The Capella family of cooled CCD imaging systems


Features:


Introduction:

PixCellent has used the very latest CCD technology to develop a range of cooled CCD camera systems that can meet the needs of a broad range of imaging applications. Cooled CCD camera systems enable extremely small differences of light intensity to be detected. Consequently, details of very low contrast phenomena can be studied against much brighter backgrounds, without saturation of the higher intensity areas. This ability to detect low contrast images, combined with the high sensitivity and wide dynamic range of the CCD, results in performance figures for cooled CCD cameras far surpassing that of most other imaging systems.
The Capella family is the latest addition to PixCellent's range of cooled CCD imaging systems. As well as providing all the traditional benefits of cooled CCD cameras, the Capella family offers unrivalled high-speed readout capabilities at very low noise levels. This makes it the ideal camera system for real-time imaging applications which require cooled CCD image quality with low noise at high readout speeds (several milion pixels per second). This readout rate is the fastest available for any cooled CCD camera and places the Capella family firmly at the head of its field.


The Capella family of High-Speed CCD Controllers


There are two models in the Capella family which provide a choice of grey level resolution and maximum speed capabilities:


System components

The Capella camera electronics unit is extremely flexible. It can be programmed to operate in fast mode at 8MHz pixel rate or operated at slower readout rates for highest sensitivity and quality. The pixel rate is programmable from approximately 500kHz to 5.5MHz using double-correlated sampling for minimum noise and at 8 MHz for set up in an uncorrelated mode (this mode is only available with Kodak CCDs). Readout noise varies with the pixel rate and CCD type used. Typical figures are shown in the table for a Capella system fitted with various CCDs.
The pixel rate is measured in MHz and defines the time taken for individual pixels to be read out from the CCD. The noise is measured in electrons and is the internal noise level that applies whenever a pixel is read out from the CCD. As the table indicates, at any speed the camera system produces remarkably low readout noise figures. This versatility makes it ideally suited for a wide range of imaging applications.


Table 1: Capella performance figures
Pixel rate Full-frame read time (seconds)   Noise (e- RMS, typical)  
(MHz) Kodak KAF0400 Kodak KAF1600 EEV CCD37  EEV CCD39 Kodak KAF400 Kodak KAF1300 EEV CCD37  EEV CCD39
8 0.06 0.22 n/a  n/a set-up set-up n/a  n/a
5.5 0.08 0.32 0.05  0.002 40 40 75  50
4 0.12 0.48 0.07  0.003 25 25 40  40
2 0.22 0.88 0.15  0.005 15 15 20  16
1 0.45 1.8 0.3  0.01 10 10 20  10
0.5 0.88 3.5 0.6  0.02 8 8 8  8


Cooled CCD camera head

For more information on the camera heads and CCDs supported by PixCellent, please refer to the Camera Head and the CCD data sheet and selection guides.


The camera head houses the CCD in a cooled environment. There are two types of head available:

The camera heads are fitted with the CCDs and use the Peltier effect to cool the CCDs down to the appropriate temperature to reduce the dark current in the CCD. The shutter speed on the camera is programmable from 1 millisecond to 4.5 hours in 1 ms steps. However, the shortest useable exposure and the maximum frame repetition rate is dependent on the type of shutter fitted in the camera head. With frame transfer CCD's exposures much less than 1 millisecond are possible with certain CCDs. The CCD37 frame transfer CCD has aminimum integration time of 1 msec, while the CCD39 has a minimum frame time of 10 microsecs.



Additional hardware

An IBM PC-compatible computer is required to control the camera system and to process the resultant images using the selected software package. Minimum hardware requirements are a Pentium class computer with a 1.2 Gbyte hard disk drive, 64MB RAM and expansion slots for the PixCellent PCI interface card. An SVGA card that is supported by Microsoft Windows 95/98 in a 1024x768 (256 colours) mode is also required, with an appropriate monitor and mouse. Optional hardware peripherals that users may require include:

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Site last updated: 12 April, 1999.