FR3008198A1 - VISUALIZATION DEVICE COMPRISING A SCREEN-CONTROLLED TRANSPARENCY SCREEN WITH A HIGH CONTRAST - Google Patents

Abstract

The general field of the invention is that of display devices comprising optical means for forming an image from an image source on a transparent screen (2), said transparent screen being arranged for operational use between an external landscape and a user. The display device according to the invention comprises a mirror (3) with controlled reflection disposed between the external landscape and said transparent screen.

Description

The field of the invention is that of visualization systems cockpits of civil and military aircraft with transparent screens.

Currently, the dashboards of modern aircraft cockpits have on most of their surface viewing screens and instruments, reducing the direct vision of the outdoor landscape in the lower cockpit area. In a number of applications, including low-level visual flight, this lack of direct vision can be troublesome. To solve this problem, it is possible to use transparent display screens placed in the field of view of the user and which project an image superimposed on the external landscape. The advantage of these screens is that it is possible to obtain large viewing surfaces visible in a large field of view at lower costs than collimated systems of the type "Headshot High". The display device then comprises an image source and a focusing optics that project this image onto the transparent display screen.

The transparent screen can be passive. In this case, it always retains the same photometric properties of transmission and diffusion. Generally, these passive transparent screens consist of a transparent surface having regularly distributed diffusing patterns.

The transparent screen can be active or transparently controlled. Under the effect of an electrical signal from control means, the screen changes from the transparent state to the diffusing state. The type of screens "PDLC", acronym meaning "Poly Dispersed Liquid Crystal", present this type of property.

By nature, these transparent display screens are necessarily diffusing so that the emitted or re-transmitted image can be perceived by the user in a sufficient field of view. In flight, the solar illumination of the cockpit can be very important. The sunlight scattered by the screen strays the main image and greatly reduces its contrast and readability. The classic solution to improve the contrast of the information presented on a screen is to increase the luminance of the screen. This implies a significant reserve of light power and therefore a significant power consumption of the viewing equipment. The luminance can also be increased in the pilot axis by channeling the luminous flux in a preferred direction, which reduces the cone of visibility. In any case, these solutions are limited by the saturation of the eye. Under strong lighting, the reflection of the sun can dazzle the pilot regardless of the luminance level of the image from the transparent screen. A last solution is to have sunshades in the cockpit. This solution is not satisfactory because it reduces the visibility of the outside world or the screen in certain areas. To remedy these drawbacks, the display device according to the invention comprises a mirror with controlled reflection disposed between the external landscape and the transparent screen. Thus, depending on the operational use and / or the degree of sunshine, this mirror is perfectly reflective, semi-reflective or transparent so as to offer the best possible comfort of use of the display device. More specifically, the subject of the invention is a display device comprising optical means making it possible to form an image originating from an image source on a transparent screen, said transparent screen being arranged for operational use between an outside landscape and a user. , characterized in that the display device comprises a mirror with controlled reflection disposed between the external landscape and said transparent screen. Advantageously, the transparent screen operates by reflection and diffusion of the image or by transmission and diffusion of the image.

Advantageously, the image is reflected by the mirror with controlled reflection and transmitted and diffused by the transparent screen. Advantageously, the transparent screen is an active liquid crystal display dispersed polymers that can be, on command, transparent or diffusing. Advantageously, the display device comprises three modes of operation which are: - Mode 1: the transparent screen has a maximum diffusion and the mirror with controlled reflection is totally reflective; - Mode 2: the transparent screen has a partial diffusion and the mirror with controlled reflection is semi-reflective; - Mode 3: the transparent screen and the mirror with controlled reflection both have a maximum transmission. Advantageously, the transparent screen is a passive screen 15 comprising a transparent face having regularly spaced diffusing patterns. Advantageously, the device comprises means for detecting the presence of fingers of a user in contact with or in the vicinity of the transparent screen, said means comprising optical recognition means or a transparent tactile surface. The invention will be better understood and other advantages will become apparent on reading the following description given by way of nonlimiting example and with reference to the appended figures in which: FIG. 1 represents a first variant embodiment of a display device according to the invention comprising a mirror with reflective reflection in reflective mode; FIG. 2 represents the preceding variant, the mirror with controlled reflection being in semi-reflective mode; FIG. 3 represents the preceding variant, the mirror with controlled reflection being in transparent mode; FIG. 4 represents a second variant embodiment of a display device according to the invention comprising a mirror with reflective reflection in reflective mode; FIG. 5 represents a third variant embodiment of a display device according to the invention comprising a mirror with reflective reflection in reflective mode.

As seen in the various figures, the display device according to the invention comprises optical means 1 for forming an image from a display on a transparent screen 2. The display may be monochrome or color. The system according to the invention can be adapted to all types of displays. Generally, the display is small, not exceeding a few centimeters. His resolution is important. It usually includes a passive matrix modulator and a powerful lighting source. The modulator may be a liquid crystal matrix called "LCD" or an electromechanical modulator with micro-mirrors or "MEMS". The sources of illumination may be light-emitting diodes, lasers or arc lamps. The projection optics on the transparent screen is conventional optics having a large magnification so as to form a very enlarged image of the display on the front face of the display screen. To ensure a compact solution, the use of a compact projector with wide-angle projection and short focusing distance called "short throw projector" is possible. The display screen can be either passive or active. If it is passive, it consists of a transparent surface with diffusing patterns regularly distributed. These patterns may include a reflective treatment. The screen can be active or transparently controlled. For example, the active screen is of the "PDLC" type, which stands for "Poly Dispersed Liquid Crystal". It comprises a layer of liquid crystal mixed with polymers, said layer being encapsulated between two transparent electrodes 30, the optical transparency and the optical diffusion of the layer being controlled by a control voltage applied to said electrodes. This voltage is of the order of a few volts to a few tens of volts depending on the thickness of the layer and the properties of the liquid crystal. It is delivered by control means according to commands from the user.

The PDLC film is encapsulated between two glass slides having undergone a treatment to optimize its optical performance and in particular its optical transmission. The face seen by the driver receives antireflection treatment to minimize specular reflections. The rear face is processed to reflect light rays coming from outside the cockpit that can create spurious reflections that can hinder the readability of the information displayed. In the absence of voltage between the two electrodes, the material is white, diffusing. It behaves like an optical diffuser that will broadcast the projected image. If a sufficient control or switching voltage is applied, the material becomes transparent. Thus, in the context of aeronautical applications, when the pilot wishes to have the best possible vision of the outside, he controls the device so that the screen is perfectly transparent. When it wishes to have control and navigation information, the screen becomes broadcast again and the desired information is projected. It is understood that, by nature, these transparent display screens are necessarily diffusing so that the emitted or retransmitted image can be perceived by the user in a sufficient field of view. In flight, the solar illumination of the cockpit can be very important. To limit scattered sunlight and maintain a correct view of the information displayed, the display device includes a mirror with controlled reflection disposed between the outer landscape and said transparent screen. This mirror is also known as "switchable mirror". For example, a mirror with controlled reflection can be achieved by means of a liquid crystal film controlled by a voltage. Depending on the voltage level, the mirror may be totally reflective, semi-transparent or totally transparent. Thus, on demand, the luminance of the external landscape can be totally or partially attenuated so as to preserve, regardless of the light environment, a good readability of the information displayed by the transparent display screen. The mirror is of sufficient size that, when the display device is operational, seen by the user, the mirror masks the display screen. As a first exemplary embodiment, FIGS. 1, 2 and 3 show a first variant embodiment of a device according to the invention in three different modes of operation. In these figures and the following, the cockpit is symbolized by a transparent canopy 10. In this first variant, the transparent screen operates by reflection. It reflects and diffuses the light from the optical means to the eye Y of an observer. The mirror 3 is disposed between the canopy 10 and the transparent screen 2. If the transparent screen is controlled transparency, it is therefore possible to vary simultaneously and independently the reflection ratio of the mirror and the transmission rate. of the transparent screen. However, the display device has three privileged modes of operation which are: Mode 1: the transparent screen has maximum diffusion and the mirror 3 is totally reflective. This mode is illustrated in Figure 1. The vision of the outside is removed and the display device projects the image on the transparent display screen. The image is perfectly contrasted. This mode is used when the pilot is flying instruments and does not need vision from the outside; - Mode 2: the transparent screen has a partial diffusion and the mirror with controlled reflection is semi-reflective. This mode is illustrated in FIG. 2. This mode is used when the driver wishes to have both information from the display device and at the same time to maintain a certain vision of the outside. It is possible to adjust the mirror transmission according to the luminance of the outdoor landscape so as to maintain a good contrast of the projected image. This adjustment can be manual or automatic depending on the external sunlight; - Mode 3: the transparent screen and the mirror with controlled reflection both have a maximum transmission. This mode is illustrated in Figure 3. In the latter mode, no more image is projected on the transparent screen. We privilege the vision of the outside. This mode is used for visual flight. In a second variant shown in FIG. 4, the transparent screen 2 operates by transmission. It transmits and diffuses the light from the optical means to the eye Y of an observer. The mirror 3 is disposed between the canopy 10 and the transparent screen 2. Of course, it is possible to operate this display device in the three previous modes of operation. This device differs essentially from the previous one by constraints of size and positioning of the elements of the different display device. Finally, in a third variant shown in FIG. 5, the transparent screen 2 also operates by transmission but the image is reflected by the mirror 3 with controlled reflection before reaching the transparent screen 15. In this case, the mirror 3 is an integral part of the optical combination of the display device. It is possible to give it some curvature to reduce the overall size of the display device. In this last variant, the mirror modulates both the transmission of the external landscape and the reflection of the projected image.

The display device may include means for detecting the presence of fingers of a user in contact with or in the vicinity of the transparent screen so as to ensure a tactile interface with the transparent screen. As a first example, said means comprise optical recognition means comprising a system of transmitters and receivers housed in the holding structure of the display screen. As a second example, said means comprise a transparent tactile surface that operates by resistive or capacitive detection.

Claims (10)

REVENDICATIONS1. A display device comprising optical means for forming an image from an image source on a transparent screen (2), said transparent screen being arranged for operational use between an external landscape and a user, characterized in that the device display comprises a mirror (3) with controlled reflection disposed between the external landscape and said transparent screen. 2. Display device according to claim 1, characterized in that the transparent screen (2) functions by reflection and diffusion of the image. 3. Display device according to claim 1, characterized in that the transparent screen (2) operates by transmission and diffusion of the image. 15 4. Display device according to claim 3, characterized in that the image is reflected by the mirror (3) with controlled reflection and transmitted and diffused by the transparent screen. 20 5. Display device according to claim 1, characterized in that the transparent screen is an active liquid crystal display dispersed polymers which can be, on command, transparent or diffusing. 6. Display device according to claim 5, characterized in that the display device comprises three modes of operation which are: - Mode 1: the transparent screen has a maximum diffusion and the mirror with controlled reflection is totally reflective; Mode 2: the transparent screen has partial diffusion and the mirror 30 with controlled reflection is semi-reflective; - Mode 3: the transparent screen and the mirror with controlled reflection both have a maximum transmission. 7. Display device according to claim 1, characterized in that the transparent screen is a passive screen comprising a transparent face having regularly spaced diffusing patterns. 8. Display device according to one of the preceding claims, characterized in that the device comprises means for detecting the presence of fingers of a user in contact with or in the vicinity of the transparent screen. 9. Display device according to claim 8, characterized in that said means comprise optical recognition means. 15 10. Display device according to claim 8, characterized in that said means comprise a transparent tactile surface. 10