CA2961398C

CA2961398C - Method for accurately determining optical parameters of a test subject in order to adapt a pair of eyeglasses to the test subject, and immobile video centering system

Info

Publication number: CA2961398C
Application number: CA2961398A
Authority: CA
Inventors: Hans-Joachim Ollendorf
Original assignee: Individual
Current assignee: Individual
Priority date: 2014-09-16
Filing date: 2015-09-16
Publication date: 2021-06-08
Anticipated expiration: 2035-09-16
Also published as: EP3195052A1; KR20170054511A; DE102014013447A1; EP3195052B1; CA2961398A1; KR102194178B1; WO2016041536A1; DE112015004209A5

Abstract

The invention relates to a method for determining optical parameters of a test subject with measurement accuracy in order to adapt a pair of eyeglasses by means of a stereo camera system (4), a mirror (3) arranged at the height of the stereo camera system, and a data-processing and data output device, in which additionally the correction data of the cameras of the stereo camera system (4), the image scales of said cameras, and information about the position of said cameras in space are stored. The test subject (1) directs his view at the mirror image of his head arising in the virtual mirror plane (5) (null viewing direction), while both cameras simultaneously record an image of the region of the head of the test subject (1) provided with the eyeglass frame (2). The direction, distance, and height position of the optical data are determined means of the software and by using the stored correction data, image scales, and position information, wherein existent size changes and distortions due to position are offset by means of correction calculations. Thus, only one recording of the face of the test subject is required to determine the centering data of the pair of eyeglasses, whereby the measurement time and thus the time burden for the test subject are significantly reduced.

Description

I
METHOD FOR ACCURATELY DETERMINING OPTICAL PARAMETERS OF A
TEST SUBJECT IN ORDER TO ADAPT A PAIR OF EYEGLASSES TO THE TEST
SUBJECT, AND IMMOBILE VIDEO CENTERING SYSTEM
FIELD OF THE INVENTION
The invention relates generally to a system and process for accurately determining optical parameters of a test subject in order to adapt a pair of eyeglasses to the test subject, and more particularly to an immobile video centering system and process therefore using a stereoscopic camera.
BACKGROUND
Methods for accurately determining optical parameters of a test subject and immobile video centering systems for determining optical parameters of a test subject already belong to the prior art. For example, a device and a system for determining optical parameters of a user are known, wherein in this method the image data at least of sub-regions of the user's head are generated from at least two different photographing directions. User data about at least a sub-region of the head or at least a sub-region of a system consisting of the user's head and a pair of eyeglasses arranged in the use position on the head can be determined from these image data, wherein the user data include location information in the three-dimensional space of predetermined points in the sub-region of the head or the sub-region of the system. Based on the user data, at least some of the optical parameters of the user are determined and are then output.
The device for carrying out this type of method comprises at least two image recording devices, a data processing system and a data output device. The image recording devices are designed such that each of them produces image data for at least sub-regions of the user's head. Their effective optical axes intersect at an angle of intersection of between 100 and 60 , or the smallest distance between them is less than 10 cm, wherein the projection of the effective optical axes onto a horizontal plane intersect at an angle of 10 to 60 , and the projections of the effective optical axes onto a vertical plane parallel to the effective optical axes intersect at an angle of 100 to 60 .
Date Recue/Date Received 2020-08-13

2 The data processing system has a device for determining user data, which is configured to identify user data about at least a sub-region of the head or at least a sub-region of a system consisting of the user's head and a pair of eyeglasses arranged in the use position on the head based on the image data that are generated.
The data processing system further comprises a parameter determination system, which is configured to identify at least some of the optical parameters of the user on the basis of the user data. Advantageously, the data processing system is a computer or microprocessor that performs the two tasks, i.e. determining both the user data and the parameters. The data output device outputs at least some of the optical parameters that have been determined for the user (EP 1 844 363 B1).
The disadvantage of this method is that it requires images to be taken from positions at different heights to the user's face and therefore arranges the camera at different heights to the user, and their effective optical axes must be oriented at particular angles to the user's face, especially the bridge of the nose, wherein the optical axis of a camera must always be oriented in a neutral viewing direction. If only one camera is used, the image must be recorded with an appropriate deflection device.
Moreover, the mirror for the camera arranged behind the user must be semi-transparent.
Furthermore, this device requires the test subject's face to be positioned relatively close to the mirror, namely less than 20 cm, which does not correspond to a natural long-distance vision situation. In practice, positioning with this level of precision is difficult to accomplish and always requires a certain amount of influence by the test subject, and so one of the essential preconditions for a reliable determination of the parameters, namely normal relaxed head and body posture by the test subject, is likewise difficult to achieve.
A further substantial disadvantage of this method is the high degree of manual effort and correspondingly large amount of time expended by both the user and the test subject, since none of the measuring points are automatically provided to the system;
they must all be marked on the monitor manually by the user.
Also known is an in situ video centering system with an assessment of the test subject's field of vision to determine the centering data for a pair of eyeglasses, having an imaging unit, a camera unit and a software-based evaluating unit for the Date Recue/Date Received 2020-08-13

3 video recordings. The imaging unit, such as a screen, is placed at head height for a test subject. At least one camera, which the test subject does not see, is placed on each of the right and left sides. Images that are visually interesting to the test subject are shown to the test subject on the imaging unit, and so he is prompted automatically and by his ability to see to assume particular distances and positions relative to the screen in order to follow the events on the screen; in other words, the test subject directs his view and/or head movements in the directions and positions required to determine the centering data for the eyeglasses without being instructed to do so simply by following the events on the screen (WO 2011/131169 Al).
Although this creates an in situ situation that is pleasant for the test subject, relaxed and not directed by instructions by an optician or considered annoying, it nevertheless requires a certain amount of concentration by the test subject when following the images. Additionally, the method is very time-consuming, since various pupil positions must be recorded in order to determine the centering data, and the test subject must therefore be stimulated to change his viewing direction over a longer period of time. Furthermore, because a screen must be provided and the images produced to provoke the attention of the test subject, the video centering system itself is still relatively complex.
A video centering system and a method for determining centering data for eyeglass lenses are also known. This mobile video centering system consists of at least one image capturing device (stereo camera system with fixed optical axes), an image processing unit with a computer and a controller, wherein all components are integrated into a mobile housing. Additionally, a screen for displaying optotypes is located on the side of the video centering system facing the test subject. In the method for determining centering data for eyeglass lenses, additional lines of sight for the test subject's various viewing situations are calculated in relation to the eyeglass frame. For this purpose, a user places the video centering system in a position characteristic for a viewing situation and, supported by a display arranged on the rear side of the device facing the user and after inspecting and correcting the position, if necessary, the user activates all image recording devices simultaneously (DE 10 2011 009 646 Al). To carry out the method, it is necessary to calibrate the image recording devices or adjust the entire system before or during the recording of the images. Also disadvantageous is the fact that the video centering system must Date Recue/Date Received 2020-08-13

4 always be held at the level of the test subject's face.
Stereoscopic measurement methods are likewise known which permit the fully automatic three-dimensional measurement of particular clearly defined geometric bodies, e.g. workpieces such as lathes or mulled parts.
When it comes to the tasks related to video centering, the conventional methods for the stereoscopic three-dimensional measurement of three-dimensional bodies (for example, by means of algorithms for identifying correlations and functions in epipolar geometry) rendered in two two-dimensional images (stereo images) are not successful for two primary reasons:
1. The known methods for stereoscopic measurement require uniquely assignable points in both two-dimensional representations (images) which have exactly the same position on the three-dimensional body, such as the corner of a cuboid. In the objects to be measured, i.e. eyeglass frame and human eye, this is not established in the first approximation.
2. The measurement task of video centering involves a determination of the optical center of the lens when the test subject is looking in a neutral viewing direction. In conventional stereo camera systems, this neutral viewing direction is not shown in the two two-dimensional representations (images) because, to do so, it would have to be ensured by means of mechanical and electronic control technology that the camera system is located at eye level for the test subject, which itself is associated with increased effort.
Finally, a method, a device and a computer program product for determining individual parameters of an eyeglass wearer are known. In this method, the optical user data are determined by multiple image recording devices arranged one above the other at equal distances from one another. The optical axes of the image recording devices that are arranged directly above one another are thus oriented parallel to one another (DE 10 2012 007 831 Al). Preferably, a special room in which the image recording device is arranged and adjusted is required for the image recordings.
Date Recue/Date Received 2020-08-13

5 The invention therefore addresses the problem of developing a method for accurately determining optical parameters of a test subject in order to adapt a pair of eyeglasses to the test subject, said method requiring less measuring time and fewer activities performed both by the operator and by the test subject. The known immobile video centering systems for determining optical parameters of a test subject in order to adapt a pair of eyeglasses to the test subject should be modified such that they require less effort and allow for a measuring process that is less demanding for the test subject.
SUMMARY OF EMBODIMENTS OF THE INVENTION
By contrast, a method for accurately determining optical parameters of a test subject in order to adapt a pair of eyeglasses to the test subject, according to at least an embodiment, has the advantage that it requires only one recorded image or only a brief series of images of the test subject's face or the region of the face occupied by the eyeglasses in order to calculate the centering data of the eyeglasses after the test subject looks into his own eyes in the mirror, which is already used in devices known from the prior art to carry out similar methods, as a result of which the test subject more or less automatically assumes the neutral viewing direction (horizontal line of sight into the distance) that is required to record the image. By simultaneously activating the at least two cameras of the stereo camera system, the measuring time and thus the time burden on the test subject are significantly reduced.
The method according to at least an embodiment also includes that the characteristic values and specific imaging properties of the at least two cameras of the stereo camera system, including their imaging errors, such as distortions, are recorded and, using a physical-mathematic model, saved in the software of the data processing and data output device as correction values, e.g. in the form of a table of values. The characteristic values of the camera can be easily determined with a suitable measuring device and/or measuring method, since the specific imaging properties of the camera adhere to the laws of trigonometry (intercept theorem). The specific imaging properties include the image size of the eyeglasses as well as the position of the concrete (discrete) height ranges of the glasses in the imaging area of the Date Recue/Date Received 2020-08-13

6 camera, both depending upon how far the glasses are from the lens plane of the at least two cameras. The characteristic values "focal distance," "position of the cameras relative to each other" and "distance range" are interpreted such that each point in space in the measurement area is recorded by both cameras. The correction calculations saved in the software make it possible to detect, for example, the optical centers of the lenses in the test subject's horizontal viewing direction, although they are not shown in the images recorded by the cameras.
In an embodiment, the optical and electronic functions of the electronic cameras, which are configured as a stereo camera system, as well as their spatial position relative to each other are determined as precisely as possible by a calibration method during the process of producing the system.
The evaluating software examines the individual stereoscopic images of the object (eyeglass frame) for known features such as the shape of the eyeglass frame or parts of the eyeglass frame shape. Three possibilities exist for this process:
1. In the event that the concrete shape of the eyeglass frame is available as a set of design or measurement data for concrete measurement, these data will be used throughout the procedure.
2. If this is not the case, the evaluation software automatically compares easily identifiable eyeglass frame moldings with the general database stored in the data processing and data output device, which contains typical eyeglass frame shapes, and selects from the database the eyeglass frame shape most closely corresponding in shape for the rest of the procedure.
3. If that is also not possible, e.g. because the shape features (edges) of the eyeglass frame detected by the software are insufficient to allocate an eyeglass frame shape from the general eyeglass frame database, then the software uses the detected eyeglass frame shape edges to determine the features necessary to measure the centering data.
Date Recue/Date Received 2020-08-13

7 The complete eyeglass frame shape that is known in detail from this process, or the features that are detected in the 3rd case, are correctly positioned by the evaluation software in all three spatial axes in the individual stereoscopic images such that a horizontal shortening of the image is realized by the horizontal torsion of the object to be adapted.
The features of the adapted eyeglass frame shapes in the individual stereoscopic images known in detail from this process are drawn up using stereoscopic measurement technology, e.g. measuring with epipolar lines.
In preparation for detecting the optical centers that are to be determined between the eyeglass frame and the test subject's pupils in a neutral viewing direction, the distances between the centers of the pupils and the known features of the eyeglass frame shapes fitted into the individual stereoscopic images are measured in the individual stereoscopic images.
Using the methods illustrated and thus the values ascertained up to this point, the evaluation software is capable of establishing a stereoscopic three-dimensional model of the eyeglass frame including the centers of the test subject's pupils.
Since the structural details, such as the structurally known distances, and the position of the aforementioned features of the eyeglass frame are known, the evaluation software also utilizes the three-dimensional model to determine the position of the cameras relative to the eyeglass frame, such as the distance and relative height of the eyeglass frame relative to the stereo camera system.
In a typical image recording situation, the height of the camera is not equal to the height of the pupil. The (apparent) optical centers of the lenses visible in the individual stereoscopic images thus do not correspond to the actual optical centers, but rather, if the camera is lower than the height of the pupil, are likewise lower.
Since the position of the pupils and thus of the eye's center of rotation are known in the three-dimensional model in addition to the positions of the eyeglass frame and the cameras, the evaluation software uses trigonometric methods to calculate the Date Recue/Date Received 2020-08-13

8 optical centers of the lenses in a neutral viewing direction.
In the case of stereoscopic recordings, the cameras in the horizontal direction are not located in the test subject's viewing direction, but each is instead placed laterally outward and outside of the viewing direction.
Therefore, the (apparent) optical centers of the lenses visible in the individual stereoscopic images do not correspond horizontally to the true optical centers, but are actually offset laterally.
The evaluation software uses trigonometric methods (theorem of intersecting lines between the test subject's viewing direction and the recording beam of the camera) to calculate the optical center according to the viewing direction in the center of the mirror between the cameras.
In an embodiment, the method proceeds in the presence of the test subject as follows:
The test subject with an anatomically well-fitting eyeglass frame is situated in front of the stereo camera system and the mirror within a distance range of between 0.5 m and 1 m (approximately arm's length) so that he is recorded by both cameras.
He is instructed to look himself in the eyes. As was mentioned above, this causes the test subject to assume a relaxed head and body position, and the test subject's gaze is fixed in a neutral viewing direction at a double distance from the mirror in the virtual mirror plane. This relaxed natural head position with a horizontal viewing direction is desirable and, to a certain extent, necessary for an accurate measurement. A
video centering device in which such a method is carried out is described further below.
All of the cameras of the stereo camera system simultaneously make a synchronized recording of at least the region of the test subject's face occupied by the eyeglass frame.
By using the saved correction data, image scales and position information described above to evaluate the positions of the eyeglass frame shapes in the imaging area of Date Recue/Date Received 2020-08-13

9 the images, the software calculates the direction, distance and height of the features.
At this point, all of the boundary conditions of the recording are known, and so any other image information about the object, such as the position of the centers of the test subject's pupils, are used for geometric measurements, since all available position-related and direction-related size changes and distortions can be offset by correction calculations.
An immobile video centering system according to an embodiment has the advantage over the prior art described above that it is designed very simply and does not require moving cameras, regardless of the size of the test subject, or optical animations for the test subject. It is possible to determine the optical parameters of the eyeglasses without orienting the cameras at the eye level of the test subject. Owing to their angular aperture, the cameras that are used record different body sizes of test subjects without having to be arranged exactly at their head level or to be adjusted to it. Using only a simple mirror, which does not have to be semi-transparent, the test subject merely has to concentrate on his own reflection, which, in the virtual mirror plane behind the mirror, appears equidistant to his own distance in front of the mirror.
The test subject automatically concentrates on his reflection, in particular on the new eyeglass frame, looks into his own eyes and thereby ensures the required neutral viewing direction. This also contributes to reducing the measurement time and thus the time burden for the test subject. An additional advantage of the video centering system is that it is less sensitive than the first-mentioned prior art publication in terms of maintaining the distance between the test subject and the mirror. As is mentioned above, the distance can vary in the range between 0.5 and 1 m.
A particular advantage of the disclosed embodiment without vertically displaceable cameras can also be seen in the fact that it becomes possible to configure the recording device with a very flat design so that it can be installed, for example, in an optician's shop like a conventional mirror, possibly hung on a wall or set up on a table.
These advantages of the disclosed immobile video centering device are achieved in that a stereo camera system is used as an electronic image recording device, said system consisting of at least two cameras, the electronic functions and optical Date Recue/Date Received 2020-08-13

10 imaging properties of which are known as precisely as possible. The related characteristic values are stored in the data processing and data output device associated with the video centering system.
The cameras are arranged immovably at the same height and at a defined horizontal distance from each other at the level of the mirror, each symmetrically to the central longitudinal axis of the mirror, i.e. their positions, their defined horizontal distance from each other and their orientations relative to the position of the test subject and relative to the mirror in the room are fixed in a defined way. Their defined optical axes are oriented exactly horizontally toward the test subject, and so the field of vision of both cameras includes at least the part of the test subject's face that is occupied by the eyeglasses. This immobilization is necessary to calculate the centering data of the glasses in order to exclude measurement errors caused by any inadvertent changes to geometric relationships. Of course, it is also possible to arrange the cameras such that their horizontal positions and orientation relative to the test subject can be changed. In that case, however, it must be ensured that they are securely fixed in place once they are positioned and oriented. The focal distance of the cameras, their horizontal spacing and distance range to the test subject are selected such that each point in space in the measurement area is recorded by the at least two cameras, which are arranged at the same level on both sides of the mirror.
According to an advantageous embodiment of the invention, the cameras are placed at mid-height of the mirror. Since mid-height of the mirror is already set at the average eye level of an adult, the cameras will certainly record the eye region of smaller and larger persons. Children may have to be placed on a stepladder or higher stool.
According to another advantageous embodiment of the invention, the cameras have a fixed focal distance. Inadvertent adjustments that could occur with zoom lenses and result in erroneous measurements are thereby prevented. Furthermore, cameras with a fixed focal distance are less expensive. For a simpler evaluation of the images as well as simpler calculation of the measurement values, it is advantageous to use cameras with the same focal distance.
Date Recue/Date Received 2020-08-13

11 According to an additional advantageous embodiment of the invention, the optical axes of the cameras in the horizontal plane are oriented at a defined angle slightly relative to each other. It is favorable for this angle to be between 4 and 12 . In this way, the overlap between the two fields of vision is broadened.
In accordance with an aspect of at least one embodiment, there is provided a method for determining centring data of a subject for fitting spectacles to the subject, using:
- a vertically arranged mirror that is disposed opposite and at an eye-height of the subject, wherein the subject wears an anatomically well-fitted spectacle frame, - an electronic image recording device comprising a stereo camera system that is fixedly disposed within a height of the mirror and symmetrically with respect to a central longitudinal axis of the mirror, and the cameras of which have fixedly defined optical axes, and - a data processing and data output device having spectacle frame data stored therein, the spectacle frame data comprising parameters of the spectacles and of the anatomically well-fitted spectacle frame, and having further stored therein correction data, image scale data and position information of the cameras of the stereo camera system, the method comprising the steps of:
causing the subject to direct his view onto a mirror image of his head in the mirror, such that the subject is looking himself in the eyes, using the stereo camera system, acquiring an image of at least an area of the subject's head that is provided with the anatomically well fitted spectacle frame and obtaining image data therefrom, comparing the obtained image data with the spectacle frame data stored in the data processing and data output device, and determining the direction, distance away and height-related position of the obtained image data using the stored correction data, image scale data and position information of the cameras of the stereo camera system, wherein existent positionally dependent dimensional changes and distortions are countered through correction calculations based thereon, and the required centring data are determined and output as measured values of the spectacles for the subject.
Date Recue/Date Received 2020-08-13

12 In accordance with an aspect of at least one embodiment, there is provided a immobile video centring system for determining centring data of a subject for fitting spectacles to the subject, comprising:
a vertically arranged mirror disposed opposite and at an eye-height of the subject, wherein the subject wears an anatomically well-fitted spectacle frame, an electronic image recording device having at least two cameras, by means of which image data for at least an area of the subject's face having the anatomically well-fitted spectacle frame is acquirable, wherein the electronic image recording device comprises a stereo camera system including the at least two cameras which:
have defined respective optical axes, are each fixedly disposed in a respective position at a defined horizontal distance from one another and with respect to a position of the subject, are each fixedly disposed at a same height and at the defined horizontal distance from one another within a height of the mirror and symmetrically about a central longitudinal axis of the mirror, and the focal length, horizontal distance and focus range of which are selected such that every point within their measuring range is acquired, and a data processing and data output device in operative communication with the electronic image recording device and having spectacle frame data stored therein, the spectacle frame data comprising parameters of the spectacles and of the anatomically well-fitted spectacle frame, and further having stored therein:
a first specific imaging property specifying an image size of the anatomically well-fitted spectacle frame as a function of the distance of the anatomically well-fitted spectacle frame from an objective plane of the at least two cameras, and a second specific imaging property specifying a position of the actual height ranges of the anatomically well-fitted spectacle frame in the imaging region of the cameras as a function of the distance of the anatomically well-fitted spectacle frame from the objective plane of the at least two cameras wherein, during use, image data acquired for the at least an area of the subject's face having the anatomically well-fitted spectacle frame are compared with the spectacle frame data stored in the data processing and data output device, and the required centring data are determined and output as measured values of the Date Recue/Date Received 2020-08-13

13 spectacles for the subject.
BRIEF DESCRIPTION OF THE DRAWINGS
Preferred embodiments of the claimed subject matter are shown in the drawings and are explained in greater detail below. The following is shown:
Fig. 1 a side view of the claimed measurement situation;
Fig. 2 a top view of the claimed measurement situation;
Fig. 3 a side view of the measurement situation in Fig. 1 with a test subject below the camera level; and Fig. 4 an image of a test subject with eyeglass frame with specific eyeglass frame features.
DETAILED DESCRIPTION OF THE DRAWINGS
Fig. 1 shows a side view of a representation of an immobile video centering system according to an embodiment. A test subject 1 with his chosen and anatomically well-fitting eyeglass frame 2 stands in front of a mirror 3 arranged vertically at head level, and a stereo camera system 4 consisting of two cameras in the present example is located at mid-height of said mirror, the two cameras of the system being arranged immovably on both sides of the mirror 3 at the same height and at a defined horizontal distance both from each other and in relation to the mirror 3 (Fig.
2). The distance between the test subject 1 and the mirror 3 or the stereo camera system 4 in the present example is ca. 1 m. For the test subject 1 looking in the mirror, a virtual mirror plane 5 appears equidistant behind the mirror 3. The test subject 1 looks into the mirror 3 in the horizontal direction, the so-called neutral viewing direction 6. The vertical field of vision 7 of the two cameras is determined by their vertical angular aperture, which in the present example is 45 . As can be discerned from Fig.
2, the two cameras in the present example are arranged in the horizontal plane with their optical axes 8 pointing toward the test subject 1 and oriented to each other at an Date Recue/Date Received 2020-08-13

14 angle of 6 . This enlarges the field of vision common to the two cameras, which is indicated by the double-headed arrow with reference sign 9. The width of the mirror 3 approximately corresponds to the width of the test subject's head 1 in the present example. In this way, the test subject 1 automatically positions himself in a region approximately in the center between the two cameras, which in turn simplifies the mathematical evaluation of the images.
Fig. 3 shows the same view of the immobile video centering system as Fig. 1, the difference being that the test subject 1 is smaller than the one in Fig. 1; in other words, his head is located in the lower region of the vertical field of vision 7 of the cameras.
Fig. 4 shows the test subject 1 wearing the eyeglass frame 2 distinguished by a selection of measurement points A through H of the eyeglass frame features, which are relevant to the measurement for the purposes of video centering, as well as the pupil centers I and J in the eyes of the test subject 1.
The measurement points represent the following features of the fitted eyeglass frame shapes:
A Outer point, inner eyeglass frame edge, top right B Outer point, inner eyeglass frame edge, lower right C Outer point, inner eyeglass frame edge, outer right side D
Outer point, inner eyeglass frame edge, inner right side E Outer point, inner eyeglass frame edge, upper left side F Outer point, inner eyeglass frame edge, lower left side G Outer point, inner eyeglass frame edge, inner left side H Outer point, inner eyeglass frame edge, outer left side.
Measurement points A, B, C and D are needed to measure the centering data, for example. Measurement points A and B as well as E and F are utilized, for instance, to determine the width of the frame lens. The distances between the centers of the pupils, which are indicated by measurement points I and J, and the distances which determine the eyeglass frame shape, such as between points C and D and between Date Recue/Date Received 2020-08-13

15 G and H, are measured in the individual stereoscopic images to identify the optical centers in a neutral viewing direction. Based on the positions of measurement points A through H and their structurally known distances, the evaluation software can also determine the positions of the cameras relative to the eyeglass frame, e.g.
the distance and relative height of the eyeglass frame to the stereo camera system.
All of the features shown here may be essential to the invention both individually and in any combination.
Date Recue/Date Received 2020-08-13

16 List of Reference Signs 1 Test subject 2 Eyeglass frame 3 Mirror 4 Stereo camera system Virtual mirror plane 6 Neutral viewing direction 7 Vertical angular aperture 8 Optical axes 9 Common field of vision A¨H Measurement points of the eyeglass frame Center point of the test subject pupil, right eye Center point of the test subject pupil, left eye Date Recue/Date Received 2020-08-13

Claims

Patent claims

1. A
method for determining centring data of a subject for fitting spectacles to the subject, using:
- a vertically arranged mirror that is disposed opposite and at an eye-height of the subject, wherein the subject wears an anatomically well-fitted specta-cle frame, - an electronic image recording device comprising a stereo camera system that is fixedly disposed within a height of the mirror and symmetrically with respect to a central longitudinal axis of the mirror, and the cameras of which have fixedly defined optical axes, and - a data processing and data output device having spectacle frame data stored therein, the spectacle frame data comprising parameters of the spectacles and of the anatomically well-fitted spectacle frame, and having further stored therein correction data, image scale data and position information of the cameras of the stereo camera system, the method comprising the steps of:
causing the subject to direct his view onto a mirror image of his head in the mirror, such that the subject is looking himself in the eyes, using the stereo camera system, acquiring an image of at least an area of the subject's head that is provided with the anatomically well fitted spectacle frame and obtaining image data therefrom, comparing the obtained image data with the spectacle frame data stored in the data processing and data output device, and determining the direction, distance away and height-related position of the obtained image data using the stored correction data, image scale data and position information of the cameras of the stereo camera system, wherein existent positionally dependent dimensional changes and distortions are countered through correction calculations based thereon, and the required centring data are determined and output as measured values of the spectacles for the subject.
Date Recue/Date Received 2020-08-13

2. An immobile video centring system for determining centring data of a subject for fitting spectacles to the subject, comprising:
a vertically arranged mirror disposed opposite and at an eye-height of the sub-ject, wherein the subject wears an anatomically well-fitted spectacle frame, an electronic image recording device having at least two cameras, by means of which image data for at least an area of the subject's face having the anatomically well-fitted spectacle frame is acquirable, wherein the electronic image recording device comprises a stereo camera system including the at least two cameras which:
have defined respective optical axes, are each fixedly disposed in a respective position at a defined horizontal distance from one another and with respect to a position of the subject, are each fixedly disposed at a same height and at the defined horizontal distance from one another within a height of the mirror and symmetrically about a central longitudinal axis of the mirror, and the focal length, horizontal distance and focus range of which are selected such that every point within their measuring range is acquired, and a data processing and data output device in operative communication with the electronic image recording device and having spectacle frame data stored therein, the spectacle frame data comprising parameters of the spectacles and of the anatomically well-fitted spectacle frame, and further having stored therein:
a first specific imaging property specifying an image size of the anatomically well-fitted spectacle frame as a function of the distance of the anatomically well-fitted spectacle frame from an objective plane of the at least two cameras, and a second specific imaging property specifying a position of the actual height ranges of the anatomically well-fitted spectacle frame in the imaging region of the cameras as a function of the distance of the anatomically well-fitted spectacle frame from the objective plane of the at least two cameras wherein, during use, image data acquired for the at least an area of the subject's face having the anatomically well-fitted spectacle frame are compared with the spectacle frame data stored in the data processing and data output device, and Date Recue/Date Received 2020-08-13 the required centring data are determined and output as measured values of the spectacles for the subject.

3. The immobile video centring system according to claim 2, wherein the at least two cameras are each positioned at an average height of the mirror that is in-termediate a top and a bottom of the mirror.

4. The immobile video centring system according to claim 2 or 3, wherein each of the at least two cameras has a fixed focal length.

5. The immobile video centring system according to claim 4, wherein each of the at least two cameras has a same focal length.

6. The immobile video centring system according to any one of claims 2 to 5, wherein the optical axes of the at least two cameras are aligned at a set angle towards one another in the horizontal plane.
Date Recue/Date Received 2020-08-13