JPH09247373A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decide document size in a short time with simple constitution. SOLUTION: The number X of white pixels while a cover is nearly is counted (104) and the number Y of white pixels while the cover is closed is counted (114). While the cover is closed, it is judged that the part of scanning lines other than a document consists of white pixels and while the cover is almost closed, it is decided that the part other than the document is not white pixels, so the difference between the number Y of white pixels and the number X of white pixels is calculated to obtain the number Z of pixels outside the document (116). Further, the difference between the number Z of the pixels outside the document and the total number (e.g. 4864) on the scanning lines is found to calculate the number A of document pixels corresponding to the part of the document on the scanning lines (118). On the basis of the number A of document pixels and the detection signal from an optical sensor for longitudinal/ lateral decision making, the document size is decided (122).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus, and more specifically, it optically scans a document placed on a plate-shaped transparent member such as a platen glass along a predetermined scanning line, The present invention relates to an image reading device that reads an image recorded on the original by converting the scanning light into an electric signal by a photoelectric conversion element.

[0002]

2. Description of the Related Art Conventionally, in a copying machine, the size of a document placed on a platen glass is detected, and the image recorded on the document is copied based on the detection result. There is known a technique for automatically determining the size of a sheet to be printed, the copy magnification, and the like. The most general method for detecting the size of a document placed on the platen glass is to detect the size of the original below the platen glass as described in JP-A-61-20936. This is a method in which one or more sensors are arranged, the presence or absence of an original at the optical sensor arrangement position is detected by the optical sensor, and the size of the original is determined based on the detection result.

However, in the above-described size detecting method, it is necessary to dispose the photosensors at different positions below the platen glass, corresponding to the originals of various sizes, and in reality, they can be placed on the platen glass. Since a large number of optical sensors are required corresponding to a large number of document sizes, there is a problem that the configuration becomes complicated.

Further, in a copying machine (so-called digital copying machine), a facsimile machine or the like which converts an image recorded on a document into digital image data and then records (copies) the image on a sheet based on the image data. Generally, a configuration is provided in which a large number of photoelectric conversion elements such as CCDs arranged in a line are provided, and an image of the original is read by scanning the original with these photoelectric conversion elements. For this reason,
There is also an apparatus of this type in which an original is scanned by a photoelectric conversion element before image reading (so-called pre-scanning) and the size of the original is detected based on a signal output from the photoelectric conversion element.

In the above detection method, since the size of the original is also detected by the photoelectric conversion element provided for reading the image, a large number of originals are newly added in accordance with the number of types of originals placed on the platen glass. Although it is not necessary to provide a sensor, it is necessary to perform a prescan every time an original is placed, so that the prescan becomes a bottleneck in improving the processing capability of the apparatus (for example, the number of copies per unit time). was there.

By the way, the size of the original document on the platen glass is generally detected by assuming that the original document is placed on the platen glass when the platen cover is closed. Since the back side is usually white, the size of the document should be detected optically when the background of the placed document is white, that is, when the light reflectance of the document is close to the light reflectance of the back side of the platen cover. Becomes difficult.

Therefore, in order to improve the certainty of detecting the size of the document, it has been proposed to form a surface having a low light reflectance on the back surface of the platen cover or to make the back surface of the platen cover a color other than white. (See Japanese Examined Patent Publication No. 62-47026).

However, if it is assumed that the light reflectance of the back surface of the platen cover is obviously lower than the light transmittance of the original whose white background is white (for example, the back surface of the platen cover is gray, black, or a mirror surface), the original However, the so-called show-through occurs in which the density of the background portion of the copied image is increased as a whole. This show-through becomes remarkable especially when copying an image recorded on a paper such as tracing paper having a small thickness and a relatively high light transmittance.

Further, when the light reflectance of the back surface of the platen cover is made significantly lower than the light transmittance of the original whose white background is white, when the platen cover is closed and the original is read in the digital copying machine. , The part of the platen glass where the original is not placed is recognized as high density (for example, black), and the image is simply copied onto the paper based on the image data obtained by reading the original. In that case, a portion corresponding to a portion on which the original document is not placed in the copied image becomes, for example, solid black, which is not preferable.

In order to avoid this, for example, after prescanning is performed to detect the size of the original, the portion of the platen glass on which the original is not placed is determined based on the detected size of the original, and the original is detected. Of the signals output from the photoelectric converter at the time of reading, the signal output corresponding to the portion on which the original document is not placed is electrically masked, or the portion on which the original document is not placed So that the density becomes 0 (white) on the image data, it is necessary to automatically change the input / output characteristics when converting the signal output from the photoelectric converter into the image data, There was a problem that the configuration became complicated.

The present invention has been made in consideration of the above facts, and an object of the present invention is to obtain an image reading apparatus having a simple structure and capable of discriminating the size of a document in a short time.

[0012]

In order to achieve the above object, an image reading apparatus according to a first aspect of the present invention optically scans a document placed on a plate-shaped transparent member along a predetermined scanning line. An image reading apparatus for reading an image recorded on the original by scanning and converting the scanning light into an electric signal by a photoelectric conversion element, and a shielding position for shielding the transparent member and a transparent member are exposed. A cover movable to the exposure position, position determination means for determining whether the cover is in the shielding position or in a shielding front position corresponding to the front of the shielding position, and when the cover is in the shielding position, White pixel number detecting means for detecting the number of white pixels per scan in each of the cases where the cover is in the front position of the cover, and a shield when the cover is in the cover position, which is detected by the white pixel number detecting means. Size determining means for determining the size of the document placed on the transparent member based on the number of hourly white pixels and the number of hourly white pixels in front of the cover when the cover is at the front side position of the cover. And

According to another aspect of the image reading device of the present invention,
2. The image reading apparatus according to claim 1, wherein the size determining means is based on a difference between the number of white pixels at the time of occlusion and the number of white pixels at the time of occlusion and is the number of original pixels corresponding to the original portion on the scanning line. Is calculated, and the size of the document is determined based on the calculated number of document pixels.

According to the image reading apparatus of the third aspect,
The image reading device according to claim 1 or 2,
The cover is characterized in that the surface facing the transparent member when the transparent member is shielded is white.

In the image reading apparatus according to the above-mentioned claim 1, when reading an image recorded on an original, the original is placed on a transparent member and the cover is moved from the exposed position to the shielded position. After that, the image reading is started by issuing a predetermined start instruction (for example, a start button operation or the like).

During such image reading, the position discriminating means discriminates whether the cover is in the shielding position or in the shielding front position corresponding to the position before the shielding position. Immediately before the cover reaches the shielding position, the position discriminating unit determines that the cover is in the shielding front position, and the white pixel number detection unit detects the white per scan at that time (when the cover is in the shielding front position). The number of pixels (the number of white pixels before blocking) is detected.

After that, when the cover is further moved to reach the shield position, the position discriminating means discriminates that the cover is in the shield position, and the white pixel number detecting means at that time (when the cover is in the shield position). The number of white pixels per scan (the number of white pixels when shielded) is detected.

By the way, when the cover is in the shielding position,
Since light from the outside does not enter the portion of the scanning line other than the original, all pixels corresponding to the portion other than the original are determined to be white pixels. On the other hand, when the cover is at the front position of the shielding, light from the outside is incident on the portion other than the original on the scanning line, and therefore all the pixels corresponding to the portion other than the original are determined not to be white pixels. Therefore, the difference between the number of white pixels at the time of occlusion and the number of white pixels at the front of occlusion corresponds to the number of pixels outside the original corresponding to the portion other than the original on the scanning line.

Therefore, the size discriminating means obtains the difference (the number of pixels outside the original document) between the number of white pixels at the time of occlusion detected and the number of white pixels before the occlusion detected by the white pixel number detecting means, and based on the number of pixels outside the original document. The size of the document placed on the transparent member is determined.

According to the first aspect of the invention, since the size of the original is determined by using the photoelectric conversion element provided for reading the image recorded on the original, a large number of sensors are exclusively used for detecting the size of the original. It is not necessary to provide the device, and the structure of the device can be simplified.

Further, since the prescan for detecting the document size is not necessary, it is possible to solve the problem that the prescan becomes a bottleneck in improving the processing capacity of the apparatus (for example, the number of copies per unit time). .

The size discriminating means obtains the difference (that is, the number of pixels outside the manuscript) between the number of white pixels at the time of occlusion and the number of white pixels at the time of occlusion before calculating the outside of the manuscript. By obtaining the difference between the number of pixels and the total number of pixels on the scanning line, the number of original pixels corresponding to the original portion on the scanning line can be calculated. Since the number of original pixels calculated here and the size of the original have a one-to-one correspondence, the size of the original can be determined based on the calculated number of original pixels.

In the cover according to the third aspect of the present invention, the surface of the cover facing the transparent member when the cover is shielded is white, so that the effect of show-through on the image quality can be eliminated. , The size of the original can be accurately detected.

Next, in the image reading apparatus according to claim 4,
The image reading device according to any one of claims 1 to 3, wherein the white pixel number detecting means is provided in each of a case where the cover is at a shielding position and a case where the cover is at a shielding front position. Binarizing means for binarizing the electric signal of each pixel in scanning based on a predetermined threshold value, and white pixel number counting means for counting the number of white pixels from the binarized information for each pixel. It is characterized by including.

An image reading apparatus according to a fifth aspect is the image reading apparatus according to the fourth aspect, further comprising threshold value setting means for setting the threshold value to a desired value. To do.

An image reading apparatus according to a sixth aspect is the image reading apparatus according to any one of the first to fifth aspects, in which scanning is performed to set the position of the scanning line to a desired position. It is characterized by further comprising line setting means.

The white pixel number detecting means described above can be configured to include a binarizing means and a white pixel number counting means, as in the invention described in claim 4. That is, in the invention according to claim 4, when the cover is located at the front position of the shielding, the binarizing means binarizes the electric signal of each pixel in one scanning based on a predetermined threshold value, and a white pixel is formed. The number counting means counts the number of white pixels (the number of white pixels before the occlusion) from the binarized information about each pixel.

Further, when the cover is in the shielding position,
The binarizing means binarizes the electric signal of each pixel in one scanning based on a predetermined threshold value, and the white pixel number counting means converts the binarized information of each pixel from the number of white pixels (when shielded). The number of white pixels) is counted.

In this way, the white pixel number detecting means can detect the number of white pixels before the occlusion and the number of white pixels during the occlusion.

By the way, when detecting the size of a document such as a catalog, a photographic document, or a document of a color background, there are cases where the document size cannot be accurately detected depending on the threshold value used for binarization. Therefore, as in the invention described in claim 5, threshold setting means for setting the threshold to a desired value is further provided, and the threshold is appropriately set by the threshold setting means. As a result, accurate document size detection can be realized.

Further, in the case of detecting the size of an original document whose surface has damage such as wrinkles and damages, accurate detection of the original document size is possible if the damaged portion and the scanning line of the scanning by the image reading device overlap. There are cases where it cannot be done. Therefore, as in the invention described in claim 6, scanning line setting means for setting the position of the scanning line at a desired position is further provided, and the scanning line and the damaged portion are provided by the scanning line setting means. Accurate document size detection can be realized by appropriately setting the positions of the scanning lines so that they do not overlap.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows an image reading apparatus 1 according to this embodiment.
An appearance of 0 is shown. The image reading apparatus 10 includes a box-shaped housing 12, and a lid-shaped document table 14 that closes an upper opening of the housing 12 is attached to an upper portion of the housing 12. The document table 14 includes a platen glass 16 which is a plate-shaped and rectangular transparent member, and a rectangular frame-shaped registration guide plate 18 arranged on the outer periphery of the platen glass 16. In this embodiment, the size of the portion of the platen glass 16 exposed from the registration guide plate 18 is set to be substantially equal to the A3 size.

FIG. 3 shows a schematic structure of an optical system arranged inside the housing 12 of the image reading apparatus 10. The vertical direction in FIG. 3 corresponds to the height direction. As shown in FIG. 3, the height of the upper surface of the registration guide plate 18 is higher than that of the platen glass 16, and the original alignment is performed at the position corresponding to the left back corner of the platen glass 16 in FIG. The mark 20 is provided. In the original, the side on which the image is recorded faces the platen glass 16 side, and
One of the corners corresponds to the corner of the platen glass 16 provided with the document alignment mark 20, and two sides of the document contact the inner surface of the registration guide plate 18 (shown in FIG. 3). The document 21 is placed on the platen glass 16 so as to be printed.

A platen cover 24 (corresponding to the cover of the present invention) is attached to the housing 12 via a pair of hinges 22 on one long side. The platen cover 24 can be rotated by a hinge 22 between an upright position (fully open position) shown in FIG. 2A and a position (not shown) at which the document table 14 is completely closed (fully closed position). It is said that. A rectangular platen cushion 26 is attached to the back side of the platen cover 24 (the side facing the platen glass 16). The platen cushion 26 is a platen glass 1
The surface of the surface facing 6 is white.

An angle sensor 28, which is an on / off switch and is provided so that the mover projects from the document table 14, is attached near the position where the one hinge 22 is arranged. The angle sensor 28 shown in FIGS.
Only the mover of is shown. The mover of the angle sensor 28 is movable in the longitudinal direction, and is provided with a biasing means (not shown) such as a spring, which is shown in FIGS.
It is held at the position shown in (A), and at this time, the angle sensor 28 is in the off state. When the platen cover 24 is rotated from the fully open position shown in FIG. 2 (A) to the fully closed position by a predetermined angle or more, as shown in FIG. 2 (B), the mover of the angle sensor 28 is placed on the back surface of the platen cover 24. By contacting and pressing, the angle sensor 28 changes to the ON state before the platen cover 24 is rotated to the fully closed position (in the state shown in FIG. 2B).

Further, as shown in FIG. 2, the platen interlock sensor 3 is provided on the rear surface of the platen cover 24 at the end opposite to the end where the hinge 22 is attached.
0 is attached. Platen interlock sensor 3
0 is configured to be in an off state when the platen cover 24 is not in the fully closed state and to be in an on state when the platen cover 24 is in the fully closed state.

As shown in FIG. 3, a scanning device 32 is provided in the housing 12. The scanning device 32 includes a lamp 34 that emits light toward the platen glass 16, a first reflection mirror 36 that reflects the reflected light from the platen glass 16 side substantially horizontally, and a light emission of the first reflection mirror 36. A second reflection mirror 38 which is disposed on the side and which emits light incident from the first reflection mirror 36 downward along a substantially vertical direction;
The third reflection mirror 40 is provided on the light emission side of the second reflection mirror 38 and reflects the light incident from the second reflection mirror 38 substantially horizontally. An image forming lens 42 and a CCD line sensor 44 are provided on the light emitting side of the third reflecting mirror 40.

FIG. 3 is a sectional view taken along the long side direction of the platen glass 16, where the lamp 34 and the reflection mirror 3 are shown.
6, 38, 40 and the imaging lens 42 extend from one end of the platen glass 16 to the other end along the short side direction of the platen glass 16 (direction orthogonal to the plane of FIG. 3; hereinafter referred to as main scanning direction). The CCD line sensor is provided by extending the light from the lamp 34 toward the platen glass 16 and the light reflected from the platen glass 16 side through the reflection mirrors 36, 38, 40 and the imaging lens 42. The light imaged on the light receiving unit 44 is a slit-like light elongated in the main scanning direction.

The CCD line sensor 44 has a large number of cells (photoelectric conversion elements of the present invention) arranged at a constant density along the main scanning direction, and the CCD line sensor 44 has a light receiving portion along the main scanning direction. The received light amount at each position is converted into an electric signal by each cell and output.

Further, the lamp 34 and the first reflecting mirror 3
6 is a sub scanning direction (arrow S in FIG. 3) orthogonal to the main scanning direction.
Direction) and is attached to a carriage member 46 that is capable of reciprocating in the housing 12 in the same direction. The second reflecting mirror 38 and the third reflecting mirror 40 are also mounted in the housing 12 along the sub-scanning direction. It is attached to a carriage member 48 capable of reciprocating inside. These carriage members 4
Reference numerals 6 and 48 are connected by a wire (not shown), and are structurally adjusted so that the optical path length until the light reflected by the original 21 reaches the light receiving portion of the CCD line sensor 44 is constant. In addition, these carriage members 46 and 48
Is moved in the sub-scanning direction by the carriage member driving unit 50 (see FIG. 4).

As shown in FIG. 4, the carriage member driving unit 50 is connected to the control unit 54, and the operation is controlled by the control unit 54. The control unit 54 is a CP not shown.
U, ROM, RAM, non-volatile RAM (NVRAM),
It is configured to include input / output ports and the like. RO of this
In M, correspondence information of the number of original pixels-original size indicating the correspondence between various original sizes and the number of original pixels of each original size as shown in FIG. 6 is stored in advance.

When the image of the original document placed on the platen glass 16 is read, the control unit 54 causes the carriage member drive unit 50 to move the carriage member 46 at a predetermined speed in the sub-scanning direction, and at the same time, to move the carriage. Member 4
8 is moved in the same direction as the moving direction of the carriage member 46 at a speed half the predetermined speed. Platen cover 2
When 4 is in the fully closed state, the light emitted from the lamp 34 is reflected by the document 21 placed on the platen glass 16 or the surface of the platen cushion 26 that is in close contact with the platen glass 16. Therefore, by moving the carriage members 46 and 48 as described above,
The optical path length from the lamp 34 to the CCD line sensor 44 is constant regardless of the position of the carriage member 46 along the sub-scanning direction.

As shown in FIG. 4, the angle sensor 28 and the platen interlock sensor 30 are connected to the control unit 54, and the detection result of each sensor is input to the control unit 54. Further, the lamp 34 is connected to the control unit 54, and the blinking of the lamp 34 is controlled by the control unit 54. Further, the CCD line sensor 44 is connected to the control unit 54 via the CCD driver 56 and the image processing unit 58.

The control unit 54 has a keyboard 64 for the operator to set a desired threshold value for the white pixel discrimination processing according to the present invention, a value input from the keyboard 64, and the control unit 54. And a display 62 for displaying a message or the like from. Further, the operator inputs a predetermined scanning line position setting command from the keyboard 64 to display a screen for setting the scanning line position as shown in FIG. 5 on the display 62 and set the position of the scanning line to a desired position. Can be set.

Various signals and data including synchronizing signals such as video clock signals and line synchronizing signals are input to the image processing unit 58 from the control unit 54. The control signal input to the image processing unit 58 controls the CCD line sensor 44 via the CCD driver 56. The CCD line sensor 44 operates at a timing synchronized with the video clock signal, and outputs a signal indicating the amount of light received by each cell at a timing synchronized with the video clock signal. The signal output from the CCD line sensor 44 is amplified by the CCD driver 56, converted into digital image data, and output to the image processing unit 58.

Such an image processing section 58 has a built-in pixel counting circuit section 58A for counting white pixels, and the pixel counting circuit section 58A includes the image processing section 5.
By determining whether or not the level of the signal input to 8 is smaller than a predetermined threshold value, white pixels are determined and the number thereof is counted.

An optical sensor 60 for detecting the orientation of the document is connected to the control section 54. The optical sensor 60 is arranged below the platen glass 16, and as shown in FIG. 5, the document is placed on the platen glass 16 in a horizontal direction (the direction in which the long side direction coincides with the longitudinal direction of the platen glass 16: SEF). If placed, the original size (B
5, A4, B4, A3, etc.) and the original is placed on the platen glass 16 in the vertical direction (the direction in which the long side direction coincides with the short side direction of the platen glass: LEF). Is arranged at a position where the presence or absence of a document can be detected at a predetermined position where the document does not exist regardless of the size of the document (the position shown as "# 0" in FIG. 5).

The image reading apparatus 10 described above constitutes a part of a digital copying machine (not shown), and the image of the original read by the image reading apparatus 10 is copied onto a sheet by the copying machine. The size and orientation of the document determined by the image reading device 10 are used for selecting a sheet and determining a copy magnification. A start button 66 for the operator to instruct the start of execution of copy processing is connected to the control unit 54.

Next, the operation of the present embodiment will be described. In the standby state where the original is not read (including the original size determination), the control unit 54 causes the scanning line of the scanning by the CCD line sensor 44 to be in the sub-scanning direction shown by the arrow S as shown in FIG. The positions of the carriage members 46 and 48 are controlled so as to be a position (so-called home position) inside about 20 mm from the left end of the registration guide plate 18. As is clear from FIG. 5, the length of the sensing area of the CCD line sensor 44 along the main scanning direction (arrow M direction) is set to be slightly longer than the length of the platen glass 16 along the main scanning direction. There is.

Next, the document size discrimination processing according to the present invention will be described. In the digital copying machine configured to include the image reading apparatus 10, when the operation such as copying is accepted, the control unit 54 automatically starts executing the control routine of FIG. 7. The state in which operations such as copying can be accepted means a state in which warming and the like after turning on the power of the apparatus is completed and various operation requests from the operator can be accepted.

At step 102, it is determined whether the angle sensor 28 is turned on. Here, when the angle sensor 28 is not on, it can be determined that the platen cover 24 is open. When the platen cover 24 is thus open (corresponding to the case where the cover of the present invention is at the exposed position), the routine proceeds to step 106, where it is determined whether or not the start button 66 has been turned on. Here, if the start button 66 is not turned on (when the start of the copy process is not instructed), the process returns to step 102.

On the other hand, in step 102, the angle sensor 2
When 8 is turned on, it can be determined that the platen cover 24 has changed from the opened state to the closed state. In this way, when the platen cover 24 is almost closed (corresponding to the case where the cover of the present invention is at the front position of the shielding), the process proceeds to step 104, and the white pixel counting process in the state where the platen cover 24 is closed is performed. . As shown in FIG. 8, the white pixel counting process starts with step 15
In step 2, the lamp 34 is turned on, and then in step 154, 20 msec is waited to stabilize the lamp 34. Further, in the next step 156, the threshold value information is notified to the image processing unit 58, and the pixel count circuit unit 58 in the image processing unit 58 is notified.
A pixel in which the output signal from the CCD 44 is smaller than the threshold value, that is, a white pixel is counted by A, and the count number (white pixel number X when the platen cover 24 is almost closed) is stored in the RAM in the control unit 54. Write in and return.

Next, in step 110 of FIG. 7, it is determined whether the platen interlock sensor 30 is turned on. Here, when the platen interlock sensor 30 is not on, it can be determined that the platen cover 24 is not in the closed state but is in a state of being closed. In this way, when the platen cover 24 is almost closed, the routine proceeds to step 112, where it is judged whether or not the start button 66 is turned on. Here, if the start button 66 is not turned on (when the start of the copy process is not instructed), the process returns to step 110.

On the other hand, when the platen interlock sensor 30 is turned on in step 110, the platen cover 2
It can be determined that 4 is in the closed state. When the platen cover 24 is thus closed (corresponding to the case where the cover of the present invention is in the shielding position), step 114
Then, the process proceeds to step S21 where white pixel counting processing is performed with the platen cover 24 closed. The white pixel count process here is the same as the control routine of FIG. 8 described above.
That is, the number of white pixels when the platen cover 24 is closed is counted, the count number (the number of white pixels Y when the platen cover 24 is closed) is written in the RAM in the control unit 54, and the process returns.

Next, proceeding to step 116 in FIG. 7, from the number Y of white pixels when the platen cover 24 is closed,
The number of pixels outside the document Z is calculated by subtracting the number of white pixels X when the platen cover 24 is almost closed. Further, in the next step 118, the number A of original pixels is calculated by subtracting the number Z of pixels outside the original from the total number of pixels on the scanning line (4864 in the present embodiment).

In the next step 122, the control unit 54 is previously operated.
Based on the document pixel number A-document size correspondence information (see FIG. 6) stored in the internal ROM, the document size candidates corresponding to the calculated document pixel number A are narrowed down, and the document size by the optical sensor 60 is used. The document size is determined based on the detection result regarding the orientation.

As described above, according to the present embodiment, the CCD line sensor 44 provided for reading the image of the original document is used to determine the original document size. It is not necessary to provide a sensor, and the document size can be detected with a simple device configuration. Further, since the back surface of the platen cover 24 (the surface facing the document) is white, the show-through does not affect the image quality.

In the present embodiment, the platen cover 2
Number of white pixels Y and platen cover 24 when 4 is closed
The embodiment has been described in which the number of white pixels X in the state of being closed is counted and the document size is determined as described above based on the number of white pixels Y and the number of white pixels X. If the book cannot be completely closed when the book is set on the platen cover 24, characters and figures are not described before the document size determination process. After the scanning lines are set at the edges of the document, the document size determination process is executed.

In this case, it is determined that the start button 66 is turned on in step 112 of FIG. 7 with the platen cover 24 being closed, and the process proceeds to step 120, where the platen cover 24 calculated in step 108 is closed. The number of white pixels X in the opened state is the number of original pixels A.
That is, if the scanning line is set at the end of the document in which characters and figures are not written as described above, only the portion corresponding to the document on the scanning line has white pixels, so that the platen cover 24 is The number of white pixels X in the nearly closed state can be regarded as the number of original pixels A.

Then, in the next step 122, the document size candidates corresponding to the document pixel number A are narrowed down based on the document pixel number A-document size correspondence information as in the above.
Further, the document size is determined based on the detection result regarding the orientation of the document by the optical sensor 60.

On the other hand, even when the original is, for example, one page of a very thick book, and the book cannot be closed even when the book is set on the platen cover 24, the original size determination is performed. Prior to the processing, a scanning line is set on an end portion or the like of the original in which characters and figures of the original are not described, and then the original size determination processing is executed.

In this case, it is determined that the start button 66 is turned on in step 106 of FIG. 7 with the platen cover 24 open, and the process proceeds to step 108, in which white pixel counting processing is performed with the platen cover 24 open. To do. The white pixel count process here is the same as the control routine of FIG. 8 described above. That is, the number of white pixels when the platen cover 24 is opened is counted, and the count number (the number of white pixels W when the platen cover 24 is opened) is written in the RAM in the control unit 54 and the process returns.

Next, in step 120 of FIG. 7, the number of white pixels W in the state where the platen cover 24 is open calculated in step 108 is set as the original pixel number A, and in the next step 122, the original pixel number A is set. -Document size candidates corresponding to the document pixel number A are narrowed down based on the document size correspondence information, and the document size is determined based on the detection result of the document orientation by the optical sensor 60.

Even in a special case in which the platen cover 24 cannot be closed as described above, accurate document size detection can be realized by setting the scanning line position appropriately as described above. You can

The operator can use the keyboard 64 to set the threshold value for determining whether or not the target pixel is a white pixel to a desired value. This threshold value setting is an arbitrary process, and the process execution can be omitted if there is no problem with a preset default threshold value.

Further, the operator inputs a predetermined scanning line position setting command from the keyboard 64,
It is also possible to display a screen for setting the scanning line position as shown in FIG. 5 on the display 62 and set the position of the scanning line to a desired position. This scanning line position setting is also an arbitrary process, and if there is no problem with the predetermined scanning line position, that is, the above-mentioned home position, the execution of the process can be omitted.

By the way, when detecting the size of an original such as a catalog, a photographic original, or an original with a color background, whether the target pixel is a white pixel when counting white pixels in the white pixel counting process of FIG. There is a case where the original size cannot be detected accurately depending on the threshold value used for determining (binarizing). In the present embodiment, the operator can set a desired threshold value from the keyboard 64. Therefore, even in the above case, the threshold value is appropriately set to realize accurate document size detection. It is possible to

The back surface of the platen cover 24 (the surface facing the document) does not necessarily have to be white by setting the threshold value appropriately. That is, in the white pixel counting process with the platen cover 24 closed, the portion reflected by the back surface of the platen cover 24 (the portion other than the original) is determined to be the white pixel. If the threshold value is set according to the light reflectance of the back surface, the back surface of the platen cover 24 may be set to a whitish gray color or a cream color.

In the case of detecting the size of an original document having damage such as wrinkles or damage on the surface, accurate detection of the original document size is possible if the damaged portion and the scanning line of the scanning by the image reading device 10 overlap. There are cases where you cannot do it.
In this embodiment, since the operator can set the position of the scanning line to a desired position, even in the above case, the position of the scanning line is prevented so that the scanning line and the damaged portion do not overlap each other. By properly setting, it is possible to realize accurate document size detection.

In the above embodiment, the size of the original is determined by using the CCD line sensor 44 provided for reading the image of the original. However, the present invention is not limited to this, and the original size of the original is not limited to this. In an image recording apparatus for recording an image of an original on a recording sheet by directly irradiating the photoconductor drum with light reflected from the original without reading the image, the image reading apparatus according to the present invention determines the size of the original. It may be provided only for the purpose.

In the above embodiment, the CCD line sensor 4 is used as a photoelectric converter including a photoelectric conversion element.
4 has been described, the present invention is not limited to this, and various known photoelectric converters such as a MOS image sensor can be applied. Further, although the platen glass 16 has been described as an example of the transparent member in the above, the transparent member can be configured by using other materials such as synthetic resin other than glass.

[0073]

As described above, according to the present invention, it is not necessary to provide a large number of sensors exclusively for detecting the size of a document, and the structure of the apparatus can be simplified. In addition, because it does not require prescanning for detecting the document size,
It is possible to solve the problem that the prescan becomes a bottleneck in improving the processing capability of the apparatus (for example, the number of copies per unit time).

In particular, in the third aspect of the invention, since the surface of the cover facing the transparent member is white when the transparent member is shielded, it is possible to eliminate the influence of the show-through on the image quality. The size of the original can be detected.

According to the fifth aspect of the present invention, by accurately setting the threshold value by the threshold value setting means, accurate document size detection can be realized.

According to the sixth aspect of the invention, the position of the scanning line is appropriately set by the scanning line setting means so that the scanning line and the damaged portion do not overlap each other.
Accurate document size detection can be realized.

[Brief description of drawings]

FIG. 1 is a perspective view showing the outer appearance of an image reading apparatus according to this embodiment.

FIG. 2A is a side view of the image reading apparatus showing a state in which the platen cover is upright, and FIG. 2B is a state in which the platen cover is rotated a predetermined angle or more from the upright state and an angle sensor is turned on. FIG. 3 is a side view of the image reading apparatus showing FIG.

FIG. 3 is a cross-sectional view showing a schematic configuration of an optical system arranged in a housing of the image reading apparatus.

FIG. 4 is a schematic block diagram showing a configuration of a control unit of the image reading apparatus and its periphery.

FIG. 5 is a plan view showing the positions of scanning lines on the platen glass.

FIG. 6 is a conceptual diagram showing the correspondence between various document sizes and the number of detected pixels.

FIG. 7 is a flow chart showing a control routine of a document size determination process executed by a control unit.

FIG. 8 is a flowchart showing a subroutine of white pixel count processing.

[Explanation of symbols]

 10 image reading device 16 platen glass (transparent member) 24 platen cover (cover) 28 angle sensor 30 platen interlock sensor 44 CCD line sensor 54 control unit 58 size detection unit 60 optical sensor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuhiko Minowa 3-7-1, Fuchu, Iwatsuki-shi, Saitama Prefecture Fuji Xerox Co., Ltd. Iwatsuki Plant (72) Inventor Hiroshi Hayashi 3-7-1, Iwatsuki-shi, Saitama Prefecture No. Fuji Xerox Co., Ltd. Iwatsuki Works (72) Inventor Daisuke Kono 3-7-1 Fuchu, Iwatsuki City, Saitama Fuji Xerox Co., Ltd. Iwatsuki Works

Claims (6)

[Claims] 1. A document placed on a plate-shaped transparent member is optically scanned along a predetermined scanning line, and the scanning light is converted into an electric signal by a photoelectric conversion element, whereby the document is formed. An image reading apparatus for reading a recorded image, the cover being movable to a shielding position for shielding the transparent member and an exposing position for exposing the transparent member, and the cover being at the shielding position or the shielding position. Position discriminating means for discriminating whether or not it is in a shielding front position corresponding to the front side of, and detecting the number of white pixels per scan in each of the case where the cover is in the shielding position and the case where the cover is in the shielding front position. White pixel number detection means, and the number of white pixels when the cover is in the shielding position and the number of white pixels when the cover is in the shielding front position, which are detected by the white pixel number detecting means. Based on the image reading apparatus having a size determination means for determining the size of a document placed on the transparent member. 2. The size determining means calculates the number of original pixels corresponding to a portion of the original on the scanning line, based on the difference between the number of white pixels at the time of occlusion and the number of white pixels at the time of occlusion. The image reading apparatus according to claim 1, wherein the size of the document is determined based on the number of pixels of the document. 3. The image reading apparatus according to claim 1, wherein a surface of the cover facing the transparent member is white when the transparent member is shielded. 4. The white pixel number detection means sets an electric signal of each pixel in one scan in a case where the cover is in a shielding position and a case where the cover is in a shielding front position to a predetermined threshold value. 4. A binarizing unit for binarizing based on the above, and a white pixel number counting unit for counting the number of white pixels from the binarized information for each pixel. The image reading device according to item 1. 5. The image reading apparatus according to claim 4, further comprising threshold setting means for setting the threshold to a desired value. 6. The image reading apparatus according to claim 1, further comprising a scanning line setting means for setting the position of the scanning line to a desired position.