JP3490127B2 - Banknote recognition device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bill validating apparatus,
In particular, the present invention relates to a bill discriminating apparatus that optically detects micro-characters printed on bills and determines whether the bills are authentic. 2. Description of the Related Art In recent years, the progress of copying technology has been remarkable, and a problem has arisen that securities such as banknotes and checks are misused by copying. [0003] In order to avoid such abuse, research for identification has been rapidly promoted so that a copy can be easily identified as a fake. In recent years, a method has been proposed in which minute characters called micro-characters are formed at the end of a bill, and when the micro-characters are copied, the micro-characters are crushed so that they can be easily identified. This method is extremely effective in detecting counterfeit banknotes. However, in order to align micro-character strings in the direction in which pixels are lined up and form an image on a linear image sensor, the direction of the banknotes must be precisely determined. There was a problem that it needed to be regulated. [0006] As described above, in order to detect micro-characters when detecting counterfeit bills, the traveling direction of the bills must be limited with high precision, and precision machines are used for peripheral devices. Needed. The present invention has been made in view of the above-mentioned circumstances, and is configured such that even when a micro character string is skewed, an image formed on an image sensor is aligned with the sensor pixel direction, thereby achieving high precision. It is an object of the present invention to provide a bill identifying device capable of distinguishing bills. Therefore, in the bill validator of the present invention, there is provided a detecting light irradiating means for irradiating detecting light to micro-characters printed on a bill, and A rod lens which is disposed in close contact with the bill with the axes substantially parallel to each other, and which cuts off a part of the surface facing the bill on the upstream side in the transport direction of the bill, and forms an image of light from the rod lens. And an image sensor for detecting the presence or absence of micro-characters. According to the above construction, the rod lens has a function of optically converting the character string so as to be aligned perpendicularly to the axis of the rod lens even when micro-characters enter in an oblique direction. In addition, since it has a function of enlarging the image and improving the resolution, even when the bill is skewed, the image forming direction coincides with the sensor pixel direction, and highly accurate detection is possible. In the case of counterfeit banknotes, microcharacters are read in a state where they are resolved and blurred at the time of copying, and microcharacters are not detected. Therefore, counterfeit banknotes are always detected with high precision. be able to. Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic explanatory view of a bill discriminating apparatus according to an embodiment of the present invention. This discriminating apparatus comprises a plurality of sensor units 10 sequentially arranged at predetermined intervals in a running direction a of a bill 1.
And a judging means 20 for comparing this output and judging whether it is a genuine note or a copy note. FIG. 2A is a front sectional view, FIG. 2B is a transverse sectional view, and FIGS. 3A and 3B show the positional relationship with the bill 16. L to illuminate banknote 16
It comprises a light source 11 such as an ED, a rod lens 12, an optical system 13 for imaging light from the rod lens 12 on a sensor, and a linear image sensor 14 for reading the spatial frequency of the imaged micro-characters. The spatial frequency of the micro character string 15 is output as an electric signal. The rod lens 12 is formed of an optical glass such as quartz, crown glass, flint glass, etc., and may be a cylinder, an elliptical cylinder, or an aspherical cylinder. For example, in the case of a cylinder having a diameter of 5 mm, the rod lens 12 has a diameter of 5 mm from the center axis of the cylinder. The skew within the degree is corrected within the range of 1 mm on the bill. In other words, there are about 4 micro-characters in a 1 mm range on a banknote, so these 4 micro-characters are optically corrected and aligned in the direction of 90 degrees with respect to the axis of the cylinder in the direction of the linear image sensor. Matches. As shown in FIGS. 1 and 2, the rod lens 12 has its axis parallel to the transport direction of the banknote 16 and is closely attached to the banknote 16, and faces the upstream banknote in the transport direction of the banknote 16. Part of the surface to be cut out. A light source and an image sensor are provided with a band-pass filter of 600 to 900 nm for wavelength selection. Here, the sensor unit 10 irradiates light from a light source 11 to a microlens 15 under "10000" at the upper left of the bill as shown in FIG. 7B, an image is formed so as to coincide with the pixel direction of the image sensor. As shown in FIG. 7B, the micro character string 15 arranged at a certain skew angle .theta. As shown in a), an image is formed so as to coincide with the pixel direction on the image sensor 13 in the same manner as the light entering at a right angle, and whether this is a genuine bill or a counterfeit bill is detected based on this read signal. FIGS. 5 and 6 are partially enlarged views of the micro characters. Here, as shown in FIG.
Means 2 for amplifying the output from the system and judging through a frequency discriminator
Since the spatial frequency is high when a micro-character is input, the sensor output also becomes a high-frequency output. In addition, what is necessary is just to use a well-known various thing as a frequency discrimination apparatus, and, in short, what is necessary is just to be able to discriminate the difference in frequency mentioned later. In this way, micro-characters can be detected very easily, and counterfeit banknotes can be easily detected. FIG. 9 shows a dummy bill (November 2, 1993).
An optical micrograph of micro-characters printed on a genuine bill, since it has not been issued as of September 9)
(a) and the output (b) from the sensor are shown. The horizontal axis indicates the pixel bit of the image sensor, and the vertical axis indicates the intensity. FIG. 10 shows an optical microscope photograph (b) of the micro-character portion of the copied dummy bill and an output (b) from the sensor. As is apparent from FIG. 9B and FIG. 10B, the frequency of the sensor output is greatly different. From this difference, the authenticity of the bill can be easily determined. In addition, by setting the wavelength of the illumination light to near-infrared light (700 to 900 nm), the influence of dirt can be eliminated, and it becomes possible to perform excellent detection of dirt without malfunction. As described above, according to the present invention, the authenticity of a genuine bill is determined based on whether or not a micro character is detected in a portion where a micro character is originally printed. This makes it possible to more accurately identify forged banknotes.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing a bill discriminating apparatus according to an embodiment of the present invention; FIG. 2 is a view showing a sensor unit of the same apparatus; FIG. FIG. 4 is a diagram showing an example of a bill to be read by the same device. FIG. 5 is an enlarged view of a micro-character portion of the same bill. FIG. 6 is an enlarged view of a micro-character portion of the same bill. FIG. 8 is a view showing an optical micrograph of a micro-character portion of a dummy bill and an output from a sensor. FIG. 10 is a micrograph of a copied dummy bill. Diagram showing an optical micrograph of a character portion and an output from a sensor [Description of References] 10 Sensor portion 20 Judging means 11 Light source 12 Rod lens 13 Optical system 14 Linear image sensor 15 Micro character string

Claims (1)

(57) [Claim 1] A detection light irradiating means for irradiating a detection light to a micro character printed on a bill, and an axis substantially parallel to a conveying direction of the bill is applied to the bill. A rod lens that is provided in close contact with the banknote and that partially cuts off a part of the surface facing the banknote on the upstream side in the transport direction of the banknote, and detects the presence or absence of micro-characters by imaging light from the rod lens. A bill discriminating apparatus comprising: