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Dream's zeroDELTA

Engineered Lightweight Mirrors

Q u a l i t y

S t a r t s

A t

T h e

S u b s t r a t e

Dream's owner and founder, Shane Santi, started learning about thermal aspects that degrade mirror performance and optical systems well over 20 years ago. Early scientific papers that quantified mirror seeing educated him to the surprisingly large amount of performance losses and quickly led him to understand the value of pursuing lightweight mirrors. He formed Dream to not only solve a problem but to combine two complementary technologies; engineered lightweight mirrors and engineered carbon fiber structures. Both provide a technology-driven performance leap and when combined create an enabling, disruptive product to traditional technologies.

Shane recognized that most lightweight mirrors were either moderately difficult to extremely difficult to process to the same smooth levels as solid mirrors. This is the problem he knew had to be solved, in order to achieve total performance. He recognized that intelligent designs and higher levels of modern engineering could be used to greatly reduce print through, as well as evaluate the mirrors for not just polishing displacements but also gravity displacements. The latter has to include the mirror mount, which is why Shane designs both the lightweight mirror and the mirror mount at the same time. He has been designing lightweight optical mirrors with FEA feedback iterations since 2003 and has more individual design and empirical use experience creating optimized lightweight glass mirrors than any other individual in the world.

"Your company does phenomenal work. There is a lot of thought and heart that goes into your products. Dream's engineering sets their lightweight mirrors apart from competitors. Your engineering goes beyond the lightweight aspect. You focus on actual performance!"
- Ted Kamprath
39 years in professional optics, using everything from million dollar test rooms to 144" Continuous Polishers. He's spent his career using the latest in technologies, methods, materials & science to finish precision optics.

Dream is at the forefront of lightweight glass mirror technology with the disruptive performance that comes with Dream's thin-featured zeroDELTAmirrors. These mirrors are the culmination of 15 years of continuous and relentlessly improvements, chasing performance and becoming a vertically-integrated company that has always had the fundamental principal that there should be just as much engineering in the geometry of the mirror as the mirror mount. Because these mirrors are produced in-house it gives Dream control over as-designed versus as-cast variance, developing new rib geometries, annealing, scheduling/delivery, and an ability to quickly modify a design from the archives. Bringing generation, grinding and polishing in-house has further and completely closed the design loop.

When the 3D design of the optic is optimized (20-30 FEM/FEA iterations is the average per mirror) around an initial support architecture (mirror mount), then modified in thickness, height, adding and moving sub ribs, adding back flanges, etc., it gives Dream's lightweight, engineered mirrors superb performance that is unrivaled in the nearly 100 year history of lightweight mirrors. See hard data; 1, 2 , 3 and 4.

"We shall look back and see how inefficient, how primitive it was to work with thick, solid mirrors, obsolete mirror-curves, ..."
- George Willis Ritchey 1928: JRASC, Vol. XXII, No. 9, November 1928.

While developing the lightweight mirrors Dream was simultaneously becoming a specialist in carbon fiber and especially CF skinned sandwich core. Like other portions of the opto-mechanical system that Dream has taken over, it is not surprising that a generic composite company would not have the desire or appreciation to make the composites to a much higher standard, which is a neccessity for the extremely tight mechanical and thermal tolerances required for opto-mechanical systems. Dream's largest custom-built (by Dream) composite oven is 12' wide and maintains temperature a full magnitude tighter than OTS aerospace composite ovens.

Dream's dedicated carbon fiber mirror mounts, backplates, platforms, large diameter tubes, trusses, etc., in combination with the Dream zeroDELTA lightweight mirrors produce athermal assemblies with ununusually high stiffness and low mass. They are better equipped and provide higher performance for today's optical systems with ever-tightening tolerances. Dream's composite parts have unusually high consistency from part to part and full instrument to full instrument; performance lives in the details. In this way the design and engineering loop has been further closed because Dream not only produces lightweight mirror blanks but also proceses them and uses them in full instruments, allowing Dream to easily surpass the performance of traditional technologies.

Shane has also been learning optics since 1994. This deep, broader-based, real-world (empirical) knowledge, coupled with vertical integration of all tasks related to processing of the mirrors allows Dream to maximize a mirror's design & features in every way. Real-world information is fed back into the designs and makes Shane's knowledge, experience and heritage unique. Dream is creating mirrors that are not just light, stiff and with a much shorter thermal time constant, but functionally optimized to a degree never seen before, making them both enabling and disruptive.

Dream's zeroDELTA lightweight mirrors were developed through our casting technology. Prior to starting Dream fusing and frit bonding technologies were investigated. Those techniques use individual glass components that are cut, assembled, then fused or frit-bonded together at lower temperatures. These methods have fundamental hurdles that make it extremely difficult to vary specific rib thicknesses, create varying sub ribs, tapered ribs, etc. Dream's cast technology offers the highest level of design freedom and therefore far greater mechanical optimization than other methods, which is one of two main reasons high-temperature cast technology was pursued.

Dream's mirrors are cast (melted) to produce a single, continuous mirror that does not suffer from the historically significant problem of bondline issues, which is why Dream chose not to pursue less expensive, lower temperature fused and frit-bonded mirrors. Since Dream's mirrors are cast they don't need expensive inspection equipment, techniques and expertise in order to uncover areas of the mirror where less than 100% bonding took place. Openly available papers have shown that even companies with 20-30 years experience with these lower temperature processes continue to have bondline issues. Dream's mirrors don't have to "act" like one piece of glass. They are one piece of glass. They won't come apart today, tomorrow or 50 years from now. The optical surface of the mirror is typically finished to fractions of a wavelength of light. The mirror doesn't need to come apart in order to have catastrophic problems.

The zeroDELTA lightweight mirrors are not pocket-milled from a solid mirror blank or boule either. Pocket-milling is also limited in its design freedoms for; rib types, depths, shapes, radii in corners, back flange widths, etc. Pocket-milling is typically 6-10 times, or more, expensive than Dream's technology and it tends to leave mass concentrations at the node of ribs.

Dream specializes in the design, engineering and in-house production of bubble-free lightweight mirrors using modern 3D CAD, FEM/FEA, CNC equipment and micro-processor controlled furnaces & annealing ovens. Dream provides industry-leading convex, concave and plano mirrors that eliminate the mechanical & thermal performance losses associated with solid mirrors, which is currently a 350 year old technology. The CTE of Dream's lightweight mirrors is 3.16x10-6/°K. Dream does not use plate glass, which has a CTE almost 3x higher (9.1x10-6/°K) and is nearly 4x more sensitive (when comparing the same thicknesses) to bending due to thermal transients; internal temperature gradients warping the figure of the optical surface. Due to the thin features of Dream's zeroDELTAmirrors, they do not support internal temperature gradients.


Print Through

definition, interferometry examples and information

Thermal Advantages

mirror seeing & the boundary layer

Mechanical Advantages

examples of mechanical advantages offered





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