Interactive overlay-driven computer display system

An interactive overlay-driven computer display system wherein the selective activation of a software "switch" by the operator each time the digitizer stylus is contiguous to the overlay, causes a visual image of the overlay (which normally has selectable menu items printed thereon) to be automatically displayed on the monitor screen.

TECHNICAL FIELD 
The present invention relates generally to computer display systems, and 
more particularly to an interactive overlay-driven computer display system 
which utilizes one or more overlays operable in conjunction with a 
digitizer tablet to input data to such computer system for computing, 
control and/or display purposes. 
BACKGROUND OF THE INVENTION 
A portion of the disclosure in this patent document contains material which 
is subject to copyright protection and to which a claim of copyright 
protection is made. The copyright owner has no objection to the facsimile 
reproduction by anyone of the patent document or the patent disclosure, as 
it appears in the United States Patent and Trademark Office patent files 
or records, but otherwise reserves all copyrights whatsoever. 
Often in the use of a computer, it is desirable to input two-dimensional 
graphic data thereto for display, control and/or for processing purposes. 
A wide variety of such devices, commonly known as "digitizers", have been 
proposed and used for such purposes. Additionally, it is well known that 
printed overlays, or menus, placed on a digitizer tablet provide a fast 
and convenient method and means for permitting operator selection 
therefrom of drawing tools, fonts, and other computer executable functions 
printed thereon. Additionally, overlays placed on a digitizer tablet 
provide an advantage over conventional means of "point-and-click" monitor 
selection of menu items in that a larger number of simultaneously viewable 
items can be presented on a digitizer tablet. Printed overlays also enable 
the computer monitor work area to be devoted entirely to the display of 
working documents with little or no area thereof devoted to 
point-and-click menu items. A typical form of digitizer is shown in U.S. 
Pat. No. 3,684,828 to Maher. The digitizer normally includes a relatively 
flat surface for supporting one or more overlays in the form of a map, 
drawing or other source of graphic data, a stylus or other pointing device 
or cursor for designating individual points on the surface of each of such 
overlays, and means defining an X-Y, or rectangular, coordinate system for 
determining the rectangular coordinates for each individually designated 
point on each of such overlays. Well known interface circuitry is provided 
for converting the thus derived rectangular coordinate data into digital 
numbers arranged in an appropriate communication format for transmission 
to a computer for further processing. The Maher patent utilizes a 
piezoelectric substrate to detect the coordinates of the designated points 
by measuring the surface wave pulses propagating through the substrate 
surface. U.S. Pat. No. 3,692,936 to Moffitt discloses an acoustic 
digitizer, whereas, U.S. Pat. No. 4,177,354 discloses a digitizer 
employing a light responsive layer and a grid system which is used in 
combination with a light spot emitting stylus to generate digital 
coordinate signals. The digitizer of U.S. Pat. No. 4,255,617 to Caru et 
al employs a cursor with a capacitive pickup in combination with a platen 
comprising a flat surface within which are embedded two orthogonal grids, 
each consisting of uniformly spaced individual conductors. U.S. Pat. No. 
4,318,096 to Thornburg et al discloses a rectangular coordinate tablet 
which is used in combination with an electrically conductive pen and an 
analog-to-digital converter to provide rectangular coordinate data to a 
computer. The tablet employs a piezoelectric audio pickup which produces a 
succession of pulses when the stylus is drawn across a textured surface 
such as a sheet of paper. Such orthogonally arranged sensors enable the 
direction of motion on a surface to be determined and "digitized" in each 
access by a bidirectional pulse counter. 
In each of the systems referred to above, it is essential that the physical 
orientation of the overlay relative to the digitizer tablet surface, 
together with the particular scale and position of the overlay on the 
tablet surface, must be such that the position of the stylus on the 
overlay corresponds to the point on the tablet that will generate the 
correct coordinate signals for addressing the correct file stored in the 
computer memory. Misalignment results in the system becoming inoperative 
for the intended purpose. 
In U.S. Pat. No. 5,010,323 issued to C. J. Hoffman, the same inventor as 
that of the present application, and which disclosure is incorporated 
herein by reference, there is disclosed a system wherein the utilized 
overlay may be physically positioned on the surface of the digitizer 
tablet in any physical orientation with respect to the coordinate axes of 
the digitizer tablet surface and, additionally, the overlay may be of any 
desired size. In the system disclosed in said '323 Hoffman patent, the 
physical orientation of the overlay on the digitizer tablet surface is 
automatically "transformed" to coincide with the coordinate axes of the 
digitizer tablet surface. Additionally, the overlay is provided with 
appropriate scaling information for automatically normalizing the size and 
position of the overlay. 
An historical disadvantage of selecting menu items from overlays by each of 
the foregoing systems, when compared with point-and-click menu selection 
from the monitor screen by means of a cursor-position generating stylus in 
the form of a mouse or pen, or a self contained cursor-position generating 
stylus (e.g. "tailless mouse"), or the like, is that it has been necessary 
in each of such prior art systems that the vision of the computer operator 
be shifted from the monitor screen to the surface of the tablet, and back 
again, each time an overlay menu item is selected. This constant back and 
forth shifting of the line of vision of the operator is reported to be a 
significant cause of operator fatigue. However, in accordance with 
applicant's invention, there is provided an interactive overlay-driven 
computer display system which obviates the need for any back and forth 
shifting of operator vision between the monitor screen and the surface of 
the tablet, as in prior systems. Greater use of peripheral vision is 
possible, with reduced need for the constant refocusing of the eyes of the 
operator. Implementation of the present invention enables digitizer 
tablets with an appropriately designed stylus to perform as well as a 
mouse (with or without a tail) in all aspects of technical performance and 
human factors of touch and feel. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, there is provided an interactive 
overlay-driven computer display system wherein the selective activation of 
a software "switch" by the operator each time the digitizer stylus is 
contiguous to the overlay, causes a visual image of the overlay (which 
normally has selectable menu items printed thereon) to be automatically 
displayed on the monitor screen. 
From the foregoing, it can be seen that it is a principal object of the 
present invention to provide a new and improved interactive overlay-driven 
computer display system. 
It is another object of the present invention to provide a new and improved 
interactive overlay-driven computer display system which effectively 
obviates the necessity for operator vision to be shifted back and forth 
between the monitor screen and the overlay. 
It is a further object of the present invention to provide a new and 
improved interactive overlay-driven computer display system which is 
capable of effectively displaying on the monitor screen thereof a visual 
image of the overlay containing selectable menu items each time the stylus 
is contiguous to the overlay. 
It is still another object of the present invention to provide a new and 
improved interactive overlay-driven computer display system which is 
capable of effectively displaying on the monitor thereof a visual image of 
the overlay containing selectable menu items whenever the stylus is 
contiguous to the overlay, all in a simple and economical manner. 
These and other objects of the present invention will become more apparent 
and better understood when taken in conjunction with the following 
description and the accompanying drawings, throughout which like 
characters indicate like parts and which drawings form a part of the 
present specification.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
With reference to FIG. 1 of the drawings, an interactive overlay-driven 
computer display system constructed in accordance with a preferred 
embodiment of the present invention comprises a graphics digitizer tablet 
10, such as a NuMonic Corp's. tablet generally referred to as the 
"GridMaster", for example, which has a relatively flat activated surface 
11 and a stylus 12 coupled to the digitizer tablet by means of a flexible 
cable 13. Use of a self contained stylus (or "puck") instead of the 
particular stylus disclosed may be preferred by some operators without 
departing from either the spirit or scope of the present invention. The 
digitizer tablet 10 senses the X and Y rectangular coordinate position of 
stylus 12 whenever it either touches or is contiguous to the tablet 
surface 11 and produces a data stream of X-Y coordinate signals 
corresponding to the physical position of point of stylus 12 relative to 
the X-Y coordinate axes of tablet surface 11, all as fully described and 
set forth in detail in the prior art previously referred to. 
The X-Y coordinate signals outputted by tablet 10 coupled to the input of a 
"soft keyboard" processor 14 by means of cable 9. Processor 14 effectively 
performs, in an electronic manner, a mathematical transformation of the 
overlay X-Y coordinate signals in a manner fully described in applicant's 
'323 patent previously referred to. The thus transformed X-Y coordinate 
signals are inputted to a computer 15 via cable 16. Computer 15 may be a 
personal computer, or the like, which contains an integrated monitor 
display 17 in the form or a cathode ray tube or liquid crystal device, or 
the like. In the preferred embodiment of the present invention, computer 
15 is a "Macintosh" personal computer as manufactured by the Apple 
Computer, Inc. For some other types of computer systems, monitor display 
17 may be a peripheral unit that is electrically coupled to computer 15. 
Additionally, processor 14 may optionally be an integral part of either 
tablet 10 or computer 15, provided the logic and memory capacities thereof 
are adequate, all as well known to those skilled in the computer art. The 
X-Y coordinate signals are inputted to computer 15 in real-time where they 
are converted to graphic information or, alternatively, are used for 
functional control of computer 15 or for control of an application program 
running on computer 15. This latter use for computer control purposes is 
frequently referred-to as "menu picking" in which predetermined computer 
controls are selected from a menu printed on an overlay, rather than being 
displayed on the viewing screen of the computer. 
With reference to FIGS. 2 and 3 of the drawings, there are illustrated 
therein two representative and typical types of overlays 18 and 24, 
respectively, which are preferably constructed either of paper, plastic, 
cardboard or other suitable inert material depending, of course, upon the 
particular type of X-Y sensing technology selected for use in the tablet. 
Overlay 18 is shown as containing only a single artwork area 19 printed 
thereon which includes five different types of commonly used graphics 
tools, commonly referred to as "Paint Tools", printed thereon, whereas 
overlay 24 is shown as having two separate artwork areas 25 and 26 printed 
thereon, each comprising a single selectable computer function in the form 
of "Image #1" and "Image #2". While each of overlays 18 and 24 contains 
only a relatively few typical representations of various selectable 
keyboard, display and/or computer executable functions, it will readily be 
obvious to one skilled in the art that any collection of the many other 
available keyboard, display and/or computer executable functions may be 
printed thereon. For example, either of the two overlays may contain a 
plurality of selectable images or tablet points that, when selected by 
stylus 12, will generate input signals to computer 15 to permit the 
operator to further interface therewith to select executable control 
functions such as RESET, ADD, DELETE, QUIT, MENU BAR, and the like. 
There are preferably printed on overlay 18 three delta points (or dots) 21, 
22 and 23 and on overlay 24 three delta points (or dots) 27, 28 and 29 
which are each physically positioned on the corresponding overlay in a 
predetermined position so as to collectively function as addressing 
control points for computer 15 in the same manner as described in detail 
in the said '323 Hoffman patent. Optionally, all of the delta points may 
be printed totally within or outside the corresponding artwork area of 
either or both of the overlays 18 and 24, or one or more points of each 
set of delta points may be located inside the respective artwork area and 
the remaining one or ones located outside thereof. The control points of 
each set, when connected by three imaginary lines, are each physically 
positioned at the vertex of a unique triangle. The relative position of 
each point with respect to the others of the same set, define the angles 
of a unique triangle whose included angles collectively represent or 
define a corresponding memory address or set of addresses within computer 
15 wherein signals representative of the respective artwork are stored. 
In FIG. 4(a), overlays 18 and 24 are shown randomly positioned on the 
digitizer tablet surface 11 with their respective X-Y coordinate axes 20 
and 31 each oriented at any angle with respect to the X-Y coordinate axes 
30 of the digitizer tablet surface 11. Thereafter, signals individually 
representative of each set of delta points 21, 22 and 23 on overlay 18 and 
of each set of delta points 27, 28 and 29 on overlay 24 are randomly 
inputted into the computer by the sequential contact of each of the points 
in each selected set by the point of stylus 12. The computer software is 
designed to effectively translate the X-Y coordinates of each selected set 
of delta points obtained from the tablet to identify a specific overlay 
description file containing information descriptive of the overlay 
geometry and functions. After the overlay representative file is 
identified, the software effectively translates and scales each succeeding 
X-Y coordinate point coincident with the overlay on the tablet, to 
effectively match the coordinate system of the overlay as stored in the 
overlay representative file stored in computer memory. After the overlay 
representative file has been addressed or "selected", the operator is 
thereafter permitted to select any of the various computer functions 
represented thereon to be either displayed and/or executed by computer 15 
in a selective manner. 
For example, in FIG. 4(a) it is assumed that the operator has previously 
touched each of the three delta points on both of overlays 18 and 24 with 
stylus 12, thereby selecting each of the representative files or images 
thereof from the computer memory in the same manner as described in detail 
in said '323 Hoffman patent. 
In accordance with the present invention, the computer software is provided 
with an additional software switch in any manner well known to those 
skilled in computer programming, such that when the software switch is 
set, a visual image of the overlay, or a predetermined part thereof, is 
immediately displayed on the monitor screen superimposed on any previously 
displayed image. For example, after representative files or images of 
overlays 18 and 24 have been selected from the computer memory as 
described above, the physical touching or the positioning of the point of 
stylus 12 in close proximity to overlay 24 causes a visual and replicated 
image thereof to be immediately projected onto monitor 17, with the 
relative coordinate position of the point of stylus 12 with respect 
thereto being depicted by the position of a visual cursor or arrow 32 on 
monitor 17 in an exact relative position to the location of the point of 
stylus 12 on overlay 24. Once overlay 24 is displayed on the monitor 
screen 17, selection of Image #1 can be carried out using point-and-click 
selection from overlay 24 as illustrated in FIG. 4(a). Whenever the point 
of stylus 12 is subsequently touching or is positioned in close proximity 
to Paint Tools Overlay 18, an image of Paint Tools overlay 18 is 
immediately projected onto monitor 17 overlaying Image #1, with the 
relative position of the point of stylus 12 with respect thereto being in 
the exact same relative position of cursor 32 on monitor 17 as shown in 
FIG. 4(b). Once the desired menu is displayed on monitor screen 17, menu 
item selection can again be carried out using point-and-click selection 
from the displayed menu. For example, as illustrated in FIG. 4(c), 
whenever the point of stylus 12 is subsequently depressed on the 
right-most or annotation tool representation on overlay 18, the annotation 
icon on the Paint Tools menu 34 displayed on monitor 17 is highlighted to 
indicate its selection. When the point of stylus 12 is subsequently moved 
away from Paint Tools overlay 18, the Paint Tools menu on monitor 17 
disappears. 
As illustrated in FIGS. 4(c) and 4(d), it is assumed that the operator has 
first selected Image #2 by depressing the point of stylus 12 on the Image 
#2 representation on overlay 24 and then has subsequently selected the 
annotation tool by depressing the point of stylus 12 on the annotation 
tool representation on overlay 18. Thereafter, the annotation tool is used 
in a well-known manner by simply dragging the point of stylus 12 on 
displayed Image #2 and the line thus drawn by the stylus thereon is 
displayed electronically on monitor 17. However, if the operator instead 
wishes to cause the computer to effectively draw an ellipse on the 
displayed Image #2 by selecting the ellipse tool from menu 34, the ellipse 
tool may likewise be selected from the tablet overlay menu without 
necessitating the shifting of the operator's vision from the monitor 
screen to either of overlays 18 and 24. After the ellipse is selected, 
stylus 12 is either moved to another portion of the overlay image or may 
be moved to an additional overlay similarly positioned on the digitizer 
tablet surface 11, such as one containing an X-Y key where the ellipse 
tool can be used to produce the desired result on monitor screen 17 in a 
well-known manner. Upon stylus 12 exiting the overlay, the overlay image 
optionally disappears and the entire screen work area may be exposed, if 
desired. Stylus 12 is typically moved to another work overlay where the 
selected tool is used to draw another object on the monitor screen and/or 
keyboard and/or computer functions can be selected from other overlays 
already positioned on the digitizer tablet surface or subsequently placed 
thereon. 
In FIG. 5 of the drawings, there is illustrated a simplified flow diagram 
comprising a sequence of logical steps numbered 1 through 16 which 
logically describes in a step-by-step manner the same procedure as 
previously described. 
Step #1: It is assumed that the same two overlays 18 and 24 shown in FIGS. 
4(a) through 4(d) have been placed on the activated surface of digitizer 
tablet 10 and that Paint Tools overlay 18 and Images overlay 24 have been 
entered into the memory of the computer via digitizer tablet 10 in 
accordance with the entry procedure described in the said '323 Hoffman 
patent or according to other alignment and entry procedures used in the 
computing industry. FIG. 4(a) illustrates this starting state. Thus, it is 
assumed that Image #1 on overlay 24 is currently being displayed on 
monitor 17, that stylus 12 is currently positioned over Image overlay 24 
and that its corresponding position is being displayed as arrow 32 on 
Image #1 displayed on the monitor. FIG. 4(a) illustrates this starting 
state. 
Step 2--Read Tablet Point: A single (X,Y) coordinate point is accepted from 
the digitizer tablet and stored for processing by other software modules. 
Step 3--Stylus Point On Image Overlay?: The (X,Y) coordinate point is 
mathematically transformed to determine if it lies on the tablet area 
covered by the Images overlay. 
YES: If the answer is YES, then the point is processed according to Step 10 
below. 
NO: If the answer is NO, then the point is further processed to determine 
if it lies on another overlay according to Step 4 below. 
Step 4--Point On Paint Tools Overlay?: The (X,Y) coordinate point is 
mathematically transformed to determine if it lies on the tablet area 
covered by the Paint Tools overlay. 
YES: If the answer is YES, processing proceeds according to Step 5 below. 
NO: If the answer is NO, processing proceeds according to Step 9 below. 
Step 5--Display Paint Tools Menu And Show Selected Tool on Menu: As soon as 
it is determined that the stylus is over the Paint Tools overlay, the 
Paint Tools menu is displayed on the monitor, superimposed on top of all 
other information displayed on the monitor. This is illustrated in FIG. 
4(b). Note that the arrow tool is shown highlighted in FIG. 4(b) to 
visually indicate that it is the currently selected tool. 
The position of the Paint Tools menu on the monitor can either be centered 
or be positioned according to the user's preference using a drag bar 
interface common in the computer industry. 
Note that the user can look either at the monitor or at the overlay to 
determine stylus position on the Paint Tools overlay or menu. The arrow 
select tool is displayed on the Paint Tools menu in the exact relative 
position as the stylus is positioned on the Paint Tools overlay. 
Step 6--Stylus Down Transition?: A transition from Stylus up to Stylus down 
is used to indicate tool selection. 
YES: If the answer is YES, the tablet (X,Y) point is further examined to 
determine if a Tool has been selected according to Step 7. 
NO: If the answer is NO, another (X,Y) point is read from the tablet 
according to Step 2. 
Step 7--New Tool Selected?: If a tool different from the current one is not 
selected, the current tool highlighting remains. 
YES: If the answer is YES, the point is processed according to Step 8. 
NO: If the answer is NO, another (X,Y) point is read from the tablet 
according to Step 2. 
Step 8--Highlight Tool On Monitor: A pen down transition on a new tool 
results in the new tool being selected and highlighted on the monitor. In 
the illustration being described, the annotation tool is selected as shown 
in FIG. 4(c). Depressing the stylus on the annotation tool causes the 
annotation tool on the monitor to be highlighted. 
After the new tool is selected, a new (X,Y) point is read from the tablet 
according to Step 2. 
As long as the stylus remains over the Tools menu, the flow diagram loop 
described above in Steps 1-8 is repeated over and over again. When the 
stylus leaves the Paint Tools overlay in Step 4 above, processing proceeds 
as follows: 
Step 9--Hide Tools: Because the stylus is neither over the Paint Tools 
overlay or the Images Overlay, there is no need to display the tools on 
the monitor. Another (X,Y) point is read from the tablet according to Step 
2 and processing continues. 
When a tablet (X,Y) point is sensed over the Images overlay in Step 3, 
processing proceeds according to Step 10 below: 
Step 10--Hide Menu On Monitor: At this point, a tool has been selected for 
use on one of the images illustrated in FIGS. 2 and 3. The Paint Tools 
menu on the monitor is hidden and processing proceeds according to Step 
11. 
Step 1--Point On Image?: As long as the stylus in not over an overlay 
image, the Paint Tool is not displayed on the monitor. 
YES: If the answer is YES, then further examine the tablet point according 
to Step 12. 
NO: If the answer is NO, then hide the Paint Tool on the monitor and 
proceed according to Step 9. 
Step 12--Same Image As Last Point?: As long as tablet points are on the 
same image as the previous point, processing continues using the existing 
image. 
YES: If the answer is YES, keep displaying the current image and proceed 
according to Step 15. 
NO: If the answer is NO, then further examine the tablet point according to 
Step 13. 
Step 13--Stylus Down Transition?: A new image is displayed only if a stylus 
down transition is sensed on an overlay image which is different from the 
image currently displayed on the monitor. 
YES: If the answer is YES, then proceed according to Step 14. 
NO: If the answer is NO, then hide the Paint Tool on the monitor and 
proceed according to Step 9. 
Step 14--Display New Image: The stylus down transition on a new image 
causes the new image to replace the existing image on the monitor. This 
transition is illustrated in FIG. 4(d). 
Step 15--Display Paint Tool On Monitor: The Paint Tool selected in Step 7 
is displayed in the same relative position on the monitor image as the 
stylus is located on the overlay image. In the example illustrated in 
3(d), the "+" annotation tool is displayed. 
Step 16--Process Tool Event: In the foregoing example with the annotation 
Paint Tool selected, each subsequent point results in a line segment being 
drawn to it on the monitor from the immediately preceding point. This 
results in a continuous line being drawn on the monitor representative of 
the line drawn on the overlay image. This is illustrated in FIG. 3(d). 
Other Paint Tool events cause the select arrow to be displayed as a 
straight line or lines, or as ovals or rectangles, or the like, to be 
drawn on the current image. 
Many variations may be made to the logic presented without departing from 
either the spirit or scope of the present invention. For example, some 
users may prefer to display a new image when the stylus first enters the 
new image area on the overlay, instead of waiting for first stylus down. 
Additionally, the Paint Tools overlay and the Images overlay may be 
combined on a single overlay and transitions to the individual tools or 
images may be used instead of overlay boundaries as set forth in Steps 3 
and 4 above. 
Having illustrated and described in detail each of the salient features, 
functions and advantages of the present invention in its preferred 
embodiment utilizing a triad of control points printed on the surface of 
the overlay, it will be readily apparent from the detailed specifications 
to those skilled in the art that the present invention will likewise find 
substantial utility to those prior art systems previously described which 
do not utilize any control points printed on the surface of the overlay 
but, for proper operation, require that the X-Y coordinate axes of the 
overlay be precisely arranged to coincide with the X-Y axes of the 
rectangular digitizer tablet. By the use of control points printed on the 
overlay surface, the overlay may be physically reduced in size to save 
space on the digitizer tablet. Additionally, if pop-up menus are used, 
overlays which are visually to small for normal viewing can be 
successfully used because menu item selection is done with the 
point-and-click selection from a readily viewable image thereof displayed 
on the monitor screen. 
Many other obvious modifications and additions may be made thereto without 
departing from the true spirit and scope of the present invention and it 
is intended by the appended claims to cover all such features, functions 
and advantages as disclosed and any obvious modifications and additions 
thereto and not to limit the invention to the exact construction and 
operation illustrated and described in the preferred embodiment. For 
example, while the preferred embodiment provides for near instantaneous 
display and disappearance of the overlay images, one or more software 
switches may be used to selectively cause certain overlays to pop-up, or 
all of them to pop-up, or it may be desired to actually prevent certain of 
the overlays from popping-up. To facilitate the desired rapid response, 
the displayed image may contain less detail than the printed image on the 
digitizer tablet. While very large overlays may not properly display on 
the monitor screen of some types of computers, or the particular computer 
may operate too slowly when large images are displayed on the monitor 
screen, it is possible to display sub-images of larger overlays. As the 
stylus moves across a large overlay, a smaller window may be displayed in 
a region of the stylus tip. In instances where pop-up menus are too slow, 
menus may optionally be displayed upon first stylus-down instead of upon 
stylus entry of the overlay. Such selection may likewise be controlled by 
means of a software switch in accordance with the teachings of the present 
invention. Use of first stylus-down would prevent distracting flashing of 
menus when the stylus passes over unwanted overlays. Upon the operator 
becoming accustomed to the positions of high use overlays on the tablet, 
it will no longer be necessary for the operator to shift vision from the 
computer screen to the tablet. Such positioning, of course, will not only 
depend upon individual operator preferences, but will likewise depend upon 
the overlay layout. 
As a further refinement of the present invention, the artwork on the 
printed overlay may be replaced entirely with a single, highly visible 
word or icon representing a preselected group of menu items. For example, 
the word "TOOLS" could replace all of the icons on the overlay, as long as 
actual menu selection is done by using the image on the monitor screen, 
rather than by using the overlay itself. Alternatively, the "TOOLS" label 
could also be displayed on the monitor screen while the stylus is used to 
search for the desired overlay without looking at the tablet. Upon first 
stylus-down on the desired overlay, a detailed image of the overlay may be 
displayed on the monitor screen for normal menu selection. Displaying 
overlay labels instead of displaying the entire overlay image enables 
faster paging and less visual activity while progressing through the 
selection process. 
There are at least three important reasons for the displayed monitor image 
to be made to be dissimilar to the corresponding overlay artwork: (1) the 
overlay artwork may be too small to be easily readable, in which case the 
monitor image is used to provide details for menu selection, and, a larger 
number of smaller overlays may be placed on the tablet and which may be 
miniatures of the monitor image, or they may be simply labeled with their 
primary function (e.g. PAINT TOOLS); (2). the key/button areas are defined 
on the overlay but do not appear on the monitor screen, which may be 
desirable when controlling Hypercard stacks as supplied by Claris Division 
of Apple Computer, Inc., whereby buttons can be freely defined on the 
cards in a conventional manner without any great concern as to their 
visual appearance. In this instance, the Hypercard stack is printed with 
buttons showing, in miniature or "thumbnail" format, and with a triad of 
control points printed thereon and, upon sequential entering of the triad 
of control points, the stack is loaded in the computer memory. Thereafter, 
when a particular card miniature printed on the overlay is touched with 
the stylus, that particular card image is displayed on the monitor screen. 
Additionally, keys/buttons on the monitor image may optionally be made 
invisible in order to present the best visual image to an audience and, 
because the keys/buttons are visible on the overlay, they can be operated 
from the digitizer tablet itself, instead of being operated in a 
conventional Hypercard manner using a display. In this instance, the 
presenter using a digitizer tablet and overlays can function successfully 
without direct view of a monitor screen as represented in FIG. 4 of the 
drawings; and, (3) overlay artwork may be represented by multiple images 
as shown in FIG. 4 whenever this is desirable for presentation control. 
Having so described and illustrated the principles of my invention in a 
preferred embodiment, it is intended, therefore, in the annexed claims, to 
cover all such changes and modifications as may fall within the scope and 
spirit of the following claims: