EP2856221A2

EP2856221A2 - Compact and energy-efficient head-up display

Info

Publication number: EP2856221A2
Application number: EP13729995.4A
Authority: EP
Inventors: Umberto Rossini
Original assignee: Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Current assignee: Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Priority date: 2012-05-28
Filing date: 2013-05-27
Publication date: 2015-04-08
Also published as: FR2991062A1; FR2991062B1; WO2013178926A3; WO2013178926A2; US20150138644A1; CA2873670A1

Abstract

The invention relates to a head-up display comprising sub-screens (24_1, 24₂,..., 24₅), the positions and dimensions of which are defined according to the length of the optical path (D) and the maximum authorised length of movement in a plane that is perpendicular to the optical path and located at a distance equal to the length of the optical path, such that the information projected by the group of sub-screens can be seen over the entire authorised length of movement. The display is characterised in that the luminous intensity of the sub-screens increases the further they are from the main optical axis of the display.

Description

HEAVY DUTY HIGH COMPACT HEAD VISITOR WITH LOW ENERGY CONSUMPTION

Field of the invention

The present invention relates to a head-up display, also called head-up display, head-up collimator or head-up display system, compact and having a large exit pupil. More particularly, the present invention relates to such a viewfinder whose energy consumption is reduced.

Presentation of the prior art

The head-up displays, also known as the HUD, of the English Head-Up Display, are augmented reality display systems that integrate visual information on a real scene seen by an observer. In practice, such systems can be placed in the visor of a helmet, in the cockpit of an aircraft or within the cabin of a vehicle. They are thus positioned at a small distance from the eyes of the user, for example a few centimeters or tens of centimeters.

Figure 1 illustrates, schematically, the operation of such a device.

A semitransparent blade 10 is placed between the eye of the user 12 and a scene to be observed 14. The objects of the scene to be observed are generally located at infinity or at an angle important distance from the observer. The semi-transparent blade

10 is placed at an angle of 45 ° to the axis between the scene 14 and the observer 12, so as to transmit the information from the scene 14 to the observer 12, without altering this information. .

To project an image seen at the same distance as the actual image of the scene and superimpose it on it, a projection system is planned. This system comprises an element for displaying an image 16, for example a screen, located at the focal point object of an optical system 18. The image displayed on the screen is thus infinitely collimated by the optical system 18. The user does not have to make an effort of accommodation, which limits the visual fatigue of the latter.

The projection system is placed perpendicular to the axis between the scene and the observer so that the beam from the optical system 18 reaches the semi-transparent plate perpendicular to this axis. The beam from the optical system 18 thus reaches the semi-transparent plate 10 at an angle of 45 ° with respect to its surface.

The semi-transparent plate 10 combines the image of the scene 14 and the image resulting from the projection system 16-18, from which

As a result, the observer 12 displays an image comprising the projected image superimposed on the image of the scene 14.

In order to visualize the image projected by the projection system 16-18, the observer's eye must be placed in the reflection zone of the beam coming from the optical system 18 on the plate 10. An important constraint to be respected is to hold account possible movements of the head of the user in front of the projector, and therefore to provide a beam output of the optical system 18 as wide as possible. In other words, it is necessary to provide an optical system 18 whose output pupil is large, for example between a few centimeters and a few tens of centimeters, so that the head movements of the observer do not imply a loss of light. projected information. Another constraint of head-up systems is to provide a relatively compact device. Indeed, significant space constraints weigh on these devices ^¬ sitifs, especially when used in aircraft cockpits or car interiors of limited volume. To limit the size of head-up systems, it is necessary to provide devices whose focal length is reduced.

Thus, it is sought to obtain devices having an output aperture, that is to say the ratio between the object focal distance of the system and the diameter of the exit pupil of the device, very low. It is known that the complexity of an optical system depends on the output aperture thereof. More particularly, the lower the opening of a device, the more complex the device. The more complex the optical system, the greater the number of optical elements it contains, especially to limit the various aberrations. This increase in the number of elementary optical elements increases the volume and the cost of the complete device, which is not desired.

In addition, it is necessary to provide devices with low energy consumption.

summary

An object of an embodiment of the present invention is to provide a compact head-up viewfinder having a large exit pupil.

An object of an embodiment of the present invention is to provide such a device whose power consumption is reduced.

Thus, an embodiment of the present invention provides a head-up viewfinder, including subscreens whose positions and dimensions are defined according to the length of the optical path and a maximum allowed movement length in a perpendicular plane. to the optical axis and located at a distance equal to the optical path length so that the information projected by all subscreens is viewed over the entire authorized movement length, characterized in that the subscreens have an increasing light intensity as a function of their distance from the main optical axis of the viewfinder.

According to an embodiment of the present invention, the positions and the dimensions of the subscreens are further defined according to the average deviation between the two eyes of a person.

According to an embodiment of the present invention, each sub-screen is associated with an optical subsystem, the subscreens being placed in the object focal plane of the optical subsystems.

According to one embodiment of the present invention, the optical subsystems are regularly distributed in a plane perpendicular to the main optical axis of the viewfinder.

According to one embodiment of the present invention, the projected information is an image that is distributed over all subscreens.

According to one embodiment of the present invention, the sub-screens are defined on the surface of a substrate.

According to an embodiment of the present invention, the subscreens are disjoint.

According to one embodiment of the present invention, along a first axis, the maximum allowed movement length is zero and the view of the observer is monocular, the subscreens being placed symmetrically on either side of the axis. main lens of the viewfinder, each subscreen having a length along the first axis equal to fL / D, the subscreens being spaced edge to edge by a distance equal to L, f and L being, respectively, the focal length and the width of the optical subsystems, where D is the length of the optical path.

According to an embodiment of the present invention, along a first axis, the maximum permitted movement length is non-zero, the observer's vision is monocular device and the device comprises a number Q of optical sub-system and sub-projectors, the subscreens being placed symmetrically on either side of the main optical axis of the viewfinder, the centers of the subscreens being placed at a distance from each other equal to fL / D + L, each sub-screen having a length along the first axis equal to f / D (L + B), within the limit of an area of a dimension equal to QfL / D centered on the optical axis of the associated optical subsystem, f and L being, respectively, the focal length and the width of the optical subsystems, where D is the length of the optical path.

According to one embodiment of the present invention, along a first axis, the maximum allowed movement length is zero and the view of the observer is binocular, the subscreens being placed symmetrically on either side of the axis. main viewfinder lens, each subscreen having a length along the first axis equal to fL / D, except the sub-screens furthest from the main optical axis having a length equal to f / D (L + y / 2), the subscreens being spaced edge to edge by a distance equal to L, f and L being, respectively, the focal length and the width of the optical subsystems, where D is the length of the optical path.

According to an embodiment of the present invention, along a first axis, the maximum allowed movement length is equal to an average difference between the two eyes of a person and the view of the observer is binocular, the subscreens being placed symmetrically on either side of the main optical axis of the viewfinder, each sub-screen having a length along the first axis equal to fL / D, the subscreens being distant edge-to-edge by a distance equal to L where f and L are, respectively, the focal distance and the width of the optical subsystems, where D is the length of the optical path.

According to an embodiment of the present invention, along a first axis, the maximum movement length allowed is greater than an average difference between the two eyes of a person, the view of the observer is binocular and the device comprises a number Q of optical sub-systems and sub-projectors, the sub-screens being placed symmetrically of on both sides of the main optical axis of the viewfinder, the centers of the sub-screens being placed at a distance from each other equal to fL / D + L, each sub-screen having a length along the first axis equal to f / D (L + By), within the limit of an area of a dimension equal to QfL / D centered on the optical axis of the associated optical subsystem, f and L being, respectively, the focal distance and the width of the optical subsystems, where D is the optical path length.

According to an embodiment of the present invention, the viewfinder comprises an odd number of sub-screens along the first axis, the intensity of illumination of the sub-screen of rank i being equal to the intensity of illumination of the sub-screen. central screen (i = 1) multiplied by the following factor:

a'-i_ =

f and L being, respectively, the focal length and the width of the optical subsystems, where D is the optical path length.

According to an embodiment of the present invention, the viewfinder comprises an even number of sub-screens along the first axis, the intensity of illumination of the sub-screen of rank i being equal to the intensity of illumination of the sub-screen. central screen (i = 1) multiplied by the following factor:

, with OI-L equal to:

LL

CC-; arctan + - - arctan

D 2f D 2f f and L being, respectively, the focal length and the width of the optical subsystems, where D is the length of the optical path.

According to an embodiment of the present invention, each sub-screen consists of a matrix of organic light-emitting diode cells.

Brief description of the drawings

These and other objects, features, and advantages will be set forth in detail in the following description of particular embodiments in a non-limitative manner with reference to the accompanying figures in which:

Figure 1, previously described, illustrates the principle of operation of a head-up display;

Figure 2 illustrates the principle of operation of a head-up display according to an embodiment of the present invention;

Figures 3 to 5 illustrate different observations made using the devices of Figures 1 and 2;

Figures 6 to 8 illustrate optical structures for determining geometric rules for designing a screen of an improved head-up display;

Figures 9 and 10 illustrate the subscreen distribution according to one embodiment of the present invention; and

FIGS. 11 and 12 illustrate rules for the formation of head-up display sub-projectors according to one embodiment of the present invention.

For the sake of clarity, the same elements have been designated with the same references in the different figures and, moreover, as is customary in the representation of the optical systems, the various figures are not drawn to scale. detailed description

In order to obtain a compact head-up viewfinder, that is to say comprising a projection system having a space of less than a few tens of centimeters and having a large exit pupil, it is planned to dissociate the projection system into several sub-planes. elementary projection systems, each projection subsystem operating in the same way and projecting a portion of an image to be superimposed on a real image.

Figure 2 schematically shows a head-up viewfinder according to one embodiment.

In FIG. 2, the device comprises a semitransparent plate 10 which is placed between the observer 12 and a scene to be observed 14. The surface of the semi-transparent plate 10 forms an angle, for example of 45.degree. axis between the scene and the observer, and does not disturb the arrival of rays from the scene to the observer. It should be noted that the semitransparent plate can be replaced by an interference filter performing the same function as a semi-transparent plate.

A projection system of an image to be superimposed on the image of the scene is planned. It comprises an image source 24, for example a screen, associated with an optical system 26. The projection system is placed here perpendicularly to the axis between the scene and the observer, and the beam that comes from the optical system 26 reached the semi-transparent plate perpendicular to this axis.

The semi-transparent plate 10 combines, i.e. superimposes, the image of the scene 14 and the projected image from the optical system 26, whereby the observer views the superimposed projected image to the real image of the scene 14. The system of Figure 2 operates in the same way as the system of Figure 1.

The optical system 26 comprises a set of optical subsystems 26A, 26B and 26C of the same focal length. The image source 24 is placed at a distance from the optical system 26 equal to the object focal distance of each of the optical subsystems 26A to 26C.

The image source 24, for example a screen, is divided into several subscreens. In the sectional view of FIG. 2, three sub-screens 24A, 24B and 24C are shown. Note that this number may be more or less important. Each sub-screen 24A, 24B and 24C is associated with an optical subsystem 26A, 26B, 26C. Contrary to what is shown, the subscreens can be shifted from the optical axes of the associated optical subsystems, as will be seen below.

We will call here the set consisting of a sub-screen and an optical sub-system a sub-projector. The projection system therefore comprises a plurality of sub-projectors.

By forming several parallel sub-projectors, it is possible to obtain a complete device presenting a total exit pupil (sum of the sizes of the exit pupils of each of the sub-projectors) of large size, while forming simple and compact optical subsystems. .

Indeed, each optical subsystem has an opening, called elemental, "moderate". The elementary aperture of an optical subsystem is defined as the ratio of its own focal distance to the size of its own exit pupil. The parallel association of the sub-projectors thus makes it possible to obtain an optical system whose opening is particularly weak insofar as, for the same distance between screen and projection optics, a large total exit pupil is obtained. , equal to the sum of the exit pupils of each optical subsystem. The optical system thus has a small opening while being formed of simple elementary optical structures. The compactness of the complete device is thus ensured.

The screen 24 is provided so that each sub-screen 24A, 24B, 24C displays part of the information, the complete information being recombined by the brain of the observer. For this, the image that one wishes to project in augmented reality is divided into blocks which are distributed on the various subscreens.

For example, the screen 24 may be comprised of a cell array comprising organic light emitting diodes ^¬ (English OLED, Organic Light-Emitting Diode) or a matrix of LCD sub-screens or picture .

In an OLED screen, one or more layers of organic materials are formed between two conductive electrodes, the assembly extending on a substrate. The upper electrode is transparent or semi-transparent and is usually made of a thin layer of silver whose thickness may be of the order of a few nanometers. When a suitable voltage is applied between the two electrodes, a phenomenon of electroluminescence appears in the organic layer.

However, with an OLED type screen, a problem of access to the electrodes can arise. In fact, to obtain a good visibility of the projected information, because of the weaknesses in transmission of the devices that may be placed at the output of the screen, it is necessary to reach a luminance at the output of the subscreens of the screen. order of 20000 Cd / m2. To obtain such luminance, it is necessary to send large currents into the upper electrode of the OLED structure, typically of the order of a few amperes to about ten amperes. However, a silver layer a few nanometers thick can not withstand such amperage.

Thus, it is sought to reduce the amount of current to be provided to an OLED screen, or to form a reduced surface screen. Here it is intended to form devices in which the subscreens are placed relative to the optical subsystems and are dimensioned in an optimized manner to ensure the practical realization of the projection system of the head-up display. Figures 3 to 5 illustrate different observations made using the devices of Figures 1 and 2.

In FIG. 3 is illustrated an image 30 which is displayed on a screen such as the screen 16 of FIG. 1 (thus with a single-shot optic). A frame 32, which surrounds the image 30, schematically represents the exit pupil of the projection device 18 of FIG. 1. In the example of FIG. 3, the exit pupil 32 is slightly wider than the displayed image. by the screen 30. In this case, the observer observes all the information contained in the image 30, as long as the observer's head remains in what is called the "eye box" the device (in English eye-box or head motion box).

This "eye box" is defined as the space where the observer can move his head while receiving all the projected information. In other words, as long as the observer's head remains in the eye box, he receives all the projected information.

FIG. 4 illustrates the view of the information by an observer, in the case where the head-up viewfinder comprises a single-pupillary optics (case of FIG. 1), when the head of the observer leaves the eye box. . In this case, the exit pupil 34 (portion seen by the observer) is shifted with respect to the image 30, which implies that only a portion 30 'of the image 30 is seen by the observer.

In Figure 5 is illustrated the vision of the information by an observer, in the case where the head-up viewfinder has a multi-pupil optical (Figure 2), when the head of the observer out of the eye box. In this case, the exit pupil 36 seen by the observer is shifted with respect to the image 30, which implies that only a portion 30 "of the image 30 is accessible to the observer. of the multi-pupillary structure of Figure 2, the portion 30 "is viewed in a fragmented manner. Indeed, in the case of a multi-pupillary optics, the image being projected by a set of under-projectors, each sub-projector has its own eye box. Thus, when the observer leaves the overall eye box of the device, it also leaves the eye box of each of the sub-projectors, which causes a fragmentation of the image seen by the observer. As a result, the final image seen by the observer consists of a set of vertical bands 30 "(in the case of a lateral displacement of the observer's head) of portions of the image 30.

Thus, the positioning and the size of the sub-screens of a head-up viewfinder with multi-pupil optics must be adapted according to a predefined desired eye box. Various cases will be described below, starting from an eye box of zero size (only one position of the observer ensures the reception of all the information), the projected image filling the whole of the surface of the exit pupil.

Figures 6 to 8 illustrate optical structures for determining geometric rules for enhanced placement of OLED subscreens.

In Figure 6, we consider an optical system comprising two sub-screens _24] _ and 242 placed on the same substrate 40, opposite two optical subsystems _26] _ and 262- The sub-screens are placed in the focal plane object of the optical subsystems (the distance separating the optical subsystems and the subscreens is equal to the object focal length f of the optical subsystems). In this example, the subscreens

24] _ ^and ^ and 242 - ^are optical subsystems 26] _ and 262 extend symmetrically on either side of the principal optical axis of the device.

In this figure, the goal is to determine the area of each subscreen useful when the observer closes an eye

(monocular vision), that is to say the portion of each sub-screen seen by the eye, if the eye is placed on the main optical axis of the device at a distance D from the optical system 26. The distance D between the optical subsystems 26 _] _ and 262 and the observer is called optical path. It will be noted that in case of a head-up display such as that of Figure 2, the optical path, and thus the distance D that we will consider later, corresponds to the light path between the optical subsystems _26] _ and 262 and the observer, for example through the semi-reflective blade 10.

As shown in FIG. 6, only a portion 42 of a subscreen 24 _] is seen by the observer's eye. Thus, if we consider an immobile observer such as that of FIG. 6 (eye box of zero size and monocular vision), only the portion 42 of the subscreen is a portion useful for observation. The remainder of the screen can thus be disconnected, or the screen 24 _] _ can be reduced to the single portion 42, for the same visibility of the information (by projecting all the information on the portion 42 of screen 24 _] _). This idea is at the basis of the sizing of the subscreens proposed here.

The portion 42 of the sub-screen 24 _] accessible by the eye has a dimension fL / D, L being the diameter of the optical subsystem 26 _] _, the edge of the portion 42 being located at a distance d = L / 2 of the main optical axis.

In the example of Figure 7 is shown a device comprising three sub-projectors consisting of three sub-screens 24 ' _] _, 24 * 2 and 24 * 3 formed on a substrate 40 facing three optical subsystems 26' _] , 26 * 2 and 26 * 3. The substrate 40 is placed in the object focal plane of the optical subsystems 26 '], 26 * 2 and 26 * 3. The central sub-projector (24 '2, 26 * 2) has its optical axis coincident with the main optical axis of the device and the peripheral sub-projectors extend symmetrically with respect to the main optical axis of the device. Here, we consider the portion 42 'of a peripheral sub-screen accessible in monocular vision by an eye placed on the main optical axis of the device, at a distance D from the optical system 26.

In this case, we obtain that the portion 42 'of the sub-screen 24' ^ peripheral accessible to the eye has a dimension equal to fL / D, L being the diameter of the optical subsystem 26 '] _, the edge of the portion 42' being located at a distance of = L + fL / 2D from the main optical axis, L being the diameter sub optical systems 26 '] _, 26' _2/26 '3.

In addition, regardless of the position of a sub-screen in a device comprising an even or odd number of sub-screens, the surface of this sub-screen visible by an eye (monocular vision) placed on the main optical axis of the device is equal to fL / D.

FIG. 8 shows the case of FIG. 6 with a projector comprising two sub-projectors each consisting of a sub-screen 24], 242 ^and an optical subsystem 26]. to the subscreen region which is accessible to an observer in binocular vision. In our case, in top view, the two eyes of the observer R and L are placed on either side of the main optical axis of the device, at a distance y / 2 of this main optical axis (y being thus the gap between the two eyes of the observer).

In this case, the right eye R, respectively the left eye L, sees a portion 42R, respectively 42L, of the sub-screen 24] _ of an area equal to fL / D, with the same references as before. However, due to the superposition of the regions seen by the two eyes, the useful surface of the sub-screen 24], that is to say the surface of the screen 24 which is seen at least by one eye of the user, has a width equal to fL / D + fy / 2D.

Here it is planned to limit the size of the screens to the useful size, that is to say actually seen by the observer. It can thus reduce the consumption of the device.

In order to define the useful area of each of the subscreens in operation, it must be taken into account that the head of the observer is likely to move, according to a maximum amplitude that is predefined. Note that, vertically, the head of an observer is less subject to movement and vision is monocular. However, The following teachings apply to both vertical head movement and lateral movement.

Subsequently, the maximum accepted movement length of the head (equal to the size of the eye box along a first axis, for example horizontal) will be called B. B thus corresponds to the maximum peak-to-peak amplitude in motion of the accepted head. Subscreen positioning rules are defined below so that if the observer's head moves in a direction a distance less than or equal to B / 2, or in an opposite direction of a distance less than or equal to B / 2, the view of the information given by all the subscreens is always complete, ie each pixel of each subscreen is seen at least by one both eyes of the observer when describing the entire eye box.

As will be seen below, the sizing and positioning rules of each of the subscreens vary according to whether it is desired to have an amplitude in motion that is zero or not authorized, and that one places oneself in binocular or monocular vision. (eg binocular vision horizontally, monocular vertically). In particular, the inventor has shown that the reasoning leading to the sizing of the sub-screens in a direction in which the vision is monocular with a non-zero eye box also applies to the case where the vision is binocular with an eye box B is greater than the distance between the two eyes y of the observer.

Figures 9 and 10 illustrate rules for positioning and sizing sub-screens on a substrate according to one embodiment.

In these two figures, there is provided a device comprising a number Q = 5 of subscreens 24 _] _ to 245 placed opposite five optical subsystems 26 _] _ to 265.

In these figures, the sub-screens _24] _ 245 are placed in the object focal plane of the optical subsystems _26] _ 265 so that, in monocular vision, the reconstituted image fill all the exit pupil. Thus, in this case, the eye box has a dimension B zero (the slightest movement of the head of the observer implies a loss of information). A simple calculation makes it possible to obtain that the subscreens have a length in the plane of the figures equal to fL / D and are separated by a distance equal to the size of the optical subsystems L.

In the case of FIGS. 9 and 10, the sub-screens are more or less offset from the optical axis of the associated optical subsystem, as a function of their distance from the main optical axis of the projection system. In these figures are shown for illustration regions 50j to 5Ο5 which are placed in the object focal plane of the optical subsystems 26j to 265 and which are centered on the optical axis of the optical subsystems 26 _] _ to 265. Each region 50j_ to 5Ο5 has a length equal to QfL / D, in this case 5fL / D. In this case, it can be seen that each sub-screen 24 _] _ to 245 is placed opposite a portion of the region 50j_ to 5Ο5 corresponding to its rank, that is to say that the subscreens at the ends of the device are placed at the ends of the regions 50j_ to 5Ο5 on both sides of the device. In addition, the illustration of the regions 50j_ to 5Ο5 makes it possible to represent the part of the image that the corresponding sub-screen must display: the sub-screens at the periphery thus display a peripheral portion of the image.

In Figure 9, an eye box is desired to obtain, always by monocular vision at a distance D of the projection device, a dimension equal to _B] _ relatively low. In this figure, the solid lines delimit the zone of the visible focal plane when the eye moves to the left in the figure (by a distance B _] _ / 2) and the dashed lines delimit the zone of the visible focal plane when the 'eye moves right in the figure (from a distance B _] _ / 2).

If you want to see a complete image regardless of the position of the eye in the eye box, the subscreen must be positioned and sized to match the field of view. overlap of visible regions at both ends of the eye box. However, to avoid the phenomena of fragmentation presented in relation to FIG. 5, the subscreens must be magnified by a distance fB / 2D on either side of the subscreen, here with B = B _] _.

In Figure 10, there is provided an eye box, still in monocular vision at a distance D from the projection device, a dimension equal to B2 relatively large. In this figure, the solid line delimits the limit of the visible focal plane when the eye moves to the left in the figure (by a distance B2 / 2) and the dashed line delimits the limit of the visible focal plane when the eye moves to the right in the figure (from a distance B2 / 2).

In the case of the size B2 eye box, if we plan to increase the size of the subscreens on each side of fB / 2D, here with B = B2, we see in this case that, for one of the sides, it is not necessary to magnify the subscreen as much, since the portion of the subscreen 24-j that protrudes from the corresponding region 50 is useless. Thus, the peripheral subscreens (in our case subscreens 24 _] _ and 245) should only grow in one direction.

It should be noted that, in a case where the vision is considered to be monocular with a nonzero eyebox, or in the case where the vision is considered to be binocular with an eyebox greater than y, each sub-screen has a dimension greater than fL / D. The image to be superimposed on the real image is in these two cases distributed over portions of each of the subscreens of dimensions equal to fL / D. The information displayed on the rest of the subscreens is redundant with the neighboring subscreens, which ensures the dimensions of the desired eye boxes.

Figures 9 and 10 provide the following sizing and positioning rules. It is chosen to form a matrix of QxQ 'sub-projectors, Q and Q' which can be odd or even. In both directions of the projector, the sub-projectors are arranged symmetrically with respect to the main optical axis of the projector.

In monocular vision, for example along the vertical axis of the observer, if a zero-eye box (B = 0) is desired, the sub-screens are placed symmetrically with respect to the main optical axis of the device, have dimensions equal to fL / D and are spaced edge-to-edge by a distance L (the centers of the subscreens are thus distant by a distance equal to L + fL / D).

If a nonzero eyebox (B ≠ 0) is desired, the subscreens are placed symmetrically and are centered in the same way as in the case of a null eyebox (the centers of the subscreens are placed at a distance from each other equal to fL / D + L), but have increased dimensions of fB / 2D on each side with respect to the case where B = 0. Thus, the subscreens have dimensions equal to f / D (L + B). The edge to edge of the subscreens is then less than L. The magnification of the subscreens is made so as not to leave an area of a dimension equal to QfL / D centered on the optical axis of the subset. the associated optical system, where Q is the number of sub-projectors in the direction considered.

In binocular vision, for example along the horizontal axis of the observer, if a zero eye box is desired (B = 0), the subscreens have dimensions equal to fL / D and are spaced edge to edge a distance L. Thus, the centers of the subscreens are distant by a distance equal to L + fL / D. The peripheral sub-screens have a dimension equal to (L + y / 2) f / D, where y is the difference between the two eyes of a person. Note that in the literature, the average difference _mQ there are between the two eyes of a person is between

60 and 70 mm, typically of the order of y _mΩ y = 65 mm. So, in practice, we can take y = y _m0 y

If we want an eyebox equal to the distance y between the eyes of the observer, all subscreens have dimensions equal to fL / D and are spaced edge to edge of a distance L. Thus, the centers of the sub-screens are thus separated by a distance equal to L + fL / D.

If an eye box is desired greater than the distance y between the eyes of the observer, the subscreens are centered in the same way as above (the centers of the subscreens are placed at a distance from each other). the others are equal to fL / D + L but are larger by (By) f / 2D on both sides, so the subscreens have a dimension equal to (L + By) f / D. subscreens is therefore smaller than L. The subscreen magnification occurs so as not to exceed an area of QfL / D dimension centered on the optical axis of the associated optical subsystem, where Q is the number of sub-projectors along the axis of movement considered.

Advantageously, the formation of screens consisting of sub-screens whose dimensions and positioning are defined in the above manner reduces the consumption of the device, since only useful portions of a screen, or only small screens, are powered. In addition, the subdivisions of the subscreens proposed above can correspond directly to the practical realization of upper electrodes of OLED screens, which can be powered by conductive tracks (not shown) of sizes adapted to the transmission of a power supply current of high amperage.

In addition, as one moves away from the optical center, each sub-screen 24-j ', 24'-j_ sees its optical subsystem 26j_, 26'_ associated at an angle more and more. closed. As a result, the composition of the image, viewed by the observer, is made with a gradient of luminance which decreases from the center to the edge of the image. Indeed, many screens, including OLED-based screens, are not Lambertian light sources that ensure, regardless of the observation point of the screen, the reception of the same luminance. It is therefore necessary to take this phenomenon into account. FIG. 11 illustrates a subscreen 24'-j which is decentered with respect to the main optical axis of the device (represented in dotted lines), associated with an optical subsystem 26 ¹ of dimension equal to L and of focal length f (the sub-screen is located at a distance f from the optical subsystem). The device comprises an odd number of sub-projectors. The subscreen 24'-j_ is the sub-screen of rank i on one side of the main optical axis of the device (i = 1 for the central sub-projector). In this figure, the angle formed between a first beam originating from the center of the subscreen 24'-1 and reaching a first end of the optical subsystem 26 ', and a second beam originating from the center of the subsystem -screen 24'-j_ and reaching a second end, opposite the first end, of the optical subsystem 26 ¹ . D being the length of the optical path to the observer, the angle ' _j _ is defined by:

The flux passing through the lens 26 varies proportion ¹ ^¬ tionally to the value 2n (1-cos ( 'j_ / 2)). The flux ratio between the central optical subsystem (i = 1) and the optical subsystem of ran i is therefore: with -j as defined above.

Here it is planned to correct the intensity of each sub-screen by increasing it by this ratio, depending on the rank of the sub-screen in the device.

FIG. 12 is a curve of the ratio r'-j as a function of the rank i of the optical subsystem in the device, on either side of the main optical axis of the device.

In this curve, it can be seen that, for a sub-screen of rank 5, the intensity of illumination of this sub-screen must be at least 1.5 times the intensity of illumination of the central sub-screen. . It will be noted that, for a device comprising an even number of sub-projectors along an axis considered, the ratio r-j is then defined with respect to the optical subsystem of rank 1 by:

with CC-j_ 1 in FIG. 8 for the ith sub-screen on either side of the optical axis of the projection system equal to:

1 1

- - - - - -

2 2 L

<¾_ = arctanl + arctan

D 2f D 2f The subscreens with ranks greater than 1 thus have their illuminance intensities compensated for this ratio with respect to the rank 1 sub-screen (the first sub-screen on either side of the optical axis main projection system).

Thus, in addition to the sizing of the sub-screens proposed in relation with FIGS. 9 and 10, provision is made for a power supply thereof adapted to their positions in the device so that the luminous intensity they provide involves a luminance received by the device. uniform observer from all subscreens.

Particular embodiments of the present invention have been described. Various variations and modifications will be apparent to those skilled in the art. In particular, it will be noted that the invention has been presented here with subscreens consisting for example of OLED, but it will be understood that the invention also applies to projection systems in which the screens consist of non-Lambertian sources different from OLED diodes, as long as the dimensions of each of the sub-screens proposed above are respected.

In addition, various embodiments with various variants have been described above. It will be noted that the man of The art may combine various elements of these various embodiments and variants without demonstrating inventive step.

Claims

1. Head-up display, comprising sub-screens (24 _] _, 242, ··· _/ 245) whose positions and dimensions are defined according to the length of the optical path (D) and a movement length permissible maximum (B) in a plane perpendicular to the optical axis and at a distance equal to the length of the optical path so that the information projected by all the subscreens is viewed over the entire permissible movement length characterized in that the sub-screens have increasing light intensity as a function of their distance from the main optical axis of the viewfinder.

The viewfinder according to claim 1, wherein the positions and dimensions of the subscreens (24], 242, 245) are further defined according to the average deviation between the two eyes (y). of somebody.

The viewfinder according to claim 1 or 2, wherein each subscreen (24], 242, 245) is associated with an optical subsystem (26, 262, 26, 265). , the subscreens being placed in the object focal plane of the optical subsystems.

4. A viewfinder according to claim 3, wherein the optical subsystems (26] _, 262, ···, 265) are regularly distributed in a plane perpendicular to the main optical axis of the viewfinder.

5. A viewfinder according to any one of claims 1 to 4, wherein the projected information is an image which is distributed over all subscreens (24] _, 242, ··· '245).

6. A viewfinder according to any one of claims 1 to 5, wherein the subscreens (24] _, 242, ··· '245) are defined at the surface of a substrate (40).

7. A viewfinder according to any one of claims 1 to 6, wherein the subscreens (24] _, 242, ··· '245) are disjointed.

8. A viewfinder according to any one of claims 2 to 7, wherein, along a first axis, said maximum allowed movement length (B) is zero and the vision of the observer is monocular, the subscreens being placed symmetrically on either side of the main optical axis of the viewfinder, each subscreen having a length along said first axis equal to fL / D, the subscreens being the edge distance and the width of the optical subsystems, where D is the length of the optical path.

9. A viewfinder according to any one of claims 2 to 7, wherein, along a first axis, said maximum allowed movement length (B) is non-zero, the view of the observer is monocular and the device comprises a number Q subsystems being placed symmetrically on either side of the main optical axis of the viewfinder, the centers of the subscreens being placed at a distance from each other equal to fL / D + L, each sub-screen having a length along said first axis equal to f / D (L + B), within the limit of an area of a dimension equal to QfL / D centered on the optical axis of the associated optical subsystem, f and L being, respectively, the focal length and the width of the optical subsystems, where D is the length of the optical path.

10. A viewfinder according to any one of claims 2 to 7, wherein, along a first axis, said maximum allowed movement length (B) is zero and the view of the observer is binocular, the subscreens being placed symmetrically on either side of the main optical axis of the viewfinder, each sub-screen having a length along said first axis equal to fL / D, except the sub-screens farthest from the main optical axis having a length equal to f / D (L + y / 2), the subscreens being spaced edge to edge by a distance equal to L, f and L being, respectively, the focal length and the width of the optical subsystems, D being the length of the optical path.

11. A viewfinder according to any one of claims 2 to 7, wherein, along a first axis, said length in maximum allowed movement (B) is equal to an average difference between the two eyes (y) of a person and the view of the observer is binocular, the subscreens being placed symmetrically on both sides of the axis main lens of the viewfinder, each subscreen having a length along said first axis equal to fL / D, the subscreens being spaced edge to edge by a distance equal to L, f and L being, respectively, the focal length and the width of the optical subsystems, where D is the length of the optical path.

12. A viewfinder according to any one of claims 2 to 7, wherein, along a first axis, said maximum allowed movement length (B) is greater than an average distance between the two eyes (y) of a person, the the viewer is binocular and the device comprises a number Q of optical sub-systems and sub-projectors, the subscreens being placed symmetrically on either side of the main optical axis of the viewfinder, the centers of sub-screens being placed at a distance from each other equal to fL / D + L, each subscreen having a length along said first axis equal to f / D (L + By), within the limit of a zone d a dimension equal to QfL / D centered on the optical axis of the associated optical subsystem, f and L being, respectively, the focal length and the width of the optical subsystems, where D is the length of the optical path.

13. A viewfinder according to any one of claims 1 to 12, comprising an odd number of subscreens along said first axis, the illumination intensity of the sub-screen of rank i being equal to the illumination intensity of the central sub-screen (i = 1)

a'-i_ = arctan f (i - 1) L + - - arctan f (i - 1) L

VDVD 2f J f and L being, respectively, the focal length and the width of the optical subsystems, where D is the optical path length.

14. A viewfinder according to any one of claims 1 to 12, comprising an even number of sub-screens along said first axis, the illumination intensity of the sub-screen of rank i being equal to the intensity of illumination of the central subscreen (i = 1) multiplied by the following factor:

<¾_ =

15. Viewfinder according to any one of claims 1 to 14, wherein each sub-screen (24] _, 242, ··· '245) comprises a diode cell array electro ^¬ organic light.