JP2925558B2 - Image reading device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an image reading apparatus having a plurality of image reading modes.

[Conventional technology]

The image scanner is provided with a shading correction white reference reflected light generator. That is, in order to obtain a total white signal as a reference for the shading correction required for electrical correction of nonuniformity and so-called _COB ⁴ theta effect of heterogeneity and sensors of a light source, provided a white reference plate, The reflected light from the white reference plate is received by a photoelectric sensor and photoelectrically converted to obtain an all white signal.

On the other hand, some image reading apparatuses have a plurality of image reading modes (methods). This is for example ADF mode and Boo
This is the k mode. As shown in Fig. 1, ADF mode is an optical system
In the Book mode, the original is placed on the platen glass 27 while the original is being conveyed in the direction of arrow B with the 24 stopped, and the image is read while the optical system 24 moves in the direction of arrow A. As described above, different image reading methods generally result in different image reading positions.

Conventionally, the shading correction method in such an apparatus is performed at one place as shown in FIG. 8, and as a reference all white signal, data obtained by reading one line of a white reference plate is set. Is common.

[Problems to be solved by the invention]

However, there is no problem in the position where the shading correction is performed in the Book mode, for example, at the location shown in FIG. 8, but the setting of the all white signal is considered to be due to the case where dust or dirt is attached to the white reference plate. It is more accurate to set the average value of the white signals read over a plurality of lines while moving the optical system than to set the white signals obtained by reading the plate for only one line.

On the other hand, in the ADF mode, for example, as shown in FIG.
In many cases, 214 is attached, and it is desirable to perform shading correction in consideration of the state of the mylar sheet at the image reading position. In other words, mylar sheet 214
If the image reading position is scratched or stained, the light amount level is lower than it should be at that portion, so it is desirable to perform shading correction at the image reading position in the ADF mode.

Further, the setting method of the all-white signal is as follows. When the white data of a plurality of lines is read as described above, for example, when the mylar sheet is scratched or stained diagonally with respect to the moving direction of the optical system 24, the image reading position is set. Even irrelevant scratches and dirt are captured as an all-white signal.

As described above, there are reading positions and methods for shading correction suitable for each of the ADF mode and the Book mode, and since it is performed by one method at one place, satisfactory shading correction cannot be performed for both.

An object of the present invention is to provide an image reading apparatus which has solved the above problems.

[Means for solving the problem]

The present invention provides a first white reference member, a second white reference member disposed at a position different from the first white reference member, and an image on a document or the first white reference member or the second white reference member. Reading means for reading the white reference member and outputting an image signal; a first reading mode for reading an image on the document while moving the document; and a second reading mode for reading an image on the document without moving the document. Mode switching means for switching between the first and second reading modes; a transparent sheet disposed in the vicinity of the first white reference member in order to smoothly move the original in the first reading mode; When the reading means reads the first white reference member via the transparent sheet in the reading mode of
Controlling the reference data for shading correction by reading a predetermined one line of the white reference member, and when the reading unit reads the second white reference member in the second reading mode, Control means for controlling to set reference data for shading correction by reading a plurality of different lines of the second white reference member.

According to the present invention, when the reading unit reads the first white reference member via the transparent sheet in the first reading mode for reading an image on the document while moving the document,
In a second reading mode in which a predetermined line of the first white reference member is read to set reference data for shading correction and an image on the document is read without moving the document, When reading the white reference member, the shading correction reference data is set by reading a plurality of different lines of the second white reference member so that the optimal shading correction can be performed in each image reading mode. Become.

〔Example〕

 Hereinafter, the present invention will be described based on examples.

(Structure) (FIGS. 1 to 3) FIG. 2 is a perspective view showing an external appearance of an embodiment of a document image reading apparatus to which the present invention is applied, and FIG.
1 is a document image reading device (hereinafter abbreviated as a reader), 2
Denotes a reader body, and illuminates an original (image facing downward) on a platen glass 27 by an original illuminating unit 24;
A document image is formed on a CCD (charge-coupled device) 22 composed of a plurality of light receiving elements arranged in the main scanning direction by a lens 26 through a lens 26. The original illumination unit 24 and the mirror 25 are movable in a sub-scanning direction perpendicular to the main scanning direction by a drive system (not shown). Reference numeral 3 denotes an automatic document feeder (hereinafter abbreviated as ADF). The original on the sheet (image is upward) on the original table 31 is conveyed in the direction of arrow B shown by the broken line in FIG. Discharged on 32.

In the figure, 21 is a control unit, 23 is a CCD driver, and the circuit configuration of both is shown in FIG. Also, reference numerals 28/33 denote the reference position index plate at the time of "book mode" / "sheet (through) mode", which is the index means for detecting the first and second original reading reference positions according to the present invention. Reference plate,
The latter 33 is installed on the same platen glass 27 having the same coordinate system as the former 28 is arranged.

(Operation) (FIGS. 2 and 3) Next, the operation of the reader 1 will be described with reference to FIGS. The reader 1 according to this embodiment includes a “sheet (through) mode” in which an ADF 3 reads an image while a general paper (sheet) original without binding is conveyed in the sub-scanning direction, and a binding such as a book (book). The original with the document illumination unit 24 and the mirror
There are two modes, a “book mode” for reading an image by moving the image 25 in the sub-scanning direction. First, the “sheet (three) mode” will be described.

(1) “Sheet Mode” The reader 1 of this embodiment is always connected to an external device (for example, a digital printer, a personal computer, or the like), communicates control signals with these external devices, and transmits data to the external device. The image information signal output is output from the interface circuit 20.
Done through 7.

In a state where the document is placed on the document placing table 31 of the ADF 3 (image is upward), instructions of various modes are input by the external device. For example, the pixel density is set to 400 dpi, 300 dpi, or 200 dpi, or the image signal is converted to a binary signal or a multi-level signal. The CPU 208 receiving this sends out a control signal to the timing signal generation circuit 209 and the selector 206 in advance to set the pixel density and the image signal. Further, it is confirmed by the reference position index plate 33 in the "sheet mode" whether or not the original illumination unit 24 of the optical system is at the original reading position (the position shown in FIG. 1) in the ADF 3.

If the document is not at the ADF document reading position, the document illumination unit 24 is moved before the reading operation is started by the next document reading start command. In this state, when a document reading start command is input from outside,
The CPU 208 outputs a lamp control signal and outputs the lamp unit 24
Is turned on, and a document feeding start command is output to the ADF3. Thus, the document placed on the document placing table 31 of the ADF 3 is transported in the direction of arrow B toward the path indicated by the broken line in FIG.

In the reader 1 of this embodiment, a stepping motor is used as a motor used for conveying the ADF 3 document and driving the optical system scanning. The scanning speed can be freely changed. Further, whether or not the leading edge of the document has reached the document illuminating position of the reader 1 can be detected by a document leading edge detection sensor (not shown) provided in the ADF 3.

Until the document reaches the document illumination position, the image formed on the CCD 22 is converted into a digital value and input to the interface circuit 207, as described later, but this is not an original image. The CPU 208 supplies a control signal of “impossible” output to the interface circuit 207 so as not to output the image signal.

Next, when the document arrives at the document illumination position, the CP
The U208 outputs a control signal of image signal output “OK” to the interface circuit 207, and the read image signals are sequentially sent to an external device.

When the trailing edge of the document has passed the document illuminating position, this is detected by the document leading edge detection sensor, and the image signal is output to the interface circuit 207 again.
Interface signal by commanding the
Reference numeral 207 stops the image signal output and outputs a document reading end signal to an external device. After this, within a predetermined time,
If an external device does not receive a document reading start command,
U208 turns off the lamp of document illumination unit 24, and ends a series of operations.

(2) "Book Mode" Next, in the "book mode", the original is placed on the platen glass 27 in FIG. 1 so that the right end is the leading end of the original (image is downward). .

In the original illumination unit 24 of the optical system, the right end in FIG. 1 is the initial position, and the reference position is checked by the reference position indicator plate 28 in the "book mode" as in the case of the "sheet mode". It is configured in. put it here,
The settings of the pixel density and the image signal before the start of the document reading are the same as those in the "sheet mode".

When a document reading start command is input from an external device, CP
U208 first outputs a lamp control signal to turn on the lamp of document illumination unit 24. Here, without immediately starting the scanning for reading the original, it waits for about 300 to 500 ms until the light amount of the lamp is stabilized. During this time, "Sheet mode"
Similarly to the case, the image signal is input to the interface circuit 207, but the image signal is not output to the external device by the control signal of the CPU 208. When a document reading start command is input from an external device, the document illumination unit 24 immediately starts scanning in the direction of arrow A in FIG. 2 after performing shading correction described later.

Platen glass 27 from the initial position of document illumination unit 24
The distance to the upper end of the original is about 2 to 3 mm. During this time, the scanning speed of the optical system by a motor (not shown) is controlled to be stable. When the document illumination unit 24 reaches the position of the document leading edge, the CPU 208
A control signal for outputting an image signal “OK” is output to 7, and the read image signals are sequentially sent to an external device.

Since the scanning length of the optical system is uniquely determined by the number of pulses for driving the motor by the CPU 208, the CPU 208 determines that the reading of the original is completed when the required number of pulses is output to the motor, and turns off the lamp. Image signal output is "not possible", motor reversal control is performed, and a document reading end signal is output to an external device. Under the motor inversion control of the CPU 208, the document illumination unit 24 advances in the direction of arrow C in FIG. 2, and stops when the reference position index plate 28 in the "book mode" detects that the original position has been reached. When the next document reading start command is not received from the external device in the section where the optical system returns, the process stops at the initial position and a series of operations is completed.

(3) Circuit Operation (FIGS. 3 and 4) Next, the circuit operation will be described based on the circuit block diagram of FIG. 3 and each signal waveform timing chart shown in FIG. The CCD 22 on the CCD driver 23 in FIG.
The timing signal generation circuit 209 on the control unit 21 (third
In FIG. 4, reference numeral 210 denotes an oscillator). Each timing signal φ ₁ , φ ₂ , φ _R , φ _SH (FIG. 4) is driven through the CCD drive circuit 203. An image analog signal output from the CCD 22 is amplified by an amplifier 201 and input to an analog / digital (A / D) converter 202. In the A / D converter 202, the image signal is converted from an analog signal into a 6-bit digital signal based on the timing signal φ _AD generated by the timing signal generation circuit 209, and output to the control unit 21.

The control unit 21 applies an image signal level non-uniformity (shading and non-uniformity) caused by the input digital image signal to the non-uniform light amount of the illumination unit 24, the non-uniform transmission of the lens 26, and the non-uniform sensitivity of the CCD 22. ) Is electrically removed by the shading correction circuit 211. The digital image signal subjected to the shading correction can be output to an external device in one of the two modes described above, that is, the binary mode and the multi-level mode. Which of the two modes is output is determined by a command from an external device.
The CPU 208 outputs a control signal to the selector 206.

In the case of the multi-level mode, a 6-bit image signal is converted into 4 bits and input to the selector 206, which is selected and input to the interface circuit 207. In the multi-level mode, the interface circuit 207 compresses a 4-bit signal for two pixels into 8 bits and outputs the signal to an external device.

In the case of the binary mode, the 6-bit image signal is converted into 1 bit by the binarization circuit 205 according to the slice level output from the CPU 208 and input to the selector 206. There are two types of slice levels. One is the slice level specified by the external device.
The CPU 208 outputs it to the binarization circuit 205, and the other one is a slice level based on background density detection. In the background density detection performed in the present embodiment, the background density detection circuit 204 detects the maximum density value (the brightest value) for each line in the image main scanning direction, and the CPU 208 captures the maximum density value and averages several lines. Is output to the binarization circuit 205 as a slice level.

The image signal binarized by the above method is supplied to the selector
The data is input to the interface 206, which is selected and input to the interface 207. In the case of the binary mode, the interface circuit 207 collectively compresses the data for eight pixels into eight bits, and outputs the resultant data to an external device.

(4) Pixel Density Conversion Method (FIG. 5) Next, a pixel density conversion method performed in this embodiment will be described. FIGS. 5A to 5C show two enlarged examples of an enable signal VE system clock signal CLK in the optical sub-scanning direction of the reader 1 and a clock signal CLK corresponding to one cycle of the VE signal. Show. (A) shows a case where the pixel density is 400 dpi, for example, one cycle of the VE signal is equivalent to one line of the optical system scanning motor, and the cycle of the clock signal CLK is the CCD22 (first and third CCDs). The same period as the timing signals φ ₁ , φ ₂ (FIG. 4) for driving (FIG. 4).

Also, FIG. (B) shows that the pixel density is 200 dpi, ie,
(A) The waveform in the case of the pixel density is 1/2 of the case of the diagram, and the period of both the signals VE and CLK is 1/2 of that in the case of the diagram (a). The VE signal is controlled by the CPU 208 (FIG. 3), and the optical system scanning motor rotates to obtain an image signal in the same cycle as in the case of FIG. The signal is output only when the signal is active. The CLK signal is supplied to the background density detection circuit 204, the binarization circuit 205, and the background density detection circuit 204 by the CPU 208 controlling the timing generation circuit 209.
An image signal is output to the interface circuit 207 once every two pixels in order to output the CLK signal shown in FIG. Therefore, both the main scanning and the sub-scanning of the optical system correspond to a half pixel density.

Similarly, in FIG. 3C, the pixel density is 1/4 of that in FIG. 3A, that is, 100 dpi.

(5) FIG. 6 is a block diagram showing the internal configuration of the shading correction circuit 211.

In the figure, reference numeral 212 denotes a storage device for storing one line of a reference white signal obtained by reading a white reference plate for shading correction by the CCD 22. Reference numeral 213 denotes a reference white signal stored in the storage device 212. CCD driver section 23/203
This divider corrects the shading of the image information by dividing the original image information sent from (FIG. 1/3) for each pixel.

FIGS. 7 and 8 illustrate the installation position of the white reference plate for shading correction according to the present invention.

FIG. 7 shows a white reference plate in the ADF mode. In the drawing, reference numeral 214 denotes a transparent sheet (mylar sheet) provided so that the original is smoothly conveyed. The original is fed in the direction of arrow B in the gap between the white reference plate 215 and the mylar sheet 212 on the sheet 214. It is being done.

FIG. 8 shows a white reference plate in Book mode. The white reference plate 216 is attached to a lower portion of the document attaching portion 217 used when placing a document on the placing glass 27.

(6) FIG. 9A shows a shading correction method in each of the ADF mode and Book mode according to the present invention.
This will be described in detail with reference to the flowcharts of FIGS. 9B and 9C.

First, wait until there is a read command in S1 of FIG. 9A, and when there is a read command, a document is set on the ADF by a document detection sensor (not shown) provided in the document insertion portion of the ADF in S2. Judge whether it is set and if set, AD
The process proceeds to S3 as the F mode, and proceeds to S11 as the Book mode if not set.

 FIG. 9B shows the case of the ADF mode.

First, the optical system 24 is used until the index plate 33 can be detected in S3 and S9.
Is moved in the direction A one line at a time. Next, in steps S4 and S10, the optical system 24 is moved in the direction C by the number of lines set in advance and set at the document reading position. Next, in S5, the white reference plate 21
4 is read, and the white signal is stored in the storage device 212.
Then, after the original is conveyed in the B direction to the original reading position in S7, the original is read while performing the above-described shading correction in S8, and the process returns to S1.

FIG. 9C shows a shading correction method in the Book mode. First, in S11 and S21, the optical system 24 is moved one line at a time in the C direction until the index plate 28 can be detected. Next, in S12, CPU2
The number of lines (10 lines in this embodiment) for reading the white plate is set in the register 218 in 08 to take an average. Next, in S13, one line of the white reference plate 216 is read, and the data is sent to the CPU 208. The CPU 208 calculates the average value in S14, and
To advance the optical system one line in the A direction. In S16, the counter is-
This operation is repeated until the counter is determined to be 0 in S17.

When the average value for 10 lines of the white reference plate is obtained in this way, in S18, the CPU 208 stores the average value in the storage device 212 in the shading correction circuit. In S19 and S22, the optical system 24 is moved to the document reading position. Then, the original is read while performing the above-described shading correction in S20, and the process proceeds to S1.
Return to

In this embodiment, the case where there are two types of image reading methods has been described, but the same applies to the case where there are three or more types.

In this embodiment, when the image reading method is determined, the shading correction method is automatically selected. However, the shading correction method may be selected on the host side, for example.

〔The invention's effect〕

As described above, according to the present invention, appropriate shading correction reference data is set in consideration of the reading state of the white reference member provided according to the reading mode, and shading is performed based on the set reference data. By performing the correction, a high-quality image signal can be output.

[Brief description of the drawings]

1 is an internal configuration diagram of FIG. 2, FIG. 2 is an external perspective view of an embodiment of a document reading apparatus to which the present invention is applied, and FIG. 3 is a circuit block diagram of a main part of FIG. FIG. 4 is a timing chart of each signal waveform, FIGS. 5 (a), (b) and (c) are explanatory diagrams of a pixel density conversion method, FIG. 6 is a block diagram showing the internal configuration of a shading correction circuit, and FIG. FIG. 8 shows a shading correction plate used in the ADF mode. FIG. 8 shows a shading correction plate used in the Book mode. FIGS. 9A, 9B and 9C show operation sequences of the present invention. It is a flowchart which shows. 1. Image reader (reader) 3. Automatic document feeder (ADF) 214 Mylar sheet 215 White reference plate in ADF mode 216 White reference plate in Book mode

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H04N 1/04-1/207 H04N 1/40-1/409 H04N 1/46 H04N 1/60

Claims (7)

(57) [Claims] A first white reference member; and a second white reference member disposed at a different position from the first white reference member.
A white reference member, an image on a document or the first white reference member or the second
Reading means for reading the white reference member and outputting an image signal; a first reading mode for reading an image on the document while moving the document; and a second reading mode for reading an image on the document without moving the document. Mode switching means for switching between the first and second reading modes; a transparent sheet disposed in the vicinity of the first white reference member in order to smoothly move the document in the first reading mode; When the reading unit reads the first white reference member via the transparent sheet in the reading mode, the reference data for shading correction is set by reading a predetermined one line of the first white reference member. And when the reading means reads the second white reference member in the second reading mode, a plurality of different white reference members of the second white reference member are provided. Image reading apparatus characterized by comprising a control means for controlling so as to set the reference data of the shading correction by reading-in. 2. The image reading apparatus according to claim 1, further comprising calculating, in the second reading mode, an average value of data obtained by reading different positions of the second white reference member read by the reading means. An image reading apparatus, comprising: 3. The image reading apparatus according to claim 1, further comprising storage means for storing said reference data. 4. The image reading apparatus according to claim 1, further comprising: a document conveying means for conveying said document, wherein said document conveying means conveys said document in said first reading mode. An image reading apparatus, comprising: 5. The image reading apparatus according to claim 1, further comprising communication means for communicating with an external device. 6. The image reading apparatus according to claim 5, wherein a reading instruction is input from said external device via said communication means. 7. An image reading apparatus according to claim 5, wherein said image signal is sent to an external device via said communication means.