The visible emission line coronagraph (VELC) on board the Aditya-L1 mission is an internally occulted reflective coronagraph. It is capable of simultaneous observations of the solar corona in imaging, spectroscopic, and spectropolarimetric modes very close to the solar limb, to 1.05 R ⊙ (R ⊙ – solar radius). Primary mirror (M1) of the VELC receives the light from both the solar disk and the corona up to 3 R ⊙ . In the VELC, occultation happens at the focus of the M1. Secondary mirror (M2) with a central hole size equal to 1.05 R ⊙ is mounted at the focal plane of M1 and serves the purpose of an internal occulter. To meet the proposed science goals of the payload, M1 surface should be super polished with good imaging characteristics. This results in stringent requirements of the surface figure and microroughness on the mirror surface. M1 is an off-axis parabola, so achieving the demanding requirements is quite challenging. At the same time, testing of M1 after development is crucial for evaluating its performance. This paper provides the details of the optical metrology tests carried out on M1 along with the results obtained and their implications on the performance of the VELC.
The human body constantly undergoes heat exchange with the environment, and that can be imaged well by thermal imaging. Some application of thermal imaging is in neurology, vascular disorders, rheumatic diseases, oncology, dentistry, and ophthalmology. Every activity described above has unique characteristics. The temperature range for inflammatory condition of the human skin varies significantly from that of an ocular surface. Specific to ophthalmology, the thermal imaging should be able to capture the subtle changes of ocular surface temperature. The existing thermal sensors used in most ophthalmic studies have a dynamic range from -20°C to 350°C and accuracy of 2°C. This paper talks about the development and calibration of a new sensor with optimization in the desired dynamic range and its demonstration for capturing the ocular surface temperature.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.