Patent ID: 8937771
Filing Date: 2015-01-20
Classification: G02B

Abstract:
1. An apparatus, comprising: a three piece prism eyepiece comprising a first prism, a second prism, and a correcting plate; the first prism having a first surface that is positioned to receive light from outside of the three piece prism eyepiece, the first prism having a second surface and a third surface, wherein at least one of the surfaces of the first prism is a free form surface; the second prism having a first surface proximate to the second surface of the first prism and having a second surface, the second surface of the second prism being flat, there being an air gap between the first surface of the second prism and the second surface of the first prism; and the correcting plate having a first surface proximate the third surface of the first prism, the correcting plate having a second surface that is flat, wherein the second surface of the second prism is in a first plane, wherein the second surface of the correcting plate is in a second plane that is parallel to the first plane, wherein the second surface of the correcting plate being configured to receive light from outside of the three piece prism eyepiece; the first prism, the second prism, and the correcting plate are configured such that light that enters the first surface of the first prism from outside of the three piece prism eyepiece is emitted from the second surface of the second prism externally of the three piece prism eyepiece; the first prism, the second prism, and the correcting plate are configured such that light that enters from outside of the three piece prism eyepiece into the second surface of the correcting plate is emitted from the second surface of the second prism externally from the three piece prism eyepiece.