WO2011058156A1

WO2011058156A1 - Device for displaying images stacked over an image of a surrounding scene, and associated manufacturing method

Info

Publication number: WO2011058156A1
Application number: PCT/EP2010/067428
Authority: WO
Inventors: Laetitia Landais; Philippe Patry
Original assignee: Sagem Defense Securite
Priority date: 2009-11-16
Filing date: 2010-11-15
Publication date: 2011-05-19
Also published as: FR2952728B1; FR2952728A1

Abstract

The invention relates to a device (1) for displaying images (5) stacked over an image (4) of a surrounding scene, comprising: a combining leaf (10) consisting of a material transparent to the image (4) of the scene, and having two surfaces (11, 12) parallel to one another, and plates (20) which are at least semi-reflective of the images (5) being stacked over the image (4) of the scene, and which are arranged at an angle relative to surfaces (11, 12) and parallel to one another in the leaf (10), the device being characterized in that the plates (20) have a characteristic size (d) which is small relative to a characteristic size of the leaf (10). The invention also relates to a method for manufacturing the aforesaid device.

Description

Image display device superimposed on an image of a surrounding scene, and method of manufacturing the same

GENERAL TECHNICAL FIELD

The present invention relates to a display device according to the preamble of claim 1.

The invention also relates to a method of manufacturing a device mentioned above.

STATE OF THE ART

As shown in FIG. 1, there is known a device 1 for viewing images superimposed on an image of a surrounding scene, comprising:

a blade 10 made of a material transparent to the image of the scene, and having two parallel faces, and

reflective or semi-reflecting lamellae to the images to be superimposed on the image of the scene, and arranged over the entire width of the blade 10, inclined in the blade 10.

The device 1 allows the transport of images to be superimposed on the image of the scene, the images being taken from a source 2 of images. Source 2 may consist of an LCD pixel array or any light image source. These images are projected to infinity and the collimated beam, consisting of images, enters the device 1 by an injection section 3. The beam is then transported in the device over an arbitrary length.

The light beam is guided by both sides and propagates by total reflection in the blade. If the index of the transparent material constituting the blade 10 is greater than that of the surrounding media, total internal reflections occur naturally when the angle of incidence of the beam rays is sufficiently large compared to the normal incidence on the face of the blade.

The beam then arrives on the lamellae 20 at least partially reflecting. The slats 20 allow the beam to emerge from the blade to be guided to an eye of a user, for example an infantryman. The beam is then superimposed on the image of the scene for the user. The foregoing device, however, has disadvantages.

As can easily be seen in FIG. 1, the strips 20 generate a modulation of the image of the scene, which is called a "louver" effect.

WO 01/27685 and US 2007/008624 disclose devices comprising such slats of great length.

PRESENTATION OF THE INVENTION

The invention proposes to overcome at least one of these disadvantages.

For this purpose, there is provided according to the invention a device according to claim 1.

The invention is advantageously completed by the features of claims 2 to 8, taken alone or in any of their technically possible combination.

The invention has many advantages.

The louver effect is suppressed or greatly diminished.

Because of the distribution of small platelets throughout the blade, the field seen by the eye of the observer is the same as if the eye was placed at the output of the source of images, but the platelets being of small dimensions and being distributed over a large part of the blade, the eye of the observer does not have the need to locate precisely in space with respect to the blade to be able to observe the images, unlike the situation of the prior art.

The invention can be applied to many fields and uses, such as the visualization of images consisting of symbols, information or video images mainly during the day, without losing contact with the backdrop so as to facilitate communication or the action within the framework of a mission which can be civil or military.

The device can of course be used at night to view video images or superimposed symbols of the scene in direct view or even in addition to the use of a night vision binocular. PRESENTATION OF FIGURES

Other features, objects and advantages of the invention will emerge from the description which follows, which is purely illustrative and nonlimiting, and which should be read with reference to the appended drawings in which:

- Figure 1, already commented, schematically shows a front view of a known device with lamellae;

FIG. 2 diagrammatically represents a first possible embodiment of a device according to the invention;

FIG. 3 diagrammatically represents a second possible embodiment of a device according to the invention;

- Figures 4 schematically show the main steps of a method of manufacturing a device according to the invention;

FIG. 5 schematically represents the distribution of platelets along a guideline in the device according to the invention, and

FIGS. 6A to 6C show schematically the definition of a characteristic dimension of a wafer.

In all the figures, similar elements bear identical reference numerals.

DETAILED DESCRIPTION

Figures 2 and 3 show diagrammatically two possible embodiments of an image viewing device 1 superimposed on an image 4 of a surrounding scene.

The images 5 come from a source 2 of images. Source 2 can consist of a matrix of LCD pixels (liquid crystal display) or

OLED (organic light-emitting diode) or any other source of light image.

The images consist of symbols, information or any video images for a wide variety of applications.

The source 2 also has an objective 8, making it possible to collimate the images 5.

The device 1 mainly comprises a combination blade 10 consisting of a material transparent to the image 4 of the scene, and exhibiting two faces 1 1 and 12 parallel to each other. An observer 7 can thus see the scene without deformation or magnification through the blade 10.

The device 1 also comprises platelets 20 at least semi-reflective to the images 5 to be superimposed on the image 4 of the scene, arranged inclined with respect to the faces 1 1 and 12.

It is understood that if the plates 20 are semi-transparent in the image 4, the image 4 of the scene is less attenuated, but the images 5 from the source 2 are on the other hand more strongly attenuated. In the case where the plates 20 are totally reflective, they form micro-mirrors.

The rays 51, 52 and 53, for example, composing an image 5, and emerging from the pupil of the objective 8, propagate in the blade 10 in the manner of a waveguide, that is to say by successive internal reflections. When a spoke 51, 52 or 53 meets a wafer 20, it is reflected and the emerging ray leaves the blade 10 with the same angle with respect to the optical axis, defined by the eye of the observer 7, that at the exit of the objective 8 of collimation.

The field seen by the eye of the observer 7 is therefore the same as if the eye was placed at the exit of the objective 8, but the plates 20 being distributed over a large part of the blade 10, the eye of the observer 7 does not have the need to locate precisely in space with respect to the blade 10 to be able to observe the image 5.

The distribution and size of the wafers 20 within the optical material of the blade 10 are made so as to optimize the quality of the transmitted images.

The wafers 20 have a characteristic dimension, i.e., a larger dimension of each wafer 20, which is small relative to a dimension D characteristic of the wafer 10, i.e. larger 10. The wafers 20 may have various shapes, such as any shape, square, circular or elliptical. The width and length of each wafer 20 are of the same order of magnitude. As indicated in FIG. 6, it is still possible to define a characteristic dimension of the plates 20, such as for example the diagonal (FIG. 6A), its largest axis in the case of an ellipse (FIG. 6B) or the diameter, or the greatest distance through the wafer 20 (Figure 6C) for example. It is therefore found that the characteristic dimension corresponds to the largest dimension of the wafer 20, whatever its shape, even irregular.

The characteristic dimension D of the blade 10 is for example its height in the case of a very elongated blade, but preferably its diameter or its diagonal (that is to say the largest dimension), and is of the order 10 mm, such as 50mm or more.

In all the definitions of d, the characteristic dimension d of the plates 20 is between 0.1 mm and 5 mm, preferably between 0.5 mm and 2 mm, to facilitate the visualization of the image 4 by the observer 7.

The ratio between the characteristic dimension of the platelets 20 and the dimension D characteristic of the plate 10 is between 0.002 and 0.5, preferably between 0.01 and 0.2.

Preferably, the plates 20 are flat and parallel to each other in the blade 10, as shown in FIGS. 2 and 3.

The wafers 20 may also be non-planar, and have a curvature, so that they can be associated with an optical power. In the case of non-flat plates, the plates 20 may be non-parallel to each other in the blade 10, depending on the desired optical power. In the case of non-flat platelets, platelets no longer intervene only as mirrors but participate in the collimation (endless reference) of the image source 2.

The density of platelets 20 at the surface in the plate 10 is between 20% and 80%, and is preferably of the order of 50%.

From the point of view of photometry, the source 2 must have sufficient luminance so that after reflection on the wafers 20, the images 5 supplied to the eye of the observer 7 are brighter than the image 4 of the scene seen through the blade 10. This depends on reflection coefficient of the plates 20, as well as their surface relative to that of the blade 10.

The platelet transmission rate may vary depending on their position in the blade 10. For example, the platelet transmission rate as a function of their Z location in the blade 10 may also be homogeneous or variable.

As shown in FIG. 5, in order to increase the relative area of platelets 20 with respect to that of blade 10, platelets 20 are distributed in blade 10 along a line 13 with respect to faces 11 and 12. do not mask each other vis-à-vis the rays of the image 5.

The arrangement of the platelets 20 can also be any, that is to say pseudo-random in the blade 10.

Furthermore, the distribution of platelets 20 can also be homogeneous according to the Z dimension, or vary according to a predetermined pattern (more platelets 20 at the bottom of the blade 10, for example at the top of the blade 10, or vice versa).

With all these parameters, there is a space for placing the eye of the observer 7 defined in FIG. 3 for example by:

- X away from the blade 10, corresponding to a pupillaire draw, X being of the order of 10 to 40 mm

- H in tolerance on the height, of the order of 30 to 60 mm, and

- L on the width, of the order of 20 to 50 mm

which is more important than in the case of the direct use of an eyepiece, which confers an ergonomic advantage to the device. The ocular domain (volume in which the eye sees the image correctly) thus allows a good visualization of the scene and the images 5 even when the observer runs for example. This is to be compared with the approximately 10 mm diameter ocular ring offered by conventional eyepieces.

Optically, the two embodiments of Figures 2 and 3 are equivalent, and can be adapted to the final application. In the embodiment of Figure 2, the device further comprises an injection mirror 6. It is understood that the inclination of the plates 20 with respect to the faces 1 1 and 12 depends on the inclination of the source 2 and the mirror 6.

Similarly, the blade 10 may be inclined or parallel to the eye of the observer 7, depending on the desired applications.

The following developments relate to a possible implementation of a method of manufacturing a device mentioned above, with reference to FIGS.

As shown in Figure 4A, a plurality of pins 100 is placed on one of the faces 1 10 of a block 101 made of a transparent moldable optical material of the family of glasses or plastics.

The pins 100 are for example of circular cross section, and have a diameter of between 0.5 mm and 2 mm. Other forms are possible.

As shown in FIG. 4B, the pins 100 are then machined, for example by diamond machining, in parallel planes forming a constant angle with the face 1 of the block 101 and at heights h which are identical or different with respect to the face 1. 10, so as to mechanically realize the platelet field 20. It is understood that if the pins 100 have a circular cross section, the plates 20 have an elliptical shape.

A totally or partially reflective thin layer deposit, possibly dichroic, is then applied by vacuum deposition techniques commonly used in optics on the pins 100 in order to make the plates 20. This must be done by protecting the face 1 10 of the block 101 located at the base of the pins 100 to avoid reducing the transmission between the image of the scene and the eye of the observer 7 by the presence of the deposit at this location.

As shown in FIG. 4C, the block 101 is then completed by an optically transparent and polymerizable material, preferably cold so as not to damage the pins 100 (such as for example an adhesive), and with a very similar index of the material of the block. 101 to finish making the blade 10 with parallel faces 1 1 and 12.

Since the indices of the two materials are very close, there is no Fresnel reflection at the transition and a parallel-sided plate 10 is then obtained with plates 20 embedded inside the material. It is recalled that an alternative embodiment consists in producing reflective plates that are no longer flat but curved in order to create optical power. In this case the plates no longer intervene only as mirrors but participate in the collimation (reference to infinity) of the image source. Lithography processes known to those skilled in the art make it possible to give the plates 20 a curvature.

Claims

1. An image viewing device (5) superimposed on an image (4) of a surrounding scene, comprising

a combination blade (10) made of a material transparent to the image (4) of the scene, and having two faces (1 1, 12) parallel to each other and a larger dimension (D), and

platelets (20) at least semi-reflective to the images (5) to be superimposed on the image (4) of the scene, arranged inclined with respect to the faces (1 1, 12) in the blade (10), each wafer (20) having a larger dimension (d),

the device being characterized in that the ratio between the largest dimension (d) of the platelets (20) and the largest dimension (D) of the blade (10) is between 0.002 and 0.5, so that the platelets (20) have a larger dimension (d) smaller than a larger dimension (D) of the blade (10).

2. Device (1) according to claim 1, wherein the largest dimension (d) of the plates (20) is between 0.1 mm and 5 mm, preferably between 0.5 mm and 2 mm, the ratio between the largest dimension (d) of the wafers (20) and the largest dimension (D) of the blade (10) being between 0.01 and 0.20.

3. Device (1) according to one of claims 1 or 2, wherein the density of platelets (20) at the surface in the blade (10) is between 20% and

80%, and is preferably of the order of 50%.

4. Device (1) according to one of claims 1 to 3, wherein the platelets are flat and parallel to each other.

5. Device (1) according to one of claims 1 to 3, wherein each wafer (20) has a curvature.

6. Device (1) according to one of claims 1 to 5, wherein the plates (20) are distributed in the blade (10) in a direction line (13) relative to the faces (1 1, 12).

7. Device (1) according to one of claims 1 to 6, wherein the platelet transmission rate varies according to their position in the blade (10).

8. Device (1) according to one of claims 1 to 7, further comprising a mirror (6) of injection.

9. A method of manufacturing a device according to one of claims 1 to 8, characterized in that it comprises the steps according to which:

- A plurality of pins (100) is assembled on one of the faces of a block (101) made of a transparent moldable optical material, of the family of glasses or plastics;

the tips of the pins (100) are formed so as to form the plates (20);

the platelets (20) are treated while protecting the face (1 10) of the block (101);

the block (101) is completed by an optically transparent and polymerizable material of index very close to the material of the block (101) to finish making the blade (10) with parallel faces (1 1, 12).

The method of claim 9, including a lithography step for curving the wafers (20).