Image reading apparatus and control method therefor, as well as storage medium

An image reading apparatus capable of increasing the detection accuracy of the size of an original and eliminating the need for an image sensor dedicated to detection of the size of an original. A first reading unit has a first light source disposed on one side of a conveyance path of an original for emitting light to one surface of the original. A second reading unit has a second light source disposed on the other side of the conveyance path for emitting light to be received by the first reading unit, an optical opening for causing the light emitted from the second light source and subsequently received by the first reading unit to pass therethrough toward the first reading unit. The original is detected on the basis of the resultant output of the first reading unit upon receipt of the light emitted from the second light source.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image reading apparatus, such as a scanner for reading the image of an original, and a control method therefor, as well as a storage medium.

2. Description of the Related Art

When reading the image of an original, a standardized size corresponding to the size of the original or the like is specified as a reading size for an image reading apparatus such as a scanner or the like. On the other hand, there is a growing demand for image reading of batch of originals in which originals of different sizes are mixed. Accordingly, there has been proposed an image reading apparatus having a function of automatically discriminating the size of an original being read.

This discrimination function is preferably used for performing image reading of batch of originals in which originals of different sizes are mixed. The discrimination function is not limited to this application but is effectively used also in a case where an original of a standardized size is read so as to eliminate the need for such efforts as selecting a size when reading an image. In general, the inherent color of an original is white or substantially white. Hence, there is known a method for detecting the image size by changing a background member arranged opposite to an image sensor to a black-colored background member and detecting a black part included in periphery of the read image data.

As an image size detecting method performed in a case where the color of a background member is set to white or substantially white, there has been proposed a method for discriminating the size of an original using a shadow produced by illumination (see Japanese Laid-Open Patent Publication (Kokai) No. 2001-285585, for example). In addition, there has been disclosed a configuration in which an illumination source and an image sensor are disposed opposite to each other across a conveyance path of originals, in order to detect the skew of an original (see Japanese Laid-Open Patent Publication (Kokai) No. H06-339007). Furthermore, there has been disclosed a method in which a read image based on reflected light and a transmissive image based on transmitted light are obtained using one illumination source and two image sensors arranged on both sides of the conveyance path of originals, thereby allowing removal of a show-through image developed in the read image using the transmissive image data (see Japanese Laid-Open Patent Publication (Kokai) No. 2002-281257, for example).

In Japanese Laid-Open Patent Publication (Kokai) No. 2001-285585 described above, however, since the size of an original is detected using information on the shadow produced by illumination, the accuracy of original size detection may degrade due to false operation if any black part is present in the outermost area of the original.

In addition, according to the methods disclosed in Japanese Laid-Open Patent Publication (Kokai) No. H06-339007 described above, though it is possible to identify the size of an original, there arises the need to arrange a dedicated image sensor or sensors, thus leading to an increase in the size and cost of an image reading apparatus. In addition, the methods disclosed in Japanese Laid-Open Patent Publication (Kokai) No. 2002-281257 described above, does not intend to identify the size of an original.

SUMMARY OF THE INVENTION

It is an object of present invention to provides an image reading apparatus, and a control method therefor, as well as a storage medium, capable of increasing the detection accuracy of the edge of an original. It is another object of present invention to eliminate the need for an image sensor dedicated to detection of the edge of an original, to thereby realize the downsizing of the image reading apparatus. It is still another object of present invention to realize the cost reduction of the image reading apparatus.

According to a first aspect of the present invention, there is provided an image reading apparatus comprising: a first reading unit disposed on one side of a conveyance path of an original and having a first light source for emitting light to one surface of the original, and adapted to receive the light emitted from the first light source and subsequently reflected at the one surface of the original and adapted to read an image of the original; a second reading unit disposed on the other side of the conveyance path and having a second light source for emitting light to be received by the first reading unit, an optical opening for causing the light emitted from the second light source and subsequently received by the first reading unit to pass therethrough toward the first reading unit, and a reference member disposed so as to be movable between a position at which the optical opening is closed and a position at which the optical opening opens and to be read by the first reading unit, and adapted to receive the light emitted from the second light source and subsequently reflected at the other surface of the original and adapted to read the image of the original; and a control unit adapted to provide a control of detecting the original on the basis of the resultant output of the first reading unit upon receipt of the light emitted from the second light source.

According to a second aspect of the present invention, there is provided an image reading apparatus comprising: a first reading unit disposed on one side of a conveyance path of an original and having a first light source for emitting light to one surface of the original, and adapted to receive the light emitted from the first light source and subsequently reflected at the one surface of the original and adapted to read an image of the original; a second reading unit disposed on the other side of the conveyance path having a second light source for emitting light to be received by the first reading unit, an optical opening for causing the light emitted from the second light source and subsequently received by the first reading unit to pass therethrough toward the first reading unit, and a reference member to be read by the first reading unit, and adapted to receive the light emitted from the second light source and subsequently reflected at the other surface of the original and adapted to read the image of the original; a moving unit adapted to move at least one of the first reading unit and the second reading unit so as to change a relative position of the first reading unit and the second reading unit; and a control unit adapted to control the moving unit to change the relative position between one relative position at which the optical opening is opposed to the first reading unit and the other relative position at which the reference member is opposed to first reading unit, and adapted to provide a control of detecting the original on the basis of the resultant output of said first reading unit upon receipt of the light having passed through said optical opening.

According to a third aspect of the present invention, there is provided an image reading apparatus comprising: a reading unit disposed on one side of a conveyance path of an original and having a first light source for emitting light to one surface of the original, and adapted to receive the light emitted from the first light source and subsequently reflected at the one surface of the original and adapted to read an image of the original; a second light source disposed on the other side of the conveyance path for emitting light to be received by the reading unit; a reference member disposed on an optical path from the second light source to the reading unit so as to cause the light emitted by the second light source to pass therethrough and to be read by the reading unit; and a control unit adapted to provide a control of detecting the original on the basis of the resultant output of the reading unit upon receipt of the light emitted from the second light source and subsequently having passed through the reference member.

According to a fourth aspect of the present invention, there is provided an image reading apparatus comprising: a reading unit disposed on one side of a conveyance path of an original and having a first light source for emitting light to one surface of the original and adapted to receive the light emitted from the first light source and subsequently reflected at the one surface of the original and adapted to read an image of the original; a second light source disposed on the other side of the conveyance path for emitting light to be received by the reading unit; a reference member disposed on an optical path from the second light source to the reading unit so as to be read by the reading unit; a black-colored member disposed so as to overlap with the reference member and formed of a light transmissive black material; and a moving unit adapted to move the reference member only or both of the reference member and the black-colored member, such that the reference member or the black-colored member is located at a position for blocking the light of the second light source.

According to a fifth aspect of the present invention, there is provided an image reading apparatus comprising: a reading unit disposed on one side of a conveyance path of an original and having a first light source for emitting light to one surface of the original, and adapted to receive the light emitted from the first light source and subsequently reflected at the one surface of the original and adapted to read an image of the original; and a second light source disposed on the other side of the conveyance path for emitting light to be received by the reading unit; a control unit adapted to provide a control of causing the second light source to emit the light except a period of time during which the reading unit receives the light emitted from the first light source to the original and adapted to provide a control of detecting the original on the basis of the resultant output of the reading unit upon receipt of the light emitted from the second light source.

According to a sixth aspect of the present invention, there is provided a method for controlling an image reading apparatus comprising a reading unit disposed on one side of a conveyance path of an original and having a first light source for emitting light to one surface of the original, and adapted to receive the light emitted from the first light source and subsequently reflected at the one surface of the original, and adapted to read the image of the original; and a second light source disposed on the other side of the conveyance path to emit light to be received by the reading unit, wherein the control method provides a control of controlling the second light source to emit the light except a period of time during which the reading unit receives the light emitted from the first light source to the original, and provides a control of detecting the original on the basis of the resultant output of the reading unit upon receipt of the light emitted from the second light source.

According to a seventh aspect of the present invention, there is provided a computer-readable storage medium storing a program for causing a computer to implement a method for controlling an image reading apparatus comprising a reading unit disposed on one side of a conveyance path of an original and having a first light source for emitting light to one surface of the original, and adapted to receive the light emitted from the first light source and subsequently reflected at the one surface of the original, and adapted to read the image of the original; and a second light source disposed on the other side of the conveyance path to emit light to be received by the reading unit, wherein the control method provides a control of controlling the second light source to emit the light except a period of time during which the reading unit receives the light emitted from the first light source to the original, and a control of detecting the original on the basis of the resultant output of the reading unit upon receipt of the light emitted from the second light source.

According to the present invention, it is possible to increase the detection accuracy of the size of an original and eliminate the need for an image sensor dedicated to detection of the size of the original, to thereby realize the downsizing and the cost reduction.

Further features and advantages of the present invention will become apparent from the following detailed description of exemplary embodiments with reference to the attached drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1is a cross-sectional view which is useful in explaining an image reading apparatus in accordance with a first embodiment of the present invention.

An image reading apparatus in accordance with a first embodiment of the present invention is configured, as shown inFIG. 1, in such a manner that when an original table7rises and then an original8loaded on the original table7abuts to a pickup roller6, the original8is picked up by the pickup roller6and fed by a feed roller4.

If the pickup roller6picks up two or more originals8at a time, a separation roller11separates the originals to feed them one by one. Then, an image on a front surface (one surface) of the original8is read by a scanning assembly (reading unit)1aand an image on a rear surface (the other surface) is read by a scanning assembly (reading unit)1b. The scanning assemblies1aand1bare located in positions substantially opposite to each other across a conveyance path10of the originals8. However, a reading position for the front surface of the original8and a reading position for the rear surface thereof are away from each other by a predetermined distance in the conveyance direction of the original8.

At the scanning assembly1a, scattered reflection light from the original8illuminated by a light source110(seeFIG. 2) is caused by imaging optics to focus on an image sensor130(seeFIG. 2). Then, an image processor of a controller14generates digital data on the basis of an electric signal photoelectrically converted and output by an image sensor130, and subsequently subjects the digital data to image-processing to thereby obtain the image data.

Here, in the present embodiment, the outline of an original is detected using the image sensor130and the imaging optics120of the scanning assembly1a, and also using a light source210(seeFIG. 2) of the scanning assembly1b, though details thereof are described later. Output signals sf and sb from the scanning assemblies1aand1bare output to the controller14.

The original having passed through the scanning assemblies1aand1bis conveyed through the conveyance path10by conveying roller pairs3and subsequently is discharged to a discharge tray9by a discharge roller5

When all of the originals loaded on the original table7are fed out, the original table7lowers to return to a home position. Moreover, an upper assembly2on which the conveyance roller3, the feed roller4and the scanning assembly1aare mounted is openable and closable around a hinge13with respect to a lower assembly12.

When the upper assembly2is opened, the conveyance roller3, the scanning assembly1a, the scanning assembly1band the conveyance path10can be cleaned directly by operator. In addition, even if the original8is jammed in the conveyance path10, the jammed original can be easily taken out by opening the upper assembly2. The opening/closing of the upper assembly2is sensed by an open/close sensor (not shown). After checking that the upper assembly2is closed, the image reading apparatus enters a standby mode.

Next, the scanning assemblies1aand1bwill be described in detail with reference toFIG. 2.

The scanning assembly1ahas a cover member101, formed from transparent glass, resin or the like, mounted on a frame100on a side of the conveyance path10. The frame100has arranged therein the light source110, the imaging optics120and the image sensor130. The image sensor130is composed of a light receiving element132and a PCB131equipped therewith, converts the reflected light from the original into an output signal, and outputs the signal.

The scanning assembly1bhas a cover member201, formed from transparent glass, resin or the like, mounted on a frame200on a side of the conveyance path10. The frame200has arranged therein a light source210, imaging optics220and an image sensor230. The image sensor230is composed of a light receiving element232and a PCB231equipped therewith, converts the reflected light from the original into an output signal, and outputs the signal.

In addition, the frame200has an optical opening202formed at a portion thereof facing the conveyance path10, so as to be positioned on an optical axis121of the imaging optics120of the scanning assembly1a. A part of light from the light source210passes through the optical opening202and enters the imaging optics120of the scanning assembly1a. Then, the controller14performs detection process of the original8based on the resultant output of the light receiving element132upon light reception, i.e., based on an output signal provided by the photoelectric conversion element132upon receiving the light from the light source210.

The present embodiment is exemplified by the fact that the light source210of the scanning assembly1barranged at a position substantially opposite to the light receiving element132of the scanning assembly1a, but not limited thereto. For example, a light emitting element may be arranged at a position other than the position opposite to the light receiving element132and subsequently light from the light emitting element may be guided into the light receiving element132through a light guide (not shown). The light emitting element and the light guide described above may configure a second light source according to the present invention.

Furthermore, the present embodiment is exemplified by the fact that a part of light from the light source210passes through the optical opening202to directly enter the imaging optics120of the scanning assembly1a, but not limited thereto. For example, as shown inFIG. 3, a reflecting surface203is disposed on the frame200, so that a part of the light from the light source210is reflected by the reflecting surface203and enters the imaging optics120.

FIG. 4is a timing chart for the output signal generation of the scanning assembly1ainFIG. 1or3.

First, as shown inFIG. 4, a three-color light source110composed of, for example, LEDs is turned on, one color at a time, in the order of R, G and B. Consequently, output signals respectively corresponding to the read information on red, green and blue are sequentially output from the image sensor130during a time “t”. Thus, a single line of the read image is obtained based on the output signals.

On the other hand, there is provided a wait time “tw” before the start of reading the next line, by shortening the time “t” with respect to a time “T” required to convey the original8by a single line. Thus, the light source210of the opposed scanning assembly1bis turned on at a time “OX” during this period of time “tw”. If the original8does not block the light at this time, the light from the light source210passes through the conveyance path and reaches the imaging optics120. If the light is blocked by the original8, only a small quantity of light having transmitted through the original8reaches the imaging optics120.

That is, the outline of the original8is projected onto the image sensor130through the imaging optics120like a silhouette. The image sensor130reads this image and provides an output signal. The controller14obtains a single line of a transmissive image on the basis of this output signal. Subsequently, the scanning assembly1astarts reading the next line.

Note that if the controller14determines that all pixels in a given single line of the transmissive image have brightness levels higher than a predetermined threshold, then it recognizes that the original8does not exist at a reading position when reading this line. Also note that if the controller14determines that pixels having brightness levels lower than the threshold exist in the transmissive image, then it recognizes that pixels which have undergone such a change in brightness compared with preceding pixel passing through the threshold, for example, as outline pixels of the original. Repeating such processing as described above enables the controller14to obtain information on the read image and on the outline of the original across the full width and full length of the original8.

Moreover, an LED to be turned on at the time “OX”, among the red, green and blue LEDs of the light source210, is preferably changed in a predetermined sequence, or at random. This makes it possible to prevent a specific LED, among the red, green and blue LEDs, from lighting over a too long period of time, thereby extending the service life of the light source.

By cutting off a background image present around the read original image from the read image on the basis of information on the outline of the original8thus acquired, it is possible to obtain an image favorably consistent with the outline of the original8.

The above-described image processing has been explained by taking, as one example, a case in which the image processing is performed by the controller14of the image reading apparatus. Alternatively, information on the read image and on the outline of the original may be transferred to a host computer connected through a cable or the like and subsequently a part or the whole of the above-described image processing may be performed by the host computer to which the information has been transferred. Still alternatively, information on the transmissive image may also be transferred to the host computer and subsequently information on the outline of the original may be acquired by the host computer.

As described heretofore, according to the present invention, the outline of the original8is detected on the basis of its transmissive image, thereby increasing the detection accuracy of the original8.

In addition, it is possible to obtain the transmissive image of the original8by utilizing the light source210of the scanning assembly1bfor reading the image on the rear surface image of the original8, thereby eliminating the need for another image sensor dedicated to detection of the size of the original or an additional light source, thereby making it possible to realize the downsizing and the cost reduction.

The present embodiment is exemplified by the fact that the scanning assemblies1aand1bare arranged so as to read both surfaces of the original8, only either one of the scanning assemblies1aand1bmay be arranged if the image reading apparatus does not have a function of reading both surfaces of the original8. In this case, a light source (second light source) used exclusively for obtaining the transmissive image of the original is arranged at a position opposite to the scanning assembly1a(or1b) across the conveyance path10thereof.

Furthermore, the present embodiment is exemplified by the fact that the optical opening202is disposed on the scanning assembly1b; however, the optical opening may be disposed on a side of the scanning assembly1a. Alternatively, as shown inFIG. 5, the optical openings102and202may be respectively disposed on the scanning assemblies1aand1b. Still further, as shown inFIG. 6, the reflecting surfaces103and203are respectively disposed on the frames100and200so that a part of light from the light sources110and210are respectively reflected by the reflecting surfaces103and203and enter the imaging optics220and120.

If the optical openings102and202are respectively disposed on the scanning assemblies1aand1band information on the outline of the original8is acquired separately for the front and rear surfaces thereof, it is possible to perform a process of clipping the images of the original from each of the read front and rear side images thereof without being affected by errors in the located positions of the scanning assemblies1aand1b. In addition, it is possible to perform such a process of clipping the images of the original as described above concurrently with the simultaneous reading of both surface images while conveying the original once.

Furthermore, if this configuration is provided in both scanning assemblies, even faster image reading is possible by operating the other scanning assembly as a sensor dedicated to detection of the outline of the original when reading arbitrarily selected one of the front and rear surfaces.

Next, a description will be made of an image reading apparatus according to a second embodiment of the present invention, with reference toFIG. 7. An image reading apparatus according to the present embodiment is identical in configuration with the above-described first embodiment, so that similar elements are denoted by same reference numerals in the drawings, and the description thereof will be omitted.

In the present embodiment, cold-cathode fluorescent lamps suitable for use in continuous lighting are used as the light sources110and210of scanning assemblies1aand1b.

In this case, control needs to be performed in such a manner that light reaches to the imaging optics120of the scanning assembly1afrom the optical opening202of the scanning assembly1bonly when necessary, since the light source210is used in continuous lighting.

Hence, in the present embodiment, a shutter240is provided between the light source210and the optical opening202, as shown inFIG. 7, so that the light of the light source210reaches the imaging optics120from the optical opening202only during a period of detecting information on the outline of the original8. This shutter240is controlled by a controller14. As the shutter240, a liquid-crystal shutter or the like is preferred from the viewpoint of response speed. In addition, the image reading apparatus may be configured in such a manner that as shown inFIG. 8, light emitted from the light source210enters the imaging optics120through a reflecting surface203disposed in the frame200. In this case, the rest of the configuration and other operations/advantages are the same as those of the above-described first embodiment.

Although in the present embodiment, the optical opening202and the shutter240are disposed on the scanning assembly1b, the optical opening202and the shutter240may be alternatively disposed on the scanning assembly1a.

Furthermore, as shown inFIG. 9, optical openings102and202and shutters140and240may be respectively disposed in the scanning assemblies1aand1b. It is preferable to provide the aforementioned shutter also in the above-described first embodiment if both surfaces of the original need to be read simultaneously. Still further, the image reading apparatus may be configured in such a manner that as shown inFIG. 10, reflecting surfaces103and203are respectively disposed in the frames100and200, so that parts of light from the light sources110and210are respectively reflected by the reflecting surfaces103and203and enter the imaging optics220and120.

Next, a description will be made of an image reading apparatus according to a third embodiment of the present invention, with reference toFIG. 11. An image reading apparatus according to the present embodiment is identical in configuration with the above-described first embodiment, so that similar elements are denoted by same reference numerals in the drawings, and the description thereof will be omitted.

In the present embodiment, LEDs are used as the light sources110and210of scanning assemblies1aand1band light guides150and250are used, in order to guide the light emitted from an LED across the full width of the original8.

InFIG. 11, the LEDs (not shown) as light sources are disposed on the near side or far side of the light guides150and250with respect to the page surface. The light guides150and250have light-guiding portions151and251for guiding light across the full reading width of the image sensors130and230and emitting portions152and252for emitting light toward the original8.

In the present embodiment, the light-guiding portion251on the scanning assembly1bis disposed on the optical axis121of the imaging optics120of the scanning assembly1aacross the optical opening202of the scanning assembly1b. The light-guiding portions151and251are designed to guide and emit almost all of light beams entering from the LEDs to the emitting portions152and252, and the light-guiding portions151and251concurrently emit small part of light beams toward the opposite scanning assembly. Also in the present embodiment, the light-guiding portion251is disposed on the optical axis121of the imaging optics120of the scanning assembly1a, so that light from the light-guiding portion251can be utilized as a light source for detecting the outline of the original8. In addition, the aforementioned light guides include those designed so that there are very small light emissions from the light-guiding portions of the light guides. If even such a light guide as described above fails to completely eliminate light emissions and emits leakage light, this leakage light may be used as the light source.

According to the present embodiment, light from the red, green and blue LEDs of the light source210is guided and emitted by the light guide250across the full width of the original in the width direction thereof. Consequently, it is possible to even more reliably guide the light into the optical opening202. The rest of the configuration and other operations/advantages are the same as those of the above-described first embodiment.

Note that in the present embodiment, if the light sources110and210for illuminating front and back surfaces of original8are turned on simultaneously in a case, for example, where the images of both surfaces of the original8are read simultaneously, there arises the need for a shutter for blocking light passing through the optical opening202, as in the above-described second embodiment.

Furthermore, although in the present embodiment, the optical opening202is disposed on the scanning assembly1b, the optical opening may be alternatively provided on the scanning assembly1aside. Still alternatively, as shown inFIG. 12, optical openings102and202may be respectively disposed on the scanning assemblies1aand1b.

Next, a description will be made of an image reading apparatus according to a fourth embodiment of the present invention, with reference toFIG. 13. An image reading apparatus according to the present embodiment is identical in configuration with the above-described first embodiment, and the scanning assemblies1aand1bare identical in basic structure with the above-described third embodiment. Accordingly, similar elements are denoted by same reference numerals in the drawings, and the description thereof will be omitted.

In the present embodiment, a reference member260for the purpose of obtaining a shading correction data for correcting the sensitivity variation or the like of the image sensor130of the scanning assembly1ais disposed at a position in which the optical opening202of the scanning assembly1bis located.

The reference member260is white or substantially white and is supported on the frame200through a rotational shaft261. In addition, the reference member260can be moved between an exposed position260′ at which the image sensor130performs reading when obtaining the shading correction data and a retracted position (a position at which the optical opening202is opened). The exposed position260′ is a position at which the optical opening202is closed. The controller14controls an actuator (not shown) such as a motor to openably and closably drive the reference member260with the rotational shaft261serving as a fulcrum.

In the present embodiment, the image reading apparatus is not only superior in detection accuracy but also capable of carrying out shading correction operation at a correct timing since leakage light from the light-guiding portions151and251can be utilized as light sources for detecting the outline of the original8. Consequently, it is possible to always obtain excellent images. The rest of the configuration and other operations/advantages are the same as those of the above-described first embodiment.

Moreover, the purpose of use of the configuration adopted in the present embodiment may be changed from the above-described shading correction to the gain adjustment of an amplifier (not shown) or the adjustment of the light quantity of the light sources, in order to correct the sensitivity of the image sensor.

Furthermore, although in the present embodiment, the optical opening202, the reference member260and the rotational axis261are disposed on the scanning assembly1b, another optical opening, reference member and rotational axis may be alternatively disposed on the scanning assembly1a. Still further, as shown inFIG. 14, the optical openings102and202, the reference members160and260, and the rotational axes161and261may be disposed respectively in the scanning assemblies1aand1b.

Next, a description will be made of an image reading apparatus according to a fifth embodiment of the present invention, with reference toFIG. 15. An image reading apparatus according to the present embodiment is identical in configuration with the above-described first embodiment and that the scanning assemblies1aand1bare substantially identical in basic structure with the above-described third embodiment. Accordingly, similar elements are denoted by same reference numerals in the drawings, and the descriptions thereof will be omitted.

The present embodiment aims to increase the degree of freedom with respect to a positional relationship between the light guide250and the optical opening202in the above-described fourth embodiment. That is, the reference member270of the scanning assembly1bis enabled to move to a position at which leakage light from the light guide250is reflected toward the imaging optics120of the scanning assembly1a.

A reference member170is stationarily placed in the scanning assembly1a. On the other hand, the reference member270of the scanning assembly1bis pivotally supported on the frame200through a rotational axis271.

The reference member270is moved between a reflection position (a position at which the optical opening202opens) at which leakage light from the light guide250is reflected toward the imaging optics120and a correction position270′ at which the shading correction data of the scanning assembly1ais obtained (a position at which the optical opening202is closed). The open-close movement of the reference member270is performed by the controller14by controlling an actuator (not shown) such as a motor.

According to the present embodiment, it is possible to obtain timely a shading correction data for the scanning assembly1aby moving the reference member270to the correction position as necessary. It is also possible to always obtain excellent images since the image reading apparatus is superior in the accuracy of detecting the outline of the original. In addition, the degree of freedom of disposing respective members composing the scanning assemblies1aand1bincreases, thus enabling even more optimum design.

Furthermore, since leakage light from the light guide250is reflected toward the imaging optics120when the reference member270is at the reflection position, it is possible to suppress the intensity of lighting by a light source at the time of detecting the outline of the original. Consequently, it is possible to further extend the service life of the light source for illuminating the original.

Still further, since a surface of the reference member270scatteringly reflects light, the reference member serves as a light source having a two-dimensional spread of illumination. Consequently, it is possible to uniformize light entering the imaging optics120of the opposite scanning assembly1a, thereby improving the accuracy of detecting the outline of the original. The rest of the configuration and other operations/advantages are the same as those of the above-described first embodiment.

The purpose of use of the configuration adopted in the present embodiment may be changed from the above-described shading correction to the gain adjustment of an unillustrated amplifier or the adjustment of the light quantity of the light sources, in order to correct the sensitivity of an image sensor.

Although in the present embodiment, the optical opening202, the reference member270and the rotational axis271are disposed on the scanning assembly1b, another optical opening, reference member and rotational axis may be alternatively disposed on the scanning assembly1a. Furthermore, as shown inFIG. 16, the optical openings102and202, the reference members170and270, and the rotational axes171and271may be respectively disposed in the scanning assemblies1aand1b.

Furthermore, even higher-accuracy detection is possible if a scanning assembly, which does not read the original at the time of single-side reading, is used exclusively as a sensor for detecting the outline of the original in a configuration in which both scanning assemblies1aand1bcan be used as sensors for detecting the outline of the original. In addition, there is no need to use the image sensor for reading the original in a time-shared manner in order to detect the outline of the original, thereby making it possible to increase reading speed or enhance image quality. In the above-described first to fifth embodiments, a translucent member may be disposed in a through-hole of the frame200so as to serve as an optical opening. Alternatively, the optical opening part of the frame200may be formed of a translucent material.

Next, a description will be made of an image reading apparatus according to a sixth embodiment of the present invention, with reference toFIG. 17. An image reading apparatus of the present embodiment is identical in configuration with the above-described first embodiment, and the description thereof will be, therefore, omitted.

Since the scanning assemblies1aand1bof the present embodiment are substantially the same in configuration with each other, only the scanning assembly1awill be explained.

Within the frame23of the scanning assembly1a, there are disposed an LED array20which is a first light source, a lens array21which is an optical system for forming reflected light from an original8into an image, a photoelectric conversion element22for converting incident imaging light into an electrical signal, an LED serving as a second light source, and an illuminator25such as a LED or fluorescent lamp. Light from the illuminator25is prevented by a slit24from scattering.

The illuminator25of the scanning assembly1ais disposed on the optical axis of the lens array21of the scanning assembly1b, and the illuminator25of the scanning assembly1bis disposed on the optical axis of the lens array21of the scanning assembly1a.

The illuminator25need not be necessarily disposed on the optical axis of the lens array21of an opposite scanning assembly. Alternatively, the emitted light may be guided onto the optical axis of the lens array21using a light guide (not shown). In this case, the light guide and the illuminator compose the second light source of the present invention.

A side of the frame23facing the conveyance path10is covered by a cover member26made of glass, resin or the like. On the rear surface of the cover member26of the scanning assembly1a, there is disposed a white or substantially white reference member27, so as to be positioned on the optical axis of the lens array21of the scanning assembly1b. On the rear surface of the cover member26of the scanning assembly1b, there is provided a white or substantially white reference member27, so as to be positioned on the optical axis of the lens array21of the scanning assembly1a. Consequently, shading correction data can be obtained by turning on the LED array20and reading the reference member27with the photoelectric conversion element22.

The controller14causes the illuminators25of the scanning assemblies1aand1bto emit light in a predetermined time after the original8passes through a registration sensor (not shown). Since the reference member27of the present embodiment has a certain degree of optical transmittance, light emitted from the illuminator25and having transmitted through the reference member27enters the lens array21of an opposite scanning assembly and is converted into an electrical signal by the photoelectric conversion element22.

After that, the original8being conveyed blocks light transmitting through the reference member27and entering the lens array21. As a result, the level of an electrical signal, which is output from the photoelectric conversion element22by photoelectrically converting the light of the illuminator25, drastically changes. Thus, the controller14can reliably detect the edges of the original8on the basis of information on this level change.

As described heretofore, according to the present embodiment, the edges of the original8are detected as a result of the light of the illuminator25having transmitted through the reference member27being blocked by the original8. Consequently, it is possible to increase the accuracy of detecting the original8.

In addition, since it is possible to detect the edges of the original8by utilizing the lens array21and the photoelectric conversion element22of the scanning assembly1bfor reading the rear surface image of the original8, there is no need for another image sensor dedicated to detecting originals. Accordingly, it is possible to reduce the size and cost of the image reading apparatus.

Although in the present embodiment, the illuminators25are respectively disposed in the scanning assemblies1aand1b, the illuminator25may be disposed only in either one of the scanning assemblies1aand1b.

Alternatively, as shown inFIG. 18, the illuminators25and the reference members27may be disposed in separate units other than the scanning assemblies1aand1b.

Furthermore, the edges of the original8are preferably detected in a continuous manner while reading images. In this case, the edges of the original are detected in a time-shared manner each time a single line of an image is read or several lines of the image are read, so that a period of time during which the LED array20which is the first light source is turned on to perform image reading and a period of time during which the illuminators25are caused to emit light to detect the edges of the original do not coincide with each other. This means that the illuminators25, which are the second light sources, are turned on preferably only when the LED arrays20, which are the first light sources, are turned off. Otherwise, when the light emitted by the first light sources is not effective for image reading even in a period of time during which the first light sources are turned on, the second light sources may be turned on.

When, for example, detecting a time at which the leading end of the original passes through an image sensor or detecting the skew of the leading end of the original before image reading is started, the illuminators25may be caused to emit light in a continuous manner. When reading only one surface of the original8, the above-described time sharing is unnecessary if a scanning assembly not used for reading is used exclusively for the purpose of detecting the edges of the original8. It is expected that improvements in detection accuracy and in the quality of read images will be achieved.

In addition, it is preferable that infrared light is used for the illuminator25and the reference member27is an infrared transmissive member. It is further preferable that the material or the thickness of the reference member27is altered to further increase the degree of whiteness thereof, so that the reference member27allows infrared light to pass therethrough but not visible light. Consequently, by reading an image using the reference member27as a background member, it is possible to further emphasize a light-colored character, such as a penciled character, written on an original. It is also possible to reliably detect the edges of the original since infrared light from the illuminator25transmits through the reference member27.

Next, a description will be made of an image reading apparatus according to a seventh embodiment of the present invention, with reference toFIG. 19. An image reading apparatus according to the present embodiment is identical in configuration with the above-described first embodiment, and that the scanning assemblies1aand1bare substantially identical in basic structure with the above-described sixth embodiment. Accordingly, similar elements are denoted by same reference numerals in the drawings, and the description thereof will be omitted.

In the present embodiment, a reference member27disposed on the back surface of a cover member26is protrudingly mounted at the leading end of a moving member28. By driving the moving member28in the directions of two-headed arrow in the drawing using a moving unit (not shown), such as a solenoid, the reference member27is enabled to move between a blocking position for blocking the light of an illuminator25and a retracted position.

When the reference member27is at a position for blocking the light of the illuminator25, it is possible to obtain shading correction data. When the reference member27is at a retracted position for not blocking the light of the illuminator25, the illuminator25is turned on to detect the edges of the original8.

Consequently, it is possible to use a low light transmittance reference member27having an even higher degree of whiteness, compared with the above-described sixth embodiment. By using this reference member as a background member at the time of image reading, it is possible to further emphasize a light-colored character, such as a penciled character, written on the original.

In addition, by turning on the illuminator25at a position to which the reference member27is retracted from the position for blocking the light of the illuminator25, it is possible to reliably detect the edges of the original, no matter what type of light, including infrared light and visible light, the light emitted by the illuminator25is. Furthermore, since the color of the background member at the time of image reading can be changed to black by setting the color of the moving member28to black, it is possible to reduce a show-through image of thin paper or the like. The rest of the configuration and other operations/advantages are the same as those of the above-described sixth embodiment.

The spectral characteristics of the LED array20which is the first light source and the spectral characteristics of the illuminator25which is the second light source may differ from each other. For example, the light emitted by the illuminator25is changed to infrared light in a case where the LED array20is changed to a continuously-lit white light source, such as a cold-cathode fluorescent lamp or a light source of arbitrary visible-light, and some elements of the photoelectric conversion element22are changed to those capable of detecting infrared light only.

This makes it possible to detect the edges of the original without being affected by the white light and the like of the LED array20for reasons of a difference in wavelength between white light emitted by the LED array20and infrared light emitted by the illuminator25.

In addition, the spectral characteristics of light emitted by the illuminator25of the scanning assembly1aand the spectral characteristics of light emitted by the illuminator25of the scanning assembly1bmay differ from each other. For example, a short-wavelength blue light source is used for the illuminator25of the scanning assembly1aand an infrared light source is used for the illuminator25of the scanning assembly1b.

This makes it possible to even more reliably detect the edges of an original by, for example, cross-checking data detected using two light sources having different spectral characteristics, even in the case of a stack of originals or the like composed of a mixture of thin and thick sheets of paper. Thus, it is possible to further improve detection accuracy. In addition, it is possible to optionally combine sources of red light, green light, blue light, infrared light and the like in accordance with the inherent color of an original.

Next, a description will be made of an image reading apparatus according to an eighth embodiment of the present invention, with reference toFIG. 20. An image reading apparatus of the present embodiment is identical in configuration with the above-described first embodiment, and that the scanning assemblies1aand1bare substantially identical in basic structure with the above-described sixth embodiment. Accordingly, similar elements are denoted by same reference numerals in the drawings, the description thereof will be omitted.

In the present embodiment, a reference member27is disposed on the rear surface of a cover member26so as to overlap with the leading end of a moving member (black-colored member)28formed of a light transmissive black material. By driving the moving member28in the directions of two-headed arrow in the drawing using a moving unit (not shown), such as a solenoid, the reference member27is enabled to move between a blocking position for blocking the light of an illuminator25and a retracted position.

Consequently, shading correction data can be obtained when the reference member27is at a position for blocking the light of the illuminator25. In addition, by using the reference member27as a background member at the time of image reading, it is possible to further emphasize a light-colored character, such as a penciled character, written on the original.

Furthermore, since the color of the background member is black when the moving member28is arranged at the position for blocking the light of the illuminator25to perform image reading, it is possible to reduce a show-through image of thin paper or the like.

Still further, it is possible to change the density of a background color to a desirable one by previously varying the density, which the moving member28has, according to a position in the moving direction thereof and by moving the moving member28as appropriate, so that a portion with a different density color is positioned on the optical axis line of a lens array21. The rest of the configuration and other operations/advantages are the same as those of the above-described sixth embodiment. In addition, it is possible to detect the edges of an original or the like using light from the illuminator25having passed through the moving member28.

The moving member28may be changed to a stationary member and the reference member27overlapped on the stationary member may be moved, without mounting the reference member27on the stationary member. In this case, it is possible to detect the edges of an original or the like using light from the illuminator25having passed through the stationary member when the reference member21is retracted from the optical axis of the lens array21. Alternatively, the reference member may be fixed to the scanning assembly1band a moving unit for moving at least either one of the scanning assemblies1band1amay be provided. With this arrangement, changing the relative position of the scanning assemblies1band1aenables to locate the reference member at the reading position of the scanning assembly1a, and to locate the optical opening of the scanning assembly1bat the reading position of the scanning assembly1aby controlling the moving unit using a controller or the like. Alternatively, another reference member may be further fixed to the scanning assembly1aand an optical opening is also disposed in the scanning assembly1a. With this arrangement, it is possible to locate the above-described another reference member at the reading position of the scanning assembly1bby controlling the moving unit, and to locate the optical opening of the scanning assembly1aat the reading position of the scanning assembly1bby controlling the moving unit.

Still alternatively, the illuminator25of only one of the scanning assemblies1aand1bmay be turned on and the other of the scanning assemblies1aand1bmay be dedicated to detecting the edges of an original. This makes it possible to save electrical power as the illuminator25of the other scanning assembly is not turned on.

Furthermore, by dedicating the other image sensor to detecting the edges of an original, it is possible to smoothly process images read by one scanning assembly. Consequently, it is possible to suppress a decrease in the speed of image reading due to processing for the detection of the edges of an original.

In addition, since there is no need for time-sharing between light emission for the purpose of image reading and light emission for the purpose of detecting the edges of an original, it is possible to improve the quality of read images. Note that in each of the above-described embodiments, the reference member may be used for the gain adjustment of an amplifier (not shown) or for the adjustment of the light quantity of the light source, rather than using the reference member to obtain shading correction data.

It is to be understood that the present invention is not limited to the foregoing embodiments described by way of example but may be modified as appropriate without departing from the subject matter thereof. The foregoing embodiments of the present invention may be modified by adding any constituent feature or features included in each of the embodiments to another embodiment.

It is also to be understood that the object of the present invention may also be accomplished by supplying a system or an apparatus with a storage medium in which a program code of software which realizes the functions of the above-described embodiment is stored, and causing a computer (or CPU or MPU) of the system or apparatus to read out and execute the program code stored in the storage medium.

In this case, the program code itself read from the storage medium realizes the functions of any of the embodiments described above, and hence the program code and the storage medium in which the program code is stored constitute the present invention.

Examples of the storage medium for supplying the program code include a floppy (registered trademark) disk, a hard disk, a magneto-optic disk, a CD-ROM, a CD-R, a CD-RW, a DVD-ROM, a DVD-RAM, a DVD-RW, a DVD+RW, a magnetic tape, a nonvolatile memory card, and a ROM. Alternatively, the program may be downloaded via a network.

This application claims the benefit of Japanese Application No. 2007-283478, filed Oct. 31, 2007, which is hereby incorporated by reference herein in its entirety.