Viewing apparatus and work station

Viewing apparatus including a transparency viewing apparatus (18, 19) and an electronic data display (58) unit mounted, preferably side-by-side in a housing.

RELATED APPLICATION 
This application is the U.S. National filing of PCT/EP94/03968, which was 
filed on Nov. 28, 1994. 
FIELD OF THE INVENTION 
The present invention relates to viewing apparatus in general and, more 
particularly, to medical viewing and display apparatus including a 
light-modulated viewing device for X-ray film. 
BACKGROUND OF THE INVENTION 
Transparencies such as medical X-ray transparencies are usually examined by 
placing them over the viewing surface of a device commonly known as an 
illuminator. Conventional illuminators normally comprise a box-like 
structure enclosing fluorescent lighting tubes behind a light-diffusing 
plate which defines the viewing area. Commonly, transparencies are 
attached to the viewing surface by pushing the upper edge of the 
transparencies under spring-loaded film-holder clips located along the top 
edge of the viewing surface. 
Standard size illuminators have a viewing surface seventeen inches high and 
fourteen inches or multiples of fourteen inches (i.e., 28 or 56 inches) 
wide. Usually, each fourteen inch width of viewing surface has its own 
fluorescent tubes and control switch. Such a viewing surface enables the 
viewing of standard size X-ray films which measure up to seventeen inches 
by fourteen inches. 
It is well known that, when the viewed transparencies do not completely 
cover the viewing surface, undesired glare is generated from areas of the 
viewing surface not covered by the transparencies. This commonly occurs 
when transparencies smaller than fourteen inches by seventeen inches are 
to be examined while being typically retained on the display area in the 
same manner as full size transparencies as described above. Furthermore, 
even if the viewing area is fully covered with transparencies, slight 
dislocation of the transparencies on the viewing surface usually results 
in glaring light streaks at the edges of the transparencies. In practice, 
annoying glare is almost constantly generated from the viewing surface 
since viewing surfaces are typically quite large (thus, they are seldom 
completely covered) and since viewing surfaces (typically illuminated by 
slow-starting fluorescent light) are normally continuously lit while 
transparencies are changed. 
Often, transparencies contain very transparent regions and very dense 
regions, which may be adjacent to each other and, frequently, the 
transparencies examined by radiologists are overexposed or underexposed or 
both. In these cases, considerable glare (and therefore deviation in 
adaptation levels) emanates through areas of the transparencies 
themselves. 
The glare from uncovered areas detracts from the visual perception of the 
person "reading" the transparencies and assess the information contained 
thereon. Specifically, the ability of the eye to discern between close 
gray levels is reduced when the light adaption level based on the 
surroundings is different from the light level of the detail. This 
phenomenon was noted by E. W. Weber who found that "the minimum 
perceptible difference in illumination stimulus is proportional to the 
level of the light stimulus". This can be stated in terms of vision by: 
.delta.L/L=K (K is a constant designated the Weber constant); wherein L is 
the adaptation level luminance and .delta.L is the minimum detectable 
difference in luminance. See, for example, "Elemente der Psychophysic", G. 
T. Fechner, Leipzig, 1860, and "Visual Psychophysics", D. Jameson and L. 
M. Hurvich (ed.), Berlin, 1972. 
Attempts have been made in the past to provide viewing devices for X-ray 
transparencies which shield the eyes of the observer from light emanating 
from light sources other than the light passing through the 
transparencies, in order to obscure light in parts of the transparencies 
and to reduce the contrast in transparencies when so required. 
Flat panel spatial light modulators such as liquid crystal devices (LCD) 
are well known. Such devices are used extensively for visual display in 
applications such as car dashboards, instrumentation panels, household 
devices, sign posts, etc. Liquid crystal arrays (LCA) are used for 
displays such as computer display monitors, TV monitors and projection 
devices. 
WO 91/10152 describes using an LCA in an improved transparency viewing 
apparatus. According to application '152, selective masking of the 
transparency viewing area is performed by a controlled LCA. In one mode of 
operation, the LCA allows passage of light only through transparency 
covered regions of the viewing surface while blocking the light in the 
remaining viewing area. In another mode of operation, the LCA allows 
passage of light only through a portion of the viewed transparency, 
defined by the observer, which is referred to as a region of interest 
(ROI). 
WO 93/01564 describes a display device which includes a mapping function. 
In a preferred embodiment of that invention, a liquid crystal array, which 
is used for masking portions of a viewing area, is also used as a 
transparency detecting and scanning device responsive to light 
transmission in the viewing area. The mapping function provides convenient 
control of the display area and, particularly, is useful for defining the 
extent of the transparency as proposed by application '152 described 
above. 
In preferred embodiments of the view boxes described in the '152 and '564 
applications employing a LCA, the light transmission of individual 
elements in the array is automatically adjusted such that the average 
light transmission through different portions of the viewing area, 
including portions outside the transparencies, are similar. This reduces 
the overall contrast of the viewed area and, therefore, provides grounds 
for a more nearly optimum visual adaptation level resulting in a better 
contrast detail discernibility of the transparencies. However, if the 
elements in the LCA are too small, the visual information on the 
transparency, perceived as differences in light transmission between 
adjacent loci on the transparency, may be lost. Thus, in order to avoid 
loss of detail, preferred dimensions for the individual LCD elements are 
at least 2 mm by 2 mm each. 
For many other applications such as, for example, computer screens, in 
which the LCA is utilized to create an image, "fine" LCAs must be used. 
Such arrays, having very small individually addressed elements, are used 
in order to create informative detail, in contrast to the "coarse" arrays 
described above which are concerned with improved contrast discernibility, 
without losing detail. 
Generally speaking, there are two basic approaches to designing LCAs having 
individually addressed LCD elements. According to a first approach, each 
LCD element in the array is directly addressed by a separate, exclusive 
pair of electrodes and electronic driving elements (typically a MOS logic 
transistor). It is appreciated that the number of driving elements and 
conductors required by this approach is equal to the number of LCD 
elements in the array, e.g. n.times.m drivers and conductors are needed 
for driving an n.times.m LCA. 
Such an arrangement, commonly referred to as "direct addressing", is very 
complicated and expensive to construct when a "fine" array is desired. 
Furthermore, an exclusive set of conductors must be used for connecting 
each driving element to its directly driven LCD element. Therefore, in 
"fine" directly addressed arrays, a substantial area of the LCA is 
inevitably occupied by addressing conductors, thereby substantially 
limiting the area covered by active LCD elements. The "overhead" of area 
uncovered by active elements limits the contrast of spatially modulated 
light generated by the LCDs. 
According to a second approach, all of the elements of each row and each 
column of the LCA are directly addressed by an individual driving element, 
with the individual LCD elements in each row and in each column connected 
in series. Thus, only n+m drivers and n+m sets of addressing conductors 
are needed in order to drive an n.times.m LCA. In order to address a given 
element in the array, the row and the column defining its location must be 
simultaneously addressed. 
Since the number of combinations in addressing the matrix is 2.sup.(n+m) 
and the number of different array arrangements is 2.sup.(n+m), it is 
appreciated that many array arrangements cannot be produced by a static 
addressing combination. In fact, only array arrangements consisting of one 
or more rectangular regions which are all addressed by the same set of 
rows, or the same set of columns, can be achieved by continuously applying 
one addressing combination. Since only n+m electrodes and drivers are 
available, multiple addressing combinations are applied periodically, 
thereby reducing the contrast in the addressed region. In spite of the 
reduced contrast, this addressing technique, commonly referred to as 
"matrix addressing", is often preferred for high resolution LCAs because 
it does not suffer from the limitations of direct addressed LCAs. 
In existing X-ray transparency viewing apparatus, the entire viewing area 
is used exclusively for viewing transparencies. Thus, any additional 
information needed by a reader during a viewing session, such as 
information regarding the patient or information related to the viewed 
transparencies, or images generated by electronic imaging devices such as 
CT or nuclear medicine images, must be obtained from information sources 
which are not associated with the viewing area. The inconvenient use of 
such separate sources, for example a computer, poses an undue burden on 
the limited attention of the viewer. 
Various imaging modalities are known in the art such as, for example, 
conventional X-Ray, CT or NMR scanners, Gamma cameras and ultrasound 
imaging devices. Occasionally, more than one of these imaging apparatus 
are used in the same clinical case in order to provide a more 
comprehensive diagnosis of the patient's condition. In such cases, several 
processing units and display devices are used simultaneously by the 
viewer. This requires time consuming dividing of the attention of the 
physician to the various devices, which are physically separated. 
Furthermore, such arrangement is uneconomical both space-wise and 
cost-wise. 
SUMMARY OF THE INVENTION 
The present inventors have confronted the seemingly inevitable conflict, 
described above, between trying to improve contrast and providing a high 
resolution liquid crystal (LC) array (LCA). This relationship between 
contrast and resolution is lamentable, since the use of high resolution 
LCAs can provide various improvements to existing transparency viewing 
apparatus. It is, therefore, an object of the present invention to provide 
an LCA combining advantages of both a "coarse" (i.e. low resolution, high 
contrast) LCA and a "fine" (i.e. high resolution) LCA. 
It is a further object of the present invention to combine, in single work 
station, an X-ray transparency viewer and other display means having the 
same or different resolution. 
In accordance with a first aspect of the present invention, there is thus 
provided an LCA including a plurality of LC elements. The LC elements are 
grouped in sub-arrays, wherein each sub-array is addressed separately from 
the other sub-arrays. In a preferred embodiment, each sub-array can be 
operated in either a low-resolution, high-contrast, mode, in which the LC 
elements in the sub-array are addressed collectively, or in a 
high-resolution mode, in which the individual elements in the sub-array 
are addressed separately using "matrix addressing". 
Further, in accordance with this first aspect of the invention, a viewing 
apparatus, including a backlight source, is provided with an LCA, as 
described in the previous paragraph, overlying the backlight source. The 
viewing apparatus is preferably further provided with a viewing surface on 
which X-ray transparencies to be viewed are mounted. 
In a preferred embodiment of this aspect of the invention, the LCA is 
located behind the viewing surface, i.e. between the backlight source and 
the viewing surface, and each sub-array of the LCA is associated with a 
corresponding elemental portion on the viewing surface. In accordance with 
a preferred embodiment of this aspect of the invention, when only part of 
the viewing surface is covered by transparencies, the boundaries of the 
regions covered by the transparencies are detected by the apparatus as 
described in WO 91/10152, the disclosure of which is incorporated herein 
by reference. When such boundaries (or the boundaries of body parts) are 
detected, the sub-arrays associated with the elemental portions of the 
viewing surface underlying the detected boundaries are operated in the 
high-resolution mode. The remaining sub-arrays are preferably operated in 
the low-resolution mode. 
According to this embodiment of the invention, each of the sub-arrays 
operating in the low resolution or the high resolution mode, i.e. the 
boundary sub-arrays, includes two portions, namely, a covered portion, 
underlying a transparency, and an uncovered portion which does not 
underlie a transparency. The covered portions of the sub-arrays are 
attenuated in the same manner as the low-resolution sub-arrays underlying 
transparency-covered elemental portions, preferably in accordance with the 
opacity of the overlying transparency, as described below. The uncovered 
portions are attenuated in the same manner as the sub-arrays outside the 
transparency-covered region, and are preferably attenuated to the average 
opacity of the transparency covered region, as described below. 
The present invention provides, in this preferred embodiment thereof, 
high-resolution adaptation to any given boundaries of the 
transparency-covered region. By operating the boundary sub-arrays at two 
different attenuation levels, one for each side of the boundary, annoying 
contrast at the edges of transparencies is avoided. Such annoying contrast 
results from a sharp drop in opacity which occurs at the edge of a 
transparency. The present invention provides high resolution compensation 
for this annoying contrast. 
In an alternative, preferred, embodiment of this aspect of the invention, 
some of the sub-arrays associated with elemental portions which are not 
covered by the transparencies, in addition to the boundary regions 
described above, are also operated in the high resolution mode. According 
to this embodiment of the invention, the sub-arrays in the high resolution 
mode are used for displaying information alongside the transparencies. The 
information, preferably relating to the transparencies in view, is 
preferably displayed using alphanumeric characters. Alternatively or 
additionally this information may include electronic images produced by 
imaging modalities such as CT, NMR or ultrasound. 
The displayed information is preferably generated by a microprocessor and 
may be based on an electronic input received by the microprocessor. In one 
realization of the invention, the electronic input is provided by optical 
sensors located at preselected loci on the viewing surface. Preferably, 
according to this realization of the invention, the optical sensors are 
operative to scan bar-coded information registered on the transparencies, 
and to generate electric signals to the microprocessor based on the 
bar-coded information. The bar-coded information can also be picked-up 
from the transparencies using external, manually operated, bar-code 
readers. 
Alternatively, the information can be registered on magnetic material at a 
preselected location on the transparency and read by a magnetic head. In a 
second realization of this preferred embodiment of the invention, the 
displayed information is alternatively or additionally based on inputs 
received from external sources other than the viewed transparencies such 
as, for example, information generated by a personal computer. The 
displayed information may include information concerning the 
transparencies in view or the patient such as, for example, names of 
patients, parts of body viewed, treatment given to the patient, medical 
history of the patient, and/or electronic images and so on. 
In another, preferred, embodiment of this aspect of the invention, the 
viewing apparatus can be operated in a "region-of-interest" (ROI) mode, in 
which the person observing the transparency defines a desired region of 
interest to be emphasized on the viewing surface. According to this 
embodiment of the invention, the sub-arrays associated with elemental 
portions inside the region of interest are all operated in the 
low-resolution mode. However, some of the sub-arrays associated with 
elemental portions outside the ROI are preferably operated in a high 
resolution mode. The sub-arrays operating at the high resolution mode may 
be used for displaying information as described above. 
In accordance with one variation of this embodiment, the sub-arrays 
underlying the boundaries of the ROI are preferably operated in the high 
resolution mode, as described above, regarding the boundaries of the 
transparency-covered regions, thereby defining more exact boundaries for 
the ROI. The viewing apparatus preferably includes a touch-screen mapping 
function, which enables the user to define a ROI by indicating an outline 
of the ROI on the screen using a finger or a pointing instrument. 
The ROI can also be determined by automatic scanning. 
According to a second aspect of the present invention, there is provided a 
work station including a user interface and a display apparatus. The 
display apparatus preferably includes a transparency viewing unit and a 
data display unit. In a preferred embodiment of this aspect of the 
invention, the transparency viewing unit is preferably a transparency 
viewing apparatus such as those described above in accordance with the 
first aspect of the invention, or any other transparency viewing device as 
known in the art. 
In accordance with one embodiment of this second aspect of the invention, 
the transparency viewing unit and the data display unit are combined in 
one display device. Such display apparatus preferably includes an LCA, as 
in the transparency viewing apparatus of the first aspect of the 
invention, underlying a viewing surface as described therein. But, 
contrary to the first aspect of the invention, a preselected portion of 
the LCA includes only sub-arrays which operate exclusively in a high 
resolution mode. 
According to this embodiment of the invention, the dimensions of the 
viewing surface are larger than those of a standard viewing apparatus, 
which are generally multiples of standard transparency dimensions. 
Therefore, a preselected section of the viewing surface is always left 
uncovered, even when the viewing surface is overlaid by transparencies to 
its full capacity. Thus, the LC sub-arrays associated with the sections of 
the viewing surface not associated with images are reserved, exclusively, 
for displaying information in the high resolution mode. As described 
above, this information may include any information, preferably 
information related to the viewed transparency and the patient. 
In accordance with another embodiment of this aspect of the present 
invention, the data display unit and the transparency viewing unit are 
parts of an integral unit; however, different display technologies are 
used for the different units. The viewing unit is preferably one of the 
embodiments of the transparency viewing apparatus described above. The 
data display unit may include any display means known in the art such as, 
for example, a TV or VGA screen, a liquid crystal display (LCD) or a light 
emitting diode (LED) display. 
In a preferred embodiment of the invention, the user interface includes a 
keyboard and, additionally or alternatively, a command "mouse". Using the 
keyboard, or mouse, the user can control different functions of the 
display unit as well as the information displayed by the display unit. The 
keyboard, or mouse, may be also used to control the operation of the 
transparency viewing unit, particularly its LCA, and to select different 
working modes for the viewing apparatus, for example a region-of-interest 
mode. 
In a preferred embodiment of the invention, the display apparatus further 
includes a film digitizer. The film digitizer preferably includes an 
optical scanner operative to scan a transparency which is displayed on the 
viewing surface and to convert the visual content of the transparency into 
appropriate digital codes. These codes may then be fed into a computer 
and, after appropriate processing, displayed as an image on a screen, 
preferably a high resolution monitor, which is preferably included in the 
data display unit. This processing can also give the boundaries of the 
ROIs. 
In a further, preferred, embodiment of the invention, the viewing apparatus 
includes a high resolution monitor for displaying digital images produced 
by medical imaging apparatus, such as a CT or NMR scanner, a gamma camera 
or an ultrasound mapping device, which are connected through appropriate 
hardware to a high resolution monitor of the data display unit. The 
display of these optional devices is preferably controlled through the 
user interface of the display apparatus.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
FIGS. 1A, 1B and 1C show three different configurations of a viewing device 
8 commonly known as a "light box", for viewing transparencies in 
accordance with a preferred embodiment of the present invention. Reference 
is also made to FIG. 1C which shows some additional details of the 
embodiments of FIG. 1 A. Light box 8 preferably includes a housing 10, 
defining five sides of a rectangular box and preferably made of a light 
opaque material. Placed within light box 8 is a battery of light sources 
12 such as, for example, a row of fluorescent light tubes. An array 14 of 
elements 15 having independently controllable opacity, for example a 
liquid crystal array (LCA), i.e. an array of liquid crystal elements, 
covers the sixth side of light box 8. LCA 14 is preferably overlaid by a 
transparent material forming a viewing surface 16. A transparency 18 is 
shown mounted on the viewing surface and is held in place by a film holder 
20. In FIG. 1A, elements 15 are illustrated as having a relatively large 
size, for clarity. In general, the size of elements 15 is small compared 
to the size of transparency 18, but should not be too small. Typically, 
elements 15 are squares of at least 2 mm by 2 mm. 
Alternatively, viewing surface 16 is the outer surface of LCA 14. 
Similarly, LCA 14 may be made of a diffusing LCA material or a diffusing 
material may underlie LCA 14. Placed within viewing device 8, and 
underlying (i.e. interior to) LCA 14 are one or more photodetectors 22, 
for sensing light passing through viewing surface 16 and LCA 14. 
The layered sequence including LCA 14 and viewing surface 16 on which 
transparencies 18 are mounted on surface 16, will be hereinafter referred 
to as a viewing area. For illustrative purposes, the viewing area is 
envisioned as including a plurality of elemental portions 17, wherein each 
elemental portion 17 covers precisely one element 15 of LCA 14. 
Outside housing 10 and preferably near the bottom of viewing surface 16 is 
an additional light source 24, such as a fluorescent light. Additionally 
or alternatively, a light source (not shown) is placed near the top of 
housing 10. Alternatively, external light sources are not present as part 
of the viewing device and ambient room lighting is the exclusive external 
source of light. 
As in the above mentioned PCT publications WO 91/10152 and WO 93/01564, the 
disclosures of which are incorporated herein by reference, LCA 14 of the 
present apparatus is utilized for controlling the opacity of the viewing 
area. By changing the light attenuation level of elements 15 in array 14, 
different illumination levels are obtained for different portions of the 
viewing area. In a preferred embodiment of the invention, the opacity of 
elements 15 underlying portions of viewing surface 16 not covered by 
transparencies 18 is set to zero or, preferably, to a non-zero value 
dependent on the opacity of transparencies 18. More preferably, the 
non-zero value is equal to the average opacity of transparencies 18. Thus, 
in a preferred embodiment, the average illumination through portions of 
the viewing area outside transparencies 18 is equal to the average 
illumination through transparency-bearing portions of the viewing area. 
In a preferred embodiment of the invention, the opacity of a each element 
15 underlying transparency 18 is adjusted, in accordance with the average 
illumination through the respective elemental portion 17, such that the 
average illumination through any of elemental portions 17 is substantially 
the same. This adjustment, suggested in the '152 application, reduces the 
contrast of the viewing area by compensating for relatively dark and 
bright areas of transparencies 18. The loci of transparencies 18 and/or 
the relative opacity of portions of transparencies 18 may be measured 
off-line, as in WO 91/10152, or determined automatically while 
transparencies 18 are mounted on viewing surface 16, as described in WO 
93/01564. In the latter case, device 8 is provided with a mapping 
apparatus (not shown in FIG. 1A) which, when operating in an opacity 
determination mode, determines the precise coverage of transparencies 18 
and, preferably, the relative opacity of different portions of 
transparencies 18. 
The results of the mapping procedure or the off-line measurement, depending 
on the type of system used, are preferably generated as an array of 
electrical signals to LCA control electronics 26 which, generally 
speaking, controls the operation of elements 15 in LCA 14. Control 
electronics 26 also receives other inputs, in accordance with preferred 
embodiments of the present invention, as described in detail hereinbelow. 
FIG. 1B shows an alternative embodiment of a work station according to the 
invention in which a transportable film device is associated with an 
electronic display. This device is similar to that of FIG. 1A, except that 
the films are transported to the work station from a magazine which store 
many films as is well known in the art. The viewing surface of the 
transportable film device may be an LCD array as in the device of FIG. 1A. 
Preferably, the density of the film is read as the film is transported to 
the viewing surface as described in PCT publication WO 91/10152, the 
disclosure of which is incorporated herein by reference and the brightness 
of various elements of the LCD array is set in accordance with these 
density measurements. 
As described below the surface of the LCA may be divided into a data 
portion 58 and a transparency display portion 56. These portions may be 
part of the same LCA or may be separate LCAs laid side by side. 
In the work station of FIG. 1B the upper portion corresponds to data 
portion 58 and is used to display information and or images which 
correspond to the films displayed on the lower (transparency display) 
portion 56 of the viewing surface. In a preferred embodiment of the 
invention a bar code on the film identifies the film. Preferably, this bar 
code is read by a bar code reader during the film's transportation to the 
viewing surface or after it arrives at the viewing surface, as described 
below, in detail with respect to FIG. 5. 
Reference is now made also to FIG. 2A which is a schematic illustration of 
LCA 14, and to FIG. 2B which illustrates an expanded section of the LCA of 
FIG. 2A, taken along curve I--I. In a preferred embodiment of the 
invention, as can be most clearly seen in FIG. 2B, each element 15 of 
array 14 is a sub-array including a plurality of small LC elements 28 
(preferably 0.1 mm.times.0.1 mm each, more typically 0.3 mm.times.0.3 mm). 
According to the addressing scheme of the present invention, each row 27 
and each column 29 of each sub-array 15 is directly connected, through 
appropriate conductors 25, to an individual driver element (not shown) in 
control electronics 26. This arrangement, commonly referred to as "matrix 
addressing", enables high resolution operation of sub-arrays 15, in which 
the individual LC elements 28 are separately addressable, using their 
row-column (27, 29) addresses in sub-array 15, by control electronics 26. 
In accordance with a preferred embodiment of the present invention, each 
sub-array 15 of LCA 14 can be operated in either of two modes of 
operation. According to a first mode, namely, a high resolution mode, each 
row 27 and each column 29 in a given sub-array 15 are separately 
addressed, by control electronics 26, thereby providing high resolution 
matrix addressing of LC elements 28 as described above. According to a 
second mode, namely, a low resolution, high contrast, mode, all of rows 27 
and all of columns 29 in the given sub-array 15 are collectively addressed 
by control electronics 26. 
It should be appreciated that the opacity of each sub-array 15 operated in 
the low resolution mode is uniform over the area thereof, while the 
opacity of each sub-array 15 operating in the high resolution mode is, 
generally, not uniform over its area. In a preferred embodiment, the 
opacity distribution across each high resolution sub-array 15 is 
controlled, based on inputs which will be described below, by control 
electronics 26. 
In a preferred embodiment of the invention, control electronics 26 includes 
an array of driver elements (not shown), preferably MOS logic transistors, 
wherein each driver element addresses one row 27 or one column 29 of one 
sub-array 15. The driver elements are preferably arranged in sub-groups, 
wherein each such sub-group addresses one sub-array 15 of LCA 14. Thus, 
when a given driver sub-group addresses in accordance with the low 
resolution mode, all the drivers in the sub-group have equal output 
levels. In contrast, when the given sub-group addresses in the high 
resolution mode, individual drivers in the sub-group may have different 
output levels. 
In general the use of matrix addressing reduces the contrast of the LCA. 
Since all of the elements cannot be individually addressed at the same 
time, time multiplexing must be used such that each element is addressed 
only during part of an addressing cycle, whose overall length is limited 
by the flicker frequency of the display and voltage cross-talk. 
In an alternative preferred embodiment of the invention, a better contrast 
can be achieved and a lesser number of drivers can be used for driving the 
elements in the arrays and sub-arrays. In this embodiment, elements and 
sub-arrays of the LCA are grouped by desired opacity. An adaptive 
addressing system is used to switch groups of elements to the same driver. 
In general such grouping is possible for groups which do not overlap in 
either x or y or for groups which have exactly the same extent in one 
direction or, in other words, have an orthogonal consistency. Orthogonal 
consistency exists for array arrangements consisting of one or more 
rectangular regions which are all addressed by the same set of rows or the 
same set of columns. 
This method of grouping has two major effects. First, it allows for a 
marked reduction in the number of required drivers, especially in a system 
for viewing transparencies where the number of size combinations of 
transparencies and ROIs is very limited as compared to the number of 
combinations of array elements. Second, since the drive allotted to each 
grouping of elements (and thus the contrast of the display) is directly 
related to the number of different combinations which must be addressed, 
the grouping of elements increases the excitation time allotted to each 
group, thereby increasing the achievable contrast. 
Since the transparencies are made up of mainly rectangular portions, most 
of which are quite large, the prospective savings in drivers and the 
increase in contrast is significant. 
Reference is again made to FIGS. 1A and 1C. As mentioned above, control 
electronics 26 receives, from optical detectors 22 or from an external CCD 
camera 39, inputs responsive to the opacity distribution throughout the 
viewing area. Based on the inputs from optical detector 22 or the CCD 
camera, control electronics 26 detects the boundaries 19 (i.e. the edges) 
of the region of surface 16 which is covered by transparencies 18, i.e. 
the transparency-covered region or by the portion of the transparency 
which contains an image. Boundaries 19, which are characterized by a sharp 
drop in the opacity of the viewing area, are preferably detected as sharp 
changes in the output of optical detector 22. Based on this criterion, 
control electronics 26 determines which elemental portions 17 of the 
viewing area are associated with boundaries 19. Alternatively, a CCD 
camera views the viewing surface from outside the housing and determines 
the boundaries and or density of the films on the viewing surface. These 
and other methods of acquiring information regarding the transparencies 
which are mounted on the viewing surface are described in detail in the 
above referenced WO 91/10152 and in WO 93/01564, the disclosure of which 
is incorporated herein by reference. 
Sub-arrays 15 associated with the elemental portions 17 underlying boundary 
19 will be hereinafter referred to as boundary sub-arrays (BSA). 
Similarly, sub-arrays 15 associated with elemental portions within 
boundaries 19 will be referred to as transparency sub-arrays (TSA) and the 
remaining sub-arrays, associated with elemental portions 17 outside 
boundary 19, will be referred to as no-transparency sub-arrays (NSA). 
It is a feature of an embodiment of the present invention that some of 
sub-arrays 15 are operated in a low resolution mode, while other 
sub-arrays 15 are operated in a high resolution mode. Preferably, the 
boundary sub-arrays 15 are operated in a high-resolution mode while the 
remaining sub-arrays 15, i.e. the TSAs and NSAs, are operated in a low 
resolution mode. 
Normally, each BSA 15 includes two components, namely, a 
transparency-covered component (TCC) and an no-transparency component 
(NTC). In accordance with a preferred embodiment of the invention, TCC and 
NTC are operated as if they were two separate sub-arrays 15 and, 
therefore, each component can be attenuated to a different opacity. Thus, 
the non-transparency side of boundaries 19 may be attenuated to a much 
higher opacity than the transparency side of boundaries 19, thereby 
substantially reducing the annoying contrast which otherwise appears at 
boundaries 19 of transparencies 18. 
It is appreciated that in the extremely rare case, wherein a segment of 
boundaries 19 falls exactly on a boarder between two elemental portions 
17, the boundary segment is defined at the borderline between the two 
elemental portions. In such cases, the two sub-arrays 15 associated with 
the above mentioned elemental portions are attenuated, independently, in 
the low resolution mode, while still yielding the desired separation 
between the two sides of boundaries 19, as described above with reference 
to TCC and NTC. 
Reference is now made also to FIG. 3, which is a block diagram of the 
electronics used by the viewing apparatus of the present invention, in 
accordance with a preferred embodiment thereof. As can be seen in FIG. 3, 
control electronics 26 includes an LCA driving unit 30. Driving unit 30 
includes a plurality of LC drivers (not shown), preferably MOS logic 
transistors, for driving LCA 14 as described above. The outputs of the 
individual drivers in unit 30 are preferably controlled by a 
microprocessor 32. Microprocessor 32 preferably receives inputs from 
photodetectors 22 or the external CCD, as described above with reference 
to FIG. 1, from an optical sensor 34 and, in a particularly preferred 
embodiment, from an external information source 36. The functions of 
optical sensor 34 and external information source 36 are described below. 
Based on the inputs from photodetectors 22, microprocessor 32 identifies 
which of sub arrays 15 underlie boundaries 19 of transparencies 18. 
Microprocessor 32 then sends appropriate commands to driving unit 30, such 
that all of the driver sub-groups in unit 30 associated with boundary 
sub-arrays (BSAs) of LCA 14 are operated in accordance with the 
high-resolution mode. The remaining driver sub-groups in unit 30 are 
preferably operated in the low resolution mode as described above. Thus, 
any sub-array other than a BSA, i.e. a transparency sub-array (TSA) or a 
no-transparency sub-arrays (NSA), is attenuated to a uniform opacity 
level. The uniform opacity level of a given TSA or NSA is preferably 
selected, in accordance with the average illumination through the 
elemental portions 17 associated with the given sub-array, such that the 
average contrast between the illuminated transparency and the portion of 
the LCA surrounding the transparency is minimized to increase the contrast 
discernibility. 
In an alternative, preferred, embodiment of the invention, a selected set 
of sub-arrays 15 other than the BSAs, i.e. NSAs or TSAs, are operated in 
the high resolution mode. The selected sub-arrays are operated, by the 
drivers of driving unit 30, in accordance with appropriate commands 
generated from microprocessor 32, as will be described below. The set of 
NSAs and/or TSAs operated in the high resolution mode may be preselected 
or, alternatively or additionally, selected by the user of the viewing 
apparatus. In this preferred embodiment, as in the previous embodiment, 
the BSAs are also preferably operated in the high resolution mode. 
It is a feature of some aspects of this embodiment of the present invention 
that information other than the viewed transparency is displayed on 
viewing surface 16. In a preferred embodiment of the present invention, 
sub-arrays 15 operating in the high resolution mode are utilized to 
display this additional information. In one embodiment of the invention, 
bar-coded information is optically registered on preselected sections of 
transparency 18. The bar-coded information is read by optical sensor 34 
which preferably includes optical scanner-heads (not shown) located at 
preselected locations near surface 16. The locations of the scanners are 
chosen such that, when standard size transparencies are placed in a 
preselected manner on surface 16, the loci of the scanners will coincide 
with the preselected bar-code sections on the transparencies. 
The bar-coded information, which preferably includes information relating 
to the transparencies in view, is translated, by optical sensor 34, to 
electric signals and transferred to microprocessor 32. Microprocessor 32 
then sends queries to a database 35 which generates required patient 
information for display. This information is transmitted by database 35 to 
microprocessor 32 which sends corresponding information-bearing signals 
via driver system 30 to some of the sub-arrays 15 operated in the high 
resolution mode. Consequently, the desired patient information is 
displayed on part of viewing area 16. The information is preferably 
displayed in alpha-numeric character form. Alternatively or additionally 
electronic images associated with the patient are displayed. 
In an alternative embodiment of the present invention, optical sensor 34 
includes a manual bar-code reader (not shown), such as a light-pen. 
According to this embodiment of the invention, the bar-coded information 
registered on the transparencies is read by manual scanning of the 
bar-codes using the bar-code reader. The bar codes are preferably read off 
the transparencies while they are being displayed on viewing surface 16. 
Alternatively, the bar-codes reader can be read from the transparencies 
before they are mounted. 
Reference is again made to FIG. 3. In a preferred embodiment of the present 
invention, microprocessor 32 receives informative inputs from external 
information source 36. Such information may include, for example, 
information relating to medical data on the patient whose X-ray 
transparencies are being analyzed. External information source 36 
preferably includes a personal computer (not shown) having the desired 
information stored in its memory. The information is interpreted by 
microprocessor 32 and generated, by virtue of preselected driver groups in 
unit 30, to preselected, respective, sub-arrays 15 operating in the high 
resolution mode. These high resolution sub-arrays provide appropriate 
display of the information, preferably including alpha-numeric text, 
graphic representations, etc. In a preferred embodiment of the invention 
database 35 is part of external source 36. 
In a preferred embodiment of the present invention, the viewing apparatus 
can also be operated in a "region-of-interest" (ROI) mode of operation. As 
described in the above mentioned application WO 93/01564, the touch-screen 
mapping function of LCA 14 can be utilized by the user to define a 
"region-of-interest" (ROI), on viewing surface 16, by touching the screen 
with a finger or a specialized pointing instrument. The outline of the 
defined ROI is detected, for example, by photodetectors 22, which sense a 
increase in opacity along the outline of the ROI. The sensed outline is 
communicated to microprocessor 32. According to this embodiment of the 
present invention, the sub-arrays 15 associated with elemental portions 17 
along the outline of the ROI are operated, by respective driver groups in 
driving unit 30, in the high-resolution mode. Sub-arrays 15 within the ROI 
are preferably operated in the low resolution mode. Sub-arrays 15 outside 
the ROI may be operated in either a high resolution mode, for displaying 
additional information as described above, or in a high resolution mode, 
providing a uniform background of preselected opacity to the ROI. 
Alternatively, transparency-covered sub-arrays (TSAs) outside the ROI are 
operated mostly in a low-resolution mode, in which case the ROI is 
emphasized by other means, for example by enhancing the average 
illumination of the ROI compared to the remainder of the viewing area, as 
described in the above-mentioned application '564. 
Reference is now made to FIG. 4, which illustrates a viewing apparatus in 
accordance with another preferred embodiment of the present invention. As 
can be seen in FIG. 4, a viewing area 46 is divided into regions 48 and 
50. The dimensions of region 48 are preferably standard light-box 
dimensions, i.e integer multiples of standard transparency sizes. The area 
of region 50, which is typically much smaller than that of region 48, may 
be chosen arbitrarily. Viewing area 46 overlies a liquid crystal array 
(LCA) similar to LCA 14 of FIG. 1A and 1C, including separately 
addressable sub-arrays. 
In accordance with one realization of this embodiment of the present 
invention, sub-arrays underlying region 48 are selectively operated in the 
high-resolution or low resolution modes as defined above, while sub-arrays 
underlying region 50 are operated exclusively in the high resolution mode 
defined above. Alternatively, region 48 may be operated as described in 
Israel Application 107782 titled "Improved Display Device" filed Nov. 28, 
1993, which is also filed concurrently under the PCT on the same date as 
the present application. The disclosure of the PCT application is 
incorporated herein by reference. Thus, region 48 is reserved exclusively 
for viewing transparencies 18, while region 50 is reserved exclusively for 
displaying high-resolution information, preferably in alphanumeric form. 
It is a feature of this, preferred, embodiment of the invention that 
high-resolution display is always provided, by region 50, even when region 
48 is covered with transparencies to its full capacity. 
In an alternative realization of this embodiment of the invention, region 
48 is operated exclusively in the low resolution mode, or may include only 
low-resolution LC elements as described in the '162 and '564 applications. 
Reference is now made to FIG. 5, which schematically illustrates a work 
station 51, including a user interface 52 and a display apparatus 54, 
constructed and operative in accordance with one, preferred, embodiment of 
the present invention. As can be seen in FIG. 5, display apparatus 54 
preferably includes a transparency viewing unit 56 and a data display unit 
58. In a preferred embodiment of the invention, transparency viewing unit 
56 is one of the transparency viewing apparatus described above, with 
reference to FIGS. 1-4, but any other transparency viewing device known in 
the art may be equally suitable, for example, that shown in the above 
referenced Israel Application and the associated PCT application. 
According to one embodiment of the invention, transparency viewing unit 56 
and data display unit 58 are integrally combined in a single viewing 
surface (not as shown in FIG. 5). According to this embodiment, display 
apparatus 54 includes an LCA and a viewing surface as described above with 
reference to the transparency viewing apparatus of FIG. 4. A preselected 
portion of the LCA (such as portion 50 of FIG. 4) may include only 
sub-arrays which operate exclusively in a high resolution-mode. 
Preferably, as in the apparatus of FIG. 4, the dimensions of the viewing 
surface of display apparatus 54 are not integer multiples of standard 
transparency dimensions. Therefore, a preselected section of the LCA can 
be used, exclusively, for displaying information in the high resolution 
mode. 
In accordance with another, preferred, embodiment of the present invention, 
as shown in FIG. 5, data display unit 58 and transparency viewing unit 56 
are integrally mounted side-by-side units which allow for transparencies 
to be conveniently viewed with other displayed information or images. Both 
units are preferably controlled by the same user interface 52. As can be 
generally seen in FIG. 5, the different components of work station 51 are 
preferably integrated into a single multi-component apparatus. 
According to this preferred embodiment of the invention, viewing unit 56 is 
preferably one component of the transparency viewing apparatus described 
above with reference to FIG. 1-3. Data display unit 58 may include any 
display means known in the art such as, for example, a TV or VGA screen 60 
or, additionally or alternatively, a liquid crystal (LC) or a light 
emitting diode (LED) display 62. 
Reference is now made also to FIG. 6, which schematically illustrates 
work-station 51 in electronic block diagram form. In a preferred 
embodiment of the invention, work station 51 further includes a control 
unit 61. Control unit 61 is preferably addressed by user interface 52 
which preferably includes a keyboard 64 and, additionally or 
alternatively, a command "mouse" 66. Keyboard 64 and mouse 66 are 
preferably employed by a user for entering preselected commands into 
control unit 61. Control unit 61, which may include a microprocessor or a 
computer, controls the different features of data display unit 58. If one 
of the embodiments of FIGS. 1-4 is used as viewing unit 56, as is 
preferably the case, control electronics 26 (FIG. 3) is preferably 
included in control unit 61. Thus keyboard 64 and/or mouse 66 preferably 
also control the operation of transparency viewing unit 56, which 
preferably includes an array such as LCA 14 of FIGS. 1-3. 
In a preferred embodiment of the invention, viewing unit 56 is operable in 
accordance with more than one working mode, as described above with 
respect to the apparatus of FIGS. 1A and 1C. In this embodiment, the 
different modes are preferably selectable via keyboard 64 or mouse 66. 
In a preferred embodiment of the present invention, work station 51 further 
includes a film digitizer 68. Film digitizer 68 preferably includes an 
optical scanner 70 for scanning prints or transparencies and generating a 
digital output corresponding to the scanned optical information. 
Preferably, optical scanner 70 is applied directly to a transparency 18 
which is displayed on the viewing surface of viewing unit 56. The digital 
output from scanner 70 is preferably fed into control unit 61 and, upon 
appropriate commands from keyboard 64, displayed as a digital image on 
screen 60. As mentioned above, screen 60 is preferably a high resolution 
monitor included in data display unit 58. 
In a further, preferred, embodiment of the invention, data display unit 58 
is also used for displaying digital images produced by medical imaging 
apparatus external to display apparatus 56. According to a preferred 
embodiment of the invention, the work station includes an interface to a 
CT or NMR scanner 74, a gamma camera 76, an ultrasound mapping device 78, 
or any other medical imaging apparatus known in the art or to a database 
in which digital images are stored. Each of these external apparatus is 
preferably connected to an appropriate processor in control unit 61. By 
providing preselected commands from keyboard 64 or mouse 66, the user can 
view images produced by any of the external apparatus on display unit 58 
together with transparencies. Such images may be versions of the 
transparency being displayed which have been processed to increase 
visibility of lesions or other abnormalities, as, for example, by spatial 
filtering. In a preferred embodiment of the invention, the images are 
viewed on a high resolution monitor of data display unit 58. 
In a preferred embodiment of the invention, the displayed image has been 
processed in accordance with one of the well known methods of computer 
aided diagnostics. In accordance with this embodiment of the invention, an 
indication is provided to the reader of the film of those areas of the 
film which the computer aided diagnostic system has determined are 
suspect. Such indication may include a pointer formed by the LCA 
underlying the suspect region, or by flashing the LCA beneath the suspect 
region. 
Since the transparencies have a substantial optical density, in a preferred 
embodiment of the invention, the region on which the transparency is 
mounted is backlighted with higher intensity light than those regions 
which have alpha-numeric or digital image data. This may be easily 
accomplished by using a higher intensity light source behind the 
transparency portions than behind the data portions of the LCA, for 
example by providing more or stronger light sources in one region than in 
the other or by attenuating the light in the data region. 
It should be appreciated that the present invention is not limited to what 
has been thus far described with reference to preferred embodiments of the 
invention. Rather, the scope of the present invention is limited only by 
the following claims: