Abstract: Systems and methods of dispersion compensation in an optical device are disclosed. A holographic optical element may include a set of different holograms in a grating medium. Each hologram in the set may have a corresponding grating vector with a grating frequency and direction. The directions of the grating vectors may vary as a function of the grating frequency. Different holograms in the set may diffract light in a particular direction so that the light emerges from a boundary of the grating medium in a single given direction regardless of wavelength. A prism may be used to couple light into the grating medium. The prism may be formed using materials having dispersion properties that are similar to the dispersion properties of the grating material. The prism may have an input face that receives perpendicular input light. The prism may include multiple portions having different refractive indices.

Abstract: A blade assembly for use with a tilling mechanism including a first blade disk. A second blade disk is coaxially mounted to rotate with the first blade disk and is positioned in a spaced apart generally parallel fashion relative to the first blade disk. The first blade disk and the second blade disk are rotatable in a first direction. A first plurality of teeth are disposed on the first blade disk. Each of the first plurality of teeth have a first leading edge which extends generally radially outwardly from the first blade disk. A second plurality of teeth are disposed on the second blade disk. Each of the second plurality of teeth has a second leading edge which extends generally linearly outwardly from the second blade disk in a direction counter to the first direction. The second leading edge forms an obtuse angle as measured relative to a line extending in the first direction tangent to the second blade disk. A second embodiment of the blade assembly is also shown herein.

Abstract: An improved blower for moving debris on a surface is provided. The blower includes a frame mounted on wheels and a motor mounted to the frame. A blower housing with an inlet opening and a discharge chute is also mounted to the frame. A fan is located in the blower housing and is drivingly connected to the motor to generate an air flow having a predetermined volumetric flow. An adjustable height, pivotable deflector is mounted in the discharge chute to split the air flow into upper and lower portions. The deflector is pivotable from a first, downwardly inclined position, to concentrate the lower portion of the air flow along the surface to create a lifting force for lifting and moving the debris while the upper portion of the air flow moves the debris outwardly, to a second position, in which the pivotable deflector is upwardly inclined to create an expanded air flow profile. The deflector height is adjustable to adjust the volumetric flow of the upper and lower portions.