Displacement information detecting apparatus

A displacement information measuring apparatus comprising:

• a light source;
• a beam splitter optical system for forming two light fluxes from a light emitted by said light source;
• two acoustic optical devices which modulate respective ones of the two light fluxes, for giving respective predetermined frequency differences to said two light fluxes from said beam splitter optical system;
• an intersecting optical system for permitting to intersect said two light fluxes of different frequency from said two acoustic optical devices near an object in which a displacement information is to be measured, said intersecting optical system including a diffraction grating upon which said two light fluxes of different frequency are incident so that said two light fluxes are diffracted, said intersecting optical system permitting to intersect two diffracted lights generating from said diffraction grating in correspondence to said two light fluxes, respectively, near said object to be measured, said two light fluxes emergent from said acoustic optical devices being incident upon said intersecting optical system in parallel condition to each other;
• and
• a light receiving device for detecting a light from said object upon which the two diffracted lights are caused to be incident by said intersecting optical system, the displacement information of said object being obtained from a beat signal corresponding to said frequency difference and obtained from said light receiving device,
• wherein said intersecting optical system is constituted such that a frequency of said beat signal may not be substantially affected by a variation of wavelength of the light fluxes incident upon said diffraction grating.

A driving system comprising:

• a driving unit;
• a detecting unit, the detecting unit including;
• (1) a light source;
• (2) a beam splitter optical system for forming two light fluxes from a light emitted by said light source;
• (3) two acoustic optical devices which modulate respective ones of the two light fluxes, for giving respective predetermined frequency differences to said two light fluxes from said beam splitter optical system;
• (4) an intersecting optical system for permitting to intersect said two light fluxes of different frequency from said two acoustic optical devices near an object in which the displacement information is to be measured, said intersecting optical system including a diffraction grating upon which said two light fluxes of different frequency are incident so that said two light fluxes are diffracted, said intersecting optical system permitting to intersect two diffracted lights generating from said diffraction grating in correspondence to said two light fluxes, respectively, near the object to be measured, said two light fluxes emergent from said acoustic optical devices being incident upon said intersecting optical system in parallel condition to each other;
• and
• (5) a light receiving device for detecting a light from said object upon which two diffracted lights are caused to be incident by said intersecting optical system, the displacement information of said object being obtained from a beat signal corresponding to said frequency difference and obtained from said light receiving device;
• wherein said intersecting optical system is constituted such that a frequency of said beat signal may not be substantially affected by variation of wavelength of the light fluxes incident upon said diffraction grating;
• and
• a control unit for controlling said driving unit based on the displacement information obtained by said detecting unit.

A displacement information measuring apparatus comprising:

• a light source;
• a beam splitting optical system for forming two light fluxes from a light emitted by said light source;
• two acoustic optical devices which modulate respective ones of the two light fluxes for giving a respective predetermined frequency difference to said two light fluxes from said beam splitting optical system;
• an intersecting optical system for permitting to intersect said two light fluxes of two different frequencies from said two acoustic optical devices, said intersecting optical system including a diffraction grating upon which said two light fluxes of different frequency are incident so that said two light fluxes are diffracted, said intersecting optical system permitting to intersect two diffracted lights generating from said diffraction grating in correspondence to said two light fluxes, respectively, near an object to be measured at the same intersection angle as an angle made with each other when they are emergent from said diffraction grating substantially independently of a variation of wavelength of the light fluxes incident upon said diffraction grating, said two light fluxes emergent from said acoustic optical devices being incident upon said intersecting optical system in parallel condition to each other;
• and
• a light receiving device for detecting a light from said object upon which the two diffracted light fluxes are caused to be incident by said intersecting optical system, the displacement information of said object being obtained on the basis of detection of said light receiving device.