Topographic optical profilometry by absorption in liquids

Abstract

Optical absorbance within a liquid is used as a photometric probe to measure the topography of optical surfaces relative to a reference. The liquid fills the gap between the reference surface and the measuring surface. By comparing two transmission images at different wavelengths we can profile the height distribution in a simple and reliable way. The presented method handles steep surface slopes (<90°) without difficulty. It adapts well to any field of view and height range (peak to valley). A height resolution in the order of the nanometer may be achieved and the height range can be tailored by adapting the concentration of water soluble dyes. It is especially appropriate for 3D profiling of transparent complex optical surfaces, like those found in micro-optic arrays and for Fresnel, aspheric or free-form lenses, which are very difficult to measure by other optical methods. We show some experimental results to validate its capabilities as a metrological tool and handling of steep surface slopes. Res. 9(3), 428-433 (1955). 11. M. Csete and Z. Bor, "Plano-concave microcuvette for measuring the absorption coefficient of highly absorbing liquids," Appl. Opt. 36(10), 2133-2138 (1997). 12. J. Johnson and T. Harris, "Full-field optical thickness profilometry of semitransparent thin films with transmission densitometry," Appl. Opt. 49(15), 2920-2928 (2010). 13. S. Ogilvie, E. Isakov, C. Taylor, and P. Glover, "A new high resolution optical method for obtaining the topography of fracture surfaces in rocks," Image Anal. Stereol. 21(1), 61-66 (2002). 14. E. Isakov, S. R. Ogilvie, C. W. Taylor, and P. W. J. Glover, "Fluid flow through rough fractures in rocks 1: high resolution aperture determinations," Earth Planet. Sci. Lett. 191(3-4), 267-282 (2001

Measurement and Visualization of Cell Thickness and Volume by Transmission-Through-Dye Microscopy

“…Apart from specific applications, TTD adds strong contrast to transparent samples and can sometimes reveal features that may escape detection with phase contrast or DIC. The method does not have to be limited to biological samples, and its use in manufacturing quality control has been suggested [5].…”

Optical determination of intracellular water in apoptotic cells

“…To find h we use the transmission‐through‐dye (TTD) method, which has a similar advantage of requiring nothing more than a standard transmission microscope. In the TTD method, a non‐penetrating dye with a strong absorption in the visible range is added to the sample, so that transmitted intensity quantitatively reflects cell thickness and volume (Antón et al 2012; Model, 2012; Schonbrun et al 2013).…”