Flash system for a camera or mobile phone with a built-in camera

Abstract

The flash system here is able to modify the flash from a flash unit to suit the subject being photographed. The camera (a digital camera or a smartphone camera) takes two very quick shots of the subject in rapid succession. The first shot serves only to gather information about the light distribution. This image is displayed on an inactive, transparent LCD screen. The first version only compensates for the lighting conditions (using a black-and-white LCD screen), while the second (with a color LCD screen) can also enhance color contrast.

Description

[0001] The invention relates to a flash generator for a camera or mobile phone with a built-in camera, which is capable of selectively illuminating the background and the objects or persons in the foreground.

[0002] When you take a picture in the dark with a flash, the objects or people in the foreground and closer to the camera are usually brighter or even overexposed by the flash, while the background remains quite dark.

[0003] Cameras or smartphones (mobile phones) with conventional flashes have the disadvantage that the flashes have a fixed radiation pattern. This can result in a picture taken by the camera that contains overexposed subjects in the foreground, while the background lighting may be insufficient. One possible solution to this problem would be to take a sequence of images with different exposure levels and then computationally overlay them. This places high demands on the camera's storage capacity and processing power, as well as on the physical strength of the user, who must have steady hands while taking the picture. In addition, this still does not achieve a sufficiently high image quality. Currently, flash units only emit a uniform light, with close objects or people being significantly more intense than distant objects or the background.The light intensity of light rays in a light cone decreases quadratically with the increase in distance. This means that, for example, at a distance of six meters, four times less light reaches the subject than at a distance of three meters from the camera. This difference in light density on the subject to be photographed creates brighter and darker areas there, which no longer optimally represent the photo. The objects that are closer to the camera appear significantly brighter in the photo than those that are in the background. With natural daylight, one does not have this problem because the entire surroundings are more or less evenly illuminated there.

[0004] Patent specification EP 2 484 106 B1 describes a light-emitting semiconductor chip for a lighting device, a lighting device for a camera, a camera, a method for operating the lighting device, and a method for operating the camera. The semiconductor chip contains a semiconductor layer sequence with an active zone provided for generating light. The active zone has, in particular, a pn junction, a double heterostructure, a single quantum well structure, and / or a multiple quantum well structure for generating radiation. The semiconductor chip contains a plurality of individually controllable emission regions. In particular, the emission regions can be operated independently of one another. Electromagnetic radiation can be generated in the emission regions at the same or at different times.Furthermore, the emission regions can be supplied with different current strengths, so that electromagnetic radiation of varying intensity can be generated from the emission regions. Preferably, the individually controllable emission regions can be switched on and off independently of one another. The emission regions can have similarly formed active zones, so that the electromagnetic radiation generated in the emission regions each has the same spectral distribution. Unfortunately, this problem is not adequately solved here. The segmented emission regions of the semiconductor chip cannot direct the light onto a multitude of targets at different distances from the camera, nor can they define or mark precise contours of individual objects.

[0005] JP 2008084600 A discloses a flash for a mobile phone camera in which the position of an LED in a reflector can be adjusted using a servo motor. This allows the overall area illuminated by the flash to be better adapted to the image section. However, the fundamental problem of potentially overexposing a subject in the foreground remains unsolved with this flash. Furthermore, such a flash is technically complex and, due to moving parts, more or less prone to failure.

[0006] The publications US 2003 / 0174499 A1, US 2008 / 0151052 A1, US 2005 / 0168965 A1 and WO 2005 / 012997 A2 each describe an arrangement of light-emitting diodes which are electrically connected in series with one another, wherein radiation profiles of the light-emitting diodes can be controlled by means of electronic components.

[0007] The invention specified in claims 1 to 24 is based on the problem of creating a flash system for a digital camera or a mobile phone with a built-in camera, which, regardless of the different distances of the objects or people to be photographed in relation to the camera, aims for more or less a similar light density and illumination intensity over the entire image recording area, within the physical limits.

[0008] This problem is solved by the features listed in patent claims 1 to 24.

[0009] Advantages of the invention are: - the digital camera or the camera in a mobile phone illuminates with similar light density the near and far areas on the subject, - no overexposed objects or people who are closer to the camera when taking pictures, - Optimization and striving to get closer to daylight conditions within the limits of what is technically feasible.

[0010] Examples of implementation are shown on the Fig. 1 to 8 described.

[0011] They show: Fig. 1 an embodiment with a system consisting of a mini image projector / video projector (e.g. laser image projector or LED projector), Fig. 2 a digital camera (or smartphone) where the video / image projector is a color image / video projector and throws the light projection in color, Fig. 3 a flash unit integrated into a camera with a light control LCD panel in front of its light output, Fig. 4 a variant with a color LCD screen, where the color contrast can be increased during recording, Fig. 5 a variant with light-emitting diodes or laser diodes and laser beam merging in the light guide element in the form of a peace sign (⍰), Fig. 6 the light beam focus system, which is used with the zoom field function, matching, coupled, Fig. 7 the illumination at close and far range (the density of the lines symbolizes the light density), Fig. 8 the projection onto the image motif.

[0012] The invention here aims at active light density compensation / adjustment, whereby the light intensity is more evenly distributed across the subject being photographed or across the photo. A consistent luminance is aimed for regardless of the distance of the subject being photographed from the camera. Objects closer to the camera are thus selectively illuminated with less light intensity than objects further away. Thus, the near objects 10 are illuminated with less light than the far objects 11 located in the same image motif. This light intensity dynamic is new in camera recording technology.Conventional camera flash systems emit light with consistent intensity across all areas. However, because the reflected light comes from objects at different distances, the light intensity will vary greatly, resulting in objects close to the camera being overexposed, while similar objects farther away will be underexposed and appear darker. This new technology addresses precisely this problem.

[0013] In addition to the light balancing effect, the invention offers another feature that can also play a positive role in night photography. It can significantly increase color contrast by illuminating the object surfaces to be photographed with the same color of light that corresponds to the color of the surface. It is known that if an object (or any surface) is illuminated with a beam of light that matches its color, it reflects these light rays much more intensely. For example, if a red jacket is illuminated with red light, it glows much more intensely than if it is illuminated with white light. In green light, it even looks gray and is barely noticeable in the dark. This effect, which visually highlights an object, can be used to create higher-contrast photo lighting at night.

[0014] The flash system here generates a flash that is modified from a flash emitter to be adapted to the image motif to be captured. The camera (a digital camera or the camera of a smartphone or even an analog camera) captures the same image motif twice in quick succession here, where a first capture is only used to collect information about the light distribution. This capture is displayed on an LCD screen that is transparent in the inactive state.

[0015] Several variants of this system are described here. The first variant only compensates for the lighting conditions (it uses a black and white LCD screen 1), while the second (with a color LCD screen 8) can also increase color contrast because it can individually control the flash light colors, whereby the colors of the surfaces 12 on the objects in the image motif areas are more intensely illuminated with the same light color that is present there. In particular, the use of laser diodes, e.g. in the RGB system with a green laser diode 13, red laser diode 14, and blue laser diode 15, results in increased color contrast. For example, a red area on an object is illuminated more intensely with a red laser, while the laser intensity of the other color laser sources is reduced. When capturing the same image, where there is a blue area, for example, this area is illuminated more intensely with a blue laser source.The entire laser illumination is controlled very selectively to specifically target each colored area of ​​an object. When taking night shots, the system can produce significantly more intense colors in the image. If, for example, you take a photo of a street with this image recording system, the close-up areas on the street will be less brightly illuminated by the flash, while the light intensity increases continuously with distance (optimally a quadratic increase in intensity as the distance doubles) This means that people close to the camera 4, but also people in the background who are perhaps a few meters further away, will be illuminated differently. People close to the camera will receive less light intensity than those a few meters further away.This ensures that everyone in the image is equally lit / exposed, rather than the foreground being brighter and the others being darker, as is the case with conventional cameras. This makes the image appear much more natural, with hardly any overexposed areas, and is close to photos taken in daylight.

[0016] On the Fig. 1 shows an exemplary embodiment. The system here consists of a mini image projector / video projector 16 (e.g. laser image projector or LED projector), which is built into the camera housing (camera or smartphone) as a flash light generator. The digital camera (or smartphone) equipped with this device can also have a conventional flash unit or a conventional flash light source 3. The user can selectively switch the flash light sources on or off. The camera takes two pictures in quick succession. A pre-shot only serves to provide information about the light distribution for the actual shot. However, this shot can also be saved as an image. For the pre-shot, the mini projector / video projector will emit the full light intensity unhindered, without projecting anything onto the subject to be recorded.For our shots, a conventional flash light source without any filter can be useful, for example, to generate the pre-shots. As soon as the pre-shot has been taken, the signal with this exact shot is sent to the projector and projected as a black and white or grayscale negative image (inverse representation) 6 onto the subject 7 to be photographed. This illuminates an image projection 19 onto the objects, people (subject), etc. to be photographed with inverse light (negative image). Therefore, everything that would appear brighter in the pre-image is illuminated with less light intensity in the second shot. This means that the people who are closer to the camera when the photo is taken are illuminated with less light than those who are further away. Immediately after the subject is illuminated with negative image projection light, the second image is captured by the camera's image sensor.This image capture is the actual shot, in which the light distribution and illumination are optimal at all levels. Because the image or video projector amplifies the light in the background and attenuates the light in the foreground, there are hardly any noticeable light differences or glare or overexposure effects visible in the image.

[0017] The execution from the Fig. Figure 2 shows a digital camera (or a smartphone with a camera) in which the video / image projector is a color image / video projector 20, projecting light in color. Here, inverse light colors (negative image colors) do not need to be emitted onto the surfaces of the image subject; instead, the light is emitted normally, as with a color projector. However, because the camera recording field 21 and the image / video projection surface 22 are arranged in a consistent manner, this means that the surfaces of the image subject are illuminated with the same light colors as they are. For example, blue areas of the image subject are illuminated more intensely with blue light, and the red areas are illuminated more intensely with red light. This happens automatically because the video projector also projects these light colors onto the objects, matching the surfaces.The light rays that are reflected back to the camera sensor 17 are much more intense than if the entire surface were illuminated with white light alone. Although red light is not emitted selectively, for example only on a red surface, despite other light colors, the red light intensity from the projector is emitted more intensely and only at the point where the red surface is. The same can also work with video recordings. In this case, provided the subject is not moving too quickly, a pre-video recording is always made that runs ahead by just a few milliseconds and is then fed to the video projector, whereby the video projector adapts its video projection to the light information from the pre-running recordings and emits it onto the subject.However, it's important to add internal color correction, performed by an electronic control system, to avoid an electronic positive feedback effect. This is because, unlike image recordings, with video recordings, the amplification of the light colors by the projector leads to even greater amplification with each image sequence, until after a short time (within seconds), the video recording becomes unusable and completely distorted.

[0018] On the Fig. Figure 3 shows an exemplary embodiment. To solve the problem of light density distribution on the subject to be photographed, an LCD panel is proposed in front of the flash output 2 of a digital camera 4 or a smartphone 5. This LCD panel, using a previously taken photo with normal flash light, depicts the dark and light areas in color inversion or brightness-light inversion display or negative image display 6. Thus, during the subsequent shot, which is also the main image, the flash light is filtered through the LCD panel so that the areas of the darkly illuminated image are illuminated with greater light intensity. Although the LCD panel or LCD screen can be a color LCD screen here, a black-and-white LCD panel 1 is also sufficient. Ultimately, it is only a matter of adjusting the light density at the light output 2 of the flash unit 3.

[0019] The pre-shot serves as information for the main image capture, in order to make the light corrections. How this is to be carried out is automatically regulated by the LCD screen 1 in front of the flash unit 3, by means of a negative image display of the subject 7 taken immediately beforehand, which acts like a light filter. It is perfectly sufficient if the pre-shot image is displayed there as a negative image. Because the LCD screen is more or less transparent when inactive, it does not completely prevent the flash light from passing through the screen. However, if a photo is displayed there in the form of negative silhouettes, the light is selectively attenuated more or less with each dark pixel. Because the display is a negative of the taken image in black and white oris shown in gray tones, where the areas are that have been more heavily exposed (bright image subject areas 23), the negative appears dark on the LCD screen (dark LCD screen area 24) and thus further prevents light from passing through. The image areas that are visible as dark in the normal image (dark image subject areas 25) and reflect less light are shown in the negative as bright spots / bright areas (bright LCD screen areas 26) that lessen the light that has to pass through the LCD screen 1. In this way, these areas receive more light when the flash is used for the main image. This means that, for example, the background in the main photo appears significantly brighter and the person in the foreground is somewhat less illuminated, which is closer to natural lighting.This results in a better-lit photo because the background is automatically illuminated brighter than the foreground objects thanks to the filter function on the LCD screen. After all, in daylight photography, the background is just as bright as the foreground. This prevents close-up shots from being overexposed. This is also what the invention attempts to achieve.

[0020] Another version is on the Fig. 4. No color video projector is used here, but a somewhat simpler, yet quite similar method is used. To achieve higher contrast in the illuminated objects, the subject is photographed beforehand using a short flash, and this photo is sent and displayed on the color LCD screen 8 for light selection immediately before the actual flash exposure. For such purposes, the color LCD screen 8 is intended to display the previously recorded image in color. The idea is to send the flash light through a light filter (color LCD screen) that contains the same visual information as the subject. And the color LCD screen, which is placed directly in front of the flash output, is ideally suited for this. The whole process takes place in milliseconds, and the user hardly notices that the subject has already been photographed.The main photo is taken with the optimized flash, which will make the colors more intense. The image display on the color LCD screen should not be a negative image, but rather a normal, positive image. However, to adjust for lighting conditions, an additional image can be quickly taken, and then the display on the color LCD screen can be displayed in black and white (gray tint) and in color inversion, or as a negative image. In this case, two actual photos would have to be taken, with a preliminary image displayed as a negative photo and in black and white on the color LCD screen before each actual photo, and a color photo in normal colors displayed directly on the color LCD screen and at very short intervals from each other before the second actual image.The two actual images (main photos) can be merged using software to achieve the best lighting conditions and contrast, or saved as separate images. All four images are captured within fractions of a second, so changes in the subject are unlikely, allowing the images to be seamlessly "layered" onto one another. An electronic control system 9 automatically coordinates the processes. When the subject is moving, e.g., in sports shots, car races, etc., only individual shots with clearly defined contrast and focus can be captured.

[0021] To achieve an even better background illumination, the camera can be equipped with a flash unit consisting of light-emitting diodes or laser diodes ( Fig. 5). When using laser diodes, at least three laser diodes must be used, each emitting in all three primary light colors – red, green, and blue (RGB). The laser beams from all three laser diodes (13, 14, 15) are combined in a light deflection element 27. Lenses, mirrors, or even a special light guide can serve as the light deflection element. The light guide has three branches (similar to the peace sign without the circle – ⍰) as light inputs 28 and a trunk 29 as the light output. The laser beams from all three laser diodes each enter a different light guide branch 28 and are combined in the trunk 29. The resulting mixed laser beam 30 contains all three RGB components of light and is similar to a white light beam.The light output of the fiber optic trunk emits a very wide cone of light, which is unsuitable for illuminating a subject. Therefore, it has a clear lens 31 (or lens system) that more or less focuses the laser beams together to such an extent that a subject in front of the camera can be well illuminated. In addition, there is a light beam focus system 18 that automatically focuses the laser beams in conjunction with the camera's zoom function to such an extent that, when zooming in heavily, the subject area to be photographed is illuminated with more focused laser beams, generating an optimal light density per unit area despite the greater distance. Here, the light beam focus system follows the zoom field function, with the camera recording field 21 and light beam focus field area 32 being aligned with one another (. Fig. 6).

[0022] The light focus system and the image projection by the flash light is shown again on the Fig. 8. Here, too, one can see that the real image motif 7 is followed by an image projection 19. When using a color LCD screen 1, the light from the flash unit is optimally distributed and does not cause overexposure. When using a color LCD screen 8, the colors are also better represented in the image, and the color contrast increases. LIST OF REFERENCE SYMBOLS 1 black and white LCD screen 2 light output 3 flash units / conventional flash source 4 Digital camera 5 smartphones 6 Negative image representation (inverse image representation) 7 Image motif 8 color LCD screen 9 Electronic control 10 close-up objects 11 distant objects 12 surfaces 13 Green laser diode 14 Red laser diode 15 Blue laser diode 16 mini image projector / video projector 17 Camera sensor 18 Light Focus System 19 Image projection 20 color image / video projector 21 Camera recording field 22 image / video projection screen 23 Bright image motif areas 24 dark LCD panel area 25 Dark image motif areas 26 bright LCD screen areas 27 Light deflection element 28 branches as light inputs / fiber optic branch 29 Trunk / fiber optic trunk as light output 30 Mix laser beam 31 lens 32 light beam focus field area QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited Patent Literature

[0000] EP 2 484 106 B1

[0004] JP 2008084600 A

[0005] US 2003 / 0174499 A1

[0006] US 2008 / 0151052 A1

[0006] US 2005 / 0168965 A1

[0006] WO 2005 / 012997 A2

[0006]

Claims

[1] Flash system for a camera or mobile phone with a built-in camera, characterized by , that it - a light-emitting device designed as a continuous light source or flash light source, which is an image or video projector, - a control system that executes the user's control command for the creation of an image twice in quick succession, the first time taking a preliminary photograph with a full flash of light from the light-emitting device or a separately installed flash source, and a second time taking the actual photograph with a renewed flash or illumination, the light of which comes from the light-emitting device, which projects a light image projection of the previously photographed image onto the image subject to be photographed, which is then illuminated with this light and photographed again, has. [2] Flash system for a camera or a mobile phone with a built-in camera, according to claim 1, characterized by that the light emitting device, which is designed as a continuous light source or flash light source, which is an image or video projector, projects a negative image or inverse light image projection of the previously photographed image motif onto the image motif to be photographed, which is then illuminated with this light and photographed again. [3] Flash system for a camera or a mobile phone with a built-in camera according to claim 1 or 2, characterized by that the light image projection of the light emission device onto the image to be photographed is in black and white or grey tones. [4] Flash system for a camera or a mobile phone with a built-in camera according to claim 1 or 3, characterized bythat the light image projection of the light emission device onto the image subject to be photographed takes place in inverse light colors / gray tones, as a negative image. [5] Flash system for a camera or a mobile phone with a built-in camera according to claim 1, characterized by that the light image projection of the light emitting device onto the image subject to be photographed takes place in light colours which are distributed in the same way as those on the surfaces of the image subject to be photographed. [6] Flash system for a camera or a mobile phone with a built-in camera according to one of the preceding claims, characterized by that the camera or mobile phone has an additional conventional flash device or light source, whereby a selectable, selective light switching can be carried out by the user. [7] Flash system for a camera or a mobile phone with a built-in camera according to one of the preceding claims, characterized by that the camera recording field and the image / video projection surface are arranged in a consistent manner. [8] Flash system for a camera or a mobile phone with a built-in camera according to one of the preceding claims, characterized by that it is equipped with a pre-recording video function that runs a few milliseconds ahead, which is then sent to the video projector, whereby the video projector adapts its video projection to the light information from the pre-recordings emitted on the image motif. [9] Flash system for a camera or a mobile phone with a built-in camera according to claim 6, characterized by , that there is an internal colour correction function carried out by an electronic control, which avoids an electronic positive feedback effect which occurs in video recordings due to the mutual amplification of the light colours by the projector and subsequent image sequences of a video recording, has. [10] Flash system for a camera or a mobile phone with a built-in camera, characterized by , that it consists of at least - a translucent, electrically controllable black and white LCD screen placed in front of the light output of a built-in flash unit, - a control unit electrically coupled to the LCD screen, which executes the user's control command for the creation of an image twice in quick succession, the first time taking a preliminary photograph with a flash and a transparent, inactive LCD screen, and a second time taking the actual photograph with another flash, the light of which passes through the electrically activated LCD screen, on which a negative or inverse image representation of the previously photographed image motif is displayed, and thus produces a light projection of the image motif onto the image motif itself, which is then photographed, consists. [11] Flash system for a camera or a mobile phone with a built-in camera, characterized by , that it consists of at least - a translucent, electrically controllable color LCD panel placed in front of the light output of a built-in flash unit, - a control unit electrically coupled to the color LCD screen, which executes the user's control command for the creation of an image twice in quick succession, the first time taking a preliminary photo with a flash and a transparent, inactive LCD screen, and a second time taking the actual photo with another flash, the light of which passes through the electrically activated LCD screen, on which an image representation of the previously photographed image motif is displayed, consists. [12] Flash system for a camera or a mobile phone with a built-in camera, according to claim 10 or 11, characterized by that the black and white LCD screen or the color LCD screen is movably installed and can be removed manually or electrically from the field of view of the flash unit. [13] Flash system for a camera or a mobile phone with a built-in camera, according to one of the preceding claims, characterized bythat the contrast of the projected light can be adjusted automatically or manually. [14] Flash system for a camera or a mobile phone with a built-in camera, according to one of claims 10 to 13, characterized by that the light transmittance of the activated black and white LCD panel or color LCD panel can be adjusted automatically or manually. [15] Flash system for a camera or a mobile phone with a built-in camera, according to one of the preceding claims, characterized by , that it has a function and control that causes two main photos to be taken at short intervals on the recording command or by pressing a button / screen touch button by the user, whereby before each main photo, an additional preliminary image is displayed as a negative photo and in black and white or grayscale image representation on the color LCD screen and before the second main photo, a color photo in normal color representation is displayed directly on the color LCD screen, is equipped. [16] Flash system for a camera or a mobile phone with a built-in camera, according to claim 15, characterized by that the two main photos are merged / integrated by built-in software, or are saved as separate images. [17] Flash system for a camera or a mobile phone with a built-in camera, according to one of the preceding claims, characterized bythat the flash light generator consists of at least one light-emitting diode or laser diode with a built-in optical light beam focusing system in the laser beam output. [18] Flash system for a camera or a mobile phone with a built-in camera, according to claim 17, characterized by that the optical light beam focusing system is equipped with an electric drive element that can be controlled via an electronic control system. [19] Flash system for a camera or a mobile phone with a built-in camera, according to one of the preceding claims, characterized by that the flash light generator consists of several laser diodes in all three basic light colors, which are brought together via a built-in light deflection element and emit a white light. [20] Flash system for a camera or a mobile phone with a built-in camera, according to one of claims 17 to 19, characterized bythat the optical light beam focusing system is coupled with a zoom function of the camera and the two can be activated together. [21] Flash system for a camera or a mobile phone with a built-in camera, according to one of claims 17 to 20, characterized by that the illumination field is formed by a light beam focusing system, consistent with the camera recording field and zoom field function, whereby the camera recording field and the illuminated light beam focus field area are placed consistently on top of each other. [22] Flash system for a camera or a mobile phone with a built-in camera, according to one of claims 19 to 21, characterized bythat the light deflection element which combines the three laser beams into one beam consists of a light guide element consisting of three light guide branches and a light guide trunk in which all three light guide branches are combined and which is equipped with a single light beam output. [23] Flash system for a camera or a mobile phone with a built-in camera, according to claim 22, characterized by that all three fiber optic branches meet at a narrow angle, at one point, and flow into the fiber optic trunk. [24] Flash system for a camera or a mobile phone with a built-in camera, according to claim 22 or 23, characterized by that the light output of the fiber optic trunk is equipped with a lens or an optical lens system that can well illuminate a field of view in front of the camera or an image subject in front of it.

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