JPH02108377A - Television display device - Google Patents

Abstract

PURPOSE:To constantly make a picture easy to see and to prevent the burn of a CRT on a boundary line by making less a luminance difference between a picture part and an overlap width part when a TV signal different in an aspect ratio showing the vertical and horizontal ratio of the screen is displayed. CONSTITUTION:The TV signal of a present NTSC system with the aspect ratio of 4:3, for example, is inputted into an input terminal 10, supplied to an NTSC decoder 11, and modulation to a luminance signal (Y signal) and two kinds of chrominance signals (C signal). Next, this signal is outputted to a non-interlace converter 12 and a timing signal is outputted to a timing genera tion circuit 13. A timing signal to control the memory of a time base compres sion circuit 14 and a timing signal to control selectors 17 and 18 are generated in a circuit 13, the Y signal and the C signal of interlace are inputted to the circuit 14, the time base compression is executed based on the timing signal of the circuit 13. After that, the Y signal is supplied to the selector 17, the C signal is supplied to the selector 18 out of the compressed signals, and an overlap width level is added to the circuit 14 output.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a television display device used to display television signals having different aspect ratios (vertical to horizontal ratios of screens).

(Prior art) In recent years, television systems (for example, a system called high-definition) in which the aspect ratio has been expanded from 4=3 of conventional television systems (for example, NTSC system) to 16:9
is proposed. When a conventional 4:3 television image is displayed on a display device with an aspect ratio of 1620, it will be displayed as shown in Figure 7(a), with no images on either side shown in the shaded area. Normally, achromatic color constant brightness (gray level) is displayed in the area. Furthermore, when displaying a 16:9 television image on a conventional 4:3 display device, it is displayed as shown in Fig. 7(b), and the upper and lower portions of the image shown in the diagonal lines are displays achromatic constant brightness (gray level) in the same way as above. Hereinafter, for convenience of explanation, the shaded area in FIGS. 7(a) and 7(b) will be referred to as the margin area of the television screen.

However, when displaying as described above, the following problems occur.

(2) When the image is dark, the margins become relatively bright, so only the sides or the upper and lower parts stand out, making the central image part difficult to see.

■As the boundary between the image area and the margin is always fixed, the CRT (picture tube) mask is deformed due to the difference in brightness between the image area and the margin, for example, as shown in Figure 7 (a).
When displaying a 16:9 television image, the border lines appear as vertical stripes (this phenomenon is called burn-in). The same applies to FIG. 7(b).

<Problems to be Solved by the Invention> As mentioned above, conventionally, when displaying preview signals with different aspect ratios, it has become difficult to see the image when it is dark, and burn-in occurs at the boundary between the image area and the margin area. There was a problem that occurred.

Therefore, the present invention is intended to solve the above problem, and when displaying television signals with different aspect ratios, it is possible to always make the image easy to see, and also to prevent the phenomenon of CRT burn-in at the border area. The purpose is to provide a television display device.

[Structure of the Invention] (Means for Solving the Problems) The television display device of the present invention includes a detection means for detecting the brightness level of a television image, and a detection means for detecting the brightness level of the image according to the brightness level detected by the detection means. and means for changing the brightness level of a constant brightness area (gray area).

(Function) In the present invention, the higher the brightness level of the displayed television image, the higher the brightness of the constant brightness area.
In addition, when the brightness level of the display image is low, the brightness of the constant brightness area is also controlled to be low, so the difference in brightness between the display image and the constant brightness area is always reduced, making the screen easier to see, and the two areas The phenomenon of burn-in on the CRT at the boundary can be prevented.

(Example) The present invention will be described below based on the example shown in the drawings.

FIG. 1 is a block diagram showing a television display device according to an embodiment of the present invention. The embodiment shown in this figure is based on the current method (
For example, a case will be described in which a television signal of the NTSC system with an aspect ratio of 4:3 is displayed on a display device with an aspect ratio of 16:9, for example.

In this figure, the input terminal 10 is connected to the current method (for example, 4
A television signal transmitted using the NTSC system with an aspect ratio of :3 is input and supplied to the NTSC decoder 11 . The NTSCF coder 11 demodulates a television signal transmitted using the current system into a luminance signal (hereinafter referred to as a Y signal) and two types of color signals (hereinafter referred to as a C signal). The demodulated Y signal and C signal are outputted to a non-interlace conversion circuit 12, and the output signal and timing signal are outputted to a timing generation circuit 13.

The timing generation circuit 13 generates a timing signal that controls the memory of the time axis compression circuit 14 and a timing signal that controls the selectors 17 and 18.

The non-interlace conversion circuit 12 converts the interlaced Y signal and C signal having 525 scanning lines into 525 scanning lines.
Convert to non-interlaced Y and C signals.

The converted Y signal and C signal are supplied to a time axis compression circuit 14 that performs time axis compression, and the Y signal is supplied to a luminance level detection circuit 15.

The time axis compression circuit 14 inputs the non-interlaced Y signal and C signal, and performs time axis compression using the timing signal from the timing generation circuit 13. The time axis compressed Y signal is sent to selector 17, and the two types of C signals are sent to selector 1.
8. The Y signal input and Y signal nozzle j of the time axis compression circuit 14 are as shown in FIGS. 2(a) and 2(b).

The brightness level detection circuit 15 integrates the input Y signal over a period of, for example, one frame, and detects the average brightness level. This detected average luminance level is supplied to the margin level generation circuit 16.

The margin level generation circuit 16 further leak-integrates the average luminance level of one frame period and generates a time constant.
A margin level is generated by the ROM and output to the selector 17. Note that the terminal 50 connected to the margin level generation circuit 16 is an input terminal for a switching signal for switching the time constant;
The terminal 60 is a terminal for supplying a reset signal when switching channels or turning on the power, and the terminal 70 is an input terminal for a switching signal for switching the characteristics of the margin level to be output (characteristics of the ROM).

The selector 17 switches between the margin level from the margin level generation circuit 16 and the Y signal output from the time axis compression circuit 14 in response to the timing signal 31 (see FIG. 2(C)) from the timing generation circuit 13. Then, the selector 17 is switched to the margin level side during the period when the timing signal S1 is at the low level (L).

As a result, a margin level is added to the output of the time axis compression circuit 14 shown in FIG. 2(b), and the output is output from the selector 17 as shown in FIG. 2(d). The Y signal to which the margin level has been added is then supplied to the matrix circuit 19.

On the other hand, the two types of time-axis compressed C signals are (・CI,
C2) is supplied to the selector 18. Selector 18
is used to switch between these C signals and a fixed midpoint level, and the lower level (L
') is switched to the midpoint level side. As a result, the selector 18 outputs the C signal to which the fixed value is added, and supplies it to the matrix circuit 19.

The matrix circuit 19 generates R (red), G (green), and B (do 1) primary color signals from the Y signal and two types of C signals. These R, G, B signals are output from output terminal 20.30.4.
0 to the tricycle cathode of a CRT (not shown).

According to the device configured as described above, an interlaced television signal transmitted in the NTSC system can be converted into an NTSC system.
After demodulating in the C decoder 11 to obtain a Y signal and two types of C signals, the non-interlace conversion circuit 12 converts them into non-interlace signals, and further converts the Y signal and C signal converted into non-interlace into a time axis compression circuit. After compressing the time axis with step 14, selector 17.
A margin level and a midpoint level are added to the signal portion corresponding to the diagonally shaded portion (margin portion). Moreover, the added margin level corresponds to the luminance signal level.

FIG. 3 shows a circuit diagram of the luminance level detection circuit 15 and margin level generation circuit 16.

In FIG. 3, the Y signal output from the non-interlaced conversion circuit 12 is input to an integrator 151, and the pixels of one frame are cumulatively tightened (integrated). This integrated value is latched by the latch circuit 152 every frame. By latching each frame in this manner, the average IEIIJ level for one frame period can be determined. This average luminance level for one frame period is output to the margin generation circuit 16.

The margin level generation circuit 16 uses a subtracter 161 degree coefficient α.
Multiplier 162. The leak integration circuit includes an accumulator 163 and a ROM (read-only memory) 164.

The leak integration circuit described above performs a smoothing operation in the time axis direction, and a switching signal for switching the time constant α is inputted to the multiplier 162 from the terminal 50. Further, a reset signal generated at the time of channel switching or power-on is inputted to the accumulator 163 from the terminal 60, and the accumulator 163 is set to an initial value. The integral value of the above leakage integration circuit is ROM1
64, and based on the input value, the ROM 164 generates a margin level of "black IT, 11 gray" - "'white" as shown in FIG.
A switching signal for switching the characteristics of the ROM 164 is also input from the terminal 70, and this switching signal changes the change characteristics (i.e., the margin level characteristics) of the ROM output with respect to the ROM input, as shown in, for example, ■, ■, and ■ in Fig. 4. Switch. The margin level determined in this way is output to the selector 17. Note that the ROM 164 may be configured with other logic circuits.

The operations of the integrator 151 and latch circuit 152 described above are as follows.
Although it has been described that the average brightness level of one frame is determined, the average brightness level of one frame or more or less (multiple lines) may be determined. Furthermore, rather than the pixels of the entire screen, roughly thinned out pixels may be integrated, or 11. of FIG. 7(a). An integrated value obtained by selectively selecting pixels near the boundary shown in L2 may also be used. In particular, when using the integral of pixels near the boundary, CRT
This is more effective for the purpose of preventing burn-in.

In addition, in the embodiment shown in FIG. 1, the brightness at the margin level is changed according to the brightness of the screen, and the hue at the margin level is set to a fixed value. However, the hue at the margin level is also changed. may be configured.

FIG. 5 shows another embodiment of the present invention, in which the hue at the margin level is also changed. The difference from the configuration in FIG. 1 is that the non-interlaced conversion circuit 12
A C level detection circuit 21 and a 02 level detection circuit 23 are provided to detect the levels of two C signals (CI, C2) outputted from the circuit, and each detection level of CI and C2 is further supplied to the margin level generation circuits 22 and 24. 1, and these margin levels are supplied to one input end of the selector 18 instead of the midpoint level in FIG. The other configurations are the same as in FIG. 1. With this configuration, the hue of the margin level can also be changed according to the color signal level.

FIG. 6 does not show another embodiment of the present invention,
The margin level created based on brightness level detection is
This configuration is such that it is added to R, G, and B signals. The difference from the configuration in FIG. 1 is that after the Y signal and C signal (CI, C2) compressed in the time axis by the time axis compression circuit 14 are supplied to the matrix circuit 19 to obtain the R, G, and B signals,
R, G,
The difference is that the margin level from the margin level generation circuit 16 is added to each signal of B. The other configurations are the same as in FIG. 1. Even with this configuration, it goes without saying that the brightness of the margin can be changed depending on the brightness of the screen.

In the above embodiment, a case is explained in which a television signal with an aspect ratio of 4:3 is received on a monitor with an aspect ratio of 16:9 (the case shown in FIG. 2(a)). As shown in FIG. 2(b), it is also possible to apply the present invention to the case where a television signal with an aspect ratio of 16:9 (or 5:3) is displayed on a monitor with an aspect ratio of 4:3.

[Effects of the Invention] As described above, according to the present invention, when displaying television signals with different aspect ratios, li! The difference in brightness between the i-image area and the margin area can be reduced, the image can always be easily viewed, and moreover, burn-in on the CRT on the boundary line can be prevented.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing a preview display device according to an embodiment of the present invention, Figure 2 is a signal waveform diagram of each part of the circuit in Figure 1, and Figure 3 is the brightness level detection circuit and margin level in Figure 1. A circuit diagram showing an example of a generation circuit; FIG. 4 is an explanatory diagram explaining input/output characteristics of a ROM used in the circuit of FIG. 3;
FIG. 5 is a block diagram showing another embodiment of the present invention, FIG. 6 is a block diagram showing another embodiment of the present invention, and FIG. 7 is a block diagram showing another embodiment of the present invention. FIG. 3 is an explanatory diagram illustrating a state in which each image is displayed on a monitor screen having an aspect ratio. 11...NTSC decoder, 12...Interremus conversion circuit, 13...timing generation circuit, 14...time axis compression circuit, 15...luminance level detection circuit, 6...margin level generation Circuit, 17°8... Selector, 19... Matrix circuit. Figure 2

Claims (3)

[Claims] (1) In a television display device that simultaneously displays a television image and a constant brightness area with no image on the screen, a detection means for detecting the brightness level of the television image, and a brightness level detected by the detection means are provided. A television display device comprising means for changing the brightness level of the constant brightness area accordingly. (2) The detection means comprises means for cumulatively adding (integrating) sample values of pixels over N frames (N is a positive integer), and means for holding the integrated output. Item 1. The television display device according to item 1. (3) The detection means is characterized by comprising means for cumulatively adding (integrating) sample values of pixels near the boundary between the television image and the constant brightness area, and means for holding the integrated output. The television display device according to claim 1.