Confocal microscopy

Confocal microscopy is a powerful tool that has become an established method in life sciences, which allows, for example, the quantification of molecular dynamics, sensing of cellular environment or studying protein interaction. A confocal microscope offers excellent spatial resolution while minimizing phototoxicity through judicious control of excitation power. However, confocal microscopy suffers from a fundamental trade-off between signal intensity and resolution: The smaller the pinhole, which ensures confocality, the better the resolution and the sectioning performance, but at the cost of lower signal intensity.

Single-photon avalanche diode (SPAD) arrays are used with an effective technique termed image scanning microscopy (ISM) to eliminate this trade-off and enable improving both the spatial resolution and signal-to-noise ratio! ISM achieves an increase in spatial resolution by replacing the conventional single-point detector with a pixel array to record multiple images from different angles. Each pixel of the SPAD array acts as a virtual small pinhole with improved lateral and axial resolution, while multiple pixels collect the signal of a virtual large pinhole. The final image – with improved resolution – is obtained by applying a mathematical method called pixel reassignment. An example on the right shows the increased spatial resolution of a confocal image using our SPAD array.