CH664888A5 - DEVICE FOR EYE EXAMINATION. - Google Patents

Description

DESCRIPTION

The present invention relates to a device for eye examination according to independent claim 1.

Cutting optics have not yet been practically used with remote lens refractors. This is because the images created by cutting optics in conjunction with the eye have extremely low light values or illuminance levels. It is extremely difficult to capture these images from afar with low light intensity.

Low light level detectors are subject to noise. In particular, the resistance or impedance between adjacent portions of the same photosensitive surface when detecting a difference in photosensitivity over a wide detection area is very small. With low resistance and correspondingly high electron mobility, the signal / noise ratio quickly interferes with the image difference that is to be recorded. There is a great difficulty in the practical implementation of capturing images with low light values.

Up to now, lens refractors have been very sensitive to the position of the eye. An exact adjustment of the eye has so far been required before an accurate lens refraction can be carried out. An automatic alignment has not previously been provided, in particular not in a form in which the positioning information is separate and different from the refraction information and does not interact with it.

In particular, known objective refractors are also sensitive to the light value or light intensity returning from the eye. For example, if a retina has a change in the light reflected back to the observer over its surface, large changes have so far occurred in the readings required for the prescription of glasses or lenses.

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The aim of this invention is to provide a cutting examination with informative lighting patterns on the retina of the human eye. Accordingly, 5 collimated light is thrown towards the eye by a light source with a cutting edge limitation. A projection system is preferably provided between the cutting edge and the eye and is used at the same time for projecting the resulting image from the eye to an image detector. The light patterns reflected by the pupil of the eye have a characteristic shape in relation to the cutting edge. The boundaries between light and dark sections of the pupil with components parallel to the cutting edge indicate components of spherical and astigmatism refraction values. Limits with components perpendicular to the cutting edge indicate components of astigmatism along axes that are at an angle to the cutting edge.

An advantage of using cutting edge examinations with respect to the human eye is that there is an informative pattern of pupil illumination that not only indicates refractive errors, but also the direction and magnitude of the correction required. Accordingly, the output signal of the detector for determining optimal correction values need not be improved by multiple readings with a shift (hunting).

Measurement results for the human eye are preferably to be created by lens refraction using at least one light source, at least one cutting edge, a combined projection and reception optics and a photo detector. The light source illuminates the eye through an aperture which is formed in such a way that at least part of the aperture boundary is rectilinear, so that it acts as a cutting edge boundary for the outgoing beam. The outgoing beam passes through the optics in a projection system, and the images created on the eye are passed through the same optics to the detector, which serves as a recording system. A single cutting edge can be used, which then serves as a cutting edge for the projected light and the light returning from the eye. In fact, any such straight and cutting-like boundary that serves as the aperture edge for both the emitting and returning light can serve this purpose, provided that the side of the boundary that is transparent to the outgoing beam is for the returning beam is opaque, and vice versa.

In a preferred embodiment of the invention, an edge illumination sequence of preferably four cutting edges is to be created for the detection or measurement of the eye. These cutting edges are preferably subdivided into mutually facing pairs. One pair of cutting edges is illuminated from opposite directions parallel to a first axis, while the second pair of cutting edges is illuminated from opposite directions parallel to a second axis, which is at a right angle to the first axis. This opposing illumination of cutting edges creates a “push-pull” effect on the resulting images. Changes in the image due to changing optical values in the refraction of the spheres and cylinders as well as the axis direction 60 can be separated from other image deteriorations, such as mirror reflection from other parts of the eye, as well as from optical flare and the like, which are caused by the optical observation device (interrogating optical train) ) come. In addition, a reduced sensitivity to the eye position is achieved.

An advantage of the described push-pull cutting examination of the eye is that two separate ones

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and counteraction-free information bases are generated. First, there is position information and then refraction information. Each of these respective locations or Refraction information bases are separate and non-interactive (non-interactive).

Another advantage of one embodiment is that accurate refractive index measurements of the eye are obtained over a wide range. The instrument is relatively insensitive to the device. Accurate refractive indices are thus achieved even if a relatively significant movement of the patient takes place during the measurement.

Another advantage of an embodiment is that a large range of pupil shapes can be detected. In addition, pupil regions whose light transmission to the receiving detector is irregular can be measured. Refraction measurements of this type are insensitive to local retinal changes which affect the amount of light returned to the detector.

An advantage of the invention in this respect is that illuminated cutting edges arranged on the circumference can be examined in succession with a single detector. During this successive examination, the components of the required optical corrector can be identified one after the other according to size and direction.

An additional advantage is that the cutting edges can each be provided with frequency-coded light separately. A simultaneous examination of multiple cutting edges can take place in this way. Furthermore, this invention creates a preferred matrix of four cutting edges for examining the eye. The cutting edges are aligned perpendicular to each other in pairs.

An advantage of these cutting edge projection systems and light value detectors is that they can be recorded in instruments of different lengths. In addition, by using infrared radiation, the patient can look at an illuminated target along a first path and can be examined along the same path to perfect the retinal image. A preferred embodiment with an examination using light-emitting diodes in the infrared spectrum is described.

Thus, an embodiment of the invention also provides a preferred detector matrix for detecting low level light that falls back from an eye that is being examined for an edge. According to the invention in this regard, the detector matrix is divided into four discrete quadrants. Each of these quadrants is photodistinct to the extent that the photosensitive elements are electrically isolated from one another. By means of this supply of light to a photodistink component, the photodetector emits a signal with a low noise component in the signal.

Furthermore, an embodiment of the invention creates a combination with a detector with photodistink elements with specialized optics for light distribution. According to this side of the invention, multi-element lenses are inserted between an image in the eye pupil with low light level and the detector. If the image with the low light level is centrally located, the light is distributed evenly over all four quadrants of the detector. In the case of a linear change in position of the centroid of the image with a low light level, a corresponding linear change in the image intensity occurs in all detector quadrants. The detector emits a signal proportional to the offset of the center of the image with a low light level.

An advantage of this embodiment according to the invention is that the detector is particularly suitable for detecting the center of images with a low light level, as they fall back when examining the cutting edge of the eye. The optical center of an image with a low light level can be displayed quickly. Corresponding corrections can be applied to the eye in order to objectively determine the required refractive correction.

Furthermore, an embodiment of the invention results in a method for measuring the reflected images with a low light level at the detector segments. According to the invention, a summation method is described in which the image is summed on two quadrants and a difference is formed to the image in the remaining pair of quadrants. By developing a ratio of the image intensity differences relative to the light received in all quadrants, an image signal is obtained which is proportional to the displacement of the projected images with a low light level.

Furthermore, an embodiment of the invention provides a lens configuration for use in detecting low level light. According to a first embodiment, a resulting cutting edge image is forwarded to a matrix of refractive optical edges or prisms. This matrix of refractive prisms results in a change in the refractive intensity when the dislocation is changed from a neutral position.

Furthermore, an embodiment of the invention results in a class of image distribution optics which can be used to displace light with optical detectors, preferably with discrete photo quadrants. According to this embodiment of the invention, an optical matrix is generated with an overall optical effect, which can best be described using lens optics of the cross-cylinder variants. A first group of cylinders (with either positive or negative refractive power) is placed in a first direction to produce a first light deviation effect. A second group of cylinders is placed in a different direction (preferably at right angles to the first direction) and arranged so that a second light deviation effect is produced. The cylinders used can be selected from pairings which can be positive / positive, negative / positive or positive / negative (in any order). The result is an overall matrix of optical elements, which generates a light distribution on each quadrant of the photodiscrete detectors.

An advantage of these lens elements when used with photodiscrete detectors is that with a larger number of discrete elements, the alignment of the lens elements with respect to a cutting edge becomes less and less critical. For example, if a large number of randomly distributed elements are used, the need for precise alignment of the cutting edges with respect to the elements completely disappears.

Furthermore, embodiments of the invention provide still other configurations of lens elements that serve to distribute light among photodiscrete detector segments in proportion to the displacement of low-intensity images. For example, conical and arbitrarily aligned prismatic segments together have an effect that can be used with the photodiscrete detectors described. A preferred embodiment of this invention contains a matrix formed by cylindrical lenses with positive and negative refractive powers

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is produced. These cylinders are arranged side by side. Positive and negative cylinders are aligned along one side of the lens. Along the opposite

On the side of the lens, positive and negative cylinders are arranged next to one another and preferably at right angles to the first arrangement. The result is a matrix of crossed cylindrical lenses. with positive spherical, negative spherical and cylindrical lenses - in the first orientation second, rotated by 90c. This specialized lens has the advantage. To distribute light evenly in a pattern that is not unlike that of a trace of various Lissajous figures.

An advantage of this lens is that when combined with a cutting edge that cuts through the lens matrix, the cutting edge can produce symmetrical detection patterns at the boundary. These patterns distribute light evenly over a certain area, and the light distributed in this way can then be detected by photodiscrete detection elements.

An advantage of the cutting edges used with the matrix of cylindrical lenses is that the electrical output signal of the detector is directly proportional to the intensity of the image and the image offset. In addition, extremely low light levels can be detected. All in all, segments of the photosensitive surface can be electrically insulated from one another.

An advantage of the cylindrical lens design is that the projection system required to detect the light is shortened. As a result, this projection system contributes to the compactness of the detector according to the invention.

Furthermore, an embodiment of the invention provides a preferred embodiment of the lens elements which are attached in front of a four-quadrant detector. According to this embodiment of the invention, negative lens surfaces are distributed next to one another in an arbitrary distribution over an optical, preferably a refractive surface. In particular, these surfaces are provided with an arbitrary orientation and a small distance. The result is an easy-to-assemble lens element.

An advantage of this embodiment of the invention is that the optical surface can be built up easily. For example, it has been found that a perfectly satisfactory optical element is obtained by using a positive shape such as a ball bearing pressed on an optical surface or a reproducing medium for an optical surface.

Another advantage of the invention is that the arbitrarily manufactured optical surface or "pebble plate" to be described eliminates the need. align the cutting edge precisely with respect to an axis of the plate. Instead, the bubble plate and the optical elements used therewith can be arbitrarily aligned with one another.

Furthermore, an embodiment of the invention provides a preferred embodiment of the matrix of cylindrical lenses in combination with a cutting edge. The light from the cutting edge is projected through the specialized optics to the eye, and light reflected by the eye again passes through adjacent sections of the specialized cylindrical lens. This results in a passage of light to the eye with a Lissajous-like distribution of light along the cutting edge. As a result, only a portion of the light so projected can be seen over the cutting edge. The rest of the light projected from the cutting edge to the eye cannot be returned to the detectors. because the physics of cutting edge examination shows these rays as invisible. The portion seen across the cutting edge is mapped back to a position immediately above the segment of the cylindrical matrix from which the projection originally occurred. A complementary deflection of light 5 occurs in this segment of the lens. This results in an increased displacement of the light.

An advantage of this embodiment of the invention is that cutting edge physics is used in combination with a predictable distribution of light at the edge of the cutting edge to block out all light except that which has the required projection angle to be visible upon return. The result is a low-level light signal with increased sensitivity, which is reflected by the eye.

Another advantage of an embodiment of the invention is that the returning light occurs on a segment of the cylindrical matrix lenses that creates a complementary deflection. This complementary deflection not only deflects the light further, but it creates an image “focus” that gives an increased and improved signal.

A further embodiment of this invention results in an illumination pattern for influencing the flare control. According to this embodiment of the invention 25, the projected light is weighted according to its intensity around the center of the detector. Two light sources are preferably directed onto opposite sides of the cutting edges used. One area is far from the cutting edge, while the other area is adjacent to the cutting edge 30. The mirrored images are a function of the lighting of both areas and are symmetrical or cancel each other out in their effect. These specular reflections form a uniform background for the detector that can go unnoticed. The remaining 35 image changes are only a function of the cutting edge, and the cutting edge images can be used to determine the direction (sense) of the correction required.

40 Furthermore, an embodiment of the invention results in a preferred combination of cutting edges and aperture for a detector using the described properties of the invention. According to this design, a detector with five apertures is described. The De-45 tector has a central aperture with a dimension of approximately 2x2 units. Four peripheral apertures are arranged to capture light from each aperture based on the dimensions lxl. Cutting edges are aligned with each aperture. The central aperture thus contains four internal cutting edges on the circumference of the central aperture with 2x2 units. The 1 x 1 apertures on the circumference contain pairs of cutting edges. These cutting edges are each aligned parallel to a cutting edge of the central aperture and turned in the opposite direction.

The advantage of this embodiment of the invention is that all light sources in the detector head are active. There are no light sources arranged only to emit light that is not used in a cutting examination. 60 Another advantage of the preferred detector head is that it can be used in particular for use with opposite detection configurations. For example, the detector head can be used to check the generated images on the basis of a “push-pull” basis. Another advantage of the preferred edge configuration is that the position information and the refraction information of the eye are separate and without counteraction.

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Furthermore, the invention results in a method and a device for the first localization of an eye for examination. This method and device uses the specialized detector head just described. First, sections along the colinear borders of the central and two peripheral apertures are illuminated. The single cutting edge of the central aperture is turned in a first direction and is generally two units in length. The paired cutting edges of the peripheral aperture are turned in the opposite direction and each have a length of one unit. All edges are examined together. The central edge, two units in length, illuminates the eye on one side of the axis, the paired and peripheral portions of the cutting edge illuminate the eye on the opposite side of the same axis. Since the eye is illuminated from both sides of the optical axes, the sensitivity to refractive errors is eliminated. However, using parallel spaced colinear boundaries, both the positioning of the optical axis to the eye and the correct distance of the eye can be created. The result is a detector that is particularly sensitive to the position of the eye in front of it.

An advantage of the described sequence for positioning the eye is that the refractive effects of eye defects are compensated for. If the cutting edges are turned in opposite directions and are of the same length, the light projection generated is not sensitive to the respective refractive errors of the eyes. Instead, the detectors illuminate all types of eyes uniformly and allow these eyes to be centered both transversely and in the direction toward or away from the detector.

Furthermore, according to the invention, a particularly suitable cutting combination is created which is sensitive to the refractive errors and insensitive to the positioning of the eye. According to this view of the invention, sections of the apertures are illuminated on their cutting edges. Typically, a cutting edge is illuminated that is turned along the central aperture. Appropriate cutting edges on the peripheral apertures are illuminated. The corresponding cutting edges are turned in the same direction, parallel, but separated from each other by the width of the central aperture. All cutting edges are aligned in the same direction.

An advantage of this aspect of the invention is that only refractive effects due to eye defects are recorded, and effects due to the positioning of the eye are largely eliminated.

The invention also results in a sequence of eye checks. In accordance with this aspect of the invention, the eye is first positioned along colinear portions of the aperture using the cutting edges illuminated in different directions. Then, cutting edges aligned in the same direction along different sections of the aperture are illuminated. The optical prescription for the eye is determined during this last-mentioned cutting edge measurement.

An advantage of this test sequence for the eye using the preferred detector according to the invention is that two discrete measurements can be carried out with the preferred detector. First, the centroid of the eye is determined using pairs of cutting edges, each of which is colinear but turned in opposite directions. Then the refraction information is determined using other pairs of cutting edges, each part of the pair being aligned in parallel, with a distance from one another, but being turned in the same direction. This information arises from the difference between the light levels reflected by the eye and the checks between the second and different pairs of cutting edges. This difference contains the refraction information, which is insensitive to position information and separate from it.

Another advantage of the invention is that the output signals of the detectors can be easily adapted to drive motors in the correction optics. The motors can be activated to compensate for errors and to achieve emmetropic refraction of the eye using correction optics.

An advantage of this device is that the eye is initially positioned precisely with respect to the objective refractor. During this positioning, all existing optical errors in the eye are ignored. After that, as soon as the eye is precisely measured with regard to the positioning, the optical errors of the eye are determined. This is also determined when small movements of the eye to be examined naturally occur. These little movements are ignored.

The invention is explained in more detail below using the drawing, for example; in the drawing shows:

1A - 1H respective representation and projections of light rays through the human eye from a cutting edge with a schematic representation of the shape of the cutting image to be seen, wherein

1A an eye with myoptic or myopic condition,

1B is a schematic of the characteristic image generated by such an eye,

IC is a refractive diagram of a positive spherical lens producing such a state,

1D an eye with a hyper-optical or “far-sighted” state,

IE shows a diagram of the characteristic image generated by such an eye,

1F is a vector diagram of a lens for generating such a state,

Fig. IG a combined vector scheme, cutting and characteristic mapping scheme of an eye with astigmatism, which is directed along 45 ° / 135 ° axes, and

1H is a combined vector scheme, cutting and characteristic mapping scheme of an eye with astigmatism, which is directed along 0 ° / 90 ° axes,

2 shows a perspective illustration of an image detector according to the prior art, an embodiment with high noise components being shown,

3 shows an embodiment of a detector with a low light level, an image of a light source being focused on dispersing prism wedges and these wedges displacing the resulting image proportionally on discrete photosensitive surfaces,

4A is a perspective view of a specialized cylindrical lens matrix that can be used with the invention, with an underlying schematic representation for explaining the lens functions,

4B shows a diagram of segments of the cylindrical lens matrix from FIG. 4A, segments with positive spherical refraction, negative spherical refraction and two components of astigmatism along different axes being shown in each case,

5 shows a perspective illustration of a four-element lens which is imaged by a spherical lens system from a light source onto an image plane,

6 is a perspective view similar to FIG. 5 with a multiple lens segment system,

Fig. 7 is a perspective view similar to FIG. 6 with

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three cutting edges obliquely covering the surface of the lens element,

8A, 8B and. 8C respective representations of lens elements and images of cutting edges arranged on the detection planes, arranged above the specialized lens elements,

9 is a perspective view of a low light level detector of the invention with particular reference to the resulting array of photodiscrete segments that have undergone coordinate transformation to measure the applicable deflection.

10A shows a schematic side view of a cutting edge examination carried out on a myopic (short-sighted) eye with a representation of the factors influencing the image generated in the eye,

10B shows a representation of a cutting edge examination with only a schematically shown cylindrical lens matrix and a representation of the preferred improvement of the image using the combination of cylindrical lens matrix and cutting edge,

11 shows a preferred embodiment of the projection system using a projection lens with weighted illumination areas both for controlling the overexposure and the background reflection,

12 shows an alternative embodiment of the system using a lens matrix both for projecting light to the eye and for receiving light from the eye,

14A is an optical diagram with reference to the lens element from FIG. 4A with an illustration of how neighboring optical elements redirect light to specific detector quadrants,

14B shows a representation of the detector quadrants produced from the same cross cylinders, negative cylinders being combined here to form negative lenses and the detector quadrants again being able to be divided into four sections, each section redirecting the incident light to a specific discrete detector segment,

14C is an illustration for demonstrating how a large number of elements reduce the requirements for the cutting edge alignment with respect to the lens segments, FIG. 15A shows a schematic illustration of cutting edges cutting the lens element according to FIG. 14B with the light distribution over the detector segments, FIG.

15B is a schematic representation of the displacement of the image shown in FIG. 15A in the X direction to explain the weighting of the image with reference to the figure,

15C is an illustration similar to FIG. 15B with an image offset in the Y direction,

16A is a schematic illustration of the improved detector head with an illustration of the 2 × 2 central aperture and the four 1 × 1 peripheral apparatuses and the respective orientation of the cutting edges,

16B is a top view of the detector according to FIG. 16A with an illustration of the apertures and cutting edges, FIG. 16C is an illustration, with the omission of a portion of the optics used, to illustrate how the detector is used to set up an eye in the correct measurement position, wherein three detector states are shown with different eye alignment,

16D shows an illustration similar to FIG. 16C with cutting edges illuminated in an examination sequence for determining the refractive corrections necessary for the eye, FIG. 16E shows a perspective illustration of an eye with images of light sources located therein, the light sources being forwarded to a position in front of the specialized optics are with the resulting projection onto an illustrated detector,

16F is an illustration of how the specular reflection at the detector plane is eliminated when tested by the objective refractor,

16G is a perspective view similar to FIG. 16E using a cutting edge which, when incorrectly positioned towards or away from the detector screen, results in a signal error,

16H shows a representation of the detector from FIG. 16G, FIG. 16J shows a perspective representation similar to FIGS. 16E and 16G using three cutting edges, FIG.

16K is a view of the detector surface from FIG. 16J with the detector correctly set up and focused, FIG.

16L is a view of the detector from FIG. 16J with the detector not being correctly aligned with respective images on the detector, but which result in the correct optical correction,

17 shows a perspective view of the preferred “bubble plate”, in which negative lens surfaces are pressed side by side into a refractive element, and

18A-18D each show schematic representations of a cutting edge and a detector surface to explain the so-called "push-pull" cutting edge examination of the eye.

A lens refractor for the eye using cutting optics will now be described. The cutting optics provide a characteristic illumination of the retina so that the components of spherical and astigmatic refraction can be identified. Provisions have been made for remote reading of the characteristic images, with the result that two orthogonally arranged cutting edge images can identify the refractive properties by sphere, cylinder and the axis values that can be used for the recipe information to indicate the direction and size of the required changes. A system of at least two orthogonally arranged (preferably four) cutting edges with rated lighting is described for detection. The use of cutting edge images is made possible by the acquisition of images with low light values in a detector with a low noise level. Light from the images is distributed proportionally over the surface on a light-sensitive element which is divided into a multiplicity of photodiscrete segments. This distribution takes place through a matrix of wedge-shaped segments, or alternatively, in the form of optical elements with cylindrical components. If this distribution of light is used in conjunction with the push-pull cutting edge patterns in the manner to be described, a detectable refractive signal with a low level results. An embodiment using an optical system which has a multiplicity of optical elements arranged next to one another, each element having the effect of crossed cylinders, is described with the detector. The result is separate, independent and non-reactive information that is related to the location on the one hand and the refraction on the other. Accordingly, the refractor described is insensitive to alignment and can adapt to a wide range of pupil shapes, being insensitive to local retinal changes in light emission.

FIG. 1A shows a human eye E with a cornea C, a lens L and a retina R when looking at a cutting edge K. The cutting edge K contains an illuminated section 14, an edge section 15 and a location 16 directly above the edge 15, from which the illuminated section of the pupil of the eye is observed. The cutting edge is typically arranged at an optical distance infinite from the eye using collimation optics (not shown). Alternatively, the projection

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the cutting edge with any known optical distance.

It can be seen that although the side 14 of the cutting edge K is illuminated or luminous, this illumination is limited along the edge 15. This means that no light can come through the lens L onto the retina R of the eye from locations that lie over the edge 15.

The term "cutting edge" is used below, taking into account the fact that three discrete functions are attracted:

First, there is a light source, second, the light source is delimited by a boundary line that forms a straight line or a cutting edge. Third, the cutting edge determines an optical path to a detector element directly above it.

The illuminated area under the cutting edge 15 creates illumination on the retina R. In Fig. 1A it is assumed that the eye E is myopic, i.e. is short-sighted. The image plane 18 on which the cutting edge K is imaged by the lens / L lies in front of the retina of the eye. A point arising on the image plane forms an illuminated oval shape 20 on the retinal surface of the eye.

If an observer is placed at a point 16 that is just looking over the top of the cutting edge, he receives light that is collected from an oval area 21 on the retina of the eye.

It can be seen that the illuminated surface 20 and the surface 21 somewhat overlap one another. An overlap area 24 is created. Rays from the area 24 can be traced to the section of the lens L which appears to be illuminated for an observer. In particular, the light appears to come from the underside of the lens L.

The appearance of the lens L is shown in FIG. 1B. This image of the lens L shows the illuminated section T generated by the light reflected by the sector 24 of the retina, the sector 24 lying within the circle 20 for the possible return light 20 to the point 16 above the cutting edge 15.

It is important that this view is characteristic of a cutting edge. It is indicated that the lens L is extremely positive, i.e. that the eye E is myopic or nearsighted.

Immediately above FIG. 1B is a schematic representation IC, which in vector form represents the extraordinary positive refractive power of the lens, which is caused by the areas Le and / or C in FIG. 1A.

1D, IE and 1F show farsightedness or hypermetropia. The cutting edge K with the illuminated section 14, the illumination ceasing at the line 15, throws light to the retina R of an eye via a cornea C and a lens Le. As shown, the focal plane or image plane 18 'is located behind the retina R. Here, too, a collimating lens is envisaged in the optical path, which results in a projection of the cutting edge at an optically infinite distance.

In the eye, the projected light creates an oval illumination surface 23 that comes from a point in the source area 14.

Viewing from a point 16 above the boundary 15 of the cutting edge K allows the observer to collect light from an oval area 25. The observer sees (FIG. IE) light coming back from an illuminated section 23 of the surface 25.

1F shows a schematic illustration of the negative deflection of the lens Le or C in vector form.

IG shows only a lens L, a cutting edge K and a retina R schematically. The lens L is in a schematic vector representation similar to FIG. IC

and 1F. In FIG. IG, the lens L is a cross-cylindrical lens with a refractive power that is oriented obliquely to the edge 15 of the cutting edge K. This lens has 45 "-135" astigmatism along meridians. The lens L has a positive refractive power along the meridian 30 and a negative refractive power along the meridian 31. It should be noted that the respective meridians 30 and 31 are preferably below 45: angles to the edge 15 of the cutting edge K. Considering the meridians 30 and 31, the distraction strength in the vicinity of these meridians can be shown. E.g. If you start clockwise from the right, the light is deflected downwards in the three o'clock position 32, in the six o'clock position 33 light is deflected to the right, in the nine o'clock position 34 light is directed upwards deflected and finally in the twelve o'clock position 35, light is deflected to the left.

An analysis of the effect of such a lens in connection with a cutting edge K can be quickly understood. Light on a side half of the lens, which passes over the cutting edge K, is deflected to the examined eye, where it can be detected. Light to the opposite segment of the lens L is deflected into the cutting edge K, where it cannot be detected. As a result, the image of the retina R has a boundary or boundary edge T which is perpendicular to the edge 15 of the cutting edge K. A segment of the lens L is illuminated, namely the area 36. As already shown, there is no sharp boundary, but rather one with a blurred edge. The term "limitation" should be understood as it is used later.

The case of a lens L with a 0 = -90 ° astigmatism is shown in Fig. 1H. In particular, a positive cylinder is set along a meridian 40 in FIG. 1H, which is oriented perpendicular to the edge 15 of the cutting edge K. A negative cylinder sits along a meridian 41 parallel to the edge 15 of the cutting edge K. The image of the retina R has an illuminated section 46 with a boundary T which is parallel to the cutting edge K.

In comparison with FIGS. 1B and IE, it can be seen that the boundaries T are located essentially in the same horizontal direction as the cutting edges. From this it can be immediately realized that an astigmatism with axes that are either parallel or perpendicular to the edge 15 of the cutting edge K appears the same as spherical components. Consequently, only one component of astigmatism can be measured when using only one cutting edge. The measurements of astigmatism components perpendicular or parallel to the cutting edge cannot be carried out. It can only be said that the information resulting from such a measurement is an indication of a «meridional» refractive power. It can be shown that this measurement makes sense and that cutting K with orientations perpendicular to the edge 15 can be assigned. In this regard, reference is made to US Pat. No. 4,070,115 dated January 24, 1978, in which cutting with different angular positions is used in the inspection of normal lenses.

Now that the characteristic light patterns, which are generated on the retina of a human eye during cutting edge examinations and are observed directly, are discussed, the effects and problems that occur when using cutting edge images for automatic detection can now be discussed.

First of all, it should be noted that the image intensity must be low for any image thrown onto the retina of the brass eye. If the image is in the visible spectrum, the retinal problems are obvious. If the image

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is either visible or infrared, the picture elements must have a sufficiently low intensity so that the eye is not burned. If it is observed that the rays are effectively focused by the lens L onto the retina R of the eye, one can immediately understand that the projected light must simply be of a fairly low level.

If the optics of the eye itself are used to look at the illuminated retina, as is the case in the classic case of the known lens refraction, only a weak image is visible. This weak image must now be captured automatically or by an apparatus if a lens refractor is to be automated. In addition, the edge or "border" of the image will be far from sharp. The entire image must then be located on the basis of a «weighting». The problems associated with projecting such weak images are discussed below.

The prior art device in Figure 2 is a low level light detector. A light source S can be moved in an XY plane P and is imaged onto a light-sensitive surface D via a lens L. The photosensitive surface D is typically a single continuous photosensitive surface and can be either photoconductive or photoresistive. Such a surface typically has a “common” first connection 50 and is monitored by electrodes 51, 52, 53, 54 at a uniform distance.

The terminals 51 to 54 are distributed symmetrically around the circumference of the photosensitive surface D. Each terminal is typically connected to the input of an amplifier 55 by lines. The amplifier 55 is designed in the usual way, amplifies an electrical signal and generates a proportional output signal X and Y at the output 56.

Difficulties arise when using an extremely low level light source S with the embodiment shown in FIG. Typically, all of the terminals 51 to 54 are connected to a single continuous conductive layer of the photosensitive material. All of these terminals are interconnected with considerable conductivity. This relatively low resistance and high conductivity must be detected by the amplifier 55 in order to generate a signal at the terminals X and Y which is proportional to the displacement of the image S 'of the light source S.

If there is high conductivity and therefore low resistance between electrical terminals, the random movement of the existing electrons generates noise. This noise is picked up by amplifier 55 and also amplified and results in a very low signal-to-noise ratio. The signal will quickly disappear or go down when the light intensity of the source S is reduced. If, for example, the light source S generates the image S 'at the detector D, the predominant signals at the terminals 51 and 52 will be lost in the noise that arises.

The problem, therefore, is to provide complementary optics and photodetectors that suppress the tendency of the detector shown in Fig. 2 to produce noise at low image intensity values.

Two versions are described. The first embodiment according to FIG. 3 results in an initially designed one. however, less preferred way of achieving low light sensitivity.

A preferred cutting-lens arrangement is then shown on the basis of the other representations. This preferred cutting / lens arrangement shows not only a new and usable lens, but also a new light detector.

First, the configuration of a plate W is explained with reference to FIG. 3 in order to understand the first possibility according to the invention. After the explanation of the plate W, the remaining optics and the operation of the system are then explained.

The plate W consists of a matrix of optical wedges. This matrix has a first upper part 60 and a second lower part 62.

For better understanding, the plate or lens W is described here as being manufactured separately. A first roof edge prism 64 sits in the middle of lens W.

The effect on light incident evenly on the top of prism 64 is easy to understand. A first portion of the light is directed to the detector segments Di and D2. A second portion of the light striking the prism 64 is directed to the detector segments D3 and D4.

If one now turns to an outside prism 65, it is seen that this prism 65 contains only one refractive surface. This refractive surface allows light incident on the upper side of the prism 65 to reach only the segments Dj and D2 and no part of the prism 65 is arranged such that it deflects light to the detector segments D3 and D4.

The prism 66 on the opposite edge of the lens W is exactly opposite, and light that passes through the prism 65 from the source S is directed to the detector segments D3 and D4, while no light reaches the detector segments D (and Di).

The intermediate prisms 67 and 68 are now easy to understand. Prism 67 has a first section that is inclined to favor segments D3 and D4 more and a second section or inclined surface that is inclined to direct light more to detector segments Di and D2 . The prism strip 68 has surfaces of the same construction, but directed more to favor the detector segments D3 and D4 and less to favor the detector segments Di and D2.

If you stop here and understand the right and upper section of the lens W, you can see immediately that the more light is deflected towards the right section of the lens W4, the more towards the detector segments D3 and D4 and the less towards Detector segments Di and D2 will be noticed.

The intermediate prisms 69 and 70 on the other side of the lens section 60 can be understood just as easily. The prism 69 has a first refractive surface which is inclined to increasingly favor the segments Di and Di and a second surface which is inclined so that light is directed to the detector segments D3 and D4 to a lesser extent. The prism strip 70 has similarly constructed, but more inclined surfaces to favor the detector segments Di and D2 and even less to favor the segments D3 and D4.

If you stop here and understand the left and upper section of the lens W, you can see immediately that the more light is directed to the left section of the lens W, the more light onto the detector segments Di and D2 and the less will be noticed on the segments Di and D4.

Section 62 of the lens is constructed analogously to section 60, but the prisms are aligned perpendicular to the prisms 64 to 70 discussed so far, i.e. they run from left to right. This divides the deflection between the detector segments Di and D4 on the one hand and D2 and D3 on the other.

If one recognizes the prism matrix formed by the plate W, it can be seen that each area of the matrix ef5

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fectively consists of an upper and a lower prism. These prisms deflect light to the detector segments in proportion to the location at which an image S 'of the source S is created.

The remaining parts of the detector consist of a source S, which is movable in an XY plane P as shown, and this source S is imaged via a lens 80 in such a way that the image S 'of a source S falls on the plate W. . Assuming that the image S 'is the same size or larger than one of the areas formed by the overlapping prism strips, the deflection of the light onto the detector segments Di to D4 will correspond to the position of the image S' on the plate W weighted. A lens 80 'is located below the plate W to direct the deflected image beams to the detector plane. This additional lens 80 'can be used optionally, but is not absolutely necessary.

The detector D is typically a photodetector and can contain light guide cells, photodiodes, photoresistors, phototransistors or other light-sensitive detectors. In particular, the segments Di, D2, D3 and D4 are photodiscrete, which means that they are completely electrically separated from one another. Each segment Di to D4 has only one electrical connection and the current between the “common” connection and the electrical connection assigned to each segment is indicative of the amount of light striking the respective detector segment.

As a preferred exemplary embodiment, a light-sensitive cell made of layers of P- and N-doped silicon glued to or connected to an aluminum surface with associated electrical connections on the top and bottom is used, as provided by the United Detector Technology Company in Culver City , California, and amplifier 55 is a conventional current / voltage converter with a downstream voltage amplifier.

If, for the description of the operation, it is assumed that an image S 'is thrown onto the lens W, the light is distributed proportionally through the prism segments of the matrix to the respective detector segments Di to D4.

A signal is generated by amplification and the logic circuitry customary in this field, which designates the X-Y position of the image S 'on the lens W. It should be noted that “X” and “Y” according to FIG. 3 are aligned with the diagonals of the detector boundary.

It should be noted that, in contrast to the embodiment according to FIG. 2, the respective detectors in FIG. 3 are photodiscrete. The resistance between any two connections is essentially infinite, i.e. there is an open circle. Only the amount of light striking the individual detector segments generates the proportional current. As a result, the detector arrangement described is essentially free of noise, which arises from the electrical interaction of the detector segments, even when very small amounts of light are incident.

The preferred lens arrangement or configuration and the preferred cutting edge will now be described with reference to FIG. 4A. This embodiment is first discussed by illustrating the makeup of a new lens with reference to FIG. 4A and with reference to FIG. 4B the optical properties of each lens segment are presented. 4A, a lens V consists of a series of cylindrical lens strips arranged side by side. Positive cylindrical lens strips 80 are inserted between negative lens strips 81, respectively. These strips 80, 81 alternate side by side so that the lens strips themselves extend parallel to the arrow 86 across the width of the lens. Together 9 664 888

These adjacent lens strips form the first half 88 of the overall lens.

A second and lower half 89 of the lens V consists of positive lens strips 83 and 5 negative lens strips 84 arranged next to one another; as with the top half, the adjacent strips extend across the entire lens parallel to the direction of arrow 87 and together form the second half or portion 89 of the lens.

10 It can be seen that the lens shown also has a composite structure and, in the actual embodiment, the dividing lines between the cylinder segments 18, 81 and 83, 84 are not visible. Typically, the entire lens is formed from one

15 uniform optical material, such as a lens plastic, which can be brought into the desired shape. As in the previously discussed example of the prism structure, this optical element can also be manufactured in such a way that it has a flat surface 20 on one side and the described deflections simultaneously on the opposite composite surface. Now that the construction of the lens has been described with reference to FIG. 4A, the optical effects of the underlying matrix are shown with the aid of FIG. 4B.

When looking at FIG. 4B, it will be remembered for the person skilled in the field of optics that two cylinders with the same refractive power, which are placed on top of one another with axes perpendicular to one another, have the same properties as a spherical lens.

30 First, a first segment of cylinder segments 80 and 83 (bottom left) is considered, and it can be seen immediately that a positive spherical lens effect C + results from this crossed arrangement of cylinders. On the other hand, a combination 35 of crossed negative cylindrical lenses 81 and 84 (top right) results in a negative spherical lens effect C—.

It is also remembered that the combination of crossed positive and negative cylinders results in an effect that corresponds to a cylinder lens. In this way, it is seen that segments 80 and 84 (bottom right) at the junction of their crossover result in a combined crossed cylindrical lens Aj. Similarly, the crossed negative and positive cylinders 81, 83 (top left) result in a combined cylindrical lens A2. 45 If you stop here and compare with Fig. 4A, you can see that each discrete lens segment can now be labeled according to its refractive power. Since the distributions shown in FIG. 4B are repeated, such a designation of a small section of the matrix 50 continues over the entire lens plate.

FIG. 4B now shows various parallel beams which are refracted or deflected as they pass through discrete lens elements. These illustrated deflections of light can be used to generate a vector description of the lens deflection. It can be seen from the lens deflections shown that each lens segment shown in FIG. 4B is provided with arrows rising from the corners of each segment, which lead to a projection of the segment surface. These arrows can be considered descriptive of the distractions generated. They are used in the following to describe the deflection generated by the plate according to the invention.

5, a point light source S projects light through a spherical lens L onto an image plane D. As is known, at all points in the system the light is again projected onto a center point S 'at the image plane D.

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A lens element V according to the invention is now used. The lens system shown or the plate V shown has a total of a matrix with four different, repeating lenses lying next to each other according to FIG. 4B. Only such a matrix of four lenses is shown in FIG. 5. In the preferred embodiment, this basic matrix is always repeated on all sides.

To designate the respective segments, the designations C +, C— given in FIG. 4B can be used for the respective positive or negative spherical lenses and the designations Ai and A2 for the astigmatic sections of the lens. Another condition for the system can now be examined. If one considers that all points S are imaged by the lens L to the points S ', it can now be asked what happens to rays passing through the neutral points of the lens segments C +, C—, Ai and A2. In any case, it turns out that the rays again lead to the point S '. The question then extends to how the remaining rays are deflected.

It is known that the vector descriptions developed in FIG. 4 can be used to describe the refraction of light. This vector description can be given for each lens around its neutral point. It is therefore first described in sequence what takes place on each remote segment of the lens C +. If one takes the main beam of the system that passes through point 114, it is known that, in the absence of the special lens V, it hits the point S '. However, because of the vector deflection against the center of the spherical lens C +, an impact will instead occur at a point 24. An analysis of a point on the positive spherical lens C + diametrically opposite can also be made and the deflection takes place from the normal point of impact S 'to a new point 25 on the image plane.

In the same way, at point 116 of plate V, a deflection to point 26 in image plane D occurs. This deflection originally redirects light intended for point S '. Finally, we find a pixel 27 for point 117 on lens C +.

The negative lens C— can now be discussed. It has a remote point 115 ', which in turn produces an image at point 25. Likewise, it contains points 116 'and 117', which in turn map around point S 'in the manner previously described.

With regard to the astigmatic segments Ai and A2 of the lens V, it can now be said that only two remaining deflections are to be described which occur for the points 115 "and 115 '" at the respective corners. Light rays originating from these points are deflected to point 25.

It will be seen later that when the special lens V is inserted from the projection S 'of the source S in the image plane D, an image results which is an equally distributed square light pattern at the focal plane D. With movements S in the direction of the X and Y axes, a corresponding movement of the square image takes place in the plane D.

6 again shows a source S which is movable in an XY plane and whose image S 'is thrown onto the image plane via a lens L. A special lens element V produces a deflection pattern in which light is contained within a square boundary with the corners 124, 126, 125, as explained with the matrix comprising four sections, FIG. 5.

The lens V is divided into lenses C +, C -, Ai and A2 in the manner described, but this time the matrix consists of more than four, namely twenty sections. All sections have the corresponding designations C +,

C—, Ai and A2 designated. Again, it should be noted that all segments of the lens project light in a square pattern. The light falls within a square boundary, which is indicated by corners 124 to 127. Similar to the case described above, when the source is shifted, the entire square image, which is determined by the corners 124 to 127, is deflected.

A position of cutting edges with different orientations to the lens elements can now be instructive. In FIG. 7, a source S is imaged via a lens L on an image plane designated here as P. Again, a special lens V is used with the same configuration described with reference to FIG. 6. This time, however, a cutting edge is placed in a position K1 over the lens and forms an aperture boundary, through which light from the source S can pass through the lens V and can then be imaged onto the image plane P through the lens L.

As explained in detail later, it is necessary that two conditions must be met by a cutting aperture arranged on the lens V.

First, the aperture edge must cross equal portions of each of the four element types (C +, C—, Ai, A2) that make up the special lens V.

Second, the aperture edge or cutting edge must be set with a certain inclination to the boundaries of the lens elements of the matrix and not parallel to them.

A particularly preferred embodiment consists of a slope of 2: 1. The preferred inclination is shown in FIG. 7. Each time two elements are crossed in the horizontal direction, the cutting edge crosses one element in the vertical direction. Other special slopes a: b also produce the desired effect, provided that a and b are integers and either a is even and b is odd or vice versa.

The cutting edge passes through the point 135 on the lens AI and the point 136 on the lens C -. It is known from the example of FIG. 5 that these two points result in images at respective points 125 and 126 on the image plane P. It must then be asked where an image for rays passing between these two points, for example the ray passing through point 140, is created. If the point 140 is recognized as a peripheral edge of a negative cylindrical lens C—, the problem is simplified. In particular, it can easily be seen that a complete negative deflection leads to the circumference of the square at a point 150. In this way it can quickly be seen that in the case of parallel rays which emerge sequentially from point 135 to point 136 on the cutting edge, they produce an image along a line 125, 150, 126.

In the case of a cutting edge K2 that falls from left to right, the deflection can be understood by applying a similar vector analysis. It starts with point 141 on the left side of the cutting edge K2 and this is located in the middle of a positive spherical segment C +. The deflection is vectorially distributed to the neutral section of the element. There is an incidence of light at point '151 of plane P. Light that falls on the cutting edge K2 at point 142, i.e. at a point in the upper portion of a positive spherical lens, it suffers a downward deflection toward the neutral point of the lens so that light is incident at point 152 in the P plane.

Light incident at point 143 falls on a boundary between two lens elements, here a completely negative lens C -. This negative spherical lens drops the light at a point 153 on the P plane.

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At point 144 it can be seen that the cutting edge K2 passes through the neutral section of a negative lens. As a result, it will strike the center of the square at location S '. Finally, light incident at point 145 is deflected to the edge of the square and incident at point 155. This results in the zigzag pattern K2 ', shown in short dashed lines.

The path of a ray cutting edge K3, which runs through the element, is now also followed for the introduction. It should be noted that the cutting edge K3 begins at point 146. This belongs to a positive spherical lens C + and deflects light to point 156 on the image plane P. At point 147 it should be noted that the light beam is at a corner of a positive spherical lens C + and a negative spherical lens C—. Light emanating from point 147 is cast to a point 127 on plane P according to the logic of FIG. 5. It can also be said that light is deflected from point 148 on the periphery of a negative lens element to point 158. Light from point 149 comes to point 159.

We have now followed cutting Kl, K2 and K3. This leaves the problem of following a more complex arrangement in the same way. This is shown in the schematic representations of FIGS. 8A and 8B.

FIG. 8A shows cutter arrangements that produce corresponding tracks or images in FIG. 8B. The light source S and the lens L are no longer shown. Thus, only the cutting edge is shown in its arrangement on the lens element V (FIG. 8A) and the trace pattern generated (FIG. 8B) is shown.

The trace of a cutting edge defined by points 180, 181, 182, 183 and 184 can be created quickly. The point 180 lies on the edge of a positive spherical lens. Remember that in the absence of plate V light from this point to the center of the imaging pattern, i.e. would be deflected to point 195, and if one also thinks that the light experiences a vectorial deflection in the diagonal direction through the lens element, it can be seen immediately that it arrives at point 194. If the point 181 on the cutting edge is viewed, it results that 181 lies on the edge of a negative cylindrical lens and is horizontally distant from a neutral segment of a negative spherical lens C—. Accordingly, the beam will hit point 191. As a result of the same considerations, light rays emanating from the piece between these two points fall on a straight line connecting the points 190 and 191.

Light from point 182 falls on the upper right corner of the image, point 192. If one thinks that it was originally directed at point 195 and one also remembers that the light is located on an edge of a lens C +, the result is the deflection to the upper right corner of the graph Fig. 8B. Light from point 183 falls on the same point as light from point 181. If one thinks that light at point 131 comes from the edge of a positive spherical lens and that the positive sphere is directed to the left, then a distraction from point 195 occurs is equal to S 'for limitation to the left, ie to point 191. Finally, light is deflected from point 184 to a point 194, which coincides with the previously mentioned point 190.

It can be seen that light emerging along a cutting edge passing through diagonal points of the lens is always recorded in a V-shape.

It is now interesting to examine light rays that pass through neutral points of the segments of the special lens V, as shown by a line connecting the points 186, 188, 185, 189, 187, 188 ', 189'.

First, the light can be easily tracked through point 185. In this case, the result is that the light is not deflected at all. No distraction results in light hitting point 195.

Light hitting the lens of Figure 8A at point 186

falls on the edge of a positive spherical lens. Therefore, it must be deflected to a point 196 in Fig. 8B. Similarly, light at point 188 falls on the edge of a negative spherical lens, and this results in an image at point 198 in Figure 8B. Similarly, light at point 189 strikes the opposite edge of a negative lens and provides imaging at point 189 after passing through the lens neutral point 195. If the cutting edge thus traverses the negative lens C—, there is a linear deflection from point 198 to point 195 and finally to point 199. At point 187 one is at the edge of a positive spherical lens and this directs to point 197 in FIG. 8B from. At point 188 'the light is at the edge of a positive spherical lens and this results in a deflection at point 198'. The crossing of the cutting edge from point 188 'to point 189' must pass through a neutral section of the lens, i.e. the figure must pass through point 195. It can be seen that point 188 'gives an image on the left edge of the square imaging area at point 198', while point 189 'gives an image of a right edge of this area at point 199'. The result is a pattern that resembles a number 8 with straight lines or a straight Lissajous figure.

8B is plotted on a background that includes a horizontal axis X and a vertical axis Y. The cutting edge traces shown lie in a square, which is delimited by the boundary lines 100, 101, 102, 103 (counted counterclockwise).

It can also be seen that each line is mapped into respective quadrants of these figures. These quadrants are referred to as 104, 105, 106 and 107. An interesting observation can be made. The length of a line resulting from a projection of the cutting edge in each quadrant is obtained is the same, namely the same in linear length and also the same in terms of the center of gravity. In particular, it can be seen that the center of gravity of the line segments is symmetrical about point 195 in all sections of the images.

FIG. 8C shows the matrix image of FIG. 8B placed on a detector. The detector contains photodiscrete quadrants Di, Dj, D3 and D4. Each of these quadrants has roughly the same area as the boundary square that encloses the deflection patterns generated by the respective cutting edges. It can be seen that the image in FIG. 8C is shifted along a diagonal 110 to the top left. As already shown, the detector segments are separated from one another by dividing lines 114 and 115.

In order to measure a deflection of the image in a proportional manner, it is necessary that the extent of a line cut off from a certain cutting edge is always proportionally distributed in each detector segment Di to D4. This proportional distribution should correspond to the direction and extent of the dislocation that has occurred. If an offset therefore takes place parallel to a diagonal 110, equal amounts of light should be incident on the detector segments Di and D3. There should be no signal difference between these segments, since otherwise an offset in a direction other than along the diagonal 110 would manifest itself.

In Fig. 8C, the trace of the cutting edge (Fig. 8A) is through the points 180, 181. 182, 183 and 184 through points 191,

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192, 194. It can now be shown and it already follows from viewing the drawing that the linear length of the light lines appearing in the detector segments Di and D3 is the same. The linear length of the segments D; and D4 appearing light line is not the same. The difference is proportional to the displacement that has occurred along the diagonal 110. The cutting edge going through points 186, 188, 185, 189, 187, 188 ', 185', 189 ', the track of which through the corresponding points 196, 198, 195, 199. 197, 198'. 195, 199 'indicated track leads to the same results and it turns out that this line path located in the detector segments Di and D3 is the same. The remaining light line path in the detector segments D; and D4 is again different from one another, to the same extent as before.

An offset along the other diagonals 111 gives a similar result. It has been shown that transfers that also occur in any other direction also obey this rule. The light path difference in the different quadrants is proportional to the displacement. This makes it possible to use this type of detector for the detection of low-level light sources with photodiscrete detector segments.

It will be seen that the center of gravity 195 or S 'can thus be tracked in its displacement according to the difference in the amount of light obtained from each detector segment, and it is therefore possible to obtain a linear output signal.

If an infinite number of cutting edges or narrow strips of light are placed over the lens elements, it can immediately be realized that a coherent, uniformly distributed light spot results within a boundary of the same shape as that of the lens elements. This light spot will then be the conjugate image of each point light source with a weakly measured image. Using a summation of these conjugate distributed images, each limited to a square, results in a particularly useful detector image that is noticeable on a detector level and that can be used to read the X and Y values for the center of gravity of a weak and distant image . This property, that you can see the focal point of a weak image, gives the great benefit of this type of detector.

Now that the structure of the lens element and the deflection within the lens element have been described, the basic device structure can be explained with reference to FIG. 9. A light source S in an XY plane P is shown here. This source S is imaged via a lens L and a lens element V. The lens element V casts a light image onto a detector surface D with photodiscrete quadrants Di to D4. In Fig. 9, the light source S illuminates the upper right quadrant of the XY plane. The image with low light intensity is thrown from the source S through the combination of lens L and special lens V onto the detector plane D. The special lens V is limited by cutting Ki to K4. These respective cutting edges result in an opaque limitation for the otherwise transparent lens V described.

There are two optical effects when the source S emits light through the lens V past the cutting edges Kj to K_t.

First, the cutting edges projected onto the detector surface D with the photodiscrete segments Di to D4 have an angle with respect to the square sides containing the illumination. Second, the resulting light from any point on the image forms a uniformly distributed square image that is shifted on the detector segments in accordance with the displacement of the source S in the plane P. Thus, when the source S shifts to the upper right quadrant of the plane in Fig. 5, the square light spot shifts to the lower left side of an XY plane. When moving downward on the left in an XY plane, the detector from FIG. 9 can read out the XY position if it is connected to a standard circuit such as the amplifier according to FIG. 1.

However, it can be seen that due to the properties 10 of the image, a coordinate transformation must be carried out, since the cutting edge directions and the coordinate directions are different. Since such coordinate transformations are well known, they are not listed here.

15 The lens element described shows an unexpected result when used to project light or to receive light over a cutting edge towards or from an eye. 10A schematically shows the path of the light that falls into the eye of a nearsighted person during a cutting examination 20. Figure 10B schematically illustrates the principle of how signal enhancement offset occurs in focused light.

Reference is made once again to FIG. 1A, in which the conditions for a short-sighted eye are generally shown as 25.

In Fig. 10B, a series of light rays that pass the cutting edge K are viewed in succession. Each of these light rays must first pass through a lens V as it passes the cutting edge. When passing through the Lin-30 se V, the light rays, depending on their position from left to right, when crossing the cutting edge, hit lens segments A1, C +, C - and A2 at the meridian point of the lens V.

FIG. 10A shows a diagram of the cutting examination according to FIG. 1A on the eye of a nearsighted person. Here the 35 physical basis of the resulting rather indefinite image on the retina is shown. A cutting edge K is formed by an illuminated section 250 below a boundary 251 and is imaged via the lens L of the myopic. This results in an image K 'of the cutting edge in front of the retinal surface R corresponding to the nearsightedness of the eye E.

With regard to the respective points to which an image of the cutting edge boundary 251 is thrown, the observation of three picked pupil points in-45 can be constructive. First, the central portion 262 of the pupil throws an image of the illuminated portion 250 onto the retina in an enlarged illuminated region 262 '. Second, the same illuminated area when projected through the pupil point 261 results in an additional enlarged retinal area 261 ', and finally a projection over the pupil point 263 results in an enlarged imaging area 263'. The entire resulting image is thus spread over an enlarged area of the retina, and this area of the retina must be viewed in accordance with the limitations of the cutting edge image via the cutting edge limiter 251. This is the section immediately above the boundary 251 (since the intermediate optics are omitted in FIG. 10A, in this case the window is located under the boundary 251 and the 60 illuminated area 250 of the cutting edge K above it).

If a straight line is drawn from point 261 over the real image of the cutting edge (in front of the retina) to the retina of the eye, one can immediately determine a limitation of the section of the retina R to be observed. By constructing a boundary line of the visible or observable area above the cutting edge boundary, an image of the boundary line at 252 'can be obtained. By constructing boundary lines from point 263

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From the image of the boundary 252 'to the retina, a window results through which light incident on the retina returns directly via the cutting edge K.

It must be taken into account here that the limitation of the image formed on the retina R is indefinite and out of focus, i.e. is not focused. As soon as a correction is made for the short-sighted eye by means of an interposed optical system, the image K 'of the cutting edge is placed closer to the retina R of the eye E. When approaching the retina of the eye, the boundary or the boundaries become sharper. As the boundaries become sharper, the unexpected result of using the displacement lens to project light to the eye and receive light from the eye is emphasized as the image boundary becomes sharper.

When passing through the respective segments Al, C +, C— and A2, the light is deflected as it passes immediately above the cutting edge with a distribution as previously described with reference to FIGS. 8A and 8B. The light tries to create a square pattern on the lens L of the eye E and then finally reaches the retina R of the eye, where the short-sightedness condition shown is generated.

Cutting edge examinations, even if they are carried out by a special element, such as element V, have one thing in common and that is that the light reflected back to the cutting edge always returns to a spot which is immediately adjacent to the light area from which the light originally emanated when one was assumes a moderate state of refractive errors. Thus, in the case shown, the illuminated cutting edge region, which in FIG. 10B is the region K (now correctly located below), returns to the cutting edge K, specifically to a point which is directly above C + or the adjacent lens segments AI, C +, C— or A2 lies.

If one further considers the schematic representation of a short-sighted eye in FIG. 10B, one knows that the light striking an area 24 'returns from an illuminated area 24 of the lens L of the eye E. Upon return, another upward deflection is created and the light is then passed to a detector.

Because of this type of light passage to the lens L of the eye E through the special lens V, two effects occur.

First, rays can never be seen that are deflected by the elements of lens V into any portion of the eye outside of upper portion 24 '. This reduces the amount of light reflected by the eye E over the top of the cutting edge and only the rays that are emitted towards the upper section of the eye are received more intensely when they return.

Second, since light rays return from diametrically opposite portions of the eye during edge inspection of the eye, light rays will have a greater overall deflection when picked up by the eye.

This results in an increased, distracted image with increased contrast.

Another way of understanding this characteristic of the invention is to analyze the process in which parallel beams leave the cutting edge one after the other from left to right. When passing through the special lens, which can also be referred to as a “Wöbbel plate” V, all the parallel rays are distributed to the patterns or figures shown in connection with FIG. 8. Only the portion of the pattern that is distributed over the upper section of the lens of the eye E is detected via the corresponding point above the cutting edge K on return. The returned portion returns from the lower portion of the eye 24 and, when passing the cutting edge K a second time, experiences a second upward deflection. This second deflection, when recorded on a photodetector, as shown in FIG. 11, results in an increased contrast due to increased light displacement when analyzing the resulting image.

Analogous to the processes just discussed, the images reflected by eyes with other optical errors can also be viewed. In any case, the light to be observed during a cutting examination arrives at a section of the eye and exits again at a diametrically opposite section. It can therefore be seen that the above-mentioned principle of increased distraction works with all visual defects. For example, for the examination of a farsighted eye shown in FIGS. 1D and IE, light entering in the lower section 23 ′ emerges in the upper section 23. Similarly, in the illustration in FIG. 1G, light entering the left section 36 'of the lens will leave the area 36. The increased distraction generated remains the same.

FIG. 11 shows how the special lens or Wöbbel plate V according to the invention covers a detection or detector aperture 200. The aperture 200 is delimited by four pairs of cutting edges, each designated A, A ', B, B', C, C 'and D, D'.

When observing these cutting edges arranged square around the detector aperture 200, it should be noted that

that only the light-emitting apertures A, B, C and D are immediately adjacent to the detector aperture 200. These light sources have their cutting edges adjacent to the aperture 200 and form the respective four cutting edge boundaries as previously shown.

It has been shown that, in addition to the observed reflections from the retina, light components reflected from the cornea and iris also return to the detector Di to D4. If only one side of the detector aperture is illuminated, a cutting edge has the effect that a weighted image is received in the detector segments Di to D4. It has therefore proven useful to illuminate the cutting edges in pairs. So if the cutting section A is illuminated, the cutting section A 'is also illuminated.

With regard to section A ', it should be noted that it maintains a distance from the cutting edge formed by element C. Because it is spaced the width of element C from detector aperture 200, essentially no light will return from source A 'due to the retinal cutting effect. The only returning light component is the light from other reflections, e.g. on the cornea, iris and the like. In order to transmit the light from the cutting edges to the eye and in turn from the eye to the detector, a lens 203 can optionally be placed between the light sources and the eye.

To ensure that the combinations of the illustrated light sources A, A 'do not contribute to the weighting of the overall displacement of the image, both light sources are provided with an effectiveness that is symmetrical to the center 201 of the light receiving aperture. To achieve this, the light source A has a slightly increased intensity compared to the light source A ', and this ratio is such that the product of the distance from point 201 to light source A times the intensity is equal to the product of the distance from point 201 to Light source A 'times its intensity. The same lighting scheme is used with respect to light sources B, B ', C, C' and D, D '.

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The light is transmitted to the eye E in the manner shown via a lens 203. This forwarding arrangement is only shown schematically. Any number of routing systems can be used.

It can be observed that each light source A to D 'is covered with a lens component. The cylindrical lens preferably has such a focal length that, in cooperation with the other optics present, the respective cutting edge is projected onto the retina R of the eye E. Light returning from the weak image on the retina R of the eye E passes through the lens element V and the detector aperture 200 and reaches the detector segments Di to D4 already described.

FIG. 12 now shows a preferred embodiment of the objective refractor according to the invention. This version shows a Wöbbel plate W, which not only covers the detector aperture 200 but also each light source. The deflection already described schematically with reference to FIG. 10 then occurs for each cutting edge. Thus, for each of the four cutting edges, an optical pattern is imaged towards the eye and each optical cutting edge allows return light to return to the detector segments Di to D4 in the manner previously shown. It can be seen that the plate W in FIG. 12 can either be operated via the section of the cutting edge that emits light to the eye, the section of the cutting edge that receives light from the eye or both (as shown in FIG. 12).

A surprising discovery was made in the development of the invention. It has been determined that each optical element formed from crossed cylindrical lenses is sufficient for the practice of the invention. It has also been determined that the crossed cylindrical lenses can be formed from any repeating combination of cylinders, including cases where the cylinders are positive and positive, negative and positive, positive and negative, and / or negative and negative. In particular, matrices composed of negative lenses were found to be very suitable, particularly if they were placed in an arbitrary distribution with respect to the cutting edges.

It was also recognized that other optical surfaces can also be used for the distribution of the light. As long as the light is evenly distributed from a central detector position to all detector quadrants and moved in proportion to the movement of the captured image on the detector segments, an optical element with multiple deflection surfaces can be used.

The word optics is to be understood to mean both mirrors and lenses. The word deflection is intended to include both refraction and reflection.

Cylinders, randomly aligned pyramids and the like are mentioned as examples of the different usable areas.

14A, a diagram of a lens arrangement is shown. A schematic representation of lens surfaces similar to that shown in Fig. 4B is used. However, arrows 301-304 are used here to show the deflection of the light at parts of the respectively negative optical section C— in the regularly arranged lens elements. As before, the lens elements are labeled C +, C -, A1 and A2.

When these elements are checked, it can be seen that with respect to the adjoining quadrants of elements C +, C—, A1 and A2, all the light incident on adjoining or adjacent quadrants is directed towards the same detector quadrant. With reference to the lower right quadrant of element C +, the upper right quadrant of element AI, the upper left quadrant of element C— and the lower left quadrant of element A2, it can be shown that all of the light striking these elements is reflected in the same direction is deflected. In addition, it can be seen that the abutting quadrants together define an area that is equivalent to each of the lens elements, and the boundary of which is shown around the deflection arrow 304. This area of common distraction is hatched evenly. All of the light striking the shaded area is directed to the quadrant div of the detector.

In the same way it can be seen that the light hitting around the arrow 303 in the area which is again hatched uniformly is directed into the quadrant Dm, the light hitting the arrow in the evenly hatched quadrant around the arrow 302 is directed to the detector quadrant Du etc. This results in areas of the lens matrix with the same size and shape as each lens element C +, C—, Ai and A2, from which all incident light is directed to the same detector quadrant.

It has now been discovered that the redirection of light can always be used with lens elements with the same refractive power in order to detect a displacement of a low light level image. In particular, it has been found that either positive cylindrical lenses, negative cylindrical lenses, or astigmatic lens elements with oppositely crossed cylinder orientations can be used to produce the optical offset used in the invention.

An example of this use of negative lens elements is shown in Figure 14B. Here is shown a series of negative lens elements C - arranged side by side. The lens elements C— can again be divided into four quadrants. These quadrants are also continuously designated Qi through Q4 in the counterclockwise direction, and light that falls in the sub-quadrants Qi,

is directed to the clock position for 10.30 a.m., light falling in Q2 to the clock position 8.30 a.m., light falling in Q3 to the clock position 4.30 a.m. and light incident in Q4 to the clock position 1.30 a.m. the light in the sub-quadrants Qi and Q2 is shifted counterclockwise, that in the quadrants Q3 and Q4 is shifted clockwise. Thus, light from the section Qi to the detector quadrant I, the detector section Q2 to the detector quadrant II, the light from the detector segment Q3 to the detector quadrant III is guided.

Furthermore, it can be seen from the diagram in FIG. 14B that a cutting edge Ki which is designed with a 2: 1 inclination leads to the same sections of the cutting edge occurring on all segments of the detector. For example, the cutting edge Ki can be used to show that an identical linear section of the cutting edge is deflected by each lens quadrant into a respective detector segment. For example, a comparison of FIGS. 14B and 15A, when checking the course of the cutting edge Kl from left to right, shows that a first quarter of the cutting edge is deflected to the detector section Du, a second section of the cutting edge Ki to the detector quadrant Dm, running across it, the third section of the cutting edge Ki to the detector quadrant Di, running across it and finally the fourth section of the cutting edge Ki to the detector quadrant Div, running across it. It can quickly be seen that identical sections of the cutting edge Ki are each deflected into different detector quadrants.

Two rules to be followed can be derived from the previous discussion if weak images are to be detected by the detector according to the invention

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len. The first rule is that when capturing a centered image, the light is distributed evenly over all quadrants (of the detector). The second rule to follow is that when the image is shifted, the light strikes the detector quadrants with weighted components. An indication of the displacement of the light by the light distribution on the various detector quadrants is effectively obtained.

In fact, this does not apply to the regularly arranged lens elements according to FIG. 14B. Instead of such a "straight-line" detection of the amounts of light occurring on the photodiscrete detector segments, it has proven necessary to differentiate between the currents at certain points in comparison to the total light signal obtained at all four quadrants. This feature of the invention is discussed below with reference to Figures 15A to 15C.

In addition, it has been shown that this is less critical with a cutting edge that runs over a plurality of elements, the oblique orientation of the cutting edge with respect to the lens matrix generated. In Fig. 14C e.g. a cutting edge with a slope of 12: 1 is shown.

From the previous discussion, there were two rules to be followed for placing the cutting edge:

First, the aperture edge or cutting edge must cross equal portions of each segment of the lens so that light from the same portions of the cutting edge is directed to separate detector quadrants, respectively. Secondly, the cutting edge must be inclined towards the boundaries of the lens elements, i.e. not parallel to these limits. A particularly preferred slope of 2: 1 size has previously been presented, with the requirement that the boundary cross at least four separate discrete elements.

If the lens elements shown are regularly arranged next to one another so that rows and columns of such elements occur, it has been shown that arranging the cutting edges in alignment with the rows and columns, or with a precisely aligned slope to the rows and columns, is a detector configuration results that the displacement of the images is not reliable.

14C it can be seen that the cutting edge traverses a large number of discrete elements and can come close to the forbidden horizontal orientation. In particular, if a large number of elements are placed next to one another in an arrangement, the cutting angle can get ever closer to the axis of a row or a column of discrete lens elements or alternatively into an oblique alignment of the elements without rendering the cutting edge ineffective.

It has even been shown that, according to FIG. 17, the lens elements can be arranged next to one another at random or at random. With regard to such a random alignment using a large number of lens elements with respect to each cutting edge, it can be seen that the light distribution is approximated as far as possible with equal proportions on the quadrants in accordance with the weighting of the overall image. With such a configuration, accurate measurements can be made.

FIG. 15A shows a detector divided into quadrants, in which a cutting edge illumination with respect to the cutting edge Ki is arranged transversely to a lens element, similarly to FIG. 14B. It can be seen that the respective detector quadrants are designated counterclockwise with Di, Du, Dm and DIV. It can also be seen that the cutting edge Ki crosses the segments or quadrants Dm, Div, Du and Di in turn. It should be noted that the detector quadrants are larger than the projected images of the cutting edge. In particular, a detector surface is preferably used which corresponds to four times the image size in order to avoid signal inequalities due to an image shift beyond the light-sensitive surface.

Displacement of an image in the X direction from the distribution shown in Fig. 15A as shown in Fig. 15B produces an interesting result. In particular, it is immediately observed that as soon as the offset occurs only in the X-axis direction, the proportion of the cutting edge in the detector segments Di plus Do or Dm plus Div remains unchanged. However, this does not apply to the distribution with respect to the detector segments Di plus Div or Du plus Dm. For example, the length of the 15 cutting edge Ki in the detector segment Dm is reduced. This portion of the cutting edge appears instead in the Div-

Likewise, shifting the image in the Y direction from the shape shown in Fig. 15A to that shown in Fig. 15C produces an interesting result. It is observed 20 that if the offset occurs only in the Y-axis direction, the proportion of the cutting edge in the detector segments Du plus Dm or Di plus Div remains unchanged. However, this does not apply to the detector segments Di plus Du or Dm plus Div. Looking at the amount of light in each quadrant while moving from the shape in Fig. 15A to that in Fig. 15C, a certain non-linearity is generated. First of all, it can be shown during the first part of the movement that the proportion of the cutting edge in the quadrant Du decreases until the entire cutting edge Ki 30 runs out of the quadrant Du. The cutting edge then runs out of the detector quadrant Di. In the detector quadrant Du there is no further reduction in light during this movement. There is therefore a non-linearity in the displacement in the Y direction if each 35 quadrant is considered separately, but the sums Dr plus Du or Dm plus Div behave linearly with the displacement in the Y direction.

It has been shown that differentiating the total sum of light with respect to the light received in certain quadrants-40th produces a signal that is proportional to the displacement in the X and Y directions. For example, the following formula gives a signal related to the displacement in the X direction if it is in this direction:

li + lii + liii + livJ

In a corresponding manner, as a result of the nonlinearity which occurs when the axis is displaced along the Y axis according to FIG. 15C, it was again determined that by differentiating certain segments with respect to the other detector segments, an amount of 55 compared to the total received light was received signal related to the Y-axis offset can be generated, which results from the following formula:

y | li + lii + liii + liv

65 Each means:

Dx the displacement in the X direction,

Dy the displacement in the Y direction,

Li is the amount of light striking the quadrant I,

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Lu the amount of light striking quadrant II,

Lui the amount of light striking quadrant III, and

Liv the amount of light striking quadrant IV. (The detector quadrants Di to Div are meant in each case).

When using most lens refractors, there is an alignment problem that is always encountered. In particular, the eye must be "identified", i.e. brought into exact alignment with the optical axis of the instrument or, in another description, brought into an «XY» alignment. If the eye is "locked" along the optical axis, the position of the eye in relation to the distance from the instrument is still important. A special aperture was developed for this side of the problem.

Figure 16A shows a detector used with the invention. In particular, four prisms 401, 402, 403, 404 are arranged in a square arrangement. The prisms in this square arrangement define a central square aperture 410 and four square peripheral or corner apertures 411, 412, 413 and 414. Each prism has an opaque surface and three milled edges, from which light is emitted. The prism 401 specifies the opaque surface 400 and the three light-emitting edge regions 415, 416 and 417.

A light-emitting diode LED is focused on each edge area via a lens. The LED is focused over the lens and from there through the prism in such a way that a greatly enlarged image of the LED is focused into the eye to be examined. In the prism 401, the LED 405 is focused by the lens 409 and experiences two refractions on and in the prism 401 (when entering and leaving the prism) and a reflection on the lateral gable surface. These light deflections emit light from the prism edge area 415. Typically, the chamfered edge portion 415 of the prism is directed so that the light from the LED is directed toward the eye. A “bubble plate” surface is preferably added to the prism optics, preferably on the surface of the first entry of the light into the prism.

In the same way, the LED 406 is caused to emit focused light by the edge region 416. while the focused light of the LED 407 passes through the edge area 417. The respective prisms 402, 403 and 404 are provided with light-emitting edge regions in the same way as the prism 401.

All the edges formed by the edges are preferably masked in such a way that light incident directly above them is passed on to the detector, while the remaining light is rejected. This masking is shown in Fig. 16A.

In particular, it should be pointed out that the corner regions of the light-emitting edge regions are masked. It can be seen like this. (FIG. 16A) that the corner regions 420 are coated on the prisms 401 and 402.

Light is emitted from the respective prisms to the eye to be examined and returns from the eye to be examined by means of projection optics already described but not shown here. The light received passes the cutting edge determined by the combination of prisms and the apertures. The light then enters the interior of a detector with the square arrangement previously shown. When entering the interior, the light passes through a special lens element or a Wöbbel plate V. (preferably the bubble plate shown in FIG. 17) and then via a focusing lens to the detector, on which an image K ″ is formed. An analysis is carried out there of the cutting image.

16B shows an image of the front of the detector as seen by the eye of the patient to be examined. It should be noted that the light emitting edges 416 on the one hand and 418 and 419 on the other hand are aligned along a horizontal upper edge of the detector. The length of the edge 416 is equal to the total length of the edges 418 plus 419. It can thus be said that the two outer edges together have the same length as the inner edge 416.

Also note that edge 416 is opposite to edges 418 and 419. If it is now assumed that the edge comprising the edge region 416 turned in one direction and the edge regions 418 and 419 turned in the opposite direction is illuminated, the same but opposite refraction effects are produced in one eye by the different edges. In other words, the edge effects do not give a weighted image with a revealing display of the spherical or cylindrical correction required. In other words, the illumination along a single edge in which the same sections are present in the opposite direction does not produce a detectable prescription correction.

With respect to the linear edge that includes the illuminated edge areas 426, 428 and 429, the same determination can be made. Since the same sections of the edge are illuminated in the opposite direction to one another, no weighting of the images in the eye is recorded either. However, with reference to Figure 16B, it can be shown that the sequential illumination of these respective images can be used in the alignment of an eye.

16C is a schematic representation, in which it is assumed that the eye shown is correctly centered in the XY plane. This alignment is carried out by measuring the image light incidence impinging on the quadrants Di, Du, Dm and Div of the detector.

The problem to be solved now is how to correctly position the eye in the Z-axis direction, i.e. the distance of the eye to the detector is determined. In the schematic representation of Fig. 16C, the respective light-emitting edge regions, i.e. the upper edge regions 416, 418 and 419 and the lower edge regions 426, 428 and 429 are shown schematically.

It is to be said here that FIG. 16C is a purely schematic illustration in which the focusing optics P are intended to achieve the convergence of the image from the edges to an active detector, and the specialized optics V as well as the patient's eye are omitted. 16C, the images for the respective cutting edge regions are shown at different distances. Of the six detector images shown, the top two images relate to the eye at the correct distance from the detector. The two middle images are the result of the detector if the eye is too close and the lower two if the eye is too far.

The right column means the images that result when the cutting edges 416, 418 and 419 are illuminated, while the left column shows images that arise when the cutting edges 428, 426 and 429 are illuminated. Typically, these images are first illuminated with a linear set of cutting edges and then generated by illuminating the second linear set of cutting edges.

In the upper images with the eye at the correct distance, it can be seen that the image formed by the cutting edges 418, 416 and 419 is the same as that when the cutting edges 428, 426 and 429 are illuminated.

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If the eye is too close, the image created by the cutting edges 418, 416 and 419 moves upwards on the detector surface. Large concentrations of the resulting images appear on the upper quadrants Di and Du- The effect on the image of the cutting edges 428, 426 and 429 is in the opposite direction, i.e. the respective images of the cutting edges largely fall on the quadrants Dm and Div-

Typically, the edges of the detector are either modulated with their own discrete signal so that the images can be separated from one another, or they are switched on alternately. In any case, the output signal of the detector from the quadrants of the detector gives an indication of the distance position of the eye (not shown).

As the two diagrams below show, the effects are reversed if the distance between the eyes is too large, i.e. the image of the edges 418, 416 and 419 moves down to the detector quadrants Dm and Div, while the image of the edges 428, 426 and 429 moves up to the quadrants Di and D '.

It can be observed that the respective resulting images of the cutting edges are symmetrical, i.e. that they are equally weighted around the center line. The reason for this is that the opposing blades have the same overall length. The result of this is that the respective cutting edge images produced are insensitive to the optical errors encountered in the eye in question.

It can be seen that the image produced is insensitive to any optical errors in the eye, but is sensitive to the positional effects of the eye when it is detected by the instrument.

If it is assumed that the eye is correctly captured,

then the measurement of the eye is carried out in such a way that cutting edges arranged in the same direction but now in different positions are illuminated. A cutting edge test using such a cutting edge group is now shown, the cutting edge test with the other cutting edges being analog and easy to understand.

A typical cutting edge examination is shown with reference to the schematic representation of Fig. 16D. The cutting edges 416, 428 and 429 are shown here. The cutting edges pass through a projection optics P to a detector with the detector quadrants D (, Du, Dm and DiV.

First of all, it should be noted that all cutting edges 416, 428 and 429 are oriented in the same direction. The image created via one eye is therefore responsible for the necessary corrections, i.e. the optical defects of the eye are sensitive. If normal vision is assumed at first, the detector segments report a minimal signal. Since the respective cutting edges are evenly distributed around the central axis of the optical instrument and produce illumination that is uniformly centered around the optical axis of the instrument, the position sensitivity of the measuring system is minimal. This means that the instrument reacts to the eye's positional errors in relation to the detector and the lighting device in a barely measurable way.

In accordance with the representations given earlier, a farsighted eye creates an image on one side of the detector, for example on the detector quadrants Di and Du. In the same way, a short-sighted eye creates an image on the opposite quadrant Dm, Div- Finally, an astigmatic eye produces an image on the quadrant on one or the other side, the quadrants Du and Dm being shown here as an example.

As the specialist immediately recognizes, the cutting edges present in the detector can be switched over. They are switched so that the opposite of the depicted images are recorded next. This results in the desired “counter-clock” effect for the instrument. In addition, the image can also be continued with the cutting edges on the left or right. That is, measurement can be performed using a cutting group on the left side and then the opposite cutting group on the right.

At this point it should be noted that the LED of each group and the detectors used with it can be modulated. As a result, the measurements can be carried out simultaneously at the same time and the modulated signals reflected by the eye can be separated from one another. Using a central visible target or fixation point for the eye, the eye can be focused on a vision target or target. This focusing of the eye then results in a lens refraction for the eye adapted to different distances.

For the selected imaging system it is to be understood that the cutting edges are all active and have a common centroid. If the images on detector D are incident, they are assigned to each quadrant with the same intensity. FIG. 16E now shows an optical “train”, and in FIG. 16F the corresponding image on the detector is shown, and the compensation of the specular reflection image with respect to the alignment of the detectors used to measure the corrections to be prescribed by the light measurement is shown there .

16E, three light sources A, B and C are shown on one eye E. The images of these light sources are guided through optics (not shown) to three real image locations, which are designated by Ka, Kb and Kc. The image Ka is located above the optical axis and is twice as long as the respective images Kb and Kc. An image of these optical conditions is passed through the specialized optics V to the detector D. The specialized optics V has already been described.

16F shows the light centroid on detector D. This centroid applies to mirror-reflected light and does not contain any optical (prescription) eye corrections.

It can be seen that each image is offset from the optical axis by a certain amount. Thus, if the detector D is either too close or too far away, the respective movements of the image from each light source remain the same.

It can be seen from Figures 16G and 16H that this is not the case when a single cutting edge is used. In FIG. 16G, a pupil with a single real-imaged light source A sends its image to the specialized optical plate V with the cutting edge Ka. This is then forwarded to the detector level by optics (not shown). Assuming that the detector plane is at the correct distance from the eye, the image would hit the center. However, since the eye is either too far or too close, the image is shifted. In particular, it will shift away from the center. The shifted image of an eye pupil is shown in FIG. 16G.

16H now shows a centered image. It can be shown that the light center is shifted in relation to the detector quadrants Di, Du, Dm and DiV. In fact, the image migration has taken place from the upper two quadrants Di and Du to the lower quadrants Dm and Div.

Now if you go back to the three-source arrangement and assume the case of light that is not specularly reflected,

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the effect of the positioning of the optics shown here can be explained (closer or further) with reference to FIG. 16J.

If the detector D is in the position Di, based on the specialized optics V and the images Ka, Kb and Kc, it can be seen that all the images essentially come to coincidence. That is, they are imaged on a central spot on detector D. However, if the detector is too far away, for example in a position D2, three images result, as are shown larger in FIG. 16L.

With a nearsighted eye, FIG. 16L shows how the three images are created. The bottom image IA will be twice as intense as the top two images IB and Ic. These images IB and Ic are each shifted in accordance with the (prescription) correction required for the eye. In view of the previous discussion, it can be seen that the shifts in the individual detector quadrants Di to Div add up in such a way that the same result is achieved as in the single image shown in FIG. 16K. It follows that the detector scheme shown is insensitive to the distance of the eye from the device.

With this explanation the description of the immediate process can now be given. First, the axial distance alignment explained with reference to FIG. 16C is carried out. As soon as the eye is roughly set up, the measurements relating to the (regulation) corrections are made. These measurements are carried out as shown in Figs. 16J, 16K and 16L. It is thus possible, if the eye is initially correctly grasped and then migrates from the original position, that the optics described are relatively insensitive to such a movement. Correct readings for the corrections are obtained, i.e. correct lens refraction.

As for mirror reflection, with reference to the illustration shown in Fig. 16F,

that the areas of the light sources are important. In particular, because the moment of the optical surfaces above and below the horizontal axes and the moment to the left and right of the vertical axes are the same, mirror reflections from the eye itself even out in the different detector segments. As a result, with the cutting edge arrangement shown, the refraction measurement values cannot be disturbed by reflected reflex light.

Another dimensioning of the cutting edge configuration is also illustrated with reference to FIG. 16J. In particular, each cutting edge Ka, Kb and Kc has the same length and the same area. The respective cutting edges are two length units away from a horizontal axis in the case of the cutting edge Ka and one length unit in the case of the cutting edges Kb, Kc. These distances are indicated by 2a for the cutting edge Ka and a for the cutting edges Kb and Kc. In this case, the cutting edges each have the same length, which is indicated in FIG. 16J.

16L now shows the unfocused centroids of the image. In particular, it can be seen that the lower image Ia is offset from the horizontal axis by a mass which corresponds to twice the distance between the centers of the two upper cutting edge images Ib, Ic. The refractive index signal is not disturbed due to axial distance errors. It should be pointed out that for the best effectiveness, the light receiving or viewing apertures in the vicinity of the cutting edges are also essentially the same moments

should have above and below the horizontal axis and to the left and right of the vertical axis.

18A to 18D show distribution patterns which are formed on the detector due to a decentered pupil with an arbitrary refractive error (ball plus cylinder refractive power with an oblique angle to the cutting edge).

Figures 18A and 18B show inspection with horizontal cutting. The cutting edge K in FIG. 18A is arranged such that the light passes through the reception area 400 under the cutting edge K and over the linear boundary 415. In the same way, in FIG. 18B an area 402 receives light that lies directly above the cutting edge 415. In FIGS. 18C and 18D, the cutting edges are directed vertically and are located here to the left and right of the pass-through or receiving areas 404 and 406, respectively. In each of FIGS Detector area shown. This is the detector with quadrants Di to DiV, which has already been discussed several times.

In the case of the illustrated image forms, it is to be understood that the light is thrown onto the detector level by the preferred optics described. The light incident on the detector plane thus does not have the appearance shown schematically on the detector surfaces in FIGS. 18A to 18D, but, as already explained, will be evenly distributed. In each case according to FIGS. 18A to 18B, the detector measures two values which are proportional to the X-centroid position times the total received light flux and the Y-centroid position times the total received light flux. Since the total flow is the same for both values, the values are actually proportional to the centroid positions according to X and Y.

In addition, it is recognized that the arrangement of source and detector is designed in such a way that each cutting edge has the same total light values and is symmetrical in every respect around the pupil image center on the detector. In this way, the measured values can be added and subtracted using a method described below, so that both refraction and pupil de-concentration information can be obtained.

In Fig. 18,

Xca = Rxa + Xp Yca = Rya + Yp,

in which

Xca = X value of the centroid position,

Yca = Y centroid position,

Rxa = displacement of the centroid from the pupil center in the X direction,

Rya = displacement of the centroid from the pupil center in the Y direction,

XP = X value of the pupil center,

Yp = Y value of the pupil center

The same applies in FIG. 18B

Xcb = Rxb + Xp Ycb = Ryp + Yp

As a result of the described distribution symmetry

Rxb = —Rxa Ryb = —Rya so that:

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Xcb = xp - Rxa Ycb = Yp - Rya-

That means:

Xca + Xcb = Xp + Rxa + Xp - Rxa = 2Xp Yca + Ycb = Yp + Rya + Yp - Rya = 2Yp.

This shows that the measured values can be added, i.e. the x-values and the y-values together to obtain values that are directly proportional to the pupil decentration. It should be noted that there is no (prescription) refractive power information here.

Similar results:

Xca - Xcb = Xp + Rxy - (Xp - Rxy) = 2Rxa Yca - Ycb = Yp + Rya - (Yp - Rya) = 2Rya

This shows that correct subtraction of the measured values leads to values that are directly proportional to the displacement of the centroid (i.e. the center of gravity determined according to the above formula) of the received pupil pattern from the pupil center itself. In addition, since these values are the displacements of the centroid in the X and X directions, both the size and the direction of this displacement result, which in turn are directly related to the refractive error, as explained earlier.

It was previously noted in this description that a parallel series of cutting edges does not provide complete refractive information (although it does result in pupil decentering). The rest of the necessary information will now be included about the second parallel row of cutting edges corresponding to Figures 18C and 18D. It should be noted that the relative position of the pupil center to the detector center is the same in all figures.

In summary, adding all X-centroid values gives a value that is proportional to the X-component of the pupil decentration. By adding all Y-centroid values, a value proportional to the Y component of the pupil decentering is obtained, and by correctly subtracting the values for parallel pairs of cutting edges, four values that are proportional to the refraction are created:

Xca - Xcb = 2Rxa Yca - Ycb = 2Rya Xcc - Xcd = 2Rxc Ycc - Ycd = 2Ryc

Then it follows that values proportional to the spherical equivalent (Seg), to the cross cylinder axis 90c / 180 + (C +) and to the cross cylinder axis 457135 ° (Cx) can be obtained if the refraction proportional values are combined in the following way:

Seg ~ Rxc + Rya C + ~ Rex - Rya Q ~ Rxa + Ryc where

C + the 0-90e cylinder power and

Cx is the 45-135 ° cylinder power.

It can be seen that the detector described can also be used to control refractive optics in such a way that the signals received on the detector surface are compared. This circuit is already described and claimed in the same applicant's US Pat. No. 4,070,115. In particular, this patent describes an invention which can be summarized as follows:

A lens measuring device is described in which continuously variable correction optical elements for spherical and cylindrical refraction are manipulated in order to measure the correction values for an optical system to be examined. A target containing a straight line is focused to maximum sharpness, the target being oriented arbitrarily with respect to the axes of the optical system to be examined. Continuously variable spherical and first astigmatic optics elements are used in the immediate vicinity of the optics to be examined and the target image is projected through the optics to be examined and the continuously variable optics. Spherical and first astigmatic corrections are then determined along at least one axis diagonally to the line target until the maximum sharpness of a projected image of the straight line results. A first component of the astigmatism correction results. A second target, again consisting of a straight line, is introduced, which is preferably inclined at 45 ° with respect to the first target. A spherical adjustment is now made again together with a diagonally directed second astigmatism correction along at least one axis lying diagonally to the second line target until there is maximum sharpness of the projected image of the straight line. The result is a second component of the astigmatism correction and the final spherical correction. Precautions for remote control of the continuously changeable optics are described in order to automatically determine the corrections.

With reference to FIG. 5 of this patent specification, a circuit diagram is specified with which a detector with four distinct quadrants can control the optical elements in order to achieve a balanced image. The adaptations of this circuit to the conditions of the described detector image can easily be made by the person skilled in the art in this field. 16G, schematic lenses for achieving such a balanced image are shown as variable spherical lenses 516.0C - 90 ° cylindrical lenses 518 and 45 ° - 135c cylindrical lenses 520. This lens arrangement is taken directly from FIG. 5 of the US patent mentioned.

A particular advantage of the invention is that the refractive power information provided by the eye does not depend on the ability of the eye to reflect light back to the detector. It may be the case that a retina has enlarged blood vessels and / or other deformations as a result of pathological changes. Such a retina is unable to return light uniformly back to the detector over the entire area. In this case, the back light obtained when examined with a cutting edge according to FIGS. 18A-18D will differ significantly in intensity from the light obtained when examined with other cutting edges. The effect of irregularities in the retina can nevertheless be compensated for by mathematically equating the total light intensity in each measurement case.

It is again pointed out that in the preceding description and the equations with reference to FIGS. 18A-18D, “light flux moments” were used with reference to the respective detector quadrants used. Throughout this description, the term "moments" should always be used in the manner set out there.

It should also be pointed out once again that the apertures used are symmetrical for trouble-free operation

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should be, and the surfaces of the apertures and the receiving or receiving surfaces (windows) should also have the same moments.

It should also be emphasized again that when using cutting edges they do not necessarily have to be at right angles to each other. For example, cutting edges that form an angle of 45: can be used. In addition, when adapting the described calculations and / or the optics and the detector surfaces, different angles can be used between the examination edges. The preferred version at the time of registration was the use of parallel and oppositely directed cutting edges in a symmetrical, right-angled version.

Any system known in the art for this application can be used as the optical system between the “Wöbbel plate” and the eye.

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27 sheets of drawings

Claims (3)

664 888 PATENT CLAIMS 1. Device for eye examination, characterized in that at least one light source (250) is provided for projecting light to an eye, that the light source is delimited by a light zone, which delimitation corresponds to first and second cutting edges (K) that the first cutting edge is substantially perpendicular to the second cutting edge, that first and second light paths (261-263) for illuminating the eye start directly from the light zone (261 '- 263') under the first and second cutting edges, that first and second light paths (252) for observation of light returning from the eye run directly over the cutting edges and that a detector device (D) connected to the light observation paths past the cutting edges is present for observing the characteristic illumination on the eye. 2. Device according to claim 1, characterized in that the light source is delimited by first (401), second (402), third (403) and fourth (404) cutting edges. that the first and third cutting edges are substantially perpendicular to the second and fourth cutting edges and that first, second, third and fourth light paths (252) to the eye are provided to observe the illumination of the eye past the respective cutting edges. 3. The device according to claim 1, characterized in that the first cutting edge and the first light path (401) are arranged opposite to the third cutting edge and the third light path (403).