GB2179152A - Coordinate reading apparatus - Google Patents
Coordinate reading apparatus Download PDFInfo
- Publication number
- GB2179152A GB2179152A GB08619521A GB8619521A GB2179152A GB 2179152 A GB2179152 A GB 2179152A GB 08619521 A GB08619521 A GB 08619521A GB 8619521 A GB8619521 A GB 8619521A GB 2179152 A GB2179152 A GB 2179152A
- Authority
- GB
- United Kingdom
- Prior art keywords
- coordinate
- tablet base
- reading apparatus
- elastic waves
- coordinate reading
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Classifications
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
- G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
- G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
- G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
- G06F3/043—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means using propagating acoustic waves
- G06F3/0433—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means using propagating acoustic waves in which the acoustic waves are either generated by a movable member and propagated within a surface layer or propagated within a surface layer and captured by a movable member
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S5/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
- G01S5/18—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using ultrasonic, sonic, or infrasonic waves
Landscapes
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- General Engineering & Computer Science (AREA)
- General Physics & Mathematics (AREA)
- Theoretical Computer Science (AREA)
- Acoustics & Sound (AREA)
- Human Computer Interaction (AREA)
- Radar, Positioning & Navigation (AREA)
- Remote Sensing (AREA)
- Position Input By Displaying (AREA)
- Length Measuring Devices Characterised By Use Of Acoustic Means (AREA)
Abstract
A coordinate reading apparatus comprises a metal or glass tablet base (31), converters (33,34,35,36) provided on peripheral portions of the tablet base, and a coordinate indicator (37) having means for generating elastic waves which are propagated through the tablet base and then received by the converters, which convert them into electrical signals. Signal processing circuitry and counters feed information to a coordinate computing circuit (Fig. 2, not shown). A reflection-preventing member (32) of rubber, aluminium or polyvinyl chloride surrounds the tablet base periphery. The coordinate indicator (37) includes two vibrators sandwiching an electrostrictive element, (Fig. 5, not shown). <IMAGE>
Description
SPECIFICATION
Coordinate reading apparatus
This invention relates to a coordinate reading apparatus.
One known apparatus for detecting coordinates by utilising elastic waves is disclosed in "IEEE Transactions on Electronic Computers"
October 1964, pages 609-611. A schematic diagram of of this apparatus is shown in Figure 1. A pulse signal is applied to converters 2,3 provided on edge portions of a tablet base 1, to generate elastic waves or elastic surface waves and simultaneously to trigger a counter 4. Elastic waves or elastic surface waves propagated through the tablet base 1 are picked up by a coordinate indicator 5 and processed by a signal processing circuit 7 thereby to trigger the counter 4 and complete its counting operation. The content of the counter 4 is proportional to the time of propagation of the elastic waves or elastic surface waves.Accordingly if the clock frequency of the counter 4 is suitably selected, the positional coordinates of the coordinate indicator 5 can be determined.
However, in this known coordinate reading apparatus it is necessary that, in order to read each coordinate, the converters 2,3 on the Xand Y-axes are driven alternately by pulses so as to apply X-axis elastic waves and Y-axis elastic waves alternately to the tablet base 1.
Therefore, it requires a relatively long period of time to read a coordinate (i.e. the sampling rate is low). This causes the omission of input coordinates in the case where coordinate values are input as they are continuously varied (for example, in the case where handwritten letters are input). For example, if the coordinate reading apparatus is used with handwritten letters input at a high handwriting speed, the number of sampling points decreases and omissions occur in the writing stroke information. As a result, if the writing stroke is displayed, omission occurs in what is displayed and, in the case where pattern recognition takes place, there is a decrease in the pattern recognition rate.
Furthermore, the known coordinate reading apparatus uses a signal representative of a combination of a plurality of types of waves, that is emitted elastic waves or elastic surface waves (hereinafter referred to as "elastic waves"), i.e. waves advancing straight toward the coordinate indicator and waves reflected once on the edge portions of the tablet base, and then reaching the coordinate indicator.
Therefore, the waveform of the signal is very complicated, and the coordinate reading accuracy becomes low. Moreover, the coordinate resolving power and stability are not satisfactory.
Although the present invention is primarily directed to any novel integer or step, or combination of integers or steps, herein disclosed and/or as shown in the accompanying drawings, nevertheless, according to one particular aspect of the present invention to which, however, the invention is in no way restricted, there is provided a coordinate reading apparatus comprising: a tablet base; converter means provided on peripheral portions of the tablet base; and a coordinate indicator having means for generating elastic waves which are propagated through said tablet base and received by said converter means.
In the preferred embodiment said coordinate indicator consists of an electrostrictive element sandwiched between vibrator means.
Said electrostrictive element and vibrator means may be of circular cross-section, the diameter of the electrostrictive element being equal or less than that of the vibrator means.
Preferably the coordinate reading apparatus includes a reflection-preventing member around at least a portion of the periphery of the tablet base for absorbing elastic waves.
According to a further non-restrictive aspect of the present invention there is a provided a coordinate reading apparatus comprising: a tablet base; means for generating elastic waves in the tablet base; and a reflectionpreventing member around at least a portion of the periphery of the tablet base for absorbing elastic waves.
Said reflection-preventing member may consist of a material the acoustic impedance value of which is substantially equal to that of said tablet base.
The invention is illustrated, merely by way of example, in the accompanying drawings, in which:
Figure 1 is a schematic diagram of a known coordinate reading apparatus;
Figure 2 is a schematic diagram of a coordinate reading apparatus according to the present invention;
Figure 3 shows a perspective view of a tablet base of a coordinate reading apparatus according to the present invention;
Figure 4a illustrates the waveform of a signal obtained in a coordinate reading apparatus which is not provided with a reflection-preventing member;
Figure 4b illustrates the waveform of a signal obtained in a coordinate reading apparatus according to the present invention which is provided with a reflection-preventing member;
Figure 4c illustrates the driving waveform of a vibrator of a coordinate reading apparatus according to the present invention; and Figure 5 shows the construction of a coordinate indicator of a coordinate reading apparatus according to the present invention.
An embodiment of a coordinate reading apparatus according to the present invention will now be described with reference to Figure 2. A tablet base 21 consists of a homogeneous, isotropic material, such as metal or glass and is used to propagate elastic waves therethrough. A coordinate indicator 22 contains an elastic wave generating electrostrictive element, which is connected to-one output terminal of a signal generating circuit 23.
Another output terminal of the signal generating circuit 23 is connected to a start trigger input terminal of a counter 24. Converters 25,26,27,28 are provided at corners of the upper surface of the tablet base 21 and adapted to receive elastic waves and convert the same into electrical signals.
The converters 25,26,27,28 are electrically connected to an input terminal of a signal processing circuit 29 an output terminal of which is connected to a stop trigger input terminal of the counter 24. An output terminal of the counter 24 is connected to an input terminal of a coordinate computing circuit 30. In Figure 2, one signal processing circuit 29 and one counter 24 are shown so as to prevent the drawing from becoming too complicated but, in practice, the converters 25,26,27,28 are connected to their respective signal processing circuits 29 and counters 24.
In this coordinate reading apparatus, a pulse signal for generating elastic waves is generated in the signal generating circuit 23 and applied to the coordinate indicator 22. A signal, which is synchronous with the rise of this pulse signal, is generated in the signal generating circuit 23 to trigger the counter 24 which starts to count. In the coordinate indicator 22 which receives the pulse signal, the electrostrictive element is vibrated to generate elastic waves.
The elastic waves are propagated through the tablet base 21 to reach the converters 25,26,27,28, in which the elastic waves are converted into electrical signals, which are then input into the signal processing circuit 29. In the signal processing circuit 29, the input signals are amplified and subjected to noise elimination and waveform shaping, and a signal representative of these signals is sent from the signal processing circuit 29 to the stop trigger input terminal of the counter 24.
The counter 24 stops counting, and holds a count which is proportional to the tme of propagation of the elastic waves. This information is subjected to computation in the coordinate computing circuit 30 to determine the distance data (corresponding to an object coordinate) between the coordinate indicator 22 and the converter. Data on the distances between the coordinate indicator and each of the converters, which have their respective signal processing circuits and counters (which are not shown in the drawings) are input into the coordinate computing circuit 30, and coordinate values are calculated by using the distance data from all the converters.
It will be appreciated that it is unnecessary that elastic waves are generated in X- and Yaxes alternately for the purpose of reading each coordinate. Consequently, coordinate sampling rate is improved.
Figure 3 shows an embodiment of a tablet base of a coordinate reading apparatus according to the present invention with a reflection-preventing member 32. A homogeneous, isotropic tablet base 31 consists, for example, of glass. The reflection-preventing member 32 consists of a material the acoustic impedance of which is substantially equal to that of the tablet base 31, and is disposed around the edges of the tablet base.
When glass is used for the tablet base 31, the material of the reflection-preventing member 32 is selected as follows. The acoustic impedance of a quartz glass tablet base is 1.45 X 106 AC-ohm. Thus the material the acoustic impedance of which is nearly equal to this is selected for the reflectionpreventing member. Materials satisfying this condition include rubber (having an acoustic impedance of 1.47 X 106 AC-ohm), aluminium (having an acoustic impedance of 1.69 X 106 AC-ohm) and polyvinyl chloride (having acoustic impedance of 1.74 X 106 AC-ohm). Rubber, aluminium and polyvinyl chloride all have high economic efficiency and processability and are excellent reflection-preventing materials.
The reflection-preventing material 32 preferably covers the whole circumference of the tablet base 31 but, even if portions of the edges are exposed, it will still have a sufficiently high reflection-preventing effect.
The reflection-preventing member 32 may be attached to the tablet base 31 using a bonding agent or by mechanical pressure.
In this coordinate reading apparatus elastic waves are emitted from a coordinate indicator 37 and received at converters 33,34,35,36.
The converters 33,34,35,36 are of the same material, have the same shape, and are provided on the upper surface of the tablet base 31 on the inner side of the reflection-preventing material 32.
The converters 33,34,35,36 may be provided on either surface of the tablet base 31.
The material used to form the converters 33,34,35,36 is a material having electrostrictive characteristics, for example, barium titanate or lead titanate zirconate. The coordinate indicator 37 contains a vibrator to generate elastic waves. When the vibrator is vibrated with the free end of the coordinate indicator 37 contacting the tablet base 31, elastic waves are generated in the coordinate indicator 37. The elastic waves are input into the tablet base 31 through the free end of the coordinate indicator 37 and propagated through the tablet base 31 to reach the converters 33,34,35,36. The vibrator is formed of a material having electrostrictive characteristics, for example, a barium titanate or lead titanate zirconate. The vibrator is operated by applying a burst pulse voltage thereto.
The waveform of a signal received at one of the converters 33,34,35,36 is shown in Figure 4b. In order to compare the effect of the coordinate reading apparatus according to the present invention with that of the known coordinate reading apparatus having no reflection-preventing member, the corresponding waveform is shown in Figure 4a. It will be appreciated that the signal in the coordinate reading apparatus with the reflection-preventing member has a smaller number of components and a "clean" waveform as compared with the. signal when no reflection-preventing member is provided. This is ascribed to the capability of the reflectionpreventing member at the edges of the tablet base absorbing the elastic waves so as to prevent the reflection thereof.
In the above-described embodiment, glass is used for the tablet base. Other materials may be used for the tablet base, as long as the reflection-preventing member consists of a material the acoustic impedance of which is substantially equal to that of the tablet base.
In the above described embodiment, the elastic waves are emitted from the coordinate indicator and received at the converters. Conversely, the elastic waves can be emitted from the converters and received at the coordinate indicator.
Figure 5 shows an example of a coordinate indicator of a coordinate reading apparatus according to the present invention. A vibrator (A) 41 is formed by conically shaping one end portion of a cylinder. At the other end of the vibrator 41 there is an electrostrictive element 42. A vibrator (E) 43 is provided on the surface of the electrostrictive element 42 which surface is opposite to the surface on which the vibrator 41 is provided. In other words, the coordinate indicator is constructed so that vibrators 41,43 hold or sandwich the electrostrictive element 42 therebetween. Lead wires 44 are connected to electrostrictive element 42, a pulse signal being applied to the coordinate indicator through the lead wires.
With this construction of coordinate indicators, elastic waves can be produced with a high efficiency for the reasons given below.
If the coordinate indicator merely consisted of the vibtrator 41 or the vibrator 43 and the electrostrictive element 42, the signal applied to the electrostrictive element would cause the vibrator to produce elastic waves and also transmit energy to the surrounding air from the surface not in contact with the vibrator.
The energy transmitted to the air is, of course, lost. By sandwiching the electrostrictive element 42 between two vibrators 41,43 the elastic waves generated by the vibrator 43 are reflected from the end surface opposite to the end surface on which the electrostrictive element is provided, and then transmitted to the vibrator 41. As a result, the oscillation of the electrostrictive element can be transmitted efficiently to the tablet base.
When the diameter of the electrostrictive element 42 is larger than that of the vibrators 41,43, the electrostrictive element 42 necessarily has parts contacting the vibrators and parts not contacting the vibrators. This causes a plurality of vibration modes to occur, and the elastic waves generated have a complicated waveform. Consequently, it becomes difficult to carry out signal processing operations. Accordingly, the electrostrictive element 42 preferably is formed to have a diameter not larger than that of the vibrators 41,43.
As described above, the coordinate reading apparatus of to the present invention is constructed simply, and adapted to generate elastic waves in the coordinate indicator, which are then received by the converters, which are provided at the corners of the tablet base.
Accordingly, producing elastic waves for determining X- and Y- coordinates separately is not required. This enables the sampling rate to be improved. Furthermore, by providing the reflection-preventing member of a material whose acoustic impedance is substantially equal to that of the tablet base, on the edge portions of the tablet base, enables unwanted waveforms to be removed, and to simplify signal processing.
Claims (10)
1. A coordinate reading apparatus comprising: a tablet base; converter means provided on peripheral portions of the tablet base; and a coordinate indicator having means for generating elastic waves which are propagated through said tablet base and received by said converter means.
2. A coordinate reading apparatus as claimed in claim 1 in which said coordinate indicator consists of an electrostrictive element sandwiched between vibrator means.
3. A coordinate reading apparatus as claimed in claim 2 in which said electrostrictive element and vibrator means are of circular cross-section, the diameter of the electrostrictive element being equal to or less than that of the vibrator means.
4. A coordinate reading apparatus as claimed in any preceding claim including a reflection-preventing member around at least a portion of the periphery of the tablet base for absorbing elastic waves.
5. A coordinate reading apparatus comprising: a tablet base; means for generating elastic waves in the tablet base; and a reflectionpreventing member around at least a portion of the periphery of the tablet base for absorbing elastic waves.
6. A coordinate reading apparatus as claimed in claim 5 in which said reflectionpreventing member consists of a material the acoustic impedance value of which is substantially equal to that of said tablet base.
7. A coordinate reading apparatus substan tially as herein described with reference to and as shown in Figures 2 to 5 of the accompanying drawings.
8. A coordinate reading apparatus using elastic waves as coordinate reading means, comprising a tablet base, converters provided on the peripheral portions of the upper surface of said tablet base, and a coordinate indicator elastic waves being generated in said coordinate indicator propagated through said tablet based and then received by said converters.
9. A coordinate reading apparatus using elastic waves as coordinate reading means, characterised in that the edge portions of a tablet base are covered with a reflection-preventing material.
10. Any novel integer or step or combination of integers or steps, hereinbefore described and/or as shown in the accompanying drawings, irrespective of whether the present claim is within the scope of, or relates to the same or a different invention from that of, the preceding claims.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP60179156A JPS6238924A (en) | 1985-08-14 | 1985-08-14 | Coordinate reader using elastic wave |
| JP60179157A JPS6238925A (en) | 1985-08-14 | 1985-08-14 | Coordinate reader using elastic wave |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8619521D0 GB8619521D0 (en) | 1986-09-24 |
| GB2179152A true GB2179152A (en) | 1987-02-25 |
| GB2179152B GB2179152B (en) | 1989-05-10 |
Family
ID=26499096
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8619521A Expired GB2179152B (en) | 1985-08-14 | 1986-08-11 | Coordinate reading apparatus |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2179152B (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0284048A2 (en) * | 1987-03-24 | 1988-09-28 | Canon Kabushiki Kaisha | Coordinates input apparatus |
| EP0296569A2 (en) * | 1987-06-25 | 1988-12-28 | Canon Kabushiki Kaisha | Coordinates input apparatus |
| EP0364983A2 (en) * | 1988-10-20 | 1990-04-25 | Canon Kabushiki Kaisha | Coordinate input apparatus |
| EP0367282A2 (en) * | 1988-11-04 | 1990-05-09 | Canon Kabushiki Kaisha | Coordinate input apparatus |
| US8847926B2 (en) | 2006-06-27 | 2014-09-30 | Egalax—Empia Technology Inc. | Touch panel with improved touch position determining capability |
Citations (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB978330A (en) * | 1962-12-21 | 1964-12-23 | Ibm | Improvements relating to the conversion of graphical data to digital form |
| US3504334A (en) * | 1968-10-16 | 1970-03-31 | Stromberg Datagraphix Inc | Rectangular coordinate indicating system employing cordless stylus |
| GB1384313A (en) * | 1971-03-30 | 1975-02-19 | Siemens Ag | Apparatus for electronic analysis of the instantaneous location of a probe on the surface of a plate |
| GB1530188A (en) * | 1975-12-17 | 1978-10-25 | Int Standard Electric Corp | Device for automatic determination of the coordinates of a point on a plane |
| GB2034475A (en) * | 1978-11-02 | 1980-06-04 | Draper Lab Charles S | Two coordinate position sensing systems |
| GB2042726A (en) * | 1979-03-07 | 1980-09-24 | Bransbury R | Pattern Logging Device |
| GB2097922A (en) * | 1981-03-25 | 1982-11-10 | Branton Robert | Positional determination |
| EP0107922A1 (en) * | 1982-09-30 | 1984-05-09 | New York Institute Of Technology | Graphical data apparatus |
| GB2141545A (en) * | 1983-06-16 | 1984-12-19 | Standard Telephones Cables Ltd | Position determination on visual display units |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0169538B1 (en) * | 1984-07-25 | 1991-05-29 | Hitachi, Ltd. | Tablet type coordinate input apparatus using elastic waves |
| JPS629424A (en) * | 1985-07-05 | 1987-01-17 | Hitachi Ltd | Coordinate input device |
-
1986
- 1986-08-11 GB GB8619521A patent/GB2179152B/en not_active Expired
Patent Citations (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB978330A (en) * | 1962-12-21 | 1964-12-23 | Ibm | Improvements relating to the conversion of graphical data to digital form |
| US3504334A (en) * | 1968-10-16 | 1970-03-31 | Stromberg Datagraphix Inc | Rectangular coordinate indicating system employing cordless stylus |
| GB1384313A (en) * | 1971-03-30 | 1975-02-19 | Siemens Ag | Apparatus for electronic analysis of the instantaneous location of a probe on the surface of a plate |
| GB1530188A (en) * | 1975-12-17 | 1978-10-25 | Int Standard Electric Corp | Device for automatic determination of the coordinates of a point on a plane |
| GB2034475A (en) * | 1978-11-02 | 1980-06-04 | Draper Lab Charles S | Two coordinate position sensing systems |
| GB2042726A (en) * | 1979-03-07 | 1980-09-24 | Bransbury R | Pattern Logging Device |
| GB2097922A (en) * | 1981-03-25 | 1982-11-10 | Branton Robert | Positional determination |
| EP0107922A1 (en) * | 1982-09-30 | 1984-05-09 | New York Institute Of Technology | Graphical data apparatus |
| GB2141545A (en) * | 1983-06-16 | 1984-12-19 | Standard Telephones Cables Ltd | Position determination on visual display units |
Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0284048A2 (en) * | 1987-03-24 | 1988-09-28 | Canon Kabushiki Kaisha | Coordinates input apparatus |
| EP0284048A3 (en) * | 1987-03-24 | 1990-02-28 | Canon Kabushiki Kaisha | Coordinates input apparatus |
| EP0296569A2 (en) * | 1987-06-25 | 1988-12-28 | Canon Kabushiki Kaisha | Coordinates input apparatus |
| EP0296569A3 (en) * | 1987-06-25 | 1990-01-10 | Canon Kabushiki Kaisha | Coordinates input apparatus |
| US4910363A (en) * | 1987-06-25 | 1990-03-20 | Canon Kabushiki Kaisha | Coordinates input apparatus with plural pulse train whose phases differ |
| EP0364983A2 (en) * | 1988-10-20 | 1990-04-25 | Canon Kabushiki Kaisha | Coordinate input apparatus |
| EP0364983A3 (en) * | 1988-10-20 | 1990-12-12 | Canon Kabushiki Kaisha | Coordinate input apparatus |
| EP0367282A2 (en) * | 1988-11-04 | 1990-05-09 | Canon Kabushiki Kaisha | Coordinate input apparatus |
| EP0367282A3 (en) * | 1988-11-04 | 1991-01-09 | Canon Kabushiki Kaisha | Coordinate input apparatus |
| US8847926B2 (en) | 2006-06-27 | 2014-09-30 | Egalax—Empia Technology Inc. | Touch panel with improved touch position determining capability |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2179152B (en) | 1989-05-10 |
| GB8619521D0 (en) | 1986-09-24 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |