WO2012063177A2

WO2012063177A2 - Flashlight device

Info

Publication number: WO2012063177A2
Application number: PCT/IB2011/054930
Authority: WO
Inventors: Christoph Dobrusskin; Jorrit Ernst De Vries
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2010-11-10
Filing date: 2011-11-04
Publication date: 2012-05-18
Also published as: WO2012063177A3; TW201229645A

Abstract

There is provided a flashlight device 100 comprising light units 121 for illuminating a target, and control means 110 for driving each light unit based on control data CD. The control means is arranged for retrieving external data ED associated with the target, and for deriving the control data CD from the external data ED. The light units, each comprises a light source 122, and optionally optical means. Each light unit is adapted for providing a predetermined illumination of a given subarea of the target in response to the control data.

Description

Flashlight device

FIELD OF THE INVENTION

The present invention relates generally to a flashlight device, and more particularly to a flashlight device comprising at least one light unit for illuminating a target, and control means for driving each light unit to illuminate a certain subpart of the target.

BACKGROUND OF THE INVENTION

Recently solid state flashlights have started to be used for replacing conventional flashlights for photographic and film- imaging purposes, security applications and the like.

WO 2007/007222 Al discloses a digital image capturing device for capturing a scene which is provided with a scan type flash. The image capturing device comprises a two dimensional array of light-exposable cells, e.g. a charge-coupled device sensor, CCD sensor, and the flash being one or more light sources for illuminating the scene when capturing it. Each light source is provided with optical means and the light sources and/or the optical means are controllable by a driver in accordance with instructions received by a microcomputer. The instructions are associated with a predetermined exposure of the individual/groups of light-exposable cells, such that synchronization of exposure and illumination of the scene may be accomplished.

The system described above is generally effective in accomplishing an illumination of a specific area of the scene at a given time. However, there is a need for controlling more than the subarea and intensity of illumination for instance when the scene to be photographed has rather large variations in the lateral depth profile of areas to be illuminated or when a rather large depth of field of an image is desired. SUMMARY OF THE INVENTION

It is an object of the present invention to at least provide an improved flashlight device. This object is achieved by a flashlight device according to the present invention as defined in the appended independent claim. Preferred embodiments are set forth in the dependent claims and in the following description and drawings.

Thus, in accordance with the present inventive concept, there is provided a flashlight device comprising at least one light unit for illuminating a target, each light unit comprising a light source, and control means for driving each light unit based on control data. The control means is arranged for retrieving external data associated with the target, and deriving the control data from the external data. Each light unit is adapted for, in response to the control data, providing a predetermined illumination of a given subarea of the target. Each light unit may optionally, in addition to the light source comprise a corresponding optical means for controlling light from the light source.

Thus, there is provided a flashlight device, which allows for providing illumination which is adapted to the specific target. The external data is typically retrieved from an external source, and is associated with the target, i.e. the scene which the flashlight device is to illuminate. When utilizing the flashlight in a camera the external data is preferably received from the camera imaging sensor, being for instance a CCD device or a CMOS device for capturing light from the scene and converting it into electrical signals. The external data may also be retrieved from other sensors which can provide information about the present scene, e.g. the auto-focus sensor of a camera, the zoom position of the lens, or a movement sensor in a camera or a security sensor of a surveillance system. Further, the flashlight device itself may be arranged with sensors for providing the external data associated with the present scene.

The retrieved external data forms the base for the control signal which may be derived by analyzing the external data and calculating the control signals according to preset instructions. The analysis may be based on face detection, smile detection, movement detection, or other image/sensor processing information. The control data is then utilized to drive the light units to illuminate individual subareas of the scene in a predetermined manner. Thereby, at least a two dimensional adaptation of the illumination of the scene, which adaptation is based on the scene, is provided.

In accordance with an embodiment of the flashlight device, the external data is retrieved from at least one of an imaging sensor matrix, an auto focusing means, an auto-light meter means, a distance meter and a movement sensor. By locally adjusting the light output of the flashlight device, an improved balance between the illumination of distant parts of the scene and parts in the scene that are close by, can be obtained. Fast moving objects can receive a shorter, more powerful flash in order to freeze the movement.

In accordance with an embodiment of the flashlight device, the predetermined illumination of said light units jointly cover a predetermined subpart of the target. This is advantageous e.g. in that more distant objects in the target can receive more light from the flashlight device, than closer object, in order to create a more natural illumination of the target.

According to embodiments of the invention, different subparts of the target may be illuminated with different light intensity. This may be useful for instance for adjusting vignetting of imaging lenses, such that e.g. dark corners in the image due to vignetting is compensated for. The vignetting of the image lenses is effectively cancelled out by arranging a gradually increasing light intensity in subparts of the target, which appears darker in the captured image. In an opposite approach vignetting effects may be used in a predetermined manner, for instance to high light a person with respect to the surroundings in a picture. By illuminating the person being placed in a normal lighted background more, a vignetting effect may be achieved for example for artistic purposes. Further, adjusting the vignetting may include analyzing a test image which is captured by the imaging sensor matrix to find e.g. naturally occurring vignetting effects in the image and then adjusting the illumination accordingly in order to decrease, increase or cancel the vignetting out.

In accordance with an embodiment of the flashlight device, the predetermined subpart of the target is selected based on contrast differences and/or color differences in the external data.

In accordance with an embodiment of the flashlight device, when the external data is retrieved from an imaging sensor matrix, and the predetermined illumination is arranged for providing a sequential illumination of at least one predetermined subarea of the target, the sequence being synchronized with a line of movement of an active imaging subarea of the imaging sensor matrix, or by a movable aperture being placed in front of the imaging sensor matrix. The movable aperture may be a slit shutter or any similar mechanical shutter device. The flashlight is synchronized with the movement of the slit along the imaging sensor matrix. This allows using the flashlight device in combination with a much shorter exposure time than with conventional electronic flash lights.

In accordance with an embodiment of the flashlight device, the predetermined illumination is adjusted based on variation of depth of the target. Thus the illumination has an adapted intensity with respect to each subpart of the scene, which depends on the distance from the device, e.g. the camera, onto which the flashlight device is arranged. Thus a more natural representation of the target is obtained.

In accordance with an embodiment of the flashlight device, the predetermined illuminations of the light units are arranged to jointly cover a predetermined subpart of the target being a moving object. This is advantageous when photographing a moving object, like the ball in ball sports, or when illuminating a moving object detected by a moving sensor in a surveillance system.

In accordance with an embodiment of the flashlight device, the control data is arranged such that the predetermined illumination has an adjusted color cast and/or color temperature. The color cast or color temperature is controlled in a predetermined way which alternatively may include analyzing the color cast or color temperature of a test image, which is captured by the imaging sensor matrix and then adjusting the illumination to a desired value. By controlling the color temperature, the illumination of scene may be selected to set a certain mode in the image, which is created when capturing the scene with a camera using the flashlight device.

In accordance with an embodiment of the flashlight device, the flashlight device further comprises at least one optical system arranged in front of the light units for providing a zoom function.

In accordance with an embodiment of the flashlight device, the flashlight device further employs a control flash being activated in order to retrieve the external data. This is advantageous for instance when photographing in dark environments.

In accordance with an embodiment of the flashlight device, the control flash is a preview version of the joint predetermined illuminations of the light units, having one of a decreased power, a different color, and a different time duration. That is, a test version of the subsequent flash, i.e. the joint predetermined illuminations of the light units, having for instance a predetermined intended light effect, is used to illuminate the scene such that the retrieved data, i.e. the test image, can be analyzed and provide control data for optimizing the subsequent flash.

In accordance with an embodiment of the flashlight device, the plurality of light units are arranged in a rectangular array or in a circular array.

The light units may be arranged in one dimensional or two dimensional arrays. As appreciated by the skilled person, any other suitable configurations of the light units are applicable within the scope of the invention. The flashlight device may further comprise a scanning means, in which case the plurality of light units, being arranged in a row, are connected to the scanning means to provide illumination of a two dimensional surface.

Further, the light sources may be solid state light sources, SSLs.

In accordance with an embodiment of the flashlight device, the light sources provide light being at least one of a visible color, infrared, and ultraviolet.

In accordance with an embodiment of the flashlight device, the light units are arranged to provide illumination of the target covering different angles of illumination. That is, the light units are arranged such that illumination is provided that covers different angles of the target and which corresponds e.g. to the field of view of a camera. This may also include the field of view for different zoom settings.

In accordance with an embodiment of the flashlight device, the light unit is a laser scanning device for providing the different angles of illumination.

In accordance with an embodiment of the flashlight device, the light source is a light emitting diode.

These and other aspects, features, and advantages of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail and with reference to the appended drawings in which:

Fig. 1 is a block diagram illustrating a flashlight device according to an embodiment of the present invention;

Figs. 2a and 2b illustrate different arrangements of light units of flashlight devices according to embodiments of the present invention;

Fig. 3 is a schematic top view illustration of a flashlight device according to an embodiment of the present invention when illuminating a target;

Fig. 4 is a schematic top view illustration of a flashlight device according to an embodiment of the present invention when illuminating a target; and

Fig. 5 is a schematic illustration of a flashlight device according to an embodiment of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention will now be described more fully hereinafter with reference to the accompanying drawings. The below embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout.

Fig. 1 is a block diagram illustrating a flashlight device 100 according to a preferred embodiment of the invention. The flashlight device 100 comprises a plurality of light units 121 arranged in a light unit matrix 120 for providing illumination of a target. Each light unit 121 comprises a light source 122, here being a light emitting diode (LED) and a corresponding optical means 123 for controlling light from the light source 122. Any suitable light sources may be used in the light units 121, e.g. organic light emitting diodes (OLEDs), inorganic LEDs, polymeric LEDs, hot cathode fluorescent lamps (HCFLs), cold cathode fluorescent lamps (CCFLs), or plasma lamps. For illustrative purposes the number of light units are selected to be twenty five in this exemplifying embodiment. However, for camera applications and utilizing LEDs as light sources, a typical number of light units is selected between 4 and 64.

Alternatively, in embodiments of the flashlight device, where the optical means are not necessary, the optical means may be omitted. Further, the optical means and the corresponding light source may be integrated in a single light unit device.

In an embodiment of the flashlight device, the light sources are selected such that the light unit matrix comprises at least two different colors of the light sources. The flashlight device may for instance be arranged with light sources for providing light within the visible-, infrared-, or ultraviolet spectra. The light unit matrix 120 is here a plurality of light units 121 arranged in a rectangular array, but may alternatively comprise light units arranged in a circular array, or even be a one dimensional array of light units, as illustrated in Figs. 2a and 2b, respectively. The latter is preferably arranged together with a scanning means (not shown) such as moving mirrors, thus allowing a single row of light sources to provide sequential illumination of a target in two dimensions. As mentioned above, other configurations of the light units are also applicable depending on the application.

To continue with reference to the embodiment in Fig. 1, each light unit 121 is connected to a control means 110 comprising a driver 112 and a process unit 111. The driver 112 is arranged for driving each light unit 121 based on control data CD provided by the process unit 111. In embodiments of the flashlight device, driving the light unit may include driving the light source e.g. with respect to intensity and color, and controlling the optical means e.g. with respect to focusing the output light and controlling the direction of the output light. The process unit 111 may include a microprocessor, a microcontroller, a programmable digital signal processor, or another programmable device. The control means 110 is adapted to receive external data ED, which here is received in the process unit 111, and based on the external data ED and computer executable code, which code is typically stored in a control means memory and comprising instructions on how to analyze and process the retrieved external data, the process unit 111 derives control data CD needed for the driver 112 to individually control each one of the light units 121 in the light unit matrix 120 in response to the external data ED.

As is readily understood by the skilled person, the flashlight device further comprises power circuits, a housing, and memory units etc. associated with the control means, i.e. the process unit. However, to simplify the description of the present inventive concept, these parts are left out in the figures and the description.

The flashlight device 100 is here connected to a camera 50. The flashlight device may alternatively be connected to, or be integrated in, a security device, or be integrated in a camera. The camera 50 comprises an image sensor matrix 51, being a CCD. The image sensor matrix 51 comprises a high number of light-exposable cells (not shown) for obtaining an image of the target. Each light-exposable cell obtains information of a corresponding subpart of the target (scene). Other suitable image sensors falling within the scope of the present invention are for instance CMOS based image sensors.

When aiming the camera 50 at a target, i.e. a scene, the flashlight device 100 is arranged to retrieve captured image data from the image sensor matrix 51 , thus to retrieve external data ED associated with the target. The external data may alternatively or in addition to the image sensor be retrieved from an auto focusing means, a zoom position sensor, an auto-light meter means, a distance meter or a movement sensor. Different external sources are applicable for providing different external data associated with the target. From the external data ED, control data CD is calculated according to functionalities, which will be further explained by means of examples herein under.

Now with reference to Fig. 3, which is a schematic top view illustration of the light unit matrix 120 of the embodiment of a flashlight device as described with reference to Fig. 1 when illuminating a target 10, the light unit matrix 120 comprises twenty five light units 121, of which five, 121a-121e, are visible in Fig. 3. Each light unit, 121a - 121e, is arranged to, in response to individual control data CD_a__e, provide a predetermined

illumination I _A-_E O f a given subarea, A-E, of a target 10. Each of the subareas A-E are thus illuminated individually, and the illumination I_A-_E is controlled with respect to e.g. intensity, focus, color etc. The light that is generated by the flash, i.e. light unit matrix 120, is subsequently reflected by the target, and finally when reaching the photographic lens of an image capturing means of the camera 50, is inversely proportional to the square of the distance of the target. When the distance of various objects, i.e. subareas A - E, in the scene has been measured with the auto-focus mechanisms of the camera 50, the output power of the output light from the flash for the directions corresponding to the various objects in the target is scaled with the square of the distance to obtain an even, more natural representation of the target on the image sensor matrix 51.

For photographic applications the flashlight device is advantageously utilized to illuminate subareas of the target that are important in the photograph and thereby enhancing the visibility of these subareas of the target. Simultaneously, subareas that are not the main object to be highlighted in the photograph are excluded, that is blacked out or at least dimmed out. Take for instance, an example of a situation as illustrated in Fig. 4, when taking a picture of a person 20 being present in a target area 10. The target surface area in whole is represented by the aggregate subareas A- K in Fig. 4a. Here the main object is the person, and to identify the subarea to be illuminated, i.e. the aggregate subareas D - H, external data may be retrieved from the autofocus and/or auto light-meter settings of the camera image sensor (not shown). The illumination from the flashlight device is selected to mainly illuminate the object of onto which the camera is focused, and providing none or less illumination to areas further out, or which are out of focus. Alternatively, the subarea to illuminate is determined by analyzing a test image provided by the image sensor matrix 51. The analysis of the test image with the aim to find a person in the image may be done by means of face detection in the test image, contrast detection in the test image, smile detection in the test image, movement detection in the test image (by retrieving several photo frames), by manual selection by the user using the image on the screen on the camera, or any other suitable analysis which is useful for detecting areas of the target 10 which may be a person, and which in this case is the main object of the photograph which is interesting to illuminate.

An opposite approach is applicable when photographing e.g. a scene of a room. External data, being a test image provided with the image sensor matrix 51 , is processed to detect subareas of the target 10 which has poor natural illumination, i.e. which appear dark in the test image. The driver of the flashlight device is set accordingly such that light units for providing illumination in the detected dark subareas provide higher intensity of the output light, than light units for providing illumination to subareas of the target which are detected as sufficiently illuminated in the test image. Thereby, subareas that need additional illumination receive illumination from the flashlight device, without risking overexposed areas in the photograph.

According to an embodiment of the fiashlight device, the test image is analyzed to detect vignetting caused for instance by the imaging lenses. That is, the control data calculated in the process unit is arranged to provide a higher intensity of the illumination of subareas of the target which is determined to, according to the retrieved target associated external data, have too low illumination. Thereby adapted illumination to adjust e.g.

vignetting of imaging lenses is provided.

In an alternative embodiment, the test image is analyzed with respect to color contents. In response to the color in the test image of the scene, the control data is arranged such that the predetermined illumination has an adjusted color cast and/or color temperature.

With this, the unnatural color of existing artificial light can be compensated for by the flashlight, by mixing light of an appropriate color with the existing artificial light, and not by substituting the artificial existing light with fiashlight as is the case in conventional flashlights.

In embodiments of the fiashlight device, a control flash may be employed when retrieving the test image as described in the previous examples, or other external data which relies on light. According to an embodiment of the flashlight device, movement measurements with a movement sensor is utilized to analyze the target, where the movement triggers the flashlight to illuminate the area of the movement, or other image/sensor processing information. This is further useful for instance in a surveillance or security system to detect moving objects and then highlighting the moving object by means of the fiashlight device according to the present inventive concept.

According to an embodiment of the flashlight device, the subarea of the target area to be illuminated is selected based on contrast differences and/or color differences in the external data. The illumination from the flashlight device is in embodiments of the present invention arranged for providing a time sequential illumination of at least one predetermined subarea of the target. Other than with conventional strobe lights, only the moving parts in the scene can be illuminated with strobe light, for example to study movements or for artistic purposes.

With reference now to Fig. 5, a flashlight device comprising a light unit matrix 120, having light units 121 arranged in rows 1-3 and columns a-d, is employed in a camera system 500. Although only the light unit matrix 120 of the flashlight device is illustrated in the figure, the fiashlight device further comprises a control means to which each light unit 121 is connected. As described above, the control means comprises a driver arranged for driving each light unit individually based on the control data CD provided by the process unit. The process unit receives external data from an image sensor matrix 51 of camera system 500. The camera system 500 further comprises a focal plane shutter 60 and an optical system 70, here being a zoom lens. The image sensor matrix 51, the focal plane shutter 60 and the lens system 70 are arranged along an optical axis "oa". The focal plane shutter 60 is an optical component in which a movable aperture 61 is arranged. The focal plane shutter 60 is arranged right in front of the image plane, here right in front of the image sensor matrix 51, that is between the image sensor matrix 51 and the optical system 70. The movable aperture 61 decides which part of the image sensor will active, while the rest of the focal plane shutter blocks out the rest of the image sensor matrix 51. By synchronizing the width and/or position of the illuminated subarea of a target 80 with the width of the aperture 61 and/or the position of the aperture 61, an advantageous effect is achieved, meaning that with even the shortest shutter speeds the flashlight device can be used, because every part of the image sensor 51 receives light generated by the flash light device.

With conventional electronic flash lights in combination with a focal plane shutter, the shortest exposure time is the exposure time, also called shutter speed, where there is a moment that the shutter is completely open. At that said moment the said conventional flash is fired. The external data for determining the drive data for the light units 121 is for instance retrieved from the active parts of the imaging sensor matrix.

As explained above, other sources for retrieving the external data from may be utilized. However, in these embodiments, the control data is then preferably extracted from that external data when combined with information regarding which parts of the imaging sensor matrix that are active at a certain moment, that is with the image captured by the imaging sensor matrix at that certain moment.

Further, the predetermined illumination is in an embodiment of the flashlight device arranged for providing a sequential illumination of at least one predetermined subarea of the target. The sequence is synchronized with a line of movement of the active imaging subarea of the imaging sensor matrix 51, or by the movable aperture 61 being placed in front of the imaging sensor matrix 51.

According to an embodiment of a flashlight device, the light units are arranged having optical means that create a wide pencil of light when all light units are switched on. When only the central light units are switched on, a narrower pencil of light is created, thus concentrating the light on a smaller subarea of the target. Thus without mechanical movements, a zoom flash light can be made, of which the beam width is changed according to the zoom position of the camera lens.

According to an embodiment of the flashlight device the light units are arranged to provide illumination of the target covering different angles of illumination. Each light unit may then illuminate a subarea of the target under a different line of incidence than e.g. an adjacent light unit. Groups of light units may be directed to a certain subpart of the target while other groups of light units are directed to another subpart of the target, and with a different line of inclination. Thereby controllable lighting effects of the target is obtained, which may be used for artistic reasons or to cancel out shadows.

According to an embodiment of the flashlight device, the light unit is a laser scanning device for providing the different angles of illumination. With a laser beam, for example being an overlap of a blue laser beam, a green laser beam, and a red laser beam, and with a scanning device comprising for example galvanic mirrors or micro-electro-mechanic system (or MEMS) mirrors and control means to modulate the output of the laser beam or laser beams, the scene can be illuminated, and the illumination of the scene can be adjusted based on information of the scene from image processing, face detection, auto exposure- meter results, etc.

Above, embodiments of the flashlight device and method according to the present invention as defined in the appended claims have been described. These should be seen as merely non-limiting examples. As understood by a skilled person, many

modifications and alternative embodiments are possible within the scope of the invention.

It is to be noted, that for the purposes of this application, and in particular with regard to the appended claims, the word "comprising" does not exclude other elements or steps, that the word "a" or "an", does not exclude a plurality, which per se will be apparent to a person skilled in the art.

Claims

CLAIMS:

1. A flashlight device (100) comprising:

at least one light unit (121) for illuminating a target, each light unit comprising a light source (122); and

control means (110) for driving each light unit based on control data;

said control means further being arranged for retrieving external data associated with said target, and deriving said control data from said external data, and wherein each light unit, in response to said control data, is adapted for providing a predetermined illumination of a given subarea of said target.

2. A flashlight device according to any preceding claim, wherein said external data is retrieved from at least one of an imaging sensor matrix , an auto focusing means, an auto-light meter means, a distance meter and a movement sensor.

3. A flashlight device according to any preceding claim, wherein said predetermined illumination of said light units jointly covers a predetermined subpart of said target.

4. A flashlight device according to claim 3, wherein said predetermined subpart of said target is selected based on contrast differences and/or color differences in said external data.

5. A flashlight device according to any preceding claim, where said external data is retrieved from an imaging sensor matrix (51), and said predetermined illumination is arranged for providing a sequential illumination of at least one predetermined subarea of said target, said sequence being synchronized with a line of movement of an active imaging subarea of said imaging sensor matrix, or by a movable aperture (61) being placed in front of said imaging sensor matrix.

6. A flashlight device according to any preceding claim, wherein said

predetermined illumination is adjusted based on variation of depth of said target.

7. A flashlight device according to any preceding claim, wherein said

predetermined illuminations of said light units are arranged to jointly cover a predetermined subpart of the target being a moving object.

8. A flashlight device according to any preceding claim, wherein said control data is arranged such that said predetermined illumination has an adjusted color cast and/or color temperature.

9. A flashlight device according to any preceding claim, further comprising at least one optical system arranged in front of said light units for providing a zoom function.

10. A flashlight device according to any preceding claim, further employing a control flash being activated in order to retrieve said external data.

11. A flashlight device according to claim 10, wherein said control flash is a preview version of the joint predetermined illuminations of said light units, having one of a decreased power, a different color, and a different time duration.

12. A flashlight device according to any preceding claim, wherein said plurality of light units are arranged in a rectangular array or in a circular array.

13. A flashlight device according to any preceding claim, wherein said light sources provide light being at least one of a visible color, infrared, and ultraviolet.

14. A flashlight device according to any preceding claim, wherein said light units are arranged to provide illumination of said target covering different angles of illumination.

15. A flashlight device according to claim 14, wherein said light unit is a laser scanning device for providing said different angles of illumination.

16. A flashlight device according to any preceding claim, wherein the light sources a light emitting diode.