JPH0444465A - Image reading method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention is applicable to facsimile machines, image scanners,
The present invention relates to an image reading method in an image reading device such as a CR.

[Conventional technology]

In the above-mentioned image reading device, the input image is generally scanned and converted into electrical signals by sensors arranged in the line direction in the sub-scanning direction perpendicular to the line direction, and each signal is converted into an electrical signal. An image reading method is used in which images are binarized and sequentially stored.

FIG. 5 is a diagram showing a schematic configuration of such a conventional image reading device, and FIG. 6 is a block configuration diagram thereof.

In FIG. 5, reference numeral 1 denotes a document on which an image to be input is drawn, and is conveyed by rollers 2 in the sub-scanning direction indicated by arrow A.

Reference numeral 3 denotes an image reading sensor (reflection type line photosensor), which consists of a light emitting element 3a that illuminates a spot on the original 1 and a light receiving element 3b that receives reflected light from the spot, and is perpendicular to the paper surface. Many are arranged in the line direction. Note that it actually includes a circuit for causing the light emitting element 3a to emit light, a circuit for converting the photocurrent from the light receiving element 3b into a voltage, and outputting the voltage.

Reference numeral 4 denotes a binary circuit, which sequentially inputs the electrical signals photoelectrically converted by each light receiving element 3b of the sensor 3 to a comparator 5, compares the level with a reference value preset by a potentiometer 6, and converts it into a binary value. and outputs a binary signal (image signal) for each pixel.

In addition to the above-described image reading sensor 3 and binarization circuit 4, FIG. A motor control section 11 and a reading control section 9 that controls each of the above sections are shown.

FIG. 7 shows the waveforms of the motor control signals (two phases) a to d sent from the motor control section 9 to the motor waste section 10 and the sensor 3.
FIG. 3 is a diagram showing the timing of reading each line by the system, the timing of binarization by the binarization circuit 4, and the timing of storage by the storage means 8.

The motor drive unit 10 receives these four motor control signals a =
d, drive the stepping motor to move roller 2.
The document 1 is conveyed in the sub-scanning direction by rotating stepwise by one line.

Reading by the sensor 3 is performed by each light receiving element receiving reflected light from the document and converting it into an electrical signal each time the stepping motor operates.

The read one line of data is transmitted to the binarization circuit 4 at the next timing, binarized, and stored in the memory of the storage means 8.

Figure 8 shows the video signal output from the sensor 3 together with the read pixels.
00%, black 50%, and black 100%.

FIG. 9 shows the result of comparing each video output voltage with a threshold level indicated by a broken line and showing it as a binary output voltage.

[Problem to be solved by the invention]

Here, in a pixel that is 50% black, there are cases where the entire reading area is uniformly 50% black, and cases where half of the reading area is white and half is 100% black. Note that this reading area is made up of the chip width of the sensor 3 and the scanning distance in the sub-scanning direction (the amount of conveyance of the document).

FIG. 10 shows cases in which a black image can be read and cases in which it cannot be read depending on the reading position in the sub-scanning direction.

As shown in the same figure (a), the black @BL corresponds to one reading area R.
If the value is sufficiently large within A, the binarized signal of the video output becomes a black level, and the binarized image becomes black.
), when the black line BL spans two reading areas RA, the black rate decreases in both reading areas RA.

The binarized signals of each video output may all be at the white level, and in that case, all the binarized images will be white.

In other words, even if images of the same document are read, the reading results may differ depending on the division position of the reading area in the sub-scanning direction.

In recent years, this type of image reading device takes advantage of the ability to read images on the document surface in multiple gradations.

Some devices provide a plurality of reference values to determine the magnitude of light reflected from the document surface, and are able to read black by changing the threshold level based on the plurality of reference values and binarizing the detection signal.

However, the conventional problem mentioned above is not a problem with the binarization circuit, but a problem with the image reading area and pixels each time the sensor reads the image, and even if you change the threshold level as described above, the root cause cannot be solved. could not be resolved.

The present invention aims to solve such problems in image reading devices.

[Means to solve the problem]

In order to achieve the above object, the present invention reads an input image while scanning it in the sub-scanning direction perpendicular to the line direction using sensors arranged in the line direction, converts it into electrical signals, and converts each of the electrical signals into black level and white. In an image reading method that binarizes into levels and stores them sequentially.

The reading width for one line is divided into n in the sub-scanning direction, and each electrical signal output from the sensor is binarized for 1/n lines and temporarily stored, and n pieces for one line corresponding to each pixel are binarized. [Function] According to the present invention, if there is even one black level signal by performing a logical operation on each of the binary signals, the binary signal of the corresponding pixel in that one line is set as the black level. In the image reading method, the image reading area for one pixel is divided into n parts in the sub-scanning direction.
One pixel is read n times and binarized, and 1
If there is a black level signal at any time, the binarized signal of that pixel is set to the black level, so there is no possibility that the reading result will differ depending on the dividing position of the reading area in the sub-scanning direction.

〔Example〕

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

FIG. 1 is a block diagram showing an example of the configuration of an image reading device that implements the image reading method of the present invention, and parts corresponding to those of the conventional example shown in FIG. 6 are denoted by the same reference numerals. The reading device includes, in addition to the same parts as the conventional example shown in FIG. 6, a storage means 12 for one line and an AND circuit 13 between the binarization circuit 4 and the storage means 8.

The configuration of the image reading sensor 3 and the binarization circuit 4, and the fact that the roller 2 is rotated by the stepping motor activated by the motor drive unit 10 to convey the document 1 in the sub-scanning direction are as shown in the image shown in FIG. Similar to the reader, but
There are differences in their effects as described below.

The one line storage means 12 stores n pieces of binarized data in a memory for each pixel of one line when one line is read into n parts and binarized.

The AND circuit 13 performs an AND operation on n pieces of binary data (line data) for each pixel stored in the storage means 12 for one line, and when even one of them is determined to be at a black level, is to determine that the binarized data of the pixel in that one line is the black level.

In this example, n=2, and the black level of the binarized data is 0"
, the white level is 1''.

The storage means 8 stores the binary data of each pixel for each line outputted from the AND circuit 13 in a memory.

The motor control unit 11 activates a stepping motor that rotates the roller 2 shown in FIG. 5 via the motor drive unit 10,
Performs control to feed the original 1/n lines at a time.

The reading control section 9 controls each of these sections, and uses a microcomputer or the like.

FIG. 2 is a seventh diagram showing the control timing according to this embodiment.
It is a figure similar to the figure.

In the conventional system shown in FIG. 7, the stepping motor is controlled in two phases by the motor control signal a=d, but in this embodiment, the document is moved one time in the sub-scanning direction by controlling the stepping motor in 1-2 phases.
/ Convey step by step by 2 lines.

The image reading sensor 3 divides one line into a first half and a second half, and reads each line at each step of conveyance.

The binarization circuit 4 compares the video output (voltage signal) of each sensor chip (corresponding to a pixel) for each 1/2 line read by the image reading sensor 3 with a preset reference voltage. Depending on the magnitude, the black level is binarized to 1'0'' or the white level is ``1'', and the binarized data is sequentially stored in the memory of the storage means 12 for one line.

After the binarization for one line is completed, the AND circuit 13 performs a logical product operation on the binary data divided into two for each pixel, and the result is stored in the storage means 8 as one line of binarized data. Store in memory.

The effects of this embodiment will be further explained with reference to FIG.

As shown in (a) of the same figure, by dividing the reading area of one line into two in the sub-scanning direction and reducing the size, the black line BL is divided into two parts.
Even when the line spans two lines, the binarized data for each reading area of the 1/2 line is determined to have a black level of "0" with respect to the threshold level, as shown in FIG. 4(b).

After that, the results are ANDed for each original line, so at least one black level is "0" for each pixel on one line.
If there is, the binarization result for one line of that pixel will be a black level of 110 II, as shown in FIG.

Therefore, the black line BL can be reliably read regardless of the division position of the reading area in the sub-scanning direction.

FIG. 4 is a flowchart showing the control operation of the reading control section 9 of this image reading apparatus.

First, reading by the image reading sensor 3 is started to start reading 1/2 line, and the stepping motor is controlled in one phase to feed the document by 1/2 line in the sub-scanning direction.

That is, reading and motor control are continued until t/2 of the reading time t for one line has elapsed.

After t/2 elapses, 1/2 read by each sensor chip
The data for one line is binarized and stored in the memory of the storage means 12 for one line.

Next, reading of the remaining 1/2 line is started, and the stepping motor is controlled in two phases to further advance the document by 1/2 line in the sub-scanning direction.

That is, reading and motor control are continued until t/2 has elapsed again, and when t/2 has elapsed, 1/2 line worth of data read by each sensor chip is binarized, and it is stored in the memory of the storage means 12 for 1 line. Make me remember.

In this way, when the original one line worth of binary data is collected, one line worth of data is read out from the memory of the one line storage means 12, and each of the divided data is subjected to logical ANDL, and the result is converted into the original data. The data is stored in the memory of the storage means 8 as one line of binary data.

Then, it is determined whether or not the document is finished, and if the answer is No, the above-described process is repeated from the beginning, and if the answer is Yes, the process is ended.

In the above-mentioned embodiment, the number of divisions n of the l line was set to 2, but if the number n is set to 3 or more, the nine-bar reading accuracy becomes higher.

Furthermore, when the read video signal is binarized, the black level may be set to 1" and the white level may be set to "0".
In that case, an OR circuit is used instead of the AND circuit 13, and if there is even one black level "1" in the divided binary data for one line, the black data is set to the black level "1".
All you have to do is make it .

〔Effect of the invention〕

As explained above, by adopting the image reading method according to the present invention, when reading an image of a document, it is possible to almost eliminate the possibility that the reading result differs depending on the dividing position of the reading area in the sub-scanning direction by the sensor. ,
Reading accuracy can be greatly improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a configuration example of an image reading device implementing the image reading method according to the present invention, FIG. 2 is a timing diagram for explaining the operation of the embodiment of FIG. 1, and FIG. FIG. 4 is a flowchart showing the control operation of the reading control unit 9 shown in FIG. 1; FIG. 5 is a schematic configuration showing the main parts of a conventional image reading device to which the present invention is applied. 6 is a block diagram showing the configuration of a conventional image reading device, FIG. 7 is a timing diagram for explaining its operation, and FIGS. 8 to 10 are same diagrams for explaining its operation and problems. It is a figure for explaining. 1... Document 2... Roller 3... Sensor for image reading 3a... Light emitting element 3b... Light receiving element 4... Binarization circuit 5... Comparator
8...Storage means 9...Reading control section 10.
...Motor parking part 11...Motor control part 12...1 line storage means 13...AND circuit '3J l), Seyoayada No. 10 (α) Nananosachinobu width binarized image (b ) Binarized image

Claims (1)

[Claims] 1. An input image is read while being scanned in a sub-scanning direction perpendicular to the line direction by sensors arranged in the line direction, and converted into electrical signals, and each of the electrical signals is converted into a black level and a white level. In an image reading method that binarizes and stores sequentially, the reading width of one line is divided into n in the sub-scanning direction, and each electrical signal output from the sensor is binarized for 1/n lines and temporarily stored. , logically performs a logical operation on n binarized signals for one line corresponding to each pixel, and if there is even one black level signal, the binarized signal of the pixel in that one line is set to black level. An image reading method featuring: