Patent Background

In photography, there has been recognized the need for providing flash illumination, at an angle that is suited to the scene coverage of a zoom lens. A zoom lens is capable of a variable range of focus from telephoto to wide-angle settings. Improved image quality may result if the flash illumination angle or spread about the center optical axis of the flash is adjusted to correspond to the scene coverage angle. Thus, at the telephoto setting the flash illumination should be well collimated, while at the wide-angle setting, the flash illumination should be spread over a relatively wide angle about the center axis. In such a camera apparatus, the flash itself may have a variable focus lens that is controlled in response to the focus setting of the zoom lens. This may also be described as a flash beam focuser, which focuses the light from the flash into a smaller or a larger area at the center of the frame (center axis of the flash).

Yet another flash-based technique that may be used to improve image picture quality in certain situations is to vary the power of the camera flash. Somewhat similar to the flash beam focusing technique described above, a variable flash power mechanism may be used to, for example, decrease the light output of the flash when exposure needs to be decreased (due to the flash being too bright). This technique is similar to the flash beam focuser in that it does not shift the angle of the peak of the spatial energy profile of the flash, relative to the center optical axis of the flash.

Patent Summary

In one embodiment of Apple's invention – an electronic camera device has an imaging sensor, a flash to illuminate the scene to be captured by the sensor, and an evaluator to detect a condition in the scene. The camera device also includes a redirector that shifts the peak of the spatial energy profile of light from the flash. The peak is to be shifted from being aimed at one region in the scene to being aimed at another region in the scene, in response to the evaluator having detected the condition in the scene. In other words, the angle of the peak of the spatial energy profile is changed, relative to a center optical axis of the flash, so as to increase illumination of, for example, a detected or selected object in the scene.

In one embodiment, detection of the condition or object in the scene may be performed automatically, through analysis of images captured by the sensor. In addition, or as an alternative, the evaluator can detect the particular condition in the scene based on the output of one or more scene condition sensor devices in the camera (e.g., ambient light sensor and auto focus sensor devices).

The combination of the flash and the redirector may be composed of a moveable flash lens system that is coupled to a flash light source element, to redirect light from the flash. The evaluator signals the moveable lens system to automatically move (e.g., pivot about an axis), so as to shift the peak of the spatial energy profile of the light. As an alternative, the combination of the flash and redirector may be implemented as a moveable flash light source element that is optically coupled to a fixed flash lens system, again to redirect light, i.e. change the angle of the peak of the spatial energy profile, in response to being signaled by the evaluator.

In another embodiment, the camera device may have a touch screen, which allows its user to manually select (via finger touch) a dark or dimly lit object or region in the scene, to be illuminated by the combination flash and redirector. The touch screen functions as a viewfinder, showing the scene before the camera. A selection may be made by the user's finger on the touch screen, which is translated to an object or region in an image of the scene. A mapping is performed between the selected object or region in the scene and the closest available angle to which the flash-redirector may be redirected, to illuminate the selected region when taking the picture. In a particular embodiment, the flash is implemented as an array of focused, but fixed light emitting diode (LED) lamps whose power is modulated or otherwise adjusted so as to illuminate the region of interest in the scene, relative to the rest of the scene (during picture taking).

One or more of the above described embodiments may help make more efficient use of the limited power and energy that is available in a portable electronic device, by limiting light output of the flash and at the same time directing or redirecting the peak of its spatial energy profile to just a subset of the scene (which may be lacking in sufficient natural light but is the primary region or object of interest in the scene). This capability is particularly desirable when, for example, taking video of a person being interviewed, because of the relatively long time interval during which the flash is turned on in such an application.

The above summary does not include an exhaustive list of all aspects of the present invention.

Overview of the Flash System

A Digital Camera Device having a Camera Flash Redirector

Apple's patent FIG. 1 illustrated below is that of a block diagram depicting a digital camera device 100 having a camera flash redirector. The device may be a portable device, such as a dedicated digital still or video camera, a smart phone or laptop/notebook computer with an integrated camera function or it may be a desktop personal computer with a built-in camera function. In this example, the device is shown as being aimed at a scene in which there is a person standing in front of a tree.

Imaging Sensor

The device has an imaging sensor 14 which could capture images of a scene. The imaging sensor may be a solid state or integrated circuit device that implements an array of sensor elements and associated analog and digital signal processing and exposure control circuitry. Examples include a complementary metal oxide semiconductor (CMOS) or a charge couple device (CCD) imaging sensor chip that is used in typical consumer grade digital still and video cameras, and in smart phones that have camera functionality.

 
An Imaging Lens System

Optically coupled to the imaging sensor is an imaging lens system 16, which is aimed at the scene. The imaging lens system may include one or more lenses to focus light from the scene onto a focal plane at which the imaging sensor may be located, to form an optical image of the scene. Other elements may be included in the lens system, such as a variable or fixed aperture, and one or more light filters, all of which may be in accordance with conventional digital camera technology.

Another option is a moveable imaging lens system that is referred to as a zoom lens or variable focus lens system, that may provide a range of focus and viewing angles, between, for example, telephoto and wide-angle.

Scene Condition Sensor Devices

The illustrated device could also include one or more scene condition sensor devices 20. These may be solid state or integrated circuit devices that have circuitry or structure that is able to sense various conditions in a remote fashion, e.g. detect objects in the scene. For example, an ambient light sensor device (ALS) can provide a measure of the level of visible light intensity in the environment surrounding the device (the so-called ambient light level). Another example is an auto focus sensor, such as one that has an infrared transmitter and receiver, which can be aimed at a particular object in the scene, to help determine a measure of the distance to or location of the object. Such information is typically used in digital cameras that have an auto focus mechanism. Such a mechanism may be able to automatically change the focus of the imaging lens system so as to track or maintain an object in the scene within focus, as the object moves relative to the camera device. This is also referred to as a locking auto focus mechanism and is based on sensing movement of the object in the scene.

About the Flash System and Redirector

The device also has a flash 22 that is associated with a redirector 24. One or more light source elements may be present in the flash, to produce a flash of light or, in the case of video capture, for a longer duration, in order to illuminate the scene while pictures are being taken at the same time. This additional light may be controlled in response to the shutter button being pressed by the user. The flash allows a picture to be taken without increasing the exposure time, thereby capturing a sharper picture even while there may be some relative movement between the device 100 and the object being illuminated. The light source for the flash may be an electrically powered gas discharge tube, such as a xenon tube, or it may be more recently developed technology such as a flash LED lamp. The flash has an optical flash center axis, which may run through the center or peak of the spatial energy profile of the light produced by the flash (see FIG. 1). In a normal setting, the optical flash center axis may be aimed at the center of the picture frame of the device.

Associated with the flash is a redirector. The redirector may redirect or shift the peak of the spatial energy profile of light from the flash, to a different angle or spot. In particular, the peak can be shifted from being aimed at one region or spot in the scene that may be aligned with the flash center axis, to being aimed at another region or spot in the scene. This is depicted in FIG. 1 by the angular movement of the spatial energy profile, in accordance with the angle ".alpha." This shift is produced in response to a control signal from an evaluator.

The Evaluator & Scene Condition Sensor

The evaluator (patent point # 18, is also referred to as a flash control unit) is responsible for setting the angle ".alpha." of the flash to illuminate a desired spot or region, by appropriately signaling the redirector based on having detected certain conditions or objects in the scene. For example, the evaluator might detect the face of a person in the scene, as suggested in FIG. 1, through automatic analysis of one or more interim images of the scene that have been captured by the sensor 14. In addition, or as an alternative, the evaluator may detect a particular condition in the scene as one where there is a bright background in one region or spot of the scene, but a dark object or spot in another region (e.g., due to the shadow of a tree). This detection may be based not just on analysis of interim images captured by the imaging sensor, but also based on information about the scene obtained by one or more of the scene condition sensor devices 20. The camera device may thus act automatically based on image analysis and sensor data (e.g., ambient light level or measured distance to a particular object), to redirect the flash 22 at the appropriate angle ".alpha." The detection may occur during an otherwise typical picture taking process, e.g. between the time that a user has initially pressed the shutter button part of the way, until the time when he has pressed the button all the way. Such flash control helps make more efficient use of the light available from the flash to illuminate just the object or spot of interest. In practice, given the spatial spread of typical energy profiles, areas close to the spot at which the peak is aimed may also be illuminated although to a much lesser extent than the peak.

A Combination Flash-Redirector

In Apple's patent FIG. 2 illustrated below we see an example of a combination flash-redirector in which a fixed light source 23 is optically coupled to a pivoting flash lens 25. The pivoting flash lens has a lens mechanism in which a lens could pivot, under control of an actuator mechanism, by approximately the angle ".alpha." relative to the flash center axis (to achieve the desired redirection angle .alpha.). The actuator mechanism may be a motorized device that could respond to an automatic control signal, or it may be a user-powered mechanical coupling. The pivoting flash lens may thus achieve the flash redirection angle ".alpha.", for a relatively collimated beam of light from the fixed light source. Apple's patent FIG. 3 is yet another example of a combination flash-redirector.

Integrated Flash and Dedicated Shutter Button

Apple's patent FIG. 4 shown below is another embodiment of the invention that's an example of digital camera device 100 having a camera body or housing 52 that has integrated therein the flash 22 and a physical shutter button 34 (e.g., a dedicated shutter button, such as one found in a dedicated still and/or video camera).

 
 
In this case, the flash 22 is made of an array of focused and aimed light source elements or lamps. These may be light emitting diode, LED, flash lamps, each having its own flash lens and/or other optical structure such as a reflector that produces a collimated or narrow beam of light as shown. The light source elements are aimed such that the beam from each element will cover a different portion of the scene (at which the imager lens system 16 of the device will be aimed). In this embodiment, the redirector 24 (see FIG. 1) may apply variable power to the array of lamps so as to illuminate the scene at variable levels (based on control signals from the evaluator 18). For example, each lamp may be controlled as being either on or off. Alternatively, additional circuitry may be added so that one or more of the lamps may have multiple, discrete power levels (between their fully on and fully off settings).

Apple credits Richard Tsai as the sole inventor of patent application 20100238344, originally filed in Q1 2009.

Notice: Patently Apple presents only a brief summary of patents with associated graphic(s) for journalistic news purposes as each such patent application is revealed by the U.S. Patent & Trade Office. Readers are cautioned that the full text of any patent application should be read in its entirety for further details. About Comments: Patently Apple reserves the right to post, dismiss or edit comments.