Telegraphy – Systems – Position coordinate determination for writing
Reexamination Certificate
2001-03-21
2004-02-10
Hjerpe, Richard (Department: 2674)
Telegraphy
Systems
Position coordinate determination for writing
C178S018030, C178S018090, C178S019010, C345S173000, C345S179000, C235S494000, C382S188000, C382S299000, C382S314000
Reexamination Certificate
active
06689966
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to pattern recognition and specifically relates to devices and methods relating to surfaces having a coding pattern available for analysis.
BACKGROUND OF THE INVENTION
In many contexts, it is desirable to be able to determine an absolute position on a surface. One example is in the digitization of drawings. Another example is when it is desirable to produce an electronic version of handwritten information. In these and other contexts in which position determination is performed, it is often desirable to use a computer program in cooperation with an input device to carry out calculations related to position determination.
U.S. Pat. No. 5,852,434, for example, discloses a device for determining an absolute position. The device includes a writing surface having a position-coding pattern used to determine X/Y coordinates, a detector for detecting the position-coding pattern and a processor for determining the position of the detector in relation to the writing surface based on the detected position-coding pattern. The device makes it possible for a user to input handwritten and hand-drawn information into a computer at the same time as the information is written/drawn on the writing surface.
A number of examples of position coding are given in U.S. Pat. No. 5,852,434. The first example shows symbols built up of three concentric circles, with the outermost circle representing the x-coordinate and the middle one representing the y-coordinate. The two outermost circles are further divided into 16 parts that specify different numbers depending on their fill pattern. Each pair of x/y coordinates is coded with a complex symbol having a special appearance. In the second disclosed example, the coordinates at every point on the writing surface are identified with the aid of a bar code, a bar code for the x-coordinate being specified above a bar code for the y-coordinate.
Devices in the prior art used for this type of detection are generally constructed to register four symbols at the same time ensuring a reliably capture of at least one symbol in its totality. This capture is necessary for the device to perform the position determination.
The prior art summarized above does not disclose, for example, a computer program used in cooperation with an input device to perform calculations related to the position determination because generally only position information is processed. The prior art has further shortcomings because the patterns used are built up of complex symbols, the information content of that indicates the actual positions. The smaller these symbols are the more difficult it becomes to produce the patterned writing surface, while increasing the risk of erroneous position determinations. On the other hand, the use of larger the symbols decreases the position resolution.
In Applicant's International Patent Application WO 00/73983, which was filed on Oct. 1, 1999 and which was not publicly available when the present application was filed and therefore does not constitute prior art, a position coding pattern is described. Moreover reference is also made to PCT/SE00/01895 and WO 01/16691, the contents of which are included by reference.
A solution therefore is required to overcome the deficiencies of the prior art.
SUMMARY OF A FEW ASPECTS OF THE INVENTION
Systems and methods consistent with the present invention may have coding patterns with a number of spatial levels and utilizing the spatial levels.
It is an object of the present invention to remedy the abovementioned deficiencies of prior art completely or partially.
More specifically, the invention relates to a product that has a surface that is provided with a coding pattern that comprises symbols that have at least two different values. The invention is characterized in that each symbol comprises a raster point and at least one marking, that the raster point is included in a raster which extends over the surface; that the value of each symbol is indicated by the location of said marking in relation to a raster point and that at least one marking comprises marking information.
In prior art, each position is coded with a complex symbol, the complete information content of which is needed for specifying position information. According to the invention, instead, a symbol is used the value of which is specified by the location of a marking in relation to a raster point. There is thus one type of symbol for each value. A device which will carry out the position determination therefore only needs to detect the occurrence of one marking. Moreover, a position-determining device according to the invention can distinguish between different markings and thereby acquire further information related to, for example, the position in question. This further marking information can advantageously vary depending on the position that is determined.
The design of the symbol according to the invention also entails that a surface which is provided with a coding pattern according to the invention becomes more aesthetically pleasing.
Furthermore, a large distance between the markings in relation to the position-information density is made possible, which has the result that the coding becomes less sensitive to movement blur.
The symbols described above can be used for coding any type of information but are advantageously used for coding positions and position-related further information via the markings of the symbols. As mentioned, in prior art each position is coded with a single symbol that therefore must be rather complex. According to the invention, on the other hand, each position can be coded with a plurality of symbols. Each individual symbol can thus be made less complex and thus simpler to detect with higher reliability.
According to the invention, the position information and position-related information are separated in that the markings of the symbols contain different types of information depending on which spatial resolution is taken into consideration. In a first spatial resolution level, the markings of the symbols are only used for specifying position information. By taking into consideration further spatial resolution levels that are higher than the first one, the further information can be coded and retrieved from the markings. An obvious advantage of this separation of information into different spatial resolution levels is that, even if reading the markings entails loss of detail information, at least the information which has been stored with the lowest spatial resolution, i.e. the existence of the markings itself, can be utilized. This will also prove to be advantageous when considering reading devices and their capability of reading information of different spatial resolution, as will be discussed further below.
In prior art, each position is coded with a symbol that is “isolated” from symbols of the surrounding positions. The position resolution is thus limited by the surface occupied by the symbol of a position. The position-coding pattern according to the invention can be built up in corresponding manner, each position being coded by an “isolated” group of symbols. In a preferred embodiment of the invention, however, each symbol contributes to the coding of more than one position. In this manner, a “floating” transition between different positions is obtained. In other words, each position is coded partly by the same symbols as the adjoining positions. The floating coding is advantageous since it makes it possible to increase the position resolution. Furthermore, it is possible to reduce the relationship between, on the one hand, the number of symbols which a position-determining device must register in order to be able to carry out a position determination reliably and, on the other hand, the number of symbols which code a position.
In a preferred embodiment, each symbol contributes to the coding of both a first and a second position coordinate. Thus, different symbols are not needed for the different coordinates, which make the position code simpler and the positi
Anoto AB
Hjerpe Richard
Tran Henry N.
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