JP5021565B2 - Five-lens imaging lens and imaging device - Google Patents

Description

  The present invention relates to an imaging lens that forms an optical image of a subject on an imaging element such as a CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor), and a digital still camera that mounts the imaging lens to perform photography. The present invention relates to an imaging device such as a camera-equipped mobile phone and an information portable terminal (PDA: Personal Digital Assistance).

  In recent years, with the spread of personal computers to ordinary homes and the like, digital still cameras that can input image information such as photographed landscapes and human images to personal computers are rapidly spreading. In addition, camera modules for image input are often mounted on mobile phones. An image sensor such as a CCD or a CMOS is used for a device having such an image capturing function. In recent years, these image pickup devices have been made more compact, and the entire image pickup apparatus and the image pickup lens mounted thereon are also required to be compact. At the same time, the number of pixels of the image sensor is increasing, and there is a demand for higher resolution and higher performance of the imaging lens. For example, performance corresponding to a high pixel of 2 megapixels or more, more preferably 5 megapixels or more is required.

  In order to meet such a demand, for example, a five-lens configuration with a relatively large number of lenses may be considered in order to achieve high resolution (see Patent Document 1 and FIG. 3). In order to achieve higher performance, it is conceivable to use an aspherical surface actively (see Patent Document 2).

Japanese Patent No. 2679017 (FIG. 3) JP 2007-264180 A

  In order to cope with recent imaging elements with higher pixel count, it is desirable to develop a lens system that has high imaging performance from the central angle of view to the peripheral angle of view while shortening the overall length. Yes. The five-lens lens described in Patent Document 1 generally has insufficient performance in order to cope with the recent increase in the number of pixels. In addition, although the imaging lens described in Patent Document 2 has a good correction of axial chromatic aberration, correction of lateral chromatic aberration is insufficient.

  The present invention has been made in view of such problems, and the object thereof is to achieve a high image formation from the central angle of view to the peripheral angle of view, with particularly good correction of axial and magnification chromatic aberrations while shortening the overall length. An object of the present invention is to provide an imaging lens capable of realizing performance, and an imaging device that can obtain a high-resolution captured image by mounting the imaging lens.

The imaging lens according to the first aspect of the present invention includes, in order from the object side, a first lens having a positive power in which the object-side surface is a convex surface, and an image-side surface in the vicinity of the optical axis that is a concave surface. A second lens having negative power in the vicinity of the optical axis, a third lens having a convex surface in the vicinity of the optical axis and having a positive power in the vicinity of the optical axis, and an image side surface in the vicinity of the optical axis. A fourth lens having an aspherical shape having a concave shape and a convex image-side surface at the periphery, and a fifth lens having a positive power near the optical axis, and satisfying the following conditional expression: It is comprised as follows.
ν2 ≦ 30 (1)
40 ≦ ν3 (2)
40 ≦ ν4 (3)
However,
ν2: Abbe number of the second lens ν3: Abbe number of the third lens ν4: Abbe number of the fourth lens.

  In the imaging lens according to the first aspect of the present invention, in the lens configuration of five as a whole, the lens configuration is optimized by efficiently using each aspherical surface and satisfying a predetermined conditional expression. By optimizing the lens, the dispersion of each lens is made appropriate according to the conditional expressions (1) to (3) while shortening the overall length, and the axial and magnification chromatic aberration is corrected well. .

An imaging lens according to a second aspect of the present invention includes, in order from the object side, a first lens having a positive power in which the object-side surface is a convex surface, and an image-side surface in the vicinity of the optical axis that is a concave surface. A second lens having negative power in the vicinity of the optical axis, a third lens having a convex surface in the vicinity of the optical axis and having a positive power in the vicinity of the optical axis, and an image side surface in the vicinity of the optical axis. A fourth lens having an aspherical shape having a concave shape and a convex image-side surface at the periphery, and a fifth lens having a positive power near the optical axis, and satisfying the following conditional expression: It is comprised as follows.
ν2 ≦ 30 (1)
40 ≦ ν3 (2)
0.2 ≦ f3 / f ≦ 0.4 (4)
However,
ν2: Abbe number of the second lens ν3: Abbe number of the third lens f: Overall focal length f3: Paraxial focal length of the third lens.

  In the imaging lens according to the second aspect of the present invention, in an overall lens configuration of five lenses, each lens shape is optimized by efficiently using an aspheric surface, and a lens configuration satisfying a predetermined conditional expression is achieved. In order to shorten the overall length, the dispersion of each lens is made appropriate according to the conditional expressions (1) to (2), and axial and magnification chromatic aberrations are favorably corrected. . Further, the field curvature is corrected well by the conditional expression (3).

  In the imaging lens according to the first or second aspect of the present invention, it is more advantageous in terms of shortening the overall length and imaging performance by properly satisfying and appropriately adopting the following preferable configurations. can do.

In particular, in the imaging lens according to the second aspect of the present invention, it is preferable that the following conditions are satisfied. Thereby, the thickness DL of the lens system is maintained in an appropriate range, which is advantageous for shortening the overall length.
1.0 ≦ DL / f ≦ 1.3 (5)
However, DL is a distance on the optical axis from the object side surface vertex of the first lens to the image side surface vertex of the fifth lens.

In the imaging lens according to the first or second aspect of the present invention, it is preferable that the following conditions are selectively satisfied as appropriate.
40 ≦ ν5 (6)
−1.0 ≦ f4 / f ≦ 0 (7)
0.8 ≦ f5 / f ≦ 4.0 (8)
0.7 ≦ | R1 / R2 | ≦ 8.0 (9)
0.75 ≦ f1 / f ≦ 5.0 (10)
1.4 ≦ TL / f ≦ 1.80 (11)
0.4 ≦ | R9 / f | ≦ 6.0 (12)
0.5 ≦ | f2 / f1 | ≦ 10.0 (13)
0.8 ≦ | f3 * (1 / f4 + 1 / f5) | ≦ 1.5 (14)
70 ≦ ν1 (15)
However,
νi: Abbe number of i-th lens fi: paraxial focal length of i-th lens R1: paraxial radius of curvature of object side surface of first lens R2: paraxial radius of curvature of image side surface of first lens R9: Paraxial radius of curvature of the object side surface of the fifth lens TL: Full length (distance on the optical axis from the most object side surface to the image plane. Air conversion length from the fifth lens to the image plane)
And

  Here, in particular, when the conditional expression (7) is satisfied, each of the third lens, the fourth lens, and the fifth lens is made of a plastic material, and each has at least one aspheric surface. Preferably it is. In addition, it is preferable that the fourth lens has a negative power in the vicinity of the optical axis.

  In particular, when the conditional expression (12) is satisfied, it is preferable that the second lens has a negative meniscus shape with the concave surface facing the image side in the vicinity of the optical axis.

  In the imaging lens according to the first or second aspect of the present invention, the first lens may be a polished glass having a spherical surface. The use of an aspherical surface for the first lens is advantageous in terms of performance. In particular, when the F number may be large, that is, a relatively dark lens system may be used, both surfaces of the first lens are made spherical. Also good.

An imaging apparatus according to the present invention includes the imaging lens according to the first or second aspect of the present invention and an imaging element that outputs an imaging signal corresponding to an optical image formed by the imaging lens.
In the imaging apparatus according to the present invention, a high-resolution imaging signal is obtained based on the high-resolution optical image obtained by the imaging lens of the present invention.

  According to the imaging lens according to the first aspect of the present invention, since the configuration of each lens element is optimized in a lens configuration of five as a whole, particularly the dispersion of each lens is configured to be appropriate. While shortening the overall length, it is possible to realize a lens system having particularly high on-axis performance from the central angle of view to the peripheral angle of view, with particularly good correction of axial and magnification chromatic aberrations.

  According to the imaging lens according to the second aspect of the present invention, in the lens configuration of five as a whole, the configuration of each lens element is optimized, and in particular, the dispersion of each lens is configured appropriately. Since it is configured to satisfy the conditions that are advantageous for correcting the curvature of field, the axial and magnification chromatic aberrations are particularly well corrected while shortening the overall length, resulting in high results from the central field angle to the peripheral field angle. A lens system having image performance can be realized.

  Further, according to the imaging apparatus of the present invention, since an imaging signal corresponding to the optical image formed by the high-performance imaging lens of the present invention is output, high-resolution imaging is performed based on the imaging signal. An image can be obtained.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 shows a first configuration example of an imaging lens according to an embodiment of the present invention. This configuration example corresponds to the lens configuration of a first numerical example (FIGS. 16 and 31) described later. Similarly, cross-sectional configurations of second to fifteenth configuration examples corresponding to lens configurations of second to fifteenth numerical examples (FIGS. 17 to 30 and FIGS. 32 to 45) described later are shown in FIG. As shown in FIG. In FIG. 1 to FIG. 15, the symbol Ri is the curvature of the i-th surface that is numbered sequentially so as to increase toward the image side (imaging side) with the surface of the lens element closest to the object side as the first. Indicates the radius. The symbol Di indicates the surface interval on the optical axis Z1 between the i-th surface and the i + 1-th surface. Since the basic configuration is the same for each configuration example, the configuration example of the imaging lens shown in FIG. 1 will be basically described below, and the configuration examples of FIGS. explain.

  The imaging lens according to the present embodiment is used for various imaging devices using an imaging device such as a CCD or CMOS, particularly for relatively small portable terminal devices such as digital still cameras, camera-equipped mobile phones, and PDAs. Is preferred. This imaging lens includes a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, and a fifth lens L5 in order from the object side along the optical axis Z1. .

An imaging apparatus according to the present embodiment includes an imaging lens according to the present embodiment and an imaging element 100 such as a CCD that outputs an imaging signal corresponding to an optical image formed by the imaging lens. . The image sensor 100 is disposed on the imaging surface (imaging surface) of the imaging lens. Various optical members CG may be arranged between the fifth lens L5 and the image sensor 100 according to the configuration on the camera side where the lens is mounted. For example, a flat optical member such as a cover glass for protecting the imaging surface or an infrared cut filter may be disposed. In this case, as the optical member CG, for example, a flat cover glass provided with a coating having a filter effect such as an infrared cut filter or an ND filter may be used.
Further, as in the twelfth configuration example (FIG. 12), the same effect as that of the optical member CG may be provided by coating the fifth lens L5 without using the optical member CG. Thereby, the number of parts can be reduced and the total length can be shortened.

  The imaging lens also has a diaphragm St. The stop St is an optical aperture stop, and is preferably disposed before and after the first lens L1. For example, it is preferable that the diaphragm St is a so-called “front diaphragm” disposed on the most object side. Here, the “most object side” means on the optical axis that is closer to the object side than the outer edge position E (see FIG. 1) of the object side surface of the first lens L1, for example, on the optical axis, This means that the first lens L1 is disposed between the object-side surface vertex position of the first lens L1 and the outer edge position E of the object-side surface of the first lens L1. In the present embodiment, the lenses (FIGS. 1 to 10) of the first to tenth configuration examples are configuration examples corresponding to the front diaphragm.

  Further, a so-called “medium stop” may be used in which the stop St is disposed on the image side of the first lens L1. For example, it can be arranged between the first lens L1 and the second lens L2. Here, “between the first lens L1 and the second lens L2” means on the optical axis the outer edge position of the object-side surface or the outer edge position of the image-side surface of the first lens L1 and the second lens L2. It is between the outer edge position of the object side surface. Naturally, this includes the case where the stop St is disposed near the image-side surface vertex position of the first lens L1 on the optical axis, and the case where the stop St is disposed near the object-side surface vertex position of the second lens L2. Meaning. In the present embodiment, the lenses (FIGS. 11 to 15) of the eleventh to fifteenth configuration examples are configuration examples corresponding to an intermediate diaphragm.

  In order to improve the performance of the imaging lens, it is preferable to use an aspherical surface for at least one of the first lens L1 to the fifth lens L5. However, for example, when the F-number may be large, that is, a relatively dark lens system may be used, for example, both surfaces of the first lens L1 may be spherical. In this case, the first lens L1 is preferably made of polished glass.

  In this imaging lens, the first lens L1 has a positive power in the vicinity of the optical axis. In the first lens L1, the object side surface is convex in the vicinity of the optical axis.

  The second lens L2 has a negative power near the optical axis. The second lens L2 has a concave surface on the image side in the vicinity of the optical axis. The second lens L2 is preferably a negative meniscus lens having a concave surface facing the image side in the vicinity of the optical axis.

  The third lens L3 has a positive power in the vicinity of the optical axis. The third lens L3 has a convex surface on the image side in the vicinity of the optical axis. As the third lens L3, it is preferable to use an aspherical surface having different concave and convex shapes in the vicinity of the optical axis and in the peripheral portion. For example, it is preferable to use an aspherical surface such that the object side surface has a concave shape in the vicinity of the optical axis and a convex shape in the peripheral portion.

  The fourth lens L4 is aspheric so that the image side surface is concave in the vicinity of the optical axis and convex in the periphery. The object side surface of the fourth lens L4 is preferably concave in the vicinity of the optical axis. The fourth lens L4 preferably has negative power in the vicinity of the optical axis.

  The fifth lens L5 has a positive power in the vicinity of the optical axis. The fifth lens L5 preferably has a convex surface on the object side in the vicinity of the optical axis. However, the object-side surface of the fifth lens L5 can be a flat surface or a weak concave surface (concave surface having a large absolute value of the radius of curvature) in the vicinity of the optical axis. For the fifth lens L5, it is preferable to use an aspherical surface having different concave and convex shapes in the vicinity of the optical axis and the peripheral portion. For example, it is preferable to use an aspherical surface such that the object-side surface has a convex shape in the vicinity of the optical axis and a concave shape in the peripheral portion.

This imaging lens preferably satisfies at least the following conditional expressions (1) to (2).
ν2 ≦ 30 (1)
40 ≦ ν3 (2)
However,
ν2: Abbe number of the second lens L2 ν3: Abbe number of the third lens L3.

Furthermore, it is preferable that the following conditions are selectively satisfied as appropriate.
40 ≦ ν4 (3)
0.2 ≦ f3 / f ≦ 0.4 (4)
1.0 ≦ DL / f ≦ 1.3 (5)
40 ≦ ν5 (6)
−1.0 ≦ f4 / f ≦ 0 (7)
0.8 ≦ f5 / f ≦ 4.0 (8)
0.7 ≦ | R1 / R2 | ≦ 8.0 (9)
0.75 ≦ f1 / f ≦ 5.0 (10)
1.4 ≦ TL / f ≦ 1.80 (11)
0.4 ≦ | R9 / f | ≦ 6.0 (12)
0.5 ≦ | f2 / f1 | ≦ 10.0 (13)
0.8 ≦ | f3 * (1 / f4 + 1 / f5) | ≦ 1.5 (14)
70 ≦ ν1 (15)
However,
ν1: Abbe number of the first lens L1 ν4: Abbe number of the fourth lens L4 ν5: Abbe number of the fifth lens L5 DL: Optical axis from the object side surface vertex of the first lens L1 to the image side surface vertex of the fifth lens L5 Distance above (see Figure 1)
f1: Paraxial focal length of the first lens L1 f2: Paraxial focal length of the second lens L2 f3: Paraxial focal length of the third lens L3 f4: Paraxial focal length of the fourth lens L4 f5: Fifth lens L5 R1: Paraxial radius of curvature of the object side surface of the first lens L1 R2: Paraxial radius of curvature of the image side surface of the first lens L1 R9: Near the object side surface of the fifth lens L5 Axis curvature radius TL: Full length (distance on the optical axis from the surface closest to the object side to the image plane. The air conversion length from the fifth lens L5 to the image plane)
And

Moreover, it is preferable that the following conditions are selectively satisfied as appropriate.
0.10 ≦ D5 / f ≦ 0.40 (16)
D6 / D8 ≦ 0.2 (17)
However,
D5: Center thickness of the third lens L3 D6: Spacing on the optical axis between the third lens L3 and the fourth lens L4 D8: Spacing on the optical axis between the fourth lens L4 and the fifth lens L5.

  In the above conditional expressions, in particular, when the conditional expression (4) is satisfied, it is preferable that the conditional expression (5) is simultaneously satisfied.

  In particular, when the conditional expression (7) is satisfied, each of the third lens L3, the fourth lens L4, and the fifth lens L5 is made of a plastic material, and each has at least one aspheric surface. It is preferable. Further, it is preferable that the fourth lens L4 has a negative power in the vicinity of the optical axis.

  In particular, when the conditional expression (12) is satisfied, it is preferable that the second lens L2 has a negative meniscus shape with a concave surface facing the image side in the vicinity of the optical axis.

  Next, operations and effects of the imaging lens configured as described above, particularly operations and effects related to conditional expressions, will be described in more detail.

  In the imaging lens according to the present embodiment, in the overall lens configuration of five lenses, each lens shape is optimized by efficiently using an aspheric surface, and the lens configuration is optimized by satisfying a predetermined conditional expression. Thus, while reducing the total length, the dispersion of each lens is made appropriate by a predetermined conditional expression related to the Abbe number, and the axial and magnification chromatic aberration is corrected well.

  In this imaging lens, the object-side surface of the first lens L1 is convex in the vicinity of the optical axis, so that the light flux after the object-side surface is narrowed, and the first lens L1 is projected on the image-side surface. Spherical aberration correction is facilitated.

In addition, the second lens L2 is a negative lens, the conditional expression (1) is satisfied with respect to the negative lens, the Abbe number ν2 is decreased, and dispersion as a negative lens is increased, thereby correcting axial chromatic aberration. Correction of chromatic aberration of magnification and curvature of field can be satisfactorily performed with the center at. Further, by satisfying the conditional expressions (2) and (3) of other Abbe numbers at the same time, it is possible to correct axial chromatic aberration and magnification more satisfactorily. Further, by satisfying the conditional expression (15), the Abbe number ν1 of the first lens L1 is increased, and the dispersion of the first lens L1 as a positive lens is reduced, so that axial chromatic aberration can be suppressed to a smaller value. it can. In order to correct chromatic aberration better, it is more preferable that the numerical range of the Abbe number satisfies the following conditions.
50 ≦ ν3 (2 ′)
50 ≦ ν4 (3 ′)
50 ≦ ν5 (6 ′)

  Regarding the aspherical shape, in particular, the fourth lens L4 and the fifth lens L5 are changed to different shapes in the central portion and the peripheral portion, so that the curvature of field from the central portion of the image surface to the peripheral portion is improved. It has been corrected. Compared with the first lens L1, the second lens L2, and the third lens L3, the fourth lens L4 and the fifth lens L5 separate the luminous flux for each angle of view. For this reason, in particular, the image-side surface of the fourth lens L4, which is a lens surface relatively close to the image sensor 100, is concave on the image side in the vicinity of the optical axis and convex on the image side in the peripheral portion. Thus, aberration correction for each angle of view is appropriately performed, and the incident angle of the light flux on the image sensor 100 is controlled to be equal to or smaller than a certain angle. Accordingly, unevenness in the amount of light in the entire image plane can be reduced, and it is advantageous for correcting curvature of field, distortion, and the like.

  In this imaging lens, by correcting the fifth lens L5 to an appropriate aspherical shape, it is possible to satisfactorily correct the image plane disparity, distortion, peripheral light amount, and light emission angle. When the fifth lens L5 has an aspherical shape, the aspherical shape can be smoothly changed between the central portion and the peripheral portion to improve the transfer performance of the aspherical shape at the time of molding.

  In general, in an imaging lens system, telecentricity, that is, the incident angle of the principal ray on the imaging element 100 is close to the optical axis (the incident angle on the imaging surface is close to zero with respect to the normal of the imaging surface). It is preferable to become. In order to ensure this telecentricity, it is preferable that the aperture stop St is disposed as far as possible on the object side, in front of and behind the first lens L1. On the other hand, when the diaphragm St is arranged at a position further away from the object-side lens surface of the first lens L1 in the object-side direction, the corresponding amount (the distance between the diaphragm St and the most object-side lens surface) is the optical path length. Therefore, it is disadvantageous in terms of downsizing the overall configuration. Therefore, for example, the aperture stop St is disposed at the same position as the object-side lens surface vertex position of the first lens L1 on the optical axis Z1, or the object-side surface vertex position and the image-side surface vertex of the first lens L1. Telecentricity can be ensured by shortening the overall length by disposing it between the positions.

  Hereinafter, the specific significance of other conditional expressions will be described.

  Conditional expression (4) relates to the focal length f3 of the third lens L3. When the upper limit of conditional expression (4) is exceeded, the power of the third lens L3 becomes too small, and the field curvature and distortion aberration mainly at an intermediate field angle of about 20 to 60% of the maximum field angle. Will get worse. If the lower limit is exceeded, the power of the third lens L3 becomes too large. For example, when widening the angle of view, the incident angle to the image sensor 100 is large at an image height of about 80% of the maximum image height. turn into. In addition, spherical aberration and field curvature are close to each other, and the tangential direction becomes excessively large particularly with respect to the image plane disparity.

  Conditional expression (5) relates to the thickness DL of the lens system on the optical axis. In order to satisfy the two requirements of shortening the total lens length and preventing the final lens surface closest to the image sensor 100 from being too close to the imaging surface, the lens system thickness DL should be within an appropriate range. There is a need to. Exceeding the upper limit of conditional expression (5) is disadvantageous for shortening the total length. Although reducing the thickness DL directly leads to a shortening of the overall length, if the thickness DL is made too small beyond the lower limit of conditional expression (5), the aberration performance deteriorates and the manufacturing and assembly sensitivity decreases sharply. End up. Increasing the number of aspheric surfaces in this imaging lens increases the sensitivity of performance degradation to variations during manufacturing. If the thickness DL is too small, performance deterioration due to variations in molding conditions of each lens element and variations during assembly increases.

Conditional expression (7) relates to the focal length f4 of the fourth lens L4. Conditional expression (7) is responsible for power balance and aberration correction of the latter half of the imaging lens (third lens L3 to fifth lens L5). If the upper limit of conditional expression (7) is exceeded, the fourth lens L4 becomes a positive lens, and the field curvature at the intermediate angle of view tends to be too under. If the negative power is weakened beyond the lower limit, it is disadvantageous for shortening the total length. In addition, the curvature of field at the intermediate angle of view tends to be over. On the other hand, if the negative power of the fourth lens L4 is increased too much, the chromatic aberration particularly near the optical axis will increase. It is preferable to suppress the negative power of the fourth lens L4 within an appropriate range. For this reason, the numerical range of conditional expression (7) is
−0.5 ≦ f4 / f ≦ −0.2 (7 ′)
It is preferable that More preferably,
−0.35 ≦ f4 / f ≦ −0.25 (7 ″)
It is preferable that

  Conditional expression (8) relates to the focal length f5 of the fifth lens L5. The fifth lens L5 is mainly used as a correction lens for final adjustment of curvature of field, light emission angle, and distortion. If the upper limit of conditional expression (8) is exceeded, the power of the fifth lens L5 becomes too weak, and in particular, distortion and field curvature in the vicinity of about 20% of the field angle on the axial and maximum field angle. , And the image plane disparity cannot be corrected effectively. If the lower limit is exceeded, the power of the fifth lens L5 becomes too strong, which is disadvantageous for shortening the overall length. Further, since the fifth lens L5 is a thin lens, when it is made an aspherical surface, the change in the wall thickness ratio adversely affects the variation of the aspherical shape at the time of molding.

  Conditional expression (9) relates to the paraxial shape of the first lens L1. Exceeding the upper limit of conditional expression (9), for example, if the radius of curvature R1 of the object side surface of the first lens L1 increases, this means that the power on the object side surface decreases, which is disadvantageous in reducing the total length. Become. In addition, ghost light is generated in which a light beam entering from outside the effective angle of view is reflected on the image side surface of the first lens L1 and further reflected on the object side surface to reach the image surface. It becomes easy to do. If the radius of curvature R1 of the object side surface of the first lens L1, for example, becomes smaller than the lower limit, this means that the power on the object side surface becomes stronger, and the spherical aberration becomes under and the distortion aberration is under. It tends to be too barrel-shaped.

Conditional expression (10) relates to the focal length f1 of the first lens L1. Exceeding the upper limit of conditional expression (10) means that the power of the first lens L1 is reduced, which is disadvantageous in reducing the overall length. If the lower limit is exceeded, it means that the power of the first lens L1 increases, and the spherical aberration tends to be under, and the distortion tends to be too barrel-shaped.
In order to obtain better performance, the numerical range of conditional expression (10) is
1.0 ≦ f1 / f ≦ 5.0 (10 ′)
It is preferable that

Conditional expression (11) relates to the total length TL of the lens system. If the upper limit of conditional expression (11) is exceeded, the total length TL becomes too large, which is disadvantageous for shortening the total length TL. Exceeding the lower limit is advantageous for shortening the total length TL, but causes a reduction in image quality.
In order to obtain better performance, the numerical range of conditional expression (11) is
1.4 ≦ TL / f ≦ 1.60 (11 ′)
It is preferable that

Conditional expression (12) relates to the paraxial radius of curvature R9 of the object side surface of the fifth lens L5. If the upper limit of conditional expression (12) is exceeded, the spherical aberration and the curvature of field will be too under, and the distortion will be too positive (pincushion type). If the lower limit is exceeded, the spherical aberration and the curvature of field will be excessive, and the distortion will be too negative (barrel type). In addition, since the power for jumping up the peripheral rays on the object side surface of the fifth lens L5 is increased, the manufacturing sensitivity is increased.
In order to obtain better performance, the numerical range of conditional expression (12) is
0.4 ≦ R9 / f ≦ 6.0 (12 ′)
It is preferable that

Conditional expression (13) relates to the balance of power between the first lens L1 and the second lens L2. If the upper limit of conditional expression (13) is exceeded, it means that the power of the first lens L1 becomes too strong with respect to the power of the second lens L2, and the field curvature becomes under and the peripheral light amount decreases. In addition, distortion tends to be on the minus side (barrel type) too much. Exceeding the lower limit means that the power of the first lens L1 becomes too weak with respect to the power of the second lens L2, which is disadvantageous in reducing the overall length.
In order to obtain better performance, the numerical range of conditional expression (13) is
1.0 ≦ | f2 / f1 | ≦ 5.0 (13 ′)
It is preferable that

Conditional expression (14) defines an appropriate power relationship among the latter three lenses (third lens L3 to fifth lens L5) of the imaging lens. If the upper limit of conditional expression (14) is exceeded, the incident angle of the principal ray on the image sensor 100 becomes large, and the telecentricity deteriorates. If the lower limit is exceeded, it is advantageous for shortening the overall length and ensuring telecentricity, but the magnification and axial chromatic aberration increase, resulting in degraded resolution performance.
In order to obtain better performance, the numerical range of conditional expression (14) is
0.9 ≦ | f3 * (1 / f4 + 1 / f5) | ≦ 1.3 (14 ′)
It is preferable that

Conditional expression (16) relates to the center thickness D5 of the third lens L3. If the upper limit of conditional expression (16) is exceeded, the thickness ratio of the third lens L3 increases when the overall length is shortened, and the surface shape becomes stable and difficult to mold during molding. Further, for example, when widening the angle of view, the incident angle to the image sensor 100 becomes large at an image height of about 80% of the maximum image height. If the lower limit is exceeded, curvature of field and distortion will be deteriorated mainly at the intermediate angle of view.
In order to obtain better performance, the numerical range of conditional expression (16) is
0.22 ≦ D5 / f ≦ 0.36 (16 ′)
It is preferable that More preferably,
0.25 ≦ D5 / f ≦ 0.36 (16 ″)
It is preferable that

Conditional expression (17) relates to the lens interval D6 between the third lens L3 and the fourth lens L4 and the lens interval D8 between the fourth lens L4 and the fifth lens L5. The lens distance D6 between the third lens L3 and the fourth lens L4 generally has a physical limit on how close it can be when assembling. Conditional expression (17) represents how much the lens distance D8 between the fourth lens L4 and the fifth lens L5 is designed with a margin from the limit. If the upper limit of conditional expression (17) is exceeded, the distance between the fifth lens L5, which is the final lens, and the image sensor 100 will generally be reduced, making it impossible to insert parallel plane plates and filters. In addition, the incident angle of the chief ray on the image sensor 100 increases, and the telecentricity tends to deteriorate. When the lower limit is exceeded, the thickness of the air lens formed by the image-side surface of the fourth lens L4 and the object-side surface of the fifth lens L5 becomes thin, and the field curvature at the intermediate angle of view, coma aberration, and Distortion cannot be corrected sufficiently.
In order to obtain better performance, the numerical range of conditional expression (17) is
D6 / D8 ≦ 0.15 (17 ′)
It is preferable that

  As described above, according to the imaging lens according to the present embodiment, the configuration of each lens element is optimized in a lens configuration of five lenses as a whole, and in particular, the dispersion of each lens is appropriate. Therefore, it is possible to realize a lens system having a high imaging performance from the central angle of view to the peripheral angle of view while correcting the axial and magnification chromatic aberrations in particular while reducing the overall length. In addition, by satisfying the preferable conditions as appropriate, manufacturing aptitude is good and higher imaging performance can be realized. In addition, according to the imaging apparatus according to the present embodiment, the imaging signal corresponding to the optical image formed by the high-performance imaging lens according to the present embodiment is output. A high-resolution captured image can be obtained up to the corner.

  Next, specific numerical examples of the imaging lens according to the present embodiment will be described. Hereinafter, a plurality of numerical examples will be described together.

  16 and 31 show specific lens data corresponding to the configuration of the imaging lens shown in FIG. In particular, FIG. 16 shows the basic lens data, and FIG. 31 shows data relating to the aspherical surface. In the field of the surface number Si in the lens data shown in FIG. 16, the surface of the lens element closest to the object side is the first (aperture St is 0th) for the imaging lens according to Example 1, and as it goes toward the image. The number of the i-th surface which has been assigned a code so as to increase sequentially is shown. In the column of the curvature radius Ri, the value (mm) of the curvature radius of the i-th surface from the object side is shown in correspondence with the reference symbol Ri in FIG. Similarly, the column of the surface interval Di indicates the interval (mm) on the optical axis between the i-th surface Si and the i + 1-th surface Si + 1 from the object side. In the column Ndj, the refractive index value for the d-line (587.6 nm) of the j-th optical element from the object side is shown. The column of νdj shows the Abbe number value for the d-line of the j-th optical element from the object side. Outside the column of FIG. 16, the values of the focal length f (mm) of the entire system are shown as various data.

  In the imaging lens according to Example 1, both surfaces of the second lens L2 to the fifth lens L5 are all aspherical. The first lens L1 is a spherical surface. The basic lens data in FIG. 16 shows numerical values of curvature radii near the optical axis (paraxial curvature radii) as the curvature radii of these aspheric surfaces.

FIG. 31 shows aspherical data in the imaging lens of Example 1. In the numerical values shown as aspherical data, the symbol “E” indicates that the subsequent numerical value is a “power exponent” with a base of 10, and the numerical value represented by an exponential function with the base of 10 is Indicates that the value before “E” is multiplied. For example, “1.0E-02” indicates “1.0 × 10 ⁻² ”.

  As the aspheric surface data, the values of the coefficients Ai and K in the aspheric surface expression represented by the following expression (A) are described. More specifically, Z is the length (mm) of a perpendicular line drawn from a point on the aspheric surface at a height h from the optical axis to the tangential plane (plane perpendicular to the optical axis) of the apex of the aspheric surface. Show.

Z = C · h ² / {1+ (1−K · C ² · h ² ) ^1/2 } + ΣAi · h ⁱ (A)
However,
Z: Depth of aspheric surface (mm)
h: Distance from the optical axis to the lens surface (height) (mm)
K: eccentricity C: paraxial curvature = 1 / R
(R: paraxial radius of curvature)
Ai: i-th order (i is an integer of 3 or more) aspheric coefficient

  In the imaging lens of Example 1, each aspheric surface is represented by effectively using the third to tenth coefficients A3 to A10 as the aspheric coefficient Ai. In the imaging lens of Example 1, the aspheric coefficients (surface numbers 1 and 2) related to the first lens L1 are all 0, which indicates a spherical surface.

  Similar to the imaging lens of the first embodiment, specific lens data corresponding to the configuration of the imaging lens shown in FIG. Similarly, specific lens data corresponding to the configuration of the imaging lens shown in FIGS. 3 to 15 are shown as Example 3 to Example 15 in FIGS. 18 to 30 and FIGS. 33 to 45. In the imaging lenses according to Examples 2 to 15, both surfaces of the first lens L1 to the fifth lens L5 are all aspherical.

  46 and 47 show values relating to the above-described conditional expressions for each example. In FIG. 46 and FIG. 47, the part with “*” added to the numerical value indicates that it is out of the numerical value range of the conditional expression.

  48A to 48C show spherical aberration, astigmatism (curvature of field), and distortion (distortion aberration) in the imaging lens of Example 1, respectively. Each aberration diagram shows an aberration with the e-line (wavelength 546.07 nm) as a reference wavelength. The spherical aberration diagram and the astigmatism diagram also show aberrations for the F line (wavelength 486.13 nm) and the C line (wavelength 656.27 nm). In the astigmatism diagram, the solid line indicates the sagittal direction (S), and the broken line indicates the tangential direction (T). FNo. Indicates the F value, and Y indicates the image height.

  Similarly, various aberrations of the imaging lens of Example 2 are shown in FIGS. Similarly, various aberrations of the imaging lenses of Examples 3 to 15 are shown in FIGS. 50 (A) to (C) to 62 (A) to (C).

  As can be seen from the numerical data and aberration diagrams described above, in each example, high imaging performance is realized along with shortening the total length.

  In addition, this invention is not limited to the said embodiment and each Example, A various deformation | transformation implementation is possible. For example, the radius of curvature, the surface interval, and the refractive index of each lens component are not limited to the values shown in the above numerical examples, and may take other values.

  In each of the above embodiments, the description is based on the premise that the fixed focus is used. However, it is possible to adopt a configuration in which focus adjustment is possible. For example, the entire lens system can be extended, or a part of the lenses can be moved on the optical axis to enable autofocusing.

1 is a lens cross-sectional view illustrating a first configuration example of an imaging lens according to an embodiment of the present invention and corresponding to Example 1. FIG. FIG. 2 is a lens cross-sectional view illustrating a second configuration example of an imaging lens according to an embodiment of the present invention and corresponding to Example 2; 3 is a lens cross-sectional view illustrating a third configuration example of an imaging lens according to an embodiment of the present invention and corresponding to Example 3. FIG. 4 is a lens cross-sectional view illustrating a fourth configuration example of an imaging lens according to an embodiment of the present invention and corresponding to Example 4; FIG. 5 is a lens cross-sectional view illustrating a fifth configuration example of an imaging lens according to an embodiment of the present invention and corresponding to Example 5. FIG. 6 is a lens cross-sectional view illustrating a sixth configuration example of an imaging lens according to an embodiment of the present invention and corresponding to Example 6. FIG. 7 is a lens cross-sectional view illustrating a seventh configuration example of an imaging lens according to an embodiment of the present invention and corresponding to Example 7. FIG. 8 shows an eighth configuration example of the imaging lens according to an embodiment of the present invention, and is a lens cross-sectional view corresponding to Example 8. FIG. 9 is a lens cross-sectional view illustrating a ninth configuration example of an imaging lens according to an embodiment of the present invention and corresponding to Example 9. FIG. 10 is a lens cross-sectional view illustrating a tenth configuration example of an imaging lens according to an embodiment of the present invention and corresponding to Example 10. FIG. 11 shows an eleventh configuration example of the imaging lens according to the embodiment of the invention, and is a lens cross-sectional view corresponding to Example 11. FIG. 12 is a lens cross-sectional view illustrating a twelfth configuration example of an imaging lens according to an embodiment of the present invention and corresponding to Example 12. FIG. 14 is a lens cross-sectional view illustrating a thirteenth configuration example of an imaging lens according to an embodiment of the present invention and corresponding to Example 13. FIG. 14 is a lens cross-sectional view illustrating a fourteenth configuration example of an imaging lens according to an embodiment of the present invention and corresponding to Example 14. FIG. 15 shows a fifteenth configuration example of the imaging lens according to the embodiment of the invention, and is a lens cross-sectional view corresponding to Example 15. FIG. It is a figure which shows the basic lens data of the imaging lens which concerns on Example 1 of this invention. It is a figure which shows the basic lens data of the imaging lens which concerns on Example 2 of this invention. It is a figure which shows the basic lens data of the imaging lens which concerns on Example 3 of this invention. It is a figure which shows the basic lens data of the imaging lens which concerns on Example 4 of this invention. It is a figure which shows the basic lens data of the imaging lens which concerns on Example 5 of this invention. It is a figure which shows the basic lens data of the imaging lens which concerns on Example 6 of this invention. It is a figure which shows the basic lens data of the imaging lens which concerns on Example 7 of this invention. It is a figure which shows the basic lens data of the imaging lens which concerns on Example 8 of this invention. It is a figure which shows the basic lens data of the imaging lens which concerns on Example 9 of this invention. It is a figure which shows the basic lens data of the imaging lens which concerns on Example 10 of this invention. It is a figure which shows the basic lens data of the imaging lens which concerns on Example 11 of this invention. It is a figure which shows the basic lens data of the imaging lens which concerns on Example 12 of this invention. It is a figure which shows the basic lens data of the imaging lens which concerns on Example 13 of this invention. It is a figure which shows the basic lens data of the imaging lens which concerns on Example 14 of this invention. It is a figure which shows the basic lens data of the imaging lens which concerns on Example 15 of this invention. It is a figure which shows the data regarding the aspherical surface of the imaging lens which concerns on Example 1 of this invention. It is a figure which shows the data regarding the aspherical surface of the imaging lens which concerns on Example 2 of this invention. It is a figure which shows the data regarding the aspherical surface of the imaging lens which concerns on Example 3 of this invention. It is a figure which shows the data regarding the aspherical surface of the imaging lens which concerns on Example 4 of this invention. It is a figure which shows the data regarding the aspherical surface of the imaging lens which concerns on Example 5 of this invention. It is a figure which shows the data regarding the aspherical surface of the imaging lens which concerns on Example 6 of this invention. It is a figure which shows the data regarding the aspherical surface of the imaging lens which concerns on Example 7 of this invention. It is a figure which shows the data regarding the aspherical surface of the imaging lens which concerns on Example 8 of this invention. It is a figure which shows the data regarding the aspherical surface of the imaging lens which concerns on Example 9 of this invention. It is a figure which shows the data regarding the aspherical surface of the imaging lens which concerns on Example 10 of this invention. It is a figure which shows the data regarding the aspherical surface of the imaging lens which concerns on Example 11 of this invention. It is a figure which shows the data regarding the aspherical surface of the imaging lens which concerns on Example 12 of this invention. It is a figure which shows the data regarding the aspherical surface of the imaging lens which concerns on Example 13 of this invention. It is a figure which shows the data regarding the aspherical surface of the imaging lens which concerns on Example 14 of this invention. It is a figure which shows the data regarding the aspherical surface of the imaging lens which concerns on Example 15 of this invention. It is the figure which showed the value regarding a conditional expression collectively about each Example. It is the figure which showed the value regarding a conditional expression collectively about each Example. 4A and 4B are aberration diagrams illustrating various aberrations of the imaging lens according to Example 1 of the present invention, in which (A) shows spherical aberration, (B) shows astigmatism (field curvature), and (C) shows distortion. FIG. 6 is an aberration diagram showing various aberrations of the imaging lens according to Example 2 of the present invention, in which (A) shows spherical aberration, (B) shows astigmatism (field curvature), and (C) shows distortion. FIG. 6 is an aberration diagram showing various aberrations of the imaging lens according to Example 3 of the present invention, in which (A) shows spherical aberration, (B) shows astigmatism (field curvature), and (C) shows distortion. It is an aberration diagram which shows the various aberrations of the imaging lens which concerns on Example 4 of this invention, (A) shows spherical aberration, (B) shows astigmatism (field curvature), (C) shows distortion aberration. It is an aberration diagram which shows the various aberrations of the imaging lens which concerns on Example 5 of this invention, (A) shows spherical aberration, (B) shows astigmatism (field curvature), (C) shows distortion aberration. It is an aberration diagram which shows the various aberrations of the imaging lens which concerns on Example 6 of this invention, (A) shows spherical aberration, (B) shows astigmatism (field curvature), (C) shows distortion aberration. It is an aberration diagram which shows the various aberrations of the imaging lens which concerns on Example 7 of this invention, (A) shows spherical aberration, (B) shows astigmatism (field curvature), (C) shows distortion aberration. It is an aberration diagram which shows the various aberrations of the imaging lens which concerns on Example 8 of this invention, (A) shows spherical aberration, (B) shows astigmatism (field curvature), (C) shows distortion aberration. It is an aberration diagram which shows the various aberrations of the imaging lens which concerns on Example 9 of this invention, (A) shows spherical aberration, (B) shows astigmatism (field curvature), (C) shows distortion aberration. It is an aberration diagram which shows the various aberrations of the imaging lens which concerns on Example 10 of this invention, (A) shows spherical aberration, (B) shows astigmatism (field curvature), (C) shows distortion aberration. It is an aberration diagram which shows the various aberrations of the imaging lens which concerns on Example 11 of this invention, (A) shows spherical aberration, (B) shows astigmatism (field curvature), (C) shows distortion aberration. It is an aberration diagram which shows the various aberrations of the imaging lens which concerns on Example 12 of this invention, (A) shows spherical aberration, (B) shows astigmatism (field curvature), (C) shows distortion aberration. It is an aberration diagram which shows the various aberrations of the imaging lens which concerns on Example 13 of this invention, (A) shows spherical aberration, (B) shows astigmatism (field curvature), (C) shows distortion aberration. It is an aberration diagram which shows the various aberrations of the imaging lens which concerns on Example 14 of this invention, (A) shows spherical aberration, (B) shows astigmatism (field curvature), (C) shows distortion aberration. It is an aberration diagram which shows the various aberrations of the imaging lens which concerns on Example 15 of this invention, (A) shows spherical aberration, (B) shows astigmatism (field curvature), (C) shows distortion aberration.

Explanation of symbols

  L1 ... first lens, L2 ... second lens, L3 ... third lens, L4 ... fourth lens, L5 ... fifth lens, St ... aperture stop, Ri ... radius of curvature of the i-th lens surface from the object side, Di: a distance between the i-th lens surface and the (i + 1) -th lens surface from the object side, Z1: an optical axis, 100: an image sensor (image plane).

Claims (12)

From the object side,
A first lens having positive power in which the object side surface is convex;
A second lens having a concave surface near the optical axis and a negative power near the optical axis;
A third lens having a convex surface in the vicinity of the optical axis and having a positive power in the vicinity of the optical axis;
An aspherical fourth lens in which the image side surface is concave in the vicinity of the optical axis and the image side surface is convex in the periphery;
A fifth lens having a positive power in the vicinity of the optical axis,
And the imaging lens of 5 sheets structure characterized by satisfy | filling the following conditional expressions.
ν2 ≦ 30 (1)
40 ≦ ν3 (2)
40 ≦ ν4 (3)
However,
ν2: Abbe number of the second lens ν3: Abbe number of the third lens ν4: Abbe number of the fourth lens. From the object side,
A first lens having positive power in which the object side surface is convex;
A second lens having a concave surface near the optical axis and a negative power near the optical axis;
A third lens having a convex surface in the vicinity of the optical axis and having a positive power in the vicinity of the optical axis;
An aspherical fourth lens in which the image side surface is concave in the vicinity of the optical axis and the image side surface is convex in the periphery;
A fifth lens having a positive power in the vicinity of the optical axis,
And the imaging lens of 5 sheets structure characterized by satisfy | filling the following conditional expressions.
ν2 ≦ 30 (1)
40 ≦ ν3 (2)
0.2 ≦ f3 / f ≦ 0.4 (4)
An imaging lens having a five-lens configuration.
However,
ν2: Abbe number of the second lens ν3: Abbe number of the third lens f: Overall focal length f3: Paraxial focal length of the third lens. The imaging lens having a five-lens structure according to claim 2, further satisfying the following conditional expression.
1.0 ≦ DL / f ≦ 1.3 (5)
However,
DL: Distance on the optical axis from the object side vertex of the first lens to the image side vertex of the fifth lens. The imaging lens having a five-element structure according to any one of claims 1 to 3, further satisfying the following conditional expression.
40 ≦ ν5 (6)
However,
ν5: The Abbe number of the fifth lens. The third lens, the fourth lens, and the fifth lens are each made of a plastic material, and each has at least one aspheric surface,
The fourth lens has negative power near the optical axis;
The imaging lens having a five-element structure according to any one of claims 1 to 4, wherein the following conditional expression is satisfied.
−1.0 ≦ f4 / f ≦ 0 (7)
However,
f: Overall focal length f4: Paraxial focal length of the fourth lens. Further, the following conditional expression is satisfied: The imaging lens having a five-element structure according to any one of claims 1 to 5.
0.8 ≦ f5 / f ≦ 4.0 (8)
However,
f5: The paraxial focal length of the fifth lens. Furthermore, the following conditional expressions are satisfied. The imaging lens having a five-lens configuration according to any one of claims 1 to 6.
0.7 ≦ | R1 / R2 | ≦ 8.0 (9)
0.75 ≦ f1 / f ≦ 5.0 (10)
1.4 ≦ TL / f ≦ 1.80 (11)
However,
R1: Paraxial radius of curvature of the object side surface of the first lens R2: Paraxial radius of curvature of the image side surface of the first lens f1: Paraxial focal length of the first lens TL: Full length (from the most object side surface) Distance on the optical axis to the image plane (Air conversion length from the fifth lens to the image plane)
And The second lens has a negative meniscus shape with a concave surface facing the image side in the vicinity of the optical axis;
Furthermore, the following conditional expressions are satisfied. The imaging lens having a five-lens configuration according to any one of claims 1 to 6.
0.4 ≦ | R9 / f | ≦ 6.0 (12)
However,
R9: The paraxial radius of curvature of the object side surface of the fifth lens. Furthermore, the following conditional expressions are satisfied. The imaging lens having a five-lens configuration according to any one of claims 1 to 6.
0.5 ≦ | f2 / f1 | ≦ 10.0 (13)
0.8 ≦ | f3 * (1 / f4 + 1 / f5) | ≦ 1.5 (14)
However,
fi: The paraxial focal length of the i-th lens. The imaging lens according to any one of claims 1 to 6, wherein the first lens is a polished glass having spherical surfaces on both sides. Furthermore, the following conditional expressions are satisfied. The imaging lens having a five-lens configuration according to any one of claims 1 to 6.
70 ≦ ν1 (15)
However,
ν1: The Abbe number of the first lens. The imaging lens according to any one of claims 1 to 11,
An imaging device comprising: an imaging element that outputs an imaging signal corresponding to an optical image formed by the imaging lens.

Images