JPH04223792A - Signal generator for frequency characteristic adjustment and method of adjusting frequency characteristic - Google Patents

Abstract

PURPOSE:To easily and effectively compensate the frequency characteristic of respective magnetic heads by easily forming reproducing signals from the magnetic heads into the desired frequency characteristic. CONSTITUTION:An adjustment signal including a frequency sweep signal ASy in which a level sequentially increases from 100 percent to more than 150 percent and a monochromatic signal ASc is generated and transmitted from a signal generation device 50, the adjustment signal is reproduced through the magnetic heads and is picture-displayed. The frequency characteristic of a reproducing signal processing part of the magnetic reproducing device is adjusted so that an inverted phenomenon or white dot phenomenon in the picture is intermediately generated as the picture.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frequency characteristic adjusting signal generator and a frequency characteristic adjusting method suitable for adjusting the frequency characteristics of a high frequency amplifying section of a video tape recorder or the like.

0002

[Prior Art] Conventionally, a video tape recorder (VTR)
Since the gap widths of the read magnetic heads used in the 1990s differ slightly during manufacture, there are variations in the read frequency characteristics of each read magnetic head. For this reason, in VTRs and the like, the frequency characteristics of the reproduced signal from the magnetic head are shaped to desired characteristics. That is, in order to compensate for the frequency characteristics of the magnetic head, a correction circuit 2 is provided in the reproduced signal processing section shown in FIG. 6, and as shown in FIG. A magnetic tape (generally referred to as an RF sweep tape) is prepared by adding markers m1, m2, m3, m4, m5, m6, and m7 to saturation recording, and a frequency sweep signal is reproduced from this RF sweep tape. The frequency characteristics of each reproducing magnetic head are compensated by shaping the frequency characteristics of the reproduced signal into desired characteristics using a correction circuit.

FIG. 6 shows a reproduction signal processing section in a VTR. This reproduction signal processing section is an RF sweep tape T.
The output end of a reproducing magnetic head 4 for reproducing recorded contents from p is connected to the input end of a preamplifier 6, and the output end of the preamplifier 6 is further connected to a correction circuit 2. The correction circuit 2 is provided with a peaking circuit 16 which is a frequency correction equalizer or the like in which a coil 10, a capacitor 12, and a variable resistor 14 are connected in parallel. Further, the output end of a reproducing magnetic head 22, which is similarly disposed 180 degrees opposite to the reproducing magnetic head 4, and the input end of a preamplifier 26 are connected. This preamplifier 26 is connected to the correction circuit 2. The correction circuit 2 is provided with a peaking circuit 36, which is an equalizer or the like in which a coil 30, a capacitor 32, and a variable resistor 34 are connected in parallel. Peaking circuit 1
The output signals from 6 and 36 are respectively supplied to fixed contacts 40a and 40b of a switcher 40, and a movable contact 40c is switched by a switching signal Sc.
The reproducing magnetic heads 4 and 22 are connected to the movable contact 40c.
Thus, the reproduction signal from the RF sweep tape Tp is continuously output.

In this configuration, the frequency sweep signal shown in FIG. 7A recorded on the RF sweep tape Tp is reproduced by the reproduction magnetic heads 4 and 22. Then, from the switcher 40 to the peaking circuit 16 or the peaking circuit 3
For example, first, one of the output signals of peaking circuit 1
6 is forcibly and continuously derived, and the output signal waveform shown in FIG. 7B is observed. The level ratio between marker m2 and marker m4 in this output waveform is determined in advance, and the variable resistor 14 is adjusted so as to achieve this determined level ratio. As a result, the reproducing magnetic head 4 is compensated for desired frequency characteristics. Similarly, the output signal of the peaking circuit 36 is continuously derived and the variable resistor 34 is adjusted to compensate the frequency characteristics of the reproducing magnetic head 22. In this way, fluctuations in the reproduction frequency characteristics due to slight differences in gap width during the manufacture of the reproduction magnetic heads 4 and 22 are compensated for.

[0005]

[Problems to be Solved by the Invention] However, in the conventional VTR correction circuit and frequency characteristic adjustment method, adjustment is conveniently performed using the level ratio of only the marker m2 and the marker m4, as shown in FIG. 7B. Therefore, it is often impossible to appropriately compensate for the frequency characteristics of the reproducing magnetic heads 4 and 22. In this case, the reproduced image may be affected by the well-known inversion phenomenon due to black overmodulation when the level of high frequencies is lowered, or the white spot phenomenon where the high level part of the chroma signal becomes white bead-like noise when the level of high frequencies is emphasized. This has the drawback that it is difficult to obtain the desired high image quality.

The present invention has been made in view of the above-mentioned problems, and is an excellent method in which the reproduced signal from a magnetic head can be easily formed into a desired frequency characteristic, and the frequency characteristics of each magnetic head can be easily and effectively compensated for. It is an object of the present invention to provide a frequency characteristic adjustment signal generation device and a frequency characteristic adjustment method.

[0007]

[Means for Solving the Problems] The present invention provides, for example, FIG.
As shown in the frequency characteristic adjustment signal generation device of FIG. 5, adjustment signal generation means (50 ) and a supply means 51 (RT) for supplying the adjustment signal sent from the adjustment signal generation means (50) to the magnetic head (62, 82) of the magnetic reproducing device (52).

Further, the frequency characteristic adjustment method of the present invention sends out an adjustment signal in which a frequency sweep signal whose level increases sequentially to a predetermined value or more and a monochromatic signal is formed, and this adjustment signal is transmitted to a magnetic reproducing device (52). ) magnetic heads (62, 82
), and identifies the inversion phenomenon in the frequency sweep signal and the white spot phenomenon in the monochromatic signal from the adjustment signal output from the magnetic head (62, 82), and reproduces the reproduction signal from the magnetic head (62, 82). This is to adjust the frequency characteristics of.

[0009]

[Operation] In the frequency characteristic adjustment signal generator of the present invention,
For example, a frequency sweep signal and a monochromatic signal whose level increases sequentially to a predetermined value or more are recorded on a magnetic recording medium RT, and the frequency sweep signal and monochromatic signal are transferred to a magnetic head (62,
82). In this case, an inversion phenomenon in a portion where the level of the frequency sweep signal exceeds a predetermined value or a white spot phenomenon in a portion where the monochromatic signal exceeds a predetermined value is identified. For example, a magnetic reproducing device (
Adjust the frequency characteristics of the reproduced signal processing section 52). As a result, the magnetic head (6) in the magnetic reproducing device (52)
2, 82) is formed to have desired frequency characteristics, and the frequency characteristics of each magnetic head can be effectively compensated for.

Furthermore, according to the frequency characteristic adjustment method of the present invention, an adjustment signal consisting of a frequency sweep signal and a monochromatic signal whose level increases sequentially to a predetermined value or more is stored in, for example, a magnetic recording medium RT, and the adjustment signal is stored in the magnetic recording medium RT, for example. An adjustment signal is reproduced from the magnetic recording medium RT by a magnetic reproducing device (52) using a magnetic head (62, 82). In this case, an inversion phenomenon in a portion where the level of the frequency sweep signal exceeds a predetermined value or a white spot phenomenon in a portion where the monochromatic signal exceeds a predetermined value is identified. This identification is performed by displaying an image. Alternatively, the frequency characteristics of the reproduction signal processing section of the magnetic reproducing device (52) are adjusted so that the respective signals showing the reversal phenomenon or the white spot phenomenon are compared and the reverse phenomenon or the white spot phenomenon occurs as an intermediate image. Thereby, the reproduction signal from the magnetic head in the magnetic reproducing device is formed to have desired frequency characteristics, and the frequency characteristics of each magnetic head can be effectively compensated.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the frequency characteristic adjustment signal generating device and frequency characteristic adjustment method of the present invention will be described in detail below with reference to the drawings. In FIG. 1, 50 is a signal generating device, and this signal generating device 50 generates and sends out an adjustment signal consisting of a frequency sweep signal ASy corresponding to a luminance signal and a monochromatic signal ASc corresponding to a chroma signal. The adjustment signal forms a frequency sweep signal ASy in section A when one screen (one field) is equally divided into four sections as shown in FIG. This frequency sweep signal ASy has a sweep frequency of 1.5 MHz to 3 MHz, for example, with a level ranging from 100% to 15% as shown in FIG.
Formed to increase to 0%. Furthermore, category B
The level of the monochromatic signal ASc is 100 as shown in Figure 3B.
% to 150%. Here, 100% is a level that does not cause the inversion phenomenon due to black overmodulation that occurs in the reproduced image when the high frequency range of the reproduced signal is reduced, or the chroma signal when the high frequency range of the reproduced signal is emphasized. This is a level at which the high-level portion of the signal does not cause white-bead-like noise. Note that the frequency sweep signal A
Sy and the monochromatic signal ASc may be formed so that their levels increase in the vertical direction. 51 is a magnetic recording device, and in this magnetic recording device 51, an adjustment signal recording tape RT on which adjustment signals supplied from the signal generator 50 are recorded is created. In this case, in order to record the frequency sweep signal ASy and the monochromatic signal ASc on the magnetic recording tape at a level of 100% or more, the operation of the level limiting circuit of the recording section (not shown) is stopped. The adjustment signal recording tape RT produced in this manner is reproduced by a VTR 52 equipped with a magnetic head for compensating frequency characteristics.

The reproduction signal processing section 52a of the VTR 52 is shown in FIG.
As shown in FIG. 2, the output end of the reproducing magnetic head 62, which is in contact with the adjustment signal recording tape RT, and the input end of the preamplifier 66 are connected. The output terminal of this preamplifier 66 is connected to the correction circuit 6
8 is connected. The correction circuit 68 is provided with a frequency correction peaking circuit 76, which is an equalizer or the like, in which a coil 70, which is an equalizer, a capacitor 72, and a variable resistor 74 are connected in parallel. Similarly, the reproducing magnetic head 6
The output end of a reproducing magnetic head 82 and the input end of a preamplifier 86, which are arranged 180 degrees opposite to each other, are connected to each other. This preamplifier 86 is connected to a correction circuit 68. The correction circuit 68 is provided with a peaking circuit 96 such as an equalizer in which a coil 90, a capacitor 92, and a variable resistor 94 are connected in parallel. Peaking circuits 76 and 9
The respective output signals from the switcher 100 are supplied to the fixed contacts 100a and 100b of the switcher 100, and the movable contact 100c selects the fixed contacts 100a and 100b according to the supplied switching signal Sc, and the reproducing magnetic head 6
The signals reproduced from the adjustment signal recording tape RT in steps 2 and 86 are successively derived. The reproduced signal derived from this is supplied to the luminance signal processing system, chroma signal processing system 110, and the like.

[0013] Then, the video signal AS from the VTR 52
d is supplied to a low-pass filter (LPF) 120, which outputs a frequency sweep signal ASy and a monochromatic signal ASc, and removes superimposed noise. The video signal ASe outputted from here is supplied to the fixed contact 122a of the observation switching switch 122. Further, a DC voltage is applied to the fixed contact 122b of the switch 122 from the DC power supply E. A composite signal ASg from the VTR 52 is supplied to the gate circuit 124,
Here, a switching signal Ss for each screen is generated. This switching signal Ss is supplied to drive the movable contact 122c of the switch 122. Movable contact 1
22c is connected to a monitor television 130, where the video signal ASe output from the LPF 120 or the DC voltage from the DC power supply E is selected by the switch 122 and supplied to the monitor television 130.

Next, the operation of this configuration and the frequency characteristic adjustment method will be explained. The signal generator 50 generates and sends out a frequency sweep signal ASy and a monochromatic signal ASc shown in FIG.
The adjustment signal recording tape RT is produced by being supplied to the magnetic tape through the magnetic tape.

The frequency sweep signal ASy and monochromatic signal ASc recorded on the adjustment signal recording tape RT are transferred to the VTR 52.
The data is reproduced by the reproduction magnetic heads 62 and 82 of the reproduction signal processing section 52a. This reproduced signal is supplied to the LPF 120 through the reproduced signal processing circuit 52a. At the same time, a composite signal ASg is supplied from the VTR 52 to the gate generation circuit 124, where a switching signal Ss for each screen is generated and derived to drive the movable contact 122c of the switch 122. Here, the video signal ASe output from the LPF 120, that is, the adjustment signal consisting of the frequency sweep signal ASy and the monochromatic signal ASc shown in FIG. The voltage is selected for each screen by the movable contact 122c of the switch 122. Here, an image shown in FIG. 5 is displayed on the monitor television 130. Figure 5(a) shows the video signal A.
3 is a diagram of a display image when the high frequency level of the frequency characteristic of Se is lowered, and the inversion phenomenon om due to black overmodulation corresponds to the division A of FIG. 2 (Aa) of the display image; FIG.
occurs in Further, FIG. 5C is a display image diagram when the frequency characteristics of the video signal ASe are emphasized in the high frequency range, and the white spot phenomenon ws in which the high level part of the chroma signal becomes a white spot noise corresponds to classification B in FIG. occurs in the image segment (Ba). Here, the variable resistors 74 and 94 in the correction circuit 68 of the VTR 52 are adjusted so that the inversion phenomenon om and the white spot phenomenon ws occur intermediately in the sections (Aa) and (Ba), respectively, as shown in FIG. 5B. Adjust alternately. In this case, the display screen of the adjustment signal consisting of the frequency sweep signal ASy and the monochromatic signal ASc and the screen free of noise due to the application of DC voltage are selected and displayed on a screen-by-screen basis, so the inversion phenomenon om occurs. The white ball phenomenon ws can be reliably visually observed and can be easily adjusted. In this case, there is a significant advantage that the mass productivity of VTRs is improved.

In this way, the frequency sweep signal ASy and the monochromatic signal ASc, whose levels increase sequentially to 100% or more, are recorded on the magnetic recording medium TR, and the frequency sweep signal ASy and the monochromatic signal ASc are transferred to the magnetic head 62.
, 82. In this case, the inversion phenomenon in the part where the level of the frequency sweep signal ASy exceeds 100% or the white spot phenomenon in the part where the level of the monochromatic signal ASc exceeds 100% is displayed as an image, and the inversion phenomenon or the white spot phenomenon in this displayed image is intermediate. The peaking circuits 76 and 96 are adjusted so that the image is generated. As a result, the magnetic heads 62 and 82 in the VTR 52
The reproduced signal from the magnetic head is formed to have desired frequency characteristics, and as a result, the frequency characteristics of each magnetic head can be effectively compensated.

Note that in this embodiment, the signal generator 50
and the magnetic recording device 51 to record the adjustment signal recording tape RT.
is created, but it can also be created using a VTR52. That is, the VTR 52 is provided with a recording section, in which the adjustment signal recording tape RT is produced, and the produced adjustment signal recording tape RT is further reproduced by the VTR 52, and the magnetic head 62 provided here, The frequency characteristics of the reproduction signal 82 may be adjusted by the peaking circuits 76 and 96 to compensate for the frequency characteristics of the magnetic heads 62 and 82.

[0018]

As can be understood from the above explanation, according to the frequency characteristic adjustment signal generating device of the present invention, an inversion phenomenon occurs where the level of the frequency sweep signal exceeds a predetermined value, or a monochromatic signal exceeds a predetermined value. The frequency characteristics of the reproduction signal processing section of the magnetic reproduction device are adjusted so that the white spot phenomenon in the overlapping area is identified and the reversal phenomenon or white spot phenomenon occurs as an intermediate image, so the magnetic head in the magnetic reproduction device The reproduced signal from is formed into the desired frequency characteristics,
The frequency characteristics of individual magnetic heads can be easily and effectively compensated for.

Further, according to the frequency characteristic adjustment method of the present invention, an adjustment signal consisting of a frequency sweep signal and a monochromatic signal whose level increases sequentially to a predetermined value or more is reproduced from the magnetic head to reproduce the adjustment signal. . In this case, the inversion phenomenon in the part where the level of the frequency sweep signal exceeds a predetermined value or the white spot phenomenon in the part where the monochromatic signal exceeds the predetermined value is identified, and the inversion phenomenon or the white spot phenomenon occurs in the intermediate image. Adjust the frequency characteristics of the reproduction signal processing section of the magnetic reproduction device. Thereby, the reproduction signal from the magnetic head in the magnetic reproducing device is formed to have desired frequency characteristics, and the frequency characteristics of each magnetic head can be easily and effectively compensated for.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of a frequency characteristic adjustment signal generating device of the present invention.

FIG. 2 is a diagram used to explain adjustment signals in the embodiment and frequency characteristic adjustment method shown in FIG. 1;

FIG. 3A is a waveform diagram of a frequency sweep signal in the adjustment signal shown in FIG. 2; B is a waveform diagram of a monochromatic signal in the adjustment signal shown in FIG. 2;

FIG. 4 is a circuit diagram showing a partial block diagram of the reproduced signal processing section in FIG. 1;

FIG. 5A is a display image diagram when the high-frequency level of the frequency characteristic is lowered, which is used to explain the operation of the embodiment shown in FIG. 1 and the frequency characteristic adjustment method; B is used to explain the operation of the embodiment shown in FIG. 1 and the frequency characteristic adjustment method, and is a display image diagram when the frequency characteristic is normal. C is a display image diagram in the case of emphasizing the high level of the frequency characteristic, which is used to explain the operation of the embodiment shown in FIG. 1 and the frequency characteristic adjustment method.

FIG. 6 is a circuit diagram showing the configuration of a reproduction signal processing section of a conventional VTR.

FIG. 7A is used to explain the operation of a conventional correction circuit;
FIG. 3 is a diagram showing recorded contents of an F-sweep tape. B is an output signal waveform diagram when an RF sweep tape is reproduced, which is used to explain the operation of a conventional correction circuit.

[Explanation of symbols]

50 Signal generator 51 Magnetic recording device 52 VTR 52a Reproduction signal processing section 76, 96 peaking circuit ASy Frequency sweep signal ASc Monochrome signal RT adjustment signal recording tape

Claims (2)

[Claims] 1. Adjustment signal generating means for generating and transmitting an adjustment signal including a frequency sweep signal and a monochromatic signal whose level increases sequentially to a predetermined value or more; A signal generating device for frequency characteristic adjustment, comprising a supply means for supplying an adjustment signal to a magnetic head of a magnetic reproducing device. 2. Sending out an adjustment signal in which a frequency sweep signal and a monochromatic signal whose level increases sequentially to a predetermined value or more, and supplying this adjustment signal to a magnetic head of a magnetic reproducing device; A frequency characteristic adjustment method characterized in that the frequency characteristic of a reproduced signal from a magnetic head is adjusted by identifying an inversion phenomenon in a frequency sweep signal and a white spot phenomenon in a monochromatic signal from an adjustment signal output from a magnetic head.