JPS6025951B2 - color encoder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a color encoder in a color television camera.

The color encoder in a color television camera is often influenced by conditions such as the camera type or price used, and its configuration varies; however, here we will discuss the color encoder in a simple color television camera. Let's discuss an example.

FIG. 1 shows an example of its configuration.

In FIG. 1, only a block diagram for obtaining a carrier color signal is shown, and a processing circuit for a luminance signal is omitted. 1st
In the figure, two different color difference signals are connected to terminals 2 and 3,
For example, RY and B-Y are input.

Of these two color difference signals, R-Y is balanced-modulated by the modulator 6 by the carrier signal CW input from the terminal 4, and the other B
-Y is balanced-modulated by a modulator 7 using a carrier wave signal CW' which is obtained by phase-shifting the carrier wave signal CW input from the terminal 4 by 900 degrees through a phase shift circuit 8. The two carrier color signals that have been balanced-modulated in this way are added from an adder circuit 1, and a blanking pulse BLK input from terminal 1 is added to remove leakage of the carrier wave signal during the blanking period of the signal. inserted. On the other hand, the burst signal is obtained by gating the burst flag pulse period of the carrier wave signal CW' in the gate circuit 9 using the burst flag pulse BF input from the terminal 5.

The burst signal created in this way and the adder circuit 1
After adding the 0 output carrier color signal in an adding circuit 11, the signal is connected to the next stage processing circuit from a terminal 12 in order to obtain an NTSC signal by adding it with a luminance signal, a composite synchronization signal, etc. To explain this using the signal waveform diagram in FIG. 2, the signal shown at 2-1 is the planking pulse BLK input from the mode 1, 2-1 indicates the horizontal planking period, and 22 indicates one horizontal scanning period. show.

The signal shown at 2-2 is the burst flag pulse BF input from the terminal 5.

The carrier color signal balanced by modulators 6 and 7 is 2-3
As shown in FIG. 2, unnecessary signal components generated due to leakage of the carrier wave signal or processing of the circuit circuit may be superimposed during the blanking period 21. To remove this, a planking pulse BLK is inserted and the color signal during the planking period is changed to 2-4.
Need to clean like. As a burst signal, a carrier wave signal as shown in 2-5 is gated by a burst flag pulse BF to obtain a signal as shown in 2-6. The signal shown at 2-7 is a signal obtained by adding the carrier color signal and the burst signal, and is output from the terminal 12.

In the conventional color encoder as explained above, the burst signal is created in a separate circuit from the carrier color signal in order to remove unnecessary signal components during the blanking period by inserting a planking pulse BLK into the carrier color signal. However, the configuration is such that the addition is performed after inserting a blanking pulse into the carrier color signal. For this reason, it has been difficult to simplify and downsize the encoder. The present invention solves these problems and provides a color encoder that has a simple configuration and is suitable for semiconductor integration.

An embodiment of the present invention will be described below based on the drawings.

Here, as in the conventional example, the luminance signal circuit is omitted. In FIG. 3, 31 is an input terminal for the blanking pulse BLK, 32 is an input terminal for the color difference signal RY, 32 is an input terminal for the burst flag pulse BF and the color difference signal B-Y, and 33 is an input terminal for the color difference signal B-Y.
34 and 35 are balanced modulators, 36 is a 90° phase shifter for the carrier signal CW, and 37 is an addition circuit for two balanced modulated color difference signals. As is clear from this configuration diagram, the color difference signal C-Y, the burst flag pulse BF, and the color difference signal B-Y are simultaneously applied to the modulators 34 and 35 via the terminals 31 and 32, respectively, to perform balanced modulation. In order to remove unnecessary signal components in the planking period excluding the burst signal period, the modulators 34 and 35 add the planking pulse BLK excluding the burst signal period, and insert the planking pulse BLK into the carrier color signal. is being carried out. FIG. 4 shows a specific example of the configuration of the present invention.

In Fig. 4, the color difference signal B-Y from the terminal P,
A burst flag pulse BF is input from 2. Resistance R
, , R2 add the two signals at the emitters of the transistors Tr, and after amplification, one is connected to the base of the transistor T through the emitter follower transistor Tr2, and the other is connected to the base of the transistor T, and the other is connected to the color difference signal output. It is connected to transistors Tr3 and Tr4 and a capacitor C, which are sample-and-hold circuits that create a reference value for the balanced modulation circuit by detecting the DC potential during the ranking period and holding it for one horizontal period. Here, P3 is the state of clamp pulse input. The reference potential thus detected and the color difference signal containing the reference potential are transmitted to transistors Tr6, Tr7 and Tr8, Tr9, whose emitters are connected in common, to resistors R, . , R,2 and R,3, R,4. These resistances R, . ,R,2 and R,3,
R, 4 are amplitude comparison transistors Tr, o, Tr, . It also serves as a load resistance connected to the collectors of Tr, 2, Tr, 3. Therefore, the bare transistor Tr8 of the transistors connected in common to the emitters
, Tr7 and T~, Th are applied to the base voltages of transistors Tr, Tr, . The DC potential varies depending on the phase of the carrier wave signal CW input to the bases of Tr, 2, Tr, 3. Therefore, each output signal from the emitter is on the high potential side with respect to the reference voltage. Since the carrier wave signal CW is output with different phases on the low potential side and the low potential side, and the carrier wave signal CW is completely suppressed at the reference potential, well-balanced balanced modulation is performed. As a means for inserting a planking pulse BLK into this balanced modulated signal, a positive direction planking pulse BLK from the terminal P6 excluding the burst signal period is used.
is added to the commonly connected emitters of the transistors T et al., Tr7 and T et al., Tr9 through the diode D or D2, and by making the emitter potential higher than the base potential during the blanking period, This is done by turning off the As a result, during the blanking period of the modulation signal, the carrier wave signal CW.
Unnecessary signal components such as leakage are completely removed. Further, transistors TrW Tr, which constitute a differential amplifier,
5, the two balanced modulated signals of the inverted carrier wave signal CW are added, so even if there is a difference in emitter potential between the blanking period and other periods as described above, the transistor Tr , 4, Tr, and 5 change in the same way, so even if a band-pass filter or the like is used as a collector load, there will be no effect due to this potential difference.

Similarly, the color difference signal RY applied to the terminal P,' is also balanced modulated, and then the transistors Tr,4' of the differential amplifier,
The collectors are connected to the same load as the transistors Tr,4,T[,5 of the B-Y signal differential amplifier, and the two balanced modulated color difference signals including the burst signal are summed. Then, a rutted color signal is outputted from terminal P4 or P5.

In FIG. 4, the configurations and operations of the two sets of balanced modulators are the same except that carrier wave signals CW and CW2 are input with signals having a phase difference of 9 degrees.

The operation of this blanking signal insertion circuit will be further explained using the signal waveform diagram shown in FIG. 5-1 is a planking pulse, 51 indicates one horizontal scanning period, and 52 indicates a planking period.

5-2 is a burst flag pulse, and in this embodiment, the planking pulse is a planking pulse excluding the burst signal period, such as 5-3, which is created by adding the two pulses 5-1 and 5-2. I am using pulse.

The signal shown at 5-4 is a color difference signal containing a burst flag pulse, and the potential shown by the dotted line 53 represents the reference potential.

Signal waveforms obtained by balanced modulation of this color difference signal with a carrier wave signal are shown in 5-5 and 5-6. Although not shown, the phases of these two carrier signals have an inverted relationship. To insert the blanking signal into these two signals, a positive blanking pulse such as 5-8 is applied from the terminal P6, and the diodes D, D2 are conductive only during the blanking period, and the transistors Tr6,
The emitter potentials of Tr7, Tr8, and T also become higher than the base potential during that period, the transistors are turned off, and unnecessary signal components during the blanking period are not output to the emitters. The signal waveforms of this emitter are shown in 5-9 and 5-10, and the potential is high only during the blanking period. When the two signals obtained in this way are added using a difference amplifier, we get
The signals output from the collector load are as shown in 5-7.

Since the two base potentials of the differential amplifier are the same, 5-
It can be seen that even if there is a potential difference between the blanking period and other signal periods as shown in FIGS. 9 and 5-10, the output waveform is not affected at all. Although not shown in the embodiment, for example, in FIG. 4, the switching transistors Tr,
.

and Tr. By turning on the transistor Tr2 during the blanking period, the base potentials of the transistors Tr6, T, etc. performing the amplitude comparison drop. Therefore, as the output of each amplitude comparison transistor, the base potential of Tr7, T~, that is, the reference potential detected from the color difference signal can be taken out, so it is easy to insert a blanking signal as in the embodiment shown in Fig. 4. can be done. As described above, the present invention has the following advantages.

Since a carrier color signal including a burst signal can be created using m2 modulators, the circuit can be simplified.

{2) It is easy to insert a blanking signal into a carrier color signal in a semiconductor integrated encoder. A circuit configuration suitable for '3' semiconductor integration can be achieved.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of a subordinate encoder, Fig. 2 is a signal waveform diagram of each part of Fig. 1, Fig. 3 is a configuration diagram showing an embodiment of the present invention, and Fig. 4 is a specific circuit diagram thereof. , FIG. 5 is a signal waveform diagram of each part of FIG. 4. 34, 35... Balanced modulator, 36... 900 phase shifter, 37... Addition circuit, Tr6, Tr7 and Tr8,
Tr9...An amplitude comparison transistor forming a duty amplifier, TrMTr,5...Differential amplifier. Figure 1 Figure 2 Figure 3 Figure 5 Box ship

Claims (1)

[Claims] 1. A carrier color signal obtained by balanced modulating a color difference signal including a burst signal with a carrier signal is made conductive during a burst signal period within a blanking period, and is blocked during other blanking periods. A color encoder characterized in that it is provided with means for inserting a blanking signal. 2. The method according to claim 1, wherein the blanking signal is inserted by controlling the emitter potential of an amplitude comparison transistor constituting a balanced modulator to cut off the carrier color signal. color encoder. 3. Claims characterized in that, as means for inserting the blanking signal, the base potential on the color difference signal input side of the amplitude comparison transistor constituting the balanced modulator is controlled and the carrier color signal is cut off. The color encoder according to item 1.