Korea Research Institute of Standards and Science

Tae-Bong Eom

Jae-Wan Kim

Jong-Ahn Kim

Chu-Shik Kang

Jong-Han Jin

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.

Absolute position measurement method, absolute position measurement apparatus and scale

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.

Apparatus and method for stabilizing frequency of laser

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.

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Daejeon, South Korea

Tae-Bong Eom