Small-angle phase functions …0:058 < < 208 † have been measured for turbid samples that were then used in a Monte-Carlo theoretical lightscattering model. The measured phase function yields excellent agreement between model predictions and long-path tank measurements.
We outline what is to our knowledge the first experimental demonstration of an excited-state Faraday filter. The filter consists of potassium vapor between crossed polarizers in a dc magnetic field and operates on the 4P((1/2)) ? 8S((1/2)) transition in potassium. The 4P((1/2)) state is populated by a linearly polarized, 10-ns light pulse from a dye laser operating at 769.9 nm. Another linearly polarized, 10-nsec pulse at 532.33 nm traverses the pumped volume of the K cell and is absorbed from the 4P((1/2)) state to the 8S((1/2)) state. The transmission of the filter is approximately 3.5% at 532.33 nm with a bandwidth of less than 10 GHz.
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SPONSOR/MONITOR'S REPORT NUMBER(S)12. DISTRIBUTION/AVAILABILITY STATEMENT Approved for public release; distribution is unlimited. 13. SUPPLEMENTARY NOTES 14. ABSTRACT Current Laser Line Scanner (LLS) sensor performance is limited in turbid water and in bright solar background conditions. In turbid water, backscattered and small angle forward scattered light reaching the receiver decreases underwater target contrast and resolution. Scattered solar energy reaching the detector also decreases detection sensitivity by increasing receiver noise. Thus, a technique which rejects unwanted, scattered light while retaining image-bearing photons is needed to improve modulation and detection techniques to the LLS. This configuration will enable us to use optical modulation to discriminate against scattered light. A nonscanning mockup of an existing LLS, the Electro-Optic Identification (EOID) sensor, has been developed with off-the-shelf components. An electro-optic modulator will be added to this systm to crate a modulated LLS prototype. Laboratory tank experiments will be conducted to evaluate the performance of the modulated LLS as a function of water clarity and solar background levels. The new system will be compared to its unmodulated counterpart in terms of target contrast. ABSTRACT Current Laser Line Scanner (LLS) sensor performance is limited in turbid water and in bright solar background conditions. In turbid water, backscattered and small angle forward scattered light reaching the receiver decreases underwater target contrast and resolution. Scattered solar energy reaching the detector also decreases detection sensitivity by increasing receiver noise. Thus, a technique which rejects unwanted, scattered light while retaining image-bearing photons is needed to improve underwater object detection and identification. The approach which we are investigating is the application of radar modulation and detection techniques to the LLS. This configuration will enable us to use optical modulation to discriminate against scattered light. A nonscanning mock-up of an existing LLS, the Electro-Optic Identification (EOID) sensor, has been developed with off-the-shelf components. An electro-optic modulator will be added to this system to create a modulated LLS prototype. Laboratory tank experiments will be conducted to evaluate the performance of the modulated LLS as a function of water clarity and solar background levels. The new system will be compared to its unmodulated counterpart in terms of target contrast.
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