JPH038631B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an image display device that displays images using an A/D converter.

(Configuration of conventional example and its problems) Conventionally, in this type of image display device, the same sampling pulse is supplied to the A/D conversion circuit even when displaying an image of a composite video signal and an image of a component signal. It is. A conventional example will be explained below with reference to FIG.

The composite video signal is supplied to a signal switching circuit 4 via an input terminal 1, and the component signal is supplied to a signal switching circuit 4 via an input terminal 2. On the other hand, the signal for selecting the above signal is supplied via the input terminal 3 to the signal switching control circuit 5 for controlling the signal switching circuit 4. In the case of the composite video signal selected by the signal switching circuit 4, it is supplied to the video signal processing circuit 6, where it undergoes various signal processing, and is output as R, F, and B color signals, and then sent to the signal switching circuit 8.
is supplied to Further, when a component signal is selected by the signal switching circuit 4, each color signal is supplied to the signal processing circuits 7 ₁ to 7 ₃ and subjected to various signal processing, and each color signal is output and supplied to the signal switching circuit 8. The signal switching circuit 8 is controlled by the signal switching control circuit 5, switches to select a signal synchronized with the signal selection of the signal switching circuit 4, and outputs the signal to the A/D converters 9 ₁ to 9 _{3 .} supply to. Hereinafter, only the color signal R will be explained.

The A/D converter ₉₁ is supplied with the color signal R and the sampling pulse generated by the sampling pulse generator ₁₀₁ , and outputs an n-bit (n is an integer of 2 or more) digital signal, which undergoes signal processing and output. Supplied to circuit ₁₁₁ . In addition, sampling pulses etc. are supplied from the sampling pulse generation circuit 10 ₁ to the signal processing and output circuit 11 ₁ , and the 1H memory,
It undergoes signal processing such as pulse width modulation and is supplied to the image display 12 via an output circuit (the same applies to color signals G and B).

In addition, in order to deflect the image display 12 in the horizontal and vertical directions, the signal selected from the signal switching circuit 4 is supplied to the synchronization signal processing circuit 13 to generate synchronization signals (horizontal synchronization signal: HD and vertical synchronization signal: VD). is obtained and supplied to the deflection signal processing output circuit 14 to apply the necessary deflection voltage to the image display 12.

By the way, when a digital component signal as shown in Figure 2 is input when the image display is installed as described above (for example, the video monitor output of a personal computer) and the image is faithfully reproduced, the image will be as shown in Figure 3. Become. However, A/D
When the converter samples at the rising edge of the sampling pulse, when the input signal is equal to or narrower than the sampling pulse width (T _A
During this period, the input signal and the sampling timing may not match, and a faithful image as shown in FIG. 5 cannot be reproduced.

(Object of the Invention) The present invention solves the above problems, and provides an image display device that can faithfully reproduce an image on an image display when a component signal of a digital signal is input and selected. The purpose is to

(Structure of the Invention) The present invention detects the signal selection of the input signal by inverting the phase of the sampling pulse of the A/D converter every line (1H) only when a component signal is selected. The image is reproduced faithfully.

(Description of Embodiment) One embodiment will be described below with reference to FIGS. 6 to 10. In FIG. 6, the sampling pulses φ ₁ , which are generated by the sampling pulse generation circuit 10 ₂ and have the same period and inverted phase (180 degrees),
φ ₂ is supplied to the sampling pulse switching circuit 16, and the switching circuit 16 is controlled by the sampling pulse control circuit 15. The sampling pulse control circuit 15 includes the signal output of the signal switching control circuit 5, a horizontal synchronization signal: HD, and a vertical synchronization signal:
VD is supplied, and the sampling pulse switching circuit 16 is controlled depending on the state of the input signal. If a composite video signal is selected as the input signal, sampling pulse φ ₁ is set to sampling pulse switching circuit 1.
6 so that it is always output. In addition, when the component signal is selected, the sampling pulses φ ₁ and φ ₂ alternate every line (1H), and the above operation is canceled every vertical period by the vertical synchronization signal: V _D. Therefore, sampling pulses of the same phase are outputted from the sampling pulse switching circuit 16 on the same line (1H). The above explanation is shown in a timing diagram as shown in FIG.

FIG. 8 shows horizontal lines from n to n+3 according to the present invention.
Input signal up to the line, sampling pulse,
In the timing diagram of the A/D converter output, a shows the n line, b shows the n+1 line, c shows the n+2 line, and d shows the n+ ₃ line. Only the period will be explained. A/
In the case where sampling of the D converter is performed at the rising edge of the sampling pulse, assuming that the sampling pulse of the n line a is _φ1 , the output of the A/D converter is at a low level. Next, n+1 line b
As explained above, the phase of the sampling pulse is reversed to _φ2 with respect to _φ1 , and the output of the A/D converter becomes high level. Next, the n+2c line is
The phase of the sampling pulse is again reversed to _φ1 , and the output of the A/D converter becomes low level. Next, on the n+3d line, the phase of the sampling pulse is reversed to _φ2 , and the output of the A/D converter becomes high level.

Similarly, according to the conventional method, as shown in FIG. 9, assuming that the sampling pulse is φ _A , the output of the A/D converter on line n is at a low level. Next, n+1 line b, n+2 line c, n+
The sampling pulse is also φ _A on the 3rd line d.
Since the phases are the same, the output of the A/D converter is low level.

Fig. 10 shows the above state reproduced on an image display device. Fig. 10 a shows the case where the image is faithfully reproduced, Fig. 10 b shows the reproduction of the conventional image, and Fig. 10 c shows the image obtained by the present invention. As is clear from this figure, the present invention can reproduce a more faithful image than the conventional example.

(Effects of the Invention) As explained above, according to the present invention, a more faithful image can be reproduced by inverting the phase of the sampling pulse line by line when a component signal of a digital signal is input. .

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the basic configuration of a conventional image display device, FIGS. 2 to 5 are diagrams for explaining the conventional example, and FIG. 6 is an image display device according to an embodiment of the present invention. 7 is a block diagram showing the basic configuration of the horizontal synchronizing signal in the same embodiment:
8 and 9 are timing diagrams of the input signal, sampling pulse, and A/D converter output in the present invention and the conventional example, respectively. FIG. 1, 2, 3... _Input terminal, 4,8...Signal switching circuit, 5...Signal switching control circuit, 6...Video signal processing circuit, _71-73 ...Signal processing circuit, _{91-9 3}
...A/D converter, 10 ₁ to 10 ₂ ... sampling pulse generation circuit, 11 ₁ to 11 ₃ ... signal processing,
Output circuit, 12... Image display, 13... Synchronization signal processing circuit, 14... Deflection signal processing, output circuit,
15...Sampling pulse control circuit, 16...
Sampling pulse switching circuit.

Claims (1)

[Claims] 1 The composite video signal input from the composite video signal input terminal is processed by the signal processing circuit, and the component signals (red, green, blue, horizontal synchronization,
Vertical synchronization signals) Each signal input from the input terminal is processed by the signal processing circuit, and the signal is supplied to the signal switching circuit, and the switching control signal is supplied from the switching control terminal to the signal switching circuit, and the above-mentioned signals are If a composite signal is selected, the selected signal and two types of sampling pulses generated by the sampling generator with the same frequency but different phases are discriminated by the control signal of the signal switching circuit. When the same sampling pulse is output and a component signal is selected, the sampling pulse is output via a sampling pulse control circuit that controls the output of two types of sampling pulses alternately for each horizontal line (1H). An image display device that supplies an analog-to-digital converter (A/D converter), supplies an A/D conversion output to a signal processing circuit, processes the signal, and supplies it to an image display device to display an image. The sampling pulse of the A/D converter is characterized in that the phase of the sampling pulse of the A/D converter is inverted every line (1H) only when a component signal is selected by determining the signal selection of the input signal. Image display device.