DE102008037176A1 - Light beam's direction determining device for use in tracking system, has front and rear plates whose form and condition are introduced in space, and evaluation unit evaluating direction of light beams based on measured striking points - Google Patents

Abstract

The device has two front and rear plates (4, 5), where the form and condition of the plates are introduced in a space. A camera (6) measures striking points (8, 9) of light beams (3) on the plates, where the light beams are emitted by a light source (2) e.g. LED. An evaluation unit evaluates a direction of the light beams based on the measured striking points. The front surface is made of glass or Plexiglas(RTM: tough transparent plastic). The surfaces have markings (10-13) to calibrate the camera. An independent claim is also included for a tracking system having a device for determining a direction of a light beam.

Description

object The present invention is an apparatus for determining the Direction of a ray of light.

The Determining the direction of a light beam has a wide variety of uses. For example is such a device in a tracking system for positional and / or orientation determination of an object can be used. A possible Application area provide image-guided surgical procedures in which the attitude of an instrument or tool in relation to is tracked on the patient. Based on this information can the surgeon can see where the instrument is going on an MR or CT scan shows and what is behind the end tip of the surgical instrument lies. These applications require very high accuracy. There the instruments used here have a long lever is in particular a high angular accuracy crucial.

Methods are known in which the attitude of an instrument has active or passive position markers and the position and orientation of the instrument is determined by measuring the position of the position markers. EP 0 847 253 B1 describes, for example, an optical position measuring system for measuring the position of a surgical instrument 13 , which infrared light emitting diodes 12 whose position is from two or more cameras 10 be determined. Although such a method is characterized by a relatively high position accuracy, even the smallest angle errors caused by the large lever lead to large position errors at the tip of the instrument. It is therefore desirable to measure the position and orientation of the instrument with the greatest possible angular accuracy.

Furthermore, in the prior art devices and methods are known which make it possible to determine the point of impact of a laser beam on a screen very accurately. CA 2,378,154 A1 describes, for example, a system where the impact point 22 a laser beam on a screen 16 with a camera 14 as well as a calculator 10 is determined. On the screen 16 In this case, a projection of the computer screen is shown and the laser beam serves as an input device for the computer.

This in CA 2,378,154 A1 However, disclosed method only allows the determination of the point of impact of the laser beam on the screen. Information about the direction of the laser beam can not be obtained here.

task It is now the object of the present invention to provide a method which allows the direction of a light beam to investigate.

These Task is achieved by a device according to the present claim 1 solved. Preferred embodiments are the subject of the dependent claims.

According to the invention Accordingly, a device for determining the direction of a light beam proposed that at least two surfaces whose shape as well as location in space is known means of measuring the impact points of the light beam through the surfaces as well as means of calculation the direction of the light beam based on the measured impact points having.

By the use of two surfaces, for each the point of impact of the light beam is determined, it is possible to clearly determine the direction of the beam. Here is the shape the surfaces arbitrarily. The present invention is not limited to flat surfaces. The shape and location The areas must only be known.

Preferably if the rear surface in the direction of the light beam is light-scattering, especially white. These are for example around the ceiling or wall of a room. Alternatively, a canvas can also be used be used.

The in the direction of the light beam front surface is preferably partially translucent. Accordingly, it is possible the point of impact of the light beam on this surface determine and at the same time enough light passes through them Surface and reaches the rear surface. The front surface is preferably made of glass or Plexiglas, the surface may be frosted.

In an alternative embodiment is in the direction of the light beam front surface into an opaque and a transparent state switchable. Preferably, the front surface is is built in a pixel structure, with each pixel in one Opaquen and a transparent state is switchable. For this purpose is For example, uses a switchable polarizing filter.

In a preferred embodiment has at least one the areas one or more marks for calibration the means for measuring the impact points on.

Furthermore, it has proven to be advantageous for the measurement of the impact points to use at least one camera. It is both possible to measure with one camera the impact points on both surfaces, as well as to use a separate camera for each surface. However, they are Other types for measuring the impact points possible.

object The present invention also provides a tracking system for position and / or orientation determination of an object, wherein the tracking system an inventive device for direction determination a light beam and the object to be tracked a directed Has light source.

Preferably the object further comprises a control unit, means for supplying energy as well as a suitable optics, wherein the optics is a Multi-faceted optics and at the light source around a laser, a Laser array, in particular an array of vertical-cavity surface-emitting Laser, VCSEL, or light-emitting diodes acts. If LEDs as Light source can be used, so it is possible in addition to the Impact points on the area also the extent of this Determine impact points. In this case, based on the ratio the expansions are closed to the distance of the light source.

Preferably the light source emits light in the visible range. To this Way, the safety of the system is improved as the human Eye causes a closing reflex if the radiation is too strong, to prevent radiation damage from visible light. Alternatively, the light source emits radiation in the infrared region.

In a further embodiment, the tracking system several, distributed in space, inventive devices on.

It is also advantageous if the object to be tracked has several, at least two, emitting light rays, the tracking system Means for measuring the points of impact of the plurality of light beams through the surfaces and further means for assigning the light rays to the corresponding light source. Such an assignment can, for example, based on the geometry of the emitted light beams as well as the measured impact points. A particularly simple one Allocation can also be achieved by using the multiple light beams be emitted in temporal change to each other. This will too referred to as time-division multiplexing.

In A preferred embodiment is the object to a, preferably medical, instrument or tool.

The Inventive tracking system preferably determines the position and / or orientation of at least two objects, which each have at least one directional light source, the system measures to identify the objects having. To enable the identification of the objects These emit preferably the light beams in temporal change to each other.

in the The following is the invention with reference to the attached Figures illustrate embodiments closer be explained.

1 shows a device according to the invention, which is used in a tracking system.

2 shows an alternative embodiment of the device according to the invention.

3 shows an object whose position and orientation is measured with the tracking system.

4 shows a tracking system comprising a plurality of devices according to the invention.

1 shows a tracking system for position and / or orientation determination of the object 1 , The object 1 has a light source 2 on, which is a ray of light 3 emitted. The device according to the invention now makes it possible to control the direction of the light beam 3 to determine. The device has two surfaces 4 . 5 , a camera 6 as well as a computing unit 7 on.

The light beam 3 enters through the front surface 4 through and hits the back surface 5 , The camera 6 records this image and forwards it to the arithmetic unit 7 Next, which evaluates the recorded data.

The front surface 4 is therefore designed teillichtdurchlässig. It is made of glass or Plexiglas, for example. To increase the scattered portion of the incident light, the surface of the surface becomes 4 matted or roughened.

However, it is in the context of the present invention, alternative embodiments for the front surface 4 possible. This area 4 For example, it can be configured in such a way that both an opaque and a transparent state are possible, with a corresponding circuit selecting one of the two states in each case.

The front surface 4 is designed for this purpose, for example, as a liquid crystal screen, LCD. A structuring of the area in individual pixels is unnecessary here. Rather, the entire front surface 4 be switched to an opaque or a transparent state. For switching between the two states, for example, a variable polarization filter can be used.

In an alternative embodiment, the front surface 4 Preferably, a pixel structure, wherein each pixel can be switched to an opaque or a transparent state. Now one pixel each is switched transparent, while the remaining pixels remain opaque. Now kick a ray of light 3 through the front plate 4 through and gets on the back plate 5 observed, so is the point of impact 8th of the beam 3 on the front surface 4 known since this point 8th corresponds to the location of the transparent pixel.

The back surface 5 is typically light scattering, preferably white. It can also be a ceiling or wall of a room or a screen. The shape of the surfaces 4 . 5 is arbitrary. Although planar surfaces are always used in the exemplary embodiments shown here, arbitrarily shaped surfaces, for example curved surfaces, are equally usable in the context of the present invention. The shape of the surfaces 4 . 5 must be known to the system.

To determine the impact points 8th . 9 of the light beam 3 on the surfaces 4 . 5 becomes a camera in the embodiment shown here 6 used the images of the two surfaces 4 . 5 records.

However, within the scope of the present invention, other means of measuring the points of impact are also known 8th . 9 conceivable. In an alternative embodiment, for each of the surfaces 4 . 5 a separate camera 6 used. Furthermore, it is possible along the surfaces 4 . 5 To wire wires with photodiodes and based on the brightness measured by the photodiodes, the impact points 8th . 9 of the light beam 3 on the surfaces 4 . 5 to investigate. This will be the wires for the front surface 4 spanned so that a sufficient proportion of the light beam through the surface 4 passes through and onto the rear surface 5 meets.

Another possibility is the surfaces 4 . 5 as very large spatially resolving photodiodes to design. The functional principle of these known as Position Sensitive Device diodes is assumed to be known at this point. It must also be ensured here that the front surface 4 teillichtdurchlässig is configured. For this purpose, the corresponding photodiode is made sufficiently thin.

At the in 1 shown embodiment, the surfaces 4 . 5 marks 10 - 13 on, which is used to calibrate the camera 6 serve. The position of the marks 10 - 13 on the surfaces 4 . 5 is known and based on these markings 10 - 13 puts the camera 6 or the arithmetic unit 7 a coordinate system in which the impact points 8th . 9 be determined.

The camera 6 is to a computing unit 7 connected, wherein the evaluation of the recorded data from the arithmetic unit 7 is performed. Furthermore, this arithmetic unit has 7 a screen 14 on. On this screen 14 For example, the calculated direction of the light beam 3 are displayed. The evaluation of the recorded data can alternatively also in the camera 6 even if it has an integrated computing unit.

The arithmetic unit 7 thus determines data regarding the direction of the light beam. They are also interfaces 25 provided, through which the data can be forwarded to other systems. For example, it is possible in this way, that of the arithmetic unit 7 data to be used in a picture-based process.

The impact point 9 of the light beam 3 on the back surface 9 have the coordinates (x ₁ , y ₁ , z ₁ ) and the point of impact 8th on the front surface have the coordinates (x ₂ , y ₂ , z ₂ ). In this case, the light source lies on a straight line g, which is given by g = (x 2 , y 2 , z 2 ) + α · (x 2 - x 1 , y 2 - y 1 , z 2 - z 1 ) where α is a real number.

Such a method for determining the direction of a light beam has a wide variety of applications. In the application example shown here, the device according to the invention is used as part of a tracking system for determining the position and / or orientation of the object 1 used. However, the invention is not limited to this use. Rather, other uses are conceivable. For example, this device can also be used to align a light source. The exact direction of emission of a light source emitting a directional beam can be measured with the device described herein and then adjusted to a desired value without knowing the position of the light source. Accordingly, the device according to the invention can be used as part of a calibration device for a laser. Other applications are, for example, in the field of scientific experiments on optics.

The 1 and 2 In contrast, show the use of the device according to the invention in a tracking system, the position and / or orientation of the object 1 certainly. At the in 1 Tracking system shown can only be the direction of the light beam 3 determine, ie it can be specified the line g, on which the light source 2 lies. 2 shows an alternative embodiment play, where by the light source 2 two beams of light 3 . 18 out. The second light beam 18 meets in the points 19 and 20 to the levels 4 . 5 on. Also these impact points 19 . 20 be from the camera 6 detected. In the arithmetic unit 7 then an assignment of the individual impact points takes place 8th . 9 . 19 . 20 to the rays of light 3 . 18 , This will be the geometry of the surfaces 4 . 5 as well as the light source 2 considered. The present invention is by no means limited to two radiated light beams 3 . 18 limited. It is quite possible that the object 1 a plurality of rays, for example in the form of a spoked wheel, radiates.

Shines the object 1 more than a ray of light 3 . 18 off, then these rays of light 3 . 18 preferably not continuously emitted, but rather in a temporal change. For this purpose, for example, a laser array is used, in which the individual laser cells emit radiation in temporal alternation. Will now be a hit point 8th . 9 . 19 . 20 a ray of light 3 . 18 on one of the surfaces 4 . 5 observed, this is the point of impact 8th . 9 . 19 . 20 without further ado the light beam emitted at that moment 3 . 18 assign. This method, which is also referred to as a time-division multiplex method, is particularly advantageous if of the object 1 a plurality of symmetrically arranged light beams 3 . 18 is emitted.

Shines the object 1 for example, rays 3 . 18 in the form of a spoked wheel, so the time division method allows easy allocation of the individual puncture points 8th . 9 . 19 . 20 to the rays 3 . 18 , In addition the light rays become 3 . 18 , which form the individual spokes, emitted one after the other. In this way, the orientation of the object 1 be determined.

Just like the beam 3 can now also for the light beam 18 a straight line are set on which the light source 2 lies. Let (x ' ₁ , y' ₁ , z ' ₁ ) and (x' ₂ , y ' ₂ , z' ₂ ) be the coordinates of the points of impact 19 . 20 of the second light beam 18 to the levels 4 . 5 so lies the light source 2 on a straight line f given by f = (x ' 2 , y ' 2 'z' 2 ) + β · (x ' 2 - x ' 1 , y ' 2 - y ' 1 'z' 2 - z ' 1 ) where β is a real number. The intersection of the two lines g and f can now be calculated directly. At this intersection is the light source 2 ,

Next to the position of the object 1 From the measured information, the exact angular orientation of the object can also be determined 1 be calculated.

In the exemplary embodiment illustrated here, the object is 1 a medical instrument 1 that in his handle 15 a light source 1 having. Furthermore, the medical instrument 1 a pole 16 on, at the end tip 17 is shaped into a tool.

Such an instrument 1 is commonly used in image-guided surgery systems. The surgeon operates the instrument 1 by means of the handle 15 which is outside the patient's body. The end tip 17 is used in an operating area in the patient's body. In this way, a small incision into the skin of the patient through which the tool is inserted is sufficient. This is known as minimally invasive surgery.

Since the surgeon accordingly the tool at the end tip 17 of the instrument 1 can not see, he is supported by an image-guided system. Before surgery, images (eg, CT or MRI images) are taken by the patient. During the procedure, the device according to the invention is used to determine the position of the surgical instrument 1 to investigate. It is first the position of the light source 2 calculated in the handpiece 15 is integrated. From the known geometry of the instrument 1 can now on the exact position of the end tip 17 getting closed.

The pre-recorded image will now be on the screen 14 displayed, wherein the determined position of the instrument 1 is displayed in it. The surgeon can thus see where the end tip is 17 in the surgical area is exactly by looking at the screen 14 viewed image displayed.

The device according to the invention is characterized in particular by the angular position of the handpiece 15 determined very precisely. Accordingly, despite the rather long lever 16 the position of the end tip 17 very accurately known.

3 shows a schematic representation of the handle 15 of the instrument 1 , At this handle 15 is the rod 16 attached. Further, the handle has 15 a control unit 22 , Medium 21 for power supply and a light source 2 on. The control unit 22 serves to control the light source 2 , The power supply, for example, a battery 21 , an accumulator or a power source.

At the light source 2 In the embodiment shown here, several vertical cavity surface-emitting lasers (VCSEL) are involved. 2 , Alternatively, other laser diodes or LEDs are used. The emitted light lies in the visible wavelength range. In this way, the security of the system for the user significantly improved because the human eye for light of these wavelengths triggers a locking mechanism to prevent damage from excessive radiation. Alternatively, infrared light can also be used. In this case, however, increased security measures are necessary.

That from the light source 2 radiated light meets an optic 23 , It is a multifaceted look 23 that's from a light source 2 bundles outgoing light into different beams and deflects these beams in different spatial directions. In this way, the light source generates 2 a spoked wheel of rays of light.

Become LEDs as a light source 2 used, the radiated rays have a certain opening angle. Accordingly has a hit point 8th . 19 on the front surface 4 a smaller diameter than a point of impact 9 . 20 on the back surface 5 , It is now possible, the diameter of the different impact points 8th . 9 . 19 . 20 to eat. If these diameters are set in relation to each other, the distance between the light source and the light source can be reduced 2 from the surfaces 4 . 5 be calculated. This information can also be used to track the object 1 be used.

4 shows a further tracking system for determining the position and / or orientation of an object 1 , The object 1 is examined in a tracking volume defined by a space.

This in 4 shown tracking system has several devices according to the invention. The surfaces 4 . 5 are arranged on the ceiling of the room, while each two surfaces 4a . 5a and 4b . 5b are arranged on two side walls of the room. Furthermore, the inventive means for measuring the impact points and at least one central processing unit for the plurality of devices. However, these means are not shown here for the sake of simplicity.

The object 1 again has a light source 2 on, from which now a spoked wheel is radiated by light rays. At the in 4 example shown, the light rays hit 3 and 18 the arranged on the left side wall surfaces 4a . 5a and further, the light beam strikes 24 on the arranged on the right side wall surfaces 4b . 5b , The points of impact of the three rays of light 3 . 18 . 24 are measured and thus three straight lines are determined on which the light source 2 can be arranged. From the intersection of the straight line, the location of the object results 1 , Furthermore, the orientation of the object can also be determined from the recorded data 1 determine. Since the orientation is measured with a very high angular accuracy, the exact position of the end tip 17 very well known.

This in 4 The tracking system shown has the advantage that a plurality of measuring points is recorded. This increases the accuracy of the measurement. Furthermore, a tracking of the object 1 even possible if some of the rays are obscured. For example, the surgeon himself could shield a large portion of the rays.

Another alternative embodiment of the device according to the invention is that as surfaces 4 . 5 the top and bottom of a glass plate is used. In this case, the entry and exit points of a light beam into the plate are determined and the direction of the beam is determined on the basis of these data.

With the tracking system according to the invention, it is also possible, the position and / or orientation of multiple objects 1 to determine. This is indicated by each of these objects 1 at least one directional light source 2 on. Furthermore, the tracking system has means for identifying the individual objects 1 on. For example, it is possible that the objects 1 emit light in temporal alternation. Since, therefore, exactly one object at a time emits a beam of light, it is easily possible, the point of impact of the light beam on one of the surfaces 4 . 5 the corresponding object 1 assigned. Again, it is a time division multiplex method.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - EP 0847253 B1 [0003]
• - CA 2378154 A1 [0004, 0005]

Claims (25)

Device for determining the direction of a light beam ( 3 . 18 . 24 ), characterized in that the device has at least two surfaces ( 4 . 5 ), whose shape and position in space is known, means ( 6 ) for measuring the impact points ( 8th . 9 . 9 . 20 ) of the light beam ( 3 . 18 . 24 ) on the surfaces ( 4 . 5 ), as well as funds ( 7 ) for calculating the direction of the light beam ( 3 . 18 . 24 ) based on the measured impact points ( 8th . 9 . 9 . 20 ) having. Apparatus according to claim 1, characterized in that in the direction of the light beam ( 3 . 18 . 24 ) rear surface ( 5 ) is light-scattering, especially white. Apparatus according to claim 1 or 2, characterized in that in the direction of the light beam ( 3 . 18 . 24 ) front surface ( 4 ) is partially translucent. Apparatus according to claim 3, characterized in that in the direction of the light beam ( 3 . 18 . 24 ) front surface ( 4 ) consists of glass or Plexiglas. Apparatus according to claim 1 or 2, characterized in that in the direction of the light beam ( 3 . 18 . 24 ) front surface ( 4 ) is switchable into an opaque and a transparent state. Apparatus according to claim 1 or 2, characterized in that in the direction of the light beam ( 3 . 18 . 24 ) front surface ( 4 ) is constructed in a pixel structure, wherein each pixel is switchable into an opaque and a transparent state. Device according to claim 5 or 6, characterized in that the front surface ( 4 ) has a switchable polarization filter. Device according to one of the preceding claims, characterized in that at least one of the surfaces ( 4 . 5 ) one or more markings ( 10 . 11 . 12 . 13 ) for calibrating the means ( 6 ) for measuring the impact points ( 8th . 9 . 9 . 20 ) having. Device according to one of the preceding claims, characterized in that the means ( 6 ) for measuring the impact points ( 8th . 9 . 9 . 20 ) around at least one camera ( 6 ). Tracking system for position and / or orientation determination of at least one object ( 1 ), wherein the tracking system comprises a device according to one of the preceding claims, characterized in that the object ( 1 ) a directional light source ( 2 ) having. Tracking system according to claim 10, characterized in that the object ( 1 ) a control unit ( 22 ), Medium ( 21 ) for energy supply and a suitable optics ( 23 ) having. Tracking system according to one of claims 10 or 11, characterized in that it is in the optics ( 23 ) is a multi-faceted look. Tracking system according to one of Claims 10 to 12, characterized in that the light source ( 2 ) is a laser or a laser array, in particular a vertical-cavity surface-emitting laser array, VCSEL array. Tracking system according to one of Claims 10 to 12, characterized in that the light source ( 2 ) are light-emitting diodes. Tracking system according to claim 14, characterized in that the tracking system further comprises means for determining the extent of the impact points ( 8th . 9 . 9 . 20 ) having. Tracking system according to one of claims 10 to 15, characterized in that the light source ( 2 ) Emitted light in the visible range. Tracking system according to one of claims 10 to 15, characterized in that the light source ( 2 ) Emits radiation in the infrared range. Tracking system according to one of Claims 10 to 17, characterized in that the tracking system a plurality of distributed in space devices according to a of claims 1 to 4. Tracking system according to one of claims 10 to 18, characterized in that the object ( 1 ) several, at least two, light rays ( 3 . 18 . 24 ) emitted. Tracking system according to claim 19, characterized in that the tracking system comprises means ( 6 ) for measuring the impact points of the plurality of light rays through the surfaces ( 4 . 5 ) and further means for assigning the light beams ( 3 . 18 . 24 ) to the corresponding light source ( 2 ) having. Tracking system according to one of claims 19 or 20, characterized in that the plurality of light beams ( 3 . 18 . 24 ) are emitted in temporal change to each other. Tracking system according to one of claims 10 to 21, characterized in that it is at the object ( 1 ) is an instrument or tool. Tracking system according to one of claims 10 to 22, characterized in that the object ( 1 ) is a medical instrument or tool. Tracking system according to one of claims 10 or 23, characterized in that the tracking system, the position and / or orientation of at least two objects ( 1 ) determines which at least one directional light source ( 2 ), the system having measures for identifying the objects ( 1 ) having. Tracking system according to claim 24, characterized in that the objects ( 1 ) the light beams ( 3 . 18 . 24 ) emit in temporal change.