JPH03223891A - Signal level display circuit - Google Patents

Abstract

PURPOSE:To adjust the level of a signal without using a measuring device by executing 1st comparison between a saw tooth signal and a level detection signal and 2nd comparison between the saw tooth signal and a reference voltage, thereby executing the 1st comparison in a 1st signal period and the 2nd comparison in a 2nd signal period. CONSTITUTION:A signal (e) from the connection point of the switches SW1 and SW2 and a vertical saw tooth voltage Vs are respectively conducted to the non-inversion input terminal and the inversion input terminal of an operational amplifier A4, which outputs a signal (d) that changes to a high level and a low level and is obtained by comparing the signal (e) and the voltage Vs and supplies it to a picture tube CRT. Therefore, in the case that the level detection signal Vi is equal to the reference voltage VR by setting the level of the reference voltage VR equal to the central potential of the saw tooth signal, an image which is equally divided up and down on a screen is obtained. When the reference voltage VR and the level detection signal Vi are different, the image which has the different ratio of an upper part to a lower part on the screen is obtained in the first half of a horizontal cycle. Thus, the level of the image signal is adjusted with a sense of viewing a level meter displayed on the screen without using the measuring device.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention provides a monitor receiver that inputs and receives an image monitor signal from various information processing devices 1 and a communication device.
The present invention relates to a signal level display circuit that allows the level of an input image signal to be adjusted while looking at the screen without using a measuring device.

(Prior Art) Computer Ifi2S and monitor receivers are generally commercialized as dedicated machines, but there is also a universal type monitor receiver that is compatible with 8 scale devices. Projection-type large-screen receivers are used to receive images by switching between several types of scoops in consideration of economic efficiency.

Since there is no industry standard for the image signals output from Combi-Two 9 devices, the signal level and synchronization frequency vary depending on each phase and model.

In monitor receivers that can connect multiple types of devices,
The difference in signal level is that the input signal level directly determines the brightness of the screen, so if the input level is low
If the screen is too large, the screen will be too blurry to look at, and if it is too large, it will be too bright or out of focus.

Furthermore, if a signal with a level higher than the dynamic range of the image signal processing circuit is input, the transistor becomes saturated and a normal screen cannot be obtained.

Therefore, in a monitor receiver that is used for all-purpose purposes rather than a dedicated machine, it is necessary to adjust the signal level. The level is adjusted accordingly.

Adjustment can be done on a factory production line if the level of the input signal is known in advance, but in the case of a universal type, it is actually done at the time of installation. Further, even if the input signal level is known in advance, in a projection-type receiver MI, the cables may be of different lengths depending on the distance between the two, and this may have to be done at the time of installation due to the difference in loss.

When making adjustments during installation, the peak value of the signal waveform is measured. Conventionally, measuring instruments such as oscilloscopes and testers were brought to the delivery site and adjustments were made while observing the waveform. In recent years, digital technology has progressed, and various scale devices have been commercialized using analog technology.For example, even when adjusting the level of an input signal, it is possible to adjust the level of an input signal by combining an electronic attenuator and digital technology. It is also easy to adjust from the remote control. However, to use the measuring device, the cabinet of the receiver must be removed in order to connect the probe terminal to the signal input circuit and image signal processing circuit within the receiver.

(Problems to be Solved by the Invention) As described above, signal level adjustment in conventional monitor receivers requires a measuring device, and is troublesome in that it is necessary to carry out errors and errors.

Furthermore, in order to connect the probe terminals, the receiver cabinet had to be removed, making it impossible to take advantage of the benefits of remote control adjustment.

The object of the present invention is to solve the above-mentioned problems and provide a signal level display circuit that allows adjustment using a receiver screen without using a measuring device.

[Structure of the Invention] (Means for Solving the Five Problems) The present invention utilizes a picture tube of a monitor receiver that displays an image signal on a screen to display a signal level that displays the level of the input image signal. a display circuit, which receives a signal level detection means for detecting the level of the inputted image signal and outputting a C level detection signal 5; and a signal of a first period of either vertical or horizontal input; a first means for generating first and second signals of different levels within each period; and a second means for generating a mud wave signal of the other vertical or horizontal period.
a reference voltage source that generates a reference voltage set to a level within the amplitude range of the mud wave signal; a first comparison between the mud wave signal and the level detection signal; and a first comparison between the mud wave signal and the level detection signal. Comparing means for performing a second comparison with a reference voltage, the first comparison being performed during the first signal period, and the second comparison being performed during the second signal period.

(Function) According to the present invention, for example, in a vertical scanning period, a first signal and a second signal having different levels are generated in the first half and the second half of each horizontal scanning period, and based on these signals, the level detecting means generates a first signal and a second signal. The level detection signal and the reference voltage from the reference voltage source are alternately output, and these are compared with the mud wave signal of the vertical period. Display this comparison output on the screen. Therefore, if the level of Motomachi (2) is set equal to the vertical potential of the sawtooth signal and the level detection signal is equal to the reference voltage, an image will be obtained in which the top and bottom of the screen are divided by 1t. However, if the Senhijin signal and the level detection signal are different, the image will have a different ratio of the top and bottom of the screen in the first half of the G,1 horizontal period.

(Examples) Hereinafter, the present invention will be explained in detail with reference to illustrated examples.

FIG. 1 is a block diagram showing an embodiment of a signal level display circuit according to the present invention. In the figure, the level-adjusted image signal S2 is led to the input terminal IN, and the input terminal IN2
A sawtooth voltage with a horizontal period (hereinafter referred to as horizontal sawtooth voltage Hs) is introduced to G, and a sawtooth voltage with a vertical period (hereinafter referred to as vertical section voltage Vs) is introduced to the input terminal IN3. For these horizontal and vertical sawtooth voltages, signal voltages obtained from a convergence circuit or a deflection circuit may be used.

NjR amplifiers A+ and A2 constitute a peak hold circuit. That is, the operational amplifier A1 has an inverting input terminal (
An image signal S2 from the input terminal IN is connected to the input terminal (+), and a rectifier diode D1 is connected between the output terminal and the inverting input terminal (-). The output terminal of the afj8 amplifier A1 is connected to the non-inverting input terminal of the operational amplifier A2 via a rectifier diode D2.

A holding capacitor C1 is connected to the connection point between the diode D2 and the non-inverting input terminal of the operational amplifier A2. The amplifier A2 shown in FIG.
A resistor R1 is connected to the inverting input terminal surface of the resistor R1. In the signal level detection circuit having such a configuration, a peak detection voltage 4 is obtained from the operational amplifier 2.

The output terminal of operational amplifier A2 is switch SW+.

The switches SW+ and SW2 are connected to the output terminal of the reference heavy pressure source VR through a series connection by SW2.As will be described later, the switches SW+ and SW2 are configured to be alternately conductive and non-conductive during the first half and after the horizontal scanning period. be done.

Operational amplifier A3 receives a ground potential signal and a horizontal sawtooth voltage H5.
The level is compared with. The horizontal sawtooth voltage [1·3 from the input terminal IN2 is introduced to the non-inverting input terminal of the operational amplifier Δ3, and the inverting input terminal is connected to the ground point. The output from the operational amplifier A2 is multiplied by the control lI signal and sent to the switch S.
It is applied to W+, and is also inverted by the inverting circuit G1 and applied to the switch SW2. Here, by making the vertical potential of the horizontal sawtooth voltage HS the same as the ground potential, the output of the operational amplifier -3 can be obtained as a binary signal with different levels in the first half and the second half of the horizontal scanning period, respectively. This 'J
If we write J-bow as the control signals of switches SW+ and SW2, then
The switches SW+ and SW2 alternately turn gJ on and off during the first half and the second half of the horizontal scanning period. As a result, a signal ◎ is formed at the connection point between the switches SW+ and SW2, in which the level detection voltage vL appears in the first half of the horizontal scanning period, and the reference voltage VR appears in the second half.

Operational amplifier A4 has the above-mentioned switch SW at its non-inverting input terminal.
The signal @ from the connection point of +, S to ■2 is led, and the vertical wave voltage VS is led to the inverting input terminal.

The σ amplifier 4 outputs a signal 0 which changes to high level and O low level by comparing these signals @ and the signal Vs, and supplies it to the picture tube CRT.

Figure 2 shows the configuration when the above signal level display circuit is incorporated into a picture tube circuit.
An image signal S1 before level adjustment is introduced. The image signal 81 is level-adjusted by a level adjuster VA comprised of an electronic attenuator that can be adjusted by remote control, and its output S2 is input to the level display circuit SL having the configuration shown in FIG. The signal from the level display circuit SL is guided to the first input terminal A of the switch SW3, which is operated to switch between normal use and level adjustment, and the direct image signal S2 from the level adjuster VA is guided to the first input terminal A of the switch SW3, which is operated to switch between normal use and level adjustment. 2 is led to input terminal B. The switching selection output of the switch SW3 is displayed on the picture tube CRT via the image signal processing circuit vP.

In the signal level display circuit configured as above, the signal applied to the input terminal IN3, in this case the vertical wave voltage Vs, is as follows:
It is necessary to set the voltage so that there is a period in which the voltage exceeds the reference voltage Vp and a period in which it does not exceed the reference voltage Vp.

FIG. 3 is a waveform diagram showing the relationship between the vertical harmonic voltage Vs and the reference voltage VR in the embodiment. In FIG. 3, the reference voltage VR
is approximately equal to the vertical potential of the vertical harmonic voltage Vs. As a result, the period Tf during which the vertical harmonic voltage vs exceeds the reference tI' voltage VR and the period T during which the vertical harmonic voltage vs does not exceed the reference tI' voltage VR become equal. Reference voltage V
If R and the vertical harmonic voltage Vs cannot be set in the above relationship, a necessary bias is added to the vertical harmonic voltage Vs r3.

Furthermore, if the vertical potential of the horizontal sawtooth voltage Hs is made equal to the ground potential, the output signal of the amplifier A3 will be at different levels in the first half and the second half of the horizontal scanning period, and in this case, the horizontal sawtooth voltage Since the voltage is of the down type, it quickly reaches a high level in the first half of the horizontal scanning period and exhibits a low level in the second half. As a result, the switch SW1 becomes conductive during the first half of the horizontal scanning period, and becomes conductive during the second half. Further, the switch SW2 is non-conductive during the first half of the horizontal scanning period and becomes conductive during the second half.

When the potential of the reference voltage VR and the level of the horizontal sawtooth voltage H5 are set as described above, the image shown in FIG. Histogram-like level display becomes possible.

That is, the operational amplifier A4 adjusts the magnitude of the vertical harmonic voltage Vs to the pixel detection voltage VL in the first half of the horizontal scanning period and at the border, respectively.
Alternatively, comparisons may be made alternately using reference voltages. The peak detection voltage VL, which does not indicate the level of the input image signal, is VL<v
In the case of R, the output of the operational amplifier A2 is at a constant level, so in the first half of the horizontal scanning period, the heavy sawtooth voltage Vs of the operational amplifier A2 is compared with the low level output Vz. At this time, the operational amplifier Δ4 outputs a comparison output @ such that the low level period is long and the high level period is short in one vertical scanning period.

On the other hand, in the latter half of the horizontal scanning period, the vertical harmonic voltage Vs and the reference voltage VR are compared, but since the reference voltage VR is made to match the vertical potential of the vertical harmonic voltage Vs, the operational amplifier The output of A4 becomes a low level in the first half of one vertical scanning period and a high level in the second half, and outputs a comparison output ■ in which the low level period and the high level period coincide. Therefore, for an image with a comparison output of 0, as shown in FIG. 4(A), if the blank part is a low level signal and the shaded part is a high level signal, then in the first half of the horizontal scanning period, the area of the blank part is is larger than the area of the shaded area, and in the second half of the horizontal scanning period, the area of the blank area is equal to the area of the shaded area. Yuri, j! to this video! ! It can be seen that the level of the i-image signal is lower than the reference voltage VR.

Moreover, when the peak detection voltage VL is V=>VR, the output of the operational amplifier A2 becomes high level, contrary to the above, and in the first half of the horizontal scanning period, the low level bright period of the operational amplifier A4tJ is short and the high level period is long. In the second half of the horizontal scanning period, a comparison output ■ in which the high level period and the low level period coincide is output. In this case, the comparison output @ is as shown in Fig. 4 (8) k, in the first half of the horizontal scanning period, the area of the blank portion is smaller than the area of the shaded portion, and in the second half of the horizontal scanning period, the area of the blank portion is smaller than the area of the blank portion. The resulting image has the same area as the shaded area.

Furthermore, in the case of vL-vR, calculation! ! ! The output of the width transducer A2 becomes equal to VR, and even in the first half of the horizontal scanning period, it is compared with the direct current that matches the vertical potential of the vertical harmonic voltage Vs, so as shown in FIG. 4(C), In both the first half and the second half of the horizontal scanning period, an image is displayed in which the area of the blank portion and the area of the diagonal line are equal.

According to the above, in order to adjust the level of the image signal, it is sufficient to adjust the level as shown in FIG. 4(C) while looking at the screen. With this method, unlike the method of reading values with an oscilloscope, etc., there is no reading error, so there is no possibility of making adjustments. As for the adjustment accuracy, as long as the M quasi-voltage VR is accurate, the accuracy and stability of the sawtooth voltage do not matter.

In the embodiment, the switches SW1. Signal to control SW2◎
is formed based on a horizontal sawtooth voltage, but a rectangular wave voltage obtained by, for example, a horizontal deflection circuit may also be used directly.

Further, the signal ◎ can be achieved even if it is not a rectangular wave whose level is inverted vertically in the horizontal scanning period, and the level may be inverted many times within the horizontal scanning period.

Furthermore, the input terminals for the horizontal sawtooth voltage and the vertical harmonic voltage may be exchanged.

Furthermore, in the peak detection circuit, if the input signal becomes too large, the peak detection voltage VL will remain at its maximum value even if the level is decreased after the input signal, so a reset circuit must be provided. Since the charge in capacitor C1 is discharged by the extremely small leakage current of capacitor C1 and the small input current of differential amplification 2; Therefore, in practice, the reset circuit can be omitted.

[Effects of the Invention] As described above, according to the present invention, it is possible to adjust the level of an image signal without using a measuring device, just by looking at a level meter displayed on a screen.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an embodiment of the signal level display circuit according to the present invention, Fig. 2 is a configuration diagram when level adjustment is performed by the circuit of the above embodiment, and Fig. 3 shows reference potential and vertical harmonics. FIG. 4 is a waveform diagram showing an example of the voltage level relationship, and FIG. 4 is a screen diagram showing an example of the level adjustment screen according to the present invention. Δ1 to A2... operational amplifier, SW 1. SW
2...Switch, G1...Inverting circuit, CRT...
Picture tube, VR...Reference voltage, VS...Vertical harmonic voltage, Hs...Horizontal sawtooth voltage, Sl, -82... Image signal.

Claims (2)

[Claims] (1) A signal level display circuit that displays the level of the input image signal using a picture tube of a monitor receiver that displays the image signal on the screen, and detects the level of the input image signal. signal level detection means for outputting a level detection signal; and a signal level detection means for receiving a first period signal of either vertical or horizontal direction and generating first and second signals of different levels within each period. a second means for generating a sawtooth signal of the other vertical or horizontal period; a reference voltage source for generating a reference voltage set to a level within the amplitude range of the sawtooth signal; Means for performing a first comparison between the sawtooth signal and the level detection signal and a second comparison between the sawtooth signal and the reference voltage, the first comparison being performed during the first signal period. ,
Comparing means for performing a second comparison is provided in the second signal period, and the signal level of the image signal is displayed by displaying the output signal of the level comparison circuit on the picture tube. signal level display circuit. (2) The comparison means is connected in series between the output terminal of the signal level detection means and the reference voltage source, and the comparison means is connected in series between the output terminal of the signal level detection means and the reference voltage source.
first and second switch circuits whose on/off states are respectively controlled by a signal and a second signal; a signal appearing at a connection point of the first and second switch circuits; and the second means. 2. The signal level display circuit according to claim 1, further comprising a comparator for comparing the level of the sawtooth wave signal from the signal level display circuit.