Multi-image And Signal Storage On A Storage Tube Target

Abstract

Method and apparatus for enabling simultaneous storage of multiple images and/or digital data on a storage tube target, and for selectively retrieving such information.

Description

This invention relates generally to information storage and display systems, and more specifically relates to systems of this type utilizing a storage tube target as a temporary depository for data to be displayed or transferred to more permanent storage.

In numerous information storage and display systems, electronic storage tubes are used as intermediate elements in facilitating the composition of data for display or storage thereof. In a typical environment, for example, a charge pattern in the configuration of selected alphanumeric characters is written onto the target of a storage tube via information supplied by a character generator or the like, such pattern constituting, perhaps, a message intended for display on a CRT device. A readout signal derived from the scanning of the target by the electron beam of the storage tube is then used to modulate the CRT device to yield the desired visual display corresponding to the charge pattern. In applications of this type, the charge pattern is normally written upon the storage tube target as a purely two-level signal, since character displays or the like are basically black and white presentations and require no intermediate gray levels. Similarly, where the information written onto the storage tube target is not a configurated pattern corresponding to characters, but is in the form of digitally encoded information, representative, for example, of a digitally encoded number, the written information is placed on the target by a two-level signal, indicative respectively of a "zero" or "one" condition.

In my patent application, Ser. No. 9,752, entitled "Data Storage and Display System," filed of even date herewith, and assigned to the assignee of the instant application, there is disclosed a system utilizing a storage tube target having separate storage areas thereon for writing character sequences in character configurated form and in digitally encoded form, respectively. Such a system, in part, addresses itself to the solution of a problem which is actually more general in nature-- that of storing several different types of information on a single storage tube target. Not only is it desirable to achieve such a result in an environment such as that just mentioned, but in numerous other instances it would be valuable to store more than one class of data on a given target. In this connection, it will be observed that the described system achieves its objectives by placing the different classes of information on completely different portions of the target. This aspect of the system is consistent with prior held approaches of storage tube technology, according to which the charge pattern on the tube target represents, at a time, but a single overall image. That is to say, that the charge present upon the target at a given point is indicative of but a single bit of information stored thereat.

In accordance with the foregoing, it may be regarded as an object of the present invention, to provide method and apparatus enabling simultaneous and coincident storage of multiple two-level images and/or digital data on a storage tube target, whereby a vast increase is enabled in the amount of information storable at a given time on said target.

It is a further object of the invention to provide method and apparatus for writing, storing in coincidence, and independently reading out multiple classes of information utilizing but a single storage tube target for said functions.

It is another object of the invention to provide an information storage and display system adapted to store multiple images and/or digital data in coincidence on a storage tube target incorporated into the system, whereby multiple classes and large quantities of information at a time may be efficiently stored for display or readout into a buffer element of the system.

Now in accordance with the present invention, the foregoing objects, and others as will become apparent in the course of the ensuing specification, are achieved by writing onto a storage tube target a first two-level image or digital pattern in a pattern of charge having a density v, a second two-level image or pattern at a density level 2v, and as desired, a third two-level image at level 4v, etc., up to a final image or pattern at level 2.sup.n v, where n is the total number of coincident images or patterns. As a consequence of this process, charge levels are present from point to point on said target, the values of which are a unique function of the coincident components thereof. In order, then, to recover from the composite charge pattern the total individual image components, the analog level of the pattern of charge on the target is converted at points thereof to a parallel binary output, the presence or absence of a binary digit in the output from a given target point being indicative of the presence or absence of the corresponding component image at such point.

The invention is diagrammatically illustrated, by way of example, in the accompanying drawings, in which:

FIG. 1 is a chart depicting how the method of the invention permits simultaneous and coincident storage of multiple images on a single-storage tube target;

FIG. 2 is a schematic flow diagram of a storage and display system utilizing multiple coincidental storage of images in accordance with the invention;

FIG. 3 is a logic diagram depicting a simple logic circuit which may be utilized as an analog to digital converter to separate the coincidentally stored images of the invention in a system such as that illustrated in FIG. 2; and

FIG. 4 is a chart setting forth the manner in which varying analog charge levels furnished to the FIG. 3 circuit results in resolution of the component images.

The present invention may be utilized with many of numerous types of storage tubes known in the art. One such suitable tube, is, for example, shown in my copending patent application Ser. No. 840,698, filed July 10, 1969 entitled "Electronic Storage Tube," and assigned to the assignee of the instant application. Such a disclosed tube includes a target comprising a conductive silicon substrate, and an overlying insulating mosaic layer of silicon dioxide. A charge image or pattern deposited on the mosaic layer by the electron gun in the tube envelope is used to modulate readout current from the tube target. The structure and composition of the mosaic and substrate is such that sustained storage and repeated nondestructive readout of the target is possible, features which are helpful for the present invention. In general, however, any conventional tube may be utilized provided (as is the case for the tube of my cited disclosure) such tube is capable of storing on the target thereof a sufficient number of delineable charge levels to yield, upon analog-to-digital conversion, outputs enabling separation of the component images thereby represented.

The principle pursuant to which the present invention operates is as follows: Initially a two-level image such as a line drawing or a "black and white" image such as a composed alphanumeric message or the like, or two-level digital data, is written onto the storage tube target at a charge density level of v, i.e., v corresponding to say "white" and zero to "black." Thereafter, by rescanning precisely the same portion of the target, a second distinct image (or other two-level information) is written in coincidence atop the first image, by writing the second image at a level 2v. If desired, a third distinct image is then written in precisely the same area by writing said third image at a level 4v, a fourth image at level 8v, etc., up to an n.sup. th image at level 2.sup.n v. As a result of such operations, it is then found that an analog signal is present from point to point on the tube target which is convertible by analog-to-digital conversion means to parallel binary outputs indicative of the separate image components.

The basic method of the invention may be better understood by referring to the chart of FIG. 1, wherein is depicted how, by the technique specified above, several distinct images may be stored. While the principle is applicable, as has been indicated, to the storage of a plurality of images, for illustration it is assumed that only three such images are involved. Assuming that such images (identified as 1, 2, and 3) are written at levels v, 2v, and 4v, it is seen that each of the total analog levels (from 0 to 7v) uniquely defines the presence or absence of a "white" signal corresponding to each of the images, identified as 1, 2, and 3 in column 12 of the FIGURE. The column 11 in the chart is seen to represent the conversion to binary output of the analog values of column 10. Thus, for example, the analog value 5v is converted to the binary output 101. If this binary output is arrayed against the column headings A, B, and C, it is clear that column A is assignable to image 1, column B to image 2, and column C to image 3. Thus, it is seen that the binary sequence 101 corresponds to the presence of a signal from images 1 and 3 at the point sampled and the absence of a signal from image 2. The other analog values are similarly analyzed in the chart to show how the analog value may be taken as a measure of the presence or absence of component images. While the phrase "image" is used repeatedly throughout this explanation, it is of course clear that the principle is applicable to coincidental storage of any two-level pattern.

In FIG. 2, a schematic flow diagram is depicted for a storage and display system 20 utilizing multiple coincidental storage of images (or other two-level patterns) in accordance with the invention. A storage tube 21 therein, of the type previously set forth, has associated therewith conventional write circuitry 22. Tube 21 will typically be operated in a secondary emission mode, with the target potential being maintained above the first crossover point. Write circuitry 22 is fed from the image sources, 23, 24, and 25, where additional sources of images may be used as desired. The image sources actually feed to level setter 26, which, in accordance with the principles set forth above, supplies signals enabling write circuitry 22 to write on the tube target at levels v, 2v, 4v etc., depending upon which of the image sources is involved.

The coincidentally stored images are read out from storage tube 21 and fed to A/D converter 27 which yields parallel binary outputs to image selector 28. Display control 29 which controls readout from storage tube 21 simultaneously activates display 30, which may conveniently be a CRT device, so that the binary output selected can be fed to the display 30 at a rate synchronized with a raster scan at the CRT present thereat to yield a visual display of the selected image. Alternatively, the selected image may, instead of being displayed, be transferred to tape storage 31 for more or less permanent retention.

In FIG. 3, a simple logic circuit, consisting of threshold, NAND, and OR gates is shown which specifically illustrates how the present invention may be utilized to separate two coincidentally stored images. Such "images" may, for example, comprise configurated alphanumeric characters and digitally encoded data therefor, such as is discussed in my previously cited patent application, Ser. No. 9,752, filed of even date herewith. This FIGURE should be considered simultaneously with the chart of FIG. 4, which sets forth the manner in which varying analog levels furnished to the FIG. 3 circuit results in resolution of the component images.

In particular, the input at terminal 32-- i.e., the output from reading of the stored charge pattern on the tube target-- is applied to threshold gates 33, 34 and 35, set respectively to respond at levels v, 2v, and 3v. It is seen that if the analog level v.sub. 1 is less that v, no signal passes from any of the threshold gates and a zero output is provided at both terminals 36 and 37, the output terminals respectively for image 1, and image 2. If the analog level v.sub. 1 is between v and 2v, a signal is present through gate 33, but not through gates 34 and 35. Under such conditions a signal is provided at the output of NAND-gate 39 and thence through OR-gate 40 and to terminal 36.

If the analog level is such that 2v< v.sub. 1 <3v, gates 33 and 34 are activated, but not gate 35. A signal is thus present for image 2 at terminal 37, but NAND-gate 39 blocks any indication for terminal 36. Finally, if the analog level is such that v.sub. 1 >3v, then signals are clearly present at both terminals 36 and 37, indicating presence of both image 1 and image 2 at the analyzed point.

While the present invention has been particularly described in terms of specific embodiments thereof, it is apparent to those skilled in the art that numerous modifications are possible without departing from the spirit of the invention and the scope of the subjoined claims.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method for storing in coincidence a plurality of two-level images on a storage tube target and reading out and resolving said images, comprising:

writing a first of said images onto said target at a charge level v, a second of said images coincident with said first image at a charge level 2v, up to an n.sup.th image written on said target at a charge level 2.sup.n v;

reading out the total signal level stored from point to point on said target as an analog value at each point;

converting said analog values to n parallel binary digit outputs; and

utilizing the presence or absence of a signal at each of said parallel binary outputs to indicate the presence or absence of a corresponding image at the point from which said analog signal is derived.

2. A method in accordance with claim 1 further including selecting one of said parallel outputs and applying said output to a display device to visualize the resolved image thereby represented.

3. Apparatus for storing in coincidence a plurality of two-level images on a storage tube target and reading out and resolving said images, comprising:

a storage tube including a storage target therein;

means for writing a first of said images onto said target at a charge level v, a second of said images coincident with said first image at a charge level 2v, up to an n.sup. th image at a charge level 2.sup.n v;

means for reading out the total signal level stored from point to point on said target as an analog value at each point;

analog-to-digital conversion means for accepting said analog readout signal and converting said signal to n parallel binary digit outputs, whereby each of said outputs provides a signal indicative of the presence or absence of a corresponding image at the point from which said analog signal is derived.

4. Apparatus in accordance with claim 3 further including means for utilizing selected of said parallel outputs to visualize said image signal associated therewith.

5. An information storage and display system, comprising:

a plurality of sources of two-level images;

a storage tube including write circuitry therefore;

means for sequentially applying the outputs from said image sources to said write circuitry and for setting the writing level of said write circuitry, so that the image from said first source is written onto the target of said storage tube at a charge level v, the image from the second of said sources at a level 2v, up to the image from the n.sup. th of said sources at a level 2.sup.n v;

means for reading out the total signal stored from point to point on said target as an analog value at each point;

analog-to-digital conversion means for accepting said analog readout signal and converting said signal to n parallel binary digit outputs, whereby each of said outputs provides a signal indicative of the presence or absence of a corresponding image at the point from which said analog signal is derived;

utilization means for said parallel outputs; and

means for selecting among said parallel outputs and transferring said selected output to said utilization means.

6. Apparatus in accordance with claim 5 wherein said utilization means comprises display means for visualizing the image corresponding to said output.

7. Apparatus in accordance with claim 5 wherein said utilization means comprises storage means for storing the image corresponding to said output.

8. A system according to claim 5 wherein said sources of two-level images are two in number, and said analog-to-digital conversion means comprises first, second, and third threshold gates set respectively to respond to levels v, 2v and 3v, a NAND gate, an OR gate, and first and second output terminals for receiving outputs corresponding to the first and second of said images; said first and second threshold gates being connected in parallel to the inputs of said NAND gate, the output of said second gate being further connected directly to said second output terminal, the output of said NAND gate being connected in parallel with the output from said third gate to said OR gate, the output from said OR gate being connected to said first output terminal.