GB2148531A

GB2148531A - Optical system for therapeutic use of laser light

Info

Publication number: GB2148531A
Application number: GB08424466A
Authority: GB
Inventors: Franz Muchel
Original assignee: Carl Zeiss AG
Current assignee: Carl Zeiss AG
Priority date: 1983-10-01
Filing date: 1984-09-27
Publication date: 1985-05-30
Also published as: GB8424466D0; GB2148531B; FR2552894A1; DE3335810C2; DE3335810A1; FR2552894B1; JPS6096242A; CH666175A5

Abstract

A combined observation and laser therapy instrument e.g. a laser ophthalmoscope. Light from laser 2 is directed by a semireflecting element into an illumination/observation beam path, via objective 4, towards the object, e.g. a patient's eye 1. Element 6 represents an optical system which corrects for the difference in focus of the laser radiation and observation light. Element 5 represents the eyepiece or an observation optical instrument. <IMAGE>

Description

SPECIFICATION Optical system for therapeutic use of laser light The present invention relates to an optical system for laser therapy and observation instruments in which there is means for reflecting the laser radiation into the observation ray path.

Laser light is used, for instance, for purposes of treatment of the eye. For example, U.S.

patent 3,769,963 of Goldman et al., Nov. 6, 1973, discloses an instrument in which a laser ligth path is combined with an operation microscope, for laser treatment of the eye. However, in this instrument, the laser radiation is conducted outside the microscope; that is, the laser beam does not pass through the optics of the microscope.

For the sake of compactness of construction, it is desirable to conduct the laser radiation through the optical system of the observation instrument, i.e., through the operation micro scope. However, if this is done, it results in a focusing problem. Because of the difference in wavelengths of the treatment light (laser light) and the observation light, considerable differ ences in focus occur for the wavelength regions used.

The object of the present invention is to provide an optical system which compensates for the difference in focus which occurs when an imaging optical system is used for different wavelength regions.

This object is achieved, according to the invention, by introducing the laser therapy beam into the path of the observation beam through a reflecting element located between the main objective and the eyepiece of the observation instrument, and by providing a correction optical system located in front of the reflecting element as seen in the direction of observation (that is, between the eyepiece and the reflecting element), this correction optical system serving to compensate for the difference in focus between the laser light and the observation light.

An advantageous embodiment of the invention is constructed in accordance with the parameters stated below.

The advantages obtained by the invention include the fact that the laser radiation required for therapeutic purposes can be conducted through the optical system of an ordinary commercial diagnostic instrument without having to tolerate any impairment in the image, and that the conducting of the laser radiation through the observation optical system makes possible a very small and compact construction of a laser therapy instrument.

In the accompanying schematic or diagrammatic drawings: Figure 1 is a diagram showing the general arrangement of the optical system of the invention within a diagnostic or observation instrument; Figure 2 is a diagram of a preferred form of the objective and Figure 3 is a diagram of a preferred form of the correction optical system.

Referring now to Fig. 1, the object being examined (i.e., the eye of a patient) is indicated at 1. Radiation from a laser indicated schematically at 2 travels in the direction of the arrowhead to a a reflecting element 3, such as a mirror, where it is deflected to pass leftwardly toward the eye 1 coaxially with the observation optical axis indicated by the horizontal dotdash line. This observation optical axis represents the optical axis of a conventional observation instrument, such as, e.g., a surgical operation microscope or a slit lamp as used in ophthalmological examination.The reflecting element 3 is partially pervious to laser target-light radiation and to observation light from the conventional light source, not shown, which illuminates the eye 1 and is reflected back therefrom, so that the target light and the observation light may be observed through the conventional observation optical system 5 of a slit lamp, operation microscope, or other observation instrument by a surgeon or other observer.

According to the invention, a correction optical system indicated schematically at 6 is located on the optical axis between the reflecting element 3 and the eyepiece or observation optical system 5, to compensate or correct for the difference in focus between the laser radiation and the observation light. Assuming that one wishes to use laser therapy radiation with a wavelength A, of 1064 mn, and laser target-light radiation with a wavelength A2 of 633 nm, and an observation light in the visible spectrum range of 480 nm to 644 nm, good results are obtained when the main objective 4 is constructed substantially in accordance with the parameters indicated in Table 1 and the correction optical system 6 is constructed substantially in accordance with the parameters indicated in Table II.

In these tables, the customary notation commonly used in lens patents is employed. The radii of the respective surfaces are indicated by the letter r with a numerical subscript identifying the particular surface, numbered consecutively from front to rear. Thicknesses and spacings are shown by d with a numerical subscript, numbering both thicknesses and spacings in a single numerical sequence. The index of refraction of each element is shown in the column headed n, and the Abbe number of the element in the column headed Vd. As usual, positive radii indicate surfaces convex toward the front or concave toward the rear, and negative radii represent surfaces concave toward the front or convex toward the rear.A single r number for two adjacent elements, with no spacing between them, indicates surfaces in contact with each other, which may be cemented.

Fig. 2 shows in detail the construction of the main objective shown only in general at 4 in Fig. 1. As seen in Fig. 2, it consists of three elements, respectively identified as 41, 42, and 43, the parameters of which are given in Table 1. Similarly, the correction optical system, indicated in general at 6 in Fig. 1, is shown in more detail in Fig. 3. It has two elements, respectively identified as 61 and 62, the parameters of which are given in Table II.

Table I Element S1 = -119.4 (nod) ( d) r1 = 486.97 41 d1 7 n 1= 1.6209 \~1 = 60.3 r2 = -105.93 d2 = 0.3 r3 = 427.81 42 d3 3 4 n3= 1.8052 V3 = 25.4 r4 = 78.298 d4= 0.3 r5 = 79.719 43 d5 = 7.7 n5 = 1.5532 V - 63.5 5 - r6= -227.12 SI = c > O Table II Element s1 = # r1 = -137.25 61 61 d1 =7 n = 1.8052 V1 = 25.4 r2 = - 91.07 62 d2 =7 n2= 1.6177 t2 = 49.8 r3 = -170.31 s' = With this construction, the objective 4 is corrected for the laser wavelength regions of 1064 nm and 633 nm, and the correction optical system 6 is corrected in such manner that, upon observation in the region of visible light (wavelengths 480 nm to 644 nm), the difference in focus which occurs as a result of the correction of the objective 4 is properly compensated. The combination of the main objective 4 with the correction optical system 6 is then also fully corrected for the wavelength region of 480 to 644 nm.

Claims

1. An optical system for laser therapy and observation instruments, comprising a main objective and an eyepiece defining an observation ray path, a reflecting element located in said observation ray path between said objective and said eyepiece for directing laser radiation into said ray path, and a correction optical system for compensating for difference in focus of laser radiation and observation light, said correction optical system being located in front of said reflecting element as seen in a direction of observation.

2. The invention defined in claim 1, wherein said reflecting element is a mirror which reflects laser radiation incoming from a lateral direction so that such laser radiation passes along said observation ray path toward said objective, said mirror being permeable by observation light and certain laser radiation returning along said observation ray path from said objective toward said eyepiece.

3. The invention defined in claim 1, wherein said objective comprises elements dimensioned and arranged substantially in accordance with the following data: Element #1 = -119.

4 (n#) (Vd) r1 = 486.97 41 d1 = 7 n1 = 1.6209 60.3 r2= -105.93 d2=0.3 r3 = 427.81 42 d3= 4 n3= 1.8052 ##= 25.4 r4 = 78.298

r5= 79.719 43 d5 = 7.7 n5 = 1.5532 #

5 = 63.5 r6= -227.12 s' = DO 4.The invntion defined in claim 1, wherein said correction optical system comprises elements dimensioned and arranged substantially in accordance with the following data: Element r1 = -137.25 61 61 d1 =7 n 1= 1.8052 # 1 = 25.4 1 - 91.07 62 d2 =7 n2= 1.6177 #2 = 49.8 r3= -170.31 s' = # 5.The invention defined in claim 1, wherein the therapy and observation instrument is designed for operation with laser therapy radiation of wavelength in the range of 480 nm to 644 nm, and wherein said objective comprises elements dimensioned and arranged substantially in accordance with the following data: Element s1 = -119.4 (n ) (f ) r1 = 486.97 41 r2 d 7 d1 n 1= 1.6209 f1 = 60.3 r2 -105.93 d2= 0.3 r3 = 427.81 42 d3 = 4 n3 = 1.8052 = 25.4 3 r4 = 78.298 d4=0.3 r5 = 79.719 43 d5 = 7.7 n5 = 1.5532 = 63.5 r6 = -227.12 51 = and said correction optical system comprises elements dimensioned and arranged substantially in accordance with the following data:: Element 1 r1 = -137.25 61 d1 7 n 1= 1.8052 25.4 r2 = - 91.07 62 al2 =7 n2= 1.6177 Y2= 49.8 r3 = -170.31 s' = oC

6. A relatively small compact instrument for combined observation and laser treatment of an eye, comprising an eyepiece and an objective defining an optical axis along which observation light may be projected toward an eye being examined and along which light may return toward an observer, means for introducing laser radiation to said axis at a point between said objective and said eyepiece to travel along said axis from said objective and said eyepiece to travel along said axis from said point toward said eye being examined with a portion of the laser radiation returning from said eye past said point of said observer, and means on said optical axis between said point and said eyepiece for compensation for difference in focus between said laser radiation and said observation light.

7. The method of improving the ability of an observer to control laser radiation therapy on the eye of a patient, which comprises: a) providing an observation instrument having an objective and an eyepiece through which the observer may look along an optical axis toward the eye of the patient; b) projecting observation light along said optical axis to illuminate part of said eye and to return by reflection from said eye toward said observer; c) projecting laser therapy radiation and laser target-light radiation along said optical axis through said objective toward said eye, said target-light radiation being reflected back toward said observer; and d) providing a correction optical system in the path of said observation light and said reflected back target-light radiation, to compensate for difference in focus caused by difference in wavelength of said observation light and said target-light radiation.