JPH0727973A - Large diameter lens system - Google Patents

Abstract

PURPOSE:To obtain a large diameter lens system in which a diaphragm can be used in common in a lens system with a very large diameter of about F0.7-0.8 and with high back-focusing capability, and provided with lens systems of standard, wide angle, and super wide angle. CONSTITUTION:This lens system is a large diameter lens system provided with a front group lens of negative power, the diaphragm, and a rear group lens of positive power in the above sequence from an object side, and satisfies the following conditions (1) to (3); (1) -0.6<f/fF<-0.2, (2) 3.5<(fB+SIGMAdR)/2Y<4.9, and (3) 4.9<(fB+SIGMAdR+S/2Y<8. Where, the focal distance of the whole system is assumed as (f), the focal distance of the front group lens as fF, the image height of a diagonal as Y (2Y: picture size), back-focusing converted to in the air as fB, the thickness of the rear group lens as SIGMAdR, and the sum of the thickness of the rear group lens and interval between the front and rear group lenses as SIGMAdR+S.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a large-diameter lens applicable to a small TV camera such as a CCTV camera, and more particularly to a large-diameter lens that enables common apertures in lens systems ranging from standard to super wide-angle.

[0002]

2. Description of the Related Art In a compact video camera of this type, a compact and high-resolution photographic element having a small size of one pixel is generally used. Therefore, a photographic lens having a small F number and a large aperture is required. Conventionally, it is about F 1.0 to 1.2. Further, in the conventional lens, it is not possible to use a common component, such as an aperture, in the lens system from the standard lens to the wide-angle lens and the ultra-wide-angle lens, which has been a factor of cost increase.

[0003]

OBJECT OF THE INVENTION The present invention is directed to F0.7 smaller than F1.0.
Very large diameter of ~ 0.8 and back
The objective of the present invention is to reduce the total cost by enabling the common use of parts, particularly the diaphragm, in a lens system having a large amount of debris, from standard to wide-angle and ultra-wide-angle lens systems.

[0004]

SUMMARY OF THE INVENTION A large-aperture lens system of the present invention comprises, in order from the object side, a front lens group having negative power, an aperture stop, and a rear lens group having positive power, and the following conditional expression (1) ) To (3) are satisfied. (1) −0.6 <f / f _F <−0.2 (2) 3.5 <(f _B + _ΣdR ) / 2Y <4.9 (3) 4.9 <(f _B + Σ _{dR + s} ) / 2Y <8, where f is the focal length of the entire system, f _{F is} the focal length of the front lens group, Y is the image height of the diagonal line (2Y is the screen size), and f _B is the back focal length when converted to air. Cass, Σ _dR : thickness of the rear lens group, Σ _{dR + S} : sum of the thickness of the rear lens group and the distance between the front and rear lens groups.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The large aperture lens system of the present invention is a lens having a simple structure in which a stop is arranged between a negative power front lens group on the object side and a positive power rear lens group.

It is advantageous to provide the diaphragm between the negative front lens group and the positive rear lens group in order to increase the back focus and reduce the lens diameters of the front and rear lens groups in a well-balanced manner. Also, CCTV cameras have an N
Since a D filter is often inserted, this position is also preferable for the aperture in order to reduce the ghost due to reflection on the surface of the ND filter and the image pickup element in connection with the conditional expression (1).

Conditional expression (1) (-0.6 <f / f _F <-
0.2, f: focal length of the entire system, f _F : focal length of the front lens group) are for clarifying the relationship between the position of the diaphragm and the front and rear lens groups. If the upper limit of conditional expression (1) is exceeded, the back focus will become small, which will hinder the mounting on the camera. If the lower limit is exceeded, the overall lens length and the diameter of the rear lens group will increase, and the power of each group will also increase. − Increases, and higher-order aberrations are likely to occur.

Conditional expressions (2) and (3) relate to the distance from the image pickup element to the diaphragm position, and are common to the diaphragms of the standard, wide-angle and ultra-wide-angle lenses with a very large aperture of F0.7 to 0.8. It is for making it possible.

Conditional expression (2) (3.5 <(f _B + Σ _dR ) /
2Y <4.9, Y: image height of diagonal line of screen (2Y is length of diagonal line of screen (screen size)), f _B : back focus when converted into air, Σ _dR : of rear lens group Thickness)
Limits the lower limit of the distance of the aperture position from the image pickup surface.If the lower limit is exceeded, the thickness of the rear lens group becomes small and a large aperture lens cannot be obtained. Is largely separated from the image pickup surface, the diaphragm cannot be shared, and the total lens length and the diameter of the rear lens group also increase. The image height Y on the diagonal line of the screen is Y = f · ta
It can be represented by nω (1+ (Dist / 100)) (where Dist (%) is distortion).

Conditional expression (3) (4.9 <(f _B + Σ _{dR + s} )
/ 2Y <8, Σ _{dR + S} : sum of the thickness of the rear lens group and the distance between the front and rear lens groups) defines the upper limit of the distance from the imaging surface of the diaphragm position. If the upper limit is exceeded, the total lens length increases. If the lower limit is exceeded, it will be difficult to use common apertures for standard, wide-angle and ultra-wide-angle lenses.

Next, examples of the present invention will be described. The present invention is applied to a standard lens system in Examples 1 and 2, a wide-angle lens system in Examples 3 and 4, and an ultra-wide-angle lens system in Examples 5 and 6, respectively.

[Embodiment 1] FIG. 1 is a lens configuration diagram of an embodiment 1 in which the large-diameter lens system of the present invention is applied to a standard lens. In Examples 1 and 2, the I-th lens group before the diaphragm S is composed of the first to fourth lenses, and is the first lens after the diaphragm S.
The II lens group includes fifth to eighth lenses.
The fifth lens and the sixth lens are cemented lenses. A plane parallel plate is located behind the eighth lens.

Specific numerical data of this lens system are shown in Table 1, and various aberrations are shown in FIG. SA in the aberration diagrams
Is a spherical aberration, SC is a sine condition, d-line, g-line, and C-line are chromatic aberration and chromatic aberration of magnification indicated by spherical aberration at respective wavelengths, S is sagittal, and M is meridional.

In the tables and drawings, r _i is the radius of curvature of each lens surface, d _i is the lens thickness or lens spacing, N is the refractive index,
ν indicates the Abbe number.

[0015]

[Table 1] F _NO = 1: 0.8 F = 12.30 ω = 19.3 f _B ＝ 6.26 + (6.0 / 1.49782) = 10.27 (back focus converted to the air) surface No. rd N ν 1 21.907 5.40 1.83400 37.2 2 -285.740 0.35 3 64.604 1.90 1.50000 72.2 4 40.142 1.60 5 -68.464 1.50 1.50000 56.5 6 8.523 6.15 7 -8.209 2.00 1.84666 23.9 8 -11.874 3.02 9 -141.119 6.81 1.84666 23.9 10 17.702 7.87 1.77250 50.7 11 -23.085 6.09 0.10 12 13 -39.173 0.10 14 15.759 5.69 1.80400 46.6 15 32.932 6.26 16 ∞ 6.00 1.49782 66.8 17 ∞

[Second Embodiment] FIG. 3 is a lens configuration diagram of a second embodiment in which the large-diameter lens system of the present invention is applied to a standard lens. Table 2 shows specific numerical data of this lens system.
The various aberrations are shown in FIG.

[0017]

[Table 2] F _NO = 1: 0.8 F = 12.30 ω = 19.1 f _B = 5.00+ (6.0 / 1.49782) = 9.01 (back focus converted to the air) surface No. rd N ν 1 20.568 5.52 1.83400 37.2 2 -793.963 0.42 3 68.425 2.05 1.48749 70.2 4 22.481 1.73 5 -2053.281 2.48 1.51633 64.1 6 8.157 4.12 7 -7.569 2.97 1.84666 23.9 8 -11.432 4.04 9 -42.945 2.00 1.84666 23.9 10 17.629 8.62 1.74100 52.7 11 15-1682 610.00 0.000 13 -285.637 2.05 14 * 16.798 6.12 1.59015 61.4 15 -99.641 5.00 16 16 ∞ 6.00 1.49782 66.8 17 ∞ * is an aspherical surface No.14; K = 0.0, A4 = -0.47153 × 10 ^-4 , A6 = -0.39021 × 10
^-6 , A8 = 0.61389 × 10 ^-9 , A10 = -0.41184 × 10 ^-10 , A12 = 0.0

[Embodiment 3] FIG. 5 is a lens configuration diagram of Embodiment 3 in which the large-diameter lens system of the present invention is applied to a wide-angle lens. In Examples 3 to 6, the I-th lens group before the diaphragm S is composed of the first to fourth lenses, and the II-th lens group after the diaphragm S is composed of the fifth to eighth lenses. The sixth lens and the seventh lens are cemented lenses. 8th
A plane parallel plate is located at the rear of the lens. Table 3 shows specific numerical data of this lens system, and FIG. 6 shows various aberrations thereof.

[0019]

[Table 3] F _NO = 1: 0.7 f = 6.20 ω = 34.7 f _B = 4.94 + (6.0 / 1.49782) = 8.95 (back focus converted to air) Surface No. rd N ν 1 35.829 1.49 1.77250 49.6 2 14.335 4.91 3 -112.034 1.29 1.51633 64.1 4 21.403 2.16 5 155.159 4.49 1.84666 23.8 6 -24.296 0.10 7 13.937 3.74 1.84666 23.8 8 8.225 17.52 -9 -75.160 6.36 1.77250 49.6 10 10-18.342 1.0 11 52.875 1.49 1.314666 23.8 12 12. 78.843 0.10 14 * 14.223 6.36 1.66910 55.4 15 76.838 4.94 16 ∞ 6.00 1.49782 66.8 17 ∞ * is aspheric No.14; K = 0.0, A4 = -0.10940 × 10 ^-4 , A6 = 0.12483 × 1
0 ^-6 , A8 = -0.19506 × 10 ^-8 , A10 = 0.97455 × 10 ^-11 , A12 = 0.
0

[Embodiment 4] FIG. 7 is a lens configuration diagram of an embodiment 4 in which the large-diameter lens system of the present invention is applied to a wide-angle lens. Table 4 shows specific numerical data of this lens system.
The various aberrations are shown in FIG.

[0021]

[Table 4] F _NO = 1: 0.8 f = 6.20 ω = 34.4 f _B = 5.29 + (6.0 / 1.49782) = 9.30 (back focus converted to air) Surface No. rd N ν 1 55.255 1.60 1.69680 55.5 2 13.315 4.30 3 218.535 4.07 1.84666 23.8 4 28.353 0.10 5 44.462 3.07 1.59551 39.2 6 8.800 2.65 7 14.950 7.13 1.84666 23.8 8 12.405 5.91 9 180.410 13.48 1.88300 40.8 10 18.539 0.10 11 -215.383 1.50 1.84666 23.8 1442 13.326 8.86 13.265 5.60 1.66910 55.4 15 154.652 5.29 16 ∞ 6.00 1.49782 66.8 17 ∞ * is aspheric No.14; K = 0.0, A4 = -0.21706 × 10 ^-4 , A6 = -0.18356 × 10
^-8 , A8 = -0.83516 × 10 ^-9 , A10 = -0.40244 × 10 ^-11 , A12 = 0.0

[Embodiment 5] FIG. 9 is a lens configuration diagram of an embodiment 5 applied to an ultra wide-angle lens of a large aperture lens system of the present invention. Table 5 shows specific numerical data of this lens system, and FIG. 10 shows various aberrations thereof.

[0023]

[Table 5] F _NO = 1: 0.82 F ＝ 3.80 ω ＝ 60.0 f _B ＝ 5.00+ (6.0 / 1.49782) = 9.01 (back focus converted to the air) surface No. rd N ν 1 25.181 2.26 1.77250 49.6 2 8.264 4.27 3 44.052 1.50 1.83481 42.7 4 9.920 2.80 5 -30.455 1.10 1.82333 37.7 6 9.216 6.34 1.84666 23.9 -18 870.81 12.81 8 285.710 6.86 1.71162 51.4 9 -24.205 0.10 -10 85.555 1.50 1.84666 23.9 11 9.889 1.58 813 -63. 17.220 9.39 1.74320 49.3 14 -24.924 5.00 15 ∞ 6.00 1.49782 66.8 16 ∞ * is an aspherical surface No.13; K = 0.0, A4 = -0.39541 × 10 ^-4 , A6 = -0.25900 × 10
^-8 , A8 = -0.23530 × 10 ^-8 , A10 = 0.20854 × 10 ^-10 ,
A12 = 0.0

[Sixth Embodiment] FIG. 11 is a lens configuration diagram of a sixth embodiment in which the large-diameter lens system of the present invention is applied to an ultra wide-angle lens. Table 6 shows specific numerical data of this lens system, and FIG. 12 shows various aberrations thereof.

[0025]

[Table 6] F _NO = 1: 0.82 F ＝ 3.80 ω ＝ 58.8 f _B ＝ 5.00+ (6.0 / 1.49782) = 9.01 (back focus converted to the air) surface No. rd N ν 1 21.469 2.05 1.77250 49.6 2 8.717 4.54 3 41.163 1.88 1.83481 42.7 4 9.288 2.78 5 -42.341 1.13 1.67003 47.3 6 6.943 6.04 1.71736 29.5 7 -24.852 16.32 8 * 96.974 4.73 1.66910 55.4 9 -19.675 0.10 10 0.186 077 237. 38.205 8.37 1.60311 60.7 14 -23.598 5.00 15 ∞ 6.00 1.49782 66.8 16 ∞ * is aspherical No.8; K = 0.0, A4 = -0.97950 × 10 ^-4 , A6 = 0.10894 × 10 ^-6 , A
8 = -0.11285 × 10 ^-8 , A10 = 0.0, A12 = 0.0

[0026]

As described above, according to the large-diameter lens system of the present invention, the lens system has a very large aperture of about F0.7 to F0.8, a large back focus, and an aperture in a standard to ultra wide-angle lens system. Can be shared.

[Brief description of drawings]

FIG. 1 is a lens configuration diagram showing a first embodiment of a large-diameter lens system according to the present invention.

FIG. 2 is a diagram of various types of aberration of the lens system in FIG.

FIG. 3 is a lens configuration diagram showing a second embodiment of the large-diameter lens system according to the present invention.

FIG. 4 is a diagram of various types of aberration of the lens system in FIG.

FIG. 5 is a lens configuration diagram showing a third embodiment of the large-diameter lens system according to the present invention.

FIG. 6 is a diagram of various types of aberration of the lens system in FIG.

FIG. 7 is a lens configuration diagram showing a fourth embodiment of the large-diameter lens system according to the present invention.

FIG. 8 is a diagram of various types of aberration of the lens system in FIG.

FIG. 9 is a lens configuration diagram showing a fifth embodiment of the large-diameter lens system according to the present invention.

FIG. 10 is a diagram of various types of aberration of the lens system in FIG.

FIG. 11 is a lens configuration diagram showing a sixth example of a large-diameter lens system according to the present invention.

12 is a diagram of various types of aberration in the lens system of FIG.

Claims (1)

[Claims] 1. A front lens group having a negative power, an aperture stop, and a rear lens group having a positive power, which are arranged in order from the object side, and satisfy the following conditional expressions (1) to (3). Large aperture lens system. (1) −0.6 <f / f _F <−0.2 (2) 3.5 <(f _B + _ΣdR ) / 2Y <4.9 (3) 4.9 <(f _B + Σ _{dR + s} ) / 2Y <8, where f is the focal length of the entire system, f _{F is} the focal length of the front lens group, Y is the image height of the diagonal line (2Y is the screen size), and f _B is the back focal length when converted to air. Cass, Σ _dR : Thickness of the rear lens group, Σ _{dR + S} : Sum of the thickness of the rear lens group and the distance between the front and rear lens groups.