JPH0897976A - Image reader - Google Patents

Abstract

PURPOSE: To adjust a read position with high accuracy and simple configuration in which an original is scanned optically to obtain image information. CONSTITUTION: An image of an original placing plane on which an original is placed is formed onto an image pickup face of a CCD 11 through a lens 10. The CCD 11 provides an output of video data VDATA synchronously with a video clock VCLK. The readable range in the main scanning direction by the image reader depends on a valid picture element number N of the CCD 11 and the readable range in the subscanning direction depends on a range by mechanical scanning. The read position deviation is adjusted by adjusting a main scanning data valid signal FSVALID and a subscanning data valid signal SSVALID before the adjustment so that the position and the size of the actual original are made coincident respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus for optically scanning a document to obtain image information.

[0002]

2. Description of the Related Art In an image reading apparatus for optically scanning a document to obtain image information, a CCD line sensor receives reflected light from the document and photoelectrically converts it to read an image. Therefore, a mounting position error and a magnification error of the CCD in the main scanning direction, a mounting error of the position sensor for determining the reading start timing of the document scanning system in the sub-scanning direction, and a scanning speed error occur. When the image is read, the position of the read image is misaligned with respect to the original, the size of the read image becomes large or small, and in the case of a reading apparatus using a 3-line color sensor, color misregistration occurs due to a magnification error. Will end up.

In order to solve such a problem, the operator measures the positional deviation on the image obtained by recording the read image with a jig such as a scale, compares it with the original, and obtains the error, which is then calculated. For example, an instruction is input to adjust the mechanical portion or electrically, or image information is displayed on a display to obtain a positional deviation amount and an instruction is input.

When the read image position is adjusted by such a reading device, an image is formed on a sheet and an operator measures the error of the position error with the original and inputs an instruction to adjust the error. Therefore, there is a problem that the skill of the operator is required for a sufficient time, the judgment criterion is ambiguous due to individual differences, and the adjustment is not properly performed, causing variations. Further, since the reading apparatus adjusts the deviation of the image forming apparatus, the gap between the lines and the scanning magnification do not match in the image reading apparatus including the three-line color sensor, and the color deviation occurs. There was such a problem.

Further, the method of displaying the image information on the display requires a special measuring jig, which causes a problem that the connection operation takes time.

A means for solving such a problem is disclosed in Japanese Patent Laid-Open No. Hei 3
It is proposed in Japanese Patent Laid-Open No. 154475, Japanese Patent Laid-Open No. 4-150367, Japanese Patent Laid-Open No. 5-014632, and the like.

In the apparatus described in Japanese Patent Laid-Open No. 3-154475, the reading device is provided with a reading device center position adjusting mode, and a test chart in which the center position of the reading line is written is read in this position adjusting mode. The center position is adjusted by variably setting the used bit in the reading device in accordance with the read information of the test chart.

Further, in the apparatus disclosed in Japanese Patent Laid-Open No. 4-150367, the amount of displacement of the document with respect to a predetermined reference position is detected, and the image pickup means is moved by the amount corresponding to the amount of displacement. The reading position is automatically adjusted by variably setting the scanning start timing.

In the apparatus disclosed in Japanese Patent Laid-Open No. 5-014632, the image information of the original is read and temporarily stored in the storage means, and the physical image information is stored based on the stored image information of the original. The error between the position and the ideal position is obtained, and the reading position is adjusted by replacing the image information in the storage means according to the error.

FIG. 11 shows the above-mentioned Japanese Patent Laid-Open No. 5-01463.
It is a schematic diagram which shows the basic composition of the conventional image reading apparatus described in the 2nd publication.

The image signal from the image pickup device 51 is stored in the memory 53 after being converted from the analog form to the digital form by the A / D converter 52, and the error between the image position and the reference position is calculated by the calculating means 54. The memory 53 is controlled by the control means 55 based on the calculation result,
The reading position is adjusted so that the error is eliminated.

[0012]

However, in the conventional apparatus described in the above publication, a new storage means for replacing the image information with an ideal position and a calculation means are required, which is expensive. There was a problem that it would end up.
In addition, since the theoretical position in the effective pixel of the reading element is compared with the actual position, a complicated image position calculation means is required that does not correspond to the actual position from the document edge. However, since the paper edge is detected by using a white paper or a black paper as the original, the accuracy is poor, and there is a drawback that the magnification and skew cannot be detected and corrected.

Therefore, an object of the present invention is to enable highly accurate adjustment of the reading position with a simple structure.

[0014]

An image reading apparatus according to the present invention comprises an image pickup means for scanning a document to read image information, and a first position storage means for storing the position of the image information read by the image pickup means. A second position storage means for storing the position of the image information in the document, a position of the image information stored in the first position storage means, and a position of the image information stored in the second position storage means. Calculating means for obtaining a difference from the position; read data valid signal generating means for generating a read data valid signal for indicating whether or not the read data is valid; and the read data valid signal generation based on the result of the calculating means. The reading data valid signal generation control means for controlling the means and the scanning speed setting means for setting the scanning speed of the imaging means based on the result of the calculation means.

Further, the image reading apparatus of the present invention comprises:
The position storage means is a memory for storing the image itself read by the image pickup means, and the second position storage means stores a value obtained by previously measuring the position of the image for measuring the displacement of the document. It is a memory.

[0016]

According to the present invention, since the data written in the line memory corresponds to the position of the image from the end of the document, the image position detecting calculation is simplified. Further, by utilizing this line memory in both the main and sub directions, the magnification in both the main scanning and the sub scanning can be detected. Further, by temporarily utilizing the line memory for shading as a storage device for measuring the displacement, it is possible to provide an inexpensive and highly accurate image reading device without adding a new storage device.

[0017]

1 is a block diagram showing the basic construction of an embodiment of an image reading apparatus of the present invention.

The image pickup means 1 is composed of, for example, a CCD line sensor, and reads the image by receiving the reflected light from the document and photoelectrically converting it by the line sensor. The image processing means 2 includes shading, color correction,
Has functions such as editing. The CPU 3 receives the information from the image processing means 2 and controls the image processing means 2 through the control means 4 to correct the positional deviation. In the present invention, as will be described in detail below, it is possible to calculate and correct the positional deviation and magnification of the reading position without providing the memory 53 as shown in the conventional example of FIG.

FIG. 2 is a block diagram showing the basic arrangement of an image reading apparatus to which the present invention is applied.

CC corresponding to the image pickup means 1 shown in FIG.
The analog image output from the D sensor 11 is supplied to the A / D converter 13 via the analog processing circuit 12 and converted into a digital image signal. The digital image signal D _IN is supplied to the shading correction circuit 14. The shading correction circuit 14 is for correcting uneven light quantity of a light source that illuminates the surface of the document, variation in sensitivity of each pixel of the CCD sensor 11, and the like. A general image reading apparatus is usually provided with this shading correction circuit. Has been. A memory 15 for storing correction data for shading correction is connected to the shading correction circuit 14,
In the shading correction circuit 14, shading correction is performed using this correction data. The image signal D _OUT after shading correction is subjected to linearity correction and color correction circuit 17 by a look-up table (LUT) 16.
Then, the image data VDATA is obtained by the color correction and the image editing processing in the editing processing circuit 18.

The timing generator 19 synchronizes the drive clock for the CCD sensor 11, the main scanning data valid signal FSVALID for the shading correction circuit 14, and this main scanning data valid signal FSVALID in synchronization with the external synchronizing signal. The delayed main scanning synchronization signal shifted by the pipeline delay of each processing is output. The delayed main scanning synchronization signal is a signal obtained by delaying the main scanning data valid signal FSVALID by the delay amount of the processing of each correction circuit, and is used for synchronizing the image signals.

The CPU 3 is connected to the timing generator 19, the shading correction circuit 14 and other processing circuits, and controls the operation of each circuit.

FIG. 3 is a schematic diagram for explaining the operation of the shading correction circuit 14. The shading correction operation will be described with reference to FIG. First, the white reference plate is read and white reference data is stored before the reading of the original is started. Therefore, first, the first switch SW1 is switched to the 3 side, that is, the memory 15 side, and the second switch SW2 is switched to the 2 side, that is, the address counter 21 side. Next, the main scan data valid signal FSVAL
Using the ID as a reset signal, the white reference data D _W is fetched into the memory 15 by the output of the address counter 21 which is incremented by the video clock VCLK. At the time of reading a document, the first SW1 is set to the 2 side, that is, the divider 22 side, and the divider 22 divides the document read data D _IN by the white reference data D _W previously stored in the memory 15. Standardize. Output data D _OUT after shading correction is 8
In the case of bits, the output data D _OUT is expressed by the following equation.

D _OUT = D _IN × 255 / D _{W In the} present invention, the shading correction memory 15 is used as a position deviation measuring memory to correct the position deviation of the reading position. The misregistration correction operation of the reading position will be described below with reference to the flowchart shown in FIG.

First, the misregistration adjustment test chart is set on the original reading surface of the image reading apparatus (step 10).
1) When execution of the adjustment mode is instructed (step 10
2), set the second switch SW2 of FIG. 3 to the 3 side, that is,
The white reference data D _W stored in the memory 15 is set on the CPU 3 side, and the read operation is performed while the address of the memory 15 is incremented by the CPU 3.
(Step 103). The white reference data D _W transferred to the CPU 3 is stored in the memory built in the CPU 3.

After the transfer of the white reference data D _W , the position deviation measuring image printed on the position deviation adjusting chart can be determined in advance so that it can be read even in consideration of the parts accuracy and the assembly accuracy. From the determined position, one line worth is taken into the memory 15 and transferred to the CPU 3 (steps 104, 105, 106, 107). The “moving to a predetermined document reading position” in step 104 means that the scanning carriage is always moved to a position where the image for measuring the displacement of the document can be read even if the dimensional error of the scanning carriage or the optical system is taken into consideration. Means to let. After that, the operation of fetching the image data line by line into the memory 15 (step 106) and transferring it to the CPU 3 (step 107) is repeated, and the data for n lines of the same pixel is cumulatively added in the CPU 3 (step 108). , 109,
110), remove abnormal values, finally take an average for each pixel (step 111), perform shading correction on the value using the white reference data (step 112), and then use the centroid method or the like. To calculate the image position (step 113). Then, a positional deviation amount is calculated based on this image position (step 114), this positional deviation amount is converted into a correction value (step 115), and the control means is set based on this correction value (step 114). 116) Perform position shift correction.

FIG. 5 shows how the misregistration measurement image printed on the misregistration adjustment chart and the image data obtained by reading this misregistration measurement image are stored in the shading memory 15. It is an explanatory view showing whether or not.

Now, as shown in FIG. 5 (a), a misregistration adjustment chart in which hook-shaped marks M1 to M4 having vertical and horizontal lines whose ends are abutted against each other at four corners of a sheet are printed is read. Consider the case.

When reading data for one line in the main scanning direction, the main scanning read data valid signal FSVALID
Position data at two positions X1 and X2 from the start position of (1) can be obtained (see (b) of the same figure). The vertical line of the mark M1 corresponds to the position X1, and the vertical line of the mark M3 corresponds to the position X2. The horizontal position is represented by the number of dots of pixels.

A main scanning data valid signal F is stored in the memory 15.
Since position data is stored based on SVALID, data at the start position of the main scanning read data valid signal FSVALID corresponds to the memory address "0".
Therefore, by setting the count number from the address "0" in the memory 15 to the address of the image position to match the distance from the document edge to the image position, the effective reading range can be matched with the document.

Here, if the distance from the document edge of the adjustment chart to the center of the image position value is values H1 and H2 calculated from the resolution and the number of dots, the main scanning registration position error ΔX and the main scanning magnification error MX are , ΔX = X1-H1 MX = (X2-X1) / (H2-H1). Since the value thus stored in the memory 15 corresponds to the value from the document edge, an error can be obtained by a simple calculation formula. Based on the main-scanning registration position error ΔX and the main-scanning magnification error MX, the main-scanning registration position is corrected by moving the main-scanning data valid signal FSVALID by ΔX. Alternatively, the interpolation calculation between two points may be electrically performed.

Similarly, also in the case of sub-scanning, the sub-scanning data valid signal SSVALID is used as a reset signal, an address to be incremented by the main scanning data valid signal FSVALID is given to the memory, and it is predetermined in consideration of variations from the positional deviation adjustment chart. When a value of several lines for one pixel is loaded into the memory from the determined position, Y from the start position of the sub-scanning data valid signal SSVALID is read.
Position data at two locations of 1 and Y2 can be obtained (Fig. 5 (c)).
reference). The vertical position is represented by the number of lines.

Assuming that the vertical distance from the document edge of the adjustment chart to the center of the image position of the marks M1 and M2 is the values V1 and V2 calculated from the resolution and the number of lines, the sub-scanning registration position error ΔY. The sub-scanning magnification error MY can be calculated as follows. The vertical distance is obtained from the resolution and the number of lines.

ΔY = Y1-V1 MY = (Y2-Y1) / (V2-V1) Based on this value, the correction of the sub-scanning registration position is realized by moving the sub-scanning data valid signal SSVALID by ΔY. The correction of the magnification error can be realized by changing the scanning speed in the vertical direction, that is, the sub-scanning direction.

Further, if the mark M3 is read at the other end to take in the data in the sub-scanning direction (see FIG. 5D) and the position Y3 is obtained, the skew amount ΔS can be calculated as follows.

ΔS = (Y3−Y1) − (V3−V1) The skew amount ΔS may be corrected by adjusting the platen guide position or the sensor mounting position.

By displaying these calculated values on the control panel or the like, the operator can easily know the adjustment amount, the mechanical adjustment work can be made efficient, and the abnormality can be detected. Also, the adjustment of items that can be adjusted electrically is
Normally, this is done automatically, but if necessary, the operator can enter instructions from the control panel. Furthermore, if the corrected data is stored in the backup memory,
It is not necessary to perform image position shift correction every time the power is turned on.

FIG. 6 is a conceptual diagram for explaining the adjustment of the reading position deviation in the main scanning direction and the sub scanning direction in the image reading apparatus of this embodiment. In the image reading apparatus, the image of the document placement surface on which the document is placed is transferred to the CCD by the lens 10.
An image is formed on the image pickup surface of 11. From the CCD 11, the video data VDATA is synchronized with the video clock VCLK.
Is output. The readable range in the main scanning direction of the image reading device is determined by the number N of effective pixels of the CCD 11, and the readable range in the sub scanning direction is determined by the mechanically scannable range. The reading position shift adjustment may be performed by adjusting the main scanning data valid signal FSVALID and the sub-scanning data valid signal SSVALID before the adjustment so that the position and the size of the original document are the same as the actual document.

Now, as shown in FIG. 6, the reading effective range defined by the main scanning data effective signal FSVALID and the sub scanning data effective signal SSVALID is located at the position where the original is placed due to a manufacturing error or the like. Suppose that they are out of alignment. In this state, if the image is read using the above-described misregistration adjustment chart, it is possible to know the deviation amounts ΔX and ΔY in the main scanning direction and the sub scanning. Therefore, according to the deviation amounts ΔX and ΔY,
By adjusting the timings of the main scanning data valid signal FSVALID and the sub-scanning data valid signal SSVALID, the edge of the document and the edge of the effective reading range can be matched.

FIG. 7 shows an example of a block diagram embodying the shading correction circuit 14 shown in FIG. The shading correction circuit 14 includes a memory 15 for shading.
It has two types of counters that generate
One is a normal shading main scanning direction counter 31 to which the main scanning data valid signal FSVALID is supplied as a clear signal CLR and the video clock VCLK is supplied as a clock CLK. The other is a sub-scanning direction counter 32 to which the sub-scanning data valid signal SSVALID is supplied as a clear signal and the main-scanning data valid signal FSVALID is supplied as a clock CLK. The main scanning direction counter 31 and the sub-scanning direction counter 32 generate addresses in the memory when loading position data in the main scanning direction into the memory and when loading position data in the sub-scanning direction into the memory. . The main scanning direction counter 31 and the sub scanning direction counter 32 correspond to the address counter 21 shown in FIG.

Since the CPU 3 reads the data in the memory 15, a selector 33 is provided so that an address bus from the CPU 3 can be selected as an address to the memory 15. The selector 33 uses the select signal from the CPU interface 3a to scan counters 31 and 3
One of the address from 2 or the address from the CPU 3 is selected and supplied to the memory 15 as the address ADDRESS. The selector 33 corresponds to the second switch SW2 shown in FIG. The memory write signal MW to the memory 15 is also supplied to the memory 15 via the gate select 34 that selects the signal generated from the video clock VCLK and the main scan data valid signal FSVALID and the read / write signal R / W from the CPU interface 3a.
Supplied as R. The output of the main scanning counter 31 and the chip select setting signal from the CPU 3 are supplied to the chip select (CS) generator 35, and the output of the chip select (CS) generator 35 is supplied to the memory 15 as the chip select signal CS. It

FIG. 8 is a timing chart showing the memory writing timing in the case of reading in the main scanning direction. The main scanning counter 31 uses the main scanning data valid signal FSVAL.
Since it is cleared by the ID (see (b) in the figure) and incremented by the video clock VCLK (see (a) in the figure), the address ADDRESS to the memory 15 (see (c) in the figure) is "0", "1", "2", ... Therefore, the main scan data valid signal FSVA
The image data S at the start position of the LID (see (d) in the figure) is stored at the address "0". The address "AE" corresponds to the last data in the data effective range ((d) in the figure).
Image data at the position of "S + AE" is stored in the address "AE". The image data S is an arbitrary position in the effective pixel of the CCD sensor 11, and changes depending on the start position of the main scanning data effective signal FSVALID. Further, the chip select signal CS of the memory 15 ((f) in the figure)
Is always valid, and the memory 15 is valid while the memory write signal MWR (see (e) in the figure) is at a high level, and data is written to the memory 15 at the rising edge of the memory write signal MWR.

FIG. 9 is a timing chart showing the memory writing timing in the case of reading in the sub-scanning direction. The sub-scanning counter 32 has a sub-scanning data valid signal SSVAL.
It is cleared by the ID (see (b) in the figure) and is incremented for each line by using the main scanning data valid signal FSVALID (see (a) in the figure) as a clock. Therefore,
In the sub-scanning counter 32, the address ADDRESS (see (c) in the figure) sequentially increases as "0", "1", "2", .... The memory write signal MWR (see (d) in the figure) is the same as the write timing in the main scanning direction to the memory 15, but a chip select signal for fetching pixel data at an arbitrary position in the effective pixel into the memory 15. C
It is controlled by S (see (e) in the figure). As the memory write signal MWR, a signal generated from the video clock VCLK and the main scan data valid signal FSVALID is normally used.
The read / write signal R / W of PU3 is used. When the chip select signal CS is low level,
Even if the memory write signal MWR is input, it is not written in the memory. The effective position and width of the chip select signal CS can be set by the CPU 3.

FIG. 10 shows another embodiment of the image reading apparatus of the present invention.

In the embodiment shown in FIG. 10, the image data obtained by reading the misregistration adjustment chart is not taken into the line memory separately for the main scanning and the sub-scanning, but for example, the line memory is divided into a plurality of areas. Then, only the region where the image exists, for example, only n pixels × m lines are fetched in the memory.

As shown in FIG. 10 (a), cross-shaped marks M5 to M8 are formed at the four corners of the misregistration adjustment chart, and this mark M5 is used when reading an image.
Only the M8 part is read and stored in the memory. That is, the area within the n pixels × m lines where the mark exists is continuously read, and the image data of n pixels per line is stored for m lines, starting from the head address of one line memory ( Refer to FIG. Therefore, the position information of both the position information in the main scanning direction and the position information in the sub scanning direction is stored simultaneously in one line memory, and it is not necessary to store the position information in the memory separately for the main scanning and the sub scanning. Can be shortened.

Further, in the case of the color image reading apparatus, since the shading correction memory has three colors, it is necessary to obtain the deviation amount for each of the three colors, but in the embodiment shown in FIG. , (C), (d),
The adjustment time can be further shortened by loading the position data of the three areas at a time into the memory.

Further, as shown in FIG. 5, even when the image position is calculated separately in the main scanning direction and the sub-scanning direction, in the case of the color image reading apparatus, the data of the adjacent lines are stored in memory for three colors. The adjustment time can be shortened by assigning to.

In the case of a color image reading apparatus, it is preferable to use green or magenta, which is the information closest to the luminance information, as the image position data.

[0050]

As described above, according to the present invention, the positional deviation of the image in the main scanning direction and the sub-scanning direction can be achieved without actual image forming operation
The function to detect magnification error and automatically adjust it can be realized without increasing the cost. Furthermore, there is no uncertainty by the operator when adjusting the positional deviation, and the adjustment work can be performed accurately in the minimum time. Since there is no subtle adjustment at the time of assembly and simplification, it is possible to contribute to a reduction in manufacturing cost and it is possible to obtain a good image with no positional deviation.

[Brief description of drawings]

FIG. 1 is a block diagram showing a basic configuration of an embodiment of an image reading apparatus of the present invention.

FIG. 2 is a block diagram showing a basic configuration of an image reading apparatus to which the present invention is applied.

FIG. 3 is a schematic diagram for explaining the operation of the shading correction circuit.

FIG. 4 is a flowchart illustrating a shading correction operation.

FIG. 5 is an explanatory diagram showing how the image data obtained by reading the displacement measurement image is stored in the shading memory.

FIG. 6 is a conceptual diagram for explaining reading position shift adjustment in the image reading apparatus of the present embodiment.

FIG. 7 shows an example of a block diagram embodying a shading correction circuit.

FIG. 8 is a timing chart showing a memory write timing in the case of reading in the main scanning direction.

FIG. 9 is a timing chart showing a memory write timing in the case of reading in the sub-scanning direction.

FIG. 10 shows a second embodiment of the image reading apparatus of the present invention.

FIG. 11 is a schematic diagram showing a basic configuration of a conventional image reading device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Imaging means, 2 ... Image processing means, 3 ... CPU, 4 ... Control means, 11 ... CCD sensor, 12 ... Analog processing circuit, 13 ... A / D converter, 14 ... Shading correction circuit, 15 ... Shading correction Memory, 16 ... Look-up table, 17 ... Color correction circuit, 18 ... Editing processing circuit, 19 ... Timing generator, 21 ... Address counter, 22 ... Divider

Claims (2)

[Claims] 1. An image pickup means for scanning a document to read image information, a first position storage means for storing the position of the image information read by the image pickup means, and a position for storing the image information in the document. Read position data; and second position storage means for calculating the difference between the position of the image information stored in the first position storage means and the position of the image information stored in the second position storage means. Read data valid signal generation means for generating a read data valid signal for instructing whether or not is valid, and read data valid signal generation control means for controlling the read data valid signal generation means based on the result of the calculation means. An image reading apparatus comprising: a scanning speed setting unit that sets a scanning speed of the imaging unit based on a result of the calculation unit. 2. The first position storage means is a memory for storing the image itself read by the image pickup means, and the second position storage means measures the position of the image for measuring the displacement of the document in advance. The image reading apparatus according to claim 1, wherein the image reading apparatus is a memory that stores a value obtained by the above.