JP2833905B2 - Image reading device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to prescan control of an image reading device.

[0002]

2. Description of the Related Art In an image reading apparatus such as a color copier, a pre-scan is executed before an image reading scan for each color is performed, and a document size detection, a document leading edge position detection, and a color / monochrome discrimination of a document are performed. Do.

FIG. 4 is a flowchart showing a prescan processing procedure in a conventional image reading apparatus. When reading is started, the lamp unit is moved and pre-scan is executed to detect the leading edge position of the document (n21 to n2).
3). When the leading edge position of the document is detected, the color information is detected next (n24), the trailing edge position of the document is detected, the prescan is completed, and the lamp unit is returned to the home position (n25 to n27, n29 to n3).
1) Perform image reading scan (n28, n3)
2). At this time, when color information is detected in n24, reading in the color mode is executed (n32), and when color information is not detected, reading in the monochrome mode is executed (n28).

[0004]

In a color copying machine, the reading size of an image and the copying mode (color or monochrome) can be set in advance. There is no need to determine color / monochrome. However, even when it is not necessary to detect the read size and the color information, the conventional image reading apparatus performs the prescan on the entire surface of the document while detecting the presence or absence of the color information.

As described above, in the conventional image reading apparatus, even when the reading size and the copy mode of the document are set, the reading size, the leading edge position of the document, and the color information are all detected by the prescan. There was a problem that it took time.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image reading apparatus capable of omitting detection in a prescan and shortening a reading time when a document reading size and a copy mode are set. It is in.

[0007]

An image reading apparatus according to the present invention includes a first means for performing scanning until a leading edge position, a trailing edge position, and the presence or absence of a color image of a document are detected during pre-scanning; A second means for performing scanning until the position and the presence or absence of a color image are detected; a third means for performing scanning until the leading edge position of the document is detected; and the second means when the image reading size is known. And selecting means for selecting the third means when reading a monochrome document with a known image reading size and selecting the first means otherwise. I do.

[0008]

According to the present invention, an image can be read by detecting the position of the leading edge of the document, the position of the trailing edge of the document, and the presence / absence of a color image by the prescan (first means).
When the image reading size and the monochrome mode are set, the pre-scan ends when the leading edge position of the document is detected (third means), and when only the image reading size is set, When the leading edge position of the document and the presence or absence of the color image are detected, the pre-scan is finished (second means). As a result, the time for the prescan can be reduced.

[0009]

FIG. 1 is a schematic diagram showing the configuration of a color copying machine having an image reading apparatus according to an embodiment of the present invention. A document table 2 made of hard glass is provided on the upper surface of the copying machine body 1, and a scanning unit 3 for reading a document (not shown) set on the document table 2 is provided below the document table 2. Have been. The scanning unit 3 includes a lamp unit 6,
It has mirrors 7, 8, and 9, a lens unit 10, and a CCD line sensor 11. A lamp unit 6 and a mirror 7 are provided so as to be movable, and read right under the document table 2 from left to right in FIG.
The mirrors 8 and 9 are arranged vertically at a predetermined angle so as to guide the original image reflected by the mirror 7 to the lens unit 10. In order to keep the optical distance between the original reading position and the lens unit 10 constant, the mirrors 8 and 9 are connected to the lamp unit 6 and the mirror 7 during scanning.
Move to the right at half the speed of. At the bottom of the scanning section 3, 3 corresponding to the lens unit 10 and R, G, B
At a predetermined interval (the document image is
(Focus on above). The above 3
In front of the two CCDs 11, R, G, and B filters are provided.

A drum-shaped photosensitive member 12 is rotatably provided at the lower portion of the copying machine main body 1, and a charger 13, an exposure device 14, and a part of the surface of the photosensitive member 12 are provided near the photosensitive member 12. Transfer belt 15, static eliminator 16, cleaner 1 pressed against
7, and a black developing tank 18, a yellow developing tank 19,
Developing devices each having a magenta developing tank 20 and a cyan developing tank 21 are provided.

FIG. 2 is a block diagram showing the configuration of the image processing section of the color copying machine. In the image reading scan, image data input from the CCD 11 as analog signals of R, G, and B is input to the level matching circuit 31. This level matching circuit 31 corrects the difference in photoelectric conversion efficiency between the RGB CCD sensors and further amplifies the difference to an appropriate value. The A / D conversion circuit 32 converts an output from the level matching circuit 31 from an analog signal to an 8-bit digital signal.

Next, the shading correction circuit 33
Of the sensitivity variation, unevenness in the light amount of the light source, unevenness in the brightness of the lens, etc., and the alignment circuit 34 corrects the deviation of the reading positions of the RGB CCD sensors to align the data. At this time, depending on the presence or absence of data,
The document position recognition circuit 38 makes the document position recognized.
The black document detection circuit 39 detects whether the document is monochrome or color based on the RGB ratio.

The gamma correction circuit 35 corrects the gradation characteristics so that the output signal of the CCD sensor and the output density of the printer become linear. That is, RG obtained from CCD sensor
Even if the B data is output to the printer as it is, the dark portion of the document is reproduced darker because the dot diameter of the printer output is usually larger than the theoretical value. Therefore, the dark portion needs to be corrected in the brighter direction and output. This correction is gamma correction and is also called tone correction. The gamma-corrected data is input to a masking circuit 36, which converts the RGB signals into color material CMY signals. UCR processing circuit 37
Then, a black component is generated from the converted CMY signal. UCR (Under Color Removal) is a method of replacing the CMY overlap (black portion) with black toner and reducing the amount of CMY color toner by that amount.
At present, the replacement ratio is generally 30% to 40%.

The sharpness / filter processing circuit 40 performs an operation such as an emphasis process on an image edge portion, and the subsequent scaling processing circuit 41, density processing circuit 42, and color balance circuit 43 are operated at any time by designation from an operation unit (not shown). Process and process data.

Finally, the data is converted into data by a tone reproduction method which matches the output characteristics of each printer by the tone processing circuit 44 and input to the exposure unit 14.

When performing copying in this color copying machine,
The lamp unit 6 and the mirror 7 move in parallel with the document table 2, and the lamp unit 6 irradiates a document set on the document table 2 with light to execute prescan. At this time, the reflected light from the original enters the light receiving surface of the CCD 11 via the mirrors 7, 8, and 9 and the lens unit 10, and is input as an electric signal to a control unit (not shown). The position of the leading edge of the document, the color information, and the size of the document are detected by the reflected light from the document. Thereafter, the lamp unit 6 and the mirror 7 move again to execute an image reading scan in a color mode or monochrome mode process, and the light reflected from the document and passed through the R, G, B filters passes through the CC.
It is incident on D11.

The R, G, and B reflected lights incident on the CCD 11 are converted from analog signals to digital signals by the image processing unit, corrected, converted to CMY signals, and converted to image data (yellow data, magenta data). , Cyan data, and black data) are input to the exposure unit 14. The surface of the photoconductor 12 is uniformly charged by a charger 13 in a dark place, and an optical image of yellow data to be written on the photoconductor 12 is given from the exposure device 14. At this time, the portion of the photoreceptor 12 that is exposed to light has a reduced resistance to remove the charged charges, and the portion that is not exposed to the light remains charged and forms a yellow electrostatic latent image. On the other hand, the developing device charges the yellow toner in the yellow developing tank 19 with a polarity opposite to that of the photoconductor 12 to visualize the latent image. The yellow toner image thus formed moves in the direction of arrow B and is transferred to the transfer belt 15. After the transfer, the charge remaining on the photoconductor 12 is removed by the charge remover 16,
The residual toner remaining on the photoconductor 12 is removed by the cleaner 17.

Next, the surface of the photoreceptor 12 is uniformly charged again by the charger 13, and an optical image of magenta data is given from the exposure unit 14. Thereafter, a magenta toner image is formed in the same manner as the yellow data, and the transfer belt 1
5 and transferred. The toner image formed from the data of each color of yellow, magenta, cyan, and black obtained by the image reading scan as described above is transferred onto the transfer belt 15 in a superimposed manner, and the final image formed on the transfer belt 15 is recorded. The toner image transferred to paper and transferred by heating or pressing is fused to a recording paper to form a permanent image.

On the other hand, when performing copying in the monochrome mode, black toner is supplied from the black developing tank 18 to the electrostatic latent image on the photoreceptor 12, and this toner image is transferred to the transfer belt 1.
5, and is transferred to a recording paper and fused to form a permanent image.

FIG. 3 is a flowchart showing a processing procedure for executing a prescan in a color copying machine. When copying is started, it is determined whether the detection of the document size is necessary (n1). If necessary, the conventional prescan is executed (FIG. 4). If the detection of the document size is unnecessary, the lamp unit 6 is moved. To start pre-scan (n
2, n3). When the leading edge position of the document is detected (n4), it is determined whether the monochrome mode is selected by an external operation key (n5). If the monochrome mode is selected, the prescan is completed and the lamp unit is moved to the home position. Then, the process in the monochrome mode is executed (n8-
n10). On the other hand, if the copy mode is not selected in n5, the prescan is continued, and the prescan ends when color information is detected (n6, n11). After this,
The lamp unit 6 is moved to the home position to execute the color mode process (n12, n13). Also,
If the rear end position of the original is detected without detecting the color information (n6, n7), it is determined that the original is a monochrome original, the prescan is completed, and the lamp unit 6 is moved (n
8, n9), and execute the monochrome mode process (n1).
0).

As described above, in this color copier, if the detection of the document size is unnecessary, the prescan is terminated when the color information is detected after detecting the leading edge position of the document, and the color information is not detected. When the rear end position of the document is detected, the pre-scan is finished, and the color mode or the monochrome mode is executed. When the monochrome mode is selected in advance when performing copying, when the leading edge position of the document is detected, the prescan is terminated and the monochrome mode is executed.

[0022]

According to the present invention, the reading time can be reduced by executing the pre-scan corresponding to the mode set at the time of reading.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of a color copying machine having an image reading apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of an image processing unit of the color copying machine.

FIG. 3 is a flowchart when a prescan is executed in the color copying machine.

FIG. 4 is a flowchart when a conventional prescan is performed.

[Explanation of symbols]

 1 Copier body 2 Platen

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) H04N 1/04-1/207 G03G 15/00 G03G 15/04-15/04 120 G03G 21/00 370- 502

Claims (1)

(57) [Claims] 1. An image reading apparatus, comprising: a platen; and a scanning unit for reading a document image set on the platen, wherein a prescan is performed before the image reading scan. First means for scanning until the leading edge position, the trailing edge position of the document and the presence or absence of a color image are detected; second means for scanning until the leading edge position of the document and the presence or absence of a color image are detected; A third means for performing scanning until detection, and a second means for selecting the image when the read size of the image is known, and a third means for reading the monochrome original when the image read size is known. And an selecting means for selecting the first means at other times.