JP2004258176A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus that makes a document written in thin characters adequately legible and reduces the amount of toner consumption. <P>SOLUTION: The black rate BR of image data to be printed is calculated. Duty that becomes smaller in percentage as the black rate BR becomes higher is set in a duty register 47. In addition, a thinning pattern type is set in a pattern type register 41 in accordance with the black rate BR. The thinning pattern stored in the pattern type register 41 is read from a thinning pattern memory 44. An AND circuit 46 calculates the logical AND of: the outputs of the thinning pattern and an Edge signal from the OR circuit 45; and image data VData to be printed. The output of the result is supplied to a level modulation circuit 48 as black pixel data to be printed. The black pixel data are transmitted to a laser diode 49 on a duty stored in the duty register 47. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, and a multifunction machine having multiple functions such as a copying function and a facsimile function.
[0002]
[Prior art]
2. Description of the Related Art Generally, in an electrophotographic image forming apparatus, a toner save mode is employed to reduce the amount of toner used. Conventional toner save modes include: a. The laser irradiation time for one dot is shortened (for example, see Patent Document 1). b. In a solid black portion, a method of thinning out black pixels (for example, see Patent Document 2) is employed.
[0003]
[Patent Document 1]
Japanese Patent Application Laid-Open No. Hei 10-181888
[Patent Document 2]
JP-A-7-46391
[Problems to be solved by the invention]
In the image forming apparatus, whether or not to perform toner save is set based on a key operation on an operation panel of the apparatus or a command from a host computer. However, in the above-described conventional toner saving method, when the toner mode is set, the toner saving is performed regardless of the content of the image. There is a problem that it is difficult to read.
[0006]
SUMMARY An advantage of some aspects of the invention is to provide an image forming apparatus that can suppress toner consumption without making it difficult to read a document including fine characters.
[0007]
[Means for Solving the Problems]
An image forming apparatus according to the present invention includes a black ratio detecting unit for detecting a black ratio of an image, an image forming unit using an electrophotographic method capable of saving toner, and an image forming unit based on the black ratio detected by the black ratio detecting unit. And a control means for controlling the toner save rate.
[0008]
The image forming apparatus of the present invention includes a document reading unit that reads an image of a document and outputs image data for each pixel, and the black ratio detection unit preferably detects the black ratio by adding the image data for each pixel. .
[0009]
In the image forming apparatus according to the present invention, the image forming unit is a laser printer, and it is preferable that toner saving is performed by at least one of laser irradiation time for each pixel and thinning out of black pixels.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in more detail with reference to embodiments. FIG. 1 shows a configuration of a multifunction peripheral (having multiple functions such as a copy function, a facsimile function, and a reading function) which is an embodiment of the image forming apparatus of the present invention.
[0011]
The MFP according to the present embodiment includes an MPU 1, an NCU 2, a MODEM 3, a ROM 4, a RAM 5, an image memory 6, a CCD line image sensor 7, an image processing unit 8, a scanner mechanism control unit 9, a reading CODEC 10 An image memory 11, an operation unit 12, a display unit 13, a communication CODEC 14, a print CODEC 15, a print image processing unit 16, a printer engine 17, a page memory 18, a system bus 19, Image buses 20 and 21 are provided.
[0012]
The MPU 1 has a function of controlling the entire MFP according to this embodiment. The MPU 1 is connected to an NCU (Network Control Unit) 2 and a MODEM 3. The NCU 2 is controlled by the MPU 1 to control the connection between the line 22 and the multifunction peripheral, and has a function of transmitting a dial pulse corresponding to a telephone number of a communication partner and a function of detecting an incoming call. The line 22 is connected to a general public switched telephone network (PSTN).
[0013]
The MODEM 3 modulates transmission data and demodulates reception data, specifically, modulates transmission data, which is a digital signal, into an analog audio signal, and sends the analog audio signal to the line 22 via the NCU 2. Through the NCU 2, the received analog audio signal is demodulated into a digital signal. The ROM 4 stores in advance programs and the like for controlling the operation of the entire MFP. The RAM 5 stores data necessary for control by the MPU 1 and data that need to be temporarily stored during a control operation. The image memory 6 stores the image data read by the CCD line image sensor 7 or the image data received from the outside via the line 22 and the MODEM 3.
[0014]
The CCD line image sensor 7 reads a document image and inputs image data to the image processing unit 8. The image processing unit 8 performs image processing such as A / D conversion, shading correction, gamma correction, binarization processing, and calculation of a black pixel value of a document on input image data. The scanner mechanism controller 9 controls a motor that drives a mechanism such as an automatic document feeder (ADF) and a carriage (not shown) of the scanner. The reading CODEC 10 encodes the read image data by MH, MR, MMR or the like in order to transmit or store the image data. The image memory 11 stores the image data processed by the image processing unit 8.
[0015]
The operation unit 12 includes, in addition to the toner save mode key 12a, a mode switching key for switching modes such as a copy mode and a fax mode, a start key, a numeric keypad for inputting numbers such as a telephone number and a fax number, a one-touch key, and a shortcut key. And keys for instructing various other operations. The toner save mode key 12a is operated when setting the toner save mode. The display unit 13 displays various information such as a telephone number, a fax number, and a remaining amount of toner of the printer, which are input by operating the operation unit 12.
[0016]
The communication codec 14 encodes the read image data for transmission. The print CODEC 15 decodes image data to be printed. The print image processing unit 16 supplies the data to be printed stored in the page memory 18 to the print engine 17 and executes the print processing.
[0017]
As shown in FIG. 2, the image processing unit 8 includes an AFE (analog front end) circuit 31, an A / D converter 32, a clock signal generation circuit 33, a shading correction circuit 34, a shading RAM 35, a gamma correction It comprises a circuit 36, a binarization circuit 37, a direct / parallel (S / P) conversion circuit 38, and an adder 39.
[0018]
The AFE circuit 31 performs analog amplification of the image data from the CCD line image sensor 7 and outputs the amplified data. The A / D converter 32 converts the analog image data from the AFE circuit 31 into multi-value digital data. The shading RAM 35 captures read data when the document is white paper or data obtained by reading a white reference plate via the AFE circuit 31 and the A / D converter 32 and stores the data as shading correction data. The shading correction circuit 34 performs shading correction based on shading correction data stored in the shading RAM 35 and outputs the output from the A / D converter 32 during document reading. The gamma correction circuit 36 has, for example, predetermined gamma correction characteristics, and performs gamma correction on image data after shading correction. The gamma correction circuit 36 is generally used for image quality adjustment. The binarization circuit 37 binarizes the output of the gamma correction circuit 36 at a predetermined threshold. The binarized image data is converted into parallel data by the serial / parallel conversion circuit 38 and output to the image bus 20.
[0019]
The adder 39 adds the black value of the image data output from the shading correction circuit 34 and the black value of its own output, accumulates a black (pixel) value amount, and outputs the resultant value to the system bus 19. The cumulative value of the black (pixel) value referred to here is the cumulative value of the black pixels of the multi-value digital, and the larger the value, the higher the black ratio.
[0020]
FIG. 3 is a block diagram showing the internal configuration of the printer image processing unit 16. The printer image processing unit 16 includes a pattern type register 41 that stores a pattern type input from the system bus 19, a line counter 42 that counts a Vsync signal, a pixel counter 43 that counts a Vclk signal, A register 41, a line register 42, a thinned-out pattern memory 44 which receives stored data and count data of the pixel counter 43 as address data at an input, an OR circuit 45 which receives an output of the thinned-out pattern memory 44 and an Edge signal at an input, An AND circuit 46 receiving an output of the OR circuit 45 and Vdata as inputs, a duty register 47 storing a duty signal from the system bus 19, and receiving a signal from the AND circuit 46 and a duty signal from the duty register 47, Les And it is configured to The modulated signal from the laser modulation circuit 48. applied to the laser diode 49.
[0021]
FIG. 4 is a block diagram showing an Edgc signal detection circuit included in the image processing circuit 16 for a printer. The Edgc signal detection circuit includes a parallel / serial conversion circuit 51 for parallel / serial conversion of image data to be printed, and line buffers 52, 53 for serially storing the output of the parallel / serial conversion circuit 51 line by line. And a pattern matching memory 54. The parallel / serial conversion circuit 51 and the line buffers 52 and 53 store three lines of image data to be printed. The rightmost three storage cells form a 3 × 3 matrix, and the center of the matrix is stored. cell _{D 0,} with ₀ outputs the current image VData, storage cells _{D 0, 0} of the surrounding storage cell _{D +1, -1 ~D + 1 +} 1 · D 0, -1 · D 0, +1 ~D -1, +1 Are input to the pattern matching memory 54. When the pattern matching memory 54 matches one of a plurality of edge patterns stored in advance, the pattern matching memory 54 outputs an Edge signal (= "1") indicating that VData is an edge of a document image.
[0022]
In the multifunction peripheral of this embodiment, when printing is performed in the toner save mode, a black ratio of a document image is obtained and a drive duty and a thinning pattern are set before printing.
[0023]
Next, with reference to a flowchart shown in FIG. 5, a process of setting the duty and the thinning pattern in the toner save mode of the multifunction peripheral according to the embodiment will be described. When this processing routine is started, first, in step ST1, the adder 39 fetches the black ratio data BR of the page. Then, the process proceeds to step ST2. In step ST2, it is determined whether or not the black ratio data BR is smaller than 0.06. If BR <0.06, the process moves to step ST3. If BR <0.06 is not satisfied, the process moves to step ST5. In step ST3, a duty of 100% is set in the duty register 47. Subsequently, the process proceeds to step ST4, where the pattern is set to all black, and the process returns. The pattern black is stored in the pattern type register 41 later.
[0024]
In step ST5, it is determined whether or not the black ratio data BR satisfies 0.06 ≦ BR <0.12. If the determination is "yes", the process proceeds to step ST6. On the other hand, if the determination is "no", the process proceeds to step ST8. In step ST6, a duty of 50% is set in the duty register 47. Subsequently, the process proceeds to step ST7, sets all black patterns, and returns.
[0025]
In step ST8, it is determined whether or not the black ratio data BR satisfies 0.12 ≦ BR <0.24. If the determination is "yes", the process proceeds to step ST9. On the other hand, if the determination is "no", the process proceeds to step ST11. In step ST9, a duty of 50% is set in the duty register 47. Subsequently, the process proceeds to step ST10, sets the pattern a shown in FIG. 6, and returns.
[0026]
In step ST11, it is determined whether or not the black ratio data BR satisfies 0.24 ≦ BR <0.48. If the determination is "yes", the process proceeds to step ST12. On the other hand, in the case of the determination of “No”, although not shown in the drawings, the duty ratio of the laser is further reduced, the process of increasing the thinning rate of the pattern is performed, and the process returns. In step ST12, a duty of 50% is set in the duty register 47. Subsequently, the process proceeds to step ST13, sets the pattern b shown in FIG. 6, and returns.
[0027]
As described above, when the black ratio BR is smaller than 0.06, the duty is set to 100% and the pattern is entirely black, and toner is not saved. However, when the BR is 0.24 or more, the duty is set to 50% and thinning is performed. The pattern is also thinned out with the pattern b, and the toner is saved by both the duty reduction and the thinning out. The setting of the duty and the thinning performed based on the value of the black ratio is not limited to the above embodiment, and may be appropriately set.
[0028]
Next, a description will be given of a document copy processing operation in the multifunction peripheral according to the present embodiment. The document image data read by the CCD line image sensor 7 is sequentially converted for each line into an AFE circuit 31, an A / D converter 32, a shading correction circuit 34, a gamma correction circuit 36, a binarization circuit 37, and a direct / parallel conversion. The data is output as image data via the circuit 38 and stored in the image memory 11 via the image bus 20. At this time, the image data output from the shading correction circuit 34 is also input to the addition circuit 39, the black pixel amount is cumulatively added, and the cumulative data BR is stored.
[0029]
At the time of printing, the black ratio data BR is read. A duty and a thinning pattern according to the black ratio data BR are set. The set pattern type (one of the all black pattern, pattern a, and pattern b shown in FIG. 6) is input to the thinning pattern memory 44 via the pattern type register 41, and the count values of the line counter 42 and the pixel counter 43 Is also input to the thinning counter 44. Each data of the thinning pattern stored in the thinning pattern memory 44 by addressing the thinning pattern memory 44 is addressed and output one by one. The thinning pattern data and the Edge signal are output from the OR circuit 45, and the logical product of the data and the image data VData is obtained by the AND circuit 46. From 48, the voltage is applied to the laser diode 49 to perform a printing operation.
[0030]
For example, when BR is 0.06 or less, there is no need to save toner, so the pattern is set to all black, and the laser diode 49 is driven at a duty of 100%. On the other hand, when the black ratio data BR is as large as 0.24 <BR <0.48, the duty is set to 50%, the pattern is set to the pattern b in FIG. 6, and the toner is reduced from both the duty reduction and the thinning. Make a save.
[0031]
In addition, in the circuit shown in FIG. 2 of the above embodiment, the multi-value data is added as it is in the adder 39, but the number of bits of the adder 39 needs to be very large due to the necessity of accumulation. Thus, for example, when 256 levels (8 bits), white is OOH, and black is FFH, the number of bits of the adder 39 is reduced by adding only the upper 4 bits of 8-bit image data. good. Thereby, the subsequent black ratio determination processing can be simplified.
[0032]
Further, instead of the adder 39, a counter for counting the number of black pixels output from the binarization circuit 38 may be provided, and this count value may be used as the black ratio.
[0033]
Also, in the circuit shown in FIG. 3 of the above embodiment, the Edge signal is also input to the laser modulation circuit 48, and when the Edge signal is input, regardless of the value set in the duty register 47, 100% of the Edge signal is input. The laser diode 49 may be driven with a duty.
[0034]
【The invention's effect】
According to the present invention, the toner save ratio is controlled by the black ratio of the document. Therefore, for a document having a small black portion such as a document written with fine characters, the toner save is not performed, or the toner save ratio is reduced to reduce the character save ratio. Prevent fainting of etc. On the other hand, for a document having a high black ratio including a solid black portion, it is possible to increase the toner save and suppress the toner consumption.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of a multifunction peripheral that is an embodiment of an image forming apparatus according to the present invention.
FIG. 2 is a block diagram illustrating an internal configuration of an image processing unit of the MFP according to the embodiment.
FIG. 3 is a block diagram illustrating an internal configuration of a print image processing unit of the multifunction peripheral according to the embodiment.
FIG. 4 is a block diagram illustrating an internal configuration of an edge signal detection circuit of a print image processing unit of the multifunction peripheral according to the embodiment.
FIG. 5 is a flowchart for explaining toner save duty and thinning pattern setting processing of the multifunction peripheral of the embodiment.
FIG. 6 is a diagram illustrating a thinning pattern for toner saving in the multifunction peripheral of the embodiment.
[Explanation of symbols]
1 MPU
2 NCU
3 MODEM
4 ROM
5 RAM
6 Image memory 7 CCD line image sensor 8 Image processing unit 9 Scanner mechanism control unit 10 CODEC for reading
11 Image memory 12 Operation unit 12a Toner save mode key 13 Display unit 14 CODEC for communication
15 CODEC for printing
16 Image Processor for Printing 17 Printer Engine 18 Page Memory 19 System Bus 20, 21 Image Bus 34 Shading Correction Circuit 39 Adder 41 Pattern Type Register 44 Thinning Pattern Memory 47 Duty Register 48 Laser Modulation Circuit 49 Laser Diode

Claims (3)

A black ratio detecting unit for detecting a black ratio of an image, an image forming unit using an electrophotographic method capable of toner saving, and a control for controlling a toner saving ratio of the image forming unit based on the black ratio detected by the black ratio detecting unit. And an image forming apparatus. 2. The image forming apparatus according to claim 1, further comprising a document reading unit that reads an image of the document and outputs image data for each pixel, wherein the black ratio detecting unit detects the black ratio by adding the image data for each pixel. Image forming apparatus. The image forming apparatus according to claim 2, wherein the image forming unit is a laser printer, and performs toner saving by at least one of laser irradiation time for each pixel and thinning of black pixels.

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