Patent ID: 8615114

Claim:
An image reading apparatus comprising: a light emitting unit that illuminates light on an object; an image capturing device that allows the object to cover thereof from above, receives incident light from the object while covered with the object and generates an electrical signal according to an intensity of the received incident light; an object detecting unit that detects the object being positioned close to the image capturing device so as to cover the image capturing device; a disturbance light intensity determining unit that turns off the light emitting unit when the object detecting unit detects the object being positioned close to the image capturing device, controls the image capturing device to acquire pixel data of a predetermined number of pixels by imaging the object while the light emitting unit is turned off, and determines a disturbance light intensity of transmitted light having transmitted the object and incident on the image capturing device based on the acquired pixel data; and a light accumulating time setting unit that sets a light accumulating time of the image capturing device based on the disturbance light intensity determined by the disturbance light intensity determining unit, wherein the disturbance light intensity determining unit compares the pixel data with a plurality of predetermined threshold values, sorts the pixel data into a plurality of ranges based on the comparison, calculates an occurrence frequency of each of the ranges, and determines the disturbance light intensity based on the calculated occurrence frequency of each of the ranges, and wherein after setting the light accumulating time of the image capturing device to a specified length based on the disturbance light intensity that is determined by the disturbance light intensity determining unit based on the pixel data acquired upon creating a first light condition, an image reading operation using the light accumulating time equal to the specific length is performed upon creating a second light condition different from the first light condition to receive light reflected by the object at the image capturing device, the light emitting unit being turned off in the first light condition, the light emitting unit being turned on in the second light condition, and the image reading operation being performed while the object covers the image capturing device.