JP2006065170A - Imaging lens and imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an extremely small imaging lens having satisfactory optical performance capable of coping with a high pixel imaging element even though the imaging lens is composed of fewer lenses (two lenses) and to provide at a low cost an imaging apparatus using the imaging lens. <P>SOLUTION: The imaging lens includes in order from the object side: a first lens G1, which has a meniscus shape whose convex face is in the direction of the object; an aperture diaphragm IR; and a second lens G2 having a positive refracting power, which has a meniscus shape whose convex face is in the direction of an image. The imaging lens satisfies the following conditional formulas (1), (2) and (3): (1) -0.25<f/f1<0.50, (2) 1.38<L/f<1.58, (3) 1.6≤n(ave)≤1.7, wherein f is the focal distance of the entire lens system, f1 is the focal distance of the first lens, L is a distance from the object side face of the first leans to an image plane (the back insertion glass is calculated using thickness acquired by air conversion), and n(ave) is the average of refraction indexes on the d-line of the two lenses composing the lens system. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an imaging lens and an imaging apparatus. Specifically, the present invention relates to an imaging lens suitable for a compact imaging device using a solid-state imaging device such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal-Oxide Semiconductor), and an imaging device using the imaging lens.

  Conventionally, camera-equipped mobile phones and digital still cameras using solid-state imaging devices such as CCDs and CMOSs are known. In such an imaging apparatus, further miniaturization is required, and an imaging lens to be mounted is required to be small and have a short overall length.

  As a small imaging lens used for the above-described purpose, a two-lens imaging lens or a three-lens imaging lens is generally used. For example, those described in Patent Literature 1 and Patent Literature 2 are known. ing.

JP 2003-215446 A JP 2003-232991 A

  In recent years, in a small image pickup device such as a camera-equipped mobile phone, the number of pixels of an image pickup device has been increased along with downsizing, and a model equipped with a high pixel image pickup device of megapixel or more has become a popular machine. For this reason, the mounted imaging lens is also required to have high lens performance that can handle such a high-pixel solid-state imaging device.

  The imaging lenses disclosed in Patent Document 1 and Patent Document 2 have a two-lens configuration and a reduction in size. However, various aberrations occur greatly, and the lens performance required for a high-pixel imaging device is satisfied. Can not.

  The present invention has been made in view of the above-described problems, and has a relatively small size that has a good optical performance that can be applied to a high-pixel imaging device while being configured with a small number of lenses of two. An object is to provide an imaging lens and an imaging apparatus using the imaging lens at low cost.

  In order to solve the above-described problems, the imaging lens of the present invention, in order from the object side, a first meniscus lens having a convex surface facing the object side, an aperture stop, and a meniscus shape positive lens having a convex surface facing the image side. Are arranged with a second lens having a refractive power of f, f is the focal length of the entire lens system, f1 is the focal length of the first lens, and L is the distance from the object side surface of the first lens to the image plane. (However, the back-inserted glass is calculated by the thickness in terms of air), and n (ave) is the average value of the refractive indices at the d-line of the two lenses constituting the lens system, the following conditional expressions (1) and (2 ) And (3) are satisfied.

(1) -0.25 <f / f1 <0.50
(2) 1.38 <L / f <1.58
(3) 1.6 ≦ n (ave) ≦ 1.7
In order to solve the above-described problem, the imaging apparatus according to the present invention, in order from the object side, a first meniscus lens having a convex surface facing the object side, an aperture stop, and a meniscus shape having a convex surface facing the image side An imaging lens configured by arranging second lenses having positive refractive power and an imaging element that converts an optical image formed by the imaging lens into an electrical signal, and the imaging lens includes f as a lens. The focal length of the entire system, f1 is the focal length of the first lens, L is the distance from the object side surface of the first lens to the image plane (however, the back insertion glass is calculated by the thickness in terms of air), n (ave The following conditional expressions (1), (2), and (3) are satisfied as the average value of the refractive index at the d-line of the two lenses constituting the lens system.

(1) -0.25 <f / f1 <0.50
(2) 1.38 <L / f <1.58
(3) 1.6 ≦ n (ave) ≦ 1.7
Therefore, in the present invention, an imaging lens having a relatively small size and good optical performance can be obtained at low cost, and a small and high-performance imaging device can be obtained by using such an imaging lens. It can be obtained at low cost.

  The imaging lens of the present invention includes, in order from the object side, a first meniscus lens having a convex surface facing the object side, an aperture stop, and a second lens having a meniscus shape having a positive refractive power facing the image side. Are arranged, f is the focal length of the entire lens system, f1 is the focal length of the first lens, and L is the distance from the object side surface of the first lens to the image plane (however, the back insertion glass is converted into air) The following conditional expressions (1), (2), and (3) are satisfied, where n (ave) is the average value of the refractive indices at the d-line of the two lenses constituting the lens system. It is characterized by.

(1) -0.25 <f / f1 <0.50
(2) 1.38 <L / f <1.58
(3) 1.6 ≦ n (ave) ≦ 1.7
In order to solve the above-described problem, the imaging apparatus according to the present invention, in order from the object side, a first meniscus lens having a convex surface facing the object side, an aperture stop, and a meniscus shape having a convex surface facing the image side An imaging lens configured by arranging second lenses having positive refractive power and an imaging element that converts an optical image formed by the imaging lens into an electrical signal, and the imaging lens includes f as a lens. The focal length of the entire system, f1 is the focal length of the first lens, L is the distance from the object side surface of the first lens to the image plane (however, the back insertion glass is calculated by the thickness in terms of air), n (ave The following conditional expressions (1), (2), and (3) are satisfied as an average value of the refractive index at the d-line of the two lenses constituting the lens system.

(1) -0.25 <f / f1 <0.50
(2) 1.38 <L / f <1.58
(3) 1.6 ≦ n (ave) ≦ 1.7
Therefore, in the present invention, it is possible to obtain a relatively small imaging lens having good optical performance corresponding to a high-pixel imaging device at a low cost while being configured with a small number of lenses of two. . Further, by using such an imaging lens, the imaging apparatus can be configured in a small size, and a high-quality image can be obtained using a high-pixel imaging device.

  In the invention described in claims 2 and 8, the object-side surface of the second lens has f as the focal length of the entire lens system and R3 as the radius of curvature of the object-side surface of the second lens. Since conditional expression (4) 0.75 <R3 / f <1.60 is satisfied, astigmatism and curvature of field can be favorably corrected.

  In the invention described in claim 3, claim 4, claim 9, and claim 10, at least the object side surface of the first lens and the image side surface of the second lens are aspherical. Since it is configured, coma and distortion can be corrected satisfactorily.

  In the invention described in claim 5, claim 6, claim 11 and claim 12, the object-side surface of the first lens has θ1 (h) at a height h (= D1 / 2). Since the inclination of the object side surface of the first lens and D1 is the effective diameter of the object side surface of the first lens, the conditional expression (5) 55 ° <| θ1 (h) | <80 ° is satisfied. Aberration can be corrected in a well-balanced manner.

  The best mode for carrying out the imaging lens and the imaging apparatus of the present invention will be described below with reference to the accompanying drawings.

  As shown in FIGS. 1, 3, and 5, the imaging lens according to the present invention has a meniscus first lens G 1 having a convex surface facing the object side, an aperture stop IR, and a convex surface facing the image side in order from the object side. A second lens G2 having a positive meniscus refractive power is arranged.

F is the focal length of the entire lens system, f1 is the focal length of the first lens, and L is the distance from the object side surface of the first lens to the image plane (however, the back insertion glass is calculated by the thickness in terms of air) ), N (ave) is the average value of the refractive indices at the d-line of the two lenses constituting the lens system, and the following conditional expression (1) −0.25 <f / f1 <0.50
(2) 1.38 <L / f <1.58
(3) 1.6 ≦ n (ave) ≦ 1.7
By satisfying the above, it is possible to construct an extremely small imaging lens having a good optical performance capable of accommodating a high-pixel imaging device at a low cost while being configured with a small number of lenses of two.

  Conditional expression (1) defines the ratio of the focal length (f) of the entire lens system to the focal length (f1) of the first lens G1, and restricts the refractive power of the first lens G1. If the lower limit of conditional expression (1) is not reached, it will be advantageous in correcting aberrations, but the total lens length will increase and the lens system will become large. On the other hand, if the upper limit value of the conditional expression (1) is exceeded, it is difficult to correct off-axis aberrations, in particular, coma and field curvature.

  Conditional expression (2) defines the ratio between the total length (L) of the lens system and the focal length (f) of the entire lens system, and defines the balance between the size of the lens system and the amount of aberration generated in the lens system. ing. If the lower limit of conditional expression (2) is not reached, it is advantageous for miniaturization, but the refractive power of each lens increases, and it becomes difficult to correct off-axis aberrations, particularly coma and field curvature. In addition, it is difficult to secure the edge thickness of each lens, which causes a problem in molding. On the other hand, exceeding the upper limit value of conditional expression (2) is advantageous in terms of aberration correction, but the total lens length increases and the lens system becomes large.

  Conditional expression (3) defines the average value of the refractive index at the d-line of the constituent lens, and restricts the refractive index of the lens used. By satisfying this conditional expression (3), the optimum refractive power on each surface can be ensured, and the lens system can be miniaturized and necessary aberration correction can be realized. In addition, in the range of the conditional expression (3), it is possible to use a resin lens that is relatively easy to obtain, and thus it is possible to reduce the cost.

  Furthermore, in the imaging lens of the present invention, the object-side surface of the second lens G2 has the following conditions, where f is the focal length of the entire lens system and R3 is the radius of curvature of the object-side surface of the second lens. It is desirable to satisfy Formula (4).

(4) 0.75 <R3 / f <1.60
Conditional expression (4) sets the ratio between the radius of curvature of the object-side surface of the second lens G2 and the focal length (f) of the entire lens system. The refractive power of the incident surface of the second lens G2 is set as follows. It prescribes. Outside the range defined by conditional expression (4), it becomes difficult to correct astigmatism and field curvature.

  Furthermore, in the imaging lens of the present invention, it is desirable that the object-side surface of the first lens G1 and the image-side surface of the second lens G2 are configured to be aspherical. As a result, coma and distortion can be corrected satisfactorily.

  In the imaging lens of the present invention, the object-side surface of the first lens G1 has an inclination of θ1 (h) at the height h (= D1 / 2) of the object-side surface of the first lens, and D1 is the first. It is desirable that the following conditional expression (5) is satisfied as the effective diameter of the object side surface of the lens.

(5) 55 ° <| θ1 (h) | <80 °
The conditional expression (5) defines the inclination of the object side surface of the first lens G1 in the light beam outermost effective portion. By satisfying this conditional expression (5), it is possible to correct off-axis aberrations in a well-balanced manner.

  Hereinafter, embodiments and numerical examples of the imaging lens of the present invention will be described with reference to FIGS. 1 to 6 and Tables 1 to 7. FIG.

  The meanings of symbols used in the numerical examples are as follows.

FNo: F number f: Focal length of the entire lens system
2ω: Diagonal angle of view Si: i-th surface counted from the object side Ri: radius of curvature of the surface Si di: surface distance between the i-th surface and the i + 1-th surface from the object side ni: Refractive index at the d-line (wavelength 587.6 nm) of the i lens νi: Abbe number at the d-line (wavelength 587.6 nm) of the i-th lens Further, the aspherical shape has an aspherical depth X from the optical axis. It is assumed that the height is H and is defined by the equation (1). Note that R is a radius of curvature, K is a conic constant, and A, B, C, D, and E are fourth-order, sixth-order, eighth-order, tenth-order, and twelfth-order aspheric coefficients, respectively.

  FIG. 1 is a diagram showing the lens configuration of a first embodiment of the imaging lens of the present invention. The imaging lens according to the first example has, in order from the object side, a first lens G1 having a meniscus positive refractive power with a convex surface facing the object side, an aperture stop IR, and a convex surface facing the image side. A second lens G2 having a meniscus shape having positive refractive power is arranged. Note that LPF is a low-pass filter interposed between the second lens G2 and the imaging plane IMG.

  Table 1 shows data of the optical system of Numerical Example 1 in which specific numerical values are applied to Example 1. In the table below, “ASP” indicates that the surface is configured as an aspheric surface, and “∞” indicates that the surface is configured as a plane.

  In the first embodiment, both surfaces s1 and s2 of the first lens G1 and both surfaces s4 and s5 of the second lens G2 are aspherical. Therefore, the fourth-order, sixth-order, eighth-order, tenth-order, and twelfth-order aspherical coefficients A, B, C, D, and E of the surfaces s1, s2, s4, and s5 in Numerical Example 1 are combined with the conic constant. It shows in Table 2.

  FIG. 2 shows spherical aberration, astigmatism and distortion in Numerical Example 1. In the spherical aberration diagram, the solid line is the d-line, the broken line is the C-line, the one-dot chain line is the spherical aberration at the g-line, and in the astigmatism diagram, the solid line is the sagittal image plane, and the broken line is the meridional Indicates the image plane.

  In Numerical Example 1, as can be seen from Table 1, the total length is as small as 5.57 mm, and it can be seen from FIG. 2 that each aberration is well corrected.

  FIG. 3 is a diagram showing the lens configuration of the second embodiment of the imaging lens of the present invention. In the imaging lens according to the second example, in order from the object side, the first lens G1 having a meniscus negative refractive power with the convex surface facing the object side, the aperture stop IR, and the convex surface facing the image side. A second lens G2 having a meniscus shape having positive refractive power is arranged. Note that LPF is a low-pass filter interposed between the second lens G2 and the imaging plane IMG.

  Table 3 shows data of the optical system of Numerical Example 2 in which specific numerical values are applied to Example 2.

  In the second embodiment, both surfaces s1, s2 of the first lens G1 and both surfaces s4, s5 of the second lens G2 are aspherical. Therefore, the fourth-order, sixth-order, eighth-order, tenth-order, and twelfth-order aspherical coefficients A, B, C, D, and E of the surfaces s1, s2, s4, and s5 in Numerical Example 2 are added together with the conic constant. Table 4 shows.

  FIG. 4 shows spherical aberration, astigmatism and distortion in Numerical Example 2. In the spherical aberration diagram, the solid line is the d-line, the broken line is the C-line, the one-dot chain line is the spherical aberration at the g-line, and in the astigmatism diagram, the solid line is the sagittal image plane, and the broken line is the meridional Indicates the image plane.

  In Numerical Example 2, as can be seen from Table 3 above, the total length is as small as 5.31 mm, and it can be seen from FIG. 4 that each aberration is well corrected.

  FIG. 5 is a diagram showing a lens configuration of a third embodiment of the imaging lens of the present invention. The imaging lens according to the third example, in order from the object side, has a first meniscus negative lens G1 having a convex surface facing the object side, an aperture stop IR, and a convex surface facing the image side. A second lens G2 having a meniscus shape having positive refractive power is arranged. Note that LPF is a low-pass filter interposed between the second lens G2 and the imaging plane IMG.

  Table 5 shows data of the optical system of Numerical Example 3 in which specific numerical values are applied to Example 3.

  In the third embodiment, both surfaces s1 and s2 of the first lens G1 and both surfaces s4 and s5 of the second lens G2 are aspherical. Therefore, the fourth-order, sixth-order, eighth-order, tenth-order, and twelfth-order aspheric coefficients A, B, C, D, and E of the surfaces s1, s2, s4, and s5 in Numerical Example 3 together with the conic constant are used. Table 6 shows.

  FIG. 6 shows spherical aberration, astigmatism, and distortion in Numerical Example 3. In the spherical aberration diagram, the solid line is the d-line, the broken line is the C-line, the one-dot chain line is the spherical aberration at the g-line, and in the astigmatism diagram, the solid line is the sagittal image plane, and the broken line is the meridional Indicates the image plane.

  In Numerical Example 3, as can be seen from Table 5 above, the total length is as small as 5.97 mm, and it can be seen from FIG. 6 that each aberration is well corrected.

  Table 7 shows numerical data of the conditional expressions (1) to (5) in the above Examples 1 to 3.

  It can be seen from Table 7 that each of Examples 1 to 3 satisfies the conditional expressions (1) to (5).

  7 to 9 show an embodiment in which the imaging apparatus of the present invention is applied to a mobile phone.

  7 and 9 show the appearance of the mobile phone 10.

  The mobile phone 10 is configured such that the display unit 20 and the main body unit 30 are connected to each other so as to be foldable at a central hinge portion. The mobile phone 10 is folded as shown in FIG. As shown, the display unit 20 and the main body unit 30 are opened.

  An antenna 21 for transmitting / receiving radio waves to / from a base station is provided at a position close to one side on the back side of the display unit 20, and the inner surface of the display unit 20 includes the antenna 21. A liquid crystal display panel 22 having a size that occupies substantially the entire side surface is disposed, and a speaker 23 is disposed above the liquid crystal display panel 22. Further, the image pickup unit 1 of the digital camera is disposed on the display unit 20, and the image pickup lens 1 a of the image pickup unit 1 faces outward through a facing hole 24 formed on the back surface of the display unit 20. Yes. Here, the term “imaging unit” is used as a configuration including the imaging lens 1a and the imaging element 1b. That is, the imaging lens 1a and the imaging device 1b need to be provided in the display unit 20 at the same time, but other parts constituting the digital camera, such as a camera control unit and a recording medium, are arranged in the main body unit 30. The concept of the imaging unit was used to clarify the good.

  Furthermore, an infrared communication unit 25 is disposed at the distal end of the display unit 20, and the infrared communication unit includes an infrared light emitting element and an infrared light receiving element (not shown).

  The main body 30 is provided with operation keys 31, 31,... Such as numeric keys "0" to "9", calling keys, power keys, etc. on the inner surface of the operation key 31, 31,. A microphone 32 is disposed below the portion where the. In addition, a memory card slot 33 is provided on the side surface of the main body 30, and the memory card 40 can be inserted into and removed from the main body 30 via the memory card slot 33.

  FIG. 9 is a block diagram showing the configuration of the mobile phone 10.

  The mobile phone 10 includes a CPU (Central Processing Unit) 50, and the CPU 50 controls the overall operation of the mobile phone 10. That is, the CPU 50 develops a control program stored in a ROM (Read Only Memory) 51 in a RAM 52 (Random Access Memory), and controls the operation of the mobile phone 10 via the bus 53.

  The camera control unit 60 controls the image pickup unit 1 including the image pickup lens 1a and the image pickup device 1b to shoot images such as still images and moving images. The obtained image information is compressed into JPEG, MPEG, etc. And then on the bus 53. The image information placed on the bus 53 is temporarily stored in the RAM 52, and is output to the memory card interface 41 as necessary, and stored in the memory card 40 by the memory card interface 41, or the display control unit 54. Is displayed on the liquid crystal display panel 22. In addition, audio information recorded through the microphone 32 at the same time as shooting is also temporarily stored in the RAM 52 together with image information via the audio codec 70, stored in the memory card 40, and displayed on the liquid crystal display panel 22. At the same time, it is output from the speaker 23 via the audio codec 70. Furthermore, the image information and the sound information are output to the infrared interface 55 as necessary, and output to the outside via the infrared communication unit 25 by the infrared interface 55, and a device including a similar infrared communication unit, For example, it is transmitted to an external information device such as a mobile phone, a personal computer, or a PDA (Personal Digital Assistance). When displaying a moving image or a still image on the liquid crystal display panel 22 based on the image information stored in the RAM 52 or the memory card 40, the camera control unit 60 decodes the file stored in the RAM 52 or the memory card 40. The image data after decompression is sent to the display control unit 54 via the bus 53.

  The communication control unit 80 transmits and receives radio waves to and from the base station via the antenna 21. In the voice call mode, the received voice information is processed and then output to the speaker 23 via the voice codec 70. The voice collected by the microphone 32 is received via the voice codec 70, subjected to predetermined processing, and transmitted.

  Since the imaging lens 1a described above can be configured to have a short depth, the imaging lens 1a can be easily mounted on a device having a limited thickness such as the mobile phone 10. In the above embodiment, an example in which the imaging device of the present invention is applied to a mobile phone has been shown. However, the imaging device of the present invention can also be applied to other information devices such as personal computers and PDAs. Of course, it has a great advantage when applied to these information devices.

  It should be noted that the specific structures, shapes, and numerical values shown in the embodiments and numerical examples described above are only examples of the implementations that are carried out in carrying out the present invention, and thus the technology of the present invention. The scope should not be interpreted in a limited way.

  Since it is small in size, particularly short in overall length and high in performance, it is suitable for use in the purpose of acquiring images in small information devices such as mobile phones, PDAs, personal computers and the like.

It is a figure which shows the lens structure of the 1st Example of this invention imaging lens. FIG. 4 is a spherical aberration diagram, astigmatism diagram, and distortion diagram in Numerical Example 1 in which specific numerical values are applied to the first example. It is a figure which shows the lens structure of the 2nd Example of this invention imaging lens. FIG. 10 is a spherical aberration diagram, astigmatism diagram, and distortion diagram in Numerical Example 2 in which specific numerical values are applied to the second example. It is a figure which shows the lens structure of the 3rd Example of this invention imaging lens. FIG. 10 is a spherical aberration diagram, astigmatism diagram, and distortion diagram in Numerical Example 3 in which specific numerical values are applied to the third example. 8 and 9 show an embodiment in which the imaging apparatus of the present invention is applied to a mobile phone, and this figure is a perspective view showing an appearance in a folded state. It is a perspective view which shows a use condition. It is a block diagram.

Explanation of symbols

  G1 ... 1st lens, G2 ... 2nd lens, IR ... Aperture stop, 10 ... Mobile phone (imaging device), 1a ... Imaging lens, 1b ... Imaging element

Claims (12)

A meniscus first lens having a convex surface facing the object side, an aperture stop, and a meniscus second lens having a positive refractive power facing the image side are arranged in order from the object side. An imaging lens that satisfies the following conditional expressions (1), (2), and (3):
(1) -0.25 <f / f1 <0.50
(2) 1.38 <L / f <1.58
(3) 1.6 ≦ n (ave) ≦ 1.7
However,
f: Focal length of the entire lens system f1: Focal length of the first lens L: Distance from the object-side surface of the first lens to the image plane (however, the back insertion glass is calculated by the thickness in terms of air)
n (ave): The average value of the refractive indexes at the d-line of the two lenses constituting the lens system. The imaging lens according to claim 1, wherein the object side surface of the second lens satisfies the following conditional expression (4).
(4) 0.75 <R3 / f <1.60
However,
f: focal length of entire lens system R3: radius of curvature of object side surface of second lens. 2. The imaging lens according to claim 1, wherein at least an object-side surface of the first lens and an image-side surface of the second lens have an aspherical shape. The imaging lens according to claim 2, wherein at least an object-side surface of the first lens and an image-side surface of the second lens are aspherical. The imaging lens according to claim 3, wherein the object side surface of the first lens satisfies the following conditional expression (5).
(5) 55 ° <| θ1 (h) | <80 °
However,
θ1 (h): inclination of the object-side surface of the first lens at height h (= D1 / 2) D1: an effective diameter of the object-side surface of the first lens. The imaging lens according to claim 4, wherein the object side surface of the first lens satisfies the following conditional expression (5).
(5) 55 ° <| θ1 (h) | <80 °
However,
θ1 (h): inclination of the object-side surface of the first lens at height h (= D1 / 2) D1: an effective diameter of the object-side surface of the first lens. A meniscus first lens having a convex surface facing the object side, an aperture stop, and a meniscus second lens having a positive refractive power facing the image side are arranged in order from the object side. An imaging lens,
An imaging apparatus including an imaging element that converts an optical image formed by the imaging lens into an electrical signal,
An imaging apparatus, wherein the imaging lens satisfies the following conditional expressions (1), (2), and (3).
(1) -0.25 <f / f1 <0.50
(2) 1.38 <L / f <1.58
(3) 1.6 ≦ n (ave) ≦ 1.7
However,
f: Focal length of the entire lens system f1: Focal length of the first lens L: Distance from the object-side surface of the first lens to the image plane (however, the back insertion glass is calculated by the thickness in terms of air)
n (ave): The average value of the refractive indexes at the d-line of the two lenses constituting the lens system. The imaging apparatus according to claim 7, wherein an object side surface of the second lens satisfies the following conditional expression (4).
(4) 0.75 <R3 / f <1.60
However,
f: focal length of entire lens system R3: radius of curvature of object side surface of second lens. The imaging apparatus according to claim 7, wherein at least an object-side surface of the first lens and an image-side surface of the second lens are aspherical. The imaging apparatus according to claim 8, wherein at least an object-side surface of the first lens and an image-side surface of the second lens are formed in an aspherical shape. The imaging apparatus according to claim 9, wherein the object side surface of the first lens satisfies the following conditional expression (5).
(5) 55 ° <| θ1 (h) | <80 °
However,
θ1 (h): inclination of the object-side surface of the first lens at height h (= D1 / 2) D1: an effective diameter of the object-side surface of the first lens. The imaging apparatus according to claim 10, wherein the object side surface of the first lens satisfies the following conditional expression (5).
(5) 55 ° <| θ1 (h) | <80 °
However,
θ1 (h): inclination of the object-side surface of the first lens at height h (= D1 / 2) D1: an effective diameter of the object-side surface of the first lens.

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