Document reading device and image formation apparatus

A document reading device includes: a reading position at which information on a document is read; a light source that radiates light toward the document passing through the reading position; a light receiving section that receives reflected light generated from the light from the light source; and a background reflection section disposed to reflect the light from the light source so as to be received by the light receiving section through the reading position. When the document is not present, the background reflection section reflects an amount of light that is greater than an amount of document-reflected light reflected by the document which is white. The background reflection section is formed by processing a specular surface so as to reflect an amount of light that is less than an amount of specularly reflected light reflected by a specular surface.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2013-134430 filed Jun. 27, 2013.

BACKGROUND

Technical Field

The present invention relates to a document reading device and an image formation apparatus.

SUMMARY

According to an aspect of the present invention, there is provided a document reading device including:

a reading position at which information on a document is read;

a light source that radiates light toward the document passing through the reading position;

a light receiving section that receives reflected light generated from the light from the light source; and

a background reflection section disposed to reflect the light from the light source so as to be received by the light receiving section through the reading position, the background reflection section reflecting an amount of light, when the document is not present, that is greater than an amount of document-reflected light reflected by the document which is white,

in which the background reflection section is formed by processing a specular surface so as to reflect an amount of light that is less than an amount of specularly reflected light reflected by a specular surface.

DETAILED DESCRIPTION

Exemplary embodiments of the present invention will be described below with reference to the drawings.

First Exemplary Embodiment

FIG. 1schematically illustrates an image formation apparatus100including a document reading device1according to a first exemplary embodiment.

<Overall Configuration of Image Forming Apparatus>

The image formation apparatus100according to the first exemplary embodiment includes a document reading device1that reads information on a document9, an image forming section2that forms an image on recording paper30that serves as an example of a recording medium on the basis of the information on the document read by the document reading device1(a read image), and a paper feed section3that stores the recording paper30and feeds the recording paper30to the image forming section2. In the image formation apparatus100, the image forming section2and the paper feed section3are disposed inside a body101, and the document reading device1is disposed above the body101with a predetermined space provided therebetween. The body101includes an eject/storage section102formed on its upper surface portion and in the space described above to eject and store the recording paper30on which an image has been formed.

The document reading device1has a housing10. A control panel110that serves as an operation section and that includes a touch panel111and plural operation buttons112is disposed on an upper portion of the housing10on the front side. The touch panel111serves as a display that displays an operation menu, a warning, a message, etc. for a user, and also receives information input for the displayed operation menu such as various settings. The operation buttons112include at least a mixed document size button112athat may be operated by the user when the document9includes documents of plural different sizes. In place of the operation button112a, the input method for mixed document sizes may be implemented by an input screen displayed on the touch panel111to allow selection of mixed document sizes, for example.

The document reading device1includes an optically transparent document platen11for placement of the document9, and a document covering12that is operable to open and close with respect to the housing10so as to cover at least the document platen11. The document platen11and the document covering12are provided on an upper surface portion of the housing10. The document covering12includes an automatic document transport section13that transports the document9to a reading position and that ejects the document9after being read, a document tray12afor placement of the document9to be fed by the automatic document transport section13, and a storage section12bthat stores the document9ejected from the automatic document transport section13.

The image forming section2includes image forming units20Y,20M,20C, and20K that form a toner image in yellow (Y), magenta (M), cyan (C), and black (K) colors, respectively, an intermediate transfer unit26that relays and transports the toner images formed by the image forming units20Y,20M,20C, and20K until being transferred to the recording paper30, and a fixing unit27that fixes the toner images transferred from the intermediate transfer unit26to the recording paper30.

The four image forming units20Y,20M,20C, and20K use substantially the same electrophotographic system except that they use toners (developers) with different colors. That is, each of the image forming units20includes a photoreceptor drum21that is rotationally driven in the direction indicated by the arrow, a charging device22that charges the surface of the photoreceptor drum21to a predetermined potential, an exposure device23of a contact type or the like that exposes the surface of the photoreceptor drum21to light on the basis of image information to form an electrostatic latent image, developing devices24Y,24M,24C, and24K that develop the electrostatic latent image formed on the photoreceptor drum21using a toner with the corresponding color to obtain a toner image, a first transfer device25of a contact type or the like that transfers the toner image on the photoreceptor drum21to the intermediate transfer unit26(an intermediate transfer belt26a) through a first transfer, and so forth. The exposure device23receives an image signal that has been subjected to predetermined image processing performed on the basis of information on the document9read by the document reading device1and image information input from outside the image formation apparatus1or the like.

The intermediate transfer unit26uses the intermediate transfer belt26awhich is endless and which circulates to pass through a first transfer position of each of the image forming units20Y,20M,20C, and20K. The intermediate transfer belt26ais rotatably supported by plural rollers such as a driving roller26b, a driven roller26c, and a tension roller26dthat applies a tension, and rotated by the driving roller26bin the direction indicated by the arrows. The intermediate transfer unit26also includes a second transfer device26dof a contact type or the like disposed at a position opposite to the driven roller26cacross the intermediate transfer belt26a.

The fixing unit27includes a housing27a, a heating rotary member27bin the form of a roller, a belt, or the like that is heated to a predetermined temperature by a heating unit and that is rotationally driven in the direction indicated by the arrow, a pressurizing rotary member27cin the form of a roller, a belt, or the like that is rotated through contact with the heating rotary member27bat a predetermined pressure, eject rollers27dthat transport the recording paper30after the fixation to be ejected to the eject/storage section102, and so forth. The heating rotary member27band the pressurizing rotary member27care provided inside the housing27a.

The paper feed section3is composed of a storage member31of a drawer type that stores plural sheets of the recording paper30of predetermined size, type, etc. in a stacked state, a feed device32such as rollers that feeds the sheets of the recording paper30stored in the storage member31to a transfer path, one sheet after another, and so forth. Plural storage members31(31A and31B) may be provided, and arranged in the vertical direction of the body101, for example. A supply/transport path28is disposed between the paper feed section3and the second transfer position of the image forming section2(between the intermediate transfer belt26aand the second transfer device26d) to transport the recording paper30fed from the paper feed section3to the second transfer position. The supply/transport path28is composed of plural transport roller pairs28ato28c, a transport guide member (not illustrated), and so forth.

<Configuration of Document Reading Device>

FIG. 2illustrates the document reading device1(such as its internal structure) according to the first exemplary embodiment.

The document reading device1has a moving document reading mode in which information on the document9in the form of a sheet placed on the document tray12aof the document covering12is read while the document9is being transported toward the storage section12bby the automatic document transport section13, and a stationary document reading mode in which the document9in the form of a sheet, a booklet, or the like placed on the document platen11on the upper surface of the housing10is read while the document9is stationary. The document reading device1allows the user to switchably select and use one of the two reading modes (functions).FIG. 2illustrates a reading stand-by state that occurs when the moving document reading mode is selected.

The document platen11is disposed on the upper surface portion of the housing10of the document reading device1. The document platen11serves as a window that allows reading of the document9placed on the document platen11in the stationary document reading mode. A reading window portion14is disposed on the upper surface portion of the housing10at a position closer to one end of the document platen11and opposite to the automatic document transport section13of the document covering12. The reading window portion14serves as a window that allows reading of the document9transported by the automatic document transport section13in the moving document reading mode. Both the document platen11and the reading window portion14are composed of a colorless and transparent glass plate or the like. Further, an illumination unit15and a light receiving section17are disposed inside the housing10. The illumination unit15radiates light toward the document9in each of the reading modes. The light receiving section17receives reflected light generated from the light from the illumination unit15. InFIG. 2, the path (optical path) along which the light emitted from the illumination unit15travels is indicated by the double-dashed line.

The illumination unit15is of a movable type so that the illumination unit15reciprocally moves in the linear reading direction (vertical scanning direction) when the document9is read in the stationary document reading mode. Specifically, the illumination unit15is composed of a first carriage (delivery member)150supported to reciprocally move in the vertical scanning direction, a light source16that emits light, a reflector152that serves as a reflection member that reflects a part of the light from the light source16toward the document9, and a first specular reflection plate153that receives reflected light from the document9etc. The light source16, the reflector152, and the first specular reflection plate153are mounted to the first carriage150. The first carriage150is guided by a rail155to reciprocally move. The rail155is disposed inside the housing10to extend along the vertical scanning direction.

As the light source16, an LED (light emitting diode) array of a line type in which plural LED chips are arranged linearly on a substrate may be used. In the light source16formed from the LED array, a light conducting member, a diffusion plate, etc. (not illustrated) forming a part of the LED array are adjusted in angle and position such that a part of light emitted from the plural LED chips is directly output toward a reading position Pr, and another part of the light is output toward the reflector152. The light source16is disposed with its line direction (the direction along the linear arrangement of the LED chips) extending along an intersecting direction (horizontal scanning direction, or the direction that is perpendicular to the sheet surface ofFIG. 2) that is substantially orthogonal to the transport direction for the document9in the moving document reading mode. Therefore, the first carriage150is a structure in an elongated form extending along the horizontal scanning direction. The reflector152is adjusted in angle and position such that a part of the light emitted from the light source16is reflected in the direction of the reading position Pr.

The illumination unit15is moved to a reference position (home position) below the reading window portion14and kept stationary in the moving document reading mode, and controlled so as to reciprocally move over an area in the vertical scanning direction below the document platen11in the stationary document reading mode.

The light receiving section17is composed of a light receiving unit170that reads an image formed from the reflected light from the document9etc. obtained from the illumination unit15, and a reflection unit175that reflects the reflected light from the document9etc. obtained from the illumination unit15and guides the reflected light to the light receiving unit170.

The light receiving unit170is disposed inside the housing10at a position closer to an end portion opposite to an end portion of the document covering12at which the automatic document transport section13is disposed. The light receiving unit170includes a solid-state imaging device171that finally receives the reflected light from the document9etc., an imaging lens172that forms an image from the reflected light from the document9etc. to guide the image to the solid-state imaging device171, and so forth. As the solid-state imaging device171, a charge-coupled device (CCD) in which one-dimensional line sensors that generate red (R), green (G), and blue (B) color signals from input light are disposed in a set of three rows may be used. The solid-state imaging device171divides the received reflected light which has been formed into an image by the imaging lens172in accordance with the colors (R, G, B), and performs a photoelectric conversion to output image signals for the R, G, and B colors as information read from the document9(voltage signals).

The reflection unit175is of a movable type so that the reflection unit175reciprocally moves in the vertical scanning direction together with the illumination unit15in the stationary document reading mode. Specifically, the reflection unit175is composed of a second carriage (delivery member)176supported to reciprocally move in the vertical scanning direction, a second specular reflection plate177that receives reflected light from the first specular reflection plate153of the illumination unit15, and a third specular reflection plate178that receives reflected light from the second specular reflection plate177. The second specular reflection plate177and the third specular reflection plate178are mounted to the second carriage176. The second carriage176is guided by a rail (not illustrated) to reciprocally move. The rail is disposed inside the housing10to extend along the vertical scanning direction. The first specular reflection plate153of the illumination unit15and the second specular reflection plate177and the third specular reflection plate178of the reflection unit175are adjusted in angle, position, etc. such that document-reflected light (indicated by the double-dashed line inFIG. 2) reflected by the document9reaches the light receiving section17(and finally the solid-state imaging device171) in the case where the document9is present at the reading position Pr.

The reflection unit175is moved to the home position described above and kept stationary together with the illumination unit15in the moving document reading mode, and controlled so as to reciprocally move over an area in the vertical scanning direction below the document platen11in the stationary document reading mode. The reflection unit175is formed such that in the stationary document reading mode, in particular, the amount of movement of the second carriage176is half the amount of movement of the first carriage150so that the length (line indicated by the double-dashed line) of the optical path from the reading position Pr for the document9to the solid-state imaging device171is not varied during movement of the illumination unit15in the vertical scanning direction. That is, the illumination unit15and the reflection unit175form a reduced imaging optical system for the light receiving unit170because of the relationship in amount of movement between the first carriage150and the second carriage176.

The automatic document transport section13includes a document transport path18having a generally U-shaped path along which the document9taken from the document tray12ais transported through the reading position Pr, at which information on the document9being transported is read, to be ejected to the storage section12b.

The reading position Pr is set at a position substantially at the center, in the transport direction for the document9, of the reading window portion14having a planar rectangular shape and disposed on the upper surface portion of the housing10at a position closer to one end of the document platen11. The reading window portion14is disposed such that the longitudinal direction of the planar rectangular shape extends along the horizontal scanning direction.

The document transport path18is composed of a loading mechanism18aof a roller type of the like that takes in the document9placed on the document tray12a, one sheet after another, first to third transport roller pairs18bto18dthat transport the document9taken in by the loading mechanism18ato the reading position Pr, first and second eject roller pairs18eand18fthat transport the document9which has been read to be ejected to the storage section12b, transport guide members18gand18hthat form a transport path (space) for the document9transported by the document transport roller pairs and eject roller pairs to guide the document9along the transport path, and so forth. The first to third transport roller pairs18bto18dand the first and second eject roller pairs18eand18fare rotationally driven at a corresponding rotational speed such that the document9is transported at a predetermined transport speed in the document transport path18. A detection sensor Sn1 is disposed near the loading mechanism18ato detect the presence or absence of the document9on the document tray12a. A detection sensor Sn2 is disposed near the third transport roller pair18dto detect the passage of the document9being transported.

In the automatic document transport section13, as illustrated inFIGS. 2 and 3, a reading guide member19is disposed at a position between the third transport roller pair18dand the first eject roller pair18eand opposite to the reading window portion14. The reading guide member19guides the document9being transported along the document transport path18to the reading position Pr, and guides the document9which has passed through the reading position Pr in the ejection direction. The reading guide member19is provided with a background reflection section4disposed on a part of its arcuate lower surface portion facing the reading window portion14to serve as a background surface. An eject guide member18jis provided between the reading window portion14and the document platen11. The eject guide member18jguides the document9which has passed through the reading window portion14toward the document transport path18for ejection provided with the first eject roller pair18e.

The background reflection section (background surface)4reflects light emitted from the light source16of the illumination unit15so as to pass through the reading position Pr and then be received by the light receiving unit170(and finally the solid-state imaging device171) of the light receiving section17. The background reflection section (background surface)4is set so as to reflect an amount of the reflected light, when the document9is not present, that is greater than the amount of document-reflected light reflected by the document9. The phrase “when the document9is not present” refers to a time when the document9transported by the automatic document transport section13is not passing through the reading window portion14(reading position Pr), or a time when the document9is not actually present (background portion) when the document9is passing through the reading window portion14. The background reflection section (background surface)4according to the first exemplary embodiment is formed by affixing a reflection member41in the form of a film to a planar portion of a dented portion19aformed in a part of the lower surface portion of the reading guide member19. The background reflection section (background surface)4has a planar shape in the shape of an elongated belt extending in the horizontal scanning direction. The background reflection section4will be discussed in detail later.

The document reading device1has a function of automatically detecting end portions and the size of the document9and a function of detecting the amount of inclination of the document9during transport from information read from the background-reflected light and the document-reflected light received by the light receiving section17utilizing the difference (light amount difference) between the amount of the background-reflected light reflected from the background reflection section (background surface)4and the amount of the document-reflected light reflected from the document9. These functions are implemented by a read image processing section (not illustrated) of the document reading device1.

That is, for the function of detecting end portions of the document9, the amount of the background-reflected light from the background reflection section4is set to be greater than the amount of the document-reflected light as discussed above. The document9is different from the background reflection section4in angle with respect to the light source16and the light receiving section17. Thus, the relationship that the amount of the document-reflected light from the document9is less than the amount of the background-reflected light is established. As a result, the presence or absence of the document9at the reading position Pr may be detected on the basis of the amount of light reflected from the document9.

Specifically, the function of detecting end portions of the document detects the leading end, the rear end, and the left and right ends of the document9in the transport direction as follows. First, in the vertical scanning direction during reading, when a transition is made from a state in which the document9is not present at (has not reached) the reading position Pr to a state in which the document9is present at (has reached) the reading position Pr, the reflected light received by the light receiving section15is changed from the background-reflected light to the document-reflected light to be reduced in light amount. Thus, the position of the leading end of the document9is detected. When a transition is made from a state in which the document9is present at the reading position Pr to a state in which the document9is not present at (has passed through) the reading position Pr, on the other hand, the reflected light received by the light receiving section15is changed from the document-reflected light to the background-reflected light to be increased in light amount. Thus, the position of the rear end of the document9is detected. Meanwhile, in the horizontal scanning direction during reading, in substantially the same manner as in the vertical scanning direction, the positions of the left and right ends of the document9are detected in accordance with a reduction in light amount due to a change in reflected light received by the light receiving section15from the background-reflected light to the document-reflected light or an increase in light amount due to a change in reflected light received by the light receiving section15from the document-reflected light to the background-reflected light. The amount of inclination of the document9during transport (reading) is calculated from the result of detecting the positions of the end portions of the document9. In the first exemplary embodiment, the amount of inclination is calculated on the basis of the result of detecting the leading end and the left and right ends.

The detection of the size of the document9is performed along with the detection of the amount of inclination of the document9.FIG. 5schematically illustrates an example of the relationship between an image processing area read by the solid-state imaging device171of the light receiving section17and information on the document (read image).

The maximum width Wm of an image processing area173iin the horizontal scanning direction, which is substantially orthogonal to the transport direction C for the document9, is prescribed by the maximum light receiving width of the solid-state imaging device171. The length L of the image processing area173iin the vertical scanning direction, which is substantially parallel to the transport direction C for the document9, is defined by the reading time determined in correspondence with the state of transport of the document9. That is, reading of the length L in the vertical scanning direction is started at a time point t1 at which the detection sensor Sn2 detects the passage of the leading end of the document9during transport, and ended at a time point t2 at which a predetermined time has elapsed since the detection sensor Sn2 detects the passage of the rear end of the document9during transport. The length L in the vertical scanning direction may be set to a value fixed in accordance with the size of the document9. InFIG. 5, reference symbol90idenotes a read image for the document9. The read image90ifor the document9illustrated in the drawing is obtained from the document9transported as inclined by an angle of α (amount of inclination) with respect to the transport direction C. A portion of the image processing area173iother than the read image90ifor the document9corresponds to a background image40iformed by the reflected light reflected from the background reflection section4.

When the (provisional) leading end and the left and right ends of the document9are discriminated in the image processing area173ias discussed earlier, information on the leading end discriminated from a time point t3 is compiled to discriminate a predicted leading end Es (the position and the length of the leading end Es as a continuous element). A width Lw of the document9in the transport direction C is computed and detected (Lw=a×b) on the basis of the number of pixels a of the solid-state imaging device171from one end to the other end of the predicted leading end Es of the document9and the length b in the document width direction per one pixel. Subsequently, when the predicted leading end Es is discriminated, the inclination angle α of the predicted leading end Es with respect to the transport direction C is computed and detected. When the (provisional) rear end of the document9is discriminated in the image processing area173i, information on the rear end discriminated from a time point t4 is compiled to discriminate a predicted rear end Ee (the position and the length of the rear end Ee as a continuous element). Consequently, the time ts required for the passage of the document9is acquired from the time point t1 and the time point t2 at which the provisional leading end and the provisional rear end, respectively, are detected in the read image90ifor the document9, and the length Ln of the document9in the transport direction C is computed and detected (Ln=V×ts) on the basis of the time ts and the transport speed V for the document9in the document transport path18.

In the case where the read image90ifor the document9read by the solid-state imaging device171is inclined (by an inclination angle α), the inclined read image90i(data) is rotated such that the inclination angle α becomes zero, and corrected into a read image for the document9with no inclination. The process of correcting an amount of inclination is implemented as an electronic inclination correction unit.

<Operation of Image Formation Apparatus>

Next, a basic operation of the image formation apparatus100will be described separately for a basic operation of the document reading device1and a basic operation of the image forming section2.

In the document reading device1, first, when the user places the document9on either the document platen11or the document tray12a, and operates the touch panel111and the operation button112on the control panel110to give a command to read the document, an operation for reading the document9is started. When the command to read the document is received, the stationary document reading mode is automatically selected in the case where the detection sensor Sn1, which detects the presence or absence of the document9on the document tray12a, detects the absence of the document9, and the moving document reading mode is automatically selected in the case where the detection sensor Sn1 detects the presence of the document9.

In the case where the stationary document reading mode is selected, the light source16of the illumination unit15starts emitting light, and the illumination unit15and the reflection unit175are driven by the first carriage155and the second carriage176, respectively, to start moving in the vertical scanning direction below the document platen11.

Consequently, the document9placed on the document platen11is illuminated by the illumination unit15which is moving, and the document-reflected light reflected by a surface of the document9facing the document platen11is reflected sequentially by the first specular reflection plate153, the second specular reflection plate177, and the third specular reflection plate178to thereafter be received by the light receiving section17. In the light receiving section17, an image is formed on the solid-state imaging device171through the imaging lens172in accordance with the document-reflected light, and output to the read image processing section or the like as information read from the document. The read image processing section samples an analog image signal (R, G, B) obtained from the solid-state imaging device171to hold the resulting signal, amplifies the signal, performs an A/D conversion on the signal to obtain digital image data (R, G, B), and so forth.

In the case where the moving document reading mode is selected, on the other hand, the illumination unit15and the reflection unit175are driven by the first carriage155and the second carriage176, respectively, to move to be stationary at the home position below the reading window portion14, and the light source16of the illumination unit15starts emitting light. A part of the light emitted from the light source16of the illumination unit15is directly radiated to the reading position Pr in the reading window portion14, and another part of the light is reflected by the reflector152to be radiated to the reading position Pr in the reading window portion14. Concurrently, the automatic document transport section13is driven to transport the document9placed on the document tray12a, one sheet after another, through the document transport path18to pass through the reading position Pr in the reading window portion14.

Consequently, as illustrated inFIGS. 2 and 4, the document9passing through the reading position Pr in the reading window portion14is illuminated by the illumination unit15which is stationary at the home position, and the document-reflected light reflected by a portion of the surface of the document9passing through the reading position Pr at that time is reflected sequentially by the first specular reflection plate153, the second specular reflection plate177, and the third specular reflection plate178to thereafter be continuously received by the light receiving section17. In the light receiving section17, an image is formed on the solid-state imaging device171through the imaging lens172in accordance with the document-reflected light, and output to the read image processing section or the like as information read from the document. After that, the sheets of the document9which have passed through the reading window portion14are sequentially ejected to the storage section12bthrough the document transport path18to be stored.

In the document reading device1, in the case where the mixed document size button112ais selected when a command to read the document is given in the moving document reading mode, for example, the read image processing section (not illustrated) detects end portions, the size, and the amount of inclination of the document9as discussed earlier. In this event, end portions, the size, and the amount of inclination of the document9are detected for each sheet of the document9transported from the document tray12aby the automatic document transport section13. In the case where the document9is inclined, the electronic inclination correction discussed earlier is performed on the information read from the document9.

Next, in the image forming section2, the following image forming operation is performed on the basis of the information read from the document9received from the document reading device1.

In an image processing section (not illustrated) of the image forming section2, first, the read information received from the document reading device1is modulated into an image signal for each of the Y, M, C, and K colors, which is transmitted to the exposure device23of the corresponding image forming unit20(Y, M, C, K). In each of the image forming units20(Y, M, C, K), then, the photoreceptor drum21which starts rotating in the direction indicated by the arrow is charged by the charging device22to a predetermined potential, and thereafter an electrostatic latent image with the predetermined potential is formed on the charged surface of the photoreceptor drum21by light exposure based on the image signal from the exposure device23.

Next, the electrostatic latent image formed on the photoreceptor drum21is developed by the corresponding developing device24(Y, M, C, K) into a toner image with a predetermined color. Subsequently, the toner image formed on the photoreceptor drum21of the image forming unit20(Y, M, C, K) is subjected to a first transfer performed by the first transfer device25onto the intermediate transfer belt26a, which rotates in the direction indicated by the arrows, in the intermediate transfer unit26, and thereafter transported by the intermediate transfer belt26ato the second transfer position facing the second transfer device26d.

In the paper feed section3, meanwhile, along with the second transfer operation for the toner image performed by the image forming section2, the recording paper30of a predetermined size, for example, stored in one of the plural storage members31A and31B is fed to be transported to the second transfer position in the image forming section2through the supply/transport path28. Then, at the second transfer position, the toner image on the intermediate transfer belt26ais subjected to a second transfer performed by the second transfer device26donto the recording paper30.

After that, the recording paper30to which the toner image has been transferred through the second transfer is introduced into the fixing unit27, and ejected to the eject/storage section102after the toner image is fixed to the recording paper30. Consequently, a predetermined image formed from the toners is formed on one surface of the recording paper30. The image forming operation described above is repeated in the same manner a number of times corresponding to the number of sheets of the document9or the number of images to be formed.

<Detailed Configuration of Document Reading Device>

In the image formation apparatus100including the document reading device1, in the case where an image is formed on the recording paper30by the image forming section2on the basis of information read from the document9from the document reading device1, the following image defect may be caused.

In an image portion91of the document9formed on the recording paper30, as illustrated inFIG. 8, a blur95may occur in the image portion91of the document9(and also on the read image), which should be white, at an end portion of the document9in a direction substantially orthogonal to the transport direction C for the document9in the document reading device1(at an end portion of the document9in the width direction during transport). The blur95occurs at an end portion of the document9in the horizontal scanning direction during reading.

According to the study conducted by the inventors, the occurrence of the blur95is mainly caused by an unevenness in brightness (luminance) of the light source16in the illumination unit15(presence of a high-brightness portion with a relatively high brightness in a part of the light source).

The presence of an unevenness in brightness (a high-brightness portion) in the light source16may vary the amount of background-reflected light from the background reflection section4received by the solid-state imaging device171of the light receiving section17, and in particular, may make the amount of light at a portion of the background-reflected light corresponding to the high-brightness portion relatively greater. Consequently, a saturated output voltage may be reached and a signal charge generated by a photoelectric conversion may overflow in a portion of pixels of the solid-state imaging device171corresponding to the portion of the background-reflected light with a greater amount of light, and the signal charge which has overflowed may be diffused into an adjacent portion of pixels. As a result, when switching is made in the light receiving section17from reception of the background-reflected light to reception of the document-reflected light, an end portion of the document9in a direction substantially orthogonal to the transport direction C may be recognized as having a luminance that is different from its actual luminance under the effect of the overflowing charge. That is, the presence of a high-brightness portion in a part of the light source16may cause the light receiving section17to receive such an amount of light that may affect information read from a document. If the end portion of the document9recognized as having a different luminance is in a white portion, a blackish blur95that bleeds into the white portion may be formed. If the end portion of the document9recognized as having a different luminance is in a colored image portion, a whitish blur95that bleeds into the image portion may be formed.

In the document reading device1according to the first exemplary embodiment, the background reflection section (background surface)4is formed to reflect an amount of light that is less than the amount of specularly reflected light that would be reflected by a specular surface. Therefore, the background reflection section4is formed to reflect an amount of light that is less than the amount of light that would be reflected by a specular surface, in addition to being basically formed to reflect an amount of light, when the document9is not present, that is greater than the amount of document-reflected light reflected by the document9as discussed earlier.

The phrase “amount of document-reflected light” indicates the amount of light that would be reflected by a white portion of the document. The configuration enables end portions of the document etc. to be detected using the difference between the amount of the background-reflected light and the amount of the document-reflected light. The term “specularly reflected light” indicates reflected light obtained when incident light is mostly regularly reflected by a specular reflection plate.

The background reflection section4is a reflection section (background surface) with its reflection performance reduced compared to the specular reflection plate while keeping the amount of the background-reflected light greater than the amount of the document-reflected light. Thus, the background reflection section4may be a reflection section with reflection characteristics in which light from the light source16is slightly diffusely reflected (irregularly reflected) to reduce the reflectivity. Consequently, even in the case where a high-brightness portion is present in a part of the light source16, light from the light source16with an unevenness in brightness is slightly diffusely reflected by the background reflection section4, and the light receiving section17receives the light in a reduced light amount. As a result, a saturated output voltage is not reached in a portion of pixels in a part of the solid-state imaging device171in the light receiving section17.

More specifically, the background reflection section4having such reflection performance (characteristics) is formed such that a digital image signal obtained by converting an electrical signal obtained from the solid-state imaging device171of the light receiving section17through a photoelectric conversion has a value of more than 255, or more than about 255, and equal to or less than 800, or equal to or less than about 800, when represented in tone levels. If the electrical signal has a tone level of equal to or less than 255, or equal to or less than about 255, the difference between the amount of background-reflected light and the amount of document-reflected light from the white portion of the document9is so small that the end portions of the document9discussed above may not be detected. If the tone level is more than 800, or more than about 800, on the other hand, a blur may easily occur.

FIG. 6illustrates the result of a test conducted to examine the luminance of background-reflected light and the presence or absence of occurrence of a blur at the time when various reflection members are used to form the background reflection section4.FIG. 7illustrates the details of the reflection members used in the test ofFIG. 6.

In order to obtain the luminance of the background-reflected light, light from the light source16formed from a white LED array with little unevenness in brightness is reflected by the background reflection section4formed from various reflection members in the document reading device1. The resulting background-reflected light is received by the light receiving section17formed from a charge-coupled device (CCD) of a three-line type. Analog electrical signals for three colors (R, G, B) obtained from the charge-coupled device (CCD) are quantized by a quantization circuit (quantization section) in the read image processing section (not illustrated), and converted into 8-bit digital image information through an A/D conversion. The luminance of the digital image information is represented in 256 tone levels. In this case, the luminance of the document-reflected light from the white portion of the document9is set to have a tone level of about 210. Consequently, if the background-reflected light from the background reflection section (background surface)4has a tone level of more than 255, or more than about 255, the maximum amplitude of the wavelength of the document-reflected light reflected by the document9is exceeded.

In this event, the background-reflected light with a tone level of more than “255”, or more than about “255”, is treated as an exception, and the light is received with a neutral density (ND) filter that reduces light to one-fourth (25%), or about one-fourth, disposed before the charge-coupled device (CCD) to examine the value in 256 tone levels. That is, if the tone level value measured with the ND filter disposed is “250”, for example, a value of “1000” is taken as the measured value of the luminance.

In order to obtain the presence or absence of occurrence of a blur, the document9is read by the document reading device1which uses a white LED array with a high-brightness portion provided in a part of the array as the light source16, and an image is formed on the recording paper30by the image forming section2of the image formation apparatus100on the basis of the read information. As the document9, a document with a colored (black) image portion21provided all over the surface is used. The document9and the recording paper30having the same size (for example, A4 size) are used.

It is found from the result illustrated inFIG. 6that a blur occurs for reflection members with the luminance of the background-reflected light having a value of more than “800”, or more than about “800”. At this value, the luminance of the background-reflected light obtained from the background reflection section (background surface)4when the amount of light from the light source16is reduced to one-fourth (25%), or about one-fourth, is less than the luminance of the document-reflected light obtained when light in a normal (non-reduced) amount is radiated from the light source16to the document9. The maximum tone level of the background-reflected light from the background reflection section (background surface)4is preferably a value that is equal to or less than three times, or about three times, the maximum amplitude of the wavelength of the document-reflected light reflected by the document9. It is found in the test that the detection accuracy of the function of detecting an end portion of a document discussed earlier starts reducing in the case where the luminance of the background-reflected light has a value that is less than 255, or less than about 255, and that is close to that of the luminance of the document-reflected light from the white portion of the document9, and that it is difficult to detect an end portion of a document in particular when the luminance of the background-reflected light is reduced to a value of around 210. With all things considered, it is found that occurrence of a blur may be suppressed in the case where the luminance of the background-reflected light is in the range of more than 255, or more than about 255, and equal to or less than 800, or equal to or less than about 800. More strictly, occurrence of a blur may be reliably suppressed in the case where the luminance of the background-reflected light is in the range of “equal to or more than 300 and equal to or less than 700”.

In the test, the inventors attempt to reduce the amount of light to be emitted from the light source16itself in the document reading device1as a method of suppressing occurrence of a blur. In this case, however, the image quality of information read from a document (a read image) is degraded, and the method is found not to be appropriate.

Consequently, it is found to be effective to reduce the reflection characteristics (reflectivity) of the background reflection section4, which reflects light from the light source16toward the light receiving section17, as a method of suppressing occurrence of a blur even in the case where an unevenness in brightness due to a high-brightness portion is present in a part of the light source16. That is, the background reflection section (background surface)4slightly diffuses (irregularly reflects) incident light, and therefore is effective in reducing the unevenness in brightness in the light source16described above, preventing a phenomenon that the saturated output voltage of the charge-coupled device (CCD) is reached.

In the first exemplary embodiment, the background reflection section (background surface)4is formed by affixing an aluminum sheet (matte film) subjected to surface roughening illustrated inFIG. 7to the dented portion19aof the reading guide member19as the reflection member41. The luminance of the background-reflected light from the background reflection section4may have an average value of about 527.5 (=(800+255)/2), the value being the center value of the range of “more than 255, or more than about 255, and equal to or less than 800, or equal to or less than about 800” described above. The specular surface film (aluminum foil sheet) illustrated inFIG. 6etc. has a reflectivity of about 90%. Therefore, it is estimated that the reflection member forming the background reflection section4may have a reflectivity of “about 50%”, which is about half the reflectivity of the specular surface film, in order to reliably obtain a good result.

Other Embodiments

In the first exemplary embodiment, an LED array of a line type, which is a point source of light, is used as the light source16in the document reading device1. However, other types of light source may also be used (such as a cold cathode fluorescent lamp (CCFL), a xenon lamp (Xe lamp), a halogen lamp, and a lamp in which an LED that emits strong light is disposed at each end portion of a light conducting member in the horizontal scanning direction to be directed inward, and light from each LED is guided through the inside of the light conducting member to be diffused in the horizontal scanning direction to be output, for example). For the light source16and the light receiving section17, a light emitting/receiving unit (for example, a contact image sensor (CIS)) formed by integrating the light source16and the light receiving section17(such as a light receiving lens and a CMOS) may also be used.

In the first exemplary embodiment, in addition, the reflection member41in the form of a film is affixed to a part of the reading guide member19as the background reflection section4in the document reading device1. However, a reflection surface portion (background surface) having necessary reflection characteristics may be directly formed on the lower surface of the reading guide member19facing the reading window portion14, for example.

In the first exemplary embodiment, further, the document reading device1is combined with the image formation apparatus100to be used. However, the document reading device1may be formed to be used singly (as a scanner), or formed to function as a document reading unit of a facsimile, for example.

It is only necessary that the image formation apparatus100should be able to form an image on the basis of information on a document read by the image reading device1, and the image forming method employed by the image forming section, the configuration and the presence or absence of an intermediate transfer, and so forth are not specifically limited. Examples of the image forming method include an inkjet recording method.