Full-Pupil Line-Scanning Confocal Microscope for Imaging Weakly Scattering Tissues: Comparison to Divided-Pupil

摘要

Confocal reflectance full-pupil and divided-pupil line-scanning microscopes provide optical sectioning and image nuclear detail in skin. Line-scanning with linear detectors is a simpler alternative to point-scanning for imaging weakly scattering epidermis and the oral epithelium. With illumination of 830 nm, a water immersion lens of numerical aperture 0.9 and slit width three times smaller than the diffraction-limited line width, the instrumental full width at half maximum (FWHM) optical sectioning (line-spread function) for the full-pupil design is 1.4 +/- 0.07 μm, which degrades through full-thickness human epidermis to 2.8 +/- 0.78 μm. The lateral resolution is 0.7±0.10 μm, which degrades to 1.6±0.28 μm through human epidermis. The divided-pupil design demonstrates instrumental optical sectioning of 1.7 μm, which degrades to 7.6 μm through human epidermis. The lateral resolution is 1.0 μm, which degrades to 1.7 μm. Heavy scattering in the dermis decreases contrast. Images of skin in-vivo show nuclear detail as expected with the predicted and experimentally verified sectioning. However, pixel crosstalk and speckle artifact degrade image quality in strongly scattering and aberrating tissues. The sources of degradation (aberration and scattering) are evaluated for the two design to assess the feasibility of these techniques for in vivo imaging.