TY - GEN
T1 - Stiffening an off-axis beam compressor mount for improved performance
AU - Penado, F. Ernesto
AU - Clark, James H.
AU - Cornelius, Frank
PY - 2010
Y1 - 2010
N2 - The Navy Prototype Optical Interferometer (NPOI) near Flagstaff, Arizona, makes use of separate smaller optical elements spaced along a Y-array and used simultaneously to simulate an equivalent single large telescope. The instrument is useful in generating and upgrading existing astronomical catalogues and investigating synthetic aperture optical imaging techniques. The NPOI is a joint collaboration between the US Naval Observatory and Naval Research Laboratory in collaboration with the Lowell Observatory. Stellar radiation (visible light) reflects off 35 cm diameter flat mirrors, also known as siderostats, toward a tilt-tip mirror, which reflects a 12 cm diameter beam through a multi-reflection relay transport system. To maximize the reflective area of the siderostat optics and achieve an increase by a factor of 8.5 in light collecting area, a beam compressor is to be installed between the siderostat and fast tip/tilt mirror. However, the present configuration of a prototype beam compressor mount (BCM) vibrates at unacceptable amplitudes, which makes it nearly impossible to optically align the mirrors. This paper presents the results of finite element analyses conducted to quantify the design limitations of the prototype beam compressor mount. The analyses indicated that the current configuration is too soft, with very low fundamental frequencies, which verified the difficulties encountered during alignment tests. Based on these results, design modifications have been proposed to increase the overall structural stiffness of the mount and increase its fundamental frequency of vibration. These modifications will mechanically stabilize the structure for the alignment of the optics, and allow integration of the compressor into the interferometer. The interferometer will then have the capability to capture more light from each siderostat and allow observations of fainter stellar targets. More generally, the results can be useful as a guide for engineers and scientists involved in the design of similar optomechanical structures.
AB - The Navy Prototype Optical Interferometer (NPOI) near Flagstaff, Arizona, makes use of separate smaller optical elements spaced along a Y-array and used simultaneously to simulate an equivalent single large telescope. The instrument is useful in generating and upgrading existing astronomical catalogues and investigating synthetic aperture optical imaging techniques. The NPOI is a joint collaboration between the US Naval Observatory and Naval Research Laboratory in collaboration with the Lowell Observatory. Stellar radiation (visible light) reflects off 35 cm diameter flat mirrors, also known as siderostats, toward a tilt-tip mirror, which reflects a 12 cm diameter beam through a multi-reflection relay transport system. To maximize the reflective area of the siderostat optics and achieve an increase by a factor of 8.5 in light collecting area, a beam compressor is to be installed between the siderostat and fast tip/tilt mirror. However, the present configuration of a prototype beam compressor mount (BCM) vibrates at unacceptable amplitudes, which makes it nearly impossible to optically align the mirrors. This paper presents the results of finite element analyses conducted to quantify the design limitations of the prototype beam compressor mount. The analyses indicated that the current configuration is too soft, with very low fundamental frequencies, which verified the difficulties encountered during alignment tests. Based on these results, design modifications have been proposed to increase the overall structural stiffness of the mount and increase its fundamental frequency of vibration. These modifications will mechanically stabilize the structure for the alignment of the optics, and allow integration of the compressor into the interferometer. The interferometer will then have the capability to capture more light from each siderostat and allow observations of fainter stellar targets. More generally, the results can be useful as a guide for engineers and scientists involved in the design of similar optomechanical structures.
KW - Beam compressor alignment
KW - Finite element analysis
KW - Fundamental frequency
KW - Light collimation
KW - NPOI
KW - Vibration analysis
UR - http://www.scopus.com/inward/record.url?scp=77958091113&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=77958091113&partnerID=8YFLogxK
U2 - 10.1117/12.860270
DO - 10.1117/12.860270
M3 - Conference contribution
AN - SCOPUS:77958091113
SN - 9780819482891
T3 - Proceedings of SPIE - The International Society for Optical Engineering
BT - Optical System Alignment, Tolerancing, and Verification IV
T2 - Optical System Alignment, Tolerancing, and Verification IV
Y2 - 1 August 2010 through 2 August 2010
ER -