Range Gated Viewing with Underwater Camera

The objective of this project report, carried out at FOI, ended up being to assess a range gated underwater camera, for the application identification of bottom objects. This dissertation was based on FMV within the framework of “arbetsorder Systemstöd minjakt (Jan Andersson, KC Vapen)”. The key part has been field trials, that have been performed in both turbid and clear water. Findings regarding the performance of the camera system have been done, based on resolution and contrast measurements during the field trials. Lab testing has been carried out to measure system specific parameters, like the effective gate profile and camera gate distances. The field trials signifies that images can be obtained at considerably longer distances with the tested gated camera, in comparison to a typical video camera. The distance where the target could be detected is increased by a factor…


1 Introduction
1.1 Background
1.2 Aim
2 Identification of Bottom Mines
2.1 Mine Countermeasures
2.1.1 Minesweeping
2.1.2 Mine Hunting
2.2 ROV Operation
3 Camera System
3.1 Gated Viewing
3.2 Hardware
3.2.1 Illuminating Unit
3.2.2 Receiver Unit
3.2.3 Delay of Laser Pulse
3.2.4 Differences between Unit I and Unit II
3.3 Software
3.3.1 Modes of Operation
3.3.2 Settings for Gating
3.3.3 Settings for Picture
3.3.4 Settings for Lens
3.3.5 Scanner Function
3.4 Summary
3.4.1 Problems
3.4.2 Suggestions for Improvements
4 Comparison with Other Systems
4.1 Other Technical Solutions for Underwater Imaging Systems
4.1.1 Laser Line Scanner
4.1.2 Pulsed Laser Line Scanner
4.1.3 Streak Tube Imaging Lidar
4.1.4 3-D Camera
4.1.5 Fluorescence Camera
4.2 Other Gated Viewing Systems
4.2.1 Canada: Laser Underwater Camera Image Enhancer LUCIE
4.2.2 USA: SPARTA See-Ray
4.2.3 Denmark: High Accuracy 3-D Laser Radar
4.2.4 USA: Short-pulse Range Gated Optical Imaging in Turbid Water
4.2.5 Singapore: Underwater Lidar Imaging
5 Optical Properties of Water
5.1 Propagation Speed
5.2 Attenuation
5.2.1 Absorption
5.2.2 Scattering
5.2.3 Attenuation Length Viewing with Underwater Camera 2005-09-06 Adam Andersson version 1.0
5.3 Wavelength Dependence
6 Laboratory Trials
6.1 Beam Characteristics
6.1.1 Beam with 25º Lens
6.1.2 Beam with Fiber Delay
6.2 Gate Characteristics
6.2.1 Measurement of the Effective Gate Profile
6.2.2 Measurement of the Gate Delay
6.2.3 Measurement of the Gate Depth
6.3 Pulse Energy Reduction with Filter
6.4 Summary of Laboratory Trials
7 Field Trials
7.1 Trial 1, Clear Water
7.1.1 Water Quality
7.1.2 Method
7.1.3 Comparative Images
7.1.4 Contrast
7.1.5 Resolution
7.2 Trial 2, Turbid Water
7.2.1 Water Quality
7.2.2 Method
7.2.3 Comparative Images
7.2.4 Contrast
7.2.5 Resolution
7.3 Evaluation of Field Trials
7.3.1 Contrast and Resolution
7.3.2 Maximal Range for Detection
7.4 Summary of Field Trials
8 Image Processing
8.1 Contrast Enhancement
8.2 Noise Reduction
8.2.1 Averaging of Several Frames
8.2.2 Median Filtering
9 Laser Safety
9.1 Laser Characteristics
9.2 Laser Classification
9.3 Minimum Safety Distances…

Source: Linköping University

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