Patent Grant
12360341
The present application is based on PCT filing PCT/JP2020/006106, filed Feb. 17, 2020, which claims priority to Japanese Patent Application No. 2019-041727, filed Mar. 7, 2019, the entire contents of each are incorporated herein by reference.
The present disclosure relates to an imaging lens, a camera, and a portable information terminal apparatus.
Digital cameras that form an image captured by an imaging lens onto an imaging element to perform image-capturing are widely used.
Among the digital cameras, there are strong requests for compact cameras with high image quality that use a relatively large imaging element having a diagonal length in a range of from about 20 to about 45 mm and that include a single-focus lens with high performance. For a further request, greater emphasis is placed on being excellent in portability, that is, being compact in addition to having high performance.
In recent years, a request increases for a compact imaging lens having an angle of view of so-called “semi-wide angle” having a half angle of view in a range of from about 25 to about 33 degrees. The semi-wide angle corresponds to a focal length in a range of from about 46 to about 33 mm in terms of a film camera having a size of 35 mm (so called Leica size).
Moreover, a relatively large imaging element has no serious disadvantage even when ambient rays are incident on a sensor obliquely by a certain degree because of improvement or optimization of an on-chip microlens and development in image processing. Specifically, even when the angle defined between a principal ray and the optical axis at the maximum image height is in a range of from about 30 to about 40 degrees, a system that sufficiently accommodates brightness shading or color shading in a sensor peripheral area can be constructed. Thus, a lens type more suitable for a decrease in size can be selected irrespective of the normal incidence of ambient rays unlike the existing type.
In this case, examples of a lens type suitable for a decrease in size in a semi-wide angle range include a substantially symmetrical type, and a telephoto type in which a lens group having a negative refractive power is disposed on an image side. PTL 1 and PTL 2 disclose such types of imaging lenses.
However, an imaging lens disclosed in PTL 1 has a design in the time of film cameras, and does not have sufficient imaging performance for a digital camera.
Moreover, an imaging lens disclosed in PTL 2 has a large lens total length (the distance from the surface disposed closest to an object side of a lens system to an image surface) and a large lens total thickness (the distance from the surface closest to the object side to the surface closest to an image side of the lens system) is large, thereby being disadvantageous in terms of a decrease in size.
[PTL 1] JP-7-270679-A
[PTL 2] JP-2013-195587-A
An object of the present disclosure is to provide a new and high-performance imaging lens having a semi-wide angle and being suitable for a decrease in size.
In view of the above, there is provided an improved imaging lens including sequentially from an object side to an image side, a first lens group, a second lens group having a positive refractive power, an aperture stop, a third lens group having a positive refractive power, and a fourth lens group having a negative refractive power. The first lens group includes, sequentially from the object side to the image side, a positive lens having a convex surface facing the object side, and a negative lens having a concave surface facing the image side. The second lens group includes a negative lens disposed closest to the object side and having a concave surface facing the object side, and a positive lens disposed closer than the negative lens to the image side and having a convex surface facing the object side. The third lens group includes, sequentially from the object side to the image side, a positive lens having a convex surface facing the image side, and a negative lens. The fourth lens group includes a negative lens having a concave surface facing the object side.
With the disclosure, a new and high-performance imaging lens having a semi-wide angle and being suitable for a decrease in size can be provided.
The accompanying drawings are intended to depict example embodiments of the present invention and should not be interpreted to limit the scope thereof. The accompanying drawings are not to be considered as drawn to scale unless explicitly noted. Also, identical or similar reference numerals designate identical or similar components throughout the several views.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.
In describing embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this specification is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that have a similar function, operate in a similar manner, and achieve a similar result.
Although the embodiments are described with technical limitations with reference to the attached drawings, such description is not intended to limit the scope of the disclosure and all of the components or elements described in the embodiments of this disclosure are not necessarily indispensable.
Referring now to the drawings, embodiments of the present disclosure are described below. In the drawings for explaining the following embodiments, the same reference codes are allocated to elements (members or components) having the same function or shape and redundant descriptions thereof are omitted below.
In
For the convenience of description, reference signs are commonly used in
Reference sign F denotes a “transparent parallel plate” intending one of various filters including an optical low-pass filter and an infrared-cut filter, and a cover glass (seal glass) for an imaging element such as a complementary metaloxide-semiconductor (CMOS) sensor. The transparent parallel plate is indicated as being “optically equivalent” to the intended component.
Reference sign Im denotes an image surface. When an imaging element is used, the light-receiving surface of the imaging element corresponds to the image surface Im. The imaging lens according to any one of the embodiments of the disclosure has a “basic configuration” as follows.
That is, the imaging lens has a four-lens-group configuration including, sequentially from the object side to the image side, a first lens group I, a second lens group II having a positive refractive power, an aperture stop S, a third lens group III having a positive refractive power, and a fourth lens group IV having a negative refractive power. The first lens group I is composed of, sequentially from the object side to the image side, a positive lens having a convex surface facing the object side, and a negative lens having a concave surface facing the image side.
The second lens group II is composed of a negative lens disposed closest to the object side and having a concave surface facing the object side, and a positive lens disposed closer than the negative lens to the image side and having a convex surface facing the object side.
The third lens group III is composed of, sequentially from the object side to the image side, a positive lens having a convex surface facing the image side, and a negative lens.
The fourth lens group IV is composed of a negative lens having a concave surface facing the object side.
In addition, the following configuration may be employed.
While the second lens group II is composed of, as described above, “a negative lens having a concave surface facing the object side” disposed closest to the object side, and “a positive lens having a convex surface facing the object side” disposed closer than the negative lens to the image side, the second lens group II may be composed of as a whole one of a subgroup of two lenses in total including one negative lens and a positive lens, and a subgroup of three lenses in total including two negative lenses and a positive lens.
That is, in examples illustrated in
The fourth lens group IV may be composed of “one of a lens and a cemented lens”, and has on the object side “a surface having a stronger refractive power than a surface on the image side”. In examples illustrated in
In this case, “the surface having a stronger refractive power than the surface on the image side” is, at least in a paraxial area, “the surface on the object side having a stronger refractive power than the surface on the image side”. In the example illustrated in
In this example, regarding the refractive powers of both surfaces of the fourth lens group IV, “the refractive power of the surface on the object side is stronger than the refractive power of the surface on the image side” in a paraxial area close to the optical axis.
The imaging lens having the above-described configuration desirably satisfies at least any one of Conditional Expressions (1) to (3), and (6) to (8) from among Conditional Expressions (1) to (8).
When Conditional Expression (3) is satisfied, at least one of Conditional Expressions (4) and (5) is desirably satisfied.
1.0<L/f<1.6 (1)
0.45<DT/f<0.80 (2)
0.4<f1P/f<1.5 (3)
0.25<r1F/f<0.55 (4)
0.8<r1F/r1R<1.6 (5)
−4.0<f4/f1<2.0 (6)
0.25<f1-2/f3-4<5.0 (7)
−1.5<r2F/f<−0.5 (8)
The conditional expressions include parameters having signs. The signs have meanings as follows:
As described above, the second lens group II and the third lens group III both have positive refractive powers, and the fourth lens group IV has a negative refractive power. The first lens group I and the fourth lens group IV may satisfy Conditional Expression (6) and hence the first lens group I may have either one of “a positive refractive power and a negative refractive power”.
The imaging lens according to the disclosure is a semi-wide angle lens having “characteristics slightly closer than a substantially symmetrical type to a telephoto type”.
“Proper lens configuration and power arrangement” not found in related art can decrease all the lens total length, lens total thickness, and lens diameter.
As described above, the “imaging lens” according to the disclosure is based on “power arrangement of a substantially symmetrical type” and “a type suitable for a relatively wide angle of view” in which positive elements are disposed in front and rear of the aperture stop S and a negative element is disposed outside the positive elements. The “imaging lens” allows easy correction of coma aberration, distortion, and lateral chromatic aberration.
Furthermore, “a surface on the object side” of the positive lens of the second lens group and “a surface on the image side” of the positive lens of the third lens group both have convex surfaces facing each other, and “a surface on the image side of the negative lens” of the first lens group and “a surface on the object side of the negative lens (element)” of the fourth lens group both have concave surfaces facing each other. Thus, the aforementioned aberrations can be corrected at higher levels.
The configuration in which “a surface on the object side of the negative lens disposed closest to the object side of the second lens group has a concave surface” included in the above-described configuration has an effect of decreasing the diameter of the first lens group and allowing “coma aberration of lower rays to be corrected” easily. The configuration is advantageous for both a decrease in size and an increase in performance.
To effectively attain a decrease in size of the semi-wide angle imaging lens, it is required to change the power arrangement of the substantially symmetrical type and to apply “power arrangement close to so-called telephoto type”. In the imaging lens according to the disclosure, “the positive lens having a relatively strong power is disposed closest to the object side of the lens system, and the negative lens of the third lens group and the negative lens of the fourth lens group are continuously disposed closest to the image side of the lens system”. Thus, power arrangement desirable for a decrease in size is provided.
In addition, the position of an exit pupil is controlled, and hence the incident angle of a principal ray at a peripheral image height onto an image surface can be set to a proper state.
As described above, the imaging lens according to the disclosure is configured such that the first lens group I and the second lens group II disposed closer than the aperture stop S to the object side each include “as a whole, four to five lenses”, the third lens group III and the fourth lens group IV disposed closer than the aperture stop S to the image side each include “as a whole, three to four lenses”, thereby having a relatively “simple configuration”. In addition, the configurations of the respective components are optimized for the purpose of use, which synthetically leads to advantageous effects not found in related art, thereby also attaining an increase in diameter, a decrease in size, and an increase in performance.
The meanings of the respective conditional expressions are described in detail below. Conditional Expression (1) determines the lens total length of the imaging lens (the distance from the surface disposed closest to the object side of the lens system to the image surface), to exhibit the advantageous effects of the disclosure most sufficiently. Conditional Expression (2) determines the lens total thickness of the imaging lens (the distance from the surface closest to the object side to the surface disposed closest to the image side of the lens system), to exhibit the advantageous effects of the disclosure most sufficiently.
The imaging lens according to the disclosure is composed of a positive lens disposed closest to the object side of the lens system and having a relatively strong power to attain “a decrease in size and an increase in performance”.
If the parameter of Conditional Expression (3) is less than or equal to the lower limit of 0.4, “the characteristics of the telephoto type rather than the symmetrical type” is enhanced, the principal point moves toward the object side, and the lens total length decreases. However, “the degree of freedom to correct various aberrations” may be likely limited, and the sensitivity to a manufacturing error may likely increase.
If the parameter of Conditional Expression (3) is more than or equal to the upper limit of 1.5, it is difficult to have required telephoto characteristics, the principal point moves toward the image side, and the lens total length may not be decreased.
If the parameter of Conditional Expression (4), which is desirably satisfied based on that Conditional Expression (3) is satisfied, is less than or equal to the lower limit of 0.25, the refractive power of the surface on the object side of the positive lens in the first lens group is excessively large, the surface may have excessive aberration and may not be sufficiently corrected. Inward coma aberration may likely remain and astigmatism may likely occur at an intermediate image height.
If the parameter of Conditional Expression (4) is more than or equal to the upper limit of 0.55, the refractive power of the surface on the object side of the positive lens in the first lens group is excessively small, the telephoto characteristics are insufficient, and the insufficient telephoto characteristics are disadvantageous for “a decrease in the lens total length.” When the lens total length is forcedly decreased in this state, outward coma aberration may likely remain and astigmatism may likely occur at a peripheral image height.
Conditional Expression (5) is to determine a desirable range of “the ratio of the curvature radius of the surface disposed closest to the object side to the curvature radius of the surface disposed closest to the image side” of the first lens group defining a parameter of Conditional Expression (5).
The surface on the object side of the positive lens included in the first lens group and the surface on the image side of the negative lens included in the first lens group “properly exchange aberrations with each other” to correct the aberration of the whole lens system.
If the parameter of Conditional Expression (5) is less than or equal to the lower limit of 0.8, spherical aberration may be likely over-corrected and inward coma aberration may likely occur.
If the parameter of Conditional Expression (5) is more than or equal to the upper limit of 1.5, spherical aberration may be likely under-corrected and outward coma aberration may likely occur.
The imaging lens according to the disclosure is configured such that “the incident angle of a principal ray, which reaches the maximum image height, onto the image surface is slightly larger than the half angle of view” to be decreased in size and increased in performance.
If the parameter of Conditional Expression (6) is less than or equal to the lower limit of −4.0, the exit pupil moves toward the image side, and the incident angle of the principal ray at the peripheral image height onto the image surface may be likely increased. If the parameter of Conditional Expression (6) is more than or equal to the upper limit of 2.0, the exit pupil moves toward the object side, and the fourth lens group may be likely increased in diameter.
Conditional Expression (7) is to balance well the refractive powers in front and rear of the aperture stop S.
If the parameter of Conditional Expression (7) is less than or equal to the lower limit of 0.25, the refractive power on the front side with respect to the aperture stop S is relatively excessively large, distortion may likely bend to the plus side in a peripheral area, inward coma aberration may likely occur, and lateral chromatic aberration with short wavelengths may likely occur inward of the screen.
If the parameter of Conditional Expression (7) is less than or equal to the upper limit of 5.0, the refractive power on the rear side with respect to the aperture stop S is relatively excessively large, distortion to the minus side may likely occur, outward coma aberration may likely occur, and lateral chromatic aberration with short wavelengths may likely occur outward of the screen.
If the parameter of Conditional Expression (8) is less than or equal to the lower limit of −1.5, coma aberration of lower rays (coma flare) may likely occur at an intermediate image height to the plus side, and astigmatism may likely occur. Furthermore, off-axis rays passing through the first lens group pass through a high position, and hence the first lens group may be likely increased in size.
If the parameter of Conditional Expression (8) is less than or equal to the upper limit of −0.5, coma aberration of lower rays (coma flare) may likely occur at an intermediate image height to the minus side, and spherical aberration may be likely over-corrected. The imaging lens according to the disclosure further desirably satisfies the following conditional expressions.
0.40<Y′/f<0.70 (9)
0.50<tan(θPmax)<0.85 (10)
In the conditional expressions, Y is “the maximum image height”, and θPmax is “an incident angle of a principal ray, which reaches the maximum image height, onto the image surface”.
Conditional Expression (8) determines the angle of view of the imaging lens, to exhibit the advantageous effect of the disclosure most sufficiently.
Conditional Expression (9) determines the incident angle of off-axis rays of the imaging lens onto the image surface, to exhibit the advantageous effect of the disclosure most sufficiently.
For the configuration of the imaging lens according to the disclosure, “the surface disposed closest to the image side of the second lens group” and “the surface disposed closest to the object side of the third lens group (the surface on the object side of the positive lens in the third lens group)” both desirably have convex surfaces.
The imaging lens according to the disclosure is based on “the power arrangement of the substantially symmetrical type” as described above. The power arrangement of the substantially symmetrical type is applied also to “the two surfaces facing each other with the aperture stop interposed therebetween” to correct coma aberration, distortion, and lateral chromatic aberration at “higher levels”.
Specifically, a conditional expression is desirably satisfied as follows:
−1.6<r3F/r2R<0.0, (11)
The surface on the image side of the negative lens included in the third lens group preferably has a concave surface. That surface is disposed to face the surface disposed closest to the object side and having the concave surface of the second lens group to balance correction of various aberrations.
Moreover, a curvature radius r3R of a surface on the image side of the negative lens included in the third lens group desirably satisfies the following conditional expression.
0.7<r3R/f<2.5 (12)
“The surface on the image side” of the fourth lens group is desirably a convex surface to arrange that surface to face a surface on the object side of the positive lens included in the first lens group, and to balance correction of various aberrations.
Specifically, a curvature radius r4R of a convex surface on the image side of the fourth lens group desirably satisfies the following conditional expression.
−1.8<r4R/f<−0.5 (13)
The surface on the object side of the fourth lens group is a concave surface. To arrange that surface to face a surface on the image side of the negative lens included in the first lens group, and to balance correction of various aberrations, the curvature radius r4F desirably satisfies the following conditional expression.
−1.2<r4F/f<−0.3 (14)
Furthermore, a refractive index nd1P of a material of the positive lens of the first lens group desirably satisfies the following conditional expression.
nd1P>1.75 (15)
If the parameter of Conditional Expression (15) is less than or equal to the lower limit of 1.75, field curvature may be likely under-corrected and astigmatism may likely remain. Note that the upper limit of Conditional Expression (15) is in a range of from about 2.0 to about 2.1 with regard to the range of the refractive index and the cost of an existing optical glass.
A refractive index nd2P of a material of the positive lens included in the second lens group desirably satisfies the following conditional expression.
nd2P>1.75 (16)
If the parameter of Conditional Expression (16) is less than or equal to the lower limit of 1.75, field curvature may be likely under-corrected and inward coma aberration may likely remain at an intermediate image height. Note that the upper limit of Conditional Expression (16) is in a range of from about 2.0 to about 2.1 with regard to the range of the refractive index and the cost of an existing optical glass.
To correct aberration more properly, it is desirable that “the first lens group and the fourth lens group have aspherical surfaces”. The aspherical surface has a large advantageous effect on correction of astigmatism, coma aberration, and distortion.
Hereinafter, ten specific examples of the imaging lenses are described.
As described above, Example 1 to Example 10 are specific numeric value examples of the lens configurations illustrated in
In Example 1 to Example 10, the maximum image height is 14.2 mm.
As illustrated in
In any of the following examples, the transparent parallel plate F is disposed so that a surface on the image side thereof is disposed at a position of about 0.7 mm from the image surface Im to the object side. However, the configuration is not limited thereby. The transparent parallel plate F may not be a plate and may be divided into a plurality of plates.
In the examples, the signs have meanings as follows:
“An aspherical surface” is expressed by the following known expression using a paraxial curvature (the reciprocal of a paraxial curvature radius) C, a height H from the optical axis, a conic constant K, and an aspherical coefficient Ai (i=2 to 14).
X=CH2/[1+√(1−(1+K)C2H2)]+A4H4+A6H6+A8H1+A10H10+A12H12+A14H14
Example 1 has the lens configuration illustrated in
(Table 1)
Data on aspherical surfaces (surfaces of surface numbers with “* mark”) are as follows.
Aspherical Surface; Seventh Surface
K=0.0, A4=−1.56039×10−4, A6=−7.36942×10−7, A8=−1.50428×10−1
Aspherical Surface; Eighth Surface
K=0.0, A4=1.69456×105, A6=−1.07652×10−6
Aspherical Surface; Thirteenth Surface
K=0.0, A4=3.47223×10−4, A6=−6.44790×10−6
Aspherical Surface; Fourteenth Surface
K=0.0, A4=4.12542×10−4, A6=−3.95877×10−6, A8=−2.65584×10−8, A10=1.00641×10−9
(Parameter Values of Conditional Expressions in Example 1)
The parameter values of the respective conditional expressions are as follows.
L/f=1.327 (1)
DT/f=0.673 (2)
f1P/f=1.078 (3)
r1F/f=0.408 (4)
r1F/r1R=0.997 (5)
f4/f1=0.045 (6)
f1-2/f3-4=0.372 (7)
r2F/f=−0.866 (8)
Y′/f=0.546 (9)
tan(θPmax)=0.691 (10)
r3F/r2R=−1.347 (11)
r3R/f=1.423 (12)
r4R/f=−0.7 (13)
r4F/f=−0.693 (14)
nd1P=1.835 (15)
nd2P=1.832 (16)
Example 2 has the lens configuration illustrated in
(Table 2)
Data on aspherical surfaces are as follows.
Aspherical Surface; First Surface
K=0.0, A4=−3.54224×10−5, A6=−4.66804×10−8, A8=−1.10660×10−8, A10=8.24552×10−11, A12=−1.19318×10−12
Aspherical Surface; Twelfth Surface
K=0.0, A4=3.45703×10−4
Aspherical Surface; Thirteenth Surface
K=0.0, A4=3.69614×10−4, A6=−4.24378×10−7, A8=5.77254×10−8, A10=−1.22381×10−9
(Parameter Values of Conditional Expressions in Example 2)
The parameter values of the respective conditional expressions are as follows.
L/f=1.267 (1)
DT/f=0.614 (2)
f1P/f=0.771 (3)
r1F/f=0.384 (4)
r1F/r1R=1.332 (5)
f4/f1=−2.589 (6)
f1-2/f3-4=1.760 (7)
r2F/f=−1.310 (8)
Y′/f=0.545 (9)
tan(θPmax)=0.682 (10)
r3F/r2R=−0.160 (11)
r3R/f=1.850 (12)
r4R/f=−0.772 (13)
r4F/f=−0.691 (14)
nd1P=1.832 (15)
nd2P=1.883 (16)
Example 3 has the lens configuration illustrated in
(Table 3)
Data on aspherical surfaces are as follows.
Aspherical Surface; First Surface
K=0.0, A4=−2.63557×10−5, A6=−6.86204×10−7, A8=9.51319×10−9, A10=−2.99238×10−10
Aspherical Surface; Thirteenth Surface
K=0.0, A4=1.30975×10−4, A6=−3.75252×10−7, A8=5.96446×10−8, A10=−8.12812×10−10
(Parameter Values of Conditional Expressions in Example 3)
The parameter values of the respective conditional expressions are as follows.
L/f=1.264 (1)
DT/f=0.632 (2)
f1P/f=0.609 (3)
r1F/f=0.335 (4)
r1F/r1R=1.256 (5)
f4/f1=0.146 (6)
f1-2/f3-4=1.296 (7)
r2F/f=−0.874 (8)
Y′/f=0.545 (9)
tan(θPmax)=0.672 (10)
r3F/r2R=−0.216 (11)
r3R/f=1.268 (12)
r4R/f=−1.024 (13)
r4F/f=−0.691 (14)
nd1P=1.834 (15)
nd2P=1.833 (16)
Example 4 has the lens configuration illustrated in
(Table 4)
Data on aspherical surfaces are as follows.
Aspherical Surface; First Surface
K=0.0, A4=−2.52197×10−5, A6=−7.06205×10−7, A8=1.01999×10−8, A10=−2.76954×10−10
Aspherical Surface; Thirteenth Surface
K=0.0, A4=9.97548×10−5, A6=−2.74503×10−7, A8=4.05280×10−8, A10=−4.40120×10−10
(Parameter Values of Conditional Expressions in Example 4)
The parameter values of the respective conditional expressions are as follows.
L/f=1.217 (1)
DT/f=0.589 (2)
f1P/f=0.537 (3)
r1F/f=0.337 (4)
r1F/r1R=1.278 (5)
f4/f1=0.296 (6)
f1-2/f3-4=0.530 (7)
r2F/f=−0.643 (8)
Y′/f=0.507 (9)
tan(θPmax)=0.629 (10)
r3F/r2R=−0.968 (11)
r3R/f=2.111 (12)
r4R/f=−0.702 (13)
r4F/f=−0.520 (14)
nd1P=1.854 (15)
nd2P=1.835 (16)
Example 5 has the lens configuration illustrated in
(Table 5)
Data on aspherical surfaces are as follows.
Aspherical Surface; First Surface
K=0.0, A4=−2.62422×10−5, A6=−4.81459×10−7, A8=3.20423×10−9, A10=−1.16410×10−10
Aspherical Surface; Thirteenth Surface
K=0.0, A4=1.22749×10−4, A6=−2.98756×10−7, A8=6.89210×10−1, A10=−9.94935×10−10
(Parameter Values of Conditional Expressions in Example 5)
The parameter values of the respective conditional expressions are as follows.
L/f=1.295 (1)
DT/f=0.653 (2)
f1P/f=0.574 (3)
r1F/f=0.408 (4)
r1F/r1R=1.343 (5)
f4/f1=−0.372 (6)
f1-2/f3-4=1.252 (7)
r2F/f=−1.080 (8)
Y′/f=0.545 (9)
tan(θPmax)=0.688 (10)
r3F/r2R=−0.270 (11)
r3R/f=1.228 (12)
r4R/f=−0.862 (13)
r4F/f=−0.691 (14)
nd1P=1.854 (15)
nd2P=1.905 (16)
Example 6 has the lens configuration illustrated in
(Table 6)
Data on aspherical surfaces are as follows.
Aspherical Surface; First Surface
K=0.0, A4=−3.29990×105, A6=−6.63571E×10−7, A8=3.34066×10−9, A10=−2.16938×10−10
Aspherical Surface; Twelfth Surface
K=0.0, A4=6.59150×10−4, A6=−9.07297×10−6
Aspherical Surface; Thirteenth Surface
K=0.0, A4=8.07148×10−4, A6=−7.24676×10−6, A8=−1.28617×10−9, A10=1.09784×10−10
(Parameter Values of Conditional Expressions in Example 6)
The parameter values of the respective conditional expressions are as follows.
L/f=1.358 (1)
DT/f=0.669 (2)
f1P/f=1.116 (3)
r1F/f=0.432 (4)
r1F/r1R=1.226 (5)
f4/f1=−0.100 (6)
f1-2/f3-4=3.573 (7)
r2F/f=−0.980 (8)
Y′/f=0.575 (9)
tan(θPmax)=0.685 (10)
r3F/r2R=−0.277 (11)
r3R/f=1.446 (12)
r4R/f=−1.505 (13)
r4F/f=−0.703 (14)
nd1P=1.821 (15)
nd2P=1.883 (16)
Example 7 has the lens configuration illustrated in
(Table 7)
Data on aspherical surfaces are as follows.
Aspherical Surface; First Surface
K=0.0, A4=−4.08710×105, A6=−4.27926×10−7, A8=−1.04734×10−8, A10=−1.48266×10−10
Aspherical Surface; Thirteenth Surface
K=0.0, A4=1.88752×10−4, A6=9.04904×10−7, A8=8.62046×10−8, A10=−1.22399×10−9
(Parameter Values of Conditional Expressions in Example 7)
The parameter values of the respective conditional expressions are as follows.
L/f=1.368 (1)
DT/f=0.683 (2)
f1P/f=1.186 (3)
r1F/f=0.401 (4)
r1F/r1R=1.263 (5)
f4/f1=0.191 (6)
f1-2/f3-4=3.114 (7)
r2F/f=−1.270 (8)
Y′/f=0.606 (9)
tan(θPmax)=0.703 (10)
r3F/r2R=−0.093 (11)
r3R/f=0.901 (12)
r4R/f=−0.944 (13)
r4F/f=−0.769 (14)
nd1P=1.821 (15)
nd2P=1.883 (16)
Example 8 has the lens configuration illustrated in
(Table 8)
Data on aspherical surfaces are as follows.
Aspherical Surface; First Surface
K=0.0, A4=−2.62065×10−5, A6=−5.73136×10−7, A8=5.83843×10−9, A10=−2.15266×10−10
Aspherical Surface; Fourteenth Surface
K=0.0, A4=1.29178×10−4, A6=−4.77236×10−7, A8=6.42635−10−8, A10=−9.22759×10−10
(Parameter Values of Conditional Expressions in Example 8)
The parameter values of the respective conditional expressions are as follows.
L/f=1.274 (1)
DT/f=0.634 (2)
f1P/f=0.646 (3)
r1F/f=0.368 (4)
r1F/r1R=1.224 (5)
f4/f1−=0.232 (6)
f1-2/f3-4=1.023 (7)
r2F/f=−0.850 (8)
Y′/f=0.545 (9)
tan(θPmax)=0.665 (10)
r3F/r2R=−0.224 (11)
r3R/f=1.239 (12)
r4R/f=−0.975 (13)
r4F/f=−0.691 (14)
nd1P=1.854 (15)
nd2P=1.883 (16)
Example 9 has the lens configuration illustrated in
(Table 9)
Data on aspherical surfaces are as follows.
Aspherical Surface; First Surface
K=0.0, A4=−2.46254×10−5, A6=−5.56469×10−7, A8=5.71488×10−9, A10=−1.90619×10−10
Aspherical Surface; Fourteenth Surface
K=0.0, A4=1.30813×10−4, A6=−3.50965×10−7, A8=5.51796×10−8, A10=−7.69857×10−10
(Parameter Values of Conditional Expressions in Example 9) The parameter values of the respective conditional expressions are as follows.
L/f=1.276 (1)
DT/f=0.633 (2)
f1P/f=0.622 (3)
r1F/f=0.373 (4)
r1F/r1R=1.225 (5)
f4/f1=−0.258 (6)
f1-2/f3-4=0.998 (7)
r2F/f=−0.912 (8)
Y′/f=0.545 (9)
tan(θPmax)=0.663 (10)
r3F/r2R=−0.194 (11)
r3R/f=1.416 (12)
r4R/f=−0.961 (13)
r4F/f=−0.691 (14)
nd1P=1.854 (15)
nd2P=1.883 (16)
Example 10 has the lens configuration illustrated in
(Table 10)
Data on aspherical surfaces are as follows.
Aspherical Surface; First Surface
K=0.0, A4=−2.57013×105, A6=−5.79335×10−7, A8=5.88906×10−9, A10=−2.51234×10−10
Aspherical Surface; Fourteenth Surface
K=0.0, A4=1.20805×10−4, A6=−1.48753×10−7, A8=3.11246×10−9, A10=−3.68347×10−10
(Parameter Values of Conditional Expressions in Example 10)
The parameter values of the respective conditional expressions are as follows.
L/f=1.273 (1)
DT/f=0.634 (2)
f1P/f=0.792 (3)
r1F/f=0.348 (4)
r1F/r1R=1.210 (5)
f4/f1=−0.351 (6)
f1-2/f3-4=1.183 (7)
r2F/f=−0.868 (8)
Y′/f=0.545 (9)
tan(θPmax)=0.650 (10)
r3F/r2R=−0.298 (11)
r3R/f=1.310 (12)
r4R/f=−1.370 (13)
r4F/f=−0.702 (14)
nd1P=1.854 (15)
nd2P=1.883 (16)
Among Example 1 to Example 10, the refractive power of the first lens group is “negative” in Example 1 and Example 7, and is “positive” in the other examples.
A broken line in each diagram for spherical aberration indicates “sine condition”. A solid line in each diagram for astigmatism indicates “sagittal” and a broken line in the diagram indicates “meridional”.
As illustrated in the respective aberration diagrams, the aberrations of the imaging lenses according to Example 1 to Example 10 are corrected at high levels, and spherical aberration and axial chromatic aberration are very small.
Astigmatism, field curvature, and lateral chromatic aberration are also sufficiently small. Coma aberration and disorder of color differences thereof are restricted even in the outermost peripheral area. Distortion is also less than or equal to 1.5% in terms of the absolute value.
The imaging lenses according to Example 1 to Example 10 each have a half angle of view in a range of from about 25 to about 33 degrees, which indicates a semi-wide angle range; has an F-number of less than 3.0, which indicates a large aperture diameter; attains decreases in sizes for all the lens total length, lens total thickness, and lens diameter; has excellent imaging performance; and is applicable to an imaging element having a resolving power of 24,000,000 pixels or more.
“A camera or in other words a portable information terminal apparatus” is described below referring to
An apparatus 30 described below is configured to “transmit information”, and hence is a portable information terminal apparatus. The portable information terminal apparatus 30 has a camera function, and uses an imaging lens according to any one of Example 1 to Example 10 as an image-capturing optical system of a camera function device of the camera function.
As illustrated in a system diagram in
An output from the light-receiving element 45 is processed by a signal processing device 42 that is controlled by a central processing unit (CPU) 40 to be converted into digital information. Image information digitized by the signal processing device 42 is processed with predetermined image processing by an image processing device 41 that is controlled by the CPU 40, and then is recorded in a semiconductor memory 44.
A liquid crystal display (LCD) monitor 38 can display an image during image-capturing, and can display an image recorded in the semiconductor memory 44. Moreover, the image recorded in the semiconductor memory 44 can be transmitted to an external device using a communication card 43 or the like.
Referring to
When a shutter release button 35 is half-pressed, focusing is performed. Focusing can be performed through movement of the whole imaging lens 31 in the optical-axis direction, or through movement of the light-receiving element 45. When the shutter release button 35 is further pressed, image-capturing is performed, and then the above-described processing is performed.
To display an image recorded in the semiconductor memory 44 onto the LCD monitor 38 or to transmit the image to an external device using the communication card 43 or the like, an operation button 37 is operated. The semiconductor memory 44 and the communication card 43 or the like are inserted into slots 39A and 39B, which are respectively dedicated for or general and common to the semiconductor memory 44 and the communication card 43 or the like.
When the imaging lens 31 is in the collapsed state, the lens groups of the imaging lens 31 may not be aligned along the optical axis. For example, the imaging lens 31 may have a mechanism in which the second lens group II is retracted from the optical axis and housed in parallel to the first lens group I. This mechanism can make the portable information terminal apparatus 30 thinner.
Since the imaging lens according to the disclosure is used for the imaging lens 31, a compact camera (a portable information terminal apparatus) with high image quality using a light-receiving element having 24,000,000 pixels or more can be provided. Although the desirable embodiments and examples of the disclosure have been described above, the disclosure is not particularly limited to such specific embodiments and examples unless otherwise particularly limited in the above description, and various modifications and changes can be made without departing from the spirit and scope of the disclosure as set forth in the appended claims.
The advantageous effects described in the embodiments and examples of the disclosure are merely desirable advantageous effects generated based on the disclosure. The advantageous effects according to the disclosure is not limited to “those described in the embodiments and examples”.
The above-described embodiments are illustrative and do not limit the present invention. Thus, numerous additional modifications and variations are possible in light of the above teachings. For example, elements and/or features of different illustrative embodiments may be combined with each other and/or substituted for each other within the scope of the present invention.
This patent application is based on and claims priority pursuant to Japanese Patent Application No. 2019-041727, filed on Mar. 7, 2019, in the Japan Patent Office, the entire disclosure of which is hereby incorporated by reference herein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2019-041727 | Mar 2019 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2020/006106 | 2/17/2020 | WO |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2020/179424 | 9/10/2020 | WO | A |
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|---|---|---|---|
| 4787718 | Cho | Nov 1988 | A |
| 20130070346 | Hsu | Mar 2013 | A1 |
| 20130321936 | Ohashi | Dec 2013 | A1 |
| 20190121062 | Ohashi | Apr 2019 | A1 |
| 20190154946 | Ohashi | May 2019 | A1 |
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| 4-212916 | Aug 1992 | JP |
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| 2013-195587 | Sep 2013 | JP |
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| Gross, Herbert, ed. Handbook of Optical Systems, vol. 3: Aberration Theory and Correction of Optical Systems. vol. 3. Wiley-Vch, 2005. (Year: 2005). |
| International Search Report issued on May 14, 2020 in PCT/JP2020/006106 filed on Feb. 17, 2020, 10 pages. |
| Number | Date | Country | |
|---|---|---|---|
| 20220026670 A1 | Jan 2022 | US |
