Spectrometer Avaspec 2048FI equipped with SONY 2048 detectors based on silicon CCD arrays.

The Charged Coupled Device (CCD) detector stores the charge, dissipated as photons strike the photoactive surface. At the end of a controlled time-interval (integration time), the remaining charge is transferred to a buffer and then this signal is being transferred to the AD converter.

CCD detectors have an enormous dynamic range, only limited by the dark (thermal) current and the speed of the AD converter. Advantages for the CCD detector are many pixels (2048), high sensitivity and high speed. Main disadvantage is the lower S/N ratio.

Detector SONY2048 specification Type CCD linear array # Pixels, pitch 2048,14 mkm pixel width/ height 14 x 56 mkm Sensitivity 240 V/lx.s Sensitivity (AvaLight-HAL, 8 um fiber) in counts per ms integration time 5000 counts/W Peak wavelength 500 nm Signal/Noise 250:1 Dark noise Ca. 10 counts PNRU*(max.) ± 5% Frequency 2 MHz *PNRU (Photo Response Non-Uniformity) - max difference between output of pixels with uniformly illuminated, divided by average signal.

The sensitivity of a detector pixel at a certain wavelength is defined as the detector electrical output per unit of radiation energy (photons) incident to that pixel.

The relation between light energy entering the optical bench and the amount hitting a single detector pixel depends on the optical bench configuration. The efficiency curve of the grating used, the size of the input fiber or slit, the mirror performance and the use of a Detector Collection Lens are the main parameters. Cylindrical Detector Collection Lens (DCL) mounted directly on the detector array.