JPH066530A - Picture read method and picture reader - Google Patents

Abstract

PURPOSE:To increase the number of read lines on a white level reference board and to suppress the effect of noise by reading one line while a scanning board is moved by plural lines in one-line time with respect to the white level reference board. CONSTITUTION:One line is read while moving a scanning board 18 by plural lines in one-line time with respect to a white level reference board 15 and its output is stored in a memory 7. On the other hand, each line of an original is read while the scanning board 18 is moved by one line each in one-line time. For example, when the resolution of a CCD 4 is 1/600 inch and the scanning board 18 is moved by 1/1200 inch per one step signal and the white level reference board 15 is read, a CPU 23 sends 12 step signals in one-line time to a motor drive control section 22, and when an original 16 is read, two step signals are sent in one-line time. Thus, the board 18 is moved by 6 lines in one-line time when the board 15 is read and the board 18 is moved by one line in one- line time when the original 16 is read.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading in which a document is irradiated with light from a light source, and reflected light from the document is received by a detection device having a plurality of photoelectric conversion elements arranged therein and converted into electric signals line by line. The present invention relates to a method, and more particularly to a method for reading a white reference plate for obtaining a correction value for the output of each element of a detection device. Further, the present invention relates to an image reading apparatus using this image reading method.

[0002]

2. Description of the Related Art In copying machines, facsimiles, scanners, etc., a document is irradiated with light and the reflected light from the document is detected by a detection device (CCD, photodiode array, etc.) in which photoelectric conversion elements are arranged in one row. An image reading device that receives light and converts it into an electric signal line by line is used. In such an image reading apparatus, the output of each element is the same even if the light and dark levels (shades) of the original are the same because of variations in the sensitivity of each element of the detection device and uneven light amount of the light source. I won't. This reading error hardly causes a problem in the case of reading two levels of black and white, but becomes a serious problem in the case of reading an intermediate level as well, and it is impossible to accurately read the level of light and dark without correction.

Therefore, conventionally, this reading error has been corrected by the method shown in FIG. In the figure, 1 is a light source,
2 is a white reference plate or original, 3 is a lens, 4 is a CCD, 5
Is an A / D converter, and the reflected light from the white reference plate or the original 2 is photoelectrically converted by the CCD 4 line by line.
The analog signal of each pixel is sequentially sent to the A / D converter 5 and converted into a digital signal. 6 is a switch, 7 is a memory for storing the correction value for the output of each element, 8 is a correction calculation section for correcting the output of each element using the correction value stored in the memory 7, and is a switch when reading the white reference plate. 6 is connected to the A side, and the output of the A / D converter 5 is the memory 7
When the original is read, the switch 6 is connected to the B side and the output of the A / D converter 5 is sent to the correction calculation unit 8.

With this configuration, one line of the white reference plate is read before the original is read and the output Wi of each element of the CCD 4 is stored in the memory 7 as a correction value. When reading a document, the output of the CCD 4 is input to the correction calculator 8 and the memory 7
The correction value is read in synchronization with the output of the CCD 4, and the output Si of each element is divided by the correction value Wi for correction. Note that i = 1 to N, and N is the number of elements of the CCD 4.

However, in this method, the white reference plate is set to 1
Since only the line is read, if there is physical noise such as dust or scratches on the white reference plate, it will be read by the CCD4.
The correction value of the element becomes an incorrect value, and white or black lines appear on the image of the document to be read thereafter.

In order to solve this problem, JP-A-59-59
The methods disclosed in Japanese Patent No. 223062 and Japanese Patent Laid-Open No. 60-51369 have been proposed. In this method, as shown in FIG. 5, in order to reduce the influence of noise on the white reference plate, a plurality of lines of the white reference plate are read, and the average value of the output of each element of the CCD 4 for these lines is corrected for each element. It is a value. That is, when reading the white reference plate, the switch 9 is connected to the C side and the switch 10 is connected to the E side to read a plurality of lines of the white reference plate, and the outputs of the respective elements of the CCD 4 corresponding to these lines are added by the adder 11.
By adding for each element, each added value i (i = 1 to N,
N: the number of elements of CCD 4) is stored in the memory 12. Switch the switch 9 to the D side and switch 10 to read the original.
Is connected to the F side, the output of the CCD 4 is input to the adder 11, and the added value is read from the memory 12 in synchronization with the output of the CCD 4 and averaged by the averaging calculation unit 13 (Wim =
i / n) and input to the correction calculation unit 14, and the output Si of each element is divided by the correction value Wim. In this averaging method,
Although the effect of reducing noise is high, when the resolution of the image reading apparatus becomes high, the number of lines to be taken in becomes very large and the above-mentioned added value becomes large, so that the capacity of the memory 12 must be increased and the cost increases. There was a problem to do.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a white reference plate capable of suppressing an increase in the number of reading lines of the white reference plate even in a high resolution image capturing apparatus and effectively reducing the influence of noise of the white reference plate. An object is to provide an image reading method.

[0008]

To achieve the above object, the first aspect of the present invention
In the image reading method described above, an original is read by an image reading apparatus in which light is emitted from a light source to a document and reflected light from the document is received by a detection device in which a plurality of photoelectric conversion elements are arranged and converted into electric signals line by line. An image reading method for correcting the output of each element of the detection device at the time of reading an original by using the output of each element of the detection device with respect to the white reference plate before reading the white reference plate. One line is read while moving a plurality of lines within the line time and the output of each element of the detection device or a value proportional thereto is taken in, and the output of each element of the detection device is corrected by the value of each element when reading a document. It is characterized by doing.

According to the second image reading method of the present invention, the original is irradiated with light from the light source, and the reflected light from the original is received by the detection device having a plurality of photoelectric conversion elements arranged therein and converted into electric signals line by line. An image reading method for correcting the output of each element of a detection device at the time of reading an original by reading a white reference plate before reading an original in an image reading apparatus and utilizing the output of each element of the detection device with respect to the white reference plate, When reading the white reference plate, multiple lines are read while moving multiple lines within one line time to calculate the average output value or a value proportional to it for each element of the detection device. The output of each element is corrected by using the value of each element.

Further, according to the first image reading apparatus of the present invention, the movable table provided so as to be reciprocally movable with respect to the document, the irradiation light source for irradiating the document supported by the movable table with light, and the module for driving the scanning table. A motor, a motor drive control unit for controlling the rotation of the motor, a CPU for sending a control signal to the motor drive control unit, and a line signal generation unit for generating a line synchronization signal indicating the start time of reading each line. , A detection device for photoelectrically converting the reflected light from the document line by line by a plurality of photoelectric conversion elements,
A / D converter that converts the analog signal from the detection device into a digital signal, the output of each element of the detection device when the irradiation light source is irradiating the white reference plate placed in front of the document, or a value proportional thereto A memory for storing, a correction calculation unit for correcting the output of each element using the value of each element stored in the memory when the irradiation light source irradiates the original, and the irradiation light source irradiates the white reference plate. In this case, the output of the A / D converter is connected to the memory, and when the irradiation light source is irradiating the original, the output of the A / D converter is connected to the correction calculation unit. When irradiating, the CPU sends a motor control signal to the motor drive control unit so as to move the scanning table by a plurality of lines within one line time from one line synchronization signal to the next line synchronization signal. While white reference plate Wherein the read one line.

Further, according to the second image reading apparatus of the present invention, a movable table provided so as to be reciprocally movable with respect to the original, an irradiation light source for irradiating the original supported by the movable table with light, and a module for driving the scanning table. A motor, a motor drive control unit for controlling the rotation of the motor, a CPU for sending a control signal to the motor drive control unit, and a line signal generation unit for generating a line synchronization signal indicating the start time of reading each line. , A detection device for photoelectrically converting the reflected light from the document line by line by a plurality of photoelectric conversion elements,
An A / D converter that converts an analog signal from the detection device into a digital signal, and adds the output of each element of the detection device for each element when the irradiation light source irradiates the white reference plate placed in front of the document. An adder, a memory for storing the output of each element from the adder or a value proportional thereto, and when the irradiation light source is illuminating the original, the output of each element is corrected using the value of each element stored in the memory. The output of the A / D converter is connected to the adder when the irradiation light source is illuminating the white reference plate, and the output of the A / D converter is connected when the illumination light source is illuminating the document. The scanning table is moved by a plurality of lines within one line time from one line synchronization signal to the next line synchronization signal when the detection device is illuminating the white reference plate, including a switch for connecting the output to the correction calculation unit. From the CPU The motor drive control unit mode - and wherein the reading a plurality of lines of the white reference plate while transmitting the data control signal.

[0012]

The present invention will be described below with reference to the accompanying drawings. In FIG. 1 showing one embodiment of the present invention, reference numeral 3 is a lens,
4 is a CCD, 5 is an A / D converter, 6 is a switch, 7 is a memory for storing a correction value, and 8 is a correction calculation unit.
Since the same portions as and have the same functions, duplicate description will be omitted. Further, 15 is a white reference plate, 16 is a document, 17 is an irradiation light source, 18 is a scanning table for moving the irradiation light source in a direction perpendicular to the line reading direction by the CCD 4, 19 is a scanning table driving motor, and 20 is a driving belt. , 21 is an idle pulley, 22 is a motor drive controller, 23 is a CPU, and 24 is a line sync signal generator. Line sync signal generator 24
Generates a line synchronization signal LSYNC that specifies the reading start time of each line. The CPU 23 receives the line sync signal from the line sync signal generator 24 and outputs the line sync signal.
A signal (STEP signal) for controlling the rotation of the motor 19 is sent to the motor drive control unit 22. Motor drive control unit 22
Is a motor 19 according to a control signal from the CPU 23.
To rotate.

In this configuration, for the white reference plate 15, the scanning table 18 is moved for one line time (from the rise of one line synchronization signal LSYNC to the next line synchronization signal LSY).
A plurality of lines are moved within the time period until the rising edge of NC) to read one line, and the output is stored in the memory 17. Further, with respect to the original 16, each line is read while moving the scanning table 18 one line at a time for one line.

For example, the resolution of the CCD 4 is 1/600 inch (600 lines / inch), and the scanning table 18 is 1
When moving 1/1200 inch per STEP signal,
As illustrated in FIG. 3, when reading the white reference plate 15, CP
From U23 to the motor drive control unit 22 within 1 line time
Two step signals are sent, and when reading the original 16, two STEP signals are sent within one line time. Thereby,
When the white reference plate 15 is read, the scanning table 18 moves 1/100 inch (6 lines) within one line time, and when the document 16 is read, it moves 1/600 inch (1 line) within one line time.

In this embodiment, one line of reference white data is obtained from the white reference plate 15. However, as shown in FIG. It is also possible to read the reference white data and average them to use as a correction value, as in the prior art shown in FIG. Further, in the configuration of FIG. 2, the added value of the output of each element of the CCD 4 is stored in the memory and the average value is averaged by the averaging unit 13 when they are read out. Alternatively, the averaged value may be stored in the memory.

[0016]

As described above, according to the first image reading method of the present invention, one line is read while moving the scanning table with respect to the white reference plate by a plurality of lines within one line time.
Since the output of each element of the detection device or a value proportional thereto is stored in the memory and used as a correction value,
Reading one line has the effect of reducing the influence of noise such as dust and scratches on the white reference plate. Further, even if the resolution of the image reading apparatus becomes high, there is flexibility in that it can be dealt with by increasing the number of lines for moving the scanning table within one line time.

Further, according to the second image reading method of the present invention, as described above, a plurality of lines are read while moving the scanning table by a plurality of lines within one line time with respect to the white reference plate. Since the sum or average value of the output of each element of the detection device is stored in the memory and used as a correction value, the effect of reducing noise such as dust and scratches on the white reference plate is high. Further, even if the resolution of the image reading apparatus is increased, the number of lines for moving the scanning table can be increased accordingly within one line time to suppress an increase in the number of read lines of the white reference plate. Therefore, it is not necessary to increase the memory capacity, and cost up can be prevented.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a first image reading method and apparatus according to the present invention.

FIG. 2 is an explanatory diagram of a second image reading method and apparatus according to the present invention.

FIG. 3 is an explanatory diagram of control signals of a CPU in the image reading apparatus of the present invention.

FIG. 4 is an explanatory diagram of a conventional image reading method for reading one line of a white reference plate.

FIG. 5 is an explanatory diagram of a conventional image reading method for reading a plurality of lines on a white reference plate.

[Explanation of symbols]

15 ... White reference plate 16 ... Original document 17 ... Irradiation light source, 18 ... Scanning table 19 ... Scanning table driving motor 20 ... Driving belt

Claims (5)

[Claims] 1. An image reading apparatus which irradiates a document with light from a light source, receives light reflected from the document by a detection device having a plurality of photoelectric conversion elements arranged therein, and converts it into an electric signal line by line, before reading the document. An image reading method for correcting the output of each element of the detection device at the time of reading an original by using the output of each element of the detection device with respect to the white reference plate and reading one line when reading the white reference plate. One line is read while moving a plurality of lines within the time, and the output of each element of the detection device with respect to the reference white or a value proportional thereto is taken in, and the output of each element of the detection device is read at the time of reading the document. An image reading method characterized by performing correction with a value. 2. An image reading apparatus in which light is emitted from a light source to a document and reflected light from the document is received by a detection device in which a plurality of photoelectric conversion elements are arranged and converted into electric signals line by line before reading the document. An image reading method for correcting the output of each element of the detection device at the time of reading an original by using the output of each element of the detection device with respect to the white reference plate and reading one line when reading the white reference plate. Reading multiple lines while moving multiple lines in time, calculate the average value of the output of each element of the detection device or a value proportional to it, and output the output of each element of the detection device when reading the document. An image reading method characterized by performing correction using the value of. 3. A movable table provided so as to reciprocate with respect to the original, an irradiation light source for irradiating the original supported by the movable table with light, a motor for driving the scanning table, and a rotation of the motor. A motor drive control unit, a CPU that sends a control signal to the motor drive control unit, a line signal generation unit that generates a line synchronization signal indicating the start point of reading each line, A detection device that photoelectrically converts the reflected light line by line, an A / D converter that converts the analog signal from the detection device into a digital signal, and detects when the irradiation light source irradiates a white reference plate placed in front of the document. A memory that stores the output of each element of the device or a value proportional thereto, a correction calculation unit that corrects the output of each element using the value of each element stored in the memory when the irradiation light source is illuminating a document. And irradiation light The output of the A / D converter is connected to the memory when the source is illuminating the white reference plate, and the output of the A / D converter is connected to the correction calculator when the irradiation light source is illuminating the document. When the detection device is illuminating the white reference plate including the switch, the CPU drives the motor so as to move the scanning table by a plurality of lines within one line time from one line synchronizing signal to the next line synchronizing signal. The control unit is
An image reading apparatus which reads one line of a white reference plate while sending a control signal. 4. A movable table provided so as to reciprocate with respect to the original, an irradiation light source for irradiating the original supported by the movable table with light, a motor for driving the scanning table, and a rotation of the motor. A motor drive control unit, a CPU that sends a control signal to the motor drive control unit, a line signal generation unit that generates a line synchronization signal indicating the start point of reading each line, A detection device that photoelectrically converts the reflected light line by line, an A / D converter that converts the analog signal from the detection device into a digital signal, and detects when the irradiation light source irradiates a white reference plate placed in front of the document. An adder that adds the output of each element of the device for each element, a memory that stores the output of each element from the adder or a value proportional thereto, an averaging operation unit that averages each value of the memory by the number of lines, irradiation The light source is the original A correction calculator that corrects the output of each element using the value of each element stored in the memory during irradiation, and the output of the A / D converter when the irradiation light source irradiates the white reference plate Is connected to the adder and includes a switch for connecting the output of the A / D converter to the correction calculation unit when the irradiation light source is irradiating the original, and one switch when the detection device is irradiating the white reference plate. The CPU drives the motor drive control unit so as to move the scanning table by a plurality of lines within one line time from the line synchronization signal to the next line synchronization signal.
An image reading apparatus that reads a plurality of lines of a white reference plate while sending a control signal. 5. The image reading device according to claim 4, wherein the averaging calculation unit is provided between the adder and the memory.