Optical apparatus and method for expanding an exit pupil

A method, comprising:

• coupling a first component of a light beam into an exit pupil expander, the first component of the light beam having a wavelength within a first spectral range;
• coupling a second component of the light beam into the exit pupil expander, the second component of the light beam having a wavelength within a second spectral range, different to the first spectral range;
• expanding the first component of the light beam in a first dimension to create an expanded first component;
• expanding, in a second dimension, the expanded first component to create a further expanded first component;
• expanding the second component of the light beam in the second dimension to create an expanded second component;
• expanding, in the first dimension, the expanded second component to create a further expanded second component;
• outputting the further expanded first component of the light beam from the exit pupil expander;
• and
• outputting the further expanded second component from the exit pupil expander collinearly with the further expanded first component;
• wherein the expanded first component of the light beam and the expanded second component of the light beam each comprise light rays that are substantially parallel to each other and are divergent;
• wherein the further expanded first component of the light beam is outputted from the exit pupil expander at a point that is spaced apart from and aligned with a point at which the further expanded second component of the light beam is outputted;
• wherein grating lines of a fifth optical arrangement used to expand the second component of the light beam in the second dimension are angled with respect to grating lines of a second optical arrangement used to couple the second component of the light beam into the exit pupil expander and grating lines of a sixth optical arrangement used to expand, in the first dimension, the expanded second component;
• and
• wherein grating lines of a third optical arrangement used to expand the first component of the light beam in the first dimension are angled with respect to grating lines of a first optical arrangement used to couple the first component of the light beam into the exit pupil expander and grating lines of a fourth optical arrangement used to expand, in the second dimension, the expanded first component.

An apparatus, comprising:

• means for coupling a first component of a light beam into the apparatus, the first component of the light beam having a wavelength within a first spectral range;
• means for coupling a second component of the light beam into the apparatus, the second component of the light beam having a wavelength within a second spectral range, different to the first spectral range;
• means for expanding the first component of the light beam in a first dimension to create an expanded first component;
• means for expanding, in a second dimension, the expanded first component to create a further expanded first component, and configured to output the further expanded first component of the light beam from the apparatus;
• means for expanding the second component of the light beam in the second dimension to create an expanded second component;
• and
• means for expanding, in the first dimension, the expanded second component to create a further expanded second component, and configured to output the further expanded second component from the apparatus collinear with the further expanded first component of the light beam from the apparatus;
• wherein the expanded first component of the light beam and the expanded second component of the light beam each comprise light rays that are substantially parallel to each other and are divergent;
• wherein the means for expanding the first component of the light beam is spaced apart from and aligned with the means for expanding the second component of the light beam;
• wherein the means for expanding the second component is configured to diffract the light beam having a wavelength in the second spectral range and not the light beam having a wavelength in the first spectral range;
• wherein grating lines of the means for expanding the second component of the light beam in the second dimension are angled with respect to grating lines of the means for coupling a second component of the light beam into the apparatus and grating lines of the means for expanding, in the first dimension, the expanded second component;
• and
• wherein grating lines of the means for expanding the first component of the light beam in a first dimension are angled with respect to grating lines of the means for coupling a first component of a light beam into the apparatus and grating lines of the means for expanding, in a second dimension, the expanded first component.