JPH0447673Y2 - - Google Patents

Description

[Detailed description of the invention] (A) Technical field of the invention This invention is an improvement of a paper detection device that detects paper processed by an optical character reading device, an optical mark reading device, a printing device, a copying machine, etc. on a paper conveyance path. It is related to.

(B) Conventional technology and problems Conventionally, there are two methods for detecting paper: a mechanical method and an optical method. However, the mechanical method has the disadvantage that the resistance value of the contact changes due to paper dust, etc. that adheres to the contact. There is. Alternatively, the movable parts become clogged with dust, the movable force tends to fluctuate, the service life is short, and false detections occur.In general, when detecting paper, the optical method, and moreover, the transmission type, is more effective. It is believed that there is.

On the other hand, a transmission type optical detection device detects the presence or absence of paper based on the difference between when the paper blocks light emission from the light emitting element and when it does not. Therefore, in the case of thin paper, most of the light emitted from the light emitting element passes through the paper and enters the light receiving element even though the paper is present. Furthermore, the amount of light entering the light-receiving element increases due to diffuse reflection from the paper itself and from the guide members on both sides, which reduces the difference between the presence and absence of paper (S/N ratio), making it easy to detect errors. .

(C) Purpose of the invention In view of the above-mentioned drawbacks, the purpose of the invention is to provide a paper detection device that can detect paper with a high S/N ratio even in the case of thin paper in optical paper detection. Our goal is to provide the following.

(D) Structure of the invention The purpose of this invention is to provide a light emitting element provided on one side of guide members disposed opposite to each other forming a conveyance path for conveying paper, and a light emitting element provided on one side of the guide member opposite to the light emitting element on the other guide member. A paper detecting device is provided with a light receiving element provided at the arranged position and detects the presence or absence of paper passing between the light emitting element and the light receiving element, wherein the guide member on the light emitting element side has a surface mirror-finished. This is achieved by providing a paper detection device characterized by the following.

(E) Embodiments of the invention Hereinafter, embodiments of the paper detection device according to the invention will be described in detail with reference to the drawings.

The figure is a diagram for explaining the present invention, and includes 1
2 is a light emitting diode, 2 is a phototransistor, 3 is paper, and 4 is a lens provided on the light emitting diode 1, which condenses diverging light output from the light emitting diode.

5 is a condensing lens provided on the phototransistor 2, 6 and 7 are guide members, and 8 is a guide member 6.
9 is a material layer having a low reflectance (approximately 10%) by coating black paint containing carbon, black galvanizing, black dyeing, etc. on the guide member 7.

In the figure, the light output from the light emitting diode 1 becomes diverging light A as shown in the figure. This diverging light A reaches the paper 3, and part of it is reflected, part of it is absorbed, and the rest passes through the paper 3.

Here, the light reflected on the paper 3 is diffusely reflected and becomes light B that returns to the guide member 6 side. Conventionally, the guide member 6 used a material with high reflectance such as nickel plating or stainless steel.
This reflected light B is diffusely reflected again and becomes light C that reaches the paper 3. Therefore, a part of this light C passes through the paper 3 again and enters the phototransistor 2 together with the light output from the light emitting diode 1 and directly passing through the paper 3.

That is, the light once reflected by the paper 3 also enters the phototransistor 2, resulting in detection with a poor S/N ratio. In order to reduce such diffuse reflection from the paper 3, the light emitting diode 1 is provided with a condensing lens 4, so that the light from the light emitting diode 1 does not become diverging light, and the light reflected from the surface of the paper 3 becomes G. Only.

Therefore, by applying a mirror finish 8 to the surface of the guide member 6, the light incident on the guide member 6 is regularly reflected from the mirror finish 8, and even if it enters the paper 3 again and is transmitted, the light is received by the phototransistor 2. Since the optical path is outside the range, detection with a good S/N ratio can be performed.

Next, the light passing through the paper 3 diverges due to unevenness on the surface of the paper, and not only the light F reaches the phototransistor 2, but a part of it becomes the light H that reaches the guide member 7. When the guide member 7 is made of a material with high reflectivity such as nickel plating or stainless steel, the light H is reflected by the guide member 7 and becomes reflected light D that reaches the paper 3. A part of the light D that reaches the paper 3 is diffusely reflected on the surface of the paper 3, becomes light E that enters the phototransistor 2 again, and the light D reaches the paper 3.
Compared to the light level when there is no paper 3, the light level when there is paper 3 includes leaked light, and the S/N ratio becomes worse as the paper becomes thinner.

In a conventional method that improves such disadvantages, a material layer 9 with low reflectivity is provided on the surface of the guide member 7 on the light receiving element side by applying carbon-containing black coating, black galvanizing, black dyeing, etc. This has been done in an attempt to prevent the aforementioned leakage light from entering the phototransistor 2, thereby improving the S/N ratio.

In the present invention, the surface of the guide member 6 provided with the light emitting diode is mirror-finished, so that the paper is regulated and conveyed so as to come into contact with the mirror-finished guide member, and the optical path of the reflected light from the guide member 6 is changed. In addition, the guide members are made to be out of the light receiving range of the light receiving element, and can be used for a longer period of time than those in which the surfaces of both guide members are painted or plated.

(F) Effect of the invention As explained above, according to the invention, in optical paper detection, even when thin paper is used, even if the paper is reflected once and then reflected back to the guide member, Since the reflected optical path at this time takes an optical path outside the light-receiving range, the reflected light does not enter the light-receiving element, and the paper can be detected with a good S/N ratio.

[Brief explanation of the drawing]

The figure is a diagram illustrating an embodiment of a paper detection device according to the present invention. In the figure, 1 is a light emitting diode, 2 is a phototransistor, 3 is paper, 4 and 5 are lenses, and 6 and 7
8 is a guide member, 8 is a mirror finish, and 9 is a material layer with low reflectance.

Claims (1)

[Claims for Utility Model Registration] A light emitting element provided on one side of opposing guide members forming a conveyance path for conveying paper, and a light emitting element provided on the other guide member at a position opposite to the light emitting element. A paper detecting device for detecting the presence or absence of paper passing between the light emitting element and the light receiving element, the guide member on the light emitting element side having a surface mirror-treated. A paper detection device characterized by: