A Large-Area PVDF Pyroelectric Sensor for CO$_{2}$ Laser Beam Alignment

Abstract

We present the design of a large-area (50 mm 50 mm) polyvynilidene fluoride (PVDF) pyroelectric sensor array for industrial CO 2 ( = 10 6 m) laser beam positioning. The array dimensions were chosen to match the area typically monitored in the alignment procedure of external optics (beam steering moving arm system, for example) used to redirect the laser beam from the laser output window to a remote working station. The instrument is provided with a tilted, high reflection, ZnSe plate which partially transmits the laser beam onto the sensor array. From positioning simulations with a Gaussian laser intensity profile with a = 3 2 mm standard deviation (equivalent spot size 3 = 20 mm), the positional accuracy along the two orthogonal array dimensions was found to be better than 0.02 mm for an 8 8 array and one order of magnitude higher for a 16 16 array. The centroid position of a CO 2 industrial laser beam was evaluated by integrating the pyroelectric current for a time comparable to the time duration (100-200 ms) of the laser pulses used in the alignment procedure.Index Terms-CO 2 industrial laser, electronic instrument, laser beam positioning, PVDF pyroelectric array.

Comparison between dielectric and pyroelectric properties of PZFNT and BST type ceramics

“…2a and 2b, respectively, showing a smooth, crack-free and dense structure with small pores between grains. The average grain size of 6.45 µm in PZFNT, and 102 µm in BST, can be correlated with the high sintering temperature of PZFNT and with the small strontium content of BST [10,11].…”

“…Two specific compositions were selected, namely Ba 0.75 Sr 0.25 TiO 3 (BST) and PbZr 0.68 Fe 0.14 Nb 0.14 Ti 0.04 O 3 (PZFNT), knowing that dopants in BST and PZT lead to lower transition temperatures, thus to larger values for the pyroelectric coefficient. One has also to mention that pyroelectric properties are usually investigated on samples of small area [10], and only few studies were performed on large area pyroelectric elements manufactured from ferroelectric polymers [11,12]. In the present study these properties are investigated on perovskite ceramic samples of large area, comparable to those used in commercial energy meters.…”

An Improved Strategy for Detection and Localization of Nodules in Liver Tissues by a 16 MHz Needle Ultrasonic Probe Mounted on a Robotic Platform

“…The error estimated in this way would be specific only of these particular points, notwithstanding they may have a certain significance in the nodules' individuation also. According to previous research [28], we individuated these centers' positions from the CIA data and compared them with their nominal positions. With reference to Figure 5 (top), we found that these differences were smaller than the scanning spatial resolution of 2 mm.…”

Laser Pulses Characterization with Pyroelectric Sensors

“…Another technology that has been demonstrated useful for sensor fabrication availed of a screen printed pyroelectric paste (Capineri b et al, 2004). Both pyroelectric materials have been employed to design and build array of sensors with different configuration and size, depending on the application (Capineri et al 1998) (Capineri et al, 2005) (Mazzoni et al,2007). Some example of pyroelectric arrays used to design monitoring devices for CO 2 power laser systems are described in the following section.…”

“…Moreover, the fabrication technology explained in the previuos section, allowed the realization of pitches between elements of about 150 μm. This value is adequate also for real-time imaging of power laser beams by devising a rotating reflector that scanned the beam section at an angular velocity adequate for granting an accurate imaging of the laser pulse (Coutouly et al, 1999)(Akitt et al, 1992 (Mann et al, 2002), (Mazzoni et al, 2007).…”