Corner Cube Prism Research Articles

Impact Force Measurement of a Spherical Body Dropping onto a Water Surface from Different Heights

The impact force of spherical body dropping onto a water surface is measured using the method which has been proposed by us. In the method, a cube corner prism is embedded in a metal spherical body. The optical center of the cube corner prism coincides with The center of gravity of the spherical body. The motion of the spherical body is measured in the optical interferometer. The velocity of the spherical body can be calculated from the Doppler frequency measured in the interferometer. The acceleration, displacement, and inertial force of the spherical body can be calculated from the velocity of the spherical body. The dropping distance of the spherical body is variable. In this experiment, the distance is set to approximately 60 mm, 150 mm, and 190 mm, so that the difference of impact force caused by the difference of initial velocity is evaluated in detail.

Impact force measurement of a spherical body dropping onto a water surface.

We propose a method for measuring the impact force of a spherical body dropping onto a water surface. The velocity of the center of gravity of a metal spherical body, in which a cube corner prism is embedded so that its optical center coincides with the center of gravity of the sphere, is accurately measured using an optical interferometer. The acceleration, displacement, and inertial force of the sphere are calculated from the velocity. The sphere is also observed using a high-speed camera. The uncertainty in measuring the instantaneous value of the impact force with a sampling interval of approximately 1 ms is estimated to be 8 mN, which corresponds to 0.8% of the maximum force of approximately 1.0 N.

Multi-interferometric displacement measurement system with variable measurement mirrors

Laser interferometers have been widely implemented for the displacement sensing and positioning calibration of the precision mechanical industry, due to their excellent measuring features and direct traceability to the dimensional definition. Currently some kinds of modified Fabry-Perot interferometers with a planar mirror or a corner cube prism as the measurement mirror have been proposed. Each optical structure of both models has the individual particularity and performance for measuring applications. In this investigation, a multi-interferometric displacement system has been proposed whose measurement mirror can be quickly and conveniently altered with a planar mirror or a corner cube reflector depending on the measuring demand. Some experimental results and analyses about the interpolation error and displacement measurements with both reflectors have been demonstrated. According to the results, suggestions about the choice of a measuring reflector and interpolation model have been presented. With the measuring verifications, the developed system with a maximum standard deviation less than 0.2081 μm in measuring range of 300 mm would be a compact and robust tool for sensing or calibrating the linear displacement of mechanical equipment.

Design, Simulation and Optimisation of a Fibre-optic 3D Accelerometer

Using an inertia pendulum comprised of two prisms, flexible beams and an elastic flake, we present a novel fibre-optic 3D accelerometer design. The total reverse reflection of the cube-corner prism and the spectroscopic property of an orthogonal holographic grating enable the measurement of the two transverse components of the 3D acceleration simultaneously, while the longitudinal component can be determined from the elastic deformation of the flake. Due to optical interferometry, this sensor may provide a wider range, higher sensitivity and better resolving power than other accelerometers. Moreover, we use finite element analysis to study the performance and to optimise the structural design of the sensor.

Polarization and far-field diffraction patterns of total internal reflection corner cubes

Many corner cube prisms, or retroreflectors, employ total internal reflection (TIR) via uncoated rear surfaces. The different elliptical polarization states emerging from the six unique paths through the corner cube complicate the far-field diffraction pattern by introducing various phase delays between the six paths. In this paper, we present a computational framework to evaluate polarization through TIR corner cubes for arbitrary incidence angles and input polarization states, presenting example output for key normal-incidence conditions. We also describe a method to produce far-field diffraction patterns resulting from the polarization analysis, presenting representative images--broken into orthogonal polarizations--and characterizing key cases. Laboratory confirmation is also presented for both polarization states and far-field diffraction patterns.

Birefringence Optical Feedback with a Folded Cavity in HeNe Laser

The birefringence optical feedback with a folded cavity in HeNe laser is investigated. A theory model based on the equivalent cavity of the Fabry—Perot interferometer is presented. The phase difference between the two intensities in birefringence feedback is twice the retardation of the wave plate. The phase difference is invariable when the length of the feedback cavity changes. With the adoption of a cube corner prism (CCP) to form a folded cavity, the fringe frequency is doubled, and the resolution of the displacement sensor based on birefringence optical feedback with a folded cavity is improved. A resistance chain of 5-fold subdivision and 4-fold logic subdivision is used as further subdivision. The resolution of λ/80 is obtained eventually; for 632.8 nm HeNe laser it is 7.91 nm. The displacement sensor based on birefringence optical feedback with a folded cavity is simple and of high resolution, large measurement range, low cost, and is of great application potential in industry.

360 mW of single-mode output power at 946 nm from a ring laser based on a specially designed Porro prism

In this paper, a nonplanar ring laser operating at 946 nm has been proposed and demonstrated by using a specially designed Porro prism together with a commercially available corner cube prism. An Nd:YAG with a shape of scalene right triangle and an undoped YAG are thermally bonded to fabricate the novel composite Porro prism. A magnetic field providing the nonreciprocal Faraday rotation is applied to the corner cube prism, which gives flexibility in choosing magneto-optic materials. The operating principle of single-frequency operation for this ring laser is illustrated in detail. A maximum continuous output power of 360 mW was achieved when the laser operated stably on the single axial mode. 473 nm single-frequency operation with 6.7 mW has also been demonstrated by intracavity doubling with LiB3O5 crystal.

A thermally-insensitive passively Q-switched Cr 4+:YAG/Nd:YAG laser

A passively Q-switched laser with Cr 4+:YAG/Nd:YAG composite crystal using a corner cube prism cavity has been realized, in which the corner cube prism is the key element as it aids the compensation of the thermal lens effect of laser crystal. Compared with plane–plane mirror cavities under the same conditions, the stability of the laser performance using the corner cube prism cavity was improved remarkably over temperatures ranging from −40 to 65 °C. The decrease of Nd:YAG stimulated emission cross section with temperature was considered to be the main reason for the increase of average output pulse energy under the same cycle for the two different cavities when the ambient temperature changed −40 to 65 °C. The mode properties produced by the prism cavity were analyzed, and the theoretical results were verified by experimental observations.

Terahertz-wave parametric oscillator with a misalignment-resistant tuning cavity

We demonstrate a terahertz-wave parametric oscillator (TPO) with a corner-cube resonator consisting of a corner-cube prism (CCP) and a flat mirror. By using the cavity configuration proposed in this Letter, the generation of tunable monochromatic terahertz (THz) waves can be achieved just by rotating the flat mirror instead of rotating the TPO cavity relative to the pump beam. The THz-wave output intensity and pulse width can be controlled periodically by rotating the CCP around the cavity axis. The TPO stability against cavity misalignment is significantly improved by at least 1 to 2 orders of magnitude compared with the conventional plane-parallel resonator configuration.

Output performance of thermally-insensitive passively Q-switched Nd:YAG laser

We study a Cr4+:YAG Q-switched Nd:YAG laser with a thermally-insensitive corner-cube-prism cavity where the corner cube prism is the key element. The corner cube prism is insensitive to misalignment in any direction. We demonstrate experimentally that a laser cavity with such a prism provides stable laser performance under violent changes of ambient temperature and the effect of the laser crystal thermal lens. The laser mode properties are analyzed by numerical simulations. We show that the numerically simulated results agree well with the experimental ones.

レーザ誘導方式深穴評価システムの開発

The probe with a 110-millimeter diameter is fabricated for measuring accuracies of extremely deep holes. It consists of a measurement unit, skid unit and a laser diode, which are used to detect the position and inclination of the probe. Measurement unit, which is mounted on the forward part of the probe, is equipped with a pentaprism and a stylus with a corner cube prism. The hole shape is detected by measuring movement of a stylus perpendicular to the hole wall using a laser interferometer. The laser interferometer is set in front of the probe. Its laser beam is radiated toward the pentaprism of the measurement unit and deflected toward the corner cube prism. The beam reflected from the corner cube prism reaches the interferometer via the pentaprism. In the present study, a probe is fabricated using skids instead of piezoelectric actuators and its performance is examined. The use of skids reduces the production cost because they are less expensive as compared to piezoelectric actuators. The results show that roundness and straightness of a deep hole measured by the probe correspond well with those by an electric micrometer and a roundness tester when measuring the gradually changing hole wall.

Greatly improved stability of passively Q-switched Ce:Nd:YAG laser by using corner cube prism

In order to solve the hard problem of laser instability, a miniature Cr4+:YAG Q-switched Ce:Nd:YAG laser with a retroreflecting corner cube prism is demonstrated. The corner cube prism is insensitive to misalignment in any direction. Laser cavity with the prism is found to meet the condition of violent change of environment temperature and the variation of thermal lens of laser crystal by our experiment. Compared with flat-flat cavity, stability of the laser with a retroreflecting corner cube prism is improved remarkably.

Excellent stability of laser passively Q-switched with a retroreflecting corner cube prism

A miniature Cr4+:YAG Q-switched, repetitive operation, conductive cooling Nd:YAG laser with a retroreflecting corner cube prism is demonstrated. The corner cube prism which is insensitive to misalignment in any direction makes it useful for the laser to adapt to the violent change of ambient temperature and also makes the laser cavity insensitive to the variation of thermal lens of the crystal. The laser has excellent stability of the average output pulse energy and the threshold voltage under different ambient temperature of −40, 25, and 55°C.

Long-term degradation of optical devices on the Moon

Forty years ago, Apollo astronauts placed the first of several retroreflector arrays on the lunar surface. Their continued usefulness for laser ranging might suggest that the lunar environment does not damage optical devices. However, new laser ranging data reveal that the efficiency of the three Apollo reflector arrays is now diminished by a factor of 10 at all lunar phases and by an additional factor of 10 when the lunar phase is near full Moon. These deficits did not exist in the earliest years of lunar ranging, indicating that the lunar environment damages optical equipment on the timescale of decades. Dust or abrasion on the front faces of the corner-cube prisms may be responsible, reducing their reflectivity and degrading their thermal performance when exposed to face-on sunlight at full Moon. These mechanisms can be tested using laboratory simulations and must be understood before designing equipment destined for the Moon.

球面角锥棱镜非稳腔钕玻璃激光器

球面角锥棱镜非稳腔钕玻璃激光器

激光干涉测长未对准误差分析

Based on analysis of laser interference length measurement principle,optical path offset model and length of optical path in cube-corner prism model are given,and a simple expression of influence relationship of misalignment error and positioning error is derived with neglecting of straightness errors and angle errors.Positioning errors measurement experiments are carried out and a quantitative estimation method for misalignment error is given.

Amplification of Optical Disk Readout Signals by Homodyne Detection

We experimentally demonstrated the amplification of optical disk readout signals by homodyne detection. This technique uses optical interference to amplify the signals. We further applied phase-diversity detection to reliably obtain the amplified readout signal. The optical system was carefully designed so that a sufficiently amplified readout signal can be obtained. In particular, we applied a corner cube prism as a reflection mirror to achieve sufficient stability of the interferometric optical system. We experimentally demonstrated a 3.6 times amplification of a Blu-ray Disc readout signal. The estimated signal-to-noise ratio (SNR) improvement for an assumed eight-layer optical disk readout signals by applying homodyne detection on the basis of the observed amplification was +7.9 dB, which significantly enables reliable readout of recorded signals. The present technique will be essential for the real commercialization of next-generation multilayer optical disk because of its outstanding ability of SNR improvement.

Alignment-free He–Ne laser with folded cavity

To solve out of operation induced by the disarrangement of cavity mirrors in half intra-cavity He–Ne lasers, a new structure of alignment-free He–Ne laser with folded cavity is invented. A corner cube prism (CCP) is used to structure a folded cavity. This novel laser can work conveniently without any adjustment. Both intensity curves of solid and hollow CCPs are studied, which indicate that it is a finely robust and stabile, and has a large changeable range (approximately, 60mm) of cavity length. Bright prospect in applications improving the nanometer laser ruler invented by our group before is also shown.

과학기술위성2호 레이저반사경의 준비행모델 개발

STSAT-2 has an on-board satellite retroreflector array for precise orbit determination. Satellite retroreflector array reflects photon emitted from laser and uses to determine precisely the distance from ground station to satellite by the round-trip travel time of photon. The retroreflector array of protoflight model has been developed and verified through environmental tests. This paper describes the protoflight model of retroreflector array and reports environmental test results. The environmental tests of protoflight model retroreflector array were performed successfully without damage of corner cube prism occurred in engineering model development.

Displacement self-sensing align-free He–Ne laser based on hollow cube corner prism folding cavity

The displacement self-sensing laser of λ/8 resolution was previously reported, without nonlinear error on principle, and with the function of self-calibration. In this paper, we report out new result: a hollow cube corner prism (HCCP) is used for the first time to realize align-free folding-cavity He–Ne laser; using this technology, we made three important improvements below: the first one is to be an align-free laser. It can work without adjustment benefiting from the HCCP's property of retro-direction reflection and the specially designed laser structure; the second one is to increase the potential resolution up to λ/16; the last one is to enhance the robust of the laser, especially the stability of the laser power when one of the cavity mirrors of laser is moved by the object to be measured, thus, to expand the measurement range. In current demonstration, the laser has a large changeable range (approximately, 60 mm) of cavity length, i.e. a large range of measurement, and high measurement accuracy of λ/16(40 nm for He–Ne laser), at the same time, it is an align-free half intra-cavity laser, which can work without adjustment. This method has prospective benefits to be applied in displacement measurement of high resolution.