System measures intersection of line of sight and eye point of regard /EPR/ for a human operator in visual scanning system. Device measures two head to reference angles with EPR system and adds them with eye to head angles, yielding a dc signal proportional to picture plane coordinates

Jex, H. R.

English

NASA Technical Reports Server

December 1971	 Brief 71-10476 
S	 NASA TECH BRIEF 
Ames Research Center	
-0 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a aubscription. basis from the National Technical Information 
Service, Springfield Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D. F. 20546. 
Eye Point-of-Regard System 
I--	 --______ --
 
+Up	 Vertical	 On 
+	 2	 A	 __)i__qI	 U	 I	 Head 
Offset 
Horizontal	 I 
[ Head _Movement _Device —1	 ^4 
•	 Legend:	 Eye 
—(---- Connector	 Point-of-Regard 
Potentiometers	
Computer 
_--_ 
Eye Movement Device	 Offset 
Horizontal Vert i
xv 1(^ 
cal  
R. eye	 L
Fil ter
X 
Y^ 	
^-/e Z;I 
:	 e+/ I Out xe 
L ^se I
EPR 
Xh
Meters 
4 
Head	 Head Outputs 
Iyx 
Point-of-Regard Outputs 
:ye  
Out in?	 A 
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Eye Outputs
-	 j(Com 
Ground 
Xe 
The problem: 
To measure the intersection of the line-of-sight 
and a selected normal picture plane (the eye point-
of-regard) for a human operator in a visual scanning 
system.
The solution: 
Measure only two head-to-reference angles with an 
eye point-of-regard (EPR) system and sum them with 
eye-to-head angles, which are measured on a corre-
sponding scale, to yield a dc signal proportional to 
(continued overleaf) 
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Aeronautics and Space Administration. Neither the United States 	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States 	 will be free from privately owned.rights.
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the picture-plane coordinates. The EPR system gives 
convenient on-line EPR coordinates in recordable 
dc voltage form, thus eliminating the need for ex-
pensive camera equipment and film data reduction. 
How it's done: 
The EPR system includes a head-movement device 
(HMD), an eye-movement device (EMD), and the 
EPR computer which receives the signal from the 
HMD and EMD and provides the system output. 
The HMD consists of two orthogonally mounted 
potentiometers connected to a reference panel by a 
rigid, telescoping linkage. The housing for the 
potentiometers provides for insertion of a disposable 
"pipestem" bite bar, with a thermoplastic bite mold, 
which is clenched between the operator's molar 
teeth (one side) during the test. As the head moves 
up and down, the wiper moves around the lower pot 
which is fixed horizontally in the housing' tele-
scoping linkage allows for forward and backward 
head displacement accompanying the rotation. Simi-
larly, left and right movements are picked up by the 
pot mounted vertically in the housing. An adjustable 
boresight, comprising a peep-sight about 25 cm from 
the eye, permits calibration and alignment checks of 
the HMD. 
The HMD is linear in azimuth and elevation 
planes for motion about its center. With the head 
20 cm to one side, a small change in elevation slope 
is present only for large azimuth angles. For the 
anticipated range of operation, however, an accuracy 
of one degree should be possible.
The EMD is a commercial model designed to 
measure the horizontal and vertical movement of the 
eye with respect to the head by a corneal-scleral 
boundary contrast technique. It is mounted in an 
eyeglass frame. 
The EPR computer sums and crossfeeds the sig-
nals from the EMD and HMD to provide an out- 
put that represents the point-of-regard independent 
of the head movement within a range of 20° vertical 
and 40° horizontal. The block diagram shows the 
connections between the potentiometers and the 
summing amplifiers; the pots control HMD zero 
offset, gain, and cross talk with the EMD. 
Note: 
Requests for further information may be directed 
to:
Technology Utilization Officer 
Ames Research Center 
Moffett Field, California 94035 
Reference: TSP7 1-10476 
Patent status: 
Title to this invention has been waived under the 
provisions of the National Aeronautics and Space 
Act (42 U.S.C. 2457 (f)) to Systems Technology, Inc., 
13766 S. Hawthorne Blvd., Hawthorne, California. 
Source: H.R. Jex of

Systems Technology, Inc.

under contract to

Ames Research Center

(ARC-10360)
S 
. 
Brief 71-10476	 Category 05 
.


Eye point-of-regard system

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