HK1088397B - Optical device with dual function of illumination and forming a figurative image - Google Patents

Description

Optical device with dual functions of illuminating and forming graphic images

Technical Field

The invention relates to an apparatus having at least one display area and comprising an optical device comprising a light guide, a portion of which is arranged to at least partly overlap with respect to the display area. The light guide has two large faces and at least one side face, and light extraction (optical extraction) features are provided in the region of the light guide portion arranged to overlap with respect to the display area. The optical device further comprises at least one light source arranged towards the side in a predetermined direction for emitting light into the light guide and cooperating with the extraction member for at least partially illuminating the display area.

Background

Devices comprising devices of this type are known from the prior art. By way of example, U.S. Pat. No.6,752,505 issued to Solid State Opto Limited on 22.6.2004 discloses a transparent film for use as a light guide for uniformly scattering light from a quasi-point light source. According to this document, optical elements may optionally be provided within the light guide to extract the light and direct it towards a Liquid Crystal Display (LCD). The main object of this document is to obtain a uniform illumination of the maximum possible intensity from the light emitted by the light source, the illumination obtained having a good compromise between sharpness and softness, since the scattering is optimized. This patent discloses how scattering can be optimized in terms of the available light sources and the surface to be illuminated, due to the distribution of the optical light extraction elements over the entire surface of the light guide.

This type of system can be used to illuminate an LCD by front or back illumination without causing the resulting display device to be too thick. However, the above document does not provide any other application or use of this type of device.

Disclosure of Invention

The main object of the present invention is to improve the known solutions of the prior art by providing an optical device, particularly for portable devices, which on the one hand illuminates the display area and on the other hand displays a luminous decorative pattern, without increasing the complexity of the structure and thus the manufacturing costs of the corresponding optical device.

The invention therefore provides in particular an apparatus of the above-mentioned type. In particular, a device having at least one display screen forming a display area and comprising an optical device comprising a light guide, a portion of which at least partially overlaps with respect to said display screen, said light guide having two large faces and at least one lateral face, said portion of the light guide comprising light extraction means, said optical device further comprising at least one light source arranged in the vicinity of said lateral face and oriented in a predetermined direction to emit light into said light guide and cooperating with said extraction means to at least partially illuminate said display screen, characterized in that the light guide further comprises at least one first set of light extractors arranged on one of the large faces. Each light extractor has a predetermined geometric feature comprising at least one light extraction surface. The set of light extractors is used to extract light from the light guide to form a graphical image in a direction similar to the direction in which the display area can be viewed. The graphical image is defined directly as a function of the geometric features of the light extractor, in particular due to the interaction of the light with the extraction surface.

Thanks to these particular features, the light-guiding means of the device according to the invention can form a luminous graphic image in addition to performing the basic function of illuminating the display area of the device. The graphical image formed may have a simple gaming, aesthetic or decorative effect, or may be used to provide information to the user of the device.

Preferably, the light extraction elements for illuminating the display area are also light extractors, which each comprise at least one extraction surface and are arranged in a second group.

The extractor can be made to extract light from the light guide by refraction or preferably by reflection.

Examples of applications in which the invention is particularly important are the following cases: in which the device of the invention is a portable electronic device of the electronic watch, portable telephone or camera type, advantageously provided with a display screen of the LCD type.

In these particular cases, therefore, the invention can be applied to the illumination of an LCD screen on the one hand and the formation of graphic images on the other hand, with the provision of only one light guide and possibly only one light source. In a watch with a completely analog display, the invention can also be used to illuminate the dial.

In a preferred embodiment, a first set of light extractors used to form the graphic image may be used to display information related to the operation of the apparatus. For example, in the case of a watch, a bell symbol may be displayed to indicate operation in an alarm mode. In the case of a telephone or camera, the light extractor may be used to indicate the function of the control member, which may be made of an optically transparent material.

A number of variations of the above-described device can advantageously be provided.

In particular, multicoloured graphical images may be formed by using multiple sets of extractors or extractor grids (networks) in the light guide, each set of extractors being associated with its own light source.

Further, a monochrome or multicolor animation can also be displayed by sequentially supplying power to the light sources based on the above-described variation.

Multiple sets of extractors can be disposed in different regions of the lightguide or interleaved in the same region. Alternatively, or in addition, two or more light guides may be arranged one above the other, each light guide carrying at least one set of extractors.

Other variations will be described in the detailed description below.

Drawings

Further characteristics and advantages of the invention will become clearer from the following detailed description of a specific embodiment, made by way of non-limiting example with reference to the accompanying drawings, in which:

fig. 1 shows an exploded perspective and schematic view of a display component of an analog timepiece according to a first preferred embodiment of the invention;

figure 2 shows a cross-sectional view of the element shown in figure 1;

FIG. 2b is a view similar to FIG. 2, showing an alternative embodiment in which the light sources are oriented perpendicular to one of the large faces of the light-guiding device;

figures 3a, 3b, 3c and 3d schematically show examples of images formed in succession to produce an animation.

Detailed Description

Fig. 1 and 2 schematically show a perspective view and a cross-sectional view, respectively, of a light guide device 1 according to the present invention.

Fig. 1 shows a possible arrangement of the light-guiding device 1 in a timepiece, i.e. between the dial 2 and the display hands, which are not shown for the sake of simplicity. The dial 2 is of a conventional type and has a time scale 3 for indicating the position of the hours and a substantially rectangular window for presenting an LCD-type screen 4.

The dial and the light guide respectively comprise central holes 6 and 7 which allow the passage of the driving means of the hands, i.e. the hour wheel and minute wheel, not shown.

In the embodiment shown in fig. 1, the light-guiding device 1 cooperates with three diodes 8, which may be of the same colour or of different colours, which function to form, on the one hand, a luminous graphic image visible above the dial 2 of the timepiece and, on the other hand, to illuminate the LCD screen 4.

From a basic principle, a single diode 8 in combination with a light extractor grid as described below is sufficient to form a graphic image. Furthermore, this single diode is also sufficient to ensure that the LCD screen 4 is illuminated at the same time.

Preferably, the light coupling between the light beam emitted by each diode 8 and the light-guiding device 1 is effected via an entry face 9. In this example, the entrance faces 9 each have the shape of a substantially cylindrical portion, so that the light beam emitted by the diode is refracted at the entrance into the light guide. Therefore, the angular spread (angular aperture) of each light beam is increased, so that most of the surface of the light guide device can be covered.

The light-guiding device 1 has two main large faces 10 and 11, as shown in fig. 1, which are substantially disc-shaped and are connected to one another by a side face 12 which is generally annular, by way of non-limiting example. The light entrance face 9 is arranged in the side face 12.

The principle of operation of the optical system described with reference to fig. 1 is illustrated in fig. 2, in which the elements described above are shown in a section along the plane marked by the letter a, which section intersects the two diodes 8 and the two sets of light extractors. Plane a contains line II-II and intersects the two major faces 10 and 11 to form a right angle.

According to the invention, the light-guiding device 1 comprises a plurality of light extractors 20 arranged in a first group and on a large face 11 located on one side of the dial 2.

The light extractors 20 each have at least one reflective surface 21 and are distributed in a predetermined grid above the large face 11, defined to correspond to an accurate graphic image, as described below.

The reflecting surface 21 has a normal (n) oriented at some predetermined angle toward the corresponding diode 8. Thus, a proportion of the light beam emitted by the diode 8 is either directly incident on the reflecting surface 21 or, after one or more pre-reflections on at least one of the large surfaces 10 and 11, strikes the reflecting surface 21.

The proportion of the light beam that interacts with the reflecting surface 21 can be adjusted according to the specific geometrical parameters of a given extractor, in particular according to the distance of the diode 8 from the reflecting surface 21 and the height of the light extractor 20 relative to the thickness of the light guide 1. The person skilled in the art does not encounter any particular difficulty in adapting these parameters as required.

As a component for illuminating the LCD screen 4, light extractors 20 are also arranged in close proximity to the second group of LCD screens 4. In the example shown in fig. 1 and 2, the set of light extractors 20 for illuminating the screen 4 is arranged above the screen 4 and extends over a surface which is much larger than the surface occupied by the screen. The light extractors are regularly arranged with their respective reflecting surfaces 21 all facing the diode 8 arranged at 6 o' clock. The person skilled in the art does not encounter any particular difficulty in optimising the number, size and position of the second set of light extractors in view of the characteristics of the LCD screen in order to illuminate the LCD screen sufficiently and uniformly.

However, for this particular embodiment of the invention, all of the light extractors of the first set, i.e., the light extractors used to form the predetermined pattern image, have substantially the same angle relative to the large face 11. As a result of this feature, the beams impinging on the reflective surface 21 of the grid are all deflected in the same direction. Thus, each reflective surface 21 of the grid forms a reflected beam. All of the reflected beams form a grid of beams, producing a graphical image in a given direction.

In the particular case shown in fig. 2, the angle between the reflecting surface 21 and the large surface 11 is substantially 45 degrees, so that a graphic image is formed in a direction substantially perpendicular to the large surface. Thus, when the person wearing the timepiece according to the invention looks at the dial in a substantially normal direction, the luminous image can be seen, provided of course that the diode 8 is powered.

Of course, the present invention is not limited to forming graphical images in a direction perpendicular to the dial. For example, it is contemplated that the graphic image may be formed in a direction at an angle of about 60 degrees relative to the dial in the direction of the 6 o' clock position to allow the user to see the image without having to rotate the forearm to a great extent.

In general, the direction of the patterned image can be adjusted by the angle which the reflecting surface makes with respect to the incident light beam, the normal (n) of the reflecting surface corresponding to the bisector of the direction of the reflecting surface of the diode on the one hand and the viewing direction of the reflecting surface on the other hand.

The light-guiding device 1 can be made of any material having the desired characteristics, including in particular transparency with respect to light propagation, in particular in the visible region. Preferably, the light guide can be made of plastic material of the PMMA type by injection molding, replication or any other suitable method, which has the advantages mainly in that the corresponding manufacturing method is simple and the cost price of the obtained product is low.

Following the foregoing description, it should be understood that reflective surface 21 constitutes a set of pixels used to form a graphic image. Therefore, the smaller the size of the reflecting surface, the better the image resolution and quality.

As already mentioned, it should be noted that the higher the light extractor is, the larger its effective surface is, and thus the larger the amount of light extracted from the light guide at the respective location. Thus, the luminous intensity of each reflected beam can be finely adjusted by the characteristics of the corresponding light extractor. On the basis of this adjustment, a "gray-scale" graphic image (within the color of the diodes used) can be formed based on a single light source.

With current manufacturing techniques, it is possible to envisage manufacturing light extractors with dimensions of the order of 10 μm, which makes it advantageously difficult for the user of the device to see the light extractor when it is not illuminated. Also, the reflective surface 21 may have a variety of shapes, such as a flat or curved shape to adjust the form of the reflected beam and to make the beam slightly divergent.

Preferably, the light extractors belong to the same grid having at least one common geometrical feature, i.e. the normal of the reflecting surface of the light extractor is contained in a plane perpendicular to both the light guide 1 and the respective entrance face 9. This feature, illustrated in figure 1, ensures that the light extraction is optimal, which is more advantageous from the point of view of the power consumption of the timepiece using the light decoration of the invention.

When the device according to the invention is implemented in the form of an electronic watch, the first set of light extractors may be arranged to display graphic images representing a watch function. Indeed, as a non-limiting example, in response to the activation of a control component of the watch, the alarm mode may be activated and the alarm trigger time may be displayed on the LCD screen 4 for a period of time. In this case, the light extractor may be arranged as a grid so as to display a mark "AL" over a predetermined area of the dial plate to indicate to the user the nature of the information displayed on the LCD screen 4 while the alarm time is displayed on the LCD screen 4. Alternatively, the first set of light extractors may be arranged to visualize a graphical image representing a clock.

Also, when the watch has a timekeeping function, a mark "CHR" or a symbol representing that a person is running may be displayed to indicate to the user that the LCD screen 4 is indicating the measurement time.

When the device according to the invention is implemented in the form of a telephone or a camera, the device may also have a number of control elements on one face with an LCD-type display. In this case, the first set of light extractors may be arranged to form a predetermined graphic image on the control member when the second set of light extractors are arranged relative to the LCD display to illuminate the LCD display. In the case of a telephone, for example, it is conceivable to form in this way conventional markings for the keys used for dialing a telephone number, in particular the numerals 0 to 9. Any structural elements located between the light guide and the keys must be transparent so as not to prevent the light beams reflected by the light extractors from passing through. These features advantageously allow phone manufacturers to make a single dial key model for a given phone model, rather than individually marking keys as is done with today's phones. The above description of the phone can of course also be applied in a similar way to the camera.

In general, one skilled in the art will be able to use multiple light sources according to particular needs. In particular, a single light source may be used to illuminate a first set of light extractors to form a graphic image and a second set of light extractors to illuminate a display area without departing from the scope of the present invention.

The arrangement shown in fig. 1 uses a light guide 1 illuminated by three light sources, advantageously enabling the formation of a multi-colour image.

To this end, the light sources emit light radiation of different colors, each light source being associated with its own light extractor grid.

According to a simple variant, each of the three light extractor grids can be arranged in an area of the light guide 1 which is located in the vicinity of the diode 8 associated with the light extractor grid, as shown in fig. 1.

Alternatively, each of the three grids may extend over a substantial portion of the entire surface of the light guide, and the grids may be interwoven. An example of a graphical image obtained by this configuration will be described below in conjunction with the detailed description of fig. 3a, 3b, 3c and 3 d.

Fig. 3a-3c schematically show the graphical images formed by each of three light extractor grids cooperating with a given light source.

The timepiece corresponding to fig. 3 comprises three diodes 8 arranged substantially opposite to the 4 o ' clock position (8 a in fig. 3), the 2 o ' clock position (8 b) and the 10 o ' clock position (8 c). A fourth diode 8d is also shown, which diode 8d together with a second set of light extractors, which are not shown in fig. 3 for the sake of clarity, illuminates the LCD screen 4.

Each of the diodes 8a, 8b and 8c is associated with a given light extractor grid. Fig. 3a shows the resulting graphical image seen by a person wearing a watch according to the present embodiment when a diode 8a is powered to emit light in the direction of the mesh associated with that diode 8 a. Likewise, fig. 3b and 3c show graphic images respectively formed when the diodes 8b and 8c are operated. Fig. 3d shows a multi-colour graphic image formed when the three diodes 8a, 8b and 8c are simultaneously powered.

Based on this 3-diode structure with three interleaved light extractor grids, a variety of operating modes can be provided.

For example, the electronic circuit of the watch according to the invention can be programmed so as to simultaneously supply the three diodes 8a, 8b and 8c in response to the actuation of the control member by the user. The advantages of the functionality obtained exceed simple aesthetic improvements, since the graphic image formed is luminous, so that the position of the hands can be seen also by the person wearing the watch in dark conditions.

Alternatively or additionally, the electronic circuit of the watch can be programmed to supply the diodes 8a, 8b and 8c in turn in response to a different activation of the control member or in response to the activation of an additional control member. It will of course be clear that the invention is not limited to the nature and mode of operation of one or more of the control members.

As an example, the three diodes may be powered simultaneously in response to a shock detected by an accelerometer disposed within the watch.

With the sequential mode of operation, a multi-color animation, i.e., an illuminated firework in the example shown in fig. 3a-3d, may be displayed.

Fig. 3a shows a first graphic image of the animation obtained by the cooperation of the light beam emitted by the first diode 8a with the first light extractor grid. The person wearing the watch can see from the top of the dial a luminous graphic image representing the trajectory left by the fireworks during their release.

Fig. 3b shows a second graphical image of the animation obtained by the cooperation of the light beam emitted by the second diode 8b with the second light extractor grid. A person wearing the watch can see a luminous graphic image representing the main deflagration event of the fireworks ignited in the first stage of fireworks.

Fig. 3c shows a third graphical image of the animation, obtained by cooperation of the light beam emitted by the third diode 8c with a third light extractor grid. The person wearing the watch can see a luminous graphical image representing the secondary deflagration of the fireworks.

Thus, when the three diodes 8a, 8b and 8c are supplied in sequence, the person wearing the watch can see the ignited fireworks and the two subsequent deflagrations.

Of course, those skilled in the art will be able to provide different variations of the animation just described without departing from the scope of the invention. For example, after displaying the third graphic image of the animation described above, the three diodes 8a, 8b and 8c may be powered simultaneously to form a complete image of fireworks.

It is noted that in the embodiment shown in fig. 3a-3d the first and second set of extractors partly overlap, which can be seen by partly covering the pattern portion of the LCD screen 4. In this case, the person skilled in the art does not encounter any particular difficulty in arranging each light extractor of a group of light extractors such that the light beam reflected by the light extractor is not disturbed by one or more light extractors of other groups.

Furthermore, based on the above description, numerous variants of a timepiece with a luminous pattern display according to the invention can be provided.

As an example, two light extractor grids may be provided on the same waveguide device, wherein the reflection directions of the light beams are different. In this case, two different graphic images are formed which can be seen from two different positions. According to an alternative embodiment, the angle between the two reflection directions should be such that the two images formed constitute a perspective view when the eyes of the observer are at a given distance above the light-guiding means.

The above description corresponds to a preferred embodiment of the invention and should in no way be considered limiting, in particular with regard to the described properties and structure of the device, in particular the presence of an LCD screen, the nature and number of control members used or the position of the diodes. Also, the invention is not limited to the described modes of operation and means for initiating the modes of operation, as these parameters can be varied by suitable programming of the control circuit. The person skilled in the art does not encounter any particular difficulty in modifying the operation of the device according to the invention to meet their specific needs.

According to a variant shown in fig. 2b, diodes 8 are used as the respective light sources oriented perpendicularly to the large face 11 of the light-guiding device 1, i.e. the direction of the light rays emitted by the light sources is substantially vertically upwards, whereas in the embodiment shown in fig. 2a the direction of the light rays emitted by the diodes 8 is substantially perpendicular to the side faces 12.

Here, the diode 8 is arranged below the light guide 1 and still close to the side face 12. The entry face 9 is parallel to the large faces 10, 11. Preferably, the peripheral portion 60 of the top major face 10 of the light guide 1 is curved towards the bottom major face 11, so that light rays emitted by the diode 8 towards the periphery of the light guide 1 can be totally reflected on the peripheral portion 60 and directed towards the reflective surface 20 associated with that diode 8.

This variant makes it possible to use as the diodes 8 top light-emitting diodes which are mounted with respect to the face of the printed circuit board, unlike side light-emitting diodes.

Many variants can be adopted without departing from the scope of the invention, for example without the presence of a dial in the watch, the light-guide device directly functioning as a dial, the drive train of the hands being modified to have an attractive appearance for the person wearing the watch. Furthermore, the light guide may of course be arranged below the display area and illuminate the display area by transmission.

Furthermore, the present invention is not limited to the use of reflective light extractors. It should be noted in particular that light extractors of the refractive type are also suitable as means for illuminating the display area. However, reflective light extractors are preferred for forming graphic images because they provide greater flexibility, particularly from the standpoint of the exit angle of the light beam from the light guide.

Other features may also be provided without departing from the scope of the invention, such as covering the sides of the light guide other than the entrance face with a reflective coating to limit light loss due to light beams reaching the sides and tending to exit the light guide.

Claims (13)

1. An arrangement having at least one display screen (4) forming a display area and comprising an optical device comprising a light guide (1) having a portion at least partially overlapping with respect to said display screen (4), said light guide having two large faces (10, 11) and at least one side face (12), said portion of the light guide comprising light extraction means (20), wherein said light guide further comprises at least one first set of light extractors arranged on one of said large faces and each having a predetermined geometrical feature comprising at least one light extraction face (21), said set of light extractors extracting light from said light guide to form a graphical image in a direction similar to the direction in which said display screen can be seen, said graphical image being directly defined as a function of said geometrical feature due to interaction of light on said extraction face (21), the optical device further comprises at least one light source (8, 8a, 8b, 8c, 8d) arranged near said side surface (12) and oriented in a predetermined direction for emitting light into said light guide and cooperating with said extraction means (20) for at least partially illuminating said display screen (4), characterized in that said light extraction means (20) for illuminating the display area are also light extractors each having at least one light extraction surface (21) and being arranged in a second group.

2. A device according to claim 1, characterized in that the light source (8, 8a, 8b, 8c, 8d) is arranged to face the side surface (12) in a predetermined direction for emitting light into the light guide and cooperates with the extraction member (20) for at least partly illuminating the display screen (4).

3. A device according to claim 1, characterized in that the light source (8) is oriented in a vertical direction to one of said large faces (10, 11).

4. Device according to claim 1, characterized in that said light extractor (20) for forming said graphic image is arranged on one large face (11) opposite to the large face through which light is extracted and said graphic image is formed, said extraction faces of said first group being reflective faces.

5. A device according to claim 4, characterized in that said light extractors (20) of said second group are arranged on a large face (10) furthest from said display screen (4), each of said light extractors of said second group also having at least one reflecting face (21).

6. The apparatus of claim 1, wherein said first and second sets of light extractors are disposed in different regions of said light guide.

7. The apparatus of claim 1, wherein said first and second sets of light extractors are disposed in an overlapping region of said light guide.

8. The apparatus of claim 1, wherein said optics include an additional light source that emits light into said light guide to interact with said first set of light extractors having light extraction surfaces oriented in a different direction than said light extraction surfaces of said second set of light extractors.

9. A device according to claim 1, characterized in that the display is a liquid crystal display (4).

10. Device according to claim 1, characterized in that the device is a mobile telephone comprising a display and a control member for dialing which is at least partially transparent and is arranged on one face of the telephone, the display being illuminated by the light extractors of the second group and the control member being provided with a marking formed by reflection of light on the light extractors of the first group.

11. Device according to claim 1, characterized in that it is an electronic watch comprising a dial (2) at least partially illuminated by the light extractors of the second group, while the light extractors of the first group are intended to display a predetermined graphic image in an area of the dial.

12. Device according to claim 11, characterised in that said dial (2) has at least one portion for a liquid crystal display (4) illuminated by said second set of light extractors.

13. Device according to claim 11 or 12, characterized in that said graphic images represent a specific operating mode of said electronic watch, said light extractors of said first group being illuminated when said operating mode is activated.