JPH0571936U - Digitizer - Google Patents

Abstract

(57) [Abstract] [Purpose] Effectively compensates the background noise existing in the digitizer tablet plate. A memory means for measuring and storing background noise in advance is provided, and a means for performing an operation for removing the stored background noise when determining the position of the digitizer is provided.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a digitizer which has a position indicator and a tablet, and determines the position coordinate indicated on the tablet surface by the position indicator.

[0002]

[Prior Art]

 There are generally many types of such digitizers. For example, there are a so-called electromagnetic coupling type in which a large number of loop coils are arranged on the tablet surface, and a so-called electrostatic coupling type in which a large number of electrodes are arranged on the tablet surface.

[0003]

[Problems to be solved by the device]

 In such a digitizer, it is desirable that the position detecting elements such as loop coils and electrodes are regularly arranged in the X direction, the Y direction, or both directions. For example, in the case of an electromagnetic coupling type digitizer in which a loop coil group is arranged on a tablet, an induced voltage is generated in the loop coil group as a position detecting element based on the magnetic field transmitted from the position indicator. Each of these induced voltages is proportional to the distance between the loop coil group and the position indicator. Therefore, when such position detecting elements have variations, an error occurs in the coordinate signals output from these digitizers. The present invention aims to improve this point.

[0004]

[Means for Solving the Problems]

 Therefore, in the present invention, the digitizer having a position indicator capable of indicating an arbitrary position on the tablet surface and outputting a coordinate signal related to the position indicated by the position indicator stores the background noise of the tablet. A noise holding means for holding and a processing means for processing the coordinate signal based on the background noise stored in the noise holding means are provided, and when the digitizer determines the pointing position coordinates of the position pointing device, The background noise held by the noise holding means is removed.

[0005]

[Action]

 The background noise described above is caused by various factors such as the interaction of these position detection elements, such as when there are variations in the position detection elements arranged on the tablet or non-uniformity of the arrangement interval. I think that the. These background noises are considered to be some noise in these digitizers. According to the experiment, in the digitizer in which the position detecting elements (X1, X2, X3, ..., Xn) are arranged, background noise (dotted line in the figure) as shown in FIG. 5 was observed. . These background noises can be considered constant as a whole. Therefore, an accurate coordinate signal can be obtained by subtracting this background noise from the actual detection output (solid line in the figure).

[0006]

【Example】

 1 to 4 are digitizers relating to a device of one embodiment of the present invention, which are cordless electromagnetic coupling type digitizers in which a so-called position indicator does not have a power source or the like. Fig. 1 shows the overall configuration of this digitizer, Fig. 2 shows the procedure for creating correction data created based on background noise, and Fig. 3 shows the procedure for applying this correction data to the position determination operation. FIG. 4 is a schematic diagram of storing and holding background noise. In FIG. 1, 1 is a receiving coil group arranged in the X direction as a position detecting element (only one is shown in the figure), and 2 is similarly arranged in the Y direction as a position detecting element. A transmitter coil group (only one is shown in the same manner), 32 is a switch, 33 is an alternating current source, 42 is a switch, 43 is an amplifier, 44 is an analog digital converter ADC, 51 is a CPU 52 is a memory, and 6 is a position indicator having a coil 61 and a load 62.

The transmitter coil group 2 is sequentially switched at predetermined intervals by the switch 32 under the control of the CPU 51. An alternating current source 33 sequentially supplies an alternating current to each oscillator coil 2. Therefore, a predetermined magnetic field is generated from each transmitting coil 2 and interacts with the coil 61 of the position indicator 6 to affect each receiving coil group 1 to induce a predetermined voltage in each receiving coil. The switch 42 sequentially switches each receiving coil 1 and connects it to the amplifier 43, and the ADC 43 detects the magnitude of the induced voltage of each receiving coil 1. Then, the CPU 51 calculates which voltage is induced in which receiving coil group 1 when a predetermined AC current is supplied to which transmitting coil group 2 to detect the position coordinate indicated by the position indicator 6. You can

By the way, in such a digitizer in which a plurality of position detecting elements are arranged on the tablet surface, background noise is generated as shown in FIG. 3 due to an arrangement interval or variation of these position detecting elements. Therefore, the apparatus of this embodiment has a memory 52 for storing and holding the background noise measured in advance for use in the coordinate determining operation.

The operation of storing the background noise can be performed before shipping the digitizer, for example. The measurement and storage operation of this background noise is performed in the following procedure. First, the position indicator 6 is not placed on the tablet surface. Next, a predetermined alternating current is supplied to the first transmitting coil 2 and the voltage appearing in each receiving coil group 1 at that time is measured and stored in the memory 52 as background noise based on the first transmitting coil 2. Then, the same operation is performed on the second transmitting coil 2, and the background noise based on the second transmitting coil 2 is stored in the memory 52. The whole background noise can be stored by successively performing this measurement and storage operation for each transmission coil 2. By this operation, the background noise is stored in the memory 52 as shown in FIG. In addition, in FIG. 4, (x1y 1) represents the detection voltage of the first receiving coil x1 when the alternating current is supplied to the first transmitting coil y1, and similarly (xnym) is the alternating current to the m-th transmitting coil 2. The voltage appearing in the n-th receiver coil 1 when is supplied is shown.

Further, in such a case, there may be variations in the sensitivity and the like of the electric components due to the ambient temperature during actual use or changes over time. Therefore, in the apparatus of this embodiment, the correction data to be actually used is created through the procedure shown in FIG. This correction data is created, for example, when the power is turned on. In step 1, when the power of the device is turned on, creation of correction data is started. In step 2, for example, the reception voltage is measured for five predetermined points (i1j1), (i2j2), (i3j3), (i4j4), and (i5j5) indicated by reference characters A to E in FIG. The measurement of the point indicated by symbol A is to measure the voltage appearing in the i1th receiving coil 1 when an alternating current is supplied to the j1th transmitting coil 2. Then, in step 3, if there is any abnormal measurement data among these five points, that data is excluded. That is, the position indicator 6 may be placed on the tablet, but this step is to eliminate the measurement result in such a state. The effective points of these five measurement data are compared with the background noise of each corresponding point stored in advance in the memory 52. (Step 5) Based on these comparison results, correction data is created in step 6. As the correction data, it is possible to average differences between points and add the average value over the entire background noise values preliminarily stored in the memory 52.

Next, the position determining operation of the digitizer will be described with reference to FIG. In step 2 of FIG. 3, alternating currents are sequentially supplied (driven) to the transmitting coil group 1 in an appropriate order, and the induced voltage of each receiving coil 1 is detected at the alternating current supply timing of each transmitting coil. When a large voltage is detected in step 3, the device recognizes that the position indicator exists in the vicinity thereof, and in step 4, the order of the drive transmission coil and the reception coil at that time is specified. In step 5, a plurality of adjacent transmitting coil groups and receiving coil groups including the specified transmitting coil and receiving coil are selected. In step 6, background noise of each measurement point selected in step 4 and its correction data are extracted. By performing this extraction, only the necessary points can be corrected and the measurement speed can be improved. Then, in step 7, the induced voltage is measured at each of the selected measurement points and the background noise is corrected. As a result, the correct position coordinates can be determined.

In the apparatus of this embodiment, the background noise of the entire apparatus is measured and stored before the apparatus is shipped. However, the apparatus is used every time the apparatus is used, that is, every time the apparatus is turned on or when necessary. Alternatively, the total background noise may be measured and updated. In this case, the apparatus can be automatically performed by providing a program for measuring and storing background noise that is selectively activated by operating a switch or the like.

[0013]

[Effect of the device]

 As described above, in this invention, the background noise of the digitizer can be effectively compensated, and accurate coordinate values can be obtained.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a digitizer according to the present invention.

FIG. 2 is a flowchart showing a procedure for creating correction data created based on background noise.

FIG. 3 is a flowchart showing a procedure of applying the correction data to a position determining operation.

FIG. 4 is a schematic diagram of storing and holding background noise.

FIG. 5 is an explanatory view schematically showing the principle of this invention.

[Explanation of symbols]

 1: reception coil group 2: transmission coil group 51: CPU 52: background noise memory

Claims (1)

[Scope of utility model registration request] 1. A digitizer having a position pointing device capable of pointing an arbitrary position on a tablet surface and outputting a coordinate signal related to the pointing position of the position pointing device, wherein noise for storing and holding background noise of the tablet is provided. Holding means and processing means for processing the coordinate signal based on the background noise stored in the noise holding means are provided, and the noise holding means is used when the digitizer determines the pointing position coordinates of the position indicator. Digitizer configured to remove background noise held by.