JPH1023224A - Image reader and digital copying machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease minimum read resolution and a minimum reduction rate, without increasing the subscanning speed of an image scanner section by selecting a combination between a line interleave number and a subscanning speed. SOLUTION: The reader is provided with a line interleave circuit 80, interleaving an image signal line by line, by I/N where N is an integer, and a combination of the integer N an a subscanning speed (v) is decided, based on N=int(r0/r) and v=v0.r0/(N.r), where r is a resolution in the subscanning speed set optionally, r0 is a predetermined reference read resolution, int() is an integer operator rounding off the fraction, and v0 is a basic subscanning speed. Since the subscanning speed, with respect to optional setting resolution (r), does not exceed v0.r0/r, a minimum zoom rate or minimum read resolution is not limited by a maximum subscanning speed of an image scanner section.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus and a digital copying machine, and more particularly, to an image reading apparatus capable of reading an image at an arbitrary sub-scanning resolution, and a digital apparatus capable of copying at an arbitrary zoom ratio. Related to a copying machine.

[0002]

2. Description of the Related Art In recent years, digital copiers have become faster and more multifunctional, and a faster first copy speed is also required for processing such as enlargement and reduction.

Hereinafter, an example of a conventional digital copying machine will be described with reference to the drawings. FIG. 6 is a block diagram showing a flow of an image signal of a conventional digital copying machine.
The image sensor 71 scans a document and converts light reflected from the document into an electric signal. The A / D converter 72 converts an analog image signal from the image sensor 71 into a digital image signal. The image processing circuit 73 performs image processing and editing processing such as edge enhancement, trimming, and halftone processing on the digital image signal. Line buffer memory 7
Reference numeral 4 controls the speed for buffering the image signal from the image processing circuit 73 and outputting it to the laser driver 78. The laser driver 78 drives a semiconductor laser 79 that outputs a laser beam for forming an electrostatic latent image.

FIG. 7 shows a schematic configuration of a conventional digital copying machine. 50 is an ADF (Auto Document Feeder), 0 is a document table, 1 is an exposure lamp, 2 is a first mirror, 3 is a constant speed unit, 4 is a second mirror, 5 is a third mirror, 6 is a half speed unit, 7 Is a lens, and 8 is an image sensor. A is an image scanner unit.

Reference numeral 40 denotes a laser scanner unit which includes a semiconductor laser, a polygon motor, a polygon mirror, and a laser optical system. 41 is a mirror, 9 is a photoreceptor drum, 10 is a main charger, 11 is a developing device, 20 is a transfer charger, 35 is a cleaner, 36 is a discharging lamp, 30 is a conveyor belt, 31 is a fixing device, 32 is a guide, 33 is a paper discharge roller, 12, 13, and 14 are paper feed rollers, 18 is a guide, 19 is a timing roller, and 34 is a sorter. B indicates a laser printer unit.

The operation of the conventional digital copying machine configured as described above will be described. The plurality of originals placed on the ADF 50 are placed one by one on the original glass plate 0 made of a transparent glass plate by the ADF. The exposure lamp 1 exposes the document. The first mirror 2 reflects reflected light from the document in the direction of the second mirror 4. Exposure lamp 1 and first mirror 2
The constant velocity unit 3 is moved at a constant speed in the direction of arrow P and scans the original. The second mirror 4 and the third mirror 5 further reflect light reflected from the first mirror. The half-speed unit 6 composed of the second mirror 4 and the third mirror 5
It moves in the same direction as the constant velocity unit 3 at half the speed of the constant velocity unit 3. Light reflected from the document is focused by the lens 7 and focused on the image sensor 8.

[0007] The image sensor 8 is a linear sensor that is long in a direction perpendicular to the paper surface. In the following description, the electrical scanning direction along the longitudinal direction of the image sensor 8 is referred to as a main scanning direction, and the mechanical scanning direction along the moving direction of the constant velocity unit 3 is referred to as a sub-scanning direction.

The photosensitive drum 9 rotates at a constant speed in the direction of arrow R. The main charger 10 uniformly charges the photosensitive drum 9. The laser light emitted from the laser scanner unit 40 is reflected by the mirror 41 and scans the photosensitive drum 9 by exposure to light to form an electrostatic latent image on the photosensitive drum 9. The developing device 11 develops the electrostatic latent image with the toner and forms a toner image on the photosensitive drum 9. Photoconductor drum 9
Above, the direction parallel to the rotation axis corresponds to the main scanning direction, and the rotation direction of the photosensitive drum corresponds to the sub-scanning direction.

The recording paper cassettes 15, 16 and 17 are
Each of them holds a plurality of recording sheets. Different types of recording paper are held for each recording paper cassette. The recording paper cassette is detachable, and a cassette holding recording paper of a required size and direction is mounted. 12, 13 and 14 are paper feed rollers for feeding the recording paper in the recording paper cassette one by one. A guide 18 guides the fed recording paper and guides it to a timing roller 19. Timing roller 1
Reference numeral 9 denotes registration for adjusting the fed recording paper to the toner image on the photosensitive drum 9 to adjust the feeding timing.

The toner image on the photosensitive drum 9 is transferred to recording paper by an electric field generated by the transfer charger 20. The transport belt 30 moves in the direction of the arrow Q, and transports the recording paper on which the toner image has been transferred to the fixing device 31. The fixing device 31 fixes the toner image on the recording paper to the recording paper by heat. The recording paper after fixing is guided to a paper discharge roller 33 by a guide 32, and is discharged to a sorter 34 by the paper discharge roller 33.
The sorter 34 includes a plurality of paper discharge trays (bins), and performs mechanical collation in copies. The sorter 34 also has a staple function and a punch function.

The toner remaining on the photosensitive drum 9 is removed by a cleaner 35. Next, the static elimination lamp 3
6 exposes the photoconductor drum 9 to erase the charge on the photoconductor.

In such a series of operations of the image scanner section and the printer section, the main scanning cycle of the image scanner section and the main scanning cycle of the printer section are the same. Therefore, enlargement or reduction copying in the sub-scanning direction can be performed by changing the sub-scanning speed of the printer unit or the image scanner unit. Normally, enlargement or reduction copying in the sub-scanning direction is performed by making the sub-scanning speed of the printer unit constant and making the sub-scanning speed of the image scanner unit different from that at the time of 1: 1 copying. When the sub-scanning speed of the image scanner unit at the time of 1: 1 copying is V0,
The sub-scanning speed Vz of the image scanner unit when the copy magnification in the sub-scanning direction is R is as follows: Vz = V0 / R. Such a conventional enlargement or reduction copy method is disclosed in, for example, JP-A-59-63868.

[0013]

In the current digital copying machines, the minimum reduction ratio is often set to 33% or 25%. In the above-described conventional configuration, for example, in the case of performing 33% reduced copy, the image scanner section needs to perform sub-scanning at three times the speed of the same-size copy. In this case, it is necessary to design a motor torque and a sub-scanning mechanism so that the image scanner unit can operate at a sub-scanning speed three times the normal speed in order to realize copying at a minimum reduction rate that is not frequently used. . This has been a factor in increasing costs.

In the case of a high-speed digital copying machine having a high copying speed at the time of 1: 1 copying, a copy reduction ratio of 33% or 25% is structurally realized because the sub-scanning speed of the image scanner becomes too high. difficult. For this reason,
The minimum reduction rate is limited to 70% or 50%.

As a method of performing reduced copying in the sub-scanning direction,
In addition to the method of changing the sub-scanning speed of the image scanner as described above, there is a method of using a page memory. In this method, reduction in the sub-scanning direction is performed by changing the rate of line thinning of an image signal read by an image scanner. The image signal for one page reduced in the sub-scanning direction is temporarily stored in a page memory and then output to a printer unit. In this method, the sub-scanning speed of the image scanner unit may be the same as that in the same-size copy even in the sub-scanning direction reduced copy.

However, since the read image is temporarily stored in the page memory and then printed, the first copy time is lengthened, and furthermore, the digital thinning is performed at an arbitrary ratio, and the image quality is degraded. There is also. If interpolation between lines is performed to avoid this image quality degradation, several lines of line buffers are required, resulting in an increase in cost.

Accordingly, the present invention provides an image reading apparatus capable of reducing the settable minimum reading resolution without increasing the sub-scanning speed of the image scanner, and a digital reading apparatus capable of reducing the minimum reduction ratio. It is intended to provide a copying machine.

[0018]

According to the present invention, there is provided an image reading apparatus which electrically scans image information of a document in a main scanning direction at a predetermined period to output an image signal for each line, A sub-scanning means for mechanically moving a main scanning position in a sub-scanning direction perpendicular to the main scanning direction at a constant sub-scanning speed v;
Line thinning means for thinning by a factor of 1;
The document image is read at an arbitrary resolution in the sub-scanning direction by appropriately determining a combination of the value of the sub-scanning speed and the value of the sub-scanning speed v.

An integer N corresponding to a thinning number and a sub-scanning speed v
By associating the two with each other to correspond to an arbitrary set resolution, the configuration of the line thinning means is simplified, and it is not necessary to increase the sub-scanning speed.

The value of the integer N and the value of the sub-scanning speed v are preferably determined based on the following equation. N = int (r0 / r) v = v0 · r0 / (N · r) where r is an arbitrary set resolution in the sub-scanning direction, r0
Is a predetermined reference reading resolution, int () is an integer conversion operator by rounding up decimal places, and v0 is a basic sub-scanning speed.

When the set resolution r in the sub-scanning direction is equal to or greater than the predetermined reference reading resolution r0, N = 1, so that line thinning by the line thinning means is not substantially performed. The set resolution r is obtained when the sub-scanning speed becomes v = v0 · r0 / r. N> 2 when the set resolution r is less than the reference resolution r0
, And the sub-scanning speed becomes v = v0 · r0 / (N · r). Therefore, the sub-scanning speed v does not exceed v0 · r0 / r for an arbitrary set resolution r.

Next, the digital copying apparatus according to the present invention comprises a reading means for electrically scanning image information of a document in a main scanning direction at a predetermined period and outputting an image signal for each line, and a main scanning position for the document. Having a sub-scanning means for mechanically moving the image signal at a constant sub-scanning speed V in the sub-scanning direction perpendicular to the main scanning direction, and a line thinning-out means for thinning out the image signal for each line by an integer N. A reading unit, and a printing unit that prints an image on a print medium based on an image signal given from the image reading unit,
An original image is copied at an arbitrary zoom ratio in the sub-scanning direction by appropriately determining a combination of the value of the integer N and the value of the sub-scanning speed V.

An integer N corresponding to a thinning number and a sub-scanning speed V
And a combination of the two to correspond to an arbitrary set zoom rate (reduction / enlargement magnification) simplifies the configuration of the line thinning means and eliminates the need to increase the sub-scanning speed.

Preferably, the value of the integer N and the value of the sub-scanning speed V can be determined based on the following equation. N = INT (R0 / R) V = V0 / (NR) where R is an arbitrary set zoom ratio in the sub-scanning direction, R
0 is a predetermined reference zoom ratio, INT () is an integer conversion operator by rounding up decimal places, and V0 is a basic sub-scanning speed at the time of 1: 1 copying.

In the case of this digital copying apparatus, as in the case of the above-described image reading apparatus, when the set zoom rate R is equal to or larger than the reference zoom rate R0 (N = 1), line thinning is not substantially performed and the digital copy apparatus is set. The obtained zoom ratio R is obtained when the sub-scanning speed becomes V = V0 / R. And
When the set zoom ratio R is less than the reference zoom ratio R0 (N>
In 2), line thinning is performed and the sub-scanning speed becomes V = V0 / (N · R). Therefore, the sub-scanning speed V does not exceed V0 / (N · R) for an arbitrary set zoom ratio R.

As the above-mentioned reference zoom ratio R0, approximately 70%
It is preferable that Usually, the frequently used zoom ratio is 70% or more, as in the case of reduced copy from A3 size document to A4 recording paper. Therefore, the reference zoom ratio R
If 0 is set to about 70%, if a higher zoom ratio is set, N = 1 as described above, and line thinning is not substantially performed, so that the first copy speed does not decrease.

As a specific configuration of the image reading unit,
An image memory for storing an image signal obtained by thinning out the lines by the line thinning means, and when the set zoom rate R is equal to or more than the reference zoom rate R0, the image signal from the reading means is given to the printing unit as it is, When the set zoom ratio R is less than the reference zoom ratio R0, it is preferable that the image signal thinned out to the line is provided to the printing unit via the storage unit. In the case of continuous copying of the same document, a reduction in copy speed can be prevented by reading the image signal from the image memory and printing it.

Further, the image signal whose line has been thinned out is binarized by a pseudo halftone processing circuit which performs area gradation processing, is stored in an image memory, and the binary image signal read out from the image memory is a binary image signal. It is preferable that the image data is converted into a multi-level image signal by a value conversion circuit and then applied to the printing unit. As a result, the required storage capacity of the image memory can be reduced.

Further, the image signal binarized by the pseudo halftone processing circuit is stored in the image memory through a compression process, and the compressed image signal read from the image memory is subjected to the decompression process to the binary image data. Preferably, it is configured to be provided to a value conversion circuit. This further reduces the required storage capacity of the image memory.

The image memory is a FIFO memory, and the image memory stores (N-
1) The image reading unit is configured to sequentially output the image signals stored in the image memory to the printing unit in order to start printing an image when an image signal corresponding to / N is stored. It is preferred that For example, in the case of N = 2, when the image signals for one-half page of the original are read and stored in the image memory, the image signals stored in the image memory are sequentially stored in the printing unit from the one stored first. Output to In this way, a decrease in the first copy speed can be improved.

[0031]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1 shows a flow of an image signal of a digital copying machine according to a first embodiment of the present invention. 1, the same components as those in FIG. 6 showing the conventional example are denoted by the same reference numerals. The image sensor 71 scans a document and converts light reflected from the document into an electric signal. The A / D converter 72 converts an analog image signal from the image sensor 71 into a digital image signal. The image processing circuit 73
Image processing and editing processing such as zoom processing, edge enhancement, trimming, and halftone processing in the main scanning direction are performed on the digital image signal. Interpolation, zoom processing in the main scanning direction
This is performed by a conventional method such as thinning.

The line thinning circuit 80 includes the image processing circuit 7
A process of thinning out the image signal from 3 to 1 / N is performed. The thinning rate N, which is an integer, is determined by the
4 to the line thinning circuit 80. The image memory 81 stores the image signal 60 from the line thinning circuit 80 for one page of the document. Line buffer memory 74
Performs a speed adjustment for buffering the image signal 60 or the image signal 61 read from the image memory 81 and outputting the buffered image signal to the laser driver 78.

Which image signal (60 or 61) is input to the line buffer memory 74 is set by the microcontroller 90 via the bus 94. In FIG. 1, a path of an image signal to which the line buffer memory 74 receives the image signal 60 is indicated by a dashed arrow D (hereinafter, referred to as an arrow D).
The path of the image signal to which the image signal 61 is input is indicated by a dashed arrow E (hereinafter, referred to as “path E”). The laser driver 78 drives a semiconductor laser 79 that outputs a laser beam for forming an electrostatic latent image.

The microcontroller 90 has RAM, R
It has an OM and controls the entire digital copying machine. The motor control circuit 91 controls a sub-scanning motor 93 of the image scanner unit using a sub-scanning motor driver 92.
The microcontroller 90 sets the sub-scanning speed to the motor control circuit 91 via the bus 94. The control panel 95 includes a liquid crystal panel, an indicator such as an LED, and setting input buttons such as numeric keys as an interface between the copying machine and the operator. The operator uses the control panel 95 to input settings such as the copy zoom ratio. The input setting values such as the zoom ratio are read by the microcontroller 90 via the bus 94.

FIG. 4 shows a flow chart when copying is performed using the digital copying machine of this embodiment. The operator uses the control panel 95 to set copy conditions such as a zoom ratio at the time of copy (S100), and instructs a copy start (S110). The microcontroller 90 calculates the line thinning rate N and the sub-scanning speed V of the image scanner unit based on the following formula (S120).

N = INT (R0 / R) V = V0 / (NR) where R is the zoom ratio in the sub-scanning direction, V0 is the sub-scanning speed of the image scanner unit at the time of equal-size copying, and INT () Is an integer conversion operator by raising the decimal part. R0 is a reference zoom ratio (reduction ratio), and line thinning is not performed in a copy of a zoom ratio R equal to or higher than the reference zoom ratio R0.
Zoom processing is performed only by setting the sub-scanning speed of the image scanner unit. Then, the original reading operation of the image scanner unit and the image forming operation of the printer unit are performed in synchronization (real-time copy mode). When a zoom ratio R smaller than the reference zoom ratio R0 is set, the read document image is read and recorded by the printer unit after one page of the document image is stored in the image memory 81 (memory copy mode). ).

For example, if the reference zoom ratio R0 is 0.7 and the set zoom ratio R is 0.5, the thinning ratio N = 2,
The sub-scanning speed V = V0. When the set zoom rate R is 0.6, the thinning rate N = 2 and the sub-scanning speed V = V0 / 1.2.
Becomes Regardless of the set zoom ratio R, the sub-scanning speed V0 does not exceed the sub-scanning speed (V0 / R0) at the zoom ratio R0.

The microcontroller 90 sets the calculated thinning rate N in the line thinning circuit 80 and sets the sub-scanning speed V in the motor control circuit 91 (S130). The microcontroller 90 checks the value of N (S140), and if N is 1, sets the path D as an input to the line buffer memory 60 (150); otherwise, sets the path E (S200). The fact that N is not 1 means that the set zoom ratio R
Is smaller than the reference zoom ratio R0.

When the path E is set, the image scanner reads one page of the document image and stores it in the image memory 81 (S160). After storing the image for one page, the document image stored in the image memory 81 is output to the printer unit (S170). S1 to print out the same original again
Step 70 is repeated (S180). If the next document to be copied exists, the process returns to step S160 after replacing the document.

When the path D is set, the reading of one page of the original by the image scanner unit and the printing by the printer unit are executed synchronously (S210). If the same document is to be printed out again, S210 is repeated again (S230). If the next original to be copied exists, replace the original, and then
Return to step.

In the digital copying machine of this embodiment, the sub-scanning speed of the image scanner does not exceed V0 / R0 at an arbitrary copy reduction ratio. The minimum zoom ratio is not limited by the scanning speed. Therefore, it is not necessary to make the torque and mechanism of the sub-scanning motor correspond to high speed only to realize the minimum zoom ratio. Furthermore, since the line thinning means only has to thin out to a fraction of an integer, the configuration is simpler than in the case where an arbitrary zoom ratio in the sub-scanning direction is realized only by digital zoom processing.

When a zoom ratio higher than the reference zoom ratio is set, the copying operation is performed in the real-time copy mode, so that the first copy speed is equal to that of the conventional copying machine. When a zoom ratio less than the reference zoom ratio is set, the copying operation is performed in the memory copy mode, so that the first copy speed is lower than that of the conventional copying machine. But,
The frequently used zoom ratio is 0.7 or more, as in the case of reduced copy from an A3 size document to A4 recording paper. Therefore, if the reference zoom rate is set to about 0.7, the first copy speed rarely decreases. In the case of continuous copying of the same document, the speed is not reduced because the data is read from the image memory and printed.

In the present embodiment, a method for reducing a decrease in the first copy speed when a zoom ratio less than the reference zoom ratio is set will be described. In FIG. 1, the image memory 81 has a FIFO configuration. When the thinning rate is N, the output of the image signal from the image memory 81 to the printer unit can be started when the image scanner unit reads (N-1) / N of the original image. For example, when N = 2, printing of an image can be started by the printer unit when the image scanner unit reads half of the original image. According to this method, the printer unit can start printing the image without waiting for one page of the document image to be stored in the image memory 81, so that the first copy speed is increased. (Embodiment 2) FIG. 2 shows the flow of image signals of a digital copying machine according to a second embodiment of the present invention. In addition,
2, the same components as those in FIG. 1 are denoted by the same reference numerals. 2 omits the microcontroller 90, the bus 94, the control panel 95, the motor control circuit 91, the sub-scanning motor driver 92, and the sub-scanning motor 93 in FIG.

Regarding the description of the operation in FIG. 2, the description of the operation of the same parts as in FIG. 1 is omitted. The pseudo halftone processing circuit 82 converts the multi-valued image signal 60 thinned out from the line into a binary image signal 66 by performing area gradation processing by error diffusion processing.
The image memory 81 stores the binary image signal 66 for one page of the document. The binary / multi-level conversion circuit 83 outputs a pseudo-halftone-processed binary image signal 65 read from the image memory 85.
Is restored to a multi-valued image signal. The binary / multi-value conversion process is
This is performed by a known method using a region identification process and a smoothing process.

The line buffer memory 74 buffers the multi-level image signal 60 from the line thinning circuit 80 or the multi-level image signal 67 from the binary-to-multi-level conversion circuit 83 and outputs the same to the PWM modulation circuit 84. Adjust the speed. Which multi-level image signal (60 or 67) is input to the line buffer memory 74 is set by the microcontroller 90 via the bus 94. 2, the line buffer memory 74 sets the path of the image signal to which the image signal 60 is input to F,
Let G be a path of an image signal having 1 as an input. The PWM modulation circuit 84 performs pulse width modulation on the multilevel image data. The laser driver 78 drives the semiconductor laser 79 based on the pulse width modulated image signal.

In the copying operation flow of the present embodiment, in FIG. 4 showing the copying operation flow of the first embodiment, “path D” is replaced with “path F” and “path E” is replaced with “path G”. Same as the ones.

In the first embodiment described above, an image memory which is unnecessary in a conventional digital copying machine is required. When the image signal is multi-valued, a large memory capacity is required, which causes an increase in cost. In the second embodiment, since the image signal is stored in the image memory 81 in the state of the binary image, the memory capacity of the image memory 81 can be reduced. Further, at the time of recording, since the binary image signal is restored to the multivalued image signal by the binary / multivalued conversion circuit 83, it is possible to prevent the copy image quality from being degraded due to the pseudo halftone processing (binary processing).

In FIG. 2, as in the first embodiment (FIG. 1), the first copy speed can be increased by forming the image memory 81 into a FIFO structure. In FIG. 2, the route F ′ may be used in the real-time copy mode instead of the route F. (Embodiment 3) Next, FIG. 3 shows a flow of an image signal of a digital copying machine according to a third embodiment of the present invention. In this figure, the same components as those in FIG. 2 are given the same numbers. Also, the microcontroller 90 of FIG.
Bus 94, control panel 95, motor control circuit 9
1. Sub-scanning motor driver 92 and sub-scanning motor 93
Are omitted in FIG.

Regarding the description of the operation of FIG. 3, the description of the operation of the same parts as in FIG. 2 is omitted. The compression circuit 86 encodes and compresses the binary image signal subjected to the pseudo halftone processing. A known JBIG is used as a compression method. The image memory 81 stores the encoded binary image signal for one page of the document. The expansion circuit 87 decodes and expands the encoded binary image signal read from the image memory 81. Binary to multi-level conversion circuit 83
Restores a decompressed binary image into a multilevel image signal.
The line buffer memory 74 buffers the multi-level image signal 60 from the line thinning circuit 80 or the multi-level image signal 67 from the binary / multi-level conversion circuit 83 and adjusts the speed for outputting to the PWM modulation circuit 84. Do.

As shown by the dashed arrows in FIG. 3, the path of the image signal to which the line buffer memory 74 receives the image signal 60 is H, and the path of the image signal to which the image signal 67 is input is I. The copy operation flow of the present embodiment is the same as the copy operation flow of the first embodiment shown in FIG. 4 in which “path D” is replaced with “path H” and “path E” is replaced with “path I”. It is.

In this embodiment, the memory capacity of the image memory 81 can be further reduced as compared with the second embodiment. Also, as in the second embodiment, at the time of recording, 2
Since the binary image signal is restored to the multi-valued image signal by the value-to-value conversion circuit 83, it is possible to prevent the copy image quality from being deteriorated due to the pseudo halftone processing. In FIG. 3, the path H ′ may be used in the real-time copy mode instead of the path H. (Embodiment 4) Next, FIG. 5 shows a flow of an image signal of an image reading apparatus according to a fourth embodiment of the present invention. This image reading apparatus uses the configuration of the sub-scanning zoom in the first embodiment in an image reading apparatus.
Of the image scanner unit. 5, the same components as those in FIG. 1 are denoted by the same reference numerals. The image sensor 71 scans a document and converts light reflected from the document into an electric signal. The A / D converter 72 is
An analog image signal from the image sensor 71 is converted into a digital image signal. The image processing circuit 73 performs image processing and editing processing such as zoom processing in the main scanning direction, edge enhancement, and halftone processing on the digital image signal. The resolution conversion processing in the main scanning direction is performed by a conventional method such as interpolation or thinning.

The line thinning circuit 80 includes the image processing circuit 7
A process of thinning out the image signal from 3 to 1 / N is performed. The thinning rate N is set by the microcontroller 90 in the line thinning circuit 80 via the bus 94. The line buffer memory 74 buffers the image signal 60 or the image signal 61 read from the image memory 81 and outputs the buffered video signal to the video data output I / F. The video data output interface 98 outputs image data and a synchronization signal such as a pixel clock, a line enable signal, and a vertical enable signal to an external device.

The microcontroller 90 has RAM, R
An OM is provided to control the entire image reading apparatus. The motor control circuit 91 controls a sub-scanning motor 93 of the image scanner unit using a sub-scanning motor driver 92.
The microcontroller 90 sets the sub-scanning speed of the image reading device to the motor control circuit 91 via the bus 94. The microcontroller 90 communicates with an external device via the external interface unit 97 and receives reading conditions such as a reading resolution and a reading area from the external device.

The microcontroller 90 calculates the line thinning rate N and the subscanning speed v of the image scanner from the set subscanning resolution r (dpi) based on the following equation.

N = int (r0 / r) v = v0 · r0 / (N · r) where r is the set reading resolution in the sub-scanning direction,
v0 is the sub-scanning speed (basic sub-scanning speed) of the image scanner unit when reading at a basic resolution (for example, 400 dpi);
int () is an integer conversion operator by raising the decimal part. r0 is a reference reading resolution. In image reading at a sub-scanning resolution r equal to or higher than the reference reading resolution r0, line thinning is not performed, and the reading resolution in the sub-scanning direction is determined only by the setting of the sub-scanning speed of the image scanner unit.

For example, if the reference reading resolution r0 is 200 d
Assuming that pi and the set sub-scanning resolution r are 150 dpi,
The thinning rate N = 2 and the sub-scanning speed v = (2/3) · v0. Regardless of the set sub-scanning resolution r, the sub-scanning speed v0 does not exceed the sub-scanning speed (V0 ・ rn / r0). The microcontroller 90 sets the calculated thinning rate N in the line thinning circuit 80 and sets the sub-scanning speed v in the motor control circuit 91.

In the image reading apparatus of this embodiment, the sub-scanning speed of the image scanner does not exceed V0 · rn / r0 at an arbitrary reading resolution. You will not be restricted. Therefore, it is not necessary to make the torque and mechanism of the sub-scanning motor correspond to high speed only to realize the minimum reading resolution.
Furthermore, since the line thinning means only has to thin out to a fraction of an integer, the configuration is simpler than in the case where an arbitrary zoom ratio in the sub-scanning direction is realized only by digital zoom processing.

[0058]

As described above, in the digital copying machine and the image reading apparatus of the present invention, since the sub-scanning speed of the image scanner section does not exceed a predetermined speed, the minimum zoom rate or the minimum reading resolution is reduced. It is no longer limited by the maximum sub-scanning speed of the unit.
As a result, it is not necessary to adapt the torque and mechanism of the sub-scanning motor to high speed only to realize the minimum zoom ratio or the minimum reading resolution, which can contribute to cost reduction.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a flow of an image signal in a digital copying machine according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a flow of an image signal in a digital copying machine according to a second embodiment;

FIG. 3 is a block diagram showing a flow of an image signal in a digital copying machine according to a third embodiment;

FIG. 4 is a flowchart for copying using the digital copying machine of FIG. 1;

FIG. 5 is a block diagram showing a flow of an image signal in an image reading apparatus according to a fourth embodiment of the present invention.

FIG. 6 is a block diagram showing a flow of an image signal in a conventional digital copying machine.

FIG. 7 is a side perspective view showing a schematic structure of a conventional digital copying machine.

[Explanation of symbols]

 Reference Signs List 8 image sensor 73 image processing circuit 74 line buffer memory 80 line thinning circuit 82 pseudo halftone processing circuit 83 binary multi-value conversion circuit 84 PWM modulation circuit 86 compression circuit 87 expansion circuit 90 microcontroller 91 motor control circuit 95 control panel

Claims (9)

[Claims] A reading means for electrically scanning image information of a document in a main scanning direction at a predetermined period in a main scanning direction and outputting an image signal for each line; and a main scanning position for the document in a sub-scanning direction perpendicular to the main scanning direction. A sub-scanning means for mechanically moving at a constant sub-scanning speed v in the scanning direction; and a line thinning means for thinning out the image signal for each line to an integer N / N. An image reading apparatus for reading a document image at an arbitrary resolution in the sub-scanning direction by appropriately determining a combination with a value of a speed v. 2. The image reading apparatus according to claim 1, wherein the value of the integer N and the value of the sub-scanning speed v are determined based on the following equation. N = int (r0 / r) v = v0 · r0 / (N · r) where r is an arbitrary set resolution in the sub-scanning direction, r0
Is a predetermined reference reading resolution, int () is an integer conversion operator by rounding up decimal places, and v0 is a basic sub-scanning speed. 3. A reading means for electrically scanning image information of a document in a main scanning direction at a predetermined period in a main scanning direction and outputting an image signal for each line, and a main scanning position with respect to the document in a sub-scanning direction perpendicular to the main scanning direction. An image reading section having sub-scanning means for mechanically moving at a constant sub-scanning speed V in a scanning direction, and line thinning means for thinning out the image signal for each line to an integer N / N, and the image reading section A printing unit that prints an image on a print medium based on an image signal given from the sub-scanning speed V by appropriately determining a combination of the value of the integer N and the value of the sub-scanning speed V A digital copying machine characterized by copying a document image at a predetermined rate. 4. The digital copying machine according to claim 3, wherein the value of the integer N and the value of the sub-scanning speed V are determined based on the following equation. N = INT (R0 / R) V = V0 / (NR) where R is an arbitrary set zoom ratio in the sub-scanning direction, R
0 is a predetermined reference zoom ratio, INT () is an integer conversion operator by rounding up decimal places, and V0 is a basic sub-scanning speed at the time of 1: 1 copying. 5. The image reading section has an image memory for storing image signals thinned out by the line thinning means, and when the set zoom rate R is equal to or higher than the reference zoom rate R0, the image reading section receives the image signal from the reading means. An image signal is provided to the printing unit as it is, and when the set zoom ratio R is less than the reference zoom ratio R0, a line-thinned image signal is provided to the printing unit via the storage unit. Item 4. A digital copying machine according to item 4. 6. A pseudo halftone processing circuit wherein said image reading section binarizes an image signal thinned by said line thinning means by area gradation processing, and an image storing said binarized image signal. A memory, and a binary / multi-level conversion circuit for converting a binary image signal read from the image memory into a multi-level image signal, wherein when the set zoom rate R is equal to or higher than the reference zoom rate R0, The multi-level image signal is directly supplied to the printing unit, and when the set zoom rate R is less than the reference zoom rate R0, the image signal obtained by thinning out the line is converted into the pseudo halftone processing circuit, the image memory, and the binary multi-level conversion circuit. 5. The digital copying machine according to claim 4, wherein the digital copying machine is configured to supply the print data to the printing unit via a printer. 7. A pseudo-halftone processing circuit for binarizing an image signal thinned by the line thinning means by area gradation processing, wherein the image reading section compresses the binarized image signal. Circuit, an image memory for storing a compressed image signal, an expansion circuit for expanding a compressed signal obtained by reading the image signal from the image memory, and a binary image converter for converting the expanded binary image signal into a multilevel image signal. A value conversion circuit, and when the set zoom ratio R is equal to or greater than the reference zoom ratio R0, the multi-valued image signal from the reading unit is directly supplied to the printing unit, and the set zoom ratio R is set to the reference zoom ratio R0. When the value is less than 1, the image signal thinned out to the line is supplied to the printing unit via the pseudo halftone processing circuit, the compression circuit, the image memory, the decompression circuit, and the binary / multilevel conversion circuit. Digital copying machine according to claim 4, wherein. 8. The digital copying machine according to claim 4, wherein said reference zoom ratio R0 is approximately 70%. 9. The image memory is a FIFO memory,
In the image memory, (N-1) /
The image reading unit is configured to sequentially output the image signals stored in the image memory to the printing unit in order to start printing an image when an image signal corresponding to N is stored. A digital copier according to claim 5, 6 or 7.