Foreword
AR augmented reality smart glasses on the current society is more mainstream wearable device AR, augmented reality is the most important support equipment in addition to phones and tablets. Previous articles, we have discussed calibration technology related to optical see-through head-mounted displays, in fact, smart AR augmented reality glasses is an optical see-through head-mounted displays. This article will be combined with some mainstream AR glasses devices currently on the market, its related calibration, tracking, interactive technology to make the discussion.
1 augmented reality smart glasses introduced AR
Smart AR AR glasses are a perspective view of the optical type head-mounted display. Why we must emphasize the characteristics of optical see it? Because in addition to optical see-through perspective as well as video, and the video see-through augmented reality after the AR screen (including real elements and virtual elements) Unified Shader presented to the user, not the virtual and physical elements of real optical integration, from a technical perspective on look simple but it can not bring the best and the reality of integration experience to the user. Therefore, the current mainstream video equipment discarded formula AR, mainly turning optical see-through type AR.
According to my understanding, the current market popular optical see-through augmented reality smart glasses AR There are two main types, if there are any omissions, please forgive me. (1) integrated intelligent glasses. Such glasses calculation unit, a power supply, the display unit are integrated, technical difficulty, expensive. For example HoloLens 2. (2) split the glasses. Such glasses typically the power calculation unit and a processing unit similar independently of mobile phones, but the display unit made of glasses, the glasses to achieve the downsizing and weight reduction. But because there is no power supply display module, connected to the intelligent processing unit by wire, causing little impact on the user experience. But I have to say this is a reasonable compromise way. Typical products split the glasses is Magic Leap One, NED + Glass X2, Nreal Light and so on.
Two or more glasses can be connected directly to a PC debugging, so there will not come up in terms of a separate PC-based glasses.
2 augmented reality smart glasses AR key technologies
If you want to make a smart AR glasses available, there are several techniques can not escape. Given AR hardware on the market has a lot of, are also considered relatively mature, there is only software technology for analysis. AR glasses technology involved include: (1) calibration technique to help users see potential; (2) tracking technology to help a user go steady; (3) interactive technology, multi-information exchange. In the FIG Google Glass as an example, showing the correlation between these three techniques.
2.1 Calibration
Compared to tracking and interactive technology, calibration technology is a key technology can easily be overlooked but essential. In view of the special principle of the optical see-through AR glasses, we often are not directly available to the human eye in the target space coordinates of the location, and the need for the human eye and AR glasses tracking system is calibrated to achieve "physical environment" - "Tracking System" - "eye imaging" this path, the guarantor eye can see accurately the reality fusion effect. There are many products that directly track the location of the camera position equivalent to the human eye, the result of this is that the human eye can see between the virtual and the physical elements are isolated from each other in the real, not registered good. Intuitive performance is the "head of a movement, a virtual object in Gone with the Wind." Therefore, these products do not usually provide a good experience for the user the actual situation integration. Currently known products, HoloLens series is made this calibration, thus providing the AR effect is also very good, there are some other products because there is no worn, so the first not comment.
AR augmented reality glasses calibration technology, actually calibrated relative positional relationship between the eye and tracking system, as well as within the parameters of the human eye. This topic has been talked about in detail in a previous article, a friend in need can refer to.
https://blog.csdn.net/zzlyw/article/details/53215105
2.2 Tracking Technology
AR glasses want to achieve integration of the physical environment and virtual elements, we must do is to be able to track virtual environment. Mainstream visual tracking techniques include marker images based on the tracking point (Image-based Tracking), based on the tracking of the object (Object-based Tracking) Construction and simultaneous localization and mapping (SLAM). In practice, the INS will be mixed into the track to improve quality.
（1）基于图像的跟踪技术，首先需要对被跟踪的图像进行预处理，得到该图像的特征点集合，然后实时状态下将视频流中的图像进行匹配。
（2）基于物体的跟踪技术，它与基于图像的跟踪技术类似，首先要把被跟踪的物体进行预处理，存储它的各类特征，然后在实时状态下对视频流中的图像进行分析，计算跟踪系统与被跟踪物体的相对位置。
（3）同步定位与地图构建技术，是不需要预处理的跟踪技术，可以在开始后同时完成定位与建图。这种方法虽然使用简单，但是没有办法像前两种方法那样轻松获取眼镜与物理环境中某一指定物体之间的相对位置。所以SLAM技术虽然发展比较成熟，但是如何与AR相结合还值得继续研究。如果对SLAM技术还没有了解的话，可以参考半闲居士的博客（https://www.cnblogs.com/gaoxiang12/）或者其他相关书籍。
2.3 交互技术
对于AR眼镜，比较方便的交互方式是语音、手势和遥控器。语音交互属于人工智能的一个重要研究领域，很多公司（如科大讯飞）已经做出了比较出色的语音交互产品，这对于AR眼镜的交互是具有重要意义的。手势交互因为不需要引入额外的交互设备，只需要用户做出手势就可以输入指令，也在一定程度上促进了AR眼镜交互技术的发展。遥控器作为传统的输入手段，虽然简单但是却能保证准确高效的输入，因此很多AR眼镜产品还是配了遥控器或者触控板作为交互设备。
3 增强现实AR智能眼镜的的发展前景
既然总说智能眼镜，那么“智能”体现在哪里呢？实现了AR算是智能了吗？当然，实现完善的AR功能是迈向“智能”的关键一步，但是仅仅从信息显示层面做提升还是有些欠缺。AR眼镜的智能还应该包括AR内容本身的智能性特征，这就要涉及到人工智能领域的研究了。因此笔者认为，增强现实AR智能眼镜的研究，绝不仅限于构建一套能够做出AR效果的眼镜，也不要局限于眼镜的穿戴舒适性，还应注意与人工智能领域的结合。
简而言之，AR已经不仅仅是AR，更是以AR为中心的多个研究领域的交汇点，并且还是一个寄托了人们美好生活愿景的研究热点。技术引领未来，希望AR智能眼镜可以像智能手机一样，为人们生活水平的提升带来强大助力。
