KR101639325B1 - Wide angle lens system for visible ray and near infrared rays - Google Patents

Abstract

The present invention relates to a wide-angle lens system for visible light and near-infrared light that can be applied to a vehicle and a surveillance camera and exhibits excellent optical performance even in a visible light and near-infrared range. A first glass lens L1 having a meniscus type convex on the object side and concave on the upper side and having a curvature radius of the object side surface 111 larger than a curvature radius of the upper side surface 112; A second plastic lens L2 having a negative focal length, concave on the object side, convex on the upper side, and formed of a material having a refractive index of 1.6 or more and having an aspheric surface on both sides; A diaphragm 160; A third plastic lens L3 having a meniscus type convex on the object side and a concave on the object side, the focal length of which is negative or positive, and which is formed of a material having a refractive index of 1.6 or more and is aspheric on both sides; A fourth glass lens (L4) formed of a material having a spherical surface, a positive focal length, a convex shape on the object side, a convex shape on the image side, and Abbe number of 50 or more; And a fifth glass lens (L5) formed of a meniscus type whose both sides are spherical, the focal distance is negative, concave toward the object side and convex upward, and made of a material having a refractive index of 1.6 or more and an Abbe number of 30 or less; The fourth glass lens L4 and the fifth glass lens L5 are bonded to each other to perform chromatic aberration correction for each wavelength; The following condition is satisfied.
0.3 < K1 / Kt < 0.8
0.01 < K2 / Kt < 0.5
0.01 < K3 / Kt < 0.5
0.7 < K4 / Kt < 1.3
0.1 < K5 / Kt < 0.6
Here, K1 is the refractivity of the first glass lens, K2 is the refractivity of the second plastic lens, K3 is the refractivity of the third plastic lens, K4 is the refractivity of the fourth glass lens, The refractive power of the glass lens, and Kt is the refractive power of the entire lens system.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0002] The present invention relates to a wide-angle lens system for visible light and near-

The present invention relates to a wide-angle lens system for visible light and near-infrared light, and more particularly to a wide-angle lens system for visible light and near-infrared light which can be applied to a vehicle and a surveillance camera and exhibits excellent optical performance even in the visible light and near- .

Generally, a camera is installed in a CCTV mobile communication terminal, a computer, a notebook, and a vehicle so that the user can view the surrounding video information or take a picture. In order to reduce the size of a mobile communication terminal and to reduce the size of a computer or a notebook computer, a camera is required to have a small size and a high image quality. In order to prevent a driver from visually disturbing the aesthetics of a vehicle camera, Is required. In addition, such a camera should have a large angle of view to obtain as wide a range of image information as possible.

1 is a view showing a conventional wide-angle lens system.

The wide-angle lens system includes, in order from the object side, a first lens L1, a second lens L2, a third lens L3, a diaphragm AS, a fourth lens L4, a fifth lens L5, A sixth lens L6 is disposed. An optical filter OF such as an infrared ray filter or a cover glass is disposed between the sixth lens 6 and the imaging plane IP.

The first lens L1 and the second lens L2 have a convex meniscus shape on the object side and the radius of curvature of the object side surfaces 1 and 3 is larger than the curvature radius of the upper surfaces 2 and 4 Big.

The third lens L3 is formed such that the object side surface 5 is convex toward the object side and the upper side surface 6 is convex upward.

The fourth lens L4 has the object side surface 7 concave toward the object side and the upper side surface 8 concave upward.

The fifth lens L5 is bonded to the fourth lens L4 to form one lens group. The fifth lens L5 is formed such that the object side face 9 is convex toward the object side and the upper side face 10 is convex upward. The sixth lens L6 is formed so that the object side surface 11 is convex toward the object side and the upper side surface 12 is convex upward.

Such a conventional wide-angle lens system is made by mixing six spherical glass lenses and an aspherical glass lens to realize a wide angle. At least five to six glass lenses should be used to guarantee the same resolution in harsh temperature conditions both inside and outside the vehicle during the hot season.

Such a wide-angle lens system has advantages of less change in resolution due to characteristics of a glass material, but in order to realize a high resolution, it is necessary to increase the number of glass lenses. Also, in order to reduce the manufacturing cost, it is required to be constituted only of a spherical glass lens. In this case, there is a limit in increasing the resolution of the wide-angle lens system.

When the number of plastic lenses is increased to increase the resolution and reduce the number of lenses, the resolution changes due to the change of the refractive index of the plastic material due to the temperature change of the plastic material in the severe temperature conditions of the vehicle and the external monitoring environment, .

In addition, such a wide-angle lens system has a problem that the optical performance of the wide-angle lens system is significantly lowered so that it can not be picked up at a satisfactory resolution in both the visible ray region and the near-infrared ray region including the wavelength band of 400 to 950 nm .

Korean Patent No. 10-1356403 has been developed to solve these problems.

The prior art patent discloses an aperture stop; An object side lens group positioned on the object side with respect to the aperture stop and having a positive refractive power as a whole; And an upper lens group positioned on the upper side with respect to the aperture stop and having a positive refractive power as a whole, wherein the following conditional expression 1 is satisfied with respect to the focal lengths of the object side lens group and the upper lens group: FO is the focal length of the object side lens group (FO &gt; 0), FI is the focal length of the upper lens group (FI &gt; 0) It is possible to provide a wide-angle lens system having a wide angle of view and low distortion while being capable of miniaturization.

However, the prior art patent discloses a wide-angle lens system for a visible light and a near-infrared light, comprising: a first glass lens of a meniscus type having a negative refracting power in order from the object side and convex on the object side, both surfaces being spherical; A second plastic lens of a meniscus type having a positive refractive power and concave toward the object side and at least one aspherical surface; A third plastic lens having a positive refractive power and at least one aspherical surface; iris; A fourth glass lens having a positive refracting power and formed of a material having an Abbe number of 50 or more and having both spherical surfaces and two-sided convex shapes; And a fifth plastic lens having a negative refractive power and formed of a material having a refractive index of 1.6 or more and having both concave surfaces and at least one aspheric surface, the manufacturing cost can be reduced by limiting the use of the glass lens to two or less, It is possible to capture a subject in high resolution both in the light ray area and the near infrared ray area, and to guarantee the resolution even in a wide temperature change (-20 ° C to 80 ° C).

However, in the prior art, there is a problem that since the plastic lens is disposed on the sensor side radiating heat, the plastic lens or the coating film is deformed due to the heat emitted from the sensor, resulting in a decrease in resolution.

Further, there are problems in that the cost of the initial development is increased because three plastic lenses are used or three plastic lenses and one polymer lens are used.

1. Korean Patent No. 10-1356403 entitled " Wide-angle lens system for visible light and near-infrared light "(registered on Apr. 2014. 22.)

SUMMARY OF THE INVENTION Accordingly, the present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a high-resolution imaging apparatus capable of capturing a subject at high resolution in both visible light and near- It is possible to guarantee the resolution even in a wide range of temperature changes (-20 ° C. to 80 ° C.), to prevent degradation in resolution due to heat emitted from the sensor, and to provide a wide angle lens system for visible light and near- .

A first glass lens having a spherical surface on both sides in the order from the object side, a focal length being negative, a meniscus type convex on the object side and concave on the image side, the curvature radius of the object side surface being larger than the curvature radius of the image side; A second plastic lens having a negative focal length, concave on the object side, convex on the upper side, and formed of a material having a refractive index of 1.6 or more and having an aspheric surface on both sides; A diaphragm; A third plastic lens having a focal length of negative or positive, convex on the object side and concave on the upper side, and being formed of a material having a refractive index of 1.6 or more and having an aspheric surface; A fourth glass lens having positive spherical surfaces, positive focal lengths, convex on the object side, convex on the upside, and made of Abbe number 50 or more; And a fifth glass lens formed of a Maniscus type whose both sides are spherical, the focal distance is negative, concave toward the object side and convex upward, and made of a material having a refractive index of 1.6 or more and an Abbe number of 30 or less; The fourth glass lens and the fifth glass lens are bonded to each other to perform chromatic aberration correction for each wavelength; The following condition is satisfied.

0.3 < K1 / Kt < 0.8

0.01 < K2 / Kt < 0.5

0.01 < K3 / Kt < 0.5

0.7 < K4 / Kt < 1.3

0.1 < K5 / Kt < 0.6

Here, K1 is the refractivity of the first glass lens, K2 is the refractivity of the second plastic lens, K3 is the refractivity of the third plastic lens, K4 is the refractivity of the fourth glass lens, The refractive power of the glass lens, and Kt is the refractive power of the entire lens system.

As described above, the wide-angle lens system for visible light and near-infrared light according to the present invention captures an image of a subject in high resolution in both the visible light region and the near-infrared region, and assures resolution even in a wide temperature range (-20 ° C to 80 ° C) There is an advantage to be able to do.

In addition, the two lenses from the sensor side are made of glass, so that the plastic lens can be prevented from being deformed by the heat generated from the sensor.

In addition, there is an advantage in that the initial development cost can be reduced while compensating the temperature by limiting the number of plastic lenses to two.

1 is a view showing a conventional wide-angle lens system.
2 is a block diagram of a wide-angle lens system for visible light and near-infrared light according to an embodiment of the present invention;
FIG. 3A is a schematic view of a wide-angle lens system for visible light and near-infrared light according to a first embodiment of the present invention; FIG.
3b to 3d are temperature-dependent resolution graphs of a wide-angle lens system for visible light and near-infrared light according to a first embodiment of the present invention in the visible light region.
3E to 3G are temperature-dependent resolution graphs of a wide-angle lens system for visible light and near-infrared light according to the first embodiment of the present invention in the near-infrared region.
4A is a schematic view of a wide-angle lens system for visible light and near-infrared light according to a second embodiment of the present invention;
4b to 4d are temperature-dependent resolution graphs of a wide-angle lens system for visible light and near-infrared light according to a second embodiment of the present invention in the visible light region.
Figs. 4E to 4G are temperature-dependent resolution graphs of a wide-angle lens system for visible light and near-infrared light according to a second embodiment of the present invention in the near-infrared region.
5A is a schematic view of a wide-angle lens system for visible light and near-infrared light according to a third embodiment of the present invention;
5B to 5D are temperature-dependent resolution graphs of a wide-angle lens system for visible light and near-infrared light according to a third embodiment of the present invention in the visible light region.
5E to 5G are temperature-dependent resolution graphs of a wide-angle lens system for visible light and near-infrared light according to a third embodiment of the present invention in the near-infrared region.

Hereinafter, a wide-angle lens system for visible light and near-infrared light according to the present invention will be described in detail with reference to the drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. The following terms are defined in consideration of the functions of the present invention, and they may vary depending on the intentions or customs of the client, the operator, the user, and the like. Therefore, the definition should be based on the contents throughout this specification.

Like numbers refer to like elements throughout the drawings.

FIG. 2 is a configuration diagram of a wide-angle lens system for visible light and near-infrared light according to an embodiment of the present invention, FIG. 3A is a configuration diagram of a wide-angle lens system for visible light and near-infrared light according to the first embodiment of the present invention, 3d is a graph of a resolution according to temperature of a wide-angle lens system for a visible light and a near-infrared light according to a first embodiment of the present invention in the visible light region, FIGS. 3e to 3g are graphs FIG. 4A is a view illustrating a configuration of a wide-angle lens system for visible light and near-infrared light according to a second embodiment of the present invention, and FIGS. 4B to 4D are cross- 4E to 4G are graphs showing the resolution according to temperature of the wide-angle lens system for visible light and near-infrared light according to the second embodiment of the present invention, FIG. 5A is a configuration diagram of a wide-angle lens system for a visible light and a near-infrared light according to a third embodiment of the present invention, and FIGS. 5B to 5C are graphs showing the resolution of the wide-angle lens system for visible light and near-infrared light according to the second embodiment, 5D is a graph of a resolution according to temperature of a wide-angle lens system for a visible light and a near-infrared light according to a third embodiment of the present invention in the visible light region, and Figs. 5E to 5G are cross- A graph of the temperature-dependent resolution of a wide-angle lens system for visible light and near-infrared light.

2, the wide-angle lens system for visible light and near-infrared light according to the embodiment of the present invention includes a first glass lens L1, a second plastic lens L2, a third plastic lens L3, an iris 160, a fourth glass lens L4, and a fifth glass lens L5. The third glass lens L3, the fourth glass lens L4 and the fifth glass lens L5 form the second lens group L1, the second plastic lens L2 forms the first lens group, Thereby forming a lens group.

The first glass lens L1 is a lens closest to the object side. The first glass lens L1 has a negative refracting power and is formed into a convex meniscus type on the object side. The first glass lens L1 is located closest to the external environment, and is formed of a glass material to withstand external scratches, humidity, and converge light of a wide angle. The first glass lens L1 is a meniscus type having a spherical surface on both sides and a negative focal length, and a curvature radius of the object side surface 111 is larger than a curvature radius of the upper surface 112. [

The second plastic lens L2 is located next to the first glass lens L1. The second plastic lens L2 is made of a plastic material, which is concave on the object side and is aspherical on both sides. The second plastic lens L2 reduces the angle of the light incident on the first glass lens L1 so that the second plastic lens L2 can be easily formed on the lens provided after the diaphragm 160. [ In addition, the second plastic lens L2 allows the light to be vertical to the diaphragm to realize a high resolution. The second plastic lens L2 is preferably formed of a material having a refractive index of 1.6 or more in order to realize high resolution and is made insensitive to a temperature change. Reference numeral 121 denotes the object side surface of the second plastic lens L2, and 122 denotes the upper surface of the second plastic lens L2.

The diaphragm 160 is located next to the second plastic lens L2. Aperture 160 adjusts the size of the aperture to adjust the amount of light passing through the lens.

The third plastic lens L3 is located next to the second plastic lens L2. The third plastic lens L3 is an aspheric surface on both sides and is formed of a plastic material. The third plastic lens L3 is formed in a convex meniscus shape toward the object side. The third plastic lens L3 reduces the angle of the light incident on the first glass lens L1 so that it can be easily formed on the lens provided next. The third plastic lens L3 is preferably made of a material having a refractive index of 1.6 or more in order to realize a high resolution with a negative or positive focal length and is made insensitive to temperature change. Reference numeral 131 denotes the object side surface of the third plastic lens L3, and 132 denotes the upper surface of the third plastic lens L3.

After the third plastic lens L3, the fourth glass lens L4 is located. The fourth glass lens L4 has a positive refractive power and is formed of a glass material of a two-sided convex shape. The fourth glass lens L4 is made of a lens which is a double-sided spherical surface, thereby lowering the manufacturing cost and facilitating the assembly. It is preferable that the fourth glass lens L4 is made of a glass lens having an Abbe's number of 50 or more in order to correct chromatic aberration for each wavelength. The Abbe number is a number indicating the property of light dispersion of the optical glass. The larger the Abbe number, the less chromatic dispersion occurs and a clear image can be obtained. Reference numeral 141 denotes an object side surface of the fourth glass lens L4, and 142 denotes an upper surface of the fourth glass lens L4.

The fifth glass lens L5 is positioned after the fourth glass lens L4. The fifth glass lens L5 has a negative refractive power. The fifth glass lens L5 is formed as a meniscus type concave on the object side. It is preferable that the fifth glass lens L5 is formed of a material having a high refractive index of 1.6 or more in order to finally realize a high resolution. Reference numeral 151 denotes an object side surface of the fifth glass lens L5, and 152 denotes an upper surface of the fifth glass lens L5.

Here, the fourth glass lens L4 and the fifth glass lens L5 are bonded to reduce chromatic aberration through chromatic aberration correction.

Further, the optical filter 170 may be positioned between the fifth glass lens L5 and the image formation plane 180. [ The optical filter 170 may be an infrared filter, a cover glass, or the like, and the optical filter 170 is not considered to affect the optical performance.

In the wide-angle lens system of the present invention, it is preferable that the second plastic lens L2 and the third plastic lens L3 have a low refractive index. Refractive power is 1 / focal length (f), which means the power of the lens. The greater the refracting power, the better the power to break the light. When a large amount of power is applied to a plastic lens, the focal distance and the like may be changed according to the temperature change, resulting in a relatively large resolution change depending on the temperature. Therefore, the second plastic lens L2 and the third plastic lens L3, which are located relatively close to the external environment, are provided with a low refraction ability in the refracting power of the entire lens system to minimize the change in resolution according to the temperature.

Further, in the wide-angle lens system of the present invention, it is preferable that the fourth glass lens L4 has the highest refractive power among the respective lenses. The glass material has a rate of change with temperature which is one-tenth of that of plastic, and has excellent reliability according to the temperature change. When a large amount of power is applied to a plastic lens, the focal distance and the like may be changed according to the temperature change, resulting in a relatively large resolution change depending on the temperature. Therefore, in the wide-angle lens system of the present invention, the fourth glass lens L4 formed of glass among the five lenses is given the highest refractive power.

Further, the fourth glass lens L4 is made of a glass lens having Abbe's number of 50 or more, and has the highest refracting power, so that the change in resolution according to the temperature change can be minimized.

The second plastic lens L2 and the third plastic lens L3 are formed of a plastic material whose both surfaces are aspherical. The second plastic lens L2 and the third plastic lens L3, which are located relatively close to the external environment, have a low refracting power to minimize the resolution change depending on the temperature. The fifth glass lens L5 closest to the image plane 180 and farthest from the external environment has a high refractive index of 1.6 or more, thereby increasing the resolution of the lens system.

In the wide-angle lens system of the present invention, only three glass lenses of the first glass lens L1, the fourth glass lens L4 and the fifth glass lens L5 are used and both sides are spherical, . Since the first glass lens L1 is located at the outermost position in direct contact with the external environment, it is possible to efficiently cope with scratches, humidity and the like by using relatively durable glass.

As described above, the wide-angle lens system of the present invention is composed of all five lenses and limits the use of the glass lens to three, thereby realizing a wide-angle high resolution while reducing the initial development cost, ~ 80 ° C). In addition, the wide-angle lens system of the present invention realizes a high resolution of a wide angle with all five lenses, so that it is possible to perform imaging at a superior resolution without adjusting focus even in the near-infrared region (700 to 950 nm).

Hereinafter, the first to fourth embodiments of the wide-angle lens system of the present invention will be described.

First Embodiment

3A is a diagram showing a configuration of a wide-angle lens system according to the first embodiment of the present invention. FIGS. 3B to 3D are temperature-dependent resolution graphs of the wide-angle lens system according to the first embodiment of the present invention in the visible light region. 3E to 3G are temperature-dependent resolution graphs of the wide-angle lens system according to the first embodiment of the present invention in the near-infrared region.

The following shows design data of the wide-angle lens system according to the first embodiment of the present invention.

lens if Radius of curvature thickness National rate Abe number Focal length Refractive ability The first glass lens The first side 100,000 0.595 1.52249 59.5 -6.61938 0.433914 Second side 3.980 2.861 Second plastic lens The first side -5.639 2.856 1.642506 22.5 20.61628 0.167343 Second side -4.739 3.580 Third plastic lens The first side 12.730 1.351 1.642506 22.5 -24.8457 0.138857 Second side 6.788 0.230 Fourth glass lens The first side 5.293 2.411 1.617998 63.4 3.479906 0.991406 Second side -2.992 0 Fifth glass lens The first side -2.992 1.146 1.784721 25.7 -11.0969 0.270546 Second side -4.987

Here, the F number is 1.96, the total focal length is 3.45 mm, and the angle of view is 126 degrees.

The focal length of the fourth glass lens L4 is the shortest. Therefore, the refractive power of the fourth glass lens L4 is the highest. The refractivity is the inverse of the focal length. If the refractive power of the lens different from the refractive power of the fourth glass lens L4 is increased, it is not preferable because the lens system is sensitive to temperature.

Kn / Kt is the absolute value of the refractive power of each lens divided by the refractive power of the entire lens, and represents the ratio of the refractive power of each lens to the refractive power of the entire lens.

The refractive power of the first glass lens L1 satisfies the following conditional expression (1).

0.3 < K1 / Kt | < 0.8 [Conditional Expression 1]

Here, K1 is the refractive power of the first glass lens L1, and Kt is the refractive power of the entire lens system.

The refractive power of the second plastic lens L2 satisfies the following conditional expression (2).

0.01 < K2 / Kt | < 0.5 [Conditional expression 2]

Here, K2 is the refraction index of the second plastic lens L2, and Kt is the refraction index of the entire lens system.

The refractive power of the third plastic lens L3 satisfies the following conditional expression (3).

0.01 < K3 / Kt | < 0.5 [Conditional expression 3]

Here, K3 is the refractive power of the third plastic lens L3, and Kt is the refractive power of the entire lens system.

The refractive power of the fourth glass lens L4 satisfies the following conditional expression (4).

0.7 <K4 / Kt | <1.3 [Conditional expression 4]

Here, K4 is the refractive power of the fourth glass lens L4, and Kt is the refractive power of the entire lens system.

The refractivity of the fifth glass lens L5 satisfies the following conditional expression (5).

0.1 < K5 / Kt < 0.6 [Conditional expression 5]

Here, K5 is the refraction index of the fifth glass lens L5, and Kt is the refraction index of the entire lens system.

The refractive powers of the first glass lens L1, the second plastic lens L2, the third plastic lens L3 and the fifth glass lens L5 are lower than the refractive power of the entire lens system Of the total. It is also understood that the refractive power of the fourth glass lens L4 occupies a high ratio in the refractive power of the entire lens system. This is to reduce the resolution change due to the temperature change by giving the first glass lens L1, the second plastic lens L2, the third plastic lens L3, and the fifth glass lens L5 relatively low refractive index. to be.

The aspherical surface used in this embodiment is obtained from the following equation (1).

[Equation 1]

Where Y is the distance in the direction perpendicular to the optical axis, c is the reciprocal of the radius of curvature at the apex of the lens, K is the Conic constant, , A, B, C, D, E, and F are aspheric coefficients.

In this embodiment, both surfaces of the second plastic lens L2 and the third plastic lens L3 are formed as aspheric surfaces. The conic constant and the aspherical surface coefficient of the second plastic lens L2 and the third plastic lens L3 are as follows.

division Second plastic lens Third plastic lens The first side Second side The first side Second side K 0 0.3726398 0 0 A4 0.001145 0.003434 0.008996 0.00991 A6 1.12E-05 -3.87E-05 -0.00031 -7.00E-05 A8 -3.08E-06 7.43E-07 -4.35E-05 -6.31E-05 A10 -4.91E-08 3.05E-07 4.81E-06 3.83E-06

Figures 3b, 3c and 3d show a resolution graph of the lens system at the respective temperatures (20 deg. C, 80 deg. C, -20 deg. C) of the visible light region.

In the graph, the horizontal axis represents the spatial frequency, and the higher the spatial frequency value, the higher the resolution. For example, the highest value 160 on the horizontal axis means that there are 160 pairs of black and white pixels (1 cycle) within 1 mm.

The vertical axis represents a modulation transfer function (MTF), which indicates the degree to which a pixel pair can be disassembled. The modulation transfer function is a function of how well the lens system passes the spatial frequency to the image plane. When a certain image (various kinds of spatial frequencies) passes through the lens system, the modulation transfer function value becomes "1" when the image is reproduced at the same brightness, and becomes "0" when the image disappears completely from the image surface.

In the graph, line color, straight line, dotted line, etc. indicate the resolution for each position. For example, in the graph, the blue solid line is the resolution of the light coming in at the center of the lens, green is 22.05 ° (half angle), red is 44.10 ° (half angle), and yellow is 63.00 ° It represents light. These line colors represent light entering the lens at four representative points (0 °, 22.05 °, 44.10 °, 63.00 °).

3B to 3D, it can be seen that the resolution of the wide-angle lens system at 20 ° C is maintained at 80 ° C and -20 ° C. Therefore, in the wide-angle lens system of this embodiment, the use of the glass lens can be limited to two and the manufacturing cost can be reduced while reducing the total number of lenses. In addition, resolution can be guaranteed even at wide temperature changes (-20 ° C to 80 ° C) while realizing high resolution at wide angle.

Second Embodiment

4A is a diagram showing a configuration of a wide-angle lens system according to a second embodiment of the present invention. 4B to 4D are temperature-dependent resolution graphs of the wide-angle lens system according to the second embodiment of the present invention in the visible light region. 4E to 4G are temperature-dependent resolution graphs of the wide-angle lens system according to the second embodiment of the present invention in the near-infrared region.

The following shows design data of the wide-angle lens system according to the second embodiment of the present invention.

lens if Radius of curvature thickness Refractive index Abe number Focal length Refractive ability The first glass lens The first side 100,000 0.590 1.768422 49.3 -5.8876 0.614852 Second side 4.317 2.231 Second plastic lens The first side -3.774 1.991 1.533436 55.7 143.3064 0.025261 Second side -4.255 3.206 Third plastic lens The first side 7.282 3.538 1.632413 23.3 56.76925 0.063767 Second side 7.415 0.174 Fourth glass lens The first side 4.938 2.333 1.618 63.4 3.373318 1.073127 Second side -2.957 0 Fifth glass lens The first side -2.957 0.585 1.805195 25.5 -7.52382 0.481138 Second side -6.285

Here, the F number is 1.99, the total focal length is 3.62 mm, and the angle of view is 127 degrees.

The focal length of the fourth glass lens L4 is the shortest. Therefore, the refractive power of the fourth glass lens L4 is the highest. The refractive power of each lens satisfies the above-described conditional expressions (1) to (5).

In this embodiment, both surfaces of the second plastic lens L2 and the third plastic lens L3 are formed as aspheric surfaces. The conic constant and the aspherical surface coefficient of the second plastic lens L2 and the third plastic lens L3 are as follows.

division Second plastic lens Third plastic lens The first side Second side The first side Second side K 0 -0.9305721 0 0 A4 0.004106 0.004054 0.003712 0.004303 A6 0.000222 -2.31E-05 -0.00014 5.73E-05 A8 -1.56E-05 2.06E-06 2.70E-06 -5.36E-06 A10 1.18E-06 4.37E-08 2.43E-07 -2.88E-07

4B, 4C and 4D show the resolution graphs of the lens system at the respective temperatures (20 DEG C, 80 DEG C, -20 DEG C) of the visible light region.

In the graph, line color, straight line, dotted line, etc. indicate the resolution for each position. For example, in the graph, the blue solid line is the resolution of the light coming into the center of the lens, green is 22.52 ° (half angle), red is 43.05 ° (half angle), yellow is 61.50 ° (half angle) It represents light.

Referring to FIGS. 4B to 4D, it can be seen that the resolution of the wide-angle lens system at 20 ° C is maintained at 80 ° C and -20 ° C. Therefore, in the wide-angle lens system of this embodiment, the use of the glass lens can be limited to two and the manufacturing cost can be reduced while reducing the total number of lenses. In addition, resolution can be guaranteed even at wide temperature changes (-20 ° C to 80 ° C) while realizing high resolution at wide angle.

Figs. 4E, 4F and 4G show a resolution graph of the lens system at the respective temperatures (20 DEG C, 80 DEG C, -20 DEG C) of the near infrared region.

4E to 4G, it is confirmed that the resolution of the wide-angle lens system at 20 ° C in the near-infrared region is sufficiently maintained even at 80 ° C and -20 ° C. Therefore, the wide-angle lens system of the present embodiment can ensure resolution even in a wide temperature range (-20 deg. C to 80 deg. C) while maintaining excellent resolution without adjusting the focus even in the near infrared region.

Third Embodiment

5A is a diagram showing the configuration of a wide-angle lens system according to a third embodiment of the present invention. FIGS. 5B to 5D are graphs showing the temperature-dependent resolution of the wide-angle lens system according to the third embodiment of the present invention in the visible light region. 5E to 5G are temperature-dependent resolution graphs of the wide-angle lens system according to the third embodiment of the present invention in the near-infrared region.

The following shows design data of the wide-angle lens system according to the third embodiment of the present invention.

lens if Radius of curvature thickness Refractive index Abe number Focal length Refractive ability The first glass lens The first side 144.527 0.496 1.496998 81.6 -8.29224 0.443788 Second side 4.002 2.867 Second plastic lens The first side -5.212 3.512 1.642506 22.5 -75.8863 0.048494 Second side -7.374 0.649 Third plastic lens The first side 8.523 3.703 1.642506 22.5 -3714.08 0.000991 Second side 7.049 0.221 Fourth glass lens The first side 5.152 2.187 1.617998 63.4 3.280336 1.121836 Second side -2.800 0 Fifth glass lens The first side -2.800 0.839 1.805189 25.5 -9.44275 0.389717 Second side -5.026

Here, the F number is 1.97, the total focal length is 3.68 mm, and the angle of view is 125 deg.

The focal length of the fourth glass lens L4 is the shortest. Therefore, the refractive power of the fourth glass lens L4 is the highest. The refractive power of each lens satisfies the above-described conditional expressions (1) to (5).

In this embodiment, both surfaces of the second plastic lens L2 and the third plastic lens L3 are formed as aspheric surfaces. The conic constant and the aspherical surface coefficient of the second plastic lens L2 and the third plastic lens L3 are as follows.

division Second plastic lens Third plastic lens The first side Second side The first side Second side K 0 0 0 0 A4 0.002892 0.014461 0.014888 0.005717 A6 -0.00013 -0.00189 -0.00236 2.51E-05 A8 -1.29E-05 0.000143 0.000251 -7.48E-06 A10 1.26E-06 -4.74E-06 -1.23E-05 -4.42E-08

In the graph, line color, straight line, dotted line, etc. indicate the resolution for each position. For example, in the graph, the blue solid line is the resolution of the light coming in at the center of the lens, green is 21.00 ° (half angle), red is 42.00 ° (half angle), yellow is 60 ° It represents light.

5B to 5D, it can be seen that the resolution of the wide-angle lens system at 20 ° C is maintained at 80 ° C and -20 ° C. Therefore, in the wide-angle lens system of this embodiment, the use of the glass lens can be limited to two and the manufacturing cost can be reduced while reducing the total number of lenses. In addition, resolution can be guaranteed even at wide temperature changes (-20 ° C to 80 ° C) while realizing high resolution at wide angle.

5E, 5F and 5G show the resolution graph of the lens system at the respective temperatures (20 DEG C, 80 DEG C, -20 DEG C) of the near infrared region.

5E to 5G, it can be confirmed that the resolution of the wide-angle lens system in the near infrared region 20 is sufficiently maintained even at 80 ° C and -20 ° C.

The wide-angle lens system for visible light and near-infrared light according to the present invention can capture a subject in a high resolution in both the visible light region and the near-infrared region, and guarantee the resolution even in a wide temperature change (-20 ° C to 80 ° C). Further, the two lenses from the sensor side are made of glass, and it is possible to prevent the plastic lens from being deformed by the heat generated from the sensor. In addition, by limiting the number of plastic lenses to two, it is possible to compensate the temperature and reduce the initial development cost.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, Various changes, modifications or adjustments to the example will be possible. Therefore, the scope of protection of the present invention should be construed as including all changes, modifications, and adjustments that fall within the spirit of the technical idea of the present invention.

111, 121, 131, 141, 151: object side surface
112, 122, 132, 142, 152: upper surface 160:
170: Optical filter 180: Image plane
L1: first glass lens L2: second plastic lens
L3: third plastic lens L4: fourth glass lens
L5: Fifth glass lens

Claims (4)

1. A wide-angle lens system for visible light and near-
A first glass having a spherical surface on both sides in the order from the object side, a focal length being negative, a convex on the object side and concave on the upper side, and a curvature radius of the object side surface 111 being larger than a curvature radius of the upper surface 112 A lens L1;
A second plastic lens L2 having a negative focal length, concave on the object side, convex on the upper side, and formed of a material having a refractive index of 1.6 or more and having an aspheric surface on both sides;
A diaphragm 160;
A third plastic lens L3 having a meniscus type convex on the object side and a concave on the object side, the focal length of which is negative or positive, and which is formed of a material having a refractive index of 1.6 or more and is aspheric on both sides;
A fourth glass lens (L4) formed of a material having a spherical surface, a positive focal length, a convex shape on the object side, a convex shape on the image side, and Abbe number of 50 or more; And
A fifth glass lens (L5) formed of a meniscus type whose both sides are spherical, the focal distance is negative, concave toward the object side and convex upward, and made of a material having a refractive index of 1.6 or more and an Abbe number of 30 or less;
The fourth glass lens L4 and the fifth glass lens L5 are bonded to each other to perform chromatic aberration correction for each wavelength;
A wide-angle lens system for visible and near-infrared rays satisfying the following conditions:
0.3 < K1 / Kt < 0.8
0.01 < K2 / Kt < 0.5
0.01 < K3 / Kt < 0.5
0.7 < K4 / Kt < 1.3
0.1 < K5 / Kt < 0.6
Here, K1 is the refractivity of the first glass lens, K2 is the refractivity of the second plastic lens, K3 is the refractivity of the third plastic lens, K4 is the refractivity of the fourth glass lens, The refractive power of the glass lens, and Kt is the refractive power of the entire lens system.
The method according to claim 1,
Wherein the fourth glass lens (L4) and the fifth glass lens (L5) are made of a material having a difference Abbe number of 30 or more.
The method according to claim 1,
Wherein the refractive power of the fourth glass lens (L4) is the highest among the respective lenses.
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