Amalia Martínez-García

Slope measurement of a phase object using a polarizing phase-shifting high-frequency Ronchi grating interferometer

An interferometric method to measure the slope of phase objects is presented. The analysis was performed by implementing a polarizing phase-shifting cyclic shear interferometer coupled to a 4-f Fourier imaging system with crossed high-frequency Ronchi gratings. This system can obtain nine interference patterns with adjustable phase shifts and variable lateral shear. In order to extract the slope of a phase object, it is only analyzed using four patterns obtained in a single shot, and applying the classical method of phase extraction.

Parallel two-step phase shifting interferometry using a double cyclic shear interferometer.

A parallel two-step polarizing phase shifting interferometer based on a Double Cyclic Shear Interferometer (DCSI) is proposed in this paper for quantitative phase imaging. The system has the advantage of retrieving the derivative phase data map directly. Due to its configuration, it presents better stability against external configurations than other types of interferometers. The DCSI generates two π-shifted interferograms, which are recorded by the CCD camera in a single-shot. The separation between parallel interferograms can be varied in the two axes for convenience. To obtain the optical phase data map, a parallel phase shift between interferograms is obtained by rotating a half wave plate retarder. We analyzed the cases of four patterns with shifts of π/2 captured in two shots; the optical phase was processed by a four-step algorithm. Related experimental results obtained for microscopic transparent samples are presented.

Dynamic temperature field measurements using a polarization phase-shifting technique

Abstract. In this study, an optical system capable of simultaneously grabbing three phase-shifted interferometric images was developed for dynamic temperature field measurements of a thin flame. The polarization phase-shifting technique and a Michelson interferometer that is coupled to a 4-f system with a Ronchi grating placed at the frequency plane are used. This configuration permits the phase-shifted interferograms to be grabbed simultaneously by one CCD. The temperature field measurement is based on measuring the refraction index difference by solving the inverse Abel transform, which requires information obtained by the fringe order localization. The phase map is retrieved by a three-step algorithm. Experimental results of a dynamic thin flame are presented.

Adjustable-window grating interferometer based on a Mach-Zehnder configuration for phase profile measurements of transparent samples

This communication describes some details of polarization modulation that are useful in phase-shifting interferometry when applied to phase profile measurements of phase objects. Since non-destructive optical techniques allow surface measurement with high accuracy, a Mach-Zehnder configuration coupled to a 4-f arrangement using phase gratings placed on the Fourier plane was implemented to analyze phase objects. Each beam of the interferometer goes through a birefringent wave plate in order to achieve nearly circular polarization of opposite rotations, with respect to each other. The interference of the fields associated with replicated beams, centered on each diffraction order, is achieved varying the spacing of windows with respect to the grating period. Experimental results are presented for cases of four and nine simultaneously captured interferograms.

Radial slope measurement of dynamic transparent samples

An interferometric method to measure the radial slope of dynamic transparent samples is presented. We have implemented a simultaneous phase shifting Mach–Zehnder radial-shear interferometer (SPS-MZRI) using a phase grating to replicate the interference patterns and phase shifts modulated by polarization; the interferometer is capable of processing the optical phase data through the acquisition of n-interferograms captured simultaneously. The SPS-MZRI is capable of obtaining the radial phase derivative and associating it with its corresponding radial slope. The experimental results for static and dynamic samples are presented in this work, as well as the experimental evidence for the generation of spiral patterns.

Single shot interferometry using a two-interferogram phase shifting algorithm

Abstract An interferometer capable of retrieving the phase information in a single shot was implemented, the system was made by taking into account the double interferogram output obtained in a Mach Zehnder interferometer and then retrieving the phase information using a two-step algorithm already encountered in the literature. By controlling the polarization properties of the system, a new polarization phase shifting technique was implemented based upon the rotation of two quarter wave retarders placed in each of the arms of the interferometer. We present the analytical model taking into account the necessary conditions presented by the demodulation method. The configuration presented does not require micro-polarizer arrays or diffraction gratings presenting the advantage of avoiding the use of conventional polarizing filters to control the phase shift. Experimental results are presented.

Slope measurement of a phase object

An interferometric method to measure the slope of phase objects is presented. The analysis was performed by implementing of a polarizing phase shifting cyclic shear interferometer coupled to a grating interferometer. This system can obtain four interference patterns with adjustable phase shifts and variable lateral shear. In order to extract the slope of a phase object, is analyzed the optical phase applying the classical method of phase extraction.

Simultaneous phase shifting interferometry based in a Mach Zehnder interferometer for measurement of transparent samples

A Mach Zehnder (MZ) interferometer was implemented to analyze a phase object using polarization phase-shifting interferometry. The Mach Zehnder interferometer produces two beams with circular polarization of opposite rotations one respect to the other. The system is coupled to a 4-f system with phase grating in the Fourier plane, interference of the fields associated with replicated beams centered on the diffraction orders is achieved by a proper choice of the beams spacing with respect to the gratings period. The optical configuration allows obtaining n-interferograms in one shot. The configuration presented does not require micro-polarizer arrays or additional software to eliminate noise caused by vibration, as the system is stable itself and uses conventional polarizing filters. Considering the object under study a thin phase object, experimental results are presented.

Automatic Generation of Movement Sequences to Robotic Arm Based on Three-Dimensional Data Obtained Through Fringe Projection Technique

The use of robotic manipulators is a subject that has become relevant in the process of automation in different branches of industrial manufacturing. Today is possible to make routines works with robotic manipulator in dangerous conditions for human operators, providing flexibility in production lines, doing multiple types of tasks and executing actions with precision and quickly. All operations of a robotic arm is controlled by a computer system that controls the mechanism positions. Since the work of these machines is to manipulate tools or pieces, it is necessary to have tridimensional information of the environment or manipulated elements. In this work, the fringe projection technique is used to obtain three-dimensional shape of an object, and based on this information to generate the trajectories of the manipulator for the painting of complex objects through paint spraying. The obtained results have been successful, generating simulated trajectories for the painting of pieces with good quality and short times compared with times using traditional methods to program sequences.

Automatic Generation of Codes for Routine of CNC Machining Based on Three-Dimensional Information Obtained by Fringe Projection

The use of machining systems by Computer Numerical Control (CNC) has notable advantages in the area of industrial production compared with traditional techniques. This facilitates a significant decrease of time, higher precision and optimization of operation parameters. The control of sequences in these systems is based on codes that define the parameters to produce the machining of a determined piece. However, the generation of these codes presents two major challenges, first, know the tridimensional information of the piece to produce, and second, define the sequence by CNC machining. In this work, the fringe projection technique is used to obtain three-dimensional information from an object and based on this information, automatically generate programming codes for the machining routine of a three-axial CNC milling machine. The results are compared to apply the fringe projection technic to recover three-dimensional shape of an object based on Least Squares Algorithm, using information from three to eight images.