The study compares three variants of focus sensors designed for the optical topography measurement of rough surface specimens with submicron accuracy. We present a theoretical analysis of the focus sensor principles and the experimental measurements with a single point laser probe. A low coherent illumination beam was provided by a monochromatic laser source and a rotating diffuser, which reduced the speckles generated by the rough surface. The reflected beam was modulated by three specific optical elements (axicon, double wedge prism, four spherical lenses) realized by a spatial light modulator. A digital camera detected the output intensity patterns that were evaluated by the intensity centroid method. The results showed a good coincidence of the surface profiles obtained by the three sensor variants with the root-mean-square deviations below one micron. We discuss the results obtained for several specimens with various surface roughness and compare the differences between the three focus sensor variants.