
47
The "full well" figure for the TC-245 CCD (number of light derived electrons required to fill up the
charge "well") is 80,000.
The dynamic range of the CCD, therefore, is 80,000 / 30 = 2667
OR expressed in dB, the dynamic range of the CCD is 20*log
10
(2667) = 68.5 dB
The dynamic range (using the more typical 20 noise equivalent electrons) = 72 dB:
A typical CCD dynamic range of 70 dB is assumed. Not all 70 dB of dynamic range is used
within the camera; Anti-blooming uses up 6 dB by setting a "knee" at Vsat/2. By setting the Vuse
OR “white clip" point slightly below Vsat/2, a dynamic range close to 62 dB is obtained which
corresponds well with the >62 dB signal-to-noise ratio of the camera.
8.4.5 What is the image format of the CCD ?
755 (Horizontal) X 484 (Vertical)
The actual number of pixels (charge collection sites) on the CCD are 755(H) X 242(V); the
process of pseudo-interlacing creates an effective matrix of 755(H) X 484(V).
8.4.6 What is meant by pseudo-interlaced operation ?
The effective vertical resolution of the CCD is doubled by means of a process called "pseudo-
interlacing".
In this process, the charge collection area represented by each pixel is electronically shifted
vertically from field to field by half of the pixel height. This is analogous to the process of
"dithering" the pixel matrix vertically at 60 Hz. The mechanism of this "dithering" operation and
more details (including a diagram) are available below.
VW
CW
VW
CW
Pixel 1
Pixel 2
Pixel 3
VW
CW
VW
CW
VW
CW
VW
CW
VW
CW
VW
CW
Pixel 241
Pixel 242
VW
CW
VW
CW
Pixel 1
Pixel 2
Pixel 3
Pixel 241
Pixel 242
Odd Field
Even Field
Odd Field
Even Field
VW = Virtual Well; CW = Clocked Well
= Centroid
(a) First transfer clock in each field
(b) Effective pixel areas and centroids
Imaging Area: showing the pseudo-interlace mechanism
Figure 8-4: Imaging Area, showing Pseudo-interlaced operation
Содержание DigitEyes Series
Страница 14: ...9 Figure 4 3 TC 245 Gate Level Drawing Texas Instruments 1994 ...
Страница 61: ...56 12 Appendix D Camera Mechanical Drawings Figure 12 1 Camera Mechanical Drawings ...
Страница 63: ...58 Figure 13 2 Camera Noise Spectrum Min Gain Bandwidth 10kHz to 4 2MHz ...
Страница 64: ...59 Figure 13 3 Camera Noise Spectrum Max Gain Bandwidth 100kHz to 4 2Mhz ...
Страница 65: ...60 Figure 13 4 Camera Noise Spectrum Max Gain Bandwidth 10kHz to full ...