Search

TWO FIBEROPTIC instruments to be used for direct visualization of the structures of the middle ear are described. Direct visualization is of considerable value in the diagnosis and presurgical evaluation of middle ear disease. Until now, visual evaluation of the middle ear has been possible only by surgical entrance or by peephole views through perforations in the tympanic membrane. Also, some indirect knowledge of the middle ear has been obtainable from the appearance of the tympanic membrane.The two instruments developed for visualization of the middle ear fulfill the following specifications: (a) the diameter of the probe is small enough to permit insertion through a perforation or myringotomy; (b) the source of light for illumination of the specimen area is located externally so as not to damage the inner ear; and (c) an image of the specimen formed at the distal end of the probe is transmitted from the middle

An infrared polariscope was constructed for photoelastic stress analysis of semiconductor materials transmitting in the 0.7 μ to 1.2 μ spectral region. The instrument which functions as either a plane or circular polariscope permits specimens up to 40-mm diam to be studied in collimated radiation. Glan–Thompson prisms are used for the polarizer and analyzer, and the associated quarter-wave plates are made of quartz. An infrared image-converter tube is used to observe the stress patterns produced by induced and frozenin stresses of specimens. A mechanical stage provides for rotary motion and lateral displacement of the specimen in two mutually perpendicular directions in a plane normal to the optical axis of the polariscope, and also allows the specimen to be stressed by a calibrated mechanical load. A material fringe value of 27 kg-cm^−1 fringe^−1 was determined for silicon and used to estimate residual stresses in a boule of silicon. Photographs of isoclinic and isochromatic fringe patterns at a wavelength of 1.1 μ are presented.

The fractional sensitivity and operational refractive index range of the rod photorefractometer have been extended by physical modifications of axially symmetric refracting elements and the mode of illumination. Optical systems using conical and cylindrical rod elements with flat or spherical entrance ends illuminated by an axial light cone or a hollow annular light cone have been studied. Expressions describing the sensitivity of these configurations are presented, and typical numerical cases are computed on an IBM 650 computer. Extension of range to specimen index close to 1.0 permits the photorefractometer to detect index changes of low refractive index media. Experimental verification of the theory is achieved.

A study of the extension of the rod and cone photorefractometer principle to the measurement of N and K, the real and imaginary parts of refractive index of absorbing fluids, is made. Theoretical analysis indicates high sensitivity in the low-absorption-coefficient region of the specimen when the illumination is incident at the interface at an angle close to the critical angle. Experiments are made on various rod configurations and results agree closely with theory.