Method for measuring the power of an optical glass

Abstract

Method for measuring the power of an optical glass. The invention relates to a system for measuring the power of an optical glass (1) comprising at least: a support for the optical glass (1) to be studied, a projection screen (2) through the optical glass (1) of an image corresponding to at least a succession of alternately light and dark sinusoidal fringes, at least one receiving device (7) associated with a measuring device positioned so as to receive at least a portion of the light beam (3) having passed through the optical glass (1), a mechanism for modifying the position relative to the optical glass (1) of the image projected through the optical glass (1). Figure to be published with the abbreviation: Fig. 1

Description

Title of the invention: Method for measuring the power of an optical glass

[0001] The present invention relates to the field of devices for measuring the optical power of a lens and more particularly to the field of devices for measuring the optical power of a glass at any point of the lens.

[0002] In the context of optical lens production and in particular in the context of precision optical lenses, it is necessary if not essential to be able to check the individual qualities of each of the lenses produced. This verification is all the more important for lenses, such as progressive lenses, in which the power differs between different points of the lens.

[0003] Currently, the devices used to determine the optical power of a lens are frontofocometers or Shack-Hartemann systems which require the positioning of the lens being checked at the optical axis of the system. In these systems, it is necessary to know the position of the glass perfectly in order to carry out an accurate measurement of the power of the lens. When using frontofocometers, since the measurements are punctual, it is essential that the measured surfaces are positioned normally relative to the measurement axis. When measuring larger surfaces, particularly in the context of Shack-Hartemann systems, these are carried out by approximation and to the detriment of the quality of the precision.Furthermore, when the glass has a surface that includes a curvature, as is often the case with optical lenses, the inclination and centering must be measured prior to measuring the optical power over the entire surface of the glass.

[0004] On the scale of industrialized production, robotization is sought so as to allow the operations of verifying the qualities of the lenses to be carried out quickly. However, in the context of verifying the power of lenses over their entire surfaces, measuring devices such as those which currently exist require either careful positioning of the lens to be verified, or a greater number of measurements so as to accurately characterize the geometry of at least one of the faces of the lens and its spatial position relative to the dedicated measuring instrument. These solutions, when they are likely to be compatible with automation, then require additional instruments so that they are often complex and expensive, and limit, if not slow down, the high speed of execution provided by robotization.

[0005] The present invention aims to overcome these drawbacks by proposing a simplified technical solution for measuring optical power across the entire surface of a lens which can avoid the need for careful positioning in relation to the measurement system, while allowing easy automation.

[0006] The invention relates to a method for measuring the power of an optical glass crossed by at least one light beam coming from an image emitted by at least one screen and corresponding to at least one succession of alternating light and dark sinusoidal fringes, comprising: - a first measurement step corresponding to the measurement of the position of a point on the image emitted by a screen arranged at a first location relative to the optical glass and the light beam of which passes through the optical glass at a determined point, the measurement being carried out at an image reception device, - a second measurement step corresponding to the measurement of the position of a second point of the same image emitted by a screen arranged at a second location relative to the optical glass and whose light beam passes through the optical glass at the determined point with the same angle of incidence as the light beam of the point emitted by the screen arranged at the first location within the framework of the first measurement, the measurement being carried out at the image reception device, - a step of determining the difference “D” in position between the optical glass and respectively, on the one hand, the position of the screen at the first location in the context of the first measurement and, on the other hand, the position of the screen at the second location in the context of the second measurement, the difference in position being determined along a perpendicular to the plane of the screen passing through the optical glass, - a step of determining the difference “d” in position on the image between, on the one hand, the first measured point of the image and, on the other hand, the second measured point of the image, the light beams of which pass through the optical glass at the determined point with the same angle of incidence, the difference in position being determined relative to a reference point on the screen, - a step of determining the angle of incidence “a” of the light beams which pass through the optical glass at the determined point, - a step of determining the refraction carried out by the optical glass at the determined point crossed by the light beams.

[0007] The invention also relates to a system for measuring the power of an optical glass capable of implementing a method according to the invention, characterized in that the

[0008]

[0009]

[0010]

[0011]

[0012]

[0013]

[0014] system includes at least: - an optical glass support to study, - a projection screen through optical glass of an image corresponding to at least one succession of alternating light and dark sinusoidal fringes, - at least one receiving device associated with a measuring device positioned so as to receive at least part of the light beam having passed through the optical glass, - a mechanism for modifying the position relative to the optical glass of the image projected through the optical glass. The invention will be better understood from the following description, which relates to the preferred embodiments, given as non-limiting examples, and explained with reference to the appended schematic drawings, in which: [Fig.l] is a schematic representation of two examples of arrangements of different elements allowing the implementation of a method for measuring the power of an optical glass according to the invention. [Fig.2] is a schematic representation of a first example of construction of a system for measuring the power of an optical glass according to the invention. [Fig.3] is a schematic representation of a second example of construction of a system for measuring the power of an optical glass according to the invention. [Fig.4] is a schematic representation of a third example of construction of a system for measuring the power of an optical glass according to the invention. [Fig.5] is a schematic representation of a fourth example of construction of a system for measuring the power of an optical glass according to the invention. The invention relates to a method for measuring the power of an optical glass 1 crossed by at least one light beam originating from an image emitted by at least one screen 2 and corresponding to at least one succession of alternating light and dark sinusoidal fringes, comprising: - a first measurement step corresponding to the measurement of the position of a point 4 on the image emitted by a screen 2 arranged at a first location 21 relative to the optical glass 1 and whose light beam 3 passes through the optical glass 1 at a determined point 5, the measurement being carried out at an image reception device 7, - a second measurement step corresponding to the measurement of the position of a second point 6 of the same image emitted by a screen 2 arranged at a second location 22 relative to the optical glass 1 and whose light beam 3 passes through the optical glass 1 at the point 5 determined with the same angle a of incidence as the light beam of the point 4 emitted by the screen 2 arranged at the first location 21 in the context of the first measurement, the measurement being carried out at the image reception device 7, - a step of determining the difference “D” in position between the optical glass 1 and respectively, on the one hand, the position of the screen 2 at the first location 21 in the context of the first measurement and, on the other hand, the position of the screen 2 at the second location 22 in the context of the second measurement, the difference in position being determined along a perpendicular to the plane of the screen 2 passing through the optical glass 1, - a step of determining the difference “d” in position on the image between, on the one hand, the first measured point 4 of the image and, on the other hand, the second measured point 6 of the image, the light beams 3 of which pass through the optical glass 1 at the point 5 determined with the same angle a of incidence, the difference in position being determined relative to a reference point of the screen 2, - a step of determining the angle of incidence “a” of the light beams 3 which pass through the optical glass 1 at the determined point 5, - a step of determining the refraction carried out by the optical glass 1 at the determined point 5 crossed by the light beams 3.

[0015] Thanks to the method of the invention, the characterization of the angle a of incidence at a given point 5 of the optical glass 1 is independent of the position of the optical glass 1 relative to the source of the light beams 3 produced by the positioning of a screen 2 at two different locations 21, 22. Indeed, the distance formed by the difference “D” of the screen locations 21, 22 is a value independent of the position of the optical glass 1 studied relative to the source of the light beams 3 and therefore of the position of the surface of the optical glass 1, in particular when this surface of the optical glass 1 has a variation such as an inclination and / or a curvature. Also, the need for a prior meticulous characterization of the position of the optical glass 1 is eliminated to determine the angle of incidence “a”.

[0016] Furthermore, it should also be noted that, since the light beams 3 coming from the screen 2 of each of the two locations 21, 22 pass through the entire surface of the optical glass 1 analyzed, the difference “D” of the screen locations 2 allows an identification of the angle of incidence a at any determined point 5 of the surface of the optical glass 1 without knowing either the geometry of the surface of this optical glass 1 or the positioning of one or other of the points 5 of this surface of the glass 1.

[0017] The characterization of the angle of incidence a of the light beams 3 at the determined point 5 of the surface of the optical glass 1 then allows, by comparison with the angle of refraction of the light beams 3 between the optical glass 1 and the device of reception 7 along an axis parallel to the optical axis, to determine the refraction at this point 5 of the glass 1. From the refraction of the glass at a point 5, and possibly from measurements of the refraction of the glass 1 within an interval of close points surrounding the point 5 considered of the glass 1 associated with a characterization of the equation of the variation of these measurements, the power at the point 5 considered of the glass 1 can be determined without difficulty, as can the focal length.

[0018] In the context of the analysis of a single-vision lens 1, the positioning of at least a portion of the lens at the optical axis between the screen 21, 22 of each of the two locations and the receiving device 7 makes it possible to characterize the power of the lens 1 at this point 5. Furthermore, since the geometric shape of a single-vision lens 1 is known and constant, the characterization of the power at a point 5 of the lens 1 is sufficient to characterize the power of the lens 1 at each of the points.

[0019] In the context of the analysis of a multifocal lens 1, the method according to the invention involves a telecentricity mechanism 10 positioned between the optical lens 1 to be analyzed and the receiving device 7. This telecentricity mechanism 10 allows a distribution of the different light beams 3 having passed through the optical lens 1 towards the receiving device 7 according to an arrangement parallel to the optical axis between the screen 21, 22 of each of the two locations and the receiving device 7. Also, by approximating the curvature of the lens 1 at its refracted surface so that this surface of the lens 1 is assimilated to a flat surface, the characterization of the refraction, the focal length and the power at each of the points 5 of the lens 1 are likely to be carried out.The telecentricity mechanism 10 thus makes it possible to operate an orientation of the light beam 3 refracted by the glass 1 along an axis parallel to the optical axis so that the characterization by the receiving device 7 of the position of the light beam 3 refracted by the glass 1 is able to overcome any variation in the thickness of the multifocal glass 1, in particular when this variation in thickness is linked to the difference in curvature between the two surfaces of the glass 1.

[0020] According to an example relating to a preferred implementation variant of the power measurement method of the invention, the step of determining the angle of incidence “a” at the determined point 5 of the optical glass 1 involves the equation: a = Arctan (d / D)

[0021] According to this implementation variant, the angle of incidence “a” of the light beams 3 in the glass 1 relative to the angle of the light beams 3 having passed through the glass 1 and oriented along an axis parallel to the optical axis is able to be characterized without difficulty. The implementation of the equation is preferably carried out by a dedicated calculation device, for example associated with a measuring device or with the receiving device 7.

[0022] According to an example relating to another variant implementation of the power measurement method of the invention capable of being combined with one of the previously detailed variants, the method involves a single screen 2, successively arranged at a first location 21 then at a second location 22 relative to the glass 1, and comprises, between the two measurement steps, a step of translating the screen 2 from the first location 21 to the second location 22. In the context of this variant implementation of the method, the screen 2 is translated along a distance which corresponds to the difference “D” in position between the optical glass 1 and each of the two locations 21, 22 of the screen 2, in particular along a perpendicular to the plane of the screen 2 passing through the optical glass 1.

[0023] According to an example relating to another variant of implementation of the power measurement method of the invention capable of being combined with some of the previously detailed variants, the method comprises, between the two measurement steps, a step of deflecting the light beam 3 which passes through a determined point 5 of the optical glass 1 and emitted by the screen 2 arranged at the first location 21 so as to allow the projection of the light beam 3 emitted by the screen 2 arranged at the second location 22 to pass through the optical glass 1 at the determined point 5 at an identical angle of incidence “a”. According to this construction variant, each of the two screens 2 remains in position at their respective locations 21, 22. On the other hand, the light beams 3 emitted by each of these screens 2 are projected alternately through the optical glass 1 to be analyzed.For example, the projection of at least one light beam 3 from each of the screens 3 through the optical glass 1 involves at least one reflection mechanism produced by means of one or more reflection means such as mirrors, or possibly even by means of a prism, and positioned along the path of the at least one light beam 3. The movement of a part of the reflection mechanism, for example by pivoting a reflection means, allows the selection of at least one light beam 3 coming from one of the two screens 2 to the detriment of the other. The reflection mechanism 91 thus acts as a selection mechanism 9 for the at least one light beam 3 projected through the optical glass 1.

[0024] According to an example relating to another variant of implementation of the power measurement method of the invention capable of being combined with some of the previously detailed variants, the method comprises steps of first and second measurements of the position of each of the points 4, 6 of the image emitted by the screen 2 respectively arranged at the first location 21 and the second location 22 and which pass through the optical glass 1 at respective determined points 5. As an example of implementation, the image emitted, on the one hand, by the screen 2 at the first location 21 and, on the other hand, by the screen 2 at the second location 22 associates a pair of coordinates for each of the points 4, 6 or pixels of the image. The image reception device 7 also associates a pair of coordinates for each of the points or pixels of the received image and produced by each light beam 3 having passed through the optical glass 1 at a determined point 5. The image emitted by the screen 2 corresponds to a succession of alternating light and dark sinusoidal fringes. The sinusoidal variation of the fringes is likely to be produced along a single axis or, alternatively, along two intersecting axes, for example perpendicular to each other, so that the image has a distribution of fringes corresponding to alternating light and dark sinusoidal variations, along two axes.A sinusoidal variation of fringes along a single axis allows the identification of coordinates relative to this single axis of variation of the fringes. Conversely, a sinusoidal variation of fringes along two intersecting axes allows a characterization of coordinates relative to each axis of variation and therefore in the entire plane of the image. Also, taking into account the particularities of the projected image, for each point of determined coordinates of the received image and having passed through the optical glass 1 at a determined point 5, it is possible to associate a point of determined coordinates of the image emitted by the screen 2 positioned at each of the locations 21, 22.The correspondences identified between the points of each of the images thus allow the characterization of the difference “d” of position on the image between, on the one hand, the first point 4 measured in the image and, on the other hand, the second point 6 measured in the image, whose light beams 3 pass through the optical glass 1 at the point 5 determined with the same angle “a” of incidence.

[0025] According to an example relating to another alternative implementation of the power measurement method of the invention capable of being combined with some of the previously detailed variants, the image emitted by each of the screens 2 comprises identical fringes. According to this alternative implementation, the alternating light and dark sinusoidal fringes have rectilinear arrangements and are parallel to each other. These fringes also have a sinusoidal arrangement whose wavelength is constant along the axis perpendicular to these fringes. In a complementary manner, the sinusoidal variation of the fringes is capable of being produced along two intersecting axes, for example perpendicular to each other, so that the image has a distribution of fringes corresponding to alternating light and dark sinusoidal variations, along two axes.Along each of the respective axes, the fringes exhibit a sinusoidal arrangement of constant respective wavelengths.

[0026] The invention also relates to a system for measuring the power of a glass 1 optical system capable of implementing a method according to the invention, characterized in that the system comprises at least: - a support 8 of optical glass 1 to be studied, - a screen 2 for projection through the optical glass 1 of an image corresponding to at least one succession of sinusoidal fringes alternately light and dark, - at least one receiving device 7 associated with a measuring device 11 positioned so as to receive at least part of the light beam 3 having passed through the optical glass 1, - a mechanism 9 for modifying the position relative to the optical glass 1 of the image projected through the optical glass 1.

[0027] The system according to the invention thus positions a screen 2 at at least a first location 21 relative to the optical glass 1 so as to project a light beam 3 through the optical glass 1, so that at least a portion of the light beam 3 is received by the reception device 7. The measuring device 11 associated with the reception device 7 makes it possible to determine the point 4, 6 of the image projected by the screen 2 at the reception device 7 through a determined point 5 of the optical glass 1.

[0028] According to an example relating to a construction variant of the system of the invention, the latter also comprises a telecentricity mechanism 10 positioned between the support 8 of optical glass 1 and the receiving device 7. This telecentricity mechanism 10 is capable of taking the form of an association of two lenses mounted in planes parallel to each other and separated by a distance corresponding to the sum of their respective focal lengths. As a complement, this telecentricity mechanism 10 is capable of integrating a diaphragm positioned between the two lenses of the mechanism, at the point where the respective focal points of the two lenses are merged. Preferably, the telecentricity mechanism 10 involves a telecentric objective.In order to obtain a parallel orientation between them of the beams 3 having passed through the optical glass 1 analyzed according to a distribution corresponding to the respective positions of the beams 3 at the exit of the optical glass 1, the telecentricity mechanism 10 is positioned as close as possible to the surface of the optical glass 1, ideally against the surface of the glass 1. By limiting, or even eliminating, the travel distance between the optical glass 1 and the telecentricity mechanism 10, the positions of the light beams 3 between them at the level of the reception device 7 are similar, or even identical, to those at the exit of the optical glass 1 at the level of the surface of the glass 1. Under these conditions, the reception device 7, in combination with the measuring device 11, is capable of precisely characterizing the correspondence between a point 5 of the optical glass 1 crossed by a beam. luminous 3 and point 4, 6 of the image of the projection screen 2.

[0029] The mechanism 9 for modifying the position of the image projected through the optical glass 1 is capable of adopting different configurations depending on the construction variant of the system.

[0030] According to an example relating to a construction variant of the system of the invention capable of being combined with some of the previously detailed variants, the mechanism 9 for modifying the position of the projected image comprises a mechanism for moving the projection screen 2 between, on the one hand, a first location 21 close to the support 8 of the optical glass 1 to be studied and, on the other hand, a second location 22 distant from the support 8 of the optical glass 1 to be studied. According to a preferred construction example, the screen 2, the optical glass 1 with its support 8 and the receiving device 7 are aligned and the screen 2 is mounted movable in translation along an axis parallel to this alignment axis of the screen 2, of the analyzed optical glass 1 and of the receiving device 7. This alignment axis corresponds substantially to the axis of travel of the light beams 3 from the projection screen 2 to the receiving device 7.The projection screen 2 is then ideally arranged in a plane substantially perpendicular to this alignment axis. According to an alternative example of construction making it possible to limit the size of the measuring system of the invention, the system comprises one or more reflectors arranged along the path of the light beams 3 from the projection screen 2 to the receiving device 7 so that the path of the light beams 3 can be integrated within a volume of shorter length than an alignment of the different elements of the system.

[0031] According to an example relating to a construction variant of the system of the invention capable of being combined with some of the previously detailed variants, the system comprises two projection screens 2 arranged at respective locations 21, 22 so that the travel lengths of the respective images projected to the optical glass 1 are different. The two screens 2 and the optical glass 1 are then aligned with the travel of the light beams 3 projected through the optical glass 1. The screen 2 positioned at the location 21 whose travel of the projected light beams 3 is the shortest is then mounted movable between two positions, under the action of the mechanism 9 for modifying the position of the projected image.A first position is defined so that, on the one hand, the image of the screen 2 is projected through the optical glass 1 and, on the other hand, the screen 2 obstructs the light beam emitted by the second screen so as to prevent the projection of the image of the beam 3 of the second screen through the optical glass 1. A second position is defined so that the screen 2 is moved away from the axis of projection of the image of the light beam 3 towards the optical glass 1, for example by translation along a perpendicular axis. dicular to the axis of projection of the image of the light beam 3 towards the optical glass 1. In this second position, on the one hand, the image projected by the displaced screen 2 is no longer able to reach the optical glass 1 and, on the other hand, the screen 2 no longer obstructs the light beam 3 emitted by the second screen so that they pass through the optical glass 1.

[0032] According to an example relating to a construction variant of the system of the invention capable of being combined with certain of the variants detailed above, the system comprises: - two projection screens 2 arranged at respective locations 21, 22 so that the travel lengths of the respective images projected to the optical glass 1 are different, - a mechanism 9 for selecting the image projected through the optical glass 1 emitted by one or other of the two projection screens 2, the mechanism 8 comprising at least one reflection means 91 movable so as to be, on the one hand, positioned on the path of the image projected by each of the screens 2 and, on the other hand, capable of blocking the path of the light beam 3 projected by a first of the two screens 3 while deflecting the path of the light beam 3 projected by the second measuring screen 2 in the direction of the optical glass 1. According to this construction variant, the mechanism 9 for modifying the position of the projected image involves a mechanism for selecting the projected image which takes the form of a reflection means 91 such as a mirror, mounted to be movable across the axis of travel of the light beam 3 projected through the optical glass 1. The reflection means 91 is thus moved between, on the one hand, a first position allowing the projection of light coming only from the screen 2 located at the first location 21 towards the optical glass 1 and, on the other hand, a second position allowing the projection of light coming only from the screen 2 located at the second location 21 towards the optical glass 1.As an example of construction, the reflection means 91 of the selection mechanism 9 is substantially positioned, on the one hand, between a first screen 2 located at the first location 21 and the optical glass 1 and, on the other hand, at the intersection of the light projection axes of each of the two screens 2. This reflection means 91 is thus capable of being movable in translation in a plane which, on the one hand, is intersecting with the light projection axis of the first screen 2 located at the first location 21 towards the optical glass 1 and, on the other hand, has an inclination with a plane substantially perpendicular to the axis of the light projection from the screen 2 located at the first location 21 towards the optical glass 1. This translation is thus carried out so that, in a first position, the reflection means 91 does not hinder the travel of the light projection from the screen 2 located at the first location 21 towards the optical glass 1, without reflection of the .light projection from the screen 2 located at the second location 21 to the optical glass 1 and that, according to a second position, the reflection means 91 is positioned across the path of the light projection from the screen 2 located at the first location 21 and reflects the light projection from the screen 2 located at the second location 21 to the optical glass 1. According to an example relating to an alternative construction, the reflection means 91 is arranged to be movable by pivoting about an axis arranged in a plane substantially perpendicular to the axis of the light projection from the screen 2 located at the first location 21 to the optical glass 1. Here too, according to a first position, the reflection means 91 does not hinder the path of the light projection from the screen 2 located at the first location 21 to the optical glass 1 and does not reflect the light projection from the screen 2 located at the second location 21 to the optical glass 1.Likewise, in a second position, the reflection means 91 is positioned across the path of the light projection from the screen 2 located at the first location 21 and reflects the light projection from the screen 2 located at the second location 21 towards the optical glass 1. Thus, the movement of a part of the reflection mechanism, for example by pivoting a reflection means 91, allows the selection of at least one light beam 3 coming from one of the two screens 2 to the detriment of the other. The reflection mechanism thus acts as a selection mechanism 9 for the at least one light beam 3 projected through the optical glass 1 by selecting the origin of the projected image from among the screens 2 positioned at two distinct locations 21, 22.

[0033] According to an example relating to a construction variant of the system of the invention capable of being combined with certain of the variants detailed above, the system comprises: - two projection screens 2 arranged at respective locations 21, 22 so that the travel lengths of the respective images projected to the optical glass 1 are different, - a mechanism 9 for selecting the image projected through the optical glass 1 emitted by one or other of the two projection screens 2, the mechanism 8 comprising at least one deflection prism 92, on the one hand, positioned on the path of the image projected by each of the screens 2 and, on the other hand, capable of modifying in the direction of the optical glass 1 the path of the light beam 3 projected by a first of the two screens 2 to the detriment of the light beam 3 projected by the second of the two screens 2. According to this construction variant, the mechanism 9 for modifying the position of the projected image involves a mechanism 9 for selecting the projected image which takes the form of a deflection prism 92 mounted to be movable across the axis of the course of light beams 3 projected through the optical glass 1. The deflection prism 92 is thus moved between, on the one hand, a first position allowing the deflection towards the optical glass 1 of the light beams 3 coming only from the screen 2 located at the first location 21 and, on the other hand, a second position allowing the deflection towards the optical glass 1 of the light beams 3 coming only from the screen 2 located at the second location 21. As an example of construction, the deflection prism 92 of the selection mechanism 9 is positioned at the intersection of the light projection axes of each of the two screens 2. According to an example relating to an alternative construction, the deflection prism 92 is arranged to be movable by pivoting around an axis perpendicular to the light projection axes of each of the two screens 2. The deflection prism 92 is pivotally mounted between at least two positions.According to a first position, the deflection prism 92 directs the light projection from the screen 2 located at the first location 21 towards the optical glass 1, while preventing a light projection from the screen 2 located at the second location 21 towards the optical glass 1. According to a second position, the deflection prism 92 directs the light projection from the screen 2 located at the second location 22 towards the optical glass 1, while preventing a light projection from the screen 2 located at the first location 21 towards the optical glass 1. Thus, the deflection prism 92 acts as a selection mechanism 9 for the at least one light beam 3 projected through the optical glass 1 by selecting the origin of the projected image from among the screens 2 positioned at two distinct locations 21, 22. According to an example of complementary construction, a surface of the deflection prism 92 has a reflection surface.When the deflection prism 92 operates a deflection in the direction of the optical glass 1 of at least one light beam 3 coming from a first of the two screens 2, this reflection surface is arranged to move away from the optical glass 1 the light projection coming from the second of the two screens 2 and thus avoid any alteration of the light beam 3 passing through the optical glass 1 to be analyzed.

[0034] It should be noted that, in the present document, the light projection axis of a screen 2 corresponds substantially to the perpendicular to the surface of this screen.

[0035] Of course, the invention is not limited to the embodiments described and shown in the attached drawings. Modifications remain possible, particularly from the point of view of the constitution of the various elements or by substitution of technical equivalents, without departing from the scope of protection of the invention.

Claims

1. Claims Method for measuring the power of an optical glass (1) crossed by at least one light beam coming from an image emitted by at least one screen (2) and corresponding to at least one succession of alternating light and dark sinusoidal fringes, comprising: - a first measurement step corresponding to the measurement of the position of a point (4) on the image emitted by a screen (2) arranged at a first location (21) relative to the optical glass (1) and whose light beam (3) passes through the optical glass (1) at a determined point (5), the measurement being carried out at an image reception device (7), - a second measurement step corresponding to the measurement of the position of a second point (6) of the same image emitted by a screen (2) arranged at a second location (22) relative to the optical glass (1) and whose light beam (3) passes through the optical glass (1) at the determined point (5) with the same angle (a) of incidence as the light beam of the point (4) emitted by the screen (2) arranged at the first location (21) in the context of the first measurement, the measurement being carried out at the image reception device (7), - a step of determining the difference “D” in position between the optical glass (1) and respectively, on the one hand, the position of the screen (2) at the first location (21) in the context of the first measurement and, on the other hand, the position of the screen (2) at the second location (22) in the context of the second measurement, the difference in position being determined along a perpendicular to the plane of the screen (2) passing through the optical glass (1), - a step of determining the difference “d” in position on the image between, on the one hand, the first measured point (4) of the image and, on the other hand, the second measured point (6) of the image, the light beams (3) of which pass through the optical glass (1) at the determined point (5) with the same angle (a) of incidence, the difference in position being determined relative to a reference point of the screen (2), - a step of determining the angle of incidence “a” of the light beams (3) which pass through the optical glass (1) at determined point (5), - a step of determining the refraction carried out by the optical glass (1) at the determined point (5) crossed by the light beams (3).

2. Power measurement method according to claim 1, characterized in that the step of determining the angle of incidence “a” at the determined point (5) of the optical glass (1) involves the equation: a = Arctan (d / D)

3. Power measurement method according to one of claims 1 or 2, characterized in that the method involves a single screen (2), successively arranged at a first location (21) then at a second location (22) relative to the glass (1), and comprises, between the two measurement steps, a step of translating the screen (2) from the first location (21) to the second location (22).

4. Power measurement method according to one of claims 1 or 2, characterized in that the method comprises, between the two measurement steps, a step of deflecting the light beam (3) which passes through a determined point (5) of the optical glass (1) and emitted by the screen (2) arranged at the first location (21) so as to allow the projection of the light beam (3) emitted by the screen (2) arranged at the second location (22) to pass through the optical glass (1) at the determined point (5) at an identical angle of incidence “a”.

5. Power measurement method according to one of the preceding claims, characterized in that the method comprises steps of first and second measurements of the position of each of the points of the image emitted by the screen respectively arranged at the first and second locations and which pass through the optical glass at respective determined points.

6. System for measuring the power of an optical glass (1) capable of implementing a method according to one of claims 1 to 5, characterized in that the system comprises at least: - a support (8) for the optical glass (1) to be studied, - a screen (2) for projecting through the optical glass (1) an image corresponding to at least one succession of alternating light and dark sinusoidal fringes, - at least one receiving device (7) associated with a device measuring device positioned so as to receive at least part of the light beam (3) having passed through the optical glass (1), - a mechanism for modifying the position relative to the optical glass (1) of the image projected through the optical glass (1).

7. Measuring system according to claim 6, characterized in that the system also comprises a telecentricity mechanism (10) positioned between the optical glass (1) support (8) and the receiving device (7).

8. Measuring system according to one of claims 6 or 7, characterized in that the mechanism (9) for modifying the position of the projected image comprises a mechanism for moving the projection screen (2) between, on the one hand, a first location (21) close to the support (8) of the optical glass (1) to be studied and, on the other hand, a second location (22) distant from the support (8) of the optical glass (1) to be studied.

9. Measuring system according to one of claims 6 or 7, characterized in that the system comprises: - two projection screens (2) arranged at respective locations (21, 22) so that the travel lengths of the respective images projected to the optical glass (1) are different, - a mechanism (9) for selecting the image projected through the optical glass (1) emitted by one or other of the two projection screens (2), the mechanism (8) comprising at least one reflection means (91) movable so as to be, on the one hand, positioned on the travel of the image projected by each of the screens (2) and, on the other hand, capable of closing the travel of the light beam (3) projected by a first of the two screens (3) while deflecting the travel of the light beam (3) projected by the second measuring screen (2) towards the optical glass (1).

10. Measuring system according to claim 6, characterized in that the system comprises: - two projection screens (2) arranged at respective locations (21, 22) so that the stroke lengths of the respective images projected onto the optical glass (1) are different, a selection mechanism (9) for the image projected through the optical glass (1) emitted by one or other of the two projection screens (2), the mechanism (8) comprising at least one deflection prism (92), on the one hand, positioned on the path of the image projected by each of the screens (2) and, on the other hand, capable of modifying in the direction of the optical glass (1) the path of the light beam (3) projected by a first of the two screens (2) to the detriment of the light beam (3) projected by the second of the two screens (2).

Images