JP2019124744A - Image capturing optical system and image capturing device - Google Patents

Abstract

To provide an image capturing optical system which is compact and yet offers a wide view angle, superior optical performance, and high stability against change in ambient temperature.SOLUTION: An image capturing optical system 10 substantially consists of a first lens L1 having negative power, second lens L2, third lens L3 having positive power, fourth lens L4 having negative power, and fifth lens L5 having positive power, arranged in order from the object side, and has a half view angle of 40 degrees or greater. An object-side surface of the second lens L2 has a negative paraxial curvature radius, and an image-side surface of the second lens L2 has a negative paraxial curvature radius. The image capturing optical system satisfies a condition expressed as: 0.2<f/TTL<0.3 ...(1), where f represents a focal length of the entire image capturing optical system, and TTL represents a distance from an apex of an object-side surface of the first lens L1 to an image plane along an optical axis AX.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a wide-angle type imaging optical system substantially consisting of five lenses, and an imaging apparatus including the same.

  In recent years, with the progress of computerization of mirrors mounted in automobiles, the demand for relatively small and wide-angle imaging optical systems suitable for rearview mirrors and door mirrors is increasing. In the case of a rearview mirror, in particular, a camera may be attached to the top of a car ceiling or a rear window, and it is assumed that the camera is exposed to severe environmental temperatures. There has been proposed an imaging optical system in consideration of such stability against environmental temperature (see Patent Document 1).

  However, the imaging optical system of Patent Document 1 is insufficient for downsizing because the horizontal angle of view is as narrow as 2ω = 60 degrees and the number of lenses is relatively large as seven.

JP, 2016-142767, A

  In view of the above circumstances, it is an object of the present invention to provide an imaging optical system which is compact but has a wide angle of view, has good optical performance, and has high stability against changes in environmental temperature. I assume.

  Another object of the present invention is to provide an imaging device provided with the above-described imaging optical system.

In order to achieve the above object, the imaging optical system according to the present invention comprises, in order from the object side, a first lens having negative power, a second lens, a third lens having positive power, and negative power Substantially consisting of a fourth lens having a positive power and a fifth lens having a positive power, the half angle of view being at least 40 degrees, and the paraxial curvature of the object-side surface of the second lens being negative; The paraxial curvature of the surface on the image side of the two lenses is negative, and the following conditional expression is satisfied.
0.2 <f / TTL <0.3 (1)
Here, the value f is the focal length of the entire imaging optical system, and the value TTL is the distance from the object side surface apex of the first lens to the image plane along the optical axis.

  According to the above imaging optical system, by making the first lens negative and the third lens positive, the first lens has a role of collecting light with a wide angle of view, and the third lens is collected by the first lens. Plays a role of properly collecting the light and guiding it to the fourth and subsequent lenses. Thereby, the second lens can be narrowed down to the role of correcting various aberrations such as astigmatism. Also, by making the fourth lens and the fifth lens a combination of negative and positive, it is possible to correct the chromatic aberration, and while the half angle of view is a wide angle of 40 degrees or more, the overall height of the optical system is high. Performance can be achieved.

  In addition, by making the paraxial curvature or the paraxial curvature radius on the object side surface and the image side surface of the second lens negative, the second lens receives light without giving large refracting power to the light emitted from the first lens. The light can be emitted to the third lens without giving a large refractive power. Thereby, the second lens has a role of correcting without deteriorating the aberration.

  In addition, when the value f / TTL of the conditional expression (1) falls below the above-mentioned upper limit, the optical system does not become too small, and a sufficient lens configuration for correcting various aberrations can be obtained. You can get it. On the other hand, when the value f / TTL of the conditional expression (1) exceeds the lower limit, the optical system does not become too large, and the optical system can be miniaturized.

According to one specific aspect of the present invention, the following conditional expression is satisfied according to the imaging optical system.
dn / dT (L1)> 3.0 × 10 ⁻⁶ (2)
dn / dT (L3)> 0.0 × 10 ⁻⁶ (3)
dn / dT (L5) <0.0 × 10 ^-6 (4)
Here, the value dn / dT (L1) is the temperature change coefficient [1 / K] of the refractive index of the d-line in the first lens, and the value dn / dT (L3) is the refractive index of the d-line in the third lens The temperature change coefficient [1 / K], and the value dn / dT (L5) is the temperature change coefficient [1 / K] of the refractive index of the d-line in the fifth lens.

  When the values dn / dT (L1) and dn / dT (L3) satisfy the conditional expressions (2) and (3), the first lens is negative and the third lens is positive. The change in refractive power of the entire optical system can be substantially offset. In addition, when the value dn / dT (L5) satisfies the conditional expression (4), it is possible to further adjust the result of the offset implemented in the conditional expressions (2) and (3) and maintain good optical performance. it can.

  In another aspect of the present invention, all the lenses from the first lens to the fifth lens are made of glass. In this case, since the glass has a smaller linear expansion coefficient than the resin material, it is possible to form an optical system having high stability against temperature change.

  In yet another aspect of the present invention, the third lens has the strongest power among the first to fifth lenses. In this case, most of the light collecting function of the imaging optical system will be borne by the third lens, and the first, second, fourth, and fifth lenses can be arranged as roles other than light collection. . Thereby, high-performance optical characteristics can be obtained.

The imaging optical system according to any one of claims 1 to 4, wherein the following conditional expression is satisfied in still another aspect of the present invention.
0.08 <(R21 / R22) / f <0.16 (5)
Here, the value R21 is the radius of curvature of the object side surface of the second lens, and the value R22 is the radius of curvature of the image side surface of the second lens.

  When the value (R21 / R22) / f satisfies the conditional expression (5), excessive refractive power is not applied to the incident light and the outgoing light of the second lens, and the aberration from the light from the first lens is aggravated. The light can be introduced into the second lens, and light can be transmitted from the second lens to the third lens without deteriorating the aberration. As a result, the occurrence of unnecessary aberrations can be reduced, and optical performance can be maintained.

  In order to achieve the above-mentioned object, an imaging device concerning the present invention is provided with the above-mentioned imaging optical system and an image sensor which picturizes the picture of an imaging optical system.

  According to the above-described imaging apparatus, by providing the above-described imaging optical system, a wide angle of view can be secured while having a small size, and has good optical performance and high stability against changes in environmental temperature. It can be done.

It is a figure explaining a lens unit provided with an imaging optical system of one embodiment of the present invention, and an imaging device. (A) is sectional drawing of the imaging optical system of Example 1, etc., (B)-(D) is an aberrational figure. (A) is sectional drawing of the imaging optical system of Example 2, etc., (B)-(D) is an aberrational figure.

  FIG. 1 is a cross-sectional view for explaining an imaging device 100 according to an embodiment of the present invention. The imaging device 100 includes a camera module 30 that forms an image signal, and a processing unit 60 that causes the camera module 30 to operate to exhibit a function as the imaging device 100.

  The camera module 30 includes a lens unit 40 having the imaging optical system 10 therein, and a sensor unit 50 for converting an object image formed by the imaging optical system 10 into an image signal.

  The lens unit 40 includes an imaging optical system 10 that is a wide-angle optical system, and a lens barrel 41 that supports the imaging optical system 10. The imaging optical system 10 includes first to fifth lenses L1 to L5. The lens barrel 41 is made of resin, metal, a mixture of resin and glass fiber, or the like, and a lens or the like is housed and held inside. When the lens barrel 41 is formed of metal or resin mixed with glass fiber, it is less likely to thermally expand than the resin, and the imaging optical system 10 can be stably fixed. The lens barrel 41 has an opening OP through which light from the object side is incident.

  The total angle of view of the imaging optical system 10 is 80 ° or more. The first to fifth lenses L1 to L5 constituting the imaging optical system 10 are directly or indirectly held on the inner surface side of the lens barrel 41 at their flange portions or outer peripheral portions, and the optical axis AX direction and the light Positioning is performed in a direction perpendicular to the axis AX. The lens barrel 41 also supports optical elements other than the lenses L1 to L5, such as the aperture stop ST and the filter F1.

  The sensor unit 50 includes a solid-state imaging device 51 that photoelectrically converts an object image formed by the imaging optical system (wide-angle optical system) 10, a substrate 52 that supports the solid-state imaging device 51, and a solid-state imaging device And a sensor holder 53 for holding the sensor 51. The solid-state imaging device 51 is, for example, a CMOS type image sensor. The substrate 52 includes wires for operating the solid-state imaging device 51, peripheral circuits, and the like. The sensor holder 53 is formed of a resin or other material, and positions the solid-state imaging device 51 with respect to the optical axis AX. The lens barrel 41 of the lens unit 40 is fixed in a state of being positioned so as to be fitted to the sensor holder 53.

  The solid-state imaging device (imaging device) 51 includes a photoelectric conversion unit 51a as an imaging surface I, and a signal processing circuit (not shown) is formed around the photoelectric conversion unit 51a. Pixels, that is, photoelectric conversion elements are two-dimensionally arranged in the photoelectric conversion unit 51a. The solid-state imaging device 51 is not limited to the above-described CMOS-type image sensor, and may be one incorporating another imaging device such as a CCD.

  A filter or the like can be disposed between the lenses constituting the lens unit 40 or between the lens unit 40 and the sensor unit 50. In the example of FIG. 1, the filter F1 is disposed between the fifth lens L5 of the imaging optical system 10 and the solid-state imaging device 51. The filter F1 is a parallel flat plate on which an optical low pass filter, an IR cut filter, a seal glass of the solid-state imaging device 51, and the like are assumed. The filter F1 may be disposed as a separate filter member, but may not be separately disposed, and the function may be imparted to any lens surface constituting the imaging optical system 10. For example, in the case of an infrared cut filter, an infrared cut coat may be applied on the surface of one or more lenses.

  The processing unit 60 includes an element driving unit 61, an input unit 62, a storage unit 63, a display unit 64, and a control unit 68. The element driving unit 61 operates the solid-state imaging element 51 by outputting a control signal to a circuit or the like associated with the solid-state imaging element 51. The element driving unit 61 receives supply of a voltage and a clock signal for driving the solid-state imaging device 51 from the control unit 68, and outputs YUV and other digital pixel signals corresponding to the output signal of the solid-state imaging device 51 to an external circuit. You can also The input unit 62 is a unit for receiving user's operation, the storage unit 63 is a unit for storing information necessary for the operation of the imaging device 100, image data acquired by the camera module 30, etc. The display unit 64 is It is a part that displays information to be presented to the user, a photographed image, and the like. The control unit 68 integrally controls the operations of the element drive unit 61, the input unit 62, the storage unit 63, and the like, and can perform various image processing on image data obtained by the camera module 30, for example. . When the imaging device 100 is used as, for example, an on-vehicle camera, appropriate image processing is performed to display an image on the driver.

  Although a detailed description is omitted, the specific function of the processing unit 60 is appropriately adjusted according to the application of the device in which the imaging device 100 is incorporated. The imaging device 100 can be mounted on a device for various uses such as an on-vehicle camera and a surveillance camera.

  Hereinafter, the imaging optical system (wide-angle optical system) 10 and the like of the first embodiment will be described with reference to FIG. The imaging optical system 10 illustrated in FIG. 1 has substantially the same configuration as an imaging optical system 10A of Example 1 described later.

  The illustrated imaging optical system (wide-angle optical system) 10 includes, in order from the object side, a first lens L1 having negative power, a second lens L2, a third lens L3 having positive power, and negative power And a fifth lens L5 having a positive power. Here, the negative first lens has a role of collecting light with a wide angle of view, and the positive third lens L3 appropriately condenses the light collected by the first lens L1, and a rear group that sandwiches the diaphragm ST. That is, it has a role of leading to the lenses L4, L5, etc. after the fourth lens L4. Thereby, the second lens L2 can be narrowed to the role of correcting various aberrations such as astigmatism. Also, by making the fourth lens L4 and the fifth lens L5 a combination of negative and positive, it is possible to correct the chromatic aberration, and while the half angle of view is a wide angle of 40 degrees or more, as the entire optical system The high performance of Furthermore, the paraxial curvature of the object side surface of the second lens L2 is negative, and the paraxial curvature of the image side surface of the second lens L2 is also negative. By making the paraxial curvature or the paraxial curvature radius on the object side surface and the image side surface of the second lens L2 negative, the second lens L2 does not give a large refracting power to the light emitted from the first lens L1. The light can be emitted to the third lens L3 without being received and given a large refractive power. That is, the second lens L2 has a role of correcting without deteriorating the aberration.

  In the present imaging optical system (wide-angle optical system) 10, the third lens L3 has the strongest power among the first lens L1 to the fifth lens L5. Here, the strength of the power is compared by the absolute value. In this case, the third lens L3 bears most of the condensing function as the imaging optical system 10, and the first, second, fourth, and fifth lenses L1, L2, L4, and L5 are condensed. It can be arranged to have other roles. Thereby, high-performance optical characteristics can be obtained.

  The first to fifth lenses L1 to L5 are formed of glass. Glass has a smaller linear expansion coefficient than a resin material, so the imaging optical system 10 can be an optical system having high stability against temperature change. In particular, in the case where use in a harsh environment such as an on-vehicle camera or a surveillance camera is assumed, it is preferable to subject the object side surface of the first lens L1 to a treatment for enhancing strength, scratch resistance and chemical resistance, It is preferable to apply a coat or a hydrophilic coat. In the imaging optical system 10 according to the embodiment, the object side surface and the image side surface are aspheric in the second lens L2 and the fifth lens L5, but the location where the aspheric surface is disposed is not limited to the above, and may be appropriately increased or decreased. be able to.

The imaging optical system 10 satisfies the following conditional expression (1).
0.2 <f / TTL <0.3 (1)
Here, the value f is the focal length of the entire imaging optical system 10, and the value TTL is the distance from the object side surface apex of the first lens L1 to the image plane or imaging plane I along the optical axis AX.

  When the value f / TTL of the conditional expression (1) falls below the above upper limit, the optical system does not become too small, and a sufficient lens configuration for correcting various aberrations can be obtained, and high performance characteristics are obtained. be able to. On the other hand, when the value f / TTL of the conditional expression (1) exceeds the lower limit value, the optical system does not become too large, and the optical system can be miniaturized.

The imaging optical system 10 satisfies the following conditional expressions (2) to (4).
dn / dT (L1)> 3.0 × 10 ⁻⁶ (2)
dn / dT (L3)> 0.0 × 10 ⁻⁶ (3)
dn / dT (L5) <0.0 × 10 ^-6 (4)
Here, the value dn / dT (L1) is the temperature change coefficient [1 / K] of the refractive index of the d-line in the first lens L1 assuming a temperature of 20 ° C. to 40 ° C., and the value dn / dT (L1) L3) is a temperature change coefficient [1 / K] of the refractive index of the d-line in the third lens L3 assuming a temperature of 20 ° C. to 40 ° C., and a value dn assuming a temperature of 20 ° C. to 40 ° C. / DT (L5) is the temperature change coefficient [1 / K] of the refractive index of the d-line in the fifth lens L5.

  When the values dn / dT (L1) and dn / dT (L3) satisfy the conditional expressions (2) and (3), the first lens L1 is negative and the third lens L3 is positive, so that the temperature change is Can substantially cancel the change of the refractive power of the entire optical system. Further, when the value dn / dT (L5) satisfies the conditional expression (4), the result of the cancellation realized by the conditional expressions (2) and (3) is further adjusted, and the optical performance as the imaging optical system 10 is good. Can be maintained.

The value dn / dT (L1) of the conditional expression (2) is desirably 6.0 × 10 ⁻⁶ [1 / K] or less, more desirably 4.5 × 10 ⁻⁶ [1 / K] or more, And it shall be 5.0 × 10 ⁻⁶ [1 / K] or less. Further, the value dn / dT (L3) of the conditional expression (3) is desirably 5.5 × 10 ⁻⁶ [1 / K] or less, and more desirably 1.0 × 10 ⁻⁶ [1 / K]. The above condition is 5.0 × 10 ⁻⁶ [1 / K] or less. The value dn / dT (L5) in the conditional expression (4) is desirably −7.0 × 10 ⁻⁶ [1 / K] or more, and more desirably −6.5 × 10 ⁻⁶ [1 / K]. Above, and -5.0 ^10-6 [1 / K] or less.

The imaging optical system 10 satisfies the following conditional expression (5).
0.08 <(R21 / R22) / f <0.16 (5)
Here, the value R21 is the radius of curvature of the object side surface of the second lens L2, and the value R22 is the radius of curvature of the image side surface of the second lens. The unit of the value (R21 / R22) / f is 1 / mm.

  When the value (R21 / R22) / f satisfies the conditional expression (5), excessive refractive power is not applied to the incident light and the outgoing light of the second lens L2, and the light from the first lens L1 is aberrated. The light can be introduced into the second lens L2 without being caused, and light can be transmitted from the second lens L2 to the third lens L3 without aggravating the aberration. As a result, generation of unnecessary aberrations can be reduced, and optical performance of the imaging optical system 10 can be maintained.

  The imaging optical system 10 may further include another optical element (for example, a lens, a filter member, and the like) having substantially no power.

  The imaging optical system 10 described above has a lens configuration as described above, so while having a small size and a bright F-number, a wide angle of view can be secured, and it has good optical performance and high resolution. And have high stability to changes in environmental temperature.

ただし、
Ａｉ：ｉ次の非球面係数
Ｒ ：曲率半径
Ｋ ：円錐定数 〔Example〕
Hereinafter, examples of the imaging optical system and the like of the present invention will be shown. The symbols used in each example are as follows.
f: Focal length of the whole system F: F number 2w: Maximum total angle of view TTL: Optical total length R: Curvature radius D: Axial top surface distance Nd: Refractive index vd for d-line of lens material Abbe number example of lens material In each of the surface numbers, the surface indicated by “*” after the surface number is a surface having an aspheric shape, and the shape of the aspheric surface has the vertex of the surface as the origin and takes the X axis in the optical axis direction. And the height in the vertical direction is denoted by "Equation 1" below.

However,
Ai: i-th order aspheric coefficient R: radius of curvature K: conical constant

Example 1
The entire specifications of the imaging optical system of Example 1 are shown below.
f = 5.46 mm
F = 2.00
2w = 90.5 °
TTL = 23.0

Data of the lens surface of the imaging optical system of Example 1 is shown in Table 1 below. In the following Table 1 and the like, the surface number is represented by “Surf. N”, the aperture stop is represented by “ST”, and infinity is represented by “INF”.
[Table 1]
Surf. NR (mm) D (mm) Nd vd
1 10.171 1.800 1.77250 49.62
2 3.236 2.641
3 * -6.769 2.500 1.83441 37.28
4 *-9.970 0.200
5 21.468 2.487 1.74400 44.72
6-5.389-0.640
7 (ST) INF 2.525
8 26.947 0.600 1.94595 17.98
9 6.895 0.500
10 * 12.869 2.353 1.49710 81.55
11 * -6.053 0.500
12 INF 0.700 1.516798 64.19
13 INF 6.834

The aspheric coefficients of the lens surface of Example 1 are shown in Table 2 below. In the following it (including lens data in Tables), and represents an exponent of 10 (for example, 2.5 × ^{10 -02)} with E (e.g. 2.5E-02).
[Table 2]
Third side
K = 0.45406E + 01, A4 = 0.14301E-02, A6 = -0.61767E-04,
A8 = 0.12024E-03, A10 = -0.28394E-04, A12 = 0.32997E-05,
A14 = -1.24773E-07, A16 = 0.00000E + 00
Fourth side
K = -0.15205E + 02, A4 = 0.16527E-03, A6 = -0.44815E-04,
A8 = 0.90563E-04, A10 = -0.19032E-04, A12 = 0.18825E-05,
A14 = -7.14977E-08, A16 = 0.00000E + 00
Face 10
K = 0.68512E + 01, A4 = -0.59757E-03, A6 = 0.56013E-03,
A8 = -0.15395E-03, A10 = 0.28412E-04, A12 = -0.31270E-05,
A14 = 1.940202E-07, A16 = -4.75915E-09
11th
K = -0.33189E + 02, A4 = -0.15927E-01, A6 = 0.46583 E-02,
A8 = -0.10369E-02, A10 = 0.15702E-03, A12 = -0.14550E-04,
A14 = 0.73934E-06, A16 = -0.15535E-07

Single lens data of Example 1 is shown in Table 3 below.
[Table 3]
Lens start surface focal length (mm)
1 1-6.898
2 3-39.005
3 5 5.997
4 8-9.813
5 10 8.614

  FIG. 2A is a cross-sectional view of the imaging optical system 10A and the like of the first embodiment. The imaging optical system 10A has a negative power and a meniscus type first lens L1 convex on the object side, a negative power and a meniscus second lens L2 convex on the image side, and a positive power And a biconvex third lens L3 having a negative power and a meniscus type fourth lens L4 convex on the object side, and a positive power and a biconvex fifth lens L5. The second and fifth lenses L2 and L5 have an aspheric surface as an optical surface. The first to fifth lenses L1 to L5 are all formed of glass. An aperture stop ST is disposed between the third lens L3 and the fourth lens L4. A filter F1 of an appropriate thickness is disposed between the fifth lens L5 and the solid-state imaging device 51. The filter F1 is a parallel flat plate on which an optical low pass filter, an IR cut filter, a seal glass of the solid-state imaging device 51, and the like are assumed. Reference symbol I indicates an imaging surface which is a projection surface of the solid-state imaging device 51. In addition, about the code | symbol F1 and I, it is the same also in the subsequent Example.

  FIGS. 2B to 2D show aberration diagrams (spherical aberration, astigmatism, and distortion) of the imaging optical system 10A of the first embodiment.

(Example 2)
The entire specifications of the imaging optical system of Example 2 are shown below.
f = 5.51 mm
F = 2.00
2w = 90.5 °
TTL = 23.0

Data of the lens surface of the imaging optical system of Example 2 is shown in Table 4 below.
[Table 4]
Surf. NR (mm) D (mm) Nd vd
1 9.806 1.570 1.77250 49.62
2 3.332 2.871
3 *-6.353 2.575 1.83441 37.28
4 * -10.312 0.200
5 21.359 2.365 1.77250 49.62
6-5.719-0.622
7 (ST) INF 2.988
8 25.137 0.600 1.94595 17.98
9 7.262 0.500
10 * 12.244 2.250 1.49710 81.55
11 * -6.775 0.500
12 INF 0.700 1.516798 64.19
13 INF 6.500

The aspheric coefficients of the lens surface of Example 2 are shown in Table 5 below.
[Table 5]
Third side
K = 0.76399E + 00, A4 = -0.34570E-03, A6 = -0.61748E-04,
A8 = 0.223425E-04, A10 = -0.41354E-05, A12 = 0.81764E-07,
A14 = 0.00000E + 00, A16 = 0.00000E + 00
Fourth side
K = -0.31129E + 01, A4 = 0.10753E-02, A6 = 0.19749E-04,
A8 = 0.15197E-04, A10 = -0.19415E-05, A12 = 0.97258E-07,
A14 = 0.00000E + 00, A16 = 0.00000E + 00
Face 10
K = 0.30518E + 01, A4 = 0.17640E-03, A6 = 0.99106E-04,
A8 = 0.12277 E-04, A10 = -0.55739 E-05, A12 = 0.78716 E-06,
A14 = -4.68843E-08, A16 = 1.01483E-09
11th
K = 0.39541E + 00, A4 = 0.68150E-03, A6 = 0.26369E-03,
A8 = -0.71120E-04, A10 = 0.15244E-04, A12 = -0.18434E-05,
A14 = 0.11522 E-06, A16 =-0.28316 E-08

Single lens data of Example 2 are shown in Table 6 below.
[Table 6]
Lens start surface focal length (mm)
1 1-7.274
2 3-28.023
3 5 6.042
4 9-10. 835
5 11 9.107

  FIG. 3A is a cross-sectional view of the imaging optical system 10B and the like of the second embodiment. The imaging optical system 10B has a negative power and a meniscus type first lens L1 convex on the object side, a negative power and a meniscus second lens L2 convex on the image side, and a positive power And a biconvex third lens L3 having a negative power and a meniscus type fourth lens L4 convex on the object side, and a positive power and a biconvex fifth lens L5. The second and fifth lenses L2 and L5 have an aspheric surface as an optical surface. The first to fifth lenses L1 to L5 are all formed of glass. An aperture stop ST is disposed between the third lens L3 and the fourth lens L4. A filter F1 of an appropriate thickness is disposed between the fifth lens L5 and the solid-state imaging device 51.

  FIGS. 3B to 3D show aberration diagrams (spherical aberration, astigmatism, and distortion) of the imaging optical system 10B of the second embodiment.

Table 7 below summarizes the values of Examples 1 and 2 corresponding to the conditional expressions (1) to (5) for reference.
[Table 7]

  As mentioned above, although an imaging optical system etc. were explained according to an embodiment, an imaging optical system concerning the present invention is not restricted to the above-mentioned embodiment or an example, and various modification is possible. For example, in the above embodiment, the second lens L2 is not limited to one having a negative power, but may have a positive power.

  Further, in the above embodiment, the filter F1 divides the filter F1 into two sheets and takes different roles in imaging with visible light or near infrared light in applications such as a car-mounted camera and a surveillance camera. It is also possible to take the configuration of.

AX: optical axis, F1: filter, I: imaging surface, L1 to L5: lens, OP: 10, 10A, 10B: imaging optical system, 30: camera module, 40: lens unit, 50: sensor unit, 51 ... Solid-state imaging device, 60 ... Processing unit, 100 ... Imaging device

Claims (6)

In order from the object side,
A first lens having a negative power,
The second lens,
A third lens having a positive power,
A fourth lens having a negative power,
A fifth lens having a positive power,
Substantially from
Half angle of view is over 40 degrees,
The paraxial curvature of the object-side surface of the second lens is negative,
The paraxial curvature of the image-side surface of the second lens is negative,
An imaging optical system characterized by satisfying the following conditional expression.
0.2 <f / TTL <0.3 (1)
here,
f: Focal length of the entire imaging optical system TTL: Distance from the vertex of the object side surface of the first lens to the image plane along the optical axis The imaging optical system according to claim 1, wherein the following conditional expression is satisfied.
dn / dT (L1)> 3.0 × 10 ⁻⁶ (2)
dn / dT (L3)> 0.0 × 10 ⁻⁶ (3)
dn / dT (L5) <0.0 × 10 ^-6 (4)
here,
dn / dT (L1): temperature change coefficient of refractive index of d line in the first lens dn / dT (L3): temperature change coefficient of refractive index of d line in the third lens dn / dT (L5): the above Temperature variation coefficient of the refractive index of d-line in the fifth lens   The imaging optical system according to any one of claims 1 and 2, wherein all the lenses from the first lens to the fifth lens are made of glass.   The imaging optical system according to any one of claims 1 to 3, wherein the third lens has the strongest power among the first to fifth lenses. The imaging optical system according to any one of claims 1 to 4, which satisfies the following conditional expression.
0.08 <(R21 / R22) / f <0.16 (5)
here,
R21: radius of curvature of the object side surface of the second lens R22: radius of curvature of the image side surface of the second lens f: focal length of the entire imaging optical system An imaging optical system according to any one of claims 1 to 5;
An imaging element for capturing an image of the imaging optical system;
An imaging apparatus comprising:

Images