WO1991011697A1

WO1991011697A1 - Device for measuring refractive properties of optical systems

Info

Publication number: WO1991011697A1
Application number: PCT/DE1991/000093
Authority: WO
Inventors: Karl-Heinz Wilms; Adolf Triller
Original assignee: G. Rodenstock Instrumente Gmbh
Priority date: 1990-02-02
Filing date: 1991-02-01
Publication date: 1991-08-08
Also published as: DE4011992A1

Abstract

A device for measuring the refractive properties of optical systems, in particular spectacles glasses or contact lenses, comprises a projection optical system which projects light beams onto a detector arrangement through the optical system under test and through a condensing diaphragm in the immediate vicinity of the optical system or in a plane conjugate with the optical system. The device has a measurement figure consisting of at least two holes. An evaluation unit determines the refractive properties of the optical system under test from the output signal of the detector arrangement. The device of the invention is characterized in that projection optical system projects at least one light beam of rectilinear cross-section, which contains the light rays that intersect the optical axis of the system and whose longitudinal axis makes an angle greater than 0° with the straight lines joining at least two holes in the condensing diaphragm, and in that the detector arrangement has at least one detector line the longitudinal axis of which makes an angle greater than 0° with the longitudinal axis of the light beam of rectilinear cross-section.

Description

- -

Device for measuring refractive properties of optical systems

Description

Technical field

The invention relates to a device for measuring the refraction properties of optical systems and, in particular, of spectacle lenses or contact lenses, in which projection optics light beams over the optical system to be measured and a field diaphragm that are in the immediate vicinity of the optical system or in an optical system System conjugate plane and has at least two holes as a measuring figure, projected onto a detector arrangement, from the output signal of which an evaluation unit determines the refraction properties of the optical system to be measured,

Such facilities are among others used for the automatic measurement of the refractive index, the cylinder effect and the cylinder axis of spectacle lenses or contact lenses and are also known under the name "apex refractive index meter".

State of the art

A known automatic apex refractive index meter, which is used in the formulation of the preamble of patent claim 1, is known, for example, from DE 25 08 611 C2.

Another known automatic vertex refractive index of a slightly different type is the "Auto-Lens eter Topcon CL-1000". In these known automatic apex refractive index sensors, the light from a real light source is transferred via a collimator lens system into a "bundle of light coming from the infinite" which strikes the spectacle lens, whose spherical refractive index and, if appropriate, its cylinder action and cylinder axis are to be determined.

A dot, line or grid mask is arranged in the plane of the spectacle lens to be measured or the contact lens or in a plane conjugate thereto. "After" the mask are two mutually perpendicular sensor lines, which measure the light distribution in two directions, which results from the fact that the quasi-parallel light of the collimator passes over the spectacle lens to be measured and the line or grid mask is projected onto the two sensor lines.

The spacing of the individual grating lines is influenced by the refraction properties of the object to be measured, that is to say, for example, the spectacle lens, so that the optical data of the spectacle lens, such as spherical refractive index and, if appropriate, cylinder action and cylinder axis, are determined by measuring the light distribution on the individual sensor lines can.

A disadvantage of the known automatic vertex refractive index meters and in particular of the device known from DE 25 08 611 C2 according to the preamble of patent claim 1, however, is that not only the distance of the individual projected is due to the refraction properties of the optical system to be measured Lines is changed, but also the position of the lines on the detector arrangement relative to the respective lines of the field diaphragm is rotated (see also FIG. 4 of DE 25 08 611 C2). The angle of rotation is in a comparatively complicated relationship with the refraction properties of the optical system to be measured. As a rule, the projected lines run obliquely to the individual lines of the detector arrangement. This grazing position of the projected grating lines on the detector arrangement, which moreover changes from spectacle lens to spectacle lens depending on its optical data, results in a comparatively large error in the determination of the distance between the projected grating lines and thus in the calculation the optical data.

In US Pat. No. 4,281,926, an apex refractive index has been proposed, in which the problem of grazing incidence of the projected grating lines on the detector arrangement is avoided by moving the detector, the construction of these apex refractive index types other than in the preamble of However, provided claim 1 is comparatively complicated due to the moving detector arrangement.

Furthermore, the known devices for measuring the refraction properties are essentially intended to determine the spherical refractive index of one- or two-strength glasses. The device known from DE-OS 36 29 676 for measuring the refractive properties of spectacle lenses can also be used to determine the so-called near-peak refractive index.

Only from DE 29 34 263 B2 is a method and a device for automatically measuring the peak refractive indices in the main sections of toric lenses known. Tion properties with all known devices for ^"measuring the Refrak¬ but it is very complicated, spielsweise so-called progressive lenses, so lenses, in which the refractive index changes continuously from the so-called remote value for so-called Nahwert to measure. It should be noted that it often happens in daily practice that unknown spectacle lenses have to be measured, that is to say spectacle lenses in which the position of the far and near reference points and the length and position of the so-called progression channel are not known.

In addition, the known devices for measuring the refraction properties are in practice not suitable for measuring small optical systems with high refractive indices, such as contact lenses.

Presentation of the invention

The invention is based on the object of specifying a device for measuring refraction properties of optical systems with a fixed detector arrangement, in which a precise determination of the refraction properties of the optical systems to be measured is possible.

In addition, the device according to the invention for measuring the refraction properties of optical systems should be able to be designed such that even more complicated optical systems, such as aspherical optical systems and in particular progressive glasses or contact lenses, can be measured.

An inventive solution to this problem is characterized in the claims. The invention is based on the basic idea of not using a parallel light beam as in the prior art, for example according to DE 25 08 611 C2 or DE 29 34 263 B2, but at least one beam with a "linear or straight line "Cross-section, ie to project a light beam, which emanates from a linear gap in the vicinity of a collimator lens system, via the optical system to be measured and the field diaphragm onto the detector arrangement.

The field diaphragm has at least one row of holes. In this case, a row of holes is understood to mean an arrangement of holes which are arranged along a straight or curved line. The connecting line of the holes arranged along a straight line (also referred to as the longitudinal axis) or the “middle line through the hole arrangement” includes an angle with the “straight line” beam. The individual holes in the row of holes thus act as "pinhole cameras", through which an image of the beam with a rectilinear cross section is projected onto the associated sensor line. The individual line images on the sensor line are thus rotated by a maximum of a few angular degrees due to the optical properties (refraction properties) of the optical system to be measured; the optical properties of the system to be measured thus influence practically only the distance between the individual projected line images.

Here, a beam with a linear or rectilinear cross section and accordingly a "line image" is understood to mean a beam or an image in which the dimensions in one direction are substantially larger than the dimensions in the direction perpendicular thereto. The dimensions in the "direction transverse to the line length" need not be "infinitely small", but only so small that a sufficiently precise determination of the position of the projected beam on the sensor line is possible. If the sensor is able to determine focal points of light spots, the “projected line” can be comparatively wide.

It is sufficient if the row of holes used according to the invention consists of two holes. However, the use of more holes, for example three or more, preferably seven holes, enables the optical properties of the system to be measured to be determined redundantly or to be centered over several determined line spacings, and thus the accuracy increase the measurement.

In any case, it is particularly advantageous if the longitudinal axis of the beam bundle includes a 90 ° angle with the row or rows of holes assigned to it and the associated detector row; as a result, the line images lie perpendicular to the axis of the respective sensor line, so that their position can be determined precisely.

To measure spherical, optical systems, for example spherical spectacle lenses, it is sufficient to use a beam of rays with a straight cross section which is projected onto the sensor line via the optical system to be measured and at least one row of holes.

In order to also be able to determine a possible cylinder action and the axial position of the cylinder axis of the optical system to be measured, however, it is in accordance with Claim 3 required to use at least two beams, each with a straight cross-section, the "strokes enclose an angle"; these bundles of rays are projected onto at least two rows of holes, which likewise enclose an angle, onto two detector or sensor lines or a detector array.

When using two beam bundles, each with a straight cross-section, it is advantageous if the longitudinal axes of the two beam bundles form an angle of 90 ° both with one another and with the connecting straight line of the assigned row of holes in the field diaphragm and the longitudinal axis of the assigned detector line (Claim 4).

In order to increase the measuring accuracy, in particular in the case of cylindrical values of the optical systems to be measured, that is to say, for example, of the spectacle lenses introduced into the beam path, it is also particularly advantageous according to claim 5 to provide two rows of holes which are parallel to one another for each beam bundle and which according to claim 6 are preferably arranged symmetrically to the optical axis of the device.

When using two beams with a rectilinear cross-section, which can in particular include an angle of 90 °, it is generally necessary to take measures to ensure that the detector lines are not overexposed by the light of the beam bundle not assigned to them ( Claim 8). Such measures can consist, for example, of using polarized light or light of different wavelengths. A particularly advantageous implementation of the means for preventing overexposure is given in claim 9:

The two rectilinear light beams required to measure the cylinder effects and prismatic displacements of an optical system are projected alternately in time in a multiplex process. If the time sequence is sufficiently fast, the projection lines appear on the sensor field almost simultaneously and can be evaluated together. It is particularly advantageous if the light paths of the individual light beams are spatially separated from one another and are projected onto separate sensor planes after passing through the same area of the measurement object. This considerably simplifies the evaluation of the line fields generated by the separate light beams. In order to avoid undesired superimposition of the line images and incorrect assignments of the light beams, the holes in the two diaphragms are arranged, for example, on arcs. According to claim 12 the desired holes sequences are opened by means of a suitable rotating disc sector at the right ^'time or covered. The different light paths are released by a sector mirror.

In any case, the device according to the invention has the advantage that by using linear light bundles as radiation sources on the sensor level, line images are generated, from whose distances the optical properties of the system to be measured can be determined. Since the measuring lens affects practically only the distance between the projected line pictures and their position rotates at most a few degrees, the measurement is carried out solution by simple distance determinations. The two-dimensional detection of the measuring point coordinates required in known systems is eliminated.

The device according to the invention thus enables the refraction properties of optical systems to be determined particularly easily and quickly and can be used in particular by the optician to determine the refractive power of spectacle lenses.

Another advantage of the device according to the invention is that the hole arrangement in the field diaphragm only has to have small dimensions, so that the device is also suitable for measuring multifocal glasses and contact lenses.

It is particularly advantageous here if, in accordance with the device for measuring the refraction properties of spectacle lenses described in DE-OS 36 29 676, the glass support for the spectacle lens to be measured is designed to be pivotable, so that the optical properties of additional parts, for example of seam parts can be measured. If necessary, further systems can be provided in the beam path, around the beam or beams with a rectilinear cross-section once "from infinity" for the determination of the long-distance refractive index and once from a "finite distance" for determining the near-end refractive index to project.

In order to determine the optical properties, in particular of progressive glasses, the invention is based on the basic consideration that it is relatively easy to determine the so-called far viewpoint in the case of an unknown progressive glass. Marked for this the ophthalmologist or optician determines the pupil position on the left or right glass. A measurement of the peak refractive index in this area yields the effective refractive index, if not perhaps the one specified by the manufacturer.

The addition and thus the near refractive index could then be measured by a straight displacement of the lens along the main line of sight.

In practice, however, it is very difficult for the optician or ophthalmologist to just move the spectacle lens on the glass surface. As a rule, it will accidentally deviate from the progression channel to the left or right; At these points, however, the properties of progressive spectacle lenses result in erroneous measurement results.

In addition, he can hardly determine the maximum refractive index gradient, since he generally has no association between the measured values and the "displacement distance".

According to the invention, the evaluation unit therefore determines the displacement of the glass from the changes in the prism components and the refraction values measured at a specific location.

This embodiment according to the invention makes it possible, in particular, to indicate on a display unit, for example a monitor, whether a lateral displacement, ie a direction perpendicular to the progression, also occurs when the spectacle lens is displaced along the progression channel. In addition, according to claim 15, a combined switching device can be present which, in a known manner, initially contains two buttons in the contact strip of the device, which are actuated when the spectacles or the spectacle rim are put on, so that the evaluation unit recognizes whether a " right or left "glass should or will be measured.

In the case of conventional apex refractive indexes, a very specific type of spectacle system - usually systems with a lower frame edge - is mandatory so that the assignment to the "right or left" side and the top and bottom of the glasses is given and thus the axes or base positions or directions of prismatic effects - but also the direction of progression of progressive lenses are displayed. A change is not planned. Curiously, it is not possible with the known refractive index gauges then to use the graded arc division determined by the Technical Committee for Glasses Optics (TABO) - which suggests that the glasses should be placed with the upper frame edge.

According to the invention, this is remedied by the combined switching device (claim 15) in that it enables the switchover to the desired form of glasses by means of an additional switch on the front of the device. The selected type of plant is z. B. a symbol, consisting of system bar and stylized Brillenfas¬ solution, shown on a display device, such as a screen.

Accordingly, the evaluation unit is able to determine the distance through the so-called progression channel of a sliding lens and the so-called internal concentration, ie the shift in the direction of the nose to pretend correctly.

Since the main line of sight is displaced nasally due to the convergence of the eyes in the near area, the evaluation unit can thus give the operator a signal that they now have to shift the eyeglass lens typically 2 to 3 mm nasally.

In addition, the features specified in claim 16 make it possible to determine the vertex refractive indices of optical systems with exceptional optical properties and, in particular, also to measure contact lenses and intraocular lenses. Since contact lenses often have aspherical and in particular elliptical matching surfaces, the evaluation unit takes into account any asphericalities when calculating the refraction properties.

According to the definition, the vertex refractive index means the paraxial vertex refractive index for a certain wavelength. This applies equally to glasses and contact lenses. Since the monochromatic (spherical) aberration is very small in spectacle lenses, no further reference is made to this in standardization. In the case of contact lenses, however, the monochromatic aberration is considerably greater as a result of the strong deflection in order to adapt to the cornea. For this reason, a distinction is made in DIN 58233, T2 between the paraxial power S '- which is not of interest in practice - and the "use" power S *, which is used when measuring with conventional power refractive indexes (Ein¬ view and pro ection SBM). Depending on the illumination of the measuring field, which is deliberately kept smaller in the KL measurement (3.5 - 4.5 mm), about 30 - 35% of the monochromatic longitudinal aberration is included in the measurement result, which is generally accepted to this day. This is taken into account in the manufacture of the contact lens, but is not discussed further.

With automatic apex refractive index meters one does not have a fully illuminated measuring field, but rather a certain number of "Scheiner-openings" which are always arranged off-axis. Thus the non-abrasion-free center of the measured material is not detected at all, but only next to this part of the strongly bent lens. From this it can be explained that there are strong deviations of the apex refractive indices from the accepted use apex if the increased monochromatic aberration in the area of the detection points is not taken into account.

The magnitude of the increased aberrations can e.g. for contact lenses with apex refractive indices between plus and minus 15 dpt

S = a * S _M * H ² + k (dpt)

describe where

a = 0.01 and

H = half the distance between the opening of the measuring mark

S _M = the uncorrected measured value

is. For lenses with higher refractive indices applies with good approximation

S = a ² * S _M 2 * H ² (dpt) Only when the relative monochromatic aberration of the contact lens (comparison with the conventional vertex) has been determined and this has been correctly compensated for before the diopter values are output, can a sensible measurement possibility for contact lenses be obtained.

The different types of contact lenses do not cause any problems on the conventional apex, which is why there is no need to make a distinction there.

This is quite different in the case of an apex refractive index of the type specified in the preamble of claim 1. Unevenness of the surfaces (in particular in the case of soft “lenses”) but also asymmetries in the image that occur with decentration have a very strong influence on the measurement result and can provide real false reports.

Depending on the type of contact lens, the position of the threshold when scanning the signals must be relocated (raised) in order to avoid the signal sediment (noise).

In the case of soft, hydrophilic lenses, the routine measurement even dispenses with the specification of the cylinder measured value and only outputs the equivalent refractive index.

Depending on the type of lenses to be measured, different measuring and compensation areas in the evaluation unit are to be addressed.

It must be specific

Ersε a) the location of the detection threshold b) the arrow height error c) the rel. monochrome Aberration d) the output of the values depending on the lens type

be taken into account.

According to the invention, this is achieved by exchanging the glass cover for spectacle lenses for one for the special systems. A signal thus triggered on sensors in the receptacle of the glass support addresses the special area of the evaluation unit, as a result of which selection buttons on the front of the device are activated and switchover to very specific correction areas of the evaluation unit.

Brief description of the drawing

The invention is described below by way of example without limitation of the general inventive concept on the basis of exemplary embodiments with reference to the drawings, to which reference is expressly made with regard to the disclosure of all details according to the invention not explained in more detail in the text. Show it:

1 is a schematic, three-dimensional representation of a device according to the invention,

2a shows the projection of a rectilinear beam onto the sensor plane with a spherical measurement object,

2b the projection of a rectilinear beam onto the sensor plane with a cylindrical measurement object,

3 shows a schematic representation of a device according to the invention with spatial separation of the light path of two rectilinear light beams,

Fig. 4 shows the arrangement of the holes on an aperture for a Device with separate light beams,

5 the projection of a light beam extended in the cylinder direction onto the sensor plane,

6a shows the course of a parallel beam path behind a converging lens,

6b the components of the prismatic effect of a spherical glass,

Fig. 7 shows the relationships in a toric effect, and

8 shows the calculation for a progressive lens.

Representation of exemplary embodiments

Fig. 1 shows schematically the basic structure of a device according to the invention. The light from a light source 1, preferably a halogen lamp, is transmitted through a collimator 2, which is shown as a single lens in the schematic representation in FIG. 1, via an optical system L to be measured, for example a lens or a spectacle lens, and a field stop _. 17, which is arranged in the immediate vicinity of the optical system L or in a plane conjugate to the optical system L, is projected onto a detector plane 21.

A diaphragm 8 is arranged in the focal plane of the collimator 2 and, in the exemplary embodiment shown, has the shape of a split cross, so that it has a horizontal and a vertical light bundle 32 with a straight line (not shown in FIG. 1 for the sake of clarity) Cross section created, both of which seem to emanate from an infinitely located slit-shaped light source and both intersect the optical axis. With 7 a field lens is designated, which is arranged adjacent to the diaphragm 8.

Ers saattzbl The field diaphragm 17, which is attached in FIG. 1 in the immediate vicinity of the lens L, has two pairs of parallel rows of holes a, b, c and d which, in the exemplary embodiment shown, each consist of three holes which are composed of one another extend in the x direction or in the y direction.

For the following description of the principle according to the invention, only the vertical light bundle 32 is considered and it is assumed that only the holes of the rows of holes a and b of the field diaphragm 17 are open. Each aperture hole acts as a pinhole camera and images the slit-shaped light source as lines -.-. A- and b -... b ₃ on the sensor level 21. Cellular sensors 21 and 21, for example CCD line sensors (Charge Coupled Device) are arranged on the sensor plane 21 in the x direction and in the y direction, of which only the sensor arranged in the ir x direction is shown in FIG. 1 and which allow the distance between the lines to be determined.

An evaluation unit (not shown) determines the refraction properties of the optical system to be measured from the distance between the lines. This will be briefly explained in the following:

2a shows the images that arise during the measurement of a spherical measurement object L on a sensor line 21 or 21. The line images produced by the two corresponding rows of holes a and b or c and d flow into one another. The refractive power of the measurement object L can be calculated from the (known) distance between the end holes and the distance between the lines P. 2b shows the line images which are caused by a cylindrical lens L, the cylinder axis of which includes an angle # 0 ° and # 90 ° with the x and y direction. In this case the lines are a-, a ₂ , -> and b ,. .

, b., the corresponding rows of holes a and b of the diaphragm 17 shifted against each other. The distance between the lines and the displacement of the lines δ represent a measure of the optical properties of the measurement object, ie of the spherical effect and the cylinder effect. In order to completely record the data of the measurement object, a further measurement with that not shown in FIG. 1 must be carried out. horizontal light beams and the corresponding, arranged in the vertical row holes of the rows of holes c and d in the aperture 17 are made. These values are recorded with the line sensor 21 in the vertical direction.

When using two beams with a rectilinear cross section, which in particular - as shown in Fig. 1 - can enclose an angle of 90 °, it is usually necessary to take measures to ensure that the detector lines arranged at an angle are not affected by the light of the each beam beam that is not assigned to it is outshone.

3 shows an embodiment of the device according to the invention in which the light paths of the two rectilinear light beams are spatially separated in order to avoid overexposure and the measurement is carried out using a multiplex method.

The light from the radiation source 1 is again projected by the condenser 2 to a field line 3 ^{'densorfläche} the con- on the entrance surface of a fiber rod 4 depicts. After bundling through a lens 5, the light emerging from the fiber rod 4 strikes a rotating sector mirror 6. The sector mirror 6, which consists of a half mirrored glass pane, alternately releases the light paths x and y. The two light paths are brought together with the aid of deflecting mirrors 9x and 9y and a beam splitting cube 10 in front of the measurement object L, for example an eyeglass lens. For both light paths, a slit diaphragm 8x and 8y is arranged behind field lenses 7x and 7y in the focal plane of the collimator 11. Seen from a support 12 for the measurement object L, the slits of the slit diaphragms 8x and 8y appear as two perpendicular radiation sources which are perpendicular to one another and which are infinite.

A filter 13 limits the spectral range to a predeterminable range of values. A deflecting mirror 14 directs the light beams onto a lens 15, which images the plane of the measurement object L onto the plane of the diaphragms 17x and 17y. In this embodiment, in contrast to FIG. 1, the perforated diaphragms 17x and 17y are arranged in a plane conjugate to the measurement object L.

The division prism 16 (Köster prism) provides for the renewed spatial separation of the light beams which are perpendicular to one another. After passing through the diaphragm 17x and 17y, the separate light beams hit two prisms 18x and 18y, which ensure that the line images imaged on the sensor levels 21x and 21y hit the central areas of the line sensors in the absence of the measurement object L.

The arrangement of the holes a'-, a ', and a' ₃ and b ¹ -, b ' ₂ and b' ₃ on the aperture 17x and the corresponding one The position of the line sensor 21x is shown in FIG. The diaphragm holes a '-, a' ₂ and a ' ₃ and b', b ' ₂ and b' ₃ are arranged on arcs symmetrically around the optical axis. The aperture 17y corresponds to the aperture 17x, but is rotated by 90 °.

In order to avoid undesired overlapping of the line images and incorrect assignments in the light bundles, the corresponding aperture holes are exposed or covered by the rotating sector disk 19. The rotation of the sector mirror 6 to release the respective light bundle and the opening of the corresponding aperture holes through the sector disk 19 are synchronized with the aid of a light beam switch or with Hall sensors. A typical duration of a complete cycle is approximately 60 ms.

Since each aperture hole designs a line image, six "light lines" strike each line sensor, which are shown for the sensor 21x in FIG. The lines a .., a ... correspond to the aperture holes 1, 2, etc. of the row a. The distances, such as Ix, Δ ₁₃ , Δ ₂ USW. are dependent on the refractive index and on the position and size of the cylindrical values of the test object. The distance P of the center point M from the origin of the coordinate is directly proportional to the prismatic effect of the measurement object L and thus, for example, to the decentration of a spherical single-lens. The evaluation unit (not shown), which can have a microcomputer circuit, for example, calculates the optical properties of the measurement object L from the measured distances.

In the exemplary embodiment described there are only three holes in each to simplify the illustration Row of holes shown. However, the measurement accuracy is increased by using a larger number of holes, for example seven holes in each row of holes, the holes in the four quadrants as a whole also being able to be arranged on an arc.

In the following, further developments of a device according to the invention for measuring the refraction properties of optical systems are described, which are particularly suitable for measuring complicated measurement objects L, such as multifocal lenses, progressive spectacle lenses and / or contact lenses.

For a general explanation of the terms and considerations used below, the course of a parallel beam behind a converging lens with the refractive index S 'is shown in FIG. 6a. The deflection of the beam from its original direction is called the prismatic effect P; the corresponding equation P = cx S ¹ is generally known. The inversion c = P / S 'forms the basis for the determination of lateral displacements of progressive lenses described below.

6b shows the components of the prismatic effect of a spherical glass in an x, y coordinate system, the origin of which lies in the optical center of the glass. Is the measuring point z. B. at point B, the path components xb, yb of the decentering result in a simple manner from the measured prism components Px, Py and the vertex power S 'of the glass. If a prism is superimposed on the glass, the optical center can of course also lie outside the glass edge. What is of interest here is not so much the position of the optical center but the fact that the relationships between prism ma P, vertex refractive index S ¹ and radiation penetration point B are linear.

xb = - Px / S '; yb = - Py / S '(1)

The following also applies to spherical lenses:

δ (xb) = -δ (Px) / S '; δ (yb) = -δ (Py) / S '(2)

The relative path coordinates of a displacement of the measuring point B can thus be calculated from the changes in the prism components and the peak power.

The formulas 1 and 2 also apply to the usual toric glasses, but the math is much more complicated here.

A toric glass is characterized by the dependence of the apex refractive index on the azimuthal direction, the difference between the extreme values S'u and S'v is referred to as the "cylinder effect".

These extreme values are symbolized in FIG. 7 by the axes u and v, which can be thought of as the axes of crossed cylinders with the corresponding refractive indices.

The coordinates xb, yb of the decentered point B are first to be calculated from the measured values of the prism Px, Py, the "main cutting values" S'u, S'v and the azimuthal orientation "axis" α.

Px = Pxu + Pxv; Py = Pyu + Pyv (3)

Px = Pu x cosα - Pv x sinα; (4) Py = Pu x sinα + Pv x cos; (5)

Pu = ü x S'v; Pv = vb x S'u (6)

Using the transformations u = x * cosα + y * sinα (7) and v = y * cosα - x * sinα (8)

you finally get:

Px = S'v * cosα (xb * cosα + yb * sinα) -

S'u * sinα (yb * cosα - xb * xinα); (9)

Py = S'v * sinα (xb * cosα + yb * sinα) +

S'u * cosα (yb * cosα - xb * sinα); (10)

Px = xb (S'v * cos 2α + S'u * sin2α) + yb (S'v * sinα * cosα - S'u * sinα * cosα); (11)

Py = xb (S'v * sinα * cosα - S'u * sinα * cosα) + yb (S'v * sin ² α + S'u * cos ² α); (12)

With the abbreviations

Cl = S'u * sin ² α + S'v * cos ² α; (13)

C2 = S'u * cos ² α + S'v * sin ² α; (14)

C3 = (S'u - S'v) sinα * cosα; (15)

('Cylinder' C = S'u - S'v)

finally the coordinates xb, yb of the decentralized point B are obtained as a function of the prism and the peak refractive power: xb = (Py * C3 + Px * C2) / (S 'u * S'v); (16) y _ = (Px * C3 + Py * Cl) / (S 'u * S'v); (17)

The path s between the penetration points B1 and B2 (FIG. 8a) can thus be easily calculated from the differences xb2-xbl, yb2-ybl, but the glass must not be twisted.

The above derivations apply to spherical or toric glasses. In the case of progressive spectacle lenses in which the refractive index and the surface astigmatism on the progressive surface change significantly, at least in the progressive zone, the values S'u, S'v and the axis α are a function of the piercing point B (xb, yb ).

The formulas 16 and 17 apply only in point B. Since an optical center can no longer be defined, a differential approach must be adopted.

In the practical application of the theoretical results, one does not need to start with differential quantities. In the immediate vicinity of B, the formulas 16 ... 19 with the vertex powers S'u, S'v and the axis α apply. With small changes δ (Px), δ (Py) of the decentration (FIGS. 8b, 8c), the refractive indices may initially be regarded as a constant, so the associated path changes δ (xb) and δ (yb) according to 18 and 19 calculate. Since the current values Px, Py, S 'and α are continuously available in automatic apex refractive index meters, one could also calculate the path from B to B * with the data from B' and thus, by averaging both results, the measurement accuracy clearly improve. The permissible maximum distance δ (s) of points B depends on the required accuracy of the distance measurement. For permissible deviations of the order of magnitude of 1 mm, δ (s) max can be set at approx. 4 mm.

It should be noted that the coordinates of the path determination refer to the fixed coordinate system of the device, not to that of the glass.

If in the formulas 16 to 19 the denominator becomes zero, since the two main average values are zero, a case distinction must be made, but this will not be dealt with here.

In addition to this path measurement, the near reference point can also be determined using a customary so-called tabo degree arc scheme based on the prism components measured at each point and the refractive values measured at each point. This determination can serve to check the determination of the near reference point on the basis of the measured refractive values.

With the device described, it is possible to carry out the path measurement using the inverse tabo-degree curve scheme.

Claims

Patent claims

1. A device for measuring the refraction properties of optical systems and in particular glasses or contact lenses, in which a projection lens (2) Lichtbün¬ del (32) over the optical system to be measured (L) and a field diaphragm (17) in the immediate vicinity of the optical system or in a plane conjugated to the optical system and having at least two holes as the measurement figure, projected onto a detector arrangement (21), from whose output signal an evaluation unit determines the refraction properties of the optical system to be measured, characterized in that that the projection optics (2) are designed in such a way that they project at least one light bundle (32) with a rectilinear cross section, which contains light rays intersecting the optical axis of the system, and its longitudinal axis with the connecting straight line of at least two holes in the field diaphragm (17) includes an angle not equal to 0 °, and that the D Detector arrangement (21) has at least one detector line (21x, 21y), the longitudinal axis of which includes an angle unequal to 0 ° with the longitudinal axis of the light beam with a linear cross section.

2. Device according to claim 1, characterized in that the longitudinal axis of the Lichtbün¬ dels with a straight cross section with the Verbindungsgera¬ the or the central connecting line of the holes in the field diaphragm and the longitudinal axis of the detector line includes an angle of 90 °.

3. Device according to claim 1 or 2, characterized in that for the determination of the cylinder effect and axis of the optical system to be measured, the projection optics have at least two light beams, each with a rectilinear cross-section, which include an angle un¬ equal to 0 ° projected at least two rows of holes on at least two detector rows or a detector array.

4. Device according to claim 3, characterized in that two light beams, two rows of holes and two detector lines are provided, each including a 90 ° angle.

5. Device according to one of claims 1 to 4, characterized in that in order to increase the measurement accuracy each light beam is assigned a pair of hole rows spaced from the optical axis.

6. Device according to claim 5, characterized in that the mutually assigned rows of holes have the same distance from the optical axis.

7. Device according to one of claims 1 to 6, characterized in that each row of holes has at least three, preferably seven holes.

8. Device according to one of claims 3 to 7, characterized in that means are provided which prevent the light beams from outshining the detector line not assigned to them.

9. Device according to claim 8, characterized in that the light beams are projected one after the other in time in a multiplex process.

10. The device according to claim 9, characterized in that means for separating the light paths of the individual light beams are provided in the light path.

11. The device according to claim 10, characterized in that a diaphragm is provided for the separate light beams, which has two sequences of at least three, preferably seven holes arranged on a circular arc symmetrical to the optical axis.

12. The device according to claim 10 or 11, characterized in that a rotating sector mirror are provided for alternating release of the light paths and a rotating sector disk are provided for opening or covering the aperture openings.

13. Device according to one of claims 1 to 12 or according to the preamble of claim 1, characterized in that for the measurement of the refraction properties of so-called. Progressive spectacle lenses which are displaced via the measuring point, the evaluation unit the displacement of the lens from the changes the prism components and the refractive indices.

14. Device according to claim 13, characterized in that the evaluation unit shows a lateral displacement and the direction of the displacement on a display unit.

HE _SAT ZBLATT

15. Device according to claim 13 or 14, characterized in that a combined switching device with switch is provided which actuates a spectacle frame with a glass ring (rim of the frame) of the glass not being measured, so that the evaluation unit recognizes whether a "left" or right "glass is measured, depending on the selected type of glasses system - according to a tabo-degree curve or inversely (rotated 180 °) - and displays the selected type of system on the display device.

16. Device according to one of claims 1 to 15 or according to the preamble of claim 1, characterized in that a signaling device is integrated which, by changing the glass support and additional selection buttons, informs the evaluation device that certain of the geometry of the measuring mask (Measurement spot) when measuring high refractive indices of small optical systems, such as contact lenses or intraocular lenses, aberrations and asymmetries that occur should be compensated in a specific way.

17. Device according to one of claims 1 to 16 or according to the preamble of claim 1, characterized in that the measuring spot for measuring klei¬ ner optical systems such as intraocular lenses can be reduced and the evaluation unit takes into account any asphericity in the calculation of the refraction properties .