U.S. patent application number 09/847142 was filed with the patent office on 2001-12-06 for keypad illumination arrangement that enables dynamic and individual illumination of keys, and method of using the same.
Invention is credited to Kaikuranta, Terho, Svarfvar, Bror.
Application Number | 20010048379 09/847142 |
Document ID | / |
Family ID | 8558314 |
Filed Date | 2001-12-06 |
United States Patent
Application |
20010048379 |
Kind Code |
A1 |
Kaikuranta, Terho ; et
al. |
December 6, 2001 |
Keypad illumination arrangement that enables dynamic and individual
illumination of keys, and method of using the same
Abstract
A keypad for a portable electronic device comprises a number of
pressable keys (402). Associated with each key, there are switching
means (501, 502, 611, 612, 620, 621, 622, 801, 1106) for realizing
a switching function as a response to the key being pressed.
Additionally there are illumination means (503, 601, 610, 623, 704,
803, 1201, 1302) for illuminating at least a part of the keypad.
The illumination means (503, 601, 610, 623, 704, 803, 1201, 1302)
comprise light sources (503, 601, 610, 623, 704, 803, 1201) such as
semiconductor light-emitting devices made of layered foil
structures. At least one of said light sources (503, 601, 610, 623,
704, 803, 1201) is located in the immediate vicinity of the
switching means (501, 502, 611, 612, 620, 621, 622, 801, 1106)
associated with at least one key.
Inventors: |
Kaikuranta, Terho;
(Piispanristi, FI) ; Svarfvar, Bror; (Kaarina,
FI) |
Correspondence
Address: |
PERMAN & GREEN
425 POST ROAD
FAIRFIELD
CT
06430
US
|
Family ID: |
8558314 |
Appl. No.: |
09/847142 |
Filed: |
May 2, 2001 |
Current U.S.
Class: |
341/22 ; 341/31;
341/34 |
Current CPC
Class: |
H04M 1/22 20130101; H01H
2219/037 20130101; H01H 2219/039 20130101; G06F 3/0202 20130101;
H01H 2215/02 20130101; H01H 2219/014 20130101; H01H 13/702
20130101 |
Class at
Publication: |
341/22 ; 341/31;
341/34 |
International
Class: |
H03M 011/00; H03K
017/94 |
Foreign Application Data
Date |
Code |
Application Number |
May 2, 2000 |
FI |
20001017 |
Claims
1. A keypad for a portable electronic device, comprising: a number
of pressable keys, associated with each key, switching means for
realizing a switching function as a response to the key being
pressed and illumination means for illuminating at least a part of
the keypad; wherein: the illumination means comprise light sources
that are semiconductor light-emitting devices made of layered foil
structures, at least one of said light sources is located in the
immediate vicinity of the switching means associated with at least
one key, said light sources constitute at least a first group of
light sources and a second group of light sources and said first
and second groups of light sources are arranged to be illuminated
separately from each other.
2. A keypad according to claim 1, wherein said light sources are
organic light-emitting diodes.
3. A keypad according to claim 2, wherein: the keypad comprises a
printed circuit board so that the switching means comprise
conductive patterns close to each other on a surface of said
printed circuit board, and said printed circuit board constitutes a
supporting substrate layer for the organic light-emitting
diodes.
4. A keypad according to claim 1, comprising: in respect of each
key, a pair of conductive patterns close to each other which
together form a key location, a number of resistive strip sections
that link conductive patterns from a number of key locations into a
resistive chain having a first end and a second end, and a number
of light sources, each of which is coupled to the second end of
said resistive chain so that the second end of said resistive chain
functions as a common coupling point to said light sources.
5. A keypad according to claim 4, comprising as many illumination
controlling lines as there are light sources coupled to the second
end of said resistive chain, each illumination controlling line
being coupled to a light source of its own, so that each of said
light sources is individually controllable.
6. A keypad according to claim 5, wherein said illumination
controlling lines are input voltage lines to the light sources.
7. A keypad according to claim 5, comprising as many switches as
there are light sources coupled to the second end of said resistive
chain, so that each of said switches is coupled to a light source
of its own, and said illumination controlling lines are control
voltage lines to the switches.
8. A keypad according to claim 5, comprising a converter for
converting illumination commands into controlling signals on said
illumination controlling lines.
9. A keypad according to claim 8, wherein said controller is a
serial to parallel controller for converting serially conveyed
illumination commands into controlling signals on said illumination
controlling lines.
10. A keypad according to claim 8, wherein said controller is
coupled to a sequence memory and arranged to respond to a certain
illumination command by writing a sequence of controlling signals
read from said sequence memory onto said illumination controlling
lines.
11. A keypad according to claim 1, wherein the illumination means
comprise a light source in the immediate vicinity of the switching
means associated with each key.
12. A keypad according to claim 1, comprising, in the following
order, the following essentially parallel layers: a mechanical
support structure, a dome layer comprising a bulging, elastically
deformable conductive dome in respect of each key, the bulging
direction of said dome being towards said mechanical support
structure, a printed circuit board so that the switching means
comprise conductive patterns close to each other on that surface of
said printed circuit board which is towards said dome layer, and a
key layer comprising a visible and touchable surface in respect of
each key; wherein said light sources are located between said
printed circuit board and said key layer.
13. A keypad according to claim 12, comprising a perforated
insulation layer between said dome layer and said printed circuit
board, and an outer cover on a distant side of said key layer.
14. A keypad according to claim 12, wherein said light sources are
organic light-emitting diodes placed immediately beneath the
visible surfaces of the keys.
15. A keypad according to claim 12, comprising a light guide
between said printed circuit board and said key layer.
16. A method for illuminating the keys of a keypad, comprising the
steps of: providing light sources that are semiconductor
light-emitting devices made of layered foil structures as
illumination means, and producing, with at least one of said light
sources, an illuminating effect where at least one key is
illuminated differently than certain other keys in the keypad.
17. A method according to claim 16, comprising the steps of:
detecting a call connection request indicating the intention of a
caller to establish a communication connection with the device
controlled through said keypad, identifying the caller and
associating the identified caller with a certain illumination
function and producing, with at least one of said light sources, an
illuminating effect representing said illumination function.
18. A method according to claim 16, comprising the steps of:
entering a specific mode where at least one key is more preferable
as the key to be pressed next than the other keys in the keypad,
selecting at least one key which in said specific mode is more
preferable as the key to be pressed next than the other keys in the
keypad, and producing, with the light source or light sources
associated with the selected key or keys, an illuminating effect
which emphasizes the preferability of the selected key or keys over
the other keys in the keypad.
19. A method according to claim 16, comprising the steps of:
entering a game mode and allowing the user of the device controlled
through the keypad to play a game with the device, detecting the
occurrence of a game event which has previously been associated
with an illuminating effect and generating said illuminating effect
with at least one of said light sources.
20. A method according to claim 16, comprising the steps of:
entering a game mode, and generating, with said light sources, an
effect of sequentially illuminating selected ones of the keys in
the keypad in order to prompt the user to press the illuminated
keys in the same order in which they were illuminated.
Description
TECHNOLOGICAL FIELD
[0001] The invention concerns generally the technology of
illuminating the keys of a keypad or keyboard. Especially the
invention concerns the technology of dynamically illuminating
individual keys or key groups of a keypad or keyboard.
BACKGROUND OF THE INVENTION
[0002] Illuminated keypads appear typically in portable electronic
apparatuses such as mobile telephones, palmtop computers and
personal digital assistants. FIG. 1a is a partial cutout exploded
view which illustrates a known structure for illuminating a keypad.
The upper surface of a printed circuit board 101 comprises a number
of contact areas where at least two conductive strips 102 and 103
come close to each other. Supported over the printed circuit board
101 and separated from it by a perforated insulation layer 104 is
an array of conductive domes 105 so that each conductive dome 105
lies directly above the conductive strips 102 and 103. A key mat
106 is located on top of the conductive domes. It is made of an
elastic material and has a bulging protrusion 107 on top of each
conductive dome. A perforated outer cover 108 comes on top of the
aforementioned structural components so that each bulging
protrusion 107 of the keymat protrudes slightly out through the
holes in the outer cover.
[0003] The key mat 106 is made of translucent silicon rubber or
some other suitable material that conducts light reasonably well so
that a number of surface-mounted light emitting diodes (SM-LEDs)
109 can be used for illuminating. The SM-LEDs 109 are soldered to
contact pads 110 and 111 so that in the assembled configuration
their principal direction of emission is through an edge of the key
mat 106 into the substance thereof. Light escaping through the
upper surfaces of the bulging protrusions 107 provides the visual
illuminating effect seen by the user. The upper surfaces of the
bulging protrusions 107 may be partly covered with an opaque layer
so that light can only escape through an opening which may have the
outline of a character or a group of characters. FIG. 1b shows the
same structure in assembled configuration.
[0004] FIG. 1c shows a simple circuit diagram of the illumination
arrangement; the keypad functionality is not shown in FIG. 1c. The
SM-LEDs 109 used for illumination constitute a serially coupled
chain, the cathode side end of which is coupled to ground
potential. The anode side end of the chain is coupled to a
microprocessor 120 which comprises a controllable switch 121
between the anode side end of the SM-LED chain and a positive
supply voltage Vcc. The microprocessor 120 comprises also means 122
for detecting the need for illumination of the keypad. The block
122 shown in FIG. 1c is typically a software process which is
arranged to monitor the functional state of the keypad-controlled
device in question and to generate an output pulse that closes the
switch 121 whenever the functional state suggests that illumination
of the keypad would be advantageous.
[0005] The illuminating arrangement of FIGS. 1a, 1b and 1c only
enables the illumination of the whole keypad at a time. It would
naturally be possible to group the SM-LEDs 109 into two or more
subchains which could be coupled to a positive voltage
independently of each other. However, even in such a further
developed arrangement it is difficult to control the propagation of
light in the substance of the key mat 106 so that only a part of
the keypad would appear to be illuminated. Increasing the number of
subchains would also directly increase the required I/O
(input/output) pin count of the microprocessor 120, which is not a
preferable trend in development. A further drawback of the
arrangement of FIGS. 1a, 1b and 1c is that the SM-LEDs 109 take a
certain space (in the order of 0.6 mm at minimum) in the vertical
direction so that the illuminated keypad arrangement becomes rather
thick.
SUMMARY OF THE INVENTION
[0006] It is an object of the present invention to provide a keypad
illuminating arrangement which can be used to dynamically
illuminate key groups and/or individual keys in a keypad or
keyboard. It an additional object of the invention to provide a
thin illuminated keypad arrangement. It is a further object of the
invention to provide a keypad illuminating arrangement which can be
reconfigured for different kind of illumination effects with
minimal effort.
[0007] The objects of the invention are achieved by using light
sources made of layered foil structures, such as polymer based
organic LEDs, for illuminating keys or key groups. Certain objects
of the invention may even be achieved though other light sources,
such as SM-LEDs, are used if the mechanical structure and/or
control electronics of the keypad are correctly designed.
[0008] The invention concerns a keypad for a portable electronic
device. The characteristic features of a keypad according to the
invention are those recited in the independent claim directed to a
keypad.
[0009] Additionally the invention concerns a method for
illuminating the keys of a keypad. The characteristic features of a
method according to the invention are those recited in the
independent claim directed to a method.
[0010] Organic LEDs, also known as OLEDs, are light-emitting
semiconductor devices that consist of a stack of very thin material
layers. A simple OLED structure consists of a transparent
substrate, an anode electrode layer, a polymeric recombination
layer and a cathode electrode layer on top of each other. According
to the first aspect of the invention, one or more OLEDs are
associated with individual keys or key groups so that they take on
the role of the known surface-mounted diodes in illuminating the
keypad. According to the second aspect of the invention the OLEDs
are integrated into the keypad structure so that one of the layers
that would exist in the keypad structure also for other reasons
also acts as the substrate layer for the OLEDs. An alternative
solution is to manufacture complete OLEDs and to attach them to the
other parts of the keypad arrangement for example by glueing or
soldering them to a surface or embedding them into an injection
moulded piece of material.
[0011] According to a third aspect of the invention an OLED or
comparable semiconductor light source used for keypad illumination
is grouped together with a solid-state switching element such as an
organic field-effect transistor, also known as OFET. The advantage
gained through such grouping comes from the fact that a single pair
of supply voltage lines can be used for a number of light sources,
and still at least one of the light sources (the one grouped
together with a switching element) can be individually switched on
or off by using a simple, low-power control signal. A converter
unit is typically required for converting the illumination
controlling commands issued by a microprocessor into switching
signals for the individual light source--switching element
pairs.
[0012] According to the fourth aspect of the invention an
illuminated keypad consists of layers so that a dome layer or dome
sheet layer is not on top of the layer comprising the contact
points but under it. Combining such an order of layers to the use
of OLEDs as light sources for illumination results in a solution
where the light sources may be located very close to the visible
surface of the illuminated keys. The advantage gained therethrough
comes from the fact that when the emitted light has only a very
short passage to travel within a transparent or translucent
substance before being emitted into air and towards the eyes of a
user, only a fraction of that electric power must be used for
illumination which was used to drive the light sources in
conventional solutions, without compromising the observable
intensity of light. A naturally occurring alternative viewpoint is
that with the same amount of electric power used for illumination
as in conventional solutions a far brighter lighting effect can be
obtained.
BRIEF DESCRIPTION OF DRAWINGS
[0013] The novel features which are considered as characteristic of
the invention are set forth in particular in the appended claims.
The invention itself, however, both as to its construction and its
method of operation, together with additional objects and
advantages thereof, will be best understood from the following
description of specific embodiments when read in connection with
the accompanying drawings.
[0014] FIG. 1a illustrates a known keypad structure in exploded
view,
[0015] FIG. 1b illustrates the keypad structure of FIG. 1a in
assembled configuration,
[0016] FIG. 1c illustrates certain electric characteristics of the
illumination arrangement of the structure of FIGS. 1a and 1b,
[0017] FIG. 2 illustrates a simple layered structure of an
OLED,
[0018] FIG. 3 illustrates a simple layered structure of an
OFET,
[0019] FIG. 4 illustrates the principle of placing both the
switching function and the illumination next to each key,
[0020] FIG. 5 illustrates an embodiment of the invention where an
OLED surrounds the conductive strips used for switching,
[0021] FIGS. 6a, 6b and 6c illustrate some alternative locations of
a key-specific OLED,
[0022] FIG. 7 illustrates a printed circuit board for a resistive
keypad with key-specific illumination,
[0023] FIG. 8 illustrates a simple circuit diagram for an
illuminated keypad,
[0024] FIG. 9 illustrates a variation of the circuit diagram of
FIG. 8,
[0025] FIG. 10 illustrates a further variation of the circuit
diagram of FIG. 8,
[0026] FIG. 11 illustrates an alternative structural principle for
a layered keypad,
[0027] FIG. 12 illustrates -the application of the principle of
FIG. 11 to OLED illumination,
[0028] FIG. 13 illustrates the application of the principle of FIG.
11 to SM-LED illumination, and
[0029] FIG. 14 illustrates a method according to an embodiment of
the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0030] To provide some additional background to the present
invention, a known simple OLED structure is shown in FIG. 2. A
transparent or translucent substrate 201 is essentially platy in
form and has two parallel planar surfaces. The main function of the
substrate layer 201 is to act as a mechanical support structure and
to allow light to pass therethrough. One suitable, exemplary
substrate material is borosilicate glass. A transparent or
translucent anode layer 202 is located on one of said planar
surfaces. In addition to being transparent or translucent to light,
the anode layer 202 must be conductive to a certain extent and have
a relatively high work function. A suitable material for the anode
layer 202 is for example indium tin oxide (ITO). That surface of
the anode layer 202 which is not against the substrate 201 is
essentially covered by a polymeric recombination layer 203 which is
also known as the active layer. It is made of e.g. poly phenylene
vinylene (PPV) and is sandwiched between the anode layer 202 and a
cathode layer 204 which is made of a conductive material having a
relatively low work function, such as aluminium. The OLED structure
may comprise additional layers such as protective coatings over the
whole stack of anode, active and cathode layers in order to isolate
it from the harmful effects of the environment.
[0031] When the OLED of FIG. 2 is coupled to a supply voltage so
that the anode layer 202 is coupled to a higher potential than the
cathode layer 204, it is biased in the forward direction. The
difference in work functions between the anode and cathode layers
causes holes to be injected from the anode layer into the active
layer and electrons to be injected from the cathode layer into the
active layer. The movement of charged particles through the active
layer means that an electric current flows therethrough.
Recombination of holes with electrons within the active layer
causes quanta of electromagnetic radiation to be emitted. When the
selection of work functions has been made properly, the emitted
quanta have a wavelength falling into the range of visible light.
The light escaping through the anode layer 202 and the substrate
201 is visually observed. Discrete emissive patterns may be formed
most simply by using a stack of continuous substrate, anode and
active layers and on top of them a number of discrete cathodes.
More elaborate patterned structures may use a number of anodes and
a number of cathodes so that for each anode-cathode pair, an
emissive pixel or picture element is formed at the point where they
overlap.
[0032] FIG. 3 illustrates a known structure of an organic FET which
can be used as a very thin solid-state switch deposited on a planar
surface. The substrate layer 301 is made of degenerated silicon and
constitutes the gate of the FET. On one planar surface of the gate
is a thin insulating layer 302 the function of which is to
electrically insulate the gate from the next layer, which is an
organic semiconductor layer 303 that constitutes the channel of the
FET. On top of the channel layer 303 there are two conductive
electrodes isolated from each other, namely the drain 304 and
source 305 of the FET.
[0033] FIG. 4 illustrates, on a rather abstract level, a keypad
illumination principle according to an embodiment of the invention.
We assume that a certain essentially rigid mechanical support
structure 401 is provided for counteracting the mechanical
depressing force caused by a user in association with pressing a
key 402. The support structure 401 may be for example a printed
circuit board located within a keypad-controlled electronic device
and held in place by support brackets that constitute a part of the
device's overall mechanical structure. The support structure 401
need not be planar. Between each key 402 and the support structure
401 there is a space 403 within which the switching function(s)
associated with the key are realized. Space 403 may comprise, for
example, the assembly of conductive strips close to each other and
an elastcally deformable conductive dome above them as in FIGS. 1a
and 1b. According to the invention, space 403 comprises also an
illumination arrangement specific to that key, which illumination
arrangement is based on the use of an OLED as the light-emitting
component.
[0034] The shape of the OLED and its location in relation to the
other components of the key structure may vary considerably. FIG. 5
illustrates schematically a solution where the conductive strips
501 and 502, which the conductive dome (not shown in FIG. 5)
connects to each other when the key is pressed, are placed in the
middle, and a nearly circular OLED element 503 goes round them on
the surface of a printed circuit board 504. In the upper
alternative enlarged portion of FIG. 5 a cross-section of the OLED
element is shown where the cathode layer 505, active layer 506,
anode layer 507 and substrate layer 508 are visible with the
relative thicknesses of the first three of these greatly
exaggerated. In the lower alternative enlarged portion of FIG. 5
the OLED forms an integrated structure with the printed circuit
board so that the board material 504 acts as the substrate. Because
the board material is not transparent and because the desired
direction of emitted light is away from the circuit board
(upwards), the layers of the OLED are here in a reverse order with
respect to the substrate if compared to that described above: next
to the substrate 504 is the cathode layer 510, on top of it the
active layer 511 and as the topmost layer the anode layer 512 which
is, as stated previously, transparent. The cathode layer 510 may
even be made exactly like other conductive pads and traces on the
printed circuit board, which further increases the degree of
integration. If the conductive dome is at least partly transparent
or translucent to light, its diameter can be selected freely in the
structure of FIG. 5. However, if the conductive dome is completely
opaque, its diameter must be smaller than at least the outer
diameter of the OLED element, and most preferably also smaller than
the inner diameter of the OLED element, so that the emitted light
may pass around the edges of the conductive dome.
[0035] FIGS. 6a, 6b and 6c illustrate schematically some other ways
of placing the OLED in the vicinity of the conductive strips which
together with the conductive dome constitute the switching parts of
a key. In FIG. 6a the conductive strips 501 and 502 are similar as
in FIG. 5, but the OLED 601 is only located on one side of them. It
would naturally be possible to place several OLEDs like the one
shown in FIG. 6a on different sides of the conductive strips and to
connect the OLEDs in series or in parallel so that they all provide
illumination simultaneously. FIG. 6b shows an arrangement where the
OLED 610 is in the middle and the conductive strips 611 and 612
constitute concentric circles around it. This kind of an
arrangement is naturally only possible if the conductive dome (not
shown in FIG. 6b) is transparent or translucent or if there is a
hole through the conductive dome for the emitted light to shine
through. FIG. 6c illustrates an exemplary arrangement of conductive
strips for a so-called polydome key where there are more then one
conductive dome (not shown in FIG. 6c) under a single key so that
the switching function depends on the part or portion of the key
which is pressed. More specifically there is a first conductive
strip 620, a second conductive strip 621 and a common conductive
strip 622. The OLED 623 is here placed partly between the dome
areas. The abovementioned possibilities of either taking a complete
OLED and attaching it to the other parts of the structure, or
integrating the OLED into the other parts so that at least one of
the OLED layers is the same as or similar to the other structural
layers, apply regardless of the position, size and shape of the
OLED.
[0036] FIG. 7 illustrates the applicability of the invention in
association with the concept of a resistive keypad. From the
applicant's previous patent application number EP 99660183.7, which
is incorporated herein by reference, there is known a functional
principle for implementing a keypad so that each key location
corresponds to a contact point between an essentially linear
resistive element and a conductive element. Especially each key
location corresponds to a certain unequivocal pair of distances
measured from the ends of the resistive element to the contact
point. The input information representing the pressing of a key is
generated by measuring the voltages between each end of the
resistive element and the contact point and mapping either their
absolute values or their ratio into a piece of input information in
a lookup table. An advantage of the resistive keypad principle is
the small number of connections required between the keypad and the
associated processing electronics.
[0037] A top view of the printed circuit board of a resistive
keypad arrangement is shown in FIG. 7. The electrical connections
that are required for the switching functions consist of a first
end 701 of the resistive strip, a second end 702 of the resistive
strip and a contact point 703 to a common conductive electrode. In
order to keep the switching function as reliable as possible, the
key locations consist of conductive strip portions in FIG. 7 and
the actual resistive material is distributed as relatively short
sections between the key locations. Cross-hatching illustrates
graphically the resistive portions. With "resistive" we mean that
the resistivity of the material is high enough to produce
meaningful differences between voltage readings if two adjacent
keys are pressed.
[0038] The OLEDs 704 are located next to each key location in FIG.
7. The conductive connections that are used to provide a voltage to
those OLEDs which should be emitting light are not shown in FIG. 7,
but it is within the capability of a person skilled in the art to
provide such connections by using, for example, a double sided or
multilayer printed circuit board.
[0039] FIG. 8 is one possible circuit diagram for an illuminated
keypad structure the layout of which follows the model of FIG. 7.
Each key location is represented in FIG. 8 as a switch 801, and the
distributed resistive sections between key locations that together
constitute a resistive path from the first end 701 to the second
end 702 appear as resistors 802. Here we assume that the second end
702 is coupled to the local ground potential. Each OLED appears in
FIG. 8 as a light-emitting diode 803. Note that the physical
locations of the graphical symbols in a circuit diagram need not
correspond to the actual relative physical locations of the
corresponding components. In the simple embodiment of FIG. 8 there
is a separate supply voltage line 811 to 819 to the anode of each
OLED, and all cathodes are coupled to ground through the second end
connection 702 of the resistive strip.
[0040] The disadvantage of the embodiment of FIG. 8 is the large
number of connections needed to separately switch on or off the
OLEDs. FIG. 9 comprises, as an addition to the circuit diagram of
FIG. 8, a serial to parallel converter 901 which takes input
signals over a serial line 902 and converts them to certain
preprogrammed illumination patterns which are implemented by
providing supply voltages to selected OLEDs through lines 911 to
919. The serial to parallel converter 901 is in its simplest
embodiment a linear shift register into which a sequence of bits is
serially written and from which at least a part of the bits of the
sequence may be simultaneously read in a parallel fashion. It may
also comprise e.g. programmable logic.
[0041] Even the embodiment of FIG. 9 comprises the disadvantage
that a relatively high current must be taken from each parallel
output of the serial to parallel converter 901 in order to make the
OLEDs emit enough light. FIG. 10 illustrates an arrangement where
each OLED 803 is accompanied by a semiconductor switching component
1001, such as a field-effect transistor. Each serially coupled
OLED-transistor pair constitutes a controllable light-emitting
entity of which there are a certain number (nine in FIG. 10)
coupled in parallel between a pair of supply voltage electrodes. In
FIG. 10 these supply voltage electrodes are the same as the first
701 and second 702 ends of the resistive strip. The gate electrode
of the FET constitutes the control input of the controllable
light-emitting entity. The control inputs are coupled to the
outputs of the serial to parallel converter 901 so that the
practical operation of the circuit is the same as of that
illustrated in FIG. 9, with the exception that now the serial to
parallel converter 901 needs to supply only a very low current to
each input.
[0042] The invention does not limit the selection of semiconductor
switching components in the arrangement of FIG. 10, but specific
advantages can be gained through the use of OFETs. Previously we
have noted that the thickness of the keypad arrangement should most
advantageously be minimized, which makes the use of OLEDs as light
sources particularly advantageous since they can be made very thin.
Additionally the OLEDs consist of layers which can even be produced
together with the other layers of the keypad structure, resulting
in a highly integrated structural solution with little or no
soldering required. OFETs share the same advantages.
[0043] If conveying illumination commands to the keypad arrangement
(including the serial to parallel converter) is too slow or
otherwise impossible, one may use a parallal to parallel mapping
circuit in place of the serial to parallel converter 901. There
could be for example four parallel input lines to the mapping
circuit and nine (or as many as there are independent light
sources) output lines therefrom. With four parallel input lines it
is possible to give 16 different illumination commands. Although
not all possible permutations of activated OLEDs are thereby
possible to produce, 16 different illumination patterns is still a
remarkable improvement over the "completely on/completely off" type
prior art illumination solutions.
[0044] In the foregoing we have implicitly assumed that the OLEDs
(and possible accompanying OFETs) are to appear on the surface of
printed circuit board. This is advantageous, since the required
electrical connections are easily implemented within the printed
circuit board, and the manufacturing process of the printed circuit
board involves in any case the controlled deposition of patterned
layers on the surface(s) thereof, which makes it easy to integrate
also the production of the OLED (and OFET) layers to the
manufacturing process. However, if a conventional solution with
conductive domes or even a continuous conductive dome sheet is
used, there remains the problem of arranging for the conduction of
light to the other side of the domes or the dome sheet.
[0045] It is possible to place the OLEDs (and OFETs) also between
the domes (or the dome sheet) and the outer structural components,
i.e. on the top side of the dome layer instead of under it. The
dome sheet, the key mat or even the outer cover of the electric
apparatus may act as the support structure for the OLEDs (and
OFETs). All these alternatives involve the further selection of
either attaching complete OLEDs (and OFETS) to the other structural
component(s) or using the other structural component(s) as integral
parts of the OLED (and OFET) structure. The latter alternative
allows for example the OLEDs to be produced in a printing process
which uses litographic methods or silk screen printing to deposit
the patterned layer structures needed.
[0046] FIG. 11 illustrates a structural principle for a keypad
which is completely new compared to all solutions described above.
The structure is shown in exploded view in order to give a better
view of its components. Within a certain electronic device there is
an essentially rigid mechanical support structure 1101. On top of
it there is a dome sheet 1102 comprising a number of conductive
domes 1103. The dome sheet 1102 is made of an elastically
deformable material and thus it resembles the known dome sheets
used in keypad arrangements. However, the dome sheet 1102 is
oriented so that the domes bulge downwards from it, i.e. into the
direction of the support structure 1101 and not upwards towards the
direction from which the user will press the keys. Small
protrusions 1104 may be provided on the surface of the support
structure 1101 to ensure a point-like contact between the support
structure 1101 and each dome 1103 in the dome sheet 1102. A
point-like contact to a dome is known to enhance the tactile feel
experienced by the user in pressing the key associated with the
dome.
[0047] On top of the dome sheet 1102 there is a printed circuit
board 1105 which is thin enough to be flexible to a certain extent.
It can be made of e.g. the known flexible printed circuit
materials, also known as flex boards or just flexes. If the concept
of resistive keyboard is used, the printed circuit board 1105 may
be made of a polymer foil (e.g. polyester) onto which the resistive
keyboard circuitry is printed; OLEDs or similar layered light
sources may be integrated into such a polymer foil. In FIG. 11 the
printed circuit board 1105 comprises, on that surface thereof which
comes against the dome sheet 1102, conductive strips 1106 at
locations which correspond to the locations of the domes 1103. In
order to provide electric isolation between the dome sheet 1101 and
those parts of the printed circuit board 1105 which should not come
into conductive contact with the dome sheet, a perforated
insulation sheet 1107 may be used between the dome sheet 1102 and
the printed circuit board 1105.
[0048] On the upper side of the printed circuit board 1105 there is
an elastic key mat 1108, which may further be covered with a
perforated outer cover 1109 if necessary. The key mat 1108 is
transparent or translucent to light and may comprise bulging
protrusions to mark the places of the keys, but the latter is not
necessary. The transparency of the key mat need not be total, as it
suffices that at least some key locations contain transparent or
translucent areas, which may have e.g. the shape of numbers or
alphabetical characters. Illumination of the keys is built into the
space 1110 which is left between the printed circuit board 1105 and
the elastic key mat 1108. A continuous key mat could be replaced
with a number of smaller submats or even with a number of
individual key surfaces.
[0049] FIG. 12 illustrates the combination of the key-specific OLED
illumination principle to the layered structure shown schematically
in FIG. 11. The layers in the keypad structure of FIG. 12 are the
same as in FIG. 11, but they are now shown in assembled
configuration. Between the upper surface of the printed circuit
board 1105 and the elastic key mat 1108 there are a number of OLEDs
1201 so that each OLED is placed directly under a key of its own.
The electric connections needed for the OLEDs 1201 can utilize the
printed circuit board 1105 as their support structure. The OLEDs
1201 can even be manufactured as integral parts of the printed
circuit board 1105, for example by printing them on the surface of
the printed circuit board, as was described earlier in association
with the other embodiments of the invention. Alternatively the
OLEDs 1201 may be attached to the elastic key mat 1108, in which
case they need to comprise (or to be coupled to) exposed contact
surfaces on that side of the OLEDs which comes against the printed
circuit board. The OLEDs can even be embedded in the substance of
either the printed circuit board or the key mat. The principal
direction of emitted light from the OLEDs is upwards, through the
keys.
[0050] FIG. 13 shows how the structural principle shown in FIG. 11
can be used to revolutionize the keypad illumination even when more
conventional light sources are otherwise used. In the structure of
FIG. 13 there is a relatively thin light guide layer 1301 between
the printed circuit board 1105 and the key mat 1108; instead of
using a separate light guide layer one could also use the key mat
1108 as the light-guiding element. Surface-mounted LEDs 1302 are
placed on the upper surface of the printed circuit board 1105 so
that when switched on, they emit light into the light guide.
[0051] The structural principle of FIG. 11, some more practical
embodiments of which are shown in FIGS. 12 and 13, allows the light
sources of the illumination arrangement to be placed so that the
passage of light from the light source to the point where it
escapes the keypad structure and goes into the direction of the
user's eye can be made very short and very easy for the light to
travel through. This fact can be utilized by two ways. Either we
may use the same amount of electrical power as in prior art
arrangements to run the illumination arrangement, in which case the
amount of light reaching the user's eye can be made larger than
before. Or we may aim at generating the same observable amount of
light, in which case much less electrical power is needed.
[0052] In the foregoing we have not considered in detail, how
should the flexible illumination possibilities brought forward by
the invention be used. The purpose of prior art keypad illumination
arrangements has been solely to enable the user to see the location
and/or the identifying characters of the keys also when ambient
light is not sufficiently bright. This is understandable, since the
prior art illumination arrangements did not produce a very high
level of illumination, and the illumination of single keys or key
groups was not possible. However, according to the invention,
single keys or key groups that constitute only a part of the whole
keypad can be separately illuminated. Additionally, placing the
light sources in an advantageous way as described earlier allows
the amount of observable light to be raised so that illumination
effects can be visible also despite of relatively bright ambient
lighting.
[0053] From known mobile telephones it is known to make the mobile
telephone identify a caller and to select a different ringing tone
according to the identity of the caller. For example, the telephone
can ba programmed to announce calls from a certain very specific
caller with a unique ringing tone, or the potential callers may be
divided into caller groups so that each group is associated with a
ringing tone of its own. The key or key group specific illumination
arrangement according to the invention may be used in similar
fashion. FIG. 14 is a state diagram where state 1401 corresponds to
the basic operational mode of a mobile telephone when it has been
switched on but it is idle. During a programming procedure at least
one caller identity has been associated with a certain illumination
pattern or a certain sequence of illumination patterns. When a call
connection request is received according to state 1402, the
telephone tries to identify the caller at state 1403. Depending on
what illumination pattern or pattern sequence, if any, has been
associated with the caller which is identified, either no
illumination effect is selected as in state 1404 or a certain
illumination pattern or patterns are used in place of or as a
complement to the acoustic ringing tone as in states 1405 and 1406.
Using a sequence of illumination patterns fast enough creates the
impression of animation: the keypad illumination plays a simple
"movie" to the user.
[0054] In many cases the user of a keypad-controlled electronic
device may be in doubt regarding which key should be pressed next.
The key-specific illumination arrangement according to the
invention may be used for user guidance. State 1407 represents a
certain situation where there is a most probable or only possible
key which the user should press next. At state 1408 that key or
those keys are identified, and at one of states 1409, 1410 or 1411
it can be marked by illuminating it while the other keys are not
illuminated, by illuminating it with higher lighting intensity than
the other keys, by flashing its illumination or by producing some
other illumination effect. Also if in a certain situation only a
limited part of a whole keypad is "active" or available for use,
this can be emphasized by illuminating only that part of the
keypad.
[0055] The illumination effects can also be used for recreational
purposes. Games are already integrated into the mobile telephones
known at the priority date of the present patent application, so
illumination of specific keys or key groups can be made a part of
the game. State 1412 represents a game mode. The first assumption
is that the illumination serves a decorative and illustrative
purpose. State 1413 represents the occurrence of a high score or
other achievement in the game which is then rewarded at one of
states 1414 or 1415 with animated and/or flashing illumination of
some kind. Another assumption is that the illumination is made an
integral part of playing a game which is played by pressing the
keys according to state 1416. An example of the latter category is
a game which tests the user's memory and reflexes so that a
sequence of keys is illuminated in succession, and the user must
press the same keys in the same order as long as he can. The
illumination functions associated with such games are represented
in FIG. 14 by states 1417 and 1418.
[0056] If we assume that the controlling of the illumination
patterns is based on the use of a serial to parallel converter as
in FIGS. 9 and 10, there are two basic approaches to the task of
generating illumination sequences. The most simple one of them in
terms of the structural and functional complexity of the serial to
parallel converter is that each command given by the microprocessor
through the serial connection to the serial to parallel converter
represents exactly one illumination pattern. In order to realize an
animation effect, which is a sequence of successive illumination
patterns, the microprocessor sends successive commands to the
serial to parallel converters. The other alternative is that a
single command means a complete sequence of illumination patterns.
According to the latter approach, when the serial to parallel
converter receives a command from the microprocessor through the
serial connection, it checks whether the command means a single
pattern or a sequence. If it means a sequence, it reads the
patterns constituting the sequence from a memory and gives the
control signals to the light sources (or light source+switch
entities) so that the patterns are produced one at a time. The pace
of changing from one pattern to another in the sequence needs to be
determined in relation to a certain clocking signal. The serial to
parallel converter may have a clock signal generator of its own to
produce the clock signal, or it may receive a clock signal from
some other parts of the electronic device.
[0057] Regardless of whether the illumination is provided in the
form of a single pattern or a sequence, there must be defined the
duration for which the illumination is on. Also for this purpose we
may define either that the illumination is on for the same duration
for which the command from the microprocessor to the serial to
parallel converter is on, or that the serial to parallel converter
comprises means for implementing a time constant so that after
having received a command from the microprocessor it keeps the
illumination effect meant by the command on until a time equal to
the time constant has passed from the moment of receiving the
command. According to still another approach the serial to parallel
converter fulfils each command immediately and makes changes only
after having received the next command, and a specific command has
been defined as the "switch off" command.
[0058] In the foregoing we have described mostly OLEDs as the light
sources which are made of layered foil structures and which are
used for key- or key group specific illumination. This is a
consequence of a fact thet OLEDs are the most important category of
light sources made of layered foil structures known at the priority
date of the present patent application. However, it should be noted
that the invention is by no means limited to the use of OLEDs, but
other solid-state light sources made of layered foil structures
could be used as well.
[0059] The above-described exemplary embodiments of the invention
should be construed as aids for comprehending the applicability of
the claims and not as explicit limitations regarding such
applicability. The features recited in depending claims are freely
combinable unless explicitly otherwise stated. Directional
expressions-such as "upper surface" or "on top of" refer only to
the directions illustrated in the drawings and do not limit the
applicability of the invention to structures only oriented in a
certain direction.
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