JPH10271412A - Video signal processing device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a video signal processing device for displaying a video on a CRT, with high chromaticity stability regardless of the input scanning frequency.
The purpose is to realize a high-fidelity image. In an image signal processing device for detecting a beam current of a reference signal superimposed on an input image signal and performing automatic cutoff adjustment, an fv conversion unit (5) for generating a voltage according to an input scanning frequency; By providing the clamp unit 6 that clamps the detected beam current of the reference signal to the output from the fv conversion unit, the detected beam current is clamped at a potential corresponding to the input scanning frequency. A constant beam current can be detected regardless of the input scanning frequency, and the cutoff level is constant regardless of the input scanning frequency, chromaticity is stabilized, and a highly stable and high-fidelity image can be realized. it can.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal processing for displaying a video on a CRT, and provides a video signal processing apparatus capable of realizing a highly stable and high-fidelity image regardless of an input scanning frequency. With the goal.

[0002]

2. Description of the Related Art A conventional video signal processing apparatus is disclosed in Japanese Patent Application Laid-Open Publication No. HEI 9-163702 as a method for performing stable and high-precision image adjustment by detecting each reference signal superimposed in a blanking period of a video signal and performing feedback control. Japanese Patent Application Laid-Open No. Sho 61-6985 has proposed an image adjusting apparatus.

FIG. 10 shows a block diagram of a conventional video display device. 10, 202 is a mixer, 205 is a gain adjustment circuit, 206 and 212 are sample and hold circuits,
208 and 214 are comparators, and 210 is a video output amplifier.

Next, the operation will be described. Input terminal 20
The video signals from 1, 3, and 4, the contrast adjustment pulse, and the luminance adjustment pulse are supplied to the mixer 202, and various pulses are mixed during the retrace period of the video signal. Mixer 2
02 from the gain control circuit 205.
Then, a contrast adjustment pulse is detected by a contrast feedback control loop constituted by the sample hold circuit 206 and the comparator 208 to perform gain adjustment. Gain adjustment circuit 2
05 from the video output amplifier 21
The video output signal is supplied to the cathode electrode and is amplified to a level at which the cathode ray tube 211 can be driven. Video output amplifier 210 and sample hold circuit 2
In the luminance feedback control loop composed of the comparator 12 and the comparator 214, the cut-off adjustment is performed by controlling the DC potential of the grid electrode of the cathode ray tube so that the beam current of the luminance adjustment pulse is always constant by detecting the beam current. Will be

As described above, by performing feedback control so that the voltage values of the contrast and brightness adjustment pulses are always fixed to the reference voltage, stable contrast and automatic cutoff control can be performed, and stable control can be performed. An image display device can be realized.

[0006]

However, in the above-described configuration, the stray capacitance of the cathode electrode and the other electrode of the CRT and the stray capacitance of the cathode current detection circuit and the printed circuit board on which the circuit is mounted exist. For,
The cathode current is detected by the cathode current detection circuit with a certain time constant. On the other hand, when displaying an image corresponding to a computer signal, since the input scanning frequency is various, the beam current of the reference signal detected by the input scanning frequency is different due to the influence of the time constant. That is, there is a problem that the cutoff level differs depending on the input scanning frequency, and the chromaticity is shifted.

Therefore, in a conventional video signal processing apparatus, stabilization of chromaticity independent of an input scanning frequency has been required.

[0008]

In order to solve this problem, a video signal processing apparatus according to the present invention detects a beam current of a reference signal superimposed on an input video signal and performs automatic cutoff adjustment. In the apparatus, fv conversion means for generating a voltage corresponding to the input scanning frequency, and clamping means for clamping a beam current of the detected reference signal to an output from the fv conversion means are provided. It is what it was.

According to the present invention, it is possible to provide a video signal processing apparatus capable of stabilizing chromaticity with a constant cutoff level regardless of an input scanning frequency and realizing a highly stable and high-fidelity image.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a video signal processing apparatus for detecting a beam current of a reference signal superimposed on an input video signal and performing automatic cutoff adjustment to generate a voltage corresponding to an input scanning frequency. -V conversion means, and a clamp means for clamping the detected beam current of the reference signal to an output from the fv conversion means. Is characterized in that the vertical retrace period of the beam current of the detected reference signal is feedback-clamped to a predetermined potential, and in the above invention, the period of the reference signal is an integer of the input horizontal scanning frequency. The beam current of the reference signal detected differently according to the input scanning frequency is clamped to a potential corresponding to the input scanning frequency. By doing so, it is possible to detect a constant beam current regardless of the input scanning frequency, the cutoff level is constant regardless of the input scanning frequency, the chromaticity is stabilized, and a highly stable and high-fidelity image is obtained. It has the effect of realizing.

According to the present invention, in a video signal processing apparatus for performing automatic cutoff adjustment by detecting a beam current of a reference signal superimposed on an input video signal, the detected beam current of the reference signal is set outside the period of the reference signal. Is characterized by comprising switching means for switching to a certain reference voltage, and differentiating means for differentiating a signal from the switching means, and in the above invention, the period of the reference signal is the input horizontal scanning frequency. Characterized in that it is an integral multiple of
The beam current of the reference signal, which is detected differently depending on the input scanning frequency due to the integration effect of the stray capacitance, is switched to a predetermined potential outside the reference signal period and differentiated, so that a constant beam current is obtained regardless of the input scanning frequency. This makes it possible to perform detection, stabilize the chromaticity at a constant cutoff level regardless of the input scanning frequency, and have the effect of realizing a highly stable and high-fidelity image.

According to the present invention, there is provided a video signal processing apparatus for performing automatic cutoff adjustment by detecting a beam current of a reference signal superimposed on an input video signal, wherein the fv conversion means generates a voltage corresponding to the input scanning frequency. And a calculation unit for calculating a voltage from the fv converter and a comparison reference voltage for performing auto cut-off adjustment. The period is characterized by being an integral multiple of the input horizontal scanning frequency, and the comparison reference potential is calculated as a potential corresponding to the input scanning frequency, and the voltage and the reference detected differently according to the input scanning frequency are calculated. By comparing with the beam current of the signal and adjusting the cutoff, the same effect as detecting a constant beam current regardless of the input scanning frequency is obtained,
The cutoff level is constant irrespective of the input scanning frequency, the chromaticity is stabilized, and an operation of realizing a highly stable and high-fidelity image is provided.

An embodiment of the present invention will be described below with reference to FIGS. (Embodiment 1) FIG. 1 shows a configuration of a video signal processing apparatus according to an embodiment of the present invention.

In FIG. 1, a is an input terminal to which a video signal is supplied, b is an input terminal to which a synchronizing signal is input, and 1 is a reference signal for detecting a cathode current during a vertical blanking period from the synchronizing signal. This is a reference signal generator for generating the Ik signal. Reference numeral 2 denotes a superimposing unit that superimposes the Ik signal on the video signal, and includes, for example, an analog switch. Reference numeral 3 denotes an amplification unit that amplifies the video signal to an amplitude sufficient to drive the cathode electrode of the CRT and applies the video signal to the cathode electrode, and includes, for example, a cascode amplifier circuit. Reference numeral 4 denotes a cathode current detector that detects the beam current of the Ik signal and converts the beam current into a voltage.
Reference numeral 5 denotes an fv converter that generates a voltage directly proportional to the input horizontal frequency based on a signal synchronized with the input horizontal frequency from the reference signal generator 1. Reference numeral 6 denotes a clamp unit that clamps the potential of the beam current converted into the voltage in the cathode current detection unit during a predetermined period in the deflection system vertical retrace period to the potential from the fv conversion unit 5. Reference numeral 7 denotes a comparison unit that samples and holds the beam current clamped at a predetermined potential from the clamp unit 6 for a predetermined period, compares the sampled and held voltage with a reference voltage, and controls a cutoff control unit. Here, the cutoff adjusting unit is for controlling the potential of the first grid (G1) of the CRT, for example, to perform automatic cutoff adjustment.

The operation of the video signal processing apparatus of the first embodiment configured as described above will be described below with reference to the operation waveform diagrams of FIGS. FIG. 3A shows a video signal supplied to the input terminal a, and FIG. 3Bv shows a vertical synchronization signal synchronized with the deflection supplied to the input terminal b.
(Bh1) indicates a horizontal synchronization signal synchronized with the deflection.

First, the reference signal generator 1 creates an Ik signal shown in FIG. 3 (ik) whose pulse width is an integral multiple of the input horizontal frequency (here, tripled as an example). The Ik signal is generated within the signal vertical retrace period shown in FIG.
The reference signal is generated in a period other than the deflection system vertical blanking period in FIG. The reason is that the cathode current detector 4
This is for detecting a very small beam current with high accuracy when the beam current is detected by the method. In the reference signal generator 1, i
In order to sample and hold the voltage during the horizontal scanning period of the k signal (here, for example, the last horizontal scanning period of the ik signal), a sampling pulse shown in FIG. 3 (sp) is created. Here, when the input horizontal frequency is
(Bh1), the ik signal of FIG.
Assuming that the input horizontal frequency is (bh2) for the sampling pulse of (sp1), the ik signal of FIG.
FIG. 3 (sp. 2) is generated.

In the reference signal generator 1, the clamp 6
In order to clamp the voltage of the signal from the cathode current detector 4 during the vertical flyback period of the deflection system, the clamp pulse shown in FIG. 3 (clp.p) is generated. Next, the reference signal generator 1
Is superimposed on the video signal by the superimposing unit 2.
The video signal on which the Ik signal is superimposed by the superimposing unit 2
, And is supplied to the cathode current detector 4.
The video signal supplied to the cathode current detector 4 is a CRT
And the cathode current detector 4 detects the beam current of the Ik signal, and converts the detected beam current into a voltage. Incidentally, the detected beam current has a certain time constant due to the presence of the stray capacitance of the cathode electrode and the other electrode of the CRT and the stray capacitance of the cathode current detector 4 and the printed circuit board on which the cathode current detector 4 is mounted. , The signal becomes approximately proportionally larger as the period of the ik signal becomes longer, that is, becomes larger in inverse proportion as the input frequency decreases.
Therefore, different input scanning frequencies (bh1) and (bh2)
Is converted as (Vik1) and (Vik2) in FIG. Next, FIG. 4C, which is a signal from the cathode current detection unit 4, is clamped by the clamp unit 6 at a potential proportional to the input frequency to obtain the signal of FIG. FIG. 4 showing a signal clamped by the clamp unit
In FIG. 4D, the voltage during the pulse period is sampled and held by the comparison unit 7 according to FIG. 4 (sp), and is compared with the reference potential. Here, since the beam current detected by the clamp unit 6 is clamped at a potential proportional to the input horizontal frequency, the voltage to be sampled and held is constant regardless of the input scanning frequency. The cutoff adjusting unit performs an automatic cutoff adjustment under the control of the comparing unit 7 so that the sampled and held potential is constant, that is, the beam current of the reference signal is constant. Here, since the sampled and held voltage is constant irrespective of the input scanning frequency, the measurement error of the beam current due to different input scanning frequencies is canceled.

Next, the clamp unit 6 and the comparison unit 7 will be described in detail with reference to a specific example shown in FIG. The video signal applied to the base of the transistor 11 is applied from the emitter to the cathode electrode of the CRT. At the same time, the transistor 11 is turned on, and the cathode current becomes equal to the resistance Ri.
Flow into k. Here, the voltage across the resistor Rik is as shown in FIG. 2C according to the input scanning frequency. Resistance R
ik, the current-to-voltage converted beam current is stored in buffer 1
1 and the impedance of the clamp capacitor C
clp. The charged beam current is supplied to the charging capacitor Cs1 via the resistor Rs1 for a predetermined period in the deflection system vertical retrace period by the FET 14 which is turned on at the timing of the clamp pulse of FIG. Is sampled and held. Capacitor C
The voltage sampled and held at s1 is calculated by the comparator 15 as f
The voltage is compared with the voltage from the −v converter 5. The comparator 15
A voltage is applied to the resistor Rclp so that the sampled and held voltage and the voltage proportional to the input horizontal frequency from the fv converter 5 become equal. Therefore, the potential of d is f−v
It is feedback clamped to the potential Vclp from the converter 5. That is, as shown in FIG. 4D, DC reproduction is performed to Vclp according to the input scanning frequency. Next, the beam current clamped to the voltage Vclp of the fv converter 5 is shown in FIG.
The FET 16 which is turned on at the timing of the sampling pulse (sp) samples and holds the charge capacitor Cs2 via the resistor Rs2 for a predetermined period of the ik signal.

Here, since the potential is clamped at a potential proportional to the input scanning frequency, FIG.
p. ) Are at the same potential and the capacitor Cs
The voltage sampled and held at 2 is constant regardless of the input scanning frequency. The voltage sampled and held by the capacitor Cs2 is compared with the reference voltage Vref by the comparator 17. The comparator 17 controls the cutoff adjusting unit so that the voltage sampled and held by the capacitor Cs2 becomes equal to the reference potential Vref, and the control causes the beam current of the ik signal to be constant. The cutoff is adjusted.

As described above, by clamping the detected beam current at a potential corresponding to the input scanning frequency, a constant beam current can be detected regardless of the input scanning frequency. However, the cutoff level is constant, the chromaticity is stabilized, and a highly stable and high-fidelity image can be realized.

The video signal processing apparatus according to the present invention has a CR
The present invention can be applied not only to a system using only T but also to an optical writing type liquid crystal light valve system using a CRT as an image writing light emitting device for optical writing.

(Embodiment 2) FIG. 5 shows a configuration of a video signal processing apparatus according to an embodiment of the present invention.

In FIG. 4, components denoted by the same reference numerals as those in the first embodiment have the same configuration as that described in the first embodiment, and a description thereof will be omitted. Hereinafter, the difference from the first embodiment will be described. Reference numeral 21 denotes an i of a signal converted into a voltage from the cathode current detection unit 4 in FIG.
A switching unit that switches the outside of the period of the k signal to a predetermined reference potential. Reference numeral 22 denotes a differentiating unit that differentiates the signal from the switching unit 21.

The operation of the switching section 21 and the differentiating section 22 of the video signal processing apparatus according to the second embodiment having the above-described configuration will be described with reference to FIG. Here, the components having the same numbers as those in the first embodiment perform the same operations as those described in the first embodiment, and the description thereof will be omitted.

The beam current detected by the cathode current detector 4 in FIG. 4C is switched by the switching unit 21 to a predetermined reference potential other than the period of the ik signal. The signal from the switching unit 21 is differentiated by the differentiating unit 22. Here, the input signal is DC-reproduced according to the duty ratio or APL of the input signal by the action of differentiation. By the way, in the cathode current detector 4, in addition to the beam current of the ik signal,
During the period of the video signal, the beam current flowing into the cathode electrode due to the video signal is simultaneously detected. Therefore, if the signal from the cathode current detector 4 is directly differentiated, the duty ratio of the beam current of the ik signal will not be reflected in the DC reproduction due to the influence of the beam current of the video signal. However, since the switching unit 21 has switched to the predetermined reference voltage outside the period of the ik signal, when the signal from the switching unit 21 is differentiated, it is inversely proportional to the pulse width of the ik signal as shown in FIG. DC regeneration is performed. Therefore, the voltage sampled and held by the comparator 7 is constant regardless of the input scanning frequency. Hereinafter, the operation of the automatic cutoff adjustment is the same as the description of the first embodiment.

Next, the switching unit 21 and the differentiating unit 22 will be described in detail with reference to a specific example shown in FIG. The video signal applied to the base of the transistor 11 is applied from the emitter to the cathode electrode of the CRT. At the same time, the transistor 11 is turned on, and the cathode current becomes equal to the resistance Ri.
Flow into k. Here, the transistor 13 which is turned on by a signal obtained by inverting the ik signal is turned on during a period other than the ik signal period, and the cathode current flows to the ground, thereby setting the potential at both ends of Rik to 0 V. Therefore, the potential at both ends of Rik is ik
The potential according to the beam current is 0 V during the signal period, except for the ik signal period. The potential generated in Rik is applied to the differential capacitor Cd and the differential resistor Rd. here,
It is appropriate that Cd and Rd are about 1000 p and about 1 MΩ, respectively.

The signal differentiated by the capacitor Cd and the resistor Rd is applied to the signal i according to the input scanning frequency as shown in FIG.
DC reproduction is performed in inverse proportion to the pulse width of the k signal, that is, DC reproduction is performed to a potential proportional to the input scanning frequency.
4D is transmitted through the buffer 32 to the FET 16.
Is applied to Therefore, as described in the first embodiment, automatic cutoff adjustment can be performed regardless of the input scanning frequency.

Thus, the detected beam current ik
By replacing the signal period with a predetermined reference potential and differentiating, a constant beam current can be detected regardless of the input scanning frequency, and the cutoff level is constant regardless of the input scanning frequency and the chromaticity is stabilized. It is possible to realize a highly stable and high-fidelity image.

The video signal processing apparatus according to the present invention has a CR
The present invention can be applied not only to a system using only T but also to an optical writing type liquid crystal light valve system using a CRT as an image writing light emitting device for optical writing.

(Embodiment 3) FIG. 7 shows a configuration of a video signal processing apparatus according to an embodiment of the present invention.

In FIG. 7, components denoted by the same reference numerals as those in the first embodiment have the same configuration as that described in the first embodiment, and a description thereof will be omitted. Hereinafter, the difference from the first embodiment will be described. Reference numeral 41 denotes an arithmetic unit for multiplying a signal from the fv converter by a comparison reference potential for performing automatic cutoff adjustment, and generates a voltage proportional to the input scanning frequency.

The operation of the operation unit 41 and the comparison unit 7 of the video signal processing device according to the third embodiment configured as described above will be described with reference to FIG. Here, the components having the same numbers as those in the first embodiment perform the same operations as those described in the first embodiment, and the description thereof will be omitted.

FIG. 9C shows the beam current detected by the cathode current detector 4. The comparator 7 samples and holds the sampling pulse of FIG. 9 (sp) for a predetermined period. ). Further, the comparator 7 compares the voltage with the voltage proportional to the input frequency from the calculator 41 and adjusts the cutoff so that the sampled and held voltage, that is, the beam current of the ik signal becomes constant. Here, as described in the first embodiment, the comparison unit 7
Is approximately proportional to the input scanning frequency, but the proportional coefficient and the arithmetic unit 41
Since the proportionality coefficient of the potential proportional to the input scanning frequency output from is adjusted to match, the beam current detected differently according to the input scanning frequency is similarly compared with a different reference potential.

Therefore, there is the same effect as detecting a constant beam current irrespective of the input scanning frequency and adjusting the cutoff so that the beam current becomes constant.

Next, a detailed description of the operation unit 41 and the comparison unit 7 will be described using a specific example shown in FIG. The video signal applied to the base of the transistor 11 is applied from the emitter to the cathode electrode of the CRT. At the same time, the transistor 11 is turned on, and the cathode current becomes equal to the resistance Rik.
Flow into Here, the voltage across the resistor Rik is as shown in FIG. 9C according to the input scanning frequency. Resistance Ri
k, the current-voltage converted beam current is shown in FIG.
p. F) which is turned on at the timing of the sampling pulse
By the ET16, the resistance Rs2 is set for a predetermined period of the ik signal.
Is sampled and held by the charging capacitor Cs2 via The voltage sampled and held by the capacitor Cs2 becomes the voltage shown in FIG. 9E according to the input scanning frequency.
On the other hand, the voltage proportional to the input scanning frequency output from the fv conversion unit 5 is multiplied by the reference potential Vref, and the calculation unit 41 generates the voltage shown in FIG. 9F proportional to the input scanning frequency. The voltage sampled and held by the capacitor Cs2 is compared by the comparator 17 with the voltage from the calculation unit 41.

Therefore, as described in the first embodiment,
Automatic cutoff adjustment can be performed regardless of the input scanning frequency.

As described above, the comparison reference potential is calculated with a potential corresponding to the input scanning frequency, the voltage is compared with the beam current of the reference signal detected differently depending on the input scanning frequency, and the cutoff is adjusted. As a result, the same effect as detecting a constant beam current irrespective of the input scanning frequency is obtained, the chromaticity is stabilized at a constant cutoff level regardless of the input scanning frequency, and high stability and high fidelity are achieved. Images can be realized.

The video signal processing apparatus according to the present invention has a CR
The present invention can be applied not only to a system using only T but also to an optical writing type liquid crystal light valve system using a CRT as an image writing light emitting device for optical writing.

[0039]

As described above, according to the present invention, it is possible to detect a constant beam current regardless of the input scanning frequency by clamping the detected beam current at a potential corresponding to the input scanning frequency. , Chromaticity stabilization is achieved with a constant cutoff level regardless of the input scanning frequency,
A remarkable effect that a high-fidelity image can be realized is obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a video signal processing device according to an embodiment of the present invention;

FIG. 2 is a configuration diagram for describing the embodiment in detail;

FIG. 3 is an operation waveform diagram for explaining the operation of the embodiment.

FIG. 4 is an operation waveform diagram for explaining the operation of the embodiment.

FIG. 5 is a configuration diagram of a video signal processing device according to an embodiment of the present invention;

FIG. 6 is a configuration diagram for explaining the embodiment in detail;

FIG. 7 is a configuration diagram of a video signal processing device according to an embodiment of the present invention;

FIG. 8 is a configuration diagram for explaining the embodiment in detail;

FIG. 9 is an operation waveform diagram for explaining the operation of the embodiment.

FIG. 10 is a configuration diagram of a conventional video signal processing device.

[Explanation of symbols]

 5 fv conversion section 6 clamp section 21 switching section 22 differentiating section 41 arithmetic section

Claims (7)

[Claims] 1. An image signal processing apparatus for detecting a beam current of a reference signal superimposed on an input image signal and performing automatic cutoff adjustment, wherein fv conversion means for generating a voltage corresponding to an input scanning frequency; An image signal processing apparatus, comprising: a clamp unit for clamping a beam current of a detected reference signal to an output from the fv conversion unit. 2. The video signal processing apparatus according to claim 1, wherein the clamping means feedback-clamps the vertical retrace period of the beam current of the detected reference signal to a predetermined potential. 3. The video signal processing device according to claim 1, wherein the period of the reference signal is an integral multiple of the input horizontal scanning frequency. 4. In a video signal processing device for detecting a beam current of a reference signal superimposed on an input video signal and performing automatic cutoff adjustment, the detected beam current of the reference signal is outside the period of the reference signal. A video signal processing apparatus comprising: switching means for switching to a constant reference voltage; and differentiation means for differentiating a signal from the switching means. 5. The video signal processing apparatus according to claim 4, wherein the period of the reference signal is an integral multiple of the input horizontal scanning frequency. 6. An image signal processing device for detecting a beam current of a reference signal superimposed on an input image signal and performing automatic cutoff adjustment, wherein fv conversion means for generating a voltage corresponding to an input scanning frequency; A video signal processing apparatus comprising: a calculation unit that calculates a voltage from the fv converter and a comparison reference voltage for performing auto cutoff adjustment. 7. The video signal processing device according to claim 6, wherein the period of the reference signal is an integral multiple of the input horizontal scanning frequency.