For example, Japanese Patent Disclosure No. 62-111376 discloses a system for optically validating bills by means of a single light emitting element that has two light emitting diode chips therein to simultaneously radiate visible and infrared rays to reduce the number of light emitting elements that have been utilized in a prior art system to independently radiate visible and infrared rays from these light emitting elements.
In another aspect, Japanese Patent Publication No. 54-26400 presents a currency validation device for testing a reflectance or transmittance ratio of visible ray to infrared ray in a predetermined range. This device comprises light sources or light emitting diodes for producing visible and infrared rays, a light receiving element for receiving each light from these light sources, a comparator for detecting a ratio of emission levels from two light sources, and a controller for adjusting an emission amount from one of two light sources to always obtain a constant ratio from the comparator. In this arrangement, one light emitting diode is freely turned on with a constant current flow without any restriction, and the other light emitting diode is turned on at a constant ratio of the emission levels to retain the ratio of light amounts between visible and infrared rays, and advantageously there is no need for keeping the absolute levels of visible and infrared rays at constant values.
In some cases, however, the discriminator could not correctly validate bills due to insufficient amount of different optical features taken out of bills. Also, as usual optical sensors utilize a photocoupler of combined light emitting and receiving elements, increased number of optical sensors for improvement of validation accuracy occupies a wider area in the discriminator, resulting in larger size of sensor structure and obstruction to optical scanning of a target area on bills.
Accordingly, an object of the present invention is to provide an optical sensing device for detecting plural optical features of valuable papers with an improved validation performance. Another object of the present invention is to provide an optical sensing device of small or compact size for detecting plural optical features of valuable papers. Still another object of the present invention is to provide an optical sensing device that can derive plural optical scanning patterns by means of less number of light emitting and receiving elements to improve accuracy in bill validation. A further object of the present invention is to provide an optical sensing device that can pick out optical patterns for different colors printed on valuable paper by means of plural lights of different wavelength irradiated on a same scan line or area on valuable papers. A still further object of the present invention is to provide an optical sensing device that can utilize inexpensive light emitting and receiving elements to reduce cost for manufacture.