JP3193582B2 - Image recording device - 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 recording apparatus such as a digital copying machine for reading an image of a document by a line sensor and recording the read image on a recording medium.

[0002]

2. Description of the Related Art Conventionally, in an image recording apparatus such as a digital copying machine, a line sensor is used for an image in a predetermined area of an original to form an image of a constant density on a recording medium even when the image density of the original changes. The image signal processing suitable for the image signal output from is performed. That is, a pseudo halftone dot method for changing the size and density of dots at the time of image recording according to the image density of a document, and a dither for binary conversion based on a result of comparing the pixel level of an image signal with a predetermined threshold value. Laws and others were being implemented.

Also, originals read by an image recording apparatus include:
In addition to originals consisting only of line drawings, such as text originals, there are also originals of photographic images having gradation in image density, and there are also originals, such as newspapers, in which both character originals and photographic originals are mixed. In order to clearly reproduce both a text document and a photo document on a recording medium, it is necessary to determine whether the document is a text document or a photo document, and perform image signal processing according to each of them. Therefore, Japanese Patent Application Laid-Open No. 58-114
In the image recording method disclosed in Japanese Patent No. 571, an image density for each predetermined area is extracted by a photoelectric conversion element over the entire range of a document, and binary data obtained by comparing the image density with a certain threshold value is obtained. Whether a document is a character document or a photo document is determined from the pattern, and optimal image signal processing is performed based on the result of the determination.

[0004]

However, the conventional image recording method requires a preliminary scan over the entire range of the document, and has a problem that the image recording operation cannot be performed at a high speed. Further, since the image density is compared with a certain threshold value and whether the document is a text document or a photo document is determined based on the comparison result, a photo document with a low image density can be accurately determined. However, since this is erroneously recognized as a character document and image signal processing is performed, there is a problem that the image quality of a recorded image is deteriorated.

According to the present invention, it is not necessary to perform a preliminary scan of an original image for discriminating a character original or a photo original, so that an image recording operation can be speeded up and an image signal corresponding to the type of the original can be obtained. An object of the present invention is to provide an image recording apparatus capable of selecting a processing accurately and realizing improvement of the quality of a recorded image.

[0006]

According to a first aspect of the present invention, there is provided a line sensor for reading a document image and outputting a density signal for each pixel, and a recording medium based on the density signal output from the line sensor. An image recording apparatus for recording an image in a document, wherein a histogram of the density signal is created for each line to extract feature data for each type of document, and for each line extracted by the document feature extracting means. Document density correction means for correcting the density signal based on characteristic data of the document , wherein the document density correction means,
The relationship between the density signal output from the line sensor and the corrected density
The person in charge of the manuscript
A plurality is stored for each type, and extracted by the document feature extracting means.
The relationship to be used based on the feature data of
It is characterized by shifting to one .

[0007] invention as set forth in claim 2, wherein the document feature
The extracting unit determines the line direction of the line sensor in the original image.
When the reading range for the direction is set, the line sensor
The total number of pixels in one line is the number of pixels in the set reading range.
By multiplying the divided value, the image signal of each line
Is characterized in that the histogram is corrected .

[0008]

[0009]

According to the first aspect of the present invention, the histogram of the density signal output from the line sensor is created for each line as the characteristic data of the document. The density signal is corrected based on the feature data of the original for each line. At this time, the relationship between the density signal and the corrected density
From the original to the newspaper with the text in between
And the relationship to use is based on the feature data of the manuscript.
Are migrated one by one. Therefore, multiple document types
From each part to the other part of the original image
Image changes at the border between document type changes
The change in density becomes smooth, and the image quality is improved.

[0010] In the invention as set forth in claim 2, the document
Reading of line direction of line sensor in image
Once the range is set, the histogram of the image signal of each line
Is set to the total number of pixels in one line of the line sensor.
It is corrected by multiplying a value obtained by dividing by the number of pixels in the range. I
Therefore, scan images of small originals such as cut-out originals.
Cover the area where the original does not exist.
The back side is not scanned as an original, and the original type
There is no misunderstanding.

[0011]

[0012]

FIG. 1 is a schematic diagram showing the configuration of a digital copying machine to which an image recording apparatus according to an embodiment of the present invention is applied. The digital copier 30 includes a scanner unit 31, a laser printer unit 32, a paper feed unit 33, and a sorter. The scanner unit 31 includes the document table 3
5, a document supply device 36 and a scanner unit 37 are provided. The laser printer unit 32 includes a laser writing unit 38 and an image forming process unit 39. The paper feed unit 33 is provided with paper feed cassettes 40 to 43.

The scanner unit 31 reads an image of a document supplied one by one to a document table 35 by a document supply device 36 with a scanner unit 37. Scanner unit 37
Includes a light source unit 44 for exposing a document and a CCD line sensor 45 for receiving light reflected on the document. The scanner unit 37 moves the lower surface of the platen 35
Moves in a direction to Cartesian in the line direction of the D line sensor 45 scans the original on the platen 35.

The laser printer unit 32 distributes the laser beam emitted from the laser writing unit 38 to the image forming process unit 39, and forms an image by electrophotography.
Paper is fed from the paper feed unit 33 to the image forming process unit 39. The image forming process unit 39 transfers the formed image onto a sheet, and conveys the image to the sorter 34 after fixing.

In the digital copying machine 31 configured as described above, the image recording apparatus of the present invention
It is provided between one CCD line sensor 45 and the laser writing unit 38.

FIG. 2 is a block diagram of a control section of the image recording apparatus. The control unit of the image recording apparatus is configured by a CPU 1 having a ROM 2 and a RAM 3. C
The PU 1 is connected to a CCD line sensor 45 via an I / O interface 4 and an A / D converter 6, and is connected to a laser driver 8 via an I / O interface 5 and a D / A converter 7. ing. A program that defines the processing operation of the CPU 1 is written in the ROM 2. Also, the memory areas MA1 to MA3 of the ROM 2
The area includes 2-bit area data for specifying an area of a histogram of an image signal to be described later, the relationship between 8-bit feature data composed of four area data, and the document type, and the output from the CCD line sensor 45. And a density conversion table showing the relationship between the output to the laser driver 8 and the output to the laser driver 8 for each document type.

The RAM 3 temporarily stores data input and output during the processing operation of the CPU 1. In the memory area MB1 of the RAM 3, an image signal for one line of the CCD line sensor 45 is stored. This memory area MB1
Classifies image signals into four levels of image density, counts them, and creates a histogram of the image signals. The A / D converter 6
The image signal for each pixel output from the CCD line sensor 45 is converted into image data of 256 gradations and input to the CPU 1. The CPU 1 converts the image data input from the A / D converter 6 into, for example, 0 to 99,
4 of 100-189, 190-219, 220-255
The pixels are classified into the density areas of the stages, and the number of pixels included in each density area is counted.

FIG. 3 is a diagram showing area data for specifying an area of a histogram of an image signal of the image recording apparatus. The image density of 256 gradations represented by the image data is
9,100-189,190-219,220-255
And the number of pixels included in each of the density regions is 0 to 499,500 to 1099,110.
It is divided into four stages from 0 to 1499, 1500 or more. "0" is assigned to each of the four pixel number ranges in each density region.
Two-bit area data of “0”, “01”, “10”, and “11” are allocated.
When one line of image data is counted in one, the number of pixels included in each density region classified into four levels is determined. The area data corresponding to the range of the number of pixels is arranged in the order of the density area to form 8-bit feature data.

FIG. 4 is a diagram showing the relationship between the characteristic data and the document type in the image recording apparatus. In the figure, the 8-bit feature data configured as described above is converted into a decimal number, and the corresponding document type is determined to be a photo document, a text document, and a newspaper document. In the figure, “0” represents a photo document, “1” represents a character document, and “2” represents a newspaper document. For example, if the feature data is decimal “11”
In the case of “01101110” representing “2”, the photo original and “01010111” in which the characteristic data represents “87” in decimal.
In the case of "1", the character document and the characteristic data are "9" in decimal.
In the case of "01011100" representing "2", the document is determined to be a newspaper manuscript.The relationship shown in FIG.

FIG. 5 shows a CCD in the image recording apparatus.
9 is a density conversion table showing a relationship between an output from a line sensor and an output to a laser driver for each document type. Up
Based on the document type determined from the above described characteristic data, the CCD line sensor is determined by the relationship R1 in FIG. 5 for a photo document, by the relationship R2 for a character document, and by the relationship R3 for a newspaper document. The output of 45 is converted into an output to the laser driver 8. Therefore, the output of the CCD line sensor 45 is corrected in a relationship according to the type of the document and is input to the laser driver 8.

FIG. 6 is a flowchart showing a processing procedure of the image recording apparatus. The CPU 1 constituting the control unit of the image recording apparatus classifies the image data input from the CCD line sensor 45 via the A / D converter 6 according to the density, and counts it in the memory area MB1 of the RAM 3 (s1, s2). At the same time, the image data is temporarily stored in an image memory (not shown) (s3). When the counting for one line is completed (s4), area data in each density area is specified (s5), and feature data is created based on the specified area data (s6). The characteristic data is converted into a decimal number to determine the type of the original (s7). The input / output relationship corresponding to the determined document type is selected in the memory area MA3 density conversion table of the ROM 2 (s8), and the image data stored in the image memory is corrected according to the selected relationship and output to the laser driver 8. (S9).

With the above-described processing, the type of the document can be determined based on the histogram of the image data for each line of the document, and the image data subjected to optimal correction can be output to the laser driver 8. Therefore, it is not necessary to pre-scan the image of the original to specify the type of the original, and even if a photograph is attached in the middle of a character original, an optimal image is provided for each line of the original image. Signal processing can be performed.

FIG. 7 is a flowchart showing another processing procedure of the image recording apparatus. The memory area MB1 of the RAM 3 is enlarged so that a histogram of image signals for 10 lines can be stored. When the storage of the image data of the current read line Ln is completed (s11)
.. S14), Fn = [Fn × 7 + F (n−1) × 4 + F (n−2) × 2 + F (n−3) + F (n−3) +... + F (n−9)] / 20 , F (ni) calculate an averaged histogram from the histogram of the read line L (ni) (s
15) Specify area data, create characteristic data, and determine the type of document (s16 to s18). The input / output relationship is selected based on the document type thus determined (s
19) The corrected image data for the current read line Ln is output to the laser driver 8 (s20). Thereafter, in the memory area MB1 of the RAM 3, the CPU 1 rewrites the histogram of the read lines Ln to L (n-8) to the area of the read lines L (n-1) to L (n-9) (s21).

With the above processing, the histogram of the read line Ln read by the CCD line sensor 45 this time is read from the read line L (n-1) to the read line L (n-
The reading accuracy can be improved by weighting and adding the histograms up to 9) and averaging them.
For example, a photograph portion 51a and a newspaper portion 5 shown in FIG.
At the time of reading the image of the document 51 having the character portion 1b and the character portion 51c, there may be a case where the document type of a part of the newspaper portion 51b is erroneously determined to be a character document as shown in FIG. This is because there are only three types of document types in the present embodiment, and some newspapers and photographs may partially have the characteristics of a text document. In such a case, the histogram of the past read lines L (n-1) to L (n-9) is weighted and added to the histogram of the current read line Ln, and the histogram is averaged. As shown in (1), it is possible to properly determine the type of the original, and it is possible to prevent a sharp change in the gradation expression of the image density, thereby preventing the image quality from deteriorating.

FIG. 9 is a flowchart illustrating a processing procedure of an image recording apparatus according to an embodiment of the invention described in claim 2. In this embodiment, the CPU 1 accepts the setting of the reading range of the original image in the line direction of the CCD line sensor 45 by an operator's key input or the like (s3).
1). When the storage of the image data of the current reading line Ln is completed (s32 to s35), the CPU 1 divides the total number of pixels of one line of the CCD line sensor 45 by the number of pixels in the set reading range, and divides the result of the division. The histogram is corrected by multiplying the number of pixels of the histogram stored in the memory area MB1 of the RAM 3 (s36). Based on the result, the area data is specified, the characteristic data is created, the document type is determined, the input / output relationship is selected, and the image data is output (s37 to s41).

With the above processing, when reading an image of a small original 52 such as a cut-out original shown in FIG. 10, the back side of the original cover is read as an original in a range where the original 52 does not exist, and the type of the original is erroneously recognized. Can be prevented.

[0027] FIG. 11 is a flowchart illustrating a processing procedure of an image recording apparatus according to an embodiment of the invention described in claim 1. In this embodiment, as shown in FIG.
A plurality of input / output relationships for each document type are stored in the density conversion table of the second memory area MA3. In FIG. 12, for example, input / output relationships R1, R5, and R10 are optimal relationships for reproducing a photo original, a text original, and a newspaper original, respectively. Correspondingly, the relationship between the characteristic data in the memory area MA2 of the ROM 2 and the document type is changed from the state shown in FIG. 4 to the character document "0" as shown in FIG. The original is replaced with “1”.

The CPU 1 sets the input / output relationship R5 in the density conversion table for the first read line L1 (s51, s52). With respect to the read line L2 and thereafter, the type of the document is determined by the processing of s1 to s7 described in FIG. 6 (s53 to s59). Thereafter, when the determined document type is a photo document, the set value Rn is shifted by one in the direction of the input / output relationship R1 (n61). When the determined document type is a text document, the set value Rn is transferred in the direction of the input / output relationship R5. (N62), and if it is a newspaper manuscript, the set value Rn is shifted by one in the direction of the input / output relationship R10 (n63). In this way, the image data is converted in accordance with the input / output relationship set in s52 and s61 to s63 and output to the laser driver 8 (s64).

By the above processing, when reading the image of the original 53 having the photograph portion 53a, the newspaper portion 53b and the character portion 53c as shown in FIG.
The change to other portions becomes slow, and the change in image density at the boundary of the change in the document type can be made smooth, and the image quality can be improved.

Further, according to this embodiment, even when the cut-out original 52 shown in FIG. 15A is set at the center of the original platen, the presence of the newspaper original is recognized as shown in FIG. Thus, the image data could be converted and output to the laser driver 8 according to the input / output relationship suitable for a newspaper manuscript.

FIG. 16 is a flowchart showing a part of a processing procedure of an image recording apparatus according to still another embodiment of the present invention. The processing of s71 to s77 is executed instead of the processing of s60 to s63 in FIG. By executing the processes of s71 to s74 after the determination of the document type, the input / output relationship in the density conversion table shown in FIG. 12 is changed only when the document type has changed m times consecutively (s75).
To s77).

By performing the delay control when the input / output relation is changed by the above processing, the reading processing of the cut-out original 52 shown in FIG.
As shown in (C), the change in the input / output relationship due to the change in the document type can be made smoother than in FIG. 17B when the processing shown in FIG. Abrupt change in density at the step can be prevented more reliably.

[0033]

According to the first aspect of the present invention, the concentration
The relationship between the signal and the corrected density
Store and use multiple items for each type of original up to newspaper
The relationships one by one based on the feature data of the manuscript
This makes it possible to scan images of originals with multiple original types.
Can slow down the transition from each part to the other.
The change in image density at the border between changes in the document type.
For obvious reasons, the image quality can be improved.

According to the second aspect of the present invention, each line
The histogram of the image signal of the
Value obtained by dividing the total number of pixels by the number of pixels in the set reading range
Multiplied by correction to reduce the size of cut-out documents
When reading an image of an original,
The back of the document cover can be read as a document.
Therefore, the type of the original can be accurately determined.

[0035]

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of a digital copying machine to which an image recording apparatus according to an embodiment of the present invention is applied.

FIG. 2 is a block diagram of a control unit of the image recording apparatus according to the embodiment of the present invention.

FIG. 3 is a diagram showing area data for specifying an area of a histogram of an image signal of the image recording apparatus.

FIG. 4 is a diagram showing a relationship between characteristic data and a document type in the image recording apparatus.

FIG. 5 is a density conversion table in the image recording apparatus.

FIG. 6 is a flowchart illustrating a processing procedure of the image recording apparatus.

FIG. 7 is a flowchart illustrating another processing procedure of the image recording apparatus.

FIG. 8 is a diagram illustrating a reading state of an image of a document including a photograph portion, a newspaper portion, and a character portion according to the embodiment.

9 is a flowchart showing a processing procedure of an image recording apparatus according to an embodiment of the invention described in claim 2.

FIG. 10 is a diagram showing a reading state of an image of a small original such as a cut-out original in the embodiment.

11 is a flowchart showing a processing procedure of an image recording apparatus according to an embodiment of the invention described in claim 1.

FIG. 12 is a diagram showing a density conversion table in the embodiment.

FIG. 13 is a diagram showing a relationship between feature data and a document type in the embodiment.

FIG. 14 is a diagram illustrating a reading state of a document including a photograph portion, a newspaper portion, and a character portion in the embodiment.

FIG. 15 is a diagram illustrating a reading state of an image of a small original such as a cut-out original in the embodiment.

FIG. 16 is a flowchart showing a part of a processing procedure of an image recording apparatus according to still another embodiment of the present invention.

FIG. 17 is a diagram showing a reading state of a document in the embodiment.

[Explanation of symbols]

 1-CPU 38-Laser writing unit 45-CCD line sensor

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Mihoko Okada 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor ▲ Saki ▼ Hiroshi Tadashi 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Masaaki Otsuki 22-22 Nagaikecho, Abeno-ku, Osaka City, Osaka Prefecture Sharp Corporation (56) References JP-A-3-88569 (JP, A) JP-A-62-23867 (JP) , A) JP-A-8-88772 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04N 1/40-1/409 G06T 5/00 G06T 7/00 B41J 2/52

Claims (2)

(57) [Claims] An image recording apparatus, comprising: a line sensor for reading an image of a document and outputting a density signal for each pixel; and recording an image on a recording medium based on the density signal output from the line sensor. by creating a histogram of the signal for each line correction and original feature extracting means for extracting feature data for each type of document, the density signal based on the feature data of the document of every one line document feature extraction means has extracted a document density correction means for the provided said original density correction means, are output from the line sensor
The relationship between the density signal and the corrected density
Store multiple items for each type of document up to the newspaper manuscript,
Based on the characteristic data of the original extracted by the original characteristic extracting means.
An image recording apparatus that shifts a relationship to be used one by one . 2. The method according to claim 1, wherein said document characteristic extracting means includes means for extracting a document image.
Set the reading range for the line sensor line direction
Set the total number of pixels in one line of the line sensor
Multiplied by the value divided by the number of pixels in the read range
2. The image recording apparatus according to claim 1, wherein the histogram of the image signal of each line is corrected .