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8.4 CCD RELATED QUESTIONS
8.4.1 What CCD sensor is used in the “DigitEyes” cameras? Who manufactures it ?
All the “DigitEyes” cameras use the TC-245 Frame Transfer CCD Imager from Texas
Instruments.
8.4.2 What other kinds of CCD sensors are out there ?
In addition to the Frame Transfer CCDs, there are Interline Transfer CCDs and CIDs (Charge
Injection Devices). The CIDs have relatively few applications; a comparison of Interline CCDs
and Frame Transfer CCDs follows:
8.4.3 How do Frame Transfer CCDs compare with Interline Transfer CCDs?
8.4.3.1 Fill Factor:
Interline transfer CCDs have gaps between the pixels due to their transfer mechanism. This
leads to lower fill factors and can present several problems in scientific measurement
applications. Frame transfer CCDs have contiguous pixels and a 100% fill factor. This is the
reason behind the higher sensitivity of the Frame Transfer CCDs.
8.4.3.2 Size of pixels:
Interline transfer CCDs with the same optical format (1/2") and same number of pixels as
comparable Frame Transfer CCDs have smaller pixels (due to the inter-pixel dead space). This
makes Interline Transfer CCDs less sensitive than their frame transfer counterparts. The smaller
optical format CCDs (1/3", and more recently, 1/4" formats) have even smaller pixel sizes and
consequently lower sensitivities. The smaller formats are cheaper to produce, and are quite
usable for security and surveillance cameras but are not suitable for scientific work.
8.4.3.3 Full Well capacity:
The smaller size of the Interline transfer CCD leads to a smaller full well capacity. Since the
noise floor is approximately the same, the decreased full well capacity leads to a lower Dynamic
Range (this translates to a lower signal-to-noise ratio in Interline CCD cameras.
8.4.3.4 Ultra-violet & Infra-red response:
To compensate for the decreased fill factor and smaller pixel sizes, plastic micro lenslet arrays
are built on top of the Interline transfer CCD surface to collect the light that would otherwise have
fallen on the "dead" inter-pixel gaps. Plastic does not offer good performance down in the UV
range below 400nm, and has other limitations at the near IR range. Frame transfer CCDs such
as the TC-245 used in DVC cameras, have spectral range of 400-1100nm with CCD glass face
plate attached. Customers doing UV work have reported response in the low 200nm range with
face plate removed; IR response up to 1100nm has been reported.
Summary of Contents for DigitEyes Series
Page 14: ...9 Figure 4 3 TC 245 Gate Level Drawing Texas Instruments 1994 ...
Page 61: ...56 12 Appendix D Camera Mechanical Drawings Figure 12 1 Camera Mechanical Drawings ...
Page 63: ...58 Figure 13 2 Camera Noise Spectrum Min Gain Bandwidth 10kHz to 4 2MHz ...
Page 64: ...59 Figure 13 3 Camera Noise Spectrum Max Gain Bandwidth 100kHz to 4 2Mhz ...
Page 65: ...60 Figure 13 4 Camera Noise Spectrum Max Gain Bandwidth 10kHz to full ...