Position detection device and optical apparatus

A position detection device, comprising:

• a magnetic generation unit that comprises:
• a first magnetism generating section that is provided on one end side along a predetermined direction and generates magnetism;
• a second magnetism generating section that is provided on another end side along the predetermined direction and generates magnetism of polarity different from that of the first magnetism generating section;
• and
• a low magnetism section that is formed in the first magnetism generating section and the second magnetism generating section such that a width of the low magnetism section varies along the predetermined direction to generate magnetism lower than those of the first magnetism generating section and the second magnetism generating section;
• and
• a magnetic detection unit that is capable of moving relative to the magnetic generation unit along the predetermined direction and that detects the magnetism generated by the first magnetism generating section and the second magnetism generating section.

A position detection device, comprising:

• a magnetic section that comprises:
• a first pole and a second pole arranged spaced apart from each other having a same magnetic polarity;
• and
• a third pole and a fourth pole arranged spaced apart from each other having a magnetic polarity different from that of the first pole and the second pole, and
• a magnetic detection unit that detects magnetism of the first pole, the second pole, the third pole, and the fourth pole, wherein
• the first pole faces the third pole, and the second pole faces the fourth pole.

A position detection method, comprising:

• generating magnetism by a first magnetism generating section provided on one end side along a direction of detection;
• generating magnetism of a polarity, which is different from a polarity of the magnetism generated by the first magnetism generating section, by a second magnetism generation section provided on another end side along the direction of detection;
• decreasing the magnetism generated by the first magnetism generating section and the second magnetism generating section by a low magnetism section formed in the first magnetism generating section and the second magnetism generating section such that a width of the low magnetism section varies along the predetermined direction;
• and
• moving the magnetic detection unit relative to the first magnetism generating section and the second magnetism generating section to detect the magnetism generated by the first magnetism generating section and the second magnetism generating section.

A position detection method comprising:

• generating magnetism by a first magnetism generating section provided on one end side along a direction of detection;
• generating magnetism of a polarity, which is different from a polarity of the magnetism generated by the first magnetism generating section, by a second magnetism generation section provided on another end side along the direction of detection;
• decreasing the magnetism generated by the first magnetism generating section and the second magnetism generating section by a low magnetism section formed in the first magnetism generating section and the second magnetism generating section along the predetermined direction;
• and
• moving the magnetic detection unit relative to the first magnetism generating section and the second magnetism generating section to detect the magnetism generated by the first magnetism generating section and the second magnetism generating section.