JPS60150385A - Signal processing device of television receiver - Google Patents

Abstract

PURPOSE:To obtain gradation with a suitable display in response to a level of a video signal by combining a video detection circuit, a level detecting circuit, a gain control circuit, a clamp circuit and an A/D converting circuit. CONSTITUTION:An output of the video detection circuit 1 is inputted to the gain control circuit 6 and the level detection circuit 7, which detects the head value of the video signal in one field and inputs a control signal in response to the value to the gain control circuit 6. The gain control circuit 6 compresses or expands the video signal by using the control signal inputted from the level detection circuit 7 so as to process the video signal as a suitable signal for the A/D conversion in one field. When the peak value of the input signal level is smaller than 100%, for example, the input/output characteristic of the gain control circuit 6 is set as shown in Fig. (a) and when the peak of the input signal level is close to 100%, the input/output characteristic of the gain control circuit 6 is set as shown in Fig. (b), and when the peak is an intermediate value as above, the input/output characteristic of the gain control circuit 6 is set to the linear (1:1) input/output characteristic.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a signal used in a stereoscopic television receiver, particularly in a device that converts a television signal from analog to digital and drives a display element with the digital signal. It relates to a processing device.

Conventional Structures and Their Problems In recent years, in order to make television receivers smaller and lighter, there has been an active movement to construct television receivers using flat displays instead of cathode ray tubes.

For example, liquid crystals, light emitting diodes, plasma displays, fluorescent display tubes, etc. are used as flat displays. Most of these flat displays use digital television signals to drive display elements, but when displaying gray scales using digital signals,
As the number of gradations increases, display quality improves, but on the other hand, the scale of the nine circuits tends to become larger and more complex. For example, when considering the case where a television m image is displayed using a simple matrix panel of liquid crystal, a pulse width modulation method is often used to control the time width of the voltage applied to the liquid crystal according to a signal. In this case, line memories for the number of gray scales below Pinot are required, and as the number of gray scale bits increases, the number of line memories also increases.

Therefore, increasing the number of gradations also increases the circuit size and complexity.

A conventional example will be described below with reference to the drawings. FIG. 1 is a block diagram showing the main parts of a conventional television receiver.

In Fig. 1, 1 is a video detection circuit, 2 is a clamp circuit, and 3 is an analog-digital (hereinafter abbreviated as AD).
4 is a conversion circuit, 4 is a drive circuit, and 5 is a display element.

In the video detection circuit 1, a video signal of a television signal is obtained by detection. The video signal is clamped by a clamp circuit 2, and the DC component is reproduced. After that, the video signal is converted from an analog value to a digital value by the AD conversion circuit 3.
The voltage is input to the drive circuit 4, and the drive circuit 4 generates a voltage for driving the display element 5.

As shown in the conventional example of FIG. 1, when a television signal is digitized and displayed, the display gradation is determined by the number of bits in the AD conversion circuit-3.

However, in order to display a high-quality image with many gradations, it is necessary to increase the number of bits in the AD conversion circuit 3. In the case of LCDs, this leads to an increase in line memory.

The circuit becomes large-scale and complicated, resulting in high costs and the television receiver itself also becomes large. Even if the drive circuit were to be integrated into an IC, the addition of two circuits would increase the chip size and the number of pins, and the problem of high cost would still be the same.

Purpose of the Invention The present invention provides signal processing that eliminates the above-mentioned drawbacks and makes it possible to configure a television receiver that is easy to view because the 9 gradations are used rationally and without waste without increasing the scale of the 9 circuits. The purpose is to provide a device.

Structure of the Invention A signal processing device for a television receiver according to the present invention includes a video detection circuit, a level detection circuit that detects an output level of the video detection circuit, and an input terminal to which the output of the video detection circuit is applied, and a control device. a gain control circuit to which the output of the level detection circuit is applied to a terminal; a clamp circuit that clamps the output signal of the gain control circuit; and an analog-to-digital conversion circuit that converts the output analog signal of the clamp circuit into a digital signal. Accordingly, it is possible to construct an easy-to-view television receiver in which one gradation is used rationally and without waste without increasing the circuit scale.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 2 is a schematic diagram of main parts showing an embodiment of the present invention. In FIG. 2, 1 to 3 are the same as those in FIG. 1, 6 is a gain control circuit, and 7 is a level detection circuit. The output of the video detection circuit 1 is input to a gain control circuit 6 and a level detection circuit 7, and the level detection circuit 7 detects the leading value of the video signal within one field and performs gain control on a control signal according to that value. Input to circuit 6. Gain control circuit 6
Then, the video signal is compressed or expanded according to the control signal input from the level detection circuit 7, and the video signal is processed to be optimal for AD conversion within one field.

Next, the characteristics of the gain control circuit 6 will be described in more detail.

As mentioned above, the characteristics of the gain control circuit 6 are to compress or expand the video signal within one field to a level corresponding to the leading value, and to use the commonly used AGC (automatic gain control). It is different from a circuit. That is, in a general AGC circuit, a constant output is obtained depending on the level of the input signal.

Although the amplification factor of a linear amplifier is changed, the gain control circuit 6 used in the present invention does not need to perform linear amplification, and the output of the AD conversion circuit 3 is adjusted so that it is optimal for displaying gradations. Compress or expand video signals. In other words, the gain control circuit 6 is a circuit that processes signals non-linearly.

Advantages I) An example of the input/output characteristics of the control circuit 6 is shown in FIG. In the example of FIG. 3, 7 has a polygonal line characteristic. By doing this, for example, if the characteristics shown in FIG. 3(a) are provided, a signal with a low level will have a fine gradation, and a signal with a high level will have a coarse gradation.

Generally, when a television image is displayed, the peak value of the signal level of a normal image is almost never 100%, and the highest level is often between 50% and 7%. Therefore, when receiving a normal image, by setting the input/output characteristics of the gain control circuit 6 as shown in FIG. 3(a), it is possible to increase the number of gradations for a low signal level. Easy-to-read display is possible even with a small number of gradations.

If you use the characteristics as shown in Figure 3cb), the gradation will be rough, and the gradation will be A11ll for a signal with a high level. As a visual characteristic, the higher the IZ degree, the better the resolution (
Gamma temporal) property 1. Therefore, if the output signal level has a proportional relationship with the brightness of the display element, the third
Figure (1)) can be approximated to the input/output characteristic (・1 visual characteristic. In this case, 100!n level-
If there is a signal at 1t, it is possible to perform an f-operation.

Using the above characteristics,9 For example, when the peak value of the input (ij level is smaller than 100+H,(,), υC(size,
The input/output characteristics of the gain control circuit 60 are set as shown in FIG. 3(a), and when the peak of the input signal level is close to 100%, the input/output characteristics of the gain control circuit 6! 1. Set the v characteristics as shown in Figure 3 0))7. In each case (rl:, profit?!)
1till IM1 circuit 6 input/output (one to one
It is possible to set the linear input/output '1, r-characteristic.

For example, when the input signal level is 75% or less, Figure 3 (a)
When the characteristic is 95% or more, the characteristic shown in Fig. 3(b) is 75
~95': When 4 (ri can be set to millinear characteristics.

If this is set to 1:, when the input signal level is small, V
CId: A large number of gradations can be applied to low-level signal parts, and the same effect as increasing the number of gradations is obtained by increasing the number of gradations by 1.
11 hours. If the input signal level is large,
Since gradation can be displayed in accordance with human visual characteristics, an easy-to-read display can be obtained.

In Figure 3, a two-stage polygonal line characteristic is shown as an example, but it is not limited to a two-stage polygonal line characteristic, but a three-stage polygonal line characteristic.

The input/output characteristics of the gain control circuit 6 can be set as a four-stage polygonal characteristic, a square characteristic, a logarithmic/exponential characteristic, or the like.

Effects of the InventionAs is clear from the above explanation, the present invention skillfully combines a video detection circuit, a level detection circuit, a gain control circuit, a clamp circuit, and an AD conversion circuit to generate a signal that responds to the level of a video signal. The effect of obtaining the optimum display gradation can be obtained.

If the structure is configured to have a level detection circuit that detects the peak value within one field, the optimum display gradation can be obtained according to the level of the video signal using the highest brightness level of one side as a reference. You can get the effect that you can.

Furthermore, the input/output characteristics of the gain control circuit are nonlinear.
: In the case of this configuration, an effect that an easy-to-read display can be obtained even with a small number of gradations can be obtained.

Although the above description has been made for a black and white television receiver (1'4), it is needless to say that the same effect can be obtained for a color television receiver (quadrant).

[Brief explanation of drawings]

Figure 1 shows the main parts of the conventional example. Figure 2 (Pronk diagram of an embodiment of the water spouting invention), Figure 3 r1. An example of the input/output! IM' characteristics of the gain control circuit used in the present invention. 6: Characteristic diagram shown. 1---Video detection circuit, 2--Clamp circuit, 3-
...AD conversion circuit, 6-...Gain side-11 circuit, 7-
・Level detection circuit.

Claims (3)

[Claims] (1) A video detection circuit, a level detection circuit that detects the output level of the video detection circuit, an input terminal of which is given the output of the video detection circuit, and a control terminal of which is given the output of the level detection circuit. A television receiver comprising a gain control circuit, a clamp circuit that clamps an output signal of the gain control circuit, and an analog-to-digital conversion circuit that converts an output analog signal of the clamp circuit into a digital signal. The signal processing device of the machine. (2) The level detection circuit is configured to detect a peak value within one field;
A signal processing device for a television receiver according to claim (1). (3) The signal processing device for a television receiver as set forth in claim (1), wherein the gain ξI control side 1 circuit has non-linear input/output characteristics.