US2338646A

US2338646A - Shading generator

Info

Publication number: US2338646A
Application number: US426566A
Authority: US
Inventors: Robert E Kessler
Original assignee: Allen B du Mont Laboratories Inc
Current assignee: Allen B du Mont Laboratories Inc
Priority date: 1942-01-13
Filing date: 1942-01-13
Publication date: 1944-01-04
Anticipated expiration: 1961-01-04

Description

Jan. 4, 1944. R, E, KEssLER 2,338,646

SHADING GENERATOR Filed Jan. l5, 1942 K flrmre/vEY Patented Jan. 4, 1944v SHADING GENERATOR Robert E. Kessler, Upper Montclair, N. J., assignor to Allen B. Du Mont Laboratories, Inc., Passaic, N. J., a corporation of DelawareA Application January 13, 1942, serial No. 26,56

1o claims.- -(ci. rvs- 7.2)

This invention relates to the generation and' It is picphasing of a high frequency sine wave. particularly useful for shading a television ture.

By this invention a sine wave can be obtained and variedover a wide range of line scanning frequencies, without complicated circuit adjustments, for the purpose of shading television pictures in which widely different scanning frequencies are used.' This is accomplished without the necessity of supplyinga special or separate synchronizing pulse to the shading generator. A sawtooth impulse is used for the input forgcnerating the sine wave and the phase may be changed over the extraordinary wide range of 360 degrees.

one of the objects''f this invention is to obtain a sine wave that can be used for shading a television picture over a wide range of scanning frequencies where a flexible scanning system is employed. yIn carrying out the invention a sawtooth signal at the horizontal scanning rate and a sawtooth signal at the vertical scanning rate are converted into sine waves and these sine Waves are used for shading an iconoscope. When the scanning rate is changed by-changing the frequency of the sawtooth signal, the frequency of the sine wavefollows automatically over a wide 'range of frequencies. 4

'I'he invention ,may be understood from the description in connection with the accompanying drawing, in which:

Fig. 1 is a block diagram showing ment of parts; and Fig. 2 is a circuit arrangement for. generating and shifting the phase of the sine wave used for shading.

As indicated in Fig. 1, a vertical synchronizing an arrangewill be obvious how the vertical synchronizing wave is also generated and phased "in asimilar manner. 'f

In Fig. 2l the horizontal synchronizing signal is applied across the resistor Rito the grid G of the vacuum tube V, the resistor R being adjusted to supply the proper bias onthis grid. The condenser C1 and inductance L1, shunted by the resistor Ra, are adjusted to resonate the plate P of the tube; Vqso as to oscillate ai; the frequency of the signal applied to the grid G. The resulting sine waves are caused to vappear through the the condenser C2 across the primary Ti of the transformer. The secondary T. of this transformer is grounded as indicated, and is loaded with a series circuit containing the condenser C:

and variable resistor Ra. By varying the resistance Re the sine wave from the secondary Tr can be shifted over a phase angle of approximately 180. The reversing switch` S between the transformer secondary Tr and the load enables the phase angle to be shifted 180 so that the sine wave can then be shifted 'along the other 180 of the 360 degrees. The Q is made low so that broad tuning, say over an octave,iis possible.

Scanning frequencies can be obtained with this invention from 15,'750 cycles per second for 525 line; v frametelevision pictures to 9,375 cycles or any other circuit adjustmentsbeing necessary.'

per second for 625 line, 15 frame television picl tures, for shading withoutv any change in tuning Thisinvention is also useful for observing a television signal at'llne frequency on an oscillograph. While doing this the sine-wave is used as a time base. When it is desired to observe a remote television signal onA an oscillograph, the horizontal synchronizing frequency sawtooth sigl nal of the television receiver is applied to the ossawtooth signal is fed to the mixer tube I indiy f cated diagrammatically; a 60-cycle sine wave from a power line is fed to the mixer tube 2; the same vertical synchronizing sawto'oth signal is fed to the parabola generator I, the output of which is fed to the mixer I; a horizontal synchronizing sawtooth signal is fed to the mixer l; the same horizontal synchronizing sawtooth signal is fed to the parabola generatori, the output of which is fed to the mixer l.; and the same horizontal synchronizing sawtooth signal is fed to the sine-wave generator l, the output of which is fed to the mixer 8. The composite signals are scope for shading the same.

led to the output tube I0 and thence to an icono- Fig. 2 shows how the horizontal synchronizing cillator input to produce a sinel wave for use in the oscillograph. The tube V of Fig. 2 and its circuits constitute an oscillator for this purpose.

While the description above has 'set forth the details for converting a sawtootlr wave over a range of horizontal scanning frequencies into a sine wave of variable phase suitable for television shading purposes, it has been found that input signals-of impulse shape and other wave forms at horizontal scanning frequencycan also be applied to the circuit of Fig.2 resulting in variable phase sine waves suitable for shading and suitable for osciliograph sweep circuits. 1

vWhatisclaimedis: l l .y 1;- In a device for generating and phasing sine waves from saw/toothv signals for shading television pictures, a vacuum tube with a biased grid to which the sawtooth signal is applied, a resonant circuit connected to the plate of said tube to cause oscillations at the frequency of the sawtooth signal, a transformer to the primary of which said oscillations are applied, and a series circuit load on the secondary of said transformer.

2. vIn a device for generating and phasing sine Waves from sawtooth signals for shading television pictures, a vacuum tube with a biased grid lto which the sawtooth signal is applied, a resonant circuit connected to the plate of said tube to cause oscillations at the frequency of the sawtooth signal, a transformer to the primary of which said oscillations are applied, a series circuit load on the secondary of said transformer, and a variable resistance in said last named circuit. i

3. In a device for generating and phasing sine waves from sawtooth signals for shading television'pictures, a vacuum tube with a biased grid to which the sawtooth signal is applied, a resonant circuit connected to the plate of said tube to cause oscillations at the frequency of the sawtooth signal, a transformer to the primary of which said oscillations are applied, a series circuit load on the secondary of said transformer, and a reversing switch in said last named circuit.

4. In a device for generating and phasing sine waves from sawtooth signals for shading television pictures. a vacuum tube with a biased grid to which the sawtooth signal is applied, a resonant circuit connected to the plate of said tube to cause oscillations at the frequency of the sawtooth signal, a transformer to the primary of which said oscillations are applied, a series circuit load on the secondary of said transformer,

quency of the sawtooth signal, a transformer to the primary of which said oscillations are applied, and a series circuit load on the secondary of said transformer.

6. In a device of the character described, means for producing from aline frequency sawtooth signal a composite signal for line frequency shading of television'pictures, said means comprising a sine wave generator and a parabola generator to which said sawtooth signal is applied, and mixers for mixing the outputs therefrom for application to an iconoscope for shading purposes. 1

7. In a device of the character described, means for producing from a line frequency sawtooth signal a composite signal for line frequency Y shading of television pictures, said means cornand a gain control connected tothe output of prising a sine wave generator and a parabola generator to which said sawtooth signal is applied, and mixers for mixing the outputs therefrom and said sawtooth signal for application to an iconoscope for shading purposes.

8. The device of claim 6, in which said sine Wave gener ator is adapted to have its phase shifted over approximately 360 degrees.

9. In a device of the character described, means for producing from a field frequency sawtooth signal a composite signal for field frequency shading of television pictures which comprises a parabola generator to which said sawtooth signal is applied and mixers for mixing the output from said parabola generator and said sawtooth signal for application to an iconoscope for shading purposes.

l0. In a device of the character described, means for producing from a field frequency sawtooth signal a composite signal for field frequency shading of television pictures which comprises a parabola generator to which said sawtooth signai is applied and mixers for mixing the output from said parabola generator and said sawtooth signal and a sine wave from a power line for application to an iconoscope for shading purposes.

ROBERT E. KESSLER.