WO2011076200A1

WO2011076200A1 - Optical marker and object detecting device

Info

Publication number: WO2011076200A1
Application number: PCT/DE2010/075157
Authority: WO
Inventors: Michael Haubner; Manuel Pabst
Original assignee: Krauss-Maffei Wegmann Gmbh & Co. Kg
Priority date: 2009-12-21
Filing date: 2010-12-07
Publication date: 2011-06-30
Also published as: DE102009059797A1

Abstract

The invention relates to an optical marker (1), in particular of an augmented reality system, having a code pattern made of differently reflecting surfaces comprising a reflective layer (12), above which a masking layer (5) is located, which has cut-outs (9) for generating the code pattern. The invention also relates to an object detecting device comprising an image acquisition unit and an optical marker (1) of said type. The reflective layer (12) may comprise a retroreflective coating (3) and/or an IR filter film (4).

Description

Optical marker and object detection device

The invention relates to an optical marker having a code pattern of differently reflecting surfaces and to an object detection device having an image capture device and an optical marker.

The optical marker can be used as part of a tracking or tracing method. Here, the marker is attached to an object, whereby it is recognizable, for example, in terms of nature, position and movement for an image capture system.

The optical marker can also be used in augmented reality systems. Augmented Reality systems use virtual, computer-based begat image content superimposed inserted into real image content. Tracing methods can also be used for positionally superimposing 3D contents with reality. For this purpose, a camera can record the reality, in which case the position and orientation of the camera relative to the object or in space can be determined, for example, by means of the optical markers visible in the scene.

The optical markers can thus be used to be arranged on individual objects, thus making the marked object detectable. By means of the marker and the corresponding code pattern, the type, the position and / or the orientation of the marked object in space can be detected. In an analogous manner, the position in the orientation of the image capture device in space can also be detected if the mark is arranged on a still object in space at a predetermined position.

The code pattern on the marker may, for example, represent an identification code which is coded, for example, via a matrix code. The optical marker tracking system detects these optical markers in the image data stream provided by the camera and calculates the position and rotation (pose) of the camera relative to the markers. Each marker can form its own coordinate system. Later, virtually generated 2D or 3D geometries can be bound to these coordinate systems.

Markers are known which carry a geometric code pattern, for example a checkerboard-like pattern or other geometric shapes, for example crosses. The flat markers, for example made of paper, have two differently reflecting surfaces, whereby the code pattern is formed. As a rule, this is a distinction by color, often with a black and white combination of the code pattern.

DE 10 2004 046 144 A1 describes an augmented reality system in which a space is detected by means of a camera, wherein a flat marker with a geometric code pattern (cross) with differently reflecting surfaces is arranged on a wall as the object of the room to be detected ,

It is an object of the invention to provide an optical marker with a high level of recognizability in a simple production process.

The invention solves the problem with the features of claim 1. Advantageous developments are part of the dependent claims. The optical marker according to the invention has a reflection layer over which lies a masking layer which has recesses for generating the code pattern.

Due to the multi-layer structure, the recognizability of the marker can be increased since the individual layers can be formed from different materials with different reflection properties. At the same time, the preparation of the marker can be carried out in a simple manner, since the layers need only be arranged one above the other, for example by gluing.

To generate the code pattern is the masking layer, which is provided with recesses so that the underlying reflective layer is visible to the outside. Preferably, the reflective layer comprises a retroreflective sheet, in particular a retroreflective sheet. Such a retroreflective sheet reflects incident light substantially in the direction from which it has fallen. This is advantageous so that a light source can be arranged in the spatial vicinity of an image capture device with a coupled light source, so that the image capture device recognizes a bright reflection layer. Thus, most of the light reflected from the retroreflective sheet is directed back to the image capture device where a high-contrast image can be captured. A retroreflective film is described, for example, in DE 696 28 766 T2.

Further preferably, the reflective layer comprises an infrared (IR) filter which is substantially impermeable in the visible region and transmissive in the infrared region. The infrared filter can preferably have a foil-shaped, in particular shiny, design.

When using an infrared filter, it makes sense to use an image capture device in the infrared range, such as an infrared camera. The advantage here is that the object and the marker need not be illuminated in the visible range but only in the infrared range. As a result, an independence from the ambient light and from radiating in the visible range, possibly interfering light sources can be achieved. Most preferably, the reflective layer comprises a retroreflective sheet and an IR filter with the IR filter disposed between the masking layer and the retroreflective sheet. Thus, the retroreflective sheet is not perceived by a viewer because the visible Light from the IR filter is not transmitted. For an infrared camera, however, the retroreflective layer is detectable.

To increase the detectability, the masking layer should therefore reflect less light in the evaluated region, in particular in the IR region, than the reflection layer. Particularly preferably, the masking layer has a matte surface, so that the recognizability of the markers can be increased even under difficult lighting conditions with interfering light sources. The mask of the matt material can thus cover the reflective reflective layer, which is particularly advantageous if a retroreflective layer and / or an infrared filter layer are used, since the latter is usually reflective or shiny, so that the matte masking can be achieved an increased contrast. As a result, less light is reflected by the masking layer than by the reflection layer, whereby the code pattern is generated.

The preferred structure can achieve increased visibility, since, for example, it can be prevented that reflections of a disturbing light source render the pattern unreadable: the matt material of the masking layer can hardly mirror, so that the interfering light source can not exert any influence here. In the case of the retroreflective layer, on the other hand, a maximum brightness is achieved anyway, so that possible disturbing reflections of a light source in the retroreflection are lost.

By suitable selection of reflection layer and masking layer, it can be achieved that the two layers have the same color in the visible range. It is particularly advantageous if the masking layer and the reflection layer are gray and / or black. As a result of that the two layers have the same color, the code pattern in the visible region is essentially not visible. The code pattern of the marker which disturbs the impression of an object can thus be avoided. The marker is preferably monochromatic.

Thus, the appearance of the tracked object is hardly affected by the preferred marker. There is no visual restlessness due to the unusual recognition pattern of the marker. To obtain sufficient stability of the marker, the reflective layer can be carried by a carrier layer. About the carrier layer, the marker can be arranged for example by means of an adhesive to an object. The carrier layer can be rigid or flexible. An object detection device according to the invention has an image capture device, for example a camera, and an already described optical marker, which can be arranged on an object to be detected. Particularly preferably, the image capture device comprises an infrared camera (IR camera). Further preferably, the object detection device further comprises an infrared radiator (IR radiator). Particularly preferably, the infrared radiator is arranged to the image capture device such that it radiates substantially in the direction of the viewing direction of the image capture device. This can be achieved in an advantageous manner in that the infrared emitter is coupled to the image capture device, in particular rigidly coupled, wherein it can be arranged for example directly on the image capture device. An inventive augmented reality system has an object detection device already described, a computer for generating the virtual image contents of the augmented reality and a display device, in particular a monitor. The computer can in this case be connected to the image acquisition device. The optical marker can thus be used according to the invention for an augmented reality system.

A preferred embodiment of the invention will be described with reference to Figures 1 to 3. Show it:

Fig. 1 an optical marker;

FIG. 2 shows the optical marker according to FIG. 1 in an exploded view; FIG.

and

3 shows an object detection device.

FIGS. 1 and 2 show an optical marker 1 with a geometric code pattern C. The marker 1 has a substantially planar design.

2 shows the plate-shaped marker 1 in an exploded view. It comprises a carrier layer 2 made of a flexible material, for example plastic. On the carrier layer 2, a film-shaped, retroreflective layer 3 is arranged.

On the passive, retroreflective sheeting 3, an IR filter foil 4 is arranged, which consists of a black, glossy material. The infra-red filter sheet is transmissive to infrared light, but substantially impermeable in the visible range, so that a viewer does not recognize substantially any reflections of the retroreflective sheeting 3. On the infrared filter film 4, a masking layer 5 is arranged, which consists of a matte, black, opaque material, such as plastic or cardboard. The masking layer 5 has recesses 9, so that at the locations of the recesses 9, the reflection layer 12, consisting of infrared filter film 4 and retroreflective sheeting 3, is visible.

The masking layer 5 thus produces the code pattern C of the optical marker 1 via the corresponding recesses 9. The code pattern C may for example be cut out or punched out of the masking layer 5.

The masking layer 5 does not extend to the edge 6 of the optical marker 1, so that in the edge region 6 of the optical marker 1, in turn, the reflection layer 12 is visible and thus part of the code pattern C.

3 shows an object detection device with an infrared camera 7, which is arranged on a stand 11. Coupled to the camera 7 is an infrared radiator 8, which radiates essentially in the direction of the viewing direction of the image capture device 7. The infrared camera 7 picks up an object 10 to be detected, on which an optical marker 1 of the type already described is arranged. In the visible range, the optical marker 1 is consistently black or gray, so that it can be integrated, for example, on a black surface of the object 10 without impairing the visual impression of the object 10. In the infrared range, however, the code pattern C is visible, so that the object 10 can be detected and tracked. For example, the type of object 10 can be determined via the marker 1. Furthermore, the position, orientation and movement of the object 10 relative to the camera 7 can be detected.

The optical marker can thus be used in augmented reality systems, in which a virtual reality and the reality are combined and partially overlaid. One way of merging real and virtual image data is described, for example, in US Pat. No. 6,166,744. A tracking method is further described in DE 10 2007 060 263 A1.

To the image capture device 7, a computer 13 is connected to detect the marker and to generate the augmented reality, to which a monitor 14 is connected to display the augmented reality.

Reference numerals:

1 optical marker

2 carrier layer

3 retroreflective layer

4 infrared filters

5 masking layer

6 edge of the marker

7 infrared camera

8 infrared emitters

9 recess

10 object

1 1 tripod

12 reflection layer

13 computers

14 monitor

Claims

Patent claims:

1 . Optical marker with a code pattern (C) made of differently reflecting surfaces, characterized by a reflection layer (12), over which lies a masking layer (5) which has recesses (9) for generating the code pattern (C).

2. Marker according to claim 1, characterized in that the reflection layer (12) comprises a retroreflective layer (3).

3. Marker according to claim 1 or 2, characterized in that the reflection layer (12) comprises an IR filter (4).

4. Marker according to claim 3, characterized in that the IR filter (4) is designed in the form of a film, in particular shiny.

5. Marker according to one of the preceding claims, characterized in that the masking layer (5) reflects less light in the visible range than the reflection layer (12).

6. Marker according to one of the preceding claims, characterized in that the masking layer (5) has a matt surface.

7. Marker according to one of the preceding claims, characterized in that the reflection layer (12) has the same color as the

masking layer (5).

8. Marker according to claim 7, characterized in that the masking layer (5) and the reflection layer (12) are gray and / or black.

9. Marker according to one of the preceding claims, characterized in that the reflection layer (12) is supported by a carrier layer (2).

10. Object detection device with an image capture device (7) and an optical marker (1) according to one of the preceding claims for arrangement on an object (10) to be detected.

11. Object detection device according to claim 10, characterized in that the image capture device comprises an IR camera (7).

12. Object detection device according to claim 10 or 1 1, characterized by an IR emitter (8).

13. Object detection device according to claim 12, characterized in that the I radiator (8) radiates essentially in the direction of the viewing direction of the image capture device (7).

Augmented reality system, characterized by an object detection device according to one of claims 10 to 13, a computer (13) for generating virtual image content of augmented reality and a display device, in particular a monitor

(14).

15. Use of an optical marker according to one of claims 1 to 9 for an augmented reality system.