JP3912411B2 - Image reading device - Google Patents

Description

  The present invention relates to an image reading apparatus such as a scanner or a copying machine provided with an automatic document feeder.

  In recent years, workstations, personal computers, and the like have become highly functional, and full-color image editing, electronic filing, OCR (optical character reader), and other character input can be processed at high speed. Along with this, flat head type color scanners that can input images easily have become widespread. However, in order to further speed up and simplify image input, an automatic document feeder (hereinafter referred to as ADF) is used in the color scanner. More machines are equipped with.

  A conventional image reading apparatus will be described below with reference to the drawings. FIG. 5 is a schematic configuration diagram of a conventional image reading apparatus. In FIG. 5, reference numeral 1 denotes an image reading apparatus main body. Reference numeral 2a denotes an original glass on which an original is placed when the user manually sets the original without using the ADF, and 2b denotes a glass window arranged at an original reading position when the ADF is used. A carriage 3 scans and reads a document. Reference numeral 4 denotes a support member having a bearing or the like inside, and is attached to the carriage 3. Reference numeral 5 denotes a shaft that supports the carriage 3 via the support member 4. The movement of the carriage 3 is restricted only in the sub-scanning direction by the shaft 5. Reference numeral 6 denotes a driving wire for transmitting a driving force to the carriage 3, 7 denotes a driving pulley, and 8 denotes a driven pulley. The driving wire 6 is connected to the carriage 3, and the driving wire 6 passes through the driving pulley 7 and the driven pulley 8. Is engaged. Reference numeral 9 denotes a drive motor, and the drive pulley 7 is connected to the drive motor 9 by a connecting shaft and a speed reduction mechanism (both not shown), and the carriage 3 is driven by rotating the drive motor 9. Reference numeral 10 denotes a driven pulley support member, and 11 denotes an urging means. The driven pulley 8 is urged in the direction of arrow A by the urging means 11 via the driven pulley support member 10 to apply tension to the drive wire 6.

  Reference numeral 12 denotes an ADF unit that continuously conveys a document to a reading position. Reference numeral 13 denotes a document tray on which documents are set. Reference numeral 14 denotes a document detection sensor that detects the presence or absence of a document. Reference numeral 15 denotes a conveyance roller, and reference numeral 16 denotes a reverse roller. A document set on the document tray 13 is conveyed by the conveyance roller 15 and the reverse roller 16 one by one to the glass window 2b. A document edge detection sensor 17 detects the leading edge and the trailing edge of the document. Reference numeral 18 denotes a conveyance roller, and reference numeral 19 denotes a guide roller disposed to face the conveyance roller 18. Reference numeral 20 denotes a conveyance roller, which brings the document into close contact with the glass window 2b and conveys the document while keeping the distance between the document surface and the carriage 3 constant. Reference numeral 21 denotes a paper discharge tray on which originals that have been read are stacked.

  FIG. 6 is a schematic configuration diagram of an optical system of a conventional image reading apparatus. In FIG. 6, 22 is a light source lamp for irradiating a document, 23 is a document reading section provided on the carriage 3, 24 is a reflection mirror for reflecting light reflected from the document, and 25 is a color image sensor for converting optical information into an electrical signal. , 26 are image forming lenses for forming an image on the color image sensor 25.

  The operation of the image reading apparatus configured as described above will be described below. When a document is set on the document tray 13 of the ADF unit 12 and the document detection sensor 14 detects the document, the drive motor 9 of the image reading apparatus main body 1 rotates, and the drive pulley 7, the drive wire 6 and the driven pulley 8 are passed through. The driving force is transmitted to the carriage 3, and the position of the carriage 3 is controlled so that the document reading portion 23 of the carriage 3 is directly below the glass window 2b. In this method, the position of the carriage 3 is fixed, and the image is read by conveying the document by the ADF unit 12.

  In this state, when a document reading command is issued from an external host (not shown), the light source lamp 22 is turned on and an ADF drive motor (not shown) provided independently of the ADF unit 12 is rotated. The transport roller 18 and the guide roller 19 are coupled to the ADF drive motor via a speed reduction mechanism, and the transport roller 18 and the guide roller 19 start rotating together with the rotation of the ADF drive motor. When the rotation of the ADF drive motor reaches a constant speed, a clutch mechanism (not shown) is controlled to rotate the conveying roller 15 and the reverse roller 16 to convey the original set on the original tray 13 one by one. Start. The reverse roller 16 uses a difference in friction between the roller and the document surface to suppress so-called double feeding in which a plurality of documents are conveyed simultaneously.

  When the leading edge of the conveyed document is detected by the document edge detection sensor 17, the clutch mechanism is controlled to stop driving transmission to the conveying roller 15 and the reverse roller 16. At this time, the document is sandwiched between the transport roller 18 and the guide roller 19, and the subsequent transport of the document is performed by the transport roller 18, and the transport roller 15 acts as a tension roller.

  The output obtained by detecting the leading edge of the document by the document edge detection sensor 17 is also used as the timing for starting the image reading.

  The conveyed original is irradiated by the light source lamp 22 through the glass window 2b, and the reflected light from the original is reflected by the reflection mirror 24, imaged on the color image sensor 25 by the imaging lens 26, and converted into an electrical signal. Is done.

  On the other hand, when the trailing edge of the document is detected by the document edge detection sensor 17 and the document detection sensor 14 further detects the document, the clutch mechanism is controlled again to rotate the conveying roller 15 and the reverse roller 16, and the document tray 13. The conveyance of the document set in is started.

  By repeating the above operation, the originals stacked on the original tray 13 are sequentially conveyed onto the glass window 2b and images are read.

  In general, in the case of a color scanner, since a monochrome (binary image) image does not require gradation reproducibility, the charge accumulation time of the image sensor is set short, and a specific color is selected from the images formed on the image sensor. By selectively binarizing (for example, a green signal), it can be read faster than a color original.

  However, in the conventional image reading apparatus, it is necessary for the user to set in advance whether the image to be read is a color (multi-valued image) or a monochrome (binary image) because it does not have a mechanism for detecting document attributes in advance. was there.

  That is, the conventional image reading apparatus has the following problems. In general, reading a color original requires time as compared with monochrome, and the amount of data is greatly increased. If a document original (binary image) is read as a color original (multi-valued image), the reading time increases and the data amount becomes 24 times (RGB 3 colors × 8 bits), which is a waste of time and quantity. There are many. Therefore, according to the purpose of use, the user sets document attributes, that is, color document (multi-valued image) / monochrome document (multi-valued image) / monochrome document (binary image) in advance.

  However, when a document having a plurality of attributes is mixed in a document that should be read continuously, the user frequently resets the document attributes and executes image reading, which improves work efficiency. There was a problem of a significant decrease.

  The present invention solves the above-described conventional problems, and even when a color document (multi-value image) / monochrome document (multi-value image) / monochrome document (binary image) is mixed in the ADF, the user can An object of the present invention is to provide an image reading apparatus that does not require prior setting.

Image reading apparatus of the present invention to achieve this object, a conveying means for conveying the original, reading means for reading the images, the image attributes in the conveying direction upstream side of the document from the reading position of the image by the reading means And a changing unit that changes an image reading condition in accordance with a detection result of the detecting unit, and the reading unit is configured to detect the leading edge of the document when the detection of the document attribute is completed by the detecting unit. Is positioned at a position that does not reach the reading means, and before the reading of the original by the reading means is started in accordance with the conditions set by the changing means, the conveying speed of the original by the conveying means is equal to the previous conveying speed or slow setting, and without temporarily stopping the conveyance of the document, the image reading unit while conveying the original document by the conveying means In which it was to take look. Thus, it is possible to detect the attribute of the image before the document reaches the position where the reading unit is arranged, and to operate the image reading apparatus optimally according to the detected attribute of the image.

Further, the present invention provides a conveying unit that conveys an original, a reading unit that is supported so as to be movable along a conveyance path of the original by the conveying unit, a driving unit that moves the reading unit, and an image by the reading unit. A detection means for detecting an image attribute upstream of the document conveyance direction and a change means for changing an image reading condition in accordance with a detection result of the detection means. When the detection of the document attribute is completed by the detection unit, the unit is arranged at a position where the leading edge of the document does not reach the reading unit , and reading of the document by the reading unit is started according to the conditions set by the changing unit. Before the document transport speed by the transport means is set equal to or slower than the previous transport speed, Without temporarily stopping the feed, it is obtained so as to read an image by the reading unit while conveying the original document by the conveying means. Thus, it is possible to detect the attribute of the image before the document reaches the position where the reading unit is arranged, and to operate the image reading apparatus optimally according to the detected attribute of the image.

In the present invention, the detection means detects whether the attribute of the image is color or monochrome.

In the present invention, the detection means detects whether the attribute of the image is binary or multivalued.

In the present invention, the detection means detects whether the attribute of the image is color or monochrome, and whether it is binary or multi-valued.

As described above, the present invention can detect the attribute of the image before the document on which the image is written reaches the reading position by the reading unit, and can change the document conveyance speed according to the attribute of the image. Before reaching the reading position by the reading means, it is possible to set the shortest reading time of the reading means or the high speed document conveying speed according to the attribute of the image. Based on this setting, the entire reading time can be shortened by reading the original with the reading means while conveying the original with the conveying means.

Further, before the document on which the image is described reaches the reading position by the reading unit, the attribute of the image is detected by referring to all the images of the document, and the conveyance speed of the document is changed according to the attribute of the image. Since the image attributes are detected by referring to all the images of the document, it is possible to detect the attribute of the image more accurately, and the reading time of the shortest reading means or the high-speed document depending on the image attributes The conveyance speed can be set accurately.

  Further, when the image attribute is received from the outside, the moving reading means can be moved to the upstream side in the document conveyance direction to read the image. Therefore, if the image attribute is known in advance, the conveyance distance of the document can be set as much as possible. By shortening it, it is possible to minimize image reading position shift.

(Embodiment 1)
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of an image reading apparatus according to an embodiment of the present invention. Here, the same reference numerals are used for the same constituent members as those in the prior art, and the description thereof is omitted. In FIG. 1, reference numeral 50 denotes an image reading apparatus main body, and reference numeral 51 denotes an ADF unit attached to the image reading apparatus main body 50. Reference numeral 27 denotes an image sensor disposed in the ADF unit 51 to detect the attribute of the document image. Reference numeral 28 denotes a light source such as a fluorescent lamp. A document transport belt 29 transports the document to the position of the carriage 3. Reference numeral 30a denotes an original reading position, and the original is read at this portion. Reference numeral 31 denotes a document discharge unit that discharges the read document.

  FIG. 2 is a block diagram of the document attribute determination unit of the image reading apparatus according to the embodiment of the present invention. In FIG. 2, 32 is a driver for controlling the image sensor 27, 33 is a line synchronization signal, and the image sensor 27 reads and outputs image data line by line every time the line synchronization signal 33 is inputted. Reference numeral 34 denotes a pixel clock, and a signal corresponding to each pixel of the image sensor 27 is output in synchronization with the pixel clock 34. An image range signal 35 is counted by the driver 32 based on the pixel clock 34 and the number of pixels of the image sensor 27 and the like, and is output in synchronization with the line synchronization signal 33. Reference numerals 36r, 36g, and 36b denote amplifiers that amplify and adjust the RGB signal levels output from the image sensor 27 independently. A CPU 37 includes three or more channels of A / D converters, and independently converts the outputs from the amplifiers 36r, 36g, and 36b into digital signals. Reference numerals 38r, 38g, and 38b denote amplifier control signals, which adjust the gains of the amplifiers 36r, 36g, and 36b. When adjusting the gain, a D / A converter that converts the digital value output from the CPU 37 into an analog level is actually required between the CPU 37 and the amplifiers 36r, 36g, and 36b. Omitted. Reference numeral 39 denotes a block synchronization signal, which is a signal obtained by dividing the pixel clock 34 by 64.

  The operation of the image reading apparatus configured as described above will be described below with reference to FIGS.

  When a document is set on the document tray 13 of the ADF unit 51 and the document detection sensor 14 detects the document, the document is not set on the document tray 13, that is, when the document detection sensor 14 has not detected the document, the control means ( The carriage 3 that has been moved to the driven pulley 8 side by the rotation of the drive motor 9 of the image reading apparatus main body 50 is transmitted to the carriage 3 through the drive pulley 7, the drive wire 6, and the driven pulley 8. The position of the carriage 3 is controlled so that the document reading unit 23 of the carriage 3 is directly below the document reading position 30a. When the document is not set on the document tray 13, the carriage 3 is moved to the driven pulley 8 side, and the user reads the images on the document sequentially from the driven pulley 8 side. This is because the setting direction of the original is the same when the image is read and when the original is set on the original glass 2a and the image is read. In this method, the position of the carriage 3 is fixed, and the image is read by conveying the document by the ADF unit 51.

  In this state, when a document reading command is issued from an external host (not shown), the light source lamp 22 inside the carriage 3 and the light source 28 inside the ADF unit 51 are turned on, and the ADF unit 51 is provided independently. An ADF drive motor (not shown) is rotated. The rotational speed of the ADF drive motor at the time of activation is set so that the document is conveyed at an image reading speed that is approximately twice as fast as the color document reading speed. The transport roller 18 and the guide roller 19 are coupled to an ADF drive motor via a speed reduction mechanism (not shown), and the transport roller 18 and the guide roller 19 start rotating together with the rotation of the ADF drive motor. When the rotation of the ADF drive motor reaches a constant speed, a clutch mechanism (not shown) is controlled to rotate the conveying roller 15 and the reverse roller 16 to convey the original set on the original tray 13 one by one. Start. The reverse roller 16 uses a difference in friction between the roller and the document surface to suppress so-called double feeding in which a plurality of documents are conveyed simultaneously.

  When the leading edge of the conveyed document is detected by the document edge detection sensor 17, the clutch mechanism is controlled to stop driving transmission to the conveying roller 15 and the reverse roller 16. At this time, the document is sandwiched between the transport roller 18 and the guide roller 19, and the subsequent transport of the document is performed by the transport roller 18, and the transport roller 15 acts as a tension roller.

  When the leading edge of the document is detected by the document edge detection sensor 17, the reading by the image sensor 27, that is, the start timing of document attribute detection is set based on this, and at the same time, the image by the color image sensor 25 inside the carriage 3. The reading start timing is set.

  The document image read by the image sensor 27 is determined by the document attribute determination unit to be color (multi-value image) / monochrome (multi-value image) / monochrome (binary image). Here, the operation of the document attribute determination unit will be described in detail.

  A white calibration tape (not shown) is attached to the document conveyance path facing the image sensor 27 in the ADF unit 51. The line synchronization signal 33 and the pixel clock 34 are always output while the power is turned on, and the image sensor 27 always outputs data.

  First, the amplifier control signals 38r, 38g, and 38b are set by the CPU 37 so that the amplifiers 36r, 36g, and 36b have predetermined gain standard values at an appropriate time after the power is turned on and the image reading apparatus is not operating. The light source 28 is turned on. As a result, the output (white level) of the image sensor 27 with respect to the white calibration tape is input to the CPU 37. Next, the CPU 37 monitors the signal levels from the amplifiers 36r, 36g, and 36b, and the amplifier control signals 38r, 38g, and 38b are monitored so that each signal level becomes the same level and the overall signal level is greatly detected. Change the setting value. In general, since the error of the black level obtained by turning off the light source 28 is smaller than the error when the white level is detected, in this embodiment, only the gain adjustment of the amplifiers 36r, 36g, and 36b by the white level is performed. . However, in order to perform more accurate adjustment, for example, it is preferable to input a black level signal and determine the offset values of the amplifiers 36r, 36g, and 36b.

  Incidentally, as described above, the line synchronization signal 33 and the pixel clock 34 are always supplied from the driver 32 to the image sensor 27, and an analog image synchronized with the pixel clock 34 is input from the image sensor 27 every time the line synchronization signal 33 is input. A signal is being output. In the present embodiment, the line synchronization signal 33 is output at a cycle of 10 ms, and the pixel clock 34 is output at a cycle of about 4.8 μs. Therefore, if the number of pixels of the image sensor 27 is 1654 pixels (A4 size, 200 dpi), the transfer of the image data output in synchronization with the pixel clock 34 is completed in about 8 ms per line.

  On the other hand, the document conveyance speed is set to 50 mm / s. Since the line synchronization signal 33 is output every 10 ms, the document is conveyed by 0.5 mm while reading one line. When this document is being conveyed, the CPU 37 monitors the RGB signal levels in synchronization with the block synchronization signal 39 during the period when the image range signal 35 is being output. At the time of this monitoring, the A / D converter built in the CPU 37 sequentially performs analog-digital conversion for each of the R, G, and B channels every 10 μs.

  In the document attribute determination process according to the present embodiment, the RGB values of the image read by the image sensor 27 are measured in units of one pixel, a histogram is generated based on the appearance frequency of the values, and a first multi-value / binary image is determined. A second process for determining a color / monochromatic image by calculating an average value of image signals obtained by periodically sampling the output image of the image sensor 27 and comparing the average value for each RGB ing.

  First, a first process for determining a binary / multi-level document will be described. After the document end detection sensor 17 detects the leading edge of the document and a predetermined time has elapsed, the CPU 37 monitors the image range signal 35. If the image range signal 35 is output, the CPU 37 cancels the interruption by the block synchronization signal 39, and thereafter. Each time the block synchronization signal 39 is input to the CPU 37, data is fetched in the order of R → G → B. Since the block synchronization signal 39 is a signal obtained by dividing the pixel clock 34 by 64, an interrupt of the CPU 37 is generated every time 64 pixels are transferred. Reading R → G → B is repeated 8 times for each interrupt.

  In this first process, only the G (Green) signal that has the highest correlation with the luminance information of the document image, that is, the luminance information is reflected most accurately is used. The CPU 37 measures the value of G data every time this G signal is read, and increments the value of a memory area (not shown) determined corresponding to this value. For example, if the data value is 0, the memory area head address + 0 is incremented, and if it is 80H, the memory area head address + 80H is incremented. By this operation, a histogram for the output data of the image sensor 27 is generated.

  When the image sensor 27 reads all originals, the CPU 37 checks the histogram, and if there are two peaks in the small value portion (white portion), the large value portion (black portion), and the binary original, there is no peak. Or, if there is one, or if the intermediate level is higher than the prescribed range, it is determined as a multi-valued document.

  Next, a second process for determining a color / monochromatic document will be described. The second process is executed using data common to the first process. First, 8 data of each color obtained for each block synchronization signal 39 is accumulated for each RGB color component and stored in a predetermined memory area. In this memory area, the number of pixels of the image sensor 27 is 1654, and the block synchronization signal 39 rises in a cycle of 64 pixels, so 1654/64 = 26 words are required per line. By repeating this accumulating operation for a period of 8 lines, each color component is read 64 times and a value obtained by accumulating measurement values is stored in each word of the memory. The CPU 37 compares the RGB values read by the image sensor 27 at the same position with each other when the reading of the eight lines is completed, and if the difference between the values exceeds a specified value, it is a color document. For example, it is determined as a monochromatic original. In this second process, the document image is divided into blocks and the document attribute is determined using the average value of the blocks. In this case, in the document scanning process, even one color block exists, that is, a color image exists in a part of the document, and the document is determined to be a color document.

  Color (multi-value image) / monochrome (multi-value image) / monochrome (binary image) is determined by the first process and the second process described above. Actually, it is possible to determine the color (binary image). However, since there is almost no medium that can be read by the image reading apparatus, if the color is determined by the second process, the result of the first process is Even if it is a binary document, it is determined as a color multi-valued document.

  The reading of the document by the image sensor 27 for detecting the document attribute is terminated when the trailing edge of the document is detected by the document edge detection sensor 17 and a predetermined time has elapsed. The leading edge of the document that has passed through the image sensor 27 is transported to the document transport belt 29 and transported along the document glass 2a to the document reading position 30a.

  When the trailing edge of the original passes through the image sensor 27 and the reading of the original by the image sensor 27 and the original attribute determination are completed, the original is the original reading position of the original 3 in the carriage 3, that is, the image reading apparatus main body 50. It has not reached 30a.

  By the way, in general, when reading a monochrome (binary image) image with a color scanner, the monochrome (binary image) image does not require gradation reproducibility, so the charge accumulation time of the color image sensor 25 is set short. Furthermore, it is only necessary to selectively binarize a specific color (for example, a green signal) from the image formed on the color image sensor 25, and it can be read at a higher speed than a color original.

  The initial setting value of the document conveying speed of the ADF unit 51 is a reading speed for a monochrome document, and the document is conveyed at a speed of, for example, about 50 mm / s. If the determination result of the document attribute by the CPU 37 is monochrome (binary image), the transport speed of the ADF unit 51 does not change and the document is read at the document reading position 30a. On the other hand, if the determination result of the document attribute by the CPU 37 is color (multi-valued image), the transport speed of the ADF unit 51 is reduced to a speed of about 25 mm / s, and after reaching the constant speed, the document moves to the document reading position 30a. pass. In this way, by reducing the transport speed of the ADF unit 51 and setting the charge accumulation time of the color image sensor 25 to about twice that of a monochrome original, an image with excellent gradation can be read with a color original. . The document that has been read is discharged from the document discharge unit 31.

  On the other hand, when the trailing edge of the document is detected by the document edge detection sensor 17 and the document detection sensor 14 detects the next document to be read next, the clutch mechanism is controlled again, and the conveying roller 15 and the reverse roller 16 are rotated. The conveyance of the document to be read next set on the tray 13 is started.

  By repeating the above operation, the originals stacked on the original tray 13 are sequentially judged for image attributes by the image sensor 27 and conveyed to the original reading position 30a to be read.

  The basic operation mode of the image reading apparatus of the present invention has been described above. Next, the operation when the reading mode is designated from the outside in the image reading apparatus of the present invention will be described with reference to FIGS.

  The image reading apparatus is connected to an external host computer or the like, and not only transfers image data read through the interface to the host, but also instructs the operation mode from the host computer, reading conditions such as resolution and reading range, and document attributes. You can receive the specification etc directly.

(Embodiment 2)
FIG. 3 is a diagram showing an operation in the second operation mode of the image reading apparatus according to the embodiment of the present invention. A reading operation in the second operation mode will be described with reference to FIGS. 3 and 6. In FIG. 3, reference numeral 30b denotes a document reading position in the second operation mode. Other configurations are the same as those in the basic operation mode of the image reading apparatus described above, and thus description thereof is omitted.

  When the image reading mode and data indicating the document attribute in the subsequent operation are transferred from an external host (not shown) and the mode designation of the image reading device is the second operation mode, the data is stored in the document tray 13 of the ADF unit 51. When the document is set and the document detection sensor 14 detects the document, the drive motor 9 of the image reading apparatus main body 50 rotates, and the driving force is transmitted to the carriage 3 via the drive pulley 7, the drive wire 6 and the driven pulley 8. The position of the carriage 3 is controlled so that the document reading unit 23 of the carriage 3 is directly below the document reading position 30b. In this method, the position of the carriage 3 is fixed, and the image is read by conveying the document by the ADF unit 51.

  When a document reading command is issued from the external host in this state, the light source lamp 22 inside the carriage 3 is turned on, and an ADF drive motor (not shown) provided independently of the ADF unit 51 is rotated. The rotation speed of the ADF drive motor at the time of activation is set to a conveyance speed in accordance with the document attribute instructed by the host computer or the like before the ADF unit 51 is activated. The transport roller 18 and the guide roller 19 are coupled to an ADF drive motor via a speed reduction mechanism (not shown), and the transport roller 18 and the guide roller 19 start rotating together with the rotation of the ADF drive motor. When the rotation of the ADF drive motor reaches a constant speed, a clutch mechanism (not shown) is controlled to rotate the conveying roller 15 and the reverse roller 16 to convey the original set on the original tray 13 one by one. Start. The reverse roller 16 uses a difference in friction between the roller and the document surface to suppress so-called double feeding in which a plurality of documents are conveyed simultaneously.

  When the leading edge of the conveyed document is detected by the document edge detection sensor 17, the clutch mechanism is controlled to stop driving transmission to the conveying roller 15 and the reverse roller 16. At this time, the document is sandwiched between the transport roller 18 and the guide roller 19, and the subsequent transport of the document is performed by the transport roller 18, and the transport roller 15 acts as a tension roller.

  When the leading edge of the document is detected by the document edge detection sensor 17, the timing for starting image reading by the color image sensor 25 inside the carriage 3 is set based on this detection.

  The leading edge of the document that has passed through the document edge detection sensor 17 is transported to the document transport belt 29 and transported to the document reading position 30b along the document glass 2a. The original is read at the original reading position 30 b, and the original after reading is discharged from the original discharge unit 31.

  As described above, in the second operation mode, the document attribute determination by the image sensor 27 is not executed. Therefore, the user specifies the document attribute from the host computer or the like in advance.

  By the way, the document reading start timing of the image reading apparatus described above is generated when the document edge detection sensor 17 detects the leading edge of the document. In the second operation mode, the distance between the document edge detection sensor 17 and the document reading position 30b is 200 mm or more (approximately the size of the document glass 2a) as compared with the basic operation mode. Little affected by document transport. That is, since the document edge detection sensor 17 and the document reading position 30b are close to each other, the document can be read from the leading edge of the document with high positional accuracy. More specifically, in the basic operation mode, the leading edge position of the document and the actual reading start position include an error of about ± 2 mm due to the influence of the document conveyance belt 29, but in the second operation mode, there is no influence of the document conveyance belt 29. Therefore, it is suppressed to ± 1 mm or less.

  Considering the usage pattern of a general image reading apparatus, for example, it is often the case that all documents are known in advance as monochrome or color. As described above, the second operation mode has an advantage that the document can be read with high positional accuracy when the document attribute is known in advance.

(Embodiment 3)
FIG. 4 is a diagram showing an operation in the third operation mode of the image reading apparatus according to the embodiment of the present invention. Next, the third operation mode will be described with reference to FIGS. In FIG. 4, 30c is a document reading start position in the third operation mode, and 30d is a document reading end position in the third operation mode. Since other configurations are the same as those in the basic operation mode of the image reading apparatus, description thereof is omitted.

  When reading is requested from an external host (not shown) at a resolution different from a predetermined standard value, or when the third mode is directly designated as the mode of the image reading device, the image reading device The mode is set to the third operation mode.

  In the third operation mode, when a document is set on the document tray 13 of the ADF unit 51 and the document detection sensor 14 detects the document, the drive motor 9 of the image reading apparatus main body 50 rotates to drive the drive pulley 7 and the drive wire 6. The driving force is transmitted to the carriage 3 via the driven pulley 8, and the position of the carriage 3 is controlled so that the document reading section 23 of the carriage 3 is directly below the document reading start position 30c.

  In this state, when a document reading command is issued from the external host, the light source lamp 22 in the carriage 3 and the light source 28 in the ADF unit 51 are turned on, and an ADF drive motor (provided independently of the ADF unit 51). Rotate (not shown). The rotational speed of the ADF drive motor at the time of activation is set so that the document is conveyed at an image reading speed that is approximately twice as fast as the color document reading speed. The transport roller 18 and the guide roller 19 are coupled to an ADF drive motor via a speed reduction mechanism (not shown), and the transport roller 18 and the guide roller 19 start rotating together with the rotation of the ADF drive motor. When the rotation of the ADF drive motor reaches a constant speed, a clutch mechanism (not shown) is controlled to rotate the conveying roller 15 and the reverse roller 16 to convey the original set on the original tray 13 one by one. Start. The reverse roller 16 uses a difference in friction between the roller and the document surface to suppress so-called double feeding in which a plurality of documents are conveyed simultaneously.

  When the leading edge of the conveyed document is detected by the document edge detection sensor 17, the clutch mechanism is controlled to stop driving transmission to the conveying roller 15 and the reverse roller 16. At this time, the document is sandwiched between the transport roller 18 and the guide roller 19, and the subsequent transport of the document is performed by the transport roller 18, and the transport roller 15 acts as a tension roller.

  When the leading edge of the document is detected by the document edge detection sensor 17, the start timing of the document conveying belt 29 is set based on this, and when the trailing edge of the document is detected by the document edge detection sensor 17, With this as a starting point, the stop timing of the document conveying belt 29 is set. Similarly, the reading start and stop timings of the image sensor 27 are also set by detecting the leading edge and trailing edge of the document by the document edge detection sensor 17.

  The leading edge of the document that has passed through the document edge detection sensor 17 is conveyed to the document conveying belt 29. The document transport belt 29 is configured to be driven by a clutch mechanism. The document transport belt 29 is driven immediately before the document enters the document transport belt 29, and the document transport belt 29 allows the document to be scanned on the document glass 2a. It is conveyed along. When the entire original is placed on the original glass 2a by this conveyance, that is, when a specified time elapses after the trailing edge of the original passes the original edge detection sensor 17, the driving of the original conveyance belt 29 is stopped.

  When the conveyance of the original is completely stopped, the driving motor 9 of the image reading apparatus main body 50 is rotated, and the driving force is transmitted to the carriage 3 through the driving pulley 7, the driving wire 6 and the driven pulley 8. The document is read while moving 23 from the document reading start position 30c to the document reading end position 30d. The moving speed of the carriage 3 is uniquely determined because the document attributes have already been determined by the CPU 37 at the start of document reading, and the reading conditions such as the resolution have been designated by the external host before the ADF unit 51 is started. Yes. When reading of the entire surface of the document is completed, the carriage 3 starts a return operation in the direction of the document reading start position 30c. Further, the document that has been read simultaneously is discharged from the document discharge unit 31 by driving the document transport belt 29 again by the clutch mechanism.

  As described above, in the third operation mode, the image sensor 27 reads a document, the CPU 37 executes document attribute determination, and the driving speed of the carriage 3, that is, the reading speed is determined according to the reading conditions such as resolution. It is the composition which becomes. In general, the driving motor for ADF mounted on the ADF unit 51 is lower in driving accuracy than the driving motor 9 mounted on the image reading apparatus main body 50 due to cost restrictions, so that the reading resolution is to be increased. When the document needs to be conveyed at a lower speed, the carriage 3 is driven using the drive motor 9 mounted on the image reading apparatus main body 50 to read the document, thereby reading the document with high resolution and high accuracy. be able to.

  As described above, the image reading apparatus of the present invention can switch a plurality of operation modes based on an instruction from an external host computer in addition to the basic operation mode. For this reason, it is possible to always obtain a good image quality at a high speed even in any use form of the user.

  In the above description, the case of determining color (multi-value image) / monochrome (multi-value image) / monochrome (binary image) as the document attribute has been described. However, multi-value image / binary image or color / monochrome The same effect can be obtained by determining the above and performing the control as described above.

  Further, in the present embodiment, a color image sensor and a fluorescent lamp are employed as the document attribute detection image sensor 27. However, when only a multi-value image / binary image is determined as the document attribute, a cheaper monochrome image is detected. A combination of an image sensor and an LED array may be used.

  According to the present invention, it is possible to detect the attribute of an image before the document on which the image is described reaches the reading position by the reading unit, and to change the image reading time according to the attribute of the image. Before reaching the reading position by the means, it is possible to set the reading time of the shortest reading means according to the attribute of the image, the overall reading time can be shortened, and the original attribute determination of the image reading apparatus It is suitable for these fields.

1 is a schematic configuration diagram of an image reading apparatus according to an embodiment of the present invention. 1 is a block diagram of a document attribute determination unit of an image reading apparatus according to an embodiment of the present invention. The figure which shows operation | movement in the 2nd operation mode of the image reading apparatus in one Example of this invention. The figure which shows operation | movement in the 3rd operation mode of the image reading apparatus in one Example of this invention. Schematic configuration diagram of a conventional image reading apparatus Schematic configuration diagram of an optical system of a conventional image reading apparatus

Explanation of symbols

2a Document glass 3 Carriage 4 Support member 5 Shaft 6 Drive wire 7 Drive pulley 8 Drive pulley 9 Drive motor 10 Drive pulley support member 11 Biasing means 13 Document tray 14 Document detection sensors 15, 18, 20 Transport roller 16 Reverse roller 17 Document Edge detection sensor 19 Guide roller 21 Discharge tray 22 Light source lamp 23 Document reading unit 24 Reflection mirror 25 Color image sensor 26 Imaging lens 27 Image sensor 28 Light source 29 Document transport belts 30a and 30b Document reading position 30c Document reading start position 30d Document reading end position 31 Document discharge unit 32 Driver 33 Line synchronization signal 34 Pixel clock 35 Image range signal 36r, 36g, 36b Amplifier 37 CPU
38r, 38g, 38b Amplifier control signal 39 Block synchronization signal 50 Image reading device main body 51 ADF unit

Claims (5)

Conveying means for conveying the original, reading means for reading the images, and detecting means for detecting an attribute of the image in the conveyance direction upstream side of the document from the reading position of the image by the reading means, according to the detection result of the detecting means And changing means for changing the image reading condition,
The reading unit is disposed at a position where the leading edge of the document does not reach the reading unit when the detection of the document attribute is completed by the detection unit;
According to the conditions set by the changing means,
Before starting the reading of the original by the reading means, the conveying speed of the original by the conveying means is set equal to or slower than the conveying speed until then, and without stopping the conveying of the original,
An image reading apparatus, wherein an image is read by the reading unit while a document is conveyed by the conveying unit. A conveying unit that conveys an original, a reading unit that is movably supported along the conveyance path of the original by the conveying unit, a driving unit that moves the reading unit, and an image reading range by the reading unit A detection unit that detects an attribute of an image on the upstream side in the conveyance direction of the document, and a change unit that changes an image reading condition in accordance with a detection result of the detection unit;
At the time of image reading, the driving unit arranges the reading unit at a position where the leading end of the document does not reach the reading unit when the detection of the attribute of the document is completed by the detection unit .
According to the conditions set by the changing means,
Before starting the reading of the original by the reading means, the conveying speed of the original by the conveying means is set equal to or slower than the conveying speed until then, and without stopping the conveying of the original,
An image reading apparatus, wherein an image is read by the reading unit while a document is conveyed by the conveying unit. 3. The image reading apparatus according to claim 1, wherein the detection unit detects whether the attribute of the image is color or monochrome. 3. The image reading apparatus according to claim 1, wherein the detection unit detects whether the attribute of the image is binary or multi-valued. 3. The image reading apparatus according to claim 1, wherein the detection means detects whether the attribute of the image is color or monochrome, and whether the attribute is binary or multivalued.

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