JP3155573B2 - Image forming device - 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 apparatus which compresses image data, stores the compressed data in a memory, and decompresses the image data upon output.

[0002]

2. Description of the Related Art FIG. 26 is a block diagram schematically showing a conventional image forming apparatus. The image reading unit 501 performs A / D conversion on image signals read by a photoelectric conversion element such as a CCD after performing amplification, black level correction, shading correction, and the like, for example, to 6-bit image data. The image processing unit 502 performs gamma correction, MTF correction, scaling processing in the main scanning direction, and the like on the image data read by the image reading unit 501, and stores the data as, for example, 1-bit binary data or 4-bit multi-value data. 503 is stored.

Here, when the image forming apparatus is used in a digital copying machine, a frame memory is used as the memory 503, and the frame memory performs image trimming, masking, black / white inversion, mirroring, and the like on image data. It is provided in the editing circuit. Therefore, the image output unit 504 can repeatedly read out the image data from the memory 503 and record the image data on a sheet, so that the image reading unit 501 can perform a plurality of copies only by reading the document once.

FIG. 27 is a block diagram schematically showing another conventional image forming apparatus. In this conventional example, the image reading unit 5
The 6-bit image data read by 01 is stored in the memory 506, subjected to the above-described image processing by the image processing unit 507 at the time of output, and output by the image output unit 508. In this case, similarly, the image processing unit 50
7 can repeatedly read the image data from the memory 506, so that the image reading unit 505 can perform a plurality of copies only by reading the document once. Further, in this apparatus, since data before image processing is stored in the memory 506, a plurality of copies are made by changing the parameters at the time of image processing and changing the image quality or the like for each copy of the same original. be able to.

[0005]

However, FIG.
In the conventional image forming apparatus shown in FIG. 2, when an A3-size original image is read at a resolution of 400 dpi and converted into a 6-bit digital value, the memory 506 stores 297
A capacity of mm × 15.7 × 420 mm × 15.7 × 6 bits バ イ ト 24 Mbytes is required, and therefore, there is a problem that a large-capacity memory 506 is required and becomes expensive. Similarly, in the conventional image forming apparatus shown in FIG. 26, since the memory 503 stores 4-bit multi-value data, 297 mm × 15.7 lines × 420 mm × 1
A capacity of 5.7 lines × 4 bits ≒ 16 Mbytes is required.

Incidentally, as shown in FIG.
If a binary compression unit 510 and a binary expansion unit 512 such as an MH (Modified Huffman) system, an MR (Modified Read) system, and an MMR (Modified Modified Read) system are provided before and after the memory 511, respectively.
Can be reduced. However, in recent digital copiers, high image quality is required and multi-value data is processed. Therefore, this method cannot store multi-value compressed data in a small-capacity memory 511.

[0007] The present invention has been made in view of the above conventional problems, Digi
It is an object of the present invention to provide an image forming apparatus capable of reducing the capacity of a memory when used in a tall copier or the like .

[0008]

In order to achieve the above object, a first means is to provide a binary image pressure for compressing binary image data.
Compression means and multi-level image compression means for compressing multi-level image data
And the binary image compression means or the multi-value image compression means
Storage means for storing a more compressed code;
2 for expanding the sign of the binary image data read from the stage
Value image decompression means, and multi-value read from the storage means
Multi-level image decompression means for decompressing the sign of the image data;
Compressed by binary image compression means and the multi-valued image compression means
Compression rate according to the data amount of each code of the
The binary image compression means and the binary image decompression means
Stage or the multi-level image compression means and the multi-level image decompression means
And means for selecting

[0009]

[0010]

[0011]

According to the first means, the first document is formed by the above-described configuration.
The compression rate is the maximum binary image pressure depending on the data amount of each code
Digital copy machine
In such a case, the capacity of the memory can be reduced.

[0012]

[0013]

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a memory unit in an embodiment of the image forming apparatus according to the present invention, FIG. 2 is an explanatory view showing the contents stored in the memory of FIG. 1, and FIG. 3 is an image forming apparatus having the memory unit of FIG. FIG. 4 is an explanatory diagram showing the operation of the binary compression unit in FIG. 1, FIG. 5 is a block diagram showing the detailed configuration of the multi-value compression unit and the multi-value decompression unit in FIG. 1, and FIG. FIG. 7 is an explanatory diagram showing the operation of the block reading unit in FIG. 5, FIG. 7 is an explanatory diagram showing the DCT coefficients in FIG. 5, and FIG.
FIG. 4 is an explanatory diagram showing a quantization matrix in FIG.

First, an image reading unit 101 shown in FIG. 3 reads a document set on a document table by a line CCD, amplifies a read signal to a predetermined level, and performs A / D conversion to obtain characteristics of an illumination system and CCD characteristics. Shading correction is performed according to the variation in sensitivity, and the result is output to the encoding unit 102 of the memory unit 100.

The encoding section 102 includes a binary compression section 513 and a multi-level compression section 514 as shown in detail in FIG.
Here, DCT (discrete cosine transform) is performed on the binary image.
And the like, the amount of data after compression increases. Similarly, when a multi-valued image is compressed by a binary method such as MH and MR, the amount of data after compression increases. Become.
Therefore, in the present embodiment, the binary compression unit 513 compresses the binary image by a binary method such as MH and MR as shown in FIG. Compresses a multi-valued image using a multi-valued method such as DCT, and
15 is stored.

When storing in the memory 515, FIG.
As shown in (a), the first document is compressed in both binary and multi-valued and stored in the respective areas (515a in the drawing). The address is read and notified to a CPU (Central Processing Unit) 519. The CPU 519 discriminates a compression method with a small data amount based on each write end address and notifies the memory management unit 518 of the compression method. The memory management unit 518 selects a compression method with a small data amount for the second and subsequent originals, and stores the compressed data of each original in the memory 5 as shown in an area 515b of FIG.
15 sequentially. That is, the code storage unit 106 illustrated in FIG. 3 includes a memory 515, a memory management unit 518, and a CPU 519.

The decoding unit 103 includes a binary decompression unit 516.
And a multi-level decompression unit 517 and a multiplexer 520. The binary extension unit 516 and the multi-level extension unit 517 are respectively
The inverse conversion of each conversion by the binary compression section 513 and the multi-level compression section 514 is performed, and the data expanded by the binary expansion section 516 and the multi-level expansion section 517 are selectively transmitted via the multiplexer 520 under the control of the CPU 519. Is output to

In the above-described embodiment, instead of selecting a compression method in which the data amount is smaller depending on the first document, if an automatic document recirculation feeding device (RDH) described later is used, each document is pre-scanned. Alternatively, a compression method with a small data amount may be selected, or the operator may select a compression method for each document.

When the compressed data is stored in the memory 515, the scale data at the time of encoding, the quantization matrix, the Huffman encoding table, the number of copies specified by the operator are added to the header of the compressed data of the first page. , Copy conditions such as a document size, a copy size, and a transfer paper size are written. When the encoded data file is read from the memory 515 and output as an image file of a computer or the like, it is desirable that the file structure be managed by another management table so that the file structure can be used as it is.

The decoding unit 103 performs decoding by using scale data, a quantization matrix, a Huffman coding table, and the like when encoding the header, and outputs the result to the image processing unit 104. The image processing unit 104 determines the number of copies of the header,
According to copy conditions such as a document size, a copy size, and a transfer paper size, a halftone process or a simple binarization process necessary for forming an image by an electrophotographic method is performed.
Uses this data to form an image on transfer paper with a photoreceptor.

Next, referring to FIG. 5 to FIG.
14 and the detailed configuration of the multi-level decompression unit 517 will be described. First, the block reading unit 301 of the multi-level compression unit 514 reads an image for each block of 8 × 8 pixels as shown in FIG.
ij is converted to a DCT coefficient value yuv.

(Equation 1)

As shown in FIG. 7, the DCT coefficient is such that the coefficient (0, 0) indicates the average density in the block, and the other coefficients (1, 0), (0, 1) ) Indicates the ratio of the low-frequency component in the block, and the higher-order coefficient indicates the ratio of the high-frequency component in the block. Therefore, the coefficient of (0,0) is a DC component, and the other coefficients are AC components. (1,0), (2,0),
Coefficients in the u direction (main scanning direction) from (3, 0) indicate the rate of change in density in the main scanning direction, and are (0, 1), (0,
2) The coefficients in the v direction (sub-scanning direction) from (0, 3)
It shows the magnitude of the density change in the sub-scanning direction. Furthermore, (1,
1), (2, 2), the coefficient in the diagonal direction of (3, 3)
It shows the magnitude of the component where the density change in the main scanning direction and the density change in the sub-scanning direction overlap.

In FIG. 5, the DCT coefficient value transformed by the DCT transform unit 302 is linearly quantized by a quantization unit 303 with a quantization step size having a different size for each coefficient, and a quantized coefficient is calculated. . The quantization step size is obtained by multiplying the quantization matrix stored in advance in the quantization matrix storage unit 306 by the scale factor set by the scale factor control unit 305, and changing the value of this scale factor. The code amount and the image quality at the time of decoding are controlled. Here, the quantization matrix is set to finely quantize low-order coefficients so as to match human visual characteristics as shown in FIG.

As for the quantized coefficients calculated by the quantizing section 303, a short code is assigned to a coefficient having a high appearance frequency by the Huffman encoding section 304, and a long code is assigned to a coefficient having a low appearance frequency. The amount is reduced and the code storage unit 307, ie, the memory 515 shown in FIG.
Is stored in

The Huffman decoding unit 30 of the multi-level decompression unit 517
8 assigns a quantized coefficient value to the code read from the code storage unit 307,
9 calculates the DCT coefficient by dequantizing the coefficient value. The quantization step size in the inverse quantization is obtained by multiplying the quantization matrix stored in advance in the quantization matrix storage unit 306 by the scale factor set by the scale factor control unit 305, as in the case of encoding. Is done.

The inverse DCT unit 310 includes the inverse quantization unit 30
The block writing unit 311 converts the DCT coefficient calculated in step 9 into original image data, and outputs this image data for each block. The image data for each block is stored in a line memory for eight lines (not shown).
When image data is accumulated in all areas of the line memory, it is output line by line.

Next, a digital copying machine to which the image forming apparatus of the present embodiment is applied will be described in detail with reference to FIGS. 9 is a side view showing the overall configuration of the digital copying machine, FIG. 10 is a plan view showing the detailed configuration of the writing unit in FIG. 9, FIG. 11 is a side view showing the writing unit in FIG.
12 is a side view showing a detailed configuration of the automatic document feeder (RDH) of FIG. 9, FIG. 13 is a perspective view showing a main part of the paper feed mechanism of FIG. 12, and FIG. 14 shows the paper feed mechanism of FIG. Front view, FIG. 1
5 is an enlarged side view showing a detailed configuration of the paper feeding mechanism of FIG. 12,
FIG. 16 is a perspective view showing a mechanism for detecting the length of a document, and FIG.
7 is an explanatory diagram showing a document width detecting sensor, FIG. 18 is a flowchart for explaining a document size detecting operation, and FIG.
FIG. 2 is a side view showing the extended state of the return mechanism of FIG.
0 is a side view showing an intermediate state of the return mechanism of FIG. 12, FIG. 21 is a side view showing a contracted state of the return mechanism of FIG. 12,
FIG. 22 is a perspective view showing the detailed configuration of the paper discharge unit shown in FIGS. 19 to 21, FIG. 23 is a flowchart for explaining the operation of the automatic document feeder (RDH) shown in FIGS. FIG. 25 is a block diagram showing a control unit of the digital copying machine shown in FIG.

Referring to FIG. 9, this digital copying machine comprises:
Copying machine body (I) and automatic circulating document feeder (RDH)
(II), sorter (III) and double-sided reversing unit (IV)
It is schematically composed of two units. The copier body (I) includes a scanner unit, a writing unit, a photoconductor unit, a developing unit, a paper feeding unit, and the like. The details will be described below.

The scanner section has a first mirror on which a reflecting mirror 1, a light source 3, and a first mirror 2 are mounted and moves in the sub-scanning direction at a constant speed, and a second mirror 4 and a third mirror are mounted. A second scanner that moves in the sub-scanning direction at half the speed of the first scanner. An original (not shown) on the contact glass 9 is optically scanned by the first scanner and the second scanner, and the reflected light is transmitted through a color filter 6 and a lens 7 to a light receiving surface of the one-dimensional solid-state imaging device 8. Image.

As the solid-state image pickup device 8, a CCD is generally used. Since the image signal read by the solid-state imaging device 8 is an analog signal, it is A / D converted and binarized and multi-valued by the processing circuit mounted on the image processing board 10 as shown in FIGS. Various processes such as gradation processing, scaling processing, and editing are performed. In order to obtain a color signal, a color filter 6 is arranged so as to be freely put in and out of the optical path. This color filter 6 is put in and out of the optical path in accordance with the scanning of the original so that various kinds of copying such as multiple transfer and double-sided copying can be performed. Done.

The image information after the image processing is written on the photoreceptor 40 in the form of a set of light points by raster scanning of a laser beam in a writing section as shown in detail in FIGS. The laser light emitted from the semiconductor laser 20 is
The light beam is shaped into a parallel light beam by the collimator lens 21, passes through the aperture 32, is shaped into a light beam having a predetermined shape, and is then compressed in the sub-scanning direction by the first cylinder lens 22 and enters the reflection surface of the polygon mirror 24.

The polygon mirror 24 is formed in an accurate polygon, and is rotated by a polygon motor 25 in a predetermined direction at a constant speed. The rotation speed is determined by the rotation speed of the photoconductor 40, the writing density, and the number of surfaces of the polygon mirror 24. The laser light incident on the reflection surface of the polygon mirror 24 is deflected at a constant angular velocity, and then corrected by the f-θ lenses 26a and 26b so as to scan the photoreceptor 40 at a constant velocity. The f-θ lenses 26a, 26
6b also has a tilt correction function.

The laser light corrected by the f-.theta. Lenses 26a and 26b is guided to the synchronization detecting light input section 30 by the synchronization detecting mirror 29 outside the image area, and is guided to the sensor by an optical fiber. Then, after a predetermined time from the cueing signal in the main scanning direction synchronized with the detection signal, image data for one line reflected by the mirror 27 is output. A latent image is formed on photoconductor 40.

On the peripheral surface of the photoconductor 40, a photoconductor layer is formed. Organic photoreceptors (OPC), as photoreceptor layers sensitive to semiconductor lasers having a wavelength of 780 nm,
Although α-Si, Se-Te, and the like are known, an organic photoconductor (OPC) is used in this embodiment. Here, when writing with the semiconductor laser 20, there are known a negative / positive process of irradiating the image portion with light and a positive / positive process of irradiating the background portion with light. Writing is performed by a positive process.

In FIG. 9, a scorotron system having a grid on the photoconductor 40 side is used as the charging charger 41, and the surface of the photoconductor 40 is uniformly (-) charged, and a laser beam is applied to the image forming area. To lower the potential of the region. As a result, the potential of the background area of the photoconductor 40 becomes -7.
50 to -800 V, while the potential of the image area is -5.
Since the voltage is about 00 V, an electrostatic latent image is formed on the surface of the photoconductor 40.

In the developing devices 42a and 42b, a bias voltage of -500 to -600V is applied to the developing roller.
The negatively charged toner is adhered to the image area of the photoconductor 40 to visualize the electrostatic latent image. The developing section of this embodiment includes two main developing units 42a and sub developing units 42b, and fills a toner replenishing unit 43a corresponding to the main developing unit 42a with black toner, and corresponds to the sub developing unit 42b. Toner replenisher 43
Filling b with a color toner enables selective development.

The transfer paper is conveyed to the position of the transfer charger 44 in synchronization with the photoreceptor 40, and developed by the developing units 42a and 42b.
Is transferred to the transfer sheet by the transfer charger 44 charging the back surface of the transfer sheet to (+). The transfer paper on which the toner image has been transferred is subjected to AC discharge by the separation charger 45 and separated from the photoreceptor 40. The remaining toner on the photoconductor 40 is removed by the cleaning blade 47 and collected in the tank 48. The remaining charge on the photoreceptor 40 is discharged by irradiating the photoreceptor 40 with a discharge lamp 49.

A photosensor 50 for detecting the reflection density on the photoconductor 40 is provided downstream of the developing units 42a and 42b in the rotation direction of the photoconductor. The density of the formed and developed pattern, such as black or halftone dots, and the density other than this pattern are read, and the density of the toner image is detected. If the density is low, a toner replenishment signal is output or the remaining amount of toner is insufficient. Output a signal.

The paper feeding section includes a plurality of cassettes 60a, 60
b and 60c, and is configured to perform double-sided copying and re-feeding by guiding the paper once transferred to the transfer position via the re-feeding loop 72. When the copy start button is pressed after one of the cassettes 60a to 60c is selected, the corresponding paper feed rollers 61a, 61b,
One of the rollers 61c rotates, and the transfer paper is conveyed until the leading end thereof contacts the registration roller 62. Then, the registration roller 62 starts rotating so that the toner image on the photoconductor 40 and the transfer paper are synchronized, and the above-described transfer is performed.

The transfer paper separated from the photoreceptor 40 is sucked and conveyed by the separation conveyance section 63, and
The toner images 4 and 65 are fixed. This transfer paper is guided to the discharge port on the sorter (III) side in the case of normal one-sided copying, and in the case of multiple copying, the switching claw 6 is used.
8, 69 return to the position of the registration roller 62 via the lower re-feeding loop 72 without changing the copy surface. In the case of double-sided copying, the copy side is reversed by the copier body (I) or the double-side reversing unit (IV). In the former case, the switching pawls 68, 69, and 71 guide the roller 70 to the tray 70 below the refeeding loop 72,
Is returned in the opposite direction by the reversal, and is guided to the re-feeding loop 72 by the switching of the switching claw 69, and is returned to the position of the registration roller 62.

Next, a detailed configuration of the automatic document feeder (RDH) will be described with reference to FIGS. As shown in FIG. 12, the RDH (III) has a cover-shaped case for covering the contact glass 9 of the copying machine main body (I). A table 201, a paper feed mechanism 270 for sequentially feeding the originals on the paper feed table 201 from below in the direction of the contact glass 9, and transporting the originals fed by the paper feed mechanism 270 to a predetermined exposure position on the contact glass 9. And a conveyor belt 2 to be discharged from the contact glass 9 after exposure.
12, a reversing mechanism 272 for reversing the surface of the document discharged by the transport mechanism 271, and a document reversed by the reversing mechanism 272.
A return mechanism 273 is provided for returning the original to a position above the upper original bundle.

Side fences 202 are provided on both left and right sides of the sheet feeding table 201 along the transport direction in the front minimum document placing range. Paper feed table 2
In the vicinity of the front end of the sheet feeding direction No. 01, two call rollers 203a and 203b having a missing circle are arranged along the transport direction, and the call rollers 203a and 203b are arranged such that the missing circle faces upward. , So as not to protrude above the document mounting surface.

As shown in FIG. 13, a slit plate 260 having a slit 261 and a positioning plate 263 for positioning a missing circle are attached to the axes of the call rollers 203a and 203b. The slit 261 of the slit plate 260 is detected by the photoelectric sensor 262,
A pressing roller 264 urged by a spring rolls on the end surface of the positioning plate 263. The call rollers 203a and 203b (the call rollers are simply denoted by reference numeral 203 when schematically shown) are provided with the slit 261 and the photoelectric sensor 1 so that each of the missing circle portions rotates in the same phase.
At 62, the rotation angle at which the sheet feeding table 201 and the missing circle portion are on the same plane is detected, and the call rollers 203a, 203b are detected.
Is stopped, and the callout rollers 203a and 203b are positioned at the stop position by the positioning plate 263 and the pressing roller 264.

As shown by the dashed line in FIG. 12, a pressing plate 204 for pressing down the leading end of the document and pressing the leading end of the original is pressed above the calling roller 203a.
The pressing plate 204 is driven by a solenoid (not shown). As shown in FIG.
In FIG. 2, a stopper 205 is provided, which is moved by a solenoid 267 (FIG. 14) with the rear end as a fulcrum, between a retracted position indicated by a broken line and an operating position indicated by a solid line. In the operating position, the toe of the stopper 205 comes into contact with the upper surface of the sheet feeding table 201 or the upper surface of the set of document bundles as shown in FIG. The skew is corrected by colliding the leading edge of the document returned to the sheet supply table 201 from the start.

The pressing roller 203 is pressed by the pressing plate 204.
The bundle of originals pressed by a
3b rotates synchronously, and is reliably conveyed to a separation position. The document set sensor 206 detects that the document bundle has been set on the sheet feeding table 201, and according to this detection signal, the call rollers 203a and 203b rotate by a fixed amount, and the document bundle is conveyed to the separation position shown in FIG. You.

The calling rollers 203a and 203b are
In cooperation with a separation mechanism composed of an endless belt 207 and a separation roller 208, the lowermost sheet of the document bundle located at the separation position is fed. The separation roller 208 rotates in the document conveying direction, and the endless belt 207
08, the separation roller 208 rotates in the opposite direction (arrow A in FIG. 12) at a speed of, for example, 1/20. Therefore, by appropriately setting the coefficient of friction between the separation roller 208 and the document, the coefficient of friction between the endless belt 207 and the document, and the coefficient of friction between the documents, one page of the document sent out by the call rollers 203a and 203b can be formed. In the case of (1), the sheet is directly conveyed in the direction of the pull-out rollers 209 and 210 on the downstream side, and in the case of two or more sheets, only the lowest one sheet is separated and conveyed.

The separation roller 208 has a built-in one-way clutch (not shown). When the registration sensor 211 provided at the discharge position of the paper feeding mechanism 270 detects the leading end of the document, the clutch is turned off and the document is pulled out. Roller 20
The wafer is conveyed to a predetermined exposure position on the contact glass 9 by 9, 210. Further, the clutch is configured to reduce the transport load on the pull-out rollers 209 and 210 when the driving of the separation roller 208 is turned off. When the registration sensor 211 detects the trailing edge of the document, the document is controlled so as to stop at a predetermined exposure position.

As shown in FIG. 16, a pulse encoder 280 having a plurality of slits is mounted on the shaft of the pull-out roller 209 through a gear in order to detect the length of the original. A photo sensor 281 is provided to detect the A photo sensor (width detection sensor) for detecting the width of the document as shown in FIG. 12 is provided near the pull-out rollers 209 and 210.
282 are arranged. FIG. 1 shows the width detection sensor 282.
As shown in detail in FIG. 7, it is arranged between the B5 vertical size and the A4 vertical size.

The size of the document is detected by the length detected by the photo sensor 281 and the width detected by the photo sensor 282, and FIG. 18 is a flowchart showing the detailed detection operation. The document size that can be conveyed by the RDH is A5 portrait, B5
There are seven types: vertical and horizontal, A4 vertical and horizontal, B4 vertical and A3 vertical, and the pulse encoder 280 is formed so that one pulse corresponds to a transport distance of 0.5 mm.

In FIG. 18, the length of the document is detected by counting the number of pulses while the registration sensor 211 is on (steps S1 to S7). When the registration sensor 211 is on, the size sensor flag is set to "1" when the width detection sensor 282 is on (step S3), and when the width sensor 282 is off, the size sensor flag is set to "0".
(Step S4). Registration sensor 211
Is turned off, the counting of the pulses is terminated (step S).
6, S7), the process proceeds to step S8 and the subsequent steps to determine the size.

First, if the size sensor flag is set, the A3 size (steps S9 and S10)
B4 size (Steps S11 and S12), A4 vertical size (Steps S13 and S14), A4 horizontal size (Steps S15 and S16), B5 horizontal size (Steps S15 and S16)
17) is determined. On the other hand, if the size sensor flag is not set, the B5 vertical size (step S1)
8, S19), A5 vertical size (steps S18, S2
0) is determined. Finally, the result of this determination is transmitted to the digital copier body (I) (step S21), and this determination is made for each document.

Returning to FIG. 12, the transport mechanism 271 of the RDH (III) has one wide endless transport belt 212 wound around a pair of rollers 265 and 266. The lower side of the conveyor belt 212 includes a plurality of pressure rollers 213.
Is pressed onto the contact glass 9 by the
The document from 0 is conveyed to a predetermined exposure position, and sent to the reversing mechanism 272 after the exposure is completed.

The reversing mechanism 272, as shown in FIG.
Reversing roller 21 provided along reversing guide 215a
5 and a pressure roller 216 pressed against the reversing roller 215
And a switching claw 214 displaceable between a position shown by a solid line and a position shown by a broken line downstream of the pressure roller 216. The switching claw 214 is switched to the position indicated by the broken line in the double-sided original mode, and reverses the original whose one side has been exposed, and sends it back to the transport mechanism 271. On the other hand, in the single-sided original mode and the double-sided original mode and both-side exposure has been completed, the switching claw 214 is switched to the position indicated by the solid line, and the original is discharged to the return mechanism 273. In addition, between the pressing roller 216 and the switching claw 214, the reversing roller 2 is provided.
A reversing sensor 217 is provided so as to face the driving belt 15, and the driving timing of the transport belt 212 is controlled by the reversing sensor 217.

The return mechanism 273 is connected to the sheet feeding table 20.
1, a paper discharge unit 218 movable in the document conveying direction, and connected to the rear of the paper discharge unit 218 to expand and contract in accordance with the movement of the paper discharge unit 218.
It has guide plates 221, 222, and 223 that form a document conveyance path between the sheet feeding table 201 and the sheet feeding table 201 behind the intermediate document 18, and an intermediate belt 227 for conveying the document from the reversing mechanism 272 to the sheet discharge unit 218. 19, 20,
FIG. 21 shows the extended, intermediate, and contracted states of the guide plates 221 to 223, respectively.

As shown in detail in FIGS. 21 and 22, the document discharged from the outlet 230 of the reversing mechanism 272 is guided to the discharge unit 218 directly or the document conveyed on the table 201 by the intermediate belt 227 is guided. For this purpose, a lower guide 229 that is inclined forward and upward is provided. Also, at a predetermined interval from the lower guide 229,
An upper guide formed as a front end of the guide plate 221 is provided.
At the entrance and exit of the transport path 18, there are two paper discharge rollers.
19 ′, 219 ″ are provided.
9 ′ and 219 ″ are driven by a motor 220. A front part of the outer cover 224 is formed as an outer cover of the sheet discharging unit 218.

The upper surface of the intermediate belt 227 has an upper running portion in front of the exit of the reversing mechanism 272,
1 are arranged so as to be the same as the upper surface, and are divided into a plurality of sections in the width direction. When the guide plate 222 extends, at a position facing each strip of the intermediate belt 227,
As shown in FIGS. 19 and 22, a driven roller 228 is provided via a leaf spring. As shown in FIG. 19, the guide plate 222 is pulled out in the
27, the driven roller 228 is pressed by the leaf spring against the intermediate belt 227 to be driven, and the document is conveyed.

Further, as shown in FIG.
When the second roller 2 moves in the arrow direction C and retracts behind the intermediate belt 227, the driven roller 228 is flipped up by the member 231 projecting above the surface of the table 201, and retracts from the intermediate belt 227, as shown in FIG. As shown, it is stored behind the outlet 230 of the reversing mechanism 272. In this state, the largest size document discharged from the outlet 230 of the reversing mechanism 272 is driven by the driven roller 228 and the guide plate 22.
2, 223 without being obstructed by
18 along the conveyance path 18 and a pair of discharge rollers 219 ', 219 "
Transported by Then, the sheet is discharged onto the sheet bundle on the sheet feeding table 201, and the skew is corrected by the stopper 205.

Here, the positioning of the paper discharge unit 218 corresponding to the document size is performed by clicking the paper discharge unit 218 in the click groove 251 provided at the position corresponding to the standard paper size in the front frame of the RDH as shown in FIG. Unit 21
8 by engaging a click pin 245 provided on the front side. Click groove 2 of click pin 245
The attachment / detachment to / from the frame 51 or the inner surface of the frame can be performed by operating a lever 252 provided on the front end surface of the paper discharge unit 218. The paper discharge unit 218 moves to a predetermined position and engages with a desired position. Can be done.

Next, the operation of the above RDH will be described with reference to FIG. First, when a plurality of originals are stacked in page order such that the image surface faces upward, and the originals are placed on the paper feed table 201 such that the leading ends contact the stoppers 205, the original set sensor 206 is turned on (step S3
1). In this case, as the side fence 202 moves, both sides of the document bundle are supported.
18 is moved to a position corresponding to the size of this document bundle.

When the copy star key of the copier body (I) is pressed to turn on the paper feed signal (step S32), the solenoid 267 of the stopper 205 and the solenoid (not shown) of the holding plate 204 are turned on (step S33). ). Therefore, the stopper 205 retracts from the leading end of the document bundle,
The holding plate 204 calls the bundle of originals and the rollers 203
a, 203b. Then, when the paper feed timer elapses a predetermined time X (step S34), the paper feed motor and the transport belt motor are turned on (step S35). Therefore, by rotation of the call rollers 203a and 203b, the document bundle is conveyed so as to advance sequentially from the lowest document, only the lowest document is separated by the endless belt 207 and the separation roller 208, and the pull-out roller 2 is separated.
09 is conveyed.

Then, the leading edge of the document is
1 (step S36), the drive of the separation roller 208 is stopped by the clutch (step S3).
7). Therefore, the document is conveyed in the direction of the contact glass 9 only by the pull-out roller 209, and then conveyed on the contact glass 9 by the conveying belt 212. The calling rollers 203a and 203b stop driving in response to a detection signal of the photo sensor 262, and stop in a state where the missing circular surface coincides with the surface of the sheet feeding table 201. After the registration sensor 211 detects the trailing edge of the document, a predetermined count value of the photo sensor 262 (step S3).
In step 8), the transport belt 212 rotates in the reverse direction, and the original is
8 and then stop (step S39).

Therefore, the original is stopped at a predetermined exposure position after the skew is corrected, and the image is read by the scanner section of the copying machine main unit (I). Then, according to a document discharge signal from the copying machine main body (I) (step S41),
The transport belt 212 rotates forward again, and the original is rotated by the reversing mechanism 272.
Is sent to the return mechanism 273 in the case of a single-sided original and in the case of a double-sided original and both-sided exposure has been completed (step S42). Then, the original is transferred to the intermediate belt 227, the sheet feeding table 201 and the guide plate 22.
Conveyed along a conveyance path constituted by 1 to 223,
The sheet is guided by a lower guide 229 of the sheet discharging unit 218 and is discharged onto the sheet feeding table 201 by sheet discharging rollers 219 ′ and 219 ″.

In this case, after the paper discharge sensor 242 of the paper discharge unit 218 detects the leading edge of the document (step S4).
4) At a predetermined timing, the stopper 205 comes into contact with the original bundle, and the leading end of the original discharged from the paper discharge unit 218 comes into contact with the stopper 205 to correct the skew and stack the original. When the paper discharge sensor 242 detects the trailing end of the document (step S45), the paper discharge motor and the reversing motor are turned off (step S46).
If the next document is not detected, the transport motor is stopped (steps S47 and S48).

Incidentally, as shown in FIG.
In the case where a claw portion is formed at an interval with respect to the sheet 5 and a rib 1a having an appropriate height is formed on the sheet feeding table 201 at an interval, the original on the sheet feeding table 201 is
The document is not pushed under the stopper 205 because it is hit by the claw 05 and hits from the upper end of the rib 1a. Further, as shown in FIG. 15, when the partition plate 241 is placed on the document bundle in advance, the partition plate 241
Is detected by the partition plate sensor 243, it is possible to detect that the document bundle has made one round.

Further, the bundle of originals that have completed one cycle is aligned to some extent, but is not sufficient, and may be in a wavy state. Therefore, before the next sheet feeding operation, the pages can be aligned by rotating the call rollers 203a and 203b and applying a vertical vibration to the document bundle. in this case,
The pressing plate 204 and the stopper 205 are evacuated to a position away from the document, and a force in the conveyance direction is generated by the call rollers 203a and 203b, so that the leading end of the document bundle reaches the vicinity of the pressure contact position between the separation roller 208 and the endless belt 207. The document is advanced, and is arranged in a wedge shape that is sequentially evacuated from the lowest document. Accordingly, the document bundle is reset so as not to hinder refeeding, and the next feeding operation is started by the feed signal.

Returning to FIG. 9, the sorter (III) selectively discharges the transfer paper discharged from the copying machine main body (I), for example, in a page order, for each page, or to a preset bin 111a to 111x. In this case, the transfer paper is conveyed by a plurality of rollers rotated by a motor 110, and is switched by bins 111a to 111
Led to 1x.

The double-sided reversing unit (IV) shown in FIG. 9 is used when performing double-sided copying by reversing the front and back of a plurality of transfer sheets. In this case, the transfer paper in the copying machine body (I) is
The next switching claw 68 is guided downward by the discharge roller 66 and
To the double-sided reversing unit (IV). And
The paper is stacked on the tray 123 by the paper discharge roller 120, and is vertically and horizontally aligned by the feed roller 121 and the side alignment guide 122. The transfer papers accumulated on the tray 123 are returned into the copying machine main body (I) by the refeeding rollers 124, and are guided directly to the refeeding loop 72 by the switching claws 69.

Next, the configuration of the control unit of the copying machine main unit (I) will be described with reference to FIGS. 24 and 25. The control unit includes a CPU 60 for performing sequence-related control.
1 and a main CPU 6 for controlling operation relations
02. CPU 60 for controlling sequence relations
Reference numeral 1 denotes a condition for setting and outputting conditions relating to paper conveyance timing and image formation, and a paper size sensor 603 as shown in FIG.
And sensors 603a related to paper conveyance such as paper ejection detection and registration detection, a double-sided unit 604, a high-voltage power supply unit 605, a driver 606 such as a relay, a solenoid, and a motor, and a laser beam scanner unit 608. ing. Laser beam scanner unit 608
Is connected to the image control circuit 609,
Reference numeral 9 denotes a circuit as shown in FIGS.

The paper size sensor 603 detects the size and orientation of the transfer paper loaded in the paper feed cassette,
Reference numeral 03a detects the presence or absence of a supply such as an oil end or a toner end, and a mechanical abnormality such as a door open or a blown fuse, in addition to the sheet discharge detection and the registration. Double-sided unit 6
Reference numeral 04 includes a motor for aligning the paper width, a side fence home position sensor, a paper feed clutch, a solenoid for changing the transport path, a paper presence / absence detection sensor, and a sensor for paper transport.

The high-voltage power supply unit 605 applies a predetermined high-voltage power to the charging charger 41, the transfer charger 44, the separation charger 45, and the bias electrodes of the developing units 42a and 42b for a duty time obtained by the PWM control. Is applied. The driver 606 includes a paper feed clutch, a registration clutch, a counter, a motor, a toner supply solenoid, a power relay, a fixing heater, and the like. The sorter unit (III) 607 is a CPU 6
01 is connected via a serial interface, and conveys the paper at a predetermined timing according to a control signal from the CPU 601 and discharges the paper to each bin.

As analog signals input to the CPU 601, a detection signal of the photosensor 50 for detecting a fixing temperature and density, a monitor current of the laser diode 20, and a reference voltage are input. The fixing temperature is determined by a fixing mechanism (rollers 64 and 65).
The on / off control or phase control of the heater is performed so as to be constant. A detection signal of the density detection photosensor 50 is detected by reading a pattern formed on the photoconductor 40 with a phototransistor at a predetermined timing, and a toner replenishment clutch is controlled to be turned on and off. End is detected. The monitor current of the laser diode 20 is controlled so as to match a reference voltage (for example, 3 mW).

Next, the main CPU 602 for controlling the operation relation will be described with reference to FIGS. 24 and 25. The main CPU 602 controls a plurality of serial ports and a calendar IC 610. In addition to the CPU 601, an operation unit 611, a scanner control circuit 612, an application unit 613, an editor unit 614, and the like are connected to the plurality of serial ports.

The operation unit 611 has a key input device for the operator and a display for displaying the status of the copying machine, and notifies the main CPU 602 of the key input information by serial communication. The main CPU 602 determines whether the display unit of the operation unit 611 is on or off based on the key input information.
The display command is notified to the operation unit 611 by serial communication. The operation unit 611 turns the display on or off according to the display command. Scanner control circuit 612
The main CPU 6 transmits information on drive control of a scanner servomotor, image processing, and image reading by serial communication.
02, RDH (II) and main CPU 602
Interface processing is performed.

The application unit 613 performs interface processing between an external device such as a facsimile or an external printer and the main CPU 602, and exchanges predetermined information. The editor unit 614 transmits image editing data such as masking, trimming, and image software input by the operator to the main CPU 602 by serial communication.
The calendar IC 610 stores the current date and time and informs the main CPU 602 at any time. Therefore, it is possible to display the current time on the display of the operation unit 611 and to control the on-time and off-time of the copying machine by the timer. it can.

The gate array 615 includes the main CPU 60
The image data is selectively output from the scanner control circuit 612 to the image control circuit 609, from the scanner control circuit 612 to the application unit 613, or from the application unit 613 to the image control circuit 609 in response to the select signal from the control unit 2. When output from the scanner control circuit 612 to the image control circuit 609, image data of a 2-bit parallel signal (in the case of binary) and a 12-bit parallel signal (in the case of multi-value) from the scanner are output from the laser beam scanner. It is transmitted in synchronization with the synchronization signal PMSYNC from the unit 608. When output from the scanner control circuit 612 to the application unit 613, a 2-bit parallel signal is output from the scanner. When output from the application unit 613 to the image control circuit 609, a 2-bit parallel signal is output. It is transmitted in synchronization with the synchronization signal PMSYNC.

[0077]

As described above, the invention according to claim 1 is described above.
According to the data amount of each code of the first document,
Select binary image compression or multi-value image compression with the largest reduction ratio
Therefore, when used in a digital copying machine or the like, the capacity of the memory can be reduced.

[0078]

[0079]

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a memory unit in an embodiment of an image forming apparatus according to the present invention.

FIG. 2 is an explanatory diagram showing storage contents of a memory in FIG. 1;

FIG. 3 is a block diagram illustrating an image forming apparatus including the memory unit of FIG. 1;

FIG. 4 is an explanatory diagram illustrating an operation of a binary compression unit in FIG. 1;

FIG. 5 is a block diagram showing a detailed configuration of a multi-level compression section and a multi-level decompression section of FIG. 1;

FIG. 6 is an explanatory diagram illustrating an operation of a block reading unit in FIG. 5;

FIG. 7 is an explanatory diagram showing DCT coefficients in FIG. 5;

FIG. 8 is an explanatory diagram showing a quantization matrix in FIG. 5;

FIG. 9 is a side view showing the overall configuration of a digital copying machine to which the image forming apparatus of FIG. 1 is applied.

FIG. 10 is a plan view illustrating a detailed configuration of a writing unit in FIG. 9;

FIG. 11 is a side view showing the writing unit of FIG. 10;

12 is a side view showing a detailed configuration of the automatic document circulating and feeding apparatus shown in FIG. 9;

13 is a perspective view showing a main part of the paper feeding mechanism of FIG.

FIG. 14 is a front view showing the sheet feeding mechanism of FIG.

FIG. 15 is an enlarged side view showing a detailed configuration of the sheet feeding mechanism of FIG.

FIG. 16 is a perspective view showing a mechanism for detecting the length of a document.

FIG. 17 is an explanatory diagram illustrating a document width detection sensor.

FIG. 18 is a flowchart illustrating an operation of detecting a document size.

FIG. 19 is a side view showing an extended state of the return mechanism of FIG.

FIG. 20 is a side view showing an intermediate state of the return mechanism of FIG.

FIG. 21 is a side view showing a contracted state of the return mechanism of FIG.

FIG. 22 is a perspective view showing a detailed configuration of the paper discharge unit shown in FIGS. 19 to 21;

FIG. 23 is a flowchart for explaining the operation of the automatic document circulating and feeding apparatus shown in FIGS. 12 to 22;

FIG. 24 is a block diagram showing a part of a control unit of the digital copying machine shown in FIG. 9;

FIG. 25 is a block diagram showing another part of the control unit of the digital copying machine shown in FIG. 9;

FIG. 26 is a block diagram illustrating a conventional image forming apparatus.

FIG. 27 is a block diagram illustrating another conventional image forming apparatus.

FIG. 28 is a block diagram illustrating a main part of another conventional image forming apparatus.

[Explanation of symbols]

 513 Binary compression section 514 Multi-level compression section 515 Memory 516 Binary decompression section 517 Multi-level compression section 518 Memory management unit 519 CPU (central processing unit) 520 Multiplexer

Continuing from the front page (72) Inventor Oji Maruyama 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Gen Moto Ichimura 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company Ricoh Company (72) Inventor Yoshimichi Kanda 1-3-6 Nakamagome, Ota-ku, Tokyo Co., Ltd. (72) Inventor Toshihiko Kuroi 1-3-6 Nakamagome, Ota-ku, Tokyo Co., Ltd. Inside Ricoh (72) Inventor Koichi Noguchi 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Katsura Nomura 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Company (72) Inventor Yasuyuki Nomizu 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (72) Inventor Shinji Yamakawa 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. 56) References JP-A-62-176268 (JP, A) JP-A-54-147073 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04N 1/4 1-1/419 H03M 7/30

Claims (1)

(57) [Claims] 1. Binary image compression for compressing binary image data
Means, multi- level image compression means for compressing multi-level image data, and the binary image compression means or the multi-level image compression means
Storage means for storing the compressed code; and a code for the binary image data read from the storage means.
A binary image decompressing means for decompressing, and a sign of the multi-valued image data read from the storage means.
A multivalued image decompressing means for decompressing, the binary image compressing means and the multivalued image compressing means
Depending on the data amount of each code of the first compressed original,
The binary image compressing means and the binary image decompressing unit having the maximum reduction ratio;
Length means or the multi-value image compression means and the multi-value image decompression
Means for selecting means .