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
  • G01J3/46—Measurement of colour; Colour measuring devices, e.g. colorimeters
  • G01J3/50—Measurement of colour; Colour measuring devices, e.g. colorimeters using electric radiation detectors
• • 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
  • G01J3/508—Measurement of colour; Colour measuring devices, e.g. colorimeters using electric radiation detectors measuring the colour of teeth

Definitions

• the invention relates to the automatic determination of shades using optical equipment provided with means for analyzing the received wavelengths, means commonly called spectrometers.
• spectrometers are particularly known for the identification of materials, in particular from the study of spectra formed by reflection on such a material.
• a spectrometer used for identifying a material shade also resides in the measurement of the different wavelengths received after reflection or through the material.
• spectrometry is known today as a means of replacing the practitioner's subjective judgment when it comes to determining the shade of a replacement material to be placed on a tooth to be treated.
• the spectrometers proposed for this typically include a light source and a light sensor followed by means of analysis of the wavelengths received. Computer processing of the data produced automatically designates the product to be placed on the tooth.
• the present application relates more specifically to the concern of determining a shade which conforms to that perceived by the human eye when the object is examined with the naked eye.
• the practitioner's concern is that the shade of the material introduced conforms to the general appearance of the tooth, as it is perceived by a person with naked eye.
• the invention proposes to respond to this concern, that is to say to propose a device and a method for automatic evaluation of the tint of an object where the determined tint truly reflects the tint perceived initially and at naked eye.
• an automatic device for determining the color of an object comprising a light source, a light sensor arranged so as to pick up from an area of the object the light reflected or having passed through the object, further comprising means of wavelength analysis on this light after reflection or crossing of the object, and comprising means for deducing a tint from the light thus sampled, characterized in that the analysis means are provided for analyzing a set of wavelengths sampled from different areas of the object and identifying the same shade from this set of wavelengths.
• the invention also proposes a method for determining the shade of an object, comprising the step consisting in illuminating the object, the step consisting in taking the light after reflection or crossing of the object, - the step consisting in analyzing wavelengths of light after reflection or crossing, the step consisting in deducing from this analysis a tint of the object, characterized in that the step consisting in taking the light is implemented in different areas of the object, the step of analyze a set of wavelengths taken from these different zones, then the step consisting of identifying the same shade from the analysis of this set of wavelengths.
• FIG. 1 shows a tooth being identified in shade according to a known method.
• FIG. 2 shows a tooth being identified in shade according to a first variant of the invention.
• FIG. 3 shows a tooth being identified in shade according to a second variant of the invention.
• this method is based on the use of a small spectrometer, suitable for use in the dental field by its maneuverability and its ability to be precisely placed.
• This spectrometer is logically designed to collect light reflected by the tooth in an area that can be described as "point”.
• FIG. 1 there is shown, on a tooth 10, a spot 20 of sufficiently small size to represent this point light sampling area.
• a chosen power illumination is specifically placed on the tooth to produce this light spot 20, within which the spectrometer takes its reflected light sample.
• the spot 20 therefore forms the light sampling zone for the spectrometric analysis.
• a wavelength range is identified by the spectrometer, a wavelength range which is considered to specifically qualify an optical color as perceived with the naked eye.
• This color is then compared, by data processing means, to different shades of replacement products to disposal, in order to identify the product having the shade closest to that perceived.
• FIG. 2 illustrates a method according to the invention, in which multiple spectrometric samples are taken, at a series of points distributed over the tooth.
• an averaging is proposed here on a distribution of spectrometric readings on the surface thereof.
• This distribution turns out to correct an inequality of perception due to multiple parameters, not necessarily pertaining to an inequality of shade proper, but rather of inequalities of translucency and inequalities of surface geometry of the tooth.
• the hypothesis according to which the tooth is an object with gradation of surface color is a theoretical modeling. allowing the implementation of the invention, more than a reality actually perceived with the naked eye.
• the means implemented here firstly consist, in addition to the illumination spectrometer and optical reading, of means for mechanical displacement of the sampling zone over a predefined path.
• the illumination spectrometer is provided with a rail and a mechanical displacement means on this rail along a segment of rectilinear displacement and of predetermined length.
• the spectrometer equipped with these means of movement on the rail is also provided with positioning means with respect to the patient, making it possible to adjust the positioning of the rail relative to the tooth, and thus the movement chosen for the survey area 20 .
• the plurality of sampling points preferably consists of a segment 30 extending longitudinally on the tooth, that is to say in progressive distance from the gum and perpendicular to it. this.
• the sampling points on this segment 20 can be chosen in variable number, which can range from a few sampling points to several thousand.
• Each sampling point corresponds to a reading of a range of wavelengths present at this point.
• these are represented with different powers, the most powerful wavelengths being considered to best represent the color present.
• the analysis means proposed here take account of all the ranges of wavelengths recorded at each sampling point, and, on average, the powers recorded for each wavelength at the different points, establish an average range of the wavelengths present on the tooth, average range consisting in other words in a survey where each wavelength considered has for power the average power encountered on the different points of the tooth.
• the strongest wavelengths in this medium range represent the color of the tooth.
• the color of the tooth can moreover be identified, in a variant that is simple to produce, by establishing an overall average of the wavelengths represented in the average range, wavelengths weighted by their respective powers in this average range.
• such a longitudinal (vertical) scan 30 is advantageously supplemented by a transverse (horizontal) scan 40 on the tooth, that is to say a scan substantially parallel to the gum tissue. .
• This transverse sweep is preferably placed halfway up the visible part of the tooth.
• all the spectrometric readings that is to say those obtained by the vertical scanning 30 and by the transverse scanning 40 are subjected to a mathematical average in order to determine a mean range of the wavelengths represented. on the tooth.
• the desired color is determined by analysis of this average range, for example by considering it as a conventional spectrometric survey.
• the device is equipped with a camera and video display means so as to display the object examined on a screen.
• the user thus examines the processing work carried out by the device, and in particular the distribution of the shades before averaging of them.
• the device is preferably provided with interactive means allowing the user to select a specific part of the object thus displayed, in order to establish the overall shade of the object from the part considered.
• the device is provided with means for controlling the previously exposed shade analysis, control means which define, under the control of the user, the particular portion of the object which must be taken into account in the shade calculation.
• the other parts of the object are, in other words, excluded from the shade calculation.
• the user selects for example a position of the object which seems to him specifically representative of the overall shade of the latter.
• the invention is not limited to these two preferred embodiments, but can also be implemented by means of a plurality of readings, and subsequent averaging, the plurality of readings being able to be distributed differently over the tooth, and this without any consideration of sweeping.
• the invention can more generally be implemented to effectively transcribe the impression in the eyes of an expert capable of evaluating a particular condition of a product.
• Another type of application is to assess the color of a work of art in order to assess its age or condition of conservation.
• the invention is also advantageously used to determine the tint of an area of a banknote, in order to determine whether it is authentic.

Landscapes

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

Applications Claiming Priority (2)

Publications (1)

Family

ID=33041730

Family Applications (1)

Country Status (4)

Citations (4)

Family Cites Families (4)

• 2003
  • 2003-04-09 FR FR0304386A patent/FR2853727B1/fr not_active Expired - Fee Related
• 2004
  • 2004-04-09 US US10/552,845 patent/US20070275343A1/en not_active Abandoned
  • 2004-04-09 EP EP04742473A patent/EP1658479A1/de not_active Withdrawn
  • 2004-04-09 WO PCT/FR2004/000888 patent/WO2004092695A1/fr active Application Filing

Patent Citations (4)

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events