DE2255027C2 - Method for compensating for stray light effects in television cameras and circuitry for carrying out this method - Google Patents

Description

Black level of the error in the white area of the signal can be transformed. This is especially the case if they are very strong Oversteering acts. According to a further development of the method according to the invention, this additional error, which can be expressed as a change in the degree of gain, by means of a corresponding one opposite control also compensated for the gain.

The invention is now to be based on one of the FIGS. 1 and 2 illustrated embodiment in more detail are explained, only the parts necessary to understand the invention are shown. It shows

F i g. 1 shows a block diagram for carrying out the method according to the invention,

2 shows a diagram of the signal current that can be removed from the pick-up tube.

At the signal electrode 1 of the television pickup tube 2, an image signal according to FIG. 2 can be picked up, which consists of a signal component A of the useful signal range and a signal component B of the overdrive range. The signal components appearing in the overdrive area and shown hatched in FIG. 2 are scanned by the beam current during the return movement, the amplitude of the signal C during this sampling being determined by the time ratio outward / return.

The image signal is supplied to a level selection stage 3, which divides the image signal into the signal component A and the amount of signal B The removable at the first output stage 3 useful signal A is fed through a preamplifier 4 to a black level control stage 6 for black girth adjustment. In addition, the amplified useful signal component A is fed to a compensation voltage generator 9, which consists of an amplifier 7 and an integration element 8 and which generates a compensation voltage that preferably corresponds to the mean value of the useful signal. This compensation voltage is fed to the control input of the black level control stage 6 with such an amplitude (controller 10) that the scattered light influence on the signal is just compensated.

The signal component B , which is fed to a further compensation voltage generator 11, consisting of an amplifier 12 and an integration element 13, can be taken off at the second output of the level selection stage 3. The compensation voltage arising at the output of this compensation voltage generator 11 is also fed to the control input of the black level control stage 6 with such an amplitude (controller 10) that the influence of scattered light resulting from the overload is also compensated.

In order to compensate for a possible influence on the white value by adjusting the black value, a partial voltage derived from these compensation voltages is also sent to the control input a gain control stage 14 is supplied. Their output signal is via a gamma control stage 16 fed to the output amplifier 17 of the television camera, at the output terminal 18 of which the stray light compensated Image signal is removable

1 sheet of drawings

Claims (4)

helite. In the case of color television cameras, in addition to patent claims: the * -pm scattered light caused by reflections on or within the storage electrode of the recording tube 1. Method to compensate for scattered light generated because the storage electrode is not light effects in television cameras, preferably 5 black, but for example in a recording color television camera, with receiving tubes, with tube of the plumbicon type being reddish-brown. which this is also the case on the storage electrode when recording a color-neutral original Charging mountains created by highlighting, while the black level is discharged by the scattered light component in the red trend of the blanking interval up to the vicinity of the useful channel by about 30 ⁰ Zo, in the Crün channel by about 10 ° ο signal area, thereby reducing ίο and Lm blue channel by about 5% raised. Color indicates that neutral dark image areas are therefore preferably compensated above the useful signal range, the stronger the higher the sation voltage is generated, which together light flux through the lens, ie the higher the simit, preferably the mean value of the useful - signal mean value of the output current of the television signal corresponding compensation voltage 15 is acquisition tube. This signal mean value thus forms the black level of the image signal controls a suitable control variable with which the scatter 2. The method according to claim 1, characterized in that the lighting effect is achieved by controlling e.g. indicates that the clamp levels of the image signal at the signal electrode are compensated the television pickup tube can detachable signal in. the useful signal and the signal component above 20 However, this method has the disadvantage that at Useful signal is divided that from the Nutzsi- exceeding the characteristic of the pickup tube gnal and from the signal component above (e.g. partial overexposure) the useful signal im after amplification and integration, one ent- amplifier channel is limited. In this case it is Speaking compensation voltage gained proportionality between luminous flux - and thus which is common to one or each of a se- 25 scattered light - and the signal mean value no longer The black level control stage of the amplifier cable is available, which means that the compensation is ineffective. nals are fed. The dark parts of the picture are therefore 3. The method according to claim 1 and 2, characterized mender overdrive strongly red-sighted, so that the characterized in that the compensation voltage picture is unusable. In addition, there is an additional gain control stage will. exposure creates a very high one in these areas 4. Circuit arrangement for carrying out the charging of the storage electrode, which indicates the Elek method according to claim 1 and 2, characterized in that the electron beam normally only after several that the signal electrode (1) can neutralize each passage. On the picture television tube (2) with the input each 35 screen there is a »Faheiner level training stage (3) for the separation of the moving objects« and for stationary objects an »on-useful signal (A) from the signal component (B) above sources «These parts of the picture are recognizable. Is connected to prevent the useful signal, that the first off this ^Appear!: Voltages, it is known, the electron transition of Pegelselektionssiufe (3), au which beam not to suppress the return run, but the useful signal is removable, 40, over a pre-strong to raise that these large charges amplifier (4) on the one hand with the signal input to just above the useful signal range limit of the black level control stage (6) and on the other hand builds. The overdrive charge is converted by a compensation voltage generator into electrical signals during the return (9) with the control input of the black level control. However, this is also connected to the scattering stage (6) and that the second output proportional to the signal component process of the level selection stage (3), at which point the signal component above the useful signal is not transmitted by the camera, which, however, can have a negative effect on the black level in the useful signal range (B) via a further compensation range. Stationary voltage generator (11) with the control object of the invention is therefore to provide a method input of the same or another black 50 to compensate for stray light effects also for value control stage is connected. indicate those television cameras whose recording röhicn with scanned electron beam during of the return can be operated without the Interfering with the black level of the output signal 55 turns. The object is achieved in that from the Si The invention relates to a method for compensating the signal component above the useful signal range, a system of scattered light effects in television cameras, compensation voltage is generated, which preferably color television cameras with recording tubes together with a preferably the mean value of the ren, in which the compensation voltage corresponding to the storage electrode also 60 useful signal at The Ladunesgebirge resulting from highlighting controls the threshold value of the image signal,
rend the blanking interval to near the useful The advantage of the method according to the invention broadly discharged, and cmc circuit connection consists in that the above-mentioned color cast of the Rules for carrying out this procedure. dark parts of the image even when the Due to the luminous flux corresponding to the transmission range from each optics of a television camera 65 generated, essentially spectrally uniform, is avoided with certainty. divided scattered light is the contrast "ines television picture. It is possible that with a compensation This is reduced, i.e. dark areas of the image are caused by the stray light error by counteracting the