JPH04140993A - Picture quality detection circuit and video printer - Google Patents

Abstract

PURPOSE:To correct print density by automatically detecting the state of input picture quality such as light or deep by a picture quality detection circuit. CONSTITUTION:The picture quality detection circuit 9 is to detect the picture quality state of an input video signal i.e., the state of the input picture quality such as light or deep, and it is comprised of a matrix circuit 10 which converts chrominance signal data of R, G, and B of one picture read out of image memory 3 to luminance signal (Y) data, and a counter circuit 11 which counts the data of the most significant bit in luminance signal data from the matrix circuit 10. A control circuit 7 as a print density correction means compares the detection data A of eight bits of the picture quality detection circuit 9 with plural preset values B1-Bn set in advance, and it is discriminated whether or not the detection data A satisfies either A<B1, B1<=A<B2, B2<=A<B3,...Bn<=A, and the print density is corrected. In such a way, the energizing time of a thermal head is corrected by controlling a print processing circuit 5, thereby, print is performed with the optimum print density.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to an image quality detection circuit suitable for detecting image quality conditions such as thin (whitish) or dark (blackish) in VTRs and the like, and to the image quality detection circuit. This invention relates to a video printer using a circuit.

<Prior Art> FIG. 4 is a block diagram of a conventional color video printer.

The input video signal is processed by R in the analog signal processing circuit l.
, G, and H color signals and A/D converter 2 synchronizes with the clock from memory control circuit 4.
The image is converted into D, written into the image memory 3, and further read out from the image memory 3 and given to the print processing circuit 5. In this printing processing circuit 5, the R, G, and B color signal data are Ye (yellow), Mg (magenta), and Cy.
Based on this complementary color data, the energization of the thermal head 6 is controlled and printing processing is performed. In addition, 7o is a control circuit that controls each part,
8 is a power supply circuit that supplies power to the thermal head 6 and various parts.

<Problems to be Solved by the Invention> Such conventional video printers are unable to automatically detect the state of the image quality, and when the input image quality is pale (whitish) or, conversely, the input image quality is dark. (darkness), the user can correct the density of the image quality by adjusting the amplitude and level of the input video signal in the analog signal processing circuit 1 by varying the contrast/brightness correction volume 20. ing.

However, it is very complicated for the user to manually correct the print density according to the input image quality, and it would be convenient if the print density could be corrected automatically.

The present invention has been made in view of the above-mentioned points, and allows automatic detection of input image quality conditions such as light (whitish) or dark (blackish) conditions, and furthermore, allows for automatic detection of input image quality conditions such as thin (whitish) or dark (blackish) conditions. The purpose of this invention is to automatically correct the print density to the optimum state according to the situation.

<Means for Solving the Problems> In order to achieve the above-mentioned object, the present invention is configured as follows.

That is, the image quality detection circuit of the present invention includes a matrix circuit that generates luminance signal data based on digitized R, G, and H color signal data, and a matrix circuit that generates required data bits of the generated luminance signal data. It is equipped with a counter for counting, and the image quality is detected based on the counted value.

Furthermore, the video printer of the present invention includes an image memory in which digitized R, G, and H color signal data is stored, and the thermal head is energized based on the color signal data read from the image memory. By controlling the
The image quality detection circuit according to claim 1, which performs printing on recording paper and detects the image quality based on color signal data stored in an image memory, and the detection output of the image quality detection circuit. A print density correction means for correcting the print density based on the print density is provided.

Effect> The image quality detection circuit having the above configuration can automatically detect the state of the input image quality such as light (whitish) or dark (blackish).

In addition, the video printer with the above configuration detects the image quality state based on the color signal data stored in the image memory and corrects the print density. / No need to perform operations such as variable adjustment of bright correction polyurethane.

<Examples> Examples of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention, and FIG.
Portions corresponding to the conventional example in the figures are given the same reference numerals.

In the figure, 1 is an analog signal processing circuit that performs predetermined signal processing such as decoding an input video signal into R, G, and H color signals and separating synchronization signals, and 2 is an R, G, and B color signal processing circuit.
An A/D that converts each color signal into A/D in synchronization with the clock.
Converter, 3 is an image memory in which A/D converted color signal data is stored, 4 is a memory control circuit that controls writing to and reading from the image memory 3, 5 is each color signal read out from the image memory 3 Data, Ye (yellow), M
This is a printing processing circuit that converts the data into complementary color data of g (magenta) and Cy (cyan) and controls the energization of the thermal head 6 based on this complementary color data to perform printing processing.

The print processing circuit 5 outputs a serial data signal, a clock signal, a latch signal, and a strobe signal shown in FIG. is latched and energized during the period when the strobe signal is at a low level.

Reference numeral 7 denotes a control circuit for controlling each part, and 8 a power supply circuit for supplying power to the thermal head 6 and each part.The above configuration is basically the same as that of the conventional example.

In this example, light (whitish) or dark (white)
In order to automatically correct the printing density according to the input image quality (blackish), the correction is made based on the R, G, and B color signal data stored in the image memory 3.
In addition to providing an image quality detection circuit 9 for detecting the image quality state,
The control circuit 7 has a function as a print density correction means for correcting the print density by correcting the energization time based on the detection output of the image quality detection circuit 9.

The image quality detection circuit 9 detects the image quality state of the input video signal, that is, the state of the input image quality such as thin (whitish) or dark (blackish). A matrix circuit 10 that converts G and H color signal data into luminance signal (Y) data, and an 18-bit counter circuit that counts the most significant bit (MSB) of the luminance signal data from this matrix circuit 10. Consists of 1.

In this embodiment, the image memory 3 is 480 (V) x 51
2(H)×3 bits, therefore, 480×512 bits of data are input to the counter circuit 11.

For example, when the entire screen is white, all bit data are "1", so the output of the counter circuit 11 is 480x512=245760 (18 pit data).
Furthermore, when the entire screen is black, all the bit data are "0", so the output of the counter circuit 11 is "0".

In other words, the count value of the counter circuit 11 corresponds to the image quality state of one screen's worth of color signal data stored in the image memory 3, i.e., light (whitish) or dark (blackish) state. .

The upper eight bits of the 18-bit detection data of this counter circuit 11 are given to a control circuit 7 having a function as print density correction means.

The control circuit 7 serving as a print density correction means compares the 8-bit detection data A of the image quality detection circuit 9 with a plurality of preset setting values B and -Bn, and detects the detection data A according to the plurality of setting values. It is determined in which region of a plurality of regions defined by the value B l - B n the print density is corrected corresponding to that region.

That is, A < B + , B l ≦ A < B t , B
It is determined which of t≦A<Bs, . . . Bn≦A is satisfied, and the print density is corrected as described below.

In this embodiment, since the detection data is the upper 8 bits, it is possible to discriminate a maximum of 240 (=245760/1024) areas and correct the print density.

Correction of printing density by the control circuit 7 is performed by the thermal head 6.
This is done as follows by correcting the energization time. That is, the 8-bit detection data A of the image quality detection circuit 9 is detected, for example, in the middle region (120th area), the input image quality is in a standard state, neither whitish nor blackish, and in this case, the conventional power supply time, e.g.
c (lowest density) to 20m5ec (highest density), and when the area is larger than the middle (for example, the 240th area), the input image quality becomes whitish,
In this case, the energization time should be longer, for example, 6 m5ec (
(lowest density) to 4oIIlsec (highest density), and conversely, when the area is smaller than the middle (for example, the first area), the input image quality becomes blackish. , 1.5m5ec (lowest concentration) to 10m5ec (highest concentration).

In this way, the control circuit 7 as a print density correction means corrects the energization time of the thermal hept 6 by controlling the print processing circuit 5 according to the value of the detection data of the image quality detection circuit 9. The image is printed at the optimum print density according to the input image quality without the user having to adjust the volume for contrast/brightness correction as in the past.

In this embodiment, the control circuit 7 serves as a print density correction means.
Although the energization time was corrected according to the detection data,
As another embodiment of the present invention, the head voltage applied to the thermal head 6 may be corrected by controlling the power supply circuit 8 without correcting the energization time.

That is, the conventional head voltage is either constant, for example, 14.2V when the resistance value of the resistor is 940Ω, or the head voltage is changed according to the detection data of the image quality detection circuit 9, for example.
The print density may be corrected by varying it within the range of 7.1V to 21.3V.

In this way, when the print density is corrected by correcting the energization time of the thermal head 6 or the head voltage to the thermal head 6, the analog signal processing circuit l adjusts the amplitude and level of the input video signal to improve the image quality. It does not impair gradation, unlike those that correct the density.

FIG. 3 is a block diagram of another embodiment of the present invention, and parts corresponding to the embodiment of FIG. 1 are given the same reference numerals.

In the embodiment described above, the print density was corrected by correcting the energization time or head voltage based on the detection data of the image quality detection circuit 9. However, the print density correction means 15 of this embodiment corrects the energization time or the head voltage. Rather than correcting the voltage, the color signal data itself in the image memory 3 is corrected,
The printer is configured to perform printing based on this corrected color signal data.

That is, the print density correction means 15 consists of a control circuit 7 and a data conversion circuit 12, and the control circuit 7I reads conversion data corresponding to the detected data from the built-in lookup table memory and sends it to the data conversion circuit I2. The data conversion circuit 12 adds or subtracts the conversion data to the color signal data from the image memory 3 and outputs it as corrected color signal data to the print processing circuit 5.
Output to D/A converter 13.

For example, when the input image quality is whitish, the image quality detection circuit 9
Based on the detected data, the printing density correction means 15 subtracts the conversion data from the data in the image memory 3, and conversely,
When the input image quality is blackish, conversion data is added to the data in the image memory 3.

In this way, in the print density correction means I5, the image quality detection circuit 9
The color signal data in the image memory 3 is corrected by adding or subtracting conversion data according to the value of the detected data.
Prints can be printed at the optimum print density according to the input image quality without the user having to adjust the volume for contrast/brightness correction as in the past.

Moreover, in this embodiment, since the color signal data itself in the image memory 3 is corrected, the corrected image can be checked on a monitor without being printed.

In addition, in FIG. 3, 14 is a D/A converter 13.
This is an encoder circuit that demodulates the A-converted color signal into a video signal and outputs it to a monitor.

The other configurations are the same as those in the above embodiment.

As yet another embodiment of the present invention, the print density correction means performs the same contrast/bright correction in the analog signal processing circuit 1 based on the detection data of the image quality detection circuit 9.
It may be configured to automatically adjust the amplitude and level of the input video signal.

In the embodiment described above, the image quality detection circuit 9 detects the image quality based on the color signal data for one screen, but as another embodiment of the present invention, Image quality may be detected based on signal data.

Although the above embodiment describes a video printer equipped with an image quality detection circuit 9, the image quality detection circuit 9 of the present invention is not limited to a video printer, and can be used to improve image quality of other video equipment, such as an electronic still camera. Of course, it can also be applied to detection.

<Effects of the Invention> As described above, according to the image quality detection circuit of the present invention, it is possible to automatically detect the state of the input image quality such as thin (whitish) or dark (blackish).

Further, according to the video printer of the present invention, the image quality state is detected based on the color signal data stored in the image memory and the printing density is corrected, so that the user can The optimum printing density is automatically adjusted without the need for variable adjustment of contrast/brightness correction polyurethane.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of the present invention, FIG. 2 is a timing chart, FIG. 3 is a block diagram of another embodiment of the present invention, and FIG. 4 is a block diagram of a conventional example. 2... A/D converter, 3... Image memory, 6... Thermal head, 9... Image quality detection circuit, 7... Control circuit (print density correction means), 15... Print density Correction means.

Claims (3)

[Claims] (1) Comprising a matrix circuit that generates luminance signal data based on digitized R, G, and B color signal data, and a counter that counts required data bits of the generated luminance signal data, An image quality detection circuit characterized by detecting image quality based on the counted value. (2) An image memory is provided in which digitized R, G, and B color signal data is stored, and energization of the thermal head is controlled based on the color signal data read from the image memory. A video printer that prints on recording paper, the image quality detection circuit according to claim 1, which detects image quality based on color signal data stored in an image memory, and the detection of this image quality detection circuit. 1. A video printer comprising: a printing density correcting means for correcting printing density by controlling at least one of head voltage and energization time of the thermal head based on the output. (3) An image memory is provided in which digitized R, G, and B color signal data is stored, and energization of the thermal head is controlled based on the color signal data read from the image memory. A video printer that prints on recording paper, the image quality detection circuit according to claim 1, which detects image quality based on color signal data stored in an image memory, and the detection of this image quality detection circuit. A print density correction means for correcting print density by converting color signal data stored in an image memory based on the output; and a monitor means for displaying a screen on which the print density has been corrected. A video printer characterized by: