JPH05130323A - Color picture reader - Google Patents

Abstract

PURPOSE:To prevent the generating of variance of color that is caused when the color images are read by a three-line image sensor and then reduced and magnified. CONSTITUTION:A CPU 13 outputs the buffer write valid signals R.WRVL, G.WRVL and B.WRVL to a buffer control part 11 in order to write the image data of R, G and B into the line buffers 11R, 11G and 11B. So that the same line is repetitively read out when the image data are magnified in the subscanning direction and then the same line is thinned when the image data are reduced respectively. At the same time, the CPU 13 repetitively reads the image data of R, G and B out of the buffers 11R, 11G and 11B in a magnification mode and then outputs the buffer read signals R.RDVL, G.RDVL and B.RDVL to thin the image data in a reduction mode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image reading apparatus for reading a color image by a 3-line image sensor in a color copying machine, a color facsimile apparatus or the like.

[0002]

2. Description of the Related Art FIG. 9 shows the structure of a general monochrome image reading apparatus, and a line buffer 1 can store digital image data of one line or more after A / D conversion. The buffer control unit 2 generates an address and a write enable signal for writing the input image data in the line buffer 1, and also generates an address and a read enable signal for reading the image data written in the line buffer 1. When the image data is enlarged or reduced in the sub-scanning direction, a CPU (central processing unit) (not shown) instructs the buffer control unit 2 to write a buffer write valid signal WRVL (WRite Valid Line) and a buffer read signal. RDVL (ReaD Valid Line) is output.

In such a configuration, when the size is reduced to 2/3, for example, the CPU writes the buffer write enable signal W.
By making RVL active for three lines and making the buffer read signal RDVL active for two lines, and thinning out one line out of the three lines without reading from the line buffer 1, as shown in FIG.
It can be doubled. Further, for example, when expanding to 4/3 times, the buffer write enable signal WRVL is made active for three lines, then made inactive for one line, and the buffer read signal RDVL is made active for four lines, and the third line is turned twice. By repeatedly reading out, it is possible to enlarge by 4/3 times in the sub-scanning direction.

When configuring a color image reading device,
For example, when the R (red), G (green), and B (blue) scan lines (reading lines) are the same as in the light source switching type, filter switching type, and mirror spectroscopy type, such a monochrome image reading device is used. It can be configured by using three systems. That is, as shown in FIG. 11, the image data stored in the R, G, and B line buffers 1 can be reduced in the sub-scanning direction by thinning it out, and can also be enlarged in the sub-scanning direction by repeatedly reading. can do.

As another conventional image reading apparatus,
A method is known in which instead of using the line buffer 1, scaling is performed by a valid / invalid signal VLDL indicating an image valid / invalid area by software of a CPU in response to a step pulse to a stepping motor which drives a scanner (when a document is fixed). ing. In this method, for example, when reading one line with two step signals, the valid / invalid signal VLDL and the step signal have the timings shown in FIG. 13 when they are reduced to 2/3 times.

That is, the CPU reads the valid / invalid signal VLDL while reading two lines with four step pulses.
Is set to a high level, and the valid / invalid signal VLDL is set to a low level during the next two step pulses. Then, the hardware fetches the read signal while the valid / invalid signal VLDL is at the high level, and the valid / invalid signal VL
While DL is at the low level, the read signal is not taken in and the size is reduced to 2/3 in the sub-scanning direction.

[0007]

However, in the case where a color image reading device for reading a color image by a three-line image sensor is constructed by the former device, as shown in FIG.
R, G, B line image sensors 10 as shown in FIG.
Since R, 10G, and 10B are displaced in the sub-scanning direction (N line in the example shown in FIG. 5) and each reading position is different at the same time, the monochrome image reading apparatus as shown in FIG. 9 is reduced using three systems. However, there is a problem that color shift occurs when enlarged. Here, when the R, G, and B line image sensors are displaced by 5 (= N) lines as shown in FIG.
When it is enlarged to / 3 times, color misregistration occurs because the lines repeatedly read out are different as shown in FIG.

In the case where the latter device constitutes a three-line color image reading device, the R, G and B line image sensors 10R,
If 10 G and 10 B are deviated by 10 lines in the sub-scanning direction and the size is reduced to ⅔, the reading position taken in as an effective line is different, which causes a problem of color misregistration.

In view of the above conventional problems, it is an object of the present invention to provide a color image reading apparatus capable of preventing color misregistration when a color image is read and reduced or enlarged by a three-line image sensor. To do.

[0010]

In order to achieve the above object, the first means includes three line buffers for storing the respective R, G and B image data read by the three-line image sensor. Each of the R, G, and B image data obtained by reading the same line by each line image sensor of the 3-line image sensor is stored in the line buffer, and the image read by the 3-line image sensor is reduced in the sub-scanning direction. In this case, the control means is provided so as to prevent the image data of the line stored in each line buffer from being read out in accordance with the reduction ratio.

In the second means, the three line buffers for storing the respective R, G, B image data read by the three-line image sensor and the respective line image sensors of the three-line image sensor are the same. Each of the R, G, and B image data obtained by reading a line is stored in the line buffer, and when the image read by the three-line image sensor is enlarged in the sub-scanning direction, each line buffer is stored in accordance with the enlargement ratio. And a control means for controlling the stored image data of the line to be read out repeatedly.

A third means is a switching means for switching the R, G, and B image data read by the 3-line image sensor line by line, and a 3-line image sensor according to the reduction ratio. And a control means for opening and closing each of the switching means at the timing of thinning out the same line read by the line image sensor.

A fourth means is a switching means for switching each of the R, G, and B image data read by the 3-line image sensor line by line, and each of the 3-line image sensor according to the enlargement ratio. And a control unit that opens and closes each of the switching units at the timing of repeating the same line read by the line image sensor.

[0014]

According to the first means, the R, G, and B image data obtained by reading the same line by each line image sensor of the three-line image sensor is stored in each line buffer by the above configuration, and the same line is used at the time of reduction. Is thinned out, so that it is possible to prevent color misregistration at the time of reduction.

In the second means, the R, G, and B image data obtained by reading the same line by each line image sensor of the three-line image sensor are stored in the respective line buffers, and the same line is repeated during enlargement. Since it is read out, it is possible to prevent color misregistration during enlargement.

In the third means, the same line read by each line image sensor of the three-line image sensor is thinned out in accordance with the reduction ratio, so that color shift at the time of reduction can be prevented.

In the fourth means, since the same line read by each line image sensor of the three-line image sensor is repeated according to the enlargement ratio, it is possible to prevent color shift at the time of enlargement.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a block diagram showing an embodiment of a color image reading device according to the present invention, FIG. 2 is an explanatory view showing data in a sub-scanning direction of a 3-line image sensor, and FIG. 3 is a sub-scanning diagram of the image reading device of FIG. 5 is a timing chart showing a main signal when the image is reduced by 2/3 times in the scanning direction, and FIG. 4 is a timing chart showing a main signal when the image reading apparatus shown in FIG. 1 enlarges by 4/3 times in the sub-scanning direction. FIG. 4 is an explanatory diagram showing a 3-line image sensor of this embodiment.

In FIG. 1, line buffers 11R, 1
1G and 11B are 3-line image sensors 10R and 10R, which are shifted by N lines in the sub-scanning direction, respectively, as shown in FIG.
It is possible to store one or more lines of R, G, and B digital image data read by 10G and 11B and A / D converted. The buffer controller 12 generates an address and a write enable signal for writing the input image data in the line buffers 11R, 11G, 11B, and an address for reading the image data written in the line buffers 11R, 11G, 11B. Generate a read enable signal.

Then, as shown in FIG. 2, when the image data is enlarged in the sub-scanning direction, the same line is repeatedly read, and when the image data is reduced, the same line is thinned out. 12 for line buffers 11R, 11G, and 11B,
Buffer write enable signals R, WRVL, G, WRVL, B, WRVL for writing G and B image data
Is output. The CPU 13 also uses the line buffer 11
R, G, B written in R, 11G, 11B respectively
Buffer read signals R and RDV for repeatedly reading each image data of
Outputs L, G / RDVL, B / RDVL. In the example shown in FIG. 2, the R, G, and B line image sensors 10R, 10G, and 10B are displaced in the sub-scanning direction, and in this case, the first 10 lines of B and the first 5 lines of G are displaced. The line image data is invalid and is discarded.

Next, the operation in the case of reducing by 2/3 will be described with reference to FIG. The CPU 13 writes a buffer write enable signal R · WRV for writing the R data from the first line in order to write the R, G, and B image data in the line buffers 11R, 11G, and 11B, respectively.
It outputs a buffer write enable signal G.WRVL for writing L and G data from the sixth line, and a buffer write enable signal B.WRVL for writing B data from the 11th line. The buffer control unit 12 converts the input image data into the line buffers 11R, 11G, 11B.
And write enable signals at the timings of the buffer write enable signals R, WRVL, G, WRVL, B, WRVL are generated. Therefore, the line buffers 11R, 11G, 11B have the same scan line, respectively. R, G, and B image data are stored.

At the time of reading, the CPU 13 controls the R, G, B
After the writing time for one line of each data of
Buffer read signals R / RDVL, G / RDVL, B
・ Make RDVL active for 2 lines and inactive for 3rd line. Therefore, since the R, G, and B data of the third line stored in the line buffers 11R, 11G, and 11B are not read out, the data can be reduced to 2/3 times in the sub-scanning direction, and in the meantime. Since the R, G, and B data of the drawn third line are the same scan line data, color unevenness can be prevented.

Next, the operation in the case of magnifying 4/3 times will be described with reference to FIG. Also in this case, the CPU 13
Buffer write enable signal R.WRVL for writing R data from the first line and buffer write enable signal G.W for writing G data from the sixth line
The buffer write enable signal B.WRVL for writing the RVL and B data from the 11th line is output, but the buffer write enable signal R.
Inactivate WRVL, G · WRVL, B · WRVL. Therefore, during the period of the fourth line, each data of the third line is stored in the line buffers 11R and 11R.
It is stored in G and 11B.

At the time of reading, the CPU 13
After the write time for each line of R, G, B data has passed, the buffer read signals R, RDVL, G, R
DVL, B and RDVL are always active. Therefore, each data of the third line is repeatedly read from the line buffers 11R, 11G, and 11B twice, so that the data can be enlarged 4/3 times in the sub-scanning direction.
Further, since the R, G, and B data of the third line read repeatedly twice are data of the same scan line, color unevenness can be prevented.

Next, a second embodiment will be described with reference to FIGS. FIG. 6 is a block diagram showing a second embodiment,
FIG. 7 is a timing chart showing main signals in FIG. 6, and FIG. 8 is a timing chart for comparing the conventional example with the second embodiment. In the second embodiment, instead of using the line buffers 11R, 11G, and 11B, the step pulse for the stepping motor that drives the scanner (when the original is fixed) is controlled by the CPU software, and the circuit shown in FIG. 6 is used. Valid / invalid signal RVL
It is configured to be thinned out and reduced by DL, GVLDL, and BVLDL.

In FIG. 6, the read signals R, G, B are shifted in the reading position in this order in the sub-scanning direction, for example, every 10 lines, and output to the processing circuit of the next stage via the switches 25R, 25G, 25B, respectively. To be done. Then, the offset line counters 21R and 21G count the line synchronization clock LSYNC, and the comparators 22R and 22G.
Are offset line counters 21R and 21G, respectively.
Of the read signal R and the offset amounts Ro and Go of the read signals G and B, that is, 20 and 10 lines,
If they match, the thinning counters 23R and 23G are set to the enable state by the enable signals REN and GEN. And thinning counters 23R, 23G, 23B
Counts the line synchronization clock LSYNC, and each valid / effective according to the reduction ratio set by the CPU (not shown).
The switches 25R, 25G and 25B are opened and closed by the invalidation signals RVLDL, GVLDL and BVLDL.

The operation of the second embodiment will be described with reference to FIG. 7. The CPU uses the line synchronization clock LSYNC.
Thus, for example, a step signal for reading two lines with four step pulses is output to the scanner stepping motor.
The reading positions of G and B are displaced in the sub-scanning direction by every 10 lines.

On the other hand, the comparators 22R and 2 shown in FIG.
2G are offset line counters 21R and 2R, respectively.
The count value of 1G is compared with 20, 10 lines, and when they match, the thinning counters 23R, 23G are set to the enable state by the enable signals REN, GEN, so that the thinning counters 23R, 23G, 23B have their reading positions in the sub-scanning direction. Counting starts with a delay of the line shifted in the direction.

Therefore, for example, when reducing to 2/3, as shown in FIG. 7, the thinning counter 23B opens the switch 25B by two lines from the head line and closes it by one line by the valid / invalid signal BVLDL, and the thinning counter 2
3G switches 25B by enable / disable signal GVLDL
Open 2 lines from the 11th line and close 1 line,
The thinning-out counter 23R opens the switch 25R by 2 lines from the 11th line and closes it by 1 line by the valid / invalid signal RVLDL, and repeats this operation every 3 lines, so that the same reading is performed as shown in detail in FIG. 8B. Lines are thinned out, and thus color shift can be prevented. Similarly, at the time of enlargement, the color shift can be prevented by opening and closing the switches 25R, 25G, and 25B so that the same reading line is repeatedly output.

In the second embodiment, since each valid / invalid signal RVLDL, GVLDL, BVLDL is generated by the circuit as shown in FIG. 6, that is, hardware, it is different from that generated by the software of the CPU. As a result, the load on the CPU can be reduced.

[0031]

As described above, according to the first aspect of the invention, R read by the 3-line image sensor,
Three line buffers for storing the respective image data of G and B, and R, G, and B in which the respective line image sensors of the three-line image sensor read the same line
Each of the image data of 3 is stored in the line buffer, and when the image read by the 3-line image sensor is reduced in the sub-scanning direction, the image data of the line stored in each line buffer is read according to the reduction rate. Since the control means for controlling so as not to provide the same line is thinned out, the same line is thinned out at the time of reduction, and therefore color shift at the time of reduction can be prevented.

According to a second aspect of the present invention, three line buffers for respectively storing R, G and B image data read by the three-line image sensor and each line image sensor of the three-line image sensor are provided. When the R, G, and B image data obtained by reading the same line are stored in the line buffer, and when the image read by the 3-line image sensor is enlarged in the sub-scanning direction, each line is expanded according to the enlargement ratio. Since the image data of the line stored in the buffer is controlled to be repeatedly read out, the same line is repeatedly read out at the time of enlargement, and thus color shift at the time of enlargement can be prevented.

According to a third aspect of the present invention, there is provided switching means for switching each of the R, G and B image data read by the 3-line image sensor,
Since the control unit that opens and closes each switching unit according to the reduction ratio is provided so as to thin out the same line read by each line image sensor of the three-line image sensor, it is possible to prevent color shift at the time of reduction. it can.

According to a fourth aspect of the present invention, there is provided a switching means for switching the R, G and B image data read by the 3-line image sensor line by line, and a 3-line image sensor according to the enlargement ratio. With the control means for opening and closing the switching means at the timing of repeating the same line read by each line image sensor, it is possible to prevent color misregistration at the time of enlargement.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a color image reading apparatus according to the present invention.

FIG. 2 is an explanatory diagram showing data in a sub-scanning direction of a 3-line image sensor.

FIG. 3 is a timing chart showing main signals when the image reading apparatus of FIG. 1 reduces by 2/3 in the sub-scanning direction.

FIG. 4 is a timing chart showing main signals when the image reading apparatus of FIG. 1 magnifies 4/3 times in the sub-scanning direction.

FIG. 5 is an explanatory diagram showing a 3-line image sensor of the present embodiment.

FIG. 6 is a block diagram showing a second embodiment.

FIG. 7 is a timing chart showing main signals in FIG.

FIG. 8 is a timing chart for comparing the conventional example and the second example.

FIG. 9 is a block diagram showing a general monochrome image reading device.

10 is an explanatory diagram showing a case where the apparatus of FIG. 9 reduces in the sub-scanning direction.

11 is an explanatory diagram showing a case where the color image reading device configured by the device of FIG. 9 reduces in the sub-scanning direction.

12 is an explanatory diagram showing a case where the 3-line image sensor color image reading device configured by the device of FIG. 9 reduces in the sub-scanning direction.

FIG. 13 is a timing chart showing a case in which another conventional color image reading device reduces in the sub-scanning direction.

[Explanation of symbols]

 10R, 10G, 10B Line image sensor 11R, 11G, 11B Line buffer 12 Buffer control unit 13 CPU (Central processing unit) 21R, 21G Offset line counter 22R, 22G Comparator 23R, 23G, 23B Thinning counter 25R, 25G, 25B switch

Claims (4)

[Claims] 1. Three line buffers for respectively storing R, G, and B image data read by a three-line image sensor, and each line image sensor of the three-line image sensor read the same line. When each image data of R, G, and B is stored in the line buffer and the image read by the 3-line image sensor is reduced in the sub-scanning direction, the lines stored in each line buffer according to the reduction ratio. A color image reading apparatus comprising: a control unit that controls so as not to read the image data. 2. Three line buffers for respectively storing R, G, and B image data read by the three-line image sensor, and each line image sensor of the three-line image sensor read the same line. When each of the R, G, and B image data is stored in the line buffer and the image read by the 3-line image sensor is enlarged in the sub-scanning direction, the lines stored in the line buffers according to the enlargement ratio. A color image reading apparatus comprising: a control unit that controls to repeatedly read the image data of. 3. A switching means for switching the R, G, and B image data read by the 3-line image sensor line by line, and a line image sensor of the 3-line image sensor according to a reduction ratio. A color image reading apparatus comprising: a control unit that opens and closes each of the switching units at the timing of thinning the same read line. 4. A switching means for switching each of the R, G, and B image data read by the 3-line image sensor line by line, and each line image sensor of the 3-line image sensor according to the enlargement ratio. A color image reading apparatus comprising: a control unit that opens and closes each of the switching units at a timing of repeating the same read line.