Systems and methods for a dual axis resonant scanning mirror
Described herein are systems and methods that implement a dual axis resonant scanning mirror to support a sensor system such as a LIDAR system. The scanning mirror may comprise: 1) a small dual axis mirror, in which each axis is moving by similar electromagnetic mechanisms can generate crosstalk between each of these electromagnetic mechanisms causing perturbations in the motion; 2) a primary axis that may need to be driven independently of the motion of a secondary axis and vice versa; 3) an optical position sensor; 4) a scanning mirror assembly that may be mounted to a scanner base via the secondary axis. The scanning mirror assembly may comprise resonant spring, resonant spring assembly, the rocking chair (with electromagnetic drive coils), the scanner base with a set of two secondary axis propulsion magnets, the mirror with a spacer and primary axis propulsion magnets, and the optical sense board.
1. A system comprising:
a spring assembly;
a primary axis sub-assembly comprising a primary axis propulsion magnet and a primary electromagnetic drive coil positioned along a first plane;
a secondary axis sub-assembly comprising a secondary axis propulsion magnet and a secondary electromagnetic drive coil positioned along a second plane, the second plane different than the first plane;
a mirror with a spacer; and
a position sense assembly, wherein the position sense assembly comprises a dye impregnated optical fiber, a positive sensitive detector, a UV/IR filter, and two UV LEDs with two corresponding prisms.
2. The system of claim 1 , wherein when dye in the dye impregnated optical fiber fluoresces due to its illumination from the two UV LEDs, visible fluoresced light is guided down the dye impregnated optical fiber to the positive sensitive detector, which determines mirror positioning.
3. The system of claim 2 , wherein the positioning of the mirror is indicated by a light spot on an active surface of the positive sensitive detector.
4. The system of claim 1 , further comprising: i) a primary axis that resonates at a frequency in an horizontal axis with an primary optical deflection, and ii) a secondary axis that is selectively controlled via a servomechanism to operate in a vertical axis with a secondary optical deflection.
5. The system of claim 4 , wherein the primary axis is driven independent of motion of the secondary axis, and vice-versa, and wherein primary axis motion involves movement of components that are positioned on the secondary axis.
6. The system of claim 4 , wherein i) the primary axis has a maximum primary optical deflection of +/−30 degrees, and ii) the secondary axis has a maximum secondary optical deflection of +/−5 degrees.
7. The system of claim 1 , wherein the spring assembly comprises a resonant spring sandwiched between two frames that create tension across a primary axis upon brazing the spring assembly.
8. The system of claim 7 , wherein the two frames comprise a coefficient of thermal expansion delta tensioners.
9. The system of claim 1 , wherein the spring assembly and mirror are suspended by a secondary axis of the spring assembly.
10. The system of claim 1 , wherein the mirror sits on the spacer, which sits directly on a primary axis of the spring assembly, and wherein the primary axis propulsion magnet sits underneath the mirror.
11. The system of claim 1 , wherein magnetic fields of i) the primary electromagnetic drive coil, and ii) the secondary electromagnetic drive coils, are orthogonal to each other, regardless of motion of the system.
12. The system of claim 11 , wherein the primary electromagnetic drive coil is disposed under a plane that a spring sits on, and wherein the magnetic field of the primary electromagnetic drive coil interacts with the primary axis propulsion magnet placed under the mirror, causing optical deflection.
13. An optical position sensor comprises a dye impregnated optical fiber, a positive sensitive detector, a UV/IR filter, two or more UV LEDs with two or more corresponding prisms.
14. The optical position sensor of claim 13 , wherein when dye in the dye impregnated optical fiber fluoresces due to its illumination from the two or more UV LEDs, visible fluoresced light is guided down the dye impregnated optical fiber to the positive sensitive detector, which measures a position of a light spot on an active surface of the positive sensitive detector.
15. The optical position sensor of claim 14 , wherein the light spot on the active surface of the positive sensitive detector determines a position of a mirror.
16. The optical position sensor of claim 13 , wherein the dye impregnated optical fiber is illuminated via two UV LEDs, and UV light is guided to the dye impregnated optical fiber via prism.