JP2649604B2 - Image quality detection circuit and video printer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an image quality detection circuit suitable for detecting an image state such as light (white) or dark (black) in a VTR or the like, and this image quality detection. The present 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 input to the analog signal processing circuit 1.
The signal is decoded into R, G, and B color signals, A / D converted by the A / D converter 2 in synchronization with the clock from the memory control circuit 4, written into the image memory 3, and further transmitted from the image memory 3. It is read out and given to the print processing circuit 5. In the printing processing circuit 5, each color signal data of R, G, B is Ye
The image data is converted into complementary color data of (yellow), Mg (magenta), and Cy (cyan), and based on the complementary color data, the energization of the thermal head 6 is controlled to perform printing processing. Incidentally, 7 ₀ control circuit for controlling each section, 8 is a power supply circuit for supplying power to the thermal head 6 and each section.

<Problems to be Solved by the Invention> In such a conventional video printer, the state of the image quality cannot be automatically detected, and when the input image quality is low (white), or conversely, the input image quality is high. For example, when the image is dark (blackish), the user changes the contrast / brightness correction volume 20 so that the analog signal processing circuit 1 adjusts the amplitude and level of the input video signal to correct the image quality density. ing.

However, it is very complicated for the user to manually correct the print density in accordance with the input image quality, and it is convenient if the print density can be automatically corrected.

The present invention has been made in view of the above points,
To be able to automatically detect the state of the input image quality such as light (white) or dark (dark), and to automatically correct the print density to the optimal state according to the change of the input image quality With the goal.

<Means for Solving the Problems> In order to achieve the above 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 B color signal data, and a highest-order data bit of the generated luminance signal data. And a counter for counting the number of images, and the image quality is detected based on the counted value.

Further, the video printer of the present invention includes an image memory for storing digitized R, G, B color signal data, and energizes the thermal head based on the color signal data read from the image memory. By controlling the
2. An image quality detection circuit according to claim 1, wherein the image quality is detected based on color signal data stored in an image memory. A print density correction means for correcting the print density by controlling the head voltage of the thermal head or by adding or subtracting color signal data stored in the image memory.

<Operation> The image quality detection circuit having the above configuration can automatically detect the state of the input image quality such as faint (white) or dark (dark).

Further, in the video printer having the above configuration, since the image quality state is detected based on the color signal data stored in the image memory and the print density is corrected, the user can adjust the contrast as in the conventional example. / The operation of variably adjusting the brightness correction volume is not required.

<Example> Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention, and portions corresponding to the conventional example of FIG. 4 are denoted by the same reference numerals.

In FIG. 1, reference numeral 1 denotes an analog signal processing circuit for performing predetermined signal processing such as decoding an input video signal into R, G, and B color signals and separating a synchronization signal; and 2, an R, G, and B color signal. A / D converter that performs A / D conversion in synchronization with the clock
An image memory for storing A / D converted color signal data,
Reference numeral 4 denotes a memory control circuit that controls writing and reading to and from the image memory 3, and 5 denotes each color signal data read from the image memory 3 by Ye (yellow), Mg (magenta), and Cy.
A printing processing circuit that converts the data into complementary color data of (cyan) and controls the energization of the thermal head 6 based on the complementary color data to perform printing processing.

The print processing circuit 5 outputs the serial data signal, clock signal, latch signal and strobe signal shown in FIG. 2 to the thermal head 6, and the thermal head 6 including the shift register And the current is supplied for a period when the strobe signal is at a low level.

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

In this embodiment, in order to automatically correct the density of a print in accordance with the input image quality such as light (white) or dark (dark), the image memory 3 is used.
Based on each color signal data of R, G, B stored in
An image quality detection circuit 9 for detecting an image quality state is provided,
The control circuit 7 has a function as a print density correction unit that corrects 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 light (white) or dark (dark), and R, R, and R for one screen read from the image memory 3. Matrix circuit 10 for converting G and B color signal data into luminance signal (Y) data
And an 18-bit counter circuit 11 for counting the most significant bit (MSB) data of the luminance signal data from the matrix circuit 10.

In this embodiment, the image memory 3 stores 480 (V) × 512
(H) × 8 bits, so that the counter circuit 11
, 480 × 512 bit data is input.

For example, when the entire screen is white, the bit data are all “1”, so the output of the counter circuit 11 is 480 × 512 = 245760 (18-bit data), and the entire screen is black. In some cases, the output of the counter circuit 11 is 0 because the bit data are all “0”.

In other words, the count value of the counter circuit 11 corresponds to the image quality state of the color signal data for one screen stored in the image memory 3, that is, the state of light (white) or dark (black). .

Top 8 of 18-bit detection data of this counter circuit 11
The bits are supplied to a control circuit 7 having a function as a print density correction unit.

The control circuit 7 as the print density correcting means compares the 8-bit detection data A of the image quality detection circuit 9 with a plurality of preset values B _{1 to} Bn, and detects the detection data A. to determine in which region of a plurality of regions defined by the value B ₁ to Bn, to correct the printing density corresponding to the region.

That is, it is determined which of A <B ₁ , B ₁ ≦ A <B ₂ , B ₂ ≦ A <B ₃ ,..., Bn ≦ A is satisfied, and the print density is corrected as described later. It is.

In this embodiment, since the detection data has the above-mentioned 8 bits, the printing density can be corrected by determining a maximum of 240 (= 245760/1024) areas.

The correction of the print density by the control circuit 7 is performed as follows by correcting the power supply time to the thermal head 6. That is, the detection data A of 8 bits of the image quality detection circuit 9 is, for example, a middle area (120-th area) of the 240 areas defined by the plurality of set values B _{1 to} Bn as described above. Area), the input image quality is
This is a standard state that is neither whitish nor blackish. In this case, the conventional energization time, for example, 3 msec (lowest density) to 20 msec (highest density) is maintained, and a region larger than the middle (for example, Area)
The input image quality is whitish. In this case, the energization time is long, for example, 6 msec (lowest density) to 40 msec (highest density), and conversely, an area smaller than the center (for example,
(First area), the input image quality is dark, and in this case, the power-on time is short, for example,
1.5 msec (lowest concentration) to 10 msec (highest concentration).

As described above, the control circuit 7 as the print density correction unit includes:
The energization time of the thermal head 6 is corrected by controlling the printing processing circuit 5 in accordance with the value of the detection data of the image quality detection circuit 9, whereby the user can adjust the contrast / brightness correction volume as in the prior art. Without adjusting the print quality, printing is performed at an optimum print density according to the input image quality.

In this embodiment, the control circuit 7 as the printing density correction means corrects the power-on time according to the detection data. However, as another embodiment of the present invention, the control circuit 7 controls the power supply circuit 8 without correcting the power-on time. Then, the head voltage to the thermal head 6 may be corrected.

That is, the conventional head voltage is constant, for example, 14.2 V when the resistance value of the resistor is 940Ω, but this head voltage is changed to, for example, 7.1 V or more according to the detection data of the image quality detection circuit 9.
The print density may be corrected in a range of 21.3V.

As described above, when the print density is corrected by correcting the energizing time of the thermal head 6 or the head voltage to the thermal head 6, the analog signal processing circuit 1
In this case, the gradation is not impaired as in the case of correcting the density of image quality by adjusting the amplitude and level of an input video signal.

FIG. 3 is a block diagram of another embodiment of the present invention;
Parts corresponding to the embodiment of FIG. 1 are denoted by the same reference numerals.

In the above-described embodiment, the print density is corrected by correcting the energization time or the head voltage based on the detection data of the image quality detection circuit 9. Instead of correcting the voltage, the color signal data itself of the image memory 3 is corrected,
Printing is performed based on the corrected color signal data.

That is, print density correction means 15, the control circuit 7 consists of _one and the data conversion circuit 12. The control circuit ₇₁ includes a data conversion circuit 12 reads the conversion data corresponding to detection data from the built-in look-up table memory And the data conversion circuit 12 converts the color signal data from the image memory 3 into
The conversion data is added or subtracted and output as corrected color signal data to the printing processing circuit 5, and the D / A converter 1
Output to 3.

For example, when the input image quality is whitish, the print density correction means 15 subtracts the conversion data from the data in the image memory 3 based on the detection data of the image quality detection circuit 9, and conversely,
When the input image quality is dark, conversion data is added to the data in the image memory 3.

As described above, in the print density correction means 15, the image quality detection circuit 9
The color signal data in the image memory 3 is corrected by adding or subtracting the conversion data according to the value of the detection data of
The printing is performed at the optimum printing density according to the input image quality without the user adjusting the contrast / brightness correction volume as in the related art.

In addition, in this embodiment, since the color signal data itself in the image memory 3 is corrected, the corrected image can be confirmed on a monitor without printing.

In FIG. 3, reference numeral 14 denotes an encoder circuit which demodulates the color signal D / A converted by the D / A converter 13 into a video signal and outputs the video signal to a monitor.

 Other configurations are the same as those in the above embodiment.

As still another embodiment of the present invention, the print density correction means automatically adjusts the amplitude and level of the input video signal in the analog signal processing circuit 1 based on the detection data of the image quality detection circuit 9 in the same manner as the contrast / brightness correction. You may be comprised so that it may adjust dynamically.

In the above-described embodiment, the image quality detecting circuit 9 detects the image quality based on the color signal data for one screen. However, as another embodiment of the present invention, the color of a specific area in one screen is The image quality may be detected based on the signal data.

In the above-described embodiment, the video printer including the image quality detection circuit 9 has been described. It is needless to say that the present invention can be applied to the case of detection.

<Effect 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 faint (white) or dark (dark).

Further, according to the video printer of the present invention, since the image quality state is detected based on the color signal data stored in the image memory and the print density is corrected, as in the conventional example, Without performing operations such as variably adjusting the contrast / brightness adjustment volume,
The print density is automatically adjusted to the optimal print density.

[Brief description of the drawings]

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)

(57) [Claims] 1. A matrix circuit for generating luminance signal data based on digitized R, G, B color signal data, and a counter for counting the most significant data bits of the generated luminance signal data. And an image quality detecting circuit for detecting the image quality based on the count value. 2. An apparatus according to claim 1, further comprising an image memory storing digitized R, G, B color signal data, and controlling energization of the thermal head based on the color signal data read from the image memory. A video printer for performing printing on a recording sheet, wherein the image quality is detected based on color signal data stored in an image memory; A print density correcting means for correcting the print density by controlling the head voltage of the thermal head based on the output. 3. An image memory for storing digitized R, G, B color signal data, and controlling energization of a thermal head based on the color signal data read from the image memory. A video printer for performing printing on a recording sheet, wherein the image quality is detected based on color signal data stored in an image memory; A print density correction means for correcting the print density by performing addition and subtraction on the color signal data stored in the 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.