JPH03223892A - Signal level display circuit - Google Patents

Abstract

PURPOSE:To adjust the level of a signal without using a measuring device by setting an output from a circuit means as a control signal and alternately switching, selecting and outputting respective outputs from 1st and 2nd comparators. CONSTITUTION:An operational amplifier A3 constitutes the 1st comparator which compares the level of a peak detection voltage Vi and a vertical saw tooth voltage Vs and an operational amplifier A4 constitutes the 2nd comparator which compares the level of a reference voltage VR by a constant-voltage source and the vertical saw tooth voltage Vs. The inversion input terminal of an operational amplifier A5 is connected to a ground potential point and a horizontal saw tooth voltage Hs from an input terminal IN3 is conducted to the non- inversion input terminal of the amplifier A5. Therefore, the outputs from the operational amplifiers A3 and A4 obtained by switching and selecting output from switches SW1 and SW2 are synthesized to a signal (d) having one path to be displayed on a picture tube CRT. Thus, the level of the image signal is adjusted with a sense of viewing a level meter displayed on a screen without using the measuring device.

Description

Detailed Description of the Invention [Objective of the Invention] (Industrial Field of Application) The present invention is directed to a monitor receiver that inputs and receives image monitor signals from various information processing devices 1 and communication devices. This invention relates to a signal level display circuit that allows the level to be adjusted without using a measuring device.

(Prior Art) Computer equipment and monitor receivers are generally commercialized as dedicated machines, but there are also universal monitor receivers that are compatible with various types of equipment. Projection-type large-screen receivers are used to select and receive images from a plurality of types in consideration of economic efficiency.

] Since there is no industry standard for the image signals output from computer equipment, the signal level and synchronization frequency vary from company to company and from model to 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 signal level is too low, the screen will be very dark and distracting, and if it is too high, it will be brighter than necessary. The image may 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 monitor receivers that are used for all-purpose purposes rather than dedicated machines, it is necessary to adjust the signal level, for example, by installing a 7 attenuator (attenuator) in the signal input circuit, or by using a variable resistor in the image signal processing circuit. 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 human input signal level is known in advance, in a projection type receiver, the length of the cable varies 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 advanced, and various analog technology devices have been commercialized.For example, when adjusting the input signal level, it is possible to adjust the input signal level from outside the receiver using a combination of electronic attenuators and digital technology. The remote control is also easy to adjust. 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 inside the receiver.

(Problems to be Solved by the Invention) As described above, signal level adjustment in a conventional monitor receiver requires a measuring device, which is troublesome as the user must bring it with him or her.

Also, because of the connection between the BU and BU terminals, the receiver keys and vignettes had to be removed, making it impossible to take advantage of remote control adjustment.

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

Configuration of the Invention] (Means for Solving the Problems) The present invention provides a monitor receiver for displaying image signals on a screen.
A signal level display circuit that displays the level of the input image (3z) using a receiver tube of Iso, which detects the level of the input image signal and outputs a level detection signal. A first circuit that compares the levels of the detection circuit, the saw blade No. 31 with either the horizontal or vertical period, and the level detection signal, and outputs signals with different levels depending on the magnitude relationship between the two sides. The comparator compares the levels of the sawtooth signal and a signal with a quasi-potential level set within the amplitude range of this sawtooth signal, and outputs No. 53 with different levels depending on the magnitude relationship between the two signals. a second comparator for inputting a signal of the other horizontal or vertical period, and a circuit means for generating an output signal exhibiting two levels R within each period; A switch circuit is provided that alternately switches and selects each output from the first and second comparators as a signal and outputs the selected output.

(Function) According to the present invention, the signals of the withstand voltage and the reference potential that depend on the image signal level are, for example, the mud wave voltage of the revision period,
Compare each using a comparator. Since the mud voltage is a signal whose potential changes with the passage of scanning time, the timing at which the level of the comparator output is inverted changes within the vertical deflection period due to changes in the DC voltage depending on the input image signal. Furthermore, the passage of one vertical period is related to the vertical direction of the screen. Therefore, if the two comparator outputs are alternately switched between the first half and the second half of the horizontal scan period and displayed on the screen as an image signal, a histogram-like level
It can be a meter.

(Example) 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 same figure, the level-adjusted image signal S2 is introduced to the input terminal IN, and the vertical period mud wave voltage (hereinafter referred to as vertical part wave voltage V-) is introduced to the input terminal 11j2.
is led to the input terminal IN3, and a horizontally periodic mud wave voltage (
A horizontal sawtooth voltage Hs (hereinafter referred to as a horizontal sawtooth voltage Hs) is derived. These vertical and horizontal sawtooth voltages are down-shaped copper waves in the example. In addition, the vertical harmonic voltage Vs and the horizontal sawtooth voltage Hs are:
It uses the signal voltage obtained from the convergence circuit or deflection circuit.

The high-quality amplifiers A+ and A2 constitute a peak hold circuit. The operational amplifier A1 has a non-inverting input terminal (
The image signal S2 from the input terminal IN is led to the input terminal (+), and a rectifier diode D1 is connected between the output terminal and the inverting input terminal (-)
is connected. The output terminal of the operational amplifier A1 is connected to the inverting input terminal of the operational amplifier A2 via a rectifying 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 inverting input terminal and the output terminal of the operational amplifier A2 are short-circuited, and the inverting input terminal and the inverting input terminal of the operational amplifier A1 are connected through a resistor R1.

The peak detection voltage vL is derived from the output terminal of the operational amplifier A2.

The operational amplifier A3 constitutes a first comparator that compares the levels of the peak detection voltage vL and the vertical harmonic voltage Vs. The J [output of the above-mentioned operational amplifier A2] terminal of the operational amplifier A3 is connected to the inverting input terminal, and the vertical harmonic voltage V from the input terminal IN2 is connected to the inverting input terminal of the operational amplifier A3.
s is being guided. Performance C) Comparison output ■ of amplifier A3 is
It becomes a high level or low level signal.

The operational amplifier A4 constitutes a second comparator that compares the levels of the reference voltage VR from the constant voltage source and the vertical harmonic voltage Vs. A reference voltage VR is applied to the J1 inverting input terminal of the operational amplifier A4, and a vertical harmonic voltage VS is applied to the inverting input terminal J. The comparison output of the amplifier A4 becomes a high level or low level signal. Note that the reference voltage V is set to a level within the amplitude range of the 1000 sawtooth voltage Vs.

A series circuit of switches SW1 and SW2 is connected between the output terminal of operational amplifier A3 and the output terminal of operational amplifier A4. These switches 5WIS~■6! is configured to repeat conduction and non-conduction alternately in the first half and the second half of the horizontal scanning period. That is, the switch S W + is controlled by the comparison output @ from the amplifier A5, and the switch SW2 is controlled by a signal obtained by inverting the output C of the operational amplifier A5 by the inverting circuit G1. The operational amplifier A5 also operates as a comparator and compares the horizontal sawtooth voltage Hs and the ground potential. The operational amplifier A5 has an inverting input terminal connected to a ground potential point, and a horizontal sawtooth voltage Hs from an input terminal 183 is introduced to a non-inverting input terminal.

The outputs of the operational amplifier Δ3 and the operational amplifier A4 obtained by the switching selection outputs of the switches SW+ and SW2 are combined into a signal 0 of one path and displayed on the picture tube CRT.

FIG. 2 shows a configuration in which the above-mentioned No. 3 level display circuit is incorporated into a receiver circuit. In Figure 2, the input terminal IN
(The image signal S1 before level adjustment is guided. The image signal S1 becomes the image signal S2 whose level is adjusted by a level adjuster VA such as an electronic attenuator that can be adjusted by remote control, and the level display having the configuration shown in FIG. The signal from the level display circuit SL is input to the circuit SL.The signal from the level display circuit SL is led to the first input terminal A of the switch SW3, which is controlled to switch between normal use and level adjustment, and the signal from the level adjuster VA. S2 is led to the second input terminal B of switch SW3.Switch S
The switching selection output from W3 is displayed on the picture tube CRT via the image signal processing circuit vP.

In the signal level display circuit having the above configuration, since the reference voltage VR is set within the amplitude range of the vertical harmonic voltage Vs, there is always a period in which the vertical harmonic voltage Vs exceeds the reference voltage VR and a period in which it does not exceed the reference voltage VR. FIG. 3 is a 1J waveform chart showing the relationship between the centroid sawtooth voltage Vs and the reference voltage VR in the embodiment.

In FIG. 3, the voltage TE VR is equal to the center potential of the orthogonal sawtooth voltage Vs. As a result, the period Tf in which the vertical mud wave voltage Vs becomes stronger than the reference voltage Vρ becomes equal to the period T1 in which it becomes smaller. If such a relationship does not exist, a DC bias is added to the vertical mud wave electric rfVs.

If the potential of the reference voltage VR is set as described above, the potential of the peak detection voltage VL, which depends on the level of the image signal S2, matches the reference voltage VR (then, the output ■ of the operational amplifier △3 and the operational amplifier A4 Output 0 matches, switch SW+,
When the output after composition by SW2 is displayed on a receiver CRT, a histogram-like level display can be performed.

FIGS. 4 and 5 are explanatory diagrams for explaining the operation of the above-mentioned embodiment. FIG. 4 (A) shows a time chart when the potential of the signal VL is smaller than VR, and FIG. ) is a screen diagram displayed on the picture tube CRT at that time, and Figure 4 (B
) shows a time chart when the voltage of peak detection voltage ■4 is larger than VR, Figure 5 (B) is a screen diagram at that time, and Figure M4 (C) shows the voltage of peak detection voltage ■ matches VR. A time chart after that is shown, and FIG. 5(C) is a screen diagram at that time.

When VL<VR If the peak detection voltage V= is smaller than the reference voltage VR, it can be considered that VR has fallen below the center potential of Vs in Figure 3, and the output ■ of the operational amplifier Δ3 is vertical. The low level period indicating V t <V s that appears first in the scanning period becomes a longer signal than the high level period indicating V7:>VS. The output O of operational amplifier A is Tf
="N), the signal has the same period of high level and low level. On the other hand, the output O of the operational amplifier A5 is a signal that exhibits a high level in the first half of the horizontal scanning period and a low level in the second half. , switch SW1.S
The signal 0 which is selectively outputted by W2 is the signal 0 produced by the switch SW1 in the first half of the horizontal scanning, and the signal 0 produced by the switch SW2 in the second half. Therefore, V
7. In the case of < VR, the signal (2) exhibits a low level due to the signal ■ during the predetermined period C from the midpoint of the vertical scan, and a high level due to the signal 0 in the second half of the horizontal scan. In the screen diagram of Figure 5, the blank part corresponds to the low level signal (No. 6), and the shaded part corresponds to the high level signal, so the screen in the case of the above signal @ is as shown in Figure 5 (A). Here, the predetermined period Tc is proportional to the level deviated from the peak detection voltage VLhXVR.

In the case of vL-・V body, if V is larger than Vp, the period of VL>Vs is,
Since it is longer than the period of VL<-Vs, the signal
As shown in Figure fB), the signal becomes a good high level period after a short low level period. Therefore, in the first half of the horizontal scan, an image is displayed based on the signal ■ whose high level period is longer than the low level period by a predetermined period Tc from the midpoint of the vertical scan, and from the second half of the horizontal scan, the signal
[Display an image whose J level and high level periods are equal (see Fig. 5B).

In the case of V = = VR In this case, as shown in Figure 4 (C), the signal ■ and 0 match, so as shown in Figure 5 (C), each The periods of high level and low level are equal, and the screen is vertically divided into two, resulting in an image in which a low level signal is displayed in the first half and a high level signal is displayed in the second half.

In this way, in this embodiment, while looking at the screen,
Just adjust the signal level so that According to the above method, unlike the method of reading values using an oscilloscope, a tester, etc., there is no reading error, there is no chance of making an adjustment error, and the adjustment is easy. Further, since the relative comparison is made on the screen regarding the reference signal VR, the accuracy and stability of Vs and Hs will not be a problem as long as the VR is made within the tolerance.

In the case of the configuration shown in Figure 2, the switch SW3 is set to the A side when adjusting the level, and set to the B side during normal image reception.
exchange. In addition, the output signal @ is the image I1F,
If it is not appropriate to input the signal to the J logic circuit vP, level conversion or blanking processing may be performed, for example.

Regarding the peak hold circuit, when detecting the level of an image signal, once the input signal becomes large, the peak detection voltage V remains at its maximum value even if the level is decreased, so a reset circuit is required. However, in reality, the cover of the capacitor C1 is discharged due to the very small leakage current of the capacitor C1 and the very small input current of the amplifier A2, so the repetition period of the input signal is lengthened. However, depending on the capacitance of the capacitor C1, the reset circuit can be omitted in practice.

In another embodiment, a horizontal sawtooth voltage of 1 is applied to the input terminal IN2.
-15, and the vertical wave voltage Vs may be applied to the input terminal IN3. FIGS. 6 and 7 are time charts and screen diagrams in the case of the above embodiment. That is, the sixth
Figure (A) (Figure 7 A) corresponds to Figure 4 (A) (to Figure 5), and Figure 6 (B) (Figure 7 B) corresponds to Figure 4 (B) (Figure 5).
Figure B), Figure 6 (C) (Figure 7 C), Figure 4 (C) (
These correspond to C) in FIG. 5, respectively.

[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 one embodiment of a signal level display circuit according to the present invention, FIG. 2 is a composition diagram when level adjustment is performed by the circuit of the above embodiment, and FIGS. FIGS. 6 and 7 are waveform diagrams, time charts, and screen diagrams for explaining the operation of the embodiment shown in the figure, and FIGS. 6 and 7 are time charts and screen diagrams for explaining other embodiments of the present invention. A1 to A5... operational amplifier, SW+, SW2...
Switch, G5...inversion circuit, CRT...picture tube,
VR...Reference voltage, Vs...Vertical wave voltage, Hs.
...Horizontal sawtooth voltage, Sl, S2... image signal. Figure 3 To Tf --- In the unlikely event (A) V〈 VR (B) VL>V (< (C) VL=VR + Hoshino ia darkness Figure 6 (A) (B) (C) Figure 7

Claims (1)

[Scope of Claims] 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, A signal level detection circuit that detects the level and outputs a level detection signal compares the levels of the sawtooth wave signal with either the horizontal or vertical cycle and the level detection signal, and then levels the signal according to the magnitude relationship between the two signals. a first comparator that outputs different signals; compares the levels of the sawtooth signal and a reference potential signal whose level is set within the amplitude range of the sawtooth signal, and adjusts the level according to the magnitude relationship between the two signals; a second comparator that outputs different signals; a circuit means that receives a signal of the other horizontal or vertical period and generates an output signal that exhibits two different levels within each period; and an output of the circuit means. as a control signal for the first and second
and a switch circuit that alternately switches and selects each output from the comparator and outputs the selected output, and the output signal of the switch circuit is displayed on the picture tube to display the signal level of the image signal. Features a signal level display circuit.