A custom CMOS imager for multi-beam laser scanning microscopy and an improvement of scanning speed

Multi-beam laser scanning confocal microscopy with a 256 x 256-pixel custom CMOS imager performing focal-plane pinhole effect, in which any rotating disk is not required, is demonstrated. A specimen is illuminated by 32 x 32 diffraction limited light spots whose wavelength and pitch are 532nm and 8.4 mu m, respectively. The spot array is generated by a microlens array, which is scanned by two-dimensional piezo actuator according to the scanning of the image sensor. The frame rate of the prototype is 0.17 Hz, which is limited by the actuator. The confocal effect has been confirmed by comparing the axial resolution in the confocal imaging mode with that of the normal imaging mode. The axial resolution in the confocal mode measured by the full width at half maximum (FWHM) for a planar mirror was 8.9 mu m, which is showed that the confocality has been achieved with the proposed CMOS image sensor. The focal-plane pinhole effect in the confocal microscopy with the proposed CMOS imager has been demonstrated at low frame rate. An improvement of the scanning speed and a CMOS imager with photo-sensitivity modulation pixels suitable for high-speed scanning are also discussed.