CA2042419A1 - Compact multiple-function periscope - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Disclosed is a multiple-function periscope, capable notable of providing for day-time vision with standard optic means and night-time optic vision, for example by means of a light intensifier tube. This multiple-function periscope, notably for armored vehicles, of the type including a reflector-based optic vision device and at least one electronic display device, for example for night-time vision, comprises, between the input reflector and the output reflector of said optic vision device, reflection means movable between two extreme positions, the first position enabling the free movement of the light rays between said input and output reflectors and the second position prompting the deflection of said light rays towards electronic processing means such as, for example, a light intensifier tube. Advantageously, in order to reduce the amount of space occupied, said electronic display device has a wide-aperture lens having a bend of about 90° in the vicinity of the image, downline with respect to said image.
Figure 2.

Description

20424~9 COMPACT MULTIPLE-FUNCTION PERISCOPE
BACKGROUND OF THE INVENTION
1. Field of the Invention The field of the invention is ~hat of periscopic vision provided by periscope or episcope.
More precisely, the invention relates to a multiple-function periscope that can be used, notably, to obtain daytime vision with standard optic means, and night-time vision, by means of a standard light intensifier for example.
The invention can be applied especially in observation instruments for armored vehicles and, notably, for tanks. More generally, the periscope of the invention may be used in all cases where the observer has to be isolated from the observed field and where it is necessary to have~ firstly, means of direct vision by optic channels and, secondly, electronic display means including, for example, a light intensifier, an infrared detector or a camera, with CCD
or other type of sensor.

2. Description of the Related Art In the particular case of armored vehicles, for daytime vision, the driver has a standard optic periscope known as a daytime channel, comprising an input reflector receiving the light rays, and an output reflector restoring the light rays to him. Depending on the type of periscope, the path of the light rays 20'~24~

between the two reflectors may be direct or may undergo one or more reflections.
The daytime channel provides for optimum vision as long as there is sufficient lighting. However, it does not allow night-time driving. For it is not possible, at least in combat position, to use lighting means integrated into the vehicle. It is therefore necessary to use an electronic night-time channel including, for example, an objective, a light intensifier tube and an eyepiece.
To pass from one mode of vision to the other, therefore, it is necessary to change the periscopes.
This dismounting and re-assembling operation is highly detrimental to the armored vehicle which is thereby completely deprived of vision for a few minutes. It is then highly vulnerable and, to avoid any risk, it has to withdraw and conceal itself while the periscopes are being changed.
Another problem posed by this technique is that of storing the periscope, when it is not being used, in the cabin of the vehicle wherein the space is most often very limited. Moreover, this periscope, when not in use, runs heavy risks of being damaged if it is not properl~ secured.
Besides, the periscope-changing operation entails a locali~ed loss of imperviousness. In particular, the vehicle is then not protected against nuclear, bacteriological and chemical risk. More generally, the xo~ 9 successive operations of dismounting and re-assembly may modify the conditions of imperviousness, notably through the wearing out of the joints.
The use of two independent periscopes for daytime and night-time use also raises problems during periods of intermediate lighting, for example at dawn and dusk, or when certain zones are illuminated and others are not illuminated. The substantial amount of time taken to change from one mode of vision to the other means that the observer cannot remain constantly in the optimum conditions of vision.
To do away with the need for this changing operation, day-and-night periscopes have been designed.
These periscopes include, in one and the same pack, a standard daytime channel and a night-time channel with light intensifier. Thus, the French patent applications 85 02575 and 85 02576 filed on 22.02.1985 present substantially parallel daytime and night-time channels wherein the input reflector is movable and directs the light rays towards either of the two channels, depending on the position selected by the driver.
These day-and-night periscopes solve a lot of the pro~lems raised by the changing of the periscopes.
However, other problems appear. The hole drilled in the armor, for the periscope, has to be big enough to enable the passage of both channels and of the means to control the movable reflector. Now, this hole is clearly a vulnerable part of the armor and should therefore be reduced to the maximum extent. The presence of movable elements outside the armor is also a factor of vulnerability. Besides, such periscopes cannot be installed, as replacements, in vehicles that do not have a daytime periscope because the existing holes in the armor of such vehicles are too small.
SUMMARY OF THE INVENTION
It is an aim of the invention to overcome the drawbacks of the prior art.
More precisely, an aim of the invention is to provide a day-and-night periscope requiring as small-sized a hole as possible drilled in the armor and, in particular, a hole with a size similar to that needed for the passage of a single daytime periscope.
A particular aim of the invention is to provide a day-and-night periscope providing for maximum imperviousness at the armor.
Another aim of the invention is to provide an periscope such as this, having no moving parts outside the armor and, more generally, having few moving parts.
Another aim of the invention is to provide an periscope such as this, occupying as restricted a v~lume as possible, so that it can be installed in many different vehicles while, at the same time, ieaving enough free space for the driver. For, the space available for an periscope, for example in a tank, ~s very limited. Notably, the following features have to be taken into account: above the armor, the passage of Z04~4~ 9 the turret and of the protection straps and, below the armor, the proximity of the steering wheel, the configuration and open position of thP door, the driving position of the driver in the "head outside"
configuration, etc.
More generally, the periscope is also aimed at meeting ergonomic constraints, both as regards the positioning of the output prism of the daytime channel and the eyepiece of the night-time channel and as regards the means for switching from one channel to the other.
Another aim of the invention is to provide a s~andard optic periscope and, furthermore, electronic displ~y means capable of including a light intensifier, optic fibers, a CCD sensor, a heat camera etc.
These aims, as well as others that shall appear here below, are achieved, according to the invention, by means of a multiple-function periscope, notably for armored vehicles, of the type including a reflector-based optic vision device and at least one electronic display device, for example for night-time vision, comprising, between the input reflector and the output reflector of said optic vision device, reflection means movable between two extreme positions, the first position enabling the free movement of the light rays between said input and output reflectors and the second position prompting the deflection of said light rays towards electronic processing means.

20424~9 Advantageously, the periscope is of the type going through the armor of said vehicle, only the input reflector of said optic vision device being external to said vehicle.
Thus the part of the periscope external to the vehicle is reduced to the maximum extent, and is identical to the emerging part in the case of a simple daytime periscope. It does not pose any particular problems of imperviousnes~, a~d can be easily adapted to existing vehicles. The movable part is limited, and is located within the vehicle, beneath the armor.
Preferably, said movable reflection means include a mirror, held by a movable strap, and means for guiding said strap between said extreme positions.
The movable strap is configured so as not to interfere with the light rays, irrespectively of its position.
In an advantageous embodiment, said guiding means include a set comprising at least one link-rod, ~ positioned so as to provide a minimum horizontal and vertical clearance for said mirror during its travel between said extreme positions.
For, it is important to reduce the clearance of the movable parts so as to minimize the overall space Z5 occupied ~y the periscope.
Preferably, said electronic display device has a wide-aperture lens having a bend of about 90~ in the 7 20~2419 vicinity of the image and downline with respect to said image.
This enables the space factor to be further reduced. Moreover, it is thus possible to reduce the total length of the electronic channel and, hence, to place the eyepiece or display screen of this channel just below the output reflector of the daytime channel, thus providing excellent visual comfort for the observer.
Advantageously, said objective includes a set of lenses with multilayer treatment and a prism.
Preferably, the hypoteneuse of sald prism is treated so as to improve the transmission balance of said objective, by at least one of the following treatments:
- silver-coating - improved aluminium-coating;
- multidielectric treatment optimized for a mean incidence of 45~.
In an advantageous embodiment, said objective includes a field glass between said prism and said electronic processing means, the concave face of said field glass being provided with multilayer treatment.
In a particular embodiment of the invention, said objective has an aperture of about F/1, a pa~axial focal length of 26 mm, an object field of about 45 and an image field with a diameter of about 20 mm.

Advantageously, said objective has a widened useful spectral band, ranging from about 450 nm to 900 nm .
To facilitate passing from one channel to the other, the periscope advantageously includes means to contro~ the passage of said reflection means from one of said extreme positions to the other, said control means jointly putting said electronic processing means into operation or out of operation.
In one particular embodiment of the invention, enabling daytime and night-time vision, said electronic display device is a light intensification channel, including a wide-aperture objective, an intensifier tube and a binocular optic system.
In another embodiment of the invention, said movable reflection means include a reflector, for example of the triangular-sectioned reflecting prism type, fixedly joined to said objective, the assembly formed by the movable reflection means and the objective being capable of pivoting about an axis substantially perpendicular to the plane defined by said assembly. This requires an increase in the width of the periscope but enables the night vision field to be increased by the use of a prism with a hi~h index.

9 20~2419 BRIEF DESCRIPTION OF THE DRAWINGS
Other features and advantages of the invention shall appear from the following description of a preferred embodiment of the invention, given by way of a non-restrictive illustration, and from the appended drawings, wherein:
- Figures 1 and 2 show sectional views of a day-and-night periscope according to the invention, respectively in the daytime vision position and in the night-time vision position;
- Figure 3 is a drawing of a bent wide-angle objective, as used in the periscopes of figures 1 and 2.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The embodiment described here below specifically concerns a day-and-night periscope, the night-time channel of which includes a light intensifier tube.
Kowever, it is clear that the invention can be applied to other means for the processing of light rays. Thus the light waves deflected by the movable mirror may be received by a camera objective, the image being restored on a display screen.
The drawing of figure 1 shows a day-and-night periscope, notably designed for armored vehicles such as tanks.
This periscope has a pac~ 10, containing the two channels, namely the da~time and night-time channels.
The pack has an upper part 11, external to the armor 12 ~o'~ 9 of the vehicle and closed by a port 13. This port 13 may include de-icing means, for example, through a conductive, anti-reflective interference treatment or a resistive silk-screen printing.
The part 11 external to the armor has a fixed, single reflector 14, common to the daytime and night-time channels, which is advantageously a triangular-sectioned prism with total reflection or one where the hypoteneuse has received a reflective treatment (aluminium-coating, silver-coating or dielectric treatment). This reflector may also be a mirror.
The prism 14 is bonded to a generally parallelepiped-shaped prism 15 going through the armor 12. The prisms 14 and 15 may also form a single prism.
It will be noted that the external and crossing parts comprise only fixed optic means, identical to those existing in the simple daytime periscopes. This provides for perfect interchangeability of equipment, the only condition being that the package should not be too ~ulky. Such an periscope may there~ore replace daytime periscopes in most existing armored vehicles without any problems.
The lower part of the pack 10, beneath the armor 12, includes additional daytime and night-time channels, and means for switching over from one channel to the other.

11 ~0424~ 9 The daytime channel includes, in addition to the prisms 14 and 15, an output reflector 16 which may advantageously be a triangular~sectioned prism that directs the light rays 17A towards the driver 18. This prism 16 may be a total reflection prism, or a prism the hypoteneuse of which has received a reflective processing (aluminium-coating, silver-coating or dielectric processing).
A parallelepiped-shaped prism 19 is bonded to this triangular prism 16. The two parallelepiped-shaped prisms 15 and 19 are separated by a space 20 in which a retractable mirror 21 may be placed. The prisms 16 and 19 may also constitute a single prism.
Thus, in daytime vision, the light rays 17 successively go through a ~irst prism 14, a first parallelepiped-shaped prism 15, an air space 20, a second parallelepiped-shaped prism 19 and a second prism 16.
The image seen by the driver 18 is substantially equivalent to that obtained by a standard periscope, with a single parallelepiped-shaped prism, without an air space 20. For, this space 20, with a small width, does not bring about any su~stantial field reduction, it being possible to co~pensate for this reduction by using a higher index than usual for these p-isms, for example an index of 1.62.

12 20~z4~ 9 It is clear that, in another embodiment, the daytime channel may be more complex and may include, for example, more than two deflections of light rays.
In the daytime vision position, the retractable mirror 21 is housed substantially in parallel to tke prism 19, in a space 22 prepared for this purpose.
This mirror is maintained by a strap 23, movable about an axis 24.
The strap 23 is shaped in such a way that it does not affect the path of the light rays. The position of the axis 24 has been chosen with precision, so that the shifting of the mirxor 21 calls for a minimum horizontal and vertical clearance, thus enabling the greatest possible reduction in the space 20 between the two prisms 15 and 19, and in the space 22 for the housing of the mirror in the daytime position.
The switching over from one channel to the other one is done by a lever 25 c~pable of pivoting by one half turn. The top position of the lever corresponds to the daytime channel and the bottom position ~figure 2) to the night-time channel.
This lever 25 draws along, around its axis, a link-rod 26 on which there is eccentrically fixed a first end of a link-rod 27, the second end of which is fixed to the mirror-holding strap 23.
A downward hal~-turn of the handle therefore makes the mirror 21 pass from the daytime position (figure 1) to the night-time ~osition (figure 2). Conversely, the 20424~ 9 return of the lever 25 to the top position causes the return to the daytime position.
The passing of the lever 25 to the bottom position automatically turns on the electronic processing means such as a light intensifier tube, for example by means of a switch actuated by a cam fixedly joined to the lever,. Thus, in a single command, the driver goes from the daytime channel to the night-time channel.
Conversely, the return to the daytime channel causes these electronic means to go off.
Another way of carrying out the day/night switching operation is to have the mirror 21 fixedly joined to the objective 28 and to make the assembly formed by the objective 28 and the mirror 21 rotate on an axis 31 so tha$, for example by a 90' rotation, the space between the prisms 15 and 19 is cleared to enable daytime vision.
The mirror 21 may then be replaced by a triangular-sectioned reflecting prism.
This configuration makes it necessary to increase the width of the periscope but, notably through a use of a prism with a high index replacing the mirror 21, it enables an increase in the field of night-time vision.
Figure 2 shows the periscope of the invention in night-time position. The retractable mirror 21 is then placed between the two parallelepiped-shaped prisms lS

14 ~0~'2419 and 19, in the air space 20, so as to direct the light rays 17B towards a wide-aperture objective 28.
It must be noted that the input prisms 14 and 15 are common to both the daytime channel and the night-time channel.
In the preferred embodiment described, the night-time channel is a light intensification channel.
Advantageously, the objective 28 is a bent objective, as described more precisely further below, in relation to figure 3.
This bent objective enables the light intensifier tube 29, necessary for night-time vision, to be positioned high enough in the pack 10 for the eyepiece 30, in which the image 17 is formed, to be placed in the vicinity of the output prism 16, so as to provide for the visual comfort of the driver 18.
The intensifier tube 29 may be of any commercially available type. Advantageously, it is a second generation tube with electrostatic focusing and wafer of microchannels such as, for example, the tube TH9311 marketed by THOMSON-CSF (registered name), the tube XX1380, marketed by P~ILIPS (registered name), or the tube MX9644/ W , marketed notably by THOMSON-CSF
(registered name).
The eyepiece 30 is advantageously a binocular device, capable of presenting, for example, an output pupil with a diameter of about 80 mm, so as to give great comfort of observation. This binocular device, 20~2419 with an apparent field of the order of 45 , corresponding to a 45 object field of the night time channel, for an overall enlargement of about 1.
The binocular device 30 may be directly coupled to the intensifier tube 29, in taking up the image given on the screen of this tube. However, to simplify the binocular device or increase viewing comfort, this coupling may be done by means of an enlarging optic fiber making it possible, for e~ample, to go from a tube 29 screen diameter to a greater binocular input diameter, for example a diameter of 40 mm.
The use of an optic fiber independent of the intensifier tube makes it possible to give the output face of the fiber a slight curvature so as to improve the quality of the binocular device 30 and, notably, the field curvature.
The binocular device 30 may also be fitted out with de-misting means, such as a heating resistor placed in the eyepiece, or a conductive, interfering treatment deposited on one face of the eye lens of the binocular device, the temperature of which is regulated by thermostat at about 35.
The bent objective 28 enables a substantial reduction in the overall space fac~or of the periscope.
Figure 3 shows a particular em~odiment of an objective such as this.
It is an objective with a wide aperture, of the order of F/1, bent at 90- in the vicinity of the image.

16 ~04Z4~9 The useful spectral band covers a widened spectrum, corresponding to the visible and to the near infra-red ranges. This useful spectral band ranges from 450 to 900 nm.
This objective enables an image of an object or scene, located between infinity and ten meters, to be formed on the photocathode of the image intensifier tube 29.
The 90 bend is made by a prism 41, with 21 mm sides. This prism 41 is integrated into the optical system which also includes six lenses 42 to 47 and a field lens 50.
This optical system can be used to obtain the following optical characteristics:
- paraxial focal length : 26.2 mm;
- aperture : F/1.0 - obiect field : 45 - image field : dia. 20 mm (which corresponds to a field edge distortion of -7.3%) Table I presents all the diopters used in this objective, and gives their thicknesses, radii, indices and useful diameters.
25The distance 4~ between the optic axis and the intensifier tube is equal to 15 mm, and the length 49 from the front of the objective to the axis is smaller than 51 mm.

17 2042~9 The maximum useful diameter is 26.2 in front, at the pupil, and gets reduced to less than 25 mm in the zone located above the tube.
The treatment used for the six lenses 41 to 47 are multilayers, optimized for the high indices. The glasses used have negligible absorption above 450 mm, given the small thickness crossed.
The transmission is thus greater than 90%
throughout the 450 nm - 850 nm spectral band for the objective alone.
The prism 41 undergoes the same multilayer treat~ent on its input and output faces. The hypoteneuse of the prism cannot work in total reflection, owing to the substantial aperture. It is therefore necessary to use a highly efficient treatment so as not to penalize the overall transmission balance.
It is possible, in particular, to use one of the following types of treatment: silver-coating, improved aluminium-coating or multidielectric treatment optimized fo~ a mean incidence of 45 .
Between the prism 41 and the photocathode of the light intensifier tube 29, the objective also includes a field glass 50 bonded to the intensifier tube. The concave face of this field glass 50 is a~so given a multilayer treatment. The plane face is left bare because of the bonding.
As has already been stated here above, the device for the electronic processing of the light rays is not 20424~9 limited to a light intensifier. It may be constituted, for example, by any type of camera sensor, enabling a display on a television type screen, and particularly on a flat panel. It is possible, notably, to use high-performance low light level CCD sensors or an assembly constituted by an intensifier tube coupled (by optic fiber for example) to a CCD sensor. In this case, it is possible to use several screens so that, for example, other passengers of the armored vehicle can also observe the exterior. Besides, it is also possible to envisage the use of images coming from other sensors such as distance cameras, heat cameras and complex information, such as maps, by day and by night.
In a particular embodiment of the invention, it is possible for the retractable mirror to take one or more intermediate positions between the two extreme positions, so as to direct the light rays towards several distinct electronic devices.

19 2 0 4 2 43i9 T~U3L~E I
_ THICXNESS RADIUS INDEX USEFUL DIAMETER
1 37.935 26.20 0.00 4.088 1.721 2 282.080 25.60 0.00 4.664 1.000 3 -4~.741 24.30 0.00 9 903 1.667 4 -29.6æ 23.90 0.00 1.074 1.000 -26.065 23.20 0.00 1.624 1.667 6 35550 23.20 0.00 7 2.851 36.329 1.000 25.80 0.00 6.276 1.783 8 -42 028 24.70 0.00 .202 1.000 9 26.363 23.60 0.00 6.994 _ 1.709 22.90 0.00 1.949 1.905 .700 l.OOD 22.00 0.00 12 O 000 22.00 x 21.00 21.000 1.871 3.370 20.00 x 19.00 14 1.134 -18.173 1.667 19.00 0.00 0.000 20.00 0.00 - 1.000 _

Claims (13)

1. A multiple-function periscope, notably for armored vehicles, of the type including a reflector-based optic vision device and at least one electronic display device, for example for night-time vision, comprising, between the input reflector and the output reflector of said optic vision device, reflection means movable between two extreme positions, the first position enabling the free movement of the light rays between said input and output reflectors and the second position prompting the deflection of said light rays towards electronic processing means.

2. A periscope according to claim 1, of the type going through the armor of said vehicle, wherein only the input reflector of said optic vision device is external to said vehicle.

3. A periscope according to either of the claims 1 or 2, wherein said movable reflection means include a mirror, held by a movable strap, and means for guiding said strap between said extreme positions.

4. A periscope according to claim 3, wherein said guiding means include a set comprising at least one link-rod, positioned so as to provide a minimum horizontal and vertical clearance for said mirror during its travel between said extreme positions.

5. A periscope according to any of the claims 1 to 4, wherein said electronic display device has a wide-aperture lens having a bend of about 90° in the vicinity of the image, downline with respect to said image.

6. A periscope according to claim 5, wherein said objective includes a set of lenses with multilayer treatment and a prism.

7. An episcope according to claim 6, wherein the hypoteneuse of said prism is treated so as to improve the transmission balance of said objective, by at least one of the following treatments:
- silver-coating - improved aluminium-coating;
- multidielectric treatment optimized for a mean incidence of 45°.

8. A periscope according to either of the claims 6 or 7, wherein said objective includes a field glass between said prism and said electronic processing means, the concave face of said field glass being provided with multilayer treatment.

9. An episcope according to any of the claims 5 to 8, wherein said objective has an aperture of about F/1, a paraxial focal length of 26 mm, an object field of about 45° and an image field with a diameter of about 20 mm.

10. A periscope according to any of the claims 5 to 9, wherein said objective has a widened useful spectral band, ranging from about 450 nm to 900 nm.

11. A periscope according to any of the claims to 10, including means to control the passage of said reflection means from one of said extreme positions to the other, said control means jointly putting said electronic processing means into operation or out of operation.

12. A periscope according to any of the claims to 11, wherein said electronic display device is a light intensification channel, including a wide-aperture objective, an intensifier tube and a binocular optic system.

13. A periscope according to either of the claims 1 or 2, and according to any of the claims 5 to 10, wherein said movable reflection means include a reflector, for example of the triangular-sectioned reflecting prism type, fixedly joined to said objective, the assembly formed by the movable reflection means and the objective being capable of pivoting about an axis substantially perpendicular to the plane defined by said assembly.