JP2008292800A - Anamorphic lens, imaging apparatus and supervising device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a compact and inexpensive anamorphic lens having a super-wide field angle and obtaining anamorphic characteristic that projection where an image nearer to a side surface is higher in height is obtained and an image is emphasized in a vertical direction. <P>SOLUTION: The anamorphic lens is equipped with a front group constituting an anamorphic optical system by arranging a first group lens G1, a second group lens G2 and a third group lens G3 from an object side, and a rear group arranged nearer to an image side than the front group and constituting an image-formation system as a whole. When it is assumed that the focal length of the first group lens G1 is f(G1), the focal length of the second group lens G2 in a vertical direction is f(G2)V, the focal length thereof in a horizontal direction is f(G2)H, the focal length of the third group lens G3 in the vertical direction is f(G3)V, the focal length thereof in the horizontal direction is f(G3)H, anamorphic magnification is M, the focal length obtained by integrating the entire lens is f, the focal length obtained by integrating the entire lens in the horizontal direction is fH, and a distance to an image surface from the end face of the first group lens is TT, they satisfy fH×θ/TT<0.1 (θ: radian). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an anamorphic lens, an imaging apparatus, and a monitoring apparatus, and more particularly, an anamorphic lens that includes an anamorphic optical system that emphasizes a peripheral image, and that is compact and inexpensive, and an imaging apparatus using the anamorphic lens And a monitoring device.

  As an anamorphic lens, in claim 1 of Patent Document 1, in a camera device that performs imaging by imaging a light beam from a predetermined visual field range on an image sensor with a lens system, the lens system has a horizontal viewing angle. A lens having a wide-angle lens system of 120 ° or more and an anamorphic lens having a distortion image ratio of 1.5 or more is disclosed.

As an anamorphic lens, Patent Document 2 discloses, in order from the object side, a front group (Gr1) having a negative optical power as a whole, an optical aperture (ST) for adjusting the amount of light, and a positive as a whole. The rear group (Gr2) having an optical power of (paragraph number 0055), the front group (Gr1) is composed of a negative lens, a negative lens, and a positive lens in order from the object side. Gr2) is composed of, in order from the object side, a cemented lens of a negative lens and a positive lens, and a positive lens (paragraph number 0057). The first lens has a function of refracting light rays with a negative optical power. The second lens further refracts the optical axis largely refracted by the first lens with a negative optical power, and in the X-axis direction (corresponding to the long side direction) of the optical image guided to the image sensor (SR). Length and Y-axis direction (equivalent to short side direction) The third lens has a function of correcting astigmatism, the fourth lens is a negative lens, and the fifth lens is a function of changing the length and ratio (widening the angle of view in the long side direction). By joining them as a biconvex positive lens, the axial chromatic aberration can be corrected well, the sixth lens corrects the non-rotationally symmetric aberration component generated by the second lens, and the image sensor (SR) ), A super-wide-angle optical system having a function of making the incident angle of light to telecentric approach (paragraph 0059) is described.
JP 2005-110202 A JP 2006-11093 A

  By the way, in general, the in-vehicle camera is installed at the front of the vehicle and is provided to check an obstacle on the front side. Therefore, a design (stereoscopic projection) that enhances the peripheral image is required in order to have a field angle of 180 degrees or more in the horizontal direction and facilitate confirmation of obstacles and intruding objects on the side surface. Also, a wide field of view is required in the horizontal direction, but a wide field of view is not necessary in the vertical direction (it is not necessary to look directly above or directly below).

  By the way, in the rotationally symmetric optical system, a mask or the like is required to narrow the field of view only in the vertical direction, and the entire surface of the image sensor cannot be used effectively. On the other hand, by using a non-rotation symmetric optical system, the aspect ratio of the image can be changed, and the entire image sensor can be used effectively. Specifically, the aspect ratio of the image is changed by changing the curvature in the horizontal and vertical directions of some lenses. Such lenses having different curvatures in each direction on the same plane are called anamorphic lenses. Here, the aspect ratio of the image corresponds to the focal length ratio in each of the horizontal and vertical directions, and is called anamorphic magnification.

  Although lenses with the above specifications have already been proposed, there is room for improvement in terms of compactness and cost that do not impair the vehicle design. Accordingly, an object of the present invention is to solve the above problems, to enhance a peripheral image, to provide an anamorphic lens, an imaging device, and a monitoring device that are compact and low in cost.

  In the present invention, means for solving the problems are as follows. The invention of claim 1 is a six-group anamorphic lens composed of two glass lenses and four resin lenses, and two of the four plastic lenses are anamorphic aspherical surfaces. And an anamorphic lens characterized in that two lenses are rotationally symmetric aspherical surfaces.

  According to a second aspect of the present invention, in the anamorphic lens according to the first aspect, the maximum field angle is 180 ° or more.

  According to a third aspect of the present invention, in the anamorphic lens according to the first or second aspect, of the front group lenses including the first group lens, the second group lens, and the third group lens, the first group lens is a glass lens. The second group lens and the third group lens are formed as non-rotationally symmetric anamorphic lenses that are made spherical so as to change the curvature in each of the horizontal and vertical directions and to have a predetermined focal length ratio. The third group lens has a predetermined refractive index and is formed to have a function of correcting longitudinal chromatic aberration and lateral chromatic aberration.

  According to a fourth aspect of the present invention, in the anamorphic lens according to any one of the first to third aspects, the rear group lens composed of the fourth group lens, the fifth group lens, and the sixth group lens is a triplet type having convex and concave portions. It is configured.

  According to a fifth aspect of the present invention, in the anamorphic lens according to any one of the first to fourth aspects, of the rear group lenses, the fourth group lens is a glass lens, and the Abbe number is higher than a predetermined value. It is characterized by that.

  According to a sixth aspect of the present invention, in the anamorphic lens according to any one of the first to fifth aspects, among the rear group lenses, the fifth group lens and the sixth lens are higher order than the second lens and the third lens. A resin-made rotationally symmetric aspherical lens using the aspherical coefficient is used.

  According to the seventh aspect of the present invention, the first group lens G1, the second group lens G2, and the third group lens G3 are disposed from the object side to form an anamorphic optical system, and are disposed closer to the image side than the front group. In an anamorphic lens having a rear group that forms an imaging system as a whole, the focal length of the first group lens G1 is f (G1), and the focal length in the vertical direction of the second group lens G2 is f (G2). ) V, the focal length in the horizontal direction is f (G2) H, the focal length in the vertical direction of the third lens group G3 is f (G3) V, the focal length in the horizontal direction is f (G3) H, and the anamorphic magnification. Where f is the focal length integrated with the entire lens, fH is the focal length in the horizontal direction with the entire lens integrated, and TT is the distance from the end surface of the first lens unit to the image plane, fH · θ / TT <0. .1 (θ: radians) Is a Fick lens.

  The invention according to claim 8 is the anamorphic lens according to claim 7, characterized in that the maximum half angle of view θ = 1.69 rad (97 °) TT = 16 (mm).

  According to a ninth aspect of the present invention, in the anamorphic lens according to the seventh or eighth aspect, the focal length f (G1) of the first group lens G1 and the focal length in the vertical direction of the second group lens G2 are defined as f (G2 ) V, the focal length in the horizontal direction is f (G2) H, the focal length in the vertical direction of the third lens group G3 is f (G3) V, the focal length in the horizontal direction is f (G3) H, and the anamorphic magnification. Where M is f (G1)>-5 (mm), 1 <(f (G2) V / f (G2) H) / M <1.70.51 <(f (G3) V / f ( G3) H) / M <1, and the material is plastic.

  The invention of claim 10 is the anamorphic lens according to any one of claims 7 to 9, wherein the Abbe number of the second group lens G2 is ν (G2), and the Abbe number ν (G3) of the third group lens G3 is Ν (G2) −ν (G3) ≧ 28f (G4) <2.6, Abbe number 60 or higher, refractive index 1.48 or higher, −1.61 <f (G5), Abbe number 25 or higher, refractive index 1. 55 or more f (G6) <5.8 and an Abbe number of 60 or more and a refractive index of 1.5 or more are satisfied.

  An eleventh aspect of the invention includes the anamorphic lens according to any one of the first to tenth aspects, and an image sensor that converts an image formed by the anamorphic lens into an electric signal. An imaging device.

  A twelfth aspect of the invention is a monitoring apparatus comprising the imaging device according to the eleventh aspect and a display device that displays an image captured by the imaging device.

  According to the anamorphic lens of the present invention, an anamorphic lens having an anamorphic magnification that enables an ultra-wide angle of view that can sufficiently cover the side of a vehicle at a compact and low price, and that an image is emphasized toward the side. System, imaging device and monitoring device using the system can be realized.

  Hereinafter, an anamorphic lens according to an embodiment of the present invention and an imaging device using the lens system will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing an optical system of an anamorphic lens of an imaging apparatus according to an embodiment.

  The anamorphic lens of this example includes a first group lens G1, a second group lens G2, and a third group lens G3 that are the front group, and a fourth group lens G4, a fifth group lens G5, and a sixth group that are the rear group. It is composed of a lens G6, and has six groups and six elements. In the drawing, I denotes an optical aperture disposed between the front group and the rear group, symbol S denotes a CCD image sensor, and symbol C denotes a cover glass of the CCD image sensor S.

  In this example, the first group lens G1 and the fourth group lens G4 are formed of glass lenses. The second group lens G2, the third group lens G3, the fifth group lens G5, and the sixth group lens G6 are made of resin lenses (plastic lenses). The fifth group lens G5 and the sixth group lens G6 are configured as rotationally symmetric aspheric lenses.

  The anamorphic lens of this example is a first group lens G1 which is a glass meniscus lens from the left side (object side), a second group lens G2 which is a plastic anamorphic lens, and a third anamorphic lens which is a plastic anamorphic lens. It includes a group lens G3, a fourth group lens G4 that is a glass positive lens, a fifth group lens G5 that is a plastic aspheric negative lens, and a sixth group lens G6 that is a plastic aspheric positive lens. The maximum angle of view of this anamorphic lens is 194 °.

  Next, characteristics of the anamorphic lens according to the present invention will be described. The main characteristics of this anamorphic lens are the following three points. Hereinafter, the case where the focal length is calculated at a wavelength of 587 nm will be described.

In the anamorphic lens according to this example, from the relationship between peripheral image enhancement and compactness, when the focal length in the horizontal direction integrating the entire lens is fH and the distance from the first lens end surface to the image plane is TT, Have the relationship.
fH · θ / TT <0.1 (θ: radians) Equation 1
Specifically, fH = 0.98 (horizontal focal length), TT = 16 (mm), and maximum half angle of view θ = 1.69 rad (97 °).

Further, in the anamorphic lens according to this example, the focal length fd of the first lens group G1 is set to −4.16 (mm) because of the anamorphic magnification. That is, the first group lens G1 has a focal length f (G1)> − 5 Formula 2
This is a glass lens.

The second lens group G2 is
1 <(fV / fH) / M <1.7 Formula 3
It is a plastic lens.
The third lens group G3 is
0.51 <(fV / fH) / M <1 Equation 4
This is a plastic lens. Here, fV: vertical focal length, fH vertical focal length, and M: anamorphic magnification.

  Furthermore, in the anamorphic lens according to this example, the relationship between the Abbe number and the refractive index of each component lens is as follows.

ν (G2) −ν (G3) ≧ 28 Equation 5
fG4 <2.6 Equation 6
And Abbe number 60 or more Refractive index 1.48 or more

-1.61 <fG5 Formula 7
And Abbe number 25 or more Refractive index 1.55 or more

fG6 <5.8 ... Formula 8
And Abbe number 60 or more Refractive index 1.5 or more

Each component lens will be described below.
[First lens group]
The first lens group G1 requires a high refractive index in order to take measures against environmental changes on its surface and to bend light rays greatly with respect to an angle of view of 190 degrees or more. Since a considerable Abbe number is required to suppress the occurrence of chromatic aberration, glass is adopted.

[Second group lens, Third group lens]
The second lens group and the third lens group are predicated on cost reduction, and resin lenses are used to realize a non-rotation target anamorphic lens. This is because, for the formation of a free-form surface of an anamorphic lens, resin is more advantageous than glass in performing injection molding.

In addition, the second group lens G2 and the third group lens G3 arranged in the front group with the stop interposed therebetween were selected as having the following characteristics.
(1) Change the curvature in each direction and adjust the focal length ratio.
(2) To obtain an aspheric surface in order to obtain a good resolution in each direction.
(3) Aspherical surface is used to enhance the peripheral image.
The focal length ratio is the aspect ratio of the image.
Here, if only the condition (2) is satisfied, it can be realized with a toroidal lens. However, in order to satisfy the conditions (2) and (3) simultaneously, it is necessary to be an anamorphic lens.

  The third group lens G3 corrects chromatic aberrations on the axis and magnification by giving a difference in Abbe number from the first group lens G1 and the second group lens G2 while having an appropriate refractive index.

The rear group lens (fourth group lens G4 to sixth group lens G6) is configured with a convex-concave convex triplet type, so that the principal point can be arranged closer to the object than the concave-convex convex type, and compactness can be achieved.
[Fourth lens group G4]
The fourth group lens G4 is a glass lens, and a lens having a high Abbe number is used to correct axial and magnification chromatic aberration.
[Fifth Group Lens G5, Sixth Group Lens G6]
The rear group lens uses a higher-order aspheric coefficient than the second group lens G2 and the third group lens G3 in order to obtain a good image over the entire field of view and a projection state in which the peripheral image is emphasized. A rotationally symmetric aspheric lens was used. In order to reduce costs, a resin lens is used.

Tables 1 and 2 show lens data. Table 1 shows the first surface to the third surface, and Table 2 shows the fourth surface to the thirteenth surface.


With the above configuration, the anamorphic lens according to the present example is characterized by an ultra-wide angle (194 °). This super wide-angle feature is achieved by the front group lens (first group lens G1 to third group lens G3). The first group lens G1 is made of a glass having a very high refractive index and can be achromatic, and the second group lens G2 is a biconcave lens (for example, a biconcave aspheric lens). Refracted. In addition, the lens configuration for that purpose can be minimized. This makes it possible to reduce the size and price of lenses.

  In addition, the anamorphic lens according to the present example has an anamorphic magnification in which the image is emphasized toward the side surface. This feature is achieved as follows. Although the peripheral image height is generally determined by the CCD size, it is necessary to relatively reduce the center to intermediate image height for stereoscopic projection. This is theoretically achieved by shortening the focal length. The role of shortening the focal length is related to the entire rear group lens. In particular, the fourth group lens G4 uses a low dispersion glass for achromatism. However, since the refractive index is low, the fourth lens group G4 is a biconvex lens in order to secure power.

Asphericalization is effective for bringing the projection close to three-dimensional. Enlarging the outermost image corresponds to making the second lens group G2 (anamorphic) and the fifth lens group G5 (biconcave lens) aspherical.
Further, although the central image needs to be relatively reduced, the aspherical surfaces of the third group lens G3 and the sixth group lens G6 (convex lens) are compatible.

  In summary, in the anamorphic lens according to this example, aspherical lenses are arranged before and after the fourth group lens G4, and the overall power is obtained by the power of the concave lenses of the second group lens G2 and the fifth group lens G5. The entire power is raised by the power of the convex lenses of the third lens group G3 and the sixth lens group G6.

  Next, the projection characteristics of the anamorphic lens according to this example will be described. FIG. 3 is a graph showing the horizontal projection characteristics of the anamorphic lens according to this example, and FIG. 4 is a graph showing the vertical projection characteristics. The horizontal axis represents the half angle of view.

As shown in FIG. 3, the anamorphic lens according to this example is in a projection state closer to 2f · tan (θ / 2) {stereoscopic projection} in the horizontal direction.
The vertical direction is as shown in FIG.

  Next, the anamorphic magnification will be described. In this example, both sides of the second group lens G2 and the third group lens G3 are anamorphized to realize an anamorphic characteristic of about 1.4 times.

  The anamorphic magnification of this lens is related to the change in focal length in each direction of the second group lens G2 and the third group lens G3. Table 3 shows changes in focal lengths in the respective directions of the second group lens G2 and the third group lens G3 with respect to anamorphic magnification changes. Moreover, the state of this change is shown in FIG.5 and FIG.6.

  FIG. 5 is a graph showing a change in focal length of the G2 lens with respect to a change in anamorphic magnification, and FIG. 6 is a graph showing a change in focal length of the G3 lens with respect to a change in anamorphic magnification. For anamorphic magnification, the focal length change was calculated in the range of about ~ 1.6. A. Table 4 shows the focal length ratio.

Equations (3) and (4) are obtained by quantifying the relationship between the directional focal length ratio and the anamorphic magnification based on this change. That is, between the practical anamorphic magnifications 1 to 1.6, the horizontal and vertical focal lengths (fV, fH) of the second group lens G2 and the third group lens G3 are calculated. From the result, the value of the focal length ratio ((fV / fH) / M) was calculated. As a basis for the calculation, a value of −2.50 to −2.52 (mm) that is actually assumed to be used is used as the horizontal focal length fH of the second lens group G2 as an initial value. As a result,
(1) Change the curvature in each direction and adjust the focal length ratio.
(2) To obtain an aspheric surface in order to obtain a good resolution in each direction.
(3) Aspherical surface is used to enhance the peripheral image.
Can be satisfied.

The aberration of an anamorphic lens having such a configuration is as follows. 7 to 12 show aberrations of the anamorphic lens according to the embodiment. 7 is a graph showing spherical aberration in the horizontal field angle direction, FIG. 8 is a graph showing astigmatism in the horizontal field angle direction, FIG. 9 is a graph showing distortion in the horizontal field angle direction, and FIG. 10 is in the vertical field angle direction. 11 is a graph showing spherical aberration, FIG. 11 is a graph showing astigmatism in the vertical field angle direction, and FIG. 12 is a graph showing distortion in the vertical field angle direction. 7, 8, 10, and 11, a solid line indicates a wavelength of 0.656 μm (red), a fine broken line indicates a wavelength of 0.587 μm (yellow), and a broken line indicates a wavelength of 0.486 μm (blue).
7 to 12, it can be seen that the anamorphic lens according to this example has excellent aberration characteristics.

  The anamorphic lens according to the present invention is not limited to the above-described embodiment, and each group lens can be configured as a combination lens. For example, the above-described second group lens G2 can be divided by a plane perpendicular to the optical axis O to be configured as a lens G2-1 and a lens G2-2, and the second group lens is made into two lenses. Thus, the chromatic aberration correction can be further improved.

  Next, an image pickup apparatus using the anamorphic lens according to the embodiment will be described. FIG. 13 is a longitudinal sectional view of an imaging apparatus according to the embodiment, and FIG. 14 is a transverse sectional view of the imaging apparatus according to the embodiment.

  The imaging device 10 is configured by arranging a first group lens G1 to a sixth group lens G6 in a cylindrical metal housing 11, and closing both ends with a front cap 12 and an end cap 13. A mounting screw portion 14 is formed outside the metal housing 11, and an optical aperture I is formed inside the housing.

  Moreover, it has the dimension and optical characteristic of the imaging device 10 or less. That is, the aperture and length dimensions of the imaging device 10 are φ16 × 11.5 mm, the dimension of the mounting screw portion 14 is M12 / P0.5, and the total optical length disposed inside is 16 mm or less. For example, L = 15.46mm, focal length 1.89mm, fy = 0.98mm, fx = 1.42mm, F number is F / 2.6, angle of view is horizontal 194 °, vertical 94.4 °, projection method is equidistant In the projection method, y = 2f · tan (θ / 2), the usable wavelength is effective from visible light to 950 nm, the near-infrared aberration is minimized, and optimization is performed only in the visible region.

  The resolution is 400 TV lines (corresponding to 73 Lp / mm) or more at the center, and 300 TV lines (corresponding to 55 Lp / mm) or more at the periphery. The back focus is 2.6 mm to 3.0 mm (in air), the CCD cover glass has a thickness of 0.75 mm, and the refractive index is 1.5. The object distance is effective from ∞ to 0.3M, and AR coating or water repellent treatment is performed. Further, the first lens part has a waterproof structure. Further, in the imaging apparatus 10 according to this example, the imaging device can be used, for example, in an imaging lens for a color CCD having 250,000 pixels.

  According to the imaging apparatus according to the present example, since the anamorphic lens described above is used, a projection image with an imaging range that is an ultra-wide angle and an image height that is emphasized toward the side surface is obtained, and the image is vertically displayed. Therefore, it is suitable for a wide range of imaging, and it has a compact and simple structure, so that it can be made inexpensive. Moreover, since it has a small F number and is suitable for use in a dark place and has a waterproof structure, it can be suitable for outdoor use such as for vehicle monitoring.

  Next, a monitoring device using the imaging device according to the embodiment will be described. FIG. 15 is a block diagram showing the structure of the monitoring apparatus according to the embodiment. In this example, the monitoring device 100 is a front or rear monitoring device attached to the vehicle. In this example, the monitoring device 100 includes the imaging device 10 and also includes the imaging device 10 configured by a color liquid crystal monitor or the like. In this example, the monitor device 110 is a display unit of the navigation device 120, displays a navigation image, and also obtains a video signal from the television tuner 130 and displays a television screen.

  The monitoring device 100 includes an image display control unit 140, and switches between a monitoring image from the imaging device 10, a navigation image from the navigation device 120, and a television image from the TV tuner 130 according to the operation of the operator. The imaging device 10 is attached to necessary locations such as the front and rear of the vehicle, and images the monitoring location.

  According to the monitoring apparatus according to the present example, since the monitoring image is acquired by the imaging apparatus using the anamorphic lens described above, the super-wide angle can be taken so that the left and right sides of the vehicle can be photographed, and the images of the left and right ends A projection image in which the height is emphasized is obtained, and an anamorphic characteristic in which the image is emphasized in the vertical direction is provided, so that it can be suitable as a vehicle monitoring device. In addition, since the image pickup apparatus has a compact and simple structure, the field of view is not obstructed even when the image pickup apparatus is attached to a vehicle. Moreover, since it has a small F number and is suitable for use in a dark place and has a waterproof structure, it can be suitable for vehicle monitoring.

  In the above example, the example in which the imaging device is used for a monitoring device mounted on a vehicle is shown, but the imaging device is not limited to this, and imaging of a portable information terminal device such as a camera-equipped mobile phone, a digital camera, a video camera, etc. The present invention can also be applied to devices, buildings such as houses and buildings, airplanes other than automobiles, and monitoring cameras of moving bodies such as ships.

It is a horizontal direction sectional view of an anamorphic lens concerning an example of an embodiment. It is a vertical direction sectional view of an anamorphic lens concerning an example of an embodiment. It is a graph which shows the horizontal direction projection characteristic of the anamorphic lens which concerns on this example. It is a graph which shows the vertical direction projection characteristic of the anamorphic lens which concerns on this example. It is a graph which shows the focal distance change of the G2 lens with respect to anamorphic magnification change. It is a graph which shows the focal distance change of the G3 lens with respect to anamorphic magnification change. It is a graph which shows the horizontal field angle direction spherical aberration of the anamorphic lens which concerns on this example. It is a graph which shows the horizontal field angle direction astigmatism of the anamorphic lens which concerns on this example. It is a graph which shows the horizontal field angle direction distortion aberration of the anamorphic lens which concerns on this example. It is a graph which shows the vertical field angle direction spherical aberration of the anamorphic lens which concerns on this example. It is a graph which shows the vertical field angle direction astigmatism of the anamorphic lens which concerns on this example. Graph showing the distortion in the vertical field angle direction of the anamorphic lens according to this example It is a longitudinal cross-sectional view of the imaging device which concerns on the example of embodiment. It is a cross-sectional view of an imaging device according to an embodiment. It is a block diagram which shows the structure of the monitoring apparatus which concerns on the example of an embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Imaging device 11 Housing 12 Front cap 13 End cap 14 Attachment screw part 100 Monitoring apparatus 110 Monitor apparatus 120 Navigation apparatus 130 Television tuner 140 Image display control part G1 1st group lens G2 2nd group lens G3 3rd group lens G4 4th Group lens G5 Fifth group lens G6 Sixth group lens C Cover glass S CCD image pickup device I Optical aperture

Claims (12)

  A six-group anamorphic lens composed of two glass lenses and four resin lenses. Of the four plastic lenses, two are anamorphic aspheric surfaces and two are rotationally symmetric. An anamorphic lens characterized by being an aspherical surface.   The anamorphic lens according to claim 1, wherein the maximum angle of view is 180 ° or more. Of the front lens group consisting of the first lens group, the second lens group, and the third lens group,
The first lens group is a glass lens,
The second group lens and the third group lens are formed as a non-rotationally symmetric anamorphic lens that is changed in curvature in each of the horizontal and vertical directions and is made spherical so as to have a predetermined focal length ratio.
3. The anamorphic lens according to claim 1, wherein the third group lens has a predetermined refractive index and has a function of correcting axial chromatic aberration and lateral chromatic aberration. 4.   The anamorphic lens according to any one of claims 1 to 3, wherein the rear group lens including the fourth group lens, the fifth group lens, and the sixth group lens is configured in a convex and concave triplet type. .   5. The anamorphic lens according to claim 1, wherein among the rear group lenses, the fourth group lens is a glass lens and has an Abbe number higher than a predetermined value.   Among the rear lens groups, the fifth lens group and the sixth lens are resin-made rotationally symmetric aspherical lenses using higher-order aspherical coefficients than the second lens and the third lens. Item 6. The anamorphic lens according to any one of Items 1 to 5. The first group lens G1, the second group lens G2, and the third group lens G3 are arranged from the object side to form an anamorphic optical system, and the image forming system is arranged on the image side from the front group to form an imaging system as a whole. In anamorphic lens with rear group,
The focal length of the first group lens G1 is f (G1), the focal length in the vertical direction of the second group lens G2 is f (G2) _V , the focal length in the horizontal direction is f (G2) _H , and the third group. The focal length in the vertical direction of the lens G3 is f (G3) _V , the focal length in the horizontal direction is f (G3) _H , the anamorphic magnification is M, the focal length obtained by integrating the whole lens is f, and the horizontal length obtained by integrating the whole lens. When the focal length in the direction is fH and the distance from the end surface of the first lens group to the image plane is TT,
fH · θ / TT <0.1 (θ: radians)
An anamorphic lens characterized by that. Maximum half angle of view θ = 1.69 rad (97 °)
TT = 16 (mm)
The anamorphic lens according to claim 7, wherein: The focal length f (G1) of the first group lens G1, the vertical focal length of the second group lens G2 is f (G2) _V , the horizontal focal length is f (G2) _H , and the third group lens. When the focal length in the vertical direction of G3 is f (G3) _V , the focal length in the horizontal direction is f (G3) _H , and the anamorphic magnification is M,
f (G1)>-5 (mm),
1 <(f (G2) _V / f (G2) _H ) / M <1.7
0.51 <(f (G3) _V / f (G3) _H ) / M <1
The anamorphic lens according to claim 7 or 8, wherein the anamorphic lens is made of plastic. When the Abbe number of the second group lens G2 is ν (G2) and the Abbe number ν (G3) of the third group lens G3,
ν (G2) −ν (G3) ≧ 28
The fourth lens group G4 is
f (G4) <2.6
And Abbe number 60 or more Refractive index 1.48 or more The 5th group lens G5 is
-1.61 <f (G5)
The Abbe number is 25 or more, the refractive index is 1.55 or more, and the sixth lens unit G6 is
f (G6) <5.8
The anamorphic lens according to any one of claims 7 to 9, wherein a relationship of Abbe number of 60 or more and refractive index of 1.5 or more is satisfied.   An imaging apparatus comprising: the anamorphic lens according to claim 1; and an imaging device that converts an image formed by the anamorphic lens into an electrical signal. A monitoring device comprising: the imaging device according to claim 11; and a display device that displays an image captured by the imaging device.