JPH05347768A - Video printer - Google Patents

Abstract

PURPOSE:To automatically adjust a sampling frequency (the number of sampling) even for a video signal with any kind of specification when it is converted to a digital signal. CONSTITUTION:A digital video signal written on image memory 2 is read out, and the number of moires generated in the video signal is counted by a moire counter part 10, and the number of sampling outputted from a clock control part 12 is fitted in the number of picture elements of one horizontal scanning line of an inputted video signal based on the number of moires.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video printer which prints out an input video signal on paper.

[0002]

2. Description of the Related Art There is a video printer as a device for printing out an image displayed on a screen of a computer monitor or a television as an image as it is on paper. Figure 7
It is a block diagram which shows the structure of the conventional video printer.
Reference numeral 1 is an A / D converter for converting an input analog video signal into a digital signal, 2 is an image memory for storing the video signal from the A / D converter 1, and 3 is an image memory 2. A color conversion unit for converting the color of the image signal into a color for printing, 4 is a printing unit for printing an image on paper or the like according to the image signal color-converted by the color conversion unit 3, and 5 is from the A / D conversion unit 1. D / A converter for converting the signal of A into an analog signal, 6 is A
A clock generator that generates a clock signal that determines the sampling number (sampling frequency) of the D / A converter 1 and the D / A unit 5, and a clock adjuster 7 that adjusts the frequency of the clock signal generated by the clock generator 6. .. In addition, 8 is
A computer which is a signal source of the video signal, and 9 is a monitor which projects the video signal converted into the analog signal by the D / A conversion unit 5.

The video signal output from the computer 8 is first converted into a digital signal by the A / D converter 1 and stored in the image memory 2, and this signal is stored in the color converter 3.
The color is converted with. The color of the video signal stored in the image memory 2 is composed of the three primary colors of light: red, green, and blue. To print the video signal on paper and reproduce those colors, You have to replace it with cyan, magenta, and yellow configurations. The video signal color-converted by the color conversion unit 3 is output to the printing unit 4, and the printing unit 4 prints the video on paper or the like according to the input video signal.

Here, since the initial setting of the sampling number by the clock signal output from the clock generator 6 is set to the number of pixels for one horizontal scanning line of the video signal from the computer 8, the horizontal scanning with the computer 8 is performed. When this video printer receives a video signal from a computer in which the number of pixels for one line is different, moire (interference fringes) occur in the video signal converted into a digital signal by the A / D converter 1. If this is left as it is, an image with moire will be printed, so this image signal should be monitored by the monitor 9 before printing.
Copy to and adjust to eliminate moire. When processing a video signal with a number of pixels different from the initial setting, first
The computer outputs a video signal for displaying a checkered pattern or the letter "H" on the entire screen of the monitor 9 as a test video signal. In the video printer, the A / D converter 1
The video signal converted into a digital signal by the above is converted into an analog signal by a D / A converter, and an image composed of the checkered pattern or the character “H” is displayed on the monitor 9. Since a moire image is displayed on the monitor 9, the operator operates the clock adjusting section 7 to change the frequency of the clock signal generated by the clock generating section 6 so as to eliminate the moire, and this video printer is operated. The number of pixels for one horizontal scanning line of the video signal input to is adjusted.

[0005]

Since the conventional video printer is constructed as described above, it is necessary to adjust the sampling frequency when processing a video signal having a pixel number which does not match the sampling number. , I needed a monitor for that. Also, if the resolution of the image of the image signal to be processed is 640 pixels horizontally and 400 pixels vertically, it does not exceed the capability of the monitor to output it.
It is easy to check the state of eliminating moire on the monitor, but if the image of the image signal to be processed has high resolution such as horizontal 1920 pixels and vertical 1035 pixels, it exceeds the ability of the monitor to output it. , Even if a fine black and white checkered pattern is displayed, the boundary between white and black is not clear, and it is very difficult to check the state of moire on the monitor. For this reason, the operator who adjusts also needs a skilled person.

The present invention has been made in order to solve the above problems, and automatically adjusts the sampling frequency (the number of samplings) when converting a video signal of any specification to a digital video signal. The purpose is to be able to adjust.

[0007]

A video printer according to the present invention converts an input analog video signal into a digital signal by sampling the analog video signal at a predetermined sampling number for each time defined by the horizontal scanning period of the video signal. Digital converting means, a clock generating means for controlling the digital converting means by outputting a signal defining the number of samplings, and a horizontal scanning line 1 of an analog video signal from the video signal converted to digital by the digital converting means. A moire detecting means for detecting a difference between the number of pixels and the number of samplings; and a clock adjusting means for controlling the clock generating means by the difference detected by the moire detecting means to adjust the frequency of the clock signal. Characterizing

[0008]

The difference between the number of pixels of one horizontal scanning line of the input analog video signal and the number of samplings when the video signal is converted into a digital signal is the number of moire generated when the image is reproduced. Since they are equal, the number of moires is detected, and the frequency adjusting means is controlled by the number of moires thus detected to make the number of samplings for digital conversion equal to the number of pixels of one horizontal scanning line of the input video signal. ..

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a video printer according to the present invention. Reference numeral 10 is a moire counting section for detecting the number of moire contained in an image from a video signal stored in an image memory 2, and 11 is a moire. Counting section 10
The moire number judging section for judging whether or not the number of moire counted in step 1 is 0, and the reference numeral 12 is a clock generated by the clock generating section 6 in the direction of setting the moire number to be 0 when the moire number judging section 11 judges that the moire number is not 0. It is a clock controller that adjusts the frequency of the signal, and is otherwise the same as FIG. 7.

The video signal output from the computer 8 is 1
The horizontal scanning line of the book is composed of 848 pixels, of which 640 pixels have an image that can be actually viewed on a monitor, and the frequency of this horizontal scanning line is 24.8.
It is 3 kHz. In order to convert this video signal to digital, the sampling timing at the time of conversion to digital must match the above video signal. That is, when the above video signal is converted into a digital signal, the horizontal frequency of the video signal is 24.83 kHz.
If sampling is performed with the sampling number 848 for each time (horizontal scanning period) represented by the reciprocal of, the video signal is correctly converted to digital. In other words, the state of this sampling is such that a video signal whose horizontal scanning line frequency is 24.83 kHz is 24.83 kHz × 848 = 21.0558.
It means that it is converted to digital at the sampling frequency of 4 MHz.

Here, the clock signal frequency setting of the clock generator 6 of this video printer is different from the above.
It is assumed that the sampling frequency of 1.179999 MHz, that is, the sampling number 853 can be sampled within the time of the reciprocal of the frequency of 24.83 kHz. In this state, when the video signal from the computer 8 is received and the video signal is converted into a digital signal by the A / D conversion unit 1, the number of pixels of one horizontal scanning line of the video signal sent and the above-mentioned predetermined value. Since the number of samplings within the time is different, the video signal converted into the digital signal has moire. The moire is equal to the difference between the pixel number and the sampling number. That is,
A video signal of which the number of pixels for one scanning line is 848 sent from the computer 8 and the number of samplings that the A / D conversion unit 1 can sample during the horizontal scanning period of the video signal 8
The difference between 53 and 53 is the number of moire patterns.

(Embodiment 1) The operation of adjusting the sampling number of the video printer of the present invention based on the above assumption will be described below. First, as shown in FIG. 2, the computer 8 outputs a video signal in a state where the character “H” is output on the entire surface when it is displayed on a monitor. This video signal has 848 pixels per horizontal scanning line. For video printers,
This video signal is converted into a digital signal by the A / D converter 1 and written in the image memory 2. At this time, since the sampling is performed at the sampling number 853 set in the clock generation unit 6, when the sampling is performed on the monitor or the like,
The moiré of the book has occurred.

This digital-converted video signal is read from the image memory 2 and the state of the signal for 640 pixels carrying the image of one horizontal scanning line is examined, as shown in FIG.
The characteristic of the gradation value as shown in FIG. The gradation value is 0 to 255 in 8 bits. This is because, as shown in FIG. 4A, the line portion of the “H” character that becomes white on the monitor (white level maximum) does not match the sampling point. If the number of pixels of one horizontal scanning line of the transmitted video signal and the number of samplings match, the state of the video signal converted to digital is parallel to the horizontal axis as shown in FIG. 3 (b). The signal distribution is divided into two straight lines. This is because, as shown in FIG. 4B, the line portion (white level maximum) of the character “H” that becomes white on the monitor and the sampling point match. As is clear from FIG. 2, when the character “H” is displayed on the entire screen of the monitor 9, the characters “H” are arranged at equal intervals and the character “H” on the sampling line extends vertically. The line portions have predetermined intervals, and white and black appear at predetermined intervals on the sampling line.

Next, the operation of the moire counting section 10, the moire number judging section 11, and the clock control section 12 in a state where moire occurs in the digitally converted video signal as described above will be described with reference to the flowchart of FIG. It will be explained using. First, in the moiré counting unit 10, 64 on one scanning line as shown in FIG. 3A is read from the image memory 2 in which the digital video signal in which moiré is generated is written.
A signal for 0 pixels is read (step S1), the first reading is counted, t = 1 is set (step S2), and then 640 pixels (dots) are divided into 8 dot units, and each of them is divided into 8 dots. Maximum value MAX (n) (n = 1,
2, ... 80) is calculated (step S3). This is because the characteristic of the gradation value when the moire is generated is as shown in FIG. 3A, and therefore the gradation value 127 (255 /
2) In the above-described original video signal, the white portion on the line of the character "H" is extracted to reduce the data amount and the processing such as calculation is facilitated.

Next, the average value M (FIG. 3A) is calculated from the maximum and minimum values of MAX (n) (step S4). Next, the sign change points of MAX (n) -M, that is, the intersection points a to g of the straight line indicated by the average value M and the curve in which the obtained data are distributed are obtained (step S5). Next, the number of the sign change points is divided by 2 to obtain the number of moire. However, as in the case of this embodiment, the sign change point ÷
If 2 = 7 ÷ 2 = 3.5, the number 4 rounded up to 3.5 is taken as the number of moire and S _t = 4 (step S
6). Here, _t of S _t is t of the number of readings counted in step S2, and in this case, S ₁ = 4. A
The video signal converted to digital by the / D conversion unit 1 is only for 640 pixels on which an image is present in one scanning line, and the number of moire generated therein is sent as the actual sampling number. It is a small number, unlike the number of moire generated due to the difference from the total number of pixels per horizontal scanning line of the video signal. That is, in the case of this embodiment, the number of actually generated moire is 5, and the number 4 of moire obtained by the moire counting unit 10 is a small number unlike the actual number 5. .. In consideration of the above, in the moire counting unit 10, when a number after the decimal point is generated in the process of the code change point / 2, the number rounded up is used as the number of moire, and the actual number of moire is used as much as possible. Try to get closer.

Next, the moire number judging unit 11 judges whether or not the number of moire is 0 (step S7), and the moire number S _t is the moire number S at the time of the previous moire detection.
If it is larger than _t-1 , the process proceeds to step S9, and if it is smaller than _t-1 , the process proceeds to step S10 (step S8). In this case, the number of moire S1 = 4>
It is 0, and since the previous moire detection has not been performed, the number of moires this time is naturally larger, so the process proceeds from step S7 to step S8 and then to step S9. In step S9, the clock control unit 12 subtracts 4 from the sampling number 853 of the clock signal frequency set in the current clock generating unit 6, and sets the sampling number 849 in the clock generating unit 6 as the frequency of the new clock signal. To do. In this state, the video signal from the computer 8 is again supplied to the D / A converter 1 controlled by the clock generator 6.
Is converted into a digital signal, and the signal is written in the image memory 2.

The moire counting section 10 reads out the video signal written in the image memory 2 (step S
1), counting that the reading is the second time, t =
2 (step S2), and the number of moire is obtained in the same manner as described above (steps S3 to S6). This time the number of moire S ₂ =
Since it has become 1 and has not become 0 yet (step S7), it is compared with the number of moire S ₁ = 4 at the time of the previous reading (step S8), and S ₂ <S _1, so that the current clock generation unit S is added to the sampling number 849 which is set to 6
₂ = 1 is added to make the sampling number 850 (step S10).

Then, the video signal converted into a digital signal again by the sampling number 850 is read from the image memory 2 (step S1), and the number S ₃ of moire is obtained in the same manner as described above (steps S2-6). This time, S ₃ = 2 (step S 7), and since this is S ₂ > S ₃ (step S 8), a clock is generated with 858 obtained by subtracting the number of moire S ₃ = 2 from the current sampling number 850 as the sampling number. Set in part 6. Then, again, the video signal converted into the digital signal at the sampling number 848 is read from the image memory 2 to obtain the number of moire. This time S ₄
= 0, and the moire number determination unit 11 determines that the number of moire has become 0 (step S7), and the series of operations is ended.

(Embodiment 2) In the above embodiment, division is made in units of 8 dots, the average value M is calculated from the maximum value MAX (n), and the sign change of MAX (n) -M. Although the point (inflection point) is obtained and the number obtained by dividing this by 2 is set as the number of moire, the number of moire may be detected based on the minimum value of MAX (n).

The operation of adjusting the sampling number in the second embodiment will be described below with reference to the flowchart of FIG. First, as in the first embodiment, the video signal converted into a digital signal is read from the image memory 2 (step S
1), processing is performed in units of 8 pixels, and the maximum value MAX (n) of each unit is obtained as in the first embodiment (step S).
3). Next, n that gives the minimum value of MAX (n) is obtained (step S11), and the cycle T of the moire that has occurred (FIG. 3A) is obtained from n of two adjacent minimum values (step S12). .. Next, as shown by G in FIG. 3A, the total number of dots in a portion less than one period T is totaled, and in the case of 1.75T or more, 2,0.75T or more and 1.75T 1 if less than, 0 if less than 0.75T
Is set as a correction value in each case (step S13).
Next, the correction value set in step S13 is set to MAX.
It is added to the number of minimum values of (n) to obtain the number of moire (step S14). After that, the same operation as that of the first embodiment is performed, and the number of pixels of one horizontal scanning line of the video signal sent from the computer 8 and A / A set in the clock generator 6 are set.
The number of samplings when the D conversion unit 1 converts it to digital is made the same.

(Embodiment 3) In the above embodiment, the number of samplings (sampling frequency) is adjusted by using the video signal sent from the computer 8 in a state where the character "H" is displayed in the full screen. However, the present invention is not limited to this, other English characters may be used, and the video signal may not be in the state of displaying them on the entire screen.
As a video signal in a state where only rows are displayed, its position may be designated and taken into a video printer.

(Fourth Embodiment) In the above embodiment, the case where the number of sampling lines to be taken in is one has been described, but the present invention is not limited to this, and continuous 10 to 50 lines may be sampled. In the case of a video signal that displays English characters, etc., there is no signal between character strings (between lines), and if a sampling line comes to this part, there will be no video signal, and the number of pixels of this video and the video Moire does not occur even if the sampling number of the printer is different,
It cannot be adjusted. Therefore, the consecutive 1
This will not happen if 0 to 50 lines are sampled.

(Embodiment 5) In the above embodiment, the initial value of the sampling number is 853. However, several kinds of initial values are prepared according to the number of pixels (horizontal frequency) of one horizontal scanning line of the signal source. It is better to be able to switch this. That is, the initial value of the sampling number is set to 848 and 14
00, and when the frequency of the horizontal scanning line of the signal source is 15 to 35 kHz, it is set to 848, and when the frequency of the horizontal scanning line of the signal source is 48 to 80 kHz, 1400.
And As a result, the number of pixels in one horizontal scanning line of the video signal output from the signal source does not significantly differ from the number of samplings in the digital conversion in the video printer, and the number of pixels in one horizontal scanning line of the input video signal. The process of adjusting the sampling number to is faster.

[0024]

As described above, according to the present invention, even if the frequency of the horizontal scanning line of the input video signal (the number of pixels for one horizontal scanning line) is various, the sampling frequency can be adjusted. Automatic adjustment is possible without the need for human-dependent adjustment, and output means (monitor) for the adjustment.
There is an effect that is unnecessary.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a video printer which is an embodiment of the present invention.

FIG. 2 is a plan view showing an image of sampling one horizontal scanning line of a video signal for displaying an “H” character to be input when adjusting the number of samplings on the entire screen.

FIG. 3 is a characteristic diagram showing a gradation value in a state in which a video signal converted into a digital signal is fetched from the image memory 2.

FIG. 4 shows the position of the maximum white level of an analog video signal,
It is explanatory drawing which shows the relationship of the position of the sampling point at the time of digital-converting.

5 is a flowchart showing the operations of a moire counting unit 10, a moire number determination unit 11, and a clock control unit 12 shown in FIG.

6 is a flowchart showing the operations of a moire counting unit 10, a moire number judging unit 11, and a clock control unit 12 in FIG.

FIG. 7 is a block diagram showing a configuration of a conventional video printer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 A / D conversion unit 2 Image memory 3 Color conversion unit 4 Printing unit 5 D / A conversion unit 6 Clock generation unit 10 Moire counting unit 11 Moire number determination unit 12 Clock control unit

Claims (1)

[Claims] 1. A video printer for converting an input analog video signal into a digital signal, processing the digital video signal and printing the video on a paper surface, etc. Digital conversion means for sampling at a predetermined number of samplings and converting into a digital signal at each time defined by the horizontal scanning period, and clock generation means for outputting a signal defining the sampling number to control the digital conversion means. A moire detecting means for detecting a difference between the number of pixels for one horizontal scanning line of the analog video signal and the sampling number from the video signal converted to digital by the digital converting means; and the moire detecting means. The frequency of the clock signal that controls and outputs the clock generation means based on the detected difference. Video printer, characterized in that it comprises a clock adjustment means for adjusting.