Enhancement of axial resolution and image contrast of a confocal microscope by a microsphere working in noncontact mode

A new technique, to the best of our knowledge, for improving the axial resolution and imaging contrast of a reflection mode confocal microscope is proposed. A 50 mu m silica microsphere is added in front of the objective lens to enhance both the focusing of illumination and the collection of reflected and scattered light from sample surfaces in noncontact mode. An adjustable pinhole is used to compensate the displacement of the focal point in the axial direction. Various samples, including grouped nanolines and nanosteps, are used to demonstrate imaging performance. By comparison to an NA 0.9 commercial confocal microscope, the new setup achieves the axial resolution up to 100 nm and increases the image contrast by 4.56 times. The entire setup offers a cost-effective solution for high imaging performance, which can be applied in many fields from nanotechnology to biology. (C) 2021 Optical Society of America

Automated summary

A new technique is proposed to improve the axial resolution and imaging contrast of a reflection mode confocal microscope, utilizing a 50 μm silica microsphere and an adjustable pinhole to achieve high-resolution imaging. The setup demonstrates success in imaging performance by enhancing both the focusing of illumination and the collection of light.