Optical projection system and method of use

#This application relates generally to optical projection systems.

#Fisheye projection of moving images into dome theaters is a well established field dating back to the Atmospherium, a fulldome projection system designed at the University of Nevada-Reno in 1960. These early systems used film with images captured using a fisheye capture lens and were the precursors to OmniMax theaters that dominated the field for over 25 years. Projection systems are discussed in U.S. Pat. Nos. 3,934,259, 3,953,111 and 4,070,098. In the late 1990s, it became possible to use digital projectors rather than film. With that came the ability to project real-time imagery as well a linear (movie) playback.

#Milton Laikin, in Lens Design 85 (Marcel Dekker, Inc. 1991), observed that fisheye lenses tend toward an equal angular pixel distribution or a linear relationship between field angle and image height known as a f-theta or f-θ in the field of optical design. Such systems are discussed in U.S. Pat. No. 5,762,413. As graphics hardware has progressed exact adherence to f-θ has become less important. Graphics hardware is capable of real time correction of arbitrary distortions.

#FIG. 1 illustrates a dome theater including a projection system according to various embodiments;

#FIG. 2 illustrates specific field points projected from a !theta lens and a light engine with an unequal angular distribution according to various embodiments;

#FIG. 3 is a plot of a projected radial pixel density of a !theta lens and an f-θ lens normalized to the on axis density according to various embodiments;

#In the following detailed description of various embodiments, reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration, and not of limitation, specific embodiments in which the subject matter may be practiced. In the drawings, like numerals describe substantially similar components throughout the several views. The embodiments illustrated are described in sufficient detail to enable those skilled in the art to practice the teachings disclosed herein. Other embodiments may be utilized and derived therefrom, such that compositional, structural, and logical substitutions and changes may be made without departing from the scope of this disclosure. The following detailed description, therefore, is not to be taken in a limiting sense. Examples and embodiments merely typify possible variations. Individual components and functions are optional unless explicitly required, and the sequence of operations may vary. Portions and features of some embodiments may be included in or substituted for those of others. The following description is, therefore, not to be taken in a limiting sense.

#All fisheye lenses tend toward f-θ distortion. This means that as one moves linearly away from the optical axis in image space, one moves linearly, in angle, away from the optical axis in object space. Some projectors use a regular array of pixels. When coupled with a traditional f-θ fisheye lens, this leads to an equal angular pixel distribution. This distribution is less than optimal in many dome theater arrangements.

#In a planetarium, for example, the majority of audience attention is within 45 degrees of the event horizon. A better lens design would place more pixels in this region and fewer in the region from 45° to 0° (the zenith). Various embodiments described herein improve the projected pixel distribution with a type of fisheye lens called !theta where the meaning of ! is taken from set theory where ! is defined as “not.”