ASTM E2566-08

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Designation: E2566 − 08
Standard Test Method for
Determining Visual Acuity and Field of View of On-Board
Video Systems for Teleoperation of Robots for Urban
Search and Rescue Applications
This standard is issued under the fixed designation E2566; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2.1.2 optotype, n—character used on a chart for testing
visual acuity.
1.1 Thistestmethodcoversthemeasurementofseveralkey
2.1.2.1 Discussion—Optotypes are generally built ona5by
parameters of video systems for remote operations. It is
5 grid, with the size for “standard” vision subtending a square
initially intended for applications of robots for Urban Search
5 min of arc on a side. This makes one grid element 1 min of
and Rescue but is sufficiently general to be used for marine or
other remote platforms. Those parameters are (1) field of view arc square.
of the camera system, (2) visual acuity at far distances with
2.1.3 tumbling E, n—specific optotype that can be drawn in
both ambient lighting and lighting on-board the robot, (3)
various orientations (facing left, right, up, or down) and in
visual acuity at near distances, again in both light and dark
various sizes to create an eye chart (see Fig. 1).
environments, and (4), if available, visual acuity in both light
2.1.3.1 Discussion—This optoptype is reported in the litera-
and dark environments with zoom lens capability.
ture as being maximally distinguishable. Eye charts with
1.2 These tests measure only end-to-end capability, that is,
Tumbling Es are available commercially for use at different
they determine the resolution of the images on the display
distances.
screen at the operator control unit since that is the important
2.1.4 standard vision, n—ability to resolve target features
issue for the user.
subtending 1 min of arc.
1.3 This test method is intended to be used for writing
2.1.5 visual acuity, n—ability to resolve features subtending
procurement specifications and for acceptance testing for
some angle, as compared with “standard” vision measured at
robots for urban search and rescue applications.
the same distance.
1.4 This test method will use the Snellen fraction to report
2.1.5.1 Discussion—AnangleΘsubtendsafeatureofsizeh
visual acuity; readers may wish to convert to decimal notation
at a distance d, of size 2h at a distance of 2d, of size 3h at a
to improve intuitive understanding if they are more familiar
distance 3d, and so on. If 2d is the “standard” measurement
with that notation. Distances will be given in metres with
distanceof6m(20ft),aneyechartforuseat3m(10ft)would
English units in parentheses following.
have characters of h high rather than 2h high and the
1.5 This standard does not purport to address all of the
measurementofvisualacuitywouldbethesame.SeeFig.2for
safety concerns, if any, associated with its use. It is the
an illustration of the angle/distance relationship.
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica- 2.1.6 Snellen fraction, n—a measure of visual acuity.
bility of regulatory limitations prior to use.
2.1.6.1 Discussion—The subject is placed a standard dis-
tance from an eye chart, typically 6 m (20 ft). The subject is
2. Terminology
asked to identify the line with the smallest characters that he
can resolve. The Snellen fraction is the ratio of the distance at
2.1 Definitions:
which that line would be resolved by a subject with standard
2.1.1 field of view, n—angle subtended by the largest object
vision to the standard test distance. Thus, a subject with
that can be imaged with the video system.
standard vision would have 6/6 (20/20) vision.
2.1.7 remote operation, n—act of controlling a distant robot
This test method is under the jurisdiction of ASTM Committee E54 on
on a continuous or intermittent basis via tethered or radio-
Homeland Security Applications and is the direct responsibility of Subcommittee
linked devices while being provided with sensory information
E54.08 on Operational Equipment.
(for example, visual information through cameras onboard the
Current edition approved Feb. 1, 2008. Published March 2008. DOI: 10.1520/
E2566-08. robot).
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2566 − 08
FIG. 1 Tumbling E Optotype in Various Orientations
FIG. 2 Angle Subtended by Various Size Objects at Various Distances
2.1.7.1 Discussion—Remote operation includes teleopera- recommended, with one providing a very wide field of view or
tion as well as forms of intermittent autonomy or assisted all together providing a very wide field of view.
autonomy.
4.3 Far Vision Visual Acuity is important for both un-
mannedairvehicles(UAVs)andgroundvehiclesforwidearea
3. Units for Reporting Visual Acuity
survey. Zoom is required for ground vehicles for wide area
3.1 The commonly used distance for measuring visual
survey.
acuity is 20 ft in the United States. This leads to the “Snellen
4.4 Near Vision Visual Acuity is important for ground
fraction” as the common measure of visual acuity: 20/20,
vehicles for wide area survey in examining objects at close
20/40, and so on.The Snellen fraction is also used in England,
range and also for small robots which operate in constrained
referred to 6 m as the standard measurement distance (6/6,
spaces.
6/12, etc.), while the rest of Europe generally used the decimal
4.5 Testing in the dark is important for small robots since
fraction equivalent: 20/20 = 6/6 = 1.0; 20/40 = 6/12=0.5, etc.
they must sometimes operate in spaces with no ambient
Measurements may be taken at any distance and the result
lighting.
scaled to the common distance.
3.2 The meaning of 6/12 (20/40 or 0.5) is that features that
5. Hazards
can be resolved at 6 m (20 ft) by the test subject are of a size
5.1 There are no hazards and no environmental issues
such that a person with “standard” visual acuity could resolve
associated with this test method.
them at 12 m (40 ft). The characters on the 6/12 (20/40, 0.5)
line of an eye chart are twice the size of the characters on the
6. Procedure
6/6 (20/20, 1.0) line. The best human vision is not 6/6 (20/20,
6.1 Field of View:
1.0), resolving 1 min of arc (1/60° = .016°) but more like 6/3.6
6.1.1 The test environment for 6.2 below is established,
(20/12, 1.7), resolving about 0.01°.
with eye charts on a wall and the robot located at a set test
4. Significance and Use
distance 6 m (20 ft) away from the wall (see Fig. 3). Vertical
lines are drawn on the wall subtending fields of view from the
4.1 Responder-defined requirements for these test methods
test distance of 20 to 60° (or more if space allows) in
are documented in a preliminary document entitled “Statement
increments of 10° and labeled.
of Requirements for Urban Search and Rescue Robot Perfor-
6.1.2 Taking the line from the robot camera to the center of
mance Standards.”
theeyechartasthecenterline,fieldofviewlinesneedonlybe
4.2 Field of View is important in terms of the ability of the
drawn to one side because of symmetry.
operator to drive the robot. Looking at the world through a
6.1.3 Determine field of view and record the result.
zoomlensislike“lookingthroughasodastraw.”Lookingwith
6.1.4 If the camera lens has a field of view beyond 60°, and
a30or40°fieldofviewlensislike“drivingwithblinderson.”
test site space does not allow further reference marks, the field
On the other hand, using a very wide field of view lens (with
of view can be calculated using trigonometry (see Fig. 4).
afieldofviewof120or150°),theoperator’suseofopticflow
Field of View 52 ϕ 52 tan h/d
~ !
to cue depth perception is severely degraded and navigating in
a tight environment is very difficult. Multiple cameras are
6.1.4.1 Beyond 100° h becomes very large and using
trigonometry may be impractical. The vendor will generally
knowthefieldofviewofthelensprovidedwiththecamera,or
Messina, E., et al., “Statement of Requirements for Urban Search and Rescue
an estimate may be made. High precision is not important in
Robot Performance Standards,” http://www.isd.mel.nist.gov/US&R_Robot_
Standards/Requirements Report (prelim).pdf determining the field of view since this only provides an
E2566 − 08
FIG. 3 Test of Visual Acuity and Field of View
operatorcontrolunitintegratestheeffectsofcamera,thesensor
within the camera, digitization of the signals, transmission of
the data, reconstruction of the images, and resolution of the
display screen. Since the visual imag
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