JPS61251363A - Image reader - Google Patents

Abstract

PURPOSE:To reduce the quantity of a hardware and facilitate adjustment of the read start position by performing analogous measurement of white level length. CONSTITUTION:In a black and white pat 4 for detecting the read operation start position, the boundary of the black part and the white part is not inclined in the entire area, but all black part and all white part are provided on the edge part. A read signal in this black and white pat allows setting a level when quantitizing an image signal. Therefore, black and white signals can be obtained over the entire scan length of a charge coupled device CCD. An output from an integrating circuit 9 is compared with the preset value in a comparator 10. A read operation start signal is outputted when they become equal. By changing this setting level, the adjustment with the black and white pat is executed as it is mounted.

Description

[Detailed Description of the Invention] [Summary] In an image reading device that reads an original image placed on a document table, the boundary between the white part and the black part of the pad for detecting the reading operation start position is diagonal, and the light receiving element COD is By integrating the signal obtained by converting the output into a binary value, the detection of the starting position of this operation is made accurate and adjustable.

[Industrial Field of Application] The present invention relates to an image reading device, and more specifically, to detecting a reading operation start position in an image reading device.

[Prior Art] FIG. 3 shows a conventional method of detecting a reading operation start position in an image reading apparatus.

In FIG. 3(a), 1 is a document table on which a document 2 is placed, 3 is a fluorescent lamp that illuminates the surface of the document, and 4 is a black and white pad for detecting the reading operation start position.

The light generated by the fluorescent lamp 3 is reflected by the original platen 1 and the original 2, and is condensed in a linear manner by the lens 5 onto a COD (charge-coupled device) 6, which is a light receiving element.

The charges stored under the electrodes of the CCD 6 are transferred to output one scanning data and enter the slice circuit 7. The output obtained by slicing at a certain slicing level by the slicing circuit 7 becomes a read operation start signal.

As shown in FIG. 3 (bl), the black and white pad 4 has a border between a white part and a black part that is located on the document table 1 or the photoelectric conversion unit 3,5.
It is perpendicular to the direction of movement of 6.

Therefore, the document table 1 or the photoelectric conversion unit 3. 5. 6 moves and reaches the boundary where the scan changes from black to white, the output of CCD 6 will exceed the slice level and a read operation start signal will be generated.

[Problems to be solved by the invention] In the conventional method described above, malfunctions are likely to occur due to dirt and dust on the document table or in the optical path, and the mounting angle and position of the black and white pads must be highly accurate. This poses a problem in that it takes time and effort to make adjustments.

The present invention aims to provide a novel image reading device that solves these problems.

[Means for Solving the Problems] FIG. 1 shows a block diagram of the principle of an image reading device according to the present invention.

In FIG. 1, 1 to 6 indicate the same objects as in FIG. The border is slanted.

In the black and white pad 4 for detecting the reading operation start position, the border between the white part and the black part is not diagonal throughout the entire area, and the black and white part is provided at the edge with a completely white part and a completely black part. In order to be able to set the level for image signal quantization using the read signal in the COD, white and black signals can be obtained over the entire scanning length of the COD.

8 is a slice circuit similar to the slice circuit 7 shown in FIG. 3; 9 is an integration circuit that integrates the output of the slice circuit 8 for one scanning period; 10 is the output of the integration circuit 9; When it compares with a preset value and matches, it outputs a read operation start signal.

[Function] FIG. 2 is a diagram showing waveforms of each part of the image reading device of the present invention, and the functions, functions, and effects of the image reading device of the present invention will be explained using this waveform diagram.

FIG. 2(a) shows an input signal to the slice circuit 8.

The figure shows that the scanning line of the photoelectric conversion unit is located near the center of black and white pad 4, and the length of the white level region in the first half of the scanning section is almost equal to the length of the black level region in the second half of the scanning section. This indicates that there is noise due to dust etc. in the level.

In FIG. 2, bl indicates the output of the slicing circuit 8, and the waveform in FIG.

FIG. 2 (0) shows the waveform of the integrated output of the integrating circuit 9.
As shown in the figure, this integrated output is a voltage corresponding to the length of the white level region.

The output of the integrator 9 is compared with the set level shown by the broken line in the comparator 10, and when they match, the output is shown in FIG. 2(d).
Outputs the read operation start signal shown in .

That is, the set level also corresponds to a certain white level area length, and the white level area length is measured as an integral value of the output of the COD.

By changing this setting level, the reading operation start position can be adjusted while leaving the black and white pads attached as they are. Therefore, it is not necessary to attach the black and white pads with high accuracy.

In this way, by measuring the white level length in an analog manner, the amount of hardware can be reduced compared to digital measurement.

Furthermore, by using an integrating circuit, it is hardly affected by noise caused by dirt or dust.

[Effects of the Invention] As explained above, according to the present invention, since the reading start position can be easily adjusted, it is not necessary to attach the black and white pads with high precision, and the influence of noise caused by dirt and dust can be reduced. Therefore, it is possible to obtain an image reading device that is free from damage, and its practical effects are great.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the principle of the present invention, FIG. 2 is a waveform diagram of each part of the image reading apparatus of the present invention, and FIG. 3 is a block diagram of a conventional example. In the drawings, 1 is a manuscript table, 2 is a manuscript, 3 is a fluorescent lamp, 4 is a black and white pad, 5 is a lens, 6 is a photodetector (COD), 7.8 is a slice circuit, 9 is an integration circuit, and 10 is a comparison circuit. The vessels and are shown respectively. Figure '43

Claims (1)

[Claims] An image reading device that reads an image of a document (2) placed on a document table (1), which is attached to an end of the document table (1) and has a white part and a black part. Pad for detecting the reading operation start position with diagonal border (4
), a slicing circuit (8) that slices the output of the reading light receiving element (6) at an arbitrary level, and a slicing circuit (8) that integrates the binarized signal output from the slicing circuit (8) using the main scanning period as a delimiter. an integrating circuit (9); and a comparator (10) that compares the output of the integrating circuit with an arbitrary set level and outputs a read operation start signal when the results match.
An image reading device comprising: