Construction of the Daniel K. Inouye Solar Telescope (DKIST) is well underway on the Haleakalā summit on the Hawaiian island of Maui. Featuring a 4-m aperture and an off-axis Gregorian configuration, the DKIST will be the world’s largest solar telescope. It is designed to make high-precision measurements of fundamental astrophysical processes and produce large amounts of spectropolarimetric and imaging data. These data will support research on solar magnetism and its influence on solar wind, flares, coronal mass ejections, and solar irradiance variability. Because of its large aperture, the DKIST will be able to sense the corona’s magnetic field—a goal that has previously eluded scientists—enabling observations that will provide answers about the heating of stellar coronae and the origins of space weather and exo-weather. The telescope will cover a broad wavelength range (0.35 to 28 microns) and operate as a coronagraph at infrared (IR) wavelengths. Achieving the diffraction limit of the 4-m aperture, even at visible wavelengths, is paramount to these science goals. The DKIST’s state-of-the-art adaptive optics systems will provide diffraction-limited imaging, resolving features that are approximately 20 km in size on the Sun.
At the start of operations, five instruments will be deployed: a visible broadband imager (VTF), a visible spectropolarimeter (ViSP), a visible tunable filter (VTF), a diffraction-limited near-IR spectropolarimeter (DLNIRSP), and a cryogenic near-IR spectropolarimeter (cryo-NIRSP). At the end of 2017, the project finished its fifth year of construction and eighth year overall. Major milestones included delivery of the commissioning blank, the completed primary mirror (M1), and its cell. Commissioning and testing of the coudé rotator is complete and the installation of the coudé cleanroom is underway; likewise, commissioning of the telescope mount assembly (TMA) has also begun. Various other systems and equipment are also being installed and tested. Finally, the observatory integration, testing, and commissioning (IT&C) activities have begun, including the first coating of the M1 commissioning blank and its integration within its cell assembly. Science mirror coating and initial on-sky activities are both anticipated in 2018.
The Daniel K. Inouye Solar Telescope (DKIST) is a 4-meter aperture, off-axis, Gregorian configuration, solar telescope currently under construction on the top of Haleakela on the island of Maui, Hawaii1. When completed, DKIST will be the world’s largest solar telescope.
The optical performance of the telescope will depend on the accurate alignment of its mirrors. During Integration Testing and Commissioning (IT&C), mirrors will be installed and aligned sequentially. The alignment will be verified by measuring the wavefront progressively at different focus locations using starlight at night with a custom-designed wavefront measurement system (WMS) that consists of a Shack-Hartmann wavefront sensor. In this paper, we will present the optical design of the WMS. We will discuss the testing and calibration process of the as-built WMS in the lab and demonstrate the final in-lab performance.
The Daniel K. Inouye Solar Telescope (DKIST) has been in its construction phase since 2010, anticipating the onset of the integration, test, and commissioning (IT&C) phase in early 2017, and the commencement of science verification in 2019. The works on Haleakala are progressing at a phenomenal rate and many of the various subsystems are either through or about to enter their Factory (or Laboratory) acceptance. The delays in obtaining site planning permissions, while a serious issue for Project Management, has allowed the sub-systems to develop well ahead of their required delivery to site. We have benefited from the knowledge that many sub-systems will be on site and ready for integration well before affecting the critical path. Opportunities have been presented for additional laboratory/factory testing which, while not free, significantly reduce the risks of potential delays and rework on site. From the perspective of IT&C this has provided an opportunity to develop the IT&C plans and schedules free from the pressures of imminent deployment.
In this paper we describe the ongoing planning of the Integration, Testing and Commissioning (IT&C) phase of the project in particular the detailed planning phase that we are currently developing.
The Daniel K. Inouye Solar Telescope (DKIST), formerly the Advanced Technology Solar Telescope (ATST), has
been in its construction phase since 2010, anticipating the onset of the integration, test, and commissioning (IT&C)
phase late in 2016, and the commencement of science verification in early 2019. In this paper we describe the
planning of the Integration, Testing and Commissioning (IT&C) phase of the project.
We present a novel and inexpensive Stokes imaging spectropolarimeter based on the Snapshot Hyperspectral Imaging Fourier Transform (SHIFT) spectrometer. A rotating quarter wave plate and stationary linear polarizer placed in front of the SHIFT spectrometer enables us to reconstruct an object’s spectra and Stokes parameters in the visible spectrum. Measurements are stored in the form of four-dimensional (4D) Stokes datacubes containing the object’s spatial, spectral, and polarization information. We discuss calibration methods, review design considerations, and present preliminary results from proof-of-concept experiments.
Recently the lens fabrication technique is developed so fast that an aspherical surface is often used to achieve better imaging performance or reduce number of elements. Especially the popularity of micro-optics and miniature imaging system makes the use of aspherical optics very common. However the metrology of aspherical micro-optics has been disregarded and outpaced by the fabrication technique. It results in the lack of ignorance of metrology for aspherical micro-optics. This paper suggests the simple and cost-effective methodology for aspherical micro-optics by using computer generated hologram (CGH). Although the CGH technique is well-known and well-established technique for relatively larger aspherical optics, it is seldom used for micro-optics testing where there is higher demand of aspherical optics testing. By reporting the success of aspherical micro-optics testing in this paper, we confirm that CGH technique will play an important role to answer new demand of metrology.
In collaboration with the Department of Biomedical Engineering at the University of Texas at Austin and the UT MD Anderson Cancer Center, a laser scanning fiber confocal reflectance microscope (FCRM) system has been designed and tested for in vivo detection of cervical and oral pre-cancers. This system along with specially developed diagnosis algorithms and techniques can achieve an unprecedented specificity and sensitivity for the diagnosis of pre-cancers in epithelial tissue. The FCRM imaging system consists of an NdYAG laser (1064 nm), scanning mirrors/optics, precision pinhole, detector, and an endoscopic probe (the objective). The objective is connected to the rest of the imaging system via a fiber bundle. The fiber bundle allows the rest of the system to be remotely positioned in a convenient location. Only the objective comes into contact with the patient. It is our intent that inexpensive mass-produced disposable endoscopic probes would be produced for large clinical trials. This paper touches on the general design process of developing a miniature, high numerical aperture, injection-molded (IM) objective. These IM optical designs are evaluated and modified based on manufacturing and application constraints. Based on these driving criteria, one specific optical design was chosen and a detailed tolerance analysis was conducted. The tolerance analysis was custom built to create a realistic statistical analysis for integrated IM lens elements that can be stacked one on top of another using micro-spheres resting in tiny circular grooves. These configurations allow each lens element to be rotated and possibly help compensate for predicted manufacturing errors. This research was supported by a grant from the National Institutes of Health (RO1 CA82880). Special thanks go to Applied Image Group/Optics for the numerous fabrication meetings concerning the miniature IM objective.
Most conventional imaging systems suffer from unwanted and unexpected stray light that is often caused by reflections and scattering from optics and opto-mechanical features. This problem is easily missed during a design procedure that concentrates on improvement of imaging performance. The problem becomes apparent at the final step of production in most cases. If an imaging system consists of micro-optics, a stray light problem may become more difficult to solve due to the system's micro-scale size.
The purpose of this stray light analysis is to improve imaging performance of the multi-modal miniature microscope (4M). The 4M device is a complete microscope on a chip, including optical, micro-mechanical, and electronic components. The 4M device is potentially a useful tool for early detection of pre-cancer due to its very compact size and capability for microscopic-scale imaging. Before actual fabrication of this device, however, we built the same geometry as the real 4M device in a commercial non-sequential ray tracing code and implemented stray light analysis of 4M device.
Our findings indicate that most of the stray light in a 4M device is created by reflection from optics that are nominally supposed to be transparent. Due to a low signal level associated with the object, it is required to add high quality anti-reflection coatings on optics to achieve reasonable SNR.
We have used non-sequential ray tracing as a simulation tool to model micro-optical systems. Ray tracing can be used to model micro-optical systems as long as the wave nature of the light is not dominant. Non-sequential ray tracing takes inherently into account the aberrations of the optical system and enables the modeling of scattering and stray light effects. We have used measured scattering properties of a hybrid-glass lens material to model scattering in an example imaging micro-optical system. We have also used non-sequential ray tracing to model a straight and a bent light-guide that can be used as chemical sensors. Modeling estimates the amount of light going through the optical system to the detector and shows the paths of the rays leaking out from the system.
We present the design and fabrication of miniaturized light sources for micro-optical systems using organic light emitting diodes (OLEDs). These devices can be integrated on a micro-optical table (MOT) using various backplanes. Acceptable angular uniformity of emitted radiance, and a brightness of more than 30,000 cd/m2 can be readily achieved with OLEDs having areas ranging from 0.0004 cm2 to 0.0363 cm2.