Showing papers by "Kenji Saitoh published in 1994"

Wavelength compensator in a helium ambience

Abstract: A wavelength compensator includes a reference vacuum tube having closed ends, wherein a laser beam enters the reference vacuum tube from one of the ends thereof and is reflected by the other end backwardly, an interference device for causing interference of the laser beam to produce an interference beam, and a light receiving device for receiving the interference beam which bears information related to a change in wavelength of the laser beam. The wavelength compensator further includes a specific arrangement which is effective to reduce vacuum deterioration of the reference vacuum tube.

System and method for detecting the relative positional deviation between diffraction gratings and for measuring the width of a line constituting a diffraction grating

Abstract: A deviation detecting system for detecting a relative positional deviation between first and second diffraction gratings, includes a light source, an illuminating device for projecting first and second light beams from the light source, having different directions of polarization, onto the first and second diffraction gratings along different directions, a first signal detecting device for detecting a first interference light signal from the first diffraction grating, being based on a combination of diffraction light of the first light beam and diffraction light of the second light beam, a second signal detecting device for detecting a second interference light signal from the second diffraction grating, being based on a combination of diffraction light of the first light beam and diffraction light of the second light, a first phase difference detecting device for detecting a phase difference between the first and second interference light signals and, a second phase difference detecting device for producing third and fourth interference light signals for correction of a phase error involved in the detected phase difference, and for detecting a phase difference between the third and fourth interference light signals. The phase error is produced by the first and second diffraction gratings which affect the phase in dependence upon the state of polarization of light impinging thereon. Also provided is a determining device for determining the relative positional deviation between the first and second diffraction gratings on the basis of a phase difference as detected by the first and second phase difference detecting device.

Apparatus and method for detecting a relative displacement between first and second diffraction gratings arranged close to each other wherein said gratings have different pitch sizes

Abstract: A method and device for measuring the relative displacement between first and second diffraction gratings includes an interference optical system forming first and second interference rays of light from light diffracted from the first and second diffraction gratings and separating the first and second interference rays of light on the basis of the difference in their direction of polarization, a first detector for detecting the first interference ray of light to generate a first detection signal, a second detector for detecting the second interference ray of light to generate a second detection signal, and signal processing section for detecting the phase difference between the first and second detection signals and for determining the relative displacement between the first and second diffraction gratings on the basis of the phase difference.

Method and apparatus for measuring positional deviation while correcting an error on the basis of the error detection by an error detecting means

Abstract: A method and apparatus for measuring the relative positional deviation between first and second diffraction gratings formed on an object includes determining the relative positional deviation of the first and second diffraction gratings while detecting and correcting an error produced in relation to detection of the positional deviation of the first and second diffraction gratings.

Positional shift-detecting apparatus utilizing optical heterodyne interference

Abstract: PURPOSE: To measure positional shifts in X direction and Y direction simultaneously by separating a diffraction light to X-direction measuring beam and Y- direction measuring beam and detecting a phase difference of two beat signals in each of the beams. CONSTITUTION: A laser light emitted from a laser 1 is made incident on a four-directional radiation unit 10 and emitted in four directions from the unit 10. Luminous fluxes illuminating a pair of diffraction gratings 7 and 8 in directions are diffracted by the pair of gratings 7 and 8. The diffraction light of a predetermined order is put into a detecting means and enters a PBS 6. A beam for measuring X-directional shift and a beam for measuring Y- directional shift are respectively introduced into a beat signal formation unit 20X and a beat signal formation unit 20Y. A phase difference sensor 30X detects a time lag of beat signals to obtain a phase difference Δϕx , and a phase difference sensor 30Y obtains a phase difference ΔϕY in the same manner. An operator 31 obtains overlapping errors of two processes in both X and Y directions, and displays the same at a display device 32.