₁₁ , a negative lens L ₃₁₂ , a positive lens L _313, and a positive lens L ₃₁₄ arranged in order from the object side.

The second lens group G ₃₂ is constituted by a negative lens L _321. The negative lens L ₃₂₁ is disposed in the vicinity of the aperture stop S, and an aspheric surface is formed on both surfaces thereof. In addition, the second lens group G ₃₂ has a function as a focus group. That is, by moving from the object side to the image side along the second lens group G ₃₂ to the optical axis to perform focusing from an infinity object to a close object.

The third lens group G ₃₃ is constituted in order from the object side, a negative lens L _331, a positive lens L _332, a positive lens L _333, a negative lens L _334, a positive lens L _335, is the placement . The negative lens L ₃₃₁ and the positive lens L ₃₃₂ are cemented. The positive lens L ₃₃₃ and the negative lens L ₃₃₄ are also cemented. The negative lens L ₃₃₁ is disposed in the vicinity of the aperture stop S. An aspherical surface is formed on the image side surface of the positive lens _L332 . Further, the cemented lens of the negative lens L ₃₃₁ and the positive lens L ₃₃₂ has the function of the image position correcting optical system. That is, image position correction is performed by moving the cemented lens of the negative lens L ₃₃₁ and the positive lens L _{332 in} a direction orthogonal to the optical axis.

  Various numerical data related to the fisheye lens according to Example 3 are shown below.

f (focal length of the whole fisheye lens system when shooting an object at infinity) = 9.708
Fno. (F number) = 2.87
ω (half angle of view) = 90.50

(Lens data)
r ₁ = 66.941
d ₁ = 2.000 nd ₁ = 1.904 νd ₁ = 31.32
r ₂ = 19.576
d ₂ = 18,000
r ₃ = -64.023
d ₃ = 2.000 nd ₂ = 1.497 νd ₂ = 81.61
r ₄ = 17.193
d ₄ = 13.333
r ₅ = 48.406
d ₅ = 4.443 nd ₃ = 1.835 νd ₃ = 42.72
r ₆ = -52.970
d ₆ = 0.300
r ₇ = 29.883
d ₇ = 3.750 nd ₄ = 1.603 νd ₄ = 60.69
r ₈ = -100.633
d ₈ = 1.630
r ₉ = -25.995 (aspherical surface)
d ₉ = 1.000 nd ₅ = 1.497 νd ₅ = 81.56
r ₁₀ = 99.439 (aspherical surface)
d ₁₀ = 8.533
r ₁₁ = ∞ (aperture stop)
d ₁₁ = 1.000
r ₁₂ = 18.802
d ₁₂ = 1.000 nd ₆ = 1.904 νd ₆ = 31.32
r ₁₃ = 9.559
d ₁₃ = 2.527 nd ₇ = 1.743 νd ₇ = 49.22
r ₁₄ = 699.037 (aspherical surface)
d ₁₄ = 2.223
r ₁₅ = -73.597
d ₁₅ = 4.608 nd ₈ = 1.743 νd ₈ = 49.22
r ₁₆ = -9.481
d ₁₆ = 1.000 nd ₉ = 1.923 νd ₉ = 20.88
r ₁₇ = -16.409
d ₁₇ = 1.333
r ₁₈ = -12.168
d ₁₈ = 2.000 nd ₁₀ = 1.923 νd ₁₀ = 20.88
r ₁₉ = -17.165
d ₁₉ = 0.100
r ₂₀ = ∞
d ₂₀ = 3.000 nd ₁₁ = 1.517 νd ₁₁ = 64.20
r ₂₁ = ∞
d ₂₁ = 14.000
r ₂₂ = ∞ (image plane)

Cone coefficient (k) and aspheric coefficient (A, B, C, D)
(9th page)
k = 0,
A = 6.5704 × 10 ⁻⁵ , B = −5.7262 × 10 ⁻⁸ ,
C = 2.6528 × 10 ⁻¹⁰ , D = −9.2352 × 10 ⁻¹³
(Tenth aspect)
k = 0,
A = 3.3331 × 10 ⁻⁵ , B = 6.0018 × 10 ⁻⁸ ,
C = 1.8044 × 10 ⁻⁹ , D = −3.88988 × 10 ⁻¹²
(14th page)
k = 0,
A = 9.22566 × 10 ⁻⁶ , B = −4.1615 × 10 ⁻⁸ ,
C = -1.6235 × 10 ^-8 , D = 2.2974 × 10 ^-10

(Numerical values related to conditional expression (1))
fv (focal length of cemented lens of negative lens L ₃₃₁ and positive lens L ₃₃₂ ) = 32.549
| Fv | /f=3.353

(Numerical value related to conditional expression (2))
f2 (the focal length of the second lens group G ₃₂₎ = - 41.347
| F2 | /f=4.259

(Numerical values related to conditional expression (3))
ff (focal length of the lens system disposed on the object side of the aperture stop S) = 62.021
Gn1B (Air distance from negative lens L ₃₁₁ to negative lens L ₃₁₂ ) = 18,000
ff / Gn1B = 3.446

(Numerical values related to conditional expression (4))
θv (image position correction angle by cemented lens of negative lens L ₃₃₁ and positive lens L ₃₃₂ ) = 3.066
f / tan θv = 181.221

(Numerical values related to conditional expression (5))
f ′ (focal length of the whole fisheye lens system when photographing a short-distance object (imaging magnification is 1/40)) = 9.754
ff ′ = − 0.046

  FIG. 6 is a diagram of various aberrations with respect to the d-line (λ = 587.56 nm) of the fish-eye lens according to Example 3 when photographing an object at infinity. In the astigmatism diagrams, S and M represent aberrations with respect to the sagittal image surface and the meridional image surface, respectively. Further, in the distortion diagram, the shift amount by the equidistant projection method (Y = fθ) is displayed (Y: image height, f: focal length of the entire optical system, θ: half angle of view).

FIG. 7 is a cross-sectional view along the optical axis showing the configuration of the fisheye lens according to the fourth example. The fish-eye lens includes a first lens group G ₄₁ having a positive refractive power, a second lens group G ₄₂ having a positive refractive power, and a third lens group G having a positive refractive power in order from an object side (not shown). ₄₃ are arranged.

An aperture stop S that defines a predetermined aperture is disposed between the first lens group G ₄₁ and the second lens group G ₄₂ . Between the third lens group G ₄₃ and an image plane IMG, filter group F such infrared cut filter is disposed. Note that the light receiving surface of the image sensor is disposed on the image plane IMG.

The first lens group G ₄₁ includes, in order from the object side, a negative lens L _411, a negative lens L _412, a positive lens L _413, a positive lens L _414, is formed are disposed. The positive lens L ₄₁₄ is disposed in the vicinity of the aperture stop S, and an aspheric surface is formed on both surfaces thereof. The positive lens L ₄₁₄ has an image position correcting optical system function. That is, image position correction is performed by moving the positive lens L ₄₁₄ in a direction orthogonal to the optical axis.

The second lens group _G42 includes a positive lens _L421 . The positive lens L ₄₂₁ is disposed in the vicinity of the aperture stop S, and aspherical surfaces are formed on both surfaces thereof. The second lens group G _42, and thereby play a function as a focus group. That is, by moving from the image side to the object side along the second lens group G ₄₂ to the optical axis to perform focusing from an infinity object to a close object.

The third lens group G ₄₃ is constituted in order from the object side, a negative lens L _431, a positive lens L _432, a positive lens L _433, a negative lens L _434, a positive lens L _435, is the placement . The negative lens L ₄₃₁ and the positive lens L ₄₃₂ are cemented. The positive lens L ₄₃₃ and the negative lens L ₄₃₄ are also cemented.

  Various numerical data related to the fisheye lens according to Example 4 are shown below.

f (focal length of the whole fisheye lens system when shooting an object at infinity) = 9.790
Fno. (F number) = 2.83
ω (half angle of view) = 90.50

(Lens data)
r ₁ = 55.428
d ₁ = 2.000 nd ₁ = 1.883 νd ₁ = 40.81
r ₂ = 15.074
d ₂ = 14.721
r ₃ = -29.643
d ₃ = 2.000 nd ₂ = 1.497 νd ₂ = 81.61
r ₄ = 20.730
d ₄ = 7.236
r ₅ = 42.366
d ₅ = 4.500 nd ₃ = 1.904 νd ₃ = 31.32
r ₆ = -52.092
d ₆ = 11.320
r ₇ = 42.954 (aspherical surface)
d ₇ = 2.213 nd ₄ = 1.497 νd ₄ = 81.61
r ₈ = -30.420 (aspherical surface)
d ₈ = 1.000
r ₉ = ∞ (aperture stop)
d ₉ = 3.778
r ₁₀ = 11.364 (aspherical surface)
d ₁₀ = 1.283 nd ₅ = 1.883 νd ₅ = 40.81
r ₁₁ = 12.910 (aspherical surface)
d ₁₁ = 1.946
r ₁₂ = 40.657
d ₁₂ = 1.000 nd ₆ = 1.946 νd ₆ = 17.98
r ₁₃ = 10.409
d ₁₃ = 2.477 nd ₇ = 1.497 νd ₇ = 81.61
r ₁₄ = 73.172
d ₁₄ = 1.997
r ₁₅ = -19.071
d ₁₅ = 3.713 nd ₈ = 1.804 νd ₈ = 46.50
r ₁₆ = -8.919
d ₁₆ = 1.000 nd ₉ = 1.904 νd ₉ = 31.32
r ₁₇ = -19.526
d ₁₇ = 0.100
r ₁₈ = 44.351
d ₁₈ = 4.406 nd ₁₀ = 1.923 νd ₁₀ = 20.88
r ₁₉ = -61.931
d ₁₉ = 0.100
r ₂₀ = ∞
d ₂₀ = 3.000 nd ₁₁ = 1.517 νd ₁₁ = 64.20
r ₂₁ = ∞
d ₂₁ = 14.000
r ₂₂ = ∞ (image plane)

Cone coefficient (k) and aspheric coefficient (A, B, C, D)
(Seventh side)
k = 0,
A = -5.0330 × 10 ^-5 , B = -3.1284 × 10 ^-7 ,
C = -1.5019 × 10 ⁻⁸ , D = −2.0603 × 10 ⁻¹⁰
(8th page)
k = 0,
A = -2.4188 × 10 ^-5 , B = -4.2655 × 10 ^-7 ,
C = -2.2010 × 10 ^-8 , D = 2.8401 × 10 ^-11
(Tenth aspect)
k = 0,
A = 1.5081 × 10 ⁻⁴ , B = 3.5068 × 10 ⁻⁸ ,
C = 6.0741 × 10 ^-9 , D = 1.0755 × 10 ^-9
(11th page)
k = 0,
A = 1.8967 × 10 ⁻⁴ , B = 9.66029 × 10 ⁻⁷ ,
C = -3.1581 × 10 ⁻⁸ , D = 2.3691 × 10 ⁻⁹

(Numerical values related to conditional expression (1))
fv (focal length of positive lens L ₄₁₄ ) = 36.194
| Fv | /f=3.697

(Numerical value related to conditional expression (2))
f2 (the focal length of the second lens group G ₄₂₎ = 77.374
| F2 | /f=7.903

(Numerical values related to conditional expression (3))
ff (focal length of the lens system disposed on the object side of the aperture stop S) = 15.415
Gn1B (air distance from negative lens L ₄₁₁ to negative lens L ₄₁₂ ) = 14.721
ff / Gn1B = 1.047

(Numerical values related to conditional expression (4))
θv (image position correction angle by positive lens L ₄₁₄ ) = 3.036
f / tan θv = 184.613

(Numerical values related to conditional expression (5))
f ′ (focal length of the entire fish-eye lens system when shooting a short-distance object (shooting magnification is 1/40)) = 9.797
ff ′ = − 0.007

  FIG. 8 is a diagram illustrating various aberrations with respect to the d-line (λ = 587.56 nm) when the fisheye lens according to Example 4 is used to capture an object at infinity. In the astigmatism diagrams, S and M represent aberrations with respect to the sagittal image surface and the meridional image surface, respectively. Further, in the distortion diagram, the shift amount by the equidistant projection method (Y = fθ) is displayed (Y: image height, f: focal length of the entire optical system, θ: half angle of view).

In the numerical data in each of the above embodiments, r ₁ , r ₂ ,... Are the curvature radii of the lenses and the diaphragm surface, and d ₁ , d ₂ ,. Thickness or spacing between them, nd ₁ , nd ₂ ,... Is the refractive index with respect to d-line (λ = 587.56 nm) of each lens, νd ₁ , νd ₂ ,. The Abbe number with respect to the d-line (λ = 587.56 nm) is shown. The unit of length is all “mm”, and the unit of angle is “°”.

  In addition, each of the above aspheric shapes has a depth of the aspheric surface Z, a curvature c (1 / r), a height from the optical axis h, a cone coefficient k, 4th order, 6th order, 8th order, 10th order. When the following aspheric coefficients are A, B, C, and D, respectively, and the traveling direction of light is positive, the following aspheric coefficients are expressed by the following equations.

  As described above, the fish-eye lens of each of the above embodiments has a small and excellent optical performance with an inner focus function and an image position correction function that enable satisfactory movie shooting by satisfying each conditional expression above. It becomes a fisheye lens having. In particular, a large image position correction angle can be ensured, and deterioration of optical performance can be prevented while sufficiently exhibiting the image position correction effect. The fisheye lens of the present invention is suitable for a small digital camera, particularly a digital single lens reflex camera. In addition, by arranging a lens or a cemented lens in which an aspheric surface is appropriately formed, the aberration correction capability can be improved with a small number of lenses.

  As described above, the fisheye lens according to the present invention is useful for a digital camera capable of taking a moving image, which is small and requires high optical performance, and is particularly suitable for a digital single-lens reflex camera.

G ₁₁ , G ₂₁ , G ₃₁ , G ₄₁ first lens group G ₁₂ , G ₂₂ , G ₃₂ , G ₄₂ second lens group G ₁₃ , G ₂₃ , G ₃₃ , G ₄₃ third lens group L ₁₁₁ , L ₁₁₂ L ₁₂₁ , L ₁₃₁ , L ₁₃₄ , L ₂₁₁ , L ₂₁₂ , L ₂₃₁ , L ₂₃₂ , L ₂₃₅ , L ₃₁₁ , L ₃₁₂ , L ₃₂₁ , L ₃₃₁ , L ₃₃₄ , L ₄₁₁ , L ₄₁₂ , L ₄₃₁ , L ₄₃₄ negative lens _{L 113, L 114, L 132} , L 133, L 135, L 213, L 221, L 233, L 234, L 236, L 313, L 314, L 332, L 333, L 335, L 413 , L ₄₁₄ , L ₄₂₁ , L ₄₃₂ , L ₄₃₃ , L ₄₃₅ positive lens S aperture stop F filters IMG image plane

Claims (4)

A first lens group having positive refractive power, a second lens group having positive or negative refractive power, and a third lens group having positive refractive power, which are arranged in order from the object side,
The second lens group is moved along the optical axis to perform focusing from an object at infinity to an object at a short distance,
At least a part of the first lens group or at least a part of the third lens group has a function as an image position correction optical system that moves in a direction orthogonal to the optical axis to correct an image position.
An aperture stop is disposed in the vicinity of the second lens group and the image position correcting optical system,
A fish-eye lens satisfying the following conditional expression:
(1) 1.0 ≦ | fv | /f≦5.0
(2) 1.0 ≦ | f2 | /f≦10.0
Here, fv is a focal length of the image position correcting optical system, f is a focal length of the whole fisheye lens system at the time of photographing an object at infinity, and f2 is a focal length of the second lens group. The first lens group includes a negative lens component;
The fisheye lens according to claim 1, wherein the following conditional expression is satisfied.
(3) 0.5 ≦ ff / Gn1B ≦ 5.0
However, ff represents the focal length of the lens system disposed on the object side of the aperture stop, and Gn1B represents the air space from the negative lens component disposed on the most object side of the first lens group to the next lens component. . The fisheye lens according to claim 1, wherein the following conditional expression is satisfied.
(4) 100 ≦ f / tan θv ≦ 6000
Here, θv represents an image position correction angle by the image position correction optical system. The fish-eye lens according to claim 1, wherein the following conditional expression is satisfied.
(5) ff ′ ≦ 0
Here, f ′ represents the focal length of the entire fish-eye lens system when shooting a short-distance object (shooting magnification is 1/40).

Images