The application relates to a method of testing an item with a spectrally precise, artificial solar spectrum including wavelengths from 200 nm to 20 microns and it also relates to a solar spectrum simulator capable of producing a light spectrum including wavelengths from 200 nm to 20 microns. The simulator comprises: a) amplitude optimization software; b) a spectrum controller; c) an emitter controller; d) heat lamp/heater generation sources including: a xenon/infrared (IR) lamp and a blackbody radiator; e) laser generation sources including an ultraviolet (UV) laser source, a visible laser source, a near infrared (NIR) laser source, a short wavelength (SW) laser source, a medium wavelength (MW) laser source, a long wavelength (LW) laser source, and a quantum cascade laser source (QCL); f) a beam combiner; g) a beam profiler; h) a spectrometer; and i) a surface on which can be placed an item to be tested.

The invention relates to a measuring arrangement for detecting an absolute reflection spectrum of a sample in a process for producing the sample. It comprises a light source for generating measurement light, a homogenizer for generating a uniform spatial illuminance distribution of the measurement light; a movable reflector and a receiver for collecting the measurement light reflected from the sample and/or the reflector. According to the invention, the reflector both for a reference measurement and for a sample measurement is positioned in an observation beam path and arranged on the same side of the sample as the light source in order to feed the reflected measurement light to the receiver.

The application relates to a method of testing an item with a spectrally precise, artificial solar spectrum including wavelengths from 200 nm to 20 microns and it also relates to a solar spectrum simulator capable of producing a light spectrum including wavelengths from 200 nm to 20 microns. The simulator comprises: a) amplitude optimization software; b) a spectrum controller; c) an emitter controller; d) heat lamp/heater generation sources including: a xenon/infrared (IR) lamp and a blackbody radiator; e) laser generation sources including an ultraviolet (UV) laser source, a visible laser source, a near infrared (NIR) laser source, a short wavelength (SW) laser source, a medium wavelength (MW) laser source, a long wavelength (LW) laser source, and a quantum cascade laser source (QCL); f) a beam combiner; g) a beam profiler; h) a spectrometer; and i) a surface on which can be placed an item to be tested.