Brightness-enhanced light source technology for medical imaging

Spontaneous luminescent decay combined with total internal reflection (TIR), harnessed in devices known as luminescence (or fluorescence) concentrators (LCs), can generate light at 10-1000 times greater intensity than pump lamps or pump LEDs can provide directly. LED pumped luminescent concentrators (LC) thus provides a low cost, high brightness, and energy efficient stable light output. Where LED light sources alone lack in intensity and brightness, LCs offer potential for high efficiency light, enhanced brightness and generation of new wavelength components whilst benefiting from the long lifetime and ruggedness of LEDs [1,2]. LCs provide a wide range of excitation and illumination applications [3,4]. However, a key challenge in using LC is in the extraction of the generated light due to the trapping of emitted light owing to the TIR. Previously, extraction boosting has been achieved using surface roughening of the LC and with the addition of extraction optics. Here, we report a fibre coupled light extraction system with the output brighter than the pump LED, and is longer lasting than a flash lamp, making it ideally suited to several industrial and medical applications for example medical imaging. In the case of medical imaging a direct replacement of lamps with LED light technology is not feasible as its high divergence insufficiently couples into the imaging system. However, LED-LCs are perfect for this purpose where high power blue indium gallium nitride (InGaN) LED arrays emitting at ~ 460 nm pumps the LCs in the form of thin rectangular slab with dimensions 100(L)×10(w)×0.5 (t) mm3. The power coupled into the LC crystal through to the fibre is estimated by means of Monte Carlo raytracing using LightTools® Illumination design software and this value is used to optimise the output power of this concentrator-based brightness enhanced light technology. It is shown, therefore, from this work that significant light can be extracted from LC crystals, which serve as light concentrators, and this allows for other applications like laser pumping, maser pumping, optical metrology, LiFi (light-fidelity), street lighting etc. as well as replacement of ageing technologies.