CCD Detection in Spectroscopy
CCDs (Charge Coupled Devices) offer state of the art scientific detection in a remarkably compact package. These integrated circuit silicon imagers offer the ultimate in spectroscopic performance including high speed, low noise and outstanding sensitivity. Additionally, these devices are extremely rugged and durable unlike PMTs (Photo-multiplier Tubes) and unlike PMTs, a CCD allows for simultaneous data acquisition over the entire wavelength region.
CCD detectors have revolutionized the field of spectroscopy and have become the detector of choice for UV/Vis, Emission spectroscopy and Raman spectroscopy. CCDs are multi-channel, silicon array detectors in which photosensitive semi conducting silicon pixels collect incident light and transfer this charge in a step-wise process. The CCD imagers used in the 400 Series Spectrophotometers are high performance linear arrays allowing the ability to acquire a full spectrum in the time it takes a scanning unit to sample a single wavelength.
The standard CCD used in the Model 410 and Model 420 UV/Vis spectrophotometers is a 2048 pixel device. The device used in the Model 430 and Model 440 spectrophotometers is a low noise, high sensitivity 3,648 pixel device offering improved resolution. Both detectors offer high-speed, full spectrum data acquisition. Additionally, both detectors are fitted with order sorting filters for elimination of unwanted second and third order interference. These detectors exhibits high quantum efficiency and readout noise which is 100x lower than conventional photo diode array detectors. This high sensitivity, coupled with an efficient spectrometer design, means that far less light is necessary for accurate absorption measurements, which in turns results in lower potential for sample heating and photo-oxidation.
Key features to look for are when choosing a detector include the number of pixels, pixel dimensions, detector sensitivity and associated noise.