APPARATUS FOR OPTICAL SEE-THROUGH HEAD MOUNTED DISPLAY WITH MUTUAL OCCLUSION AND OPAQUENESS CONTROL

1 . 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 S 4 , reflective surface S 5 and refractive surface S 6 ;

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 S 1 , reflective surface S 2 , reflective surface S 1 ′ and refractive surface S 3 ;

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.

2 . The display of claim 1 , wherein the objective optics is disposed upon a. front layer of the display.

3 . The display of claim 2 , wherein the mirror is disposed upon a front layer of the display wherein the spatial light modulator is disposed on a back layer of the display, at or near an intermediate image plane of the see-through path, between the mirror and the beam splitter.

4 . The display of claim 3 , wherein the microdisplay is disposed on the back layer of the display, facing a different side of the beam splitter.

5 . The display of claim 4 , wherein the beam splitter is disposed such that the see-through path is merged with the virtual view path and the light from the merged path is directed to the eyepiece.

6 . The display of claim 5 , wherein the eyepiece is disposed upon the back layer of the display.

7 . The display of claim 1 incoming light from the external scene enters the objective optics through the refractive surface S 4 , then is reflected by the reflective surface S 5 and exits the objective optics through the refractive surface S 6 and is folded by the mirror toward the back layer and forms an intermediate image at its focal plane on the spatial light modulator, whereupon the spatial light modulator modulates the light in the see-through path to occlude portions of the see-through view, whereupon the spatial light modulator transmits the modulated light into the beam splitter, whereupon the light from the microdisplay enters the beam splitter, whereupon the beamsplitter merges the modulated light M the see-through path with the light in the virtual view path and folds toward the eyepiece for viewing, whereupon the light from the beam splitter enters the eyepiece through the refractive surface S 3 , then is consecutively reflected by the reflective surfaces S 1 ′ and S 2 , and exits the eyepiece through the refractive surface S 1 and reaches exit pupil, where the viewer's eye is aligned to see a combined view of a virtual view and a modulated sec-through view.

8 . The system of claim 1 , where the refractive surface S 1 and the reflective surface S 1 ′ are