Range Finding Applications Research Articles

Application of Laser Scanning in Internal Surveying of Premises and Development of 3D Model of Building

Nowadays, along with the classical and experienced surveying methods, modern technologies are rapidly developing and entering into the economy. Laser scanning has many benefits and uses. Application of this technology results in a point cloud from which it is possible to create three-dimensional models which can represent topographic properties, structure dimensions, and spatial relationships. The aim of the research is to investigate the application of three-dimensional laser scanning in the internal surveying of premises and in the development of the 3D model buildings. The task of the research is to apply the application of laser rangefinder and ultrasonic rangefinder method in the scanning of a building that is characterized by complex architecture, an interior garden, many protrusions, and a special layout of windows and doors. The use of the Stonex X300 laser scanner and Stonex M6 laser rangefinder has been described as well. To achieve the goals and objectives of the research, laser telemetry and ultrasonic telemetry method, method of three-dimensional modeling, as well as analysis of scientific literature, mathematical calculation methods, and analysis of documents and factual materials have been used. As the result of the investigation 3D model of a building consisting of 47 individual point clouds was developed. The main conclusion is that three-dimensional modeling as a computer graphics method for the three-dimensional representation of any object or surface can be used.

Piezoelectric Micromachined Ultrasonic Transducers with a Cost-Effective Bottom-Up Fabrication Scheme for Millimeter-Scale Range Finding

This study proposes a novel piezoelectric micromachined ultrasonic transducer (PMUT), fabricated on a metal foil. Using a bottom-up, cost-effective micromachining technique, the PMUTs made of electrodes, a piezoelectric film, or electrode-sandwiched structures with versatile patterns were implemented on a large-area foil thinner rather than regular paper. The proposed microfabrication facilitated the PMUT to be able to generate ultrasonic waves with fundamental and harmonic resonances. The fourth-order resonances of the fabricated PMUT functionally operated at an ultrasonic spectrum of approximately 30 kHz as an ultrasonic emitter. The developed PMUT was paired with a microelectromechanical system (MEMS) microphone module for range-finding applications in the range of several tens of millimeters. A signal-processing scheme was developed to extract the representative pattern from the acquired signals that were emitted and received. The pattern enabled finding the distance between the PMUT and the microphone using time-of-flight and strength-variation technology. The developed PMUT-microphone pair demonstrated its range-finding performance, displaying an error of less than 0.7% using the time-of-flight method.

Miniaturized pulsed laser source for time-domain diffuse optics routes to wearable devices.

We validate a miniaturized pulsed laser source for use in time-domain (TD) diffuse optics, following rigorous and shared protocols for performance assessment of this class of devices. This compact source (12×6 mm2) has been previously developed for range finding applications and is able to provide short, high energy (∼100 ps, ∼0.5 nJ) optical pulses at up to 1MHz repetition rate. Here, we start with a basic level laser characterization with an analysis of suitability of this laser for the diffuse optics application. Then, we present a TD optical system using this source and its performances in both recovering optical properties of tissue-mimicking homogeneous phantoms and in detecting localized absorption perturbations. Finally, as a proof of concept of in vivo application, we demonstrate that the system is able to detect hemodynamic changes occurring in the arm of healthy volunteers during a venous occlusion. Squeezing the laser source in a small footprint removes a key technological bottleneck that has hampered so far the realization of a miniaturized TD diffuse optics system, able to compete with already assessed continuous-wave devices in terms of size and cost, but with wider performance potentialities, as demonstrated by research over the last two decades.

Few-Layer Black Phosphorus Carbide Field-Effect Transistor via Carbon Doping.

Black phosphorus carbide (b-PC) is a new family of layered semiconducting material that has recently been predicted to have the lightest electrons and holes among all known 2D semiconductors, yielding a p-type mobility (≈105 cm2 V-1 s-1 ) at room temperature that is approximately five times larger than the maximum value in black phosphorus. Here, a high-performance composite few-layer b-PC field-effect transistor fabricated via a novel carbon doping technique which achieved a high hole mobility of 1995 cm2 V-1 s-1 at room temperature is reported. The absorption spectrum of this material covers an electromagnetic spectrum in the infrared regime not served by black phosphorus and is useful for range finding applications as the earth atmosphere has good transparency in this spectral range. Additionally, a low contact resistance of 289 Ω µm is achieved using a nickel phosphide alloy contact with an edge contacted interface via sputtering and thermal treatment.

3 nJ, 100 ps laser pulses generated with an asymmetric waveguide laser diode for a single-photon avalanche diode time-of-flight (SPAD TOF) rangefinder application

An asymmetric waveguide laser diode with a thick active layer operated with enhanced gain switching is shown to be able to produce ∼100 ps, ∼25 W optical pulses in fundamental transverse mode with ∼15 A, ∼1.5 ns injection current pulses. A pulsed time-of-flight distance measurement demonstration utilizing this laser diode and a SPAD detector indicates centimetre-level precision and compensated accuracy from uncooperative targets at tens to hundreds of metres in a measurement time of a fraction of a second.

The Passively Q-switched Microchip Nd:YAG Laser Optimization for Rangefinder Applications

The Passively Q-switched Microchip Nd:YAG Laser Optimization for Rangefinder Applications

Electrowetting retroreflectors: Scalable and wide-spectrum modulation between corner cube and scattering reflection

Corner cube and spherical retroreflectors are ubiquitous in conspicuity and range-finding applications since they reflect light back to the illumination source with unmatched efficiency. We report here a switchable electrowetting retroreflector platform that provides multiple novel features, including (a) using <0.5 μJ/cm2 electrical energy to switch from a light scattering state, (b) low loss and wide spectrum as limited only by the absorption spectrum of water, (c) use of ultrasimple self-assembly of 103–105 liquid lenslets/in.2 on a polymer/Al corner-cube substrate, and (d) change in retroreflected irradiance of >10:1 over a ±30° field of view.

Far-field timing effects with passively Q-switched lasers

Pulse-timing effects in the far field of a passively Q -switched microchip laser that are caused by the changing cavity mode during pulse emission are described. Measurements are performed on a passively Q -switched Nd:YAG laser that produces 3-ns pulses, and delays in pulse arrival times of up to ~270 ps are observed between the center and the off-axis position. The measured data agree well with a simple analytical model. Pulse delays of this order are important, for instance, in high-precision range-finding applications.

A coarse/fine search PN code acquisition scheme

A parallel two-stage acquisition technique is described for direct sequence spread spectrum (DS/SS) range finding applications. The technique offers hardware complexity that scales better with code length than matched filter correlators while providing better performance than sequential detection using comparable hardware.

Pn photodiodes for pulsed laser rangefinding applications realized in standard CMOS/BiCMOS processes

This paper describes simulation of the operation of integrated high-speed pn photodiodes and verification of the results by means of measurements performed with two types of photodiode, one implemented in a standard 0.8 μm CMOS process and the other in a standard 1.2 μm BiCMOS process. The measured rise times and responsivities of the photodiodes were <5 ns and 0.28 A/W in the CMOS process and 30 ns and 0.31 A/W in the BiCMOS process. Furthermore, the suitability of the photodiode for 3D vision was investigated by designing an array of photodetectors and measuring the isolation between the detector blocks. The results confirm that the photodetectors and receiver for a pulsed laser rangefinder can be implemented on the same chip in a standard process without any process modifications.

Absolute distance measurement with an optical feedback interferometer

An important use of the self-mixing effect inside a frequency-modulated single-mode laser diode is in laser velocimetry and range-finding applications. The optical beam reflected by a target and injected into the laser diode cavity modulated by a reshaped current is mixed with the light inside the cavity, causing variations of the optical output power. A theoretical analysis of this effect is proposed, based on the determination of the beat frequencies of the optical power variations, to improve the accuracy of laser distance measurement. A resolution of ?1.5 mm from 50 cm to 2 m is obtained when thermal effects are taken into account.

Two-wavelength laser interferometry using superheterodyne detection

In two-wavelength interferometry, synthetic wavelengths are generated in order to reduce the sensitivity or to extend the range of unambiguity for interferometric measurements. Here a novel optoelectronic technique, called superheterodyne detection, is presented, which permits measurement of the phase difference of two optical frequencies that cannot be resolved by direct optoelectronic heterodyne detection. This technique offers the possibility for operation of two-wavelength interferometry in real time with arbitrary synthetic wavelengths from micrometers to meters in length. Preliminary experimental results are reported. An optical arrangement for absolute range-finding applications using tunable-laser sources (e.g., semiconductor lasers) is proposed.

Optical range finder for 15–10-m distances

A time of flight method is suggested for measuring distances in large manipulator range-finding applications. Light pulses of a SH laser diode are used. Special attention was paid to reducing the pulse amplitude variations in the transit time measurement. Preliminary results with a prototype have proved the method to be highly usable in measuring position, orientation, and shape of the objects within a 1.5–10-m range. The resolution of the distance measurement is ±1 mm with a measuring time of 10 msec.

A compact time measuring unit for use with a laser range finder

A time measuring unit is described which is useful for incorporating in portable laser range finders. The unit possesses some special features which are essential for range finding applications. These include, among others, minimum range gating and multiple target discrimination.

Noise measurements on germanium avalanche photodetectors

In this paper the overall-noise in a photodetection system, consisting of a Germanium avalanche-photodiode and a low-noise amplifier is determined. It turns out, that the main contributions to the overall-noise stem from the bulk- and guardring leakage currents and from the amplifier. The main parameter of interest for laser rangefinder applications is the noise-equivalent signal current, being equal to the peakvalue of the equivalent noise current at the amplifier input, divided by the avalanche multiplication factor. It turns out, that the optimum bias conditions for low-noise operation are rather temperature dependent. It is argued that current control is preferable to voltage control in order to stabilize against temperature variations. The optimum bias conditions and the corresponding minimum noise-equivalent signal currents are measured as functions of the ambient temperature. Besides the noise measurements the dynamic responses of some types of photodetectors are compared. It turns out, that various types of photo-responses are possible, dependent on the construction details of the device.

A Discussion on recent research in air pollution - The application of a pulsed-light rangefinder (lidar) to the study of chimney plumes

Lidar observations, depending on the detection of backscatter from a pulse of light by particles along its path, have been used to study chimney plumes and their environment. Important technical improvements to the basic equipment have included the use of swept gain and the development of a brightness modulated display. A number of examples of lidar scans through plumes are presented to demonstrate the value of the improved display. Lidar observations of plumes over periods of about an hour have been used to predict the concentration of pollution at the ground. In neutral conditions, the predictions were significantly better than predictions based only on meteorological data. Observations of the rise and growth of a plume have suggested that, in the equation of motion describing the rise of a plume element, the rate of change of upward momentum should be equated to about one-half rather than the whole of the buoyancy force. Finally, a technique of analysis leading to vertical profiles of aerosol concentration in the lower layers of the atmosphere is outlined. These profiles often reveal features that are vital to a full understanding of plume behaviour.