Reflected Bragg Imaging Studies and Preliminary Results for Improved Optical Design
Because of the right angle geometry between the sound field and the interrogating light wedge, Bragg imaging is ideally suited for the study of reflected images. In order to improve the intensity and the clarity of these reflected images, a pulsed dye laser has been developed and tested. The laser has a variable pulse repetition frequency to a maximum of about 15 pps and operates at a wavelength of 590 nanometers with a maximum power of 5mW. The dye laser is fired through an SCR circuit using a delayed trigger from the transducer generator. Image photographs of various test objects will be presented and system resolution limitations will be discussed.
Efforts have also been directed toward improving the optical design for Bragg imaging systems. The systems that have been described in the literature incorporate several optical components with low f-numbers in order to produce high quality images. Furthermore, these components must have dimensions comparable to the desired image size and for optimal imaging should be diffraction limited. As such, production costs of the individual elements can be excessive. Alternate lens systems have been studied and a design realized which utilizes one large cylindrical triplet lens, one small cylindrical triplet lens, and prisms. Since only the large cylindrical component should offer any production difficulty this optical system would result in substantial cost reduction. Design considerations will be discussed and compared to those of conventional systems.
KeywordsLine Source Sound Field Spherical Aberration Acoustical Image Flash Lamp
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