Xenon colors answered (technical)
12-30-2003, 04:28 PM
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Xenon colors answered (technical)
Happened to have a Minolta CS100 color meter at home so I measured the spots from the headlamps on the wall a few feet from the car. Because of the short distance there was some variation over the Xe spot, because some parts of the arc are hotter than others. I think the measurements are a good average.
First off, the color does change pretty drastically in the first two minutes. The first measurement I took was about 5400K, and as the lamp warmed up the CCT dropped to 4100K (red arrow and dots), which isn't that blue, BTW. What is happening is the mercury is evaporating as the lamp heats up, and the 585nm line of the mercury makes the arc become more yellow. Straight Xenon would have a color temp of 6000K or so. I think the mercury and some halogen in the lamp work to clean the tungsten off the bulb surface. Just a guess.
For grins, I measured the high beam halogens. They have a CCT of 3900K, but are much greener than a 3900K blackbody. Lastly, I measured the PIAA H3 (I5455) fog lamps, and they are a good match to the Xenons when warmed up.
<img src="http://dlpoptics.com/CCTchartaudi.jpg">
First off, the color does change pretty drastically in the first two minutes. The first measurement I took was about 5400K, and as the lamp warmed up the CCT dropped to 4100K (red arrow and dots), which isn't that blue, BTW. What is happening is the mercury is evaporating as the lamp heats up, and the 585nm line of the mercury makes the arc become more yellow. Straight Xenon would have a color temp of 6000K or so. I think the mercury and some halogen in the lamp work to clean the tungsten off the bulb surface. Just a guess.
For grins, I measured the high beam halogens. They have a CCT of 3900K, but are much greener than a 3900K blackbody. Lastly, I measured the PIAA H3 (I5455) fog lamps, and they are a good match to the Xenons when warmed up.
<img src="http://dlpoptics.com/CCTchartaudi.jpg">
12-30-2003, 04:54 PM
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That is the "super white" PIAA, I see from this page....
<A HREF="http://shop.store.yahoo.com/rodi/xxxpiah3.html">PIAA bulbs</A> -- The "15455" is the "super white," billed as 3800K. The "super plasma" which I am using (by mistake) actually match the Xenon well, but are billed as 5000K. They don't seem terribly blue to me, though.
Can you describe the Y axis of your chart?
Thanks, this is very useful.
Can you describe the Y axis of your chart?
Thanks, this is very useful.
12-30-2003, 05:49 PM
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A brief explaination of x and y...
The cones in the eye have a blue-yellow, a green-magenta, and a cyan-red sensitivity. From experiments the sensitivity of the eye to light at various wavelengths can be reduced to three values, X, Y, and Z. A two-dimensional projection of this space is the x and y in the graph. Blue is about .145,.08, green about .30, .64, and red about .65, .35 in x and y. White is about .33, .33, meaning that X, Y, and Z are about the same.
See the link for more.<ul><li><a href="http://www.efg2.com/Lab/Graphics/Colors/Chromaticity.htm">explaination of XY color space</a></li></ul>
See the link for more.<ul><li><a href="http://www.efg2.com/Lab/Graphics/Colors/Chromaticity.htm">explaination of XY color space</a></li></ul>
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12-30-2003, 08:22 PM
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Lately, projector design. The DLP TV's are...
based on some work that I did, as is the DLP Cinema projector. Color science is one of the things you have to know at the system level.
If you get a chance to go to CES, stop by the TI booth.
If you get a chance to go to CES, stop by the TI booth.