White-Light Interferometric 3D Optical Profilometer

What is the White-Light Interferometric 3D Optical Profilometer?

A non-contact profiler using vertical scanning white-light interferometry to map areas with sub-nanometer vertical resolution and Sa, Sq and step height outputs. It is the right choice for smooth surfaces, MEMS, films and optics where contact could damage the sample.

Overview

A white-light interferometer splits broadband illumination into a reference and a sample beam inside an interferometric objective, such as a Michelson, Mirau or Linnik type. A piezo stage scans the objective vertically while a camera records the fringe intensity at each pixel. The position of maximum fringe contrast gives the height at that pixel. Vertical resolution is below 0.1 nm for phase-shifting mode and about 1 nm in coherence-scanning mode, with scan ranges from a few micrometers to 10 mm. Objectives from 2.5× to 100× provide fields of view from 0.05 mm to 5 mm. Stitching extends areas. Areal parameters from ISO 25178, such as Sa, Sz and Sdr, and step heights are calculated. Steep slopes above about 30° and transparent films need care.

How does it work?

A stylus profilometer drags a diamond tip, usually with a 2 µm or 5 µm radius, across the surface at a constant speed under a small force, and a transducer converts its vertical displacement to an electrical signal. The raw profile is filtered with a Gaussian filter into roughness and waviness using a cut-off wavelength such as 0.8 mm, and parameters such as Ra, Rz and Rq are calculated according to ISO 4287. Optical profilers use white-light interferometry, confocal microscopy or focus variation to determine height at each pixel by analyzing fringe contrast or sharpness while scanning vertically. They produce areal maps with parameters defined in ISO 25178, such as Sa and Sq, without touching the sample.

What are the key features?

• Vertical scanning interferometry with piezo or linear stage
• Turret with 2.5× to 100× interferometric objectives
• Vertical resolution below 0.1 nm in phase-shifting mode
• Automatic stitching for large area and form measurement
• ISO 25178 areal parameter and step height software
• Active vibration isolation table option for stable scans

What are the technical specifications?

A typical white-light interferometric 3d optical profilometer configuration offers vertical resolution of < 0.1 nm (PSI); ~1 nm (CSI), vertical scan range of Up to 10 mm, objectives of 2.5×–100×, field of view of 0.05–5 mm, lateral resolution of 0.35–4 µm (objective-dependent) and camera of 1–5 MP. Values are indicative of the product class; the exact figures for each configuration are confirmed on the quotation and the calibration documents supplied with the instrument.

Which applications is it used for?

The White-Light Interferometric 3D Optical Profilometer is used in MEMS and semiconductor topography, optical surface roughness, polished metal and ceramic analysis and thin film step height. Across the wider Surface Profilometers class, laboratories also deploy it for machined part surface finish, semiconductor film step height and optical component roughness.

Which standards and certifications apply?

Relevant standards and methods include ISO 4287, ISO 21920-2, ISO 25178-2, ISO 4288 and ASTM D7127. Certification candidates for this model are CE, ISO 9001 manufacturing and Laser/LED safety classification; each is to be confirmed for the specific configuration before shipment, and certificates are supplied only where they have been issued.

Place the instrument on a vibration isolation table or heavy bench and away from drafts, since nanometer-level signals are easily disturbed. Calibrate vertical and horizontal scales with certified step-height or roughness standards at defined intervals, and check stylus wear or tip radius regularly. Clean samples before measurement and mount them level. Specify cut-off length, evaluation length and filter type in the method, because Ra depends on them. Keep stylus force low for soft materials and inspect for scratches. Optical systems need objective cleaning and periodic lateral calibration with grid standards.

How do I select the right White-Light Interferometric 3D Optical Profilometer?

Select this variant for smooth or delicate surfaces that need areal 3D data, nanometer resolution and no contact. It is less suited to very rough, steep or opaque-sparkling surfaces where a confocal or stylus system is better. In an RFQ, specify objectives, scan range, stitching, sample size and vibration isolation.

How does it compare with other Surface Profilometers variants?

The main choice is between contact and non-contact. Stylus instruments are traceable, tolerant of steep flanks and dirt, and are the reference for ISO 4287 roughness on machined parts, but they can scratch soft surfaces and cannot reach features smaller than the tip radius. Optical profilers map areas quickly, suit delicate coatings, MEMS and films, and give 3D parameters, but struggle with transparent, very steep or highly reflective or absorbing surfaces. Consider vertical range and resolution, lateral resolution, scan length, sample size and weight, vibration isolation, software filters, and whether the work follows ISO 21920, ISO 25178 or ASTM D7127. Portable roughness testers suit shop-floor checks.