1. Color adjustment for LED
projection system
Color, Imaging and Illumination Center
Graduate Institute of Engineering
National Taiwan University of Science and
Technology 1
2. Motivation
Color mixing can create a rich color changes.
LED projection system is able to show the
correct brightness and color.
Goals
Calibration, characterization, conversion.
Analysis spectral, brightness and color.
LED as a light source to be considered in the
CRI (Color rendering) and the relationship
between surface and color of projection.
Whitewashed walls
2
3. Experimental design
Set up Experiments
• Projection system • Brightness stability time.
• Projection angle fixed at 15 • Spectral radiance distribution.
degrees elevation. • Primary transform matrix &
• 40cm from the surface to be inverse.
projected. • Electro-optical transfer
• Projection surface function.
• Assuming homogeneity • Find out D65.
refection of different • Analysis color differences.
measuring points.
• Range 30cm to 180cm on
the ground range.
3
4. Warm up & Spectral radiance
distribution
200
Start to stabilize about 50 minutes
Tristimulus Values(cd/m^2)
195
190
185
Y(white)
180
175
170
0 25 50 75 100
Time (minutes)
0.02
0.018
Monochromatic spectrum in full compliance
0.016
with the overlay of white light spectrum.
Radiance(W/m^2*sr)
0.014
0.012
white
0.01
red
0.008
green
0.006
blue
0.004
0.002
0
380 405 430 455 480 505 530 555 580 605 630 655 680 705 730 755 780
Wavelength (nm) 4
5. Primary transform matrix & inverse
Electro-optical transfer function
Digital count from 0 to 255 in increments of 8.Thus 33
levels of emission were measured for each of the three
channels. A total of 99 samples.
Forward model
1.0
0.8
Releative Intensity
0.6
Red
Green
Backward model 0.4
Blue
0.2
0.0
0 32 64 96 128 160 192 224 256
Code Value
5
6. Find out D65
1.0
0.8
0.6
color
0.4
gamut
0.2
0.0
0.0 0.2 0.4 0.6 0.8 1.0
D65 WHITE RED GREEN BLUE
x 0.3125 0.2544 0.6963 0.1916 0.1274
y 0.3300 0.2240 0.3032 0.7088 0.0768
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9. Discussion
Color difference becomes large, and found that
the brightness value(Y) is the greatest impact.
Especially, the greater of difference in white .
We found the tristimulus values f D65 is even
o
larger than the original, confirmed that bright
light in the case of output, resulting in increased
chromatic aberration.
Summary
Analysis spectral and Uniformity.
Define the D65 .
Verify the color difference.
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