JPS639269A - Reader - Google Patents

Abstract

PURPOSE:To obtain a picture signal with a constant density by dividing an electric signal corresponding to an object to be read converted by a conversion means by a white reference signal corresponding to the line from a white reference board so as to correct the variation of the reflectance of the white reference board. CONSTITUTION:The image of an original 0 is formed on a line image sensor 7, converted into an electric signal, converted into a digital signal by an A/D conversion circuit 9 via an amplifier 8 and outputted to a correction means 10. On the other hand, a white reference board 45 required for the shading correction is provided at the rear face of a stopper 44 being the set reference of the original 0. A shading correction circuit 10 generates a white reference signal being the mean value of white reference data supplied in response to the read of the white reference board 45. The digital signal from the original 0 is divided by the white reference signal to correct the variation of sensitivity of the sensor 7 for the picture signal and the variation of luminous quantity in the main scanning direction. Then a correction coefficient in response to the voltage of the white reference aignal is multiplied to correct the level of the picture signal and the result is outputted to a binarization circuit 60.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field).

The present invention relates to a reading device applied to, for example, an image information storage device.

(Prior art) Conventionally, a reading device in an image information file device performs shading correction on the read image signal and then
It has become a value. In this case, the reflected light for one line read from the white reference board is stored in advance as white reference data, and the image signal read from the original (object to be read) is divided by the white reference data. It is designed to correct unevenness in light amount in the main scanning direction and unevenness in sensitivity of photoelectric converters and the like.

However, since the reflectance of the white reference plate differs slightly depending on the device, when shading correction is performed using white reference data according to the reflected light, there will be density differences in the image signals obtained by each device. There were drawbacks.

In addition, if the white reference plate is dirty due to changes over time, the dirt will cause differences in the light reflected from the white reference plate, so the white reference data obtained will vary depending on the position of the white reference plate. comes out.

In other words, when the image signal is divided by the white reference data corresponding to the reflected light read from a dirty position on the white reference plate, an error occurs in the shading correction, and the signal level after the shading correction becomes high. .

(Problems to be Solved by the Invention) This invention solves the problem that when shading correction is performed using white reference data corresponding to reflected light, a degree difference occurs in image signals obtained by each device, and shading correction This eliminates the disadvantage that the subsequent signal level becomes high, and it corrects for variations in the reflectance of the white reference plate that occur depending on the device or due to changes over time, making it possible to obtain an image signal of a constant degree. The purpose is to provide a reading device.

[Structure of the Invention] (Means for Solving the Problems) The reading device of the present invention includes a converting means for converting a read signal read from an object to be read into an electric signal, and is provided near a manuscript table. A white reference plate, a generating means for generating a white reference signal corresponding to light from the white reference plate, and correcting an electric signal corresponding to the object to be read according to a voltage value of the white reference signal generated by the generating means. a storage means for storing correction coefficients; a reading means for reading out the correction coefficients from the storage means; and a reading means for dividing the electric signal converted by the conversion means by the white reference signal generated by the generation means; a correction means for correcting the electric signal corresponding to the object to be read by multiplying it by a correction coefficient read out by a correction coefficient; and a binary value for binarizing the signal corrected by the correction means by comparing it at a slice level. It consists of means for converting.

(Function) The present invention eliminates sensitivity unevenness of the conversion means in the electric signal by dividing the electric signal corresponding to the object to be read converted by the conversion means by the white reference signal corresponding to the light from the white reference plate. The signal level is corrected by multiplication in the main scanning direction, and the corrected signal is binarized.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 schematically shows a reading device of the present invention. That is, a document table (transparent glass) 1 is fixed to the upper surface of the main body (not shown), which supports a document ○ as an object to be read. The original O placed on this original table 1 is processed by an optical system consisting of an exposure lamp 2 and mirrors 3, 4, and 5 reciprocating along the lower surface of the original table 1 in the direction of arrow e.
Exposure scanning is performed during the reciprocation. In this case, mirror 4.5 moves at half the speed of mirror 3 so as to maintain the optical path length. The light reflected from the original O by the scanning of the optical system, that is, the light reflected from the original O by the light irradiation of the exposure lamp 2, is reflected by the mirror 3.4.5, passes through the lens 6, and passes through the line as a conversion means. The document 0 is guided to an image sensor (COD) 7, and an image of the document 0 is formed on the line image sensor 7.

This line image sensor 7 converts the formed image into a corresponding electrical signal and outputs it to an A/D conversion circuit 9 via an amplifier 8. This A/D conversion circuit 9 includes an amplifier 8
Converts the signal supplied from the line image sensor 61 to a digital signal via the line image sensor 61,
It is output to the shading correction circuit 10 (correction means).

On the other hand, a document stopper 44 is provided near the document table 1, which serves as a reference for setting the document O. On the back side of the document stopper 44, on the same plane as the document table 1, there is a white space necessary for shading correction. White reference plate 4 for reading reference data
5 is provided.

The shading correction circuit 10 generates a white reference signal as an average value from white reference data corresponding to 16 lines of reflected light supplied in response to reading of the white reference plate 45, for example, and generates a white reference signal as an average value of the white reference data. The line image sensor 7 in the image signal is divided by dividing the digital signal (image signal) supplied according to the reading of the original O by
After correcting the sensitivity unevenness and light amount unevenness in the main scanning direction, and correcting the level of the image signal by multiplying by a correction coefficient according to the voltage value of the white reference signal,
This is a circuit that outputs to the binarization circuit (binarization means) that performs the following (after).

This shading correction circuit 10 includes, for example, a delay circuit 41, a NAND circuit 42, an amplifier 4, as shown in FIG.
3. A line memory 50 that stores white reference data for 16 lines, an adder 53, a divider 55, and a delay circuit 5 as an output latch circuit for the line memory 50.
It is made up of two.

That is, the white reference data (digital signal @) supplied from the A/D conversion circuit 9 is sequentially supplied to the NAND circuit 42 and the adder 53 via the delay circuit 41. The NAND circuit 42 is supplied with a shading correction enable period signal and a CLK (clock) signal from a master timing circuit from a CPU, which will be described later. The output of the adder 53, that is, the white reference data of the first line is
By setting the output of the delay circuit 59 to "0" by a clear signal supplied from the CPU, the data is stored in the line memory 50 via the amplifier 43. By canceling the clear signal supplied to the delay circuit 59, the white reference data of the second line is added to the white reference data of the first line outputted from the line memory 50 in the adder 53.
3 and stored in the line memory 50. Thereafter, the white reference data from the 3rd line to the 16th line are sequentially accumulated and stored in the line memory 50.

Then, the white reference data for 16 lines is stored in the line memory 5.
After storing 0, document 0 is read. Upon reading the original O, the image signal (digital signal) supplied from the A/D conversion circuit 9 is sent to the divider 5 via the delay circuit 41.
5. At this time, the average value of the white reference data for 16 lines is stored in the divider 55 by deleting the white reference signal from the line memory 50 via the delay circuit 59, that is, the lower 4 bits of the output of the delay circuit 59. Supplied.

Thereby, the divider 55 divides the image signal by the white reference signal, thereby correcting the sensitivity unevenness of the line image sensor 7 and the light amount unevenness in the main scanning direction as shading correction. Note that the line memory 50, adder 53, delay circuit 59, etc. constitute a generating means.

Further, in the divider 55, when performing shading correction, the level of the corrected signal is corrected by multiplying it by a correction coefficient supplied from the CPU, which will be described later.

The output of the divider 55 is supplied to a binarization circuit 60.

This binarization circuit 60 uses a predetermined binarization threshold supplied from the CPU, which will be described later, to the shading correction circuit 1.
This circuit binarizes the signals supplied from the 0 divider 55 by comparing them. For example, rO as a black signal
A J signal is output, and a "1" signal is output as a white signal. The output of the binarization circuit 60 is supplied to the serial/parallel conversion circuit 16.

The signal converted into a parallel signal by this serial/parallel conversion circuit 16 is outputted to a control section (not shown) of an image file device (not shown) via an interface 18.

Further, the CPU 19 as a control section controls the entire system according to a line synchronization signal (LSYNC) from the master timing circuit 20. That is, driver 21
By controlling this, the pulse motor 22 that moves the optical system is driven, and by controlling the driver 23, the exposure lamp 2 is driven.

Further, during shading correction, the CPU 19 determines the voltage value of the white reference signal, reads out a correction coefficient corresponding to this voltage value from the ROM 46 (storage means), and supplies it to the divider 55 of the shading correction circuit 10. It is something. That is, as shown in FIG. 3, the ROM 46 has voltage values x1, x2,..., x4, for example.
Corresponding to the correction coefficients 0.94, 0.90. ..., 0
．． Table (a) in which 82 is stored, voltage value x1,
x2,...

Corresponding to ×4, the correction coefficient is 0.92.0.88°...
, 0.80 are stored in table (b). Note that the above tables (a>, (b)) are selected by the dip switch 47. For example, when table (a) is selected by the dip switch 47, the voltage value x 1 is determined. If so, the CPU 19 reads the correction coefficient 0.94 from the ROM 46 and outputs this correction coefficient 0.94 to the divider 55 of the shading correction circuit 10. Also, if the table (b) is selected by the DIP switch 47, In the state where the voltage value x 1 is determined, the CPU 19
reads the correction coefficient 0.92 from the ROM 46, and applies this correction coefficient 0.92 to the divider 5 of the shading correction circuit 10.
Output for 5.

Next, the operation in the above configuration will be explained. For example, now when the reading device is powered on, the CPU i
9 controls the driver 21 to drive the pulse motor 22 to move the optical system, and also controls the driver 23 to light the exposure lamp 2.

As a result, the light from the exposure lamp 2 is irradiated onto the white reference plate 45, and the reflected light from the white reference plate 45 is converted into an electrical signal by the line image sensor 7, and converted into a digital signal by the A/D conversion circuit 9. and is supplied to the shading correction circuit 10.

The shading correction circuit 10 sequentially adds up 16 lines of white reference data supplied from the A/[) conversion circuit 9 by reading the white reference plate 45, and stores the integration result in the line memory 50.

After this, the operator can access the operator panel (not shown)
In addition to selecting and switching the document size, etc., the density and the like are also selected, and the document 0 is placed on the document table 1.

Then, when a command signal to start document reading is supplied to the CPtJ 19 via the interface 18 from the control section of the external device, that is, the control section (not shown) of the image file device, the CPU 19 controls the driver 21 and starts the pulse motor 22. In addition to driving the optical system, the driver 2
3 to turn on the exposure lamp 2. Thereby, the light from the exposure lamp 2 is irradiated onto the original O, and the reflected light from the original O is guided to the line image sensor 7 via the mirror 3.4.5 and the lens 6.

Then, the line image sensor 7 converts the image formed by the guided light into a corresponding electrical signal and outputs it to the A/D conversion circuit 9 via the amplifier 8. This A/D
The conversion circuit 9 converts the signal supplied from the line image sensor 7 via the amplifier 8 into a digital signal, and outputs the digital signal to the shading correction circuit 10. Then, this shading correction circuit 10 performs shading correction on the supplied digital signal.

That is, the signal supplied from the A/D conversion circuit 9 is supplied to the divider 55 via the delay circuit 41. At this time, the accumulated white reference data for 16 lines is stored in the line memory 50, and is outputted to the divider 55 as a white reference signal via the delay circuit 59. Also,
The divider 55 is supplied with a correction coefficient corresponding to the voltage value of the image signal from the CPtJ19. As a result, the divider 55 performs shading correction on the image signal by dividing the image signal by the white reference signal, and also corrects the signal level by multiplying the corrected signal by the correction coefficient, and multiplies the signal level. The result is output to the binarization circuit 60.

Thereby, the binarization circuit 60 compares the signal supplied from the divider 55 with the threshold supplied from the CPU 19, and if the signal is higher than the threshold, determines "white" and outputs the NJ times signal. However, if the signal is below the threshold, it is determined that it is "black" and a "0" signal is output.

The output of the binarization circuit 60 is supplied to the serial/parallel conversion circuit 16, and is outputted to the image file (not shown) device via the interface 18.

Note that when there is an a-plane difference between a signal output to an image file device (not shown) and a signal output from another reading device, there is a difference in reflectance between the white reference plates of each device. judge it as something. In this case, the dip switch 47
By switching the settings and selecting another correction coefficient table stored in the ROM 46, you can multiply the correction coefficient according to the voltage value of the white reference signal, that is, the correction coefficient according to the reflectance of the white reference plate. Then, the multiplication result is sent to a binarization circuit 60.
By outputting the signals to each other, it is possible to make the density of the signals obtained by each reading device uniform.

As described above, the white reference signal used for shading correction is the average value of 16 lines of white reference data. Therefore, correction errors due to differences in reflectance caused by the position of the white reference plate due to contamination due to changes over time can be kept to a minimum.

In addition, by multiplying the shading-corrected signal by a correction coefficient corresponding to the voltage value of the white reference signal, it is possible to prevent the signal level after correction from becoming too high. Two types of correction coefficients corresponding to the voltage values are provided, and an appropriate correction coefficient can be selected according to the reflectance of the white reference plate. Therefore, by selecting a correction coefficient corresponding to the reflectance, it is possible to prevent density differences from occurring in image signals obtained by each device.

In addition, in the above embodiment, the correction coefficients are shown in tables (a) and (
b), but the explanation is not limited to this; for example, by changing the coefficients or their combinations, three or four types can be created.
By selecting the type..., more accurate correction can be made according to the reflectance.

In addition, although it has been described that reading the white reference data from the white reference plate is performed when the power is turned on, it may also be performed, for example, every time the original O is read, or every time a predetermined period of time has elapsed. Wave.

[Effects of the Invention] As detailed above, according to the present invention, it is possible to correct variations in the reflectance of the white reference plate that occur depending on the device or due to changes over time, and to obtain an image signal of a constant density. equipment can be provided.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention; FIG. 1 schematically shows the overall configuration, FIG. 2 schematically shows the configuration of the shading correction circuit, and FIG. 3 shows the configuration of the ROM. FIG. 3 schematically shows an example; 7... Line image sensor (conversion means), 9...
A/D conversion circuit, 10...shading correction circuit (
correction means), 19... CPU (reading means), 45...
・White reference plate, 46...ROM (memory means), 47...
・Dip switch, 50...Line memory, 53・
... Adder, 55... Divider, 60... Binarization circuit (binarization means).

Claims (2)

[Claims] (1) A reading device that reads an object to be read on a document table, converts it into a two-dimensional signal, and outputs it, comprising: a conversion means that converts the read signal read from the object to be read into an electrical signal; and a converter in the vicinity of the document table. A white reference plate provided, a generation means for generating a white reference signal corresponding to the light from the white reference plate, and an electric signal corresponding to the object to be read according to the voltage value of the white reference signal generated by the generation means. storage means for storing a correction coefficient for correcting the correction coefficient; reading means for reading out the correction coefficient from the storage means; and dividing the electrical signal converted by the conversion means by the white reference signal generated by the generation means; a correction means for correcting the electric signal corresponding to the object to be read by multiplying it by a correction coefficient read by the reading means; and binarizing the signal corrected by the correction means by comparing it at a slice level. A reading device characterized by comprising a binarization means. (2) The reading device according to claim 1, wherein the white reference signal generated by the generating means is an average value of white reference data obtained for a plurality of times with respect to the white reference plate. .