Apparatus for providing laser countermeasures to heat-seeking missiles

The present invention was made with United States Government support under Contract number N00173-05-C-6020. The Government has certain rights in the present invention.

1. Technical Field

The present invention relates to countermeasures for heat-seeking missiles in general, and in particular to an apparatus for providing laser countermeasures to missiles launched against airborne helicopters and aircraft.

2. Description of Related Art

Advanced Man-Portable Air Defense Systems (MANPADS) present a significant threat to airborne fixed-wing aircraft and helicopters. Several existing Missile Warning Systems (MWS), including the Common Missile Warning System (CMWS), are capable of detecting and reporting missile threats with high detection confidence. In addition, laser-based infrared countermeasure (IRCM) systems can also provide the needed protection from MANPADS for many types of aircraft.

However, the coarse angular tracking capabilities of MWSs are insufficient for directed employment of IRCMs. As a result, conventional IRCM architectures have to reply on secondary tracking systems that employ cryo-cooled infrared focal planes and large gimbals, which substantially increases system cost and mass. In addition, conventional IRCM systems tend to have complex pointer/tracker-turret assemblies that are typically very expensive. Thus, the cost and mass of conventional IRCM systems have been too prohibitively high to be implemented for all but a few selected number of high-value aircraft.

Consequently, it would be desirable to provide an improved IRCM system that is more cost effective.

In accordance with a preferred embodiment of the present invention, a laser-based infrared countermeasure system includes a set of receive optics, a dichroic filter, first and second detectors, a lens module and a laser. Receive optics are configured to receive optical information. The lens module reflects the optical information from the receive optics to the dichroic filter. The dichroic filter selectively splits the optical information to the first and second detectors. The first and second detectors, each of which is formed by a single-pixel detector, detects a potential missile threat from the optical information. Based on information collected by the first and second detectors, the laser sends laser beams to neutralize any missile threat.

All features and advantages of the present invention will become apparent in the following detailed written description.

The invention itself, as well as a preferred mode of use, further objects, and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein:

FIG. 1 is a block diagram of an infrared countermeasure system, in accordance with a preferred embodiment of the present invention;

FIG. 2 is a block diagram of the optical components of the infrared countermeasure system from FIG. 1 , in accordance with a preferred embodiment of the present invention;

FIG. 3 illustrates a single-pixel detector, in accordance with a preferred embodiment of the present invention; and

FIG. 4 illustrates a multi-pixel detector, in accordance with a preferred embodiment of the present invention.

Referring now to the drawings and in particular to FIG. 1 , there is illustrated a block diagram of an infrared countermeasure (IRCM) system, in accordance with a preferred embodiment of the present invention. As shown, an IRCM system 100 includes a set of receive optics 110 , a detector 115 , an image processor 140 , a laser-pointer unit 120 , and a set of transmit optics 126 . Receive optics 110 point to various directions in order to obtain image data from different parts of the environment. The collected image data are then sent to a detector 115 . Detector 115 may be formed by multiple detectors as will be explained later in details.

After receiving pertinent optical information from detector 115 , image processor 140 maps all targets of interest and prioritizes the target information based on respective intensities. Image processor 140 also provides active interrogations on the optical information to determine whether or not there is a real threat.

When a real threat, such as an incoming heat-seeking missile, is confirmed, image processor 140 activates laser-pointer unit 120 to send laser beams from transmit optics 126 to neutralize the threat. Image processor 140 provides modulation control and direction control to laser-pointer unit 120 for laser beam emissions.

Laser-pointer unit 120 includes a mid-infrared laser 121 , beam-shaping optics 122 and a fiber selector 123 . A laser beam is directed into the end of one of the fibers within a fiber bundle 125 . Fiber bundle 125 is routed along or through the platform to transmit optics 126 . The far ends of fiber bundle 125 and transmit optics 126 are configured to form output laser beams in various directions.

With reference now to FIG. 2 , there is depicted a block diagram of the optical components within IRCM system 100 from FIG. 1 , in accordance with a preferred embodiment of the present invention. As shown, the optical components includes an optical tracking module 210 , a lens module 220 , a dichroic filter 230 , a band 1 detector 115 a and a band 4 detector 115 b . Optical tracking module 210 , which includes a pointer and a set of fast-steering mirrors, is configured for detecting any incoming missile such as a missile 270 . Lens module 220 directs the optical information obtained by optical tracking module 210 to dichroic filter 230 . In turn, dichroic filter 230 selectively splits and sends the appropriate optical information to band 1 detector 115 a and band 4 detector 115 b accordingly. Based on the information collected by band 1 detector 115 a and band 4 detector 115 b , laser 121 may send laser beams to neutralize missile 270 .

For the present embodiment, band 1 detector 115 a detects optical information of approximately 2 micron wavelength, and band 4 detector 115 b detects optical information of approximately 4 micron wavelength. Lens module 220 is preferably an off-axis paraboloid lens.

In accordance with a preferred embodiment of the present invention, each of band 1 detector 115 a and band 4 detector 115 b is made up of a single-pixel detector, such as a single-pixel detector 310 , as shown in FIG. 3 . The information collected by single-pixel detector 310 are sent to a pre-amplifier 320 , an amplifier 330 , an anti-alias filter 340 and an analog-to-digital converter 350 . Image processor 140 (from FIG. 1 ) performs match filtering on the laser pulses information from analog-to-digital converter 350 .

The output bandwidth of detector 310 is preferably greater than 40 MHz, and is Nyquist-sampled (greater than 8 7 samples per second). Basically, the output bandwidth of single-pixel detector 310 must be high enough to resolve individual laser pulses with high fidelity. To maximize compatibility across a wide variety of lasers, a higher bandwidth (>40 MHz for example) is preferred.

The single-pixel detector approach has the lowest bandwidth requirement, but its tradeoffs are longer timelines and reduced target tracking capabilities. As a modification, the single-pixel detector approach can be augmented by adding a few more detectors to form a multi-pixel detector module, as depicted in FIG. 4 . As shown, a multi-pixel detector module 400 includes one high-speed single-pixel detector 410 surrounded by eight low-speed single-pixel detectors 420 . With the 3×3-pixel detector configuration, the eight low-speed single-pixel detectors 420 operate at a relatively low bandwidth intended for passive detection. High-speed single-pixel detector 410 , on the other hand, operates at a relatively high bandwidth for active as well as passive detections. The 3×3-pixel detector module enables target tracking at a relatively high rate by using passive signatures without drastically increasing data bandwidth.

As has been described, the present invention provides an improved IRCM system to heat-seeking missiles.

While the invention has been particularly shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.