GB2089045A

GB2089045A - Tablet for an X-Y Co-ordinate Digitizer

Info

Publication number: GB2089045A
Application number: GB8133891A
Authority: GB
Original assignee: OSAWA SHOKAI KK
Current assignee: OSAWA SHOKAI KK
Priority date: 1980-11-11
Filing date: 1981-11-10
Publication date: 1982-06-16
Also published as: DE3144817A1; JPS5784068U

Abstract

A digitizer tablet for providing an XY co-ordinate read-out for image resolution has two glass plates 4,4 min which are held in face contact, one plate 4 has a matrix of mutually insulated X-co-ordinate and Y-co-ordinate wires 8,8 min which are recessed into the face of plate 4 which is in contact with the plate 4 min . The close proximity of the X and Y co-ordinate wires 8,8 min and the low thermal co-efficient of expansion of the plates 4,4 min provide a digitizer of high accuracy. Positions of an inductive cursor 2 on the tablet are given in terms of X and Y coordinates by processors 10 feeding a processor 3. <IMAGE>

Description

SPECIFICATION Tablet for a Digitizer Abstract of the Disclosure This invention relates to a tablet for a digitizer which is used for a X-Y coordinate read out device for image resolution.

The tablet of the invention comprises a pair of glass plates which are held by a holder so as to face each other. A plurality of X-coordinate wires and Y-coordinate wires are provided in one of the glass plates on the inner face thereof so as to be disposed in a manner perpendicular to each other to form a matrix.

Background of the Invention In general, a digitzerfor image resolution comprises a tablet, a cursor and a controller. The digitizer may be of a tablet driving type or of a cursor driving type, depending on which component to which an input signal is applied.

Also, the digitizer may be of magnetically inducing type, of field coupling type or of transfer time type, depending on its system. In the magnetically inducing system, an electromotive force is induced at a coil by magnetical induction and a position at which an article is placed is determined by a phase or an amplitude of the electromotive force. In the field coupling system, the position of the article is determined by a value of the capacitance detected by being coupled with the approaching article. In the transfer time system, the position of the article is determined by measuring the time in which a sonic wave or an oscillating wave transferring through a medium arrives or by detecting a distorted wave by magnetostriction.Of late, the field coupling system affected by an electrical conductor and the transfer time system affected by environment conditions have been replaced by the electrically inducing system which is relatively not affected by environment conditions and is stable in its operation.

In such an electrically inducing system, since the precision at which the position of the article is detected depends on the positions of wires looped and disposed in a manner perpendicular to each other, the prior tablet comprises wires provided on a printed board in a matrix pattern to assure the precision with which the wires are provided. Since the wires are separately provided on both faces of the printed board by etching. This causes the wires on the opposite faces to be spaced by the distance corresponding to the thickness of the printed board and, as a result, the precision on detection to be lowered.

Furthermore, conventional resin of which the printed board is composed has a coefficient of linear expansion much larger than other material such as glass. Thus, it will be noted that the measurement largely depends on the environmental temperature so as to have no stable precision.

Summary of the Invention Accordingly, it is a principal object of the invention to provide a tablet for a digitizer in which a measurement can be made with higher precision.

It is another object of the invention to provide a tablet for a digitizer in which a measurement can be made without being affected by the environmental temperature.

It is another object of the invention to provide a tablet for a digitizer in which an image projection and a plot resolution are possible on either of front and back faces of the tablet.

In accordance with the invention, there is provided a tablet for a digitizer comprising a pair of glass plates held by a holder so as to face each other and a plurality of X-coordinate wires and Y coordinate wires provided in one of said glass plates on an inner face thereof so as to be disposed in a manner perpendicular to each other to form a matrix pattern.

Brief Description of the Drawing Figure 1 illustrates a digitizer including a tablet constructed in accordance with the invention, a portion of the tablet being broken away for clarification; and Figure 2 is a front view of the tablet used in the digitizer of Figure 1.

Detailed Description of the Embodiment Referring now to Figure 1 , there is shown a digitizer including a tablet 1 constructed in accordance with the invention, a cursor 2 and an indication processor 3 which is connected to the tablet 1 and the cursor 2 for indicating the Xcoordinate and Y-coordinate position at which an article is placed.

The cursor 2 has a sensor of coil provided therein although not shown. This is used for outlining an article or image on the tablet to electromagnetically sense it.

As shown in Figure 2, the tablet 1 comprises a pair of glass plates 4 and 4' which are faced with each other. A holder 5 holds the glass plates 4 and 4' so that they never move relative to each other. The holder 5 includes a pair of rectangular base plates 6 and 6' which may be formed of glass and which are disposed in a perpendicular manner as shown in Figure 1. The glass plates 4 and 4' may be adhered to the base plates 6 and 6', respectively. The holder 5 also includes four holding blocks 7 which each have a bolt 7a extending through the base plates 6 and 6' at the corner thereof and a nut 7b threadedly engaging with the bolt 7a.

The tablet 1 also comprises a plurality of Xcoordinate wires 8 and Y-coordinate wires 8' which are provided in one of the glass plates 4 and 4' on the inner surface thereof so as to be disposed in a manner perpendicular to each other to form a matrix pattern. Of course, the Xcoorinate wires 8 and Y-coordinate wires 8' are insulated from each other. The X-coordinate and Y-coordinate wires 8 and 8' may be placed in grooves provided in the one glass plate 4 or 4'.

The grooves may be substantially semicircular in section and formed by etching the glass plate with hydrogen fluoride. The lines for the grooves may be drawn on the glass plate by a graduator or by a photograph. The X-coordinate and Ycoordinate wires 8 and 8' may have the diameter of 25/1000 to 30/1000 millimeter so as not to prevent the field of vision. Thus, it will be noted that the image of the article may be clearly viewed through the tablet 1. Of course, the Xcoordinate and Y-coordinate wires 8 and 8' are looped and may be provided in any arbitrary pattern. Since the glass plate on which the wires 8 and 8' are provided has a coefficient of linear expansion of 5x 10-6 mm/ C, if it has a length of 25 cm, it varies in its length by 25/1000 to 4.5/1000 mm with variation of 20"C.

Data processors 10 and 10' for X-ccordinate and Y-coordinate are mounted on the projecting ends 6a and 6'a of the base plates 6 and 6'. The processors 10 and 10' are connected to the indication processor 3 so that an image signal is controlled.

It should be noted that the X-coordinate wires 8 and Y-coordinate wires 8' are disposed close to each other because they are provided on one surface of the one glass plate 4 or 4' in a matrix manner. This causes the position of the image to be detected with a higher precision because a magnetic output becomes higher. Also, since the X-coordinate and Y-coordinate wires 8 and 8' are provided on the glass plate having a lower coefficient of linear expansion, the wires are always positioned at proper places. It should be also noted that image projection of plot resolution may be made at either of the front and back faces of the tablet 1.

While one preferred embodiment of the invention has been described and illustrated with reference to the accompanying drawing, it will be understood by those skilled in the art that it is by way of example, and that various changes and modifications might be made without departing from the spirit and scope of the invention, which is intended to be defined only to the appended

Claims

claims. Claims

1. A tablet for a digitizer comprising a pair of glass plates held by a holder so as to face each other and a plurality of X-coordinate wires and Ycoordinate wires provided in one of said glass plates on an inner surface thereof so as to be disposed in a manner perpendicular to each other to form a matrix pattern.

2. A tablet for a digitizer as set forth in Claim 1, wherein said holder includes a pair of base plates of glass and holding blocks to securely hold said glass plates between said pair of base plates.

3. A tablet for a digitizer as set forth in Claim 2, wherein each of said holding block has a bolt extending through said base plates at the corner thereof and a nut threadedly engaging with a bolt.

4. A tablet for a digitizer as set forth in Claim 2, wherein said base plates are of rectangle and are disposed in a manner perpendicular to each other.

5. A tablet for a digitizer as set forth in Claim 4, wherein X-coordinate and Y-coordinate data processors are mounted on the projecting ends of said rectangular base plates.