EP2589225A1 - Procédé et dispositif d'imagerie multispectrale au moyen d'un capteur rgb numérique - Google Patents

Procédé et dispositif d'imagerie multispectrale au moyen d'un capteur rgb numérique

Info

Publication number
EP2589225A1
EP2589225A1 EP11710051.1A EP11710051A EP2589225A1 EP 2589225 A1 EP2589225 A1 EP 2589225A1 EP 11710051 A EP11710051 A EP 11710051A EP 2589225 A1 EP2589225 A1 EP 2589225A1
Authority
EP
European Patent Office
Prior art keywords
spectral
bands
images
pixel
image
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.)
Withdrawn
Application number
EP11710051.1A
Other languages
German (de)
English (en)
Inventor
Janis Spigulis
Dainis Jakovels
Uldis Rubins
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Latvijas Universitate
Original Assignee
Latvijas Universitate
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
Application filed by Latvijas Universitate filed Critical Latvijas Universitate
Publication of EP2589225A1 publication Critical patent/EP2589225A1/fr
Withdrawn legal-status Critical Current

Links

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
    • G01J3/28—Investigating the spectrum
    • G01J3/2823—Imaging spectrometer
    • 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
    • G01J3/462—Computing operations in or between colour spaces; Colour management systems

Definitions

  • Invention relates to methods of digital colour image processing, in particular - to selection of images corresponding to more than three different spectral bands from a single-shot RGB data set.
  • Digital RGB sensors comprise integrated three colour (blue, green and red) spectral filters; they also can be used for multi-spectral imaging in various combinations with external spectral filters (US 7612822 B2, US 2009290124 Al , JP 2008136251 A).
  • Another way of getting multi-spectral images is sequential illumination of the object by several light sources, each emitting at different spectral region (e.g. LEDs of different colours - WO 2008093988 Al) and taking an image at each spectral band of the illumination.
  • the mentioned methods are useful, but their drawback is the necessity to take several consecutive images of the same object at different spectral bands.
  • the process is time- consuming.
  • the object properties can change during this process, e.g.
  • CCD or CMOS http:/ broadcastengineering.com/hdtv/ccd-cmos/) is transformed into colour format by determining first the numerical values Rj, G; un B; (i - the pixel number) of signals detected at this particular pixel in the red (R), green (G) and blue (B) spectral bands, and then adjusting for each pixel the colour that corresponds to the specific RiGjBj combination.
  • Spectral sensitivities of the R-, G-, and B-channels are determined by absorption properties of the filtering coatings and of the photo-detector material, e.g. silicon.
  • the specific spectral sensitivity curves of the three channels one can find in specifications of serially produced RGB sensors; they can also be measured experimentally.
  • Goal of this invention is to increase efficiency of multi-spectral imaging by increasing the number of images extracted from a single-shot RGB colour image data set and related to different spectral bands.
  • the method is characterized in that: (i) the discrimination level of the RGB output signals is variable instead of being fixed. It opens possibility to select more than the six known spectral intervals (additionally to the R-, G-, and B-bands), so increasing the number of multi- spectral images extracted from a single-shot colour image data set; (ii) the spectral selection is additionally being performed by using the crossing points of two spectral sensitivity curves (B-G, G-R or B-R) that correspond to fixed wavelengths. New spectral intervals are selected in the vicinity of these crossing points, with the conditions:
  • Fig. 1 presents curves of the R-, G- and B-channel relative spectral sensitivities for a typical RGB sensor, and the way how a variable signal discrimination level S is used for additional selection of the spectral images;
  • Fig. 2 illustrates how the crossing points of the curves representing relative spectral sensitivities of the R-, G- and B-channels are being applied for additional selection of the spectral images
  • Fig. 3 shows the set-up scheme of the proposed device for obtaining of multi-spectral images.
  • Fig. 1 The essence of the method (i) is being illustrated in Fig. 1.
  • the R-, G- and B-channel relative spectral sensitivity curves provided by manufacturer or measured experimentally, are exploited, and their amplitudes are normalized so that the highest value of the registered signals does not exceed the maximum output signal of any channel, e.g. the number 255 in 8-bit system.
  • the objective diaphragm or illumination intensity is adjusted so that the sensor operates linearly, i.e. the numerical values of the R;, Gj and B, signals are proportional to the intensity of the detected Optical signals (for instance, in the range between 0 and 255).
  • the situation (a) means that the spectral range of radiation detected by the i-pixel is in the region where two spectral sensitivity curves are overlapping - see Fig. l .
  • simultaneous registration of some B; and Gj values at the lowest discrimination level So means that the spectral range of incident radiation lies between ⁇ and ⁇ 14 (the wavelength corresponding to the points 6 and 14).
  • narrower spectral intervals can be specified - either ⁇ 6 ... ⁇ (if Bj > Gj), or ⁇ ... ⁇ 14 (if B; ⁇ Gi).
  • the spectral interval of incident radiation in this case is even narrower, between g and ⁇ 2 - more specifically, either Xg ... ⁇ (if Bj > Gj) or ⁇ ... ⁇ 12 (if Bj ⁇ Gj).
  • simultaneous registration of two values R; and Gj at discrimination level Si indicates to some other spectral interval of the incident radiation, in particular ⁇ 17 ... ⁇ 18 (if R; ⁇ Gj) or ⁇ ]8 ... ⁇ 9 (if Ri > Gj), and so on.
  • the registered spectral interval may correspond to some specific regions of the B, G or R sensitivity curves - ⁇ 4 ... ⁇ 10 (for B-channel at S 3 ), ⁇ ... ⁇ ] 6 (for G-channel at S 3 ), or ⁇ 8 ... ⁇ 21 (for R-channel at S 2 ).
  • the registered spectral interval narrows - for instance, at level S 4 only radiation of spectral band ⁇ 5 ... ⁇ 7 can be registered in the B-channel, and only the interval ⁇ .. ⁇ ⁇ 5 can be registered in the G-channel.
  • the discrimination level reaches the peak value of the B-, G- or R-band
  • appearance of signal in this particular band means that monochromatic radiation of wavelength that corresponds to the band peak wavelength has been recorded in the respective pixel.
  • registration of signal only at one of the three colour bands at lower discrimination levels leads to conclusion that the registered spectral interval is out of the overlapping zones of any two bands.
  • the signal recorded only in the B-channel at the discrimination level Si indicates to the spectral interval ⁇ 2 ... ⁇ 8 , while that exceptionally in the G-channel - to the interval ⁇ 3 ... ⁇ 7 and that exceptionally in the R-channel - to the interval ⁇ 9 ... ⁇ 22 .
  • the proposed solution that the discrimination level of RGB output signals is flexibly variable instead of being fixed is opening more options to select different specific spectral intervals for the needs of multi-spectral imaging.
  • the essence of method (ii) is being illustrated in Fig. 2.
  • the spectral interval ⁇ 3 ... ⁇ b can be extracted in the vicinity of the B-G crossing point, the interval ⁇ ⁇ ... ⁇ ⁇ - in the vicinity of the G-R crossing point, and the interval ⁇ ⁇ ... ⁇ ⁇ - in the vicinity of the B-R crossing point.
  • the spectral intervals can be narrowed or expanded by the respective decrease or increase of the a, b and c values.
  • the set-up scheme of the device for implementation of one or both of the above-mentioned methods is illustrated in Fig.3.
  • the device comprises:
  • a multi-spectral light source e.g. a set of light emitting diodes (LEDs) and/or laser diodes (LDs) that illuminates the object to be imaged (C), e.g. skin surface
  • an objective-supplied digital RGB sensor D
  • D that converts the object image into digital format by providing a specific set of the Rj, Gj and Bj values to each pixel of the image, and stores the whole RGB data set in the storage device (E)
  • a converter (F) that converts the data of the RGB set into a set of spectral intensities accordingly to the selected discrimination level which is determined by the discriminator (H);
  • an image selector (I) that selects a number of spectral images from the RGB data set accordingly to the chosen spectral intervals and performs multi- spectral analysis by appropriate software
  • an output device e.g. monitor of PC, that collects and displays the obtained multi-spectral imaging information.

Landscapes

  • Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Mathematical Physics (AREA)
  • Theoretical Computer Science (AREA)
  • Color Television Image Signal Generators (AREA)
  • Spectrometry And Color Measurement (AREA)

Abstract

L'invention porte sur des procédés de traitement d'image couleur numérique, en particulier sur la sélection d'images correspondant à plus de trois bandes spectrales différentes à partir d'un seul ensemble de données RGB. Dans le procédé d'imagerie multispectrale proposé, l'objet est éclairé simultanément dans plusieurs bandes spectrales, et les valeurs de signaux Ri, Gi et Bi détectés au niveau de chaque pixel i de l'image sont identifiées. Elles sont en outre comparées l'une à l'autre et à un niveau de discrimination de signal S déterminé de manière externe qui permet d'enregistrer seulement une ou deux des bandes R, G et/ou B dans la plage de sensibilité spectrale du capteur. Pour augmenter le nombre d'images spectrales disponibles, les valeurs S sont continûment variables jusqu'à la plus haute de toutes les valeurs de signal possibles de la bande R, G ou B, à condition qu'une réponse optique linéaire du capteur RGB soit assurée. Selon la valeur S, deux situations sont analysées - si les signaux de deux bandes de couleur sont enregistrés simultanément (c'est-à-dire B et G, G et R ou B et R), ou si les signaux sont enregistrés au niveau d'une seule bande de couleur - et, après analyse logique, l'intervalle spectral du rayonnement enregistré par pixel est identifié. Chaque image spectrale est ensuite formée à partir des pixels ou des groupes de pixels qui correspondent à une plage spectrale sélectionnée particulière. Un dispositif d'imagerie multispectrale qui met en œuvre ce procédé comprend une source de lumière multispectrale, un capteur RGB numérique équipé d'un objectif, un dispositif de stockage d'ensemble de données RGB, un convertisseur pour convertir les données RGB en un ensemble d'intensités spectrales conformément au niveau de discrimination de signal sélectionné, un sélecteur d'images pour sélectionner les images relatives à chaque bande spectrale particulière, et le dispositif de sortie, par exemple un moniteur d'ordinateur personnel.
EP11710051.1A 2010-06-29 2011-03-07 Procédé et dispositif d'imagerie multispectrale au moyen d'un capteur rgb numérique Withdrawn EP2589225A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
LVP-10-98A LV14207B (lv) 2010-06-29 2010-06-29 Metode un ierīce multispektrālu attēlu iegūšanai ar digitālo RGB sensoru
PCT/LV2011/000003 WO2012002787A1 (fr) 2010-06-29 2011-03-07 Procédé et dispositif d'imagerie multispectrale au moyen d'un capteur rgb numérique

Publications (1)

Publication Number Publication Date
EP2589225A1 true EP2589225A1 (fr) 2013-05-08

Family

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Family Applications (1)

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EP11710051.1A Withdrawn EP2589225A1 (fr) 2010-06-29 2011-03-07 Procédé et dispositif d'imagerie multispectrale au moyen d'un capteur rgb numérique

Country Status (3)

Country Link
EP (1) EP2589225A1 (fr)
LV (1) LV14207B (fr)
WO (1) WO2012002787A1 (fr)

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2013135311A1 (fr) 2012-03-13 2013-09-19 Latvijas Universitate Procédé et dispositif permettant de former des images de la réflectance spectrale à plusieurs bandes de longueurs d'onde
US9593982B2 (en) 2012-05-21 2017-03-14 Digimarc Corporation Sensor-synchronized spectrally-structured-light imaging
US9060113B2 (en) 2012-05-21 2015-06-16 Digimarc Corporation Sensor-synchronized spectrally-structured-light imaging
US9066021B2 (en) * 2012-10-18 2015-06-23 Ortho-Clinical Diagnostics, Inc. Full resolution color imaging of an object
US9621760B2 (en) 2013-06-07 2017-04-11 Digimarc Corporation Information coding and decoding in spectral differences
CN111982837A (zh) * 2020-08-27 2020-11-24 中国气象科学研究院 一种植被生态参数遥感估算模型的转换方法
DE102021118559A1 (de) * 2021-07-19 2023-01-19 Senorics Gmbh Verfahren und System zur Analyse einer Probe anhand von Daten

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Publication number Priority date Publication date Assignee Title
JP4633129B2 (ja) 2003-11-11 2011-02-16 オリンパス株式会社 マルチスペクトル画像撮影装置
CN1875638A (zh) * 2003-11-11 2006-12-06 奥林巴斯株式会社 多谱图像捕捉装置
US7855786B2 (en) * 2006-01-09 2010-12-21 Bae Systems Spectral Solutions Llc Single camera multi-spectral imager
JP2010517460A (ja) 2007-01-29 2010-05-20 ジョンイル パク マルチスペクトル映像取得方法およびその装置
US7670001B2 (en) 2007-04-25 2010-03-02 Richard Spaide Reflectance measurement of macular pigment using multispectral imaging

Non-Patent Citations (1)

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Title
See references of WO2012002787A1 *

Also Published As

Publication number Publication date
LV14207B (lv) 2010-11-20
WO2012002787A1 (fr) 2012-01-05
LV14207A (lv) 2010-09-20

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