2020 was a relatively busy year for Apple's under-display project with three new patent applications (01, 02 and 03). The three patent applications explored various methods of bringing this feature to future iPhones. Apple also was granted a patent in September 2020.  

Today the US Patent & Trademark Office published yet another patent application from Apple relating to under-display Touch ID. More specifically, Apple's invention generally relates to an under-display optical fingerprint sensor with narrow field-of-view (NFV) collimator and a thin-film transistor (TFT)-based organic imager.

An optical fingerprint sensor may be particularly advantageous for verification and/or authentication in an electronic device and, more particularly, a portable device, for example, a portable communication device. The optical fingerprint sensor may be carried by the housing of a portable communication device, for example, and may be sized to sense a fingerprint from a single finger. Where an optical fingerprint sensor is integrated into an electronic device or host device, for example, as noted above, the authentication can be performed quickly, for example, by a processor of the host device. The challenges facing the optical fingerprint sensor include consistency in performance over time, as the glass-air interfaces are not stable enough for small area matching.

However, the large-area sensors using complementary metal-oxide-semiconductor (CMOS) are not cost effective. Separation of different reflection rays at various angles is another challenge, as many illumination patterns have to be used to separate the reflection rays, which leads to a long (e.g., a few seconds) image capture time. This is what Apple's invention addresses.

Under-Display with NFV Collimator & Organic Imager

Apple's invention is directed to an apparatus for fingerprint sensing with a narrow field-of view (NFV) collimator and an organic imager. The apparatus includes a touch-display layer, a collimator layer and a pixelated image sensor.

The touch-display layer can be an organic light-emitting diode (OLED) display that is covered by a transparent layer (e.g., a cover glass layer) and can emit light to illuminate a surface touching the transparent layer and allows transmission of reflected light from the surface to underlying layers including the collimator layer and the organic imager.

The collimator layer can collimate the reflected light, and the organic imager is a pixelated image sensor that can sense the collimated reflected light.

In one or more implementations, the collimator collimates the reflected light to enable a one-to-one imaging ratio between an area of the finger surface touching the transparent layer and an area of a corresponding image formed on the pixelated image sensor. In other words, the reflected light reaching a pixel of the organic imager through the collimator layer is transmitted through an area of the organic imager approximately equal to an area of the pixel.

The pixelated image sensor can be a thin-film transistor (TFT)-based organic imager. In some embodiments, the collimator layer is a fiber-optics plate made of a collection of optical fiber films bundled with an opaque separator material.

In one or more implementations, the collimator layer is a micro-aperture plate including transparent glass or resin embedded in an opaque glass or resin material. The collimator layer of the subject technology can achieve a NFV of approximately +/-3 degrees and a transmission within a range of about -6 dB to 0 dB.

In some implementations, a micro-lens layer is formed on top of the micro aperture plate to separate angled illumination reflections. A total feature signal-to-noise ratio (FSNR) value of the touch-display layer and the underlying layers amounts to more than about 12 dB.

The surface touching the transparent layer is a surface of a human finger including ridges and valleys, and the collimator layer's purpose is to separate weak reflections resulting from angled illumination of walls of valleys.

Apple's patent FIGS. 1A-1B below are diagrams illustrating an example of an under-display optical fingerprint sensor and a corresponding signal-level chart; FIG. 6 is a flow diagram illustrating an example method for providing an under-display optical fingerprint sensor.

Apple notes that the under-display optical fingerprint sensor of the subject technology can be readily integrated into an iPhone or Apple Watch.

Under-display (and/or in-display) fingerprint technology for Touch ID has been rumored to be coming to a future iPhone for some time now and most recently repeated in a Bloomberg report posted last week.

For more details, review Apple's patent application number 20210019017 here. Considering that this is a patent application, the timing of such a product to market is unknown at this time.