WO1998009562A1

WO1998009562A1 - Keratometric device

Info

Publication number: WO1998009562A1
Application number: PCT/EP1997/004839
Authority: WO
Inventors: Günter Rudolph; Beate Möller
Original assignee: Carl Zeiss Jena Gmbh
Priority date: 1996-09-07
Filing date: 1997-09-05
Publication date: 1998-03-12
Also published as: JP2000500056A; DE19726291A1

Abstract

This invention concerns a keratometic device in which parallel light rays (2a, 2b) are directed at the cornea (13). A rotatable optical unit (7) is provided in the rays reflected by the cornea and an image of these rays is formed on a photoelectric receptor (16).

Description

Keratometric arrangement

Field of the Invention

The invention relates to a keratometric arrangement in which illuminating rays of parallel light are directed onto the cornea, a rotatable optical unit in which radiation reflected from the cornea is provided and this radiation is imaged on a photoelectric receiver arrangement.

PRIOR ART In ophthalmic optics and ophthalmology, keratometric arrangements (also known as ophthalmometers) are primarily used to determine the radii of curvature of the cornea. However, they are also used to measure contact lenses, to assess progressive changes in the cornea (e.g. keratoconus) and also to search for refractive errors caused by the cornea. Radii are generally determined with all of these arrangements; By converting with the surface refractive index formula you get a corneal refractive index that can be read directly on most devices.

Keratometers that work on the principle of coincidence have become established in device technology. All coincidence devices are based on the same measuring principle, according to which two test marks are projected onto the cornea and the image distances of the test marks reflected from there are determined. If the dimensions of the object (at least two separate test marks or points) and the distance from the image to the object are known, the radius of curvature can be determined therefrom. The test marks are reflected in a central zone of the cornea with a diameter of approximately 3.2 mm With these devices, distance independence is of great importance. With the use of collimators in the illumination beam path, the first distance error is excluded because the test marks are imaged infinitely. The distance between the test object and the device therefore has no influence on the size of the mirror images of the test marks. The measuring beam path fulfills the second condition of distance independence, it is telecentric; an aperture diaphragm in the focus of an objective ensures that non-parallel beams are masked out and therefore do not come to detection. A change in the distance between the test specimen and the objective thus has no influence on the accuracy of the measurement.

Keratometers based on the coincidence principle are very inexpensive and enable an exact determination of the radius. It is disadvantageous that the measuring process itself as well as the evaluation of the measurement data can only be carried out by experienced operators

To remedy this, automatic keratometers were developed in which several measurement marks, predominantly generated by infrared LEDs with a known geometric arrangement (points, lines, circles), are imaged on the cornea. The position of their mirror images is detected by detection devices and then evaluated by computer programs with regard to the main curvature direction and the associated radii. CCD lines or complete CCD cameras are used as detectors. Automatically measuring keratometers should meet the two conditions of distance independence and allow a low relative error. Automatic keratometers have recently been developed which operate on the principle of image rotation with a fixed light source and a fixed detection device.

Such a keratometric arrangement is published, for example, in US Pat. No. 4,770,523. Here, parallel light from two slit-shaped light sources reaches the cornea via an optical unit that can be rotated about a reference axis and a lens. Before hitting the cornea, the two bundles of light are aligned axially symmetrically with respect to the reference axis and are inclined at the same angle with respect to the reference axis. The light reflected by the comea is mapped onto a linear receiver, again via the lens and the rotatable optical unit arranged between the light sources and the lens. The disadvantage here is that the rotatable optical unit and the lens must have large dimensions because the full illumination aperture is transmitted to the optical unit via a transmission lens. This has a disadvantageous effect on the overall size of the entire arrangement. In addition, the arrangement described is not for point-shaped light sources are suitable, slit-shaped light sources first have to be generated in order to compensate for emigration of the beam paths to the side of the receiver line

In US Pat. No. 4,660,946 an annular illumination source is provided, which is imaged onto the cornea in parallel rays on the cornea in parallel rays. Here, too, the parallel rays are aligned axially symmetrically to the reference axis before they strike the cornea and at equal angles! inclined in relation to the reference axes The light reflected from the cornea is first split into several partial beams in a telecentric beam path and then reaches a receiver line

The disadvantage here is that the production of the ring-shaped cylinder liner is quite complex, on the other hand, the ring-shaped cylinder liner produces a collimating effect even in directions that are undesirable for the function of the arrangement

In US Pat. No. 4,597,648, light guides are used to create a plurality of point light sources arranged on the circumference of a circle. The exit ends of a large number of optical fibers are arranged at regular intervals on a ring and thus cause annular illumination of the cornea. The evaluation of the reflected light source images takes place via a rotating Pechan-Pπsma and a receiver line

Due to the non-telecentric beam path, additional means are required to check the focus position of the image, which has a disadvantageous effect on the size of a keratometer that works according to this principle

A further keratometric arrangement is described in GB 21 7781 3 A. Here two point-shaped light sources are arranged symmetrically to an optical axis, the light coming from the two light sources is directed onto a surface which has optically characteristic features and which is to be measured (cornea ) In that of This surface of the reflected beam path provides a pair of doubling optical elements for image splitting, which can be pivoted relative to one another about an axis of rotation perpendicular to the optical axis, as a result of which two images of the reflected radiation can be displaced in opposite directions and must be brought to coincidence.

It is also disadvantageous here that the measuring process and the evaluation of the data can only be carried out by trained and experienced personnel.

Description of the invention

Based on the state of the art, the object of the invention is to develop a generic arrangement such that the overall structure of the arrangement is further simplified and / or the overall size is reduced while maintaining the possibility of automatic measurement value acquisition.

According to the invention, this object is achieved in an arrangement of the type mentioned above in that a cylindrical lens is provided in the beam path between the rotatable optical unit and the receiver arrangement.

Due to the fact that the cylindrical lens only images in one plane, there is the advantage in particular when using line-shaped receiver arrangements that even when the eye is displaced laterally to the illumination plane or with an astigmatic eye, the images of the light sources lie on the receiver line. Thereby, it is not necessary more, to produce first slit-shaped light sources to prevent chen to a seitli ^¬ Emigration and a consequent falsification of measured values.

It is also advantageous to provide telecentric diaphragms in the beam paths in front of and behind the rotatable optical unit, onto which the illuminating radiation and also the light reflected by the cornea are imaged; between the telecentric diaphragms and the rotatable optical unit, optical elements for generating beam paths parallel to the optical axis, which are directed at the rotatable optical unit, should be arranged.

This can be avoided with simple means that the full illumination aperture must be transmitted to the rotatable optical unit via a transmission lens, so that this can be made much smaller and consequently the overall structure of the arrangement can be carried out in a significantly smaller size.

It is also advantageous if a combination of at least one optical assembly for generating parallel light with at least one axicon is provided for generating the parallel light between the illumination source and the cornea, the axicon being oriented such that the incident on the axicon parallel light is directed onto the cornea. An axicon is understood to mean a diffractive, refractive or reflective element which distributes a coaxially incident bundle of parallel light over a coaxial ring around the optical axis. An axicon designed as a reflective element has, for example, a reflective circular cone surface with the opening angle α, which is analogously created by the rotation about the optical axis of a straight line inclined by α / 2 relative to the optical axis. For example, a reflective axicon with a-90 ^{'can be} formed in order to distribute the coaxially incident parallel bundle over a coaxial ring; in a special case, the circular cone surface is not inclined against the optical axis, so that a circular cylinder surface is obtained as the reflecting surface of the axicon, which can be formed, for example, from the mirrored inner surface of a hollow cylinder. The optical assembly for generating the parallel light can be a radiation source with a collimator in front.

In connection with the present invention, a particularly advantageous embodiment is that the axicon is designed as a reflective element which has a mirror surface curved to form a circular cylinder surface. It consists of a hollow cylinder, the inner wall of which is mirrored and which is arranged in the beam path in such a way that the central axis of curvature of the mirror surface lies in the axis of rotation of the rotatable optical unit. The advantage is that remains with this easy to manufacture component of the parallel beam path and optical construction ^¬ elements can be eliminated, must produce only immediately before the cornea again parallel light.

In a particularly preferred embodiment, in which two illuminating beams of parallel light are directed onto the cornea, the rotatable optical unit is designed as a reflective element. This can be provided with two reflecting surfaces which enclose an angle of 90 ^' . The two reflecting surfaces should be in the two illuminating beam paths as well as in the beam paths of the light reflected from the cornea, the axis of rotation of the reflective element being in the axis of symmetry of the illuminating beam paths as well as the reflected beam paths, and the line of intersection in which the two reflecting surfaces penetrate is oriented perpendicular to the axis of rotation.

This design of the rotatable optical element in connection with its arrangement in the radiation path results in a significant reduction in its dimensions and leads to a keratometric arrangement of small size.

A 90 ^' prism can advantageously be provided as the reflective element; On the other hand, it is also conceivable to design the reflective element as a 90 ^' angle mirror.

To generate the two illuminating beam paths, two separate radiation sources can be provided, each of which is followed by a collimator, both illuminating beam paths being directed onto the rotatable reflective element.

In addition to this, at least one axicon can also be provided in the beam path between the rotatable reflective element and the cornea, as a result of which, as already described above, the parallel beam path is retained despite the influence of the radiation direction and optical components that are only present can be omitted generate parallel light from the cornea.

In this context, it is advantageous if a second axicon is arranged in the illuminating beam path in front of the rotatable reflective element, especially when the first axicon with a relatively small radius of curvature, based on its symmetry, is arranged between the rotatable reflective element and the cornea to the optical axis. The second axicon compensates for undesired deflection of parts of the beam path coming from the reflective element or prevents the formation of a focal line lying in the radius of curvature. The two axicon should have the same opening angle α of the reflecting surface to the optical axis, provided that they are designed as reflecting elements, have the same grating constant if they are designed as diffractive elements and have the same prism angle, provided that they have optically refractive properties.

An alternative embodiment to avoid an undesired focal line is to be arranged instead of the second axicon before the rotatable reflective element is a cylinder lens ^¬. A deflection device for changing the radiation direction in the direction of the receiver arrangement can be provided in the beam path of the light reflected by the cornea behind the reflective element. This makes it possible to position the receiver arrangement spatially next to the direction of the main beam paths, so that a disruptive influence on the beam path is excluded.

In addition, a device for coupling out an observation beam path, for example a perforated mirror, can be provided. This advantageously means that adjustments and measurements can also be carried out manually.

Particularly preferably, instead of the deflection device and the perforated mirror in the beam path of the light reflected from the cornea, a beam splitter should be provided, which serves both to redirect the radiation direction in the direction of the receiver arrangement and to couple out an observation beam path.

The quality of the imaging of the radiation reflected from the cornea onto the receiver arrangement can be influenced by arranging at least one lens and a diaphragm in front of the rotatable reflective element and further optical elements, including a cylindrical lens, after the deflection device. For the same reason, additional optics for imaging the telecentric diaphragm into the reflective element can also be provided between the deflection device and the rotatable reflective element.

It is also conceivable to arrange the deflection device for changing the radiation direction in the direction of the receiver arrangement between two lenses transmitting the illuminating radiation. The lenses can have recesses for the free passage of the reflected light.

In a further particularly preferred embodiment, in which not only two BL LEVEL ^¬ beam paths parallel light, but an annular and collimated light is directed onto the cornea, the rotary optical unit is also formed as a reflective element. This can have two reflecting surfaces which enclose an angle of 90 '. The reflective element should be arranged so that the two reflecting surfaces are located in the beam paths of the light reflected by the cornea, the axis of rotation of the reflective element being symmetrical. axis of the reflected ray paths and the intersection line, in which the two reflecting surfaces penetrate each other, is aligned perpendicular to the axis of rotation

As in the embodiment described further above, at least one axicon can be provided in the beam path between the rotatable reflective element and the cornea, as a result of which the parallel beam path is retained and optical components which produce parallel light only directly in front of the cornea can be omitted To generate the ring-shaped illumination directed directly at the cornea, at least one axicon arranged at least one radiation source can be provided

Within the scope of the invention there is an embodiment in which a collimator, a first axicon and a second axicon (for generating an annular collimated and axially parallel illuminating radiation), a perforated mirror (for laterally fading in the axially parallel illuminating radiation in the direction of the eye) and a third axicon (for changing the direction of the illumination on the cornea) may be provided, the perforated mirror being arranged in such a way that the light reflected from the cornea passes through the recess in the perforated mirror to the rotatable reflective element

In a further embodiment, it is provided that to generate the annular collimated lighting, a plurality of radiation sources are arranged distributed over a circumference, a telecentric diaphragm arrangement in front of the radiation sources and a lens in the illuminating beam path between the diaphragm arrangement and the core, the telecentric diaphragm arrangement has in its center a recess through which the light reflected from the cornea reaches the rotatable reflective element

Brief description of the drawings

The invention is explained in more detail below with the aid of exemplary embodiments. The associated drawings illustrate in accordance with

1 shows an embodiment of the arrangement according to the invention with a cylindrical lens in front of the receiver arrangement. FIG. 2 shows an embodiment with axially parallel light in the rotatable optical unit Fig. 3 shows an embodiment with annular lighting

FIG. 4 shows an embodiment with a rotatable 90 ^' psma and a flexing axicon in a perspective view. FIG. 5 shows the embodiment according to FIG. 4 in a sectional view

6 shows an embodiment with a rotatable 90 ^′ prism and reflecting axicon in FIG

Sectional view Fig 7 shows an example of the design of the Axicon

8 shows an embodiment with ring-shaped illumination and a rotatable 90′-pma

9 shows an embodiment with transmission lenses in reflected light

Detailed description of the drawings

1 shows two radiation sources 1 a and 1 b, for example laser diodes for the wavelength 780 nm, each of which emits a light bundle 2a and 2b. Each light bundle is assigned a collimator 3a, 3b. Both light bundles pass through the lens 4, a first telecentric aperture 5, one Lens 6, a rotatable optical element 7, for example a Dove-Pπsma, a lens 8, a second telecentric aperture 9, a lens 1 0, which is followed by a diffractive axicon 1 1, and strike the cornea 1 as separate bundles of parallel light 3 of a human eye 1. Between the axicon 1 1 and the cornea 1 3, both illuminating rays are inclined symmetrically to a reference axis, in this case the optical axis 1 2. The illumination level reflected by the cornea 1 3 passes through the axicon 1 1, which has optically active zones only in an outer region, and is returned in the same way through the lens 10, the telecentric aperture 9, the lens 8, the rotatable optical element 7, the lens 6, the telezentπsche aperture 5, the lens 4 and is then imaged via a cylinder lens 15 on a CCD receiver line 16

The Dove-Pπsma used as a rotatable optical element 7 lies with its axis of rotation in the optical axis 1 2. If the optical element 7 is rotated about its axis of rotation when this arrangement is operated, both the illumination plane and the image of the CCD receiver line 16 are rotated around the optical axis 1 2, so that a curvature measurement can take place over the entire cornea 1 3, since there is a change of the radius of curvature on the cornea 1 3 also the distance of the illumination radiation represented in pixels changes in the measurement plane spanned by the illumination and the receiver line 1 6. The respective radius of curvature is determined, for example, as follows from the distance between the light source images on the receiver line 16:

The pixel spacing on the line is measured using discriminators and a first counter that pays the CCD pixels between the rising edges. The value is transferred to a second and third counter, which at the end of the measurement process should contain the maximum and minimum pixel spacing, corresponding to the radii of curvature in the two main sections. A first angle counter simultaneously pays the position of an angle encoder, which indicates the angle of rotation of the prism. At the next angular step, the first payer reaches the pixel distance corresponding to the new position of the image. This is now compared with the status of the second and third payer. Depending on whether it is smaller or larger, it is transferred to the second or third counter. A second angle counter takes over the value of the first angle counter when the second or third counter reading is changed

At the end of a revolution (or a half or a quarter revolution, depending on the design of the arrangement), the maximum pixel distance is in the second counter, the minimum pixel distance in the third counter and the position of the relevant main axis assigned to the counter values in the second and third counters in the second counter . The radius of curvature is proportional to the pixel distance, so that after another counter conversion the radius of curvature can be displayed directly.

Another embodiment variant of the invention is shown in FIG. In contrast to the previously described embodiment variant, here a plurality of radiation sources 1c are distributed over a circular circumference, in the beam path of which a telecentric diaphragm arrangement 17 and a lens 18 are arranged so that the illuminating light strikes the cornea 13 in a ring-shaped and collimated manner. The illuminating radiation strikes the cornea 1 3 concentrically and inclined to the optical axis 1 2 and is reflected from there. As in the embodiment variant described above (FIG. 1), the light reflected by the cornea 1 3 is also transmitted via the lens 1 8, the telecentric diaphragm 9, a lens 8, the rotatable optical element 7 (in this case also a Dove prism), the lens 6, the telecentric diaphragm 5, the lens 4 and the cylindrical lens 15 on the CCD receiver line 16. The Dove prism is also rotatable about the optical axis 1 2. If this arrangement is operated when Prism rotated about the optical axis 1 2, the image of the receiver line 1 6 is rotated about the optical axis 1 2, so that the curvature measurement can take place over the entire cornea 1 3, whereby, as in the example according to FIG. 1, during the rotation the pixel spacing changed according to the radius of curvature of the cornea 1 3 in the measuring plane spanned by the receiver line 1 6. Here too, the respective radius of curvature can be determined from the distance between the light source images on the CCD receiver line 1 6

Another advantageous embodiment is shown in FIG. 3. Here, a single radiation source 1 d is provided, in the beam path 2 d of which a collimator 1 9 and an axicon 20 are arranged. This axicon 20 is also embodied here as a diffractive optical element Parallel light is another Axteon 21, which is followed by a perforated mirror 22 and another Axicon 23, also as a diffractive optical element, in the further beam path.Here, too, an annular collimated illumination strikes the cornea 1 3 at an angle to the optical axis 1 2 Light reflected from the cornea 1 3 passes unaffected by the axicon 23, since it has optically active zones only on the outer circumference, and passes through the lens 24, through the recess 43, further via the telecentric aperture 9, the lens 8, the rotatable optical element 7, the lens 6, the telezentπsche aperture 5, the lens 4 and the cylindrical lens 1 5 on the CCD receiver line 1 6

Also in this exemplary embodiment, a Dove prism is used as the rotatable optical element 27, which is rotatably supported about the optical axis 12. When this arrangement is operated, the illumination radiation reflected by the cornea 1 3 is emitted, as in the examples described above the CCD receiver line is imaged If the Dove-Pπsma is rotated about its optical axis 1 2, the image of the CCD receiver line 1 6 is rotated about the optical axis 1 2, so that the curvature measurement can take place over the entire cornea 1 3, with the rotation of the pixel distance corresponding to the radius of curvature of the cornea 1 3 in the measuring plane spanned by the illumination and the CCD receiver line 1 6 changes. The distance of the light source images on the CCD receiver line 1 6 is a measure of the respective radius of curvature on the cornea 1 3

A likewise advantageous embodiment of the invention is shown in FIGS. 4 and 5. FIG. 4 shows a perspective illustration, while FIG. 5 shows the same embodiment in section through the optical axis 1 2. 5 shows the illuminating radiation 2e, 2f rotated into the plane of the drawing. Two point-shaped radiation sources 1 e and I f are provided, each of which is followed by a collimator 3e and 3f. The two bundles of parallel light 2e, 2f are first directed onto the outer optically effective area of an axicon 26 and from there, likewise as parallel light, onto a rotatable reflecting element 27. The reflecting element 27 is designed as a prism, in which the under 90 ' reflecting surfaces 27a, 27b inclined towards one another are extended to their common intersection line 35. The axis of rotation of the 90 ^" prism lies in the plane spanned by the irradiation directions of the illuminating beams 2e and 2f, and simultaneously forms the bisector of the angle enclosed by the two illuminating beams 2e and 2f The illuminating radiation 2e and 2f reflected by the 90 ^' -Pπsma 27 passes the inner region of the optically active zones of the Axicon 26 and is thereby directed onto the cornea 1 3. In the beam path of the illuminating light reflected from the cornea 1 3 there is a lens 28 and a telecentric aperture 29 arranged in the wide Ren beam path, a radiation plate 30 is provided, on the plate surface, an observation beam is first hidden and imaged into a CCD camera 32 via a lens 31. The undeflected part of the beam path reaches the rotatable 90 ^" prism 27, from there it is directed in the direction again reflects the radiation plate 30 and is imaged from its divider surface in the direction of the CCD receiver line 34, which is preceded by a cylinder liner 33 and, by way of example, a filter 34. As in the embodiments described above, the distance between the light source images on the CCD receiver line 34 is a measure of the Radius of curvature in the plane spanned by the illuminating rays

In a further exemplary embodiment according to FIG. 6, the illuminating beam paths of parallel light 2e and 2f emanating from two point-shaped radiation sources, each with a downstream collimator (neither of which is shown), are directed onto a rotatable optical prism 27. The rotatable prism 27 has two reflector surfaces 27a and 27b which are inclined at an angle of 90 ° to one another and which abut one another in the angle apex or in their common line of intersection 35

The direction of rotation of the prism 27 is indicated by R. The axis of rotation 59 of the rotatable optical prism 27 lies within the plane spanned by the illuminating beam paths 2e and 2f and at the same time forms the bisector of the angle enclosed by the two illuminating beams 2e and 2f. The illumination beam paths 2e ^′ and 2f reflected by the prism 27 are reflected on the mirror surface 57 of a directed the element 56, which is designed as a hollow cylinder with a mirrored inner surface (see FIG. 7).

Because of the congruent center axis 58 arranged congruently with the axis of rotation 59, the two illuminating beam paths 2e ^' and 2f rotating with the prism 27 are directed onto the cornea 1 3 also arranged in the axis of rotation 59

A lens 28 and a telecentric diaphragm 29 are arranged in the beam path of the illuminating light reflected by the cornea 13. In the further beam path, a beam splitter 30 is provided, on the splitter surface of which an observation beam path 36 is first masked out and imaged into a CCD camera 32 via a lens 31

The undeflected part of the beam path coming from the cornea 1 3 reaches the rotatable prism 27, is reflected there again in the direction of the beam splitter 30 and from its splitter surface is imaged on the CCD receiver line 34, which is preceded by a cylindrical lens 33 and a filter 34 .

As described above, the distance between the light source images on the CCD receiver line 34 is a measure of the radius of curvature in the plane spanned by the illuminating rays.

If the prism 27 is rotated about its axis when this arrangement is operated, both the illumination plane and the image on the CCD receiver line 34 are rotated about the optical axis 1 2. The curvature measurement can thus take place over the entire cornea 1 3 because with a change in the radius of curvature on the cornea 1 3, the distance between the illumination beam paths shown in pixels also changes in the measurement plane, which is spanned by the illumination and the CCD receiver line 34. The respective radius of curvature is determined from the distance between the pixels on the CCD receiver line 34.

As previously described, the electronic evaluation is carried out with evaluation electronics arranged downstream of the CCD receiver line 34. Analogous to the previously described embodiments of the invention, a cylindrical lens can be arranged as a correction element in each of the illuminating beam paths 2e and 2f, ie in front of the rotatable prism 27 (not shown here in the drawing). This compensates for an undesired divergence of the illumination beam paths 2e ^' and 2f reflected from the mirror surface 57 onto the cornea 1 3 perpendicular to the plane of the drawing in FIG. 1, which may be caused due to the curvature radius of the mirror surface 57 being too small.

Further refinements of the invention are shown in FIGS. 8 and 9. In FIG. 8, as in FIG. 2, a plurality of radiation sources 1 c are arranged on a circumference around the optical axis 1 2 in order to generate the annular collimated illumination. A telecentric diaphragm arrangement 1 7 is provided in front of the radiation sources 1 c and a lens 1 8 is provided in the illuminating beam path between the diaphragm arrangement 1 7 and the cornea 1 3. In its center, the telecentric diaphragm arrangement 17 has a recess 44 through which the light reflected from the cornea 1 3 passes via a telecentric diaphragm 45, a lens 4 and the beam splitter 46 to the rotatable reflective element 39 and from there, analogously, for example 4 or FIG. 5, again reaches the beam splitter 46 and is diverted from its splitter surface onto the cylinder ledges 40 or the CCD receiver line 41.

In FIG. 9, two transmitting lenses 48, 49 are provided in the illuminating beam paths 2g, 2h of two radiation sources 1g, 1h, each with an upstream collimator 3g, 3h, which are directed onto the cornea 1 3 via a rotatable reflective element 47. In this case, the rotatable reflective element 47 is again a 90 ^' prism. Recesses 48a, 49a are machined into the centers of the lenses 48, 49. A lens 52, a perforated mirror 50 with a recess 50a, a telecentric diaphragm 53 and a beam splitter 51 are arranged in the beam path of the light reflected by the cornea 13. A lens 52 is arranged upstream of the hole mirror 50.

In this embodiment shown as an example, the light reflected by the cornea 1 3 first passes through the recess 49 a, is then directed in part by the lens 52 onto the perforated mirror 50 and in part is imaged in the telecentric diaphragm 52. While the first partial beam is directed through the optically effective surface of the perforated mirror 50 as an observation beam path via the lens 55 onto the CCD camera 33, the second partial beam reaches the rotatable reflective element 47 through the telecentric diaphragm 53 and the beam splitter 51 from there back to the beam splitter 51 reflected and directed from the dividing surface onto the CCD receiver line 34. Here, the image spacing of both light source images is evaluated as described above.

Claims

claims

1 keratometric arrangement, in which illuminating rays of parallel light are directed onto the cornea, a rotatable optical unit is provided in the radiation reflected from the cornea and this radiation is imaged on a photoelectric receiver arrangement, characterized in that in the beam path between the rotatable optical unit (7) and the receiver arrangement (1 6) a cylinder liner (1 5) is provided

2 keratometric arrangement according to claim 1, characterized in that in the beam paths in front and behind the rotatable optical unit (7) telezentπ see diaphragms (5, 9) are provided, on which the illumination radiation and that of the cornea (1 3) reflected Light are imaged and that in each case optical elements for generating axially parallel beams in the direction of the rotatable optical unit (7) are provided between the tele-aperture (5, 9) and the rotatable optical unit (7)

3 keratometric arrangement according to claim 1 or 2, characterized in that between the illumination source and the cornea (1 3) a combination of at least one element for generating parallel light with at least one axicon (1 1) is provided, the axicon (1 1 ) is a diffractive, refractive or reflective element and is arranged in the illuminating beam path in such a way that the parallel light incident on the axicon (1 1) is directed onto the cornea (1 3)

4 keratometric arrangement according to claim 3, characterized in that the axicon is designed as a reflective element (56) which has a curved surface to a circular mirror surface (57), the reflective

Element (56) is arranged so that the Krummungsmittenachse (58) of the flat mirror (57) with the axis of rotation (59) of the rotary optical unit (7) together ^¬ falls

5. Keratometric arrangement, in particular according to the preamble of claim 1, in which two illuminating beams parallel light are directed to the cornea, characterized in that the rotatable optical unit is designed as a reflective element (27), which both in the course of the two lighting - beam paths (l e. lf) as well as in the course of the beam paths of the

Cornea is reflected light.

6 Keratometric arrangement according to claim 6, characterized in that the rotatable reflective element (27) is designed as a 90 ^' prism, the axis of rotation of which lies in the axis of symmetry of the illuminating beam paths (2e, 2f) as well as the reflected beam path, the intersecting line (35 ), in which the two reflecting surfaces (27a, 27b) penetrate, is oriented perpendicular to the axis of rotation

7 keratometric arrangement according to claim 5 or 6, characterized in that two separate radiation sources (le, lf) are provided for generating the two illuminating beam paths (2e, 2f), each of which is followed by a collimator (3e, 3f) that both illuminating beam paths ( 2e, 2f) are directed onto the rotatable reflective element (27) and an axicon (26a) is provided in the beam path between the rotatable reflective element (27) and the cornea (1 3).

8 keratometric arrangement according to claim 7, characterized in that a cylindrical lens is arranged in the illuminating beam path in front of the rotatable reflective element (26b) and / or in the illuminating beam path in front of the rotatable reflective element (27).

9. Keratometric arrangement according to one of claims 5 to 8, characterized in that in the beam path of the light reflected from the cornea (1 3) a deflection device for changing the radiation direction in the direction of the receiver arrangement (34) and / or a perforated mirror Decoupling of an observation beam path (36) is provided.

1 0. Keratometric arrangement according to one of claims 5 to 9, characterized in that in the beam path of the light reflected from the cornea (1 3) in front of the rotatable reflective element (27) at least one lens (28), a telezen tsche aperture (29) and additional optics for imaging the telezentπsche aperture (29) in the reflective element (27) are provided

Keratometric arrangement according to Claim 5, characterized in that lenses (37, 38) transmitting the illuminating radiation are arranged in the beam path upstream and downstream of the deflecting device and have recesses for the free passage of the reflected light ύ and / or in the beam path of the cornea (1 3 ) reflected light in front of the receiver arrangement (34) a cylinder liner (33) is provided

Keratometric arrangement, in particular according to the preamble of claim 1, in which a ring-shaped and collimated illumination is directed towards the cornea, characterized in that the rotatable optical unit is designed as a reflective element (27) which is in the course of the beam path from the cornea reflected light is classified

Keratometric arrangement according to claim 1 2, characterized in that the rotatable reflective element (39) is formed with two reflecting surfaces (39a, 39b) which enclose an angle of 90 ', its axis of rotation concentric with the direction of irradiation of the cornea ( 1 3) reflected light and the intersection line (42), in which the two reflecting surfaces (39a, 39b) penetrate each other, is oriented perpendicular to the axis of rotation and at least one axicon is provided for generating the annular collimated lighting

Keratometric arrangement according to claim 1 2 or 1 3, characterized in that in the beam path of a light source (1 d) a collimator (1 9), a first axicon (20) and a second axicon (21) for generating an annular collimated and axially parallel Illumination radiation, a perforated mirror (22) for laterally fading in the axially parallel illuminating radiation in the direction of the eye and a third axicon (23) for changing the direction of the illumination onto the cornea (1 3) are provided, the perforated mirror (22) being arranged in such a way that the light reflected from the cornea (1 3) passes through the recess (43) in the perforated mirror (22) to the rotatable reflective element (39) Keratometric arrangement according to claims 1 to 3, characterized in that in order to generate the annular collimated illumination, a plurality of radiation sources (lc) are arranged distributed over a circumference, a telecentric diaphragm arrangement (1 7) in front of the radiation sources (1 c) and in the illumination beam path between the diaphragm arrangement ( 1 7) and the cornea (1 3) a lens (1 8) are provided, the telecentric diaphragm arrangement (1 7) having a recess (44) in its center through which the light reflected by the cornea (1 3) for rotatable reflective element (39)