JP2005212388A - Data processor for printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform processing of data for driving a recording head. <P>SOLUTION: A data processing section 20 performs the processing of data in parallel with the driving of a thermal head 8 in pipe-line processing. The data processing section 20 is equipped with a first processing circuit 26 and a second processing circuit 28 in order to perform the pipe-line processing in the two stages and an intermediate buffer section 27 is provided between the processing circuits 26, 28. The processing is respectively performed by the processing circuits 26, 28 by each one line for every line cycle. The processing time period of each processing can be reduced and the line cycle can be reduced so that the printing time period can be reduced. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a printer data processing apparatus used in a printer.

  Various printers that drive a recording head based on image data and record a color image on recording paper are known. When recording a color image with such a printer, it is necessary to perform various data processing on the image data and convert it into data for driving the recording head with a head driver.

  For example, in a color thermal printer that records color images by heating a color thermal recording paper with a thermal head as a recording head, the image data is processed according to the energization time (heat generation amount) of the thermal head heating element as data processing. In addition to data conversion, various data processing according to the characteristics of the recording method is required. Color space conversion processing, three-dimensional color conversion processing according to the characteristics of the recording paper, contour enhancement processing, An energy conversion process for converting data indicating gradation into heat energy to be generated by the heating element of the thermal head, a thermal history correction calculation process, a conversion process to drive data, and the like are performed.

  In order to obtain a printing speed capable of maintaining commerciality, a series of data processing as described above is performed by a high-speed CPU such as a RISC (Reduced Instruction Set Computer) processor or a high-speed computing unit such as a DSP (Digital Signal Processor). And a large-capacity work memory are used to sequentially perform processing in units of planes and lines. Also, normally, before actually driving the thermal head, for example, a series of processing from color space conversion processing to three-dimensional color conversion processing is sequentially performed in units of planes and stored in the work memory, and the remaining processing is performed on the line. By performing the processing sequentially in line units in synchronization with the recording of the print head, a part of the processing is performed in parallel with the driving of the thermal head, thereby shortening the preparation time before starting printing and substantially reducing the printing time. I am trying.

  In addition, as described in Patent Document 1, various processes are performed from a work memory for each process by a configuration in which a computing unit (CPU) and a memory are connected by a bus regardless of a unit of plane and a unit of line. The procedure of reading out the image data to the device, processing it, and writing the processing result back to the work memory has been repeated.

JP 2000-172630 A

  By the way, in order to shorten the printing time, it is possible to shorten the one-line recording period for recording one line or shorten the preparation time before starting printing. In order to shorten the one-line recording period, it is necessary to reduce the number of processes performed in parallel with the driving of the thermal head or to perform a higher speed calculation.

  However, in the former, the number of processes to be executed before the start of printing is increased, and the line recording period is shortened by executing the process using a higher-speed computing unit and reducing the number of data processes in parallel with the line recording. However, in recent years, the size of image data has increased with the increase in image quality, and the use of a high-speed computing unit corresponding to that increases the manufacturing cost, which is not preferable.

  On the other hand, in the latter, because the configuration is such that the arithmetic unit and the memory are connected by a bus as described above, the overhead due to the data transfer is large when data is input / output to / from the work memory for each processing, so the speed is limited. There is. For this reason, the use of a higher-speed computing unit or a memory that can be accessed at a higher speed still causes a significant increase in manufacturing cost.

  SUMMARY An advantage of some aspects of the invention is that it provides a printer data processing apparatus suitable for increasing the printing speed.

  In order to achieve the above object, according to the first aspect of the present invention, predetermined processing is performed on input data for one line for each line period in which one line is recorded, and output data for one line that has been processed is then processed. By outputting as the input data of the stage, it is provided between each of the data processing means and a plurality of data processing means for performing the data processing in the pipeline processing, and in the next stage data processing means for each line cycle. One line of input data is output, and one line of output data from the preceding data processing means is provided with one or more intermediate buffers written as data to be output in the next line cycle It is.

  According to the second aspect of the present invention, for each line cycle, data for one line is output as input data for the first stage data processing means, and image data for a new line is to be output in the next line cycle. The line memory means to be written as, and one line of data subjected to the data processing are output for each line cycle, and one line from the last stage data processing means is output as data to be output in the next line cycle. Print buffer means in which the output data for the remaining minutes are written.

  In the invention according to claim 3, the line memory means is composed of two line memories, and while reading data from one line memory, the data is written to the other line memory, This is a double buffer configuration in which the line memory for reading and writing is switched.

  In the invention according to claim 4, the print buffer unit is composed of two buffer memories, and while data is being read from one buffer memory, data is written to the other buffer memory and line by line In this configuration, the buffer memory for reading and writing is switched to a double buffer configuration.

  According to a fifth aspect of the present invention, the intermediate buffer is constituted by a buffer memory for one line that alternately reads out the data of the line to be read and writes the data of the line to be written in pixel units.

  According to a sixth aspect of the present invention, line control means for controlling the timing of pipeline processing is provided, and the line control means executes pipeline processing for a preset number of line cycles at the time of printing, and then executes pipeline processing. The processing is temporarily stopped, and the pipeline processing is resumed in response to the recording sheet having a constant speed.

  According to the seventh aspect of the present invention, an interface for communicating with an external CPU is provided, and the line cycle is set by the CPU via this interface.

  According to the present invention, image data is configured such that, for each line cycle for recording one line, a plurality of stages of data processing means for performing data processing by pipeline processing and an intermediate buffer between the data processing means are provided. Since the data processing for driving the recording head is performed, the pre-processing before printing, the one-line recording period for recording one line can be shortened, and the printing can be performed at high speed. It becomes like this. In addition, since it is not necessary to use a large-capacity work memory or a high-speed processor, the manufacturing cost can be reduced.

  An outline of a thermal recording type printer embodying the present invention is shown in FIG. The CPU 2 controls each part of the printer. The CPU 2 exchanges data and various commands between the ROM 4, the image memory 5, and the print control LSI 7 via the system bus 3. The ROM 4 stores a program for executing a print sequence and various parameters, and the CPU 2 controls each unit according to the program of the ROM 4. In the image memory 5, image data of an image to be recorded is written.

  The print control LSI 7 which is a data processing apparatus for a printer has a function of performing predetermined data processing on image data read from the image memory 5 in order to drive the thermal head 8 and record an image on color thermal recording paper. Also, the thermal head 8 has a function of controlling the up / down of the thermal head 8 and the conveyance of the color thermal recording paper.

  The memory card 9 is detachable from the printer, and is connected to the CPU 2 when attached. In this memory card 9, for example, an image taken with a digital camera is recorded as compressed image data. Image data of an image to be recorded is read from the memory card 9 by the CPU 2, decompressed by the CPU 2, and written into the image memory 5. As the image data, for example, the YCbCr (4: 2: 2) format composed of luminance data, blue color difference data, and red color difference data is used, but not limited to this format, such as JPEG format or TIFF format. Various types of data may be used, and red, green, and blue image data, and yellow, magenta, and cyan image data may be used.

  The thermal head 8 as a recording head includes a heating element array in which a large number of, for example, 1024 heating elements are arranged in a line, and the heating position is a pressure contact position where the heating element array is pressed against a color thermal recording paper for printing. And a retreat position away from the color thermal recording paper.

  As is well known, color heat-sensitive recording paper has a cyan heat-sensitive color forming layer, a magenta heat-sensitive color developing layer, a yellow heat-sensitive color developing layer, and a transparent protective layer sequentially arranged on a support. The thermosensitive coloring layers are arranged in the order of recording. The yellow thermosensitive coloring layer loses its coloring ability when irradiated with 420 nm ultraviolet rays (near ultraviolet rays) and the magenta thermosensitive coloring layer with 365 nm ultraviolet rays.

  Each heat-sensitive color forming layer requires a large color heat energy in order to develop color as the depth increases. In this color thermal recording paper, the yellow thermal coloring layer has the lowest coloring thermal energy, and the cyan thermal coloring layer has the highest coloring thermal energy. The coloring thermal energy is composed of bias thermal energy immediately before the thermosensitive coloring layer develops color and gradation thermal energy corresponding to the gradation value, that is, the coloring density of the pixel to be recorded. The bias thermal energy is a constant value for each thermosensitive coloring layer, but the gradation thermal energy increases as the color density increases.

  The thermal head 8 heats the color thermal recording paper being conveyed from the upstream side to the downstream side of the conveyance path to record one color image line by line. After the recording of one color image is completed, the color thermal recording paper is returned from the downstream side to the upstream side of the conveyance path, and then the next one color is transferred while the color thermal recording paper is conveyed again from the upstream side to the downstream side. Are recorded line by line. In this way, the thermal head 8 records a color image in three color planes sequentially by reciprocating movement of the color thermal recording paper. Further, after each yellow image and magenta image is recorded, the color thermosensitive recording paper is irradiated with ultraviolet rays from an unillustrated optical fixing device so that the previous color thermosensitive coloring layer does not develop color during the recording of the next color. The color developing ability of the thermosensitive coloring layer already recorded on the surface is lost.

  The swing motor 11 and the transport motor 12 are driven by the print control LSI 7. The swing motor 11 moves the thermal head 8 between the press contact position and the retracted position. The carry motor 12 drives a paper feed roller and a carry roller (not shown) to feed the color thermal recording paper and carry it at the time of recording. In the printing period in which the thermal head 8 is driven to record an image, the conveyance motor 12 is driven so that the color thermal recording paper is moved line by line at a predetermined line cycle.

  The head position sensor 13a detects that the thermal head 8 is set at the press contact position and the retracted position. The transport position sensor 13b detects the leading edge of the color thermal recording paper. When the thermal head 8 is moved to the press contact position when the leading edge of the color thermal recording paper is detected, the transport position sensor 13b is brought into contact with the thermal head 8 several lines before the recording area of the color thermal recording paper. Further, it is arranged in the vicinity of the downstream side of the thermal head 8.

  The head temperature sensor 14 a is attached to the thermal head 8 and measures the head temperature of the thermal head 8. The environmental temperature sensor 14b measures the environmental temperature in the printer. The head temperature and environmental temperature measured by these temperature sensors 14a and 14b are used for thermal history correction.

  The print control LSI 7 includes a CPUIF (interface) 15, an interrupt control circuit 16, a line control unit 17, a motor control unit 18, a sensor input unit 19, a data processing unit 20, and a head control unit 21. The CPUIF 15, line control unit 17, motor control unit 18, sensor input unit 19, data processing unit 20, and head control unit 21 are connected to an internal bus 22 provided in the print control LSI 7. Data and various commands can be exchanged between each other. The CPUIF 15 is connected to the CPU 2 via the system bus 3 and controls data exchange between each unit of the print control LSI 7 and the CPU 2.

  The interrupt control circuit 16 sends an interrupt signal to the CPU 2 in response to signals from each part in the print control LSI 7. The interrupt control circuit 16 receives a line cycle signal from the line control unit 17 and an interrupt request signal from the sensor input unit 19. The CPU 2 reads the image data from the image memory 5 in response to the interrupt signal corresponding to the line cycle signal, and receives the interrupt signal corresponding to the interrupt request signal from the sensor input unit 19 to input the print control LSI 7. Control the start of printing and the start of printing.

  The line control unit 17 generates a line cycle signal having a constant line cycle, which becomes a data processing timing signal. The line cycle signal is sent to the interrupt control circuit 16, the data processing unit 20, and the motor control unit 21, respectively. The period from the line cycle signal to the generation of the next line cycle signal is a one-line recording period in which one line is recorded. The line cycle is transferred from the motor control unit 18 to the transport motor during the printing period in which the thermal head 8 is driven. 12 has the same cycle as the carrier pulse output to 12.

  At the time of recording an image of one color, the line control unit 17 responds to a processing start instruction from the CPU 2 and transmits a number of line cycle signals corresponding to the number of stages of pipeline processing of the data processing unit described later. When transmission of the line cycle signal is stopped and a print start signal is input after that, the line cycle signal is restarted at the timing synchronized with the carrier pulse after waiting for a line cycle corresponding to the preset number of delays. . The print start signal is input from the motor control unit 18 immediately before the conveyance speed of the color thermal recording paper 20 becomes constant as will be described later. As a result, the data processing circuit 20 performs processing for the number of lines delayed by the data processing circuit 20 prior to the actual driving of the thermal head 8.

  Further, the line control unit 17 sends a data valid signal and a line valid signal, which will be described later, to the data processing unit 20 and the head control unit 21, and performs data processing by the data processing unit 20 and driving timing of the thermal head 8 by the head control unit 20. Control.

  The motor control unit 18 controls driving of the swing motor 11 and the transport motor 12. The motor control unit 18 drives the swing motor 11 according to an instruction from the CPU 2 to move the thermal head 8 between the press contact position and the retracted position. Further, the motor control unit 18 sends a conveyance pulse to drive the conveyance motor 12 to convey the color thermal recording paper. The carrier pulse is also sent to the line control unit 17, and the carrier pulse and the line cycle are synchronized during the printing period.

  The speed of the transport motor 12, that is, the transport speed of the color thermal recording paper, becomes faster as the transport pulse period is shorter. At the time of recording, the motor control unit 18 sends the carrier pulse based on an acceleration / deceleration table that defines the cycle of the carrier pulse and the number of generated pulses. The acceleration / deceleration table includes an acceleration period for accelerating the color thermal recording paper to a predetermined conveyance speed, a printing period for conveying the thermal recording paper at a predetermined conveyance speed and actually recording with the thermal head 8, and a deceleration at the end of conveyance. The period and the number of pulses for each period are specified.

  The period of the conveyance pulse in the printing period is constant for conveying the color thermal recording paper at a constant speed, and the period is the same as the line period as described above. Also, during the acceleration period, the conveyance pulse cycle is gradually shortened so that the conveyance speed is accelerated to the conveyance speed during the printing period, and during the deceleration period, the conveyance pulse period is reduced so that the conveyance speed gradually decreases. Has been gradually getting longer.

  The number of transport pulses in each period is set by the CPU 2 in accordance with the size of the color thermal recording paper to be recorded. In this example, since the line cycle and the carrier pulse cycle are different depending on the color to be recorded, the line cycle and the carrier pulse cycle are set in the line controller 17 and the motor controller 18 by the CPU 2 prior to the recording of each color. .

  The motor control unit 18 generates a print start signal at the end of the acceleration period, that is, immediately before starting the transmission of a fixed period of carrier pulses, and sends this to the line control unit 17. Thus, as described above, the transmission of the line period signal is resumed after waiting for a period corresponding to the predetermined number of delays from the print start signal. The number of delays is determined according to, for example, the length from the position where the thermal head of the color thermal recording paper is pressed to the leading edge of the recording area and the number of pulses in the acceleration period.

  Detection signals from the position sensors 13a and 13b and the temperature sensors 14a and 14b are input to the sensor input unit 19. When detecting that the thermal head 8 has moved to the pressure contact position based on the detection signal from the head position sensor 13a, the sensor unit 19 sends an interrupt request signal to the interrupt control circuit 16 in order to start printing. When the leading end of the color thermal recording is detected by the transport position sensor 13b, an interrupt request signal is sent to the interrupt control circuit 16 in order to move the thermal head 8 to the press contact position.

  Further, the sensor input unit 19 has an A / D converter, converts detection signals from the head temperature sensor 14a and the environmental temperature sensor 14b into digital information of the head temperature and the environmental temperature, and converts them into an internal bus. The data is sent to the data processing unit 20 via 22.

  Image data read from the image memory 5 by one line by the CPU 2 is input to the data processing unit 20. As will be described in detail later, the data processing unit 20 performs data processing by pipeline processing in units of lines and creates energization time data for recording the image by driving the thermal head 8. Output.

  The head controller 21 receives energization time data for one line from the data processor 20. The head controller 21 heats the color thermal recording paper by causing the corresponding heating element of the thermal head 8 to generate heat based on the energization time data. Thus, one color image is recorded line by line on the color thermal recording paper.

  The head control unit 21 compares a counter that is counted up at regular intervals during one line period for recording one line, or when the energization time data is large by comparing the count value of this counter with each energization time data. A comparator for one line whose output is “H level”, or a circuit that generates heat by energizing the heating element of the corresponding thermal head 8 when the output of the comparator is “H level” while the strobe signal is being input. Etc.

  During each one-line recording period, energization time data for one line is read from the data processing unit 20 by the head control unit 21, and the strobe having the same length as the maximum energization time during the one-line recording period therein. A signal is generated. The counter in the head controller 21 is reset at the start of recording of one line and counts up every predetermined unit time. As a result, each heating element of the thermal head 8 is energized only for the time represented by the corresponding energization time data to generate heat, and the thermal energy for color development at the density indicated by the image data based on the energization time data is color heat sensitive. Give to the recording paper.

  Further, the head control unit 21 is provided with a resistance value measurement unit 21 a that measures the resistance value of each heating element of the thermal head 8. For example, immediately after the printer is turned on, the resistance value measurement unit 21a is controlled by the CPU 2 to measure the resistance value of each heating element. Each measured resistance value is sent to the CPU 2 and a correction value for correcting the heat energy to be generated by the heating element is calculated for each heating element based on the resistance value. Each correction value is sent to the data processing unit 20 and set.

  FIG. 2 shows the configuration of the data processing unit 20. The data processing unit 20 includes a line memory unit 25, a first processing circuit 26, an intermediate buffer unit 27, a second processing circuit 28, and a print buffer unit 29. In the line memory unit 25, the intermediate buffer unit 27, and the print buffer unit 29, data reading (reading) and writing (writing) are controlled by a controller (not shown). The first processing circuit 26 and the second processing circuit 28 serve as data processing means, and perform pipeline processing with a two-stage data processing means.

  The line memory unit 25 receives image data for each line by the CPU 2 every time a line period signal is generated, that is, every line period. The line memory unit 25 includes a first line memory 25a and a second line memory 25b. While image data is being read from one line memory, image data is written to the other line memory. And a double buffer configuration in which writing and reading can be switched for each line. This is because the image data for one line to be processed next is stored in the line memory unit 25 while the image data for one line is read and processed in the first processing circuit 26 during one line recording period. This is because it needs to be written. As image data, luminance data and color difference data are written and read out.

  The line memory unit 25 is enabled to read when the line valid signal L0 from the line control unit 17 is input, performs a read operation while the data valid signal D0 is input, and the data valid together with the image data. The signal D1 is sent to the first processing circuit 26.

  The first processing circuit 26 sequentially captures image data for one line input together with the data valid signal D1, performs first processing, and sequentially outputs it. This first process is a luminance process sampled and created at a 4: 2: 2 ratio, a synchronization process for converting each color difference data into 1: 1: 1 data, and this image data is converted into Y (yellow), It consists of a color space conversion process for converting to M (magenta) and C (cyan) gradation data, and an edge enhancement process for enhancing the outline of the gradation data. The first processing circuit 26 sequentially outputs the gradation data of the color to be recorded out of the gradation data obtained by performing the first process to the intermediate buffer unit 27 together with the data valid signal D2.

  Similar to the line memory unit 25, the intermediate buffer unit 27 has a double buffer configuration, and includes a first intermediate buffer memory 27a and a second intermediate buffer memory 27b each having a storage capacity for one line. When the gradation data from the first processing circuit 26 is input together with the data valid signal D2, the gradation data for one line is written into one intermediate buffer memory set to the writing, and the line controller 17 When the line valid signal L3 and the data valid signal D3 are input, gradation data for one line is read from the other intermediate buffer memory set to read.

  Writing and reading of the intermediate buffer unit 27 is performed for each line cycle, and within one line recording period, reading of gradation data for one line written one cycle before (during the previous one line recording period). And gradation data for a new line is written. The gradation data read from the intermediate buffer unit 27 is sent to the second processing circuit 28 together with the data valid signal D4.

  The second processing circuit 28 performs the second process on the gradation data output from the intermediate buffer unit 27 together with the data valid signal D4, and sequentially outputs it together with the data valid signal D5. The second processing includes energy conversion processing, thermal history correction, resistance value positive processing, and energization time conversion processing.

  In the energy conversion process, the gradation data is converted into a thermal energy value to be generated by the heating element with a parameter corresponding to the color development characteristics of the color thermal recording paper. In the thermal history correction, the thermal energy generated in the heating element is increased or decreased by a parameter corresponding to the thermal storage state of the thermal head 8. In the resistance value positive process, a correction value based on the resistance value measured by the resistance value measuring unit 21a is used as a parameter to perform correction for preventing density unevenness. Each parameter used in the energy conversion process and the resistance value positive process is set in the second processing circuit 28 by the CPU 2 before image recording before recording. In the thermal history correction, the head temperature and the environmental temperature measured by the temperature sensors 14a and 14b are used as part of the parameters.

  The print buffer unit 29 has a double buffer configuration similar to that of the line memory unit 25 and the intermediate buffer unit 27, and includes a first print buffer memory 29a and a second print buffer memory 29b. The print buffer unit 29 is supplied with energization time data for one line and a data valid signal D5 from the second processing circuit. When the data valid signal D5 is input, the energization time data being input is sequentially fetched and held in the print-side print buffer memory, and read out by the head controller 21 in the next line cycle.

  A series of processing from reading from the line memory unit 25 to writing to the intermediate buffer unit 27 for one line of data is completed within one line recording period. Similarly, a series of processing from reading from the intermediate buffer unit 27 to writing to the print buffer unit 29 is completed within one line recording period. Further, from the line memory unit 25 to the print buffer unit 29, data and signals can be directly exchanged between the respective units by a bus prepared separately from the internal bus 22.

  Next, the operation of the above configuration will be described. When the power supply of the printer is turned on, the resistance value measurement unit 21a is automatically operated, and the resistance value of each heating element of the thermal head 8 is measured. The resistance value of each heating element obtained by this measurement is sent to the CPU 2 via the internal bus 22, the CPUIF 15, and the system bus 3. Then, based on each measured resistance value, a correction value corresponding to each heating element is calculated by the CPU 2, and each correction value is sent to the data processing unit 20 via the system bus 3, CPUIF 15, and internal bus 22. 2 is set in the processing circuit 28 as a parameter for resistance value correction processing.

  When a print instruction is given by operating an operation unit (not shown) after the power is turned on, image data to be recorded is read from the memory card 9 by the CPU 2, and image data obtained by decompressing the image data is stored in the image memory. 5 is written.

  The motor control unit 18 is given a head-up instruction from the CPU 2. Upon receipt of this instruction, the motor control unit 18 drives the swing motor 11 to set the thermal head 8 at the retracted position. When the head position sensor 13a detects that the thermal head 8 is set at the retracted position, an interrupt request signal is sent from the sensor input unit 19 to the interrupt control circuit 16, and an interrupt signal is sent to the CPU 2.

  In response to the interrupt signal, the CPU 2 gives a feed instruction to the motor control unit 18 to drive the transport motor 12. The feed motor and the transport roller are rotated by driving the transport motor 12, and the color thermal recording paper is fed from the paper feed cassette toward the thermal head 8.

  When color thermal recording paper is fed and the leading edge of the color thermal recording paper is detected by the transport position sensor 13b, an interrupt request signal is sent from the sensor input unit 19 to the interrupt control circuit 16, and an interrupt signal is sent to the CPU 2. Sent. In response to this interrupt signal, the CPU 2 instructs the motor controller 18 to stop the transport motor 12 and to bring down the thermal head 8.

  The motor control unit 18 stops the conveyance motor 12 and stops the conveyance of the color thermal recording paper. After the conveyance is stopped, the swing motor 11 is driven to set the thermal head 8 at the press contact position and press the color thermal recording paper.

  When the head position detection sensor 13a detects that the thermal head 8 has been set at the pressure contact position as described above, an interrupt request signal from the sensor input unit 19 is sent to the interrupt control circuit 16, and an interrupt signal is sent to the CPU 2. Is entered. In response to the input of this interrupt signal, the CPU 2 reads the first line of image data from the image memory 5 and sends it to the line memory unit 25 of the data processing unit 20 via the system bus 3, CPUIF 15, and internal bus 22. Since the line memory unit 25 is configured to write data to the first line memory 25a in the initial state, the image data of the first line is written to the first line memory 25a.

  When the writing of the image data of the first line is completed, as shown in FIG. 3, an instruction to start processing is output from the CPU 2 and sent to the line control unit 17 and the motor control unit 18 via the CPU IF 15. Upon receiving this processing start instruction, the motor control unit 18 starts sending the carrier pulse to the carrier motor 12 based on the acceleration / deceleration table. As a result, the color thermal recording paper is accelerated from the stopped state and is conveyed at a constant conveyance speed.

  On the other hand, when receiving an instruction to start processing, the line control unit 17 starts sending a line cycle signal to the interrupt control circuit 16, the data processing unit 20, and the head control unit 21 immediately after that, and On the other hand, transmission of the line valid signal L0 is started. The line valid signal L0 is continuously output until the first process for one color image is completed. Note that the numbers appended to the waveforms indicating the read and write timings in FIG. 3 indicate the line numbers.

  Simultaneously with the start of transmission of the line cycle signal L 1, the first data valid signal D 0 is sent from the line control unit 17 to the line memory unit 25. When the data valid signal D0 is input while the line valid signal L0 is being input, each image data of the first line is sequentially read from the first line memory 25a at a predetermined processing rate. The first data valid signal D1 is sent to the first processing circuit 26 during the period when the image data of the first line is being output.

  Upon receiving the first data valid signal D1, the first processing circuit 26 sequentially fetches the image data output from the line memory unit 25 during the input of the data valid signal D1, and performs the first process on the fetched image data. And output. At this time, the first processing by the first processing circuit 26 is performed in synchronization with the reading of the image data from the line memory unit 25, that is, at a predetermined processing rate.

  By performing the first processing, the image data (luminance data, blue color difference data, red color difference data) is converted into yellow, magenta, and cyan gradation data, subjected to contour enhancement processing, and then recorded. The color to be processed, that is, yellow gradation data, is sequentially output to the intermediate buffer unit 27 together with the data valid signal D2 at a predetermined processing rate.

  Since the intermediate buffer unit 27 is initially configured to write data to the first intermediate buffer memory 27a, the intermediate buffer unit 27 receives the data valid signal D2, and the yellow gradation data of the first line input together with the data valid signal D1 is the first. The data is sequentially written into the intermediate buffer memory 27a.

  After the yellow gradation data of the first line is written into the first intermediate buffer memory 27a, the second line cycle signal is generated. In synchronism with this line cycle signal, the line control unit 17 starts to send the line valid signal L3 for yellow image, and sends the first data valid signal D3 to the intermediate buffer unit 27.

  In response to the input of the data valid signal D3 together with the line valid signal L3, the yellow gradation data of the first line is sequentially read from the first intermediate buffer memory 27a of the intermediate buffer unit 27 at a predetermined processing rate. This is performed and sent to the second processing circuit 28 together with the first data valid signal D4.

  The yellow gradation data sequentially output from the intermediate buffer unit 27 is sequentially taken into the second processing circuit 28 by the input of the first data valid signal D4, and the second processing is performed at a predetermined processing rate. The first data valid signal D5 is output together. Thereby, the yellow gradation data of the first line is output as energization time data subjected to the thermal history correction and resistance correction processing.

  The energization time data of the first line obtained as described above is sent from the second signal processing circuit 28 to the print buffer unit 29 together with the first data valid signal D5. When the data valid signal 5 is input to the print buffer unit 29, the energization time data of the first line is sequentially fetched and held in the first print buffer memory 29a.

  Incidentally, the first line cycle signal generated after the writing of the image data of the first line to the line memory unit 25 is completed is input to the interrupt control circuit 16. Then, an interrupt signal is sent to the CPU 2. Upon receipt of this interrupt signal, the CPU 2 reads out each image data of the second line from the image memory 5 and sends it to the line memory unit 25.

  Since the first line memory 25a is switched for reading and the second line memory 25b is switched for writing when the writing of the image data of the first line is completed, the line memory unit 25 has changed the image of the second line. Data is sequentially written into the second line memory 25b without conflicting with the reading of the image data of the first line.

  In synchronization with the generation of the second line cycle signal, the second data valid signal D0 is sent from the line control unit 17 to the line memory unit 25, so that the second line image is output from the second line memory 25b. Data is read and sent to the first processing circuit 26 together with the second data valid signal D1. Each image data of the second line is subjected to the first processing by the first processing circuit 26, converted into yellow gradation data, and sent to the intermediate buffer unit 27 together with the second data valid signal D2. At this time, since the second intermediate buffer memory 27b is used for writing in the intermediate buffer unit 27, the yellow gradation data of the second line is written into the second intermediate buffer memory 27b. Therefore, it does not compete with the reading of the first line.

  Further, in synchronization with the second line cycle signal, the image data of the third line is read from the image memory 5 and sent to the line memory unit 25. When the second line cycle signal is generated, reading of the image data of the first line from the first line memory 25a is completed, and the first line memory 25a is switched for writing. Then, the image data of the third line is written in the first line memory 25a. At this time, the second line image data is read from the second line memory 25b as described above.

  As described above, the energization time data of the first line is written in the print buffer unit 29, the yellow gradation data of the second line is written in the intermediate buffer unit 27, and the image data of the third line is written in the line memory unit 25. Then, the generation of the line period signal is temporarily stopped. In this way, the pre-processing is advanced to the state where the image data of the third line is written in the line memory unit 25, the generation of the line cycle signal is temporarily stopped, and the print start standby state is set. Thus, the thermal head 8 can be driven immediately in response to an instruction to start printing.

  After the generation of the line cycle signal is temporarily stopped, the acceleration period ends and the print period starts. A print start signal is sent from the motor control unit 18 to the line control unit 17 immediately before the print period starts. Then, the line control unit 17 waits for the input of carrier pulses for a preset number of delays (two cycles in this example), and then resumes sending the line cycle signal at a timing synchronized with the carrier pulses. That is, the pipeline processing is resumed in response to the constant conveyance speed of the color thermal recording paper.

  Simultaneously with the third line cycle signal generated immediately after the restart of the transmission, the line control unit 17 starts to transmit the line valid signal L6 to the head control unit 21. This line valid signal L6 is sent out until the recording of the last line of an image of one color is completed.

  When the line valid signal L6 is input, the head control unit 21 reads energization time data for one line from the print buffer unit 29 for each input of the line cycle signal, and based on this, the heating elements of the thermal head 8 are read out. Come to drive. Therefore, when the third line cycle signal is generated, the head controller 21 reads the energization time data of the first line from the first printer buffer memory 29a, and the heating element of the thermal head 8 is driven based on this. The As a result, the first line of the yellow image is recorded on the color thermal recording paper.

  On the other hand, in the same manner as described above, an interrupt signal and each data valid signal are transmitted in synchronization with the third line cycle signal, and the yellow gradation data of the second line of the second intermediate buffer memory 27b is subjected to the second processing. It is sent to the circuit 28. The energization time data obtained by performing the second process on the yellow gradation data is sent to the print buffer unit 29 and written into the second print buffer memory 29b. Further, the yellow gradation data of the third line is sent from the first line memory 25a to the first processing circuit 26, and the yellow gradation data obtained by performing the first processing is written into the first intermediate buffer memory 27a. Further, the image data of the fourth line read from the image memory 5 is written into the second line memory 25b.

  Thereafter, when the fourth line cycle signal is generated, the energization time data of the second line is read out to the head controller 21 in the same manner as described above. Thereby, each heating element of the thermal head 8 is driven based on the energization time data of the second line, and the second line of the yellow image is recorded on the color thermal recording paper. The energization time data obtained by performing the second process on the yellow gradation data of the third line is written in the first print buffer memory 29a, and the yellow scale obtained by performing the first process on the yellow gradation data of the fourth line. The tone data is written into the second intermediate buffer memory 27b. Further, the image data of the fifth line read from the image memory 5 is written into the first line memory 25a. Thereafter, the third and subsequent lines of the yellow image are recorded in the same manner.

  The portion of the color thermal recording paper on which the yellow image is recorded is optically fixed by being irradiated with near ultraviolet rays from an optical fixing device (not shown). When the recording of the last line of the yellow image is completed and the light fixing up to the rear end of the color thermal recording paper is completed, the color thermal recording paper is returned after the thermal head 8 is moved to the retracted position. If the leading edge of the color thermal recording paper is detected by the conveyance position sensor 13b during the conveyance, the conveyance is stopped and the thermal head 8 is pressed against the color thermal recording paper.

  After the thermal head 8 is pressed against the color thermal recording paper, parameters, line cycle, etc. are set according to magenta, and then the first and second processes are performed by pipeline processing in the same procedure as in the case of a yellow image. The magenta image is recorded line by line.

  The portion of the color thermal recording paper on which the magenta image is recorded is photofixed by irradiating with ultraviolet rays from a photofixer. When the recording of the last line of the magenta image is completed and the light fixing up to the rear end of the color thermal recording paper is completed, the pressure contact by the thermal head 8 is released, and then the color thermal recording paper is returned. If the leading edge of the color thermal recording paper is detected by the conveyance position sensor 13b during the conveyance, the conveyance is stopped and the thermal head 8 is pressed against the color thermal recording paper. After the thermal head 8 is pressed, a cyan printing process is started, and a cyan image is recorded line by line in the same procedure as described above.

  As described above, since the pipeline processing is performed so as to process each stage of data for each line in synchronism with the line recording, the line cycle can be shortened and the printing speed can be increased. At the same time, a large-capacity memory for data processing becomes unnecessary.

  In the above embodiment, the intermediate buffer unit has a double buffer configuration. However, when the processing rate is four times or more of the system clock, the double buffer configuration has a control by shifting the read and write timings. In other words, a line memory for one line can be used.

  FIG. 4 shows an example in which the intermediate buffer unit is constituted by a line memory for one line. The dot enable is a signal serving as a reference for processing timing of one pixel, and is repeatedly generated at a cycle four times the system clock. That is, the processing rate is four times the system clock. Both reading and writing are performed at a cycle four times the system clock, and the timing is shifted by two system clock cycles. As a result, it is possible to prevent the reading and writing from competing while the intermediate buffer unit is constituted by a line memory for one line.

  In each of the above-described embodiments, the intermediate buffer unit is provided between the first processing circuit and the second processing circuit so that the processing is performed in units of lines for each line period. While the data of the (i + 1) -th pixel in one line is processed by one processing circuit, the processing may be advanced so that the data of the i-th pixel of the same line is processed by the second processing circuit.

  In each of the above embodiments, one thermal head is used and a color image is recorded while the thermal recording paper is reciprocated three times. However, a thermal head is provided for each color. Alternatively, a three-head, one-pass system may be used in which a color image is recorded while the color thermal recording paper is conveyed once in one direction. In this case, a print control LSI configured in the same manner as described above is provided for each thermal head. Then, while controlling the conveyance motor with one print control LSI, and by starting the drive of the thermal head with the number of delays corresponding to the position of each thermal head, according to the print start signal from this print control LSI, A 3-head 1-pass color thermal printer can be easily constructed.

  Although the thermal printer has been described above, the present invention can be applied to a thermal melting type printer, an ink jet type printer, and the like. Further, the number of stages of pipeline processing is not limited to two, but may be three or more. For example, a processing circuit that performs each of a synchronization process, a color space conversion process, an outline enhancement process, an energy conversion process, a thermal history correction, a resistance value correction process, and an energization time conversion process may be provided, and the pipeline process may have seven stages.

1 is a block diagram illustrating an outline of a configuration of a thermal printer that embodies the present invention. It is a block diagram which shows the structure of the data processing part which performs a pipeline process. 6 is a timing chart showing the operation timing of the print control LSI. An example in which the intermediate buffer unit is configured by a line memory for one line is shown in a timing chart.

Explanation of symbols

2 CPU
5 Image memory 8 Thermal head 7 Print control LSI
17 Line control unit 20 Data processing unit 25 Line memory unit 26, 28 Processing circuit 27 Intermediate buffer unit 29 Print buffer unit

Claims (7)

In a printer data processing apparatus that is used in a printer that drives a recording head to record an image line by line, and performs data processing for driving the recording head on image data.
By performing predetermined processing on input data for one line and outputting processed output data for one line as input data for the next stage for each line cycle for recording one line, the data is obtained by pipeline processing. A plurality of stages of data processing means for processing and each data processing means are provided, and for each line period, input data for one line is output to the next stage data processing means, and the previous stage data A printer data processing apparatus, comprising: one or more intermediate buffers in which output data for one line from the processing means is written as data to be output in the next line cycle.   Line memory means for outputting data for one line as input data for the first stage data processing means for each line period, and for writing image data for a new line as data to be output in the next line period; A print in which data for one line subjected to the data processing is output for each line cycle, and output data for one line from the data processing means at the final stage is written as data to be output in the next line cycle. 2. The printer data processing apparatus according to claim 1, further comprising buffer means.   The line memory means is composed of two line memories. While reading data from one line memory, the line memory means writes data to the other line memory, and reads and writes each line. 3. The data processing apparatus for a printer according to claim 2, wherein the data processing apparatus has a double buffer configuration in which a memory is switched.   The print buffer unit is composed of two buffer memories, and writes data to the other buffer memory while reading data from one buffer memory, and reads and writes data for each line. 3. The data processing apparatus for a printer according to claim 2, wherein the data processing apparatus has a double buffer configuration in which a memory is switched.   5. The intermediate buffer includes a buffer memory for one line that alternately reads out data of a line to be read and writes data of a line to be written in units of pixels. The data processing apparatus for a printer according to any one of the above.   Line control means for controlling the timing of pipeline processing is provided, and this line control means temporarily stops pipeline processing after executing pipeline processing for a predetermined number of line periods during printing, 6. The printer data processing apparatus according to claim 1, wherein the pipeline processing is resumed in response to the recording paper having a constant speed.   7. The printer data processing apparatus according to claim 1, further comprising an interface for communicating with an external CPU, wherein the line cycle is set by the CPU via the interface. .

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