Abstract: Optical systems including an image surface and a stop surface are described. First second and third optical lenses, a partial reflector, a multilayer reflective polarizer and a quarter wave retarder are disposed between the image surface and the stop surface. A plurality of major surfaces are disposed between the image surface and the stop surface with each major surface convex toward the image surface along orthogonal first and second axes. At least six different major surfaces have six different convexities.

Abstract: Optical systems including an image surface, a stop surface, a partial reflector disposed between the image surface and the stop surface, a reflective polarizer disposed between the stop surface and the partial reflector, and a quarter wave retarder disposed between the reflective polarizer and the partial reflector are described. The reflective polarizer is convex along two orthogonal axes. The reflective polarizer may be a thermoformed multilayer reflective polarizer.

Abstract: Integral optical stacks and optical systems including an image surface, a stop surface and an integral optical stack disposed between the image surface and the stop surface are described. The integral optical stack includes an optical lens, a partial reflector, a multilayer reflective polarizer and a quarter wave retarder. At least one chief light ray transmitted through the stop surface and the image surface passes through the stop surface at an incident angle of at least 40 degrees.

Abstract: Optical systems including first and second optical stacks and adapted to provide an adjustable dioptric correction are described. The first optical stack includes a first optical lens and a partial reflector. The second optical stack is convex along orthogonal first and second axes and includes a second optical lens and a reflective polarizer. The reflective polarizer has at least one first location having a radial distance r1 from an optical axis of the second optical stack and a displacement s1 from a plane perpendicular to the optical axis at an apex of the reflective polarizer, where s1/r1 is at least 0.1. A quarter wave retarder is disposed between the second optical stack and the first optical stack.

Abstract: Methods of making optical films and optical stacks are described. A method of making an optical stack includes providing a thermoform tool centered on a tool axis and having an external surface rotationally asymmetric about the tool axis; heating an optical film resulting in a softened optical film; conforming the softened optical film to the external surface while stretching the softened film along at least orthogonal first and second directions away from the tool axis resulting in a conformed optical film rotationally asymmetric about an optical axis of the conformed film where the optical axis coincident with the tool axis; cooling the conformed optical film resulting in a symmetric optical film rotationally symmetric about the optical axis; and molding an optical lens on the symmetric optical film resulting in the optical stack.

Abstract: A head-mounted display including a first optical system is provided. The first optical system includes an image surface, a stop surface, a first optical stack disposed between the image surface and the stop surface and a second optical stack disposed between the first optical stack and the stop surface. The first optical stack includes a first optical lens and a partial reflector. The second optical stack includes a second optical lens, a multilayer reflective polarizer and a first quarter wave retarder disposed between the multilayer reflective polarizer and the first optical stack. The multilayer reflective polarizer may be convex toward the image surface along orthogonal first and second axes.

Abstract: A disk cartridge includes a rotatable disk, a cartridge case for housing the disk, and a U-shaped shutter slidably disposed on the front wall of the cartridge case. The cartridge case includes a head access opening formed adjacent the front wall. The access opening is opened and closed by the shutter which is biased closed by a spring. A projection mounted on the shutter contacts and locates the spring between one of the cartridge case side walls and the projection.

Abstract: A disk cartridge includes a rotatable disk, a cartridge case for housing the disk, and a U-shaped shutter slidably disposed on the front wall of the cartridge case. The cartridge case includes upper and lower walls, and a head access opening formed in both walls adjacent the front wall to access the disk. The access opening is opened and closed by the shutter which is biased closed by a spring. A projection mounted on the shutter contacts and locates the spring between one of the cartridge case side walls and the projection. A tab is mounted on the cartridge case and contacts the projection to stop movement of the shutter when the shutter is biased in the closed position.