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EP-3916468-B1 - OPTICAL APPARATUSES AND METHODS

EP3916468B1EP 3916468 B1EP3916468 B1EP 3916468B1EP-3916468-B1

Inventors

  • JÄRVENPÄÄ, Toni Johan

Dates

Publication Date
20260506
Application Date
20200529

Claims (15)

  1. An apparatus (10) comprising: a first substrate (12) comprising a first incoupling diffractive optical element (14) configured to couple light into the first substrate (12), and a first outcoupling diffractive optical element (18) configured to output, from the first substrate (12), light that has been coupled into the first substrate (12); and a second substrate (20) comprising a second incoupling diffractive optical element (22) configured to couple light into the second substrate (20), and a second outcoupling diffractive optical element (24) configured to output, from the second substrate (20), light that has been coupled into the second substrate (20); wherein the diffractive features of the first and second incoupling diffractive optical elements (14, 22) are substantially inverse of each other and the diffractive features of the first and second outcoupling diffractive optical elements (18, 24) are substantially inverse of each other, and wherein the first and second substrates are stacked and at least a portion of the first and second substrates overlap.
  2. An apparatus (10) as claimed in claim 1, wherein the diffractive optical elements are sealed within the stack.
  3. An apparatus (10) as claimed in claim 1, or 2, wherein the second incoupling diffractive optical element (22) is configured to couple into the second substrate (20) light that has passed through the first incoupling diffractive optical element (14) without being coupled into the first substrate (12).
  4. An apparatus (10) as claimed in claim 3, comprising polarization rotation means and/or wavelength dependent filtering means between the first and second incoupling diffractive optical elements (14, 22).
  5. An apparatus (10) as claimed in any of claim 1 to 4, comprising a third substrate, the third substrate comprising a third incoupling diffractive optical element configured to couple light into the third substrate, and a third outcoupling diffractive optical element configured to output, from the third substrate, light that has been coupled into the third substrate, wherein: the third incoupling diffractive optical element is configured to couple into the third substrate light that has passed through the first incoupling diffractive optical element (14) without being coupled into the first substrate (12); and the diffractive optical elements of the first and second substrates are configured to operate in a first spectral range and the diffractive optical elements of the third substrate are configured to operate in a second, at least partially different, spectral range.
  6. An apparatus (10) as claimed in claim 5, comprising a fourth substrate, the fourth substrate comprising a fourth incoupling diffractive optical element configured to couple light into the fourth substrate, and a fourth outcoupling diffractive optical element configured to output, from the fourth substrate, light that has been coupled into the fourth substrate, wherein: the fourth incoupling diffractive optical element is configured to couple into the fourth substrate light that has passed through the first incoupling diffractive optical element (14) without being coupled into the first substrate (12); and the diffractive features of the third and fourth incoupling diffractive optical elements are substantially inverse of each other and the diffractive features of the third and fourth outcoupling diffractive optical elements are substantially inverse of each other.
  7. An apparatus (10) as claimed in claim 5 or 6, wherein the first, second, third and fourth substrates are stacked and at least a portion of the first, second, third and fourth substrates overlap.
  8. An apparatus (10) as claimed in any preceding claim, wherein the first substrate (12) comprises a first intermediate diffractive optical element configured to expand in a first and/or second dimension an exit pupil of light coupled into the first substrate (12); and wherein the second substrate (20) comprises a second intermediate diffractive optical element configured to expand in the first and/or second dimension an exit pupil of light coupled into the second substrate (20), wherein the first and second dimensions are different and wherein the first and second intermediate diffractive optical elements are substantially inverse of each other.
  9. An apparatus (10) as claimed in any preceding claim, wherein at least one of: substrate thickness, substrate shape, substrate materials, diffractive optical element materials and coatings differ between the first and second substrate.
  10. An apparatus (10) as claimed in any preceding claim, wherein the outcoupling diffractive optical elements are configured to expand an exit pupil of light coupled into the respective substrates.
  11. A system comprising an apparatus (10) as claimed in any preceding claim, a light source configured to provide light to at least the first incoupling diffractive optical element (14), wherein the apparatus (10) is configured to expand the exit pupil of the light source.
  12. An electronic device comprising a system as claimed in claim 11, and at least one user input device.
  13. A method comprising: providing a first substrate (12) comprising a first incoupling diffractive optical element (14) configured to couple light into the first substrate (12), and a first outcoupling diffractive optical element (18) configured to output, from the first substrate (12), light that has been coupled into the first substrate (12); and providing a second substrate (20) comprising a second incoupling diffractive optical element (22) configured to couple light into the second substrate (20), and a second outcoupling diffractive optical element (24) configured to output, from the second substrate (20), light that has been coupled into the second substrate (20); wherein the diffractive features of the first and second incoupling diffractive optical elements (14, 22) are substantially inverse of each other and the diffractive features of the first and second outcoupling diffractive optical elements (18, 24) are substantially inverse of each other, and wherein the first and second substrates are stacked and at least a portion of the first and second substrates overlap.
  14. A method as claimed in claim 13, wherein providing first substrate (12) comprises using, directly or indirectly, a master mould; and wherein providing the second substrate (20) comprises using, directly or indirectly, the master mould.
  15. A method as claimed in claim 13, or 14, wherein the diffractive optical elements are sealed within the stack.

Description

TECHNOLOGICAL FIELD Embodiments of the present disclosure relate to optical apparatuses and methods. Some relate to optical apparatuses and methods for expanding an exit pupil. BACKGROUND Optical apparatuses, such as exit pupil expanders, are often used in augmented reality and heads-up display systems. It some circumstances it can be beneficial to improve the efficiency and/or uniformity of such optical apparatuses. WO2006/064325 (D1) relates to an exit pupil extender wherein, according to D1, the relative amount of different color components in the exit beam is more consistent with that of the input beam. According to D1, in order to compensate for the uneven amount in the diffracted color components in the exit beam, the exit pupil extender, comprises a plurality of layers having additional diffraction gratings so as to increase the amount of diffracted light for those color components with a lower amount. Additionally, according to D1, color filters disposed between layers to reduce the diffracted light components with a higher amount. WO2018/154576 (D2) relates to an optical assembly for optical aperture expansion that combines facet reflective technology with diffractive technology. According to D2, at least two diffractive components having opposite optical power (matching) are used, so that chromatic dispersion introduced by the first diffractive component will then be cancelled by the second diffractive component. According to D2, the two diffractive components are used in combination with a reflective optical component to achieve more efficient aperture expansion (for near eye display), reducing distortions and noise, while also reducing design constraints on the system and individual components, as compared to conventional techniques. According to D2, the assembly eliminates and/or reduces the need for polarization management, while enabling wider field of view. In addition, according to D2, embodiments can have reduced nonuniformity, as compared to conventional single technology implementations, since the distortion patterns of the two technologies do not correlate. WO2015/113718 (D3) relates to a plasmonic optical security component comprising two layers made of transparent dielectric material and a metal layer arranged between said transparent dielectric material layers in order to form two dielectric-metal interfaces. According to D3, the metal layer is structured to form, on a first coupling region, a first periodic, two-dimensional coupling array which is capable of coupling surface plasmon modes, which are supported by said dielectric-metal interfaces, to an incident light ray, the first coupling array having a profile which does not have point symmetry in any of the directions thereof, and, on a second coupling region, a second periodic, two-dimensional coupling array which is capable of coupling surface plasmon modes, which are supported by said dielectric-metal interfaces, to an incident light ray, the second coupling array having a profile which does not have point symmetry in any of the directions thereof and is different from that of the first coupling array. BRIEF SUMMARY The present invention provides an apparatus and method as claimed in the appended claims. According to the claimed invention, the first and second substrates are stacked and at least a portion of the first and second substrates overlap. In examples, the diffractive optical elements are sealed within the stack. In examples, the second incoupling diffractive optical element is configured to couple into the second substrate light that has passed through the first incoupling diffractive optical element without being coupled into the first substrate. In examples, the apparatus comprises polarization rotation means and/or wavelength dependent filtering means between the first and second incoupling diffractive optical elements. In examples, the apparatus comprises a third substrate, the third substrate comprising a third incoupling diffractive optical element configured to couple light into the third substrate, and a third outcoupling diffractive optical element configured to output, from the third substrate, light that has been coupled into the third substrate, wherein: the third incoupling diffractive optical element is configured to couple into the third substrate light that has passed through the first incoupling diffractive optical element without being coupled into the first substrate; andthe diffractive optical elements of the first and second substrates are configured to operate in a first spectral range and the diffractive optical elements of the third substrate are configured to operate in a second, at least partially different, spectral range. In examples, the apparatus comprises a fourth substrate, the fourth substrate comprising a fourth incoupling diffractive optical element configured to couple light into the fourth substrate, and a fourth outcoupling diffractive optical element configured to output, from t