Stereo Effect Research Articles

Stereosehen bei alternierender Bilddarbietung

The threshold values for stereopsis with alternating monocular presentation of the corresponding member of a stereo pair was examined in relationship to the stimulus duration and the interocular delay. The maximum interocular delay for short stimulus durations was approximately 190 msec. The maximum stimulus duration was between 400-500 msec. At this stimulus duration the interocular delay must approach zero if stereopsis is to be maintained. In the threshold region the stereo effect diminished. One can possibly explain this phenomenon as a partial sensorial fusion. For normal appreciation of stereopsis, the critical frequency was about 2 Hz over the threshold values found with a given stimulus duration.

Applications of Through-Focus Dark Field Image Shifts to Phase Identification

Image shifts in out-of-focus dark field images have been used in the past to determine, for example, epitaxial relationships in thin films. A recent extension of the use of dark field image shifts has been to out-of-focus images in conjunction with stereoviewing to produce an artificial stereo image effect. The technique, called through-focus dark field electron microscopy or 2-1/2D microscopy, basically involves obtaining two beam-tilted dark field images such that one is slightly over-focus and the other slightly under-focus, followed by examination of the two images through a conventional stereoviewer. The elevation differences so produced are usually unrelated to object positions in the thin foil and no specimen tilting is required.In order to produce this artificial stereo effect for the purpose of phase separation and identification, it is first necessary to select a region of the diffraction pattern containing more than just one discrete spot, with the objective aperture.

Theory and Errors in Stereo Electron Microscopy

It is often desirable in transmission electron microscopy to know the vertical spacing of points of interest within a specimen. However, in order to measure a stereo effect, one must have two pictures of the same area taken from different angles, and one must have also a formula for converting measured differences between corresponding points (parallax) into a height differential.Assume (a) that the impinging beam of electrons can be considered as a plane wave and (b) that the magnification is the same at the top and bottom of the specimen. The first assumption is good when the illuminating system is overfocused. The second assumption (the so-called “perspective error”) is good when the focal length is large (3 x 107Å) in relation to foil thickness (∼103 Å).

Wavefront Reconstruction with Diffused Illumination and Three-Dimensional Objects*

Holograms of transparencies have been produced in diffused light. The reconstructions are free from flaws and are of a quality comparable to pictures produced by conventional photography with incoherent light. Holograms of three-dimensional scenes have been produced by reflected light. Such holograms produce three-dimensional reconstructions having all the visual properties of the original scene: parallax between near and distant objects, a requirement to refocus the eyes when viewing objects in different parts of the scene, and a stereo effect equal to that of ordinary stereo photography.

Two-channel power amplifier circuits of the parallel type

A new power amplifier is described which amplifies both stereo signals by means of a single push-pull-like pair of transistors or tubes. This circuit is derived from the parallel-type push-pull amplifier and combines to advantage, especially its output-transformerless operation, with the possibility of controlling the stereo effect or producing an unlimited number of phantom stereo signals. All basic alternatives of this circuit are derived and a complete two-channel amplifier is described, which in essence is a Lin quasi-complementary amplifier adapted for stereo. The amplifier includes, in one of its branches, a built-in polarity inverter so that it can be used with any conventional stereo signal source. In addition to the outputs for the two flanking speakers, it is provided with a sum-signal output for the center speaker, and means of contracting or expanding the stereophonic basis. Owing to the sliding operating point of its power stage, it exhibits properties similar to those of a class A-B amplifier, as far as transistor dissipation and supply-current economy are concerned. Finally, the new amplifier is compared with two single-acting stages and the resulting advantages are evaluated. An analogy is drawn between this amplifier and the modern stereo disk recording.

The Roentgen Anatomy of the Knee Joint: An Experimental Analysis

Introduction THROUGH their classical investigations concerning the analysis of bone form and bone transformation, Wolff and the earlier writers in the second half of the last century presented us with an understanding of bone architecture. Surprisingly enough this has never been followed by a systematic and detailed analysis of the skeleton as it presents itself in the living by means of the x-ray method. Here we see the three dimensions of bodily form, lacking depth, projected on the film in two planes only, thus making definition of the bony pattern an object of special analytical investigation. While study of the x-ray pattern of bones is based essentially on analysis of the bone architecture advanced by anatomists, roentgenology may, on the other hand, furnish information valuable to the anatomist. An impression of “the typical” (Francke) features of bone architecture, which cannot be secured by study of separate bone sections, will be produced by an x-ray image, which is the resultant of all the superimposed layers of bone in a given projection. Furthermore, radiographic study is the only method of analysis of normal and pathologic bone structure in the living, and in valuable anatomical specimens which should not be subjected to dissection. Most authors who have concerned themselves with interpretation of the x-ray pattern of bones have used the method of comparative study of object and radiogram. This in itself proved insufficient to solve the more difficult problems of radiographic analysis. The study of Spalteholz specimens, i.e., of bones made translucent by chemical treatment, while of distinct advantage in the analysis of radiograms, is of limited value for many of the problems of this paper. Besides, good results on larger and more complicated adult bones are hard to obtain and the specimens on the market are rather expensive. Stereography, although well fitted to give us an image comparable to the true object, is also unable to supply us with exact information as to the anatomical substrate of a certain line in the x-ray film. “Summation pictures cannot be united to a stereo effect since the real points pertaining to them are present neither on the picture nor in the object” (Francke). The object of the present report is the systematic analysis of the roentgenogram of the knee joint which requires detailed study on account of its complicated appearance and the clinical importance of the region. Methods of Study Four experimental methods of x-ray analysis were utilized. Roentgenograms were made before and after the following procedures: (1) Chemical decalcification of the bony cortex or the spongious structure. Details of this method, which was used to determine the limitations of x-ray diagnosis of osteoporosis, are discussed in a previous paper (Lachmann and Whelan).