LiCONiX 200 Series Manual - Sci.Electronics.Repair FAQ

200 Series
Helium Cadmium
Lasers
Operating
Manual
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IilELLES CElOi
U S E R
M A N U A L
F O R
S E R I E S
H E L I U M
Customer please note:
the manual.
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Telex:9103796475
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4200
C A D M I U M
&
3 2 0 0
L A S E R S
Final Test Sheets are at the back of
L A S E R
S A F E T Y
_
._
Before operating this equl'pment, users should refer to ANSI
Standard 2136.1 which outlines precautions for safe operation of laser equipment and specifically recommends that:
1.
Users should have initial eye examinations prior to
operating laser equipment followed by periodic
re-examinations.
Users
should use appropriate eye protection when
2. .
operating laser equipment.
This equipment is powered by a high voltage power supply
capable of high current output. High voltage terminals in
the power supply and in the laser head are not exposed,
however, extreme caution should be used in servicing this
equipment. In normal use there is no need to operate this
equipment with the cover removed, however, if the cover must
be removed BEWARE (IF HAZARDOUS ELECTROMAGNETIC and LASER
RADIATION.
AVOID DIRECT EXPOSURE TO THE BEAM. DO NOT STARE
INTO BRIGHT DISCHARGES. STRICT OBSERVANCE OF THE FOLLOWING
WARNING LABELS IS ADVISED.
---
w
i6
(
DANGER
USER RADIATION :
WHEN OPEN. AVOID
DIRECT EXPOSURE,/
.TDBEAM.
These lasers have a max.
cw power output of 100 nW.
See Figure 1 for radiation
pattern.
This label is
displayed on the left hand
side front of the laser head
cover.
This label installed on the
inside surface of each
resonator end plate just
above the rubber dust cap
on the N and NB versions only
AVOID EXPOSURE
USER VISIBLE AND INVISIBLE
RADlAllON IS EMITlED FROM
THIS APERTURE
Y
This label is installed on
This label is installed on
the side of the power supply
the laser head cover
as well as on the laser tube.
directly over the laser
emission indicator.
3.
These lasers comply with DHE!*! radiation performance
standards, 21CFR Subchapter J.
i
LIMITED WARRANTY
All mechanical, electrical, and optical parts and
assemblies when operated under normal conditions and in
accordance with the product instructions are warranted to be
free from defects in workmanship and materials for the first
full year following delivery of the equipment.
ADJUSTMENT will be allowed under warranty only if: the
equipment has not been subjected to abuse, improper
installation or application, alteration, accident, negligence
in use, storage, transportation, or handling; the original
equipment identifications have not been removed, defaced, or
altered; and, LICONIX inspection and test reveals that the
equipment does not meet our specifications.
PARTS and LABOR - New or factory-built replacements for
defective parts will be supplied for one (1) year from date
of delivery of the equipment. Replacement parts are
warranted for the remaining portion of the original warranty
period. There will be no charge for repair of products under
warranty where the repair work is done by LICONIX; however,
LICONIX shall not be responsible for shipping or
transportation charges which shall be the sole responsibility
of the owner.
REPLACEMENT OF LASER TUBES - LASER TUBES WILL BE
REPLACED UNDER WARRANTY IF OUTPUT POWER FALLS BELOW 50% OF
MINIMUM SPECIFIED POWER WITHIN ONE YEAR FROM DATE OF
SHIPMENT OR WITHIN 2000 OPERATING HOURS, WHICHEVER COMES
FIRST. A replacement tube will be supplied at no cost during
the warranty period in exchange for a defective tube,
however, the obligation of LICONIX herein does not extend to
the replacement of a laser tube that has been physically
damaged due to abuse, improper installation or use,
alteration, accident, negligence, improper storage or
handling.
NOT COVERED - Cleaning and ordinary mechanical and
electronic adjustment of the instrument if these be the cause
of failure are not covered by this warranty; nor is damage
due to abuse, improper installation or application,
alteration, accident, negligence in use, improper storage,
transportation or handling. This warranty shall not apply
where the original equipment identifications have been
removed, defaced, or altered.
ii
DAMAGE IN SHIPMENT - Your laser product should be
inspected andtested as soon as it is received. The product
is packaged for safe delivery. If the product is damaged in
any way, you should immediately file a claim with the
carrier, or if insured separately, with the insurance
company. LICONIX will not be responsible for damage
sustained in shipment.
CLAIMS ASSISTANCE - Contact LICONIX or your local
distributor for assistance. Give full details of the
problem. Helpful information or shipping instructions will
be given to you. Estimates of the charges for non-warranty
or other service work will be supplied, if requested, before
work begins. Please use the original shipping carton when
returning the product for repair.
DISCLAIMER - THIS WARRANTY SHALL BE IN LIEU OF ALL OTHER
WARRANTIES EXPRESS OR IMPLIED, AND SHALL BE IN LIEU OF ALL
WARRANTIES OF FITNESS AND MERCHANTABILITY. LICONIX SHALL NOT
BE LIABLE FOR INCIDENTAL OR CONSEQUENTIAL DAMAGES OF ANY
NATURE OR KIND WITH RESPECT TO ANY PRODUCTS OR SERVICES SOLD
OR RENDERED HEREUNDER, AND UNDER NO CIRCUMSTANCES WILL
LICONIX' LIABILITY EXCEED THE COST OF REPAIR OR REPLACEMENT
OF THE DEFECTIVE ITEM OF EQUIPMENT. LICONIX NEITHER ASSUMES
NOR HAS AUTHORIZED ANY OTHER PERSON T.0 ASSUME FOR IT ANY
OTHER LIABILITY.
iii
T A B L E
O F
C O N T E N T S
PAGE
OPERATING INSTRUCTIONS
1.0
Introduction
1
1.1
Recommendations to User
1
1.2
Specifications - 3200/4200
Specifications - 3300/4300
3
4
2.0
System Configuration
5
2.1
Laser Head, General
5
2.2
Power Supply, General
6
3.0
Operation of the Laser System
7
3.1
System Set-Up
7
3.2
System Operation
7
3.3
Changing Mirror Sets - 4200NB
Series Only
9
SERVICE INSTRUCTIONS
TROUBLE SHOOTING GUIDE
Starting Problems
A)
13
B)
Lasing Problems
14
Cl
Power Oscillation
14
D>
High Noise
15
El
Inferior Mode
15
Laser Alignment & Mirror
Adjustment
17
Optics Service & Cleaning
4200NB Series Only
23
APPENDICES
I
II
IV
Cadmium Level & Helium Level
Adjustment
c
Noise Control
V
Mode Walking
III
25
28
31
iv
1.0
INTRODUCTION
This user manual is for use with the LICONIX Series 4200N and
Series 4200NB lasers, the detailed specifications and
characteristics of which are given in the appropriate data
sheets, pages 3 and 4.
1.1
Recommendations To User:
1.1.1
Incoming Inspection: On receipt the laser should be unpacked,
inspected for shipping damage and if none is evident, tested
for satisfactory operation.
1.1.2
Ventilation: Provide adequate ventilation so that the ambient
temperature of the air is in the range of 20-30 degrees C. The
lasers will operate satisfactorily over a greater range, lo-40
degrees C, but some power drop off may be experienced at the
extremes.
1.1.3
Mounting: Mount the laser horizontally or warranty will be
voided. The lasers have been designed for cooling by natural
convection with air flow in through base pan and out through
blue cover. Vertical mounting or mounting on side will defeat
this design and possibly result in irreparable damage.
1.1.4
Mounting Plates: Two each g"x1.25" mounting plates are shipped
with the laser head. They are 0.25 inches thick and position
the beam 2.75 inches above the mounting surface (3.25" for the
4230/40 N and NB lasers). Two additional l/2" shim plates are
supplied with the 4230/40 N & NB systems in order to position
the beam 3.25" above the mounting surface, the minimum distance
to assure adequate cooling. Attach the mounting plates with 832x1/2" screws to the rectangular blocks which protrude through
the head base pan. The laser head may now be secured to an
optical table or reference surface by means if l/4-20 bolts
through the slots in the mounting plates. The slots are spaced
21" apart longitudinally (36" for 4230/4240 N & NB lasers) and
8 inches apart transversely.
The front end of the laser resonator is connected to the user's
optical surface via a kinematic transverse flex plate. The
rear end of the laser is linked to the optical surface via a
ball and pin assembly which gives precise height and lateral
positioning but permits relative longitudinal expansion of the
resonator and the user's mounting surface. The laser base pan
and cover are largely decoupled through soft rubber grommets
from the resonator. Non flatness in the user's mounting
surface in the lengthwise direction will not impact the
resonator alignment because of the flex plate design in the
front end bounting.
-l-
1.1.5
Use The Correct Line Voltage: The 4207/10/14 systems will
operate within specification at a line voltage of 117VAC + 10%.
The 4230/40 models reqire 117VAC + 5%. European models are
wired for nominal 220VAC and Japanese models for 100VAC. All
models operate on 50 or 60 Hz lines.
In the event of a brown out - a low line condition - the
discharge may extinguish. The laser will restart automatically
when normal line voltage is restored.
1.2
Specifications: See following pages for full specifications
and dimensional outlines on all model laser heads and power
supplies.
-2-
2.0
SYSTEM CONFIGURATION:
The 4200/3200 N and MB laser systems are
each made up of two components, a laser head and a power
The head and 4200 supply are connected by two cables:
supply.
one for control functions and one for high voltage power to the
laser tube.
The head and 4240 supply are connected by three
cables; one for control functions and two for high voltage
power to the laser tube.
2.1
Laser Head, General:
2.1.1
Mechanical/Optical
Features:
The laser head is a self-cooled structure utilizing vent holes
in the top and bottom surfaces for free movement of air. No
external cooling system is required.
The air vents should be
kept clear and open.
The beam exits through a small opening in
the end opposite the cables.
This end is equipped with a
finger operated safety beam block.
A small removable panel is
provided on one side of the blue cover to permit access to the
control electronics.
2.1.2
Electronic
Features;
The laser head contains several interconnected electronic
systems which serve to keep the discharge (plasma) tube
operating under optimum conditions. These are:
1.
The Helium Pressure Control System
2.
The Cadmium Vapor Pressure Control System
3.
The Noise Control System
4.
The Emission Indicator System
These systems are adjusted at the factory and normally do not
require user adjustment. No external controls are provided.
Access for service is through the small removable access panel.
2.1.3
Controls And Indicators;
The
The BEAM BLOCK control is the only control on the head.
It glows
EMISSION INDICATOR is the only indicator on the head.
when the power supply is on.
-5-
2.2
Power Supply, General:
2.2.1
Electronic Features:
The power supply accepts AC power from the primary source and
converts it into levels of DC and AC as needed by the control
electronics in the laser head. The regulated DC high voltage
required by the tube is produced by the power supply and
delivered to the head by the coaxial high voltage cable.
Control voltages and interlock functions are carried by the
control cable. A line fuse is mounted on the rear panel near
the AC inlet receptacle.
2.2.2
Controls, Connectors and Indicators:
Name
Function
POWER
Key switch controls AC power; ON (1) or
OFF (0).
CONTROL POWER
Connector for control cable to provide low
voltage DC and 117VAC to the laser head.
HV OUTPUT
Provides High Voltage DC to the laser tube
in the head.
REMOTE LINE
SWITCH
Connector with mating half to provide
remote (safety) control of AC power to
power supply.
POWER ON
Light glows when power supply turned ON.
DISCHARGE ON
Light glows when laser tube in ON (i.e., gas
in tube is ionized by HV and a plasma or
discharge is established.)
-6-
3.0
OPERATION OF THE LASER SYSTEM
After unpacking, inspect all components of the laser for
If any damage is found contact the carrier for onsite
damage.
All claims, in case of damage, should be directed
inspection.
Contact LiCONiX
to the carrier.
Retain all packing materials.
for further instructions.
3.1
System Set-up (refer to Figure 1):
Properly interconnect the head and power supply using the
cables provided.
If using a 424OPS, be sure to connect cables
marked "HVl" and "HV2" into proper HV outputs 1 and 2,
respectively.
With the key switch in the OFF position (key
removed from the lock-switch) connect the AC power cable into
the rear of the power supply and then into a suitable AC power
outlet.
Be sure the AC power source matches the designation on
the label near the fuse on the power supply rear panel.
IN OVERSEAS USE MAKE CERTAIN THAT THE GREEN WIRE IN THE POWER
LINE CABLE GOES TO GROUND OR EARTH.
Verify that the REMOTE LINE SWITCH connector (removable half
with internal jumper) is in place on the rear panel of the
power supply.
Be certain that the multipin connector is fully
engaged.
Set the laser head on any flat surface on its four feet or on
the mounting plates provided.
Make sure that the cooling vents
are not obstructed in any way.
DO NOT remove any covers or
panels.
Close the BEAM BLOCK or provide an external block for the laser
beam.
CAUTION - USE OF CONTROLS OR ADJUSTMENTS OR PERFORMANCE OF
PROCEDURES OTHER THAN THOSE SPECIFIED HEREIN MAY RESULT IN
HAZARDOUS RADIATION EXPOSURE.
3.2
System
Operation:
Insert the AC power KEY and turn it clockwise to its alternate
The POWER ON indicator should
position.
Power is now ON.
glow.
-7-
3.2.1
Discharge Start:
The laser tube discharge (plasma) should
This is apparent when the inside of the laser head is
start.
The DISCHARGE ON light on the
illuminated by white light.
power supply should be ON.
3.2.2
Output Delay: A f t e r e s t a b l i s h m e n t o f d i s c h a r g e i n t h e l a s e r
tube a delay of approximately two and one half minutes will
This is the warm up period for
elapse before lasing occurs.
the cadmium reservoir in the laser head.
Laser light output will build rapidly over the next thirty
seconds, dip to zero, a n d b u i l d a g a i n t o i t s f i n a l l e v e l a f t e r
about ten minutes.
3.2.3
Beam Block:
The BEAM BLOCK may be opened at any time, but
caution should be used to assure that direct eye exposure to
the beam is avoided.
The BEAM BLOCK may be used to stop laser
light emission from the laser without shutting down the system.
3.2.4
Hot Laser Restart:
When the laser (running and hot) is shut
down momentarily either by the KEY SWITCH or by operation of
one of the protective interlocks, it will not restart
immediately.
Leave the KEY SWITCH in the ON position and wait.
The Automatic Restart function will cycle the system through a
number of start cycles (3-9 minutes cooling, 10 seconds of
A few
restart conditions) until the discharge strikes again.
If the
minutes later it will deliver laser light as before.
shutdown was due to an overcurrent fault, it will be necessary
to turn the keyswitch to the off position for approx. 10
If the fault
seconds, then back on to reset a latch circuit.
condition has been cleared, the laser should restart following
cool-down.
If it does not or if it starts and shuts down
again, see the service section of this manual.
3.2.5
Operating specifications should be confirmed after an initial
warm up period of 30 minutes.
3.2.6
Occasionally in a new laser system a slight power instability
If a power fluctuation of f 10%
may develop after shipment.
with a period of 1-5 seconds is observed allow the laser to
Several hours of operaoperate until the oscillation stops.
tion may be necessary.
3.2.7
If standard specifications are not observed see Trouble
S h o o t i n g i n S e r v i c e S e c t i o n o r c a l l t h e f a c t o r y 408/496-0300
and ask for Customer Service.
-8-
3.3
Changing Mirror Sets - 4200NB Systems
Never touch mirrors with fingers (may damage
coating).
Notes: 1.
Laser should be on for at least one half hour.
2.
3.3.1
Equipment Needed: 1.
::
4.
5.
3.3.2
Methanol (in eye dropper)
Lens tissue
Q-tips (wooden long cotton sterile
swabs).
Two Allen alignment wrenches
Mirror extractor tool
Mirror Set Removal:
Step 1.
Unscrew and remove mirror nut on both ends of laser.
2.
Remove wave springs.
3.
Using the extractor tool (or your finger i? thumb) in
the hole of the mirror assembly, pull the mirror holder
straight out.
4.
Clean mirrors to be installed by the recommended
technique (refer to Appendix II).
5.
IF NEEDED clean Brewster windows with Q-tip and
methanol (Q-tip should be almost dry).
6.
Clean balls on mirror assemblies (3 each) and seating
ring in laser head with Q-tip.
Mirror Nut
f
/Wave sprtiny
Mirror Assembly
( MSeatins ring
z
-9-
3.3.3 Mirror Set Insertion:
Step 1.
Insert mirror making sure alignment pin is down.
2.
Insert wave spring.
3.
Install mirror nuts and align holes in mirror nuts with
adjustment screws just before maximum tightening.
4.
There should now be laser light output.
a.
b.
c.
5.
If not:
Reclean optics
Check laser alignment (refer to Appendix I)
Check optics for coating damage (contact LiCONiX).
Maximize power by using laser 'walking' technique
(refer to Appendix V).
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Note:
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Telephone (408j 734-4331
TWX: 910 3796475
IASTBUCTIOlfS
- - - - - m - - - - -
The information in this section is
intended as an aid to the user in
assessing problems with the operation
of the laser, and as a guide to assist
experienced users in resolving routine
problems. It is NOT intended to be a
textbook on lasertheory and trouble
shooting. If there is any question
about the procedures contained in this
section, or associated hazards, contact
Liconix Service Department.
CAUTION! I
These procedures could result in exposure
to hazardous laser radiation or bright
light sources. They should be performed
only by persons who are familiar with the
hazards involved.
WARNING11
If possible avoid removing the laser head
cover when the laser is operating. If the
cover must be removed beware of hazardous
electromagnetic and laser radiation. Do
not stare into bright discharges. Beware
of high voltages.
The cover may be removed if necessary as
Remove the two Allen head screws
follows.
on the front black bezel. Slide the bezel
forward off the laser head. Lift up the
front end of the perforated cover and pull
it forward from under the rear bezel.
-12-
L E m
A S
-P m E
-
N O T
- E
-
The following Trouble Shooting Section has been designed to help the
customer identify an operational problem and correct the problem where
possible.
The guide is broken down into sections relating to specific problems:
A) Starting problems B) No or low power output C) Power oscillation
D) High noise and E) Inferior mode.
The Trouble Shooting Guide will refer the user to one or a number of
appendices where detailed information may be obtained. It is important
to make the tests recommended in the sequence given. We have arranged
the appendices and the information therein in order to facilitate a
logical check out of the laser. Appendix I deals with simple mirror
alignment - the more complex mode walking techniques is described in V.
Appendix II covers cleaning of removable mirrors in the B style lasers.
Appendix III deals with the adjustments of cadmium vapor pressure and
helium gas pressure for optimum performance while Appendix IV details
some problems relating to noise control. Adjustments in this area are
best done under factory advice.
12.1
SERVICE INSTRUCTIONS
1.0 TROUBLE SHOOTING GUIDE
A.
Starting Problems
A.1 Key switch in ON position but Power ON & Discharge ON
lights not lit.
Suggested Action/Possible Cause:
1.
Line cord not connected.
2.
Check fuse at rear of supply.
3.
Remote line switch circuit open.
A.2 Power ON light on PS lit but Discharge ON light not lit
and no discharge in laser head.
Suggested Action/Possible /Cause:
1.
Laser is in restarting cycle, or the overcurrent latch
circuit has been set and power supply must be turned
off for greater than 10 seconds, then on again to
restart.
2.
Control cable not connected.
3.
Open circuit in control cable or in head wiring. .
4.
Open or short circuit in HV cable or in head wiring
(anode pin connector).
5.
Defective tube, break in glass, tube at atmospheric
pressure.
6.
Internal low voltage fuses in power supply open.
7.
Defective power supply
A.3 Model 4240PS.
ON light lit.
Power ON light lit but only one Discharge
Suggested Action/Possible Cause:
1.
Open or short circuit in HV cable.
2.
Defective power supply.
c
Defective head electronics - one side.
3.
-13-
B.
Lasing Problems (assumes Power ON & Discharge ON lights of the
power supply are both lit)
B.l No lasing output 10 minutes after turn on.
Suggested Action/Possible Cause.
1.
Beam block closed on front bezel.
2.
Mirror misalignment. See Appendix I for Mirror
Adjustment & Alignment.
3.
Shutter has become dislodged in shipping.
Appendix I.
4.
Contamination of optics. See Appendix II for Optics
cleaning (NB series only).
5.
Incorrect cadmium level.
See
See Appendix III for advice
on checking and adjustment.
6.
Incorrect helium gas pressure, normally very low.
Appendix III for advice.
7.
Discharge gas contaminated.
See
Return to factory.
B.2 Output power low after 30 minute warm up.
Suggested Action/Possible Cause:
1.
c.
See suggested explanations above under B and check
out in order.
Power Oscillation
C.l A power oscillation of lo-30% with a period of 1-5 seconds
(sometimes present on a new system after transportation).
Suggested Action/Possible Cause:
1.
Allow the laser to run without adjustment until
oscillation stops. May require one hour to 24 hours.
2.
Remove head inspection panel and either short TP4 to
TP6, or TP5 to ground. This will cut the power to the
cadmium reservoir heater. Run in this manner for
lo-15 minutes and then remove short.
3.
Connect voltmeter between TP4 and TP5 on head PCB (see
p&ge 16). Adjust cadmium control pot (Fig 2) so that
V4-5 increases by .02 volts. If after one hour of
oscillation continues repeat above step, i.e. increase
V4-5 by an additional 0.02 Volts. When oscillation
stops readjust pot so that V4-5 is same as initially.
-14-
D.
High Noise
Equipment needed:
Frequency counter,
>lMHz response.
1 MOhm impedance
D.l A number of factors can contribute to a high noise
condition in the laser output.
Suggested Action/Possible Cause:
1.
Remove laser head inspection panel and measure
voltages at TPl, TP3 and TP4-TP5. Compare these
readings to those recorded on the Final Test Sheet.
Also record the frequency by means of a frequency
counter by placing the probe on TP8. Record the
reading. Refer to Appendix IV for a more complete
discussion on noise control.
If the measured readings on the test points differ
significantly from the final test sheet data contact
the factory for help.
E.
Inferior Mode
E.l A degradation of the normal fundamental or Gaussian mode
to a donut or other higher order mode.
Suggested Action/Possible Cause:
1.
Tube deterioration, new tube indicated.
2.
Contaminated optics. For "N" models return head to
factory for examination. For "NB" models see Appendix
II for optics cleaning.
E.2 Occasionally a ring pattern centered or off center is seen
in the radiation pattern on expanding the mode. The
pattern can be due to:
Sugggested Action/Possible Cause:
1.
An interference pattern (Newtons rings) due to multiple reflections within the output mirror. A spatial
filter can be used to clean up the beam if needed.
2.
Slight mode scattering from within the tube setting up
an inteference pattern in the near field. Normally
the mode will be perfectly clean in the far field.
-15-
-
-16-
-"-I=Y.--
APPENDIX I
1.0 LASER ALIGNMENT and MIRROR ADJUSTMENT
1.1 Caution:
USE OF CONTROLS OR ADJUSTMENTS OR PERFORMANCE OF
PROCEDURES OTHER THAN THOSE SPECIFIED HEREIN MAY
RESULT IN HAZARDOUS RADIATION EXPOSURE.
1.2 User Controls:
Front mirror vertical adjustment.
Front mirror horizontal adjustment.
Rear mirror vertical adjustment.
Rear mirror horizontal adjustment.
Main power switch.
1.3 Equipment Needed:
Calibrated laser power meter - Liconix Model 45PM or equivalent.
Set of Allen drivers.
One each transmission diffraction grating - Edmund Scientific
Stock #40,272.
One each fluorescent card.
2.0 4200N Lasers Only:
The 4200N series lasers have been designed for minimal mechanical
adjustment during the life of the laser tube. The laser tube is
cushion mounted in the mechanical resonator structure for maximum
protection against damage in shipment. The mounting is stable
under all normal shipping or operating conditions. The laser
mirrors are mounted on tilt plates which are bolted to the
resonator end plates. The tube-mirror-resonator structure is
extremely rugged and can withstand substantial severe shocks and
vibration.
2.1 On first receipt and check out of the system's specifications the
laser power output should be compared with specified power.
Occasionally very severe handling in shipment and/or experience
of substantial temperature changes in transport may result in
some slight misalignment of the mirror-tube system. If specified
power is not produced after a 30-minute warmup on initial
inspection and test proceed as follows.
-17-
2.2 No Lasing Is Observed.
408/496-0300.
Contact Liconix Service Dept.,
2.3 Lasing Is Observed But Power Is Less Than Specified Power:
Remove the front black bezel and move to one side exposing the
resonator end plate and the mirror tilt plate mounted thereon.
Place the sensor head of the laser power meter in the beam and
note the output power.
Using a small flat bladed screwdriver or a 5/64 hex driver attempt
very slight adjustments of the top adjustment screw on the mirror
tilt plate. Note any power change. Adjustments of only a few
degrees of angular rotation of the screwdriver should be
attempted. Maximize the power. Attempt similar adjustments to
the lower adjustment screw. Again maximize the power. These
adjustments should be adequate to restore full power operation.
In an extreme case of misalignment it may be necessary to adjust
the rear mirror tilt plate also. However if this seems necessary
you should first contact the factory for advice.
2.4 Periodic Field Service:
If the 4200N series lasers are subject to substantial temperature
changes in operation or if operated at room ambient temperatures
in excess of 30 degrees C some slight mirror-tube misalignment may
occur after one to two thousand hours of operation causing a
temporary power decrease. It is advisable that units installed in
OEM systems in the field receive a periodic check at least once
per year or after approximately 2000 hours of operation.
Following the procedure outlined above in Section 2.3 the output
power should be measured and if substantially below
specifications by 25% or more the mirror tilt plate adjustment
should be made as described above in order to restore maximum
operating power.
2.5 Alignment Procedure - Mode Walking: See Appendix V, page 31.
This procedure should be used if severe misalignment has occurred.
-18-
3.0
MODEL 4200NB LASERS ONLY:
The interchangeable mirror mounts of the 4200NB series lasers
are designed for ease of change between blue (442nm) and uv
(325nm) operation and may require periodic alignment and
checking. This section contains advice on how to achieve the
best power and performance from the 4200NB lasers.
3.1
System Lasing But Power Is Low:
3.1.1 Laser Mirror Alignment for Optimum Power:
Although the laser head is designed for long term stable
operation without attention to mirror alignment, some changes
may have occurred during shipment or after operation for some
time. It may be necessary to make some readjustment. Please
refer to the final test sheet accompanying the laser. If your
laser does not perform with substantially the same power output
as indicated on the test sheet, follow the instructions below.
3.1.2 Alignment Procedure:
Close beam block on the front of the laser. Turn front knurled
mirror nut such that the two holes through the nut are at 45
degrees to the vertical. Open the beam block. Provide a power
meter to read beam power. Using the Allen drivers supplied with
the laser, first adjust the front mirror vertical and then
horizontal aligning screws for maximum power. Only a very
slight adjustment should be required. Finally adjust the rear
vertical adjustment and then the horizontal for optimum power.
3.1.3 Alignment Procedure - Mode Walking. See Appendix V, page 31.
3.2
System Will Ionize But Will Not Lase And Electrical Parameters
Are Correct:
3.2.1 Use of Fluorescent Card to Detect Lasing:
Place the fluorescent card in the expected path of the laser
beam. Make slight adjustments in both directions to the
vertical and horizontal adjusting screws at the rear end of the
laser using the Allen ball drivers. Look for a flash of laser
light on the card. If seen, attempt to align mirror so laser
beam is maximized. Use the power meter. Attempt same at front
end of laser and adjust for maximum power.
If successful in achieving lasing, go to 3.2.7. If
unsuccessful go to 3.2.2.
-19-
3.2.2 Check for Bore Obstruction'by
Dislodged
Shutter Disk:
BE SURE
TEST!
- OFF- BEFORE MAKING THIS
- LASER IS
Remove the black knurled nut on the rear or cable end of the
laser head. Shine a flashlight down the bore from one end and
look into the other end. If the bore is free of obstructions
proceed to 3.2.4. If the bore ap,pears to be blocked or
obstructed go to 3.2.3.
3.2.3
If you cannot see light through the bore, the shutter(s) may
have been knocked loose from their external retaining magnets
during shipping. The shutter disks should be visible when
looking into the tube from the side, one near the anode pin and
the other in the tube near the connecting elbow to the cathode.
To check, remove the blue cover by removing the front black
bezel and sliding the cover forward and up. If the shutters
(disks) are found to be dislodged and blocking the bore line of
sight, use a strong magnet to relocate shutter(s) to their
retaining magnets. Try again to achieve lasing (Section 3.1).
If successful replace cover and go to 3.2,.7. If still
unsuccessful go to Section 3.2.4.
/
3.2.4
L Shutter
Shutter
Check Brewster Windows:
Remove screws which fasten bellows cap plate to resonator end
plate. Remove snap clamp and slide bellows back from window
if necessary to expose windows. Check for Cd dust or chips on
inside surface of Brewster window. If Cd chips are found on
the inside of the Brewster windows, replace the bellows cap
and return the laser head to LiCONix for repair.
If there is no obvious dust on the inside of the window;,
proceed to 3.2.5
1
\
Cd dust on inside surface of
Brewster windoLl
z
-200
3.2.5 Use of Diffraction Grating, Optimum Cadmium Level:
The cover should be removed for this test. Turn on laser and
allow it to warm up for l/2 hour. Approximately half way along
the insulated capillary bore there is a longitudinal slit in
the ins.ulation coating. Looking through the Diffraction
Grating while holding it approximately 6 inches from the tube,
multiple images of this slit can be seen off-axis. DO NOT
CONTACT THE TUBE WITH.THE GRATING. These images are each
different in color (red, yellow green, and blue). A second red
image representing the Cd concentration should be visible
between the strong red and yellow images.
Both red lines should be about equal in intensity. If so, go
to Step 3.2.6. If not, electronics may have failed. Consult
Appendix III.
3.2.6 Alignment of Mirrors - Set Up:
Equipment needed:
A HeNe laser ( 1mW) with a fluorescent target card having a
small beam aperture hole on the output end of the laser and two
small lab jacks. HeNe laser beam diameter should be <l.Smm.
Aperture hole in
escent target card
-21.
1.
Remove both front and rear mirror holders. Prepare the
small HeNe laser on two small lab jacks to facilitate
directing the beam down through the bore of the problem
HeCd laser.
2.
After set-up, turn on the HeNe laser and note spot size and
spot appearance.
3.
Set the HeCd laser about six inches away from the output
end of the HeNe laser head leaving access room for mirror
adjustment and directing the beam from the HeNe into the
front end of the HeCd laser.
4.
Align the HeNe beam cleanly through the tube bore. Make
sure the HeNe beam spot has the same size and appearance
as in 2. above. Correct alignment of the HeNe beam through
the HeCd bore is very important.
5.
Clean all optics (Brewster windows and mirrors with
methanol and cotton covered Q-tip). See Appendix II.
6.
Insert rear RR mirror in the rear end of the laser, insert
spring and nut and adjust mirror to get a retroreflection
back into the HeNe beam. Reflected beam will be visible on
the target fluorescent card mounted on the output of the
HeNe laser or on a microscopic slide held in the beam
between the HeNe and the subject laser.
7.
Slip the front mirror into its housing about half way in.
(Note: Key pin should be down). Then wiggle the front
mirror around so that the retro-reflection of this mirror
closely.coincides .with the HeNe beam. On passing through
correct alignment of the front mirror a bright flash of
white-green light will be seen on the fluorescent card.
This is the HeCd lasing. Note the position of the red HeNe
beam at the flash, then fully insert front OC mirror
assembly followed by spring and nut. Then adjust the OC
mirror to get the retro-reflection back to where it was
when lasing occurred. Having achieved lasing proceed to
next section. If unable to achieve lasing contact the
factory.
3.2.7 Power Optimization:
Having achieved lasing the mirror alignment should be optimized
by the "mode walking" procedure, see Appendix V. (One walks
the mode in the bore by adjustment of the mirrors.)
-22.
APPENDIX II
1.0
OPTICS SERVICE - CLEANING, 4200NB MODELS ONLY
All optical surfaces in the 4200NB models are sealed to give
long operation without cleaning. However at some time
cleaning may be necessary. It is recommended that the
procedures in Appendix I be performed first.
The
but
can
you
1.1
procedures for cleaning laser optics are perhaps tedious
necessary since even small losses within the laser cavity
have a pronounced effect on the power output. We suggest
follow carefully the instructions given below.
Supplies required:
Reagent grade methanol.
Deionized or distilled water.
Reagent grade acetone.
Lens tissue, Kodak type.
Sterile wooden Q-tips (Caution: DO NOT USE PLASTIC OR PAPER
STEM Q-TIPS. THE PLASTIC MAY DISSOLVE IN ACETONE AND BE
DEPOSITED ON THE WINDOWS. AVOID GLUE OR BINDER TYPE Q-TIP.>
A pair of clean hemostat tweezers.
1.2
Cleaning of Brewster Windows:
The Brewster windows should only be cleaned if absolutely
necessary to clean them. Need to clean the Brewster window
surfaces will arise if a considerably greater scattering of
laser light is observed from the outside of the window as
compared to the inside. The surface can be observed by
sliding back the flexible rubber bellows covering the
Brewster windows. If a condition of excessive scatter from
the outside surface of one or both Brewster windows is
observed then cleaning will be necessary and one should
proceed as follows.
1.2.1
Make sure the mirrors are well aligned before attempting
the cleaning. Do not disturb the front or back mirror
adjustments or remove the rear mirror. Using either a
Q-tip or lens paper, soaked in methanol, folded and held
in a hemostat, wipe once across the center of the Brewster
window. Next, replace the bellows assembly and check
power. If the window was dirty an increase in power
should be seen if cleaned correctly.
-230
1.2.2
Compare the scattered light from the inside surface to the
outside surface. The outside surface scattering should be
less than or equal to the inside surface. If the power is
lower check the adjustments on the front mirror alignment.
If the outside surface of the Brewster window still has excess
scattered light, repeat procedure. Depending on the type of
contamination on the Brewster window it may be necessary to
clean the surface first with distilled water followed by
acetone since the contamiation may not be soluble in methanol.
Use methanol for final cleaning. Repeat same procedure for
rear Brewster window.
1.3
Cleaning of the Reflectors:
Attempt to clean only one optic at
a time.
--P
Remove front mirror end cap. Withdraw the mirror holder with
the extractor tool provided or the index finger and thumb.
Place holder on the table with mirror surface facing up.
Examine the surface for spots, dust or film. Take a lens
tissue, Kodak lens cleaning paper for example, and with an eye
dropper deposit a drop of methanol on the lens tissue near the
center. Place the wetted tissue on the mirror surface and draw
the tissue over the surface permitting the mirror surface to
dry before the edge of the tissue is reached. Do not allow the
methanol to dry on the mirror. Replace the mirror holder in
the resonator followed by the wavy spring washer and retaining
cap or nut.
If the mirror had been dirty, and was'cleaned correctly,
an increase in power should be observed. Very slight mirror
plate adjustment may be necessary. As in the case of the
Brewster window, the contamination on the mirror may not be
soluble in methanol. If you suspect this is true, first
clean mirror with distilled water and then acetone. Repeat
procedure for rear mirror. A final cleaning with methanol
is recommended.
-24.
APPENDIX III
1.0 CADMIUM LEVEL and HELIUM LEVEL ADJUSTMENT
In this section it is assumed that EITHER
1) lasing has not been achieved even though care has been taken
to check for correct mirror alignment (Appendix I) and the
optics have been cleaned (Appendix II), OR
2) that the output power is below specifications in spite of
alignment and optics cleaning.
The next logical step is to check for the correct cadmium level
in the discharge.
A quick spectroscopic determination of the cadmium/helium level
can be made with an inexpensive transmission diffraction grating
such as the Edmund Scientific Stock 840,272. See Appendix I,
paragraph 3.2.5.
1.1 Turn on system and allow to warm up for 30 minutes.
1.2 Remove the blue head cover.
slide cover forward and up.
Remove front black bezel first and
1.3 Note a small (l/4" long) opening in the insulation towards the
center of the capillary bore. The discharge light should be
clearly visible through the opening. See 3.2.5 of Appendix II.
1.4 Observe the opening through the diffraction grating and note
particularly the red lines in the spectrum. If the intensity of
the two red lines (one is a helium line, and the second is a
cadmium line) is approximately equal, then the cadmium level is
It helps to have the room lights turned off for this
correct.
observation.
1.5 If the red lines are equal but no lasing or very weak lasing
only has been achieved it may be that the 'tube is old and
inefficient. If tube is new check again for bore obstruction
alignment or contaminated optics. Finally call the factory
for help - 408/496-0300 and ask for Customer Service.
1.6 If the red lines are unequal or only one red line is visible
(helium) proceed to next section.
-25.
2.0
ADJUSTMENT OF LASER HEAD PCB FOR CORRECT CADMIUM AND HELIUM LEVEL
(Refer to PCB assy drawing 903-157, page 16)
2.1
Note potentiometer R16 and R21 towards the right hand side of the
board. Locate also test points 1, 3, 4 & 5.
2.2
Equipment Required to Carry Out These Tests:
Laser power meter, Liconix Model 45PM or equivalent.
Digital multimeter, Fluke 8020A or equivalent.
Small blade screw driver.
2.3
Potentiometer R21 can be adjusted to control the cadmium level in
the discharge. Potentiometer R16 is used to set and maintain the
helium gas pressure level. The control potentiometers have been
preset at the factory for optimum performance (power and noise).
They should not be adjusted except in the case of performance
substantially at variance with expectations.
2.4
Consult the Final Test Sheet which is the last page of this manual
and refers specifically to the performance of the tube in your
laser head. Note the voltage readings recorded for TPI, TP3 and
TP4-5.
TPl voltage is proportional to the tube anode to cathode voltage.
Its value is a function of both helium gas pressure and cadmium
vapor pressure.
TP3 voltage is a settable reference voltage controlled by pot R16.
TP4-5 voltage is a settable reference voltage by means of which
the cadmium reservoir temperature and hence the cadmium vapor
pressure is held constant by feedback control.
-26.
Typical values of these Tests Point Voltages are:
#4207/4210
#4230/4240
TPl & TP3
to ground
6.5 + 0.5
7.0 + 0.5
TP4-5
1.00 + 0.2
1.2 fr 0.2
Measure voltages at TPl, TP3, TP4-5, record and compare
with Final Test Sheet.
If the measured voltages are very close to the test sheet
record do not make any adjustments. Contact the factory and
discuss your service procedure. If the measured voltages
differ from the Final Test Record some adjustment may be
necessary or an electronic problem may be indicated.
If TP4-5 differs by more than 0.02V from the initial setting,
Note
reset TP4-5 to original setting in steps of 0.025V.
power changes at each step. Allow three minutes between
steps. If power is seen to increase continue adjustment of
TP4-5 until acceptable power is reached. In this process
TPl will be seen to change also decreasing as TP4-5 is
increased and increasing for decrease of TP4-5. Do not
let TPl drop below TP3 by more than 0.5V. Adjust TP3 by
pot R16 to maintain TP3 approximately equal to TPl. Finally
set TP3=TPl when adjustment of TP4-5 is complete.
If power decreased on adjustment of TP4-5 return TP4-5 to
best power setting and call the factory. If TP4-5 is closely
equal to initial value on test sheet and if TPl differs from
TP3 by more than 0.2V an electronic malfunction may be
indicated. If TPl<TP3 the tube helium pressure is low.
Contact the factory for further advice.
If TPl, TP3, and TP4-5 are all approximately equal to
original settings one can conclude that the electronic
control circuitry is functioning correctly and no
adjustment is indicated. The cadmium vapor pressure and
the helium gas pressure are close to optimum.
r
-270
APPENDIX IV
1.0 NOISE CONTROL
Depending on the customer's application the 4200N series lasers
may be equipped with noise control circuitry or the circuitry may
be disabled. Refer to the Final Test Sheet which accompanies this
manual. Note the entry for TP8. If the TP8 entry is zero then
the noise suppression circuitry has been disabled. If the TP8
entry is approximately 350Khz then the noise suppression
circuitry has been enabled.
1.1 If the noise suppression electronics has been enabled, proceed to
Section 3.0 below.
1.2 If the noise suppression circuitry has been disabled, proceed to
Section 2.0 below.
'1.3 Equipment needed:
1)
2)
3)
4)
5)
6)
Model 45PM Laser Power Meter
Model 40D Fast Optical Detector
True rms voltmeter HP #3400A
Oscilloscope with >IMHz bandwidth
Multimeter, Fluke 8020A or equivalent
Small blade screw driver
2.0 SYSTEMS WITHOUT NOISE SUPPRESSION CIRCUITRY
(TP8 on Final Test Sheet will show a zero reading)
Minimum noise is achieved by adjustment of the cadmium level by
means of pot R21. Measure TPl, TP3 and TP4-5 and compare with the
values recorded on the Final Test Sheet for your laser tube.
If all voltages are equal or very nearly equal to original
settings the laser is functioning under feedback control and most
likely noise performance is close to optimum for that tube.
To test for minimum noise make small adjustments, & 0.025 volts,
to TP4-5 by means of pot R21. Note changes in noise and power.
Allow at lease three minutes between adjustments. If noise is
improved reset TP3 to equal TPl by adjustment of R16.
If the measured voltages are not equal to original settings as
recorded on the Final Test Sheet, note the variations:
-28.
Allowable variations in TPl, f. 0.1 volts
TP3, & 0.05 volts
TP4-5, + 0.02 volts
Normally TP3 & TP4-5 will be unchanged since they are manually set
reference voltages. TPl depends on the helium gas pressure and
the cadmium vapor pressure values in the tube. A change in TP4-5
of greater than 0.02 volts may indicate a circuit malfunction.
Attempt small adjustments of TP4-5 of 0.025 volts and note effect
on noise and power. Allow at lease three minutes between changes.
Set for optimum noise. Readjust R16 to set TP3=TPl. If no
improvement can be achieved contact the factory.
If TP4-5 and TP3 are unchanged from original settings, but TPl is
either high or low by more than 0.1 volts a helium pressure
control problem is indicated. If TPl>TP3 a high pressure helium
condition is indicated which typically is accompanied by a high
noise content on the beam. Contact the factory for further
advice.
If TPl<TP3 a low pressure helium condition is indicated. Normally
this will be associated with a low noise and low power output.
Set TP3 equal to TPl after noting the values and report the
condition to the factory.
In general adjusting
simultaneously yield
TP4- 5 is to a value
noise setting. This
output and noise.
TP4-5 for minimum noise will not
maximum power. The preferred setting of
slightly greater than (by 0.025V) the minimum
will yield a good compromise between power
3.0 SYSTEMS WITH NOISE SUPPRESSION CIRCUITRY
(TP8 on Final Test Sheet will read approx. 350KHz)
In addition to the test equipment requirements noted under 1.3
above, a frequency counter capable of >lMHz will be useful. Model
Max 100 by Global Specialities Inc. or equivalent will suffice.
Noise suppression circuitry is adjusted at the factory for minimum
noise performance. Typical noise performance values are:
<1X rms noise, 10 Hz-1OMHz
Peak to peak noise ofw6% as measured by
means of oscilloscope and fast detector
-29.
If the noise performance of your system differs substantially
from these levels proceed as follows:
Compare with
3.1 Record the voltage values at TPl, TP3 & TP4-5.
initial values recorded on the Final Test Sheet for your system
which will be found at the end of this manual. Variations in
these readings of more than 0.02V for TP4-5 and of more than O.lV
in TPl should be brought to the attention of the Liconix Service
Department.
3.2 If the measured voltages are within allowable limits then measure
the frequency of TP8 by means of the frequency counter. Compare
with the Final Test Sheet record. Typical reading is 350 KHz. If
the frequency has changed by more than 10 KHz contact the factory.
3.3 If the frequency is within 1OKHz of the factory set level attempt
& l/2 turn on pot R34 near the left hand side of the head PCB
while observing the noise either on an oscilloscope or on the rms
voltmeter. Set for minimum noise and record the frequency at TP8.
Attempt small adjustments of the amplitude pot R36 to reduce the
peak to peak ripple. When the noise begins to increase turn the
pot ccw until the noise increases 0.15% rms above the minimum
level.
-30.
APPENDIX V
1.0 MODE WALKING - 4200NB SERIES ONLY
The procedure of mode walking, if properly applied, optimizes the
alignment of the mirrors with one another and with the capillary
bore of the laser tube. Ideally the bore axis of the laser tube
. should be accurately colinear with the laser mode axis. This
latter axis is defined as the line joining the centers of
curvature (the line of centers) of the two mirror surfaces forming
the laser cavity. The procedure to be described adjusts the line
of centers to be colinear with the axis of the capillary bore.
Equipment required:
An analog laser power meter such as the LiCONiX Model 45PM or
equivalent.
TWO Allen drivers for NB lasers or two flat blade drivers for N
style lasers.
1.1
Turn
1.2
Using the Allen drivers make adjustments as necessary to the
vertical and horizontal adjustment screws first at one end and
then at the other end in order to optimize the power.
1.3
Make a small cw misalignment to the vertical adjustment at one end
so as to decrease the power by about 10% on the meter.
1.4
At the opposite end, also on the vertical adjustment screw,
attempt to recover the 10% drop and exceed the initial power by a
cw or a ccw adjustment. If after the adjustment the power exceeds
the original power an improvement in alignment has been achieved.
Repeat Steps 1.3 and 1.4 until a maximum is reached.
1.5
If after the compensating adjustment in 1.3 above the power is
less than original then reverse the initial cw adjustment made to
the first mirror adjust plate and attempt a further adjustment in
the same direction (now ccw) so as to decrease power again by
about 10%.
the laser power on and allow the laser to come to thermal
equilibrium, about 30 minutes. Place power meter sensor head in
the beam and NOTE the power output.
-310
-ZC-