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Conformal, Random Access Beam Steering for Broadband Systems


TECHNOLOGY AREA(S): Air Platform, Sensors


OBJECTIVE: Demonstrate a conformal, thin, broadband and rapid optical beam steering device without gimbals.


DESCRIPTION: There is a critical DoD need for a new class of broadband, random access electro-optic sensors on lightweight, airborne platforms. A conformal, thin, broadband and rapid steering beam steering device would overcome the usual, disadvantages of traditional optical systems and electro-optical devices beam steering devices, which use heavy and power-hungry gimbals and optical components making large mechanical motions. Non mechanical optical beam steering devices have been demonstrated. Most use electrically- controlled optical diffraction to steer the optical beam. These devices operate over a narrow wavelength band, since the diffraction induced steering angle depends sensitively on the wavelength of light. These narrowband devices are not suitable for broadband optical applications.

Most passive electro-optic (EO) systems are broadband. Also there are laser systems, such as femto-second pulsed lasers and supercontinium lasers that are broadband and will allow broadband light detection and ranging (LIDAR) systems. Providing broadband beam steering for lidar and passive EO systems could enable new LIDAR capabilities using these super continuum lasers, and new passive EO systems capability.

As a baseline this effort will require operation in either the near IR wavelength region or the mid IR wavelength region. The proposed effort should discuss extending this capability to the visible and to either the NIR region or MWIR region, which ever band is not covered by the baseline approach.

Threshold performance objectives are a 10 cm diameter aperture, a 60 degree field of steering in both angular dimensions, > 75% optical transmission efficiency , broadband operation over at least 10 percent bandwidth, beam quality no worse than 3 times diffraction limit, and < 1 msec beam steering time. It is desire able to exceed these goals if possible. It is desirable to keep physical size small, with the beam steerer no deeper than the diameter of the clear aperture beam steering device. A key aspect of the approach is that the beam steering concept must be compatible with conformal windows on aircraft (i.e. windows that conform to the airframe surface). Beam steering approaches should be capable of operating bi-directionally, that is, as optical transmitters and receivers.


PHASE I: Determine feasibility of possible EO beam steering approaches and evaluate their performance. The Phase I effort should result in (1) detailed physical optics simulation of light propagation through the component(s), (2) assessment of the beam steering dynamic behavior and electrical properties, and (3) preliminary evaluation of the expected size, weight, and power consumption of a prototype implementation.


PHASE II: Demonstrate the Phase I concept via laboratory brassboard experiments, and develop a preliminary design of a device for field experiments. In Phase II, a Phase I concept will be reduced to practice and performance validated in a laboratory setting. The experiments conducted should result in empirical and/or analytic knowledge that will be used in the preliminary prototype design effort. The laboratory brassboard may not directly meet the desired threshold objectives, but should at a minimum provide characterization data and demonstrate by analysis that the performance objectives can be met. The preliminary design should focus on a demonstration system which could be utilized in a field experiment and would directly meet the performance objectives. Phase II deliverables include: (1) laboratory brassboard design, (2) report of brassboard experiment results, (3) preliminary design package for field test device.


PHASE III DUAL USE APPLICATIONS: A Phase III system could be applied to a number of commercial applications, including: 1) LIDAR measurements of wind velocities, aerosol characterization, and terrain mapping, 2) compact surveillance systems in security applications. A commercially focused Phase III effort would choose a viable commercial use and build a prototype system optimized for that application.

The DoD currently uses a large number of broadband EO systems, and active EO systems (e.g. LIDAR) are increasingly of interest as well. The use of optical systems such as these is limited by the need for a turret to house the beam director. This protrusion causes aerodynamic drag that limits range and speed of the platform. Additionally, the wake turbulence can limit the useful speed and field-of-regard regime of the sensor systems. A Phase III effort would focus on increasing the TRL level of the technology to a point that is compatible with an airborne demonstration on a relevant military air platform. The effort would include any necessary component technology development, but primarily be a detailed design, integration and test phase. Phase III would include a final test and evaluation of the beam steerer with both an active EO system and a broadband passive EO sensor.


KEYWORDS: beam steering, electro-optics, remote sensing, conformal, optics 

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