Reference beam technology for spectrophotometers
The optical system
Using reference beam technology, the spectrophotometers achieve maximum accuracy in the visual and non-visual wavelength range. The light source according to the model and consists of a tungsten-halogen lamp in the XD 7000, while the XD 7500 is equipped with a xenon flash lamp. With an output of up to 500 million flashes, the UV light source is designed to last the life of the instrument and is a cost-effective replaceable part as opposed to the usual deuterium lamps. By means of a grating monochromator and beam splitter behind the exit slit, the respective required wavelength is precisely demarcated and allows a wave length accuracy of +/- 1 nm.
The principle in detail
The light emitted by the light source falls through the entrance slit on the monochromator and is deflected by the grating situated towards the exit slit. This mechanism, along with the limitation after the exit slip, enables the selected wavelength to be accurately reproduced. The semi-transparent mirror deflects the reference beam while allowing the light beam to pass through to the sample in the cuvette. The photodiodes act as detectors and transmit these signals to the microprocessor. The result is calculated and issued as a value in the display.