JPS63142960A - Image reader - Google Patents

Abstract

PURPOSE:To enable the optimum reading of a halftone image to be performed even when an original such as a photograph is placed on the entire plane of an original reading window, by providing a reference white board outside the image reading area of the end part of the original reading window. CONSTITUTION:A first white board 4A is provided at the peripheral part of the original reading window 4 in parallel with a main scan direction, and also, a second white board 4B is provided in parallel with a sub scan direction. An image scanner projects the first white board 4A first, and fetches an output signal from a CCD obtained by the above projection in a white line level reading part in an image reading processing part. From the reference white line level reading part, the output signal of the area of the first white board 4A neighboring to the second white board 4B is stored as a base white level. The image scanner is moved in a direction of (b), and by following to the light quantity distortion of a fluorescent lamp 9A, the optimum reading of the halftone image can be obtained.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to an optical image reading device such as a facsimile,
In particular, the present invention relates to an image reading device capable of reading a halftone image of a document such as a photograph having shading by scanning the document with an optical section.

<Prior Art and its Problems> Normally, an image reading device such as a facsimile machine is of a type that optically reads images attached to a document one by one while sequentially conveying one sheet of the document. However, in order to read a book manuscript image using this method, it is necessary to copy this image once onto a sheet of paper and then read the copied manuscript.

Therefore, in recent years, a facsimile machine has been developed that has an image reading device in which the document is fixed and an optical section scans the image surface of the document.

This image reading device reads images using a fluorescent lamp as a light source, but half-tone images cannot be obtained due to differences in light intensity between the ends and center of the fluorescent lamp, changes in ambient temperature, changes in light intensity due to deterioration, etc. In order to cope with the distortion of the document, a threshold level is determined as a reference white level based on the white level of the document holding member or the white level of the edge of the document.

However, with the former reference white level determination method, if the original covers the entire image reading window or when reading the image of a book original, the white level of the original holding member cannot be read; However, there was a problem in that the white level could not be read if there were blank areas at the edges of the photograph, etc.

The present invention solves the above-mentioned problems and provides a grayscale image reading system that performs gradation division that follows the difference in light intensity between the ends and center of a fluorescent lamp during image reading operation, as well as changes in light intensity due to ambient temperature and deterioration. The object of the present invention is to provide an optical part scanning type image reading device that is possible.

<Means for Solving the Problems> The image reading device of the present invention includes a document reading window which is made of glass or the like and is a document reading area, and a portion parallel to the main scanning direction around the document reading window. A first white plate, a second white plate provided in a peripheral part of the document reading window parallel to the sub-scanning direction, the document reading window, and the first and second white plates are scanned. It features an image scanner.

<Function> According to the image reading device of the present invention, even when a document such as a photograph is placed on the entire surface of the document reading window, it is possible to properly read a halftone image υ, and also to read a similar halftone image υ even in a book document. It can be made readable.

<Embodiment> FIG. 1 shows an external view of an image reading device of the present invention, that is, a facsimile machine, in which 1 is the main body of the facsimile machine, 2 is an original pressing plate, 3 is an original pressing member, and 4 is a glass etc. A document reading window, 5 a telephone, 6 an operation panel, 7 a document, and 8 an image recording paper.

FIG. 2 is a cross-sectional view of the facsimile machine shown in FIG. 1, where 9 is an image scanner, 9A is a light source composed of a fluorescent lamp for illuminating the document, and 9B is a light source that focuses reflected light from the document. A focusing lens, 9C, reads the focused reflected light.
It is a CD image sensor. In addition, this image scanner 9
is configured to read the original image by sequentially moving in the b direction. 10 various image processing circuits and
A facsimile processing section 11 includes a facsimile transmission control circuit, etc., and a recording section 11 records received image data.

Figure 3 shows the main parts of the image reading device of the present invention, and 4 is a document reading window made of glass or the like.

At the periphery of the document reading window 4, a first white plate 4A is provided parallel to the main scanning direction, and a second white plate 4B is provided parallel to the sub-scanning direction. Reference numeral 9A is the light source described above, and the light source 9A is configured to move in the b direction so as to illuminate all of the document reading window 4, the first white plate 4A, and the second white plate 4B.

Next, the movements of the first white plate 4A and the second white plate 4B will be described in detail with reference to the image reading processing block diagram shown in FIG. 4 and the inverted output signal waveform diagram from the CCD image sensor 9C shown in FIG.

Generally, a fluorescent lamp constituting a light source has a disadvantage that the amount of light at the ends is smaller than at the center.

FIG. 5 shows this state. The solid line indicates the white level, and in this state the threshold value (VT) shown in the figure
Therefore, when the output signal from the CCD image sensor 9C is sliced, it is determined to be a black image after slicing, even though it is actually white, and the result is output. Therefore, as shown in FIG. 6, accurate image output can be obtained by correcting the threshold value (vT) in accordance with the white level. The first white plate 4A is provided to obtain a reference white level necessary for performing the above operation. That is, to start the image reading operation, the image scanner 9 first irradiates the first white plate 4A, and the output signal from the CCD obtained thereby is sent to the reference white line level reading section 1 of the image reading processing section 10.
Take it into 0A. The captured signal is supplied as a basic white line level to the basic threshold level calculation unit 10B, and a corresponding threshold level is calculated and stored in the basic threshold level storage unit 10D. Incidentally, from the reference white line level reading section 10A, the output signal of the area of the first white board 4A adjacent to the second white board 4B is used as the basic white level and is supplied to the basic white level storage section 10C and stored. When the threshold level (VT) as shown in FIG. 6 is determined in the above manner, the image scanner 9 moves in the b direction and reads the appropriate halftone image by following the light amount distortion of the fluorescent lamp 9A. However, with the fluorescent lamp 9A, there is not only a difference in light intensity between the edges and the center, but also changes in light intensity due to ambient temperature, lighting time, deterioration from use, etc., and image reading will continue until this point. Large unevenness occurs in the read image, making it impossible to read an appropriate halftone image. Therefore, it is necessary to detect this change in the amount of light, and the second white plate is used to detect this change.

In other words, the output signal from the CCD image sensor 9C includes the image signal obtained from the document reading window and the second white plate 4B.
The image signal is taken into the image reading section 10H, and the reference white level is taken into the reference white level reading section 10E. The captured reference white level is compared with the white level previously stored in the basic white level storage section 10C in the white level comparison section 10F. This comparison result is supplied to the basic closure level calculation unit LOG, and if the reference white level is higher (lower) than the basic white level, the threshold level /L/total value stored in the basic closure level storage unit 10D is This is the threshold level of the image signal output from the CCD image sensor-9C, and α
It undergoes slicing processing in the value processing section. Figure 7 shows this corrected threshold value (7 lines), and by repeating the above process every time one line image is read, it is possible to perform halftone reading that is optimal for the fluorescent lighting conditions. becomes.

Although the Takagi embodiment has been described using one threshold value to simplify the explanation, it goes without saying that there are threshold values for N gradations in halftone image reading.

<Effects> As described above, according to the present invention, by providing the reference white plate outside the image reading area at the edge of the document reading window, it is possible to optimally place an original such as a photograph at the edge of the document reading window. Not only is it possible to read halftone images, but also optimal image reading is possible for printed originals as well.

[Brief explanation of the drawing]

Figure 1 is an external view of the facsimile, Figure 2 is a sectional view of the facsimile, Figure 3 is a diagram showing the image reading device, Figure 4 is a diagram showing the image reading processing block, and Figures 5 and 6 are CCD.
A diagram showing the relationship between the output signal from the image sensor and the threshold value, and FIG. 7 is a diagram showing the fluctuated threshold value. 4... Original reading window, 9A... Light source, 4A...
1st white board, 4B... 2nd white board.

Claims (1)

[Scope of Claims] 1. A document reading window that holds a document so that it can be loaded and is provided as the maximum image reading area, a light source for irradiating the document with light, and a photoelectric conversion device that receives reflected light from the document. an image scanner that has at least a photoelectric conversion element for performing the above-mentioned scanning, and sequentially reads images of the document while moving in a sub-scanning direction; and an image signal corresponding to the density of the document based on an output signal from the photoelectric conversion element. an image processing circuit for outputting a first white plate, a first white plate provided in a peripheral part of the original reading window parallel to the main scanning direction; An image reading device capable of reading grayscale originals, comprising: a second white plate provided in a portion parallel to the sub-scanning direction.