Haidinger's brushes with common spectral distribution

Publisher’s version / Version de l'éditeur:

Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n’arrivez pas à les repérer, communiquez avec nous à PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca.

Questions? Contact the NRC Publications Archive team at

PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. If you wish to email the authors directly, please see the first page of the publication for their contact information.

https://publications-cnrc.canada.ca/fra/droits

L’accès à ce site Web et l’utilisation de son contenu sont assujettis aux conditions présentées dans le site LISEZ CES CONDITIONS ATTENTIVEMENT AVANT D’UTILISER CE SITE WEB.

Building Research Note, 1981-07

READ THESE TERMS AND CONDITIONS CAREFULLY BEFORE USING THIS WEBSITE. https://nrc-publications.canada.ca/eng/copyright

NRC Publications Archive Record / Notice des Archives des publications du CNRC : https://nrc-publications.canada.ca/eng/view/object/?id=e37f6a7e-375b-4b08-b2c0-c1f6787dce1b https://publications-cnrc.canada.ca/fra/voir/objet/?id=e37f6a7e-375b-4b08-b2c0-c1f6787dce1b

NRC Publications Archive

Archives des publications du CNRC

This publication could be one of several versions: author’s original, accepted manuscript or the publisher’s version. / La version de cette publication peut être l’une des suivantes : la version prépublication de l’auteur, la version acceptée du manuscrit ou la version de l’éditeur.

For the publisher’s version, please access the DOI link below./ Pour consulter la version de l’éditeur, utilisez le lien DOI ci-dessous.

https://doi.org/10.4224/40000538

Access and use of this website and the material on it are subject to the Terms and Conditions set forth at

Haidinger's brushes with common spectral distribution

I tA I 1)IN(;ERq S SlEUSIiES W I T I J CObBtON SPECTRAL I'lTSTRTBU'rIONIIS

M.S. Rea

1 1 a i d i 1 1 g e r ' ~ byushe5 a r e an entoptic phenomenon associated w i t h

polarized, s h o r t wavelength l i g h t . ( I n unpolarizcd l i g h r or light cun~poscd o n l y of wavelengths longer t h a n a b o u t 520 nm, Haidingcr's

I ~ ~ U S I I C S will not bc seen.) A good description of Haidinger" b m s h e s

i l l " w h i t c v ' l i g h t was given by Helmholtz (1924, p . 3 0 4 ) . He s t a t e s :

" . . . i f t h e cye is d i r e c t e d to a f i e l d emitting polarised l i g h t ,

tlaj cli.nger ' s polarisation brushes appear at the point of fixation..

.

lllc h r i g l l t c r s p o t s bounded by t h e two branches of a hyperbola look

17111 i s h on a whi t e field.. . t h e d a r k brush separating them, which is narrowest i n t h e c e n t r e and broader toward its ends, is yellowish i n COIQUI". "

A s I I a i d i n g e r t s brushes produce an apparent luminance (as well as c o l o u r ) inhomogeneity i n t h e v i s u a l f i e l d , t a r g e t s l y i n g i n s i d e and outside t h e attenuated area of t h e b r u s h e s will have d i f f e r e n t

v i s j h i l i t i c s , cven although their photometric luminances a r e t h e same.

l l n l c s s t h e s ~ > c c t r a l distrihutians, degrees of polarization and retinal

locations of t h c t a r g e t on t h e background are taken into account, 1~11otornctrp w i l l n o t accurately p r e d i c t visibility. E s t i m a t e s o f t h e m;~gnitudc! o f Haidinger

s

scsccnt; o r h i g h intensity discharge ( H I D ) l i g h t s , have not heen made.

A s s m a l l changes in contrast and luminance can occasionally affcct

v i s i l ~ i l i t y (Rea, 19811, i t is i m p o r t a n t T o have a quantitative estimate of t h e discrepancy between s u b j e c t i v e and phoeoelectric ;Isscssments o f luminance. I n the experiment now described, d i r e c t mc;~surements were made ( u s i n g human s u b j e c t s ) o f t h e relative v i s i -

h i l i t y o f polarized and unpolarized t a r g e t s produced by cool white fluorescent (CWF) lamps, a l i g h t source commonly installed in o f f i c e and industrial s c t t i n g s .

I i k c I l e l m h o l t z , many investigators have hypothesized t h a t I l a i d i n g c r ' s l ~ r u s h e s a r e a direct result o f the partially dichroic, spectrally selscxive, macular screening p i g m e n t , e . g . , Bone (19801, Ronc and Sparrock (1971), LIeVries

er

recently been d e s c r i b e d by Walker (1977, p . 179): "To schematize the

absorption characteristics, one draws pigment elements laid o u t in

r a d i a l l i n e s from a center. The maximum absorption occurs along a diameter of such a pattern when t h e diameter is perpendicular to the

sense of polarization of the light incident on t h e macula l u t e a . For

example, suppose you hold t h e polarizing filter so that vertically

p o l a r i z e d light enters t h e eye. Then the maximum absorption of the blue in the incident light takes place along a horizontal d i a m e t e r .

If you r o t a t e the f i l t e r , maximum absorption occurs along other dia-

meters, always perpendicular to whatever sense of polarization you

happen to g i v e

your

Fimre 1 is a schematic diagram of t h i s model. Tt d e p i c t s the macula iutea as a radially symmetric, p a r t i a l l y d i c h r o i c , yellow pigment l y i n g interior to t h e phatoreceptors. The documented phena- menological appearance o f Haidinger's brushes under vertically pola- r i z e d light is also depicted.

If Haidinger's brushes arise from incomplete dichroism o f the macula lutea's radial f i b r e s , then by knowing the luteals spectral absorption a t each p o l a r i z e d wavelength one could p r e d i c t the magnitude of the a t t e n u a t i o n by Haidinger's brushes for any known s p e c t r a l d i s - tribution incident on the eye. I n t h e experiments d e s c r i b e d , t h e s p e c t r a l absorption of the macula lutea was cstimated. From this

estimate t h e magnitude of Haidinger's brushes was predicted for a v a r i e t y of sources i n c l u d i n g CWF. The predicted magnitude of the Maidinger's b r u s h e s effect was compared w i t h the empirically measured magnitude f a r a CWF spectral distribution.

APPARATUS

Figure 2 is a schematic diagram of the apparatus employed for the

Haidingerts b r u s h e s measurement. It was rigidly fixed to a t a b l e t o p . The light box provided the test fields, It was constructed from an i n v e r t e d , fluorescent lurninaire w i t h wooden side extensions and

lid. The i n t e r i m of the box was white and the outside b l a c k . A holder b e h i n d t h e front of the light box supported the circular f i e l d a p e r t u r e and t h e various f i l t e r s used in t h e experiment. Twe

fluorescent lamps (Sylvania F40 cool w h i t e ) and a ballast were in the bottom o f the light box. Light e m i t t e d through the aperture was

reflected from a sheet sf white Kashmir matte paper tacked to t h e i n s i d e of the l i d (34 deg from horizontal). The spectral r e f l e c t a n c e of the paper was very f l a t , except i n the short wavelength region

[ F i g u r e 3 ) . A temperature probe fixed to the inside of the l i g h t box

was used to monitor temperatures, which for all t e s t conditions d i d not vary by more than 2 K.

'I'hree t y p e s o f f i l t e r were inserted in the l i g h t box h o l d e r < l u r i n g t h e experiment: a P o l a r o i d ( H N 3 8 3 , a 462 m m monochromatic

interference f i ltes and two kinds of n e u t r a l d e n s i t y filters

[Wratten 96 and Schott glass N G 9 ) , These filters were used in various

c o m b i n a t i o n s t o g i v e approximately t h e same luminance f o r a l l t h e experimental conditions.

S u b j e c t s viewed the focused t c s t E i e l d w i t h t h e r i g h t eye through

t h c o p t i c a l c e n t r e of Blackwell Visual Task Evaluator (VTE), Model

-7X (Blackwell, 1970). The s u b j e c t changed the intensity of t h e test f i e l d by rotating an lnconel continuous neutral d e n s i t y wedge l i n k e d to the contrast control d i a l on the VTE. The test f i e l d

(diam - 39 min ) I was presented t o t h e observer intermittently ( F i g u r e 4) on a black background w i t h a black surround. A single

f i x a t i o n l i g h t ( d i m = 1 1 min ) 2 was positioned to the left of o r above t h e test f i e l d w i t h a beam splitter in t h e VTE. The absolute transmission o f the Inconel wedge and the beam splitter were measured t h r o u g h the VTE; the r e s u l t s of these measurements were nearly t h e same a s t h o s e supplied by t h e manufacturer. ( s e e Appendix A ) .

CONDITIONS

To d e t e r m i n e the magnitude o f Haidinger's brushes f o r a vertically polarized

CWF

so t h a t t h e small test f i e l d would l i e e i t h e r i n s i d e or outside t h e nrca attenuated by t h e brushes, i . e . , to the right o f or below the

f i x a t i o n s p o t . T h u s , t h e t e s t f i e l d was l o c a t e d under t h e r i g h t half

of t h e b r u s h e s or in The open area under the isthmus of the brushes

(1:i gurc 1 3

.

I f t h e d i f f u s e d e n s i t y o f t h e macular pigment and t h e r e c e p t o r population o f the subject" eye were radially symmetric about t h e

f i x a t i o n point, t h e n o n l y t h e threshold transmission values f o r t h e

polarized test f i e l d would have to be measured. The r e l a t i v e

opacity o f Haidinger's brushes t o polarized light would simply be t h e r a t i o of maximum (below the f i x a t i o n point] t o minimum (to the r i g h t of

1

T h e diameter of t h e test f i e l d was determined indirectly by

visually m a t c h i n g t h e s i z e of a known f i e l d a p e r t u r e to the s i z e o f a known tcst E i e l d and computing t h e magnification produced by t h e VTE optics. Thus, knowing t h e tesl f i e l d s i z e w i t h o u t any

optics and multiplying i~ by t h e m a g n i f i c a t i o n of t h e VTE, t h e t e s t f i e l d size was determined.

3 L

l'hc diameter o f t h e fixatian l i g h t was determined by matching irs s i z e to a known f i e l d s i z e rnagni f i e d by t h e VTE.

t h c fixation p o i n t ) th~eshold transmissions. To e n s u r e t h a t t h e maximum and minimum threshold v a l u e s f o r t h e polarized f i e l d

c h a r a c t e r i z c ~ l o n l y the polarization effects of Haidinger's brushes [nnd n o t chc specrral sensitivity d i f f e r e n c e s between t h e t w o

r e t i n a 1 locations), t h r e s h o l d measurements were a l s o made to t h e l e f t O F a n d 1,elow t h e

f i x a t i o n

If Haidingerls brushes a r e t h e r e s u l t of r a d i a l alignment o f f i b r e s of t h c macular lutea, t h c n t h e hypothesized dichroic fibres sl-iould have t h e same r e l a t i v e spectral a h s o r p t i ~ n t o p o l a r i z e d light

35 t h e m a c ~ r l a s lutca docs f a r unpolarized l i g h t . The spectral

a l ~ s o r p t i n n of the macular pigment is distributed as shown in F i p r e 5, w i t h its p c a k a t about 460 nm.

A 4 0 2 m u intcrfercnce f i l t e r was used t o present monochrorn:ltic test I-Eclrl..; t o tllc r i g h t of o r under t h e subject's fixation l o c a t i o n . As w i t h tllc C W 1 : t e s t f i e l d , b o t h polarized and unpolarized f i e l d s were

[ ~ r c s u n t c r l

.

TIru degree O F polarization of the t e s t f i e l d f o r t h e v a r i o u s c x p e s i m e n t n l conditions was determined with a variable analyses a t t a c h e d to t h e front o f a Pritcllard telephotometer [Model 1980A)

.

(Appendix A) and d e g r e e s at polarization [Appendix B)

.

3 5 w e l l a s the d e g r e e s and o r i e n t a t i o n s o f p o l a r i z a t i o n , as seen by

t h u s u b j e c t s , a r e presented i n Table I. The degree of polarization

was ~ ~ r o l ~ a b l y somewhat less for t h e 462 nm conditions owing to reduced po1:lrization by t h e s e Polaroid d i c h r o i c filters at s h o r t wavelengths.

('I'wo crossed p o l a r o i d s o f this t y p e t r a n s m i t dim, v i o l e t l i g h t . ] Thc " u n p o l a r i z e d l r c o n d i t i o n s were n o t O p e r c e n t since t h e 3 4 deg m g l e o f r e f l e c t a n c e from t h e whixe paper p a l a x i z e d t h e l i g h t to some

c x t c n t

.

Refore d a t a were c o l l e c t e d i n s t r u c t i o n s were r e a d to t h e s u b j e c t ljy the experimenter (Appendix C ) . The subject's r i g h t eye was adapted to t h e d a r k f o r a t l e a s t 5 min. The chin r e s t was positioned sa that t h c subject's r i g h t eye was a l i g n e d in t h e center o f t h e eyepiece to view t h e t e s t f i e l d .

D u r i n g tl-ic experiment t h e s u b j e c t r o t a t e d the contrast wedge of t h e VTE to 3 position t h a t corresponded to his a b s o l u t e threshold for t h c i n t e r m i t t e n t t e s t f i e l d . The s u b j e c t was i n s t ~ u c t e d to realign h i s cye b e f o r e each t r i a l . As well, t h e s u b j e c t was i n s t r u c t e d t o keep h i s c y e f i x e d on t h e dim fixation s p o t f o r each setting.

Data were c o l l e c t e d in a dark roam. B a f f l i n g and an e y e

p a t c h c o v e r i n g t h e subject's Left e y e minimized t h e possibility

t h a t s t r a y light might reach t h e subject during t h e experiment.

Every subject viewed all e i g h t of t h e experimental conditions

(2 F i x a t i o n locations x 2 degrees of polarization x 2 spectral

d i s t r i b u t i o n s ) . Each subject viewed aPI experimental c o n d i t i o n s f o u r times in a counterbalanced order and made f i v e settings e a c h time an experimental condition was presented. Mean and median s e t t i n g s were used to make the estimates of the Haidinger's brushes

cf fec t

.

F i f t e e n volunteers from t h e DBRJNRC research s t a f f participated

in t h e experiment. A l l had excellent vision in t h e s i g h t e y e , as determined by a b a t t e r y of visual s c r e e n i n g t e s t s from a Keyssone

Oporthalmic Telcbinocular. Five s u b j e c t s wore c o r r e c t i v e l e n s e s d u r i n g screening and t h e experimenr. A l l but one were n a i v e

r e g a r d i n g t h e experimental hypo~heses. Three were female. S u b j e c t s

ranged in age from 23 lo 4 2 y e a r s , with a m e d i a n age of 30 ycars. RESULTS

Let Xsfi equal t h e r e l a t i v e sensitivity of a s u b j e c t , i, to

a t e s t f i e l d o f particular specr~al distributions, of a c e r t a i n d e g r e e of polarization, f , located immediately to the r i g h t o f a

f i x a t i o n p o i n t , R, o r below a f i x a t i o n p o i n t , B. Then:

where t i s t h e median threshold transmission of t h e v a r i a b l e

continuous n e u t r a l d e n s i t y wedge. J n t h i s experiment:

i is 1 to 15

s _{i s , nominally, CWF}

_{o r}

f is, nominally, completely p o l a r i z e d ,

P,

unpolarized, U

Let QSi h e a measure o f the opacity o f a subject's, i,

L l a i d i n g e r ' s b r u s h e s f o r s p e c t r a l distribution, s , corrected f o r t h e unpolarized s p e c t r a l sensitivity (of t h e subject) at two retinal locations. Then:

T h e v a l u e s e n t e r e d in Table TI, based upon 15 s u b j e c t s [ s e e

Appendix

n)

t h e I l a i d j n g e r b r u s h e f f e c t .

Tt shouXd h e made c l e a r t h a t t h e estimates of the a t t e n u a t i o n

of polarized l i g h t by Haidingerfs brushes are n o t artifactually

Jcpcndent upon t h e d i f f e r e n c e s

i n

from e q u a r i o n ( 3 ) t h a t Xsfi is not d e p e n d e n t upon t h e new values

o f t e s t luminance:

As l o n g , t h e r e f o r e , a s the same test field is used f o r t o p and l c f t fixation l o c a t i o n s within polarized and unpelarized t e s t c o n d i t i o n s , t h e differences i n luminance for t h e p o l a r i z e d and unpolarized test f i e l d s [as well as t h e i r absolute values) a r e unimportant to the estimate of Haidinger's brushes.

Attenuation, A , can by absorption or reflection be d e f i n e d a s :

whcre, a g a i n , O5 i s opacity for a p a r t i c u l a r spectral distribution and 1/05 is transmission. In order to make the attenuation v a l u e s o b t a i n c d u n d e r t h e s e experimental conditions more g e n e r a l , let HBS

b e t h c attenuation o f p o l a r i z e d light per t o t a l polarization used

to producc it:

where As is d e f i n e d a s in e q u a t i o n [ 4 ] and

TP i s d e f i n e d a s in e q u a t i o n ( E l ) in Appendix, E.

S

I l l 3 is t h e r e f o r e t h e magnitude o f t h c attenuation by Haidinger's

S

b n ~ s h e s per

u n i t

pcr cent luminance l o s t from a perfectly polarized f i e l d under t h e attenuated areas o f Hxidinger's b r u s h e s relative to t h e luminance l o s t from an unpolarized f i e l d a t t h e same location and o f t h e same s p c c t r a l distribution.

The HE v a l u e s obtained for t h e spectral distributions used

i n

t h i s e x p e r i m e n t were converted to percentages and a r e presented

in

' k h l o T T I . It should b e recalled that t h e spectral reflectance of t h o Kashmir paper (Figure 33 was not t h c same a t 311 wavelengths. 'Thc IIBcwI: values i n Table I1 I are t h e r e f o r e o n l y nominally like CWF.

The assumption that Haidingervs brushes are produced by

dicilroism of the rnacular pigment was tested. The s p e c t r a l a t t e n u - a t i o n of t h e rnacular pigment (Wyszecki and Stiles 1967, p . 4 2 1 ) was normalized at 462 rim t o the mean ( 0 . 0 1 4 0 ] and median C0.0916) Ill3462 values i n T a b l e 111. From this normalization the hypothetical

luminance attenuations at all other polarized wavelengths weTe determined. Using thase normalized values it was possible t o

p r e d i c t t h e luminance attenuation of a polarized field by Haidinger's

brushes w i t h a spectral distribution combining C I I : (Wyszecki and

Stiles, 1 9 6 7 , Table 1.12) and t h e spectral ~ e f l e c t a n c e o f t h e Kashmir paper [Figure 31. These p r e d i c t e d HBCWF values are a l s o

p r e s e n t e d in T a b l e 111,

The close agreement between t h e observed and predicted attenu-

a t i o n of the brushes in T a b l e IT1 strongly supports the notion that

t h e mncular pigment i s radially dichroic and accounts f o r Haidinger's

l ~ r u s h c s . This conclusion has also been reached by a variety o f researchers from t h e .time o f Welrnhaltz (19241. T h i s is the first time, however, that a d i r e c t comparison has been made using t h e same

subjccts w i t h l i g h t s of d i f f e r e n t spectral distribution.

The normalized values used to predict

HBCWF

employed in realistic settings, including CWF unaffected

by

spectral r e f l e c t a n c e

of

Figure 6 graphically depicts xhe attenuation af polarized

luminance distributed as CWF by the dichroic-bisefringent analyser in

t h e e y e ( i - e . , Haidingervs brushes). The absolute h e i g h t at every u a v e l e n g t l ~ interval represents the spectral distribution of CWF.

T h e s i n g l e hashed r e g i o n represents t h e mean estimate o f polarized

luminance reduction by Haidinger's brushes obtained from this expe-

riment. The e x t r a , s o l i d r e g i o n and t h e hashed region represent t h e

median estimate of polarized luminance reduction hy KaidingerTs

brushes o b t a i n e d

i n

T h c luminance attenuations f o r other typical sources a r e

presented i n T a b l e

IV

w i t h photometric measurements of polasized and unpolarized light.

It is important to stress, that t h e s e values should n o t be used

1) Thc spectral power distribution of t h e lamps will v a r y a c c o r d i n g t o a c t u a l operation and installation characteristics.

2 'Illc. . ' ; ~ ~ * ~ t r : b l d i s t r i ? ) ~ r t j ~ i ~ o f t h e 13n111s i s r a r e l y sccn djrectly I J ~ t ! ) ~ * cycl; r:~tlar*r i t is ;I spectr:ll d i s t r i b u t i o n coril,lcd w i t h

t h c spectral reflectance o f t h e material b e i n g illuminated t h a t Jetermincs t h e spectral distribution r e a c h i n g t h e e y e .

3) The d e g r e e of polarization reflected from a task is r a r e l y completely polarized or unpolarized.

4 ) ?'here is some question a s to the t r u e spectral a b s o r p t i o n of

the rnacular pigment. Recently, Pease and Adams (1980) have

presented e v i d e n c e that t h e rnacular pigment absorbs a t s i g n i f i - c a n t l y longer wavelengths t h a n t h o s e o b t a i n e d by Brown and Wald (196.7)- (Whether the agreement between predicted and pmpirical attenuation by Haidingerls b r u s h e s f o r a CWF s p e c t r a l

r l i s t r i tlution TIOW presented was f o r t u i t o u s o r n o t may have

t o bc rccxnmined. For example, one m i g h t t e s t f o r a polarization e f f e c t

wirl~

5) Thc retinal location of t h e target m u s t be taken i n t o account. TII t l ~ c s c experiments, care was taken to p l a c e the small t a r g e t t o t h c right o f and below the f i x a t i o n point. Any o t h e r location w i l l produce d i f f e r e n t r e s u l t s .

6 ) Extending t h e above comment, t h e birefringence o f the cornea will

produce different magnitudes of t h e effect, depending upon the incident

lane

polarization will produce different degrees of elliptically

p o l a r i z e d light a s it p a s s e s t h r o u g h t h e cornea t o t h e macular pigment (Bone, 19803. T h u s , t h e e f f e c t w i l l be larger o r smaller,

depending upon the alignment of the corneal fibres in relation to t h e incident plane of polarization. Furthermore, large i n d i v i d u a l d i f f e r e n c e s can be found in the alignment of the c o r n e a l f i h r e s . Bone (19801, for example, found that t h e o r i e n - t a t i o n v a r i e d between 0 and 77 d e g . i n h i s subjects. Thus, p h y s i c a l l y specifying the orientation of p o l a r i z a t i o n t r r i l l n o t e n a b l e one to p r e d i c t accurateIy t h e maximum magnitude of t h e e f f e c t f a r a particular individual without a l s o knowing t h e preferential o r i e n t a t i o n ~f I ~ f s c o r n e a l f i b r e s .

7 ) T h e r e a r c i r ~ d i v i d u a l differerlces in t h e d e n s i t y of macular pigment (Rone and S p a r r o c k 1971; Spencer 1967). Similarly,

it appears that individuals having t h e same d e n s i t y o f rnacular pigmcnt may have d i f f e r e n t proportions of f i b r e alignment in t h c macular pigment (Bone, 1980). More or less a t t e n u a t i o n could t h e r e f o r e h e expected, depending upon the population b e i n g

I\ 11 o r f l ~ c s c . c f f c c t s w i l l producc discrcp:tnc i c s h c t w r ~ c i ~ ttlr

v ; ~ l t t u s given J n Table I\! :ind t h o s e t h a t might bc Eourld under 3

d i f f e r e n t s e t o f conditions. Nevertheless, t h e values g i v e " b a l l

park1' estimates f o r t h e discrepancies between photometric measure-

1 1 1 r r 1 t : ; :lrttl tllc v i s j 1 , j l i t y of polarized and ~ m p o l a r i z e d stimuli, a n d

I I (.:r\t sivtl r c l ; ~ t i v e c l ; t ~ r t ; ~ t c s r1.F e r r o r t l ~ ; l t might h c cxpectcd f o r

v:ar I ~ I I : > 1 icllt 5011rf-t-<.

In sunimnry, t h e d a t a i n d i c a t e t h a t small e r r o r s may be en- countered i n making photometric measurements of polarized l i g h t corn-

p r j s c d o f s h o r t wavclcngths. T h e d a t a suppost t h e n o t i o n that t h e error is produced by the d i c h r o i c macular s c r e e n i n g pigment.

Estimates are a l s o g i v e n of t h e p o t e n t i a l photometric e r r o r associated w i t h l i g h t s o u r c e s commonly used in industrial and office s e t t i n g s .

It i s pointed o u t , however, t h a t t h e s e estimates m u s t b e used with c a u t i o n when making c o r r e c t i o n s in a given s i t u a t i o n .

ACKNOWLEDGEMENTS

T h c a u t h o r wishes ta express h i s thanks to 0 . Guzzo for testing s u b j c c t s and performing many computations; to M. aLleZlette f o r making

several computations; to R . Robertson f o r making spectral photomet~ic

measurements of t h e white s h e e t , f o r providing the spectral power distributions of t h e v a r i o u s H I D sources, and f o r commenting on the m a n u s c r i p t ; 3 . J e f f r e y f o ~ measuring the temporal response of t h e

Visual T a s k Evaluator; and t h e s t a f f members who k i n d l y p a r t i c i p a t e d as v o l u r l t e e r sub j e c t s j n t h e experiment.

Ihis p r o j cct was funded j ointly by t h e Illuminating Engineering

1:cscarch I r ~ s t i t u t e of North America and by t h e National Research

(:ou~ic i t of (::inadti, U i v i s i o n o f Dui l d i n g Research.

B l a c k w e l l , H . R . , 1970. Development of procedures and instruments f o r v i s u a l t a s k evaluation. Illuminating Engineering, Vol. 65, p . 267. Bonc, R . A . , 1980. The role of t h e macular pigment i n the d e t e c t i o n

of p o l a r i z e d l i g h t . Vision Research, Vol. 20, p . 2 1 3 .

Bonc, R.A. and Sparrack, J . , 1 9 7 1 . Comparison o f macular pigment d c n s i t i e s i n l~uman eyes. V i s i o n Research, Vol. 11, p. 1057.

Brown, I ) . # . and WaPd, G., 1963. Visual. pigments in human and monkey r e t i n a s , N a t u r e , V o l . 2 0 0 .

IlcVries, I I . L . , A. Spoor, and R . Jielof., 1953. Properties o f the eye with r e s p e c t to p o l a r i z e d l i g h t . Physica, Vol. 1 9 , p. 419.

f l e l m h o l t z , fi., 1924. Handbook o f Physiological Optics. Menasha, Wisconsin, Banta.

M ; l r k s , A . M . , 1 9 5 9 . MuLtilayer polarizers and their application to

gcncral polarized lighting- Illuminating Engineering, Vol. 5 4 ,

1 1 . 1 2 3 .

Pease, P.L. and A . J . Adams, 1980. 'Green' cone sensitivity and t h e difference spectrum o f t h e macular pigment, Presented to t h e Topical Meeting on Recent Advances in Vision by t h e Optical

Society of America, Sarasota, Florida.

Rea, M.S. Visual performance with realistic methods

of

c o n t r a s t . Journal o f t h e 11Luminating Engineering Socrlety, Vol. 10, No. 3 , p - 164,

Somers, W . W . and G . A . F r y , P r i v a t e c o m u n i c a t i o n .

S p e n c e r , J.A., 1967. An investigation of Maxwell's s p o t . British

J o u r n a l of Physiological Optics, V o l . 24, p . 103.

Walker, I . , 1977. Studying p o l a r i z e d light with quarter-wave and h:llf-wave p l a t e s of o n e ' s own making. Scientific American, p. 172. Wyszecki,, G . and W.S. Stiles, 1 9 6 j . Colour Science, J. Wiley

B

TABLE I

PHYSICAL SPECIFICATIONS OF TEST FIELDS AS SEEN BY SUBJECTS

Degree and Orientation Luminance

of Polarization (%] (cd m-2) Pokari z e d CIVI;' 98 - 4 (V] 0 . 1 5 1 I l n p o l a r i z e d CHI: 2 3 . 4 (W) 0.159 3 Polarized v i o l e t 93.1 [V) 0.163 t l n y ~ o l a r i z c d v i o l e t 4 3 . 4 (H) 0.162 ' ~ c h o t t g l a s s NC9 and Polaroid H N 3 8 7

-

-

TABLE I1

HAIDINGER BRUSH OPACITIES

Median 1.22 .I3845 1 . 0 6 ,0250

-

"'These CWF v a l u e s have not been adjusted to compensate f o r the low

r e f l e c t a n c e o f rhc Kashmir paper at short wavelengths.

TABLE 111

ATTENUATION OF HATDINGER'S BRUSHES PER U N I T POLARIZATION

(%I

Observed P r e d i c t e d

HB462 nrn l l B ~ ~ ~ * IIRmI,. *

Mean 7.40 1.73 2.01

Median 9 . 1 6 2.75 2.49

*

TABLE I V

PIIEDI(:TEI) 1,tMPNANCE ATTENUATION BY I 1 A 4 D I N G E R 5 BRUSHES (I'nlc CENT) FOR COMPLETELY POMKI ZED VERSUS UNPOLARIZED LIGHT

IIASEII lJPON MEAN AND MEDIAN VALUES OBTAINED UNDER EXPERIMENTAL COYDITIONS

t: 1 !lo rcsccrst 1 K4

h5

--

Warm White Deluxe S o f t White

Cool White Deluxe

Mercury Arc

Iligh Pressure Xenon 2.40

I l i g h Pressure Sodium Clear Mercury

Mercury Deluxe White

ll:rom Wyszecki and S t i l e s , 1967. Table 1 . 1 2 21:rom NRC, l l i v i s i o n of Physics, Optics Section

E Y E P t F N 5 R A D l A l F I B A E S L I N E A R POLAR l Z r R I I - 11 I C t i H O I C . S I I U R T W A V E L E N G T H A B S O R B I N G . S C R E E N I N ( ; I ' I G M E N I I N f R O N r O F R E C E P T O R S C . I U M I N O U S F I E L D E M I T T I N G W H I T E . V F R l l C A l l Y P O l A l l l L F D I I C H T F I L U I 1 L I S C I I E h l k l l C D I A G R A M O F IF#€ H A l D l N G E R E R I I S H E F F E C T S H M l R I F PAPER I E C E

1

W A V E L E N G T H , nrn F I G U R E 3 S P E C T R A L R E F L E C T A N C E OF W H I T E KASHMIR M A T T E P A P E R ( W I T H NO UV R A D I A T I O N O N S A M P L E l I R 6 0 9 6 - 1 S C A L E . nhr F I G U I I E I

s

S P E C T H A L A B S O R P T N O N O F M A C U L A K P T G A l F N T A F T E R W Y S Z E C K I AND S T I L E S

-

AI'PENIIJX A

'I'RANSMI SS 1 ON OF TI lE CONTRAST CONTROL WEDGE, V ' K MODEL .?X SERTAI, Z S U P P L l E D B Y M A N U F A C T U R E R M E A S U R E D I N DBR L A B O R A T O R Y 0 I O f l so0 1200 DVM R E A D I N G

APPENDIX B FROM MARKS (1959): max - min = P rnax + min where

max = t h c maximum luminous intensity transmitred t h r o u g h a

linear d i c h r o i c polasoid rotated about ehe optical a x i s of a photometer

m i 1 1 = tlae minimum luminous i n t e n s i t y

P = t h e d e g r e e o f polarization emitted from a luminous f i e l d

I f the field is, s a y , horizontally polarized then, max - min

E 1 V

= P maxh + min

_v

Converting max and min to luminous i n t e n s i t y p ~ o p o ~ t i o n s

H

-

1-1 = max lmax + min

ti I I

v

V' = t h e p r o p o r t i o n o f v e r t i c a l l y poIarized Light a t the cycpiecc of t h e VTE

If x e q u a l s the proportion of light changed

in

from vertical t o h o r i z o n t a l polarization, then

H = the proportion o f horizontally polarized l i g h t e n t e r i n g t h e o b j e c t i v e lens of the VTE

V = t h e proportion of vertically polarized l i g h t entering the

o b j e c t i v e lens of t h e VTE

Whcn an u n p o l a r i z e d field is viewed through t h e VTE, then,

so t h a t from ( 5 ' ) 2x = P'

As m e a s u r e d , P P = 0 , 0 1 3 6 5 at t h e eyepiece o f t h e VTE i n

an

u n i f o r m f i e l d . When more horizontally pola-rized l i g h t is at t h e

VTE

e y e p i e c e therefore,

When more vertically polarized light i s at t h e VTE eyepiece

As corroboration, measurements were taken o f the change in

polarization induced by the VTE o f a field vertically polarized 9 9 . 7 p e r cent. The v e r t i c a l polarization actually measured at t h e eyepiece

was 97.9 per c e n t ; t h e predicted v a l u e from equation (B7) was 98.4 p e r c e n t . An e r r o r of 5 p e r cent w a s considered satisfactory, and

equations ( 8 6 ) and (B7) were used a s a characterization o f the

VTE

APPENDIX C

Your task i n this experiment 4 s to s e t a f l a s h i n g t a r g e t disk

to 'It h r e s h o l d .

''

Iwtwccn j u s t v i s j b l c and j u s t invisible.

'I'lic t a r g e t disk :1nd a fixation spot should b c seen wit11 your r i g h t c y c t h r o u g h t h e eyepiece in f r o n t o f you. Target t h r e s h o l d s are s e t i n t h i s experiment by moving t h e "threshold d i a l " on t h e left s i d e of t h c b l a c k box. 'I'he t e c h n i q u e you should use t o set threshold is knorm as l'brackcting.lT To bracket t h e stimulus, r o t a t e the threshold dial

back and f o r t h so t h a t the flashing d i s k alrernates between v i s i b l e and i n v i s i b l e . You've reached threshold when you bisecx the visible and

invisible p o i n t s .

The variability in s e t t i n g thresholds may be reduced if you follow three i n s t r u c t i o n s : 1) Place the black patch over your r i g h t eye for f i v e m i n u t e s before setting thresholds and when not setting t h r e s h o l d s , I j u r i n g t h r e s h o l d s e t t i n g s , move t h e patch t o y o u r left eye. 21 Keep

your eye r i g i d l y f i x a t e d on t h e small fixation s p o t when s e t t i n g

-thresholds, Although your eye may t e n d to wander, make your threshold settings o n l y when you a r e looking a t t h e f i x a t i o n s p o t . 3) Alignment t h r o u g h thc eyepiece is critical. Before each threshold setting move t l ~ o t h r e s h o l d d i a l s o t h a t the d i s k is f a i r l y v i s i b l e ; t h e n m a k e t h e disk and t h e fixation light a s v i s i b l e a s you can by moving t h e position

of y'011r e y e . Keep it i u that p o s i t i o n and make your t h r e s h o l d s e t t i n g . 'l't-ic cxpcri m e n t e r will r e m i n d you of t h e s e instructions p e r i o d i c a l l y

APPENDIX

D

RESULTS OF

EXPERIMENT

FIFTEEN

(1. B . C . 0.7447 1.1405

7 . N . N . 0.8472 1.0351

8 . A . L . 5.7691 1.5560

1 2 . R.S. 1.2345 1 . 2 1 4 8

13. R . P . 0.9353 1 , 4 0 6 0

M t n f r o m t h e 15 s u b j e c t s were q u i t e variable. There were several values l e s s t h a n 1.0 for O s j , indicating that t h e d i f f e r e n t i a l sensitivity to unpolarized l i g h t aT the two r e t i n a l locations was greater f o r unpolarized t h a n f o r polarized tcst fields.

APPENDIX E

? l ~ e O3 values in Table I 1 are t h e relative opacities of t h e rniicular nnalyser to polarized l i g h t . The sum o f the crossed and t h e u n c r o s s e d degrees o f polarization of t h e test f i e l d s with respecr to t h c analyser ( f o r a given spectral distribution) g i v e s t h e total

polarization u s e d to produce t h e opacity-based attenuations. Because

thcrc were f o u r f i e l d s used to e s t i m a t e t h e Haidingeris brushes

;~ttcnuation ( f o r each spectral d i s t r i b u t i o n ) , t h e t o t a l polarization i s t h e sum of t h e crossed and uncrossed polarizations in the four f i e l d s .

Looking at t h e polarizations when t h e t e s t f i e l d s o f a p a r t i c u l a r

sl~cctral distribution ( s ) were polarized (PI, rhe crossed polarization, to t h e right of f i x a t i o n ( R ) , was 0.984 f o r CWF, a s was the uncrossed

1101ari z a t i o n , Zlclow f i x a t i o n ( B ) , For t h e nominally unpslarized f i e l d s

[[I) the crossed polarization (B) was 0.034 for CIW a s w a s t h e uncrossed ] , o l r r r i z a t i a n (R)

.

'I'ota2 polarization

(TP]

+ uncrossed polarization

TP

s PRs U B s

w h e r e

I" i s a s i n Equation ( 3 6 3 , and