JPS59143983A - Paper detector - Google Patents

Abstract

PURPOSE:To achieve a highly accurate detection with a simple construction by memorizing a video signal obtained from an image sensor at each specified frequency of scannings to compare a value determined by a value being memorized with the video signal. CONSTITUTION:When there is no paper, the value VB is previously written into a memory 8 for memorizing a video signal 5 from an image sensor 4 at a specified frequency of scannings. When video signal 5 is larger than a value given by multiplying it by a specific coefficient K1 (K1>1) with a multiplier 9, it is detected with a comparator 11 and a latch circuit 13 is set to detect that a paper 1 reaches the reading position. In the subsequent scanning, as the value of the memory 8 is rewritten to VH, the video signal 5 is compared with the value given by multiplying VH by K2 (0<K2<1) with a multiplier 10 by a comparator 12. When the video signal 5 is smaller than it, the latch circuit 13 is reset to detect the exhaustion of the paper 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field in which the Invention Appears] The present invention relates to a paper detection device [α] useful for, for example, an optical character reading device. For more details,
The present invention relates to a paper detection device that detects the presence or absence of paper by detecting a change in the level of a video signal from an image sensor in an apparatus that uses an image sensor to read characters recorded on a paper. It is something.

[Description of prior art]

FIG. 1 is an explanatory diagram of the configuration of a paper detection device in a conventional optical character reading device (g). In this figure, 1 is the paper to be read, 2 is the amount of light, 6 is the lens, and 4 is the lens. 6
It is an image sensor that forms an image of characters recorded on a sheet of paper via a TI'C. For example, a stelaph (not shown) in the vertical direction indicated by the arrow.

The image sensor 4 electrically scans and reads all the characters on the paper 1 in the direction of force, and outputs five video signals. here,
The position information of the reading line on paper 1 is given in advance as a distance F4& from the top edge of paper 1 as a format). )are doing. The top edge of the paper 1 is the reference position, and this reference position is notified by the paper detection device 6 using a photoswitch, and the removal start signal ii#7 is obtained. I'll do it like this.

The paper detection device 6 is provided with a narrow slit (11) to reduce the amount of light in order to increase detection accuracy. , Ko('1.J
have.

Such conventional devices have the disadvantage of being complicated and expensive in construction, and also have the disadvantage that detection becomes impossible if the slits become clogged with dust or the like.

[Object of the present invention]

The present invention has been made in view of the shortcomings in the prior art, and aims to realize a device that can perform highly accurate detection with a simple configuration.

The apparatus according to the present invention includes means for storing a video signal obtained from an image sensor every predetermined number of scans, means for comparing the video signal with a value stored in the storage means and determined by the value 'fr'. : It is characterized by detecting the presence or absence of paper as well as changes in the level of the video signal.

[Explanation of Examples]

FIG. 2 is a block diagram showing an example of a device according to the present invention. Components that perform the same functions as those in FIG. 1 are given the same reference numerals. In Fig. 2, 8 is an image sensor.
A memory 9, 1o stores the video signal 5 from 4 for every predetermined number of scans, and 4. A multiplier that calculates 2 to , 11.72 is a multiplier 9, 1
A comparator 16 which compares the output of 0 with the video signal 5 is a latch circuit controlled by the output of each comparator 11 and 12.

FIG. 6 is a waveform diagram showing an example of a video signal obtained from the image sensor 4, and the horizontal axis shows time. In this figure, the reason why the level is high in the center and low on both sides is due to the shading of the lens 3. VH
is the level when the white part of the paper is being picked up, and VB is the level when looking at the background when there is no paper. The memory 8 reads the video signal 5 each time it is scanned, and compares the output of the memory 8 with a value obtained by multiplying the output of the memory 8 by a constant value (-,
Signal 7 ya from the latch circuit 16 indicating the presence or absence of paper:
obtain.

That is, in FIG. 3, an area is secured at the left end of the paper 1 indicated by the diagonal movement in the vertical direction where white is always guaranteed, and by detecting changes in the video signal in this range,
The influence of a decrease in the level of the video signal due to characters recorded on the paper 1 or black printing is excluded.

First, when there is no paper, the value (level) stored in the memory 8 is VB, and a predetermined coefficient IKI is added to it.
When the video signal 5 becomes thicker than the value multiplied by (i<1>1), this is detected by the comparator 11 and the latch circuit 16 is set. By doing this, you will receive one sheet of paper.
(21) can be detected.

In the next scan, the value in memory 8 is rewritten to Vn, VHvc K2 (0<I(2<1)f multiplied by 1), and the video signal 5 is compared with the comparator 12, and K2
・■) If the video signal 5 becomes small, the latch circuit 1
3-i1J is set, thereby detecting that paper 1 is running out. This type of operation is a so-called differential operation that detects the difference between the value of the previous scan and the value of the current scan, and because the background cannot be made sufficiently black, a sufficient difference between VH and VB cannot be obtained. We can respond reliably to any situation.

In addition, in the above explanation, it was assumed that the level change when paper 1 is taken in and out can be optically analyzed b times in one scan.
When the level of the video signal changes slowly with a certain slope, writing to the memory 8 is performed once every two or three scans.
You may also do this one time at a time. Alternatively, if the background is sufficiently black and the difference between VH and VB cannot be obtained sufficiently, you can increase the single slice level in kB and compare the magnitude of video signal 5 with this. J2.

[Effects of the present invention]

As explained above, according to the present invention, the presence or absence of paper can be detected by scanning the video No. 13 two or three times or less, and can be performed with high precision. Well, since it uses the video signal from the image sensor for character reading, there is no need for +1 or precautions such as slits, and the overall 4j↓ composition becomes 1 to 5 single.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the configuration of the haiku paper detection device in the optical component layout and the pick-up device, and FIG. 2 is an illustration of the device according to the present invention.
In the block diagram shown in FIG. 61, there is a waveform of the video signal obtained from the image sensor.・Memory, 11.12... Comparator. Agent Shin Kuzuno - Dream I Figure No. 312!l H -104 Open

Claims (1)

[Claims] (1) A device configured to read characters recorded on a sheet of paper with an image sensor, comprising a memory means for storing video signals obtained from the image sensor every predetermined number of scans; A sheet of paper characterized in that a comparison means is provided for comparing a value determined by a value stored in a memory means with the video signal, and the presence or absence of the sheet is detected based on a change in the level of the video signal. Performance device.