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:
The present invention pertains to a device and a method for measuring a via hole of a silicon wafer, wherein it is possible to precisely measure the depth of the via hole without damaging the wafer. Broadband infrared light is radiated to a silicon wafer which has a superior light transmission property, so that the depth of the via hole may be measured from the light which is reflected from each boundary surface of the wafer and the interference signal of reference light. The via hole measuring device according to the present invention includes: a light source unit for generating broadband infrared light; and an interferometer for radiating the light generated from the light source unit to a silicon wafer, so as to measure the depth of a via hole formed on the wafer according to the spectrum period of the interference signal of the light, which is reflected from the silicon wafer.
Abstract:
The present invention provides an absolute position measurement method, absolute position measurement device, and scale. The scale includes a scale pattern formed by replacing repetitively arranged pseudo-random codes with a sequence of N-stage linear feedback transition resisters by using a first symbol having a first width and representing a first state and a second symbol having the first width and representing a second state. The first symbol is divided into two or more first symbol areas, the second symbol is divided into two or more second symbol areas, and there is at least one overlap area having the same structure due to the overlap of the first symbol and the second symbol.