JP3733227B2 - Image processing apparatus and method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image processing apparatus and method thereof, and more particularly to an image processing apparatus and method for performing shading correction.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in an image processing apparatus that reads a document image on a sheet, a line head type scanner unit in which photoelectric sensor groups are arranged by the width of the sheet size is arranged in a direction perpendicular to the arrangement direction of the sensor groups. The flat head type that reads the original while moving was the mainstream.
[0003]
This type is capable of high-speed and high-precision image reading, but requires a photoelectric sensor for the width of the paper, and is therefore unsuitable for personal use due to restrictions on the size and cost of the device.
[0004]
On the other hand, by arranging a photoelectric sensor in a direction parallel to the paper feed direction on the carrier portion on which the print head is mounted, not only printing but also image reading at a relatively low cost is possible. In recent years, personal word processors and the like equipped with a type of scanner-equipped printer unit have been commercialized.
[0005]
This serial type scanner will be described in more detail. By replacing the print head unit and the scanner unit, a group of photoelectric sensors arranged in parallel to the paper feed direction (Y-axis direction) is perpendicular to the paper feed direction. This is a method of reading an original by repeating an image input operation while moving in the direction (X-axis direction) and a paper feeding operation in which the photoelectric sensor group is moved relative to the original paper in the Y-axis direction.
[0006]
[Problems to be solved by the invention]
In the image processing apparatus for serial type image reading shown in the above conventional example, as shown in FIG. 2, the scanner unit is designed to have a size replaceable with the printer head. For this reason, compared with a flat head type scanner, more severe control is required for electrical noise and temperature characteristics.
[0007]
In particular, it greatly affects the shading correction function, which is one of the basic functions of the scanner. As shown in FIG. 5, the shading correction function is a function that compensates for a decrease in the amount of light at both ends of the light emitting unit and variations in light receiving characteristics of each light receiving element. In general, the reading value of a white reference value measurement document serving as a reference value (in the flat head type, the white reference measurement document is located outside the reading area) is used as shading correction data, that is, white reference data. use.
[0008]
In the data after shading correction by normal white reference data shown in the middle of FIG. 5, the read data corresponding to the black portion of the document is at a level close to 0 (absolute black), and the other is a decrease in the light amount at both ends of the issuing portion. Is corrected, and a relatively flat value is obtained. However, as shown in the lower part of FIG. 5, when noise occurs by chance during white reference measurement and shading correction is performed with the white reference data thereafter, the original portion corresponding to the noisy pixel is correct. The read image data cannot be obtained.
[0009]
It is difficult to clearly distinguish between a partial white reference value drop due to such electrical noise and a normal value based on the characteristics of the light receiving element. Is removed.
[0010]
For example, white reference data excluding the influence of noise is acquired by averaging a plurality of white reference measurement values. Specifically, the process of measuring the white reference value and sorting based on the size is repeated a plurality of times, and when sorting of the measured values for the total number of samples is completed, a predetermined number of parts are cut from the top and bottom, The white reference value is determined based on the average value based on the remaining number of samples.
[0011]
In this case, the larger the number of samples, the higher the noise removal rate, but at the same time, the problem of temperature characteristics arises. As shown in FIG. 6, the output of the LED, which is a light source, rapidly decreases after lighting in accordance with the temperature characteristic change of the electric elements in the scanner unit. Of course, the white reference measurement may be performed at a relatively stable timing (for example, 60 seconds after the LED is turned on). However, since the output characteristics of the LED are always changing, the measurement time of the white reference value is determined several times. Must be kept to the minimum necessary. Furthermore, considering the case where the white reference measurement point on the white reference document is dirty, as shown in FIG. 6, there must be a plurality of white reference value measurement points.
[0012]
As described above, in the measurement of the white reference value in the micro scanner unit as shown in FIG. 2, the time required from the first measurement at the first measurement point to the last measurement at the last measurement point. It is important to shorten the time.
[0013]
The present invention has been made to solve the above problems, and provides an image processing apparatus and method capable of reducing the processing time required for measuring the white reference value and determining the final white reference value. The purpose is to do.
[0014]
[Means for Solving the Problems]
As a means for achieving the above object, an image processing apparatus of the present invention comprises the following arrangement.
[0015]
That is, Arranged in line Image input means for reading and inputting a document image by a plurality of light receiving elements, and a reference by the input means concentration The document was scanned multiple times and entered Of the light receiving element Transfer means for transferring and storing a plurality of input values for each element in a predetermined area, and a plurality of input values stored in the predetermined area by the transfer means Sort by size for each element Process The average value is obtained by excluding a predetermined number of input values at both large and small ends, and Per element concentration Statistical means for determining a reference value, and determined by the statistical means The concentration Hold the reference value concentration Reference value holding means and the input value for each element by the input means concentration Based on the reference value shading Correction means for correcting, and in the transfer means Of the input value of the nth line Transfer / store processing and statistical means Sorting of input values of the n-1st line And control means for controlling the processing to be performed in parallel.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment according to the present invention will be described in detail with reference to the drawings.
[0018]
<First Embodiment>
[Device configuration]
FIG. 1 is a schematic view of a scanner device according to this embodiment. In the figure, reference numeral 1 denotes a scanner apparatus main body, 2 a scanner unit which is an image reading means, 3 a carrier unit for holding the scanner unit 2, and 4 digital image data A / D converted by the scanner unit 2. A flexible cable for transferring to a main control unit (not shown), 5 is a carrier drive unit for scanning the carrier unit 3 on which the scanner unit 2 is mounted in a direction perpendicular to the paper feed direction, and 6 is a document sheet. A paper feed unit for moving the carrier unit 3 in a direction perpendicular to the scanning direction, 7 is an input / output connector that provides a path for commands and image data between the host computer 8 and the scanner device 1, and 9 is for feeding original paper. This is a paper feed tray. In addition, as a unit not shown, the mechanical drive system such as the paper feed unit 6 and the carrier unit 3 is controlled, and the image data read by the scanner unit 2 is edited and processed as necessary to set the input / output connector 7. A main control unit or the like for transferring to the host computer 8 via the host computer 8 is provided.
[0019]
2 is an external perspective view of the scanner unit 2 shown in FIG. 1. The scanner unit 1 can be used as a printer by replacing it with a print head unit (not shown). The scanner unit 2 has a size of about 40 mm × 45 mm × 25 mm. It is an ultra-compact unit that integrates the basic functions of a scanner inside the unit. When the scanner unit 2 is mounted on the carrier unit 3, the terminal of the carrier unit 3 comes into contact with the terminal 10 of the scanner unit 2, and the scanner unit 2 and the main control unit are connected via the cable 4.
[0020]
FIG. 3 is a block diagram showing a detailed configuration of the scanner unit 2 shown in FIG. The scanner unit 2 includes a light emitting unit 11 that irradiates the reading surface, and 128 light receiving elements (first light receiving element to 128th light element) that are arranged at a density of 360 dpi in the paper feeding direction in order to receive reflected light from the reading surface. A light receiving unit 12 composed of a light receiving element), an A / D conversion unit 13 that converts an analog voltage by the light receiving unit 12 into a digital value, and an offset register 14 that holds an absolute black level from the value after A / D conversion. A subtracting unit 15 for subtracting the value, a shading correcting unit 17 for performing shading correction on the subtracted image data with the content (white reference value) held in the shading RAM 16, and final image data to the main control unit side The transfer unit 18 for serial transfer and the scan specified by the main control unit via the head register setting signal 20 are used. Various operations in the unit 2 (LED on / off, measurement of the offset value, the measurement of the white reference value, reading, etc. of the document) composed from the internal register setting unit 19 for controlling the. The light emitting unit 11 and the light receiving unit 12 constitute a scanner head 100.
[0021]
The head register setting signal 20 is also connected to the offset register 14 and the shading RAM 16, and has a circuit configuration that can be written from the main control unit side. The various operations described above executed in the scanner unit 2 are executed in synchronization with the synchronous clock CRST21 sent from the main control unit.
[0022]
FIG. 4 is a block diagram showing a detailed configuration of the scanner engine 22. In the figure, the scanner engine 22 is configured around an MPU 23 that performs main control. The MPU 23 is a so-called one-chip microcomputer that incorporates a ROM section in which operation procedures of the MPU 23, various tables for motor control, and the like are described, and an internal work RAM used for the calculation of the MPU 23 and the like. In the periphery of the MPU 23, there is a 1 megabyte external RAM 24 for storing the image data transferred from the scanner unit 2, and the image data from the scanner unit 2 is serial / parallel converted and then in the area of the external RAM 24 designated by the MPU 23. An image data storage control unit 25 that stores image data in order from a specified address, and a data bus 26 that includes an address line and a data line and enables access to the external RAM 24 area from both the MPU 23 and the image data storage control unit 25. In response to a control signal from the host PC interface control unit 27 and MPU 23 for receiving a command from the host computer 8 via the input / output connector 7 or transferring read image data to the host computer 8 Unit 3WD A stepping motor 28 for use, the motor driver 30 for controlling the current amount of the stepping motor 29 for paper feeding is disposed. Both the carrier and paper feed stepping motors 28 and 29 are designed with a gear ratio such that the carrier and the original paper move 1/360 inch by one pulse (one step) of the motor.
[0023]
The MPU 23, the image data storage control unit 25, and the scanner unit 2 are synchronized by a CRST (Column Read Start Timing) signal 21 output from the MPU 23. That is, every time the carrier unit 3 moves 1/360 inch, the MPU 23 outputs the CRST signal 21 as a one-shot signal, and the scanner unit 2 uses this signal as a trigger for image data for one column as an image clock signal (SCLK). 31 and the image data signal (SDATA) 32 are transferred to the image data storage controller 25 as serial data. The image data storage controller 25 stores the image data in the external RAM 24 via the data bus 26 in order from the top address indicated by the storage address after the transferred serial data is converted into 8 bits as a unit and converted into parallel data. Go.
[0024]
However, in cases other than the image data reading operation (offset scan, white reference measurement, etc.), the control on the carrier unit 3 side is cut off under the control of the MPU 23, and only the control on the scanner unit 2 side is executed.
[Basic processing for white reference value setting]
Hereinafter, the white reference value setting operation in the scanner apparatus 1 of the present embodiment will be described with reference to the flowchart of FIG. 7A.
[0025]
The white reference value held in the shading RAM 16 in the scanner unit 2 is lost when the scanner unit 2 is replaced or the scanner unit 2 is turned off. The MPU 23 manages power supply to the scanner unit 2 and always grasps whether or not the white reference value has been acquired.
[0026]
When a scan command is sent from the host computer 8, the MPU 23 returns a warning that the white reference value is not acquired if the white reference value is not acquired. Upon receiving this warning, the scanner driver on the host computer 8 side prompts the user to feed the white reference acquisition paper using a pop-up menu. The user sets the white reference paper in the paper feed tray and clicks the OK button on the pop-up menu. When the scanner driver detects that the OK button is clicked, it issues a white reference acquisition command to the scanner device 1, and the scanner device 1 executes white reference value acquisition processing based on the control flowchart shown in FIG. (Illustrated).
[0027]
The MPU 23 rotates the LF motor 29 via the motor control unit 30 and executes paper feeding until the white reference paper reaches sufficiently below the scanner unit 2 (for example, 1800 pulses (360 × 5 inches)) (S701). ).
[0028]
The MPU 23 rotates the carrier motor 28 to move the carrier unit 3 so that the reading position of the scanner unit 2 is 4 inches from the home position of the carrier unit 3 (hereinafter, point A) (S702).
[0029]
At this point (point A), the white reference value measurement process described later is executed, and the statistically processed white reference value final data stored in 128 bytes from 878000h of the external RAM 24 is transferred to 128 bytes from 878100h. (S703).
[0030]
The MPU 23 further moves the carrier unit 3 to the right by 360 pulses (S704), and executes the same processing as S703 at the point B, which is 1 inch away from the point A. The final data in 128 bytes from the 878000h of the external RAM 24 Is transferred to 878200h (S705).
[0031]
The MPU 23 further moves the carrier unit 3 to the right by 1 inch (S706), performs white reference value measurement processing at the point C as described above, and stores the final result in 878300h of the external RAM 24 (S707). Thus, the reason for measuring the white reference value at three points is to eliminate the influence of the stain on the surface of the white reference sheet.
[0032]
Three points of white reference values, the white reference value at point A (878100h), the white reference value at point B (878200h), and the white reference value at point C (878300h), stored as above in the external RAM 24 From this, the final white reference value α is calculated (S708), and this value α is written to the shading RAM 16 in the scanner unit 2 via the head register setting signal 20 (S709). Thereby, the white reference value setting process in this embodiment is completed.
[White reference value final data calculation process]
Details of the white reference value final data calculation process executed in S708 will be described below based on the flowchart of FIG. 7B.
[0033]
By the processing of S703, the white reference value measurement value at the first light receiving element of the light receiving unit 12 at point A is stored in 878100h of the external RAM 24, and the white reference value at the 128th light receiving element is stored in 87817Fh. Similarly, at the point B, the value at the first light receiving element is stored in 878200h, the value at the 128th light receiving element is stored in 87727Fh, and at the point C, the value of the first light receiving element is stored at 878300h and at the 128th light receiving element. Is stored in 87837Fh.
[0034]
When dirt or dust happens to be attached to the measurement point, the white reference value obtained by reading the portion is lower than the values at other points. Therefore, by comparing the white reference values of the same light receiving element at the three points A point, B point, and C point, and using the largest value as the white reference value of the light receiving element, the above-mentioned dirt and dust It becomes possible to eliminate the influence of. That is,
First, n indicating the light receiving element number is initialized with 1 (S711). Next, the size comparison is performed on the white reference values of the first (n) light receiving elements at the points A, B, and C stored in the RAM area at the address (S712). Then, the maximum value is adopted as the white reference value of the first (n) light receiving element and stored in 879000h (S713).
[0035]
Then, 1 is added to the light receiving element number n (S714), and when n is 128 or less, which is the number of light receiving elements on the scanner head 100, the process branches to step S712, and the white reference value for the next light receiving element is determined. The determination is repeated (S715). When n becomes 129, the white reference final data calculation process is terminated. As a result, the white reference values from the first light receiving element to the 128th light receiving element are sequentially stored in 128 bytes from 879000h of the external RAM 24.
[White reference value measurement processing]
Next, details of the white reference value measurement process executed in steps S703, S705, and S707 will be described.
[0036]
The present embodiment is characterized in that sorting processing of the white reference value measured last time is performed in parallel with the measurement and transfer processing of the white reference value. By this parallel processing, the processing time can be shortened as compared with the case where the measurement / transfer processing and the sorting processing are performed separately.
[0037]
First, the structure of the work RAM used in the white reference value measurement process and the sorting process described later will be described with reference to FIGS.
[0038]
As shown in FIG. 12, 6400 bytes (128 bytes × 50 bytes) from 80000h to 8618FFh on the external RAM 24 as a work area for automatically storing the white reference value measured on the scanner unit 2 side by the image data storage control unit 25. Times) area is secured. Note that the image data storage control unit 25 of the present embodiment is configured by an ASIC, and in the automatic storage by the ASIC to be described later, the white reference value of the first light receiving element in the first measurement is 860000h, and the 128th in the 50th time. The white reference value of the light receiving element is stored in 8618FFh. Hereinafter, the image data storage control unit 25 is referred to as ASIC 25.
[0039]
In this embodiment, the sorting process is executed in parallel with the automatic storage process by the ASIC (image data storage control unit 25). This sorting process is a process of rearranging the measured white reference values in order of size, and a work area of 3 blocks is used on the external RAM 24. Hereinafter, these three work areas will be described.
[0040]
First, 256 bytes from 872000h of the external RAM 24 are a work area (not shown) for calculating the accumulated white reference value. For example, 2 bytes from 872000h are 50 white reference measurements in the first light receiving element. The sum of the values will be stored.
[0041]
The following is the lower data storage area shown in FIG. The lower data in the first light receiving element is stored in 32 bytes from 870000h. 2 bytes are one set, Low Byte indicates the measured value, and High Byte indicates the measurement number. The work area can support up to 16 lower data, but is limited to 10 in this embodiment. By the sorting process described later, the array of 10 data stores 10 small white reference values among the white reference values in the light receiving element, and the largest white reference value among the 10 data is the leading address (first light receiving light). The element is stored in 2 bytes from 870000h).
[0042]
Similarly, for the higher data, a higher data storage area shown in FIG. 14 is prepared, and the white reference value and the number of times of measurement are measured for the 10 highest white reference measured values for each light receiving element. The number is one set and is stored in the area from 871000h to 871FFFh. The difference from the lower data storage area is that the smallest white reference value of 10 in the arrangement order of 10 is stored at the head address.
[0043]
Hereinafter, the white reference value measurement process of the present embodiment will be described in detail with reference to the flowchart of FIG.
[0044]
In the white reference value measurement process of the present embodiment, the measurement of the offset value and the white reference value, the start of transfer of the measurement value, and the like are performed via the head register setting signal 20 by the INT7 interrupt process described later. Controlled by commanding 2.
[0045]
First, a work area for sorting processing in the external RAM 24 is initialized with 00h for the lower data storage area, FFh for the higher data storage area, and 00h for the cumulative value calculation work area (S801). Next, the MPU 23 issues an LED turn-off command to the light emitting unit 11 of the scanner head 100 via the head register setting signal 20 (S802). Then, after waiting for 10 milliseconds until the afterglow is completely eliminated (S803), an offset flag to be referred to in the INT7 interrupt process described later is set (S804), the number of times of measurement n is set to 1, and the storage start of the automatic storage process by the ASIC An address (hereinafter, storage pointer P) is initialized with 860000h (S805). Hereinafter, the storage start address of the nth measurement value is represented by Pn.
[0046]
As described above, the internal operation of the scanner unit 2 basically operates in synchronization with the signal CRST21 sent from the MPU via the ASIC 25. In the scanner unit 2, the cycle of the CRST 21 corresponds to the white reference value measurement time, and the carrier unit 3 moves by one pulse (1 dot / 360 inches) in the cycle of the CRST 21 even during actual image reading. In other words, when 360 dpi reading is performed, the time for irradiating the document surface with a width of 1 dot becomes the cycle of CRST21. In the present embodiment, the 512 μs cycle is the CRST 21 cycle.
[0047]
In the offset value and white reference measurement processing in the scanner unit 2, the first two pulses are used for warm-up to clear the buffer in the scanner unit 2, and the actual measurement is performed after the third pulse. Is done. In this embodiment, the white reference value is measured at the seventh pulse, the offset value measurement result is stored in the offset register 14, and the white reference value measurement result is stored in the 128-byte shading RAM 16.
[0048]
Also, the process of automatically transferring the measured values in the offset register 14 and the shading RAM 16 to the external RAM 24 in the scanner engine 22 designated in step S805 via the ASCI 25 is executed in synchronization with the CRST 21. Also in this case, since it is sent via several stages of buffers, the actual storage timing in the external RAM 24 is five pulses after the scanner unit 2 and the ASIC 25 are instructed to start automatic transfer. For this reason, a total of 15 pulses of CRST21 output is set in the ASIC 25 for measurement and automatic transfer (S806).
[0049]
The start of measurement of the offset value and the white reference value and the start of transfer of the measurement value are controlled by being instructed to the scanner unit 2 via the head register setting signal 20 by the INT7 interrupt processing described later. Here, the generation of INT7 after two pulses of CRST21, which is the activation, is set in the ASIC 25 (S807).
[0050]
The ASIC 25 is instructed to start output of the CRST 21 (S808), polls a flag set in the final process of the INT7 process described later, and waits for the end of output of the CRST 21 (S809). When the CRST output ends, the same value as the contents of the offset register 14 in the scanner unit 2 is stored in 860000h of the external RAM 24. This value is transferred to an offset value calculation work (not shown) (S810), the number of times of measurement n is incremented by 1 (S811), and if the number of times of measurement n is 10 or less, the process branches back to step S806, where the offset value The measurement process is repeated (S812).
[0051]
When the offset measurement for 10 times is completed, the upper and lower two samples are cut for noise removal, and then the average value (β) of the remaining six samples is calculated (S813). By writing β to the offset register 14 in the scanner unit 2 via the head register setting signal 20, the setting process of the offset register 14 is completed (S814), that is, the absolute black level is determined.
[0052]
Next, the white reference value measurement process is started. The basic control is the same as the offset value setting process described above. However, in the case of acquiring the offset value, the LED of the light emitting unit 11 is turned off. However, in the case of acquiring the white reference value, the processing is performed in a state where the LED is lit. For this reason, the influence of noise and the temperature rise inside the scanner unit 2 is increased. For this reason, the number of times of measurement is 50, and a device for speeding up the processing procedure is incorporated.
[0053]
First, an LED lighting command is issued to the scanner unit 2 (S815). Then, after waiting for 10 milliseconds as a delay until command execution (S816), a white reference flag used in INT7 interrupt processing described later is set (S817). Then, the number of measurements and the storage address are set in the same manner as in the above-described step S805 (S818), and the 15-pulse CRST output is set in the ASIC 25 for white reference measurement and measurement value transfer (S 819 ) After setting the ASIC 25 to issue INT7 at the second pulse CRST21 (S820), the ASIC25 is instructed to start outputting CRST21 (S821), and the first white reference value measurement / transfer process is started. To do. Note that the measured white reference value is only held in the work area by the setting of the storage destination address in the step S818, and this work is included in the INT 7 described later. area The ASIC 25 is set with reference to the value of.
[0054]
Thereafter, the output of CRST 21 is awaited in the same manner as in step S809 (S822), the number of measurements is increased by 1 for the next measurement, and the storage destination address of automatic transfer by ASIC 25 is increased by 128 (S823). Here, as shown in FIG. 12, the white reference value of the first light receiving element is stored in 860000h and the white reference value of the 128th light receiving element is stored in 86007Fh in the first measurement, and 860080h (860000h + in the second measurement). The white reference value is stored in 128 bytes from 128).
[0055]
Then, processing similar to the processing from step S819 to S821 in the first measurement is performed, and the second measurement / transfer processing is started (S824, S825, S826).
[0056]
Here, a sorting process to be described later is executed for the 128-byte white reference value stored in the previous measurement / transfer process (S827). That is, in parallel with the n-th white reference measurement and transfer process by the scanner unit 2 and the ASIC 25, the MPU 23 executes a sorting process (statistical process) for the n-1th white reference measurement value. This sorting process will be described later.
[0057]
Steps S822 to S827 are repeated until the number of measurements exceeds 50 (S828). When 50 measurements are completed, lower data and higher data constructed as shown in FIGS. 13 and 14 are sorted by the sorting process. Similarly, the value of the lower data and the higher data is subtracted from the contents of the accumulated value work area accumulated by the sorting process, and the average value γ of 30 samples is calculated (S829). Then, the value of γ is stored in 128 bytes from 878000h of the external RAM 24 (S830), the white reference value measurement process is completed, that is, the absolute white level is determined.
[Sort processing (statistical processing)]
Details of the sorting process executed in step S827 will be described below with reference to the flowchart of FIG. By the single sorting process shown in this flowchart, among the 128 reference pixels × 50 white reference measurement values in the work area shown in FIG. It is checked whether it should be stored in the data storage area.
[0058]
First, the value of the white reference value head storage address in the previous measurement is set to P for convenience (S901). Next, as the light receiving element number m, the first light receiving element is handled as No. 0 (S902), the 128th light receiving element is handled as No. 127, and from the white reference value of the first light receiving element, accumulated value data, lower data, higher data Start updating.
[0059]
The white reference measurement value of the mth light receiving element is stored at the address P + m. This value is set as A for convenience in the register of the MPU 23 (S903). Then, A is added to the contents of the 2-byte cumulative value work area for the (m + 1) th light receiving element (S904).
[0060]
The head address of the lower data storage area for the (m + 1) th light receiving element is set to LT for convenience (S905). For example, the leading address LT of the lower data storage area for pixel number m = 2 (that is, the third light receiving element) is 870040h as shown in FIG.
[0061]
Then, the sorting work pointer LSP is initialized to 0 (S906), and the content of the address (LT + LSP) of the lower data storage area is set to B (S907). If the white reference measurement value A is smaller than the value B already stored in the lower data storage area (S908), the white reference measurement value A is added to the LSP by assuming that the white reference measurement value A should be stored in the lower data storage area. The process returns to step S907 until the LSP exceeds 20 (S910).
[0062]
If the white reference measurement value A is larger than the value B already stored in the lower data storage area in step S908, the check of whether A should be stored in the lower data storage area ends, and based on the LSP value at that time, The ten pieces of data in the mth pixel in the lower data storage area are rearranged (S911).
[0063]
When the sorting for the lower data storage area is completed in this way, the sorting for the higher data storage area is started next, which is substantially the same as the sorting for the lower data storage area described above, and thus detailed description is omitted. . However, the method of comparing the white reference measurement value A and the stored data B in step S915 is the reverse of that in step S908.
[0064]
As described above, the sorting of the mth pixel with respect to the higher data storage area is completed up to step S918. Subsequently, 1 is added to the pixel number m (S919), and the processing of steps S903 to S919 is repeated up to the 128th pixel (S920), whereby the white reference from the first pixel to the 128th pixel by one measurement is obtained. The measured values are sorted.
[INT7 interrupt processing]
In the following, the measurement is started by measuring the offset value (absolute black level) or the white reference value (absolute white level) during the white reference measurement process, and in parallel with the sorting process in the foreground, the background The INT7 interrupt process executed in step 1 will be described with reference to the flowcharts of FIGS.
[0065]
The INT7 interrupt is input from the ASIC 25 to the MPU 23 as an external interrupt when the number of outputs of the CRST 21 reaches the number set in the INT7 setting register in the ASIC 25. The processing that generates the INT7 interrupt includes the above-described three types of processing of offset value measurement, white reference value measurement, and image data reading. In the present embodiment, the processing for reading image data is described below. I will omit the explanation.
[0066]
● INT7 interrupt in offset value processing
With reference to FIG. 10, the INT7 interrupt in the offset value processing will be described.
[0067]
First, the offset flag set in step S804 of FIG. 8A is checked (S101), and in the case of 1, the offset processing after step S102 is executed.
[0068]
In step S806 of FIG. 8A, a 15-pulse CRST output is set. In this embodiment, of the 15 pulses, the offset value measurement start is performed at the second pulse, the offset value measurement end and the offset value read start are performed at the 7th pulse, and the offset value read end is performed at the 12th pulse. The scanner unit 2 must be commanded from the MPU 23 via 20. In order to determine these three types of control, a work area called INT7SN (Sequence Nomber) is used. That is, if INT7SN = 0, an offset value measurement start command is issued to the scanner unit 2 (S103), 1 is set in INT7SN for the next sequence (S104), and 5 is also used for starting the next sequence. The ASIC 25 is set so as to generate INT7 at the CRST21 after the pulse (S105), and the interrupt process is temporarily terminated.
[0069]
Then, after outputting 5 pulses of CRST21, INT7 is generated again, the same processing as in steps S101 and S102 is performed, and then the processing branches to processing of INT7SN = 1. In order to stop the measurement of the offset value commanded in step S103 to the scanner unit 2, an offset value measurement end command is issued (S106), and 2 is set in INT7SN for the next sequence (S107). Then, in order to automatically store the offset value by the ASIC 25, 860000h is set in the data storage address setting register in the ASIC 25 (S108). Similarly, the data storage control register in the ASIC 25 permits the offset value transferred from the scanner unit 2 to be stored in the external RAM 24 on the scanner engine 22 (set to 860000h in S108) (S109). Thereafter, an offset value read start command is issued to the scanner unit 2 so that the 1-byte offset value stored in the offset register 14 in the scanner unit 2 is transferred to the scanner engine 22 (S110).
[0070]
From the scanner unit 2, the 1-byte offset value is converted into 8-bit serial data and transferred to the scanner engine 22 side with a transfer clock of 2 megahertz. The number of transfers is one per CRST21. On the scanner engine 22 side, the serial data is once buffered in the ASIC 25, serially converted from 8-bit serial to 1 byte in the ASIC 25, and then stored in the address on the external RAM 24 set in step S108. . For this reason, even if a read start command is issued in step S110, data is not immediately stored in a predetermined address on the external RAM 24, and a delay corresponding to several pulses of the CRST 21 is required. In the present embodiment, the ASIC (image data storage control unit) 25 is designed so that data is stored in the external RAM 24 after 5 pulses of the CRST 21. For this reason, in order to start the offset value read end process, which is the next sequence in INT7, the ASIC 25 is set so that INT7 is generated again after outputting 5 pulses of CRST21 (S111), and the interrupt process is temporarily performed. finish.
[0071]
Then, after outputting 5 pulses of CRST21, INT7 is generated again, processing similar to steps S101 and S102 is performed, and processing branches to processing of INT7SN = 2. In order to stop reading the offset value (transfer of the offset value from the scanner unit 2 to the scanner engine 22 side) commanded to the scanner unit 2 in step S110, an offset value read end command is issued to the scanner unit 2 (S112). . Then, 3 is set in INT7SN for the next sequence (S113).
[0072]
The CRST output end flag is set in order to notify the foreground that the background processing has been completed (S114), and the INT7 interrupt processing relating to the offset value is completed.
[0073]
● INT7 interrupt in white reference value processing
With reference to FIG. 11, the INT7 interrupt in the white reference value processing will be described.
[0074]
If the offset flag is 0 and the white reference flag is 1 in step S101 of FIG. 10, the INT7 interrupt process for the white reference value shown in FIG. 11 is executed. The basic structure of the INT7 interrupt processing related to the white reference value is similar to the offset value interrupt processing described above.
[0075]
When INT7SN = 0, a white reference value measurement start command is issued to the scanner unit 2 (S117), 1 is set in INT7SN for the next sequence (S118), and 5 pulses are also used to activate the next sequence. The ASIC 25 is set so that INT7 is generated in the later CRST 21 (S119), and the interrupt process is temporarily terminated.
[0076]
After outputting 5 CRST pulses, INT7 occurs again, the same processing as in steps S101 and S116 is performed, and the processing branches to processing of INT7SN = 1. In order to stop the measurement of the white reference value commanded to the scanner unit 2 in step S117, a white reference value measurement end command is issued (S120), and 2 is set in INT7SN for the next sequence (S121).
[0077]
In the process of step S823 shown in FIG. 8B, the storage address of the white reference value being measured is held in the work area by the foreground process. With reference to the contents of this work area, the value (Pn) is set in the data storage address setting register in the ASIC 25 (S122). Then, storage of the white reference value by the ASIC 25 is enabled as in step S109 (S123), and a white reference value read start command is issued to the scanner unit 2 (S124).
[0078]
When this command is received, the white reference measurement value held in the 128-byte RAM inside the scanner unit 2 is subjected to parallel-serial conversion in order from 1-byte data corresponding to the first light receiving element, and a 128 × 8-bit serial number is obtained. Data is transferred to the ASIC 25 on the scanner engine 22 side with a transfer clock of 2 MHz. In the ASIC 25, the white reference measurement value is serial-parallel converted again, the white reference measurement value at the first light receiving element is referred to as the Pn address on the external RAM 24, and the measurement value at the second light receiving element is referred to as the Pn + 1 address. The data is stored sequentially. Then, in order to start the white reference value read end process, which is the next sequence in INT7, the ASIC 25 is set so that INT7 is generated again after CRST output after 5 pulses (S125), and the interrupt process is temporarily performed. finish.
[0079]
Then, after outputting 5 pulses of CRST21, INT7 occurs again, the same processing as in steps S101 and S116 is performed, and the processing branches to processing of INT7SN = 2. In order to stop the reading of the white reference value commanded to the scanner unit 2 in step S124 (transfer of the white reference value from the scanner unit 2 to the scanner engine 22), a white reference value read end command is issued to the scanner unit 2. (S126), 3 is set in INT7SN for the next sequence (S127). Then, in order to notify the foreground that the processing in the background has ended, the CRST output end flag is set (S128), and the INT7 interrupt processing relating to the white reference value is ended.
[0080]
The white reference value acquisition process of the present embodiment has been described above with reference to the flowcharts of FIGS. 8A to 11, and this timing chart is shown in FIG. According to the figure, while the n-th white reference value is measured and transferred by the scanner unit 2 and the ASIC 25 in the background, the n-1th white reference value is sorted in the foreground. I understand that.
[0081]
The effects obtained by performing such parallel processing are shown in FIG. In the figure, the upper part shows the total processing time required when the white reference value measurement / transfer process and the sorting process are divided, and the lower part shows the total processing time by the parallel processing of this embodiment. That is, according to the parallel processing of the present embodiment, the overall processing time can be shortened to the time required for 50 sorting processes as compared with the conventional division processing. At the same time, since the n + 1th white reference value can be measured immediately after the transfer of the white reference value measured at the nth time, the time for measuring the white reference value for 50 times is shortened.
[0082]
In the present embodiment, as an example of a method for removing the influence of noise, an example is described in which averaging is performed using values obtained by removing 10 samples from the upper and lower samples from 50 measurement data. It is not limited to the method, and it is also possible to perform more advanced statistical processing using, for example, standard differences. In this case, the sorting process in this embodiment may be changed to the statistical process.
[0083]
In the present embodiment, the monochrome scanner using the monochromatic LED as the light source of the scanner unit 2 has been described. However, for example, in the case of a color scanner using three types of light sources of R, G, and B, noise and temperature rise This problem is expected to become even more severe. Therefore, the present invention is more suitably applied to a color scanner, and the effect can be expected more.
[0084]
Further, in the present embodiment, the RAM address as each work area has been specifically described for the convenience of explanation, but of course, this address is not limited to the present embodiment.
[0085]
As described above, according to the present embodiment, the white reference value measurement time and the final white reference are obtained by performing statistical processing after performing the white reference value measurement / transfer processing and sorting processing in parallel. Processing time until the value is determined is shortened. Therefore, it is possible to calculate a white reference value that minimizes the influence of noise and LED output fluctuation accompanying the downsizing of the scanner unit 2.
[0086]
Then, by performing shading correction based on the white reference value, it is possible to read the image without unevenness.
[0087]
<Other embodiments>
Note that the present invention can be applied to a system including a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.), or a device (for example, a copier, a facsimile device, etc.) including a single device. You may apply to.
[0088]
Another object of the present invention is to supply a storage medium recording a program code of software for realizing the functions of the above-described embodiments to a system or apparatus, and the computer (or CPU or MPU) of the system or apparatus stores the storage medium. Needless to say, this can also be achieved by reading and executing the program code stored in the.
[0089]
In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention.
[0090]
As a storage medium for supplying the program code, for example, a floppy disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.
[0091]
Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an OS (operating system) operating on the computer based on the instruction of the program code. It goes without saying that a case where the function of the above-described embodiment is realized by performing part or all of the actual processing and the processing is included.
[0092]
Further, after the program code read from the storage medium is written into a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, the function expansion is performed based on the instruction of the program code. It goes without saying that the CPU or the like provided in the board or the function expansion unit performs part or all of the actual processing, and the functions of the above-described embodiments are realized by the processing.
[0093]
【The invention's effect】
As described above, according to the present invention, it is possible to set a highly accurate white reference value while suppressing the influence of noise and temperature characteristics of the scanner unit. Therefore, by performing shading correction using this white reference value, it is possible to read an image without unevenness.
[0094]
[Brief description of the drawings]
FIG. 1 is an external view of a scanner device according to an embodiment of the present invention.
FIG. 2 is an external view of a scanner unit in the present embodiment.
FIG. 3 is a block diagram showing a configuration of a scanner unit in the present embodiment.
FIG. 4 is a block diagram showing a configuration of a main control unit in the present embodiment.
FIG. 5 is a diagram illustrating shading correction.
FIG. 6 is a diagram illustrating an example of white reference value measurement points for shading correction.
FIG. 7A is a flowchart of white reference value setting processing in the present embodiment.
FIG. 7B is a flowchart of white reference value setting processing in the present embodiment.
FIG. 8A is a flowchart of white reference value measurement processing in the present embodiment.
FIG. 8B is a flowchart of white reference value measurement processing in the present embodiment.
FIG. 9 is a flowchart of a sorting process in the present embodiment.
FIG. 10 is a flowchart of interrupt processing (for offset value) in the present embodiment.
FIG. 11 is a flowchart of interrupt processing (for white reference value) in the present embodiment.
FIG. 12 is a diagram showing a white reference measurement value storage image in the present embodiment.
FIG. 13 is a diagram showing a lower data storage image in the present embodiment.
FIG. 14 is a diagram showing an image of storing higher data in the present embodiment.
FIG. 15 is a timing chart of white reference value measurement / transfer / sorting processing in the embodiment;
[Explanation of symbols]
1 Scanner device
2 Scanner unit
3 Carrier unit
4 Flexible cable
5 Carrier drive unit
6 Paper feed unit
7 I / O connector
8 Host computer
9 Paper tray
10 Scanner unit contact terminal
11 Light emitting part
12 Light receiver
13 Image data A / D converter
14 Offset register
15 Subtraction circuit
16 Shading data (white reference value) storage RAM
17 Shading correction part
18 Digital image data transfer unit
19 Internal register setting section
20 Head register setting signal
21 CRST (scanner unit / ASIC / MPU synchronization signal)
22 Scanner engine
23 MPU
24 External RAM for storing image data
25 Image data storage controller (ASIC)
26 Address data bus
27 Host PC interface controller
28 Carrier motor
29 LF motor
30 Motor controller
31 Image data transfer clock signal
32 Image data signal

Claims (9)

Image input means for reading and inputting a document image by a plurality of light receiving elements arranged in a line ;
Transfer means for transferring and storing a plurality of input values for each element of the light receiving element input by reading the reference density document a plurality of times by the input means in a predetermined area;
A plurality of input values stored in the predetermined area by the transfer means are sorted for each element according to the magnitude relationship, and an average value is obtained by excluding a plurality of predetermined input values for both large and small ends, and for each element. Statistical means for determining the concentration reference value of
A concentration reference value holding means for holding said concentration reference value determined by the statistical means,
Correction means for correcting shading the input value for each element by the input means based on the density reference value;
Control means for controlling the transfer / storage process of the input value of the nth line in the transfer means and the sort process of the input value of the n-1st line by the statistical means;
An image processing apparatus comprising: Said image input means and said concentration reference value holding means, and the correction means is provided in the detachable unit to the image processing apparatus, the input value by the input means to be temporarily held on the concentration reference value holding means The image processing apparatus according to claim 1, wherein: 3. The image processing apparatus according to claim 2 , wherein the transfer means transfers and stores a plurality of input values once held in the previous density reference value holding means in the unit to a predetermined area in the image processing apparatus. . The control unit controls the transfer / storage process in the transfer unit and the statistical process by the statistical unit to be performed in parallel by sending a predetermined synchronization signal and command to the unit. The image processing apparatus according to claim 2 . 3. The image processing apparatus according to claim 2 , wherein the control unit stores the reference value determined by the statistical unit in the density reference value holding unit in the unit.   The density reference value is determined by reading the plurality of times at a plurality of positions of the reference density document, and the maximum value among the density reference values at the plurality of positions for each element is held in the density reference value holding unit. The image processing apparatus according to claim 1, wherein: An image processing apparatus in which a unit including image input means for reading and inputting a document image by a plurality of light receiving elements arranged in a line is detachable,
Transfer means for transferring and storing a plurality of input values for each element of the light receiving element input by reading the reference density document a plurality of times by the input means in a predetermined area;
A plurality of input values stored in the predetermined area by the transfer means are sorted for each element according to the magnitude relationship, and an average value is obtained by excluding a plurality of predetermined input values for both large and small ends, and for each element. Statistical means for determining the concentration reference value of
Control means for controlling the transfer / storage process of the input value of the nth line in the transfer means and the sort process of the input value of the n-1st line by the statistical means;
Within the unit, the concentration reference value holding means for holding said concentration reference value determined by the statistical means,
In the unit, correction means for correcting shading the input value for each element by the input means based on the density reference value;
An image processing apparatus comprising: A measurement process in which a reference density original is read and input a plurality of times by a plurality of light receiving elements arranged in a line , and
A transfer step of transferring and storing a plurality of input values for each of the light receiving elements input in the measurement step in a predetermined area;
A plurality of input values stored in the predetermined area by the transfer step are sorted for each element in a size relationship, and an average value is obtained by removing a plurality of predetermined input values for each of the large and small ends, and for each element. A statistical process for determining the concentration reference value of
A holding step of storing the density reference value determined by the statistical process on the concentration reference value holding means,
A correction step of correcting the shading of the input value for each element based on the density reference value,
An image processing method , wherein the transfer process of the input value of the nth line and the sorting process in the statistical process of the input value of the n-1st line are performed in parallel. A computer-readable memory storing a program code for image processing in an image processing apparatus provided with an input means for reading a document image by a plurality of light receiving elements arranged in a line ,
A code of a measurement process for reading and inputting a reference density original document a plurality of times by the input means;
A transfer process code for transferring and storing a plurality of input values for each of the light receiving elements input in the measurement process in a predetermined area;
A plurality of input values stored in the predetermined area by the transfer step are sorted for each element in a size relationship, and an average value is obtained by removing a plurality of predetermined input values for each of the large and small ends, and for each element. A statistical process code for determining the concentration reference value of
And code holding step of storing the density reference value determined by the statistical process on the concentration reference value holding means,
A correction process code for correcting the shading of the input value for each element based on the density reference value,
The transfer process of the input value of the nth line by the code of the transfer process and the sort process in the transfer process of the input value of the n-1st line by the code of the statistical process are performed in parallel. Readable memory.

Images