WO2013174505A1

WO2013174505A1 - Display with double-image suppression

Info

Publication number: WO2013174505A1
Application number: PCT/EP2013/001493
Authority: WO
Inventors: Jérôme Wroblewski
Original assignee: Continental Automotive France; Continental Automotive Gmbh
Priority date: 2012-05-23
Filing date: 2013-05-21
Publication date: 2013-11-28
Also published as: FR2990907B1; FR2990907A1

Abstract

The invention relates to a display (1) including a transmitter element (6) such as a pixelated LCD screen for displaying a luminous pattern, arranged on the back surface of a display (8), a front transparent wall (2) positioned between the transmitter element and a user (11) viewing the transmitter element due to a direct light path (3) between the transmitter element and the eye of the user so that a double image or an optical replica can be formed due to an indirect light path (4, 5), the optical replica having a luminance L_ dblimg, wherein the double image area has a background luminance L such that the contrast CR, expressed as CR = (L_fond + L_dblimg)/ background L, is lower than a predetermined value such as 1.5.

Description

Display with dual image deletion

The present invention relates to display devices with dual image suppression, in particular a display device for a motor vehicle.

It relates more particularly to a display device 1 for a motor vehicle, as shown in Figure 1, comprising a display bottom surface 8 and a transmitter element 6 for displaying at least one pattern. This transmitting element 6, for example an LCD segment (abbreviation for "Liquid Crystal Display", ie a liquid crystal display), a matrix of pixels, a TFT screen (abbreviation for "Thin Film Transistor"). ", Ie a screen using" thin-film "field effect transistors), tell-tales, etc., is disposed on said display background surface 8. A transparent front wall 2 is interposed between the emitter element 6 and a user 11 observing the emitter element by means of a direct light path 3 between the emitter element 6 and the user's eye 11.

According to the prior art, illustrated in FIG. 1, the transparent front wall 2 has an inner surface 9 facing the emitter element 6, this inner surface of the pane being able to be inclined with respect to the surface of the window. 8. It follows that an indirect path 4, 5 of light can be formed between the emitter element 6 and the eye of the user 11. Said indirect path includes a first reflection on the inner surface 9 of the transparent front wall 2 and a second reflection on a bottom surface portion of the display 8, called "dual image area" 7 in which is formed an optical replica 6b of the transmitter element 6, as shown on Figure 1.

For some applications, the transparent front wall 2 must be coated with a semi-reflective layer. In this case, the visibility of said optical replica becomes annoying for the user, because of the greater intensity of the first reflection.

To overcome this drawback, the applicant proposes here a display device in which said replica has a luminance L_dblimg, and wherein said double-image zone has a luminance L_fond, the display device being remarkable in that the value of L_fond is such that the CR contrast of the double image area, expressed as CR = (L_fond + L_dblimg) / L_fond, is less than a predetermined value.

Thanks to these arrangements, it is possible to make invisible the optical replica in such a display device even though the transparent front wall has a semi-reflective layer.

In various embodiments of the invention, one or more of the following provisions may also be used: The contrast CR may advantageously be less than 2, preferably the contrast CR is less than 1.5; whereby the deletion of the double image is improved;

• the transmitter element is a pixelated LCD screen; which is a very flexible solution for displaying and adjusting the value of L_basic locally;

The transparent front wall may comprise a semi-reflective layer; so that a mirror effect can be obtained or an overlay display can be obtained;

• the reflection coefficient of the semi-reflective layer may be greater than 30% in the visible spectrum;

The device may further comprise an auxiliary transmission device arranged in front of the transparent front wall, adapted to generate an auxiliary optical image which is reflected on the transparent front wall and which is superimposed on the direct path coming from the transmitting element ; whereby a combined display with effect of depth is obtained;

The transparent front wall can be a glass pane or be made of transparent plastic material, which is a very economical solution;

The transparent front wall may comprise an outer surface provided with an antireflection treatment, which makes it possible to eliminate undesirable and multiple reflections between the inner and outer faces of the transparent front wall;

The double image zone may be configured to emit light such that the value of L_bond is greater than a predetermined threshold; whereby it is not necessary to use a specific light source;

The device may further comprise ambient lighting arranged between the transparent front wall and the bottom surface of the display, and configured to project light onto the bottom surface of the display, so that all double image phenomena globally, for all the emitting elements.

Other aspects, objects and advantages of the invention will appear on reading the following description of one of its embodiments, given by way of non-limiting example. The invention will also be better understood with reference to the accompanying drawings in which:

- Figure 1 shows schematically an optical display device according to the prior art.

FIG. 2 diagrammatically represents an optical display device according to the invention, and

- Figure 2A shows in detail the reflection zone. In the different figures, the same references designate identical or similar elements.

FIG. 1 represents a schematic side view of a display device, in particular for a motor vehicle according to the prior art, as discussed above.

FIG. 2 represents a schematic side view of a display device 1 according to the invention, in particular for a motor vehicle. A set of indicators comprises a plurality of indicator elements, transmitters of active or passive lights, in order to inform the driver and / or the occupants of the vehicle. In the illustrated example, a transmitter element 6, comprising at least one information pattern to be displayed, is configured to emit, when activated, light rays, in particular rays representing a direct light path 3 between transmitter element 6 and the eye of a user 11 or an observer.

In the example shown, the emitter element 6 is disposed on a bottom surface of the display 8, or close to it. The display bottom surface 8 faces the user 11 while the back panel 12 of the display is turned to the opposite direction.

In the example shown, the transmitter element 6 displays the current speed of the vehicle ("67 Km / h"), which information is constantly changing, which promotes the perception of the double image by the user because of the appearance dynamic information displayed.

In addition, the display device 1 comprises a transparent front wall 2 having at least a substantially flat portion interposed between the transmitter element 6 and the user. The direct path 3 passes through the transparent front wall 2 in the region of the substantially flat portion.

The transparent front wall 2, also called 'flange', can be a glass pane or a plastic blade or any other material. This transparent front wall 2 comprises an inner surface 9 and an outer surface 19. Preferably, the inner 9 and outer 19 surfaces are parallel to one another and flat. It is also possible to locally have a particular geometric layout to have a non-zero angle between the inner 9 and outer 19 surfaces, so as to create a favorable prismatic effect to eliminate in this area double-image type spurious reflections between the faces 9 and 19.

Advantageously, the transparent front wall 2 may comprise a semi-reflecting layer 9a, disposed on the inner surface 9 or outer 19. The semi-reflecting property of the transparent front wall may be dictated by the need for a mirror effect on this wall before transparent 2 when the transmitter elements 6 are all off (display device off). Another reason requiring a semi-reflective property of the transparent front wall 2 is the addition of an auxiliary transmission device 15, adapted to generate an auxiliary optical image 15i which, by reflecting on the transparent front wall 2, for to reach the eye of the user 11, along a path 25a, 25b is superimposed on the direct path 3 from the transmitter element 6. This auxiliary transmission device 15 is arranged under a cap 20 arranged above and forward relative to the display device 1 itself, that is to say on the side and away from the outer surface 19 of the transparent front wall 2.

The auxiliary transmission device 15 (device which can be integrated in a cap 20 equipped and also called "low-definition display") generates one or more auxiliary light patterns which are reflected on this semi-reflecting layer 9a (reflection noted K3 on the Figure 2A). By superimposing on the image of the emitter element 6, but with a longer optical path, the conjugate multiple images create a three-dimensional effect of depth display for the user.

For this reflection to be sufficient, the reflection coefficient of the semi-reflecting layer 9a will be chosen to be typically greater than 30% in the visible spectrum, preferably greater than 50%. This semi-reflecting layer can be obtained for example by a deposition of aluminum or aluminum-based compound.

In the example illustrated, the semi-reflecting layer 9a is disposed on the inner surface 9, but it could also be disposed on the outer surface 9.

More particularly, the transparent front wall 2 is inclined relative to the bottom display surface 8 at an angle of between 10 and 30 degrees, for example close to 20 degrees.

As explained above with regard to the phenomenon of the double image, an indirect path 4, 5 of light can be formed between the emitter element 6 and the eye of the user 11. Said indirect path 4, 5 comprises, after a first portion 5a, a first coefficient reflection K1 on the inner surface 9 of the transparent front wall 2 and, after a second portion 5b, a second coefficient reflection K2 on a bottom surface portion 8. In this area called "dual image area" 7, an optical replica 6b of the transmitter element 6 is formed. This optical replica 6b can be perceived by the user's eye 11 by means of the third portion 4 of this indirect path. Part of this third portion 4 of this indirect path is also reflected on the semi-reflective layer 9a.

More precisely, the optical replica 6b has a luminance L_dblimg, which results from the two aforementioned reflections:

L_dblimg = K1 x K2 x L_emiss, L_emiss being the luminance of the transmitter element 6 (for example 400 cd / m ² or more).

As indicated above, the semi-reflecting layer 9a has a coefficient greater than 30%, for example of the order of 50%. The same is true for the first reflection K1 which has a coefficient of the order of 50%, much higher than was usual in the prior art. The coefficient K2 is equivalent to what was known in the prior art, between 1% and 10%, typically 4%.

An optical replica of luminance is thus obtained:

L_dblimg = K1 x K2 x L_emiss,

namely 2% of L_emiss in the illustrated example.

To ensure that the double image 6b is not perceived by the user 11, especially at night, the luminance of the background is adapted in the area where the double image 6b is supposed to be created.

According to the invention, the double image zone 7 is configured to present a luminance of value L_fond such that the contrast CR of the double image zone 7, expressed by CR = (L_fond + L_dblimg) / L_fond, is less than a value predetermined.

According to a first alternative, the double image zone 7 is configured to emit a small quantity of light 17, such that L_fond is greater than a predetermined threshold. This can be achieved by controlling, by means of the LCD screen, a gray pixel color, on an area corresponding to the double image area. The borders 7a of the double image area 7 can be controlled so as not to create an edge and to "connect" continuously without significant gradient to the black background areas around the double image area 7.

Advantageously, the contrast CR is less than 2, preferably the contrast CR is less than 1.5. With this, the user does not perceive the double image, even in the night conditions which represents the most penalizing configuration.

According to a second alternative, there is provided ambient lighting 16 arranged between the transparent front wall 2 and the bottom surface of the display 8. This ambient lighting 16 is configured to project light onto the bottom surface of the display panel 8. the double image zone 7 so that the luminance L_fond is greater than the predetermined threshold indicated above. The ambient light source 16 is preferably hidden from the view of the user, behind the transparent front wall 2, in the lower part or in the upper part.

It should be noted that the bottom surface of the display 8 may be slightly grained. It should be noted that the outer surface 19 may include antireflection treatment to eliminate certain undesirable reflections from light objects outside the display device 1.

It should be noted that the transmitter elements 6 can be part of a single digital display 10 TFT active matrix or other.

Claims

Display device (1) for a motor vehicle comprising:

A bottom display surface (8),

A transmitting element (6) of at least one luminous pattern to be displayed, consisting of a pixelated LCD screen disposed on the bottom surface of the display (8),

A transparent front wall (2) having at least a substantially plane portion interposed between the emitting element (6) and a user (11) observing the emitter element (6) by means of a direct path (3) of light between the emitting element (6) and the user's eye (11), the transparent front wall (2) having an inner surface (9) opposite the emitter element (6), the inner surface (9) of the transparent front wall (2) being inclined with respect to the bottom surface of the display (8), so that an indirect path (4, 5) of light can be formed between the transmitting element ( 6) and the eye of the user (11), said indirect path (4, 5) having a first reflection (K1) on the inner surface (9) of the transparent front wall (2) and a second reflection (K2 ) on a display surface portion, said double image zone (7) in which an optical replica of the transmitter element (6) is formed, said replica an optic having a luminance of value L_dblimg,

characterized in that said double image area (7) has a luminance value L_fond such that the CR contrast of the double image area (7), expressed as CR = (L_fond + L_dblimg) / L_fond, is less than 1, 5 .

2. Display device according to one of claims 1, wherein the transparent front wall (2) comprises a semi-reflective layer.

3. Display device according to claim 2, wherein the reflection coefficient (K1, K3) of the semi-reflective layer is greater than 30% in the visible spectrum.

4. Display device according to one of claims 2 to 2, further comprising an auxiliary transmission device (15) arranged in front of the transparent front wall (2), adapted to generate an auxiliary optical image (15i) which is reflected on the transparent front wall (2) and which is superimposed on the direct path (3) coming from the transmitting element (6).

5. Display device according to one of claims 1 to 4, wherein the transparent front wall (2) is a glass pane or transparent plastic material.

6. Display device according to one of claims 1 to 5, wherein the transparent front wall (2) comprises an outer surface (19) provided with antireflection treatment.

The display device according to one of claims 1 to 6, wherein the dual image area (7) is configured to emit light such that L_fond is greater than a predetermined threshold.

8. Display device according to one of claims 1 to 6, further comprising ambient lighting (16) arranged between the transparent front wall (2) and the bottom display surface (8), and configured to project light on the bottom surface of the display (8).