JP3780749B2 - Image forming apparatus and document reading apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an original reading apparatus provided with an improved automatic density control means and an image forming apparatus provided with the original reading apparatus.
[0002]
[Prior art]
The original is conveyed to the reading position one by one, the image of the original passing through the reading position is read and converted into an electrical signal to obtain image information, and an image is formed on the recording paper based on the obtained image information A so-called digital copying apparatus is widely used as an image forming apparatus. Many of such digital copying apparatuses are equipped with an automatic density control function for forming an image having an appropriate density on various originals by controlling the density of an image to be recorded in accordance with the density of the original.
[0003]
FIG. 1A is a block diagram of an image information processing system in an image forming apparatus having an automatic density control function, and FIG. 1B is a diagram showing a document.
[0004]
In the case of copying from a binary image such as a character, among the image information, as shown in FIG. 1B, image information having a certain width P0 at a part of the leading edge of the document is previously prepared. 111, the document density information is created. The image information from the reading unit 110 is input to the γ conversion unit 113 which is a density control unit after image processing such as filter processing and scaling processing is performed in the image processing unit 112. The γ conversion unit 113 performs γ conversion processing on the image information from the image processing unit 112 based on the document density information created by the document density creation unit 111, thereby forming an image with an optimum density. In this way, the image information is converted into image information whose density is controlled and the γ-converted image information is stored in the image memory 114, and then output from the image memory 114 to the image forming means 115 to form an image.
[0005]
On the other hand, in the case of copying a multi-tone image such as a photographic image, in order to obtain document density information from the entire surface of the document, the document that has been read once is returned to the transport path, transported again to the scanning position, and then scanned again. The image information obtained by the first reading is taken into the document density information creating unit 111 and calculation processing is performed to create the document density information, and the image information obtained by the second reading is taken into the image processing unit 112, The γ conversion unit 113 performs density control so that an image can be formed with an optimum density based on the document density information from the document density information creating unit 111, and an image is formed.
[0006]
The image information read as described above is taken into the γ conversion unit 113 through the image processing unit 112. However, as described above, a part of the image is previously transmitted while the image information is transmitted from the reading unit 110 to the γ conversion unit 113. The document density information creating unit 111 processes the information or the entire image information to create the document density information.
[0007]
[Problems to be solved by the invention]
When the automatic density adjustment processing is performed based on the image information of the leading end portion P0 having a predetermined width, which is a part of the image information obtained by reading the original G in FIG. 1B, the original density information creating unit 111 has the predetermined width. Since it takes time to capture image information, perform arithmetic processing, and control, it does not make it in time, so for the leading end portion P1 of a width of several millimeters of the original G, automatic use of the original density information created by the original density information creating means 111 is used. The density adjustment process cannot be performed. For this purpose, automatic density adjustment processing is performed from the portion P2 following the tip portion P1 having a width of several millimeters. Thus, in order to generate a region where the automatic density adjustment process cannot be performed, a constant density adjustment process is performed on the most advanced portion P1 regardless of the density of the original G. Therefore, depending on the paper quality of the document and the image density, there is a problem that a density difference is generated between the most advanced portion P1 and the portion P2 other than P1. Further, the control is complicated by using two density processing means in combination.
[0009]
SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems in automatic density control, and an image forming apparatus and an original in which appropriate automatic density control is performed and reduction in image forming efficiency caused by automatic density control is reduced. An object is to provide a reader.
[0010]
[Means for Solving the Problems]
The purpose of the present invention is to
(1) Reading means for conveying originals one by one to a reading position, reading an image of the original passing through the reading position, and outputting image information;
A document density information creating unit that creates image density information by processing image information of only the leading edge of the image as part of the image information of the document obtained from the reading unit;
A delay unit that inputs image information from the reading unit and delays and outputs the image information so that the head is delayed from the document density information output by the document density information creating unit;
Based on the original density information the document density information creation means outputs the image information density control means and said density control means processes the output to control the density of the image formed on the recording paper of the delay means outputs And an image forming apparatus having an image forming means for forming an image on a recording paper, and
(2) a reading unit that conveys originals one by one to a reading position, reads an image of the original that passes through the reading position, and outputs image information;
A document density information creating unit that creates image density information by processing image information of only the leading edge of the image as part of the image information of the document obtained from the reading unit;
Delay means for inputting image information from the reading means, delaying the image information so that the head is delayed from the original density information output by the original density information creating means,
Document reading apparatus characterized by having a density control means for the document density information creation unit processes the output of the delay unit based on the original density information to be outputted, to control the density of the image,
Achieved by:
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Figure 2 is a sectional view of an image forming apparatus according to the shape condition of the present invention.
[0012]
The document reading unit includes an automatic document feeder 1 and a document reader 2. The document reading apparatus 2 includes a first mirror unit 23 including a lamp 231 and a first mirror 232, a V mirror unit 24 including a second mirror and a third mirror, an imaging lens 25, and a CCD 26. When reading a document conveyed by the automatic document feeder 1, the first mirror unit 23 and the V mirror unit 24 move to the left in FIG. 2, and the first mirror unit 23 is positioned below the slit 21. Yes.
[0013]
The document placed on the document placement table 11 of the automatic document feeder 1 is separated by the document separating means 12 and conveyed on the slit 21 by the document conveying means 13. The original moving on the slit 21 is irradiated with light by the lamp 231, and the light reflected from the original is incident on the CCD 26 through the first mirror 232, the second mirror 241, the third mirror 242 and the imaging lens 25. To do. In the CCD 26, incident light is photoelectrically converted to read an image of the document in the main scanning direction (the direction perpendicular to the paper surface in the figure), while the document is moved in the sub-scanning direction by the document conveying means 13, so Images can be read. Image information read by the CCD 26 is appropriately sent to an image forming means, subjected to image processing, and supplied to a laser writing system 33 described later.
[0014]
When the document is directly placed on the platen glass 22, the first mirror unit 23 and the V mirror unit 24 are moved along the platen glass 22 in the right direction in FIG. Can be read.
[0015]
The image forming unit 3 is a unit that forms an image on a recording sheet conveyed at a predetermined process speed based on image information obtained by the document reading device 2. The image forming means 3 is based on image data read by a photosensitive drum 31 having a photoconductive photosensitive layer and carrying a toner image, a charger 32 which is a charging means for uniformly charging the photosensitive drum 31, and a CCD 26. A laser writing system 33 which is an image writing means for forming a latent image by exposure scanning on the photosensitive drum 31, and a developing means for developing a latent image on the photosensitive drum 31 to form a toner image. The developing unit 34, a transfer unit 35 that is a transfer unit that transfers the toner image carried on the photosensitive drum 31 onto a separately conveyed recording paper, and the recording paper onto which the toner image has been transferred from the photosensitive drum 31. It has a separator 36 as a separating means for separating, a cleaning means 37 for removing the toner remaining on the photosensitive drum 31 after the transfer, and a fixing means 38 for fixing the toner image on the recording paper. As shown in the figure, a charger 32, a laser writing system 33, a developing device 34, a transfer device 35, a separator 36, and a cleaning unit 37 are disposed around the photosensitive drum 31.
[0016]
The photosensitive drum 31 is rotated in a direction indicated by an arrow by a driving unit (not shown), and is uniformly charged by the charger 32, formed a latent image by the laser writing system 33, and developed by the developing device 34. A toner image is formed based on the read image information.
[0017]
The recording paper storage means 4 is a recording paper storage means for storing a plurality of recording papers in a stacked state. In the present embodiment, a plurality of recording paper storage units 4 A to 4 C are arranged in a multistage manner below the image forming unit 3 as the recording paper storage unit 4.
[0018]
The transport unit 5 is a transport unit that transports the recording paper from the recording paper storage unit 4 to the image forming unit 3. The recording paper stored in each of the recording paper storage units 4 </ b> A to 4 </ b> C is transferred to the intermediate transport roller 51. It is comprised so that it can convey to the conveyance path 5B through -53. Then, the recording paper is transferred from the storage means 4A to 4C through the loop forming roller 55, the toner image on the photosensitive drum 31 is transferred to the recording paper, fixed by the fixing means 38, and sent by the fixing paper discharge roller 61 of the paper discharge section 6. Then, the sheet is discharged to the discharge tray 64 by the discharge roller 63 via the switching means 62. Although it is possible to form the image on both sides of the recording paper by transporting it downward by the switching means 62, this operation is omitted.
[0019]
Whether the document is a multi-value density image such as a photograph or a binary density image such as text is set in advance on the operation panel of the copying apparatus.
[0020]
FIG. 3 is a block diagram of an image information processing system of the image forming apparatus according to Embodiment 1 of the present invention.
[0021]
Reference numeral 110 denotes a reading unit having the CCD 26 in FIG. 1, which reads an image of a document, performs luminance / density conversion, and outputs image information S1. 111 is a document density information creating means for creating a document density histogram from a part S2 of the image information S1 and creating document density information S3 used as a conversion coefficient for γ conversion. 112 is a filter process and a scaling process. Image processing means for performing image processing such as 113, γ conversion unit 113 as density control means for converting γ value which is the gradation characteristic of the image, 114 an image memory for storing a large number of pieces of image information, and 115 for a laser This is an image forming unit that forms an image on a photosensitive member by exposure and transfers it to form an image on a recording sheet.
[0022]
A delay memory 116 as a delay unit provided between the image processing unit 112 and the γ conversion unit 113 is configured by a FIFO memory which is a pre-read first-out memory. The delay memory 116 performs a delay process on a continuously input signal and continuously outputs a signal delayed by a predetermined time. Image information is output from the reading unit 110 to the γ conversion unit 113 through the image processing unit. The transmission time and the image information from the reading unit 110 are processed, and a delay process that is greater than the difference between the time when the original density information S2 is input to the γ conversion unit 113 is performed.
[0023]
The operation of the delay memory 116 will be described with reference to FIG. Image information S1 is input to the delay memory 116. Further, the document density information creating unit 111 receives the image information S2 of the leading edge of the document, and the document density information S3 is output from the document density information creating unit 111 based on the image information S2. The delay memory 116 outputs the image information S4 delayed so that the head is delayed from the document density information S3, and the γ conversion unit 113 performs γ conversion processing based on the document density information S3 on the image information S4. .
[0024]
The reference example to be described next solves the problem of double-reading in reading a multi-tone original.
In FIG. 5, a delay memory 117 serving as a delay unit including a RAM is provided between the image processing unit 112 and the γ conversion unit 113. The delay memory 117 is, for example, a memory that stores image information for one page of the screen, and is delayed by temporarily saving the image information. As the delay memory 117, a memory having a capacity capable of storing image data of a maximum size image to be formed is used. If a plurality of delay memories 117 are used, it is possible to store image information about half or a fraction of the screen. Embodiment 2 has the configuration shown in FIG.
[0025]
The operation of the delay memory 17 will be described with reference to FIG.
[0026]
The image information T1 from the reading unit 110 is input to the delay memory 117 and the document density information creating unit 111. The document density information creating unit 111 performs arithmetic processing at the stage when the image information T1 for one screen is taken in, and outputs document density information T2. The delay memory 117 performs delay processing by temporarily saving the input image information T1, and outputs the image information T3 to the γ conversion unit 113. The delay memory 117 outputs the image after the document density information T2 is output. Information T3 is output. As a result, the γ conversion unit 113 adjusts the density by performing γ conversion processing based on the document density information T2 on the image information T3.
[0027]
【The invention's effect】
According to the present invention, image information obtained by reading a document is branched into two, thereby processing a part of the image information to generate document density information, and using the document density information, the read image information is converted to an optimum density. In the density control process so as to obtain an image of the above, since it takes time to obtain the document density information, a density difference is generated in a part of the formed image. In the present invention, the delay is controlled by the delay means so that the processing time and timing are matched, and the automatic density control processing can be performed on all the image information of the document. A high-quality image in which the density of the entire screen was uniformly controlled without being generated was obtained.
[Brief description of the drawings]
FIG. 1 is a block diagram of an image information processing system in a conventional image forming apparatus.
FIG. 2 is a cross-sectional view of the image forming apparatus according to Embodiment 1 of the present invention.
FIG. 3 is a block diagram of an image information processing system of the image forming apparatus according to the first embodiment of the present invention.
FIG. 4 is a time chart of image information processing according to Embodiment 1 of the present invention.
FIG. 5 is a block diagram of an image information processing system of an image forming apparatus according to a second embodiment of the present invention.
FIG. 6 is a time chart of image information processing in Embodiment 2 of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Automatic document feeder 2 Document reading device 3 Image formation means 4 Recording paper storage means 5 Conveyance means 6 Paper discharge means 110 Reading means 111 Document density information creation means 112 Image processing means 113 Gamma conversion part 114 Image memory 115 Image formation means 116 , 117 Delay memory G

Claims (4)

Reading means for conveying originals one by one to a reading position, reading an image of the original passing through the reading position, and outputting image information;
A document density information creating unit that creates image density information by processing image information of only the leading edge of the image as part of the image information of the document obtained from the reading unit;
A delay unit that inputs image information from the reading unit and delays and outputs the image information so that the head is delayed from the document density information output by the document density information creating unit;
Based on the original density information the document density information creation means outputs the image information density control means and said density control means processes the output to control the density of the image formed on the recording paper of the delay means outputs And an image forming unit for forming an image on a recording sheet.   2. The image forming apparatus according to claim 1, wherein the delay unit is configured by a memory that continuously inputs image information and continuously outputs image information delayed by a predetermined time with respect to the input image information. apparatus. Reading means for conveying originals one by one to a reading position, reading an image of the original passing through the reading position, and outputting image information;
A document density information creating unit that creates document density information by processing image information of only the leading edge of the image as a part of the image information of the document obtained from the reading unit;
Delay means for inputting image information from the reading means, delaying the image information so that the head is delayed from the original density information output by the original density information creating means,
An original reading apparatus comprising density control means for processing the output of the delay means based on the original density information output by the original density information creating means and controlling the density of an image. 4. The document reading apparatus according to claim 3, wherein the delay unit is configured by a memory that continuously inputs image information and continuously outputs image information delayed by a predetermined time with respect to the input image information. apparatus.

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