KR100788546B1 - Imaging lens - Google Patents

Abstract

The imaging lens 100 of the present invention has a first lens 1 having a positive meniscus with a convex surface facing the object side in order from an object side, and a second lens having a meniscus having negative power ( 2) and a third lens 3 having positive power are arranged, and the second and third lenses 2 and 3 function as correction lenses. Strong power is applied to the first lens 1, and both surfaces of the second and third lenses 2 and 3 are aspherical. When f is the composite focal length of the imaging lens, f1 is the focal length of the first lens, f is the distance from the incident surface on the object side of the first lens 1 to the imaging surface, Σd, and the Abbe number of the second lens is υd2. , The following conditional expression is satisfied.

0.50 <f1 / f <1.5 (1)

0.50 <Σd / f <1.5 (2)

50> υd2 (3)

It is possible to realize a compact and inexpensive imaging lens capable of high quality photography.

Description

Imaging lens {IMAGING LENS}

1 is a block diagram of an imaging lens according to Embodiment 1 to which the first invention of the present application is applied.

2 is a block diagram of an imaging lens according to Embodiment 2 to which the first invention of the present application is applied;

3 is an aberration diagram of an imaging lens according to Embodiment 1 shown in FIG. 1;

4 is aberration diagrams of the imaging lens according to the second embodiment shown in FIG. 2;

5 is a configuration diagram of an imaging lens according to Example 3 and Example 5 to which the first invention of the present application is applied;

6 is a block diagram of an imaging lens according to Embodiment 4 to which the first invention of the present application is applied.

Fig. 7 is aberration diagrams of the imaging lens according to the third embodiment shown in Fig. 5;

8 is aberration diagrams of the imaging lens according to the fourth embodiment shown in FIG. 6;

Fig. 9 is aberration diagrams of the imaging lens according to the fifth embodiment shown in Fig. 5;

10 is a block diagram of an imaging lens according to Embodiment A to which the second invention of the present application is applied;

FIG. 11 is an aberration diagram of the imaging lens according to Example A of FIG. 10; FIG.

12 is a configuration diagram of an imaging lens according to Example B and Example C to which the second invention of the present application is applied.

FIG. 13 is an aberration diagram of the imaging lens according to Example B of FIG. 12; FIG.

14 is an aberration diagram of an imaging lens according to Example C to which the second invention of the present application is applied;

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a compact and lightweight imaging lens used in a vehicle-mounted camera, a surveillance camera, a digital camera, a camera mounted on a mobile phone, etc. using a light receiving element such as a CCD or CMOS.

It is preferable that the imaging lens incorporated in a surveillance camera, a digital camera, or the like using a light receiving element such as a CCD or a CMOS has a substantial reproducibility of a subject. In recent years, the CCD itself and the CCD camera have been miniaturized, and as a result, the demand for miniaturization and compactness is inevitably increased for the imaging lenses to be incorporated therein. In addition, light-receiving elements, such as CCDs, have undergone high pixel resolution of one million units as opposed to the miniaturization of CCDs. The imaging lens used for the camera using this is inevitably required to exhibit high optical performance. Conventionally, aberration correction has been performed using a plurality of lenses in order to exhibit high optical performance.

Further, a light receiving element such as a CCD or a CMOS has a feature that a light beam angle accommodated in each pixel is limited. In the camera in which the optical system that ignores this is assembled, the amount of ambient light decreases, causing shading. Conventionally, to cope with these, a method of providing an electrical correction circuit, a method of disposing a microlens paired with a light receiving element, or expanding a light receiving angle with respect to an element surface has been adopted. Alternatively, the position of the exit pupil was as far as possible from the upper surface.

On the other hand, a space for inserting a low pass filter, an infrared cut filter, or the like is required between the imaging lens and the CCD. Therefore, there is a restriction that the back focus of the imaging lens should be lengthened to some extent.

Here, JP-A 2002-228922 discloses an imaging lens having a high resolution, a small number of lenses, and a compact structure. The imaging lens disclosed herein is composed of three groups of four, and the second lens group and the third lens group are composed of a single lens. In addition, an aspherical surface including an inflection point is employed as the lens surface.

The object of the present invention is to make the maximum exit angle to the element surface of the light receiving element smaller than the angle of view in order to prevent shading, and also to cope with 1 million units of high pixelation. The present invention proposes a lightweight and compact imaging lens capable of performing aberration correction.

In addition, an object of the present invention is to adopt an aspherical surface that does not include an inflection point on the lens surface, aberration correction can be performed to cope with million pixels of high pixels, which is advantageous for production, lightweight and compact with a small number of components It is to propose an imaging lens.

In order to achieve the above object, the imaging lens according to the first invention of the present application is composed of three groups of three elements, and in order from the object side, the convex surface is a positive meniscus that is positive toward the object side. A first lens, a second lens which is a meniscus having a negative power subsequent thereto, and a third lens having a positive or negative power; Is designed to function as a correction lens. In addition, a stronger power is applied to the first lens than the second and third lenses. Furthermore, at least both surfaces of the first lens, the second lens, and the third lens are aspherical. In addition, at least one aspherical inflection point is formed on the aspherical surface of the third lens.

Here, with respect to the first lens, at least one lens surface of both lens surfaces may be an aspherical surface.

In addition, the imaging lens of the present invention is a composite focal length of the imaging lens f, the focal length of the first lens f1, the distance from the incident surface on the object side of the first lens to the imaging surface Σd, the second lens When the Abbe number is represented by νd2, it is preferable to satisfy the following conditional expression.

0.5 <f1 / f <1.5 (1)

0.5 <Σd / f <1.5 (2)

50> υd2 (3)

Conditional Expression (1) is a condition for stably maintaining spherical aberration and keeping the entire lens system compact. When the lower limit is lowered, the lens system can be made compact, but it is difficult to correct spherical aberration. If the upper limit is exceeded, on the contrary, spherical aberration is easily corrected, but the entire lens system cannot be compactly constructed. By satisfying this conditional expression, the lens system can be made compact while maintaining the spherical aberration in a good state.

In the present invention, by making the first lens a positive meniscus lens with the convex surface facing the object side, and satisfying such a configuration and conditional expression (1), the overall length of the imaging lens can be further shortened.

Next, conditional expression (2) is also a condition for maintaining the whole lens system more compactly. In particular, with respect to an imaging lens employed in a mobile phone-mounted camera, it is necessary to make the entire lens system small and to shorten the entire length of the lens system. In order to satisfy this requirement, it is preferable to set the optical system so as to satisfy the conditional expression (2). Below the lower limit of the conditional expression (2), the lens system can be made compact, but various aberration correction becomes difficult. It is also undesirable to exceed the upper limit because the lens system becomes large.

Conditional Expression (3) is a condition for stably maintaining axial chromatic aberration and off-axis chromatic aberration by setting the Abbe number of the second lens to 50 or less.

Next, the third lens of the imaging lens according to the present invention is a surface convex toward the image plane side of the image plane side lens surface, and at the same time, one or more on the object side lens surface and the image plane lens surface. It is preferable to form an aspherical inflection point of. By forming the lens surface in this way, coma aberration and astigmatic aberration can be corrected well, and distortion can also be corrected well.

Here, when the imaging surface is a CCD or a CMOS, the light beam angle accommodated in each pixel is restricted, and the light beam angle increases toward the periphery of the screen. In order to alleviate this phenomenon, it is preferable to set the inflexion aspherical surface such that the peripheral portion of the lens surface of the third surface of the third lens is convex toward the image surface side, so that the maximum exit angle of the main light beam is 30 degrees or less. Do. In this way, aspherical correction is performed to prevent shading occurring in the periphery of the screen.

On the other hand, the imaging lens according to the second invention of the present application is composed of three groups of three elements, the first lens being a meniscus having a positive power of the convex surface facing the object side in order from the object side, and the concave surface. The second lens, which is a meniscus having positive or negative power toward the object side, and the third lens having positive power, are arranged.

In addition, among the lens surfaces of the first lens, the second lens, and the third lens, the shape of at least one lens surface is defined as an aspherical shape in which an inflection point does not appear in the effective lens surface region.

As described above, the imaging lens of the present invention is a lens system composed of three groups of three, and since the first lens disposed on the object side is a positive meniscus lens with the convex surface facing the object side, the overall length of the lens system is shortened. can do. In addition, by making the lens surface on the object side of the second lens into a concave surface, the position of the exit pupil can be lengthened, whereby shading can be prevented. Furthermore, since the aspherical surface shape which does not have an inflection point is employ | adopted for a lens surface, deterioration of the resolution resulting from the processing error of a lens, an assembly error, etc. can be suppressed and it is suitable for production.

Herein, the imaging lens of the present invention has a composite focal length of the imaging lens f, a back focus BF, a focal length of the first lens f1, a curvature of the object-side lens surface of the third lens Ra, and an image plane of the third lens. When the curvature of the side lens surface is Rb, it is preferable to satisfy the conditional formulas (A) to (C).

0.5 <f1 / f <1.5 (A)

0.25 <BF / f <1.0 (B)

1.0 <│ Rb / Ra│ (C)

The conditional formula (A) is a condition for stably maintaining spherical aberration and keeping the entire lens system compact. Below the lower limit, the lens system can be made compact, but it is difficult to correct spherical aberration. On the contrary, when the upper limit is exceeded, the correction of spherical aberration becomes easy, but the entire lens system cannot be compactly constructed. By satisfying this conditional expression, the lens system can be made compact while maintaining the spherical aberration in a good state.

In the present invention, the first lens is a positive meniscus lens whose convex surface faces the object side, and by satisfying such a configuration and the conditional expression (A), the overall length of the imaging lens can be further shortened.

Conditional formula (B) is also a condition for maintaining the entire lens system more compactly. In particular, with respect to an imaging lens employed in a mobile phone-mounted camera, it is necessary to make the whole lens system small and to shorten the entire length of the lens system. In order to satisfy this requirement, it is preferable to set the optical system so as to satisfy the conditional expression (B). If the lower limit of the conditional expression (B) is below, the lens system can be made compact, but organic spaces between the lens system and the imaging surface such as the CCD are eliminated, and various aberration correction becomes difficult. On the contrary, when the upper limit is exceeded, the lens system becomes large, which is not preferable.

The conditional formula (C) relates to the exit pupil and the back focus, which is not preferable because the exit pupil and the back focus are shortened when the absolute value of the curvature Ra is greater than or equal to the absolute value of the curvature Rb.

Next, in the case where the imaging surface is a CCD, a CMOS, or the like, in order to ensure substantial aperture efficiency, the light beam angle accommodated in each pixel is restricted. In order to alleviate this phenomenon, it is preferable to lengthen the exit pupil to correct the maximum exit angle of the main beam to 30 degrees or less. In this way, shading occurring in the periphery of the screen can be prevented. Moreover, distortion correction can be performed favorably by setting an aspherical shape suitably.

Hereinafter, with reference to the drawings, each embodiment of the imaging lens composed of three groups of three according to the present invention will be described.

(Example 1)

1 shows an imaging lens according to Embodiment 1 to which the first invention of the present application is applied. The imaging lens 100 of the present example includes a first lens 1 which is a meniscus having a positive power in which the convex surface faces the object side in order from the object side toward the image plane 6 side, Through the diaphragm 4, the concave surface has the 2nd lens 2 which is the meniscus which has the negative power toward the object side, and the 3rd lens 3 which has the positive power, 2nd, 3rd The lens functions as a correction lens. In this example, both lens surfaces of each lens 1, 2, 3 are all aspherical. In addition, in this example, the cover glass 5 is arrange | positioned between the 2nd lens surface R6 of the 3rd lens 3 and the imaging surface 6.

In the third lens 3, an aspherical inflection point is formed at approximately 50% of the aperture on the first lens surface R5, and an aspherical inflection point is approximately 25% of the aperture at the second lens surface R6. Formed. Thereby, the ring-shaped part around the lens of the said 3rd lens 3 forms the convex surface with respect to the imaging surface side, and the maximum exit angle of the chief ray is adjusted to 22 degree | times with respect to 63 degrees of whole viewing angles.

Lens data of the entire optical system of the imaging lens 100 according to the present example is as follows.

F number: 3.5

Focal Length: f = 5.7mm

Overall length: Σd = 7.06mm

Table 1A shows lens data of each lens surface of the imaging lens 100 according to the present example, and Table 1B shows aspherical coefficients for defining the aspherical shape of each lens surface.

TABLE 1A

FNo. 3.5 f = 5.7 mm Σd = 7.06 mm

i R d Nd υd One* 1.73 1.0 1.5247 56.2 2* 4.46 0.15 3 0.00 0.4 4 0.00 0.5 5 * -1.052 0.8 1.585 29.0 6 * -1.50 0.1 7 * 5.75 1.2 1.5247 56.2 8* 15.25 1.336 9 0.00 0.6 1.51633 64.2 10 0.00 0.9779 11

(* Indicates aspherical surface)

TABLE 1B

i k A B C D One 4.740865 × 10 ^-2 5.067696 × 10 ^-3 4.581707 × 10 ^-3 -6.222765 × 10 ^-3 3.890559 × 10 ^-3 2 3.767275 × 10 ^-1 3.143529 × 10 ^-3 -1.939397 × 10 ^-2 9.886734 × 10 ^-2 -9.132532 × 10 ^-2 5 -3.275267 × 10 ^-1 1.603653 × 10 ^-2 6.356242 × 10 ^-2 2.087871 × 10 ^-5 -3.891845 × 10 ^-2 6 -1.071306 -7.703536 × 10 ^-3 1.776501 × 10 ^-2 7 2.361313 -1.916465 × 10 ^-2 6.266366 × 10 ^-4 5.086988 × 10 ^-6 6.795863 × 10 ^-7 8 0.00 -2.213400 × 10 ^-2 7.502348 × 10 ^-4 -3.884072 × 10 ^-5 -1.070020 × 10 ^-5

In Table 1A, i denotes the order of the lens planes counted from the object side, R denotes the curvature of each lens plane, d denotes the distance between the lens planes, Nd denotes the refractive index of each lens, and υd denotes the Abbe number is shown. In addition, the lens surface with an asterisk (*) in i indicates that it is an aspherical surface.

The aspherical shape employed in the lens surface is expressed by the following equation when the axis in the optical axis direction is X, the height in the direction orthogonal to the optical axis is H, the cone coefficient is k, and the aspherical coefficient is A, B, C, D.

In addition, the expression which shows the meaning of each symbol and aspherical shape is the same also in Example 2, 3, 4, 5. In this example, since f1 / f = 0.84, Σd / f = 1.24, and vd2 = 29, the respective conditional expressions (1) to (3) are satisfied.

3 is aberration diagrams illustrating various aberrations of the imaging lens 100 according to the first embodiment. In the figure, SA represents spherical aberration, OSC represents sine condition, AS represents astigmatism, and DIST represents distortion. T of astigmatism AS denotes a tangential plane, and S denotes a sagittal plane. In addition, the aberration diagram shown in the lower part of the figure shows the lateral aberration, in the drawing, DX represents the X aberration in the lateral direction with respect to the X pupil coordinates, and DY represents the Y aberration in the lateral direction with respect to the Y pupil coordinates. The meanings of these symbols are also the same in the aberration diagrams showing the various aberrations of Examples 2, 3, 4, and 5.

(Example 2)

2 is a configuration diagram of an imaging lens according to Embodiment 2 to which the first invention of the present application is applied. In the imaging lens 110 of the present example, the first lens 11 and the aperture stop 14, which are positive meniscus lenses with the convex surface facing the object side, in order from the object side toward the imaging surface 16 side, in order. Through this, the second lens 12, which is the negative meniscus lens whose concave surface faces the object side, and the third lens 13, which are both convex lenses, are arranged. An aspherical inflection point is formed on the first lens surface R5 on the object side of the third lens 13 at approximately 48% of the lens aperture. In addition, the second lens surface R6 on the image surface side is an extension of the convex surface. By forming the lens surface of the third lens 13 in this manner, the maximum exit angle of the chief ray is 23.5 degrees with respect to the total angle of view of 63 degrees. In addition, each lens surface of the 1st lens 11, the 2nd lens 12, and the 3rd lens 13 of this example is also an aspherical surface. Moreover, also in this example, the cover glass 15 is arrange | positioned between the 2nd lens surface R6 of the 3rd lens 13 and the imaging surface 16. As shown in FIG.

Lens data of the entire optical system of the imaging lens 110 according to the present example is as follows.

F number: 3.5

Focal Length: f = 5.7mm

Overall length: Σd = 6.985mm

Table 2A shows lens data of each lens surface of the imaging lens 110 according to the present example, and Table 2B shows aspherical surface coefficients for defining the aspherical shape of each lens surface. In this example, since f1 / f = 0.70, Σd / f = 1.23, and vd2 = 29, the respective conditional expressions (1) to (3) are satisfied. 4, the aberration diagram is shown.

TABLE 2A

FNo. 3.5 f = 5.7 mm Σd = 6.985 mm

i R d Nd υd One* 1.386 1.0 1.5247 56.2 2* 3.087 0.15 3 0.00 0.18 4 0.00 0.47 5 * -0.953 0.9 1.585 29.0 6 * -2.016 0.1 7 * 6.57 1.2 1.5247 56.2 8* -6.15 1.336 9 0.00 0.6 1.51633 64.2 10 0.00 1.0489 11

(* Indicates aspherical surface)

TABLE 2B

i k A B C D One -2.414289 × 10 ^-1 1.704389 × 10 ^-2 -7.630913 × 10 ^-4 1.397945 × 10 ^-2 -5.89427 × 10 ^-3 2 7.215993 × 10 ^-1 -3.474378 × 10 ^-3 -7.800064 × 10 ^-2 9.886734 × 10 ^-2 -9.132532 × 10 ^-2 5 5.484851 ×× 10 ^-1 1.097456 × 10 ^-1 -2.023164 × 10 ^-1 5.6317 100 × 10 ^-1 -5.506715 × 10 ^-1 6 -1.456663 -2.197336 x 10 ^-2 -1.003731 × 10 ^-2 7 -3.168123 -1.446476 × 10 ^-2 1.192514 × 10 ^-3 3.793835 × 10 ^-5 -7.112863 × 10 ^-6 8 0.00 -1.342604 × 10 ^-3 -1.088183 × 10 ^-3 -8.566835 × 10 ^-6 7.766112 × 10 ^-6

In the imaging lenses 100 and 110 of the first and second embodiments, lenses having aspherical surfaces on both sides of the lens surface are used as the first lenses 1 and 11 on the object side. It is also possible to use a lens whose both surfaces are spherical, or a lens whose at least one lens surface is aspherical among the lens surfaces of both surfaces.

(Example 3)

5 shows an image pickup lens according to Embodiment 3 to which the first invention of the present application is applied. The imaging lens 120 of the present example includes a first lens 21 which is a meniscus having a positive power in which the convex surface faces the object side in order from the object side toward the image plane 26 side, and subsequent to this. Through the diaphragm 24, the concave surface has a second lens 22 which is a meniscus having negative power toward the object side, and a third lens 23 having negative power. The lens functions as a correction lens. The cover glass 25 is arrange | positioned between the 3rd lens 23 and the imaging surface 26. As shown in FIG. In the third lens 23, the second lens surface R6 on the imaging surface side is formed such that the ring-shaped portion around the lens is convex with respect to the imaging surface side, and the maximum exit angle of the chief ray is 24 degrees or less.

In this example, among the lenses 21, 22, and 23, both surfaces of the lens surface of the first lens 21 are spherical. On the other hand, in the second and third lenses 22 and 23, as in the first and second embodiments, both lens surfaces are aspherical.

Lens data of the entire optical system of the imaging lens 120 according to the present example is as follows.

F number: 3.5

Focal Length: f = 5.7mm

Overall length: Σd = 6.46mm

Table 3A shows lens data of each lens surface of the imaging lens 120 according to the present example, and Table 3B shows aspherical coefficients for defining the aspherical shape of each lens surface. In this example, since f1 / f = 0.73, Σd / f = 1.13, and vd2 = 29, the respective conditional expressions (1) to (3) are satisfied. 7 shows the aberration diagram.

TABLE 3A

FNo. 3.5 f = 5.7 mm Σd = 6.46 mm

i R d Nd υd One 1.621 1.0 1.5247 56.2 2 5.009 0.15 3 0.00 0.4 4 0.00 0.5 5 * -1.207 0.8 1.585 29.0 6 * -1.644 0.1 7 * 10.993 1.2 1.5247 56.2 8* 7.773 1.336 9 0.00 0.6 1.51633 64.2 10 0.00 0.3726 11

(* Indicates aspherical surface)

TABLE 3B

i k A B C D 5 -2.567837 × 10 ^-1 3.208279 × 10 ^-2 -1.916911 × 10 ^-1 3.791361 × 10 ^-1 -3.067684 × 10 ^-1 6 -9.161619 × 10 ^-1 -2.732818 × 10 ^-3 1.984030 × 10 ^-2 7 6.274432 -2.566783 × 10 ^-2 3.344091 × 10 ^-3 8.712945 × 10 ^-5 -2.670618 × 10 ^-5 8 0.00 -3.171232 × 10 ^-2 1.875582 × 10 ^-3 -2.705621 × 10 ^-4 1.570770 × 10 ^-5

(Example 4)

6 is a configuration diagram of an imaging lens according to Embodiment 4 to which the first invention of the present application is applied. In the imaging lens 130 of this example, the first lens 31 and the aperture stop 34, which are positive meniscus lenses with the convex surface facing the object side, in order from the object side toward the image plane 36 side, and the aperture stop 34. Through this, the second lens 32, which is a negative meniscus lens whose concave surface faces the object side, and the third lens 33 having positive power are arranged. A cover glass 35 is disposed between the third lens 33 and the imaging surface 36. The third lens 33 is formed such that the ring-shaped portion around the lens is a convex surface with respect to the imaging surface side, and the maximum exit angle of the chief ray is 24 degrees or less.

In this example, in each of the lenses 31, 32, and 33, both surfaces of the lens surface are spherical. On the other hand, in the second and third lenses 32 and 33, as in the first, second and third embodiments, both lens surfaces are aspherical.

Lens data of the entire optical system of the imaging lens 130 according to the present example is as follows.

F number: 3.5

Focal Length: f = 5.7mm

Overall length: Σd = 6.66mm

Table 4A shows lens data of each lens surface of the imaging lens 130 according to the present example, and Table 4B shows aspherical coefficients for defining the aspherical shape of each lens surface. In this example, since f1 / f = 0.77, Σd / f = 1.17, and vd2 = 29, the respective conditional expressions (1) to (3) are satisfied. 8 is aberration diagrams thereof.

TABLE 4A

FNo. 3.5 f = 5.7 mm Σd = 6.66 mm

i R d Nd υd One 1.626 1.2 1.4970 81.6 2 4.76 0.15 3 0.00 0.4 4 0.00 0.5 5 * -1.036 0.8 1.585 29.0 6 * -1.51 0.1 7 * 4.90 1.1 1.5247 56.2 8* 6.80 0.81 9 0.00 0.6 1.51633 64.2 10 0.00 1.0 11

(* Indicates aspherical surface)

TABLE 4B

i k A B C D 5 -6.210503 × 10 ^-1 3.611876 × 10 ^-2 -2.806078 × 10 ^-1 5.465 960 × 10 ^-1 -4.831922 × 10 ^-1 6 -1.143408 4.811894 × 10 ^-3 1.896129 × 10 ^-3 7 1.531998 -2.174083 × 10 ^-2 2.450461 × 10 ^-3 -2.581896 × 10 ^-4 1.113489 × 10 ^-5 8 0.00 -3.318003 × 10 ^-2 4.413864 × 10 ^-3 -5.477590 × 10 ^-4 2.739709 × 10 ^-5

(Example 5)

Next, with reference to FIG. 5 again, in the imaging lens 120 of Embodiment 3, instead of the first lens 21 in which both surfaces of the lens surface are formed as spherical surfaces, one lens surface is formed as an aspherical surface, and the other The imaging lens 140 using the first lens 41 having a spherical lens surface is described. In FIG. 5, the imaging lens 140 and the first lens 41 are indicated by parentheses in the reference numerals, and the configuration of the other parts is the same as in the third embodiment, and therefore, the same reference numerals will be described.

The imaging lens 140 of this example has a first lens 41 which is a meniscus having a positive power of the convex surface facing the object side in order from the object side toward the image forming surface 26 side, and subsequent to this. Through the aperture 24, the concave surface has a second lens 22 which is a meniscus having negative power toward the object side, and a third lens 23 having positive power. The lens functions as a correction lens. The cover glass 25 is arrange | positioned between the 3rd lens 23 and the imaging surface 26. As shown in FIG. In the third lens 23, the second lens surface R6 on the imaging surface side is formed such that the ring-shaped portion around the lens is convex with respect to the imaging surface side, and the maximum exit angle of the chief ray is 24 degrees or less.

In this example, among the lenses 41, 22, and 23, the first lens 41 has an aspherical surface of the first lens surface R1 on the object side of the lens surfaces on both sides, and the second lens on the imaging surface side. The surface R2 is spherical. On the other hand, the lens surfaces on both sides of the second and third lenses 22 and 23 are both aspherical.

Lens data of the entire optical system of the imaging lens 140 according to the present example is as follows.

F number: 3.5

Focal Length: f = 5.7mm

Overall length: Σd = 7.07mm

Table 5A shows lens data of each lens surface of the imaging lens 140 according to the present example, and Table 5B shows aspherical surface coefficients for defining the aspherical shape of each lens surface. In this example, since f1 / f = 0.83, Σd / f = 1.24, and vd2 = 29, the respective conditional expressions (1) to (3) are satisfied. 9, the aberration diagram is shown.

TABLE 5A

FNo. 3.5 f = 5.7 mm Σd = 7.07 mm

i R d Nd υd One* 1.77 1.0 1.5247 56.2 2 4.973 0.15 3 0.00 0.4 4 0.00 0.5 5 * -1.074 0.8 1.5850 29.0 6 * -1.584 0.1 7 * 5.516 1.2 1.5247 56.2 8* 19.41 1.336 9 0.00 0.6 1.51633 64.2 10 0.00 0.985 11

(* Indicates aspherical surface)

TABLE 5B

i k A B C D One -4.356005 × 10 ^-2 8.423055 × 10 ^-3 -4.071931 × 10 ^-3 4.637228 × 10 ^-3 -1.088690 × 10 ^-3 5 -3.998108 × 10 ^-1 3.950244 × 10 ^-2 -4.246316 × 10 ^-2 1.535713 × 10 ^-1 -1.460498 × 10 ^-1 6 -1.324467 -1.748017 × 10 ^-3 1.297864 × 10 ^-2 7 3.313169 -2.172623 × 10 ^-2 1.551952 × 10 ^-3 -2.195645 × 10 ^-5 -1.380375 × 10 ^-5 8 0.00 -2.288283 × 10 ^-2 1.359618 × 10 ^-3 -1.163401 × 10 ^-4 1.446310 × 10 ^-6

(Example A)

10 is a configuration diagram of an imaging lens according to Embodiment A to which the second invention of the present application is applied. The imaging lens 200 of the present example includes a first lens 201 which is a meniscus having positive power toward the object side from the object side toward the image plane 206 side, and an aperture ( 204, a second lens 202 which is a meniscus having a negative power toward the object side, and a third lens 203 having a positive power are arranged. A cover glass 205 is disposed between the second surface 203b of the third lens 203 and the imaging surface 206.

Here, lens surfaces 201a and 201b on both sides of the first lens 201, lens surfaces 202a and 202b on both sides of the second lens 202, and lens surfaces 203a on both sides of the third lens 203. 203b) is an aspherical surface. In addition, all of the aspherical shapes employed in the present example do not exhibit an inflection point in the effective lens surface area on each lens surface.

Lens data of the entire optical system of the imaging lens 200 is as follows.

F number: 2.8

Focal Length: f = 3.65mm

Back Focus: BF = 1.863mm

Focal length of the first lens 201: f1 = 3.769 mm

Tables 6A and 6B show lens data of each lens surface of the imaging lens 200 and aspherical surface coefficients for defining the aspherical shape of each lens surface.

TABLE 6A

FNo. 2.8, f = 3.65 mm

i R d Nd υd One* 1.153 0.8 1.5247 56.2 2* 2.105 0.15 3 0.00 0.35 4* -1.066 0.7 1.5850 29.0 5 * -1.546 0.1 6 * 3.180 0.9 1.5247 56.2 7 * 60.657 0.563 8 0.00 0.3 1.51633 64.2 9 0.00 1.0

(* Indicates aspherical surface)

TABLE 6B

i k A B C D One 4.577272 × 10 ^-1 -3.645425 × 10 ^-3 -2.554281 × 10 ^-2 2.607501 × 10 ^-2 2 -2.153226 5.788633 × 10 ^-2 4.7621418 × 10 ^-1 4 -2.641633 × 10 ^-2 5 -6.245341 × 10 ^-1 6 -1.167034 × 10 1.864785 × 10 ^-2 -1.905218 × 10 ^-3 -6.772919 × 10 ^-4 2.049794 × 10 ^-4 7 -1.749072 × 10 ⁵

In Tables 6A and 6B, i denotes the order of the lens surface counted from the object side, R denotes the curvature on the optical axis L of the lens surface, d denotes the distance between the lens surfaces, and Nd denotes the The refractive index is represented, and υd represents the Abbe number of each lens. In addition, the lens surface with an asterisk (*) in i indicates that it is an aspherical surface. The aspherical shape employed in the lens surface can be represented by the formula disclosed in the description of the first embodiment.

In addition, the expression which shows the meaning of each symbol and aspherical shape is the same also in the following Examples B and C.

In this example, the focal length f1 of the first lens 201 is a value within the range of 0.5f (= 1.825mm) and 1.5f (= 5.475mm), and satisfies the conditional expression (A). In addition, the value of BF / f is 0.5109... The conditional expression (B) is satisfied. Further, the curvature Ra of the lens surface 203a on the object side of the third lens 203 is 3.180, and the curvature Rb of the image surface lens surface 203b is 60.657, so that Rb / Ra = 19.074... The conditional expression (C) is satisfied. Moreover, the maximum exit angle of chief ray is 30 degrees or less.

11 is aberration diagrams showing various aberrations of the imaging lens according to the embodiment A; FIG. 11A shows spherical aberration SA, FIG. 11B shows astigmatism AS, and FIG. 11C shows aberration DIST. T of astigmatism AS represents a tangential (direction) top surface, and S represents a spherical top surface. Fig. 11 (d) is an aberration diagram showing lateral aberrations, DX represents lateral X aberrations with respect to X pupil coordinates, and DY represents lateral Y aberrations with respect to Y pupil coordinates. The meanings of these symbols are the same in Examples B and C described later.

(Example B)

12 is a block diagram showing an imaging lens according to Example B to which the second invention of the present application is applied. The imaging lens 210 has a first lens 211, a diaphragm 214, and a concave surface, each of which is a meniscus having a positive power from the object side toward the imaging surface 216 and the convex surface toward the object side. The second lens 212, which is a meniscus having positive power toward the object side, and the third lens 213 having positive power, are arranged in this order. The cover glass 215 is arrange | positioned similarly to Example A between the 3rd lens 213 and the imaging surface 216. FIG. In this example, the lens surfaces 211a and 211b on both sides of the first lens 211, the lens surfaces 212a and 212b on both sides of the second lens 212 and the image surface side of the third lens 213. The lens surface 213b is an aspherical surface. In addition, in each aspherical shape, an inflection point does not appear in the effective lens surface area | region in each lens surface.

Lens data of the entire optical system for the imaging lens of this example is as follows.

F number: 3.5

Focal Length: f = 3.5mm

Back Focus: BF = 1.992mm

Focal length f1 of the first lens 211 = 4.733 mm

In Tables 7A and 7B, the lens data of each lens surface of the imaging lens 210 and the aspherical surface coefficient for defining the aspherical shape of each lens surface according to the present example are displayed.

TABLE 7A

FNo. 3.5, f = 3.50 mm

i R d Nd υd One* 1.155 0.8 1.5850 29.0 2* 1.475 0.25 3 0.00 0.25 4* -1.234 0.8 1.5247 56.2 5 * -1.31 0.15 6 5.87 0.75 1.6070 29.9 7 * -27.245 0.3 8 0.00 0.6 1.51633 64.2 9 0.00 1.092 10 11

(* Indicates aspherical surface)

TABLE 7B

i k A B C D One 6.288194 × 10 ^-1 8.880798 × 10 ^-3 -3.552012 × 10 ^-2 5.541189 × 10 ^-2 -2.595815 × 10 ^-3 2 5.605423 -5.846783 × 10 ^-2 3.132873 × 10 ^-1 7.279427 -2.513030 × 10 4 2.369842 1.156048 × 10 ^-1 1.324990 5 4.089558 × 10 ^-1 5.253695 × 10 ^-2 1.227547 × 10 ^-1 -5.871821 × 10 ^-2 9.212771 × 10 ^-2 7 0.00 -1.935001 × 10 ^-2 1.343275 × 10 ^-3

In this example, the focal length f1 of the first lens 211 is a value within the range of 0.5f (= 1.75mm) and 1.5f (= 5.25mm), and satisfies the conditional expression (A). In addition, the value of BF / f is 0.549... The conditional expression (B) is satisfied. Furthermore, the curvature Ra of the object-side lens surface 213a of the third lens 213 is 5.87, and the curvature Rb of the image-side lens surface 213b is -27.245, so that Rb / Ra = 4.641. This satisfies the conditional expression (C). Moreover, the maximum exit angle of chief ray is 30 degrees or less.

13A to 13D are aberration diagrams showing various aberrations of the imaging lens 20 of this example.

(Example C)

The configuration of the imaging lens according to Embodiment C to which the second invention of the present application is applied is the same as that of the imaging lens 210 of Embodiment B, with the convex surface in the order from the object side toward the imaging surface 216. The first lens 211 which is a meniscus having positive power toward the lens, the aperture 214, the second lens 212 which is a meniscus having negative power toward the object side, and the positive surface A third lens 213 having a power of is arranged. A cover glass 215 is disposed between the third lens 213 and the imaging surface 216. By the way, in this example, the lens surfaces 211a and 211b on both sides of the first lens 211, the lens surfaces 212a and 212b on both sides of the second lens 212 and the lens surfaces on both sides of the third lens 213. 213a and 213b are each aspherical surface. In addition, in each aspherical shape, an inflection point does not appear in the effective lens surface area | region in each lens surface.

Lens data of the entire optical system for the imaging lens of this example is as follows.

F number: 2.8

Focal Length: f = 3.60mm

Back Focus: BF = 1.967mm

Focal length f1 of the first lens 211 = 3.844 mm

In Tables 8A and 8B, lens data of each lens surface of the imaging lens according to the present example and aspherical surface coefficients defining the aspherical surface shape of each lens surface are displayed.

TABLE 8A

FNo. 2.8, f = 3.60 mm

i R d Nd υd One* 1.109 0.85 1.5247 56.2 2* 1.814 0.25 3 0.00 0.25 4* -0.908 0.7 1.585 29.0 5 * -1.638 0.1 6 * 3.115 0.95 1.5247 56.2 7 * -4.464 0.4 8 0.00 0.3 1.51633 64.2 9 0.00 1.267 10 11

(* Indicates aspherical surface)

TABLE 8B

i k A B C D One 3.430395 × 10 ^-1 5.175761 × 10 ^-3 1.822436 × 10 ^-3 -3.968977 × 10 ^-2 4.390863 × 10 ^-2 2 -1.192756 × 10 2.602025 × 10 ^-1 2.316038 × 10 ^-1 4 4.565904 × 10 ^-1 5 -7.957068 × 10 ^-1 -1.046904 × 10 ^-1 7.812309 × 10 ^-3 6 -2.865732 × 10 -1.057338 × 10 ^-2 1.542895 × 10 ^-2 -6.212535 × 10 ^-3 8.950 190 × 10 ^-4 7 -2.000000 -7.488042 × 10 ^-3

In this example, the focal length f1 of the first lens 211 is a value within the range of 0.5f (= 1.80mm) and 1.5f (= 5.40mm), and satisfies the conditional expression (A). In addition, the value of BF / f is 0.546... The conditional expression (B) is satisfied. Furthermore, the curvature Ra of the object-side lens surface 213a of the third lens 213 is 3.115, and the curvature Rb of the image-side lens surface 213b is -4.464. Therefore, Rb / Ra | This satisfies the conditional expression (C). In addition, the maximum exit angle of chief ray is 30 degrees or less.

14A to 14D are aberration diagrams showing various aberrations of the imaging lens according to the present example.

(Other embodiment about 2nd invention)

In Examples A and C, the lens surfaces on both sides of the first to third lenses are all aspherical. In Example B, the lens surfaces on both sides of the first lens and the lens surfaces on both sides of the second lens and the third lens The lens surface on the image surface side is an aspherical surface. Of course, at least one lens surface of these lens surfaces may be an aspherical surface, and the other lens surface may be a spherical surface.

As described above, the imaging lens according to the first invention of the present application is a lens composed of three groups of three, the second lens and the third lens are correction lenses, and the first lens disposed on the object side has a positive menis. As a lens, the convex surface faces the object side. As a result, the overall length of the lens system can be shortened. In addition, since the lens surface of the third lens is an aspherical surface having one to a plurality of aspherical inflection points, shading can be prevented by satisfactorily correcting various aberrations and reducing the maximum exit angle of the chief ray. Moreover, aberration correction can be made favorable by the two correction lenses of a 2nd lens and a 3rd lens. Therefore, according to the present invention, a small and compact imaging lens corresponding to one million units of high pixels can be obtained.

The imaging lens according to the second invention of the present application is a lens system composed of three groups of three, and since the first lens disposed on the object side is a positive meniscus lens with the convex surface facing the object side, The overall length can be shortened. Further, by making the lens surface on the object side of the second lens a concave surface, the position of the exit pupil can be lengthened, thereby preventing shading. Furthermore, since the aspherical surface shape which does not have an inflection point is employ | adopted as a lens surface, deterioration of the resolution caused by the processing error, assembly error, etc. of a lens can be suppressed and it is suitable for production. Thus, according to the present invention, a compact and compact imaging lens suitable for production, corresponding to one million units of high pixels, and having a small number of constituent lenses can be obtained.

Claims (5)

It has a 1st lens, a 2nd lens, and a 3rd lens arrange | positioned in order from an object side, The first lens is a meniscus lens having a positive power of the convex surface toward the object side, The second lens is a meniscus lens having a positive power of the concave surface facing the object side, The third lens is a lens having positive power, Among the lens surfaces of the first lens, the second lens, and the third lens, the shape of any one of the lens surfaces is an imaging lens defined in an aspherical shape in which an inflection point does not appear in the effective lens surface region. When the combined focal length of the imaging lens is f and the focal length of the first lens is f1, 0.5 <f1 / f <1.5, When the curvature of the lens surface on the object side of the third lens is Ra, and the curvature of the image-side lens surface is Rb, 1.0 <│Rb / Ra│ Imaging lens. It has a 1st lens, a 2nd lens, and a 3rd lens arrange | positioned in order from an object side, The first lens is a meniscus lens having a positive power of the convex surface toward the object side, The second lens is a meniscus lens having a negative power of the concave surface toward the object side, The third lens is a lens having positive power, Among the lens surfaces of the first lens, the second lens, and the third lens, the shape of any one of the lens surfaces is an imaging lens defined in an aspherical shape in which an inflection point does not appear in the effective lens surface region. When the combined focal length of the imaging lens is f and the focal length of the first lens is f1, 0.5 <f1 / f <1.5, When the curvature of the lens surface on the object side of the third lens is Ra, and the curvature of the image surface lens surface is Rb, 1.0 <│Rb / Ra│ Imaging lens. The method of claim 1, When the combined focal length of the imaging lens is f and its back focus is BF, 0.25 <BF / f <1.0 Imaging lens. The method of claim 2, When the combined focal length of the imaging lens is f and its back focus is BF, 0.25 <BF / f <1.0 Imaging lens. The method according to any one of claims 1 to 4, An imaging lens with a maximum exit angle of main beam of 30 degrees or less.

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