U.S. patent number 4,884,137 [Application Number 07/168,137] was granted by the patent office on 1989-11-28 for head mounted video display and remote camera system.
This patent grant is currently assigned to Varo, Inc.. Invention is credited to Robert D. Fallstrom, Charles M. Hanson, Vaughn J. Koester.
United States Patent |
4,884,137 |
Hanson , et al. |
November 28, 1989 |
Head mounted video display and remote camera system
Abstract
A video system is disclosed having a weapon-mounted video camera
(12) transmitting video signals to a remotely located video display
(14). The video display is mounted to the helmet (40) of a soldier
(36), and includes a sight reticle (50) superimposed on the image
of the target (46) so that the soldier (36) can aim the weapon (38)
by moving it until the target object (46) as displayed by the video
display (14) is aligned with the sight reticle (50). A low
probability of transmission interception of the video signals is
accomplished by using a nonvisible light carrier wavelength in free
space, which wavelength is characterized by a high degree of
absorption due to atmospheric water vapor.
Inventors: |
Hanson; Charles M. (Richardson,
TX), Koester; Vaughn J. (Dallas, TX), Fallstrom; Robert
D. (Richardson, TX) |
Assignee: |
Varo, Inc. (Garland,
TX)
|
Family
ID: |
26863831 |
Appl.
No.: |
07/168,137 |
Filed: |
March 14, 1988 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
883994 |
Jul 10, 1986 |
4786966 |
Nov 22, 1988 |
|
|
Current U.S.
Class: |
348/158;
348/E7.088; 398/106; 348/164; 224/401; 89/41.05; 224/181; 224/929;
224/930 |
Current CPC
Class: |
F41G
3/165 (20130101); F41G 3/2611 (20130101); G02B
27/017 (20130101); G02B 27/0172 (20130101); G02B
27/0176 (20130101); G02B 27/023 (20130101); G09B
9/006 (20130101); H04N 7/185 (20130101); G02B
2027/0132 (20130101); G02B 2027/0138 (20130101); G02B
2027/0156 (20130101); G02B 2027/0159 (20130101); G02B
2027/0178 (20130101); G02B 2027/0187 (20130101); G02B
2027/0198 (20130101); Y10S 224/93 (20130101); Y10S
224/929 (20130101) |
Current International
Class: |
F41G
3/16 (20060101); G02B 27/01 (20060101); F41G
3/26 (20060101); F41G 3/00 (20060101); G02B
27/02 (20060101); G09B 9/00 (20060101); H04N
7/18 (20060101); G02B 27/00 (20060101); H04N
007/18 (); H04N 005/33 (); H04N 007/22 (); H04B
009/00 () |
Field of
Search: |
;358/93,108,113 ;455/617
;224/181 ;89/41.05 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Britton; Howard W.
Attorney, Agent or Firm: Baker, Mills & Glast
Parent Case Text
RELATED APPLICATIONS
This is a divisional application of application Ser. No.
06/883,994, filed July 10, 1986 and entitled "Head Mounted Video
Display and Remote Camera System", now U.S. Pat. No. 4,786,966,
issued Nov. 22, 1988.
Claims
What is claimed is:
1. A video system, comprising:
an imaging system for generating video signals representative of an
object;
a video receiver and display remotely located from said imaging
system;
an optical link operating between a short UV and a far IR
wavelength for transmitting said video signals between said imaging
system and said video receiver;
means for presenting to the person different images superimposed
one on another so that plural images can be viewed simultaneously,
said presenting means comprising a partially reflecting mirror
disposed in the paths of two images; and
means removably attachable to a person's head, including means for
mounting thereto said video display in a position such that the
person can view the display without the use of the person's hands
and wherein the person can move about in an unimpeded manner.
2. The video system of claim 1 further including means for movably
mounting said display to said attachable head means so that said
display can be moved out of the line of sight vision of the person;
and
means for pivotally mounting said receiver to said attachable head
means and being integral with said display.
3. The video system of claim 1 further including a night vision
goggle attachable to said attachable head means so that an object
can be viewed simultaneously by the use of said video display and
said night vision goggle.
4. The video system of claim 1 further including in said video
camera, means for transmitting said video signals to said video
display through a free space transmission medium with a wavelength
of greater than approximately 150 nanometers; and
means for transmitting video signals from said imaging system to
said display through a physical medium.
5. The video system of claim 1 wherein said video display comprises
a vacuum fluorescent video display.
6. A video system of claim 1 further including in said transmission
system means for transmitting the video signals with a carrier
wavelength having a high degree of atmospheric absorption according
to a desired atmospheric parameter.
7. The video system of claim 1 further including a plurality of
remotely located video displays, each said display including means
for receiving the video signals and displaying the object toward
which said video imaging system is directed.
8. The video system of claim 1 further including a plurality of
video transmission systems, each transmitting at a different
carrier frequency.
9. The video system of claim 1 further including illumination means
for transmitting nonvisible light in a travel path of the person,
and said imaging system includes means for receiving the nonvisible
light reflected from objects in the travel path, and means for
transmitting video signals representative of the objects in the
travel path, whereby said video display displays the travel path to
the person.
Description
TECHNICAL FIELD OF THE INVENTION
The present invention relates in general to video systems, and more
particularly relates to video cameras, displays and transmission
apparatus for transmitting video signals under covert
conditions.
BACKGROUND OF THE INVENTION
There are many situations in which it is desirable to obtain a
closeup view of a situation or event from a remote location. In
military application, this is highly desirable for the safety of
combat troops. Other situations occurring in a civilian setting
require the same type of safety requirements.
The aiming and firing of a gun emplacement situated in the combat
zone may be controlled remotely by personnel not located at the
combat zone. In this situation, a video camera can be located at
the gun site to obtain a closeup view of defensive positions, and
at the same time transmit video signals of the combat zone scene to
remotely located troops who can control the aiming of the gun. In
another situation, it would be highly desirable to mount a video
camera to the rifle of an infantryman, and a video display to his
helmet, thereby allowing the soldier to aim the rifle without
engaging the weapon in the normal aiming position. The infantryman
could even remain in a hidden position and aim the gun through the
use of the video display, all without exposing his body to the
enemy.
With regard to the foregoing applications, it is often desirable
that the video transmission from the camera to the remote display
remains unavailable to the enemy so that such information cannot be
used to the enemy's advantage. While elaborate encoding or
encryption techniques could be employed to maintain the video
transmission somewhat secret, such techniques require additional
equipment, thereby adding to the weight, cost and reliability
concerns to the system.
Helmet-mounted video display systems have been employed for
assisting combat pilots in maneuvering aircraft and for weapons
deployment. In these systems, control cables are generally
connected between the helmet and the aircraft cockpit so that any
movement of the pilot's head results in the corresponding movement
of the weaponry. With this type of arrangement the video display
and helmet are fixed to the aircraft and thus are useless for
ground operations where mobility is important.
From the foregoing, it may be seen that a need has arisen for a
field operated video system which provides for remotely located
video camera and display equipment, as well as transmission
capabilities therebetween.
SUMMARY OF THE INVENTION
In accordance with the present invention, a video system with
remotely locatable equipment is disclosed which substantially
eliminates or reduces the problems associated with the prior art
techniques.
In accordance with a principal feature of the invention, a
weapon-mounted video camera operates in conjunction with a
head-mounted video display, thereby enabling military personnel to
aim the weapon without assuming a line of sight position with
respect to the aiming apparatus of the weapon. According to various
embodiments of the invention, the video camera may be responsive to
visible light, infrared radiation, thermal radiation or other
particular radiation properties of the environment which enable an
accentuated view of the scene or situation.
In accordance with another important feature of the invention, the
video display may operate in conjunction with an image splitter
disposed in the person's line of sight, thereby enabling the person
to observe a superimposed scene of the object within his line of
sight, as well as the object appearing on the video display.
In accordance with a correlary feature of the invention, the
head-mounted video display can be operated in conjunction with
night vision apparatus to provide additional viewing capabilities,
as well as used in conjunction with helmet apparatus which allows
the display to be easily removed out of the person's line of sight
vision.
With regard to yet another feature of the invention, the video
transmission between the camera and display equipment can be
transmitted through a physical medium, such as a metallic conductor
or a fiber optic bundle, or by free space radiation. In an
embodiment of the invention, a free space radiation frequency of
about 1.39 micrometers (um) permits the transmission of a video
signal for only a short distance before the signal becomes
significantly attenuated, due to atmospheric absorption. In this
manner, the transmission of a video signal is maintained secret or
has a low probability of intercept within the immediate area of
activity.
Still another important feature of the invention involves the
network distribution of the transmitted video signals such that an
image from a single video camera can be observed by plural persons
having appropriate display equipment. Also, video signal networking
is disclosed for enabling a single person to selectively view the
image generated by plural remotely located video cameras.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing and other features and advantages will be apparent
from the following and more particular description of the preferred
embodiments of the invention, as illustrated in the accompanying
drawings in which like reference characters refer to the same parts
throughout the different views. Referring to the drawings:
FIG. 1 is a block diagram of the video camera and display system
according to the invention;
FIG. 2 illustrates a typical application of a rifle-mounted video
camera operating with a free space transmission of video signals to
a helmet-mounted video display;
FIG. 3 illustrates an alternative embodiment of the invention in
which both the video camera and display are helmet mounted;
FIG. 4 illustrates a vehicle guidance system including an outside
mounted video camera transmitting a video image to the driver
concealed within the vehicle;
FIG. 5 illustrates an application of the invention utilizing an
air-to-ground free space transmission of an image, and a
ground-to-ground physical transmission medium;
FIG. 6 is an isometric view of one embodiment of a helmet-mounted
image display system employing holographic display techniques;
FIG. 7 is an isometric view of a headgear-mounted image display
system employing a beam splitter which can swing out of the user's
line of sight;
FIG. 8 illustrates helmet-mounted video display apparatus for
allowing split image viewing of the video image as well as the
object in the person's line of sight;
FIG. 9 illustrates head gear incorporating both a video display and
night vision equipment;
FIG. 10 is an oblique view of a video display, hingeably mounted to
a headgear;
FIG. 11 is a side view of the headgear mounted video display of
FIG. 10;
FIG. 12 illustrates night vision equipment mounted to a helmet, and
coupled by a physical transmission medium to a display;
FIG. 13 is a cross-sectional view of an armored military vehicle
having omnidirectional image transmitting capabilities within the
vehicle;
FIG. 14 depicts in block diagram form the major components of the
video display equipment;
FIG. 15 illustrates alternative switchable transmission paths
between a video camera and a remotely located video display
according to the invention;
FIG. 16 graphically depicts the atmospheric absorption
characteristics with respect to transmission carrier
wavelength;
FIG. 17 shows a networking scheme used between a single video
camera and a plurality of remotely located display units;
FIG. 18 shows another networking scheme used in selectively viewing
one of a plurality of images generated by plural remotely located
video cameras;
FIG. 19 illustrates a helmet-mounted switching arrangement for
selective presentation of an image from one of the plural cameras
shown in FIG. 18;
FIG. 20 illustrates a vehicle guidance system for use in connection
with low probability of intercept of nocturnal activities; and
FIG. 21 illustrates a nonvisible light transmitter for use in
conjunction with the system of FIG. 20.
DETAILED DESCRIPTION OF THE INVENTION
The principles and concepts of the invention are best understood by
referring first to FIG. 1 of the drawings. The video system
according to the invention is shown generally as reference
character 10, and includes an imager shown as a video camera
section 12 employed separate and apart from an imager shown as a
video display 14. With regard to the example of FIG. 1, the object
to be viewed is shown as an armored vehicle 16, and the image
thereof provided by the video display equipment 14 is shown as
reference character 18.
More particularly, the video camera 12 includes an optical imaging
system 20 coupled to a video processing sensor system 22 which, in
turn, is coupled to a video transmitter system 24. Optionally
provided integral with the camera is a video display unit 26. The
optical imaging system 20 comprises a lens and filter assembly for
providing a clear and accurate image of the vehicle 16 to the
processing system 22. The optical imaging system 20 may be of the
conventional type which provides optical correction and adjustment
of objects characterized by visible light radiation. The system 20
may also be of the type which processes infrared characterizations
of the object. A resultant image of the particular type of
characterization is coupled to the video processing system 22. The
optical imaging system 20 may also be of the type which is
responsive to thermal radiation which is characteristic of the
object, or include night vision capabilities. The noted types of
imaging systems are readily available, and adaptable to the video
camera 12 according to the invention.
Once a visible image of the object 16 is created by the optical
imaging system 20, such image is presented to the video processing
system 22 for converting the optical image into a standard
electrical video format. While not limited to the raster/scan type
of video system, such a technique is well known in the art and can
thus be easily adapted to the present invention. In essence, the
video processing system 22 produces an electrical signal
representation of the optical image and couples the electrical
signals to the video transmitter 24. The electrical video signal is
also coupled to the optional video display 26 which is integral to
the camera 12. The optional video display system 26 converts the
electrical signals of the object 16 back into an optical
characterization thereof so as to be observable by a person. With
the provision of the integral video display unit 26, a viewer can
initially set up the camera 12 and use such display 26 for aligning
the camera 12 with respect to a particular scene. This can be done
without operating the video transmitter 24, and thus no signal is
radiated in the immediate area of the camera 12.
The video transmitter system 24 provides the transmitting equipment
to produce a video signal appropriate for transmitting over a
desired medium. In the depiction of FIG. 1, the transmitted signal
27 is shown transmitted in a free-space medium. That is, the video
signal is transmitted through the atmosphere without a physical or
hardware connection between the camera 12 and the remote video
display 14. The video transmitter system 24 can be of the type
adapted for modulating the video signal onto an electrical carrier
of a desired frequency, or onto a carrier in a frequency band which
is in the visible light range, or above such range. In those
situations where the camera 12 and video display 14 are mounted
adjacently on a combat helmet, the video transmitter system 24 may
be dispensed with entirely, whereupon the electrical video signal
is coupled directly to the video display 14 by a coaxial cable, or
other suitable conductor. In other applications where the video
camera 12 is located in the immediate area of the video display 14,
and where the transmission of the video signal is to remain
absolutely secure, the transmission medium may include a fiber
optic bundle. In this event, the video transmitter system 24 would
include an electrical to optical converter.
The remotely located video display 14 is provided with a video
receiver system 28 for receiving the video signal transmitted by
the camera 12. The video receiver system 28 is coupled to a video
monitor system and display 30 which regenerates an optical image of
the object 16 from the electrical characterization of such image.
An optical viewer 32 comprises a lens arrangement for providing
optical correction, magnification or other adjustment for
presentment of the image to the viewer 34. As noted in FIG. 1, the
image 18 can be observed either from the remotely located display
14 or the optional integral video display 26, if provided.
Referring now to FIG. 2, there is shown an application of the
invention which is envisioned to be advantageous for combat
personnel. A soldier 36 is equipped with a rifle 38 to which a
video camera 12 is mounted. The video camera 12 is fastened to the
rear portion of the rifle barrel and above the sight mechanism so
as to provide an unobscured aim of the rifle, should the soldier
use the weapon in a conventional manner. The video camera 12 is
shown equipped with an infrared or thermal detector, comprising the
optical imaging system 20. With this arrangement, objects can be
identified by the nature and extent of the heat emitted, and
recognized by the solder 36 in the video display 14 by the solder
36.
In accordance with conventional combat protection gear, the soldier
36 is provided with a helmet 40. Mounted to the helmet 40 is the
video display equipment 14 which receives free space video
transmissions from the camera 12 to thereby provide the solder 36
with an infrared (IR) generated image without having to
continuously look through a rifle-mounted IR equipment. The video
display 14 is shown fastened to the helmet by a strap 42, which
strap is fixed to the helmet by rivets (not shown) or other
suitable means. The video display 14 is also depicted receiving
free-space transmissions of the camera-generated video image. The
solder 36 is outfitted with a screen 44, goggles or other similar
eyewear on which the image of the object can be holographically
presented. The image 46 is shown removed and disposed in a frame 48
in the manner presented by the display 14 to the soldier 36. The
image 46 can also be superimposed on a reticle 50 which provides
the soldier 36 information such as range, size, elevation, etc.
Holographic projection systems are well-known in the art and are
readily adaptable for use in the noted example.
The application of the invention shown in FIG. 2 provides many
advantages to the combat solder. For example, a gunner in an
armored vehicle equipped with the camera 12 and the helmet-mounted
display 14 of the invention can reload or carry on other operations
while watching a target through the head-mounted display. As an
additional advantage, the invention may significantly reduce the
time to thus aim and fire the weapon. In the case of a foot soldier
equipped with a camera-mounted rifle 38 and a helmet-mounted video
display 14, the soldier can aim the weapon from a full defilade
position and shoot from the hip. With the provision of the
head-mounted video display 14, a solder can also wear a gas mask
without impairing or making more difficult the aiming of the weapon
38. This is a result of a soldier not having to rest the gun on his
shoulder for aiming through the conventional sights. Rather, he
need only concentrate on the head-mounted video display 14. Not
only does the invention eliminate eye and neck strain should a
prolonged conventional aiming position be required, but is also
eliminates the motion or agitation of the rifle which has the
effect of losing aim on the target. This is particularly important,
for example, in an armored vehicle where a conventional control
panel-mounted video display moves to the same extent as the vehicle
according to the roughness of the terrain. Hence, it becomes very
difficult for the observer to concentrate on the wiggling video
image. In accordance with an important feature of the invention,
the head-mounted feature of the video display system secures the
display, and thus the video image of the object with respect to the
observer's eyes.
FIG. 3 illustrates another embodiment of the invention wherein both
the video camera 12 and the display 14 are helmet-mounted. The
video camera 12 shown in FIG. 3 is provided with a thermal or
infrared detector 52. Again, a video image of the thermal
representation of the object is transmitted by free space 54 to the
video display 14. The video camera 12 can be mounted to the helmet
40 by any suitable securing means. The image 56 displayed to the
soldier 36 is shown as a motorized gun emplacement, thereby
yielding an indication of the thermal characteristics of the motor
and the personnel around the target.
FIG. 4 illustrates an additional application of the invention. A
video camera 57 is mounted exterior to an armored vehicle 58 for
providing a view of the terrain in front of the vehicle 58. The
video image of the object is again transmitted by free space
techniques to a receiver 59. The receiver 59 may be coupled by a
coax or fiber optic line to a video display (not shown) mounted to
the helmet of the tank driver. The driver (not shown) can then
assume other duties within the vehicle without having to constantly
look through a periscope, peephole or at a dash-mounted CRT
display.
FIG. 5 depicts another application of the invention. An aircraft 60
can fly into a position of surveillance of a target 61 and relay an
image thereof to ground personnel 62. Based upon the image
displayed on the helmet apparatus 63 of the ground personnel 62,
appropriate gun control parameters can be keyed into a remote fire
control unit 64 to aim the vehicle mounted weapon 65 at the target
61. The remote control 64 is connected to the vehicle mounted
weapon 65 by a secure fiber optic fire control link 66.
FIGS. 6 and 7 illustrates other helmet-mounted video display
arrangements where the corresponding parts thereof are identified
by the same reference characters as shown in FIGS. 2 and 3. In this
arrangement, the display screen 44 is formed integral with the
video display 14, and the combination is pivotally mounted to the
helmet 40 by a screw 67. The display screen 44 and the display unit
14 can be rotated upwardly out of the line of sight of the soldier.
Display screen 44 is transparent so the soldier may see through the
screen when he is not focussing on images on the screen. The
display unit 14 houses the projection and display optics as well as
the video link receiver and power supply. A video receiver fish eye
objective lens and detector assembly 68 receive the free space
optical radiation of an image transmitted from a remote location.
The remote image transmitter may be a gun-, vehicle- or
aircraft-mounted, or mounted to a tripod.
FIG. 7 illustrates a headgear 69 equipped with the video display
14. The headgear 69 is mounted to the user's head by a strap 70.
The helmet 40 fits over the headgear strap 70 and provides
conventional protection. In this embodiment, a beamsplitter video
screen 71 provides the medium upon which the image is protected by
the display unit 14. The beamsplitter screen 71 is hinged 72 so
that it can be removed from the soldier's line of sight. A focus
and lateral adjustment 73 provides three axis adjustments to
properly focus the projected image in front of the user's eye. An
off-on switch 74 is manually operated to render the electrical
circuits of the display unit 14 operational.
FIGS. 8-11 illustrate various other embodiments of the invention
secured to the head of a soldier. In FIG. 8 a video receiver 75 is
mounted to a face frame 76 which is fastened to the person's head
by an adjustable headdress strap 77. The face frame 76 is molded in
the general shape of the facial features surrounding a person's
eyes and nose. A helmet 40 may be worn over the display headdress,
and thus the cranial protection of the person need not be
compromised. The helmet 40 is secured to the head of a person by a
combined chin strap 78 and a depending side strap 79.
The video receiver 75 is secured to the face frame 76 and is thus
made integral therewith so that the video receiver 75 ideally
follows the motions of the observer's head. The video receiver 75
is connected by a cable 80 to an electrical or optical antenna for
receiving transmissions from a remotely located camera. Provided
with the video receiver 75 is an image viewer or screen 81, such as
a vacuum fluorescent display, a cathode ray tube, an
electroluminescent display, or a liquid crystal display. All such
types of displays can be obtained in miniature form suitable for
use as described herein. One type of miniature display particularly
suitable for use is the vacuum fluorescent display described in
U.S. Pat. No. 4,081,716, and may be obtainable from ISE
Electronic's Corp., ISE, Japan. This display is approximately 7 mm
by 10 mm, operates on only 15 volts and thus is ideally suited both
as to size and weight for use with the invention.
The optical viewer 81 is optically coupled to the receiver 75 so as
to present an image to the person corrected with respect to focus,
magnification and other appropriate parameters. As noted in FIG. 8,
the optical viewer 81 redirects the image from a horizontally
directed image plane to a vertical image plane adjacent one of the
observers's eyes. A partially reflecting mirror 82 is mounted to
the optical viewer 81 at an angle of about 45 degrees, and is
disposed directly under the exit lens 83 of the optical viewer 81.
The redirected image of the object is thus reflected from the
mirror 82 and presented for viewing to the observer.
Because the mirror 82 is only partially reflecting, the person can
also see objects that are disposed on the opposite side of the
mirror 82. Thus, the person has available for viewing with one eye
superimposed objects, namely the video image from the display 81,
as well as objects in the line of sight vision of the observer. The
reflecting mirror 82 is mounted within a frame which is pivotally
mounted 84 to the optical display 81. The person can thus swing the
reflecting mirror 82 upwardly and out of the line of sight vision
of the eye with which it is aligned. Hence, the person can observe
the surroundings in the event a video display is not desired.
Additionally, a switch 86 is mounted to the face frame 76 for
providing electrical power control of the video receiver 75. The
switch 86 is wired to the video receiver 75 to provide on-off
operation. The switch 86 is mounted at the foremost part of the
face frame 76 so as to be readily accessible for operation by the
wearer of the headdress.
FIG. 9 illustrates an adaptation of a video display 88 with night
vision equipment 90 to provide the viewer 92 with alternative image
characterizations of an object. With this arrangement, the video
display 88 and the night vision equipment 90 are disposed in the
line of sight division of the respective left and right eye of the
observer 92. The face frame 94 of this embodiment fits flush
against the face of the wearer 92, and includes an outwardly
extending shell 96 which houses the video display 88 and night
vision equipment 90. The video display 88 and night vision
equipment 90 are secured within the face frame shell 96 and are
thereby protected. The face frame 94 is secured to the head of the
wearer 92 by an adjustable strap 98. With this arrangement, the
vision equipment 88 and 90 can only be removed by removing the face
frame 94 from the head of the wearer 92.
The night vision equipment 90 includes a conventional image
intensifier tube 100 which presents an electronic light amplified
presentation of the object, with only very small amounts of light
illuminating the object. In accordance with the conventional night
vision equipment, starlight is sufficient to illuminate a distant
object for easy viewing on the backside of the image intensifier
tube 100. The video display 88 has an inherent narrow field of
vision. Thus, objects peripheral to the line of sight vision, as
viewed through the video system, are generally not displayed. This
creates a disorienting affect when it is necessary for a person to
freely move about. The tendency is, for the wearer who depends
entirely on the video system, to constantly look from side to side
to effectively increase the field of view. When the night vision
equipment is provided which has a much larger field of view, the
wearer 92 can look through both the video display 88 and the night
vision equipment 90 and gain advantage of both types of optical
equipment. In other words, when a viewer is equipped with the
optical apparatus shown in FIG. 9, the night vision equipment 90
can be used to view the general environment disposed in front of
the person 92, while the video display 88 permits the wearer 92 to
then focus on objects which would not otherwise be in the line of
sight vision.
A headgear-mounted video display is shown in FIG. 10. A helmet may
or may not be needed with this alternative. The headgear 102
provides a headdress to which a flat panel video monitor or display
104 is hingeably mounted.
In FIG. 11 a helmet 40 is shown worn over the video display
headgear 102. The headgear 102 is shown for mounting the video
display 104 adjacent the eyes of a wearer 106. The details of the
headgear 102 are disclosed in more detail in U.S. Pat. No.
4,703,879, and entitled Night Vision Goggle Headgear. The video
display 104 is mounted by a pivotal connection 108 to an
overhanging frame structure 110 so that the video display 104 is
cantilevered in front of the viewer's eye. The frame structure 110
is formed integral with a headband 112 of the headgear 102. Straps
114, 116, 118 and 120 secure the headgear 102 to the wearer's head.
With this arrangement, a helmet 40 can be easily worn, if desired,
over the headgear 102 and thus facilitate full vision capability as
well as protection.
A video display system is shown in FIG. 12 receiving an image from
helmet-mounted night vision equipment 121. The night vision
equipment 121 is fixed to the helmet 40 so that whenever the user
turns his head, the corresponding view is displayed by the display
unit 14. The night vision equipment provides an image of the object
through a physical conductor 122 to the display unit 14. The
physical conductor 122 may comprise a coaxial cable or fiber optic
cable. This embodiment is tailored to the exclusive use of the
display in low light conditions. However, the night vision
equipment can be replaced with a thermal or infrared sensitive
unit.
FIG. 13 is illustrative of yet another application of the
invention, wherein an armored vehicle receives video transmissions
123 from a remotely located imager (not shown). A receiver unit 124
mounted within the vehicle retransmitts the video image
omnidirectionally. In this manner, each person within the vehicle
who is equipped with a head mounted display 125 can observe the
image. There is a low probability of intercept of the video signals
retransmitted within the vehicle due to the enclosed nature
thereof.
FIG. 14 illustrates a detailed block diagram of a video display
receiver system 126 of the invention. In the exemplary receiver
system 126, an optical to electrical transducer 127 receives free
space radiation 128 from a video transmitter (not shown) encoded
with information relating to the object. The radiation 128 may be
characterized by a wavelength either in the visible light range, or
shorter. The optical to electrical transducer 127 may comprise, for
example, a material disposed in the path of the radiation 128 and
responsive to the particular wavelength of the radiation 128. The
material thus produces an electrical output representative of the
modulated free space video signal. A video demodulator 129 is
coupled to the transducer 127 for demodulating a video signal into
constituent electrical components suitable for driving a video
display. A video display driver 130 receives the coded signal from
the video demodulator 129 and drives a display 132 so that an image
of the object is displayed thereon. The video display driver 130 is
of conventional design and adapted to drive a raster/scan type of
display, if such type of display is employed. If a matrix type of
display is used, the driver 130 would be adapted for individually
addressing each element of the matrix with a signal having
characteristics of the brightness with which the element should be
illuminated. Preferably, the display 132 is of the miniature,
lightweight, low power type suitable for mounting to the helmet or
headgear of a wearer. A vacuum fluorescent display of the type
disclosed in the noted patent has these qualities.
An eyepiece assembly 134 is disposed in the output optical path of
the display 132 and comprises plural lenses, such as 136, for
interfacing the image on the display 132 to the human eye 138. The
eyepiece assembly 134 may include the various combinations of lens
types to suit individual needs. In addition, the eyepiece assembly
134 may be used in conjunction with the partial reflecting mirror
82 of FIG. 8.
With reference now to FIG. 15, there are shown the details of an
arrangement for coupling a video camera transmitter 140 to the
video display receiver 126. The imager or camera 140 is shown
mounted on a tripod 141. As described above, the video camera
transmitter 140 can be located remotely from the head-mounted video
display receiver 126, such as on a weapon, a vehicle or also on a
tripod. These suggested mounting locations are only exemplary, and
are not to be interpreted as limiting the applicability of the
invention to particular situations. The arrangement of FIG. 15
provides dual modes of video transmission between the video camera
transmitter 140 and the video display receiver 126. In one mode of
operation, the video information is transmitted in a free space
medium 128 from the transmitter 140 to the receiver 126. In another
mode of operation, the modulated video signal is transmitted from
the transmitter 140 to the receiver 126 by a physical medium, such
as a fiber optic or a coaxial cable 144. The physical medium 144
can be advantageously used in those situations where the utmost
security of the video signal is desired, or where the atmospheric
conditions do not permit an acceptable medium for a free space
transmission.
The video camera transmitter 140 includes a video transmitter 146
for transmitting a modulated video signal of the image on a pair of
output conductors 148 and 150. Transmitter line 148 drives an
electrical to free space transducer 152 for transmitting the free
space video signal 128. Transmitter conductor 150 drives the
physical conductor 144 with appropriate video signals. Physical
conductor 144 can be of the coaxial type, in which event the
signals on video transmission line 150 are electrical in nature.
However, the physical conductor 144 can also be a fiber optic
bundle, wherein the signals in transmission line 150 would be
converted to modulated light signals.
The electrical to light transducer 152 of the video camera
transmitter 140 includes a reflector 154 for providing a desired
directional radiation characteristic. When it is desired to
transmit a highly directional modulated video signal in free space
128, the reflector 154 can be shaped in a parabolic form to focus
the transmitted video signal in a beam collimated in a desired
direction. In the alternative, the video signal may be transmitted
omnidirectionally, wherein any video display receiver in the area
would be capable of receiving the video signal. The electrical
transducer 152 further includes a light transmitting element 156
which converts the video signal on transmission conductor 148 into
modulated light signals. The nature of the materials comprising the
element 156 determines primarily the wavelength of the transmitted
energy in free space 128. Materials are presently available to
provide free space transmissions from the short ultraviolet
spectrum to the far infrared spectrum.
The video display receiver 126 is provided with an optical to
electrical transducer 159 for converting the free space 128
transmission of the video signal into corresponding electrical
representations. Further details of the transmitter transducer 156
and the receiver transducer 159 will be disclosed below. A focusing
lens 160 is disposed in the path of the free space video signal 128
for focusing the light radiation on the electrical transducer 159.
The lens 160 is preferably constructed of a material which has a
low degree of attenuation to the particular wavelength of the free
space transmission. Of course, the material with which the optical
to electrical transducer 159 is constructed is also highly
responsive to the particular frequency or wavelength of the free
space radiation.
The video display receiver 126 is provided with a feature in which
the image chosen to be displayed on the video display 132 is
automatically switchable from the free space transmission medium
128 to the physical medium 144. An automatic selection means 160 is
provided for automatically selecting the physical medium 144 when
the cable is connected to the video display receiver 126, and for
selecting the free space transmission 128 when the physical medium
144 is disconnected. To that end, the video display receiver 126
includes a switch 162 switchable between a first position 164 and a
second position 166 in response to the electrical energization of
an associated relay coil 168. When the switch 162 is in the first
position 164, the video signal transmitted on the physical medium
144 is coupled to the video demodulator 129. On the other hand,
when the switch 162 is switched to the second position 166, the
free space transmission 128 of the video signal is coupled to the
video demodulator 129.
The automatic switching mechanism 160 further includes a physical
medium connection arrangement 170 for ohmically connecting the
physical medium 144 to the video display receiver 126. Also
included is a ground detector 172 coupled between the ohmic
connection arrangement 170 and the switching relay 168. For
purposes of illustration, when the physical medium 144 is a coaxial
cable carrying electrical video signals, such cable is commonly
terminated with a BNC type metallic connector 174. The BNC
connection 174 is attachable to a corresponding coaxial cable 176
fastened to a frame part 178 of the video display receiver 126.
Also mounted to the frame 178 is a spring-loaded probe assembly 180
insulated from the frame 178. Disposed on the other side of the
frame 178 is the spring-loaded end 182 which is conductive and
engagable with the metallic connector 174. Thus, when the physical
medium 144 is appropriately attached to the video display receiver
126, the metallic connector 174 makes electrical contact with the
spring-loaded end 182.
In accordance with conventional connections, the metallic connector
174 is connected internally to a shield or ground conductor of the
cables 144 and 176. As noted in FIG. 15, the coaxial cable 176
includes a signal conductor 184 for carrying the video signals, and
a shield conductor 186 for providing electromagnetic shielding to
the signal conductor 184. When the physical conductor 144 is
connected to the coaxial cable 176 by connector 174, the potential
of the grounded shield 186 is transferred through the connector 174
to the probe 180, and then coupled to the ground detector 172. When
a ground potential appears on the conductor 180, the ground
detector 172 detects this as a connection of the physical medium
144 to the video receiver 126, whereupon relay 168 is operated. The
ground detector 172 can be, for example a logic NOR gate for
providing a logic output high in response to input logic low levels
representative of the ground potential on the shield conductor 186
and the conductor 184.
The relay contacts 162 are shown in FIG. 15 in the operated
position, illustrating that when the physical medium 144 is
connected to the video display receiver 126, the signal carried on
conductor 184 is coupled to the video demodulator 129. When the
connector 174 of the physical medium 144 is disconnected from the
video display receiver 126, the ground potential will be removed
from conductor 180, whereupon the output 188 of the ground detector
172 will be driven to a logic low, thereby releasing relay 168. The
switch 162 will then make contact with the second contact 166 and
thereby automatically couple the free space transmission 128 of the
video signal to the video demodulator 129. Those skilled in the art
may devise other physical conductor switching arrangements 170 or
detectors 160 which will operate with equal effectiveness.
In accordance with another important feature of the invention, the
wavelength for transmitting the video signal is selected so as to
provide transmissions having a low probability of intercept,
thereby preventing the reception of the signals by the enemy or
other unauthorized persons. One technique for accomplishing the
transmission having a low probability of intercept is to assure
that the transmission of the video signal is restricted to a
narrowly defined area. When the transmission medium for the video
signal is a physical conductor, the reception of the signal is
limited only to the receiver connected therewith. The secrecy
problem is exacerbated when it is desired to transmit the video
information through the atmosphere. With the free space
transmission of signals, the area of reception is less defined, and
is determined by many atmospheric conditions which are susceptible
to change at unpredictable times.
In accordance with one aspect of the head mounted video display
system, one wavelength selected for transmitting the video signal
in free space is chosen such that a predictable signal absorption
occurs, notwithstanding day, night or weather conditions. This
assures that the video signal will not be received beyond a maximum
peripheral area surrounding the transmitter. While many parameters
of the atmosphere exist which affect the absorption of a radiated
wave, the water vapor content of the atmosphere has been chosen as
the parameter to which absorption of a particular transmission
wavelength is correlated. Reference is made to FIG. 16 where there
is graphically depicted the transmittance of a radiated wave as a
function of water vapor normally occurring in the atmosphere. The
transmittance is represented by the vertical axis of the graph,
while the wavelength of the radiated signal is shown on the
horizontal axis. It can be noted from the graph of atmospheric
absorption that at various fairly well defined wavelengths
excessive signal attenuation occurs. For example, at a wavelength
of about 1.1 um, the absorption represented by reference character
190 is at a maximum. At about 1.4 and 1.9 um the absorption of the
signal is again at a maximum level.
From the graph of FIG. 16, the atmospheric transmission of a signal
transmitted at a wavelength of 1.39 .mu.m is about 0.001 percent.
It can be seen that by selecting a wavelength in this range, the
atmospheric absorption thereof does not permit the signal to reach
distant areas. As a result, it is assured that the video signal
modulated on such a wavelength will not extend beyond the area of
its intended reception. In the preferred form of the invention, the
transmission of the video signal at a wavelength of about 1.39 um
provides certain advantages over the other frequencies associated
with the other maximum absorption peaks. Transmitters and receivers
operating in this wavelength range are not unduly complicated and
do not require the attention to additional considerations, as does
the transmission or reception at the other noted wavelengths. While
one could provide video transmissions at 0.9 and 1.1 um, the
atmospheric attenuation is somewhat less than at 1.39 um. The
absorption of the signal at a wavelength of 1.9 um is substantially
identical to that associated with the 1.39 um wavelength, but
additional cooling may be required for the transmitter and
receiver.
The foregoing analysis can also be made to select a transmitting
wavelength having desired absorbtion characteristics based on other
atmospheric elements. For instance, particular wavelengths can be
selected to achieve desired absorbtion characteristics in carbon
dioxide or ozone.
A transmitting element 156, such as shown in FIG. 15, fabricated of
either a gallium indium arsenide (GaIAs) material or a gallium
arsenide antimonide material emits frequencies in the 1.39 um range
when driven or excited by an electrical signal. When so driven, the
transmitting element 156 will radiate a carrier frequency in the
1.39 .mu.m range and communicate the video information modulated
thereon. The lens 160 in the video display receiver 126 can be
constructed of glass, arsenic trisulphide sapphire, cadmium
sulphide or magnesium oxide. With such materials, optical
processing of the free space transmission is possible without
attenuation of the signal by the lens itself. The optical to
electrical transducer 159 may be constructed of a material similar
to that of the transmitting element 156 and thereby convert the
free space radiated video signal into a corresponding electrical
signal. For optimum response to a free space transmitted wavelength
of 1.39 .mu.m, the optical to electrical transducer 159 is
perferably constructed of the same materials as the transmitting
element 156.
Shown in FIGS. 17 and 18 are additional features of the invention.
The utility of the invention is enhanced when using plural remote
video display receivers, even though only a single video camera is
operational, or is available. FIG. 17 illustrates a single
rifle-mounted video camera transmitter 196 and a plurality of
helmet-mounted video display receivers 198-204. In this
application, the video transmitter 196 is provided with a
transmitter element (not shown) fabricated of a material which
transmits the video image in free space at a desired wavelength. In
a similar manner, the video display receivers 198-204 are each
provided with a material which is responsive to the same wavelength
radiation to thereby receive and decode the video signal as
modulated by the transmitter 196. Thus, each video display receiver
198-204 is contructed to allow each of the corresponding persons
wearing the helmet-mounted device to view the same object toward
which the rifle 206 is aimed. This is especially advantageous in
training maneuvers where plural soldiers can view a target sighted
from a single weapon. Indeed, with the arrangement set forth above,
military trainees need not even be disturbed from classroom
instructions on weapons targeting in order to witness the actual
sighting and targeting of the remotely located weapon and
target.
The details of another networking technique according to the
invention are shown in FIG. 18. Here, a single video display
receiver 208 is helmet-mounted to a soldier 210 who can selectively
receive free space transmissions of different video signals from
rifle-mounted cameras 212, 214 and 216. Each soldier 218-222
carrying a respective rifle 224-228 is equipped with a
helmet-mounted video display receiver 230-234 so that the
particular objects captured by the respective video cameras 212-216
can be seen by the respective soldiers 218-222. The transmitting
wavelength of the video equipment provided the soldier 218 will
preferably be different from the wavelength used by the equipment
of soldiers 220 and 222. The latter two soldiers 220 and 222 may
also be using different wavelength equipment. In this situation,
the transmitting and receiving elements with which each soldier
218-222 is equipped will be constructed of different materials, and
thus will be nonresponsive to the transmission or reception of the
other soldier' equipment. Alternatively, the modulation frequencies
of the various transmitters may be different, and the soldier can
select which scene he will view by tuning a filter in his
receiver.
As noted above, the video display receiver 208 is selectively
responsive to the transmission of each of the video camera
transmitters 212-216. Associated with video receiver 208 is a
switch 236 which allows the helmet wearer 210 to selectively
receive the video signal of one of ten transmitters 212-216.
Conventional switches are available for switching or controlling
different video channels. With this arrangement soldier 210, who
may be an instructor, can judge the aiming or firing technique of
each soldier trainee 218-222 without being in the immediate
vicinity of each such trainee. A significant advantage is gained by
using this arrangement since a military instructor 210 and a
soldier trainee 218, for example, can simultaneously view the same
object toward which the video camera transmitter 212 is
directed.
In FIG. 19 an exemplary switching arrangement 236 is shown,
adaptable for use in the example of FIG. 18. Micrometer wavelength
radiation, denoted again by reference character 128, emitted form
any of the video camera transmitters 212-216 is focused by an
object lens 158 onto a plurality of micrometer wavelength sensitive
elements 238, 240 and 242. Each element 238-242 is responsive to a
different narrow band of wavelengths which correspond to the
different wavelengths transmitted by the respective video camera
transmitters 212-216. In other words, element 238 is responsive to
a free space wavelength transmitted only by video camera
transmitter 212. Elements 240 and 242 receive only transmissions
from respective camera transmitters 214 and 216. The manually
operated switch 236 is switchable by the soldier 210 to position
244, 246 and 248 corresponding to the free space video camera
transmitters 212-216. The single video signal selected by the
soldier 219 is then switched through the manually operated switch
236 to the video demodulator 129 of FIG. 14. The switch 236 may
also be ganged to a similar switch in the demodulator 129 to change
an oscillator frequency such that one given video, IF (intermediate
frequency) frequency is produced, notwithstanding which video
transmission frequency or wavelength is selected. It is of course
possible to switch or multiplex more than the number of free space
transmissions shown in FIG. 18, as well as make the switchable
connection within the video display receiver at points other than
in the video demodulator 129.
In yet another application of the invention, a combination video
transmitter and display receiver can be used to facilitate a low
probability of detection of vehicular movement at night. FIG. 20 is
illustrative of a vehicle 250 equipped with apparatus incorporating
the principles and concepts of the invention. A driver 252 of the
vehicle 250 is provided with a video display receiver 254 which can
receive micrometer wavelength video transmissions either through
free space, or through a physical medium as described above. The
vehicle 250 is equipped with standard incandescent lamps 256 and
258, as well as a pair of transmitters 260 and 262 for transmitting
radiation in the nonvisible light spectrum. The nonvisible light
spectrum can comprise radiation wavelengths between short
ultraviolet and far infrared. In this application, it desirable to
select a wavelength which is highly susceptible to atmospheric
absorption. In this manner, the lamps 256 and 258 may be turned off
and transmitters 260 and 262 turned on. The driver 252 can detect
the light from lamps 256 and 258 with his receiver 254 while a
remote observer is not able to detect the light.
Provided also is a receiver/transmitter unit 264 which has a
receiver input 266 responsive to the nonvisible light reflected
from objects in the path of the vehicle 250. The unit 264 further
includes a transmitter 268 for transmitting free space radiation to
a video display receiver 254. Characterizations of the terrain or
objects in the path of the vehicle 250 are thus transmitted by
transmitter 268. It should be noted that the wavelength of
radiation transmitted by transmitters 260 and 262 need not be the
same as that transmitted by the transmitter 268. However, the
receiver element (not shown) in the input 266 of the unit 264 must
be responsive to radiation wavelengths in the range emitted by
transmitters 260 and 262. By using different transmission
wavelengths in transmitters 260, 262 and 268, an appropriately
equipped soldier 252, or other similarly equipped foot soldier, can
look straight into the main transmitters 260 and 262 without
saturating or otherwise affecting the quality of the image
displayed on the helmet-mounted display 254.
In order to flood the path ahead of the vehicle 250 with radiation
of a desired wavelength, a number of small individual transmitters
can be provided in each transmitter unit 260 and 262. A vehicular
micrometer wavelength transmitter is shown in exemplary form in
FIG. 21. Each element (which may for example be an LED) of an array
of transmitting elements 272 is mounted in a small parabolic
reflector 270 (see exploded view in FIG. 21). An electrical cable
274 provides the driving energy for exciting the elements 272 so
that radiation of the desired wavelength can be emitted. The
reflectors 270 have reflective interior surfaces 276 so that a
majority of the energy radiated from each of the elements 272 is
directed in a forwardly direction in the path of the vehicle 250.
Each radiating element 272 need not be driven by a separate signal,
but rather all radiating elements may be driven together by a
common driving electrical signal on cable 274.
From the foregoing, a video transmitter and display receiver
arrangement is disclosed which provides a significant advantages
when used either in military or civilian applications. The
invention may find a variety of applications in the civilian
environment, such as in news reporting, fire fighting or law
enforcement. When used in connection with the free space
transmitting features described above, the invention provides
additional measures of security in that the reception of the video
signal is limited to a relatively predefined area.
In a video transmitter and display receiver such as described
above, many changes can be made which are not relevant to the novel
features as taught by the invention. Bearing this in mind, the
specific embodiments disclosed herein are intended to be merely
exemplary of the invention and not restrictive thereof, since
various modifications readily apparent to those familiar with the
art can obviously be made without departing from the spirit and
scope of the invention as claimed hereinbelow. Moreover, not all
features of the invention are required to be implemented together,
but rather one or more of the features may be employed with an
existing system to take advantage of the individual feature.
* * * * *