JP4261498B2 - Image reading device - Google Patents

Description

  The present invention relates to an image reading apparatus that reads an image of a document.

Conventionally, the detection of the document size in an image reading apparatus such as a copying machine, a scanner, or a facsimile is performed when a document is placed on the platen glass. This is done using a sensor that detects the presence or absence of a document at a predetermined position above. When the placed document is pulled in by the sheet feeder, the document size in the main scanning direction is detected by detecting the position of the document guide plate, and the document size in the sub scanning direction is detected at the head in the sub scanning direction. And it was done using a sensor that detects when the tail passes.
JP-A-10-010651 JP-A-10-090807 Japanese Patent Application Laid-Open No. 08-083033

  However, in the prior art, it is necessary to provide hardware for detecting the document size such as a sensor in the image reading apparatus, which increases the cost.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an image reading apparatus that can detect the document size without providing hardware such as a sensor for detecting the document size.

An image reading apparatus according to claim 1 includes a reading unit that reads an image from a document,
Document data storage means for storing document data which is image data read by the reading means;
A pattern image provided with a predetermined image provided on the back side of the document at a position where the reading unit reads the document;
Comparison data storage means for preliminarily storing comparison data that is image data when the back surface is read by the reading means;
The document data stored in the document data storage means and the comparison data stored in the comparison data storage means are compared to determine the degree of coincidence at each position. Edge position recognition means for recognizing the border of the document as the edge position of the document in the document data;
Size calculation means for obtaining the size of the document from both end positions of the document recognized by the edge position recognition means ,
The end position recognition means includes
Difference calculation for calculating a difference between pixels of comparison data stored in the comparison data storage means and pixels at a plurality of predetermined positions of the document data stored in the document data storage means corresponding to the pixels Means,
A first coincidence determining unit that determines whether or not each difference calculated by the difference calculating unit is within a predetermined value, and is matched when the difference is within a predetermined value; ,
For each pixel of the comparison data for which the difference is calculated by the difference calculation unit, when it is determined that at least one of the determination results by the first match determination unit for the pixel matches, the pixel of the comparison data is Second coincidence determining means for determining that the original data coincides;
When the non-matching pixels based on the determination result by the second matching determination unit continue for the predetermined number of pixels from the outside in the main scanning direction to the inside, an end for determining the continuous start position as the end position of the document Position determination means .

  According to this configuration, the document position data is read from the document and the background by the reading unit and stored in the document data storage unit and the background data of the image pattern stored in advance in the comparison data storage unit. The edge position of the document is recognized by the edge position recognition means, and the size of the document is obtained by the size calculation means using this edge position.

An image reading apparatus according to a second aspect is the image reading apparatus according to the first aspect , wherein the end position determination means advances the search for the consecutive inconsistent pixels in parallel from both ends in the main scanning direction. Is.

An image reading apparatus according to a third aspect is the image reading apparatus according to the first or second aspect , wherein the difference calculating means includes a pixel of the comparison data, a pixel of the document data at a position matching the pixel, and The difference between the pixels before and after the predetermined number of pixels is calculated.

An image reading apparatus according to a fourth aspect is the image reading apparatus according to any one of the first to third aspects, wherein the difference calculating means is provided for every predetermined number of pixels in the main scanning direction in the comparison data. Only the pixel is a target for calculating the difference.

An image reading apparatus according to a fifth aspect is the image reading apparatus according to any one of the first to fourth aspects, wherein a lattice pattern is used as the image pattern formed on the back surface.

An image reading apparatus according to a sixth aspect is the image reading apparatus according to any one of the first to fifth aspects, wherein a low-density image is used as the image pattern formed on the back surface.

  According to the first aspect of the present invention, since the document size can be detected without providing hardware such as a sensor for detecting the document size, the document size can be detected at a low cost.

Furthermore, according to the first aspect of the present invention, the end position of the document can be easily recognized. In addition, since one pixel of the comparison data is matched with a plurality of pixels of the document data, a more accurate document size can be detected even if the pixel position of the image pattern on the back side is read slightly inaccurately. can do. Also, since the pixel value difference is determined to be the same when it is within a predetermined value, it is possible to detect a more accurate document size even when the pixel value of the image pattern on the back side is read slightly inaccurately. Can do.

According to the second aspect of the invention, since both ends of the original in the main scanning direction are detected in parallel, the original size can be detected more quickly.

According to the third aspect of the present invention, it is determined whether one pixel of the comparison data is coincident with the pixel of the document data at the position matching the pixel and the pixels corresponding to the predetermined number of pixels at the positions before and after the pixel. Therefore, even when the pixel position of the image pattern on the back side is read slightly inaccurately, a more accurate document size can be detected.

According to the fourth aspect of the invention, since the data to be compared can be reduced by comparing less data, the document size can be detected more quickly.

According to the fifth aspect of the present invention, since the image formed on the document and the background image pattern are less likely to match at the boundary of the document, the image formed on the document and the back surface are formed. It is easy to determine the boundary with the image that is being displayed.

According to the sixth aspect of the present invention, since the image pattern has a low density and the original is not seen through, there is less show-through when the image is read from the original.

  Embodiments according to the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing a mechanical schematic configuration of a sheet feeder portion of an image reading apparatus according to an embodiment of the present invention. The image reading apparatus is, for example, a copying machine, a scanner, a facsimile machine, or a multifunction machine having both functions. The documents 112 are placed with the reading surface facing down, and are pulled in the direction of the arrow A one by one by a document drawing mechanism (not shown) of the sheet feeder. A reading sensor 113 that reads an image of the original is fixed at a predetermined position below the position where the original is pulled into the sheet feeder in the sheet feeder. The reading sensor 113 is composed of a CCD (charge coupled device) or the like, and can read, for example, one scanning line in the main scanning direction of the document at a time. The reading sensor 113 reads the entire surface of the document by repeating reading of one scanning line in the main scanning direction with respect to the document 112 to be pulled in all scanning lines. In the sheet feeder, a predetermined image pattern is drawn on a portion 111 on the back side of the document with respect to the reading sensor 113 and read by the reading sensor 113 when the document is not placed. This image pattern is preferably set so that the boundary with the original is clear for all types of original images, for example, a low-density lattice pattern 114 without being transferred to the original. When a document is placed, the reading sensor 113 reads the document and the image pattern on the back located outside the document together.

  Next, the functional configuration of the scanner 1 which is an image reading apparatus according to an embodiment of the present invention will be described. FIG. 2 is a block diagram illustrating a functional configuration of the scanner 1. The scanner 1 includes an image reading unit 11, a document data storage unit 12, a comparison data storage unit 13, an end position recognition unit 14, and a size calculation unit 15 as functional units. Here, the description about the output of the image data of the scanner 1 is omitted.

  The image reading unit 11 reads an image from a document, and its mechanical configuration corresponds to the sheet feeder portion of the image reading apparatus shown in FIG. The image reading unit 11 writes the read image data (document data) in the document data storage unit 12.

  The document data storage unit 12 stores image data of a document read by the image reading unit 11. The document data storage unit 12 is configured by, for example, a RAM (random access memory). The document data stored in the document data storage unit 12 includes an image of the document and the image pattern on the back surface of the outer area.

  The comparison data storage unit 13 stores in advance an image pattern on the back surface that is read by the reading sensor 113 when a document is not placed. The comparison data storage unit 13 is composed of, for example, a RAM. The comparison data storage unit 13 reads and stores the back image pattern immediately before reading the document data. The image pattern reading time may be, for example, an arbitrary time before reading the document data, or the manufacturing time of the scanner 1 in the factory. The image pattern stored in the comparison data storage unit 13 is image data when the image of the document is read (this image data includes the image of the document and the background image pattern around it). And used to detect the outer edge position of the document. The comparison data storage unit 13 may be a line memory already used for use at the beginning of image processing, for example, or may be a dedicated line memory for storing comparison data. Good. When the line memory used for image processing is diverted, the present invention can be implemented at a lower cost.

  The edge position recognition unit 14 determines, for example, whether each pixel in one scanning line in a predetermined main scanning direction is in the document or outside the document with respect to the document data stored in the document data storage unit 12. It recognizes the positions of both ends of the document in the main scanning direction. Details of the configuration and processing of the end position recognition unit 14 will be described later.

  The size calculation unit 15 obtains the size of the document in the main scanning direction from the both end positions in the main scanning direction from the both end positions of the document recognized by the end position recognition unit 14. The size calculation unit 15 subtracts the number of pixels outside the both end positions recognized by the end position recognition unit 14 from the total number of read pixels in the main scanning direction read by the reading sensor 113 (that is, the main scanning direction of the document). The length obtained by multiplying the number of pixels) by the length occupied by one pixel is calculated as the document size in the main scanning direction.

  Next, the configuration and processing details of the end position recognition unit 14 will be described. FIG. 3 is a diagram illustrating data processed by the end position recognition unit 14. 2, the end position recognition unit 14 includes a difference calculation unit 141, a first match determination unit 142, a second match determination unit 143, and an end position determination unit 144.

  The difference calculation unit 141 reads out the data in the comparison data storage unit 13 as comparison source data (comparison source data in FIG. 3) and, at the same time, a predetermined one scanning line in the main scanning direction of the document data storage unit 12, for example, the center in the sub scanning direction. Are read out as comparison destination data (comparison destination data in FIG. 3). Then, the difference calculation unit 141 has a predetermined number (comparison target pixels) centered on each pixel of the comparison source data at every predetermined number of pixels, for example, every five pixels, and the pixel of the comparison destination data at the same pixel position as the comparison source pixel. Number), for example, a difference from five pixels. The arrows shown between the pixel of comparison source data and the pixel of comparison destination data in FIG. 3 indicate the comparison source pixel and the comparison destination pixel for that pixel. The difference result in FIG. 3 shows the difference between the comparison source pixel and the comparison destination pixel.

  The first coincidence determination unit 142 checks whether or not the difference obtained by the difference calculation unit 141 is a predetermined number, for example, 9 or less, and if the difference is 9 or less, the comparison source pixel and the comparison destination pixel If the difference is greater than 9, it is determined that the comparison source pixel and the comparison destination pixel do not match. In the pixel match determination result of FIG. 3, “◯” is shown for the difference result determined to match, and “X” is shown for the difference result determined to be mismatch. When this is implemented, for example, “1” may be used in the case of matching, and “0” may be used in the case of mismatching.

  The second match determination unit 143 determines a match with the comparison target data for each comparison source pixel. Hereinafter, a group (for example, five) of comparison target pixels with respect to the comparison source pixel is referred to as a block. If there is at least one match in the block as a pixel position determination result, the second match determination unit 143 determines that the block is a match. If there is no match in the block, it is determined that the block does not match. In the block coincidence determination result of FIG. 3, “◯” is shown in the block determined to be coincident as the determination result for each block. “X” is shown in the block determined to be non-position.

  The edge position determination unit 144 sets the start pixel of the original when the mismatch in the block match determination result of the second match determination unit 143 continues for a predetermined number, for example, three in the direction from the outside to the inside of the scanning line. Is determined to be the outermost pixel. The paper edge determination in FIG. 3 shows the block matching determination result and the position determined as the edge of the original paper based on the result.

  The difference calculation unit 141, the first coincidence determination unit 142, the second coincidence determination unit 143, and the end position determination unit 144 perform the above processing from both ends of the scan line to the inside, so that the main scanning direction of the original paper Can be detected at both ends. If the processing from the both ends toward the inside is performed in parallel, both ends of the original paper can be detected more quickly.

  Next, the flow of determination processing of the edge position of the original paper will be described. 4, 5, and 6 are flowcharts showing the flow of the end position determination process for one end of the original paper. 4 is a flowchart showing the overall flow, and FIGS. 5 and 6 are flowcharts of subroutines of the flowchart shown in FIG.

  In step S <b> 1, the image reading unit 11 reads an image (including the background) of one document using the reading sensor 113 while pulling one of the placed documents, and stores it in the document data storage unit 12. Write.

  In step S2, the difference calculation unit 141 determines from the image data stored in the document data storage unit 12 one scan line in a predetermined main scanning direction, for example, a position within about 5 mm from the head in the document drawing direction in the sub-scanning direction ( One scanning line at the nearest readable line is desirable (comparison data in FIG. 3). The one scanning line is read out for comparison in the course of reading an image from the original in step S1, that is, when one scanning line in the predetermined main scanning direction (position within about 5 mm from the head) is read. It is desirable.

  In step S3, the difference calculation unit 141 reads the image data stored in the comparison data storage unit 13 (comparison source data in FIG. 3).

  In step S <b> 4, the difference calculation unit 141 assigns a predetermined value “3” as an initial value to the comparison source pixel number N, and assigns a predetermined value, for example “−2”, as an initial value to the comparison destination offset L. The pixel number is a number that is continuously assigned with the pixel position at one end of the scanning line read by the reading sensor 113 being “1” and the other end being “Nmax”. The initial value “−2” of the comparison destination offset L is a number obtained by subtracting 1 from the number of pixels (comparison target pixel) of comparison destination data for comparing (taking a difference) one pixel of comparison source data and dividing by 2. With a negative sign. In the present embodiment, the number of comparison target pixels is “5”. The initial value of the comparison source pixel number N is a number obtained by adding the initial value of the comparison destination offset L to the number of comparison target pixels.

  In step S5, the difference calculation unit 141, the first match determination unit 142, and the second match determination unit 143 determine whether or not the pixel of the comparison source pixel number N of the comparison data matches the document data. Details of this processing will be described later with reference to the flowchart of FIG.

  In step S6, if it is determined in step S5 that the pixel of comparison source pixel number N in the comparison data matches the original data (YES in step S6), step S9 is used to compare the next pixel in the comparison data. Proceed to If it is determined in step S6 that the pixel of the comparison source pixel number N in the comparison data does not match the document data (NO in step S6), the process proceeds to step S7. In step S7, the edge position determination unit 144 performs document edge position determination processing because the pixel N may be the edge of the document sheet. Details of this processing will be described later with reference to the flowchart of FIG. In step S8, the end position determination unit 144 ends the process when the end position of the document is specified in step S7 (YES in step S8). If the end position of the document is not specified in step S8 (NO in step S8), the process proceeds to step S9 to compare the next pixel of the comparison source data.

  In step S9, the difference calculation unit 141 increments the comparison source pixel number N by a predetermined number, for example, five. In step S10, the difference calculation unit 141 checks whether or not the comparison source pixel number N is equal to or less than the maximum number of N (same as the number of pixels read by the reading sensor 113) Nmax, and if N is equal to or less than Nmax ( If YES in step S11, the process returns to step S5 to perform processing for the next N. If N is larger than Nmax in step S10 (NO in step S10), the process proceeds to step S11. In step S11, since the end of the document was not found, an error message “Document size could not be detected” is displayed on the operation unit (not shown), for example.

  Next, a subroutine showing details of the processing in step S5 in FIG. 4 will be described. FIG. 5 is a subroutine flowchart showing details of the processing in step S5.

  In step S51, the difference calculation unit 141 checks whether or not the value obtained by adding the comparison source pixel number N and the comparison destination offset L is smaller than 1, and if it is smaller than 1 (YES in step S51), Since there is no comparison target pixel, the process proceeds to step S56 in order to increase the comparison target offset by one. In step S51, when the value obtained by adding the comparison source pixel number N and the comparison destination offset L is 1 or more (NO in step S51), since the comparison destination pixel exists, the process proceeds to step S52.

  In step S52, the difference calculation unit 141 calculates a difference between the pixel N of the comparison source data and the pixel (N + L) of the comparison destination data. The difference result of FIG. 3 shows an example of the difference result data. In step S53, the first match determination unit 142 checks whether the difference calculated in step S52 is a predetermined value, for example, 9 or less. If the difference is 9 or less (YES in step S53), Assuming that the comparison source pixel and the comparison destination pixel obtained in step S52 match, the process proceeds to step S54. In step S54, it is recorded that the comparison results of the comparison source pixel and the comparison destination pixel obtained in step S52 are the same. If the difference is not 9 or less in step S53 (NO in step S53), it is determined that the comparison source pixel obtained in step S52 and the comparison destination pixel do not match, and the process proceeds to step S55. In step S55, it is recorded that the comparison result between the comparison source pixel and the comparison destination pixel obtained in step S52 is inconsistent. An example of the determination result data is shown in the pixel match determination result of FIG.

  In step S56, the difference calculation unit 141 increments the comparison destination offset L by 1 and changes the comparison destination pixel to the next pixel. In step S57, it is checked whether or not the comparison destination offset L is a predetermined maximum value (number obtained by reversing the sign of the initial value of the comparison destination offset), for example, 2 or less. If it is 2 or less (YES in step S57). Since the comparison with all the pixels of the comparison target pixel number has not been completed, the process returns to step S51 to perform the comparison process with the next comparison target pixel. In step S57, if the comparison destination offset L is larger than 2 (NO in step S55), it means that the comparison with all pixels of the comparison target pixel number has been completed, so the process proceeds to step S58. In step S58, the second coincidence determination unit 143 checks whether or not at least one of the comparison results with all pixels of the comparison target pixel number is coincident, and if at least one coincides (step S58). If YES, the process proceeds to step S59. In step S59, the second match determination unit 143 determines that the pixel N of the comparison data matches the document data, records this, and returns from the subroutine. If no match is found in step S58 (NO in step S58), the process proceeds to step S60. In step S60, the second match determination unit 143 determines that the pixel N of the comparison data does not match the document data, records this, and returns from the subroutine.

  Next, a subroutine showing details of the processing in step S7 in FIG. 4 will be described. FIG. 6 is a flowchart of a subroutine showing details of the processing in step S7.

  In step S71, the end position determination unit 144 checks whether or not the pixel of the comparison source pixel number (N−1) immediately before the current comparison source pixel number N is determined to be matched, and is determined to be matched. If yes (YES in step S71), the process proceeds to step S72. In step S72, the end position determination unit 144 indicates that the current pixel N does not match and the previous pixel (N-1) matches, so that the pixel N may be the end of the document. Therefore, while substituting 1 for the consecutive mismatch number C and substituting the value of the comparison source pixel number N for the end position pixel number E, the process returns from the subroutine.

  If it is determined in step S71 that the pixel of the comparison source pixel number (N-1) immediately before the current comparison source pixel number N is not coincident (NO in step S71), the process proceeds to step S73. In step S73, the end position determination unit 144 determines that the current pixel N does not match and the previous pixel (N-1) also does not match. Move up one step. In step S74, the end position determination unit 144 checks whether the continuous mismatch number C is a predetermined number, for example, 3 or not, and if it is not 3 (NO in step S74), the continuous mismatch number has not yet reached 3. Therefore, the subroutine returns to determine whether the next pixel matches. In step S74, when the consecutive mismatch number C is 3 (YES in step S74), the process proceeds to step S75. In step S75, the edge position determination unit 144 determines that the pixel value stored in the edge position pixel number E is the pixel number indicating the edge position of the document because the continuous mismatch has reached 3. Return from.

  In the description of the document edge position determination process, the process for finding the edge of the document for the first time from one end in the main scanning direction has been described. However, by performing the above process from both ends of the document data, Both ends of the main scanning direction can be detected. In the above description, the document edge detection process is repeated until N reaches Nmax. However, when the detection process is performed in parallel from both ends, it is not necessary to do this, and one process performed the determination process. For the block, the other process does not need to be determined. That is, the process may be terminated when N has reached the comparison source pixel for which the process has been completed in the other detection process.

  As described above, in this embodiment, since the size of the original is detected using the image data of the original written in the memory, hardware such as a sensor for detecting the original size is provided in the image reading apparatus. The document size can be detected without providing it.

  In addition, this invention is not limited to the thing of the said embodiment, The aspect described below can be employ | adopted. In the above embodiment, a low-density grid pattern is used for the back image pattern, but it is not show-through on the original (that is, low density), and the boundary with the original is easy to understand (that is, it is difficult to have the same pattern and color as the original). ) An image pattern is desirable and not necessarily a low density grid pattern. Further, when using a lattice pattern, it is possible to detect the document edge more accurately by using a pattern having a lattice as small as possible.

  In the above embodiment, the size of the document in the main scanning direction is obtained from the data for one scanning line in the main scanning direction. You may make it ask for the size of. In this way, for example, if an average of the sizes of a plurality of scanning lines is used, a more accurate size can be obtained. If the maximum size of a plurality of scanning lines is used, the size of a larger portion can be obtained for a sheet having a different size in the main scanning direction depending on the position in the sub scanning direction.

  In the above embodiment, the document size in the main scanning direction is obtained. However, the document size in the sub scanning direction may be obtained by the same method.

  Further, in the above-described embodiment, the case where an image is read while pulling the document with the sheet feeder (the document moves and the reading sensor 113 does not move) has been described as an example. However, the document is placed on the platen glass. Even when an image is read (the reading sensor 113 moves without moving the document), the size of the document can be detected by the same method.

  In the above embodiment, the pixel match determination is performed for all the pixels in the block, and then the block match determination is performed. However, it is determined that the pixel matches one pixel in the block. At this point, the block determination may be matched, and the pixel match determination for the remaining pixels may be omitted. In this way, it is possible to shorten the time for pixels that are not subjected to pixel matching determination.

  In the above embodiment, the number of pixels in one block (number of pixels to be compared) is the same as the number of pixels between pixels used as comparison source pixels in the comparison source data (that is, 5). It is not necessarily the same.

  The document size may be detected by using the comparison source data and the comparison destination data in the above embodiment in reverse (that is, the document data is the comparison source data and the comparison data is the comparison destination data).

FIG. 3 is a perspective view illustrating a mechanical configuration of a sheet feeder portion of the image reading apparatus according to the embodiment of the present invention. 1 is a block diagram illustrating a functional configuration of an image reading apparatus according to an embodiment of the present invention. It is a figure which shows the data processed in recognition of the end position in one Embodiment of this invention. 6 is a flowchart showing a flow of document edge detection processing in an embodiment of the present invention. 6 is a flowchart illustrating a flow of a subroutine for document edge detection processing in an embodiment of the present invention. 6 is a flowchart illustrating a flow of a subroutine for document edge detection processing in an embodiment of the present invention.

DESCRIPTION OF SYMBOLS 1 Image reader 11 Image reading part (reading means)
111 Rear view of sheet feeder
114 Lattice pattern 12 Document data storage unit (document data storage means)
13 Comparison data storage unit (comparison data storage means)
14 End position recognition unit (end position recognition means)
141 Difference calculation unit (difference calculation means)
142 1st coincidence determination part (1st coincidence determination means)
143 Second match determination unit (second match determination means)
144 Edge position determination unit (edge position determination means)
15 Size calculator (size calculator)

Claims (6)

Reading means for reading an image from a document;
Document data storage means for storing document data which is image data read by the reading means;
A pattern image provided with a predetermined image provided on the back side of the document at a position where the reading unit reads the document;
Comparison data storage means for preliminarily storing comparison data that is image data when the back surface is read by the reading means;
The document data stored in the document data storage means and the comparison data stored in the comparison data storage means are compared to determine the degree of coincidence at each position. Edge position recognition means for recognizing the border of the document as the edge position of the document in the document data;
Size calculation means for obtaining the size of the document from both end positions of the document recognized by the edge position recognition means ,
The end position recognition means includes
Difference calculation for calculating a difference between pixels of comparison data stored in the comparison data storage means and pixels at a plurality of predetermined positions of the document data stored in the document data storage means corresponding to the pixels Means,
A first coincidence determining unit that determines whether or not each difference calculated by the difference calculating unit is within a predetermined value, and is matched when the difference is within a predetermined value; ,
For each pixel of the comparison data for which the difference is calculated by the difference calculation unit, when it is determined that at least one of the determination results by the first match determination unit for the pixel matches, the pixel of the comparison data is Second coincidence determining means for determining that the original data coincides;
When the non-matching pixels based on the determination result by the second matching determination unit continue for the predetermined number of pixels from the outside in the main scanning direction to the inside, an end for determining the continuous start position as the end position of the document An image reading apparatus comprising: a position determination unit . The image reading apparatus according to claim 1 , wherein the end position determination unit advances the search for the consecutive inconsistent pixels in parallel from both ends in the main scanning direction. It said difference calculation means, a pixel of the comparison data, according to claim 1 or 2 for calculating the difference between the predetermined number of pixels of the pixel of the pixel and the preceding and position of the original data of the position that matches the pixel The image reading apparatus described in 1. It said difference calculation means, an image reading apparatus according to claim 1 of interest for calculating the difference only predetermined number of pixels every other pixel in the main scanning direction in the comparative data. As an image pattern formed on the rear surface, the image reading apparatus according to any one of claims 1 to 4, using a grid pattern. Wherein an image pattern formed on the back, the image reading apparatus according to any one of claims 1 to 5 used a low density image.

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