Optical interference apparatus and position detection apparatus

A position detection apparatus for detecting a position relative to an object to be detected, comprising:

• a light source;
• a beam splitter for splitting a light beam from said light source;
• a reference surface by which one split light beam from said beam splitter is reflected to propagate backward through the optical path, the light beam from said reference surface and the other split light beam which emerges from said beam splitter, is reflected by an object to be detected, and returns, being combined by said beam splitter and the two split light beams emerging from said beam splitter as convergent light;
• a detection element for detecting the combined light beams while they are brought to interference with each other, a position relative to the object being detected on the basis of detection by said detection element;
• and
• an optical element having a function of converging a light beam or changing a divergent state of the light beam, said optical element being inserted in an optical path of one of the split light beams emerging from said beam splitter, and the light beams reflected from converging positions of the two split light beams being combined at said beam splitter as spherical waves with curvatures equal to each other owing to an effect of said optical element.

An information recording and/or reading apparatus comprising:

• a signal system for recording and/or reading information on/from an information medium by using a head for recording and/or reading information;
• position detection means for detecting a position of a member on which said head is provided, said position detection means including:
• (1) a light source,
• (2) a beam splitter for splitting a light beam from said light source,
• (3) a reference surface by which one split light beam from said beam splitter is reflected to propagate backward through the optical path, the light beam from said reference surface and the other split light beam which emerges from said beam splitter, is reflected by said member on which said head is provided, and returns, being combined by said beam splitter and the two split light beams emerging from said beam splitter as convergent light,
• (4) a detection element for detecting the multiplexed light beams while they are brought to interference with each other, a position relative to said member on which said head is provided being detected on the basis of detection by said detection element, and
• (5) an optical element having a function of converging a light beam or changing a divergent state of the light beam, said optical element being disposed in an optical path of one of the split light beams emerging from said beam splitter, and the light beams reflected from converging positions of the two split light beams being combined at said beam splitter as spherical waves with curvatures equal to each other owing to an effect of said optical element;
• and
• a head position control system for controlling a position of said head on the basis of detection by said position detection means.

A method of producing an information medium comprising:

• the step of recording and/or reading information on/from an information medium by using a head for recording and/or reading information;
• the position detection step of detecting a position of a member on which the head is provided, the step including:
• (1) the step of emitting light from a light source,
• (2) the step of splitting light beam from the light source by using a beam splitter,
• (3) the step of reflecting one split light beam from the beam splitter and making the light beam propagate backward through the optical path, combining the light beam from the reference surface with the other split light beam which emerges from the beam splitter, is reflected by the member on which the head is provided, and returns, and the two split light beams emerging from the beam splitter as convergent light,
• (4) the step of detecting the combined light beams while they are brought to interference with each other, a position relative to the member on which the head is provided being detected on the basis of the detection, and
• (5) the step of making one of the split light beams emerging from the beam splitter pass through an optical element having a function of converging a light beam or changing a divergent state of the light beam, the light beams reflected from converging positions of the two split light beams being combined at the beam splitter as spherical waves with curvatures equal to each other owing to an effect of the optical element;
• and
• the head position control step of controlling a position of the head on the basis of detection in the position detection step.