Multi-wavelength Risley prisms for laser bore-sighting
Techniques disclosed herein provide for substantially uniform steering of multiple laser beams of a laser rangefinder having different wavelengths, such as a rangefinder laser beam and a visible laser beam. This can allow a user of the laser rangefinder to use the visible laser beam to bore sight the range-finding laser beam to a weapon onto which the laser rangefinder is mounted. The uniform steering of the multiple laser beams can be done through the utilization of a Risley prism assembly with one or more Risley prisms having a center portion through which one laser beam travels and at least one annulus through which a second laser beam travels.
1. A laser rangefinder comprising:
a first laser configured to emit a first laser beam having a first wavelength;
a second laser configured to emit a second laser beam having a second wavelength smaller than the first wavelength; and
a Risley prism assembly comprising one or more rotatable Risley prisms having a center portion and an annulus, wherein the center portion has a wedge angle greater than a wedge angle of the annulus;
wherein:
the first laser is configured to emit the first laser beam through the center portion of the one or more rotatable Risley prisms; and
the second laser is configured to emit the second laser beam through the annulus of the one or more rotatable Risley prisms.
2. The laser rangefinder of claim 1 , wherein each rotatable Risley prism of the one or more rotatable Risley prisms comprises a respective larger optical wedge coupled with a respective smaller optical wedge.
3. The laser rangefinder of claim 2 , wherein, for each rotatable Risley prism of the one or more rotatable Risley prisms, the respective larger optical wedge is coupled with the smaller optical wedge such that:
the center portion of the respective rotatable Risley prism comprises a portion where the respective smaller optical wedge is coupled with the larger optical wedge, and
the annulus of the respective rotatable Risley prism comprises a portion where the respective larger optical wet overlaps the respective smaller optical wedge.
4. The laser rangefinder of claim 1 , wherein the first wavelength is 633 nm.
5. The laser rangefinder of claim 1 , wherein the second wavelength is 1550 nm.
6. The laser rangefinder of claim 1 , further comprising a third laser configured to emit a third laser beam having a third wavelength smaller than the second wavelength, wherein:
the annulus comprises a first annulus;
the one or more rotatable Risley prisms further comprise a second annulus;
a wedge angle of the second annulus is less than the wedge angle of the first annulus; and
the third laser is configured to emit the third laser beam through the second annulus of the one or more rotatable Risley prisms.
7. The laser rangefinder of claim 1 , further comprising:
a receiver unit configured to detect reflected laser light from the first laser beam and provide output data; and
a processing unit configured to calculate a range based at least in part on the output data from the receiver unit.
8. The laser rangefinder of claim 7 , further comprising an output interface configured to provide an indication of the calculated range.
9. The laser rangefinder of claim 1 , wherein the Risley prism assembly comprises a first pair and a second pair of rotatable Risley prisms, and wherein, for mutually orthogonal X, Y, and Z directions in which the first laser and the second laser are configured to respectively emit the first laser beam and the second laser beam substantially along the Z direction:
the first pair of rotatable Risley prisms are configured to adjust an outgoing angle of the first laser beam and the second laser beam along the X direction when subject to rotational movement; and
the second pair of rotatable Risley prisms are configured to adjust an outgoing angle of the first laser beam and the second laser beam along the Y direction when subject to rotational movement.
10. The laser rangefinder of claim 9 , wherein the rotational movement for the first pair of rotatable Risley prisms or the second pair of rotatable Risley prisms comprises rotating the Risley prisms of the respective pair in opposite directions about an axis along the Z direction.
11. A method for multi-wavelength laser beam steering at a laser rangefinder, the method comprising:
receiving, at a Risley prism assembly of the laser rangefinder, a first laser beam having a first wavelength and a second laser beam having a second wavelength smaller than the first wavelength, wherein:
the Risley prism assembly comprises one or more rotatable Risley prisms having a center portion and an annulus, and
the center portion has a wedge angle greater than a wedge angle of the annulus;
redirecting the first laser beam using the center portion of the one or more rotatable Risley prisms; and
redirecting the second laser beam using the annulus of the one or more rotatable Risley prisms.
12. The method of claim 11 , wherein each rotatable Risley prism of the one or more rotatable Risley prisms comprises a respective larger optical wedge coupled with a respective smaller optical wedge.
13. The method of claim 12 , wherein, for each rotatable Risley prism of the one or more rotatable Risley prisms, the respective larger optical wedge is coupled with the smaller optical wedge such that:
the center portion of the respective rotatable Risley prism comprises a portion where the respective smaller optical wedge is coupled with the larger optical wedge, and
the annulus of the respective rotatable Risley prism comprises a portion where the respective larger optical wet overlaps the respective smaller optical wedge.
14. The method of claim 11 , wherein the first wavelength is 633 nm.
15. The method of claim 11 , wherein the second wavelength is 1550 nm.
16. The method of claim 11 , wherein the annulus comprises a first annulus, the method further comprising:
receiving, at the Risley prism assembly of the laser rangefinder, a third laser configured to emit a third laser beam having a third wavelength smaller than the second wavelength; and
redirecting the second laser beam using a second annulus of the one or more rotatable Risley prisms, wherein a wedge angle of the second annulus is less than the wedge angle of the first annulus.
17. The method of claim 11 , further comprising:
detecting, with a receiver unit of the laser rangefinder, reflected laser light from the first laser beam; and
calculating a range based at least in part on the detecting of the reflected laser light.
18. The method of claim 17 , providing, with an output interface of the laser rangefinder, an indication of the calculated range.
19. An optical assembly for a laser rangefinder, the optical assembly comprising two pairs of rotatable Risley prisms wherein:
for each rotatable Risley prism of each pair of rotatable Risley prisms, the respective rotatable Risley prism has a center portion and an annulus, wherein the center portion has a wedge angle greater than a wedge angle of the annulus; and
the two pairs of rotatable Risley prisms are aligned such that:
center portions of the rotatable Risley prisms are configured to steer light from a first laser beam having a first wavelength in a direction; and
annuluses of the rotatable Risley prisms are configured to steer light from a second laser beam having a second wavelength shorter than the first wavelength in substantially the same direction as the first laser beam.
20. The optical assembly of claim 19 , wherein for mutually orthogonal X, Y, and Z directions in which the optical assembly is configured to receive the first laser beam and the second laser beam traveling in a direction substantially along the Z direction:
a first pair of the two pairs of rotatable Risley prisms is configured to adjust an outgoing angle of the first laser beam and the second laser beam along the X direction when subjected to a rotational movement; and
a second pair of the two pairs of rotatable Risley prisms is configured to adjust an outgoing angle of the first laser beam and the second laser beam along the Y direction when subjected to a rotational movement.