这一代iPad Pro 2020总体来说算是硬件规格上的小改,就连A12Z都可以认为是不同体质版的A12X。不过它在后摄上加入了一枚传说中的LiDAR激光雷达,苹果明确宣称这是一颗采用dToF技术的深度感知模块。需要明确的是,LiDAR就是一种采用ToF(Time of Flight)技术的3D感知应用,一般来说车载激光雷达多见dToF方法——后面我们将详述这种技术的本质。
TechInsights对外公开的拆解数据显示,这枚LiDAR所用的传感器像素阵列的分辨率是3万像素,尺寸4.18 x 4.30mm,单像素尺寸10μm,供应商是索尼[1]。这其中有几点是比较令人在意的,包括dToF技术、索尼的ToF图像传感器。
iPad Pro 2020的LiDAR内部,来源:TechInsights 虽然早在iPad Pro推出之际,就已经有许多媒体都提到,iPad Pro 2020采用的LiDAR接收端传感器,很可能是索尼或意法半导体的方案,TechInsights的拆解则坐实了索尼作为供应商的说法。但实际上,就已公开的资料来看,索尼并没有公开在售的dToF方法相关技术,当然并不排除其中存在的各种合作,或者索尼研究的新技术率先给苹果使用:这在以往也并非新鲜事。
iPhone X的Face ID系统发射器发出的红外光点,与iPad Pro 2020的LiDAR发射端发出的红外光点数量比较,原理与技术上的差异,导致两者的光点密度差别很大,来源:iFixit[8] 不过这些技术至少现在并没有应用于移动设备的例子,如果说iPad Pro 2020的dToF方法应用的是SPAD传感器,则在这个设备尺寸以及5米测量距离内,而且还是消费型电子产品,SPAD传感器的3万像素或许着实称得上是高像素。 有关iPad Pro 2020是否采用SPAD传感器(TechInsights并未公开这部分分析信息),我们查到前两年苹果的一份专利储备,展示的就是一种3D感知系统,或者说就是ToF[9]。这个专利中提到了LiDAR相关技术——针对的就是消费领域的应用,包括VCSEL光源,而光电探测器选择的就是SPAD。“这种探测器能够以很高的时间抵达分辨率,在数十皮秒内捕获单独的光子”。 苹果一项有关LiDAR的专利,来源:Patently Apple 加上苹果已经在宣传中明言iPad Pro 2020的3D感知所用就是dToF方法,那么我们有理由猜测这可能就是个SPAD传感器。即便似乎从现有技术来看,整个LiDAR模组看起来还是比较奢侈和黑科技。不过前文提到TechInsights认为,这枚传感器来自索尼。问题是从我们查到的资料来看,索尼似乎并没有造SPAD传感器的历史,SoftKinetic的长项也在iToF,而非dToF。
[1] TechInsight’s Twitter - Twitterhttps://twitter.com/techinsightsinc/status/1244050881705844737[2] Softkinetic - Wikipediahttps://en.wikipedia.org/wiki/Softkinetic[3] STMicroelectronics’ Time-of-Flight Sensors and the Starship Enterprise Show up in the iPhone 7 Series - TechInsightshttps://www.techinsights.com/blog/stmicroelectronics-time-flight-sensors-and-starship-enterprise-show-iphone-7-series[4] Zhang Chao, CMOS SPAD Sensors for 3D Time-of-Flight Imaging, LiDAR and Ultra-High Speed Cameras, 2019[5] LiDAR in a Chip, FlightSense™, Introduction to Time of Flight - STMicroelectronicshttps://www.st.com/content/ccc/resource/sales_and_marketing/presentation/product_presentation/group0/e0/84/0c/fb/11/ec/49/1d/SensorsLive_LiDAR_Chip/files/SensorsLive_LiDAR_Chip.pdf/jcr:content/translations/en.SensorsLive_LiDAR_Chip.pdf[6] Panasonic Develops Long-range TOF Image Sensor with High Ranging Accuracy - Panasonichttps://news.panasonic.com/global/press/data/2020/02/en200218-2/en200218-2.html[7] Canon & EPFL Report Performance of the World’s Smallest 2.2um SPAD Pixel - f4 NEWShttp://www.f4news.com/2020/04/18/canon-epfl-report-performance-of-the-worlds-smallest-2-2um-spad-pixel/[8] 12.9” iPad Pro 2020 Teardown: What does the LiDAR scanner look like? – iFixithttps://www.youtube.com/watch?v=xz6CExnGw9w[9] Major Apple Patents Reveal work on next-gen LiDAR Systems using VCSELs for 3D Sensing Systems and Headset - Patently Applehttps://www.patentlyapple.com/patently-apple/2018/11/major-apple-patents-reveal-work-on-next-gen-lidar-systems-using-vcsels-for-3d-sensing-systems-and-headset.html[10] 3D imaging and sensing: now it is rear 3D sensing turn to be the leading growing application - Yole Developpementhttp://www.yole.fr/3D_Imaging_Sensing_ToF_Adoption.aspx[11] Huawei Leads Imaging Chip Area Arms Race, Sony Wins Big with i-ToF, Emergence of Event-Driven Vision Sensors - TechInsightshttps://www.techinsights.com/blog/imaging-sensing-end-year-highlights[12] Better Time of Flight: Sony DepthSense 3D Sensor Explained - LUCIDhttps://thinklucid.com/tech-briefs/sony-depthsense-how-it-works/[13] STMicroelectronics Ships 1 Billionth Time-of-Flight Module - STMicroelectronicshttps://www.st.com/content/st_com/en/about/media-center/press-item.html/t4210.html