Abstract: The subject matter described herein includes a curved VPH grating with tilted fringes and spectrographs, both retroreflective and transmissive, that use such gratings. A VPH grating according to the subject matter described herein includes a first curved surface for receiving light to be diffracted. The grating includes an interior region having tilted fringes to diffract light that passes through the first surface. The grating further includes a second curved surface bounding the interior region on a side opposite the first surface and for passing light diffracted by the fringes.

Abstract: The subject matter described herein includes a curved VPH grating with tilted fringes and spectrographs, both retroreflective and transmissive, that use such gratings. A VPH grating according to the subject matter described herein includes a first curved surface for receiving light to be diffracted. The grating includes an interior region having tilted fringes to diffract light that passes through the first surface. The grating further includes a second curved surface bounding the interior region on a side opposite the first surface and for passing light diffracted by the fringes.

Abstract: The subject matter described herein includes a curved VPH grating with tilted fringes and spectrographs, both retroreflective and transmissive, that use such gratings. A VPH grating according to the subject matter described herein includes a first curved surface for receiving light to be diffracted. The grating includes an interior region having tilted fringes to diffract light that passes through the first surface. The grating further includes a second curved surface bounding the interior region on a side opposite the first surface and for passing light diffracted by the fringes.

Abstract: The subject matter described herein includes a curved VPH grating with tilted fringes and spectrographs, both retroreflective and transmissive, that use such gratings. A VPH grating according to the subject matter described herein includes a first curved surface for receiving light to be diffracted. The grating includes an interior region having tilted fringes to diffract light that passes through the first surface. The grating further includes a second curved surface bounding the interior region on a side opposite the first surface and for passing light diffracted by the fringes.

Abstract: Disclosed is a lightweight reflecting system for the concentration of solar radiation in which the reflecting optic is approximately sinusoidal in cross section and is maintained in this shape by minimal contact with a support frame. The reflector can be a flexible rectangular sheet deformed into a generally sinusoidal trough by compression between fixed or adjustable end supports. The sinusoid can be adjusted to be less than half a cycle by torsion applied to each end of the flexible sheet. A reflective film, polished metal, or similar material on the reflector surface can concentrate sunlight along a diffuse band rather than a sharp line, providing improved concentration levels for photovoltaic cells. The reflectors and their support frames can be mounted singly or severally on a tracking device that maximizes instantaneous power output by orienting the collectors toward the sun.

Abstract: Disclosed are photovoltaic collection systems, friction drives, and method for tracking the sun and avoiding wind damage without the use of complicated or expensive mechanical systems. In particular, disclosed is friction drive system for coupling a support beam supporting a photovoltaic collection assembly to a support pillar. The frictional drive system can include a plurality of wheels positioned for rotatably and pivotably coupling the support beam to the support pillar such that the support beam will slip with respect to the support pillar under application of a wind torque of a predetermined amount. Further, at least one motor can apply torques to the wheels for moving the support beam with respect to the support pillar.

Abstract: Disclosed is a lightweight reflecting system for the concentration of solar radiation in which the reflecting optic is approximately sinusoidal in cross section and is maintained in this shape by minimal contact with a support frame. The reflector can be a flexible rectangular sheet deformed into a generally sinusoidal trough by compression between fixed or adjustable end supports. The sinusoid can be adjusted to be less than half a cycle by torsion applied to each end of the flexible sheet. A reflective film, polished metal, or similar material on the reflector surface can concentrate sunlight along a diffuse band rather than a sharp line, providing improved concentration levels for photovoltaic cells. The reflectors and their support frames can be mounted singly or severally on a tracking device that maximizes instantaneous power output by orienting the collectors toward the sun.