US2155033A

US2155033A - Picture reproducer

Info

Publication number: US2155033A
Application number: US752046A
Authority: US
Inventors: Barthelemy Rene
Original assignee: Compteurs Schlumberger SA
Current assignee: Compteurs Schlumberger SA
Priority date: 1933-11-14
Filing date: 1934-11-08
Publication date: 1939-04-18
Anticipated expiration: 1956-04-18

Description

April 18, 1939. R. BARTHELEMY PICTURE REPRODUCER Filed NOV. 8, 1934 '0 K Box'i'helem IN VE NTOQ.

Pun ATTY.

Patented Apr. 18, 1939 UNITED STATES PATENT OFFICE PICTURE REPRODUCER Montrouge, France Application November 8, 1934, Serial No. 752,046 In France November 14, 1933 3 Claims.

In most devices for the reconstruction of images by means of a cathode ray oscillograph, the cathode beam is oscillated by means of two sets of plates perpendicular to one another. The beam describes juxtaposed parallel lines to reproduce the image on the screen at one end of the oscillograph.

According to the present invention, the cathode beam is moved to and fro behind a slit which it illuminates. The successive lines are juxtaposed to constitute the image, a moving optical system being in the path of the light issuing from the slit.

A synchronous motor produces the releasing impulses of the oscillograph which control the forward and backward movement of the beam at the frequency of the lines. The motor moves also the optical system, usually a drum carrying Wide mirrors, which casts the image in the direction perpendicular to the lines of analysis at a speed, say of 16 to 24 images per second.

This arrangement permits the diminishing of the effect of the modulation on the size of the light spot. In effect, as this luminous spot moves along a straight line, an obturator can be placed before the ground glass fluorescent screen of the oscillograph. The obturator is provided with a rectilinear slit of a suitable width which allows the appearance only of that part of the spot which corresponds to the width of a single analysis line. The apparatus is so adjusted that the strongest modulation gives a white corresponding to the maximum concentration of the cathode beam and in this manner the display which corresponds to the dark parts is not substantially restrained and good definition of the image is obtained whatever the amplitudes of the modulation may be.

The oscillograph can be of the usual type, not specially adapted for use with television systems, and the modulation can be applied to the focusing anode. Moreover, the apparatus need only have two deflecting plates instead of four.

The present arrangement permits the dimensions of the image to be increased; one can, in effect, utilize the complete diameter of the fluorescent screen for the length of the image, whereas in prior structures only two-thirds of the diameter could be used.

Other improvements permitting the light issuing from the slit to be modulated while maintaining constant the intensity of the cathode beam will be described in detail hereinafter.

The invention will be best understood with the aid of the following description and the annexed drawing in which Figs. 1 to 3 exemplify three diagrammatic embodiments of the device.

A cathode ray oscillograph T (Fig. 1) is provided with a cathode K, a focusing cylinder W, one or more accelerating anodes A, two deflecting plates P1 and P2, and a fluorescent screen E. In front of this screen is placed an opaque diaphragm D provided with a slit F1, F2 perpendicular to the plates P1 and P2. The width of this slit is a function of the width of the lines of analysis of the image and is such that the successive lines reproduced are juxtaposed. The apparatus is adjusted in such a manner that the point of impact of the cathode beam on the screen E moves behind the slit F1, F2.

The fluorescent screen can be limited to the useful part which is disclosed by the slit F1, F2. Moreover the screen diaphragm assembly can have an elongated form in the direction of the slit, for example, it may be elliptical or in the form of a very flat rectangle. This arrangement is particularly useful for the obtaining of large images. In front of the screen E is a rotating mirror drum M, the mirrors being parallel to the axis of rotation and being symmetrical with respect to this axis. The axis of rotation is itself parallel to the slit F1, F2. Each mirror will produce a synthesis of the image, by juxtaposing the successive lines for an observer placed, for example, at O, and to the observer the reflected rays seem to emanate from a real image behind the oper-; ating mirror.

On the axis of this drum, or on a shaft connected thereto by a train of gearing B (Fig. 2), is mounted the. rotor' of a synchronous motor S. This latter is fed for example by the alternating current mains and drives a phonic wheel generator R. The point voltages of this generator release a device C such as a Thyratron which controls the movement of the cathode beam, by the action of plates P1, P2.

The mirror drum may be replaced by a lens disc projecting the image of the cathode spot on to ground glass screen Without departing from the scope of the present invention (see Fig. 3).

In order to obtain a projection on to a screen of ground glass, one of the most practical processes consists in constituting a beam with a fixed lens L (Figure 2) of large aperture, placed at a suitable distance from the fluorescent spot and in directing this beam on to a turning drum provided with mirrors; this method avoiding the grave deformations which arise with the devices described above and not requiring mirrors of large dimensions.

If it be so arranged that the entire image must be screened by one of the mirrors of the drum, the latter must turn at a relatively low speed which gives rise to difficulties in the synchronous motor as well as in the dimensioning of the toothed wheel for releasing the device 0. On the other hand, difiiculties can equally be encountered in the use of reduction gears on ac count of the required precision.

One improvement consists in mounting the mirror drum directly on the motor shaft which turns, for example, at a speed of twenty five revolutions per second, in placing the observer of the screen at such a distance from this drum and in turning the mirrors in such a manner that each provides a fraction of the height of the image. The total image will be obtained after one complete revolution. Under these conditions, the mirrors will not be all perpendicular to the radius of the drum but will remain parallel with its axis.

In the device which has just been described the variations of intensity of the luminous flux leaving the slit F1, F2 are obtained by modulating the cathode beam by the application of the modulation voltage between the cathode K and one of the anodes.

Another improvement of this device consists in maintaining the intensity of the cathode beam constant and in displacing the said beam in a direction perpendicular to the slit F1, F2 in such a manner that in order to obtain clear surfaces, the spot of impact of the cathode beam on the screen E is seen in its entirety through the slit F1, F2 and so that, for the darkest surfaces, the spot disappears partially or wholly behind the opaque part of the diaphragm. A slight displacement of the spot, of the order of a millimeter, is obtained by the application of the modulating voltage to a pair of deflecting plates P1 and P2 (Figure 2) perpendicular to the plates P1 and P2 which control the sweeping; and adjustable continuous voltage is connected in series with the modulating voltage which, in general, can be less than one volt. This continuous voltage enables the mean position of the spot on the slit to be adjusted in the absence of modulation. Its variation will enable the value of the black parts to be increased, contrasts to be accentuated and, if need be, the whole image to be reversed if, for example, the mean position of the spot is fixed towards the top of the slit in place of arranging it towards the bottom thereof.

With this device there is no risk of the displays of the spot being a function of the modulation since the intensity and speed of the electronic beam remain constant. This will permit the use of this intensity at the maximum and will permit the obtaining of a very large quantity of light from the tube.

The method which has just been described gives a powerful modulation which is rather difficult to regulate, because the amplitude of the displacement of the spot must be very exactly adjusted.

Another improvement produces a variable light behind the rectilinear slit of the oscillograph because the luminous impression on the eye varies inversely to the rapidity of displacement of the spot.

The principle of this consists in applying to the pair of deflecting plates P1 and P2 producing the vertical deviation of the spot, a high frequency voltage modulated by the image current.

Calculation and experiment show that the speed of passage of the luminous spot in front of the slit is proportional to the amplitude of the modulation at each instant, subject, of course,

"to" the use of an auxiliary frequency which is clearly greater than the highest frequencies contained in this modulation.

The spot is then moved under the influence of two components:

(1) 'A component of constant speed which moves it in the direction of the slit and which provides the exploration of a line of the image;

(2) A component, perpendicular to the slit, of high frequency and of an amplitude which is variable as a function of the modulation voltage, the direction of application of this component being so chosen that the clear parts of the image correspond to the smallest amplitudes'of the auxiliary oscillation.

Thus I obtain great speed of displacement of the beam perpendicularly to the slit when the dark parts are transmitted and the beam' is only slightly displaced and at a slow'speed when the clear parts appear.

The slit then appears to be variably illumi nated and all the feeble variations of illumination are faithfully transmitted. In order to utilize the maximum possible amount of light, I provide a minimum amplitude for the oscillation of the beam equal to the width of the slit and place the slit in the mean position of the beam.

In order to increase the definition in the horizontal direction, the beam can be concentrated to a maximum so that a much better definition of the limit frequency can be'obtained than with a diameter of the moving luminous point which is at least equal to the width of the line'of analysis. 7 V

The local oscillation modulated by the image current need not be above a dozen. volts and can be reduced to one volt under the influence of the clear parts. An oscillator valve of small power is thus suflicient.

One can even do without such a lamp by providing in the transmission an auxiliary carrier wave of a frequency of some hundreds of kilocycles, modulated by the image current and by applying this carrier wave, without detection, and through the intermediary of an ordinary amplifier to the deflecting plates P1 and P2 of the tube.

What I claim is:

1. In an apparatus for the reconstitution of images, the combination with a cathode ray 'oscillograph comprising two deflecting plates imparting a backward and forward movement to the cathode beam, a luminous screen, in the path of the cathode beam, and an opaque diaphragm adjacent said screen and having a slit swept by the cathode beam, of a rotatable disc arranged outside of said oscillograph, means to rotate said disc at a predetermined speed, and a series: of lenses mounted on. said disc along a circle concentric with the axis of rotation of said disc to be placed successively in the path of the light rays emanating from said slit and to deflect said rays at successively varying angles so as to juxtapose the successive luminous images of said slit along parallel lines when said disc is rotated.

2. A device as claimed in claim 1, wherein said means to drive the rotatable disc includes a synchronous motor, said device comprising further a generator of periodic current for feeding a predetermined amplitude to said deflecting plates, said generator being driven by said synchronous motor.

3. In an apparatus for the reconstruction of images, the combination with a cathode ray oscillograph comprising two deflecting plates imparting a backward and forward movement to the cathode beam, a luminous screen in the path of the cathode beam, an opaque diaphragm adjacent said screen and having a slit swept by the cathode beam, and two auxiliary deflecting plates perpendicular to said first mentioned defiecting plates to imp-art to the cathode beam, a displacement perpendicular to said slit, of a rotatable disc arranged outside of said oscillograph, a series of lenses mounted on said disc along a circle concentric with the axis of rotation of said disc to be placed successively in the path of the light emanating from said slit and to deflect said rays at successively varying angles so as to juxtapose the successive luminous images of said slit along parallel lines when said disc is rotated, a fixed optical system positioned between said lenses on said disc and said slit at a suitable distance from the latter to converge the light emanating from said slit, a discharge tube for feeding periodic currents of a predetermined amplitude to said first deflecting plates, a phonic wheel controlling said discharge tube, a synchronous motor to drive said rotatable disc and said phonic wheel, and means to feed to said auxiliary plates an amplitude in accordance with the modulations of the image current.

RENE BARTHELEMY.