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EP-4348337-B1 - AN OPTICAL WAVEGUIDE ARRANGEMENT FOR REDUCING INTERFERENCE PATTERNS

EP4348337B1EP 4348337 B1EP4348337 B1EP 4348337B1EP-4348337-B1

Inventors

  • BLOMSTEDT, Kasimir

Dates

Publication Date
20260513
Application Date
20220523

Claims (12)

  1. An optical waveguide arrangement comprising: - a light source arranged to transmit a light signal to at least one optical waveguide of the optical waveguide arrangement; - the at least one optical waveguide, wherein the at least one optical waveguide is arranged to receive the light signal from the light source and to convey the light signal to a human eye, to generate a waveguide-based display; and - at least one processor configured to control the light source, wherein the at least one processor is configured to cause shaping of a spectrum of the light signal during a period of time, said period of time corresponding to a persistence time of vision of the human eye, wherein the at least one processor is further configured to cause shaping of a spectrum of the light signal between a first wavelength and a second wavelength during said period of time and said shaping of the spectrum comprises sweeping a distinct spectral characteristic of the light signal during said period of time; and wherein the distinct spectral characteristic of the light signal is swept continuously during said period of time.
  2. An optical waveguide arrangement according to claim 1, wherein the distinct spectral characteristic of the light signal is swept uniformly during said period of time.
  3. An optical waveguide arrangement according to any of the preceding claims, wherein the distinct spectral characteristic of the light signal is swept by about 2 nanometres during said period of time.
  4. An optical waveguide arrangement according to any of the preceding claims, wherein said shaping of the spectrum comprises changing an amplitude of the light signal as a function of a wavelength such that lower amplitudes are used at end points of a sweeping wavelength range compared to a highest amplitude in the sweeping wavelength range.
  5. An optical waveguide arrangement according to any of the preceding claims, wherein said shaping of the spectrum comprises changing a spectral shape of the light signal during said period of time to achieve a smooth spectral profile.
  6. An optical waveguide arrangement according to any of the preceding claims, wherein said shaping of the spectrum comprises changing an intensity of the light signal during said period of time to achieve a smooth spectral profile.
  7. An optical waveguide arrangement according to any of the preceding claims, wherein the light source is a laser source and the light signal is a laser signal.
  8. An optical waveguide arrangement according to any of the preceding claims, wherein said period of time is about tens of milliseconds corresponding to the persistence time of vision of the human eye, preferably 5 - 200 milliseconds, like 20 milliseconds.
  9. An optical waveguide arrangement according to any of the preceding claims, wherein the at least one processor is configured to cause said shaping of the spectrum of the light signal during said period of time to shorten an effective coherence length of the light signal.
  10. A head-mounted display or a head-up display comprising an optical waveguide arrangement according to any of the preceding claims.
  11. A method for an optical waveguide arrangement, comprising - transmitting by a light source a light signal to at least one optical waveguide of the optical waveguide arrangement; - receiving by the at least one optical waveguide the light signal from the light source and conveying the light signal to a human eye, to generate a waveguide-based display; and - controlling the light source by at least one processor to cause shaping of a spectrum of the light signal during a period of time, said period of time corresponding to a persistence time of vision of the human eye; and - causing, by the at least one processor, shaping of a spectrum of the light signal between a first wavelength and a second wavelength during said period of time, wherein said shaping of the spectrum comprises sweeping a distinct spectral characteristic of the light signal during said period of time; and wherein sweeping the distinct spectral characteristic of the light signal happens continuously during said period of time.
  12. A computer program comprising instructions which, when the program is executed by an apparatus, cause the apparatus to perform a method according to claim 11.

Description

FIELD Embodiments of the present invention relate in general to an optical waveguide arrangement and more specifically to an optical waveguide arrangement for reducing interference patterns. BACKGROUND Head-Mounted Displays, HMDs, and Head-Up Displays, HUDs, can be implemented using optical waveguide technology, as for example described in documents US 2020/373734 A1, US 2019/179078 A1 and US 2019/011722 A1. Optical waveguides, such as diffractive waveguides, may be used with light sources having narrow spectral bandwidth, e.g., lasers and optically filtered Light-Emitting Diodes, LEDs. Such waveguides typically suffer from interference patterns visible in the virtual image though. These interference patterns may be cylindrically symmetric for example, such as Newton rings. The interference patterns are an undesired effect since those weaken the quality of the image produced by the display. There is therefore a need to provide an optical waveguide arrangement for reducing interference patterns. SUMMARY OF THE INVENTION According to some aspects, there is provided the subject-matter of the independent claims. Some embodiments are defined in the dependent claims. According to a first aspect of the present invention, there is provided an optical waveguide arrangement comprising a light source arranged to transmit a light signal to at least one optical waveguide of the optical waveguide arrangement, the at least one optical waveguide, wherein the at least one optical waveguide is arranged to receive the light signal from the light source and to convey the light signal to a human eye, to generate a waveguide-based display and at least one processor configured to control the light source, wherein the at least one processor is configured to cause shaping of a spectrum of the light signal during a period of time, said period of time corresponding to a persistence time of vision of the human eye; and wherein the distinct spectral characteristic of the light signal is swept continuously during the period of time. According to a second aspect of the present invention, there is provided a head-mounted display or a head-up display comprising the optical waveguide arrangement of the first aspect. According to a third aspect of the present invention, there is provided a method comprising transmitting by a light source a light signal to at least one optical waveguide of the optical waveguide arrangement, receiving by the at least one optical waveguide the light signal from the light source and conveying the light signal to a human eye, to generate a waveguide-based display and controlling the light source by at least one processor to cause shaping of a spectrum of the light signal during a period of time, said period of time corresponding to a persistence time of vision of the human eye; and wherein sweeping the distinct spectral characteristic of the light signal happens continuously during the period of time. According to a fourth aspect of the present invention, there is provided a non-transitory computer readable medium having stored thereon a set of computer readable instructions that, when executed by at least one processor, cause an apparatus to at least perform the method. According to a fifth aspect of the present invention, there is provided a computer program comprising instructions which, when the program is executed by an apparatus, cause the apparatus to perform the method. BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 illustrates an example system in accordance with at least some embodiments of the present invention;FIGURE 2 illustrates an exemplary operation of a waveguide in accordance with at least some embodiments of the present invention;FIGURE 3 illustrates an example apparatus capable of supporting at least some embodiments of the present invention;FIGURE 4 illustrates a first example of shaping of a spectrum of a light signal in accordance with at least some embodiments of the present invention;FIGURE 5 illustrates a second example of shaping of a spectrum in accordance with at least some embodiments of the present invention; andFIGURE 6 is a flow graph of a method in accordance with at least some embodiments of the present invention. EMBODIMENTS Embodiments of the present invention relate to an optical waveguide arrangement for reducing interference patterns, such as Newton rings. In accordance with at least some embodiments of the present invention, interference patterns may be reduced by sweeping a distinct spectral characteristic, such as a distinct spectral peak, of a light signal during a period of time, wherein said period of time corresponds to the persistence time of vision of the human eye, which may also be referred to as an averaging/integration time of the human eye. The human eye may be considered as a detector and thus, the persistence time of vision of the human eye equals the coherence time of the corresponding detector. It should be noted that in embodiments of the present invention co