The development of the laser has provided the plasma physics with important tools. The recent studies concerning the interactions of the laser beam with plasma, especially the study in which the author is engaged, are reviewed. They are divided into three categories. One is the nonlinear effect of gaseous matters caused by the heavy intense laser beam which gives a method to produce plasma. The second is the laser interferometry which is a very capable method to measure the plasma beyond the cut-off range of microwaves. The last one is, the scattering of laser beam by electrons, which is used as excellent diagnostics.
Direct measurements of spatial coherence of ruby laser beam show that, it is not fully coherent als is generally assumed to be, but is partially coherent. From the relation obtained experimentally betweens they directionality and coherence of laser beam, the light beam, from a usual ruby laser is, found equivalent to that from a spatially incoherent light source situated at infinity. From this correspondence, spatial coherence on the emission surface of laser light cans be calculated by the Fourier transform of the intensity distribution on far-field patterns. This matter is experimentally ascertained.
With the purpose of finding the frequency limit in modulating directly a GaAs injection laser, the current dependence of time response of laser output is examined. Approximate expressions theoretically derived for the output rise and fall times show that the rise time decreases as the current increases and that, when the operational conditions are the same, the fall time is shorter than the rise time. These theoretical outcomes are in reasonable agreement with results obtained by experiment. The factors effective in improving the time response are discussed. The spontaneous radiative recombination life-time of electrons in the used GaAs diode is about 0.5 nsec.
The general condition for “equal astigmatism” in Seidel region for a single lens used as a spectacle lens for correcting astigmatic vision have been deduced for a lens with a toric surface in front and a spherical in the rear. The condition takes the form of an equation of the 11th order with respect to the reciprocal of the radius of curvature of the lens surface in case when the thickness of the lens is finite and the object plane is at finite distance, while it is reduced to an equation of the 8 th order in case when the object plane is at infinity. Gleichen's condition for equal astigmatism for a thin lens with its object plane placed at infinity can readily be deduced as a special case of our general condition. Several examples of spectracle lenses for astigmatic eyes, designed from the solutions of our general equation as the starting values and later refined by fine correction, showed excellent performance of equal astigmatism within an angular field as large as 80°.
For wax layer of wax-polished painted smooth surfaces, specular reflectance curves of p-polarized monochromatic light incident at angles near Brewster's angle are obtained by measurement, the electric vector of the light being parallel to the plane of incidence. The layer thickness, found graphically from minimum of the curve by referring to data obtained by calculating the formula of film reflection, is different for different wavelengths (641, 548 and 435mμ) of used light unless, the surface of substrate is optically flat. The informations on varied states of wax spread on the surface are obtained from the characteristics of the specular reflectance curves. The dependence of the layer thickness on wavelength is interpreted by the surface irregularities. The layer thickness is found less than 800Å.
Two dimensional X-ray image-let it be called the effective object-is calculated from a three dimensional real object by introducing a discrete strata model. Fourier spectrum of the effective object can be obtained in spatial frequency domain from an equation by taking into account the optical transfer functions of the focal spot of X-ray tube. Comparisons between calculated and observed X-ray images for cylindrical and square objects show good correspondence. X-ray images formed in tomography are obtained by the discrete strata model with optical transfer functions of image motions, and the transfer functions are shown to be obtainable by two derived equations from the locus of a point image. The blurred effects of the X-ray image by image motions are discussed for a linear motion, a circular motion and a discrete motion by using single figures of merits for image evaluation. The discrete motion may be concluded to be the most effective motion in tomography.
The optical image of a chart, seen through a diffusing screen, decreases its contrast as the distance between the diffusing screen and the chart is increased. If the diffusing screen, especially of small diffusibility, is moved farther away, the image becomes sharper and increases its contrast again. The former image of poor contrast is due to diffuse light in proportion to intensity distribution and the latter one of sharp contrast to direct light. In case of the diffusing screen moved apart, the intensity of diffuse light decreases gradually, but the intensity of direct light remains constant. Intensity distribution curves of diffuse light, emitted from one point of the diffusing screen, can be given approximately by an error function, and in case of the diffusing screen that produces reappearance of sharper image, the direct light component is superposed to the error function. The contrast transfer function in case of reappearance decreases quickly in gain near zero spatial frequency and the decrease stops.
A 100 kV d-c generator has been constructed. The generator is of Cockcroft-Walton type operating at 125 kc/s, and the voltage drop due to stray capacitance is compensated by means of series inductors. Filaments of rectifier tubes are fired by means of secondary coils of series inductors. The generator can provide the load current up to 1mA at 100 kV.
A grating prism is such a prism that the faces of a polygon prism which is used for measurement of angle are substituted by plane gratings, it can be used in the same way as a polygon prism for measurement of angle. With the grating prism, higher order images of the grating act as if the number of faces of the polygon prism are increased, and we have many reference angular positions. For instance, a 90 lines/mm grating hexaprism at λ=589 μy corresponds to a polygon prism of 234 faces.