KR200422729Y1 - Optical system for security camera with special lens arragement - Google Patents

Abstract

The present invention relates to an optical system for surveillance cameras using a special lens array, which is a negative [(-) Power] magnification lens having a convex surface on an object side and a concave surface on an image side, and comprising: a first lens formed of a spherical surface; A second lens having a positive ((+) Power] magnification lens having a convex surface or a concave surface on an object side and a convex surface on an image side, and having a spherical surface; A third lens having a positive [(+) Power] magnification lens having convex surfaces on both the object side and the image side, and having a spherical surface; A fourth lens having a negative [(-) Power] magnification lens having a concave surface on the object side and a concave or convex surface on the object side, and formed of an ultra-high refractive spherical lens; It is characterized in that the technical configuration to include an aperture for selectively converging the light incident from the first lens.

According to the present invention, by arranging a special high refractive spherical lens, the brightness and resolution of the optical system can be greatly improved, and the compact manufacturing of the optical system enables easy mounting in a narrow space and can be used in a CCD camera or a CMOS camera. It is possible to provide brightness and resolution comparable to that of the aspherical lens without the aspherical lens, and to provide the mega-pixel performance even with the aspherical lens.

Description

OPTICAL SYSTEM FOR SECURITY CAMERA WITH SPECIAL LENS ARRAGEMENT}

1 is a view showing an optical system characterized by an angle of view of 78 degrees of the arrangement of the optical system for surveillance cameras according to the present invention.

2 is a view showing an optical system characterized by an angle of view of 92 degrees of the arrangement of the optical system for surveillance cameras according to the present invention.

3 is a view showing an optical system characterized by an angle of view of 120 degrees of the arrangement of the optical system for surveillance cameras according to the present invention.

4A to 4D are diagrams showing aberration characteristics of an optical system characterized by an angle of view of 78 degrees shown in FIG.

5A to 5D show aberration characteristics of an optical system characterized by a 92 degree angle of view shown in FIG.

6A to 6D are diagrams showing aberration characteristics of the optical system characterized by the 120-degree field of view shown in FIG.

Explanation of symbols on the main parts of the drawings

10: first lens 20: second lens

30: third lens 40: fourth lens

50: aperture 60: window glass

70: imaging device

The present invention relates to an optical system for surveillance cameras, and more specifically, to arrange a spherical ultra-high refractive lens and to utilize a special spherical lens property to maximize the brightness and resolution. It relates to the optical system for surveillance cameras used.

Existing low-cost surveillance cameras have been mainly used in closed spaces such as parking lots and elevators in apartments or in places where people such as factories are not suitable for direct monitoring.

Conventional spherical lenses used in such surveillance cameras have a problem of deteriorating optical performance due to large image curvature or distortion and a significant decrease in ambient light amount of less than 30% to less than 60%. Lenses should be used, which makes it difficult to apply the existing optical system and development of a lens suitable for a CMOS camera has not been made until now.

In addition, the market is rapidly growing, and accordingly, the application fields are diversified, and thus, there is a demand for a camera having better optical performance as well as an improvement in image sensor technology.

The present invention was conceived in view of the above-described problems, and its purpose is to arrange spherical ultrahigh refractive lenses and to make the most of the properties of special lenses to achieve the brightness comparable to the performance of optical systems using aspherical surfaces. It has a special lens array to overcome the problem that the resolution of the existing optical system for surveillance cameras does not rise above a certain level and to achieve mega-pixel performance. It is to provide an optical system for.

In addition, the present invention is designed to form an ambient light ratio of more than 90% to solve the difference in brightness between the center and the surrounding of the lens to provide a surveillance camera optical system using a special lens array that can be used throughout CCD and CMOS cameras To provide.

The present invention for achieving the above object is a negative [(-) Power] optical system having a convex surface on the object side and a concave surface on the object side in the optical system for surveillance cameras composed of a plurality of spherical lenses are arranged and assembled A first lens having a magnification lens and formed into a spherical surface; A second lens having a positive ((+) Power] magnification lens having a convex surface or a concave surface on an object side and a convex surface on an image side, and having a spherical surface; A third lens having a positive [(+) Power] magnification lens having convex surfaces on both the object side and the image side, and formed of spherical len; A fourth lens having a negative ((-) Power) magnification lens having a concave surface on the object side and a concave or convex surface on the object side, and formed of an ultra-high refractive spherical lens; And an aperture for selectively converging the light incident from the first lens.

Here, the fourth lens is preferably one selected from Hoya's FDS1 lens, Schott's SF58 lens, SF59 lens, Ohara's PBH21 lens, PBH71 lens, and PBH72 lens.

When the focal length, which is the distance from the first lens to the image, is f, and the rear focal length, which is the distance from the image side surface to the image of the fourth lens, is B, satisfying a condition of 1.28 ≦ B / f ≦ 2.78 desirable.

When the optical length, which is the distance from the first lens to the fourth lens, is T and the focal length of the entire lens system is f, it is preferable to satisfy the condition of T / f ≦ 4.53.

The fourth lens preferably satisfies a condition in which the refractive index n is 1.90 ≦ n ≦ 1.95 and the dispersion ratio v is 20 ≦ v ≦ 22.

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

The optical system for surveillance cameras using the special lens array of the present invention is composed of three spherical lenses with positive and negative magnification and one special ultra-high refractive spherical lens with negative magnification. In this configuration, chromatic aberration is corrected to provide brightness and resolution comparable to optical performance of an optical system including an aspherical lens.

1 to 3 are views showing the arrangement according to the field of view characteristics of the optical system for surveillance cameras using a special lens array according to the present invention, Figure 1 is an arrangement state having an angle of view of 78 degrees, Figure 2 is an angle of view of 92 degrees It is an arrangement state with a characteristic, FIG. 3 is a figure which has an arrangement state with an angle of view characteristic of 120 degree | times.

1 to 3, the optical system for surveillance cameras using a special lens array according to the present invention is a lens system formed of four spherical lenses 10, 20, 30, 40, and aperture 50 And a window glass 60 and an imaging device 70.

In this case, an optical filter (not shown) such as an IR cutoff filter for color correction of color may be further provided in front of the object side of the window glass 60.

The lens system comprises: a first lens (10) which is a negative ((-) Power) magnification lens having a convex surface (R1) on an object side and a concave surface (R2) on an image side; A second lens 20 which is a positive ((+) Power] magnification lens having a convex surface or a concave surface R3 on an object side and a convex surface R4 on an 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; The fourth lens 40 is a negative ((-) Power) magnification lens having a concave surface R7 on the object side and a concave or convex surface R8 on the image side.

Here, the object side surface R3 of the second lens 20 has a concave surface when forming a 78 degree angle of view as shown in FIG. 1, and when forming a 92 degree and 120 degree field of view as shown in FIGS. 2 and 3. It is preferable to configure it to have a convex surface.

In addition, the image side surface R8 of the fourth lens 40 has a convex surface when forming an angle of view of 78 degrees as shown in FIG. 1, and when forming an angle of view of 92 and 120 degrees as shown in FIGS. 2 and 3. It is preferable to comprise so that it may have a concave surface.

The first lens 10 to the fourth lens 40 are all spherical lenses. In particular, the fourth lens 40 is composed of a spherical special lens having an ultra high refractive index, and chromatic aberration is achieved by combining and distributing an appropriate magnification. By improving, the brightness and resolution can be greatly improved.

As the first lens 10, it is preferable to use a spherical lens having a relatively large dispersion coefficient of a crown series, which may be used, for example, a Hoya BACD lens or a BAC4 lens. have.

The second lens 20 and the third lens 30 are composed of a general high refractive spherical lens of the flint-crown series, so as to match the overall power of the lens system.

The fourth lens 40 may preferably use a flint series ultra-high refractive spherical lens. In particular, the fourth lens may be a Hoya FDS1 lens or a Schott SF58 lens. SF59 lens, Ohara PBH21 lens, PBH71 lens and PBH72 lens selected from any one.

Here, in general, the ultra-high refractive lens is not applied to a high-brightness CCTV surveillance camera due to the phenomenon that the light transmittance of the high refractive material is significantly decreased, but in the present invention, the ultra-high refractive fourth lens is aberration. It has the characteristics of the most compact and thinnest lens that can be corrected.

In addition, in the present invention, the special lens of the fourth lens 40 having the ultra high refractive index is arranged to be close to the image side, and the lens shape considering the refractive index and the dispersion ratio is overcome to overcome the sudden decrease in the transmittance which is a disadvantage of the ultra high refractive lens. It eliminated the darkening of the image and rather increased the brightness.

The diaphragm 50 is installed between the first lens 10 and the second lens 20, and performs the function of selectively converging the light incident from the first lens 10.

The window glass 60 is installed between the fourth lens 40 and the image pickup device 70 to prevent protection of the image pickup device 70 and the inflow of foreign substances.

The imaging device 70 includes a CCD sensor or a CMOS sensor, and converts light into an electrical signal to perform image input.

Furthermore, the first lens 10 and the second lens 20 are arranged to be spaced apart by a predetermined interval with the aperture 50 interposed therebetween, and the third lens 30 and the fourth lens 40 face each other. The abutment chromatic aberration can be corrected at the same time by bringing the abutment into contact with each other.

In other words, the optical system of the present invention combines three general spherical lenses 10, 20, 30 and one special ultra-high refractive spherical lens 40, which are provided for focus control and lens power. By assembling and distributing at an appropriate magnification, the aberration correction is improved, and in particular, the correction state of spherical aberration and tangential field curvature is improved, and the mass productivity is improved.

In addition, in the present invention, the optical length of the optical system is 21.5mm, the aperture ratio is F / 2.5, and the angle of view (clock angle) is configured to form 78 degrees, 92 degrees, and 120 degrees, and the first lens 10 to the fourth The lens 40 is designed to satisfy the following conditions 1,2,3.

[Condition 1]

1.28 ≤ B / f ≤ 2.78

Here, f is a focal length that is the distance from the first lens 10 to the image f, and a back focal length that is the distance from the image side surface to the image of the fourth lens 40 is B.

[Condition 2]

T / f ≤ 4.53

Here, the distance from the first first lens 10 of the optical system to the last fourth lens 40 is T, and the focal length of the entire lens system is f.

[Condition 3]

1.48≤n≤1.80, 35≤v≤65 [First Lens]

1.48≤n≤1.80, 40≤v≤85 [second lens]

1.48≤n≤1.80, 40≤v≤85 [Third Lens]

1.90 ≦ n ≦ 1.95, 20 ≦ v ≦ 22 [Fourth Lens]

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

In addition, Tables 1 to 3 below show the results of analyzing the radius of curvature, the center interval, the refractive index, the dispersion coefficient (dispersion rate), and the like of the optical system of the present invention configured by the above-described configuration and conditions. Each optical system data is shown accordingly.

[Table 1] Optical system data with 78-degree field of view

Lens surface Radius of curvature (r) Interval (d) Refractive index (n) Dispersion rate (v) Remarks First side (R1) 1.8305 0.1373 1.5891 61.25 2nd side (R2) 0.6178 1.1029 - - 0.1538 iris Page 3 (R3) -26.313 0.7643 1.6968 57.88 Fourth side (R4) -1.3312 0.0114 Page 5 (R5) 2.5211 0.9152 1.6968 57.88 Page 6 (R6) -1.0525 0.0915 1.9229 20.88 Joint surface Page 7 (R7) -1.0525 0.0915 1.9229 20.88 Joint surface 8th page (R8) -4.0919 0.0458 - - 0.5034 1.5168 64.20 Optical Filters and Window Glasses - - 1.0981 Imaging device

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

[Table 2] Optical system data with 92-degree field of view

Lens surface Radius of curvature (r) Interval (d) Refractive index (n) Dispersion rate (v) Remarks First side (R1) 2.5874 0.1552 1.5891 61.25 2nd side (R2) 0.7444 1.2471 - - 0.0370 iris Page 3 (R3) -14.955 1.0537 1.6968 55.46 Fourth side (R4) -1.6216 0.0129 Page 5 (R5) 2.1256 1.0841 1.6968 55.46 Page 6 (R6) -1.1902 0.1035 1.9229 20.88 Joint surface Page 7 (R7) -1.1902 0.1035 1.9229 20.88 Joint surface 8th page (R8) -13.581 0.0517 - - 0.5692 1.5168 64.20 Optical Filters and Window Glasses - - 0.9143 Imaging device

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

[Table 3] Optical system data with 120 degree angle of view

Lens surface Radius of curvature (r) Interval (d) Refractive index (n) Dispersion rate (v) Remarks First side (R1) 7.8331 0.1841 1.5891 61.25 2nd side (R2) 0.8827 1.4789 - - 0.0614 iris Page 3 (R3) * 6.3032 1.1878 1.6968 55.46 Page 4 (R4) * -2.1103 0.0153 Page 5 (R5) * 2.6356 0.8591 1.6968 55.46 Page 6 (R6) -1.4114 0.1227 1.9229 20.88 Joint surface Page 7 (R7) -1.4114 0.1227 1.9229 20.88 Joint surface Page 8 (R7) -10.446 0.0614 - - 0.6750 1.5168 64.20 Optical Filters and Window Glasses - - 1.3354 Imaging device

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

The present invention is a focal length measurement of the entire lens system by the resolution measurement measured by the PROFILE PROJECTOR and the effective diameter, spherometer f, the rear focal length is B, the first first lens 10 of the optical system When the distance to the last fourth lens 40 is T, the angle of view measurement value θ by the projection inspector, and the center CR and the periphery PR of the resolution measurement value are the aperture ratio (f / dl = F / 2.5), the present invention It can be seen that the lens shape and the lens arrangement of the optical system satisfy all of the conditions 1, 2, and 3 described above.

That is, [condition 1]

1.28 ≤ B / f ≤ 2.78,

[Condition 2]

With T / f ≤ 4.53,

[Condition 3]

1.48≤n≤1.80, 35≤v≤65 [First Lens]

1.48≤n≤1.80, 40≤v≤85 [second lens]

1.48≤n≤1.80, 40≤v≤85 [Third Lens]

1.90≤n≤1.95 and 20≤v≤22 [fourth lens] are satisfied.

Therefore, the optical system for surveillance cameras using a special lens array according to the present invention exhibits optical performance with an optical field length of 21.5 mm, an aperture ratio of F / 2.5, and an angle of view (clock angle) of 78 degrees / 92 degrees / 120 degrees.

On the other hand, Figures 4a to 6d is an analysis graph showing the aberration characteristics of the optical system for surveillance cameras using a special lens array having different angle of view characteristics of 78 degrees, 92 degrees and 120 degrees in the present invention.

4A, 5A, and 6A show meridian aberrations and spherical aberrations in regions 0, 0.7, and 1.0 on the optical axis, respectively, and FIGS. 4B, 5B, and 6B show meridian top surface curvature according to a focal length (T). : Shows astigmatism of Tangential Field Curvature) and Sagittal Field Curvature (S), FIGS. 4C, 5C, and 6C show distortion, and FIGS. 4D, 5D, and 6D It shows lateral chromatic aberration. At this time, in FIG. 4B, FIG. 5B, and FIG. 6B, the curved surface curvature S is a line which has (x) mark, and the meridional surface curve T is a line which has (-) mark.

As shown in the analysis graphs of FIGS. 4A to 6D, the optical system for a surveillance camera using a special lens array according to the present invention shows values of images in almost all fields adjacent to an axis, so that spherical aberration, meridian surface aberration, and powder powder. It shows that the correction state of distortion and chromatic aberration is good, and that the design which has improved the brightness is achieved.

In addition, in view of the fact that the distortion aberration in the optical system is minimized when the image distance and the object distance are similar, the conventional optical system corrects the distortion aberration by adjusting the shape of the lens, the arrangement of the refractive power, and the position of the aperture. In the present invention, by arranging a special spherical lens of ultra high refractive index, it is possible to improve the correction state of spherical aberration and meridian aberration and to improve brightness.

As described above, according to the optical system for surveillance cameras using a special lens array according to the present invention, by arranging a special ultra-high refractive spherical lens, the brightness and resolution of the optical system can be greatly improved, and the optical system can be miniaturized and manufactured. Easily mounting the optical system in one space as well as to extend the application range.

In addition, since the field of view has a much wider angle of view than the standard lens, a wide area can be photographed, and it is possible to have a brightness and resolution comparable to that of the aspherical lens, and also mega pixels (Mega-) only by the configuration of the spherical lens. It is possible to manufacture optical system that shows pixel level performance.

Furthermore, it is an optical system in which the ambient light ratio is formed to be 90% or more by good correction of aberration, which can eliminate the difference in brightness between the center of the lens and the surroundings, thereby providing usefulness for use in CCD and CMOS cameras.

Claims (5)

In the optical system for surveillance cameras composed of a plurality of spherical lenses are arranged and assembled, A first lens having a convex surface on the object side and a concave surface on the image side, the first lens having a spherical surface; A second lens having a positive ((+) Power] magnification lens having a convex surface or a concave surface on an object side and a convex surface on an image side, and having a spherical surface; A third lens having a positive [(+) Power] magnification lens having convex surfaces on both the object side and the image side, and having a spherical surface; A fourth lens having a negative [(-) Power] magnification lens having a concave surface on the object side and a concave or convex surface on the object side, and formed of an ultra-high refractive spherical lens; And an aperture for selectively converging light incident from the first lens. The method of claim 1, The fourth lens comprises a special lens array comprising one selected from Hoya's FDS1 lens, Schott's SF58 lens or SF59 lens, Ohara's PBH21 lens, PBH71 lens and PBH72 lens. Surveillance camera optical system using. The method of claim 1, When a focal length that is the distance from the first lens to the image is f and a rear focal length that is the distance from the image side surface to the image of the fourth lens is B, 1.28 ≤ B / f ≤ 2.78 Surveillance camera optical system using a special lens array characterized in that satisfying the phosphorus conditions. The method of claim 1, When the optical length that is the distance from the first lens to the fourth lens is T and the focal length of the entire lens system is f, T / f ≤ 4.53 Surveillance camera optical system using a special lens array characterized in that satisfying the phosphorus conditions. The method of claim 1, The fourth lens of claim 4, wherein the refractive index (n) is 1.90≤n≤1.95, and the dispersion ratio (v) satisfies the condition that 20≤v≤22.

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