JPS63157573A - Picture quality adjusting device - Google Patents

Abstract

PURPOSE:To improve the picture quality adjustment by varying the characteristic of a noise reducing circuit so as to prevent the deterioration in the quality of reproduced signal when a picture quality adjusting control voltage reaches respective limit voltage for the sharp picture quality and soft picture quality. CONSTITUTION:A reproduced video signal at an input terminal 1 is inputted to an adjusting circuit 3 via a de-emphasis circuit 2 and an output video signal is varied for the sharp picture quality and the soft picture quality by adjusting a control voltage Vi. The output video signal is fed to an adder circuit 13 and an LPF 5 of a noise rejecting circuit 12. The output of the LPF 5 is fed to an adder circuit 13 via an amplifier 9, an amplitude limiter 10 and a polarity inverting circuit 11. The picture quality adjusting control voltage Vi is compared with upper/lower limit reference voltages E1, E2 at a comparator circuit 21 and when the voltage exceeds the limit voltages, the characteristic of the noise reducing circuit 12 is made variable to give emphasis or attenuation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image quality adjusting device that is installed in a reproducing circuit section of a video tape recorder and adjusts the image quality of a reproduced video signal. 1. Prior Art Conventionally, the image quality adjustment device provided in the reproduction circuit section of a video tape recorder generally includes an image quality adjustment circuit consisting of a beam width path, etc., and a series circuit of a high-pass filter, a width limiter, and a polarity inverter. 1. A noise removal circuit that extracts the small amplitude component of the high frequency frequency of the output video signal of the image quality adjustment circuit and inverts its polarity, and an addition circuit that adds the output signal of the removal circuit to the output video signal of the adjustment circuit and outputs the result. ! ! It is equipped with l-road. Then, by operating a variable resistor for image quality adjustment operation provided in one image quality adjustment circuit, increasing the control voltage i of the sliding piece of the variable resistor,
When the control voltage is decreased and varied, the frequency characteristics of the gain of the image quality adjustment circuit change by the amount of change in the control voltage, and the high frequency components of the reproduced video signal input to the image quality adjustment circuit are adjusted to FL and attenuated in proportion to the amount of change. The video signal of the image quality adjustment circuit is variably adjusted to sharp image quality and soft image quality by the amount of change. In addition, the noise removal circuit extracts a small amplitude component below a predetermined level of high frequency set by the characteristics of the high-pass filter from the output video signal of the image quality adjustment circuit, and inverts the polarity, and outputs the image quality adjustment circuit. Since the video signal and the output signal of the noise removal circuit are added in the adder circuit,
A video signal obtained by removing the small amplitude component of the high frequency from the output video signal of the image quality adjustment circuit, that is, a noise-reduced video signal is output from the adding circuit. Therefore, the reproduced video signal output from the adder circuit is adjusted to the desired image quality from sharp image quality to soft 1III quality by the image quality adjustment operation=j variable low resistance operation, and the high frequency is adjusted by the noise reduction circuit. The result is a signal with reduced pulse-like noise components and non-pulse-like noise components. On the other hand, Japanese Patent Application Laid-Open No. 60-139073 discloses that, in order to adjust the image quality of a video signal of a television receiver, an output video signal of an image quality improving means comprising a peaking circuit or the like similar to the above-mentioned image quality adjustment circuit, The output of the noise reduction means is formed in the shape of a transversal filter with taps using the delay circuit 2 and the logic circuit, and removes only the pulse-like signal having a frequency near the frequency region of the noise component from the output video signal of the image quality improvement means 1. For example, when the video signal is added with the same time axis and at an addition ratio that changes in proportion to the operation of the variable resistor for image quality adjustment as described in AiJ, and sharp image quality is achieved, the detailed information component (@Kana An image quality improvement device is described that removes and reduces pulse-like noise components without losing picture components. [Problems to be Solved by the Invention] By the way, in the case of the above-mentioned conventional image quality adjustment device installed in the playback circuit section of a video tape recorder, when the image quality is adjusted to a sharp image quality by the variable resistor for image quality adjustment operation, the image quality is adjusted to 1.
Since the high frequency of the output video signal of the image quality adjustment circuit is emphasized, the noise component is also emphasized, and at this time, the level of the noise component input to the noise reduction circuit increases, and the reproduced video signal output from the adder circuit increases. As the image quality becomes sharper, noise components increase, noise on the playback screen becomes larger, and the playback quality deteriorates. However, when adjusting to soft image quality using the variable resistor for 1liiI quality adjustment operation, 1 image quality adjustment L! Since the high frequency component of the output video signal of the 21-way is attenuated, the high frequency component of the output video signal as well as the noise component is reduced by the noise reduction circuit, and in this case, the reproduced video signal output from the adder circuit is Not only the noise component is reduced, but also the original high frequency component is reduced, and detailed information components due to the high frequency component on the playback screen are lost, resulting in deterioration of the playback quality. That is, the playback of the video tape recorder Ir:! In the case of this type of conventional image quality adjustment circuit provided in the U-way section, there is a problem that the reproduction quality deteriorates due to the image quality adjustment. On the other hand, in the case of the image quality improvement device described in the above-mentioned publication, since non-pulse noise is not reduced, the band is relatively narrow, such as the playback video signal of a video tape recorder, and one small amplitude of high frequency However, regardless of whether it is in the form of a pulse or not, if it becomes a noise component, there is a problem that a good noise reduction effect cannot be achieved. The present invention uses a simple configuration to adjust the image quality of a reproduced video signal, such as a reproduced video signal of a video tape recorder, in which a small amplitude component of a high frequency is a noise component, without deteriorating the reproduction quality. Consider it a technical issue. [Means for solving point a] This invention has been made with the above points in mind,
An image quality adjustment circuit that emphasizes and attenuates high frequency components of an input video signal in proportion to the amount of change in the control voltage based on increases and decreases in the control voltage of a sliding piece of a variable resistor for image quality adjustment operation. and a series circuit of a high-pass filter, an amplitude limiter, and a polarity inverter, and extracts only the small amplitude component of the high frequency range of the output video signal of the adjustment circuit, and outputs a signal with the inverted polarity of the small amplitude component. An image quality adjustment device that includes a removal circuit and an addition circuit that adds the output signal of the removal circuit to the output video signal and outputs the resultant signal is configured to adjust the preset threshold reference voltages for sharp image quality 2 and soft image quality to the respective threshold voltages set in advance. Compare with the control voltage. A comparison circuit is provided for outputting a detection signal for an enhancement command and an attenuation increase command for the noise removal characteristic when the control voltage reaches each of the two reference voltages, and the removal circuit is provided with a detection signal for both the detection The image quality adjusting device is characterized in that a characteristic changing means is provided for changing the noise removal characteristics of the noise removal circuit to emphasize and attenuate characteristics, respectively, by inputting each signal. [Operation] Therefore, the noise reduction circuit extracts pulse-like and non-pulse-like noise components in order to extract small amplitude components at high frequencies, and at this time, pulse-like signal components with a larger loss width than the noise components are extracted. is not extracted, the noise component can be reduced with a good noise reduction effect.
When the control voltage of the sliding piece of the variable resistor for image quality adjustment operation reaches the limit reference voltage for sharp image quality, the noise removal characteristics of the noise removal circuit are changed to emphasis characteristics, and the amount of reduction of small amplitude components of high frequencies is large. When the control voltage of the sliding piece reaches the limit reference voltage for lift image quality, the noise removal characteristic of the noise removal circuit is changed to an attenuation characteristic. In the output video signal of the adder circuit, the amount of reduction of small amplitude components of high frequencies is reduced, and the loss of detailed information components is reduced, thereby preventing deterioration of reproduction quality. Since it is only necessary to add the characteristics and characteristics, the device can be formed easily and inexpensively. [Embodiment] Next, the present invention will be explained in detail with reference to FIG. 1 showing an embodiment of the invention. Figure 1 shows the case where it is installed in the playback circuit section of a video tape recorder. In the figure, fl+ is the video input terminal into which the playback video signal is input, and 12) is the input terminal (1)
The de-emphasis circuit (31 is an image quality adjustment circuit connected to the de-emphasis circuit 121, which includes a peaking circuit, etc.) and the variable resistor for image quality adjustment operation (by the DC control voltage of the sliding piece 41) The frequency characteristics of the gain are varied, and the high frequency components of the input video signal are emphasized and attenuated in proportion to the increase and decrease in the a turtle pressure Vl. 2. The variable resistor (4) is connected to the positive power supply terminal. (10B) and the ground. +b+ This is a RC type high-pass filter, and the first filter capacitor (6) and the second capacitor are connected between the output terminal of the adjustment circuit (3) and the ground. 1 resistor (7), 2nd capacitor (8
) are connected in series. (9) is a buffer amplifier connected to the connection point of capacitor (6) and resistor 7), that is, the output terminal of filter (5), αG is an amplitude limiter connected to amplifier (9), and +lll is a limiter a polarity inverter connected to αO,
1I21 is the filter (5), amplifier (91, limiter α
This is a noise reduction circuit consisting of a series circuit of O, inverter (11). (1"3 is an adjustment circuit (31 output video signal and inverter (11:
1141 is the video output terminal connected to the adder circuit (131). These are the second and third resistors for forming the limit reference voltage of The fourth and fifth resistors are connected in series to form the soft image quality limit reference voltage, and a preset lift image quality limit reference voltage E2 is generated at the connection point. (19+ and 21m are the control voltage Vi Non-inverting input terminal (+
) 1 inverting input terminal (-), the reference voltage 1EfEB1 is applied to the inverting input terminal (-・) of the comparator (!9), and the non-inverting input terminal of the comparison 4 (Based on the tram E (+) force is applied, Vi ≧El
, Vi ≦E2K fx le(!:, comparator α91
, 1201 output high-level detection signals for noise removal characteristic enhancement commands and attenuation commands, respectively. +211 is the resistor (16) to Q81F5 and comparator (19
This is a comparison circuit consisting of 1 and 2. Second, look at the comparator via the NPN type filter (5)! ! 91. ! The collector of the transistor is connected to the connection point of the resistor (7) and the capacitor (8). 2, C are transistors E, (8th and 9th resistors for bias provided between the base of 231 and the ground, n,
(X!l is the third filter capacitor and the 10th resistor installed in series between the connection point of the capacitor (6) and resistor (7) and the collector of the transistor.) The emitters of are both grounded. In addition, a characteristic variable means is formed by the transistors E, Hl:FJ, resistors N, !2!J, and a capacitor.The reproduced video signal at the input terminal i11 is is input to the adjustment circuit (3) via the de-emphasis (2) path (21), and at this time, by operating the variable resistor (41) and increasing or decreasing the control voltage Vi from the midpoint voltage, the adjustment circuit (
3) The high frequency component of the output video signal is controlled by the control voltage v
The emphasis and attenuation are varied in proportion to the amount of change in 1, and the variable resistance (
By operating 4), the output video signal of the adjustment circuit (31) is varied between sharp image quality and soft image quality. Also, when the control 'filling pressure 1' becomes E2<Vi<Et, the comparators Q!l, H The output signals of both are held at low level, and transistors w and 1231 are both turned off.Furthermore, when both transistors w and @ are turned off, the characteristics of filter (5) are capacitor + 61. (81, resistor (7) The output video signal of the adjustment circuit (3) is maintained at the basic characteristic determined by the filter (
6), and if both transistors β and IA are off at this time, the high frequency components of the input video signal are extracted with the aforementioned basic characteristics and output to the amplifier (9). Then, the output signal of the filter (61) via the amplifier (9) is input to the limiter αO, which extracts only small amplitude components below the limiter level of the input signal, that is, a predetermined level. (
11), only the small amplitude component of the high frequency of the output video signal of the adjustment circuit (3) is extracted and output, and at this time,
A component having a frequency set by the characteristics of the filter (5) or higher and an amplitude higher than the limiter level of the limiter αO is extracted and output to the inverter 111, regardless of whether it is a pulse or not. Furthermore, the polarity of the small amplitude component of the input high frequency is reversed by the inversion difficult piece. Then, the output video signal of the adjustment circuit (31) and the inverter (1
1) are added by the adder circuit 1I31, the video signal output from the adder circuit (131) is a small amplitude component of the high frequency, that is, a pulse-like component, from the output video signal of the adjustment circuit (3). Therefore, the reproduced video signal outputted from the adder circuit 713 to the output terminal -141 is a signal obtained by removing the original reproduced video signal from the input terminal (11) through the operation of the variable resistor +41. By the way, the signal is adjusted to sharp image quality or soft image quality, and the noise component is well reduced. By the way, the image quality is adjusted to be excessively sharp by operating the variable resistor (4), and the capacitor +61. +81. resistor (7) With the noise removal characteristics of the reduction circuit IJ based on the filter characteristics of , comparator (1
91 outputs a high level detection signal. When the pi-level detection signal is output from the comparator, the transistor A is turned on, the cutoff frequency of the filter (6) is lowered, and the signal is output from the filter (5) to the limiter αO via the amplifier (91). The lowest frequency of the signal becomes lower than when the transistor is off, the noise removal characteristics of the low frequency circuit 121 are emphasized and varied, the amount of noise reduction of the video signal output from the adder circuit 131 increases, and the noise component increases. 710 is suppressed to prevent deterioration in playback quality.On the other hand, the noise is adjusted to excessively soft quality by operating the variable resistor 14), and the noise of the capacitor +61,181.The reduction circuit based on the filter characteristics of the resistor (7) +121 is suppressed. The removal characteristic reaches a limit where the detailed information component of the video signal output from the adder circuit t13 decreases and the reproduction quality begins to deteriorate, and when the control voltage Vi reaches E2, a high level detection signal is output from the comparator 4. Then, when a high-level detection signal is output from the comparator ■, the transistor turns on, the cutoff frequency of the filter (6) increases, and the limiter αO is output from the filter (61) via the amplifier (9). The lowest frequency of the signal outputted from the transformer (c) becomes higher than when the transformer (c) is off, the noise removal characteristic of the reduction circuit 121 is attenuated and varied, and the amount of noise reduction of the video signal outputted from the addition circuit α3 decreases. At this time,
Decrease in detail information components is suppressed and deterioration in reproduction quality is prevented. Therefore, in the case of the above embodiment, a comparison circuit @J is added to the conventional image quality adjustment circuit, and a variable resistor (4
8 in the entire adjustment range of 1, it is possible to perform image quality adjustment while preventing deterioration of playback quality, and the reduction amount tI5nz allows all pulse-like and non-pulse-like small amplitude components of high frequencies to be extracted as noise components. Therefore, noise components can be removed with good noise reduction characteristics. 8. In the above embodiment, the characteristics of the filter 161 were varied by the detection signals of the comparators, and the noise removal characteristics of the reduction circuit 1z were varied; however, the detection signals of the comparators aS and c2[11 Amplifier (91 gain or IJ Mitter αO limiter level variable to reduce Ig circuit +12
The noise removal characteristic of No. 1 may be varied. Furthermore, the invention can also be applied to image quality adjustment devices for various video playback devices such as video disc playback devices. [Effects of the Invention] As described above, according to the image quality adjustment circuit of the present invention, noise is generated when the control voltage of the sliding piece of the variable resistor for image quality adjustment operation reaches the limit reference voltage of each of sharp image quality 2 and soft image quality. With a simple configuration that changes the characteristics of the reduction circuit to emphasize and attenuate, it is possible to adjust the image quality by adjusting the entire adjustment range of the variable resistor and preventing deterioration of playback quality.Moreover, the noise reduction circuit allows high-frequency Because all pulse-like and non-pulse-like small amplitude components of the frequency are extracted. It is possible to remove noise components with good noise reduction characteristics.

[Brief explanation of the drawing]

Figure 1 shows the image quality adjustment system of this invention! FIG. 2 is a block diagram of an embodiment. (3)...Image quality adjustment circuit, (4)...Variable resistor for image quality adjustment operation, 15)...High pass filter, (10...
pregnancy width limiter. (111...Polarity inverter, lI21...Noise reduction circuit, (13...Addition circuit, (21)...Comparison (b) path. Agent: Patent attorney Fuji 1) Ryuta's procedural amendment ( Voluntary) March 23, 1986

Claims (1)

[Claims] (1) Based on the increase or decrease of the control voltage of the sliding piece of the variable resistor for image quality adjustment operation, the high frequency components of the input video signal are emphasized or attenuated in proportion to the amount of change in the control voltage. It consists of a series circuit of an image quality adjustment circuit, a high-pass filter, an amplitude limiter, and a polarity inverter, and extracts only small amplitude components of high frequencies of the output video signal of the adjustment circuit,
An image quality adjustment device comprising: a noise removal circuit that outputs a signal with an inverted polarity of the small amplitude component; and an addition circuit that adds an output signal of the removal circuit to the output video signal and outputs the resultant signal; and a soft image quality limit reference voltage are compared with the control voltage, and when the control voltage reaches each of the reference voltages, a detection signal is output for an enhancement command and an attenuation command for the noise removal characteristic. An image quality adjustment device comprising a circuit, and characterized in that the removal circuit is provided with characteristic variable means for enhancing and attenuating the noise removal characteristics of the removal circuit by inputting each of the detection signals. .