JPH03223889A - Signal level display circuit - Google Patents

Abstract

PURPOSE:To know and adjust the level of an inputted image signal without using a measuring device by comparing the image signal with a 1st reference voltage, controlling it based on the output of a comparator, and alternately switching and selecting the image signal and a 2nd reference voltage from a voltage source. CONSTITUTION:As to the screen of an output signal (d) by the switching operation of switches SW1 and SW2, the display area of the image signal becomes darker than the display area of the reference voltage VR when the level of the image signal S2 is lower than the reference voltage VR. On the contrary, when the level of the image signal S2 is higher than the reference voltage VR, the display area of the image signal becomes brighter than the display area of the reference voltage VR. When the image signal S2 is equal to the reference voltage VR, the brightness of the display area of the image signal coincides with that of the reference voltage VR. The level of the inputted image signal is adjusted so that a character can not be discriminated while viewing the screen. Thus, the level of the inputted image signal is adjusted by the use of a video displayed on the screen without using the measuring device.

Description

[Detailed Description of the Invention] [LI aspect of the invention] (Industrial Application Field) This invention provides a monitor receiver that inputs and receives image monitor signals from various information processing equipment 9 communication equipment,
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 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. For large screen projection receivers,
Considering economic efficiency, it is used to select and receive images from multiple types.

Since there is no industry standard for image signals output from computer equipment, signal levels and synchronization frequencies 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 level is too low, the screen will be very dark and distracting, and if it is too high, it will be unnecessarily dark. Bright? It may cause a fetish or a 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 and are not dedicated machines, it is necessary to adjust the signal level. For example, by installing an attenuator in the signal input circuit, or by using a variable resistor in the image signal processing circuit. I'm trying to adjust the levels.

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, the cables may be of different lengths depending on the distance between the two stations, 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 devices have been commercialized using analog technology.For example, when adjusting the input signal level, the combination of electronic attenuators and digital technology can be used to adjust the level of the receiver. It is also easy to adjust the remote control from outside. 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 or image signal 98 raccoon circuit in the receiver.

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

Additionally, 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 1 of the Invention (Means for Solving the Problems) This invention provides a monitor receiver that displays image signals on a screen! &
A signal level display circuit for displaying the input image (!I low signal level) using a picture tube of the machine, the signal level display circuit comparing the image signal with a first reference voltage and determining that the level of the image signal is at a first level. a comparator that outputs signals of different levels when higher and lower than the first reference voltage, and a second
a voltage source that generates a reference voltage; and a switch circuit that is controlled based on the output of the comparator and alternately switches and outputs the image signal and the second reference voltage from the voltage source.

(Operation) According to the present invention, while the level of the input image signal does not match the second reference voltage, an image based on the input image signal can be distinguished from an image based on the second FP-voltage. When the level of the input image signal becomes equal to the second reference voltage, an image based on the input image signal becomes indistinguishable from an image based on the second reference voltage. This makes it possible to know and adjust the level of the input image signal without using a measuring device such as an oscilloscope or a lasso.

(Embodiments) The present invention will be explained in detail below using illustrated embodiments.

FIG. 1 is a configuration diagram, not showing an embodiment, of a signal level display circuit according to the present invention. In the figure, the level-adjusted image signal S2 is introduced to the input terminal IN.

Operational amplifier A1 constitutes a comparator, and its inverting input terminal (-) is connected to the ground potential point, and its non-inverting input terminal (A) is connected to the ground potential point.
The image signal S2 from the input terminal IN1 is guided to the input terminal IN1. The comparison output ■ from the operational amplifier A1 controls the switching of the switch SW1, and also controls the switching of the switch SW2 via the inverting circuit G1.
is controlled by switching. The switches SW1 and SW2 are connected in series, and one switch SW1 receives an image signal from the input terminal IN1 and selectively outputs it intermittently.

The other switch SW2 receives the reference voltage VR and selectively outputs it intermittently. An output signal 0, which is a combination of the above intermittent selection outputs, is derived at the connection point between the switches SWt and S~v2. This signal 0 is displayed on the picture tube CRT.

FIG. 2 shows a configuration in which the signal level display circuit described above is incorporated into a picture tube circuit. In Figure 2, input terminal IN
An image signal S1 before level adjustment is introduced. The image signal S1 is level-adjusted by a level adjuster VA comprising an electronic attenuator that can be adjusted by remote control, and its output 82 is input to the level display circuit SL having the configuration shown in FIG. The signal from the level display circuit SL is transmitted to the first switch SW3, which is operated to switch between normal use and level adjustment.
At the input terminal Δ, the direct image signal S2 from the level adjuster VA is led to the second input terminal B of the switch SW3. The switching selection output of the switch SW3 is displayed on the picture tube CRT via the image signal processing circuit vP.

That is, in the signal level display circuit J5 having the above configuration, the image signal 82 has a signal period in which it is higher than the ground potential,
There are periods when the signal is low. During the period when the image signal S2 is higher than the ground potential, the level of the output O of the operational amplifier Δ1 is high level, and the output level of the inverting circuit G1 is low level. Each switch S~V1. Assuming that SW2 becomes conductive when a high-level control signal is applied and becomes non-conductive when a low-level control signal is applied, during the period when the image signal S2 is higher than the ground potential, switch SW1 becomes conductive and switch SW2 becomes non-conductive. Therefore, the image signal S2 becomes the output signal 0
The output is selected and displayed on the screen. In addition, during the period when the image signal S2 is lower than the ground potential, the switch SW
1 becomes non-conductive, the switch SW2 becomes conductive, and the reference voltage VR is selectively outputted as an output signal @ and displayed on the screen.

A screen with an output signal of 0 due to such switching operations of the switches SWI and SW2 is created when the level of the image signal S2 is the reference voltage V.
When smaller than R (82<VR), the brightness of the display area of the image signal is 03 times smaller than the brightness of the display area of the reference voltage VR.
(Conversely, the level of the image signal S2 is the reference voltage V
When higher than R (S2>VR), the brightness of the display area of the image signal is brighter than the display area of the reference pressure VR. Further, when the image (, Ii'?r 32 is equal to the reference voltage VR (S2-VR), the brightness of the display area of the image signal and the brightness of the display area of the US voltage VR match.

FIG. 3 shows a screen when a character signal is input as the image signal S2. FIG. 3(A) shows the screen when 82<VR, and the display area of the text portion is darker than the display area of the back tab at the reference voltage VR.

FIG. 3(B) shows a screen when 82>VR, and the display area of the text portion is brighter than the display area of the background portion. FIG. 3(C) shows the screen when 82=VR, and the display area of the character part and the display area of the background part match.

As described above, when adjusting the level of the input image @signal, look at the screen as shown in Figure 3 (C). Just adjust the level so that the characters cannot be distinguished. This eliminates the need for a measuring device, and allows adjustment without opening the receiver's TV screen even when adjusting using a remote control.

It has been confirmed through experiments that the adjustment accuracy of the above adjustment method can be visually detected up to a difference of 2 to 3% because two surfaces with different brightness are in contact with each other on the screen.

Therefore, the adjustment accuracy can also be adjusted with an error of 2 to 3%.

In order to deal with high-frequency image signals, it is necessary to use a comparator with excellent frequency characteristics for the operational amplifier A1, but the purpose can be achieved even if the high-frequency components are cut off without intentionally doing so. Further, it may be more convenient to do so because errors caused by the frequency characteristics of the image signal processing circuit vP can be eliminated.

In the case of the configuration shown in FIG. 2, the switch SW 3 is switched to the A side during level adjustment, and switched to the B side during normal image reception. Note that the output signal ■ is sent directly to the image signal processing circuit v.
If inputting to P is not appropriate, level conversion or blanking processing may be performed, for example.

[Effects of the Invention] As described above, according to the present invention, the level of the input image signal can be adjusted based on the video displayed on the screen without using a measuring device.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a 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 is a level adjustment according to the present invention. It is a screen diagram showing an example of a screen. A1... operational amplifier, SWI, SW2... switch, G1... inverting circuit, CRT... picture tube, VR...
-Reference voltage, S+, S2... image signal. Figure 1 Figure 2

Claims (1)

[Scope of Claims] A signal level display circuit that displays the level of the inputted image signal using a picture tube of a monitor receiver that displays the image signal on the screen, a comparator that outputs signals of different levels when the level of the image signal is higher and lower than the first reference voltage when compared with a reference voltage; a voltage source that generates a second reference voltage; a switch circuit that is controlled based on the output and alternately switches and outputs the image signal and a second reference voltage from the voltage source, and displays the output signal of the switch circuit on the picture tube. 1. A signal level display circuit characterized in that the signal level of an input image signal is displayed.