WO1988005577A1

WO1988005577A1 - Improvements in or relating to touch keypad systems

Info

Publication number: WO1988005577A1
Application number: PCT/GB1988/000021
Authority: WO
Inventors: Ronald Peter Binstead
Original assignee: Ronald Peter Binstead
Priority date: 1987-01-15
Filing date: 1988-01-14
Publication date: 1988-07-28
Also published as: GB8915931D0; AU1105388A; GB2223986A; GB8700849D0

Abstract

A display can be controlled through one or more thicknesses of glass and one or more air gaps using a transparent keypad through which the display can be observed. The display may be a TV type or LCD, etc.

Description

IMPROVEMENTS IN OR RELATING TO TOUCH KEYPAD SYSTEMS

The present invention relates to touch keypad systems and more particularly to systems which include a transparent or semi transparent keypad allowing a viewer to see through the keypad to a display situated behind the keypad. The term "touch" iff- defined to include proximity wherein no actual contact need occur. The keypad may therefore be situated behind a sheet of glass or plastics material which can be of the double glazed type and the keypad may be spaced away from the rear face of the glass.

The invention requires the provision of one or more sensitive areas which operate as individual keys. In its simplest form only one area may be provided but normally several areas are provided thereby providing a plurality of keys. To be able to detect and distinguish between areas touched selection circuity such as described in my

PCT Patent Application No. GB85/00168 is_. preferably used.

It is an object of the present invention to provide a transparent touch keypad system which is operable through glass or transparent plastics material. It is also an object of the present invention to provide a transparent keypad which can be attached to the front screen of a VDU for viewing the VDU through the keypad.

The present invention provides a touch keypad system including a^' visual display system unit, a transparent keypad comprising a plurality of sensitive areas, in which the keypad is operable through glass by touching the glass the display being viewed at least in part through the keypad. For the purposes of the present invention glass is defined to include plastic.

In a preferred embodiment the keypad is attached to the front of the VDU and the VDU is positioned adjacent to one side of a sheet of glass or plastic tn-: VDU being controllable by touching the opposite side of the glass or plastic.

In this preferred embodiment the system includes means for distinguishing the touching of a key of the keypad attached to or in close proximity to the screen of a VDU in the presence-of static developed by the VDU.

Embodiments of the present invention will now be described with reference to the accompanying drawings in whic :-

Figure 1 shows diagrammatically in side cross section a display system according to the present inventon;

Figure 2 shows diagrammatically the visual display unit VDU and transparent keypad in front elevation;

Figure 3 shows in greater detail a keypad used in the system of Figure 2;

Figure 4 shows an alternative design of keypad;

Figure 5 shows in cross section a first design of keypad;

Figure 6 shows in cross section a second design of keypad; and

Figure 7 shows diagrammatically an electrical circuit of the keypad of the present invention. Figures 8 to 13 show in cross section various designs of keypad and display. ith reference now to

Figure 1 the display system comprises a visual display unit 10 a transparent keypad 20 and a sheet of glass (as defined) , for example a window 30 against which the keypad 20 is in a first embodiment affixed. The keypad is operated by touching the window 30 with for example a finger F. The keypad may be operated by bringing the finger F into close proximity to the glass window 30 without actually touching the window. The glass may be single, double or triple glazed, the keypad being sensitive enough to work through several layers of glass and ^■the air gaps in between. The VDU can be any type of display, e.g. CRT liquid crystal, fluorescent or projected, etc. The keypad has, associated therewith a control box 40 which is able in known manner to control the VDU either directly or for example to control a video recorder (not shown) associated therewith. The keypad is stuck or otherwise fixed to the window 30 or is in proximity behind the window being supported by separate means and by touching the window the display on the VDU 10 may be changed. The VDU display may be used to indicate the areas of the screen to be touched to alter the display. To suit various mounting techniques the VDU and keypad may be positioned as shown pressed against the glass 30 without any substantial gaps or spaced apart as indicated by gaps 50 and/or 60. The keypad is sufficiently sensitive to be operable with a substantial gap 50. Gap 60 is preferably small to prevent parallax between displayed touch area and the keys.

The sensitive areas of the keypad in front of the display may be constructed by for example sputter coating indium oxide onto a polyester film or depositing tin onto glass.

In an alternative embodiment the keypad may be fixed to the front of the VDU 10. The VDU 10 may then be positioned close to the inside of a window 30 and providing the air gap between the window glass and the keypad is relatively small the keypad and hence the VDU may be operated by touching the window as shown. Fixing the transparent keypad to the front of a CRT display (e.g. a TV) however causes the keypad to be subjected to the static produced by the TV and it is necessary to counter this as shown in Figure 7 by for example connecting a capacitor C in the output lead from each key to isolate the detection circuitry in control box 40 from the static (d.c.) voltage.

With reference now to Figure 2 the keypad 20 is shown as viewed through window 30. The sensor areas are indicated at 21 and contact areas are shown at 22. Individual output leads 23 join the contact areas 22 with the control box 40 which may be of the form as described in co-pending British Patent Application No. The control box may be provided with appropriate output drives for control of the VDU (or video recorder). An area 24 surrounding the sensor areas 21 may be connected via lead 25 to ground to improve the sensitivity of the keypad and help eliminate static.

An individual key is shown in greater detail in Figure 3, the sensitive area 21 extending as shown over the contact area 22. The conductive sensor area 21 is isolated from other sensors by a non-conductive zone 26.

In Figure 4 the sensor areas 21 are within a central area 27 which is visible in front of the VDU. The contact areas 22 may be screened behind an opaque surround 28 for cosmetic purposes.

The contact areas 22 may be glued to the sensor areas 21 as shown in Figure 6 or may be glued to the opposite side as shown in Figure 5.

An alternative solution to the static problem is to provide a sheet 31 of plastics material with a conductive coating of for example indium oxide 32 which is grounded. The coating 32 will remove the static from the VDU allowing the keypad to sense in a normal manner.

If there are no problems of static or a separate in line capacitor is used the connector 22 may be directly connected to the transparent conductive film 21 by for example conductive adhesive or a push on connector.

In the upper key contact of Figure 5 the transparent conductive coating forming the sensitive area 21 is applied for example by sputtering indium oxide onto one side of a glass or plastics sheet 29, the contact 22 being affixed to the other side. The glass or plastic sheet 29 forms the dielectric capacitor C required for anti-static properties as referred to with reference to Fiσure 7. In Figure 6 the sheet 29 forms a shield or guard sheet in front of for example a VDU 10 enabling the sensitive areas and contacts to be protected against damage. The capacitor C may be formed as shown in the upper contact by introducing a sheet of for example polyester 41 to form a dielectric between the sensitive areas 21 and contact area 22 at the point of the contact area. Conveniently the sheet 41 may be double_^ sided tape providing adhesive contact on both sides.

Figures 8 to 13 show various possible exemplary key arrangements for displays where static voltages are present and for those where there is no problem of static such as in LCD displays. The same reference numerals are used to designate the various parts as_. in figures 1 to 7. Figures 8, 9 and 10 show possible construction methods where there is no problem of static.

Figure 8 is a cross section of a display unit 10, such as a fluorescent or liquid crystal display where the sensors are on the inside of the front glass panel of the unit .

Figure 9 is a cross section of a display unit where the sensors are on the outside of the front glass panel of the unit. ^' Figure 10 shows sensors mounted on a separate sheet of glass or door plastic and situated between the viewer/operator and the display.

Figures 11, 12 and 13 show possible construction methods where there is a problem of static. Figure 11 shows the construction of the pick-up terminals where they are isolated from the sensor areas by a thin sheet of non-conductive material. This prevents high voltages reaching the electronic circuit.

Figure 12 shows a layer of transparent conductive material 31 placed between the VDU and the sensors. When this is grounded the static is eliminated. Figure 13 shows how the grounded transparent shield and the sensors may be mounted on either side of the same sheet of glass' or clear plastic.

Claims

1. A touch keypad system including a visual display system unit, a transparent keypad comprising a plurality of sensitive areas, in which the keypad is operable through glass by touching the gla-≤s the display being viewed at least in part through the keypad.

2. A touch keypad system as claimed in Claim 1 in which the keypad is attached to the front of the VDU and the VDU is positioned adjacent to one side of a sheet of glass the VDU being controllable by touch the opposite side of the glass or plastic.

3. A touch keypad system as claimed in Claim 1 or Claim 2 in which the system includes means for distinguishing the touching of a key of the keypad attached to or in close proximity to the screen of a VDU in the presence of static developed by the VDU.

4. A touch keypad system as claimed in claim 1 or claim 2 in which the display is an incandescent, fluorescent, LCD or other display in which static voltages are not generated.

5. A touch keypad system as claimed in claim 1 in which the visual display unit is positioned behind a sheet of glass close to the glass but not touching such that there is an air gap between the VDU and the glass.

6. A touch keypad system substantially as decribed with reference to the accompanying drawings.