KR200406969Y1 - Optical system for wide angle camera - Google Patents

Abstract

 The present invention relates to an optical system for a wide-angle camera, and in particular, to provide a wide-angle camera optical system that can be easily mounted in a narrow space and excellent in securing the amount of ambient light.

The present invention has a first lens having a convex surface on the object side and a concave surface on the image side, and being a negative magnification lens; A second lens having a concave surface on the object side and a convex surface on the image side and being a positive magnification lens; A third lens having a concave surface on the object side and a convex surface on the image side, and having a positive magnification lens and being an aspherical lens; A fourth lens which is a positive magnification lens having convex surfaces on the object side and the image side, respectively; A fifth lens which is a negative magnification lens having concave surfaces on the object side and the image side, respectively; An IR cut-off filter disposed in front of the object side of the third lens and configured to remove light in an infrared (IR) region for improving image quality; Characterized in that it comprises a configuration including an aperture to selectively converge the light from which the infrared region is removed by the IR cut-off filter.

According to the present invention, it exhibits optical performance of 16.4mm of optical length, F / 2.5 of an aspect ratio, and 160 degrees of clock angle, and it is possible to realize miniaturization of optical system by reducing the overall length, and it is easy to install in a narrow space. There is an effect to further improve the use and to exhibit a stable optical performance.

Description

Optical system for wide-angle camera {OPTICAL SYSTEM FOR WIDE ANGLE CAMERA}

1 is a view showing the arrangement of the optical system for a wide-angle camera according to an embodiment of the present invention.

2 is a view showing the arrangement of the optical system for a wide-angle camera according to another embodiment of the present invention.

3 is a view showing a sag (Sag) of the aspherical lens of the optical system for a wide-angle camera according to the present invention.

4 to 7 illustrate aberration characteristics of the optical system for the wide-angle camera of FIG. 1.

8 to 11 illustrate aberration characteristics of the optical system for the wide-angle camera of FIG. 2.

Explanation of symbols on the main parts of the drawings

10: first lens 20: second lens

30: third lens 40: fourth lens

50: fifth lens 60: IR cut-off filter

70: aperture 80: window glass

90: imaging device

The present invention relates to an optical system for a wide-angle camera, and more particularly, excellent in securing ambient light, easy to mount in a narrow space, and exhibiting improved optical performance than conventional ultra-wide-angle cameras. The present invention relates to an optical system for a wide-angle camera that can be used in a CCD or CMOS camera for general purpose, while at the same time minimizing size and reducing cost.

In general, a wide angle camera uses a lens having an angle of view greater than 85 degrees and is suitable for a wide range of shooting. A CCD camera using a charge coupled device (CCD) and a CMOS using a complementary metal oxide semiconductor (CMOS) An example is a camera.

However, the lens used in the wide-angle camera is usually made of a glass material, which acts as a factor to increase the cost, and also is easy to generate image curvature or distortion, significantly reducing the amount of ambient light to less than 30% to 60% By doing so, there was a problem of greatly reducing the optical performance of the camera.

In particular, a CMOS camera having a lens having an ambient light amount of 70% or more should be used for its optical performance. However, it is difficult to apply the lens and development of a lens suitable for a CMOS camera has not been made until now.

Furthermore, due to the rapid growth of the market and the diversification of application fields, there is a demand for the improvement of image sensor technology and better optical performance, and the development of smaller and smaller lenses.

The present invention has been devised to solve the problems described above, and its purpose is to allow the ambient light ratio to be 90% or more so as to resolve the difference in brightness between the center and the periphery of the lens. It is to provide an optical system for a wide-angle camera that can be applied to use throughout the camera.

In addition, another object of the present invention is to provide an optical system for a wide-angle camera that can be easily mounted in a narrow space while improving the optical performance and to reduce the optical field than before.

Further, another object of the present invention is to improve the optical performance through the proper use of aspherical surface, as well as to reduce the number of components provided and to achieve the performance required by the market It is to provide an optical system.

The present invention for achieving the above object is a first lens having a convex surface on the object side and a concave surface on the image side, and a negative magnification lens; A second lens having a concave surface on the object side and a convex surface on the image side and being a positive magnification lens; A third lens having a concave surface on the object side and a convex surface on the image side, and having a positive magnification lens and being an aspherical lens; A fourth lens which is a positive magnification lens having convex surfaces on the object side and the image side, respectively; A fifth lens which is a negative magnification lens having concave surfaces on the object side and the image side, respectively; An IR cut-off filter disposed in front of the object side of the third lens and configured to remove light in an infrared (IR) region for improving image quality; The IR cut-off filter is characterized by having a configuration including an aperture to selectively converge the light from which the infrared region is removed.

In addition, the second lens may be configured to have an aspherical surface together with the third lens.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings and diagrams.

1 is a view showing the arrangement of the optical system for a wide-angle camera according to an embodiment of the present invention, as shown in Figure 1, the optical system for a wide-angle camera according to an embodiment of the present invention is a convex surface (R1) A first lens 10 having a concave surface R2 on the image side and having a negative ((-) Power) magnification lens; A second lens 20 which is a meniscus-shaped spherical surface having a concave surface R3 on the object side and a convex surface R4 on the image side, and which is a positive (+) Power magnification lens; A third lens 30 having a concave surface R5 on the object side and a convex surface R6 on the image side, both sides being aspherical, and being positive ((+) Power] magnification lenses; A fourth lens 40 which is a positive [(+) Power] magnification lens having convex surfaces R7 and R8 on the object side and the image side, respectively; A fifth lens 50 which is a negative ((-) Power) magnification lens having concave surfaces R9 and R10 on the object side and the image side, respectively; An IR cut-off filter (60) disposed in front of the object side of the third lens (30) to remove light in an infrared (IR) region for improving image quality; The filter 60 includes a diaphragm 70 configured to selectively converge the light from which the infrared region is removed.

In this case, in front of the image of the fifth lens 50, the window glass 80 for protecting the image pickup device and preventing the inflow of foreign substances into them and the image pickup device 90 for inputting image information are sequentially arranged. The element 90 includes a CCD or a CMOS.

The first lens 10 and the second lens 20 are arranged in close contact with the lens and the lens close to each other, the second lens 20 and the third lens 30 is an IR cut-off filter 60 The fourth lens 40 having a positive refractive power and the fifth lens 50 having a negative refractive power are fitted to be in surface contact with each other. To make contact arrangement.

The diaphragm 70 is arranged to be in contact with the upper surface of the IR cut-off filter 60.

2 is a view showing the arrangement of the optical system for a wide-angle camera according to another embodiment of the present invention, the optical system for a wide-angle camera according to another embodiment of the present invention as shown in FIG. All of the configurations are the same as those of the example, except that the second lens 20 has an aspherical surface on the convex surface R4, which is the second surface, and is only composed of meniscus type aspherical lenses instead of spherical lenses. There is this.

That is, the present invention according to one embodiment and another embodiment as described above is to have an aspherical structure of the third lens 30 or an aspherical structure of the second lens 20 and the third lens 30. 3 or 4 spherical lenses [(10) (20) (40) (50)] and one or two aspherical lenses ((20) (30)] shall be composed by combining The distribution of magnification and the selection of a productive lens improve productivity.

In particular, by utilizing the aspherical coefficient of the third lens 30, which is an aspherical lens having a positive refractive index, to correct the spherical aberration and tangential field curvature and to ensure that the correction state is good. Of course, it is possible to improve not only the center but also the brightness of the surroundings. The second lens 20 having the aspherical surface has an additional function of correcting distortion in the form of a meniscus.

The first lens 10, which is a spherical lens, functions to determine an angle of view (clock angle) that characterizes a wide angle. In the case of the second lens 20, which is a spherical lens, the distortion is corrected in a meniscus shape. Is the main function.

The fourth lens 40 and the fifth lens 50, which are spherical lenses, function to correct junction chromatic aberration by a bonding arrangement which is brought into contact with each other so as to be in surface contact with each other. The adjustment function will be performed.

The optical system according to the present invention having such a configuration is designed to reduce the total length of the existing 24.5mm to 16.4mm while satisfying the following conditions, and to form an aperture ratio F / 2.5 and a viewing angle (view angle) of 160 degrees.

[Condition 1]

1.4 ≤ B / f ≤ 2.4

Here, the focal length of the entire lens system is f, and the back focal length from the tenth surface R10 of the fifth lens to the focal point is B.

[Condition 2]

T / f ≤ 6.9

The distance from the first first lens 10 to the last fifth lens 50 of the optical system is referred to as the optical field T, and the focal length of the entire lens system is f.

[Condition 3]

Xo1-Xa1 <0 [second surface R4 of the aspherical second lens]

Xo2-Xa2 <0 [First surface R5 of aspherical third lens]

Xo3-Xa3> 0 [second surface R6 of the aspherical third lens]

Here, when the convex surface R4 of the second lens 20 is an aspherical surface, the sag of the reference spherical surface is referred to as Xo1 and the sag by the aspherical surface is referred to as Xa1.

When the concave surface R5 of the third lens 30 is an aspherical surface, the sag of the reference spherical surface is called Xo2, and the sag by the aspherical surface is called Xa2.

When R6, which is the convex surface of the third lens 30, is an aspherical surface, the sag of the reference spherical surface is called Xo3, and the sag by the aspherical surface is called Xa3.

(However, the dimensions of each unit satisfy the absolute value and the calculated values satisfy the real value.)

[Condition 4]

1.49≤n≤1.90, 35≤v≤85 [first lens]

1.58≤n≤1.95, 18≤v≤30 [second lens]

1.49≤n≤1.90, 35≤v≤85 [Third Lens]

1.60≤n≤1.90, 40≤v≤60 [Fourth Lens]

1.58 ≦ n ≦ 1.95, 18 ≦ v ≦ 30 [Fifth Lens]

Where n is the refractive index of the lens and v is the dispersion of the lens.

Next will be described the operation of the optical system according to the present invention is implemented to satisfy the above conditions (conditions 1 to 4).

FIG. 3 shows a sag Xa and a spherical surface in an aspherical surface in the optical system for the wide-angle camera according to the present invention, when the height of the optical is Y in the plane where the curvature on the optical axis of the reference sphere is C (= 1 / R). As a graph showing Sag Xo in, comparing Sag Xa in an aspherical lens and Sag Xo in an aspherical lens, Equation 1 (for spherical lens) and Equation 2 (for aspheric lens) It can be represented as.

[Equation 1]

[Equation 2]

Where C is the curvature (C = 1 / R; R is the radius of the lens), Y is the height, K is the conic constant, and AD / AE / AF / AG represents the aspherical coefficient, respectively.

When the above conditions 1 and 2 are satisfied through this equation, the optical system can reduce the optical field of the existing 24.5 mm to 16.4 mm, the aperture ratio (f / dl) F / 2.5, the viewing angle (view angle) 160 degrees Will form.

In addition, Table 1 and Table 2 show the data of the optical system according to an embodiment of the present invention and another embodiment, showing the curvature radius of the lens, the center interval, the refractive index of the lens and the dispersion coefficient of the lens.

[Table 1] Data of the optical system according to an embodiment of the present invention

Lens surface Radius of curvature (r) Interval (d) Refractive index (n) Dispersion rate (v) Remarks First side (R1) 27.918 0.3046 1.7130 53.94 2nd side (R2) 1.5787 1.1452 Page 3 (R3) -7.9893 1.0152 1.8466 23.78 Fourth side (R4) -4.1066 0.9782 - - 0.3553 1.5168 64.20 IR cut-off - - 0.1274 iris Page 5 (R5) -2.2777 1.1675 1.5310 55.90 Aspheric surface Page 6 (R6) -1.1533 0.0305 Aspheric surface Page 7 (R7) 2.7919 1.2183 1.7200 50.34 8th page (R8) -1.7767 0.2030 1.8466 23.78 Joint surface Page 9 (R9) -1.7767 0.2030 1.8466 23.78 Joint surface Page 10 (R10) 9.0315 1.4055 - - 0.3807 1.5168 64.20 Window glass - - - Image pickup device

Here, each of the data is a value normalized to 1.0 mm of effective focal length (EFL).

K = 0.0, AD = -1.360882E-01, AE = 0.00000E-00, AF = -5.704512E-01, AG = 0.00000E-00 of the fifth surface R5;

K = 0.0, AD = 2.087184E-02, AE = -1.299881E-02, AF = 0.00000E-00, and AG = 0.00000E-00 on the sixth surface R6.

[Table 2] Data of the optical system according to another embodiment of the present invention

Lens surface Radius of curvature (r) Interval (d) Refractive index (n) Dispersion rate (v) Remarks First side (R1) 27.918 0.3046 1.7725 49.62 2nd side (R2) 1.6244 1.1565 Page 3 (R3) -50.761 1.1167 1.6070 26.90 Fourth side (R4) -4.4746 1.1218 Aspheric surface - - 0.3553 1.5168 64.20 IR cut-off - - 0.1506 iris Page 5 (R5) -2.2777 1.1675 1.5310 55.90 Aspheric surface Page 6 (R6) -1.1533 0.0305 Aspheric surface Page 7 (R7) 2.4670 1.3452 1.7200 50.34 8th page (R8) -1.7767 0.2030 1.8466 23.78 Joint surface Page 9 (R9) -1.7767 0.2030 1.8466 23.78 Joint surface Page 10 (R10) 4.2487 1.2882 - - 0.3807 1.5168 64.20 Window glass - - - Image pickup device

Here, each of the data is a value normalized to 1.0 mm of effective focal length (EFL).

K = 0.0, AD = -1.237510E-03, AE = -1.745141E-03, AF = 0.00000E-00, AG = 0.00000E-00 on the fourth side (R4),

K = 0.0, AD = -1.360922E-01, AE = 0.00000E-00, AF = -5.704798E-01, AG = 0.00000E-00 on the fifth side (R5),

K = 0.0, AD = 2.087229E-02, AE = -1.299927E-02, AF = 0.00000E-00, and AG = 0.00000E-00 on the sixth surface R6.

The present invention has an effective diameter (dl: mm) and a spherometer measuring the inner diameter of the entire lens system by f, the rear focal length B, and the first first lens of the optical system. 10), the distance from the last fifth lens 50 to T, the angle of view measured value θ by the projection inspector, the aperture ratio (f / dl = F / 2.5) of the center CR and the periphery PR of the resolution measurement value, and the second In the aspherical surface of the lens 20 and when the third lens 30 satisfies the aspherical surface (Table 2), when the sag of the reference sphere is Xo and the sag by the aspherical surface is Xa, the lens of the optical system according to the present invention. It can be seen that the shape, lens arrangement, and the like satisfy all of the conditions 1, 2, 3, and 4 described above.

That is, [condition 1]

1.4 ≤ B / f ≤ 2.4,

[Condition 2]

With T / f ≤ 6.9,

[Condition 3]

Xo1-Xa1 <0 [second surface R4 of the aspherical second lens]

Xo2-Xa2 <0 [First surface R5 of aspherical third lens]

Xo3-Xa3> 0 [second surface R6 of the aspherical third lens], and

[Condition 4]

1.49≤n≤1.90, 35≤v≤85 [first lens]

1.58≤n≤1.95, 18≤v≤30 [second lens]

1.49≤n≤1.90, 35≤v≤85 [Third Lens]

1.60≤n≤1.90, 40≤v≤60 [Fourth Lens]

1.58? N? 1.95, and 18? V? 30 [Fifth Lens] are satisfied.

Therefore, the optical system for the wide-angle camera according to the present invention exhibits optical performance of 16.4 mm in optical length, an F / 2.5 of an aspect ratio, and an angle of view of 160 degrees, and sends an image of an object to the image pickup device at a wide angle of view of 160 degrees. In addition to ensuring the field of view, by securing a ratio of more than 90% of the ambient light ratio, the difference in brightness between the center and the periphery of the lens can be resolved to obtain a clear image of the object.

4 to 11 are analysis graphs showing aberration characteristics of the optical system for a wide-angle camera according to one embodiment of the present invention and another embodiment.

4 and 8 show the meridian aberration and the nodular phase aberration in the areas 0, 0.7, and 1.0 on the optical axis, respectively, and FIGS. 5 and 9 show the tangential field curvature (T) and the nodal phase curvature ( S: shows astigmatism of Sagittal Field Curvature, FIG. 6 and FIG. 10 show percent distortion, and FIG. 7 and FIG. 11 show lateral chromatic aberration.

As shown in the analysis graph of FIGS. 4 to 11, the optical system for the wide-angle camera according to the present invention shows that the values of the images are shown adjacent to the axis in almost all fields, thereby correcting spherical aberration, meridian aberration, percent distortion, and chromatic aberration. This indicates that the condition is good and that a very effective design can be made to improve the brightness of the surroundings as well as the center.

As described above, according to the optical system for a wide-angle camera according to the present invention, the optical performance of 16.4mm optical field length, F / 2.5 of an aspect ratio, 160 degrees of a clock angle is achieved, and the optical system can be miniaturized by reducing the overall length. At the same time, by arranging one or two aspherical lenses, not only the manufacturing cost can be reduced, but also by securing 90% or more of the ambient light ratio, the difference between the center of the lens and the brightness of the surroundings can be eliminated. It can be applied to CCD and CMOS cameras.

In addition, the present invention is not only easy to be mounted in a narrow space by the implementation of miniaturization, but also can be extended to the application range, and the formation of a wide angle of view and aberration correction exhibits good performance.

Furthermore, the present invention not only enables the improved and stable optical performance through the proper use of aspherical surface, but also reduces the components as well as the material cost compared to the existing configuration, thereby providing the performance required by the market. It can be said.

Claims (5)

A first lens having a convex surface on the object side and a concave surface on the image side, and being a negative magnification lens; A second lens having a concave surface on the object side and a convex surface on the image side and being a positive magnification lens; A third lens having a concave surface on the object side and a convex surface on the image side, and having a positive magnification lens and being an aspherical lens; A fourth lens which is a positive magnification lens having convex surfaces on the object side and the image side, respectively; A fifth lens which is a negative magnification lens having concave surfaces on the object side and the image side, respectively; An IR cut-off filter disposed in front of the object side of the third lens and configured to remove light in an infrared (IR) region for improving image quality; An optical system for a wide-angle camera, characterized in that the configuration comprising an aperture for selectively converging the light from which the infrared region is removed by the IR cut-off filter. The method of claim 1, The second lens is an optical system for a wide-angle camera, characterized in that aspherical configuration is possible with the third lens. The method of claim 1, If the focal length of the entire lens system is f and the rear focal length is B, 1.4 ≤ B / f ≤ 2.4 Optical system for a wide-angle camera, characterized by satisfying the phosphorus conditions. The method of claim 1, If the distance from the first lens surface of the optical system to the last lens surface is T and the focal length of the entire lens system is f, T / f ≤ 6.9 Optical system for a wide-angle camera, characterized by satisfying the phosphorus conditions. The method of claim 1, The first to fifth lenses, 1.49≤n≤1.90, 35≤v≤85 [first lens] 1.58≤n≤1.95, 18≤v≤30 [second lens] 1.49≤n≤1.90, 35≤v≤85 [Third Lens] 1.60≤n≤1.90, 40≤v≤60 [Fourth Lens] 1.58 ≦ n ≦ 1.95, 18 ≦ v ≦ 30 [Fifth Lens] Optical system for a wide-angle camera, characterized by satisfying the refractive index (n) and dispersion (v) corresponding to the conditions.

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