Laser Doppler multi-beam differential vibration sensor for real-time continuous visualization of buried objects in multiple frequency bands.

Laser-acoustic detection of buried objects, such as landmines, uses elastic waves in the ground and a laser vibrometer to create a vibration image of the ground surface. A decision on the presence of a buried object is made by analyzing vibration images for multiple vibration frequencies. With traditionally used laser Doppler vibrometers, the vibration imaging data are saved to a computer memory to be analyzed, which increases the detection time.

Application of line-scan CMOS camera in multi-beam heterodyne differential laser Doppler vibration sensor.

The possibility of using a line-scan digital CMOS camera as a photodetector in a multi-beam heterodyne differential laser Doppler vibration sensor has been investigated. Application of the line-scan CMOS camera allows for selection of a different number of beams for a particular application in the sensor design, and for a compact design of the sensor. It was demonstrated that a limitation of the maximum measured velocity caused by the camera limited line rate can be overcome by selecting the beams separation on the object and the value of shear between images on the camera.

Laser Doppler multi-beam differential vibration sensor based on a line-scan CMOS camera for real-time buried objects detection.

Laser Doppler vibrometers (LDVs) traditionally used for ground vibration sensing in laser-acoustic detection of buried objects are limited to operation from a stationary platform due to their sensitivity to the motion of the LDV itself. In order to overcome this limitation a novel Laser Multi-Beam Differential Interferometric Sensor (LAMBDIS), has been developed. The LAMBDIS allows for measurements of vibration fields with interferometric sensitivity, while having low sensitivity to the motion of the sensor itself.

Multi-beam heterodyne laser Doppler vibrometer based on a line-scan CMOS digital camera.

Multi-beam laser Doppler vibrometers (MB-LDVs) have an advantage over scanning single-beam laser Doppler vibrometers (LDVs) due to the reduction in measurement time and their ability to measure non-stationary and transient events. However, the number of simultaneously interrogated points in current MB-LDVs is limited due to the complexity of the electronic hardware, which increases with the number of measurement channels. Recent developments of high-speed line-scan CMOS cameras suggest that their use in MB-LDVs can reduce the hardware complexity and increase the number of measurement channels.