Digital image overlay in image intensified and day sight system

1. An optical system for overlaying a first image of a scene and a second image of the scene, comprising;

a first imaging device comprising a first objective lens providing the first image;

a second imaging device comprising a second objective lens an image display, and collimation optics providing the second image; and

a waveguide comprising:

a first diffraction grating configured to receive the first image;

a second diffraction grating configured to receive the second image; and

a guide portion disposed between the first diffraction grating and the second diffraction grating configured to convey the second image to the first grating,

wherein the first diffraction grating is configured to overlay the first image and the second image.

2. The system of claim 1 wherein the first diffraction grating is configured to overlay the first image and the second image in an effectively transparent mode.

3. The system of claim 1 wherein the first diffraction grating comprises an input coupler to the waveguide and the second diffraction grating comprises an output coupler from the waveguide.

4. The system of claim 3 wherein the first grating and/or the second grating comprises a reflective diffraction grating and/or a transmissive diffraction grating.

5. The system of claim 1 , wherein the first image predominantly comprises a first color and the second image predominantly comprises colors other than the first color.

6. The system of claim 1 wherein the waveguide comprises a planar waveguide.

7. The system of claim 6 wherein the waveguide comprises a substantially rigid structure.

8. The system of claim 1 wherein the first imaging device is selected from the group consisting of an analogue daylight optic and an image intensified night vision device.

9. The system as claimed in 1 , wherein the second imaging device comprises a a thermal camera.

10. The system as claimed in 9 , wherein the second imaging device and the collimation optics operate at one times magnification.

11. A method for combining a first image and a second image with a planar waveguide comprising a first coupler to a first diffraction grating in optical communication with the waveguide and a second coupler to a second diffraction grating in optical communication with the waveguide, comprising the steps of:

receiving a first image of a scene by a first objective lens of a first imaging device:

receiving a second image of the scene by a second objective lens of a second imaging device;

receiving the first image from the first imaging device by a first input coupler to the first diffraction grating;

receiving the second image from the second imaging device by a second input coupler to the second diffraction grating;

conveying the second image from the second diffraction grating to the first diffraction grating via the waveguide; and

overlaying the second image and the first image to produce a combined image.

12. The method of claim 11 , further comprising the step of providing visual access to the combined image via an output coupler to the planer waveguide of the first diffraction grating.

13. The system of claim 1 , wherein a combined magnification of the second image by the second optical device and the collimation optics is substantially the same as a magnification of the first optical device, and the first image of the scene and the second image of the scene appear to have substantially the same size as seen by viewer.