JP2004297128A - Image reading apparatus, image reading program and image reading method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reading apparatus, an image reading program, and an image reading method for reading an original of a read object with an optimum exposure amount even when a spot exists in the original of the reading object. <P>SOLUTION: The image reading apparatus includes: a lighting means for lighting an original with a prescribed exposure amount; a preliminary read means for preliminarily reading an image of the original lighted by the lighting means to obtain image data; a division means for dividing the image data obtained by the preliminary read means into a plurality of regions; an extract means for extracting a maximum luminance value in the regions for each of the regions divided by the division means; an average calculation means for calculating the average of the maximum luminance values of the regions extracted by the extract means; an exposure determination means for determining the exposure amount by the lighting means in main reading; and a main reading means for causing the lighting means to light the original with the exposure amount determined by the exposure determination means and reading the image of the original to obtain image data. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image reading apparatus that reads an image of a document, an image reading program for causing a computer to control the image reading apparatus, and an image reading method.
[0002]
[Prior art]
In an image reading apparatus that reads an image of a document, a preliminary scan (so-called pre-scan) is performed before the main scan to determine an exposure amount during the main scan. Specifically, a pre-scan is performed with a predetermined exposure amount, and the maximum luminance value in the obtained image data is obtained. The exposure amount at the time of the main scan is multiplied by an appropriate multiple of the exposure amount at the time of the prescan so that the obtained maximum luminance value coincides with the maximum value that can be obtained by the A / D conversion (255 for 256 gradations). Amount.
[0003]
[Problems to be solved by the invention]
When an image is read using such an image reading apparatus, if there is a bright spot in the document, the exposure amount at the time of the main scan is determined so as to match the bright spot. For this reason, if the difference in luminance level between the bright spot and the portion other than the bright spot is large, the exposure amount is insufficient, and the entire image obtained by reading may be dark.
[0004]
SUMMARY OF THE INVENTION An object of the present invention is to provide an image reading apparatus, an image reading program, and an image reading method capable of performing reading with an optimal exposure amount even if a bright spot exists in a document to be read.
[0005]
[Means for Solving the Problems]
The image reading apparatus according to claim 1, an illumination unit that illuminates the original with a predetermined exposure amount, a preliminary reading unit that preliminary reads an image of the original illuminated by the illumination unit and obtains image data, A dividing unit that divides the image data obtained by the preliminary reading unit into a plurality of regions; an extracting unit that extracts a maximum luminance value in the region for each of the regions divided by the dividing unit; Average value calculating means for calculating an average value of the maximum luminance value for each area extracted by the above, and the exposure amount by the illumination means at the time of main reading based on the average value calculated by the average value calculating means An exposure amount determining means for determining the amount of light; illuminating the original by the illumination means with the exposure amount determined by the exposure amount determining means; reading an image of the original to obtain image data; Characterized by comprising preparative means.
[0006]
2. The image reading apparatus according to claim 1, wherein the division unit divides the image data obtained by the preliminary reading unit into at least one of a main scanning direction and a sub scanning direction. In the direction of.
An image reading apparatus according to a third aspect is the image reading apparatus according to the first or second aspect, wherein the number of divisions by the division unit is variable.
[0007]
An image reading program according to claim 4, comprising: an illuminating unit for illuminating the original with a predetermined exposure amount; and a reading unit for reading an image of the original illuminated by the illuminating unit and obtaining image data. A program for realizing control of the apparatus by a computer, wherein a preliminary reading procedure of preliminarily reading an image of the document illuminated by the illuminating means and obtaining image data; and A division procedure of dividing image data into a plurality of areas, an extraction procedure of extracting a maximum luminance value in the area for each of the areas divided by the division procedure, and a maximum of each of the areas extracted by the extraction procedure. An average value calculating step of calculating an average value of the luminance values, and based on the average value calculated by the average value calculating step, the illumination unit at the time of the main reading is used. An exposure amount determining step of determining the exposure amount, and a main reading step of illuminating the original by the illumination means with the exposure amount determined by the exposure amount determining step, reading an image of the original, and obtaining image data. Are realized by a computer.
[0008]
An image reading method according to claim 5, wherein an illumination step of illuminating the original with a predetermined exposure amount, a preliminary reading step of preliminary reading an image of the original illuminated by the illumination step and obtaining image data, A dividing step of dividing the image data obtained in the preliminary reading step into a plurality of areas; an extracting step of extracting a maximum luminance value in the area for each of the areas divided by the dividing step; An average value calculating step of calculating an average value of the maximum luminance value for each of the regions extracted by the method, and the exposure amount by the illumination step at the time of main reading based on the average value calculated by the average value calculating step. An exposure amount determining step of determining the amount of light, illuminating the original by the illumination step with the exposure amount determined by the exposure amount determining step, reading an image of the original, and obtaining image data. Characterized by comprising a preparative process.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Hereinafter, as an example of the image reading apparatus of the present invention, an image reading apparatus that reads an image printed on a film document by transmitted illumination will be described.
<< 1st Embodiment >>
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.
[0010]
FIG. 1 is a block diagram illustrating a configuration of the image reading apparatus according to the first embodiment.
As shown in FIG. 1, the image reading device 1 includes a scanner main body 2 and an adapter 4 for holding a film original 3. The adapter 4 is detachable from the scanner main body 2 and is attached to the scanner main body 2 by being inserted into the slot 5 of the scanner main body 2.
[0011]
As shown in FIG. 1, an optical block 6, a motor 7, and a control unit 8 are provided in the scanner main body 2.
The optical block 6 includes an illumination light source 9 disposed above the slot 5, a lens 10 disposed below the slot 5, and a line CCD 11.
[0012]
The illumination light source 9 is composed of light-emitting diodes (LEDs) of each color of RGB, and is sequentially turned on or off according to a drive signal (described later) from an LED drive circuit 12 constituting the control unit 8. The exposure time changes according to the interval of the drive signal from the LED drive circuit 12. By changing the exposure time, the amount of exposure from the illumination light source 9 to the film original 3 can be changed.
[0013]
The illumination light from the illumination light source 9 is linear light along the x direction (main scanning direction) in FIG. For this reason, the optical path of the illumination light from the illumination light source 9 and the film original 3 intersect at a predetermined line along the x direction (hereinafter, referred to as a “read line 13”).
The lens 10 forms an image of the linear light guided below the film original 3 via the reading line 13 on the imaging surface of the line CCD 11.
[0014]
The line CCD 11 is an image sensor in which a plurality of pixels are arranged one-dimensionally in the x direction, and accumulates charges corresponding to incident light in each pixel. The electric charge accumulated in each pixel of the line CCD 11 is transferred through a transfer path in accordance with a drive signal (described later) from a CCD drive circuit 14 constituting the control unit 8, and is output to the outside as an analog image signal.
[0015]
The motor 7 moves the optical block 6 stepwise at fine intervals in the y-direction (sub-scanning direction) based on a drive signal (described later) from a motor drive circuit 15 constituting the control unit 8. When the optical block 6 is moved in the y direction by the motor 7, the above-mentioned read line 13 also moves in the y direction.
The control unit 8 includes a signal processing circuit 16, an A / D converter 17, a CPU 18, a ROM 19, a memory 20, and an external interface 21 in addition to the LED drive circuit 12, the CCD drive circuit 14, and the motor drive circuit 15 described above. ing.
[0016]
Each of the LED driving circuit 12, the CCD driving circuit 14, and the motor driving circuit 15 outputs a driving signal in accordance with an instruction from the CPU 18.
The signal processing circuit 16 performs signal processing such as amplification on the analog image signal output from the line CCD 11 and outputs the analog image signal to the A / D converter 17. The A / D converter 17 converts the analog image signal processed by the signal processing circuit 16 into a digital signal, and outputs the digital signal to the CPU 18 as digital image data for one line. This image data is temporarily stored in the memory 20.
[0017]
The CPU 18 executes various controls in the image reading apparatus 1 while referring to control programs and various data stored in the ROM 19. The control program stored in the ROM 19 includes a program describing a procedure for reading an image of the film original 3 held by the adapter 4.
The external interface 21 is a driver (for example, a SCSI interface) for connecting the image reading apparatus 1 of the present invention to an external host computer 22. The image reading apparatus 1 is connected to an external host computer via the external interface 21. 22.
[0018]
Note that the host computer 22 is also provided with an operation unit (not shown) such as a keyboard that receives a user operation such as an instruction to execute prescan and main scan.
A general flow of reading an image in the image reading apparatus 1 having the above-described configuration will be described with reference to FIG.
[0019]
When a power supply (not shown) is turned on, in step S1, the CPU 18 performs an initial operation via each unit.
Here, the initial operation is a process of moving the optical block 6 in the scanner main body 2 to a predetermined reading start position.
In step S2, the CPU 18 determines whether or not an instruction to set the film original 3 and pre-scan has been issued. The determination as to whether or not the film original 3 has been set is realized by a sensor (not shown) for detecting the presence or absence of the film original 3 provided in the adapter 4. It is assumed that the processing is performed via the operation unit of the computer 22. The set film original 3 is automatically positioned at a predetermined position.
[0020]
Then, the CPU 18 repeats the step S2 until the setting of the film original 3 and the instruction of the prescan are performed.
In step S3, the CPU 18 performs pre-scanning and exposure amount determination processing via each unit. Note that the pre-scan is performed at a predetermined resolution lower than the main scan. The exposure amount determination process is a process of determining the exposure amount during the main scan based on the result of the prescan (details will be described later).
[0021]
In step S <b> 4, the CPU 18 determines whether or not the user has issued a main scan instruction via the operation unit of the host computer 22. Then, the CPU 18 repeats the step S4 until a main scan instruction is issued.
In step S5, the CPU 18 performs a main scan via each unit under the exposure time according to the exposure amount determined in step S3 and other predetermined conditions (such as resolution).
[0022]
In step S6, the CPU 18 outputs the image data obtained by the main scan to the external host computer 22 via the external interface 21, and ends a series of processing.
Here, the pre-scanning and exposure amount determination processing performed in step S3 will be described with reference to FIGS.
[0023]
When a pre-scan instruction is issued via the operation unit of the host computer 22, in step S11, the CPU 18 reads one line via each unit.
That is, the CPU 18 outputs a drive signal to the LED drive circuit 12 and the CCD drive circuit 14 to read one line. Image data read by the line CCD 11 is output to the CPU 18 via the signal processing circuit 16 and the A / D converter 17. Then, the CPU 18 records the image data for one line in the memory 20, sets the value of a counter (not shown) in the memory 20 to 1, and proceeds to step S12.
[0024]
In step S12, the CPU 18 equally divides one line of image data into P groups (1 group to P group), obtains the maximum luminance value for each group, and stores the maximum luminance value in a block in the memory 20. Record as
Here, as shown in FIG. 4, the blocks are respective areas when the image data to be read is equally divided in P in the x direction and equally divided in Q in the y direction. It is assumed that the number of divisions P in the x direction and the number of divisions Q in the y direction are recorded in the memory 20 in advance.
[0025]
As shown in FIG. 4, when all image data at the time of completion of reading is composed of image data of m pixels in the x direction and image data of n lines in the y direction, one block is in the x direction. Is composed of image data for (m ÷ P) pixels, and in the y direction is composed of image data for (n ラ イ ン Q) lines.
Hereinafter, P blocks arranged in the x direction are collectively referred to as a “block group”.
[0026]
The CPU 18 first equally divides one line of image data into one group to a P group. Next, the CPU 18 obtains the maximum value of the luminance for each group. Then, the CPU 18 records the obtained maximum value as the maximum luminance value in the block in the memory 20 in association with the group numbers 1 to P.
In step S13, the CPU 18 reads the next line.
[0027]
That is, the CPU 18 outputs a drive signal to the motor drive circuit 15 and moves the optical block 6 to a position where the next line is read. Then, as in step S11, the CPU 18 reads one line via each unit. Then, the CPU 18 records the obtained image data in the memory 20, increases the value of a counter (not shown) in the memory 20 by 1, and proceeds to step S14.
[0028]
In step S14, as in step S12, the CPU 18 equally divides one line of image data into P groups, and obtains the maximum value of luminance for each group.
In step S15, the CPU 18 determines whether the maximum luminance value in the block recorded in the memory 20 is smaller than the maximum luminance value obtained in step S14. If the maximum luminance value in the block is smaller, the CPU 18 proceeds to step S16. If the maximum luminance value in the block is larger, the CPU 18 proceeds to step S17.
[0029]
In step S16, the CPU 18 replaces the maximum luminance value in the block recorded in the memory 20 with the maximum luminance value obtained in step S14.
That is, the CPU 18 records the maximum luminance value obtained in step S14 in the memory 20 as a new maximum luminance value in a block.
The processing described in steps S15 and S16 is performed for each group. That is, the replacement of the maximum value is performed only for the group whose maximum luminance value in the block is smaller than the maximum value of the luminance obtained in step S14.
[0030]
In step S17, the CPU 18 determines whether reading of (n ÷ q) lines (for one block group) has been completed.
That is, the CPU 18 determines whether reading of (n 分 の q) lines has been completed by determining whether the value of the counter in the memory 20 has reached (n ÷ q) times. Then, when the reading of (n） q) lines is completed, the CPU 18 proceeds to step S18.
[0031]
On the other hand, if the reading for (n ÷ q) lines is not completed, the CPU 18 returns to step S13, and repeats the processing of steps S13 to S17 until the reading for (n ÷ q) lines is completed. .
In step S18, the CPU 18 determines whether reading of all the block groups has been completed.
[0032]
For example, the memory 20 is provided with a counter (not shown) for counting the number of blocks to be read, and the CPU 18 determines that the value of the counter has reached Q (the number of all block groups) times. By determining whether or not reading has been completed, it is determined whether or not reading of all the block groups has been completed.
When the reading for all the block groups is completed, the process proceeds to step S20, and when the reading for all the block groups is not completed, the process proceeds to step S19.
[0033]
In step S19, the CPU 18 sets the next block group to be read.
First, the CPU 18 outputs a drive signal to the motor drive circuit 15 and moves the optical block 6 to a position where the next line is read. Then, the CPU 18 returns to step S11, and repeats the processing of steps S11 to S19.
[0034]
Therefore, the CPU 18 repeats the processing of steps S11 to S19 until reading of all the block groups (all the lines) is completed, and obtains the maximum intra-block luminance value for all the blocks.
In step S20, the CPU 18 reads out the maximum luminance values in the (P × Q) blocks recorded in the memory 20, and obtains an average value.
[0035]
In step S21, the CPU 18 determines an exposure amount during the main scan based on the average value obtained in step S20.
The CPU 18 determines the exposure amount at the time of the main scan so that the average value obtained in step S20 matches the maximum value that can be obtained by A / D conversion (255 for 256 gradations). Then, the CPU 18 records the determined exposure amount in the memory 20, and ends a series of processing.
[0036]
As described above, according to the first embodiment, image data obtained by pre-scan is divided into a plurality of blocks. Then, the maximum luminance value in the block is obtained for each block, and the average value of the luminance values is calculated. Then, the exposure amount at the time of the main scan is determined based on the average value. Therefore, even if there is a bright spot in the document to be read, reading can be performed with an optimal exposure amount.
[0037]
<< 2nd Embodiment >>
Hereinafter, a second embodiment of the present invention will be described with reference to the drawings.
The configuration of the image reading apparatus according to the second embodiment is the same as that of the first embodiment, and a description thereof will be omitted. Hereinafter, the description will be given using the same reference numerals as those of the first embodiment.
However, in the second embodiment, a CPU (not shown) of the host computer 22 (hereinafter, referred to as “host-side CPU”) and a memory (hereinafter, “host-side memory”) are used for various controls in the image reading device 1. ), And ROM. The host CPU executes various controls in the image reading device 1 while referring to control programs and various data stored in the ROM of the host computer 22. The control program stored in the ROM of the host computer 22 includes a program describing a procedure for reading an image of the film original 3 held by the adapter 4.
[0038]
The general flow of image reading in the image reading apparatus 1 of the second embodiment is the same as that of the first embodiment, and a description thereof will be omitted. However, a series of processes for reading an image in the second embodiment is performed based on an instruction from the host CPU.
Hereinafter, a prescan and an exposure amount determination process, which is different from the process in the image processing apparatus 1 of the first embodiment, will be described with reference to FIGS. 4 and 5.
[0039]
When a pre-scan instruction is issued via the operation unit of the host computer 22, in step S31, the host-side CPU reads one line via each unit.
[0040]
The host CPU first outputs a drive signal to the LED drive circuit 12 and the CCD drive circuit 14 to read one line.
In step S32, the host-side CPU transfers one line of image data to the host computer 22 via the signal processing circuit 16, the A / D converter 17, and the external interface 21. Then, one line of image data input from the scanner main body 2 is recorded in the host side memory, the value of a counter (not shown) in the host side memory is set to 1, and the process proceeds to step S33.
[0041]
In step S33, the host-side CPU determines whether reading for all lines has been completed.
The host-side CPU determines whether reading of all the lines has been completed by determining whether the value of the counter in the host-side memory has reached the total number of lines (n in FIG. 4). . If the reading of all the lines has been completed, the process proceeds to step S34. If the reading of all the lines has not been completed, the process returns to step S31, and the processes of steps S31 to S33 are repeated.
[0042]
In step S34, the host-side CPU equally divides the image data recorded in the host-side memory into (P × Q) blocks as shown in FIG. Here, P is the number of divisions in the x direction (main scanning direction) recorded in the host side memory in advance, and Q is the number of divisions in the y direction (sub scanning direction) recorded in the host side memory in advance. This is the number of divisions.
[0043]
In step S35, the host-side CPU obtains the maximum value of the luminance for each block, and records it in the host-side memory as the maximum luminance value in the block. Therefore, the maximum luminance value in the (P × Q) blocks is recorded in the host side memory.
In step S36, the host-side CPU reads the maximum luminance value in the (P × Q) blocks recorded in the host-side memory, and obtains an average value.
[0044]
In step S37, the host CPU determines the exposure amount during the main scan based on the average value obtained in step S36, as in step S21 of the first embodiment.
Then, the host CPU records the determined exposure amount in the host memory, and ends a series of processing.
[0045]
As described above, according to the second embodiment, the image data obtained by the pre-scan is transferred to the host computer 22 and divided into a plurality of blocks. Then, the maximum luminance value in the block is obtained for each block, and the average value of the luminance values is calculated. Then, the exposure amount at the time of the main scan is determined based on the average value. Therefore, even if there is a bright spot in the document to be read, reading can be performed with an optimal exposure amount.
[0046]
In particular, the processing time can be shortened by transferring the obtained image data to the host computer 22 while performing the pre-scan and performing the processing collectively after the end of the pre-scan.
In the second embodiment, an example is shown in which the data is transferred to the host computer 22 every time one line is read. However, the memory 20 in the scanner body 2 is used as a buffer memory, and the data is transferred to the host computer 22 in a predetermined amount at a time. You may do it.
[0047]
Further, in each of the above embodiments, the number of divisions P in the x direction (main scanning direction) and the number of divisions Q in the y direction (sub scanning direction) are predetermined values, but may be variable. In this case, the number of divisions may be set by a user operation, or the number of divisions may be automatically set according to the user's request for accuracy and speed. For example, the number of divisions may be increased when a user requests high-precision reading, and the number of divisions may be decreased when a high-speed reading is requested.
[0048]
In particular, in the second embodiment, at the time when the pre-scan is completed, a luminance histogram of the image data is obtained, and the number of divisions may be increased if a bright spot exists by analyzing the histogram. In each of the above embodiments, the example in which the film original is read using the transmitted illumination is described, but the combination of the original to be read and the illumination may be any combination.
[0049]
Further, in each of the above embodiments, the example in which the exposure time at the time of the main scan is changed according to the exposure amount determined based on the result of the pre-scan has been described. Alternatively, the light amount of the illumination light source 9 during the main scan may be changed according to the determined exposure amount. Further, both the exposure time during the main scan and the light amount of the illumination light source 9 may be changed.
[0050]
Further, in each of the above embodiments, the example in which the optical block 6 is moved and the relative positional relationship between the optical block 6 and the film original 3 is changed has been described, but the film original 3 may be moved, Both the optical block 6 and the film original 3 may be moved.
[0051]
【The invention's effect】
As described above, according to the present invention, there is provided an image reading apparatus, an image reading program, and an image reading method capable of reading with an optimal exposure amount even if there is a bright spot in a document to be read. Can be provided.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of an image reading device according to a first embodiment.
FIG. 2 is a flowchart showing a rough flow of image reading in the image reading apparatus according to the first embodiment; FIG. 3 is a flowchart showing a control procedure of the image reading apparatus at the time of pre-scan and exposure amount determination processing.
FIG. 4 is a diagram illustrating division of image data obtained by prescan.
FIG. 5 is a flowchart illustrating a control procedure of the image reading apparatus at the time of prescan and exposure amount determination processing.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Image reading apparatus 2 Scanner main body 3 Film original 4 Adapter 5 Slot part 6 Optical block 7 Motor 8 Control part 9 Illumination light source 10 Lens 11 Line CCD
12 LED drive circuit 13 read line 14 CCD drive circuit 15 motor drive circuit 16 signal processing circuit 17 A / D converter 18 CPU
19 ROM
Reference Signs List 20 memory 21 external interface 22 host computer

Claims (5)

Illuminating means for illuminating the document with a predetermined exposure amount;
Preliminary reading means for preliminary reading an image of the document illuminated by the illuminating means and obtaining image data;
Dividing means for dividing the image data obtained by the preliminary reading means into a plurality of areas;
Extracting means for extracting a maximum luminance value in the area for each of the areas divided by the dividing means,
Average value calculation means for calculating the average value of the maximum luminance value for each area extracted by the extraction means,
Based on the average value calculated by the average value calculation means, the exposure amount determination means for determining the exposure amount by the illumination means at the time of the main reading,
An image reading apparatus, comprising: a main reading unit that illuminates the document by the illuminating unit with the exposure amount determined by the exposure amount determining unit, reads an image of the document, and obtains image data. The image reading device according to claim 1,
The image reading apparatus according to claim 1, wherein the dividing unit divides the image data obtained by the preliminary reading unit in at least one of a main scanning direction and a sub-scanning direction. The image reading device according to claim 1 or 2,
The number of divisions by the division means is variable. Illuminating means for illuminating the document with a predetermined exposure amount;
A computer-readable storage medium storing a program for reading an image of the document illuminated by the illuminating unit and controlling the image reading apparatus including a reading unit configured to obtain image data,
Preliminary reading procedure for preliminary reading an image of the document illuminated by the illuminating means and obtaining image data;
A division procedure of dividing the image data obtained by the preliminary reading procedure into a plurality of areas;
An extracting step of extracting a maximum luminance value in the area for each of the areas divided by the dividing procedure,
An average value calculation step of calculating an average value of the maximum luminance value for each area extracted by the extraction step,
Based on the average value calculated by the average value calculation step, an exposure amount determination step of determining the exposure amount by the illumination unit at the time of main reading,
Image reading wherein the document is illuminated by the illuminating means with the exposure amount determined by the exposure amount determining step, an image of the document is read, and a main reading step of obtaining image data is realized by a computer. program. An illumination step of illuminating the original with a predetermined exposure amount,
Preliminary reading step of preliminary reading an image of the document illuminated by the illumination step and obtaining image data;
A dividing step of dividing the image data obtained in the preliminary reading step into a plurality of regions;
An extracting step of extracting a maximum luminance value in the area for each of the areas divided by the dividing step,
An average value calculation step of calculating an average value of the maximum luminance value for each of the regions extracted by the extraction step,
Based on the average value calculated by the average value calculation step, an exposure amount determination step of determining the exposure amount by the illumination step at the time of main reading,
A main reading step of illuminating the document in the illumination step with the exposure amount determined in the exposure amount determining step, reading an image of the document, and obtaining image data.

Images