JP4902598B2 - Image reading device - Google Patents

Description

  The present invention relates to an image reading apparatus that scans an image of an object to be read such as a document and reads the image.

  In an image reading apparatus, an object to be read having irregularities such as a book may be scanned. Since the binding portion of the book is uneven, the binding portion appears as a shadow in the read image. This shadow is caused by a lamp that irradiates the object to be read. In order to eliminate the shadow, the light quantity of the lamp should be increased. Even if the object to be read is uneven, sufficient reflected light is obtained and no shadow appears. However, the power supplied to the lamp is limited and impractical.

In the image reading apparatus described in Patent Document 1, the unevenness of the document is detected, and the light amount or irradiation direction of the lamp is changed according to the distance from the lamp to the document. As a result, a read image free from shadows and distortions can be obtained.
JP-A-10-290328

  In the above image reading apparatus, the object to be read is irradiated by one lamp. Therefore, it is necessary to change the light quantity of the lamp and the irradiation direction. However, when changing the light quantity of the lamp, it is necessary to change it within the range of electric power that can be supplied to the lamp, and there is a limit naturally. In the image reading apparatus, the positions of the mirror and the lens are fixed with respect to the lamp. Therefore, even if the irradiation direction is changed with respect to the unevenness of the read object, light can be irradiated only from one direction to the depression such as the binding portion. Therefore, it is not possible to irradiate light evenly on the inclined portion of the unevenness, and the read image may be uneven.

  In view of the above, an object of the present invention is to provide an image reading apparatus that can read an image of an object to be read without unevenness by using a plurality of lamps without increasing the amount of light of the entire lamp. To do.

  The present invention includes a scanning unit that scans an image of an object to be read in a reading area, and the scanning unit includes a plurality of lamps that irradiate the object to be read, and includes a control unit that adjusts the light quantity ratio of each lamp. It is a thing.

  The control unit adjusts the light amount ratio of each lamp in order to eliminate the influence on the read image caused by the shadow caused by the unevenness of the read object. By changing the light quantity of each of the plurality of lamps, the light quantity ratio of each lamp also changes. As a result, the amount of light applied to the unevenness of the read object changes, and the amount of reflected light from the read object increases. As a result, it is possible to eliminate the influence that the shadow image that can be formed into the read image becomes light and other images are difficult to see.

  When the lamps are arranged on both sides of the reading area, the control unit varies the light amount of the lamp on one side and the light amount of the lamp on the other side according to the shadow that can be formed on the object to be read. A dark portion cannot be formed on the unevenness of the object to be read, and a shadow hardly appears in the read image.

  The control unit adjusts the light amount ratio by changing the light amount of each lamp so that the total light amount of the entire lamp is constant and the sum of the light amount of one lamp and the other lamp is constant. Since the light quantity of the entire lamp does not change, the lamp can be controlled within a predetermined power range.

  The scanning unit moves in a moving direction orthogonal to the scanning direction while scanning for each line in the scanning direction in the reading area, and each lamp is arranged on the upstream side and the downstream side in the moving direction across the reading area, and is controlled. The unit decreases the light amount of the upstream lamp and increases the light amount of the downstream lamp, and then increases the light amount of the upstream lamp and decreases the light amount of the downstream lamp in accordance with the shadow formed along the scanning direction. . When the unevenness of the object to be read is parallel to the scanning direction, the adjustment of the amount of light can effectively eliminate the influence of the shadow, and the object to be read can be read evenly.

  The control unit determines the light amount of each lamp based on the luminance of the read image. The amount of reflected light changes due to the unevenness of the object to be read, and the brightness of the read image changes according to the amount of reflected light. Therefore, the presence or absence of unevenness can be determined by detecting the luminance of the read image.

  When scanning in the scanning direction in the reading area, the control unit detects the luminance of the read image for each line and adjusts the light amount ratio. When a shadow image appears in the read image, the brightness of the read image decreases. In such a case, the light amount ratio is adjusted.

  That is, the control unit adjusts the light amount ratio when the total luminance of the read image for one line does not exceed the threshold value, and outputs the read image when the threshold value is exceeded. The control unit outputs the read image having the highest luminance when the total luminance of the read images for one line does not finally exceed the threshold value. When the total luminance of the read image does not exceed the threshold value, a shadow image appears. Therefore, when the light quantity ratio of the lamp is adjusted, the total luminance increases and it becomes difficult for a shadow image to appear.

  An optical sensor for detecting the amount of light reflected from the object to be read is provided, and the control unit adjusts the light amount ratio based on the amount of light received by the optical sensor. Instead of detecting the presence or absence of unevenness of the read object based on the luminance of the read image, the presence or absence of unevenness can be detected by directly detecting the amount of reflected light.

  According to the present invention, by adjusting the light irradiated from a plurality of directions on the unevenness of the object to be read, it is possible to make it difficult for a shadow image to appear in the read image, and to obtain a high-quality read image. it can. In addition, by adjusting the light amount of the lamp within the range of power that can be supplied to the lamp, efficient irradiation can be achieved.

  An image reading apparatus according to the present embodiment is shown in FIG. The image reading apparatus includes an image reading unit 1 that reads an image by scanning an object to be read on which an image is recorded. The image reading unit 1 is built in a cabinet. A mounting table 2 made of transparent glass is provided on the upper surface of the cabinet, and a reading object such as a sheet-like document or book is mounted on the upper surface of the mounting table 2. Although not shown, the cabinet is provided with a document cover that covers the placement table 2 so as to be openable and closable, and an automatic document feeder is mounted on the document cover.

  The image reading unit 1 includes two lamps 3 and 4, first to third mirrors 5 to 7, an imaging lens 8, and an image sensor 9, and includes two scanning units on which the lamps 3 and 4 and mirrors 5 to 7 are mounted. 10 and 11. The image reading unit 1 is disposed below the mounting table 2. The upper surface of the mounting table 2 serves as a mounting surface 12 for the object to be read.

  The lamps 3 and 4 illuminate a document placed on the placement table 2. The lamps 3 and 4 are made of fluorescent lights or LEDs, and are arranged in the front-rear direction of the cabinet. The front-back direction of the cabinet (the direction perpendicular to the drawing) is the scanning direction. A reflecting plate 13 is provided around the lamps 3 and 4, and light from the lamps 3 and 4 irradiates the mounting surface 12 of the mounting table 2.

  Each of the mirrors 5 to 7 and the imaging lens 8 constitute an imaging optical system that forms an image of light reflected from the document on an image sensor 9 made of a CCD. The imaging lens 8 is obtained by fixing a plurality of lenses to a substantially cylindrical frame member. As the frame member, aluminum, glass-containing resin, or the like is used.

  The plurality of mirrors 5 to 7 guide light from the document to the imaging lens 8. The light emitted from the lamps 3 and 4 is irregularly reflected on the surface of the document placed on the placing table 2. The light reflected downward from the surface of the document is reflected by the first mirror 5, then reflected by the second mirror 6 and the third mirror 7 in order, and guided to the imaging lens 8. The light that has passed through the imaging lens 8 forms an image on the image sensor 9. The image sensor 9 converts an optical signal into an electric signal and outputs it as an image signal.

  The first mirror 5 is mounted on the first scanning unit 10 together with the lamps 3 and 4. The second and third mirrors 6 and 7 are mounted on the second scanning unit 11. Each scanning unit 10, 11 scans the document while moving.

  The first scanning unit 10 is driven by a drive system including a drive motor, a pulley, and a wire, and reciprocates in the cabinet width direction (left-right direction in the drawing). The first scanning unit 10 moves at a constant speed V in the moving direction of the arrow A1 during scanning. After the reading is completed, it moves in the return direction of arrow A2. The second scanning unit 11 is also driven by the same drive system, and moves in the reading direction A1 at a speed (V / 2) that is half the speed V of the first scanning unit 10.

  The reading position of the original by the movement of the scanning units 10 and 11 is from the scanning start end P1 to the scanning end. The first scanning unit 10 moves from an initial position corresponding to the start end P1 to an end position corresponding to the end. The region from the initial position to the end position is the moving area of the first scanning unit 10. Similarly, the initial position and end position of the second scanning unit 11 are determined, and the moving area of the second scanning unit 11 is half of the moving area of the first scanning unit 10. The end position is determined by the size of the document.

  With the movement of the first scanning unit 10 and the second scanning unit 11, the mirror group moves along the mounting table 2. While the first scanning unit 10 and the second scanning unit 11 are moving, the speed ratio between them is maintained at 2: 1, so that the optical path length from the document surface to the imaging lens 8 is kept constant. As a result, an image of the document from the scanning start end P1 to the scanning end is formed on the image sensor 9.

A reference white plate 15 for shading correction is provided on the mounting table 2 facing the initial position of the first scanning unit 10 . When the first scanning unit 10 moves below the reference white plate 15, an image of the reference white plate 15 is formed on the image sensor 9. Thereby, white correction data is created.

  In order to detect the position of the first scanning unit 10, a plurality of position sensors (not shown) are provided. The position sensor is, for example, a photo interrupter, and the position sensor outputs a detection signal when the light shielding plate provided in the first scanning unit 10 passes through the slit of the photo interrupter. The arrival of the first scanning unit 10 at the initial position or the end position is detected. The rotation of the drive motor is controlled according to the detection signal, and the movement of the first scanning unit 10 and the second scanning unit 11 is controlled. For this reason, the scanning units 10 and 11 stop when they reach the end of the moving area.

  The main image reading unit 1 includes two lamps 3 and 4. The lamps 3 and 4 are respectively arranged on the upstream side and the downstream side in the moving direction. When the two lamps 3 and 4 irradiate the mounting table 2, the irradiation light overlaps on the mounting surface 12. This overlapping area is a reading area. That is, the first lamp 3 on the upstream side and the second lamp 4 on the downstream side are in symmetrical positions with respect to the reading area. The center of light emitted from each of the lamps 3 and 4 is condensed at one point, and one line is formed in the scanning direction. The image reading unit 1 scans a document for each line. When the scanning units 10 and 11 move in the movement direction, images are read one line after another.

  As shown in FIG. 2, the image reading apparatus includes an image reading unit 1, an image processing unit 20, a storage unit 21, a communication unit 22, and a control unit 23. The image reading apparatus is communicably connected to an external device such as a computer or a printer.

  In the image reading unit 1, the document is irradiated with light, and the light reflected from the document is guided to the imaging optical system and is read by the image sensor 9. The image signal of the document read by the image sensor 9 is output to the image processing unit 20. The image processing unit 20 performs A / D conversion on the image signal from the image sensor 9 to convert it into image data, and performs image processing such as color conversion processing and filter processing on the converted image data. Further, it performs shading correction in cooperation with the image reading unit 1. The storage unit 21 temporarily stores image data to be processed when the image processing unit 20 performs image processing on the image data. In addition, the storage unit 21 holds the processed image data until it has been transferred to the external device via the communication unit 22. The communication unit 22 receives image data from the storage unit 21 via the image processing unit 20 and transfers it to an external device. The communication unit 22 performs bidirectional communication with an external device through a network such as a LAN or the Internet. In the external device, predetermined processing is performed on the image data. Then, an image is output by printing, display, or the like, or image data is stored.

  The control unit 23 controls the operation of the entire apparatus and executes reading of the image of the read object. The control unit 23 includes a CPU, a ROM that stores a program to be executed, a RAM that provides a working storage area, and the like.

  The image processing unit 20 and the communication unit 22 are integrated with a control unit 23 such as a CPU, a non-volatile memory for storing setting values of each block for performing image processing, and circuit blocks for image processing and communication. A circuit using an LSI or the like can be used. The storage unit 21 is a DRAM or other type of memory element. The storage unit 21 may be a storage device such as an HDD or an SSD.

  Here, when the book is placed on the placement table 2, the binding portion of the book becomes uneven with respect to the placement surface 12. When a reading object having such irregularities is read, as shown in FIG. 3A, the image of the binding portion becomes black and a shadow image appears in the read image. In the vicinity of the binding portion, a light shadow appears in the read image, and an image such as a character cannot be read. Therefore, the control unit 23 executes a book mode for eliminating the influence on the read image caused by the shadow caused by the unevenness of the read object. When the book mode is executed, the control unit 23 controls the driving of the lamps 3 and 4 to vary the light amount of the lamps 3 and 4 according to the shadow.

  The control unit 23 makes the total light amount of the entire lamp constant, changes the light amount of each lamp 3 and 4 so that the total light amount of the lamp 3 on one side and the light amount of the lamp 4 on the other side becomes constant, Adjust the light intensity ratio. That is, the control unit 23 decreases the light amount of the upstream first lamp 3 and increases the light amount of the downstream second lamp 4 in accordance with the shadow appearing along the scanning direction, and then increases the upstream first lamp 3. And the light quantity of the second lamp 4 on the downstream side is lowered. At this time, the control unit 23 detects the position of the shadow formed by the unevenness of the read object based on the luminance of the read image. When the shadow is detected, the light amount ratio of the lamps 3 and 4 is adjusted.

  The operation of the image reading apparatus when the book mode is executed will be described with reference to FIG. A book is placed on the placing table 2 as an object to be read having unevenness. The book is placed horizontally, and the binding portion of the book is parallel to the scanning direction. When the user operates the scan start button, the control unit 23 returns the scanning units 10 and 11 to the initial positions (S100).

  When scanning is started, the scanning units 10 and 11 move in the movement direction (sub-scanning direction) by one line, and the image reading unit 1 reads the image of the read object in the reading area for one line ( S110). At this time, the control unit 23 sets the light amount ratio of the lamps 3 and 4 to 100: 100. That is, the light quantity of both lamps 3 and 4 is the same.

  The control unit 23 calculates a total value obtained by summing the luminances of all pixels in the read image for one line input from the image reading unit 1 (S120). The control unit 23 determines whether or not the total value exceeds the threshold value (S130). This threshold value for luminance is used as a reference for determining the presence or absence of unevenness. If there are irregularities, the light emitted from the lamps 3 and 4 is diffusely reflected, and the amount of reflected light from the object to be read is reduced. Then, the brightness of the read image becomes low, and the total brightness value becomes smaller than the threshold value. In the read image when the total luminance value is smaller than the threshold value, an image such as a character cannot be clearly seen due to the influence of the shadow that appears.

  As shown in FIG. 5, when the object to be read is in close contact with the placement surface 12 and there is no unevenness, the total luminance value is equal to or greater than the threshold value. The control unit 23 determines that there is no unevenness, and stores the read image of one line in the storage unit (image memory) 21 (S140). When the control unit 23 confirms that the read line is not the final line (S150), the control unit 23 moves the scanning units 10 and 11 by one line, and reads the image of the next line.

  As shown in FIG. 6, when the reading area reaches the binding portion, the amount of light reflected by the object to be read decreases, and the total luminance value becomes less than the threshold value. The control unit 23 determines that the surface is uneven, and executes light amount adjustment (S160).

  The controller 23 first initializes the count value C to 1 (S200), and clears the temporary storage memory (S205). Then, referring to the light amount table shown in FIG. 7A, the light amounts of the lamps 3 and 4 are set (S210). The control unit 23 drives the lamps 3 and 4 according to the light amounts of the first lamp 3 and the second lamp 4 at the count value C. The light amount table is created in advance and stored in a nonvolatile memory.

  As shown in FIG. 6, when the upstream side in the moving direction of the binding portion is in the reading area, the light amount of the first lamp 3 is less than the light amount of the second lamp 4. For example, the light quantity ratio between the first lamp 3 and the second lamp 4 is 50: 150. Further, as shown in FIG. 8, when the downstream side in the moving direction of the binding portion is in the reading area, the light amount of the first lamp 3> the light amount of the second lamp 4. For example, the light quantity ratio between the first lamp 3 and the second lamp 4 is 150: 50. In either case, the total amount of light from each of the lamps 3 and 4 is constant.

  When the image reading unit 1 reads an image for one line, the control unit 23 calculates the total luminance value of all the pixels of the read image (S220), and determines whether the total value exceeds the threshold (S230).

  When the total luminance value is less than the threshold, the control unit 23 increments the count value C by 1 (S250) and confirms that C = 21 is not satisfied (S260), and then the first lamp at the count value C + 1. The lamps 3 and 4 are driven in accordance with the light quantity of the 3 and second lamps 4.

  The control unit 23 determines again whether the total luminance value exceeds the threshold value. When the total value is equal to or greater than the threshold value, the control unit 23 stores the read image at this time in the storage unit 21 (S280). Then, the next line image is read.

  When the total luminance value does not exceed the threshold value, the control unit 23 changes the light amounts of the lamps 3 and 4 stepwise according to the light amount table. Each time, as shown in FIG. 7B, the control unit 23 stores the luminance total value and the read image for one line in the temporary storage memory for each count value. When C = 21 (S260) and finally the total luminance value does not exceed the threshold, the control unit 23 extracts the read image when the total luminance value is the highest from the temporary storage memory (S270). The read image is stored in the storage unit 21 (S280).

  As shown in FIG. 9, when the reading region passes the binding portion, the control unit 23 equalizes the light amounts of the lamps 3 and 4. That is, the light amount ratio is 100: 100. When the image reading is completed up to the final line (S150), the control unit 23 outputs the read image through the communication unit 22. Then, the image reading unit 1 turns off the lamps 3 and 4 and returns the scanning units 10 and 11 to the initial position.

  Thus, in the binding part of a book, it becomes a dent where both sides became an inclined surface. When the inclined surface on one side in the moving direction is read, the light amount of the lamps 3 and 4 facing this inclined surface is increased, and the light amount of the lamps 3 and 4 facing the other inclined surface is decreased. For example, as shown in FIG. 6, when the upstream inclined surface is read, the light quantity of the second lamp 4 facing the inclined surface is increased. Therefore, the amount of reflected light from the inclined surface increases and the brightness of the read image increases. At this time, since the light amount of the entire lamp is constant, the light amount is adjusted within the range of power that can be supplied to the lamps 3 and 4. Therefore, it is not necessary to use extra energy.

  As a result, as shown in FIG. 3B, the shadow image of the binding portion in the read image becomes light and an image of characters and the like near the binding portion can be seen. In addition, since the amount of light is controlled in the same manner with respect to the left and right inclined surfaces, there is no difference between the left and right read images in the binding portion, and a read image with no unevenness can be obtained.

  Further, even if the total luminance value of one line of the read image does not exceed the threshold value, the read image having the highest luminance is output. Therefore, the read image is brighter than the shadow image, and a read image that is not affected by the shadow is obtained.

  In the above image reading apparatus, a reduction optical system scanner using an imaging lens and a CCD is used. As shown in FIG. 10, a CIS (Contact Image Sensor) 25 and a Selfoc lens 26 (registered) are used as an image sensor. And a 1 × magnification optical system scanner.

  In the above description, the luminance of the read image is used to detect unevenness of the object to be read. Instead, an optical sensor that detects reflected light from the object to be read is provided. The optical sensor is disposed at one end in the scanning direction of the scanning unit 10 so as to receive reflected light from the end of the reading object that does not interfere with the reading operation. The control unit 23 determines the presence or absence of unevenness based on the amount of light received by the optical sensor. When the amount of received light is greater than or equal to the reference value, it is determined that there is no unevenness, and when the amount of received light is less than the reference value, it is determined that there is unevenness. As a result, it is possible to quickly determine whether or not the control of the lamp light amount is necessary, and the time for the reading process can be shortened.

  In addition, this invention is not limited to the said embodiment, Of course, many corrections and changes can be added to the said embodiment within the scope of the present invention. The image reading apparatus is not limited to a single machine such as a scanner, but may be incorporated in an image processing apparatus such as a copier, a facsimile machine, or a multifunction machine. Further, the image reading apparatus may be a handy scanner.

  In the image reading apparatus described above, the book mode is automatically executed, but the execution of the book mode can be selected. When the user selects the book mode when reading an object to be read having irregularities, the control unit executes the book mode. In this case, since it is known that a shadow image appears in the read image, the control unit regards the light amount of the lamp as a shadow image when a linear or curved black image appears in the read image. Adjust and scan again. It can handle shadows of various shapes.

  Two or more lamps may be provided. For example, a plurality of lamps are arranged side by side along the scanning direction. The unevenness of the object to be read is not limited to the one that is long in parallel with the scanning direction like the binding portion of the book, and can cope with a case where the unevenness is partially uneven. The amount of light can be varied only for the lamp facing the unevenness.

  Further, the scanning unit may be provided not only in the moving direction but also in the scanning direction, and a plurality of lamps are arranged in parallel with the scanning direction. When the book is placed vertically, the binding portion is parallel to the moving direction. In this case, when the lamp moves in the scanning direction, the amount of light of each lamp is varied according to the binding portion.

FIG. 2 is a diagram illustrating an image reading apparatus according to the present invention, where (a) is in a state before the start of scanning, and (b) is in a state at the end of scanning. Control block diagram of image reading apparatus (A) The figure which shows the read image where the shadow appeared, (B) The figure which shows the read image which excluded the influence of the shadow Image reading flowchart The figure which shows the image reading apparatus which is reading the part without the unevenness | corrugation of to-be-read object The figure which shows the image reading apparatus which is reading the upstream of the binding part of a to-be-read object (A) The figure which shows a light quantity table, (b) The figure which shows the content memorize | stored in the temporary memory at the time of book mode execution The figure which shows the image reading apparatus which is reading the downstream of the binding part of a to-be-read object The figure which shows the image reading apparatus which is reading the part without the unevenness | corrugation of to-be-read object The figure which shows the image reading apparatus provided with the other image pick-up element

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image reading part 2 Mounting stand 3 1st lamp 4 2nd lamp 10 1st scanning unit 11 2nd scanning unit 21 Memory | storage part 23 Control part

Claims (4)

An image reading unit that scans an object to be read placed on a mounting table and reads an image of the object to be read, and a control unit that controls the image reading unit to read an image of the object to be read with the door, the image reading unit includes a plurality of lamps for irradiating the object to be read was placed on the mounting table, mounting the lamp, the object to be read object while moving along the mounting table A scanning unit that scans and scans the image of the object to be read, and the plurality of lamps are respectively arranged on the upstream side and the downstream side in the moving direction in which the scanning unit moves. When the downstream lamp irradiates the mounting table, a reading area is a region where the irradiation light of the upstream lamp and the irradiation light of the downstream lamp overlap on the mounting surface of the mounting table, The upstream lamp and the downstream lamp The scanning unit is positioned symmetrically across the reading area, and the scanning unit moves in the moving direction while scanning each line in the scanning direction orthogonal to the moving direction in the reading area. In order to eliminate the influence of the shadow caused by the unevenness on the read image when reading the object to be read having unevenness , the upstream light amount and the downstream lamp light amount are kept constant while the upstream light amount is constant. Execute book mode to control to change the light quantity of the lamp on the side and the lamp on the downstream side ,
When execution of the book mode, the control unit, and the light quantity of the upstream side of the lamp light quantity and the downstream side of the lamp for each line in the same irradiating the object to be read was read image for each line When the luminance value is detected and the total value of the luminance values of all the pixels in the read image for one line is equal to or greater than the threshold value, the read image is stored and the next one-line image is read. Is smaller than the threshold value, the light quantity of the upstream lamp and the downstream lamp is changed stepwise while keeping the total light quantity of the upstream lamp and the downstream lamp constant. When the scanned image is read and the total luminance value exceeds the threshold value, the scanned image at this time is stored, the next one-line image is read, and finally the total luminance value reaches the threshold value. When not exceeding, the total luminance value An image reading apparatus that stores a read image when the image is highest and reads the next one-line image . The controller sets the light amounts of the upstream lamp and the downstream lamp with reference to a light amount table prepared in advance when the light amounts of the upstream lamp and the downstream lamp are changed stepwise. 2. The image reading apparatus according to claim 1, wherein each lamp is driven in accordance with each light quantity, and a read image is stored each time. The optical sensor for detecting reflected light from the reading object is provided in the scanning unit, the control unit, instead of using the brightness of the read image, when the received light amount is equal to or larger than the reference value of the light sensor, the Reading the image of the object to be read when the light quantity of the upstream lamp and the light quantity of the downstream lamp are the same while keeping the total light quantity of the upstream lamp and the downstream lamp constant. When the amount is less than the reference value, the light amount of the upstream lamp and the downstream lamp is changed while the total amount of light of the upstream lamp and the downstream lamp is kept constant, and the target the image reading apparatus according to claim 1 or 2, wherein the reading the image of the reading matter. The scanning unit is movable in the scanning direction, the plurality of lamps are arranged parallel to the scanning direction, when the scanning unit is moved in the scanning direction, the control unit, the upstream side of the lamp and while the total amount of the downstream side of the lamp constant, the read image according to any one of claims 1 to 3, characterized in that the control for changing the light quantity of the upstream side of the lamp and the downstream side of the lamp apparatus.

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