JP2000009455A - Sheet size detector and image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the sheet size surely under any conditions by generating a high frequency oscillation on a sheet mounting table and utilizing an ultrasonic wave thus generated for identification. SOLUTION: A high frequency oscillation is generated on a document mounting table 1 by operating a shaker 5. A sheet document is then pressed against the document mounting table 1 by mounting it on the table 1 and closing a cover 2. When a high frequency oscillation is generated on the document mounting table 1 in that state, an ultrasonic wave of some natural frequency is generated from a part where the sheet document is present and an ultrasonic wave of some other natural frequency is generated from the part where the sheet document is not present. An image reader 100 judges whether the sheet document is present or not at each position on the table 1 utilizing the difference of natural frequencies and discriminates the document size to any of regular sizes of document based on the judging results.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet size detecting device for detecting the size of a sheet placed on a sheet placing table, and an image of the sheet placed on the sheet placing table provided with the sheet size detecting device. The present invention relates to an image reading apparatus that generates an image signal by scanning.

[0002]

2. Description of the Related Art In a document reading apparatus, there are the following methods for detecting the size of a document set on a document table. (B) A plurality of optical sensors each having a light emitting unit and a light receiving unit are arranged at predetermined positions below the document table, and light is emitted upward from the light emitting unit of each sensor, and the reflected light is transmitted to each light receiving unit. And size is determined based on the detection status. This method is disclosed, for example, in Japanese Patent Application Laid-Open No. 8-95170. (B) A method in which an image sensor detects the size of a document during pre-scanning. This method is disclosed in, for example, Japanese Patent Application Laid-Open No. 5-562.
No. 30 discloses this.

[0003]

In the conventional document size detection method, when the light transmittance of the document paper is high, or when the color of the document paper and the color of the pressing surface of the document cover are the same system,
The document size may not be detected. For example, when the original paper is an OHP sheet, or when the color of the pressing surface of the original cover is yellow and the background of the original paper is yellow, the original size cannot be detected.

Japanese Unexamined Patent Publication No. Hei 8-95170 discloses a technique for detecting the size of a document having a high light transmittance by switching the light receiving sensitivity of an optical sensor to the minimum sensitivity capable of detecting the reflected light from the document pressing surface. Is disclosed. But,
In this technique, there is a problem that the accuracy of detection is reduced in order to minimize the sensitivity.

An object of the present invention is to make it possible to reliably detect the size of a sheet on a sheet mounting table even when the sheet has a high light transmittance or when the color of the sheet and the color of the sheet pressing surface are the same. With the goal. For example, when an OHP paper original having a high light transmittance or an original of the same color as the pressing surface of the original cover is placed on the original placing table, it is an object to reliably detect the size of the original.

[0006]

According to a first aspect of the present invention, there is provided a sheet size detecting apparatus for detecting a size of a sheet placed on a sheet placing table, wherein the sheet placing table generates high-frequency vibration. A sheet comprising: a vibrator; detecting means for detecting ultrasonic waves generated by the high-frequency vibration; and identifying means for identifying a size of a sheet placed on a sheet placing table based on a detection result of the detecting means. It is a size detection device.

According to a second aspect of the present invention, in the first aspect, the detecting means detects ultrasonic waves at a plurality of predetermined positions,
The identification means is a sheet size detection device that identifies which fixed size sheet is based on a combination of the presence or absence of the sheet at each of the predetermined positions.

According to a third aspect of the present invention, there is provided an image reading apparatus which scans an image of a sheet placed on a sheet placing table to generate an image signal. An image reading apparatus provided with the image reading apparatus.

According to a fourth aspect of the present invention, in the third aspect, the detecting means is provided on a moving body for scanning the image of the sheet, and the detecting means is provided at a predetermined timing during scanning. An image reading device that detects ultrasonic waves at a plurality of predetermined positions by detecting sound waves.

[0010]

FIG. 2 is a schematic diagram showing the configuration of an apparatus according to an embodiment. The illustrated apparatus 100 exposes and scans a sheet original placed on a transparent original placing table 1 with an image surface facing downward, guides the image reflected light to a CCD line image sensor 4f, and performs photoelectric conversion. Is an image reading apparatus that generates digital image data by sending an electric signal generated by the image processing unit 7 to an image processing unit 7 (FIG. 1A) and performing known image processing.

The exposure scanning of the original image is performed by moving a moving unit A having an exposure lamp 4a, a first mirror 4b, etc., along the lower surface of the original table 1 to the left in FIG. (Slit light, shown by a dashed line in the figure) from the first mirror 4b via the second mirror 4c and the third mirror 4d in the moving unit B, and further via the lens unit 4e inserted in the optical path. , CCD line image sensor 4
This is done by leading to f. Here, mobile unit B
Moves in the same direction at half the speed of the mobile unit A. In the figure, reference numeral 2 denotes an openable and closable document cover for pressing a document, and 3 denotes a white reference plate for shading correction. It should be noted that the configuration shown is an example, and for example, the photoelectric conversion element is not necessarily required to be the CCD 4f, and other known elements may be used.

In the present apparatus 100, digital image data generated by exposure scanning of a document image is sent to a printer unit (not shown) and used for image recording on paper. That is, the apparatus 100 is configured as a part (image reading unit) of a digital copying machine. The image recording method includes, for example, an electrophotographic method using laser exposure, but is not limited to this, and may use LED exposure. Further, a known method other than the electrophotographic method may be used. The present device 10
0 may be configured as a part (image reading unit) of the facsimile apparatus. In addition, the present apparatus 100 may be configured as a single image reading apparatus and used by connecting to, for example, a personal computer or the like.

In the image reading apparatus 100, the document table 1
A vibrator 5 is provided at one end (the left end in the figure), and the vibrator 5 is operated to generate high-frequency vibration on the document table 1. As the vibrator 5, for example, an ultrasonic vibrator is used, and is operated together with the ultrasonic detection receiver 6 in accordance with a command from an image processing unit (FIG. 1A) 7 including a CPU.

When high frequency vibration is generated on the document table 1, ultrasonic waves are generated from the document table 1 (see FIG. 1A). The natural frequency of the ultrasonic wave differs depending on the presence or absence of a document on the document table 1. In other words, when the sheet document is placed on the document placing table 1 and the document cover 2 is closed, the sheet document is pressed against the document placing table 1 and, in this state, high-frequency vibration is generated on the document placing table 1, so that the sheet document portion An ultrasonic wave having a certain natural frequency is generated from (in the document set area), and an ultrasonic wave having another natural frequency different from the above is generated from a portion where the sheet document is not present (outside the document set area). .

In the image reading apparatus 100, the presence or absence of a sheet document at each position of the document table 1 is determined by using the difference in the natural frequency, and based on the determination result, the document size is reduced to a fixed size. Either is identified. In particular,
The ultrasonic wave generated from the document table 1 is transmitted to each position in the longitudinal direction of the moving unit A (50 m from the upper end of the document table 1 in FIG. 3).
m, 240 mm, and 270 mm) at predetermined timings during prescan by three receivers (ultrasonic sensors) 6a, 6b, and 6c provided at respective positions corresponding to the predetermined timings. The presence or absence of a document at each position is determined based on the natural frequency of the ultrasonic wave, and the document size is determined based on the determination result.

That is, as shown in FIG. 1B, prior to the pre-scan, the vibrator 5 and the receiver 6 (6a, 6b, 6)
c) is operated (S1), and the detection signals of the respective receivers 6a, 6b, 6c are taken into the CPU in the image processing unit 7 at a predetermined timing during the pre-scan. This allows
The natural frequency of the ultrasonic wave at a plurality of positions (positions indicated by hatched portions 1) to 3) in the document table 1 is detected (S2).
When the pre-scan is completed, the exciter 5 and the three receivers 6
After turning off a, 6b and 6c (S3), each position 1) is determined based on the natural frequency of the ultrasonic wave at each of the plurality of positions 1) to 3).
The presence / absence of a sheet document in 3) is determined. By comparing and comparing the result of the determination with the table of FIG. 1C, the size of the sheet document is changed to the standard size (B5Y (horizontal), A4Y).
(Horizontal), A4T (vertical), B4T (vertical), A3T (vertical))
(S4). In FIG. 1C, 0 indicates that there is no original, and 1 indicates that there is an original.

In the above description, the sheet original size is as shown in FIG.
As shown in (1), when the presence or absence of a sheet at a plurality of detection positions 1) to 3) is determined, the size is determined based on the fact that it can be uniquely determined as any of the standard sizes.
For example, when there is a document at the position 1) and there is no document at the other positions 2) and 3), the sheet document size is uniquely determined as the A4T size, as is apparent from FIG. The same applies to other standard sizes, which are uniquely determined from the presence or absence of a sheet at the detection positions 1) to 3).

In the above description, the presence or absence of a sheet document is determined at three positions 1) to 3). However, the accuracy may be increased by determining at four or more positions. When there are few types of fixed sizes to be identified, the processing can be simplified by discriminating at two or less positions.

[0019]

According to the present invention, high-frequency vibrations are generated on the sheet mounting table to generate ultrasonic waves, and the size of the sheet is determined based on the fact that the natural frequency of the ultrasonic waves differs between the position where the sheet exists and the position where the sheet does not exist. Is identified, it is possible to reliably detect even when the light transmittance of the sheet is high or when the color of the sheet and the color of the sheet pressing surface are of the same system.

[Brief description of the drawings]

FIG. 1A is a block diagram showing the configuration of an apparatus according to an embodiment, FIG. 1B is a flowchart showing a document size detection processing procedure, and FIG. 1B is an explanatory diagram showing the relationship between output at each position of a receiver and document size. (C).

FIG. 2 is a schematic diagram showing a main part of the device of the embodiment.

FIG. 3 is an explanatory diagram of a relationship between a document size and an ultrasonic detection position.

[Explanation of symbols]

 1 Platen 5 Shaker 6 Receiver (ultrasonic sensor)

Claims (4)

[Claims] 1. A sheet size detecting device for detecting the size of a sheet placed on a sheet mounting table, comprising: a vibrator for generating high-frequency vibration on the sheet mounting table; Detection means for detecting sound waves, identification means for identifying the size of the sheet placed on the sheet mounting table based on the detection result of the detection means,
A sheet size detection device having: 2. The apparatus according to claim 1, wherein said detecting means detects ultrasonic waves at a plurality of predetermined positions, and said identifying means determines which sheet is present based on a combination of presence or absence of a sheet at each of said predetermined positions. A sheet size detection device that identifies whether a sheet is a standard size. 3. An image reading apparatus that scans an image of a sheet placed on a sheet placing table to generate an image signal,
An image reading device comprising the sheet size detection device according to claim 1. 4. The apparatus according to claim 3, wherein said detecting means is provided on a moving body for scanning an image on a sheet, and said detecting means detects an ultrasonic wave at a predetermined timing during scanning. An image reading apparatus that detects ultrasonic waves at a plurality of predetermined positions by using the apparatus.