JPS6344230B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in an apparatus for displaying an image by converting a digital video signal into an analog video signal using a D/A converter.

An analog video signal obtained by converting a digital video signal by a D/A converter has a level that changes in a stepwise manner. Discontinuities were noticeable, and sometimes the brightness and darkness of the image became contour lines, creating circular corridors, resulting in poor image quality and difficulty in viewing.

The present invention provides an apparatus for displaying an image by converting a digital video signal into an analog video signal using a D/A converter, by increasing the number of steps of the digital video signal or the analog video signal. The purpose is to provide a device that improves image quality.

The feature of the present invention is to convert digital video signals into D/A
The present invention is characterized in that a delay circuit and an adder are provided for a device that displays an image by converting it into an analog video signal using a converter.

Embodiments of the invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of an embodiment, where 1 is a digital video signal source and 2 is a D/A converter.

Reference numeral 3 denotes a delay circuit, which delays the input video signal by a time equal to one horizontal scanning time plus 1/2 of the horizontal scanning time between one pixel.

4 is an adder, 5 is an attenuation circuit, and 6 is a television receiver.

Next, the operation of the above configuration will be explained. A digital video signal from a digital video signal source 1 is input to a D/A converter 2, where it is converted into an analog video signal having stepwise level changes and output. A part of this analog video signal is input to the adder 4 as is, and the other part is input to the delay circuit 3. The analog video signal input to the delay circuit 3 is
The output is delayed by one horizontal scanning time plus 1/2 of the horizontal scanning time between pixels, and is input to the adder 4. Since the adder 4 adds two analog video signals that have a step-like level change and a time lag, the number of steps in the analog video signal output from the adder 4 is increased.
This analog video signal is converted to 1/1 in the attenuation circuit 5.
2 level and input to the television receiver 6,
Displayed as an image.

FIG. 2 shows the transition in which the number of steps of the analog video signal increases in the example.

11 in FIG. 2a is the brightness level of a real image with uniform brightness level changes concentrically, and 4
It is indicated by the brightness level of the stairs. H ₀ , H _-1 , H _-2
etc. are representatively selected horizontal scanning lines.
V ₁ is a representatively selected vertical position line. The intersection of the horizontal scan line and the vertical line indicates a pixel.

Reference numeral 12 in FIG. 2b is an analog video signal representing the brightness level 11 of the real image along the horizontal scanning line H ₀ in FIG. 2a.

13 in Figure 2c is the horizontal scanning line of Figure 2a
The analog video signal representing a brightness level 11 along H _-1 is delayed by 1/2 of the horizontal scanning time between pixels to represent a brightness level 11 along the horizontal scanning line _H0 in FIG. 2a. It is added to the analog video signal and then averaged.

In FIGS. 2b and 2c, the vertical axis shows the level of an analog video signal representing a brightness level 11, and the horizontal axis shows the pixel spacing.

14 in FIG. 2d is plotted on the vertical position line V ₁ of the analog video signal representing the brightness level 11 along each horizontal scanning line H ₀ , H _-1 , H _-2 etc. of FIG. 2a. be.

15 in FIG. 2e indicates the previous horizontal scanning for each analog video signal representing the brightness level 11 along each horizontal scanning line H ₀ , H _-1 , H _-2 , etc. in FIG. 2a. The analog video signal representing the brightness level 11 along the lines H _-1 , H _-2 , H _-3, etc., delayed by 1/2 of the horizontal scanning time between pixels, is added to the averaged analog video signal. They are plotted on the vertical position line V ₁ when displayed along the horizontal scanning lines H ₀ , H _-1 , H _{-2 ,} etc., respectively.

The horizontal axis in FIGS. 2d and 2e represents the level of an analog video signal representing a brightness level 11, and the vertical axis represents the pixel spacing.

In the above explanation of the operation, the output of the D/A converter 2 is an analog video signal such as 12 in FIG.
The image is an analog video signal with an increased number of steps as shown in 13 in Figure c, whereas if an image quality improvement device is not installed, the image is displayed as an analog video signal as shown in 12 in Figure 2 b. When an image quality improvement device is provided, the image is displayed using an analog video signal such as 13 in FIG.

Also, in FIG. 1a, for example, the vertical position line V ₁
The analog video signal observed above is 14 in FIG. 2 d when the image quality improvement device is not installed, whereas it is a staircase signal as shown in 15 in FIG. 2 e when the image quality improvement device is installed. As the number increases, discontinuities in brightness and darkness are generally less noticeable in the vertical direction as well.

As described above, discontinuities in brightness and darkness become less noticeable in both the horizontal and vertical directions, and the overall image quality improves.

As another embodiment, as shown in FIG. 3, the number of steps can be quadrupled by increasing the number of delay circuits 3a, 3b, and 3c and changing the circuit configuration. Furthermore, by changing the circuit configuration, the number of steps can be arbitrarily doubled, further improving image quality.

Moreover, as shown in FIG. 4 as another example,
A part of the digital video signal is input to the delay circuit 3, and the output digital video signal of the delay circuit 3 is
It is also possible to input the digital video signal that is input to the A converter 2a and not delayed to the D/A converter 2b, and input the analog video signal output from the D/A converters 2a and 2b to the adder 4. Further, as shown in FIG. 5, a part of the digital video signal is input to the delay circuit 3, and the output digital video signal of the delay circuit 3 and the undelayed digital signal are input to the adder 4, and the output of the adder 4 is inputted to the adder 4. A digital video signal can also be input to a D/A converter. The functions and effects of these embodiments are the same as those of the first embodiment except that the order of D/A conversion, delay, and addition is different.

The present invention is not limited to the above-described embodiments, and replacement with equivalents is possible, all of which are within the technical scope of the present invention.

As described in detail above, according to the present invention, when converting a digital video signal into an analog video signal and displaying an image, the number of steps of the video signal is increased by the image quality improvement device, so that the number of steps of the quantization step is increased. Even a small number of digital video signals can be displayed as an inconspicuous image with discontinuous brightness and darkness, and the image quality can be improved.

[Brief explanation of drawings]

The drawings show individual embodiments of the present invention, and FIG. 1 is a block diagram, FIG. 2 is an operational diagram, and FIG.
4 and 5 are block diagrams. 1...Digital video signal source, 2, 2a and 2b...D/A converter, 3, 3a, 3b and 3
c... Delay circuit, 4... Adder, 5... Attenuation circuit, 6... Television receiver.

Claims (1)

[Scope of Claims] 1. A device configured to display an image by converting a digital video signal into an analog video signal by a D/A converter, including a delay circuit into which the video signal is input, and an output of this delay circuit. comprising an adder that inputs the video signal that is not delayed with the video signal;
An image quality improvement device characterized by increasing the number of steps of the analog video signal. 2. The image quality improvement device according to claim 1, wherein the delay circuit is configured to set a delay time equal to one horizontal scanning time plus a fraction times the time required to horizontally scan between one pixel.