Optical Profilometer Product

Overview

An optical profilometer measures surface topography—the 3D shape of a sample—by analyzing how light reflects from different elevations. When the objective lens focuses on the surface, only photons scattered from the in-focus plane contribute to the signal; out-of-focus light is rejected by a confocal aperture or by computing depth-from-focus on a broadband illumination image. By stepping the Piezo Z-Stage vertically through the sample and capturing an image at each position, software reconstructs a height map with nanometer precision. Motorized XY Scanning Stage scanning then tiles the full sample, building a complete 3D topographic model from which roughness, waviness, and form deviations are calculated.

The Optical Head contains the objective lens and confocal aperture (if confocal) or white-light optics (if interferometric). Light from the Illumination Source illuminates the sample, and the Detector Assembly captures the reflected light. The Piezo Z-Stage uses a piezoelectric stack to move the objective in steps as small as 10 nm, scanning a vertical distance of 100 µm or more. The XY Scanning Stage hosts the sample and can traverse it under stepper-motor control, allowing the operator to map multiple fields. The Motor & DAQ Electronics board triggers the Z-stack acquisition and reads photodiode signals via an ADC, and the Analysis Processor uses a GPU to reconstruct the 3D surface from the stack of 2D images. The Vibration Isolation Base isolates the whole assembly from floor vibration that would blur the sub-micrometer focus.

How it works

For confocal operation, the objective focuses light to a diffraction-limited spot on the surface. Scattered light passes back through the objective and a pinhole (the Confocal Aperture), which blocks out-of-focus rays. Only light returning from the focal plane transmits, so the Detector Assembly signal peaks when the objective is precisely in focus. By sweeping the Piezo Z-Stage vertically and recording the photodiode output at each step, software identifies the focus position where signal is brightest; that Z-value is the surface height at that lateral position. Scanning the XY Scanning Stage raster-fashion across the sample and recording focus height at every point yields a full 3D map.

For white-light operation without confocality, the broadband Illumination Source illuminates a small field. Image contrast is highest when the objective is exactly in focus on the surface, so software uses correlation or sharpness metrics to find the Z-position of maximum contrast—again yielding height.

The Analysis Processor computes surface statistics on the 3D data: arithmetic mean roughness (Ra), root-mean-square roughness (Rq), peak-to-valley (Rmax), waviness, and form deviation. It can export the raw height matrix as a 3D point cloud or process it according to ISO 25178 (3D surface texture) or ISO 13565 (profile roughness) standards.

Lateral resolution is diffraction-limited: for a 10× objective in visible light, it is roughly 1 µm; for 100×, about 0.3 µm. Vertical resolution is determined by Z-stage step size and focus detection precision; typically 5–10 nm for modern instruments.

Applications

Profilometry is essential in manufacturing quality control, verifying surface finish on machined parts, ground optics, and coated substrates. Semiconductor fabs use it to measure wafer roughness and thin-film surface morphology. Materials researchers employ it to characterize fracture-surface topology, wear tracks, and coating uniformity. In optics manufacturing, profilometry measures lens and mirror figure—the deviation from ideal shape. In biomedical research, it documents cell and tissue topography at sub-cellular resolution. In corrosion studies, it tracks pit depth and the evolution of degradation on metals. In tribology, it quantifies wear patterns on bearings and seals.