Confocal scanning is a microscopy imaging technique that utilizes an aperture at the confocal plane of the objective. Out-of-focus light is thus prevented from entering the imaging system and only the in-focus plane on the sample is captured. 2D profiles and 3D surface images can be captured by scanning the aperture mechanically or digitally.
Optical interferometry makes use of the optical path difference between light reflected in the two arms of the interferometer (reference and sample) to yield an spatial interference pattern (interferograms) that contains information on the surface topology of the sample. Various variations of the approach can be used for particular applications.
Focus Variation vertically scans either optics (with very low depth-of-field) or the sample to obtain a continuous set of images of the surface. An algorithm determines which points in each frame are in focus, and an entire image is built up using all in-focus points from all frames.
No moving parts
For confocal scanning, the S neox uses Sensofar’s patented technology, based on a microdisplay. The ferroelectric liquid crystal on silicon (FLCoS) microdisplay is a fast switching device that makes the scanning of confocal images fast and very stable. Combining this approach with Sensofar’s high NA objectives (0.95), vertical resolution is reduced to below 1 nm. Additionally, as there are no moving parts in the sensor head, there are no maintenance and alignment issues, and the effective lifetime of the sensorhead is unlimited.
New piezo-capacitive elements control the fine vertical tracking of the sensor head, resulting in resolution down to 0.01 nm and linearity of 0.03%. And when measuring step heights, accuracy is down to 0.5%.
Outstanding lateral resolution
The Rayleigh criterion states that two points are resolved when the first minimum of one Airy disk is aligned with the central maximum of the second. Lateral resolution is thus improved when short wavelength light and a very high NA objective are used. Additional factors – such as incoherent illumination and the imaging conditions provided by the confocal technique itself – serve to lower the K-factor. These aspects allow the S neox to outperform all other optical profilers on the market.
The S neox uses a high-resolution CCD sensor of up to 1360×1024 pixels in combination with high-resolution displays of 2560×1440. The images acquired with S neox do not need to be up or down-scaled, so they always appear sharp, vivid and realistic on-screen.
Each pixel in real color
The same red, green and blue LEDs are used to sequentially illuminate the surface under inspection. Three monochromatic images are taken and compounded into a high-resolution color image. The benefits of this approach are high color fidelity and saturation, as well as real pixel-to-pixel color information. In contrast to color cameras based on a Bayer matrix of pixels, the S neox does not need to interpolate the color information between pixels.