Confocal slit divided-aperture microscope: applications in ear research

A confocal, scanning slit microscope that uses separate portions of the objective aperture for illumination and imaging rays achieves a high degree of optical sectioning. This capability permits visualization of individual cells within the intact inner ear in guinea pigs and cats, and it facilitates directing a laser heterodyne interferometer beam so that vibration of selected cells can be measured. A concentric singlet lens is added to the front of a long-working-distance microscope objective to increase the numerical aperture from 0.4 to 0.53 while retaining a working distance of 6 mm. The measured optical-sectioning capability is compared with the theoretical performance and with the calculated curve for a full-aperture pinhole confocal system.