DEVICE FOR EMITTING FLASH LIGHT

A device for emitting flash light is specified.

One object to be achieved is to provide an improved device for emitting flash light, for example a device with reduced build-in depth.

This object is achieved, inter alia, by the subject-matter of the independent claim. Advantageous embodiments and further developments are subject of the dependent claims and can further be extracted from the description and the figures.

According to at least one embodiment, the device for emitting flash light comprises at least one light source for producing flash light. The light source may comprise one or more optoelectronic semiconductor components, like LEDs or laser diodes. The flash light produced by the at least one light source is, for example, visible light, particularly white light .

According to at least one embodiment, the device comprises a light guide. The light guide is configured to transport or guide the flash light from the at least one light source. For example, the light guide comprises or consists of plastic. The light guide may have the form of a platelet. For instance, the light guide is a solid body. It may be formed in one piece. Particularly, the light guide is configured to guide the flash light by means of total inner reflection (TIR light guide) . According to at least one embodiment, the device comprises an exit area for coupling out flash light from the device. The exit area is, in particular, a dedicated area of the device which is transparent or translucent for visible light and/or for the flash light of the at least one light source. For example, in plan view onto the exit area, the exit area has the form of a circle or a rectangle.

According to at least one embodiment, the light guide comprises an inlet side which faces the light source. For example, a main emission side of the light source faces and is parallel to the inlet side of the light guide. The main emission side of the light source is the side of the light source via which the major part of the emitted flash light is emitted .

The light source, particularly the main emission side thereof, may touch the inlet side of the light guide. Alternatively a gap is formed between the inlet side of the light guide and the light source. The extension of the gap, measured perpendicularly to the inlet side, is, for example, at most 0.3 mm or at most 0.1 mm.

According to at least one embodiment, the light guide comprises an outlet side which faces the exit area. The outlet side may be a main side of the light guide, i.e. a side with the largest extension. Particularly, the outlet side may be parallel to a main extension plane of the light guide. The inlet side and/or the outlet side may be flat within the limits of manufacturing tolerances.

For example, in plan view of the exit area of the device, the exit area overlaps with the outlet side. By way of example, a major part, e.g. at least 75% of the outlet side of the light guide overlaps with the exit area. For example, in this plan view, a major part of the outlet side is visible through the exit area.

According to at least one embodiment, the device is configured such that flash light from the light source is coupled into the light guide via the inlet side and is afterwards coupled out of the light guide via the outlet side. Thus, when the light source emits flash light, this flash light hits the inlet side of the light guide, is coupled into the light guide at the inlet side, is then transported within the light guide to the outlet side and is then coupled out from the light guide via the outlet side. Afterwards, the flash light leaves the device via the exit area .

For example, the device is configured such that a major part, i.e. more than 50%, for example at least 75%, of the flash light emitted by the light source is coupled into the light guide via the inlet side. For instance, a major part, for example at least 75%, of this coupled-in flash light is then coupled out of the light guide via the outlet side.

According to at least one embodiment, the inlet side of the light guide is oblique to the outlet side. For example, an angle between the inlet side and the outlet side is between 45° and 135° inclusive or between 60° and 120° inclusive or between 80° and 100° inclusive. By way of example, the inlet side and the outlet side are perpendicular to each other. In other words, the main radiation direction of the flash light when coupled out via the outlet side and the exit area is oblique, e.g. perpendicular, to the main radiation direction of the flash light as emitted by the at least one light source and as coupled in at the inlet side . By way of example , the at least one light source and the inlet side lie on the same height with respect to the outlet side or with respect to the main extension plane of the light guide .

In at least one embodiment , the device for emitting flash light comprises at least one light source for producing flash light , a light guide for guiding the flash light , and an exit area for coupling out flash light from the device . The light guide comprises an inlet side which faces the light source and an outlet side which faces the exit area . The device is configured such that , during operation, flash light from the light source is coupled into the light guide via the inlet side and is afterwards coupled out of the light guide via the outlet side . The inlet side is oblique to the outlet side .

Since the light source is arranged at a side of the light guide which is oblique to the side of the light guide through which the flash light is emitted, the build-in depth of the light source can be signi ficantly reduced . Particularly, the light guide and the light source can be arranged adj acent to each other with the light guide having a thickness which is approximately the thickness of the light source . The build-in depth is then, approximately, only the larger one of the thicknesses of the light guide and the light source .

According to at least one embodiment , the device is a camera . For example , besides the light guide and the light source , the device comprises an image sensor, like a pixelated chip . The image sensor may be a CCD or CMOS sensor . Additionally, the camera may comprise one or more optical elements , like lenses , for proj ecting an image onto the image sensor . According to at least one embodiment , the device is a smartphone or a tablet PC . Also other portable consumer devices , like a digital camera or a smart watch, are possible for the device .

According to at least one embodiment , the device further comprises a housing . The housing may be the housing of a camera or a smartphone or a tablet PC, for example . The housing may be exposed and configured to be touched by a user of the device . Thus , the housing may form the outer body of the device .

According to at least one embodiment , the housing is opaque for visible light at least in sections . Additionally or alternatively, the housing may be opaque for the flash light at least in sections . The housing is , for example , formed of plastic or metal .

According to at least one embodiment , the light source is hidden behind an opaque section of the housing in plan view of the exit area . That is , in plan view of the exit area, the at least one light source is completely overlapped by the opaque section of the housing . Consequently, the light source is not visible from the outside of the device for a user of the device . This may improve the optical appearance of the device .

The exit area is , for example , formed by a transparent or translucent area of the housing, i . e . transparent or translucent with respect to visible light and/or the flash light . Alternatively, the exit area may be formed by an opening in the housing . For example , in plan view of the exit area, the exit area is completely surrounded by an opaque section of the housing.

Additionally or alternatively, the at least one light source may be hidden behind a different element than the housing, e.g. behind an interior element of the device.

According to at least one embodiment, the light guide comprises a third side opposite to the outlet side. The third side is, for example, also oblique to the inlet side, e.g. perpendicular to the inlet side. The third side may be parallel to the outlet side and/or to the main extension plane of the light guide. For example, the thickness of the light guide, measured between the outlet side and the third side, is smaller than any extension of the outlet and/or third side. For example, the thickness of the light guide is at most 25% or at most 10% of the smallest extension of the light guide along the outlet side. The thickness of the light guide constitutes, for example, an extension of the inlet side of the light guide.

The first, second and third sides are, in particular, outer surfaces of the light guide.

According to at least one embodiment, a scattering structure for scattering the flash light coming from the inlet side towards the outlet side is arranged at the third side. That is, the scattering structure is configured to scatter the flash light. The scattering structure may be formed in the third side or on top of the third side. The scattering structure may comprise a plurality of scattering elements distributed over the third side, e.g. a graining, or may be a homogeneous coating, e.g. white coating. According to at least one embodiment , the scattering structure is a 2D- or a 3D-structure .

In case of a 2D-structure , the structure is , for example , a pattern printed onto the third side . A 2D-structure is herein understood as a structure with a much smaller extension in a direction perpendicular to the third side than parallel to the third side . For example , the maximum extension of the 2D- scattering structure or of each scattering element thereof in the direction perpendicular to the third side is , for example , at most X/ 4 or at most X/ 8 , wherein X is the wavelength at which the flash light has a ( global ) intensity maximum . The extension of each scattering element parallel to the third side is , for example , at least X/ 4 or at least X/2 or at least X .

In case of a 3D-scattering structure , the scattering structure may comprises a plurality of scattering elements in the form of protrusions and/or recesses extending in a direction perpendicular to the third side . The scattering elements may be formed in the light guide and/or out of the light guide . For example , the extensions of the scattering elements in the direction perpendicular and/or parallel to the third side are at least X/ 4 or at least X/2 or at least X .

According to at least one embodiment , the scattering ability of the scattering structure varies along the third side . For example , the distance between the scattering elements and/or the si zes of the scattering elements and/or the geometrical form of the scattering elements varies along the third side . By way of example , the scattering structure is varied such that the scattering ability in a region closer to the inlet side is larger than in a region further away from the inlet side . For example , the third side is designed such that the scattering ability is largest at the center of the third side and decreases from the center towards the edges of the third side . "Scattering ability" herein means the probability that the flash light is scattered by the scattering structure .

According to at least one embodiment , a maximum thickness of the light guide , measured in a direction perpendicular to the outlet side , deviates from the thickness of the light source , measured in the same direction, by at most 50% or at most 20% . The thickness of the light source is , for example , defined by an extension of the main emission side thereof . For example , the thickness of the light source and/or the light guide is between 0 . 2 mm and 0 . 5 mm inclusive .

According to at least one embodiment , the device comprises several light sources . All features disclosed herein in connection with one light source are also disclosed for all other light sources . Particularly, each of the light sources may be a light source for producing flash light .

According to at least one embodiment , the light sources each face an inlet side of the light guide which is oblique to the outlet side , particularly perpendicular to the outlet side . For example , in plan view of the outlet side , the light sources are arranged around the light guide . During operation, flash light from each light source may be coupled into the light guide via the inlet side facing the respective light source and may be coupled out of the light guide via the outlet side . By way of example, at least some of the light sources of the device are independently and individually controllable so that they can emit flash light individually and independently of each other. For this purpose, the device may comprise a control unit configured to independently and individually address/control the light sources.

According to at least one embodiment, at least two of the light sources are configured to emit flash light of different wavelength ranges. This means that the flash lights of the two light sources have different wavelength ranges. For example, the wavelength at which the flash light of one of the light sources has its intensity maximum differs from the wavelength at which the flash light of another light source has its intensity maximum by at least 50 nm or at least 100 nm. For example, the at least two light sources emit different colored flash lights and/or flash lights of different temperatures (CCT) .

The flash lights of the different light sources may be mixed in and by the light guide so that the flash light emitted by the device is homogenously mixed. For example, two light sources of different color or CCT are arranged adjacent to each other and emit flash light into the same direction and onto the light guide.

According to at least one embodiment, the device is configured to emit flash light of at least two different light sources into two different solid angle regions. For example, at least some light source are each uniquely assigned to a solid angle region so that flash light from a light source is predominantly, e.g. to at least 80%, or solely emitted into the assigned solid angle region. Different solid angle regions do not overlap with each other, for example. The solid angle regions are herein understood to be the solid angle regions into which the flash light is emitted directly after leaving the device through the exit area .

According to at least one embodiment, one of the solid angle regions surrounds, particularly completely surrounds, another one of the solid angle regions. For example, the solid angle regions are arranged concentrically. Thus, hitting a surface, for example, the flash light from one light source forms an illumination pattern, e.g. a ring, on the surface which surrounds the illumination pattern, e.g. a circle, formed by the flash light of another light source. For instance, depending on which light sources are operated, more focused or more diffused flash light can be emitted.

According to at least one embodiment, the solid angle regions are contiguous regions without interruptions. Thus, the solid angle regions assigned to the different light sources lie next to each other. When hitting a surface, the illumination patterns assigned to the flash lights of the different illumination patterns lie adjacent to each other. With such an arrangement, tricky scenes can be illuminated, for example .

Different solid angle regions assigned to different light sources can be realized by corresponding scattering structures of the third side. Additionally or alternatively, optical elements in or in front of the exit area of the device can be used to emit flash light of different light sources into different solid angle regions. In case of more than two light sources , each of the light sources may be uniquely assigned to a solid angle region . All features disclosed in connection with two light sources and the assigned solid angle regions are also disclosed for the further light sources and the assigned solid angle regions .

According to at least one embodiment , at least two light sources are arranged on opposite sides of the light guide and face these opposite sides . In other words , flash light from the at least two light sources is coupled into the light guide on opposite sides .

In case of more than two light sources , the light sources may surround the light guide in plan view of the outlet side of the light guide . For example , the light sources are arranged symmetrically around the light guide .

According to at least one embodiment , the exit area is assigned a lens . For example , the exit area is formed by the lens or at least one lens is arranged in front of the exit are , i . e . between the exit area and the light guide .

According to at least one embodiment , the device comprises a backside element which is arranged on a side of the light guide opposite to the exit area . For example , when the at least one light source is turned of f , the backside element is visible through the exit area and through the light guide . In this way, the optical appearance of the device in the region of the exit area can be designed as desired . For example , the backside element can be colored so that when the at least one light source is turned of f , the exit area appears in the color of the backside element . The backside element is , for example , white , black or any other color or is structured . The backside element may be a sheet or foil . It may be in direct contact with the light guide or may be spaced from the light guide .

Hereinafter, the device for emitting flash light will be explained in more detail with reference to the drawings on the basis of exemplary embodiments . The accompanying figures are included to provide a further understanding . In the figures , elements of the same structure and/or functionality may be referenced by the same reference signs . It is to be understood that the embodiments shown in the figures are illustrative representations and are not necessarily drawn to scale . In so far as elements or components correspond to one another in terms of their function in di f ferent figures , the description thereof is not repeated for each of the following figures . For the sake of clarity, elements might not appear with corresponding reference symbols in all figures .

Figures 1 to 5 show di f ferent exemplary embodiments of the device for emitting flash light in di f ferent views , and

Figures 6 to 8 show di f ferent exemplary embodiments of the device for emitting flash light in plan view and the resulting illumination patterns on an illuminated surface .

In the exemplary embodiment of figure 1 , the device 100 for emitting flash light is a smartphone or a tablet PC . The device 100 comprises a housing 4 , which is , for example , made of a material which is opaque for visible light and/or the flash light . The device 100 comprises an exit area 3 through which the flash light is emitted out of the device 100 . The device 100 further comprises a camera 6 for taking pictures and/or videos arranged next to the exit area 3 .

Figure 2 shows the device 100 of figure 1 in cross-sectional view along the line AA' of figure 1 . Figure 3 shows the same device 100 in an enlarged view illustrating paths of the flash light beams .

The device 100 comprises light sources 1 arranged opposite to each other, said light sources 1 , when operated, producing and emitting flash light . The flash light is , for example , white light . The light sources 2 may each comprise at least one LED . Furthermore , the device 100 comprises a light guide 2 , which is , for example , made of plastic .

The light guide 2 is formed as a solid body platelet with inlet sides 21 , an outlet side 22 and a third side 23 . The outlet side 22 and the third side 23 form main sides of the light guide 2 , lie opposite to each other and are parallel to each other . The inlet sides 21 connect the outlet side 22 with the third side 23 and run obliquely, namely perpendicularly, to the outlet side 22 . A 3D-scattering structure 24 is formed in the third side 23 . The scattering structure 24 comprises a plurality of scattering elements , namely recesses , formed in the third side 23 . The si zes of the recesses , particularly their depths , is largest in a center region of the third side 23 and decreases in the direction towards the inlet sides 21 . The si zes of the recesses are , for example , greater than the wavelength X at which the produced flash light has its intensity maximum .

The inlet sides 21 face the light sources 1 so that flash light from the light sources 1 is coupled into the light guide 2 via the inlet sides 21 . The flash light is then guided inside the light guide 2 by means of total internal reflection in the direction parallel to the outlet side 22 until it is scattered by the scattering structure 24 ( see , in particular, figure 3 ) . Thereby, the flash light is scattered in the direction towards the outlet side 22 , through which it is coupled out of the light guide 2 . Finally the flash light leaves the device 100 through the exit area 3 . As the si zes of the recesses increase in the direction away from the inlet sides 21 , the scattering probability for the flash light also increases with increasing distance from the inlet sides 21 so that the scattering ability of the scattering structure 24 is largest at the center of the third side 23 . This allows to produce homogenous flash light .

As can be further seen in figures 2 and 3 , the opaque housing 4 is aligned with the light sources 1 in the direction parallel to the outlet side 22 so that , in plan view of the exit area 3 , the light sources 1 are hidden behind the opaque housing 4 and are , therefore , not visible for an external viewer .

The exit area 3 is transparent or translucent for the flash light . For example , the exit area 3 is formed by a transparent or translucent material and is part of the housing 4 or it may simply be an opening in the opaque housing 4 . In contrast to what is shown in figure 2 , the exit area 3 may also be formed by a lens configured to form the flash light .

When viewed in plan view of the exit area 3 , i . e . in a direction perpendicular to the outlet side 22 , and when the light sources 1 are turned of f ( do not emit flash light ) , a backside element 5 of the device 100 is visible for an external viewer through the light guide 2 and the exit area 3 . The backside element 5 is , for example , a colored foil or sheet so that the exit area 3 appears in this color .

Figure 4 shows a further exemplary embodiment of the device 100 . In contrast to the previous exemplary embodiment , the scattering structure 24 is not a 3D-scattering structure but a 2D-scattering structure . For example , the scattering structure 24 is a pattern printed onto the third side 23 , wherein the extensions of the scattering elements of the pattern, measured in the direction perpendicular to the third side 23 , are small compared to the wavelength X, e . g . at most X/ 8 .

Figure 5 shows the device 100 according to any of the previous exemplary embodiments in plan view of the outlet side 22 of the light guide 2 . As can be seen, the device 100 actually comprises a plurality of light sources 1 which are each configured to emit flash light . The light sources 1 are , for example , individually and independently controllable . The light sources 1 are arranged symmetrically around the light guide 2 and each face an inlet side 21 of the light guide 2 , said inlet sides 21 each running perpendicularly to the outlet side 22 .

Some of the light sources 1 may be configured to emit flash lights of di f ferent wavelength ranges . For example , each of the four pairs of directly adj acent light sources 1 comprises one light source 1 for emitting flash light of one particular color or CCT and another light source 1 for emitting flash light of another particular color or CCT . The flash lights of the different light sources 1 may be mixed in the light guide

2.

Figure 6 shows an exemplary embodiment of the device 100, again in plan view of the outlet side 22 of the light guide 2. Four light sources 1 are arranged symmetrically around the light guide 2. The light sources 1 are, for example, individually and independently controllable. On the right side of figure 6, a simulated illumination pattern is shown. The illumination pattern is produced when the flash light of the device 100 is projected onto a flat surface. As indicated in figure 6, each of the four light sources 1 is uniquely assigned to a different area A, B, C, D on the surface. Thus, the flash light of each of the light sources 1 is emitted into a uniquely assigned solid angle region. Therefore, by individually turning on and off the different light sources 1, flash light can be emitted into different solid angle regions or onto different areas of the surface, respectively.

In the present case, the flash light of the light source 1 furthest to the left is emitted into the upper left area A of the surface. The flash light of the light source 1 furthest up is emitted into the upper right area B of the surface. The flash light of the light source 1 furthest to the right is emitted into the lower right area C of the surface. The flash light of the light source 1 furthest down is emitted into the lower left area D of the surface.

Figure 7 shows the same as figure 6, but now the borders between the different areas A, B, C, D on the screen assigned to the different light sources 1 are indicated. Figure 8 shows an exemplary embodiment of the device 100 , wherein the flash lights of the di f ferent light sources 1 are also emitted into di f ferent solid angle regions and consequently into di f ferent areas A, B, C, D on the surface . However, in this case , the solid angle regions and the corresponding areas on the screen are not contiguous , interruption- free areas lying next to each other as in figures 6 and 7 , but the solid angle region / area on the screen A assigned to the light source 1 furthest to the left surrounds the solid angle region / area on the screen B assigned to the light source 1 furthest up . This solid angle region / area on the screen B surrounds the solid angle region / area on the screen C assigned to the light source 1 furthest to the right . And, finally, the solid angle region / area on the screen C surrounds the solid angle region / area on the screen D assigned to the light source 1 furthest down .

This patent application claims priority to German patent application 10 2022 118 395 . 5 , the disclosure content of which is hereby incorporated by reference .

The invention described herein is not limited by the description in conj unction with the exemplary embodiments . Rather, the invention comprises any new feature as well as any combination of features , particularly including any combination of features in the patent claims , even i f said feature or said combination per se is not explicitly stated in the patent claims or exemplary embodiments . Reference sign list

1 light source

2 light guide 3 exit area

4 housing

5 backside element

6 camera

21 inlet side 22 outlet side

23 third side

24 scattering structure

100 device

A to D areas on a surfaces