JPH0365559B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to a digital binary signal derived in parallel to a pattern signal for visually distinguishing forward and backward portions of image information displayed on an image display device such as a cathode ray tube.・Regarding the color difference signal matrix circuit that adds G and B3 primary color signals to synthesize color difference signals for coloring each part, the output color difference signals are output in accordance with standard values so that they can display regular reproduced colors. This is how it was done. [Background of the Invention] Generally, when displaying image information in color on an image display device such as a cathode ray tube, the display screen is divided into a predetermined number of pixels, and a pattern signal is assigned to each pixel to specify the brightness. The R, G, and B three primary color signals that specify the color are added to each pixel and sent to the color difference signal matrix circuit, and this circuit synthesizes the color difference signal that is the difference signal between the R, G, and B three primary color signals and the pattern signal. The image is then output to an image display device. In this case, the pattern signal Y is a digital signal that assigns "1" or "0" to pixels representing the information part (forward part) of the image and pixels representing the background part, and R specifies a color for each pixel.・G and B3 primary color signals are also expressed as digital signals. The table shows the forward part and background part in each color (white, yellow, cyan, green, magenta, red,
3 is a logic value table showing logic values input to a color difference signal matrix circuit when expressing colors (blue, black).

[Problems with background technology]

In this way, color difference signals can be synthesized, but in this method, after color decoding with a multiplier, the emitter follower transistor _Q19 ,
A _Q20 level shift stage and a differential amplifier synthesis stage are required, and these have the following disadvantages. (1) The output reference potential varies due to variations in resistors R ₇ and R ₈ in the level shift stage, variations in current sources I ₃ and I ₄ , and variations in V _BE of transistors Q ₁₉ and Q ₂₀ . (2) The gain of the composite output varies due to variations in the resistors R ₉ , R ₁₀ , and R ₁₁ . (3) The circuit size, especially the number of current sources, is disadvantageous in terms of power consumption, device area, and reliability when integrated. Due to the reasons mentioned above, there was a problem in that the displayed colors were not displayed vividly. [Objective of the Invention] The present invention has been made in view of the above circumstances, and the present invention enables precise display of colors reproduced from a digital signal specifying coloring and a pattern signal specifying a pattern, and further reduces the circuit scale. An object of the present invention is to provide a color difference signal matrix circuit. [Summary of the Invention] That is, the present invention includes a multi-line resistor interposed between a power supply terminal and an output terminal for converting the output obtained by decoding a digital signal specifying coloring into a voltage corresponding to each color, and a white resistor at the middle end thereof. The decoding output for specifying black and the decoding output for coloring the background are uniformly applied, so that the DC level of the color difference signal output as a color is constant. [Embodiment of the Invention] FIG. 3 is a circuit diagram showing an embodiment of the present invention. The configuration of this figure will be explained. First, a symbol signal Y that is displayed on the screen and distinguishes between the forward part and the background part of the symbol is input to the Y input terminal 11Y, and becomes a differential input to the bias terminal 11o, which is supplied with a predetermined bias. It is applied between the bases of transistors 12 and 13 forming a differential pair. The differential pair of transistors 12 and 13 have a first current source 14 on the common emitter side between them and ground, and the current of the first current source 14 is switched and outputted in accordance with the symbol signal Y. The collector of one of the transistors 12 of the differential pair transistors 12 and 13 is a differential pair transistor 15, which is switched by the B signal among the R, G, and B three primary color signals that are output in parallel to specify coloring. Connected to 16 common emitters. This common emitter is provided with a second current source 17 between it and ground. Due to its configuration, when the transistor 12 is turned on, the sum of the output current I ₆ of the first current source 14 and the output current of the second current source 17 is derived to the common emitter of the differential pair transistors 15 and 16. can do. The bases of the differential pair transistors 15 and 16 are connected to a bias terminal 18o and a B input terminal 18B, respectively. Next, the collector of transistor 15 is connected to the common emitters of differential pair transistors 19 and 20, and the collector of transistor 16 is connected to the common emitters of differential pair transistors 21 and 22, respectively. These differential pair transistors 19, 20 and differential pair transistors 21, 22 are arranged in a balanced manner at the same circuit position, and the bases of the transistors 19 and 21 are connected in common and connected to the bias terminal 23o. The bases of the transistor 20 and the transistor 22 are commonly connected to a G input terminal 23G to which a G signal is input. Thus, each differential pair transistor 1
9, 20 and differential pair transistors 21, 22 are G
When the signal has a logic value “1”, the transistors 20, 2
2 is conductive, and the differential pair transistors 15, 1 in the previous stage
The collector output of No. 6 is switched and output to the next stage. Subsequently, the respective collector outputs of the differential pair transistors 19 and 20 are respectively led out to the common emitters of the final stage differential pair transistors 24 and 25 and the differential pair transistors 26 and 27, and in balance with these, the collector outputs of the differential pair The respective collector outputs of transistors 21 and 22 are led out to the respective common emitters of differential pair transistors 28 and 29 and differential pair transistors 30 and 31. These differential pair transistors 24, 25, 26, 27, 28, 29, 30, which are on the same circuit level,
Of 31, transistors 25, 27, 29, 31
are connected in common, and each base of the R signal is connected in common.
It is connected to the input terminal 32R. Further, the bases of the transistors 24, 26, 28, and 30 are commonly connected and connected to a bias terminal 32o. Further, the collectors of the transistors 24 and 31 are connected to the middle end 39 of the multi-row resistors 33 to 38 (the resistor 35
and 36), and is also connected to the collector of transistor 13 of the differential pair of transistors 12 and 13 which switch and output the first current source according to the symbol signal. This transistor 2
Collector outputs 4 and 31 provide black and white color difference signal amplitudes, respectively. In addition, each collector output of the transistors 25, 29, 27 is connected to each resistor 33, 3 on the power supply terminal 40 side from the middle end 39 of the multi-row resistor.
4 and 35 to obtain red, magenta, and yellow color difference signal amplitudes, respectively. Further, the collector outputs of the transistors 30, 26, 28 are applied to one end of each resistor 38, 37, 36 closer to the output terminal 41 than the middle end 39 of the multi-row resistor,
This is to obtain the color difference signal amplitudes of cyan, edge color, and blue, respectively. Note that a power supply terminal 40 to which power supply voltage Vcc is supplied is connected to one end of the resistor 33, and an output terminal 41 is connected to one end of the resistor 38. As is clear from FIG. 3, according to the present invention, an emitter follower transistor that creates color difference signals on the positive side and negative side with the white/black level as a boundary, unlike the conventional one.
Q ₁₉ , Q ₂₀ , output differential amplifier Q ₂₁ to combine them,
Q ₂₂ is not required, and the current source is also 2.
Consists of only one. It should also be noted that the color amplitude ratio between the forward color and the background color is the ratio of the sum of the output currents I ₆ and I ₇ of the first and second current sources 14 and 17 to the output current I ₆ of the first current source 14. It is decided by As a result, the first and second current sources 14,
Even if the size of 17 is made smaller than before, the amplitude difference between the forward color and the background color can be obtained. Now, when cyan is specified in the forward section,
The logic inputs of R=0, G=1, B=1, Y=1 in the previous table are R/G/B input terminals 32R, 23G, 18B.
and Y input terminal 11Y. This causes the transistor 12 of the differential pair transistors 12, 13 to conduct, so that the first current source output _I6 flows through the transistor 12 to the emitters of the differential pair transistors 15, 16. At this time, since B=1, the transistor 16 becomes conductive, and a current of I ₆ +I ₇ passes through the transistor 16 and flows to the emitters of the differential pair transistors 21 and 22. At this time, since the transistor 22 is conductive since G=1, the current I ₆ +I ₇ passes through the transistor 22 and flows into the differential pair transistors 30 and 3.
Flows into the 1st emitsuta. At this time, from R=0,
The transistor 30 becomes conductive, the current I ₆ +I ₇ flows through all the multi-row resistors 33 to 38, and the output led to the output terminal 41 is Vcc-(R ₁ +R ₂ +R ₃ +R ₄ +R ₅ +
R ₆ ) (I ₁ + I ₂ ) (R ₁ to _{R 6} are resistors 33 to 38
resistance value). Also, if red is specified in the forward section,
Transistor 12 → Transistor 15 → Transistor 19 → Transistor 25 becomes conductive, and the decode output for obtaining a red color difference signal is transmitted to Transistor 2.
Guided by the collector of 5. The output at this time is
Since the other transistors are disconnected from the multi-row resistor, the power supply voltage Vcc is directly applied to the output terminal 41. In addition, when displaying the forward section in white/black, current I ₆ + I ₇ flows to the middle end 39 of the multi-row resistor, and the power supply voltage
Since Vcc is reduced by R ₁ + R ₂ + R ₃ , output terminal 4
The output of 1 becomes Vcc-(R ₁ +R ₂ +R ₃ )(I ₆ +I ₇ ). Also, if you want to color the background part, use transistor 1.
3 conducts and always lowers the voltage of (R ₁ + R ₂ + R ₃ ) I ₆ . Therefore, the output when cyan color is specified is
Vcc-( _R1 + _R2 + _R3 )( _I6 + _I7 )-( _R4 + _R5 + _R7 ) _I6
For red color, it becomes Vcc-(R ₁ +R ₂ +R ₃ )I ₆ .
Furthermore, to specify white/black, use Vcc-(R ₁ + R ₂
+R ₃ )(I ₆ +I ₇ ). FIG. 4 shows the output waveform when the forward portion changes from cyan to yellow to edge to magenta to blue to red. White/black parts are Vcc- (R ₁ + R ₂ + R ₃ ) (I ₆ +
The output when displaying cyan, edge, and blue colors with _I7 ) is on the negative side of this level, and red, magenta,
The output of each yellow color is on the positive side. The broken line is the output waveform when displaying the background part. In FIG. 5, a compensation circuit 42 is provided for matching the white/black level (DC level) of the forward color with the white/black DC level of the background color. This compensation circuit 42 is constructed by connecting the collector-emitter paths of transistors 43, 44, and 45 in series, which are applied to the bases of bias voltages ref1, ref2, and ref3, and passes through three stages of differential pair transistors when coloring the forward section. Therefore, three of them are provided in series corresponding to that number. Note that this compensation circuit 42 is not necessary if the base of the transistor used is high. Next, FIG. 6 shows an example of use of the present invention. That is,
The burst signal is superimposed on the color difference signal. This superposition can be achieved by simply adding a new differential pair of transistors 46 and 47 equipped with a current source 48. The collectors of each transistor 46, 47 are connected to the power supply terminal 40 and the common emitter of differential pair transistors 15, 16, respectively. Then, a burst signal is applied to the base of transistor 47.
BF is applied, and a predetermined bias voltage ref4 is applied to the base of the transistor 46. [Effects of the Invention] As explained above, according to the present invention, the circuit for varying the DC level of the color difference signal is removed and the output is configured to be the conventional composite output as it is, so the circuit scale can be expanded. It is possible to obtain highly accurate color difference signals without any interference. Furthermore, since there are fewer current sources that determine the amplitude ratio between the forward color and the background color than in the past, and the sum of the current sources is used for the amplitude ratio, there is an advantage that power consumption is extremely low.

[Brief explanation of drawings]

Figure 1 is a circuit diagram showing a conventional color difference signal matrix circuit, Figure 2 is a waveform diagram showing operating waveforms when specified colors are changed in order to explain the conventional method of obtaining color difference signals, and Figure 3 is a waveform diagram showing operating waveforms when designated colors are changed in order. A circuit diagram showing one embodiment of the present invention, FIG. 4 is a waveform diagram showing a color difference signal obtained by the present invention, and FIG. 5 shows another embodiment in which a compensation circuit is provided in the circuit of FIG. 3. Circuit diagram FIG. 6 is a circuit diagram showing an example of use of the present invention. 11Y, 18B, 23G, 32R...Input terminal, 11o, 18o, 23o, 32o...Bias terminal, 12, 13, 15, 16, 19, 20,
21, 22, 24, 25, 26, 27, 28, 2
9, 30, 31...transistor, 14, 17...
...Current source, 40...Power terminal, 41...Output terminal.

Claims (1)

[Scope of Claims] 1. A circuit that obtains a color difference signal by decoding a pattern signal that distinguishes between a forward part and a background part of a pattern displayed on a screen, and a parallelly derived digital signal that specifies coloring. a first current source, a second current source, and a changeover switch that inputs the symbol signal and switches the output of the first current source accordingly;
depending on the bit content of the digital signal, and
a multiplier that switches and selects the sum of the first and second current source outputs or the current of only the second current source output as a decode output according to the state of the changeover switch; and a multiplier that changes the decode output to a voltage corresponding to each color. The multi-row resistor is interposed between the power supply terminal and the output terminal, and the middle end has a decoding output for specifying white and black, and the first current for coloring the background part. A color difference signal matrix circuit characterized in that a source output is applied. 2. The first current source output applied to the middle end of the multi-row resistor is a white color output from the multiplier by a compensation circuit interposed between the middle end and one output end of the changeover switch. 2. The color difference signal matrix circuit according to claim 1, wherein the color difference signal matrix circuit is corrected to a voltage that matches a decoded output specifying black color. 3. Claim 1, wherein the decoded output of the multiplier is superimposed with the output of a third current source for supplying a burst signal.
The color difference signal matrix circuit according to item 2.