JPH0685572B2 - Printing equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing device for printing a still image signal using, for example, a thermal head.

Background Art and Its Problems For example, image information is transmitted through a telephone line. There are the following devices for receiving such image information. In FIG. 1, a terminal (100) from a telephone line is normally connected to a telephone (300) through a switch (200), and when image information is being transmitted, the switch (200) is switched and a decoder ( 400)
Connected to. Then, for example, a composite color image signal is formed from the image information transmitted by the decoder (400), and this image signal is supplied to the television receiver (500) and a video image corresponding to the transmitted image information is displayed. .

It has been proposed to print further projected images on paper in such devices. In that case, for example, a thermal printer (600) is used, a part of the image signal is supplied to the device (600), and a clock signal is supplied from the decoder (400) to the device (600).

The thermal printer (600) is configured as follows, for example. In FIG. 2, the still image signal from the decoder (400) is repeatedly supplied to the input terminal (1).
The image signal from the input terminal (1) is supplied to the sample hold circuit (2). A pixel clock signal S _C1 of, for example, 6 MHz corresponding to each pixel of the image signal from the decoder (400) is supplied to the AND circuit (4a) and the counter (4b) through the terminal (1 ′). Further, the image signal from the input terminal (1) is supplied to the sync separation circuit (3),
The vertical sync signal is separated. The separated horizontal synchronizing signal HD is supplied to the reset terminal of the counter (4b), and the counter (4b) forms a signal corresponding to the period from the horizontal synchronizing signal HD to the left end of the effective screen. This signal is supplied to the AND circuit (4a). The pixel clock signal S _C1 from the AND circuit (4a) is supplied to the clock terminal of the sample pulse generation circuit (5), and the horizontal synchronizing signal HD is supplied to the load terminal. Further, the vertical sync signal VD from the sync separation circuit (3) is supplied to the frequency divider circuit (6) to form a frame pulse signal Sf which is inverted every field period. The frame pulse signal Sf is supplied to the clock terminal of the frame counter (7) to form a numerical value that is incremented by "1" every two fields (frames). This numerical value is supplied to the generation circuit (5).
Then, for example, the above-mentioned numerical value is loaded in the generating circuit (5), and the numerical value is down-counted for each pixel clock, and when it becomes "0", the sample pulse Sp is formed. This sample pulse Sp is supplied to the sample hold circuit (2).

Therefore, in this sample hold circuit (2), pixel information aligned in the same vertical direction on the still image after a predetermined time counted by the counter (4b) has elapsed from the position of the horizontal synchronizing signal HD in an arbitrary field. Are sequentially sampled and held by the sample pulse Sp generated from the generation circuit (5) for each horizontal scanning.
If the pixel information arranged in the same vertical direction is referred to as vertical unit pixel information, the sample and hold operation of the vertical unit pixel information is completed in one vertical period, and then shifted to the right in the horizontal direction by one. Pixel information in vertical units is sampled and held. This is achieved by increasing the value loaded from the frame counter (7) in the generator circuit (5) by one. In this way, the sample and hold operation of pixel information in vertical units is completed in one vertical period, a new vertical synchronizing signal arrives, the frame counter (7) is counted up, and the load value of the generation circuit (5) is only 1. Up, and the sample position in the sample and hold circuit (2) is shifted one position to the right in the horizontal direction, which is sequentially repeated to sample and hold the information of one still image.

The signal from the sample hold circuit (2) is supplied to the AD conversion circuit (8) and AD-converted with, for example, 5 bits and 32 gradations. Further, the sample pulse Sp is supplied to the conversion circuit (8) through the delay circuit (9), and the digital signal AD-converted at the timing of this delay pulse is taken out from the conversion circuit (8). This digital signal is supplied to the RAM (10) having addresses corresponding to the number of horizontal scanning lines. Further, the sample pulse Sp is supplied to the clock terminal of the address counter (12) through the switch circuit (11). This counter (1
The value of 2) is supplied to the address pin of RAM (10).

Therefore, in this RAM (10), an image signal at a position delayed by a predetermined time from the horizontal synchronizing signal HD of each horizontal scanning line is digitized and stored in each address in an arbitrary field.

Further, the frame pulse signal Sf from the frequency dividing circuit (6) is taken out through the inverter (13), and the switch circuit (11) is switched by the signal ▲ ▼ from the inverter (13). Also, the pixel clock signal S from the terminal (1 ')
_C1 is supplied to, for example, a 1/10 frequency divider circuit (14), and this frequency-divided clock signal S _C2 is supplied to an address counter (12) through a switch circuit (11). Inverters (13)
Is supplied to the write / read control terminal of the RAM (10).

Therefore, the digital signal stored in the RAM (10) in an arbitrary field is sequentially read out in the next field, and the area of the arbitrary field in the RAM (10) stores pixel information in vertical units for one vertical period. The writing and the reading are alternately repeated inside.

The read digital signal is supplied to the comparator (15). Further, the timing signal St indicating that the reading of the final address from the address counter (12) is completed is supplied to the gradation counter (16), and the gradation signals which increase by "1" by 1 to 31 are formed. This gradation signal is supplied to the comparator (15). The comparison output is supplied to shift store registers (17a) and (17b) having bits corresponding to the number of horizontal scanning lines connected in series. Further, the divided clock signal S _C2 from the frequency dividing circuit (14) is registered in the registers (17a) and (17b).
It is supplied to the clock terminal of. Further, the timing signal St from the address counter (12) is transferred to the registers (17a), (1
It is supplied to the store terminal of 7b).

Therefore, the gradation set by the gradation counter (16) and RAM (1
The digital signal from (0) is compared, and binary signals indicating the gradation or more and the following are supplied to the registers (17a) and (17b). Then, the signals supplied to the registers (17a) and (17b) are stored in the store section at the timing signal St indicating that the reading of the final address is completed, and the gradation counter (16) is stored at the timing signal St. The set gradation is increased by "1". Furthermore, this new gradation and the digital signal are repeatedly compared, and the comparison output is the register (17a),
(17b), and at this time, the previous signal is held in the store section. Ie register (17
In each of the bits of a) and (17b) of the store section, for example, a signal of "1" is held during the period when the corresponding digital signal is equal to or less than the gradation from the gradation counter (16), and the gradation of the digital signal is A PWM signal corresponding to is formed.

Further, the frame pulse signal Sf from the frequency dividing circuit (6) is supplied to the set terminal of the flip-flop (18). Further, the signal Sr from the gradation counter (16) indicating that the comparison of the final gradation is completed is supplied to the reset terminal of the flip-flop (18). The Q output of the flip-flop (18) is supplied to the control terminals of the registers (17a) and (17b), during which the signal of each bit stored in the registers (17a) and (17b) is output to output the number of horizontal scanning lines. It is supplied to a thermal head (19) having a minute printing portion.

Therefore, a PWM signal corresponding to the gradation of the signal of the corresponding scanning line is supplied to each printing unit of the thermal head (19), and the printing density is changed according to the driving time, and printing with gradation is performed. . That is, an image signal at a position delayed by a predetermined time from the horizontal synchronizing signal HD of each horizontal scanning line is printed with a density corresponding to the gradation. This is repeated for the number of pixels in the horizontal direction to print an image of one color.

Further, the platen (20) around which the printing paper is wound is rotationally driven by the motor (21). The motor (21) drives the platen (20) according to the pixel information of the vertical unit which is read from the RAM (10) and subjected to gradation processing every vertical period and then supplied to the thermal head (19). Pixel information in vertical units is arranged horizontally on a printing paper to print a still image.
The rotation of the motor (21) is transmitted to the frequency generator (22), and the power generation signal is supplied to the phase comparison circuit (24) through the frequency dividing circuit (23). Further, the frame pulse signal Sf from the counter (6) is supplied to the comparison circuit (24), and the phase difference between them is detected. This detection output is supplied to the motor (21) through the amplifier (25) to servo the rotation of the platen (20).

Further, for example, cyan, magenta, yellow, and black color signals are prepared as image signals, and sublimation type cyan, magenta, yellow, and black color ink ribbons are sequentially switched, and the thermal head (19) and the printing paper are printed. The first color is printed with an arbitrary color signal, and then the platen is returned to the print start position and the ink ribbon is switched to print with the next color signal. It is also possible to carry out printing, and this is repeated so that multicolor printing is carried out. In this case, it is detected that the platen has returned to the print start position, the print start signal Ss is formed by this detection, and the frame counter (7) is reset by this print start signal Ss. Even at the start of printing of the first color, it is detected that the platen has reached the print start position after, for example, a manual print start instruction, and the print start signal Ss is formed.

In this way, the still image signal can be printed using the thermal head.

However, in such a device, the decoder (40
For 0), multiple types with different resolutions are prepared according to the user's request. In other words, all decoders have a common vertical period and horizontal period because they send a signal to a common television receiver (500), but the number of pixels in the horizontal direction is set to improve the resolution in the horizontal direction. There are multiple types of decoders that can decode more. It is obvious that many finer characters can be displayed on a still image by improving the resolution in this way.

Pixel clock signal sent from the decoder for this
There are three types of Sc1 frequencies, for example, 6 MHz, 7 MHz, and 10 MHz. In that case, in the above-mentioned device, one pixel is printed for each frame, while the platen (20) is operated by the frame pulse signal Sf.
Since it is driven at a constant speed by the servo of, the image is expanded in the horizontal direction when the device supplies a signal of 7 MHz or 10 MHz to the device adjusted at 6 MHz, and the image is distorted. That is, the picture frame is horizontal only 7/6, 10/6
It will be doubled.

Further, the period until the left end of the effective screen detected by the counter (4b) changes, and correct detection cannot be performed.

SUMMARY OF THE INVENTION In view of the above points, the present invention has a simple structure and prevents image distortion.

SUMMARY OF THE INVENTION According to the present invention, a still image signal related to an arbitrary clock signal is repeatedly supplied, the still image signal is sampled, and the sampling timing is sequentially changed.
In the printing apparatus in which the sampled signal is supplied to the print head and the printing paper is driven according to the clock signal to print the still image signal, the still image signal synchronizing signal is multiplied. Forming a reference signal, detecting the frequency of the clock signal using this reference signal, and controlling the drive amount of the printing paper according to this frequency, a printing device, An image without distortion can be obtained with a simple configuration.

Embodiment In FIG. 3, the horizontal synchronizing signal HD from the separation circuit (3)
Is supplied to the PLL circuit (26), for example, a reference signal S of 1 MHz
x is formed. This signal Sx is supplied to the clock terminal of the counter (4b). Then, by counting "16" by this counter (4b), a signal for a period (16 μsec) from the horizontal synchronizing signal HD to the left end of the effective screen is formed.

Further, the pixel clock signal S _c1 is supplied to the clock terminal of the counter (27), and the reference signal Sx is supplied to the counter (27).
It is supplied to the reset terminal of. As a result, from the counter (27), when the clock signal S _c1 is 6 MHz, “6”, 7 MHz
A value of "7" is detected at z, and a value of "10" at 10 MHz.
Further, the detected value is supplied to the frequency dividing circuit (23) and the frequency dividing ratio is controlled, whereby the driving amount of the platen (20) during one pixel printing is controlled. Others are the same as in FIG.

Then, in this device, for example, by adjusting so that the driving amount at 7 MHz and 10 MHz is 6/7 and 6/10 respectively at 6 MHz, the image frame is always constant and an image without distortion is obtained. be able to.

In addition, as a configuration for changing the driving amount, a plurality of frequency generators (22) may be provided in accordance with each frequency, and the power generation output thereof may be switched according to the detected value and supplied to the frequency dividing circuit (23).

EFFECTS OF THE INVENTION According to the present invention, a distortion-free image can be obtained with a simple configuration.

[Brief description of drawings]

FIG. 1 is a block diagram of an example of an image transmission device, FIG. 2 is a block diagram of a conventional device, and FIG. 3 is a block diagram of an example of the present invention. (20) is a platen, (21) is a motor, (22) is a frequency generator, (23) is a frequency divider circuit, (24) is a phase comparison circuit, (2
6) is a PLL circuit, and (27) is a counter.

Claims (1)

[Claims] 1. A plurality of types of still image signals having different numbers of pixels in the same horizontal section and a plurality of types of clock signals corresponding to the number of pixels in the same horizontal section are input, and the still image signals are repeatedly supplied. The pixels in the same vertical direction are sequentially sampled in one vertical period, the sampled signals are supplied to the print head, and the signals in pixel units in the same vertical direction are supplied to the print head every vertical period. In a printing apparatus for printing on a printing paper which moves in the horizontal direction of the still image signal, a synchronous clock signal generating means for generating a synchronous clock signal in synchronization with the synchronous signal of the still image signal, and the clock signal as a clock terminal. And a counter for inputting the synchronous clock signal to the reset terminal. Determination means for determining the type of the clock signal input according to the state of the counter, and control means for controlling the speed at which the printing paper is fed horizontally to the printing head in accordance with the determination result of the determination means. An image printing apparatus characterized by having.