Abstract: Provided are an absolute position measurement method, an absolute position measurement apparatus, and a scale. The scale includes a scale pattern formed by replacing repeatedly arranged pseudo-random-codes with a sequence of a linear feedback shift register of N stages using a first symbol with first width representing a first state and a second symbol with second width representing a second state. The first is divided into two or more first symbol areas of different structures, and the second symbol is divided into two or more second symbol areas of different structures. There is at least one overlap area in which the first symbol and the second symbol overlap each other to have the same structure.

Abstract: Provided are an absolute position measurement method, an absolute position measurement apparatus, and a scale. The scale includes a scale pattern formed by replacing repeatedly arranged pseudo-random-codes with a sequence of a linear feedback shift register of N stages using a first symbol with first width representing a first state and a second symbol with second width representing a second state. The first is divided into two or more first symbol areas of different structures, and the second symbol is divided into two or more second symbol areas of different structures. There is at least one overlap area in which the first symbol and the second symbol overlap each other to have the same structure.

Abstract: Provided are a transparent substrate monitoring apparatus and a transparent substrate monitoring method. The transparent substrate monitoring apparatus includes a light emitting unit emitting light; a double slit disposed on a plane defined in a first direction and a second direction intersecting a propagation direction of incident light and includes a first slit and a second slit spaced apart from each other in the first direction to allow the light to pass therethrough; an optical detection unit measuring an intensity profile or position of an interference pattern formed on a screen plane; and a signal processing unit receiving a signal from the optical detection unit to calculate an optical phase difference or an optical path difference.

Abstract: A frequency-stabilized laser apparatus and a method for stabilizing the frequency of a laser are disclosed. A semiconductor laser emits a beam. An external reflector has a resonance frequency and feeds back the emitted beam to the semiconductor laser if the frequency of the emitted beam is equal to the resonance frequency. An interference signal generator generates an interference signal for detecting the wavelength of the emitted beam and a controller detects the wavelength of the beam from the generated interference signal. According to the frequency-stabilized laser apparatus and the method for stabilizing the frequency of the laser, it is possible to stabilize the frequency of the beam emitted from the semiconductor laser and output the beam having the stable frequency for a long period of time.

Abstract: A shape measurement apparatus and method using a laser interferometer are disclosed. The shape measurement apparatus includes a plurality of laser devices, which generate beams, emit a beam of a specific frequency from among the generated beams, and output interference signals for detecting wavelengths of the generated beams, and a controller for detecting the wavelengths of the generated beams from the outputted interference signals, and controlling the laser devices on the basis of the detected wavelengths. The optical unit projects the beam of the laser device on a target object, and generates an interference pattern of the object. Several shutters are closed and opened. If the shutters are closed, they prevent the beam of each laser device to be projected on the optical unit. An image pickup unit captures the interference pattern.

Abstract: A shape measurement apparatus and method using a laser interferometer are disclosed. The shape measurement apparatus includes a plurality of laser devices, which generate beams, emit a beam of a specific frequency from among the generated beams, and output interference signals for detecting wavelengths of the generated beams, and a controller for detecting the wavelengths of the generated beams from the outputted interference signals, and controlling the laser devices on the basis of the detected wavelengths. The optical unit projects the beam of the laser device on a target object, and generates an interference pattern of the object. Several shutters are closed and opened. If the shutters are closed, they prevent the beam of each laser device to be projected on the optical unit. An image pickup unit captures the interference pattern.

Abstract: A frequency-stabilized laser apparatus and a method for stabilizing the frequency of a laser are disclosed. A semiconductor laser emits a beam. An external reflector has a resonance frequency and feeds back the emitted beam to the semiconductor laser if the frequency of the emitted beam is equal to the resonance frequency. An interference signal generator generates an interference signal for detecting the wavelength of the emitted beam and a controller detects the wavelength of the beam from the generated interference signal. According to the frequency-stabilized laser apparatus and the method for stabilizing the frequency of the laser, it is possible to stabilize the frequency of the beam emitted from the semiconductor laser and output the beam having the stable frequency for a long period of time.

Abstract: Disclosed herein is a method and apparatus for simultaneously measuring a displacement and angular variations. The method and apparatus of the present invention allows light radiated from a single light source to be placed along a light axis so as to simultaneously measure a distance (displacement) and angular variations that are different physical quantities, so that the displacement and angular variations of the measuring device of a precision measuring apparatus or machining device of a machine tool moved by a stage can be simultaneously measured without an Abbe error.

Abstract: Disclosed is an atomic force microscope. A Fabry-Perot interferometer where the intensity of light reflected at a cantilever through an optical fiber varies sensitively to a displacement of the cantilever is constructed to accurately measure a distance between the optical fiber and the cantilever. A Fabry-Perot resonator is formed by the optical fiber having an end of a concave mirror shape and a reflective surface of the cantilever. A displacement of a cantilever tip is measured by detecting a signal reflected at the resonator and a feedback signal corresponding to a variation in the displacement of the cantilever tip is generated. The displacement of the cantilever tip is kept constant by actuating a piezoelectric element in a Z-axis direction.

Abstract: Disclosed is an atomic force microscope. A Fabry-Perot interferometer where the intensity of light reflected at a cantilever through an optical fiber varies sensitively to a displacement of the cantilever is constructed to accurately measure a distance between the optical fiber and the cantilever. A Fabry-Perot resonator is formed by the optical fiber having an end of a concave mirror shape and a reflective surface of the cantilever. A displacement of a cantilever tip is measured by detecting a signal reflected at the resonator and a feedback signal corresponding to a variation in the displacement of the cantilever tip is generated. The displacement of the cantilever tip is kept constant by actuating a piezoelectric element in a Z-axis direction.

Abstract: Disclosed is a method for correcting a nonlinearity error in a two-frequency laser interferometer which measures the phase angle using 90° phase mixing technique and a method for measuring a phase angle by using the same. The phase angle correcting method includes the steps of: calculating ellipse parameters, such as amplitudes, offsets and a phase difference of two sine and cosine output signals from the nonlinearity error correcting electronics; calculating an adjusting voltages for correcting offsets, amplitudes and a phase of the output signals; conducting a correction wherein offsets of output signals become zero, amplitudes are same, and a phase difference beyond 90° between the output signals becomes zero; and applying the output signals whose offsets, amplitudes and phase are corrected to Equation (&thgr;=arctan(Iy′/Ix′)) to calculate the phase angle.