We use Optical Character Recognition (OCR) during our scanning and processing workflow to make the content of each page searchable. You can view the automatically generated text below as well as copy and paste individual pieces of text to quote in your own work.
Text recognition is never 100% accurate. Many parts of the scanned page may not be reflected in the OCR text output, including: images, page layout, certain fonts or handwriting.
Fig. 7. Development of the deformation of the medium with time.
which takes the function of damping. If we watch one given image point we observe the following process: At the beginning of the image period, the cathode ray passing the image point deposits an electrical charge within a very short time < 10~7 sec. The electrostatic forces become effective at once and the deformation of the surface begins according to an exponential law (cf. Fig. 6). The time constant is proportional to the quotient of the surface tension and the viscosity. For a nonconductive Eidophor the deformation would tend to reach a definite final value (Fig. 6a). As, however, the charge diminishes according to an exponential function, the forces causing the deformation are diminished as well (Fig. 6b), so that both causes result in a development of the deformation as illustrated in Fig. 6c. For a whole series of successive image periods, a development as illustrated in Fig. 7 results. For all practical purposes, a remainder of 10% of the deformation, at the end of the image period, is toleraable. This time law of the deformation allows an effective light-storage of about 70%. _
As is easily seen, the Eidophor image constantly carries a certain average negative charge which exercises a constant average mechanical pressure on the oil surface. If the oil film were left to itself it would be pushed out of the image field in the course of time. To prevent this, the Eidophor carrier is slowly
being turned so that the oil film in the image field is constantly renewed. Since the rotation is very slow, its influence on the image is practically nil.
The maximum amplitude of the deformation is only a few thousandths of a millimeter. Consequently, the oil surface must be of the highest quality as even the smallest deficiencies result in an undesirable brightening-up of the screen. Fortunately this trouble can be removed to a certain extent in a comparatively easy way. If the relationship between the dimension of the raster elements and the other dimensions of the schlieren-optical system is appropriately chosen, the deflection of the light is accompanied by diffraction, which allows for a schlieren system of lower imaging quality to be used successfully.
We can now make the second bar system 7', 2' (Fig. 8) somewhat wider than the optical image of the slits 7, 2. The result is an elimination of the brightening-up effect of certain deformations, deformations exceeding a certain area now remaining without effect.
This new layout of the schlieren-optical system has made it possible to design a new simplified projector which is also reduced in size. Its diagram is shown in Fig. 9. The schlieren lens was replaced by a spherical mirror. Instead of two separate bar systems we now use a single one which comes twice in action. It consists of a number of mirror strips
350
April 1953 Journal of the SMPTE Vol. 60