Patent ID: 7583826
Filing Date: 2009-09-01
Classification: G06K,H04N

Abstract:
1. An image reading apparatus comprising: a detecting surface adapted to have a detecting object placed thereon; a sensor array comprising a plurality of sensors arranged to read an image pattern of the detecting object placed on the detecting surface; and a contact detector which detects whether the detecting object has been brought into contact with the detecting surface and determines whether the detecting object that has been brought into contact with the detecting surface is a predetermined specific detecting object, wherein the contact detector comprises: wherein the detecting circuit (i) detects, upon contact of the detecting object with both the first detection electrode and the second detection electrode, a third signal waveform excited to the second detection electrode, (ii) compares the third signal waveform with a threshold voltage that is preset based on a capacitance component and a resistance component of the specific detecting object, and (iii) detects whether the detecting object has been brought into contact with the detecting surface and determines whether the detecting object is the specific detecting object when the threshold voltage is included within a range of a voltage amplitude of the third signal waveform; and wherein the threshold voltage is set either to a voltage that is higher than an upper limit value of the third signal waveform excited to the second detection electrode in a state in which the detecting object does not come into contact with the detecting surface, or to a voltage that is lower than a lower limit value of the third signal waveform excited to the second detection electrode in a state in which the detecting object does not come into contact with the detecting surface.