Elliptical LCD bar graph with path outline-defining segments

A liquid crystal analog display device that displays along a predetermined path defined by a path outline. It includes a backplane defining the path outline; a plurality of display segments disposed along the path; a display segment backplane; a plurality of outline segments associated with the display segments for further defining the path outline; means for applying an electric potential to the display and outline segments; means for applying an electric potential to the path outline backplane so that there is an a.c. field across the path outline segment and the path outline backplane sufficient to maintain the path outline image; and means for selectively applying an electric field across the display segments and the display segment backplane for establishing an analog image display. There is also disclosed means for applying an electric potential to the backplane defining picket outlines so that there is an a.c. field across the picket outline backplane and the associated display segment sufficient to maintain the picket outline image.

FIELD OF INVENTION 
This invention relates to a liquid crystal display device having a defined 
path outline and major pickets, and more particularly to such a device 
having an elliptical or otherwise bent path. 
BACKGROUND OF INVENTION 
Liquid crystal display devices are commonly used in calculators, watches, 
electronic thermometers, and the like. Generally information is presented 
numerically or in analog form such as a bar graph. Conventional numeric 
displays provide an accurate value, but reading the numeric display 
becomes difficult when displayed values move quickly between higher and 
lower values. For these situations an analog bar graph display device is 
easier to read. 
LCD bar graphs are analog displays having a plurality discrete segments 
which represent quantitative increments, i.e, a scale on the graph. 
Increasing the number of segments increases the resolution of the bar 
graph, but at the expense of increasing the overall length of the bar 
graph. For example, a bar graph having 100 segments provides 1% step 
increments from 0 up to full scale. Scales with this resolution are 
generally 31/2 to 4 inches long. Attempts to reduce the overall length of 
the high resolution bar graphs by reducing the width of each segment is 
generally limited by economical considerations for low cost displays and 
by the difficulty in visually resolving the small increments. While 
curving the path of the display or folding it back on itself condenses the 
display into a smaller area, it raises the problem of defining the path of 
the display so viewers will know what to expect. This is difficult because 
the drive circuits and lead patterns prevent a display of the path outline 
in close proximity to the bar graph display where it will do the most 
good. It is also valuale major pickets available to provide an easy 
understanding of the display position. 
SUMMARY OF INVENTION 
It is therefore an object of this invention to provide a condensed liquid 
crystal display device. 
It is a further object of this invention to provide such a device which can 
condense both a high-resolution analog display and a numerical display 
into a small area. 
It is a further object of this invention to provide such a device which 
shows the path of the display and the higher order scale. 
It is a further object of this invention to provide a panel meter having a 
condensed analog display. 
The invention results from the realization that a truly effective path 
outline and major pickets can be provided for a liquid crystal analog 
display in close proximity to the display segments without crossing leads 
so that unconventional paths as well as straight paths may be easily 
defined for the viewer. 
This invention features a liquid crystal analog display device that 
displays along a predetermined path defined by a path outline. The device 
includes a backplane defining the path outline and a plurality of display 
segments disposed along the path. There is a display segment backplane and 
a plurality of outline segments associated with the display segment for 
further defining the path outline. There are means for applying an 
electric potential to the display and outline segments, and means for 
applying an electric potential to the path outline backplane so that there 
is an a.c. field across the path outline segment and the path outline 
backplane sufficient to maintain the path outline image. There are means 
for selectively applying an electric field across the display segments and 
the display segment backplane for establishing an analog image display. 
In a preferred embodiment, the path may be elliptical and the outline 
segments may be disposed in close proximity to produce the illusion of a 
continuous outline. The path outline may include two boundaries, one on 
each side of the path. In addition, a digital display may accompany the 
analog display. The segments may be energized by leads extending outside 
of the path and may further include means for blocking electro-optic 
effects caused by the leads. The means for blocking may include an opaque 
material. 
The invention also features a liquid crystal analog display device that 
displays along a predetermined path including a number of major pickets 
representing a delineation of higher order scale value. There is a 
backplane defining the picket outlines, a plurality of display segments 
disposed along the path, and a display segment backplane. There are means 
for applying an electric potential to the display segments and means for 
applying an electric potential to the backplane for defining the picket 
outline so there is an a.c. field across the picket outline backplane and 
the associated display segment sufficient to maintain the picket outline 
image. There are means for selectively applying an electric field across 
the display segments and a display segment backplane for establishing an 
analog image display. 
In a preferred embodiment an associated display segment overlies the picket 
outline backplane and a portion of an adjacent spaced display segment 
backplane for establishing an a.c. electric field across that associated 
display segment and display segment backplane for creating the image of a 
segment at the picket when the analog display reaches a value of that 
picket. The display segment may overlie equal widths on each of the 
display segment backplane, and picket outline backplane. The space between 
the backplane may be equal in width to that of the overlay of the display 
segment on the backplanes.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
This invention may be accomplished by a liquid crystal display (LCD) device 
having an analog display that establishes a bent path which maximizes the 
available display area of the device. The display is condensed into a 
smaller area than is possible with conventional devices. 
A liquid crystal analog panel meter 10 according to this invention is shown 
in FIG. 1. Panel meter 10 has an elliptical bar graph 12 for 
electro-optically displaying a measured value. The elliptical shape of the 
bar graph 12 is preferred because it provides a simple, uniform shape 
which allows a plurality of bars or segments 14 to be compressed into a 
small display area. Bar graph 12 includes an outline 16 which indicates 
the path of the graph and major pickets 18 which are equally distributed 
along the bar graph for dividing the graph into a higher order scale. The 
displayed image of a segment at a major picket is formed of two segments 
spaced apart. Preferably the two segments and the space are all of equal 
width. This is not shown in proportion in FIG. 1, but is explained in more 
detail with respect to FIG. 6A. The outlines 16 are formed by path outline 
segments -7 associated with each segment 14 in conjunction with the 
outline backplane shown in more detail with respect to FIG. 2. The outline 
segments 17 are discrete and very closely spaced, typically 0.005, so that 
when energized the outlines 16 appear as solid lines. In the preferred 
embodiment, both outlines 16 and major pickets 18 are electro-optically 
displayed when meter 10 is energized. A numerical scale is placed around 
the outside perimeter of the graph 12 adjacent to major pickets 18 to 
indicate linear or nonlinear quantities such as temperature, percent, 
CO.sub.2, rpm, ph, etc. The numbers of the higher order scale may be 
electro-optically displayed or deposited on the front of the display using 
an adhesive or other suitable means. In the preferred embodiment a numeric 
digital readout 20 is positioned within a partially enclosed area 22 for 
indicating a measured value that is different than the analog value shown 
on bar graph 12. Alternatively, the digital display may reflect the same 
proportionate value shown on bar graph 12. 
The construction of the analog panel meter 10 is illustrated in FIG. 2. 
Meter 10 consists of two plates of glass 24, 26 separated by a thin layer 
of liquid crystal 28 contained by seal 30. The inside surfaces of glass 
plates 24 and 26 are striated for aligning the molecules of the liquid 
crystal 28 to lie parallel to each plate's surface. In the preferred 
embodiment, the induced direction on one glass plate is rotated 90 degrees 
with respect to the other for creating a twisted nematic effect until an 
electric field is applied across the crystal. Polarizing films 29 and 31 
are secured to the outside surfaces of the glass plates 24, 26 using 
conventional methods. 
On the inside of each of the glass plates are transparent conductors for 
selectively applying an electric field across the liquid crystal layer. 
The transparent conductors, which may consist of tin oxide or indium 
oxide, are etched on the surfaces of each plate using conventional 
methods. When an electric field is applied, bars 14, outline 16 and major 
pickets 18 are images which appear behind front plate 24 and lie along a 
bent path as shown by arrow 15 as described below. 
As also shown in FIG. 3, conductors on the front or top plate 24 include 
outline backplanes 36 for displaying the path outline of meter 10 and a 
plurality of discrete bar graph segment backplanes 38. Transparent 
conductors are as shown in black in FIGS. 3 and 5 for clarity. In this 
construction the interior portion of the outline is connected to the 
exterior portion by eleven major pickets 40 uniformly distributed between 
the discrete backplanes 38. 
The rear or bottom conductors, FIG. 5, include one hundred one discrete 
display elements which are connected in groups of eight and which 
serpentine across the plurality of backplanes 38 formed on the front plate 
24 and are arranged in a bent path. Associated with display elements 42 
are a plurality of path outline segments 44 overlying outline backplane 36 
on the front plate 24 and display segments 42 which are displayed as bars 
14 when they are selectively energized. At each picket 18 there is a 
segment 42 overlying two backplanes 38 and 40, FIG. 6A, with a space 41 
between them. Regardless of the state of segment 42 picket 18 is always 
on. The image which normally appears as picket 18 is created by segment 42 
and backplane 40. When the displayed value actually causes segment 42 to 
be turned on, then the image which appears on picket 18 includes not only 
that produced by segment 42 and backplane 40 but also that produced by 
segment 42 and backplane 38 with a space 41 between them. Thus space 41 
appears as the major picket overlying segment 42. The shift which 
accomplishes this involves such small dimensions that the eye is tricked 
into seeing a reversal of the major picket image when the segment 42 is 
on. A backplane 50 and a plurality of segments 52, FIGS. 3 and 5, are also 
provided on the plates 24, 26 for creating a digital display. Each of 
backplanes and segments are connected to pads 54 at the edges of plates 
24, 26 by leads 56 as shown. 
Referring to FIG. 4, an opaque material 32 such as black paint is 
silkscreened on top of glass plate 24 to match the area surrounding the 
exterior outline of bar graph 12 for blocking the field generated between 
leads 56 interconnecting display segments 42 and backplanes 38. 
Bar graph 12 is constructed so that after the last display segment 46 the 
higher-value segments 46 remain off while preceding segments 46 remain on. 
This allows backplanes 38 on front plate 24 to be driven in one of three 
modes by multiplex drive unit 58. The three modes include an ON mode, an 
OFF mode, and an ACTIVE or UNIQUE mode. In the ON mode the potential 
applied between backplane 38 and its underlying display element 42 is 
always sufficient to electro-optically display each of its bars 14. In the 
OFF mode the reverse is true. The potential between backplane 38 and its 
underlying display segment 42 is minimized to keep its bars 14 from being 
displayed. In the ACTIVE mode, the signal applied to the backplane is such 
that the potential between the backplane and the display segment is 
dependent on the signal supplied to the display segment. In other words, a 
bar 14 appears when an ON waveform is supplied to a display segment, and 
no bar appears when an OFF waveform is applied to a display segment. 
Major pickets 18 and outline 16 are continuously displayed when the meter 
10 is energized by controlling the potential outline between backplane 36 
and display segments 42. Outline backplane 36 is driven by waveform D, 
FIG. 7, and display elements 42 are driven by waveform D or C of FIG. 7. 
The combination of drive signals results in outline 16 and major pickets 
18 being continuously displayed. Segments 52 and backplane 50 of the 
digital display 20 are independently driven by their own backplane and 
signal drives in a conventional manner. 
In the preferred construction of the active mode, backplane 38 and display 
segments 42 of bar graph 12 are driven by waveforms shown in FIG. 7. 
Backplane 38 is driven with a three-level waveform while display segments 
42 are selectively driven, by multiplexed drive unit 58, FIG. 6B, with 
either an ON waveform or an OFF waveform. This type of multiplexed drive 
scheme is known to those skilled in the art. For example, a similar drive 
scheme is described on the data sheet for component model No. ICL7182 
available from Intersil. 
Although a panel meter has been described above in terms of an elliptical 
bar graph, this is not a limitation of this invention. Other design 
arrangements of display elements and backplanes are possible. For example, 
the outline of the bar graph may consist of a series of dots. Further, the 
mode of displaying bars may be limited to only that bar which indicates 
the measured value. Still further, polarizers may be used to give a white 
on black display. Edge o back lighting may also be included to improve 
brightness and permit viewing in darkness. Also, the major pickets or the 
outline may be permanently deposited on the face of the display by using 
an adhesive or other suitable means. 
Although specific features of the invention are shown in some drawings and 
not others, this is for convenience only as each feature may be combined 
with any or all of the other features in accordance with the invention. 
Other embodiments will occur to those skilled in the art and are within the 
following claims: