Information│蘋果公布了最新的VR專利，一款眼球追蹤的緊湊型VR頭盔

文 Roadtovr

編譯 HaloVR

美國專利局(United States patent Office)在今日發布的一項專利申請中，蘋果公司描述了一款設計緊湊、舒適的VR頭盔。蘋果專利的標題為「Optical System for Head-mounted Display」。顯然，蘋果重新設計了傳統的光學系統，目標是創建一款更為緊湊的VR頭顯。

蘋果在專利文件中寫道：「如果設計不注意，頭顯可能會變得十分笨重，而且佩戴使用會令人疲憊。頭顯的光學系統可能會採用笨重而巨大的透鏡排列。長時間佩戴搭載這種光學系統的頭顯可能會令用戶感到不舒服。因此，市場渴望優化的頭顯。」

在深入閱讀蘋果的專利描述後，發現「反折射」光學系統是這一設計的基礎，亦即採用包括反射元件和折射元件（包括不同的偏振元件）來沿著光路操縱光線。

反折射光學元件通常用於望遠鏡和顯微鏡等高放大倍率光學系統，而這種光學元件能夠「摺疊」光路以形成更緊湊的布局。光線在穿過一個典型的透鏡時不再是簡單地彎曲，而是在反折射光學元件中沿著光路來回多次反彈，然後再從另一側出射。

微型顯示器雖然體積小，但像素密度高。由於其體積緊湊，這十分適用於虛擬現實。然而，微型顯示器同時需要具有高倍率的透鏡。高倍率透鏡通常需要設計成非常粗厚，又或者是採用菲涅耳設計（當前的消費者頭顯十分普遍，但菲涅爾設計同樣存在自身的挑戰）。從專利可以看出，蘋果似乎正在研究用反折射光學元件來創建一種緊湊的高倍率光學元件，以搭配微型顯示器的使用。蘋果專利中提及了微型顯示器，但為了確保專利在法律上能夠覆蓋更大的範圍，文件同時提及了其他類型的顯示器。

專利文件進一步描述了一系列偏振元件的作用，它們會把一定的光線反射回顯示器以被偏振器吸收。蘋果解釋說，這是為了保持對比度，並且避免用戶感知到雜散的光線（不必要/未對準的光線）。

儘管這份專利主要集中在光學元件的光學設計和排列上，但蘋果同樣在描述製造該設計的各種方法上（據說可能會增加系統的耐久性和清晰度）投資了大量的筆墨。

至於專利的其他部分，蘋果同時談及了這種頭顯的可能性，包括把一系列的感測器用於各種追蹤任務。另外，蘋果專門闡釋了攝像頭可以用於檢測環境（以及內向外追蹤）和感知用戶的眼睛位置。對於後者，這很有可能是用於注視點渲染等眼動追蹤任務。

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儘管蘋果對AR和VR十分感興趣，蘋果手上拿著一系列尚未應用的相關專利。所以雖說這項專利探討了在頭顯製作上的部分實際細節，但最好還是把這份專利看作是「蘋果可能在考慮這種設計」，而不是說「蘋果正在實施這種設計」。蘋果現在正在日益把AR和VR納入至他們的生態系統中，包括在MacOS中擁抱VR，並且在iOS上推出了ARKit。對於後者，社區中的許多人都猜測這是作為最終蘋果AR頭顯產品上市前的墊腳石。

In a patent filed in 2017 and issued today by the United States Patent Office, Apple describes a VR headset designed to be compact and comfortable.

Spotted by Patently Apple, Apple』s patent titled Optical System for Head-mounted Display makes it clear up front that this particular design is aimed at creating a VR headset that』s more compact, specifically by redesigning the optical system.

「If care is not taken, a head-mounted display may be cumbersome and tiring to wear. Optical systems for head-mounted displays may use arrangements of lenses that are bulky and heavy. Extended use of a head-mounted display with this type of optical system may be uncomfortable. It would therefore be desirable to be able to provide improved head-mounted [displays].」

Digging through the patent』s dense description, it becomes clear that a 『catadioptric』 optical system is fundamental to this design, one which uses both reflective and refractive elements, including varying polarization elements, to manipulate light along the optical path.

Catadioptric optics, commonly used in high magnification optical systems like telescopes and microscopes, 『fold』 the optical path to create a more compact arrangement. Rather than light being simply bent as it passes once through a typical lens, in a catadioptric optic the light bounces back and forth a number of times along its optical path before eventually emerging from the other side.

Microdisplays, which are small but offer high pixel density, are desirable for VR because of their compact size but require lenses with high magnification. Lenses with high magnification often need to be very thick, or can be reduced to a Fresnel design (as is common on consumer VR headsets today), though the Fresnel approach introduces its own set of challenges. It seems likely that Apple is investigating the use of catadioptric optics as a means of creating a compact, high magnification optic specifically to be used in conjunction with a microdisplay. Microdisplays are mentioned in the patent, though, wanting the patent to be as broad as legally possible, other types of displays are mentioned as well.

The patent further describes a series of polarizing elements which are used to reflect some of the light back toward the display to be absorbed by a polarizer. The document explains this is to maintain contrast and avoid stray (unwanted/misaligned) light from being seen by the wearer.

While the patent largely focuses on the optical design and arrangement of optical elements, a significant portion describes varying approaches to manufacturing the design, which are said to potentially increase the durability and clarity of the system.

Among other details, the patent also touches on the possibility of such a headset including a bevy of sensors for various tracking tasks, and specifically notes that cameras could be employed for measuring the environment (as with inside-out tracking) and sensing the user』s eye position. The latter likely being used for eye-tracking applications like foveated rendering.

While Apple is clearly interested in AR and VR, the company has no shortage of patents for technologies which it has never used. So while it』s interesting that this patent delves into some practical details of manufacturing, it』s better to consider patents a look at what the company may be thinking rather than precisely what they』re doing. That said, Apple is increasingly involving AR and VR in its ecosystem, including embracing VR on MacOS, and launching ARKit on iOS, which many suspect to be a stepping stone toward an eventual AR headset product offered from the company.

【本文由haloVR發布，2018年02月09日】