JPH05145709A - Digital image producing device - Google Patents

Abstract

PURPOSE:To improve the recognizing precision by a pre-processing scanning operation by making this scanning speed variable and controlling a speed level to be suited to the recognition processing that is necessary for the designated image processing. CONSTITUTION:An image scanner 2 carries out the pre-scanning before the original scanning in response to the requested image processing and then carries out the necessary recognition processing. Meanwhile a system controller 31 transmits the drive signal to a scanner control circuit 42 in accordance with the types and the contents of the detection and recognition processing which are needed for execution of various types of image processing. Thus the speed of a scanner driving motor 45 is changed. As a result, the images can be read at an optimum speed for recognition of the pre-scanning. Then the detection and recognition processing accuracy can be improved by the pre-scanning operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital image forming apparatus such as a digital copying machine.

[0002]

2. Description of the Related Art In recent years, some kinds of digital copying machines automatically detect a document size, recognize an image area, and further, an image area such as a character area and a photograph area, a color area and a monochrome area, and the like. In some cases, the image processing is switched by separating the image processing. Further, it is also practiced to detect a specific color image on a document and change it to an image of another color.

In order to obtain information for such detection and recognition, there is a method in which preprocessing scanning (press scanning) is performed prior to the original scanning for image formation. Here, the press scanning speed is set to the linear velocity at the maximum reduction ratio so as to keep the speed as fast and stable as possible in order to improve the copying speed and avoid the trouble of press scanning. There is. For example, in the case of an apparatus having a variable power range of 25% to 400%, press scanning is performed at a scanning speed of 25%.

On the other hand, in an image input device (image scanner) of this type of digital copying machine, three CCD image sensors having the number of pixels for one line are arranged in parallel,
There is also one in which R, G, and B spectral filters are attached to each of them, and R, G, and B image data is obtained by spectrally separating the input light from the original. In the case of such a color reading system, the R, G, B image data will be displaced due to the difference in the physical position of each CCD image sensor. For example, as shown in FIG. 4, this deviation is dealt with by using a correction memory 1 such as a delay memory to perform line-to-line correction according to the distance between CCD image sensors. Here, this is based on the assumption of a certain magnification, for example, at the same magnification, and in order to cope with the change in the linear velocity due to the change of the magnification, interpolation calculation between lines is performed even for a deviation within one line. I am trying to do it.

[0005]

However, even if such a calculation correction is used, a slight deviation from the actual image data will occur. This shift leads to a color shift in particular. Therefore, it is not preferable to use the misaligned data for detection and recognition by prescanning because it causes erroneous detection and recognition.

In the case of recognition by comparing patterns of image data, erroneous recognition obviously increases in scaled data. In particular, in this type of digital copying machine, since the scaling in the main scanning direction is generally performed by electrical processing based on calculation, the output from the scanner becomes image data in which only the sub-scanning direction is scaled. Therefore, it is necessary to use an irregular pattern as the pattern to be compared, or to use data in which the scaling in the main scanning direction is performed in advance.

After all, the conventional one has a problem in the accuracy of various recognition processes.

[0008]

According to a first aspect of the present invention, color detection is performed based on image data read by pre-processing scanning before scanning for image formation.
A control means for variably controlling the speed of the preprocessing scanning is provided in a digital image forming apparatus which is designed to perform some recognition processing such as pattern recognition.

In this case, in the invention described in claim 2, the control means for controlling to the highest speed among the reading speeds suitable for the specified recognition processing, and in the invention described in claim 3, the reading specified by the operator. A control means for controlling the speed is used.

[0010]

By changing the speed of the preprocessing scanning and controlling the speed by the control means according to the contents of the designated recognition processing, the accuracy of the recognition processing by the preprocessing scanning is improved.

Particularly, by controlling the reading speed suitable for the designated recognition processing to the highest speed, the accuracy of the recognition processing can be improved while minimizing the time required for the preprocessing scanning.

Further, by controlling the reading speed designated by the operator, the accuracy of the recognition processing by the scanning for preprocessing can be improved under the operator's judgment.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. First, the structure and operation of a digital color copying machine to which the present invention is applied will be described with reference to FIG. This apparatus is roughly classified into an image scanner 2 and an automatic document feeder (ADF) mounted on the image scanner 2.
3, a laser printer 4, and an operation board 5.

The image scanner 2 is for sub-scanning by mechanically driving the image reading portion arranged below the contact glass 6 in the left-right direction in the drawing. The light emitted from the illumination lamp 7 exposes the surface of the document set on the contact glass 6 and is reflected according to the density of the document image. The reflected light from this document passes through a plurality of mirrors and lenses and is incident on the dichroic prism 8. The dichroic prism 8 converts the incident light into R,
Disperse into three colors of G and B. The three dispersed lights are one-dimensional image sensors (CCDs) arranged at different positions.
It is incident on the image sensor 9). Therefore, 3 CCDs
The image sensor 9 simultaneously reads R, G, and B color components for one line in the main scanning direction on the original image. Then, the original image is two-dimensionally read by the sub scanning of the image reading unit.

In the ADF 3, the calling roller 11 is displaced downward to abut on the upper surface of the original with respect to the original placed on the original table 10, and is rotated to feed the original. The fed-out document is prevented from being double-fed by the separation roller 12, and only one sheet is fed to the pull-out roller 13. Thereafter, the original is conveyed and set on the contact glass 6 to a predetermined position by the pull-out roller 13 and the conveying belt 14. As a result, the image scanner 2 is used for reading. After the reading is completed, the conveyor belt 14 is re-driven, the original is ejected, and the next original is conveyed and set.

The calling roller 11 and the separation roller 12 are driven by a paper feed motor (not shown), and the pullout roller 13 and the conveyor belt 14 are driven by a conveyor motor (not shown).

Next, the laser printer 4 will be described. Reproduction of the image is performed on the drum-shaped photoconductor 15. Around the photoconductor 15, a charging charger 16, an optical writing unit 17, a developing unit 18, a transfer drum 19, a cleaning unit 20, and the like are sequentially arranged according to a well-known electrophotographic process.

First, the surface of the photoconductor 15 is the charging charger 1.
It is uniformly charged to a high potential by the corona current generated by 6. When the surface of the charged photoconductor 15 is irradiated with laser light from the optical writing unit 17, the charging potential changes according to the light intensity, and an electrostatic latent image is formed according to the presence or absence of laser light irradiation. Here, the optical writing unit 17 is provided with a laser diode (not shown) as a light source, and the laser light emitted from the laser diode is deflected by the polygon mirror 22 rotated at a constant speed by the polygon motor 21. While receiving the fθ lens 23,
The surface of the photoconductor 15 is irradiated with spots via the mirror 24. At this time, in the control device, 2 for each pixel unit to be recorded.
A value signal (with / without recording) is applied to the laser diode so that each pixel position is synchronized with the rotational deflection position of the polygon mirror 22. That is, the laser beam is controlled to be turned on / off according to the density (recording / non-recording) of the pixel at each scanning position of the image.

Therefore, the potential distribution formed on the photosensitive member 15 forms an electrostatic latent image corresponding to the light and shade of the original image. The latent image is developed by the developing unit 18 to be a visible image. In this example, magenta M, cyan C,
Developing units 18M and 18 for yellow Y and black BK
C, 18Y, and 18BK are provided, and toners of different colors are held. In the case of the printer of this example, since any one of the four developing devices is selectively energized to perform the developing operation, the electrostatic latent image is visualized with the toner of M, C, Y or BK color. It

On the other hand, the transfer paper 26 fed from the cassette 25 is sent to the transfer drum 19 via the registration rollers 27, and is held while being wound around the surface of the transfer drum 19. The visible image on the photoconductor 15 is transferred onto the transfer paper 26 by the action of the transfer charger 28 while being close to the surface of the transfer drum 19. In the single-color mode, the transfer paper 26 on which the toner image has been transferred is separated from the transfer drum 19, is subjected to a fixing process by the fixing device 29, and is discharged onto the paper discharge tray 30. On the other hand, in the case of the full color mode, it is necessary to superimpose toner images of four colors of M, C, Y and BK on the same transfer paper 26. Therefore, for example, after forming a BK color toner image on the photoconductor 15 and transferring the BK color toner image onto the transfer paper 26, the transfer paper 26 is not separated from the transfer drum 19. A color toner image is formed, and this toner image is transferred onto the transfer paper 26 again. Similarly for the B and Y color toner images, the same transfer paper 2 held on the transfer drum 19 is used.
6) Overlay and transfer. That is, by repeating the process of forming and transferring the toner image four times, four
A full color image is formed with the colors overlapping. After the transfer of all toner images is completed, the transfer paper 26 is transferred onto the transfer drum 1.
The sheet is separated from sheet No. 9, is subjected to the fixing process by the fixing device 29, and is discharged onto the sheet discharge tray 30.

Next, FIG. 3 shows the configuration of the electrical components of such a digital copying machine. The control of each unit 2, 3, 4, 5 is performed by a system controller 31 which is constituted by a microcomputer or the like and serves as control means. Also,
The synchronization control circuit 32 generates a clock pulse that serves as a reference for control timing, and inputs various signals to output signals in order to synchronize the signals between the units.

The image scanner 2 A / D-converts the R, G, and B color image signals read from the original and outputs each as 8-bit color image information. This image information is output to the laser printer 4 after undergoing various processes such as γ correction in the image processing unit. In this example, in the image processing unit, the γ correction circuit 33, complementary color generation circuit 34, U
CR black generation circuit 35, selector 36 and gradation processing circuit 3
7 units are provided. In complementary color generation, R,
Each information of G and B is converted into information of each color of Y, M and C which are complementary colors. In UCR black generation, a black component included in a color obtained by combining all the input Y, M, and C is extracted and output as BK, and the black component is removed from the remaining signals. Therefore, for example, the minimum value detection circuit and the under color removal circuit are included. That is, the minimum value detecting circuit detects the smallest gradation level of the C, M and Y image signals as an achromatic color signal and outputs it.
A black (BK) signal is generated based on this achromatic signal. In the under color removal circuit, a value (C-BK, MB) obtained by subtracting the black image signal BK from the input image signal (C, M, Y).
K, Y-BK) are output as C ', M', and Y ', respectively.

The selector 36 is the system controller 31.
In response to an instruction from, any one of Y, M, C, and BK to be input is selected and output to the gradation processing circuit 37. The gradation processing circuit 37 converts the input 8-bit density information into 2
Although digitized, it is configured to perform dither processing to enable halftone image output. The laser diode of the laser printer 4 is modulated based on the binarized image information.

Next, the structure of the image scanner 2 is shown in FIG.
Will be described. The analog image signal output from the CCD image sensor 9 is amplified and light amount corrected by the signal processing circuit 38, and converted into a digital multilevel signal by the A / D converter 39. This signal is subjected to correction processing by the shading correction circuit 40, and further subjected to line correction between the three CCD image sensors 9 by the interline correction circuit 41 having the configuration shown in FIG. It is output as value data. Here, the scanner control circuit 42 controls the lamp control circuit 43, the timing control circuit 44, and the scanner drive motor 45 according to an instruction from the system controller 31. The lamp control circuit 43 turns on / off the illumination lamp 7 and controls the light amount according to an instruction from the scanner control circuit 42. A rotary encoder 46 is connected to the drive shaft of the motor 45,
The position sensor 47 detects the reference position (home position) of the sub-scanning drive mechanism.

The timing control circuit 44 outputs each signal according to the instruction from the scanner control circuit 42. That is, when reading is started, a transfer signal for transferring data for one line to the shift register and a shift clock pulse for outputting the data in the shift register bit by bit are given to the CCD image sensor 9. For the image reproduction system control unit, a pixel synchronizing clock pulse CLK, a main scanning synchronizing pulse LSYNC and a main scanning effective period signal LGAT.
Output E. This pixel synchronization clock pulse CLK is C
The signal is almost the same as the shift clock pulse given to the CD image sensor 9, and the main scanning synchronization pulse LSYNC is almost the same as the main scanning synchronization signal PMSYNC output from the beam sensor of the optical writing unit 17, but the image reading is performed. If not, output is prohibited. The main scanning effective period signal LGATE is the output data DAT.
It is a signal that becomes H level at the timing when A is regarded as valid data.

When the scanner control circuit 42 receives a reading start instruction from the CPU 46, it turns on the illumination lamp 7,
The scanner drive motor 45 is started to drive, the timing control circuit 44 is controlled, and the reading by the CCD image sensor 9 is started. Further, the sub-scanning effective period FGATE is set to the H level. This signal FGATE becomes L level when the time required to scan the maximum reading length in the sub-scanning direction has elapsed after being set to H level.

According to the required image processing, the image scanner 2 as described above performs prescanning and performs necessary recognition processing prior to the original scanning. Here, in the present embodiment, the reading speed at the time of prescanning is not fixed but is variable and controlled by the system controller 31. That is, the system controller 31
Is the detection necessary to perform the various image processing instructed,
A drive control signal is sent to the scanner control circuit 42 according to the type and content of the recognition process to switch the speed of the scanner drive motor 45. As a result, the reading is performed at the optimum reading speed (for example, the speed corresponding to the same magnification) for recognition in the prescanning, so that the accuracy of the detection / recognition processing by the prescanning becomes high. In this case, the optimum reading speed is not limited to one, but when there are plural reading speeds, the highest reading speed is set. This makes it possible to minimize the time required for press scanning, which is different from the original image reading,
The annoyance associated with press scanning can be reduced. At the time of the original scanning after the prescanning, the designated image processing is performed, so that the scanning speed is controlled to be the scanning speed calculated based on the designated magnification.

Further, the operation board 5 of this embodiment is constructed so that the operator can appropriately set and input the reading speed during such prescanning. When the operator inputs an instruction, the system controller 31 controls the speed of the scanner drive motor 45 via the scanner control circuit 42 according to the input data, and the read speed of the prescanning is changed. Therefore, it is possible to effectively deal with a case where high recognition accuracy is required even if the time required for prescanning is long.

[0029]

As described above, according to the present invention, the speed of the preprocessing scanning is variable, and the speed can be controlled by the control means according to the contents of the designated recognition processing. The accuracy of the recognition process by can be improved.

In particular, according to the second aspect of the present invention, the reading speed suitable for the designated recognition processing is controlled to the highest speed, so that the time required for the preprocessing scanning can be suppressed to the minimum necessary. It is possible to improve the accuracy of recognition processing by press scanning while reducing the annoyance of scanning.

According to the third aspect of the invention, since the reading speed specified by the operator is controlled,
Under the judgment of the operator that the time required for the prescanning process may be sacrificed, the accuracy of the recognition process by the preprocessing scanning can be further improved.

[Brief description of drawings]

FIG. 1 is a block diagram mainly showing an image scanner showing an embodiment of the present invention.

FIG. 2 is a schematic front view showing the configuration of a digital color copying machine.

FIG. 3 is a schematic block diagram of an entire electrical system.

FIG. 4 is a block diagram showing a conventional example.

[Explanation of symbols]

 31 Control means

Claims (3)

[Claims] 1. A digital image forming apparatus in which some recognition processing such as color detection and pattern recognition is performed based on image data read by scanning for pre-processing before scanning for image formation. A digital image forming apparatus comprising a control means for variably controlling the speed of pre-processing scanning. 2. The digital image forming apparatus according to claim 1, further comprising a control unit for controlling a reading speed suitable for a designated recognition process to a maximum speed. 3. The digital image forming apparatus according to claim 1, wherein the digital image forming apparatus is control means for controlling a reading speed designated by an operator.