United States Patent Office
3,006,993 VIDEO EFFECTS GENERATOR Charles F. ISarndt, 1109 Madison Lane, Alexandria, Va. Filed Sept. 20,1957, Ser. No. 685,271 1 Claim. (CI. 178—7.2)
This invention relates to a video effects generator and more particularly to a device that allows two sources of video information to be controlled so that the resulting picture is a montage or mixture of the two original pictures or sources of video information.
The primary object of the present invention resides in providing the effect in a video picture as if one picture were first present and then controlled areas or holes were knocked out of the picture and a second picture were inserted in these controlled areas or holes. These areas can be of any shape and in any position in the picture. The relative shape of these areas is controlled as well as the relative size in the resultant picture as will be hereinafter described.
To carry out the invention, an electronic switching arrangement is employed. The circuit functions by using control pulses of proper polarity and phasing to control which position of each picture is allowed to pass to form the final output picture.
In the prior art the pulse former for a control signal for two video sources has usually consisted of electronic circuits which are relatively complex thus requiring considerable line-up procedure and relatively constant attention for proper .adjustment. Geometric shapes of comparatively regular nature were employed, usually not easily controllable as to location in the raster, or rectangular shaped light pattern on the face of a cathode ray tube, for operating purposes. Such shapes as ellipse, crescent, star, triangle have not been practical for use in existing systems of control pulse formers. It is therefore a further and important object of the invention to provide means which will enable various geometrical shapes to be utilized for operating purposes to obtain new and unusual video effects.
These, together with various ancillary objects and features of the invention which will become apparent as the following description proceeds, are attained by this video effects generator, preferred arrangement of parts being shown in the accompanying drawings, by way of example, wherein:
FIGURE 1 is a schematic illustration of one of the functions of the video effects generator;
FIGURE 2 is a schematic diagram illustrating the manner in which switching occurs to provide the desired output from the two separate video sources;
FIGURE 3 is a schematic diagram of the various components utilized in the invention;
FIGURE 4 is an elevational view of one of the masks which may be utilized in the invention;
FIGURE 5 is a schematic wiring diagram of the important electrical components of the invention;
FIGURE 6 is a schematic wiring diagram of the electrical components of the electronic switching system of the invention.
The video effects generator comprising the present invention functions to allow a montage to control the shape, size and position between the pictures from two sources. The simplest consists of a "wipe" where the effect is of one picture forcing another picture off the screen with either a vertical or horizontal division between the two pictures during the process. Such a wipe can be best seen schematically in FIGURE 1.
In FIGURE 1, the picture as indicated at 10 is eventually replaced with the picture as indicated at 12 with the vertical line as at 14,16 and 18 moving in a horizontal direction. If a "split screen" is used, only the condition as
indicated at 20 would be used using the right half of one
picture and the left half of the other. Of course, any
suitable geometrical shapes can be employed.
The effect as is schematically illustrated in FIGURE 1
g is created by "killing" one picture at intervals while the other picture is allowed to pass through the equipment, and vice versa. Thus the signals are keyed by an electronic switching action which is effectively a high speed single pole, double-throw switch action. This will be discussed below, with particular reference to FIGURE 1 and one of the apertures in the mask.
The switching action is electronically accomplished by the circuits that will pass one signal when a positive pulse is present at the control circuit and will pass the other
25 when a negative pulse is present. Thus, the signal from video source 24 will be passed when there is a positive pulse present while the signal from video source 26 will pass to the output 28 when a negative pulse is present. As shown, the negative pulse is schematically at 30. Thus,
20 it is necessary to develop pulses which are properly phased time-wise to do the switching action during the scanning time of the TV system. The invention employs means performing the control pulses with complete flexibility as to shape, size and position of a multitude of patterns.
25 Referring to FIGURE 3, a moving spot of light is used to form a raster or rectangular shape light pattern on the face of a cathode ray tube 40. The height and width of this pattern is controlled by use of the circuits to be hereinafter described. This raster is similar to that formed
30 on a TV receiver screen inasmuch as the spot scans in a linear fashion with time in one direction with a fast fly back, in synchronism with the TV scanning system The main difference is that the phosphor of the cathode tube 40 has a very fast decay time after scanning, in the
35 order of several micro-seconds at the most. The light emitted from the phosphor after the electron beam has passed a spot on the face of the tube has no appreciable effect. Thus, essentially a spot of light scans an area on the screen of the tube 40. Disposed in alignment with the cathode ray tube 40 is a photo-electric cell 42. A mask 44 is preferably mounted on the cathode ray tube between the cathode ray tube and the photo-electric cell 42. FIGURE 4 shows a possible arrangement of the mask. Means are provided to shift the raster to one of the po
45 sitions as indicated at 46, 48, 50, 52, 54, 56, 58 and 60. These rectangular dotted lines indicate the maximum size of the raster due to the clipping action of the electronic components of the invention to be further described, it being realized that the raster size can be reduced to any
gg minimum size desired.
Of course the horizontal or vertical size can also be . changed independently of each other allowing any desired change in the aspect ratio (ratio of height to width) of the raster, thus a comparable change in the aspect ratio of
55 the resultant keyed shape.
As the beam moves from behind the mask light will emanate through one of the suitable openings such as indicated to be of crescent shape for example as indicated at 62, of triangular shape as at 64, of cruciform shape as
6Q at 66, or of any other suitable shape such as star shape or the like. These other shapes may be placed in the positions that are in blank as at 48 and 54 as shown.
Light passing through the mask will impinge on the face of the photo-electric cell as at 68 and passes into the
6g amplifier and clipper as at 70 which then passes a key control signal 72 through the keyer 74.
At the keyer, the impulses from the video sources as at 24 and 26 are keyed and are delivered as the output 28. In order to understand the operation of the control
70 circuitry of the cathode ray tube 40, attention is directed to FIGURE 5. To trace out the operation of the circuits, the grid 98 of tube 100 is fed horizontal drive pulses