ata sheet - docs-apac.rs-online.com · generator lens producing a beam angle of 106° fitted. ......

This data sheet covers the following items:

IntroductionThese devices have been designed as complete laserdiode systems for original equipment manufacturer(O.E.M.) use and although their output powers havebeen set in accordance with BS(EN)60825, they are notcertified lasers as defined in the specification. Whenincorporated in a piece of equipment it may benecessary for additional safety features to be addedbefore equipment complies fully with the standard.Read BS(EN)60825 before using any of these products.

Description These laser modules consist of a laser diode, lens anddriver circuit housed in a metal case. The modulebody is electrically isolated. Electrical connections aremade via flying leads. The lens is a single element ofhigh refractive index glass which produces a highquality collimated beam over a long distance. Itsposition can be adjusted to bring the beam to afocused spot using the special key provided. The BetaCW and TX series standard collimating lens may bereplaced by a line generating lens which produces afan shaped beam that can be focused to a fine, straightline, (RS stock no. 194-032) is supplied with a linegenerator lens producing a beam angle of 16° fitted,(RS stock no. 213-3613) is supplied with a linegenerator lens producing a beam angle of 106° fitted.The lens on the Beta Cameo series cannot be replacedwith a line generating lens.

Device RS stock no.

Beta Cameo Series0.8mW continuous wave 213-35901mW continuous wave 213-35623mW continuous wave 213-35843mW continuous wave 213-3607

Device RS stock no.

Beta TX series1mW modulating 564-5043mW modulating 194-0043mW modulating 111-368Beta CW series1mW continuous wave 194-0101.5mW continuous wave 111-3463mW continuous wave 111-3523mW continuous wave 194-0263mW line generator 194-0323mW Wide angle line generator 213-3613Single standard lens 194-048Line generator lens 194-054Line generator lens wide angle 213-3629Laser diode holder 213-3641

1502621233Issued March 2002

Laser diode modules

Data Pack F

ata Sheet

Continuous wave lasers Beta CW seriesGeneral characteristics

Parameter RS stock no./Value Units111-346 194-010 111-352

Nominal wavelength 635 670 670 785 nm

Maximum power output 1.5 1 3 3 mW

Typical power output stability (@ 20°C) 2 %

Typical power output temperature dependence 15 µW/°C

Operating voltage +4.5 to +5.5 –8 to –12 Volts

Typical operating current at minimum voltage 30 - 75 25 - 45 50 - 80 mA

Typical operating current at maximum voltage 30 - 75 25 - 50 50 - 85 mA

Power supply rejection ratio (50Hz-100kHz) 1.0 0.6 %/V

TTL disable voltage – >4 Volts

Maximum TTL pulse rate – 10 Hz

Mean time to failure (MTTF) @ 30°C 4,500 80,000 20,000 32,000 Hours

Connections 250mm flying leads

Red lead +ve supply –

Black lead – –ve supply

Green lead 0 0 Volts

Blue lead – TTL disable

194-032194-026213-3613

Optical characteristics

The spot size is determined by optical measurement. The relationship of the spot size to illumination istherefore the size to the human eye will appear bigger.

Mechanical details

15.2

5mm

(0.6

in)

46.0mm

(1.81in)

Focusingkey slots

INV

ISL

AS

ER

RAV

OID

EXP

OS

CLA

SS II

Ia L

ATo

BS7

192,

IEC8

10m

W M

ax

Ser

ial N

o.:DA

N


Beam size 4.5 × 2.5 3.5 × 2.5 4.5 × 2.5 mm

Minimum focus (lens extended) 25 – 25 mm

Spot size at minimum focus >50 – >50 Micron

Polarisation ratio 90:1 80:1 100:1 60:1

Pointing stability <0.05 mRad

Output aperture 6.0 3.5 6.0 mm

Angular deviation of beam to case (front cell) <5 mRad

2

1502621233

194-032194-026

16° Fan106° Fan

213-3613

4.5 3 2.5

1(EV)2

Weight: 30g (1.05oz)Material: Black finished brass

Absolute maximum ratings

Power supplies and earthingLaser modules which operate from a negative voltagecan be run from an unregulated supply within the rangeof –8 to –12V. By operating at the lower (–8V) end of thepower supply range, less heat will be dissipated withinthe device and hence the expected life will increase.Laser modules which operate from a positive voltagemay only be run from a supply which has beenregulated to at least 5%, within the limits specified.For all laser modules the case is isolated from thesupply voltages.

It is advisable for any floating power supplies to havethe ‘0’ volts connection (and if used, the heatsink) takento ground. If this is not done, then in electrically noisyenvironments, the power supply leads can act asaerials. Under these conditions any noise picked upcan damage the laser module. If a heatsink is not used,then the barrel of the laser module should begrounded.

TTL disableThis feature is only available on laser modules whichoperate from a negative supply voltage.An input of between +4 and +7V applied to the TTLdisable input will turn the laser ‘off ’ and an input of 0Vwill turn it ‘on’. If it is not in use it may be left floating.The laser may be pulsed ‘on’ and ‘off ’ using this inputto a frequency of at least 10Hz.

Heat sink requirementsWhen operating above their minimum supply voltageand/or at elevated temperatures above 30°C ambient,an additional heat sink must be used. If the casetemperature of the embedded laser diode shouldexceed its maximum specification, premature or evencatastrophic failure may occur.To help dissipate heat from the laser modules thefollowing graphs have been provided which show theadditional surface area of 2mm thick aluminium platerequired by each model when operated from differentsupply voltages and in different ambient temperatures.It has been assumed that good contact exists betweenthe module and the additional heat sink to ensure lowthermal resistance.For maximum effect position, the heat sink so that itcontacts the module just to the rear of the fluted frontsection (this may require peeling back the label) anduse thermally conductive cream between surfaces.

RS stock no./Value Parameter 111-346 194-010 194-026

111-352 194-032 213-3613

Supply voltage +6.0V –12.7V

TTL disable input voltage – –3 to +7V

Operating temperature –10 to +30°C –10 to + 40°C–10 to +50°C

Storage temperature –40 to +85°C

When using a proprietary heat sink, the followingequation may be used:

∅h ~ Tc – Ta – (∅m + ∅c) Iop × Vop

Where:∅h = Thermal resistance of additional heat sink (°C/W)∅m = Thermal resistance of laser module (°C/W)∅c = Thermal resistance of contact, module to heat

sink (°C/W)Tc = Maximum operating case temperature for laser

diode (°C)Ta = Maximum expected ambient temperature (°C)Vop = Operating voltage of laser module (V)Iop = Operating current @ Vop (A)

∅m + ∅c for these laser modules is typically 10°C/Wassuming a good thermal contact between module andheat sink.Tc is specified for each module as follows:

Example:If:∅m + ∅c = 10, Tc = 50°C, Ta = 35°C, Vop = 10V, Iop = 78mAThen: ∅h ~ 50 – 35 – 10

0.078 × 10

~ 9.2°C/W

Expected lifeThe laser diode device contained within each module,while being a semiconductor, is a complex electro-optical material, the structure of which determines thewavelength of the light emitted. The mechanism whichultimately causes the laser diode to fail is the formationof dislocations or gaps in the material structure. Laserdevices which operate in the visible region of thespectrum have a more brittle structure than those thatoperate in the infra-red and in consequence producedislocations at a faster rate.The rate at which dislocations form during normal use isrelated to the temperature at which the laser diodeoperates. Where possible every means should be usedto minimise temperature, such as working at lowervoltage levels, reducing operating ambients andproviding adequate heat sinking, all of which willcontribute to maximise the operating life. The figuresquoted for ‘mean time to failure’ (MTTF) reflect thedifferences in device structure and operating power.

RS stock no. °C111-352 60 111-346 40 194-026 50 194-010 50194-032 50

213-3613 50

Based on 2mm aluminium plate

12V

10V

8V

0

20

Add

ition

al h

eats

ink

(cm

2 )

Ambient temperature (°C)

21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40

20

40

60


12V

10V

8V

0

20

Ad

diti

on

al h

ea

tsin

k (c

m2)


21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

20406080

100120140160180200220240

Based on 2mm Aluminium Plate5.5V

5V

4.5V

0

2

4

6

8

10

12

14

16

18

20

20 21 22 23 24 25 26 27 28 29 30

Additi

onal h

eats

ink

(cm

2)


Continuous wave lasers Beta Cameo seriesGeneral characteristics

Parameter RS stock no./Value Units213-3562 213-3590 213-3584 213-3607

Nominal wavelength 635 670 635 670 nmMaximum power output 1 0.8 3 3 mWTypical power output stability (@20°C) <3 %Typical power output temperature dependence 15 µW/°COperating voltage +4.5 to 5.5 VoltsTypical operating current at minimum voltage 65 mATypical operating current at maximum voltage 68 mAPower supply rejection ratio (50Hz-100kHz) 1 %/VMean time to failure (MTTF) @ 30°C 4,500 20,000 4,500 20,000 HoursConnections 2 pin socket (Pre wired plug supplied)Red lead +ve supplyGreen lead 0 Volts

3

1502621233

RS Stock no. 111-346

RS Stock nos. 194-010, 194-026, 194-032 and 213-3613

RS Stock no. 111-352

Mechanical details


Power supplies and earthingThe Beta Cameo must be operated from a regulated,positive supply of 5 volts. The case, which may beconnected externally to earth, is isolated from thesupply.Connections are made via the two pin latchingconnector, the mating half is supplied pre-wired, with500mm of 7 3 0.2mm PVC insulated wire (red ispositive and green is 0V).

Heat sink requirementsWhen operating above their minimum supply voltageand/or at elevated temperatures above 30°C ambient,an additional heat sink must be used. If the casetemperature of the embedded laser diode shouldexceed its maximum specification, premature or evencatastrophic failure may occur.The module should be mounted into a metal bracket orbulkhead using the threaded barrel. Thermal transfercream can be used to improve contact and heatdissipation.When using a proprietary heat sink, the followingequation may be used:

Where:Øh = Thermal resistance of additional heat sink

(°C/W)Øm = Thermal resistance of laser module (°C/W)Øc = Thermal resistance of contact, module to heat

sink (°C/W)Tc = Maximum operating case temperature for laser

diode (°C)Ta = Maximum expected ambient temperature (°C)Vop = Operating voltage of laser module (V)Iop = Operating current @ Vop (A)Øm + Øc for these laser modules is typically 10°C/Wassuming a good thermal contact between module andheat sink.Tc is specified for each module as follows:

Example:If:Øm + Øc = 10, Tc = 50°C, Ta = 35°C, Vop = 5V, Iop = 68mAThen:

RS stock no. °C

213-3562 40

213-3590 50

213-3584 40

213-3607 50

RS stock no./ValueParameter 215-3562 215-3590

215-3584 215-3607

Supply voltage +8V

Operating temperature -10 to +30°C -10 to +40°C

Storage temperature -40 to +85°C

Focussingkey slots

10.0 13.0 1.8

M12 x 1.0

14.0

14.0

4

1502621233

Øh ~ - (Øm + Øc) Tc - Ta

Iop 3 Vop

Øh ~

~ 34.1°C/W

- 10 50 - 35

0.068 3 5


The spot size is determined by optical measurement. The relationship of the spot size to illumination is therefore the size to the human eye will appear bigger.

Parameter RS stock no./Value Units213-3562 213-3590 213-3584 213-3607

Beam size 4.5 3 2.5 mmMinimum focus (lens extended) 25 mmSpot size at minimum focus >50 MicronPolarisation ratio 10:1Pointing stability <0.05 mRadOutput aperture 2.0 5.2 mmAngular deviation of beam to case (front cell) <5 mRad

1(EV)2

Weight: 15g (0.53oz)Material: Nickel plated brass barrel and black plastic

rear cap

Modulated lasers Beta TX seriesGeneral characteristics


The spot size is determined by optical measurement. The relationship of the spot size to illumination istherefore the size to the human eye will appear bigger.


Beam size 3.5 × 2.5 4.5 × 2.5 mmMinimum focus (lens extended) 25 mmSpot size at minimum focus >50 MicronPolarisation ratio 80:1 100:1 60:1Pointing stability <0.05 mRadOutput aperture diameter 3.5 6.0 mmAngular deviation of beam to case (front cell) <5 mRad


Nominal wavelength 670 670 785 nmMaximum power output 1 3 3 mWTypical power output stability (@ 20°C) 2 %Typical power output temperature dependence 15 µW/°COperating voltage –8 to –12 VoltsTypical operating current at minimum voltage 75 85 mATypical operating current at maximum voltage 110 115 mAPower supply rejection ratio (50Hz-100kHz) 0.6 %/VTTL disable voltage >4 VoltsMaximum TTL pulse rate 10 HzInterlock ‘enable’ –5 to +2.5 VoltsModulation type Analogue or digitalModulation signal levels into 50Ω for linear response 500mV pk to pkMaximum modulation signal levels into 50Ω

(see also maximum ratings) 8V pk to pkModulation frequency band width (–3dB points) 100Hz to 50MHzFrequency range 100Hz to 100MHzModulation depth (Pulse) 90 %Mean time to failure (MTTF) @ 30°C 80,000 20,000 32,000 HoursConnections 250mm flying leadsBlack lead –ve supplyGreen lead 0 VoltsBlue lead TTL disableWhite lead InterlockYellow and green twisted pair Modulation input

5

1502621233

1(EV)2

1502621233

6

Mechanical details

15.2

5mm

(0.6

in)

75.0mm

(2.95in)Focusing

key slots

AVOI

D EX

POSU

RELa

ser R

adia

tion

emitt

ed fr

omap

ertu

re

LAS

ER

RA

AVO

ID E

XP

OB

EA

10m

W M

axCL

ASS

IIIb

LASE

DA

NG

RS

Co

Mod

el:


Power supplies and earthingThese laser modules can be run from an unregulatedsupply within the range of –8 to –12V. By operating at thelower (–8V) end of the power supply range, less heatwill be dissipated within the device and hence theexpected life will increase. This may be particularlynecessary for applications where they operate in a highambient temperature.For all laser modules the case is isolated from thesupply voltages.

It is advisable for any floating power supplies to havethe ‘0’ volts connection (and if used, the heatsink) takento ground. If this is not done, then in electrically noisyenvironments, the power supply leads can act asaerials. Under these conditions any noise picked up candamage the laser module. If a heatsink is not used, thenthe barrel of the laser module should be grounded.

Heat sink requirementsWhen operating above their minimum supply voltageand/or at elevated temperatures above 30°C ambient,an additional heat sink must be used. If the casetemperature of the embedded laser diode shouldexceed its maximum specification, premature or evencatastrophic failure may occur.To help dissipate heat from the laser modules thefollowing graphs have been provided which show theadditional surface area of 2mm thick aluminium platerequired by each model when operated from differentsupply voltages and in different ambient temperatures.It has been assumed that good contact exists betweenthe module and the additional heat sink to ensure lowthermal resistance.

For maximum effect position the heat sink so that itcontacts the module just to the rear of the fluted frontsection (this may require peeling back the label) anduse thermally conductive cream between surfaces.When using a proprietary heat sink, the followingequation may be used:∅h ~ Tc – Ta – (∅m + ∅c)

Iop × Vop


12V

10V

8V

0

20

Add

ition

al h

eat s

ink

(cm

2 )


21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40

50

45

40

35

30

25

20

15

10

5


12V

10V

8V

0

20

Add

ition

al h

eat s

ink

(cm

2 )


21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40

200

180

160

140

120

100

80

60

40

20

RS stock no./ValueParameter 564-504

194-004 111-368

Supply voltage –12.7V

TTL disable input voltage –3 to +7V

Modulation input voltage –1 to +7V

Interlock input voltage –5 to +2.5V

Operating temperature –10 to +40°C –10 to +50°C

Storage temperature –40 to +85°C

Weight: 55g (1.94oz)Material: Black finished brass

Additional heat sink vs ambient temperatureRS stock no. 194-004 and 564-504

Additional heat sink vs ambient temperatureRS stock no. 111-368

7

1502621233

Where:∅h = Thermal resistance of additional heat sink (°C/W)∅m = Thermal resistance of laser module (°C/W) ∅c = Thermal resistance of contact, module to heat

sink (°C/W) Tc = Maximum operating case temperature for laser

diode (°C) Ta = Maximum expected ambient temperature (°C)Vop = Operating voltage of laser module (V) Iop = Operating current @ Vop (A)∅m + ∅c for these laser modules is typically 10°C/Wassuming a good thermal contact between module andheat sink.Tc is specified for each module as follows:

Example:If:∅m + ∅c = 10, Tc = 50°C, Ta = 30°C, Vop = 10V, Iop = 93mAThen: ∅h ~ 50 – 30 – 10

0.093 × 10

~ 11.5°C/W

Expected lifeThe laser diode device contained within each module,while being a semiconductor, is a complex electro-optical material, the structure of which determines thewavelength of the light emitted. The mechanism whichultimately causes the laser diode to fail is the formationof dislocations or gaps in the material structure. Laserdevices which operate in the visible region of thespectrum have a more brittle structure than those thatoperate in the infra-red and in consequence producedislocations at a faster rate.The rate at which dislocations form during normal useis related to the temperature at which the laser diodeoperates. Where possible every means should be usedto minimise temperature, such as working at lowervoltage levels, reducing operating ambients andproviding adequate heat sinking, all of which willcontribute to maximise the operating life. The figuresquoted for ‘mean time to failure’ (MTTF) reflect thedifferences in device structure and operating power.

ModulationThe modulation signal applied may be of anywaveform, sinusoidal, digital or a mixture of both. It isessential, however, that its voltage does not exceed +7Vor goes below –1V relative to the 0V connection. If the500mV peak to peak signal is exceeded thenpremature failure could occur due to thermal effects.The modulation input is ac coupled.

The efficiency of modulation drops below 100Hz andabove 50MHz due to the electronics circuit. Thesefrequencies are approximately where the amplitude ofthe laser light modulation drops by 3dB (0.7) of the mid-band amplitude for a constant modulation voltage. Thetotal frequency range however extends beyond100MHz.The impedance of the modulation input is 50Ω. Ideallyat all frequencies a 50Ω co-axial cable should be used, driven from a signal source with a 50Ω output impedance. At frequencies below 1MHzhowever, this is not always necessary.Figure 1 shows a typical digital 50Ω modulation drivegiving approximately 250mV peak to peak input signal.

An alternative scheme using any TTL gate to obtain amodulation input of 500mV peak to peak is shown inFigure 2.When applying modulation to the laser module it isimportant to understand how the laser emission occurs.

+5V

74HCT04*(RS stock no.301-369)

2K2

270Ω

62Ω

0V

50Ω

0V

BC184 (RS stock no. 294-283or similar)

Connections viascreened cableor twisted pair

*All unused inputs tobe tied to ground Laser module

+5v

74HCT04*(RS stock no.301-369)

470Ω

56Ω

0V

50Ω

0V

Connections viascreened cableor twisted pair

*All unused inputs tobe tied to ground

100μf

Laser module

RS stock no. °C564-504 50 194-004 50 111-368 60

Figure 1

Figure 2

8

1502621233

As current is applied light starts to be emitted, theintensity of which increases as the current increases. Ata threshold level laser light starts to be emitted, theintensity of which increases with increasing current at afar greater rate. Modulation should be restricted to thatpart of the light due to laser emission (i.e. above thethreshold). It is possible to modulate about 90% of thelaser emission using a square wave signal and keepingwithin the specified input voltage limits. Within therange 0 to 500mV peak to peak, modulation is linear,above that there is a linearity error which varies fromdiode to diode. The modulation factor is typically–7.7µW/mV above the threshold. The minus signindicates that a rise in modulation voltage produces afall in laser intensity.

InterlockThe interlock input is provided to allow a keyswitch orsome other contacts to be used to turn the laser on oroff. The ‘enable’ time is approximately 40mS. Theinterlock input must be connected to 0V to ‘enable’ thelaser.

Any voltage applied to this input must not exceed+2.5V or be less than –5V.

TTL disableA TTL disable function is provided which can be usedto turn the laser off and on. The ‘enable’ time for thisinput is the same as the interlock, approximately 40mS.

An input voltage above 4V will turn the laser off. Whennot in use, this input can be left floating or if preferred,connected to 0V.Any voltage applied to this input should not exceed+7V or be less than –3V.

Operation dataWhen the laser module is switched on there is an‘enable’ time of approximately 40mS. This slow startlimits the possibility of any spikes reaching the diodeand causing catastrophic failure.The lens will have been adjusted to give the optimumoutput beam. The standard collimator for instance willhave been set to give a well collimated beam over a 10metre range. If the lens needs to be adjusted, insert thetabs of the key in the lens slots so that the beam passesthrough the centre of the key uninterrupted. Rotate thelens with the key to produce the desired spot.

The wavelength of the laser output varies withtemperature as shown in Figure 6.

0 10 20 30 40 50 60

668

670

672

674

676

678

680

Case temperature TC (°C)

Lasi

ng p

eak

wav

elen

gth λ

p (n

m)

lasermodule

Any TTLgate 1K8

0V

TTL disable

lasermodule

Externalcontacts

10K

–5V

0V

10K

Figure 3 A typical schematic showing externalcontacts connected

Figure 4

Figure 5

Figure 6 Temperature dependence – Lasingspectrum

1502621233

9

Temperature also affects the laser diode by altering thethreshold current. An increase of 25°C increases thethreshold current and therefore the supply current ofthe laser module by about 10mA. Operating at thehigher current reduces the life of the diode andtherefore every effort should be made to maintain theoperating temperature of the laser module at theminimum practicable for the application.

Controlling output powerThe drive circuit used in these modules employs thickfilm surface mount technology to achieve its small sizeand high reliability. Incorporated within it are twopotentiometers which control the intensity of the outputbeam. Neither of these should be adjusted as they mayresult in the power exceeding the limits stipulated forits safety classification, or even the failure of the laserdiode.The output power is set at the factory using a highlyaccurate laser power meter, the calibration of thisinstrument is traceable to international standards. Thepower set is the total light emitted through the lens. Ifthe lens is removed, a higher power will be emitted but,due to the natural divergence of the laser diode, thepower density will be lower.Line generating optics may be fitted as an alternativelens system but these generally are less efficient than astandard collimator and have such a large divergence,that the power density when integrated over a circularaperture of 7mm diameter will be much less.

PolarisationThe light emitted from a laser diode module is linearlypolarised and has a polarisation ratio which varies withoutput power. The polarisation ratio also varies acrossthe beam in relation to the intensity distribution. Thetable of optical characteristics shows the polarisationratios for the different modules. For applications wherea high polarisation ratio is required, a module with ahigher power should be used together with anaperture placed co-axially which reduces the beamdiameter.

Beam position and pointing stabilityThe position of the laser beam with respect to the laserhousing depends on a number of factors including theposition of the laser die within its mount, theconcentricity of the mechanics of the housing and theeccentricity in the lens mount and focusing system.Change any one and the position of the laser spot islikely to move.These modules have been designed to minimise suchvariations so that the emitted laser beam remainsparallel to the case within 5m Radians.However, variations in operating temperature can alsocause mechanical movements which can alter thebeam position during operation. Measurementscarried out on these modules show that suchmovements (beam pointing stability) are less than5µRadians per °C.

Applications

Notes:1. Resistor VR1 alters the sensitivity of the circuit,

increasing the value increases the sensitivity.2. RS stock no. 194-379 configured in this way rejects

ambient and low frequency (50 and 100Hz)variations in light falling on the photodiode.

3. Other configurations are possible with this deviceincluding synchronous detection systems.

4. When using a small area PIN diode, light collectioncan be greatly improved by using a lens to focus thebeam onto the surface. This lens need not be of anyspecial quality and can even be a Fresnel lens madefrom moulded plastic.

DensitometerIn the application shown in Figure 8, the output beam ofa laser module is modulated by some frequency FMOD.This is also fed to the lock-in amplifier (or phasesensitive rectifier/demodulator) as the reference signal.The lock-in amplifier demodulates the detector outputrejecting noise signals not in phase synchronism withthe reference frequency. This system obviates the needfor mechanical chopper wheels and their associatedcontrol electronics normally required with other typesof laser. This type of system is capable of working witha beam attenuation of at least 1000.

+12V

0V

10μf

k

a

Amb

Sens

0V Vss

Cap

O/P 2

Vcc

VR1

100K

10μf

–12V

Set VR1 to give1V pk-pk at O/P 2

for maximumbandwidth

0V

Figure 7 RS stock no. 194-379 configured as anambient light compensatedmodulated detector

Figure 8

1502621233

10

Proximity measurementIn this application the laser projects a beam of light ontothe surface or object being detected, the photometriccentre of the return beam is detected by a linearposition sensing detector. The laser and detector areconfigured so that they are effectively one unit. As thedistance between laser and surface changes, the returnbeam travels across the linear PSD. The distancebetween laser and object can either be calculated bytriangulation, or set specifically by varying the distanceuntil the return beam is centred on the detector.

Data transmission or beam break safety applicationfor medium distancesIn this system, Lens 1 increases the beam size so thateven when air turbulence is present, some light willalways fall onto the detector. Lens 2 improves captureof the beam onto the detector. A lens of 60mm focallength instead of the standard collimating lens wouldproduce a beam of about 25mm diameter. If the beamis broken, transmission will be interrupted, it istherefore essential in data transmission applicationsthat the equipment is sited where there is little chanceof this happening. For safety and security applicationsbeam break is used to detect the presence of people orobjects passing through the beam, in this case the databeing transmitted by the laser would be in the form of acoded ‘word’.

Smoke or fog detector This type of detector consists of a laser module whichprojects a beam of modulated light through theatmosphere and a detector which receives the signal.The presence of fog or smoke will attenuate the beamreducing the amplitude of the signal. The use of areference beam eliminates any change in the outputintensity of the laser.

Alternatively the laser and detector can be mountedside by side so that the system responds to backscattered light. In this configuration the detector islooking for the laser signal and will only see it whenthere is sufficient fog or smoke present. As this systemdoes not operate by changes in amplitude, the need fora reference beam is eliminated for most applications.

Detector

Oscillatoror

encoder

Laser diodemodule

Back scattered light

Collecting lens

Lock-in amplifier

Detector

Oscillatoror

encoderReferencedetector

Laser diodemodule

Beam splitterCollecting lens

Lock-in amplifier

Detector

Lens 1

Laser

Oscillatoror

encoder

Lens 2

Laser

Linear PSD

Detected surface

11

1502621233

lignmentThere are many applications for devices to alignobjects or position objects to a given point. The alignerdescribed is ideal where there are changes in ambientlight which could otherwise affect the accuracy of theresult. By using the diametrically opposite quadrants ofa quadrant detector, the position of a spot of light fallingon the detector can be accurately identified. When thesignal in each quadrant is equal, the spot is aligned withthe centre of the detector. Any extraneous light fallingon part of the diode would register as a shift in positionbut by using a modulated laser beam to produce thespot, it has no effect.

Two such systems used side by side on the item to bealigned not only give greater accuracy in the XYposition, but also registers rotational errors. The spotsof light from lasers 1 and 2 show not only vertical andhorizontal position, but as the spot from laser 1 is belowthe centre of detector 1 and that from laser 2 is abovethe centre of detector 2, there is an element of rotationillustrated by the line joining the two spots.

Laser spot 1Laser spot 2

Detector 1 Detector 2

Oscillator

Laser

Amplifier

Amplifier

Quadrantdetector

Line generating lens (RS stock no. 194-054 and 213-3629)

Laser module

Line generating lens

Front cell Locking ring

Collimating lens

DescriptionThe line generator is a combination system consistingof a spherical lens to focus or collimate the light emittedfrom the laser diode and a cylindrical lens whichgenerates the line. By rotating the front cell assemblythe beam can be focussed or collimated, a locking ringis used to secure the final position. The line generator isrotated using the key supplied with the laser diodemodule in order to produce the best line.The length of the line produced by the line generator isdependent on the focal length of the cylindrical lenswhile the thickness is dependent on the size of thefocussed spot produced by the spherical lens. Thegreater the operating distance, the larger and thickerthe line.

AdjustmentRemove the line generator lens by unscrewing it fromthe front using the key provided. Focus the output beamto a spot at the distance required and tighten the lockingring against the main body. Replace the line generatorlens so that it sits flush with the end of the front cell, thenrotate it to achieve the best straight line.

SpecificationLength (extending beyond laser) –––––– approx. 9mmDiameter ––––––––––––––––––––––––––––––– 15.0mmAngle of fan ––––––––––––– 16° (RS stock no. 194-054)

106° (RS stock no. 213-3629)

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Collimating lens (RS stock no. 194-048)

The collimating lens consists of a single element ofhigh index glass with a laser quality anti-reflectioncoating on both surfaces. This design is simple yethighly efficient, producing very low divergencecoupled with well defined spots of light at short,medium and long range.

SpecificationNumber of elements ––––––––––––––––––––––––––––1Focal length ––––––––––––––––––––––––––––––––––––10.0mmNumerical aperture –––––––––––––––––––––––––––––0.175Working distance –––––––––––––––––––––––––––––––7.9mmMinimum clear aperture –––––––––––––––––––––––––3.5mm

Replacing lensesLenses may be replaced by simply unscrewing oneand screwing in another. It is necessary to use the ‘key’supplied with the laser diode unit when removing orfitting the collimating lens.

Laser diode holder (RS stock no. 213-3641)

This laser diode holder has been designed for usewith the Beta CW and TX series laser diodescombining a simple method of directing the laserbeam with an additional heatsink. The laser diode unitis clamped into the holder by an M3 bolt while two M4screws and an M4 bolt provide the means for pointingand locking the laser beam in the direction required.On the rear of the main block are two M3 threadedholes which enable heatsink fins to be attached. In thebase plate there is a choice of mounting holeconfigurations by which the unit may be secured.

Laser classification

All laser devices produce beams of intensemonochromatic light which can present potentialbiological hazards. These hazards depend on anumber of factors including the wavelength, the poweror energy of the beam and the emission duration. Theeye is the most vulnerable organ as it will tend to focuslight from the laser on to the retina, thereby increasingthe energy density many times. If the irradiance of thelaser is high enough, skin damage can also result fromexposure to the beam.RS stock nos. 111-368 and 111-352 produce infra-redradiation of a power and wavelength equivalent to aClass IIIb laser product which could cause retinaburns, cataracts and even skin burns if the correctsafety procedures are not followed.Laser safety is covered by BS(EN)60825 whichrequires laser products to be classified according totheir beam characteristics. This standard is essentialreading for all laser users.Depending on the version the laser diode modulesproduce continuous wave radiation with a nominalwavelength of between 635 and 785nm. While they areclassified as O.E.M. devices, they conform to thewavelength and output power conditions of eitherClass II, Class IIIa or Class IIIb laser products.For an O.E.M. Iaser diode module to comply with thefull requirements of a certified laser product asdescribed in BS(EN)60825, it may need the addition ofa visible ‘on’ indicator, a beam shutter and a keyswitch. However, any product which incorporates alaser must be certified in its own right, irrespective ofwhether the incorporated laser is certified or not. Theway in which the laser is used within the product mayalso alter its original classification. It is therefore theresponsibility of the manufacturer of the product toensure compliance with the relevant standards.Class II laser products emit visible light and whilethey are not inherently safe, eye protection is normallyafforded by the aversion responses, including the blinkresponse. Accidental viewing is not hazardous even ifoptical aids* are used, but the user should avoidstaring into the beam. No skin damage will result fromexposure to the beam. RS stock no. 194-010, 213-3562and 213-3590 conforms to the wavelength and powerlimits of a Class II product.

40.0 5.05.0

6.0

6.0

28.0

4 holes M4 clear2 slots 4.5 rad x 8.0long on centre line

40.050.0

0.54Mounting detailsO Ring Fitted Around Lens Assembly

5.50

6.60 Max

M11

x 0

.5 P

itch

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lass IIIa laser products emit visible light and whilethey are not inherently safe, eye protection is normallyafforded by the aversion responses, including the blinkresponse. However, accidental viewing may behazardous if optical aids* are used. The user should notstare into the beam and a safety officer's approvalshould be obtained before using any form of opticalinstrument. No skin damage will result from exposureto the beam. RS stock nos. 111-346 and 194-032conform to the wavelength and power limits of a ClassIIIa product.Class IIIb laser products may emit visible or invisibleradiation, they are potentially hazardous if a directbeam or a specular reflection is viewed by anunprotected eye (intrabeam viewing). RS stock no. 111-352, 194-026, 194-004, 111-368, 213-3613, 213-3584and 213-3607 conforms to the wavelength and powerlimits of a Class IIIb product.The following precautions should be taken to avoiddirect beam viewing and to control specularreflections:1. The laser should only be operated in a controlled

area.2. Care should be taken to prevent unintentional

specular reflections.3. The laser beam should be terminated where

possible at the end of its useful path by a materialthat is diffuse and of such a colour and reflectivity asto make beam positioning possible while stillminimising reflection hazards.

4. Eye protection is required if there is any possibility ofviewing the direct or specularly reflected beam, orof viewing a diffuse reflection not complying with theconditions of item (3).

5. The entrances to controlled areas should be postedwith laser warning signs.

Any company or organisation which intends usingClass IIIb lasers, or lasers which have comparableoutput powers and wavelengths, should appoint asafety officer whose duty is to ensure that the correctsafety procedures are followed at all times.

GeneralAll laser diode modules are supplied with adjustableand removable optics for which the special keysupplied with each unit is required. Focusing the beamto a small intense spot will not increase the risk ofintrabeam viewing**.Removal of the entire optical assembly will subject theuser to the full radiated power of the laser diode.However, the divergence of the laser beam from thediode surface is such that the energy density is low andwill not subject the user to any hazard greater than thatnormally associated with its classification.Any modification or alteration which may affect anyaspect of the performance or intended function of theseproducts will require to be examined and re-classifiedif necessary. The person or organisation performingany such modification or alteration is responsible forensuring the re-classification and re-labelling of theproduct in accordance with BS(EN)60825 in total.

It is good practice to ensure that whenever possible, thelaser beam from the laser diode module is terminatedat the end of its useful path by diffusely reflectingmaterial. It is also good practice to ensure that if thelaser system is to be left switched on when not in use,the supplied plastic cap is used to terminate the beamat the laser aperture.The laser diode modules, while being O.E.M. products,are supplied with labels showing their classification forwavelength and output power conforming toBS(EN)60825 and 21 CFR Part 1040.10. Reproductionsof these labels are shown opposite.Notes:

* Optical aids are, spectacles, binoculars, telescopes, magnifiers and similar devices.

**Intrabeam viewing means all viewing conditions whereby the eye is exposed to laser radiation, other than extended source viewing.

Label positions

Product label on rearsurface

Warning label on sidesurface

635nm2.8mW125018S 00114

!

INV

ISL

AS

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RAV

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EXP

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CLA

SS II

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BS7

192,

IEC8

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Ser

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Warning label Product label

AV

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EX

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Las

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tem

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aper

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CA

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DO

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Warning label Product label

Modulated Beta TX lasers

Continuous wave Beta CW lasers

Continuous wave Beta Cameo lasersRS stock no. label on top surface

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The information provided in RS technical literature is believed to be accurate and reliable; however, RS Components assumes no responsibility for inaccuracies oromissions, or for the use of this information, and all use of such information shall be entirely at the user’s own risk.No responsibility is assumed by RS Components for any infringements of patents or other rights of third parties which may result from its use.Specifications shown in RS Components technical literature are subject to change without notice.

RS Components, PO Box 99, Corby, Northants, NN17 9RS Telephone: 01536 201234An Electrocomponents Company © RS Components 1997

Warning and product labels

AVOID EXPOSURELaser Radiationemitted fromaperture

CAUTIONLASER RADIATION

DO NOT STARE INTO BEAM

1mW Max 670nmCLASS II LASER PRODUCT

To BS(EN)60825 (1991), 21 CFR Part 1040.10

Class II

Class IIIa

LASER RADIATIONDO NOT STARE INTO BEAM

OR VIEW DIRECTLYWITH OPTICAL INSTRUMENTS

CLASS IIIa LASER PRODUCTTo BS(EN)60825 (1991), 21 CFR Part 1040.10

1.5mW Max 633nm Laser Radiationemitted from aperture

AVOID EXPOSURE

Serial No.: Date:Stock No.: 111-346

RS Components

DANGER

CAUTIONLASER RADIATION

DO NOT STARE INTO BEAM

CLASS II LASER PRODUCTTo BS(EN)60825 (1991), 21 CFR Part 1040.10

1mW Max 670nm Laser Radiationemitted from aperture

AVOID EXPOSURE

Class II


RS Components

AVOID EXPOSURELaser Radiationemitted fromaperture



3mW Max 670nmCLASS IIIa LASER PRODUCT

To BS(EN)60825 (1991), 21 CFR Part 1040.10

Class IIIa

DANGER

Class IIIa





AVOID EXPOSURE


RS Components

DANGER

AVOID EXPOSUREInvisible

Laser Radiationemitted from

aperture

INVISIBLELASER RADIATION

AVOID EXPOSURE TOBEAM

3mW Max 785nmCLASS IIIb LASER PRODUCT

To BS(EN)60825 (1991), 21 CFR Part 1040.10

Class IIIb

DANGER

Class IIIb

INVISIBLELASER RADIATION

AVOID EXPOSURE TO BEAM



AVOID EXPOSURE


RS Components

DANGER

Stock No.:

XXX-XXX

Serial No.: Date:

RS Components

Modulated lasers Continuous wave lasers

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