Optics: measuring and testing – Position or displacement
Reexamination Certificate
2001-05-16
2003-08-19
Stafira, Michael P. (Department: 2877)
Optics: measuring and testing
Position or displacement
Reexamination Certificate
active
06608688
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to optical instruments for position measurement, and more particularly, is directed to wireless optical instruments for position measurement.
BACKGROUND OF THE INVENTION
Systems using wired optical instruments for position measurement are known. One such system is an a FlashPoint 5000 system (FP5000) which is commercially available from Image Guided Technologies, Boulder, Colo. The FP5000 system includes multiple instruments, a camera system and a control unit. The control unit sends synchronization signals to the instruments via instrument cables and a break out box (if equipped). A measurement camera system includes two or more camera heads. By receiving the synchronization signals, infrared light emitting diodes (LEDs) on the instruments flash in synchronization with the camera frame rate (individually or in groups, time multiplexed). Each of the cameras images light emitted by the LEDs, and the measurement system uses the images to provide data. The data are converted to measurement angles by the measurement system and the measurement angles are sent to the control unit. The control unit converts the measurement angles to x, y and z coordinates of the LEDs. The control unit can convert the locations of the LEDs to an x, y, z position of the instrument and an orientation of the instrument. The instrument can, in addition, transmit instrument data to the control unit via the instrument cable. This information includes: button states, calibration data, probe ID, type and serial number, probe tip length, temperature and pressure.
Although wired optical instruments are satisfactory in the majority of applications, the requirement for a wire to connect the instrument to the control unit can be cumbersome. Thus, there is a need in the art for a system using a wireless optical instrument for position measurement.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide a system using a wireless instrument for position measurement.
Another object of the present invention is to provide an apparatus and method of use thereof in which a wireless optical instrument is synchronized with a controller.
It is yet a further objective of the present invention to provide a method of anticipating when an optical indicator should emit light.
Yet another object of the present invention is to provide a method where additional wireless instruments can be introduced into an optical field and assigned a particular multiplexed time slot.
Yet another object of the present invention is to provide a method of time multiplexing multiple optical instruments in an optical field.
These and other objects of the present invention are achieved by a wireless instrument tracking system. The wireless instrument tracking system is used for determining the location of at least one point in a three dimensional space relative to a three dimensional instrument tracking system. Advantageously, a first wireless instrument can be placed into the optical field with the wireless instrument including a wireless receiver and at least two optical position indicators. Two optical position indicators are required to compute orientation, but if only the location of the instrument is needed, one optical position indicator would suffice. The optical position indicators are typically light emitting diodes (LEDs) and communicate with corresponding position measurement sensors across a wireless optical link. The wireless optical link is time multiplexed with repetitive time frames divided into time slots. Each LED emits an infrared signal or flashes in a respective time slot of a time frame. The measurement sensors are preferably charge coupled device (CCD) cameras. The LEDs are synchronized with the cameras and once synchronized each LED flashes in a different time slot in synchronization with the camera frame rate (individually or in groups). Additional wireless instruments can be placed into the optical field. In a non-auto configuring system, each instruments is preassigned to a particular time slot Because each instrument is pre-assigned a time slot, a carrier signal can be used to trigger the emitters. Advantageously, in an automatically configuring system, additional wireless instruments are not assigned a particular time slot but instead use one time slot as a search channel. The additional instrument is called an unconfigured instrument. The unconfigured instrument or instruments (for example, at startup) are dynamically assigned to a particular time slot by the controller. Collisions are arbitrated using known arbitration schemes such as an ALOHA scheme.
The foregoing objects are also achieved by a wireless instrument tracking system for determining the location of at least one point in three dimensional space relative to a three dimensional instrument tracking system. The instrument tracking system includes a first wireless instrument, including a receiver and at least one optical position indicator. At least two corresponding sensors sense optical signals emitted from the at least two optical position indicators across an optical link. A controller includes a transmitter which can transmit signals to the receiver across a wireless link and means are provided for determining the location of the one optical position indicator relative to the coordinate system.
The foregoing objects are also achieved by a method of determining a location of at least one point in an optical field, the optical field being a three dimensional space relative to a three dimensional coordinate system. A first wireless instrument is placed into the optical field. The first wireless instrument includes a receiver and at least one optical position indicator. The first wireless instrument is synchronized with a controller. The controller includes a transmitter that can transmit signals to the receiver across a wireless link. The optical position indicator may also transmit data and synchronization to receivers associated with the controller, by modulating the output from the position indicators.
The system transmits synchronization signals to the instruments via the wireless link. Upon receiving the synchronization signals, the infrared LEDs on the instruments flash in synchronization with the camera frame rate. The measurement camera array images the LEDs, converts the data to measurement angles and sends it to the control unit. The control unit converts the measurement angles to x, y and z coordinates of the LEDs, and eventually, if required, to an x, y, z position and orientation of a rigid body having multiple LEDs are attached to. The instruments can, in addition, transmit instrument data to the control unit via the wireless link. The data can include button states, calibration data, probe ID, type and serial number, probe tip length, temperature and pressure.
Still other objects and advantages of the present invention will become readily apparent to those of ordinary skill in the art from the following detailed description, wherein the preferred embodiments of the invention are shown and described, simply by way of illustration of the best mode contemplated of carrying out the invention. As will be realized, the invention is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, all without departing from the invention. Accordingly, the drawings are to be regarded as illustrative in nature, and not as restrictive.
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Faul Ivan
Pasquini Ronald M.
Schulz Waldean A.
Skelton Brett R.
Image Guided Technologies Inc.
McCracken & Frank
Stafira Michael P.
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