Gwangju Institute of Science and Technology

Electronics and Telecommunications Research Institute

Korea Photonics Technology Institute

Byeong Ha Lee

Min Su Kim

Jung Jin Ju

In Hee Shin

Jong Bae Kim

Joo Beom Eom

Jaesung Ahn

Byeong Il Lee

Anjin Park

Young Gue Kim

Tae Il Yoon

Myoung Jin Kim

The present disclosure relates to an apparatus and method for measuring the velocity of a surface wave using a laser ultrasound imaging technique. A method of measuring the velocity of a surface wave according to an embodiment of the present disclosure includes: emitting a laser pulse to a target material; obtaining wavefront image of a surface wave, which propagates on a surface of the target material due to the laser pulse, by emitting a probe beam to the target material; and determining a velocity of the surface wave based on variation of the wavefront image according to a time delay between the laser pulse and the probe beam.

Apparatus and method for measuring velocity of acoustic surface wave using full-field laser ultrasound imaging technique

The present invention relates to a three-dimensional oral cavity scan device for a digital impression that obtains a three-dimensional image by processing a two-dimensional image acquired by photographing a three-dimensional subject in an oral cavity. The device includes: a pattern mask converting parallel light incident thereto into structured light; a piezoelectric plate where a mechanical vibration is generated on a surface thereof by an AC voltage applied thereto; and a power supply unit applying the AC voltage to the piezoelectric plate, wherein the piezoelectric plate moves the pattern mask in a longitudinal direction of the piezoelectric plate by using the mechanical vibration. The device can reduce noise and vibration by moving the pattern mask with an electrical method. In addition, the device can accurately measure depth of teeth by electrically controlling a focal length of structured light projected on the teeth.

Three-dimensional oral cavity scan device using piezoelectric element based pattern module and variable focus lens

The invention discloses an in-line polarization-state converter. In the polarization converter, a laser beam is radiated onto the side of a photosensitive optical fiber. The laser beam causes the refractive index of an optical fiber core to asymmetrically vary. Birefringence is induced in a core mode of the optical fiber by the variation in the asymmetrical refractive index. An optical fiber segment having the birefringence is generally disposed on a waveguide path of the optical fiber to change the polarization state of an optical signal passing through the optical fiber segment. That is, the phase of the optical signal passing through the optical fiber is changed by radiation of laser beams, which results in a variation in polarization state. The polarization converter disposed on the waveguide path is covered with a metal tube in order to prevent the polarization converter from being bent or broken. In addition, optical fiber connectors are provided at both ends of the polarization converter for easy connection.

In-line polarization-state converter

Provided is a resonant cascaded difference frequency generator that is capable of improving the conversion efficiency of the second-order nonlinear optical phenomena by resonating the second harmonic wave of a pump light. The resonant cascaded difference frequency generator includes: a nonlinear medium, which receives a pump light and a signal light and then generates the second harmonic wave of the pump light through second harmonic generation, in a cascaded way generates a converted light of a difference frequency through difference frequency generation between the signal light and the second harmonic wave; and a resonant structure that resonates the second harmonic wave of the pump light on the basis of the nonlinear medium.

Cascaded difference frequency generator using resonant structure

Growing community of inventors

Gwangju, South Korea

Byeong Ha Lee