Help in calculating chromaticity coordinates, please.

[pink lisa]

Dear All,

I was wondering if anyone could help me.

I am measuring the spectra of LEDs using an HR2000 Ocean Optics Spectrometer.

My problem is I don't know how to calculate the CIE Chromaticity colour co-ordinates from this. Does anyone have any advice how to do this in Labview? However, my main problem is I am not very good at programming so advice in not really very technical terms would be fabulous.

Thanks for reading this.

Love,

Lisa

xxx

[GerdW]

Hello lisa,

this may help you:
http://www.neuro.sfc.keio.ac.jp/~aly/polygon/info/color-space-faq.html

There you will find many color space conversions.

Btw. is it not enough to have your name "pink lisa" but to have pink text? 😉

[pink lisa]

Thanks GerdW, I will take a look at that now.

[ThomasD]

______________________________________________________________
Btw. is it not enough to have your name "pink lisa" but to have pink text? 😉
______________________________________________________________

And don´t  forget the pink rose!

[pink lisa]

So Cheeky! 😉

[TimM(AE)]

Hi Lisa

I don’t now anything about the hardware that you are using but I am guessing that you are reading in some RGB values which then need to be converted.

You said you don’t know much about programming I think you can do what you want fairly easy as long as you have the IMAQ Vision tool kit.

I have posted up a little example for converting RGB to CIE (XYZ) using “IMAQ RGBToColor2” VI which is in the colour utilities pallet which is part of the IMAQ vision package. There is lots of different conversion VIs if I have got the wrong one.

Hope this helps

Tim

NI UK AE

Quick note you can post on the Machine Vision forum which is stuff related to IMAQ Vision and measuring stuff using cameras etc

[Green Arthur]

Lisa

I have the same problem, but am using a Specbos 1201 Spectroradiometer.  It can calculate the colour co-ordinates independently, or it can give a spectrum measurement in Watts per squaremeter per namometer, but doesn't let you convert between the two.  I am trying to measure the light through a piece of glass, so I need to calibrate out the glass using it's transmission characteristic. 

So far this is what I have worked out:  The CIE publish the values of their colour curves, and you can integrate the values on these curves with the values from the spectrometer to get the X,Y co-ordinates.  They sell the values of the curves on disk, but there is a licence agreement, so it would appear that it is not legitimate to hand out free software to convert spectrum to XY, UV, U'V' or brightness measurements.

I am now looking at knocking up some code to do these things.  Please let me know if you have found anything that does this already.  I can't believe it hasn't been done on LabView already.

Stay pink, it's brilliant.

Arthur

[jeti]

Lisa,

first of all you need a calibrated spectrometer, a so called "spectroradiometer".
A simple spectrometer gives not realistic results due to the device function, which
is not linear versus the spectrum.
A work around is to calibrate the spectrometer you have against a
certified (NIST) calibration light source with known spectral emission
to get the transfer function of the spectrometer. Then you can convolute the measurement results
from your device with this found transmission function.
This resulting curve you have to convolute seperately with the CIE XYZ curves (eg. in 1 nm steps).
Now you have to normalize the Y convolution integral to Y=100. This Y normalisation factor has to be
used for the X convolution and Z convolution too.

To calculate the x,y coordinates follow this equations: x=X/(X+Y+Z)  and y=Y/(X+Y+Z).

To go more in background have a look at our website www.jeti.com/basics/
The CIE curves data you can free of charge download from www.cvrl.org the colour vision
database.

By the way: A simpler and more effective way is to use a ready made spectroradiometer like our specbos 1201,1301, 1401
which includes already the calibration set and gives directly all the photoradiometric values.
A comfortable software (Lab Windows CVI based) , Lab View Instruments and DLL's are in the scope of delivery.
Moreover this device can directly controlled via USB (virtual COMport) by SCPI commands like other measurement devices
(Multimeter, Oscilloscopes e.t.c.). 

[pink lisa]

Thanks for the advice everybody. It has come in useful.

Lisa

x

[은하철도]

hi!

It is calculating chroaticity coodinates VI.

It is wroten Labview7.1