The iPhone camera remains significantly restricted when compared to devices such as DSLRs which are designed to accept interchangeable lenses.
Photographers havebeen using add-on lenses as a way of supplementing the iPhone's capabilities with wide-angle, telephoto, macro and even fisheye options. However, these lenses bring with them an inevitable reduction in image quality.
US Patent No. 10,031,312 describes a 'small format camera system for mobile devices' which can detect when an external lens is being used and automatically apply adjustments and corrections to mitigate any quality-reducing factors.
Below is a brief description of the patent:
A small format factor camera system for mobile devices that provides improved image quality when using accessory lenses. The system may detect an accessory lens attached to the camera, either via sensing technology or by analyzing captured images. The system may analyze image data to determine current alignment (e.g., optical axis alignment, spacing, and/or tilt) of the accessory lens relative to the camera lens, and may shift the camera lens on one or more axes using a mechanical or optical actuator, for example to align the camera lens optical axis with the accessory lens optical axis. The system may also determine optical characteristics of the accessory lens, either via sensing technology or by analyzing captured images, and may apply one or more image processing functions to images captured using the accessory lens according to the determined optical characteristics of the accessory lens.
The external lens could be detected either directly with specially designed sensors or by inspecting captured images for tell-tale distortions. The intersting part is how then adjustments are made in order to optimize image quality. This is achieved in several ways, including mechanically altering the position of the phone's built-in lens in one or more axes to ensure perfect alignment, as well as through image processing after taking the photo.
The types of movement needed to adjust the lens position could be carried out by hardware not dissimilar to existing optical image stabilization technologies already present in Apple's cameras although, from the description, it does look like new camera hardware would be required to pull off all of the tricks in the patent.
It would be interesting to see Apple come up with some official iPhone add-on lenses, especially if supported by these new optimization technologies.