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.

Integral optical stacks and optical systems including the integral optical stack are described. The integral optical stack may include first and second lenses, a partial reflector, a reflective polarizer curved about two orthogonal axes, and a quarter wave retarder. The reflective polarizer is curved about two orthogonal axes and includes at least one layer that is substantially optically biaxial at at least one first location on the at least one layer away from an optical axis of the optical stack and substantially optically uniaxial at at least one second location away from the optical axis.

Optical systems including a partial reflector, a reflective polarizer, and a quarter wave retarder disposed between the partial reflector and the reflective polarizer are described. The reflective polarizer is curved about two orthogonal axes and has at least one location having a radial distance r1 from an optical axis passing through an apex of the reflective polarizer 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. The optical system is adapted to provide an adjustable dioptric correction.

A distance meter telescope having a telescope lens, a laser receiver, a display unit, a laser emission module, a beam splitter assembly and an eyepiece; the laser receiver receives a laser beam emitted from the laser emission module; the beam splitter assembly has a roof prism, a prism separation board, a first semi-penta prism and a second semi-penta prism; the roof prism has a light input surface, a roof surface, and an output surface; the first semi-penta prism has a first entering and reflective surface for output light, a first input and output surface and a first gluing surface; the second semi-penta prism has a second entering and reflective surface for output light, a second input and output surface and a second gluing surface. The beam splitter assembly makes the light beam passing through the telescope lens, the laser light beam received by the laser receiver and the light beam from the display unit coaxial. Accordingly, product size can be reduced and the prisms can be shared.

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.

A multilayer reflective polarizer convex along orthogonal first and second axes orthogonal to an optical axis passing thorough an apex of the multilayer reflective polarizer is described. The multilayer reflective polarizer has at least one first location having a radial distance r1 from the optical axis and a displacement s1 from a plane perpendicular to the optical axis at the apex, where s1/r1 is in a range of about 0.2 to about 0.8. The multilayer reflective polarizer may have at least one inner layer substantially optically uniaxial at at least one first location away from the apex. For an area of the reflective polarizer defined by s1 and r1, a maximum variation of a transmission axis of the reflective polarizer may be less than about 2 degrees.

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 and a curved multilayer reflective polarizer. A quarter wave retarder is disposed between the multilayer reflective polarizer and the partial reflector. The multilayer reflective polarizer and the partial reflector may be convex toward the image surface along orthogonal first and second axes.

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.

Integral optical stacks and optical systems including the integral optical stack are described. The integral optical stack may include first and second lenses, a partial reflector, a reflective polarizer curved about two orthogonal axes, and a quarter wave retarder. The reflective polarizer is curved about two orthogonal axes and includes at least one layer that is substantially optically biaxial at at least one first location on the at least one layer away from an optical axis of the optical stack and substantially optically uniaxial at at least one second location away from the optical axis.

A multilayer reflective polarizer substantially rotationally symmetric about an optical axis passing thorough an apex of the multilayer reflective polarizer and convex along orthogonal first and second axes orthogonal to the optical axis is described. The multilayer reflective polarizer has at least one first location having a radial distance r1 from the optical axis and a displacement s1 from a plane perpendicular to the optical axis at the apex, where s1/r1 is at least 0.1. The multilayer reflective polarizer may have at least one inner layer substantially optically uniaxial at at least one first location away from the apex. For an area of the reflective polarizer defined by s1 and r1, a maximum variation of a transmission axis of the reflective polarizer may be less than about 2 degrees.