A phase-shift resolving equation is established by combining the phase-shift interference and tomographic ability of a point detector. The theoretical measuring range of confocal microscopy is extended from the single-side linear range of an axial main lobe into the almost complete envelope of an axial main lobe, and the axial tomographic measurement is thus made resistible to the reflectance disturbance and power drift of a laser source. Experimental results indicate that the axial resolution is 0.5nm and lateral precision for grating width measurement is 0.14μm when NA=0.85 and λ=632.8nm. It can therefore be concluded that the proposed phase-shift resolving confocal microscopy can be used to achieve the high axial resolution, wide range and reflectance disturbance inhibition necessary for the measurement of microstructures made of different or hybrid material with high steps.
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