Operation microscope with OCT system and operation microscope illumination module with OCT system

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DESCRIPTION

Operating microscope with OCT system and illumination module of an operating microscope with OCT system.

The invention concerns an operating microscope that includes a path of observation rays to examine an area of ​​an object, an illumination device that comprises an illumination optics that reproduces the image of a light field diaphragm illuminated by a source towards infinity. of light to provide a parallel path of illumination rays, wherein the illumination optics have a first group of lenses and a second group of lenses, an objective that is arranged in the parallel path of illumination rays to reproduce the diaphragm image of the light field over the area of ​​the object, and an OCT system (Optical Coherence Tomography System) to examine the area of ​​the object, where the OCT system comprises an OCT scanning ray path that is driven through the target.

The invention also concerns an operating microscope illumination module for connection to an operating microscope, comprising a housing for a first optical conductor in order to provide illumination light, a luminous field diaphragm that can be illuminated with light coming from of the optical conductor, an illumination optic that reproduces the light field diaphragm image to infinity to provide a parallel path of imaging rays, wherein the illumination optic features a first group of lenses and a second group of lenses, and a mirror of illumination that serves to make the illumination light coming out of the diaphragm of the light field, with parallel path of imaging rays, be deflected towards the object area through the main objective of the microscope.

An operating microscope of the kind mentioned at the beginning is known from EP 0 815 801. This operating microscope contains an OCT system which generates an OCT scanning beam path from a short coherence laser radiation. The OCT system contains an analysis unit to evaluate interference signals. It comprises a device for scanning the OCT exploration ray path with two scanning mirrors that can be adjusted around two axes of movement. The OCT scanning beam path in the operating microscope is coupled, via a dividing mirror, to the illumination beam path of the operating microscope. It is diverted with it towards the area of ​​the object through the main objective of the microscope.

An illumination module of an operating microscope of the kind mentioned above contains the OPMI operating microscope system^® Visu 200 by Cari Zeiss. This lighting module is designed to be attached to the base body of an operating microscope. It comprises as illumination optics two groups of lenses that transform a luminous field panel illuminated with light from the optical conductor into a parallel path of imaging rays that runs perpendicular to the optical axis of the main objective of the microscope when the illumination module is connected. to the operating microscope. The illumination module contains two illumination mirrors that deflect illumination light parallel to the optical axis of the main objective of the microscope.

An OCT system allows the non-invasive representation and measurement of structures within a tissue by means of optical coherence tomography. As an optical imaging procedure, optical coherence tomography makes it possible in particular to generate sectional or volume images of biological tissue with micrometer resolution. A corresponding OCT system comprises a source for temporally incoherent and spatially coherent light with a coherence length l_c, which is fed to a probe beam path and a reference beam path. The probe beam path is directed towards the tissue to be examined. The OCT system superimposes a laser radiation - which, due to scattering centers in the tissue, is irradiated back towards the probe beam path - laser radiation from the reference beam path. Due to the overlap, an interference signal is generated. From this interference signal the position of scattering centers for the laser radiation in the examined tissue can be determined.

For OCT systems, the construction principle of the "time domain OCT" and the "Fourier domain OCT" is known.

The structure of a "time domain OCT" is described, for example, in document US 5,321,501 with the aid of the figure in column 5, line 40 - column 11, line 10. In this system the length of the optical path of the reference ray path by means of a fast moving reference mirror. Light from the probe and reference ray paths is superimposed on a photodetector. When the optical path lengths of the reference and probe ray paths coincide, an interference signal is generated at the photodetector.

A Fourier domain OCT is explained, for example, in WO 2006/100544 A1. To limit the length of the optical path of a probe beam path, light from the probe beam path is again superimposed on the light of a reference beam path. However, unlike a "time domain OCT", for a measurement of the optical path length of the probe beam path the light from the probe and reference beam paths is not fed directly to a detector, rather, it is first decomposed spectrorally by means of a spectrometer. The spectral intensity thus generated of the superimposed signal of the probe and reference ray paths is then captured with a detector. By evaluating the detector signal, the optical path length of the probe beam path can be obtained again.

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The problem of the invention is to create an operating microscope with an OCT system having a small construction volume and whose construction principle makes possible a simple retrofitting of operating microscopes for OCT, as well as providing an illumination module of an operating microscope with Integrated OCT system for connection to an operating microscope.

This problem is solved by means of an operating microscope of the kind mentioned at the beginning, in which a coupling element is provided in the path of illumination rays between the first group of lenses and the second group of lenses, which couples the path of OCT scanning beams with the illumination beam path, and this problem is also solved with an illumination module of an operating microscope of the kind mentioned at the beginning, wherein a housing is provided for a second optical conductor of an OCT system to provide an OCT scanning beam path, wherein the operating microscope illumination module comprises a coupling element that is arranged between the first group of lenses and the second group of lenses and coupling the OCT scan beam path with the illumination beam path.

In a further development of the invention, the coupling element in the operating microscope or in the illumination module of the operating microscope is designed as a dividing mirror, in particular as a flat mirror or a dividing die.

In a further development of the invention, the objective arranged in the parallel path of illumination beams in the operating microscope is configured as a main objective of the microscope and is traversed by the observation beam path of the operating microscope. In this way, a particularly compact construction of the operating microscope is achieved.

In a further development of the operating microscope, a deflection device for illumination light is provided on the objective side remote from the object, which deflects the illumination light from the illumination device towards the objective. In this way, illumination close to the axis of the observation ray paths is possible, which can be advantageous for ophthalmological operations.

In a further development of the invention, the deflection device is designed as a beam splitter which is traversed by the observation beam path of the operating microscope. In this way, illumination light can be directed towards the area of ​​the object in the observation beam paths of the operating microscope.

In a further development of the invention, the operating microscope contains an OCT system for scanning the OCT scanning ray path with a first scanning mirror. Preferably, a second scanning mirror is further arranged, the first scanning mirror being movable about a first axis of rotation and the second scanning mirror being movable about a second axis of rotation, and the first axis of rotation being and the second axis of rotation laterally offset from one another by a right angle. In this way, a scan of the area of ​​the object with a vertically running hatched pattern is possible.

In a further development of the invention, the operating microscope comprises an OCT system with an optical conductor having a light exit section for the OCT scanning ray path, which is movably attached. In this way, an OCT scanning plane can be varied in the area of ​​the object and it is possible to adjust the system for different OCT wavelengths taking into account the optical components designed for visible light in the observation ray path.

In a further development of the invention, the operating microscope comprises an OCT system with an adjustable collimation optic that transforms the OCT scanning beam path with the second group of lenses of the illumination optic into a substantially parallel scanning beam path. In this way, it is possible to shift the OCT scanning plane in the operating microscope relative to the scanning plane of the scanning beam optical paths of the system.

Preferably, the illumination module of the operating microscope comprises a device for scanning the OCT exploration beam path. This scanning device can have, for example, a first scanning mirror and a second scanning mirror. Since the first scan mirror can be moved around a first axis of rotation and the second scan mirror can be adjusted around a second axis of rotation, the first axis of rotation and the second axis of rotation being laterally offset by one. relative to another at a right angle, an area of ​​the object with a vertically running hatched pattern can be scanned.

In a further development of the invention, the light exit section of the optical conductor for the OCT scanning beam path is movably attached to the illumination module of the operating microscope in order to thus be able to adjust the OCT scanning plane.

Since an adjustable collimation optic is provided in the illumination module of the operating microscope, by means of which the OCT scanning beam path can be transformed with the second group of lenses of the illumination optic into a beam path of substantially parallel scanning, it is possible to shift the OCT scanning plane of the OCT system relative to an observation plane for optical paths of observation rays.

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Advantageous embodiments of the invention are represented in the figures and are described below.

They show:

Figure 1, an operating microscope with an illumination module in which an OCT system is integrated;

Figure 2, a section of the main objective of the microscope along the line II-II of Figure 1;

Figure 3, a section of the lighting module with OCT system;

Figure 4, an intensity distribution of the OCT scanning light beam exiting the optical conductor of the OCT system in the operating microscope; Y

Figure 5, an intensity distribution of the OCT scanning light beam in the OCT scanning plane located in the area of ​​the object of the operating microscope.

The operating microscope 100 of FIG. 1 has a main objective 101 with an optical axis 102 and a focal plane 103 that is housed in a base body 104 of the operating microscope. The main objective 101 of the microscope is traversed by stereoscopic light beam paths 105 from a binocular tube 106. The operating microscope 100 contains a zoomizable magnifying system 107.

To illuminate the area 108 of an object, the operating microscope 100 has an illumination module 120 as its illumination device. This illumination module 120 contains a housing 121 for a first optical conductor 122 that provides illumination light 123 from a source of light. light not represented in more detail. The illumination light 123 exiting the first optical conductor 122 illuminates an adjustable light field diaphragm 124. A lighting optic is arranged in the lighting module 120. The illumination optics comprise a first group of lenses 125, a second group of lenses 126, and four mirror elements 127, 128, 129, and 130.

The mirror element 127 deflects the outgoing illumination light from the first group of lenses 125 towards the mirror element 128, from where said light reaches the second group of lenses 126. The first group of lenses 125 and the second group of lenses 126 form towards infinity the image of the light field diaphragm 124. Thus, illumination light 123 exits from the second group of lenses 126 with a parallel ray path. The optical axis 120 of the illumination beam path runs on the exit side of the second group of lenses 126 in a direction perpendicular to the optical axis 102 of the main objective 101 of the microscope. The light is guided towards an illumination mirror 130 having a perforation 131. The illumination mirror 130 deflects the illumination light in a direction parallel to the optical axis 102 of the main objective 101 of the microscope and brings it to the area 108 of the object.

The lighting module 120 also comprises a lighting mirror 132 to which lighting light is fed which reaches the lighting mirror 130 through the perforation 131.

The illumination mirror 132 can be adjusted according to the double arrow 133 in a direction perpendicular to the optical axis 102 of the main objective 101 of the microscope. This makes it possible to adjust the angle of incidence for the illumination light in the area 108 of the object.

To vary the intensity of the guided illumination light in the area of ​​the object, adjustable diaphragms 134, 135 have been associated with the illumination mirrors 130, 132. By adjusting the diaphragms 134, 135, the intensity of the conducted illumination light can be varied. through the main objective 101 of the microscope.

The lighting module 120 has a housing 150 for a second optical conductor 151 that is connected to an OCT system 152.

The OCT 152 system enables OCT imaging for examination of area 108 of the object. It comprises a unit for the generation and analysis of an OCT 153 exploration ray path.

The OCT 152 system is preferably integrated into a tripod console of the operating microscope, not shown in more detail. However, in principle it could also be housed in the lighting module 120.

The scan beam path 153 exiting the optical conductor 151 is led to a first scan mirror 154 and a second scan mirror 155 of an OCT scan unit 156. This path passes through a condenser lens 157 after the scan unit OCT 156.

The beam of rays 160 from the OCT scanning unit 156 is directed towards the mirror element 128. The mirror element 128 acts as a dividing mirror. It almost completely reflects the illumination light exiting the optical conductor 122, but is permeable to the OCT scanning ray path. Thus, the OCT scanning ray path 153 is superimposed on the illumination light 123. The mirror element 128 is realized in the lighting module 120 as a mirror element with flat plates. However, it could also be configured as a divisor die.

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The light from the OCT scanning ray path 153 is conducted by the illumination mirrors 130, 132 with the illumination light towards the region 108 of the object. The condenser lens 157, the second lens group 126 of the illumination optics in the illumination module 120, and the main objective 101 of the microscope concentrate the OCT scan ray path 153 on an OCT scan plane 170. The OCT scanning plane 170 is the plane of the geometric reproduction of the exit end of the optical conductor 173 in the area 108 of the object, fixed by the optical elements in the OCT scanning beam path with the OCT scanning unit 156, the condenser lens 157, mirror element 128, mirror element 130, mirror element 132, and main objective 101 of the microscope. In other words, the corresponding geometric image of the output end of the optical conductor is located in the OCT scanning plane 170. To adjust the OCT scanning plane, on the one hand, the condenser lens 152 is movably held by means of a regulating drive 171 according to the double arrow 172. On the other hand, the exit end 173 of the optical conductor 151 for the OCT scanning beam path can be displaced according to the double arrow 175 by means of a regulating device 17 4. When adjusting the scanning plane OCT 170, the reference ray path is readjusted whenever necessary in the OCT system.

Light backscattered to the OCT scanning beam path reaches the OCT system 152 through the microscope main objective 101, mirror elements 132, 130, lens group 126, and mirror element 128. The light from OCT backscattered scan from the object area is interfered with there by OCT radiation from a reference ray path. The interference signal is captured by means of a detector and evaluated by a computer unit that determines from this signal a difference in the length of the optical path between scattering centers for OCT light in the area of ​​the object and the length of the path of the the light on the reference branch.

Figure 2 is a section along the line II-II of Figure 1. This figure shows the illumination mirrors 130, 132 and explains the path of the stereoscopic observation ray paths 105 in the operating microscope 100 of the Figure 1. The main objective 101 of the microscope is traversed by two stereoscopic partial ray paths 105a, 105b. The optical axis 102 of the main objective 101 of the microscope is located in the center of this objective.

Figure 3 shows the OCT scanning unit 156 of the operating microscope 100 of Figure 1. The first scanning mirror 154 and the second scanning mirror 155 are rotatably arranged by means of servo drives 301, 302 about two axes 303 , 304 running perpendicular to each other. This enables the OCT 305 scanning ray path to be scanned on a 306 plane.

Figure 4 shows the front section 402 of the optical conductor 151 of figure 1. The optical conductor 151 acts as a single-mode fiber for light of wavelength λ = 1310 nm. The diameter d of the fiber core of the optical conductor 122 satisfies the relationship

<img file="ES2348744T3_D0001.tif" />

where NA is the numerical aperture of the front surface of the optical conductor. Preferably, the diameter d of the fiber core of the optical conductor 122 is within the range of 5 pm &lt;d &lt;10 pm. In this parametric range the optical conductor 122 conducts light with Gaussian wave modes. The OCT 401 scanning light beam exits the optical conductor 151 with a radiation profile of approximately Gaussian shape, which is characterized by a size parameter W₀ and an aperture parameter θ₀, where it is fulfilled:

<img file="ES2348744T3_D0002.tif" />

For a fiber core diameter of d₀ = 10 pm and a wavelength λ₀ = 1310 nm, thus, as a measure for the divergence of the rays, an opening angle of θ₀.0.0827 rad.

The front surface 402 of the optical conductor 151 is imaged, through the main objective 101 of the microscope, on the area 107 of the object, in the scanning plane OCT 170, by means of the scanning mirrors 154 and 155 in the microscope 100 of FIG. 1, condenser lens 157, mirror element 128, second group of lenses 126, mirror element 130, and mirror element 132.

Figure 5 shows the evolution of the intensity distribution of the OCT 4 01 scanning light beam in a direction perpendicular to the OCT 501 scanning plane. In the OCT 501 scanning plane the intensity distribution of the OCT scanning radiation has a narrowing very small. Outside the OCT scan plane, the diameter of the OCT scan ray path increases. Since the OCT scanning light beam

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401 exits the optical conductor 151 of FIG. 4 with a radiation profile of approximately Gaussian shape, the condenser lens 157 and the main objective 101 of the microscope produce for the OCT scanning light beam, in the OCT scanning zone 170, a so-called Gaussian beam 500 of the OCT 401 scanning light beam. This Gaussian beam 500 is characterized by the confocal parameter z as a measure of the longitudinal extension of the waist of the Gaussian beam and by the waist parameter W as a measure of the diameter of the very small narrowing 502 of the OCT 401 scanning light beam, that is, for the diameter of your waist, being fulfilled that:

where λ is the wavelength of the OCT scanning light beam. Between the size parameter W of the Gaussian beam 500 and the size parameter W0 of the scanning light beam 401 shown in FIG. 4, which exits the optical conductor 151, the following relationship holds:

<img file="ES2348744T3_D0003.tif" />

where β is the parameter for increasing or decreasing the aforementioned geometric reproduction of the output end of the optical conductor 151 of FIG. 1 in the OCT scanning plane. β is linked to the focal length fi of the condenser lens 157 in Figure 1 and the focal length f₂ of the main objective of the microscope by the following relationship:

<img file="ES2348744T3_D0004.tif" />

The size of the structures that can be resolved with the OCT 401 scanning light beam is determined by the diameter of this beam in the OCT 170 scanning plane, that is, by the waist parameter W. If, for example, an application requires a lateral resolution of the OCT system in the operating microscope of approximately 40 pm, the cross-section of the OCT 401 scanning light beam on the surface has to amount, according to Nyquist's theorem, to approximately 20 p.m. Therefore, at a given wavelength λ for the scanning light ray OCT 153 of figure 1, the increase in optical reproduction in the OCT ray path must be chosen appropriately for a desired resolution of the OCT system 152. and the diameter of the fiber core in the optical conductor 151.

The confocal parameter z as a measure of the longitudinal extent of the waist of the Gaussian beam determines the zone of axial depth from which backscattered light can be detected in the OCT 153 scanning ray path of figure 1: The smaller the confocal parameter z, the greater the loss of lateral resolution of the OCT system if an object scanned with OCT radiation is moved away from the OCT 170 scan plane, since the location of the centers of Dispersion can only be located within the "funnel" defined by the height parameter W and the confocal parameter z.

Since, on the one hand, the axial resolution of an OCT system is limited by the coherence length l_c of the light of the light source used in the OCT system and, on the other hand, the lateral resolution of the OCT system decreases when its depth travel exceeds the extension provided with the confocal parameter z, the adjustment of the confocal parameter z is favorable. depth stroke of the OCT system.

For a given wavelength λ of the OCT 4 01 scanning light beam, the possible lateral resolution of the OCT system of FIG. 1 then results, since the wavelength λ and the confocal parameter z fix the waist parameter W. optical units in the OCT scanning ray path 153 of FIG. 1 and the dimensioning of the fiber core of the optical conductor 151 must then be chosen so that the corresponding size parameter W.

The operating microscope 100 is designed so that the focal plane 170 of the main objective 101 of the microscope coincides for the visible spectral zone and the OCT scanning plane 160. The size 502 of the OCT scanning light beam shown in Figure 5 is located then in the focal plane of the operating microscope.

As an alternative to this design of the operating microscope, an offset from the OCT scanning plane and the focal plane of the operating microscope can also be provided. Preferably, this offset is not greater than the confocal parameter z of the scanning light beam oCt in the region of the scanning plane OCT. This enables, for example, an area of ​​an object located immediately below the focal plane of the operating microscope to be visualized by OCT. However, it may also be relevant to provide for certain applications a defined offset that exceeds the confocal parameter, for example to be able to examine with the operating microscope.

ES 2 348 744 T3 the anterior side of the cornea of ​​a patient's eye and at the same time visualize by means of the OCT system the posterior side of the cornea of ​​the patient's eye or its lens.

Since the OCT scanning plane is further away from the main objective 101 of the microscope of FIG. 1 by the Rayleigh parameter z, the depth stroke for the OCT system in the area of ​​the object can be maximized.

A modified embodiment of the operating microscope 100 explained with the aid of FIG. 1 contains a focusable main objective of said microscope with an adjustable focal length. This measure also enables the translation of an OCT scanning plane and the variation of the geometric reproduction of the exit end of the optical conductor in the OCT scanning plane.