Scanner Assembly Research Articles

Polarization Image Laser Line Extraction Methods for Reflective Metal Surfaces

In this work, we propose a novel pipeline method for laser line extraction from images with a polarization image sensor. The proposed method is specifically developed for strong laser beam reflections from metal surfaces. For the preprocessing stage, we propose a demosaicing algorithm for color polarizer filter array (CPFA) sensors. This can be implemented by using either one-quarter or full resolution of the sensor. In addition, we propose two methods for optimizing the information available in a 12-channel color polarization image. The first method is based on the minimum linearly polarized irradiance, and the second method is based on the linear polarization intensity. These preprocessing and optimization methods are combined with laser line extraction methods. The laser line extraction is done with either the polarized finite impulse response (FIR) center of gravity (COG), where the laser line coordinates are computed from the filtered laser intensity distribution, or with the polarized FIR-Peak, where the laser line coordinates are calculated from the first derivative of the filtered laser signal. The performance of the proposed algorithms is studied experimentally using a laser line scanner assembly, made of a polarization camera, and a laser line projector operating in the blue wavelength range.

High-speed wide-angle interleaved scanning technique for a 3D imaging lidar

In this paper, we describe a novel interleaved scanner for an eye-safe 3D scanning lidar system to measure aerodynamic phenomena in a wind tunnel using elastic backscatter from seeding particles. The scanner assembly consists of a rotating polygon scanner for line scanning along the fast axis, a galvanometer (galvo) scanner for scanning along the slow axis, angular position sensors, and motor controllers. The polygon scanner sweeps the lidar beam at up to 10,000 lines/s across a 27 deg angular field of regard in the fast axis, while the galvo scanner covers an angular range of 20 deg in the slow axis. Using this scanner, the lidar can perform nonintrusive flow visualization, velocimetry, and hard target mapping at millimeter-scale spatial resolution to a standoff range of 5 m at an update rate of 50 Hz for the full field of regard. An interleaved scanning methodology for the acquisition of two snapshots of 3D lidar intensity data with a 100 µs time offset is discussed. The design of the control and data acquisition electronics is described. The effects of rapid scanning on the response of a narrow field-of-view lidar are addressed. The design of the scanner is scalable and can be tailored to meet the requirements of other applications by increasing or decreasing the standoff range, angular field of regard, and scan rate.

Simple, contrast based, compartmentalization in 3D reconstruction from CT images

We are interested in different procedures and techniques to preprocess and postprocess the data in computedtomography reconstruction methods to achieve the better contrast, resolution or other types of the functionalanalysis of the data. We report the straightforward application of the imaging artifacts treating technique,that is the elimination of the overexposure artifact due to the presence of the metal object, for producingthe elementary image compartmentalization results with the artificial bone sample CT data. Thus, the highabsorption artifacts removal technique is given the complimentary function of the structural analysis andrevealing the metal pins scaffolding skeleton. The basic multilevel thresholding is used to reveal thetargeted structures. The results could be extremely useful for the noisy, unfiltered X-ray source, single rundata sets. The data have been supplied by the homemade CT scanner assembly and processed with thecustom reconstruction software developed specifically for this setup. OpenCV package tools for the C/C++libraries compiled with the MS Visual Studio IDE compiler were extensively used.

Laser use vs. handpiece for tooth preparation: A preliminary in vitro study

The key fields of research of dental lasers have focused on the use of different wavelengths on hard and soft tissues; however it is not clear whether they can be used for tooth preparation for full coverage restorations or not. The objective of this study was to investigate the possibility of tooth preparation for full coverage restorations using a scanner assembly added-on Er:YAG laser system and compare the tooth preparation durations performed with dental drills and the laser. The 20 freshly extracted human molar teeth were allocated to two groups (A and B) of 10. Group A was prepared with dental drills, whereas group B was prepared with a scanner assembly added-on Er:YAG laser system. The preparation duration means of the groups were calculated and analyzed by one-way analysis of variance. The difference between group A (20, 2±1, 9 min) and B (45, 2±|3, 1 min) (P<0.01) was significant. Laser preparation took more time than the conventional rotary instrumentation. The recommended amount of tooth reduction for full coverage restorations could be accomplished by the laser tooth preparation. Tooth preparation using Er:YAG laser with laser application for wide area system took more time than the rotary instruments.

Relative humidity control for atomic force microscopes

We describe the design and performance of a relative humidity (RH) control chamber for use with atomic force microscopes (AFM) in which the tip is scanned across the stationary sample. The small volume (∼9cm3) chamber encloses the sample, the cantilever holder, and a commercial humidity/temperature sensor. The RH is controlled by passing a controlled ratio of dry and humid nitrogen gas across the sample. This unique design prevents exposure of the scanner assembly to humid gas and maintains all of the functionalities of the AFM system with no measurable degradation of its performance. Using this system, the RH at the sample position can be varied between 5% and 95% and controlled to within ±0.2% during an AFM measurement. To demonstrate the performance of the RH control chamber in imaging and force spectroscopy modes, we have characterized the RH-dependent swelling of small chitosan droplets with diameters of 3–40μm, and the RH dependence of capillary forces between the AFM tip and a mica surface.

Glue-free tuning fork shear-force microscope

A scanning near-field optical microscope without any glued parts is described. Key elements are the optical fiber probe/tuning fork junction and the piezotube scanner assembly. In both cases, fixation is achieved by means of controlled pressure and elastic deformation. The avoidance of glued connections was found to improve the Q factor of the shear-force sensor as well as to facilitate the replacement of the fiber probe and other parts of the scanner head. We present approach curves and shear-force images that demonstrate the performance and stability of the system.

A portable inductive scanning system for imaging steel-reinforcing bars embedded within concrete

A novel portable scanning system and inductive sensor that produces images of steel-reinforcing bars embedded within concrete by an inductive principle is described. The sensing element, which comprises a field-compensated receiving coil, detects the magnetic field generated by the steel bars due to eddy currents induced on their surfaces by an excitation coil. The sensor is mounted within a purpose-designed computer-controlled x– y scanner used to collect data within a 400×400 mm 2 area in 18 min, using a scan step of 1 mm along the x-axis and 2 mm along the y-axis. This scanner assembly is fabricated from a unique combination of plastic components to avoid disruption of the magnetic field as signals are acquired. The sensor is translated within the frame using remotely placed stepper motors, and images are generated with a grey-scale resolution of 16 bits/pixel. These images are then enhanced using application-specific image processing techniques developed by the authors. The complete system incorporates fully integrated control, acquisition and processing software, which makes it convenient for on-site use.

Low-temperature atomic force microscope using piezoresistive cantilevers

This article describes the design of an easy-to-operate low-temperature atomic force microscope (AFM) that incorporates piezoresistive cantilevers. The instrument is easier to build and to operate at cryogenic temperatures than AFMs based on laser deflection schemes or interferometers because no mechanical adjustments of the instrument are necessary after a change of temperature. The effects of thermal expansion on the AFM’s tip-to-sample distance are minimized by the use of a double tube scanner assembly. The design includes a simple mechanism that locks the sample holder in place as the temperature is lowered. This AFM is compact and rigid, enabling it to be used in a conventional cryogenic liquid-storage Dewar. All of the materials used in the construction of the AFM are ultra-high-vacuum compatible.

A high-speed variable-temperature ultrahigh vacuum scanning tunneling microscope

An ultrahigh vacuum scanning tunneling microscopy (STM) system capable of collecting constant-current STM images at rates exceeding 1 image/s at temperatures up to 900 K was designed, built, and tested. The microscope uses an inchworm to push a scanner assembly through a quartz tube towards the sample. When the scanner is within tunneling range of the surface, the inchworm is decoupled from the scanner, resulting in a small, rigid mechanical loop with a high resonant frequency. The cylindrical symmetry and the use of low thermal expansion materials reduces image distortion due to thermal drift. An analog proportional-integral controller with tilt correction is used to maintain a constant tunnel current. A personal computer running Microsoft WINDOWS ’95 is used to control all other instrument functions, as well as for data acquisition, manipulation, and storage. Problems associated with the non real time nature of the operating system were overcome by collecting the STM images within a virtual device driver. By taking advantage of the WINDOWS ’95 multimedia functions, the time required to display and save images was reduced below 5 ms using a standard personal computer with no special hardware other than data acquisition cards. Sample STM images of Pd(111) and halogens adsorbed on Cu(100) are presented.

A versatile scanning tunnelling microscope for use in air

A scanning tunnelling microscope for use in air is described. Despite the apparent simplicity of the stage it is capable of high performance and this is largely due to its inherent stability resulting from miniaturisation and the use of stressed cantilever beams. It also employs a novel three-axis piezo scanner assembly which provides a fast response. Because of its stability, the microscope can be used in areas suffering from high levels of acoustic noise and vibration without additional isolation.

Thermal roughening studied by scanning tunneling microscopy

We have used scanning tunneling microscopy to observe the thermal roughening transition at the Ag(115) surface. For this purpose, a scanner and crystal assembly was employed that minimizes the lateral thermal drift of our microscope. Images were taken from room temperature, where the surface was smooth, up to 260 °C, where the surface is in the rough state. The topographs vividly demonstrate how the stepped metal surface goes through its roughening transition by the proliferation of kinks in the step edges. The roughening temperature of Ag(115), TR, is estimated to be 78±20 °C.

Processor-Controlled Microdensitometry

A new scheme of densitometric data collection is described which comprises a digital filtering technique and process control program. A 6502-based PET 2001/32K microcomputer and an Elscan model 2500 specular microdensitometer are interfaced through the standard 6522 VIA port chip. An Analog Devices ADC80/12 monolithic A/D converter is used to digitize the analog output of the light photometering system. Additionally, control of the optical scanner assembly is provided through processor-driven 4-phase TTL logic circuitry. The technique applies to any analog signal of interest, either for filtering purposes or for recording directly into memory for later waveform or transient analysis. The maximum data gathering rate is 40 kHz, limited by the A/D conversion time of 25 μs.

Laser Color Recording Directly on Nine-Inch Color Film

A Laser Color Recorder is described which yields Landsat or similar high-resolution images directly on photographic color film. This development, sponsored by NASA Goddard Space Flight Center, provides the capability for transferring computer-formatted magnetic tape data directly to positive or negative color imagery. Designed to circumvent the current task of reconstructing color images by combining individual (monochrome) color separation negatives, this recorder yields Landsat pictures, directly, with growth potential for the recording of advanced, high-resolution color image sensor data. Three individual laser beams, representing the three primary colors, are modulated separately, then combined precisely to form a single beam of light. This synthesized beam, in which the instantaneous hue and intensity are determined by the modulating signals, is focused on the recording film through a rotating scanning mirror. The entire scanner assembly is translated across the format length to form a raster image directly on the photographic color film.

Precision Automatic Measuring of X-Y Coordinates

This paper reports the development of a computer-controlled machine for non-contact inspection of manufactured parts The machine, called PAMM (Precision Automatic Measuring Machine), is capable of providing on-the-fly measurements accurate to within 100 microinches. The intersection of a rotating spiral slot with a stationary linear slot produce as moving aperture for scanning in small increments overa projected, enlarged image of a part. The scanner assembly moves along an overhead cantilever beam in the x direction, and the part being inspected moves in the y direction along the machine base; position in each direction is monitored by a separate laser interferometer. In the paper conventional methods of coordinate measuring are briefly reviewed, the details of the new design are presented, some experimentally obtained measurements are given, measurement errors induced by photodetector shot noise and aperture roughness are analyzed, and the computer-control and data-analysis techniques are discussed.

A Plasma Scanner and Data Processing System for Current-Voltage Curves

A new plasma diagnostic tool, called a plasma scanner, has been developed for use in obtaining current cross sections and current-voltage characteristics of a hollow cathode magnetically confined arc plasma in argon. The scanner assembly consists of an annular copper arc anode, a boron nitride baffle, a boron nitride scanning wheel, and a plane copper current collector. To obtain current cross sections the wheel was rotated at 1 rpm. To obtain current-voltage characteristics, the wheel was stopped with the collector exposed to the plasma through a chosen scanner hole. Most of the data were produced in an arc of 20 A and 45 V. A cylindrical Langmuir probe provided data for comparison. The scanner showed a sharp increase in electron current in the center of the arc, whereas the probe did not. Typical temperatures derived from the scanner were 4 eV while temperatures obtained using the probe were 3.2 eV. Electronic equipment gave a direct readout of the inverse of the electron temperature.