augmented reality smart glasses in the smart factory...

Received March 29, 2017, accepted May 8, 2017, date of publication May 12, 2017, date of current version June 28, 2017.

Digital Object Identifier 10.1109/ACCESS.2017.2703952

Augmented Reality Smart Glasses in the SmartFactory: Product Evaluation Guidelines andReview of Available ProductsANNA SYBERFELDT, OSCAR DANIELSSON, AND PATRIK GUSTAVSSONDepartment of Engineering Science, University of Skövde, 54128 Skövde, Sweden

Corresponding author: Anna Syberfeldt ([email protected])

ABSTRACT Augmented reality smart glasses (ARSG) are increasingly popular and have been identifiedas a vital technology supporting shop-floor operators in the smart factories of the future. By improving ourknowledge of how to efficiently evaluate and select the ARSG for the shop-floor context, this paper aimsto facilitate and accelerate the adoption of the ARSG by the manufacturing industry. The market for ARSGhas exploded in recent years, and the large variety of products to select from makes it not only difficultbut also time consuming to identify the best alternative. To address this problem, this paper presents anefficient step-by-step process for evaluating the ARSG, including concrete guidelines as to what parametersto consider and their recommended minimum values. Using the suggested evaluation process, manufacturingcompanies can quickly make optimal decisions about what products to implement on their shop floors.This paper demonstrates the evaluation process in practice, presenting a comprehensive review of currentlyavailable products along with a recommended best buy. This paper also identifies and discusses topicsmeriting research attention to ensure that the ARSG are successfully implemented on the industrial shopfloor.

INDEX TERMS Augmented reality smart glasses, smart factory, augmented reality, industrial operatorsupport.

I. INTRODUCTIONThe fourth industrial revolution is here, involving a paradigmshift towards smart factories that use new technologiesand production philosophies to realize short product life-cycles and extreme mass customization in a cost-efficientway [1], [2]. The smart factory concept is intended to enableextremely flexible production and self-adaptable productionprocesses with machines and products that act both intel-ligently and autonomously by implementing concepts suchas the Internet of Things and cyber–physical systems [3].This paradigm shift and new way of undertaking productionwill dramatically change conditions for operators workingon the shop floor, as their work tasks will no longer bestatic and predetermined, but instead dynamic and constantlychanging [4], [5]. This will put high demands on operatorability to be flexible and adaptable. To successfully meetthese demands, operators must be equipped with efficienttechnology that supports optimal decision making and action.In recent years, augmented reality smart glasses (ARSG)have been identified as a powerful technology supporting

shop-floor operators undertaking various tasks such as assem-bly, maintenance, quality control and material handling.Initial studies have produced successful results and gainswith respect to both productivity and quality have beenreported [6], [7]. ARSG are essentially a head-up transparentdisplay integrating a wearable miniature computer that addsvirtual information to what the user sees [8]. The overlay-ing of virtual information on the real worldview is called‘‘augmented reality,’’ and applying this concept makes it pos-sible to enhance a human’s perception of reality [9]. ARSGare hands-free devices that present information at eye level,just where it is needed, making them an ideal user inter-face for an industrial operator. Furthermore, using camera-based object recognition, ARSG can detect the specific objectthe user is looking at, providing context-aware informationdynamically adjusted to the specific situation [8]. Equippingoperators with ARSG therefore makes it possible to auto-matically provide the exact information needed, at the righttime and place, to handle a specific situation or work taskoptimally.

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A. Syberfeldt et al.: ARSG in the Smart Factory: Product Evaluation Guidelines and Review of Available Products

FIGURE 1. ARSG shipments (adopted from [10]).

The obvious benefits of ARSG have caused interest inthe technology to grow rapidly in recent years, and theirdevelopment is currently driven by several business sectors,such as gaming, sports, and tourism. Shipments of ARSGare expected to explode in coming years, increasing from114,000 units shipped in 2015 to 5.4 million units shippedin 2020 (Fig. 1). In total, it is expected that around 12.2 mil-lion units will be shipped over this five-year period, for annualgrowth of 115% [10].

There are many vendors of ARSG and a vast range ofproducts to choose from on the market, but despite thisgeneral availability, very few manufacturing companies haveadopted ARSG. At first glance this might seem surprisingconsidering the obvious benefits of using ARSG on shopfloors, but at least two major reasons can be identified forthis lack of adoption. First, today’s products are primar-ily marketed either as general consumer products (typicallytargeting entertainment, sports, and/or gaming) or as profes-sional office products (typically targeting product design).Second, the products are highly heterogeneous with largedifferences in design, technology, and functionality that makeit very difficult to assess their strengths and weaknesses froma holistic perspective and to compare products with eachother. This vast range of heterogeneous products makes itboth complicated and time-consuming for a manufacturingcompany to identify the optimal product for its unique shop-floor context, and this fact creates a threshold for adoptingARSG. In this study, we intend to eliminate this thresholdand facilitate the quick and convenient introduction of ARSGon industrial shop floors. This is done by suggesting anefficient step-by-step process for evaluating ARSG based onseveral concrete parameters. These parameters are providedwith recommended values that are set, and justified, fromthe shop-floor perspective. The rationale is that by using thesuggested process, manufacturing companies can efficientlyperform evaluations and quickly make optimal decisions as towhat products to buy. To demonstrate how the process worksin practice, a comprehensive review and evaluation of ARSGcurrently available on the market is undertaken as part of thestudy. Based on careful analysis of the evaluation results, weformulate a general recommendation as to the current best

product to buy for the shop floor. Furthermore, the paper alsoidentifies several important topics meriting future researchattention in order to ensure the successful implementation ofARSG on industrial shop floors.

The next section continues by describing the conceptsof ARSG and augmented reality in greater detail for read-ers unfamiliar with the concepts. The suggested evaluationprocess and its application for evaluating currently avail-able products are thereafter presented in sections III and IV,respectively. The findings of the evaluation are discussed insection V, while section VI presents the conclusions of thestudy and outlines important topics for future research.

FIGURE 2. Augmented reality in the game Pokemon Go.

II. BACKGROUNDThe concept of augmented reality was introduced in 1992to denote a head-up, see-through display that Caudel andMizell [11] had designed as part of a research project. Caudeland Mizell [11] described the concept as follows: ‘‘Thistechnology is used to ‘augment’ the visual field of the userwith information necessary in the performance of the currenttask, and therefore we refer to the technology as ‘augmentedreality’’’ [11, p. 660]. It is important to distinguish betweenaugmented reality and virtual reality as these two conceptsare not the same [12]. In virtual reality, users are completelyimmersed in a virtual world and cannot see the real worldaround them. In contrast, augmented reality merges the vir-tual and real worlds by overlaying virtual information onthe user’s perception of the real world. Azuma [13] definesaugmented reality as a system having three characteristics:(a) the ability to combine real and virtual objects, (b) theability to be interactive in real time, and (c) the ability to use3D objects. It should be noted that augmented reality includesmore senses than just the visual, potentially applying to allsenses, including hearing, touch, and smell [14]. Examplesof information that can be overlaid on the real environmentin order to create augmented reality are images, audio, video,and touch or haptic sensations [12]. Today, the broad adoptionof augmented reality is seen mainly in gaming, sports, andtourism and new solutions targeting these business areas aredeveloping rapidly. The major breakthrough of augmentedreality occurred in 2016 when the popular game Pokemon Go(Fig. 2) was released around the world.

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FIGURE 3. Various devices and optics used in augmented reality.

The implementation of augmented reality is generallybased on some form of real-world anchor used for navigationand to provide context-based information to the user [15].The most common form of anchor is a unique pattern imagesuch as a data matrix, but other forms of anchors can beused, such as a geometric form that the system can detectautomatically. By connecting virtual objects to anchors, itbecomes possible to orient and also correlate virtual objectsto real-world objects [15]. To enable the user to see thevirtual objects and interact with the system, some sort ofhardware device is used. There are three categories of suchdevices [16]: (a) head-worn devices, (b) hand-held devices,and (c) spatial devices. These devices implement one ofthe following types of optics to visualize information to theuser:

• Video—the real and virtual worlds are merged into thesame view and the user’s view is completely digital

• Optical—virtual objects are overlaid directly on the viewof the real world

• Retinal—virtual objects are projected directly onto theretina using low-power laser light

• Hologram—virtual objects are shown in the real worldusing a photometric emulsion that records interferencepatterns of coherent light

• Projection—virtual objects are projected directly ontoreal-world objects using a digital projector

An overview of the various devices and type of optics imple-mented is shown in Fig. 3.

The various devices and optics used to realize augmentedreality each have strengths and weaknesses, depending onthe purpose of the particular application. For the industrialshop floor, glasses are generally superior since they freethe operator’s hands and are mobile and easily portable.As previously mentioned, there is a wide variety of ARSGimplementing various technologies and coming in variousdesigns. Some glasses provide a simple head-up display thatserves as a second screen accessible at a glance, while othersimplement more complex solutions such as retinal projectionor holographic display. A typical pair of ARSG is shown inFig. 4.

The next section presents guidelines for evaluating ARSGalong with a discussion of the relevant parameters to considerin the evaluation.

FIGURE 4. Example of ARSG.

III. GUIDELINES FOR EVALUATING AND SELECTINGAUGMENTED REALITY SMART GLASSESTo help manufacturing companies efficiently identify the bestof the vast range of alternative ARSG, this paper suggests astructured and straightforward process that guides the userthrough the evaluation and selection of ARSG. The guide-lines are specifically designed for ARSG to be used on theindustrial shop floor and the process includes three majorsteps covering the assessment of a total of 18 parameters, asdescribed in the following.

A. STEP 1: CREATE A LIST INCLUDING ALL PRODUCTSTHAT FIT THE PURCHASING BUDGETThe first thing to do is to find out how much money is bud-geted for a pair of ARSG. Many elaborate and ‘‘exclusive’’glasses are on the market, but if they are unaffordable, it isa waste of time evaluating them. To determine the maximumcost per pair of glasses, first count how many operators onthe shop floor will use glasses simultaneously, and then add10–20% to that number to provide spares in case of breakage.The purchasing budget is then divided by the number ofglasses needed, giving the upper cost limit per pair of glasses.

Now identify all products available on the market that fitthe budget. An Internet search is the best way to start, usingsearch terms such as ‘‘augmented reality smart glasses’’,‘‘augmented reality glasses’’, ‘‘augmented reality head-updisplays’’ and ‘‘smart glasses’’. Reviews of white papers andresearch articles as well as direct contacts with various retail-ers are also useful for finding products. When conducting theinventory, one should keep in mind that many vendors marketproducts that are just prototypes or not yet available forpurchase, so ensure that the products identified as interestingcan really be bought as ready-made off-the-self products.

B. STEP 2: SHORTEN THE LIST BY ELIMINATINGOBVIOUSLY UNSUITABLE PRODUCTSWhen the list of potential products is complete, the next stepis to evaluate these products based on a few critical parame-ters. The aim of doing this is to quickly narrow down the listso as not to waste time comprehensively evaluating productsthat are ultimately not of interest. We have identified fiveparameters specifically relevant to an industrial shop floorthat should be evaluated in this step: (1) powering, (2) weight,(3) field of view, (4) battery life, and (5) optics. Thesefive parameters are discussed further below and settings arerecommended. Removing from the list all products not meet-ing the recommended settings results in a limited number

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FIGURE 5. Illustration of field of view.

of affordable products that fulfill the basic requirements andmerit further evaluation in the next step of the process.

• PoweringARSG can be powered in two ways, through either abattery pack or an ordinary computer. For the industrialshop floor, battery power is essential as it is impossiblefor an operator to carry a computer throughout the work-day (or even for shorter periods). Some ARSG comewith computer powering only and should be eliminatedimmediately as they are unusable in practice by indus-trial operators.

• WeightSince ARSG are meant to be worn more or less thewhole day by operators, their weight is critical. A pairof normal glasses weighs about 20 grams, but no ARSGavailable today are even close to this weight. To be real-istic, we set the recommended upper limit to 100 grams(about five times the weight of normal glasses) to allowmost users to wear the glasses for at least a few hours.If glasses are much heavier than 100 grams, we believethey will cause too much physical strain and affect theoperator negatively.

• Field of ViewThe field of view denotes the area in which virtualobjects can be seen via the ARSG, as illustrated inFigure 5. The field of view is a crucial parameter as itdirectly affects how much information can be shown tothe user and where it can be placed. The horizontal fieldof view is especially important, as a large horizontal fieldof viewmakes it is possible to display information on theperiphery, keeping the center of view clear for seeing thereal world. A human’s natural field of view is almost180 degrees horizontally, but today’s ARSG are farfrom matching this. We believe that a realistic, accept-able minimum field of view in ARSG is 30 degrees(horizontally). A smaller field of view than this shouldnot be accepted as it not only severely limits the informa-tion that can be presented and where, but also forces theuser to constantly more his/her head to align the narrowinformation area with the real-world objects of interest.The drawbacks of too small a field of view and theirnegative impacts on the user are illustrated in Fig. 5.As clear from the figure, a considerably larger field

of view than the recommended 30-degree minimum ishighly desirable for really good user experience, but withcurrent technology 30 degrees is reasonable.

• Battery LifeAs previously mentioned, an operator on the industrialshop floor is supposed to wear ARSG more or lessthroughout the working day and a durable battery isnecessary to enable this. For integrated batteries, thebattery life must be at least nine hours, or if fast chargingis possible, four hours (since the battery can then berecharged during the lunch break). For non-integratedbatteries that can be hot-swapped, the battery life shouldbe at least two hours since swapping more frequentlythan every other hour would be too time-consuming.

• OpticsAs described in section II, three types of optics canbe implemented in ARSG for visualizing information:video, optical, and retinal projection. For the industrialshop floor, a product that implements either an opticalor a retina-based solution should be selected and video-based solutions should be avoided. Video-based solu-tions unavoidably have latency in what the user seescompared with what is happening in the real world. Thisis because time is required to capture the video feedof the real world, merge graphic objects with it, andthen show it to the user. Furthermore, with video, theoperator’s sight is completely digitized and technologydependent, which is too risky in case of, for example,a power failure in the glasses. There are indeed video-based glasses that implement only a very small videoscreen that does not completely digitize the user’s sight,but these solutions are problematic in that they createa blind spot in the user’s field of view. The industrialshop floor is generally a high-risk environment withautomated machines, robots, trucks, chemicals, etc., andit is critical that the operator’s sight not be negativelyaffected, so that he/she can be constantly aware ofwhat is happening in the environment. With optical see-through, the graphic image is projected directly on thereal world, making it possible to directly synchronizewhat the user sees with the information shown. Theadvantages of optical see-through are that the user hasa direct, unaltered view of the real world without anylatency and that the graphic information can be exactlyoverlaid on real-world objects. We argue that theseadvantages of optical see-through make the solutionmuch more suitable for the industrial shop floor than isvideo see-through, as information shown to the operatormust be in exact real time for the operator to be efficientand not become frustrated.

C. STEP 3: MAKE A COMPREHENSIVE EVALUATION OFALL REMAINING PRODUCTS AND SELECT THE BEST ONEStep 2 will have provided a list of affordable products thatmeet the most important demands, and now it is time tocomprehensively evaluate these products. We have identified

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12 parameters that we recommend evaluating in this step toensure that the best product is ultimately identified. It mightseem like a lot of work to evaluate 12 parameters, but mostparameters are quantitative and therefore easily assessed and,since steps 1–3 of the process have helped shorten the list,only a few products are left to evaluate in this step. Theparameters to be evaluated are described in Table 1 alongwith recommended minimum/maximum values and explana-tions of why they are relevant. For the table to be completeand include all parameters considered in the evaluation as awhole, the four parameters from step 2 are also included.

The next section continues by describing how the parame-ters presented in the table have been used to evaluate productscurrently available on the market.

IV. REVIEW OF AUGMENTED REALITY SMART GLASSESCURRENTLY ON THE MARKETThis section presents a comprehensive market inventory andevaluation of ARSG, starting in section A with a presenta-tion of the research method used in the study, followed insection B by an overview of the identified products.

A. RESEARCH METHODThe research method chosen for the product evaluation is thatof a systematic review, which defines a structured processfor identifying and analyzing artifacts (in this case ARSG)from multiple sources [17]. A systematic review is based ona clearly formulated question, identifies relevant artifacts toevaluate, and appraises the quality of these artifacts based onexplicit criteria [17]. The systematic review performed herefollows the five standard phases described, for example, byKhan et al. [18], as follows:

1) PHASE 1: DEFINE A QUESTIONThe question to be answered by this review is: Which of theARSG available on the market is best suited to the industrialshop floor? This question is formulated in linewith the overallpurpose of the paper, to provide the manufacturing industrywith recommendations as to the choice of ARSG to adopt onshop floors.

2) PHASE 2: IDENTIFY RELEVANT ARTIFACTSIn a systematic review, the artifacts to be studied shouldmatch certain explicit criteria. In this case, the following threekeywords were used as matching criteria in searching forproducts:

- smart glasses- augmented reality glasses- augmented reality head-up displayThe keywords were used separately, that is, matching one

criterion (i.e., keyword) was enough for a product to beincluded in the review. The search for products was extensiveand continued for six intensive weeks, to achieve a completemarket inventory. The searchwas conducted very carefully byfour independent researchers to reduce the risk of missing anyrelevant product to an absolute minimum. The Internet was

the main resource for finding products, but business reports,research papers, white papers, and trend reports were alsosources for the study. It should be noted that only productscurrently available for sale were included in the study, mean-ing that concept solutions and prototypes were excluded.

3) PHASE 3: ASSESS THE QUALITY OF THE ARTIFACTSThe relevant products identified were assessed based on theparameters defined in Table 1. Technical specifications andinformation on vendor websites were the main sources ofinformation. In cases in which information for answeringa specific question was missing, the vendor was contactedand asked for information. Some vendors chose not to sharespecific information, however, and for those products certainparameters remained unknown.

4) PHASE 4: SUMMARIZE THE FINDINGSThe parameter values of all products were compiled intotables following the same format as Table 1 to give a conve-nient overview and facilitate comparison. After compiled intotables, all product information gathered was double checkedby a person other than the one who originally found it toensure that it was completely correct.

5) PHASE 5: INTERPRET THE FINDINGSIn this last step of the systematic review, the productswere carefully analyzed and their strengths and weaknessesconcerning industrial shop-floor application were identified.Based on the findings, recommendations were formulated forthe industry.

In the following subsection, the results of steps 2–4 arepresented. Results of step 5 are presented in section V.

B. OVERVIEW OF IDENTIFIED PRODUCTSA careful search for ARSG found a total of twelve products,presented alphabetically in Table 2. The search was per-formed January 2017. As previously mentioned, only ARSGthat are currently for sale and can be bought by anyone areincluded in the review. Products ‘‘to be released soon’’ werenot considered, nor were products available only in the formof developer kits that ‘‘ship only to selected partners’’. It canbe noted that many products fall into these two categories, forexample Microsoft’s HoloLens, Eyesight Raptor and MagicLeap.

The next section continues by discussing the presentedproducts and providing recommendations based on thefindings.

V. COMPARATIVE EVALUATION ANDRECOMMENDATIONSThis section discusses the identified products based on theirparameter values and provides a comparative evaluation andanalysis of the products. Furthermore, recommendations as towhich products are the most suitable for the industrial shopfloor are given.

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TABLE 1. Parameters to evaluate. TABLE 1. (Continued). Parameters to evaluate.

A. OVERALL COMPARISON OF PRODUCTSThe 12 products found in the review are discussed basedon the 18 parameters evaluated and comparative remarks aremade.

1) PRICEThe price range is really wide for ARSG: the cheapestreviewed glasses cost USD 499 (Recon Jet) while themost expensive ones cost USD 3995 (Atheer AiR Glass).We believe that for ARSG to be used extensively in themanufacturing industry and worn by virtually all shop-flooroperators, the price must be modest so that companies canafford them. Obviously, the price limit depends on the pur-chasing budget of the company, but we estimate that themaximum cost is generally around USD 1000. A price muchhigher than this will often create a threshold for making theinvestment, especially since of a pair of ARSG—like wear-able consumer products in general—cannot be expected tolast much longer than a few years. However, one can certainlyexpect ARSG prices to decline significantly in coming years,as they start to become broadly adopted and therefore mass-produced consumer products (similar to the development ofmobile phones).

2) POWERINGOf the 12 products found, only one comes with computerpowering only—Penny C Wear Extended. This model isconnected to an external computer, which can be quite smalland also possibly battery powered. That virtually all productsare battery powered is a positive sign, meaning that there aremany products that could potentially be used on the industrialshop floor.

3) WEIGHTAs with the price, the weight range of the glassesis large. The lightest glasses weigh around 70 grams(Penny C Wear Extended, Epson Moverio BT-200, VuzixM100, and SmartEyeglass), while the heaviest weigh

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five times more—350 grams (Atheer AiR Glass). As pre-viously mentioned, a normal pair of glasses weighs about20 grams,meaning that even the lightest pair of ARSGweighsseveral times as much as normal glasses. We believe that thisis serious problem, as even the lightest pair of ARSG willlikely cause physical strain if worn for extended periods. As itis now, in practice ARSG can only be used for limited periods,possibly one or a few hours, before the operator needs to takethem off. This is a serious problem that the manufacturersof the glasses much carefully address in upcoming productseries.

4) FIELD OF VIEWField of view is an important parameter for ARSG as itdefines the area in which the user can see augmented-realitycontent while wearing the glasses. The reviewed glasses havehorizontal fields of view ranging from 10◦ (Recon Jet) to 46◦

(Atheer AiRGlass). Remarkably, many products have a reallysmall field of view of 20◦ or less. A small field of viewmight work for applications in domains such as sports ortourism, but for applications on the industrial shop floor, toosmall a field of view is unacceptable and makes the glassespractically unusable.

5) BATTERY LIFEThe battery life of the reviewed glasses ranges from 1 hour(Sime G3) to 8 hours (Atheer AiR Glass). It should be notedthat the battery life is highly dependent on how the glassesare used and how much computing power is consumed (theoperator might not use the full functionality of the glassesconstantly). When stating the battery life, the vendors areunspecific about the conditions under which the stated batterylife was measured, so the values provided by the vendorsshould be interpreted with some caution.

6) OPTICSOf the reviewed products, four implement video see-through(ODG R-7, Recon Jet, Sime G3, and Vuzix M100) andeight optical see-through. As discussed in section II, video-based solutions have several drawbacks in the context ofthe industrial shop floor and should therefore be avoided.What the user sees in the augmented video feed and the realworld cannot be fully synchronized in video-based solutions;furthermore, either the user’s sight is completely digitized or,if only a small screen is used, a blind spot is created in theuser’s sight. With optical see-though, the user has a direct,unimpeded view of the real world without any latency, so thissolution should be selected for the industrial shop floor.

7) CAMERAAll products except Penny C Wear Extended integrate acamera that supports documenting scenarios and can sendlive video streams to a remote expert. However, two ofthe products integrate a camera whose quality is probablyinsufficient for the intended application scenario, namely,Epson Moverio BT-200 and Recon Jet. The camera in the

first product supports a resolution of only 0.3 MP, while thecamera in the second products supports 1.2 MP. Such lowresolution results in pictures and videos of low quality thatis generally unacceptable.

8) OPEN APIAll reviewed glasses provide an open API and support third-party development. This is positive, as it enables buyers todevelop their own software and to customize the user expe-rience according to the scenario at hand. Industrial operatorsoften face complex work tasks that require advanced func-tionality in the user interface, functionality seldom providedby the original system. An open API permits full customiza-tion of the user interface and of how the system works, andwithout this capability the ARSG would be more or lessuseless for industrial applications.

9) AUDIOAll reviewed glasses except Penny C Wear Extended have anintegrated microphone and speakers. As discussed, a micro-phone is essential for enabling the user to use voice com-mands and to communicate with other operators or the teammanager, while speakers are essential for communication andfor complementing the user’s visual view with voice instruc-tions. The fact that almost all products integrate both micro-phone and speakers is positive and facilitates their adoptionon the industrial shop floor.

10) SENSORSA wide variety of sensors are supported by the reviewedglasses: inertial measurement unit, gyroscope, compass, cam-era, accelerometer, GPS, gesture tracking, spatial tracking,barometer, hygrometer, pressure, ambient light, and IR. Allproducts support multiple sensors, although no single productsupports all the aforementioned sensors. Which sensors areneeded depends on the particular application scenario, andit is impossible to pinpoint specific sensors that are morecritical than others. However, in general, the more sensors thebetter, as they allow the ARSG to be used for many purposesand in many application scenarios.

11) CONTROLSThe reviewed products implement various kinds of function-ality for controlling and interacting with the glasses. All prod-ucts except Penny C Wear Extended support voice control,either through built-in functionality or by integrating a micro-phone combined with supporting the Android OS, which isshipped with voice control. Voice control support is clearlyadvantageous, as it makes it possible for the user to controlthe system while his/her hands are occupied. This happensfrequently on the industrial shop floor, for example, whenundertaking maintenance, assembly, or quality controls. Twoof the products (Vuzix M100 and Atheer AiR Glass) alsosupport gesture control in addition to voice control, whichis also a great advantage. With gesture control, it becomespossible for the user to interact with the system in noisy

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TABLE 2. Augmented reality mart glasses.

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TABLE 2. (Continued). Augmented reality mart glasses.

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TABLE 2. (Continued). Augmented reality mart glasses.

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environments where voice control is impossible, which arecommon in industry. With gesture control, it also becomespossible for the user to provide the system with spatial infor-mation, which is impossible with voice control only. Support-ing both voice and gesture control is doubtless a strength, asthe benefits of both can be utilized. It should be noted thatPenny C Wear Extended supports hands-free control througha jaw bone click sensor, but this functionality is limited tosimple selections/confirmations in the user interface and nosophisticated commands can be given.

12) PROCESSORSSince ARSG are supposed to provide the operator with infor-mation in real time and potentially undertake quite complexgraphics rendering, it is important that they have enoughcomputing power. We recommend a dual-core processer as aminimum, as this is usually powerful enough and permits thedistribution of parallel computation over four cores. Of the12 reviewed products, three are equipped with a single-coreprocessor considered too weak for heavier processing (LasterWave, Recon Jet, and SmartEyeglass).

13) STORAGEThe amounts of data that can be stored by the reviewedglasses differ greatly, ranging from 4 GB (Optinvent ORA 2)to 256 GB (Penny CWear Extended). We recommend at leastaround 30GB of storage, as we believe that it is important thatgraphic objects, videos, and audio files be locally storable inthe glasses, to ensure that they can be used without a WiFiconnection or if the connection is unreliable.

14) MEMORYThe memory capacities range from 512 MB (Laster Wave)to 4 GB (Penny C Wear Extended, which is connected to acomputer). Half of the products implement 1 GB of RAMor less (Epson Moverio BT-200, Epson Moverio BT-2000,Laster Wave, Optinvent ORA, Recon Jet, and Vuzix M100).Most of the reviewed products implement 1–2 GB of RAM.We believe that 1 GB of memory is insufficient, as the oper-ating system as such often requires around 1 GB of RAM.In ARSG, complex real-time calculations and fast graphicsrendering must be performed, so at least 2 GB of memory isneeded. The larger the memory the better, as a larger share ofthe operations can be performed in the main memory, therebyspeeding up the calculations and rendering.

15) CONNECTIVITYAll glasses reviewed support WiFi and thus the possibilityof wirelessly connecting the glasses to a network, which isa clear advantage. A wireless connection makes it possibleto conveniently update the software, download informationcontent, and control the support system from a central server.

16) OPERATING SYSTEMAndroid absolutely dominates the operating system marketfor ARSG, all products expect Penny CWear Extended being

FIGURE 6. Applying the guidelines on the 12 products covered in thereview.

based on this system. Android is such a big actor becausethis operating system has the biggest market share of mobiledevices in general (e.g., mobile phones, tablets, and smartwatches) in combination with the system being much moreopen than its competitors (mainly Windows and iOS).

17) DURABLE AGAINST DUST AND WATERDust is common on many shop floors, usually originat-ing from various machining operations. Moisture and watersplashes might also occur, caused, for example, by washingoperations or water-based cooling. If the shop floor wherethe glasses are to be used is subject to dust and/or water, itis important that the ARSG provide IP capsuling that meetsrequirements. Electronics in general are sensitive to both dustand water and cannot withstand either for extended peri-ods. Of the reviewed glasses, only two products are durableagainst dust and water—Recon Jet and EPSON BT-2000.

B. RECOMMENDED PRODUCTTo provide a general recommendation as to which ARSGto buy, while testing the suggested evaluation process inpractice, the guidelines presented in section III are applied tothe 12 products covered by the review. Since the recommen-dation is supposed to be general, the five parameters based onuser preferences (i.e., price, operating system, sensors, dura-bility against water, and durability against dust) have beenomitted. The results of applying the guidelines are presentedin Figure 6 and illustrated in form of a funnel that step-by-step

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eliminates different alternatives and in the end pinpoints arecommended product (Epson Moverio BT-300).

VI. CONCLUSIONS AND FUTURE WORKThe aim of this paper is to take the manufacturing industryone step closer to the broad adoption of ARSG by improvingour knowledge of how to efficiently evaluate and select suchglasses for the industrial shop floor. The paper presents a step-by-step process for evaluating ARSG, including concreteguidelines on which parameters to consider in the evaluationalong with recommended settings. The idea is that by usingthe suggested evaluation process, manufacturing companiescan quickly make optimal decisions as to what products toimplement on their shop floors. The evaluation process isdemonstrated in practice by undertaking a comprehensivereview of products currently available on the market. Thereview demonstrates that many sophisticated products areavailable on the market today, but that they are remarkablyheterogeneous. The products implement different technolo-gies and come with different designs and features, givingthem different strengths and weaknesses. The suggested eval-uation process is clearly needed, since assessing the productsand identifying the best buy for the industrial shop floor arenon-trivial tasks in the absence of supporting guidelines.

Of the currently available products, the study finds thatEpson-Moverio BT-300 seems to be the best general choicefor the industrial shop floor. This product is the only one thatmakes it through the whole evaluation process and fulfills allbasic requirements. However, it should be pointed out that thetechnology is developing very rapidly and that new productsare introduced every year, meaning that superior productsmight soon appear on the market. A fresh evaluation shouldtherefore always be undertaken each time ARSG are to bebought in order to ensure an optimal choice.

This review not only demonstrates the suggested evalua-tion process and identifies a recommended product, but alsoreveals that considerable work remains to be done beforeARSG are really ready for mass adoption in the manufactur-ing industry. We have identified five topics that we believeparticularly merit further examination to ensure the success-ful implementation of ARSG on the industrial shop floor.These topics are discussed below.

A. EXTENDING THE FIELD OF VIEWThe field of view is doubtless one of the most challengingissues in ARSG. The natural human field of view is almost180 degrees horizontally, but the widest field of view oftoday’s off-the-self ARSG is only 46 degrees. The field ofview has a great impact not only on the user experience butalso on what can actually be done with the glasses, therebygreatly affecting both the perceived and actual gains accruedfrom using ARSG. The manufacturers of ARSG should, webelieve, prioritize extending the field of view of their prod-ucts, and this parameter will likely be the determining one forcustomers when selecting among products. Glasses having afield of viewmatching that of a humanmust be striven for and

are not unrealistic in the longer run. In themeantime, a field ofview of about 90 degrees (half the human field of view) wouldbe great and would considerably enhance the user experience.

B. MAKING THE GLASSES WEARABLECurrent ARSG are not really wearable, and this fact hinderstheir everyday use on the industrial shop floor. First, theglasses weigh toomuch and for this reason cannot be worn forextended periods. Second, most products come with a cablerunning from the glasses to a handheld device carried by theoperator, and this cable is disturbing and often in the way.Third, it is really difficult—almost impossible—to wear theglasses if already wearing ordinary glasses. Manufacturers ofARSG have three important challenges to address to makeARSG really wearable: reducing the weight, eliminatingcables, and designing products usable by people with visualdefects.

C. DEVELOPING GUIDELINES FORUSER INTERFACE DESIGNDesigning user interfaces for ARSG requires a completelydifferent approach from designing user interfaces for othermobile devices, such as tablets and smart phones. One impor-tant aspect is low information content, as the idea is toenhance the world, not block it out with lots of graphicobjects. There is currently a lack of general guidelines forhow to design efficient user interfaces making use of aug-mented reality [19], and developing such guidelines specifi-cally with ARSG in mind is an important research topic forthe future. Only with a really good user interface can shop-floor operators get really good support in carrying out theirwork tasks and realizing the full benefits of ARSG.

D. ENABLING BENCHMARK EVALUATIONIn line with the previous topic of user interface design,comparing designs with each other to identify the best onecalls for an effective and objective benchmarking method.There is currently no such benchmark method for evaluatingthe efficiency of augmented reality-based design [20], andthis is a clear lack. Developing a method for the benchmarkevaluation of user interfaces for ARSGmerits attention in thefuture.

E. IMPROVING VOICE-BASED INTERACTIONIN NOISY ENVIRONMENTSInteraction with ARSGmust be hands free in industrial shop-floor applications, as the operator must use his/her hands inperforming work tasks. The most common way to implementhands-free interaction is through voice commands, whichhave been shown to work well, for example, in home andoffice environments. However, the industrial shop floor dif-fers greatly from these environments in that it is subject toconsiderable noise from machines and transportation. In thepresence of noise, voice recognition becomes a great chal-lenge and special functionality must be implemented in thesoftware to reduce the noise and identify the right commands

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with high certainty [21]. This challenge is apparently notbeing considered in the context of ARSG, and we believe thisis an important topic for further research.

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ANNA SYBERFELDT received the M.Sc. degreein computer science from the University ofSkövde, Sweden, in 2004, and the Ph.D. degreefrom the De Montfort University, U.K., in 2009.She is currently an Associated Professor withthe University of Skövde. Her research interestsinclude virtual engineering, operator support sys-tems, and advanced ICT solutions with applica-tions in manufacturing and logistics.

She has published over 70 scientific articles andis the Leader of the Production and Automation Engineering ResearchGroup, University of Skövde. This research group includes 45 researchersinvolved within the area of virtual engineering. The group’s research is toa large extent applied and carried out in close cooperation with industrialpartners, mainly within the manufacturing industry.

OSCAR DANIELSSON received the B.Sc. degreein computer science and the M.Sc. degree inautomation engineering from the University ofSkövde, Sweden, in 2013 and 2015, respectively,where he is currently pursuing the Ph.D. degreewithin industrial informatics.

From 2013 to 2015, he was a Research Assis-tant with the Department of Engineering Science,University of Skövde, Sweden. His research inter-ests include operator support systems, augmented

reality, and human–robot collaboration.

PATRIK GUSTAVSSON received the B.Sc. andM.Sc. degrees in automation engineering from theUniversity of Skövde, Sweden, in 2013, where heis currently pursuing the Ph.D. degree in industrialinformatics.

From 2013 to 2015, he was a Research Assistantwith the Department of Engineering Science, Uni-versity of Skövde. His research interest includesproduction and automation technology, augmentedreality, and human–robot collaboration.

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