DE19904374A1 - Touch sensitive input surface with frame structure of vertical cavity surface emitting lasers and light receivers - Google Patents

Abstract

Input surface (1) has sensor frame structure (3a,b), strip of circuit board, coupled to flat element (2), e.g. LCD screen or notebook computer input screen. Vertical cavity surface emitting lasers (6) are used as light emitters, emitting light (16) parallel to surface. Light receivers receive light and produce electrical signal for received light intensity.

Description

The invention relates to an input surface according to the Oberbe handle of claim 1 and a circumferential sensor frame structure to be placed on a flat element, in particular re screen according to the preamble of claim 9.

In many areas of technology are becoming increasingly touching sensitive areas for the input of data for the control of electrical devices. Compared to conventional Chen input means such as keyboards and the like often make it simpler, more comfortable and above all more intuitive device operation.

In the article "Touch sensitive technologies", electronics industrie, 1998, issue 4, pages 88 to 91 are different described touch-sensitive technologies. For this ar It is known to have luminescent diodes (LED) on the top and to arrange the side edge of a screen and that of the LED emitted light on the opposite Detect side of the screen using phototransistors a person approaches it with a finger or pen Screen, becomes part of that emitted by the LED Beams of light when sufficiently close to the screen shaded by the finger / pen. Through an evaluation the electrical emp. output by the phototransistors Catch signals can determine the position of the finger / pen become.

The disadvantage is that with this system only a relative ßig low spatial resolution is achieved, which is why it for the Production of small-format screens not or only be is suitable.

Another disadvantage of this system is that it does not work parallax free since the level at which the  Extend light beams, offset to that through the image screen surface defined contact level.

The invention is based on the object of an input surface, in particular to create screen area (touch screen) that can have small lateral dimensions. It also aims the invention is based on a rotating sensor frame structure to create the retrospectively on a flat element, in particular flat screen to realize a kleinfor mat input surface can be placed.

The characteristics are to solve the mentioned task of claims 1 and 9 provided.

By using semiconductor laser diodes as light sensors that is achieved that the individual from the light transmitters emitted light beams have a low beam divergence sen. As a result, all light rays of all light beam crossing the surface of the flat element del have a high degree of parallelism. One from an object (Finger or pen) caused local shadowing of the emitted light bundle then always produces a clearly abge delimited and defined shadows in the area of light receiver. An impairment of the shadow cast by disturbing secondary light from neighboring, not shaded Semiconductor laser diodes practically do not occur. Thereby enables the location of objects with small lateral dimensions (e.g. pen tip) safely detected and can be determined by evaluation.

It is also advantageous that with semiconductor laser diodes very small distance between neighboring light beams becomes reachable. This allows one for small format users sufficiently high surface density of the light beams become. With the previously used LED is due to their Size a comparable surface density of the light beams not reached.  

Ver. Are particularly advantageous as semiconductor laser diodes tical resonator laser diodes (VCSEL: vertical-cavity surface emitting laser). On the one hand, VCSELs have particular small beam divergences (2 ° or less) and can on the other hand, with extremely small lateral dimensions solutions (about 10 µm). They are suitable there forth in particular to achieve the inventive light curtain with a high beam of light te.

Another advantage of VCSEL is that it costs cheaper than most other semiconductor laser diodes (et wa edge emitting laser diodes) can be produced.

A preferred embodiment of the invention is characterized net is characterized in that the sensor frame structure is a ladder includes plate strip on which the semiconductor laser diodes are arranged in a len-like manner. The high of PCB strip can be less than 2 mm and in particular which are less than 1 mm. This allows the for small-format input surfaces required low overall height Realize the frame structure. Furthermore, the equipment such a printed circuit board strip with semiconductor Laser diodes (VCSEL) can be automated and are therefore inexpensive feasible.

According to a further preferred embodiment variant of the Er invention are several semiconductor laser diodes line-like ne juxtaposed on a single semiconductor ingot arranges. In this monolithic version is a ge the shortest possible distance between adjacent laser diodes reachable.

The sensor frame structure can either be the flat element surrounded in the manner of a border or it can open be placed on the surface of the flat element. On  The advantage of the latter solution is that it is the after armor of screens and the like allowed.

Further preferred embodiments of the invention are in the Subclaims specified.

The invention is described below with the aid of embodiment variants explained with reference to the drawing; in this shows:

Figure 1 is a schematic perspective view of an input surface according to the Invention with a partially shown sensor frame structure.

Fig. 2 is a schematic perspective view of a Seitenele element of the frame structure;

Fig. 3 is a schematic perspective view of an assembled with a plurality of VCSEL chips PCB strip;

FIG. 4 shows a schematic illustration of a semiconductor ingot with monolithically formed VCSEL; FIG. and

Fig. 5 is a schematic representation of the layer structure of a VCSEL.

According to FIG. 1, an input surface 1 has a flat element 2 with a rectangular plan, for example, and a sensor frame structure encircling the flat element 2 . The surface of the flat element 2 is designated by the reference character 2 a. From the circumferential sensor frame structure in Fig. 1, two opposing Be tenelemente 3 a and 3 b and an intermediate third side element is shown, which is identical to the side element 3 a table. At the third side member 3 a gegenüberlie constricting side of the flat element 2 is a further, not shown side member present, the element with the Seitenele 3 b is identical.

The flat element 2 can be an LCD screen or generally realize a touch surface, such as that used in a notebook (computer) for manual cursor control.

The input surface 1 can be used, for example, as an input unit in a mobile phone, palm top, car radio, copier, etc. It can also be used in household appliances (for example washing machines or the like).

The side elements 3 a, 3 b of the sensor frame structure each consist of a plastic profile part 4 , which serves as a carrier for a printed circuit board 5 a or 5 b.

On the printed circuit board 5 a ei ne plurality of semiconductor laser diodes in the form of VCSEL 6 are arranged in a linear arrangement. The PCB strip 5 a opposite PCB strip 5 b carries light receivers, which can be designed in the form of photodiodes or phototransistors, and which are covered in the illustration in FIG. 1 by the printed circuit board strip 5 b.

Each VCSEL 6 emits a laser light bundle 16 which strikes a light receiver on the opposite printed circuit board 5 b and is detected by the latter. For this purpose, each light receiver provides an electrical signal at an output 7 which is representative of the light intensity incident in the respective receiver. The outputs 7 are connected in a manner not shown to an evaluation circuit which determines with respect to each light receiver whether the received light intensity is above or below a predefinable limit intensity. If the light intensity is above the limit intensity, the evaluation circuit determines that there is no shadowing of the light receiver in question; otherwise shading of this light receiver is determined by the evaluation circuit.

By means of the two side elements 3 a oriented at right angles to one another with light-emitting VCSEL 6 , a surface 2 a of the flat element 2 is completely covered by a light curtain in the form of a close-meshed light beam grating 17 (shown in sections).

The frame geometry and the distribution of light transmitters (VCSEL) and light receivers via the frame structure is in selectable in many ways. For example, among other things rem an annular frame structure and / or an alternie arrangement of light transmitters and light receivers hen.

If an object (finger, pen tip) is guided through the light curtain at a certain location, then light bundles 16 of both light-emitting side elements 3 a are shadowed by the object. The two shadow areas projected by the object onto the opposite side elements 3 b are each detected by means of the evaluation circuit and used to determine the location coordinates of the object.

If the light receivers have a comparable or higher line density than the VCSEL 6 , the spatial resolution of the input surface 1 is essentially defined by the distance S between adjacent VCSEL 6 (ie the distance between two adjacent light beam axes) and the beam divergence of the VCSEL. Both with increasing distance 5 and with an increase in beam divergence, the achievable spatial resolution of input surface 1 generally decreases, and thus its suitability for miniature applications.

Fig. 2 shows a side element 3 a of the sensor frame structure in an enlarged view. The circuit board 5 a is taken up to about half the height by extrusion coating or the like in the plastic profile part 4 . The VCSEL 6 are preferably located in the upper half of the printed circuit board 5 a and are arranged in the vicinity of the edge 8 of the plastic profile 4 facing away from the same.

The construction shown in FIG. 2 creates a mechanically stable frame structure with a low overall height. The distance A between the edge 8 and the VCSEL 6 can, for example, 0.2 mm and the total height H of the printed circuit board 5 a can be, for example, about 1.0 mm. The height of the VCSEL 6 above the surface 2 a of the flat element 2 can also be kept small by suitable positioning and mounting of the side elements 3 a, 3 b on the flat element 2 . As a result, a practically parallax-free ar processing input surface 1 can be achieved with a sensor frame structure which only protrudes slightly beyond the surface 2 a.

Fig. 3 shows the circuit board 5 a in an enlarged Dar position. On the printed circuit board 5 a runs a Lei terbahn 9 , which forms a common first electrical contact for the VCSEL 6 . The VCSEL 6 are here in the form of individual VCSEL chips 10 , which are soldered side by side on the common interconnect 9 . On the beam-side upper side of each VCSEL chip 10 , a contact pad 11 is applied, which is in electrical contact via a bonding wire 12 with a second electrical contact-making interconnect structure 13 on the printed circuit board 5 a.

In the arrangement shown in FIG. 3, the distance S between the light beam axes of the VCSEL chips 10 can be approximately 0.5 mm or less.

A smaller distance S in the range of approximately 25 μm to 1 mm can be achieved by the embodiment variant shown in FIG. 4 with a monolithic design of the VCSEL 6 in a common semiconductor bar 14 . The semiconductor bar 14 has a common electrode on its rear side (not visible) and is provided with contact pads 11 'on its front side. The contact pads 11 ′ correspond to the contact pads 11 shown in FIG. 3. They are electrically connected via a conductor bridge 15 to a ring electrode 6.2 that defines a light exit window 6.1 of the VCSEL 6 .

The length L of the semiconductor ingot 14 may for example be 1 to 10 cm, that is, the side member 3 a may be comprised of a single semiconductor ingot fourteenth The height H 'of the semiconductor bar 14 can be, for example, between 100 μm and 1 mm, ie very low-profile sensor frame structures can be achieved.

The semiconductor bar 14 can either be soldered to the printed circuit board 5 a (see FIG. 2) instead of the individual VCSEL chips 10 or it can be provided with a suitable plastic coating or be cast with an epoxy resin to form a frame structure.

Fig. 5 shows a schematic sectional view of the layer structure of a VCSEL. 6 The VCSEL 6 is constructed on a semiconductor substrate (for example GaAs) 20 , over which a first stack 21 of epitaxially applied mirror layers 21 a, 21 b, an active zone 22 and a second stack 23 of mirror layers 23 a, 23 b are arranged. The layer stacks 21 and 23 each consist of alternating GaAs layers 21 a, 23 a with a low band gap and layers 21 b, 23 b made of AL _x Ga _1-x As with a high aluminum content (for example x = 0.96) and a high band gap. The active zone 22 here has a two-dimensional quantum layer 25 lying between two barrier layers 24 . The reference numeral 26 designates two optional oxide insulation layers provided with a central apparatus, which serve to control the lateral mode profile of the emitted light bundle 17 . Bottom side of the layer structure described is a Gegenelek electrode 27 and the top of the ring electrode 6.2 can be seen .

By suitable dimensioning of the resonant and insulation layers 21 , 23 ; 26 , a small beam divergence of 2 ° or less can be achieved.

Reference list

1

Input area

2nd

flat element

2nd

a surface of the flat element

3rd

a, b side element of the frame structure

4th

Plastic profile part

5

a, b PCB strip

6

VCSEL

6.1

Light emission window

6.2

Ring electrode

7

output

8th

free margin

9

Conductor track

10th

VCSEL chip

11

,

11

'' Contact pad

12th

Bond wire

13

Trace structure

14

Semiconductor bars

15

Ladder bridge

16

Laser light beam

17th

Beam grids

20th

Substrate

21

first stack

21

a, b mirror layers

22

active zone

23

second stack

23

a, b mirror layers

24th

Barrier layer

25th

Quantum layer

26

Insulation layer

27

Counter electrode

Claims (9)

1. Input area with

• - A flat element ( 2 ), and
• - With the flat element ( 2 ) coupled sensor frame structure ( 3 a, 3 b), which
  • - A plurality of light transmitters ( 6 ) which emit light bundles ( 16 ) running essentially parallel to a surface ( 2 a) of the planar element ( 2 ), and
  • - A plurality of light receivers, which receive the light bundles ( 16 ) after crossing the surface ( 2 a) of the flat element ( 2 ) and output an electrical signal representative of the received light intensity,

includes
wherein the light transmitter ( 6 ) and the light receiver are so distributed over the sensor frame structure ( 3 a, 3 b) that based on an evaluation of the electrical signals, the position of a part of the light beam ( 16 ) obscuring object can be determined, thereby characterized in that the light transmitters are semiconductor laser diodes ( 6 ). 2. Input surface according to claim 1, characterized in that the semiconductor laser diodes ( 6 ) are vertical re sonator laser diodes (VCSEL; 6). 3. Input surface according to claim 1 or 2, characterized in that the sensor frame structure ( 3 a, 3 b) comprises a Leiterplattenlei ste ( 5 a) on which the semiconductor laser diodes ( 6 ) are arranged in a row like a row. 4. Input surface according to claim 3, characterized in that the height (H) of the printed circuit board ( 5 a) is less than 2 mm, in particular less than 1 mm. 5. Input surface according to one of the preceding claims, characterized in that the semiconductor laser diodes ( 6 ) in the vicinity of a longitudinal edge ( 8 ) of the printed circuit board ( 5 a) are arranged. 6. Input surface according to one of the preceding claims, characterized in that a plurality of semiconductor laser diodes ( 6 ) are formed in a common semiconductor bar ( 14 ). 7. Input surface according to one of the preceding claims, characterized in that the sensor frame structure ( 3 a, 3 b) rotates around the edge of the flat element ( 2 ) in the manner of an enclosure. 8. Input surface according to one of claims 1 to 6, characterized in that the sensor frame structure ( 3 a, 3 b) on the surface ( 2 a) of the flat element ( 2 ) is placed. 9. All-round sensor frame structure for placing on a surface of a flat element, in particular screen, with

• - A plurality of in side elements ( 3 a) of the frame structure provided light transmitters ( 6 ) which transmit light beams ( 16 ) extending in an opening plane of the frame structure, and
• - A plurality of light receivers that receive the light bundles ( 16 ) after crossing the opening of the frame structure and emit a representative electrical signal for the received light intensity,

wherein the light transmitter ( 6 ) and the light receiver are so distributed over the frame structure ( 3 a, 3 b) that based on an evaluation of the electrical signals, the position of an egg nen part of the light beam ( 16 ) shading object is determinable, characterized that the light transmitters are semiconductor laser diodes ( 6 ), in particular vertical resonator laser diodes (VCSEL).