JP6544233B2 - Calibration method of image reading apparatus and image reading apparatus - Google Patents

Description

  The present invention relates to an image reading apparatus which picks up an object to be read such as a document or a sheet using a line sensor in which a plurality of sensor chips are linearly arranged.

  A line sensor (also referred to as a one-dimensional imaging element) in which a plurality of imaging elements are linearly arranged as an image reading apparatus applied to a copying machine, a scanner, a facsimile, a bill reading apparatus, etc. Scan to generate image data corresponding to a sheet. At this time, the line sensor scans a line in the main scanning direction with the direction in which the plurality of imaging elements are linearly arranged as the main scanning direction, and conveys the object to be read in the subscanning direction perpendicular to the main scanning direction Then, two-dimensional image data is generated by shifting and connecting new scans.

  The line sensor is composed of a sensor chip having a plurality of imaging elements arranged linearly in the main scanning direction, and has a configuration in which a plurality of sensor chips are further arranged in the main scanning direction.

  Since the sensor chip is manufactured by semiconductor manufacturing technology, the intervals between the imaging devices on the sensor chip are relatively equal, but a line sensor in which a plurality of sensor chips are further arranged in the main scanning direction is a sensor chip. The spacing between sensor chips on the line sensor tends to vary because it is manufactured in a mechanical alignment process. In addition, the spacing between sensor chips is often different from the spacing between imaging elements, and simply arranging the image data read for each sensor chip in the main scanning direction, the boundary portion of the sensor chip on the image data is There is a problem that it becomes discontinuous.

  Therefore, under the condition that the distance between sensor chips is larger than the distance between image sensors, pixels are inserted in the boundary portion by interpolation processing so that the image data does not become discontinuous at the boundary portion of the sensor chip. There is a method (see, for example, Patent Document 1).

JP 2003-101724 A (pages 5-7, FIG. 3)

  In order to realize the method of Patent Document 1, it is necessary to know the distance between the imaging devices and the distance between the sensor chips. However, since the sensor chips are mechanically attached, errors may occur at the time of attachment, which may not always be linear, and the intervals between the sensor chips may not necessarily be equal. In the configuration of the line sensor of Patent Document 1, since there is no imaging element between sensor chips, the distance between sensor chips can not be calculated from the image data read by the line sensor, and the distance between sensor chips is calculated. For this purpose, it is necessary to use means such as direct measurement of the positional relationship of the sensor chip.

  The present invention has been made to solve the problems as described above, and even if there is a design position and an error in the positional relationship of the sensor chip, direct measurement of the positional relationship of the sensor chip one by one It is an object of the present invention to provide an image reading apparatus which fulfills the intended purpose of outputting image data which does not become discontinuous at the boundary portion of a sensor chip by performing calibration without correction.

In the calibration method of the image reading apparatus according to the present invention, a line sensor which arranges in the main scanning direction a sensor chip in which a plurality of imaging elements are provided in the main scanning direction and picks up an object to be read facing the sensor chip. And calibration of an image reading apparatus including an image combining unit that generates combined image data by performing enlargement or reduction on a captured image of each of the sensor chips based on combining information and adjusting and combining the combining position. A method of setting a calibration document having a calibration pattern in which a predetermined reference position is set as the composite information, and a row of dots arranged in a zigzag form and a straight line along the main scanning direction are drawn. As the reading object, the document distance from the calibration document to the line sensor is Acquires the synthesized image data by a plurality of distance setting, the relationship of the captured image for each of the sensor chips obtained in each of the original distance and the original distance, the sub-scanning direction shift amount for each of the sensor chip, the sensor offset of the amount of overlap between every chip, and the calculated height offset of the object to be read direction for each sensor chip, and the sub-scanning direction shift amount of the resulting the sensor chip, each between before Symbol sensor chip The offset amount of the overlap amount and the height offset amount in the direction of the object to be read of each of the sensor chips are set as the combined information.

  According to the present invention, a sensor chip is obtained from composite image data obtained using, as the reading object, a document having a calibration pattern in which point rows arranged in a staggered manner and straight lines along the main scanning direction are drawn. The position where the sensor chip is provided is the design position and the error, because the offset amount of the sub scanning direction, the offset amount of the overlap amount, and the height offset amount of the reading object direction for each sensor chip are calculated and set as composite information. Provides an image reading device that achieves the intended purpose of outputting image data that does not become discontinuous at the boundary of the sensor chip by performing calibration without directly measuring each one even if It will be possible to

FIG. 1 is a functional block diagram showing a schematic configuration of an image reading apparatus 1 according to a first embodiment. FIG. 2 is a diagram showing a schematic configuration of an imaging unit 11; It is a figure which shows the design of the document for calibration. FIG. 6 is a view showing an example of image data obtained by reading a calibration document. FIG. 6 is a view showing an overlap area on image data obtained by reading a calibration document. FIG. 7 is a diagram showing the processing procedure of the calibration method according to the first embodiment. It is a figure which shows the relationship between a document distance and the point sequence space | interval in the image data acquired with each sensor chip. It is a figure which shows the approximation formula of the document distance and the point sequence space | interval in each sensor chip. FIG. 6 is a diagram showing a relationship between a document distance and an overlap amount in image data acquired by each sensor chip. It is a figure which shows the approximation formula of the original distance and the overlap amount in each sensor chip. FIG. 7 is a diagram showing a processing procedure of a magnification calculation method according to Embodiment 1. FIG. 2 is a view showing an image reading apparatus provided with a calibration unit.

Embodiment 1
FIG. 1 is a functional block diagram showing a schematic configuration of the image reading apparatus 1 according to the first embodiment. The image reading apparatus 1 includes an imaging unit 11, an A / D conversion unit 12, a memory 13, and an image combining unit 14. The calibration device 2 used at the time of calibration to calibrate the image reading device 1 includes a point train interval measurement unit 21, an overlap amount estimation unit 22, and a calculation unit 23.

  The imaging unit 11 is a line sensor that generates an image signal SI by optically scanning an object to be read. The imaging unit 11 is provided with N (N is an integer of 2 or more) sensor chips in which M (M is an integer of 2 or more) imaging elements are linearly arranged. Here, the arrangement direction of the imaging element and the sensor chip is referred to as a main scanning direction.

  FIG. 2 is a view showing a schematic configuration of the imaging unit 11. In FIG. 2, the sensor chip A, the sensor chip B, and the sensor chip C are arranged in the main scanning direction on the substrate. That is, since three sensor chips are arrayed in FIG. 2, N is illustrated as three.

  Further, M sensor elements are arranged in the main scanning direction on each sensor chip (not shown). The sensor chip is generally manufactured by semiconductor manufacturing technology, and the displacement of the imaging device on the sensor chip is small. However, when the sensor chip A, the sensor chip B, and the sensor chip C are arranged on the substrate, the sensor chip is manufactured in the process of mechanically arranging the sensor chips, so the position for each sensor chip is the reference position determined by design. On the other hand, the deviation width in the main scanning direction, the sub scanning direction, and the height direction tends to vary, and the deviation width is larger than the arrangement deviation of the imaging element on the sensor chip.

  In FIG. 2, the lens A is provided at a position facing the sensor chip A. Similarly, the lens B is provided at a position facing the sensor chip B, and the lens C is provided at a position facing the sensor chip C. Each lens has a structure that widens the angle of view taken by the sensor chip. As a result, when the object to be read at a position opposite to each other is scanned via the lens, the reading range of each sensor chip can be expanded. It is possible to eliminate the loss of image data of the object to be read. Further, by providing this lens in an integral structure with the sensor chip, the distance between the sensor chip and the lens can suppress variations in the manufacturing process. In addition, it may be integrated with the sensor chip as an optical system (cell) composed of a lens and a stop.

  Referring back to FIG. The A / D converter 12 converts the image signal SI obtained by the optical scanning of the imaging unit 11 into digital image data DI.

  The memory 13 stores image data DI.

  The image combining unit 14 enlarges or reduces the N captured images based on the combining information D13, and adjusts the combining position to combine to generate combined image data Dout. The composite information D13 includes information on the sub-scanning direction shift amount for each sensor chip, the offset amount of the overlap amount, and the height offset amount of the reading object direction for each sensor chip, or the adjustment amount based thereon. By adjusting based on the composite information D13, composite image data can be obtained in which the widths in the main scanning direction are uniform for the N captured images and the overlapping part of the images is eliminated.

  Here, if there is no error with the design in the process of arranging a plurality of sensor chips in the main scanning direction, the amount of deviation in the subscanning direction for each sensor chip with respect to the predetermined document position, the offset amount of overlap amount, and each sensor chip The height offset amount in the direction of the object to be read is a value at the reference position based on the design, and the composite information D13 can be determined. In the present invention, by performing calibration after the step of arranging a plurality of sensor chips in the main scanning direction, the combined information D13 is more suitable for the image reading apparatus than the one determined based on the design. It can be set.

  The image combining unit 14 may be externally input with respect to the combined information D13, or may store the combined information D13 at the reference position based on the design as rewritable data as initial information.

  Next, a calibration method of the image reading apparatus according to the present embodiment will be described.

  FIG. 3 is a design of an original (calibration original) having a calibration pattern used in the calibration mode. The calibration document is composed of a straight line extending in the main scanning direction and a series of points arranged in a zigzag at equal intervals in the main scanning direction. The straight line is used to detect a shift in the sub scanning direction. The point sequence is used to detect the amount of overlap in the main scanning direction. Although two straight lines are shown in FIG. 3, any number of straight lines may be used as long as it is one or more. Further, although in FIG. 3 the point sequence is configured to have four stages, any number of stages may be used as long as the number of point sequences is two or more.

  In calibration, the image data is acquired by arranging the distance between the calibration document used as a reading object and the line sensor at a specified distance. The specified distance is implemented for two or more types of distances, and this is realized by analyzing the acquired two or more types of image data.

  FIG. 4 shows an example of image data obtained by the reading device 1 acquiring image data of a calibration document. FIG. 4 shows an example in which each sensor chip is deviated in the main scanning direction, the sub scanning direction, and the height direction. As shown in FIG. 4, when the sensor chips arranged on the line sensor are arranged offset in the sub scanning direction, the straight line extended in the main scanning direction of the calibration document is as shown in FIG. It becomes image data which has been shifted and synthesized for each sensor chip. In addition, when each sensor chip disposed on the line sensor is displaced in the main scanning direction, the width of the overlap area of the calibration document is different from the width of the overlap area based on the design. Become. In addition, when each sensor chip disposed on the line sensor is offset in the height direction, the distance between the point row portions of the calibration document is different from the distance between the point row portions based on the design. Become.

FIG. 5 is a view showing the relationship between the image data of FIG. 4 and the deviation amount. FIG. 5 shows image data when arrayed with the sensor chip A, the sensor chip B, the sensor chip C, the sensor chip D, and the sensor chip E from the left. Here, T _k (k is a variable representing any one of the N sensor chips) indicates an average value of the distance between point sequences on the sensor chip k. OV indicates the amount of overlap in the main scanning direction between the sensor chips, and the amount of overlap in the main scanning direction between the sensor chip A and the sensor chip B is denoted as OV _AB .

As shown in FIG. 5, from the composite image data Dout from the image reading apparatus using the above-described calibration document, the amount of deviation of a straight line extending in the main scanning direction, the distance between point arrays for each sensor chip, and the sensor chip The amount of overlap can be measured.

The point train interval measurement unit 21 of the calibration device 2 in FIG. 1 measures the interval of point trains for each sensor chip from the image combination data Dout output from the image reading device 1. Measurement can be simplified as measurement of only one point. A measurement that measures the interval between multiple point sequences and calculates the average by the calculation unit 23 and uses it as the average value T _k of the intervals between the point arrays of the corresponding sensor chip is more appropriate than the measurement of only one point You can get the value.

  The overlap amount estimation unit 22 estimates an overlap amount between sensor chips from the image combination data Dout output from the image reading device 1.

  The overlap amount estimation unit 22 calculates the similarity of an area (hereinafter also referred to as an overlap area) in which reading ranges overlap between adjacent sensor chips for image data generated by N sensor chips. And estimate and output the overlap amount. The similarity is an index indicating the degree of similarity from the image data of each adjacent sensor chip.

  Here, since the width of the overlap area when the sensor chip and the lens are disposed at the reference position and the specified document distance is known information based on the design, the overlap estimated by the overlap amount estimation unit 22 is The amount of deviation in the main scanning direction between sensor chips can be obtained by comparing the amount with the amount of overlap at the reference position based on the design. Here, the document distance indicates the distance between the sensor chip or a lens provided integrally with the sensor chip and the object to be read.

  The calculating unit 23 determines the amount of deviation in the sub-scanning direction of the sensor chip and each sensor chip from the measurement result of the point train interval measurement unit 21, the estimation result of the overlap amount estimation unit 22 and the setting value of the document distance when measured. The overlap offset amount and the height offset amount in the reading object direction for each sensor chip are calculated.

  Next, the processing procedure of the calibration method in the calibration mode will be described. FIG. 6 is a processing procedure of the calibration method according to the present embodiment.

  In step 1, the distance between the calibration document and the line sensor is set to the specified distance. As the designated distance, one of two or more types of set distances is set for calibration.

  In step 2, the image reading apparatus 1 is operated to acquire image data of a calibration document at the distance of the document placed.

  In step 3, with respect to the image data of the calibration document, the interval in the main scanning direction of the point sequence is measured for each sensor chip. Although there are a plurality of points for each sensor chip and a plurality of intervals are also measured, the representative value is taken as the interval of the point sequence to the sensor chip. The average value of the intervals of all the points may be used as the representative value, or the median of the intervals of all the points may be used as the representative value. For these measurements, for example, the composite image data Dout is output and measurement is performed outside the image reading device 1 (the calibration device 2). As described above, by performing measurement externally as calibration in the manufacturing process, it is not necessary to provide the image reading device 1 itself with a measurement unit for measuring the interval in the main scanning direction of the point sequence from the composite image data Dout. Can be reduced. Even if the image reading device 1 is provided with a measurement unit that measures the interval in the main scanning direction of the point sequence from the composite image data Dout, the intended purpose can be achieved.

  In step 4, the image data in the vicinity of the boundary between the sensor chips is superimposed on the image data when the calibration document is scanned to search for a position where the deviation disappears, and the amount of deviation in the subscanning direction of the sensor chip Calculate the lap amount. The process of step 4 is performed by the overlap amount estimation unit 22.

  In step 5, it is checked whether the processing from step 1 to step 4 has been performed for all set distances among the set distances for calibration. If not performed for all the set distances, the process returns to step 1 and the process for the remaining set distances is performed. If all set distances have been set, the process proceeds to step 6.

  In step 6, the amount of deviation in the sub-scanning direction for each sensor chip is calculated. Up to step 5, the amount of deviation in the sub-scanning direction has been calculated for all sensor chips and all set distances. In step 6, for the same sensor chip, a representative value of the amount of deviation in the sub-scanning direction at all set distances is taken as the amount of deviation in the sub-scanning direction of the sensor chip. The average value of the sub-scanning direction shift amounts at all set distances may be used as a representative value, or the median of the sub-scanning direction shift amounts at all set distances may be used as a representative value.

  In step 7, the relationship between the distance between the point sequences and the document distance is calculated. Up to step 5, the interval of point trains has been calculated for each set distance for all sensor chips. The average value of the intervals of point sequences of all the sensor chips is calculated for each set distance.

  FIG. 7 is a view showing the relationship between the distance between point sequences and the document distance. The longer the document distance, which is the distance between the sensor chip and the calibration document, from the interval of the point sequence pattern on the calibration document, the longer the point sequence seen in the image data captured by the sensor chip. The distance becomes narrower.

FIG. 8 is a diagram showing the relationship between the document distance and the distance between point sequences found in image data captured by the sensor chip. The horizontal axis indicates the document distance, and the vertical axis indicates the distance between point sequences observed in the image data captured by each sensor chip. Also, an average value T _A of the sensor chip acquired sequence of points apart from the image data A for three points P _1, P _2, and P ₃ the original distance as set distance for calibration indicated by open squares, represents an average value T _B of the sensor chip image data of the acquired sequence of points from the interval of B in × mark was the mean value T _C of the spacing of the point sequence obtained from the image data of the sensor chip C in open circles. Thus, the relationship between the distance between the point sequences and the document distance can be approximated by a linear expression.

Sensor chip A and the average value T _A spacing sequence of points acquired by the distance P _A between the _document, the sensor chip B and the average value T _B of the distance P column spacing points obtained in _B with the _original, the sensor chip the average value of C and the sequence of points obtained by the distance P _C between the original spacing as from T _C calculates an average value of interval point sequences in each original distance. The relationship between the distance PT _k between the sensor chip _k and the document (original document distance) and the average value T _k of the intervals of the point sequence in the sensor chip k can be approximated by the first linear expression shown in equation (1) . Here, k is shown as a variable representing any one of the N sensor chips.

ここでは、原稿距離ＰＴ_ｋの単位は［ｍｍ］とし、Ｔ_ｋの単位は画素数とする。ＫＥＩＴ_ｋは近似一次式の傾き［ｍｍ／画素］であり、ＯＦＴ_ｋは近似一次式の切片［ｍｍ］である。

Here, the unit of the document distance PT _k is [mm], and the unit of T _k is the number of pixels. KEIT _k is the inclination [mm / pixel] of the approximate linear expression, and OFT _k is the intercept [mm] of the approximate linear expression.

In step 8, the relationship between the document distance and the magnification is calculated. In the imaging unit 11 of the present embodiment, the document distance to be used normally and the resolution at that time are determined based on the design. The intervals of the point sequence on the document are all equally spaced, and the interval is S [mm]. Assuming that the standard document distance is P ₀ [mm] and the resolution at that time is Q ₀ [dpi: dots per inch], 1 inch is converted to 25.4 [mm] and the point array of the sensor chip k is converted. A scaling factor R _k [times] with respect to the average value T _k [pixel] of the interval is calculated by equation (2).

  From the equations (1) and (2), the relation between the document distance and the magnification is expressed by the equation (3).

  In step 9, the relationship between the overlap amount and the document distance is calculated. Up to step 5, the overlap amount in the main scanning direction has been calculated for each set distance between all the sensor chips. The average value of the amount of overlap between all the sensor chips is calculated for each set distance.

  FIG. 9 is a diagram showing the relationship between the overlap amount and the document distance. As the document distance, which is the distance between the sensor chip and the calibration document, increases with respect to the interval of the point sequence pattern on the calibration document, the overlap amount seen in the image data captured by the sensor chip increases The distance between

FIG. 10 is a diagram showing the relationship between the document distance and the overlap amount found in the image data captured by the sensor chip. The horizontal axis indicates the document distance, and the vertical axis indicates the overlap amount found in the image data captured by each sensor chip. Further, as a set distance for calibration P _1, P _2, and the three points P ₃ indicates the mean value OV _A overlap amount acquired from the image data of the sensor chip A in open squares, the sensor chip B the average value OV _B overlap amount acquired from the image data shown in × marks, exhibited a mean value OV _C overlap amount acquired from the image data of the sensor chip C in open circles. Thus, the relationship between the distance between the point sequences and the document distance can be approximated by a linear expression.

Sensor chip A and the average value OV A overlap amount obtained by the distance P _A between the _document, the sensor chip B and the average value of the obtained overlap amount by the distance P _B between the original OV _B, and the sensor chip C the average value of the overlap amount obtained by the distance P _C between the document and calculates the average value of the overlap amount in each document distances as OV _C. Then, the relationship between the distance PV _k between the sensor chip _k and the document (document distance) and the average value OV _k of the overlap amounts at the sensor chip k can be approximated by the second linear expression shown in equation (4) . Here, k is shown as a variable representing any one of the N sensor chips.

Here, the unit of OV _k is the number of pixels. KEIV _k is the inclination [mm / pixel] of the approximate linear expression, and OFV _k is the intercept [mm] of the approximate linear expression.

Here, the relational expression of the following equation (5) is established by substituting PT _k into the document distance PV _k of the sensor chip k from the equations (1) and (4). Further, OV _k which satisfies the equation (5), that is, when the document distance PV _k = PT _k is set as an overlap amount OVJ _k which should be originally present in the sensor chip k.

In step 11, the overlap amount OVj _k is inherent to every sensor chip, to calculate the original is overlap amount OVI should between the sensor chip. The calculation formula of the overlap amount OVI _AB that should originally exist between the sensor chip A and the sensor chip B is as shown in the equation (6).

In step 12, the offset amount OFOV [pixel] of the overlap amount is calculated. The calculation formula of the offset amount OFOV _AB of the overlap amount between the sensor chip A and the sensor chip B is as shown in the equation (7).

In step 13, the offset OFP _k of the height for each sensor chip is calculated. The calculation formula is shown in Formula (8). The unit of OFP _k is millimeter.

Here, P _i represents the i-th set distance, and T _ki is the point sequence of the sensor chip k at the document distance P _k at the sensor chip k when it is set to the i-th set distance. It represents an interval. AVG () is a function that takes an average value for all settings set for calibration.

  Thus, in step 6, the amount of deviation in the sub-scanning direction for each sensor chip is calculated, and in step 12, the amount of offset for the amount of overlap between sensor chips is calculated. Calculate the offset amount.

  Next, the magnification calculation procedure will be described. FIG. 11 is a flow chart showing a magnification calculation procedure using the calibration result according to the present embodiment.

  At step 101, the document is placed at an unknown document distance with respect to the image reading apparatus 1.

  At step 102, image data is acquired.

  In step 103, using the overlap amount estimation unit 22, image data near the boundary between the sensor chips are superimposed to search for a position at which the shift disappears, and a composite position (sub-scanning direction shift amount and overlap amount) is calculated. .

  In step 104, with respect to the overlap amount calculated in step 103, the offset amount of the overlap amount calculated in calibration is externally input and subtracted. The processing content is shown in equation (9). By this processing, the deviation in the main scanning direction for each sensor chip is corrected. The processing of step 104 is executed by the switching unit 53 of the image reading device 1.

Here, OVI _AB shows overlap amount obtained by subtracting the offset amount between the sensor chip A and the sensor chip B. OV _AB indicates the overlap amount calculated in step 103 between the sensor chip A and the sensor chip B. OFOV _AB indicates the offset amount of the overlap amount calculated by calibration between the sensor chip A and the sensor chip B.

In step 105, the overlap amount OVJ for each sensor chip is converted. Assuming that sensor chips are arranged in alphabetical order from A to Z in the line sensor, the overlap amount OVJ _B of the sensor chip B is the sensor chip A adjacent to the sensor chip B calculated by the equation (9) and It is obtained from the average of each overlap amount OVI _AB with C and the overlap amount OVI _BC . For the sensor chip A and the sensor chip Z which are both ends of the array, the overlap amount with the adjacent sensor chip calculated by the equation (9), that is, in the sensor chip A, between the sensor chip A and the sensor chip B. and OVI _AB, in the sensor chip Z and _{OVI YZ} between the sensor chip Z and the sensor chip Y. The conversion equation is shown in equation (10).

In step 106, the document distance P for each sensor chip is calculated from the overlap amount OVJ for each sensor chip. The calculation formula is shown in formula (11). In the equation (11), KEIV _k and OFV _k are parameters in the sensor chip k calculated at the time of calibration, and are passed from the outside of the image reader 1.

In step 107, the true document distance PI _k is calculated by subtracting the height offset amount OFP _k from the document distance P _k calculated in step 106. The calculation formula is shown in formula (12).

In step 108, the magnification R _k of the document is calculated from the true document distance PI _k . The magnification R _k of the document is calculated from the true document distance PI _k according to the equation (3) calculated in step 108 at the time of calibration.

The magnification R _k calculated in this manner is passed to the image combining unit 14 and used in enlargement or reduction before combining the images.

  By using the calibration procedure according to the embodiment described above, the amount of deviation in the sub-scanning direction for each sensor chip of the imaging unit 11, the amount of offset for the amount of overlap between sensor chips, and physical measurement The offset amount of height for each sensor chip can be grasped. By grasping these amounts, even when the document placed at an unknown document distance is read, it becomes possible to calculate the magnification of the document according to the above-mentioned magnification calculation procedure, and with the appropriate magnification for the image data Can be carried out.

  FIG. 12 shows the point sequence interval measurement unit of the image reading device 1 with respect to the point sequence interval measurement unit 21, overlap amount estimation unit 22, and calculation unit 23 used in the calibration procedure according to the present embodiment shown in FIG. FIG. 15 shows a diagram in which an overlap amount estimation unit 16 and a calculation unit 17 are configured. The point sequence interval measurement unit 15 and the point sequence interval measurement unit 21 have the same action. Similarly, the overlap amount estimation unit 16 and the overlap amount estimation unit 22 have the same operation, and the calculation unit 17 and the calculation unit 23 have the same operation. As shown in FIG. 12, the image reading apparatus 1 includes the point sequence interval measuring unit 15, the overlap amount estimating unit 16, and the calculating unit 17 so that the owner of the image reading apparatus 1 can directly perform calibration. It plays an effect. Although the input from the point train interval measurement unit 15 and the overlap amount estimation unit 16 is the output from the memory 13, the method and place using the image combination data Dout after setting the combination information D13 as in the calibration mode It goes without saying that the purpose of the period can be achieved.

Reference Signs List 1 image reading device 11 imaging unit 12 A / D conversion unit 13 memory 14 composite information generation unit 2 calibration device 21 point train interval measurement unit 22 overlap amount estimation unit 23 calculation unit

Claims (3)

A line sensor that arranges in the main scanning direction a sensor chip in which a plurality of imaging elements are provided in the main scanning direction, and picks up an object to be read facing the sensor chip;
A calibration method of an image reading apparatus, comprising: an image combining unit that generates combined image data by performing enlargement or reduction on a captured image for each of the sensor chips based on combining information and adjusting and combining the combining position. There,
A calibration document having a calibration pattern in which a predetermined reference position is set as the composite information, and a point sequence arranged in a zigzag form and a straight line along the main scanning direction are described as the reading object Acquiring the composite image data by setting a plurality of distances for the document distance from the calibration document to the line sensor;
From the relationship between the captured image of each of the sensor chips obtained for each of the document distances and the document distance, the sub-scanning direction shift amount for each of the sensor chips , the offset amount of the overlap amount for each of the sensor chips , and Calculate the height offset amount in the reading object direction for each sensor chip,
Setting the sub-scanning direction shift amount of the resulting the sensor chip, and a pre-Symbol offset amount of the amount of overlap between every sensor chip and the height offset of the object to be read direction for each of the sensor chip as the combined information And a calibration method of the image reading apparatus. Setting a distance for the document distance between the calibration document and the line sensor;
Calculating a sub-scanning direction shift amount for each of the sensor chips based on the shift amount of a straight line in the composite image data from the composite image data obtained at the document distance;
Approximating the relationship between the distance between the point sequence of each sensor chip and the document distance from the image data of the sensor chip obtained at each of the document distances by a first linear expression;
Calculating a relation between the document distance and the magnification of the image data in the sensor chip from the first linear expression and the interval of the point sequence of the calibration document;
Approximating the relationship between the overlap amount in the main scanning direction and the document distance for each of the sensor chips with a second linear expression;
Calculating an overlap amount that should originally exist for each of the sensor chips from the document distance and the second linear expression;
Calculating an offset amount of the overlap amount between the sensor chips from the overlap amount in the main scanning direction and the overlap amount to be originally present;
2. The calibration of the image reading apparatus according to claim 1, further comprising the step of: calculating a height offset amount in the reading object direction for each of the sensor chips from the document distance and the first linear expression. Method. A line sensor that arranges in the main scanning direction a sensor chip in which a plurality of imaging elements are provided in the main scanning direction, and picks up an object to be read facing the sensor chip;
An image combining unit configured to generate combined image data by performing enlargement or reduction on a captured image of each of the sensor chips based on combining information, adjusting a combining position, and combining;
In the calibration mode, a calibration having a calibration pattern in which a predetermined reference position is set as the composite information, and a row of dots arranged in a staggered manner and a straight line along the main scanning direction are depicted A setting unit configured to set a plurality of distances for the document distance from the calibration document to the line sensor, using the document as the reading object;
From the relationship between the captured image of each of the sensor chips obtained for each of the document distances and the document distance, the sub-scanning direction shift amount for each of the sensor chips , the offset amount of the overlap amount for each of the sensor chips , and A calculation unit for calculating the height offset amount in the direction of the object to be read of each sensor chip;
The setting unit has a sub-scan direction displacement amount of the resulting sensor chip, and a pre-Symbol offset amount of the amount of overlap between every sensor chip and the height offset of the object to be read direction for each of the sensor chips An image reading apparatus set as the composite information.

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