Spatially multiplexed X-Y lateral shear interferometer with varying shears using holographic lens and spatial Fourier transform

Abstract

Current methods in shear interferometry provide shear only along one direction at a time. We propose a method in which interferograms with shear along the x, y, and xy directions can be obtained simultaneously from a single exposure recording via the concept of spatial multiplexing. The method utilizes holographic lenses, which have been recorded on a single plate with their optical centers translated along the x and y directions. The phase information is extracted through the Fourier transform method. In addition, this technique also provides a method to obtain interferograms with shear in multiples of the original shear along the x and y axis in one single frame capture due to the nonlinearity inherent in the phase holographic lens.

Measurement of temperature and temperature profile of candle flame using holo-shear lens and Fourier fringe analysis technique

“…24,26,28,29,[31][32][33] Figure 1 shows the schematic of the experimental setup used for the recording of a holo-shear lens. It can function both as negative and positive spherical lens.…”

“…Optical interferometric techniques provide fullfield temperature data inside transparent hot objects. [21][22][23][24][25][26][27][28][29][30][31][32][33] A holo-shear lens is a simple device which can be used as lateral shear interferometer. These techniques, if used properly, are highly accurate and precise.…”

“…These techniques are of a noncontact and noninvasive type. 24,26,28,29,[31][32][33] In this paper, a holo-shear lens made on dichromated gelatin (DCG) is used as a lateral shear interferometer for the measurement of the temperature and temperature profile of a gaseous (candle) flame. A large number of optical interferometric methods such as classical interferometry, 1,2 holographic interferometry, 3-6 moiré deflectometry, 7 Talbot interferometry, [8][9][10] speckle shearing interferometry, 11,12 lateral shearing interferometry, [13][14][15] Lau phase interferometry, 16 and digital holographic interferometry 17,18 have been widely used for the measurement of the temperature field in gaseous flames and to study the phase objects.…”