KR100260464B1 - Device for determining the topography of a reflecting surface - Google Patents

Abstract

A method and apparatus for determining the surface state of a reflecting surface will be described in detail. The projection pattern is projected onto the surface, thus sensing and evaluating the formed reflection pattern. In order to improve the consistency of the structure of the projection pattern and the structure of the reflection pattern, the projection pattern includes a recognition mark for distinguishing consecutive black / white or light / dark areas. Color marking or shading is particularly advantageous. A hollow cone shaped projection 17 is used to provide a projection pattern over the cornea of the eye 3, with a transparent ring 19 arranged on the side wall 18, and a ring-shaped light source 20. Is surrounded by. The color video camera 26 is used as a detector.

Description

Apparatus for determining surface condition of reflective surfaces

1 shows a reflection pattern of a projection pattern composed of several concentric circles on a spherical surface of the human cornea,

2 shows an example of a reflection pattern corresponding to the case of the cornea deviating from the spherical shape,

Figure 3 illustrates the structure of an arrangement capable of carrying out the method according to the static projection body and the device according to the invention,

4-6 show images of the two centrosomes at different positions of the cornea in the Z-axis direction with respect to the image sensor.

* Explanation of symbols for main parts of the drawings

1: eye 2: contour

3: corneal surface 4, 5, 6, 7, 8, 9, 10: ring

11, 12: centroid 13, 14: gap

15, 16: dent 17: projection

18: side wall 19, 21, 22: passage

20: neon tube 23, 24: line

25: small hole aperture 26: inlay detector

27: laser unit 28: laser line

The present invention relates to a process and apparatus for determining the surface shape of a reflective surface according to the claims of the present invention.

Corneal measurement methods based on this type of method, in particular Moire-type injection methods, are known as video corneal measurements. This is a projection of so-called placeholder discs, that is, alternating black and white rings on the human cornea. Reflections from the corneal surface are recorded in an automated video camera. Of particular interest is the distance or distortion of the reflective structure compared to standard measurements.

In the case of cornea measurement, standard measurements are made by known surfaces necessary for accurate evaluation / calculation of the corneal surface. Analysis of the warpage recorded from standard measurements can provide information about the radius of the corneal curvature and the deflection in the circular plane seen in astigmatism.

Processes of this type are known from US Pat. Nos. 4,978,213, 4,863,260 4,772,115.

In this method, the association of reflections and scanning in the projection ring is often difficult and proved to be mistaken. This defect is particularly difficult when the gap is formed in the reflective form of the initial ring projected onto the cornea because of defects in the corneal surface. Incorrect association of reflective structures independent of a particular scanned projection ring is a significant mistake, for example an incorrect measurement of corneal radius or a false measurement of corneal surface distortion at the required sphere.

The use of fleshy linears in addition to ring-shaped projections is known. However, this does not solve the above problem.

Also, the usual procedure is extremely sensitive to eye misalignment in the Z-axis, which is the connecting side between the corneal apex and the inlay unit.

It is therefore an object of the present invention to present a method for measuring the surface state of a reflecting surface, in particular the cornea, which ensures a reliable combination of reflected and scanned projections on the structural surface.

In addition, an apparatus suitable for carrying out such a method is provided.

This object is achieved by a method and an apparatus based on the foregoing form by means of the features according to the claims. The features described in the dependent claims describe further advantages of the invention.

According to the invention at least three separate recognition marks are used within the projection projected onto the surface to characterize the projection of the structure. This may be done by additional recognition indications other than black / white and light / dark indications. This use of specially designated areas within the projection can create additional criteria associated with the shape of the structure reflected from the reflecting surface for the projection projected onto the surface along with the light and dark areas. The number of coalition criteria may be increased by using some recognition to further improve this coalition. When using at least three marks in different colors, the black-white marks may be omitted.

According to a particularly advantageous embodiment, at least one color display is used as a recognition display. Providing such a color display allows the reflective type of the structure to be easily associated with each projection type. In particular, it can be recognized because the two displays overlap with each other in mixed colors.

It is also conceivable to use different recognition indicators, such as shading. Basically, in the case of shadows, the cognitive mark only pays attention to the fact that it is recognizable in a projection type consisting of uniformly continuous black / white marks or contrast marks.

The method according to the invention for determining the shape of the reflecting surface is applicable to almost all of the obvious technical fields such as spheres. In particular, this method can be used to measure the surface condition of the eye cornea.

This can be done by projecting a ring-shaped white light source of transparent and different colors onto the projection. However, it is also possible to provide optical hose arrangements of different nuclei in diode arrangements.

According to a preferred embodiment, the projection used in the side wall is formed of a hollow ring or in particular a hollow cone or colored ellipsoid of the cavity. The use of such a cavity with concave surfaces arranged on the side walls facing the eye is designed to be relatively small in diameter with respect to the Z axis. As mentioned above, the Z axis is formed as the extension axis of the phase recognition unit relative to the surface to be measured.

Suitably an inlay detector of a color video camera is used. However, it is also possible to use individual color filters for black and white cameras. In this case the measurement of the individual coloring is carried out continuously by replacing each filter.

Advantageously, the reflected signal from the corneal surface is measured as an integral of its intensity. This can compensate for changes in peripheral contrast that may be randomly distributed and offset each other.

In particular, it is recommended to perform signal processing automatically on a processor-controlled measurement unit with an output monitor. According to a particularly advantageous embodiment the output is in the form of a climbing line representing the part of the surface which has the same reflectivity during the measurement. Therefore, the deviation from the standard measurement can be directly seen and no further interpretation of the measurement data is necessary. Transparencies may be selected that contrast to different forms of explanation, such as opacity, to make an immediate derivative of the phase points of the measurements determined through interpolation, eg through interpolation.

Along with this automated measurement unit, the contrast unit can be controlled. This means that with each result of the measurement unit all projection unit parameters are automated or mutually optimized for maximum clarity of the surface state.

Of particular importance in the aforementioned method is to obtain good adjustment of the surface, in particular the corneal surface, for the inlay unit in the z-direction. The level of imaging in the overall arrangement is highly dependent on this distance. Adjustment in the Z-axis direction can be effected by scanning at least two central objects in the projection at a specific angle between each projection axis. The middle of the cranial projection axis represents the exact Z-position of the disturbance. The movement of this position in the z-direction is reflected in this arrangement by lateral movement of the central purpose reflected images relative to each other. The central object can be colored and the overlap of these objects is shown in a beneficially mixed color.

The central object is generated by a laser line extending at a certain angle with respect to the Z-axis and traversed at the desired location.

The resulting error without the exact arrangement of the Z-positions can be corrected by the predicted deviation in the required position through calculation by the measuring method.

In medical applications, especially when determining the surface condition of the corneal surface of the eye, a measuring device operated in accordance with the above-described procedure may enable the surgeon to recognize the corneal site with the deviation from the required position and to immediately provide appropriate treatment. It can also be coupled directly to the surgical microscope.

By using a high resolution camera with each zoom lens, the technique can also be used for measurements requiring resolution in the micrometer range. Therefore, it is possible to measure the minimum change in the rough surface in the small surface area of the cornea.

While using static projections, various methods can be considered to form each cavity ellipsoid.

The possibility is provided by the so-called foil technique, in which a circular, multicolor ring of color foil is formed first, subsequently mated into the ellipsoid of the projection head and finally fused. A further possibility is the so-called sandwich technique or multilayer technique, in which a ring is formed from several colored plexiglass blocks and cut by a lathe or milling unit to provide each corresponding thickness and color. The rings are fixed negatively and attached together. Such elements can be produced by interlayer casting of plastics of different colors. As a result, the elements on the shelves are tailored to the shape of the disturbances.

In the third embodiment, the transparent plexiglass blank and the ring are precisely scribed corresponding to the lateral position of the collar ring. The overall blank is black. In the grooved ring, black is removed and replaced with each transparent color.

The solution of the difficulties due to the embodiment of the present invention and the association between the projection pattern and the reflection pattern is for illustration only with reference to the following drawings.

FIG. 1 shows an image of the eye 1 of the almond shape 2 as recorded in the above-described inlaying system. The line inside the circumference 2 represents the outline of the cornea 3. Some of the reflection rings 4-10 are concentric circles about the Z-axis (corneal apex in the camera). As will be described in detail below, the two centrosomes are located within these rings. The distances and concentric circles and concentric circles of the rings 4-10 correspond to the reflected phases of the healthy cornea on the circular surface.

In contrast, FIG. 2 is the corresponding image of the modified cornea, as in the case of astigmatism. The 4'-8 'structure represents an absolute concentric reflection pattern and a circular projection ring. Such an image can be deformed by the non-circular corneal surface. In part, even in the case of the images (5 ', 6') of each inherent closed projection ring, they have gaps (13, 14, 13 ', 14') and are usually black / white for other structures (7 ', 8'). The photographs show significant dents 15 and 16. While no ordinary black / white photograph can explain any differences, this substructure 15 can be associated with the projection ring as formed by the reflecting rings 5, 6, 7 of the healthy cornea (first). Due to this ambiguity of association, the interpretation of these data to determine the surface state is necessarily wrong.

According to the invention, the rings 4-10 and the structures 4'-8 'are colored by the corresponding color of the projection pattern. Thus, even in the case of highly deformed reflection images (FIG. 2), a clear association is possible.

Figure 3 structurally illustrates the arrangement for carrying out the measuring method according to the present invention. The projection 17 is located in front of the eye 1 with the arcuate cornea 3.

Projection 17 includes a cone-shaped community with sidewalls 18 having ring-shaped transparent and differently colored passages 19. The cone-shaped projection 17 receives light from the outside by the ring-shaped neon tube 20. The cranial rays 23, 24 generated in differently colored ring-shaped passages 21, 22 illustrate the projection of the ring structure on the cornea. Light rays 23 'and 24' reflected from the cornea 3 are emitted through the small aperture stop at the narrow end of the cone-shaped projection 17.

The centers 11 and 12 irradiated to generate the image in FIGS. 4 to 6 at a particular angle between the projection axes in a plane coincident with the Z axis depend on the corneal position on the Z-axis with respect to the intersection of the projection axes. 4 to 6 show the corneal surface 3 and the image of the centroid in front of, exactly at and after the intersection. The phased arrangement of the centroids 11, 12 determines the Z-position of the corneal surface 3 and does not evaluate it.

3 shows that one projection side is formed by the laser line 28 generated by the laser unit 27. The laser line 28 forms, for example, a central body 11 on the cornea, the laser unit 27 is disposed outside of the projection body and the passage of the laser line 28 where the projection body crosses the Z axis at the desired position is Includes a small hole in the wall to be. The laser unit can be turned off after being arranged on the Z-axis.

Claims (1)

Apparatus for determining the surface state of a reflecting surface, comprising: projecting a projection pattern representing three or more recognition marks of different colors distinguishable from black and white on one surface to form a mirror reflection pattern generated through reflection from the surface A projection unit for; An image sensing unit for detecting a mirror reflection pattern; Apparatus for determining the surface state of a reflecting surface comprising an evaluation unit for comparing a mirror reflection pattern and a projection pattern and for indicating the recognition of the same color of the mirror reflection pattern and the projection pattern for characterization of the surface.