JPH05173063A - Photographic lens - Google Patents

Abstract

PURPOSE:To attain a wide angle while holding the compact formation and high performance of a photographing lens by arranging a negative meniscus lens having a convex on the object side as the 1st lens counted from the object side, arranging a negative meniscus lens having a concave on the object side as a lens most close to the image face side, constituting lenses following an iris of positive and negative lenses arranged from the object side, and satisfying respective lenses with specific conditions. CONSTITUTION:The photographing lens having the iris is provided with the negative lens having the convex on the object side as the 1st lens counted from the object side and the negative meniscus lens having the concave on the object side as the lens most close to the image face side, constitutes a lens group following the iris of the positive and negative lenses and satisfies these lenses with the shown inequalities I to V. In the inequalities I to V, PHIf is the power of the 1st lens counted from the object side, PHIF is the power of a lens group (pre-group) arranged before the iris, PHIR is the power of a lens group (post group) following; the iris, and PHI(+) is the power of a positive lens in the post group.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photographic lens, and more particularly to a wide-angle photographic lens most suitable for a panoramic camera or the like.

[0002]

2. Description of the Related Art In recent years, a lens shutter camera is required to have a wide angle lens. Particularly in panoramic cameras, widening of the angle is strongly desired.

As a conventional wide-angle photographic lens, a retrofocus type often used for a lens for a single-lens reflex camera, a symmetric type such as Topogon, and Japanese Patent Laid-Open No. 58-219509.
Reverse retro type as seen in No. etc. (via the diaphragm,
It is known that the object side lens group has a positive refracting power and the image side lens group has a negative refracting power), and is made compact.

[0004]

However, the retrofocus type is not suitable for downsizing because the back focus is large, and the symmetric type such as the Topogon or the like has a field curvature when it is attempted to downsize and increase the aperture. Is difficult to correct, and it is difficult to achieve high performance. In most of the above-mentioned retro-retro type, the lens group before the diaphragm is composed of three positive, negative, and positive lenses (so-called triplet). Deterioration of (field curvature and astigmatic difference around the screen) cannot be completely corrected by the group after the diaphragm, and eventually it is difficult to achieve high performance.

Therefore, in view of such a situation, an object of the present invention is to provide a photographic lens having a wide angle while achieving compactness and high performance.

[0006]

In order to achieve the above object, the present invention is a photographic lens having a diaphragm, in which the first lens from the object side is a negative lens convex to the object side, The lens on the surface side is a negative meniscus lens concave to the object side, the lens group after the diaphragm is composed of a positive lens and a negative lens from the object side, and the following conditional expressions (1) to (5) are satisfied. Is characterized by. -1.8 <φl / φ <-0.70 …… (1) 0.3 <φl / φf <4.0 …… (2) -3.5 <φF / φf <-0.3 …… (3) -1.2 <φR / φF <1.0 …… (4) 0.05 <φ (+) / φ <1.9 (5) where φ: power of the entire system φl: power of the lens closest to the image plane (hereinafter also referred to as the “final lens”) φf: object side To the first lens (hereinafter “first lens”)
(Also called) power φF: lens group before the aperture (hereinafter also referred to as "front group")
Power φR: Lens group after the aperture (hereinafter also referred to as "rear group")
Power φ (+): power of the positive lens in the rear group.

The conditional expression (1) limits the power of the final lens. If the lower limit of conditional expression (1) is exceeded, the negative power will become too strong. As a result, the lens back becomes too short, the lens diameter increases, and aberration correction becomes difficult. If the upper limit of conditional expression (1) is exceeded, the lens back becomes long and the total length becomes large.

Conditional expression (2) represents the relationship between the negative power of the first lens and the negative power of the final lens. If the lower limit of conditional expression (2) is exceeded, the overall length will become longer, and it will not be compact. On the other hand, if the upper limit of conditional expression (2) is exceeded, the effect of suppressing the curvature of field by the first lens cannot be sufficiently exerted.

The conditional expression (3) represents the relationship between the positive power of the front lens group and the negative power of the first lens. Conditional expression
Beyond the upper limit of (3), the overall length becomes longer and it is not compact. If the lower limit of conditional expression (3) is exceeded,
The aberration generated in the front group becomes too large, and the aberration cannot be suppressed in the rear group.

The conditional expression (4) represents the relationship between the power of the front group and the power of the rear group. If the upper limit of conditional expression (4) is exceeded, the overall length will become longer, and it will not be compact. If the lower limit of conditional expression (4) is exceeded, the power of the front lens unit will become too large, making it difficult to correct aberrations.

If the lower limit value of the conditional expression (5) is exceeded, it becomes impossible to suppress the tilt of the field curvature to the over side, and if the upper limit value is exceeded, the power of the rear group becomes too strong and the total length becomes large.

It is desirable that the front lens group be composed of three lenses, a negative meniscus lens having a convex surface on the object side, a positive lens, and a positive or negative lens. More preferably, it is composed of four negative meniscus lenses having a convex surface on the object side, a positive lens, a negative lens and a positive lens.
Further, in the rear group, it is desirable to have two lenses, in order from the object side, of a positive lens and a negative meniscus lens concave to the object side.

Focusing is generally carried out as a whole, but since the power of the front group is sufficiently strong, even if only the front group is extended, good proximity performance can be obtained with a small amount of extension.

Next, in the present invention, preferable conditions will be described in the case where the front lens group has a negative / positive / negative / positive four-element structure and the rear group has a positive / negative two-element structure in order from the object side. In addition, as those having these configurations, for example, Embodiment 1 described later
~ 3 can be mentioned.

It is preferable that the front lens group be configured to satisfy the following conditional expression (6). -1.5 <φ3 / φ <-0.2 (6) where φ3 is the power of the third lens (hereinafter also referred to as the “third lens”) from the object side.

If the lower limit of conditional expression (6) is exceeded, the positive power of the second lens (hereinafter also referred to as the "second lens") from the object side becomes too strong, making it difficult to suppress spherical aberration. If the upper limit is exceeded, the overall length becomes longer and the device becomes less compact.

Further, it is preferable that the following conditional expression (7) is satisfied. 1.6 <Nd2 (7) where Nd2 is the refracting power of the second lens. If the lower limit of conditional expression (7) is exceeded, Petzval sum increases and field curvature increases.

Since it is necessary to suppress axial chromatic aberration to some extent between the first lens and the second lens, the following conditional expression
It is preferable to satisfy (8). 5 <ν2-ν1 <35 (8) where, ν1: Abbe number of the first lens, ν2: Abbe number of the second lens.

If the lower limit of conditional expression (8) is exceeded, it is necessary for both the first lens and the second lens to have strong power in order to obtain axial chromatic aberration. It becomes difficult to suppress it with a lens. If the upper limit of conditional expression (8) is exceeded, it is necessary for both the first lens and the second lens to have weak power in order to obtain axial chromatic aberration.
A sufficient refracting power cannot be given to the front group, which makes it difficult to make it compact.

It is desirable that the shape of the first lens element of the negative meniscus lens element convex to the object side should satisfy the following conditional expression (9). 1.0 <(R1 + R2) / (R1-R2) <7.0 (9) where R1: the object side surface of the first lens (hereinafter also referred to as the “first surface”)
Radius of curvature R2: radius of curvature of the image-side surface of the first lens (hereinafter also referred to as “second surface”).

When the lower limit of conditional expression (9) is exceeded, the principal point position of the first lens moves to the object side, effectively increasing the negative power and increasing the total length. If the upper limit of conditional expression (9) is exceeded, spherical aberration will fall to the over side, making correction difficult, and the principal point position will move to the image plane side, effectively reducing the negative power and making the image too weak. It becomes difficult to suppress the surface curvature.

For the shape of the positive second lens, the following conditional expression
It is desirable to have a configuration that satisfies (10). -6.5 <(R3 + R4) / (R3-R4) <1.0 (10) Where, R3: Object side surface of second lens (hereinafter also referred to as “third surface”)
Radius of curvature R4: radius of curvature of the image side surface of the second lens (hereinafter also referred to as the “fourth surface”).

When the upper limit of conditional expression (10) is exceeded, the principal point position of the second lens moves to the image plane side, effectively reducing the distance between the second and third lenses, so that the Petzval sum is However, the field curvature increases and the field curvature cannot be completely corrected. Conditional expression (10)
If the lower limit of the above is exceeded, the curvature of the third surface becomes too strong, and it becomes difficult to manufacture the lens.

The following aspherical surfaces are preferably provided in the front lens group. In other words, since the first lens is a negative lens, the second lens has the positive power in the front group, so that the spherical aberration is greatly inclined to the under side, and the lower ray of the off-axis light is increased. It is flipped up and coma easily occurs.
In order to correct this, it is desirable to introduce an aspherical surface into the front lens group that intensifies the negative power toward the off-axis, and the negative power increases toward the off-axis from the image-side surface of the third lens. It is more desirable to use an aspherical surface that becomes strong. The amount of deviation of the aspherical surface from the reference spherical surface at that time is calculated by
And it is desirable to satisfy (12).

0.5 × 10 ^-5 <ΔXFb (HZ) / F <0.15 × 10 ^-3 (11) 0.1 × 10 ^-3 <ΔXFb (HM) / F <0.5 × 10 ^-2 ...... (12) Here ΔXFb (H): Amount of deviation from the reference spherical surface at a distance H from the optical axis in a plane perpendicular to the optical axis (provided that the image surface side is positive) HZ = 0.4Hmax HM = 0.8Hmax Hmax: Effective surface diameter F: Focal length of the entire system.

If the lower limits of the conditional expressions (11) and (12) are exceeded, spherical aberration will be tilted to the under side and correction will be difficult. If the upper limits of conditional expressions (11) and (12) are exceeded, the spherical aberration due to the aspherical surface will largely fall to the over side, making it difficult to correct other surfaces.

Further, it is preferable that the rear lens group be constructed so as to satisfy the following conditional expression (13). -0.5 <R (-) / F <-0.15 (13) where R (-) is the curvature of the object side surface of the negative lens.

If the lower limit of conditional expression (13) is exceeded, field curvature will increase and correction will not be possible, and if the upper limit is exceeded, lens manufacture will become difficult.

The front group has a shape in which the first negative lens is placed in front of the triplet, and the Petzval sum is sufficiently small due to the effect of the first lens, but the field curvature in the off-axis meridional direction is small. The fall to the under side, which is a characteristic of triplets, is emphasized more. In order to return the tilt to the under side of the image surface, it is desirable to use an aspherical surface in the rear group in the direction of weakening the positive power. Furthermore, it is more preferable to use an aspherical surface on the image plane side of the positive lens or the negative lens so as to satisfy the following conditional expressions (14) and (15) in the direction of weakening the positive power as it goes off-axis. ..

0.1 × 10 ^-4 <ΔXR (HZ) / F <0.5 × 10 ^-3 (14) 0.5 × 10 ^-3 <ΔXR (HM) / F <1.0 × 10 ^-1 (15) Here ΔXR (H): The amount of deviation from the reference spherical surface at a distance H from the optical axis in a plane perpendicular to the optical axis (provided that the image plane side is positive).

When the lower limit values of the conditional expressions (14) and (15) are exceeded, the tilt of the field curvature to the under side cannot be suppressed, and when the upper limit value is exceeded, the field curvature is overcorrected, and thus the over side. It becomes difficult to correct in other aspects.

Next, in the present invention, preferable conditions in the case where the front group has, in order from the object side, negative / positive / negative or negative / positive / positive three-element configuration and the rear group has positive / negative two-element configuration. Will be described. Note that examples of these configurations include, for example, Example 4 and Example 5 described later.

It is preferable that the front lens group be configured to satisfy the following conditional expression (16). -1.5 <φ3 / φ <1.5 (16)

If the lower limit of conditional expression (16) is exceeded, it becomes difficult to suppress spherical aberration because the positive power of the second lens becomes too strong. If the upper limit is exceeded, the overall length becomes long, resulting in compactness. Disappear.

Further, it is preferable that the following conditional expression (17) is satisfied. 1.6 <Nd2 (17) If the lower limit of conditional expression (17) is exceeded, Petzval sum increases and field curvature increases.

Since axial chromatic aberration must be suppressed to some extent between the first lens and the second lens, the following conditional expression (1
It is preferable to satisfy 8). 10 <ν2-ν1 <35 (18)

If the lower limit of conditional expression (18) is exceeded, it is necessary for both the first lens and the second lens to have strong power in order to obtain axial chromatic aberration. It becomes difficult to suppress it with a lens. If the upper limit of conditional expression (18) is exceeded, it is necessary for both the first lens and the second lens to have weak power in order to obtain axial chromatic aberration.
A sufficient refracting power cannot be given to the front group, which makes it difficult to make it compact.

It is desirable that the shape of the first lens element of the negative meniscus lens element convex to the object side should satisfy the following conditional expression (19). 1.0 <(R1 + R2) / (R1-R2) <8.5 …… (19)

If the lower limit of conditional expression (19) is exceeded, the principal point position of the first lens moves to the object side, effectively increasing the negative power and increasing the total length. If the upper limit of conditional expression (19) is exceeded, the position of the principal point moves to the image plane side, effectively reducing the negative power and making it difficult to suppress curvature of field.

The following aspherical surfaces are preferably provided in the front lens group. In other words, since the first lens is a negative lens, the second lens has the positive power in the front group, so that the spherical aberration is greatly inclined to the under side, and the lower ray of the off-axis light is increased. It is flipped up and coma easily occurs.
In order to correct this, it is desirable to introduce an aspherical surface into the front group that strengthens the negative power toward the off-axis, and the surface closest to the diaphragm is made an aspherical surface, and the negative power increases toward the off-axis. It is more desirable to use an aspherical surface that becomes strong.
The amount of deviation of the aspherical surface from the reference spherical surface at that time preferably satisfies the following conditional expressions (20) and (21).

0.5 × 10 ⁻⁵ <ΔXFb (HZ) / F <0.2 × 10 ⁻³ (20) 0.2 × 10 ⁻³ <ΔXFb (HM) / F <0.6 × 10 ⁻² (21)

If the lower limits of the conditional expressions (20) and (21) are exceeded, spherical aberration is greatly inclined to the under side and correction becomes difficult. If the upper limits of the conditional expressions (20) and (21) are exceeded, the spherical aberration due to the aspherical surface is greatly inclined to the over side, and it becomes difficult to correct it on other surfaces.

Further, it is preferable that the rear lens group be composed of two lenses, positive and negative, and satisfy the following conditional expression (22). -0.5 <R (-) / F <-0.15 …… (22)

If the lower limit of conditional expression (22) is exceeded, field curvature will increase and correction will not be possible, and if the upper limit is exceeded, lens manufacture will become difficult.

Since the first lens is a negative lens, the Petzval sum is sufficiently small. Therefore, off-axis, the image plane returns to the over side by a high-order effect, and therefore it is desirable to use an aspherical surface in the rear lens group in the direction of strengthening the positive power. Further, on the image plane side of the positive lens, the following conditional expressions (23) and (24) are provided in a direction in which positive power is strengthened as it goes off axis.
It is more desirable to use an aspherical surface so that

-0.1 × 10 ^-4 <ΔXR (HZ) / F <-0.6 × 10 ^-3 (23) -0.2 × 10 ^-3 <ΔXR (HM) / F <-0.8 × 10 ^-2 ...... (twenty four)

If the upper limits of the conditional expressions (23) and (24) are exceeded, the tilt of the field curvature to the over side cannot be suppressed, and if the lower limits are exceeded, the field curvature and spherical aberration are overcorrected. Therefore, they both fall to the under side, making it difficult to correct on other surfaces.

Next, in the present invention, the front lens group comprises two lenses, in order from the object side, a negative lens and a biconvex positive lens, and the rear lens group comprises two lenses, a positive lens and a negative meniscus lens concave on the object side. The preferable conditions in this case will be described. Incidentally, examples of those having these configurations include, for example, Example 6 described later.

In the above structure, more preferably, in order from the object side, the front group includes a negative meniscus lens having a convex surface on the object side and a biconvex positive lens, and the rear group has a positive meniscus lens having a concave surface on the object side and an object side. It may consist of a concave negative meniscus lens.

In the front lens group, it is desirable that the shape of the first lens, which is a negative meniscus lens concave on the object side, satisfies the following conditional expression (25). 1.0 <(R1 + R2) / (R1-R2) <7.0 …… (25)

When the lower limit of conditional expression (25) is exceeded, the principal point position of the first lens moves to the object side, effectively increasing the negative power and increasing the total length. If the upper limit of conditional expression (25) is exceeded, spherical aberration will fall to the over side, making correction difficult, and the principal point position will move to the image side, effectively reducing the negative power and making the image too weak. It becomes difficult to suppress the surface curvature.

It is desirable that the shape of the second lens, which is a biconvex positive lens, satisfy the following conditional expression (26). -0.1 <(R3 + R4) / (R3-R4) <1.0 …… (26)

If the lower limit of conditional expression (26) is exceeded, the principal point position of the second lens moves toward the object side, effectively reducing the distance between the first and second lenses, and increasing the Petzval sum. However, the field curvature cannot be completely corrected. Conditional expression (26)
When the value exceeds the upper limit of, the spherical aberration generated in the second lens becomes excessive and correction becomes difficult.

The following aspherical surfaces are preferably provided in the front lens group. In other words, since the first lens is a negative lens, the second lens has the positive power in the front group, so that the spherical aberration falls to the under side and the rays below the off-axis light are largely repelled. Coma is likely to occur. In order to correct this, it is desirable to introduce an aspherical surface into the front lens group, which strengthens the negative power as it goes off axis.

Further, it is preferable that the rear lens group has a constitution which satisfies the following conditional expression (27). -0.5 <R (-) / F <-0.15 …… (27)

If the lower limit of conditional expression (27) is exceeded, curvature of field will increase and correction will not be possible, and if the upper limit is exceeded, lens manufacture will become difficult.

Since the Petzval sum is sufficiently small in the first lens having a negative refracting power, the tilt of the image surface is returned to the over side of the image surface by the high-order effect and the distortion is increased to the positive side off-axis. In order to prevent it, it is desirable to use an aspherical surface in the rear group in the direction of increasing positive power. Further, it is more preferable to use an aspherical surface on the image side of the positive lens in the rear group in the direction of increasing positive power as it goes off-axis so as to satisfy the following conditional expressions (28) and (29).

0.1 × 10 ^-4 <ΔXR (HZ) / F <0.8 × 10 ^-3 (28) 0.5 × 10 ^-3 <ΔXR (HM) / F <0.1 × 10 ^-1 (29)

If the lower limits of conditional expressions (28) and (29) are exceeded, the tilt of the image plane to the over side and the distortion increase to the positive side become too large, and if the upper limits are exceeded, overcorrection occurs. Therefore, the tilt of the image surface to the under side and the negative increase of the distortion become large.

A lens group having a positive refracting power is arranged in front of the stop, and a lens group having a negative or weak positive refracting power is arranged after the stop, that is, the reverse retro or the rear group has a weak positive refraction. A compact optical system can be achieved by using a symmetric lens type close to an inverse retro type that has power.

In this type of optical system, when the lens closest to the object side is a positive lens, a lens structure desirable for aberration correction as a front group is a positive meniscus lens convex to the object side in order from the object side, and a negative meniscus lens. It is a so-called triplet or tesser type having three or four lenses including a lens, a positive lens or a positive cemented lens. However, with this lens configuration, the Petzval sum becomes positively large, and the field curvature increases. Further, the sagittal image plane in the middle band of the screen falls to the under side, and largely falls to the over side around the screen. On the other hand, if you try to eliminate the astigmatic difference in the middle band of the screen by controlling the meridional image, the astigmatic difference around the screen becomes large, and conversely, if you try to correct the periphery, the middle band difference will be It gets bigger. From this, it is understood that when the lens closest to the object side is a positive lens, it is difficult to correct the field curvature and the astigmatic difference, and it is not suitable for widening the angle.

In the present invention, in order to solve this problem, the lens closest to the object side in the front group is a negative lens convex toward the object side. As a result, it is possible to reduce the positive increase of the Petzval sum, and to reduce the tilt of the field curvature to the under side and the astigmatic difference in the periphery of the screen. Further, since the negative lens can reduce the incident angle of the peripheral off-axis light that enters the first lens at a large angle after the second lens, other aberrations can be easily corrected. Therefore, high performance can be achieved in the entire angle of view. Further, if the lens on the object side is made negative, it is disadvantageous for making the overall length compact, but it can be made compact by giving the lens on the image side a sufficiently strong negative refracting power.

Further, in a wide-angle and compact lens, a shortage of peripheral light quantity becomes a problem. However, by making the first lens a negative lens, the pupil position can be brought out to the object side, and a sufficient peripheral light quantity can be obtained. The advantage that it can be obtained also arises.

[0064]

EXAMPLES Examples of the photographic lens according to the present invention will be shown below. However, in each example, ri (i = 1,2,3, ...) is the radius of curvature of the i-th surface counted from the object side, and di (i = 1,2,3, ...) is Shows the i-th axial upper surface distance from the object side,
3, ...), νi (i = 1,2,3, ...) indicates the refractive index and Abbe number of the i-th lens from the object side for the d-line. Also, F
Indicates the focal length of the entire system, and FNO indicates the open F number.

Further, in the examples, the surface with the radius of curvature marked with * indicates that it is a surface composed of an aspherical surface, and the expression of the following numerical expression 1 expressing the surface shape (f (r)) of the aspherical surface is shown. Shall be defined in.

<Example 1> F = 24.0 FNO = 3.6 [radius of curvature] [axis upper surface spacing] [refractive index] [Abbe number] r1 9.844 d1 1.800 N1 1.79850 ν1 22.60 r2 6.970 d2 1.600 r3 8.606 d3 2.200 N2 1.77250 ν2 49.77 r4 12.531 d4 1.400 r5 -71.819 d5 1.200 N3 1.58400 ν3 29.99 r6 * 19.679 d6 0.700 r7 21.921 d7 1.800 N4 1.83500 ν4 42.98 r8 -42.760 d8 0.900 r9 ∞ (diaphragm) d9 2.680 r10 -34.107 d10 2.900 N5 1.71 3003 10.530 d11 4.710 r12 -9.109 d12 1.800 N6 1.58400 ν6 29.99 r13 * -23.367

[Aspherical surface coefficient] r6: ε = 0.93926 × 10 A4 = -0.55121 × 10^-Five  A6 = 0.43235 × 10^-Five  A8 = -0.57218 x 10^-6  A10 = 0.16224 × 10^-7  r13: ε = 0.28185 × 10 A4 = 0.22898 × 10^-Four  A6 = 0.45977 × 10^-6  A8 = -0.38405 x 10^-8  A10 = 0.31082 × 10^-Ten

<Example 2> F = 24.3 FNO = 3.62 [radius of curvature] [axis upper surface spacing] [refractive index] [Abbe number] r1 11.111 d1 1.800 N1 1.75000 ν1 25.14 r2 6.886 d2 1.500 r3 7.593 d3 2.400 N2 1.77250 ν2 49.77 r4 11.493 d4 1.500 r5 -22.298 d5 1.000 N3 1.62004 ν3 36.32 r6 * 30.223 d6 0.700 r7 14.487 d7 1.800 N4 1.72900 ν4 53.48 r8 -23.318 d8 0.900 r9 ∞ (iris) d9 2.600 r10 -54.535 d10 2.500 N5 30.58.30 -11.926 d11 4.200 r12 -8.518 d12 1.800 N6 1.79850 ν6 22.60 r13 -18.575

[Aspherical surface coefficient] r6: ε = 0.51448 × 10 A4 = 0.12517 × 10^-3  A6 = 0.84931 x 10^-Five  A8 = -0.57643 x 10^-6  A10 = 0.16177 x 10^-7  A12 = -0.24361 × 10^-12  r11: ε = 0.71065 A4 = 0.10413 × 10^-3  A6 = -0.11395 x 10^-Five  A8 = 0.48306 x 10^-7  A10 = 0.71928 × 10^-9  A12 = 0.67743 × 10^-11

<Example 3> F = 24.3 FNO = 3.62 [radius of curvature] [axis upper surface spacing] [refractive index] [Abbe number] r1 13.464 d1 1.800 N1 1.75000 ν1 25.14 r2 6.440 d2 1.500 r3 8.537 d3 2.400 N2 1.85026 ν2 32.15 r4 14.101 d4 1.700 r5 -13.296 d5 1.000 N3 1.62004 ν3 36.32 r6 -29.965 d6 0.500 r7 14.384 d7 1.800 N4 1.65830 ν4 58.52 r8 -20.403 d8 0.900 r9 ∞ (iris) d9 2.600 r10 -40.111 d10 2.500 N5 1.58340 -13.027 d11 4.200 r12 -6.609 d12 1.800 N6 1.83350 ν6 21.00 r13 -11.391

[Aspherical surface coefficient] r11: ε = 0.10864 × 10 A4 = 0.10222 × 10-³  A6 = 0.37798 x 10^-6  A8 = 0.22788 × 10^-7  A10 = 0.54568 × 10^-9  A12 = 0.53202 × 10^-11

<Example 4> F = 24.3 FNO = 3.62 [radius of curvature] [axis upper surface spacing] [refractive index] [Abbe number] r1 100.000 d1 1.200 N1 1.67339 ν1 29.25 r2 18.661 d2 1.000 r3 8.066 d3 3.000 N2 1.77250 ν2 49.77 r4 55.957 d4 1.000 r5 38.331 d5 1.000 N3 1.67339 ν3 29.25 r6 * 11.485 d6 1.000 r7 ∞ (diaphragm) d7 2.600 r8 -80.617 d8 2.400 N4 1.69680 ν4 56.47 r9 * -10.696 d9 4.200 r10 -6.897 d10 1.800 N5 1.5955 -15.604

[Aspherical surface coefficient] r6: ε = 0.53920 × 10 A4 = 0.29228 × 10^-3  A6 = 0.12770 x 10^-Four  A8 = -0.27287 x 10^-6  A10 = 0.16177 x 10^-7  A12 = -0.33209 × 10^-12  r9: ε = 0.22718 × 10 A4 = 0.15257 × 10^-Four  A6 = -0.68847 × 10^-Five  A8 = 0.19960 x 10^-6  A10 = -0.39712 × 10^-8  A12 = 0.14235 × 10^-11

<Example 5> F = 24.3 FNO = 3.62 [radius of curvature] [axis upper surface spacing] [refractive index] [Abbe number] r1 11.379 d1 1.801 N1 1.83350 ν1 21.00 r2 * 8.379 d2 1.501 r3 7.051 d3 2.412 N2 1.77250 ν2 49.77 r4 6.940 d4 2.331 r5 11.493 d5 1.807 N3 1.60000 ν3 64.38 r6 76.844 d6 0.900 r7 ∞ (diaphragm) d7 2.604 r8 76.922 d8 2.503 N4 1.61800 ν4 63.39 r9 * -14.401 d9 4.201 r10 -6.978 d10 1.11 N5 1.68 1.68 17.012

[Aspherical surface coefficient] r2: ε = 0.13108 × 10 A2 = -0.10364 × 10^-Four  A4 = 0.16161 x 10^-Four  A6 = 0.71054 x 10^-6  A8 = 0.55614 x 10^-8  A10 = 0.44010 × 10^-13  A12 = -0.17870 × 10^-14  r9: ε = 0.14555 × 10 A4 = -0.26042 × 10^-Four  A6 = -0.23640 x 10^-6  A8 = -0.15315 x 10^-8  A10 = -0.14577 × 10^-Ten  A12 = -0.16054 × 10^-12

<Example 6> F = 29.0 FNO = 4.0 [radius of curvature] [axis upper surface spacing] [refractive index] [Abbe number] r1 * 16.405 d1 3.200 N1 1.84666 ν1 23.82 r2 * 11.441 d2 4.500 r3 51.780 d3 4.142 N2 1.51728 ν2 69.68 r4 -10.228 d4 1.200 r5 ∞ (aperture) d5 9.221 r6 * -28.567 d6 2.700 N3 1.58340 ν3 30.23 r7 -23.642 d7 6.029 r8 -10.358 d8 1.044 N4 1.75450 ν4 51.57 r9 -35.486

[Aspherical surface coefficient] r1: ε = 0.32316 × 10 A4 = −0.16252 × 10^-3  A6 = -0.99176 × 10^-6  A8 = -0.24327 x 10^-7  r2: ε = 0.26034 × 10 A4 = -0.13957 × 10^-3  A6 = -0.34878 x 10^-6  A8 = -0.42525 x 10^-7  r6: ε = -0.18981 × 10 A4 = 0.29818 × 10^-Four  A6 = 0.52162 x 10^-6  A8 = 0.13294 × 10^-8

1, FIG. 3, FIG. 5, FIG. 7, FIG. 9 and FIG.
[Fig. 6] is a lens configuration diagram corresponding to Examples 1 to 6, respectively.

The first and second embodiments are, in order from the object side, a front group consisting of a negative meniscus lens convex to the object side, a positive meniscus lens convex to the object side, a biconcave negative lens and a biconvex positive lens. And a diaphragm (S), and a rear group including a positive meniscus lens concave on the object side and a negative meniscus lens concave on the object side. The image-side surface of the biconcave negative lens in the front group and the image-side surface of the negative meniscus lens in the rear group in Example 1 are aspherical surfaces. The image side surface of the biconcave negative lens in the front group and the image side surface of the positive meniscus lens in the rear group in Example 2 are aspherical surfaces.

In the third embodiment, in order from the object side, a negative meniscus lens convex to the object side, a positive meniscus lens convex to the object side, a negative meniscus lens concave to the object side, and a biconvex positive lens are provided. , A stop (S), and a rear group consisting of a positive meniscus lens concave on the object side and a negative meniscus lens concave on the object side. The image-side surface of the positive meniscus lens in the rear group is an aspherical surface.

The fourth embodiment comprises, in order from the object side, a front group consisting of a negative meniscus lens convex to the object side, a positive meniscus lens convex to the object side, and a negative meniscus lens concave to the image side,
It is composed of a diaphragm (S) and a rear group consisting of a positive meniscus lens concave on the object side and a negative meniscus lens concave on the object side. The image-side surface of the negative meniscus lens in the front group, which is concave toward the image side, and the image-side surface of the positive meniscus lens in the rear group, are aspherical surfaces.

In the fifth embodiment, in order from the object side, a front group consisting of two negative meniscus lenses convex to the object side and a positive meniscus lens convex to the object side, a diaphragm (S), a biconvex positive lens and The rear lens unit is composed of a negative meniscus lens concave on the object side. The image side surface of the negative meniscus lens on the object side in the front group and the image side surface of the biconvex positive lens in the rear group are aspherical surfaces.

In the sixth embodiment, in order from the object side, the front group consisting of a negative meniscus lens convex to the object side and a biconvex positive lens, a diaphragm (S), a positive meniscus lens concave to the object side, and the object side And a rear group consisting of a concave negative meniscus lens. Both surfaces of the negative meniscus lens in the front group and the object side surface of the positive meniscus lens in the rear group are aspherical surfaces.

2, FIG. 4, FIG. 6, FIG. 8, FIG. 10 and FIG.
2A and 2B are aberration diagrams corresponding to Examples 1 to 6, respectively. The solid line (d) represents the aberration with respect to the d line, and the broken line (SC) represents the sine condition. Further, the broken line (DM) and the solid line (DS) represent astigmatism on the meridional surface and the sagittal surface, respectively.

Table 1 shows φl / φf in conditional expression (2), φF / φf in conditional expression (3), and conditional expressions in Examples 1 to 6
Table 2 shows φR / φF in (4) and φl / φ in conditional expression (1).
Is Nd2 in conditional expressions (7) and (17), and ν2− in conditional expressions (8) and (18).
ν1, (R1 + R2) / (R1-R2) in conditional expressions (9), (19), (25), (R3 + R4) / (R3-R4 in conditional expressions (10), (26) Table 3 shows R (-) / F in conditional expressions (13), (22), and (27), and φ in conditional expression (5).
(+) / Φ, φ3 / φ in conditional expressions (6) and (16) are shown.

Tables 4 to 7 show the conditional expressions (11), (12), (14), (15), (20), (21), (23), (24), (28), (2
9) and corresponding aspherical surfaces (1st, 2nd, 3rd, 6th, 9th,
Values related to the amount of deviation (Dev /
F) is shown.

[0087]

[Equation 1]

[0088]

[Table 1]

[0089]

[Table 2]

[0090]

[Table 3]

[0091]

[Table 4]

[0092]

[Table 5]

[0093]

[Table 6]

[0094]

[Table 7]

[0095]

As described above, according to the present invention, the first lens element from the object side has a negative lens element convex to the object side as the first lens element. By making a good correction and having a negative lens as the final lens closest to the image surface, it is possible to achieve compactness, and by satisfying the conditional expressions (1) to (5), the image surface Compactness can be achieved while suppressing the occurrence of bending. Therefore, it is possible to realize a photographic lens having a wide angle while achieving compactness and high performance.

[Brief description of drawings]

FIG. 1 is a lens configuration diagram of a first embodiment of the present invention.

FIG. 2 is an aberration diagram of Example 1 of the present invention.

FIG. 3 is a lens configuration diagram of a second embodiment of the present invention.

FIG. 4 is an aberration diagram of Example 2 of the present invention.

FIG. 5 is a lens configuration diagram of a third embodiment of the present invention.

FIG. 6 is an aberration diagram of Example 3 of the present invention.

FIG. 7 is a lens configuration diagram of a fourth embodiment of the present invention.

FIG. 8 is an aberration diagram of Example 4 of the present invention.

FIG. 9 is a lens configuration diagram of Example 5 of the present invention.

FIG. 10 is an aberration diagram of Example 5 of the present invention.

FIG. 11 is a lens configuration diagram of Example 6 of the present invention.

FIG. 12 is an aberration diagram of Example 6 of the present invention.

[Explanation of symbols]

 (S)… Aperture

Claims (1)

[Claims] 1. A photographic lens having a diaphragm, wherein the first lens from the object side is a negative lens convex toward the object side, and the lens closest to the image side is a negative meniscus lens concave toward the object side. A photographic lens characterized in that the lens unit after the aperture is composed of a positive lens and a negative lens from the object side, and satisfies the following condition: -1.8 <φl / φ <-0.70 0.3 <φl / φf <4.0 -3.5 <φF / φf <-0.3 -1.2 <φR / φF <1.0 0.05 <φ (+) / φ <1.9 where φ is the power of the entire system φl is the power of the lens closest to the image plane φf is the object side From the first lens power φF: Power of lens group before aperture φR: Power of lens group after aperture φ (+): Power of positive lens in lens group after aperture