POSITIONING SYSTEM AND METHOD

• US 20160209203A1
• Filed: 01/14/2016
• Published: 07/21/2016
• Est. Priority Date: 01/15/2015
• Status: Active Grant

• Current Assignee: Atracsys Sàrl (Smith & Nephew PLC)
• Original Assignee: CSEM Centre Suisse D'Electronique et de Microtechnique SA
• Inventors: BAUR, Charles, FRANZI, Edoardo, CHEBIRA, Amina, GRENET, Eric, HASLER, David
• Granted Patent: US 10,094,651 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: A61B 2090/309 using white LEDs
• CPC Class Codes: A61B 90/30 Devices for illuminating a surgical field, the devices having an interrelation with other surgical devices or with a surgical procedure
• CPC Class Codes: G01B 11/002 for measuring two or more coordinates
• CPC Class Codes: G01S 5/163 Determination of attitude using inertial means G01C9/00; control of attitude G05D1/49

Abstract

A positioning system, in particular, six-dimensions positioning system of a shadow sensor with respect to a constellation of light sources is provided. The sensor can be a shadow sensor and has a mask and a 2D imager. By recording the shadow of the mask cast by each light source on the imager, and by properly multiplexing the light sources, the system can compute the 6D position of the shadow sensor with respect to the constellation of light sources. This computation is based, in part, on treating the shadow of the mask cast on the imager as the equivalent of the projection of light in a pinhole or projective camera. In one embodiment, the system is applied in a surgical domain. In another embodiment, the system is rapidly deployed.

Claims

1. A positioning system, in particular a six dimensional (6D) positioning system, comprising:

a plurality of light sources;

at least one shadow sensor configured to sense shadows cast on the shadow sensor by light emitted from the light sources, said shadow sensor comprising an imager;

a processor;

wherein

the maximum distance between any of said light sources is larger than fifty times a width or a height of said imager;

the processor is configured to;

sync a shadow sensing with a pulsing of the light sources;

distinguish between the sensed shadows from each of the light sources;

determine two dimensional positions corresponding to each of the light sources based on the sensed shadows; and

compute a six dimensional of the at least one shadow sensor with respect to the light sources based on the determined 2D positions.

2. The positioning system according to claim 1, wherein the system comprises several shadow sensors and wherein the processor is configured to compute the 6D position of said several shadow sensors.

3. The positioning system according to claim 1, wherein the number of light sources is equal or higher than three, the system comprises an assembly comprising two shadow sensors with known relative position and wherein the processor is configured to compute the 6D position of said assembly.

4. The positioning system according to claim 1, wherein the shadow sensor comprises a mask, the mask having repetitive elements and a distinctive element, and wherein as light from the light sources passes through the mask, a shadow of the mask is cast on the imager.

5. The positioning system according to claim 1, wherein the processor is configured to distinguish between the sensed light from each of the light sources based at least in part on temporal modulation of the light sources.

6. The positioning system according to claim 1, wherein each shadow sensor further comprises a photodiode for syncing the shadow sensing with the pulsing of the light sources and/or for identifying which light source is emitting light.

7. The positioning system according to claim 1, wherein the 6D position of the shadow sensor is computed by considering the shadow sensor as a pinhole camera so as to use projective geometry computations.

8. The positioning system according to claim 1, comprising at least a surgical tool and a surgical lamp, at least one shadow sensor being placed on a surgical tool and all the light sources whose sensed shadows are used by the processor in the 6D computation being placed in or on the surgical lamp, and wherein the light sources are positioned at fixed relative locations within or on the surgical lamp.

9. The positioning system according to claim 8, wherein the light sources are connected and wherein a radio link is used to sync the shadow sensor.

10. The positioning system according to claim 1, comprising a set of at least two light source modules, each light source module comprising:

a light source;

communication means for communicating with other light source modules;

a clock;

fixation means for fixing the module on a support, e.g. a wall, a ceiling, a furniture, said fixation means comprising e.g. a magnet.

11. The positioning system according to claim 10, a light source module comprising a battery and RF communication means, the system comprising a wired network connecting said light source module with at least one other light source module.

12. The positioning system according to claim 10, each light source module comprising a battery and the communication means being RF communication means.

13. A method for estimating a position, in particular a six dimensional (6D) position, of a shadow sensor with respect to a plurality of light sources, the shadow sensor being configured to sense shadows cast on the shadow sensor by light emitted from the light sources, said shadow sensor comprising an imager, the maximum distance between any of said light sources being larger than fifty times a width or a height of said imager, the method comprising;

sync a shadow sensing with a pulsing of the light sources;

distinguish between the sensed shadows from each of the light sources;

determine two dimensional (2D) positions corresponding to each of the light sources based on the sensed shadows; and

compute a 6D position of the at least one shadow sensor with respect to the light sources based on the determined 2D positions.

14. The method of the previous claim, further comprising the following steps:

sense shadows cast on an assembly comprising at least two shadow sensors with known relative positions, by light emitted from the light sources,

record a projection of at least three points from a fixed location, each point corresponding to the (3D) position in space of a light source, a projection of a point being recorded as the two dimensional (2D) positions of the sensed shadows cast by said light source on each shadow sensor of said assembly;

compute the three dimensional position of each point with respect to said fixed location;

repeat said recording and computing steps from a different fixed location, so as to obtain M recordings comprising each the projection of a set of the same Q light sources, M and Q being integer numbers satisfying a predetermined constraint;

estimate the three dimensional (3D) relative position of every light source within a common reference frame.

15. The method of claim 13, further comprising the following steps:

sense shadows cast on the shadow sensor by light emitted from the light sources, wherein at least two light sources are at a fixed position with respect to each other;

record a projection of at least six points from a fixed location, each point corresponding to the (3D) position in space of a light source, a projection of a point being recorded as the two dimensional (2D) position of the sensed shadow cast by said light source on said shadow sensor;

repeat said recording and computing steps from a different fixed location, so as to obtain N recordings comprising each the projection of a set of the same P light sources, N and P being integer numbers satisfying a predetermined constraint;

compute the three dimensional (3D) relative position of every light source within a common reference frame, said position being defined up to a scale factor;

scale every computed three dimensional (3D) relative position so that the computed three dimensional (3D) relative position of said at least two light sources matches said known fixed position.