Two-dimensional Optical Scanning Research Articles

Assessment of Internal Structure of Spun Concrete Using Image Analysis and Physicochemical Methods.

Taking into account the possibilities offered by two imaging methods, X-ray microcomputed tomography (µCT) and two-dimensional optical scanning, this article discusses the possibility of using these methods to assess the internal structure of spun concrete, particularly its composition after hardening. To demonstrate the performance of the approach based on imaging, laboratory techniques based on physical and chemical methods were used as verification. Comparison of obtained results of applied research methods was carried out on samples of spun concrete, characterized by a layered structure of the annular cross-section. Samples were taken from the power pole E10.5/6c (Strunobet-Migacz, Lewin Brzeski, Poland) made by one of the Polish manufacturers of prestressed concrete E-poles precast in steel molds. The validation shows that optical scanning followed by appropriate image analysis is an effective method for evaluation of the spun concrete internal structure. In addition, such analysis can significantly complement the results of laboratory methods used so far. In a fairly simple way, through the porosity image, it can reveal improperly selected parameters of concrete spinning such as speed and time, and, through the distribution of cement content in the cross-section of the element, it can indicate compliance with the requirement for corrosion durability of spun concrete. The research methodology presented in the paper can be used to improve the production process of poles made of spun concrete; it can be an effective tool for verifying concrete structure.

Two-dimensional optical scanning for large-field-of-view optical image generation applications

Optical image generation is a very important step in many optical imaging system applications. However, current optical image generation systems (OIGS) produce a fixed simple grid image with a small field of view (FOV) because of the physical limitation of the OIGS itself. Here, we use proposed an optical image generation method using optical scanners to achieve a large FOV and images defined by the user. The combination of two scanners implements the two-dimensional optical scanning for obtaining the improvement of field-of-views (FOV) in two-dimensional (2D) directions. Here, three important findings, including scanning optical configurations, an analog-to-digital-based scanning pattern, and a scanning imaging model, of 2D optical scanning in the image generation with a large field of view are reported. The proposed method can improve the FOV with 20° in the 2D directions. These three results are very valuable references for the application of image generation. The proposed method has potential applications in multiple fields, such as camera calibration, computation imaging, and image compression.

Integrated Wavelength Beam Emitter on Silicon for Two-Dimensional Optical Scanning

A novel integrated on-chip wavelength-based beam emitter is proposed and fabricated to realize two-dimensional optical scanning. By combining both wavelength division filters and emission array, 80 × 8 far-field optical beam spots are achieved with a field of view of 6° × 4°. Both collimation and projection modes are tested and 64 wavelength channels are realized in 10 nm bandwidth from 1550 to 1560 nm. This device can be used for LIDAR, optical wireless communication, and high-speed infrared imaging applications.

Forward imaging OCT endoscopic catheter based on MEMS lens scanning

This Letter reports a fully packaged microelectromechanical system (MEMS) endoscopic catheter for forward imaging optical coherence tomography (OCT). Two-dimensional optical scanning of Lissajous patterns was realized by the orthogonal movement of two commercial aspherical glass lenses laterally mounted on two resonating electrostatic MEMS microstages at low operating voltages. The MEMS lens scanner was integrated on a printed circuit board and packaged with an aluminum housing, a gradient index fiber collimator, and an objective lens. A home-built spectral-domain OCT system with 60 kHz A-line acquisition rate was combined with the endoscopic MEMS catheter. Three-dimensional images of 256×256×995 voxels were directly reconstructed by mapping the A-line datasets along the Lissajous patterns. The endoscopic catheter can provide a new direction for forward endoscopic OCT imaging.

Solving inverse problems for optical scanning holography using an adaptively iterative shrinkage-thresholding algorithm

Optical scanning holography (OSH) records a three-dimensional object into a two-dimensional hologram through two-dimensional optical scanning. The recovery of sectional images from the hologram, termed as an inverse problem, has been previously implemented by conventional methods as well as the use of l₂ norm. However, conventional methods require time consuming processing of section by section without eliminating the defocus noise and the l₂ norm method often suffers from the drawback of over-smoothing. Moreover, these methods require the whole hologram data (real and imaginary parts) to eliminate the twin image noise, whose computation complexity and the sophisticated post-processing are far from desirable. To handle these difficulties, an adaptively iterative shrinkage-thresholding (AIST) algorithm, characterized by fast computation and adaptive iteration, is proposed in this paper. Using only a half hologram data, the proposed method obtained satisfied on-axis reconstruction free of twin image noise. The experiments of multi-planar reconstruction and improvement of depth of focus further validate the feasibility and flexibility of our proposed AIST algorithm.

A Method to Measure Beam Deflections in Different Resonance Modes Piezoresistively and its Incorporation into 2D Optical Microscanners

This paper describes a sensing technique to detect beam deflections caused by the two different vibration modes, i.e. bending and torsion modes of a micro cantilever, separately with two piezoresistor bridge circuits. Fabrication process to incorporate this detection circuitry into a two-dimensional optical microscanner together with the signal processing circuitry for self-sustaining vibrations are presented, which enables a compact feedback control of the two-dimensional optical scanning. Prototype optical scanners with this detection circuitry and magnetostirictive actuation have been fabricated with MEMS technology and tested to verify this technology.

Scanning ultrafast Sagnac interferometry for imaging two-dimensional surface wave propagation

We describe an improved two-dimensional optical scanning technique combined with an ultrafast Sagnac interferometer for delayed-probe imaging of surface wave propagation. We demonstrate the operation of this system, which involves the use of a single focusing objective, by monitoring surface acoustic wave propagation on opaque substrates with picosecond temporal and micron lateral resolutions. An improvement in the lateral resolution by a factor of 3 is achieved in comparison with previous setups for similar samples.

Micro XY stages with spider-leg actuators for two-dimensional optical scanning

We propose a micromachined XY stage consisting of eight ‘L’ shaped (spider-leg) stage-suspension springs and rotational comb-drive actuators for two-dimensional microlens scanner. The new design features rotational comb drives that are attached to the rotational hinge, where the movement of the comb drive is constrained to rotation only. The mechanism ensures stable and satisfactory in-plane motion. We designed a microlens-type optical scanner utilizing the spider-leg actuator. Silicon was used as a lens material because it is mechanically stable and optically transparent to infrared light around the wavelength of 1.55 μm. The microlens scanner was fabricated by lens-profile-transferring to the structural layer of a silicon on insulator (SOI) wafer by the reactive ion etching (RIE) from thermally reflowed photo resist (PR) and continuing two deep RIEs. The XY stage moved more than 55 μm independently in the X and Y directions with applied voltage of 40 V. The optical coupling loss between the faced microlens-pair showed 10.5 dB with microlenses of a 1 mm diameter, which can be applied to the optical cross connect (OXC).

Axial and radial development of microdischarges of barrier discharges in N2/O2 mixtures at atmospheric pressure

Microdischarges (MDs) of filamentary barrier discharges (BDs) in air and N2/O2 gas mixtures at atmospheric pressure were investigated using the techniques of spatially resolved cross-correlation spectroscopy (CCS) and short exposure time photography (ICCD-camera). The BDs were generated in symmetric discharge cells (configuration of the type ‘glass–glass’) with two semi-spherical electrodes in order to localize the repetitive MDs at a fixed position. In the case of CCS measurements, the MD development was imaged through spatio-temporal distributions of the radiation intensity of the (0–0) transition of the 2nd positive system of molecular nitrogen (λ = 337 nm). Two-dimensional optical scanning of the MD channel (in the axial and radial directions of the MD) was carried out for a BD operated in a gas mixture consisting of 6 vol% O2 and 94 vol% N2. This gas composition had been found to provide the extremely high stability of the discharge that was necessary for the time-consuming scanning procedure. In the middle of the gap, the MD channel diameter was found to be about 0.3 mm and to expand towards both electrodes. With dielectrics, outward propagating discharges were observed. Short exposure time photos of the MDs taken using an ICCD-camera under the same experimental conditions as for the CCS measurements revealed a branched structure of these discharges on the surfaces, not only on the cathode but on the anode as well. The influence of voltage amplitude on the spatio-temporal distribution of individual MDs of a BD in air was investigated using the CCS-instrument operated in a so-called ‘direct start–stop’ mode which enabled statistical analysis of the MD sequences within a time range of about 30 µs.

Scanning heterodyne optical interferometers

Compact, high performance, scanning heterodyne optical interferometers are introduced for interferometric phase-based measurement applications. The novel, in-line, almost common-path optical interferometer design offers robustness to externally induced phase noise via mechanical vibrations, thermal effects, and other environmental effects. Novel instrument designs are introduced for both transmissive and reflective interferometry. These instruments use acousto-optic devices or Bragg cells to implement rapid (e.g., <50 μs/scan spot) optical scanning of the test medium. Although the read optical beam scans a given test region, the double Bragg diffraction optical design of the instrument makes the final interfering output beams stationary on the two high speed photodetectors used for radio frequency signal generation via heterodyne detection. One photodetector acts as the fixed phase reference, while the other fixed photodetector picks up the test medium phase information as the optical beam scans the test region. The transmissive design instrument is built in the laboratory using flint glass Bragg cells. A typical 120 MHz heterodyne detected signal output had a carrier-to-noise ratio of 108.9 dBc/Hz measured at a +160 kHz offset using a spectrum analyzer resolution bandwidth of 30 kHz. The corresponding single-sideband phase noise was estimated at −101.57 dBc/Hz at 160 kHz offset. The measured instrument radio frequency dynamic range was ∼60 dB or an equivalent of 30 dB optical dynamic range, with a 1/1000 of a fringe cycle phase measurement accuracy. Test medium optical phase mapping was successfully tested with the instrument using a large area, 6 μm thick, birefringent-mode nematic liquid crystal cell. Our instrument allows the use of high continuous wave or peak power, broad spectral linewidth, coherent light sources. The instrument can have a high 50% optical power efficiency. High speed two-dimensional optical scanning of a test medium is possible with our instrument by using a fixed one-dimensional output high speed detector array, or via the use of high speed nonmechanical electro-optic deflectors.

Development of a Miniature Two-Dimensional Optical Scanner. 1st Report. Scanning Principle and Fundamental Performances.

A new miniature two-dimensional optical scanner is proposed as part of the work to reduce the size of conventional scanners and to realize two-dimensional optical scanning of a large area. The proposed miniature optical scanner is composed of a small two-dimensional resonator made of a single-crystal silicon plate 0.2 mm thick and a 5 mm×5 mm×10 mm multilayer piezoelectric actuator to excite the resonator; the size of the external form is 15 mm×15 mm×10 mm. The resonator can vibrate in two orthogonal directions due to the bending and torsional vibrations of a small plate spring which supports the resonator, and can then reflect a laser beam two-dimensionally onto a mirror surface which is fabricated on the resonator. The natural frequencies of bending and torsional vibrations are greatly different from each other, namelys 288 Hz and 121Hz, respectively, and the Q-values of those vibrations are also very high, about 200 and 150, respectively. The horizontal, vertical or two-dimensional directions of the optical scan can thereby be easily switched by selecting and controlling the driving frequency of the piezoelectric actuator, and a large optical scanning area, 10 degrees and 16 degrees in horizontal and vertical directions, respectively, is obtained.