Lambda Rms Research Articles

Measurement of the optical turbulence produced by a drone

At present, new approaches for the use of Multirotor Unmanned Aerial Vehicle or multirotor drones in high precision optical applications are rising. However, the optical turbulence effects generated by multirotor drones are not entirely understood. These optical effects can reduce the performance of the optical instruments that they transport. This paper presents measurements of the wavefront deformation generated by the temperature fluctuations and the airflow of a drone's propulsion system. To do so, we used a single arm of a DJI S800 EVO Hexacopter (professional drone) and measured its operating temperature with a commercial infrared camera. The resulting temperature variation, between a switched-off propulsion system at room temperature and one running at its maximum performance, was 34.2{\deg} C. Later, we performed two different interferometric tests, Takeda's method, and the phase-shifting technique, using a ZYGO interferometer. These tests show that the total deformation over an incident wavefront to the propeller airflow is lower than 0.074 \lambda PV and 0.007 \lambda RMS (HeNe laser, \lambda=633nm). We conclude that the optical turbulence produced by a drone propulsion system is negligible.

Development of a segmented grating mount system for FIREX-1

A mount system for segmented meter-sized gratings has been developed, which has a high precision grating support mechanism and drive mechanism to minimize both deformation of the optical surfaces and misalignments in setting a segmented grating for obtaining sufficient performance of the pulse compressor. From analytical calculations, deformation of the grating surface is less than 1/20 lambda RMS and the estimated drive resolution for piston and tilt drive of the segmented grating is 1/20 lambda, which are both compliant with the requirements for the rear-end subsystem of FIREX-1.

Wavefront error measurement of high-numerical-aperture optics with a Shack-Hartmann sensor and a point source

We developed a new, to the best of our knowledge, test method to measure the wavefront error of the high-NA optics that is used to read the information on the high-capacity optical data storage devices. The main components are a pinhole point source and a Shack-Hartmann sensor. A pinhole generates the high-NA reference spherical wave, and a Shack-Hartmann sensor constructs the wavefront error of the target optics. Due to simplicity of the setup, it is easy to use several different wavelengths without significant changes of the optical elements in the test setup. To reduce the systematic errors in the system, a simple calibration method was developed. In this manner, we could measure the wavefront error of the NA 0.9 objective with the repeatability of 0.003 lambda rms (lambda = 632.8 nm) and the accuracy of 0.01 lambda rms.

Opto-Mechatronics Issues in Solid Immersion Lens-Based Near Field Recording

Current developments in the solid immersion lens (SIL) based near-field recording technology are briefly introduced and research results including design, analysis, and experiments in CISD are reported. Also, the concept and performance of the novel optics using SIL is described throughout this paper. To increase the center thickness tolerance of SIL and decrease chromatic aberration, we add the replicated lens on SIL and the diffractive optical element (DOE). As a result of this design, it is confirmed that the SIL thickness tolerance of the replicated SIL optics is from -15 up to 7 mum at 0.035lambda rms, and wavefront aberration is less than 0.035lambda rms through variation of wavelength from 401 up to 412 nm

Test Results on Homogeneity of Expansion for a 18-m ULE Lightweight Mirror

Interferometric texts were performed on a 1.8-m ULE lightweight mirror at different uniform temperature conditions to determine figure changes due to expansion coefficient inhomogeneity. The conclusions of the experiment were: (1) The rms value of surface figure changes due to material inhomogeneities were found to be 0.036lambda over a 42 degrees C soak range at 6328 A. (2) Time variations of surface figure change were found to be insignificant over periods of up to 6 days. (3) No hysteresis remained after returning to figuring temperature (the measurement uncertainty was less than 0.023lambda rms at lambda = 6328 A). (4) Analytical predictions of surface figure change based on alpha inhomogeneity data were in close agreement with measurements.