JPH026709Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a circuit for monitoring a video signal in an apparatus for recording, for example, a television signal on paper using a heat-sensitive dye sublimation type photosensitive material to obtain a so-called hard copy.

As a device for obtaining hard copies as mentioned above,
For example, the one shown in FIG. 1 has been proposed. In the figure, 1 is an input terminal to which, for example, a video signal of a still image is repeatedly supplied. Note that, for example, a color video signal of the NTSC system is supplied to the input terminal 1a, and this signal is supplied to the decoder 2 to form red, green, blue, and black video signals. In addition, the input terminals 1r, 1g, and 1b are red and
Green and blue video signals are supplied, and these signals are supplied to a forming circuit 3 to form a black video signal. These video signals are supplied to the multiplexer 4, and one of the red, green, blue, and black video signals is taken out.

These video signals are supplied to a switch circuit 5 and are sequentially extracted, for example, every vertical period, and the extracted signals are supplied to an edge enhancement circuit 6. The signal from this emphasis circuit 6 is supplied to a switch circuit 7, and the above-mentioned four video signals are respectively taken out. These signals are each supplied to the gamma correction circuit 8, and gamma correction is performed in accordance with the printing characteristics of the hard copy. These corrected signals are each supplied to the adjustment circuit 9, where arbitrary adjustments are made.

These adjusted video signals are sent to switch circuit 1.
0 and sequentially taken out every vertical period as described above. This extracted signal is supplied to a sample and hold circuit 12 through a correction circuit 11 depending on the thermal inertia of the head and the like.

In this sample and hold circuit 12, the circuit is driven at a predetermined delay timing from a horizontal synchronizing signal for each horizontal scanning line, so that, for example, as shown in FIG. 2, signals on a straight line in the vertical direction of the screen are sequentially sampled. will be held. This sampled and held signal is supplied to the AD conversion circuit 14 through the amplifier 13, and the obtained digital data is sequentially stored in the memory 15.

The data stored in this memory 15 is sequentially read out and supplied to the PWM circuit 16 to form a
PWM signals are applied to latch circuits 17 equal to the number of horizontal scan lines. And these latch circuits 1
During the period when the output of 7 is "1", the head 18 corresponding to each horizontal scanning line is driven.

Furthermore, the head 18 is moved horizontally by a predetermined amount every predetermined printing period, and the timing of driving the sample and hold circuit 12 is changed in accordance with this feed. The contents of the memory 15 are then updated, and this is sequentially performed to print the still image supplied to the input terminal 1.

Note that the colors to be printed are cyan, magenta, and yellow, but these are complementary colors to red, green, and blue, respectively, and by driving the heads 18 in opposite phases, printing in the above colors can be performed. can.

In such an apparatus, adjustments can be made to obtain a good hard copy by, for example, changing the density range, tone, and hue of the printed image.

As a circuit for this purpose, the inventor of the present application previously proposed the following circuit.

In other words, FIG. 3 mainly corresponds to the adjustment circuit 9 in FIG. 1, and originally there are four systems: cyan (red), magenta (green), yellow (blue), and black, but here Only one strain is shown. Note that all four systems are equivalent circuits.

In the figure, a video signal from a γ correction circuit 8 is supplied to a mixing circuit 22 through an amplifier 21. Further, the horizontal synchronizing signal HD is supplied to the pulse forming circuit 23, and a pulse signal corresponding to the white level is formed at a predetermined timing within the horizontal blanking period.
This pulse signal is supplied to a mixing circuit 22 and mixed into a video signal. This mixed signal is supplied to a clamp circuit 25 through an amplifier 24. Furthermore, the horizontal synchronizing signal HD is supplied to the clamp pulse forming circuit 26 to form a clamp pulse during the period of the above-mentioned pulse signal, and this clamp pulse is supplied to the clamp circuit 25 to clamp the white level to a predetermined value. This clamped signal is then supplied to the switch circuit 10. In addition, 8R, 21
R, 23R, 24R, and 25R are variable resistors for adjusting each circuit.

In this circuit, when the variable resistor 8R is adjusted, γ of the video signal is adjusted, and the tone of the screen is adjusted.

Further, by adjusting the variable resistor 21R, the white level of the video signal is adjusted. If the gain of the amplifier 21 is changed here, the video signal is changed as shown in FIGS. 4A and 4B, for example. On the other hand, the pulse signal from the forming circuit 23 is mixed at a predetermined pulse height during the blanking period. Since this mixed signal is clamped by the clamp circuit 25, the level (pedestal level) during the blanking period remains unchanged, and only the white level of the video signal is adjusted.

On the other hand, when the variable resistor 24R is adjusted, the black level of the video signal is adjusted. If the gain of the amplifier 24 is changed here, the video signal is changed as shown in FIGS. 5A and 5B, for example. At this time, the pulse height of the pulse signal mixed during the blanking period is also changed at the same time. This signal is then clamped by the clamp circuit 25, so that the white level of the video signal remains unchanged and only the pedestal level (black level) is adjusted.

Further, by adjusting the variable resistors 23R and 25R, the DC level of the signal can be arbitrarily adjusted.

By adjusting these white level, black level, and DC level, the density range of the screen can be adjusted.

Furthermore, after completing the above concentration range adjustment,
There may be cases where it is desired to adjust γ again. In this case, adjusting γ generally changes the signal level.
However, since this change in level can be considered equivalent to a change in the gain of the amplifier 21, it can be corrected by readjusting the variable resistor 21R for adjusting the white level in the circuit described above.

Further, by arbitrarily performing the above-mentioned adjustment for each of the four systems, the hue can be adjusted.

By the way, in such a device, there is a demand for monitoring the adjusted video signal when performing the above-mentioned adjustment. In that case, for example, it is conceivable to take out the output signal of the switch circuit 10 and supply it to a monitor receiver.

However, in this case, the density range of printing is narrow, and the density range of a monitor receiver is generally wider. For this reason, even if the image is displayed normally on the monitor screen, when it is printed, the narrow density range of the print may cause so-called washed-out whites or washed-out blacks.

In view of these points, the present invention is designed to enable display equivalent to printing on a monitor receiver. An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 6, a video signal from a switch circuit 10 is supplied through a γ correction circuit 31 to a limiter circuit 32 that regulates the maximum level of the signal, and a signal from this limiter circuit 32 is supplied to a limiter circuit 33 that regulates the minimum level of the signal. through mixing circuit 34
supplied to Further, a composite synchronization signal of the video signal is supplied to the mixing circuit 34 through the amplifier 35. This mixed signal is then supplied to a monitor receiver 37 through an amplifier 36. Note that 31R, 32R, 3
3R, 35R, and 36R are variable resistors for adjusting each circuit.

In this circuit, the correction amount of the γ correction circuit 31 is adjusted so as to inversely correct the correction amount of the above-mentioned γ correction circuit 8. Note that in this case, the correction amount is a value that does not include the correction amount in the explanation of FIG. 3 above.

Further, the restriction level of the limiter circuit 32 is adjusted so as to match the white level of the print density range. Furthermore, the restriction level of the limiter circuit 33 is adjusted so as to match the black level of the print density range.

Therefore, in the video signal from the switch circuit 10, the gamma of the print is reversely corrected, and the white level and black level are further regulated in accordance with the density range of the print. A composite synchronizing signal is mixed with this regulated signal at a predetermined level, and this mixed signal is made to a predetermined level by an amplifier 36 and is supplied to a monitor receiver 37.

In this way, the video signal is supplied to the monitor receiver, but according to the present invention, the level of the video signal is regulated according to the density range of printing, so if it exceeds this level due to adjustment etc. The display looks similar to crushed whites and crushed blacks on the screen. Therefore, by making adjustments while looking at this monitor screen, it is possible to reliably know the occurrence of crushed whites and crushed shadows, and to easily make desired print adjustments.

Furthermore, there is no need to prepare a specially adjusted monitor receiver, and monitoring can be performed with a normal receiver.

[Brief explanation of the drawing]

1 to 5 are diagrams for explaining an example of a printing device, and FIG. 6 is a configuration diagram of an example of the present invention. 31 is a gamma correction circuit, 32 and 33 are limiter circuits, 35 and 36 are amplifiers, and 37 is a monitor receiver.

Claims (1)

[Scope of utility model registration request] It has a circuit that performs gamma correction and white level and black level adjustment of the input video signal, and when visually recording the above-mentioned corrected and adjusted signal on paper, the above-mentioned corrected and adjusted signal is A monitor circuit of a recording device configured to output as a monitor output via a white level regulation circuit, a black level regulation circuit, and a γ inverse correction circuit corresponding to the density range.