Apple patents lightfield-like imaging system for iPhones
Apple has filed a patent for camera hardware that allows for post-capture focusing. The patent describes a camera for a mobile device that can take normal high resolution images but can also take low-resolution "refocusable" images.
If the hardware ever made it to market, it would function as both a normal smartphone camera but also address the growing popularity of the lightfield camera market. Chinese manufacturer Oppo is incorporating the MEMS autofocus technology into a new smartphone, enabling post-focusing. Meanwhile Nokia's Refocus app and the Focus Twist app for iOS are using software for post-capture focusing.
Here is an excerpt of one of the more exciting parts of the patent:
With conventional digital camera systems, if a focus error was made during image capture so that the scene object of interest is out of focus, there is no way to correct the focus error post capture. An advantage of the plenoptic imaging system of FIG. 3 is that the focus position of a captured image can be adjusted at a later time after the image has been captured. For example, a user interface can be provided that enables a user to evaluate refocused image corresponding to different focus positions and save the refocused image corresponding to the preferred focus position. However, a disadvantage of plenoptic cameras is that the refocused images necessarily have a substantially lower spatial resolution that the native spatial resolution of the sensor array 220. This reduction in resolution is typically by a factor of 16.times. to 36.times.. As a result, the image quality of the refocused image will be significantly lower than a properly focused image captured using a conventional digital camera system using the same sensor array 220.
U.S. Patent Application Publication 2010/0026852 to Ng et al., entitled "Variable imaging arrangements and methods therefor," provides a method for switching between a low resolution refocusable mode and a higher resolution mode. The method is based on moving the imaging sensor closer to the microlens array. However, even when the imaging sensor is in direct contact with the microlens array, the microlenses will still impart artifacts to the captured image that effectively reduces the resolution of the captured image. For example, the intersection lines between the microlenses will impart repetitive aberrations in the captured image and the thickness of the microlens array will make it impossible to position the sensor at the focus plane of the main lens.
There remains a need for a method to enable a camera system to be switched or changed between a low resolution refocusable mode and a high resolution non-refocusable mode.
If we're being hopeful, we can guess that this new patent might have something to do with Apple's recent acquisition of 3D sensor company PrimeSense. But realistically, there is no way of knowing whether this patent will ever see production.
Read the whole patent and check out all the diagrams here.
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