NNERS 
as always 
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The tests 
| exposure 
film type, 
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formance 
tests were 
the scans, 
Klaus J. Neumann 
  
2 LINEARITY AND INFLUENCE OF INTEGRATION TIME, COLOR BALANCE 
The sensor is an RGB tri-linear CCD sensor from Kodak with the type designation KLI-10203. Due to the design of the 
objective lens, only 5632 of the 10200 active pixels are used per color channel. The pixels have a physical size of 7um 
x 7 um. The optical system is of the 1:1 mirror optics type. This provides scan swaths with a nominal width of 39424 
um. The software permits direct setting of the integration time in steps of 0.1 ms. The integration time is adjustable 
within a range from 0.1 ms to 25.5 ms. All the tests were conducted without a lookup table, i.e. a 1:1 lookup table was 
used for the scans. The A/D converters used with the CCD camera have a 10-bit resolution, the data output format is 8 
bit-per pixel (24-bit for RGB). 
The first test pattern was a calibrated gray scale on film from Kodak, called photographic step tablet No. 3, with 21 
densities from 0-3 oD (oD ... optical density) in steps of 0.150D. The scan pixel size was 7 um. Only the central part of 
each gray scale was used for the analysis. 
greyvalue-density diagramm (7 pm) 
  
—e-— Blaukanal 
sen #-- Grünkanal 
—#— Rotkanal 
  
  
  
optical density 
> 
C 
  
— 
2e: 
t O0 N 
; 
0,75 4 
0,6 4 
0,45 
0,3 
0,15 
  
  
  
  
  
  
  
  
  
0 03 06 0,9 12 1,5 1,8 21 2,4 27 
LOG(G) 
Figure 2. Linearity of the CCD sensor. 
As it can be seen in Fig. 2, a linear behavior of the scanner can be assumed for a density range from 0 to 2.1 oD, while 
the behaviour of the three spectral channels is very similar. With high optical densities ( > 2.1 oD), the behavior 
becomes non-linear and the densities can be hardly separated from the neighbouring ones. This fact has to be taken into 
account in the computation of the lookup table and integration time. The integration time will be optimized for the 
minimum density value of the aerial image (brightest part). 
A further test provided a gray level/integration time diagram showing the mean values of the gray levels over an 
integration time interval of 0.1 ms to 3 ms. The test pattern was a homogeneous gray glass plate with a density of 
0.3171 oD. The scan pixel size was 7 um. 
The results seen in Fig. 2 can be described as 
The results seen in Fig. 3 can be described as 
log (G)- f (oD) 
G = f (integration time ) 
where G is the greyvalue. 
As Fig. 3 shows, again the three spectral channels have similar behaviour, while the gray level intensity increases 
linearly with integration time. 
  
International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part Bl. Amsterdam 2000. 215