| 摘要 |
PURPOSE: To correct the reflectance and accurately detect the existence of printing when the reflectance drops by judging as to whether there is a printing on a medium or not on the basis of a print judging reference which has been set. CONSTITUTION: A drive circuit 24 drives an LED array 25 and a CCD image sensor 26, and when a bankbook, etc., (printing medium) 13 is led to the printing data sensing position, light from the array 25 is cast onto the printing column of the bankbook 13. The reflected beam of light thereby is sensed through a lens 28 as the printing data by the sensor 26. The printing data is amplified by an amplifier 29, converted by an A/D converter 30, and subjected to analysis made by a CPU 21. The CPU 21 sets a print judging reference in accordance with the value of the analyzed data and stores the obtained result in a non- volatile RAM 31. From the set vale of the reference, judgment is made as to whether the ground color of the bankbook 13 influences the sensing of existence of printing or not. If yes, the reflectance as the reference is corrected, and sensing whether printed or unprinted is made precisely with the reflectance in well accordance with the ground color. |
