1、Designation: E2566 08E2566 17Standard Test Method forDetermining Visual Acuity and Field of View of On-BoardVideo Systems for Teleoperation of Robots for UrbanSearch and Rescue Applications1This standard is issued under the fixed designation E2566; the number immediately following the designation in
2、dicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.INTRODUCTIONThe robotics community needs ways to mea
3、sure whether a particular robot is capable of performingspecific missions in unstructured and often hazardous environments. These missions decompose intoelemental robot tasks that can be represented individually as standard test methods and practices. Theassociated test apparatuses and performance m
4、etrics provide a tangible language to communicatevarious mission requirements. They also enable repeatable testing to establish the reliability ofessential robot capabilities.The ASTM International Standards Committee on Homeland Security Applications (E54) specifiesstandard test methods and practic
5、es for evaluating individual robot capabilities. These standardsfacilitate comparisons across robot models, or across various configurations of a particular robotmodel. They support robot researchers, manufacturers, and user organizations in different ways.Researchers use them to understand mission
6、requirements, encourage innovation, and demonstratebreak-through capabilities. Manufacturers use them to evaluate design decisions, integrate emergingtechnologies, and harden systems. User organizations leverage the resulting robot capabilities data toguide purchasing, align deployment objectives, a
7、nd focus training with standard measures of operatorproficiency. An associated usage guide describes how such standards can be implemented to supportthese various objectives.The overall suite of standards addresses critical subsystems of remotely operated response robots,including maneuvering, mobil
8、ity, dexterity, sensing, energy, communications, durability, proficiency,autonomy, logistics, safety, and terminology. This test method is part of the sensing test suite andaddresses the acuity of onboard cameras.1. Scope1.1 This test method covers the measurement of several key parameters of video
9、systems for remote operations. It is initiallyintended for applications of robots for Urban Search and Rescue but is sufficiently general to be used for marine or other remoteplatforms. Those parameters are (1) field of view of the camera system, (2) visual acuity at far distances with both ambient
10、lightingand lighting on-board the robot, (3) visual acuity at near distances, again in both light and dark environments, and (4), if available,visual acuity in both light and dark environments with zoom lens capability.1.2 These tests measure only end-to-end capability, that is, they determine the r
11、esolution of the images on the display screenat the operator control unit since that is the important issue for the user.1.3 This test method is intended to be used for writing procurement specifications and for acceptance testing for robots for urbansearch and rescue applications.1.4 This test meth
12、od will use the Snellen fraction to report visual acuity; readers may wish to convert to decimal notation toimprove intuitive understanding if they are more familiar with that notation. Distances will be given in metres with English unitsin parentheses following.1 This test method is under the juris
13、diction of ASTM Committee E54 on Homeland Security Applications and is the direct responsibility of Subcommittee E54.08 onOperational Equipment.Current edition approved Feb. 1, 2008Jan. 1, 2017. Published March 2008February 2017. Originally approved in 2008. Last previous edition approved in 2008 as
14、E2566 08. DOI: 10.1520/E2566-08.10.1520/E2566-17.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurat
15、ely, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
16、11.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Terminology2.
17、1 Definitions:2.1.1 field of view, nangle subtended by the largest object that can be imaged with the video system.2.1.2 optotype, ncharacter used on a chart for testing visual acuity.2.1.2.1 DiscussionOptotypes are generally built on a 5 by 5 grid, with the size for “standard” vision subtending a s
18、quare 5 min of arc on a side. Thismakes one grid element 1 min of arc square.2.1.3 tumbling E, nspecific optotype that can be drawn in various orientations (facing left, right, up, or down) and in varioussizes to create an eye chart (see Fig. 1).2.1.3.1 DiscussionThis optoptype is reported in the li
19、terature as being maximally distinguishable. Eye charts with Tumbling Es are availablecommercially for use at different distances.2.1.4 standard vision, nability to resolve target features subtending 1 min of arc.2.1.5 visual acuity, nability to resolve features subtending some angle, as compared wi
20、th “standard” vision measured at thesame distance.2.1.5.1 DiscussionAn angle subtends a feature of size h at a distance d, of size 2h at a distance of 2d, of size 3h at a distance 3d, and so on. If2d is the “standard” measurement distance of 6 m (20 ft), an eye chart for use at 3 m (10 ft) would hav
21、e characters of h high ratherthan 2h high and the measurement of visual acuity would be the same. See Fig. 2 for an illustration of the angle/distancerelationship.2.1.6 Snellen fraction, na measure of visual acuity.2.1.6.1 DiscussionThe subject is placed a standard distance from an eye chart, typica
22、lly 6 m (20 ft). The subject is asked to identify the line withthe smallest characters that he can resolve. The Snellen fraction is the ratio of the distance at which that line would be resolvedby a subject with standard vision to the standard test distance. Thus, a subject with standard vision woul
23、d have 6/6 (20/20) vision.2.1.7 remote operation, nact of controlling a distant robot on a continuous or intermittent basis via tethered or radio-linkeddevices while being provided with sensory information (for example, visual information through cameras onboard the robot).2.1.7.1 DiscussionRemote o
24、peration includes teleoperation as well as forms of intermittent autonomy or assisted autonomy.3. Units for Reporting Visual Acuity3.1 The commonly used distance for measuring visual acuity is 20 ft in the United States. This leads to the “Snellen fraction”as the common measure of visual acuity: 20/
25、20, 20/40, and so on. The Snellen fraction is also used in England, referred to 6 mFIG. 1 Tumbling E Optotype in Various OrientationsE2566 172as the standard measurement distance (6/6, 6/12, etc.), while the rest of Europe generally used the decimal fraction equivalent:20/20 = 6/6 = 1.0; 20/40 = 6/1
26、2=0.5, etc. Measurements may be taken at any distance and the result scaled to the common distance.3.2 The meaning of 6/12 (20/40 or 0.5) is that features that can be resolved at 6 m (20 ft) by the test subject are of a size suchthat a person with “standard” visual acuity could resolve them at 12 m
27、(40 ft). The characters on the 6/12 (20/40, 0.5) line of aneye chart are twice the size of the characters on the 6/6 (20/20, 1.0) line. The best human vision is not 6/6 (20/20, 1.0), resolving1 min of arc (1/60 = .016) but more like 6/3.6 (20/12, 1.7), resolving about 0.01.4. Significance and Use4.1
28、 Responder-defined requirements for these test methods are documented in a preliminary document entitled “Statement ofRequirements for Urban Search and Rescue Robot Performance Standards.”24.2 Field of View is important in terms of the ability of the operator to drive the robot. Looking at the world
29、 through a zoomlens is like “looking through a soda straw.” Looking with a 30 or 40 field of view lens is like “driving with blinders on.” On theother hand, using a very wide field of view lens (with a field of view of 120 or 150), the operators use of optic flow to cue depthperception is severely d
30、egraded and navigating in a tight environment is very difficult. Multiple cameras are recommended, withone providing a very wide field of view or all together providing a very wide field of view.4.3 Far Vision Visual Acuity is important for both unmanned air vehicles (UAVs) and ground vehicles for w
31、ide area survey.Zoom is required for ground vehicles for wide area survey.4.4 Near Vision Visual Acuity is important for ground vehicles for wide area survey in examining objects at close range andalso for small robots which operate in constrained spaces.4.5 Testing in the dark is important for smal
32、l robots since they must sometimes operate in spaces with no ambient lighting.5. Hazards5.1 There are no hazards and no environmental issues associated with this test method.6. Procedure6.1 Field of View:6.1.1 The test environment for 6.2 below is established, with eye charts on a wall and the robot
33、 located at a set test distance6 m (20 ft) away from the wall (see Fig. 3). Vertical lines are drawn on the wall subtending fields of view from the test distanceof 20 to 60 (or more if space allows) in increments of 10 and labeled.6.1.2 Taking the line from the robot camera to the center of the eye
34、chart as the center line, field of view lines need only bedrawn to one side because of symmetry.6.1.3 Determine field of view and record the result.6.1.4 If the camera lens has a field of view beyond 60, and test site space does not allow further reference marks, the field ofview can be calculated u
35、sing trigonometry (see Fig. 4).Field of View52 52 tan21h/d!6.1.4.1 Beyond 100 h becomes very large and using trigonometry may be impractical. The vendor will generally know the fieldof view of the lens provided with the camera, or an estimate may be made. High precision is not important in determini
36、ng the fieldof view since this only provides an indication as to the limitations of the view of the operator when driving the robot. 10 resolutionis adequate.adequate.6.1.5 If the robot is equipped with multiple cameras, all cameras used for remote driving shall be measured.6.2 Visual AcuityFar Visi
37、on with Ambient Illumination:2 Messina, E., et al., “Statement of Requirements for Urban Search and Rescue Robot Performance Standards,” http:/www.isd.mel.nist.gov/US 2.0 to 0.1or 0.07). The optotypes thus subtend 2.5 min of arc at the smallest to 50 or 75 min of arc at the largest. As noted earlier
38、, a 3 mFIG. 3 Test of Visual Acuity and Field of ViewFIG. 4 Geometry of Field of View DeterminationE2566 174eye chart can be used at 6 m and the results scaled (the 6/6 line on a chart designed for 3 m represents 6/3 acuity when used at6 m). If necessary, larger optotypes can be printed to extend th
39、e measurement range to 6/180 (20/600; 0.03), at which point theoptotoypes would subtend 2.5. If the robot has zoom capability, a close range eye chart (for testing reading ability, typically foruse at 40 cm (16 in.) should be mounted below the larger eye chart. Using the 40 cm chart at 6 m and succe
40、ssfully reading the6/4.5 (20/15, 1.33) line with a zoom lens would be equivalent to 6/0.3 (20/1, 20.0) vision since 600/40 = 15; 15 1.33 = 20.0.6.2.3 The robot is placed so that the camera under test is 6 m (20 ft) from the eye charts. The lowest line that can be read onthe operator control unit scr
41、een without zoom is determined and recorded.6.2.4 If the robot has a zoom lens, the lens is run to maximum zoom and the lowest line that can be read is recorded.6.2.5 When mpeg coding is used for video compression, the operator should report only the lowest line at which all four barsof the “E” are
42、distinguishable. The discrete cosine transform used in mpeg coding highlights the asymmetric side bar of the “E”with the lowest spatial frequency filter and allows interpretation of the orientation of the characters below the level at which thecharacter can actually be distinguished. Care should be
43、taken not to introduce a bias in this case.6.3 Visual AcuityNear Vision with Ambient Illumination:6.3.1 This test establishes the ability of the operator to use the robot to examine objects at close distances.6.3.2 An eye chart designed for testing visual acuity for reading is used. The typical test
44、 distance is 40 cm (16 in.).6.3.3 Place the eye chart at the distance for which it was designed from the camera. The eye chart should be mounted at theheight of the camera. Illumination at the eye chart should be 1000 lux.6.3.4 Read the lowest line that can be distinguished on the operator control u
45、nit screen and record the result.6.3.5 Use the zoom and read the lowest line that can be resolved and record the result. Zoom lenses can lose focus at closeranges, so only a portion of the full zoom capability will be available.6.3.6 As noted above, only the line at which all four bars of the “E” ca
46、n be distinguished should be reported.6.4 Visual AcuityFar Vision with Illumination from the Robot:6.4.1 This test determines the visual acuity available to the operator at the operator control unit when the robot is operating inthe dark.6.4.2 The same test as 6.2 is run in a dark environment (ambie
47、nt illumination at the eye chart of 1000 lux, which corresponds to typical goodindoor lighting.E2566 175FIG. 5 Example Data Collection Form for Visual Acuity and Field of View TestsE2566 1768.3.2 Asecond source of bias is introduced when mpeg coding is used for compressing the video for transmission
48、. The discretecosine transform used in mpeg coding picks up the asymmetric side bar of the “E” with the lowest spatial frequency filter andallows interpretation of the orientation at a level below which the four bars of the “E” can be distinguished. This is particularlynoted when the camera lens has
49、 zoom capability as operators are observed moving the zoom back and forth to match the spatialfilter size to the character size. As noted in Section 6, the operator must be directed to report only the level at which all four barsof the “E” character can be distinguished.9. Keywords9.1 field of view; remote operation; robots; teleoperation; urban search and rescue; video systems; visual acuityASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users
