CCD, PDA Detector Definitions

CCDs (Charge Coupled Devices)

These are two-dimensional detector arrays built onto a silicon chip. The pixels are read out sequentially. The device acts like an electronic reusable photographic film - the pixels accumulate light intensity information until they are read out. They are then ready for a new "exposure".

The main difference between CCDs used in sensitive measurement applications, such as spectroscopy, and those used in cameras and camcorders, is the quality of the CCD required for the job. The most demanding spectroscopic applications require CCDs that have very low pixel noise, excellent uniformity of response, and high quantum efficiency -- in some detectors down into the ultraviolet region. The available response range is from 200 nm (with UV enhancement) to 1000 nm. Lower cost, camera-quality CCDs can sometimes be used in less demanding applications.

In spectroscopy, the two-dimensional capability is suited to multiple fiber optic inputs as well as 2-dimensional solid state array detectors. The fibre positions form one dimension and spectral wavelength the other dimension; so that multiple spectra are obtained simultaneously. A wide variety of detector sizes and pixel sizes are available.

For best signal-to-noise ratios (SNR), detector cooling is recommended, which may be either TE (thermoelectric) or LN (liquid nitrogen) cooling.

Imaging CCD Cameras

PDAs (Photodiode Arrays)

These are linear arrays of photodiode detectors on a single strip of silicon. Frequently used in moderate to high light level applications, PDAs are available as single or double arrays. Double arrays are convenient for two-channel instruments. PDAs may be used uncooled, or cooled to achieve lower detector noise. They typically cost less than CCDs and have similar spectral sensitivity in the range 200 nm to 1000 nm.

Infra-red (IR) Detector Arrays

For spectra in the NIR region, from 1 to 2.5 microns wavelength, InGaAs detectors are usually employed. We also offer spectrographs, monochromators, and diffraction gratings for use in the NIR region.

Picosecond Sources and Detectors

Our NanoLED sources represent the best performance to price ratio nanosecond and picosecond light sources. Used with our TBX miniature picosecond photon counting detector you can create the ultimate time-domain spectroscopy systems.