On September 19, the U.S. Patent and Trademark Office officially granted Apple a patent relating to their iPhone 15 Pro Max telephoto camera that implements a four-fold prism which Apple calls a Tetraprism.

Various embodiments described herein relate to an optical system for cameras, in particular, small form factor telephoto cameras. In some embodiments, such telephoto cameras may be integrated in small, mobile multipurpose devices, e.g., smartphones, tablet, pad, wearable devices, and the like. In some embodiments, the optical system may include a plurality of lenses, a prism, and an image sensor. In some embodiments, the prism may be arranged, optically, between the plurality of lenses and the image sensor along the optical transmitting path of light captured by the plurality of lenses to the image sensor.

In some embodiments, the prism may have at least four surfaces, which Apple had described the iPhone 15 Pro Max having a tetraprism. For instance, the prism may include a parallelogram prism, while a first surface of the prism is parallel to a third surface of the prism and a second surface of the prism is parallel to a fourth surface of the prism. In some embodiments, the prism may be arranged such that the first surface may be positioned facing the plurality of lenses, whilst the third surface may face the image sensor. In some embodiments, the second and fourth surfaces of the prism may each include a reflective coating (or reflector), such that the second and fourth surfaces may reflect light at respective surfaces and the first and third surfaces of the prism may reflect light when the incident angle of the light is close to or greater than a critical angle at respective surfaces.

In some embodiments, as shown in FIG. 1 below, optical system #100 may include prism #110 arranged, optically, between lens group #105 and image sensor #115 along the optical transmitting path of light from lens group to image sensor. In some embodiments, the prism may include at least four surfaces. For instance, as shown in FIG. 1, prism #110 may include a parallelogram prism, while a first surface (Prism S1) of prism 110 is parallel to a third surface (Prism S3) of the prism and a second surface (Prism S2) of the prism is parallel to a fourth surface (Prism S4) of the prism.

Apple's patent FIG. 1 below illustrates optical system #100 may include prism #110 arranged, optically, between lens group #105 and image sensor #115 along the optical transmitting path of light from lens group 105 to the image sensor. In some embodiments, the prism may include at least four surfaces. For instance, as shown in FIG. 1, prism #110 may include a parallelogram prism, while a first surface (Prism S1) of the prism is parallel to a third surface (Prism S3) of the prism and a second surface (Prism S2) of the prism is parallel to a fourth surface (Prism S4).  

For more details, review Apple's granted patent 11762174.