JPH10164330A - Image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the throughput of printing by estimating the expansion time of non-expanded data and setting the time to start output. SOLUTION: In a memory unit, at the time of printing, compressed image data inside a code memory 303 are expanded by an expander 304 and the expansion speed of the expander 304 is the same as the compression speed of a compressor 302. Then, by obtaining the compression speed for each block inside certain images beforehand at the time of compression, the expansion speed is predicted. That is, a CPU 106 divides the images into the plural blocks and calculates an image output start timing by which image output (printing) does not pass expansion for each block. Then, without waiting for the completion of the expansion of all the images equivalent to one page, at the time of reaching the image output start timing, the report of image output permission is informed and the image output is started from an output memory 306. Thus, the throughput is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention reads an image,
The present invention relates to an image forming apparatus that compresses and stores the image, and expands and outputs the image during printing.

[0002]

2. Description of the Related Art Image forming apparatuses such as digital copiers are
The original is read as a digital image and recorded on paper.
The read image data is stored in the memory. When an image for one page is read, the image data is read from the memory and output to the printing device. Storing the read image in the memory enables various image processing. When reading an image, the read data is compressed and stored in a memory. This allows
Reduce the amount of data stored in memory. During printing, the data in the memory is expanded and the image is printed on paper.

[0003]

SUMMARY OF THE INVENTION In a copying machine, in order to print an original document quickly, all the original documents are read,
The printer device feeds the paper first. In this way, by sequentially feeding paper, it is possible to prevent a decrease in throughput due to a delay in paper supply when an image is formed on paper.
However, regarding the output of image data for printing, the time for decompression must also be considered. Conventionally, 1
Image output was not performed until all page images had been decompressed. For this reason, when the compression rate of the original image is low, or in a saving copy mode in which a plurality of original images are formed on one page, the time required for decompression becomes longer, and the time for which the paper waits before the timing roller becomes longer. There is. Therefore, even if the paper is supplied in advance, the throughput is reduced. In order not to reduce the throughput, it is desirable that the next image output can always be started within the sheet interval of the printer device regardless of the compression ratio of the original image and the saving copy mode.

An object of the present invention is to provide a digital copying machine capable of starting the next image output within the sheet interval of the printer device regardless of the compression ratio of the original image and the saving copy mode.

[0005]

In the image forming apparatus according to the present invention, the compression unit divides the document image data read by the reading unit into predetermined blocks, compresses the blocks into blocks, and stores the data in the first memory. I do. The decompression means reads and decompresses data from the first memory in block units,
In the memory of The printing means reads out the image data from the second memory and outputs the image. here,
The setting means sets a time to start outputting image data from the second memory by estimating a decompression time of the undecompressed data. In this way, the image output start timing can be estimated so that the print does not overtake the elongation.
Image output can be started without waiting for completion of decompression of all images for one page, thereby improving print throughput.

Preferably, the decompression time is estimated in units of blocks, and the setting means sets the second decompression time based on the decompression time of all blocks and the output time of image data.
Set the time until the output of image data from the memory of. Since compression and decompression are performed in block units, the decompression time can be estimated in block units. Preferably, in the setting unit, the estimation of the extension time differs for each block. For example, decompressing and writing to memory,
In a block where reading from the memory is performed at the same time, the time until the output of image data from the second memory is started is set based on the slowest decompression time. Preferably, the estimation of the decompression time is performed based on the compression time. At the time of image compression performed before decompression of a document image, the compression time of each block is measured. When decompression is performed after compression, the decompression time can be estimated from the compression time measured for each block, and the decompression time of the entire image can be estimated based on this. In this way, the image decompression time can be estimated based on the actually measured data on compression. Preferably, the extension time is estimated based on the size of the document.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, one embodiment of an image forming apparatus according to the present invention will be described.
A digital copying machine according to an embodiment will be described with reference to the accompanying drawings. (1) Configuration of Copying Machine FIG. 1 schematically shows the overall configuration of a digital copying machine 1. The digital copying machine 1 includes a reading device 200, a printer device 300, a document conveying unit 500, and a re-conveying unit 600. The document feeder 500 automatically transfers the document set on the document feed tray 510 to the document glass 18.
The document is conveyed upward, and after the reading device 200 has read the document, the document is discharged to the discharge tray 511. The size of the document is detected by sensors 551 and 552. Reader 200
Comprises a scanning system 10, an image signal processing unit 20, and the like. The scanning system 10 reads a document on the platen glass 18 and converts it into an image signal. In the scanning system 10, a document is irradiated by an exposure lamp 11 mounted on a scanner 19 that moves below a platen glass 18. Light reflected from the document passes through a first mirror 12, fixed mirrors 13a and 13b, and a condenser lens 14, and is incident on a photoelectric conversion element 16 using a CCD array or the like. The photoelectric conversion element 16 converts the reflected light of the image of the original into an electric signal,
Output to The image signal processing unit 20 processes the input electric signal and outputs image data to the memory unit 30. The memory unit 30 outputs the input image data as it is to the printer device or compresses and stores it in a memory.

The printer device 300 includes a print processing unit 40,
The optical system 60 includes an image forming system and the like. Print processing unit 4
0 drives the semiconductor laser 61 of the optical system 60 based on image data input from the reading device 200. In the optical system 60, the beam emitted from the semiconductor laser 61 is deflected by the polygon mirror 65 and is guided to the exposure position on the photosensitive drum 71 via the main lens 66 and the reflection mirrors 67, 68, 69. As a result, a latent image of a document image is formed on the photosensitive drum 71.

The image formation is performed by an electrophotographic system in an image forming system. The latent image formed on the photosensitive drum 71 is developed, transferred and fixed on a sheet to form an image on the sheet. In the development transfer system, the photosensitive drum 71, which is driven to rotate counterclockwise in FIG. 1, is uniformly charged by the charging charger 72, and is developed by the developing device 73 after exposure. The developed toner image is transferred to a sheet by a transfer charger 74. The paper is separated by the separation charger 75. In the transport system, paper is supplied from cassettes 80a and 80b. The size detection sensors 91 and 92 detect the sizes of the sheets in the cassettes 80a and 80b that store the sheets.
The sheet is guided to the photosensitive drum 71 via the sheet guide 81 and the timing roller 82, and is conveyed to the fixing roller 84 by the conveying belt 83 after the above-described transfer. In the fixing system, a fixing roller 84 fixes an image on paper by heat, and thereafter,
A discharge roller 85 discharges the sheet.

A re-feed unit 600 is an additional device used for double-sided copying or the like, and temporarily stores sheets discharged from the main body of the copying machine and returns the sheets to the photosensitive member. In other words, the switching claw 601 switches between the discharge to the discharge tray 721 and the re-feed of the sheet discharged from the discharge roller 85. In the case of re-feeding, the paper is fed to the re-feeding unit 60.
Store in 0 once. In the re-transport system, the re-feed unit 60
0 are transported by horizontal transport rollers 86a to 86c.
Conveyed by. Then, in order to form an image again, the paper is transported to the printer device 300 with the front and back reversed in the double-sided mode and not reversed in the combined mode. In the re-transport system of the printer 300, the sheet transported from the re-feed unit 600 is transported to the timing roller 82 via horizontal transport rollers 86a to 86c.

(2) Control System of Copier Next, the control unit 100 will be described. FIG. 2 and FIG.
FIG. 2 is a block diagram illustrating a configuration of a control unit 100 of the copying machine 1. The control unit 100 is composed mainly of eight CPUs 101 to 108. Each of the CPUs 101 to 108 has a ROM 111 to 118 storing a program and a RAM 121 to 118 serving as a work area for program execution.
128 are provided. The CPU 106 is provided in the memory unit 30 (see FIG. 4).

The CPU 101 controls input and display of signals from various operation keys on an operation panel (not shown). Although not shown, the operation panel includes various keys such as a copy start key and a mode selection key, and a display device. The CPU 102 controls each unit of the image signal processing unit 20. The CPU 103 controls the driving of the scanning system 10. The CPU 104 controls the print processing unit 40, the optical system 60, and the image forming system 70. Where the CPU
104 obtains the size of the copy sheet stored in the sheet cassettes 80a and 80b based on the signals from the cassette detection sensors 211 and 212. The CPU 105 controls the control unit 10
Processing for adjusting the overall timing of 0 and setting the operation mode is performed. The CPU 106 is a memory unit 3
By controlling 0, the read image data is compressed and temporarily stored in the code memory 303, and then read out and output to the print processing unit 40. Thereby, the reading device 200
And the printer device 300 are independently controlled to improve the copy speed. The CPU 107 controls the document transport unit 500. The CPU 108 controls the re-feed unit 600. Serial communication by interruption is performed between these CPUs 101 to 108, and commands, reports,
Other data is exchanged.

(3) Compression and decompression of image data using image memory Next, processing of image data will be described. In the present embodiment, one page of image data is processed by being divided into a plurality of blocks. Data read from the document is converted into digital image data in the image signal processing unit 20. The image data is compressed in the memory unit 30 in block units and stored in the code memory in block units. At the time of image reproduction, the compressed data in the code memory is expanded and read in block units. First, the image signal processing unit 20
The image signal processing unit 20 includes an A / D converter, a shading correction unit, and the like. The image signal processing unit 20 quantizes an input signal from the photoelectric conversion element 16 into 8-bit image data for each pixel, performs various processes, and sends the processed data to the memory unit 30 as image data D2.

Next, the memory unit 30 will be described with reference to the block diagram shown in FIG. When the image is read, the image data D2 from the image signal processing unit 20 is read.
Is first transferred to the input page memory 301. The image transferred to the input page memory 301 is sent to the compressor 30
2 is compressed in block units. The compressed data is transferred to the code memory 303 and stored. The code memory 303 is, for example, an A4 size 5 at 400 dpi.
This is a multi-port memory having a capacity of 0 pages. The compression speed of the compressor 302 depends on the data of the read image. The compression speed is high for a document having many characters, and is low for an image having many images such as photographs. In the compressor 302, the highest compression speed and the lowest compression speed are defined.

At the time of printing, the compressed image data in the code memory 303 is expanded by an expander 304. If image rotation is required, rotation processing is performed by the rotator 305 in block units at the time of decompression, and rotation processing and decompression processing are performed simultaneously. The decompressed image data is transferred to the output page memory 306. Here, in the saving copy mode in which a plurality of original images are formed on one page, for example,
Decompression is performed so that two originals are reproduced on one sheet. The memory unit 30 is controlled by the CPU 106 according to a program stored in the ROM 116. Worst extension rate V _min and the output speed (printing speed) V _p is stored in the ROM 116. Further, parameters necessary for operating the program (compression time t _c for each block) and the like are stored in the system RAM 126. In this memory unit 30, the decompressor 3
The expansion speed of 04 is the same as the compression speed of the compressor 302. Therefore, the decompression speed can be predicted by previously obtaining the compression speed for each block in a certain image at the time of compression. When one page of image data D3 is generated in the output page memory 306 by decompression, the image data D3 is transferred from the output page memory 306 to the print processing unit. The data transfer indicated by the thick arrow in the figure can be performed independently and in parallel to improve the copy speed. Each of the image data has a D (not shown).
DMA transfer is performed by the MA controller.

When the document image is temporarily stored, the code memory 303 is managed by a code management table provided in the RAM 126. FIG. 5 shows the correspondence between the code management table and its compressed data in block units in the code memory 303. In the compression of image data, in order to compress the image data stored in the input page memory 301 in block units, the code memory 303 includes
As shown on the right side of the figure, image data for one page is divided and stored in block units. Therefore, the code management table includes an image unit information table T1 for storing information of one image unit in the document and a block management information table T2 for storing information of divided block units.
The image unit information table T1 stores information such as the image size in units of one page before compression, the compression size, and where the block unit information is stored. The block management information table T2 includes information on where the divided image data is, a compression size in block units,
The measured compression time and the like are stored.

Next, the operation sequence of the copying machine 1 in reading and printing will be described with reference to the CPUs 101 to 106.
Command (Q), report (A) exchanged between
Or, the explanation will be focused on the data flow. FIG. 6 shows a schematic sequence of the document reading operation. Here, a sequence when the automatic image transport device 500 is used will be described. First, the CPU that manages the entire sequence
105 requests the CPU 107 for controlling the document feeder to replace the document. In response to this, the CPU 107 starts document conveyance and returns a document set report using the document size detection result as a parameter. When the size is determined, the CPU 105 issues a reading and compression request to the CPU 106 at the same time. The CPU 105 also issues a reading request to the CPU 102 that controls image processing. Then, the CPU 102 requests a scan to the CPU 103 that controls the image reading apparatus. When a document scan is started by the CPU 103 and the scanner 19 reaches the image area, the read data is read according to the image processing mode set by the CPU 102.
(Image data D2) is transferred from the image signal processing unit 20 to the memory unit unit 30. The CPU 106 that controls the memory unit 30 divides the input page memory 301 into predetermined blocks in advance according to the document size.
The CPU 106 checks the progress of image input, sets the addresses of the compressor 302 and the code memory 303 on a block basis at a predetermined timing, and activates each unit. As a result, the compression process is performed by the compressor 302, and the code data is stored in the code memory 303. At this time, the time tc from the start to the end of compression of each block is measured, and the result is stored in the block management information table T2 in the code management table. When the compression processing of the first block is completed, the CPU 106 notifies the CPU 105 of the completion of compression of one block (see FIG. 9). Furthermore, CP
U106 calculates an image output start timing at which printing does not overtake decompression from the worst compression time according to the read size and the print time required for image output (see FIG. 11). And when that timing is reached,
The CPU 106 notifies the CPU 105 of an image output permission report. Further, when the compression processing of all the blocks is completed, the CPU 106 notifies the CPU 105 of the completion of the compression.

FIG. 7 shows a schematic sequence of the printing operation. In the print operation, a copy image is printed on a sheet based on the image data D3 read from the output page memory 306. This figure is closely related to FIG. 6, as described next. When the document set report shown in FIG. 6 is received, the CPU 105 determines the size of the document. Therefore, the CPU 105 determines which paper cassette 80a or 80b to feed paper from, and uses the paper cassette as a parameter for the CPU 104.
To request paper feed. In selecting a paper cassette, it is also determined whether the original is T (vertical direction) or Y (horizontal direction). If sheets of the same size as the document are present in the sheet cassettes 80a and 80b in both the vertical (T) and horizontal (Y) directions, in order to advance the image output start timing, sheets that can be expanded without image rotation, that is, Select the paper in the same direction as the original. When starting paper feeding, the CPU 104 returns a paper feeding report to the CPU 105. When the fed paper reaches the timing roller 82 and preparation for image output is completed, the CPU 104 transmits an image output request report to the CPU 105. Upon receiving the one-block compression completion report shown in FIG. 6, the CPU 105 requests the CPU 106 to expand the data. The CPU 106 refers to the code management table (FIG. 5) in the RAM 126 to read addresses from the code memory 303 in block units,
Each unit is started by setting the data amount and the like. Thus, the decompression process is started, and one block of image data is written to the output page memory 305.

If the image output permission report shown in FIG. 6 has been received from the CPU 106 after the activation of the decompression process, the image output start command is transmitted to the CPU 106 and the CPU 10.
4 and require. In response to this, the CPU 106
Is the output page memory 30 for the internal hardware.
4 to set the bus connection state for outputting the image data D3 to the print processing unit 40. In addition, the CPU 104
The paper transport from the timing roller 82 is started so that the leading edge of the image coincides with the image output start timing. Thus, the image data D3 read from the input page memory 304 is output to the print processing unit 40, and printing is performed. When the printing is completed, the CPU 106 and the CPU 1
04 sends a print completion report and an ejection completion report to the CPU 105. The CPU 105 receiving these reports gives a memory clear request to the CPU 106 as necessary.

As described above, in the memory unit 30, the CPU 106 calculates the image output start timing at which the print does not overtake the decompression from the worst compression time according to the read size and the print time required for the image output. . That is, the image is divided into a plurality of blocks, and the image output start timing at which the image output (print) does not exceed the expansion is calculated for each block. When the image output start timing is reached without waiting for the completion of decompression of all images for one page, the CPU 105 notifies the CPU 105 of a report of image output permission. Image output from the output page memory 306 is started. This improves the throughput. The concept of calculating the image output start timing at which the print does not overtake the expansion is as follows. The time from the start of the decompression to the image output start timing at which the output of the image data from the output page memory 306 is started is set so that the print does not overtake the decompression by estimating the decompression time of the undecompressed data. . Here, the extension time is estimated for each block, and based on the estimated extension time for all blocks and the output time of the image data,
Set the image output start timing. The image output start timing is calculated from the actually measured value of the compression time for each block of the image and the time required for printing. In this calculation, the number of dots in each block, the worst compression speed, the worst expansion speed, the image output speed (print speed _Vp ), and the like are taken into consideration. The number of blocks is determined from the detected document size and the size of one block.

The method of estimating the extension time differs depending on the block. For example, in the first block in which the process of expanding and writing to the output page memory 306 and the process of reading from the output page memory 306 are performed simultaneously, the image output start timing is set to 1 using the worst expansion time V _min (known). When the expansion of the block is completed, it is estimated that the print will not overtake the expansion. If the compression time by the compressor and the decompression time by the decompressor are the same, the decompression time is equal to the measured compression time. This embodiment corresponds to this case. In the memory unit 30, the compressor 30
2 and the expansion time of the expander 304 are the same.
Since the decompression time can be estimated from the compression time, the decompression time can be estimated based on the measured value of the compression time. For the first block, the image output start timing from the worst compression speed
Calculate tx ₁ . For the second and subsequent blocks, the decompression start time (tx ₁ , tx ₂ , …).
Then, the latest decompression start time among the obtained times (tx ₁ , tx ₂ ,...) Is set as the image output start timing.

In the above, the method of estimating the decompression time from the actually measured value of the compression time for each block has been described.
However, the method of estimating the extension time is not limited to this. As another embodiment, it is also easy to calculate the compression ratio from the read image size Bdot and the compression size in each block, and estimate the decompression time in each block according to this and the operating speed of the compressor / decompressor. it can.

Hereinafter, an algorithm for calculating an image output start timing at which a print does not overtake decompression will be described with reference to an example shown in FIG. It is assumed that the compressor 302 and the expander 305 have the same configuration, and that compression and expansion are performed at the same speed. In FIG. 8, the average decompression speed is shown assuming that the image of one page is divided into four blocks and the measured value of the compression speed is the same for all the blocks for easy understanding. The number of expanded dots in each of the first to fourth blocks is Bdot ₁ , Bdot ₂ , Bdot
dot ₃ and Bdot ₄ . Where Bdot ₁ , Bdot ₂ and Bdot
dot ₃ is the same, but Bdot ₄ is less. Further, the decompression start time is t = 0, and the worst compression speed (decompression speed) is V _min
(bps) and the printing speed is V _p (bps). First, the calculation of the first block will be described. When the expansion of the first block (the number of dots Bdot ₁ ) is completed, the image output start time for preventing the print from overtaking the expansion is tx.
_Set to ₁ . The actually measured compression time indicates the entire time from the start to the end of the first block. When the compression time is replaced with the expansion speed, it becomes the average expansion speed in the block. However, since the compression speed within a block is not uniform, the compression speed may have been, in part, the highest compression speed or the worst compression speed. Therefore, the first block has the worst compression (decompression) speed V _min
It is necessary to calculate with. The decompression time required at the worst decompression speed V _min is Bdot ₁ / V _min . If the print start time (image output start time) taking the worst decompression time of the first block into consideration is tx ₁ , then (Bdot _{1 / V min -tx 1) * V} p = Bdot than ₁ the above equation, the print start time tx ₁ are as follows. _{tx 1 = Bdot 1 (1 /} V min -1 / V p) (1) also start the print at this time tx _1, printed after completing the first block extension will not overtake extension.

Next, the calculation of the second block will be described. At the time when the expansion of the second block (the number of dots Bdot ₁ + Bdot ₂ ) has been completed, the possible image output start time to prevent the print from overtaking the expansion is tx ₂ . Although the compression time of the second block is actually measured, it is necessary to calculate the worst compression (decompression) speed in the same manner as in the first block. However, since the terms of the first block can be applied measured value tc ₁ compression time, when obtaining the _{((tc 1 + Bdot 2 /} V min) -tx 2) * V p = Bdot 1 + Bdot tx 2 from ₂ above equation, Print startup time tx ₂ considering the worst extension time of the second block is as follows. _{tx 2 = tc 1 + (Bdot} 2 / V min - (Bdot 1 + Bdot 2) / V p) (2)

Next, the calculation of the Nth block will be described. The number of dots N-th block and Bdot _N, the image output start enabled time for printing at the time the N-th block of the extension is completed to prevent overtaking the extension and tx _N. For the expansion of the Nth block, the compression time is actually measured, but it is necessary to calculate at the worst compression (expansion) speed in the same manner as described above. However, N from the first block
Found compression time with respect to -1-th block tc _m [m
= 1,2,3, ..., N-1] can be applied, so ((tc _m [m = 1,2,3, ..., N-1] total + Bdot _N / V _min )
−tx _N ) * V _p = Bdot _m [m = 1, 2, 3,..., N] From the above equation, the print start time tx _N considering the worst decompression time of the Nth block is as follows. Become. _{tx N = tc m [m =} 1,2,3, ..., N-1] + (Bdot N / V min -Bdot m [m = 1,2,3, ..., N] total / V _p) of ( 3) In FIG. 8, tx ₃ and tx ₄ coincide with each other, but this is a coincidence and generally they are different.

Therefore, the actual measured compression time tc _{m of} each block
When the image output start timing tc is obtained, the compression time is obtained as the average speed in each block, so even if the average speed is higher than the worst compression speed, the compression speed temporarily becomes the worst in the block. In consideration of the above, the image output start timing for the first block is calculated from the worst compression speed as in the above calculation.
tx ₁ is calculated. For the second and subsequent blocks, even if the calculation is performed at the worst decompression speed from the previous measured compression time at the worst decompression speed, all blocks are printed under the condition that the print does not overtake decompression.
(tx ₁ , tx ₂ , ..., tx _n ) are calculated. Then, the latest time t of the decompression start time in each block is set as the image output start timing. By estimating the decompression time in advance and starting printing early, the throughput is improved.

FIGS. 9 to 11 are flowcharts showing compression processing, decompression processing, and output processing by the CPU 106 that controls the memory unit 30, respectively. In the compression processing shown in FIG. 9, first, in step S10, how many blocks the document is divided into is calculated. That is, the document size
From (S) and the size to be processed per block (B),
The number of blocks N is obtained. Next, m is initialized to 0 in step S12, and data input is started in step S14.
In step S16, the input data is compressed,
In step S18, it is determined whether compression for one block has been completed. When the compression is completed, the image data is stored in the code memory 303 in step S20, and in step S22.
In the case of the first block compression, a one-block compression completion report is output. Next, in step S24, this 1
Stored in the management table the measured time tc _m required for compression processing block block management information T2 (Figure 5). Then, in step S26, m is incremented by one, and the process returns to step S14 for processing of the next m-th block. On the other hand, if it is determined in step S28 that the compression for N blocks, that is, for all blocks has been completed, step S3
At 0, the compression completion is notified to the CPU 105, and the compression processing ends.

In the decompression process shown in FIG. 10, first, in step S40, it is determined whether it is the decompression start timing. That is, since decompression is possible if compression of at least one block has been completed, it is determined here whether or not it is decompression start timing on the condition that compression of one block has been completed. If decompression start timing, then at step S42, the counter n _d showing the extended block reset to 0, and reads the data from the code memory 303 in step S44. In step S46,
The read data is expanded, and in step S48,
It is determined whether the extension has been completed. If the decompression has been completed, it is stored in the output page memory 306 in step S48, the counter is incremented by one in step S50, and the process returns to step S44 to process the next block. However, if it is determined in step S52 that all blocks have been decompressed, the decompression process ends.

In the output processing shown in FIG. 11, the decompression of the first block is started (N in step S62).
O) In step S60, the time from the start of decompression to the reading of data from the output page memory 306 is obtained based on the compression time, the number of dots, the worst decompression time, and the read time of each block (Equation (1), (2), (3)). Then, the latest time t of the decompression start time in each block
Is the image output start timing. Next, when decompression of the first block starts (YES in step S62), in step S64, a time t is set, and counting of a timer is started. If it is determined in step S66 that the time t has elapsed, an image output permission report is output to the CPU 105 in step S68. When an image output start request is received from the CPU 105, data reading from the output page memory 306 starts. Let it. Then, when the data output is completed, the CPU 105 is notified of the print completion in step S70. Thus, the time required to expand each block
Since reading from the output page memory 306 is started by estimating t, the reading does not overtake the expansion.
Furthermore, since reading can be started without waiting for the end of expansion of one page, productivity can be improved.

[0030]

As described above, in printing a document, image data can be output without waiting for completion of decompression of all images per page, so that printing can be started quickly and throughput can be improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional front view showing an overall configuration of a copying machine according to the present invention.

FIG. 2 is a block diagram illustrating a configuration of a control unit of the copying machine.

FIG. 3 is a block diagram illustrating a configuration of a control unit of the copying machine.

FIG. 4 is a block diagram illustrating a configuration of a memory unit.

FIG. 5 is a diagram illustrating a relationship between image information and a code memory.

FIG. 6 is a diagram showing a schematic sequence of a document reading operation.

FIG. 7 is a diagram illustrating a schematic sequence of a printing operation.

FIG. 8 is a diagram showing the relationship between decompression and printing.

FIG. 9 is a flowchart of a compression process.

FIG. 10 is a flowchart of a decompression process.

FIG. 11 is a flowchart of an output process.

[Explanation of symbols]

 30 memory unit, 105 overall control CPU, 106 memory CPU, 301 input page memory, 302 compressor, 303 code memory, 304 decompressor, 306 output page memory.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Eiichiro Kawasaki 2-3-13 Azuchicho, Chuo-ku, Osaka-shi, Osaka Inside Osaka International Building Minolta Co., Ltd. (72) Eiichi Yoshida Azuchi, Chuo-ku, Osaka-shi, Osaka Osaka International Building Minolta Co., Ltd. (72) Inventor Yoshikazu Ikenoue 2-3-1-13 Azuchicho, Chuo-ku, Osaka-shi, Osaka

Claims (6)

[Claims] 1. A reading device for reading a document image, compression means for dividing the read document image data into predetermined blocks, compressing the blocks in units of blocks, and storing the compressed data in a first memory; A digital copying machine having a decompression means for reading and decompressing data in units and storing the data in a second memory; and a printing means for reading data from the second memory and outputting an image; An image forming apparatus comprising: setting means for setting a time to start reading by estimating a decompression time of undecompressed data. 2. The image forming apparatus according to claim 1, wherein the estimating of the decompression time is performed for each block.
An image forming apparatus configured to set a time until output of image data from the second memory is started based on the estimated decompression time of all blocks and the output time of image data. . 3. An image forming apparatus according to claim 1, wherein said setting means is configured such that the estimation of the decompression time differs for each block. 4. The image forming apparatus according to claim 3, wherein, in a block in which a process of decompressing and writing to the memory and a process of reading out from the memory are simultaneously performed, the second memory is decompressed based on the slowest decompression time. An image forming apparatus for setting a time until output of image data is started. 5. The image forming apparatus according to claim 1, wherein the estimating of the decompression time is performed based on a compression time. 6. The image forming apparatus according to claim 1, wherein the extension time is set based on a document size.