JP2010093375A - Image reading apparatus and image forming apparatus with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reading apparatus capable of properly acquiring white reference data depending on an image reading speed and preventing scale-up of a white reference member and an apparatus body: and to provide an image forming apparatus with the image reading apparatus. <P>SOLUTION: The image reading apparatus 21 includes: a light source 1, a reflection plate 2, a first carriage 8, a second carriage 9, a contact glass 25 and a white reference plate 55. The image reading apparatus acquires the white reference data while varying the timing from the movement of the first and second carriages 8, 9 from a stopping position and start of acquiring the white reference data, depending on an image reading speed such as a color mode, a monochromatic mode or an original fixed system and a sheet-through system. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image reading apparatus used for a digital copying machine, an image scanner, and the like to scan and read a document and an image forming apparatus including the image reading apparatus, and more particularly to creation of white reference data.

  2. Description of the Related Art Conventionally, in an image reading apparatus mounted on a copying machine using an electrophotographic process, a document is conveyed so that a sheet-like document is sequentially sent to a document placing table and discharged from the document placing table after reading. Some are equipped with devices. In such an image reading apparatus, a sheet-through method in which a document is automatically conveyed and read by a document conveying device while the document press is closed, and the document press is opened and closed each time reading is performed on a document placement table (contact glass). Two types of reading methods are possible: a document fixing method in which one document is replaced one by one.

  Further, in such an image reading apparatus, an image is read by using a color sensor corresponding to red (R), green (G), and blue (B) and a monochrome (B / W) sensor of four colors. There is a case. Shading correction is performed using a white reference plate (white reference member) in order to read an appropriate image with each sensor. However, if the white reference data is not sufficiently created in such shading correction, the image quality is sufficient. It will be difficult to ensure.

Thus, a method for appropriately performing shading correction has been proposed. For example, Patent Document 1 discloses a method for performing shading correction in an optimum region by providing four black marks on a white reference plate. ing.
JP 2004-120599 A

  However, although the method of Patent Document 1 discloses a method for detecting the position of a white reference member for creating white reference data, the white reference data is obtained according to image reading modes having different image reading speeds. The method for making is not disclosed.

  In recent years, when performing image reading, different image reading modes are set according to user needs, for example, a color mode for reading a color image and a monochrome mode for reading a monochrome image, or a sheet-through method and a document fixing method, respectively. For example, image reading modes having different image reading speeds can be set. Then, by separately setting the image reading speed of the CCD sensor according to the image reading mode, desired image quality improvement, high productivity, and the like are realized in each image reading mode.

  In such a case, it is necessary to bring the carriage movement speed close to the image reading speed of the CCD sensor. However, as described above, the image reading speed of the CCD sensor differs depending on the image reading mode, and therefore, the time from the carriage stop position until the image reading speed is reached. The time and the moving distance of the carriage in such time vary depending on the image reading mode. That is, the position where the white reference data can be acquired in the white reference member differs in the sub-scanning direction depending on the image reading speed.

  Further, in order to suppress the influence on the image of the black spot when the black reference member has a black spot, the white reference member is widely read in the sub-scanning direction, and black data derived from the black spot with respect to the white reference data is mixed. The ratio needs to be relatively small. Further, in recent years, the number of CCD sensors in which the distances between R, G, B, and B / W sensors are increasing has increased, and the range necessary for reading the four color sensors on the white reference plate has become wider.

  For this reason, if white reference data is acquired with the same carriage operation and timing in each image reading mode, it is necessary to lengthen the white reference plate in the sub-scanning direction, which may increase the size of the white reference member. Further, as the white reference member increases in size, the apparatus main body may increase in size.

  As described above, in order to appropriately acquire the white reference data according to the image reading speed and suppress the influence of the black spot, it is necessary to lengthen the white reference plate in the sub-scanning direction, thereby avoiding the enlargement of the apparatus main body. However, it is difficult to appropriately acquire the white reference data according to the image reading mode. In particular, in a CCD sensor in which the intervals between the sensors are separated, it is more difficult to appropriately acquire such white reference data.

  In view of the above problems, the present invention includes an image reading apparatus capable of appropriately acquiring white reference data according to an image reading speed and preventing the white reference member and the apparatus main body from being enlarged, and the image reading apparatus. An object is to provide an image forming apparatus.

  To achieve the above object, the present invention has a light source that illuminates a document in the scanning direction and a mirror that guides reflected light from the document as image light, and can be moved in the sub-scanning direction, and the scanning unit And a photoelectric conversion member that converts the image light guided by the electric signal into an electrical signal, and in an image reading apparatus that reads a document at a predetermined document reading position, the image reading device is positioned at a position different from the document reading position in the sub-scanning direction. A white reference member for acquiring white reference data by a scanning unit is disposed, the photoelectric conversion member can be read at a plurality of different image reading speeds, and the scanning unit moves from a predetermined stop position to move the white color The timing until the acquisition of the reference data is started is variable according to the image reading speed of the photoelectric conversion member.

  According to the present invention, when the scanning unit moves from the stop position toward the white reference member as a data acquisition direction, the scanning unit moves a predetermined amount from the stop position in a direction opposite to the data acquisition direction. Then, the acquisition of the white reference data is started while moving in the data acquisition direction.

  Further, the invention is characterized in that the scanning unit starts acquiring the white reference data while directly moving in the data acquisition direction from the stop position at at least one of the plurality of image reading speeds. It is said.

  According to the present invention, when the image reading speed is the first image reading speed, the scanning unit directly moves in the data acquisition direction from the stop position, and starts acquiring the white reference data. When the second image reading speed is higher than the image reading speed, the scanning unit moves a predetermined amount in the opposite direction from the stop position, and then starts acquiring the white reference data while moving in the data acquisition direction. It is characterized by that.

  According to the present invention, when reading a document that is a fixed document and has a monochrome image, the scanning unit starts acquiring the white reference data while moving directly from the stop position in the data acquisition direction. It is a feature.

  Further, the invention is characterized in that an acceleration from the stop position of the scanning unit to the start of acquisition of the white reference data is varied according to the image reading speed.

  In the invention, it is preferable that a moving speed of the scanning unit when reading the white reference member is 70% or more of a predetermined reference moving speed corresponding to the image reading speed.

  Further, the present invention is characterized in that after the white reference data is acquired, the document is continuously read.

  The present invention also provides an image forming apparatus including the image reading apparatus having the above-described configuration.

  According to the first configuration of the present invention, the white reference member for obtaining the white reference data by the scanning unit is arranged at a position different from the document reading position in the sub-scanning direction, and the photoelectric conversion member is arranged in a plurality of different ways. The white reference data can be read at an image reading speed, and the timing from when the scanning unit moves from a predetermined stop position until the acquisition of white reference data starts is varied according to the image reading speed of the photoelectric conversion member. The moving speed of the scanning means at the time of acquisition can be made appropriate, white reference data can be appropriately acquired according to the image reading speed, and the white reference member and the apparatus main body can be prevented from being enlarged.

  According to the second configuration of the present invention, in the image reading apparatus having the first configuration, the scanning unit moves in the data acquisition direction after moving a predetermined amount in the direction opposite to the data acquisition direction from the stop position. On the other hand, by starting the acquisition of the white reference data, it is possible to increase the moving distance necessary for accelerating the scanning unit, and to sufficiently increase the moving speed of the scanning unit until the start of the acquisition of the white reference data. Thereby, the timing until the white reference data is acquired can be varied more effectively according to the image reading speed. In addition, since the reading area of the white reference member can be narrowed, it is possible to further prevent the white reference member and the apparatus main body from being enlarged.

  According to the third configuration of the present invention, in the image reading apparatus having the second configuration, the scanning unit directly moves from the stop position in the data acquisition direction at least one of the plurality of image reading speeds. By starting the acquisition of the white reference data while moving, the white reference data can be acquired in a shorter time, and more appropriate white reference data can be acquired according to the image reading speed.

  According to the fourth configuration of the present invention, in the image reading apparatus having the third configuration, when the image reading speed is the first image reading speed, the scanning unit moves directly from the stop position in the data acquisition direction. The acquisition of white reference data is started, and when the second image reading speed is higher than the first image reading speed, the white reference data is moved while moving in the data acquisition direction after the scanning unit has moved a predetermined amount in the opposite direction. It was decided to start acquiring.

  Thus, when the image reading speed is low, white reference data is acquired in a short time without moving the scanning means in the opposite direction, and when the image reading speed is high, the scanning means is moved in the opposite direction from the stop position. It is possible to increase the moving speed sufficiently by moving the white reference member and to prevent the white reference member and the apparatus main body from being enlarged. Accordingly, it is possible to obtain more appropriate white reference data according to the image reading speed.

  According to the fifth configuration of the present invention, in the image reading apparatus having the third or fourth configuration, when reading a document that is a fixed document and has a monochrome image, the scanning unit is moved from the stop position. By starting acquisition of white reference data while moving directly in the data acquisition direction, white reference data can be acquired in a short time when reading a fixed monochrome image. Since the time can be shortened, the image reading efficiency is improved.

  According to the sixth configuration of the present invention, in the image reading apparatus of the first configuration, the acceleration from the stop position of the scanning unit to the start of acquisition of the white reference data can be varied according to the image reading speed. Thus, since the speed of the scanning unit can be made appropriate before the start of acquisition of the white reference data, the timing until the white reference data is acquired can be varied more effectively. In addition, since the reading area of the white reference member can be narrowed, it is possible to further prevent the white reference member and the apparatus main body from being enlarged.

  According to the seventh configuration of the present invention, in the image reading apparatus having the first to sixth configurations, the moving speed of the scanning unit when reading the white reference member is a predetermined reference corresponding to the image reading speed. By setting the moving speed to 70% or more of the moving speed, it is possible to obtain white reference data that avoids the influence of black data derived from black spots even when black spots or the like exist on the surface of the white reference member. Can be prevented.

  Further, according to the eighth configuration of the present invention, in the image reading apparatus having the first to seventh configurations, after the white reference data is acquired, the document is continuously read to start reading from the image reading start. Since the time until the image is output can be shortened, efficient image reading can be performed.

  According to the ninth configuration of the present invention, white reference data is appropriately obtained according to the image reading speed by using the image forming apparatus including the image reading apparatus having the first to eighth configurations. Appropriate image formation can be performed, and an increase in size of the apparatus can be prevented.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a front sectional view showing the internal configuration of an image forming apparatus equipped with the image reading apparatus according to the first embodiment of the present invention, and FIG. 2 shows the internal configuration of the image reading apparatus of the present embodiment. FIG. 3 is a front sectional view, and FIG. 3 is a top view.

  As shown in FIG. 1, the image forming apparatus 100 is a so-called in-cylinder discharge type digital copying machine, and mainly includes a main body housing 20 and an image reading device 21 disposed on the main body housing 20. Yes. Various mechanisms, which will be described later, are provided in the image reading device 21 for reading an image of a document as an electrical signal. On the other hand, the main body housing 20 is based on an electrical signal of a document image read by the image reading device 21. Various mechanisms to be described later are provided for transferring the image onto the paper.

  The main body housing 20 includes a lower housing 20a and a connection housing 20b that is positioned along the left side and is connected to the image reading device 21. The lower housing 20a accommodates and feeds paper. A paper feeding unit for forming a toner image on the paper, a fixing unit for fixing the toner image on the paper, and the like. A paper discharge unit for conveying and discharging is provided. Further, an in-cylinder discharge space 22 is formed on the right side of the connecting housing 20b immediately below the image reading device 21 so as to be largely open toward the right side and the front surface. A paper discharge tray 23 for receiving and stacking paper discharged horizontally from the right side surface of the connecting housing 20b is provided.

  On the upper surface of the image reading device 21, a contact glass 25 and an operation panel (not shown) exposed on the front side are disposed. Further, above the image reading device 21, a document pressing unit 28 equipped with a document conveying device 27 that conveys a sheet-like document to the first image reading unit R <b> 1 in the contact glass 25 is a hinge unit on the back of the image reading device 21. It is supported so that it can be opened and closed freely.

  The document presser 28 can take a closed state in which the document reading operation is performed by closing the contact glass 25 and an open state in which the document presser 28 is opened. In the document fixing method that does not use the document conveying unit 27, each time the document is read, the document pressing unit 28 is opened and closed, and the document is read one by one in the second image reading unit R2 of the contact glass 25.

  The document transport device 27 includes a document feed tray 29 having a document guide 29a for aligning and stacking a plurality of documents, and a document feed tray 29 positioned above the first image reading unit R1 in the contact glass 25. A document cover 30 that protrudes, and a document discharge tray 31 that is formed directly on a part of the upper surface of the document presser 28 at the side of the document cover 30. A document transport path d that reaches the document discharge tray 31 is formed.

  In the document cover 30, document conveyance means including a pickup roller 32, a conveyance roller pair 33, a registration roller pair 34, and a discharge roller pair 35 is provided in order from the upstream side along the document conveyance path d. Among these, the conveyance roller pair 33 is composed of a drive roller 33a and a separation roller 33b. The separation roller 33b rotates in the opposite direction to the drive roller 33a only when the rotational load is lower than a predetermined torque, and the rotational load is reduced. When the torque exceeds a predetermined torque, the drive roller 33a is driven to rotate.

  A document pressing unit 36 is disposed between the registration roller pair 34 and the discharge roller pair 35 so as to face the first image reading unit R1 in the contact glass 25 and presses the document toward the first image reading unit R1. And a white reference plate (white reference member) 55 disposed between the first and second image reading units R1 and R2. The white reference plate 55 is disposed between the first and second image reading units R1 and R2 in a state where the white reference plate 55 is fitted into the holding member 57. The document conveyance path d is curved so as to be reversed between the conveyance roller pair 33 and the first image reading unit R1.

  The document transport path d is provided with a plurality of sensors for detecting whether or not a document exists. For example, a document detection sensor S 1 is provided at the center of the document feed tray 29, a paper feed sensor S 2 is provided downstream of the transport roller pair 33, and a discharge sensor S 3 is provided downstream of the discharge roller pair 35. ing. The documents set on the document feed tray 29 are sequentially conveyed one by one by the document conveying means through the document conveying path d, and sequentially discharged onto the document discharge tray 31 after passing through the first image reading unit R1. . The document discharged on the document discharge tray 31 is taken out by the user's hand.

  Next, a sheet-through type document conveyance operation using the document conveyance unit 27 will be described. In the sheet-through type document conveying operation, first, a plurality of documents set with the image surface facing upward on the document feeding tray 29 is subjected to a predetermined pressure by a lifting plate 37 biased upward by a spring member 37a. Is pressed against the pickup roller 32. Here, when the copy start button on the operation panel is turned on, the pickup roller 32 and the conveyance roller pair 33 are rotationally driven by a primary paper feed driving means (not shown).

  The document set on the document feed tray 29 is normally fed by the pickup roller 32 to the upper pair of transport rollers 33. The plurality of originals sent to the conveyance roller pair 33 are separated by the separation roller 33b and are conveyed toward the registration roller pair 34 after being separated by the separation roller 33b. At that time, after the leading edge of the document is detected by the sheet feeding sensor S2, the document is conveyed by a predetermined distance, and then the driving roller 33a and the pickup roller 32 of the conveying roller pair 33 are stopped by the operation of the primary sheet feeding driving means. Is stopped and the primary paper feeding is completed. The document that has been primarily fed is stopped with its leading end pressed against the nip portion of the registration roller pair 34 and with its leading end being bent.

  Secondary feeding is started after a predetermined time has elapsed since the completion of primary feeding. That is, the registration roller pair 34 is rotationally driven by the operation of the secondary paper feed driving means (not shown). The original is conveyed by the registration roller pair 34 to the discharge roller pair 35 via the first image reading unit R1, and is finally discharged onto the original discharge tray 31 by the discharge roller pair 35. At this time, the completion of image reading of one original is detected by detecting the passage of the rear end of the original by the discharge sensor S3.

  Here, the discharge sensor S3 has a counting function that counts the number of documents every time the document feed and conveyance is completed. If the document detection sensor S1 detects a subsequent document, the second and subsequent document conveyance is performed. Will continue as above. When the document passes through the first image reading unit R1, it is conveyed while being lightly pressed against the contact glass 25 by the document pressing unit 36, and the image of the document is read through the first image reading unit R1. It has become.

  Next, the configuration of the image reading device 21 for reading an image of a document as an electrical signal will be described with reference to FIGS. In the frame 21a of the image reading device 21, a lamp 1 which is a light source for irradiating light in the scanning direction (X direction in FIG. 3) toward the image surface of the document, and the light from the lamp 1 is efficiently emitted from the document. Reflecting plate 2 for giving to the image surface, first mirror 3 for directly receiving and reflecting the reflected light of the original, second mirror 4 for receiving and reflecting the reflected light from the first mirror 3, and the second A lens barrel 6 holding a third mirror 5 that receives and reflects the reflected light from the mirror 4, a lens group (not shown) that introduces and collects the reflected light from the third mirror 5, and the lens barrel A CCD sensor (photoelectric conversion member) 7 that receives an original reflected light condensed by the lens group 6 and converts it into an electric signal is disposed on the base plate 10. The optical path of the original reflected light is indicated by a one-dot chain line.

  Here, the lamp 1, the reflecting plate 2 and the first mirror 3 are integrally fixed on the first carriage 8 (scanning means), and the second mirror 4 and the third mirror 5 are the second carriage (scanning means). The first carriage 8 and the second carriage 9 are independent of each other, but can reciprocate in cooperation with each other.

  That is, when the original image reading operation is performed by the above-described sheet through method, the first carriage 8 moves from the stop position shown in FIGS. 2 and 3 to the first image along the sub-scanning direction (Y direction in FIG. 3). The first carriage 8 and the second carriage 9 reciprocate (scan) the first image reading unit R1 while maintaining the optical path length of the document reflected light constant. On the other hand, in the original fixing method, the first carriage 8 and the second carriage 9 reciprocate through the second image reading unit R2 while maintaining the optical path length of the original reflected light constant. Further, the first carriage 8 and the second carriage 9 are driven by a carriage drive motor 53 (see FIG. 4) not shown here.

  Under such a configuration, the document reflected light irradiated from the lamp 1 and reflected by the image surface of the document is reflected by the first mirror 3 to the third mirror 5 and introduced into the lens group in the lens barrel 6. The light is condensed by the lens group and formed on the CCD sensor 7. The CCD sensor 7 performs photoelectric conversion processing, and the original image is read as an electric signal.

  Next, the configuration of various mechanisms provided in the main body housing 20 for transferring the image to the sheet based on the electric signal of the read document image will be described below with reference to FIG. First, the sheet feeding unit will be described. Under the lower housing 20a, sheets of various sizes (mainly sheets) are stored, and a sheet feeding cassette 40 that can be taken in and out from the front is disposed. The sheets P stored in the sheet feeding cassette 40 are: The sheets are fed one by one by the feeding roller 40a. Further, an openable and closable manual feed tray 41 that is pulled down as necessary is provided on the left side surface of the lower portion of the lower housing 20a, and a sheet (paper or OHP sheet) P ′ set on the manual feed tray 41 is provided. Are fed one by one by the feeding roller 41a.

  Next, an image forming unit for forming a toner image on a sheet and a fixing unit for fixing the toner image on the sheet will be described. Above the paper feed cassette 40 in the lower housing 20a, a photosensitive drum 42 constituting a main image forming unit, a charging device 43, a laser exposure unit 44, a developing device 45, A transfer roller 46 and a cleaning device 47 are provided. A fixing device 48 is disposed in the lower housing 20a above the transfer roller 46 and directly below the connecting housing 20b.

  The photosensitive drum 42 is made of positively chargeable amorphous silicon, and rotates clockwise in FIG. 1 at a predetermined peripheral speed when driven. The surface of the photosensitive drum 42 is uniformly charged by corona discharge generated from the charging device 43 to which a high voltage is applied, and then the beam from the laser exposure unit 44 based on the electrical signal of the original image from the CCD sensor 7. By the light irradiation, an electrostatic latent image composed of a predetermined light potential and dark potential portion is formed.

  Further, the electrostatic latent image rotates to the developing position by the rotation of the photosensitive drum 42. The developing roller 45a, which is a constituent element of the developing device 45, is made of stainless steel and has a fixed magnet inside. The developing roller 45a is rotatably supported with a predetermined gap from the photosensitive drum 42, and in the same direction as the photosensitive drum 42 when driven. At a predetermined peripheral speed. The developing device 45 is filled with, for example, a positively charged magnetic toner having a volume average particle diameter of 9 μm (median diameter measured by a Coulter counter), and a toner thin film is formed on the surface of the developing roller 45a by a magnetic blade (not shown). A layer is formed. A predetermined developing bias voltage is applied to the developing roller 45a. The toner that has reached the developing region flies from the surface of the developing roller 45a by the developing bias voltage, and is attracted to the electrostatic latent image on the surface of the photosensitive drum 42 to form (develop) the toner image.

  Here, the sheet P (or P ′) that is fed one by one from the paper feed cassette 40 (or the manual feed tray 41) and reaches the registration roller pair 49 has a toner image on the photosensitive drum 42 approaching the transfer roller 46. In synchronization with this, the registration roller pair 49 feeds the sheet upward while adjusting the conveyance timing, and is conveyed between the photosensitive drum 42 and the transfer roller 46 through the conveyance path T1. Then, most of the toner in the toner image is transferred onto the sheet P when the leading edge of the sheet P and the leading edge of the toner image pass through the transfer roller 46.

  The toner remaining on the surface of the photosensitive drum 42 without being transferred onto the sheet P is removed from the photosensitive drum 42 by the cleaning device 47. On the other hand, the sheet P on which the toner image is transferred is sent to the fixing device 48. The fixing device 48 has a pair of fixing rollers including a heating roller 48a and a pressure roller 48b, and the toner image on the sheet P passing through the nip is heated and pressed by the pair of fixing rollers to be fixed. As a result, a fixed transfer image is formed on the sheet P.

  The sheet P that has passed through the fixing device 48 is conveyed into the connecting housing 20b along the vertical conveyance path T2 that is directed vertically upward. In the connection housing 20b, a conveyance roller pair 50 connected to the vertical conveyance path T2 and a discharge roller pair 51 for discharging the sheet P to the paper discharge tray 23 are disposed. The sheet P sent out from the conveyance roller pair 50 reaches the discharge roller pair 51 through the conveyance path T3 and is discharged from the discharge roller pair 51 to the paper discharge tray 23.

  FIG. 4 is a block diagram illustrating an example of a control path of the image reading apparatus. In addition, since various controls of each part of the image forming apparatus 100 are performed when the image reading apparatus 21 is used, the entire control path is complicated. Therefore, here, only a portion of the control path that is necessary for implementing the present invention will be described.

  The control unit 60 is, for example, a CPU (Central Processing Unit), and controls the driving of the first carriage 8 and the second carriage 9 by transmitting a control signal to the carriage drive motor 53 in accordance with a set program. At the same time, the light emission timing of the lamp 1 in the first carriage 8 is controlled. Further, as will be described later, an electrical signal transmitted from the CCD sensor 7 is subjected to resolution processing, scaling processing or gradation processing as necessary to create image data. Further, the control unit 60 sets the reference moving speed, the required moving time, and the moving operation of the first carriage 8 according to the set image reading mode, and the reading result of the white reference plate 55 from the CCD sensor 7. Receive and create white reference data.

  The storage unit 61 includes an image memory 70, a ROM (Read Only Memory) 71, and a RAM (Random Access Memory) 72. The image memory 70 converts the image data created in the control unit 60 into a digital signal and stores it. To do. The ROM 71 and RAM 72 store basic programs and processing contents used in the control unit 60, and also relate to the image reading speed of the CCD sensor 7, the acceleration and reference movement speed and movement of the first carriage 8, the number of times white reference data is acquired, and the like. Parameters etc. are stored.

  In the image reading apparatus 21 of the present invention, high-speed reading (image reading speed) by the CCD sensor 7 is possible in the monochrome mode, and low-speed reading is possible in the color mode, and high-speed reading is possible when reading a character document. Therefore, when reading a photographic document or the like, reading at a low speed is possible. In the sheet-through method, reading is performed at a high speed, and in the document fixing method, reading is performed at a low speed. In the first embodiment, an image reading operation in the monochrome mode and the color mode in the document fixing method will be described.

  Here, as a method for creating the white reference data, the first carriage 8 reads the white reference plate 55 a plurality of times while moving in the sub-scanning direction (original transport direction), and the average value is used as the white reference data. Is generally used. By taking the average value in this way, the density unevenness of the white reference plate 55, the sensitivity unevenness of each pixel of the CCD sensor 7, the variation in data due to electrical noise, etc. are reduced, and the occurrence of variations in the white reference data is prevented. Thus, unevenness in the read image such as stripes and bands can be eliminated.

  If the number of times of obtaining the white reference data for calculating the average value increases, it becomes easier to eliminate the image unevenness, but it is necessary to make the white reference data 55 longer in the sub-scanning direction. Accordingly, considering the size of the white reference plate 55, for example, it is appropriate that the number of acquisition times of the white reference data is about 64 times or 128 times.

  The moving speed of the first carriage 8 in the sub-scanning direction is also important for obtaining appropriate white reference data. For example, when a black spot having a specific size exists on the surface of the white reference plate 55, if the moving speed of the first carriage 8 is slower than the image reading speed of the CCD sensor 7, the CCD sensor 7 acquires data from the black spot. Since the number of times increases, there is a possibility that even if the acquired white reference data is averaged, the influence of black spots remains and a streak image is generated.

  For example, when a black spot having a diameter of 0.1 mm exists on the white reference plate 55, the image reading speed of the CCD sensor 7 is 600 dpi, and the moving speed of the first carriage 8 is a speed corresponding to the image reading speed (600 dpi) (reference). If the movement speed has been reached, black data derived from black dots is mixed in a section of 3 pixels (1 pixel = 0.042 mm) in the sub-scanning direction. However, immediately after the first carriage 8 starts moving from the stop position, the moving speed is much slower than the image reading speed of the CCD sensor 7 in the early stage of acceleration of the first carriage 8.

  For example, if a black spot having a diameter of 0.1 mm exists at a point where the moving speed of the first carriage 8 reaches only ¼ of the image reading speed of the CCD sensor 7, the CCD sensor 7 moves in the scanning direction (perpendicular to the document conveying direction). The first carriage 8 can move only a distance corresponding to 1/4 pixel in the sub-scanning direction while reading one line in the direction). Thereby, when reading a black spot having a diameter of 0.1 mm, black data is mixed in a section of 10 pixels, and the influence of the black spot is increased.

  The image reading apparatus 21 of the present invention can select a plurality of image reading modes (image reading speeds) as described above in accordance with diversification of user needs. That is, image reading modes having different image reading speeds are provided between color images and monochrome images, or between image quality priority and productivity priority. Therefore, it is necessary to appropriately acquire the white reference data according to the image reading speed in each image reading mode. Therefore, as shown below, by starting acquisition of white reference data at different timings for each image reading mode, it is possible to avoid the enlargement of the white reference plate 55 and the apparatus main body and obtain a good read image. did.

  FIG. 5 is a diagram showing the relationship between each line sensor of the CCD sensor and the reading position on the white reference plate. The CCD sensor 7 includes three color line sensors 7a, 7b and 7c for red (R), green (G) and blue (B), and a monochrome (B / W) line sensor 7d. As shown in FIG. 5, the four line sensors 7a to 7d are arranged at predetermined intervals so as to be positioned downward from the top in the order of R, G, B, B / W line sensors 7a to 7d. Yes.

  The four line sensors 7a to 7d are arranged such that the reading positions on the white reference plate 55 are spaced apart from each other by about 0.5 mm in the sub-scanning direction (left-right direction in FIG. 5). ing. That is, the reading position on the white reference plate 55 is approximately 1.5 mm apart in the sub-scanning direction between the R line sensor 7a and the B / W line sensor 7d that are located farthest apart.

Here, in the first carriage 8, the acceleration from the stop position to the start of acquiring the white reference data on the white reference plate 55 is set to 2000 mm / sec ² in both the color mode and the monochrome mode. At this time, since the reference movement speed is different between the color mode and the monochrome mode as described above, the time until the first carriage 8 reaches the reference movement speed from the stop position, that is, after the first carriage 8 starts moving, the white reference The travel time (timing) required to start acquiring data differs. Thereby, the acquisition position of the white reference data on the white reference plate 55 is different between the color mode and the monochrome mode.

  Also, due to the line gap of the CCD sensor 7, the reading position of the white reference plate 55 is in the sub-scanning direction in the monochrome mode using the B / W line sensor 7d and the color mode using the R, G, B line sensors 7a to 7c. Since they are different, it is necessary to acquire white reference data in consideration of such a line gap. In particular, in the color mode, it is necessary to appropriately acquire white reference data in all of the R, G, and B line sensors 7a to 7c regardless of the line gap of about 1 mm between the R and B line sensors 7a to 7c. .

  Therefore, considering the number of times white reference data is acquired, the time difference until the start of acquisition of white reference data, the influence of the line gap, and the like, the time required to move the first carriage 8 can be varied according to the image reading mode. It was. Thereby, even if a black spot having a diameter of about 1 mm exists, a good read image in which occurrence of image density unevenness is prevented can be obtained.

  FIG. 6 is a diagram showing a white reference data acquisition range when the carriage movement time is changed between the monochrome mode and the color mode, and FIG. 7A is a diagram showing the color mode in FIG. FIG. 7B shows the monochrome mode. In FIGS. 6 and 7, for convenience, the first carriage 8 and the second carriage 9 interlocked therewith are shown together as a carriage.

In the present embodiment, in the color mode, the reference movement speed of the first carriage 8 is 47.5 mm / sec, the required movement time is 20 msec, and the white reference data acquisition count is 128 times. On the other hand, in the monochrome mode, the reference moving speed of the first carriage 8 is 95 mm / sec, the required moving time is 35 msec, and the white reference data acquisition count is 128 times. As described above, the acceleration of the first carriage 8 is 2000 mm / sec ² in both modes, and the acceleration is continued at the acceleration until the first carriage 8 reaches the reference movement speed in both modes.

  As shown in FIGS. 6 and 7A, in the color mode, the moving time is set to 20 msec, so that the first carriage 8 moves from the stop position (the dashed-dotted arrows in the drawing) toward the white reference plate 55. Acceleration is started in the acquisition direction (outlined arrows) (dotted arrows in the figure), and after 20 msec, the moving speed of the first carriage 8 reaches about 40 mm / sec, and then in each R, G, B line sensor White reference data can be acquired (each solid arrow in the figure).

  Thereby, the moving speed at the start of white reference data acquisition of the first carriage 8 can be about 84% of the reference moving speed (47.5 mm / sec), which can be close to the image reading speed of the CCD sensor 7. it can. Therefore, even when there is a black spot, as described above, the mixture into the white reference data is reduced, the influence of the black spot on the read image can be suppressed, and the occurrence of unevenness in the read image can be suppressed. Can do.

  On the other hand, as shown in FIG. 6 and FIG. 7B, in the monochrome mode, if the required moving time is 20 msec as in the color mode, the moving speed of the first carriage 8 is about 40 mm / sec, as described above. White reference data must be obtained from when it arrives. In such a case, since the acquisition of the white reference data is started at a moving speed that is about ½ or less of the reference moving speed (95 mm / sec), black data that is about twice as large as the actual black spot size is obtained. It will be mixed into the white reference data.

  However, by setting the required moving time to 35 msec, the white reference data can be acquired after the moving speed of the first carriage 8 reaches about 70 mm / sec (about 74% of the reference moving speed). The influence on the white reference data can be reduced. Therefore, even when there is a black spot, the mixture of white reference data is reduced, the influence of the black spot on the read image can be suppressed, and the occurrence of unevenness in the read image can be suppressed.

  As described above, the moving time is set to 20 msec in the color mode, and the moving time is set to 35 msec in the monochrome mode. The moving speed of the first carriage 8 is sufficiently large and the white reference data is acquired during acceleration. White reference data can be acquired in a narrow range, and an increase in the size of the white reference plate 55 can be avoided.

  However, in both modes, the acquisition of white reference data is started after the first carriage 8 reaches the reference movement speed, and white reference data is acquired while moving at a constant speed (ie, acceleration is 0) at the reference movement speed. Of course, it is possible to set so as to. That is, the travel time in the color mode can be 23.75 msec, and the travel time in the monochrome mode can be 45 msec. In addition, the white reference data can be acquired during deceleration after the first carriage 8 reaches a constant speed.

  In such a case, the distance that the first carriage 8 moves before the start of white reference data acquisition becomes longer, and the reading width of the white reference plate 55 may increase in the sub-scanning direction. Accordingly, the time required for the movement takes these into consideration, and the line gap, the white reference data acquisition count, the image reading speed of the CCD sensor 7, the acceleration of the first carriage 8, and the length of the white reference plate 55 in the sub-scanning direction. It can be set as appropriate in consideration of the width (width), the degree of black data mixing, and the like.

  The moving speed of the first carriage 8 when acquiring the white reference data is preferably 70% or more of the reference moving speed. By setting it to 70% or more, the moving speed of the first carriage 8 can be brought close to the image reading speed of the sensor 7 by the CCD, and the black data can be prevented from being mixed due to black dots. From this point of view, for example, when the above-described first carriage 8 acquires white reference data during acceleration, deceleration, or constant speed, the speed of the first carriage 8 maintains 70% or more of the image reading speed. It is preferable that the acquisition of the white reference data starts and ends during that time.

  Next, an image reading operation of the image reading device 21 in the present embodiment will be described. When the monochrome mode or the color mode is set by an operation panel (not shown), the control unit 60 reads parameters from the ROM 71 and the RAM 72 according to the selected mode, and reads the image reading speed of the CCD sensor 7 and the first carriage 8. Set the reference movement speed, the time required for movement, and the number of times white reference data is acquired.

  Based on this setting, the white reference plate 55 is scanned while the first carriage 8 is moved, and the reflected light from the white reference plate 55 passes through the first to third mirrors 5 and the lens group in the lens barrel 6. The image is formed on the CCD sensor 7. And it outputs to the control part 60 as an electrical signal of a predetermined level by a photoelectric conversion process. The control unit 60 that has received such an electrical signal creates white reference data.

  As described above, by changing the time required for moving the first carriage 8 according to the image reading mode, the moving speed of the first carriage 8 when acquiring the white reference data can be made appropriate. Therefore, it is possible to suppress the influence of mixing black data and to create appropriate white reference data, thereby suppressing image density unevenness. Further, it is possible to prevent the white reference plate 55 and the apparatus main body from being enlarged.

  In this embodiment, since the acceleration is constant in each image reading mode and the moving time is longer in the image reading mode in which the image reading speed is higher, the influence of the black data in each mode on the white reference data is affected. In addition, the white reference plate 55 and the apparatus main body can be prevented from being enlarged. Moreover, it can be set as a simpler structure.

However, in addition, for example, the acceleration of the first carriage 8 can be varied according to the image reading mode. For example, the acceleration may be 2000 mm / sec ² in the color mode, the acceleration may be 4000 mm / sec in the monochrome mode, and the required time for movement may be 20 msec in both modes.

  Further, for example, in the monochrome mode, the acceleration of the first carriage 8 can be made twice or more larger than that in the color mode, and the time required for movement can be made shorter than that in the color mode. The acceleration of the first carriage 8 can be changed as appropriate by changing the current value of a motor (not shown) that drives the first carriage 8.

  In this way, by changing the acceleration of the first carriage 8 according to the image reading mode, the speed of the scanning unit can be made appropriate until the start of the acquisition of the white reference data, and thus the white reference data is acquired. This timing can be varied more effectively. In addition, since the reading area of the white reference member can be narrowed, it is possible to further prevent the white reference member and the apparatus main body from being enlarged.

  As described above, in the present embodiment, the required movement time is varied between the color mode and the monochrome mode. However, the movement operation of the first carriage 8 and the second carriage 9 linked thereto is particularly limited to the present embodiment. In addition, it can set suitably according to an apparatus structure etc. in addition.

  FIG. 8 is a diagram illustrating a carriage movement operation of the image reading apparatus according to the second embodiment of the present invention. In FIG. 8, for the sake of convenience, the first carriage 8 and the second carriage 9 interlocked therewith are shown together as a carriage. In the present embodiment, the movement operation of the first carriage 8 in the color mode is different from that in the monochrome mode, so that the first carriage 8 moves from the stop position in the monochrome mode and the color mode, and the white reference data. The timing until the start of acquisition is changed.

  In the color mode, R, G, and B line sensors 7a to 7c are used. For this reason, as shown in FIG. 6 described above, it is necessary to use a region other than the white reference data acquisition range by the B / W line sensor 7d in the white reference plate 55, and accordingly, the white reference plate 55 is used in the sub-scanning direction. Need to be long.

  Therefore, as shown in FIG. 8, in the color mode, the first carriage 8 is temporarily moved by a predetermined amount in the direction opposite to the data acquisition direction (outline arrow) (back operation in the figure), and then the white reference data is displayed. It was decided to move toward the acquisition direction (dotted line arrow in the figure). The predetermined amount can be appropriately set according to the apparatus configuration, image reading speed, and the like. Since other configurations are the same as those of the first embodiment, description thereof is omitted.

  According to this embodiment, it is possible to increase the moving distance necessary for the acceleration of the first carriage 8 in the monochrome mode, and it is possible to sufficiently increase the moving speed of the first carriage 8 before the start of the acquisition of the white reference data. Therefore, white reference data can be acquired by the R, G, B line sensors 7a to 7c within the white reference data acquisition range by the B / W line sensor 7d in the monochrome mode (solid arrow in the figure). In addition, since the length of the white reference plate 55 in the sub-scanning direction can be reduced, it is possible to prevent the white reference plate 55 from becoming large and the apparatus main body from being enlarged.

  In the first and second embodiments, the color mode and the monochrome mode are exemplified as modes having different image reading speeds. However, the image reading modes are not particularly limited as long as the image reading speeds are different. In addition, it can be set as appropriate according to the device configuration, user needs, and the like.

  FIG. 9 is a diagram illustrating the carriage movement operation of the image reading apparatus according to the third embodiment of the present invention. In FIG. 9, for the sake of convenience, the first carriage 8 and the second carriage 9 interlocking therewith are shown together as a carriage.

  In the present embodiment, the document fixing reading mode (first image reading speed) using the document fixing method and the document conveyance reading mode (second image reading speed) using the sheet-through method are used as modes in which the image reading speed is different. And to be applied to. In the document conveyance reading mode, since productivity is generally given priority, the image reading speed is set higher than in the document fixing mode.

For example, the acceleration of the first carriage 8 is set to 2000 mm / sec ² as in the first and second embodiments, and the first carriage 8 is moved from the stop position in the data acquisition direction (white arrow) in the document fixed reading mode. The moving time is set to 35 msec as in the monochrome mode in the first and second embodiments.

  At this time, if the document conveyance speed (reference movement speed) in the document conveyance reading mode is 140 mm / sec, the movement speed of the first carriage 8 is about 70 mm / sec even if 35 msec has elapsed from the start of acceleration of the first carriage 8. Only reached to. Accordingly, the moving speed of the first carriage 8 reaches only about ½ of the reference moving speed, and the black data is often mixed into the white reference data.

  At this time, for example, if the required moving time in the document conveyance reading mode is 60 msec, the moving speed of the first carriage 8 reaches about 120 mm / sec, and the influence on the white reference data due to the mixing of the black data is reduced. Can do. However, in such a case, the moving distance of the first carriage 8 increases until the required moving time elapses, and the white reference data acquisition range is white as shown in (1) in document conveyance reading in FIG. There is a risk of exceeding the reference plate 55. For this reason, it is necessary to enlarge the white reference plate 55, and there is a possibility that the apparatus main body will be enlarged accordingly.

  Therefore, in the document conveyance reading mode, as in the second embodiment described above, the first carriage 8 is once moved by a predetermined amount in the direction opposite to the data acquisition direction, and then the first carriage 8 is used to acquire the white reference data. The carriage 8 is moved in the data acquisition direction. As a result, as shown in the document conveyance reading (2) in FIG. 9, the white reference data can be reliably acquired within the predetermined range of the white reference plate 55. Since other configurations are the same as those of the first and second embodiments, description thereof is omitted.

  As described above, since the white reference data can be acquired from substantially the same region of the white reference plate 55 in the document fixed reading mode and the document conveyance reading mode, appropriate white reference data can be generated more stably. it can. Further, since the white reference data can be acquired in a shorter time by directly moving the first carriage 8 from the stop position in the data acquisition direction in at least one image reading mode, it is more appropriate according to the image reading speed. White reference data can be acquired.

  In particular, here, when reading a document having a monochrome image in the document fixed reading mode, the first carriage 8 is moved directly from the stop position in the data acquisition direction. Therefore, when reading a fixed monochrome image, the white reference data is read. Can be acquired in a short time, the time from white reference data acquisition to document reading can be shortened, and the image reading efficiency can be improved.

  In addition to such a configuration, for example, in an image reading mode in which the user is frequently used, white reference data can be acquired simply by moving the first carriage 8 directly from the stop position in the white reference data acquisition direction. In the image reading mode with a low use frequency, the white carriage reference data can be acquired in a shorter time in the mode with a high use frequency by temporarily moving the first carriage 8 in the opposite direction.

  In the first to third embodiments, as described above, the first carriage 8 is directly moved in the data acquisition direction from the stop position in at least one image reading mode. However, the first carriage 8 is moved in all image reading modes. It is also possible to set to move in the direction opposite to the white reference data acquisition direction and then move in the white reference data acquisition direction.

  In the first to third embodiments, when the user inputs an image reading start through an operation panel (not shown), the white reference data is acquired by the moving operation of the first carriage 8, and the white reference data is continuously acquired after the white reference data is acquired. The document can be set to be read. As a result, it is possible to reduce the first copy time required for the user to place a document on the contact glass 25 and to output a copy image, a scanned image, etc. from the input of the image reading start. It can be performed.

  In particular, in the third embodiment, when reading a monochrome image in the document fixed reading mode, the white reference data is acquired while the first carriage 8 moves from the stop position in the white reference data acquisition direction, and after such acquisition, Since the original can be scanned while the first carriage 8 moves in the opposite direction, the first time can be further shortened.

  In addition, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the meaning of this invention. For example, in the above embodiment, the dedicated control unit 60 for reading the electrical signal output from the CCD sensor 7 as image data is provided, but it can also be used as the control unit of the image forming apparatus main body. In the above embodiment, the white reference plate is used as the white reference member. However, the white reference plate is not particularly limited as long as the white reference data can be acquired. For example, white reference paper can also be used.

  In addition, as an image forming apparatus on which the image reading apparatus of the present invention is mounted, only a digital multifunction peripheral is shown here, but the present invention is an image forming apparatus of another type such as an analog type copying machine or a color copying machine. Of course, the present invention can also be applied to an image scanner separate from the image forming apparatus.

  The present invention includes a light source that illuminates a document in the scanning direction and a mirror that guides reflected light from the document as image light, and is capable of moving in the sub-scanning direction, and image light guided by the scanning unit. An image reading apparatus that reads an original at a predetermined original reading position, and the scanning means outputs white reference data at a position different from the original reading position in the sub-scanning direction. A white reference member for acquisition is arranged, the photoelectric conversion member can be read at a plurality of different image reading speeds, and the scanning unit starts to acquire the white reference data by moving from a predetermined stop position. The timing until is varied according to the image reading speed of the photoelectric conversion member.

  Thereby, the moving speed of the scanning means at the time of obtaining the white reference data can be made appropriate, the white reference data can be appropriately obtained according to the image reading speed, and the white reference member and the apparatus main body can be enlarged. Can be prevented. Also, the timing until the white reference data is acquired by starting the acquisition of the white reference data while moving in the data acquisition direction after the scanning unit has moved a predetermined amount in the direction opposite to the data acquisition direction from the stop position. Can be more effectively varied in accordance with the image reading speed, and the white reference member and the apparatus main body can be prevented from becoming larger.

  In addition, at least one of the plurality of image reading speeds, the scanning unit starts acquiring white reference data while directly moving in the data acquisition direction from the stop position, so that the scanning unit is not moved in the opposite direction. In this case, white reference data can be acquired in a shorter time, and more appropriate white reference data can be acquired according to the image reading speed.

  In addition, when the image reading speed is the first image reading speed, the scanning unit starts acquiring white reference data while moving directly from the stop position in the data acquisition direction, and the second reading speed is larger than the first image reading speed. At the image reading speed, after the scanning means has moved in the opposite direction, starting the acquisition of white reference data while moving in the data acquisition direction makes it possible to acquire more appropriate white reference data according to the image reading speed It becomes.

  Also, when scanning a document that is a fixed document and has a monochrome image, the scanning means starts acquiring white reference data while moving directly in the data acquisition direction from the stop position, thereby improving image reading efficiency. To do. In addition, by changing the acceleration from the stop position in the scanning unit to the start of obtaining the white reference data according to the image reading speed, the timing until obtaining the white reference data can be changed more effectively. An increase in the size of the white reference member and the apparatus main body can be further prevented.

  Further, by setting the moving speed of the scanning means when reading the white reference member to be 70% or more of a predetermined reference moving speed corresponding to the image reading speed, white reference data that avoids the influence of black data derived from black spots is used. Acquisition can be performed, and deterioration in image quality can be prevented. In addition, after obtaining the white reference data, it is possible to perform efficient image reading by continuously reading the document. Further, by using the image forming apparatus provided with the image reading apparatus, it is possible to appropriately acquire the white reference data according to the image reading speed and perform appropriate image formation, and to prevent the apparatus from becoming large.

1 is a front sectional view showing an internal configuration of an image forming apparatus equipped with an image reading apparatus according to a first embodiment of the present invention. These are front sectional views showing the internal configuration of the image reading apparatus of the present embodiment. These are top views showing an internal configuration of the image reading apparatus of the present embodiment. FIG. 3 is a block diagram illustrating an example of a control path of the image reading apparatus. These are figures which show the relationship between each line sensor of a CCD sensor, and the reading position in a white reference board. FIG. 10 is a diagram illustrating a white reference data acquisition range when the time required for moving the carriage is changed between the color mode and the monochrome mode. FIG. 7 is a diagram showing a white reference data acquisition range in FIG. 6, FIG. 7A is a diagram showing a color mode in FIG. 6, and FIG. 7B is a diagram showing a monochrome mode. These are figures which show the movement operation | movement of the carriage of the image reading apparatus which concerns on 2nd Embodiment of this invention. These are the figures which show the movement operation | movement of the carriage of the image reading apparatus which concerns on 3rd Embodiment of this invention.

Explanation of symbols

1 lamp (light source)
3-5 Mirror 7 CCD sensor (photoelectric conversion member)
7a R line sensor 7b G line sensor 7c B line sensor 7d B / W line sensor 8 First carriage (scanning means)
9 Second carriage (scanning means)
21 Image Reading Device 27 Document Conveying Device 53 Carriage Drive Motor 55 White Reference Plate (White Reference Member)
60 Control Unit 61 Storage Unit 100 Image Forming Apparatus R1 First Image Reading Position R2 Second Image Reading Position d Document Transport Path

Claims (9)

A scanning unit having a light source for illuminating a document in the scanning direction and a mirror for guiding reflected light from the document as image light, and movable in the sub-scanning direction; and image light guided by the scanning unit is converted into an electrical signal An image reading apparatus that reads a document at a predetermined document reading position.
A white reference member for obtaining white reference data by the scanning unit is disposed at a position different from the document reading position in the sub-scanning direction,
The photoelectric conversion member can be read at a plurality of different image reading speeds,
An image reading apparatus characterized in that a timing until the scanning unit moves from a predetermined stop position and starts acquiring the white reference data is varied according to the image reading speed of the photoelectric conversion member. When the direction from the stop position toward the white reference member is the data acquisition direction,
The scanning means starts acquiring the white reference data while moving in the data acquisition direction after moving a predetermined amount from the stop position in a direction opposite to the data acquisition direction. The image reading apparatus described.   3. The white reference data acquisition is started while the scanning unit directly moves in the data acquisition direction from the stop position at at least one of the plurality of image reading speeds. The image reading apparatus described in 1. When the image reading speed is the first image reading speed, the scanning unit moves directly from the stop position in the data acquisition direction to start acquiring the white reference data,
When the second image reading speed is higher than the first image reading speed, the scanning unit moves a predetermined amount in the opposite direction from the stop position and then moves in the data acquisition direction while moving the white reference data. The image reading apparatus according to claim 3, wherein acquisition is started.   The scanning unit starts acquisition of the white reference data while directly moving in the data acquisition direction from the stop position when reading a fixed original document having a monochrome image. 5. The image reading apparatus according to 3 or 4.   The image reading apparatus according to claim 1, wherein an acceleration from the stop position of the scanning unit to the start of acquisition of the white reference data is varied according to the image reading speed.   7. The moving speed of the scanning unit when reading the white reference member is 70% or more of a predetermined reference moving speed corresponding to the image reading speed. Image reading device.   The image reading apparatus according to claim 1, wherein after reading the white reference data, the document is continuously read.   An image forming apparatus comprising the image reading apparatus according to claim 1.

Images