Wavelength variation measuring apparatus

Claim 2

A wavelength variation detecting apparatus comprising: light source means; light dividing means for dividing a light beam from said light source means into two light beams; frequency difference imparting means for causing a frequency difference between said two light beams comprising acoustooptic elements disposed in paths of the two light beams divided by said light dividing means, respectively; geometrical length difference between optical paths imparting means for causing a geometrical length difference between optical paths of said two light beams, the geometrical length difference between optical paths caused by said geometrical length difference imparting means being substantially constant at least during detection of any variation in the wavelength of said light source means; light combining means for combining said two light beams between which the frequency difference and the geometrical length difference are imparted; and photoelectric detection means for detecting a beat signal in the combined beams of constant geometrical length difference between optical paths; and means for detecting any variation in the wavelength of said light source means by using a result of the detecting of the beat signal in the combined beams of constant geometrical length difference between optical paths performed by said photoelectric detection means.

Claim 3

A wavelength variation detecting apparatus according to claim 1, wherein said light dividing means, said frequency difference imparting means, said geometrical length difference optical paths imparting means, and said light combining means are placed on one and the same base plate having a coefficient of thermal expansion of 1×10 -5 /°C. or less.

Claim 4

A wavelength variation detecting apparatus according to claim 2, wherein the material of said base plate is one or a compound of invar, superinvar, low thermal expansion casting, low thermal expansion glass, ceramics and quartz glass.

Claim 5

A wavelength variation detecting apparatus according to claim 1, wherein said frequency difference imparting means has shifting means capable of shifting the light frequency to the optical path of at least one of the two light beams from said light dividing means.

Claim 6

A wavelength variation detecting apparatus according to claim 1, wherein said light source means is provided with a semiconductor laser.

Claim 7

An apparatus according to claim 1, wherein the means for detecting any variation includes comparing means for comparing the beat signal with a beat signal which substantially corresponds to the frequency difference caused by said frequency difference imparting means so as to detect the variation in the wavelength of said light source means.

Claim 8

A wavelength variation stabilizing apparatus comprising: a light source whose wavelength is controllable; a light divider for dividing a light beam from said light source into two light beams; a frequency difference imparting device for causing a frequency difference between said two light beams comprising acoustooptic elements disposed in paths of the two light beams divided by said light divider respectively; a geometrical length difference between optical paths imparting device for causing a geometrical length difference between optical paths of said two light beams, the geometrical length difference between optical paths caused by said geometrical length difference between optical paths imparting device being substantially constant at least during detection of any variation in the wavelength of said light source; a light combining device for combining said two light beams between which the frequency difference and the geometrical length difference are imparted; a photoelectric detector for detecting a beat signal in the combined beams of constant geometrical length difference between optical paths; a variation detector for detecting any variation in the wavelength of said light source by using a result of detecting of the beat signal in the combined beams of constant geometrical length difference between optical paths performed by said photoelectric detector; and feedback control means for controlling feedback to said light source on the basis of said variation detector and stabilizing the wavelength of said light source.

Claim 9

A wavelength variation stabilizing apparatus comprising: a light source whose wavelength is controllable; a light divider for dividing a light beam from said light source into two light beams; a frequency difference imparting device for causing a frequency difference between said two light beams comprising acoustooptic elements disposed in paths of the two light beams divided by said light divider respectively; a geometrical length difference between optical paths imparting device for causing a geometrical length difference between optical paths of said two light beams, the geometrical length difference between optical paths caused by said geometrical length difference between optical paths imparting device being substantially constant at least during detection of any variation in the wavelength of said light source; a light combining device for combining said two light beams between which the frequency difference and the geometrical length difference are imparted; a photoelectric detector for detecting a beat signal in the combined beams of constant geometrical length difference between optical paths; a variation detector for detecting any variation in the wavelength of said light source by using a result of detecting of the beat signal in the combined beams of constant geometrical length difference between optical paths performed by said photoelectric detector; and feedback control means for controlling feedback to said light source on the basis of said variation detector and stabilizing the wavelength of said light source.

Claim 10

An apparatus according to claim 7, wherein said variation detector comparing device for comparing the beat signal with a beat signal which substantially corresponds to the frequency difference caused by said frequency difference imparting device so as to detect the variation in the wavelength of said light source.

Claim 11

A correcting apparatus comprising: a light source; a light divider for dividing a light beam from said light source into two light beams; a frequency difference imparting device for causing a frequency difference between said two light beams; geometrical length difference between optical paths imparting device for causing geometrical length difference between optical paths of said two light beams, the geometrical length difference between optical paths caused by said geometrical length difference optical paths imparting device being substantially constant at least during detection of any variation in the wavelength of said light source; a light combining device for combining said two light beams between which the frequency difference and the geometrical length difference are imparted; a photoelectric detector for detecting a beat signal in part of the combined beams of constant geometrical length difference between optical paths to thereby detect any variation in the wavelength of said light source, the rest of the combined beams being directed to an object to be measured for obtaining measurement data; and variation detector for detecting any variation in the wavelength of said light source by using a result of detecting the beat signal in the combined beams of constant geometrical length difference between optical paths performed by said photoelectric detector: the measurement data obtained by the rest of said combined beams being corrected with a signal from a variation detector as a measurement data correction signal.

Claim 12

A correcting apparatus comprising: a light source; a light divider for dividing a light beam from said light source into two light beams; a frequency difference imparting device for causing a frequency difference between said two light beams; geometrical length difference between optical paths imparting device for causing geometrical length difference between optical paths of said two light beams, the geometrical length difference between optical paths caused by said geometrical length difference optical paths imparting device being substantially constant at least during detection of any variation in the wavelength of said light source; a light combining device for combining said two light beams between which the frequency difference and the geometrical length difference are imparted; a photoelectric detector for detecting a beat signal in part of the combined beams of constant geometrical length difference between optical paths to thereby detect any variation in the wavelength of said light source, the rest of the combined beams being directed to an object to be measured for obtaining measurement data; and variation detector for detecting any variation in the wavelength of said light source by using a result of detecting the beat signal in the combined beams of constant geometrical length difference between optical paths performed by said photoelectric detector: the measurement data obtained by the rest of said combined beams being corrected with a signal from a variation detector as a measurement data correction signal.

Claim 13

An apparatus according to claim 9, wherein said variation detector includes a comparing device for comparing the beat signal with a beat signal which substantially corresponds to the frequency difference caused by said frequency difference imparting device so as to produce a signal for correcting the variation in the wavelength of said light source.

Claim 14

A wavelength variation detecting apparatus comprising: light source means; light dividing means for dividing a light beam from said light source means into two light beams; frequency difference imparting means for causing a frequency difference between said two light beams; geometrical length difference between optical paths imparting means for causing a geometrical length difference between optical paths of said two light beams; and light combining means for combining said two light beams between which the frequency difference and the geometrical length difference are imparted, part of said combined beams being guided to an interference optical system, wherein a beat signal in the rest of said combined beams which is divided from the part in an optical path between said light combining means and the interference optical system is detected to thereby detect any variation in the wavelength of said light source means.

Claim 15

A wavelength variation detecting apparatus comprising: light source means; light dividing means for dividing a light beam from said light source means into two light beams; frequency difference imparting means for causing a frequency difference between said two light beams; geometrical length difference between optical paths imparting means for causing a geometrical length difference between optical paths of said two light beams; and light combining means for combining said two light beams between which the frequency difference and the geometrical length difference are imparted, part of said combined beams being guided to an interference optical system, wherein a beat signal in the rest of said combined beams which is divided from the part in an optical path between said light combining means and the interference optical system is detected to thereby detect any variation in the wavelength of said light source means.

Claim 16

An apparatus according to claim 11, wherein the optical path length difference caused by said optical path length difference imparting means is substantially constant at least during detection of any variation in the wavelength of said light source means.

Claim 17

An apparatus according to claim 11, further comprising comparing means for comparing the beat signal with a beat signal which substantially corresponds to the frequency difference caused by said frequency difference imparting means so as to detect the variation in the wavelength of said light source means.

Claim 18

A wavelength variation detecting method comprising: an illuminating step of providing an illuminating light beam from a light source; a light dividing step of dividing the light beam from said light source into two light beams; a frequency difference imparting step of causing a frequency difference between said two light beams using acoustooptic elements disposed in paths of the two light beams divided in said light dividing step, respectively; geometrical length difference between optical paths imparting step of causing a geometrical length difference between optical paths of said two light beams, the geometrical length difference between optical paths caused by said geometrical length difference between optical paths imparting step being substantially constant at least during detection of any variation in the wavelength of said light source; a light combining step of combining said two light beams between which the frequency difference and the geometrical length difference are imparted; and a photoelectric detecting step of detecting a beat signal in the combined beams of constant geometrical length difference; and a variation detection step of detecting any variation in the wavelength of said light source by using a result of detecting the beat signal in the combined beams of constant geometrical length difference between optical paths performed in said photoelectric detecting step.

Claim 19

A wavelength variation detecting method comprising: an illuminating step of providing an illuminating light beam from a light source; a light dividing step of dividing the light beam from said light source into two light beams; a frequency difference imparting step of causing a frequency difference between said two light beams using acoustooptic elements disposed in paths of the two light beams divided in said light dividing step, respectively; geometrical length difference between optical paths imparting step of causing a geometrical length difference between optical paths of said two light beams, the geometrical length difference between optical paths caused by said geometrical length difference between optical paths imparting step being substantially constant at least during detection of any variation in the wavelength of said light source; a light combining step of combining said two light beams between which the frequency difference and the geometrical length difference are imparted; and a photoelectric detecting step of detecting a beat signal in the combined beams of constant geometrical length difference; and a variation detection step of detecting any variation in the wavelength of said light source by using a result of detecting the beat signal in the combined beams of constant geometrical length difference between optical paths performed in said photoelectric detecting step.

Claim 20

A method according to claim 14, wherein said variation detecting step includes a comparing step of comparing the beat signal with a beat signal which substantially corresponds to the frequency difference caused in said frequency difference imparting step so as to detect the variation in the wavelength of said light source.