Note: Descriptions are shown in the official language in which they were submitted.
Nr~nted:l0-05-2002 DESC EP00981504.4 - PCTHU 00 0011
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Binocular display device
The invention relates to a display device containing a
beam-splitter unit. The utilisation of mirrors, prisms and
semitransparent mirrors for splitting or uniting light beams has
been known of for a long time. For example, the subject of USA
patent No. 4,924,853, (Jones et aL), is a device uniting two
optical paths, containing two prisms one after the other and the
reflective surfaces of these direct the beams coming from
different directions onto the same optical path. Hungarian
patent No. 186 558 also shows a device uniting two optical
paths, where a mirror and a semitransparent reflective mirror,
one after the other, direct the beams coming from different
directions onto the same optical path. These solutions require
quite a lot of space since they need two optical units for uniting
the optical paths.
The international patent application No. WD 85/04961
shows a solution in which an X-cubic prism is used to split the
optical paths, and the beam coming from one direction is
directed onto two different optical paths by intersecting
reflective surfaces. The mass of this device is relatively large,
which is disadventageous in certain cases, for example, in the
case of display units fitted on the head.
It is known that in many fields of life it is necessary to
enlarge the angle of view of an object source for the viewer,
and there are many different types of technical means for doing
this, from simple loupes, through microscopes and
laparoscopes to telescopes. In monocular devices the
enlargement of the angle of view of the object source can only
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be seen with one eye. However, looking only with one eye is not
natural, after a longer period it can even be disturbing,
consequently it is essential to have devices which make it
possible for both eyes to view the object source, therefore, a
binocular device is needed, different forms of which are known
and used.
A common feature of the known binocular devices is that
they all contain a beam-splitter unit which splits the beam
starting from the object source, such as a computer display
fitted on the head, into two and directs it towards the left eye
and the right eye. The beam splitting devices are the reflective
surfaces of mirrors or prisms, which surfaces can be completely
reflective or semitransparent.
Basically a beam can be split in two ways. In the first case
the first sections of the two light paths from the object source
to the left eye-ground and from the object source the right eye-
ground form an angle, because they are travelling, for example,
towards two non-transparent reflective surfaces placed next to
each other in a V shape, reflecting the beams in different
directions. In the second case the first sections of the light
paths coincide, and then the sputter unit, which is a
semitransparent surface, lets through a part of the beams and
reflects the rest in a different direction.
A device representing the f"first case above, is the subject of
Japanese patent description No. 06110013 {Tosaki et a1); of the
Japanese patent description No. 07287185 {Akishi et al); and
USA patent description No. 5,682,173 (Holakovszky et al). In
these devices mirrors arranged in a V shape are used to split
the Iight paths. A common disadvantage of these solutions is
that as neither of the mirrors are placed opposite the screen,
but one of them is placed slightly to the Ieft and the other one
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slightly to the right, trapezoid distortion occurs, end if the
screen is placed too close to the meeting edges of the V-mirrors,
then from certain points of the screen the beams do not even
get to both mirrors. For this reason, quite a large distance
should be kept between the screen and the V-mirrors,
according to practical experience it should be twice the screen
diagonal, which, on the one part, results in the increase of the
constructional size of the device, and, on the other part, the
distance between the screen and the lenses coming after the V-
mirrors will be large, which reduces the feasible enlargement of
the picture, because in the interest of comfortable viewing of
the distant virtual picture the screen must be at a distance
from the lenses equal to their focal length, and lenses with a
greater focal length enlarge to a lesser degree.
In the case of binocular devices, for reasons of symmetry, the
micro-display must be placed between the two eyes, and if
there is a large distance between the micro-display and the V-
mirrors, the device will be protruding like a beak, which, in the
case of devices worn on the head, is unfavourable from an
aesthetic point of view and because of
the greater pressure exerted on the bridge of the nose. USA
patent No. 5,682,173 solves this problem by placing two more
mirrors in the light path between the screen and the V-mirrors,
and so the light path is reflected twice at an angle of 90°. In the
case of patent specification No. 07287185 one single mirror is
placed in the light path between the screen and the V-mirrors
for the same purpose.
The second case of optical beam-splitting above, when the
first sections of the light paths coincide, and then a splitter
unit, which has a semitransparent surface, lets through a part
of the beams and reflects the rest in a different direction, is
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dealt with by the above mentioned patent application No. WO
85/04951 (Moss), which uses a well-known optical element,
namely an X-cubic prism, the internal surfaces of which are
semitransparent reflective surfaces, to split the beam coming
from the object source. In this device the distance between the
screen and the X-cubic prism can, in principle, be reduced to
zero. However, the X-cubic prism is a solid body, and so it is
heavy, the production and sticking together of the four right-
angled prisms forming the X-cubic prism is expensive,
complicated and labour intensive.
U.S. Pat. No. 5,739,955 (Marshall, WO 99/39237 (Ophey)
and WO 98/ 10323 (Holmes) patent descriptions describe a
beam-splitter unit containing two rectangular shaped
semitransparent mirrors the side planes of which intersect each
other in space, but the mirrors themselves do not intersect
each other, because they are positioned shifted in space (below
and above each other) and they touch each other only at one
point as it is clearly shown in figure 2 of WO 99/39237
(Ophey), figure I of WO 98 J 10323 (Holmes) and figure 1 of U.S.
Pat. 5,739,955 (Marshall). Their position corresponds to the
diagonal cross sections - of opposite directions, at an angle of
90° - of two cubes placed on top of each other so that their
sides and four edges (e1, e2, e3 es e4) are each other's
continuations, so that one of the mirrors corresponds to the
diagonal cross section between the opposing a 1 and e3 edges of
the lower cube, while the other mirror corresponds to the
diagonal cross section between the opposing edges e2 and e4 of
the upper cube. The disadvantage of the arrangement is that it
makes the light paths from the light source to the left eye and
from the light source to the right eye asymmetrical, and on the
other part this arrangement obviously demands more space
than the arrangement in which the two semitransparent
mirrors form two intersecting diagonal cross sections of the
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same hypothetical cube (between edges a 1 and e3, and between
edges e2 and e4). .
In U.S. Pat. No. 2,973,683 (Rowe) semitransparent,
dichroic minors that cross each other are used to unite light
beams. The advantage of the device is that the volume is
minimal, because it uses semitransparent mirrors that are
slipped into one another and that cross one another, so taking
up a single place. Due to the thin plates - as opposed to the
solid X-cubic prisms - the weight is also minimal. While,
however, in the case of the precise grinding of the internal
semitransparent surfaces - forming the diagonal planes of the
cube - they meet at a single, extremely thin edge, in the case of
the transparent plates with thickness v that cross each other, a
crossover body is formed (a prism with cross-section v~v) which,
in practice, behaves as an opaque body and causes a shadow
line in an image projected through or looked at through the
crossed plates. Such a shadow line passing through the middle
of the picture is exceptionally disturbing and is completely
impermissible in the case of a television or monitor picture.
The task of our invention is to provide an optical beam-
splitter unit which overcomes the disadvantages of the other,
presently known solutions designed for solving the same task
and which has the smallest possible mass; which can be
practically placed as close to the object source as desired, is
capable of reflecting any point of the object source in two
directions.
A further task of the invention is to provide binocular object
enlarging devices made by the use of the above optical beam-
splitter unit that are free of the imperfections of the other,
presently known devices detailed earlier, and the mass and
dimensions of which are small enough to be suitable to be used
comfortably as a binocular screen-display fitted on the head.
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The beam-sputter unit of the binocular display device
according to the invention is based on the recognition that two
infinitely thin semitransparent mirrors crossing each other in
an X-shape are theoretically suitable for the simultaneous
solving of the above enumerated four tasks, because they
perfectly split and direct in two directions the light beam
arriving parallel with their bisector plane and at right angles to
their intersection line, partly by transmitting and partly by
reflecting it. In reality, however, there are no infinitely thin
plates, and overly thin glass plates break, overly thin plastic
plates bend, and if they are made thicker, the crossing zone of
the mirrors creates an increasingly large shadow band. This
crossing zone behaves in a certain - optical - sense as a non-
transparent body and throws a strip shadow on the picture,
and means increasing reflection fading. This shadow band is
extremely disturbing for the person looking at the picture and
in most cases - especially in the case of a video picture or
computer screen - it is impermissible. Nevertheless, we
recognised that if we construct an optical beam-splitter unit
made of planoparallel plates at right angles to each other,
which touch each other along one edge, and their end faces
starting at this edge are optically flat, and their lateral faces
starting at this edge towards the direction of the light beam to
be split are semitransparent reflective surfaces, furthermore, if
these planoparallel plates about one or two transparent bodies
in a way that the end faces fall on the continuation of its, or
their plane surfaces) that are either semitransparent reflective
surfaces, or they consist of a semitransparent reflective surface
and a completely reflective surface, the above mentioned
shadow zone can be completely eliminated, and an optical
beam-splitter unit can be made _ that satisfies all the four
requirements of the task.
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The binocular display device according to our invention is
based on the recognition that it can be constructed with
minimal dimensions and mass if
- the light beam starting at the screen of the microdisplay is
split by two reflecting surfaces with dimensions corresponding
to the screen, that cross each other in an X-shape, because
these direct the beam to the left and to the right in the same
volume;
- the optical beam-splitter unit with the smallest mass is
that according to this patent application, because the light
planoparallel plates have two continuous reflective surfaces;
- the largest degree of enlargement of the microdisplay
screen and at the same time the most compact arrangement
can be achieved by focusing units placed into the light path
near to the two opposite sides of the optical beam-sputter unit;
- when not in use the size of the device can be further
reduced by folding in the jointed mirrors;
- the device that can be miniaturised with the above
measures can be so small, that it can be placed crossways in
the housing of a portable telephone; and its weight can be so
small, that a carrying device is not needed (for example, a
helmet, a headband, or spectacle-frame or nose clip.) for
mounting it to the head, but it can be fixed to the bridge of the
nose with a clip.
- When the device that may be clipped to the bridge of the
nose is not in use it is most favourable to wear it as a medallion
on a retaining Ioop similar to a necklace, in this case the device
is always "at hand", similarly to a wristwatch we will be always
carrying it, and if necessary it can be put on in one movement;
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- By forming the retaining loop as an electric cable and
fitting it with two earphones fitted on opposing sections a
device providing pictures and sound may be created in the
simplest way, because in such a case the mechanical
supporting instrument of the earphones is the electric
connection cable itself;
- From the point of view of weight, volume distribution and
aesthetic reasons it is favourable to place the other electronic
units necessary for the operation of the device as far as possible
from the display unit, while being worn in a control unit at the
nape of the neck;
- It is favourable to build into the display unit or the
control unit either a microdisplay drive circuit, a radio
frequency transceiver circuit, a digital ,television reception
circuit, a microprocessor and current supply for the purpose of
wireless connection with external sound, data arid video signals
(e.g. by mobile telephone, portable computer, game console,
DVD player, digital television transmitter);
- It is also practical to build a microphone into the housing
of the display unit, because then the device may be used as an
information technology device terminal or as an independent
information technology device; according to our recognition in
this way we get a personal communicator that may be worn
continuously and which may reach the sensing organs on the
head in the following way:
a. / one of the earphones is placed into an ear, and you
talk into the microphone at your neck (mobile telephone
function);
b./ both earphones are placed into the ears (the sound
heard has better acoustic properties; stereo sound possibility),
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you talk into the microphone at your neck or one held in front
of your mouth;
c. / the display unit is clipped onto the bridge of the
nose (virtual monitor function);
d. / the display unit is clipped onto the bridge of the
nose, one or both of the earphones are placed into the ears
(video glasses function, with mono, more acoustic or stereo
sound).
We note that as described later in detail the display unit rnay
also be supplemented with a miniature video camera, which
extends the functions further.
On the basis of the recognition described above in detail
the set task was solved with a binocular display device
containing an optical beam splitter unit with reflective surfaces
intersecting each other at an angle of 90°, first focusing
elements and mirrors in front of the eyes encompassing the
above beam sputter unit, where
- the optical beam splitter unit consists of two transparent
planoparallel plates having semitransparent reflective surfaces,
starting from a common intersection line and diverging towards
the beam to be split, and at least one body of a transparent
material connected to the planoparallel plates,
- the above planoparallel plates have end plates starting
from the above common intersection line,
- the above end plates are plane and optically flat surfaces
practically polished to be transparent,
- the above end plates are perpendicular to the side plate
belonging to them,
- the body or bodies have semitransparent reflective
surfaces falling in the plane of the above end plates forming
their continuations starting from them.
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An advantageous realisation of the optical beam-splitter unit
according to the invention is characterised by that
- it has further second and third planoparallel plates uthich
lie in the continuation of the first and second planoparallel
plates with light reflecting surfaces diverging towards the light
beam to be split and which abut the first and second
planoparallel plates as transparent bodies.
- all the planoparallel plates are made of the same material
with equal thickness and refractive index and they are oblate
parallelepiped shaped and they join each other along edges
parallel to each other and they form, in the section at right
angles to the joining edges, an X-shaped unit.
We note here that all the side faces of all the planoparallel
plates are, naturally, optically flat. An optically flat surface is
understood as a flat surface the surface roughness of which is
less than o = 10 A. A semitransparent surface is to be
understood as a surface that partly transmits and partly
reflects natural or polarized light.
The above defined construction of the optical ~ beam-
sputter unit contains a first, a second, a third and a fourth
pianoparallel plate of thickness v and refractive index n,
arranged in an X shape in a way that the two lateral faces of
the first and the third planoparallei plate are each bordered by
the same planes, and similarly the two lateral faces of the
second and the fourth planoparallel plate are each bordered by
the same planes, the first end face of the first planoparallel
plate towards the third planoparallel plate is in the same plane
as the lateral faces of the second and fourth planoparallel plate
towards the first planoparallel plat, and it is an optically flat
surface, the second end face of the second planoparallel plate
towards the fourth planoparallel plate is in the same plane as
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the lateral faces of the third planoparallel plate towards the
second planoparallel plate, and it is an optically flat surface.
The lateral face of the first planoparallel plate towards the
second planoparallel plate, the lateral face of the second
planoparallel plate towards the frst planoparallel plate, the
lateral face of the third planoparallel plate towards the
second planoparallel plate and the lateral face of the fourth
planoparallel plate towards the first planoparallel plate are
semitransparent reflective surfaces. The first end face makes
the semitransparent reflective surfaces of the second
planoparallel plate and the fourth planoparallel plate
continuous reflective surfaces, and similarly the second end
face makes the semitransparent reflective surfaces of the first
planoparallel plate and the third planoparallel plate continuous
reflective surfaces, because being optically flat surfaces they
reflect the beams falling onto them under the limit angle of total
internal reflection.
The direction which falls in the bisector plane of the
planes of the semitransparent reflective surfaces of the first
planoparallel plate and the second planoparallel plate and is at
right angles to the intersection line of the above
semitransparent reflective surfaces and points towards the
intersection Iine is called the receiving direction, because the X-
mirror optical beam-splitter unit described above splits the
beam coming from this direction perfectly, and the rectangular
area between the external parallel edges of the semitransparent
reflective surfaces of the first planoparallel plate and the second
planoparallel plate, with a plane at right angles to the receiving
direction is called the receiving side, because the object source
can be placed here or further away from here.
A subject of the invention is a binocular display device,
which has an optical beam-splitter unit, and, furthermore,
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contains focusing elements and minors in front of the eyes,
and which is characterised by that its beam-splitter unit is an
X-mirror optical beam-splitter unit according to the invention
and that two focusing elements are positioned at two opposite
sides of the optical beam splitter unit as seen from the direction
of the light beam arriving to the semitransparent reflective
surfaces of the optical beam-splitter unit - i.e. from the
receiving direction - and the common optical axis of these
focusing elements is at right angles to the receiving direction,
and on both sides, mirrors in front of the eyes are positioned
outside these focusing elements, and the reflective surfaces of
these mirrors are at an angle S of 45~ ~ 15~ to the mentioned
optical axis, and the intersection line of the planes of the
reflective surfaces of these mirrors is parallel to the
intersection line of the mirror-crossing intersection line of the
semitransparent reflective surfaces of the optical beam-splitter.
It is favourable if the optical beam-splitter unit, the
focusing elements and the mirrors in front of the eyes are
encased with a cover which contains a light admitting opening
in front of the mirrors in front ~of the eyes and at the receiving
side of the optical beam-splitter unit. Furthermore, it is also
advantageous if the optical beam-splitter unit and the focusing
elements are fitted in a housing which has a light admitting
opening for the focusing elements and which. is covered by a
cover-plate, and the mirrors in front of the eyes are attached to
a first slider and a second slider the stems of which protruding
into the housing are toothed racks, which are parallel to each
other, and in between them there is a cogwheel that connects
them and can move them in opposite directions.
According to a further construction example, the device
contains an object source that can be, for example, the screen
of a microdisplay. In this case it is favourable if the plane of the
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microdisplay unit's screen is parallel to the plane determined
by the mirror-crossing intersection line and by the optical axis,
and is placed at the receiving side of the optical beam-splitter
unit, and it is also favourable if the device contains at least one
light source lighting the screen of the microdisplay unit, such
as an LED. It can be also practical if that it contains a light
source illuminating through the microdisplay unit from behind,
which is placed between the microdisplay unit and the device
casing. According to a further construction example on the two
sides of the optical beam-sputter unit, in the light path, there is
a liquid crystal shutter at right angles to the axis of the
focusing elements.
It can be favourable if the device contains two clip plates
which for a single unit with the device casing.
Another realisation of the picture display device is
characterised by that on the side of the device casing closer to
the head of the user of the device there are two hook rails made
as one with the device casing, and their generators are parallel
to each other; favourably the device contains a clip adapter
fitted in between the haok rails, which clip adapter practically
consists of a bent plate following the curve of a dent in the
device casing, and two clip plates and wing plates the span
width of which is equal to the distance between the hook rails.
Another realisation of the picture display unit is
characterised by that it contains at least one microdisplay drive
circuit, and/or a radio frequency receiver-transmitter circuit,
and/or a power source and/or a microprocessor.
According to a further favourable realisation above one end
of the casing there is a CCD picture recording chip sensitive to
the infrared range, and above its other end a front lens is
placed in a way that the third optical axis of the front lens is at
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right angles to the detecting surface of the CCD picture
recording chip. Above the eye mirror in front of the right eye a
reflecting element reflective in the infrared range, transparent
i'n the visible light wavelength range is placed in the light path
between the right eye and the detecting surface.
Advantageously, above the front lens, there is an infraLED, and
its light is guided towards the reflecting element.
It can be also practical if on top of the device casing above
the dent in the device casing created for the nose, there is a
picture recording CCD chip with a detecting surface in a plane
parallel to the plane determined by the optical axis of the
focusing elements and the mirror-crossing intersection line,
and in front of it, above the microdisplay unit there is a second
front lens with an optical axis at right angles to the detecting
surface.
In the following construction example we use a reflective
microdisplay, which needs to be illuminated at right angles to
the plane of the screen. In this instance it is favourable to form
the X-mirror optical beam-splitter unit from extremely thin
(0.1-0.2 mm thick) planoparallel plates, and to illuminate the
screen through these. In the interest of the light of the light
source illuminating the screen, or directly reflected by the X-
mirrors not shining into the eyes, between the light source and
the beam-splitter unit we place a polarising plate polarising in
the one direction, and in the light path we place a polarising
plate on both sides of the beam-sputter unit polarising in the
other direction (at right angles to the previous one), so only
light beams that have been reflected from the screen the
polarity of which has been changed get through the latter two
polarising plates.
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If the light reflecting surfaces of the X-mirror shaped
beam-splitter unit are optical layers that partly reflect and
partly transmit the polarised light, in such a case the number
of optical surfaces or elements that cause a large degree of light
intensity loss is reduced, and due to this as compared to the
that of the previous example the intensity of the light reaching
the eye is increased by many times, or we can attain the same
light intensity with a much smaller capacity light source
consuming much less power.
In a further construction example two ends of a flexible
retaining loop are fixed to the opposite ends of the console
containing the eye mirrors of the display unit containing the
micro display, the optical beam-splitting unit, the focusing
elements, the eye mirrors, the display housing and the bridge of
the nose clip, in which loop there are electric cables, and to
which there is an earphone fixed per branch mechanically and
electrically. The length of the retaining loop is longer than the
diameter of the wearer's head taken at nose Ievel. In the section
of the retaining loop to most distant from the display unit there
is a control unit containing the electronics for the microdisplay
drive, a power supply, a microprocessor, a radio frequency
transceiver circuit and a digital television receiving circuit, in
which the one branch of the retaining loop is fixed permanently
and the other branch is fixed so that is may be disconnected.
In the following we will describe the invention in detail
using the appended figures, which contain favourable
realisations of the optical beam-splitter unit; figures helping the
understanding of their functioning; as well as examples of
advantageous realisations of the binocular picture display unit.
The content of the figures is as follows:
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Figure l: the left reflection beam path of known
intersecting semitransparent mirrors;
Figure 2: the right reflection beam path of known
intersecting semitransparent mirrors;
Figure 3: a cross-section sketch of one example of the
possible realisations of the optical beam-splitter unit of the
binocular display device according to the invention;
Figure 4: show further examples of the realisation
possibilities of the optical beam-splitter unit in exploded
perspective;
Figure 5: sketch of the arrangement of one realisation of
the bonocular display device;
Figure 6: the device as in figure 5, but in perspective;
Figure ?: sketch view of a further realisation of the
binocular display device according to the invention from above;
Figure 8: the binocular display device according to figure
7, with fixed mirrors in front of the eyes, in a compact casing,
viewed from the receiving direction, in perspective;
Figure 9: another example of the binocular display device
with adjustable mirrors in front of the eyes, in exploded
perspective;
Figure 10: the moving mechanism of the sliders of the
device in figure 9 viewed from above;
Figure 11: the device in figure 9, assembled, in
perspective;
Figure 12: the arrangement sketch of another realisation
of the binocular display device in perspective;
Figure 13: the clip adapter used with the device shown in
figure 12, in perspective;
Figure 14: shows a realisation of the display device with
its eye mirrors folded in towards the focusing elements, fitted in
a camcorder;
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Figure 1 S: the device like in figure 14, also fitted in a
camcorder, with its eye mirrors folded out;
Figure 16: a further realisation of the binocular display
device according to the invention, fitted in a mobile telephone,
with its eye mirrors folded out, in perspective, shown during
use;
Figure 17: sketch of a realisation of the binocular display
device containing an emissive microdisplay unit and LCD
shutters, viewed from above;
Figure 18: a realisation of the binocular display device
according to the invention, with a microdisplay driving circuit,
radio frequency receiver-transmitter circuit, a power source and
a microprocessor; in front-view;
Figure 19: a realisation of the binocular display device
with an eye movement detecting system, in perspective;
Figure 20: a vision aid and night vision binocular display
device realised according to the invention in perspective;
Figure 21: shows a sketch from above of a realisation of
the binocular display device according to the invention,
containing a reflective microdisplay and the elements
illuminating it from the front;
Figure 22: shows the binocular display device as in
figure 21 in side view; .
Figure 23: shows the binocular display device that can
be worn as a necklace while being worn, on the wearer's head
and neck, in perspective.
In figures 1 and 2 the beam path of a known, traditional X-
mirror beam splitter unit causing a shadow line can be seen,
belonging to the prior art, namely the planoparallel plate 1
corresponds to the dichroic mirror 21 shown in figure 8 of
U.S. Pat. No. 2,973,683 (Rowe) patent description, while the
planoparallel plates 2 and 3 correspond to the dichroic mirror
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22.
As it can be seen in figures 1 and 2, an X-mirror optical
beam-splitter unit has been constructed from planoparallel
plates l, 2, 3 with transparent and semitransparent surfaces as
shown by the figures in a cross section perpendicular to the
intersection line 4 of the minor crossing. The figures show only
the crossing zone of these reflecting surfaces. The planoparallel
plates 2, 3 with their uneven, rough, thin surfaces 2a, 3a
produced during normal cutting processes abut the wide
lateral faces of planoparailel plate 1 perpendicularly to these
lateral faces. If realised this way, then a zone with a width t, as
shown in the pictures 1 and 2, does not take part in the
reflection of the light beam denoted by the number 5 and an
arrow. For the sake of better lucidity figure 1 shows only light
beams a-k going to the left, figure 2 those going to the right.
As it can be seen in figure 1 when beam a reaches the
semitransparent reflective surface of plate 1, it is partly
reflected back at right angles, with half intensity, and it partly
goes inside plate 1 with half intensity. The beam reflected back
at right angles reaches the semitransparent reflective surface of
plate 2, and is partly reflected back towards the object source,
not shown here, with quarter intensity, and after refraction it
partly goes inside plate 2 with quarter intensity, and then after
being refracted again it leaves to the left - considering the
situation shown in the drawing - at right angles to the receiving
direction S, i.e. to the receiving direction denoted by an arrow.
Beams b, c and d have the same beam path.
Beam a reaches the semitransparent reflective surface of
plate 2 first, and it is partly reflected back at right angles
towards plate 1 and from there towards the abject source, and
after being refracted it partly goes inside plate 2, and disperses
on tr'~.e uneven and rough, that is, not optically flat surface of
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the end face 2a of plate 2. Beams f and g have the same beam
path. When beams h, i, i and k reach the semitransparent
reflective surface of plate 2, they are partly reflected back with
half intensity towards plate l and from there towards the object
source, and partly after being refracted they go inside plate 2
with half intensity, and then after being refracted again they
exit from there and reach the semitransparent reflective surface
of plate 1, where they are partly reflected back with quarter
intensity and exit, and partly after being refracted they go
inside plate 1 with quarter intensity. As it can be well seen in
figure i, beams g, f, a arriving in the range between beams d
and h do not take part in the picture display on the left, which
means a screening - a shadow zone - with width t in the
picture.
The reference numbers and signs in figure 2 have been used
according to their meaning in figure 1. Beams a-a and i-1 take
part in the picture display on the right as described above with
relation to figure 1, but beams f, g and h arriving in the range
between beams a and i disperse on the uneven, rough, not
optically flat surface of the end face 3a of plate 3, so in this
case, too, a zone with a width t does not take part in the
reflection.
Figure 3 shows a construction example of the optical beam-
splitter unit according to the invention, which has a first
planoparallel plate 6 and a second planoparallel plate 7, and it
also has a transparent body 10 made also of a transparent
material, and according to this construction example, the
thickness of plates 6, 7 differs from each other. Plates 6, 7 join
each other at their edges 9a, 9b, and their lateral faces 6a, 7a
starting at these 9a, 9b edges and-facing each other and made
to be semitransparent reflective surfaces are at an angle of
a=90° to each other. (In figure 3 we show in cross-section
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perpendicular to the joining edges 9a, 9b the crossing zone of
the parts composing the optical beam-splitter unit.) The end
faces 6b, 7b that start at the lateral faces 6a, 7a, and are
perpendicular to these lateral faces - i.e. the angles J3 shown in
figure 3 are right angles -, are optically flat, which means that
they are ground completely smooth and polished until
transparent. Surfaces 7a, 6b being in the same plane in
consequence of the described and depicted geometrical
conditions as well as the surfaces 10a, lOb of body 10 also
being in a common plane and in the continuation of the 7a, 6b
surfaces are semitransparent reflective surfaces. We note here,
that body 10 must not fill the space between the end faces 6b,
7b, this can be empty, too, because, as we well see later, the
surfaces of body 10 that abut end faces 6b, 7b - if body 10 is
transparent - do not play any role.
According to figure 3 when the light beam arriving from the
receiving direction 5 denoted by an arrow reaches the
semitransparent reflective surface of planoparallel plate 6 it
partly goes inside plate 6 and is reflected on its end face 8 and
then exits at its opposite lateral face, is partly reflected back,
and reaches the reflective surface of the other planoparallel
plate 7 where it is partly reflected back (this is not shown in the
figure) and then partly enters plate 7 and after another
reflection exits at its opposite lateral face. Light beam a splits
into beams a' and a", which are perpendicular to the receiving
direction 5, and they exit in opposite directions towards left and
right eyes, that's while take part in the picture display, and as a
result of this the disturbing shadow line in the middle of the
picture as mentioned in connection with figures 1 and 2, is
eliminated.
Figure 4 shows a possible practical way of attaching the
planoparallel plates 11-14 - made of a transparent material,
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e.g. glass - of the optical beam-splitter unit 22, X-shaped as
seen from above, according to the construction shown in
figures 3 to each other. According to this the X-shaped unit fits
into the X-shaped slots 18 engraved into the surfaces of bearing
plates 17 and 19 with thickness v' > _v (only slot 18 made on the
surface of bearing plate 17 is shown in the picture). Bearing
plates 17 and I9 are parallel to each other, and the slots are
engraved in their surfaces facing each other. The width of the
slots is practically the same as the width v of plates 11-14, and
their depth fits also the size of the plates fitting into them. The
planes of bearing plates 17 and 19 are perpendicular to the
planes of the planoparallel plates.
In the case of the above construction example the lower of
the two square, from above, bearing plates 17, 19 serves as
base plate, the upper as cover plate. Plates I 1- I4 can be stuck
in the slots 18 - falling geometrically into the diagonals of the
bearing plates - along the surfaces of their end faces
perpendicular to their reflecting surfaces. In this construction
plates 11-I4 join along edges 9 in a way that the four
planoparallel plates touch each other along one edge each, and
their end faces encase an empty quadratic prism shaped area
8, a penetration prism.
According to another construction not shown in the
figure the square shaped planoparallel plates I I-14 made of a
transparent material are injection moulded plastic plates, and
on their edge surfaces at right angles to the intersection line of
the reflective surfaces they have locking pins with an axis
parallel to the above intersection line, and so they can be fitted
into the holes on the receiving optical device.
There are many other ways of attaching the planoparallel
plates of the optical beam-splitter unit.
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Figures 5 and 6 show the optical beam-splitter unit 22,
c~~hich is X-shaped in top view, constructed from four
transparent planoparallel plates as can be seen, for example, in
figures 4, and denoted here by a single reference number. There
are two first focusing elements 24 placed on both sides of the
optical beam-sputter unit. The semitransparent reflective
surfaces of unit 22 are marked with dotted line. The common
optical axis 23 of the first focusing elements 24 crosses the
mirror-crossing intersection line 4 of the planoparallel plates,
and it falls into the bisector plane of the semitransparent
reflective surfaces. The first focusing elements 24 are multi-
element composite achromatic lens systems - in this particular
case they have four elements, from the direction of their optical
axis 23 they are rectangular, that is they are bordered by
planes, and these planes coincide with the overall planes of the
X-mirror optical beam-splitter unit 22 parallel to the optical
axis 23 of the first focusing elements 24. Two mirrors in front of
the eyes 25 are positioned on the two sides of the first focusing
elements 24, and the reflective surfaces of the mirrors are at an
angle of 45~ ~ 15~ to their optical axis 23. The intersection Iine
of the planes of the reflective surfaces of these mirrors (not
shown in the figures, it is outside the surface of the drawing) is
parallel to the mirror-crossing intersection line 4. In figure 10
we marked the path of an incident beam a which is guided by
the semitransparent surfaces of the X-mirror optical beam-
splitter unit 22 (see also figure 3) to the left eye 26 and to the
right eye 27 of the person using the device partly by
transmission and partly by reflection. The lenses of the
focusing element 24 forming a four-element achromatic lens
system can be attached to each other by sticking them
together. As we have already mentioned, the first focusing
elements 24 are rectangular from the direction of their optical
axis 23, that is they are bordered by planes, and these planes
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coincide with the two edges of the optical beam-splitter unit 22
that are the closest to the receiving side and also with its two
edges that are most distant from the receiving side, and also
with the lower and upper border surfaces that are
perpendicular to the mirror crossing intersection line 4. The
mirrors in front of the eyes 25 are plane glass mirrors with their
faces towards the first focusing elements 24 being mercurated.
Their shape is a trapezoid to fit the shape of the light path,
their two edges are parallel to the mirror-crossing intersection
line 4, their other edges are convergent in the direction of the
edge closer to the eye.
The binocular display device according to figures 5 and 6,
due to its small space demand, small weight and compact
construction, can be used favourably as a binocular display
unit for instruments and optical devices based on enlarging,
such as endoscopes, laparoscopes, microscopes and telescopes.
The elements of the device are attached to each other
practically, either with their own frame or case, or with the
frame or case of the above mentioned instruments and optical
devices.
The binocular display device according to figures 7 and 8
also has an X-mirror optical beam-splitter unit 22 (figures 3
and 4) with two first focusing elements 24 on its both sides,
and a further mirror in front of the eyes 25 on both sides
similarly to the construction shown in figures 5 and 6. These
binocular display devices are encased by a casing 28 which has
light admitting openings 28a, 28b of a size corresponding to the
size of the light path, located in front of the mirrors that are in
front of the eyes 25 and on the side of the X-mirror optical
beam-splitter unit 22 facing the receiving direction 5. In the
light admitting opening 28a there is a focusing element 29. As
can be seen in figure 8, the casing 28 encases the optical
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elements of the device in a compact way; the position of the
openings 28a and 28b can be seen well also in figure 8. The
device shown in figures 7, 8 is a binocular loupe according to
its characteristics, and looking in its light admitting openings
28a, 28b the user can see with both eyes the enlarged picture
of the object source being at the focal length or closer in the
receiving direction in the trajectory of the light. The object
source that is exactly at the focal length seems to be infinitely
distant, and reducing the distance the virtual distance of the
virtual picture is also reduced and any desired virtual picture
distance, for example, the usual half meter used for viewing
objects in the hands, can be set. The centres of the mirrors in
front of the eyes should be approximately equal to the distance
between the pupils of the person using the device in order to
avoid distortion and to be able to see the whole picture, and for
this purpose one needs devices with different eye mirror
distances, according to the changing distance of the human
pupils that is in most of the cases between 55 and 70 mm. In
practice it is enough to produce a binocular loupe with 3 mm
increments, that is, with six different distances (with 55, 58,
6I, 64, 67 and 70 mm eye mirror centre distances, and the
person using the device can use that best fits his or her size.
An advantage of this construction is that it does not contain
any moving parts, it does not need to be adjusted, the
disadvantage is that it has to be produced in six different sizes
and the same device cannot be used by persons of different
pupil distance.
The device according to figures 9-1 I is a binocular loupe
where the X-mirror optical beam-splitter unit 22, as shown, for
example, in figures 4, with pairs of first focusing elements 24
on its both sides is encased in a casing 30 which has light
admitting openings at its two ends and in the middle of one of
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its longer sides, and there are ledges 3I on its internal side
walls made by wall-thinning, at the ends of the side walls there
are threaded fixing holes 32. From the top the X-mirror optical
beam-sputter unit 22 and the first focusing elements 24 are
closed with an insert plate 33 supported on the ledges with its
projections, and in the centre of the insert plate 33 there is a
hole 34, and on its two opposing sides there are two pegs 35.
On the above projections there are flanges 36 which form a
constraint path from the external side for the stem of the first
slider 37 and the second slider 38 moving above the insert plate
33. On the internal sides of the first slider 37 and the second
slider 38 facing each other the constraint path is created by a
cogwheel 39 and the pegs 35 of the insert plate 33. When
the cogwheel 39 turns, it engages into the tooth racks 40
made in the stems of the first slider 37 and the second slider
38, and it moves the first slider 37 in one direction and the
second slider 38 in the opposite direction. The cogwheel 39 has
one axle, and it is made in one piece with the grooved wheel 4 ~
the axle 42 of which fits into the hole 34 of the insert plate 33
downwards, and into the blind hole situated in the centre of the
cover plate 43, not marked here, upwards. The cover plate 43 is
of the same size as the housing 30, the four open-end holes 44
in its four corners have the same axes as the four holes 32 of
the housing 30, and with the screws 45 the cover plate 43 can
be fixed to the housing 30.
According to figure 10, when the grooved wheel 41 is turned
in the first direction 46, the cogwheel 39 made in one piece
with it moves the first slider 37 in the second direction 47 and
the second slider 38 in the third direction 48. The movement is
stopped by the projection at the end of the tooth racks 40 in the
one direction, and by the stubs 34 at the tapered ends of the
first slider 37 and the second slider 38 in the other direction.
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According to figure 11 the cover plate 43 of the assembled
device leaves the edge of the grooved wheel 41 free on certain
sections, and if it is turned by the tip of a finger, the mirrors in
front of the eyes 25 fitted on the first slider 37 and the second
slider 38 move at the same time either towards the housing 30,
or in the opposite direction.
Since in the construction according to the previous
description the mirrors in front of the eyes are mounted onto
sliders inside the casing, which makes the adjustment of the
distance between the mirrors in front of the eyes possible
according to the pupil distance, along the direction parallel to
the optical axis of the focusing elements, so the same device
can be used by everybody. The sliders are cogwheels with their
axes parallel to each other, forced to a rectilinear motion by a
constraint path, and connected to each other by a cogwheel
with an axle fixed to the casing, and placed in between the
cogged sides of the cogwheels to form a system, and by means
of this by turning the adjusting grooved wheel on the same axle
as the cogwheel the two sliders and with them the two eye
mirrors move parallel to each other, but in opposite directions,
facilitating the positioning of both mirrors in front of the eyes.
Since the semitransparent reflective surfaces of the optical
beam-sputter unit reduce the light intensity to a quarter of tie
original one, it is practical to illuminate the object source for
compensating the reduction and to ensure better illumination,
so it is favourable if the device contains a light source directed
at the object source, for example, a white light emitting LED
and a small sized power source. The use of a binocular loupe is
more advantageous than the use of a monocular one, because
it better suits the human way of seeing using two eyes, you do
not need to close one eye, or squint with it, so you can work
comfortably with this binocular device when performing long or
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often-repeated medical, cosmetic investigations and precision-
mechanical work. A binocular loupe used especially for work
purposes is best used fitted to the head of the person using it,
with the help of a headband, spectacle frame or nose-bridge
clip. It is advantageous if the binocular loupe is connected to
the headband or spectacle frame with an articulated
mechanism, so in breaks from using the device it can be
pushed up over the forehead.
Vile shall describe in the following constructions containing
an object source. This object source is located in front of the
receiving side of the X-mirror optical beam-splitter unit
according to the invention, in a plane at right angles to the
receiving direction. The object source can be non-transparent,
translucent or transparent, lit or lit through by the external
environmental light, lit or lit through by a light source or
luminous by itself. According to its concrete effective form it
can be a microfilm frame, diapositive film frame, paper picture,
drawing or printed text, electronic screen or other object
source.
According to the construction example in figur es Z 2 and ~ 3
in front of the receiving side of the X-mirror optical beam-
splitter unit 22 of the picture display device functioning as a
virtual display, on its side facing the arrow 5 indicating the
receiving direction there is a microdisplay unit 49 as an object
source with a light emitting screen, 49a, and the unit 22 is
enclosed from two sides by two focusing elements on each side,
and outside the focusing elements there is one mirror in front
of each eye, arranged as in the construction examples in figures
and 6, 7 and 8, as well as in figures 9- I 1. The plane of the
screen 49a is parallel to the mirror-crossing intersection line 4.
The screen 49a is supplied with the necessary voltage and
electric signals through a cable 50, from a voltage and video-
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signal source not shown here. The X-mirror optical beam-
splitter unit 22, the first focusing elements 24 and the
microdisplay unit 49 are built in a device casing 51 which
contains light admitting openings 51a, 51b between mirrors 25
and the pairs of first focusing elements 24, and on its side
opposite the rnicrodisplay unit 49 between the planoparallel
plates of unit 22 opposite to the microdisplay 49, there is a
dent 52 using the space not falling in the light path, to suit the
bridge of the nose. On the two sides of the dent 52 there are
hook rails 53 the generator of which is parallel to the mirror-
crossing intersection line 4 of the X-mirror optical beam-splitter
unit 22, and due to these hook rails 53 the device can be put
on a bearing plate, not shown here, with a width suiting the
distance between the bays of the hook rails 53. For example, if
the mentioned bearing plate is in the middle of a spectacle
frame, the device can be pulled onto this, and if it fits exactly,
the device can be moved up and down the bearing plate and it
can be stopped anywhere, for example, exactly in front of the
pupils.
The mirrors in front of the eyes 25 are each attached to a
mirror holding unit 54, which are connected to the sliders 56
by the help of joints having axes parallel to the mirror-crossing
intersection line 4 of unit 22, which joints are moved by the
cogwheel-toothed rack mechanism that can be studied in detail
in figures 9 and 10 and also explained above in details (not
shown here), if the grooved wheel 57 is turned with the tip of a
finger of the user of the binocular display device. The mirror-
holding units 54 with the brackets stretching before the eyes,
connected to joints 55 can be folded in together with the
mirrors 25 on them towards the first focusing elements 24,
thus significantly reducing the volume of the binocular display
device. The real dimensions of the binocular display device with
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its mirrors folded in can be so small (e.g. 1.5x2.5x3.5 cm) that
it can be placed after usage in the hollow made in the casing of
any of the video signal sources (not shown here) for this
purpose, or it can be connected to the connector made on the
casing 51.
The clip adapter shown in figure 13, and marked as one
unit with the reference number 58 consists of a bent plate 59
following the curve of the dent 52 in the device casing 5I
according to figure 12, clip plates 60 continuing this curve, and
elastic wing plates 61 protruding on two sides towards the hook
rails 53. The clip adapter 58 is attached to the device casing 51
so that the ends of the wing plates 61 are guided in between
the hook rails 53. In the figure the position of the clip plates 60
with respect to the user's bridge of the nose is shown with a
broken line, the clip adapter can be fixed by forcing open the
elastic plates. The clip plates 60 in their position drawn by
dotted lines fit tightly to the bridge of the nose from both sides
due to their elasticity like a pince-nez. The clip plates 60 can
also be made in one piece with the device casing 5I, in this
case the clip adapter 58 and the stud 53 are not needed.
A light emitting object source can be built into the
binocular display device according to figure 12 as a virtual
display unit, in front of the receiving side of the X-mirror optical
beam-splitter unit, such as an AMEL (active-matrix
electroluminescent), OLED (organic light-emitting diode), FED
(field-emission display), AMOLEP (active-matrix organic
light-emitting polymer), OEL (organic
electroluminescent) or VFOS (vacuum-fluorescent-on-silicon)
micro display unit, which is supplied with the voltage and the
electric signals needed for its operation through a cable 50 - as
mentioned before - from a video-signal source carried by the
person using it (mobile telephone, communicator, palmtop
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computer, DVD player, video-game, video-camera recorder,
digital camera, etc.). The device according to the invention can
also be built into the above video-signal sources, in this case
the person using the device must Iift the video-signal source to
his/her eyes and look into the eye mirrors of the binocular
display device. The use of a combined solution can be
advantageous when the binocular display unit can also be
viewed fixed to the video signal source, and when taken out of
it, can also be attached to the head, especially in the case of
mobile telephones, video cameras and digital cameras. Such a
construction is shown in figures 14 and 15, where the device
according to the invention as shown in figures 5 and 6 is
applied as a viewfinder, as a monitor, built in the end of a
palmcorder 62 video-camera opposite to the objective 63, so
that the optical axis 23 of the first focusing elements 24 (figure
15), not shown here, is at right angles to the second optical axis
64 of the objective 63. When not in operation, the binocular
display device is placed in a hollow made inside the camera
casing, with the mirrors in front of the eyes 25 folded in, and
this hollow is closed by a cover 65. When the sliding button 66
is pulled back, the device in mechanical connection with it
slides out of the hollow on a constraint path created by the
camera casing, opening down the cover 65 in front of it, and the
mirrors in front of the eyes 25 open out completely with the
help of spring joints 55 (See figure 15). Instead of this
mechanical driving mechanism another version can be
constructed vThere the device is pushed out and pulled back by
an electric motor at the push of a button.
Consequently the binocular display device according to the
invention can be used as a viewfinder/monitor in video
cameras and their versions that also contain a picture-
recording device (camcorders).
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Traditionally two types of viewfinder are used: one of
them is a normal one eye monitor where the microdisplay
screen built in the video-camera is to be viewed with one eye
through a front lens, which is not natural, tiring and makes the
other eye squint. In the other case on the casing of the video-
camera there is a flat panel monitor which can be folded out,
but it is small in order to suit the size of the portable video-
camera, it can be as big as half of a palm at the maximum, and
it cannot be seen very well, the details of the pictures can
hardly be seen.
In the construction example of figures 14 and 15 the
picture of the binocular display device can be viewed locally by
opening out the mirrors in front of the eyes, or the device can
also be taken out of the video-camera and fixed on the head. As
modern palm-sized video-cameras (palmcorders) are thinner
than the distance between the pupils, when such a video-
camera is lifted up in between the two eyes it cannot be seen
with both eyes at the same time, as you should go cross-eyed to
do that, only the eye mirrors with their bearing piece folded
out in front of the eyes are screening for both eyes. This results
in an optical effect that in all directions around the non-
transparent, bright, contrasted virtual picture seen in the
mirrors in front of the eyes there is a clear view at least for one
of the eyes, that is the video-camera practically disappears from
the field of view. For those making a recording it is especially
advantageous fihat while they are looking at the picture of the
viewfinder with both eyes, they see the whole area around the
picture, and nothing is screened from the view.
According to figure 15 the binocular display device
according to the invention, as a viewfinder, is built in the end of
a mobile telephone 67, in other words the device is the
viewfinder of a mobile telephone. The virtual picture is
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displayed after the mirrors in front of the eyes 25 have been
opened completely mechanically or by a motor.
Since the mobile telephone's own small screen is suitable
for displaying only little picture or text information, for example
an Internet web-site or a whole E-mail page cannot be read at
this size. For this reason it is advantageous to build the
binocular display device according to the invention in the
casing of the mobile telephone or connect it to the mobile
telephone's battery charger connection end as an external
adapter. According to figure I6 in the present construction the
binocular display device is placed in the end of the mobile
telephone with the mirror in front of the eyes folded in, and by
folding out the mirrors in front of the eyes and lifting them up
in front of the eyes it can be viewed locally, or it can be taken
out of the casing of the mobile telephone and attached onto the
head.
The construction of the binocular display device according
to the invention shown in figure 17 contains an emissive type,
for example, an OLED 49 microdisplay. This construction is
similar to that shown in figure 12, so the reference numbers
used there are also used in figure 17. In the light path between
the X-mirror optical beam-splitter unit 22 and the first focusing
elements 24 there are liquid crystal shutters 69 which become
dark or transparent influenced by the voltage, with the picture
frequency of the microdisplay unit 49, in alternating phases.
According to figure 18 between the X-mirror optical beam-
splitter unit 22 or the pairs of first focusing elements 24 and
the device casing 51 there is a microdisplay driving circuit 77, a
radio frequency receiver-transmitter circuit 78, a power source
79 and a microprocessor 80. Using these arrangements the
binocular display device can be as compact as possible, no
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wires are needed for connecting it to the control signal, video
signal and power sources and the necessary computations,
picture processing and other tasks can be solved locally.
The binocular display device equipped with a system
detecting the movements of the eye according to the
construction example in figure 19, corresponds basically to the
device in figure 12, with the exception that here above one end
of the casing 51 there is a CCD picture recording chip 81
sensitive in the infrared range, and above its other end a front
lens 82 is placed in a way that the third optical axis 83 of the
front lens 82 is at right angles to the detecting surface 84 of the
CCD picture recording chip 81. Above the eye mirror 25 in front
of the right eye 27 a reflecting element 85 reflective in the
infrared range, light-admitting in the visible light wavelength
range is placed, made in one unit with the mirror in front of
the eye 25, in a size and at an angle so that it reflects the
beams starting from the pupil 86, iris 87 and sclera 88 of the
right eye 27 onto the detecting surface 84 through the front
lens 82. In the interest of even lighting of the right eye 27,
above the front lens 82 there is an infraLED 89 placed at an
angle that the infrared beam starting from it is projected onto
the reflecting element 85, and after it is reflected back from
there, it is projected onto the right eye 27. The CCD picture
recording chip 81, the front lens 82 and the infraLED 89 are
encased with a casing, not shown here, which contains a light
admitting opening at the front lens 82, and which is combined
with the device casing 51.
The picture detected by the CCD chip 81 is analysed with
the help of a picture processing program by a microprocessor
built into the binocular display device or connected to it with a
cable, and from the movement and position of the contour of
the iris and/or the pupil it calculates the point on the screen of
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the microdisplay unit where the eye Iooks, and displays a
cursor there, and it also detects the momentary hiding of the
contour of the iris and/or the pupil by the eyelid (blinking), and
it clicks interpreting it as a command. In order to increase the
contrast of the dark pupil and the lighter iris, or the iris and
the white of the eye {sclera) independently from the external
light conditions and the disturbing sparkling of the eyes, the
iris and its immediate environment should be preferably lit with
infrared light, because the users do not see it, they are not
disturbed by it.
The construction example presented in figure 20 is a
vision aid and night vision device and is basically the binocular
display device according to figure 12, but here on top of the
device casing 5I, above the dent 52 created for the nose, there
is a CCD picture recording chip 90, above the microdisplay unit
49 there is a front lens 91 placed in a way that the optical axis
92 of the front lens 91 is at right angles to the detecting surface
93 of the CCD chip 90. The CCD picture recording chip 90 and
the front lens 91 is encased with a cover, not shown here,
which contains a light admitting opening at the front lens 91
and is combined with the device casing 51. The detecting
surface of the picture recording CCD chip 90 falls in a plane
parallel to the plane defined by the optical axis of the first
focusing elements 24 and the mirror-crossing intersection line
of the beam-splitter unit 22 (see intersection line 4 1I1 figure
12). The picture recorded by the CCD chip 90 appears on the
screen 49a of the microdisplay 49 (not shown in figure 20) with
a light intensity that - depending on the actual setting - is
multiple of the original intensity, and in this case the utilisation
of this device is advantageous for people with reduced vision
capability, who cannot adequately orient themselves under
weak illumination conditions, for example, in the evenings or in
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half light. If the CCD is sensitive in the near infrared range,
displaying this infrared picture on the screen of the
microdisplay makes the orientation possible of the person using
the device even in total darkness provided that the area is
irradiated by an infrared light source.
As can be seen in figures 21 and 22, the microdisplay 49
placed at the receiving side of the element 22 made of very thin
semitransparent mirrors is a reflective type, the display
screen 49a of which is illuminated from the front by the
Fresnel lens 94 located on the other side (as seen from the
display) of the element 22, the greater part of which or alI of it
is located in the space between planoparallel plates 13 and 14
and this Fresnel lens 94 makes the light-beam of the LED 95
parallel and projects it to the screen 49a through the first
polariser 96 and the semitransparent surfaces of element 22.
The light beam arrives from the screen 49a to the eye through
the X-mirror element 22, the second polariser 97a or third
polariser 97b, the first focusing element 24 and the eye mirror
25.
According to the construction example in figures 23 view
of a binocular display device which contains eye mirrors 25a, a
microdisplay 49b placed between the eye mirrors 25a, a beam-
splitting unit 22a, focusing elements 24a, a display housing
56a, a microphone 108, a nose clip 60a and a flexible retaining
loop 105 that is longer than the diameter of the head of the
wearer at nose level it contains. The retaining loop 105 is
formed in part of wholly as electric cable, contains two
earphones 106, a control unit 107, and either the control unit
107 or the display housing 56a contains any of the following:
the microdisplay drive electronics, a radio frequency transceiver
circuit, a digital television receiving circuit, a microprocessor
and a power source.
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An advantage of the optical beam-splitter unit according to
the invention is that it has a minimal space demand and
minimal mass, that it can be placed as close to the object
source, as you like, and the picture of the device is of
exceptional quality. The advantages of the binocular picture
display device are similarly its small space demand and its
small mass, that it is simple to manufacture and the very many
application possibilities.
The invention is not restricted to the construction
examples of the unit, or of the device cited here, but in the area
of the protected solutions defined by the claims many different
constructions of it can be realised. So, for example, in the
interest of enlarging the image further focusing elements and
semitransparent or completely transparent mirrors may be
placed.
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