Iris imaging system using circular deformable mirror mounted by its circumference
View Patent ↗A rapid iris acquisition, tracking, and imaging system can be used at longer standoff distances and over larger capture volumes, without the active cooperation of subjects. Eye reflections from the subjects' eyes are used to steer a high resolution camera to the eyes in order to capture images of the irises. A circular deformable minor driven by one or more annular forces can be used to focus the camera. A circular mirror substrate is mounted by its circumference onto a minor mount and driven by an annular drive element that contacts the minor substrate along a ring. If the annular drive element has a certain diameter relative to the circumference of the mirror substrate, the mirror substrate will be deformed in the shape of a sphere.
1. An iris imaging system comprising an imaging subsystem, the imaging subsystem comprising:
a camera for capturing images of irises with sufficient resolution for biometric identification;
a light source for producing light to illuminate eyes; and
a fine tracking system for steering the camera to eyes, based on an eye reflection of the light illuminating the eyes, the fine tracking system including:
a deformable mirror for both steering the camera to the eyes and adjusting a wavefront of the eye reflected light, the deformable mirror including a circular mirror substrate attached by a flexible joint around which the mirror substrate can tilt to an annular mechanical drive element, the circular mirror substrate mounted on a circumferential mirror mount, the circular mirror substrate having a reflective front surface and a back surface, the circumferential mirror mount substantially preventing translation of the mirror substrate relative to the mirror mount but permitting the mirror substrate to tilt locally relative to the mirror mount, and the annular mechanical drive element applying an annular force to the back surface of the mirror substrate;
a wavefront sensor for sensing the wavefront of the eye reflected light; and
a controller coupled between the deformable mirror and the wavefront sensor, for adjusting the deformable mirror based on the sensed wavefront.
2. The iris imaging system of claim 1 , wherein the camera captures images of irises with a resolution of 200 microns or better.
3. The iris imaging system of claim 1 , wherein the imaging subsystem can cover a capture volume of at least 1 cubic meter.
4. The iris imaging system of claim 1 , wherein the camera can capture iris images at a standoff of at least 5 m.
5. A deformable mirror, comprising:
a circular mirror substrate mounted on a circumferential mirror mount, the circular mirror substrate having a reflective front surface and a back surface, the circumferential mirror mount substantially preventing translation of the mirror substrate relative to the mirror mount but permitting the mirror substrate to tilt locally relative to the mirror mount; and
an annular mechanical drive element that applies an annular force to the back surface of the mirror substrate, the annular mechanical drive element being attached to the back surface of the mirror substrate by a first flexible joint around which the mirror substrate can tilt when the annular force is applied.
6. The deformable mirror of claim 5 , wherein the circumferential mirror mount includes a first ring, the first ring having a rounded top edge fastened to the back surface of the mirror substrate by a second flexible joint around which the mirror substrate can tilt when the annular force is applied to the mirror substrate.
7. The deformable mirror of claim 6 , wherein the second flexible joint is an adhesive joint.
8. The deformable mirror of claim 7 , wherein the second flexible joint is formed from a soft RTD glue.
9. The deformable mirror of claim 6 , further comprising a ring clamp that secures the first ring in place.
10. The deformable mirror of claim 5 , wherein the annular mechanical drive element includes a second ring, the second ring having a rounded top edge fastened to the back surface of the mirror substrate by the first flexible joint.
11. The deformable mirror of claim 10 , wherein the first flexible joint is an adhesive joint.
12. The deformable mirror of claim 11 , wherein the first flexible joint is formed from a soft RTD glue.
13. The deformable mirror of claim 5 , wherein:
the circumferential mirror mount includes a first ring, the first ring having a rounded top edge fastened to the back surface of the mirror substrate by a second flexible joint around which the mirror substrate can tilt in a radial direction when the annular force is applied to the mirror substrate; and
the annular drive element includes a second ring, the second ring having a rounded top edge fastened to the back surface of the mirror substrate by the first flexible joint.
14. The deformable mirror of claim 13 , wherein the diameters of the first ring and the second ring are selected such that the reflective front surface deforms in a spherical shape when the annular force is applied to the mirror substrate.
15. The deformable mirror of claim 5 , wherein the annular drive element includes:
a permanent magnet fastened to the back surface of the mirror substrate; and
a voice coil positioned at an offset from the back surface of the mirror substrate.
16. The deformable mirror of claim 15 , wherein the voice coil is positioned at an angle relative to the mirror mount.
17. The deformable mirror of claim 5 , wherein the annular drive element includes:
a variable shape fluid-tight housing filled with a pressurized fluid, the housing transmitting the annular force to the back surface of the mirror substrate when the housing changes shape; and
an actuator that changes a volume of the housing, thereby causing the housing to change shape.
18. The deformable mirror of claim 5 , further comprising:
a second circular mirror substrate mounted on a second circumferential mirror mount, the second circular mirror substrate having a reflective front surface and a back surface, the second circumferential mirror mount substantially preventing translation of the second mirror substrate relative to the second mirror mount but permitting the second mirror substrate to tilt locally relative to the second mirror mount, the annular mechanical drive element also applying a second annular force to the back surface of the second mirror substrate.
19. The deformable mirror of claim 18 , wherein the two mirror substrates deform to a shape with a same optical power.
20. The deformable mirror of claim 18 , wherein the two mirror substrates deform to a shape with opposite optical powers.
21. A deformable mirror comprising:
a circular mirror substrate having a reflective front surface and a back surface;
a circumferential mirror mount comprising an outer ring with a rounded top edge and a first soft RTD glue joint fastening the back surface of the mirror substrate to the rounded top edge of the outer ring, the first RTD glue joint substantially preventing translation of the mirror substrate relative to the outer ring but permitting the mirror substrate to tilt around the rounded top edge of the outer ring;
an inner ring with a rounded top edge and a second soft RTD glue joint fastening the back surface of the mirror substrate to the rounded top edge of the inner ring, the second RTD glue joint substantially preventing translation of the mirror substrate relative to the inner ring but permitting the mirror substrate to tilt around the rounded top edge of the inner ring;
a permanent magnet fastened to a back side of the inner ring; and
voice coil positioned at an offset from the back surface of the mirror substrate.