See-through near-to-eye display with eye prescription

An optical apparatus for a head mounted display, comprising:

• an image source coupled to emit image light;
• an optical combiner having an eye-ward side and an external scene side and including a partially reflective diffraction grating that is at least partially reflective to the image light incident through the eye-ward side of the optical combiner and at least partially transmissive to external scene light incident through the external scene side of the optical combiner;
• an image lens disposed in an optical path of the image light between the image source and the eye-ward side of the optical combiner to apply a first corrective prescription to the image light emitted from the image source;
• and
• an external scene lens disposed over the external scene side of the optical combiner to apply a second corrective prescription to the external scene light that passes through the optical combiner,
• wherein the optical combiner combines the image light with the scene light to form a combined image that is corrected according to the first and second corrective prescriptions and propagates along a common viewing path extending along an eye-ward direction from the eye-ward side.