OPTRA's Risley-prism based Compact Beam Steerings (CBS) provides an alternative approach to a gimbal and galvanometer based system for scanning and pointing a laser beam. The fundamental technology is a pair of rotating wedges, or Risley Prisms. The advantages of this type of system are:
- Compactness
- Insensitivity to vibration
- Low moment of inertia
- Independent rotational axes (no carried axes, no need for slip rings)
- Robustness
- Speed
When a prism pair is oriented as shown in (a), they both refract light in the same direction and act as a single prism with twice the prism angle of either. In (b), each prism has been rotated about the optical axis by the same angle, but in opposite directions. In this case the beam remains close to the plane defined by the optic axis and the refracted beam shown in (a). In (c), each prism has been rotated by 90 deg and they combine to act as a parallel plate – with no net angular deviation. Thus, any point in a circular field of regard can be achieved by adjusting the angle between the prisms to obtain the desired deflection off-axis, and then rotating the pair to steer the beam in the desired direction.
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Circular scan patterns can be generated by rotating the prisms in the same direction at constant velocities. This mode of operation is useful for trepanning, and is another very attractive features of prism-pair
assemblies - the ability to generate scan patterns by rotating the prisms at
different velocities to obtain spiral, rosette, and pinwheel scans:
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OPTRA has developed Risley Prism laser beam
steering systems for applications in collision avoidance LIDAR, Free-space
optical communications, and Infrared Countermeasures satisfying a wide range of
customer specifications.
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Infrared
Countermeasures
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Optical
Communications
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Optical
Avoidance
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Steering/Scanning
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Steering
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Steering
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Scanning
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Wavelength Range
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2.0 - 4.7 micron
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1.54 - 1.57 micron
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1.54 - 1.58 micron
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Beam Diameter
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3mm (.118")
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120mm (4.0")
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25mm (1.0")
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Field of Regard (FOV)
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120 degrees
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120 degrees |
120 degrees |
Pointing Accuracy
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1 mrad
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0.7 mrad
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1 mrad
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Size
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2.3 inch diameter
3.5 inch length
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10.8 inch diameter
8.7 inch length
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3.4 inch diameter
1.7 inch length
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Weight
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2.3lb
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55lb
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2.3lb
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| 10mm (0.4") Dia Clear Aperture CBS System for Infrared Countermeasures |
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| 120mm (4.75") Dia Clear Aperture CBS System for Optical Communications |
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| 25mm (1.0") Dia Clear Aperture CBS System for Optical Avoidance |
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