Yesterday the US Patent & Trademark Office published a patent application from Apple that relates to projection systems, and more specifically to small form factor projection systems such as the one found in Apple's Face ID system hidden within the iPhone's notch.

Apple's continuation patent covers a compact folded projection system (also referred to as a projector) that may, for example, be used in small, mobile multipurpose devices such as smartphones and tablet or pad devices.

Embodiments of the projection system may include a laser light source (e.g., an array of small lasers such as a vertical-cavity surface-emitting laser (VCSEL) array), a folded lens system comprising a lens stack including two or more refractive lenses or lens groups and a light folding element (e.g., a prism), and a diffractive beam splitter that includes at least one diffractive surface.

The light folding element provides a "folded" optical axis for the lens system (e.g., by bending the optical axis 90 degrees) to reduce the Z-height of the projection system. The laser light source emits light (ray bundles) that are refracted by the lenses in the lens stack to the light folding element.

In some embodiments, the lens stack includes two lenses with refractive power, arranged in order from the laser light source (referred to as the "object side" of the projection system) to the light folding element: a first lens with aspheric shape, referred to as a field lens, and a second lens referred to as a collimating lens. In some embodiments, the field lens has high order aspheric surfaces that correct for distortion and telecentricity in the lens system.

In some embodiments, the collimating lens defines the diameter of the exit pupil, the object divergence, and the minimal spot diameter of the object. In some embodiments, the lens stack includes at least one refractive lens between the field lens and the collimating lens to further correct the image quality across the field of view of the lens system.

In some embodiments, the lens system is telecentric on the object side to make it suitable to project the array of laser light sources. In some embodiments, the diffractive beam splitter is located at the exit pupil of the lens system to avoid duplication artifacts.

Apple's patent FIG. 1 below illustrates components of an example compact projection system; FIG. 2 illustrates the diffractive beam splitter replicating the field of view of the lens system to produce a larger field of view for the projection system.

Apple's patent FIG. 3 below illustrates a device that includes a camera and a projection system as illustrated in FIGS. 1 and 2.

Continuation Patent Specifics

Yesterday's patent wasn't about a new invention application but rather a continuation patent wherein Apple is updating and/or adding specific technologies, features and/or methods that they want to legally extend, protect and fold into their existing granted patent which is legally permittable. Any change and/or addition to their invention is restricted to Apple's patent claims that are legally binding.   

Apple's 2020 granted patent covered patent claims that basically covered 3 specific areas of their invention as follows: 

1. A Folded lens system (claims #1-10)
2. A Folded projection system (claims #11-2)
3. A Device (claims #23 and 24)

Apple's continuation patent that was published yesterday completely rewrote the patent claims for this invention by cancelling the entire set of 24 patent claims found in their 2020 granted patent.  

Apple replaced the 24 patent claims found in the granted patent with 20 new patent claims. Being a continuation patent, the claims are numbered #25 – 44 instead of 1-20. Apple legally has to show that it's a continuation patent rather than a new patent so that they're able to maintain the priority date of the invention.

Below are a few of the 20 new claims protecting their "Folded Projection System" that's a part of the Face ID camera set.

Patent Claim #25: "A projection system, comprising: a light source; a lens system comprising: a lens stack comprising a field lens and a collimating lens; and a light folding element; and a diffractive beam splitter; wherein the lens stack refracts light emitted by the light source on a first optical axis to the light folding element; wherein the light folding element redirects the light received from the lens stack to the diffractive beam splitter on a second optical axis; and wherein the diffractive beam splitter replicates the light to generate a larger field of view for the projection system than an internal field of view of the lens system."

Patent Claim #26: "The projection system as recited in claim 25, wherein the field lens has at least one aspheric surface to correct for distortion and telecentricity."

Patent Claim #37: "The projection system as recited in claim 25, wherein the light source is a vertical-cavity surface-emitting laser (VCSEL) array."

Patent Claim #38: "The projection system as recited in claim 25, wherein the light folding element is a prism composed of a plastic or glass material with a refractive index that positions an exit pupil of the lens system at an active diffractive surface of the diffractive beam splitter."

Patent Claim #41: "The lens system as recited in claim 39, wherein the light folding element is a prism composed of a plastic or glass material with a refractive index that positions an exit pupil of the lens system at an active diffractive surface of the diffractive beam splitter."

You could review the full 20 patent claims of Apple's continuation patent 20210026153 here.