EP1631186A1

EP1631186A1 - Method and device for determining a movement of a human eye

Info

Publication number: EP1631186A1
Application number: EP04739667A
Authority: EP
Inventors: Dirk MÜHLHOFF; Mario Gerlach
Original assignee: Carl Zeiss Meditec AG
Current assignee: Carl Zeiss Meditec AG
Priority date: 2003-06-12
Filing date: 2004-06-07
Publication date: 2006-03-08
Also published as: US7784944B2; DE10326527A1; DE10326527B4; WO2004110261A1; DE10326527B8; US20060279698A1

Abstract

Disclosed is a device for determining a movement of a human eye (1) located in front of said device. The inventive device comprises an illumination apparatus by means of which optical radiation can be produced and can be emitted as an illumination beam (13, 13', 13") in order to illuminate at least one area on the cornea (7) of the eye (1), a distance determining apparatus (17) by means of which the illumination beam (13, 13', 13") reflected by the cornea (7) as a detection beam (14, 14', 14") can be received in a time-resolved manner and a distance signal corresponding to a distance of the cornea (7) from a reference plane (12, 12', 12") that is defined relative to the distance determining apparatus (17) can be generated by using the received optical radiation of the detection beam (14, 14', 14"), and an evaluation unit (11) by means of which a position signal or movement signal corresponding to a position or movement of the eye (1) can be generated by using the distance signal.

Description

Method and device for determining the movement of a human eye

The present invention relates to a method and a device for determining a movement of a human eye, the cornea of the eye being illuminated with optical radiation.

Various methods have been developed in ophthalmology to treat a patient's ametropia by changing the cornea of the patient's corresponding eye. Laser curvature can be used to specifically change the curvature of the cornea in a human eye. Examples of this are the known methods denoted by the acronyms LASIK, PRK and LASEK. In these methods, a treatment laser beam is scanned over the pupil surface to be corrected, which causes a change in the cornea. This change in the corneal geometry must take place at defined positions relative to the visual axis of the eye in order to be able to improve or eliminate the ametropia.

During the treatment period, however, the eye carries out a large number of voluntary and, above all, involuntary movements, for example saccades, microsaccades, torsional movements, etc., which are accompanied by a corresponding movement of the visual axis. However, such movements prevent a precise alignment of the treatment laser beam with respect to the visual axis during the treatment.

Various methods are used to reduce or prevent such deviations.

A first class of procedures attempts to completely suppress eye movement. For this purpose, so-called applanation objects, for example plates or curved contact glasses, connected to a treatment device, are used, which are held by mechanical pressure and / or vacuum on the front section of the eye. The mechanical coupling of the eye to the treatment device suppresses eye movement relative to the treatment device. The treatment laser beam can therefore be precisely aligned relative to the visual axis of the eye. However, the use of such applanation objects is often undesirable.

In a second class of methods, the effects of eye movement on the alignment of the treatment laser beam relative to the visual axis are compensated for by targeted and timely tracking of the treatment laser beam in accordance with the eye movement. For this it is necessary to record the movement of the eye.

The motion detection is mostly based on a video capture of the anterior segment of the eye and a subsequent digital image processing and evaluation. Typical features of the eye, for example the pupil edge or the transition between iris and sclera, can be recorded and their movement and position can be determined.

In further methods for motion detection, the pupil edge, the scleral border or artificially applied marks are scanned, as in EP 125 28 72.

A compensation signal is then generated from the determined position and movement data and is used to position the treatment laser beam.

However, the video-based methods have the disadvantage that the movement and position signals are generated with insufficient speed or frequency. Rapid eye movements cannot be tracked by the method, so that there are considerable deviations between the target position of the treatment laser beam and the actual position of the treatment laser beam with respect to the visual axis in the case of high accuracy requirements for the alignment of the treatment laser beam with respect to the visual axis of the eye of the eye can come.

In addition, the movement of the eye is only detected in two spatial dimensions that are essentially perpendicular to the visual axis of the eye.

The present invention is therefore based on the object of providing a method and a device for determining an eye movement which enables rapid determination of the eye movement with high accuracy.

The object is achieved by a method for determining a movement of an eye, in which optical radiation is radiated onto the cornea of the eye as an illuminating beam will be formed using the optical radiation reflected by the cornea as a detection beam, time-resolved distance signals corresponding to the distance of the cornea from a predetermined reference plane, and from the distance signals position or movement signals corresponding to a position or movement of the eye are formed.

The object is further achieved by a device for determining a movement of an eye with an illuminating device that generates optical radiation during operation and emits as an illuminating beam for illuminating at least one area on the cornea of the eye, with a distance determining device that resolves the time from the cornea as Detected radiation bundle received back and receives a distance signal using the received optical radiation of the detection beam corresponding to a distance of the cornea from a reference plane, which is defined relative to the distance determining device, and with an evaluation device that uses the distance signal corresponding to a position or movement signal a position or movement of the eye.

The method according to the invention can be carried out with the device according to the invention.

The invention takes advantage of the fact that the cornea of the eye has a typical shape, approximately that of a section of an ellipsoid or toroid surface, in particular a spherical cap, and thus from the measurement of the distance of the cornea from one in relation to the invention Device at least during operation, the reference plane essentially orthogonal to the detection beam using the shape of the cornea whose position or change in position can be determined.

According to the invention, the distance is measured without contact with optical radiation, which in the context of the invention can also include infrared radiation and / or visible light. To generate the optical radiation, the lighting device is provided in the device according to the invention, which in particular contains a radiation source for the optical radiation. In addition, further deflecting or beam-shaping elements can be provided in order to form the illuminating beam.

In order to avoid perception of the illumination beam by the patient, infrared radiation is preferably used.

The bundle of illuminating rays is radiated onto the cornea of the eye, where an illuminated spot or light spot is created. The cornea then becomes the optical one Radiation from the illumination beam is reflected back as a detection beam, preferably reflected. Depending on the type of optical interaction (reflection, backscattering), the illuminating beam can be reflected on different layers of the cornea, for example the epithelium, the Bowman membrane, the desertion membrane and / or the endothelium.

Using the optical radiation reflected by the cornea as a detection beam, time-resolved distance signals are then formed corresponding to the distance of the cornea from the specified reference plane. For this purpose, the device according to the invention has the distance determination device, which receives at least part of the detection beam and forms a distance signal from its properties alone or in conjunction with those of the illuminating beam. The reference plane has a fixed position relative to the distance determining device and can be given in particular by the position of the distance determining device and / or the lighting device. The device preferably also has a head holder, in which the head can be held in a predetermined position with the eye, so that movements of the eye can be largely excluded by moving the head.

The distance determination device can in particular have a photodetector for receiving at least a part of the detection beam which is sensitive to at least one wavelength of the optical radiation used. The signals of the photodetector can be converted into the distance signals in an analog and / or digital manner by a detection circuit.

The temporal resolution, which is determined, inter alia, by the detection frequency of the photodetector and the processing speed of the detection circuit, is preferably so great that rapid changes in the position or the state of movement of the eye are also detected precisely.

Finally, position or movement signals corresponding to a position or movement of the eye are formed and output from the distance signals. For this purpose, the device according to the invention has an evaluation device which is connected to the distance determination device for receiving the distance signals via a signal connection and by means of which a position or movement signal corresponding to a position or movement of the eye can be formed using the distance signal. While the position signal relates to the current position of the eye, a movement signal is understood to be a signal that indicates a change in position between at least two different acquisition times or, after division by a corresponding time interval, a corresponding speed.

The formation of a position or movement signal takes place on the basis of an assumption about the shape of the cornea in the area of the illumination beam or a corresponding model. In particular, as mentioned above, when measuring in the area of the apex of the cornea, it can be assumed that the cornea in this area approximately has the shape of an area of an ellipsoid surface, in particular a spherical cap, the radius of which can either be generally accepted as an average or determined individually , In more precise models, different radii can be used for different layers. In this case it is important to know at which of the layers the illuminating beam is most strongly reflected.

From the distance of the illuminated spot from the reference plane and the known direction of the illumination as well as the detection beam, the position or movement of the spherical cap or cornea and thus of the eye can then be determined on the basis of the model of the cornea.

The position or movement signal can be determined in an analog or digital manner. The operations to be carried out here are simple in comparison to the video-based methods described in the introduction and can therefore be carried out particularly quickly digitally, preferably analogously.

The position or movement signal can then be output digitally or analog.

The method according to the invention and the device according to the invention therefore allow particularly simple and rapid determination of the eye movement.

The possible spatial resolving power of the method according to the invention or the device according to the invention for the position of the eye depends, inter alia, on the ratio of the diameter of the area or spot illuminated by the illumination beam on the cornea to a radius of curvature of the cornea. It is preferred in the method according to the invention that the illuminating beam on the cornea has a diameter between 2 μm and 20 μm. In the device according to the invention it is preferred that the illumination device is designed such that during operation a diameter of the illumination beam on the cornea of the eye arranged in front of the device is between 2 μm and 20 μm. In this diameter range, a better resolution is achieved than in the case of illuminating light beams with smaller diameters, in which, depending on the one used Wavelength of the optical radiation diffraction effects can worsen the spatial resolution. A diameter of 10 μm is particularly preferably used. To adjust the beam diameter on the cornea, the illuminating device can preferably have a beam-shaping optic. The beam-shaping optics can in particular comprise at least one aperture and one or more lenses.

The distance can be determined using various optical distance determination methods.

A first alternative essentially uses an interferometric method. It is preferred in the method according to the invention that a reference beam is coupled out of the illuminating beam, the reference beam is superimposed with the detection beam, and the distance signal is formed by detecting interference of the superimposed beams. In the device according to the invention, it is preferred for the distance determination device to have an interferometer section, with which an interferometer is produced during operation together with the cornea. The cornea acts as an element reflecting optical radiation. A reference beam is thus coupled out of the illuminating beam, which is superimposed with the illuminating beam reflected by the cornea as a detection beam. While the reference beam travels a known, time-constant or variable optical path, the optical path length that the illuminating beam travels as a detection beam after coupling out and after reflection on the cornea depends on the position of the cornea. Interferences that can be detected by means of a detection device of the distance determination device occur when the resulting optical path difference is smaller than the time coherence length of the optical radiation of the illumination beam. Such a method enables a simple optical structure.

The method according to the invention and the device according to the invention can particularly preferably be designed similarly to an optical coherence tomograph. In the method according to the invention, it is preferred that the optical path length for the reference beam before the overlay, the illumination beam according to the department of the reference beam and / or the detection beam before the overlay is varied with a predetermined time program so that the intensity of the superimposed reference and detection beams is time-resolved is detected in accordance with the time program, and that a distance signal is formed from the detected intensity. In the device according to the invention, it is preferred for the lighting device to be designed to emit optical radiation with a predetermined temporal coherence length the interferometer section is at least one beam splitter arranged in the path of the illuminating beam for forming a reference beam from the optical radiation of the lighting device, at least one optical functional element for superimposing the reference beam on the detection beam and a device for varying the optical path length of the path of the reference beam between the beam splitter and the optical functional element or the optical path length of the path of the illuminating beam after the beam splitter and / or between the spot illuminated by the illuminating beam on the cornea and the optical functional element in accordance with a predetermined time program, and the distance determining device has a detection device by means of which the intensity of the superimposed reference and detection beams according to the time program detectable and at a distance signal can be implemented. In particular, the distance between the cornea can be determined by determining at which optical path length difference an interference occurs. The occurrence of interference presupposes that the amount of the path length difference is smaller than the time coherence length. In this development, a simple device can be used, which can scan a large distance range with high accuracy. The optical functional element can in particular also be part of the device for varying the optical path length.

In order to achieve a particularly good resolution in the distance determination, it is preferred that the temporal coherence length of the optical radiation used is between 1 μm and 10 μm.

The optical path length can in principle be varied as desired. For example, it is possible to change the refractive index along at least part of the path. In the method, however, it is preferred that a reflector is moved back and forth linearly to vary the optical path length. In the device according to the invention, it is preferred that the device for varying the optical path length comprises a linearly reciprocable reflector. In this way, the optical path length can be changed particularly easily, even over larger areas, and at the same time the position of the reflector can be easily determined. For the movement of the reflector, a corresponding drive device can be provided, in particular, by means of which position signals can be emitted which reflect the position of the reflector and thus the length of the optical path of the reference beam.

In another variant of the method, it is preferred that, in order to vary the optical path length, a plurality of reflecting surface sections are rotated about an axis which have different distances from the axis in the radial direction. In the device according to the invention, it is preferred that the device for varying the optical path length comprises a reflector arrangement which can be rotated or pivoted about an axis by a drive and which has a plurality of reflecting sections each having a different distance from the axis. The rotation is particularly preferably carried out at a constant rotational frequency either continuously or in steps. The axis of rotation can in particular be oriented orthogonally to the direction of the reference beam. With such an arrangement, the optical path length can be changed during a revolution of the mirror at a constant speed. In addition, the mechanical requirements for the mounting of the reflector arrangement are not very high, since imbalances can be avoided by appropriate mass distribution in the reflector arrangement. If an arrangement with several flat reflector surfaces is used, the distances between adjacent reflector surfaces preferably differ by one to two temporal coherence lengths. This results in a particularly good distance resolution.

In a second alternative for determining the distance, it is preferred in the method according to the invention that the illuminating beam is focused for at least one wavelength in a predetermined range for possible positions of the cornea, that the detection beam is focused in the area of a fine pinhole by means of detection optics, whose opening for the wavelength lies in an object plane assigned to the wavelength in the predetermined range for possible positions of the cornea in relation to the conjugate plane in relation to the detection optics, and that the distance signal is formed by detection of the optical radiation passing through the fine pinhole. In the device according to the invention, it is preferred that the device has illumination optics for focussing the illumination beam for at least one wavelength in a predetermined range for possible positions of the cornea, and that the distance determining device includes detection optics in a detection beam path, a fine pinhole arranged downstream thereof and one after the pinhole arranged detection device for detecting the optical radiation behind the fine pinhole, wherein a plane of an opening of the fine pinhole with respect to the detection optics for the wavelength to a wavelength associated object plane in the area for possible positions of the cornea in relation to the Detection optics is conjugated. A fine pinhole is understood to mean a pinhole with a very small opening, which is often also referred to as a "pinhole" or "pinhole screen". By means of the illuminating device, the optical radiation is focused for at least one wavelength in the predetermined range for possible positions of the cornea, the optical radiation illuminating the cornea. The range for possible positions of the cornea is predefined and defined in relation to the distance determination device. In particular, it is determined by the imaging geometry of the illumination optics. When using the invention, the patient's eye is to be brought into this area by appropriate positioning of the patient. A significant proportion of the optical reflected by the cornea Radiation will only pass through the pinhole and reach the detection device if the real or virtual focus of the illumination beam reflected by the cornea is around in the object plane assigned by the device to the wavelength or in an area with a width corresponding to the depth of field of the detection optics this object plane lies. In particular, the focus can be on the surface of the cornea. This focus is then imaged in the opening of the pinhole and can pass through it. The distance from the cornea to the reference plane can be determined from the position of the object plane to the reference plane when optical radiation passes through the pinhole. In this respect, the known method of confocal detection of reflected light on surfaces is used. This development allows the use of lighting devices regardless of the coherence properties of the emitted optical radiation that can be achieved thereby.

In one embodiment of the method according to the invention, it is then preferred that the area of possible distances from the cornea to the reference plane be scanned by changing the distance between the object plane and the fine pinhole. On the one hand, a predetermined distance range can be scanned by moving the object plane assigned to the wavelength. This can be done in particular by moving the lighting and / or detection optics and / or by changing the focal length of the lighting and / or detection optics. A change in the focal lengths can be made possible, for example, by using a motorized zoom lens. On the other hand, it is possible to move the pinhole in the direction of the detection beam path to scan the distance range. Finally, a combination of these methods is also possible. In the device according to the invention it is therefore preferred that the position of the illumination and / or detection optics and / or the pinhole and / or the focal length of the illumination and / or detection optics can be changed within a predetermined range by means of a drive. A significant portion of the detection beam will pass through the pinhole if the real or virtual focus of the illumination beam reflected by the cornea is in the object plane conjugated to the plane of the opening of the pinhole. The distance signal can then be formed by correlating the detection of a corresponding intensity with the corresponding position or focal length of the corresponding optical component. This development allows the use of simple optical components, in particular if the optical radiation from the illuminating beam is very narrow-band.

In order to enable a particularly rapid determination of the distance, it is particularly preferred in the method according to the invention that optical radiation of different wavelengths is used, and the illumination and / or the detection beam by at least one optical one which is subject to strong chromatic longitudinal aberration Functional element is performed. “Strong” is understood to mean that the longitudinal aberration is greater than the Rayleigh length. For example, this can be a highly dispersive element, which is why, to simplify matters, the term “strongly dispersive element” is used below.

A distance signal can be formed by determining the wavelength of the optical radiation behind the pinhole. In the device according to the invention, it is preferred that optical radiation of different wavelengths can be emitted by means of the lighting device, and that a beam-shaping lens of the lighting device, the lighting lens and / or the detection lens has strong longitudinal aberration. In this way, for different wavelengths, mutually spaced object planes conjugated to the pinhole are simultaneously formed, so that a corresponding distance range can be scanned at the same time.

If the beam-shaping optics and / or the illumination optics are highly dispersive, the portions of the illumination beam bundle that may be reflected on the cornea with different wavelengths are focused on planes in the region of the cornea that are spaced apart and assigned to the respective wavelengths. Then only those parts of the cornea that are reflected back with a significant intensity will pass through the pinhole, the focus of which lies in the object plane corresponding to the wavelength.

If the detection optics have strong longitudinal aberration, portions of the detection beam are focused at different distances from the pinhole according to their wavelength, so that only those parts of the illumination beam reflected by the cornea pass through the pinhole that are imaged in the pinhole. These are parts whose focus lies after or upon reflection on the cornea in the assigned object plane. The wavelength then corresponds to a certain distance between the cornea and the device. In this way the use of moving components such as e.g. Rotating or oscillating mirrors can be avoided.

In order to achieve a good resolution with at the same time low demands on the intensity radiated onto the eye, it is preferred that the illuminating beam bundle in the object plane assigned to the wavelength has essentially the same diameter as the pinhole. The beam diameter is preferably in the range between 2 μm and 20 μm. A beam diameter of approximately 10 μm is particularly preferred.

Optical radiation with different wavelengths can be provided in different ways. This is the case with one embodiment of the method according to the invention preferred that alternating illuminating beams of optical radiation in at least two different spectral ranges are used in a predetermined time sequence. In the device according to the invention, it is preferred for the lighting device to be designed to emit optical radiation in at least two different spectral ranges in a predetermined time sequence. The wavelengths can preferably be changed at a frequency which is so high that rapid eye movement can still be tracked, for example at frequencies above 100 Hz, preferably above 10 kHz. For this purpose, the lighting device can have at least two radiation sources for emitting optical radiation of different wavelengths and / or different colors. For example, appropriately controlled light-emitting diodes or lasers can be used. As a result, the optical radiation power delivered to the eye is kept very low. In addition, radiation sources of low average power can be used.

In another embodiment of the method according to the invention, it is preferred that the illuminating beam bundle comprises optical radiation in a spectral range. In the device according to the invention, it is preferred for the lighting device to comprise a radiation source for emitting optical radiation in a predetermined spectral range. For this purpose, the spectral range is preferably selected in relation to the position and width as a function of the chromatic longitudinal aberration of the dispersive functional element or the illumination and / or detection optics. The width is preferably in the range of about Δ λ>. The spectral range can in particular be between 400 nm and 700 nm. A continuum of focal positions can thus be obtained, which allows an exact determination of the distance. Illumination devices for emitting optical radiation in a spectral range are very easy to manufacture, since they can have, for example, an incandescent lamp or a white light LED as radiation sources. The latter is characterized, among other things, by a very low heat development and a low emission of heat radiation occurring outside the desired spectral range. Furthermore, a superluminescent diode can be used, the emission spectrum of which has a spectral band in the red range between 635 nm and 670 nm with a width between 20 nm and 50 nm.

The distance from the portion of the detection radiation that passes through the pinhole can be used to draw conclusions about the distance or to form a distance signal. In one embodiment of the method according to the invention, it is preferred that the intensity of the detection beam behind the fine pinhole is detected spectrally and temporally resolved to form the distance signal. In the device according to the invention, it is preferred that the detection device for spectrally and temporally resolved detection the optical radiation is formed behind the fine pinhole. For this purpose, the detection device can in particular have a spectrometer. However, a color-sensitive photodetector is particularly preferably used. This embodiment is characterized by a particularly simple and robust structure. The color of the optical radiation received can then be used to easily conclude the distance between the cornea and the device. This type of detection is suitable for the two lighting alternatives described above, the frequency with which the optical radiation is detected in the case of the first alternative being so small that all the colors used are emitted equally frequently during a detection cycle. Since all wavelengths in the sensitivity range of the photodetector can be detected at the same time, eye movement can be followed very quickly, particularly in connection with the second illumination method described above.

In another embodiment of the method according to the invention, in which optical radiation with wavelengths changing over time is used for illumination, it is preferred that the timing of the change in the spectral ranges of the

Illumination beam the intensity of the detection beam behind the fine

Pinhole is detected with formation of the distance signal. In the case of the invention

For this purpose, it is preferred that the detection device is designed for the temporally resolved detection of the optical radiation behind the fine pinhole. The

In this embodiment, the detection device can have a simple photodetector, which need only be sensitive to the wavelengths used. However, spectral resolution is not necessary. To be in sync with the change of

In order to be able to detect wavelengths of the optical radiation that pass through the pinhole, in particular a corresponding detection circuit can detect the signals of the

Evaluates photodetector, be coupled to a circuit of the lighting device that controls the change of the spectral ranges of the optical radiation.

In order to be able to use a compact device for determining the eye movement, it is preferred in the method according to the invention that the illuminating beam is radiated onto the cornea at an angle of incidence of less than 10 °, preferably less than 5 °. The angle of incidence is understood to mean the angle between the illuminating beam and a normal to a tangential surface on the area of the cornea illuminated by the illuminating beam. A particularly favorable solution is obtained if the illuminating radiation has a high numerical aperture, so that the angle of incidence is significantly smaller than the convergence angle of the illuminating radiation resulting from the numerical aperture. Particularly preferably, the beam direction is essentially orthogonal to at least in a central position of the eye the cornea aligned. Due to the simple beam path, this arrangement also allows a particularly simple determination of the distance.

This arrangement uses the illumination radiation used particularly efficiently, since the radiation reflected by the cornea can be absorbed by the detection optics to the maximum.

In the device according to the invention, it is preferred for the illumination optics and the detection optics to have a common objective. In this case, a semitransparent reflector can be arranged in the illumination beam path, which directs the detection beam out of the illumination beam path. Alternatively, a semitransparent reflector can be arranged in the detection beam path, which couples the illuminating beam into the detection beam path - counter to the direction of the detection beam. In this way, the device only needs to have a corresponding lens, which considerably simplifies the construction. In addition, complex adjustments that are otherwise necessary can be dispensed with.

It is particularly preferred that the common lens has strong longitudinal aberration. In this way, a chromatic aberration is brought about both in the focusing of the illuminating beam and in that of the detection beam, which leads to a particularly large overall aberration. This in turn allows a better resolution when determining the distance.

In principle, the method according to the invention can be used to determine the movement of the eye in only one direction. However, it is preferred that at least two different areas on the cornea are illuminated with at least two different illuminating beam bundles, that using the optical radiation which is reflected by the cornea in each case as a detection beam bundle, temporally resolved distance signals are formed with respect to the spacings of the cornea from respectively corresponding predetermined reference planes and that the distance signals position or movement signals with respect to a position or movement of the eye in at least two spatial directions are formed. In the device according to the invention, it is preferred that one or more illuminating devices for forming two bundles of illuminating rays of optical radiation for illuminating two different areas on the cornea of the eye are designed such that time-resolved ones are discarded from the two areas on the cornea by means of one or more distance determining devices Detection beam of optical radiation can be received and distance signals using the received optical radiation of the detection beam according to distances of the cornea from two reference planes can be formed, each of which is defined for one of the detection beams relative to the distance determination device, and that the evaluation device is designed to form position or movement signals corresponding to a position or movement of the eye in two spatial directions using the distance signals. Since the cornea is approximately rotationally symmetrical to the optical axis of the eye, the movement in only one spatial direction can also be determined more precisely in this way, since a movement in two spatial directions could lead to errors when evaluated assuming a movement in only one spatial direction. The various previously described embodiments of the method according to the invention or the device according to the invention can be used for each of the illuminating beam bundles and the associated detection beam bundles at least analogously. If only one lighting device is used, it can either comprise two separate radiation sources or also only one radiation source and a beam splitter, by means of which two separate lighting beams can be formed. The distance can be determined using the preferred embodiments and developments of the method according to the invention described above. Accordingly, the lighting device or lighting devices and the

Distance determination device or distance determination devices may be designed in accordance with the previously described preferred embodiments and developments of the device according to the invention. A different method can be used for each illuminating beam.

In order to obtain complete information about the movement of the eye, it is preferred that at least three different areas of the cornea, which form corners of a triangle, are illuminated with at least three different bundles of illuminating rays using the optical radiation which is reflected back by the cornea as a detection beam in each case resolved distance signals are formed with respect to the distances of the cornea from respectively corresponding predetermined reference planes, and that position or movement signals in relation to a position or movement of the eye in three spatial directions are formed from the distance signals. In the device according to the invention, it is preferred that one or more illuminating devices for forming three illuminating light bundles of optical radiation for illuminating three different areas on the cornea of the eye, which form the corners of a triangle, are designed such that one or more distance determining devices time-resolved from the Detection beams of optical radiation reflected by three areas on the cornea can be received and distance signals can be formed using the received optical radiation of the detection beams corresponding to distances of the cornea from three reference planes, which are each defined for one of the detection beams relative to the distance determination device, and that the evaluation device for formation by location or Motion signals corresponding to a position or movement of the eye in three spatial directions is formed using the distance signals. In this way, the position of the cornea can be determined quickly and easily in three dimensions. If only one lighting device is used, it can either comprise two separate radiation sources or also only one radiation source and a beam splitter, by means of which three separate lighting beams can be formed. The distance can be determined using the preferred embodiments and developments of the method according to the invention described above. Accordingly, the lighting device or lighting devices and the distance determination device or distance determination devices can be designed in accordance with the previously described preferred embodiments and developments of the device according to the invention. A different method can be used for each illuminating beam.

The invention is explained in more detail below using the drawings as an example. Show it:

1 shows a schematic perspective illustration of a patient during a laser surgical treatment with a laser surgical instrument which comprises a movement determination device according to a first preferred embodiment of the invention,

2 shows a schematic representation of the laser surgical instrument in FIG. 1 with one eye,

3 shows a schematic representation of the eye in FIG. 2 and three illuminating and detection beams of the movement determination device in FIG. 2,

4 shows a schematic representation of an eye and part of the movement determination device in FIG. 2 with a detection unit for a direction of movement of the eye and an evaluation device,

5 shows a schematic illustration of a signal curve of a photodetector of the detection unit in FIG. 4 during operation,

6 shows a schematic illustration of an eye and part of a movement determination device according to a third embodiment,

7 shows a schematic representation of an eye and part of a movement determination device according to a fourth embodiment, 8 is a diagram illustrating the chromatic longitudinal aberration of a focusing optics in the movement determination device in FIG. 7,

9 shows a schematic illustration of focus positions near a pinhole of the movement determination device in FIG. 7,

10 shows a schematic illustration of an eye and a part of a movement determination device according to a fifth embodiment,

FIG. 11 shows a schematic illustration of focus positions of illuminating light beams of the movement determination device in FIG. 8 near the cornea of the eye and

12 shows a schematic illustration of an eye and a part of a movement determination device according to a sixth embodiment.

1, an eye 1 of a patient is treated by means of a treatment laser beam 3 emitted by a laser-surgical instrument 2. For this purpose, the patient's head is held in a head holder 4, which assumes an initially adjustable, but fixed position during operation relative to the laser-surgical instrument 2 and can in particular be connected to it.

The laser surgical instrument 2 is shown in more detail in a schematic representation in FIG. 2. On the one hand, it has the actual treatment unit 5 and, on the other hand, a movement determination device 6 for determining a movement of the eye 1 during the treatment and output of corresponding movement or position signals. Furthermore, a fixation light source, not shown in the figures, can be provided, onto which the patient can fix his gaze during the treatment and thus suppress arbitrary movements of the eye.

The treatment unit 5 has a treatment laser, not shown in the figures, with treatment laser optics for focusing and moving the treatment laser beam 3 onto the cornea 7 of the eye 1. The treatment optics for moving the treatment laser beam 3 can be adjusted by means of a control device 8, which is only shown roughly schematically.

The control device 8 moves the treatment laser beam 3 on the one hand as a function of a path predetermined by the treatment when the cornea 7 is stationary and on the other hand as a function of an involuntary movement of the eye 1 which is detected by the movement determination device 6. The control device 8 compensates a change in the relative position between the treatment laser beam 3 and the eye 1 or the cornea 7, which is caused by voluntary and / or involuntary eye movements, for example saccades, microsaccades, torsional movements, etc., by a corresponding movement of the treatment laser beam 3 connected to outputs of the movement determination device 6, via which it detects the movement or Position signals of the movement determination device 6 receives.

The movement determination device 6 has three identically designed detection units 9, 9 ′, 9 ″, which are connected to an evaluation device 11 via signal connections 10.

The detection units 9, 9 ″, 9 ″ each detect a distance between the cornea 7 and the reference planes 12, 12 ′ and 12 ″, which are spatially permanently assigned to the detection units. For this purpose, each of the detection units uses optical radiation as an illuminating beam 13, 13 ′ and 13, respectively "is radiated onto the cornea 7 and the optical radiation reflected by the cornea 7 is received as a detection beam 14, 14 'and 14" which is orthogonal to the respective reference plane. The position of the reference planes 12, 12' and 12 "is up to the orthogonal one Orientation to the respective detection beam is arbitrary, but fixed relative to the respective detection device. Using the detection beams 14, 14 'and 14 ", a distance signal is then formed in a time-resolved manner, which signals the distance between the cornea 7 and the respective reference plane.

The detection units 9, 9 'and 9 "can be aligned with one another (cf. FIG. 3) in such a way that the illuminating beams 13, 13' and 13" illuminate spots 15, 15 ', 15 "on the cornea 7, which approximate to the Corners of a triangle or spherical triangle lie here, these spots preferably lying on the edge of the cornea or in areas in which the topography deviates the most from a spherical shape. The illuminating beam bundles 13, 13 'and 13 "fall onto the cornea at an angle of incidence 7, which is less than about 10 ° to a normal to the cornea 7.

The evaluation device 11 receives the distance signals from the three detection units 9, 9 ′, 9 ″ and uses them to determine movement or position signals which are output to the treatment unit 5.

To form the movement or position signals, it is assumed that the cornea 7 has the shape of a spherical cap with a known radius in the section that can be reached by the illuminating light beams. More accurate measurements are possible if the shape of the Cornea was measured with a topography device and this data is available to the evaluation unit 11.

Depending on the required accuracy, a mean corneal curvature of the human eye can be assumed or the corneal curvature can be determined individually for a patient. For this purpose, either a separate determination can be made before the start of the treatment or the corneal curvature can be determined in the course of the movement determination by analyzing the distance data if a purely random movement of the eye 1 can be assumed with the same probability in all directions.

The structure and function of the detection units 9, 9 'and 9 "will now be explained in more detail using the example of the detection unit 9.

An illumination unit 16 emits optical radiation as an illumination beam 13 onto a distance-determining device 17, which comprises a section 18 of an interferometer, which together with the cornea 7 forms a Michelson interferometer, and a detection device, which has a photodetector 19 with a downstream detection circuit 20 (cf. Fig. 4).

The lighting unit 16 has a laser for generating an illuminating beam 13 with optical radiation of a predetermined coherence length of approximately 5 μm in a narrow wavelength range around e.g. 780 nm and a beam shaping device arranged downstream of the laser in the beam path and not shown in the figures, with which the illuminating beam 13 can be shaped into an essentially parallel beam.

The lighting units of the three detection units 9, 9 'and 9 "form an illumination device in the sense of the invention.

The interferometer section 18 has a beam splitter 21 which is arranged in the beam path of the illuminating beam 13 at an angle of 45 °. Part of the illuminating beam 13 is deflected as a reference beam 22 into a reference arm 23 of the interferometer section 18, while the other part passes the beam splitter 21 and is coupled into a measuring arm 24.

The reference arm 23 has a reflector 25 which is oriented orthogonally to the direction of the reference beam 22 and which, by means of a reflector drive 26 only shown schematically, in the direction of the reference beam 22 between predetermined positions with a predetermined time program can be moved back and forth. The reflector drive 26 is connected to the detection circuit 20 via a connecting line, via which it transmits position signals with respect to the position of the reflector 25 to the detection circuit 20. The optical path length for the reference beam 22 in the reference arm 23 from the beam splitter 21 via the reflector 25 and back to the beam splitter 21 can therefore be varied in time in accordance with the time program.

In the measuring arm 24, in the beam path of the illuminating beam 13, the beam splitter 21 is followed by an illuminating optic 27, shown only roughly schematically in FIG. 4, which focuses the illuminating beam 13 in the area of the cornea 7 of the eye 1. The illuminating optics 27 are designed such that the focus in the direction of the illuminating beam 13 has an extent that corresponds approximately to the expected changes in distance between the cornea 7 and the reference plane 12. The illuminating beam 13 creates an illuminated spot 15 with a diameter of approximately 10 μm on the cornea 7 (see FIG. 3).

The optical radiation of the illuminating beam 13, which is reflected back by the cornea 7 as the detection beam 14, is reflected back by the illuminating optics 27, which thus simultaneously function as the detection optics, onto the beam splitter 21, which deflects a portion of the detection beam 14 onto the photodetector 19.

The portion of the detection beam 14 deflected by the beam splitter 21 is therefore superimposed on the reference beam 22 passing through the beam splitter 21.

Depending on the optical path length of the reference arm 23 and the measuring arm 24, interference can occur between these beams, which can be detected with the photodetector 19. FIG. 5 shows a typical signal curve as a function of the path L of the reflector 25. Initially, no interference occurs since the difference in the optical path lengths is greater than the temporal coherence length of the illuminating beam 13. If the amount of the difference in the optical path lengths falls below the coherence length, it occurs but for interference. Since there are several jumps in the index of refraction in the cornea 7 of the eye, at each of which a reflection takes place, there are to a certain extent several measuring arms with correspondingly different optical path lengths. Initially, interference occurs at layer L1, which is due to the reflection on the cornea, then further interference at layers L2 and L3 when reflecting on the subsequent jumps in refractive index, e.g. between stroma and Bowmann's membrane.

The photodetector 19 receives the superimposed beams. The detection circuit 20 detects corresponding intensity signals and position signals of the reflector drive 26 with respect to the reflector 25 with a predetermined frequency (eg 400 kHz), which is higher than the frequency with which the reflector 25 is moved back and forth. The detection circuit 20 senses only the occurrence of the first interference and the corresponding position L1, from which the optical path length of the reference arm 23 and thus, apart from the coherence length, the optical path length of the measuring arm 24 can be determined. It then outputs a distance signal corresponding to the position L1, which is a measure of the distance of the cornea 7 from the beam splitter 21 or the reference plane 12. The inaccuracy of the distance is given by the temporal coherence length of the optical radiation.

In order to obtain the shortest possible time coherence length and thus high distance resolution, lasers or superluminescent diodes with a wide emission spectrum are preferably used, since the time coherence length (i.e. the coherence length in the beam direction) decreases with increasing emission bandwidth.

In a further second embodiment, instead of the linearly moved reflector 25, a reflector arrangement which can be rotated about an axis of rotation orthogonal to the reference beam 22 is used. The reflector arrangement has reflector surfaces which are arranged at equal angular distances from one another about the axis of rotation and which have increasing distances from the axis of rotation in the same steps. The optical path length of the reference arm can then be changed by rotating the reflector arrangement, with corresponding angular position signals being output to the detection circuit instead of the position signals.

A movement determination device according to a third embodiment differs from the movement determination device in FIG. 2 by the design of the detection units. Otherwise, it is designed in the same way and connected to the treatment unit 5. Furthermore, lighting units of the detection units also form lighting devices of the movement determination device here. The same reference numerals are therefore used for the same or analog components, and the corresponding explanations also apply here.

The detection unit 28 shown in FIG. 6 does not use an interferometer, but instead uses a structure for determining the distance by means of a confocal image.

An illumination unit 29 generates an illuminating beam 13 for illuminating the cornea 7. In the linear beam path of the illuminating beam 13, a semitransparent mirror 30 and an only schematically shown illuminating lens 31 with an objective are arranged at an angle of 45 ° to the illuminating beam 13, so that Illuminating beam 13 passes through the semi-transparent mirror 30 and is focused by the illumination optics 31 in a predetermined area for possible positions of the cornea 7. The area is determined by the position of the detection unit 28 and the imaging geometry of the illumination optics 31, so that the cornea 7 must be brought into this area by appropriate positioning of the patient.

The optical radiation from the illuminating beam 13 is reflected back by the cornea 7 as a detection beam 14.

Arranged in the beam path of the detection beam 14 are the illumination optics 31, the semitransparent mirror 30 deflecting the detection beam 14, a focusing optics 32 shown only schematically and, downstream from this, a fine pinhole 33 with an opening diameter of approximately 10 μm. The fine pinhole is also called "pinhole". The illumination optics 31 and the focusing optics 32 therefore form detection optics.

Downstream of the pinhole 33 is a photodetector 34, which is connected to a detection circuit 35.

The lighting unit 29 comprises a narrow-band light-emitting diode 36 or a laser as the radiation source and, downstream, a beam-shaping optics 37, only shown schematically, in which the divergence of the optical radiation emitted by the light-emitting diode 36 is reduced by means of two lenses or lens systems and an aperture arranged in between.

The position of the focusing optics 32 along the direction of the detection beam 14 can be adjusted by a drive 38 according to a predetermined time program. Alternatively, the optics 31 can also be adjusted, as a result of which the focal plane of the LED and pinhole 33 remain conjugated to one another, which leads to pronounced peaks and thus better signals. The drive 38 is connected to the detection circuit 35 in order to transmit position signals which represent the position of the focusing optics 32. The range of possible positions is selected such that an object plane 39 in the predetermined range for possible positions of the cornea 7 by changing the position of the focusing optics 32 and thus the position or focal length of the detection optics to a plane leading through an opening of the pinhole 33 in Conjugation is feasible.

The semi-transparent mirror 30, the illumination optics 31, the focusing optics 32, the drive 38, the fine pinhole 33, the photodetector 34 and the detection circuit 35 thus form a distance determination device. The parallel illuminating beam 13 emitted by the illuminating unit 29 is focused by the illuminating optics 31 in the area of the cornea 7. The illuminating beam 13 generates an illuminated spot 15 on the cornea 7 and is at least partially reflected. The resulting detection beam 14 is focused in the area of the pinhole 33 by means of the illumination optics 31, the semi-transparent mirror 30 and the focusing optics 32. A significant portion of the detection beam 14 can therefore only pass through the pinhole 33 if, depending on the position of the cornea 7, the real or virtual focus of the illumination beam 13 reflected on the cornea 7 lies in the object plane 39 conjugated to the pinhole 33. Otherwise, only a small proportion of the detection beam 14 reaches the photodetector 34. If the latter does not exceed a predetermined threshold value, no detection beam 14 is detected by the detection circuit 35.

In order to be able to determine the position of the cornea 7 during movement, the object plane 39 is shifted by adjusting the position of the focusing optics 32 and thus the position and focal length of the detection optics with the predetermined time program.

The detection circuit 35 operates cyclically with a predetermined cycle frequency which is so large that movement of the eye is tracked with a desired temporal and spatial resolution. In each cycle, upon detection of a detection beam 14 on the photodetector 34, it determines the position of the object plane 39 and thus the distance of the cornea 7 from the reference plane 12 on the basis of the position signal of the drive 38 and outputs a corresponding distance signal.

An advantageous embodiment results if the optics used are color-corrected. Then broadband light sources can be used. Alternatively, instead of the position of the object plane 39, the position of the pinhole 33 can be varied with the focusing optics 32 in a fixed position.

A movement determination device according to a fourth embodiment, which enables a better S / N ratio, differs from the movement determination device according to the third embodiment by the detection units 40. Otherwise, it is designed in the same way and connected to the treatment unit 5. The same reference numerals are therefore used for the same or analog components, and the corresponding explanations also apply here. Here, too, lighting units of the detection units are also lighting devices of the movement determination device. This embodiment dispenses with an adjustable position of the focusing optics 32. Instead of the position-adjustable, color-corrected focusing optics 32, a highly dispersive focusing optics 41 is used. Furthermore, an illumination unit 42 is used instead of the illumination unit 29 and a photodetector 43 is used instead of the photodetector 34.

8 shows an example of the dispersion of highly dispersive focusing optics 41 in the form of a diagram in which the wavelength λ is shown as a function of the change dF in the focus position.

In this way, with fixed positions of the illuminating and focusing optics 31 and 41, for each wavelength, a different object plane is conjugated to the opening of the pinhole 33, from which an illuminated spot 15 of the corresponding wavelength can be imaged on the pinhole 33. Conversely, an object is imaged in one plane depending on the wavelength in different conjugate planes in the area of the pinhole 33. This is shown in FIG. 9 for partial light beams 44, 44 'and 44 "of the illuminating beam 13, the foci of which are spaced apart from one another along the direction of the detecting beam 14. Only when the focus of the portion 44 of the illuminating beam 13 reflected by the cornea is in the opening of FIG Perforated aperture 33 is imaged, a portion of the detection beam sufficient for detection can reach the photodetector 43. Other portions are suppressed.

In order to be able to use this property, the lighting unit 42 is used which, in contrast to the lighting unit 29, has light-emitting diodes for red, green and blue light, and a control circuit by means of which the various light-emitting diodes are switched on alternately with a predetermined time program. The light-emitting diodes and the control circuit are shown roughly schematically in FIG. 7 only by a rectangle 45. With each changeover, the control circuit emits a corresponding color signal via a connection to a detection circuit 46, which replaces the detection circuit 35.

The photodetector 43 is essentially equally sensitive to the optical radiation that can be emitted by the illumination unit 42. Alternatively, wavelength-dependent changes in sensitivity can be corrected by calibration and the use of calibration factors (which are suitably stored).

A distance determination device in the sense of the invention is thus provided by the semi-transparent mirror 30, the illumination optics 31, the focusing optics 41, the fine pinhole 33, the photodetector 43 and the detection circuit 46. During operation, illuminating beams 13 are now radiated onto the cornea 7 with alternating red, green and blue light and focused in the area of the cornea 7. Each time the color changes, a corresponding color signal is output to the detection circuit 46.

The illuminated spot 15 formed on the cornea 7 is then imaged by means of the detection optics, which comprises the illumination optics 31, the semitransparent mirror 30 and the focusing optics 41. The detection beam 14 can only pass through the pinhole 33 if the focus of the illumination beam 13 reflected by the cornea 7 for the wavelength just used lies in an object plane conjugated to the plane of the opening of the pinhole 33.

When a signal from the photodetector 43 is detected, the detection circuit 46 converts a color signal from the illumination unit 42 received at the same time into a distance signal which results from the focus position at the wavelength just used. The distance signal is formed from the comparison of the individual signals.

A movement determination device according to a fifth embodiment differs from the movement determination device according to the third embodiment by the design of the detection units. Otherwise, it is designed in the same way and connected to the treatment unit 5. Furthermore, lighting units of the detection units also represent lighting devices of the movement determination device. The same reference numerals are therefore used for the same or analog components, and the corresponding explanations also apply here.

The identically designed detection units 47, one of which is shown in FIG. 10, differ from the detection units of the third exemplary embodiment in each case by a modified illumination unit 48, a color-corrected focusing optics 49, a three-channel spectrometer 50, which replaces the photodetector 34, and a modified one Detection circuit 51.

The illumination unit 48 now has a white light source that operates in continuous operation as the radiation source and a beam bundle-forming optic 53 that is prone to longitudinal defects (also referred to here as “highly dispersive”).

Through the use of the beam bundle-forming optics 53, which has strong longitudinal aberration, the illuminating beam bundle 13 in the area of the cornea is wavelength-dependent in different directions in the direction of the illuminating beam bundle 13 staggered planes focused in the area of the cornea. This is illustrated in FIG. 11, in which the focus positions in front of the cornea 7 for three partial beams 54, 54 'and 54 "of the colors red, green and blue are shown. While the focus for the blue light is closest to the illumination optics 31 , are those for green light and, still further, those for red light shifted towards the cornea 7.

The detection optics now include the color-corrected illumination optics 31, the semitransparent mirror 30, and the color-corrected focusing optics 49, so that the object plane 39 conjugated to the plane of the pinhole 33 assumes an essentially identical, fixed position for the wavelengths used.

A significant proportion of the detection beam 14 of a wavelength can only pass through the pinhole 33 if the corresponding focus of the illumination beam 13 reflected by the cornea 7 is close to or on the object plane 39 which is conjugated to the plane of the pinhole 33 with respect to the detection optics ,

The three-channel spectrometer 50 receives, with a predetermined detection frequency (e.g. 10 kHz), the beam of rays transmitted through the pinhole 33 and outputs a signal to the detection circuit 51 for each of the channels red, green and blue. This spectrometer can be constructed as a color splitter cascade with assigned photo receivers, or e.g. as a photodiode line, each element of the line being covered with a different color filter.

The detection circuit 51 determines a distance of the cornea 7 from the reference plane 12 and, based on the intensities received in the three channels and the dispersive properties of the beam-shaping optics 53, or the wavelength-dependent position of the foci of the illumination beam 13 reflected by the cornea outputs a corresponding distance signal to the evaluation device 11.

The semi-transparent mirror 30, the illumination optics 31, the focusing optics 49, the fine pinhole 33, the spectrometer 50 and the detection circuit 51 form a distance determining device.

A movement determination device according to a sixth embodiment differs from the movement determination device according to the fifth embodiment in the design of the detection units. Otherwise, it is designed in the same way and connected to the treatment unit 5. It is therefore used for the same or analog components the same reference numerals are used and the corresponding statements also apply here.

The detection units 55 differ from the detection units 47 of the fifth exemplary embodiment in the design of the illumination unit 56, which furthermore has the white light source 52, but now has a color-corrected beam-shaping lens 57, and the lighting lens 58, which has a highly dispersive lens 59 with a lens similar to that in FIG 8 has the dispersion shown.

Since the illumination optics 58 and in particular the highly dispersive objective 59 are also part of the detection beam path, the dispersive effects, which were described in connection with the fourth and fifth exemplary embodiments, add up. This results in a better spatial separation of the foci for different wavelengths, which improves the accuracy of the distance determination.

At the same time, a very high detection speed is achieved, as in the previous exemplary embodiment, since the temporal resolution is practically only limited by the detection speed of the spectrometer 50.

Otherwise, the detection unit works like that of the fifth exemplary embodiment, but the determination of the distance signal is determined taking into account the dispersive effects in the illumination and detection beam paths.

Claims

claims

1. Device for determining a movement of an eye (1) with an illumination device (16, 29, 42, 48, 56) that generates optical radiation during operation and as

Illumination beam bundle (13, 13 ', 13 ") for illuminating at least one area on the

Cornea (7) of the eye (1) emits, a distance determining device (17), the time-resolved than that of the cornea (7)

Detection beam (14, 14 ', 14 ") reflected back illumination beam (13, 13', 13") detected and a distance signal using the received optical radiation of the detection beam (14, 14 ', 14 ") corresponding to a distance of the cornea (7) of a reference plane (12, 12 ', 12 "), which is fixed relative to the distance determination device (17), and an evaluation device (11), which uses the distance signal to position or move a signal corresponding to a position or movement of the eye (1) generated.

2. Apparatus according to claim 1 or 2, wherein the illumination device (16, 29, 42, 48, 56) is designed such that a diameter of the illuminating beam (13, 13 ', 13 ") on the cornea (7) during operation of the eye (1) arranged in front of the device is between 2 μm and 20 μm.

3. Device according to one of the preceding claims, wherein the distance determining device (17) has an interferometer section (18) which forms an interferometer during operation together with the cornea (7).

4. The device according to claim 3, wherein the illumination device (16) is designed to emit optical radiation with a predetermined time coherence length, the interferometer section (18) at least one beam splitter arranged in the path of the illumination beam (13, 13 ', 13 ") (21) for forming a reference beam (22) from the optical radiation of the lighting device (16), at least one optical functional element (21) for superimposing the reference beam (22) on the Detection beam (14, 14 ', 14 ") and a device (25, 26) for varying the optical path length of the reference beam (22) between the beam splitter (21) and the optical functional element (21) or the optical path length of the path of the illuminating beam ( 13, 13 ', 13 ") after the beam splitter (21) and / or between the spot (15, 15', 15") illuminated by the illuminating beam (13, 13 ', 13 ") on the cornea (7) and the has an optical functional element (21), and the distance determining device (17) comprises a detection device (19, 20) which detects the intensity of the superimposed reference and detection beam bundles (22; 14) accordingly and converts it into a distance signal.

5. The device according to claim 4, wherein the means (25, 26) for varying the optical path length comprises a linearly reciprocable reflector (25).

6. The device according to claim 4, wherein the means for varying the optical path length has a reflector arrangement which can be rotated or pivoted about an axis and which has a plurality of reflecting sections each having a different distance from the axis.

7. The device according to claim 1 or 2, which has an illumination optics (31, 58) for focusing the illumination beam (13, 13 ', 13 ") for at least one wavelength in a predetermined range for possible positions of the cornea (7), and at the distance determining device (17) has detection optics (31, 32; 31, 41; 31, 49; 49, 58) in a detection beam path, a fine perforated diaphragm (33) arranged downstream of this in a diaphragm plane and one arranged after the perforated diaphragm (33) Detection device (34, 35; 43, 45; 50, 51) for detecting the optical radiation behind the fine pinhole (33), the plane of the diaphragm being conjugated to an object plane (39) assigned to the wavelength, which is in an area for possible positions the cornea (7).

8. The device according to claim 7, wherein the position of the illumination and / or detection optics (31, 32; 31, 41; 31, 49; 49, 58) and / or the pinhole (33) and / or the

Focal length of the illumination and / or detection optics (31, 32; 31, 41; 31, 49; 49, 58) and / or the position of the light spot can be changed by means of a drive (38).

9. The device according to claim 7, in which with the lighting device (42, 48, 56) optical radiation of different wavelengths can be emitted, and a beam-forming end

Optics (53) of the lighting device (48), the lighting optics and / or the detection optics is dispersive (31, 41; 49, 58).

10. The device according to one of claims 7 to 9, wherein the illumination device (42) is designed to emit optical radiation in at least two different spectral ranges.

11. The device according to one of claims 7 to 9, wherein the illumination device (48, 56) comprises a radiation source (52) for emitting optical radiation in a predetermined spectral range.

12. Device according to one of claims 7 to 11, wherein the detection device (50, 51) for spectrally and temporally resolved detection of the optical radiation behind the fine

Pinhole (33) is formed.

13. The apparatus of claim 10, wherein the detection device (43, 45) for the temporal change of the spectral ranges of the illuminating beam (13, 13 ', 13 ") detection of the optical radiation is formed behind the fine pinhole (33).

14. Device according to one of claims 7 to 13, wherein the illumination optics (58) and the detection optics (58, 49) have a common lens (59).

15. The apparatus of claim 14, wherein the common lens (59) has a certain longitudinal color error.

16. Device according to one of the preceding claims, with at least one lighting device (16, 29, 42, 48, 56), which emits two illuminating beams (13, 13 ', 13 ") and the two different areas on the cornea (7) of the Illuminated eye (1), and at least one distance determining device (17), which receives time-resolved detection beams (14, 14 ', 14 ") thrown back by the two areas on the cornea (7) and distance signals corresponding to distances of the cornea (7) from two reference planes (12, 12 ', 12 "), the reference planes (12, 12', 12") each being fixed for one of the detection beams (14, 14 ', 14 ") relative to the distance determining device (17) and the evaluation device ( 11) evaluates the distance signals and forms position or movement signals corresponding to a position or movement of the eye (1) in two spatial directions.

17. Device according to one of claims 1 to 15, with at least one lighting device (16, 29, 42, 48, 56), which emits three illuminating beams (13, 13 ', 13 ") and the three different corners of a triangle forming areas the cornea (7) of the eye (1), illuminate, and at least one distance determination device (17) which is thrown back by the three areas on the cornea (7) in a time-resolved manner Detection beam (14, 14 ', 14 ") receives and forms distance signals corresponding to distances between the cornea (7) from three reference planes (12, 12', 12"), the reference planes (12, 12 ', 12 ") each for one of the Detection beams (14, 14 ', 14 ") are fixed relative to the distance determination device (17), and the evaluation device (11) evaluates the distance signals and forms position or movement signals corresponding to a position or movement of the eye (1) in three spatial directions.

18. Method for determining a movement of an eye (1), in which optical radiation is radiated as an illuminating beam (13, 13 ', 13 ") onto the cornea (7) of the eye (1), using that from the cornea (7 ) as optical radiation beams (14, 14 ', 14 ") thrown back, time-resolved distance signals corresponding to the distance of the cornea (7) from a predetermined reference plane (12, 12', 12") are formed, and from the distance signals position or movement signals are formed according to a position or movement of the eye (1).

19. The method of claim 18, wherein the illuminating beam (13, 13 ', 13 ") on the cornea (7) has a diameter between 2 microns and 20 microns.

20. The method according to claim 18 or 19, in which from the illuminating beam (13, 13 ', 13 ") a reference beam (22) is coupled out, the reference beam (22) with the detection beam (14, 14', 14") is superimposed and the distance signal is formed by detection of interference of the superimposed beams.

21. The method according to claim 20, wherein the optical path length for the reference beam (22) before the superposition, the illuminating beam (13, 13 ',

13 ") is varied according to the department of the reference beam and / or the detection beam (14, 14 ', 14") before the superposition, the intensity of the superimposed reference and detection beams (14, 14', 14 ") is detected in a time-resolved manner, and off a distance signal is formed from the detected intensity.

22. The method according to claim 21, in which a reflector (25) is moved to vary the optical path length.

23. The method according to claim 22, in which, in order to vary the optical path length, a plurality of reflecting surface sections are rotated about an axis which have different distances from the axis in the radial direction.

24. The method according to claim 18 or 19, wherein the illuminating beam (13, 13 ', 13 ") is focused for at least one wavelength in a predetermined range for possible positions of the cornea (7), the detection beam (14, 14', 14 ") is focused by means of detection optics (31, 32; 31, 41; 31, 49; 49, 58) into the area of a fine pinhole (33) lying in a diaphragm plane, the diaphragm plane being conjugated to an object plane assigned to the wavelength ( 39), which lies in a predetermined range for possible positions of the cornea (7), and the distance signal is formed by detection of the optical radiation passing through the fine pinhole (33).

25. The method according to claim 24, in which the range of possible distances between the cornea (7) and the reference plane (12, 12 ', 12 ") is scanned by changing the distance between the object plane (39) and the fine pinhole (33).

26. The method according to claim 24, in which optical radiation of different wavelengths is used, and the illumination and / or the detection beam (14, 14 ', 14 ") is guided through at least one highly dispersive optical functional element (41; 53; 59) ,

27. The method according to claim 24, in which illumination beam bundles (13, 13 ', 13 ") with optical radiation in at least two different spectral ranges are used alternately in a predetermined time sequence.

28. The method according to any one of claims 24 to 27, wherein the illuminating beam (13, 13 ', 13 ") comprises optical radiation in a spectral range from 400 to 1700 nm.

29. The method according to any one of claims 26 to 28, wherein the intensity of the detection beam (14, 14 ', 14 ") behind the fine pinhole (33) is detected spectrally and temporally resolved.

30. The method according to claim 27, in which the intensity of the detection beam (14, 14 ', 14 ") is detected behind the fine pinhole (33) in a manner coordinated with the change in the spectral ranges of the illuminating beam (13, 13', 13").

31. The method according to any one of claims 18 to 30, wherein the illuminating beam (13, 13 ', 13 ") is irradiated onto an area on the cornea (7) at an angle of incidence less than 10 °, preferably less than 5 °.

32. The method according to any one of claims 18 to 31, in which at least two different illuminating beams (13, 13 ', 13 ") have at least two different ones Areas on the cornea (7) are illuminated using the optical radiation reflected by the cornea (7) in each case as a detection beam (14, 14 ', 14 "), time-resolved distance signals with respect to the distances of the cornea (7) from corresponding ones predetermined reference planes (12, 12 ', 12 ") are formed, and position signals or movement signals relating to a position or movement of the eye (1) in at least two spatial directions are formed from the distance signals.

33. The method according to any one of claims 18 to 31, wherein at least three different areas on the cornea (7) are formed with at least three different illuminating beams (13, 13 ', 13 "), which form corners of a triangle, using the of distance signals with respect to the distances of the cornea (7) from the respective predetermined reference planes (12, 12 ', 12 ") are formed in a temporally resolved manner to the cornea (7) in each case as optical radiation reflected back as detection beams (14, 14', 14"), and position or movement signals in relation to a position or movement of the eye (1) in three spatial directions are formed from the distance signals.

34. The apparatus of claim 1, wherein the illumination and detection radiation is guided out of the eye in synchronism with a therapy beam.