Optical – Paul Wu's Blog

Liquid Surface Tension Measurement by Pendant Drop Method

In the coating applications, liquid surface tension measurement is critical, which include liquid-air interfacial tension and liquid-substrate (solid) interfacial tension. Contact angle measurement is a common method for the surface tension measurement; however liquid surface tension might not be available for the measurement. Pendant drop method is a good for this purpose.

Determine the crystalline phases of PVDF film by FTIR

Poly (vinylidene fluoride), PVDF, has different crystalline phases, such as alfa, beta, gamma, delta, epsilon, depending on film processing methods. Among them, alfa, beta, and gamma are the major phases, particularly the beta phase which determines PVDF’s pyro-, piezo-, and ferroelectric properties.

Photo elasticity based stress analysis

Mechanic deformation can lead to the optical property change in an optical media, which is called photo elasticity. Therefore, this principle is commonly adopted to investigate the stress distribution in a material.

Aggregation-induced emission (AIE)

Contrary to the well-known aggregation caused quenching of chromophore, there are certain materials show no or weak emission at solution, but strong emission when aggregated, e.g. in solid films. The phenomenon is called aggregation induced emission (AIE).

Optical path for reflection/transmission measurement in Perkin Elmer spectrophotometer

The following figure from Perkin Elmer shows the optical path for transmission and reflection measurements using an integrating sphere.

Color and measurement (ASTM E1164)

The color of an object is determined by illuminant (light source), object, and observer (detector, eyes).

Gloss measurement-ASTM D 523

Gloss is a measure of object’s surface property, e.g. shiny, metallic, or matte. It measures the percentage of spectral reflection.

Photo elastic modulator

photo elastic modulator

Photo elastic modulator (PEM) is one the critical components in a phase modulated ellipsometer, which modulates phase and amplitude changes in detected signal, based on that Psi and Delta will be measured and n, k, d, and others accordingly in principle.

Ellipsometry

Ellipsometry is a powerful tool in thin film field to characterize film properties, e.g. refractive index (n), extinction coefficiency (k), surface roughness, crystallinity, etc.

Transmittance/Haze/Clarity measurement-ASTM D 1003

As a simplified view, light is incident upon a sample, three processes occur: transmission, absorption, and reflection, as schematically shown in the follow figure, including retroflection, diffuse reflection, specular reflection, diffuse transmission, and specular transmission.