JP3189319B2 - High brightness adjustment device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-brightness adjusting device suitable for use in a display color television receiver or the like for displaying an image brighter than a standard state.

[0002]

2. Description of the Related Art Various structures have been proposed as a conventional brightness adjusting device for a color television receiver. FIG. 6 shows a general structure of a color television receiver using such a brightness adjusting device. It is shown.

In FIG. 6, an RF signal received by an antenna 1 is converted into an intermediate frequency signal by a tuner 2 and then detected by a video detection circuit 3 into a composite video signal.
Supplied to The switching circuit 4 switches between the external video signal supplied to the external video signal terminal T ₁ and the detection signal of the composite video received from the antenna 1.

The video signal selected by the switching circuit 4 is supplied to a luminance signal / chroma signal separation circuit 5 and separated into a luminance signal (hereinafter referred to as Y signal) and a chroma signal (hereinafter referred to as C signal).

[0005] The Y signal is adjusted for sharpness (SHP) through an image quality adjustment circuit 6 and supplied to a matrix circuit 8. On the other hand, the C / C separated by the Y / C signal separation circuit 5
The signal is supplied to the chroma decoder 7 and the color signal (CO
L) and the hue signal (HUE) are adjusted, and the C signal is converted into RY and BY color difference signals. The color difference signals RY and BY are supplied to the matrix circuit 8. The matrix circuit 8 supplied with the Y signal and the color difference signals RY and BY converts the Y signal and the RY and BY signals into three primary color signals of R (red), G (green) and B (blue). Convert.

Next, in the video processing circuit, a contrast adjustment for adjusting the magnitude of the video signal to adjust the degree of lightness and darkness of the color image, and an adjustment circuit for interlockingly adjusting the color density at the same ratio as the contrast. The CRT 13 is driven via, for example, a PNP transistor 12 of a video drive amplifier circuit 11 via a picture adjustment circuit 9 (hereinafter referred to as a picture adjustment circuit) and a brightness adjustment circuit 10.

The picture adjustment circuit 9 and the brightness adjustment circuit 10 have an average value ABL (average automatic brightness limiting circuit) 15 for preventing the beam current of the CRT from becoming excessive.
And a peak level limiting circuit 14.

The peak level limiting circuit 14 converts the R, G, and B currents flowing through the cathode of the CRT 13 into the resistance value R of the resistor 16 based on the beam current I _K flowing through the resistor 16 connected to the collector of the PNP transistor 12. The picture adjustment voltage PIC · V supplied to the picture adjustment circuit 9 when the value of the product I _K · R with the current exceeds a fixed reference potential V ₀ of the differential amplifier 18 for comparison is reduced to reduce the picture level. It is made to apply a limiter.

Further, the average value ABL is a high pressure blow of CRT13.
Beam current ΔI detected from the _KIn the integration circuit 17
Integrates and outputs the output of the integrating circuit 17 to a differential amplifier for comparison.
19 and 20 and these differential amplifiers 19 and 20
Reference level flows to the R, G, B cathodes of CRT13.
I, the averaged beam current_KThis criterion is based on
When the value is exceeded, the picture adjustment voltage PICV
By narrowing the inest adjustment voltage BRT · V
Limits the increase in system current.

[0010]

As described in the above-mentioned conventional configuration, in order to make the screen of the CRT 13 bright, a CR is required.
An operation is performed to raise the peak luminance by increasing the drive level (picture level) of T13 or increase the intermediate luminance by increasing the level of the average value ABL.

When the peak luminance is increased by the above picture adjustment, the deterioration of the spot characteristics at the peak is conspicuous, and as a countermeasure against this, the peak beam limiting circuit 1 as shown in FIG.
When 4 is added, there is a problem that the picture level is suppressed, the peak luminance cannot be increased to a predetermined luminance or more, and high luminance adjustment cannot be performed.

Further, when an attempt is made to obtain a high-luminance screen by the average value ABL level, the beam current ΔI _K is permanently increased, and the life of the CRT 13 is significantly shortened. In particular, the reference level of the average value ABL is a value derived from the life of the CRT 13 and is set at the maximum value. Therefore, there is a problem that this reference voltage cannot be increased, and high brightness cannot be achieved. there were.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. It is an object of the present invention to minimize the deterioration of peak spot characteristics, increase the brightness of an image, and increase the beam current ΔI _K. It is an object of the present invention to provide a high-brightness adjusting device capable of increasing the intermediate brightness without increasing the brightness.

[0014]

As shown in FIG. 1, a high-brightness adjusting apparatus according to the present invention is provided with an adjusting means 9 for adjusting the contrast and color density of a video signal to a video processing circuit. And a correction means 24 for correcting linearity. The limiter reference level of the peak beam limiting means 14 of the adjusting means 9 for adjusting the contrast and the color density is switched by interlocking with the linearity correcting means 24. The brightness is adjusted.

[0015]

In the high-brightness adjusting apparatus of the present invention, the linearity correction circuit is controlled in conjunction with the on / off operation of the high-brightness (high-brightness) switching means so as to increase the limiter level of the CRT drive signal. As a result, a device that can perform high-brightness adjustment can be obtained.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the high brightness adjusting device of the present invention will be described below in detail with reference to FIGS. In FIG. 1, portions corresponding to those in FIG. 6 of the conventional example are denoted by the same reference numerals, and redundant description will be omitted.

In FIG. 1, reference numerals 1 to 8 have the same configuration as in FIG. 6. In this example, the R, G, and B primary color signals output from the matrix circuit 8 are supplied to a linearity correction circuit 24, After the correction is performed, the image data is supplied to the picture adjustment circuit 9 and the brightness adjustment circuit 10. The linearity correction circuit 24 may be interposed between the picture adjustment circuit 9 and the brightness adjustment device 10.

The configuration of reference numerals 11 to 20 other than the reference numeral 14 shown in FIG. 1 is also the same as that of FIG. 6, and the reference voltage terminal of the differential amplifier 18 constituting the peak beam limiting circuit 14 is a reference voltage switching switch. is connected to the 21 sections a, one fixed contact b of the switch 18 described above is connected to a voltage source 22 of the reference potential V ₀ as in the conventional described above, one is grounded in the voltage source 22. The fixed contact c is connected to a voltage source 23 having a reference potential V1, and _one of the voltage sources 23 is grounded.

The linearity correction circuit 24 has an input terminal T ₂
And the contact piece a switches to the fixed contact c when the high brightness is turned on so that the switches on the reference voltage sources 22 and 23 of the peak beam limiting circuit 14 are switched. The reference potential V ₁ of the reference voltage source 23 is
2 is selected to be larger than the reference potential V _{0 such} as V ₁ > V ₀ .

A description will be given of the linearity correction circuit 24 having the above configuration. Figure 2 is the curve 25 and 26 from electrostatic theory shows the characteristics of the luminance level L (proportional to the anode current I _K) with respect to the driving voltage V _E of the CRT13 is represented by the number 1.

[0021]

(Equation 1)

Accordingly, it is understood that when the peak value is considered to be fixed, the lower the gamma value γ, the higher the luminance L in the intermediate portion.

Therefore, when the correction is to be performed at a stage preceding the driving circuit of the CRT 13, the correction as shown by the curve 28 in FIG. 3 is necessary. That is, in FIG. 3, when the horizontal axis x indicates an input and the vertical axis y indicates an output, a circuit having a configuration as shown in FIG. 4 is used as a linearity correction circuit for obtaining input / output characteristics as shown by a curve 28. obtain.

FIG. 4 shows the principle configuration of the linearity correction circuit. T ₃ and T ₄ are input / output terminals, and the input signal x shown in FIG. ₃ is supplied to the input terminal T ₃ . The input signal x is supplied to the subtraction circuit 32 in addition to the addition circuit 30 and the multiplication circuit 31. Now, assuming that the input signal x is 0 ≦ x ≦ 1, X ₂ is formed in the multiplication circuit 31 and the input terminal T
₃ outputs x ² obtained by the multiplying circuit 31 from the supplied input signal x by subtracting the x-x ² is supplied to the amplifier 33.

The amplifier 33 controls the γ correction amount. Kx (1-x) is output from the output of the amplifier 33 and supplied to the addition circuit 30. In the adder circuit 30, x supplied to the input terminal T ₃ and the output kx of the amplifier 33 are output.
(1-x) in the are added the output terminal T ₄ y = x + kx
(1-x) is output.

An embodiment of another specific configuration of the above-described principle circuit will be described with reference to FIG. In FIG. 5 the resistor R ₁ and the amplifier 3
The series circuit of the series connection point of the 3 diode CD resistor R ₂ and the end voltage source 34 which is grounded is connected, the input terminal T
₃ the output signal y of the input signal x to the output terminal T ₄ is output to. The circuit of the diode CD including the voltage source 34 is set to the black level + α−V _BE so that α determines the displacement point. According to this circuit configuration, the characteristic curve 35 is formed by a broken line substantially similar to the curve 28 shown in FIG. 3, and the linearity of the intermediate luminance can be corrected with a simple configuration.

In the above-described embodiment, the case where the switching means of the high brightness circuit is manually switched to operate in conjunction with the linearity correction circuit has been described, but an ABC circuit (automatic brightness control circuit) for detecting the intensity of external light is described. The on / off of the high-brightness circuit may be automatically switched or varied using the above-mentioned method.

Further, the on / off switching or variation of the high brightness circuit is performed according to the input mode, and the adjustment means for other modes, for example, hue, color, brightness, etc., and the linearity correction circuit are linked. You may.

According to the present invention, by increasing the limiter level of the peak beam limiting circuit and simultaneously correcting the γ value of the drive signal for driving the CRT and lowering the linearity to a predetermined value, the peak luminance and the intermediate luminance Can be raised together, and an effective high-brightness adjusting device can be obtained which is effective for high-brightness adjustment of a color television receiver for display or placed in a place with bright external light.

[0030]

According to the high brightness adjusting device of the present invention, it is possible to increase the brightness of an image while minimizing the deterioration of the peak spot characteristic, and to increase the intermediate brightness without increasing the beam current. Can be

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a color television receiver using a high-brightness adjusting device of the present invention.

FIG. 2 is a diagram illustrating a luminance used for describing a high luminance adjusting device according to the present invention.
It is a drive voltage characteristic diagram.

FIG. 3 is an input / output characteristic diagram for describing a high-brightness adjusting apparatus according to the present invention.

FIG. 4 is a principle diagram of a linearity correction circuit used in the high-brightness adjusting apparatus of the present invention.

FIG. 5 is a circuit diagram of a linearity correction circuit used in the high-brightness adjusting apparatus of the present invention.

FIG. 6 is a configuration diagram of a color television receiver using a conventional luminance adjustment device.

[Explanation of symbols]

 Reference Signs List 9 picture adjustment circuit 10 brightness adjustment circuit 11 drive amplifier 12 PNP transistor 14 peak beam limiting circuit 22, 23 voltage source 24 linearity correction circuit

Continuation of the front page (56) References JP-A-2-114771 (JP, A) JP-A-60-97786 (JP, A) JP-A-3-106269 (JP, A) Jpn. , U) (58) Fields surveyed (Int. Cl. ⁷ , DB name) H04N 5/235-5/243 H04N 5/20-5/202 H04N 5/57-5/59

Claims (1)

(57) [Claims] 1. An image processing circuit comprising: adjusting means for adjusting the contrast and color density of an image signal; and linearity correcting means for correcting linearity, and adjusting the contrast and color density. A high-brightness adjusting apparatus characterized in that high-brightness adjustment is performed by switching a limiter reference level of a peak beam limiting means in conjunction with the linearity correcting means.