JPS60243786A - Defect detector for sheet paper - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Embodiments of the Invention] The present invention relates to a paper sheet defect detection device for detecting cuts, perforations, etc. in banknotes, etc., for example.

[Technical background of the invention and its problems]

FIG. 1 shows a conventional device of this type. Paper sheets @ 11 such as banknotes are transferred to the running path 12 by a conveying means (not shown).
The vehicle is driven in the direction indicated by the arrow. A light emitting element 13.1 is placed in the middle of this running path 12 so that the optical axis is perpendicular to the running path 12.
4 and light receiving elements 15 and 16 are arranged facing each other,
Further, between the travel path 12 and the light receiving elements 15 and 16, there is a lens If! which forms an image of the transmitted light of the paper sheet 11 on the light receiving element 15, 16. , 1B are arranged. With such a configuration, if there is a cut □ or a pinhole-like perforation □ in the traveling paper sheet, the light transmitted through these is detected by the light receiving element 15.16. These defects are now being detected.

By the way, FIG. 2 shows the light-receiving surface 20 of the light-receiving element 15, 16 and the transmitted light image of the paper sheet 11 formed on the light-receiving surface 20, superimposed on each other. As shown in the figure, when the details of the cut 111 are smaller than the light receiving surface 20, the light receiving surface 20
Direct light enters only one part, and the other part has a cut 1
1, the transmitted light of the paper sheet 11 at the peripheral portion of the paper sheet 1 enters.

Therefore, the detection performance of the light receiving element is degraded by this transmitted light. In other words, since the light transmittance of the paper used for this type of paper sheet is generally high, it is difficult to distinguish between those without cuts and those with cuts, etc., which are extremely small. Ta.

[Purpose of the invention]

This invention has been made based on the above circumstances, and its purpose is to provide a paper sheet in which defects in the paper sheet can be reliably detected without being affected by the light transmittance of the paper sheet. The present invention aims to provide a defect detection device.

[Summary of the invention]

This invention uses infrared rays in a wavelength band that has low transmittance through paper sheets as a light source for detection, and uses an infrared light receiving element that detects this wavelength band as a light receiving element.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. Note that the same parts as in FIG. 1 are given the same reference numerals.

In FIG. 3, the optical axis is located in the middle of the traveling path 12.
Infrared light source 3 is directly connected to 2.

32 are arranged. This infrared light source 31.32 is a lamp using a material such as sapphire that transmits infrared rays as a bulb material, and the infrared light source 31.32 emits a light of about 2.9 μm, which has a low transmittance for this type of paper sheet. ±0.1
Infrared rays of μm (wavelength) are generated.

Figure 4 shows an example of the infrared spectral transmission characteristics of paper.
D, wavelength approximately 2.9 tim (wave number approximately 34001/c
rn), OH group, wavelength approximately 3.5 μm (wave number approximately 29001
/m2), the absorption by OH groups is strong and the transmittance is low. In this example, the transmittance is particularly low at approximately 2.9 μm.
is using the band.

The infrared light sources 31 and 32 are provided with infrared detectors 33 and 34, such as PbS and Pb5e, facing each other across the travel path 12, and these infrared detectors 33
, 34 are respectively provided with filters 35 and 36 having a passband of 2.8 to 3.0 μm. Furthermore, for example, there is a carbon
Lenses 37 and 38 for infrared light made of a F 2 or the like are provided, and the transmitted light of the paper sheet 11 is imaged by these lenses 37 and 38 on the infrared detectors J J and J 4, respectively.

FIG. 5 shows a detection output signal according to this embodiment, and FIG. 6 shows a conventional detection output signal. According to this embodiment, the infrared rays generated by the infrared light sources 31 and 32 hardly pass through the paper sheet 11. Therefore, if there is a defect in the paper sheet 11, the infrared detector 33°3
As shown in FIG. 5(a), the output signal of No. 4 has a level difference between the defective portion 5 and the surrounding portion 52 as shown in FIG. 6(a).
K is larger than in the conventional case.

Therefore, even extremely small defects can be reliably detected without being misidentified, and detection accuracy can be improved.

In FIGS. 5 and 6, (a) shows the detection output signal of paper sheets with low transmittance and defects, respectively, and (
b) shows detection output signals of paper sheets with high transmittance and no defects. In addition, Fig. 6 shows the wavelength from 0.5 to
1 μm, and was measured using an St light receiving element.

Although lamps are used as the infrared light sources 31 and 32 in the above embodiment, the present invention is not limited to this, and it is also possible to use a metal sheath heater or the like having a surface temperature of about 800°C.

It goes without saying that other modifications can be made without departing from the gist of the invention.

〔Effect of the invention〕

As described in detail above, according to the present invention d, - it is possible to provide a paper sheet defect detection device capable of reliably detecting defects on sheets without being affected by the light transmittance of the paper sheets; .

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram showing an example of a conventional paper sheet defect detection device, Fig. 2 is a diagram shown to explain the relationship between paper sheet defects and the light-receiving surface, and Fig. 3 is a diagram showing the present invention. FIG. 4 is a schematic configuration diagram showing one embodiment of the related paper sheet defect detection device, and FIG. 5 is a characteristic diagram showing the relationship between infrared wavelength (wave number) and transmittance. FIG. 6 is a diagram showing detected waveforms of the conventional method and the present invention, respectively. 1..paper sheets, 1..cut, 11. ...
Perforation, 31.32... Infrared light source, 33.34...
Infrared detector, 35.36...Filter, 37°38
···lens. Figure 3 2

Claims (1)

[Scope of Claims] 1) An infrared ray generating means for generating infrared rays with low transmittance to paper sheets, and an infrared detecting means provided opposite to the infrared ray detecting means, the infrared detecting means A defect detection device for paper sheets, characterized in that the output signal is used to detect defects in paper sheets interposed between an infrared ray generating means and an infrared detecting means. 2) The paper sheet defect detection device according to claim 1, wherein the infrared detecting means has a filter on a light receiving surface that passes only a wavelength band in which absorption by paper sheets is large. 3) The paper sheet defect detection device according to claim 1, wherein the infrared ray generating means comprises an infrared lamp. 4) The paper sheet defect detection device according to claim 1, wherein the infrared ray generating means comprises a heater. 5) The paper sheet defect detection device according to claim 1, wherein an image of incident light is formed on the light receiving surface of the infrared detection means via an infrared lens.