JPS6238088A - Television receiver - Google Patents

Abstract

PURPOSE:To match the white balance with all gradations, and for example, since the saturation of the blue fluorescent body is faster than others, to prevent the phenomenon that the color comes to be yellow due to the white peak by changing the broken line characteristic of a gamma correcting circuit inserted into the video signal system in accordance with the level of the pulse signal for adjusting the luminance. CONSTITUTION:At present, when the level of the pulse signal for adjusting the luminance supplied from an input terminal 4 is large, namely, the time when the luminance of the picture displayed at the cathode ray tube is dark is thought. A sampling signal supplied to a timing signal input terminal 31 is supplied to an FET 44, and thereby, the pulse signal for adjusting the luminance included in the output from a buffer circuit 41 is extracted, supplied to the base of a transistor 51 through a voltage follower 46, the transistor 51 is turned on, and the broken line characteristic of the gamma correcting circuit, for example, is bent as shown by an actual line (a) in the figure. The inclination of the broken line characteristic is determined by the dividing ratio of a resistor 42 and a variable resistor 54.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a television receiver suitable for use, for example, in a color video projector.

[Summary of the invention]

This invention adjusts brightness by using a reference pulse inserted into a predetermined portion of a video signal, and changes the polygonal line characteristics of a gamma correction circuit inserted into a video signal system according to the level of this reference pulse. By doing this, the white balance is matched at all gradations.

[Conventional technology]

Conventionally, various circuits have been proposed for adjusting contrast and brightness in television receivers, but the present applicant proposed in Japanese Patent Application No. 59-128114 that the contrast and brightness can be adjusted independently. We proposed a circuit that does this. Figure 4 is an example.

That is, in FIG. 4, (1) indicates a video signal input terminal, which supplies the video signal supplied to the video signal input terminal (fl) to the mixer (2), and also serves as a pulse signal input terminal for contrast adjustment. The contrast adjustment pulse signal supplied to the input terminal (3) and the brightness adjustment pulse signal supplied to the brightness adjustment pulse signal input terminal (4) are respectively supplied to the mixer (2), and a predetermined portion of the video signal, for example horizontal The contrast adjustment pulse signal and the brightness 1B adjustment pulse signal are mixed during the blanking period, and this mixed signal is supplied to the gain control amplifier (5), and its output is sent to the cathode ray tube ( 7) is supplied to the cathode.

In this case, the output of the gain control amplifier (5) is supplied to the sample and hold circuit (8), and this sample and hold circuit (
8) is sampled and held using a sampling signal with the same timing as the pulse signal supplied to the contrast adjustment pulse output input terminal (3) from the timing signal input terminal (9), and this sampled and held potential is applied to the comparator. The reference value supplied to one input terminal of the comparator (10) and the reference signal input terminal (11) is supplied to the comparator (1
0), and this comparison output controls the gain of the gain control amplifier (5) to adjust the contrast of the image displayed on the cathode ray tube (7) by δ)! It's like being adjusted.

Also, the magnitude of the beam current can be detected by the video amplifier (6), and this detection signal is sent to the sample and hold circuit (
12) and is supplied to this sample hold circuit (12) from the timing signal input terminal (13), which is sampled at the same timing as the pulse signal supplied to the luminance gate adjustment pulse signal input terminal (4). The reference value which is supplied to the sample and hold element as well as the reference signal input terminal (15) is supplied to the other terminal of the comparator (14), and this comparison output is used to control the cathode ray tube. (7) Control the beam current,
The brightness of the image displayed on the cathode ray tube (7)! It's like being infiltrated.

However, with only the configurations (1) to (15),
When the contrast is adjusted by the gain control amplifier (5), the magnitude of the brightness adjustment pulse signal in the output signal naturally changes, so the brightness also changes, so it is necessary to adjust the brightness again after adjusting the contrast. This required complicated operations.

Therefore, the present applicant solved this inconvenience by providing a circuit for obtaining the necessary contrast adjustment pulse signal and brightness adjustment pulse signal before the input terminals (31, (41). In other words, in FIG. ) indicates a contrast compression signal generation circuit, and a gate circuit (
22) and a gate signal at a predetermined timing within the horizontal blanking period of the video signal from the timing signal input terminal (9) is supplied to the gate signal input terminal of this gate circuit (22). A signal of a predetermined level from the contrast tlIil adjustment signal generation circuit (21) is gated, and a predetermined level of contrast is applied to the output side of this gate circuit (22), that is, the contrast adjustment pulse output input terminal (3) of the mixer (2). m layering pulse signals are obtained.

Further, a signal of a predetermined level from the brightness adjustment signal generation circuit (23) is supplied to the multiplier (24), and the contrast 11i1
The multiplication signal is multiplied by a signal of a predetermined level from the adjustment signal generation circuit (21), and this multiplied signal is supplied to the gate circuit (25), which is gated with a gate signal of a predetermined timing that does not overlap with the timing signal. ), that is, the brightness adjustment pulse signal input terminal (4) of the mixer (2), the brightness adjustment pulse signal which is this multiplication signal is obtained.

According to such a circuit, a pulse signal for contrast adjustment,
Since the contrast and brightness are adjusted using the brightness tlliI adjustment pulse input pulse signal, which is configured to be a constant multiple of this pulse signal, the brightness is not affected at all even when the contrast is adjusted. can be adjusted independently and with simple operations, so it is suitable for use in high-quality color display devices and the like.

[Problem that the invention seeks to solve]

By the way, if we consider the case where a television receiver is used as, for example, a color video projector, the relationship between the voltage applied between the cathode and the grid of a cathode ray tube and the luminance is nonlinear, and the relationship between the voltage applied between the cathode and the grid of the cathode ray tube and the luminance is nonlinear, and the red, green, and blue phosphors Because of this, there is a problem that the white balance does not match at all gradations. This problem is particularly noticeable in projection type color display devices due to the brightness of the tube surface.For example, the blue phosphor saturates faster than other color phosphors, causing the color to yellow at the white peak. Hail. However, the circuit configuration shown in FIG. 4 cannot deal with this problem.

In view of this, the present invention provides a television receiver that can adjust white balance at all gradations even when used in color video projectors and the like.

[Means for solving problems]

In the television receiver according to the invention, a video signal in which a reference pulse is inserted at a predetermined portion is inputted to one of the cathode and the grid of a cathode ray tube (7), the level of the reference pulse is detected, and the video signal is inserted between the cathode and the grid. In addition to controlling the potential of the other side of the grid to adjust the brightness, a gamma correction circuit (30) is inserted into the video signal system, and each gamma correction circuit (30) is inserted into the video signal system.
0) is configured to change the polygonal line characteristic according to the level of the reference pulse.

[Effect]

A video signal with a reference pulse in a predetermined portion is input to one of the cathode and grid of the cathode ray tube (7), and the level of the reference pulse is detected and the potential of the other of the cathode and grid is controlled to adjust the brightness. Make adjustments.

In addition, a gamma correction circuit (30
) is changed according to the level of the reference pulse. This allows you to adjust the timing of each color's light emission and match the white balance for all gradations.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail based on FIGS. 1 to 3.

FIG. 1 shows the overall configuration of this embodiment in a neo-style manner. In the same figure, parts corresponding to those in FIG. 4 are designated by the same reference numerals, and detailed explanation thereof will be omitted.

In Figure 1, (iR), (IG) and (IB
) are input terminals to which red, green, and blue primary color signals are supplied, respectively, and the red, green, and blue primary color signals from these input terminals (IR), (IG), and (1B) are mixed, respectively. (2R), (2G) and (2B) as well as the contrast m phasing pulse signal supplied to the contrast adjustment pulse signal input terminal (3) and the brightness adjustment pulse signal input terminal 4). The pulse signal for brightness adjustment is sent to the mixer (2R), (211;) and (2
B), and the contrast pulse signal and the luminance 1!il adjustment pulse signal are mixed in a predetermined portion of each of the red, green, and blue primary color signals, for example, during the horizontal blanking period.

In addition, the mixer (2R) supplies a red signal obtained by mixing the contrast 'eIA adjustment pulse signal and the luminance halftone pulse signal to the gain control amplifier (5R), and the output thereof is sent to the gamma correction circuit (30R) and the video amplifier. (6R) to the cathode of the red cathode ray tube (7R). In this case, the output signal of the gain control amplifier (5R) is supplied to the pulse signal input terminal (3) for contrast 1 from the timing signal input terminal (9R) which is supplied to the sample and hold circuit (8R). The sampling signal is sampled and held at the same timing as , and the sampled and held potential is supplied to one input terminal of the comparator (IOR), and the base 'f-signal input terminal (
The reference signal supplied to the IIR) is adjusted to a predetermined value and supplied to the other input terminal of the comparator (101?), and this comparison output controls the gain of the gain control amplifier (5R). The contrast of the image displayed on the cathode ray tube (7R) is adjusted.

Also, the brightness m from the timing signal input terminal (31R)
A sampling signal with the same timing as the pulse signal supplied to the adjustment pulse signal input terminal (3) is supplied to the gamma correction circuit (30R), and the signal is sent from the gain control amplifier (5R) to the gamma correction circuit (30R). The brightness adjustment pulse signal included in the supplied output is extracted, and the bending point of the gamma correction line of the gamma correction circuit (30R) is changed according to the level of the brightness adjustment pulse signal. For example, when the level of the pulse signal for brightness adjustment is high (when the brightness is dark), the polygonal line characteristic of the gamma correction circuit (30R) is as shown by the solid line a in Figure 3, but the level of the pulse signal for brightness netting is (when the luminance is bright), the curved line characteristics of the gamma correction circuit (30R) are changed as shown by the broken line in FIG. 3, and the point at which the gamma correction curved line bends becomes earlier.

In addition, the magnitude of the beam current can be detected by the video amplifier (6R), and this detection signal is supplied to the sample and hold circuits (1, 2R).
The timing signal input terminal (13R) is supplied to the timing signal input terminal (12R).
) is sampled and held using a sampling signal with the same timing as the pulse signal supplied to the brightness adjustment pulse signal input terminal (4), and this sampled and held potential is supplied to one input terminal of the comparator (14R). The reference value supplied to the reference signal input terminal (15R) is supplied to the other input terminal of the comparator (141?), and this comparison output is supplied to the grid of the red cathode ray tube (7R). ) to control the beam current of the red cathode ray tube (7
R) to adjust the brightness of the image displayed.

In addition, green signal system circuit (32G) and blue signal system circuit (
32B) is configured to have a circuit similar to that of the mixer (2G) and the following red signal system circuit (32R). Additionally, the saturation of the blue phosphor is faster than the saturation of the red and green phosphors, so in order to compensate for this, the gamma correction circuit uses a red signal system circuit (32R) and a green signal line circuit (32R).
G) only, and do not insert it into the blue signal system circuit (32B).

Figure 2 shows an example of a specific circuit configuration of the gamma correction circuit inserted into the red signal system circuit (32R) and the green signal system circuit (32G). The input terminal (40) connected to the video amplifier (Fig. 1) is connected to the output terminal (43) connected to the video amplifier (Fig. ) is connected to one main electrode of a switching element, such as an FBT (44), and this F
The other main electrode of the ET (44) is connected to the non-inverting input terminal of the voltage follower (46) via the resistor (45), and the non-inverting input terminal of the voltage follower (46) is connected to the capacitor (47). It should be grounded through the cable. Also,
Resistor (48) with parallel connection of control electrode of FET (44)
and the timing signal input terminal (31) via the capacitor (49).
As described above, 1) is supplied with a sampling signal having the same timing as the brightness adjustment pulse signal supplied to the brightness adjustment pulse signal input terminal (4) (FIG. 1).

In addition, the inverting input terminal of the voltage follower (46) is interconnected with its own output terminal, and the output terminal is connected to the resistor (5
0) through a switching element such as a transistor (5
1), the base of the transistor (51) is connected to the slider of the variable resistor (53) via the resistor (52), and the other end of the variable resistor (53) is connected to the negative power supply. Terminal-
Vcc, and further connect the collector of the transistor (5) to the negative power supply terminal -Vcc, and connect its emitter to the resistor (42) and output terminal (43) via the J-shaped resistor (54). Connect the points.

Now, if we consider that the level of the luminance halftone pulse signal supplied from the input terminal (4) (Fig. 1) is high, that is, when the luminance of the image displayed on the cathode ray tube is dark, the timing signal input terminal ( 31) is supplied to the FET (44), a brightness adjustment pulse signal included in the output from the buffer circuit (41) is extracted, and the brightness adjustment pulse signal is extracted from the transistor (51) via the voltage follower (46). ), this transistor (51) is turned on, and the curved line characteristic of the gamma correction circuit bends as shown by the solid line a in FIG. 3, for example. In addition, the slope of the polygonal line characteristic is the resistor (42) and the variable resistor (54).
) is determined by the division ratio.

On the other hand, if the level of the brightness adjustment pulse signal supplied from the input terminal (4) (Fig. 1) becomes smaller in this state,
In other words, when the brightness of the image displayed on the cathode ray tube becomes brighter, the level of the brightness adjustment pulse signal extracted by the FET (44) decreases, and the output level of the voltage follower (46) also decreases, so the transistor (5
The base potential of 1) becomes lower, and the transistor (51) turns on earlier than in the previous state, that is, when the level of the brightness adjustment pulse signal is high. As a result, the polygonal characteristic of the gamma correction circuit is shown in Figure 3. The broken line has now become a blur, and the line bends earlier than before. This adjusts the balance of red and green light emission against blue,
The white balance at all tones, especially at the peak and intermediate tones, will match.

〔Effect of the invention〕

As described above, according to the present invention, the polygonal line characteristics of the gamma correction circuit inserted into the video signal system are changed in accordance with the level of the reference pulse, that is, the brightness adjustment pulse signal inserted into a predetermined portion of the video signal. The white balance can be adjusted at all gradations, and for example, the blue phosphor saturates faster than other phosphors, which prevents phenomena such as yellowing of the color at the white peak. Another advantage is that the white balance does not change even if the brightness tonality is adjusted.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing one embodiment of the present invention, Fig. 2 is a circuit block diagram showing an example of the main part of the invention, and Fig. 3 is for explaining the operation of Figs. 1 and 2. FIG. 4 is a configuration diagram showing an example of a conventional example. (IR), (IG) and (IB) are input terminals for red signal, green signal and blue signal respectively, (2R),
(2G) and (2B) are mixers, (4) is a pulse signal input terminal for brightness adjustment, (6R) is a video amplifier, (1
2R) is a sample hold circuit, (14R) is a comparator,
(30R) is a gamma correction circuit, (32R), (3
2G) and (32B) are red signal system, green signal system, and blue signal system circuits, respectively. , 1. Input bt detour line special punch diagram Conventional @ II configuration diagram Fig. 4

Claims (1)

[Claims] A video signal with a reference pulse inserted at a predetermined portion is input to one of the cathode and the grid of the cathode ray tube, the level of the reference pulse is detected, and the potential of the other of the cathode and the grid is controlled to adjust the brightness. A television receiver characterized in that a gamma correction circuit is also inserted into the video signal system, and the polygonal line characteristics of the gamma correction circuit are changed in accordance with the level of the reference pulse.