Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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MODULAR NIGHT-VISION SYSTEM WITH FUSED OPTICAL SENSORS
The domain of the invention relates to a modular visualization
system allowing the optical fusion of images. The invention relates, for
example, to the fusion of intensified images and infrared images.
Field-glass-type, night-vision observation visualization systems are
frequently used by foot soldiers for night missions. A night-vision field-
glass
comprises a light-intensifying tube to amplify the residual light of a dimly
lit
observation scene. This residual light originates from the light of the moon
or
the light of the stars. Conventional night-vision goggles with light
intensification comprise a lens focusing the beams on a photocathode which
converts light into electrons, an electronic amplification stage, a phosphor
screen and an optical projection system picking up the image formed on the
phosphor screen comprising one or two eyepieces. This optical system is
possibly folded. The image intensifier or IL conventionally uses a second-
generation tube, i.e. comprising an "S20" or "S25" multi-alkali photocathode
or a third-generation intensifier with an AsGa or AsGaP photocathode. The
responses of the photocathodes cover the visible spectrum with a slight
extension towards the near infrared.
The applicant previously filed a French patent application with
publication number FR 2 863 718 on 12/16/2003. This application describes
a folded optical architecture of a light-intensifying monocular field-glass.
Moreover, this document discloses an embodiment with two eyepieces
enabling fusion of the intensified image with a video image formed on a
screen. Light-intensifying field-glasses intended to be worn directly by a
user
for night missions are of unit magnification.
A light-intensifying field-glass provides the observer with a faithful
perception of natural images. The human eye easily becomes accustomed to
images of this type. However one of the disadvantages of field-glasses of this
type is the observation of a scene in a condition of very low luminosity, for
example inside buildings or during nights with no moon or with an overcast
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sky. The residual light becomes too weak for the night-vision visualization
system to be effective.
To solve this problem, vision field-glasses exist comprising an
image sensor sensitive to the temperature of objects. Unlike an IL tube,
which performs the function of both image sensing and its display, an infrared
detector is merely an image-capturing instrument. The imaging system differs
greatly according to the spectral band concerned.
The visible and near infrared bands produce images which
originate from the reflection of ambient light on objects, the light source
being
the sun, moon or stars, etc. The reflectivity of the objects depends greatly
on
the incident wavelength: Contrast inversions may then occur when the
wavelength changes. This property can be exploited to detect objects hidden
against a background, by comparing the responses given in different spectral
bands.
In the 0.4 pm - 2 pm domain, two bands must be taken into
consideration. The first region extends approximately from 0.4 pm to 1 pm,
which coincides more or less with the sensitivity band of silicon. The SWIR
band between 1.3 pm and 2 pm and meaning "Short Wave Infra Red" is the
band where the vibration state changes of the OH radical known as "Night
Glow" of the high layers of the atmosphere converge. Sensors sensitive in
this band are essentially based on InGaAs technologies, although other
technologies based on MCT or Ge up to 1.8 pm are also available. These
detectors are therefore more effective in overcast weather when the light
from the moon or stars is reduced.
Passive imaging based on thermal infrared follows a totally
different principle. It detects heat sources. An ambient light background is
no
longer required. A plurality of spectral bands are possible: Far infrared,
known by the name "LWIR" meaning "Long Wave Infra Red", covering the 8-
12 pm spectrum and its sub-bands, and medium infrared, known by the
name "MWIR" meaning "Medium Wave Infra Red", covering the 3-5 pm
band, which mixes actual transmission mechanisms and solar reflection. The
MWIR band is suitable above ail when very hot sources need to be detected,
whereas the LWIR spectrum is intended more for the observation of objects
at ambient temperature.
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Infrared devices are particularly useful for applications in which hot
objects hidden by vegetation need to be detected. However, a thermal image
presents a disorienting appearance for the observer, quite different from the
rendering of visible or near infrared images.
A second important point must be considered. As previously
mentioned, a light-intensifying tube combines two functions in a single
component:
= Image sensing and amplification;
= The display of the image on a phosphor screen.
The image formed on the phosphor screen cannot simply be
transformed into an electronic video signal. It can only be observed using an
optical projection system. In the 0.4-2 pm band, other image-sensing
technologies based on CMOS or CCD sensors provide access to a video
signal. They cannot perform the second function, i.e. the display function,
without an auxiliary module. Compared with light-intensifying tubes, these
sensors are generally less sensitive and have a lower resolution and a higher
energy consumption. In the infrared band, the image display function requires
an auxiliary screen.
Sensor-fusion solutions exist to solve these problems. The
American patent application US 2007/0084985 is known from the prior art.
This document describes an optical fusion device comprising an intensified
channel and an infrared channel visualized on a screen and a camera. It
involves a monocular device. The device comprises four channels, an image-
sensing channel for the intensified channel and an image-sensing channel for
the infrared channel, a display channel for a recording camera, and also for
the projection eyepiece. The intensification device can be used with or
without the camera module of the display channel in the embodiment with the
independent camera module, as described in paragraph 14 of the text of the
description. The camera module can then be connected by means of a
connector. This device has the disadvantage of being monocular only.
Furthermore, it enables fusion only with a predetermined IR camera which is
not adaptable according to requirements. This system also consumes energy
when the intensified channel and the IR channel are used simultaneously. An
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energy storage module connected to an electronic system is used by the
night-vision device to power ail the functional components.
The American patent application US 2008/0302966 is also known
from the prior art. This document describes an intensified-channel, night-
vision device which can be connected to an IR camera. Any type of IR
camera can be used and can easily be connected to the night-vision system
by an attachment means using clips. According to this fusion system, two
intensified channels are present, and the image of the screen of the IR
channel is projected onto a single intensified channel. Consequently, the
fused image appears on a single output channel and the night-vision system
can be used only in monocular use for a fused view mode.
The patent EP 1857854 is known from the prior art, describing
modular-architecture, panoramic, night-time goggles comprising an online
light-intensifying optical module, an "HUD" ("Head Up Display") module and a
camera module. According to this architecture, a light-intensifying module
can be complemented by the HUD module to fuse the intensified images with
information from an external system. The function of the camera is to record
the images composed of intensified images and information originating from
the HUD. These goggles present a modular architecture but do flot allow the
fusion to be carried out with the intensified channel and the IR channel.
The object of the invention is to propose a night-vision system
enabling the fusion of intensified images and images generated by an IR
sensor. The object of the vision system is to provide a modular monocular or
binocular system to adapt the IR sensors according to observation
conditions. The system must also offer good autonomy of use in both
intensified-vision mode and fused-vision mode.
More precisely, the invention is a modular visualization system
comprising at least three modules,
the first module MDB being an observation device comprising a
first mechanical body in which a first channel comprising a display screen, a
second image-capturing channel comprising a lens OB1 and at least image-
sensing means, a relay optical system and an eyepiece Ci are arranged,
the image of the first channel and the image of the second channel being
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fused and collimated by the relay optical system and the eyepiece Cl
towards the eye of an observer;
the second module MDAUX being an image-sensing device
comprising a second mechanical body in which a lens 0B2 and a sensor are
arranged to generate a digital image, and;
the third module MDEX being an external device performing at
least a power supply function;
the visualization system being such that:
the first module MDB comprises a first data connector Cl
associated with a first mechanical coupling means Si;
the second module MDAUX comprises a second data connector
C2 associated with a second mechanical coupling means S2 and a third data
connector C3 associated with a third mechanical coupling means S3, and;
the third module MDEX comprises a fourth data connector C4
associated with a fourth mechanical coupling means S4;
the connectors Cl, C2, C3 and C4 and the mechanical coupling
means Si, S2, S3 and S4 are arranged in such a way that the visualization
system allows at least the following three configurations:
in a first configuration, the first connector Cl is connected to the
fourth connector C4, the first module MDB and the third module MDEX thus
being mechanically coupled;
in a second configuration, the first connector Cl and the second
connector C2 are coupled to display the digital image of the sensor on the
screen and the third connector C3 is coupled to the fourth connector C4, the
second module MDAUX thus being mechanically coupled, on the one hand,
to the first module MDB and, on the other hand, to the third module MDEX;
in a third configuration, at least the first module MDB functions in
stand-alone mode.
Advantageously, the sensing means of the first module MDB are a
light-intensifying tube or a detector implemented in "CMOS" or "CCD" or
"InGaAs" or "ILCMOS" or "ILCCD" or "EBCMOS" or "EBCCD" technology.
Advantageously, the image display screen of the first module MDB
is implemented in "OLED" technology.
Advantageously, the first module MDB comprises:
- a means for attachment to a helmet receiving support, or;
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- a second optical output channel comprising a second eyepiece,
the relay optical system transmitting the image from the first and
the second optical input channels to each of the output channels,
or;
- a diaphragm, the aperture of which is controlled at ambient light
level, said first module MDB comprising means suitable for setting
said diaphragm to the closed position in order to protect the field-
glass.
Advantageously, the second module MDAUX comprises:
- a sensor sensitive to radiation belonging to the visible and near
infrared bands, or;
- a sensor sensitive to radiation between 1 and 12 pm of the
spectral band.
Advantageously, the third module MDEX also performs an image-
generating function in order to transmit images, or is a helmet power supply
device comprising a means for attachment to a helmet support.
The invention also relates to combat equipment for a foot soldier
comprising at least a helmet, a weapon and the modular system as
previously defined. In a first variant, the first module MDB and the second
module MDAUX are mounted on the helmet. In a second variant, the first
module MDB is mounted on the helmet and the second module MDAUX is
mounted on the weapon and is used as a sighting component of said
weapon.
The night-vision field-glasses for a foot soldier according to the
invention can thus be configured with an IR vision module or without an IR
vision module in a very simple manner thanks to the arrangement of the
different connectors on the observation base module and on the IR module.
The use, on the one hand, of a base module performing the optical and
electronic functions for the fusion of the images, and, on the other hand, of
an auxiliary module performing the IR image-sensing functions allows the
visualization system to be adapted according to operational requirements.
This allows the sensitivity of the IR vision module to be adapted very quickly
according to observation conditions by modifying the IR vision module only.
This modularity also allows a troop of foot soldiers to equip themselves with
a
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first batch of observation goggles and a second reduced batch of IR cameras
which they can exchange with one another. The first advantage of this
modularity is a reduction in the overall cost of the equipment of a combat
section. A second advantage is the reduction in the weight and the power
consumption of the equipment when the IR module is not necessary.
The invention will be more readily understood and other
advantages will become evident from reading the non-limiting description
which follows, referring also to the attached drawings, in which:
Figure 1 shows an embodiment of the base module of the display
system also comprising the light-intensifying optical system;
Figure 2 shows an embodiment of the auxiliary module of the
visualization system comprising the IR sensor;
Figure 3 shows the base module and the auxiliary module coupled
together for an optical-fusion use, the connector of the external power supply
module being connected to the auxiliary module;
Figure 4 shows the base module, the auxiliary module and the
external power supply module coupled together.
As shown in Figure 4, a night-vision visualization system
according to the invention comprises a base module MDB, an auxiliary
module MDAUX with an IR sensor and an external power supply module
MDEX. These modules enable the configuration of a night visualization
system with optical fusion of intensified images and infrared images. The
external power supply module MDEX can be adapted according to energy
requirements. The auxiliary module MDAUX used can be adapted in such a
way as to comprise an IR sensor sensitive in the required spectral bands. For
example, a group of foot soldiers may have a plurality of auxiliary modules
MDAUX which can be used on the same base module MDB, each one being
sensitive in a specific spectral band. The sensitivity band of the auxiliary
module MDAUX is preferably complementary or partially overlaps the
sensitivity band of the light-intensifying module MDB.
The external power supply module MDEX performs the power
supply function for the electronic components of the base module MDB and
also the auxiliary module MDAUX when this power supply module is coupled
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with the auxiliary module MDAUX. The external power supply module may be
a system performing the power supply function but also other functions, such
as, for example, the transmission of images originating from a graphical
generation unit. These images may originate from a computing system
processing a variety of information useful to the observer, for example
location, orientation assistance, target-detection information, etc.
Figure 1 shows a non-limiting embodiment of the base module
MDB. Its shape and dimensions may differ.
The base module MDB comprises, on a first channel, a lens OB1
and a device for intensifying the light within the mechanical body and flot
shown in Figure 1. This lens OBI comprises a protective cap in Figure 1. The
sensing means of the first module MDB can also be a detector implemented
in "CMOS" or "CCD" or "InGaAs" or "ILCMOS" or "ILCCD" or "EBCMOS" or
"EBCCD" technology.
It also comprises a second channel transporting the image to be
fused with the image of the lens 061. This second image-sensing channel
implements a display screen on which the image of the auxiliary module is
displayed. The elements of the second channel and the screen are also
inside the mechanical body and are flot therefore shown in Figure 1. These
elements do not pose any particular implementation problems for the person
skilled in the art.
The display screen is preferably an OLED ("Organic Light-Emitting
Diode") photoemissive screen, but may be of any other type. A reduced-size
flat screen is preferably used.
The mechanical body comprises a relay optical system to
transport the images from the first image-sensing channel and the second
image-sensing channel to the eyepieces Ci . The second function of this
relay optical system is the fusion of the image of the first image-sensing
channel and the image of the second image-capturing channel. A semi-
reflective strip can be used to fuse, through reflection and transmission,
light
beams originating from the two input channels. Other optical devices known
to the person skilled in the art, such as separator cubes, can be used to
carry
out the fusion and the transport of the images to the eyepieces ()Ci.
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The base module MDB shown in Figure 1 comprises two
eyepieces 0C1. An optical architecture of this type capable of transporting
the images from two image-capturing channels to one or two eyepieces with
fusion of the images does flot pose any particular technical problems to the
person skilled in the art. Reference can be made on this subject to the
French patent application with publication number FR 2863718 of the
applicant which describes an optical architecture with one or two eyepieces
comprising an image-sensing channel with a lens and a display channel with
a screen.
The base module MDB may comprise a diaphragm, the aperture
of which is controlled at ambient light level, in which case the module MDB
comprises means suitable for setting said diaphragm to the closed position in
order to protect the field-glass.
According to one essential characteristic of the invention, the
mechanical body of the base module MDB comprises a first electronic
connector Cl and a mechanical coupling means SI. The connector Cl can
be connected to an external device, its first function being the transmission
of
digital data from a video stream to the display screen of one of the image-
sensing channels. The internai electronic means comprise data buses,
electronic cards, electronic data bus control components and any other
electronic means necessary to transmit to the screen video data to be
displayed.
The connector S1 also serves to provide the power supply of the
electronic components. An internai power supply circuit receives the power
supply signais according to a voltage level adapted to the internai electronic
circuits.The mechanical coupling means Si is associated with the
electronic connector Cl in such a way as to mechanically couple the
connector of an external device coupled to the connector Cl of the base
module, the connector of the external device also being associated with a
coupling means compatible with the mechanical coupling means SI. Thus,
the coupling means S1 joins together the base module and the external
module connector. The connector Cl is integrated into the surface of the
mechanical body of the base module MDB.
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Figure 2 shows a non-limiting embodiment of an auxiliary module
MDAUX according to two angles of view. The first angle of view on the left
part of Figure 2 allows the rear surface and a side surface of the auxiliary
module to be visualized. In this view, the auxiliary module is not coupled
with
an external connector. The second angle of view is a front view of the
auxiliary module and the latter is connected to an external connector CEX.
The auxiliary module MDAUX comprises an image sensor allowing
video images crossing a lens 0B2 to be recorded. This lens comprises a
protection cap in Figure 2. The sensor is preferably sensitive in a spectral
band of the infrared domain, the aim being to fuse the images produced by
the sensor with the images generated by the base module MDB. The
auxiliary module comprises the electronic means for transmitting the video
data to a connector C2 mounted on the surface of the mechanical body of the
auxiliary module. These electronic means notably comprise a computer to
control the data buses, the power supply circuits being fed by at least one
connector of the auxiliary module.
According to one embodiment of the auxiliary module MDAUX, a
first connector C2 is present on the side surface and a second connector C3
is present on the rear surface. The arrangement of the connectors C2 and C3
is configured in such a way that it is possible to couple simultaneously the
connectors C2 and C3 with connectors of external devices. The connectors
C2 and C3 are associated with mechanical coupling means S2 and S3
respectively. The shapes of the mechanical coupling means S2 and S3 are
compatible.
The connector C2 and the mechanical coupling means of the
auxiliary module MDAUX can be connected to the connector Cl of the base
module MDB. Figure 3 shows the configuration of the night-vision system
when these two modules MDB and MDAUX are connected and mechanically
coupled. The connector Cl of the observation device MDB positioned on a
side surface, the left surface looking at the device from the side of the lens
061, is coupled with the connector C2 of the infrared image-sensing device
MDAUX positioned on the right surface looking at the device IR from the side
of the lens 0B2.
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The connector C3 of the image-sensing device is connected to a
connector C4 of an external module serving as a power supply and possibly
being able to perform some control and image-sensing functions. The
external module is then a more complete system than a simple power supply
module. The connectors Cl and C2 are mechanically coupled by the
coupling means Si and S2. These coupling means are, for example, a
threaded hole for the coupling means Si and a fixing screw for the coupling
means S2. The connectors C3 and C4 are mechanically coupled by the
coupling means S3 and S4. These coupling means are, for example, a
113 threaded hole for the coupling means S3 and a fixing screw for the
coupling
means S4. The person skilled in the art knows how to design any type of
coupling means to provide the coupling between two connectors.
This configuration of the visualization system allows the system fo
be used according to three operating modes. In a first operating mode, only
the night vision of the modular visualization system is used. The eye of the
observer sees only the images originating from the intensifier tube.
In a second operating mode, the night vision is complemented with
images displayed on the accompanying screen, optically fusing these images
with those of the intensified channel formed on the phosphor screen of the
intensifier tube. The image displayed on the auxiliary screen originates from
the video stream transmitted by the connector Cl of the base module MDB.
In a third operating mode, the night vision is not activated and the
visualization system is used in remote-vision mode. The eye of the observer
then sees images originating from the IR auxiliary module.
The different modes are activated and controlled using control
buttons placed on the front of the field-glass, with the following controls:
- On/Off and intensifier tube gain control, and;
- On/Off and video screen luminosity control.
The invention is clearly not limited to this type of controls and other
control interfaces can be proposed. A simple interface adapted to a military
use is preferred.
The modes can also be activated by the system by sending the
corresponding controls via the communication interface of the connector Cl.
In this case, the controls located on the field-glass remain active.
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The image of the intensifier tube, such as the screen image, are
visible in both eyepieces. The OLED screen image is visible, either alone if
the intensifier is switched off, or superimposed on the image provided by the
intensifier when the latter is switched on.
A supplementary source emitting a light at a wavelength to which
the intensifier is sensitive provides the lighting, if necessary, in the field
of
vision to enable operation at a short distance in an extremely dark
environment. Map reading, handling operations, movements, for example,
are thus facilitated.
In one embodiment, a photodiode located on the front of the field-
glass enables the automatic shut-off of the intensifier in the event of
prolonged excessive lighting in order to protect the tube. In a different
embodiment, the observation device MDB comprises a diaphragm, the
aperture of which is controlled at ambient light level, said observation
device
MDB comprising means suitable for setting said diaphragm to the closed
position in order to protect the field-glass in cases where the amblent light
is
too intense.
Figure 4 shows the night-vision visualization system configured
with a base module connected by the connector Cl to an auxiliary module on
its connector C2 which is connected by its connector C3 to a specific power
supply module. This power supply module is adapted according to the energy
requirements of the auxiliary module. Moreover, it offers the advantage of
providing a greater autonomy than a system powered by a power supply
module integrated into the system, i.e. a battery module. An integrated
battery system of this type is not ideal for a modular visualization system.
Any type of auxiliary sensor module comprising a connector
compatible with the connector Cl of the auxiliary module can be used. The
connector C2 of the auxiliary module and the connector C4 of the power
supply module or of a system module are similar. This arrangement provides
a modularity allowing the night visualization system to be used with or
without
an auxiliary module, with optical fusion activated or not. The connector
interface and the simple mechanical coupling means simplify the change
from a first configuration to a second configuration. Another advantage is the
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possibility to equip a group of foot soldiers without the need for each foot
soldier to have his own IR sensor module. Each foot soldier has an
intensifier-tube observation device, whereas a batch of IR sensor modules
can be shared within the troop, thereby reducing the equipment cost.
A base module MDB can be used at night in a "hands-free"
application. In this case, they can be attached to a helmet via an adjustable
support F1 as shown in Figure I. This support may differ according to
applications. It allows the base modules to be hooked onto the helmet of the
foot soldier and ensures the positioning of the field-glass in front of the
eyes
and its retraction to allow direct vision.
The base modules allow a plurality of possible modes of use. In a
first mode, the night visualization system is connected to an equipment
network. In a second mode, the system is in a stand-alone configuration
connected to a power supply device which can be hooked directly onto the
carrier, on a helmet or belt. In a third mode, the visualization system
comprises an auxiliary module and a base module enabling image fusion, a
mode in which an image provided by a different sensor forming on the screen
of the base module is superimposed on the intensified image.
The invention is also applied to night-vision field-glasses enabling
optical fusion. It preferably applies to light-intensifying field-glasses for
foot
soldiers. Thus, combat equipment for foot soldiers may comprise at least a
helmet, a weapon and the modular system according to the invention. In a
first variant, the first module MDB and the second module MDAUX are
mounted on the helmet of the foot soldier. In a second variant, the first
module MDB is mounted on the helmet and the second module MDAUX is
mounted on the weapon and is used as a sighting component of said
weapon, the foot soldier thus being able to sight without needing to break
cover, by day and by night.
However, other applications of the modular system according to
the invention for the general public domain or other military applications are
possible.
