US3735125A - Slit lamp - Google Patents

Abstract

A slit lamp in which a telecondenser is connected behind the incandescent lamp which consists of several positive and at least one negative lens element whereby a slot diaphragm is arranged close to the last negative lens of the telecondenser.

Description

United States Patent 1 Wilms SLIT LAMP [75] Inventor: Karl-Heinz Wilrns, Munich, Germany [73] Assignee: Optische Werke G. Rodenstock, Munich, Germany 22 Filed: 061. 9, 1970 21 App1.No.: 79,547

[30] Foreign Application Priority Data Oct. 29, 1969 Germany ..P 19 54 312.5

[52] U.S. Cl. ..240/4L3, 128/6, 128/23, 240/2 M, 240/41.15

[51] Int. Cl. ..F2lv 13/04 [58] Field of Search 240/41.3,41.15, 240/41 R, 1 R, 2 R, 2 M; 128/6, 395, 23;

[ 1 May 22, 1973 [56] References Cited UNITED STATES PATENTS 3,533,685 10/1970 Littmann 61 al ..351/14 3,405,994 10/1968 Altman 61 a1 ..351/14 3,407,019 10/1968 Wilkinson ..351/14 3,586,424 6/1971 Schenk 61 a1. ..351/14 1,680,663 8/1928 Campbell .351/14 x Primary Examiner-Richard L. Moses Att0meyCraig, Antonelli, Stewart & Hill 5 7 ABSTRACT A slit lamp in which a telecondenser is connected bebind the incandescent lamp which consists of several positive and at least one negative lens element whereby a slot diaphragm is arranged close to the last negative lens of the telecondenser.

7 Claims, 2 Drawing Figures SLIT LAMP The present invention relates to an illumination installation for slit lamps with a high light-yield.

Slit lamps project into the forward part of an eye to be examined a bright slit whereby details are observed in the illuminated portions by means of a microscope. It is necessary in that connection for the exact observation of the illuminated eye portion that the slit lamp produce a photometric output as high as possible.

I-Ieretofore incandescent lamps of 25 to 30 Watts have been used for that purpose. However, the incandescent lamps of this power produce a considerable amount of heat which is undesirable especially on the adjacent adjustable slot diaphragm. Simultaneously therewith, a relatively slight structural length of the illuminating optics is desirable in order to improve the handling of slit lamps.

The present invention provides a slit lamp in which a high light-yield producing only a slight amount of heat and with simultaneous small structural length of the illumination apparatus. This is achieved according to the present invention by the use of a telecondenser comprising an assymetrical lens arrangement having a relatively strong negative lens on the side of the image is subdivided in one embodiment into two lenses of which the first lens is arranged in front of the slot diaphragm and the second behind the slit group in the direction of normal passage of the rays through the apparatus. The negative lens behind the slot diaphragm thereby acts as an image-field flattening element between the slit and the adjoining objective. This second negative lens which is arranged as close as possible behind the slot diaphragm acts simultaneously as an element of the objective or lens connected behind the slot diaphragm which thus effectively becomes a teleobjective.

By this arrangement which additionally is characterized by a distinctly slight structural length, a very high magnification of the incandescent lamp filament (about times) can be achieved which leads to a particularly high photometric output of the slit lamp. The condenser magnification makes it possible to achieve with an incandescent lamp of only 15 Watts of input power, an intensity of illumination or brightness in the slit image of about A million lumens whereby the bright slit image is 8.5 mm. long.

In another embodiment of the present invention, the negative lens of the telecondenser on the image side is not subdivided so that the slot diaphragm lies between the last positive element and the negative element on the image side of the telecondenser. The negative lens of the telecondenser again cooperates with the seriesconnected objective which has thus also been constituted a tele-objective.

In both cases the negative condenser element is utilized in the manner of a Smith lens for the elimination of the image-field curvature of the objective which is series-connected behind the same. The slit image is thereby reproduced well-flattened on the eye portion.

Accordingly, it is an object of the present invention to provide an illumination apparatus for slit lamps which avoids by simple means the aforementioned shortcomings and drawbacks encountered in the prior art.

Another object of the present invention resides in a slit lamp which assures a relatively high light output without the production of an undesirable, excessively large amount of heat.

A further object of the present invention resides in an optical apparatus of the type described above which can be easily manipulated and, at the same time, provides an improved light intensity as well as very small image curvature.

These and other objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawing which shows, for purposes of illustration only, two embodiments in accordance with the present invention, and wherein:

FIG. 1 is a somewhat schematic cross-sectional view of a first embodiment of an illumination installation for slit lamps in accordance with the present invention with a sub-divided negative lens of the telecondenser; and

FIG. 2 is a somewhat schematic cross-sectional view through a second embodiment of an illumination installation for slit lamps in accordance with the present invention with a unitary negative lens made in one part of the telecondenser.

Referring now to the drawing wherein like reference numerals are used throughout the various views to designate like parts and more particularly to FIG. 1, reference numeral 1 designates in this figure a conventional incandescent lamp to which is coordinated a telecondenser 2 that contains a conventional slot diaphragm 3 intermediate the sub-divided negative lens elements 2c and 2d arranged on the two sides of the slot diaphragm 3. The slit image 3' is projected into the eye to be examined, by an objective 4 of conventional construction, series-connected behind the telecondenser 2, and by a deflecting prism 5. The negative lens 2d arranged behind the slot diaphragm 3 in the normal direction of travel of the rays acts simultaneously as an element of the objective 4. This brings about a particularly spacesaving arrangement of the objective 4 which becomes thereby in its effect a tele-objective.

The embodiment of FIG. 2 is substantially similar to that of FIG. 1 with the only difference that the negative element of the telecondenser 2 is not sub-divided so that the slot diaphragm 3 is arranged between the positive lens elements 2a and the single negative lens element 2b of the telecondenser 2.

Since the various lens elements and parts of the optical apparatus shown and described in connection with FIGS. 1 and 2 are conventional, a detailed description thereof is dispensed with herein for the sake of unnecessary duplication. It might be mentioned that the variouslens elements are designed in accordance with conventional, existing practices for the type of lenses involved, utilizing conventional glasses as also generally known.

While I have shown and described only two embodiments in accordance with the present invention, it is understood that the same is not limited thereto but is susceptible of numerous changes and modifications as known to those skilled in the art, and I therefore do not wish to be limited to the details shown and described herein but intend to cover all such changes and modifications as are encompassed by the scope of the appended claims.

What I claim is:

1. A slit lamp comprising:

a light source;

I that the light source is an incandescent lamp.

A slit lamp according to claim 1, characterized in that said at least one negative lens element consists of two negative lenses which are arranged on the two sides of said slot diaphragm in the direction of passage of the light rays.

4. A slit lamp according to claim 1, characterized in that said slot diaphragm is arranged between the positive elements, on the one hand, and a single negative element.

5. A slit lamp with an objective downstream of said assymmetrical lens arrangement, according to claim 4, characterized in that the negative lens downstream of said slot diaphragm assumes together with the objective the function of a tele-objective and simultaneously serves as an image flattening lens in connection with the reproduction of said slot diaphragm.

6. A slit lamp according to claim 5, characterized in that said at least one negative lens element consists of two negative lenses which are arranged on the two sides of said slot diaphragm in the direction of passage of the light rays.

7. A slit lamp according to claim 5, characterized in that said slot diaphragm is arranged between the positive elements, on the one hand, and a single negative element.

Claims (6)

1. A slit lamp comprising: a light source; an assymmetrical lens arrangement disposed to direct the light from said light source along a prescribed path, said assymmetrical lens arrangement including a plurality of positive lens elements disposed adjacent one another, and at least one negative lens element disposed on the side of said plurality of positive lens elements downstream of said light source; and a slot diaphragm disposed adjacent said at least one negative lens element. 2. A slit lamp according to claim 1, characterized in that the light source is an incandescent lamp.

3. A slit lamp according to claim 1, characterized in that said at least one negative lens element consists of two negative lenses which are arranged on the two sides of said slot diaphragm in the direction of passage of the light rays.

4. A slit lamp according to claim 1, characterized in that said slot diaphragm is arranged between the positive elements, on the one hand, and a single negative element.

5. A slit lamp with an objective downstream of said assymmetrical lens arrangement, according to claim 4, characterized in that the negative lens downstream of said slot diaphragm assumes together with the objective the function of a tele-objective and simultaneously serves as an image flattening lens in connection with the reproduction of said slot diaphragm.

6. A slit lamp according to claim 5, characterized in that said at least one negative lens element consists of two negative lenses which are arranged on the two sides of said slot diaphragm in the direction of passage of the light rays.

7. A slit lamp according to claim 5, characterized in that said slot diaphragm is arranged between the positive elements, on the one hand, and a single negative element.

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