JP2669642B2 - Image reading device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to an image reading apparatus, and more particularly, to an image reading apparatus that improves image quality during image enlargement processing.

(Prior Art) Recently, in an image reading device such as a digital copier or a scanner device, it is required not only to read an image of a document but also to enlarge or reduce the image.

Conventionally, when performing an image enlargement process in an image reading apparatus, the same pixel is read twice at a predetermined enlargement timing in the main scanning direction, and the same line is read twice at a predetermined enlargement timing in the sub-scanning direction. ing.

That is, in the conventional image reading apparatus, as shown in FIG.
Image data for one line (image data for one line divided for each pixel) is read from the (Charge Coupled Device), and a drive signal is output to the step motor at a drive timing synchronized with the main scanning synchronization signal to output a sub signal. To scan.

At the enlargement timing, the main scanning synchronization signal for reading the CCD output DATnA is output and the CCD output DATnA is read, but the drive signal synchronized with this is not output to the step motor and sub scanning is not performed. The image data of the same line is read as the CCD output DATnB by the next main scanning synchronization signal, and the drive signal is output at this timing.

Therefore, at the enlargement timing, the same line is read twice, and the image is enlarged in the sub-scanning direction.

(Problems to be Solved by the Invention) However, in such a conventional image reading apparatus, in order to perform the sub-scanning in the sub-scanning direction by the reading width, the step motor is driven only once, and at the enlargement timing. Since the sub-scan is stopped, the same line cannot be read twice, which causes a shift, and even if abrupt drive is performed to read the next line, the shift affects the image quality. There was a problem.

That is, until the expansion timing, the step motor 1
Sub-scanning is performed at a constant speed by a predetermined reading width (for example, 1/12 mm) with a degree of drive. When the enlargement timing is reached, the step motor is not driven and sudden braking is applied. However, even if sudden braking is applied to a sub-scan at a constant speed, it does not stop abruptly, and the image data read by the main-scan synchronizing signal, that is, the image reading point is as shown in FIG. Assuming that the n-th line is the enlargement timing, the same n-th line is not read twice but read at a position shifted in the direction of the (n + 1) -th line as shown by a broken line. That is, DATnA is a CCD output at the position of the solid line, and DATnB is a CCD output at the position of the broken line. This shift in the reading position also affects the reading position of the next line and subsequent lines, deteriorating the image quality.

Therefore, according to the present invention, the sub-scanning is performed with a step width smaller than the reading width in the sub-scanning direction, and when the image is enlarged, the sub-scanning is performed to the intermediate position of the reading width to perform reading in the sub-scanning direction. An object of the present invention is to improve the image quality at the time of image enlargement by performing the image enlargement process to reduce the speed fluctuation of the sub-scan at the time of image enlargement, and to set an accurate reading position.

(Structure of the Invention) In order to achieve the above object, the present invention divides reflected light of light illuminated on a document for each pixel, performs main scanning for each line at a predetermined reading timing, and based on a sub-scanning signal. In an image reading device that performs sub-scanning at a predetermined step width,
One step width in the sub-scanning direction is set to be smaller than the reading width in the sub-scanning direction, and when the image is enlarged, the sub-scanning signal is appropriately thinned to perform sub-scanning to an intermediate position of the reading width, and at the intermediate position. It is characterized by reading an image.

 Hereinafter, a specific description will be given based on examples of the present invention.

 1 to 4 are views showing an embodiment of the present invention.

FIG. 1 is a main part circuit block diagram of the image reading apparatus 1. The image reading apparatus 1 has a CPU (Central Processing Unit).
2, a motor driver 3 and an image reading means 4.

The motor driver 3 uses the drive timing signal MT from the CPU 2
The CPU 2 outputs a drive pulse to a sub-scanning step motor (not shown) in synchronization with the above, and the CPU 2 outputs a drive timing signal MT to the motor driver 3 at a predetermined cycle.

The image reading unit 4 is formed by a CCD (Charge Coupled Device) or the like, and divides the reflected light of the light applied to the document into pixels and performs photoelectric conversion. The image reading means 4 reads an image in synchronization with the main scanning synchronization signal ST input from the CPU 2 and outputs read image data. The drive timing signal MT is
As shown in FIG. 2, normally, the period has twice the period of the main scanning synchronization signal ST, and the output timings of the main scanning synchronization signal ST and every other drive timing signal MT are synchronized.

 Next, the operation will be described.

When not enlarging the image, the CPU 2 outputs the main scanning synchronization signal ST to the image reading means 4 to cause the image reading means 4 to read the image, as shown in FIG.
The driving timing signal MT is output to the motor driver 3 at a cycle twice as long as the main scanning synchronization signal ST to perform sub-scanning. Every other output timing of the main scanning synchronization signal ST and the drive timing signal MT is synchronized. Accordingly, the stepping motor performs sub-scanning at a step width that is half the reading width in the sub-scanning direction, and an image is read from the image reading unit 4 at a rate of one for every two sub-scans. As a result, the sub-scanning is performed at a constant speed, and the image is periodically read at the timing of the main scanning synchronization signal ST. Therefore, as shown in FIG. 3, the image reading means 4 reads an image accurately at every predetermined reading width.

Next, when the image enlargement process is performed, the number of readings per page of the original is increased in accordance with the enlargement ratio. Therefore, in the present embodiment, between the main scanning synchronization signal ST and the main scanning synchronization signal ST at the enlargement timing. In addition to thinning the drive timing signal MT output to the motor driver 3 to read an image at each normal reading width position, the image is also read at a sub-scanning position that is half the normal sub-scanning width.

That is, as shown in FIG. 2, when DATnA is read by the main scanning synchronization signal STnA of the nth line of the main scanning synchronization signal ST, the drive timing signal MT is output to the motor driver 3 and the sub-scanning is performed by half the reading width. To do. However, after that, the drive timing signal MT output between the normal main scanning synchronization signal ST and the main scanning synchronization signal ST is cut once, and the main scanning synchronization is performed with the image reading unit 4 at the position where the sub scanning is performed by half the reading width. signal
Output STnB and read the image. The drive timing signal MT is output to the motor driver 3 in synchronization with the output of the main scan synchronization signal STnB, the sub-scan is performed by half the reading width, and the main scan synchronization signal STn _{+ 1} is output again. Therefore, the image is read again at the position where the sub-scan is performed by the normal reading width from the output position of the main scanning synchronization signal STnA, and the normal reading operation is performed until the next enlargement timing comes. Therefore, since the sub-scanning is performed with a step width that is half the normal reading width, even if the drive timing signal MT is thinned out at the enlargement timing, the speed variation of the sub-scanning is small, and the sub-scanning is completely stopped and the same. As shown in FIG. 4, the line is not read twice, and the reading is performed at a position (n-th line B) which is sub-scanned by half the normal reading width, so that the speed fluctuation of the sub-scan is further reduced. be able to. As a result, the image quality at the time of the enlargement processing can be improved. Further, compared with the case where the same line is read twice, the intermediate position of the reading width is read, so that the image quality is smooth and the quality is further improved.

Although the sub-scanning step width is half the normal reading width in the above-described embodiment, the present invention is not limited to this, and any sub-scanning step width that can suppress sub-scanning speed fluctuations may be used.

(Effects) According to the present invention, it is possible to reduce the speed fluctuation of the sub-scanning at the time of image enlargement, to set an accurate reading position, and to improve the image quality at the time of image enlargement.

[Brief description of the drawings]

1 to 4 are diagrams showing an embodiment of the image reading apparatus of the present invention. FIG. 1 is a block diagram of a main part of the image reading apparatus, and FIG. 2 is a main scanning synchronization signal ST. Timing chart showing the relationship between the timing signal MT and the output image,
FIG. 3 is a diagram showing image reading points at the time of non-magnification, and FIG. 4 is a diagram showing image reading points at the time of image enlargement processing. 5 and 6 are views showing a conventional image reading apparatus.
FIG. 6 is a diagram showing the relationship between the main scanning synchronization signal, the drive timing signal and the output image, and FIG. 6 is a diagram showing image reading points during the image enlargement processing. 1 ... image reading device, 2 ... CPU, 3 ... motor driver, 4 ... image reading means.

Claims (1)

(57) [Claims] 1. An image reading apparatus which divides reflected light of light applied to an original into pixels and performs main scanning for each line at a predetermined reading timing and sub-scans at a predetermined step width based on a sub-scanning signal. In step 1, the step width in the sub-scanning direction is set to be smaller than the reading width in the sub-scanning direction, and when the image is enlarged, the sub-scanning signal is appropriately thinned to perform sub-scanning to a position in the middle of the reading width. An image reading device for reading an image at a position.