WHAT IS LATERAL RESOLUTION?
Lateral resolution is the smallest distance between two points or surface features that an imaging or measurement system can distinguish as separate in the x-y plane of the sample. It defines the system’s ability to resolve fine details across the sample surface.
In optical systems, lateral resolution is fundamentally limited by diffraction and depends mainly on the wavelength of light and the numerical aperture of the objective. In 3D optical metrology, lateral resolution should not be confused with lateral sampling, which refers to the pixel spacing on the sample surface.
FACTORS DETERMINING LATERAL RESOLUTION
Lateral resolution depends primarily on:
Wavelength of light: shorter wavelengths generally improve lateral resolution.
Numerical aperture (NA): a higher NA increases the ability of the optical system to resolve fine surface features.
Optical aberrations: distortions in the optical system can reduce the effective resolution.
Objective quality and optical design: the correction level and design of the objective influence real measurement performance.
Sampling density of the detector: the detector must sample the image with sufficient density to represent fine features correctly, but sampling alone does not determine optical resolution.
Measurement technique: different 3D optical metrology techniques may provide different effective lateral resolution depending on the sample, signal quality, and data processing.
In surface metrology, selecting the appropriate lateral resolution is essential to ensure that the measured data captures the relevant features of the surface without sacrificing unnecessary field of view, acquisition time, or measurement stability.
