Optical target

Abstract

Optical Target The optical target (1) is designed to be placed on a surface and comprises: - a target support (2); - a first zone forming an optical reflector (9) for the λ laser and infrared frequencies, and placed on the target support. The optical target (1) includes a second zone (10) forming a filter permeable to infrared radiation and impermeable to λ laser radiation, the second zone (10) being superimposed on the first zone (9) and having a recess in its center. Figure for the abbreviation: Figure 1

Description

Title of the invention: Optical target

[0001] The present invention relates to an optical target of the type intended to be placed on a surface, the optical target comprising:

[0002] - a target support;

[0003] - a first zone forming an optical reflector on the X and laser frequencies infrared, and placed on the target support.

[0004] Such an optical target is more particularly intended to use in conjunction a laser projector and an infrared position tracking system.

[0005] In shipbuilding, it is known that to facilitate the welding of metal parts inside a room, laser projection can be used to indicate the exact position of the parts before welding. This allows for greater precision and faster execution compared to the traditional method of positioning by measuring and marking. In order to avoid positioning errors, a preliminary calibration phase of the laser projector is necessary to adapt the projection to the room environment.

[0006] One way to calibrate the projector is to measure the geometric coordinates of a number of reference points in three dimensions of space within the room's frame of reference. The reference points are points whose coordinates within the room are known. The position and orientation of the laser projector are determined by triangulation, establishing the distance and orientation of each reference point relative to the laser projector. The greater the number of reference points, the greater the accuracy.

[0007] To automate this measurement, manufacturers most often use targets to mark the reference points. A target generally consists of an optical prism or a photoreflective marker. A target center search phase is performed to precisely identify the target's position: the laser projector illuminates the area where the target is located, captures the laser beam's reflection in a photodiode, and refines the search and positioning by reducing the illumination area until acceptable accuracy is achieved. In the case of photoreflective markers, they are chosen to be circular and their diameter is on the order of a few millimeters to facilitate finding the target center.

[0008] When it is necessary to move the laser projector, for example when objects obstruct the laser projection, a recalibration phase of the laser projector must be performed. To facilitate this recalibration phase, a device capable of dynamically tracking the relative position of the laser projector in the room and thus accurately determining its position in real time can be used. Generally, the tracking devices used are optical, such as cameras, and utilize infrared radiation, allowing the position of markers placed within the room to be tracked. These markers can be photoreflective. In this case, the larger their diameter, the easier it is for the system to identify the marker in the image. Optimally, the marker diameter is on the order of tens of millimeters.

[0009] The two devices, laser tracer and dynamic tracking device, are generally separate pieces of equipment that have different requirements in terms of targets: - The laser projection device uses photo-reflective targets of rather small diameter for calibration, typically a few mm (3 mm); - The infrared technology-based position tracking device uses photo-reflective targets of rather average diameter, typically a few tens of mm (from 10 to 20 mm), to correctly track the position in space of an object.

[0010] It is easy to see that it could be advantageous to physically and software-couple the two devices in order to automate the recalibration procedure. Ideally, the targets of both devices could be positioned in the same locations, which minimizes the number of targets and increases accuracy by eliminating the need to know the relative position of the laser projector targets with respect to the targets of the position tracking device. Furthermore, it is easy to mount the laser projector and the position tracking device together, for example, using a common rigid support and providing for data exchange between the two pieces of equipment.

[0011] However, when the two systems are to be used jointly, the target size constraints are conflicting. One solution would be to use target sizes acceptable to both systems, for example 10 millimeters, but this compromise would be at the expense of projection accuracy, as positioning errors would accumulate.

[0012] An object of the present invention is to provide a target that can be compatible with the requirements of a laser projector and a position tracking device.

[0013] For this purpose, the invention relates to an optical target of the aforementioned type, in which the optical target comprises a second zone forming a filter permeable to infrared radiation and impermeable to X-ray laser radiation, the second zone being superimposed on the first zone and having a recess in its center.

[0014] According to other advantageous aspects of the invention, the target comprises one or more of the following features, taken individually or in all technically possible combinations:

[0015] - the target support has an interface for attaching the target support to an editing interface;

[0016] - the mounting interface allows the target to be placed on a surface by means of a fastening device;

[0017] - the first zone forms a disk and the second zone forms a ring whose outer diameter is identical to the diameter of the first zone;

[0018] - the diameter of the first zone is between 10mm and 30mm, preferably between 12mm and 15mm;

[0019] - the inner diameter of the second zone is between 2mm and 5mm, preferably between 2.5mm and 3.5mm;

[0020] - the target support is equipped, on the face opposite the first zone, with a means mechanical support on a mounting interface;

[0021] - the mounting interface comprises, on the face opposite the target support, a outgrowth intended to cooperate with a footprint made on an installation surface;

[0022] - the protrusion is formed by a nipple with a diameter adapted to the size of the impression;

[0023] - the protrusion is formed by a spring-loaded, retractable needle in a housing provided in the mounting interface.

[0024] The invention will become clearer upon reading the following description, given solely by way of non-limiting example, and made with reference to the drawings in which:

[0025] [Fig-1] [Fig. 1] is a perspective view of the optical target according to one embodiment of the invention;

[0026] [Fig.2] [Fig.2] is a perspective view of the underside of the optical target and a mounting interface according to one embodiment of the invention;

[0027] [Fig.3] [Fig.3] is a perspective view of a target support according to one embodiment of the invention;

[0028] [Fig.4] [Fig.4] is a perspective view of the target support of [Fig.3] equipped with a target centering device according to an embodiment of the invention;

[0029] [Fig.5] [Fig.5] is a perspective view of the target support of [Fig.4] equipped with the target centering device and an infrared filter according to an embodiment of the invention;

[0030] [Fig.6] [Fig.6] is a perspective view of the underside of the mounting interface equipped with the target according to an embodiment of the invention according to an embodiment of the invention;

[0031] [Fig.7] [Fig.7] is a cross-sectional view of the mounting interface equipped with a protrusion intended to cooperate with a recess made on a wall;

[0032] [Fig.8] [Fig.8] is a cross-sectional view of the mounting interface equipped with a spring-loaded pin;

[0033] [Fig.9] [Fig.9] is an overview illustrating the operation of the target.

[0034] With reference to figures 1 to 7, a first embodiment of an optical target 1 according to the invention is described.

[0035] The optical target 1 includes a target holder 2 adapted to be rigidly mounted on a mounting interface 3, for example by means of a pin 4 of the mounting interface which is press-fitted into a bore 5 of the target holder 2. The target holder has at least one slot 6 which allows the target holder 2 to be detached from the mounting interface 3 using, for example, the end of a flathead screwdriver. The target holder 2 has an axis of symmetry X, substantially coinciding with the axis of the bore 5.

[0036] The target support 2 includes a reflective area 7 suitable for reflecting laser radiation of X-ray wavelengths and in the infrared range. For example, the laser has an X-ray wavelength between 520 nanometers and 525 nanometers. In one embodiment, the reflective area 7 consists of a pellet (for example, the flat markers from Advanced Realtime Tracking) with a diameter of, for example, 18 millimeters. The diameter of the target support is designed so that the pellet can be easily positioned, for example, by gluing it in place.

[0037] A target centering device 8 formed by a ring of material opaque to X-ray and infrared laser radiation (for example, acrylonitrile butadiene styrene (ABS)) cooperating with the target support 2. The target centering device 8 may, for example, have an inner diameter of 14 millimeters. The centering device 8 is positioned above the pad 7 so as to obtain a reflective surface 9 perfectly centered with respect to the center of the target support 2. Advantageously, the target centering device 8 is tightly mounted on the target support.

[0038] A second zone 10, opaque to X-ray laser radiation and permeable to infrared radiation, is formed by a ring. This ring has an outer diameter equal to the inner diameter of the target centering device 8. The inner diameter of the second zone 10 can be 3 millimeters. This ring can be made of black plexiglass. This ring is positioned above the reflective surface 9. Advantageously, this ring is tightly fitted into the target centering device 8.

[0039] The mounting interface 3 has, on its surface opposite the target support, a protrusion 12, centered with respect to the axis of symmetry X of the target support 2, formed, according to an embodiment shown in [Fig. 7], by a lug with a diameter of 1 millimeter and a height of 1 millimeter. This protrusion 12 allows centering on an imprint 13 formed on a wall 14. The imprint is made, for example, by punching the wall 14.

[0040] The mounting interface 3 has on its surface opposite the target support 2 two recesses 15, 16 of depth p allowing to stick two permanent magnets 17, 18 of thickness slightly less than p (for example, p reduced by 0.1 millimeter).

[0041] Alternatively, according to an embodiment of [Fig.8], the protrusion 12 is constituted by a retractable pin 19 in a housing 20 and held in position by a spring 21. This arrangement allows the protrusion to adapt to the depth of the impression 13.

[0042] Advantageously, the outer diameter of the target support 2 is between 20 and 30 millimeters.

[0043] The use of the target according to the invention will be more easily understood by reading what follows and illustrated by [Fig.9].

[0044] According to one embodiment, a mobile trolley 22 supporting a laser projection device 23 and a position tracking device 24 is arranged in a room 25, the room having a wall 14 and a floor 26. The laser projection device 23 and the position tracking device 24 are mechanically fixed and cannot move relative to each other. The trolley is equipped with casters 27 allowing it to be moved on the floor 26. The laser projection device 23 and the position tracking device 24 are software-linked and have a data exchange system, such as a computer bus (not shown) known from the prior art.

[0045] This data exchange system allows the position tracking device 24 to transmit its position to the laser projection device 23. The laser projection device 23 then knows its position in the room 24 because its relative position with respect to the position tracking device 24 is known by construction.

[0046] Targets 1 according to the invention are arranged at known locations in room 24, for example on the wall 14. By visualizing the targets 1 and triangulating them, the position tracking device 24 is able to determine its position in space. It transmits its position via the computer bus to the laser projection device 23, which then calculates its own position in room 25.

[0047] The laser projection device 23 can then target the targets 1 and refine its position in space. The laser projection device 23 can then project the locations of the parts to be welded, for example, onto the wall 14.

[0048] The optical target 1 according to the invention therefore makes it possible to automate the recalibration procedure of the laser projection device 23.

Claims

Demands

1. Optical target (1) intended to be disposed on a surface, the optical target (1) comprising: - a target support (2); - a first zone forming an optical reflector (9) on X-ray and infrared laser frequencies, and disposed on the target support; characterized in that the optical target (1) comprises a second zone (10) forming a filter permeable to infrared radiation and impermeable to X-ray laser radiation, the second zone (10) being superimposed on the first zone (9) and having a recess in its center.

2. Optical target according to claim 1, characterized in that the target support (2) has an interface (5) allowing the target support to be fixed on a mounting interface (3).

3. Optical target according to claim 2, characterized in that the mounting interface (3) allows the target (1) to be placed on a surface by means of a fixing device (17, 18)

4. Optical target according to any one of the preceding claims, characterized in that the first zone (9) forms a disk and the second zone (10) forms a ring whose outer diameter is identical to the diameter of the first zone.

5. Optical target according to claim 4, characterized in that the diameter of the first zone (9) is between 10mm and 30mm, preferably between 12mm and 15mm.

6. Optical target according to claim 4 or 5, characterized in that the inner diameter of the second zone (10) is between 2mm and 5mm, preferably between 2.5mm and 3.5mm.

7. Optical target according to any one of the preceding claims, characterized in that the target support (2) is provided, on the face opposite the first zone (9), with a mechanical means of holding (4, 5) on a mounting interface (3).

8. Optical target according to any one of claims 2 to 7, characterized in that the mounting interface (3) comprises, on the face opposite the target support (2), a protrusion (12) intended to cooperate with an imprint (13) provided on an installation surface (14).

9. Optical target according to claim 8, characterized in that the protrusion (12) is formed by a nipple of diameter adapted to the size of the imprint.

10. Optical target according to claim 8 or 9, characterized in that the protrusion (12) is formed by a needle (19) mounted on a spring (21), and capable of retracting into a housing (20) provided in the mounting interface (3).