Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
  • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
  • G01J3/02—Details
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
  • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
  • G01J3/02—Details
  • G01J3/0278—Control or determination of height or angle information for sensors or receivers
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
  • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
  • G01J3/46—Measurement of colour; Colour measuring devices, e.g. colorimeters
  • G01J3/50—Measurement of colour; Colour measuring devices, e.g. colorimeters using electric radiation detectors
  • G01J3/51—Measurement of colour; Colour measuring devices, e.g. colorimeters using electric radiation detectors using colour filters
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
  • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
  • G01J3/46—Measurement of colour; Colour measuring devices, e.g. colorimeters
  • G01J3/50—Measurement of colour; Colour measuring devices, e.g. colorimeters using electric radiation detectors
  • G01J3/51—Measurement of colour; Colour measuring devices, e.g. colorimeters using electric radiation detectors using colour filters
  • G01J3/513—Measurement of colour; Colour measuring devices, e.g. colorimeters using electric radiation detectors using colour filters having fixed filter-detector pairs

Definitions

• the invention relates to a device and a non-invasive spatio-colorimetric measurement method of a three-dimensional object in low relief.
• the present invention relates to the field of spatio-colorimetric diagnosis, also called field of colorimetric metrology.
• the document No. WO 05/080929 0 has a device for measuring colorimetric characteristics of a tooth in a plurality of points and in two-dimensional space.
• document No. WO 06/002703 discloses a device composed of several light-emitting diodes emitting light beams of different colors on an object. The light beams are then reflected by the object and then received by a detection system and a central image processing unit. Thus, each point of the image is analyzed so as to determine the spectrum consisting of different color levels corresponding to the different emission wavelengths of the light-emitting diodes. From these color levels, the central processing unit calculates, for each point of the analyzed surface, the corresponding colorimetric coordinates.
• the device described in this document makes it possible to determine a two-dimensional colorimetric mapping of the analyzed object.
• the combination of spatial and colorimetric measurements for three-dimensional objects has a wide field of application in the dental field, biometrics, industrial or artistic metrology, etc. More particularly, the fact of simultaneously measuring the spatial coordinates, according to the parameters of the space of the analyzed object, makes it possible to appreciably improve the quality of the results.
• the value of the colorimetric coordinates depends directly on the position of the measured object vis-à-vis lighting means since the amount of light received by an object decreases proportionally to the square of the distance separating it from these means lighting.
• the greater the angle defined between the normal to the analyzed object and the emitted light beam the more the quantity of light reflected, in the context of a diffuse reflection, decreases.
• the approximations made by the devices of the state of the art generate significant errors which at least partially distort the quality of the colorimetric analysis carried out.
• the present invention aims at overcoming the drawbacks of the state of the art mentioned above by proposing a device and a spatio-colorimetric measurement method of a three-dimensional object making it possible to model the bas-reliefs and the colorimetric coordinates of this object numerically. according to a multitude of points of analysis.
• the invention also aims to propose a method for calculating the colorimetric mapping of a three-dimensional object taking into account the parameters of the measuring device.
• the measuring device proposes to combine lighting means with monochromatic detection means, of which at least two twin detection means sensitive to substantially identical wavelength of light wavelength ranges. to determine, by stereoscopic effect, the low relief of the analyzed object.
• the subject of the invention is a device for the spatio-colorimetric measurements of a three-dimensional object comprising a detection head constituted by means for illuminating the object and at least four means of detecting the light reflected by the object, the device further comprising a data processing unit received by the detection means, wherein at least two twin detection means are sensitive to substantially identical wavelength ranges of light.
• the use of at least two twin detection means sensitive to substantially identical wavelength ranges of light makes it possible to calculate, by stereoscopy, the distance of the points analyzed with respect to the detection means.
• the spatial coordinates of the object can be determined according to the three directions of the space and the colorimetric coordinates can be corrected according to the position of the analysis points relative to the detection head (distance and normal to the area).
• the simultaneous implementation of several monochromatic detecting means, each sensitive and complementary to a part of the visible wavelength domain makes it possible, by means of a calculation algorithm, to compose a digital image color of the analyzed objects. This method provides better accuracy than color matrix photonic sensors and a lower acquisition rate than sequential multi-spectral monochromatic photonic detection systems.
• twin detection means comprise twin filtration elements associated with at least one photonic matrix sensor
• the photonic matrix sensor is divided into several zones respectively receiving the light rays coming from each of the twin filtration elements.
• the zones of the photonic sensor do not need to be synchronized with respect to each other;
• Photonic matrix sensors are CMOS sensors so that even if a pixel is violently saturated with photons, it has little effect on neighboring pixels.
• a bilinear interpolation taking into account the colorimetric values of the pixels surrounding a point of analysis is however provided so as to smooth the results obtained;
• the two twin detection means are sensitive to a wavelength range substantially equal to the wavelength range of the green, which makes it possible to obtain results that are particularly relevant as regards the topology of the objects analyzed;
• the two primary detection means are sensitive, one at a range of the blue wavelength range, the other at a range of the red wavelength range;
• the lighting means consist of a central light source around which the detection means are arranged;
• the lighting means consist of an annular lighting source arranged around the detection means, which is advantageous because the illumination is thus substantially homogeneous for all the points of analysis;
• the detection head is capped with a partitioning nozzle of predetermined depth so as to reduce the calculation time of the process. Indeed, the iterative calculation is thus performed between a minimum distance corresponding substantially to the depth of the partition end and a maximum distance corresponding to the depth of field of view;
• the invention also relates to a spatio-colorimetric measurement method of a three-dimensional object comprising the steps of: emitting at least one light radiation to illuminate the object to be analyzed, receiving the light rays reflected by the object on at least four detection means, and transfer the light information collected by the detection means to a processing unit.
• the light rays reflected by the object are detected by at least two sensing means-sensitive-light-waves of substantially identical wavelength ranges.
• the method comprises, beforehand, a calibration step of the detection means
• the processing unit determines, by iterative calculation, the relative position of a plurality of analysis points with respect to the detection head in order to take account of the position of these points with respect to the light source and to the means detection to adjust the colorimetric coordinates of the analyzed object; the processing unit determines, by stereoscopy, the distance of a plurality of analysis points with respect to the detection means;
• the processing unit determines the coordinates of the normal to the surface of the object, in a plurality of analysis points
• the iterative calculation of the depth is carried out between a minimum depth, corresponding to the distance between the detection means and the end of a partition tip, and a predetermined maximum depth;
• the iteration step is substantially equal to the size of the field corresponding to a pixel for the predetermined minimum depth.
• the measured value is thus substantially isotropic;
• the processing unit deviates from the analysis points whose intensity of the colorimetric values exceeds a predetermined value by calibration so that the errors due to the specular reflection are identified; the method comprises a step of calculating the colorimetric coordinates of a plurality of weighted analysis points according to the position of said analysis points;
• the colorimetric coordinates of each point are adjusted by bilinear interpolation so as to respect the linearity of the colorimetry of the analyzed object.
• FIGS. 2a and 2b schematic representations of a first embodiment of a detection head according to the invention comprising annular lighting means
• the device makes it possible to carry out a spatio-colorimetric measurement of a three-dimensional object 2, in one embodiment. occurrence of a tooth.
• any other three-dimensional object 2 low relief that is to say whose topology has no undercut, could also be the subject of such a spatio-colorimetric measurement.
• the measured three-dimensional object could be a painting, a piece produced in the industry, a ticket, etc.
• the device according to the invention preferably comprises a detection head 4 and a support case 6 connected to a processing unit 8 of the information coming from the detection head 4.
• the processing unit 8 is separated from the support housing 6 and connected thereto via communication means 10. This configuration makes it possible in particular to reduce the dimensions of the support housing 6 as well as the production costs of the device measurement. The device is thus compact so that it can be easily handled with one hand by an operator.
• the processing unit 8 could also be integrated into a more stable support 8 in order to improve the accuracy of the results and to measure larger objects 2.
• the digital data collected by the detection head 4 are transmitted, by means of communication means.
• the detection head 4 has dimensions adapted to the size of the three-dimensional object 2 measured so as to reduce the processing time of the information provided by the detection head 4 to the processing unit 8.
• FIGS. 2a and 2b are diagrammatic representations of a first embodiment of a detection head 4 according to the invention.
• the detection head 4 comprises central lighting means 14 and four optical detection means 16 arranged around and equidistant from the central lighting means 14.
• the annular illumination means 14 comprise light sources 14 a broad spectrum in the visible range. It would be conceivable to use more or fewer light sources 14a. Nevertheless, the experimental results have shown that from eight light sources 14a, the resolution at each point of analysis is relatively constant. The illumination provided by the means of i-é € lairage-44-annu ⁇ areas is ongoing and the power is likely to be adjusted to the needs of the measure.
• the annular illumination means 14 also advantageously comprise a frosted glass 14b, or holographic, located downstream of the light source 14a in order to improve the homogeneity of the illumination.
• the annular light source 14 could consist of a circular neon tube.
• the optical detection means 16 consist of an infrared filter 16a eliminating the infrared parasites to which are sensitive CMOS-type photonic sensors (presented below).
• the infrared filter 16a is a BG40 filter from SCOTT.
• the detection means 16 further comprise four filter elements 16b, 16c disposed behind the optical elements 16a and in the center of the annular illumination means 14.
• the elements of filtration 16b, 16c are lenses for both filtering and focusing the light rays from the object analyzed to the photonic sensors (presented below).
• optical axes of these four filter elements 16b, 16c are substantially parallel to each other and substantially in the same direction as the axis of propagation of the annular illumination means 14.
• the filter elements 16b, 16c may also have convergent optical axes to the same point, or to different points, or a composition of these different possibilities.
• a first pair of primary filtration elements 16b consists of a blue filtration lens, reference B440 at the company HOYA, and a red filtration lens, reference DG570 at the company SGHO-TTr-De-prefereneer this pair of filter elements is arranged symmetrically with respect to the central axis of the annular illumination means.
• the detection means 16 also comprise a pair of twin filtration elements 16c having a substantially identical bandwidth.
• these twin filter elements 16c are green lenses, for example G550 reference lenses at the company HOYA.
• These twin filtration elements 16c are advantageously arranged so as to form a symmetry of revolution about the central axis of the annular illumination means 14.
• a 16 ° photonic sensor subdivided into four quadrants respectively in correspondence with the four filtration elements
• 16b, 16c is arranged behind the filter elements 16b, 16c so as to receive the light rays propagated through these filtering elements
• This photonic sensor 16e is preferably a CMOS sensor.
• the combination of the twin filter elements 16c with the corresponding photonic sensor area 16e forms the twin detection means (16c, 16e).
• the combination of the primary filter elements 16b with the corresponding photonic sensor area 16e forms the primary detection means (16b, 16e).
• the detection head 4 consists of detection means 16 having four filter elements 16b, 16c arranged around central lighting means 14, preferably positioned behind a diffusing filter
• the detection means 16 have two primary filtration elements 16b, respectively of red and blue color, and two twin filtration elements 16c, of green color 16c.
• the two twin filtration elements 16c are interposed between the two primary filtration elements 16b so as to maintain a symmetry with respect to the axis of revolution of the detection head 4.
• the twin filtration elements 16c could also be arranged side by side.
• the detection head 4 comprises four independent and synchronized photonic sensors 16e, also arranged behind the filter elements 16b, 16c so as to receive the light rays propagated through these filter elements 16b, 16c.
• the detection head 4 is preferably capped with a partition tip 20 of predetermined depth to define a chamber in which the object analyzed is not disturbed by the external light.
• the depth of the partition tip 20 defines the minimum depth of observation. Indeed, the object 2 analyzed can not be located at a variable distance from the detection means 16 which corresponds to a predetermined tolerance distance forward or backward of the nominal distance of the bulkhead 20.
• This partitioning tip 20 has a depth of a few centimeters in the context of a portable measuring device or a few meters in the context of a device mounted on a support.
• the depth of the partitioning tip 20 is five times greater than the depth of the object 2 to be measured.
• the width and height of the object 2 analyzed are preferably about three times greater than the depth of the object to be measured.
• the device according to the invention can be maintained through the support housing 6 and actuated by the control circuit 9 of the device.
• the operator first performs a calibration of the measuring device by placing a white surface against the partition endpiece 20.
• the duration of the measurement is determined so that the maximum intensity of the or photonic sensors, does not exceed approximately 85% of the maximum admissible intensity.
• any specular effects will result in an intensity equal to the maximum allowable intensity and may therefore be detectable.
• the partitioning tip 20 of the measuring device according to the invention is then placed against the object 2 to be analyzed, so that the object is at least partially protected from the external light.
• the method according to the invention consists, in a second step, in performing at least one measurement, or scanning, non-invasive and of a very short duration. Indeed, this measurement is performed without contact and using lighting means 14 of perfect safety. On the other hand, the measurement time may be less than one-tenth of a second. During this second measurement, the light rays emanating from the illumination means 14 propagate towards the analyzed object 2 before being reflected towards the detection means 16.
• the twin detection means constituted by the twin filtration elements 16c and the corresponding matrix sensors 16e, make it possible, by stereoscopic calculation in the processing unit 8, to determine the spatial coordinates of the analyzed points of analysis.
• the twin detection means receive the light reflected on the object under the same spectral conditions.
• the values obtained by the twin detection means should be equal.
• the value of the luminous intensity reemitted by a point of the analyzed object can be expressed by the following relations:
• Lo 0 L Pc D and Lo ⁇ ⁇ Lp where cos (b G ) xd, 2G cos (b D ) xd, ID
• - Lo 0 represents the value of the light intensity retransmitted by an analysis point, determined from a right sensor
• - LOG the value of the luminous intensity re-emitted by an analysis point, determined from a left sensor
• - I_PD the light energy received by the pixel of the right sensor after diffuse reflection on the object
• - Lp G the light energy received by the pixel of the left sensor after diffuse reflection on the object
• the method according to the invention provides for iteratively calculating: - for each potential depth of a point of analysis between a minimum depth and a predetermined maximum depth, the depth for which the values of the luminous intensity (LOG, LOD) re-emitted by an analysis point and calculated from the twin detection means, are the closest.
• the minimum depth advantageously corresponds to the depth of the partitioning endpiece 20 while the maximum depth corresponds to the depth of the field of view.
• the iteration step is substantially equal to the size of the field corresponding to a pixel for the predetermined minimum depth.
• the processing unit 8 determines at this stage a pair of data corresponding to the depth of a plurality of analysis points and the light intensity re-emitted by said analysis points corresponding to the length range of the detection means. twins. The processing unit thereby deduces the coordinates (x, y, z) of each analysis point of the measured object. From these data, the processing unit 8 also determines the normal at each analysis point to be able to restore the color at this point of analysis. This operation is done by calculating the average plane passing through each point of analysis.
• the processing unit 8 finally determines, from the values of the luminous intensity collected by the primary and twin detection means, the colorimetric mapping of the analyzed object. This map is weighted according to the spatial position of the analysis points and in particular the distance of these points of analysis vis-à-vis the detection means 16 and the direction of the normal to the surface of the object in each of these points of analysis.
• the filter elements 16b, 16c could be composed of lenses combined with color filters.
• the device according to the invention could also be composed of four pairs of detection means 16 or more, with the aim of improving the quality of the results, in particular on a colorimetric level.
• CMOS photonic matrix sensors with CDD sensors or any other type of photonic sensor.

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• Physics & Mathematics (AREA)
• Spectroscopy & Molecular Physics (AREA)
• General Physics & Mathematics (AREA)
• Spectrometry And Color Measurement (AREA)
• Investigating Or Analysing Materials By Optical Means (AREA)

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• 2008
  • 2008-01-23 CA CA2712968A patent/CA2712968A1/fr not_active Abandoned
  • 2008-01-23 US US12/864,132 patent/US20120004884A1/en not_active Abandoned
  • 2008-01-23 CN CN2008801280233A patent/CN102084228A/zh active Pending
  • 2008-01-23 EP EP08761797A patent/EP2257778A1/fr not_active Withdrawn
  • 2008-01-23 KR KR1020107017994A patent/KR20100126302A/ko not_active Ceased
  • 2008-01-23 JP JP2010543536A patent/JP2011510315A/ja active Pending
  • 2008-01-23 WO PCT/FR2008/000081 patent/WO2009092868A1/fr not_active Ceased

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