JP5272668B2 - Imaging lens, camera, and portable information terminal - Google Patents

Description

  The present invention relates to an imaging lens, a camera, and a portable information terminal device.

  Along with the large expansion of the digital camera market, the demands of users for digital cameras are diverse. The digital camera with zoom function is also very popular, but many users like the “compact camera with a high-performance single focal length imaging lens” and its high performance. Small and large diameters are strongly expected.

  In terms of "high performance" in the above compact camera, in addition to having a resolution that corresponds to an image sensor of at least 10 million pixels to 20 million pixels, "From the full aperture, there is little coma flare, high contrast, and the periphery of the angle of view. There are demands such as “no image distortion”, “no chromatic aberration and no undesired coloring even in a portion with a large luminance difference”, and “a straight line can be drawn as a straight line with little distortion”.

In terms of “large aperture”, from the viewpoint of differentiation from a general compact camera equipped with a zoom lens, the F number is required to be at least F2.4 or less, and many people desire F2.0 or less.
As for the “field angle of the photographic lens”, there are many users who want a certain wide angle, and the half angle of view of the imaging lens is 38 degrees or more (corresponding to 28 mm in focal length converted to a so-called Leica plate which is a 35 mm silver salt camera) .) Is desirable.

There are many types of imaging lenses for digital cameras, but as a typical configuration of a “wide-angle single focal length imaging lens” such as the imaging lens of the present invention, it has been negatively applied to the object side. And a so-called “retro focus type” in which a lens group having a positive refractive power is disposed on the image side.
Due to the characteristics of the area sensor that has a color filter and microlens for each pixel, the exit pupil position should be kept away from the image plane so that the peripheral luminous flux is "incident at an angle close to perpendicular to the light receiving surface of the area sensor". The existence of the requirement is the main reason why the retrofocus type is adopted.
However, since the retrofocus type has a large asymmetry in refractive power arrangement, correction of coma aberration, distortion aberration, lateral chromatic aberration and the like tends to be insufficient.
Conventionally known retrofocus type imaging lenses that achieve a half angle of view of around 38 degrees with a relatively large aperture are those described in Patent Documents 1 to 3 and the like.

The imaging lens described in Patent Document 1 has a large aperture of F1.4, but has large astigmatism and curvature of field, and it is difficult to say that “sufficient performance up to the periphery” is achieved near the full aperture. .
The imaging lens described in Patent Document 2 is insufficient in terms of F2.8 and the size of the aperture from the recent required level, and astigmatism, field curvature, and lateral chromatic aberration are sufficiently corrected. It is difficult to say that this imaging lens has also achieved “sufficient performance up to the periphery”.
Each of the imaging lenses described in Patent Documents 1 and 2 has a distortion aberration exceeding 2% in absolute value.

  In the imaging lens described in Patent Document 3, astigmatism, curvature of field, and distortion are corrected well. However, there is still room for improvement in terms of “large diameter and small size”.

Japanese Patent Laid-Open No. 06-308385 JP 09-218350 A JP 2006-349920 A

  The present invention has been made in view of the above-mentioned circumstances, and has a half angle of view: a wide angle of about 38 degrees, a large aperture having an F number of about 2.0 or less, a relatively small size, astigmatism and an image plane. Curvature, lateral chromatic aberration, coma color difference, distortion, etc. are sufficiently reduced to have a resolution corresponding to an image sensor with 10 to 20 million pixels, and a point image from the full aperture to the periphery of the angle of view with high contrast It is an object of the present invention to realize a high-performance imaging lens that does not collapse, generates unnecessary coloring even in a portion with a large luminance difference, and can draw a straight line without distortion.

The imaging lens of the present invention is a “single focal length imaging lens” and has the following characteristics.
That is, the first lens group located on the object side and the second lens group located on the image side with the aperture stop interposed therebetween. That is, the first lens group and the second lens group are “defined by the aperture stop”.

The “first lens group” includes a first F lens group having negative refractive power on the object side, and a first R lens group having positive refractive power on the aperture side, that is, the image side. And the first R lens group forms the “widest air gap in the first lens group”.
The “second lens group” includes, in order from the aperture stop side, a second F lens group including a first positive lens, a first negative lens, a second negative lens, and a second positive lens, and a second R that includes one lens. And a lens group. The second lens group has a positive refractive power as “the second lens group itself”. The second F lens group also has a positive refractive power.
The first positive lens and the first negative lens, and the second negative lens and the second positive lens of the second F lens group are cemented.
Curvature radius of “joint surface of first positive lens and first negative lens”; r _S1 , radius of curvature of “joint surface of second negative lens and second positive lens”: r _S2 , focal length of entire system: f _A The conditions:
_{(1) -2.4 <r S1 /} f A <-0.8
_{(2) 1.0 <r S2 /} f A <2.6
Satisfied.

In the imaging lens according to claim 1, the first R lens group includes “one positive lens”.
In the imaging lens according to claim 2, the first R lens group includes “one cemented lens having a positive refractive power as a whole”.
The imaging lens according to claim 1 or 2 , wherein the focal length of the entire system: f _A and the focal length of the first lens group: f ₁ are:
(3) 0.0 <f _A / f ₁ <0.8
Is preferably satisfied ( Claim 3 ).

  By satisfying the condition (3), the flatness of the image plane can be further improved.

The imaging lens according to claim 1, 2 or 3 , wherein the second lens group has a total length: L _2F and a distance from the most object side surface of the imaging lens to the image plane: L in the second lens group. :
(4) 0.1 < _L2F / L <0.25
Is preferably satisfied ( claim 4 ).

  When the condition (4) is satisfied, each aberration can be corrected more favorably.

The imaging lens according to any one of claims 1 to 4 , wherein in the first lens group, an interval between the first F lens group and the first R lens group: A _1F-1R , and the total length L ₁ of the first lens group is ,conditions:
(5) 0.35 <A _1F-1R / L ₁ <0.7
Is preferably satisfied ( claim 5 ).

  By satisfying the condition (5), it is possible to more effectively suppress the occurrence of spherical aberration accompanying the increase in diameter.

The imaging lens according to any one of claims 1 to 5 , wherein in the second F lens group of the second lens group, the Abbe number of the first positive lens: ν _d and the anomalous dispersion: Δθ _{g, F} are: conditions:
(6) ν _d > 80.0
(7) Δθ _{g, F} > 0.025
Is preferably satisfied ( claim 6 ).
The above-mentioned “anomalous dispersion: Δθ _{g, F} ” has an Abbe number: ν _d as a horizontal axis, a partial dispersion ratio: θ _{g, F} = ( _ng− n _F ) / (n _F −n _C ) as a vertical axis. In the orthogonal coordinate system, when the straight line connecting the glass type: K7 (specifically, OHARA glass type name NSL7) and the glass type: F2 (specifically, OHARA glass type name PBM2) is used as a standard line, It is an amount defined as “deviation from standard line (distance in the vertical axis direction)” of the glass type (glass type of the first positive lens). The above n _g , n _F and n _C are the refractive indices for the g line, F line and C line, respectively.

  Chromatic aberration can be corrected more satisfactorily by using a glass type that satisfies the conditions (6) and (7).

The imaging lens according to any one of claims 1 to 6 , wherein the first F lens group in the first lens group is "two negative meniscus lenses having a convex surface facing the object side, arranged continuously from the object side". has the configuration, it is preferable image-side surface of at least one lens of these two negative meniscus lens is aspheric (claim 7).

With the configuration of this seventh aspect , it is possible to more effectively suppress the occurrence of aberrations, and particularly to correct distortion aberrations satisfactorily.

In the imaging lens according to any one of claims 1 to 7 , it is preferable that "one lens constituting the second R lens group" of the second lens group has an aspherical surface ( claim 8 ).
By adopting such a configuration, “coma aberration can be corrected more satisfactorily without taking an unnecessarily complicated configuration”.

In the imaging lens according to any one of claims 1 to 8 , it is preferable to perform focusing on a finite distance object by moving all or a part of the second lens group ( claim 9 ).
Such a method is suitable for focusing on a finite distance object.
A camera of the present invention is a camera having the imaging lens according to any one of claims 1 to 9 as a photographing optical system ( claim 10 ). A portable information terminal device according to the present invention includes the imaging lens according to any one of claims 1 to 9 as a “photographing optical system of a camera function unit” ( claim 11 ).
As mentioned above, retrofocus imaging lenses generally have negative refractive power on the object side and positive refractive power on the image side, and distortion and lateral chromatic aberration due to the asymmetry of refractive power distribution. Etc. are likely to occur, and reduction of these aberrations becomes a major issue. In addition, with the increase in diameter, it becomes difficult to correct “coma aberration and coma color difference”, and problems are accumulated.
The imaging lens of the present invention has been made by finding that the above-mentioned problem in correcting aberrations can be solved by the configuration as described above.

The first lens group includes a negative refractive power (first F lens group) on the object side, and a positive refractive power (first R lens group) on the image side (aperture stop side) in order. By ensuring a relatively large distance between the first lens group and the first R lens group (the widest air distance in the first lens group), it is possible to secure a sufficient angle of view and correct various aberrations including spherical aberration. Both are compatible.
The first R lens group disposed on the aperture stop side in the first lens group and the second F lens group on the aperture stop side in the second lens group face each other with the aperture stop interposed therebetween, and both have positive refractive power There is also an aspect in which coma aberration is controlled by the balance of these.

The configuration and role of the second F lens group greatly characterizes the imaging lens.
In the imaging lens of the present invention, the second F lens group has a “main imaging function” and is “the most important lens group in terms of aberration correction”. The second F lens group is based on positive, negative, and positive “so-called triplets” as the refractive power arrangement, but the central negative refractive power is divided into two, positive, negative, negative, and positive four lenses. The configuration.
Since the aperture stop is disposed on the object side of the second F lens group, the “first positive lens and first negative lens pair” and the “second negative lens and second positive lens pair” generate off-axis rays. The height is different, and it is possible to effectively reduce both the longitudinal chromatic aberration and the lateral chromatic aberration by using this. Furthermore, by using the second negative lens as a design parameter, the degree of freedom in design is increased, and “reduction of coma aberration color difference” becomes possible.

  In each lens surface in the second F lens group, “each aberration is greatly exchanged” in order to reduce the final aberration amount, and the manufacturing error sensitivity tends to be high. By using a pair of one negative lens as a cemented lens and also joining a pair of the second negative lens and the second positive lens, the substantial manufacturing error sensitivity is reduced, and stable performance is easily obtained. It also leads to a reduction in the parts of the lens barrel that actually holds the lens.

  Further, as expressed in the conditions (1) and (2), the cemented surface of the first positive lens and the first negative lens has a shape of “convex to the image side”, and the second negative lens and the second positive lens The joint surface has a shape of “convex to the object side”. With such a configuration, the “image-convex cemented surface” of the first positive lens and the first negative lens mainly has a role of correcting axial chromatic aberration, and the second negative lens and the second positive lens. The “convex surface convex on the object side” mainly has a role of correcting the chromatic aberration of magnification so that the entire chromatic aberration can be corrected effectively.

Conditions (1) and (2) are for correcting chromatic aberration in a well-balanced manner while keeping monochromatic aberration sufficiently small.
Condition (1) parameter: r _S1 / f _A is lower limit: -2.4 or parameter (2) parameter: r _S2 / f _A is higher than 2.6: chromatic aberration correction Is not preferable because “spherical aberration is insufficiently corrected or introverted coma remains”. On the other hand, the parameter of the condition _(1): or r S1 / _{f A} is greater than -0.8, or condition (2) _parameters: and r S2 / _{f A} is less than 1.0, when the priority of the chromatic aberration correction “Spherical aberrations are overcorrected or outward coma remains,” which is not preferable.

  The second R lens group has a “role balance and control of exit pupil distance”. Needless to say, having positive refractive power is effective in securing the exit pupil distance, but if the exit pupil distance can be short, it contributes to "shortening the total lens length with negative refractive power". It is also possible to make it.

According to the configuration of the imaging lens of the present invention, as described above, it is possible to obtain “a great effect on aberration correction”, a half angle of view: a wide angle of about 38 degrees, and an F number: 2.0. “Very high image performance” can be achieved even under severe conditions of a large aperture of less than or equal to the degree.
The imaging lens of the present invention naturally has positive refractive power as a whole, and the second lens group has “positive refractive power” as in claims 1 and 2 .
The refractive power of the first lens unit in the imaging lens according to claim 1 or 2 can be positive or negative. When the refractive power of the first lens group is negative, the imaging lens of claim 1 is a “retro focus type”, but when the negative refractive power of the first lens group is increased to some extent, “the asymmetry of the refractive power arrangement”. The above-mentioned weakness of the retrofocus type appears that the correction of coma, distortion, lateral chromatic aberration, etc. tends to be insufficient.

From such a viewpoint, it is preferable that the refractive power of the first lens group satisfies the condition (3).
The first lens group also has a “wide converter added to the second lens group” aspect. From the viewpoint of a wide converter function, it is desirable that the first lens group be an “afocal system”. However, the imaging lens of the present invention focuses not only on widening the angle, but on the realization of high performance. From the viewpoint of actual aberration correction, the first lens group is completely afocal. It is not the best.

When the parameter of condition (3): f _A / f ₁ is smaller than 0.0, the refractive power of the first lens group becomes negative, and the positive refractive power of the second lens group must be increased, and the image plane This causes a problem that the bending of the lens becomes large or negative distortion becomes large.

When the parameter of condition (3): f _A / f ₁ is larger than 0.8, the imaging action of the second lens group, which is “the main lens group that bears the main imaging action and is also the most important in terms of aberration correction”. The first lens group is likely to generate relatively large aberrations, and the manufacturing error sensitivity is likely to be higher than necessary.

The parameter (3) parameter f _A / f ₁ for regulating the refractive power of the first lens group is more preferably slightly narrower than the condition (3), and the following condition:
(3A) 0.0 <f _A / f ₁ <0.7
And more preferably, the conditions:
(3B) 0.0 <f _A / f ₁ <0.4
It is preferable to satisfy
Also, the total length of the 2F lens group: L _2F is, the distance from the surface closest to the object side of the imaging lens to the image plane: conditions should be satisfied for L (4) are both longitudinal chromatic aberration and lateral chromatic aberration This is an effective condition for effectively reducing.

  In the imaging lens of the present invention, since the aperture stop is disposed on the object side of the second F lens group as described above, the “first positive lens and first negative lens pair” and the “second negative lens, “Actual chromatic aberration and lateral chromatic aberration are effectively reduced” by utilizing the fact that the height of off-axis rays differs between “a pair of two positive lenses”. Condition (4) is such a function. As a condition for working most effectively, the total length of the second F lens group is regulated.

When the parameter of condition (4): L _2F / L is smaller than 0.1, the “difference in the height of off-axis rays” in the second F lens group becomes small, and the above function becomes difficult to work. There is a risk that the correction is insufficient.
When the parameter of condition (4): L _2F / L is larger than 0.25, the second F lens group occupies space unnecessarily, and the relationship with other lens groups is lost, so that field curvature, astigmatism, coma There is a risk that aberrations may become unbalanced.

The parameter of condition (4): L _2F / L is the condition for better aberration correction:
(4A) 0.1 <L _2F /L<0.2
Is preferably satisfied.

In the first lens group, the condition (5) that the distance between the first F lens group and the first R lens group: A _1F-1R and the total length of the first lens group: L ₁ should satisfy is a further favorable aberration. This is an effective condition for correction.

That is, for better aberration correction, the distance between the first F lens group and the first R lens group should be set appropriately, and the parameter (A _1F-1R / L ₁ ) in the condition (5) is set to 0. If it is smaller than 35, the spherical aberration tends to be undercorrected, and conversely if it is larger than 0.7, the spherical aberration tends to be overcorrected.

By constructing the first positive lens with so-called “special low dispersion glass” that satisfies the conditions (6) and (7) in claim 6, the “secondary spectrum of chromatic aberration” is effectively reduced, and a better correction is achieved. The state can be realized.

Further, as in claim 7 , the first F lens group is “a configuration in which two negative meniscus lenses having a convex surface facing the object side are continuously arranged from the object side”, and the image side surface of at least one of the lenses By making the aspherical surface, it is possible to further improve the aberration correction.

  By dividing the negative refractive power of the first F lens group into two meniscus lenses and preventing the occurrence of excessive aberration on a specific surface, astigmatism and the like can be corrected better as a whole lens system, By making the image side surface having a large curvature an aspherical surface, a large effect can be obtained in correcting distortion aberration, and a role of correcting coma aberration and the like can be provided.

The second R lens of the second lens group is composed of one lens as described above, and it is desirable that this lens has an aspherical surface as in the eighth aspect .
The second F lens group is composed of two sets of cemented lenses and has a sufficient degree of freedom in correcting aberrations. Since the second R lens is sufficient even with a simple configuration, it is reduced to a single-lens configuration for miniaturization. By providing an aspherical surface, coma aberration can be mainly corrected better.

  The aspheric surfaces of the first F lens group and the second R lens group are preferably provided at the same time so as to complement each other and to function more effectively.

Focusing on a finite distance object is performed by moving the entire imaging lens by moving the whole or part of the second lens group, as in claim 9 . Since the weight can be reduced, it is advantageous for speeding up focusing and power saving.

  Further, when the imaging lens of the present invention is incorporated in a camera as a photographic optical system, when it is not in use, it has a mechanism for shortening the distance between the lens groups and the back focus portion and storing it in a compact manner. There is a merit that the mechanism for this can be shared with the focusing mechanism.

  As described above, according to the present invention, a “new imaging lens having a single focal length” can be realized. This imaging lens has a wide angle of half angle of view: about 38 degrees, a large aperture of about 2.0 or less, astigmatism, curvature of field, lateral chromatic aberration, coma aberration, as shown in the examples described later. Resolving power corresponding to an image sensor with 10 to 20 million pixels by sufficiently reducing chrominance and distortion, etc., in a portion with a large luminance difference from the full aperture to the high contrast and the peripheral part of the angle of view. In addition, unnecessary coloring does not occur, a straight line can be drawn without distortion, and a relatively small size can be realized.

  Therefore, by mounting this imaging lens, a small-sized and high-quality camera and a portable information terminal device can be realized.

Hereinafter, embodiments will be described.
1 to 6 show six examples of imaging lens embodiments.
1 to 6 corresponds to Examples 1 to 6 described later. In order to avoid complications, the reference numerals in these drawings are the same, the reference numeral 1F indicates the first F lens group, the reference numeral IR indicates the first R lens group, the reference numeral 2P1 indicates the first positive lens, the reference numeral 2N1 indicates the first negative lens, the reference numeral 2N2 Indicates a second negative lens, reference numeral 2P2 indicates a second positive lens, and reference numeral 2R indicates a second R lens group.

  An aperture stop that defines the first lens group and the second lens group is denoted by S. In FIG. 1 to FIG. 6, symbol F denotes a cover glass (seal glass) of various filters such as an optical low-pass filter and an infrared cut filter, and an image sensor such as a CCD sensor, and a single transparent parallel equivalent to these. Displayed as a flat plate, symbol I indicates an image plane (light receiving surface of the image sensor).

  The image forming lens whose embodiment is shown in FIGS. 1 to 6 includes a first lens group located on the object side and a second lens group located on the image side with the aperture stop S interposed therebetween. The first lens group includes a first F lens group 1F having negative refractive power on the object side, and has a widest air interval in the first lens group, and has a positive refractive power on the aperture stop S side. The first R lens group 1R having

The second lens group as a whole has a positive refractive power, and includes a first positive lens 2P1, a first negative lens 2N1, a second negative lens 2N2, and a second positive lens 2P2 in order from the aperture stop S side. The lens unit includes a second F lens group having a positive refractive power and a second R lens group 2R including one lens.
The first positive lens 2P1 and the first negative lens 2N1, and the second negative lens 2N2 and the second positive lens 2P2 of the second F lens group are cemented.

  As can be seen from Examples 1 to 6 corresponding to these embodiments, the imaging lenses of these embodiments all satisfy the conditions (1) to (7).

  Before giving a specific example of the imaging lens, one embodiment of the form information terminal device will be described with reference to FIG. 13 and FIG.

  The portable information terminal device has a camera as a “part having a photographing function”.

FIG. 13 shows the appearance of the apparatus, and FIG. 14 shows the system configuration.
As shown in FIG. 14, the portable information terminal device 30 includes an imaging lens 31 and a light receiving element (an electronic imaging element in which pixels are two-dimensionally arranged) 45 and is formed by the imaging lens 31. The light receiving element 45 reads the “image of the object”.

As the imaging lens 31, the imaging lens according to any one of claims 1 to 9 , more specifically, the imaging lenses of Examples 1 to 6 described later are used. The light receiving element 45 has a pixel number of 10 million to 20 million pixels.

  The output from the light receiving element 45 is processed by the signal processing device 42 under the control of the central processing unit 40, converted into digital information, and the digitized image information is received by the image processing device 41 under the control of the central processing unit 40. After being subjected to predetermined image processing, it is recorded in the semiconductor memory 44.

  The liquid crystal monitor 38 can display an image being image-processed by the image processing device 41 or can display an image recorded in the semiconductor memory 44. The image recorded in the semiconductor memory 44 can be transmitted to the outside using a communication card 43 or the like.

  As shown in FIG. 13, when the imaging lens 31 is carried, it is in a retracted state as shown in FIG. 13A. When the user operates the power switch 36 to turn on the power, as shown in FIG. The lens barrel is paid out. Reference numeral 33 denotes a finder.

Focusing is performed by half-pressing the shutter button 35. Focusing can be performed by moving the whole or a part of the second lens group as in claim 9. However, the focusing is not limited to this, and the movement of the first lens group or the light receiving element 45 in the lens optical axis direction is possible. It can also be performed by movement, and if necessary, can also be performed by a combination of these methods. When the shutter button 35 is further pressed, shooting is performed, and thereafter the above-described processing is performed.

  When an image recorded in the semiconductor memory 44 is displayed on the liquid crystal monitor 38 or transmitted to the outside using a communication card or the like, the operation button 37 shown in FIG. 13C is used. A semiconductor memory, a communication card, and the like are used by being inserted into dedicated or general-purpose slots 39A and 39B, respectively.

  When the imaging lens 31 is in the retracted state, each group of imaging lenses does not necessarily have to be aligned on the optical axis. For example, the second F lens group of the second lens group (consisting of two sets of cemented lenses and having a large space for closing in the optical axis direction in the second lens group) is retracted from the optical axis and another lens is retracted. As a mechanism that is accommodated in parallel with the group, the portable information terminal device can be further reduced in thickness.

In addition, the part except the communication function by communication cards etc. 43 from embodiment of FIG. 13, FIG. 14 is embodiment of the camera of Claim 10. FIG.

  In such a portable information terminal device, any of the imaging lenses of Examples 1 to 6 is used as the imaging lens, so that the resolution corresponding to the imaging element 45 of 10 to 20 million pixels can be displayed with high contrast from the open aperture. The point image does not collapse to the peripheral part of the corner, no unnecessary coloring is generated even in a portion with a large luminance difference, a straight line can be drawn without distortion, and the size is relatively small.

  Six specific examples of the imaging lens are shown below.

  Throughout Examples 1 to 6, the maximum image height is 4.80 mm. In addition, the unit having the time limit of length is “mm”.

The meanings of symbols in each embodiment are as follows.
f: Focal length of the entire system
F: F number
ω: Half angle of view
R: radius of curvature
D: Face spacing
N _d : Refractive index
ν _d : Abbe number
K: Aspheric conical constant
A ₄ : Fourth-order aspheric coefficient
A ₆ : 6th-order aspheric coefficient
A ₈ : 8th-order aspheric coefficient
A ₁₀ : 10th-order aspheric coefficient
A ₁₂ : 12th-order aspheric coefficient
A ₁₄ : 14th-order aspheric coefficient
A ₁₆ : 16th-order aspheric coefficient
A ₁₈ : 18th-order aspheric coefficient
The aspherical surface is expressed as follows using the reciprocal of the paraxial radius of curvature (paraxial curvature): C, height from the optical axis: H, depth in the optical axis direction: X, the above conic constant, and aspheric coefficient. Is done.

X = CH ² / [1 + √ {1- (1 + K) C ² H ² }]
+ A ₄・ H ⁴ + A ₆・ H ⁶ + A ₈・ H ⁸ + A ₁₀・ H ¹⁰ + A ₁₂・ H ¹² + A ₁₄・ H ¹⁴ + A ₁₆・ H ¹⁶ + A ₁₈・ H ¹⁸ .

"Example 1"
f = 6.00, F = 1.92, ω = 39.0
Surface number RDN _d ν _d Δθ _{g, F}
01 17.915 1.20 1.49700 81.54 0.0280 OHARA S-FPL51
02 6.474 2.28
03 10.587 1.27 1.51633 64.06 -0.0045 OHARA L-BSL7
04 * 5.000 11.43
05 17.508 3.51 1.69100 54.82 -0.0079 OHARA S-LAL9
06 -33.849 5.11
07 Aperture 3.05
08 39.197 3.05 1.49700 81.54 0.0280 OHARA S-FPL51
09 -8.187 0.80 1.78470 26.29 0.0146 OHARA S-TIH23
10 -29.420 0.10
11 14.787 0.80 1.72825 28.46 0.0123 OHARA S-TIH10
12 10.565 2.82 1.69100 54.82 -0.0079 OHARA S-LAL9
13 -33.173 2.40
14 * 17.744 1.00 1.51633 64.06 -0.0045 OHARA L-BSL7
15 16.286 5.38
16 ∞ 1.24 1.51680 64.20 Various filters
17 ∞.

“Aspherical surface” (surface marked with “*”. The same applies to the following embodiments.)
4th page
K = -0.82391, A ₄ = 1.51453 × 10 ^-4 , A ₆ = -8.03748 × 10 ^-6 , A ₈ = 2.33697 × 10 ^-7 ,
A ₁₀ = -1.16222 × 10 ^-8
14th page
K = -26.92849, A ₄ = 9.33931 × 10 ^-5 , A ₆ = -1.79865 × 10 ^-5 , A ₈ = 3.06532 × 10 ^-7 ,
A ₁₀ = -3.57164 × 10 ^-9 .

"Numeric value of conditional expression parameter"
r _S1 / f _A = -1.36
r _S2 / f _A = 1.76
L _2F / L = 0.164
f _A / f ₁ = 0.192
A _1F-1R / L ₁ = 0.580.

"Example 2"
f = 5.90, F = 2.04, ω = 39.2
Surface number RDN _d ν _d Δθ _{g, F}
01 12.229 1.20 1.71300 53.87 -0.0084 OHARA S-LAL8
02 6.993 2.34
03 11.666 1.46 1.51633 64.06 -0.0045 OHARA L-BSL7
04 * 5.000 13.88
05 12.778 2.42 1.80610 40.93 -0.0052 OHARA S-LAH53
06 -8.157 0.80 1.85026 32.27 0.0036 OHARA S-LAH71
07 -32.381 2.55
08 Aperture 3.00
09 15.291 2.12 1.49700 81.54 0.0280 OHARA S-FPL51
10 -6.828 0.80 1.68893 31.07 0.0092 OHARA S-TIM28
11 -548.914 0.63
12 -9.532 0.80 1.71736 29.52 0.0110 OHARA S-TIH1
13 12.818 1.94 1.83481 42.71 -0.0082 OHARA S-LAH55
14 -39.742 0.10
15 * 24.958 1.95 1.76802 49.24 -0.0081 HOYA M-TAF101
16 -13.517 6.19
17 ∞ 1.24 1.51680 64.20 Various filters
18 ∞.

"Aspherical surface"
4th page
K = -0.41935, A ₄ = -5.42080 × 10 ^-5 , A ₆ = -2.48263 × 10 ^-5 , A ₈ = 7.57412 × 10 ^-7 ,
A ₁₀ = -2.30755 × 10 ^-8
15th page
K = 0.0, A ₄ = -3.94481 × 10 ^-4 , A ₆ = 7.14419 × 10 ^-7 , A ₈ = 6.43089 × 10 ^-8 ,
A ₁₀ = -2.58953 × 10 ^-9 .

"Numeric value of conditional expression parameter"
r _S1 / f _A = -1.16
r _S2 / f _A = 2.17
L _2F / L = 0.143
f _A / f ₁ = 0.604
A _1F-1R / L ₁ = 0.628.

"Example 3"
f = 6.00, F = 1.95, ω = 39.1
Surface number RDN _d ν _d Δθ _{g, F}
01 22.824 1.20 1.48749 70.24 0.0022 OHARA S-FSL5
02 6.600 2.27
03 11.856 1.28 1.51633 64.06 -0.0045 OHARA L-BSL7
04 * 5.000 11.53
05 18.323 1.81 1.69350 53.18 -0.0072 OHARA L-LAL13
06 * -26.515 4.31
07 Aperture 4.61
08 43.943 1.99 1.49700 81.54 0.0280 OHARA S-FPL51
09 -9.000 1.00 1.74077 27.79 0.0130 OHARA S-TIH13
10 -32.779 0.20
11 19.707 1.00 1.69895 30.13 0.0103 OHARA S-TIM35
12 9.972 2.28 1.60300 65.44 0.0045 OHARA S-PHM53
13 -36.934 2.87
14 * 15.450 1.26 1.51633 64.06 -0.0045 OHARA L-BSL7
15 37.405 6.03
16 ∞ 1.24 1.51680 64.20 Various filters
17 ∞.

"Aspherical surface"
4th page
K = -0.82391, A ₄ = 7.26169 × 10 ^-5 , A ₆ = -5.10959 × 10 ^-6 , A ₈ = 4.38244 × 10 ^-8 ,
A ₁₀ = -6.97612 × 10 ^-9
6th page
K = 0.0, A ₄ = 2.05935 × 10 ^-5 , A ₆ = -1.04777 × 10 ^-6 , A ₈ = 8.84156 × 10 ^-8 ,
A ₁₀ = -2.25119 × 10 ^-9
14th page
K = -26.92849, A ₄ = 5.11073 × 10 ^-4 , A ₆ = -2.92185 × 10 ^-5 , A ₈ = 7.49033 × 10 ⁻⁷ ,
A ₁₀ = -1.06280 × 10 ^-8 .

"Numeric value of conditional expression parameter"
r _S1 / f _A = -1.50
r _S2 / f _A = 1.66
L _2F / L = 0.142
f _A / f ₁ = 0.243
A _1F-1R / L ₁ = 0.637.

Example 4
f = 6.00, F = 1.96, ω = 39.1
Surface number RDN _d ν _d Δθ _{g, F}
01 25.683 1.20 1.48749 70.24 0.0022 OHARA S-FSL5
02 7.430 2.64
03 16.000 1.20 1.51633 64.06 -0.0045 OHARA L-BSL7
04 * 4.763 3.85
05 25.619 1.42 1.83481 42.71 -0.0082 OHARA S-LAH55
06 127.934 8.75
07 32.911 1.59 1.66672 48.32 -0.0024 OHARA S-BAH11
08 -23.844 0.70
09 Aperture 5.16
10 13.187 2.36 1.49700 81.54 0.0280 OHARA S-FPL51
11 -10.110 1.00 1.72047 34.71 -0.0019 OHARA S-NBH8
12 -19.398 0.50
13 30.091 1.65 1.75520 27.51 0.0133 OHARA S-TIH4
14 8.000 1.49 1.49700 81.54 0.0280 OHARA S-FPL51
15 15.165 1.20
16 * 13.879 2.00 1.51633 64.06 -0.0045 OHARA L-BSL7
17 -31.006 6.96
18 ∞ 1.24 1.51680 64.20 Various filters
19 ∞.

"Aspherical surface"
4th page
K = -0.40687, A ₄ = -3.60864 × 10 ^-4 , A ₆ = -2.38402 × 10 ^-5 , A ₈ = 6.28983 × 10 ^-7 ,
A ₁₀ = -2.42525 × 10 ^-8
16th page
K = 0.0, A ₄ = -4.01894 × 10 ^-4 , A ₆ = 3.25574 × 10 ^-6 , A ₈ = -2.41480 × 10 ^-7 ,
A ₁₀ = 3.20689 × 10 ^-9 .

"Numeric value of conditional expression parameter"
r _S1 / f _A = -1.68
r _S2 / f _A = 1.33
L _2F / L = 0.154
f _A / f ₁ = 0.183
A _1F-1R / L ₁ = 0.424.

"Example 5"
f = 6.00, F = 1.95, ω = 39.1
Surface number RDN _d ν _d Δθ _{g, F}
01 29.662 1.20 1.48749 70.24 0.0022 OHARA S-FSL5
02 7.518 3.11
03 15.500 1.20 1.51633 64.06 -0.0045 OHARA L-BSL7
04 * 5.069 3.41
05 35.236 1.58 1.80440 39.59 -0.0045 OHARA S-LAH63
06 -160.735 10.84
07 37.658 1.79 1.60300 65.44 0.0045 OHARA S-PHM53
08 -19.258 2.30
09 Aperture 6.13
10 16.288 2.22 1.49700 81.54 0.0280 OHARA S-FPL51
11 -11.455 1.00 1.72151 29.23 0.0111 OHARA S-TIH18
12 -25.036 0.20
13 12.552 1.34 1.84666 23.78 0.0175 OHARA S-TIH53
14 8.000 1.74 1.49700 81.54 0.0280 OHARA S-FPL51
15 14.244 2.97
16 * 13.690 1.50 1.51633 64.06 -0.0045 OHARA L-BSL7
17 81.181 5.04
18 ∞ 1.24 1.51680 64.20 Various filters
19 ∞.

"Aspherical surface"
4th page
K = -0.85535, A ₄ = 3.24166 × 10 ^-6 , A ₆ = -2.56520 × 10 ^-6 , A ₈ = -3.63511 × 10 ^-8 ,
A ₁₀ = -1.39606 × 10 ^-9
16th page
K = 0.0, A ₄ = -3.27966 × 10 ^-4 , A ₆ = 3.00723 × 10 ^-6 , A ₈ = -2.59822 × 10 ^-7 ,
A ₁₀ = 4.26578 × 10 ^-9 .

"Numeric value of conditional expression parameter"
r _S1 / f _A = -1.91
r _S2 / f _A = 1.33
L _2F / L = 0.132
f _A / f ₁ = 0.238
A _1F-1R / L ₁ = 0.469.

"Example 6"
f = 6.00, F = 1.95, ω = 39.1
Surface number RDN _d ν _d Δθ _{g, F}
01 22.012 1.20 1.48749 70.24 0.0022 OHARA S-FSL5
02 7.749 2.64
03 15.507 1.20 1.51633 64.06 -0.0045 OHARA L-BSL7
04 * 5.077 10.90
05 23.488 1.61 1.83400 37.16 -0.0037 OHARA S-LAH60
06 -49.774 5.62
07 Aperture 3.20
08 71.630 2.01 1.49700 81.54 0.0280 OHARA S-FPL51
09 -8.151 1.00 1.69895 30.13 0.0103 OHARA S-TIM35
10 -25.309 0.20
11 20.224 1.00 1.64769 33.79 0.0070 OHARA S-TIM22
12 9.811 2.30 1.49700 81.54 0.0280 OHARA S-FPL51
13 -18.713 4.34
14 * 16.584 1.46 1.51633 64.06 -0.0045 OHARA L-BSL7
15 97.102 6.91
16 ∞ 1.24 1.51680 64.20 Various filters
17 ∞.

"Aspherical surface"
4th page
K = -0.83616, A ₄ = 1.06538 × 10 ^-4 , A ₆ = -2.50034 × 10 ^-6 , A ₈ = 9.83448 × 10 ^-9 ,
A ₁₀ = -1.85737 × 10 ^-9
14th page
K = 0.0, A ₄ = -2.40864 × 10 ^-4 , A ₆ = 3.17695 × 10 ^-6 , A ₈ = -1.91600 × 10 ^-7 ,
A ₁₀ = 2.94310 × 10 ^-9 .

"Numeric value of conditional expression parameter"
r _S1 / f _A = -1.36
r _S2 / f _A = 1.63
L _2F / L = 0.137
f _A / f ₁ = 0.049
A _1F-1R / L ₁ = 0.621.

FIG. 7 shows aberration diagrams related to Example 1.
The broken line in the spherical aberration diagram represents “sine condition”, the solid line in the astigmatism diagram represents “sagittal”, and the broken line represents “meridional”. The same applies to other aberrations.
FIG. 8 to FIG. 12 sequentially show aberration diagrams related to Examples 2 to 6.

  As is apparent from these aberration diagrams, the aberration is corrected at a high level in each example, and the spherical aberration and the longitudinal chromatic aberration are so small that they do not cause a problem. In addition, astigmatism, curvature of field, and lateral chromatic aberration are sufficiently small, and coma and disturbance of color difference are well suppressed to the outermost part, and distortion is 2.0% or less in absolute value. .

  From these examples, by constructing the imaging lens as in the present invention, the half angle of view is as wide as about 38 degrees, and the F number is about 2.0 or less, but a very large image performance. It is clear that can be secured.

1 is a diagram illustrating a lens configuration of Example 1. FIG. 6 is a diagram illustrating a lens configuration of Example 2. FIG. 6 is a diagram illustrating a lens configuration of Example 3. FIG. FIG. 6 is a diagram illustrating a lens configuration of Example 4. 10 is a diagram illustrating a lens configuration of Example 5. FIG. 10 is a diagram illustrating a lens configuration of Example 6. FIG. FIG. 6 is an aberration diagram for Example 1. FIG. 6 is an aberration diagram for Example 2. FIG. 6 is an aberration diagram for Example 3. FIG. 6 is an aberration diagram for Example 4. FIG. 9 is an aberration diagram for Example 5. FIG. 10 is an aberration diagram for Example 6. It is a figure for demonstrating one Embodiment of a portable information terminal device. It is a figure for demonstrating the system configuration | structure of a portable information terminal device.

Explanation of symbols

1F First F lens group
1R 1R lens group
S Aperture stop
2P1 first positive lens
2N1 first negative lens
2N2 second negative lens
2P2 second positive lens
2R Second R lens group

Claims (11)

Consists of a first lens group located on the object side and a second lens group located on the image side across the aperture stop,
The first lens group includes a first F lens group having negative refractive power on the object side, and has a widest air interval in the first lens group, and one positive lens on the aperture stop side. The first R lens group consisting of
The second lens group has a positive refractive power as a whole, and has a positive refractive power formed by sequentially arranging a first positive lens, a first negative lens, a second negative lens, and a second positive lens from the aperture stop side. And a second R lens group having one lens and a second R lens group having one lens,
The first positive lens and the first negative lens, the second negative lens and the second positive lens of the second F lens group are cemented, respectively.
The radius of curvature of the cemented surface of the first positive lens and the first negative lens; r _S1 , the radius of curvature of the cemented surface of the second negative lens and the second positive lens: r _S2 , and the focal length of the entire system: f _A conditions:
_{(1) -2.4 <r S1 /} f A <-0.8
_{(2) 1.0 <r S2 /} f A <2.6
A single focal length imaging lens characterized by satisfying Consists of a first lens group located on the object side and a second lens group located on the image side across the aperture stop,
  The first lens group includes a first F lens group having a negative refractive power on the object side, and has a widest air interval in the first lens group, and is positively refracted as a whole on the aperture stop side. A first R lens group composed of one cemented lens having power,
  The second lens group has a positive refractive power as a whole, and has a positive refractive power formed by sequentially arranging a first positive lens, a first negative lens, a second negative lens, and a second positive lens from the aperture stop side. And a second R lens group having one lens and a second R lens group having one lens,
  The first positive lens and the first negative lens, the second negative lens and the second positive lens of the second F lens group are cemented, respectively.
  Radius of curvature of the cemented surface of the first positive lens and the first negative lens; r _S1 , Radius of curvature of the cemented surface of the second negative lens and the second positive lens: r _S2 , Focal length of the whole system: f _A But the condition:
  (1) -2.4 <r _S1 / F _A  <-0.8
  (2) 1.0 <r _S2 / F _A  <2.6
A single focal length imaging lens characterized by satisfying The imaging lens according to claim 1 or 2,
  Focal length of entire system: f _A , Focal length of the first lens group: f ₁ But the condition:
  (3) 0.0 <f _A / F ₁  <0.8
An imaging lens characterized by satisfying The imaging lens according to claim 1, 2 or 3,
Total length of the second F lens group in the second lens group: L _2F The distance from the most object side surface of the imaging lens to the image plane: L is the condition:
  (4) 0.1 <L _2F /L<0.25
An imaging lens characterized by satisfying The imaging lens according to any one of claims 1 to 4,
  Distance between the first F lens group and the first R lens group in the first lens group: A _1F-1R , Total length L of the first lens unit ₁ But the condition:
  (5) 0.35 <A _1F-1R / L ₁  <0.7
An imaging lens characterized by satisfying The imaging lens according to any one of claims 1 to 5,
  Abbe number of the first positive lens in the second F lens group of the second lens group: ν _d And anomalous dispersion: Δθ _{g, F} But the condition:
  (6) ν _d  > 80.0
  (7) Δθ _{g, F}  > 0.025
An imaging lens characterized by satisfying The imaging lens according to any one of claims 1 to 6,
  The first F lens group in the first lens group has a configuration in which two negative meniscus lenses having a convex surface facing the object side are continuously arranged from the object side, and at least one of the two negative meniscus lenses. An imaging lens, wherein the image side surface of the lens is an aspherical surface. The imaging lens according to any one of claims 1 to 7,
  An imaging lens, wherein one lens constituting the second R lens group of the second lens group has an aspherical surface. The imaging lens according to any one of claims 1 to 8,
  An imaging lens characterized in that focusing on a finite distance object is performed by moving all or part of the second lens group. A camera having the imaging lens according to any one of claims 1 to 9 as a photographing optical system. A portable information terminal device comprising the imaging lens according to claim 1 as a photographing optical system of a camera function unit.

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