Iec 62906 5 2 2016

IEC 62906 5 2 Edition 1 0 201 6 06 INTERNATIONAL STANDARD Laser display devices – Part 5 2 Optical measuring methods of speckle contrast IE C 6 2 9 0 6 5 2 2 0 1 6 0 6 (e n ) ® colour ins ide THIS PUB[.]

IEC 62906-5-2

Editio 1.0 2 16-0

Laser display devices –

Part 5-2: Optical measuring methods of speck le contrast

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IEC 62906-5-2

Editio 1.0 2 16-0

Laser display devices –

Part 5-2: Optical measuring methods of speck le contrast

CONTENTS

FOREWORD 4

1 Sco e 6

2 Normative referen es 6

3 Terms, definition an a breviation 6

3.1 Terms an definition 6

3.2 Ab reviation 6

4 Stan ard me s rin con ition 7

4.1 General 7

4.2 Stan ard me s rin en ironmental con ition 7

4.3 Me s rement co rdinate s stem 7

4.4 Darkro m con ition 8

4.5 Stan ard con ition of me s rin eq ipment 8

4.5.1 General 8

4.5.2 Adju tment of LDD 9

4.5.3 Con ition of me s rin eq ipment 9

4.6 Scre n con ition 10 4.6.1 General 10 4.6.2 Re ort 10 5 Me s rin method of sp ckle contrast 10 5.1 Sp ckle contrast me s rement of sti image 10 5.1.1 Purp se 10 5.1.2 Me s rin con ition 10 5.1.3 Me s rin the monoc romatic speckle contrast of front projection 10 5.1.4 Me s rin the monoc romatic speckle contrast of re r projection 12 5.2 Cal bration an diag osis of the LMD 12 5.2.1 General 12 5.2.2 Cal bration proced re an diag osis for the hig est C s 13 5.2.3 Cal bration proced re an diag osis for the lowest C s 13 An ex A (informative) Sp ctral b haviour of the LD 15 A.1 Sp ctral b haviour of a sin le-lon itu inal mode LD 15 A 2 Sp ctral b haviour of a multi-lon itu inal mode LD 1

5 An ex B (informative) Recommen ation on imagin sen or pixel size 16 An ex C (informative) Fu damental formulation of sp ckle contrast an the efects of me s rement varia les 18 C.1 Fu damental formulation 18 C.2 Ef ect of o servation distan e an iris radiu 18 An ex D (informative) Pos ible er ors an their sources 2

Bibl ogra h 21

Fig re 1 – Co rdinate s stem for projection direction an viewin direction 8

Fig re 2 – Example of me s rement ge metries for monoc romatic sp ckle contrast of front projection 1

Fig re 3 – Example of me s rement ge metries for monoc romatic sp ckle contrast

of re r projection 12

Fig re A.1 – Example of sp ctral b haviour of a sin le-lon itu inal mode LD 15

Fig re A.2 – Example of sp ctral b haviour of a multi-lon itu inal mode LD 15

Fig re B.1 – Minimum s bjective sp ckle grain size as a fu ction of the F-n mb r 17

INTERNATIONAL ELECTROTECHNICAL COMMISSION

Part 5-2: Optical measuring methods of speckle contrast

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International Stan ard IEC 6 9 6-5-2 has b en pre ared by IEC tec nical commite 1 0:

Electronic display devices

The text of this stan ard is b sed on the fol owin doc ments:

Ful information on the votin for the a proval of this stan ard can b fou d in the re ort on

votin in icated in the a ove ta le

This publcation has b en drafed in ac ordan e with the ISO/IEC Directives, Part 2

A lst of al p rts in the IEC 6 9 6 series, publ s ed u der the general title Laser displa

The commit e has decided that the contents of this publ cation wi remain u c an ed u ti

the sta i ty date in icated on the IEC we site u der "htp:/we store.iec.c " in the data

related to the sp cific publ cation At this date, the publ cation wi b

• reconfirmed,

• with rawn,

• re laced by a revised edition, or

• amen ed

A bi n ual version of this publ cation may b is ued at a later date

IMPORTANT – The “colour inside” logo on the cov r pa e of this publ c tion indic te

that it contains colours whic are con idere to be us ful for the cor e t u dersta ding

of its conte ts Us rs s ould therefore print this publ c tion using a colour printer

LASER DISPLAY DEVICES –

Part 5-2: Optical measuring methods of speckle contrast

This p rt of IEC 6 9 6 sp cifies the stan ard me s rement con ition an me s rement

method for determinin the monoc romatic sp ckle contrast of laser display devices (LDDs)

The LDDs may in lu e h brid typ s u in b th a laser or lasers, an sp ntane u emis ion

-b sed l g t sources, s c as LEDs

NOT Th mo o hromatic sp c le c ntrast me sureme ts d n t in lu e ima e q alty is u s

The folowin doc ments, in whole or in p rt, are normatively referen ed in this doc ment an

are in isp n a le for its a pl cation For dated referen es, only the edition cited a pl es For

u dated referen es, the latest edition of the referen ed doc ment (in lu in an

amen ments) a pl es

IEC 6 8 5-1, Safety of laserp roducts – Part 1: Equ ip me t clas ificato a d re uireme ts

IEC 6 9 6-1-2:2 15, Laserdispla de vices – Part 1-2: Vocab u lary a d lete r symb ols

MTF mod lation tran fer fu ction

NA n merical a erture

PPUT projection plane u der test

PSF p int spre d fu ction

SNR sig al to noise ratio

4 Standard mea uring c nditions

An LDD is fe tured by u in coherent or p rtialy-coherent lg t sources Sp ckle is cre ted

p rtic larly by coheren e of the lg t sources Therefore, me s rin method an eq ipment

p rtic larly desig ed for sp ckle are neces ary

When car yin out o tical me s rements of LDD, the me s rin en ironment, eq ipment an

method s al b compl ant with IEC 6 8 5-1 for h man safety

4.2 Sta dard me s ring e vironme tal conditions

Optical me s rements related to sp ckle s al b car ied out u der the stan ard

en ironmental con ition , at a temp rature of 2 °C ± 3 °C, a relative h midity of 2 % to

8 %, an pres ure of 8 kPa to 10 kPa When diferent en ironmental con ition are u ed,

they s al b noted in the re ort

4.3 Me s reme t coordinate s stem

The projection direction is the direction of a b am comin from the LDD to the projection

plane u der test (PPUT) The projection direction is defined by two an les: the an le of

in l nation θ (relative to the s rface normal of the PPUT) an the an le of rotation φ (also

cal ed azimuth an le) as i u trated in Fig re 1 a) Althou h the azimuth an le is me s red in

the cou ter-clockwise direction, it is related to the direction on a clock face as fol ows: φ = 0°

is the 3 o'clock direction (" ig t"), φ = 9 ° the 12 o'clock direction ("top"), φ = 180° the

9 o'clock direction ("lef") an φ = 2 0° the 6 o'clock direction ("b tom")

The viewin direction is the direction u der whic the o server lo ks at the p int of interest

on the device u der test (DUT), in lu in the projection plane u der test (PPUT) Durin the

me s rement, the lg t me s rin device (LMD) simulates the o server, by aimin the LMD at

the p int of interest on the DUT from the viewin direction The viewin direction is defined by

two an les: the an le of in lnation θ (relative to the s rface normal of the DUT) an the an le

of rotation φ (also cal ed azimuth an le) as i u trated in Fig re 1 Althou h the azimuth an le

is me s red in the cou ter-clockwise direction, it is related to the direction on a clock face

as fol ows: φ = 0° is the 3 o'clock direction (" ig t"), φ = 9 ° the 12 o'clock direction ("to "),

φ = 18 ° the 9 o'clock direction ("lef ") an φ = 2 0° the 6 o'clock direction ("b t om")

a) P UT (scre n) for fro t proje tio b) P UT (scre n) for fro t proje tio ,

or D T (LDD) for re r proje tio

Figure 1 – Coordinate sy tem for proje tion dire tion a d viewing dire tion

4.4 Darkroom condition

The LDD s ould b me s red u der control ed l g tin con ition Unwanted b ckgrou d

i umination ex e t the l g t generated by the LDD itself s al b minimized, typical y by

i uminatin the display in a darkro m The darkro m luminan e contribution from the

b ckgrou d i umination, whic is the me s rement i umination reflected of the DUT, s al b

≤ 1/2 of the lowest black level of the display If this con ition is not satisfied, then

b ckgrou d s btraction is req ired an it s al b noted in the re ort It is recommen ed that

the b ckgrou d for e c pixel of the imagin device b s btracted In ad ition, if the

sen itivity of the LMD is inadeq ate to me s re at these low levels, then the lower l mit of the

It is as umed that al me s rements are p rformed by p rson el ski ed in the general art of

radiometric an electrical me s rements as the purp se of this stan ard is not to give a

detai ed ac ou t of go d practice in electrical an o tical exp rimental ph sic Furthermore,

it is neces ary to en ure that al eq ipment is s ita ly calbrated as is known to ski ed

p rson el an that record of the cal bration data an trace bi ty are k pt

It is as umed that al me s rements are p rformed u der normal o eration con ition as

u ed in the finis ed prod ct by the en u er u les req ested otherwise

Stan ard eq ipment con ition are given b low An deviation from these con ition s al b

noted in the re ort

Me s rements s al b started af er the LDD, the l g t source, an me s rin in truments

ac ieve sta i ty

If the me s rement is not car ied out u der the darkro m con ition , de en in on the

a pl cation, the i umination/detection ge metry an the l g t source sp ctral b haviour s al

4.5.2 Adjustme t of LDD

The LDD s al b me s red at the factory default mode The LDD may b also me s red at

ad itional modes (e.g brig t or movie mode)

b) distan e from projection plane to LDD (ex e t re r projection),

c) distan e from projection plane to LMD,

d) projection direction as given in 4.3,

e) viewin direction as given in 4.3,

f p larization con ition if not o eratin in the factory default mode,

g) centre wavelen th of the LDD,

h) sp ctrum of the LDD if not o eratin in the default monoc romatic mode,

i) o tical s stem p rameters of LMD,

1) imagin len F-n mb r

2) iris diameter

3) sp ctral c aracteristic of the o tical fi ter of the LMD (when they were a pled)

j) sp cification of two-dimen ional imagin device,

The sp ckle of e c primary colour general y s al b me s red in terms of the sp ctrum of

the LDs whic l ne-width is mu h nar ower than LEDs either in the case of sin le lon itu inal

or in the case of multi-lon itu inal mode o eration (se An ex A) Sp ctral me s rement of

s c a nar ow l ne-width req ires mu h hig er resolution: a sp ctrometer, or a sp ctrum

analy er may b u ed

The me s rement s al b p rformed con iderin the fol owin asp cts

• A sp ctrometer or a sp ctrum analy er s al b ca a le of coverin a wavelen th ran e of

at le st 3 0 nm to 7 0 nm an s al have p larization sen itivity les than 2 %

• Care s al b ta en to en ure that the LMD has enou h sen itivity an d namic ran e to

p rform the req ired task

• The relative u certainty an re e ta i ty of al the me s rin devices s al b maintained

by fol owin the recommen ed cal bration s hed le in tru ted by the in trument s p l er

• The DUT s al b o erated at its inten ed image refres rate

4.6 Scre n condition

The s re n is an imp rtant comp nent of the LDD in the me s rement of sp ckle If the DUT

contain a s re n as one of the comp nents of the prod ct, the me s rement s al b car ied

out u in the s re n

4.6.2 Report

The fol owin sp cification related to s re n gain s al b noted in the re ort:

• viewin an le c aracteristic,

• p a gain,

• half gain an le

NOT 1 Th d finitio s a d me sureme t meth ds of th se p rameters are sh wn in th IC M informatio

displa me sureme ts sta d rd, 2 12, Ap e dix B17 [3]

The s re n s ould b held rigidly or the me s rement res lts mig t b afected, p rtic larly

for lon exp s re times

NOT 2 Th IC M d c me t [3] in th biblo ra h is refere b c use th re is n oth r a pro riate refere c

so rc for th scre n g in for this d c me t, b t in th future, more a pro riate d c me t wi b refere

5 Measuring methods of spe kle contrast

5.1 Spe kle contra t me s reme t of sti l ima e

5.1.1 Purpos

The purp se of this method is to determine the sp ckle contrast of an LDD The main foc s of

this me s rin method is to me s re the s re n sp ckle contrast

5.1.2 Me s ring conditions

The a p ratu con ists of the fol owin :

• a drivin p wer source,

• a drivin sig al eq ipment,

• an imagin device,

• an imagin len an iris,

• a s re n for front projection display

An LMD con istin of an imagin len , iris an imagin device s ould b b sed on the MT or

the PSF of the h man eye p rce tion [2] The imagin device s c as a CCD or a CMOS

output sig al s ould have a lne r resp n e to the in ident lg t a ove the dark c r ent noise

level Ful wel ca acity s ould b large enou h for the me s rement not to b afected by

s ot noise The SNR is more than 10 an the dark c r ent noise is les than 0,1 electron

The imagin device s ould have enou h resolution to resolve the minimum s bjective sp ckle

grain size cau ed by the iris (se An ex B)

NOT For th n ise of th ima in se sor, refer to Ch pter 3: Ph to Tra sfer Noise So rc s in [4] For th

c ara teristics of th ima in se sor, refer to An e D

5.1.3 Me s ring the monoc romatic spe kle contra t of front proje tion

The me s rement s al b p rformed as fol ows:

a) Place the DUT in front of the s re n The projection distan e s ould b the same as the

nominal prod ct desig values

b) Place the LMD as in icated in Fig re 2 The me s rement distan e s ould b the same

as the inten ed au ien e viewin distan e

The me s rement distan e stron ly de en s on the DUT For example, a me s rement

distan e of thre times the image heig t is recommen ed for a ful HD projector A

me s rement distan e of 5 m is recommen ed for a cinema projector

The imagin device s al b placed at the conju ate focal plane of the s re n

c) The projection image of the DUT is a sp tial y u iform p t ern ( ypical y a primary colour R,

G or B) The sp ckle s ould b me s red for al primaries, when multi-primary s stems

are me s red The image size s al b larger than the field of view of the LMD

d) Set the colour fiter if neces ary, for example avoidin an u neces ary o tical sig al The

fi ter s ould tran mit the primary colour c an el of the projected image It is recommen ed

to a ply the o tical fi ter that tran mits the primary colour se arately to me s re the

sp ckle contrast of e c lg t source

e) Foc s the LMD to the projected image on the s re n

f It is recommen ed to al g the DUT an LMD at an a pro riate an le to avoid sp c lar

reflection to the LMD Foc s the LMD on the s re n

g) Ca ture the image The exp s re time s al b determined so as not to saturate the

Figure 2 – Ex mple of me s reme t geometrie for

monoc romatic spe kle contra t of front proje tion

NOT 1 Th c lo r fiter set in fro t of th D T h s a b n p s pro erty for e tra tin o ly th v ry n row

“mo o hromatic” b n width of lasers g n ratin sp c le (se An e A) It is o tio al p rtic larly wh n th oth r

lg t so rc s afe t th sp c le c ntrast (se IEC 6 9 6-1-2:2 15, 2.3.5) Th cros talk in olvin th oth r lg t