Detection device, optical path length measurement device, measurement instrument, optical member evaluation method, and temperature change detection method

A detection apparatus characterized by comprising:

• a light supplying unit supplying first light having a predetermined wavelength and a predetermined frequency and second light having a frequency shifted with respect to said first light;
• an irradiation unit irradiating a measurement object with one of said first light and said second light;
• a superimposition unit superimposing one of said first light and said second light applied to said measurement object by said irradiation unit on the other one of said first light and said second light;
• and
• a phase detecting unit detecting a phase of a beat produced by superimposition of said first light on said second light by said superimposition unit based on an alternating-current electric signal producing a difference in optical frequency for said first light and said second light.

A detection apparatus characterized by comprising:

• a light source emitting probe light having a first wavelength and reference light having a second wavelength different from said first wavelength;
• a frequency shifter branching light emitted from said light source into light having a first frequency and light having a second frequency;
• an irradiation unit irradiating a measurement object with light having said first frequency, branched by said frequency shifter;
• a photocoupler superimposing light having said first frequency, exiting from said irradiation unit, on light having said second frequency;
• a filter branching light exiting from said photocoupler into light having said first wavelength and light having said second wavelength;
• a first photodiode outputting an electric signal matching light having said first wavelength, branched by said filter;
• a second photodiode outputting an electric signal matching light having said second wavelength, branched by said filter;
• and
• a lock-in amplifier measuring a change in electric signal output from said first photodiode on the basis of the electric signal output from said second photodiode.

An optical path length measuring apparatus characterized by comprising:

• a light source emitting probe light having a first wavelength and reference light having a second wavelength different from said first wavelength;
• a frequency shifter branching said probe light into first probe light and second probe light, and said reference light into first reference light and second reference light, and shifting frequencies of said first probe light and said first reference light or said second probe light and said second reference light;
• an irradiation unit irradiating a measurement object with said first probe light and said first reference light;
• a superimposition unit superimposing said first probe light and said first reference light applied to said measurement object by said irradiation unit on said second probe light and said second reference light;
• and
• a phase detecting unit detecting a phase of a beat produced by superimposition of said first probe light and said second probe light on the basis of a beat produced by superimposition of said first reference light and said second reference light,
• wherein when the wavelength of said probe light emitted from said light source, a change in phase of said beat is detected by said phase detecting unit to measure an optical path length of said measurement object.

A method for evaluating an optical member characterized by comprising the steps of:

• producing first probe light having a first frequency, first reference light having a second frequency different from said first frequency, second probe light having a frequency shifted from said first frequency in a predetermined amount, and second reference light having a frequency shifted from said second frequency in said predetermined amount;
• irradiating an optical member with said first probe light and said first reference light;
• superimposing said first probe light and said first reference light applied to said optical member on said second probe light and said second reference light;
• detecting a phase of a beat produced by superimposition of said first probe light and said second probe light on the basis of a beat produced by superimposition of said first reference light and said second reference light;
• and
• measuring optical characteristics of said optical member based on the detected phase of said beat.

A method for evaluating an optical member characterized by comprising the steps of:

• irradiating an optical member with one of first light having a predetermined wavelength and a predetermined frequency and second light having a frequency different from the frequency of said first light;
• superimposing one of said first light and said second light applied to said optical member on the other one of said first light and said second light;
• detecting a phase of a beat produced by superimposition of said first light and said second light, based on an alternating-current electric signal matching a difference in frequency between said first light and said second light;
• and
• measuring chromatic dispersion of a measurement object based on the detected phase of said beat.

A method for detecting a change in temperature characterized by comprising the steps of:

• irradiating a detection object with one of first light having a predetermined wavelength and a predetermined frequency and second light having a frequency different from the frequency of said first light;
• superimposing one of said first light and said second light applied to said detection object on the other one of said first light and said second light;
• and
• detecting a phase of a beat produced by superimposition of said first light on said second light to detect a change in temperature of said detection object.

A method for detecting a change in temperature characterized by comprising the steps of:

• producing first probe light having a first frequency, first reference light having a second frequency different from said first frequency, second probe light having a frequency shifted from said first frequency in a predetermined amount, and second reference light having a frequency shifted from said second frequency in said predetermined amount;
• irradiating an optical member with said first probe light and said first reference light;
• superimposing said first probe light and said first reference light applied to said optical member on said second probe light and said second reference light;
• detecting a phase of a beat produced by superimposition of said first probe light and said second probe light on the basis of a beat produced by superimposition of said first reference light and said second reference light;
• and
• detecting a change in temperature of a detection object based on the detected phase of said beat.