Position detection apparatus, lens apparatus, image pickup system, and machine tool apparatus

A lens apparatus comprising:

• a lens displaceable in an optical axis direction;
• and
• a position detection apparatus configured to detect a position of the lens, the position detection apparatus comprising:
• a scale which includes a pattern circumferentially and periodically formed on a circle whose center is a predetermined point, the scale being configured to rotate depending on a displacement of the object;
• a sensor unit relatively movable with respect to the scale;
• and
• a signal processor configured to process an output signal of the sensor unit to obtain position information of the object,
• wherein the sensor unit comprises:
• a first detector configured to detect a first partial pattern formed in a first region apart from the predetermined point by a first distance in a radial direction on a half line starting from the predetermined point of the scale;
• and
• a second detector configured to detect a second partial pattern formed in a second region apart from the predetermined point by a second distance different from the first distance, and
• wherein the signal processor is configured to reduce an error component contained in the position information due to a difference between a rotation center of the scale and the predetermined point based on a first detection signal outputted from the first detector and on a second detection signal outputted from the second detector.

An image pickup system comprising:

• a lens apparatus comprising:
• a lens displaceable in an optical axis direction;
• and
• a position detection apparatus configured to detect a position of the lens, the position detection apparatus comprising:
• a scale which includes a pattern circumferentially and periodically formed on a circle whose center is a predetermined point, the scale being configured to rotate depending on a displacement of the object;
• a sensor unit relatively movable with respect to the scale;
• and
• a signal processor configured to process an output signal of the sensor unit to obtain position information of the object,
• wherein the sensor unit comprises:
• a first detector configured to detect a first partial pattern formed in a first region apart from the predetermined point by a first distance in a radial direction on a half line starting from the predetermined point of the scale;
• and
• a second detector configured to detect a second partial pattern formed in a second region apart from the predetermined point by a second distance different from the first distance, and
• wherein the signal processor is configured to reduce an error component contained in the position information due to a difference between a rotation center of the scale and the predetermined point based on a first detection signal outputted from the first detector and on a second detection signal outputted from the second detector, and
• an image pickup apparatus including an image pickup element configured to perform a photoelectric conversion of an optical image formed via the lens.

A machine tool apparatus comprising:

• a machine tool including at least one of a robot arm and a conveyer configured to convey an object to be assembled;
• and
• a position detection apparatus configured to detect at least one of a position and an attitude of the machine tool, the position detection apparatus comprising:
• a scale which includes a pattern circumferentially and periodically formed on a circle whose center is a predetermined point, the scale being configured to rotate depending on a displacement of the object;
• a sensor unit relatively movable with respect to the scale;
• and
• a signal processor configured to process an output signal of the sensor unit to obtain position information of the object,
• wherein the sensor unit comprises:
• a first detector configured to detect a first partial pattern formed in a first region apart from the predetermined point by a first distance in a radial direction on a half line starting from the predetermined point of the scale;
• and
• a second detector configured to detect a second partial pattern formed in a second region apart from the predetermined point by a second distance different from the first distance, and
• wherein the signal processor is configured to reduce an error component contained in the position information due to a difference between a rotation center of the scale and the predetermined point based on a first detection signal outputted from the first detector and on a second detection signal outputted from the second detector.