System and method for cleaning the display screen of a touch screen device

A procedure for cleaning a display screen in a touch screen based telephone such that features of the telephone are not inadvertently activated is described. The procedure operates by causing the telephone (actually, a processor in the telephone) to enter a "clean screen" mode in response to a request from the user to clean the display screen. While in the "clean screen" mode, all signals generated in response to the user touching the display screen are ignored. In this matter, while in the "clean screen" mode, the user is able to clean the display screen without inadvertently activating any features of the telephone. The telephone automatically determines when the user has finished cleaning the display screen. When it is determined that the user has finished cleaning the display screen, the telephone leaves the "clean screen" mode and enters an "active screen". While in the "active screen" mode, all signals generated in response to the user touching the display screen are processed.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates generally to touch screen devices, and more 
particularly to a system and method for cleaning the display screen of a 
touch screen device. 
2. Related Art 
In a touch screen device, user input is received via the device's display 
screen. Typically, a menu of options is displayed on the device's display 
screen. Each option corresponds to a feature provided by the device. A 
user selects one of the options by touching the appropriate part of the 
display screen. 
Touching a touch screen device's display screen will result in the 
accumulation of oil and/or dirt on the display screen. Thus, to ensure 
proper operation, the display screen must be periodically cleaned. Such 
cleaning necessarily involves touching the display screen. 
Conventional touch screen devices cannot differentiate between "screen 
touches" made to enter user input and screen touches made to clean the 
display screen. Consequently, the cleaning of a touch screen device's 
display screen may result in the inadvertent activation of the device's 
features, thereby resulting in improper operation of the device, and 
perhaps even damage to the device. 
A conventional solution to this problem requires the removal of power to 
the device (i.e., turning the device off) while the device's display 
screen is cleaned, or at least removal of power from the device's display 
screen. However, this solution is inadequate for many types of touch 
screen devices, particularly devices which use their display screens to 
provide status information to users. In such devices, removal of power 
frown the display screen is not advantageous since it would then be 
impossible to provide status information to users. Also, this solution is 
inadequate since it requires that users remember to turn the device back 
on. 
Thus, what is required is a system and method for enabling a user to clean 
a touch screen device's display screen without inadvertently activating 
the device's features, and without removing power from the device or from 
the display screen. 
SUMMARY OF THE INVENTION 
The present invention is directed to a touch screen based telephone having 
the capability of enabling a user to clean the telephone's display screen 
without inadvertently activating any features of the telephone. The 
telephone (actually, a processor in the telephone) operates by entering a 
"clean screen" mode in response to a request from the user to clean the 
display screen. While in the "clean screen" mode, all signals generated in 
response to the user touching the display screen are ignored. In this 
matter, while in the "clean screen" mode, the user is able to clean the 
display screen without inadvertently activating any features of the 
telephone. 
The telephone operates to determine when the user has finished cleaning the 
display screen. When it is determined that the user has finished cleaning 
the display screen, the telephone leaves the "clean screen" mode and 
enters an "active screen". While in the "active screen" mode, all signals 
generated in response to the user touching the display screen are 
processed. 
The telephone operates to determine when the user has finished cleaning the 
display screen by determining whether the user failed to touch the display 
screen for a predetermined amount of time, and by detecting whether the 
telephone's handset has transitioned from on-hook to off-hook. The 
telephone determines that the user has finished cleaning the display 
screen if it is determined that the user failed to touch the display 
screen for the predetermined amount of time, or the handset has 
transitioned from on-hook to off-hook. 
Further features and advantages of the present invention, as well as the 
structure and operation of various embodiments of the present invention, 
are described in detail below with reference to the accompanying drawings. 
In the drawings, like reference numbers indicate identical or functionally 
similar elements.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The present invention is directed to a system and method for enabling a 
user to clean a touch screen device's display screen without inadvertently 
activating any of the device's features (other than the "clean screen" 
feature), and without removing power from the device or from the display 
screen. For convenience purposes, the present invention is described 
herein in terms of a touch screen based telephony product, such as a 
telephone. However, it should be understood that the present invention 
includes all types of touch screen products. In particular, the present 
invention includes touch screen devices which use their display screens to 
provide status information to users, such that removal of power from the 
display screen is not advantageous since such power removal makes it 
impossible to provide status information to users. 
FIG. 1 is a block diagram of a touch screen based telephone 102 according 
to a preferred embodiment of the present invention. The telephone 102 
includes a processor 104, such as a central processing unit (CPU), that is 
connected to a communication medium, such as a bus 106. The bus 106 
connects elements of the telephone 102 (such as the processor 104) to 
other elements of the telephone 102 (such as application specific 
components 112, described below). However, these elements may be connected 
to one another using other means. For example, elements of the telephone 
102 may be connected to each other using a plurality of dedicated lines, 
or a combination of the bus 106 and dedicated lines. 
The processor 104 operates in accordance with control logic 110 stored in a 
memory device 108, such as a random access memory (RAM), which is also 
connected to the bus 106. Preferably, control logic 110 represents a 
software program, such that the processor 104 operates in accordance with 
instructions in the software program. 
The telephone 102 also includes application specific components 112, which 
in the preferred embodiment include telephone related components. More 
particularly, the application specific components 112 include telephony 
communication components that are necessary to enable the telephone 102 to 
establish and maintain communication links over a telephone line. As shown 
in FIG. 2, the application specific components 112 include a handset 202, 
a switch hook 204, an on-hook/off-hook transition detector 208, and other 
telephony components 206. The structure and operation of these telephony 
communication components will be apparent to persons skilled in the 
relevant art. As such, the following details pertaining to the application 
specific components 112 are provided for the convenience of the reader. 
The handset 202 is either "off-hook" or "on-hook". Traditionally, the 
handset 202 is "on-hook" when it is resting on the switch hook 204. The 
handset 202 is "off-hook" when it is lifted from the switch hook 204. 
However, with modern telephones, such as "hands-free" telephones and 
"facsimile capability" telephones, it is more accurate to discuss the 
state of the electronic line switch (ELS) which controls the connection of 
the product to the local exchange office's end office. When the ELS is 
connected to the local exchange company's end office, the product is 
off-hook; depending upon the product's features, the handset may be 
physically on-hook or off-hook. When the ELS is not connected to the local 
exchange company's end office, the product is on-hook. 
The on-hook/off-hook transition detector 208 is coupled to the switch hook 
204, and detects when the handset 202 transitions from on-hook to 
off-hook. 
Returning to FIG. 1, the telephone 102 also includes a touch screen module 
114, which includes a display screen 118 and a touch screen interface 116. 
The display screen 118 is divided into a plurality of sectors. A unique 
identifier (preferably a unique digital code) is assigned to each of the 
sectors. The touch screen interface 116 monitors the screen 118 and 
detects when the screen 118 is touched. When a user touches the screen 
118, the touch screen interface 116 determines which sector of the screen 
118 was touched, and then sends the digital code associated with that 
sector to the processor 104 via the bus 106. In this manner, the processor 
104 is made aware of any and all sectors of the screen 118 which are 
touched. Touch screen technology is well known and, thus, the structure 
and operation of the touch screen module 114 will be apparent to persons 
skilled in the relevant art. 
The telephone 102 maintains a number of graphical images called "display 
pages" that are displayed preferably one at a time on the screen 118. 
These display pages are stored in the RAM 108. Alternatively, these 
display pages are stored in memory (not shown) contained in the touch 
screen module 114. For example, display pages may be stored in read only 
memory (ROM) (not shown), or a combination of RAM 108 and ROM, or may be 
generated in whole or in part by software algorithms. 
Each display page includes one or more icons that resemble buttons. 
Accordingly, these icons are called "touch screen buttons", or simply 
"buttons". The buttons are arranged on the display pages such that when a 
display page is displayed on the screen 118, each button is positioned 
over a unique set of the sectors of the screen 108. That is, no two 
buttons (of a display page displayed on the screen 118) are positioned 
over the same sector of the screen 118. 
Generally, each button corresponds to a feature that is provided by the 
telephone 102. For example, suppose a display page has a "re-dial last 
number" button, and a user presses this button (that is, touches that part 
of the screen 118 that coincides with the display of this button). The 
touch screen interface 116 detects the pressing of the "re-dial last 
number" button, and sends the digital code(s) corresponding to the screen 
sector(s) coincident with the "re-dial last number" button to the 
processor 104 via the bus 106. The processor 104, operating in accordance 
with the control logic 110, performs predetermined functions when it 
receives these digital code(s). In particular, the processor 104 instructs 
the application specific components 112 to re-dial the last number dialed. 
The telephone 102 includes a "set up" display page 302, which is shown in 
FIG. 3. A user navigates to this display page 302 (that is, causes the 
"set up" display page 302 to be displayed on the screen 118) using various 
navigational buttons that are contained in the display pages. These 
navigation buttons may include a "next menu" button, a "previous menu" 
button, and a "go to the set up display page" button (these buttons are 
not shown). 
The "set up" display page 302 includes a "set clock" button 304, a "set 
area code" button 306, and a "clean screen" button 308. The "set up" 
display page 302 may also include additional buttons, such as navigational 
buttons. 
As indicated above, the buttons 304, 306, 308 in the "set up" display page 
302 correspond to features that are provided by the telephone 102. When a 
user presses the "set clock" button 304, the processor 104 allows the user 
to enter the current date and time. When a user presses the "set area 
code" button 306, the processor 104 allows the user to enter an area code 
that will be used as a default when dialing telephone numbers. 
When a user presses the "clean screen" button 308, the processor 104 
enables the user to clean the display screen 118 without inadvertently 
activating any of the features of the telephone 102 (other than the "clean 
screen" feature), and without removing power from the telephone 102 or 
from the display screen 118. Preferably, this task is automatically 
performed by the processor 104 operating in accordance with the control 
logic 110. Alternatively, the telephone 102 is made to perform this task 
using hardware components only, such as a hardware implemented state 
machine. 
This "clean screen" feature makes the telephone 102 particularly 
advantageous. The telephone 102 uses the display screen 118 to display 
status information to the user. For example, this status information may 
include the current date and the current time, the number of recorded 
messages (where the telephone 102 is also an answering machine), 
information identifying the lines in use and the lines which are available 
for use, message forwarding information, system diagnostic information, 
incoming calls information, etc. If it was necessary to turn off the 
display screen 118 to clean the display screen 118, then it would not be 
possible to use the display screen 118 to display this status information. 
By providing this feature, users can clean the display screen 118 while 
still receiving status information, and without inadvertently activating 
any of the features of the telephone 102. Also, with the present 
invention, it is not necessary for users to remember to turn the display 
screen 118 back on, since it was never turned off. 
The manner in which the telephone 102 enables the user to clean the display 
screen 118 without inadvertently activating any of the features of the 
telephone 102 (other than the "clean screen" feature), and without 
removing power from the telephone 102 or from the display screen 118, 
shall now be described with reference to a flowchart 402 presented in FIG. 
4. This flowchart 402 is of sufficient detail to enable a person skilled 
in the relevant art to generate relevant portions of the control logic 
110, or to generate a comparable hardware implemented state machine. 
The processor 104 periodically performs the steps of flowchart 402. 
Alternatively, the processor 104 performs the steps of flowchart 402 on an 
interrupt driven basis. For example, when the user presses the "clean 
screen" button 308, an interrupt is generated that causes the processor 
104 to perform the steps of flowchart 402 (other than steps 406 and 408). 
Prior to performing the steps of flowchart 402, the processor 104 is in an 
active screen mode. While in the active screen mode, the processor 104 
considers the display screen 118 to be active and, as such, processes all 
display screen sector codes sent to it from the touch screen interface 
116. Such processing typically involves the invocation of features of the 
telephone 402, but the actual operation of the processor 104 upon receipt 
of the display screen sector codes is a function of the control logic 110. 
The flowchart 402 begins with step 404, where control immediately passes to 
step 406. 
In step 406, the processor 104 determines whether the user pressed the 
"clean screen" button 308. Preferably, the processor 104 performs step 406 
by comparing each display screen sector code sent to the processor 104 
from the touch screen interface 116 to the code assigned to the "clean 
screen" button 308. If there is a match, then the processor 104 determines 
that the user pressed the "clean screen" button 308. 
If the processor 104 determines in step 406 that the user did not press the 
"clean screen" button 308, then processing of the flowchart 402 is 
complete, as indicated by step 408. 
If, instead, it is determined in step 406 that the user pressed the "clean 
screen" button 308, then step 412 is performed. In step 412, the processor 
104 leaves the active screen mode and enters a clean screen mode. While in 
the clean screen mode, the processor 104 ignores all signals sent from the 
touch screen module 114 to the processor 104. In other words, the 
processor 104 does not process any display screen sector codes sent to it 
from the touch screen interface 116. In this manner, the user is able to 
clean the display screen 118 without inadvertently invoking any of the 
features of the telephone 102. 
The processor 104 remains in the clean screen mode until either: (1) the 
handset 202 goes off-hook or an on-hook to an off-hook ELS transition 
occurs (see step 416, described below); or (2) the user does not touch the 
display screen 116 for a predetermined amount of time (see step 418, 
described below). If either of these events occurs, then the processor 104 
assumes that the user has finished cleaning the screen, and returns to the 
active screen mode (see step 428, described below). Thus, in the present 
invention, it is not necessary for the user to remember to turn the 
display screen 116 back on. In the present invention, the display screen 
116 is never turned off, and the processor 104 switches automatically 
between the active screen mode and the clean screen mode. 
Also in step 412, the processor 104 displays a "clean screen" display page 
502 (see FIG. 5) on the screen 118. The "clean screen" display page 502 
has a cleaning instructions area 504 and a status information area 506. 
Cleaning instructions specific to the particular touch screen module 114 
used (and the particular display screen 118 used) are presented in the 
cleaning instructions area 504. Ideally, the user follows these 
instructions when cleaning the display screen 118. The processor 104 
displays status information in the status information area 506 (see step 
424, described below). Thus, status information is provided to the user at 
all times, including when the user is cleaning the display screen 118. 
In step 414, the processor 104 resets a counter to zero. This counter is 
maintained in the RAM 108, or alternatively may be maintained in a 
hardware register (not shown). 
In step 416, the processor 104 determines whether the handset 202 is 
off-hook. The processor 104 preferably performs step 416 by accessing the 
on-hook/off-hook transition detector 208, which detects when the handset 
202 has transitioned frown on-hook to off-hook. Preferably, the 
on-hook/off-hook transition detector 208 generates an interrupt when it 
detects a transition from on-hook to off-hook. This interrupt causes the 
processor 104 to immediately process step 428 (discussed below). 
If the handset 202 is off-hook, then the processor 104 assumes that the 
user has finished cleaning the screen (or is no longer interested in 
cleaning the screen) and is in the process of answering an incoming 
telephone call or initiating an outgoing telephone call. Accordingly, if 
in step 416 it is determined that the handset 202 is off-hook, then the 
processor 104 in step 428 leaves the clean screen mode and returns to the 
active screen mode. As discussed above, while in the active screen mode, 
the processor 104 does not ignore signals (i.e., display screen sector 
codes) sent to the processor 104 from the touch screen interface 116. 
Instead, the processor 104 processes all display screen sector codes sent 
to it from the touch screen interface 116. Processing of flowchart 402 is 
complete after step 428, as indicated by step 430. 
If in step 416 it is determined that the handset 202 is not off-hook, then 
step 418 is performed. In step 418, the processor 104 determines whether 
the counter is equal to a predetermined counter value. In essence, in step 
418 the processor 104 determines whether a predetermined amount of time 
has passed since the user has touched the screen 118. If this 
predetermined amount of time has passed since the user has touched the 
screen 118, then the processor 104 assumes that the user is no longer 
cleaning the screen 118, and returns to the active screen mode (step 428). 
Preferably, this predetermined amount of time is equal to 60 seconds, 
although this value is implementation dependent and depends on various 
factors, such as any alternate means for returning the screen to normal 
operation, the complexity of the cleaning process, the nature of the 
product, etc. 
If in step 418 the processor 104 determines that the counter is not equal 
to the predetermined counter value, then step 420 is performed. In step 
420, the processor 104 determines whether the screen 118 was touched since 
the last time that step 420 was performed (note that step 420 is part of a 
control logic loop). The processor 104 preferably makes this determination 
by determining whether the touch screen interface 116 has sent to the 
processor 104 any display screen sector codes since the last time that 
step 420 was performed. Note that the processor 104 does not process these 
display screen sector codes (since it is in the clean screen mode), but 
instead just notes if any has been sent to it. In other words, the 
processor 104 does not invoke any features of the telephone 102 upon 
receipt of these display screen sector codes. 
If in step 420 it is determined that the screen 118 was not touched, then 
the processor 104 performs step 424 (described below). If, instead, it is 
determined that the screen 118 was touched, then the processor 104 assumes 
that the user is still cleaning the screen 118. Accordingly, the processor 
104 resets the counter to zero (step 422). The processor 104 then performs 
step 424. 
In step 424, the processor 104 displays status information in the status 
information area 506 of the "clean screen" display page 502. This may 
involve displaying new status information, and/or updating status 
information that is already displayed in the status information area 506. 
The processor 104 generates and/or obtains such status information in a 
well known manner. 
After updating status information in step 424, the processor 426 in step 
426 increments the counter. The processor 426 then returns to step 416 to 
continue processing while in the clean screen mode. 
While various embodiments of the present invention have been described 
above, it should be understood that they have been presented by way of 
example only, and not limitation. Thus, the breadth and scope of the 
present invention should not be limited by any of the above-described 
exemplary embodiments, but should be defined only in accordance with the 
following claims and their equivalents.