Light source device and image projection device having a light source device

An optical system configured to monitor a state of a diffuser, the optical system comprising:

• the diffuser,
• a light source emitting at least one light beam,
• a projector,
• a transmissive or reflective spatial light modulator of the projector, a sampler, a detection system,
• and an analyzer;
• and
• wherein the light source is configured to illuminate the diffuser, the at least one light beam comprises at least one bundle of rays of light exiting the diffuser being for illumination of the transmissive or reflective spatial light modulator of the projector,
• the optical system further comprising the sampler configured to sample the at least one light beam exiting the diffuser and to re-direct the light beam sample towards the detection system, wherein the detection system is configured to receive the light beam sample and is coupled to an analyzer configured to generate a signal when an anomaly is detected in a distribution of a light intensity in a cross-section of the light beam sample, wherein the anomaly is detected as a decrease in intensity ratio between a peripheral position and a central position of the at least one bundle of rays or wherein the anomaly is detected as a change in full width at half maximum (FWHM), and
• wherein the optical system is configured to have the at least one light beam incident on an aperture in an aperture plane and wherein the sampler is configured to sample a light distribution in the aperture in the aperture plane, and the aperture is filled with light and the optical system is configured to have all rays of light that exit the diffuser with a same angle ending up at a same point in the aperture.