Marker for optical tracking, optical tracking system, and optical tracking method
The present disclosure provides a marker with a pattern formed thereon, which includes an optical system. At least a part of the pattern that uniquely appears depending on a direction in which the pattern is viewed from an outside of the marker through the optical system, is visually identified from the outside of the marker. The pattern includes a plurality of rows of binary-coded sequences. The binary-coded sequence of each of the plurality of rows includes aperiodic sequences that are repeatedly arranged. The aperiodic sequences included in the binary-coded sequence of one row of the plurality of rows are different from the aperiodic sequences included in the binary-coded sequence of another row of the plurality of rows, and each of the aperiodic sequences includes a plurality of sub-sequences that are arranged in a predetermined order.
1. A marker with a pattern formed thereon, comprising:
an optical system, wherein:
at least a part of the pattern that uniquely appears depending on a direction in which the pattern is viewed from an outside of the marker through the optical system, is visually identified from the outside of the marker;
the pattern includes a plurality of rows of binary-coded sequences;
the binary-coded sequence of each of the plurality of rows includes aperiodic sequences that are repeatedly arranged;
the aperiodic sequences included in the binary-coded sequence of one row of the plurality of rows are different from the aperiodic sequences included in the binary-coded sequence of another row of the plurality of rows; and
each of the aperiodic sequences includes a plurality of sub-sequences that are arranged in a predetermined order.
2. The marker according to claim 1 , wherein the plurality of rows of binary-coded sequences include a first binary-coded sequence and a second binary-coded sequence that are adjacent in a column direction, and
wherein a number of bits of each of the sub-sequences included in the first binary-coded sequence is different from a number of bits of each of the sub-sequences included in the second binary-coded sequence.
3. The marker according to claim 2 , wherein the pattern further include a third binary-coded sequence positioned in a m-th row from the first binary-coded sequence in the column direction and a fourth binary-coded sequence positioned in the m-th row from the second binary-coded sequence in the column direction,
wherein the aperiodic sequence included in the third binary-coded sequence is equal to the aperiodic sequence included in the first binary-coded sequence, and the aperiodic sequence included in the fourth binary-coded sequence is equal to the aperiodic sequence included in the second binary-coded sequence, and
wherein m is a natural number of 2 or more.
4. The marker according to claim 3 , wherein the pattern includes:
a first sequence group including the first and second binary-coded sequences;
a second sequence group including the third and fourth binary-coded sequences; and
a meta-sequence configured to separate the first and second sequence groups from each other.
5. The marker according to claim 4 , wherein the meta-sequence is different from the binary-coded sequences that are included in the first and second sequence groups.
6. The marker according to claim 5 , wherein the meta-sequence is a sequence in which different binary codes are alternately repeated, or is comprised of only the same binary code.
7. The marker according to claim 1 , further comprising a pattern plane on which the pattern is formed,
wherein different binary codes that are included in the binary-coded sequences of the pattern formed on the pattern plane are made of materials that have different reflectivities from each other.
8. The marker according to claim 1 , further comprising a pattern plane on which the pattern is formed,
wherein the optical system includes a lens, and the pattern is formed in a portion where a focal point of the lens is formed on the pattern plane.
9. The marker according to claim 8 , wherein the pattern plane has a flat or curved surface, and the lens allows the focal point to be formed on the flat or curved surface.
10. The marker according to claim 1 , wherein the aperiodic sequence is a PRBS (Pseudo-Random Binary Sequence) or De Bruijn Sequence.
11. The marker according to claim 1 , wherein if at least a part of the pattern is captured as a pattern image in the outside of the marker, a size of a region where at least a part of the pattern is captured on the pattern image varies with at least one of a distance from a location in which the pattern image is captured to the marker or a location of the marker.
12. An optical tracking system comprising:
one or more markers on which a pattern is formed;
one or more capturing units configured to include one or more capturing elements that obtains a pattern image of the pattern; and
a processor configured to track locations and postures of the one or more markers based on information that is extracted from at least a part of the pattern included in the pattern image, wherein:
the pattern includes a plurality of rows of binary-coded sequences; the binary-coded sequence of each of the plurality of rows includes aperiodic sequences that are repeatedly arranged; the aperiodic sequences included in the binary-coded sequence of one row of the plurality of rows are different from the aperiodic sequences included in the binary-coded sequence of another row of the plurality of rows; and each of the aperiodic sequences includes a plurality of sub-sequences that are arranged in a predetermined order.
13. The optical tracking system according to claim 12 , wherein the optical tracking system extracts one or more sequence blocks from the pattern image and then tracks the one or more markers, and wherein the one or more sequence blocks include a part of the plurality of rows of binary-coded sequences.
14. The optical tracking system according to claim 13 , wherein the one or more sequence blocks have a size of j×1 in which j denotes a number of binary-coded sequences that are included in the one or more sequence blocks and 1 denotes a number of bits of a longest sub-sequence among the plurality of sub-sequences included in the one or more sequence blocks.
15. The optical tracking system according to claim 13 , wherein the processor determines postures or IDs of the one or more markers based on the one or more sequence blocks.
16. The optical tracking system according to claim 15 , wherein the part of the plurality of rows of binary-coded sequences are sub-sequences that are included in each of the plurality of rows of binary-coded sequences, and
wherein the processor determines a location of a sub-pattern represented by the one or more sequence blocks in the pattern based on the sub-sequences, and determines the postures of the one or more markers based on the location of the sub-pattern.
17. The optical tracking system according to claim 15 , wherein the part of the plurality of rows of binary-coded sequences are sub-sequences that are included in each of the plurality of rows of binary-coded sequences, and
wherein the processor determines location information on the one or more sequence blocks in the plurality of binary-coded sequences based on the sub-sequences, and determines the IDs of the one or more markers based on the location information.
18. The optical tracking system according to claim 12 , wherein the one or more capturing units include two or more capturing units, or the one or more capturing elements include two or more capturing elements, and
wherein the processor determines the locations of the one or more markers based on triangulation by using pattern images that are obtained by the two or more capturing units or by the two or more capturing elements.
19. The optical tracking system according to claim 18 , wherein the processor determines the locations of the one or more markers based on central coordinates of a region of the pattern on each of the pattern images and triangulation by using a geometric relationship between directions in which the two or more capturing units or the two or more capturing elements view the one or more markers.
20. The optical tracking system according to claim 12 , wherein the processor determines the locations of the one or more markers based on a size of a region of the pattern and central coordinates of the pattern region, on the pattern image obtained by the one or more capturing units.
21. The optical tracking system according to claim 12 , wherein the one or more markers include two markers that has a predetermined geometric relationship,
wherein the capturing units capture pattern images of patterns that are formed on the two markers, respectively, and
wherein the processor determines the locations of the two markers based on the predetermined geometric relationship and a relationship between a location of at least a part of the patterns on the pattern images and a location of at least a part of the pattern on each of the markers.
22. The optical tracking system according to claim 12 , wherein the plurality of rows of binary-coded sequences include a first binary-coded sequence and a second binary-coded sequence that are adjacent in a column direction, and
wherein a number of bits of each sub-sequence included in the first binary-coded sequence is different from a number of bits of each sub-sequence included in the second binary-coded sequence.
23. The optical tracking system according to claim 22 , wherein the pattern further includes a third binary-coded sequence positioned in a m-th row from the first binary-coded sequence in the column direction and a fourth binary-coded sequence positioned in the m-th row from the second binary-coded sequence in the column direction,
wherein the aperiodic sequence included in the third binary-coded sequence is equal to the aperiodic sequence included in the first binary-coded sequence, and the aperiodic sequence included in the fourth binary-coded sequence is equal to the aperiodic sequence included in the second binary-coded sequence, and
wherein m is a natural number of 2 or more.
24. The optical tracking system according to claim 12 , wherein the one or more markers include a first lens,
wherein the pattern is implemented on a pattern plane on which a focal point of the first lens is formed, and
wherein the one or more capturing units include a second lens that is configured such that at least a part of the pattern, which is visually identified from the one or more markers in a direction in which the capturing units view the one or more markers through the first lens, is captured on the one or more capturing elements, and obtains a pattern image of at least a part of the pattern in a focal length of the second lens.
25. The optical tracking system according to claim 24 , further comprising a light source configured to emit light onto the one or more markers in order to enhance the light incident on the second lens through the first lens with respect to at least a part of the pattern.
26. An optical tracking method for tracking a marker on which a pattern is formed, the method comprising:
obtaining, by one or more capturing elements included in one or more capturing units, a pattern image of at least a part of the pattern; and
proceeding, by a processor, information extracted from at least a part of the pattern included in the pattern image and tracking a location and a posture of the marker, wherein:
the pattern includes a plurality of rows of binary-coded sequences; the binary-coded sequence of each of the plurality of rows includes aperiodic sequences that are repeatedly arranged; the aperiodic sequences included in the binary-coded sequence of one row of the plurality of rows are different from the aperiodic sequences included in the binary-coded sequence of another row of the plurality of rows; and each of the aperiodic sequences includes a plurality of sub-sequences that are arranged in a predetermined order.
27. The method according to claim 26 , wherein the tracking the location and the posture of the marker comprises extracting one or more sequence blocks from the pattern image, and wherein the one or more sequence blocks have a size of j×1 in which j denotes a number of binary-coded sequences that are included in the one or more sequence blocks and 1 denotes a number of bits of a longest sub-sequence among the sub-sequences included in the one or more sequence blocks.
28. The method according to claim 27 , wherein the tracking the location and the posture of the marker comprises determining the posture of the marker based on the one or more extracted sequence blocks.
29. The method according to claim 28 , wherein the determining the posture of the marker comprises:
determining a location of a sub-pattern represented by the one or more sequence blocks in the pattern based on the sub-sequences that are included in each of the plurality of rows of binary-coded sequences that are included in the one or more sequence blocks; and
determining the posture of the marker based on the determined location of the sub-pattern.
30. The method according to claim 26 , wherein the one or more capturing units include two or more capturing units, or the one or more capturing elements include two or more capturing elements, and
wherein the tracking the location and the posture of the marker comprises determining the location of the marker based on triangulation by using pattern images that are obtained by the two or more capturing units or by the two or more capturing elements.
31. The method according to claim 30 , wherein the determining the location of the marker based on the triangulation comprises determining the location of the marker based on central coordinates of the pattern region on each of the pattern images and triangulation by using a geometric relationship between directions in which the two or more capturing units or the two or more capturing elements view the marker.
32. A computer-readable recording medium that stores a program that includes instructions for executing operations of the optical tracking method according to claim 26 .