Rotation direction detecting apparatus

A rotation direction detecting apparatus comprising:

• a turntable mounted on a rotary shaft of a motor and provided with a predetermined signal pattern, said predetermined signal pattern being formed so that one selected from reflection and non-reflection of light and transmission and non-transmission of light is alternately and continuously repeated by rotation of said motor;
• a photo-detecting unit for detecting said signal pattern of said turntable;
• a rotation direction judging unit for judging a direction of rotation of said motor on the basis of said signal pattern detected by said photo-detecting unit;
• and
• a velocity calculating unit for calculating a rotational velocity of said motor on the basis of the direction of rotation judged by said rotation direction judging unit, wherein said signal pattern is set as a pattern in which high-level regions and low-level regions are repeated alternately at a 2:1:1:2 ratio;
• said rotation direction judging unit judges that said motor is rotating in a direction of normal rotation when leading edges of said signal pattern detected by said photo-detecting unit are arranged at regular intervals, and judges that said motor is rotating in a direction of reverse rotation when leading edges of said signal pattern detected by said photo-detecting unit are arranged at irregular intervals;
• and
• said velocity calculating unit calculates the rotational velocity of said motor on the basis of a distance between adjacent leading edges when said rotation direction judging unit judges that said motor is rotating in the direction of normal rotation, and calculates the rotational velocity of said motor on the basis of a distance between two leading edges located on opposite outer sides of three continuous leading edges when said rotation direction judging unit judges that said motor is rotating in the direction of reverse rotation.