JPH0865506A - Picture reader - Google Patents

Abstract

PURPOSE: To obtain picture information with uniform black level and high quality by preparing highly accurate dark shading correction data. CONSTITUTION: A dark shading correction data calculating part 27 calculates the averaged data of plural dark output data fetched from a fixed line sensor 13 and then calculates the deviation of the averaged data from the dark output data outputted from the sensor 13. If the deviation is not included within a prescribed range, the averaged data are updated by repeatedly executing averaging processing. When the deviation is included within the prescribed range, the averaged data are stored in a dark shading correction data storing part 28 as dark shading correction data Di. A shading correction part 31 executes shading correction for the picture data based upon white shading correction data Ki stored in a white shading correction data storing part 30 and the data Di.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading device, and more particularly to an image reading device capable of improving the quality of read image information.

[0002]

2. Description of the Related Art Conventionally, an image reading device for optically reading a document placed on a platen glass has been used in, for example, a copying machine or a facsimile machine. FIG. 4 is a perspective view showing the mechanical structure of a conventional image reading apparatus. In the figure, reference numeral 1 denotes a document, which is placed on a platen glass 2 and fixed by a platen cover 3. The full rate carriage 4 is composed of a halogen lamp 5, a reflection plate 6, a light shielding member 7, and a mirror 8 and is a sub-scanning direction orthogonal to a main scanning direction which is a line direction of a solid-state line sensor 13 which will be described later. In the direction of arrow A, the original 1 is read while mechanically sub-scanning.

Reference numeral 9 denotes a half rate carriage composed of a pair of mirrors 10 and 10. The half rate carriage 9 moves in the direction of arrow A at the same time as the movement of the full rate carriage 4 at a speed half that of the full rate carriage 4. It is like this. The mirrors 8 and 10 emit the reflected light of the document 1 illuminated by the halogen lamp 5 to the imaging lens 11. The imaging lens 11 focuses the reflected light of the document 1 illuminated by the halogen lamp 5 and outputs it to the infrared cut filter 12. The infrared cut filter 12 removes the infrared component of the reflected light, and the solid line sensor 1 described above is used.
3 up supply. The solid-state line sensor 13 converts the imaged optical information into an electric signal and outputs the electric signal to the output signal processing unit 20.

FIG. 5 is a block diagram showing the configuration of the output signal processing section 20 of the conventional image reading apparatus. In the figure, the output signal of the solid line sensor 13 is amplified by an amplifier circuit 21 and then supplied to a sample hold circuit 22. The sample hold circuit 22 removes reset noise of the image signal and supplies it to the A / D converter 23. A
The / D converter 23 converts the image signal into a digital signal and supplies the digital signal to the white shading correction data calculation unit 24 and the white shading correction circuit 26.

The white shading correction data calculation unit 24 is provided with a white reference plate 1 shown in FIG.
Data for white shading correction is created from the signal obtained by reading 4. The white shading correction processing aims to obtain uniform and high-quality image data by removing the influence of uneven sensitivity in the main scanning direction of the solid-state line sensor 13 and uneven light amount in the main scanning direction of the halogen lamp 5. The white shading correction data calculation unit 24, assuming that the input signal of each pixel to the white reference plate 14 shown in FIG. 4 is Wi and the output target value after white shading correction for the white reference plate 14 is W, Ki
The white shading correction data Ki is calculated by the calculation of = W / Wi. The white shading correction data Ki is stored in the white shading correction data storage unit 25.

Also, the white shading correction circuit 2
Reference numeral 6 performs shading correction on the image data when the actual document is read using the white shading correction data Ki stored in the white shading correction data storage unit 25. That is, in the white shading correction circuit 26, the input signal is Ii, the output signal is Oi, and the white shading correction data storage unit 2
Assuming white shading correction data Ki from 5, the calculation of Oi = Ki × Ii is performed.

Next, the operation of the above-mentioned conventional image reading apparatus will be described. First, the original 1 placed on the platen glass 2 is fixed on the platen glass 2 by the platen cover 3. Next, as a pre-stage of reading the original,
The full rate carriage 4 is moved to directly below the white reference plate 14 shown in FIG. 4, and the halogen lamp 5 is turned on. The reflected light of the white reference plate 14 illuminated by the halogen lamp 5 is
After being focused by the imaging lens 11 via the mirrors 8 and 10, an image is formed on the solid line sensor 13 through the infrared cut filter 12. The imaged optical information is converted into an electric signal by the solid-state line sensor 13 and supplied to the output signal processing unit 20.

The output signal of the solid line sensor 13 with respect to the white reference plate 14 described above is amplified by the amplifier circuit 21, and then reset noise is removed by the sample hold circuit 22. Further, after being supplied to the A / D converter 23 and converted into a digital signal, it is supplied to the white shading correction data calculation unit 24. The white shading correction data calculation unit 24 calculates the white shading correction data Ki by the above-described calculation and stores it in the white shading correction data storage unit 25.

Next, the full-rate carriage 4 mechanically subscans the original 1 in the direction of arrow A shown in FIG. 4, which is a subscanning direction orthogonal to the main scanning direction which is the line direction of the solid line sensor 13. read. At this time, the half rate carriage 9 simultaneously moves in the direction of arrow A at a speed half that of the full rate carriage 4. The reflected light of the document 1 illuminated by the halogen lamp 5 is reflected by the mirrors 8, 1
It is focused by the imaging lens 11 via 0, and is focused on the solid line sensor 13 through the infrared cut filter 12. The solid-state line sensor 13 converts the imaged optical information into an electric signal and supplies the electric signal to the output signal processing unit 20.

The output signal of the above-mentioned solid-state line sensor 13 is amplified by the amplifier circuit 21, the reset noise is removed by the sample hold circuit 22, and it is supplied to the A / D converter 23 to be converted into a digital signal. . The image data converted into the digital signal is subjected to shading correction in the white shading correction circuit 26 by the white shading correction data Ki stored in the white shading correction data storage unit 25 in accordance with the above-described calculation. As a result, the white shading correction circuit 44 outputs an output signal Oi (= Ki × Ii) having a uniform white level.

[0011]

In the conventional image reading apparatus described above, the white level of the read image data is made uniform by the white shading correction, but the white level of the read image data is made uniform by the dark shading correction. Since the uniformization is not performed, there is a problem that the high-density portion of the original cannot be read with high accuracy and high-quality image information cannot be obtained.

Also in an image reading apparatus that performs dark shading correction, the accuracy of the dark shading correction data is insufficient, and the dark shading correction causes the quality of the read image information to deteriorate. This is due to the variation in the sensor output signal during dark reading, and in general, the variation in the sensor output signal during dark reading is
It can be divided into two factors. (1) Variation in sensor output level for each pixel during dark reading (2) Random noise component included in output level of each pixel

In dark shading correction, it is possible to correct the former (1) variation in the output level for each pixel. However, since the dark shading correction data used for the correction also includes the latter random noise component (2), this random noise component affects the dark shading correction.
On the contrary, there is a problem that the quality of the read image information is deteriorated.

The present invention has been made in view of the above-mentioned circumstances, and provides an image reading apparatus capable of uniforming the black level of image data by dark shading correction and obtaining high-quality image information. It is an object.

[0015]

In order to solve the above-mentioned problems, according to the invention of claim 1, in an image reading apparatus for shading-correcting image information of a document based on output data of an image sensor When the instruction signal is supplied, the averaged data is calculated by averaging a plurality of dark output data of the image sensor, and when the output instruction signal is supplied, the averaged data is dark-shaded corrected. Correction data calculating means for outputting as data, accuracy calculating means for calculating a deviation of the averaged data with respect to dark output data of the image sensor, and if the deviation is outside a predetermined range,
Correction data that supplies the output instruction signal to the correction data calculation unit while the acquisition instruction signal is supplied to the correction data calculation unit to repeatedly execute the averaging process, and if the deviation is within a predetermined range And a creation control means.

[0016]

According to the present invention, first, the correction data calculating means calculates the averaged data by averaging a plurality of dark output data of the image sensor. Then
The accuracy calculating means calculates the deviation of the averaged data from the dark output data of the image sensor, that is, the variation. When the deviation is not within the predetermined range, the correction data creation control means supplies the acquisition instruction signal to the correction data calculation means, causes the averaging process to be performed again, and calculates new averaged data. . Next, for this new averaged data, similarly, it is determined whether the deviation is within a predetermined range, and the averaging process is repeated until it falls within the predetermined range. Then, when the deviation falls within a predetermined range, the correction data creation control means outputs the averaged data as dark shading correction data. As a result, highly accurate dark shading correction data can be created, and the dark shading correction data is used to perform dark shading correction on the read image information of the document, so that it is possible to obtain high-quality image information. .

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. A. Configuration of Example A-1. Configuration of Image Reading Device FIG. 1 is a perspective view showing a mechanical configuration of the image reading device according to the present invention. It is to be noted that FIG.
The same reference numerals are given to the portions corresponding to, and the description will be omitted. In the figure, reference numeral 40 denotes an output signal processing unit in the image reading apparatus of this embodiment, which is different from the image reading apparatus shown in FIG. In the following description, the output signal processing section 40 will be described.

A-2. Configuration of Output Signal Processing Unit FIG. 2 is a block diagram showing the configuration of the output signal processing unit in the image reading apparatus of this embodiment. Note that the portions corresponding to those in FIG. In the figure, reference numeral 27 denotes a dark shading correction data creation unit, which is an output that the solid line sensor 13 outputs when the halogen lamp 5 is turned off subsequent to the creation of the white sharding correction data before the reading of the document. Dark shading correction data Di is created based on the signal and stored in the dark shading correction data storage unit 28. The dark shading correction data storage unit 28 stores the dark shading correction data D
i is supplied to the white shading correction data calculation unit 29 and the shading correction circuit 31.

The white shading correction data calculation unit 29 is created by the dark shading correction data creation unit 27 and the signal obtained by reading the white reference plate 14 shown in FIG. 1 before the reading of the document. The white shading correction data Ki is created based on the dark shading correction data Di stored in the dark shading correction data storage unit 28. That is, the white shading correction data calculation unit 29
For the pixel i, the input signal of each pixel to the white reference plate 14 is Wi, the output target value after shading correction for the white reference plate W is W, the dark shading correction data is Di, and the dark output target value after shading correction is If D, the white shading correction data Ki is calculated by the calculation Ki = (WD) / (Wi-Di) and stored in the white shading correction data storage unit 30.

Further, the shading correction circuit 31 corrects the image data output by the A / D converter 23 based on the white shading correction data Ki and the dark shading correction data Di when reading the original. That is, the shading correction circuit 3
1, the input signal is Ii, the output signal is Oi, the correction coefficient from the white shading correction data storage unit 30 is Ki,
If correction data Di is obtained from the dark shading correction data storage unit 28, the calculation of Oi = Ki * (Ii-Di) + D is performed.

A-3. Configuration of Dark Shading 27 Next, the dark shading correction data creation unit 27 described above will be described. FIG. 3 is a block diagram showing the detailed arrangement of the dark shading correction data creation unit of this embodiment. In the figure, reference numeral 271 denotes a dark shading correction data calculation unit that receives the output signal of the A / D converter 23, for example, 16 times in total, calculates the average value of the dark output signal for each pixel, and outputs the dark shading correction data Di. As a result, the calculation result is output to the accuracy calculation unit 272. This averaging process is for removing peculiar random noise for each pixel. Further, when the dark shading correction data calculation unit 271 receives the capture instruction signal S1 from the dark shading correction data creation control unit 273 described later, the dark shading correction data calculation unit 271 captures the dark output signal again and calculates the average value, while the dark shading When the output instruction signal S2 is supplied from the correction data creation control unit 273, the average value is output to the accuracy calculation unit 272 as dark shading correction data Di.

Next, the accuracy calculation section 272 uses the dark output signal (16th output signal) supplied from the A / D converter 23 to perform dark shading correction supplied from the dark shading correction data calculation section 271. Calculate the accuracy of the data. That is, the data of the i-th pixel of the dark output signal supplied from the A / D converter 23 is Ri, i
If the dark shading correction data Di of the pixel is used, the accuracy evaluation value H is calculated by the calculation of H = σ (Ri−Di) / σRi. Here, σRi represents the variation of the dark output signal in one line, and σ (Ri-Di)
Shows the variation in one line of the value obtained by subtracting the dark shading correction data Di from the dark output signal Ri for each pixel. Therefore, according to the accuracy evaluation value H,
It is possible to know how much the dark shading correction data Di calculated by the dark shading correction data calculation unit 271 matches the actual dark output signal. Accuracy evaluation value H output from the accuracy calculation unit 272
Is a dark shading correction data creation control unit 273.
Is supplied to.

Next, the dark shading correction data creation control unit 273 evaluates the accuracy evaluation value H based on the evaluation standard L set in advance. At this time, when the accuracy evaluation value H does not reach the evaluation standard L (allowable variation), that is, when L ≦ H, the acquisition instruction signal S1 described above is output to the dark shading correction data calculation unit 27.
The dark shading correction data calculation unit 271 supplies the dark output signal again to newly calculate the dark shading correction data. Then, the dark shading correction data creation control unit 273 performs the same processing as described above on the newly calculated dark shading correction data as well.
The accuracy evaluation value H is calculated and evaluated. This process is repeatedly performed until it is determined that the accuracy evaluation value H has reached the evaluation standard L, that is, L> H. At this time, an upper limit value of the number of times of repeating the above process may be provided in the evaluation criteria.

On the other hand, when the accuracy evaluation value H reaches the evaluation standard L, that is, when L> H, the dark shading correction data is supplied by supplying the above-described output instruction signal S2 to the dark shading correction data calculation unit 271. The dark shading correction data is stored in the storage unit 28 and the dark shading correction data creation is terminated. The rate of change of the accuracy evaluation value H, which is repeatedly calculated, may be added to the evaluation standard.

B. Operation of Embodiment Next, the operation of this embodiment will be described. First, the full rate carriage 4 is moved to the reading position of the white reference plate 14,
The white reference plate 14 is illuminated by the halogen lamp 5. The reflected light of the white reference plate 14 is focused by the imaging lens 11 via the mirrors 8 and 10, and the infrared cut filter 1
An image is formed on the solid line sensor 13 through 2. The imaged light information is converted into an electric signal by the solid-state line sensor 13 and supplied to the output signal processing unit 40. The output signal of the solid line sensor 13 with respect to the white reference plate is
After being amplified by the amplifier circuit 21, the reset noise is removed by the sample hold circuit 22. And A /
After being supplied to the D converter 23 and converted into a digital signal, it is supplied to the white shading correction data calculation unit 29.

Next, the halogen lamp 5 is turned off, and the output signal of the solid line sensor 13 is supplied to the output signal processing section 20 as a dark output signal. In the output signal processing unit 20,
After the dark output signal is amplified by the amplifier circuit 21,
The reset noise is removed by the sample hold circuit 22. Further, after being supplied to the A / D converter 23 and converted into a digital signal, it is supplied to the dark shading correction data creation unit 27.

Dark shading correction data creation unit 2
In 7, the dark output signal is supplied to the dark shading correction data calculation unit 271. The dark shading correction data calculation unit 271 calculates an average value of 16 output signals (dark signals) of the A / D converter 23, and supplies the average value to the accuracy calculation unit 272 as dark shading correction data Di. At the same time, the 16th output signal of the A / D converter 23 is supplied to the accuracy calculation unit 272. The accuracy calculation unit 272 uses the dark output signal output from the A / D converter 23 to calculate the accuracy of the dark shading correction data supplied from the dark shading correction data calculation unit 271 by the above-described calculation. That is, the accuracy evaluation value H is H = σ (Ri-Di) /
It is calculated by the calculation σR i.

Next, the accuracy evaluation value H is supplied to the dark shading correction data creation control section 273 and compared with a preset evaluation standard L. Here, when the accuracy evaluation value H does not reach the evaluation reference L, the dark shading correction data calculation unit 217 receives the acquisition instruction signal S1.
To supply the dark output signal again. In this case, the dark shading correction data calculation unit 217 receives the output signal of the A / D converter 23 a total of 16 times again, and the dark shading correction data of the previous time which has been temporarily stored is combined with 32 pixels of each pixel. The average value of the batch dark output signals is calculated again. The calculation result is supplied to the accuracy calculation unit 272 as new dark shading correction data Di. In the accuracy calculation unit 272, for the new dark shading correction data,
As described above, the accuracy evaluation value H is calculated again. The accuracy evaluation value H is evaluated by the dark shading correction data creation control unit 273, and the above-described processing is repeated until the evaluation criterion L is reached. On the other hand, when the accuracy evaluation value H reaches the evaluation reference L, that is, when the variation becomes sufficiently small and L> H, the dark shading correction data calculation unit 271 is supplied with the output instruction signal S2 and dark Shading correction data D
i is stored in the dark shading correction data storage unit 28.

In the white shading correction data calculation unit 25, the signal obtained by reading the white reference plate 14 described above and the dark shading correction data D are obtained.
Based on i and, for pixel i, Ki = (WD) /
The calculation of (Wi-Di) is performed, the white shading correction data Ki is calculated, and stored in the white shading correction data storage unit 26.

By the above processing, the dark shading correction data Di and the white shading correction data Ki are obtained. Next, the full rate carriage 4
The original 1 is read while mechanically sub-scanning in the direction of arrow A shown in FIG. 1, which is a sub-scanning direction orthogonal to the main scanning direction that is the line direction of the solid-state line sensor 13. At this time, the half rate carriage 9 simultaneously moves in the direction of arrow A at a speed half that of the full rate carriage 4. The reflected light of the document 1 illuminated by the halogen lamp 5 is focused by the imaging lens 11 via the mirrors 8 and 10, and is focused on the solid line sensor 13 through the infrared cut filter 12. The image-formed optical information is the solid line sensor 13
Is converted into an electric signal by and supplied to the output signal processing unit 40.

The output signal of the solid-state line sensor 13 is amplified by the amplifier circuit 21, the reset noise is removed by the sample hold circuit 22, and the signal is supplied to the A / D converter 23 and converted into a digital signal. It is supplied to the shading correction circuit 31. The shading correction circuit 31 performs A / D conversion based on the white shading correction data Ki stored in the white shading correction data storage unit 30 and the dark shading correction data Di stored in the dark shading correction data storage unit 28. The image data output by the device 23 is corrected. That is, in the shading correction circuit 31, the output signal Oi is calculated and output by the calculation of Oi = Ki * (Ii-Di) + D.

As described above, in the present embodiment, the dark shading correction data creation unit 271 repeatedly takes in the dark output signal and calculates the average value thereof for each pixel to obtain the dark shading correction data Di.
In addition to reducing the random noise component included in the dark shading correction data Di, the accuracy of the calculated dark shading correction data Di is confirmed, and if the accuracy is insufficient, the dark output signal is further captured to finally obtain a highly accurate dark Shading correction data Di is created. Therefore, in the image reading apparatus according to the present embodiment, since dark shading correction can be performed using the highly accurate dark shading correction data, uniform and high-quality image reading can be performed even on the high density portion of the document. You can

[0033]

As described above, according to the present invention, it is possible to reduce the variation in the output level of the sensor for each pixel at the time of dark reading, and to reduce the random noise component contained in the output level of each pixel. Therefore, it is possible to create highly accurate dark shading correction data, and by performing dark shading correction using this dark shading correction data, it is possible to obtain the image information with a uniform black level and high quality.

[Brief description of drawings]

FIG. 1 is a perspective view showing a structure of an image reading apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of an image reading apparatus in this embodiment.

FIG. 3 is a block diagram showing a configuration of an output signal processing unit in the image reading apparatus of the present invention.

FIG. 4 is a perspective view showing a structure of a conventional image reading device.

FIG. 5 is a block diagram showing a configuration of an output signal processing unit in a conventional image reading device.

[Explanation of symbols]

1 Original 2 Platen Glass 3 Platen Cover 4 Full Rate Carriage 5 Halogen Lamp 6 Reflector 7 Light-shielding Member 8 Mirror 9 Half Rate Carriage 10 Mirror 11 Imaging Lens 12 Infrared Cut Filter 13 Solid Line Sensor (Image Sensor) 14 White Reference Plate 21 Amplifier circuit 22 Sample-and-hold circuit 23 A / D conversion circuit 27 Dark shading correction data creation unit 28 Dark shading correction data storage unit 29 White shading correction data calculation unit 30 White shading correction data storage unit 31 Shading correction unit 40 Output signal processing unit 271 Dark shading correction data calculation unit (correction data calculation unit) 272 Accuracy calculation unit (accuracy calculation unit) 273 Dark shading correction data creation control unit (correction data Data generation control means) S1 taking instruction signal S2 output instruction signal Di dark shading correction data H accuracy evaluation value (deviation) L predetermined range

Claims (1)

[Claims] 1. An image reading apparatus for shading-correcting image information of an original based on output data of an image sensor, when a capture instruction signal is supplied, averages a plurality of dark output data of the image sensor. Thus, while calculating the averaged data, when the output instruction signal is supplied, the correction data calculation means for outputting the averaged data as dark shading correction data, and the averaged data for the dark output data of the image sensor. If the deviation is outside a predetermined range, the correction data calculating means is supplied with the acquisition instruction signal to repeatedly execute the averaging process, while the deviation is within a predetermined range. If within range,
An image reading apparatus comprising: a correction data creation control unit that supplies the output instruction signal to the correction data calculation unit.