JP5651549B2 - Image reading apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to an image reading apparatus and a technique for detecting the occurrence of condensation on a transparent member on which an original is placed in an image forming apparatus including the image reading apparatus.

  Conventionally, in an image reading apparatus, a document placed on a plate-shaped transparent member is irradiated with light through the transparent member by a light source such as a fluorescent lamp or an LED, and reflected light from the document is converted into a photoelectric conversion element. The document image data obtained by reading the image of the document is generated by photoelectrically converting the image and outputting it.

  Further, for example, in Patent Document 1 below, in order to determine that condensation has occurred, a data pattern obtained by reading the reflection plate for one scanning line when condensation has not occurred is stored in a line memory in advance. Whether or not dew condensation has occurred by comparing the data pattern stored in the line memory in advance with the data obtained by reading the reflecting plate for one scanning line at the time of the determination. Techniques for determining whether or not are described.

JP-A-60-192454

  However, in the technique described in Patent Document 1, in order to determine that condensation has occurred, one line in the main scanning direction of a member (reflection plate) for determining condensation when no condensation has occurred. It was necessary to provide a storage area sufficient to store data obtained by reading a minute (one scan line) image as a plurality of pixels.

  Therefore, the present invention has been made in view of such circumstances, and reduces the amount of data to be stored in order to determine that condensation has occurred on the transparent member on which the document is placed. An object of the present invention is to provide an image reading apparatus and an image forming apparatus capable of performing the above.

An image reading apparatus according to the present invention includes a plate-like transparent member on which a document is placed, a light source that irradiates light to the document through the transparent member, and at least a part of the image of the document by pixel values. An image reading unit including a plurality of pixel detection units that read as a plurality of pixels whose brightness is expressed, a dew condensation determination member disposed in a part of the transparent member, and light irradiation by the light source is not performed. A black reference data acquisition unit that acquires a plurality of pixel values read by the plurality of pixel detection units as black reference data by causing the image reading unit to read the image, and all the black reference data included in the black reference data the result of dividing the sum of the pixel values by the number of the all pixel values, and the black reference pixel value calculation unit that calculates as a black reference pixel value, a storage unit for storing the black reference pixel value, prior to the said light source Data acquisition processing for acquiring condensation determination data indicating pixel values respectively corresponding to the plurality of pixel detection units by causing the image reading unit to read an image of the condensation determination member while irradiating the condensation determination member with light. A condensation determination data acquisition unit that performs the difference between each pixel value indicated by the condensation determination data and the black reference pixel value stored by the storage unit, and a condensation determination corresponding to each pixel detection unit that has read each pixel. Condensation determination correction value generation unit that calculates as a correction value and when at least one of the plurality of condensation determination correction values is larger than a predetermined condensation determination threshold value, condensation occurs on the transparent member A dew condensation determination unit that determines that the

  When light from a light source is irradiated onto a transparent member where condensation occurs, the light is irregularly reflected at the portion where condensation occurs and the reflectance increases. The image read in this state becomes brighter than when no condensation occurs. On the other hand, the brightness of an image read without irradiating light does not change regardless of whether or not condensation occurs. Therefore, the difference between the brightness of the image read without irradiating light and the brightness of the image read with irradiating light becomes larger when condensation occurs on the transparent member. That is, it is possible to determine whether or not condensation has occurred on the transparent member based on the difference between the brightness of the image read without irradiating light and the brightness of the image read by irradiating light. it can.

According to the configuration of the present invention, a plurality of pixel values read by a plurality of pixel detection units are acquired as black reference data by causing an image reading unit to read an image without performing light irradiation with a light source. . Then, a result obtained by dividing the sum of all the pixel values included in the acquired black reference data by the number of all the pixel values is calculated as a black reference pixel value and stored in the storage unit. Further, a difference between each pixel value indicated by the condensation determination data and the black reference pixel value stored in the storage unit is calculated as a condensation determination correction value, and based on a comparison result between the condensation determination correction value and the condensation determination threshold value. Then, it is determined whether or not condensation occurs on the transparent member.

  Here, the plurality of pixel values read by the plurality of pixel detection units are unlikely to vary between pixels because the plurality of pixel detection units are configured in the same image reading unit, and the calculated black color It is considered that the value is substantially equal to the reference pixel value. In other words, by assuming that the black reference pixel values stored in the storage unit indicate a plurality of pixel values read by a plurality of pixel detection units without performing light irradiation by the light source, the light irradiation by the light source is performed. Instead of storing the plurality of pixel values read by the plurality of pixel detection units in the storage unit without performing it, the data to be stored in the storage unit can be limited to only the black reference pixel values.

Further, the black reference data acquisition unit is read by the plurality of pixel detection units a plurality of times by causing the image reading unit to read the image a plurality of times without performing light irradiation by the light source. The plurality of pixel values are acquired as the black reference data, and the black reference pixel value calculation unit calculates a sum of all the pixel values for the plurality of times included in the black reference data for all the pixel values for the plurality of times. The result obtained by dividing by a number is preferably calculated as the black reference pixel value.

According to this configuration, since the black reference pixel value is calculated as a result of dividing the sum of all the pixel values for a plurality of times included in the black reference data by the number of all the pixel values for the plurality of times , the black reference data The reading error of the image reading unit included in is reduced, and a black reference pixel value with high accuracy is calculated.

  The condensation determination data acquisition unit acquires the plurality of condensation determination data by repeating the data acquisition process a plurality of times, and corresponds to the same pixel detection unit among the plurality of acquired condensation determination data. An average value of pixel values is calculated as a new pixel value corresponding to each of the plurality of pixel detection units, the new plurality of pixel values are acquired as new condensation determination data, and the condensation determination correction value generation unit is It is preferable to calculate each of the dew condensation determination correction values by using the new dew condensation determination data as the dew condensation determination data.

  According to this configuration, a plurality of new pixel values constituting new condensation determination data to be used as the condensation determination data are pixel values corresponding to the same pixel detection unit among the plurality of condensation determination data. It is calculated as an average value. For this reason, the reading error of the image reading unit included in the dew condensation determination data is reduced, and dew condensation determination data including accurate pixel values is generated.

The image reading unit includes a plurality of image reading units, each of the image reading units is configured by a physically independent chip, and the black reference data acquiring unit acquires black reference data corresponding to each of the image reading units. The black reference pixel value calculation unit calculates a black reference pixel value corresponding to each of the image reading units based on the plurality of black reference data, and the storage unit corresponds to each of the image reading units. The condensation determination data acquisition unit acquires a plurality of condensation determination data corresponding to each of the image reading units, and the condensation determination correction value generation unit includes the plurality of condensation determination data and the plurality of condensation determination data. It is preferable to calculate the dew condensation determination correction value corresponding to each pixel detection unit of each image reading unit based on the plurality of black reference pixel values stored in the storage unit.

  According to this configuration, a black reference pixel value that is an average value of pixel values read by a plurality of pixel detection units without performing light irradiation by a light source is different for each physically independent chip. Also, black reference data corresponding to each image reading unit is acquired, black reference pixel values corresponding to each image reading unit are calculated, and stored in a storage unit provided corresponding to each image reading unit. can do.

  Between image reading units configured with different chips, the variation in pixel values to be detected is larger than the variation in pixel values within the same chip. Therefore, corresponding dew condensation determination data is acquired for each physically independent chip, that is, for each image reading unit. Then, based on the plurality of condensation determination data and the plurality of black reference pixel values stored in the plurality of storage units, a condensation determination correction value corresponding to each pixel detection unit of each image reading unit is calculated. Then, using the dew condensation determination correction value corresponding to each pixel detection unit of each calculated image reading unit, whether dew condensation has occurred at a position that can be read by the image reading unit in the transparent member for each image reading unit By determining whether or not, it is possible to reduce the influence of variation in characteristics between chips. As a result, the accuracy of determining the occurrence of condensation is improved.

  Further, the dew condensation determination unit has a predetermined number or more of dew condensation determination correction values larger than the dew condensation determination threshold among the dew condensation determination correction values corresponding to the pixel detection units of the image reading units. When present, it is preferable to determine that condensation has occurred at a position of the transparent member that can be read by each of the image reading units.

  According to this configuration, among the condensation determination correction values corresponding to each pixel detection unit of each image reading unit, when the number of condensation determination correction values larger than the condensation determination threshold is greater than or equal to a predetermined reference number, It is determined that condensation occurs at a position that can be read by each image reading unit in the transparent member. For this reason, when there is at least one condensation determination correction value larger than the condensation determination threshold value among the condensation determination correction values corresponding to each pixel detection unit of each image reading unit, each image reading unit in the transparent member Compared with the case where it is determined that condensation has occurred at a readable position, the possibility that the determination is erroneously determined can be reduced.

  The image reading unit further includes a reading control unit that reads an image of the document while moving the image reading unit in a sub-scanning direction relative to the document, and the dew condensation determination member is configured to read the image of the document on the transparent member. It is arranged in a direction opposite to the direction in which the image reading unit is moved by the reading control unit from the position at which reading is started, and the reading control unit before the image reading unit reads the image of the document. Further, it is preferable to cause the dew condensation determination unit to perform the determination.

  According to this configuration, dew condensation is determined before the image of the original is read by the image reading unit. For this reason, it is possible to avoid unnecessarily causing the image reading unit to read the image of the document in a state where condensation occurs on the transparent member.

  Moreover, it is preferable that the said dew condensation determination member is black.

  According to this configuration, since the dew condensation determination member is black, the influence of light irregular reflection due to dew condensation is greater than when the dew condensation determination member is not black, that is, dew condensation occurs on the transparent member. The difference between the corresponding pixel values becomes large between the condensation determination data at the time and the condensation determination data when the condensation does not occur on the transparent member. This also increases the difference between the condensation determination correction value when condensation occurs on the transparent member and the condensation determination correction value when condensation does not occur on the transparent member. And the accuracy of the determination of the occurrence of condensation can be improved.

  An image forming apparatus according to the present invention includes the image reading device and an image forming unit that forms an image using data read by the image reading unit.

  According to the present invention, there is provided an image reading apparatus and an image forming apparatus capable of reducing the amount of data to be stored in order to determine that dew condensation has occurred on a transparent member on which an original is placed. It becomes possible to do.

1 is a longitudinal sectional view illustrating an example of a configuration of a multifunction peripheral as an example of an image forming apparatus according to the present invention. 1 is a schematic side view illustrating an example of a configuration of an image reading apparatus of a multifunction peripheral. It is a top view which shows an example of a transparent member. 1 is a block diagram illustrating a schematic configuration of an image reading apparatus. It is explanatory drawing which shows an example of black reference data, a black reference pixel value, condensation determination data, and condensation determination correction data. 6 is a flowchart illustrating an example of document reading control by a reading control unit. FIG. 3 is a schematic side view showing another example of the configuration of the image reading apparatus of the multifunction machine different from FIG. It is a top view which shows an example of a some image reading part. It is explanatory drawing which shows an example of black reference | standard data, a black reference | standard pixel value, condensation determination data, and condensation determination correction data in the structure of 4th embodiment.

[First embodiment]
Embodiments of an image reading apparatus and an image forming apparatus according to the present invention will be described below with reference to the drawings. In the following embodiment, an embodiment in which the image forming apparatus according to the present invention is integrated into a multifunction machine having functions such as a copy, a scanner, a facsimile, and a printer will be described as an example.

  FIG. 1 is a vertical cross-sectional view schematically showing the internal configuration of the multifunction machine 1 according to the present embodiment. A multifunction device 1 shown in FIG. 1 includes an image reading device 2 and a device body 3.

  The image reading apparatus 2 includes a document feeding unit 21 and a scanner unit 22.

  The document feeding unit 21 realizes ADF, and includes a document tray 231, a sheet feeding roller 232, a transport drum 233, a sheet discharge roller pair 234, and a sheet discharge tray 235.

  The document tray 231 is a place where the document is placed. The documents placed on the document tray 231 are taken one by one by the paper feed roller 232 and conveyed to the conveyance drum 233. The document that has passed through the transport drum 233 is discharged to a discharge tray 235 by a discharge roller 234.

  The scanner unit 22 optically reads an image of a document and generates image data. The scanner unit 22 includes a contact glass 221, a light source 222, a first mirror 223, a second mirror 224, a third mirror 225, a first carriage 226, a second carriage 227, an imaging lens 228, and a CCD (Charge) serving as a line sensor. Coupled Device) 229.

  The contact glass 221 constitutes an example of a transparent member according to the present invention, and constitutes a surface on which a document is placed. The light source 222 and the first mirror 223 are supported by the first carriage 226, and the second mirror 224 and the third mirror 225 are supported by the second carriage 227. As the light source 222, for example, a white fluorescent lamp such as a white LED is used. When light is emitted from the light source 222 toward the document via the contact glass 221, the first mirror 223, the second mirror 224, and the third mirror are used. The reflected light reflected from the original is guided to the CCD 229 by the 225, the first carriage 226, the second carriage 227, and the imaging lens 228.

  The CCD 229 constitutes an example of the image reading unit according to the present invention, and is a so-called one-dimensional image sensor constituted by one physically independent chip. The CCD 229 has a light receiving surface composed of a plurality of light receiving elements (an example of a pixel detection unit according to the present invention) arranged in a line in the main scanning direction, and the main scanning direction 1 of the document condensed on the light receiving surface. Image data for one line in the main scanning direction is output by photoelectrically converting the reflected light for the lines with the plurality of light receiving elements. That is, the image data for one line in the main scanning direction is composed of values (pixel values) indicating the brightness of the reflected light corresponding to each of the plurality of light receiving elements (pixel detection units).

  As a document reading method in the image reading apparatus 2, there are a flat bed reading mode for reading a document placed on the contact glass 221 and an ADF reading mode for reading a document while the document is taken in by ADF.

  In the flat bed reading mode, the light source 222 irradiates the document through the contact glass 221, and the reflected light for one line in the main scanning direction in which the pixels of the CCD 229 that is a one-dimensional image sensor are arranged is the first mirror 223, The light is reflected in the order of the second mirror 224 and the third mirror 225 and enters the imaging lens 228. The light incident on the imaging lens 228 is imaged on the light receiving surface of the CCD 229.

  Such an operation is performed line by line in parallel with the movement of the first carriage 226 and the second carriage 227 in the direction orthogonal to the main scanning direction (sub-scanning direction, arrow Y direction). The CCD 229 simultaneously processes document image data for one line in the main scanning direction, and outputs the image data to an A / D converter 216 (see FIG. 4) described later in units of one line.

  In the ADF reading mode, the originals placed on the original tray 231 are taken into the original conveyance path one by one by the paper feed roller 232, and the image reading position PS provided in the conveyance path from the conveyance drum 233 to the discharge tray 235. When the document passes above, the light source 222 irradiates the document, and the reflected light for one main scanning line is reflected in the order of the first mirror 223, the second mirror 224, and the third mirror 225 to the imaging lens 228. Incident. The light incident on the imaging lens 228 is imaged on the light receiving surface of the CCD 229.

  Such an operation is performed line by line in parallel with the conveyance of the document by the conveyance drum 233. The CCD 229 simultaneously processes document image data for one line in the main scanning direction, and outputs the image data to an A / D converter 216 (see FIG. 4) described later in units of one line.

  Further, the document feeder 21 includes a document reversing mechanism including a switching guide 236, a reversing roller 237, and a reversing conveyance path 238.

  The switching guide 236 is switched to the upper side after reading the back side during single-sided reading and double-sided reading, and the document that has passed through the transport drum 233 is discharged onto the discharge tray 235 by the discharge roller 234. The switching guide 236 is switched to the lower side after the surface reading at the time of double-sided reading, and the document that has passed through the conveying drum 233 is conveyed to the nip portion of the reverse roller 237. Thereafter, the switching guide 236 is switched to the upper side, and the reverse roller 237 rotates in the reverse direction, whereby the document is re-conveyed to the conveyance drum 233 via the reverse conveyance path 238.

  That is, the original whose surface is read by the first reading is reversed and re-conveyed using the original reversing mechanism including the switching guide 236, the reversing roller 237, and the reversing conveyance path 238, so that the CCD 229 reads the back side again. Can be performed.

  The apparatus main body 3 includes a plurality of paper feed cassettes 461 that contain paper (recording media), a recording unit 40 that forms an image on paper conveyed from the paper feed cassette 461, and one sheet from the paper feed cassette 461. Paper feed rollers 462 that are fed out one by one and conveyed to the recording unit 40, the stack tray 6 disposed on the left side, and conveyance rollers 463 and 464 that convey the paper that has passed through the recording unit 40 to the stack tray 6 or the discharge tray 48. And.

  The apparatus main body 3 further includes a manual feed tray 471, a size of paper that is not stored in any paper feed cassette from the manual feed tray 471, or a paper that has already been subjected to image formation on one side (back paper). ), An arbitrary recording medium such as an OHP sheet can be placed, and is fed into the apparatus main body 3 one by one by a paper feed roller 472.

  The recording unit 40 constitutes an example of the image forming unit according to the present invention. The recording unit 40 outputs a laser beam based on the image data generated by the scanner unit 22 to expose the photosensitive drum 43, and the photosensitive drum. An exposure device 42 that forms an electrostatic latent image on the surface of 43, a developing device 44 that forms a toner image on the photosensitive drum 43 based on the electrostatic latent image, and a toner image formed on the photosensitive drum 43 A transfer device 41 that transfers the toner image onto the paper, and a fixing device 45 that heats the paper on which the toner image is transferred and fixes the toner image onto the paper.

  In addition, an operation unit 5 is provided in front of the apparatus body 3. The operation unit 5 includes a touch panel 51, a numeric keypad 53, a start key 55, and the like. The touch panel 51 displays various operation screens and various operation buttons for the user to input various operation commands. The numeric keypad 53 is used to input execution conditions such as the number of recording sheets (number of copies to be printed), and the start key 55 is used to input an instruction to start execution of image forming processing by the recording unit 40. It is done.

  FIG. 2 is an enlarged view of the inside of the document feeder 21 and the scanner unit 22. FIG. 3 is a plan view of the contact glass 221 (a view of the contact glass 221 looking up from below). As shown in FIGS. 2 and 3, the contact glass 221 is outside the area (original reading area) where the original to be read indicated by the rectangular area in FIG. From the image reading position PS, the direction in which the reading of the document is advanced, that is, the moving direction (+ Y direction in the drawing) of the first carriage 226 and the second carriage 227 (the −Y direction in the drawing). Further, a white reference plate 10 and a black reference plate 11 as an example of a dew condensation determination member according to the present invention are attached.

  The white reference plate 10 is a white belt-like member attached to the contact glass 221 so as to extend in the main scanning direction (a direction orthogonal to the paper surface in FIG. 2 and an X direction in FIG. 3). Is a black belt-like member attached to the contact glass 221 so as to extend in the main scanning direction. Here, black means a color having a light reflectance of 30% or less.

  Next, the electrical configuration of the multifunction machine 1 will be described. FIG. 4 is a block diagram illustrating an electrical configuration of the multifunction machine 1. As shown in FIG. 4, the multifunction device 1 includes a CPU 211, a RAM 212, a ROM 213, a reading control unit 214, an ASIC 215, an A / D conversion unit 216, a shading correction unit 217, an image processing unit 218, These units, the scanner unit 22 and the operation unit 5 are connected by a data bus BUS so that they can communicate with each other.

  The CPU 211 controls the overall operation of the multifunction device 1 and controls the operation of each unit in the multifunction device 1 according to a program stored in the ROM 213 or an unillustrated HDD. In the present embodiment, the CPU 211 particularly functions as the condensation determination data acquisition unit 12, the black reference data acquisition unit 13, and the black reference pixel value calculation unit 14. Details of the dew condensation determination data acquisition unit 12, the black reference data acquisition unit 13, and the black reference pixel value calculation unit 14 will be described later.

  The RAM 212 is a memory used as a work area when the CPU 211 controls the operations of the multifunction machine 1 and the image reading apparatus 2 according to the program. The ROM 213 is a memory that stores the program, various setting values, and the like.

  The reading control unit 214 performs control to read the image of the document for each line in the main scanning direction while moving the CCD 229 in the sub scanning direction relative to the document. Specifically, the reading control unit 214 performs illumination operation by the light source 222, movement operation of the first carriage 226 and the second carriage 227 in the sub-scanning direction, conveyance operation of the document in the sub-scanning direction by the document feeding unit 21, and The light receiving operation of the CCD 229 is controlled to cause the scanner unit 22 to read the image of the document.

  An ASIC (Application Specific Integrated Circuits) 215 is configured to be able to execute a process for determining the occurrence of condensation on the contact glass 221 at high speed with dedicated hardware. Specifically, the ASIC 215 includes a condensation determination correction value generation circuit 15 as a condensation determination correction value generation unit according to the present invention, a condensation determination circuit 16 as a condensation determination unit according to the present invention, and a memory according to the present invention. A register 17 as a unit is incorporated. The details of the condensation determination correction value generation circuit 15, the condensation determination circuit 16, and the register 17 will be described later.

  The A / D conversion unit 216 performs A / D conversion for converting image data of a document for one line in the main scanning direction, which is an analog electric signal output from the scanner unit 22, into digital image data having a predetermined number of bits. Process.

  The A / D conversion unit 216 outputs the image data after the A / D conversion processing to the shading correction unit 217, the condensation determination data acquisition unit 12, the black reference data acquisition unit 13, and the like.

  The shading correction unit 217 is configured to be capable of high-speed processing using dedicated hardware such as an ASIC, for example, and performs shading correction on the image data output via the scanner unit 22 and the A / D conversion unit 216.

  For example, the shading correction unit 217 outputs the white reference data obtained by causing the CCD 229 to read the image for one line in the main scanning direction of the white reference plate 10 as a plurality of pixels and the CCD 229 without irradiating the light from the light source 222. The black reference in which an image for one line in the main scanning direction is read as a plurality of pixels without performing light irradiation by the light source 222 by performing A / D conversion processing on the analog electrical signal by the A / D conversion unit 216. A difference in pixel value between corresponding pixels is calculated with respect to the data. Then, with respect to the result obtained by dividing the difference between the pixel values of the corresponding pixels between the original image data obtained by reading the image for one line in the main scanning direction of the original and the black reference data by the calculated difference, Shading correction is performed by multiplying the maximum pixel value.

  As a result, shading correction is performed on the original image data to be image-formed, and uneven distribution of illumination by the light source 222 and sensitivity differences between the pixels of the CCD 229 are corrected. The shading correction unit 217 is not limited to this, and may be configured to perform shading correction by other methods. The shading correction process performed by the shading correction unit 217 may be implemented as a program executed by the CPU 211.

  The image processing unit 218 is configured to be capable of high-speed processing with dedicated hardware such as an ASIC, for example, and the image data output from the A / D conversion unit 216 or the image data after shading correction processing output from the shading correction unit 217 For this, various image processing is performed. For example, the image processing unit 218 performs correction processing such as level correction and gamma correction, image processing processing such as image data compression or expansion processing, enlargement or reduction processing on the image data. Note that various image processing performed by the image processing unit 218 may be implemented as a program executed by the CPU 211.

  In the following, various processes performed by the dew condensation determination data acquisition unit 12, the black reference data acquisition unit 13, the black reference pixel value calculation unit 14, the dew condensation determination correction value generation circuit 15, and the dew condensation determination circuit 16 are stored in the register 17. Data to be described in detail.

  As shown in FIG. 5A, the black reference data acquisition unit 13 performs A / D conversion on the analog electrical signal output from the CCD 229 by the A / D conversion unit 216 without irradiating light from the light source 222. By performing the processing, an image for one line in the main scanning direction is read as a plurality of pixels 1, 2,..., N−1, n without irradiating light from the light source 222. Pixel values B (1), B (2),..., B (n−1), B (n) are acquired, and the acquired pixel values B (1) to B (n) are stored in the RAM 212. .

  Pixel values B (1) to B (n) represent the brightness of the pixels 1 to n in 256 steps of 8 bits (0 to 255), respectively. The pixel value, for example, indicates that 0 is the darkest and 255 is the brightest. The pixel values B (1) to B (n) constitute black reference data B for one line in the main scanning direction. Hereinafter, the numbers in parentheses attached to the pixel values indicate the corresponding pixel numbers (the numbers of the light receiving elements included in the CCD 29).

  The black reference data acquisition unit 13 may be configured not to newly acquire the black reference image data B when the black reference image data B is already stored in the RAM 212.

  As shown in FIG. 5A, the black reference pixel value calculation unit 14 includes a plurality of pixel values B (1) to B (n) that constitute the black reference data B acquired by the black reference data acquisition unit 13. An average value is calculated, and the calculated average value is defined as a black reference pixel value Bd (Bd = (B (1) + B (2) +... + B (n−1) + B (n)) / n).

  Then, the black reference pixel value calculation unit 14 outputs the calculated black reference pixel value Bd to the ASIC 215. In accordance with this, the ASIC 215 is configured to store the black reference pixel value Bd input from the black reference pixel value calculation unit 14 in the register 17.

  As shown in FIG. 5A, the condensation determination data acquisition unit 12 uses a CCD 229 to convert an image for one line in the main scanning direction of the black reference plate 11 into a plurality of pixels 1, 2,. By reading as n, pixel values C (1), C (2),..., C (n−1), C (n) of each pixel are acquired. Condensation determination data C for one line in the main scanning direction is constituted by the pixel values C (1) to C (n).

  The condensation determination data acquisition unit 12 then outputs the condensation determination data C for one line in the main scanning direction to the ASIC 215. In accordance with this, the ASIC 215 is configured to input the condensation determination data C for one line in the main scanning direction input from the condensation determination data acquisition unit 12 to the condensation determination correction value generation circuit 15.

  As shown in FIG. 5A, the dew condensation determination correction value generation circuit 15 has a pixel value C (1) in the dew condensation determination data C input from the dew condensation determination data acquisition unit 12 for each of the plurality of pixels 1 to n. ) To C (n) and the black reference pixel value Bd stored in the register 17 to determine the dew condensation determination correction values C ′ (1), C ′ (2),..., C ′ (n−1). ) And C ′ (n) (for example, in the case of pixel n, C ′ (n) = C (n) −Bd). Condensation determination correction data C 'for one line in the main scanning direction is constituted by the condensation determination correction values C' (1) to C '(n). The condensation determination correction value generation circuit 15 is configured to output the calculated condensation determination correction data C ′ for one line in the main scanning direction to the condensation determination circuit 16.

  The condensation determination circuit 16 generates condensation on the contact glass 221 based on the comparison result between the condensation determination correction data C ′ input from the condensation determination correction value generation circuit 15 and the condensation determination threshold value stored in the register 17 in advance. A control signal indicating whether or not Note that the dew condensation determination threshold is determined in advance based on an experimental value such as causing the contact glass 221 to dew and performing a test operation, and is stored in the register 17.

  Specifically, the dew condensation determination circuit 16 selects one dew condensation determination correction value C ′ (1) from the dew condensation determination correction data C ′ for one line in the main scanning direction input from the dew condensation determination correction value generation circuit 15. ) To C ′ (n) are determined to be larger than the dew condensation determination threshold, a control signal indicating that dew condensation has occurred on the contact glass 221 is output. On the other hand, when the dew condensation determination circuit 16 determines that all the dew condensation determination correction values C ′ (1) to C ′ (n) in the dew condensation determination correction data C ′ are not larger than the dew condensation determination threshold, the contact glass A control signal indicating that no condensation has occurred is output to 221.

  That is, an example of the image reading apparatus according to the present invention includes the image reading apparatus 2, the condensation determination data acquisition unit 12, the black reference data acquisition unit 13, the black reference pixel value calculation unit 14, and the condensation determination correction value. A generation circuit 15, a dew condensation determination circuit 16, and a register 17 are provided.

  When the contact glass 221 where condensation occurs is irradiated with light from the light source 222, the light is irregularly reflected at the portion where condensation occurs and the reflectance increases. The image read in this state becomes brighter than when no condensation occurs. On the other hand, the brightness of an image read without irradiating light does not change regardless of whether or not condensation occurs. Therefore, the difference between the brightness of the image read without irradiating light and the brightness of the image read with irradiating light is larger when condensation occurs on the contact glass 221. That is, it is determined whether or not condensation occurs on the contact glass 221 based on the difference between the brightness of the image read without irradiating light and the brightness of the image read by irradiating light. Can do.

  According to the configuration of the first embodiment, by causing the CCD 229 to read an image without irradiating the light from the light source 222, a plurality of pixel values B (1) to B (1) read by the plurality of light receiving elements of the CCD 229 are read. B (n) is acquired as the black reference data B. Then, the average value of the acquired plurality of pixel values B (1) to B (n) is calculated as the black reference pixel value Bd and stored in the register 17.

  The difference between the pixel values C (1) to C (n) indicated by the condensation determination data C and the black reference pixel value Bd stored in the register 17 is the condensation determination correction value C ′ (1) to C ′ ( n), and it is determined whether or not condensation has occurred in the contact glass 221 based on a comparison result between the condensation determination correction values C ′ (1) to C ′ (n) and the condensation determination threshold. .

  Here, the plurality of pixel values B (1) to B (n) read by the plurality of light receiving elements of the CCD 229 have a variation between pixels because the CCD 229 is configured by one physically independent chip. It is unlikely to occur and is considered to indicate a value substantially equal to the calculated black reference pixel value Bd. That is, the black reference pixel value Bd stored in the register 17 can be regarded as indicating a plurality of pixel values read by a plurality of light receiving elements of the CCD 229 without performing light irradiation by the light source 222. Accordingly, instead of storing all the plurality of pixel values B (1) to B (n) read by the plurality of light receiving elements of the CCD 229 without irradiating the light from the light source 222, the register 17 Can be limited to only the black reference pixel value Bd.

  Hereinafter, the reading control of the document by the reading control unit 214 will be described in detail with reference to FIG.

  When an instruction for reading a document is input to the reading control unit 214 by the operation of the operation unit 5 by the user and the instruction is received by the CPU 211 (S1), the reading control unit 214 causes the black reference data acquisition unit 13 to receive a black reference. After the data B is acquired (S2), the black reference pixel value Bd is calculated by the black reference pixel value calculation unit 14, and the calculated black reference pixel value Bd is stored in the register 17 (S3). Next, the reading control unit 214 causes the condensation determination data acquisition unit 12 to execute a data acquisition process for acquiring the condensation determination data C, and causes the condensation determination correction value generation circuit 15 to output the acquired condensation determination data C. (S4).

  Then, the dew condensation determination correction value generation circuit 15 uses the dew condensation determination data C input from the dew condensation determination data acquisition unit 12 and the black reference pixel value Bd stored in the register 17 to dew condensation determination correction value C ′ (1 ) To C ′ (n) is generated, and the generated condensation determination correction data C ′ is output to the condensation determination circuit 16 (S5).

  Next, in the condensation determination circuit 16, any one of the condensation determination correction values C ′ (1) to C ′ (n) among the condensation determination correction data C ′ input from the condensation determination correction value generation circuit 15 is registered. 17 is determined to be larger than the condensation determination threshold value stored in advance in 17, a control signal indicating that condensation has occurred on the contact glass 221 is output (S <b> 6; YES), and all the condensation determination correction values C ′. When it is determined that (1) to C ′ (n) are not larger than the dew condensation determination threshold, a control signal indicating that dew condensation has not occurred on the contact glass 221 is output (S6; NO).

  When the control signal indicating that no condensation occurs on the contact glass 221 is output from the condensation determination circuit 16 (S6; NO), the reading control unit 214 moves the first carriage 226 and the second carriage 227 to the white reference plate. Then, the image of the white reference plate 10 is read by one line in the main scanning direction by the CCD 229, and the read white reference data is stored in the RAM 212 (S7).

  Then, the reading control unit 214 moves the first carriage 226 and the second carriage 227 to the document reading start position PS and then completes reading of all the lines in the main scanning direction of the document (S10; NO). The image of the original is read by the CCD 229 for each line in the main scanning direction (S8).

  The read document image data for one line in the main scanning direction uses the black reference data B acquired in step S2 and the white reference data stored in the RAM 212 in step S7. The shading correction is performed by 217 (S9). In this way, the document image data for all lines in the main scanning direction subjected to the shading correction in steps S1 to S10 is used for image formation.

  On the other hand, when a control signal indicating that condensation has occurred on the contact glass 221 is output from the condensation determination circuit 16 (S6; YES), the reading control unit 214 does not cause the CCD 229 to read the document, for example, A warning message indicating that condensation has occurred on the contact glass 221 is displayed on the touch panel 51 of the operation unit 5 (S11).

  As described above, since the dew condensation is determined before the image of the original is read by the CCD 229, it is avoided that the image of the original is unnecessarily read by the CCD 229 in a state where the dew condensation is generated on the contact glass 221. be able to.

[Second Embodiment]
In the following description of the second embodiment, only portions different from the first embodiment will be described in detail, and description of the same portions as the first embodiment will be omitted.

  In the configuration of the second embodiment, the black reference data acquisition unit 13 generates a plurality of predetermined black reference data B (m times) as shown in FIG. 5B in step S2 (FIG. 6). . In the following, the black reference data generated for the i-th time is indicated as black reference data Bi, and collectively referred to as black reference data B. Further, a pixel value corresponding to the jth pixel in the black reference data Bi generated for the i-th time is denoted as Bi (j).

  Accordingly, in step S3 (FIG. 6), the black reference pixel value calculation unit 14 performs the plurality of times (m times) for each of the plurality of pixels 1 to n as shown in FIG. 5B. , Bm of pixel values (for example, in the case of pixel n, the average value of B1 (n), B2 (n),..., Bm (n)) The average pixel values Bav (1), Bav (2),..., Bav (n−1), Bav (n) are calculated (for example, in the case of pixel n, Bav (n) = (B1 (n) + B2 (n) +... + Bm (n)) / m). The black average pixel values Bav (1) to Bav (n) constitute average black reference data Bav for one line in the main scanning direction. The pixels 1 to n correspond to the light receiving elements included in the CCD 229.

  Then, the black reference pixel value calculation unit 14 calculates the sum Bav (1) + Bav (2) +... + Bav of the calculated black average pixel values Bav (1) to Bav (n) for the plurality of pixels 1 to n. (N-1) + Bav (n) is divided by a plurality of pixels n, and the division result is obtained as a black reference pixel value Bd (Bd = (Bav (1) + Bav (2) +... + Bav (n−1) ) + Bav (n)) / n).

  According to the configuration of the second embodiment, since the black reference pixel value Bd is calculated as an average value of a plurality of pixel values for a plurality of times (m times) included in the black reference data B, it is included in the black reference data B. The reading error of the CCD 229 is reduced, and the accurate black reference pixel value Bd is calculated.

[Third embodiment]
In the following description of the third embodiment, only the parts different from the first embodiment or the second embodiment will be described in detail, and the description of the same parts as the first embodiment or the second embodiment will be omitted.

  In the configuration of the third embodiment, in step S4 (FIG. 6), the condensation determination data acquisition unit 12 generates a predetermined number (k times) of condensation determination data C as shown in FIG. 5C. . In the following description, the dew condensation determination data generated for the i-th time is indicated as dew condensation determination data Ci, and when collectively referred to, it is indicated as dew condensation determination data C. In addition, a pixel value corresponding to the j-th pixel in the dew condensation determination data Ci generated for the i-th time is denoted as Ci (j).

  And the dew condensation determination data acquisition part 12 is the pixel value (for example, in the case of pixel n, C1 in the dew determination data C1, C2,..., Ck for each of the plurality of pixels 1 to n. (N), C2 (n),..., Ck (n)) are converted into condensation determination average pixel values Cav (1), Cav (2),. (N) is calculated respectively (for example, in the case of pixel n, Cav (n) = (C1 (n) + C2 (n) +... + Ck (n)) / k). The condensation determination average pixel values Cav (1) to Cav (n) constitute average condensation determination data Cav for one line in the main scanning direction.

  The condensation determination data acquisition unit 12 then calculates the average condensation determination data Cav including the calculated condensation determination average pixel values Cav (1), Cav (2), ..., Cav (n-1), Cav (n). Is output to the condensation determination correction value generation circuit 15 as new condensation determination data.

  In accordance with this, the condensation determination correction value generation circuit 15 stores the average condensation determination data Cav as the new condensation determination data input from the condensation determination data acquisition unit 12 and the register 17 in step S5 (FIG. 6). Using the black reference pixel value Bd thus generated, the condensation determination correction data C ′ composed of the condensation determination correction values C ′ (1) to C ′ (n) is generated, and the generated condensation determination correction data C ′ is generated. It is output to the condensation determination circuit 16.

  According to the configuration of the third embodiment, a plurality of new pixel values Cav (1) to Cav (n) constituting new condensation determination data to be used as the condensation determination data C are a plurality of condensation determinations. It is calculated as an average value of pixel values corresponding to the same pixel among the data C1 to Ck. For this reason, the reading error of the CCD 229 included in the condensation determination data C is reduced, and the condensation determination data C including accurate pixel values is generated.

[Fourth embodiment]
In the following description of the fourth embodiment, only portions different from the first embodiment, the second embodiment, or the third embodiment will be described in detail, and the first embodiment, the second embodiment, or the third embodiment will be described. The description of the same parts as in FIG.

  In the configuration of the fourth embodiment, as shown in FIG. 7, the scanner unit 22a is configured to be movable integrally with the light source 222a, instead of the mirror groups 223, 224, 225, the imaging lens 228, and the CCD 229. The CIS (Contact Image Sensor) 24 is provided.

  As shown in FIG. 8, each CIS 24 includes a plurality of (q) light receiving elements (another example of the pixel detection unit according to the present invention) and physically independent chips each including R1 to Rq (according to the present invention). Another example of the image reading unit is configured by arranging a plurality (h) of them in the main scanning direction (X direction in the figure).

  That is, the image data for one line in the main scanning direction read by the CIS 24 is the same as the total number (q × h) of light receiving elements (pixel detection units) provided in a plurality (h) of chips P1 to Ph. It is constituted by the pixel value of this pixel. However, the number of light receiving elements provided in each chip and the number of chips provided in the CIS 24 are not limited to the above.

  In accordance with this, the ASIC 215 is provided with a register 17 associated with each of the chips P1 to Ph. The register 17 is configured by one physically independent register, and a storage area associated with each of the chips P1 to Ph may be provided, or each of the chips P1 to Ph may be provided. A plurality of registers that are physically associated and associated with each other may be provided.

  In step S2 (FIG. 6), the black reference data acquisition unit 13 does not irradiate light by the light source 222a, and q light receiving elements R1 provided in each of the chips P1 to Ph as shown in FIG. The analog electrical signal output from .about.Rq is subjected to A / D conversion processing by the A / D converter 216, thereby reading an image for one line in the main scanning direction without irradiating light by the light source 222a. As a result, the pixel values of the pixels 1 to q corresponding to the q light receiving elements R1 to Rq provided in the chips P1 to Ph (for example, in the case of the t-th chip Pt, B (t, 1) to B (T, q)) is acquired.

  The black reference data Bp1 to Bph corresponding to each of the chips P1 to Ph is configured by the q pixel values of the acquired chips P1 to Ph (for example, in the case of the t-th chip Pt, the black reference data). Data Bpt is composed of B (t, 1) to B (t, q)).

  Accordingly, the black reference pixel value calculation unit 14 corresponds to each of the chips P1 to Ph acquired by the black reference data acquisition unit 13 as shown in FIG. 9 in step S3 (FIG. 6). Average values of a plurality of pixel values (for example, B (t, 1) to B (t, q) in the case of the chip Pt) constituting the black reference data Bp1 to Bph are calculated, and each of the calculated average values is calculated. Is a black reference pixel value Bd (v) corresponding to each of the chips P1 to Ph (where v in parentheses indicates a chip number. For example, in the case of the t-th chip Pt, Bd (t) = ( B (t, 1) + B (t, 2) +... + B (t, q)) / q).

  Then, the black reference pixel value calculation unit 14 outputs the black reference pixel values Bd (1) to Bd (h) corresponding to the calculated chips P1 to Ph to the ASIC 215. In accordance with this, the ASIC 215 converts the black reference pixel values Bd (1) to Bd (h) input from the black reference pixel value calculation unit 14 to the black reference pixel values Bd (1) to Bd (h), respectively. Is stored in the register 17 associated with each of the chips P1 to Ph (for example, the black reference pixel value Bd (t) is stored in the register 17 associated with the chip Pt. ).

  Further, in the configuration of the fourth embodiment, the condensation determination data acquisition unit 12 is equivalent to one line in the main scanning direction of the black reference plate 11 by the scanner unit 22a as shown in FIG. 9 in step S4 (FIG. 6). By reading an image, the pixel values of the pixels 1 to q corresponding to the q light receiving elements R1 to Rq respectively provided in the chips P1 to Ph (for example, in the case of the t-th chip Pt, C (t, 1) to C (t, q)).

  Condensation determination data Cp1 to Cph corresponding to each of the chips P1 to Ph are configured by the q pixel values of the acquired chips P1 to Ph (for example, in the case of the t-th chip Pt, the condensation determination is performed). The data Cpt is composed of C (t, 1) to C (t, q)).

  Then, the condensation determination data acquisition unit 12 outputs the condensation determination data Cp1 to Cph corresponding to each of the acquired chips P1 to Ph to the ASIC 215. In accordance with this, the ASIC 215 inputs the condensation determination data Cp1 to Cph corresponding to each of the acquired chips P1 to Ph input from the condensation determination data acquisition unit 12 to the condensation determination correction value generation circuit 15. It is configured.

  Accordingly, in step S5 (FIG. 6), the condensation determination correction value generation circuit 15 includes a plurality of pixels 1 in the condensation determination data Cp1 to Cph input from the condensation determination data acquisition unit 12, as shown in FIG. For each pixel of .about.q, the difference between the pixel value in the condensation determination data Cp1 to Cph and the black reference pixel value corresponding to each of the chips P1 to Ph stored in the register 17 is determined as the condensation corresponding to the pixel. Each is calculated as a determination correction value.

  For example, the condensation determination correction value C ′ (t, i) corresponding to the i th pixel in the condensation determination data Cpt corresponding to the t th chip Pt is calculated as C (t, i) −Bd (t). .

  Note that the dew condensation determination correction values C′p1 to C′ph corresponding to the respective chips P1 to Ph are configured by the q dew condensation determination correction values corresponding to the respective chips P1 to Ph. (For example, the dew condensation determination correction data C′pt corresponding to the t-th chip Pt is composed of C ′ (t, 1) to C ′ (t, q)).

  The condensation determination correction value generation circuit 15 is configured to output the condensation determination correction data C′p1 to C′ph corresponding to each of the calculated chips P1 to Ph to the condensation determination circuit 16. Yes.

  In accordance with this, the dew condensation determination circuit 16 determines the dew condensation determination correction data C′p1 to C ′ corresponding to each of the chips P1 to Ph input from the dew condensation determination correction value generation circuit 15 in step S6 (FIG. 6). Based on the comparison result between ph and the black reference pixel values Bd (1) to Bd (h) corresponding to each of the chips P1 to Ph stored in the register 17 associated with each of the chips P1 to Ph. Then, a control signal indicating whether or not dew condensation has occurred at positions where the chips P1 to Ph of the contact glass 221 can be read is output.

  Specifically, the condensation determination circuit 16 has, for each of the chips P1 to Ph, any one of the condensation determination correction values among the condensation determination correction data corresponding to the chip input from the condensation determination correction value generation circuit 15. When it is determined that the value is larger than the dew condensation determination threshold, a control signal indicating that dew condensation has occurred at a position in the main scanning direction that can be read by the chip on the contact glass 221 is output.

  On the other hand, when the dew condensation determination circuit 16 determines that all the dew condensation determination correction values of the dew condensation determination correction data corresponding to the chip are not larger than the dew condensation determination threshold for each chip P1 to Ph, the contact glass 221 is used. A control signal indicating that no condensation has occurred at a position in the main scanning direction that can be read by the chip is output.

  According to the configuration of the fourth embodiment, the average values of the pixel values read by the plurality of light receiving elements R1 to Rq are different for each physically independent chip P1 to Ph without performing light irradiation by the light source 222a. Even in this case, the black reference data Bp1 to Bph corresponding to the chips P1 to Ph are obtained, and the black reference pixel values Bd (1) to Bd (h) corresponding to the chips P1 to Ph are calculated. Then, it can be stored in the register 17 provided corresponding to each of the chips P1 to Ph.

  Among the physically different chips P <b> 1 to Ph, the pixel value variation to be read is larger than the pixel value variation in the same chip. Therefore, the condensation determination data Cp1 to Cph corresponding to each of the physically independent chips P1 to Ph are acquired, and the condensation determination data corresponding to the chip and the black corresponding to the chip stored in the register 17 are acquired. Based on the reference pixel value, the condensation determination correction value for the pixel corresponding to each of the light receiving elements R1 to Rq of the chip is calculated. Then, by using the calculated dew condensation determination correction value, it is determined for each of the chips P1 to Ph whether or not dew condensation has occurred at a position that can be read by the chip on the contact glass 221. It is possible to reduce the influence of variations. As a result, the accuracy of determining the occurrence of condensation is improved.

  Note that the black reference data may be constituted by pixel values obtained by reading some pixels in an image for one line in the main scanning direction without performing light irradiation by the light source 222a. For example, this configuration can be realized by restricting and using only some of the plurality of chips P1 to Ph arranged side by side in the main scanning direction. In accordance with this, the dew condensation determination data may be constituted by pixel values obtained by reading a part of the plurality of pixels in the image for one line in the main scanning direction of the black reference plate 11. Then, in accordance with this, using the dew condensation determination correction value for the plurality of pixels generated using the black reference pixel value calculated from the black reference data and the dew condensation determination data, in the transparent member You may comprise so that it may be determined whether the dew condensation has generate | occur | produced in the position corresponding to the said some some pixel.

  Further, in the configuration of the fourth embodiment, as in the second embodiment, the black reference data acquisition unit 13 acquires the black reference data Bp1 to Bph corresponding to each of the chips P1 to Ph multiple times, respectively. The black reference pixel value calculation unit 14 calculates an average value of a plurality of pixel values for a plurality of times included in the black reference data Bp1 to Bph corresponding to each of the chips P1 to Ph acquired a plurality of times. You may comprise so that it may calculate as black reference pixel value Bd (1)-Bd (h) corresponding to each of P1-Ph.

  Also in the configuration of the fourth embodiment, as in the third embodiment, the condensation determination data acquisition unit 12 acquires the condensation determination data Cp1 to Cph corresponding to each of the chips P1 to Ph a plurality of times. The average value of the pixel values for the plurality of times is calculated for each of the plurality of pixels 1 to q included in the dew condensation determination data Cp1 to Cph corresponding to each of the chips P1 to Ph acquired a plurality of times, You may comprise so that the new dew condensation determination data Cp1-Cph corresponding to each of each chip | tip P1-Ph which consists of the average value corresponding to the pixel of the said calculated several pixels 1-q may be calculated.

  In any configuration of the first embodiment to the fourth embodiment, the dew condensation determination circuit 16 is connected to each chip input from the dew condensation determination correction value generation circuit 15 (the configurations of the first embodiment to the third embodiment). In this case, a dew condensation determination threshold value in which a dew condensation determination correction value equal to or more than a predetermined reference number among the dew condensation determination correction values corresponding to each light receiving element (each pixel) of one chip constituting the CCD 229 is determined. The control signal indicating that condensation has occurred at a position that can be read by each chip in the contact glass 221 may be output when the contact glass 221 is larger.

  In this case, when the number of dew condensation determination correction values larger than the dew condensation determination threshold among the dew condensation determination correction values corresponding to each light receiving element of each chip is greater than or equal to a predetermined reference number, It is determined that condensation has occurred at a position that can be read by the chip. Therefore, when there is at least one condensation determination correction value larger than the condensation determination threshold value among the condensation determination correction values corresponding to each light receiving element of each chip, it can be read by each chip in the contact glass 221. Compared with the case where it is determined that condensation has occurred at the position, the possibility that the determination is erroneously determined can be reduced.

  In the above-described embodiment, a monochrome multifunction peripheral has been described as an example of the image forming apparatus according to the present invention. However, the present invention is not limited thereto, and the image forming apparatus according to the present invention includes a color multifunction peripheral, The image forming apparatus may be a printer, a copier, a scanner, or a FAX (which may be either monochrome or color, respectively) including the image reading apparatus according to the present invention.

  For example, in the configuration of the first embodiment, the multi-function device 1 is simplified so as not to include the shading correction unit 217, and in accordance with this, the processing is simplified so as not to perform the processing of step S7 and step S9 in FIG. May be configured.

  The black reference plate 11 may be a color different from black. However, when the black reference plate 11 is black, the influence of diffused reflection of light due to condensation increases, that is, the condensation determination data when condensation occurs and the condensation determination data when condensation does not occur The difference between the pixel values corresponding to each other increases. In other words, the difference between the condensation determination correction value when condensation occurs and the condensation determination correction value when condensation does not occur is larger, so that the condensation is smaller than when the black reference plate 11 is not black. Fine adjustment of the determination threshold is facilitated, and the accuracy of determination of the occurrence of condensation can be improved.

  Further, the present invention is not limited to the configuration of the above embodiment, and various modifications can be made. The configuration and processing shown in FIGS. 1 to 9 are merely examples of the embodiment according to the present invention, and are not intended to limit the present invention to the above embodiment.

1 MFP (image forming device)
11 Black reference plate (condensation judgment member)
12 Condensation Determination Data Acquisition Unit 13 Black Reference Data Acquisition Unit 14 Black Reference Pixel Value Calculation Unit 15 Condensation Determination Correction Value Generation Circuit (Condensation Determination Correction Value Generation Unit)
16 Condensation judgment circuit (condensation judgment part)
17 Register (storage unit)
2 Image reading device 211 CPU
214 Reading control unit 22, 22a Scanner unit 229 CCD (image reading unit)
24 CIS
221 Contact glass (transparent material)
222, 222a Light source 40 Recording unit (image forming unit)
B Black reference data Bd Black reference pixel value C Condensation determination data C ′ Condensation determination correction data P1 to Ph Chip (image reading unit)
R1 to Rq light receiving element (pixel detection unit)
PS image reading position (position where reading of the original image starts)

Claims (8)

A plate-like transparent member on which a document is placed;
A light source for irradiating the original with light through the transparent member;
An image reading unit including a plurality of pixel detection units for reading at least a part of the image of the document as a plurality of pixels whose brightness is represented by pixel values;
A dew condensation determination member disposed on a part of the transparent member;
A black reference data acquisition unit that acquires a plurality of pixel values read by the plurality of pixel detection units as black reference data by causing the image reading unit to read an image without performing light irradiation by the light source; ,
A black reference pixel value calculation unit that calculates a result of dividing the sum of all pixel values included in the black reference data by the number of all the pixel values, as a black reference pixel value;
A storage unit for storing the black reference pixel value;
Data for acquiring condensation determination data indicating pixel values respectively corresponding to the plurality of pixel detection units by causing the image reading unit to read an image of the condensation determination member while irradiating the condensation determination member with light by the light source. A condensation determination data acquisition unit for executing the acquisition process;
Condensation determination correction for calculating the difference between each pixel value indicated by the dew condensation determination data and the black reference pixel value stored by the storage unit as a dew condensation determination correction value corresponding to the pixel detection unit that has read each pixel A value generator,
Among the plurality of condensing determination correction value, at least if one condensation determination correction value is larger than a predetermined dew determination threshold, the the determined dew determination unit condenses on the transparent member has occurred,
An image reading apparatus comprising: The black reference data acquisition unit
By causing the image reading unit to read the image a plurality of times without irradiating light from the light source, the plurality of pixel values read by the plurality of pixel detection units a plurality of times are obtained as the black reference data. Get as
The black reference pixel value calculation unit
2. The image reading according to claim 1, wherein a result of dividing the sum of all the pixel values included in the black reference data by the number of all the pixel values corresponding to the plurality of times is calculated as the black reference pixel value. apparatus. The dew condensation determination data acquisition unit
The data acquisition process is repeated a plurality of times to acquire the plurality of dew condensation determination data, and an average value of pixel values corresponding to the same pixel detection unit among the acquired plurality of dew condensation determination data is calculated. Calculate as a new pixel value corresponding to each of the pixel detection unit, to obtain the new plurality of pixel values as new condensation determination data,
The dew condensation determination correction value generation unit
The image reading apparatus according to claim 1, wherein each of the dew condensation determination correction values is calculated by using the new dew condensation determination data as the dew condensation determination data. A plurality of the image reading units are provided,
Each of the image reading units is constituted by a physically independent chip,
The black reference data acquisition unit acquires black reference data corresponding to each of the image reading units,
The black reference pixel value calculation unit calculates a black reference pixel value corresponding to each of the image reading units based on the plurality of black reference data,
The storage unit is provided corresponding to each of the image reading units,
The dew condensation determination data acquisition unit acquires a plurality of dew condensation determination data corresponding to each of the image reading units,
The dew condensation determination correction value generation unit corresponds to each pixel detection unit of each image reading unit based on the plurality of dew condensation determination data and the plurality of black reference pixel values stored in the plurality of storage units. The image reading apparatus according to claim 1, wherein a dew condensation determination correction value is calculated.   The condensation determination unit includes a predetermined number or more of condensation determination correction values larger than the condensation determination threshold among the condensation determination correction values corresponding to the pixel detection units of the image reading units. 5. The image reading apparatus according to claim 1, wherein it is determined that condensation has occurred at a position of the transparent member that can be read by each of the image reading units. A reading control unit for reading the image of the document while moving the image reading unit in the sub-scanning direction relative to the document;
The dew condensation determining member is disposed in a direction opposite to a direction in which the image reading unit is moved by the reading control unit from a position at which reading of an image of a document is started on the transparent member.
The image reading apparatus according to claim 1, wherein the reading control unit causes the dew condensation determination unit to perform the determination before causing the image reading unit to read an image of a document.   The image reading apparatus according to claim 1, wherein the dew condensation determination member is black. An image reading apparatus according to any one of claims 1 to 7,
An image forming unit that forms an image using data read by the image reading unit;
An image forming apparatus comprising:

Images