Abstract:
An image forming device includes a scanner, a first setting portion configured to set a reading scale factor for an image from a document, a second setting portion configured to set the size of an image formed medium, a determining portion configured to determine to which of divided ranges the reading scale factor set by the first setting portion belongs, a moving section configured to move the scanner at a specified moving speed corresponding to the range determined by the determining portion, a calculating section configured to calculate a distance the scanner moves based on the reading scale factor and the size of the image formed medium, and a storing portion configured to store the image read by a photoelectric converting device while the moving section is moving the scanner at the moving speed corresponding to the reading scale factor.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to an image forming device such as a digital copier, a digital composite device, or a facsimile device which has a function for reading an image. More specifically, the present invention relates to zoom control performed by the image forming device to read an image from a document to form a scale factor changed image. 
   A conventional image forming device comprises image reading means for reading an image, image storage means for storing the image data read by the image reading means, image forming means for reading the image data stored in the image storage means and forming an image on a sheet on the basis of the image data, and setting means for setting an operator specified scale factor for the image on the document, the operator specified scale factor being a final image formation scale factor specified by the operator. The image forming device has zoom control that forms a scale factor changed image. Further, the image reading means for reading an image is composed of a first carriage on which a light source irradiating the document with light and a mirror reflecting reflected light from the document to a light receiving side are mounted, a second carriage on which a mirror reflecting the reflected light from the document to the light receiving side is mounted, a lens that forms an image, and photoelectric converting means (CCD) for converting the image into an electric signal. The photoelectric converting means (CCD) receives the reflected light for the image as line-like reflected light traveling in a main scanning direction. The photoelectric converting means then converts the reflected light into an electric signal. The photoelectric converting means may be called a CCD line sensor. 
   In this case, the first and second carriages are called a scanner. The first and second carriages are driven with wires. The second carriage moves at a speed half that of the first carriage. Further, the speed at which the first carriage of the scanner moves is defined as the speed at which the document is read (the moving speed of the first carriage will hereinafter be referred to as a scanner moving speed or reading speed). 
   A proposal has been made of the following technique. A conventional digital copier or digital composite device uses the image reading means to move a lens that forms an image in association with a reading scale factor of 100%, thus reading the image from the document. The 100% image data (hereinafter referred to as scale factor-equalized image data) is stored in an internal memory. The scale factor of the scale factor-equalized image data is changed in accordance with the operator specified scale factor. Then, a scale factor-changed image can be re-formed on the sheet (see, for example, Document 1 or Document 2). 
   However, this technique performs control that stores the scale factor-equalized image data in the internal memory and changes the scale factor of the image data in accordance with the operator specified scale factor. Accordingly, a problem with this technique is that the relevant burden on the memory or image scale factor changing process becomes heavier, which reduces the number of pages for image data which can be read. 
   On the other hand, instead of the above control, another type of image forming device performs control which, upon reading, reads the image while changing the scanner moving speed in accordance with the operator specified scale factor and which then stores the scale factor-changed image data in the internal memory, the control subsequently forming the corresponding scale factor-changed image on the sheet. This control differs from the above and, upon reading, reads the image having its scale factor changed. This control varies the scanner moving speed in increments of 1% in accordance with the operator specified scale factor, which ranges widely from, for example, 25 to 400%. It is thus necessary to employ a motor that does not vibrate vigorously over a wide range of scanner moving speeds, as well as its driving circuit. This disadvantageously increases costs. Thus, in recent years, a technique called hybrid zoom control has been proposed (Document 3). 
   In hybrid zoom control, the document is read using a predetermined reading scale factor and at a reading speed corresponding to the reading scale factor, and stores and holds the read data in the storage section. Image processing is then executed, that is, enlargement, contraction, or scale factor equalizing to enable a scale factor-changed image to be output. The predetermined scale factor may be the same as or different from the operator specified scale factor. If the operator specified scale factor is the same as the predetermined reading scale factor, the image processing is an image scale factor equalizing process. If the operator specified scale factor is larger than the predetermined reading scale factor, the image processing is an image enlarging process. If the operator specified scale factor is smaller than the predetermined reading scale factor, the image processing is an image contracting process. 
   The employment of the hybrid zoom control eliminates the need to vary the scanner moving speed in increments of 1% in accordance with the operator specified scale factor, which ranges widely from, for example, 25 to 400%. This in turn obviates the need for an expensive scanner motor and its driving circuit, thus reducing the cost. 
   [Patent Document 1] Jpn. Pat. Appln. KOKAI Publication No. 2003-87522 (Document 1) 
   [Patent Document 2] Jpn. Pat. Appln. KOKAI Publication No. 2003-87522 (Document 2) 
   [Patent Document 3] Jpn. Pat. Appln. KOKAI Publication No. 2001-77980 (Document 3) 
   BRIEF SUMMARY OF THE INVENTION 
   As described above, the hybrid zoom control is free from the disadvantage of increasing the burden on the memory or image scale factor changing process. It is an object of the present invention to provide an image forming device that can use the hybrid zoom control to reduce the burden on the memory or image scale factor changing process to obtain high-quality scale-factor-changed images. 
   That is, the present invention employs the hybrid zoom control in which one of predetermined reading speeds is selected in accordance with an operator specified scale factor and an image is read at the predetermined reading speed, the hybrid zoom control then controlling image processing inside the device to change the scale factor of the image and subsequently storing the resultant image. Accordingly, a required read area is read in accordance with a reading scale factor. The present invention can thus provide an image forming device that can reduce the burden on the memory or image scale factor changing process to obtain high-quality scale-factor-changed images. 
   An image forming device according to an aspect of the present invention comprises a photoelectric converting means for reading an image from a document as line-like reflected light traveling in a main scanning direction, scanning means for relatively moving the photoelectric converting means and the image from the document, first setting means for setting a reading scale factor for the image from the document and second setting means for setting the size of an image formed medium. 
   The image forming device also includes determining means for determining to which of a plurality of divided ranges the reading scale factor set by the first setting means belongs, moving means for moving the scanning means at a specified moving speed corresponding to the range determined by the determining means, the specified moving speed varying with the ranges and calculating means for calculating a distance the scanning means moves on the basis of the reading scale factor set by the first setting means and the size of the image formed medium set by the second setting means. 
   The image forming device further includes storing means for storing the image read by the photoelectric converting means while the moving means is moving the scanning means at the moving speed corresponding to the reading scale factor over the moving distance calculated by the calculating means, in a storage area based on the moving distance and moving speed of the scanning means, processing means for changing a scale factor of the image data stored in the storage area to one corresponding to a difference between the reading scale factor set by the first setting means and a reading scale factor corresponding to the moving speed of the scanning means and image forming means for forming an image on the image formed medium on the basis of the image data having its scale factor changed by the processing means. 
   An image forming device according to another aspect of the present invention comprises a photoelectric converting means for reading an image from a document as line-like reflected light traveling from a document as line-like reflected light traveling in a main scanning direction, scanning means for relatively moving the photoelectric converting means and the image from the document, first setting means for setting a reading scale factor for the image from the document and second setting means for setting the size of an image formed medium. 
   The image forming device also includes selecting means for selecting a second reading speed corresponding to a reading scale factor of 50% when the reading scale factor set by the first setting means is within the range of 25 to 50%, selecting a first reading speed corresponding to a reading scale factor of 100% when the reading scale factor set by the first setting means is within the range of 51 to 100%, and selecting a third reading speed corresponding to a reading scale factor of 200% when the reading scale factor set by the first setting means is within the range of 101 to 400%, moving means for moving the scanning means at the reading speed selected by the selecting means and calculating means for calculating a distance the scanning means moves on the basis of the reading scale factor set by the first setting means and the size of the image formed medium set by the second setting means. 
   The image forming device further includes storing means for storing the image read by the photoelectric converting means while the moving means is moving the scanning means at the moving speed corresponding to the reading scale factor over the moving distance calculated by the calculating means, in a storage area based on the moving distance and moving speed of the scanning means, processing means for changing a scale factor of the image data stored in the storage area to one corresponding to a difference between the reading scale factor set by the first setting means and a reading scale factor corresponding to the moving speed of the scanning means and image forming means for forming an image on the image formed medium on the basis of the image data having its scale factor changed by the processing means. 
   Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate presently preferred embodiments of the invention, and together with the general description given above and the detailed description of the preferred embodiments given below, serve to explain the principles of the invention. 
       FIG. 1  is a sectional view of the general configuration of a digital copier illustrating an embodiment of the present invention; 
       FIG. 2  is a block diagram illustrating a control system of the digital copier; 
       FIG. 3  is a flow chart illustrating a reading process executed by a scanner; 
       FIG. 4  is a diagram illustrating a area read by the scanner; and 
       FIG. 5  is a diagram illustrating another example of the configuration of a scanner section. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   An embodiment of the present invention will be described below with reference to the drawings. 
     FIG. 1  is a sectional view showing the general configuration of a digital copier  1  serving as an example of an image forming device according to the present invention. 
   As shown in  FIG. 1 , the digital copier  1  comprises a device main body  2 . A scanner section  4  serving as reading means and a printer section  6  functioning as image forming means are provided in the device main body  2 . 
   A copy board  8  on which a reading object, that is, documents D are placed is provided on a top surface of the device main body  2 . Further, an automatic document feeding device  9  (hereinafter referred to as ADF) is disposed on the top surface of the device main body  2 ; ADF serves as conveying means for automatically feeding the documents D onto the copy board  8 . 
   The documents D placed on a document tray  9   a  of ADF  9  are conveyed using a conveying guide (not shown). The documents D are then discharged onto a discharge tray  9   c  via a platen roller  9   b . Thus, while being conveyed by the platen roller  9   b , the documents D are exposed and scanned using an exposure lamp  10  of a scanner section  4 , described later. Images are thus read from the documents D. 
   The documents D are set in the document tray  9   a  of ADF  9  with their read surface upward. The documents D are loaded one by one starting with the uppermost one. 
   The scanner section  4  disposed in the device main body  2  has an exposure lamp  10  composed of, for example, a halogen lamp to illuminate the documents D conveyed by ADF  9  or placed on the copy board  8 , and a first mirror  12  that polarizes reflected light from the documents in a predetermined direction. The exposure lamp  10  and the first mirror  12  are mounted on a first carriage  14  disposed below the copy board  8 . 
   The first carriage  14  is placed so as to move parallel to the copy board  8 . The first carriage  14  is reciprocated below the copy board  8  by a scanner motor  16  (driving motor) via a toothed belt (not shown) or the like. The scanner motor  16  is composed of a stepping motor. 
   Further, a second carriage  18  that can move parallel to the copy board  8  is disposed below the copy board  8 . Second and third mirrors  20  and  22  are mounted on the second carriage perpendicularly to each other and sequentially polarize reflected light from the document D which is polarized by the first mirror  12 . The rotating force of the scanner motor  16  is transmitted to the second carriage  18  via the toothed belt or the like. The second carriage  18  moves in unison with the first carriage  14 . Furthermore, the second carriage  18  moves along and parallel to the copy board  8  at a speed half that of the first carriage  14 . 
   A scanner is composed of the first carriage  14  and second carriage  18 . The first carriage  14  and the second carriage  18  are driven using wires. The second carriage  18  moves at a speed half that of the first carriage  14 . Here, the speed at which the first carriage  14  of the scanner moves is defined as the speed at which the documents are read. (The moving speed of the first carriage will hereinafter referred to as a scanner moving speed or reading speed.) 
   Further, an image forming lens  24  and a CCD sensor (line sensor)  26  are disposed below the copy board; the image forming lens  24  focuses reflected light from the third mirror  20  mounted on the second carriage  18  and the CCD sensor  26  receives the reflected light focused by the image forming lens  24 . The image forming lens  24  is disposed in a surface containing the optical axis of light polarized by the third mirror  22 . The CCD sensor  26  photoelectrically converts the incident reflected light in accordance with an image processing clock provided by a main CPU described later. The CCD sensor  26  thus outputs an electric signal corresponding to the document D read. 
   When the document D conveyed by the ADF  9  is read, a position irradiated with light from the exposure lamp  10  is fixed, as shown in  FIG. 2 . Further, when the document D placed on the copy board  8  is read, the position irradiated with light from the exposure lamp  10  is shifted from left to right along the copy board  8 . 
   On the other hand, a printer section  6  comprises a laser exposure device  28  operating as latent image forming means. An electrostatic latent image is formed on a peripheral surface of a photosensitive drum by scanning the peripheral surface of the photosensitive drum  30  using laser light from the laser exposure device  28 . 
   Further, the printer section  6  has the rotatable photosensitive drum  30  disposed almost in the center of the device main body and closer to its right end, and which operates as an image carrier. The peripheral surface of the photosensitive drum  30  is exposed to laser light from the laser exposure device  28  to form a desired electrostatic latent image. The peripheral surface of the photosensitive drum  30  is integrated with a charger  32  that charges the peripheral surface of the drum to a predetermined charge, a developing device  34  that supplies toner as a developer to the electrostatic latent image formed on the peripheral surface of the photosensitive drum  30  to develop the image at a desired image density, and a releasing charger  36  that separates an image formed medium fed from a cassette  48  or  50  described later, that is, copy paper P, from the photosensitive drum  30 . The following components are sequentially arranged on the peripheral surface of the photosensitive drum: a transfer charger  38  that transfers a toner image formed on the photosensitive drum  30  to the paper P, a releasing pawl  40  that releases the copy paper P from the peripheral surface of the photosensitive drum  30 , a cleaning device  42  that removes toner remaining on the peripheral surface of the photosensitive drum  30 , and a static eliminator  44  that eliminates electrical charge from the peripheral surface of the photosensitive drum  30 . 
   The upper cassette  48  and lower cassette  50  that can be withdrawn out of the device main body are disposed below the device main body  2  so that they are stacked. Sheets of copy paper P of different sizes are charged in the respective cassettes  48  and  50 . A manual tray  54  is provided on a side of the upper cassette  48 . 
   A conveying path  56  is formed in the device main body  2 ; the conveying path  56  extends from the cassettes  48  and  50  through a transfer section located between the photosensitive drum  30  and the transfer charger  38 . A fixing device  58  having a fixing lamp  58   a  is provided at a terminal of the conveying path  56 . A discharge port  60  is formed above the fixing device  58 . 
   A paper feeding roller  62  and a separating roller  63  are provided near the upper cassette  48  and the lower cassette  50 ; the paper feeding roller  62  and the separating roller  63  take the sheets of paper P out of the cassettes  48  and  50  one by one. Further, the conveying path  56  is provided with a large number of paper feeding roller pairs  64  that convey the copy paper P through the conveying path  56 , the paper being taken out by the paper feeding roller  62  and separating roller  63 . 
   In the conveying path  56 , a resist roller pair  66  is provided upstream of the photosensitive drum  30 . The resist roller pair  66  corrects the inclination of the copy paper P taken out and aligns the leading end of the toner image on the photosensitive drum  30  with the leading end of the copy paper P. The resist roller pair  66  then feeds the copy paper P to the transfer section at the same speed as the one at which the peripheral surface of the photosensitive drum  30  moves. A pre-aligning sensor  68  is provided in front of the resist roller pair  66 , that is, close to the paper feeding rollers  64 , to detect that the copy paper P has arrived. 
   The paper feeding roller pairs  64  feed sheets of copy paper P taken by the paper feeding roller  62  out of the cassettes  48  and  50  one by one, to the resist roller pair  66 . Then, the sheets of copy paper P have their leading ends aligned by the resist roller pair  66  and are then fed to the transfer section. 
   In the transfer section, the transfer charger  38  transfers a developer image, that is, a toner image, formed on the photosensitive drum  30  onto the paper P. The copy paper P to which the toner image has been transferred is released from the peripheral surface of the photosensitive drum  30  under the effect of the releasing charger  36  and releasing pawl  40 . The copy paper P is then transferred to the fixing device  58  via a conveying belt (not shown) partly consisting of the conveying path  56 . Then, the fixing device  58  melts and fixes the developer image to the copy paper P. A discharge roller pair  70  then discharges the copy paper P through the discharge port  60 . 
   An automatic double side device  74  is provided to the right of the conveying path  56  to reverse the copy paper P having passed through the fixing device  58  and then feed the paper P to the conveying path  56  again. 
   The discharge port  60  is provided with directing lever (not shown) to direct the copy paper P discharged from the discharge port  60 , onto a discharge tray  72  in the device main body  2  or to an external conveying mechanism  76 . The external conveying mechanism  76  is installed in an upper cavity portion  78  of the discharge tray  72  in the device main body  2  to convey the copy paper P discharged from the discharge port  60 , to the exterior of the device main body  2 . 
   Further, a finisher  80 , which is an optional device, is installed on a side of the device main body  2 . The finisher  80  is supplied with the copy paper P conveyed by the external conveying mechanism  76  (the back surface of the paper P is printed). 
   The finisher  80  uses a stapler  81  to staple a number of documents (paper P) supplied at their rear ends, the documents constituting a book. The finisher  80  then collects the documents on a tray  82 . The tray can be moved up and down and lowers on the basis of the loading of the documents. 
   Further, the copy paper P supplied to the finisher  80  is conveyed through a reverse conveying path  83 . The copy paper P is discharged onto a tray  84  with its printed surface upward. 
   An operation panel (described later) is provided in the upper part of a front surface of the device main body to give instructions concerning various copying conditions, such as a copy scale factor and an instruction for the start of copying. 
   The digital copier  1  may be used for a single purpose or may also be used as a network printer. 
   In this case, the digital copier  1  is connected to personal computers (PC; no shown) and servers (not shown) via a local network (LAN) (not shown). 
   With reference to  FIG. 4 , description will be given of the internal configuration of a control circuit of the digital copier  1 . 
   Description will now be given of the configuration of a control system of the digital copier. 
     FIG. 2  is a block diagram schematically showing electric connections in the digital copier and the flow of signals for control. 
   As shown in  FIG. 2 , the digital copier  1  main body is composed of a main control section  100 , a scanner section  4 , a printer section  6 , and an operation panel  90 . Further, the digital copier  1  main body connects to the finisher  80  and ADF  9 , which are optional devices. The operation panel  90  connects to, for example, an operation panel CPU  91  that controls the whole operation panel, a print key  92  that gives an instruction for the start of copying, an input device  93  provided with, for example, a plurality of pushbutton switches, or a touch panel, used to input the number of sheets to be copied or printed, a scale factor, a specification for partial copying, and the coordinates of an area for the partial copying, and ten keys  94  utilized to set the number of sheets to be copied. 
   The main control section  100  is composed of a system CPU  101 , a ROM  102 , a RAM  103 , an NVM  104 , an image processing section  106 , and the like. 
   The system CPU  101  controls the whole main control section  100 . The ROM  102  stores various control programs. The RAM  103  temporarily stores data. The NVM (NonVolatile RAM)  104  is a nonvolatile memory backed up by batteries (not shown). A shared RAM (not shown) is provided for bidirectional communications between the system CPU  101  and the printer CPU  131  and between the system CPU  101  and the printer CPU  131 . 
   The image processing section  106  consists of an image processing circuit or the like to execute image processing such as trimming, masking, or the compression or decompression of an image. The image processing section  106  compresses image data read by the scanner section  4  to convert the data into an image file. Further, the image processing section  106  converts the image data into an image file. 
   Now, the scanner section  4  will be described. The scanner section  4  is composed of a scanner CPU  131 , a ROM  132 , an internal memory  133  such as a RAM, a shading correcting ASIC  134 , a CCD driver  135 , a scan motor drive  136 , and an exposure lamp regulator  137 . 
   The scanner CPU  131  controls the whole scanner section  4 . The ROM  132  stores control programs and the like. The shading correcting ASIC  134134  consists of an A/D converting circuit, a shading correcting circuit, a gamma correcting circuit, and the like which process a signal from the CCD sensor  26 . The CCD driver  135  controls the CCD sensor  26 . The scan motor driver  136  drives the scan motor  16 . The exposure lamp regulator  137  controls the lighting of the exposure lamp  10 . The scanner CPU  131  makes various settings for the scan motor driver  136  to control the scan motor  16 . A scan image is enlarged or contracted on the basis of an INPUT scale factor set by an operator using the input device  93 . However, the INPUT scale factor is reflected in a main scanning direction (the direction of the CCD line sensor) by the system CPU  106  by setting a scale factor for the image processing section  106 . The INPUT scale factor is reflected in a sub-scanning direction (the moving direction of the scanner) by varying the moving speed of the scanner for enlargement or contraction. In other words, the rotation speed of the scan motor can be varied on the basis of a driving pulse for the scan motor  16  indicated by the scanner CPU  131  to the scan motor driver  136  as well as a set excitation system. This operation enables a change in the scanner moving speed, which is a reading speed. 
   This embodiment will be described in connection with the scan motor  16  composed of a two-phase stepping motor. 
   The scan motor  16  is controlled by the scanner  131  by setting, for the scan motor driver  136 , eight values for seven signals concerning the control of the motor and a memory mapped address with which a scan motor driving current value is set for D/A. The driving of the scanner include acceleration (through up), equal-speed, and deceleration (through down) driving. The scanner moves a distance slightly longer than the document. 
   Now, the printer section  6  will be described. The printer section  6  is composed of a printer CPU  141 , a ROM  142 , a RAM  143 , a laser driver  145 , a polygon motor driver  146 , a main motor driver  147 , the charging charger  38 , the fixing lamp  58   a , a heat roller temperature sensor  58   b , and the like. 
   The printer CPU  141  controls the whole printer section  6 . The laser driver  145  controls the laser exposure device  27 . To form an electrostatic latent image on the photosensitive drum  30 , serving as an image carrier, the laser driver  145  controls light emissions from the semiconductor laser of the laser exposure device  28 . Further, the laser driver  145  controls the rotation of the polygon motor  29  to guide light from the semiconductor laser  28  to the photosensitive drum  30 . The main motor driver  146  controls the rotation of a main motor (not shown). 
   A specific description will be given of the embodiment configured as described above. Description will be given of a control sequence for the scanner according to the present embodiment. Specifically, a sequential description will be given in brief of control performed during a process from power-on to scanning. The order of control will be shown below using (1) to (6). 
   &lt;Powering on the Digital Copier&gt; 
   (1) Operation of initializing the scanner 
   (2) Peak detection control 
   (3) Operation of moving the indicator 
   &lt;Starting Copying&gt; 
   Black shading process (if black shading is carried out only once rather than for every correction, it is executed in (4)) 
   Process of moving the scanner to its home position (process of moving the scanner to its home position during a normal scan) 
   Scan Operation (Forward or Backward) 
   The control of the scanner in (1) to (6) will be described. 
   Description will be given of the process of initializing the scanner in (1). 
   A position sensor  19  for the scanner is placed near an end of a frame of the scanner section  4 . The scanner is moved, and the position sensor  19  senses part of the scanner  19 . The scanner  19  is stopped after being allowed to move a predetermined distance after being sensed by the position sensor  19 . 
   The description of the following operations is omitted: the (2) peak detection control, the (3) operation of moving the indicator, the (4) black shading correcting process, and the (5) process of moving the scanner to its home position. 
   The scan operation in (6) will be described. 
   The scan operation reads a document. The scanner operates as follows. For a normal scan, the scanner first moves a distance equal to the [document size]+[accelerating or decelerating distance] from a scan start position in a forward direction. After the movement, the scanner is stopped for a specified time without turning off excitation. The document is read during the forward movement. Then, the scanner is moved backward to return to the scan start position. The scanner is then stopped at the scan start position. The scanner continues to be excited for a specified time. Then, the excitation is turned off. The scan operation has been described. 
   Now, description will be given of hybrid zoom control employed in the embodiment of the present invention. 
   In hybrid zoom control, document is read using a predetermined reading scale factor and at a reading speed corresponding to the reading scale factor and temporarily stores the read data in the storage section. The hybrid zoom control subsequently executes image processing, that is, enlargement, contraction, or scale factor equalizing to enable a scale factor-changed image to be output. The predetermined scale factor may be the same as or different from the operator specified scale factor. If the operator specified scale factor is the same as the predetermined reading scale factor, the image processing is an image scale factor equalizing process. If the operator specified scale factor is larger than the predetermined reading scale factor, the image processing is an image enlarging process. If the operator specified scale factor is smaller than the predetermined reading scale factor, the image processing is an image contracting process. 
   According to an embodiment of the present invention, the operator inputs a specified scale factor through the input device, which is a setting section. The control section determines the operator specified scale factor to select one of first, second, and third reading speeds that are predetermined ones. The first reading speed corresponds to a reading speed of 100%. The second reading speed is higher than the first one and corresponds to a reading speed of 50%. The third reading speed is lower than the first one and corresponds to a reading speed of 200%. 
   This control has a step of selecting the second reading speed if the operator specified scale factor input is at most 50% and a step of selecting the first reading speed if the operator specified scale factor input is at most 100%, and otherwise selecting the third reading speed. 
   The embodiment will be sequentially described with reference to the flowchart in  FIG. 3  and  FIG. 4 . 
   The operator sets a specified scale factor and a sheet size (STEP  1 ). The operator then depresses a start key (STEP  2 ). The main control section  100  determines the scale factor specified by the operator to select one of the predetermined reading speeds. The reading scale factors are 50, 100, and 200%. The first reading speed corresponds to a reading speed of 100%. The second reading speed corresponds to a reading speed of 50%. The third reading speed corresponds to a reading speed of 200%. 
   The control is not related to any document size, so that conditions for the document size are omitted. If the operator specifies a scale factor of 50% and A4-sized sheets on which images are to be formed, the second reading speed is selected (STEP  3  and STEP  5 ). In this case, the operator specified scale factor is equal to the reading scale factor. Accordingly, the turn-off of image scale factor changing (scale factor equalizing process) is selected. The actual read area of the document is twice as large as the A4 size in accordance with the operator specified scale factor (this is equivalent to an A3 size). This read area is held in the internal memory  133  (STEP  8 ). Using the area held in the internal memory  133  as a document size for a scan operation, the carriage is moved forward a distance equal to the [document size]+[accelerating or decelerating distance] from the scan start position, to perform a reading operation (STEP  9 ). An image scale factor changing process (scale factor equalizing process) is executed on the image read by the scan operation (STEP  10 ). The image data is output to the image forming section to finish the scan (STEP  11 ). 
   If the operator specifies a scale factor of 25% and A4-sized sheets on which images are to be formed, the second reading speed is selected (STEP  3  and STEP  5 ). In this case, the operator specified scale factor is smaller than the reading scale factor. Accordingly, image contraction scale factor changing is selected. The actual read area of the document is four times as large as the A4 size in accordance with the operator specified scale factor. However, since the maximum size is A3 (if the A sizes are used), an area twice as large as the A4 size (this area is equivalent to the A3 size) is held in the internal memory  133  (STEP  8 ). Using the area held in the internal memory  133  as a document size for a scan operation, the carriage is moved forward a distance equal to the [document size]+[accelerating or decelerating distance] from the scan start position, to perform a reading operation (STEP  9 ). An image scale factor changing process (contraction scale factor changing process) is executed on the image read by the scan operation (STEP  10 ). The image data is output to the image forming section to finish the scan (STEP  11 ). 
   If the operator specifies a scale factor of 100% and A4-sized sheets on which images are to be formed, the first reading speed is selected (STEP  3 , STEP  4 , and STEP  6 ). In this case, the operator specified scale factor is equal to the reading scale factor. Accordingly, the turn-off of image scale factor changing (scale factor equalizing process) is selected. The actual read area of the document is equal to the A4 size in accordance with the operator specified scale factor. This read area is held in the internal memory  133  (STEP  8 ). Using the area held in the internal memory  133  as a document size for a scan operation, the carriage is moved forward a distance equal to the [document size]+[accelerating or decelerating distance] from the scan start position, to perform a reading operation (STEP  9 ). An image scale factor changing process (scale factor equalizing process) is executed on the image read by the scan operation (STEP  10 ). The image data is output to the image forming section to finish the scan (STEP  11 ). 
   If the operator specifies a scale factor of 75% and A4-sized sheets on which images are to be formed, the first reading speed is selected (STEP  3 , STEP  4 , and STEP  6 ). In this case, the operator specified scale factor is smaller than the reading scale factor. Accordingly, image contraction scale factor changing is selected. The actual read area of the document is 1.33 times as large as the A4 size in accordance with the operator specified scale factor. This read area is held in the internal memory (STEP  8 ). Using the area held in the internal memory  133  as a document size for a scan operation, the carriage is moved forward a distance equal to the [document size]+[accelerating or decelerating distance] from the scan start position, to perform a reading operation (STEP  9 ). An image scale factor changing process (contraction scale factor changing process) is executed on the image read by the scan operation (STEP  10 ). The image data is output to the image forming section to finish the scan (STEP  11 ). 
   If the operator specifies a scale factor of 200% and A4-sized sheets on which images are to be formed, the third reading speed is selected (STEP  3 , STEP  4 , and STEP  7 ). In this case, the operator specified scale factor is equal to the reading scale factor. Accordingly, the turn-off of image scale factor changing (scale factor equalizing process) is selected. The actual read area of the document is half the A4 size in accordance with the operator specified scale factor. This read area is held in the internal memory  133  (STEP  8 ). Using the area held in the internal memory  133  as a document size for a scan operation, the carriage is moved forward a distance equal to the [document size]+[accelerating or decelerating distance] from the scan start position, to perform a reading operation (STEP  9 ). An image scale factor changing process (scale factor equalizing process) is executed on the image read by the scan operation (STEP  10 ). The image data is output to the image forming section (printer  6 ) to finish the scan (STEP  11 ). 
   If the operator specifies a scale factor of 150% and A4-sized sheets on which images are to be formed, the third reading speed is selected (STEP  3 , STEP  4 , and STEP  7 ). In this case, the operator specified scale factor is smaller than the reading scale factor. Accordingly, image contraction scale factor changing is selected. The actual read area of the document is larger that the one set using a reading driving scale factor, in accordance with the operator specified scale factor and. An area 0.67 times as large as the A4 size is held in the internal memory (STEP  8 ). Using the area held in the internal memory  133  as a document size for a scan operation, the carriage is moved forward a distance equal to the [document size]+[accelerating or decelerating distance] from the scan start position, to perform a reading operation (STEP  9 ). An image scale factor changing process (contraction scale factor changing process) is executed on the image read by the scan operation (STEP  10 ). The image data is output to the image forming section to finish the scan (STEP  11 ). 
   If the operator specifies a scale factor of 300% and A4-sized sheets on which images are to be formed, the third reading speed is selected (STEP  3 , STEP  4 , and STEP  7 ). In this case, the operator specified scale factor is larger than the reading scale factor. Accordingly, image enlargement scale factor changing is selected. The actual read area of the document is smaller that the one set using a reading driving scale factor, in accordance with the operator specified scale factor. An area 0.33 times as large as the A4 size is held in the internal memory  133  (STEP  8 ). Using the area held in the internal memory  133  as a document size for a scan operation, the carriage is moved forward a distance equal to the [document size]+[accelerating or decelerating distance] from the scan start position, to perform a reading operation (STEP  9 ). An image scale factor changing process (enlargement scale factor changing process) is executed on the image read by the scan operation (STEP  10 ). The image data is output to the image forming section to finish the scan (STEP  11 ). 
   As described above, according to the embodiment of the present invention, the image forming device employs the hybrid zoom control which selects one of the predetermined reading speeds in accordance with the operator specified scale factor and which then reads the image at the predetermined reading speed, the hybrid zoom control then controlling the image processing inside the device to change the scale factor of the image and subsequently storing the resultant image. Accordingly, the required read area is read in accordance with the reading scale factor. Therefore, the present invention can provide an image forming device that can reduce the burden on the memory or image scale factor changing process to obtain high-quality scale-factor-changed images. 
   In the embodiment of the present invention, the reading scale factor is limited to 50, 100, and 200%. However, the reading scale factors may be changed or the number of such scale factors may be increased. 
   Alternatively, instead of using the document feeding device to move the scanner, it is possible to use reading means for reading the document while conveying it at a predetermined speed. In this case, the speed at which the document is conveyed is the reading speed. The read area of the document can be similarly controlled. 
   In this case,  FIG. 5  shows the general configuration of the scanner section  151  such as the one described above. 
   The scanner section  151  is composed of a main body  152  incorporating a reading optical system and a sheet-feeder-type automatic feeding device  153  mounted on the main body  152 . 
   Transparent glass  154  is provided on a top surface portion of the main body  152 . A white reference plate (shading correcting plate)  155  is provided below a left end of the glass  4 ; the white reference plate is used to read a reference value for shading corrections. A document irradiated position  154   a  associated with document reading corresponds to a part of the surface of the glass  4  which is located on the right side of the white reference plate  155 . 
   A xenon lamp  156  and a carriage  158  are provided in the main body so as to be movable (in the direction in which the document is conveyed); the xenon lamp  156  serves as an exposure lamp and a mirror  157  is mounted on the carriage  158 . As the carriage  158  moves, a position irradiated with light from the xenon lamp  156  moves between the two points, that is, between the document irradiation position  154   a  and the read position of the white reference plate  155 . Before the document is read, the irradiated position is placed at (moves to) the reading position of the white reference plate  155 . After the white reference plate  155  has been irradiated with light for reading, the irradiated position is placed at (moves to) the document irradiated position  54   a . While the document is being read, the position irradiated with light from the xenon lamp remains fixed to the document irradiated position  154   a.    
   While the document is being read, the xenon lamp  156  is located as shown by a solid line in  FIG. 5 . While the white reference plate  115  is being read, the xenon lamp  156  is located as shown by a broken line in  FIG. 5 . 
   When the position irradiated with light from the xenon lamp  156  corresponds to the document irradiated position  154   a , the xenon lamp  156  emits light of a certain width traveling in the main scanning direction (the length direction of the xenon lamp  156 ), to the document irradiated position  154   a ; the width corresponds to a part of the document which is to be read. The document is thus exposed. 
   Further, a mirror  159  and a CCD line sensor  160  are provided in the main body  152 . The mirror  159  is fixed to the main body  152 . Thus, light emitted by the xenon lamp  159  and then reflected by the white reference plate  155  or document irradiated position  154   a  is guided to the CCD line sensor  160  via the mirrors  157  and  159  and an image forming lens (not shown). The CCD line sensor  160  photoelectrically converts the incident reflected light to output an electric signal corresponding to the reflected light. Further, a signal processing section  161  is supplied with the electric signal output by the CCD line sensor  160 . The signal processing section  161  executes processing such as amplification, A/D conversion, shading correction, or the like. The processed image data is output to an external apparatus such as a personal computer (PC) or a printer (not shown). 
   The automatic feeding device  153  is composed of a copy board  162  on which a plurality of documents are placed, a conveying system  163  such as a conveying roller which loads and conveys the documents from the copy board  162  one by one via the document irradiated position  154   a  (in the sub-scanning direction), and a tray  164  to which the documents conveyed by the conveying system  163  to pass through the document irradiated position  154   a  are discharged. 
   That is, the present invention is not limited to the above embodiments. In implementation, variations may be made to the components of the embodiments without departing from the spirit of the present invention. Further, various inventions can be formed by appropriately combining a plurality of components disclosed in the above embodiments. For example, it is possible to omit some of the components shown in the embodiments. Moreover, the components included in different embodiments may be appropriately combined together. 
   Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.