METHOD AND DEVICE FOR MEASURING AT LEAST ONE DIMENSION OF AN OBJECT

Description

[0001] The invention relates to a method for measuring at least one dimension of an object. It also relates to a measuring device. It also relates to a method for manufacturing an object that incorporates the measuring method.

[0002] The development of machine tools pursues the goal of improving precision, which is achieved by reducing machining errors. As one example among many, mechanical watchmaking constantly strives to improve the manufacturing precision of components in order to enhance movement performance and assembly yields in production. Other examples include the automotive, medical, aerospace, and electronics industries.

[0003] This pursuit of improvement is hampered by the operating conditions of machine tools. This is particularly true for cam-operated or CNC lathes, but also for all other machines using a material removal process, especially chip formation. Further improving the intrinsic accuracy of these machines through conventional means, such as optimizing the design or the precision of the guides, proves difficult. Indeed, residual machining errors, such as those due to thermal deformation, static deformation, the non-repeatability of repositioning moving parts (tool support devices), and tool wear, have reached a minimum threshold that seems difficult to overcome. These residual errors, however, remain too significant for certain applications, such as watchmaking.

[0004] Machine tools are poorly suited to performance improvement through the implementation of in-situ sensors, as these are severely affected by the harsh environment created by the presence of cutting fluid and chips. Several approaches have been explored to improve repeatability performance by using sensors that measure either the workpieces, the tool positions, or certain moving parts of the machine during manufacturing, and then using these measurements to control or correct the machine in real time.

[0005] Machine tools, such as automatic lathes (but also lathes, transfer machines, etc.), generally include one or more devices for correcting machining errors detected during part production. These devices are either digital tool offsets in the case of a CNC machine tool, or micrometer screw offsets in the case of cam-operated machines. The correction(s) are generally made manually by the operator monitoring the machine during production.

[0006] Various systems exist for measuring the moving parts of machines, such as position sensors mounted on machine axes, for example LVDT inductive sensors or optical scales. However, these sensors do not directly measure the dimensions of the manufactured part.

[0007] There are also direct part measurement solutions such as laser barriers, other optical gauge systems, or systems using a different physical principle. In principle, this type of measurement works by triggering a contact. The measurement is then "read" from the machine tool's axis tracking systems. This approach of measuring via axis tracking sensors does not achieve the desired performance. Furthermore, in the case of small parts, most of these solutions are very "invasive" and therefore particularly difficult to implement.

[0008] In summary, due to their inherent flaws, none of these measurement solutions can achieve the resolution and repeatability necessary to accurately measure the dimensions (diameters, lengths) of an object, and in particular of a watch component of the type of millimeter-sized object of revolution.

[0009] Document JP2008102040 describes a measuring device for measuring the diameter and concentricity of different sections of a cylindrical part by rotating the part. No information is provided regarding the positioning of the part within the optical system.

[0010] Document FR2646904 describes a method for measuring the diameter of a cylindrical object along its length by means of vertical and rotational displacement. A one-dimensional illumination and detector are used. The object's positioning within the system is not specifically addressed.

[0011] US2002041381 describes an apparatus for measuring the diameter and concentricity of a cylindrical object in a telecentric optical system, combining two sensors, one one-dimensional and the other two-dimensional. The object's positioning within the system is not addressed.

[0012] US2012194673 describes a reflecting microscope measurement system with a table that can be moved along the optical axis to acquire a series of images at different working distances. This series of images allows the focal points of the different levels of the part to be determined; an image is then taken at each z-position of interest for measuring the dimensions of interest.

[0013] JP2003042894A and JPS6491007A relate to the optical measurement of the diameter and shape of a glass fiber rotated while immersed in a liquid with a refractive index close to that of the glass constituting the fiber. FR1039322A relates to the measurement of jewels for watchmaking by light projection and viewing through the eyepiece of a microscope, the jewel being immersed in a container filled with a liquid. DE 21 48 972 A1 describes an optical apparatus for measuring watch parts with a pulse sensor.

[0014] The aim of the invention is to provide a measurement method for improving the measurement accuracy of manufactured objects, particularly those manufactured by material removal or material deposition. Specifically, the invention proposes a method for performing a rapid, accurate, and reliable measurement of a dimension of a small object, thus simplifying and improving the reliability of measuring an object's dimensions. Furthermore, the invention proposes a method for performing a precise measurement of several dimensions of the same object simultaneously and rapidly, within the manufacturing environment, in the machining fluid, without prior cleaning of the object.

[0015] According to a first aspect, a measurement method according to the invention is defined by claim 1.

[0016] According to the first aspect, different modes of execution of the process are defined by dependent claims 2 to 7.

[0017] According to the first aspect, a measuring device according to the invention is defined by claim 8.

[0018] According to the first aspect, different embodiments of the measuring device are defined by dependent claims 9 and 10.

[0019] According to the first aspect, a manufacturing process according to the invention is defined by claim 11.

[0020] The attached drawing represents, by way of example, an embodiment of a device according to the invention and an execution of a measurement method according to the invention. There figure 1 is a diagram of an embodiment of a device according to the invention. figure 2 This is a side view of a part to be machined, mounted on a measuring fixture. figure 3 is a graph illustrating the effect of working distance on apparent measurement. figure 4is a graph illustrating the effect of tilt on the apparent measurement. figure 5 is a graph illustrating the effect of combining tilt and working distance on the apparent measurement. figure 6 is a flowchart of one execution method of the measurement process according to the invention. figure 7 is a diagram of a first embodiment of a timepiece manufactured according to the invention. figure 8 is a diagram of a second embodiment of a timepiece manufactured according to the invention.

[0021] An embodiment of a device 100 for measuring a dimension L of an object 1 or a part is described below with reference to the figure 1The device, along with the measurement method described below, is particularly well-suited for measuring small components, especially millimeter-sized objects of revolution, particularly those less than 10 mm in size, and can be used in a machine tool environment. The device and method are especially well-suited for measuring the dimensions of watch components.

[0022] We assume that the object has a first axis 2, for example, an axis of revolution. The device includes: a first optical system 11 having an optical axis 113, hereinafter referred to as the second optical axis 113, and comprising an optical sensor 111 associated with a lens 112, a data acquisition element 31 from the optical sensor, a data processing element 32, an actuator 41 or object displacement element relative to the first optical system, in particular an angular displacement element of the first axis relative to the second axis and / or an object displacement element in rotation around the first axis and / or an object translation element along the second axis.

[0023] According to the invention, the device for measuring the dimension L of the object 1 comprises, in addition to the first optical system 11 comprising an optical sensor 111 associated with a lens 112: a container 21 containing a machining fluid 22, the container comprising at least one transparent wall 211. Advantageously, the measuring device comprises a collimated light source having an optical axis 123, hereinafter referred to as the third optical axis 123 or a second telecentric lighting optical system 12 comprising a light source 121 associated with a telecentric lens 122 having an optical axis 123, hereinafter referred to as the third optical axis 123, in particular a third axis coinciding with the second axis.

[0024] The optical sensor can be a two-dimensional optical sensor, a CMOS camera, or a CCD camera.

[0025] The first and second axes are advantageously orthogonal or substantially orthogonal.

[0026] Advantageously, the optical sensor 111 is associated with a telecentric lens 112.

[0027] The measuring device is designed to operate in a machining environment. More specifically, the measuring device enables dynamic measurement by implementing relative movement of the object with respect to the measuring plane of the 2D telecentric optical sensor. The measuring device is designed to operate with the object immersed in a liquid. The object can be supported by a manipulator that allows relative movement of the object with respect to the sensor's measuring plane. The object can also be held, for example, by a machining center spindle or a gripper, while the optical sensor or measuring device is mounted on a displacement element 41 or actuator that allows it to perform relative movements of the measuring plane with respect to the workpiece.

[0028] The measuring device is filled with liquid, in particular cutting oil or machining fluid, or another compatible fluid of the same nature as the machining fluid without degrading the measurement, provided that the fluid is clean and homogeneous. This is made possible by the fact that transparent walls 211, 212, in particular formed by optical glass plates placed on each side of the container, are substantially, or even perfectly, identical. The device thus becomes symmetrical with respect to refractive indices, with the effect that any optical changes undergone by light entering the container are corrected upon exiting.

[0029] The processing element 32 includes a computer 321 and a memory 322. The processing element may also include control elements for the actuator 41.

[0030] The measuring device may also include a human-machine interface 33. The processing element 32 is then connected to the human-machine interface 33. The interface includes, in particular, a display element for the calculated or determined value of dimension L. The element may also display any other data, including apparent values ​​of the dimension and / or dimensions and / or the reference value. The human-machine interface may further include a data and command input element.

[0031] The acquisition element and / or the processing element can be implemented in a computer. In particular, the acquisition element may include a first software module and / or the processing element may include a second software module. The human-machine interface 33 may be the human-machine interface of the computer.

[0032] An execution method for measuring a dimension L of object 1 is described below with reference to figures 3 to 6 .

[0033] We assume that the object has a first axis 2, in particular an axis of revolution.

[0034] The method includes the use of a measuring device as described above, in particular the use of the first optical system 11 comprising the optical sensor 111 and having the second optical axis 113. The first optical system is arranged to form on the sensor 111 a clear image of the object.

[0035] Thus, in a first step 510 of the process, the measuring device 100 is provided. The measuring device is provided on site,that is to say that the measuring device is disposed and / or positioned relative to the part without the placement of the part being modified in relation to a machine, the part being in place on the machine to undergo shaping by material removal or by material deposition.

[0036] The measuring device can be provided so that the part can be measured after shaping by material removal or material deposition, for example during the shaping of one or more subsequent parts. The machine is a machining center, in particular a screw machine.

[0037] It should be noted that this step of supplying the measuring device can be performed at any time during the workpiece modification process on the machine. It can be performed even before the workpiece has undergone any modification on the machine. Alternatively, or in addition, it can be performed between two modifications of the workpiece on the machine, for example, between two machining phases. It can also be performed after the workpiece has undergone one or more modifications on the machine.

[0038] Advantageously, in this step 510, a machining fluid or a fluid of similar and / or compatible chemical nature is placed in the measuring device's container; that is, a fluid that will not affect the workpiece or the workpiece forming process carried out within the machine after the workpiece has been immersed in this fluid. The measuring device is positioned relative to the workpiece and the machine so that the workpiece is immersed in the fluid in the container. Preferably, the fluid is of such a nature that the workpiece can be immersed in it without prior cleaning of the workpiece.

[0039] The positioning of the part is ensured, for example, using one or more chucks and / or one or more clamps and / or one or more spindles and / or a gripping system, for example a vacuum gripping system.

[0040] In a second step 520, the workpiece is held or set in motion relative to the measuring device, in particular relative to the first optical system. The motion advantageously includes a rotational movement of the workpiece about the first axis 2. Preferably, this movement of the workpiece is achieved by rotating the chuck(s) and / or the collet(s) and / or the spindle(s) and / or the gripping system mentioned previously. This movement is, for example, produced by the machine. Alternatively, this movement is produced by a device auxiliary to the machine. Alternatively or additionally, a device allows the measuring device to be moved relative to the workpiece.

[0041] Additionally, the workpiece can be moved so that its first axis 2 is angularly displaced relative to the second axis 113, in particular around a fourth axis 3 or around an axis substantially parallel to this fourth axis 3. Preferably, this movement includes an angular sweep of a sector such that, during this sweep, the first axis 2 and the second axis 113 are at least transiently orthogonal. This movement is, for example, produced by the machine. Alternatively, this movement is produced by a device auxiliary to the machine. Alternatively or additionally, the actuator 41 can be used to move the measuring device relative to the workpiece.

[0042] In addition, the workpiece can be moved translationally along the second axis 113 relative to the measuring device, in particular relative to the first optical system 11. Preferably, this movement includes a sweep of a segment such that, during this sweep, the workpiece is at least transiently at an optimal working distance from the first optical system 11. This movement is, for example, produced by the machine. Alternatively, this movement is produced by an auxiliary device on the machine. Alternatively or additionally, the actuator 41 of the measuring device can be used to move the measuring device relative to the workpiece.

[0043] In a third step 530, at least one series of data is collected from the optical sensor while the object is moving relative to the first optical system, as explained previously. Specifically, the illumination data received at different times at the various pixels of the optical sensor 111 are transmitted to the data acquisition element 31. The output of this acquisition element provides at least one series of data comprising several apparent values ​​or dimensions of at least one dimension L that is to be quantified. The processing performed at this acquisition element is known to those skilled in the art. It allows the determination of a distance separating two pixels of the optical sensor corresponding to the image of two edges or two characteristic features of the part, and the deduction from this distance of an apparent dimension of the part, taking into account the optical system, particularly the lens 112.In other words, a data set corresponds to a series of apparent dimensions corresponding to different relative positions of the part with respect to the first optical system.

[0044] Advantageously, the object movement element 41 relative to the first optical system allows the object to be moved at a constant or substantially constant speed during step 530. Preferably, the object movement element 41 relative to the first optical system is not a stepper motor or an actuator used as a stepper motor. In step 530, at least one data set is acquired from the optical sensor while the object is moving relative to the first optical system. Thus, the data are not acquired or collected while the object is stationary, unlike a solution where the object is moved between two successive phases during which the object is stationary and during which the data are acquired or collected.

[0045] In this third step, at least one data set is advantageously acquired while the object is immersed in the liquid 22. Data acquisition is therefore carried out through the wall 211 of the container 21 and through the liquid. If a second optical system 12 is present, the light rays have also passed through the wall 212 of the container.

[0046] Additionally, the data acquisition step includes obtaining at least one second set of data relating to a standard 91, 92, or a gauge. This second set of data concerns a calibrated dimension, which is therefore precisely known, and allows for the correction, in the subsequent processing step, of the data set comprising several apparent values ​​of at least one dimension L.

[0047] Advantageously, the acquisition step includes obtaining at least one additional set of data relating to at least one additional dimension L', L", ... of the object. This at least one additional set of data can concern any dimension of the object, such as a diameter, length, width, thickness, depth, or height, comprising several apparent values ​​of the dimension. A key advantage of the invention is that it allows for the acquisition of several sets of data, relating to the same dimension and / or to different dimensions, during the same acquisition step, and therefore allows for the determination of several dimensions in a single step.

[0048] In a fourth step 540, at least one data series is processed to quantify said dimension L. The processing includes determining the value of dimension L by calculation based on the apparent values ​​of dimension L obtained previously.

[0049] The calculation may include an average calculation of apparent values, in particular the value determined or calculated at the end of the processing step may be the average of the apparent values ​​of the data series.

[0050] Alternatively or in addition, the calculation may include interpolation of apparent values, in particular polynomial interpolation, and / or local extremum extraction. These calculations are known to those skilled in the art.

[0051] Alternatively or complementarily, the calculation may include a correction of apparent values, based on a second set of data concerning the calibrated dimension which is therefore known precisely.

[0052] Optionally, in an additional step, the value of dimension L or the different dimensions can be used to control the machine tool, i.e. to correct the machining parameters in order to best target the desired dimension values, by a control loop or closed loop.

[0053] Thus, the measurement is carried out according to the following principles: The workpiece is set in motion relative to a measuring plane 4 associated with the first optical system 11 (and corresponding to the ideal working distance) so that the workpiece passes through "perfect positioning," i.e., with the dimension to be measured lying within the measuring plane 4. Throughout the movement sequence, the measuring device's sensor collects several images (e.g., 30 images per second), and the acquisition element extracts the desired apparent values ​​(apparent dimensions). The processing element determines the evolution of the apparent dimension as a function of the workpiece's movement parameters relative to the measuring device and then performs a digital fit, for example, using a polynomial approximation of degree 2, 4, 6, or 8, as appropriate.The evolution function, that is, the relationship linking the apparent dimension to position data of the part relative to the measuring device, has an extremum. The value of the extremum is extracted from the polynomial approximation; this is then the measurement value retained, i.e., the measurement of the dimension.

[0054] Dynamic measurement of the part eliminates errors in part positioning within the optical field, which are primarily of two types: I. Distortion of apparent quantities as a function of working distance; II. Warping of the part due to its orientation in the optical field (non-perpendicularity of the dimension to be measured with respect to the direction of the light rays used for the measurement);

[0055] These different effects are illustrated on the figures 3 to 5 and will be described in more detail later.

[0056] The measurement is performed in an environment designed to mitigate problems related to the presence of a liquid film on the workpiece and on the optics of the measurement system. If the workpiece is covered in liquid, as is the case during or at the end of machining, it is placed in the measuring device's container filled with a fluid, thus eliminating the need to clean and dry the workpiece.

[0057] Advantageously, the measurement method uses the first optical system 11, comprising the optical sensor 111 associated with the lens 112 and the container 21 containing the machining fluid 22 or a fluid of similar chemical composition in which the object is immersed. The measurement method therefore advantageously includes the acquisition of dimensional data through the wall 211 of the container and the fluid.

[0058] Advantageously, the measurement method includes the use of a collimated light source with a third optical axis 123 or a second telecentric illumination optical system 12 comprising a light source 121 associated with a telecentric lens 122 with a third optical axis 123. The collimated light source or the second optical system creates a parallel ray optical field. An object placed in this field blocks rays, and a backlit image is thus formed at the sensor 111.

[0059] The invention also relates to a method for manufacturing an object comprising implementing the measurement method described above and / or using a measuring device described above. Thus, the invention also relates to a manufacturing method in which the measurement method according to the invention is implemented and / or the measuring device according to the invention is used.

[0060] The part may be a watch movement 110 or a watch part 120, in particular a wristwatch, comprising an object or part described previously. figures 7 and 8 schematically represent the first and second embodiments of a timepiece manufactured according to the invention.

[0061] The solution is therefore compatible with the machining environment (cutting fluid) and makes it possible to measure, on site or just at the machine output, in a few seconds, the diameters and lengths of the machined parts with a resolution of the order of 0.015 µm and a repeatability of the order of ±0.2 to 0.5µm.

[0062] Tests were carried out with two types of devices: A Keyence TM-006 device equipped with a telecentric lens offering 0.4X magnification and a corresponding 6mm diameter field of view. A device capable of integrating three magnifications of 0.5X, 1X, and 2X, providing three field of view sizes ranging from 14 x 10.7mm to 3.6 x 2.7mm, with a 1628 x 1238 pixel (2-megapixel) camera and stabilized green LED illumination.

[0063] A test bench was used to perform an initial characterization of the various devices used, as well as to characterize the effect of the measurement medium, namely air, a cutting fluid, and a benzene-type cleaning product. Part 1 was held by two clamps 91 and 92 of calibrated diameter, serving as a measurement standard and allowing a reference measurement to be taken simultaneously with the measurement of the part, as shown in the diagram. figure 2 .

[0064] The measurement stability results confirm the Gaussian statistical nature of the measurements, allowing the average value of several images to be used as a dimension measurement. Long-term stability of ±0.1 µm (3 Sigma for diameter measurements) was achieved. Repeatability test results are below ±0.1 µm.

[0065] Characterizing the effect of cutting fluid in the measuring device using Blasomill B22 machining fluid reveals that the presence of machining fluid degrades measurements, but to a perfectly acceptable degree. With measurements averaged over 60 images, the effect of the fluid is virtually imperceptible in some cases, even when using the maximum 2X magnification, which is generally the most sensitive to the presence of particles.

[0066] There figure 2This illustrates a barrel tree, which is a typical example of an object to be measured with the measuring device described previously. The following are typical characteristics of objects that can be measured: Object dimensions from 1mm to 20mm; Dimensional tolerance range from ±1 to ±50µm; Wide range of characteristics to be measured: length, span, diameter, chamfer, square, presence of a protruding element on the periphery of a part, particularly a part of revolution (for example a hook)...

[0067] Measurements taken using different methods and in different environments show that the measured value (extracted by image analysis) is noisy, with a Gaussian distribution. The dispersion is low, well below 1 µm. From 15 averaged measurements, the static repeatability (i.e., without moving the part, with 60 seconds between each measurement) reaches a range of less than 0.1 µm.

[0068] The part is measured in a container filled with a machining fluid without significant degradation of the performance of the measuring device.

[0069] The effect of the liquid is noticeable in terms of dispersion, which increases by an average of 50%. Static repeatability remains within perfectly acceptable levels. At the measured values ​​level, the results after calibration are virtually identical to those obtained in air.

[0070] If the position of the part relative to the measuring device is changed, the measured values ​​pass through optima that are the "true values" in the geometric sense (i.e., with proper alignment and optical focus). This eliminates errors due to the part's positioning. The correct value in the metrological sense can be obtained by calibrating the device. This can be done by calibrating the device beforehand and / or afterward, or by simultaneously measuring a gauge block or a standard 91, 92, for example.

[0071] The effect of the distortion of quantities as a function of working distance is illustrated on the figure 3 The graph shows on the x-axis the working distance WD (expressed relative to the ideal working distance) and on the y-axis the apparent size measured when measuring at least one dimension L of a barrel shaft.

[0072] The distortion effect of the part is due to the non-perpendicularity of the dimension being measured relative to the light rays of the optical field used for the measurement. The apparent dimension or height Lm of dimension L is defined as a function of the angle α formed by the dimension being measured and the direction perpendicular to the optical axis, and of the depth P of the part at the dimension, by the equation: Lm α = L ⋅ cos α + P ⋅ sin α .

[0073] The measured dimensions are subject to the effects mentioned above, which combine linearly, that is to say, they overlap: Maximum or minimum at optimal working distance; Minimum or maximum at zero tilt.

[0074] There figure 4This illustrates an example of the geometric effect (due to the workpiece's inclination T) and the effect of the working distance WD on the measurement. The effect is represented as the difference in length relative to the nominal value, as a function of the workpiece's inclination angle on the x-axis and the working distance on the y-axis.

[0075] We can see, therefore, that the measuring device allows us to determine, in particular, the diameters and lengths of a small watch component. The measurement is fast and reliable, especially thanks to image acquisition and dynamic dimensional measurement while the part is moving relative to the device's optical field. The exact dimensions are then determined by processing the measurements taken from the different images. Ultimately, the measuring device allows us to deduce, through mathematical processing, a clear image for each dimension to be measured from a multitude of blurry images. In other words, for a given dimension, the optical sensor provides a series of data defining several different values. This series is then processed to obtain the exact value of the dimension.

[0076] The magnification of the optical system can be chosen so that the sensor can acquire an image of the entire object without having to move the object or the sensor. Alternatively, the magnification of the optical system can be chosen so that the sensor can acquire an image of the portion of the object that includes the critical dimensions to be measured.

[0077] As seen previously, the measurement is carried out in a machining fluid, which greatly simplifies the use of the device in an industrial production environment.

[0078] The measurement principle can be applied, in particular, to components of revolution with cylindrical symmetry. It is also possible to determine the concentricity of the part by rotating the component around its axis of symmetry, as well as to determine the dimensions of non-cylindrical or asymmetrical parts, such as the square or hook of a barrel arbor. Measuring other types of parts is, of course, also possible.

[0079] In all embodiments of the invention, the optical sensor can be a two-dimensional optical sensor, a CMOS camera, or a CCD camera.

[0080] In all embodiments according to the invention, the obtaining step may include obtaining at least one series of data relating to a standard 91, 92 or to a gauge.

[0081] In all embodiments according to the invention, the processing may include determining the value of the dimension by calculation based on the apparent values ​​of the dimension, using at least one series of data relating to the standard 91, 92 or the gauge.

[0082] Throughout this document, "dimension of an object" means, in particular, its length, width, depth, thickness, height, or diameter if it is an object with a shape of revolution.

[0083] The proposed solution allows: To overcome the adverse environment of the machine tool's machining zone, which generally degrades the accuracy and repeatability of measurements. This is achieved by measuring the workpiece directly in a fluid, which is either the lubrication or machining fluid used for machining, or another compatible fluid of similar chemical composition. This method enables high-quality optical measurements: by using the machining fluid as the measurement medium, problems with cleaning the workpiece, errors arising from interface issues on the workpiece (presence of a liquid film on the workpiece), and problems related to the cleanliness of the optics in the machining environment are avoided. A very large number of measurements can be performed per time interval (the measurement lasts only a few tenths of a second) thanks to the use of a high-resolution, high-frequency camera and very fast image analysis intelligence.This principle allows either retaining only the average value of each desired dimension, or, preferably, using the value of a digitally adjusted curve for the measurements, particularly for small parts, or combining both methods. This ensures very high reliability of the results. The measurements of the part's dimensions (e.g., diameters or lengths) are taken using a measurement system employing a collimated light source, telecentric optics coupled to a high-resolution, high-frequency CCD or CMOS camera, and a kinematic system for manipulating the part or sensor, enabling dynamic measurements. The dynamic measurement and data processing allow for the extraction of a measurement value corresponding to a "perfect" alignment of the part and eliminate optical focusing errors.To perform dimensional measurements from a single series of images, without having to return to the "perfect" position—corresponding in particular to the ideal tilt and working distance (focal plane and zero tilt)—to obtain the final value of the dimension to be measured. Such repositioning, which is implemented in current measuring machines, is often very time-consuming, to the detriment of machine efficiency, and is never perfect due to positioning errors inherent in the finite accuracy and hysteresis of the movement mechanisms. This repositioning error leads to an unavoidable measurement error in the final value of the dimension to be measured.To perform measurements of several dimensions of the object simultaneously, based on the same series of images, by digitally adjusting the different apparent dimensions according to the object's position in the optical field (inclination and working distance, in particular). Therefore, there is no need to acquire a specific image or series of images for each dimension to be measured. To achieve resolutions on the order of 0.015 µm. The measurement resolution depends on the optical magnification, the pixel size of the camera sensor, and the number of available shades of gray. The stated resolution can be improved through advancements in cameras (higher pixel density) and optics. To eliminate potential deviations in the measurement chain by using an onboard reference, measured periodically.The speed of measurement allows for frequent measurements of a reference part, thereby preventing most potential drifts in the measuring device itself (relative measurement or control). This ensures an extremely precise relative measurement against a reference standard. The measurement solution could be used in any machining center or material deposition machine. It could also be used to implement closed-loop control of the machine tool, limiting and correcting the difference between the measured dimension and its setpoint, regardless of external drifts or disturbances.

[0084] The main advantages of this approach, compared to existing devices, are: Image acquisition is done in motion; Image acquisition (including measurement) is in full field (no kinematics or image summation); The ability to tilt the part relative to the optical system eliminates the need for a setup; The measurement is in the same environment as the manufacturing process (machining, material deposition).

[0085] The solution also has another significant advantage: it allows several dimensions to be measured at the same time, meaning that a single implementation of the process can generate several sets of data, all relating to a different dimension (length, diameter, or other).

[0086] The combination of part movement and continuous image acquisition allows for control of: Effects due to parts: diameter / length ratio, tool radii, tool wear... Measuring lengths by finding the minimum or maximum length depending on the inclination.

Claims

1. Method for measuring at least one dimension (L) of an object (1) joined to a machine tool, by an attachment, the method comprising the use of a first optical system (11) comprising an optical sensor (111) associated with a lens (112) and of a container (21) containing a machining liquid (22), in which the object is submerged, the measuring method comprising acquisition of data on at least one dimension through at least one wall (211) of the container and the liquid without prior removal of the object from the machine, the object (1) having a first axis (2) and the first optical system (11) having an optical second axis (113), the data acquisition being carried out while the object is making a movement relative to the first optical system, and in particular making a movement such as to angularly move the first axis relative to the second axis and / or a movement such as to rotate the object about the first axis and / or a movement such as to translate the object along the second axis.

2. Measuring method according to the preceding claim, the measuring method comprising: - a step of processing at least one data series to quantify said at least one dimension.

3. Measuring method according to the preceding claim, characterized in that the optical sensor is associated with a telecentric lens (112).

4. Measuring method according to Claim 2 or 3, characterized in that the method comprises the use of a collimated light source having an optical third axis (123) or of a lighting telecentric second optical system (12) comprising a light source (121) associated with a telecentric lens (122) having an optical third axis (123), in particular a third axis coincident with the second axis.

5. Measuring method according to any of Claims 2 to 4, characterized in that a data series comprises a plurality of apparent values of the at least one dimension, each apparent value of the data series in particular being associated with a given, or even unique, position of the object with respect to the first optical system and / or characterized in that a plurality of data series delivered by the optical sensor and relating to a plurality of dimensions are obtained simultaneously, in particular from the same series of images and from the same phase of movement of the object with respect to the first optical system.

6. Measuring method according to any of Claims 2 to 5, characterized in that the processing comprises determining the value of the at least one dimension by calculation based on the apparent values of the at least one dimension, the calculation including a calculation of an average of the apparent values and / or the calculation including an interpolation of the apparent values, in particular a polynomial interpolation.

7. Measuring method according to any of Claims 2 to 6, characterized in that the step of obtaining the at least one data series is carried out while the object is submerged in the liquid (22), the data being obtained through the at least one wall (211) of the container (21) and through the liquid.

8. Measuring system comprising a device (100) for measuring at least one dimension (L) of an object and a machine tool, the device being arranged relative to the workpiece and to the machine tool in such a way that the attachment of the workpiece, which is joined to the machine tool by said attachment, is not modified with respect to the machine tool, the device (100) for measuring at least one dimension (L) of the object comprising: - a first optical system (11) comprising an optical sensor (111) associated with a lens (112), and - a container (21) containing a machining liquid (22), the container comprising at least one transparent wall (211), the object (1) having a first axis (2), the lens (112) being a telecentric lens (112) having an optical second axis (113), the device comprising: - an element (31) for acquiring data delivered by the optical sensor, - an element (32) for processing the data, the device comprising an element (41) for moving the object relative to the first optical system, and in particular an element for angularly moving the first axis relative to the second axis and / or an element for rotating the object about the first axis and / or an element for translating the object along the second axis.

9. Measuring system according to Claim 8, characterized in that the device (100) comprises a collimated light source having an optical third axis (123) or a lighting telecentric second optical system (12) comprising a light source (121) associated with a telecentric lens (122) having an optical third axis (123), in particular a third axis coincident with the second axis.

10. Measuring system according to either of Claims 8 and 9, characterized in that the first and second axes are orthogonal or substantially orthogonal.

11. Method for manufacturing an object comprising implementation of the measuring method according to any of Claims 1 to 7 and / or use of a measuring system according to any of Claims 8 to 10.