Planar Sensor Array Research Articles

Investigation of an ultrasonic monopulse image restoration method

An algorithm for reconstructing the image of the region sensed by a plane single-pulse wave is synthesized (as a particular case of a general solution) and investigated. Reflected signals are received by a planar array of sensors (transducers) that generates the sensing wave. The influence of the sensing signals’ waveforms and the configuration of the transmit-receive array of transducers on the image quality is analyzed. The results of numerical simulation are presented.

Geometries for five-hole-type probes with planar sensor arrays

Geometries for five-hole-type probes with planar sensor arrays

Correlation of mechanical imaging and histopathology of radical prostatectomy specimens: a pilot study for detecting prostate cancer.

A new modality termed mechanical imaging has recently been developed. We determined whether mechanical imaging could be used to detect prostate cancer in radical prostatectomy specimens. Stress patterns on the surface of excised prostates were evaluated using the data obtained from a planar piezoelectric resistive force sensor array. Seven radical prostatectomy and 2 cystoprostatectomy specimens were manually palpated and evaluated by the mechanical imager. The prostates were histopathologically analyzed for the presence of cancer. The results of the manual palpation, mechanical imaging and pathological analysis were correlated. Mechanical imaging correlated closely with nodules palpated in all specimens and in 1 it revealed a suspicious area undetected by palpation, which on subsequent histological analysis demonstrated carcinoma. Mechanical imaging can detect areas of heterogeneity in prostate tissue which correlate with cancer. Our findings provide the basis for the development of a transrectal mechanical imaging probe for prostate cancer detection.

CORRELATION OF MECHANICAL IMAGING AND HISTOPATHOLOGY OF RADICAL PROSTATECTOMY SPECIMENS: A PILOT STUDY FOR DETECTING PROSTATE CANCER

Purpose A new modality termed mechanical imaging has recently been developed. We determined whether mechanical imaging could be used to detect prostate cancer in radical prostatectomy specimens. Materials and Methods Stress patterns on the surface of excised prostates were evaluated using the data obtained from a planar piezoelectric resistive force sensor array. Seven radical prostatectomy and 2 cystoprostatectomy specimens were manually palpated and evaluated by the mechanical imager. The prostates were histopathologically analyzed for the presence of cancer. The results of the manual palpation, mechanical imaging and pathological analysis were correlated. Results Mechanical imaging correlated closely with nodules palpated in all specimens and in 1 it revealed a suspicious area undetected by palpation, which on subsequent histological analysis demonstrated carcinoma. Conclusions Mechanical imaging can detect areas of heterogeneity in prostate tissue which correlate with cancer. Our findings provide the basis for the development of a transrectal mechanical imaging probe for prostate cancer detection.

Fiber optic sensor array for multi-dimensional strain measurement

A planar fiber optic strain sensor array (FOSSA) able to measure multi-dimensional strains inside a material has been developed and tested. Three-dimensional strain measurement is a developing technology that can eventually be employed for many applications including monitoring the strain field inside composite parts and structures, sensing for adaptive structures and intelligent vehicle highway systems and health monitoring systems for civil structures. A planar configuration was chosen to reduce the manufacturing difficulty and structural degradation of embedding optical sensors in more than one plane. Two extrinsic Fabry-Pérot interferometric sensors (EFPIs) and one polarimetric sensor were used to form the planar sensor array. The two EFPIs extract two normal strain components along the x and y axes. A polarimetric sensor in the same plane was used to extract the third normal strain acting on the z axis. The sensor array was embedded in an epoxy resin block and a load of 1000 lbs was applied normal to one face with a loading machine. The strains extracted from the embedded optical fiber sensors compared well with strains measured with surface bonded electrical strain gages. The difference in measured strain between the electrical strain gages and the fiber optic sensors was typically less than 3.4% on all three principal strain axes.

Three-Dimensional Structural Strain Measurement with the Use of Fiber-Optic Sensors

Three-dimensional strain sensing inside a structure is not feasible with conventional strain sensing techniques such as electrical strain gauges, which are limited to surface measurements. Three-dimensional strain measurement inside a structure would find uses in a variety of new applications: enhanced understanding and detection of composite failure modes, such as delamination; sensing for adaptive structural control; intelligent vehicle highway systems; and structural health monitoring systems for civil structures. The latter application could involve remotely monitoring structural integrity during and after an earthquake, for example. A fiber-optic strain sensor array (FOSSA) in a planar, patch-like configuration was developed, and accurate measurement of the three principal strains inside a simple structure was demonstrated. The planar configuration was chosen to avoid the difficulty and structural degradation of embedding optical sensors in three planes. Two extrinsic Fabry-Perot interferometric (EFPI) sensors and one polari-metric sensor form the planar sensor array. The two EFPI sensors were placed perpendicular to each other in the sensor plane to extract the two normal strain components along the x and y axes. The polarimetric sensor embedded in the plane was used to extract the third normal strain acting on the z axis. The sensor array was embedded in an epoxy resin cube and loaded to 454 kg (1,000 1b) with a loading machine. The strains that were measured correlated well with the external strains measured with surface-bonded electrical strain gauges. The variation in measured strain between the two sensor systems was less than 4 percent for all three principal axes.

Manifold of a planar array and its effects on the accuracy of direction-finding systems

The authors are concerned with the accuracy of azimuth and elevation estimates provided by a planar array of sensors and its relation to the array manifold differential geometry. The paper builds on previously published results regarding the influence of manifold differential geometry on the detection and resolution capabilities of linear arrays. The manifold of a planar array is introduced in terms of two families of constant-azimuth and constant-elevation curves, and their differential geometry is analysed as a function of array configuration. Circular approximation is subsequently employed to derive novel expressions for the Cramer–Rao lower bound on azimuth and elevation estimates in terms of the arc lengths and first curvatures of the respective constant-parameter manifold curves. The scenarios considered include the cases of a single emitter as well as that of two closely spaced uncorrelated emitters of arbitrary powers. The results obtained are demonstrated for the cases of two practical array configurations.

Eddy current testing by upgraded microloop magnetic sensor array

AbstractA micro‐eddy current testing (ECT) probe, which consists of a planar microloop inductive magnetic sensor array and a pancake‐type exciting coil, was developed to upgrade the ECT technology, especially as it is used for inspecting steam generator tubing in a pressurized nuclear power plant (PWR). Eddy currents and resultant magnetic fields are perturbed due to a flaw in a conductor. The flaw is detected via perturbation of the electromotive force (EMF) and phase from the array. Flaws manufactured by electric discharge machining in INCONEL 600 planar specimens, the thickness of which was 1.25 mm, were detected and reconstructed by using stacked database and simplified algorithm. Even an outer‐edged 10 percent flaw could be detected. Measured EMF and phase signals were compared with numerical results obtained by using a three‐dimensional eddy current and field analysis code and then verified. The experiment confirmed that the spatial resolution of detection of the micro‐ECT probe is superior to that of the conventional pancake‐type ECT probe. Finally, it was demonstrated that it is possible to establish the same measurement speed using the micro‐ECT probe as it is by using the pancake‐type ECT probe.

Approximate evaluation of the spectral density integral for a large planar array of rectangular sensors excited by turbulent flowa)

An approximate numerical procedure has been developed for rapidly evaluating the spectral density integral that predicts the output of a planar array of many sensors excited by turbulent boundary layer pressure fluctuations. This procedure is particularly useful in cases where the transfer function factor of the integrand is not a simple function of the wave numbers in the flow and transverse directions. The procedure exploits the facts that the entire integrand is a separable function of these two wave numbers and, when the number of sensors is large, the array function factor of the integrand is a rapidly varying function of wave number, characterized by many similar shaped lobes. In addition, a model for multilayered media is employed to provide the transfer function for boundary conditions that closely correspond to reality. Results generated by this procedure were compared to those from an exact evaluation of the integral which is possible if the transfer function is taken to be constant; there was agreement to within 0.2 dB or better over a broad frequency interval. Some results for a realistic transfer function are presented, such as the case of an elastomeric layer backed by an elastic plate with the sensors embedded at an arbitrary position within the layer.

Approximate evaluation of the spectral density integral for a large planar array of rectangular sensors excited by turbulent flow

An approximate numerical procedure has been developed for rapidly evaluating the spectral density integral that predicts the output of a planar array of sensors excited by turbulent boundary layer pressure fluctuations. This procedure is particularly useful in cases where the transfer function factor of the integrand is not a simple function of the wave numbers in the flow and transverse directions. The procedure exploits the facts that the entire integrand is a separable function of these two wave numbers and, for large arrays, the array function factor of the integrand is a rapidly varying function of wave number, characterized by many similar-shaped lobes. In addition, a model for multilayered media is employed to provide the transfer function for boundary conditions that closely correspond to reality. Results generated by this procedure were compared to those from an exact evaluation of the integral that is possible if the transfer function is taken to be constant; there was agreement to within 0.2 dB or better over a broad frequency interval. Some results for a realistic transfer function are presented, such as the case of an elastomeric layer backed by an elastic plate with the sensors embedded at an arbitrary position within the layer. [Work supported by NAVSEASYSCOM 06UR.]

Planar and finger-shaped optical tactile sensors for robotic applications

Progress is described regarding the development of optical tactile sensors specifically designed for application to dexterous robotics. These sensors operate on optical principles involving the frustration of total internal reflection at a waveguide/elastomer interface and produce a grey-scale tactile image that represents the normal (vertical) forces of contact. The first tactile sensor discussed is a compact, 32*32 planar sensor array intended for mounting on a parallel-jaw gripper. Optical fibers were employed to convey the tactile image to a CCD camera and microprocessor-based image analysis system. The second sensor had the shape and size of a human fingertip and was designed for a dexterous robotic hand. It contained 257 sensing sites (taxels) distributed in a dual-density pattern that included a tactile fovea near the tip measuring 13*13 mm and containing 169 taxels. The design and construction details of these tactile sensors are presented, in addition to photographs of tactile imprints. >

Hough transform analysis of data from a planar array of image sensors

This paper suggests that a planar array of cameras can provide a multidimensional image space which is more structured than conventional images. This simplifies the subsequent analysis using a Hough transform. Possible applications and choice of array configuration are discussed, an initial implementation is described and results are presented.