Apparatus for optical see-through head mounted display with mutual occlusion and opaqueness control

A optical see-through head-mounted display comprising:

• a. a microdisplay for generating an image to be viewed by a user, the microdisplay having a virtual view path associated therewith;
• b. an objective optics, facing the external scene, positioned to receive the incoming light from the external scene and to focus the incoming light, where the objective optics is a one-reflection freeform prism comprising three optical freeform surfaces:
• refractive surface S4, reflective surface S5 and refractive surface S6;
• c. a transmission-type spatial light modulator upon which the objective optics focuses the incoming light, the spatial light modulator having a see-through path associated therewith and capable of modifying light from an external scene to block portions of a see-through view that are to be occluded to combine the see-through path with the virtual view path such that the opaqueness of the see-through path can be modulated and the virtual view occludes parts of the see-through view and vice versa;
• d. a beamsplitter positioned to merge a digitally generated virtual image from a microdisplay and a modulated see-through image of an external scene passing from a. spatial light modulator, producing a. combined image;
• e. an eyepiece positioned to magnify the combined image, where the eyepiece is a two-reflection freeform prism comprising three optical freeform surfaces:
• refractive surface S1, reflective surface S2, reflective surface S1′ and refractive surface S3;
• f. an exit pupil facing the eyepiece, the light passing from the eyepiece through the exit pupil whereupon the user observes the combined view of the virtual and see-through views in which the virtual view occludes portions of the see-through view;
• g. a roof mirror positioned to reflect light from the objective optics into the spatial light modulator, wherein the roof mirror adds an additional reflection to the see-through path to revert the see-through view so as to maintain parity between the external scene and the see-through view presented to the viewer.