JPH03278791A - Picture recorder - Google Patents

Abstract

PURPOSE:To suppress the deterioration in the S/N of a chroma signal by devising the picture recorder such that either an amplitude of the chroma signal of a picture to be recorded or a level of a luminance signal is reflected onto a recording level of the chroma signal. CONSTITUTION:An integration circuit 16 detects an average level of a luminance signal whose synchronizing signal levels are arranged by a clamp circuit 15, a DC amplifier 17 applies DC amplification to an output of the integration circuit 16 and the result is fed to an adder 13. Moreover, a DC voltage in response to the amplitude of the chroma signal is outputted to an adder 13. The adder 13 adds the output voltages of the integration circuit 12 and the DC amplifier 17 and the result is given to a control amplifier 6. The output voltage level of the adder 13 gets higher as a video signal corresponding to a dark color and a blacky color of a picture to be recorded is inputted to a BPF 1. Thus, the chroma signal is recorded without deterioration of the S/N.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image recording device, and more particularly to an image recording device capable of controlling the level of a chroma signal recorded on a storage medium.

[Prior Art] In an image recording device that replaces a home VTR (video tape recorder), the chroma signal and luminance signal of the image to be recorded are generally separately processed so as to be suitable for recording on a storage medium. It is processed. The processed chroma signal and luminance signal are then combined and recorded on a magnetic tape as a video signal for recording.

FIG. 6 is a schematic block diagram of a recording system of a conventional VTR.

Referring to the figure, a video signal of an image to be recorded is input from the outside, and is band-limited by a BPF (band pass filter) 1 to remove a luminance signal component. As a result, from BPFL, 3.58MHz±500k
Only chroma signals with a carrier frequency of Hz are output.

ACC (automatic chromaCont
rol) circuit 2 adjusts the burst signal contained in the chroma signal from the BPFI to a constant amplitude 1 and supplies it to the converter 3 so that chrominance demodulation is performed correctly from the chroma signal during reproduction. The converter 3 converts the chroma signal whose burst level has been adjusted by the ACC circuit 2 into 4
．． 62 by multiplying by the 2MHz carrier signal.
Low frequency conversion to 9kHz±500kHz.

The chroma signal that has been low frequency converted by the converter 3 is subjected to burst emphasis by a burst emphasis circuit 4 by increasing only the level of the burst signal component by 6 dB. Next, an LPF (low pass filter) 5 removes unnecessary frequency components such as 4 and 2 MHz, which are the carrier signal components, from the chroma signal to which burst emphasis has been applied.
Only the Hz signal component is provided to the adder 7 as the chroma signal to be recorded.

The adder 7 is provided with an FM-modulated luminance signal of an image to be recorded. This FM given to the adder 7
The luminance signal is input to the VTR from the outside and is separated from the video signal, and is subjected to contour correction, band limitation,
It is created by performing processing such as time alignment with the chroma signal and then FM modulating it with an FM modulator.

Note that in FIG. 6, a circuit section for creating an FM luminance signal is not shown.

Adder 7 superimposes the chroma signal from LPF 5 on the FM luminance signal. This superimposed signal is applied to the head 9 via the recording amplifier 8. As a result, the video signal of the image to be recorded is recorded on the magnetic tape 10 by the head 9.

[Problems to be Solved by the Invention] As described above, the conventional image recording device converts the chroma signal whose burst level has been adjusted into the FM luminance signal with the same amplitude, regardless of the levels of the luminance signal and chroma signal. are recorded in a superimposed manner.

This caused the following problems.

For example, when a chroma signal with the same amplitude is superimposed on an FM luminance signal, the relative magnitude of the amplitude of the chroma signal component in the superimposed image signal with respect to the level of the luminance signal component will vary depending on whether the level of the luminance signal is low or high. is larger as the level of the luminance signal is lower. In other words, the lower the level of the luminance signal, the higher the mixing ratio of the chroma signal to the luminance signal at the time of superimposition.Also, when a chroma signal with a large amplitude and a chroma signal with a small amplitude are superimposed on a luminance signal of the same level, In the signal after superimposition, the mixing ratio of the chroma signal to the luminance signal is greater in the portion where the chroma signal with a large amplitude is superimposed.Therefore, the noise contained in the chroma signal is noticeable in such a portion. That is, in a portion where the luminance signal level is low or a portion where the chroma signal has a large amplitude, the deterioration of the S/N ratio of the chroma signal in the superimposed signal is emphasized.

The amplitude of the chroma signal corresponds to the saturation (density) of the color, and the level of the luminance signal corresponds to the brightness of the image. Therefore, when an image reproducing device reproduces the signals recorded on the magnetic tape and obtains a reproduced image, the areas where the luminance signal level is low are not the same as the dark areas because the mixing ratio of the chroma signal to the luminance signal is large. Colors appear darker than they actually are, and the deterioration of the S/N ratio of the chroma signal is noticeable in areas where the amplitude of the chroma signal is large, making noise in the dark areas noticeable.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide an image recording device that realizes recording that can provide a reproduced image with good color image quality regardless of the level of the luminance signal and chroma signal during reproduction. That's true.

[Means for Solving the Problems] In order to achieve the above objects, an image recording apparatus according to the present invention includes a first detection means for detecting the amplitude of a chroma signal of an image to be recorded, and a first detection means for detecting the amplitude of a chroma signal of an image to be recorded. the second detection means for detecting the level of the luminance signal of the cabinet 1; and at least one of the detection output of the detection means of the cabinet 1 and the detection output of the second detection means. The apparatus includes a control means for controlling the amplitude of the chroma signal of the image to be recorded, and a means for mixing the chroma signal whose amplitude has been controlled by the control means with the luminance signal of the image to be recorded and recording it on a recording medium.

[Function] Since the image recording device according to the present invention is configured as described above, when the chroma signal is recorded on the recording medium, the chroma signal is recorded on the recording medium based on at least one of its amplitude and the level of the corresponding luminance signal. After the amplitude is controlled, it is recorded on a recording medium. In other words, the recording level of the chroma signal,
At least one of the amplitude of the chroma signal and the level of the luminance signal of the image to be recorded is reflected. For this reason, the recording level of the chroma signal corresponding to the dark or dark parts of the image to be recorded is controlled to suppress the deterioration of the S/N ratio of the chroma signal in the signal after mixing with the luminance signal. It becomes possible to do so.

[Embodiment] FIG. 1 is a schematic block diagram of a recording system of a home VTR according to an embodiment of the present invention.

Referring to FIG. 1, in addition to the conventional functional blocks included in the conventional recording system shown in FIG. 3. 58MHz emphasis amplifier 11,
An integrating circuit 12 and an adder 13 provided after the amplifier 11, a 3.5 MHz) wrap circuit 14 that receives an external video signal together with the BPFI, and a wrap circuit 14 provided between the trap circuit 14 and the adder 13. , clamp circuit 15. Integrating circuit 16. and a DC amplifier 17.

From the video signal given to the recording system, BPFL, AC
C circuit 2. Converter 3. Burst emphasis circuit 4
．． A low-frequency converted chroma signal is derived by the same operation as the conventional LPF 5. The chroma signal output from the LPF 5 is input to the control amplifier 6.

On the other hand, the video signal given to the recording system is also input to the trap circuit 14. The trap circuit 14 detects a carrier wave frequency of 3.58 MHz of the chroma signal from the video signal.
Remove the signal component of As a result, the chroma signal is removed from the video signal, and the luminance signal component is extracted. The luminance signal component extracted by the trap circuit 14 is subjected to sync tip clamping by the clamp circuit 15 so that the synchronization signal level is constant.

FIG. 5 is a diagram showing the output waveform of the clamp circuit 15. As shown in FIG. 5, in the luminance signal output from the clamp circuit 15, the synchronization signal part is constant
It is.

Next, the integrating circuit 16 detects the average level of the luminance signals whose synchronizing signal levels have been made equal by the clamp circuit 15. The DC amplifier 17 DC amplifies the output of the integrating circuit 16 and outputs the result. As a result, the DC amplifier 17 outputs a DC voltage at a level corresponding to the brightness level of the input video signal. This DC voltage is input to adder 13.

Specifically, the DC amplifier 17 outputs a lower level voltage as the output level of the integrating circuit 16 is higher, that is, as the video signal of the dark part of the recorded image is inputted. On the other hand, the higher the amplitude of the output signal of the ACC circuit 2 is, the higher the voltage level is outputted from the integrating circuit 12, that is, the higher the video signal of a dark-colored portion of the image to be recorded is input. Therefore, the output voltage of the adder 13 becomes higher when a video signal corresponding to a dark color portion and a dark portion of the image to be recorded is input.

Now, the output of the ACC circuit 2 constituting the chroma signal processing system, that is, the chroma signal in which the burst signal has been adjusted to a constant level, is processed by the 3.58 MHz emphasis amplifier 11.
The frequency component in which the chroma signal component is concentrated is amplified and provided to the integrating circuit 12. The integrating circuit 12 is connected to the amplifier 11
The chroma signal output from the chroma signal is integrated and its amplitude is detected. As a result, the integrating circuit 12 outputs a DC voltage whose voltage corresponds to the amplitude of the chroma signal. This DC voltage is input to adder 13.

Adder 13 adds the output voltages of integrating circuit 12 and DC amplifier 17. This added voltage is applied to the control amplifier 6.

The control amplifier 6 controls the amplitude of the low-frequency converted chroma signal output from the LPF 5 according to the output voltage level of the adder 13 and supplies it to the adder 7 .

The adder 7 superimposes the chroma signal provided from the control amplifier 6 on the FM luminance signal created in the same manner as in the prior art and outputs the superimposed signal. The output of the adder 7 is given to the head 9 via the recording amplifier 8 as in the conventional case, and is applied to the magnetic tape 1.
Recorded as 0.

Although a circuit section for creating an FM luminance signal is not shown in FIG. 1, this circuit section is constructed in the same manner as that in a conventional VTR.

Specifically, the control amplifier 6 is configured to increase the amplitude of the chroma signal output from the LPF 5 as the output voltage level of the adder 13 increases.

Therefore, the higher the output voltage level of the adder 13,
The mixing ratio of the chroma signal to the FM luminance signal in the adder 7 increases.

As mentioned above, the output voltage level of the adder 13 becomes higher when the video signal corresponding to the dark and dark parts of the image to be recorded is input to the BPFI. Therefore, the amplitude of the chroma signal applied from the control amplifier 6 to the adder 7 becomes larger when a darker color image and a darker image are recorded, and the mixing ratio of the chroma signal to the luminance signal in the adder 7 becomes larger.

As a result, chroma signals corresponding to dark parts and dark parts of the image are recorded at high levels on the magnetic tape 10. Therefore, the chroma signals in the dark and dark areas recorded on the magnetic tape 10 have better S/N ratios than in the past. Therefore, magnetic tape 1
According to the video signal reproduced from 0, better color display than before is performed in dark areas and dark areas during reproduction.

FIG. 2 is a circuit diagram showing an example of the configuration of the 3.58 MHz emphasizing amplifier 11 and the integrating circuit 12, and FIG. 3 is a circuit diagram showing a specific example of the configuration of the integrating circuit 16 and the DC amplifier 17. , FIG. 4 is a circuit diagram showing an example of the configuration of the control amplifier 6 and the adder 13.

The control amplifier 6 is a variable gain amplifier circuit that receives the output of the adder 13 as a control signal and changes its gain according to the level of this control signal. This is a variable gain amplifier circuit.

Referring to FIG. 2, the 3.58MHz emphasis amplifier 11 is as follows:
A parallel resonant circuit including an NPN transistor Q1 provided between a power supply Vcc and ground, an NPN transistor Q2 whose base receives the emitter output of the transistor Q1, an additional coil L and a capacitor C1 connected to the collector of the transistor Q2. including. The emitter of transistor Q1 is grounded via resistor R1. The emitter of transistor Q2 is grounded via resistor R4,
The collector of transistor Q2 is connected to power supply VCC through resistors R2 and R3. The parallel circuit is provided between the collector of the transistor Q2 and the connection point of the resistors R2 and R3, and has a resonant frequency of 3.58M.
Hz.

The chroma signal output from the ACC circuit 2 in FIG. 1 is applied to the transistor Q2 as the emitter output of the transistor Q1. The chroma signal given to transistor Q2 is converted to 3.58MH by the parallel resonant circuit.
The frequency component of z is amplified and taken out from the collector of transistor Q2. The collector output of the transistor Q2 is connected to the integrating circuit 1 via the coupling capacitor C2.
2 at the connection point of resistors R5 and R6.

Integrating circuit 12 includes resistors R5 and R6, an NPN transistor Q3 whose base receives a voltage at a connection point between these resistors, and a capacitor C3 provided between the emitter of transistor Q3 and ground. Transistor Q3 is
The emitter is grounded through a resistor R7, and the base is biased to about 0.7 V from the ground by a power supply voltage divided by resistors R5 and R6. Capacitor C
The chroma signal applied to the connection point via the transistor Q3 is rectified by the transistor Q3 to become a positive half-wave signal, which is output from the emitter of the transistor Q3.

The emitter output of transistor Q3 is integrated by capacitor C3, and after its alternating current component is cut off, it is input to adder 13 in FIG.

Referring to FIG. 3, the integration circuit 16 of FIG. 1 includes, for example, resistors R8, R
9 and a chemical capacitor C4. The luminance signal subjected to sync tip clamping by the clamp circuit 15 in FIG.
is integrated by a time constant circuit connected in series. The integrated output of the integrating circuit 16 is connected to the resistor R9 and the capacitor C4.
is taken out from the connection point of and input to the DC amplifier 17.

The DC amplifier 17 includes a PNP transistor Q4 whose base receives the voltage at the connection point, and an NPN transistor Q whose base receives the collector output of the transistor Q4.
5. Transistor Q4 is connected to power supply Vcc and ground via resistors R10 and R11, respectively, and transistor Q5 has its emitter grounded via resistor R12.

The collector current of transistor Q4 is
The lower the base voltage, the more it increases. Therefore, the integrated output of the integrating circuit 16 is inverted and amplified and output from the collector of the transistor Q4.

Therefore, the output level of the DC amplifier 17 becomes higher as the level of the luminance signal is lower. The output of the integrating circuit, which is inverted and amplified by transistor Q4, is transmitted to transistor Q5.
After being converted to a low impedance by , the signal is input to the adder 13 in FIG.

Referring to FIG. 4, the control amplifier 6 of FIG. 1 includes, for example, a coupling capacitor C5, a series connection of resistors R13 and R14, and
an NPN transistor Q6 whose gate receives the voltage at the connection point of the transistor Q6, an NPN transistor Q7 whose base receives the collector voltage of the transistor Q6, a coupling capacitor C6, and an NPN transistor whose base receives the output of the adder 13.
PN type transistor Q8.

For example, the adder 13 connects the output end (second
Resistors R19 and R20 are connected between the output terminal of the DC amplifier 17 (the emitter of the transistor Q3 in FIG. 3) and the output terminal of the DC amplifier 17 (the emitter of the transistor Q5 in FIG. 3).
consists of a series connection of The output of the integrating circuit 12 and the output of the DC amplifier 17 are connected to resistors R19 and R20.
are added at the connection point of and applied to the base of transistor Q8 in control amplifier 6.

In the control amplifier 6, the transistor Q6 is connected to the power supply Vcc and the ground through resistors R15 and R16, respectively, the emitter of the transistor Q7 is grounded through the resistor R7, and the emitter of the transistor Q6 and the emitter of the transistor Q8 are connected to each other through the resistor R18. connected via.

The low frequency converted chroma signal output from LPF5 in FIG. 1 is applied via capacitor C5 to the base of transistor Q6 biased by the power supply voltage divided by resistors R13 and R14. Transistor Q6 AC amplifies the chroma signal input to its base. The chroma signal amplified by transistor Q6 is applied to the base of transistor Q7 as the collector output of transistor Q6. Transistor Q7 is
Impedance conversion is performed on the chroma signal output from the collector of transistor Q6. The impedance-converted chroma signal is applied from the emitter of transistor Q7 to adder 7 in FIG. 1 via capacitor C6.

On the other hand, since the output of the adder 13 is input to the base of the transistor Q8, the higher the output voltage of the adder 13, the more
From the emitter of transistor Q8, resistors R18 and R
The alternating current flowing through Q16 to ground increases and tends to raise the emitter voltage of transistor Q6. In response, transistor Q6 operates to increase collector current and prevent changes in emitter voltage in order to hold the emitter voltage constant. Therefore, the higher the output voltage level of adder 13, the higher the collector output of transistor Q6. In other words, the higher the output voltage level of the integrating circuit 12 and the DC amplifier 17, the higher the output voltage level of the LPF 5.
The chroma signal from the FM luminance signal is amplified by a high amplification factor in the transistor Q6, and the mixing ratio of the chroma signal to the FM luminance signal in the adder 7 of FIG. 1 becomes high.

Note that in the above embodiment, two elements, namely, the amplitude of the chroma signal indicating the color density and the level of the luminance signal indicating the brightness of the image, are used to control the recording level of the chroma signal. However, by sending the control signal to the control amplifier 6 to only one of the outputs of the integrating circuit 12 and the DC amplifier 17, only one of the two elements controls the recording level of the chroma signal. It may be used for

If the recording level of the chroma signal is controlled only by the amplitude of the chroma signal, which indicates the density of the color, only the S/N ratio of the chroma signal in the dark part of the color can be improved, and the recording level of the chroma signal is controlled by the brightness. When controlled only by the signal level, only the S/N ratio of the chroma signal in dark parts of the image can be improved.

Therefore, if the recording system is configured as described above,
The color image quality of either dark or dark parts of the reproduced image is improved.

In the above embodiment, the luminance signal obtained using a trap circuit that removes the chroma signal component was used as the luminance signal used to detect the brightness (luminance level) of the image. A luminance signal obtained by separating YC from a video signal may be used.

In the above embodiment, the present invention is applied to a VTR that uses magnetic tape as a recording medium for recording, but it is also possible to apply the present invention to an image recording device that uses other recording media. be.

[Effects of the Invention] According to the present invention, it is possible to record an image including a dark portion or a darkly colored portion without deteriorating the S/N ratio of the chroma signal. Therefore, the color image quality of a reproduced image obtained from a recording medium recorded by the image recording apparatus according to the present invention is improved compared to the conventional one.

[Brief explanation of drawings]

FIG. 1 is a schematic block diagram showing the recording system of a home VTR according to an embodiment of the present invention, and FIG. 2 is a 3,58M
A circuit diagram showing a specific example of the configuration of the Hz emphasizing amplifier 11 and the integrating circuit 12, FIG. 3 is the integrating circuit 16 in FIG.
and a circuit diagram showing an example of the configuration of the DC amplifier 17,
FIG. 4 is a circuit diagram showing an example of the configuration of the control amplifier 6 and adder 13 in FIG. 1, and FIG.
A diagram showing the output signal waveform of the clamp circuit 15 in the figure,
FIG. 6 is a schematic block diagram showing the configuration of a recording system of a conventional home VTR. In the figure, 1 is a BPF, 2 is an ACC circuit, 3 is a converter, 4 is a burst emphasis circuit, 5 is an LPF, and 6
1 is a control amplifier, 7 and 13 are adders, 8 is a recording amplifier, 9 is a head, 10 is a magnetic tape, 11 is 3.
58MHz emphasis amplifier, 12 and 16 are integrating circuits, 1
4 is a 3.58 MHz) wrap circuit, 15 is a clamp circuit, and 17 is a DC amplifier. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (3)

[Claims] (1) An image recording device that records an image on a recording medium as a video signal including a chroma signal and a luminance signal, comprising: amplitude detection means for detecting the amplitude of the chroma signal; and based on the detection output of the amplitude detection means. An image recording apparatus comprising: means for controlling the amplitude of the chroma signal; and means for mixing the chroma signal whose amplitude has been controlled by the control means with the luminance signal and recording the mixture on the recording medium. (2) An image recording device that records an image on a recording medium as a video signal including a chroma signal and a luminance signal, comprising: a level detection means for detecting the level of the luminance signal; and a detection output of the level detection means. An image comprising: means for controlling the amplitude of the chroma signal; and means for mixing the chroma signal whose amplitude has been controlled by the control means with the luminance signal and recording it on the recording medium. Recording device. (3) An image recording device that records an image on a recording medium as a video signal including a chroma signal and a luminance signal, comprising: first detection means for detecting the amplitude of the chroma signal; and detecting the level of the luminance signal. a second detection means for controlling the amplitude of the chroma signal based on a detection output of the first detection means and a detection output of the second detection means; and a means for controlling the amplitude of the chroma signal by the control means. An image recording apparatus comprising: a means for mixing the chroma signal and the luminance signal and recording the mixture on the recording medium.