WO2006089757A1 - Device and method for determining refraction - Google Patents

Abstract

The invention relates to a device and a method for determining the refraction of optical imaging errors which can be described by a set of basic two-dimensional functions. An optical observation system is provided which comprises several optical elements that can be introduced into an observation channel. According to the invention, at least one set (11, 12) of at least two optical compensation elements (13, 14) which correspond to associated functional components of the basic two-dimensional functions describing the imaging errors is introduced into the observation channel, said at least two compensation elements being twistable or transversally movable relative to each other in order to adjust different total amplitude values of the respective sum of the functional components. The invention is used for subjectively determining eye refraction, for example.

Description

 Description Apparatus and method for refraction determination

The invention relates to an apparatus and a method for refraction determination of optical aberrations that can be described by a set of surface area functions, with an observation optical system comprising a plurality of optical elements that can be introduced into an observation channel.

An important field of application of such devices and methods is the subjective refraction determination in the human eye, in which mainly refractive anomalies of the human eye are determined based on statements of the examined person to his visual perception. In a conventional procedure, which is routinely limited to the correction of defocus, astigmatism and prismatic errors, different measuring glasses are held in appropriate combination temporally one after another in front of the examined eye and used to improve the visual impression in a used measuring goggles. The examined person is asked to compare the respective optotype image with a previously shown with regard to its image quality.

Basically, aberrations are divided into symmetric and asymmetric aberrations. For example, e.g. the spherical refractive error is a symmetrical aberration which is corrected by introducing spherical measuring glasses. In contrast, astigmatism is an asymmetry error that is corrected with corresponding cylindrical glasses.

For subjective refraction determination of the ocular astigmatism, the so-called cross-cylinder method is additionally used. You uses a cross cylinder element in the form of a combination of a plus and a minus cylinder lens whose refractive indices are equal in magnitude, but have opposite signs, and the optical axes are perpendicular to each other, see, for example, the published patent DE 25 55 387 A1. The cross cylinder is manually held one after the other in both axial positions in front of the eye. The examined patient is asked to give the better of the two related visual impressions. An examiner familiar with the refraction measurement can make corresponding corrections of the cylinder thickness on the basis of the patient statement. The different presentation is effected by the turning of the cross cylinder element. The procedure is repeated until the patient perceives both visual impressions as equally good.

Following the same principle, the axial position of the cylindrical lens of the eye is determined. For this purpose, the cross-cylinder element is placed in front of the eye to be examined such that it deviates in its orientation by 45 ° from the previously determined cylinder axis of the eye. The process is again repeated until the patient no longer recognizes a difference between the two visual impressions. As long as one of the two visual impressions is judged better than the other, the cylinder axis is adjusted accordingly.

The correction of astigmatic refractive errors is usually done with cylindrical lenses, which have a dispersive effect. However, a change of the minus cylinder during the subjective refraction determination simultaneously alters the spherical component, which must be compensated in the measurement goggles by presetting appropriate spherical lenses. Thus, for this test variant, a measuring glass set with a large number of spherical and cylindrical correction glasses is required in order to determine all refractive errors that may occur in practice. If, instead of the negative cylinder measuring glass, a cross cylinder measuring glass is used in the measuring goggles, the spherical value does not need to be corrected. Even in this case, however, a complete measuring glass replacement of cross cylinder elements is required.

In principle, a subjective refraction measurement can also be carried out exclusively with cross cylinders. To determine the astigmatism further eye examination devices in the form of so-called phoropter are known. Patent specification DE 1 051 532 discloses a device attached to such a phoropter in which cross-cylinder lenses are rotatably mounted side by side in a pivotable holder.

In the published patent application DE 28 49 337 A1 a transverse cylinder mechanism is described in which the cross cylinder consists of two separate cylindrical lenses. It is also known to use only a cross cylinder on which all adjustments to the required pivoting and turning are present, see e.g. U.S. Pat. Nos. 3,498,699 and 3,698,799.

In the patent DE 24 12 059 C2 an eye examination optics is proposed, which comprises a negative concave spherical and a positive convex spherical lens in the manner of a Galileifernrohrs and in the beam path following two pairs of oppositely rotatable, negative and positive cylindrical lenses. By changing the axial distance along the optical axis between the two spherical lenses, a spherical rupture force component is adjustable. The two lenses of each cylindrical lens pair have oppositely equal Brecht forces, and in a neutral starting position, the two pairs of cylindrical lenses are offset from one another at a predeterminable angle of, for example, 45 °. By selecting predetermined positions of the relative counter-rotation between the paired cylindrical lens elements, substantially all practical table relevant cylindrical angular power values and axial positions can be generated regardless of the setting of the spherical power. Alternatively, an eye examination optics with a variable spherical and a variable astigmatic lens element are proposed, which are each made with specific location-dependent thickness so that for a suitably limited field of view, the spherical or astigmatic refractive power by transverse displacement, ie a displacement transverse to the optical axis of the system , can be changed. The variable astigmatic lens element is a special anamorphic lens whose cylindrical lens power and cylindrical lens rotation are dependent on the displacement distance and angle of a viewpoint segment on the lens. This lens element may be formed, for example, by two substantially parallel optical boundary layers of corresponding surface form and a transparent optical medium located between the boundary layers.

The human eye, in addition to defocusing and astigmatism, usually also has higher order aberrations, which may appear as wavefront aberrations and may degrade the retinal image and vision performance. The total aberrations of the human eye and any other optical systems today, e.g. with wavefront aberrometers, e.g. with those who work according to the so-called Shack-Hartmann principle. As is known, the total wavefront aberrations can be mathematically broken down into a sum of individual aberration errors by a set of surface basis functions, in particular the Zernike polynomials being used as such a set of surface basis functions.

Aberration errors of lower orders, such as defocus and astigmatism, correspond to refractive anomalies, whereas higher order aberrations tion, such as coma and spherical aberration, can not be compensated or corrected with sphero-cylindrical lens combinations. For the detection of higher-order aberrations according to the Shack-Hartmann principle and for their mathematical evaluation by means of zeron polynomials, see, for example, US Pat. No. 5,777,719 and the publication Liang et al., Optical Society of America 1994, page 1949, directed. The aberrations are subdivided into the different orders, eg, tilt is a first order aberration, defocus and astigmatism are second order aberrations, coma and tristimulus are third order aberrations, and spherical aberration, quadrature, and other higher order astigmatism errors are fourth order aberrations.

One problem with objective measuring instruments is that they only detect monochromatic aberrations and it is not known exactly to what extent the individual higher order aberrations influence the visual impression in humans in the case of white light. A subjective refraction determination of higher order aberrations is not possible by the objective wavefront aberration measurement. Therefore, it can not be clarified with this procedure whether an operative, irreversible correction of the individual higher-order aberrations actually causes an increase in the visual performance of a patient and therefore improves the imaging quality. For the human brain is to a certain extent able to compensate aberrations through learning processes. Thus, an operative correction of such higher order aberration, as would be detected by an objective wavefront aberration measurement, could possibly result in a poorer optical imaging quality postoperatively.

The objective determination of higher-order aberrations is used particularly in patients whose eyes have abnormally strong aberrations, eg due to impairments of optical measurements. such as keratoconus or after keratoplasty. A subjective examination of the objectively determined values is not possible. The conical protrusion of the cornea in keratoconus leads to a significant deterioration in vision, which is characterized by a particularly large number of aberrations and distortions with a deep effect on the optical imaging quality. The refractive peculiarities associated with keratoconus are often referred to as irregular astigmatism, which is equivalent to higher order aberrations, and can not be corrected with conventional sphero-cylindrical ophthalmic lenses. The irregular corneal geometry causes different, constantly fluctuating visual effects. Keratoconus patients are increasingly being supplied with contact lenses in advanced cone that have different geometries and provide different visual effects.

The decomposition of wavefront aberrations into a set of orthogonal rotationally invariant surface basis functions for the purpose of evaluating and classifying the various corresponding aberrations is described, for example, in the textbook by Born and Wolf, Principles of Optics, to which further details in this respect may be referred, in particular with regard to possible representations of such surface basis functions , for example, for Jacobi polynomials, a Gram-Schmid orthogonalization or Zemike polynomials are suitable. Orthogonal functional systems have the advantage that the amplitudes, i. Coefficients that decompose a wavefront aberration function into additive contributions of the individual functions of the area basis function set do not depend on how many functions of the function set are considered. In addition, the associated aberrations can be independently determined and corrected.

The patent DE 101 03 763 C2 describes a method and a device of the type mentioned for subjective determination of higher order aberrations that make use of a decomposition into Zernike polynomials and in which the observation optics comprise a set of individual plates with optically active structures, each corresponding to a particular amplitude of a defined Zemike polynomial. Within the scope of a respective measurement process, for each aberration associated with a particular Zernike polynomial, different plates are introduced one after the other into the observation channel, which belong to different amplitudes of the relevant Zernike polynomial. By subjective comparison judgment then that amplitude correction is determined, which subjectively compensates the relevant aberration subjectively best.

The invention is based on the technical problem of providing a device and a method of the type mentioned, which allow a refraction determination of optical aberrations also higher order with relatively little effort.

The invention solves this problem by providing a device having the features of claim 1 or 3 and a method having the features of claim 9 or 11. According to the invention at least one set of at least one or two optical compensation elements is used, which at the same time in the Observation channel can be introduced and correspond with associated functional components of the aberrations describing Flächenbasefunktionensatzes. In this case, the compensation elements are mutually rotatable or transversely displaceable and chosen so that different total amplitude values of the relevant function component sum can be adjusted by their rotation or displacement.

This has the advantage that for the amplitude correction of a respective aberration already one or two compensation elements be sufficient, which only have to be rotated against each other or transversely shifted to set different amplitude values. This significantly reduces the number of compensation elements needed overall for refraction determination or correction of the various aberrations that occur in practice. After all, one set of only two compensation elements can suffice for each aberration, without the need for different compensation elements for each amplitude value.

In a further development of the invention according to claim 4, the compensation elements are chosen so that can be varied continuously or stepwise in opposite rotation or transversal displacement by appropriate rotating or shifting the associated total amplitude value amount between zero and a maximum value.

In one embodiment of the invention according to claim 5, the optical compensation elements are selected based on a set of orthogonal, rotation-invariant surface basis functions, such as Jacobi or Zernike polynomials. This has the advantage that the correction contributions of different compensation element sets belonging to different aberrations are independent of each other.

In a development of the invention according to claim 6, a respective compensation element set for correcting a corresponding aberration includes a pair of mutually rotatable or transversely displaceable compensation elements, each formed according to a combination of an odd and a straight component of the selected surface basis functions with single amplitude values of opposite sign. By appropriate angular orientation of their axes or location-dependent shaping then the total amplitude value in its amount by turning or transversely shifting the two compensation elements continuously between zero and the sum of the amounts of the individual amplitude values are changed.

In a further development of the invention according to claim 7, the at least two compensation elements are selected so that their associated function component sum of the same order of the surface basis function set is how their individual functional components and different total amplitude values are adjustable by mutual rotation. Thus, e.g. when using Zernike polynomials by combining two non-rotationally symmetric compensation elements of the same order an adjustable in its amplitude compensation element of the same order can be modeled. The further developed according to claim 12 method corresponds to such an approach.

In a further development of the invention according to claim 8, the at least two compensation elements are selected so that by mutual transverse displacement their Funktionskomponentensumme of other, e.g. lower order of the surface basis function set is how their individual function components and different total amplitude values are adjustable. In the case of Zernike polynomials, it is in particular also possible to model a rotationally symmetrical optical compensation element with adjustable amplitude of two mutually transversely displaceable asymmetric optical compensation elements. The further developed according to claim 13 method corresponds to such an approach.

In one embodiment of the inventive method according to claim 14, a plurality of compensation element sets for compensating a plurality of associated aberrations are inserted into the observation channel simultaneously or by successive addition in succession. introduced. This realizes a measuring process within the scope of the refraction determination, in which several aberrations can be detected and compensated without having to exchange compensation elements in the observation channel.

Advantageous embodiments of the invention are illustrated in the drawings and will be described below. Hereby show:

1 is a schematic perspective view of a pair of oppositely rotatable compensation elements for correcting a particular aberration in the context of a subjective refraction determination,

FIG. 2 shows a perspective view of two pairs of compensation elements arranged one behind the other in an observation channel, which correspond in each case to the functional principle illustrated in FIG. 1 for correcting each associated aberration, and FIG

Fig. 3 is a schematic perspective view of a single compensation element for a further embodiment of the invention.

1 schematically illustrates a pair 1 of optical compensation elements 2, 3, also referred to below as test lenses, which are suitable for the correction or compensation of an associated aberration in the context of a subjective refraction determination. The pair of test lenses 1 is part of an observation optics and can be introduced into an observation channel of the same. The observation optics includes, in addition to the shown further pairs of test lenses for compensation of other associated aberrations. Moreover, the associated device for subjective refraction determination of a conventional structure and includes, as needed, other conventional components, which requires no further explanation here. The provision of the test lens pairs in this example is based on a decomposition of wavefront aberrations according to the known zernike polynomials Z _n , _m in any known form of representation, for example the representation chosen in the mentioned textbook by Born and Wolf. Any wavefront aberration W (p, θ) can accordingly be represented in polar coordinates (p, θ) as the sum of the individual orthorormal Zernike polynomials Z _n , _m (p, θ) as follows:

In this case, the index n indicates the ordinal number of the Zernike polynomial in the radial direction, while the index m indicates the frequency of the angle θ per 360 °, non-zero values resulting only in the condition that nm is even. Zemike polynomials with even index n and the value zero for the index m are always rotationally symmetric, all others are asymmetric and angle dependent. A positive value for the index m represents the change in an x direction and a negative value one in a y direction of a Cartesian xyz coordinate system. The individual Zernike polynomials are known to be associated with a particular aberration, respectively, and the coefficient c _Thus , _n , m in the above decomposition describes the contribution of the respective aberration to the wavefront aberration W. Since the Zernike polynomials form an orthonormal set of functions in the unit circle, the individual coefficients c _n , _{m are} independent of the polynomial decomposition length. In a special known representation, the Zernike polynomials are distinguished by even and odd polynomials which are the shape

Z _n - ^m (p, θ) = R _n ^m (p) sin (mθ) Z _n ^m (p, θ) = R _n ^m (p) cos (mθ) that is, they can be represented as the product of a pure radial function R _n ^m (p) with the pure angular function sin (mθ) or cos (mθ), where the radial function R _n " ¹ is nonzero only for even differences of nm and in In this case, it can be represented by a sum of polynomials of the variable θ.

Based on such Zernike decomposition of the possible wavefront aberrations, the pairs of test lenses are chosen such that each pair of test lenses compensates for an associated aberration. In other words, the test lens pairs corresponding to the Zernike functions with the running indices n and m are selected for correcting an associated aberration of order X and are therefore also referred to hereafter as [X (n, m)] test lens pairs. In an advantageous choice of test lens, the two test lenses 2, 3 of the respective [X (n, m)] test lens pair 1, as shown schematically in FIG. 1, correspond to a combination of one odd and one even component of the orthonormal Zernike Polynomials, ie the minus and plus components of the same, as follows:

a- [C _nrm Z _n, - _m (p, θ) + C _{n, n m} Z, _m (p, θ)] - b- [C _{n. m} Z _n , -m (p _I θ + π / m) + C _n , _m Z _n , _m (p _l θ + π / m)],

wherein they have individual amplitude values a, -b, which have opposite signs and can be the same size or different in size, and are arranged offset in their axial position by the angle π / m to each other. As can be seen directly from the above relationship, the total amplitude value resulting for the [X (n, m)] pair of test lenses 1 can be varied continuously from zero to a maximum value corresponding to the sum of the individual amplitude values by the two test lenses 2, 3 are synchronously rotated by equal angular amounts in opposite directions. Specifically results for a maximum angle of rotation α of ± π / (2 m) and a relative Achswinkel- would be π / m a total amplitude value of zero. This position of the test lenses 2, 3 is illustrated in FIG. 1 by means of corresponding positions 5, 6 of a respective marking or handling pin for the respective test lens 2, 3. The maximum total amplitude value, which corresponds to the magnitude sum of the maximum individual amplitude values of the two test lenses 2, 3, results for a rotation angle α of 0 °, ie for a parallel position of the test lens axes, in FIG. 1 by a coincident angular position of the marker / handling pins 5 ', 6 ¹ illustrated.

Consequently, when the pair of test lenses 1 is introduced into the observation channel of observation optics which extends along an optical axis 4 shown in FIG. 1 in the z-direction, ie parallel to the axis of rotation of the test lenses 2, 3 and perpendicular to their principal planes, may be suitably opposed Rotation of the two test lenses 2, 3 any amplitude amount between zero and the maximum possible value to compensate for the relevant Zernike function Z _n , _m or Z _n . _m associated with aberrations can be achieved. Thus, through the pair of test lenses 1, an infinite base set of individual test lenses with different amplitudes can be generated over the entire amplitude range of interest to produce any wavefront in the unit circle and thus compensate for the aberration of a considered order. In particular, any desired asymmetrical aberration of the relevant order can thus be compensated without explicit consideration of the rotationally symmetric component of this aberration order. At least one Zernike polynomial can have an order greater than two.

The above-mentioned conditions apply to a sufficient approximation as long as the test lenses 2, 3 are arranged sufficiently closely spaced behind one another, ie, in particular for the "thinner" approximation. Lenses. On the other hand, with larger lens pitch deviations can be corrected by one or a few additional correction lens elements.

As is clear from the above considerations, a great advantage of the invention is the fact that from the combination of the two same or similar [X (n, m)] lenses 2, 3 in the form of the lens pair 1 each amplitude strength for each axis position can be set and generated to compensate for a currently considered aberration, ie the number of required test lenses is minimized to two or only a little more per aberration. In addition, the uncomfortable and time-consuming change of glasses in the subjective refraction determination eliminates the need to set different amplitudes, i. Strengths by instead the two test lenses 2, 3 of the lens pair 1 are rotated in opposite directions. Based on the subjective statements of an examined person to his visual perception corresponding changes can be made during an investigation by the opposite rotation of the two lenses 2, 3, until the person examined reaches its best visual acuity with respect to the imaging error.

For this purpose, a corresponding ophthalmological device can be provided as an optometric device for subjective refraction determination, which has the observation optics with the observation channel in which for each aberration such a test lens set with a pair of oppositely rotatable, corresponding with the associated aberration test lenses or compensation elements can be introduced.

Fig. 2 shows schematically and simplifies such an observation channel with an optical axis 10, along the succession more "_

Pair of test lenses can be introduced, of which in FIG. 2 a first pair of test lenses 11 and a second pair of test lenses 12 are explicitly shown as being representative of any further ones. The first pair of test lenses 11 includes two closely adjacent, thin lenses 13, 14 in the manner of Fig. 1, which are rotatable synchronously by equal angular amounts in opposite directions of rotation with a twisting mechanism in the desired manner described above for Fig. 1. The twisting mechanism each includes a sprocket 15, 16, with each of the test lenses 13, 14 is rotatably connected. The sprockets 15, 16 are annular and have on their facing surfaces on a toothing. A thumbscrew with a rotary handle 17 acts as a control element and has a gear portion 18 which is in engagement with the two serrations of the sprockets 15, 16. In this way, a rack and pinion gear is formed, which symbolizes rotation of the operating handle 17 of the thumbscrew, as symbolized by a rotary arrow D, an opposite rotation of the two sprockets 15, 16 and thus with these non-rotatably coupled test lenses 13, 14 by the same angular amounts, such as illustrated with the rotation arrows D1 and D2. Thus, the test lenses 13, 14 continuously between an axis zero position, symbolized by an angle ß relative to a 0 ° orientation, and a maximum rotational position with the angular positions -α and + α synchronously rotated in opposite directions. Optionally, a scale, not shown, is attached to the surface of the sprockets 15, 16, from which the total effect of the current aberration error compensation by the pair of test lenses 11 can be read.

The second pair of test lenses 12 analogously includes two oppositely rotatable with the same adjustment test lenses 19, 20, the only difference from the first pair of test lenses 11 is that the two test lenses 19, 20 to another combination of Zernike polynomials and therefore to a include other aberrations. It is understood that instead of the twisting mechanism shown, the twisted positioning of the respective two test lenses can be effected in any other conventional manner.

Thus, this ophthalmological device allows a subjective refraction determination or correction or compensation of aberrations, which has the advantage that the examined person for each aberration and especially for higher order aberrations by the associated, introduced into the observation channel [X (n m)] - pair of test lenses can compare the uncorrected with the corrected visual impression subjectively. It can thus be determined whether the correction of the individual aberrations and in particular of the higher-order aberrations actually leads to a visual acuity increase and thus to an improvement in the optical imaging quality of the eye. From this point of view, the correction of such aberrations can lead to an improvement in vision and hence in imaging quality, especially in patients suffering from optical pathology.

A particular advantage of the invention is that the different test lens pairs 11, 12 can be arranged simultaneously in the observation channel. Because of their selection on the basis of a set of orthogonal surface basis functions, it is ensured that the test lens pairs 11, 12 arranged one behind the other do not interfere with each other, since they are respectively assigned orthogonal functions. Thus, first, for example, the first pair of test lenses 11 of FIG. 2 may be introduced into the observation channel as a [X (n1, m1)] pair of test lenses for correcting an aberration corresponding to the Zernike polynomials with the indices n1 and m1, and this aberration be optimally corrected by suitable rotation of the two test lenses 13, 14. Subsequently, in Rather, another aberration pertaining to Zernike polynomials with the indices n2 and m2, where n2 ≠ n1 and / or m2 ≠ m1, is by introducing the second pair of test lenses 12 as a [X (n2, m2)] pair of test lenses into the observation channel in front of or behind the first pair of test lenses 11 and suitable opposite rotation of its test lenses 19, 20 can be compensated without this having any interference with the already existing aberration compensation by the first pair of test lenses 11.

By means of the procedure according to the invention for the subjective determination of aberrations including those of a higher order, the examined person is gradually guided to optimally correct the entire aberrations, wherein the individual aberrations can be determined and compensated separately from one another according to the selected set of orthogonal basis functions. It is understood that alternatively, this method and apparatus can also be used for aberration determination in optical devices.

In other words, it is possible to proceed according to the invention for refraction determination as follows. Basically, for each index n from zero to infinity and for each index m from zero to n, with nm straight, a best [X (n, m)] test lens pair is determined, in practice a finite subset of function set indices n, m which provide the relevant contributions to which the other contributions, in particular very high orders, are usually negligible. The [X (n, m)] pair of test lenses is then introduced into a turning device of the type normally used for refraction determination and held ready for the person to be examined. In order to determine the best axial position, a coarse determination is first carried out in the angular interval [0.2π / m] in, for example, the four blind directions [a (π / 2-m)], where a = 0, 1, 2, 3. In each case, a turn survey is made, as for refraction determination known, ie the test lens pair is the investigator first held in the one and then in the 180 ° rotated position. The turning axis, about which the 180 ° turn occurs, corresponds in FIG. 2 to the stem or gear axis around which the rotation with the rotary arrow D takes place. After the rough determination, the exact determination of the best axial position is then carried out by the above-described opposing rotation of the two test lenses 2, 3 of the [X (n, m)] test lens pair 1 with a respective turn survey. This completes the determination of the [X (n, m)] amount of the refraction determination for the selected function set index pair (n, m).

As mentioned above, there is no change in this determined amount when introducing test lenses for other (n, m) function set index pairs because of the orthogonality of the selected function set. It is also possible, as also mentioned above, to store and set several pairs of test lenses for different (n, m) index pairs at the same time.

For the above-described embodiments, two asymmetric (ie m ≠ o) n. Order test lenses were used, the combination of which produces a correspondingly asymmetrical correction element of the same order n whose amplitude is determined by mutual rotation of the two test lenses about the optical system axis between a minimum and a minimum a maximum value can be adjusted. The invention also includes the possibility of two asymmetric test lenses n. Order transversely, ie transverse to the optical axis to arrange slidably, whose individual amplitudes have opposite signs, in generalization of the above to DE 24 12 059 C2 mentioned anamorphic lens element. It can be seen that, for example, with reference to the above Zernike polynomials, by combining two such asymmetrical lens elements of order (n, m) by means of a suitable transverse mutual displacement, a correction element of another order (n ', m') is simulated whose amplitude is e- benfalls continuously adjustable, equivalent to the above-described opposing rotation of the test lens elements used there to the [X (n ', m')] - contribution to the Determine refraction or Achslagebestimmung.

Thus, e.g. when using a test lens pair of the order (3.1) by mutual displacement in the x direction, as symbolized by an arrow Tx in Fig. 1, a correction element of the order (2.0) are simulated by corresponding displacement in the y direction, as symbolized by an arrow Ty in Fig. 1, a correction element of order (2, 2).

Thus, the above-described procedure is possible not only for the aspheric but also for the spherical contributions, i. a corresponding spherical correction element, e.g. is represented by a generalization of the variable spherical lens element mentioned in DE 24 12 059 C2. Combining and appropriate transverse relative displacement of two asymmetric (2n + 1, ± 1) -test lens elements is possible thus simulating a spherical correction element of the Zernike polynomial order (2n, 0), the amplitude of which can be changed continuously for the associated spherical contribution.

In the embodiments described above with reference to Figures 1 and 2, the amplitude can be variably adjusted by using each pair of test lenses, as explained. By the likewise described, coupled turning of the respective lens pair about a turning axis perpendicular to its optical axis, the axial position can be determined. It turns out that a refraction determination for arbitrary orders of a corresponding orthonormal set of functions, such as the Zemike polynomial, is already possible using only one test lens or one compensation element per respective functional component of the underlying surface basis functions. Fig. 3 shows for such an embodiment, a compensation element 30 with stem axis 31, wherein by corresponding conventional means, the compensation element 30 is rotatable about its optical axis and about a turning axis perpendicular thereto reversible. In the following, more detailed explanations are given for the refraction determination with the aid of this compensation element 30, the indices n and m introduced above being used for the underlying surface basis functions, here the Zernike polynomials, and γ = 1807m being a so-called stalk angle and η = 2γ = 3607m being a so-called Marking angle corresponding to provided on the compensation element 30, known per se markers 32 (eg, red / g green / white marks) corresponds.

With a set of preferably several of the elements 30 of FIG. 3 for different amplitudes, it is possible to realize a device for refraction determination of optical aberrations that can be described by a set of surface basis functions, with an observation optical system that has several optical elements (cross lenses) that can be introduced into an observation channel. includes. The observation optics comprise at least one set of at least one optical compensation element which corresponds to associated functional components of the surface aberrations describing aberrations and can be introduced into the observation channel and can also be used for axis position determination by being rotatable about the optical axis and perpendicular to the optical axis Defined axis is reversible, in generalization of the operation of the known cross cylinder. The element forms an X (n, m) lens with variably , -

adjustable amplitude, which is freely rotatable about the optical axis, so that the axes of maximum and minimum amplitude can be aligned parallel to any other axis of refraction perpendicular to the optical axis, and the said, any X (n, m) lens with variably set amplitude perpendicular to the optical axis about defined axes (these are eg in Figure 1 either the stem axis 5 'and 6 ") and an additional axis, which is determined by maximum and minimum amplitudes, is reversible m = 2 corresponds this is a generalization of the well-known Jackson cross-cylinder, for m = 1 it corresponds to a cross-Komalinse.

In the case of the pair of lenses, a Zernike pair of lenses X (n, m) is provided with variably adjustable amplitude, which is arbitrarily rotatable about the optical axis, so that both the axes with maximum and minimum amplitude (that is, for example, in FIG. which passes through the mark (o) and (-)) as well as the axes without amplitude (that is in Figure 3, for example, the stem axis in the stalk angle 1807 (2 * m) according to TABO scheme) parallel to any other, perpendicular to the optical axis can be aligned, and this said, arbitrarily rotated Zernike lens pair X (n, m) with variably set amplitude perpendicular to the optical axis about a defined axis (this is in Figure 3, for example, either the stem axis or the axis through the markings ( 0) and (-)) is reversible. As with the known cross-cylinder (m = 2!), One can then amplify or weaken the amplitude by means of a turn survey, as well as determine the axis position by turning it over, as explained in the text. For example, for a "cruciform three-bladed lens" (m = 3), as indicated in FIG. 3, the two markings (o) according to the TABO scheme would be for a 0.1 at the angle a * 3607 (2 * m) = 0 ^* 360 / (2 * 3) ° = 0 ° and at an angle of 1 * 360 / (2 * 3) ° = 60 °, the two marks (-) at the two angles a * 3607 (2 * m) + 180 °; a? 0, 1). In the individual element 30 of FIG. 3, this forms a Zernike lens Z (n, m) of certain amplitude (in one set several elements 30 of different amplitudes can be used), which is arbitrarily rotatable about the optical axis, so that both the axes with maximum and minimum amplitude (eg, in Figure 3, the axis passing through the mark (o) and (-)) and the axes without amplitude (eg, in Figure 3, the stem axis in the stick angle = 1807 (2 *) m) according to TABO scheme) parallel to any other, can be aligned perpendicular to the optical axis refraction axis, and said said arbitrarily rotated Zernike lens Z (n, m) perpendicular to the optical axis about a defined axis (this is in Figure 3 For example, either the stem axis or the axis by the markers (0) and (-)) is reversible. As with the known cross cylinder (m = 2!) You can then increase the amplitude or weaken by turning survey, as well as by turning survey, as explained in the text, determine the Achslage. For example, for a "cruciform three-blade lens" (m = 3), as indicated in Fig. 3, the two markings (o) according to the TABO scheme would be at a 0.1 angle α * 360 ^o / (2 * m) = 0 * 360 / (2 * 3) ^o = 0 ° and at an angle 1 * 360 / (2 * 3) ° = 60 °, the two marks (-) at the two angles a * 3607 (2 ^* m) + 180 °; a? 0.1).

It should be noted that the eye-glasses system in an eye-refraction determination forms a pair of lenses in which the two optical compensation elements of FIGS. 1 and 2 can be regarded as negative refractive deficit and far-point refraction in the eye and together form an X (n, m). Forming a lens.

Although in the above description of advantageous embodiments, reference has been made mainly to the Zernike polynomials, it is to be understood that alternatively other known orthonormal surface basis functions, such as Jacobi functions, Gram-Schmid orthogonalization or wavelets, can be chosen whose basis is suitable, against each other rotatable compensation elements are provided. Depending on the required behavior with regard to rotations, a respective compensation element can also correspond to only one function term, instead of the above-described additive combination of two function terms, such as a minus and plus component. The preparation of corresponding compensation elements or test lenses results for the skilled person readily from the selected correspondence with the corresponding surface basis functions.

Claims

claims 1. An apparatus for refraction determination of optical aberrations that can be described by a set of surface basis functions, comprising observation optics comprising a plurality of optical elements that can be introduced into an observation channel, characterized in that the observation optics comprise at least one set of at least two optical compensation elements (13, 14 ) which correspond with associated functional components of the surface basis functions describing the aberrations and can be introduced one after the other into the observation channel and are rotatable or transversely displaceable relative to one another to set different total amplitude values of the respective functional component sum. 2. Apparatus according to claim 1, further characterized in that the respective at least two optical compensation elements for Achslagenbestimmung to a predetermined, perpendicular to an optical axis turning axis are reversible. 3. An apparatus for refraction determination of optical aberrations, which are described by a set of surface basis functions, with an observation optics comprising a plurality of optical elements insertable into an observation channel, characterized in that the observation optics comprises at least one set of at least one optical compensation element (30) each corresponding to an associated function component of the surface basis functions describing the aberrations, and into the observation channel and rotatable about an optical axis and about a set, perpendicular to the optical axis turning axis is reversible. 4. Apparatus according to claim 1 or 2, further characterized by means (15 to 18) for rotating or transversely shifting the at least two compensation elements (13, 14) such that the total amplitude value is variable continuously or stepwise between zero and a maximum value. The apparatus of any one of claims 1 to 4, further characterized in that the set of surface basis functions is a set of orthogonal rotation-invariant surface basis functions. A device according to any one of claims 1, 2, 4 and 5, further characterized in that the at least two compensation elements (13, 14) each correspond to a combination of a straight and an odd function component of the set of surface basis functions and have single amplitude values of opposite sign , 7. Device according to one of claims 1, 2 and 4 to 6, further characterized in that the at least two compensation elements are selected so that their associated function component sum of the same order of the surface basis function set as their associated function components, and the total amplitude value of the function component sum is adjustable by mutually rotating the two compensation elements. 8. Device according to one of claims 1, 2 and 4 to 7, further characterized in that the at least two compensation elements are selected so that their function component sum of another order of the Flächenbasisfunktionionssatzes as their associated function components, and the total amplitude value of the function component sum is adjustable by transverse mutual displacement of the two compensation elements. 9. A method for refraction determination of optical aberrations which are writable by a set of surface basis functions, characterized in that at least one set of at least two optical compensation elements (13, 14) is introduced into an observation channel of observation optics, the at least two compensation elements corresponding to associated function components of the aberrations describing area base functions are selected and are successively introduced into the observation channel and rotated to set different total amplitude values of the relevant function component sum against each other or moved transversely. 10. The method of claim 9, further characterized in that the respective at least two optical compensation elements for Achslagenbestimmung be turned by a predetermined, perpendicular to an optical axis turning axis. A method of refracting optical aberrations that are writable by a set of surface basis functions, characterized in that at least one set of at least one optical compensation element (30) is introduced into an observation channel of observation optics, the at least one compensation element corresponding to associated functional components the surface basis functions describing the aberrations are selected and introduced into the observation channel and rotated about an optical axis and then turned around a turning axis for axis position determination. 12. The method of claim 9 or 10, further characterized in that the at least two compensation elements are selected so that their function component sum of the same order of the surface basis function set as their associated functional components, and that the Gesamtamplitu- denwert the function component sum by mutual rotation of the two compensation elements is adjusted. 13. The method according to claim 9, 10 and 12, further characterized in that the at least two compensation elements are selected such that their function component sum is of a different order of the area basis function set as their associated function components and the total amplitude value of the function component sum by transversal shifting of the both compensation elements is adjusted. 4. The method according to any one of claims 9, 10, 12 and 13, further characterized in that a plurality of sets of at least two optical compensation elements for the compensation of different aberrations are successively introduced into the observation channel.