JP5318297B2 - Imaging lens for solid-state imaging device - Google Patents

Description

  The present invention relates to an imaging lens for a solid-state imaging device used in a small imaging device used in a small and thin electronic device such as a portable terminal or PDA (Personal Digital Assistance).

  In recent years, with the expansion of the market for portable terminals equipped with an imaging device, a small solid-state imaging device having a high pixel count has been mounted on the imaging device.

  Corresponding to such downsizing and increase in the number of pixels of the image pickup device, the image pickup lens is also required to have higher performance in terms of resolution and image quality.

  In order to meet the demand for higher performance, imaging lenses made up of multiple lenses have become commonplace, with a five-lens configuration that allows higher performance compared to a two- to four-lens configuration. An imaging lens has also been proposed.

  For example, in Patent Document 1, in order from the object side, a first lens having a positive refractive power having a convex surface on the object side and a meniscus-shaped first lens having a negative refractive power with a concave surface facing the image surface side. Two lenses, a meniscus third lens having a positive refractive power with the convex surface facing the image surface side, and a negative refractive power having a concave surface on the optical axis and a concave surface on the optical axis. An imaging lens has been disclosed which has a configuration of a fourth lens having a fifth lens having both positive and negative refractive powers and both surfaces being aspherical and aiming for higher performance.

  Further, in Patent Document 2, in order from the object side, an aperture stop, a first lens having a positive refractive power, a second lens having a negative refractive power joined to the first lens, and a concave surface on the object side. A meniscus third lens having a concave surface facing the object side, a meniscus fourth lens having a concave surface facing the object side, and a meniscus fifth lens having a convex surface facing the object side and at least one surface being aspheric. An image pickup lens aiming at high performance by disposing is disclosed.

JP 2007-264180 A JP 2007-298572 A

  However, the imaging lenses described in Patent Document 1 and Patent Document 2 aim for high performance by using a five-lens configuration. From the viewpoint of optical length, however, the imaging lenses can be made compact and thin. Was insufficient.

  In view of the above-described circumstances, an object of the present invention is to obtain an imaging lens for a solid-state imaging device that is small in size, high in performance, and can cope with cost reduction.

  The said subject is solved by making the imaging lens for solid-state image sensors into the following structures.

The imaging lens for a solid-state imaging device according to claim 1, in order from the object side, a first lens having a positive refractive power with a convex surface facing the object side on the optical axis, and a concave surface facing the image side on the optical axis. A second lens having negative refractive power, a third lens having negative refractive power and having a convex surface facing the object side on the optical axis, and a convex surface facing the image side on the optical axis A meniscus fourth lens having a positive refractive power and a meniscus fifth lens having a negative refractive power with the concave surface facing the image side on the optical axis, with respect to the radius of curvature of the fourth lens, The following conditional expression (13) is satisfied.
1.4 <r7 / r8 <3.0 (13)
However,
r7: radius of curvature of the fourth lens object side surface r8: radius of curvature of the fourth lens image side surface

The imaging lens for a solid-state imaging device according to claim 2 satisfies the following conditional expressions (1) and (2) with respect to an Abbe number of a material used for the first lens and the second lens. Be a lens.
45 <ν1 <90 (1)
22 <ν2 <35 (2)
However,
ν1: Abbe number of the first lens at the d-line ν2: Abbe number of the second lens at the d-line

Conditional expression (1) defines the Abbe number of the first lens. If that falls below the lower limit of condition (1), the difference between the dispersion value and the second lens is reduced, the correction of chromatic aberration becomes insufficient. On the other hand, when the upper limit is exceeded, the balance between axial chromatic aberration and lateral chromatic aberration is deteriorated, resulting in performance deterioration at the periphery of the screen.

Conditional expression (2) defines the Abbe number of the second lens. If that falls below the lower limit of condition (2), the balance of the axial chromatic aberration and lateral chromatic aberration becomes worse, resulting in performance degradation at the periphery of the screen. On the other hand, when the upper limit is exceeded, the difference in dispersion value from the first lens is small, and correction of chromatic aberration is insufficient.

  4. The imaging lens for a solid-state imaging device according to claim 3, wherein at least one of the first lens, the second lens, the third lens, the fourth lens, and the fifth lens has an aspheric shape, and is made of a resin material. This is a so-called plastic lens.

  By using a resin material that is inexpensive and has high production efficiency, and the first lens, the second lens, the third lens, the fourth lens, and the fifth lens are manufactured, the cost can be reduced.

  According to a fourth aspect of the present invention, there is provided a photographing lens for a solid-state imaging device, wherein the aperture stop is disposed on the object side of the first lens.

  By providing the aperture stop closer to the object side than the first lens, the CRA (Chief Ray Angle) is easy to make small, and it becomes easy to secure the light quantity in the peripheral part of the image plane where the light quantity decreases.

  The imaging lens for a solid-state imaging device according to claim 5 is configured such that the object side surface and the image side surface of the fifth lens have an aspherical shape having at least one inflection point from the center to the periphery.

  It is possible to secure off-axis performance and CRA by making the object side surface and the image side surface of the fifth lens have an aspherical shape having at least one inflection point from the center to the periphery of the lens. become.

The imaging lens for a solid-state imaging device according to claim 6, wherein the first lens and the second lens satisfy the following conditional expressions (3) and (4).
0.50 <f1 / f <1.00 (3)
−1.50 <f2 / f <−0.65 (4)
However,
f: Composite focal length of the entire imaging lens f1: Focal length of the first lens f2: Focal length of the second lens

Conditional expression (3) defines the focal length range of the first lens with respect to the focal length of the entire system. If that falls below the lower limit of condition (3), the focal length of the first lens becomes short, it becomes difficult to correct spherical aberration and coma. On the other hand, when the upper limit is exceeded, the optical length becomes too long, which is contrary to the thinning of the imaging lens that is the object of this patent.

Conditional expression (4) defines the focal length range of the second lens with respect to the focal length of the entire system. If that falls below the lower limit of condition (4), will be the power of the second lens is insufficient, correction of chromatic aberration becomes insufficient. On the other hand, if the upper limit is exceeded, the focal length of the second lens becomes too short, making it difficult to correct spherical aberration and coma aberration, and the error sensitivity at the time of manufacture becomes severe.

8. The imaging lens for a solid-state imaging device according to claim 7, wherein the fourth lens and the fifth lens satisfy the following conditional expressions (5) and (6).
0.9 <f4 / f <1.50 (5)
−1.70 <f5 / f <−0.85 (6)
However,
f: Composite focal length of the entire imaging lens f4: Focal length of the fourth lens f5: Focal length of the fifth lens

Conditional expression (5) defines the focal length range of the fourth lens with respect to the focal length of the entire system. If that falls below the lower limit of condition (5), the focal length of the fourth lens becomes short, correction becomes difficult of astigmatism and coma aberration also becomes severe error sensitivity at the time of manufacture. On the other hand, when the upper limit is exceeded, lateral chromatic aberration and astigmatism are insufficiently corrected, and desired performance cannot be obtained.

Conditional expression (6) defines the focal length range of the fifth lens with respect to the focal length of the entire system. If that falls below the lower limit of condition (6), will be the power of the fifth lens is insufficient, it becomes difficult to shorten the optical length. On the other hand, when the upper limit is exceeded, it becomes difficult to make the CRA at a low angle, or error sensitivity at the time of production at a low image height becomes severe.

In the imaging lens for a solid-state imaging device of the present invention, the first lens and the third lens may satisfy the following conditional expression (7).
−0.15 <f1 / f3 <0.37 (7)
However,
f1: Focal length of the first lens f3: Focal length of the third lens

Conditional expression (7) defines the ratio between the focal length of the first lens and the focal length of the third lens. If that falls below the lower limit of condition (7), the focal length of the third lens becomes too short negative, so that it becomes difficult to correct aberrations. On the contrary, when the upper limit is exceeded, the focal length of the third lens becomes positive and too short, the balance of astigmatism and coma becomes worse, and the error sensitivity at the time of manufacture becomes severe.

The imaging lens for a solid-state imaging device according to claim 8, wherein the second lens, the third lens, and the fourth lens satisfy the following conditional expression (8).
0.0 <f2 · 3 · 4 (8)
However,
f2, 3 and 4: Composite focal length of the second lens, the third lens and the fourth lens

Conditional expression (8) defines the combined focal length of the second lens, the third lens, and the fourth lens. If that falls below the lower limit of condition (8), too strong negative power of the second lens, or error sensitivity at the time of production becomes too severe, too weak positive power of the fourth lens, the non Correction of point aberration and distortion becomes difficult.

The imaging lens for a solid-state imaging device according to claim 9, wherein the first lens, the second lens, the third lens, the fourth lens, and the fifth lens have the following conditional expressions (9), (10), It is an imaging lens characterized by satisfying (11).
f1 <| f2 | <| f3 | (9)
f1 <f4 <| f3 | (10)
f1 <| f5 | <| f3 | (11)
However,
f1: focal length of the first lens f2: focal length of the second lens f3: focal length of the third lens f4: focal length of the fourth lens f5: focal length of the fifth lens

The conditional expression (9) defines the magnitude relationship between the powers of the first lens, the second lens, and the third lens, that is, the focal length. If that falls below the lower limit of condition (9), the negative power becomes too strong in the second lens, or is an optical length is long, the error sensitivity at the time of production becomes severe. On the contrary, when the upper limit is exceeded, the power of the third lens becomes too strong, and it becomes difficult to ensure off-axis performance.

The conditional expression (10) defines the magnitude relationship between the powers of the first lens, the third lens, and the fourth lens, that is, the focal length. If that falls below the lower limit of condition (10), only the power of the fourth lens becomes too strong, or it optical length is long, the correction of astigmatism and distortion aberration becomes difficult. On the contrary, when the upper limit is exceeded, the power of the third lens becomes too strong, and it becomes difficult to ensure off-axis performance.

Conditional expression (11) defines the magnitude relationship between the powers of the first lens, the third lens, and the fifth lens, that is, the focal length. If that falls below the lower limit of condition (11), too strong negative power of the fifth lens, it becomes difficult to correct coma and astigmatism. On the contrary, when the upper limit is exceeded, the power of the third lens becomes too strong, and it becomes difficult to ensure off-axis performance.

  Here, although the third lens has the weakest power, the aspherical surfaces on the front and rear surfaces work effectively to alleviate the aberration generated in the second lens. In particular, the fourth-order aspheric coefficient plays an effective role and plays an important role in obtaining the performance unique to the five-element configuration.

The imaging lens for a solid-state imaging device according to claim 10 is an imaging lens that satisfies the following conditional expression (12) with respect to a radius of curvature of the first lens.
−0.40 <r1 / r2 <0.10 (12)
However,
r1: radius of curvature of the first lens object side surface r2: radius of curvature of the first lens image side surface

The conditional expression (12) defines the lens shape of the first lens. If that falls below the lower limit of condition (12), it becomes disadvantageous to shortening the optical length, also becomes severe error sensitivity at the time of manufacture of the first lens. Conversely, when the upper limit is exceeded, it becomes difficult to maintain the aberration balance, and desired performance cannot be obtained.

Conditional expression (13) defines the lens shape of the fourth lens. If that falls below the lower limit of the condition (13) becomes too weak power of the fourth lens, the correction of aberrations cause performance degradation becomes difficult. On the other hand, when the upper limit is exceeded, the power of the fourth lens becomes too strong or the lens has a low meniscus degree. In this case, it becomes difficult to maintain the aberration balance, and desired performance cannot be obtained.

The imaging lens for a solid-state imaging device according to claim 11 is an imaging lens that satisfies the following conditional expression (14) with respect to the optical length and focal length of the entire imaging lens system.
1.05 <L / f <1.30 (14)
However,
L: Distance from the front surface of the first lens to the image plane f: Composite focal length of the entire imaging lens system

The conditional expression (14) is defined by the relationship between the optical length of the entire imaging lens system and the focal length. If that falls below the lower limit of the condition (14), the optical length is too short, the correction of aberrations becomes difficult, the error sensitivity at the time of manufacture may become too severe. Conversely, when the upper limit is exceeded, the optical length becomes too long, making it difficult to reduce the thickness of the imaging lens.

The imaging lens for a solid-state imaging device according to claim 12, wherein the effective diameter of the first lens satisfies the following conditional expression (15):
0.30 <CA1 / f <0.50 (15)
However,
CA1: Aperture stop diameter f: Total focal length of the entire imaging lens system

Conditional expression (15) defines the brightness and Fno of the imaging lens. If that falls below the lower limit of the condition (15), Fno becomes too large, often do not meet the required brightness. On the other hand, when the upper limit is exceeded, Fno becomes too small, or the distance between the stop (Fno light flux regulating plate) and the first lens front becomes too long, and in any case, desired optical performance cannot be obtained.

  According to the present invention, an image sensor with high resolution can be obtained by providing a five-lens configuration including the first lens to the fifth lens and giving the third lens a role that is not in the conventional four-lens configuration. A high-performance lens in which various aberrations are well corrected so as to cope with an increase in size and a high-definition pixel can be provided at a low cost with a compact configuration.

It is sectional drawing of the imaging lens which shows Example 1 of this invention. FIG. 4 is a diagram showing various aberrations. It is sectional drawing of the imaging lens which shows Example 2 of this invention. FIG. 4 is a diagram showing various aberrations. It is sectional drawing of the imaging lens which shows Example 3 of this invention. FIG. 4 is a diagram showing various aberrations. It is sectional drawing of the imaging lens which shows Example 4 of this invention. FIG. 4 is a diagram showing various aberrations. It is sectional drawing of the imaging lens which shows Example 5 of this invention. FIG. 4 is a diagram showing various aberrations. It is sectional drawing of the imaging lens which shows Example 6 of this invention. FIG. 4 is a diagram showing various aberrations.

  Examples of the present invention will be described below with specific numerical values. In the first to sixth embodiments, the aperture stop S, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, and the fifth lens L5 from the object side, the parallel plane glass IR, and the image plane It consists of an ordered array.

  In the first to sixth embodiments, at least one of the second lens L2, the third lens L3, the fourth lens L4, and the fifth lens L5 has an aspherical shape and is made of a resin material. In addition to being a plastic lens, the aperture stop S is disposed on the object side of the first lens L1. In the following Examples 1, 2, 3, 4, and 6, the third lens has a positive refractive power, and in Example 5, the third lens has a negative refractive power. 1, 2, 3, 4, and 6 are shown as reference examples.

The object side surface and the image side surface of the fifth lens L5 have an aspherical shape having at least one inflection point from the center of the lens to the peripheral portion. The following aspherical expression is used, where the vertex is the origin, the Z axis is taken in the direction of the optical axis, and the height in the direction perpendicular to the optical axis is h.

However, the symbols used in the above aspheric type and each example are as follows.
Ai: i-order aspherical coefficient r: radius of curvature K: conical constant f: focal length F: F-number d: axial distance nd: refractive index of lens material with respect to d-line ν: Abbe of lens material In the following (including lens data in the table), a power of 10 (for example, 4.5 × 10 ⁻⁰⁴ ) is expressed using E (for example, 4.5E-04), and the surface number of the lens data Were given in order with the object side of the first lens L1 as one surface.

  Numerical data of the imaging lens of Example 1 is shown in Table 1. 1 is a sectional view of the imaging lens, and FIG. 2 is a diagram showing various aberrations.

  Table 2 shows numerical data of the imaging lens of Example 2. 3 is a sectional view of the imaging lens, and FIG. 4 is a diagram showing various aberrations.

  Table 3 shows numerical data of the imaging lens of Example 3. 5 is a sectional view of the imaging lens, and FIG. 6 is a diagram showing various aberrations.

  Table 4 shows numerical data of the imaging lens of Example 4. FIG. 7 is a sectional view of the imaging lens, and FIG. 8 is a diagram showing various aberrations.

  Numerical data of the imaging lens of Example 5 is shown in Table 5. FIG. 9 is a sectional view of the imaging lens, and FIG. 10 is a diagram showing various aberrations.

  Table 6 shows numerical data of the imaging lens of Example 6. FIG. 11 is a sectional view of the imaging lens, and FIG. 12 is a diagram showing various aberrations.

  With respect to Example 1 to Example 6, values corresponding to the following conditional expressions (1) to (17) are shown in Table 7 below.

Conditional expression (1) relates to the Abbe number of the material used for the first lens L1, and conditional expression (2) relates to the second lens L2.
45 <ν1 <90 Conditional Expression (1)
22 <ν2 <35 Conditional expression (2)
However,
ν1: Abbe number of the first lens at the d-line ν2: Abbe number of the second lens at the d-line

Conditional expression (3) defines the focal length range of the first lens L1 with respect to the focal length of the entire system, and conditional expression (4) defines the focal length range of the second lens L2 as the focal length of the entire system. It is specified for distance.
0.5 <f1 / f <1.00 Conditional Expression (3)
−1.50 <f2 / f <−0.65 Conditional Expression (4)
However,
f: Composite focal length of the entire imaging lens f1: Focal length of the first lens f2: Focal length of the second lens

Conditional expression (5) defines the focal length range of the fourth lens L4 with respect to the focal length of the entire system, and conditional expression (6) defines the focal length range of the fifth lens L5 as the focal length of the entire system. It is specified for distance.
0.9 <f4 / f <1.50 Conditional Expression (5)
−1.70 <f5 / f <−0.85 Conditional Expression (6)
However,
f: Composite focal length of the entire imaging lens f4: Focal length of the fourth lens f5: Focal length of the fifth lens

Conditional expression (7) defines the ratio of the focal length of the first lens L1 and the focal length of the third lens L3.
−0.15 <f1 / f3 <0.37 Conditional Expression (7)
However,
f1: Focal length of the first lens f3: Focal length of the third lens

Conditional expression (8) defines the combined focal length of the second lens L2, the third lens L3, and the fourth lens L4.
0.0 <f2 · 3 · 4 Conditional Expression (8)

Conditional expression (9) defines the power of each of the first lens L1, the second lens L2, and the third lens L3, that is, the relationship between the focal lengths. The conditional expression (10) is the first lens. The respective powers of L1, the third lens L3, and the fourth lens L4, that is, the relationship between the focal lengths, are defined, and the conditional expression (11) indicates that the first lens L1, the third lens L3, and the fifth lens L5. It defines the magnitude relationship between each power, that is, the focal length.
However,
f1 <| f2 | <| f3 | Conditional expression (9)
f1 <f4 <| f3 | Conditional expression (10)
f1 <| f5 | <| f3 | Conditional expression (11)

Conditional expression (12) defines the lens shape of the first lens L1.
−0.40 <r1 / r2 <0.10 Conditional Expression (12)
However,
r1: radius of curvature of the first lens object side surface r2: radius of curvature of the first lens image side surface

Conditional expression (13) defines the lens shape of the fourth lens L4.
1.4 <r7 / r8 <3.0 Conditional Expression (13)
However,
r7: radius of curvature of the fourth lens object side surface r8: radius of curvature of the fourth lens image side surface

Conditional expression (14) is defined by the relationship between the optical length of the entire imaging lens system and the focal length.
1.05 <L / f <1.30 Conditional Expression (14)
However,
L: Distance from the front surface of the first lens to the image plane f: Composite focal length of the entire imaging lens system

Conditional expression (15) defines the brightness and Fno of the imaging lens.
0.30 <CA1 / f <0.50 Conditional Expression (15)
However,
CA1: Aperture stop diameter f: Composite focal length of the entire imaging lens system

Conditional expression (16) defines the focal length range of the second lens L2 with respect to the focal length of the entire system, and defines a case where conditions more severe than conditional expression (4) are satisfied.
−1.30 <f2 / f <−0.75 Conditional Expression (16)
However,
f: Composite focal length of the entire imaging lens system f2: Focal length of the second lens

Conditional expression (17) defines a case where conditions more severe than the conditional expression (13) that defines the lens shape of the fourth lens L4 are satisfied.
1.45 <r7 / r8 <2.0 Conditional Expression (17)
However,
r7: radius of curvature of the fourth lens object side surface r8: radius of curvature of the fourth lens image side surface

As shown in Table 7, Examples 1 to 6 of the present invention satisfy all the conditions of the conditional expressions (1) to (17), and the Abbe numbers of the first lens L1 and the second lens L2 are set as follows. Regarding the conditional expressions (1) and (2) to be specified, if the lower limit of the conditional expressions (1) and (2) is exceeded, the difference in the dispersion value with the second lens L2 becomes small, and the correction of chromatic aberration becomes insufficient. On the contrary, when the upper limit is exceeded, the balance between the axial chromatic aberration and the lateral chromatic aberration is deteriorated and the performance is deteriorated at the peripheral portion of the screen. However, if the conditional expressions (1) and (2) are satisfied, The balance of lateral chromatic aberration is also good, performance deterioration at the periphery of the screen can be prevented, and chromatic aberration correction is also good.

The conditional expression for specifying the first lens L1 and second lens L2 each focal length range for the focal length of the entire system (3), relates to (4), if that falls below the lower limit of condition (3) Since the focal length of the first lens L1 becomes too short, it becomes difficult to correct spherical aberration and coma. Exceeding the upper limit on the contrary, with thinning of the image pickup lens optical length is too long it becomes difficult, if that falls below the lower limit of condition (4), the power of the second lens L2 becomes insufficient If the correction of chromatic aberration becomes insufficient and the upper limit is exceeded, the focal length of the second lens L2 becomes too short, making it difficult to correct spherical aberration and coma, and the error sensitivity at the time of manufacture is also low. Although it becomes severe, satisfying conditional expressions (3) and (4) makes it possible to correct spherical aberration and coma aberration well, and also the power of the second lens L2 is sufficient, so that correction of chromatic aberration is good. Also, the correction of spherical aberration and coma aberration is improved.

Condition the focal length range defined with respect to the focal length of the entire system relates (5) of the fourth lens L4, if that falls below the lower limit of condition (5), the focal length of the fourth lens L4 becomes shorter However, correction of astigmatism and coma becomes difficult, and error sensitivity at the time of manufacture becomes severe. Conversely, if the upper limit is exceeded, lateral chromatic aberration and astigmatism are insufficiently corrected, and the desired performance is obtained. However, by satisfying the condition of the conditional expression (5), astigmatism and coma can be easily corrected, and lateral chromatic aberration and astigmatism can be easily corrected, and desired performance can be obtained.

Conditional expression that defines the focal length range of the fifth lens L5 with respect to the focal length of the entire system relates (6), if that falls below the lower limit of condition (6) is that the power of the fifth lens L5 is insufficient It becomes difficult to shorten the optical length, and conversely, if the upper limit is exceeded, it becomes difficult to make the CRA at a low angle or the error sensitivity at the time of production at a low image height becomes severe. By satisfying the condition of Expression (6), it becomes possible to eliminate the power shortage of the fifth lens L5 and shorten the optical length, and it is easy to set the CRA at a low angle, and the low image height. The error sensitivity at the time of manufacturing is also improved.

Conditional expression that defines the focal length and the ratio of the focal length of the third lens L3 of the first lens L1 relates (7), if that falls below the lower limit of condition (7) is the focal length of the third lens L3 is a negative If the upper limit of the third lens L3 exceeds the upper limit, the focal length of the third lens L3 becomes too short and the balance of astigmatism and coma becomes worse, resulting in manufacturing errors. Although the sensitivity becomes severe, aberrations can be corrected easily by satisfying the condition of the conditional expression (7), and the focal length of the third lens L3 is not excessively shortened. The balance is also good.

The second lens L2, the conditional expression for defining the composite focal length of the third lens L3 and fourth lens L4 relates (8), if that falls below the lower limit of condition (8), the negative power of the second lens L2 Becomes too strong and the error sensitivity at the time of manufacture becomes too severe, or the positive power of the fourth lens L4 becomes too weak and it becomes difficult to correct astigmatism and distortion, but the condition of conditional expression (8) By satisfying the above, astigmatism and distortion can be easily corrected.

The first lens L1, each power of the second lens L2, and third lens L3 that is, the conditional expression for defining the magnitude relation of the focal length relates to (9), if that falls below the lower limit of condition (9), If the negative power of the second lens L2 becomes too strong, the optical length becomes long, or the error sensitivity at the time of manufacture becomes severe. On the contrary, if the upper limit is exceeded, the power of the third lens L3 becomes too strong and off-axis. Although it becomes difficult to ensure performance, by satisfying the condition of conditional expression (9), the optical length can be set short and off-axis performance can be easily ensured.

The first lens L1, each power of the third lens L3, and the fourth lens L4 that is, relates to conditional expression for specifying the size relationship of the focal length (10), if that falls below the lower limit of condition (10), If the power L4 of the fourth lens becomes too strong and the optical length becomes long, or correction of astigmatism and distortion becomes difficult, and if the upper limit is exceeded, the power L3 of the third lens becomes too strong, Although it is difficult to ensure off-axis performance, satisfying the condition of conditional expression (10) facilitates correction of astigmatism and distortion, and also ensures off-axis performance.

The first lens L1, each power of the third lens L3, and the fifth lens L5 that is, relates to conditional expression for specifying the size relationship of the focal length (11), if that falls below the lower limit of condition (11), When the negative power of the fifth lens L5 becomes too strong and it becomes difficult to correct coma and astigmatism. On the contrary, when the upper limit is exceeded, the power of the third lens L3 becomes too strong to ensure off-axis performance. However, when the condition of the conditional expression (11) is satisfied, correction of coma and astigmatism can be facilitated and off-axis performance can be easily secured.

It relates conditional expressions that define the lens shape of the first lens L1 (12), in the case that falls below the lower limit of condition (12), it becomes disadvantageous to shortening the optical length, the time of production of the first lens L1 The error sensitivity also becomes severe, and conversely, if the upper limit is exceeded, it becomes difficult to maintain the aberration balance and the desired performance cannot be obtained. However, the optical length can be shortened by satisfying the condition (12). In addition, the aberration balance can be kept good and desired performance can be obtained.

Further, conditional expression for specifying the shape of a lens of the fourth lens L4 relates (13), if that falls below the lower limit of the condition (13), the power is too weak in the fourth lens L4, difficult to correct various aberrations However, if the upper limit is exceeded, the power of the fourth lens L4 becomes too strong, or the lens has a low meniscus degree. Although the performance cannot be obtained, by satisfying the condition of the conditional expression (13), it becomes easy to correct various aberrations, and it becomes easy to maintain the aberration balance, and the desired performance can be obtained.

Further, conditional expression for specifying the relationship between the optical length and the focal length of the imaging lens system relates to (14), in the case that falls below the lower limit of the condition (14), only the optical length becomes short, the various aberrations corrected However, when the upper limit is exceeded, the optical length is too long, and it is difficult to reduce the thickness of the imaging lens. However, conditional expression (14) By satisfying the above condition, it becomes easy to correct various aberrations, and it is advantageous for reducing the thickness of the imaging lens without making the optical length too short.

Furthermore, the brightness of the imaging lens, conditional expression for specifying the Fno relates (15), in the case that falls below the lower limit of the condition (15), Fno becomes too large, it often does not satisfy the required brightness On the contrary, when the upper limit is exceeded, Fno becomes too small, or the distance between the stop (Fno light flux regulating plate) and the first lens L1 becomes too large, and in either case, desired optical performance cannot be obtained. By satisfying the condition of the conditional expression (15), desired optical performance can be easily obtained.

Further, the second lens L2, the third lens L3, the fourth lens L4 and the fifth lens L5 is taken at least one surface is aspherical, because a so-called plastic lens fabricated of a resin material, low cost Thus, by using a resin material with good production efficiency and manufacturing at least the second lens L2, the third lens L3, the fourth lens L4, and the fifth lens L5, the cost can be reduced.

  Further, by arranging the aperture stop S on the object side of the first lens L1, the CRA (Chief Ray Angle) can be easily reduced, and the light quantity can be secured in the peripheral portion of the image plane where the light quantity decreases.

  Further, the object side surface and the image side surface of the fifth lens L5 have an aspherical shape having at least one inflection point from the center to the periphery of the lens, thereby ensuring off-axis performance and CRA. Is possible.

  As mentioned above, although each Example of this invention was explained in full detail, this invention is not limited to each said Example, A various deformation | transformation implementation is possible within the range of the summary of this invention.

L1 1st lens L2 2nd lens L3 3rd lens L4 4th lens L5 5th lens S Aperture stop

Claims (12)

A photographic lens for a solid-state image sensor, in order from the object
A first lens having positive refractive power with a convex surface facing the object side on the optical axis;
A second lens having negative refractive power with a concave surface facing the image side on the optical axis;
A meniscus third lens having negative refractive power and having a convex surface facing the object side on the optical axis;
A meniscus fourth lens having a positive refractive power with a convex surface facing the image side on the optical axis;
A meniscus fifth lens having negative refractive power with a concave surface facing the image side on the optical axis,
The imaging lens for a solid-state imaging device, wherein the following conditional expression (13) is satisfied with respect to the radius of curvature of the fourth lens.
1.4 <r7 / r8 <3.0 (13)
However,
r7: radius of curvature of the fourth lens object side surface r8: radius of curvature of the fourth lens image side surface The imaging lens for a solid-state imaging device according to claim 1, wherein the following conditional expressions (1) and (2) are satisfied with respect to an Abbe number of a material used for the first lens and the second lens.
45 <ν1 <90 (1)
22 <ν2 <35 (2)
However,
ν1: Abbe number of the first lens at the d-line ν2: Abbe number of the second lens at the d-line   The first lens, the second lens, the third lens, the fourth lens, and the fifth lens are so-called plastic lenses in which at least one surface has an aspherical shape and is made of a resin material. The imaging lens for a solid-state imaging device according to claim 1 or 2.   The imaging lens for a solid-state imaging device according to any one of claims 1 to 3, wherein the aperture stop is disposed on the object side of the first lens.   5. The object side surface and the image side surface of the fifth lens have an aspherical shape having at least one inflection point from the center to the periphery of the lens. An imaging lens for a solid-state imaging device according to Item. The imaging lens for a solid-state imaging device according to any one of claims 1 to 5, wherein the first lens and the second lens satisfy the following conditional expressions (3) and (4). .
0.5 <f1 / f <1.00 (3)
−1.50 <f2 / f <−0.65 (4)
However,
f: Composite focal length of the entire imaging lens f1: Focal length of the first lens f2: Focal length of the second lens The imaging lens for a solid-state imaging device according to any one of claims 1 to 6, wherein the fourth lens and the fifth lens satisfy the following conditional expressions (5) and (6). .
0.9 <f4 / f <1.50 (5)
−1.70 <f5 / f <−0.85 (6)
However,
f: Composite focal length of the entire imaging lens f4: Focal length of the fourth lens f5: Focal length of the fifth lens The imaging for a solid-state imaging device according to any one of claims 1 to 7, wherein the second lens, the third lens, and the fourth lens satisfy the following conditional expression (8). lens.
0.0 <f2 · 3 · 4 (8)
However,
f2, 3 and 4: Composite focal length of the second lens, the third lens and the fourth lens The first lens, the second lens, the third lens, the fourth lens, and the fifth lens satisfy the following conditional expressions (9), (10), and (11): The imaging lens for a solid-state imaging device according to any one of claims 1 to 8.
f1 <| f2 | <| f3 | (9)
f1 <f4 <| f3 | (10)
f1 <| f5 | <| f3 | (11)
However,
f1: focal length of the first lens f2: focal length of the second lens f3: focal length of the third lens f4: focal length of the fourth lens f5: focal length of the fifth lens The imaging lens for a solid-state imaging device according to any one of claims 1 to 9, wherein the following conditional expression (12) is satisfied with respect to a radius of curvature of the first lens.
−0.40 <r1 / r2 <0.10 (12)
However,
r1: radius of curvature of the first lens object side surface r2: radius of curvature of the first lens image side surface 11. The imaging lens according to claim 1, wherein the following conditional expression (14) is satisfied with respect to the optical length and focal length of the entire imaging lens system.
1.05 <L / f <1.30 (14)
However,
L: Distance from the front surface of the first lens to the image plane f: Composite focal length of the entire imaging lens system The imaging lens for a solid-state imaging device according to any one of claims 4 to 11, wherein the following conditional expression (15) is satisfied with respect to a diameter of the aperture stop.
0.30 <CA1 / f <0.50 (15)
However,
CA1: Aperture stop diameter f: Total focal length of the entire imaging lens system

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