Alignment methods for Cassegrain and RC telescope with wide field of view

Yang, Ho‐Soon; Lee, Yun-Woo; Kim, Eugene D.; Choi, Young‐Wan; Rasheed, Ad. Aziz Ad.

doi:10.1117/12.558998

Cited by 11 publications

(7 citation statements)

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“…The alignment becomes more difficult when the field of view is relatively large. This was observed while aligning a +/-1 deg field of view Cassegrain telescope [3]. Even though the on-axis interferogram showed sufficiently low RMS wave front error (WFE), the RMS WFEs of the opposite off-axis fields were unacceptably unbalanced.…”

Section: Development Of Secondary Mirrormentioning

confidence: 92%

Development of Cassegrain type 0.9-m collimator

et al. 2005

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Collimator is essential to evaluate and assemble the other telescopes. Its diameter should be larger than that of the target telescope for the correct use. We are currently developing the Cassegrain type collimator of which diameter is 0.9 m. The primary mirror is light-weighted so that its weight is only 70 kg. Due to its structure, the primary mirror can be supported only at the backside of the mirror. This mirror is tested with the combination of null Hartmann test and interferometer. The secondary mirror is tested with a Hindle method. This method requires 600 mm high quality spherical mirror. The distance between the primary and secondary mirror is maintained by the Carbon composite material. The assembly of two mirrors is carried out by the computer aided alignment method. The whole structure is designed to maintain the performance of the collimator under +/-5 degrees of temperature variation.

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Section: Development Of Secondary Mirrormentioning

confidence: 92%

Development of Cassegrain type 0.9-m collimator

et al. 2005

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“…When attempting to determine the number of field points required to align a wide field system, the measurement of one on-axis field point does not yield sufficient information to obtain insight into the full field performance [4,5]. If only one on-axis field point is measured, the results would certainly indicate misalignment, but it could also be due to manufacturing errors and even setup disturbances because the various contributors cannot be independently isolated by a single measurement.…”

Section: Simulation Study Of the Field Sampling Effectmentioning

confidence: 99%

“…One of the issues that exist when aligning wide FOV systems is the determination of how many field points should be measured. There is the need for both on-axis and off-axis measurements [4,5,6]. Ideally, a large number of field points should be measured, although measurement of the entire field is often challenging, time-consuming, and unrealistic.…”

Section: Introductionmentioning

confidence: 99%

Multi-field merit-function-based regression method for Wide Field Infrared Survey Telescope grism system alignment

et al. 2019

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The grism, slitless spectrometer aboard the Wide Field Infrared Survey Telescope (WFIRST) enables a survey of emissionline galaxies. To facilitate its opto-mechanical alignment, a six-degree-of-freedom element was fabricated using alignment fiducials and integral flats and used to measure a wavefront by using an infrared interferometer placed at various field points over a 20×14-degree field of view in the grism coordinate frame. Modeling identified E2 to be the most sensitive element to the grism WFE and was used to efficiently align the system. The merit function regression method for a wide field of view was further used to verify the higher efficiency and accuracy of the proposed alignment technique compared with the conventional sensitivity table method.

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“…Many researchers have developed the reverse-optimization algorithm for the purpose of aligning off-axis systems such as Three Mirror Anastigmat (TMA) or the wide-field optical system [2][3][4][5]. The method attempts to discover the misalignment of the components by measuring the system WFE from several different fields.…”

Section: Introductionmentioning

confidence: 99%

Merit function regression method for efficient alignment control of two-mirror optical systems

Kim¹,

Yang²,

Lee³

et al. 2007

Opt. Express

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The precision alignment of high-performance, wide-field optical systems is generally a difficult and often laborious process. We report a new merit function regression method that has the potential to bring to such an optical alignment process higher efficiency and accuracy than the conventional sensitivity table method. The technique uses actively damped least square algorithm to minimize the Zernike coefficient-based merit function representing the difference between the designed and misaligned optical wave fronts. The application of this method for the alignment experiment of a Cassegrain type collimator of 900mm in diameter resulted in a reduction of the mean system rms wave-front error from 0.283 lambda to 0.194 lambda;, and in the field dependent wave-front error difference from +/-0.2 lambda to +/-0.014 lambda in just two alignment actions. These results demonstrate a much better performance than that of the conventional sensitivity table method simulated for the same steps of experimental alignment.

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Alignment methods for Cassegrain and RC telescope with wide field of view

Cited by 11 publications

References 0 publications

Development of Cassegrain type 0.9-m collimator

Development of Cassegrain type 0.9-m collimator

Multi-field merit-function-based regression method for Wide Field Infrared Survey Telescope grism system alignment

Merit function regression method for efficient alignment control of two-mirror optical systems

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