New scheme of ship

By Fred Cole,2014-03-09 09:34
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New scheme of ship

    New scheme of ship-borne IRSTS

    Xing lei

     (Chang chun University of Science and Technology School of Optoelectronic Informationchang chun ,china)

Abstract: The missions of ship -borne infrared search and tracking system IRSTS as

    well as its significance of improving combat capability of naval surface ship were summarized. The development history and the major disadvantages of the first and the second generation ship -borne IRSTS were introduced. According to the new characteristics of future naval combat, the requirements for new generation IRSTS driven by future combat were analyzed. Based on the requirements of high data update ratewide field of view surveillancehigh sensitivityhigh resolution as well as strong

    capability for complex clutter rejectiondistributed aperture staring infrared sensor

    system scheme was considered as the technology solution for new generation ship-borne IRSTS. The technical schemes of new generation ship - borne IRSTS of USA,UK and France were summarized. Moreoverthe advantages and disadvantages of full stare ing scheme and step-staring scheme were analyzed.

    Key words: Ship-borne IRSTS; IRFPA; Staring; Step-staring

0 development background and needs analysis [ 1-3]

    Ship borne infrared search and track system is a kind of detection and tracking of low altitude

    And the threat to the passive surveillance system, it uses a target because the skin of aerodynamic heating and / or ejected the plume radiation infrared radiation detection with

    Tracking target. Ship borne infrared search and track system can provide panoramic surveillance

    Ability, can improve the surface ship to air and surface threat perception Force, due to the passive work, the RF clutter and interference, and in the radiation control becomes more and more important combat environment can realize the electromagnetic static

    Silent. Infrared sensor can be associated with other NAVAL SHIPBOARD sensor ( especially ray

    And electronic warfare sensor ) complement each other, the infrared sensor with high angle

    Degree of resolution, and the infrared spectrum can effectively avoid radar in Offshore surface under conditions of multiparty effect, and the radar has a high distance Resolution, when the two sensor outputs are combined, can be on the target A more robust, more accurate tracking, shortening the route decision time.

    Navy infrared search and track system development began in twentieth Century 70 Time, then, considering the infrared search and track system 's main mission is to make Passive alarm sensor to detect the sea-skimming anti-ship missiles, and for point defense System or confrontation system to provide target indication. Focus on the development of mining engineering

    Scanning infrared detector ( sensor head to rotate to achieve 1 ~ 2 Hz

    Update rate ) system, and the optimization is achieved through the open ocean conditions The long-range detection (horizontal search ).

    However, infrared search and track system after a long

    Time to maturity. Although the construction of a large number of prototype, early View of the development of system false alarm rate are not acceptable, nor the stability Enough, the precipitation, foggy or high humidity environment performance degrades significantly, it

    The greatest distance is relatively limited, and the size is very large, heavy quality ( thus, limiting the carrier height, corresponding ground also limits its vision ). The results, the first generation of the infrared search and track system until the 1980's The medium was put into force by using.

    With the passage of time, the infrared detector technology, processor performance and The algorithm has significantly improved, the development of the infrared search and track system

    Enough tactically, meaningful distances reliably from the clutter central discern Target, while achieving acceptable false-alarm rate. More complex optical design Can achieve, infrared search and track system scanner hardware size and quality Volume is reduced, this can be an infrared search and track system is mounted on the mast

    In order to increase the coverage, and reduce the fitness effects of warship. The equipment of the second generation of infrared search and track system is still used Scanning system, but the use of a long line infrared focal plane array, and the use of Time delay and integral in rotation sensor swept every position

    On a separate detector unit of a plurality of serial output delay, and product Into a single output to improve signal to noise ratio.

    However, this scanning system has some inherent limitations,

    In order to guarantee the required scan rate, each pixel dwell time only For tens of microseconds magnitude, resulting in low signal to noise ratio, causing the probe

    And track judgments between the significant delay, the false alarm rate also have adverse effects.

    In addition, due to the scanning system inherent lower refresh rates, weakened High resolution imaging of the benefits brought about by the. Moreover, a single mast mounted scanning sensor head field will be affected by the mast mounted on deck and other attached

    Belonging to limit, will produce the observed blind area. In addition, scanning infrared search and

    Tracking system including a complex mechanism, therefore, appears in the key system fault

Loss when the redundancy.

    In twenty-first Century, the Navy relate more to coastal operations,

    Rather than just pure sea combat, often involves asymmetric conflict

    Ingredients, battleship will encounter a fast approximation attack aircraft and UAV New threats such as. Because the radar cross section of small, lack of the radial velocity of the letter

    Interest and close to the ship in the sea clutter, the radar system can not be good. Measurement of these new threats, therefore, infrared search and track system became The ideal searching, tracking systems, and, due to the formation of red External image, infrared search and track system has to provide target recognition The ability of the additional advantage of. However, these new threats to infrared search With the tracking system have more than the first generation and the second generation of infrared search and track system

    The greater the pitch angle of coverage: usually need 10 degrees pitch angle of the overlying magnitude

    Cover. At the same time, the Navy still need their high value ship to

    A new generation of stealth sea-skimming missile defense. Due to its high radial velocity Degree, these threats requires early detection target, so that the Ship borne Combat System

    The more time for processing, therefore, the infrared search and track The sensitivity of the system put forward higher requirements: infrared search and track system

    Systems should be designed as the sea-skimming missiles just out of the horizon can detect To, usually in 10 mile.

    New combat mission is an urgent need for a new generation of infrared search and track system

    EC has a step of the improvement to the coast, such as to be adapted to the seaside Combat environment, such as a large viewing area ( preferably hemispherical cover, unlike Earlier infrared search and track system for sea-skimming missiles water Flat search function ), but must be able to respond to ordinary, emergency and conflict time

    The various air and surface targets. In coastal areas, and even

    Harbor regional threats of terrorism, infrared search and track system must be able to Detection of unconventional threats, such as small aircraft, at the same time to sea-skimming Guide

    t military and stealthy threat carries a high level of defense, and must be Bomb tha

    With the farther detecting distance to meet mission requirements. In view of the infrared sensor

    The purchase cost is high, the system of refrigeration type infrared sensor. Eye will directly affect the reliability and life cycle cost.

    On a new generation of naval shipboard infrared search and track system for the main And can be categorized into the following 6 aspects.

    ( 1) in the spatial coverage

    Large space coverage of this design include the need for panorama drive

    Observation and observation without blind area, and has a large elevation angle coverage to

    At the same time detecting air and surface targets.

    The existing scan infrared search and track system includes a passage in the party A direction for continuous scanning search infrared sensor head, due to The mast installation constraints, this centralized structure will lead to large Blind spot ( near the mast. ). In order to provide a panoramic view of the cover, a new generation of red

    External search and tracking system design will be interested in the range of 360 degrees field of view is divided into a few

    A field, each field by an infrared sensor coverage, each sensor

    The field and adjacent to the sensor's field of view slightly overlapping to ensure space Cover, and in the azimuthally direction 360 degrees tracking continuity. Such distributed

    The sensor head has many advantages, because each sensor can be single Only installed in different position. In a single mast top.

    Loading solutions, sensor can be located on a single around the mast.

    ( 2) image quality

    Need to provide high resolution, high frame rate image in order to combat personnel Situation awareness, observation of motor threat assessment and target identification, complete destruction, use

    In the purpose of infrared image requires appropriate infrared image should have high Image resolution and high frame rate, video in a digital format for transmission to be Battle Staff in order to eliminate the noise or the digital-analog conversion caused by the artifact, and shortening

    Delay time.

    ( 3) performance

    On the performance of the main requirements include: long detection distance, to build aircraft time

    A short, low rate of false tracks. Access frequency and bandwidth of the spectrum of these two parameters

    Reasonable choice to achieve such high performance is the key.

    High frequency acquisition can through the use of a large number of data reduction concept Noise, high rate by gaze provides high route refresh rate will effectively Clutter suppression. Background distribution analysis ( spatial and temporal distribution ) show:

    10 Hz monitoring frequency close to the different types of context ( the sea, since the However the ground ) the time constant of the mean of the distribution, able to cope with the sun shining.

    Have proved that: high acquisition rate is a false alarm and clutter suppression Insurance approach.

    High frequency will significantly reduce the track correlation range. When acquiring a high rate

    , two times for the deviation between the very small, corresponding to a given Track detection door can be reduced, in the detection of inner door to produce more than one virtual

    The police ( and subsequently generates error probability will decrease the association ).

    ( 4) the availability, reliability and maintainability characteristics Photoelectric system availability, reliability and maintainability characteristics optimization

    Mainly based on the component selection, maintenance strategy and the realization of the product.

    Diameter. Based on the concept of the third generation of staring IR search and tracking system using static

    The sensor design, no external moving parts, reducing the fault

    Probability. Using highly reliable cooler but also improve the reliability of the system Key factors.

    ( 5 ) the ships integrated

    As a driver, easy in ship integrated in order to simplify

    Ship integrated task requirements of the infrared search and track system quality and body

    Area minimization. Complete gaze structure combined with the principle of optical multiplexing and

    Each sensor using single uncooked focal plane array can make the volume

And the weight is reduced to an acceptable level.

    At the top of structure or mast available space is also a ship

    Integration to solve the problem, allowing an infrared search and track system sensor Unit and a signal processing unit is the distance from the face set for ship To provide some flexibility.

    ( 6) with upgrading improvement potential

    A new generation of infrared search system must be for the next ten years and even Decades of technology evolution and prediction have upgraded and improved space. Because the red

    External sensor is an infrared search and track system performance is a key unit, A new generation of infrared search and track system must be able to achieve the future focal plane array

    The column plug, so as to adopt more high-performance devices to improve the system Performance. With the evolution of the combat management system interface is also the infrared search and track

    System upgrade and improve a way.

    1 solutions

    On the diversity of needs of technical solution is based on the distribution of Type of staring infrared sensor infrared search and track system, such Third generation solutions using multi sensor head ( distributed aperture infrared Sensor ) to overcome the naval installation constraints, and at a high rate to provide uninterrupted

    Panoramic alert, wide azimuth angle coverage, fast data refresh and The earlier track confirmation. It adopts the sound system design to make it occupy The least space, reduce maintenance, simplify the logistics support, and the battle Use maximum, thereby reducing the cost of whole life cycle.

    In the concrete realization can be divided into complete gaze design and step Gaze design.

    1.1 - staring system

    Normal completely gaze is designed based on the mounted on a mast or Cloth on ships of more than a dozen infrared cameras, each IR camera cover Cover a small part of the field of view, as the need for a large number of infrared detection

    Device, will lead to a high cost, low reliability solutions.

    The United States, Britain and France had started their will be staring array Technology application in ship borne infrared search and track in the plan. On the generation of 360 degrees

    Scan ship borne infrared search and track system for the refresh rate is only 0.5. 1 Hz, the main purpose of the plan is to speed up the processing speed; another Purpose is through the use of a longer integration time increase sensitivity. They The analysis has proved that : the whole way, having a staring

    Large aperture optical and highly stable sensor of infrared search and Navy Tracking system has the highest performance.

    However in the naval shipboard infrared search and track system used in gaze

    Focal plane array technology is an obstacle is encountered: radar and even fly Machine on the infrared missile approach warning system, infrared search and Only a trace system design parameters to help processor from clutter resolution Don't make a missile threat -- resolution, shipboard infrared search tracking system can

    To and must good use of resolution. For a given sensitive unit scale Inch w infrared focal plane array, if want to high angular resolution covering To cover the airspace, the total length of the detector will be very long. Such as 100 u red spatial resolution, the detector array element size of 25 ~ m, Then the detector for a length of 2 w / M = 1.57. Therefore, the staring array technology Surgery for 360 degree level monitoring using wide angle observation technology, this need

    To be integrated using asymmetric resolution, reduced resolution, separation of optical System and line of sight step technology.

    The United States Office of naval research is funded development for ship borne red Searching and tracking distributed aperture sensor [1, 4], the sensor includes 3 A 5 : 1 aspect ratio wave array ( using the visual system.

    Division 2560 x 512 medium wave infrared focal plane arrays ) and 2.56 / 1 range Ratio of asymmetric optical system the staring sensors, general asymmetric ratio 12.8: 1, that will be assigned to the low horizon detector search area The domain is appropriate. Employing such a measure can be achieved on the dark tone Fast missile detection sensitivity, resolution and just beyond the horizon for being a threat

    The goal, then must emphasize the elevation direction resolution.

    The British Ministry of defense research and Navy infrared search and track system. Verification prototype shown in [4] using two staring infrared camera and separation field

    Learning system provides the skyline panoramic monitoring, the staring infrared detection

    Device than the current scan infrared search and track system for higher sensitivity and speed of updates, demonstration prototype for the installation of two sets of commercial

    640 x 512 medium wave detector, but is designed to ensure the future Using a 1024 x 768 pixels detector. In order to make commercial camera Panoramic coverage, made by using field optical system, which can be 640 x The 512 pixel detector field of view is transformed to provide a 5 : 1. Than, this method effectively to cover all of the ship around the horizon The focal plane detector number is reduced by half.

    France's Artemis [3 ] design is based on a novel optical design ( light Spatial multiplexing ) full gaze concept, it only uses 3 sensing

    Device in order to make the above mentioned defects minimum, while maintaining full gaze concept

    High performance levels.

    Artemis infrared search and track sensor unit with 10 Hz frequency

    Rate on medium wave infrared ( 3 ~ 5 m) to finish the scene access, orientation field Greater than 120 degrees or 26 degrees, field of view. Infrared search and track sensor unit

    Using space principle of optical multiplexing, using a single with the first In the infrared focal plane array passive infrared imaging device in the field of view of each

    A separate area at a high rate to obtain initial image. For each of the initial image With the use of strap down inertial measurement unit ( its output with the frigate ins Navigation system unit ) receives initial image absolute attitude angle of sight Measurement of.

    Spatial multiplexing is used for continuous rotation around the line of sight imaging Rectangular prism ( periscope ) completed, principle of optical multiplexing as in Figure 2

    Show. Because of the prospect of the output mirror, looking into the mirror 's optical constant, into

    Like the sight and the exit pupil is continuously converted into a circle, and in the infinite objects without image motion. Using this principle, in the 6 partial beam with map

    Like the sight was converted to make the image field to the sensor field a. Fixed area, the middle of the seventh region of direct access, without slant beam. When the

    Images of the exit pupil is not covered, in each region of the image acquisition is In the partial beam device with the front sight cross when completed.

1.2 step - staring solution [1, 5]

    Although the complete staring system may have the highest performance ( high Resolution imaging of 100 rad grade, high refresh rate of at least 10 Hz ), but in In the future years within their cost will still be very high. Because the infrared search and

    Tracking system of basic cost is proportional to the desired refrigeration type infrared camera

    Machine number and the associated optical system and processing all the video signal The computing power needed.

    Based on this consideration, some designers trying to limit sensor

    Specification and number to reduce the system cost, but it will obviously reduce As the sensor resolution ( 1 mead ), because each imaging array will Must cover a large area, unless using some type of regional sweep

    Description, in this case, the system became a step - staring system. But mining Step - staring out the infrared search and track system for identification Transducer possibilities, also hindered it from background clutter recognition Real goals. Moreover, using the" time" is also reduced by scanning

    In the infrared search and tracking system image refresh rate, must consider the image High refresh rate can compensate reduces resolution to the infrared search

Tracking the performance of the system.

    It is easy to be 640 x 512 infrared imaging array and readout set

    A circuit so that the infrared sensor can exceed 100 Hz refresh rate fast Photo mode. Usually, the Navy infrared search and track system application Monitor the scene to return does not require such a high refresh rate. Therefore, using the

    Some type of structure so that the image sensor eye movement in the horizontal direction 360 degree coverage can help to reduce the required number of sensors. The conventional frame system has not adapted to obtain rapid stepping - at work For, as the frame system usually has large inertia, on the stability of Lee, but for the stepper is unfavorable. The optical invariant" light Learn multiplex" is a notable method, but this method

    Need some more complex fixed and the movement of the optical component. In order to simplify the structure of the system, a solution is the infrared camera Like machine mounted in a frame on a horizontal platform, a horizontal platform is Servo control, in order to complete the image obtaining synchronous step motion. France Sagem DS using commercial off-the-shelf components, in 4 when s revisited In 12 degree observation field, however, for automatic target detection and Trace air threat, the refresh rate is low, in the two scanning between target will show a significant angle movement.

    In order to make full use of infrared focal plane array FPA staring imaging high frame Frequency ( usually 100 Hz ), for the infrared search and track system, must seek A quick step solution. To this end, France VAMPIR in design

    NG infrared search and track system uses a modified step - stare.

    Case. Based on the second generation of line array infrared camera experience, Sagem DS.

    At VAMPIR NG, a method using 3 ~ 5 m focal plane array

    Refrigeration type infrared camera Navy infrared search and track system, and the use of

    A high quality mirror with a small scanner to cancellation in the sensing The integration time eye movement.

    VAMPIR NG optical design includes 4 movable shaft:

    ( 1 ) the sighting axis sensor head panoramic scanning; ( 2) pitching Shaft support designed to manipulate the infrared sensor center located in the constant The real position of the elevation angle of elevation ( height ) mirror, regardless of ship rolling

    How to turn and yaw motion; ( 3) the alignment shaft and pitching the scanner axis. Improved step stare optical design as shown in Figure 3, the infrared light Through the external window into the sensor head, the first reflection occurs in transport

    Dynamic height mirror, folding mirror # 1 can make the designer

    In a very wide azimuth angle range minimum height reflecting mirror, the first group Lens constituting a scanning mirror in the prior reducing entrance pupil size Telescope design, folding mirror # 2 make the system more compact. Pick

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