JP2854468B2 - Reading position correction device for image reading device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reading position correcting apparatus, and more particularly to a reading position correcting apparatus for an image reading apparatus which scans an original image by using a plurality of line sensors arranged in a main scanning direction.

[0002]

2. Description of the Related Art For example, an image reading apparatus such as a scanner includes a plurality of line sensors arranged in a main scanning direction in order to cope with an increase in the size of a document. An image (original image) of an original relatively moving in the scanning direction is read. In an image reading apparatus using a plurality of line sensors of this type, misalignment occurs due to inaccuracy of position adjustment of the plurality of line sensors, and also due to a mechanical operation after the position adjustment, a temperature change, or the like. It is necessary to correct the image data for this displacement.

Conventionally, in this type of image reading apparatus, a reference pattern parallel to the main scanning direction is provided in a part of a scanning start area of a document table, and the reference pattern is scanned prior to image scanning by a line sensor. The displacement of the line sensor in the sub-scanning direction is counted in units of the number of main scanning lines, and the image data is corrected based on the counted value (see Japanese Patent Application Laid-Open No. 56-8 / 1981).
0959).

However, usually, the displacement amount of the line sensor does not become the displacement amount of the interval of the main scanning line.
If the shift amount is corrected in the unit of the main scanning line as in the conventional configuration, the correction accuracy cannot be sufficiently improved. SUMMARY OF THE INVENTION It is an object of the present invention to improve the accuracy of correction for positional deviation between line sensors in the sub-scanning direction.

[0005]

A reading position correcting apparatus according to the present invention is a reading position correcting apparatus for an image reading apparatus in which an original image is scanned by a plurality of line sensors arranged in a main scanning direction. This device includes a shift amount calculating unit and a correcting unit. The shift amount calculating means calculates the read position shift amount of the plurality of line sensors in the sub-scanning direction in units of measurement intervals shorter than the main scanning line interval. The correction means
The image data obtained from the plurality of line sensors is corrected based on the calculated shift amount.

[0006]

In the reading position correcting apparatus according to the present invention, the shift amount calculating means calculates the reading position shift amount of the plurality of line sensors in the sub-scanning direction in a unit of measurement shorter than the main scanning line interval. Then, based on the calculated shift amount, the correction unit corrects the image data obtained from the plurality of line sensors.

Here, the shift amount is measured in a unit of measurement shorter than the main scanning line interval, and the image data is corrected based on the measured shift amount. Therefore, the image data is corrected more finely than the main scanning line interval. The correction accuracy for the displacement of the line sensor in the sub-scanning direction is improved.

[0008]

FIG. 1 shows an image reading apparatus (hereinafter referred to as a scanner) 1 employing an embodiment of the present invention. The scanner 1 includes a lower frame 2 and an upper frame 3 arranged on the lower frame 2. An original placing scan 4 is arranged on the upper surface of the lower frame 2. Upper frame 3
The digitizer 22 and the operation panel 14 are arranged on the upper surface of the. The operation panel 14 has an input key 15 and a display unit 16.

The document placing apparatus 4 has a document table 5 movable in the sub-scanning direction indicated by an arrow in FIG. 2, and a drive mechanism 13 including a motor 19 for driving the document table 5. Platen 5
Has a configuration in which a document 6 up to 19 × 25.4 inches can be placed, and the document 6 is sandwiched between a pair of upper and lower glass plates. A reference line 18 parallel to the main scanning direction (the depth direction in FIG. 2) is formed in the scanning start area on the lower glass plate of the document table 5 where the document 6 is not arranged. The reference line 18 is used to measure the displacement of the later-described CCD line sensors 10a to 10d in the sub-scanning direction. In the center of the lower frame 2,
A slit light source 7 for slit exposure of a transparent original is disposed below the original placing device 4.

The upper frame 3 includes a reflection light source 8 for slit exposure of a reflection original, an optical system 9, and four CCD line sensors 10a to 10d arranged in parallel in the main scanning direction.
And are arranged. The CCD line sensor 10a
To 10d are 7500 CCs corresponding to the respective pixels.
It is composed of D elements. As a result, 1 in the main scanning direction
A 9-inch original 6 can be read at a resolution of 1500 lines / inch using 30,000 pixels. The optical system 9 includes a reflection mirror 11 that bends the light from the document 6 in the horizontal direction by 90 °, and four lenses 12 for imaging the light from the document 6 on the CCD line sensors 10a to 10d. I have.

The outputs of the CCD line sensors 10a to 10d are supplied to CPU 20 via A / D converters 23a to 23d.
Is given to the data correction units 17a to 17d. CPU
Reference numeral 20 mainly includes a microcomputer 21 and a memory 21 such as a ROM and a RAM. CPU 20
Controls the scanner 1 and calculates the amount of deviation of the CCD line sensors 10a to 10d in the sub-scanning direction in units of 1/10 of the main scanning line interval (2.7 μm in this example).
The shift amount data is output to the data correction units 17a to 17d. Further, the CPU 20 gives a pulse signal to the motor 19 via the motor driver 24 so as to have a speed corresponding to the magnification. The number of pulses of this pulse signal is 10 pulses output between the main scanning lines. That is, this pulse signal becomes a reference of 1/10 unit of the main scanning line interval.

The data correction units 17a to 17d have the same configuration. FIG. 3 shows only the data correction unit 17d in detail, and the data correction units 17b to 17d are described below.
The detailed description of is omitted. As shown in FIG. 3, the data correction unit 17a has seven line memories 31 to 37 connected in series. Line memories 31 to 37
Is composed of a shift register having a capacity capable of storing image data for one CCD line sensor (data of 7,500 pixels in this example). Therefore, the line memories 31 to 37 can store image data delayed by 1 to 7 main scanning lines (that is, data before 1 to 7 main scanning lines). The outputs of the CCD line sensor and the outputs of the line memories 31 to 37 are supplied to two multiplexers 38 and 39.
Given to. The multiplexers 38 and 39 are of the 8-input / 1-output type. The outputs of the multiplexers 38 and 39 are provided to A input terminals of multipliers 40 and 41, respectively.

As described above, the CPU 20 calculates the shift amount of the line memories 31 to 37 in the sub-scanning direction by a measurement unit smaller than the main scanning line interval (for example, 1/10 of the line interval).
Unit). If the measured shift amount is, for example, 2.
Assuming that there are four lines, of the data of the shift amount,
The integer part data I (that is, “2”) is given to the integer register 43. Data I + 1 (ie, “3”) obtained by adding “1” to the data I is stored in the integer register 44.
Given to. Data D of the decimal part of the deviation amount data
(Ie, “0.4”) is provided to the decimal register 46. Data 1 minus the decimal data D from "1"
D (ie, “0.6”) is provided to the decimal register 45.

Data I stored in integer register 43 is applied to multiplexer 38. Multiplexer 38
Then, the input terminal is selected based on the data I. For example, when the integer data I is “2”, the terminal to which the data of the line memory 32 is input is selected. Data I + 1 stored in integer register 44 is applied to multiplexer 39. The multiplexer 39 selects an input terminal based on the data. When the integer data I is "2", the terminal to which the data of the line memory 33 is input is selected. That is, the output from the line memory delayed by one main scanning line from the line selected by the multiplexer 38 is selected. The data 1-D stored in the decimal register 45 is
B input terminal. The decimal data D stored in the decimal register 46 is supplied to the B input terminal of the multiplier 41.

The multiplier 40 multiplies the image data from the multiplexer 38 by the decimal data 1-D, and provides the multiplication result to the C input terminal of the adder 42. The multiplier 41 multiplies the image data from the multiplexer 39 by the decimal data D, and supplies the multiplication result to an E input terminal of the adder 42. In the adder 42, the input values are added (C + E) and output to an image processing unit (not shown).

Here, when the shift amount is detected in units of 1/10 of the main scanning line, the data of the line memory shifted by the integer data and the data of the line memory further shifted by one line are compared with the data. Are weighted with decimal data and added and output. That is, when there is a 2.4 line shift, it is considered that there is a shift of 0.6 for two lines and a shift of 0.4 for three lines, and the interpolation processing as described above is performed to correct the image data. Add.

Next, the operation of the above embodiment will be described mainly in accordance with the control operation of the CPU 20. CPU 20
4 and 5 showing the control operation of step S1.
Then, an initial setting is performed. Here, processing such as setting the document table 5 at the initial position and setting such as setting the initial value of the shift amount to 0 are performed. In step S2, it is determined whether or not a shift detection command has been issued by operating the input key 15 of the operation panel 14. This command is usually issued when the apparatus is carried in and every predetermined period. This makes it possible to detect the amount of deviation of the CCD line sensor in the sub-scanning direction and the amount of deviation due to aging until the time of carrying in. In step S3, it is determined whether or not a condition setting command such as setting of a setup condition has been issued. In step S4, it is determined whether a scan start command has been issued. If the determination in step S4 is NO, the process proceeds to step S5, performs other general processing, and returns to step S2.

If it is determined in step S2 that a shift detection command has been issued, the process proceeds to step S6. In step S6, a shift detection subroutine shown in FIG. 5 is executed. Here, first, in step S10, the motor 19 is driven to move the document table 5 in the sub-scanning direction. In step S11, a variable i for counting the number of times of detecting the shift amount is set to "1". In step S12, the process waits for one of the CCD line sensors 10a to 10d to detect the reference line 18. Until the reference line 18 is detected, the process proceeds to step S16. In step S16, the variable i is CCD
It is determined whether or not the number of line sensors exceeds "4", and the process returns to step S12 until the number exceeds "4".

If it is determined in step S12 that any of the CCD line sensors 10a to 10d has detected the reference line 18, the process proceeds to step S13. In step S13, it is determined which CCD line sensor is detected. In step S14, reads the number of pulses PL _i of the pulse signal given to the motor 19 at that time the memory 21
To be stored. In step S15, the variable i is incremented.

In step S16, it is determined whether or not the variable i has exceeded "4". If YES, the process proceeds to step S17 and the motor 19 is stopped. Here, four CCs
This means that the shift amount of the D line sensors 10a to 10d in the sub-scanning direction can be detected in units of the number of pulses (1/10 unit of the main scanning line interval). At step S18, the read pulse number PL _i, and calculates the shift amount P _x of each of the CCD line sensor. For example, as shown in FIG.
If it is assumed that the D line sensors 10a to 10d are displaced, C at the time when the reference line 18 is detected in step S14
Pulses PL ₁ of CD line sensor 10a is 10 pulses, the pulse number PL ₂ of the CCD line sensor 10c is 15 pulses, number of pulses PL ₃ of the CCD line sensor 10b is 20 pulses, the CCD line sensor 10
Assuming that the pulse number PL _{4 of} d is 34 pulses, in step S 18, the shift amount P ₁ = 0 and the shift amount P ₂ = PL ₂
−PL ₁ = 5, shift amount P ₃ = PL ₃ −PL ₁ = 10, and shift amount P ₄ = PL ₄ −PL ₁ = 24.

In step S18, the shift amount P _x (x: 1 to 1)
When 4) is calculated, the process moves to step S19. In step S19, an integer from the calculated shift amount P _x data I
_x and fractional data D _X obtained by the following equation. (P _x × M) / L = I _x + D _x where M is the reading magnification, and L is the number of pulses output at one main scanning line interval at the original size (reading magnification of 100%).

Assuming that 10 pulses are output per one main scanning line interval (L = 10), I ₂ = 0 at the shift amount P _2.
And D ₂ = 0.5, the deviation amount P ₃ in I ₃ = 1 and D ₃ =
In the case of 0 and the shift amount P ₄ , I ₄ = 2 and D ₄ = 0.4.
In step S20, the calculated integer data I _x and decimal data D _x are stored in the memory 21 and the process returns to the main routine.

If it is determined in step S3 of FIG. 4 that a condition setting command has been issued, the process proceeds to step S7. Step S
In step 7, the input conditions are set in the memory 21. If it is determined in step S4 that a scan start command has been issued, the process proceeds to step S8. In step S8, the integer data I _x and the decimal data D _x are output to the data correction units 17a to 17d. In step S9, scanning control such as moving the document table 5 in the sub-scanning direction or turning on one of the light sources 7 and 8 is performed, and the process proceeds to step S5.

On the other hand, in step S8, the data correction units 17a, 17 to which the integer data I _x and the decimal data D _x have been input.
In d, each data is stored in the integer register 43 and the decimal register 46. Also, 1 from the integer data I _x
The large integer data I _x +1 is stored in the integer register 44, and the data 1-D _x is stored in the decimal register 45. When the CCD line sensors 10a to 10d receive image data from the original 6, interpolation processing is performed in real time during scanning by the following interpolation formula.

M _{(x, n)} = M _{(x, n, m)} × (1−D _x ) + M _{(x, n, m + 1)} × D _x where x is a value from 1 to 4. , And the numbers of the determination order of the CCD line sensors. n is the number of each pixel of the CCD line sensor, and m is the number of the line memories 31 to 37. M _{(x, n)} is the corrected interpolation data, M _{(x, n, m)} is the image data delayed by I _x lines stored in the line memory, and M _{(x, n) , m + 1 )} is image data delayed by one line. That is, the data output by switching the multiplexers 38 and 39 by the integer data I _x stored in the integer register 43 and the integer data I _x +1 stored in the integer register 44 are the two image data described above. . Then, the two image data and the decimal data stored in the decimal registers 45 and 46 are respectively multiplied by the multipliers 40 and
Multiplied by 41. The result of the multiplication is added by the adder 42, and the calculation of the above-mentioned interpolation formula is performed.

In this case, since the amount of displacement is measured in units of measurement intervals smaller than the interval of the main scanning line, and the interpolation processing is performed on the image data accordingly, more accurate correction can be performed. In particular, when reading is performed at a high magnification, the amount of deviation between the CCD line sensors increases in accordance with the magnification. By performing such interpolation processing, the effect of the amount of deviation can be further suppressed and the image quality of a reproduced image can be improved. .

[Other Embodiments] (a) Instead of calculating the interpolation calculation by hardware, D
The calculation may be performed by software using an SP (Digital Signal Processor). (B) In the above-described embodiment, the shift amount of the line sensor is detected by detecting the reference line. However, the shift amount of the line sensor may be detected by other means such as directly detecting by an optical means.

[0028]

In the reading position correcting apparatus according to the present invention, the shift amount calculating means calculates the shift amount in units of measurement intervals shorter than the main scanning line interval, and corrects the image data based on the calculated shift amount. Therefore, it is possible to improve the correction accuracy for the displacement of the plurality of line sensors in the sub-scanning direction.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of a scanner employing one embodiment of the present invention.

FIG. 2 is a schematic sectional view thereof.

FIG. 3 is a block diagram of a data correction unit.

FIG. 4 is a flowchart of a CPU.

FIG. 5 is a flowchart of a CPU.

FIG. 6 is a schematic diagram showing a shift of a CCD line sensor in a sub-scanning direction.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Scanner 4 Document mounting device 5 Document table 6 Document 10a-10d CCD line sensor 17a-17b Data correction part. 20 CPU 21 Memory 40, 41 Multiplier 42 Adder

Claims (1)

(57) [Claims] 1. A reading position correcting device for an image reading device for scanning an original image by using a plurality of line sensors arranged in a main scanning direction, wherein a main scanning is performed by determining a reading position deviation amount of the plurality of line sensors in a sub-scanning direction. A reading position correction of an image reading apparatus, comprising: a shift amount calculating unit that calculates a measurement interval unit shorter than a line interval; and a correcting unit that corrects image data obtained from the plurality of line sensors based on the shift amount. apparatus.