The Differential Absorption Lidar (DIAL) method is reviewed and performance evaluations are presented for a NO₂ detection system. Discussions on the preferred wavelengths for candidate gases, and a review of a new laser radar DIAL performance equation are presented. Applications in the areas of drug interdiction, forest fire detection and combustion research, and military uses are discussed.

The passage of commercial and military aircraft through invisible fresh volcanic ash clouds has caused damage to many airplanes. On December 15, 1989 all four engines of a KLM Boeing 747 were temporarily extinguished in a flight over Alaska resulting in $DOL80 million for repair. Similar aircraft damage to control systems, FLIR/EO windows, wind screens, radomes, aircraft leading edges, and aircraft data systems were reported in Operation Desert Storm during combat flights through high-explosive and naturally occurring desert dusts. The Defense Nuclear Agency is currently developing a compact and rugged lidar under the Aircraft Sensors Program to detect and estimate the mass density of nuclear-explosion produced dust clouds, high-explosive produced dust clouds, and fresh volcanic dust clouds at horizontal distances of up to 40 km from an aircraft. Given this mass density information, the pilot has an option of avoiding or flying through the upcoming cloud.

The Phillips Laboratory is developing CO₂ laser technology for making long range sensing measurements at multiple wavelengths in the 9 - 11 micron regime. A line selectable CO₂ system that operates on both the P and R transitions at 9.6 and 10.6 microns is described. The device characteristics and laboratory calibration procedures designed to insure accurate measurements are discussed. The system is capable of making atmospheric gas measurements using either atmospheric backscatter or topographic reflection. Results of laboratory measurements using an SF₆ absorption cell are presented. The techniques for data reduction and post processing are described. Included is the approach taken to perform the data reduction using multiple wavelengths for gas analysis and identification. Results will be used for design of a high power airborne system designed for a variety of military and environmental applications.

In single-shot laser radar speckle noise, drop-outs, outliers, and eventually, non-cooperative targets are to be considered in order to ensure high accuracy and reliability of measurement data. The most common approach for the stabilization of laser radar data is temporal averaging over several shots. This, however, is not in all cases the best method for the reconstruction of noisy imagery data. It is shown that principal-component filtering can yield a remarkable improvement of accuracy and robustness of range data.

This paper studies range images of man-made objects in outdoor environments. Our objective is to give the description of terrain, separate man-made objects from background and localize it. With the aim of this, a slope surface fitting method is proposed and applied to homogeneous dense high images derived from the range images, then a terrain description is constructed and the object detection algorithm is proposed. The final results show that our method works effectively.

One of the most important aspects in the navigation of ALV is computer vision or machine vision. Usually, it is achieved by using multisensor fusion technology. As we know, laser radar is a typical sensor in this project, especially in the situation that there is an obstacle in a road. It is often effective to describe the relationship between road and obstacle by using height matrix from range data. However, when the front view is more complicated, such as a wall or a building on which exists a hole or a corridor big enough for ALV to go through, the above method may not be well done. For this reason, we propose a novel approach by using two matrixes from the range data to solve the problem. The main idea is that from the range data we figure out two matrixes, one is the height matrix, representing the height of the object from the horizontal plane, the other is the depth matrix representing the depth of the object from the laser radar vertical plane. By using the information of both height and depth, we can understand the front environment more precise and better.

In the field of laser radars, there has been limited work on long-wave pulse-burst waveforms with pulse widths in the nanosecond regime. This waveform has several advantages over other waveforms, e.g., excellent range resolution with small doppler ambiguities. Phillips Lab has developed a flexible ladar to provide the means of obtaining images and signatures of hard body objects under controlled laboratory conditions. The transmitter laser is also capable of frequency agility operation to support remote sensing experiments. A coherent, pulse-tone, pulse-burst CO₂ TEA laser radar operating at 10.6 micrometers is described. The pulse train is obtained by actively mode locking with an intracavity germanium standing wave acousto- optic modulator. Approximately two hundred pulses per burst are transmitted at a repetition rate of 83 MHz. Injection seeding and cavity matching produces a pulse tone waveform. An overall transceiver system bandwidth of 1 GHz is employed. The device was developed as a flexible platform to support scaled risk reduction and phenomenology experiments.

Scanning objects in an extended scene or large architectural structures, i.e., building, bridges, etc., is an essential task for numerous applications. In this paper we present the concept of a chirped laser radar with a range of up to 100 m and a design resolution of 3 (DOT) 10^-5 realized with an optoelectronic signal processor. The scanning signal is a 1 microsecond(s) long chirped pulse with 100 MHz bandwidth, centered at 300 MHz. This signal is generated by a voltage controlled oscillator that is driven by a direct digital synthesizer (DDS). The DDS facilitates the generation of a signal of the required quality. We present the design concept of an external optronic modulator (OM) consisting of two Bragg cells, capable of intensity modulation of incoherently superimposed laser radiation of different wavelengths. The properties of the chirp signal are used on the OM. The return signal is analyzed via an optoelectronic signal processor that measures the time delay between the target signal and the reference signal. The optoelectronic signal processor consists of two Bragg cells and has two different output channels. Both channels evaluate the time delay of the two signals from the compressed pulses. In this paper we present the evaluation of both channels. First experimental results indicate that the signal analysis gives a resolution of 5 (DOT) 10^-4. The evaluation of the second channel is not entirely completed yet. We present experimental results achieved with the radar using a single laser diode, which is intensity modulated by variation of the diode current, and scanning of co-operative targets.

Due to underestimation of rough surface scattering at retro-reflection direction, consideration of enhanced backscattering (i.e. opposition effect) can be critically important in developing laser radar signatures. This is illustrated by the comparison of two signature models of the same airplane--one developed using bidirectional reflectance measurement data at one degree from the retro-direction, and the other developed from monostatic measurement data at true retro-direction. The unique instrument used to obtain the laser reflectance data, the reflectance data itself, and the software ensemble used to develop the signature are described and discussed.

According to optical basic theory, an analytical solution for nonlinearity of the scanning with tetrahedral column rotation mirror is obtained, and a nonlinear curve of the rotating mirror scanning is given. On the basis of the theoretical analysis, a single-chip double-face-mirror two-dimension scanning system is designed, and this system can overcome effectively the nonlinear feature of the polyhedral column rotating-mirror pendulum-mirror system, and also bring a convenience for succedent real-time image treatment by computer.

The Optical Radar System (ORAS) provides a complete set of data to derive three-dimensional surface contours of bodies or of body-like scenes primarily in industrial environment. In addition, the intensity as back-scattered from the object is recorded in order to create combined (3-D and conventional) images for special tasks in object characterization. ORAS as described in this paper is based on the time of flight principle. Its specifications, measurement results and applications are presented.

Scanning objects in an extended scene or large architectural structures, such as buildings, is an essential task used in numemus applications. In this paper we present the concept of a chirped laser radar with a range of 100 m and a design resolution of 3•iO that exhibits an optoelectronic signal processing. The scanning signal is a 1 jis long chirped pulse with 100 MHz bandwidth and is centered at 300 MHz. This signal is generated by a voltage controlled oscillator (VCO) that is driven by a direct digital synthesizer (DDS). The requirements imposed on the quality of the chirped signal are very high. These include temperature stabilization of the VCO and a programmed correction of its non-linear frequency response. The DDS facilitates the generation of a clean signal of the desired quality. The return signal is analyzed via an optoelecironic signal processor that measures the time delay between the target signal and the reference signal. The optoelectronic signal processor consists of two Bragg-cells and has two different output channels. Both channels evaluate the time delay of the two signals from the compressed pulses. In this paper we present the evaluation of the first channel, that measures this delay as a function of time. First experimental results indicate that the signal analysis of this channel gives a resolution of 5 lO. The evaluation of the second channel is not entirely completed yet. We present experimental results achieved with the radar using a single laser diode, which is intensity modulated by variation of the diode current, and scaiining of co-operative targets.

The realisation of a coherent frequency modulated continuous wave LIDAR aimed for the accurate measurement of short distances employing a distributed feedback tunable twin-guide laser diode is demonstrated. A single shot relative accuracy of 8*105 (8jim) has been achieved at a distance of 10cm. The results presented here prove the predictions calculated from theory.

The evaluations of limiting LFM-CW-Lidar's performances are obtained. The comparison of different ways of gas pollutions monitoring are represented. The probing lasers energetics and modulation unstability's and nonlinearity's affect are considered. The experimental setup's functional scheme is presented.

A simple device for small particles detection is presented, consisting of a single-mode diode or gas laser with external cavity. The basis of the measurement is the selfmixing that occurs in the laser active medium when the radiation, scattered back by the moving particle into the laser resonator, interferes with the field inside it and causes changes of a pump current. Information about the number, velocity and size of particles can be derived by processing the current pulses. This compact device is capable of detecting a single microndiameter particle movement.

A Lidar system designed by the authors to detect and observe the tracks of effluents emitted by ships at sea under propulsion by combustion of fossil fuels could have many useful applications. A prototype system uses a frequency-doubled Nd:YAG laser as the transmitter, at wavelengths of 0.53 and 1.06 micrometers , and examine the return for Rayleigh, Mie, fluorescence, and Raman scattering (hence called Advanced Rayleigh-Raman-Mie, ARRM), to determine thermodynamic and chemical conditions out to a given distance surrounding the Lidar operating station. We discuss the business potential of the system, its application to a number of technical and environmental problems, the potential for job creation by the use of such systems, and their value to both the users and the rest of society. One such application is discussed to a limited extent: wide-area surveillance for fire detection, in both urban and rural applications. Conversations with the City of Huntsville's Fire Department have revealed that the system is a quantum leap in fire detection, reporting, and hence firefighting response. Constant motion through the sky of a beam of green light could be a public nuisance. Therefore in an urban setting use of a primary surveillance transmitter consisting of a frequency-doubled CO2 laser is necessary for initial detection of the thermodynamic and fluid-dynamic indications of the rising plume, from the Mie and Rayleigh scattering. After each detection of a new plume, the system switches to the Nd:YAG transmitter for detailed characterization of the plume from the measured ARRM parameters.

An overview is given to the methods of laser spot displacement control for compensation of eye movements during the eye microsurgery operations. Two major techniques were experimentally investigated: (1) with a mirror controlled electro-mechanically, and (2) having acousto-optic Bragg cells with controlled spatial frequency of diffraction grating. In both cases, displacements of 2 mm from the point of sight fixation were realized with an accuracy 0.1 mm and 0.01 mm respectively. Attention is paid to the methods combining TV techniques with spatial coding of light irradiation for reflexes tracking.

Coherent laser radar receivers often generate electronic signals having very wide information bandwidths. 50 MHz bandwidths are routine and 2 GHz bandwidths are not uncommon. Processing wide bandwidth data to remove noise and to extract the required information can exceed the practical limits of electronic techniques. This paper presents the results of the development of an optoelectronic signal processing system for a coherent laser radar system. The system can accommodate signals up to 500 MHz having a duration as short as 17 microseconds or as long as 143 milliseconds.

A great number of articles, special reference books and monographs are dedicated to the problem of underwater objects visibility. However many important problems remain unsolved. It concerns the underwater objects visibility through rough surface mainly. The present article is dedicated to the main aspects of this problem, exactly to the underwater objects observation with the aid of certain devices using artificial (laser) illumination. The notion of the image signal/noise ratio is introduced which takes into account both shot noises and signal fluctuations caused by a random air/water interface. Various methods of image formation for optic observation systems are considered. It is shown that the best results are obtained with the aid of the system, which has the maximum space and time averaging of fluctuations during the signal formation. Most important is the conclusion that the equivalence of two most popular methods of image formation (known in the theory visibility in turbid media) is violated, when observation is performed through a rough sea surface. In the considered case the best parameters has a system, which uses a pulsed laser beam of illumination with a wide aperture and a multi-unit receiver with time gating. The examples of calculation of the main characteristics of such systems are given.

The spatial modulated wavefront conjugated laser signals structure destruction out of the isoplanatic zone theoretically and experimentally examined and the results of experimental investigations are cited. The method of laser signals structure disturbances diminishing is suggested. It is based both on reemitted laser signal wavefront conjugation and amplitude spatial modulation of this signal in the plane of optical systems aperture. The spatial filters for arbitrary nontemporal structure of laser signals in object plane are offered. It was proved that some atmospheric lies exist along which there are no influence of atmospheric turbulence on spatial structure of laser signals. The efficiency of the suggested method was examined experimentally by Earth-lied atmospheric line of 500th meters length and IAG wavefront conjugated pulse laser. The possibility of amplitude and phase spatial structure of laser signals maintain and its parameters guidance out of the isoplanatic zone is confirmed.

An influence of phototarget illuminance on laser measuring systems resolving power is considered. The adaptive method of laser measuring systems resolving power correction in high illuminance conditions is suggested and investigated. The mathematical calculations and experimental investigations results are cited.

The PERCEPTRON LASAR System is based on light detection and ranging (LIDAR) technology. Non-contact laser datacameras provide true 3D images which eliminate depth ambiguities and make previously difficult or even impossible robot guidance applications feasible. THE LASAR DATACAMERA In standard 2D intensity images factors like complex image structure shadows and highlights combined with the lack of depth information (along the Z axis) make it extremely difficult to extract features robustly. In contrast with 3D range images generated by a LASAR datacamera the depth information is measured directly and reported in a digital image format. Field of View The LASAR datacamera is available with measurement working depths (Z axis) from 2 m to 40 m. 214 ISPIE Vol. 2271 O-8194-1595-2/94/$6. OO LASAR Datacamera Horizontal Field of View Measurement Volume y Vertical Typical Scanned Field of View

This paper discusses some areas of industrial applications of accuracy laser rangefinders and laser rangefinding techniques that reguire noncontact survey and profile measurements to be made to points of diffusely reflecting objects that are difficult to reach. Structural layouts and characteristics are given for phase and pulsed laser rangefinders.