EP1658479A1 - Device and method for evaluation of the shade of an object by spectrometry - Google Patents

Device and method for evaluation of the shade of an object by spectrometry

Info

Publication number
EP1658479A1
EP1658479A1 EP20040742473 EP04742473A EP1658479A1 EP 1658479 A1 EP1658479 A1 EP 1658479A1 EP 20040742473 EP20040742473 EP 20040742473 EP 04742473 A EP04742473 A EP 04742473A EP 1658479 A1 EP1658479 A1 EP 1658479A1
Authority
EP
Grant status
Application
Patent type
Prior art keywords
object
characterized
light
means
spectrometric
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP20040742473
Other languages
German (de)
French (fr)
Inventor
Jean-Pierre Tretout
Original Assignee
Jean-Pierre Tretout
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date

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Classifications

    • GPHYSICS
    • G01MEASURING; TESTING
    • G01JMEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRA-RED, VISIBLE OR ULTRA-VIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/46Measurement of colour; Colour measuring devices, e.g. colorimeters
    • G01J3/50Measurement of colour; Colour measuring devices, e.g. colorimeters using electric radiation detectors
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01JMEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRA-RED, VISIBLE OR ULTRA-VIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/46Measurement of colour; Colour measuring devices, e.g. colorimeters
    • G01J3/50Measurement of colour; Colour measuring devices, e.g. colorimeters using electric radiation detectors
    • G01J3/508Measurement of colour; Colour measuring devices, e.g. colorimeters using electric radiation detectors measuring the colour of teeth

Abstract

The invention relates to a device for the automatic determination of the shade of an object (10), comprising a light source, a light sensor, arranged such as to sample the light reflected or passed through the object (20, 30, 40) in a region of the object, and further comprising means for the determination of the wavelength of said light after reflection or passing through the object, said means providing a spectrometric recording corresponding to the sampling region. The above is characterised in that the means for analysis are provided to analyse a number of such spectrometric samples corresponding to different regions (20, 30, 40) of the object (10) and to identify an average spectrometric value from said set of spectrometric samples.

Description

"Device and method hue evaluation of an object spectroscopy"

The invention relates to the automatic determination of dyed with optical equipment provided with means for analyzing the received wavelength, commonly called spectrometers means.

Widely used for multiple applications, spectrometers are particularly known for the identification of materials, especially from the study of spectra formed by reflection on such matters.

A spectrometer used for the identification of a material hue lies also on the measurement of different wavelengths received after reflection or passage of the material.

already been proposed such a hue measurement and already in several areas, particularly in the dental field, primarily concerned by this application. Thus, spectrometry is now known as replacement of subjective judgment means the practitioner when it comes to determine the hue of a replacement material to build a tooth to be treated. Spectrometers proposed for this, typically include a light source and a light sensor monitoring means for analyzing the received wavelengths. Computer processing of the data produced is the product automatically set up on the tooth.

Such a process, in other applications requiring identification of shade is also suitable, even when it is not put in place a replacement then.

Thus, it is desirable that the data entry for color encountered is automated in many technical fields.

The present application relates specifically to the concern of determining a color consistent with that perceived by the human eye when the subject is examined with the naked eye. So when it comes to filling the cavity of a tooth, the concern of the practitioner is that the color of the material introduced is consistent with the general appearance of the tooth, as perceived by a person with naked eye.

Automatic methods for determining tooth shades proposed so far proved insufficient as to this concern.

Indeed, the colors indicated by the existing systems often prove not match the perception to the eye color of a tooth. The reasons, which are the cause of this drawback, mainly reside in the fact that the tooth is partially translucent and irregular in surface shape.

The invention proposes to address this concern, that is, to provide a device and an automatic evaluation method of the tint of an object when the determined hue truly reflects the hue initially perceived and the naked eye.

This object is achieved according to the invention thanks to an automatic device for determining the color of an object, comprising a light source disposed a light sensor so as to take on an area of ​​the object or reflected light having passed through the object, further comprising wavelength analysis means of this light after reflection or passing through the object, and comprising means for deriving a color from the light thus collected, characterized in that the analysis means are provided for analyzing a set of wavelengths collected in different areas of the object and identifying a same hue from this set of wavelengths.

Also provided in the invention a determination of an object hue method comprising the step of illuminating the object, the step of sampling the light after reflection or passing through the object, - step of analyzing wavelengths of light after reflection or passage, the step of deducing from this analysis a hue of the object, characterized in that it implements the step of taking light in different areas of the object, the step of analyzing a set of wavelengths collected in these areas, and then the step of identifying a same hue from the analysis of this entire lengths waves.

Other features, objects and advantages of the invention will become apparent from reading the detailed description that follows, with reference to the accompanying figures in which:

- Figure 1 shows a tooth being hue identification in accordance with a known method.

- Figure 2 shows a tooth being color identification according to a first variant of the invention.

- Figure 3 shows a tooth being hue identification in accordance with a second variant of the invention.

firstly be described with reference to Figure 1, the method exploited so far for the identification of the shade of a tooth prior to placement of a tinted replacement material thereon.

this method first Note that relies on the use of a small-sized spectrometer, suitable for use in the dental field by its maneuverability and its ability to be precisely placed.

This spectrometer is logically provided to collect light reflected by the tooth in a zone that can be termed "spot".

Thus in Figure 1, there is shown a tooth 10, 20 a small enough spot to represent that point light pick-up area. A selected power illumination is specifically placed on the tooth to produce the light spot 20, in which the spectrometer directs its sampling reflected light. The spot 20 thus form the light collection area for spectrometric analysis.

In the reflected light, a wavelength range is identified by the spectrometer, wavelength range that is considered to be specifically describing an optical color as perceived by the naked eye.

This color is then close by data processing means, of various shades of available alternatives, to identify the product with the most similar to that perceived hue.

Although spectrometers available have a very satisfactory precision in themselves, it turns out that the shifts occurring between the hue and thus identified as that of the tooth as seen with the naked eye, the result of a approach that is too sensitive to imperfections color and geometry of the object, here the tooth.

It turns out, in other words, the so identified hue is exactly that of the tooth to the point where the identification is carried out and this, although appearing representative in the eyes of the practitioner, is still the seat an unpredictable offset.

In Figure 2, there is shown, a similar tooth 10, a bright spot "point" 20, also similar to that of Figure 1. However, it was identified as part of the invention, that the differences in hue obtained by spectrometric measurements can be greatly reduced by considering a tooth as a surface having a progressive hue gradually on the surface of it, although this gradation is not visible to the naked eye. In seeking more to achieve a mathematical average this imagined color gradation, it comes at a particularly advantageous result.

According to this new approach identified specifically, Figure 2 illustrates a method according to the invention wherein multiple spectrometric samples are taken in a series of points distributed on the tooth. As a principle fix an uneven distribution of color perception on the tooth, it is proposed here averaging over a distribution Spectrometric readings on the surface of it.

This distribution proves correct inequality perception due to multiple parameters, not necessarily under a shade of inequality in itself, but rather inequality translucency and surface geometry inequality of the tooth.

In these inequalities, the hypothesis that the tooth surface is a color gradation object is a theoretical model for the implementation of the invention, rather than a reality actually perceived by the naked eye.

The following describe how the plurality of samples is preferably implemented, and the associated means and the preferential distribution to be implemented on the tooth.

The means used here consist of all, the spectrometer further illumination and optical statement, means for mechanically moving the pick-up area on a predetermined path. Thus, the spectrometer illumination is provided with a rail and a mechanical moving means on the rail along a rectilinear motion segment and predetermined length.

Preferably, the spectrometer provided with the rail moving means is also provided with means for patient vis-à-vis positioning, for adjusting the positioning relative to the tooth rail, and thus the displacement selected for the survey area 20 .

Thus, according to the illustration of Figure 2, the plurality of sampling points preferably consists of a segment 30 extending longitudinally on the tooth, that is to say, gradual removal of the gum and perpendicular to celle- this. Sampling points in this segment 20 can be chosen in varying numbers, ranging from a few sampling points to several thousand.

Such positioning of these points on the longitudinal axis of the tooth turns provide a particularly faithful shade of identification to that perceived by the naked eye.

Each sampling point corresponds to a statement of a range of wavelengths present at this point. In this range of wavelengths present at a point, these are shown with different powers, the most powerful wavelengths being considered best representing the color present.

The analysis means proposed herein take into account all the wavelength ranges taken at each sampling point, and, by average powers recorded for each wavelength at the various points, establish an average length range wave present on the tooth, midrange consisting in other words in a statement where each wavelength is considered to power the average power encountered on the various points of the tooth.

The strongest wavelengths in this range represent the average color of the tooth.

The color of the tooth can also be identified in a simple variant to achieve, by establishing an overall average of the wavelengths represented in the middle range, weighted wavelengths by their respective powers in this medium range.

However, according to a second variant illustrated in Figure 3, such a longitudinal scan (vertical) 30 is advantageously associated with a cross-scan (horizontal) 40 of the tooth, that is to say a substantially parallel scanning gum .

This transverse scan is preferably positioned at mid-height of the visible part of the tooth.

Also in this case, all statements spectrometric, that is to say those obtained by the vertical scan 30 and the cross-scan 40 are subjected to a mathematical average to determine an average range of wavelengths represented on the tooth.

In other words, the desired color is determined by analysis of the average range, for example by considering it as a classic statement spectrometric.

In a preferred variant, endows the device with a camera and video display means to display the object examined on a screen.

On this screen, one defers shades taken from each of the points of the object, so that the displayed representation door hues such as identified by the device.

The user then reviews the processing work of the device, including the distribution of shades before averaging them. The device is preferably provided with interactive means allowing the user to select a specific part of the displayed object and to establish the overall tint of the object from the Party. In other words, the device is provided with means to control the hue of analysis presented above, control means which define, under control of the user, the particular portion of the object to be taken into account in calculating the hue. The other parts of the object are, in other words, excluded from the calculation of hue. Thus, the user selects such a position of the object that it seems specifically representative of the overall tone of the latter. The invention is not limited to these preferred embodiments, but can also be implemented via a plurality of records, and subsequent averaging, the plurality of survey can be distributed differently on the tooth, and this without any scanning consideration.

The concern here satisfied, that faithfully recreate the perception of general color as seen with the naked eye, is also present in other types of applications just as concerned with the present invention.

Thus, the invention may generally be implemented to efficiently transcribe the impression in the eyes of an expert can evaluate a particular condition of a product.

Thus, it turns out that the implementation of a spectrometer and a multiplicity of readings distributed over a wide area of ​​an object is an advantage in the case of evaluating a color on fruit, which is desired to automatically assess the maturity from this color, or any perishable goods.

Another type of application is to evaluate the color of a work of art in order to assess their age or storage conditions.

Also advantageously used the invention to determine the color of an area of ​​a banknote to determine if it is authentic.

Claims

1. Apparatus for automatically determining the color of an object (10), comprising a light source, a light sensor arranged to be taken from a region of the object the light reflected or passed through the object (20, 30, 40), further comprising wavelength analysis means of this light after reflection or passing through the object, these means delivering a spectrometric statement corresponding to the sampling region, characterized in that the means analysis are provided for analyzing a set of such records spectrometric corresponding to different zones (20, 30, 40) of the object (10) and identifying means spectrometric measurement from this set of spectrometer readings.
2. Device according to Claim 1, characterized in that it comprises means provided for automatically moving the light pick-up area over a large area of ​​the surface of the object.
3. Device according to claim 1 or claim 2, characterized in that the device is arranged to collect the light in a plurality of points (20, 30, 40) on a surface having a relief.
4. Device according to any one of the preceding claims, characterized in that the apparatus further includes a camera and means for displaying an image of the object (10) as taken by the camera, as well as means for transferring the image on a series of hues taken respectively to said plurality of sampling points (20, 30, 40) at their corresponding location on the object (10) displayed on the screen.
5. Device according to claim 4, characterized in that it comprises means enabling a user to perform a spatial selection of the object represented on the screen, means being provided to translate this spatial selection in the form of a selection of sampling points from light samples taken on these specifically positioned points in this space selection, and to calculate the overall hue from light sampling performed on these points.
6. Device according to any one of the preceding claims, characterized in that it is intended for determining the shade of a tooth (10).
7. Device according to any one of the preceding claims, characterized in that it includes displacement means of a spectrometric sensor according to a sampling line (30, 40) extending over the object (10).
8. Device according to any one of the preceding claims, characterized in that it comprises means for using the mean spectrometric statement to define the hue of a material added thereafter to the object (10).
9. A method for determining color of an object (10), comprising the step of illuminating the object (10), the step of sampling the light after reflection or passing through the object, the step of analyzing wavelengths of light after reflection or passage, to establish a spectrometric record of a considered object zone (10), the step of deducing from this analysis a hue of the object, characterized in that it implements the step of taking light into different zones (20, 30, 40) of the object (10), the step of analyzing a set of wavelengths levied these different zones (20, 30, 40) for establishing a plurality of spectrometric readings corresponding to these areas, and then the step of identifying means spectrometric measurement from this set of spectrometer readings.
10. The method of claim 9, characterized in that it is applied to determining the shade of a tooth (10).
11. The method of claim 10, characterized in that the plurality of points described at least one segment (30) oriented longitudinally to the tooth (10), that is to say substantially perpendicular to the gum.
12. The method of claim 10 or claim 11, characterized in that at least a portion of the plurality of sampling points (20, 30, 40) describes a segment (40) substantially aligned with the gum, is -to say perpendicular to the main axis of the tooth (10).
13. A method according to any one of claims 9 to 12, characterized in that it comprises the step of moving a spectrometric sensor according to a sampling line (30, 40) extending over the object (10) .
14. A method according to any one of claims 9 to 13, characterized in that it comprises the step of using the mean spectrometric statement to define the hue of a material added thereafter to the object (10) .
EP20040742473 2003-04-09 2004-04-09 Device and method for evaluation of the shade of an object by spectrometry Pending EP1658479A1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
FR0304386A FR2853727B1 (en) 2003-04-09 2003-04-09 Device and method of hue evaluation of an object by spectrometry
PCT/FR2004/000888 WO2004092695A1 (en) 2003-04-09 2004-04-09 Device and method for evaluation of the shade of an object by spectrometry

Publications (1)

Publication Number Publication Date
EP1658479A1 true true EP1658479A1 (en) 2006-05-24

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP20040742473 Pending EP1658479A1 (en) 2003-04-09 2004-04-09 Device and method for evaluation of the shade of an object by spectrometry

Country Status (4)

Country Link
US (1) US20070275343A1 (en)
EP (1) EP1658479A1 (en)
FR (1) FR2853727B1 (en)
WO (1) WO2004092695A1 (en)

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2637368B1 (en) * 1988-09-09 1990-12-07 Bertin & Cie A method of determining the color of an object, in particular a dental prosthesis
US5766006A (en) * 1995-06-26 1998-06-16 Murljacic; Maryann Lehmann Tooth shade analyzer system and methods
US6249348B1 (en) * 1998-11-23 2001-06-19 Lj Laboratories, L.L.C. Integrated spectrometer assembly and methods

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO2004092695A1 *

Also Published As

Publication number Publication date Type
US20070275343A1 (en) 2007-11-29 application
FR2853727B1 (en) 2006-05-05 grant
WO2004092695A1 (en) 2004-10-28 application
FR2853727A1 (en) 2004-10-15 application

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