Image forming apparatus for forming image on record medium

An image forming apparatus to form an image on a record medium, comprising:

• a record medium supply mechanism to supply a record medium one by one;
• a record medium conveyance path to convey the record medium supplied from the record medium supply mechanism to a record medium discharge unit;
• a laser light source to irradiate a laser light to a surface of a record medium;
• a line sensor which has plural optical sensors for the laser light source to receive a reflected light of the laser light from the record medium to output an output signal converted into an electric signal,
• when the record medium totally reflects the laser light, the line sensor is arranged so that an axis of a sensor of the line sensor in a longitudinal direction is positioned on a plane to which a light path of the laser light irradiated from the laser light source and reflected by the record medium belongs;
• a signal processing device to determine a kind of the record medium based on the output signal;
• and
• an image forming unit that is arranged on a downstream side of the record medium conveyance path with respect to the line sensor and forms an image to the record medium conveyed through the record medium conveyance path;
• when the record medium is being conveyed,
• the laser light source irradiates the laser light to the record medium for a definite time,
• the line sensor receives the reflected light of the laser light from the record medium for the definite time and outputs the output signal converted into the electric signal, and
• the signal processing device compares a distribution state of an average of the received light intensity for the definite time at the received light position with a previously determined distribution state, and determines the kind of the record medium.