Simulation and polishing experiment of aspheric mirror with pre-filled surface figure

Null Lenses for Testing Surface Figure of Aspheric Mirrors

Journal of Optics ◽

10.1007/bf03549688 ◽

1987 ◽

Vol 16 (3) ◽

pp. 58-66

Author(s):

P. Nageswara Rao ◽

K. K. Banerjee ◽

H. S. Singh

Keyword(s):

Surface Figure

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Microwave Holographic Surface Measurement of the Tidbinbilla 64-m Antenna

Publications of the Astronomical Society of Australia ◽

10.1017/s1323358000017082 ◽

1983 ◽

Vol 5 (2) ◽

pp. 270-272 ◽

Cited By ~ 2

Author(s):

Y. Rahmat-Samii ◽

S. Gulkis ◽

G.S. Levy ◽

B.L Seidel ◽

L.E. Young ◽

...

Keyword(s):

High Speed ◽

Survey Methods ◽

Low Cost ◽

Single Frequency ◽

Surface Measurement ◽

Antenna Aperture ◽

Phase Fluctuations ◽

Surface Deviations ◽

Antenna Surface ◽

Surface Figure

The ‘holographic’ technique for accurately measuring the surface figure of large reflector antennas, described by Bennet et al, (1976) and Scott and Ryle (1977), has many advantages over older conventional survey methods. These include high speed, low cost, and the absence of any need for additional complex mechanical or optical survey devices. In essence, the technique consists of measuring the complex far-field response of the antenna at a single frequency using a terrestrial, satellite-borne or celestial radiation source of small angular diameter. This two-dimensional pattern is then Fourier-transformed to yield the complex illumination function across the antenna aperture. Antenna surface deviations are manifested as phase fluctuations in this function. In practice, a second antenna is needed to provide a phase reference.

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Application of LIDAR technology for rail surface monitoring and quality indexing

Proceedings of the Institution of Mechanical Engineers Part F Journal of Rail and Rapid Transit ◽

10.1177/0954409717727200 ◽

2017 ◽

Vol 232 (5) ◽

pp. 1398-1406 ◽

Cited By ~ 3

Author(s):

Masood Taheri Andani ◽

Abdullah Mohammed ◽

Ashish Jain ◽

Mehdi Ahmadian

Keyword(s):

Doppler Frequency ◽

Light Detection And Ranging ◽

Doppler Lidar ◽

Frequency Range ◽

Absorption Properties ◽

Surface Conditions ◽

Lidar Measurements ◽

Rail Inspection ◽

Surface Monitoring ◽

Surface Figure

This paper investigates the application of Doppler Light Detection and Ranging (LIDAR) sensors for the assessment of the top of rail lubricity condition and layer material. Different top of rail conditions are distinguished by the system using a new pair of rail surface indices defined based on LIDAR measurements. These indices provide quantitative representations of the top of rail condition due to the fact that Doppler frequency range and spectral magnitude of a backscattered LIDAR beam are functions of the rail surface figure as well as the light absorption properties of the surface material. Laboratory tests are conducted to demonstrate the feasibility of the proposed top of rail indexing operation. The results indicate that LIDAR sensors are capable of detecting and distinguishing between different top of rail surface conditions. Instrumenting rail inspection vehicles with Doppler LIDAR systems reduces reliance on empirical top of rail lubricity and surface assessments (such as observing the sheen of the rail or tactilely sensing various residues on the rail), in favor of reliable and repeatable measurements.

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