Method for measuring at least one dimension of an object

Abstract

To provide a method for making it possible to render measurement of a dimension of an object simpler and more reliable.SOLUTION: A method of measuring at least one dimension (L) of an object (1) having a first axis (2) includes the use of a first optical system (11) including an optical sensor (111) and having a second optical axis (113). The measuring method includes the steps of: obtaining at least one series of data from the optical sensor when the object is in a movement relative to the first optical system, notably an angular movement of the first axis relative to the second axis and / or a rotational movement of the object about the first axis and / or a translational movement of the object along the second axis; and processing the at least one series of data to quantify the at least one dimension.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an optical method for measuring at least one dimension of an object. The present invention also relates to a method for manufacturing an object, in particular a machining method using such a measuring method. The present invention further relates to an object created by the above manufacturing method. The present invention finally relates to a timepiece movement or a timepiece, in particular a wristwatch, including such an object.

[0002] The development of machine tools aims to improve accuracy by reducing machining errors. As one of many examples, a mechanical watch can be cited, which aims to improve the accuracy of manufacturing parts in order to improve the performance of the movement and the processing capacity of the assembly production line. Other examples relate to the automotive, medical, aerospace, aviation, and electronics industries.

[0003] The search for such improvements has become difficult due to the working conditions of machine tools. This is particularly true for lathes for bar stock, whether of the cam type or numerically controlled, but also for all other machines having a process of removing material by chip generation. For example, it is difficult to further improve the inherent accuracy of these machines by ordinary methods, such as optimizing the accuracy of structures and guides. In fact, the remaining machining errors, such as thermal distortion, static distortion, non-reproducibility of the positioning of moving elements (machines supporting tools), and tool wear, have already reached the minimum threshold, and further improvement is difficult. However, the remaining errors are too large in some applications, such as watchmaking.

[0004] Machine tools are not suitable for improving performance by installing sensors in place. This is because sensors deteriorate significantly due to the harsh environment caused by the presence of cutting fluid and chips. Some methods for improving repetitive accuracy have been studied by using sensors to measure the position of the workpiece and the tool or specific operating elements of the machine during the manufacturing process, and then using the measurement in real time for machine control or correction.

[0005] Machine tools such as lathes for bars (or lathes, transfer machines, etc.) generally include one or more devices for correcting machining errors recognized during the manufacture of the workpiece. These devices are either numerical tool correctors in the case of numerically controlled machine tools or micrometer screw tightening devices in the case of cam-type machines. The correction is generally performed manually by an operator monitoring the machine on the production line.

[0006] There are various systems for measuring movable mechanical elements, such as position sensors mounted on the spindle of the machine, such as LVDT dielectric sensors or optical scales. However, such sensors do not measure the dimensions of the manufactured workpiece.

[0007] There are also solutions for directly measuring the workpiece, such as laser barriers, other optical gauge systems, or systems using other physical laws. In principle, this type of measurement operates by causing contact. The measurement is then read on the axis tracking system of the machine tool. With the approach of measurement via the axis tracking sensor, the required performance cannot be obtained. Furthermore, in the case of small workpieces, many of these solutions are very "intrusive" and thus very difficult to implement.

[0008] In summary, due to their inherent drawbacks, none of these measurement solutions can achieve the resolution and reproducibility required to accurately measure the size or dimensions (diameter, length) of an object, particularly a clock part of the rotating object type on the millimeter scale.

[0009] Patent Document 1 discloses a measuring device that measures the diameter and concentricity of various regions of a cylindrical workpiece by rotating the workpiece. No information is given regarding positioning the workpiece in the optical system.

[0010] Patent Document 2 discloses a method for measuring the diameter along an object of a cylindrical object by vertical displacement and rotational displacement. An illumination system and a one-dimensional type detector are used. There is no particular mention of positioning the object in the system.

[0011] Patent Document 3 discloses an apparatus for measuring the diameter and concentricity of a cylindrical object in a telecentric type optical system using a combination of two sensors, one of which is of the one-dimensional type and the other is of the two-dimensional type. Positioning the object in the system is not the subject of this document.

[0012] Patent Document 4 discloses a measurement system of the reflection microscope type including a table movable along the optical axis for acquiring continuous images at different operating distances. The continuous images enable determination of the focus at various heights of the workpiece. Then, for measurement of the dimension of interest, images are taken at each respective position z of interest.

Prior Art Documents

Patent Documents

[0013]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0014] The object of the present invention is to provide a measurement method for improving the accuracy of measurement of manufactured objects, particularly objects manufactured by material removal or material deposition. In particular, the present invention provides a method capable of performing rapid, accurate, and reliable measurement of the dimensions of small-sized objects, that is, a method capable of making the measurement of the dimensions of an object simpler and more reliable. Further, the present invention enables accurate measurement of multiple dimensions of the same object simultaneously and rapidly, in a manufacturing environment, without pre-cleaning the object, in a machining fluid or a compatible liquid.

[0015] Claim 1 defines the measurement method according to the present invention.

[0016] Dependent claims 2 to 5 define various embodiments of the method.

[0017] Claim 6 defines the measuring device according to the present invention.

[0018] Dependent claims 7 to 8 define various embodiments of the measuring device.

[0019] Claim 9 defines the measurement method according to the present invention.

[0020] Claim 10 defines the measurement according to the present invention Method to be defined.

[0021] Claim 11 defines the Measuring device according to the present invention.

[0024] The accompanying drawings show, by way of example, an embodiment of the device according to the present invention and an embodiment of the measurement method according to the present invention.

Brief Description of the Drawings

[0025]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

[0026] An embodiment of an apparatus 100 for measuring the dimension L of an object 1 or a workpiece will be described below with reference to FIG. 1. The apparatus, and the measurement method described below, are particularly suitable for measuring small parts, especially rotating millimeter-scale objects, particularly objects of 10 mm or less, and can be used in a machine tool type environment. The apparatus and method are particularly suitable for measuring the dimensions of watch parts.

[0027] Here, it is assumed that the object has a first axis 2, for example, a rotation axis. The apparatus includes the following. - A first optical system 11 having an optical axis 113, referred to as the second optical axis 113 in the following description, and including an optical sensor 111 that preferably cooperates with a lens 112, - An element 31 for acquiring data from the optical sensor, - An element 32 for processing the data, - An actuator 41 or element for moving an object relative to a first optical system, in particular an element for angularly moving a first axis relative to a second axis, and / or an element for rotationally moving an object around a first axis, and / or an element for linearly moving an object along a second axis.

[0028] Instead of or in addition to the above, the device for measuring the dimension L of the object 1 includes, in addition to the first optical system 11 including the optical sensor 111 cooperating with the lens 112, - A container 21 for containing a liquid 22, in particular a machining liquid or a liquid having similar chemical properties, the container having at least one transparent wall 211, including.

[0029] The measuring device advantageously includes a telecentric illumination second optical system 12 including a collimating light source having an optical axis 123, which is referred to as the third optical axis 123 in the following description, or a light source 121 cooperating with a telecentric lens 122 having an optical axis 123, which is referred to as the third optical axis 123 in the following, in particular a third axis coinciding with the second axis.

[0030] The optical sensor may be a two-dimensional optical sensor or a CMOS video camera or a CCD video camera.

[0031] The first and second axes are advantageously orthogonal or substantially orthogonal.

[0032] The optical sensor 111 advantageously cooperates with the telecentric lens 112.

[0033] The measuring device is designed to function in the air or in an environment compatible with a machining environment. More specifically, the measuring device enables dynamic measurements, including moving an object relative to the measurement plane of a two-dimensional telecentric optical sensor. The measuring device is designed to function on objects in the air or on objects immersed in a liquid. The object may be supported by a manipulator that enables relative movement of the object with respect to the measurement plane of the sensor. The object may be gripped by a spindle or a gripper of a machine tool, for example when an optical sensor or a moving element 41 or an actuator by which the measuring device can move the measurement plane relative to the workpiece is installed. Alternatively, instead of being gripped during measurement, the object may be freely movable in air or in a liquid bath.

[0034] The measuring device may be filled with a liquid, in particular a cutting oil or a machining fluid, or another liquid compatible with or of similar nature to the machining coolant, provided that the quality of the measurement is not degraded and that the liquid is clean and homogeneous. This is made possible in particular by the fact that the transparent walls 211, 212, formed in particular by optical glass plates located on both sides of the container, are substantially or completely identical. The device is thus symmetric from the point of view of the refractive index, and as a result, all optical changes to the light incident on the device are corrected when the light exits the device.

[0035] The processing element 32 includes a processor 321 and a memory 322. The processing element may also include elements for controlling the actuator 41.

[0036] The measuring device may also include a human-machine interface 33. In that case, the processing element 32 is connected to the human-machine interface 33. The interface particularly includes elements for displaying a calculated or determined value of the dimension L. The element may also display other data, in particular the apparent value of the dimension and / or the dimension and / or the calibration standard. The human-machine interface may also include elements for capturing data and commands.

[0037] The acquisition element and / or the processing element may be implemented by 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 a human-machine interface of a computer.

[0038] An embodiment of a method for measuring the dimension L of an object 1 will be described below with reference to FIGS. 3 to 6.

[0039] It is assumed that the object has a first axis 2, in particular a rotation axis.

[0040] The method includes the use of the above-described measuring device, in particular the first optical system 11 including the optical sensor 111 and having a second optical axis 113. The first optical system forms a clear image of the object on the sensor 111.

[0041] For this purpose, in a first step 510 of the method, the measuring device 100 is provided. The measuring device can be arranged and / or positioned relative to the workpiece in its original position, i.e., without changing the setting relative to the machine of the workpiece, and the workpiece is installed on the machine in order to be shaped by material removal or material deposition. Alternatively, the measuring device may be provided measurably, for example, during the formation of one or more successive workpieces, after being shaped by material removal or material deposition. In particular, the machine may be a machine tool, especially a lathe for bars.

[0042] It is noted that the step of providing the measuring device may be carried out at any stage of the process of modifying the workpiece on the machine. The step may be carried out before the workpiece is modified on the machine. Instead of or in addition to this, the step may also be carried out between two stages of modifying the workpiece on the machine, for example, between two machining stages. Instead of or in addition to this, the step may also be carried out after one or more stages of modifying the workpiece on the machine have been completed. Alternatively, the step of providing the measuring device may be carried out after machining is completed and the workpiece is removed from the machine.

[0043] During step 510, advantageously, within the container of the measuring device, there is contained a machining fluid, a cleaning fluid, or a liquid of similar chemical and / or compatible properties, that is, a liquid that does not affect the workpiece nor the formation process of the workpiece mechanically after the workpiece is immersed in the liquid. The measuring device is arranged with respect to the workpiece and / or the machine such that the workpiece is immersed in the liquid within the container. The properties of the liquid are preferably such that the workpiece can be immersed in the liquid without the need for prior cleaning of the workpiece.

[0044] For example, the workpiece is gripped, for example, by one or more spindles and / or one or more clamps and / or one or more spindles and / or a gripping system such as a vacuum gripping system.

[0045] In a second step 520, the workpiece continues to move or is moved with respect to the measuring device, in particular with respect to the first optical system. The movement advantageously includes the rotation of the workpiece around a first axis 2. The movement of the workpiece is brought about by the rotation of the above-mentioned spindle or spindles, and / or clamp or clamps, and / or spindle or spindles, and / or the gripping system described above. The movement is brought about, for example, by a machine. Alternatively, the movement is brought about by an auxiliary device cooperating with the machine. Instead of or in addition to this, the device enables the measuring device to be movable with respect to the workpiece.

[0046] In addition to this, the workpiece may be moved such that the first axis 2 is angularly displaced around an axis that is substantially parallel to the second axis 113, in particular the fourth axis 3 or the fourth axis 3. The movement preferably includes an angular scanning of a sector such that the first axis 2 and the second axis 113 are at least temporarily orthogonal during the scanning. The movement is brought about, for example, by a machine. Alternatively, the movement is brought about by an auxiliary device cooperating with the machine. Instead of or in addition to this, the actuator 41 can move the measuring device with respect to the workpiece.

[0047] In addition to this, the workpiece can be translated along the second axis 113 with respect to the measuring device, particularly with respect to the first optical system 11. The movement preferably includes the scanning of segments such that the workpiece is at least temporarily at an optimal operating distance from the first optical system 11 during the scanning. The movement is effected, for example, by a machine. Alternatively, the movement is effected by an auxiliary device cooperating with the machine. Instead of or in addition to this, the actuator 41 of the measuring device can move the measuring device with respect to the workpiece.

[0048] In a third step 530, as described above, at least one continuous data is collected from the optical sensor while the object is moving with respect to the first optical system. In fact, at the levels of the various pixels of the optical sensor 111, the received illumination data is transmitted to the data acquisition element 31 at different times. From the output of the acquisition element, at least one continuous data including a plurality of apparent dimensions or a plurality of values of at least one dimension L for which quantification is required is obtained. The processing performed at the level of the acquisition element is known to those skilled in the art. The optical system, particularly the lens 112, can determine the distance separating two pixels of the optical sensor corresponding to the images of two ends or two characteristic elements of the workpiece, and can infer the apparent value of the dimension of the workpiece from the distance. In other words, the continuous data corresponds to the apparent values of the continuous dimensions corresponding to different positions of the workpiece with respect to the first optical system.

[0049] Advantageously, the element 41 for moving the object with respect to the first optical system can move the object at a constant or substantially constant speed during step 530. Preferably, the element 41 for moving the object with respect to the first optical system is not a stepping actuator or an actuator used as a stepping motor. In step 530, at least one continuous data is collected from the optical sensor while the object is moving with respect to the first optical system. However, no data is collected when the object is stationary, and the object is moved between two consecutive stages of data collection.

[0050] During this third step, while the object is immersed in liquid 22, at least one continuous data is advantageously obtained. For this reason, the data is obtained through the wall 211 of the liquid 21 and also through the liquid. When the second optical system 12 is present, the light rays also pass through the wall 212 of the container.

[0051] In addition to the above, the step of acquiring data includes obtaining at least one second continuous data related to the calibration standards 91, 92 or the pinge gauge. This second continuous data is related to calibrated dimensions that are accurately known and, in subsequent processing steps, makes it possible to correct the continuous data including multiple apparent values of at least one dimension L.

[0052] The step of acquiring data advantageously includes acquiring at least one additional continuous data related to at least one additional dimension L’, L”,... of the object. This at least one additional continuous data may be related to any dimension of the object including multiple apparent values of the dimension, such as diameter, length, width, thickness, depth, height, etc. The decisive advantage of the present invention is that multiple continuous data related to the same dimension and / or different dimensions can be acquired in the same step of acquiring data, and multiple dimensions can be determined in a single step.

[0053] In the fourth step 540, at least one continuous data is processed and the dimension L is digitized. The processing includes determining the value of the dimension L by calculation based on the apparent value of the dimension L obtained in the previous step.

[0054] The calculation can include calculating the average of the apparent values, and in particular, the value determined or calculated after receiving the processing step may be the average of the apparent values of the continuous data.

[0055] Alternatively or in addition to this, the calculation may include interpolation of the apparent values, in particular polynomial interpolation, and / or extraction of extreme values. These calculations are known to those skilled in the art.

[0056] Alternatively or in addition, the calculation may include correcting the apparent value based on second consecutive data regarding accurately known, calibrated dimensions.

[0057] Optionally, in an additional step, the value of dimension L or the various dimensions may be used for the control of the machine tool, i.e., to better target the required dimension value using a servo control loop or closed loop, or may be used to correct machining parameters.

[0058] The measurement is thus provided based on the following principles. - The workpiece is moved relative to the measurement plane 4 associated with the first optical system 11 (corresponding to the ideal operating distance) such that the workpiece passes through the "perfect position", i.e., the position where the dimension to be measured lies within the measurement plane 4. - Over a series of movements, the sensor of the measuring device collects a plurality of images (e.g., 30 images per second), and the acquisition element extracts the required apparent value (apparent dimension). - The processing element determines the opening law of the apparent dimension as a function of the movement parameters of the workpiece relative to the measuring device, and then proceeds to numerical correction (fitting), for example, by a 2nd, 4th, 6th, or 8th order polynomial approximation depending on the situation. - The opening law function, i.e., the relationship linking the apparent dimension to the data reflecting the position of the workpiece relative to the measuring device, is characterized by extreme values. The values of the extreme values are extracted by polynomial approximation, and then the measured value, i.e., the measurement of the dimension, is retained.

[0059] The measurement during the dynamic movement of the workpiece can avoid mainly two types of errors when the workpiece is positioned in the optical field. I. The distortion of the apparent value as an effect of the operating distance, II. The buckling of the workpiece due to the posture within the optical field (the dimension to be measured is not perpendicular to the direction of the light rays used for measurement).

[0060] Such various effects are shown in FIGS. 3 to 5 and are described in detail below.

[0061] The measurement can be carried out in a medium that makes it possible to reduce the presence of a liquid film on the workpiece and problems related to the optics of the measurement system. When the workpiece is covered with a liquid, such as during or after machining, the workpiece to be measured is introduced into a container of the measuring device filled with a liquid that does not require the workpiece to be washed and dried.

[0062] The measuring method advantageously comprises a first optical system 11 including an optical sensor 111 cooperating with a lens 112 and a container 21 containing a machining fluid 22 in which the object is immersed or a liquid of similar chemical properties. The measuring method thus advantageously includes obtaining dimensional data via the wall 211 of the container and the liquid.

[0063] Advantageously, the measuring method includes the use of a telecentric illumination second optical system 12 including a collimated light source having a third optical axis 123 or a light source 121 cooperating with a telecentric lens 122 having a third optical axis 123. The collimated light source or the second optical system makes it possible to create an optical field with parallel light rays. An object located in the optical field blocks the light rays, whereby an image is formed in silhouette at the height of the sensor 111.

[0064] The present invention also relates to a method for manufacturing an object, including the use of the measuring method described above and / or the use of the measuring device described above. For this reason, the present invention relates to a manufacturing method using the measuring method according to the present invention and / or the measuring device according to the present invention.

[0065] The present invention further relates to an object 1 or workpiece 1 manufactured using the manufacturing method described above.

[0066] Finally, the present invention relates to a watch movement 110 or a watch 120, in particular a wristwatch, including the object or workpiece described above. FIGS. 7 and 8 schematically show first and second embodiments of a watch according to the present invention.

[0067] This solution is suitable for machining environments (cutting fluids) and enables the measurement of the diameter and length of machined workpieces within seconds, either on-site or immediately after leaving the machine, with a resolution of approximately 0.015 μm and a repeatability accuracy of ±0.2 to 0.5 μm.

[0068] Tests were conducted on two types of devices. - Keyence TM 006 device, including a telecentric lens with a magnification of 0.4× and a corresponding optical field with a diameter of 6 mm. - A device that enables the integration of three magnifications of 0.5×, 1×, and 2×, providing optical fields of three sizes from 14×10.7 mm to 3.6×2.7 mm, including a video camera with 1628×1238 pixels (2 million pixels) and illumination by a stabilized green LED.

[0069] A test bench was used to show the first characteristic evaluation of the various devices used and the characteristics of the measurement environment, i.e., the influence of air, cutting fluid, and benzene-type cleaning products. Workpiece 1 serves as a calibration standard and is gripped by two calibrated-diameter clamps 91, 92 that enable the implementation of reference measurements simultaneously with the measurement of the workpiece shown in Figure 2.

[0070] The measurement stability results confirm the Gaussian statistical nature of the measurement, which enables the use of the average value of multiple images as the dimension measurement. A long-term stability of ±0.1 μm (3σ for dimension measurement) was obtained. The results of the repeatability accuracy test consist of values of ±0.1 μm or less.

[0071] According to the characteristic evaluation of the influence of the cutting fluid present in the measuring device by Blasomill B22-type machining fluid, although the presence of the machining fluid deteriorates the measurement, it is found to be completely within the acceptable range. In measurements averaged over 60 or more images, the influence of the presence of the liquid is, in principle, imperceptible in some cases, even when using the 2× maximum magnification, which is the most sensitive to the presence of particles.

[0072] Figure 2 shows a perfume box lid, which is a typical example of an object measured using the above-described measuring device. Typical characteristics of measurable objects are as follows. - The dimensions of the object are from 1 mm to 20 mm. - The dimensional tolerance is in the range of ±1 to ±50 μm. - The general types of features to be measured are length, span, diameter, chamfer, angle, workpiece, especially the presence of protruding elements around a rotating workpiece (such as a hook), etc.

[0073] Measurements obtained using different methods in different environments show that in the Gaussian distribution, the measured values (extracted by image analysis) have a lot of noise. The variance is small, less than 1 μm. In 15 average measurements, the static repeatability accuracy (i.e., the repeatability accuracy without movement of the workpiece, with a 60 - second interval between measurements) reaches a range of 0.1 μm or less.

[0074] The workpiece can be measured in the air or in a liquid, especially in a container filled with a machining oil or a cleaning liquid, without significantly degrading the performance of the measuring device.

[0075] The influence of the liquid can be perceived at the stage of variance, with an average increase of 50%. The static repeatability accuracy remains completely within the acceptable range. At the level of the measured values, the calibrated results are virtually the same as those in the air.

[0076] When the position of the workpiece with respect to the measuring device is corrected, the measured value passes through the optimum value, which is the "true value" in the geometric sense of the term (i.e., after truing and optical focusing). Thus, errors caused by workpiece positioning can be bypassed. The exact value in the metrological sense of the term is obtained by calibrating the device. Here, the device can be calibrated before and / or after, and for example, a pin gauge or calibration standards 91, 92 can also be measured simultaneously.

[0077] Figure 3 shows the influence of the distortion of values as a function of the operating distance. The graph shows on the horizontal axis the operating distance WD (expressed relative to the ideal operating distance) and on the vertical axis the apparent value when measuring at least one true dimension L of the perfume box.

[0078] The influence of the buckling of the workpiece is caused by the fact that the dimension to be measured is not perpendicular to the rays of the optical field used for the measurement. The dimension or apparent dimension Lm of dimension L is defined by the following formula as a function of the angle α formed in a direction perpendicular to the optical axis with the dimension to be measured and the depth P of the workpiece at the height of the dimension.

[0079]

Equation

[0080] The measured dimensions depend on the above-mentioned influences and are linearly combined, i.e., superimposed, as follows. At the optimal operating distance, maximum or minimum. At 0 slope, minimum or maximum.

[0081] Figure 4 shows an example of the geometric influence (caused by the tilt T of the workpiece) and the influence that the operating distance WD has on the measurement. The influence is represented as the length difference relative to the nominal value as a function of the tilt angle of the workpiece plotted on the horizontal axis and the operating distance plotted on the vertical axis.

[0082] It can thus be seen that such a measuring device makes it possible to determine, in particular, the diameter and length of watch parts of small size. The measurement is rapid and reliable, in particular by image acquisition and dynamic measurement of dimensions during the movement of the workpiece relative to the optical field of the device. The exact dimensions are determined afterwards by processing the measurements on various images. In the final analysis, based on a large number of blurred images, the measuring device can deduce by mathematical processing a sharp image for each dimension to be measured. In other words, for the same dimension, continuous data defining a plurality of different values of the dimension are obtained from the optical sensor. The continuous data are processed to obtain the exact value of the dimension.

[0083] The magnification of the optical system can be selected such that the sensor can acquire an image of the entire object without the need to move the object or the sensor. Alternatively, the magnification of the optical system can also be selected such that the sensor can acquire an image of a portion of the object that includes the critical dimension(s) for which measurement is required.

[0084] As described above, the measurement can be performed in a liquid bath, such as a machining oil bath, which simplifies the use of the device in an industrial manufacturing environment.

[0085] The measurement principle can be applied particularly to rotating parts having cylindrical symmetry. By rotating the part around the axis of symmetry, the concentricity of the workpiece can be grasped, and similarly, the dimensions of non-cylindrical or asymmetric parts, such as the corner or hook of a perfume box, can be grasped. Of course, measurement of other types of workpieces is also possible.

[0086] In all embodiments of the present invention, the optical sensor may be a two-dimensional optical sensor or a CMOS video camera or a CCD video camera.

[0087] In all embodiments of the present invention, the step of obtaining data may include obtaining at least one continuous data related to calibration standards 91, 92 or a pin gauge.

[0088] In all embodiments of the present invention, the processing may include determining the value of the dimension based on the apparent value of the dimension, using at least one continuous data related to calibration standards 91, 92 or a pin gauge. Operation Thereby, the determination of the value of the dimension may be included.

[0089] As used herein, "dimension of an object" particularly means length or width or depth or thickness or height or diameter if the object has a rotational shape.

[0090] According to the proposed solution, the following becomes possible. - Avoiding undesirable environments in the machining area of the machine tool that generally deteriorate the measurement accuracy and repeatability. This is achieved by measuring the workpiece directly in a liquid, which is either a lubricant or a machining oil used in machining, or another liquid having compatible or similar chemical properties. This method enables high-quality optical measurements. Using the machining oil as the measurement medium can avoid problems such as cleaning the workpiece, errors caused by boundary problems of the workpiece to be measured (the presence of a liquid film on the workpiece), and problems related to the cleanliness of the lens in the machining medium. - By using a high-resolution high-frequency video camera and very fast image analysis intelligence, performing a very large number of measurements per time interval (the measurement takes only a fraction of a second). This principle enables storing only the average value of each required dimension, or preferably using the values of the mathematically fitted curve of the measurement for particularly small-sized workpieces, or using a combination of the two methods. This ensures reliable results. - Measuring dimensions (such as diameter and length) using a collimated light source, a telecentric lens connected to a high-resolution high-frequency CCD or CMOS video camera, and a kinematic system that operates the workpiece or sensor enabling dynamic measurement of the workpiece. Dynamic measurement and data processing make it possible to extract measurement values corresponding to the "perfect" alignment of the workpiece and eliminate optical focus errors. - To obtain the final value of the dimension to be measured, performing the dimension measurement based on a single continuous image without the need to return to the "perfect" position corresponding to the particularly ideal tilt and working distance (focal plane and zero tilt). Such repositioning implemented in existing measuring machines often requires long times that are disadvantageous to the effectiveness of the machine and will never be absolutely perfect due to positioning errors inherent in the finite precision and hysteresis of the displacement means. This repositioning error results in an inevitable measurement error for the final value of the dimension to be measured. - By performing a numerical fit on various apparent dimensions as a function of the position of an object in the optical field (in particular, its inclination and working distance), measurements of multiple dimensions of the object can be simultaneously carried out based on the same continuous image. It is not necessary to obtain an image or continuous image specific to each dimension to be measured. - Achieve a resolution of about 0.015 μm. The resolution of the measurement depends on the optical magnification, the size of the pixels of the sensor of the video camera, and the number of possible gray levels. The indicated resolution can be improved by improving the video camera (higher pixel density) and the quality of the lens. - Avoid any deviation of the measurement system through a built-in reference that is measured periodically. In fact, the speed of the measurement allows frequent calibration work, thus preventing much of the potential drift (relative control or measurement) of the measuring device itself. For this reason, the measurement will be obtained with respect to a very accurate calibration standard. - This measurement method can be used in all machine tools that remove material or all machines that deposit material. - This measurement method can be used for the closed-loop servo control of machine tools to limit and correct the difference between the measured dimension and its set value, regardless of disturbances and drifts.

[0091] The advantages of this approach compared to existing machines are mainly as follows. - Images are acquired while in motion. - Image acquisition (including measurement) is over the entire field of view (without kinematics or image addition). - By tilting the workpiece with respect to the optical system, the need for a support can be eliminated. - The measurement is carried out in the same environment as the manufacturing process (machining, deposition of material).

[0092] This solution also has other significant advantages. The solution allows the simultaneous measurement of multiple dimensions, that is, by using the measurement once, a plurality of continuous data related to different dimensions (length, diameter, etc.) can be generated respectively.

[0093] The combination of workpiece movement and continuous image acquisition enables the following controls. - Effects caused by the workpiece such as the diameter / length ratio, tool radius, tool wear, etc. - Measurement of length by finding the minimum or maximum length as a function of inclination.

Explanation of Signs

[0094] 1 Object 2 First axis 11 First optical system 12 Telecentric illumination second optical system 21 Container 100 Device 111 Optical sensor 112 Lens 113 Second axis 121 Light source 122 Telecentric lens 123 Third optical axis 211 Transparent wall

Claims

1. A method for measuring at least one dimension (L) of an object (1), the method comprising the use of a first optical system (11) including an optical sensor (111), obtaining continuous data from the optical sensor while the object is moving relative to the first optical system, processing the continuous data to quantify the at least one dimension, comprising: the step of obtaining the continuous data is performed when the object is immersed in a machining fluid or a liquid of similar chemical properties, and the continuous data is obtained through at least one wall (211) of a container (21) containing the liquid and through the liquid, the step of obtaining the continuous data is such that the object blocks a light beam and the optical sensor acquires an image formed as a silhouette, measurement method.

2. The optical sensor cooperates with a telecentric lens (112), The measurement method according to claim 1.

3. comprising the use of a collimated light source or the use of a second telecentric illumination optical system (12) including a light source (121) cooperating with a telecentric lens (122), The measurement method according to claim 1 or 2.

4. The continuous data includes a plurality of apparent values of the at least one dimension, and each of the apparent values of the continuous data is associated with the position of the object relative to the first optical system, and / or a plurality of continuous data regarding a plurality of dimensions are obtained simultaneously from the optical sensor, The measurement method according to any one of claims 1 to 3.

5. The processing includes determining a value of the at least one dimension by calculation based on a plurality of apparent values of the at least one dimension, and the calculation includes calculating an average of the apparent values and / or interpolating the apparent values, The measurement method according to any one of claims 1 to 4.

6. An apparatus (100) for measuring at least one dimension (L) of an object (1), a first optical system (11) including an optical sensor (111), an element (31) for acquiring continuous data from the optical sensor, an element (32) for processing the continuous data, in a measuring apparatus comprising: the measuring apparatus includes an element (41) for moving the object relative to the first optical system, and / or an element for the rotational movement of the object, and / or an element for the translational movement of the object. The measuring device includes a container (21) for containing a machining fluid or a liquid with similar chemical properties, and the container has at least one transparent wall (211). The element for acquiring the continuous data acquires, from the optical sensor, an image formed by a silhouette in which the object blocks a light beam. Measuring device (100).

7. A telecentric illumination second optical system (12) including a collimating light source or a light source (121) cooperating with a telecentric lens (122). The measuring device according to claim 6.

8. The axial direction of the object (1) and the optical axis direction of the telecentric lens (112) are orthogonal or substantially orthogonal. The measuring device according to claim 7.

9. The object (1) is an object coupled to a machine tool via a support, and the measuring method includes acquiring data representing the at least one dimension via at least one wall (211) of the container and the liquid without previously removing the object from the machine tool. The measuring method according to any one of claims 1 to 5.

10. The object is a part of a watch. The measuring method according to any one of claims 1 to 5 and 9.

11. The object is a part of a watch. The measuring device according to any one of claims 6 to 8.

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