JPS63164673A - Color original reader - Google Patents

Abstract

PURPOSE:To prevent the forming of read image that includes color blurring by detecting an edge that appears in a read image, comparing the positions of appearing edges with each other, and discriminating the shifting of an image. CONSTITUTION:An edge comparison part 32 compares, during the time when an image of green color component and blue color component is being read, an edge position information AD outputted from an edge sampling part 31 and a reference edge position information ADr stored in a buffer memory 31 with each other in the line-unit, and in case difference points of edge positions are present more than a prescribed number, generates a positional shifting line signal LN. A comparator 34 compares an accumulation value CL with a positional shifting line number reference value CLr, and forms a positional shifting warning signal AR if the CL exceeds the CLr. As long as the positional shifting warning signals AR are outputted, there is a positional shifting in the image signals. Therefore, the read action is repeated from the beginning.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a color document reading device that separates and reads images of a document in a one-page sequential manner.

[Prior Art] There are various types of color document reading devices that separate and read a document image into a plurality of color components, one of which is a so-called frame sequential method.

This field-sequential color document reading device uses an optical system to scan the read document multiple times and separates the document image into multiple color components by switching the light source color or color separation filter color for each scan. The structure is very simple compared to other systems, and the device can be realized at low cost.

However, when reading a thick document (so-called book document) in color using such a color document reading device using the field sequential method, the following inconvenience occurs.

That is, when reading a book original, it is necessary to maintain the position of the original so that the original does not shift until the scanning of the optical system is repeated for the number of color separations.

If the original is misaligned during the process, the color component images read after that do not match the color component images read before, which may cause color misalignment when the scanned images are combined. Ta.

[Objective] The present invention has been made in order to eliminate the disadvantages of the prior art, and an object of the present invention is to provide a color document reading device that can prevent color shift in a read image.

[Configuration] In order to achieve this object, the present invention detects the edges appearing in the read image, compares the edge positions appearing in the read image of each color component, and calculates the deviation of the image based on the comparison result. is determined.

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 illustrates an optical system of a color document reading apparatus according to an embodiment of the present invention. This device is.

A color image is formed by providing a color separation filter that separates the image into three primary colors just before the line image sensor.

In the figure, the image surface of a book document 2 placed so that the document surface is in contact with the contact glass 1 is illuminated by a light source 3, and the reflected light is sequentially reflected by mirrors 4 and 5. The colors are separated through a one-color separation filter 7, and an image is formed on a line image sensor 9 through a lens 8.

The light source 3 and the mirror 4 are mounted on the same traveling body 10, and the mirror 5°6
is mounted on a traveling body 10 that moves at 1/2 the speed of the traveling body 1o while synchronizing with this traveling body 10. As a result, the light source 3 and the mirrors 4, 5.6 scan the image surface of the book original 2 in the sub-scanning direction.

An example of a color separation filter is shown in FIG.

In the figure, the color separation filters 7 include a red filter Fr for reading the red component of an image formed in a rectangular shape, a green filter Fg for reading the green component of the image, and a color filter Fg for reading the blue component of the image. It consists of a filter FT with a blue filter Fb arranged adjacent to it, a guide mechanism GD that guides the filter FT in a direction perpendicular to the optical axis, and a drive mechanism DR that reciprocates the filter FT.

When the optical system reciprocates once, the color components imaged on the line image sensor 9 are switched by sequentially switching filters FT that intersect with the optical axis.

FIG. 3 shows an example of a signal processing system.

In the figure, an image signal AV output from a line image sensor 9 is applied to an analog/digital converter 22 via an amplifier 21, and a digital image signal D having a predetermined number of bits is input.
It is converted to v. This digital image signal DV is applied to a halftone processing section 23 and an edge detection section 24.

The halftone processing unit 23 converts the digital image signal DV into a pseudo halftone signal DG by processing using a well-known dither matrix or the like. One page of this halftone signal DG is stored in one of the page memories 26, 27, and 28 via the switch 25.

The switch 25 selects the page memory 26 when the line image sensor 9 is reading a red component image, and the page memory 27 when the line image sensor 9 is reading a green component image.
, and select the page memory 28 when reading a blue component image.

As a result, the page memory 26 receives the halftone signal DGr of the red component of the image, the page memory 27 receives the halftone signal DGr of the green component of the image, and the page memory 28 receives the halftone signal DGb of the blue component of the image. Each is accumulated.

In this way, the halftone signals DGr, DGg, and DGb of the red component, green component, and blue component stored in the page memories 25, 26, and 27, respectively, are transferred to the switch 2.
9 to the next stage device (not shown).

The edge detection section 24 detects that the digital image signal DV is located on an edge by a well-known Laplacian process or the like, and the detection signal DD is applied to the edge sample section 30.

The edge sample section 30 generates the address of the pixel to which the detection signal DD is output from the edge detection section 24 as edge position information AD. That edge location information A
D is added to the buffer memory 31 and edge comparison section 32.

Now, assuming that the color components of an image are formed in the order of a red component, a green component, and a blue component, the edge position information AD output from the edge sample unit 31 when the first red component image is being read is However, the buffer memory 31
is stored as reference edge information ADr.

The edge comparison unit 32 compares the edge position information AD output from the edge sample unit 31 when the green component and blue component images are being read with the reference edge position information ^ which is stored in the buffer memory 31. If there is a predetermined number or more of differences in edge position in that line compared to the unit, a positional deviation line signal LN is generated. This positional deviation line signal LN is counted by a counter 33, and its integrated value CL is added to a comparator 34. In addition.

The integrated value CL of the counter 33 is cleared to O when processing of the green component image is completed.

The comparator 34 compares the integrated value CL with the signal output from the reference value setter 35 and the reference value CLr for the number of misaligned lines,
When the integrated value CL exceeds the reference value CLr for the number of misaligned lines, a misalignment warning signal AR is generated and output to the next stage device.

In this way, with the edges in the red component image as a reference, the deviations of the edges in the green component image and the edges in the blue component image are detected, respectively. Normally, edges that appear in an image appear in almost the same position regardless of each color component, so by determining whether these edges match, the image when reading the image of each color component is It is possible to determine the positional deviation of.

As a result, when the positional deviation warning signal AR is output, the image signal obtained at that time (halftone signal DG
r, DGg, DGb), there is a positional shift.

Therefore, when this positional deviation warning signal AR is output, it is sufficient to notify the operator of the positional deviation warning through an appropriate display and repeat the reading operation from the beginning.

In this way, it is possible to know whether or not a positional shift has occurred in the obtained color image signal, so that finally a color image signal without any positional shift can be obtained.

Note that the configuration of the color separation filter and its color switching mechanism are not limited to those of the embodiments described above. Furthermore, the present invention can be similarly applied to a device that switches the color of a light source.

Furthermore, a method for determining an image shift based on the edge detection results may be other than that of the embodiment described above.

[Effects] As explained above, according to the present invention, edges appearing in a read image are detected, edge positions appearing in the read image of each color component are compared, and image deviation is determined based on the comparison results. Since the image data is determined, it is possible to prevent the formation of a read image containing color misregistration.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an example of an optical system according to an embodiment of the present invention, FIG. 2 is a schematic perspective view showing an example of a color separation filter, and FIG. 3 is a block diagram showing an example of a signal processing system. be. 6... Color separation filter, 9... Line image sensor, 24... Edge detection section, 30... Edge sample section, 31... Buffer memory, 32... Edge comparison section, 33...・Counter, 34...Comparator, 35・
・Reference value setter・

Claims (1)

[Claims] In a color document reading device that reciprocates the optical system multiple times in the sub-scanning direction of the document to be read and switches the color components to be read during the reciprocating motion, the color image is separated into images of multiple color components and read. The apparatus includes an edge detection means for detecting edges, a comparison means for comparing edge positions appearing in the read image of each color component, and a discrimination means for determining image deviation based on the output of the comparison means. A color document reading device characterized by detecting color misregistration that appears.