JP6725888B2 - Wide-angle optical system, lens unit, and imaging device - Google Patents

Description

The present invention relates to an image pickup wide-angle optical system suitable for a vehicle-mounted camera and the like, a lens unit having the wide-angle optical system, and an image pickup apparatus.

2. Description of the Related Art In recent years, image pickup devices such as CMOS and CCD have been downsized and the number of pixels has been increased, and image pickup devices equipped with these image pickup devices have also been downsized. At the same time, an imaging lens mounted on this type of imaging device is required to have both good optical performance and miniaturization. In particular, for in-vehicle and surveillance camera applications, small size, high performance, low cost, and wide angle are required, and further, environmental resistance for outdoor use tends to be emphasized.

Patent Documents 1 and 2 propose, as an imaging lens mounted on a vehicle-mounted camera, a wide-angle imaging lens composed of five lenses having a power arrangement starting from negative, negative, and positive in order from the object side. There is. Patent Document 1 proposes a wide-angle imaging lens that is easy to manufacture and has high performance by cementing a negative fourth lens and a positive fifth lens and optimizing the shape of the cemented surface. It is hard to say that it is small enough for the sensor. Further, in Patent Document 2, a configuration is proposed in which the fourth lens is positive, the fifth lens is negative, and the focal length of the front group and the focal length of the rear group are optimized to satisfy small size, high performance, and wide angle. However, the image side of the first lens is close to the processing limit around the effective diameter, and considering the margin of the optical surface considering the assembly error etc. It is hard to say.

JP, 2013-205715, A JP2012-88702A

The present invention has been made in view of the background art described above, and an object of the present invention is to provide a wide-angle optical system for imaging which is small in size, high in performance, wide-angle, and low in cost.

Another object of the present invention is to provide a lens unit and an image pickup apparatus having the wide-angle optical system as described above.

To achieve at least one of the above-mentioned objects, a wide-angle optical system that reflects one aspect of the present invention is made of glass having a convex shape on the object side and a concave shape on the image side in order from the object side, and both surfaces are spherical. A negative first lens, a negative second lens having an aspherical surface on at least one surface and having a concave shape on the image side, a positive third lens, a diaphragm, and a fourth lens having an aspherical surface on at least one surface. It substantially consists of a lens and a fifth lens having at least one aspherical surface, and satisfies the following conditional expression.
1.10≦D14/Hmax≦1.80 (1)
0.40≦D23/Hmax≦0.70 (2)
4.0≦TTL/Hmax≦5.5 (3)
4.0≦φ1/Hmax≦5.5 (4)
3.0≦R1/R2≦3.43 (6)
1.00≦D12/f≦1.2 (8)
here,
D14: Distance on the optical axis from the object side surface of the first lens to the image side surface of the second lens D23: Distance on the optical axis from the image side surface of the first lens to the object side surface of the second lens Hmax: Maximum image height ( The maximum image height corresponds to half the diagonal length of the detection surface of the image sensor.)
TTL: total optical length φ1: optical surface diameter of the object side surface of the first lens (the optical surface diameter means the diameter of a region where a spherical surface or an aspherical surface exists)
R1: radius of curvature of the object side surface of the first lens
R2: radius of curvature of image side surface of first lens D12: center thickness of first lens f: focal length of entire system

To achieve at least one of the above objects, a lens unit that reflects one aspect of the present invention includes the wide-angle optical system described above and a lens holder that holds the wide-angle optical system.

In order to achieve at least one of the above-described objects, an imaging device that reflects one aspect of the present invention includes the above-described lens unit and an imaging element that projects an image by the lens unit.

It is a figure explaining a lens unit and an imaging device which have a wide-angle optical system of a 1st embodiment. 5 is a cross-sectional view of the image pickup lens and the like of Example 1. FIG. 6 is a cross-sectional view of an image pickup lens and the like in Example 2. FIG. It is a figure explaining the lens unit etc. which are provided with the wide-angle optical system of 2nd Embodiment.

[First Embodiment]
FIG. 1 is a sectional view showing an image pickup apparatus 100 according to the first embodiment of the present invention. The image pickup apparatus 100 includes a camera module 30 for forming an image signal, and a processing unit 60 that causes the camera module 30 to operate to exhibit the function of the image pickup apparatus 100.

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

The lens unit 40 includes an imaging lens 10 that is a wide-angle optical system, and a lens holder 41 that incorporates the imaging lens 10. The imaging lens (wide-angle optical system) 10 is an ultra-wide-angle lens or a fish-eye lens, and includes five lenses L1 to L5. The lens holder 41 is made of resin or the like, and accommodates and holds the lens and the like inside. The lens holder 41 has an opening OP1 through which light from the object side is incident and an opening OP2 through which light rays are emitted toward the image side.

The total angle of view of the imaging lens (wide-angle optical system) 10 is 160° or more. Since the radial size of the optical system tends to increase as the angle of view increases, the details will be described later, but in the imaging lens 10 having the lens configuration according to the present embodiment, the total angle of view is 160° or more. When the value is extremely increased, the effect of miniaturization will be exhibited particularly. The total angle of view of the imaging lens 10 is preferably 170° or more.

Of the imaging lens (wide-angle optical system) 10, the first to fourth lenses L1 to L4 are in contact with the inner peripheral surface 41a of the lens holder 41 on the side surfaces (that is, the edges) of their flanges or outer peripheral portions, and Positioning is performed in the direction perpendicular to the axis AX. For example, in the case of the first lens L1, the side surface 4a of the flange portion (outer peripheral portion) 3a is in contact with the inner peripheral surface 41b of the portion of the lens holder 41 where the diameter and inner diameter are enlarged. The first to fifth lenses L1 to L5 are housed in the lens holder 41 without using a spacer. That is, the first to fifth lenses L1 to L5 are in contact with only the front and rear lenses, the aperture stop ST, the light-shielding stop FS, or the lens holder 41 by the annular flange portion extending substantially perpendicular to the optical axis AX, and are joined together. Bonded to each other by the agent. Here, the inter-lens facing surfaces of the first to fifth lenses L1 to L5 excluding the object side of the first lens L1 and the image side of the fifth lens L5, that is, mutual positioning is performed in the optical axis AX direction. The part is formed in a region other than the curved optical surface. Specifically, the image-side inter-lens facing surface 3a2 of the flange portion 3a of the first lens L1 is in contact with only the image-side inter-lens facing surface 3b1 of the flange portion 3b of the second lens L2. Similarly, the image-side facing surface of the second lens L2 is in contact with only the light blocking diaphragm FS. The object-side facing surface of the third lens L3 contacts only the light-shielding stop FS, and the image-side facing surface of the third lens L3 contacts only the aperture stop ST. The object-side facing surface of the fourth lens L4 contacts only the aperture stop ST, and the image-side facing surface of the fourth lens L4 contacts only the object-side facing surface of the fifth lens L5. However, the fourth lens L4 and the fifth lens L5 have a structure in which the outer circumference is fitted by the outer circumference fitting portion 5a provided on the flange portion 3e of the fourth lens L4. In this way, by adopting the structure in which the lenses are fitted to each other on the outer circumference, the relative movement of the two lenses L4 and L5 in the direction perpendicular to the optical axis AX is limited.

As described above, by adopting the structure in which the first to fifth lenses L1 to L5 are positioned by the flange portion without using the spacer, not only the cost can be reduced but also an extra assembly error can be suppressed. Further, by adopting a structure in which the fifth lens L5 is fitted to the flange portion 3e of the fourth lens L4 on the outer periphery, the coaxiality can be maintained, so that a lens shift error can be avoided and collision between optical surfaces can be avoided. it can. Although there is a risk that a thickness error or a lens tilt error will occur at the cemented portion between the fourth lens L4 and the fifth lens L5 due to the non-uniformity of the cementing agent thickness, the two lenses L4 and L5 are abutted against each other with their flanges. With the structure, the nonuniformity of the thickness of the bonding agent can be eliminated.

In the first lens L1 closest to the object side of the imaging lens 10, a step 6d is formed on the side surface 4a of the flange portion 3a, and an annular space is formed between the first lens L1 and the lens holder 41. .. An elastic waterproof member 2a, such as an O-ring, can be inserted into the annular space. The waterproof member 2a has a lower side surface portion 1a among the side surfaces 4a of the flange portion 3a and the inner circumference of the lens holder 41. It is sandwiched between the surface 41b and the surface 41b to hermetically seal the inside of the lens holder 41. The waterproof member 2a can prevent the force along the optical axis AX from being applied to the first lens L1 and the like.

The sensor unit 50 includes a solid-state imaging device 51 that photoelectrically converts a subject image formed by the imaging lens (wide-angle optical system) 10, a substrate 52 that supports the solid-state imaging device 51, and the solid-state imaging device 51 via the substrate 52. And a sensor holder 53 for holding. The solid-state image sensor 51 is, for example, a CMOS type image sensor. The substrate 52 includes wiring for operating the solid-state imaging device 51, peripheral circuits, and the like. The sensor holder 53 is made of resin or other material, and not only positions the solid-state image pickup element 51 with respect to the optical axis AX, but also supports the filter F so as to face the solid-state image pickup element 51. The sensor holder 53 is fixed in a state of being positioned so as to be fitted into the lens holder 41 of the lens unit 40. In the illustrated example, the lens unit 40 and the sensor unit 50 are integrally fixed, but not limited to this, for example, the lens unit 40 can be movable with respect to the sensor unit 50 to enable focusing.

The solid-state imaging device (imaging device) 51 has a photoelectric conversion unit 51a as an imaging surface I or a detection surface, 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, but may be one in which another image sensor such as a CCD is incorporated.

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 outputs YUV and other digital pixel signals to an external circuit (specifically, a circuit attached to the solid-state imaging device 51) or a voltage for driving the solid-state imaging device 51 from the control unit 68. The solid-state imaging device 51 is operated by receiving the supply of the clock signal. The input unit 62 is a unit that receives a user operation, the storage unit 63 is a unit that stores information necessary for the operation of the imaging device 100, image data acquired by the camera module 30, and the like, and the display unit 64 is This is a part for displaying information to be presented to the user, a captured image, and the like. The control unit 68 comprehensively controls the operations of the element driving unit 61, the input unit 62, the storage unit 63, and the like, and can perform various image processes on the image data obtained by the camera module 30, for example. ..

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

Hereinafter, the imaging lens (wide-angle optical system) 10 and the like of the first embodiment will be described with reference to FIG. The imaging lens 10 illustrated in FIG. 1 has the same configuration as the imaging lens 11 of Example 1 described later.

The illustrated imaging lens (wide-angle optical system) 10 is a retrofocus type optical system, and has a five-element configuration having a power arrangement starting from negative, negative, and positive in the order from the object side. More specifically, the imaging lens 10 includes, in order from the object side, a glass negative first lens L1 having a convex shape on the object side and a concave shape on the image side, and an image having an aspherical surface on at least one surface. A negative second lens L2 having a concave shape on the side, a light blocking diaphragm FS, a positive third lens L3, an aperture diaphragm ST, a fourth lens L4 having an aspherical surface on at least one surface, and at least one surface. And a fifth lens L5 having an aspherical surface.

The weather resistance of the first lens L1 arranged at a position exposed to the outside air is improved by making the first lens L1 from glass. Furthermore, by making the first lens L1 a glass lens having spherical surfaces on both sides that can be easily processed, the imaging lens 10 can be made more inexpensive. The second to fifth lenses L2 to L5 are plastic or resin lenses. Thereby, the imaging lens 10 can be made lightweight and inexpensive. The second, fourth and fifth lenses L2, L4 and L5 may be lenses made of plastic or resin, and the third lens L3 may be lenses made of glass. In the case of a fixed focus optical system that does not perform automatic focusing (AF), a focus shift due to a temperature change becomes a problem, but by using a glass lens as the third lens L3, the focus shift can be suppressed more effectively. When the third lens L3 is a plastic lens, the focus shift is, for example, about +24 μm/+30° C., and when the third lens L3 is a glass lens, the focus shift is, for example, about +2 μm/+30° C.

The first lens L1 is a negative aspherical lens whose object side surface L1S1 has a convex shape and which has a meniscus shape of being convex toward the object side on a paraxial line. The second lens L2 is a negative aspherical lens whose object side surface L2S1 has a convex shape and which has a meniscus shape of being convex toward the object side on a paraxial line. The third lens L3 is a positive aspherical lens having a paraxial biconvex shape. The fourth lens L4 is a negative aspherical lens whose object side surface is convex, whose image side surface is concave, and which has a meniscus shape which is convex toward the object side at a paraxial axis. The fifth lens L5 is a positive aspherical lens having a paraxial biconvex shape. Further, the fourth lens L4 and the fifth lens L5 are cemented. By configuring the fourth and fifth lenses L4 and L5 in this way, it is possible to preferably correct chromatic aberration.

For the second lens L2, the maximum surface angle within the effective diameter of the image side surface L2S2 is 60° or more. Here, the surface angle of the image side surface L2S2 is an angle formed by the normal line of the image side surface L2S2 with respect to the optical axis AX. Since the first lens L1 is made of glass, and the negative power that the first lens L1 can have is limited due to processing restrictions, the second lens L2 is large in order to favorably correct the field curvature in the entire system. It will have negative power. Therefore, it is desirable that the maximum surface angle of the image side surface L2S2 of the second lens L2 be as large as the above.

The imaging lens (wide-angle optical system) 10 satisfies the following conditional expressions (1) to (4).
1.10≦D14/Hmax≦1.80 (1)
0.40≦D23/Hmax≦0.70 (2)
4.0≦TTL/Hmax≦5.5 (3)
4.0≦φ1/Hmax≦5.5 (4)
Here, the value D14 is the distance on the optical axis AX from the object side surface L1S1 of the first lens L1 to the image side surface L2S2 of the second lens L2, and the value D23 is the second side from the image side surface L1S2 of the first lens L1. The value Hmax is the maximum image height, the value TTL is the optical total length, the value φ1 is the optical surface of the object side surface L1S1 of the first lens L1, and the value Hmax is the distance to the object side surface L2S1 of the lens L2 on the optical axis AX. Is the diameter. Regarding the value Hmax, the maximum image height corresponds to half the diagonal length of the detection surface or the imaging surface I of the solid-state imaging device 51. Further, with respect to the value φ1, the optical surface diameter means a diameter of a region where a spherical surface or an aspherical surface exists.

As described above, in the compact imaging lens (wide-angle optical system) 10 that has the power arrangement starting from negative, negative, and positive in order from the object side and satisfies the formulas (3) and (4), the formula (1) By satisfying both (1) and (2), it is possible to secure suitable optical performance with a low-cost wide-angle optical system having a small number of five lenses and using a glass spherical lens that is easy to process as the first lens L1. You can Specifically, in the wide-angle optical system having a five-lens configuration, the first and second lenses L1 and L2 can be obtained by satisfying the range of Expression (1) while adopting the configuration of the low-height lens as Expression (3). By arranging the total negative power of L2 at an appropriate position of the optical system, it is possible to secure the optical performance regarding aberration, telecentricity, back focus, and the like. Further, in the five-lens optical system, by adopting the configuration of the small-diameter lens as in the formula (4), the range of the formula (2) is satisfied, so that the interval between the first and second lenses L1 and L2 is appropriately set. It is possible to reduce the size to a small value and to secure the optical performance related to the aberration, the peripheral light amount ratio, and the like.

The imaging lens (wide-angle optical system) 10 further satisfies the following conditional expression (5).
0.65≦(D23+SAG3)/SAG2≦1.0 (5)
Here, the value D23 is the distance on the optical axis AX from the image side surface L1S2 of the first lens L1 to the object side surface L2S1 of the second lens L2, and the value SAG2 is the optical surface of the image side surface L1S2 of the first lens L1. The SAG amount at the end, and the value SAG3 is the SAG amount at the end of the optical surface of the object side surface L2S1 of the second lens L2. By satisfying the above formula (5), both miniaturization in the radial direction and high performance can be achieved. By setting the value (D23+SAG3)/SAG2 of the above expression (5) to the lower limit or more, it is possible to prevent the effective diameter of the object side surface L2S1 of the second lens L2 from becoming too small, and it becomes easy to correct the aberration. Further, by setting the value to be equal to or less than the upper limit of the expression (5), it is not necessary to assume a configuration in which a light blocking member or the like is inserted between the first and second lenses L1 and L2, and therefore, the object side surface L2S1 of the second lens L2 is The degree of freedom in the surface shape is secured, and the aberration can be easily corrected. Unless otherwise specified in this specification, the optical surface means a region where a spherical surface or an aspherical surface exists, and the optical surface end means an outer edge of a region where a spherical surface or an aspherical surface exists, and is not always effective. It does not mean the circumference of the diameter.

The imaging lens (wide-angle optical system) 10 further satisfies the following conditional expressions (6) and (7).
3.0≦R1/R2≦ 3.43 (6)
1.85≦φ2/R2≦1.95 (7)
Here, the value R1 is the radius of curvature of the object side surface L1S1 of the first lens L1, the value R2 is the radius of curvature of the image side surface L1S2 of the first lens L1, and the value φ2 is the image side surface of the first lens L1. It is the optical surface diameter of L1S2. By satisfying the above equations (6) and (7), the curvature difference between the object side surface L1S1 of the first lens L1 and the image side surface L1S2 of the first lens L1 is sufficiently large, and the image side surface L1S2 of the first lens L1 is deep. Since it is a surface, the thickness of the side surface or edge of the first lens L1 can be made sufficiently thick, so that a sealing means such as an O-ring can be easily inserted into the flange portion 3a or the outer peripheral portion of the first lens L1 and the environment resistance can be improved. It can have an excellent configuration. By setting the values R1/R2 of the above formula (6) to the lower limit or more, it is possible to prevent the difference in curvature from becoming small and to make the edge sufficiently thick, while suppressing the increase of the outer diameter to achieve the miniaturization. be able to. Further, by setting the value to be equal to or less than the upper limit of the expression (6) and to set the value φ2/R2 of the expression (7) to be equal to or higher than the lower limit, it is possible to preferably correct the field curvature. By setting the value to be equal to or less than the upper limit of the above formula (7), it is possible to avoid approaching the processing limit of the spherical surface polishing of glass, and it is possible to suppress lack of accuracy and cost increase.

The imaging lens (wide-angle optical system) 10 further satisfies the following conditional expression (8).
1.00 ≤ D12/f ≤ 1.2 (8)
Here, the value D12 is the distance on the optical axis AX from the object side surface L1S1 of the first lens L1 to the image side surface L1S2, that is, the center thickness of the first lens L1, and the value f is the entire system, that is, the imaging lens 10. The focal length. When the center thickness of the first lens L1 made of glass satisfies the above expression (8), it is possible to obtain a suitable negative power while ensuring the workability. By setting the value D12/f in the above formula (8) to the upper limit or less, it is possible to prevent the core thickness from becoming too thick to obtain a suitable negative power, and the first lens obtained by polishing glass or the like. It is possible to prevent the workability of L1 from deteriorating. Further, by setting the value to be equal to or more than the lower limit of the above formula (8), it is possible to reduce the possibility that the core becomes too thin and the lens is cracked due to an impact or the like.

The imaging lens (wide-angle optical system) 10 further satisfies the following conditional expression (9).

−0.6≦f12/f345≦−0.4 (9)
Here, the value f12 is the combined focal length of the first and second lenses L1 and L2, and the value f345 is the combined focal length of the third to fifth lenses L3 to L5. In this case, since the appropriate retro focus is achieved, the back focus does not become too long, and the configuration is advantageous for reducing the overall optical length.

The imaging lens (wide-angle optical system) 10 further satisfies the following conditional expression (10).
0.20≦φ4/φ1≦0.34 (10)
Here, the value φ4 is the optical surface diameter of the image side surface L2S2 of the second lens L2, and the value φ1 is the optical surface diameter of the object side surface L1S1 of the first lens L1. By making the light beam diameter sufficiently small on the front side of the optical system, it is possible to make a configuration in which a ghost is less likely to occur without disposing a light shielding member between the first lens L1 and the second lens L2, for example. In an optical system in which the value φ4/φ1 in the above formula (10) is equal to or less than the upper limit, since the light flux diameter is relatively small on the front side of the optical system, it is possible to reduce the possibility of ghosting. Further, in the optical system that is equal to or more than the lower limit of the above formula (10), the angle of the lens surface or the optical surface does not become too large, so that it is possible to avoid deterioration of workability and moldability. The imaging lens 10 more preferably satisfies the following conditional expression (10)′.
0.25≦φ4/φ1≦0.30 (10)′

The imaging lens (wide-angle optical system) 10 may further include other optical elements (for example, a lens, a filter member, etc.) having substantially no power in addition to the lenses L1 to L5.

The lens unit described above includes the image pickup lens (wide-angle optical system) 10 described above, and can be small in size, high in performance, wide-angle, and low in cost. Further, the imaging device 100 including the lens unit 40 can realize a high-performance device at low cost.

〔Example〕
Specific examples of the wide-angle optical system of the present invention will be described below. The symbols used in each example are as follows. The unit for length is mm.
f: focal length of the entire wide-angle optical system Fno: F value 2w: total angle of view R: radius of curvature D: axial upper surface spacing nd: refractive index of lens material with respect to d-line vd: Abbe number of lens material

[Example 1]
The basic optical parameter values of the wide-angle optical system of Example 1 are shown below.
f=1.00
Fno=2.0
2w=190°

The data of the optical surface, that is, the lens surface of Example 1 is shown in Table 1 below. In Table 1 and the like, the surface number is represented by “Surface” and the infinity is represented by “INF”. In the surface number, the lens surface is represented by "L1S1", the object surface is represented by "OBJ", the aperture stop ST is represented by "STOP", the object side surface of the parallel plate is represented by "CGS1", and the image side surface of the parallel plate is represented. Is represented by "CGS2". In the description of the lens surface, the first half symbol Ln (n=1 to 5) indicates the nth lens (specifically, the first to fifth lenses), and the latter symbol S1 indicates the nth lens. Refers to the object side surface of the lens, and the symbol S2 indicates the image side surface of the nth lens. The value D of the axial upper surface distance means the distance from the surface of the column to the surface of the lower left column. Specifically, for example, the value D on the right side of the image side surface “CGS2” of the parallel plate indicates the axial upper surface distance from the image side surface of the parallel plate to the image pickup surface I (or the image forming surface).
[Table 1]
Surface RD nd vd
OBJ INF INF
L1S1 11.9000 1.000 1.8042 46.5
L1S2 3.6900 1.237
L2S1 2.5301 0.806 1.5351 56.0
L2S2 0.6911 1.645
L3S1 2.7189 1.868 1.6347 23.7
L3S2 -2.7284 0.168
STOP INF 0.204
L4S1 10.4310 0.422 1.6347 23.7
L4S2 1.6931 0.015 1.5140 42.8
L5S1 1.6931 2.098 1.5351 56.0
L5S2 -1.5364 1.158
CGS1 INF 0.700 1.5168 64.1
CGS2 INF 0.150

ただし、
Ａｉ：ｉ次の非球面係数
Ｒ ：曲率半径
Ｋ ：円錐定数
〔表２〕
L2S1面
K=-6.6386E-01, A4=-2.3341E-02, A6=-1.1318E-05,
A8=2.3004E-04, A10=-2.3118E-05, A12=7.6550E-07
L2S2面
K=-1.6744E+00, A4=2.7670E-01, A6=-1.0869E-01,
A8=2.6885E-02, A10=5.6580E-03, A12=-3.7341E-03
L3S1面
K=-1.1611E+01, A4=7.5016E-02, A6=-3.4005E-02,
A8=1.8369E-02, A10=-7.2239E-03, A12=1.8623E-08
L3S2面
K=-2.7266E+01, A4=-4.2468E-02, A6=-4.0880E-03,
A8=3.5047E-03, A10=-6.1412E-04, A12=1.0703E-07
L4S1面
K=-3.8674E+01, A4=1.3640E-01, A6=1.0469E-01,
A8=-1.2562E+00, A10=2.1564E+00, A12=-1.1897E+00
L4S2面
K=3.0722E-01, A4=1.0364E+00, A6=-1.6201E+00,
A8=1.0653E+00, A10=-2.7874E-01, A12=-3.1274E-04
L5S1面
K=3.0722E-01, A4=1.0364E+00, A6=-1.6201E+00,
A8=1.0653E+00, A10=-2.7874E-01, A12=-3.1274E-04
L5S2面
K=-9.4546E+00, A4=-1.8172E-01, A6=1.3415E-01,
A8=-6.1393E-02, A10=1.2367E-02, A12=3.6185E-06
なお、以上の表２及びこれ以降の表において、１０のべき乗数（例えば２．５×１０^−０２）をＥ（例えば２．５Ｅ−０２）を用いて表している。Table 2 below shows the aspherical coefficients of the lens surfaces of Example 1. The shape of the aspherical surface is expressed by the following equation, where the vertex of the surface is the origin, the X axis is in the optical axis direction, and the height in the direction perpendicular to the optical axis is h.

However,
Ai: i-th order aspherical coefficient R: radius of curvature K: conic constant [Table 2]
L2S1 side
K=-6.6386E-01, A4=-2.3341E-02, A6=-1.1318E-05,
A8=2.3004E-04, A10=-2.3118E-05, A12=7.6550E-07
L2S2 side
K=-1.6744E+00, A4=2.7670E-01, A6=-1.0869E-01,
A8=2.6885E-02, A10=5.6580E-03, A12=-3.7341E-03
L3S 1 side
K=-1.1611E+01, A4=7.5016E-02, A6=-3.4005E-02,
A8=1.8369E-02, A10=-7.2239E-03, A12=1.8623E-08
L3S2 side
K=-2.7266E+01, A4=-4.2468E-02, A6=-4.0880E-03,
A8=3.5047E-03, A10=-6.1412E-04, A12=1.0703E-07
L4S 1 side
K=-3.8674E+01, A4=1.3640E-01, A6=1.0469E-01,
A8=-1.2562E+00, A10=2.1564E+00, A12=-1.1897E+00
L4S2 side
K=3.0722E-01, A4=1.0364E+00, A6=-1.6201E+00,
A8=1.0653E+00, A10=-2.7874E-01, A12=-3.1274E-04
L5S 1 side
K=3.0722E-01, A4=1.0364E+00, A6=-1.6201E+00,
A8=1.0653E+00, A10=-2.7874E-01, A12=-3.1274E-04
L5S2 side
K=-9.4546E+00, A4=-1.8172E-01, A6=1.3415E-01,
A8=-6.1393E-02, A10=1.2367E-02, A12=3.6185E-06
In addition, in the above Table 2 and the subsequent tables, a power of 10 (for example, 2.5×10 ⁻⁰² ) is represented by using E (for example, 2.5E-02).

Table 3 below shows characteristic values related to the conditional expressions (1) to (10) of the first embodiment.
[Table 3]
f 1.00
f12 -1.34
f345 2.64
Hmax 2.45
D14 3.04
D12 1.00
D23 1.24
D24 2.04
D1L 9.46
TTL 11.47
φ1 11.40
φ2 7.09
φ4 3.07
SAG2 2.67
SAG3 0.72
R1 11.90
R2 3.69

FIG. 2 is a cross-sectional view of the imaging lens 11 and the like that are the wide-angle optical system of Example 2. The imaging lens 11 includes a first lens L1 having a negative meniscus convex on the object side, a second lens L2 having a negative meniscus convex on the object side, a biconvex positive third lens L3, and a convex negative lens on the object side. It includes a meniscus fourth lens L4 and a biconvex positive fifth lens L5. A light blocking diaphragm FS is arranged between the second lens L2 and the third lens L3, and an aperture diaphragm ST is arranged between the third lens L3 and the fourth lens L4. An image pickup surface I is arranged on the image side of the fifth lens L5 via a filter F which is a parallel plate.

(Example 2)
The basic optical parameter values of the wide-angle optical system of Example 2 are shown below.
f=1.03
Fno=2.06
2w=186°

The data on the lens surfaces of Example 2 are shown in Table 4 below.
[Table 4]
Surface RD nd vd
OBJ INF INF
L1S1 12.4307 1.200 1.8042 46.5
L1S2 3.6209 1.528
L2S1 2.5279 0.700 1.5351 56.0
L2S2 0.7235 1.599
L3S1 3.0569 2.023 1.6347 23.7
L3S2 -2.8597 0.266
STOP INF 0.203
L4S1 8.0470 0.400 1.6347 23.7
L4S2 1.2667 0.010 1.5140 42.8
L5S1 1.2667 1.937 1.5351 56.0
L5S2 -1.6446 0.235
CGS1 INF 0.700 1.5168 64.1
CGS2 INF 1.332

Table 5 below shows the aspherical coefficients of the lens surfaces of Example 2.
[Table 5]
L2S1 side
K=-6.1436E-01, A4=-2.2597E-02, A6=-1.1960E-04,
A8=2.3215E-04, A10=-2.5160E-05, A12=9.7645E-07
L2S2 side
K=-1.6201E+00, A4=2.5915E-01, A6=-1.0250E-01,
A8=2.8110E-02, A10=4.0820E-03, A12=-3.5570E-03
L3S 1 side
K=-1.5161E+01, A4=6.8443E-02, A6=-3.9483E-02,
A8=2.3069E-02, A10=-8.1684E-03, A12=1.8623E-08
L3S2 side
K=-1.8082E+01, A4=-3.5104E-02, A6=-1.6265E-02,
A8=1.0817E-02, A10=-1.9445E-03, A12=1.0703E-07
L4S 1 side
K=-4.0000E+01, A4=7.4143E-02, A6=1.0516E-01,
A8=-1.0603E+00, A10=1.9489E+00, A12=-1.1897E+00
L4S2 side
K=-5.3270E+00, A4=9.7699E-01, A6=-1.3880E+00,
A8=9.3363E-01, A10=-2.5616E-01, A12=-3.1274E-04
L5S 1 side
K=-5.3270E+00, A4=9.7699E-01, A6=-1.3880E+00,
A8=9.3363E-01, A10=-2.5616E-01, A12=-3.1274E-04
L5S2 side
K=-1.0019E+01, A4=-1.8729E-01, A6=1.3938E-01,
A8=-6.7634E-02, A10=1.4010E-02, A12=3.6185E-06

Table 6 below shows characteristic values relating to the conditional expressions (1) to (10) of the second embodiment.
[Table 6]
f 1.03
f12 -1.35
f345 2.66
Hmax 2.36
D14 3.43
D12 1.20
D23 1.53
D24 2.23
D1L 9.87
TTL 12.13
φ1 11.40
φ2 7.05
φ4 2.95
SAG2 2.79
SAG3 0.78
R1 12.43
R2 3.62

FIG. 3 is a cross-sectional view of the imaging lens 12 and the like that are the wide-angle optical system of Example 2. The imaging lens 12 includes a first lens L1 having a negative meniscus convex on the object side, a second lens L2 having a negative meniscus convex on the object side, a biconvex positive third lens L3, and a convex negative lens on the object side. It includes a meniscus fourth lens L4 and a biconvex positive fifth lens L5. A light blocking diaphragm FS is arranged between the second lens L2 and the third lens L3, and an aperture diaphragm ST is arranged between the third lens L3 and the fourth lens L4. An image pickup surface I is arranged on the image side of the fifth lens L5 via a filter F which is a parallel plate.

Table 7 below summarizes the values of Examples 1 and 2 corresponding to the conditional expressions (1) to (10) for reference.
[Table 7]

[Second Embodiment]
The wide-angle optical system and the like of the second embodiment will be described below. The wide-angle optical system of the second embodiment is a modification of the wide-angle optical system of the first embodiment, and items that are not particularly described are the same as those of the first embodiment.

FIG. 4 shows a lens unit 40 and the like that incorporates the imaging lens 110 that is the wide-angle optical system of the second embodiment. In this case, the fourth lens L4 is a positive aspherical lens having a paraxial biconvex shape, and the fifth lens L5 has a concave object side surface, and a meniscus shape having a paraxial convex surface toward the image side. Is a negative aspherical lens having By configuring the fourth and fifth lenses L4 and L5 in this way, it is advantageous for correction of chromatic aberration. The fourth lens L4 and the fifth lens L5 may be cemented together.

Although the wide-angle optical system has been described above according to the embodiment, the wide-angle optical system according to the present invention is not limited to the above-described embodiment, and various modifications can be made.

Claims (18)

From the object side,
A negative first lens made of glass having a convex shape on the object side and a concave shape on the image side, both surfaces of which are spherical;
A negative second lens having an aspherical surface on at least one surface and having a concave shape on the image side;
A positive third lens,
Aperture,
A fourth lens having an aspherical surface on at least one surface,
Substantially consisting of a fifth lens having at least one aspherical surface,
A wide-angle optical system that satisfies the following conditional expression.
1.10≦D14/Hmax≦1.80 (1)
0.40≦D23/Hmax≦0.70 (2)
4.0≦TTL/Hmax≦5.5 (3)
4.0≦φ1/Hmax≦5.5 (4)
3.0≦R1/R2≦3.43 (6)
1.00≦D12/f≦1.2 (8)
here,
D14: Distance on the optical axis from the object side surface of the first lens to the image side surface of the second lens D23: Distance on the optical axis from the image side surface of the first lens to the object side surface of the second lens Hmax: Maximum image height TTL: Total optical length φ1: Optical surface diameter of the object side surface of the first lens
R1: radius of curvature of the object side surface of the first lens
R2: radius of curvature of the image side surface of the first lens D12: center thickness of the first lens f: focal length of the entire system The wide-angle optical system according to claim 1, which satisfies the following conditional expression.
0.65≦(D23+SAG3)/SAG2≦1.0 (5)
here,
D23: Distance on the optical axis from the image side surface of the first lens to the object side surface of the second lens SAG2: SAG amount at the optical surface end of the image side surface of the first lens SAG3: On the object side surface of the second lens SAG amount at the optical surface edge The wide-angle optical system according to claim 1, which satisfies the following conditional expression .
1.85≦φ2/R2≦1.95 (7)
Here,
R2: radius of curvature of the image side surface of the first lens φ2: optical surface diameter of the image side surface of the first lens The wide-angle optical system according to claim 1, wherein a maximum surface angle within an effective diameter of an image side surface of the second lens is 60° or more. The wide-angle optical system according to any one of claims 1 to 4, which satisfies the following conditional expression.
−0.6≦f12/f345≦−0.4 (9)
here,
f12: Composite focal length of the first and second lenses f345: Composite focal length of the third to fifth lenses The wide-angle optical system according to claim 1, wherein the total angle of view is 160° or more. The wide-angle optical system according to any one of claims 1 to 6, wherein the second to fifth lenses are plastic lenses. The wide-angle optical system according to any one of claims 1 to 6, wherein the second, fourth, and fifth lenses are plastic lenses, and the third lens is a glass lens. The wide-angle optical system according to claim 1, wherein an object side surface of the second lens has a convex shape. The wide-angle optical system according to any one of claims 1 to 9, wherein the third lens has a biconvex shape with at least one aspherical surface. The fourth lens is a negative lens having a concave shape on the image side, the fifth lens is a positive lens having a biconvex shape, and the fourth and fifth lenses are cemented. The wide-angle optical system according to any one of 1. The wide-angle optical system according to any one of claims 1 to 10, wherein the fourth lens is a positive lens having a biconvex shape, and the fifth lens is a negative meniscus lens having a concave shape on the object side. The wide-angle optical system according to claim 12, wherein the fourth and fifth lenses are cemented. The wide-angle optical system according to any one of claims 1 to 13, wherein the fifth lens has a structure that is fitted around the flange of the fourth lens. The inter-lens facing surface excluding the object side of the first lens and the image side of the fifth lens is formed in a region different from the optical surface, and the front and rear lenses and the diaphragm are formed by a flange portion substantially perpendicular to the optical axis. The wide-angle optical system according to any one of claims 1 to 14, wherein the wide-angle optical system is in contact with only the light shielding member or the lens holder. The wide-angle optical system according to any one of claims 1 to 15, which satisfies the following conditional expression.
0.20≦φ4/φ1≦0.34 (10)
here,
φ4: optical surface diameter of the image side surface of the second lens φ1: optical surface diameter of the object side surface of the first lens A wide-angle optical system according to any one of claims 1 to 16,
A lens unit comprising: a lens holder that holds the wide-angle optical system. The lens unit according to claim 17,
An image pickup device comprising: an image pickup device for projecting an image by the lens unit.

Images