DE1077251B - Circuit arrangement with a television receiving tube - Google Patents

Description

GERMAN

The beam current in television picture pick-up tubes was previously determined by means of a potentiometer from Hand set. To deal with fluctuations in operating voltage and changes as a result of heating to be able to correct changes occurring during the operation of the television camera, the beam current was readjusted manually with the potentiometer mentioned during operation. These known arrangements for regulating the jet current are afflicted with serious shortcomings. So it means a for the cameraman or the person responsible for the supply of the camera additional burden to always readjust the jet current by hand. In addition, due to the signs of aging unavoidable fluctuations in the beam current caused by the cathode of the image pick-up tube not covered by it. These deficiencies are particularly severe in image pickup tubes which the image signal is generated by scanning the image electrode with slow electrodes, especially with vidikons. The noise-useful ratio is generally determined by the changing beam current of the image signal as well as the contrast deteriorated significantly.

Various circuit arrangements are already known for supplying individual operating voltages or To regulate currents in image pickup tubes depending on certain recording conditions. So is it is known to control the sensitivity of an image pickup tube, in particular an orthicon, in Depending on the average image brightness, a control voltage, e.g. B. from the image signal, to derive which different electrodes are fed to the image pickup tube. In particular is a circuit arrangement known for regulating the potential of the collector electrode.

In order to maintain a uniform modulation in orthicon image pickup tubes, it is also known to regulate the beam current depending on the scene brightness. The regulation is carried out by Utilization of the secondary electrons generated during image generation, which are collected and stored will. A voltage proportional to the image signal is derived from these secondary electrons and serves to control the beam current in direct proportion to the secondary electrons, which themselves represent a measure of the average image brightness. In these known circuits is thus an influence on the beam current. In contrast, it is disadvantageous with Vidikon image pickup tubes when the beam current changes. A change in the beam current causes in addition to the deterioration of the noise-useful ratio, a change in focus and a reduction in contrast.

Circuit arrangement
with a television pickup tube

Applicant:

Max Grundig,
Fürth (Bay.), Kurgartenstr. 37

Michael Obiemski, Nuremberg,
has been named as the inventor

The invention was therefore based on the object

ao a simple and reliable control circuit for To keep the beam current constant. This is achieved by the fact that in an image pickup tube, in which the image signal is generated by scanning with slow electrons, in particular of the Vidikon type, the beam current during the scan at a preferably presettable value is kept constant in that a control voltage derived from the beam current for a Control circuit at a resistor in the anode or cathode circuit of the image pickup tube is removed and a preferably amplified manipulated variable obtained from the control circuit is fed to the control grid (Wehnelt cylinder) of the image pickup tube. So it becomes the Beam current itself derived a controlled variable in order to generate the beam current with the help of the control of the Wehnelt cylinder keep constant. The derivation of the control variable can be achieved in that it is in Anode circuit of the receiving tube due to an existing return blanking in the form of voltage pulses is taken and after rectification for the control of the control circuit is used. It is advisable to provide means to control the jet stream before the start-up Camera or shortly after commissioning to a predetermined value.

The control variable can be obtained, for example, in that the at the cathode of the Image pick-up tube, direct voltage proportional to the beam current to the grid of a direct current amplifier tube is supplied that the blanking pulses simultaneously supplied to the cathode by an i? C combination can be screened out and that the amplified DC voltage at a voltage divider

»9 759/176

Claims (6)

3 4 in the anode circle of this tube and the presetting of the jet current. Is fed to the image pickup tube by changing control grids. In this case, the cathode resistance is high and the cathode or grid bias is namely the control grid is shifted to a negative value before the start of the regulation. From tense. By controlling the DC voltage. 5 structural reasons, it is often expedient, for example, amplifier tube with the DC voltage component "the way around the television camera is small to half the cathode voltage shifts the anode voltage, the control circuit in the control device under the control tube, and with the help of a between gene and only with plug contacts over suitable A negative voltage and a voltage divider connected to the anode of these lines in the camera cable with the image pick-up tube 1 tube result in a connection At eifier practically executed lines shown and labeled 22,
th circuit arrangement .. a change resulted. FIG. 2 shows a preferred embodiment of the voltage at the control grid (Wehnelt cylinder) of the invention, in which the derivative of the control variable is approximately −100 to −10 VoFt, "when applied to the voltage 15 for the Control circuit from the anode circuit of the divider was about -150 volts. After a short image recording tube takes place !. The cathode 2 of the image time is a state of equilibrium at the Wehnelt recording tube 1 is on the one hand. This resistor 3 is connected in parallel with fluctuations in the image pick-up tube and also a diode 23, which, irrespective of fluctuations in the heating voltage, has the effect that the cathode remains the DC amplifier tube during the scanning times. The cathode bias is also independent of aging, so it is practically at ground potential ial. This causes the cathode of the image pickup tube to appear. The interferences superimposed on the output pulses The cathode of the image pickup tube is known to be short-circuited and can no longer be blanked with the aid of blanking pulses. It will get 25 gnalelectrode and distort the picture. From now, interfering pulses can also be connected to a positive voltage source, which can cause interference in the anode 12 of the image pickup tube 1 via an image during the scanning times. These interferences are transmitted by the capacitor 13, which drops off at the load resistor 25, to the signal electrode and are then easily amplified in the low pulse of a rectifier arrangement 14, 15 with an image signal amplifier As is known, to maintain the level, while both amplitudes of a few millivolts cause visible brightness fluctuations in the diodes 14 and 15 together to produce a pure peak equal image. ■ This rectifier arrangement is to be caused Finding the voltage source by a preferred embodiment of FIG. 35. The control circuit obtained with the aid of this arrangement for keeping the beam current direct voltage constant will be eliminated in a simple manner from the grid 16 of the direct voltage Image recording DC voltage is then taken from the anode 18 during the scanning times with the aid of a diode 40 tube connected in parallel to the control grid 11 of the image recording and the cathode resistor. The basic bias voltage of the cathode is connected to ground with low resistance. This diode is acted upon with the aid of a controllable resistor 20 that the disturbances become ineffective, they are adjusted and thereby the beam current reference value prevents but at the same time the control of the beam is given. In this arrangement, too, it is expedient to flow from the cathode. According to the invention, the amplification circuit in the control unit in this case is to be accommodated from the pulses in the anode circuit and, with the help of additional lines, pulses are obtained by peak rectification, one in the camera cable with the anode and the control DC voltage, which connect the grid of a grid. DC voltage amplifier tube is supplied, and the connected to the anode 18 of the tube 17 this amplified DC voltage is then prevented by the rectifier 19 that the grid bias anode This DC voltage amplifier tube is temporarily positive when the image pickup tube 1 is removed, taken and in turn the control grid of the image recording z. B. when switching on or with a possible exception tube fed. changing the tube 17. Further details of the invention will become apparent. The invention is not limited to the illustrated and Hand of the drawings, which limits two circuit arrangements described, represent examples, explained in more detail. 55 but can with professional modifications in In Fig. 1, a control circuit according to the invention is the details also realized in another way. shown in which the control voltage can be converted from the without compromising the concept of the invention. Cathode circuit is derived. From the Kassen. In particular, the tubes and equal In method 2 of the image pickup tube 1, the DC voltage converter is replaced by suitable semiconductor elements voltage to the grid 6 of a DC voltage amplifier 60,
tube 7 fed. The ones coming from port 24 Blanking pulses are thereby provided by the i? C combination patent claims:
nation 4, 5 screened out. The cathode resistance of the The image pickup tube is denoted by 3. From the 1st circuit arrangement with a television on anode of the tube 7 is the amplified DC voltage tube, in which the image signal is reduced via one of the two resistors 8 and 9, scanning is generated with slow electrons, existing, applied to a negative bias voltage in particular 'of the Vidikon type, thereby identified voltage divider removed and over the counter-mark that the beam current during the distance 10 the control grid 11 of the image acquisition scanning on a preferably presettable tube 1 supplied. The potentiometer 21 is used to 70 value is kept constant that a control voltage derived from the beam current for a control circuit (7, 17) at one in the anode or cathode circuit of the image pickup tube (1) lying resistor (25, 3) removed is and a preferably amplified manipulated variable obtained from the control circuit dem Control grid (Wehnelt cylinder 11) is fed to the image pickup tube. 2. Circuit arrangement according to claim 1, characterized in that the control variable im Anode circuit of the receiving tube by means of the return blanking that occurs Voltage pulses are taken and after rectification for the control of the Control circuit is used. 3. Circuit arrangement according to claim 1 or claim 2, characterized in that the The cathode of the image pick-up tube has a low resistance during the scanning times with the aid of a diode (23) is connected to ground and that from the pulses in the anode circuit (12) by peak rectification (14, 15) a DC voltage is obtained, which the grid (16) of a DC voltage amplifier tube (17) is supplied, and that the amplified DC voltage is removed from the anode (18) of this DC voltage amplifier tube and is fed to the control grid (11) of the image pickup tube. 4. Circuit arrangement according to claim 1 or claim 2, characterized in that the direct voltage lying on the cathode (2) of the image pickup tube, the beam current proportional direct voltage to the grid (6) of a direct voltage amplifier tube (T) is supplied that the blanking pulses simultaneously supplied to the cathode by an i? C combination (4, 5) can be screened out and the amplified DC voltage is taken from a voltage divider (8, 9) in the anode circuit of this tube (7) and fed to the control grid (11) of the image pickup tube (1). 5. Circuit arrangement according to claim 1 and one or more of the preceding, characterized in that the point of use of the DC voltage amplifier tube and thus the beam current preset to a certain value will. 6. television camera using a circuit arrangement according to claim 1 and one or more of the preceding, characterized in that the control circuit in one Housed in the control unit and connected to the image pickup tube by means of lines in the camera cable connected to the TV camera. Considered publications: German Patent No. 944 964; U.S. Patent Nos. 2,465,667, 2,463,038; "Elektronic Engineering", November 1955, pp. 502 to 505; Dillenburger, "Introduction to German Television Technology", Verlag Schiele und Schön, 1953, P. 154. 1 sheet of drawings © 909 759/176 3.