KR200406967Y1 - Optical system for wide angle camera with aspheric surface - 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, to secure the amount of ambient light and to implement the image quality of mega-pixel or more.

The present invention is a negative lens having a convex surface on the object side and a concave surface on the image side; A second lens having a convex surface on the object side and a negative magnification lens having a concave surface on the image side; A third lens which is a positive magnification lens having convex surfaces on both the object side and the image side; A fourth lens having a positive magnification lens having a concave surface on the object side and a convex surface on the image side, and being an aspherical lens; A fifth lens which is a positive magnification lens having convex surfaces on both the object side and the image side; A concave / planar sixth lens which is a negative magnification lens having a concave surface on the object side and a plane on the image side; The technical feature of the present invention is to provide an aperture disposed in front of the object side of the fourth lens and including an aperture for selectively converging the light incident from the third lens.

According to the present invention, it is possible to realize the miniaturization of the optical system by reducing the optical field from 24.5mm to 12.4mm with the use of aspherical surface and proper arrangement, so that it can meet the specifications required by the market as well as its application range. In addition, it can achieve wide-angle F / 2.5, optical angle of 160 degrees, and stable megapixel performance to enable mega pixel quality.

Description

Optical system for wide angle camera using aspherical surface {OPTICAL SYSTEM FOR WIDE ANGLE CAMERA WITH ASPHERIC SURFACE}

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

2 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.

3 to 6 is a view showing aberration characteristics of the optical system for a wide-angle camera according to the present invention,

3 is a graph showing the meridian top surface aberration and the nodular phase aberration on the optical axis,

4 is a graph showing the astigmatism of the meridian top surface curvature and the curvature top surface curve,

5 is a graph showing the percent distortion,

6 is a graph showing side chromatic aberration.

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: sixth lens

70: aperture 80: window glass

90: imaging device

The present invention relates to an optical system for a wide angle camera using an aspherical surface, and more particularly, to secure an excellent amount of ambient light, to be easily installed in a narrow space, and to show improved optical performance than a conventional ultra wide angle camera, as well as an upcoming market. The present invention relates to an optical system for a wide-angle camera using an aspherical surface, which can realize image quality of mega-pixel or higher while simultaneously miniaturizing the size and reducing the unit cost according to the needs of the user.

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

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% There was a problem that the optical performance of the camera is greatly reduced thereby.

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 have a ratio of 90% or more of ambient light so that the difference between the center of the lens and the brightness of the surroundings can be solved. To provide an optical system for a wide-angle camera to enable.

In addition, the other object of the present invention is to make the compact size to improve the optical performance while facilitating the installation in a narrow space, and to achieve a megapixel performance while reducing the optical field nearly half than before An optical system for a camera is provided.

Furthermore, another object of the present invention is to provide a special coating treatment of one of the spherical lenses provided with the use of an aspherical surface to function as a general lens or to function as an IR cut-off filter or color filter. It is to provide the optical system for wide-angle camera that can be used regardless of the presence or absence, as well as to be used as a black and white or digital (color) camera, and to achieve the performance required by the market.

The present invention for achieving the above object is a first lens which is a negative magnification lens having a convex surface on the object side and a concave surface on the image side; A second lens having a convex surface on the object side and a negative magnification lens having a concave surface on the image side; A third lens which is a positive magnification lens having convex surfaces on both the object side and the image side; A fourth lens having a positive magnification lens having a concave surface on the object side and a convex surface on the image side, and being an aspherical lens; A fifth lens which is a positive magnification lens having convex surfaces on both the object side and the image side; A concave / planar sixth lens which is a negative magnification lens having a concave surface on the object side and a plane on the image side; It is characterized in that it is disposed in front of the object side of the fourth lens, and composed of an aperture for selectively converging the light incident from the third lens.

In this case, the special coating may be formed on the spherical surface of the third lens or the second lens to function as a general lens, an IR cut-off filter, or a color filter, so that the optical system may be variously used regardless of the filter. It is desirable to.

In addition, the second lens is characterized in that the aspherical surface in addition to the fourth 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 the wide-angle camera using the aspherical surface according to the present invention, as shown in Figure 1, the optical system for the wide-angle camera using the aspherical surface according to the present invention has a convex surface (R1) on the object side A first lens 10 which is a negative ((-) Power) magnification lens having a concave surface R2 on the image side; A second lens 20 which is a negative [(-) Power] magnification lens having an aspherical convex surface R3 on the object side and a concave surface R4 on the image side; A third lens 30 which is a positive [(+) Power] magnification lens having convex surfaces R5 and R6 on both the object side and the image side; A fourth lens 40 that is a positive ((+) Power] magnification lens having a concave surface R7 on the object side and a convex surface R8 on the image side, and is an aspherical lens; A fifth lens 50 which is a positive [(+) Power] magnification lens having convex surfaces R9 and R10 on both the object side and the image side; A concave / plane sixth lens 60, which is a negative ((-) Power) magnification lens having a concave surface R11 on the object side and a plane R12 on the image side; It is disposed in front of the object side of the fourth lens 40, and comprises a configuration including an aperture 70 for selectively converging the light incident from the third lens (30).

In front of the image side of the sixth lens 60, a window glass 80 for protecting the image pickup device and preventing the inflow of foreign substances into them and an image pickup device 90 for inputting image information are sequentially arranged. 90 includes a CCD or a CMOS.

The first lens 10, the second lens 20, and the third lens 30 allow the lens and the lens to be in close contact with each other and be arranged side by side.

In this case, the third lens 30 has an optical design of a special coating for preventing aberration, distortion, and diffuse reflection on the lens surface. It is desirable to enable the use of the optical system as well as to enable the miniaturization of the optical system. That is, the multilayer film is coated on the surface of the third lens 30 to function as a general lens or to alternately vacuum materials having different refractive indices (for example, TiO ₂ / SiO ₂ or Ta ₂ O ₅ / SiO ₂ ). It can be deposited to have an IR cut-off filter or to form a photoresist with gelatin to function as a color filter. This makes it possible to extend the miniaturization and application range of the optical system while showing the filter elimination effect and the function of the filter without the filter through the specificity of the optical design.

In other words, the IR cut-off filter selectively removes unnecessary infrared (IR) light in color photographing, and recognizes long-wavelength light (light after red) that the human cannot feel as a red area in the image pickup device. It is a filter to prevent the image from becoming a red light as a whole by the noise, color filter (color compensation filter) is the color of the real part (object) This filter creates a color close to the image of).

At this time, the specific coating of the above-described optical design is only the embodiment performed on the third lens 30, which is a spherical lens, but this is the configuration of the most preferred embodiment is not particularly limited to this will be apparent, the same effect For this purpose, a special coating may be applied to the surface of the fourth surface R4 having the spherical surface of the second lens 20.

As shown in FIGS. 3 to 6, the fourth lens 40 is an aspherical lens and minimizes the mutual gap through a combination with the third lens 30 utilizing the specificity of the optical design as well as the aspherical design freedom. In addition, it enabled an optical system showing excellent aberration characteristics. On the contrary, the conventional optical lens has a disadvantage in that an optical field is lengthened by arranging the lenses corresponding to the arrangement of the third lens and the fourth lens by simply arranging the lenses to be spaced at regular intervals with an aperture between them.

In addition, the fifth lens 50 having the positive refractive power and the sixth lens 60 having the negative refractive power are brought into contact with each other so as to be in surface contact with each other to be bonded to each other, and the aspherical fourth lens ( By adjusting the design variable in combination with 40), it is possible to minimize the chromatic aberration as shown in FIG.

The present invention of such a configuration is to be composed by assembling the four spherical lenses (10, 30, 50, 60) and two aspherical lenses 20 and 40 in combination, but at an appropriate distribution ratio. And the productivity is improved by selecting a productive lens.

Furthermore, by providing aspherical lenses 20 and 40, the two aspherical lenses are utilized to the maximum (adjusting aspherical coefficients) to correct aberration, i.e., correct the state of spherical aberration and tangential field curvature. It was.

At this time, the optical system according to the present invention was designed to form a ratio of F / 2.5 and an angle of view of 160 degrees, while reducing the overall length from 14.5mm to 12.4mm, while satisfying the following conditions.

[Condition 1]

1.3 ≤ B / f ≤ 2.0

The focal length of the entire lens system is f, and the back focal length from the twelfth surface R12 of the sixth lens 60 to the focal point B is referred to as f.

[Condition 2]

T / f ≤ 5.4

Here, the distance from the first first lens 10 to the last sixth lens 60 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 [First surface R3 of aspherical second lens]

Xo2-Xa2 <0 [First surface R7 of aspherical fourth lens]

Xo3-Xa3> 0 [second surface R8 of the aspherical fourth lens]

Herein, when the convex surface R3 of the second lens 20 is an aspherical surface, the sag of the reference spherical surface is Xo1 and the sag by the aspherical surface is Xa1.

When R7, the concave surface of the fourth lens 40, 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 R8, which is the convex surface of the fourth lens 40, is aspherical, 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]

1.49≤n≤1.90, 35≤v≤85 [second lens]

1.58≤n≤1.95, 18≤v≤30 [Third Lens]

1.49≤n≤1.90, 45≤v≤60 [Fourth Lens]

1.60≤n≤1.90, 40≤v≤60 [Fifth Lens]

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

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

Next, the operation of the optical system for the wide-angle camera using the aspherical surface according to the present invention, which is implemented to satisfy the above conditions (conditions 1 to 4).

FIG. 2 is a view showing sag Xa and spherical surface in an aspherical surface in the optical system for a 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 these equations, the optical system can reduce the optical field of the existing 24.5 mm to 12.4 mm, an aperture ratio (f / dl) of F / 2.5, and an angle of view of 160 degrees. Will form.

In addition, Table 1 below shows the data of the optical system for a wide-angle camera according to the present invention, and shows 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 the present invention

Lens surface Radius of curvature (r) Interval (d) Refractive index (n) Dispersion rate (v) Remarks First side (R1) 10.791 0.3270 1.5688 56.04 2nd side (R2) 1.5679 0.8258 Page 3 (R3) 16.349 0.2452 1.5310 55.90 Aspheric surface Fourth side (R4) 1.3352 0.3293 Page 5 (R5) 2.6486 0.8447 1.8467 23.78 General lens function, IR-cut-off function, color filter function Page 6 (R6) -13.913 0.3770 - - 0.0000 iris Page 7 (R7) -1.9232 0.8229 1.5310 55.90 Aspheric surface 8th page (R8) -0.9570 0.0327 Aspheric surface Page 9 (R9) 2.9973 1.2534 1.7200 50.34 Page 10 (R10) -2.0709 0.2180 1.8467 23.78 Joint surface Page 11 (R11) -2.0709 0.2180 1.8467 23.78 Joint surface Page 12 (R12) ≤ 0.9631 - - 0.4087 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 = -7.800153E-04, AE = 0.00000E-00, AF = 0.00000E-00, AG = 8.631864E-05 of the third side R3,

K = 0.0, AD = -4.887460E-01, AE = 0.00000E-00, AF = -1.603194E-00, AG = 0.00000E-00 on R7;

K = 0.0, AD = 7.367865E-03, AE = −2.686623E-02, AF = 3.143640E-03, AG = −4.734288E-02 on the eighth page R8.

The fifth surface R5 of the third lens 30 is a surface that enables the function of an IR cut-off filter, a color filter, or a general lens by using optical characteristics.

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 sixth lens 60 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 test value, and the second When the aspherical surface of the lens 20 and the fourth lens 40 satisfy the aspherical surface, the sag of the reference sphere is Xo and the sag of the aspherical surface is Xa, and the lens shape and lens arrangement of the optical system according to the present invention It can be seen that etc. satisfy all of the conditions 1, 2, 3, and 4 described above.

That is, [condition 1]

1.3 ≤ B / f ≤ 2.0,

[Condition 2]

With T / f ≤ 5.4,

[Condition 3]

Xo1-Xa1 <0 [First surface R3 of aspherical second lens]

Xo2-Xa2 <0 [First surface R7 of aspherical fourth lens]

Xo3-Xa3> 0 [second surface R8 of the aspherical fourth lens], and

[Condition 4]

1.49≤n≤1.90, 35≤v≤85 [first lens]

1.49≤n≤1.90, 35≤v≤85 [second lens]

1.58≤n≤1.95, 18≤v≤30 [Third Lens]

1.49≤n≤1.90, 45≤v≤60 [Fourth Lens]

1.60≤n≤1.90, 40≤v≤60 [Fifth Lens]

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

Is satisfying.

Therefore, the optical system for the wide angle camera using the aspherical surface according to the present invention exhibits optical performance of 12.4mm optical field length, F / 2.5 of an aspect ratio, and an angle of view (view angle) of 160 degrees. As well as ensuring a wide field of view, it also secures more than 90% of the ambient light ratio, eliminating the difference in brightness between the center of the lens and surroundings, so that a clear image of the object can be obtained. It enables the miniaturization and the mega pixel quality.

3 to 6 are analysis graphs showing aberration characteristics of the optical system for a wide angle camera using an aspherical surface according to the present invention.

Here, FIG. 3 illustrates the meridian top surface aberration and the nodular top surface aberration in the 0, 0.7, and 1.0 regions on the optical axis, respectively, and FIG. 4 shows the tangential field curvature (T) and the sagittal field curvature (S). 5 shows astigmatism of FIG. 5, FIG. 5 shows Distortion, and FIG. 6 shows Chromatic Lateral Aberration.

As shown in the analysis graph of FIGS. 3 to 6, the optical system for the wide angle camera using the aspherical surface according to the present invention shows the values of the images adjacent to the axis in almost all fields, such as spherical aberration, meridian surface aberration, percent distortion, The correction state of chromatic aberration is in good condition, and it indicates that a very effective design is made to improve the brightness of the surroundings as well as the center.

That is, in the conventional general optical system, as compared with correcting aberration characteristics by adjusting the shape of the lens and the arrangement of the refractive power and the position of the aperture, the present invention provides the aspherical second lens 20 having a negative refractive power. Spherical aberration and meridian image by placing the fourth lens 40, which is an aspherical lens having positive (+) refractive power, close to the diaphragm 70, which is the overall optical center, to be disposed at a position spaced apart from the aperture 70 The correction state of the aberration is good, the brightness of the surroundings as well as the center is improved, and the number of lenses constituting the optical system is reduced and the aberration of the optical system is minimized.

As described above, according to the optical system for the wide-angle camera using the aspherical surface according to the present invention, the optical system can be miniaturized by reducing the optical length from 24.5mm to 12.4mm with the use of an aspherical surface and an appropriate arrangement. In addition to being able to meet the specifications required by the specification, the application range can be extended, and the optical performance of the aperture ratio F / 2.5 and the viewing angle of 160 degrees is achieved, and the stable optical performance enables the implementation of the megapixel quality. .

In addition, the present invention is not only easy to be mounted in a small space by implementing the miniaturization, but also has a good performance of forming a wide angle of view and correcting aberration, thereby ensuring an ambient light ratio of 90% or more, thereby increasing the brightness of the center and surroundings of the lens. The difference can be resolved so that a clear image of the object can be obtained.

Furthermore, the present invention is designed to be combined with an aspherical surface, but by applying a special coating to a spherical lens of a specific position to remove the existing IR cut-off filter or color filter, while exhibiting the same function to reduce the material cost It provides the usefulness of using the optical system of the present invention in a monochrome or digital camera with or without a filter.

Claims (6)

A first lens having a convex surface on the object side and a negative magnification lens having a concave surface on the image side; A second lens having a convex surface on the object side and a negative magnification lens having a concave surface on the image side; A third lens which is a positive magnification lens having convex surfaces on both the object side and the image side; A fourth lens having a positive magnification lens having a concave surface on the object side and a convex surface on the image side, and being an aspherical lens; A fifth lens which is a positive magnification lens having convex surfaces on both the object side and the image side; A concave / planar sixth lens which is a negative magnification lens having a concave surface on the object side and a plane on the image side; An optical system for an aspherical camera using an aspherical surface, which is disposed in front of the object side of the fourth lens and comprises an aperture for selectively converging light incident from the third lens. The method of claim 1, An optical system for an aspherical camera using an aspherical surface, characterized in that it is configured to function as a general lens, an IR cut-off filter or a color filter by forming a special coating on the surface of the third lens or the second lens. The method of claim 1, And the second lens has an aspherical surface together with the fourth lens. The method of claim 1, If the focal length of the entire lens system is f and the rear focal length is B, 1.3 ≤ B / f ≤ 2.0 Optical system for a wide-angle camera using an aspherical surface 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 ≤ 5.4 Optical system for a wide-angle camera using an aspherical surface characterized by satisfying the phosphorus conditions. The method of claim 1, The first to sixth lenses, 1.49≤n≤1.90, 35≤v≤85 [first lens] 1.49≤n≤1.90, 35≤v≤85 [second lens] 1.58≤n≤1.95, 18≤v≤30 [Third Lens] 1.49≤n≤1.90, 45≤v≤60 [Fourth Lens] 1.60≤n≤1.90, 40≤v≤60 [Fifth Lens] 1.58 ≦ n ≦ 1.95, 18 ≦ v ≦ 30 [Sixth Lens] An optical system for a wide-angle camera using an aspherical surface, which satisfies the refractive index (n) and dispersion (v) conditions.

Images