Auto Collimator

AUTOCOLLIMATORS AND ACCESSORIES RANGE

MEASURING ANGLE, STRAIGHTNESS, FLATNESS,SQUARENESS , PARALLELISM

THE AUTOCOLLIMATOR RANGEFOR MEASURING ANGLE, STRAIGHTNESS,FLATNESS, SQUARENESS, PARALLELISM

THE PRINCIPLES OF AUTOCOLLIMATION

Used extensively in workshop, tool rooms, inspection departments and quality control laboratories throughout the world,Taylor Hobson Autocollimators - developments of the renowned Hilger and Watts products - are sensitive opticalinstruments designed for the accurate measurement of small angular displacements. There are five models in thiscomprehensive range, from the simple Minidekkor to the ultra precision DA20, each produced as a result of the company'scommitment to quality optics and backed by a dedicated staff with considerable experience.

Figures A and B illustrate the basicprinciples of Autocollimation.

Light from an origin point O iscollimated (made parallel) by a highquality objective lens. If the collimatedbeam falls perpendicularly onto a planereflecting surface, the light is reflectedback along its original path and isbrought to a focus at a point coincidentwith the origin point (as Figure A). Ifthe reflector is tilted through an angle, the reflected beam is deflectedthrough an angle 2, and the image I isdisplaced laterally from the origin 0.

The amount of displacement is given byd=2f where f is the focal length of thelens, and is in radians.

Given that f is a known constant for theAutocollimator, measurement of thedisplacement d enables the tilt to beascertained.

A practical Autocollimator is illustratedin Figure C.

Light from an illuminated targetgraticule at the focus of an objectivelens is directed towards the lens by abeam splitter. After reflection by amirror on the workpiece, the lightreturns through the Autocollimator andpasses through the beam splitter,forming an image of the targetgraticule in the plane of an eyepiecegraticule.

The eyepiece graticule and thereflected image of the target graticuleare viewed simultaneously through theeyepiece.

The image of the target graticule isalways seen in focus and at constantmagnification in the eyepiece, regard-less of the distance between the Auto-collimator and the reflecting surface.

However, at long working distancesonly a portion of the reflected targetgraticule may appear in the eyepiece,owing to the failure of obliquelyreturning rays to enter theAutocollimator. This will result in arestricted measuring range.

Displacement of the image ismeasured by various means, asdetailed in the descriptions ofindividual auto-collimators within thisbrochure.

Figure A

Figure B

Figure C

Reflector squareto beam

Incident beam Reflectedbeam

Origin point O

Reflectortilted

Image I

Originpoint C

Reflected beam from tilted reflector

Reflectoronworkpiece Objective

Reflected beam when reflector is square to beam

Beam splitter Eyepoecegraticule

AUTOCOLLIMATION IN PRACTICECHECKING, MEASURING, INDEXING & MONITORING

Taylor Hobson Autocollimators are usedin conjunction with reflecting mirrors orsurfaces for the accurate measurementof small angular deviations from adatum angle.

The main advantages of Taylor HobsonAutocollimators are:

n High accuracy angle measurementn Easy to set up and operaten Non contact measurementn Calibration traceable to international

standardsn High performance and repeatable

measurementn Choice of visual or photo electronic

systems

Their main applications include:

n Checking straightness of machinetool slideways

n Setting the angle of machine toolheads

n Checking dividing heads for theirangular displacements

n Measuring very small anglesn Indexing small angles preciselyn Measuring small linear

displacementsn Checking flatness of bed plates and

surface tables

DA20 Autocollimator with reference index table used to calibrate a polygon

Precision Machine Tool alignment using DA20 Autocollimator

Measuring straightness using a reflector and carriage

Autocollimator

Autocollimator

Reflector on carriage

Surface being checked

Mounted reflector oncarriage

Corner reflector

VISUAL AUTOCOLLIMATORS. EASY TO USE AND READ

The visual Autocollimators areextremely accurate instruments with awide variety of applications, particularlyfor checking straightness and flatnessand for angular indexing.

They are normally supplied with theeyepiece positioned for straight throughviewing, although the TA51 is availablewith the eyepiece positioned for rightangle viewing if required. All modelshave a long eyepoint - convenient forspectacle wearers. Measurements aremade using a graticule in the eyepieceviewing system with or withoutmicrometers.

The Taylor Hobson VA900 and TA51Autocollimators incorporate a micro-meter in the eyepiece viewing systemfor the precise measurements ofangular displacement. The TA51 hastwo micrometers, one in each axis ofmeasurement.

On single axis types, the instrument isrotated through 90 degrees to measurein a second plane perpendicular to thefirst.

The micrometer is used to move theeyepiece graticule across the field ofview until it coincides with the reflectedtarget graticule image. The angulardisplacement of the reflector can thenbe read directly from the micrometerscale.

The field of view as observed though theAutocollimator eyepiece is shown above.

For measuring horizontal displacementin a single axis instrument, the micro-meter drum is rotated to move the twinsetting lines across the field of viewuntil they straddle the vertical line of thereflected image.

The instrument reading is then the sumof the indicated positions of micrometerand turn counter scale.

The TA51 Autocollimator is normallysupplied with a light field graticule.Only one setting line is used in instr-uments fitted with dark field graticules.

GRATICULES TO SUIT YOURREQUIREMENTS

The VA900 and Minidekkor Auto-collimators are normally fitted with darkfield graticules as standard for a bettervisual contrast from low reflectivitysurfaces or a small cross sectionreflector. However, light field graticulevariants can be supplied on request.

Checking a TB100 Clinometer with the TA51Autocollimator

TA60 DUAL AXIS MINIDEKKORCode 142/10n Lightweight and portablen Wide range of measurementn Can measure X and Y Axes at the

same timen Can measure components of low

reflectivity or with small surface area

The TA60 Minidekkor is an inexpensivevisual Autocollimator using a two axesgraticule for general measuring dutiesin workshop and tool room.

Only 152mm (6in) long for straightthrough viewing or 203mm (8in) long forright angle viewing, it is an idealinstrument for inclusion in a fitters toolkit for use outside the factory.

The standard Minidekkor is providedwith a dark field graticule, forming anilluminated cross line image on a darkbackground. This offers the advantageof clear images being obtained from lowreflectivity surfaces such as unsilveredglass, and from surfaces as small as3mm (0.125in) in diameter.

With the addition of a microscopeobjective and linear measuring device,the Minidekkor can be used for meas-uring radius of curvature of a lens ormirror and, for example, the spacing ofelectrodes enclosed in a glass envelope.

This Autocollimator is supplied asstandard without mounting fixtures.Therefore, when ordering it is importantto consider the applications and selectthe appropriate mounting accessories.

Eyepiecegraticule

Targetgraticule

Micrometer

Beam splitter

Objective

Reflectoronworkpiece

Reflected beam when reflector is square to beam

Reflected beam from tilted reflector

Example : Horizontal settingMicrometer = 27.1 seconds

Turn counter = 4 minutes 30 secondsReading = 4 minutes 57.1 seconds

Each graduation equals 0.5 minute (Scale)Each graduation = 0.2 second (Micrometer)Double setting lines straddle reflected image

Field of view through eyepiece

TA51 MICROPTIC DUAL AXIS AUTOCOLLIMATORCode 142/13

n Ideal for checking machine slides for straightness and squareness

n Checking flatness of surface tables

n Checking angular indexing tables and polygons

n Low reflectivity surfaces

VA900 MICROPTIC DUAL AXISAUTOCOLLIMATORCode 112/2208n Lightweight high accuracy instrument

n Ideal for precise measurement ofangle of components such as prismsand for checking straightness,flatness and angular indexing

n Wide range using combination ofgraticule and micrometer

The VA900 Microptic Autocollimator is adual axis, lightweight, highly accurateinstrument. It is ideally suited for theprecise measurement of angles or com-ponents such as prisms, for checkingstraightness, flatness or angularindexing. Measurement of the two axesis made using a combination of theinstruments two axes graticule andsingle micrometer.

This Autocollimator is supplied asstandard without mounting fixtures.Therefore, when ordering, it isimportant to consider the applicationand select the appropriate mountingaccessories.

TA51 Autocollimator

VA900 Graticule

The VA900 Microptic Dual Axis Autocollimator

The TA60 Minidekkor

The DA instruments are highly versatileAutocollimators which use the latestlight source and detector technology toprovide dual axis operation with digitaldisplay.

Whereas the wide range DA400 is usedfor a variety of applications, typically inthe machine tool industry, the ultra highprecision DA20 is used primarily understrict environmental conditions inlaboratories.

Each Autocollimator has an eyepiecewith an independent visual channel toassist initial setting up procedures.

The electronic unit display is readablefrom several metres. Also incorporatedis a signal strength display to ensurecorrect set up and results.

Measured values of angular displace-ment are displayed in digital form.

An RS232 interface is provided forconnection to various types of accessorycomputer. Among other applications,this allows computer processing ofstraightness, flatness, angle andpolygon (rotary devices) measurement.A remote control switch is available,enabling the Autocollimator andElectronic Unit to be positionedremotely from the operator.

The DA20 and DA400 dual axis Auto-collimators can be provided softwarewhich includes a straightness(squareness and twist) program, aflatness (Union Jack or Moody) programand a polygon or rotary analysis package.

DA20 DIGITAL DUAL AXISAUTOCOLLIMATORCode 137/1939n High accuracy dual axis operation

with digital display

n Independent visual channel to assistin setting up

n Direct analogue display, readablefrom several metres

n RS232 interface provided

n Software programs for flatness,straightness and rotary analysis

n Ideal for ultra-precisionmeasurement and indexing of smallangles

n Suitable for calibration of polygons,rotary tables and encoders

PHOTOELECTRONIC AUTOCOLLIMATORS

DUAL AXIS MEASUREMENT

WITH DIGITAL DISPLAY

DA20 Photoelectronic Autocollimator

Reflectortilted

Collimating lens

IR Detector

IR Diode

Display

LED

Target graticule

Eyepiece

Eyepieceview

Semireflector

Referencegraticule

DA400 DIGITAL DUAL AXIS AUTOCOLLIMATORCode 142/78

DA400 Autocollimator

Checking surface table flatness with a DA400Autocollimator

Checking a machine tool slideway using a DA400 Autocollimator

n Wide measurement range

n Dual axis operation and display

n Independent visual channel to assistin setting up

n RS232 and analogue outputs (IEEEoption available)

n Full software package

n Wide range of applications

Using a computer allows automatic calculation using the selected program, withresults on the screen display and printout of measurement results. This enables amore efficient method of measurement, speeding up meas-uring times andminimising the risk of human error in taking the reading.

Communication between microcomputer and operator is in simple interactiveWindows TM based program, enabling inexperienced personnel to carry out meas-urements. Each stage of measurement to be carried out is prompted by the screendisplay which also indicates when any error of operation has occurred.

A C C E S S O R I E S

L E V E L L I N G B A S E S A N D S TA N D S

LEVELLING BASECode 142/76

Normally included as standard withAutocollimators TA51, DA20 and DA400.

The levelling base provides support forthe Autocollimator, enabling the unit tobe levelled and to bring its axis parallel tothe surface being measured. Itincorporates clamps to securely hold theAutocollimator without damage.

Three pads are included for use underthe foot screws. There is no necessity toremove the Autocollimator from the baseafter use, as the Autocollimator carryingcase is constructed to accommodate bothitems.

Spacing between front and back footscrews: 205mm (8in) Spacing between the two back footscrews: 130mm (5in) Height of Autocollimator axis when baseis resting on the pads: 76mm (3in)without pads: 67mm (2.5in) Range of angular adjustments:

approx 3 Approximate weight: 3.4kg (7.5lb)

ADAPTOR BUSHES, Code 112/2257

A set of two bushes to convert standardlevelling bases to 38mm (1.5in) diameterfor use with VA900.

VERTICAL BASE WITH ADJUSTINGBRACKETCode 112/3451-01 for TA60, 25.4mm (1in) dia clampCode 112/3450-01 for VA900, 38mm (1.5in) dia clamp

A multipurpose stand of sturdyconstruction for general bench use,comprising epoxy granite surface plate,and ground cast iron column and bracket.The Autocollimator clamping bracket hasindependent clamping and rotationaladjustments, enabling the bracket to beturned without disturbing the heightadjustment.

Available for use with 25.4mm (1in),38mm (1.5in) and 67mm (2.5in) diameterautocollimators.

Surface Plate Area: 220x`150mm(8.7x5.9in)

Maximum Height Adjustment aboveSurface Plate: 200mm (8in)Flatness of Surface: 5m (0.0002in)Approx Weight: 7.6kg (16.8lb)

R E F L E C T O R SA N D O T H E RA C C E S S O R I E S

STANDARD GLASS REFLECTOR50mm (2 inch)Code 142/24 mounted

A reflector is an integral part of anyAutocollimator system. Successfulautocollimation requires a reflector ofadequate flatness, reflectivity anddiameter; this reflector meets all of theserequirements. The parallelism of thefaces is such that negligible error isintroduced when the unmounted reflectoris back mounted. The mounted versioncan be used horizontally or vertically.Steel reflectors can be supplied to specialorder.

Diameter: 50mm (2.0in) nominal

Faces Parallel to Within: 5 secs Faces Flat to Within: 0.08m (3in) Centre height ofMounted Reflector: 37mm (1.5in) Weight Unmounted: 130g (9oz) Mounted: 1.1kg (2.5lb)

LARGE GLASS REFLECTORMOUNTED 100mm (4 inch)Code 142/26

Offering a large reflective surface, this isnormally used in conjunction with areflector carriage and mounted reflectorfor calibrating a surface plate. It enablesseveral calibration lines to be traversedwithout the Autocollimator being moved,thereby saving setting up time.

ADJUSTABLE BASECode 112/2316

This accessory has a 200mm (8in) rangeof adjustment and can be set to theappropriate step interval length forflatness and straightness measurement.

It provides a base for the Autocollimatorreflector, with self aligning seating padsadjustable to a graduated scale. Thisbase can also be used for mounting aTalyvel level unit.

Reflector mounted on adjustable base with side

feet, for two axis straightness measurement

SIDE FEETCode 137/1947For use with the Adjustable Base whenmeasuring in two axes.

POLYGONSCode 142/35 : 12 sided glass,nominal face angle 30

The angle between the 0 datum face andany other face is within 5 seconds of thenominal values. A calibration chart isprovided with each polygon, giving theactual angles to 0.1 second of arc to anaccuracy of determination of 1 second.

Other polygons up to 72 sidesd and insteel or chrome carbide can be suppliedto special order.

ANGLE GAUGES (Set of 8)Code 142/32Gauge Angles : 90/60/30, 14, 9, 3, 1,30 min, 15 min, 5 minAccuracy of Angle: 2 secondsFace Length: 50mmFace Width: 13mmWorking faces flat to within:

0.13m (5in)

These gauges can be wrung togetheradditively or subtractively to form anyangle from 0 to 90 in 5 minute steps asa comparison standard. The facesthemselves can be used as a reflector.

CUBE REFLECTORCode 142/25Can be used as general purpose reflectorand for providing a 90 angle standard inthree planes, for setting or checkingperpendiculars.

Size of Faces: 38mm (1.5in) squarePolished Faces: Three (two adjacentfaces perpendicular to the base and oneparallel to the base) Accuracy of 90 Angle: 3 secs Weight: 0.43kg (1lb)

Other cubes can be supplied to requiredspecifications to special order. Forexample, as above but with an accuracyof 90 1 sec or with four or five polishedfaces.

OPTICAL SQUARECode 142/77Aperture: 38mm (1.5in) 90 angleaccurate to within 1 sec

This square comprises a mounted pent-agonal prism and is used to deviate theautocollimator beam through 90. It maybe used when checking the straightnessof two surfaces which are at right anglesto one another or when checkingparallelism.

TA48 SMALL ANGLE GENERATORCode 137/1918Autocollimators require periodiccalibration to verify their capability forprecise measurement. Users cancalibrate their own Autocollimators usingthe Small Angle Generator. This device isalso suitable for testing angle gauges,electronic levels, level vials used in blocklevels etc.

Total Measuring Range: 200 mins of arc One Revolution of Micrometer Drum:0.635mm (0.025in) moving the Auto-collimator beam through 5 minutes of arc Drum Graduations: 1 second of arc Vernier Readings to: 0.1 second of arc

FIXED TEST WEDGECode 137/1940The fixed wedge can be used to quicklycheck the accuracy of any Auto-collimator. It introduces a fixed angle ofdeviation nominally of 60 seconds byrotating the wedge from minimum tomaximum deviation and comparing thiswith the readings on the Autocollimator. AUKAS certificate is optionally available.

Centre Height: 75mm (3in)Weight: 1kg (2.25lb)Working Diameter: 50mm (2in)

SOFTWARE PROGRAM 112/2337A full software package is available tosupport the DA series of Autocollimators.The package includes flatnessmeasurement (Union Jack or Moody)straightness measurement (includingtwist and squareness) and the polygonangular indexing program. All programsbenefit from the ability to interface toTalyvel 3 and 4 levels and the DA seriesautocollimators. Statistical filtering andedit facilities add to user confidence andflexibility of approach (Grid patternflatness is also applicable to Talyvelsystems).

FLATNESS PROGRAMThe rectangle and diagonal (Union Jackor Moody) method for flatnessmeasurement offers simple, interactive,menu driven software which displays orprints out an initial diagram of thesurface to be measured, together withsurface generator lines and instructionson the method of entering surface data.Mult-iple measuring steps can be takenalong each generator line.

After the selected number of measuringsteps have been entered, the programcalculates and displays the shape of eachgenerator line and the flatness of thesurface.

During measurement, readings can beautomatically entered into the computer,using the remote data entry lead. This isparticularly useful when measuring largesurfaces. Alternatively readings can beentered manually via the computerkeyboard, as would be necessary whenusing a Visual Autocollimator.

Values are displayed/printed out initiallyas arc seconds and then converted tomicrometers or millionths of an inchunits (m or 0.000001in units).

Measurement results of flatness aredisplayed/printed out as an isometricdiagram or certificate. In addition, thedisplay/printout gives the maximumdeviation from flatness over the entiresurface. To comply with internationalstandards a minimum zone calculation isused to generate flatness errors.

COMPUTER BACKED AUTOCOLLIMATION

ELECTRO-OPTICS SOFTWARE FOR WINDOWS TM

STRAIGHTNESS PROGRAMThe straightness program will permitstraightness measurement oncomponents such as machine toolslideways, shafting and rolls.

The methods and procedure for use aresimilar to those described for flatnessmeasuring.

Multiple measurements can be taken forstraightness measurement in a singleaxis or two axes, results being presentedin both tabular form and also as astraightness graph. Twist and square-ness measurement is also available inthis package. Analysis is to LSL or ENDSZERO, with appropriate graphicalrepresentation of results.

POLYGON PROGRAM

A software package for the calibration ofrotary devices and polygons with up to 72faces allows single or bi-directionalcalibration of rotary devices, with resultsin both angular index accuracy andpyramidal error. The operator has achoice of single or multiple runs with thecomputation of mean values.Measurements can also be performedautomatically using various auto-measure functions.

TWIST PROGRAM

The twist program allows straightnessmeasurements to be carried out on oneguideway and then compared to thestraightness of a second guideway (forthis option a Talyvel levelling system isrequired-see separate brochure).

THE AUTOCOLLIMATOR RANGE

T E C H N I C A L D A T ATYPE TA60 VA900 TA51 DA20 DA400

CODE 142/10 112/2208 142/13 137/1939 142/78

Accuracy over 1 min of arc ++ sec 6 1 0.5 0.1+++ 0.2+++

Accuracy over total range sec 30 1 2 0.2 4

Range of measurement min 60x60 10

900

sec (1500ext) 20 400

Range in eyepiece sec 10,800 2,800 1,140 1,800 12,600

Direct reading to sec 60 0.5 0.2 0.01 0.1

Working distance* m 0.5 1 9 5 5

for full measuring range ft 1.5 3 30 15 15

Maximum working distance m 3 5 20 10 20ft 9 15 60 30 60

Readout means Graticule Micrometer Micrometer Digital Digital

& Graticule Display Display

Measurement axes 2 2 2 2 2

Light source for measurement ** 6V 2 Watts 6V 2 Watts 6V 2 Watts Infra-red Infra-red

Lamp Lamp Lamp LED LED

Light source for viewing Yellow LED Yellow LED

Barrel diameter approx mm 25 38 57 57 57

in 1 1.5 2.25 2.25 2.25

Approximate overall length mm 150+ 330 420 490 245

in 6.2 13 16.5 19.5 10

Approximate weight kg 0.5 1.7 4.8 5 2

lb 1.1 3.8 10.5 11 4.4

Computer interface No No No RS232 RS232

analogue analogue

Mains supply 90-26V with selector 50-60 Hz 90-260 V with selector for

100, 120, 200, 240 V 48-63 Hz

* Longer distances may be possible at proportionally reduced range+ Straight through viewing. For right angle viewing length is 200mm (8in)++ For the DA instruments the accuracy is over a central range of 20 seconds for DA400 and 10 seconds for DA20.+++ Note: the best accuracy that can be certified and traceable to international standards is 0.2 seconds.NB : All autocollimators are affected by the condition of the air path between the instrument and the reflector. To obtain

maximum accuracy, this must be as short as possible and may need to be shielded from draughts and convection currents.

UKAS CERTIFICATEAutocollimators and certain accessories can be supplied with a National Accreditation of Measurement andSampling (UKAS) certificate which gives an independent and authoritative traceable guarantee of instrumentperformance and accuracy. Regular service and UKAS calibration will guarantee that the performancespecification is traceable to International Standards.

Autocollimator 1E SM 11/04

Taylor Hobson Francerond Point de lEpine des Champs,

78990 Elancourt, France

Tel: +33 130688930 Fax: +33 130 68 89 39

e-mail: [email protected]

Taylor Hobson GermanyPostfach 4827, Kreuzberger Ring 6

65205 Wiesbaden, Germany

Tel: +49 611 973040 Fax: +49 611 97304600


Taylor Hobson ItalyVia de Barzi, 20087 Robecco Sul Naviglio (MI), Italy

Tel: +39 0294693401 Fax: +39 029469 3450


Taylor Hobson Liaison OfficeEastern Europe

Cumberlandstrasse 5/6, A-1140 Vienna, Austria

Tel: +43 1877 557112 Fax: +43 1877 557116


Taylor Hobson JapanSankyo Meguro Bldg, 5-37, 4-Chome, Kamiosaki,

Shinagawa-Ku, Tokyo 141-0021, Japan

Tel: +81 334 945110 Fax: +81 334 945119


Taylor Hobson KoreaHungkuk Life Building. 5th Floor 6-7, Soonae Dong

Pundang-Ku, Seongnam, Kyungki-Do, 463-020, Korea

Tel: +82 31 713 1371 Fax: +82 31 713 1372


Taylor Hobson China OfficeUnit 814, 8/F Tower 1, Cheungsha Wan Plaza

833 Cheung Sha, Wan Road, Kowloon, Hong Kong

Tel: +852 2526 1967 Fax: +852 2526 0225


Taylor Hobson USA1715 Western Drive, West Chicago,

Illinois 60185. USA.

Tel: +1 630 621 3099 Fax: +1 630 231 1739


198 8

ELECTRO OPTICAL METROLOGY

Taylor Hobson has been selling electro-optical metrol-ogy products since the last 1930s and the rangeincludes Micro Alignment Telescopes (used for check-ing and setting straightness and alignment) Autocolli-mators (for accurate measurement of small angulardisplacements), clinometers and "Talyvel" electroniclevels. Used in a range of applications in industriessuch as machine tools, aerospace, marine and steelrolling, the Taylor Hobson range combines high accu-racy and repeatability with fast response and opera-tional convenience.

To provide focused technical support to all its electro-optical metrology customers, Taylor Hobson has a dedi-cated technical support centre:

Spectrum MetrologyCustomers with electro-optical measurement needsoften require not only equipment but also advice onsolving a specific manufacturing or calibration problem.With many years experience in electro-optical metrol-ogy, Spectrum Metrology provides rapid technical andapplication support via phone, fax, e-mail or on-sitevisits. A full demonstration and training facility is avail-able either on-site or in Spectrum Metrology's demon-stration room.

Spectrum Metrology is also the authorised repair agentto Taylor Hobson for the electro optical metrologyrange and holds a wide stock of ex-demonstrationequipment for hire or sale.

Spectrum Metrology can be contacted on Tel: (44)(0)116 276 6262Fax: (44)(0)116 276 6868, E-mail: [email protected]: http://www.spectrum-metrology.co.ukUnit 8 Ireton Avenue, Leicester, LE4 9EU, England

Taylor Hobson LimitedPO Box 36, 2 New Star Road, Leicester, LE4 9JQ, England.

Tel: +44 116 276 3771 Fax: +44 116 246 0579


Internet: http://www.taylor-hobson.com

TAYLOR HOBSONA8248 ISO9001

www.taylor-hobson.com

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Auto Collimator