WO2004001970A2

WO2004001970A2 - Sensor device and display device

Info

Publication number: WO2004001970A2
Application number: PCT/IB2003/002389
Authority: WO
Inventors: Wilhelmus J. R. Van Lier
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2002-06-20
Filing date: 2003-06-05
Publication date: 2003-12-31
Also published as: WO2004001970A3; AU2003233132A1

Abstract

Keyboard comprising e.g. LEDs (12) to generate light beams within a transparent flexible substrate which receives keys (2) .The fluctuation of light intensity in different directions is detected by means of e.g. photodiodes (13).

Description

Sensor device and display device

The invention relates to a sensor device comprising an optical waveguide and at least one light source along a part of an edge of the optical waveguide, and associated photosensitive elements wherein, during operation, keys interrupt the light path of the light from the light source. The invention particularly relates to a keyboard device for use in a (portable) display device. Such display devices find an Increasingly wider application in, for example, mobile telephones. However, the invention may also be used in other display devices such as organizers, laptop computers and the like. Due to the increasing miniaturization, the demand for integration of the display screen with the keyboard device, but also with other functions is increasing. In general sensor devices for use in keyboard devices comprise for each key a separate hole in the optical waveguide via which the keypad contacts a dome shaped contact on a PC- board. The optical waveguide generally is used to illuminate the keys. Such sensor devices however are sensitive to dust and contamination, while also the reliability of switching diminishes during use, until after a certain number of switching cycles the contacts have deteriorated so much that the whole device stops functioning.

It is an object of the invention to solve this problem by providing a sensor device in which integration of components is realized as much as possible and. To this end a sensor device according to the invention comprises at least one light source along different parts of an edge of the optical waveguide, and associated photosensitive elements while, during operation, keys interrupt the light path of the light from the light source, while the optical waveguide comprises an optically transparent, flexible material. By introducing flexible material for the optical waveguide the sensor device is less sensitive to mechanical tolerances and mechanical wear, increasing the lifetime of the sensor device. Since no separate holes in the- optical waveguide- are-needed any longer, a- great variety of keyboard devices can be realized using only one type of optical waveguide. Moreover, since a contact measurement is replaced by a measurement of light intensity, this can be adapted to a sliding scale, adding key sensitivity to the sensor device (pressure measurement, which introduces the possibility of setting a threshold).

The invention is based on the recognition that light can be guided along the locations of the keys in the flexible transparent substrate, in which at least a part of the light is reflected when a key is depressed. The variation of light intensity is detected by means of the photosensitive element, for example, a photodiode. This photosensitive element (and also the light source) is situated, for example, along a part of the edge of the optical waveguide. The light source may be formed by, for example, a LED.

Said optical waveguide may form part of a larger assembly, for example, a substrate in which also further operating elements for the relevant apparatus (for example, a microphone) have been realized.

The sensor device may of course also be integrated in other apparatus. These and other aspects of the invention are apparent from and will be elucidated with reference to the embodiments described hereinafter.

In the drawings:

Fig. 1 is a plan view of a mobile phone comprising a sensor according to the invention, Fig. 2 is a cross-section taken on the line II-II in Fig. 1, while

Fig. 3 is a plan view of a part of a substrate in which the sensor has been realized, and

Fig. 4 shows the principle of the sensors working principle. The drawings are diagrammatic and not drawn to scale. Corresponding components are generally denoted by the same reference numerals.

Figs. 1 and 2 show a device 1 according to the invention, in this case a mobile phone comprising, schematically shown, the customary keys 2, a display 3 and a microphone 4, having a membrane 11 in a housing 5. In this example, the display is a liquid crystal display device with a layer of- liquid-crystal material (not shown) between two substrates^, 7." The display 3 may be of the active (AMLCD) or the passive type. The display 3 is fixed in this example on a transparent support (substrate) 8, situated on a wall 10 of the housing 5. On the same wall (in this example) an optical waveguide 9 is provided. The optical waveguide 9, according to the invention, comprises an optically transparent, flexible material such as for example a synthetic material like e.g. silicones

As shown in Figure 3 the optical waveguide 9 has at least one light source which, in this example, consists of, for example, a LED 12, as well as photosensitive elements 13 which, in this example, consist of, for example, photodiodes. The light sources are situated along apart of the edge of the optical waveguide, as well as photosensitive elements

The optical waveguide 9 is constructed in such a way that the light spreads over the area of the optical waveguide 9, as indicated by arrows 14.

When a key 2 is depressed (Figure 4), the light is reflected within the optical waveguide, as indicated by arrows 14', and may also be partly deflected into the associated keypads 9. The intensity of the light indicated by arrows 14', which is passed, is then also dependent on the distance from the LED's 12,12' when the keys are depressed (situation of Figure 4b).

The variation of light intensity is detected by means of the photosensitive element, in this example the photodiodes 13,13'. The light may also be detected at other locations after it has been guided from the optical waveguide to a suitable location by means of mirrors or other optical elements. For detection of the variation of photocurrent in the photodiode, generated by variation of exiting light in there are various possibilities such as amplification by means of a suitable amplifier. The LED's 12 may alternatively emit light pulse- wise.

For example when two LED's are separately put ON and OFF, the photo diodes will, dependent on the coordinates of the touch will measure a light level from the LED's 12, 12' (see Table)

With these four results the'XY coordinates and^'the pressure on the light guide is found. Thfs pressure measurement is for a touch-screen an extra advantage. The invention is of course not limited to the embodiments shown. For example, light sources other than LED's may be used. The waveguide 9 may be combined with (part of) the backlight 6. Instead of a liquid crystal display device, other display devices may be used alternatively such as those that are based on electrophoresis, electroluminescence, P(O)LEDs and, for example, mechanical mirrors. Moreover, the sensor is applicable in completely different fields, for example, in data entry devices having, for example, a memory function (for example, semiconductor memories or a recording function for writable ROMs) or in electronic typewriters.

The protective scope of the invention is not limited to the embodiments described hereinbefore.

The invention resides in each and every novel characteristic feature and each and every combination of characteristic features. Reference numerals in the claims do not limit their protective scope. Use of the verb "comprise" and its conjugations does not exclude the presence of elements other than those stated in the claims. Use of the article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

Claims

CLAIMS:

1. A sensor device comprising an optical waveguide and at least one light source along a part of an edge of the optical waveguide, and associated photosensitive elements wherein, during operation, keys interrupt the light path of the light from the light source, the optical waveguide comprising an optically transparent, flexible material.

2. A sensor device as claimed in claim 1 wherein the light beams from a light source, viewed transversely to a surface of the optical waveguide, extend at an angle to each other.

3. A sensor device as claimed in claim 1 or 2, wherein the light source comprises at least two independently switchable light sources

4. A sensor device as claimed in claim 1 or 2, wherein the photosensitive element is situated along a further part of the edge of the optical waveguide.

5. A sensor device as claimed in claim 1 or 2, wherein keys are light transmissive.

6. A display device comprising a sensor device as claimed in claim 1 or 2.

7. A data entry device having at least a memory function and comprising a sensor device as claimed in claim 1 or 2.