GB2300325A - Solid-state beam scanner for ladar systems - Google Patents

Abstract

A solid-state beam scanner for use in laser detection and range (LADAR) system is described. Generation of a far-field vertical scan pattern is accomplished without moving parts by passing a pulsed laser beam through a holographic diffraction grating (HDG) to physically create an odd number of spatially overlapping laser beams. The overlapping laser beams generated by the HDG are subsequently transmitted through an acousto-optical (AO) scanner where the number of deflection angles is set in combination with the number of laser beams generated by the HDG (and the pulsed laser's divergence) to fill the far-field's scan pattern. The ability to adjust the combination of the number of HDG generated beams and AO scanner deflection angles, allows the design of a LADAR system that can be utilized to create a wide range of scan patterns; thereby optimizing a LADAR system's use of available data processing capability. The use of a solid-state beam scanner in accordance with the invention allows for the elimination of a conventional LADAR system's mechanically mounted and rotated mirror (galvanometer) assembly, resulting in a ruggedized optical system, capable of withstanding high g-forces and improved resistance to mechanical failure.

Description

SOLID-STATE BEAM SCANNER FOR LADAR SYSTEMS The invention relates in general to the field of optical image processing and, more particularly, to optical laser detection and ranging (LADAR) systems. Specifically, the invention describes a solid-state beam scanner that allows for the elimination of a conventional LADAR system's mechanically mounted and rotated mirror.

Optical laser detection and ranging (LADAR) systems that use stabilized gimbaled laser seekers to separate and align laser beams for (1) transmission of laser light to a far-field and (2) processing of reflected laser signals are known in the field. Example prior art LADAR systems include U.S. Patents 4,024,392 entitled Gimbaled Active Optical System; 5,200,606 entitled Laser Radar Scanning System; and 5,224,109 entitled Laser Radar Transceiver. Each referenced patent is commonly owned by the assignee of this application and is hereby incorporated in their entirety by reference.

As shown in FIG. I, a conventional LADAR system 100 is comprised of an optical transmitter subsystem 105, an optical receiver subsystem 110 and a processing unit 115. The optical transmitter and receiver subsystems are generally enclosed within a gimbal assembly 120. Functionally, the optical transmitter subsystem 105 generates a vertical scan laser beam which is transmitted toward a target(s) in a far-field. The gimbal assembly 120 sweeps the transmitted laser signal in azimuth to create a two axis array of laser light in the far-field. A portion of the transmitted laser signal is reflected back to the LADAR system 100 where it is received by the optical receiver unit 110. The optical receiver unit 110 converts the reflected laser signal to an electrical signal and routes it to the processing unit 115. The processing unit 115 extracts, for example, target range information.It will be recognized by one of ordinary skill in the field that FIG. l represents a very simplified view of a real LADAR system. In particular, a LADAR system's optical transmitter and receiver subsystems often use many of the same optical elements. That is, transmitted and reflected laser signals are routed and manipulated by common optical components within the LADAR system. LADAR systems are typically used for missile guidance and control systems.

Correct operation of a LADAR system requires the generation of a scan pattern, or raster, of laser beams in the far-field. Further, each beam must be spaced at a specific angle relative to the beams which surround it. To achieve high frame rates, that is, to generate a large number of scan patterns in the far-field in a short time, a LADAR system must be able to generate and position a large number of beams in a very short time. However, as the number of laser beams increases and the time frame for their generation decreases (both features are important for practical LADAR systems), it becomes increasingly difficult to scan and process these beams.

Prior art LADAR systems use optical transmitter subsystems that employ mechanical scanners to generate their far-field scan raster. See, for example, the LADAR system described in U.S. Patent No. 5,200,606. A simplified block diagram of a typical prior art optical transmitter subsystem 105 for generating a far-field scan raster in a LADAR system is shown in FIG. 2. In the illustrative system, a gallium aluminum arsenide (GaA1As) laser 200 pumps a solid-state laser which, in turn, emits the laser light energy employed for illuminating a target in the far-field. The Galas pumping laser 200 produces a continuous signal of wavelengths suitable for pumping the solid-state laser 210. Further, pumping laser 200 has sufficient output power to actuate the solid-state laser 210, typically in the range of 10 to 20 watts.The pumping laser is fixedly mounted on a housing, whereas the solid-state laser is mounted on a stabilized gimbaled frame for movement with the optical subsystem.

Output from the pumping laser 200 is transmitted through a lens 205 and fiber optic cable which has sufficient flexibility to permit scanning movement of the optical subsystem during operation.

Output from the solid-state laser is reflected through a series of turning mirrors 215 to a beam expander 220 whose purpose is to expand the diameter of the beam while simultaneously decreasing the beam's divergence. Next, the beam is passed through a beam segmenter 225 for dividing the beam into a plurality of beam segments arrayed on a common plane, initially spatially overlapping, and diverging in a fan shaped pattern. The divergence of the beams is not so great as to produce separation of the beams within the optical subsystem 105, but is sufficient to provide a small degree of separation at the target/far-field.

Output from the segmenter 225 is reflected by a tuming mirror 230, passed through an aperture of an apertured mirror 235, and then reflected from a scanning mirror 240 in a forward direction (relative to the optical subsystem's direction of movement). The scanning mirror 240 is pivotally driven by a scanning drive motor 245. The combination of scanning mirror 240 and motor 245 is typically referred to as a galvanometer 250.

A series of lenses 255 and an afocal Cassegrainian telescope 260 is provided for further expanding the emitted laser beam and reducing its divergence. Finally, the emitted laser light beam is transmitted toward a target in a far-field. The result of a single transmitted beam, in the far-field, is to generate a spot or pixel in the far-field. As previously mentioned, the entire optical subassembly 105 is mounted on a stabilized gimbal so that it may be rotated in the azimuth. It is noted that the optical assembly of FIG. 2 does not show the LADAR system's receiver portion; that is, that part of the LADAR system responsible for receiving, routing, and processing the reflected laser signals. One of ordinary skill in the field would realize that an operational LADAR system would include these elements.

In the context of the instant invention, it is important to realize that prior art optical systems, such as that shown in FIG. 2, use a mechanical galvanometer 250 to produce a vertical line pattern in the far-field. This vertical line pattern is swept in azimuth (by a stabilized gimbal in which the entire optical subsystem is typically mounted) to generate a far-field scan raster or matrix. As LADAR data rates increase, the rotating mirror 240 becomes a limiting factor in system performance because scanning speed is limited by the required scanning efficiency (i.e., what percentage of each scan is linear with respect to the total scan), mirror flexing, and motor torque.

Another limitation of prior art laser scanning systems that use a rotating mirror assembly is their inability, or reduced capacity, to operate effectively in high stress or harsh environments.

LADAR systems employed as one element in a missile's tracking and guidance system must be able to operate under high g-force conditions - circumstances in which the use of a rotating mirror is incompatible. For example, an interceptor missile typically executes 10-g maneuvers during target acquisition on tracking. Such high g-force maneuvers can cause considerable flexing and other mechanical disturbances in the operation of a rotating mirror and result in reduced quality laser scan patterns in the far-field.

Further, as an interceptor missile begins to close on its target, the LADAR's signal processing unit can become overloaded due to the number of (return signal) pixels which must be processed.

Typically, to reduce the total number of target (and surrounding area) pixels, the image is undersampled. In many current systems this is accomplished by not processing specific image rows and columns to create an under-sampled scan pattern. The ignored rows and columns represent laser, detector, and electronic processing which is essentially wasted since it is ignored by the LADAR's signal processing unit.

An additional limitation in prior art LADAR systems employing a rotating mirror assembly is the need for large and/or heavy motors 245. These equipment increases the weight and complexity of a LADAR system while simultaneously reducing its reliability (e.g., mean time between failure).

The above cited operational limitations of a LADAR system employing mechanical far-field vertical scan pattern generation highlight the need for a new scanning technique. Implementation of a solid-state beam scanning system in accordance with the invention will provide a more rugged laser scanning system that will also allow faster scanning rates while retaining the necessary angular separations between the laser beams required for reflected laser signal processing.

A ruggedized solid-state beam scanner subsystem for use in laser detection and range (LADAR) system is described. Generation of a far-field vertical scan pattern is accomplished without moving parts by passing a pulsed laser beam through a holographic diffraction grating (HDG) to physically create an odd number of spatially overlapping laser beams. The overlapping laser beams generated by the HDG are subsequently transmitted through an acousto-optical (AO) scanner where the number of deflection angles is set in combination with the number of laser beams generated by the HDG (and the pulsed laser's divergence) to fill the far-field's scan pattem.The ability to adjust the combination of the number of HDG generated beams and AO scanner deflection angles, allows the design of a LADAR system that can be utilized to create a wide range of scan patterns; thereby optimizing a LADAR system's use of available data processing capability.

The use of a solid-state beam scanner in accordance with the invention allows for the elimination of a conventional LADAR system's mechanically mounted and rotated mirror (galvanometer) assembly. A LADAR system comprising the inventive solid-state beam scanner achieves a ruggedized optical system better able to withstand the high g-forces inherent in many environments such as an interceptor missile. Additional benefits of the claimed solid-state beam scanner include the ability to obtain faster scanning rates, improved accuracy and efficiency of the vertical scan pattern, reduced system's cost, and improved resistance to mechanical failure.Further, a solid-state beam scanner in accordance with the invention can automatically adjust the resolution of its far-field scan pattern, by adjusting the number of deflection angles which the AO scanner generates in a given vertical scan pattern, to compensate for the processing capabilities of an associated signal processing unit.

Figure 1 is a simplified block diagram of a conventional LADAR system.

Figure 2 is shows a simplified block diagram of a prior art optical transmitter subsystem's beam scanner employing a mechanical galvanometer.

Figure 3 is a block diagram of a solid-state beam scanner in accordance with the invention.

Figure 4 shows a series of illustrative far-field scan patterns generated by changing the number of angular offset's generated by the scanner's acousto-optic scanner.

One illustrative embodiment of the invention is described below as it might be implemented using solid-state optical processing technology. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual implementation (as in any development project), numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system- and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and timeconsuming, but would nevertheless be a routine undertaking of electrical/optical engineering for those of ordinary skill having the benefit of this disclosure.

As previously mentioned, a LADAR system's scan rate refers to the rate of generating a matrix of laser beams (preferred to as a scan raster) in a far-field. From this matrix, LADAR system receiver(s) recover and analyze the reflected laser signals to determine, for instance, target range information. Thus, a LADAR system's far-field raster scan has two elements: (I) a vertical scan pattem of one or more laser beams and (2) a horizontal scan of these one or more vertical beams to generate a matrix or raster.A solid-state beam scanner in accordance with the invention replaces the prior art mechanical method of generating a vertical scan pattern (e.g., using a galvanometer) with a completely solid-state embodiment that includes a holographic diffraction grating and an acousto-optic scanner.

Structural Description A solid-state beam scanning subsystem 300 in accordance with the invention generates a farfield vertical scan pattern without moving parts. In overview, a solid-state beam scanner in accordance with the invention is shown in FIG. 2. A solid-state laser 305 generates a pulsed laser beam which is passed through a beam expander 310, a holographic diffraction grating (HDG) 315, and an acoustooptic scanner (AO) 320. Output from the AO scanner is a diverging vertical scan pattern 325 and represents the output from a solid-state beam scanner subsystem. The number of unique deflection angles that the AO scanner generates is controlled by acousto-optical deflection control unit 330.

In an operational LADAR system, as in prior art system's, the solid-state beam scanner subsystem of FIG. 3 is mounted in a stabilized gimbal that rotates in azimuth to generate a matrix or scan pattern in the far-field. Thus, a solid-state beam scanner in accordance with the invention is directed to the efficient and non-mechanical generation of a vertical scan pattern in the far field.

In a preferred embodiment, the solid-state laser 305 can be a Neodymium doped yttrium aluminum garnet (YAG), a yttrium lithium fluoride (YLF), or Nb:YVO4 laser operable to produce pulses with widths of 10 to 20 nanoseconds with peak power levels of approximately 10 kilowatts, and repetition rates of between 10 and 120 kilohertz. Equivalent average power of the solid-state laser 305 is in the range of from 1 to 4 watts. The preferred range of wavelengths of the output radiation is in the near infrared range, e.g., 1.047 or 1.064 microns. Output from the solid-state laser is a pulsed TEMoo gaussian laser beam.

The beam expander's 310 function is to expand the diameter of the solid-state laser's TEMoo output beam while simultaneously decreasing the beam's divergence. This use of a beam expander is the same as described in the prior art system of FIG. 2.

The holographic diffraction grating (HDG) 315 is a passive transmissive optical element that has a computer generated diffractive hologram etched on one surface. Functionally, the HDG takes a single pulsed TEMoo gaussian laser beam (generated by the solid-state laser 305) and converts it into N TEMoo gaussian laser beams. The number N of diffracted beams produced from a single input beam can be tailored, but is always odd in number. In a preferred embodiment N is 23. It should be noted that one of ordinary skill will realize that N could be different. For instance, N could be 9. The engineering decision of whether to make N = 9 or N = 23 (or any other odd number) depends primarily upon: 1. The number of times the original laser beam can be divided while maintaining a useable power.

If N is large the power of the original laser beam, for a given far-field distance, must be greater.

Alternatively, if the source laser's power is fixed, then for larger N, the possible far-field distance is greatly reduced.

2. The larger the value of N, the larger the number of simultaneously received reflected laser beams will need to be processed at the LADAR's receiver. Thus, if N is large a corresponding large number of pulse converters and signal processing capability will be needed. (A limiting factor in many practical LADAR systems, is the number of "received signal" channels available to process received reflected laser signals.

While the HDG's N output laser beams are spatially overlapping (vertically aligned), their angular separation is so small that all the beams remain overlapping within the optical subsystem 300 (diverging in the far-field), for purposes of illustration only they are shown as diverging in FIG. 3.

For each output pulse from the solid-state laser 305, the acousto-optic scanner (AO) 320 deflects its N TEMoo input beams to a new angular offset position (i.e., one spot or pixel -in the farfield), where the AO scanner has M such offset positions. In a preferred embodiment M = 9. Thus, for a first pulsed laser beam input the AO scanner deflects the incoming N input beams to a position in the far-field. For a second input, the AO scanner offsets its pulsed input beam by a single beam/pixel.

This process is repeated each M (i.e., 9) input pulses. The result of this operation is the rapid generation of an interlaced vertical scan beam in the far-field 325: a single vertical scan pattern is comprised of 23 (N) laser beams that have been interlaced 9 (M) times.

The specific number of deflection angles M is set in combination with the number of spatially overlapping laser beams N generated by the HDG 315 and the laser 305 divergence so as to fill the farfield scan/raster pattern. The reason this approach is necessary, and unique for LADAR applications, is that in a given time interval only a limited number of parallel data channels are generally available for processing reflected laser signals (i.e., laser signals reflected from objects in the far-field).

Typically, the number of parallel data channels available to process these reflected laser signals determines the value of N - the number of beams generated by the HDG 315. If an unlimited number of processing channels were available, a single HDG with N x M output beams would be used and the AO scanner 320 would be unnecessary. However. since the number of parallel data channels is often one of a LADAR system's limiting factors, this approach provides a unique solution.

A suitable AO scanner 320 may have its optical material made from, for example, tellurium dioxide (TeO2 ) whose surfaces are anti-reflective coated. Additionally, an AO scanner needs to be selected to have an acceptable beam separation - a beam separation that is large enough to separate the interlace of the HDG 315 generated N beams in the far-field. An AO scanner suitable for use in the invention would be well-known to those of ordinary skill in the field.

Another unique feature of the instant invention is its use of an acousto-optical deflection control unit 330 to adjust the number of AO scanner 320 beam deflection angles M generated at any given time. By adapting the value of M a solid-state laser beam scanner in accordance with the invention can compensate, as a function of target proximity, for the available capacity of the LADAR's associated signal processing unit.

The deflection control unit 330 includes a radio frequency (RF) driver capable of generating a different frequency for each of the AO scanner's M deflection angles. By adjusting the instantaneous value of M as a function of target proximity, a solid-state means of effecting under-sampling can be implemented. See "Operational Scenario" below for more discussion on this aspect of the instant invention.

The use of a solid-state beam scanner in accordance with the invention allows for the elimination of a conventional LADAR system's mechanically mounted and rotated mirror (galvanometer) assembly. Unlike the galvanometer, the solid-state beam scanner is a rigidly fixed series of optical components with no moving parts. As such, it is able to withstand considerably more lateral and axial g-loading than a galvanometer. Estimates of the g-loads likely to be encountered in a deployed submunition system are on the order of 50 to 70 g's. These estimated loads would be higher for a maneuvering interceptor missile employing a LADAR system. At these g-force levels the resulting mirror warping evident in a LADAR system using a galvanometer would result in much lower signal-to-noise ratio of the LADAR's reflected laser signal and three dimensional image mapping errors which could result in the loss of target during a maneuver.

A LADAR system comprising the inventive solid-state beam scanner is, therefore, a ruggedized optical system - better able to withstand the high g-forces inherent in many application environments such as an interceptor missile.

Operational Summary: Solid-State Beam Scanner For a first pulse from the solid-state laser 305, the HDG 315 generates N spatially overlapping laser beams. These N spatially overlapping laser beams are directed into the far-field by the AO scanner 320. Each set of N beams generated by the HDG are interlaced by the AO scanner to form a single complete vertical scan line in the far-field 325. That is, a first pulsed laser beam passes through the system and generates 23 (N) pixels/laser beam dots in the far field (see the black or filled-in dots in FIG. 3). A second pulsed laser beam passes through the system and is offset by the AO scanner by l pixel (see the empty dots below the initial "filled-in" dots in FIG. 3). This process is repeated 9 (M) times until an entire vertical scan line is generated in the far-field.Thus, a single vertical scan line in the far-field is created by interlacing M N-pixel laser beams. A complete far-field scan raster is generated by sweeping the vertical scan line in the azimuth. This, in tum, is typically done by mounting the solid-state beam scanner system in a gimbal mechanism.

As would be known to those of ordinary skill in the field, a complete LADAR system employing a interlaced vertical scan circuit in accordance with the invention, would combine the solidstate beam scanner subsystem 300 with, as a minimum, (l) a means to rotate the entire assembly in the azimuth to generate a complete matrix or scan raster in the far-field, (2) receivers to capture the reflected laser light from the far-field, (3) signal processing means to analyze the received reflected laser signals, and (4) suitable power supplies..

Operational Scenario Now consider a typical operational scenario for an interceptor missile based LADAR system 100 comprising the solid-state laser beam scanner of the instant invention. Initially, the LADAR system scans the far-field at long range searching for a target. The scan pattern during this phase, referred to as the target search phase, of operation is a two axis array of pixels with no gaps between the rows and columns. An example (partial) scan pattern for M = 6 and N = 5 is shown in FIG. 4A.

(The values of N = 5 and/or M = 6 is illustrative only and is not restrictive.) The scan pattern of FIG.

4A represents a baseline scan raster pattern.

As the missile closes in on its target, the number of pixels striking the target (and reflected back to the LADAR's receiving subsystem) increases. At some point the LADAR's target recognition processor can become overloaded due to the number of pixels which must be processed. In prior art systems, it is the LADAR target recognition processor that determines which rows and columns of the reflected laser signal to process and which to ignore.

In a LADAR system employing the inventive solid-state laser beam scanner, the acoustooptical deflection control unit 330 changes the value of M. By reducing the number of AO scanner deflection angles M from an initial high value used during the target search phase (M = 6 in FIG. 4A) to successively lower numbers as the missile approaches its target (M = 3 in FIG. 4B, M = 2 in FIG.

4C, and M = 1 in FIG. 4D) and simultaneously increasing the azimuth scan rate, lower resolution scan patterns are generated. The lower resolution scan patterns effect a reduction in LADAR signal processing requirements. An increased azimuth scan rate can be achieved in the instant invention by increasing the angular scan rate voltage applied to the gimbal system. As would be known to a worker of ordinary skill in the field, this is a conventional technique for increasing the azimuth scan rate. One benefit of the instant invention is that its design does not impact the design of a LADAR's gimbal system.

Some Advantages of the Invention Advantages of a solid-state beam scanner in accordance with the invention and a LADAR system incorporating it include: 1. Improved Performance. The instant invention eliminates the rotating mirror found in prior art systems and, thereby, improves the quality and performance of the generated vertical scan image.

In prior art systems anomalies in the vertical scan image are caused by the mechanical means of generating a vertical scan image. That is, by the galvanometer's 250 rotating mirror. These anomalies result from mirror flexing caused by the rapid rotation of the mirror which, in turn, distort far-field pixels in an inconsistent manner and change the reflected laser signal received over different portions of the scan.

2. Improved Redness. A LADAR system incorporating a solid-state beam scanner in accordance with the invention provides improved ruggedness. In particular, the structure of the preferred embodiment allows a LADAR system to operate effectively in high stress or harsh environments, e.g., in high g-force (50+ g's) conditions such as those found in interceptor missile applications.

3. Improved Vertical Scan Efficiencv. A solid-state beam scanner in accordance with the invention has no mechanical fly-back time associated with the generation of its vertical scan pattern and thus, can achieve 100% vertical scan efficiency. In contrast, mechanical designs such as those employing a galvanometer have a certain scan efficiency associated with their mechanical properties. At nominal scan rates for instance (e.g., 100 Hz vertical scan rate), a mechanical galvanometer has a "fly-back" time that typically reduces a LADAR system's vertical scan efficiency by 20%.

4. Improved Vertical Scan Accuracv. The instant invention's use of an acousto-optic scanner eliminates any non-linearity in the vertical scan pattern that results from the inaccurate or imprecise control of a galvanometers rotational speed. Thus, the accuracy of the generated vertical scan pattern is improved.

5. Lower Cost. A beam scanner in accordance with the invention uses the combination of a holographic diffraction grating and an acousto-optic scanner to replace the mechanical galvanometer of prior art systems. In addition to being less expensive, HDGs and AO scanners (1) have no moving parts and (2) are typically lighter. All these factors contribute to making a LADAR system employing the inventive beam scanner more robust - less prone to mechanical failure.

It will be appreciated by those of ordinary skill having the benefit of this disclosure that numerous variations from the foregoing illustration will be possible without departing from the inventive concept described herein. Accordingly, it is the claims set forth below, and not merely the foregoing illustration, which are intended to define the exclusive rights claimed in this application program.

Claims (21)

1. A ruggedized laser detection and ranging system for (1) generating a transmitted laser signal into a far-field, (2) receiving a portion of the transmitted laser signal that is reflected back to the ruggedized laser detection and ranging system, said portion of the transmitted laser signal referred to as a reflected laser signal, and (3) processing the reflected laser signal, said ruggedized laser detection and ranging system comprising: (a) a solid-state optical transmitter subsystem further comprising (1) a neodymium doped yttrium vanadium oxide (Nb:YVO4) pulsed laser source for generating laser pulses having widths of between 10 and 20 nanoseconds and a laser pulse repetition rate of between 10 and 120 kilohertz, said laser pulses forming a laser beam, (2) a beam expander operatively coupled to said Nb::YVO4 pulsed laser source for expanding said laser beam, (3) a holographic beam segmenter operatively coupled to said beam expander for generating nine spatially overlapping laser beams in response to the expanded laser beam, (4) a tellurium dioxide acousto-optic scanner having surfaces coated with an anti reflective compound and operatively coupled to said holographic beam segmenter for deflecting said nine spatially overlapping laser beams through a maximum of eight specified angular offsets, and (5) an acousto-optical deflection control unit operatively coupled to said tellurium dioxide acousto-optic scanner for dynamically adjusting the number of specified angular offsets from between one and eight; (b) a stabilized gimbal assembly for rotating said solid-state optical transmitter subsystem in azimuth;; (c) a receiver optical subsystem operatively coupled to said stabilized gimbal assembly for receiving said reflected laser signal; and (d) a processing unit operatively coupled to said receiver optical subsystem for processing said reflected laser signal.

2. A ruggedized solid-state vertical beam scanner for a laser detection and ranging system comprising: (a) a neodymium doped yttrium vanadium oxide (Nb:YVO4) pulsed laser source for generating a plurality of laser beam pulses having widths of between 10 and 20 nanoseconds and a laser beam pulse repetition rate of between 10 and 120 kilohertz, said laser pulses forming a laser beam; (b) a beam expander operatively coupled to said Nb::YVO4 pulsed laser source for expanding said laser beam said; (c) a holographic beam segmenter operatively coupled to said beam expander for generating nine spatially overlapping laser beams in response to said expanded laser beam; (d) a tellurium dioxide acousto-optic scanner having surfaces coated with an anti-reflective compound and operatively coupled to said holographic beam segmenter deflecting said nine spatially overlapping laser beams through a maximum of eight specified angular offsets, and (e) an acousto-optical deflection control unit operatively coupled to said tellurium dioxide acousto-optic scanner for dynamically adjusting the number of specified angular offsets from between one and eight.

3. A ruggedized solid-state vertical beam scanner for a laser detection and ranging system comprising: (a) a pulsed laser source for generating a laser beam; (b) a beam expander operatively coupled to said pulsed laser source for expanding the laser beam; (c) a holographic beam segmenter operatively coupled to said beam expander for generating a plurality of laser beams in response to the expanded laser beam; (d) an acousto-optic scanner operatively coupled to said holographic beam segmenter for deflecting said plurality of laser beams through a plurality of specified angular offsets to generate a vertical scan beam; and (e) an acousto-optical deflection control unit operatively coupled to said acousto-optic scanner for dynamically adjusting the number of said plurality of specified angular offsets.

4. A laser detection and ranging system incorporating the solid-state vertical beam scanner of claim 3 and including an optical receiver subsystem and processing unit.

5. The solid-state vertical beam scanner of claim 3, wherein said pulsed laser source is selected from the group consisting of neodymium doped yttrium aluminum garnet, neodymium doped yttrium lithium fluoride, and neodymium doped yttrium vanadium oxide (Nb:YVO4).

6. The solid-state vertical beam scanner of claim 3, wherein said pulsed laser source generates laser pulses having widths of between 10 and 20 nanoseconds and a laser pulse repetition rate of between 10 and 120 kilohertz.

7. The solid-state vertical beam scanner of claim 3, wherein said holographic beam segmenter generates nine spatially overlapping laser beams in response to said expanded laser beam.

8. The solid-state vertical beam scanner of claim 3, wherein said acousto-optic scanner is a tellurium dioxide acousto-optic scanner having surfaces coated with an anti-reflective compound.

9. The solid-state vertical beam scanner of claim 3, wherein said acousto-optic scanner has a maximum of eight specified angular offsets.

10. A ruggedized laser detection and ranging system for (I) generating a transmitted laser signal into a far-field, (2) receiving a portion of the transmitted laser signal that is reflected back to the ruggedized laser detection and ranging system, said portion of the transmitted laser signal referred to as a reflected laser signal, and (3) processing the reflected laser signal, said ruggedized laser detection and ranging system comprising:: (a) a solid-state optical transmitter subsystem further comprising (1) a pulsed laser source for generating a laser beam, (2) a beam expander operatively coupled to said pulsed laser source for expanding the laser beam, (3) a holographic beam segmenter operatively coupled to said beam expander for generating a plurality of laser beams in response to the expanded laser beam, and (4) an acousto-optic scanner operatively coupled to said holographic beam segmenter for deflecting said plurality of laser beams through a plurality of specified angular offsets to generate a vertical scan beam; (b) a stabilized gimbal assembly for rotating said solid-state optical transmitter subsystem in azimuth; and (c) a receiver optical subsystem operatively coupled to said gimbal for receiving said reflected laser signal.

11. A ruggedized laser detection and ranging system of claim 10 and including a processing unit operatively coupled to said receiver optical subsystem for processing said reflected laser signal.

12. The ruggedized laser detection and ranging system of claim 10 wherein, (a) said pulsed laser source is a neodymium doped yttrium vanadium oxide (Nb:YVO4) pulsed laser source that generates laser beam pulses having widths of between 10 and 20 nanoseconds and a laser beam pulse repetition rate of between 10 and 120 kilohertz; (b) said holographic beam segmenter generates nine spatially overlapping laser beams in response to each expanded laser beam pulse; and (c) said acousto-optic scanner is a tellurium dioxide acousto-optic scanner having surfaces coated with an anti-reflective compound.

13. A ruggedized solid-state vertical beam scanner for a laser detection and ranging system comprising: (a) a neodymium doped yttrium vanadium oxide (Nb:YV04) pulsed laser source that generates laser beam pulses having widths of between 10 and 20 nanoseconds and a laser beam pulse repetition rate of between 10 and 120 kilohertz; (b) a beam expander operatively coupled to said Nb:YVO4 pulsed laser source for expanding each laser beam pulse; (c) a holographic beam segmenter operatively coupled to said beam expander for generating nine spatially overlapping laser beams in response to each expanded laser beam pulse; and (d) a tellurium dioxide acousto-optic scanner having surfaces coated with an anti-reflective compound and operatively coupled to said holographic beam segmenter for deflecting said plurality of laser beam pulses through specified angular offsets to generate a vertical scan beam.

14. A ruggedized solid-state vertical beam scanner for a laser detection and ranging system comprising: (a) a pulsed laser source for generating a laser beam; (b) a beam expander operatively coupled to said pulsed laser source for expanding the laser beam; (c) a holographic beam segmenter operatively coupled to said beam expander for generating a plurality of laser beams in response to the expanded laser beam; and (d) an acousto-optic scanner operatively coupled to said holographic beam segmenter for deflecting said plurality of laser beams through specified angular offsets to generate a vertical scan beam.

A A laser detection and ranging system incorporating the solid-state vertical beam scanner of claim 14 and including an optical receiver subsystem and processing unit.

16. The solid-state vertical beam scanner of claim 14, wherein said pulsed laser source is selected from the group consisting of neodymium doped yttrium aluminum gannet, neodymium doped yttrium lithium fluoride, and neodymium doped yttrium vanadium oxide (Nh:YVO4).

17. The solid-state vertical beam scanner of claim 14, wherein said pulsed laser source generates laser pulses having widths of between 10 and 20 nanoseconds and a laser pulse repetition rate of between 10 and 120 kilohertz.

18. The solid-state vertical beam scanner of claim 14, wherein said holographic beam segmenter generates nine spatially overlapping laser beams in response to said expanded laser beam.

19. The solid-state vertical beam scanner of claim 14, wherein said acousto-optic scanner is a tellurium dioxide acousto-optic scanner having surfaces coated with an anti-reflective compound.

20. The solid-state vertical beam scanner of claim 14, wherein said acousto-optic scanner has a maximum of eight specified angular offsets.

21. A solid-state vertical beam scanner for a laser detection and ranging system, or a laser detection and ranging system containing it, substantially as described herein with reference to Figure 3 and/or Figure 4 of the accompanying drawings.