Range Finder Systems Research Articles

Review of Piezoelectric Micromachined Ultrasonic Transducers for Rangefinders

Piezoelectric micromachined ultrasonic transducer (pMUT) rangefinders have been rapidly developed in the last decade. With high output pressure to enable long-range detection and low power consumption (16 μW for over 1 m range detection has been reported), pMUT rangefinders have drawn extensive attention to mobile range-finding. pMUT rangefinders with different strategies to enhance range-finding performance have been developed, including the utilization of pMUT arrays, advanced device structures, and novel piezoelectric materials, and the improvements of range-finding methods. This work briefly introduces the working principle of pMUT rangefinders and then provides an extensive overview of recent advancements that improve the performance of pMUT rangefinders, including advanced pMUT devices and range-finding methods used in pMUT rangefinder systems. Finally, several derivative systems of pMUT rangefinders enabling pMUT rangefinders for broader applications are presented.

A Digital Signal Processing System for Terrestrial Laser Range Finding Systems

This paper presents a digital processing system for terrestrial laser range finding systems. It is mainly comprised of a commercial digital signal processor with 400 MHz. For the signal digitization, an analog-to-digital converter with a 12-bit resolution is sampled with 50 MS/s. Such a digital system architecture has several advantages: automatic gain control, coherent multi-pulse averaging, digital signal filtering, upsampling, and advanced peak detection methods. When combined with a suitable laser and detector unit, the digital system outperforms the classic analog threshold-based laser finders with regard to required laser output power, multitarget discrimination, and peak detection accuracy. The best results were achieved using a matched filter, compared to wavelet denoising techniques and classic Savitzky-Golay filtering. Finally, this system architecture allows for a small-sized, lightweight, battery-operated, and energy-efficient, class 1 eye-safe laser range finder, capable of measuring distances up to multiple km with accuracy and precision of better than 1 m to uncooperative targets.

Continuous-wave Laser on Er,Yb-Codoped Pentaborate Crystal

We report, for the first time to our knowledge, a diode-pumped continuous-wave microchip Er,Yb:YMgB5O10 laser. The purpose of this work was to study the growth technique, spectroscopic properties and continuous-wave laser performance of Er3+,Yb3+:YMgB5O10 novel crystal. Absorption and luminescence spectra as well as kinetics of luminescence decay were studied. Ytterbium-erbium energy transfer efficiency was determined. The output characteristics (output power, slope efficiency, laser wavelength) of Er3+,Yb3+:YMgB5O10 laser were determined.Two intensive absorption bands with peaks centered at 937 nm and 976 nm were observed in the absorption spectra at the wavelength near 1 μm. The maximum value of absorption cross-section was determined to be 1.5·10–20 cm2 at 976 nm for polarization E//Ng . A number of narrow lines were observed in the absorption spectra in the 1425–1575 nm spectral range (transition 4I15/2 → 4I13/2 of erbium ions). The lifetime of the upper laser level 4I13/2 of Er3+ ions was determined to be 390 ± 20 μs. The ytterbium-erbium energy transfer efficiency for YMgB5O10 crystal with 2 at.% of Er3+ and 11 at.% for Yb3+ was close to 84 %. The maximal continuous-wave output power of 0.2 W with slope efficiency of 8 % regarding to absorbed pump power was realized at the wavelength of 1570 nm. With the improvement of cavity parameters the output laser performance of the Er,Yb:YMgB5O10 crystal can be further enhanced.Taking into account high thermal conductivity of ≈ 6.2 W·m–1·K–1, the Er,Yb:YMgB5O10 crystal can be considered as a good gain medium for 1.5 μm lasers for applications in laser rangefinder and LIDAR systems.

Segmentation-Based Color Channel Registration for Disparity Estimation of Dual Color-Filtered Aperture Camera.

Single-lens-based optical range finding systems were developed as an efficient, compact alternative for conventional stereo camera systems. Among various single-lens-based approaches, a multiple color-filtered aperture (MCA) system can generate disparity information among color channels, as well as normal color information. In this paper, we consider a dual color-filtered aperture (DCA) system as the most minimal version of the MCA system and present a novel inter-color image registration algorithm for disparity estimation. This proposed registration algorithm consists of three steps: (i) color channel independent feature extraction; (ii) feature-based adaptive weight disparity estimation; and (iii) color mapping matrix (CMM)-based cross-channel image registration. Experimental results show that the proposed method can not only generate an accurate disparity map, but also realize high quality cross-channel registration with a disparity prior for DCA-based range finding and color image enhancement.

Analysis of object positioning accuracy provided by range-finding systems of various types

The accuracy of determining the aircraft coordinates by range-finding systems of various types was analyzed. Consideration was given to cooperative processing of range-finding, aggregate and difference range measurements made by multilateral surveillance systems..

Femtosecond laser range finders based on traditional cross correlation method and frequency resolved dispersion compensation method

In order to realize high range accuracy, two laser range finder systems using broadband femtosecond lasers as optical sources are discussed and compared in detail. One system uses a traditional cross correlation method, and the other system uses a frequency resolved dispersion compensation method. Better than 0.65μm distance accuracy and ambiguity range of pulse-to-pulse separation can be realized in both systems. In the system using the traditional cross correlation method, submicron step resolution of the scanning system should be maintained to yield an authentic cross correlation graph. While in the system using the frequency resolved dispersion compensation method, no scanning system is required as the signal is spectrally resolved into several channels and the process is finished in software. In the system using the frequency resolved dispersion compensation method, the influence of channel number is much more significant than that of channel spacing and individual channel bandwidth. And the channel spacing should be a multiple integral of the laser repetition rate to facilitate the measurement; otherwise the optical path difference must be controlled to less than a pulse-to-pulse separation. Both systems are well suited to the range lidar requiring submicron distance accuracy, and can be applied in the future space missions.

Precision rangefinders based on a two-wave injection laser

Recirculation and pulse-phase methods of measuring the range, based on a two-wave injection laser, are proposed for precision laser rangefinder systems. The radiator of the rangefinder consists of a laser diode with an asymmetric quantum-size heterostructure that generates probe radiation at two different wavelengths, depending on the pump current. The system makes it possible to obtain information on the propagation rate of radiation in the medium along the observation line and to take into account its value when calculating the range from the optical delay, and this enhances the distance-measuring accuracy.

3D reconstruction and visualization [Guest Editors' Introduction

We have entered an era where the acquisition of 3D data is ubiquitous, continuous, and massive. These data come from multiple sources including high-resolution, geo-corrected imagery from aerial photography and satellites; ground-based close-up images of buildings and urban features; 3D point clouds from airborne laser rangefinding systems, such as Lidar; imagery from synthetic aperture radar; and other sources. To make these data really useful, they should be employed to model the real world, and the model should then be available for interactive exploration and analysis. However, the modeling aspect is not straightforward since almost all the collected data has holes (due to obstructions or poor acquisition conditions), and no single acquisition mode is likely to produce complete models. The overall modeling problem is then one of fusing multisource data consistently and accurately. As acquisition modes are automated and models are produced, there will be an exponential explosion in the amount of data available for analysis and exploration. Based on these needs and issues, we formulated this special issue, which provides a sampling of the latest and most interesting research in several of these areas. The articles included are briefly summarized.

Robot navigation inspired by principles of insect vision

Recent studies of insect visual behaviour and navigation reveal a number of elegant strategies that can be profitably applied to the design of autonomous robots. The peering behaviour of grasshoppers, for example, has inspired the design of new rangefinding systems. The centring response of bees flying through a tunnel has led to simple methods for navigating through corridors. Experimental investigation of the bee's “odometer” has led to the implementation of schemes for visually driven odometry. These and other visually mediated insect behaviours are described along with a number of applications to robot navigation.

Introduction To The Feature Issue On Recent Advances In Lithium Niobate Optical Technology

HE functionality of waveguide and bulk LiNbO optical devices has increased dramatically over the past few years. Recent advances in the technologies of rare-earth doping and domain engineering in this material have demonstrated the potential for commercially attractive lasers and nonlinear optical sources which are compact, efficient, inexpensive, and manufacturable. These devices could find use in a wide range of applications including telecommunications, range finding, military counter measures, optical data storage, remote sensing, and reproduction graphics. Although there have been many excellent papers highlighting research into these various applications, the aim of the invited collection given here is to present work which illustrates the transition from research to potential commercialization. Readers are encouraged to explore the many references to related work cited in these papers. Highlights of the invited collection include the following. • Diffusion-doped Er:LiNbO waveguide laser sources that are packaged, pigtailed, and compatible with fiber sysPublisher Item Identifier S 0018-9197(97)07561-1. tems. This includes tunable lasers for WDM applications and pulsed lasers for soliton sources. • Bulk-doped Nd: and Er:LiNbO waveguide lasers illustrating active mode-locking and -switching. • Numerical modeling of -switched Er-doped waveguide lasers which may assist in the design of eye-safe rangefinding systems • Domain-engineered second harmonic generating sources in bulk and waveguide geometries for visible light generation with emphasis on stability of pump sources and packaging. • Domain-engineered optical parametric oscillators fabricated in bulk LiNbO that operate in the 3‐4- m range with greater than 3 W of CW output power.

Integrated sensor and range-finding analog signal processor

The authors present experimental results from an array of cells, each of which contains a photodiode and the analog signal-processing circuitry needed for light-stripe range finding. Prototype circuits were fabricated through MOSIS in a 2- mu m CMOS p-well double-metal, double-poly process. This design builds on some of the ideas that have been developed for ICs that integrate signal-processing circuitry with photosensors. In the case of light-stripe range finding, the increase in cell complexity from sensing only to sensing and processing makes the modification of the operational principle of range finding practical, which in turn results in a dramatic improvement in performance. The IC array of photosensor and analog signal processor cells that acquires 1000 frames of light-stripe range data per second-two orders of magnitude faster than conventional light-stripe range-finding methods. The highly parallel range-finding algorithm used requires that the output of each photosensor site be continuously monitored. Prototype high-speed range-finding systems have been built using a 5*5 array and a 28*32 array of these sensing elements.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

WATSON/I: WATerloo's SONically guided robot

Watson is designed to act as a messenger robot carrying mail and parcels between the rooms of an office building. To find its way, the navigation subsystem must send ultrasonic waves, under program control, and measure the proximity of objects in the environment. This information can then be used in planning the next move which is passed to the drive subsystem. The drive subsystem, also under program control, must translate moves into independent rotations of the two drive wheels. The drive subsystem can be programmed to measure the actual wheel rotations and correct local deviations from the planned course, while the navigation subsystem is in overall control. The main motive behind the design of Watson is that of building an aid to teaching and research. As an aid to teaching, it provides the students with a programmable machine of manageable complexity with tangible interfaces to the real world. This kind of programming experience, though in great need, is not easily gained through the conventional modes of access to computers. Watson also provides researchers with a tool for investigating the potential of using inexpensive sonar range finding systems in the navigation of mobile robots. Such robot's view of the world is that of a flatland. Flatlands have properties of theoretical interest and Watson should prove useful as a vehicle for testing these properties. This paper deals with the description of the hardware and programming model of Watson.

Integrated Laser/Radar Satellite Ranging and Tracking System

A laser satellite ranging system that is mounted upon and integrated with a microwave tracking radar is reported. The 1-pulse sec/ruby laser transmitter is attached directly to the radar's elevation axis and radiates through a new opening in the radar's parabolic dish. The laser photomultiplier tube receiver utilizes the radar's existing 20-cm diam f11 boresight telescope and observes through a similar symmetrically located opening in the dish. The laser system possesses separate ranging system electronics but shares the radar's timing, computer, and data handling[equation]recording systems. The basic concept of the laser[equation]radar is outlined together with a listing of the numerous advantages over present singular laser rangefinding systems. The developmental laser hardware is described along with preliminary rangefinding results and expectations. The prototype system was assembled to investigate the feasibility of such systems and aid in the development of detailed specifications for an operational system. Both the feasibility and desirability of such systems integrations have been adequately demonstrated.

YAG:Nd^+3 Laser Target Designators and Range Finders

This paper describes the implementation of a Q-switched YAG:Nd(+3) laser into target designator and range finder systems. Because of the wide range of temperature encountered in field applications, emphasis is given to the development of a temperature insensitive design incorporating electronic compensation and thermal equalization. Information is also given on cooling systems and degradation of the coolant when subjected to intense uv radiation. Developments anticipated in the near future that will have considerable impact on laser target designators and range finders are listed.

Performance Prediction of Range Finder Systems

Starting with the threefold concept of a range finder system, target, range finder, and operator, equations are developed and explained which enable prediction of performance of such a system, based on assumed parameters, in terms of probability versus range. Two cases are discussed: (1) when the range finder system is used by itself and performance criterion is expressed as some small percentage of the true range, and (2) when the range finder is used in conjunction with a weapon system and performance criterion relates to the probability of obtaining hits on vertical targets at various distances from the range finder—weapon system combination.