JP3190894B2 - Image forming method and image forming apparatus for laser printer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method and an image forming apparatus for a laser printer which collects a plurality of image data bands composed of a plurality of dot lines to form an image for one page of printing paper.

[0002]

2. Description of the Related Art A print image generation timing of a laser printer having a so-called band drawing concept in which a plurality of image data bands (bands) composed of a plurality of dot lines are collected to form an image for one page of printing paper. There are mainly two types, one of which is the so-called real-time drawing that generates the print image of the next band while the print image of one band is being transferred to the printer engine (video transfer time). The other is so-called pre-rendering in which all print images of a page are generated before printing of one page is started.

[0003] Among them, the real-time drawing can start the printing operation before generating all the print images for one page, so that the time of the printing process can be shortened. When the paper is fed and the printing operation is started, the image of the next band must be generated according to the traveling speed of the printing paper, and if the image generation of the next band is If the delay is too long, there is a problem that a correct image cannot be printed.

[0004] Although the pre-rendering does not have such a problem, it takes a long time to start the printing operation because all the print images for one page must be generated before the printing operation starts. However, there is a problem that it takes a long time for the entire printing process.

[0005] The pre-drawing also requires a large-capacity image memory as an image memory for holding the generated print image. When storing a print image in an image memory, a small amount of memory is used by using a technique called image compression so that a print image for one page can be held in a small image memory as much as possible, because it causes an increase in price. The device is designed so that print images can be stored in a large capacity, thereby increasing the efficiency of memory usage.

In this case, as in the case of real-time drawing, the compressed print image is expanded in accordance with the running speed of the printing paper and transferred to the printer engine as a video image.

The operation of generating a print image that expands such print data into a print image that is a set of dots and the operation of expanding a compressed image are performed by one control unit (CP).
Since the operations cannot be performed at the same time in U), when the decompression operation is performed, the generation operation of the print image must be temporarily stopped.

[0008]

As means for storing the generated print image in the image memory, means for compressing and storing the print image (image data) without fail in order to increase the efficiency of memory use (compression mode) ) And means (uncompressed mode) for storing a print image (image data) without compressing it by mounting an image memory with a sufficient capacity to increase the processing speed.

In real-time drawing, if the compression mode is adopted, the capacity of the image memory can be reduced, but the expansion of the next band must be performed before the printing of one band is completed. Therefore, during the expansion operation of the compressed band, the operation of generating the print image of the next band cannot be performed, and the print image generation operation is awaited. Therefore, it takes a long time for the entire printing process.

When the non-compression mode is adopted, the print image generating operation does not have to wait, so that the time for the entire print processing can be shortened. However, since a large-capacity image memory must be provided, the laser Printer prices rise. When the image memory shortage occurs, the printing of the page currently being printed is completed, and the next print image is waited until the area holding the print image of the page in the image memory is released. Has to be performed, so that a waiting time occurs.

The present invention solves the problems of the conventional image forming means of a laser printer. In real-time drawing, a print image generating operation and a compressed image decompressing operation are simultaneously performed even with a small-capacity image memory. An object of the present invention is to provide an image forming means of a laser printer capable of reducing the occurrence of an opportunity to be performed and reducing the overall time of the printing process because the occurrence of waiting time is reduced.

[0012]

An image forming method for a laser printer according to the present invention is a band drawing concept for collecting a plurality of image data bands composed of a plurality of dot lines to form an image for one page of printing paper. A print image generation method of a laser printer for performing real-time drawing for generating a print image of a next band while transferring a print image of one band to a printer engine unit, wherein the print image is held. While there is room in the image memory, the image data is stored as uncompressed band data in units of the image data band. Converting the uncompressed band data into compressed band data and storing it in the image memory.

The image forming apparatus of the laser printer according to the present invention has a band drawing concept of collecting a plurality of image data bands composed of a plurality of dot lines to form an image for one page of printing paper. A print image generation device of a laser printer for performing real-time drawing for generating a print image of a next band while transferring a print image of a band to a printer engine unit, and an intermediate device for holding print data input from a higher-level device A data storage unit and a print image generation operation for expanding the print data held in the intermediate data storage unit into a print image in band units, of which uncompressed uncompressed print images stored in an image memory without compression A drawing unit for storing band data in the image memory; and a compressed image of a print image generated by the drawing unit and stored in the image memory. A compression unit that compresses a print image in band units and stores it as compressed band data in the image memory; the uncompressed band data sent from the drawing unit and the compressed band data sent from the compression unit The image memory for storing the compressed band data, expanding the compressed band data and sending it as uncompressed band data to a video output unit, the uncompressed band data from the image memory and the expanded A video output unit for sending the compressed band data to the printer engine unit in band units to output and print, and operations of the intermediate data storage unit, the drawing unit, the compression unit, the image memory, the decompression unit, and the video output unit And a control unit for controlling the compression unit. It determines whether there is sufficient storage area in said image memory when storing print image generated by expanding the image memory in the set,
When there is sufficient storage area, the drawing unit sends the image data to the image memory. When there is not enough storage area, the compression processing is performed by sending uncompressed bands to the compression unit sequentially from the first band of the same page. It is intended to be.

[0014]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of an image forming apparatus for a laser printer according to the present invention, FIG. 2 is a flowchart showing the operation of the embodiment of FIG. 1, and FIG. State diagram showing the storage status of image data,
FIG. 4 is a timing chart showing the operation of the embodiment of FIG.

In FIG. 1, an image generation device 10 includes an intermediate data storage unit 1, a compression determination unit 2, a drawing unit 3, a compression unit 4, an image memory 5, a decompression unit 6, and a video output unit 7.
And a control unit (CPU) 8.

The intermediate data storage unit 1 holds data to be printed out (print data) input from the host device 20 in the form of character pattern data or raster data, together with a drawing command.

When storing a print image generated by developing the image into a set of dots in the drawing unit 3 in the image memory 5, the compression determination unit 2 has a sufficient storage for storing the print image in the image memory 5 without compression. It is determined whether or not there is an area. If there is a sufficient storage area, an uncompressed print image is sent from the drawing unit 3 to the image memory 5 for storage. The uncompressed bands are sequentially sent from the bands to the compression unit 4 to perform compression processing, and the compressed print image is sent to the image memory 5 as compressed band data and stored.

The drawing unit 3 performs a print image generation operation of expanding the print data held in the intermediate data storage unit 1 into a print image which is a set of dots in band units, and does not compress (uncompress) the data. The print image stored in the image memory 5 is stored in the image memory 5 as uncompressed band data 51.

The compression unit 4 compresses a print image stored in the image memory 5 out of the print images generated by the drawing unit 3.
The image data is compressed in band units and stored as compressed band data 52 in the image memory 5.

The image memory 5 stores the uncompressed band data 51 sent from the drawing unit 3 and the compressed band data 52 sent from the compression unit 4 in a mixed manner. In addition to the image data storage area 50 for storing the uncompressed band data 51 and the compressed band data 52, a work area 53 used when converting a part of the uncompressed band data 51 into the compressed band data 52 is provided. are doing.

The expansion section 6 expands the compressed band data 52 and sends it to the video output section 7 as uncompressed band data.

The video output unit 7 sends the uncompressed band data 51 of the image memory 5 and the image data obtained by expanding the compressed band data 52 by the expansion unit 6 to the printer engine unit 15 in band units to output and print them.

The control unit 8 controls the operations of the intermediate data storage unit 1, the drawing unit 3, the compression unit 4, the image memory 5, the decompression unit 6, and the video output unit 7.

Next, the operation of the image forming apparatus of the laser printer configured as described above will be described with reference to FIGS.

The intermediate data storage unit 1 holds data to be printed and output, which is input from the host device 20 in the form of character pattern data or raster data, together with a drawing command.

When the image generating apparatus 10 starts an image generating operation from this state, it first sends print data for each band from the intermediate data storage unit 1 to the drawing unit 3 and develops the print data as a set of dots into a print image. The print image is stored in the image memory 5 without being compressed. This operation is performed for all the bands of the first page, and when the generation and storage of the first page print image are completed, the generation and storage of the second page print image are performed. When the generation and storage are completed, the generation and storage of the print image of the third page are continued. During such an operation, the compression determination unit 2 constantly monitors whether or not the next band can be stored in the image memory 5 as the uncompressed band data 51.

When the compression determining section 2 determines that there is no more area in the image memory 5 for storing one band of uncompressed band data (steps 21 and 22 in FIG. 2), the non-compressed band data is sequentially read from the first band of the page. Compressed band data 51
Is searched (step 23), and when an uncompressed band is found (step 24), the uncompressed band data 51 of the band is returned to the compression unit 4 and compressed there. Compressed band data 52
And temporarily stored in the work area 53 (step 25).

Subsequently, the area from which the uncompressed band data 51 has been extracted for compression in the image memory 5 is released (step 26), and the compressed band data stored in the work area 53 is transferred and stored there (step 26). Step 27). As a result, empty areas further increase, and the next uncompressed band data is stored in those empty areas.

If no uncompressed band is found in step 24, the process waits until printing of the page currently being output and printed is completed and the area storing the printed image is released (step 28). .

If it is determined in step 22 that there is an area in which the uncompressed band data can be stored, the uncompressed band data is stored (step 29), and the processing of the next band is performed (step 30).

For example, as shown in FIG. 3A, the image data 5a of the first page to the image data 5c of the third page, and the image data 5d-1 of the first band of the image data 5d of the fourth page. From the third band of image data 5d-
3 is stored as uncompressed band data. If it is determined that the remaining empty area 5d-4 has no capacity to store the image data of the fourth band of the fourth page as uncompressed band data, FIG. As shown in (b), the image data 5d-1 of the first band of the image data 5d of the fourth page.
Is the uncompressed band data, the data is compressed by the compression unit 4 and temporarily stored in the work area 53 of the image memory 5, and the image data of the first band of the fourth page is deleted and stored in the work area 53. The stored compressed band data is transferred to the area where the uncompressed band data of the first band of the fourth page is stored. During this time, the image data 5a of the first page is output from the video output unit 7 to the printer engine unit 15 and output printing is performed.

As a result, the area becomes an area storing the compressed band data 5d-1a of the first band of the fourth page and an empty area 5d-1b. Therefore, the uncompressed area of the fourth band of the fourth page is added to the empty area 5d-1b and the empty area 5d-4 next to the area 5d-3 storing the image data of the third band of the fourth page. It becomes possible to store band data. If these two free areas alone are not enough to store the uncompressed band data of the fourth band of the fourth page, the image data 5 of the second band of the fourth page
Similar processing is performed for d-2.

When storing the uncompressed band data of the fourth band on the fourth page, the data can be divided and stored in the free area 5d-1b and the free area 5d-4. The uncompressed band data 5 of the second band and the third band of the fourth page in the area after 1b
d-2 may be packed and stored, and the uncompressed band data of the fourth band of the fourth page may be stored in an area obtained by combining the two empty areas thereafter.

The uncompressed band data 51 and the compressed band data 52 stored in the image memory 5 are sequentially output from the first band data in accordance with a video output (output for printing an image) command. Is sent to the printer engine unit 15 and output and printed.
At that time, the uncompressed band data 51 is directly transmitted to the printer engine unit 15 via the video output unit 7 as it is.
The compressed band data 52 is output to the decompression unit 6 so as to be in the same format as the uncompressed band data 51.
And then decompressed there and sent to the video output unit 7. The video output unit 7 outputs the data sent from the decompression unit 6 to the printer engine unit 15 as it is.

FIG. 4 is a timing chart showing the operation of the CPU 8 at this time. FIG. 4A shows the compressed band data (compressed band) in the first to third bands, and non-compressed data in the fourth to fifth bands. Compressed band data (uncompressed band)
(B) shows the operation of the CPU 8 in the case of
CPU 8 in the case where all of the first to fifth bands are compressed band data (compressed bands)
The operation of FIG.

In FIG. 4A, the video output signal 61 output from the video output unit 7 continuously outputs the first to fifth bands (in a laser printer, the video output signal is basically Performed continuously). On the other hand, CPU8
The processing operation 62 of the first band to the third band
Before the output of each band is started, a band expansion process 63 is performed on each band. This decompression processing 6
3 is completed in a shorter time than the output time of the video output signal 61 in the video output unit 7, so that the pre-drawing of the subsequent page or the A compression process 64 is performed.

When the extension processing of the third band is completed, the fourth band
Since there is no need to perform the decompression processing for the band to the fifth band, the CPU 8 outputs the video output signal 61 for the fifth band.
Until the output of is completed, the pre-drawing or compression processing 63 of the subsequent page can be continuously performed. Note that the first to third band expansion processes may be performed continuously, and the pre-drawing or compression processing of the subsequent page may be performed continuously from the time when the third band expansion process ends.

In the case of FIG. 4B, the video output signal 66
Are continuously output at the same time as the video output signal 61 in FIG. 4A, but since the processing operation 67 of the CPU 8 has to perform the decompression processing 68 of all the bands,
It takes longer than the decompression process 63 of FIG. 4A by the decompression process for the fourth to fifth bands. Therefore, the time for the pre-rendering or compression processing 69 of the subsequent page is shortened. Therefore, in the case of FIG. 4A, the use efficiency of the CPU 8 is improved more than in the case of FIG.

In the above-described embodiment, the compression judging section judges whether or not there is enough free space in the image memory to store the succeeding band. The configuration may be such that the unit is omitted.

A work area is provided in the image memory, and data obtained by compressing the uncompressed band data by the compression unit is temporarily stored in the work area, and then the area storing the uncompressed band data is opened to open the work area. Is configured to store the compressed band data stored in the compressed band data. When compressing the uncompressed band data, the area storing the uncompressed band data is immediately released and the compressed band data is stored. Can be stored directly thereafter, and the work area can be omitted.

[0042]

As described above, the image forming method and the image forming apparatus of the laser printer according to the present invention, when performing the pre-rendering of the succeeding page while performing video output in band units for image printing, When there is room, store as uncompressed band data in band units, and when there is insufficient space to store the next band as uncompressed band data, convert uncompressed band data to compressed band data in order from the first band By storing the image data in the image memory, the CPU can be used efficiently with a small image memory, so that the cost of the laser printer can be reduced and the speed of the print output can be improved. This has the effect.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an embodiment of an image forming apparatus of a laser printer according to the present invention.

FIG. 2 is a flowchart showing the operation of the embodiment of FIG.

FIG. 3 is a state diagram showing a storage state of image data in an image memory according to the embodiment of FIG. 1;

FIG. 4 is a timing chart showing the operation of the embodiment of FIG.

[Explanation of symbols]

 Reference Signs List 1 intermediate data storage unit 2 compression determination unit 3 drawing unit 4 compression unit 5 image memory 5a image data of first page 5b image data of second page 5c image data of third page 5d image data of fourth page 5d-1 Image data of the first band 5d-2 Image data of the second band 5d-3 Image data of the third band 5d-4 Empty area 5d-1a Compressed data of the first band 5d-1b Empty area 6 Decompression unit 7 Video output unit 8 Control unit (CPU) 10 Image generation device 15 Printer engine unit 20 Host device 21 to 30 Step 50 Image data storage area 51 Uncompressed band data 52 Compressed band data 53 Work area 61 66 Video output signal 62 67 CPU processing 63/68 Decompression 64/69 Pre-rendering or compression of subsequent pages

(56) References JP-A-7-195753 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41J 5/30 G06F 3/12

Claims (6)

(57) [Claims] An image data band consisting of a plurality of dot lines is collected to form an image for one page of printing paper, and a print image of one band is sent to a printer engine unit. A method of generating a print image of a laser printer for performing real-time drawing for generating a print image of the next band during transfer, wherein a non-image data band unit is not used while the image memory holding the print image has room. When the area for storing the next image data band as the uncompressed band data is insufficient as the compressed band data is stored, the uncompressed band data is converted into the compressed band data in order from the first band of the same page, and An image forming method for a laser printer, comprising storing in a memory. 2. When a work area is provided in the image memory and the uncompressed band data is converted into compressed band data, the converted compressed band data is temporarily stored in the work area, and then the uncompressed band data is stored in the work area. 2. The image forming method for a laser printer according to claim 1, further comprising: opening an area storing data, and storing the compressed band data temporarily stored in the work area. 3. When storing the uncompressed band data in the image memory, the compression determining unit determines whether or not there is a sufficient area for storing the uncompressed band data in the image memory. 3. The image forming method for a laser printer according to claim 1, wherein the image forming method includes: 4. A band drawing concept that collects a plurality of image data bands composed of a plurality of dot lines to form an image for one page of printing paper, and prints a print image of one band to a printer engine unit. What is claimed is: 1. A print image generating apparatus for a laser printer for performing real-time drawing for generating a print image of a next band during transfer, comprising: an intermediate data storage unit for holding print data input from a higher-level device; Perform a print image generation operation of expanding the print data held in the unit into a print image in band units, and store the uncompressed print image stored in the image memory without compression in the image memory as uncompressed band data. A drawing unit, and compressing a print image of the print images generated by the drawing unit and storing the compressed print image in the image memory in band units; A compression unit that stores the compressed band data sent from the drawing unit and the compressed band data sent from the compression unit; a compression unit that stores the compressed band data sent from the drawing unit; A decompression unit for decompressing data and sending it to a video output unit as uncompressed band data; and a printer engine unit for converting the uncompressed band data from the image memory and the decompressed compressed band data from the decompression unit into band units. A video output unit for sending and printing the intermediate data storage unit, the drawing unit, the compression unit, the image memory, the decompression unit, and the video output unit; and a set of dots in the drawing unit. When storing a print image generated by developing the image memory in the image memory, sufficient storage in the image memory It is determined whether or not there is an area, and if there is sufficient storage area, the image data is sent from the drawing unit to the image memory.If there is not enough storage area, the uncompressed band data is sequentially read from the first band of the same page. An image forming apparatus for a laser printer, comprising: a control unit that sends the data to a compression unit to perform a compression process. 5. A band drawing concept that collects a plurality of image data bands composed of a plurality of dot lines to form an image for one page of printing paper, and prints a print image of one band to a printer engine unit. What is claimed is: 1. A print image generating apparatus for a laser printer for performing real-time drawing for generating a print image of a next band during transfer, comprising: an intermediate data storage unit for holding print data input from a higher-level device; Perform a print image generation operation of expanding the print data held in the unit into a print image in band units, and store the uncompressed print image stored in the image memory without compression in the image memory as uncompressed band data. A drawing unit, and compressing a print image of the print images generated by the drawing unit and storing the compressed print image in the image memory in band units; A compression unit that stores the uncompressed band data sent from the drawing unit and the compressed band data sent from the compression unit as compressed data in the image memory; When storing a print image generated by developing a set of dots in the image memory in the image memory, it is determined whether or not there is a sufficient storage area in the image memory. When there is not enough storage area to be sent to the image memory, a compression judging unit for sequentially sending uncompressed band data to the compression unit from the first band of the same page to perform the compression process, and expanding the compressed band data. A decompressor for sending uncompressed band data to a video output unit, and the uncompressed band data from the image memory and the decompressed band from the decompressor. A video output unit that sends band data and image data to the printer engine unit in band units to output and print, and the intermediate data storage unit and the drawing unit and the compression unit and the image memory and the decompression unit and the video output unit; An image forming apparatus for a laser printer, comprising: a control unit that controls an operation of the compression determining unit. 6. The image memory according to claim 4, wherein a working area for temporarily storing the converted compressed band data when converting the uncompressed band data into compressed band data is provided in the image memory. Item 6. An image forming apparatus for a laser printer according to Item 5.