STUDY SUMMARY - IPMU

More documents

Recommendations

Info

<strong>SUMMARY</strong> REPORT WIDE FIELD FIBER-FED OPTICAL MULTI-OBJECT SPECTROMETER (WFMOS) Figure 3.6-2: 1100 Series Camera from Spectral Instruments, Inc. The optical design of the camera and its position on Subaru is shown in Figure 3.6-3. Since the camera is looking back at the fiber field via the primary, the camera is focused at infinity. The system is designed to be compact while giving very good image quality across the field with little field distortion. The CCD detector window is coated with a narrow-band filter to reduce chromatic and stray lights effects. The backlit fiber sources are matched to the narrow band filter and are visible for daytime work on the telescope. Telescope Primary Wide Field Corrector Metrology Camera Figure 3.6-3: Optical Layout of the Subaru Telescope and the Metrology Camera 3.7 Field Element The Wide Field Corrector design assumes a filter and Dewar glass window of 30-mm diameter. When WFMOS is installed, the WFC remains, but the filter and Dewar window inherent in HSC are removed. A trade study was performed to consider whether alternate designs would provide significant advantage over the flat window. The factors considered were flat image plane, coupling efficiency, ease of fabrication, image quality, tolerances and ease of applying blocking spots. While no replacement window would be the least expensive, a simple shift in the focal plane is not sufficient to provide good coupling to the fibers, due to the residual spherical aberration and field curvature. Our design, therefore, incorporates a flat optical element that serves as a replacement for HSC’s Dewar window and filter. An important aspect of the optical performance of the WFC is the lack of “telecentricity”: the chief ray is not normal to the focal surface at the edge of the field. We evaluated the loss of fiber 29
<strong>SUMMARY</strong> REPORT WIDE FIELD FIBER-FED OPTICAL MULTI-OBJECT SPECTROMETER (WFMOS) coupling efficiency due to this effect and the potential of additional optical elements to compensate. Through our optical modeling, we have determined that the loss of throughput due to lack of telecentricity is very nearly identical to the loss of light from vignetting in the WFC. Additional optical elements designed to improve telecentricity do not actually significantly improve the throughput and have, therefore, not been incorporated in our design. The WFMOS Field Element coupling efficiency at the fiber tips is shown in Figure 3.7-1. The blue line indicates the coupling efficiency without the as-built performance of the Subaru Primary and WFC. The red line gives the overall coupling performance including the Primary, WFC and average seeing of 0.7 arc seconds. The black line shows the goal of 0.80 coupling efficiency. In addition, the Field Element has 2400 small, opaque spots (“Blocking Spots”) deposited on the side closest to the fiber positioners. There is one Blocking Spot per patrol region and each Blocking Spot obscures a tiny fraction (
Page 1 and 2: WIDE FIELD FIBER-FED OPTICAL MULTI-
Page 3 and 4: One of three identical Schmidt Spec
Page 5 and 6: SUMMARY REPORT WIDE FIELD FIBER-FED
Page 37: SUMMARY REPORT WIDE FIELD FIBER-FED
Page 89 and 90:
SUMMARY REPORT WIDE FIELD FIBER-FED
Page 91 and 92:
Page 93 and 94:
Page 95 and 96:
Page 97 and 98:
Page 99:
show all

STUDY SUMMARY - IPMU

Create successful ePaper yourself

Delete template?

Save as template?