Optics mount with 180° angle of view from both sidesH. Houtman Citation: Review of Scientific Instruments 58, 1188 (1987); doi: 10.1063/1.1139437 View online: http://dx.doi.org/10.1063/1.1139437 View Table of Contents: http://scitation.aip.org/content/aip/journal/rsi/58/7?ver=pdfcov Published by the AIP Publishing Articles you may be interested in Common-path optical coherence tomography with side-viewing bare fiber probe for endoscopic opticalcoherence tomography Rev. Sci. Instrum. 78, 113102 (2007); 10.1063/1.2804112 Fast response wide viewing angle liquid crystal cell with double-side fringe-field switching Appl. Phys. Lett. 83, 5154 (2003); 10.1063/1.1635982 CH 4 dissociation on Ru(0001): A view from both sides of the barrier J. Chem. Phys. 116, 5781 (2002); 10.1063/1.1456509 Scaling Mount Planck I: A view from the bottom Phys. Today 54, 12 (2001); 10.1063/1.1387576 Improving the thermal stability by anchoring both ends of chromophores in the sidechain nonlinear opticalpolymers Appl. Phys. Lett. 63, 2168 (1993); 10.1063/1.110573

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Optics mount with 1800 angle of view from both sides H. Houtman

Department of Physics, University of British Columbia, Vancouver, British Columbia, Canada V6T 2A6

(Received 19 February 1987; accepted for publication 30 March 1987)

A simple design for a stable, general-purpose optics mount is ~e~cribed, ,,:ith indepen?~nt, self­locking angular adjustments about two orthogonal axes. Requmng only sImple mac~mmg and readily available parts, the design allows unrestricted access for incident and transmltted beams.

INTRODUCTION

General-purpose optics mounts are useful in any optics labo­ratory, to be kept on hand until needed, so that the numbe~ ~f specialized mounts requiring special design may be mlnt­mized. High-precision angle mounts based on the three­point support I for m~rrors, et~lons, g,;~t~ngs, a~? laser ~eftec­tors have been descnbed prevIOusly,·- 111 addItIOn to gImbal mounts,7 also available commercially. 8 The usefulness of the mount cannot be defined solely in terms of its angular resolu­tion or rigidity because, to the experimenter, it is equally important to preserve the choice of inci~ent, refle~ted, ~nd transmitted beam directions until the optiCS mount IS on sIte. The mounts2

-8 have been found to be too bulky to allow

optical beams to pass through or nearby the optics, as re­quired. Over the course of several experiments9

-11 it h~s be­

come clear that a smaller mount which allows unrestrIcted access for all incident and transmitted beams is indispensa­ble. The subject of this article is the design of such a mount, intended for mounting optics or optics holders having the standard diameters of 25.4, 38.1, 50.8, and 76.2 mm.

l. DESIGN

Two views of the mount suitable for 50.S-mm optics or optics holders are given in Fig. 1. The diagram is drawn to the scale indicated, but for this and other sizes, the dimen­sions indicated are listed in Table 1. The two annular alumi­num plates are held, at three centerpunch depressions, onto steel adjustment screws with conical ends, by two tension springs S located to provide equal force of about 4.0 N to the three screws. The cone semiangle on the screws is 20°, while the centerpunch depressions have a cone semiangle of 25°, allowing up to ± 5° swing. Although the contact point on the movable plate traces out an arc as the screws are ad­vanced from minimum to maximum, the slight change in direction required of the screws to maintain proper contact is well within that allowed for standard thread tolerances. The angular range for each mount is listed in Table 1.

To prevent wobble and backlash, locking screws are in­stalled to force a I-mm3 polyethylene block against the thread of each adjustment screw; this also provides a consid­erable degree of lubrication '2 for the screw thread. While such a self-locking arrangement13 effectively locks the ad­justment screw, and prevents its rotation induced by vibra­tions in the table, it still allows for adjustments to be made, without releasing the lock. On micrometer screws, which

could be installed as substitute in these mounts, 3 an analo­gous friction adjustment is usually installed under the barrel. Differential screws, especially those with an automatic fast/slow feature '4 could be used if finer resolution is re­quired. A spring-clip loaded split-nut' arrangement for ad­justment screws including differential screws has been de­scribed previously'S in applications such as Mach-Zehnder interferometer mirrors.

Flanges which are usually used to hold optics hide part of the front and rear surfaces, and also restrict the angle of view. In the system shown in Fig. 1, a different method is used to hold the optic or holder. Slotted, 2-56 UNC, nylon set screws 13 are used to hold the optic by slight pressure from the outside. The optical beam is usually brought through the component at mid-plane M-O-M', at incidence angles up to 90°. To reduce the effects of strain-induced birefringence on the beam, and to prevent possible burning of the set screws by high-power cw laser beams, these screws are mounted at 52° from the mid-plane as indicated, Simple auxiliary holders for holding the optic by its perimeter have been found helpful to hold the optic during installation.

In addition to the circular mount of Fig. 1, analogous

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FIG. 1. Elevation and cross-section view of optics mount for 50.8-mm-diam optics or optics holder. Three adjustment screws and two tension springs S are located on a circle of radius r, at the angles indicated relative to horizon­tal (M-O-M') and vertical centerlines.

1188 Rev. Sci. Instrum, 58 (7), July 1987 0034-6748/87/071188-02$01.30 @ 1987 American Institute of Physics 1188

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TABLE I. Parameters for the four mount sizes. Dimensions a, b, c, d, e, and r are defined in Fig. L

Optic Optic diameter thickness Adjustment a b

(mm) (mm) screw thread (mm) (mm)

25.4 9.5 2-56 UNC 27.4 26.2 38.1 9.5 2-56 UNC 40.9 39.1 50.8 12.7 2-56UNC 55.6 52.1 76.2 14.7 4-40UNC 81.0 77.5

mounts of rectangular, square, or other shape are easily de~ signed for use with optics or optics holders of these shapes. The design of mount in Fig. 1 also allows the placement of adjustment screws with three springs on a threefold symme­try arrangement, 1200 apart, which may be preferable ifit is to be mounted under pressure or vacuum. When the optic is properly mounted, a strong mechanical shock may dislodge, but will generally not cause the release of the optic.

It USES

The mount is useful for holding mirrors, beam splitters, etalons, wedges, polarizers, and gratings. The wedged fiats are routinely used as variable beam splitters; for incidence angles from 0°-90., the reflection varies from 4% to 100% for a component having a refractive index of 1.5. The 25.4-mm mounts have been used extensively in a Fabry-Perot interferometer for mUltipass dark-ground photography, 9

and in the intricate arrangement of beam splitters, po­larizers, and mirrors in a picosecond CO2 laser. !O The 50.8~ mm mounts were used in a four-frame Mach-Zehnder inter~ ferometry arrangementl 1 with four 76.2-mm mounts used to support the Mach-Zehnder mirrors. The mounts may also be used to hold thin optics of - 3 mm, but if unrestricted angle of view from both sides is required, we use a single, 3~ mm plate with nylon set screws, in a nonadjustable mount.

For the purpose of evaluating and comparing the resolu­tion with the other mounts mentioned, it is useful to define

1189 Rev. ScLlnstrum., Vol. 58, No.7, July 1987

Angular c d e r range

(mm) (mm) (mm) (mm) (deg) a

38.1 3.2 5.6 J5.8 ±5 310 57.2 3.2 7.9 24.4 ±4 471'1 76.2 3.9 9.4 32.8 ±3 643

108.0 4.6 11.7 48.3 ±3 676

the angular gain a = dtjJ/dfJ as the ratio of the differential rotation d¢ of the adjustment screw required to bring about a differential rotation de of the optic. Calculations indicate that the angular gain a of the mounts in Table I are compara­ble to those of 260 for Ref. 2, 508 for Ref. 3, 594 for Ref. 5, 594 for Ref. 6, and 396 for Ref. 8, all slightly lower than 2030 for the larger mount of Ref. 7.

Financial support of the Natural Sciences and Engineer­ing Research Council of Canada is gratefully acknowledged.

'J. E. Furse, J. Phys. E 14, 264 (1981). 2R, R. Giedt and R. W. F. Gross, Rev. Sci. Instrum. 40, 1238 (1969). 'I. S. Falconer and E. Peklo, Rev. Sci. lnstrum. 42, 151 (1971). 4M. Gundersen, H. B. Lloyd, and B. W. Poarch, Rev. Sci. Instrum. 43, 333 (1972).

'E. E. Bergmann, Rev. Sci. Instrum. 43, 548 (1972). 6J. R. Peke\sky, Rev. Sci. lnstrum. 50, 258 (1979). 7P. W. Pace and J. B. Atkinson, Rev, Sci. lnstrum. 47,1215 (1976). "Model no. 10.203, Lansing Research Corporation, 705 Willow Avenue, Ithaca, NY 14850.

9H. Houtman and J. Meyer, AppL Opt. 23, 2178 (1984). '0H. Houtman and J. Meyer. J. App!. Phys, 61, 843 (1987). J 'H. Houtman, L. E. Legault, and J. Meyer, App!. Opt. 26, 1106 (1987). 12R. H. Willens, Rev. Sci. Instrum. 31, 574 (1960). "Nylon set screws and soft-tip screws are available, for example, from

Winfred M. Berg Inc., 499 Ocean Avenue, East Rockaway, NY 11518. I·C. L. Stong, Sci. Am. 200, 155 (1959). "D. C. Barnes, J. Phys, E 7,704 (1974).

Optics mount 1189

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