Color Imaging Lab Research Interests 2010

Departamento de Departamento de ÓÓptica, Facultad de Ciencias, ptica, Facultad de Ciencias, Universidad de Granada, 18071Universidad de Granada, 18071--Granada (SPAIN)Granada (SPAIN)

Colour Imaging Lab

www.ugr.es/local/colorimg

Research interests, 9th April 2010

Colour Imaging LabUniversidad de Granada

www.ugr.es/~colorimg

Javier Romero Eva M. Valero

Clara Plata

Javier

Hernández-Andrés

Permanent staff:

Ph.D. students

Raul Luzón

Juan Luis

Nieves

Juan Ojeda

Chromatic

frequencies - SMSF

Colour

discrimination

Chromatic contrast

sensitivity

Colour vision

Optics correlation

Education in optics



Colour constancy

Color and spectral

characterization

Temporal changes

Artificial illuminants

Color invariants

Objects under

natural light

IlluminantsReflectances

Colour images

Multispectral

images

Identification and

reconstruction

3D objects Optimal sensors

Atmospheric optics

Imaging devices

Calibration

Noise estimation

Multispectral

imaging

Spectral estimation

algorithms

Colour and Spectral Imaging

Spectral information recovery from RGB responses

● Our approach: camera digital counts calculation (simulated

RGB data, with or without added color filters)

700

400

( ) ( ) ( )i ir S T Q

λλ λ λ

=

= ∑

+

● Multispectral image capture

problem

� Recovering spectral information about objects and illuminants

simultaneously with an RGB camera.

� Spectral-imaging learning-based algorithm that directly relates

camera sensor outputs and illuminant spectra.

Color constancy and illuminant estimation

0 5 10 15 20 250

1

2

3

4

5

6x 10

4

RGB error

GFC= 0.9771RMSE= 0.0274Color diff.= 1.5AE= 12.2

400 450 500 550 600 650 7000

0.05

0.1

0.15

0.2

0.25

0.3

0.35

Wavelength (nm)R

elat

ive

units

… and on surface relief.

Reflected light from objects depends on reflectance (albedo) and

illumination…

RGB cameras to recover normals, albedoand spectral information

Spectral image acquisition Photometric- stereo+

400 450 500 550 600 650 700

0.2

0.25

0.3

0.35

0.4

0.45

0.5

Wavelenght (nm) N

RGB cameras to recover normals, albedoand spectral information

•Image rendering

Natural illumination

380 400 450 500 550 600 650 700 750 780-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

long de onda (nm )

V 1V 2V 3V 4V 5

daylight

Daylight and skylight spectra have complex and spiky spectral

profiles, with spatially and temporally variable absorption bands.

Low dimension

representation

models: PCA,

ICA, NNMF, …

Multispectral system for skylight illumination

�Multispectral system: Skylight spectral information at each

pixel of the image

� Skylight spectra: most basic feature in atmospheric optics: to

be used for estimating, for example, the Aerosol Optical Depth

(AOD), the Angström Alpha parameter (α) and the Cloud

Optical Depth (COD).

400 500 600 7000.000

0.005

0.010

0.015

0.020

0.025

0.030

spec

tral

rad

ianc

e (W

/m2 nm

str)

wavelength (nm)

Illuminant invariants

�Color-invariant descriptors:

Analysis of illuminant invariants in color imaging.



Since 2001, we published...

International ISI journal papers: 31• Journal of the Optical Society of America A• Applied Optics• Vision Research• Color Research and Applications• Journal of the Imaging Science and Technology• American Journal of Physics• Optical Review• Displays• J. Math. Imaging and Vision • PNAS (Proceedings of the National Academy of Sciences)

Proceedings in International meetings: 34

I+D+I Proyects and contracts: 7

4 from the Spanish Ministry of Science and Innovation

1 from the Junta de Andalucía Excellence projects

2 from private companies (Robotiker-Tecnalia; Chromasens)



International Conferences

10th Congress of the International Colour Association (AIC’05)

419 papers (208 oral + 211 posters) and 538

participants, 36 sessions, 24 invited speakers

Colour vision and ageing, Applied colorimetry, Colour physics, Colour vision,

Colour vision with natural images, Colour education, Multispectral colour

science, Environmental colour design, Photoreceptors and colour vision

mechanisms, Colour appearance, Colour emotion, Camera and displays

characterization, Evaluation of image quality, Colour preference, Gamut

mapping, Computational colour constancy, Colour in architecture, Art and

colour, Colour in computer vision, Colour, culture and design, Colour

differences



Instruments:Liquid Cristal Tunable Filters: VariSpec VIS from CRi (400-720 nm)

Narrow band filters and wide band filters

Monochrome cameras: Retiga SRV 1394 cooled.

RGB cameras: Retiga Q1300C

Retiga EXI Fast cooled

ProgRes C14 cooled



Instruments:

Scanner 3 D (del Centro de Instrumentación Científica)

Hyperspectral Imaging based on Volume Bragg Gratings

(PhotonEtc, 400-1000 nm, FOV: 15°x6°)

Color samples: Color Checker, Color Checker DC,

Munsell, NCS, muestras propias con textura y otros.



Instruments:

Spectroradiometers:

• SpectraScan PR650 Photoresearch (380-780 nm)

• LI-COR 1800 (300-1100 nm)

• GER-2600 from SpectraVista (350-2500 nm)

• AvaSpec 2048 SPU from Avantes (360-860 nm)

Other instruments (goniocolorimeters, spectrophotometers, ...)



...Teaching activities:

Primera ventana a la Ciencia “Lo que el ojo no ve” en la 4ª fase del

Parque de las Ciencias.

Desde Noviembre de 2008 a Agosto de 2009

Optics and Photonics News, May 2009

Yu Hu (China)

Summer internships 2009

Natalia Lybova(Rusia)

Sweet Khisa(Bangladesh)

Pierre-Alexandre Jay (France)

Yu Hu (China)With MULTISCAN

Talha Ahmed (Pakistan)

Master thesis students in Granada

January-June 2010

The EMJD VISOR (Erasmus Mundus Joint Doctorate in VISion, Optics and Robotics)

UdGUdG

HWHW

UGRUGR

UBUB

UJMUJM

GUCGUC

UJOUJO

� To foster the excellence in theoretical and applied research in the field computer vision, optics, colour

science and robotics.

The EMJD VISOR (Erasmus Mundus Joint Doctorate in VISion, Optics and Robotics)

Color Imaging Lab Research Interests 2010

Technology

colour imaging labuniversidad

colour physics

colour education

colour preference

colour appearance

colour emotion

colour differences

colour imaging lab universidad