JP6982276B2 - Imaging optical system and imaging device - Google Patents

Description

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

In recent years, the computerization of mirrors mounted on automobiles has progressed, and the demand for relatively small and wide-angle imaging optical systems suitable for rearview mirrors and door mirrors has increased. In particular, in the case of a rear-view mirror, the camera may be mounted on the ceiling of the car or the upper part of the rear window, and it is assumed that the camera will be exposed to harsh environmental temperatures. An imaging optical system has been proposed in consideration of such stability with respect to an environmental temperature (see Patent Document 1).

However, the image pickup optical system of Patent Document 1 has a narrow horizontal angle of view of about 2ω = 60 degrees and a relatively large number of lenses of 7, which is insufficient for miniaturization.

Japanese Unexamined Patent Publication No. 2016-142767

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

Another object of the present invention is to provide an image pickup apparatus provided with the above-mentioned image pickup optical system.

In order to achieve the above object, the imaging optical system according to the present invention applies a first lens having a negative power, a second lens, a third lens having a positive power, and a negative power in order from the object side. The fourth lens having a positive power and the fifth lens having a positive power are substantially formed, the half angle of view is 40 degrees or more, the paraxial curvature of the surface of the second lens on the object side is negative, and the second lens is present. 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 apex of the side surface of the object of the first lens to the image plane along the optical axis.

According to the image pickup 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 collects light with the first lens. It has the role of appropriately condensing the collected light and guiding it to the fourth and subsequent lenses. As a result, the second lens can be focused on the role of correcting various aberrations such as astigmatism. Further, by combining the 4th lens and the 5th lens with negative and positive combinations, chromatic aberration can be corrected, and the half angle of view is as wide as 40 degrees or more, but the optical system as a whole is high. Performance can be improved.

Further, by making the paraxial curvature or the paraxial radius of curvature on the side surface of the object and the side surface of the image of the second lens negative, the second lens receives the light without giving a large refractive power to the light emitted from the first lens. , Light can be emitted to the third lens without giving a large refractive power. As a result, the second lens has a role of correcting the aberration without deteriorating it.

Further, when the value f / TTL of the conditional expression (1) is less than 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 can be obtained. Obtainable. On the other hand, when the value f / TTL of the conditional expression (1) exceeds the above lower limit, the optical system does not become too large and the optical system can be miniaturized.

In the imaging optical system according to the present invention, all the lenses from the first lens to the fifth lens are made of glass and satisfy the following conditional expression.
4.5 × ^10-6 <dn / dT (L1) <5.0 × ^10-6 … (2)
dn / dT (L3)> 0.0 × ^10-6 … (3)
-6.5 x ^10-6 <dn / dT (L5) <-5.0 x ^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. It is a temperature change coefficient [1 / K], and the value dn / dT (L5) is a 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, so that it depends on the temperature change. It is possible to almost cancel the change in 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 carried out by the conditional expression (2) and (3) can be further adjusted, and good optical performance can be maintained. can.

If all of the lenses from the first lens to the fifth lens Ru made of glass, glass by linear expansion coefficient than the resin material is small, it can have high stability optical system to temperature changes ..

In yet another aspect of the invention, the third lens has the strongest power of the first to fifth lenses. In this case, the third lens is responsible for most of the focusing function as the imaging optical system, and the first, second, fourth, and fifth lenses can be arranged as roles other than the focusing function. .. This makes it possible to obtain high-performance optical characteristics.

The imaging optical system according to any one of claims 1 to 4, further comprising satisfying the following conditional expression.
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), an excessive refractive force is not applied to the incident light and the emitted light of the second lens, and the light from the first lens aggravates the aberration. It can be guided into the second lens without any deterioration, and light can be transmitted from the second lens to the third lens without aggravating the aberration. As a result, it is possible to reduce the occurrence of unnecessary aberrations and maintain the optical performance.

In order to achieve the above object, the image pickup apparatus according to the present invention includes the above-mentioned image pickup optical system and an image pickup element for photographing an image of the image pickup optical system.

According to the above-mentioned image pickup apparatus, by providing the above-mentioned image pickup optical system, a wide angle of view is secured in spite of its small size, it has good optical performance, and it has high stability against changes in environmental temperature. It can be.

It is a figure explaining the lens unit and the image pickup apparatus provided with the image pickup optical system of one Embodiment of this invention. (A) is a cross-sectional view of the image pickup optical system of Example 1, and FIGS. (B) to (D) are aberration diagrams. (A) is a cross-sectional view of the image pickup optical system of Example 2, and FIGS. (B) to (D) are aberration diagrams.

FIG. 1 is a cross-sectional view illustrating an image pickup apparatus 100 according to an embodiment of the present invention. The image pickup apparatus 100 includes a camera module 30 that forms an image signal, and a processing unit 60 that exerts a function as the image pickup apparatus 100 by operating the camera module 30.

The camera module 30 includes a lens unit 40 having a built-in image pickup optical system 10 and a sensor unit 50 that converts a subject image formed by the image pickup optical system 10 into an image signal.

The lens unit 40 includes an image pickup optical system 10, which is a wide-angle optical system, and a lens barrel 41 that supports the image pickup optical system 10. The image pickup optical system 10 is composed of 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 houses and holds a lens or the like inside. When the lens barrel 41 is formed of a metal or a resin mixed with glass fiber, it is less likely to undergo thermal expansion than the resin, and the imaging optical system 10 can be stably fixed. The lens barrel 41 has an opening OP for incident light from the object side.

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 flanges or outer peripheral portions, and are directly or indirectly held in the optical axis AX direction and light. Positioning is performed in the 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 ST and the filter F1.

The sensor unit 50 includes a solid-state image pickup element 51 that photoelectrically converts a subject image formed by the image pickup optical system (wide-angle optical system) 10, a substrate 52 that supports the solid-state image pickup element 51, and a solid-state image pickup element via the substrate 52. A sensor holder 53 for holding the 51 is provided. The solid-state image sensor 51 is, for example, a CMOS type image sensor. The substrate 52 includes wiring, peripheral circuits, and the like for operating the solid-state image sensor 51. The sensor holder 53 is made of resin or other material, and positions the solid-state image sensor 51 with respect to the optical axis AX. The lens barrel 41 of the lens unit 40 is fixed so as to be fitted to the sensor holder 53.

The solid-state image sensor (image sensor) 51 has a photoelectric conversion unit 51a as an image pickup 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 image sensor 51 is not limited to the CMOS type image sensor described above, and may incorporate another image sensor such as a CCD.

A filter or the like can be arranged 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 arranged between the fifth lens L5 of the image pickup optical system 10 and the solid-state image pickup element 51. The filter F1 is a parallel flat plate assuming an optical low-pass filter, an IR cut filter, a seal glass of the solid-state image sensor 51, and the like. The filter F1 may be arranged as a separate filter member, but it is not arranged as a separate body, and the function can 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 a plurality of lenses.

The processing unit 60 includes an element drive unit 61, an input unit 62, a storage unit 63, a display unit 64, and a control unit 68. The element drive unit 61 operates the solid-state image pickup element 51 by outputting a control signal to a circuit or the like attached to the solid-state image pickup element 51. The element drive unit 61 receives a voltage or clock signal for driving the solid-state image sensor 51 from the control unit 68, and outputs a YUV or other digital pixel signal corresponding to the output signal of the solid-state image sensor 51 to an external circuit. You can also do it. The input unit 62 is a part that accepts user operations, the storage unit 63 is a part that stores information necessary for the operation of the image pickup apparatus 100, image data acquired by the camera module 30, and the display unit 64. It is a part that displays information to be presented to the user, captured images, and the like. The control unit 68 comprehensively 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 the image data obtained by, for example, the camera module 30. .. When the image pickup device 100 is used as, for example, an in-vehicle camera, appropriate image processing is performed to display an image to the driver.

Although 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 image pickup apparatus 100 is incorporated. The image pickup device 100 can be mounted on devices for various purposes such as an in-vehicle camera and a surveillance camera.

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

The illustrated imaging optical system (wide-angle optical system) 10 has a first lens L1 having a negative power, a second lens L2, a third lens L3 having a positive power, and a negative power in order from the object side. It is substantially composed of a fourth lens L4 having a positive power and a fifth lens L5 having a positive power. Here, the negative first lens has a role of collecting light having a wide angle of view, and the positive third lens L3 appropriately collects the light collected by the first lens L1 and sandwiches the aperture ST. That is, it has a role of leading to the lenses L4, L5 and the like after the fourth lens L4. As a result, the second lens L2 can be narrowed down to the role of correcting various aberrations such as astigmatism. Further, by combining the fourth lens L4 and the fifth lens L5 with negative and positive combinations, chromatic aberration can be corrected, and the half angle of view is as wide as 40 degrees or more, but the entire optical system as a whole. It is possible to improve the performance of the lens. Further, 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 radius of curvature on the side surface of the object and the side surface of the image of the second lens L2 negative, the second lens L2 emits light without giving a large refractive power to the light emitted from the first lens L1. It can receive and emit light to the third lens L3 without giving a large refractive power. That is, the second lens L2 has a role of correcting the aberration without deteriorating it.

In the present imaging optical system (wide-angle optical system) 10, the third lens L3 has the strongest power among the first lens L1 and the fifth lens L5. Here, the strength of power is compared by an absolute value. In this case, the third lens L3 is responsible for most of the light-collecting function of the image pickup optical system 10, and the first, second, fourth, and fifth lenses L1, L2, L4, and L5 are focused. It can be arranged with a role other than. This makes it possible to obtain high-performance optical characteristics.

The first to fifth lenses L1 to L5 are made of glass. Since glass has a smaller coefficient of linear expansion than that of a resin material, the imaging optical system 10 can be an optical system having high stability against temperature changes. In particular, when it is assumed that the first lens L1 is used in a harsh environment such as an in-vehicle camera or a surveillance camera, it is preferable to treat the side surface of the object of the first lens L1 to improve strength, scratch resistance, and chemical resistance, and it is water repellent. It is preferable to apply a coat or a hydrophilic coat. In the image pickup optical system 10 of the embodiment, in the second lens L2 and the fifth lens L5, the side surface of the object and the side surface of the image are aspherical surfaces, but the locations where the aspherical surfaces are arranged are not limited to the above, and may be increased or decreased as appropriate. be able to.

The image pickup 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 apex of the side surface of the object of the first lens L1 to the image plane or the imaging surface I along the optical axis AX. In the present specification, the value TTL is a distance that does not convert the filter F1 into air even if it is present, that is, an actual distance.

When the value f / TTL of the conditional expression (1) is less than the above upper limit value, the optical system does not become too small, 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 above lower limit value, the optical system does not become too large and the optical system can be miniaturized.

The image pickup optical system 10 satisfies the following conditional expressions (2) to (4).
4.5 × ^10-6 <dn / dT (L1) <5.0 × ^10-6 … (2)
dn / dT (L3)> 0.0 × ^10-6 … (3)
-6.5 x ^10-6 <dn / dT (L5) <-5.0 x ^10-6 ... (4)
Here, the value dn / dT (L1) is a 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 is a value dn / dT (1 / K). L3) is the 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 the value dn assuming a temperature of 20 ° C. to 40 ° C. / DT (L5) is a 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 changes. It is possible to almost cancel the change in the refractive power of the entire optical system due to the above. Further, when the value dn / dT (L5) satisfies the conditional expression (4), the cancellation result realized by the conditional expression (2) and (3) is further adjusted, and good optical performance as the image pickup optical system 10 is obtained. Can be maintained.

Conditional expression (3) for values dn / dT (L3) is of desirably set to 5.5 × ^{10 -6} [1 / K] or less, more preferably 1.0 × ^{10 -6} [1 / K] or higher And, ^{it shall be 5.0 × 10-6} [1 / K] or less .

The image pickup 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 side surface of the object 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), an excessive refractive force is not applied to the incident light and the emitted light of the second lens L2, and the aberration of the light from the first lens L1 is aggravated. It can be guided into the second lens L2 without causing the light to be transmitted, and light can be transmitted from the second lens L2 to the third lens L3 without aggravating the aberration. As a result, it is possible to reduce the occurrence of unnecessary aberrations, and it is possible to maintain the optical performance of the image pickup optical system 10.

The image pickup optical system 10 may further include other optical elements (for example, a lens, a filter member, etc.) having substantially no power.

Since the image pickup optical system 10 described above has the lens configuration as described above, the optical system is small and has a bright F number, yet a wide angle of view is secured, and it has good optical performance and high resolution. Moreover, it has high stability against 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 embodiment are as follows.
f: Focal length of the whole system F: F number 2w: Maximum total angle TTL: Optical total length R: Radius of curvature D: Axis top spacing Nd: Refraction coefficient of lens material with respect to d line vd: Abbe number of lens material Each Example In, the surface in which "*" is described after each surface number is a surface having an aspherical shape, and the aspherical shape has the apex of the surface as the origin and the X-axis in the optical axis direction, and the optical axis. The height in the vertical direction is defined as h and is represented by the following "Equation 1".

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

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

The data of the lens surface of the imaging optical system of Example 1 is shown in Table 1 below. In Table 1 and the like below, 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 aspherical coefficient of the lens surface of Example 1 is 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
4th 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
Page 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 = 1.89402E-07, A16 = -4.75915E-09
Page 11
K = -0.33189E + 02, A4 = -0.15927E-01, A6 = 0.46538E-02,
A8 = -0.10369E-02, A10 = 0.15702E-03, A12 = -0.14550E-04,
A14 = 0.773934E-06, A16 = -0.15535E-07

The 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 according to the first embodiment. The imaging optical system 10A has a negative power and a meniscus type first lens L1 that is convex toward the object side, a meniscus type second lens L2 that has a negative power and is convex toward the image side, and positive power. It includes a biconvex third lens L3, a meniscus-type fourth lens L4 having negative power and convex toward the object, and a biconvex fifth lens L5 having positive power. The second and fifth lenses L2 and L5 have an aspherical surface as an optical surface. The first to fifth lenses L1 to L5 are all made of glass. An aperture stop ST is arranged between the third lens L3 and the fourth lens L4. A filter F1 having an appropriate thickness is arranged between the fifth lens L5 and the solid-state image sensor 51. The filter F1 is a parallel flat plate assuming an optical low-pass filter, an IR cut filter, a seal glass of the solid-state image sensor 51, and the like. Reference numeral I indicates an image pickup surface which is a projection plane of the solid-state image pickup device 51. The same applies to the reference numerals F1 and I in the following examples.

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

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

The 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 aspherical coefficient of the lens surface of Example 2 is shown in Table 5 below.
[Table 5]
Third side
K = 0.76399E + 00, A4 = -0.34570E-03, A6 = -0.61748E-04,
A8 = 0.23425E-04, A10 = -0.41354E-05, A12 = 0.81764E-07,
A14 = 0.00000E + 00, A16 = 0.00000E + 00
4th side
K = -0.31129E + 01, A4 = 0.10753E-02, A6 = 0.119749E-04,
A8 = 0.15197E-04, A10 = -0.19415E-05, A12 = 0.97258E-07,
A14 = 0.00000E + 00, A16 = 0.00000E + 00
Page 10
K = 0.30518E + 01, A4 = 0.17640E-03, A6 = 0.99106E-04,
A8 = 0.12277E-04, A10 = -0.55739E-05, A12 = 0.78716E-06,
A14 = -4.68843E-08, A16 = 1.01483E-09
Page 11
K = 0.39541E + 00, A4 = 0.68150E-03, A6 = 0.26369E-03,
A8 = -0.71120E-04, A10 = 0.15424E-04, A12 = -0.18434E-05,
A14 = 0.11522E-06, A16 = -0.28316E-08

The single lens data of Example 2 is 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 according to the second embodiment. The imaging optical system 10B has a negative power and a meniscus type first lens L1 that is convex toward the object side, a meniscus type second lens L2 that has a negative power and is convex toward the image side, and positive power. It includes a biconvex third lens L3, a meniscus-type fourth lens L4 having negative power and convex toward the object, and a biconvex fifth lens L5 having positive power. The second and fifth lenses L2 and L5 have an aspherical surface as an optical surface. The first to fifth lenses L1 to L5 are all made of glass. An aperture stop ST is arranged between the third lens L3 and the fourth lens L4. A filter F1 having an appropriate thickness is arranged between the fifth lens L5 and the solid-state image sensor 51.

3 (B) to 3 (D) 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]

Although the image pickup optical system and the like have been described above according to the embodiment, the image pickup optical system according to the present invention is not limited to the above embodiment or the embodiment and can be variously modified. For example, in the above embodiment, the second lens L2 is not limited to the 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 pieces and gives them different roles when imaging with visible light or near-infrared light in applications such as in-vehicle cameras and surveillance cameras. It is also possible to take a configuration such as.

AX ... Optical axis, F1 ... Filter, I ... Imaging surface, L1 to L5 ... Lens, OP ... Aperture, 10,10A, 10B ... Imaging optical system, 30 ... Camera module, 40 ... Lens unit, 50 ... Sensor unit, 51 ... Solid-state image sensor, 60 ... Processing unit, 100 ... Image pickup device

Claims (4)

From the object side,
The first lens with negative power and
With the second lens
With a third lens that has positive power,
With the 4th lens with negative power,
The fifth lens with positive power and
From to substantial
The half angle of view is 40 degrees or more,
The paraxial curvature of the surface of the second lens on the object side is negative.
The paraxial curvature of the image-side surface of the second lens is negative.
All the lenses from the first lens to the fifth lens are made of glass.
An imaging optical system characterized by satisfying the following conditional expression.
0.2 <f / TTL <0.3 ... (1)
4.5 × ^10-6 <dn / dT (L1) <5.0 × ^10-6 … (2)
dn / dT (L3)> 0.0 × ^10-6 … (3)
-6.5 x ^10-6 <dn / dT (L5) <-5.0 x ^10-6 ... (4)
here,
f: Focal length of the entire imaging optical system TTL: Distance from the apex of the side surface of the object of the first lens to the image plane along the optical axis.
dn / dT (L1): Coefficient of variation of the refractive index of the d-line in the first lens
dn / dT (L3): Coefficient of variation of the refractive index of the d-line in the third lens
dn / dT (L5): Coefficient of variation of the refractive index of the d-line in the fifth lens The imaging optical system according to claim 1 , 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 and 2 , wherein the imaging optical system satisfies the following conditional expression.
0.08 <(R21 / R22) /f<0.16 ... (5)
here,
R21: Radius of curvature of the side surface of the object of the second lens R22: Radius of curvature of the side surface of the image of the second lens f: Focal length of the entire imaging optical system The imaging optical system according to any one of claims 1 to 3.
An image sensor that captures an image of the image pickup optical system and
An imaging device characterized by being provided with.

Images