東海大学紀要情報通信学部
Proc. Schl. ITE Tokai Univ.
vol.3,No2,2010,pp.13-18
Vol. ,No. ,2010,pp. -Paper
Paper

Investigation of the Influence of Display Type on Smooth Pursuit Eye
Movement when Viewing a Moving ImagebyYusuke HORIE*1, Yuta KAWAMURA*1, Akiyuki SEITA*2

and Mitsuho YAMADA*1(Received on Oct. 21, 2010 and accepted on Feb. 10, 2011)

Abstract
We have studied the relation between the various displays and the position error of Smooth pursuit eye movement(SPEM) while pursuing a rapidly moving target by increasing the number of experimental trials beyond that of theprevious report. Focusing on CRT, EL, LCD and PDP, we showed the results of the position error of SPEM in each subject.
Generally, as for the accuracy of SPEM to the speed change of the target, the same tendency was shown among displays
which were used in this paper.

Keywords: smooth pursuit eye movement，frame rate，liquid crystal display (LCD), motion blur

1. INTRODUCTION

rapidly moving image [1]. Moreover, we compared an LCD
driven at 240 Hz with that driven at 120 Hz in terms of theaccuracy of the SPEM [2]. From these experiments, we found

Recently, high-definition and large-size displays havethethat the SPEM varied according to the abilities of thebyindividual subjects. Therefore, we increased the number ofincreasing the number of scanning lines, the improvement ofexperiment trials and examined the differences among thethe color reproducibility of the color filter and the speed-up

subjects. Moreover, we added PDP, EL, and CRT in additionof the frame rate are attracting attention. Specifically, forto LCD to our investigation. We found that the difference

LCD, which has shown image quality degradation for

between the performance results of 120 Hz drive LCD andhigh-speed moving images, a 120 Hz drive has become

the 240 Hz drive LCD were not that different. We measured

standard, and 240 Hz drive displays have also been developed.

the response characteristics of the 120 Hz and 240 Hz LCD

SPEM is said to be driven by the human brain to detect theand reviewed the reasons. We found some differences

speed of a moving object. We assumed that reproduction

between LCD and PDP at lower target speeds.

become popularforhomeachievementmuchhigher-resolutionofuse.

Moreover,displaysquality of a moving image on a display would influence the2. CHARACTERISTIC OF EYE MOVEMENT

pursuing accuracy of SPEM. Whether or not we discern thedeterioration of image quality when an image is moving
speedily depends on whether or not we can follow theIn the oculomotor system, there are generally three kinds

deteriorated part of the image with the fovea, which has theof eye movements, i.e. a small involuntary eye movement, abest eyesight. Therefore, we investigated the accuracy ofSPEM and a saccade. When one fixates at the stationary point

SPEM as a measure to evaluate the display characteristics ofon the image, our eye still moves randomly and continuously

various displays for high-speed moving images. We havelittle by little. This eye movement is called a small

reported that the response characteristics of the LCD

involuntary eye movement.

influenced the accuracy of SPEM in the viewing of a
*1 Graduate school of Engineering, Tokai University*2 East Japan railway Company

SPEM is said to be specifically driven by detecting the speed

Among eye movements, theingredient of a moving image. Saccade, an eye movement
characterized by rapid, discontinuous movement, creates
what has been called “saccadic suppression”, or the declineof object recognition during saccade; by contrast, therecognition during SPEM declines very little.

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evaluating the image quality of the moving image, theobserved in the boundary of the moving object and thecharacteristic of SPEM is considered to be an importantbackground (Figure 2).

Here, we studied the accuracy of SPEM when

The second factor is the slowness of the response speed. Inpursuing a speedily moving target displayed on the various

LCD, a white-color light source is provided from thedisplays. We defined the position error between the eyebacklight. The image is displayed when this light is passed

position and the target position as the measure of thethrough color filters that change the transmitted light into theaccuracy of SPEM when pursuing a speedily moving target.

three primary colors of RGB via a liquid crystal panel that

When we pursue the moving image, generally, a saccade

controls the transmitted light volumes of each pixel. The

occurs at first, and then SPEM succeeds. There is latency inliquid crystal panel changes the permeability of the light by

the saccade, so that the saccade starts moving 160 - 200 ms

the application of voltage to the liquid crystal molecules,

later after the target movement.

controlling the direction of polarization. The response speed

factor.

When the speed of theof this mechanism is slower than those of other displays.

object is too fast for SPEM to pursue, saccades and SPEMs
alternately occur as shown in Figure 1. One study found thatthe maximum speed of sustained SPEM was about 30
degrees/sec. Recently, it has been claimed that SPEM canpursue a moving image of at most 100 degrees/sec with again of about 0.9 (Gain is defined as the oculomotor speed /the object speed). When exceeding 100 deg/sec, the varianceexpands to the oculomotor speed, mainly to about 80 deg/sec.

Figure 2.Display characteristic of a hold type

4.METHOD OF EXPERIMENT AND ANALYSISThe experimental setup is shown in Figure 3.
A head-chin rest was used to immobilize the subject's head.
The viewing angle of the display from the subject was 30
degrees, which is said to be the natural limit at which we cansee an object only by eye movement. Exceeding these values,
head movement was used as well as eye movement [4]. TKK
2930 of Takei & Co. (the scleral reflection method) was usedto measure the eye movement. After the calibration of the eye
movement, the experiment was started. First, a fixation point

Figure 1.Characteristics of smooth pursuit eye movement [3]was displayed in the center of the display① and the subject
3. CAUSE OF IMAGE QUALITY DEGRADATION FOR

was instructed to gaze at it in order to check the offset of theHIGH-SPEED MOVING IMAGESeye movement caused by the slip of the head movement. Next,
after the fixation point was erased②, a fixation point forMotion blur is one of the principal factors of the image

either the left or right was displayed③ to suggest to thequality degradation that occurs when a moving image issubject the starting point of the moving target. The target

displayed by LCD. There are two factors involved. One is themoved from the direction ④ where a fixation point wasfact that the LCD is a hold-type display. For such displays,displayed at speeds of 5 deg/sec, 10 deg/sec, 20 deg/sec, or

the viewer moves his or her eyes continually along the30 deg/sec speed at random times (Figure 5). We made thismoving image. The LCD keeps displaying the same image

one set and repeated 40 sets in all. A slit was cut in the center

during one field, e.g. 1/60th of a second. On the human retinaof the object of the cross-tip in order that the subject could

that is pursuing the moving image, the current image will

pursue the target as correctly as possible. The subject wasoverlap with the previous image. Therefore, a blur isinstructed to chase the target as faithfully as possible, and we―2―− 14 −Proc. Sch. ITE
Tokai University

Yusuke HORIE・Yuta KAWAMURA・Akiyuki SEITA・Mitsuho YAMADA

Times Times Times Times Timesmeasured eye movement. We defined the difference between
the target position and the subject’s eye position as theposition error. We compared the position error to analyze theobtained results. Displays used in the experiment, theirluminance during the experiment and their viewing distances
are shown in Table 1~2. As the frame rates of EL and PDP, 60
Hz were used, since they were only available commercially
up to now.
The subjects were three male students at our university
who have normal eyesight, with a visual acuity of more than
1.0 (20 / 20) including corrected vision.
After the experiments, we drew a figure that showed theFigure 5 Experiment procedure

position of the eye along the vertical axis and the lapse of

Table 2. Luminance of Target and Backgrounds

time along the abscissa at each session (Figure 6). From thisfigure, the data for times when the latency of the saccade, thesaccade and blinking occurred and when the accuracy of
SPEM degraded just before the target reached the end of thedisplay were discarded.
Applying the above procedure, the difference between thetarget position and the subject's eye position during SPEM
was estimated as mentioned before.

Figure 6. An Example of the data set during an experiment

Figure 3. Environment of experiment

Figure 4. Scleral reflection method
Table 1. Display size and Viewing Distance
Figure 7.

Example when the obtained data was discarded

5. RESULT
5.1

Results for CRT

The difference in the position error between 60 Hz and 120
Hz was small in subject 1. The position error for 120 Hz wassmaller than that for 60 Hz in subject 2. The differences inVol. XXXI, 2009―3―− 15 −Investigation of the Inﬂuence of Display Type on Smooth Pursuit Eye Movement when Viewing a Moving Image

Times, Times and Times

the position error between 60 Hz and 120 Hz were small forthe image speeds of less than 20 deg/sec in subject 3.
However subject 3’s position error for 60 Hz at 30 deg/sec
was larger than that for 120 Hz. The position error increased
according to the target speed in all subjects.

Figure 11. Results of EL

5.3

Results for LCD

Figure 8. Results of CRT (Subject 1)

Figure 12. Results of LCD (Subject 1)

Figure 9. Results of CRT (Subject 2)

Figure 13. Results of LCD (Subject 2)

Figure 10. Results of CRT (Subject 3)

5.2

Results for EL

The variance of the position error was small among subjects.
It increased according to the target speed, as with CRT.

Figure 14. Results of LCD (Subject 3)―4―− 16 −Proc. Sch. ITE
Tokai University

Yusuke HORIE・Yuta KAWAMURA・Akiyuki SEITA・Mitsuho YAMADA

Times Times Times Times Times

Figures 12, 13, and 14 show the results of the SPEM

6.2

position error when viewers pursued a target on LCD. In eachEL

As with the other displays, the position error increased

subject, the difference in position error between the 120 Hz

according to the target speed in all subjects, and theand 240 Hz moving image was small. The position error

difference in position error between subjects was very small.

increased with the target speed only in subject 2. In subject 2,This suggests that there was not a very large difference in thethe position error was larger than that of other subjects for atarget moving at 30 deg/sec.

visibility of the moving image among subjects for EL.

5.4

6.3

Results for PDP

LCD

The difference in position error between 120 Hz and 240
Hz was small in all subjects. This suggests that there is not alarge difference in display characteristics at 120 Hz and 240
Hz. To clarify this result, we measured the display
characteristics of LCD as depicted in 6.4.
6.4 Display methods of 120Hz and 240Hz
To investigate why the difference between the position
errors for 120 Hz and 240 Hz was small, we measured theresponse characteristics of the LCD by the optical responsetime measurement tester T10 (Konika Minolta Holdings).

Figure 15. Results of PDP

Figure 16 shows an example of the response waveform for

The differences in the position errors by subject are shownthat both methods applied the same frequency to drive thethe LCD used in the experiment. As a result, it was clarified
LCD. Thus, it was suggested that LCD was also driven at 240

in Figure 11. The difference among subjects is small. The

Hz in the case of the 120 Hz drive and that the same image

position error increased according to the target speed.

might be continuously displayed every two frames as shownin figure 16. This could be one of the causes why little

5.5

Comparison

difference was observed in the accuracy of SPM whileof the results for LCD and PDP

pursuing a moving target displayed at 120 Hz and at 240 Hz.

The difference of the position error in each subject
between LCD and PDP was small. The errors themselvestended to increase with the target speed. At 5 deg/sec-10
deg/sec, the position errors of LCD are equal to or slightly
larger than PDP, depending on the subject. However, theposition errors were almost the same and at most 1 deg-2 deg
difference between the two displays for targets faster than 20
deg/sec.
6. DISCUSSION
6.1

CRT

Figure 16. Example of the response waveform of the LCD used inAs the reason why the distinctive difference of the position

the experimenterror did not appear in subject 1, it is considered that thissubject was accustomed to the pursuing experiment because

6.5

the experiment for CRT was executed last for this subject.
Subject 2 might not be very good at pursuing an object

PDP. A tendency for the position error of SPM to increase atmoving as fast as 30 deg/sec, since the position error was

target speeds above 10 deg/sec was observed.

larger than that of other subjects for both 60 Hz and 120 Hz
moving images. In subject 3, little difference was observed

6.6

for the movement less than 20 deg/sec, but the position error

Comparison of LCD and PDP

Since the position error above 20 deg/sec showed almost

increased for that at 30 deg/sec and the influence of thethe same degrees in LCD and PDP, it was considered that therefresh rate was seen.

Vol. XXXI, 2009

PDP

There were few differences among individuals viewing the―5―− 17 −Investigation of the Inﬂuence of Display Type on Smooth Pursuit Eye Movement when Viewing a Moving ImageTimes, Times and Times

differences in the display methods had not produced

ITS APPLICATIONS 2009.9.8-9, CHIBA in Japaneseconspicuous effects. However, at 5 deg/sec-10 deg/sec, the（JIQA2009）

position error of LCD was equal to or larger than that of PDP.

[3] Meyer, C.H., Lasker, G.L. and Robinson, D.A., The upperThis result suggests that the difference in display methods

limit of human smooth pursuit velocity, Vision Research, 25,

between LCD and PDP may have influenced SPEM forpp.561-563 (1985)

slower image velocities.

[4] Bahill A.T.,Adler D. and Stark L.:”Most naturally
occurring human saccades have magnitudes of 15 deg orless”,Invest.Ophthalmol.,14,pp.468-469.1975

7. SUMMARY[5] Yusuke Horie, Akiyuki Seita, Kosuke Nawa, and Mitsuho
We have studied the relation between the various displays

Yamada. “Consideration of smooth pursuit eye movementand the position error of SPEM while pursuing a rapidly

while viewing a speedily moving image for the evaluation ofmoving target by increasing the number of experimental trials

the display”, Winter session of ITE in Japanese.(2008)

beyond that of the previous report. In this paper, focusing on[6] Akiyuki Seita, Yuki Ogata, Kosuke Nawa, and Mitsuho

CRT, EL, LCD and PDP, we showed the results of theYamada, “Perception of a Digitally Deteriorated Image andposition error of SPEM in each subject.

Eye Movement Characteristics while Pursuing a SpeedilyMoving Target”, IMQ2008, Poster Presentations, [F-4] Poster

As a result of CRT, the difference of the frame rate did not

Session1, (2008)

influenceded in the accuracy of SPEM less than 10 deg/sec.
But, the accuracyof SPEM tended to decline a little by thesubject more than 20 deg/sec.
As a result of EL, the decline of the accuracy of SPEM wasobserved according to the increase of the target speed. Also,
differences among the subjects are few.
Difference of the accuracy of SPEM was not observed
between the results of 120Hz and those of 240 Hz in LCD.
However, the decline of the accuracy of SPEM was also
shown at the target speeds more than 20 deg/sec by thesubject.
Generally, as for the accuracy of SPEM to the speed changeof the target, the same tendency was shown among displays
which were used in this paper.
In the future, we will analyze the influence on SPEM
accuracy of targets slower than 10 deg/sec as well as thosefaster than 30 deg/sec. Moreover, we are planning to perform
experiments changing the brightness of the targets and of thebackgrounds. Here, we focused on eye movement while
viewing a moving image. However, we also think it isimportant to compare subject evaluations regarding therecognition of image degradation with the results obtained
above [6].
REFERENCES[1] Kosuke Nawa, Akiyuki Seita, Yuki Ogata, and Mitsuho
Yamada, “Consideration of the Accuracy of the Smooth
Pursuit Eye Movement Among Various Types of Display”,
IMQ2008, Poster Presentations, [F-6] Poster Session 1,(2008)[2] Yusuke Horie, Akiyuki Seita, and Mitsuho Yamada.”
Study of smooth pursuit eye movement while pursuing aspeedily moving image when the frame rates are changed.”JAPAN WORKSHOP ON IMAGE MEDIA QUALITY AND―6―− 18 −Proc. Sch. ITE
Tokai University