A couple of Apple patents in the last year have surfaced illustrating their work on a new breakthrough zoom lens system with an advanced telephoto lens. Today marks the third major patent application regarding such a system. This time around, Apple focuses on a folded telephoto camera lens system. It's obvious that Apple is trying to deliver a revolutionary new dynamic for iDevice cameras and considering that Apple now possesses advanced camera technology from both PrimeSense and LiNX, Apple could take a giant leap ahead of their competitors if they bring their new camera technology to market in a timely manner. For sure Apple's competition isn't standing still. Just yesterday the Korean press reported that Samsung had made a small-scale investment in Canadian-based Bubl Technology. Bubl is working on a new 360º camera. So the race is on to deliver next-gen experiences with mobile camera systems. Will we see any of Apple's camera advances for the iPhone 7? Yes, more than likely. The only question is to what extent.
Apple's Patent Background
The advent of small, mobile multipurpose devices such as smartphones and tablet or pad devices has resulted in a need for high-resolution, small form factor cameras for integration in the devices. However, due to limitations of conventional camera technology, conventional small cameras used in such devices tend to capture images at lower resolutions and/or with lower image quality than can be achieved with larger, higher quality cameras. Achieving higher resolution with small package size cameras generally requires use of a photosensor with small pixel size and a good, compact imaging lens system. Advances in technology have achieved reduction of the pixel size in photosensors. However, as photosensors become more compact and powerful, demand for compact imaging lens system with improved imaging quality performance has increased.
Apple Invents a Folded Telephoto Lens System
Apple's patent generally relates to camera systems, and more specifically to lens systems for small form factor cameras.
More specifically Apple's invention is to provide future iDevices with a high-resolution telephoto camera in a small package size. A camera is described that includes a photosensor and a compact folded telephoto lens system. In embodiments, folding the optical path of the camera lens system may facilitate achieving a small form factor for the camera lens assembly, and may also facilitate achieving a high resolution optical lens system using a relatively small number of lens elements in the small form factor. Embodiments of folded telephoto lens system are described that may provide a larger image and with longer effective focal length than has been realized in conventional small form factor cameras. Embodiments of a telephoto camera including the folded telephoto lens system may be implemented in a small package size while still capturing sharp, high-resolution images, making embodiments of the camera suitable for use in small and/or mobile multipurpose devices such as cell phones, smartphones, pad or tablet computing devices, laptop, netbook, notebook, subnotebook, and ultrabook computers. In some embodiments, a telephoto camera as described herein may be included in a device along with a wider-field small format camera, which would for example allow the user to select between the different camera formats (telephoto or wide-field) when capturing images with the device.
Embodiments of a folded telephoto lens system are described that may include four lens elements with refractive power. However, more or fewer lens elements may be used in some embodiments. In various embodiments, a light path folding element such as a plane mirror or a prism element may be used to fold the light optical path by redirecting or reflecting the light from a first optical axis on to a second optical axis. In at least some embodiments, at least one of the object side and image side surfaces of at least one of the lens elements is aspheric.
In at least some embodiments, the folded telephoto lens system includes a folded optical axis (referred to herein as AX) that includes a first (object side) optical axis and a second (image side) optical axis, a first group (referred to herein as GR1) of refractive elements, a light path folding element (e.g., a prism or plane mirror) that folds the light optical path by redirecting or reflecting the light from the first optical axis on to the second optical axis, a second group (referred to herein as GR2) of refractive elements, and a photosensor at the image plane. At least some embodiments may also include an infrared filter. At least some embodiments of a folded telephoto lens system may include zooming capabilities for focusing an object scene at infinity (object distance from camera .gtoreq.20 meters) to near object distance (<1 meter). For example, in various embodiments, the first group (GR1), the second group GR2, and/or the photosensor at the image plane may be zoomed, moved or translated for focusing an object scene from far distance (.gtoreq.20 meters) to near distance (<1 meter).
In at least some embodiments, the lens system may be a fixed folded telephoto lens system configured such that the absolute value of the effective focal length f of the lens system is at or about 14 millimeters (mm) (e.g., within a range of 8 mm to about 14 mm), the F-number (focal ratio) is within a range from about 2.4 to about 10, the field of view (FOV) is at or about 26 degrees, and the total track length (TTL) of the unfolded lens system is within a range of 8 mm to 14 mm. The total track length (TTL) of a telephoto lens system is the distance on the optical axis (AX) between the front vertex at the object side surface of the first (object side) lens element and the image plane. In embodiments of the folded telephoto lens system, the unfolded total track length (TTL) of the lens system may be defined as the distance on the folded optical axis (AX) between the front vertex at the object side surface of the first (object side) lens element and the image plane. In other words, the TTL for the folded telephoto lens system is the sum of the absolute values of the distances on the folded axis, AX, between the front vertex at the object side surface of the first (object side) lens element and the reflecting surface of light path folding element (mirror or prism) and the absolute value of the distance between the reflecting surface and the image plane.
The sum of the absolute values of the distances may be used here since by optical design convention, the algebraic signs of the optical parameters (such as radii of curvatures, distances, focal length, etc.) change signs following a reflecting surface. More generally, the lens system may be configured such that the telephoto absolute value ratio (TTL/f) of the folded lens system satisfies the relation,
Apple's patent FIG. 21B illustrates a compact folded telephoto lens system of a future camera that may include a light path folding element and four lens elements. The system also includes refractive power having a convex object side surface; a light path folding prism that folds the optical axis from AX1 to AX2; a third lens element with negative refractive power; and a fourth lens element with positive refractive power.
In addition, in at least some embodiments, at least one of the object side and image side surfaces of at least one of the four lens elements is aspheric. In addition, at least some embodiments may include an IR filter, for example located between the fourth lens element and the photosensor.
Apple credits Romeo Mercado as the sole inventor of this patent application which was originally filed in Q2 2014. Considering that this is a patent application, the timing of such a product to market is unknown at this time.
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