JP2022108327A - Imaging lens and imaging apparatus - Google Patents

Abstract

To reduce the entire optical length and cancel the curvature of field.SOLUTION: An imaging lens system 11 is composed, in order from an object side, of a first lens L1 having a negative power, and having a convex shape on the object side and a concave shape on an image side, a meniscus second lens L2 having a convex shape on the object side and a concave shape on the image side, a third lens L3 having a positive power, and having a convex shape on the object side and a convex shape on the image side, a fourth lens L4 having a negative power, and having a concave shape on the object side and a convex shape on the object side where the image side has a concave shape, a fifth lens L5 having a positive power, and having a convex shape on the object side and a convex shape on the image side, and a sixth lens L6 having a positive power, and having a convex shape on the object side and a convex shape on the image side. When the focal length of the entire lens system is f, the focal length of the sixth lens L6 is f6, the thickness of the sixth lens L6 is d6, and the entire optical length is TTL, the following conditional expressions (1) and (2) are satisfied. (1) 1.0<f6/f<1.4, and (2) 0.13<d6/TTL<0.15.SELECTED DRAWING: Figure 1

Description

The present invention relates to an imaging lens and an imaging device.

In recent years, in-vehicle cameras are required to have higher resolution optical systems. As such an imaging lens system, Patent Document 1 discloses an imaging lens system that satisfies the conditional expression 0.5≤t6/f (t6: center thickness of the sixth lens L6, f: focal length of the entire lens system). Have been described.

On the other hand, in-vehicle cameras that are installed outside the vehicle must have a short overall optical length to reduce air resistance.

Japanese Patent Application Laid-Open No. 2016-065954

As a solution for shortening the optical total length of the imaging lens system of Patent Document 1 without lowering the resolution, increasing the power of the lens having positive power is conceivable. However, even if the power of the fifth lens is increased to the design limit in the imaging lens system of Cited Document 1, the curvature of field cannot be eliminated. That is, although the overall optical length can be shortened by reducing the thickness of the fifth lens, the curvature of field cannot be eliminated. As described above, if an attempt is made to shorten the total optical length of the imaging lens system of Cited Document 1, there is a problem that the imaging performance deteriorates due to the occurrence of curvature of field.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image pickup lens system and an image pickup apparatus which have a short overall optical length and can eliminate curvature of field.

The imaging lens system of one embodiment has negative power in order from the object side, the first lens L1 has a concave shape on the object side and a concave shape on the image side, and the first lens L1 has a convex shape on the object side and a concave shape on the image side. A second lens L2 of a certain meniscus, having positive power, convex on the object side and convex on the image side. A third lens L3, having negative power, concave on the object side and concave on the image side. A fourth lens L4 having a concave shape on the object side, a fifth lens L5 having positive power, a convex shape on the object side and a convex shape on the image side, a positive power and a convex shape on the object side. is composed of a sixth lens L6 having a convex shape on the image side, f is the focal length of the entire lens system, f6 is the focal length of the sixth lens L6, d6 is the thickness of the sixth lens L6, and TTL is the total optical length. When defined, the following conditional expressions (1) and (2) are satisfied.
1.0<f6/f<1.4 (1)
0.13<d6/TTL<0.15 (2)

According to the imaging lens system of one embodiment, field curvature can be eliminated by having a short total optical length and satisfying the Petzval condition.

According to the present invention, it is possible to provide an imaging lens system and an imaging apparatus that have a short overall optical length and can eliminate field curvature.

1 is a cross-sectional view showing the configuration of an imaging lens system according to Example 1; FIG. 4 is a spherical aberration diagram in the imaging lens system of Example 1. FIG. 4 is a field curvature diagram in the imaging lens system of Example 1. FIG. 4 is a distortion aberration diagram in the imaging lens system of Example 1. FIG. FIG. 8 is a cross-sectional view showing the configuration of an imaging lens system according to Example 2; FIG. 10 is a spherical aberration diagram in the imaging lens system of Example 2; FIG. 10 is a field curvature diagram in the imaging lens system of Example 2; FIG. 10 is a distortion aberration diagram in the imaging lens system of Example 2; FIG. 11 is a cross-sectional view showing the configuration of an imaging lens system according to Example 3; FIG. 11 is a spherical aberration diagram in the imaging lens system of Example 3; FIG. 11 is a field curvature diagram in the imaging lens system of Example 3; FIG. 11 is a distortion aberration diagram in the imaging lens system of Example 3; FIG. 11 is a cross-sectional view showing the configuration of an imaging lens system according to Example 4; FIG. 11 is a spherical aberration diagram in the imaging lens system of Example 4; FIG. 11 is a field curvature diagram in the imaging lens system of Example 4; FIG. 11 is a distortion aberration diagram in the imaging lens system of Example 4; FIG. 11 is a cross-sectional view showing the configuration of an imaging lens system according to Example 5; FIG. 11 is a spherical aberration diagram in the imaging lens system of Example 5; FIG. 11 is a field curvature diagram in the imaging lens system of Example 5; FIG. 11 is a distortion aberration diagram in the imaging lens system of Example 5; 10 is a cross-sectional view of an imaging device according to Embodiment 2; FIG.

To solve the above problem, the following three factors are required to eliminate field curvature (satisfy the Petzval condition).
1. power of the lens2. Refractive index of the lens3. number of lenses

Here, the power of the lens is related to the curvature and thickness, but in shortening the total length, there are restrictions due to other elements such as the lens barrel, so the degree of freedom in design is low. In addition, since the refractive index of the lens is limited by the glass material, etc., the degree of freedom in design is low. Therefore, in the optical lens and imaging apparatus according to the present embodiment, the Petzval condition is satisfied by the number of lenses due to the above restrictions.

Specifically, in the optical lens and imaging apparatus according to this embodiment, the power of the positive power lens is increased in order to shorten the total optical length. Therefore, the refractive indices of the second lens L2 and the fifth lens L5 are increased. As a result, the curvature of field was improved, but it was necessary to further eliminate the curvature of field.

Therefore, in the optical lens and imaging device according to the present embodiment, the number of lenses is increased by one from Patent Document 1 (Japanese Patent Application Laid-Open No. 2016-065954) to increase the number of lens surfaces. Due to the increase in the number of lens surfaces, under the condition that field curvature does not occur (that is, the Petzval condition), the increase in the number of lenses has increased the number of terms in the equation, making it possible to make adjustments to satisfy the Petzval condition. That is, by increasing the number of lenses from 5 to 6, the overall optical length can be shortened while maintaining the optical performance.
An optical lens and an imaging device according to this embodiment will be described below.
(Embodiment 1: Imaging lens system)
The imaging lens system of Embodiment 1 has negative power in order from the object side, the first lens L1 has a concave shape on the object side and a concave shape on the image side, and the first lens L1 has a convex shape on the object side and a concave shape on the image side. A second meniscus lens L2 having positive power, convex on the object side and convex on the image side. A third lens L3 having negative power, concave on the object side and having an image side of A fourth lens L4 having a concave shape on the object side which is concave, a fifth lens L5 having a positive power, a convex shape on the object side and a convex shape on the image side, a positive power and a convex shape on the object side. The focal length of the entire lens system is f, the focal length of the sixth lens L6 is f6, the thickness of the sixth lens L6 is d6, and the total optical length is TTL. is defined to satisfy the following conditional expressions (1) and (2).
1.0<f6/f<1.4 (1)
0.13<d6/TTL<0.15 (2)

According to the imaging lens system of Embodiment 1, field curvature can be eliminated by having a short total optical length and satisfying the Petzval condition.

The imaging lens system of the first embodiment has the following conditional expression (3), ( 4) and may be satisfied.
|f2/f|<4.8 (3)
Nd2≧1.90 (4)
Nd3≧1.90 (5)

According to the imaging lens system of Embodiment 1, it becomes easier to correct curvature of field.

The imaging lens system of Embodiment 1 may satisfy the following conditional expression (6) when the focal length of the fourth lens L4 is defined as f4 and the focal length of the fifth lens L5 as f5.
-0.8<f4/f5<-0.5 (6)

According to the imaging lens system of Embodiment 1, the total length can be suppressed by satisfying the lower limit, and chromatic aberration can be corrected by satisfying the upper limit.

Next, an example corresponding to the imaging lens system of Embodiment 1 will be described with reference to the drawings.
(Example 1)
FIG. 1 is a cross-sectional view showing the configuration of the imaging lens system of Example 1. As shown in FIG. In FIG. 1, the imaging lens system 11 includes, in order from the object side to the image side, a first lens L1, a second lens L2, a third lens L3, an aperture stop (STOP), a fourth lens L4, and a fifth lens L5. , and a sixth lens L6. The imaging plane of the imaging lens system 11 is indicated by IMG.

The first lens L1 is a lens with negative power. An object-side lens surface S1 of the first lens L1 is concave toward the object side. An image-side lens surface S2 of the first lens L1 faces a concave surface.

The second lens L2 is an aspherical lens with positive power. The object-side lens surface S3 of the second lens L2 is convex toward the object side. The image-side lens surface S4 of the second lens L2 is concave toward the image side.

The third lens L3 is a lens with positive power. An object-side lens surface S5 of the third lens L3 is convex toward the object side. The image-side lens surface S6 of the third lens L3 is concave toward the image plane side.

The fourth lens L4 is a lens with negative power. An object-side lens surface S9 of the fourth lens L4 is concave toward the object side. The image-side lens surface S10 of the fourth lens L4 is concave toward the image plane side.

The fifth lens L5 is a lens with positive power. An object-side lens surface S11 of the fifth lens L5 is convex toward the object side. The image-side lens surface S12 of the fifth lens L5 is convex toward the image plane side.

The fourth lens L4 and the fifth lens L5 form a cemented lens. That is, the image-side lens surface S10 of the fourth lens L4 and the object-side lens surface S11 of the fifth lens L5 are in contact with each other. For example, the fourth lens L4 and the fifth lens L5 are preferably bonded with an adhesive layer having an axial thickness of 0.02 mm.

The sixth lens L6 is an aspherical lens with positive power. An object-side lens surface S13 of the sixth lens L6 is convex toward the object side. The image-side lens surface S14 of the sixth lens L6 is convex toward the image plane side.

The IR cut filter 12 is a filter for cutting light in the infrared region. The IR cut filter 12 is handled integrally with the imaging lens system 11 when the imaging lens system 11 is designed. However, IR cut filter 12 is not an essential component of imaging lens system 11 . Also, the diaphragm may be provided closer to the object side than the first lens L1.

Table 1 shows lens data of each lens surface in the imaging lens system 11 of the first embodiment. Table 1 presents, as lens data, the radius of curvature (mm) of each surface, the surface spacing (mm) at the center optical axis, the refractive index Nd for the d-line, and the Abbe number Vd for the d-line. A surface marked with "*" indicates that it is an aspherical surface. Also, in Table 1, for example, "-6.522528E-03" means "-6.522528×10 ^-3 ". Numerical expressions are the same for the following tables.

The aspherical shape adopted for the lens surface is 4th, 6th, 8th, 10 When the aspheric coefficients of the next, 12th, 14th and 16th orders are A4, A6, A8, A10, A12, A14 and A16, respectively, they are expressed by the following equations.

Table 2 shows the aspherical coefficients for defining the aspherical shape of the aspherical lens surface in the imaging lens system 11 of the first embodiment.

Next, aberration will be described with reference to the drawings. FIG. 2 is a spherical aberration diagram in the imaging lens system of Example 1. FIG. In FIG. 2, the horizontal axis indicates the position where the light beam intersects the optical axis Z, and the vertical axis indicates the height at the pupil diameter. Also, FIG. 2 shows simulation results with light rays having wavelengths of 0.436 μm, 0.486 μm, 0.546 μm, 0.588 μm and 0.656 μm.

FIG. 3 is a field curvature diagram of the imaging lens system of Example 1. FIG. In FIG. 3, the horizontal axis indicates the distance in the Z direction of the optical axis, and the vertical axis indicates the image height (angle of view). In FIG. 3, S indicates astigmatism on the sagittal plane, and T indicates astigmatism on the tangential plane. In addition, FIG. 3 shows the simulation results with a light beam having a wavelength of 0.546 μm.

FIG. 4 is a distortion aberration diagram in the imaging lens system of Example 1. FIG. In FIG. 4, the horizontal axis indicates the amount of image distortion (%), and the vertical axis indicates the image height (angle of view). As shown in FIGS. 2 to 4, it can be seen that the aberrations are well corrected.

Next, the characteristic values of the lens will be explained. Table 3 shows the results of calculating the characteristic values of the imaging lens system 11 of Example 1. In Table 3, in the imaging lens system 11, f is the focal length of the entire lens system, f1 is the focal length of the first lens L1, f2 is the focal length of the second lens L2, f3 is the focal length of the third lens L3, and f3 is the focal length of the third lens L3. The focal length of the fourth lens L4 is f4, the focal length of the fifth lens L5 is f5, the focal length of the sixth lens L6 is f6, the combined focal length of the second lens L2 and the third lens L3 is f23, and the effective focal length is EFL. , the total optical length is TTL, the thickness of the first lens L1 is d1, the thickness of the second lens L2 is d2, the thickness of the third lens L3 is d3, the thickness of the fourth lens L4 is d4, and the thickness of the fifth lens L5 Each characteristic value is shown when the thickness of the lens L6 is d5 and the thickness of the sixth lens L6 is d6. In Table 3, the unit of focal length and center thickness is mm. Also, the various focal lengths in Table 3 were calculated using light with a wavelength of 0.546 μm.

(Example 2)
FIG. 5 is a cross-sectional view showing the configuration of the imaging lens system of Example 2. As shown in FIG. In FIG. 5, the imaging lens system 11 includes, in order from the object side to the image side, a first lens L1 having negative power, a second lens L2 having positive power, a third lens L3 having positive power, It consists of an aperture stop (STOP), a fourth lens L4 with negative power, a fifth lens L5 with positive power, and a sixth lens L6 with positive power. The imaging plane of the imaging lens system 11 is indicated by IMG. Also, the imaging lens system 11 may include an IR cut filter 12 . Also, the shape and material of each lens are the same as in the first embodiment.

Table 4 shows the lens data of each lens surface in the imaging lens system 11 of Example 2. Table 4 presents, as lens data, the radius of curvature (mm) of each surface, the surface spacing (mm) at the central optical axis, the refractive index Nd for the d-line, and the Abbe number Vd for the d-line. A surface marked with "*" indicates that it is an aspherical surface.

Table 5 shows the aspherical coefficients for defining the aspherical shape of the aspherical lens surface in the imaging lens system 11 of Example 2. In Table 5, the aspheric shape adopted for the lens surface is represented by the same formula as in the second embodiment.

Next, aberration will be described with reference to the drawings. FIG. 6 is a spherical aberration diagram in the imaging lens system of Example 2. FIG. In FIG. 6, the horizontal axis indicates the position where the light beam intersects the optical axis Z, and the vertical axis indicates the height at the pupil diameter. Also, FIG. 6 shows simulation results with light rays having wavelengths of 0.436 μm, 0.486 μm, 0.546 μm, 0.588 μm and 0.656 μm.

FIG. 7 is a field curvature diagram in the imaging lens system of Example 2. FIG. In FIG. 7, the horizontal axis indicates the distance in the Z direction of the optical axis, and the vertical axis indicates the image height (angle of view). In FIG. 7, S indicates astigmatism on the sagittal plane, and T indicates astigmatism on the tangential plane. In addition, FIG. 3 shows the simulation results with a light beam having a wavelength of 0.546 μm.

FIG. 8 is a distortion aberration diagram in the imaging lens system of Example 2. FIG. In FIG. 8, the horizontal axis indicates the amount of image distortion (%), and the vertical axis indicates the image height (angle of view).
As shown in FIGS. 6 to 8, it can be seen that the aberrations are well corrected.

Next, the characteristic values of the lens will be explained. Table 6 shows the results of calculating the characteristic values of the imaging lens system 11 of Example 2. Each item in Table 6 indicates each characteristic value similar to Table 3. Also, the various focal lengths in Table 6 were calculated using light with a wavelength of 0.546 μm.

(Example 3)
FIG. 9 is a cross-sectional view showing the configuration of the imaging lens system of Example 3. As shown in FIG. In FIG. 9, the imaging lens system 11 includes, in order from the object side to the image side, a first lens L1 having negative power, a second lens L2 having positive power, a third lens L3 having positive power, It consists of an aperture stop (STOP), a fourth lens L4 with negative power, a fifth lens L5 with positive power, and a sixth lens L6 with positive power. The imaging plane of the imaging lens system 11 is indicated by IMG. Also, the imaging lens system 11 may include an IR cut filter 12 . Also, the shape and material of each lens are the same as those of the first embodiment, except that the second lens L2 is a spherical lens.

Table 7 shows the lens data of each lens surface in the imaging lens system 11 of Example 3. Table 7 presents, as lens data, the curvature radius (mm) of each surface, the surface spacing (mm) at the center optical axis, the refractive index Nd for the d-line, and the Abbe number Vd for the d-line. A surface marked with "*" indicates that it is an aspherical surface.

Table 8 shows the aspherical coefficients for defining the aspherical shape of the aspherical lens surface in the imaging lens system 11 of Example 3. In Table 8, the aspherical shape adopted for the lens surface is represented by the same formula as in the third embodiment.

Next, aberration will be described with reference to the drawings. FIG. 10 is a spherical aberration diagram in the imaging lens system of Example 3. FIG. In FIG. 10, the horizontal axis indicates the position where the light beam intersects the optical axis Z, and the vertical axis indicates the height at the pupil diameter. Also, FIG. 10 shows simulation results with light rays having wavelengths of 0.436 μm, 0.486 μm, 0.546 μm, 0.588 μm and 0.656 μm.

FIG. 11 is a field curvature diagram of the imaging lens system of Example 3. FIG. In FIG. 11, the horizontal axis indicates the distance in the Z direction of the optical axis, and the vertical axis indicates the image height (angle of view). In FIG. 11, S indicates astigmatism on the sagittal plane, and T indicates astigmatism on the tangential plane. In addition, FIG. 3 shows the simulation results with a light beam having a wavelength of 0.546 μm.

FIG. 12 is a distortion diagram of the imaging lens system of Example 3. FIG. In FIG. 12, the horizontal axis indicates the amount of image distortion (%), and the vertical axis indicates the image height (angle of view).
As shown in FIGS. 10 to 12, it can be seen that the aberrations are satisfactorily corrected.

Next, the characteristic values of the lens will be explained. Table 9 shows the results of calculating the characteristic values of the imaging lens system 11 of Example 3. Each item in Table 9 indicates each characteristic value similar to Table 3. Also, the various focal lengths in Table 9 were calculated using light with a wavelength of 0.546 μm.

(Example 4)
FIG. 13 is a cross-sectional view showing the configuration of the imaging lens system of Example 4. As shown in FIG. In FIG. 13, the imaging lens system 11 includes, in order from the object side to the image side, a first lens L1 having negative power, a second lens L2 having positive power, a third lens L3 having positive power, It consists of an aperture stop (STOP), a fourth lens L4 with negative power, a fifth lens L5 with positive power, and a sixth lens L6 with positive power. The imaging plane of the imaging lens system 11 is indicated by IMG. Also, the imaging lens system 11 may include an IR cut filter 12 . Also, the shape and material of each lens are the same as in the first embodiment.

Table 10 shows the lens data of each lens surface in the imaging lens system 11 of Example 4. Table 10 presents, as lens data, the radius of curvature (mm) of each surface, the surface spacing (mm) at the central optical axis, the refractive index Nd for the d-line, and the Abbe number Vd for the d-line. A surface marked with "*" indicates that it is an aspherical surface.

Table 11 shows the aspherical coefficients for defining the aspherical shape of the aspherical lens surface in the imaging lens system 11 of Example 4. In Table 11, the aspheric shape adopted for the lens surface is represented by the same formula as in the fourth embodiment.

Next, aberration will be described with reference to the drawings. FIG. 14 is a spherical aberration diagram in the imaging lens system of Example 4. FIG. In FIG. 14, the horizontal axis indicates the position where the light beam intersects the optical axis Z, and the vertical axis indicates the height at the pupil diameter. Also, FIG. 14 shows simulation results with light rays having wavelengths of 0.436 μm, 0.486 μm, 0.546 μm, 0.588 μm and 0.656 μm.

FIG. 15 is a field curvature diagram in the imaging lens system of Example 4. FIG. In FIG. 15, the horizontal axis indicates the distance in the Z direction of the optical axis, and the vertical axis indicates the image height (angle of view). In FIG. 15, S indicates astigmatism on the sagittal plane, and T indicates astigmatism on the tangential plane. In addition, FIG. 3 shows the simulation results with a light beam having a wavelength of 0.546 μm.

FIG. 16 is a distortion aberration diagram in the imaging lens system of Example 4. FIG. In FIG. 16, the horizontal axis indicates the amount of image distortion (%), and the vertical axis indicates the image height (angle of view).
As shown in FIGS. 14 to 16, it can be seen that the aberrations are well corrected.

Next, the characteristic values of the lens will be explained. Table 12 shows the results of calculating the characteristic values of the imaging lens system 11 of Example 4. Each item in Table 12 indicates each characteristic value similar to Table 3. Also, the various focal lengths in Table 12 were calculated using light with a wavelength of 0.546 μm.

(Example 5)
FIG. 17 is a cross-sectional view showing the configuration of the imaging lens system of Example 5. As shown in FIG. In FIG. 17, the imaging lens system 11 includes, in order from the object side to the image side, a first lens L1 having negative power, a second lens L2 having positive power, a third lens L3 having positive power, It consists of an aperture stop (STOP), a fourth lens L4 with negative power, a fifth lens L5 with positive power, and a sixth lens L6 with positive power. The imaging plane of the imaging lens system 11 is indicated by IMG. Also, the imaging lens system 11 may include an IR cut filter 12 . Also, the shape and material of each lens are the same as those of the first embodiment, except that the second lens L2 is a spherical lens.

Table 13 shows the lens data of each lens surface in the imaging lens system 11 of Example 5. Table 13 presents, as lens data, the curvature radius (mm) of each surface, the surface spacing (mm) at the center optical axis, the refractive index Nd for the d-line, and the Abbe number Vd for the d-line. A surface marked with "*" indicates that it is an aspherical surface.

Table 14 shows the aspherical coefficients for defining the aspherical shape of the aspherical lens surface in the imaging lens system 11 of Example 5. In Table 14, the aspheric shape adopted for the lens surface is represented by the same formula as in the fifth embodiment.

Next, aberration will be described with reference to the drawings. 18 is a spherical aberration diagram in the imaging lens system of Example 5. FIG. In FIG. 18, the horizontal axis indicates the position where the light beam intersects the optical axis Z, and the vertical axis indicates the height at the pupil diameter. Also, FIG. 18 shows simulation results with light rays having wavelengths of 0.436 μm, 0.486 μm, 0.546 μm, 0.588 μm and 0.656 μm.

FIG. 19 is a field curvature diagram in the imaging lens system of Example 5. FIG. In FIG. 19, the horizontal axis indicates the distance in the Z direction of the optical axis, and the vertical axis indicates the image height (angle of view). In FIG. 19, S indicates astigmatism on the sagittal plane, and T indicates astigmatism on the tangential plane. In addition, FIG. 3 shows the simulation results with a light beam having a wavelength of 0.546 μm.

FIG. 20 is a distortion diagram of the imaging lens system of Example 5. FIG. In FIG. 20, the horizontal axis indicates the image distortion amount (%), and the vertical axis indicates the image height (angle of view).
As shown in FIGS. 18 to 20, it can be seen that the aberrations are satisfactorily corrected.

Next, the characteristic values of the lens will be explained. Table 15 shows the results of calculating the characteristic values of the imaging lens system 11 of Example 5. Each item in Table 15 indicates each characteristic value similar to Table 3. Also, the various focal lengths in Table 15 were calculated using light with a wavelength of 0.546 μm.

(Embodiment 2: Application example to imaging device)
In FIG. 21, the imaging device 21 includes an imaging lens system 11 and an imaging device 22 . The imaging lens system 11 and the imaging device 22 are housed in a housing (not shown). The imaging lens system 11 is the imaging lens system 11 described in the first embodiment above.

The imaging element 22 is an element that converts received light into an electric signal, and for example, a CCD image sensor or a CMOS image sensor is used. The imaging element 22 is arranged at the imaging position of the imaging lens system 11 .

As described above, according to the image pickup apparatus of the second embodiment, it is possible to provide an image pickup apparatus that has a short overall optical length and can eliminate curvature of field.

It should be noted that the present invention is not limited to the above embodiments, and can be modified as appropriate without departing from the scope of the invention. For example, Example 2 may be applied to Examples 1-5. In addition, if the refractive index of the sixth lens L6 is increased, the imaging performance deteriorates. Therefore, in the optical lens and the imaging device according to the present embodiment, when the refractive index of the sixth lens L6 is N6, 1.55<N6< 1.8 is desirable.
Further, in the optical lens and imaging apparatus according to the present embodiment, 40<v6ν6<70 and ν5=67, where ν6 is the Abbe number of the sixth lens L6 and ν5 is the Abbe number of the fifth lens L5. is desirable. Here, the sixth lens L6 has a role of correcting chromatic aberration.

11 Imaging lens system 12 IR cut filter 21 Imaging device 22 Imaging device L1 First lens L2 Second lens L3 Third lens L4 Fourth lens L5 Fifth lens L6 Sixth lens STOP Aperture IMG Imaging plane

Claims (4)

The first lens, which has negative power in order from the object side, has a concave shape on the object side and a concave shape on the image side,
a second meniscus lens having a convex shape on the object side and a concave shape on the image side;
a third lens having a positive power, a convex shape on the object side and a convex shape on the image side;
a fourth lens having negative power, concave on the object side, concave on the image side, and concave on the object side;
a fifth lens having a positive power, a convex shape on the object side and a convex shape on the image side;
Consisting of a sixth lens having a positive power and having a convex shape on the object side and a convex shape on the image side,
When the focal length of the entire lens system is defined as f, the focal length of the sixth lens is f6, the thickness of the sixth lens is d6, and the optical total length is TTL, the following conditional expressions (1) and (2) are satisfied. imaging lens system.
1.0<f6/f<1.4 (1)
0.13<d6/TTL<0.15 (2) When the focal length of the second lens is defined as f2, the refractive index of the second lens is defined as Nd2, and the refractive index of the third lens is defined as Nd3, the following conditional expressions (3), (4) and and are satisfied. 1. The imaging lens system according to 1.
|f2/f|<4.8 (3)
Nd2≧1.90 (4)
Nd3≧1.90 (5) 3. The imaging lens system according to claim 1, wherein the following conditional expression (6) is satisfied when the focal length of the fourth lens is defined as f4 and the focal length of the fifth lens is defined as f5.
-0.8<f4/f5<-0.5 (6) an imaging lens system according to any one of claims 1 to 3;
and an imaging device arranged at a focal position of the imaging lens system.

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