title: Visualization of two-dimensional phase gradients by subtraction of a reference periodic pattern.
abstract: We describe a simple method for visualization of phase objects. The phase object is placed between a printed two-dimensional periodic pattern and a CCD camera. The ray deflection that is due to the phase object distorts the image of the pattern. This image is subtracted from a reference image and then, by squaring and low-pass filtering, a measurement of the two-dimensional refractive-index changes is obtained. Because the optical system does not require special alignment or illumination, the method presented has potential application for detection of gas leaks in industrial environments.
authors.forename: C D
authors.initials: CD
authors.lastname: Perciante
authors.forename: J A
authors.initials: JA
authors.lastname: Ferrari