JP3264484B2 - Image reading apparatus, image processing method in image reading apparatus, and storage medium - Google Patents

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, an image processing method in the image reading apparatus, and a storage medium, and more particularly to an automatic document feeder (ADF).
The present invention relates to an image reading apparatus, an image processing method in the image reading apparatus, and a storage medium which are suitable for making the output image density almost the same at the time of copying, etc.

[0002]

2. Description of the Related Art Conventionally, in a facsimile provided with an automatic document feeder (ADF) and a document table, when a document is read from an ADF, for example, as shown in FIG. Diffusely reflected light / stray light 102
(Arrows in the figure) enter the light receiving element 103. On the other hand, when reading the original from the platen, for example, as shown in FIG.
As a result, the irregularly reflected light and stray light do not enter the light receiving element 103. In the figure, reference numeral 301 denotes an image sensor.

In a conventional facsimile, when image data is stored in a memory, the output resolution is set to a low resolution, and when the image data is not stored in the memory, the output resolution is set to a high resolution. Output. However, the same luminance-density conversion table is used in both cases where image data is output at a low resolution or output at a high resolution.

[0004]

However, in the above-described prior art, when an original is read from the ADF, irregularly reflected light / stray light enters the image sensor.
The read luminance value is larger than when the original is read from the platen. For this reason, there is a disadvantage that the output image density at the time of copying or the like is reduced.

[0005] In the above-mentioned prior art, when the output resolution is different, the recording dot width is different. For this reason, the gradation of the recording device varies depending on the output resolution.
There is a disadvantage that the densities are different even if they are output with the same density value during recording.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and a first object is to reduce the output image density at the time of copying or the like regardless of whether the original is read from the ADF or the original platen. It is an object of the present invention to provide an image reading device, an image processing method in the image reading device, and a storage medium that have substantially the same density.

The present invention has been made in view of the above-mentioned point, and a second object of the present invention is to provide an image processing apparatus in which the output image density at the time of copying or the like is substantially the same even when the output resolution is different. It is an object to provide a reading device, an image processing method in an image reading device, and a storage medium.

[0008]

In order to achieve the above object, an image reading apparatus according to claim 1 reads an original.
Reading means for outputting a luminance value of the read original document;
Pixel density conversion means for converting the resolution of the brightness value,
Multiple types of brightness / density conversion that define the correspondence between brightness values and density values
Storage means for storing a table;
Brightness / density conversion means for converting the value into a value, based on the density value
An image memory for storing image data;
Output means for outputting to the outside, wherein the reading means
To read one original and make multiple copies
When outputting by the output means, the pixel density conversion means
The step converts the luminance value of the original to a low resolution, and
The degree conversion means outputs the low-resolution output stored in the storage means.
The resolution is converted to the low resolution using a brightness / density conversion table for power.
The converted luminance value is converted to a density value, and the converted
Image data to be stored in the image memory, and
The stage converts the image data stored in the image memory to a low resolution image data.
And read one document by the reading means.
One copy and output by the output means.
The resolution conversion is not performed by the pixel density conversion means.
The brightness density conversion means is stored in the storage means.
Using the brightness-density conversion table for high-resolution output
The luminance value of the original is converted into a density value, and the output means
Image data based on the converted density value is stored in the image memory.
Output at high resolution without accumulation in
You.

[0009] To achieve the above object, a second aspect is provided.
The image reading method of the image reading device according to
In the reading method, the original is read and the read original is read.
A reading step of outputting a luminance value of a document, and a resolution of the luminance value
A pixel density conversion step of converting the brightness value into the density
A brightness / density conversion step of converting the value into a value, based on the density value
An image memory step of storing image data;
And an output step of outputting the data to the outside.
Therefore, one original is read, and multiple copies are made.
When outputting in the output step, the pixel density change is performed.
The converting step converts the luminance value to a low resolution, and
The conversion step includes a step of defining a correspondence between the luminance value and the density value.
Stores several kinds of brightness density conversion tables in storage means
Using the brightness / density conversion table for low resolution output
And converts the luminance value converted to the low resolution into a density value.
And converts the image data based on the converted density value into the image memo.
The output step is stored in the image memory.
Image data is output at a low resolution.
To read one original, make one copy, and
When the output is performed by the force step, the pixel density converting step
Does not perform resolution conversion, and performs the brightness / density conversion step as described above.
Brightness-density conversion for high-resolution output stored in memory
Using a table to convert the brightness value of the document into a density value,
The output step includes the step of outputting image data based on the converted density value.
Output at high resolution without storing in the image memory
It is characterized by doing.

[0010]

[0011]

[0012]

[0013]

[0014]

[0015]

[0016]

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

[1] First Embodiment First, the external appearance of a reading apparatus (facsimile) according to a first embodiment will be described with reference to FIGS.
4, the reading apparatus includes an apparatus main body 400 having an operation unit 403 provided with a start button and the like, and a document stacking unit 404 mounted on the upper part of the apparatus main body 400 so as to be openable and closable. An automatic document feeder (ADF) 401 for automatically feeding the loaded documents and a document loading sensor 402 for detecting the loading of the documents are provided above the document loading unit 404. Also, in FIG.
A document table 5 on which a document is placed is placed on the upper surface of the apparatus main body 400.
01 is provided, and a pressure plate 502 is provided on the lower surface of the document stacking unit 404. The other mechanisms are not related to the present invention, and thus the description is omitted.

Next, the internal structure of the reading apparatus according to the first embodiment will be described with reference to FIGS. In FIG. 2, a reading apparatus includes a light source 101 for emitting light, a light receiving element 103 for receiving light emitted from the light source 101, a white reference 104, and a document reading position 10 inside the apparatus main body.
5 and so on are provided. In the figure, reference numeral 102 denotes irregularly reflected light / stray light,
Reference numeral 106 denotes an original. Also, in FIG.
An image sensor 301 (see FIG. 1) is provided on the side of the document table 501, and a document table 501 on which the document 106 is loaded and a pressure plate 502 are disposed above the light source 101.
The other mechanisms are not related to the present invention, and thus the description is omitted.

FIG. 6 is a diagram showing a relationship between a normal luminance value and a density value. FIG. 7 is a diagram showing the contents of a brightness / density conversion table (see FIG. 1) which defines the correspondence between the brightness value and the density value in the reading apparatus according to the first embodiment.

Next, the electrical configuration of the reader according to the first embodiment will be described with reference to FIG. The reading apparatus includes an image sensor 301, a brightness correction unit 302, a brightness / density conversion unit 303, and a brightness / density conversion table (RA
M) 304, ROM 305, and binarization processing unit 306
, The transmission unit 307, the recording output unit 308, and the recording device 3
09, an image memory 310, and a pixel density conversion unit 311.

The image sensor 301 reads the original from the leading end to the trailing end by dividing it into a number of fine lines. Brightness correction unit 3
Reference numeral 02 denotes an LSI, which performs A / D conversion of the output voltage of the image sensor 301 and stores the luminance value of one line of the white reference in a memory in the luminance correction unit 302. The brightness / density conversion unit 303 refers to the brightness / density conversion table in FIG.
The obtained luminance value is converted into a corresponding density value. The correspondence relationship between the luminance value and the density value is stored in the luminance / density conversion table (RAM) 304. The ROM 305 stores a plurality of types of luminance density conversion tables.

The binarization processing unit 306 includes a luminance / density conversion unit 3
The multi-value → binarization process is performed on the density value converted by step S03. The multi-value → binarization processing method will be described later. The transmission unit 307 transmits the binary image data to the outside. The recording output unit 308 supplies the binary image data to the recording device 309. The recording device 309 records image data. The image memory 310 stores various image data. The pixel density conversion unit 311 performs a pixel density conversion based on the density value converted by the luminance density conversion unit 303.

Next, the operation of the reading apparatus (facsimile) according to the first embodiment having the above configuration will be described with reference to FIGS.

ADF 401 of a reading device (facsimile)
Or a document is placed on the platen 501,
After closing the pressure plate 502, the user presses the start button of the operation unit 403 to start reading the document. When reading of a document is started, first, the light source 101 is turned on for shading correction (correction of color unevenness of an input image), and reflected light of the light applied to the white reference 104 enters the light receiving element 103.

In this case, the light receiving element 103 has minute light receiving elements arranged in a line, and can read one fine line. One light receiving element is one pixel,
A voltage is output for each pixel according to the intensity of the reflected light.

The luminance correction unit 302 performs A / D conversion on the output voltage, and accumulates a luminance value for one line of the white reference in a memory in the luminance correction unit 302. A document loading sensor 402 provided in the ADF 401 determines whether the document is read from the ADF 401 or from the document table 501. ADF
In the reading at 401, after the image sensor 301 moves to a position where the reading position 105 can be read, the document is conveyed, and the leading to trailing ends of the document are read in a number of fine lines. Further, in reading on the document table 501, the image sensor 301 moves and reads from the leading edge to the trailing edge of the document by dividing into a large number of fine lines.

The luminance value of one line read by the image sensor 301 is normalized by the corresponding luminance value of the white reference 104 at the same pixel position, and the number of processing gradations (for example, 64 gradations) is integrated. And the brightness of each pixel. Normally, the luminance value and the density value have a relationship shown in FIG. 6 with the horizontal axis representing luminance and the vertical axis representing density. Even if the same original is read, when reading from the ADF 401, the original
Brightness is higher than when reading from above. Therefore, when the luminance density is converted based on the same luminance density conversion table shown in FIG. 7, the converted densities are different.

The following processing is a feature of the first embodiment of the present invention. Regardless of whether reading from the ADF 401 or reading from the document table 501, reading from the ADF 401 is performed so that almost the same density is obtained. Compared to the case of reading from the platen 501, a luminance / density conversion table having a larger density value output with respect to the luminance value is stored in the ROM 30 in which a plurality of types of luminance / density conversion tables are stored.
5 to the RAM 304.

After performing other necessary correction processing, the luminance / density conversion unit 303 refers to the luminance / density conversion table in FIG. To the corresponding density value. For example, if the luminance value is 2, it is converted to a density value 24 when reading from the ADF 401, and converted to a density value 22 when reading from the document table 501.

Further, the binarization processing unit 306 performs a multi-value → binarization process on the density value converted by the luminance / density conversion unit 303. In this case, there are various multi-value → binarization processing methods. In the error diffusion method, the middle value of the gradation (for example, 31 in the case of 64 gradations) is set as a threshold value with respect to the density value of the pixel of interest. If so, it is determined to be black, and if less than the threshold, it is determined to be white.
At this time, the binarization process is performed while distributing the pixels to surrounding pixels at a fixed distribution, using the density difference between the density value of the target pixel and black (density 63) or white (density 0) as an error. Thereafter, the binary image data obtained by the binarization processing unit 306 is used as image data by the transmission unit 307 and the recording output unit 308.

As described above, according to the first embodiment, the reading device includes the ROM 305 storing a plurality of types of luminance / density conversion tables that define the correspondence between the luminance value and the density value;
A document stacking detection sensor 402 for detecting whether to read from the DF 401 or the document table 501;
When reading from F401, a luminance / density conversion unit 303 that performs a luminance / density conversion using a luminance / density conversion table having a larger density value output with respect to the luminance value than when reading from the document table 501 is provided. ADF
In either case of reading from the document table 401 or reading from the document table 501, control can be performed so that the output image density at the time of copying or the like becomes substantially the same.

[2] Second Embodiment A reading apparatus (facsimile) according to a second embodiment is
As in the first embodiment, the apparatus main body 4 having an operation unit 403 provided with a start button, a number button, and the like.
00, a document table 501, and an automatic document feeder (ADF)
The image processing apparatus includes a document 401, a document stacking sensor 402, and a pressure plate 502 (see FIGS. 4 and 5).

The reading apparatus according to the second embodiment has a light source 101, a light receiving element 103, a white reference 104, a document reading position 105, An image sensor 301 is provided (see FIGS. 2 and 3).

The reading apparatus according to the second embodiment is similar to the reading apparatus according to the first embodiment.
01, a luminance correction unit 302, and a luminance density conversion unit 303
, A luminance / density conversion table (RAM) 304, and a ROM
305, a binarization processing unit 306, a transmission unit 307, a recording output unit 308, a recording device 309, and the image memory 31
0 and a pixel density conversion unit 311 (see FIG. 1 described above).
reference).

Next, the operation of the reading apparatus (facsimile) according to the second embodiment having the above configuration will be described with reference to FIGS.

For example, when one document is read by using the ADF 401 and a plurality of copies are made, the same document cannot be read a plurality of times. Therefore, when the image memory is small, the pixel density conversion unit 311 reads the luminance. After the value is converted to a low resolution, the brightness and density are converted, and the binarized image data is stored in the image memory 310 and stored in the recording device 309.
Is switched to a lower resolution and output. ADF401
In the case of reading one original using, and performing one copy, image data is not stored in the image memory 310, and the recording device 309 is switched to high resolution for output.

The luminance / density conversion tables for high-resolution output and low-resolution output are stored in the ROM 30 for reading the ADF 401 and reading on the document table 501, respectively.
5

In the case where one document is read using the ADF 401 and a plurality of copies are made, or in the case where one document is read using the ADF 401 and one copy is made, a reading device (facsimile) is used in each case. A
After the originals are stacked on the DF 401, reading is started by pressing the number button and the start button in the case of copying a plurality of sheets, or by pressing the start button in the case of copying only one sheet. When reading of a document is started, first, the light source 101 is turned on for shading correction, and the white reference 1 is set.
The reflected light of the light radiated to 04 enters the light receiving element 103.

In this case, the light receiving element 103 has minute light receiving elements arranged in a line, and can read one fine line. One light receiving element is one pixel,
A voltage is output for each pixel according to the intensity of the reflected light.

The luminance correction unit 302 performs A / D conversion of the output voltage, and accumulates a luminance value for one line of the white reference in a memory in the luminance correction unit 302. In reading with the ADF 401,
After the image sensor 301 moves to a position where the reading position 105 can be read, the document is conveyed, and the document is read from the leading end to the end of the document in a number of fine lines. The luminance value for one line read by the image sensor 301 is used as the white reference 104 at the corresponding pixel position.
And the number of processed gradations (for example, 64 gradations)
Are integrated to obtain the luminance of each pixel.

As described above, for example, when one original is read using the ADF 401 and a plurality of copies are made,
Since the same document cannot be read a plurality of times, the image data is stored in the image memory 310. When the image memory is small, the pixel density conversion unit 311 converts the read luminance value to a low resolution, thereby reducing the memory consumption. Further, as described above, when one document is read using the ADF 401 and one copy is performed, it is not necessary to accumulate image data in the image memory 310, so that processing is performed with high resolution without pixel density conversion. Depending on whether the image output is performed at a low resolution or a high resolution, the output dot diameter is different, so that the gradation characteristics are different. For this reason, even if binary image data converted from multi-level to binary from the same density value is output, the output density will be different.

The following processing is a feature of the second embodiment of the present invention. The low-resolution output and the high-resolution output are performed so as to obtain almost the same density even when outputting at low resolution. In the case of the output, the luminance density conversion table for low resolution output is written from the ROM 305 to the RAM 304. When outputting at a high resolution, a high-resolution luminance / density conversion table is written from the ROM 305 to the RAM 304.

After performing other necessary correction processing, the obtained luminance value is converted into a corresponding density value by the luminance / density conversion unit 303 with reference to the luminance / density conversion table written in the RAM 304. Further, the binarization processing unit 306 performs a multi-value → binarization process on the density value converted by the luminance / density conversion unit 303.

When the image data is not stored in the image memory 310, the binary image data obtained by the binarization processing unit 306 is transferred to the recording output unit 308. Thereafter, the data is output from the recording output unit 308 to the recording device 309. Further, it is also possible to transmit the binary image data to the transmission unit 307. On the other hand, when storing image data in the image memory 310,
After the binary image data obtained by the binarization processing unit 306 is accumulated in the image memory 310, the binary image data is transferred from the image memory 310 to the recording output unit 308 a plurality of times. Thereafter, the data is output from the recording output unit 308 to the recording device 309. Further, the binary image data can be transmitted to the transmitting unit 307 a plurality of times.

As described above, according to the second embodiment, the reading device includes a ROM 305 storing a plurality of types of brightness / density conversion tables that define the correspondence between brightness values and density values, Depending on the recording device 309 that can be changed and the output resolution when the image is recorded by the recording device 309, that is, when outputting at a low resolution, the luminance / density conversion is performed using the luminance / density conversion table for low resolution output. If the output is performed at a high resolution, the luminance / density conversion unit 3 performs the luminance / density conversion using the luminance / density conversion table for high resolution output.
03, the output image density at the time of copying or the like can be controlled to be substantially the same in either case of outputting at low resolution or outputting at high resolution.

The present invention may be applied to a system constituted by a plurality of devices or to an apparatus constituted by a single device. A storage medium storing software program codes for realizing the functions of the above-described embodiments is supplied to a system or an apparatus, and a computer (or CPU or MPU) of the system or the apparatus executes the program code stored in the storage medium. Needless to say, this can also be achieved by executing the reading.

In this case, the program code itself read from the storage medium implements the functions of the above-described embodiment, and the storage medium storing the program code constitutes the present invention.

As a storage medium for supplying the program code, for example, a floppy disk, hard disk, optical disk, magneto-optical disk, CD-ROM, CD
-R, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.

When the computer executes the readout program code, not only the functions of the above-described embodiment are realized, but also the OS or the like running on the computer is actually executed based on the instructions of the program code. It goes without saying that a part or all of the above-described processing is performed, and the functions of the above-described embodiments are realized by the processing.

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, based on the instructions of the program code, It goes without saying that the CPU included in the function expansion board or the function expansion unit performs part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.

[0052]

As described above , according to the present invention ,
Multiple copies can be made even if the memory capacity of the image memory is small.
Can be performed. Also, regardless of the output resolution,
The output resolution density during copying should be maintained at approximately the same density.
Can be.

[0053]

[0054]

[0055]

[0056]

[0057]

[0058]

[0059]

[0060]

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an electrical configuration of a reading device according to first and second embodiments of the present invention.

FIG. 2 is a cross-sectional view illustrating an internal structure of the reading device according to the first and second embodiments of the present invention.

FIG. 3 is a cross-sectional view illustrating an internal structure of a main part of the reading device according to the first and second embodiments of the present invention.

FIG. 4 is a perspective view showing an external structure of the reading device according to the first and second embodiments of the present invention.

FIG. 5 is a perspective view showing a state where a platen is exposed by opening a pressure plate of the reading apparatus according to the first and second embodiments of the present invention.

FIG. 6 is an explanatory diagram showing a relationship between a normal luminance value and a density value.

FIG. 7 is an explanatory diagram showing the contents of a luminance / density conversion table in the reading device according to the first embodiment of the present invention.

[Explanation of symbols]

 301 Image sensor 303 Brightness / density conversion unit 304 Brightness / density conversion table 305 ROM 309 Recording device 401 Automatic document feeder 402 Document stacking sensor 501 Document platen

Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H04N 1/04-1/207 H04N 1/38-1/393 H04N 1/40-1/409 H04N 1/46 H04N 1 / 60 G06T 1/00 400-460 G06T 1/60 450

Claims (3)

(57) [Claims] An original is read and the read original is
Reading means for outputting a luminance value; pixel density converting means for converting the resolution of the luminance value; and a plurality of types of luminance densities defining correspondence between the luminance value and the density value
Storage means for storing a conversion table, and brightness / density conversion means for converting the brightness value into the density value
And an image memory for storing image data based on the density value
And output means for outputting the image data to the outside, wherein the reading means reads one document and
When copying and outputting by the output unit,
The pixel density conversion means reduces the luminance value of the document to a low resolution.
And the brightness / density conversion means is stored in the storage means.
Using the brightness / density conversion table for low resolution output
Converting the luminance value converted to the low resolution into a density value,
Image data based on the converted density value is stored in the image memory.
The output means stores the image stored in the image memory.
The image data is output at a low resolution, and one document is read by the reading means.
When the output is performed by the output means,
The pixel density conversion means does not perform resolution conversion, and
The degree conversion means outputs the high-resolution output stored in the storage means.
The brightness value of the document is calculated using a brightness / density conversion table for power.
Into a density value, and the output means outputs the converted density.
Storing image data based on values in said image memory
Image reading device characterized by high-resolution output
Place. 2. An image reading method for an image reading apparatus, comprising : reading an original; and outputting a luminance value of the read original.
Reading step, a pixel density conversion step of converting the resolution of the luminance value, and a luminance density conversion step of converting the luminance value to the density value
And an image memory for storing image data based on the density value.
And an output step of outputting the image data to the outside, wherein one document is read by the reading step,
When copying and outputting by the output step,
The pixel density conversion step converts the luminance value to a low resolution .
The brightness / density conversion step includes the step of calculating the brightness value and the density value.
Stores multiple types of brightness / density conversion tables that define the correspondence
Brightness density for low resolution output stored in the storage means
The luminance value converted to the low resolution using the conversion table
Is converted to a density value, and image data based on the converted density value
Is stored in the image memory, and the output step is performed in the image memory.
The image data stored in the memory is output at a low resolution, and one document is read in the reading step, and one
If the output is performed by the output step,
In the pixel density conversion step, resolution conversion is not performed, and the luminance
The degree conversion step is a step of converting the high resolution output stored in the storage means.
The brightness value of the document is calculated using a brightness / density conversion table for power.
Is converted to a density value, and the output step includes
Storing image data based on values in said image memory
Image reading method characterized by high-resolution output
Law. 3. An image processing method according to claim 2 is realized.
Software to the system or device, and
Read and executed by system or system computer
A storage medium stored as a possible program.