Multi-channel image with RCM.
Re-scan Confocal Microscopy (RCM) is a new super-resolution technique based on standard confocal microscopy extended with an optical (re-scanning) unit that projects the image directly on a CCD-camera. This new microscope has improved lateral resolution (170 nm at 488 nm light), and strongly improved sensitivity, while maintaining the sectioning capability of a standard confocal microscope. This technology is useful for biological applications, where the combination of high-resolution and high-sensitivity is required (but not very high imaging speed).
During scanning, re-scan mirrors (SM2) move faster than the first scan mirrors (SM1), which magnifies the image on the camera chip compared to the sample, and eventually results in the higher resolution of the image. The resolution of the system can be improved with the re-scan step by a factor of √2 (i.e. 1.41 times), compared to Abbe’s resolution limit by changing the angular amplitude of the re-scanner (SM2). Reduction of pinhole is no longer necessary to increase resolution – in fact, closing down the pinhole will only limit the amount of light passing through, and increase the signal to noise ratio due to weaker signal. Since the re-scan is purely optical method, and no further image processing is required, there is also no time cost of improving the resolution.
Data from above-mentioned article comparing resolution with various pinhole sizes for both confocal microscopy and RCM.
Together with the open pinhole (AU=2), this provides an exceptional image with high resolution and superior signal to noise ratio. The lateral resolution of the RCM is increased to 170nm compared to 240nm of regular confocal microscope and the signal to noise ratio is 4x better.
Comparison between standard confocal microscopy (left) and RCM (right). RCM gives resolution improvement by a factor of √2.