Off axis microinterferometric tomography system – Business – Small Business

Off axis microinterferometric tomography system - Business - Small Business

In this paper we discuss modeling and design issues of microinterferometric tomography system (MiTS) for out-door non-destructive optical fiber inhomogeneity inspection. Presented system is a monolithic microdevice complete system is necessary. There are many optical modeling methods of them could be used to simulate complete system. These methods either require to much computer power or simply would produce inaccurate
results. Therefore to simulate complete system in a reliable way a number of methods is used in different system regions.

The received final results are used to study the reconstruction and imaging problems of the MiTS system. Optical Diffraction Tomography (ODT) [1] used for measurement of internal 3D complex refractive-index distribution is now well established technique. Although the ODT can be successfully used in tasks such as fiber, waveguide refractive index characterization, it is still a laboratory tool with limited utility for the outdoor applications. Therefore in this paper we explore design of integrated microinterferometric tomography system.

The system is built as a monolithic block with reduced vibration and it suits for tasks of outdoor measurements [2, 3]. In the paper we compare two different system designs, with on and off axis illuminations. We compare both configurations by means of numerical simulations. Therefore accurate and efficient modeling method of the system is necessary. Unfortunetly no single modeling tool can accomplish such a task. We use combination of three methods: free space propagation (FSP) [4], finite difference time domain method (FDTD) [5] and wave propagation method (WPM) [6]. With the FDTD method the grating diffraction orders magnitudes are characterized. The WPM is numerically much more efficient tool and it is applied at the object structure region.

At all the other system regions the FSP method is applied. In the Fig. 1 below the setup configuration of microinterferometric tomography system with off axis illumination is presented. The system is built from monolitic integrated Mach-Zehnder interferometer using the grating beamsplitter and recombiner (interferometer body), illumination and detection
difficulty in obtaining undistorted integrated image of measured structure. structure [7]. In the system the object is illuminated with off axis illumination beam and then the beam propagation direction is changed at the recombining grating. Therefore the obtained integrated object images are highly distorted. Such a distortion must be corrected using numerical algorithms. The main purpose of such an imaging correction algorithm is introduction of the object beam deflection at recombining grating.

The image correction algorithm consists of three steps. In the first step distorted
deflection is introduced, what simulates the grating in the imaging The above system was simulated using the combination of two methods: free space propagation and wave propagation methods. For this system the grating can be treated approximately with thin element grating equation coefficients. The simulated object is a fiber of 50 mm
-3 diameter with the refractive index of cladding ncl=1.48352, and core nco= 1.49352. In Fig. 2 below plots of projection images received from standard optical system imaging (a) and with application of mentioned above imaging correction algorithm (b) are presented using solid line. The projection plots are compared with the theoretical object projections (doted lines).

You may also like...

Leave a Reply