Surgical microscope having an illuminating system and control unit therefor

A surgical microscope (100) has a viewing optic (101, 104, 115) which allows a viewing person to view the enlarged display of an object region (116) in a viewing area (117). The viewing optic (101, 104, 115) has a continuously adjustable magnification system (104) with which a viewing optic adjusting unit (119) is associated. The surgical microscope (100) has an adjustable illuminating system (150), which provides illuminating light (151) for the object region (116), to illuminate the object region in an illuminated area (152) using illuminating light (151) of adjustable radiation intensity. An illumination system control unit (175) is provided in the surgical microscope (100), the control unit being connected to the viewing optic adjusting unit (119) for receiving information as to the adjusted magnification of the viewing optic (101, 104, 115).

FIELD OF THE INVENTION

The invention relates to a surgical microscope having a viewing optic which permits the magnified presentation of an object region in a viewing area to a viewing person. The viewing optic includes a continuously adjustable magnification system to which an adjusting unit for the viewing optic is assigned. The surgical microscope also has an adjustable illuminating system which makes illuminating light available for the object region in order to illuminate the object region in an adjustable illuminated area with illuminating light of adjustable radiation intensity. An illumination system control unit is provided which is connected to the viewing optic adjusting unit for receiving data as to the adjusted magnification of the viewing optic. The control unit is operatively connected to the illumination system in order to adjust the same for an adaptation of the size of the illuminated area to the size of the viewing area.

BACKGROUND OF THE INVENTION

A surgical microscope of the kind described above is disclosed in U.S. Pat. No. 5,140,458. There, a surgical microscope is described which has a viewing optic having an adjustable magnification and an illuminating unit having an adjustable illuminating optic. A coupling of the viewing optic to the optic of the illuminating unit is provided in order to adapt the size of the illuminated area to the size of the viewing area when varying the magnification of the viewing optic.

The surgical microscope disclosed in U.S. Pat. No. 5,748,367 discloses a surgical microscope having an adjustable imaging focal intercept. The surgical microscope has an illuminating system with which illuminating light can be generated for the object region. The focal intercept of the illuminating system is configured to be variable in order to be able to adapt the focal intercept of the illuminating system to the imaging focal intercept of the surgical microscope. A coupling mechanism is provided which couples the illuminating focal intercept to the imaging focal intercept of the surgical microscope. The magnification of the microscope and therewith the viewing area diameter changes when varying the imaging focal intercept. For this reason, the coupling of the illuminating focal intercept and the imaging focal intercept effects an adaptation of the diameter of the illuminated area to the diameter of the viewing area in the surgical microscope.

An adjustable illuminating system for a surgical microscope is also described in German utility model registration 203 10 548 U1. This system permits focusing the illuminating light for different illuminated area diameters. In this way, also the radiation intensity of the illuminating light in the illuminated area can be correspondingly varied.

U.S. Pat. No. 7,505,201 describes a method to optimally adjust the light power in the object plane for incident light microscopes which can be especially configured as surgical microscopes. When adjusting the illuminating system, the light intensity, which reaches the object region, can be controlled to prevent thermal damage to biological tissue under investigation with the microscope which damage can be attributed to excessively intense illuminating light.

High power light sources such as xenon lamps are used in surgical microscopes which are designed for neurosurgery and ENT surgery. In addition to the desired effect of a bright illumination of the object region, these light sources have the disadvantage that the tissue in the object region can be heated by the illuminating light made available by these light sources notwithstanding filtering out UV-light and infrared light. This brings with it the danger of thermal damage. Depending upon the power setting, the work distance and the bundling of the illuminating light directed to the object region, phototoxic reactions can be triggered in the tissue under investigation by the illuminating system in such surgical microscopes. There then occurs damage to the tissue.

In systems corresponding to the state of the art, it is left to the discretion of the viewing person, that is, as a rule, the operating surgeon, which radiation intensity the viewing person selects for illuminating the object region. The danger is well known to cognizant persons in this field that patient tissue can be damaged with illuminating light made available by the illuminating system in the surgical microscope. The manufacturers of surgical microscopes call attention to this danger in operating manuals and it is recommended to work with a light source power which is as low as possible. Surgeons often select a low lamp power setting at the start of a surgical procedure. With increasing the magnification of the optical viewing system in the surgical microscope, one must then, however, increase the light quantity directed to the region of surgery because, otherwise, the viewing area is too dark. When working with a surgical microscope, the area, which is illuminated by the illuminating system, is mostly set larger than the viewing area even when corresponding systems offer the possibility of reducing the illuminated area. This is because surgeons often do not use the possibility of reducing the illuminated area during a surgical procedure in a corresponding surgical microscope. However, the body tissue of the patient can be unnecessarily subjected to illuminating light.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a surgical microscope which permits a surgeon to illuminate a region of surgery with an illuminating light in such a manner that the viewing image is sufficiently bright without danger of thermal damage to the patient tissue because of the illuminating light.

This object is realized with the surgical microscope of the kind described above wherein the illuminating system control unit controls the illuminating system in dependence upon the adjusted magnification of the viewing optic so that, in a first magnification range, the size of the illuminated area is varied in the object region at constant radiation intensity of the illuminating light and, in a second magnification range, the size of the illuminated area is adjusted while changing the radiation intensity.

In a further embodiment of the invention, the illuminating system includes an adjustable optic component assembly for adjusting the illuminated area. This adjustable optic component assembly preferably includes at least one displaceable lens element and an adjustable illuminated field diaphragm. A very reliable operation of the surgical microscope is made possible because the optical component assembly has a common drive element for the displacement of the lens element and the adjustment of the illuminated field diaphragm.

A rotatable shaft is provided as a drive element in accordance with another embodiment of the invention. Especially an electric motor is suitable for driving this shaft. Alternatively or in addition, a rotary knob can be assigned to the rotatable shaft for rotating the same.

According to another embodiment of the invention, the common drive element operates in such a manner on an illuminated field diaphragm adjusting mechanism that a drive force, which is introduced into the drive element, is transmitted to the illuminated field diaphragm when opening the illuminated field diaphragm as well as when closing the illuminated field diaphragm. Such an adjusting mechanism is capable of introducing relatively high adjusting forces into the illuminated field diaphragm. In this way, a reliable operation of the illuminated field diaphragm is possible even with frequent opening and closing over long time spans even though the actuating forces for the diaphragm increase over time because of mechanical wear of the movable elements.

According to another embodiment of the invention, the illuminating system includes a light source for the illuminating light. The light source is assigned a unit for adjusting an illuminating luminous flux of illuminating light from the light source. Preferably, the illuminating system contains a “Siebblende” for the adjustment of the illuminating luminous flux. A “Siebblende” is a diaphragm having a plurality of apertures formed therein and is hereinafter referred to as an apertured diaphragm. In this way, a threshold value for the phototoxicity for illuminating light, which is directed to the object region, can be precisely maintained.

In a further embodiment, an adjusting unit is assigned to the magnification system and adjusts the magnification of the viewing optic to a value selectable by the viewing person.

In another embodiment of the invention, the transmission of the viewing optic is essentially constant in the first magnification range and the transmission of the viewing optic decreases with increasing magnification in the second magnification range.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

The surgical microscope100ofFIG. 1has a viewing optic having a focusable microscope main objective system101defining an optical axis110. The viewing optic of the surgical microscope includes a continuously adjustable magnification system104through which left and right viewing beam paths (111,112) pass. The magnification system104is a three member zoom having displaceable lenses. The surgical microscope100permits a viewing person to view an object region116in a viewing area117with adjustable magnification by looking into a binocular tube113having an ocular optic115.

An adjusting unit119is assigned to the focusable main objective system101and an adjusting unit118is assigned to the adjustable magnification system104. Each of the adjusting units (118,119) includes a motor drive (not shown).

The surgical microscope100has an illuminating system150. The illuminating system150makes the illuminating light151available in an illuminated area152in the object region116. The illuminating system150includes a xenon lamp153as a light source to which an apertured diaphragm (Siebblende)154is assigned. The light from the xenon lamp153is directed to a light conductor155via the apertured diaphragm154. The illuminating system150includes an illuminated field diaphragm157. This diaphragm157is illuminated by an illuminating light156exiting from the light conductor155. The illuminating system150includes further an adjustable optic unit158and an adjustable mirror element159. The illuminating light160, which exits from the illuminated field diaphragm157, is directed to the object region116via the adjustable optic unit158and the adjustable mirror element159and generates there the illuminated area152.

An illuminating system control unit175is assigned to the illuminating system150. The illuminating system control unit175is connected to a unit176for controlling the power of the xenon lamp153and a unit177for adjusting the apertured diaphragm154. The unit for adjusting the apertured diaphragm177includes a motoric actuator (not shown inFIG. 1).

The adjustable optic unit158and the adjustable illuminated field diaphragm157conjointly define an adjustable optic component assembly180. The illuminating system150includes an adjusting unit178for adjusting the optic unit158and the illuminated field diaphragm157. The adjusting unit178likewise includes a motoric actuator (not shown inFIG. 1).

The mirror element159in the illuminating system150is configured so as to be adjustable. The illuminating system150has a drive unit179for adjusting the mirror element159and this drive unit is likewise connected to the illuminating system control unit175.

By displacing the mirror element159, the adjustable optic unit158and the illuminated field diaphragm157, the size of the illuminated area152in the object plane of the microscope main objective system101can be adapted to the size of the viewing area117in the surgical microscope100. For this purpose, the illuminating system control unit175having the adjusting units (118,119) for the focusable main objective system101is connected to the magnification system104.

An input unit190is assigned to the illuminating system control unit175. This input unit190permits a configuration of the illuminating system control unit175. In this way, the illuminating system control unit175can be adjusted for changed imaging parameters of the viewing optic in the surgical microscope when there is an exchange of the ocular optic115or of the microscope main objective101. The information as to the magnification of the ocular optic115is stored in the illuminating system control unit175. The instantaneously selected adjustment of the main objective system101and of the magnification system104is supplied by the adjusting units (118,119) to the illuminating system control unit175.

The illuminating system control unit175computes the size of the viewing area117from the magnification of the ocular optic115, the magnification of the magnification system104and the adjustment of the microscope main objective system101. More specifically, the diameter DSof the viewing area117in the object plane is computed. The object plane corresponds to the focal plane of the microscope main objective system101.

For the computed diameter DSof the viewing area, the drive unit179for the mirror element159as well as the adjusting unit178for the optic component assembly180having the adjustable optic unit158and the illuminated field diaphragm157is so driven that the illuminated area152is adapted to the viewing area117of the surgical microscope100. The illuminated area152is generated in the object region116by the illuminating system150. An advantageous adaptation of the illuminated area152and the viewing area117comprises to adjust the diameter DLof the illuminated area152to the diameter DSof the viewing area117. It is, however, also possible to so vary the diameter DLof the illuminated area152that this diameter is always somewhat greater than the diameter DSof the viewing area.

The illuminating system control unit175controls the optic component assembly180in the illuminating system150so that for large to medium illuminated areas, that is, sizes up to the medium illuminated area diameter DL, the optic unit158is adjusted without a simultaneous variation of the illuminated field diaphragm157.

In contrast, to adjust medium and small illuminated areas, that is, for medium and small diameters DLof the illuminated area, the adjustment of the optic unit158is held unchanged and only the opening of the illuminated field diaphragm157is varied.

Because of the automatic coupling of the illuminated area size to the viewing area size, it is always ensured that, for the surgeon operating with the surgical microscope100, the regions of the object field are illuminated with these regions being viewable in the binocular viewing unit of the surgical microscope. At the same time, it is so effected that tissue structures, which lie outside of the viewing area of the surgical microscope, are not subject to unnecessary loading by the illuminating light. More specifically, these tissue structures of the patient are protected against unwanted warming.

FIG. 2is a schematic of the surgical microscope100ofFIG. 1for an adjustment of the viewing optic and the illuminating optic for low magnifications. The illuminated area152covers the viewing area217and, with respect to its size, the illuminated area corresponds to the size of the viewing area217.

FIG. 3schematically shows the surgical microscope100ofFIG. 1for an adjustment of the viewing optic and the illuminating optic for high magnification. The illuminating area352likewise covers the viewing area317and again has a size which corresponds to the size of the viewing area.

FIG. 4shows a diagram400wherein, with a curve401, the transmission T of the viewing optic (101,104,115) is plotted against corresponding diameters of the viewing area for the surgical microscope100, more specifically, the ratio of the light quantity, which exits from the ocular optic115, is plotted against the light quantity from the object region116by the microscope main objective system101. The diameter DSof the viewing area changes when changing the magnification of the viewing optic (101,104,115), for example, the magnification system104is adjusted or the focus of the microscope main objective system101is shifted. For the form of the surgical microscope100ofFIG. 1, it applies that with increasing magnification, the diameter DSof the viewing area reduces monotonically, that is, the size of the viewing area and the diameter thereof is clearly reversibly linked to the optical magnification of the viewing optic (101,104,115) in the optic system.

The transmission T of the viewing optic (101,104,115) in the surgical microscope100ofFIG. 1as a function of the viewing area diameter has a first section402wherein the magnification is comparatively small. In section402, the transmission T of the viewing optic (101,104,115) changes practically not at all with increasing magnification, that is, with decreasing diameter DSof the viewing area.

This behavior of the transmission T of the viewing optic changes with a specific magnification which corresponds to a characteristic viewing area diameter DS*. Above this magnification, the transmission behavior T of the viewing optic decreases greatly in a second section403with increasing magnification. In diagram400, the characteristic viewing area diameter DS* delimits the section402with respect to the section403of the curve401for the transmission T of the viewing optic.

In the surgical microscope100ofFIG. 1, the illuminated area152is adapted to the size of the viewing area117for a comparatively low magnification in that the adjustable optic component assembly180in the illuminating system150is so varied that a bundling of the illuminating light takes place with a reduction of the viewing area by increasing the magnification of the viewing optic. An increase of the illuminance B in the illuminated area152of the illuminating light in the surgical microscope100ofFIG. 1accompanies a bundling of the illuminating light. In order to compensate for this increase in light intensity, the intensity of the illuminating light156, which illuminates the illuminated field diaphragm157in the system, is attenuated by adjusting the lamp power of the xenon lamp153and by adjusting the apertured diaphragm154.

Illuminating light156illuminates the illuminated field diaphragm157in the illuminating system150of the surgical microscope100ofFIG. 1.FIG. 5presents a diagram500with a curve501which shows, qualitatively, the intensity of the illuminating light156plotted in dependence upon the illuminated area diameter DLadjusted with the system.

InFIG. 5, the first section502corresponds to the section402ofFIG. 4. In the first section502, the light intensity I decreases with increasing magnification. In a second section503, which corresponds to the second section403ofFIG. 4, the intensity I increases with increasing magnification. The adjustment of the illuminating system150is especially matched to the magnification adjusted with the viewing optic (101,104,115) in such a manner that the illuminance B of the illuminating light in the illuminated area in the object region has the course corresponding to the curve601shown inFIG. 6by the diagram600. More specifically, the illuminating system control unit175in the surgical microscope100ofFIG. 1controls the illuminating system150in dependence upon the adjusted magnification of the viewing optic (101,104,115) in such a manner that, in a first magnification range602, the size of the illuminated area152at constant illuminance B of the illuminating light in the object region116is varied and, in a second magnification range603, the size of the illuminated area152is adjusted by changing the illuminance B. The illuminating system150in the surgical microscope100ofFIG. 1is so controlled that the brightness impression of the viewed image in the binocular tube113is constant for a viewing person over the entire magnification range adjusted with the viewing optic (101,104,115) in the surgical microscope100.

For adjusting the illuminated area152and the illuminance B of the illuminating light in the object region116, the illuminated field diaphragm157and the optic unit158are adjusted in the illuminating system150of the surgical microscope100by means of the adjusting unit178via a motorized actuating element and, at the same time, the intensity of the illuminating light156is adapted with this light being made available by the xenon lamp153at the illuminated field diaphragm157.

The coupling of the illuminated area and viewing area in the surgical microscope100requires that the illuminating system must be designed for a very high number of operating cycles because, with each adjustment of the viewing optic in the surgical microscope, the illuminating system is also varied. It is assumed that for a coupling of the viewing optic and the illuminating system in the surgical microscope, the illuminating system is adjusted 220,000 times in a time span of 10 years. In this case, a powerful drive is needed in the adjusting mechanism for the illuminated field diaphragm in the illuminating system because frequent movements of corresponding lamellae in the illuminated field diaphragm in order to reduce the opening of the lamellae or to increase the opening cause wear of the movable units of the diaphragm because of friction. Over a time span of 10 years, this can mean that the adjusting force, which is needed for a movement of the illuminated field diaphragm, increases by more than 20 times approximately 0.05 N to greater than 1.00 N. For these high adjusting forces, a return spring is, as a rule, not designed with this return spring being conventional in illuminated field diaphragms. In order to nonetheless ensure a reliable adjustment of the diaphragm over a correspondingly long time span, it must be ensured that, for the adjustment of the illuminated field diaphragm in each operating situation, an adequately large adjusting force is introduced into the diaphragm.

The coupling of the illuminated area and the viewing area as in the surgical microscope100therefore requires a correspondingly robust structure of the illuminating system150provided therein.

FIGS. 7,8and9show a component assembly700in the surgical microscope100which complies with these requirements.FIGS. 7,8and9show different perspectives of the component assembly700.

The component assembly700includes the adjustable microscope main objective790defining an optical axis795and includes a receptacle701for a light conductor (not shown). The illuminated field diaphragm702of the surgical microscope is mounted behind this receptacle. The illuminated field diaphragm702is configured to be adjustable and can be opened and closed by moving an adjusting element703in correspondence to the double arrow704.

The component assembly700contains an illuminating optic705having an illuminating lens706and an illuminating mirror707. The illuminating lens706is held in a holder708which is movably supported on guide rails (709,710). Depending upon the position of the illuminating lens706along the guide rails (709,710), the illuminating light, which exits from the illuminated field diaphragm702, is guided more or less intensely bundled to the illuminating mirror707which directs the light to the object region of the surgical microscope.

The component assembly includes a drive shaft720as a common drive element for the illuminated field diaphragm702and the holder708of the illuminating lens706. A positioning motor721having a gear assembly722is assigned to the drive shaft720. The positioning motor721acts on the drive shaft720via the gear assembly722and moves the drive shaft about a rotational axis723. Furthermore, a rotary knob725is assigned to the drive shaft in order to ensure a manual movement of the drive shaft720.

The component assembly700includes a first drive lever730. This first drive lever730is rigidly connected to the drive shaft720. The lever acts with a roller bearing731on a guide sled732which is connected to the holder708for the illuminating lens706. By rotating the drive shaft720about the rotational axis723in the rotational direction indicated by arrow733, the guide sled732is moved in the direction of arrow734.

A second drive lever740is provided in the component assembly700for adjusting the illuminated field diaphragm702. This second lever740is rotatably supported about the rotational axis723of the drive shaft720. Two guide rails (741,742) are formed on the second drive lever which act upon an actuating lug743on the positioning element of the illuminated field diaphragm702.

By rotating the drive shaft720, the second drive lever740is moved only in a specific rotational range of the drive shaft720in correspondence to the double arrow750. This rotational movement is transferred via the guide rails (741,742) to the actuating lug743of the illuminated field diaphragm702for a displacement movement which corresponds to the double arrow704.

An entraining element760arranged spatially fixed to the drive shaft720is provided for coupling drive shaft720and the second drive lever740. This entraining element760controls a latching device751. This latching device751acts via a spring element (not shown) on the entraining element760and is moved in correspondence to a control curve752formed on the entraining element. In a specific rotational position of the first drive lever730, this drive lever works on the second drive lever740with an entraining nose753and the latch device751. A rotational movement of the drive shaft720is then also transmitted to the second drive lever740. In this way, an adjusting mechanism for the illuminated field diaphragm702is provided which can introduce a drive force into the adjusting element703of the illuminated field diaphragm702for opening the diaphragm as well as for closing the diaphragm.

In the surgical microscope100shown inFIG. 1, a coupling of the illuminated area, which is generated by the illuminating system150, to the viewing area of the viewing optic (101,104,115) is realized. It is advantageous, to optionally provide in the surgical microscope also the possibility of controlling the illuminated field independently of the adjustment of the viewing optic. For this purpose; a switchable coupling mechanism of illuminated area and viewing area is integrated into the surgical microscope.