Multi-wavelength VCSEL array to reduce speckle
View Patent ↗Embodiments of the invention describe an illuminator having a light source to originate an illumination beam, wherein the light source further comprises a set of vertical-cavity surface emitting lasers (VCSELs), including a first VCSEL having a first laser emission wavelength, and a second VCSEL having a second laser emission wavelength different than the first laser emission wavelength. Thus, by varying laser emission wavelengths of VCSELs in a VCSEL array, embodiments of the invention produce low-contrast speckle, and do not limit the imaging capabilities of the host illumination system. In some embodiments of the invention, vertical external cavity surface emitting lasers (VECSELs) are utilized to produce the above described varying laser emission wavelengths.
1. An apparatus comprising:
an illuminator having a light source configured to originate an illumination beam, wherein the light source comprises a single-chip array of at least four vertical-cavity surface emitting lasers (VCSELs) sharing common electrodes and configured to produce four or more different emission wavelengths to form the illumination beam, including a first VCSEL having a first laser emission wavelength of the four or more different emission wavelengths, and a second VCSEL having a second laser emission wavelength of the four or more different emission wavelengths different than the first laser emission wavelength; and
an illumination path to direct the illumination beam towards an object, wherein the four or more different emission wavelengths are configured to produce a full-width-half-maximum of between approximately 3 nm and 20 nm for the illumination beam.
2. The apparatus of claim 1 , wherein the first VCSEL includes a first laser cavity length and the second VCSEL includes a second laser cavity length different than the first cavity length.
3. The apparatus of claim 1 , wherein the first VCSEL includes a first set of mirrors configured to define a first resonant cavity, and the second VCSEL includes a second set of mirrors configured to define a second resonant cavity different than the first resonant cavity.
4. The apparatus of claim 3 , wherein the first and second VCSELs each comprise a vertical external cavity surface emitting laser (VECSEL).
5. The apparatus of claim 4 , wherein the first and second set of mirrors include mirrors forming an external cavity for both the first and second VECSELs and formed on a single substrate.
6. The apparatus of claim 1 , further comprising a distributed Bragg reflector (DBR), wherein the first VCSEL includes a first effective optical path length formed by the DBR, and the second VCSEL includes a second optical path length formed by the DBR and different than the first optical path length.
7. The apparatus of claim 1 , wherein the at least four VCSELs are arranged in a two dimensional array having a spectral gradient from relatively short to relatively long wavelengths varying spatially from one side of the array to another, radially outward from a center of the array, randomly across the array, and/or within sub-sections of the array.
8. The apparatus of claim 1 , wherein the first VCSEL includes a first emitter diameter and the second VCSEL includes a second emitter diameter different than the first emitter diameter.
9. The apparatus of claim 1 , wherein active cavity regions of the first VCSEL and the second VCSEL comprise different refractive indexes.
10. A system comprising:
a power supply;
a power controller;
a light source configured to generate an illumination beam based on power received from the power source and regulated by the power controller, wherein the light source further comprises a single-chip array of at least four vertical-cavity surface emitting lasers (VCSELs) sharing common electrodes and configured to produce four or more different emission wavelengths to form the illumination beam, including a first VCSEL having a first laser emission wavelength of the four or more different emission wavelengths, and a second VCSEL having a second laser emission wavelength of the four or more different emission wavelengths different than the first laser emission wavelength;
an illumination path to direct the illumination beam towards an object; and
a light receiver including one or more photosensitive elements, and imaging optics configured to receive light from the illumination beam reflected from a surface of the object and to image the received light onto the one or more photosensitive elements, wherein the four or more different emission wavelengths are configured to produce a FWHM of between approximately 3 nm and 20 nm for the illumination beam and to reduce a peak to peak speckle noise intensity, as measured by the light receiver, by more than fifty percent as compared to a single emission wavelength illumination beam.
11. The system of claim 10 , wherein the first VCSEL includes a first laser cavity length and the second VCSEL includes a second laser cavity length different than the first cavity length.
12. The system of claim 10 , wherein the first VCSEL includes a first set of mirrors configured to define a first resonant cavity, and the second VCSEL includes a second set of mirrors configured to define a second resonant cavity different than the first resonant cavity.
13. The system of claim 12 , wherein the first and second VCSELs each comprise a vertical external cavity surface emitting laser (VECSEL).
14. The system of claim 13 , wherein the first and second set of mirrors include mirrors forming an external cavity for both the first and second VECSELs and formed on a single substrate.
15. The system of claim 10 , the light source further comprising:
a distributed Bragg reflector (DBR), wherein the first VCSEL includes a first effective optical path length formed by the DBR, and the second VCSEL includes a second optical path length formed by the DBR and different than the first optical path length.
16. The system of claim 10 , wherein the at least four VCSELs are arranged in a two dimensional array having a spectral gradient from relatively short to relatively long wavelengths varying spatially from one side of the array to another, radially outward from a center of the array, randomly across the array, and/or within sub-sections of the array.
17. The system of claim 10 , wherein the first VCSEL includes a first emitter diameter and the second VCSEL includes a second emitter diameter different than the first emitted diameter.
18. The system of claim 10 , wherein active cavity regions of the first VCSEL and the second VCSEL comprise different refractive indexes.
19. The system of claim 10 , wherein the light receiver is sensitive to the near-infrared and/or short-wave infrared spectrum.
20. The system of claim 10 , wherein the at least four VCSELs are arranged in a two dimensional array having a circular, square, or pentagonal shape.