In the case of a lighting device of the type described in the introduction, a primary light can be generated by means of the primary light source. During operation of the lighting device, said primary light hitherto has impinged on a disk-shaped, rotating first support wheel having a plurality of different phosphor regions. The different phosphor regions generate differently wavelength-converted light (that is to say light of different colors or different spectral compositions). As a result of the rotation of the support wheel, the phosphor regions are successively activated and a temporally serial sequence of differently colored secondary light sections is thus generated. The phosphor regions are typically arranged in an annular fashion on the first support wheel and form sectors thereof.
However, the primary light currently incident on a phosphor region is typically not completely converted, and so the secondary light emitted by said phosphor region includes both a (usually dominant) wavelength-converted light component and an undesired non-wavelength-converted primary light component. In order to be able to output a substantially pure wavelength-converted light component, an associated filter region is disposed downstream of such a phosphor region and filters out the primary light component of the secondary light. Depending on the type of wavelength-converted light and the proportion thereof in the secondary light, a different filter region can be used in order to optimize an efficiency of the lighting device. In order to be able to provide a filter region matching a phosphor region, the filter regions are arranged in an annular fashion on a circular-disk-shaped second support wheel. The second support wheel has to be operated synchronously with the first support wheel in order to be able to maintain a high efficiency and to avoid color corruption as a result of non-matching combinations of phosphor regions and filter regions.
The output light beam present downstream of the second support wheel is temporally serially composed analogously to the secondary light, wherein the individual (temporally serial) sections thereof in each case correspond to a predetermined combination of a currently active phosphor region and an associated filter region. The relative duration of the sections can be set via the length of the phosphor regions (and thus the corresponding length of the associated filter region). If the sequence of the sections occurs rapidly enough, the individual sections are no longer resolved by a human observer, and the output light beam is perceived as a uniform mixed light. The individual sections act as different color components of the mixed light.
The support wheels are typically angled with respect to one another and have to be precisely synchronized, which necessitates a considerable constructional outlay, e.g. owing to the use of high-quality and thus expensive drive motors for the support wheels and on account of complex synchronization control. A probability of failure of the support wheels is also comparatively high.