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Advanced optical microscopy techniques, that can resolve in depth as well as laterally, are an important technology in bio-medical research for building up three-dimensional images of objects of interest. Examples range from confocal and multiphoton microscopy where a laser spot is scanned across the sample, to wide-field techniques such as grid projection structured illumination microscopy and spinning disk methods. However, in almost all cases, mechanical movement is used in the microscope in order to realise the optical sectioning or to build an entire image. This can be a significant restriction, either because it limits the speed of operation or it makes miniaturisation of the microscope difficult for applications such as endoscopy.The micro-led array technology developed under this project offers a route to solve both these problems. A patterned led device can produce the sort of structured illumination that is common to all these optical sectioning techniques, and, being directly electrically driven, it can also provide the rapid reconfiguration of that structured illumination needed to produce images in real time. In addition the small device size and the lack of moving parts makes these devices ideal candidates for endoscopic applications.

As an example we have produced a line array device consisting of 120 LED bars of 17 mm width and 3.6mm length. Each bar can be individually addressed by our drive electronics and the whole array can be updated at a rate of 60,000 frames per second. Using this device we have successfully demonstrated both grid projection and line scanning confocal microscopy techniques as shown in the images below of fluorescence from stained pollen grains.

Fig. 1 Picture of the micro-stripe LED array

Fig. 2 X20 magnification images of stained pollen grains (a) conventional image, (b) structured illumination image, (c) line scanning confocal image.

The LED array technology is applicable in several other areas of bio-medical imaging by virtue of allowing the projection of patterned illumination onto an object. In particular, we are also looking at using these devices in two –dimensional array format for photo-bleaching and photo-activation applications.