Optical system with variable image scale

Details Optical system with variable image scale Optical system with variable image scale

1995-06-14

1998-03-24

Nelms, David C.

Optical: systems and elements

Lens

With variable magnification

359683, G02B 1514

Patent

active

057319103

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

a) Field of the Invention
The invention is directed to an optical system with variable image scale for imaging an image which is generated by microscope in the plane of the CCD matrix of a video camera.
b) Description of the Related Art
Video outputs on microscopes are required for various operations such as viewing on a monitor, producing video prints, computer-aided image processing or file storage.
If the intermediate image is produced on the CCD matrix without an adapting optical system, an optimal image scale or image section will seldom result. Special video adapting equipment in the form of Homal lenses or projection lenses may help to remedy this defect, but zoom systems are more advantageous.
The required zoom range is given by the quotient of the diameter of the CCD matrix to the microscope intermediate image with approximately 8.8 mm/2 mm=0.4 as the smallest value to the quotient of the resolution of the CCD matrix and intermediate image with 10 m/5 m=2 as the largest value.
In so doing, it is taken into account that the resolution achieved in automatic image evaluation will be roughly twice the resolution achieved visually. For this purpose, an image correction corresponding to the high-resolution color camera must be made with the given technical mating or connection dimensions.
Zoom systems with finite transmission length, e.g., for facsimile printing or copiers, which can theoretically be used in combination for such purposes are known (DE 3544148, DE 3418639). However, the disadvantages of such systems with respect to overall length, number of optical components and required range of the image scale are hardly acceptable.
U.S. Pat. No. 3,454,321 describes a pancratic system formed of two moving lenses with positive lens power. Its overall length is relatively great. Further, the intermediate image that is formed lies between the lenses, i.e., an additional lens system would be necessary in order to generate a real image on the CCD matrix. The indicated magnification scales are not suitable for solving the problem addressed here.


OBJECT AND SUMMARY OF THE INVENTION

The primary object of the present invention is to realize a video zoom adaptation arrangement which enables all image scales required in practice for currently available and anticipated types of video camera and which, in spite of this requirement, makes do with few optical components and accordingly offers an economical and efficient solution for the user.
This object is met according to the invention in an optical system with variable image scale for imaging an image which is generated by a microscope in the plane of the CCD matrix of a video camera comprising three lens groups with positive focal length. The three optical components including a first lens group which is stationary and a second and third lens group which are arranged after the first lens group, as viewed in the imaging direction, so as to be displaceable along the optical axis for varying the image scale. The first lens group is constructed as a meniscus which is arranged in front of the image generated by the microscope and whose final surface is dispersive for correcting the field curvature and is situated in front of an intermediate image which is produced by the first lens group. Particularly advantageous further developments of the invention are indicated in the dependent claims and are explained more fully in the following description.
The optical system according to the invention is formed of three components with positive lens power, the first component, as viewed in the direction of light, being a stationary achromatic lens group, while the second and third components are achromatic groups which are displaceable along the optical axis.
The first lens group is advantageously constructed as a lens which is arranged before the image B generated by the microscope and whose final surface is dispersive for correcting the field curvature and lies near the intermediate image ZB, while, on the other hand, its first surface lies ne

REFERENCES:
patent: 4130350 (1978-12-01), Koizumi
patent: 4525042 (1985-06-01), Muchel
patent: 4563060 (1986-01-01), Yamagishi
patent: 5076676 (1991-12-01), Saito
patent: 5321446 (1994-06-01), Mossig
patent: 5359417 (1994-10-01), Muller et al.
patent: 5371626 (1994-12-01), Betensky
Patent Abstracts of Japan, unexamined applications, P field, vol. 16, No. 345, issued 27 Jul. 1992 and JP, A, 4-104116 (Touyou Kougaku Kougiyou K.K.).

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