IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY, VOL. 43, NO. 1 , FEBRUARY 1994 19

Active-Infrared Overhead Vehicle Sensor Robert A. Olson, Robert L. Gustavson, Richard J. Wangler, and Robert E. McConnell, I1

Abstract-An active-infrared overhead vehicle sensor capable of detecting vehicle (moving or stationary) presence, classifying type of vehicle, and measuring vehicle speed is described. The results of tests conducted at a street intersection in Orange County, Florida are presented. The test results demonstrate that the sensor reliably (99.4%) detects vehicles including cars, trucks, buses, and motorcycles and measures their speed to within kl milh (1.6 km/h) at speeds up to at least 50 mi/h (80 km/h).

I. INTRODUCTION HE HIGHWAY congestion which is now commonplace in T all large metropolitan areas is a daily blight to commuters

and a tremendous burden to the country in terms of wasted time, wasted fuel, and environmental pollution. The aim of the intelligent vehicle-highway systems (IVHS) concept is to apply new technology to improve transportation efficiency and safety and protect the environment. Of vital importance to the IVHS concept are the sensors which provide the information, such as vehicle presence, speed, count, and classification, needed to maintain a safe and efficient flow of traffic.

This paper describes the design and performance of an active-infrared overhead vehicle sensor which employs a pulsed time-of-flight laser range finder to detect the presence of moving or stationary vehicles. Since the first report [ l ] of a laser range finder in 1961, these devices have been used for applications as varied as military target detection [ 2 ] , aircraft obstacle avoidance [3], and spacecraft docking [4]. To our knowledge, this is the first report of a laser range finder being used as a vehicle sensor.

For traffic surveillance applications, the sensor is mounted on a roadside pole or on cables or a mast arm over the highway. A bifurcated fan-shaped beam of 904 nm radiation emitted by a diode-laser array is directed toward a vehicle. Although most of the radiation is specularly reflected away, a small amount is diffusely reflected back to the sensor where it is detected by a pair of silicon photodiodes. The round-trip propagation time of a laser pulse is proportional to the range to the vehicle. The presence of a vehicle is indicated by a reduction in the range reading from the road surface. Vehicle speed is computed from the measured time interval between the interceptions of the two laser beams. An on-board microprocessor is used for the determination of vehicle presence, speed, count, and classification. A real-time clock is used to time-tag the data to provide vehicle count and average speed for each hour of the day.

Manuscript received December 10, 1992; revised March 5 , 1993. This work was supported in part under a U.S. Department of Transportation SBIR program.

The authors are with Schwartz Electro-optics, Inc., Orlando, FL 32804. IEEE Log Number 92 1 1226.

Because the active-infrared overhead vehicle sensor accu- rately [fl mi/h (1.6 kmb)] measures vehicle speed as well as counts vehicles, it provides the basic data from which other traffic parameters, such as flow rate and mean speed, can be derived. But, the distinguishing feature of this sensor, which sets it apart from other vehicle detectors, is its ability to accurately measure vehicle height profiles. This unique capability can be utilized to classify vehicles or to monitor vehicle height to ensure clearance at overpasses or toll booths. The active-infrared overhead vehicle sensor's classification potential is manifest in the vehicle height profiles shown in Section IV.

11. SYSTEM ANALYSIS For proper operation, the laser range finder must achieve

a signal-to-noise ratio (SNR) which is sufficient to ensure a high probability of detection with a low false a l m rate. The SNR which yields a probability of false alarm of one per loo0 pulses for a range gate of 15 m can be calculated following the analysis in [5, Section 81. The calculation yields a required voltage SNR of 7 or a power SNR of 17 dB.

We now must calculate the laser range finder S N R to ensure it exceeds 17 dB. This requires knowledge of the received signal and background power. The received background power can be calculated using the following equation:

pB = L ~ A ~ R ~ A A T R T F ~ - " ~ (1)

where LA = pEx/7r is the spectral radiance of the back- ground/vehicle due to reflected solar radiation, p is the back- ground/vehicle reflectance, Ex is the solar spectral irradiance, AR is the receiver aperture area, f l ~ = 01101 is the receiver solid-angle FOV, 811 and 01 are the receiver angular FOVs in directions parallel and perpendicular to the diode laser junction, AA is the optical filter bandpass, TR is the receiver lens transmission, TF is the optical filter transmission, o is the atmospheric extinction coefficient, and R is the range to the vehicle.

The received signal power can be calculated from the following equation:

where L = p , E ~ / r is the radiance of the vehicle due to diffusely reflected transmitter radiation, pv is the vehicle re- flectance, ET = P ~ e - " ~ / ( R ' f l n ~ ) is the transmitter irradiance at the vehicle, PT is the peak power exiting the transmitter aperture, f l ~ is the transmitter beam solid angle, and the other symbols are as previously defined. For a beam-filling target where OR > OT, f l ~ is determined by f l ~ and S ~ R I R T = 1.

0018-9545/94$04.M) 0 1994 IEEE

80 IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY, VOL. 43, NO. I , FEBRUARY 1994

0 20 40 60 80 Ranga (ml

Fig. 1. Dependence of range finder SNR upon range.

pulse rise time yields a propagation time error of f 6 x 10-los, which is equivalent to an error in range measurement of &9 cm. To this error must be added the range error due to the 1% accuracy of the analog range measurement circuit, which, for a nominal range of 6 m, is 1k6 cm. Thus, the vehicle sensor can detect absolute vehicle height profiles to within &15 cm (or better for SNR >17 dB).

Fundamental to the active-infrared overhead vehicle sensor technique is the transmission of a short pulse of near-infrared radiation through the atmosphere. The amplitude of the retum signal received by the vehicle sensor is proportional to the at- mospheric transmittance T, = e-uT, where T is the path length and o- is the wavelength-dependent extinction coefficient. The extinction coefficient can be related to visibility through the

The range finder SNR is given by [6]

P j R: (3) SNR = (2qpbRo + i:,)Af expression [5]

where R, is the photodiode responsivity, q is the electron charge, 22, is the amplifier mean square noise current per unit bandwidth, and Af is the noise bandwidth. This is the ratio of the square of the signal current to the sum of the squares of the background noise current and the amplifier noise current. The silicon PIN photodiode we are using has a responsivity of 0.5 A/W at 904 nm. The low-noise high-speed differential transimpedance amplifier has a rms noise current in, of about 5 PA/HZ'/~.

The parameter values required to compute the SNR are readily available, except for reflectance, which is the ratio of reflected to incident flux. Values of vehicle reflectance for black (0.5%) and silver-gray (27%) automobile finishes were obtained from bidirectional reflectance distribution function measurements made by W. Lynn at Wright Laboratory using a 1.06 pm laser scatterometer. The measurements were made within 1" of retroreflection for an angle of incidence of 25'.

Equation (3) was used to calculate the SNR as a function of range for the following parameter values: p~ = 0.3, Ex = 0.075 W/cm2 . pm, 811 = 0.203 rad, 81 = 0.005 rad, AR = 22.2 cm2, Ax = 0.04pm, TR = 0.9, TF = 0.8, PT = 30W, o- = 0.125 km-' (standard clear day), R, = 0.5 A m , in, = 5 pA/Hz'l2, Af = 91.6 MHz, and pv = 0.005 and 0.27. Plots of SNR versus range are shown in Fig. 1. The intersection of each curve with the 17 dB line indicates the maximum range capability compatible with a probability of false alarm of 0.001. The maximum ranges are 1 1 m for a vehicle reflectance of 0.5% and 78 m for a vehicle reflectance of 27%. The slant range to the roadway for a vehicle sensor mounted at a typical height of 6 m and an angle of incidence of 45' is 9.5 m, which is well within the sensor's 11 m range capability for vehicle reflectance of 0.5%.

The accuracy of the laser range finder can now be calculated. Skolnik [7] has derived an equation for the error in the round- trip propagation time measurement due to the uncertainty (induced by noise and finite rise time) in measuring the time at which the leading edge of a retum pulse of amplitude A crosses a threshold set at A/2. The error in round-trip propagation time is

6t = tr /(2 SNR)l/* (4)

where t , is the retum-pulse rise time. Using the 17 dB value of SNR required for good detection statistics along with the 6 ns

o-, = 3.912/RV ( 5 )

where o, is the average extinction coefficient for the visible spectrum and R, is the visibility range.

The effect of weather (rainfall, fog) on vehicle sensor performance can be demonstrated by calculating the minimum visibility at which the sensor can operate. Since sensor oper- ation is predicated upon detecting a retum signal from the roadway, it will be assumed that the limiting condition for sensor operation is the detection of the laser pulse reflected from a surface of 10% reflectance (appropriate for macadam). Using (2) to calculate the received signal power as a function of o for a 10% reflectance and a nominal range of 10 m yields

pS = (1.53. 10-5)e-20u. (6)

This can be equated to the value of PS needed to achieve an SNR of 17 dB, as calculated from (3), to yield (T = 0.156 m-'. The visible extinction coefficient o, corresponding to the 904 nm extinction coefficient (0.156 m -l) can be obtained from the value (1.39) of the ratio of o, to the 904 nm o obtained from the plot of u versus wavelength in [5, Figure 7-31. Equation ( 5 ) can then be used to calculate a visibility range of 18 m.

This analysis indicates that the active-infrared overhead vehicle sensor will continue to sense vehicles until heavy fodrainfall reduces the visibility range to 18 m. Corresponding to the change in visibility from 23.5 km (standard clear day) to 18 m, the received signal power decreases by a factor of 22.6 from 1.53. lop5 W to 6.76. lop7 W. This suggests that a measurement of the retum-signal amplitude can be used to ascertain the existence of poor highway visibility conditions. This capability could be put to good use in warning freeway drivers to slow down because of dangerously low visibility conditions ahead.

111. SYSTEM DESIGN Pulsed time-of-flight laser range finders are comprised of

three major elements: laser transmitter, optical receiver, and range measurement circuit. The laser transmitter generates a laser pulse of the appropriate wavelength, power, and beam di- vergence, triggered at a predetermined repetition rate. The laser

OLSON et 01.: ACTIVE-INFRARED OVERHEAD VEHICLE SENSOR 81

M m D

Fig. 2. Active-infrared overhead vehicle sensor block diagram.

receiver converts incoming laser retums into discrete logic- level pulses. The range measurement circuit determines laser pulse time-of-flight by measuring the time interval between transmitted and received laser pulses.

The vehicle sensor's laser range finder employs a GaAs diode-laser-array transmitter and a silicon PIN photodiode re- ceiver in a side-by-side configuration. The transmitter consists of the diode laser and its driver circuit, a collimated lens, and a dual-wedge prism, which divides the collimating laser output into two beams propagating at an angle 0 with respect to each other. At street level, the two beams are separated by a distance given by Re, where R is the distance from the overhead vehicle sensor to the street. The optical receiver is comprised of an objective lens, spectral filter, two detectors/amplifiers, analog multiplexer, and threshold detector. Retum signals are focused upon the two detectors spaced apart by f0 in the focal plane of the receiver lens of focal length f. A microprocessor- controlled multiplexer alternately selects one channel and then the other for threshold detection and subsequent range measurement.

A block diagram of the active-infrared overhead vehicle sensor is shown in Fig. 2. Major system components are discussed in the following sections.

A . Transmitter

The laser diode used in the vehicle sensor is a single heterostructure GaAs injection laser diode array having 120 W output at 40 A pulsed current drive. The laser driver produces a 40 A peak current pulse with a 4 ns rise time and a 10 ns pulse width. A monostable multivibrator generates the laser

trigger pulses at a pulse repetition frequency of 3 kHz. This diode emits at 904 nm, which is an ideal wavelength for the silicon photodiode receiver used.

The 3.96 mm by 0.002 mm laser diode junction emits radiation into a 10' by 40" solid angle. A fast (f/ l .S) multielement lens having an effective focal length of 24 mm is used to collimate the diode laser emission, resulting in a beam divergence 011 = 3.96/24 = 165 mrad parallel to the diode junction and 0 1 = 0.002/24 = 0.083 m a d perpendicular to the diode junction.

A 200 V dc-dc converter is used to generate the high voltage necessary to pulse the laser. The transmitter circuit is contained inside an aluminum enclosure to reduce electrical interference.

B. Receiver

The optical detection circuitry converts optical radiation reflected from the vehiclehoad to first, an equivalent electrical analog of the input radiation and finally, a logic-level signal. The receiver has two detectors which are time multiplexed using a high-speed analog multiplexer. The multiplexer is controlled by a single logic-level control line from the mi- croprocessor. The output of the multiplexer is connected to a threshold detector which converts the analog retum pulses to logic-level pulses. The logic-level signals are processed within the range counter logic to yield analog range data, which is read by the microprocessor. The receiver is designed so that it can be configured by the microprocessor to use only one detector or both detectors.

The two silicon photodiodes operate as current sources. The transimpedance amplifiers convert the detector current pulses

82 IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY, VOL. 43, NO. 1, FEBRUARY 1994

into voltage pulses. Each amplifier offers a transimpedance of 28 kR when operated in the differential mode.

A narrow-band (40 nm) optical filter limits the solar irradi- ance, permitting only 904 nm radiation to reach the detector. The narrow-band filter transmission is 275% at 904 nm.

The analog portion of the optical receiver is contained within a Faraday shield. This shield permits the circuit to operate in a “field-free” region where the gain is achieved without additional noise introduction.

C. Range Measurement Circuit In order to measure range, it is necessary to accurately

measure the propagation time of the laser pulse to the target and back to the receiver. Either digital or analog circuitry may be used for the time interval measurement.

The digital technique uses the laser pulse to open a gate circuit permitting clock pulses into a counter which accu- mulates the count until the received retum pulse closes the gate. This method of measuring range has an uncertainty of c / ( 2 f c ) , where f c is the clock frequency. Until recently, digital counting circuits have been limited to frequencies in the 100 to 500 MHz range. Using a 500 MHz clock, the uncertainty due to count ambiguity is approximately f 3 0 cm. The high- speed logic circuits used in a 500 MHz counter can require as much as 10 W of power.

The analog technique was chosen for the active-infrared overhead vehicle sensor because of its better resolution, smaller size, simpler circuitry, lower power consumption, and lower cost when compared with the digital technique. The analog range measurement circuit, known as a time- to-amplitude converter (TAC), has an accuracy of 1% of measured range and a resolution of f 5 cm. The TAC employs a constant-current source to charge a capacitor to obtain a linear voltage ramp whose instantaneous value is a measure of elapsed time. The circuit is designed so that the voltage across the range-measurement capacitor begins ramping down from the positive power supply when the laser fires. The ramp is stopped when either a reflected pulse is received or the end of the measurement period is reached. The TAC output is then converted to digital by an 8-bit A/D converter inside the microprocessor. The start-timing pulse for the TAC is produced using optical detection of the transmitted laser pulse. A fiber-coupled PIN photodiode and 120 MHz transimpedance amplifier are used for the start pulse detection.

D . Peak Detector

A major problem encountered when measuring range to vehicles is the low level of retum signals from windshields and poorly reflecting black metal or plastic areas. This can result in range readings which are close to those for the street level and would, therefore, indicate that a car was not present. This range measurement error, which is proportional to the magnitude of the variation in retum-signal level, is known as timing walk. This problem is solved by accurately measuring the peak of the return signal with a high-speed peak detector and having the microprocessor apply a correction factor to the range measurement based on the retum-signal level. A very

Fig. 3. Vehicle sensor field-of-view.

low level of the signal is itself an indication of the presence of a car. The vehicle sensor will indicate the presence of a car when either the range reading is shorter than that to the street or the return-signal level is much smaller than that from the street.

E. MicroprocessorlSofnYare

An Intel 87C196KC microprocessor is used for the deter- mination of vehicle presence, speed, count, and classification. The microprocessor is also used to automatically adjust range and signal amplitude thresholds to compensate for changing environmental conditions.

At present, the vehicle sensor software is designed to detect the presence of vehicles, classify vehicles as cars or trucks, count the cars and trucks, and calculate vehicle speed and flow rate. The software constantly monitors devices and data within the vehicle sensor so that it can automatically adjust to changing environmental conditions. The software is upgradable and provides flexibility in adapting the vehicle sensor for specific installations.

For presence detection, the software first measures the range to the road. When the range falls below a predetermined threshold, the software signals that a vehicle is present. The threshold is determined by calculating the minimum, maxi- mum, and average range to the road for 100 measurements. The maximum error is then calculated by subtracting the aver- age from the maximum range measurement and the minimum from the average range measurement. The threshold is set to the maximum error. The software classifies the vehicle as either a car or a truck by examining the amount of range change, a truck producing a larger range change than a car.

After a vehicle is classified as a car or a truck, a corre- sponding counter is incremented. The software will keep an accurate count of cars and trucks for up to 24 hours. The software maintains counters for each hour of the day. This provides the user with flow rate data.

The software will also calculate vehicle speed and maintain a running average for each hour of the day. The software determines speed by calculating the time it takes a vehicle to pass between two beams. The software uses a timer that is automatically incremented every microsecond by the mi-

OLSON et a/.: ACTIVE-INFRARED OVERHEAD VEHICLE SENSOR

SE0 Autosense I n t e r f a c e Software

83

V e r 1.02 Se1 .ftests

Q u i t o u t p u t s Conf ig Range D e t e c t

D e t e c t : OFF Show Presence

Clear Data Vehicle Count: 604 FI- F i l e output

V e h i c l e Speed: 4 2 MPH F2- T i m e I n t e r v a l Presence . .... : YES

Waiting for V e h i c l e s ... Esc-Qui t

Fig. 4. Computer display for vehicle sensor data outputs.

croprocessor. The timer is reset to zero when the first beam detects the presence of a vehicle and is read when the vehicle is detected by the second beam. The software automatically calculates the distance between the beams by applying the law of cosines to the triangle formed by the two beams and the distance between them at street level (shown as W in Fig. 3). The speed is calculated by taking the distance between the beams and dividing it by the time it takes to travel that distance.

F . Interface As depicted in Fig. 2, the vehicle sensor has two outputs-a

relay output and an RS-232 serial computer interface. The relay output provides an input for traffic-actuated signal control applications, functioning in a manner similar to that of an inductive loop. The relay is energized as long as the sensor detects vehicle presence and de-energized when no vehicle is detected. The electrically isolated relay contacts (common, normally open, and normally closed) are available at the sensor’s interface cable, making it compatible with the type 170 controller.

The serial computer interface is needed to transfer the large amount of data resulting from the measurement of various vehicle parameters to a remote computer for reduction and display. The 19.2 kbaud, full duplex, RS-232 serial computer interface, when used in conjunction with a remote computer and appropriate interface/display software, can be used to transmit a variety of data in real time, including vehicle height profiles which can be used for vehicle classification and vehicle height-clearance monitoring. An example of the computer display is presented in Fig. 4. This display, which is updated each time a vehicle is detected, shows vehicle count, truck count, vehicle speed, and presence. It also shows vehicle and truck counts and average speed for a selected time interval. The serial computer interface also provides access to the 24 hour time-tagged data (average speed, vehicle count, and truck count) stored in the sensor. The serial computer interface is useful for freeway surveillance applications where a real-time knowledge of various traffic parameters is needed.

Fig. 5. Photograph of vehicle sensor.

IV. SENSOR PERFORMANCE

In order to evaluate vehicle sensor performance under realistic traffic conditions, a vehicle sensor (see Fig. 5 ) was installed, with the cooperation of the Orange County Traffic Engineering Department, at a street intersection in Orange County, FL. The sensor was mounted on cables strung across the street such that it was 20 ft (6.1 m) above the center of a lane and aimed at a point 5 ft (1.5 m) in front of the stop bar across the lane. A color video camera mounted to the top of the sensor provided a visual record (stored on video recorder) of the vehicles passing beneath the sensor. Vehicle presence, count, and speed outputs generated by the sensor were also displayed on the video screen.

In tests conducted on May 29, June 4, June 10, and August 5, 1992, the sensor counted 1,874 of the 1,885 vehicles which passed beneath it, resulting in a detection percentage of 99.4%. All of the undetected vehicles were black (low reflectance) and were traveling to one side of the lane so that only a fraction of each laser beam was intercepted; this led to an SNR insufficient for vehicle detection. To some extent, this was due to the hot weather during testing-as the sensor heated up, the SNR decreased due to the 1% per C O fall-off in laser power which

84 IEEE TRAI VSACTIONS ON VEHICULAR TECHNOLOGY, VOL. 43, NO. I , FEBRUARY 1994

SPEED MEASUREMENT ERROR (mi/h)

Fig. 6. Speed-measurement-error histogram.

occurs with increasing temperature. This situation has since been improved by replacing the GaAlAs diode laser array with one fabricated from InGaAs, which has a peak-power temperature coefficient which is about one fourth of that for GaAlAs.

Sensor speed measurements were compared to readings obtained with a radar gun having an accuracy of f l mi/h (1.6 km/h). A histogram of the differences between values of speed measured by the vehicle sensor and by the radar gun is shown in Fig. 6. The most probable error was -1 mi/h (1.6 km/h), which implies that either the radar gun measurement was 1 mi/h (1.6 km/h) low or the sensor measurement was 1 mfi (1.6 km/h) high.

Vehicle range and intensity profiles obtained for a truck and a station wagon, which were simultaneously videotaped from the side of the road, are shown in Figs. 7 and 8, respectively. Notice that the vehicles are profiled accurately even in the windshield region where the intensity of the return signal is very low. This demonstrates the efficacy of the intensity- dependent range correction in mitigating the effect of timing walk on range measurements at low return-pulse amplitude. Although the values of height and length determined by the vehicle sensor for the passing truck could not be confirmed, the numbers are credible for that type of vehicle. In the case of the station wagon, the length and height of a similar vehicle were later ascertained using a tape measure; the measured values of 4.72 m and 1.32 m were in good agreement with the 4.97 m and 1.34 m values generated by the vehicle sensor. Vehicle height profiles such as those shown in Figs. 7 and 8 can be used to classify vehicles as cars, trucks, motorcycles, etc., by employing the appropriate identification algorithm.

V. CONCLUSION

Over-the-roadway testing of the active-infrared overhead vehicle sensor has shown it to be an accurate and versatile sensor of moving or stationary vehicles in a municipal traffic environment. The major results of the tests were:

1. 99.4% vehicle detection; 2. f l mph speed measurement accuracy; 3. well-resolved vehicle height profiles suitable for vehicle

identification

Q)

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a 3 . 5 7 m

Q)

E m w I

a 3 . 5 7 m

Fig. 7. Photograph and range and intensity profiles of a truck.

I I I I I I

Q) I m c m a

I I I

c. I I .- cn c Q, Y

r( I

I IJ I

Fig. 8. Photograph and range and intensity profiles of a station wagon.

Applications of the sensor for traffic signal control, on- and off-ramp monitoring, freeway surveillance, and vehicle separation and height-clearance monitoring at toll booths are under consideration.

ACKNOWLEDGMENT

The authors wish to express their appreciation to S. Wilmarth and R. Smith of the Orange County Traffic Engineering Department for their cooperation in testing the vehicle sensor at an Orange County, FL street intersection.

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M. L. Stitch. E. J. Woodbury, and J. H. Morse, “Optical ranging system uses laser transmitter,” Electron., vol. 34, p. 51, Apr. 21, 1961. R. C. Hamey, “Military applications of coherent infrared radar,” Proc. SPIE. vol. 300, p. 2, 1981. C. J. Buczek, W. J. Green, G. F. Gurski, and R. J. Mongeon, “Laser obstacle terrain avoidance warning system,” ECOM, Rep. 72-0145-3, 1975. Optoelectronic Docking System, NASA Tech. Brief MSC-21159, John- son Space Center, Houston, Tx. 1987. Electro-optics Handbook. Lancaster, PA: RCA Corp., 1974. P. P. Webb, R. J . Mclntyre, and J. Conradi, “Properties of avalanche photodiodes,” RCA Rev., vol. 35, p. 234, June 1974. M. I. Skolnik, Introduction to Radar Systems. New York: McGraw- Hill, 1962, p. 464.

Robert L. Gustavson received the B.S. degree cum laude in electronics from the University of Central Florida, Orlando, FL, in 1981. During his career, he has worked on the development of over 20 laser rangefinder systems including several real-time imaging LADAR systems used for autonomous seeker applications. He is currently a Principal Electronic Engineer with Schwartz Electro-Optics specializing in electronic circuit design for high- performance diode-laser rangefinders.

area. In 1984 he partii where he is currently a Division.

Robert A. Olson received the B.S. and M.S. degrees in physics from Ohio University, Athens, OH, in 1958 and 1960, respectively. During his career he has worked on the development of plasma diagnostic techniques at United Technologies Re- search Center, closed-cycle laser research at Sys- tems Research Laboratories, and COz waveguide laser development at Litton Laser Systems. He is currently a Principal Engineer with Schwartz Electro-optics specializing in optical system design.

Richard J. Wangler received the B.S.E.E. degree in 1960 and the M.S.E.E., degree in 1962, both magna cum laude from the University of Florida, Gainesville, FL. Following graduation, he joined the Martin Marietta Corporation where he applied sta- tistical communication theory to millimeter-wave- communication and missile-guidance problems. In 1972 he joined Intemational Laser Systems as En- gineering Director of the Special Program Division. In this capacity he directed the development of products germane to the laser engagement scoring

cipated in the founding of Schwartz Electro-Optics Vice President and Director of the Advanced Sensors

Robert E. McConnell, 11, received the B.S. degree in computer science from the University of Central Florida, Orlando, FL in 1986. Following graduation, he worked for Whitman Engineering, Inc. on the development of one- and two-dimensional signal- processing algorithms. Since 1990, he has been a Senior Software Engineer at Schwartz Electro- Optics concerned mainly with the development of software for laser imaging radar systems.