The Ohio State University College of Mathematical & Physical Sciences Department of Astronomy

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MODS Blue Camera Optics

MODS Blue Camera design view. The Red cameras will look essentially the same (the difference is in the optics). This view shows the shutter, the integrated filter wheel, and part of the CCD dewar mounting pieces (the green box is a placeholder for structures that will be inside the CCD dewar proper). The adjustable truss design is also visible in this view. The actual camera will be enclosed and light-tight.
[AutoCad drawing by Tom O'Brien].

MODS Camera Primary Mirror blank. This is one of four lightweight pyrex honeycomb mirrors manufactured by Hextek Products in Tuscon, AZ. This is a finished blank shown after slumping into the approximate curved surface and ready for polishing. Three of the four camera primary mirror blanks have been made and accepted. A fourth cracked during slumping and a new blank is being made. The cracked blank was delivered to OSU where we will use it to prototype the camera primary cell and support system.
[Photo courtesy of Hextek].

Fused-silica parent out of which the two corrector lenses for the blue cameras (MODS1 and MODS2) will be made. The ovals show the high-quality glass sectors in the larger parent that will become the corrector lenses for the MODS blue cameras. It was manufactured by Corning Glass Works in Corning, New York. Transmission interferograms of the blank show that the glass as formed exceeds our index homogeneity specification. It is now sitting in the Corning plant awaiting shipping to whoever we award the final optics contract.
[Photo courtesy of Corning Glass].

Optical raytrace of the MODS decentered Maksutov-Schmidt Cameras. The view is along the long axis of the camera primary and corrector, showing the basic light path (this is not an engineering diagram).
[Code-V raytracing by Paul Byard].

MODS Collimator Mirrors

Engineering model of the MODS collimator mirrors and their 3-axis active support system. The outer "diamond" frame enclosing both is where the collimators attach to the main structure of MODS. The blue collimator is on the left and the red collimator is on the right.
[AutoCad drawing by Tom O'Brien].

MODS Collimator Mirror blank (one of 4). Like the camera primary mirrors, we are using lightweight pyrex honeycomb mirrors manufactured by Hextek Products of Tucson, AZ. The collimator mirrors are also slumped. All 4 Hextek blanks have been accepted and will be shipped soon to REOSC Optique in St. Pierre du Perray, France for figuring and polishing.
[Photo courtesy of Hextek.]

Prototype MODS collimator support frame being prepared for testing in the OSU mechanical lab. The frame is a welded, hollow steel tube (rectangular cross-section). Inside, the triangular structure is the collimator mount support (which would hold the eventual collimator cell, not yet fabricated, from behind). Tom O'Brien is shown working on installing the three linear actuators used for focus piston and flexure-compensation steering (tip/tilt) motions. This prototype will be used to quantify the tip/tilt/focus precision and repeatability of our collimator mount design.
[Photo by R. Pogge]

Close-up of one of the three linear actuators on the collimator support, showing the blade and torsion flexures that connect the actuator to the collimator frame. Harmonic reducing gears on the actuator motors give us a linear stroke resolution of approximately +/-0.2 microns (actual performance is being measured with this prototype at this time).
[Photo by R. Pogge]