GB2323934A - Optical six element lens system - Google Patents
Optical six element lens system Download PDFInfo
- Publication number
- GB2323934A GB2323934A GB9810041A GB9810041A GB2323934A GB 2323934 A GB2323934 A GB 2323934A GB 9810041 A GB9810041 A GB 9810041A GB 9810041 A GB9810041 A GB 9810041A GB 2323934 A GB2323934 A GB 2323934A
- Authority
- GB
- United Kingdom
- Prior art keywords
- lens
- focal length
- lens group
- group
- surface facing
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B13/00—Optical objectives specially designed for the purposes specified below
- G02B13/04—Reversed telephoto objectives
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B9/00—Optical objectives characterised both by the number of the components and their arrangements according to their sign, i.e. + or -
- G02B9/62—Optical objectives characterised both by the number of the components and their arrangements according to their sign, i.e. + or - having six components only
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Lenses (AREA)
Abstract
A lens system 22, for a charge coupled device (CCD) camera, comprises: a first lens group 12 with a first la and a second Ib lens and having a negative focal length. The first lens la has a negative focal length and a convex surface facing an object and a concave surface facing an image. The second lens Ib has a negative focal length and is disposed further from the object than the first lens and the second lens having a concave surface facing the image. A third lens group 1112 has, in order, a first IIIa, a second IIIb and a third IIIc lens, the first lens IIIa having a negative focal length with both surfaces being concave, the second lens IIIb having a positive focal length with a convex surface facing toward the image and the third lens IIIc having a positive focal length with both surfaces being convex. A second lens group 112 has a positive focal length with both surfaces being convex, the second lens group being between the first and the third lens groups.
Description
LENS SYSTEM FOR A CHARGE COUPLED DEVICE CAMERA
This invention relates to a lens system for a charge coupled device (CCD) camera.
A lens system of a CCD camera typically uses optional lenses such as telescopic lenses, wide viewing angle lenses, etc. With CCD technology, it is possible to obtain high definition images. A CCD camera has a lens mount for holding lenses. Typical mounts are C-mount and CS-mount, whereas the optional lenses are typically retro-focus type lenses.
The optical characteristics of a retro-focus type lens are as follows. First, if the distortion aberration has a negative value, it increases for a wide view angle lens with an image angle greater than 60". Second, the back focal length increases, thereby making it difficult to obtain high definition by improving the aberration balance.
Third, a retro-focus type lens system needs a highly refractive concave lens arranged at a front position. This increases the absolute value of the spherical aberration coefficient, which represents the difference between the central focal point of the lens center and the focal point of a peripheral surface of the lens. Hence, there must be provided a means to correct the aberration in the rear portion.
These characteristics make it difficult to obtain a high definition CCD camera for use in factory automation (FA). Moreover, a lens system satisfying the high definition requirements is not compact and light. To address such problems, a FA CCD camera employs a lens system designed to have an extremely small size and light weight. Additionally, CCD camera use in FA and vision system apparatus for checking the normal operation of various machines is rapidly increasing. Such apparatus includes a head separated lens system that employs a connecting wire making it possible to separate the lens mount and the lens system.
According to the present invention, there is provided a lens system for a charge coupled device (CCD) camera, comprising:
a first lens group with a first and a second lens and having a negative focal length, the first lens of the first lens group having a negative focal length and a convex surface facing an object and a concave surface facing an image, the second lens of the first lens group having a negative focal length and being disposed further from the object than the first lens and the second lens having a concave surface facing the image;
a third lens group having a first, a second and a third lens, the first lens of the third lens group having a negative focal length with both surfaces being concave, the second lens of the third lens group having a positive focal length with a convex surface facing toward the image and the third lens of the third lens group having a positive focal length with both surfaces being convex, the second lens being between the first lens and the third lens and the first lens being oriented closer than the second lens to the first lens group; and
a second lens group having a positive focal length with both surfaces being convex, the second lens group being between the first lens group and the third lens group.
The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: - Fig. 1 is a schematic diagram illustrating the construction of a standard type lens system of a CCD camera according to an embodiment of the present invention;
Fig. 2 is a graph illustrating the spherical aberration of the lens system of Fig. 1;
Fig. 3 is a graph illustrating the astigmatic aberration of the lens system of Fig. 1;
Fig. 4 is a graph illustrating the distortion aberration of the lens system of Fig. 1; and
Fig. 5 illustrates the chromatic aberration of the lens system of Fig. 1.
Reference will now be made in detail to a standard-type lens system Xr a CCD camera according to o+t embodiment of the present invention, as illustrated in Figs.1 - 5.
As embodied herein, and referring Fig. the standard type lens system 22 includes a first lens group I2, a second lensgroup II2, and a third lens group III2. An iris diaphragm 24 is between the second lens group II2 and the third lens group is III2. A filter 26# mounted behind the third lens group III2. The first lens group I2 includes a first lens Ia having a negative focal length with a first convex lens surface rl facing toward
the object > the lens surface being concave A second lens Ib of the first lens group I2 has a negative focal length with
the lens surface r4tbeing concave, thus producing s combined focal length wiK a negative value. The second lens group II2 has
a positive focal length with both r5, r6 being convex.
The third lens group III2 includes a first lens IIIa having a
negative focal length with both A r8, r9 being concave, a second lens IIIb having a positive focal length with the Is surface rll being convex, and a third lens IIIc having a positive
focal length with both p r12, r13 being convex.
The present standard-type lens system of the present invention, as embodied herein, has a fixed focal length with three lens groups consisting of six lenses. The lens groups I2, 112, III2 have a negative, a positive and a positive focal length respectively. The first lens Ia of the first lens group I2 is a concave lens (with respect to the object) having a negative focal length, and the second lens has a positive focal length. The third lens group III2 includes a concave lens joined to a convex lens edge to edge and another convex lens behind them. In this way, the back focal length issecured enough to satisfy the standard-type lens system of a head separated CCD camera used in factory automation (FA) - This standard-type lens system satisfe5the relationships:
Fb
0.9 < < 1.3 --- Formula (1)
F
d7
0.8 < < 1.2 --- Formula (2) d6
F represents the combined focal length of the lens system, Fb the back focal length, d6 OL distance between the second lens group II2 and the iris diaphragm 24, and d7 a central distance between the iris diaphragm 24 and the first lens
IIIa of the third lens group III2.
The formula (1) is used to specify the combined focal length and the back focal length, which makes it possible to produce a compact lens system. In this case, if the upper limit is exceeded, the distortion aberration increases. It is difficult to correct the aberration. Therefore, the performance of the lens system is degraded. If the lower limit is exceeded, the correction of the aberration is readily accomplished. The back focal length, however, is hard to secure for use in both color and black/white.
The formula (2) specifies the distance within the operating range for mounting the iris diaphragm 24 between the first lens group namely the first lens group I2 and the'second lens group II2 and the rear lens group namely third lens group III2. In this case, when the upper limit is exceeded, the operational distance of the iris diaphragm 24 is secured enough, but correction of the aberration is hard to make. If the lower limit is exceeded, the correction of the aberration may be readily accomplished, thereby improving the performance of the lens system 22. It is difficult, however, to obtain the distance for mounting the iris diaphragm 24.
Further, the standard-type lens system of the present embodiment satisfies the relationship:
2 1 1
0.1 < [ E --- x ---x 102 ] < -0.3 --- Formula (3) 1=1 FGI vd,,
FGI represents the focal length of the "i"th lens of the first lens group numbered I2 from the object and vdGI the
Abbe number of the "i"th lens of the third lens group III2 numbered from the object.
The formula (3) is used to correct the chromatic aberration, which is an optical lens defect causing color fringes because the lens material brings different colors of light to focus at different points. If the value deviates from the scope of the formula, a magnification chromatic aberration occurs in the upper part of the lenses out of the optical axis. It is especially difficult to correct the chromatic aberration of the g-line with a bluish color wavelength.
In addition, the standard type lens system gor head separated type CCD camera satisfies the relationships:
3 1 10 < [ # x F ] c 20 --- Formula (+)
1=1 d1 13 1
80 < [ E ------ x Fb ] < 100 --- Formula (5 I=8 d1
dI represents the central distance of the "i"th lens,
F the combined focal length of the lens system 22 and Fb the back focal length of the lens system 22.
The formulae (4) and ( 5) are used to limit the whole length of the lens system 22 and the length of the second lens group
II2. When these relationships are not satisfied, one cannot obtain a compact construction and readily correct aberration problems. Moreover, in this case, the back focal length is not secured, thereby making it difficult to construct a lens system used for both color and black/white image.
Table 2 shows the characteristic values of the present embodiment when the lens number FNO is 1.6, the combined focal length F 5.5237, the back focal length Fb 5.7602, and the image angle W 63.310. In Table 2, the reference symbol ri (i = i, 2, ...) represents the radius of the curvature of each lens surface, di(i = 1, 2, ...) the distance or thickness between two adjacent lens surfaces, ndi the refractive index of each lens for wavelength "d", and vdi the Abbe number of each lens for wavelength "d".
Table 2
Lens
Surface No. r d nd vd 1. 11.410 1.30 1.48749 70.44
II. 4.635 1.26 1.51680 64.20
III. 27.311 0.80 1.84300 37.34
IV. 5.257 3.25 1.84666 23.78
V. 12.625 2.19 1.62041 60.34
VI. -lG.994 2.01 1.58913 61.25 VII. # 1.91 VIII. -16.7220 0.70
IX. 10.376 0.24
X. 32.133 1.94
XI. -6.825 0.10
XII. 9.282 2.30
XIII. -15.452 0.00 XIV. # 3.46 XV. w There is provided s standard-type lens system for
head separated CCD camera, which has the image angle greater than 690 and produces high definition images.
Claims (5)
1. A lens system for a charge coupled device (CCD) camera, comprising:
a first lens group with a first and a second lens and having a negative focal length, the first lens of the first lens group having a negative focal length and a convex surface facing an object and a concave surface facing an image, the second lens of the first lens group having a negative focal length and being disposed further from the object than the first lens and the second lens having a concave surface facing the image;
a third lens group having a first, a second and a third lens, the first lens of the third lens group having a negative focal length with both surfaces being concave, the second lens of the third lens group having a positive focal length with a convex surface facing toward the image and the third lens of the third lens group having a positive focal length with both surfaces being convex, the second lens being between the first lens and the third lens and the first lens being oriented closer than the second lens to the first lens group; and
a second lens group having a positive focal length with both surfaces being convex, the second lens group being between the first lens group and the third lens group.
2. A system according to Claim 1, satisfying the following relationship:
Fb
0.9 < < 1.3
F
d7 0.8 < < 12 c 1.2 d6
where F represents the combined focal length of the lens system, Fb represents the back focal length, d6 represents a distance between the second lens group and an iris diaphragm disposed between the second lens group and the third lens group and d7 represents a central distance between the iris diaphragm and the first lens of the third lens group.
3. A system according to Claim 1 or 2, satisfying the following relationship:
2 1 1
0.1 < [ z ~~~~~ x ~~~~~ x 102 ] < -0.3 1=1 FGI VdGI
where FGI represents the focal length of the "i"th lens of the first lens group numbered from the object and vdGI represented the Abbe number of the "i"th lens of the third lens group numbered from the object.
4. A system according to any of Claims 1, 2 and 3, satisfying the following relationships:
3 1
10 < [E x F ] < 20 1=1 d 13 1
80 < [E x Fb ] < 100
I=8 d1 where d1 represents the central distance of the "i"th lens, F represents the combined focal length of the lens system and Fb represents the back focal length of the lens system.
5. A lens system, substantially as herein described with reference to the accompanying drawings.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| KR1019950000175A KR100266265B1 (en) | 1995-01-06 | 1995-01-06 | Tele type lens group for ccd camera |
| KR1019950000178A KR100272330B1 (en) | 1995-01-06 | 1995-01-06 | Standard type lens of head separating type ccd camera |
| GB9600012A GB2296783B (en) | 1995-01-06 | 1996-01-02 | Lens system for a charge coupled device camera |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB9810041D0 GB9810041D0 (en) | 1998-07-08 |
| GB2323934A true GB2323934A (en) | 1998-10-07 |
Family
ID=27268062
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9810041A Withdrawn GB2323934A (en) | 1995-01-06 | 1996-01-02 | Optical six element lens system |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2323934A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5857308A (en) * | 1991-05-18 | 1999-01-12 | Aea Technology Plc | Double lid system |
Citations (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB741511A (en) * | 1953-08-04 | 1955-12-07 | Gordon Henry Cook | Improvements in or relating to optical objectives |
| GB870880A (en) * | 1959-04-13 | 1961-06-21 | Taylor Taylor & Hobson Ltd | Improvements in or relating to optical objectives |
| GB1066527A (en) * | 1963-05-31 | 1967-04-26 | Zeiss Stiftung | Photographic wide-angle and semi-wide-angle objective of extremely high light-gathering power |
| US3507559A (en) * | 1965-12-07 | 1970-04-21 | Nippon Kogaku Kk | Retrofocus type wide angle objective lens |
| GB1421931A (en) * | 1972-05-01 | 1976-01-21 | Asahi Optical Co Ltd | Wide-angle lens system of retrofocus type |
| GB1422743A (en) * | 1972-06-07 | 1976-01-28 | Nippon Kogaku Kk | Retrofocus type wide-angle photographic lens |
| GB1433720A (en) * | 1973-09-27 | 1976-04-28 | Asahi Chemical Co | Objective lens systems |
| GB1474404A (en) * | 1973-08-01 | 1977-05-25 | Canon Kk | Wide angle objectives having a non-spherical surface |
| GB1499274A (en) * | 1975-03-22 | 1978-01-25 | Zeiss C | Extremely high speed objective |
| US4412726A (en) * | 1980-01-17 | 1983-11-01 | Minolta Camera Kabushiki Kaisha | Fish eye lens system |
| EP0548529A1 (en) * | 1991-12-23 | 1993-06-30 | International Business Machines Corporation | Reverse telephoto argon objective lens |
| GB2284682A (en) * | 1993-12-08 | 1995-06-14 | Asahi Optical Co Ltd | Retrofocus standard lens and wide angle lens with front lens group focusing |
| US5434713A (en) * | 1992-03-26 | 1995-07-18 | Nikon Corporation | Fisheye lens having a short distance compensating function |
-
1996
- 1996-01-02 GB GB9810041A patent/GB2323934A/en not_active Withdrawn
Patent Citations (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB741511A (en) * | 1953-08-04 | 1955-12-07 | Gordon Henry Cook | Improvements in or relating to optical objectives |
| GB870880A (en) * | 1959-04-13 | 1961-06-21 | Taylor Taylor & Hobson Ltd | Improvements in or relating to optical objectives |
| GB1066527A (en) * | 1963-05-31 | 1967-04-26 | Zeiss Stiftung | Photographic wide-angle and semi-wide-angle objective of extremely high light-gathering power |
| US3507559A (en) * | 1965-12-07 | 1970-04-21 | Nippon Kogaku Kk | Retrofocus type wide angle objective lens |
| GB1421931A (en) * | 1972-05-01 | 1976-01-21 | Asahi Optical Co Ltd | Wide-angle lens system of retrofocus type |
| GB1422743A (en) * | 1972-06-07 | 1976-01-28 | Nippon Kogaku Kk | Retrofocus type wide-angle photographic lens |
| GB1474404A (en) * | 1973-08-01 | 1977-05-25 | Canon Kk | Wide angle objectives having a non-spherical surface |
| GB1433720A (en) * | 1973-09-27 | 1976-04-28 | Asahi Chemical Co | Objective lens systems |
| GB1499274A (en) * | 1975-03-22 | 1978-01-25 | Zeiss C | Extremely high speed objective |
| US4412726A (en) * | 1980-01-17 | 1983-11-01 | Minolta Camera Kabushiki Kaisha | Fish eye lens system |
| EP0548529A1 (en) * | 1991-12-23 | 1993-06-30 | International Business Machines Corporation | Reverse telephoto argon objective lens |
| US5434713A (en) * | 1992-03-26 | 1995-07-18 | Nikon Corporation | Fisheye lens having a short distance compensating function |
| GB2284682A (en) * | 1993-12-08 | 1995-06-14 | Asahi Optical Co Ltd | Retrofocus standard lens and wide angle lens with front lens group focusing |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5857308A (en) * | 1991-05-18 | 1999-01-12 | Aea Technology Plc | Double lid system |
Also Published As
| Publication number | Publication date |
|---|---|
| GB9810041D0 (en) | 1998-07-08 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |