Research Note 85-90

FINAL EVALUATION OF THE LIGHT PEN AS THE KEY COMPONENT

IN A MICROCOMPUTER-BASED SIMULATOR 0

Beth W. Thomas and James E. Schroeder

A)

ARI FIELD UNIT AT FORT BENNING, GEORGIA

Seward Smith, Chief

TRAINING RESEARCH LABORATORY

Harold F. O'Neil, Jr., Director D Tl

ELECTE

OCT 24 I

U. S. Army

Research Institute for the Behavioral and Social Sciences

September 1985

Aoproved for Public release; distribution unhimitec,

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1. REPORT NUMBER 12. GOVT ACCESSION NO. 3. RECIPIENT'S CATALOG NUMBER

ART Research Note 85-90 _

- 4. TITLE (and Subtitle) 5. TyPE OF REPORT & PERIOD COVERED

Research Note

Final Evaluation of the Light Pen as the Kuy Feb 84 - Jul 85

Component in a Microcomputer-Based Si.mulator 6. PERFORMING ORG. REPORT NUMBER

7. AUTHOR(*) S. CONTRACT OR GRANT NUMBER(&)

Thomas, Beth W. and Schroeder, James E.

9. PERFORMING ORGANIZATION NAME AND ADDRESS 10. PROGRAM ELEMENT, PROJECT, TASK AREA & WORK UNIT NUMBERS

US Army Research Institute for the Behavioral

and Social Sciences Fort Benning Field Unit 2Q263743A794

P.O. Box 2086, Fort Benning. GA 31905-0686 322 5710

1I. CONTROLLING OFFICE NAME AND ADDRESS 12. REPORT DATE

US Army Research Institute for the Behavioral September 1985

and Social Sciences, 5001 Eisenhower Avenue, 13. NUMBER OF PAGES

Alexandria, VA 22333-5600 9A

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Unclassified

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Approved for public release; distribution unlimited.

* 17. DISTRIBUTION STATEMENT (of the abstract entered In Block 20, It different from Report)

18. SUPPLEMENTARY NOTES

19. KEY WORDS (Continue on reverse aide if necessary ad Identify by block number)

Marksmanship, microcomputer, simulator, trainer, light pen

20. ABSTRACT "Colt-me m reeurs side if necessay and ide"Ify by block number)

The US Army Reserach Institute's Fort Benning Field Un ib urrently developS-ing a low-cost, part-task simulator/trainer that will traii d;-ferent weapon

systems. The Multipurpose Arcade Combat Simulator (MACS) a specially

designed light pen as the key component to determine where a weapon is aimed.

In a previous study, Schroeder and Cook (1983) investigated the effects of a

number of variables on the reliability of a prototype light pen (e.g., ambient

light, glare, distance from the monitor to the light pen, screen brightness,

.screen color, equipment warm-up, and trigger switch closure). Subsequently, the

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SECURITY CLASSIFICA t("N OF 'IS PAiE* Whsn Dote Enteard)

light pen hardware was improved. The major purpose of the present work was to

replicate the earlier light pen evaluation with the newly improved light pen.

A second goal was to assess the accuracy of the new light pen on two different

microcomputers. The new light pen was found to be significantly more reliable

than its predecessor on both microcomputers and well within the acceptable

limits of accuarcy for a marksmanship.

,For

El

[u

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Dl r I 5'n /la

SEC6RITYC L A I FI C A TtON OF THIS PAG'i~hen Date EntOred)

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S- . 2:.i - K.:>-~

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[. . . . ..- ~ -~ - - . - - - . . . . . .•- - _~ _ . -* -.

FINAL EVALUATION OF THE LIGHT PEN AS THE KEY COMPONENT IN A MICROCO11PUTER-BASED

SIMULATOR

CONTENTS

Page

INTRODUCTION .......... ......................... . .1

APPARATUS ....... .. ..........................

RESULTS AND DISCUSSION .......... .................... 2

Screen Brightness and Screen Position ..... .......... 2

Lightpen Sensitivity and Distance from the Monitor . . .. 5

Screen Color .......... ....................... 8

Ambient Light ........... ....................... 8

Equipment Warmup ........ ..................... .13

Trigger-Switch Closure ....... .................. .... 22

GENERAL DISCUSSION ......... ...................... .22

REFERENCES ........... .......................... .26

LIST OF TABLES

Table la. Light-Pen Reliability at

Different Screen Positions (APPLE lie) ......... 3

2a. The Effects of Screen Brightness on

Light-Pen Reliability ....... ............... 6

3a. Effects of Different Screen Colors .... ......... 9

4a. Effects of Ambient Light ...... .............. .11

5a. Effects of Direct Glare ...... .............. .14

6a. Test 1: Long-Term Warmup Effects ... ......... .18

7a. Test 2: Short-Term Warmup Effects .. ......... .. 20

8a. The Effects of Trigger-Switch Closure .. ....... .23

lb. Light-Pen Reliability at Different

Screen Positions (Commodore) ...... ........... 4

2b. The Effects of Screen Brightness on

Light-Pen Reliability for the Commodore ... ...... 7

3b. Effects of Different Screen Colors on

the Commodore ................................ 10

4b. Effects of Direct Glare on the Commodore ........ .12

5b. Effects of Ambient Light on the Commodore ...... .. 16

6b. Test 1: Long-Term Warmup Effects ... ......... .19

7b. Test 2: Short-Term Warmup Effects .. ......... .. 21

8b. Light-Pen Reliability at Different

Screen Positions for the Commodore ... ........ .24

Aiii

.........................................
INTRODUCTION

The Multipurpose Arcade Combat Simulator (ACS) is being developed by

the US Army Research Institute's Fort Benning Field Unit as a low-cost

trainer/simulator alternative for small weapon systems. The heart of the system

is a microcomputer that is programmed to present realistic target scenarios on

ijuthE liLor. !he key hardware element is a specially designed light pen, which

reads the raster scan on a television or monitor at a distance of 4 to 20 feet

and allows the computer to access X and Y coordinates signifying where the

weapon is pointed. Using the input from the light pen, the computer shows the

soldier where he would have hit (immediate feedback) and other relevant training

information. The system was designed to be flexible in that the light pen can

be detached from one weapon (e.g., the M1l6AI rifle) and attached to another

weapon (e.g., the ,'72A2 light antitank weapon). For a more detailed description

of the original MACS system, see Schroeder, (1983).

An earlier investigation by Schroeder and Cook (1983) provided

important information about the reliability of the light pen and the effects of

specific real-world variables on the accuracy and reliability of an early

prototype light pen. One major finding from that work was that the screen

brightness affected both the accuracy (location) and reliability (variability)

of the light pen readings. Also, position on the screen affected the

reliability of the light pen readings. In addition, there was a significant

interaction between screen brightness and position on the screen in their joint

effect on the light pen's reliability. Other test results determined little or

no effect on the light pen readings for some other real-world variables;

ambient light, glare, equipment warm-up, and trigger-switch closure. The

general conclusion of the earlier investigation was that the prototype light pen

was probably acceptable as the key component for a >116AI simulator/trainer if

certain software precautions and corrections were made.

Due to the results of the initial analysis of the prototype light pen,

hardware improvements were made. The purpose of the present effort was to

replicate the earlier general analysis with the newly improved light pen to

determine if the new light pen is resistant to real-world variables and whether

it is accurate and reliable enough to be used in a MI6AI rifle marksmanship

trainer.

APPARATUS AND PROCEDURE

The hardware configurations for the current testing consisted of an Apple

- lie computer with two disk drives, an Apple Language Card to enable Pascal

programming, a Commodore 64 computer with one disk drive, a Symtec light pen

which had been specially constructed for long distance use, and a Sony 12-inch

monitor.

For testing purposes, two programs were written (both for the Apple lie and

Commodore 64). The first program initially painted the screen green. Next, the

program took repeated readings of the X and Y coordinates frow the pen, each

time placing a white dot on the screen to indicate the light pen's position and

then painting that position green again. The purpose of this program was to

. ... ..... .. .. . . .... . . .. p• . -•" -•
allow the experimenters to determine the location of the point of aim for the

light pen and in later testing, to help calibrate what turned out to be a very

complex system. The latter point will be discussed in a later section.

The second program was the data collection program. It was written to be

flexible (i.e., different screen colors were an option and the program could

* collect samples of different sizes). For all program runs, the light pen was

secured in a stable position. When executed, the program collected a number of

readings for both the X and Y coordinates (either 10 or 100 readings for each).

The program would then print both arrays in the order they were collected.

Next, the means and standard deviations for both sets were calculated and

printed. The measure of most importance for the following tests was the

standard deviation since it reflects the reliability of the light pen. It is

important to note that the basic unit for all measurements in this paper was the

pixel (picture element). One difference between this investigation and the

earlier Schroeder and Cook investigation was that in the current test program, a

white dot was placed on the screen after each light pen pair of readings was

collected. This dot represented where the light pen was aimed. In the earlier

study, no such dot was painted. In Apple high resolution graphics mode, the

screen is composed of a 280 x 192 matrix of pixels with 0 to 279 pixels on the X

coordinate (left to right) and 0 to 191 pixels on the Y coordinate (bottom to

top). In Commodore high resolution graphics mode, the screen is composed of a

20 x 200 matrix of pixels with 0 to 299 pixels on the X coordinate (left to

right) and 0 to 191 pixels on the Y coordinate (top to bottom). However, the

resolution of the Symtec X coordinates on the Commodore are half of the

resolution of the screen (i.e., 0 to 160, left to right); the Y coordinates are

*- not effected.

All testing was done in a darkened room unless otherwise specified. The

computer(s) and monitor were placed on a heavy wooden stand in a darkened room

with no ambient light. The testing was conducted during the daylight hours in a

conference room with heavy shades over the windows. The light pen was cradled

on a cast iron tripod with height adjustable from 3 feet to 7 feet. This tripod

allowed easy aiming adjustments of the light pen along with a secure and stable

position. The height of the light pen was adjusted to be parallel with the

center of the monitor. This testing environment was selected because it

provided a reasonable representation of the setting in which ZIACS would

eventually ue fielded. All testing was conducted with the X, Y, and synch

adjustments on the light pen Apple card held constant. Unless otherwise

specified, all testing was done with the light pen trigger switch closed and the

light pen positioned 8 feet from the monitor. Screen brightness was set high

for tests unless otherwise specified.

RESULTS AND DISCUSSION

Screen Position and Screen Brightness

The first test measured the reliability of the light pen at different

screen positions (e.g., upper left, lower left, upper right, lower right, and

center). One hundred readings were taken per screen position. Columns 1-4 and

13-14 of Table la (Apple) and Table lb (Commodore) are baseline readings for

the center of the screen. Reliability was best measured with the standard

deviations of the X readings (Sx) and the standard deviations of the Y readings

2

- ', , . , ,.- ... . , . . , , ,,,,.. ,.
- - - . - - -. N- -.- ,.• - , - .. 

,7

Table la

Liht Pen Reliability at Different Screen Positions* (Apple lIe)

_ 2 3 4 5 6 7

Screen -Upper Upper Lower

Position Center Center Center Center Left Left Left

Sx .56 .67 .39 .77 .47 .51 .37

Sy .00 .00 .00 .10 .00 .10 .05

X 130.97 131.36 130.87 130.37 33.76 34.20 16.16

Y 92.00 92.00 92.00 92.01 16.00 16.01 177.00

-S 9 10 11 12 13 14

Screen Lower Lower Lower Upper Upper

Position Left Right Right Right Right Center Center

Sx .43 .50 .49 .49 .98 .27 .24

I I I

Sv .05 .0 .00 o .00 .00

X 16.27 261.49 261.59 256.42 ;256. 11 1V0.92 140.94

177.00 , 130.00 180.00 21.00 0.( 7 7.00 97.00

All ::,eans and Standard deviations are reportCd in pixels (Picture etements).
Table lb

Light Pen Reliability at Different Screen Positions (Commodore 64)

1 2 3 4 5 6 7

Screen Upper Upper Lower

Center Center Center Center Le Le Le

Position Left Left Left

Sx 0 .1 .48 .44 .96 .85 .39

Sy 0 0 0 0 .26 .24 0

118 117.99 117.34 117.25 40.98 41.09 44.81

y 145 145 145 145 69.07 69.06 216

8 9 10 11 12 13 14

Screen Lower Lower Lower Upper Upper Center Center

Position Left Right Right Right Right

Sx .42 0 0 0 0 .14 .14

Sy 0 0 0 0 0 0 0

x 44.77 186 186 176 176 116 115.98

216 215 215 73 73 133 133

4

• . .. -. .. . . . . . . . . . .., .. . - ... -. .. . , ,. . . , . . . i . .. .
(Sy). Reliability increased (both Sx and Sy decreased) when the light pen was

directed toward the center of the screen. This finding is contrary to that

found in the earlier light pen by Schroeder and Cook (1983). There were

negligible differences among the various screen positions; the average standard

deviations for X and Y were .51 and .03 using the Apple le and .28 and .04

using the Commodore 64 compared to 2.55 and 1.72 from the earlier light pen.

Brightness of the monitor is difficult to directly measure and calibrate

- without special equipment. Rather, the following calibration method was used.

First, the center of the screen was determined and marked. Next, a diagonal

line was drawn from the center of the screen to the lower right corner of the

monitor. This line was then marked off in 1cm increments from the center of the

screen. For a given reading in Table 2, the light pen was aimed at the :.ark

representing that distance (i.e., 3cm). Next, the screen brightness was

adjusted until the light pen was on the threshold of not registering (i.e., any

decrease in brightness would result in no light pen reading). Finally, the

light pen was re-aimed at the center of the screen and 100 readings takcwn. Tile

statistical results of those readings are shown in Tables 2a and 2b. The

columns in Table 2 represent an ordinal measure of screen brightness, increasing

from left to right (i.e., the screen brightness had to be increased to go from a

3cm to a 4cm screen, increased even more to go to a 5cm screen, etc.). The

light pen readings were taken in the following counterbalanced sequence (numbers

represented cm from the center of the screen) 3, 4, 5, 6, 7, 8, 9, 10, 10, 9, 8,

7, 6, 5, 4, 3, 4, 6, 8, 10, 10, 8, 6, and 4. Of course, the markings on the

screen could affect both the location and the reliability of the light pen, so

care was taken never to aim the light pen too close to the markings. The

findings are substantially different for both computers from the results of the

earlier light pen study in which reliability of the light pen was found to be

inversely related to screen brightness. The correlations between X and Y

readings over the different brightness tests were very low; the highest

correlation was -.29 and the average correlation was -.01 for the Apple lie and

" for those data collected with the Commodore 64. This compares with an average

correlation of -. 76 for the earlier light pen. Overall, the results of the

brightness test for the new light pen represent a highly significant improvement

over the earlier light pen.

Light-Pen Sensitivity and Distance from the Monitor

The one adjustment that can be made on the light pen itself is the light pen

sensitivity. The effects of the brightness of the monitor's screen and the

light pen sensitivity were found to be additive. By adjusting the light pen

sensitivity, all of the changes in readable screen size and reliability

discussed in the screen brightness section above can be effected. In fact, when

the light pen is moved to a new distance from the screen, the light pen

sensitivity would probably have to be adjusted to a level that would (1) allow

light pen readings to be made and (2) allow some flexibility for the

adjustments of the monitor's screen brightness (e.g., one should be able to

adjust the screen brightness to a comfortable viewing Level while keeping

reliable readings).

As the light pen was moved away from the screen, the readable portion of the

* screen was reduced in size from the periphery inward. There were no problems

moving the light pen back 15 feet. However, for training purposes that distance

is unwise because the soldier would lose the ability to :;ee the details of the

tar et scene and feedback oi the monitor. As the light p -n is moved back, the

- li":JIt pen sensitivity and/or the monitor's screen brightness has to be increased

....., :,_i . i i_ h~ l i i t 31 t i-l 75 i i i f il ~ i-' - i i 75 7 L'i 
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accordingly for both computers. Currently, most of the MACS software has

targets which have been scaled for distances of 8-10 ft., depending on the size

of the monitor.

Screen Color

Tests of the earlier light pen revealed that because changes in screen

color affected screen brightness, both the reliability of the light pen as

measured by the standard deviations of X and Y and the actual light-pen values

as measured by mean X and Y were affected by changes in screen color. More

specifically, the "darker" the colors, the smaller the readable screen and the

more accurate the light pen in the center of the screen. In addition, the color

of the screen was also found to influence the mean light pen readings. This

fact (as well as many others reported in this paper) was already known and was

incorporated into the earlier MACS design. More specifically, the scr, en on

which the light pen is being aimed must be of one brightness (and, therefore,

probably one color) if the light pen is to maintain its accuracy. If the scene

were to incorporate graphics features wiL'. mixed colors and/or brightness, the

*" light pen could yield widely disparate readings. Tables 3a and 3b show the

general effect of screen color on light-pen readings for the new light pen.

Brightness was again a factor in the readability of the light pen during this

test. Decreased reliability was observed with both violet and blue because

those colors were very low in screen brightness. However, screen color did not

*. have the extreme effect with the new light pen that was evident with the early

[" prototype. Also, although the mean light-pen readings were affected by color,

* the effect was not as extreme with the new light pen on either computer system

i as it was with the early light pen. More specifically, the greatest difference

- in mean readings between two colors for the new light pen was 3.14 pixels

(orange X and blue X) using the Apple lie; while the greatest difference for the

earlier light pen was 17.82 pixels (also orange X and blue X). This represents

a significant improvement over the earlier light pen. The greatest difference

*in mean readings between two colors for the new light pen using the Commodore 64

was 0.90 pixels (green X and blue X). Variation was less with the Commodore 64

" so this system might provide more reliable readings on simulations requiring

that graphic feature colors be mixed.

Ambient Light

Because the IACS system will be used in a number of unpredictable settings,

and because the light pen is obviously sensitive to at least one light source

(the monitor), the effects of various sources of ambient light and glare were

investigated. In order to assess the effects of ambient light, a 100 watt

* incandescent lamp was used as the extraneous source of light. This light was

placed in a number of "worst case" positions in order to assess the resistance

of the light pen to such ambient light sources. In one case, the lamp was

placed on the top of the monitor (less than 12 inches from the center of the

screen) facing directly at the light pen. In another case, the lamp was turned

* directly on the face of the monitor (less than 15 inches from the center of the

monitor). Finally, the lamp was physically moved about, flashing towards the

light pen and then toward the monitor while readings were being taken. Between

each test measurement, a control sample was taken with negligible ambient light.

The results of these tests are shown in Tables 4a and 4b. As can be seen, there

was little if any effect due to the ambient light sources in either mean

readings or standard deviations. For this test, a different version of the test

8
Table 3a

Effects of Different Screen Colors- (Apple I7)

I I

I I34 5

Color Oran e (;ret'n Violet Blue I te

x 133.09 I 1'32. 63 F 132. 85 130.22 130. 11

Y 106.00 104.0 0( 103.-5 103.93 10 4.00

Sx .67 .51 3.39 2.04 .31

Sy .00 .00 50 .26 00

6 7 3 9 10

Color White Blue Violet Green Orange

X 130.50 129.90 133.03 132.81 133.30 " 1 1

y 104.00 103.98 103.40 104.00 106.00 1 I

Sx .50 1.04 3.2 ) .67

0 1

Sv .00 .14 .49 .0) .00 1

All means and standard deviaLions are repcrtcd in p ixels(picture elements).

9
Table 3b

Effects of Different Screen Colors (Commodore 64)

1 2 3 4 5 6

Color Green Orange Violet Blue(dk) Blue(lt) White

120 120 120.67 120.1 119.95 120.12

y 133 133 133 133.54 133 133

Sx 0 0 .47 1.59 .22 .33

Sy 0 0 0 .37 0 0

7 8 9 10 11 12

Color White Blue(it) Blue(dk) Violet Orange Green

X 120.16 119.7 121 120.34 120 121.60

y 133 133 133 133 133 132.04

Sx .40 .50 .48 0 0 .98

Sy 0 0 0 0 0 .20

10

* . . . .'-. . . . . . . '- . '.'- . .-¢ ..-' .'. -.-. , " ...-.-. ''' °. -' .. ,- , . - . " "- -, , . '. .. ', .. . . - ..' - - . -
Table 4a

Effects of Ambient Light* (Apple lHe)

1 2 3 4 56

Light Light Directly

Source of Directly Directly Illuminating

Ambient None Facing None Facing None M1onitor's

Light Light Pen Light Pen Screen

Sx .73 .70 .70 .73 .62 .51

Sy .00 .00 .00 .00 .00 .00

X 138.34 139.00 138.97 138.90 138.77 138.28

Y 97.00 97.00 97.00 97.00 97.00 97.00

7 8 9 ____ 10

Source of Directly

Ambient None Illuminating None Flashing Light

Light 'Monitor's __________ _________ Screen _____________

Sx .67 .66 .54 .81

Sy .00 .00 .00 .00

X 139.30 138.61 138.03 139.65

Y 97.00 97.00 97.00 97.00

*All means and standard deviations are reported in pixels (picture elements).
Table 4b

Effects of Ambient Light (Commodore 64)

1 2 3 4 5 6

Source of Light Light Directly

Ambient None Directly None Directly None Illuminating

Light Facing Facing Montior' s

_ _ _ _ Light Pen _Light Pen Screen

Sx .49 0 0 .14 .43 .40

Sy 0 0 0 0 0 0

x 121.4 122 122 120.02 121.76 121.80

137 137 137 137 137 137

7 8 9 10 11

Source of Light F

Ambient None Illuminating None Light

Light Monitor's

--Screen

Sx .49 0 .20 .87 .74

Sy 0 0 0 .14 0

x 120.59 120 121.04 120.78 125.16

Y 137 137 137 136.98 137

12

__'7
program was used. In this version, a white dot was painted momentarily on the

screen to indicate where the light pen was pointed. Since this procedure could

only decrease the reliabilty of the light pen, the values shown in Table 4 are

very conservative estimates of the reliability of the light pen. As in the

tests of the early light pen, there was no effect due to ambient light. Unlike

the earlier tests, the overall reliability of the light pen was quite high.

Another source of light may have a more direct effect on the light pen's

accuracy. It seemed possible that direct glare reflecting from the monitor

straight at the light pen could have a large effect on the readings yielded by

the light pen. To test this possibility, two tests were conducted. In Test I,

the light source was situated directly above the light pen (within 6 inches).

In Test 2, the light source came from overhead and 8 feet behind the light pen.

In both tests, the lamps were directed at the screen and adjusted so that the

experimenters, when looking over the light pen, could not see the spot on the

screen where the light pen was aimed because of the reflection of the lamp

(using the first test program described above). The results of both tests are

shown in Tables 5a and 5b. Again, as with the early light pen, there was no

effect on either mean or standard deviation of the light pen readings.

Nevertheless, if fielded, it would probably be wise to advise users to (1) keep

the lighting constant within a training period, (2) if lighting changes occur,

then rezero the weapon, and (3) try to avoid direct glare that reflects

straight at the light pen. Direct glare should be avoided because of its effect

on the shooter's ability to see the target.

Equipment Warm-up

Two tests were conducted to determine whether changes in the hardware of

the systems due to equipment warm-up had any effect on the accuracy of the light

pen. Both short-term and long-term warm-up effects were assessed. In both

these tests, the dependent variable was the reliability of the light pen as

measured by sx and sy; and the independent variable was the amount of time that

had passed since the equipment was turned on. Test I investigated long-term

warm-up effects. One hundred readings were taken at the center of the screen at

the time of power-up and then were taken every 5 minutes for a total duration of

65 minutes. As shown in Tables 6a and 6b, there was little change in the

standard deviations over long-term warm-up. The largest variance was found in

the initial test and then reliability stabilized. The results do not differ

from the test of the earlier light pen except that the overall reliability was

much higher.

Test 2 investigated short-term warm-up effects. The test was run

immediately after power-up and then every minute for the next 19 m-nutes. The

number of readings was reduced from 100 to 10 in order to complete the test in

the one-minute period. The results of the tests are shown in Tables 7 a and 7b.

Standard deviations appeared relatively stable over trials, although somewhat

elevated in comparison to those observed during the long-term warm-up of Test I.

There was no appreciable change in reliability for the Apple lie but there was a

significant increase in reliability over the first 3 minutes for the Commodore

64. In summary, warm-up effects do not seem to be a significant factor for the

new light pen, but to be conservative, the equipment should probably be turned

on for 5 minutes before any serious shooting is done.

13
Table 5a

Effects of Direct Glare* (Apple lIe)

Testi

i12 3 4 5

No N o N o

Condition Glare Glare Glare Glare Glare

x 134.86 122.02 121.91 122.32 122.51

y 97.99 102.00 102.00 102.00 102.00

Sx .84 .51 .43 .58 .59

Sy ..0 .00 .00 .00 .00

6 7 8 Means

No No

Condition Glare Glare Glare Glare Glare

x 121.98 121.90 122.18 125.30 122.13

y 102.00 102.00 102.00 101.00 102.00

Sx .47 .54 .30 f .60 .52

Sy .00 .0 .00 .03 .00

All means and standard deviations are reported in pixels (picture elements).

14
Table 5a (Continued)

Effects of Direct Clare (Apple lie)

Test 2

I 32 3_ 4 5

No 2 No No

Condition Glare Glare Glare G I are Glare

x 140.92 140.66 140.22 140.57 140.38

y 98.00 98.00 98.00 98.00 98.00

Sx .46 .52 .51 .59 .51

Sy .00 .00 .00 .00 .00

6 7 S Mean s

NO No

Condition Glare Glare Glare Glare Glare

140.69 140.51 1.3',.41 140.51 140.58

y 98.00 98.00 98.00 98.00 98.00

Sx .58 .50 - 5 .50 .56

Sy .00 .00 .00 .00 .00

15
Table 5b

Effects of Direct Glare (Commodore 64)

Test 1

12 3 4 5

No No No

Condition Glare Glare Glare Glare Glare

X 120 120 120 120 120

Y138 138 138 138 138

Sx 0 0 0 0 0

Sy 0 0 0 0 0

MEANS

6 7 8

ConitonNo No

Godto lare Glare *Glare Glare Glare

x 120 120 120 120 120

y 138 138 138 138 138

Sx 0 0 0 0 0

Sy 0 0 0 0 0

*Adjusted for switch closure

1b
Table 5b (Continued)

Effects of Direct Clare (Commodore 64)

Test 2

2 3 4 5

No No No

Condition Glare Glare Glare Glare Glare

X 125.32 119.01 119 119 119

141.97 138 138 138 138

Sx 3.23 .1 0 0 0

Sy 3.78 0 0 0 0

MFANS

6 7 8

ConditionNo 

No

Condition Clare Glare *Glare Glare Clare

x 119 119 119 120.26 119

y 138 138 138 133.79 138

SK 0 0 0 .76 0

Sy 0 0 0 .65 .02

17

. . . . . :.. ... . . . . . . . . , ," , .,
Table 6 a

Test 1: Long-Term Warm Up Effects*

(100 Readings/Sample and Maximum Screen Brightness) (Apple lie)

Time Initial 5 Min. 10 Min. 15 Min. 20 Min. 25 Min. 30 Min.

139.37 136.24 136.17 136.62 136.24 136.45 136.51

Y 102.10 102.00 102.00 102.00 102.00 102.00

Sx 1.38 .61 .64 .63 .51 .61 .63 j 1

Sv .30 .00 .00 .00 .00 .00 .00

Time 35 'in. 40 Min. 45 Min. 50 Min. 55 Min. 60 M in. 65 Min.

x 136.45 136.46 136.42 136.59 136.65 136.94 136.79

Y 102.00 , 102.00 102.00 102.00 102.00 102.00

Sx .67 .56 J .70 .64 .70 .71 .73

.00 .Or) .00 .00 .0) .00

* .ll ::.od;L; .i:Id - t~:v rJ deviitions are reported in pixel!s (picture elements).

18
Table 6b

Test 2: Long-Term Warm Up Effects

(100 Readings/Sample and Maximum Screen Brightness) (Commodore 64)

Time Initial 5 Min 10 Min 15 Min 20 Min 25 Min 30 Min

x 85.02 85 85 85 85 84.94 85.5

Y 142 142 142 142 142 142 142

Sx .14 0 0 0 0 .24 .50

Sy 0 0 0 0 0 0 0

Time 35 Min 40 Min 45 Min j 50 Min 55 Min 60 Min 65 Yin

X 84.29 84.05 84.01 84.06 84.04 84.04 84.08

Y 142 142 142 142 142 142 142

Sx .46 .22 .30 .24 .20 .20 .27

Sy 0 0 0 0 0 0 0

O 19

S . -

. . . . . . . . ...
4i

Table 7a

Test 1: Short-Term Warm Up Effects

(10 Readings/Sample and Adjusted 8-cm Screen) (Apple Ile)

T ime 0 1 Min 2 Min 3 Yin 4 Min 5 Min 6 Min

x 126.10 12 .80 127.60 127.70 129.00 128.30 128.10

y 99.20 99.00 99.60 99.00 99.40 99.10 99.10

Sx 1.20 1.32 1.43 1.49 1.41 1.64 1.29

Sy .42 .47 1.58 .00 .97 .57 .32

Time 7 Min 8 Min 9 Min 10 Min 11 ",in 12 Min 13 Min

X 128.10 127.20 126.70 126.00 127.10 126.80 127.30

y 99.00 99.10 99.10 99.10 98.90 99.00 98.90

Sx 1.37 1.62 .67 .94 1.60 1.40 1.70

Sy .00 .32 .32 .32 .32 .47 .32

Time 114 Min 15 Min 16 Min 17 Min 18 Min 19 Min

127.80 127.80 126.90 127.10 126.80 127.60

y 98.70 98.80 98.80 98.b0 98.50 98.60

Sx 1.40 L.76 1.52 1.45 2.82 1.38

Sy .48 .42 .42 .42 .53 .52

* All means and standard deviations arc reported in piixels (picture elements).
Table 7b

Test 2: Short-Term Warm Up Effects

(10 Readings/Sample and Adjusted 8-cm Screen) (Conunodore 64)

Time 0 1Min 2 tin- 3 Min 4 '.'in 5 Min 6 Min

x 116.96 116.82 117.58 117.55 117.42 117.33 117.91

Y 133.34 133.41 133.03 133 133 133 133.03

Sx 2.10 2.31 .91 .59 .68 .51 1.1

Sy .48 .49 ,17 0 0 0 .17

Time 7 ",in 8 Min 9 Min 10 Min 11 Y.!in 12 Min 13 Min

x 117.31 117.82 117.72 117.61 117.72 117.31 117.1

Y 133 133 133 133 133 133 133

Sx .53 .5 .53 .51 .51 .46 .33

S. 0 0 0 0 0 0 0

Ti:.e 14 Min 15 Yin 16 in 17 Min 18 "in 19 Yin

X 117.6 117.57 117.42 117.1 117.03 117

1 33 133 133 133 133 133

s, .53 ,54 .52 .30 .39 .32

Sy 0 0 0 0 0 0

I2

---0 . i .. . - . . - ..i .--i ' .-, ' - - - -- .- " . : i .
Trigger-Switch Closure

The following test was conducted to ensure that the switch closure in the

trigger mechanism had no effect on the readings made by the light pen. In the

following tests, everything was kept constant except the independent variable;

trigger-switch closure. On control runs, the connection that activates the

light pen readings was shorted so that the test program initiated the reading

procedure. On the experimental runs, the closure was made manually with the

switch. The switch was not the actual trigger switch because pulling the

trigger switch would probably destroy the steady position of the weapon.

* Rather, a similar external switch was wired in parallel with the trigger switch

and physically removed from the light pen and cradle so that a steady position

could be maintained for the light pen. On each test, 10 X and I readings were

recorded. The results are shown in Tables 8a and 8b. There were virtually no

differences in means or standard deviations due to switch closure. These

results are similar to those found with the early light pen.

GENERAL DISCUSSION

The overall finding of the present research was that the reliability of the

new light pen has increased for all tests. The brightness of the screen, which

had a major effect on the light pen reliability in the first prototype, appears

to have little effect on the new light pen. This also applies to other

variables that affect screen brightness: sensitivity adjustment on the light

pen; color, tint, and sharpness of the monitor; and distance of the monitor from

the light pen. Nevertheless, persons using the system should be advised to keep

* all the brightness variables as constant as possible (e.g., sharpness, color,

hue, etc.) and that if changes are intentionally or accidentally made, to rezero

the weapon.

The addition of the white feedback light in the programs did not appear to

affect the reliability of the light pen in a substantial way. This is

encouraging as there are plans to employ the system in machine training in which

* immediate shot group feedback would be desirable.

An acceptable level of accuracy for the MACS light pen readings would be

accomplished if the simulator's shot group were similar to the "average" shot

group of the "average" M16. Empirical evidence indicates the mean extreme

spread of three-round shot groups for a cradled M16 is 2.11cm at 25m (see

Osborne, Morey, and Smith, 1980). The 59 weapons used by Osborne et al. were a

representative sample from two categories of rifles at Fort Benning: the

weapons pool and OSUT training. Based on the finding from Osborne et al. and

the statistical guidelines provided by Grubbs (1964), the unbiased estimate of

the population standard deviation is .87cm at 25m. The monitor used in the

present testing had a high resolution viewing width of 19.05cm and a height of

15.72cm. This makes the size of an Apple pixel on the screen equal to .068cm

(width) by .082cm (height). Similarly, the dimensions of a Commodore 64 pixel

are .119cm (width) by .079cm (height). To a viewer standing 10 ft. from the

monitor, the Apple pixel represents an area of .558cm by .673cm at a range of

25m. Similarly, the Commodore pixel would represent an area of .976cm by .648cm

at 25m. Since the standard deviation of the 116 is .87cm at 25m (both

horizontal and vertical), and the size of an Apple pixel is .558cm by .673cm at

that range, then the maximum acceptable standard deviation for the Apple would

be 1.559 for the horizontal and 1.293 for the vertical. Similarly, since the

* size of a Commodore pixel is .9 76cm by .648cm, then the maximum acceptable

2'

" " " " " ° " " " " " "" °" " • . . . . • . . . .. . . . .. " ...
Table 8a

The Effects of Trigger-Switch Closure* (Apple lle)

1 2 3 4 5 6 7 8 9

Condition Shorted Switch Shorted Switch Shorted Switch Shorted Switch Shorted

X 141.70 141.20 142.00 141.30 141.30 141.10 142.10 141.10 140.70

y 95.00 95.00 95.00 95.00 95.00 95.00 95.00 95.00 95.00

Sx .48 .63 .47 .48 .67 .32 .74 .32 .48

Sy .00 .00 .00 .00 .00 .00 .00 .00 .00

Means

10 11 12 13 14 15 16

Condition Shorted Switch Shorted Switch Shorted Switch Shorted Switch Shorted

143.70 143.30 142.50 142.20 142.30 143.10 136.80 141.93 141.25

Y 95.00 95.00 95.00 95.00 95.00 95.00 96.00 95.00 95.13

Sx 1.06 .67 .71 .42 .67 .88 .42 .60 .58

Sy .00 .00 .00 .00 .00 .00 .00 .00 .00

* All means and standard deviations are reported in pixels (picture elements).

23

. .. ..-....-. ... ..... .... .
Table 8b

The Effects-of Trigger-Switch Closure (Commodore 64)

1 2 3 4 5 6 7 8 9

Condition Shorted Switch Shorted Switch Shorted Switch Shorted Switch Shorted

88.87 88.72 88.5 88.54 88.49 88.32 88.47 88.25 88.23

y 131 131 131 131 131 131 131 131 131

.37 .45 .5 .5 .5 .47 .5 .43 .42

Sy 0 0 0 0 0 0 0 0 0

Means

10 12 12 13 14 15 16

Condition Switch Shorted Switch Shorted Switch Shorted Switch

x 88.11 88.22 88.10 88.06 88.18 88.09 88.06 88.37 88.29

y 131 131 131 131 131 131 131 131 131

Sx .31 .42 .30 .24 .39 .29 .24 .41 .39

Sy 00 0 0 0 0 0 0 0

24

[.

q.
standard deviation for the Commodore system would be .891 for the horizontal and

1.343 for the vertical. Inspection of the current summary tables indicates that

the basic raw light-pen readings meet these requirements in virtually all cases.

In addition, in all current MACS programs (as in the original MACS software),

multiple readings are taken and then an ordinal measure of central tendancy such

as the median is determined. This procedure has a dramatic effect in reducing

even further the standard deviations of the light pen readings. In the results

of the present paper, only means and standard deviations of raw light pen

readings were reported. When those readings are grouped in sets of 5 readings

and the medians of those sets are determined (as is the case in the typical MACS

program), the standard deviation of the resulting averages drops considerably.

For example, in the test conducted to determine the effects of brightness on the

light pen's reliability for the 8cm screen, the original mean standard

deviations for the four sets of 100 raw readings for X and Y were 1.06 and .00

(for the Apple lie) and .27 and .00 (for the Commodore 64). These readings were

taken in a "worst case" situation, i.e., when the light pen was aimed at the

center of the screen. When each of those sets of 100 raw readings was divided

into 20 sets of 5 scores and the medians determined, the standard deviations for

X and Y dropped to .65 and .00 (Apple lie) and .22 and .00 (Commodore 64)

respectively.

The adaptations to the light pen increased reliability significantly. It

also appears that this new pen along with the Commodore 64 model computer will

provide greater reliability and a more accurate account of shot location.

Software is currently being developed to increase the rate of light pen readings

* by using machine language subroutines and interrupts on the Commodore.

In summary, the new hardware design appears to have been successful in

increasing the reliability of the light pen. The software feature will also be

undergoing changes to increase the speed of data collection, creating further

possibility for the MCS system.

25
REFERENCES

Grubbs, F.E. Statistical measures of accuracy for riflemen and missile

engineers. Havre De Grace, Md., 1964

*Osborne, A.D., Morey, J.C., and Smith, S. Adequacy of MI6A1 Rifle

Performance and Its Implications for Marksmanship Training.

ARI Research Report, 1265, September 1980.

-. Schroeder, J.E., Multipurpose Arcade Combat Simulator (MACS).

Submitted for publication, 1983.

Schroeder, J.E. and Cook, W.A., Jr. Preliminary Evaluation of the

Light Pen as the Key Component in a Micro-Computer-Based

Simulator. ARI Research Note, June 1983.

26

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