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Each detector image shows the nuller (low frequency fringes) and the auxiliary interferometer (high frequency fringes) output. In image (a) the left side of the nuller output (bounding box labled L) is nulled, the right side of the nuller output (bounding box labeled R) is near the midfringe intensity, and the fringe patterns in the auxiliary interferometer (labeled d and s for delay and static, respectively) appear to be nearly aligned. Note that only partial fringes are sampled inside the bounding boxes. In image (b) the delay line is positioned to null the right half of the nuller output, whereas the left null bounding box intensity is near midfringe. The shift in the delay line is evidenced by the downward shift of its fringes from image (a) to (b).
Source publication
We describe a white light fringe scanning and pupil bisecting method of measuring the optical path difference (OPD) between arms of a monolithic nulling interferometer that is designed to enable direct imaging of planetary companions and the environments around nearby stars. This measurement is used to determine the differential thicknesses of opti...
Contexts in source publication
Context 1
... d s where left and right null refer to the relative positions of the nuller output pupils observed on the monitor. It should be noted that the a change of sign from the left to right side of the above map indicates a reversal of pupil location at the output relative to the input for a given beam. An auxilliary alignment and phasing interferometer (shown in red and purple in Fig. 2) was included in the optical layout to ensure that the phase delayed beams were parallel when in- jected into the monolith. The zero OPD search space was increased by tilting M2 to produce a high fringe count across the auxilliary interferometer pupil. After completing these steps, the laser was replaced with a halogen source. The SMA and DLA were then successively positioned at zero OPD relative to M2 in order to make white light fringes observable in either half of the auxilliary interferometer pupil (see Fig. 3). Once the beams were aligned and coarsely phased, the DLA was scanned with a long period triangle wave signal. Images of the time varying intensities were taken over many scan periods to mitigate environmental effects. To determine the white light fringe spacing in physical units, a small amount of tilt was added to the input beams such that the fringe pattern observed in the nuller output resembled those observed in the auxiliary interferometer shown in Fig. 3. Images of the fringes produced by the halogen source, and then the red HeNe were recorded. The pixel intensities were summed in each row in one nuller output pupil half for both light sources in order to generate a 1D intensity signal versus row number. Peaks were then located in the Fourier transforms of these signals to calculate per pixel fringe spacings, ζ halogen and ζ 632.8 , the ratio of which is used to recover the white light central ...
Context 2
... d s where left and right null refer to the relative positions of the nuller output pupils observed on the monitor. It should be noted that the a change of sign from the left to right side of the above map indicates a reversal of pupil location at the output relative to the input for a given beam. An auxilliary alignment and phasing interferometer (shown in red and purple in Fig. 2) was included in the optical layout to ensure that the phase delayed beams were parallel when in- jected into the monolith. The zero OPD search space was increased by tilting M2 to produce a high fringe count across the auxilliary interferometer pupil. After completing these steps, the laser was replaced with a halogen source. The SMA and DLA were then successively positioned at zero OPD relative to M2 in order to make white light fringes observable in either half of the auxilliary interferometer pupil (see Fig. 3). Once the beams were aligned and coarsely phased, the DLA was scanned with a long period triangle wave signal. Images of the time varying intensities were taken over many scan periods to mitigate environmental effects. To determine the white light fringe spacing in physical units, a small amount of tilt was added to the input beams such that the fringe pattern observed in the nuller output resembled those observed in the auxiliary interferometer shown in Fig. 3. Images of the fringes produced by the halogen source, and then the red HeNe were recorded. The pixel intensities were summed in each row in one nuller output pupil half for both light sources in order to generate a 1D intensity signal versus row number. Peaks were then located in the Fourier transforms of these signals to calculate per pixel fringe spacings, ζ halogen and ζ 632.8 , the ratio of which is used to recover the white light central ...
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Citations
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