JPH09186871A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image reader by which useless interruption of reading is avoided. SOLUTION: Shading data 601 written in a protect SRAM at preliminary scanning and shading data 602 read from a shading data and written in a DRAM at original reading are compared in an optional corresponding range. From n-th bit to an m-th bit from the head of both data are divided into d- divisions and blocks of divided bit string are compared to calculate a matching rate of data bits. Then the matching rate of each block is calculated based on (matching bit number)/(bit number of one block), and when the matching decision rate for a decided block exceeds the matching rate of all blocks, it is decided that the shading data in the shading memory is not destroyed.

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 reading an original image used in a facsimile machine or the like with an image sensor.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram showing an example of a conventional image reading apparatus. This device uses a CCD sensor as an image sensor.

The CCD sensor 2 converts the light quantity of the read original image into an electric quantity and outputs it, and is driven by a clock signal supplied from the driver circuit 4. CCD sensor 2
The image signal output from the amplifier is amplified to a proper level by the amplifier circuit 6, only the portion corresponding to the original image is extracted in the sample hold circuit 8, and the black output level of the image signal is biased in the processing circuit by the DC reproducing circuit 10. Match the voltage.

The peak hold ABC circuit performs the image binarization process in consideration of the background density of the original image (AB
C: AUTO BACKGROUND CONTROL
Therefore, the peak value of the output is detected during reading of one line, and the shading correction circuit 14 detects the CC value.
The non-uniformity of the output signal due to the variation of the light receiving sensitivity of the D sensor 2 and the deviation of the reading mechanism system is electrically corrected.

The corrected signal is sent to the A / D converter 16
By using the reference signals of the peak hold ABC circuit 12 and the shading correction circuit 14, the video signal after DC reproduction is binarized and the image data is output. The read control unit 18 manages and controls the clock timing and control signal timing of each of the above units, finally receives the image data binarized by the A / D converter 16, and performs image processing. The MPU 19
Is controlled by

FIG. 6 is a circuit diagram showing in detail the peak hold ABC circuit 12 and shading correction circuit 14 shown in FIG.

Here, 12 surrounded by a dotted line corresponds to a peak hold ABC circuit, and 14 corresponds to a shading correction circuit. The video signal 24 output from the DC reproducing circuit 10 is divided by the voltage dividing resistors 26 and 28,
It is input to the analog switch 30. The analog switch 30 is closed in the ABC range by the control output signal from the read control unit 18.

The comparator 32 compares the input video signal level with the current peak value and opens / closes the analog switch 36 according to the comparison result. The analog switch 36 is closed when the peak hold capacitor 38 for holding the peak value of the video signal is charged,
The peak value signal 42 is charged by the charging resistor 34 and discharged by the discharging resistor 38 by opening the analog switch 36.

The buffer amplifier 44 has a peak value signal 42.
Is input to the analog switch 46 via the charging resistor 45. The analog switch 46 is opened / closed by the memory read data signal 59, and is closed when the shading capacitor 52 is charged, and the charging resistor 45 is connected.
Is charged. Further, the analog switch 48 controls the memory read data 5 inverted by the inverter 50.
9, the shading capacitor 52 is closed when discharged, and discharged by the discharge resistor 54.

The comparator 56 compares the video signal 24 with the reference data 60 which is the discharge output from the shading capacitor 52, outputs the memory write data signal 57, and stores the shading correction data in the shading memory 58. Then, the memory read data 59 that is output from the shading memory 58 is output, and the analog switches 46 and 48 are opened and closed. Writing and reading of the shading correction data to and from the shading memory is controlled by the memory control signal 64 output from the read control unit 18.

The analog switch 66 is the comparator 3
The input signal to the (-) input 2 is switched between the peak value signal 42 and the reference signal 60. This switching is performed by the control output signal 6 output from the reading control unit 18.
6 is performed.

Next, the reading operation of the image pickup apparatus shown in FIGS. 5 and 6 will be described.

First, prior to the reading of the first page of the document, a prescan operation for reading a white reading background (reference white background) provided in the apparatus for storing a shading waveform for shading correction is performed. To do.

In FIG. 6, the analog switch 30 is closed by the ABC range signal 62, and the video signal 24 is input to the (+) input of the comparator. On the other hand, since the analog switch 66 is set to the peak value 42 side by the switch changeover signal 68, the held peak value 42 is input to the (−) input of the comparator 32. Signal)> (peak value), the analog switch 36 is closed, the peak hold capacitor 38 is charged through the charging resistor 34, and the peak value 42 is increased. Conversely (video signal)
If <(peak value), the analog switch 36 remains open and the peak value 42 does not change. As a result, finally the peak value 42 matches the peak value of the video signal 24.

The peak value 42 is stored in the buffer amplifier 44.
It is transmitted later via. Here, the comparator 56
Is the video signal 24 input to the (+) input,
The (-) input reference signal 60 is compared, and if (video signal)> (reference signal), the memory write data signal 57 becomes 1 (high), and if (video signal) <(reference signal), 0 (low). ).

In the pre-scan mode, the memory control signal 64 causes the comparator output 57 to be written in the memory 58 and at the same time output as the memory read signal 59. As a result, the memory read signal 59 becomes 1 (high
In the case of h), the analog switch 46 is closed, the analog switch 48 is opened, and the peak value 42 charges the shading capacitor 52 via the buffer amplifier 44 and the charging resistor 45. Conversely, the memory read signal 59
Is 0 (low), the analog switch 46 is opened, the analog switch 48 is closed, and the shading capacitor 52 is discharged through the discharge resistor 54.

By repeating the above-mentioned charging / discharging of the shading capacitor 52, a waveform which is similar to the video signal waveform of the current reading line by the charging / discharging of the shading capacitor 52 appears on the reference signal, and at the same time, this charging / discharging data is stored in the memory 58. (Shading data)
Is accumulated. Normally, it takes time to charge the peak hold capacitor 38 with the peak value, so the above prescan operation is repeated over several lines,
I am trying to get the shading data. Memory 5
8 can be backed up, but cannot directly access the MPU because it is not connected to the data bus of the entire system. Therefore, it cannot be protected.

Next, the actual document reading operation will be described. The ABC range signal 62 closes the analog switch 30 within the ABC range with respect to the document width, but in this example, (document width) = (ABC range), the analog switch 30 is closed during document reading. I shall.

Therefore, the original reading video signal 24 is
Although it reaches the (+) of the comparator 32, when the document is read, the analog switch 66 is operated by the switch switching signal 68.
Is set on the reference signal 60 side, the reference signal 60 is input to the (−) of the comparator 32, and the video signal 24 and the reference signal 60 are matched by opening and closing the analog switch 36 in the same manner as above by comparing both. To work.

On the other hand, by the memory control signal 64, the shading correction data stored previously for each line to be read is read from the shading memory 58, and analog data is read according to the shading data of 1 (high) and 2 (low). Switches 46, 48
Is opened and closed to reproduce the shading waveform obtained in the prescan for the reference signal 60 by charging and discharging the shading capacitor 52.

The reference signal thus obtained is input to the reference input (REF) of the A / D converter 16 shown in FIG. 5, while the video signal is input to the analog input (Vin) of the A / D converter 16. So
Accurate binarized image data that has undergone shading correction is obtained and sent to the reading control unit 18.

One page is read by repeating the above operation of one line in the sub-scanning direction.

[0023]

However, in the conventional image reading apparatus as described above, a reading mechanism for prescan operation such as a reading white background (reference white background) is provided in the apparatus, so that the structure is complicated. It has become a factor that hinders the cost increase and the freedom of the device design.

Further, in an image reading apparatus that holds shading data obtained by one pre-scan operation in a memory and uses the data permanently, a voltage drop of a backup battery or an abnormal voltage due to long-time power OFF. When the internal data of the shading memory was destroyed by (lightning surge, static electricity etc), a normal halftone image could not be obtained.

On the other hand, in the image reading apparatus which permanently uses the shading data, the same data bus is used as in the case where the normal reading operation is performed in order to judge whether or not the shading data is destroyed. Since the shading data in the image processing storage means is read, there is a case where the reading cannot be correctly performed with a probability of 100%.

Further, when the data can be read out 100% correctly, the shading data in the image processing storage means may be destroyed within a range where there is no problem in actual use. In these two situations, a comparison is made between the read shading data in the image processing storage means and the shading data held in the shading data confirmation means, and it is judged that the data has been destroyed, and actually, Was not destroyed, and there was a problem that fixed (straight line) shading data was selected even when there was no problem in actual use.

[0027]

The present invention has been made to solve the above problems, and is obtained by reading a document image into a read image signal and a reference member read by the reading unit. The first and second storage means for storing image data are compared with the image data respectively stored in the first and second storage means before the reading of the original image by the reading means, and the coincident bits are compared. Detecting means for detecting the destruction of the image data according to the number, and reading the original image by the reading means when the detecting means does not detect the destruction of the data, and the obtained image signal is stored in the first storing means. And a control means for controlling so as to perform correction using the image data stored in.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing an embodiment of the present invention. Further, FIG. 2 shows the peak hold ABC circuit and the shading correction circuit 14 of FIG.
FIG. 3 is a detailed circuit configuration diagram of a shading data confirmation circuit. 1 or 2, the same configurations as those of FIG. 5 or 6 which describe the conventional device are denoted by the same reference numerals and the description thereof will be omitted. However, the reading sensor 2
It is a contact sensor (CS).

In FIG. 1, memory protection means 13
Is the SRAM 71 connected to the system bus of FIG.
For protecting the memory without outputting the chip select signal.

The operation of the image reading apparatus according to this embodiment will be described with reference to the flowchart of FIG.

First, regarding the operation of shading data generation, the operation is performed in the pre-scan mode as in the prior art. The reading control unit 18 of FIG. 1 is set to the prescan mode, and in step S1, a message "Please set the white reference document" is displayed on the display unit 17. Then, in step S2, it is detected whether or not there is a white reference document, and in step S3, the analog switch 66 is set to the P side. In step S4,
The white reference document is fed to the reading position of the sensor, and in step S5, the white reference document is read. The reading position of the white reference on the white reference document is the position closer to the leading end in the range from the leading end of the document to the center of the document with respect to the flowing direction of the document.

A video signal is output from the sensor and input to the peak hold ABC section after direct current reproduction. The analog switch 66 is on the P side because of the prescan mode, and in step S6, the comparison result of the reference signal corresponding to the peak value of the video signal and the video signal, that is, the shading data is written in the shading memory 58. This is simultaneously output to the memory read signal 59 and input to the S / P conversion circuit 70. Where M
Using the DMA function of PU, the parallel shading data output from the S / P conversion circuit 70 is protected S
Write to RAM. When the reading of the white reference document is completed and the writing of the shading data to the protected SRAM is completed, the pre-scan mode ends. Then, in step S7, the memory 71 is set to the protected state by the memory protector 13 of FIG.
In step S8, the white reference document is ejected.

Next, the operation for confirming whether the data in the shading memory is destroyed will be described. This operation is always performed before reading the document every time.

First, in reading an original, the reading control unit 18 of FIG. 1 is set to the reading mode, and the memory control signal 64 is output from there. By this signal, the shading data is output from the shading memory 58 to the memory read signal 59. The shading data is converted into parallel data by the S / P conversion circuit and MP
It is written in the DRAM 73 using the U DMA function.

Here, the shading data written in the protect SRAM 71 during the prescan,
By comparing with the data written in the DRAM 73, it is determined whether or not the data in the shading memory is destroyed. FIG. 4 is a diagram for explaining this determination method. In FIG. 4, the shading data 601 written in the protect SRAM 71 during the pre-scan and the shading data 602 read from the shading memory and read in the DRAM 73 from the shading memory are compared in a corresponding arbitrary range. In the present embodiment, the n-th bit to the m-th bit from the beginning of both data are divided into d, and the one-value ratio of data bits is calculated between the blocks of the divided bit strings. In the comparison between the blocks, it is compared whether or not there is a match from the first bit of one block to the last bit of one block. Then, the matching rate for each block is calculated by (the number of matched bits) / (the number of bits of one block), and when the matching determination rate for each block exceeds a predetermined matching determination rate for all blocks. It is determined that the shading data in the shading memory has not been destroyed, and image processing is performed using the shading data in the shading memory 58 when reading the document.

Here, the coincidence determination ratio for each block is
The block on the leading side (the leading edge side of the document) of the shading data is the largest, and the matching determination ratio is gradually reduced toward the trailing edge side. This is because the bits 1 and 0 of the shading data correspond to charging / discharging (charging = 1, discharging = 0) of the shading capacitor in FIG. 6, so if the charging / discharging error occurs on the leading side, the entire shading waveform will be displayed. Is largely collapsed.

If it is determined that the data has been destroyed, the shading data switching signal 77 is output from the reading control section 18 to switch the analog switch 76 to the + VCC side, and the analog switch 1 (high).
Enter h). By doing so, the peak value of the document (image) charged in the peak hold capacitor 38 is charged in the shading capacitor through the analog switch 46. That is, the shading waveform for performing the shading correction has a constant value waveform (linear waveform) in which the peak value of the document is linear. Even in this case, the image quality is deteriorated, but it is possible to continue reading while ensuring a certain degree of quality.

In this case, the shading data is in error on the display means, and a message is displayed to the effect that a prescan is performed in order to register the shading data again. By performing a specific operation, the user can easily re-register the shading data by entering the shading data generation operation described above.

As described above, in the present embodiment,
The mechanism for prescan operation such as reading white background (reference white background) is deleted, the original reading mechanism is simplified, and the cost can be reduced. The reference may not be white but may be gray, for example. Also, the passage of documents (eg ADF)
Also improved reliability. The shading data created by scanning the white standard document is used for long-term power OFF.
If it is destroyed by the voltage drop of the backup power supply due to F or abnormal voltage (lightning surge, static electricity etc.),
Instead of using the shading data, the fixed (peak value of the image) shading data is used to reduce the image quality, but it is possible to maintain a certain quality and continue reading. In addition, the pre-scan operation was performed again, and shading data was newly created, thereby making it possible to restore the reading function to the initial performance.

[0040]

As described above, in the image reading apparatus according to the present invention, the reading means for converting the original image into the read image signal and the image data obtained by reading the reference member by the reading means are stored. The image data stored in each of the first and second storage means are compared with the image data stored in each of the first and second storage means before the reading of the original image by the reading means is started. Means for detecting the destruction of the document, and the document image is read by the reading means when the destruction of the data is not detected by the detecting means, and the obtained image signal is stored in the image data stored in the first storage means. And a control means for controlling so as to perform correction.

Since the destruction of the stored image data is detected according to the number of bits as described above, when the destruction is within the usable range of the data, the image using the data is not interrupted without interrupting the reading operation. Signals can now be corrected.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an image reading apparatus according to an embodiment.

FIG. 2 is a configuration block diagram of an image reading apparatus according to an embodiment.

FIG. 3 is a flowchart of a prescan operation in the embodiment.

FIG. 4 is an explanatory diagram of a data destruction determination method according to the embodiment.

FIG. 5 is a configuration block diagram of a conventional image reading apparatus.

FIG. 6 is a configuration block diagram of a conventional image reading apparatus.

[Explanation of symbols]

 14 Shading correction circuit 71 Protect S-RAM 72 MPU 73 D-RAM

Claims (5)

[Claims] 1. A reading unit for converting a document image into a read image signal, first and second storage units for storing image data obtained by reading a reference member by the reading unit, and a document by the reading unit. Before starting image reading, the first
And detecting means for comparing the image data respectively stored in the second storage means and detecting the destruction of the image data according to the number of coincident bits, and the reading when the destruction of the data is not detected by the detecting means. An image reading apparatus, and a control unit that controls so that the obtained image signal is corrected using the image data stored in the first storage unit. . 2. The image processing apparatus according to claim 1, wherein when the detection unit detects the destruction of the image data, the image is obtained by using predetermined image data other than the image data stored in the first and second storage units. An image reading apparatus characterized in that the control means controls so as to correct a signal. 3. The image data obtained by reading the white reference by the reading means before the start of reading the original image is used when the detection means detects the destruction of the image data. An image reading apparatus characterized in that the control means controls so as to correct the image signal. 4. The detecting means according to claim 1, wherein the detecting means divides a bit string of image data stored in each of the first and second storing means into a plurality of blocks and compares the corresponding blocks. An image reading device characterized by. 5. The method according to claim 4, wherein the ratio of the number of matching bits, which serves as a criterion for the data destruction judgment by the detecting means, is more matched in the end block than in the ratio of the first block among the divided blocks. An image reading apparatus characterized in that a ratio of performing is set small.