Analytical Sciences

Reliable Evaluation of the Lateral Resolution of a Confocal Raman Microscope by Using the Tungsten-dot Array Certified Reference Material

Nobuyasu ITOH and Nobuyasu HANARI

National Metrology Institute of Japan (NMIJ), National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba, Ibaraki 305-8563, Japan

Confocal Raman microscopes are widely used in various applications because they provide physical and chemical information at a submicron scale. A high lateral resolution in the confocal Raman microscope is essential for obtaining high-quality images. We used an array of tungsten dots at a 600 nm pitch on a Si substrate of the certified reference material (NMIJ CRM 5207-a) to reliably evaluate the lateral resolution of a confocal Raman microscope at various pinhole sizes. The precision of the mapping scale in the x- and y-pitches was confirmed from Si signal profiles, and the lateral resolution was evaluated by a straight-edge method using scale indicators in the reference material. Because these procedures are applicable to other confocal Raman microscopes with popular specifications (532 nm laser, 100× objective lens, numerical aperture 0.9, step size 0.1 μm), they are suitable for both a reliable evaluation of the lateral resolution of a confocal Raman microscope and for daily checks on the precision of its mapping scale.

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