JP6561714B2 - Imaging lens system, imaging device, and portable information terminal device - Google Patents

Description

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

  In order from the object side to the image side, a first lens group having a positive power, an aperture stop, and a second lens group having a positive power are arranged, and the first lens group is arranged from the object side to the first F lens group and the first R. An imaging lens system that includes a lens group and performs focusing (focusing operation) by changing the distance between the first F lens group and the second R lens group is known (Patent Document 1).

  An object of the present invention is to realize a novel imaging lens system in which a first lens group having a positive power is disposed on the object side and a second lens group having a positive power is disposed on the image side of the aperture stop.

The imaging lens system according to the present invention includes, in order from the object side to the image side, a first lens group having a positive power, an aperture stop, and a second lens group having a positive power. The lens group includes a 1a lens group that is disposed on the object side and has a negative power, and a 1b lens group that is disposed on the image side and has a positive power. A negative lens L11, a positive lens L12, and a negative lens L13 are arranged in order from the image side to the image side, and the first b lens group includes a positive lens L14, a positive lens L15, and a negative lens in order from the object side to the image side. L16 is arranged, and the surface distance between the negative lens L13 and the positive lens L14 is the largest in the group of the first lens group, and the first lens group includes the first lens unit during focusing from an infinite object to a close object. One lens group is fixed, Lens unit moves toward the object side, the focal length of the first lens group: f1, the focal length of the entire system: f is the condition:
(1) 2.0 <f1 / f <5.0
Satisfied.

  As described above, according to the present invention, the first lens group having a positive power, the aperture stop, and the second lens group having a positive power are arranged in order from the object side to the image side. An image lens system can be realized.

FIG. 2 is a diagram illustrating a cross section of the imaging lens system of Example 1. FIG. 6 is a diagram showing a cross section of an imaging lens system of Example 2. 6 is a diagram showing a cross section of an imaging lens system of Example 3. FIG. 6 is a diagram illustrating a cross section of an imaging lens system of Example 4. FIG. FIG. 3 is an aberration diagram in a state in which the imaging lens system of Example 1 is focused on an object at infinity. FIG. 6 is an aberration diagram in a state in which the imaging lens system of Example 1 is focused on an object with a magnification of −0.05. FIG. 6 is an aberration diagram in a state in which the imaging lens system of Example 1 is focused on an object with a magnification of −0.1. FIG. 6 is an aberration diagram of the imaging lens system of Example 2 in a state where focusing is performed on an object at infinity. FIG. 10 is an aberration diagram in a state in which the imaging lens system of Example 2 is focused on an object with a magnification of −0.05. FIG. 10 is an aberration diagram in a state where the imaging lens system of Example 2 is focused on an object with a magnification of −0.1. FIG. 10 is an aberration diagram for the imaging lens system of Example 3 when the lens is focused on an object at infinity. FIG. 10 is an aberration diagram in a state where the imaging lens system of Example 3 is focused on an object with a magnification of −0.05. FIG. 12 is an aberration diagram in a state where the imaging lens system of Example 3 is focused on an object with a magnification of −0.1. FIG. 10 is an aberration diagram for the imaging lens system according to Example 4 when focusing on an object at infinity. FIG. 12 is an aberration diagram in a state in which the imaging lens system of Example 4 is focused on an object with a magnification of −0.05. FIG. 12 is an aberration diagram in a state where the imaging lens system of Example 4 is focused on an object with a magnification of −0.1. It is a figure which shows the external appearance of one Embodiment of a portable information terminal device, (A) is a perspective view of the front side, (B) is a perspective view of the back side. It is a block diagram which shows the system configuration example of the portable information terminal device of FIG.

Hereinafter, embodiments will be described.
1 to 4 show four embodiments of the imaging lens system. In order to avoid complication, the reference numerals are shared in FIGS.
1 to 4, the left side is the “object side” and the right side is the “image side”. In these embodiments, it is assumed that an image of an object by the imaging lens system is picked up by a solid-state image sensor, and in the drawing, symbol Im indicates an image plane (matches the light-receiving surface of the solid-state image sensor). . The symbol G on the object side of the image plane Im indicates the cover glass and various filters of the solid-state imaging device as transparent parallel plates equivalent to these.

Referring to FIG. 1 as a representative, the imaging lens system is configured by arranging a first lens group G1 on the object side of the aperture stop S and a second lens group G2 on the image side of the aperture stop S. Yes.
Both the first lens group G1 and the second lens group G2 have “positive power”.
The first lens group G1 includes a 1a lens group G1a and a 1b lens group G1b in order from the object side to the image side.
The first-a lens group G1a includes a negative lens L11, a positive lens L12, and a negative lens L13 in order from the object side, and has “negative power”.
The first lens group G1b has “positive power” in which a positive lens L14, a positive lens L15, and a negative lens L16 are arranged in this order from the object side.

The negative lens L13 closest to the image side of the first a lens group G1a and the positive lens L14 closest to the object side of the first b lens group G1b are “maximum surface spacing (between adjacent lens surfaces) in the first lens group G1. Distance on the optical axis) ”.
In the embodiment shown in FIGS. 1 to 4, the second lens group G2 arranged on the image side of the aperture stop S includes, in order from the object side, a negative lens L21, a positive lens L22, a positive lens L23, a negative lens L24, A positive lens L25 is arranged.
The negative lenses L21 and L24 are “concave on the object side”.
The lens configuration (lens configuration, number of lenses, etc.) of the second lens group is not limited to the examples in FIGS. 1 to 4, and configurations other than those shown in these drawings are also possible.

In the imaging lens system of the present invention, the first lens group G1 is fixed and the second lens group G2 moves to the object side during “focusing from an object at infinity to a near object”.
The focal length of the first lens group G1 is f1, and the focal length of the entire system is f.
(1) 2.0 <f1 / f <5.0
Satisfied.
As described above, in the imaging lens system of the present invention, the first lens group G1 having a positive power disposed on the object side of the stop S is composed of the 1a lens group G1a and the 1b lens group G1b.
The first-a lens group G1a includes a negative lens L11, a positive lens L12, and a negative lens L13 in order from the object side to the image side. By setting the power distribution of the first-a lens group G1a having negative power to “negative / positive / negative” from the object side and the second lens from the object side to the positive lens L12, other aberrations can be sufficiently suppressed. However, “sufficient correction of distortion” becomes possible.

In addition, since the 1a lens group G1a and the 1b lens group G1b form a “maximum surface separation in the first lens group G1”, the aberration generated in the 1a lens group G1a is 1b. The lens group G1b can be sufficiently corrected.
Furthermore, the 1b lens group G1b is composed of the positive lens L14, the positive lens L15, and the negative lens L16, so that the “positive power” of the first b lens group G1b is the positive lens L14 and the positive lens L15. Can be shared. With this configuration, it is possible to reduce the aberration generated on the lens surfaces of the lenses L14 to L16.
When the first lens group G1 has the above-described configuration, it is possible to realize a “large-diameter imaging lens system in which spherical aberration, coma and the like are sufficiently corrected”.
When focusing from an infinitely distant object to a close object, the first lens group G1 is fixed. That is, the distance between the first lens group G1 and the image plane Im does not change during focusing.

When the parameter of condition (1): f1 / f is large (small), the positive power of the first lens group G1 is relatively small (large) with respect to the positive power of the entire system.
When the upper limit of the condition (1) is exceeded, the positive power of the first lens group G1 becomes too small, and in order to secure the power required for the entire system, “excessive positive power” is applied to the second lens group G2. Therefore, it is difficult to correct aberrations in the second lens group G2.
If the lower limit of condition (1) is exceeded, the positive power of the first lens group G1 becomes excessive, and it is difficult to correct aberrations in the first lens group G1.
By performing the above-described focusing within a range where the condition (1) is satisfied, it becomes possible to sufficiently correct “the field curvature caused by the object distance change accompanying the focusing”.

When focusing from an infinitely distant object to a close object, as described above, the second lens group G2 moves to the object side. At this time, the aperture stop S can also be moved. However, if the “aperture stop S is fixed” at the time of focusing, the mechanism for performing the focusing can be further simplified.
When the aperture stop S is fixed during focusing as described above, it is preferable that the following condition (2) is satisfied.
(2) 0.2 <Ds2 / f <0.5
Here, Ds2 is “the distance between the aperture stop and the second lens group when focusing on an object at infinity”, and f is “the focal length of the entire system”.
When the upper limit of the condition (2) is exceeded, the distance between the aperture stop S and the second lens group G2 becomes excessive, the off-axis rays passing through the second lens group G2 become excessively high, and correction of various aberrations tends to be difficult.
When the lower limit of the condition (2) is exceeded, the “interval between the aperture stop S and the second lens group G2” necessary for focusing becomes narrow, and it is difficult to perform focusing up to a short distance while suppressing curvature of field. .

The imaging lens system according to the present invention preferably satisfies any one or more of the following conditions (3) to (6) together with the above condition (1).
When “focusing is performed with the aperture stop fixed”, it is preferable that any one or more of the following conditions (3) to (6) is satisfied together with the above conditions (1) and (2).
(3) 0.15 <Dab / D1 <0.4
(4) 0.2 <D1a / D1 <0.5
(5) -1.6 <f1_5 / f1_6 <-0.8
(6) 0.5 <f1_4 / f1_5 <1.5.

The meanings of symbols in the parameters in the conditions (3) to (6) are as follows.
“D1” is the “group thickness (distance on the optical axis from the lens surface closest to the object side to the lens surface closest to the image side)” of the first lens group G1.
“Dab” is a surface interval between the first-a lens group G1a and the first-b lens group G1b.
“D1a” is the “group thickness (the distance on the optical axis from the most object-side lens surface to the most image-side lens surface of the 1a lens group G1a)” of the 1a lens group G1a.
“F1_5” is the focal length of the positive lens L15 of the 1b lens group G1b.
“F1 — 6” is the focal length of the negative lens L16 of the 1b lens group G1b.
“F1_4” is the focal length of the positive lens L14 in the 1b lens group G1b.
“F1_5” is the focal length of the positive lens L15 in the first-b lens group G1b.

When the parameter (Dab / D1) of the condition (3) increases, the surface distance: Dab between the first-a lens group G1a and the first-b lens group G1b becomes relatively larger than the group thickness: D1 of the first lens group G1. growing.
As described above, in the present invention, the surface distance: Dab is set to “maximum in the first lens group G1”, and the aberration generated in the first a lens group G1a is determined by the size of the surface distance: Dab. Correction is possible with the 1b lens group G1b.
If the lower limit of the condition (3) is exceeded, the surface separation: Dab becomes narrow, and it is difficult to sufficiently correct the aberration generated in the 1a lens group G1a with the 1b lens group G1b.
When the upper limit of the condition (3) is exceeded, the surface separation: Dab increases, but the “group thickness” of the first a lens group G1a and the first b lens group G1b decreases. For this reason, the thickness of the lenses constituting these lens groups is reduced, and in this case as well, it is difficult to sufficiently correct the aberration generated in the 1a lens group G1a with the 1b lens group G1b.

If the upper limit of condition (4) is exceeded, the “group thickness” of the 1a lens group G1a becomes excessive, the lenses constituting the 1b lens group G1b become thin, and the aberration generated in the 1a lens group G1a is It is likely to be difficult to effectively correct with the first b lens group G1b.
When the lower limit of the condition (4) is exceeded, the “group thickness” of the 1a lens group G1a becomes too small, and the thickness of the lenses constituting the 1a lens group G1a becomes thin. For this reason, a large aberration tends to occur in the 1a lens group G1a, and it is difficult to effectively correct this aberration in the 1b lens group G1b.

  Note that the condition (4) is preferably satisfied together with the condition (3).

Condition (5) is a condition for regulating the “ratio of power of the positive lens L15 and the negative lens L16” in the first-b lens group G1b.
When the positive lens L15 and the negative lens L16 generate “aberrations opposite to each other” and cancel each other, the correction of the aberration becomes easy. When the condition (5) is satisfied, such “cancellation of aberrations opposite to each other” can be performed satisfactorily.
If the upper limit of condition (5) is exceeded, the positive power of the positive lens L15 becomes excessive, and correction of aberrations occurring in the positive lens L15 tends to be insufficient. When the lower limit of the condition (5) is exceeded, the negative power of the negative lens L16 becomes excessive, and correction of aberrations generated in the positive lens L15 tends to be excessive.

Condition (6) is a condition for regulating the power ratio between the positive lens L4 and the positive lens L5 of the first-b lens group G1b. The positive lenses L4 and L5 constitute the “positive power component” of the first-b lens group G1b. The positive power component is shared by the two positive lenses L4 and L5, and Aberrations occurring on each surface can be suppressed.
Outside the range of condition (6), the balance of the positive power distribution of the positive lenses L14 and L15 is likely to be lost, and it is difficult to reduce aberrations due to power sharing.
As described above, in the embodiment shown in FIGS. 1 to 4, the second lens group G2 disposed on the image side of the aperture stop S includes, in order from the object side, the negative lens L21, the positive lens L22, the positive lens L23, A negative lens L24 and a positive lens L25 are arranged. The negative lenses L21 and L24 are “concave on the object side”.
As described above, the lens configuration (lens configuration, the number of lenses, etc.) of the second lens group 2G is not limited to the examples of FIGS. 1 to 4, and configurations other than those shown in these drawings are possible. However, the configuration example of the second lens group 2G shown in FIGS. 1 to 4 is a preferable example.

As shown in Examples 1 to 4 to be described later, the imaging lens system shown in FIGS. 1 to 4 has various aberrations while suppressing the incident angle of the imaging light beam to the image plane Im small. Sufficient correction is possible.
From the viewpoint of ease of lens manufacturing and low cost of manufacturing the imaging lens system, it is preferable that all lenses constituting the imaging optical system of the present invention are configured as “spherical lenses”.
Examples 1 to 4 of the imaging lens system to be described later are all composed only of spherical lenses.

In addition, in this specification, L11 to L16 and L21 to L25 are “part of the name of each lens” as described in the claims.
That is, for example, “negative lens L11” is “a negative lens named negative lens L11”.

In FIG. 1 to FIG. 4, L11 to L16 and L21 to L25 which constitute “a part of the name” of this lens are also used as “a symbol representing the corresponding lens”.
As described above, “L11 to L16, L21 to L25” are part of the lens names. Therefore, the lens forms and materials described in the claims are described in the embodiments and examples. Needless to say, it is not limited to the above.

Before showing a specific embodiment of the imaging lens system, an embodiment of a portable information terminal device using the imaging lens of the present invention will be described.
An embodiment of the portable information terminal device will be described with reference to FIGS. 17 and 18.
As shown in FIG. 18, the system configuration of the portable information terminal device shown in FIG. 17 includes a photographing lens 1 as an imaging optical system and a light receiving element 13 that is a “solid-state imaging device”, and is formed by the photographing lens 1. An image of the subject to be photographed is picked up by the light receiving element 13.

The output from the light receiving element 13 is processed by the signal processing device 14 under the control of the central processing unit 11 and converted into digital information.
The image converted into digital information is displayed on the liquid crystal monitor 7 and stored in the semiconductor memory 15 or used for communication to the outside by the communication card 16. The portion excluding this communication function constitutes an “imaging device”.

As the photographic lens 1, the imaging lens system according to any one of claims 1 to 8 is used, and specifically, "imaging lens system" of Examples 1 to 4 described later can be used. .
The “monitored image” can be displayed on the liquid crystal monitor 7 or an image recorded in the semiconductor memory 15 can be displayed.
The photographing lens 1 is in the “collapsed state” as shown in FIG. 17A when the camera is carried, and the lens barrel is extended from the housing 5 when the power is turned on by operating the power switch 6 (FIG. 17B). It is. When the lens barrel is extended, the taking lens system 1 is in a state of “focusing on an object at infinity”.

Focusing is performed by “half-pressing” the shutter button 4.
Focusing is performed by moving the second lens group. When the shutter button 4 is further pressed, shooting is performed, and thereafter the above processing is performed.
When an image recorded in the semiconductor memory 15 is displayed on the liquid crystal monitor 7 or transmitted to the outside using the communication card 16 or the like, the operation button 8 is operated. The semiconductor memory 15 and the communication card 16 are inserted into dedicated or general-purpose slots 9 for use.
When the photographing lens 1 is in the “collapsed state”, the lens groups of the imaging lens system do not necessarily have to be arranged on the optical axis. For example, if the second lens group is retracted from the optical axis to be “stored in parallel with the first lens group”, the portable information terminal device can be further reduced in thickness.
In this case, since the first lens group G1 has a larger “group thickness” than the second lens group G2, the retraction of the first lens group from the optical axis is more effective in “thinning the retracted state”. Can contribute.

  In the portable information terminal device shown in FIGS. 17 and 18, as described above, the portion excluding the communication function constitutes an “imaging device”, and this imaging device is an “imaging function unit” of the portable information terminal device. The imaging lens system of the present invention is used as an “imaging optical system”.

  Hereinafter, four specific examples of the imaging lens system will be described. In all of Examples 1 to 4, the maximum image height is 8.0 mm.

  In each embodiment, the parallel flat plate (indicated by reference numeral “G” in FIGS. 1 to 4) disposed on the image plane side of the second lens group is an optical low-pass filter, an infrared cut filter, or the like as described above. These are intended for various filters and cover glass (seal glass) of light receiving elements.

The meanings of the symbols in the examples are as follows.
f: Focal length of the entire system
F: F number
ω: Half angle of view (degrees)
R: radius of curvature
D: Surface spacing
N _d : Refractive index
ν _d : Abbe number
φ: Effective beam diameter
The unit of “amount having a dimension of length” is “mm” unless otherwise specified.

"Example 1"
Focal length f: 16.00mm, F number: F1.84, angle of view 2ω: 52.7 degrees
The data of Example 1 is shown in Table 1.

"Variable interval"
The “variable interval” is a surface interval between the aperture stop and the second lens group, and changes with zooming. In Example 1, the variable interval is the interval (D11) between the surface number 11 and the surface number 12.

  The variable intervals of Example 1 are shown in Table 2. “Inf” in the upper row indicates a state in which an object at infinity is in focus, “× 0.05” indicates a state in which an object with an imaging magnification of −0.05 times, and “× 0.10” indicates a result. Image magnification: This is a state in which an object of -0.10 times is focused. The same applies to the following embodiments.

"Condition Parameter Values"
Table 3 shows the values of the parameters in the conditions (1) to (6).

"Example 2"
Focal length f: 16.00mm, F number: F1.80, angle of view 2ω: 52.5 degrees
The data of Example 2 is shown in Table 4.

"Variable interval"
In Example 2, the variable interval is the interval between the surface number 12 and the surface number 13.

  Table 5 shows the variable intervals of Example 2.

"Condition Parameter Values"
Table 6 shows the values of the parameters of the conditions (1) to (6).

"Example 3"
Focal length f: 16.00mm, F number: F1.84, angle of view 2ω: 52.6 degrees
The data of Example 3 is shown in Table 7.

"Variable interval"
In Example 3, the variable interval is the interval between the surface number 12 and the surface number 13.

  Table 8 shows the variable intervals of Example 3.

"Condition Parameter Values"
Table 9 shows the values of the parameters of the conditions (1) to (6).

Example 4
Focal length f: 15.99mm, F number: F1.81, angle of view 2ω: 52.7 degrees
The data of Example 4 is shown in Table 10.

"Variable interval"
In Example 4, the variable interval is the interval between the surface number 12 and the surface number 13.

  Table 11 shows the variable intervals of Example 4.

"Condition Parameter Values"
Table 12 shows the values of the parameters of the conditions (1) to (6).

  5 to 7 are aberration diagrams of the imaging lens system of Example 1. FIG. FIG. 5 is an aberration diagram in a state of focusing on an object at infinity, FIG. 6 is an aberration diagram in a state of focusing on an object with a magnification of −0.05 times, and FIG. 7 is an object with a magnification of −0.1 times. FIG. 6 is an aberration diagram in a state in which the lens is in focus.

  8 to 10 show aberration diagrams of the image forming lens system of Example 2. FIG. FIG. 8 is an aberration diagram in a state of focusing on an object at infinity, FIG. 9 is an aberration diagram in a state of focusing on an object with a magnification of −0.05 times, and FIG. 10 is an object with a magnification of −0.1 times. FIG. 6 is an aberration diagram in a state in which the lens is in focus.

  11 to 13 show aberration diagrams of the imaging lens system of Example 3. FIG. FIG. 11 is an aberration diagram in a state of focusing on an object at infinity, FIG. 12 is an aberration diagram in a state of focusing on an object with a magnification of −0.05 times, and FIG. 13 is an object with a magnification of −0.1 times. FIG. 6 is an aberration diagram in a state in which the lens is in focus.

  14 to 16 show aberration diagrams of the imaging lens system of Example 4. FIG. FIG. 14 is an aberration diagram in a state of focusing on an object at infinity, FIG. 15 is an aberration diagram in a state of focusing on an object with a magnification of −0.05 times, and FIG. 16 is an object with a magnification of −0.1 times. FIG. 6 is an aberration diagram in a state in which the lens is in focus.

  In each aberration diagram, the broken line in the spherical aberration represents “sine condition”, the solid line in the astigmatism diagram represents “sagittal”, and the broken line represents “meridional”. The thin line is an aberration curve with respect to “d line” and the thick line is “g line”.

  In each embodiment, various aberrations are corrected at a high level, and spherical aberration and longitudinal chromatic aberration are so small that they do not cause a problem. Astigmatism, curvature of field, and lateral chromatic aberration are sufficiently small, coma and disturbance of the color difference are well suppressed to the outermost periphery, and distortion is also 1 in absolute value at an imaging magnification of -0.05 times. 0.0% or less.

  In addition, the “change in field curvature” accompanying the change in the object distance due to focusing is sufficiently suppressed.

  These imaging lens systems of Examples 1 to 4 have very good image performance while having a large aperture with a half field angle of about 52 degrees and an F number of about 1.8. The number of lenses is as small as 11, and astigmatism, curvature of field, lateral chromatic aberration, coma color difference, distortion and the like are sufficiently reduced. In addition, it has a resolution corresponding to a solid-state image sensor with 6 to 10 million pixels, and it can draw a straight line without distortion from a full aperture to a high contrast with no distortion of the point image. Therefore, it is possible to realize an imaging device and a portable information terminal device that are small and have a very high image quality.

  As described above, according to the present invention, the following imaging lens system, imaging device, and portable information terminal device can be realized.

[1]
A first lens group (G1) having a positive power, an aperture stop (S), and a second lens group (G2) having a positive power are arranged in order from the object side to the image side. The group includes a 1a lens group (G1a) arranged on the object side and having negative power, and a 1b lens group (G1b) arranged on the image side and having positive power, and the 1a lens group. Includes a negative lens L11, a positive lens L12, and a negative lens L13 in order from the object side to the image side, and the 1b lens group includes a positive lens L14 and a positive lens L15 in order from the object side to the image side. The negative lens L16 is arranged, and the surface distance between the negative lens L13 and the positive lens L14 is the largest in the first lens group (G1), and during focusing from an object at infinity to a near object. The first lens group (G1) is fixed, And moving lens group (G2) is to the object side, the focal length of the first lens group: f1, the focal length of the entire system: f is the condition:
(1) 2.0 <f1 / f <5.0
Imaging lens system satisfying the above (Examples 1 to 4).

[2]
The imaging lens system according to [1], wherein the aperture stop (S) is fixed at the time of focusing from an object at infinity to an object at a short distance (Examples 1 to 4).

[3]
[2] In the imaging lens system according to [2], the distance between the aperture stop (S) and the second lens group (G2) when focusing on an object at infinity: Ds2, the focal length of the entire system: f is the condition:
(2) 0.2 <Ds2 / f <0.5
Imaging lens system satisfying the above (Examples 1 to 4).

[4]
The imaging lens system according to any one of [1] to [3], wherein a surface interval between the 1a lens group (G1a) and the 1b lens group (G1b): Dab, a group thickness of the first lens group S: D1 is the condition:
(3) 0.15 <Dab / D1 <0.4
Imaging lens system satisfying the above (Examples 1 to 4).

[5]
The imaging lens system according to any one of [1] to [4], wherein the group thickness: D1a of the first lens group: D1a and the group thickness: D1 of the first lens group are:
(4) 0.2 <D1a / D1 <0.5
Imaging lens system satisfying the above (Examples 1 to 4).

[6]
In the imaging lens system according to any one of [1] to [5], the focal length of the positive lens L15: f1_5 and the focal length of the negative lens L16: f1_6 of the first b lens group (1Gb) are: conditions:
(5) -1.6 <f1_5 / f1_6 <-0.8
Imaging lens system satisfying the above (Examples 1 to 4).

[7]
In the imaging lens system according to any one of [1] to [6], the focal length of the positive lens L14: f1_4 and the focal length of the positive lens L15: f1_5 of the first b lens group (G1b) are: conditions:
(6) 0.5 <f1_4 / f1_5 <1.5
Imaging lens system satisfying the above (Examples 1 to 4).

[8]
The imaging lens system according to any one of [1] to [7], wherein the second lens group (G2) is a negative lens L21 having a concave surface on the object side in order from the object side to the image side. An imaging lens system (Examples 1 to 4) including a positive lens L22, a positive lens L23, a negative lens L24 having a concave surface on the object side, and a positive lens L25.

[9]
An imaging lens system according to any one of [1] to [8], wherein all lenses are spherical lenses (Examples 1 to 4).

[10]
An imaging apparatus having the imaging lens system according to any one of [1] to [9] as an imaging optical system (FIGS. 17 and 18).

[11]
[10] The imaging apparatus according to [10], wherein the imaging lens system (1) captures an image by a solid-state imaging device (13) (FIGS. 17 and 18).

[12]
A portable information terminal device (FIGS. 17 and 18) having the imaging lens system according to any one of [1] to [9] as an imaging optical system (1) of an imaging function unit.

[13]
The portable information terminal device according to [12], wherein the imaging device according to [11] constitutes an imaging function unit (FIGS. 17 and 18).

The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the specific embodiments described above, and the invention described in the claims unless otherwise specified in the above description. Various modifications and changes are possible within the scope of the above.
For example, the imaging lens system can be used as an imaging optical system for “silver salt photography or video camera”.

  The effects described in the embodiments of the present invention are merely a list of suitable effects resulting from the invention, and the effects of the present invention are not limited to those described in the embodiments.

G1 first lens group
G2 second lens group
G1a 1a lens group
G1b 1b lens group
S Aperture stop
G filter, etc.
Im image plane

JP 2014-174234 A

Claims (13)

In order from the object side to the image side, a first lens group having a positive power, an aperture stop, and a second lens group having a positive power are arranged.
The first lens group includes a 1a lens group disposed on the object side and having negative power, and a 1b lens group disposed on the image side and having positive power,
The 1a lens group includes a negative lens L11, a positive lens L12, and a negative lens L13 in order from the object side to the image side.
The 1b lens group includes a positive lens L14, a positive lens L15, and a negative lens L16 in order from the object side to the image side.
The surface interval between the negative lens L13 and the positive lens L14 is the largest in the first lens group,
During focusing from an object at infinity to a near object, the first lens group is fixed, and the second lens group is moved toward the object side,
The focal length of the first lens group: f1 and the focal length of the entire system: f are the conditions:
(1) 2.0 <f1 / f <5.0
An imaging lens system that satisfies The imaging lens system according to claim 1,
An imaging lens system in which the aperture stop is fixed during focusing from an object at infinity to a near object. An imaging lens system according to claim 2,
When focusing on an object at infinity, the distance between the aperture stop and the second lens group: Ds2, and the focal length of the entire system: f are the conditions:
(2) 0.2 <Ds2 / f <0.5
An imaging lens system that satisfies The imaging lens system according to any one of claims 1 to 3,
The distance between the first a lens group and the first b lens group: Dab, and the first lens group thickness: D1 are:
(3) 0.15 <Dab / D1 <0.4
An imaging lens system that satisfies The imaging lens system according to any one of claims 1 to 4,
The group thickness of the first lens group: D1a and the group thickness of the first lens group: D1 are:
(4) 0.2 <D1a / D1 <0.5
An imaging lens system that satisfies An imaging lens system according to any one of claims 1 to 5,
In the first b lens group, the focal length of the positive lens L15: f1_5 and the focal length of the negative lens L16: f1_6 are:
(5) -1.6 <f1_5 / f1_6 <-0.8
An imaging lens system that satisfies The imaging lens system according to any one of claims 1 to 6,
In the first b lens group, the focal length of the positive lens L14: f1_4 and the focal length of the positive lens L15: f1_5 are:
(6) 0.5 <f1_4 / f1_5 <1.5
An imaging lens system that satisfies An imaging lens system according to any one of claims 1 to 7,
The second lens group includes, in order from the object side to the image side, a negative lens L21 having a concave surface on the object side, a positive lens L22, a positive lens L23, a negative lens L24 having a concave surface on the object side, and a positive lens L25. An imaging lens system. An imaging lens system according to any one of claims 1 to 8,
An imaging lens system in which all lenses are spherical lenses.   An imaging apparatus comprising the imaging lens system according to claim 1 as an imaging optical system. The imaging apparatus according to claim 10,
An image pickup apparatus for picking up an image by an imaging lens system with a solid-state image pickup device.   A portable information terminal device comprising the imaging lens system according to any one of claims 1 to 9 as an imaging optical system of an imaging function unit.   The portable information terminal device according to claim 12, wherein the imaging device according to claim 11 constitutes an imaging function unit.

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