Optic Mounts

Every optical system begins with a source and ends at a detector, but between those endpoints lies a chain of components — mirrors, lenses, filters, beam splitters, waveplates — each of which must be held in a precise position and orientation. The device responsible for holding an optical component is an optic mount. While the distinction may seem trivial, the quality of the mount directly determines the quality of the optical system it supports. A mirror that drifts by 2 µrad shifts a beam by 4 µrad at the reflection — enough to walk a focused spot off a detector at modest working distances.

Optic mounts serve three functions. First, they retain the optic — physically holding it in place without inducing stress that would deform the optical surface or create birefringence in transmissive elements. Second, they provide adjustment — tip, tilt, rotation, or translation as required by the application. Third, they interface the optic to the broader optomechanical infrastructure: posts, post holders, cage systems, breadboards, and optical tables. The selection of a mount is therefore not a simple purchasing decision but a systems engineering problem that balances adjustment range, stability, distortion budget, and cost [1, 3].

It is important to distinguish mounting from positioning. A mount holds an optic and may provide angular adjustment (tip/tilt). A positioning stage translates or rotates a component along or about a defined axis with calibrated travel. The two are complementary: a mirror mount provides beam steering, while a translation stage beneath it provides lateral alignment. This topic addresses mounts — the devices that hold and orient individual optical components. For the translation and rotation stages beneath optic mounts, see Manual Stages.

2.1Overview

Optic mounts fall into six broad categories, distinguished by their adjustment mechanism and the type of optic they are designed to hold. The most common by far is the kinematic mount, which provides tip and tilt adjustment using the principles of exact constraint. Gimbal mounts rotate the optic about its center, eliminating the beam translation inherent in kinematic designs. Flexure mounts use elastic deformation of the mount body itself for angular adjustment, offering compact size and resistance to shock. Fixed mounts provide no angular adjustment and simply hold an optic in a defined position. Rotation mounts allow continuous rotation about the optical axis, essential for polarizers and waveplates. Specialty mounts address specific optic geometries such as prisms, pellicles, and cube beam splitters [1, 6].

2.2Kinematic Mounts

The kinematic mount is the workhorse of the optics laboratory. Its design follows the principles of kinematic determinacy: each of the six degrees of freedom is constrained exactly once, yielding a system with no redundant constraints and excellent thermal stability. In a typical two-adjuster kinematic mount, a front plate holds the optic and pivots against a back plate. Two fine-pitched screws, tipped with steel ball bearings, push the front plate to provide tip and tilt adjustment. A third contact point — a ball seated in a conical recess — serves as the fixed pivot. Steel springs between the plates provide preload to maintain contact at all three kinematic points [1, 3, 6].

Kinematic mounts are available for optics from Ø7 mm to beyond Ø300 mm, in both two-adjuster and three-adjuster configurations. Two-adjuster mounts provide tip and tilt; three-adjuster mounts add axial (Z) translation by driving all three screws together. The primary limitations of kinematic mounts are cross-coupled motion between the adjustment axes (because the pivot point moves with each adjustment) and beam translation during tilt (because the rotation axis is behind the optic, not at its center) [6].

2.3Gimbal Mounts

A gimbal mount uses two concentric rings that each rotate about an axis passing through the center of the optic surface. This places the rotation axes at the optic center, eliminating both cross-coupling and beam translation. Gimbal mounts offer significantly larger angular travel than kinematic mounts — often a full 360° in both axes — and are the preferred choice for laser cavity alignment, interferometer tuning, and any application where beam translation during adjustment is unacceptable. The tradeoff is greater size, higher cost, and generally lower stiffness than an equivalent kinematic mount [1, 6].

2.4Flexure Mounts

Flexure mounts achieve angular adjustment through elastic deformation of thin structural elements (flexures) machined or welded into the mount body. The advantages are compact size, monolithic construction (no sliding contacts), and resistance to shock — the optic cannot separate from the mount during vibration because there are no loose kinematic contacts. Flexure mounts are popular in OEM instruments and systems that must survive shipping. The disadvantages are limited travel range (typically half that of a kinematic mount) and greater susceptibility to thermal drift, because the thin flexure elements have low thermal mass and respond quickly to environmental temperature changes [6].

2.5Fixed Mounts

Fixed mounts hold an optic without providing angular adjustment. The most common example is the lens mount — a cylindrical housing with internal SM threading and a retaining ring that clamps the optic axially. Fixed mounts are appropriate when the optic does not require alignment (e.g., a filter in a collimated beam) or when alignment is achieved at a higher level (e.g., by adjusting the entire lens tube assembly). Fixed mounts are available for optic diameters from Ø5 mm to Ø4″ and are compatible with cage systems and lens tube assemblies via SM threading standards [8].

2.6Rotation Mounts

Rotation mounts provide continuous 360° rotation about the optical axis (the Z-axis). They are essential for polarizers, waveplates, and any component whose orientation about the beam axis must be set precisely. Typical rotation mounts feature a graduated angular scale with 1° or 2° markings and a fine-adjustment micrometer for sub-degree positioning. A locking thumbscrew holds the rotational position once set. Rotation mounts accept optics via SM-threaded bores and retaining rings [8].

2.7Specialty Mounts

Prism holders use clamping arms with V-cut or flat contact surfaces to grip rectangular or triangular optics without threaded bores. Pellicle holders accommodate extremely thin membrane beam splitters that cannot tolerate any axial clamping force. Flip mounts allow an optic to be swung in and out of the beam path on a hinged platform with a detent at 90°. These specialty mounts solve specific geometric challenges that the standard categories do not address [8].

3.1Degrees of Freedom and Exact Constraint

Any rigid body in three-dimensional space possesses six degrees of freedom: three translations (x, y, z) and three rotations (θ_x, θ_y, θ_z). A mount is kinematic when the total number of physical constraints equals exactly six — one for each degree of freedom, with no redundancy. This principle, called exact constraint or kinematic determinacy, ensures that the mount's behavior is fully predictable. If fewer than six constraints are applied, the optic can move in uncontrolled directions. If more than six are applied, the system is over-constrained, and internal stresses arise that change unpredictably with temperature, vibration, or assembly torque [1, 3].

The practical consequence of exact constraint is thermal stability. In a kinematic mount, each contact point is free to slide or rotate in the directions it does not constrain. When the mount expands or contracts with temperature, the contacts accommodate the dimensional change without distorting the optic or shifting its angular position. An over-constrained mount, by contrast, fights its own thermal expansion — the resulting internal stresses warp the optic surface and shift its orientation unpredictably [1, 6].

3.2Cone-Groove-Flat Geometry

The most common implementation of exact constraint in optic mounts is the cone-groove-flat (also called ball-cone-vee-flat) configuration. Three steel ball bearings on the movable front plate contact three mating surfaces on the fixed back plate:

The first ball seats in a conical (or trihedral) recess. The cone provides three independent contact points, eliminating all three translational degrees of freedom (x, y, z). This ball serves as the fixed pivot of the mount. The second ball rests in a V-groove oriented radially toward the cone. The two walls of the groove provide two contact points, eliminating two rotational degrees of freedom. The third ball rests on a flat surface, providing one contact point and eliminating the last rotational degree of freedom. The total is 3 + 2 + 1 = 6 independent constraints — exactly kinematic [1, 3, 6].

In a two-adjuster kinematic mirror mount, the second and third balls are attached to fine-pitched adjustment screws. Turning a screw advances the ball, tilting the front plate about the pivot. The two screws are positioned on diagonal corners of the mount body, with the cone pivot on a third corner. This diagonal arrangement maximizes the lever arm for each adjuster while keeping the mount footprint compact [6, 8].

3.3Pivot Location and Cross-Coupled Motion

In a kinematic mount, the pivot point (the ball-in-cone) is located behind the optic, not at its center. This has two consequences. First, when the mount is adjusted, the optic both rotates and translates — the center of the mirror moves along its surface normal. For beam steering this is usually negligible, but for laser cavities and interferometers, where mirror spacing must remain constant during alignment, the translation is problematic. Second, the rotation axes of the two adjusters are not fixed in space — they shift with each adjustment, so the axes are not exactly orthogonal to each other or to the optical axis. This means that turning one adjuster produces a small parasitic rotation in the other axis, called cross-coupling [3, 6].

Gimbal mounts solve both problems by placing the rotation axes at the optic center, but at higher cost and lower stiffness. Hybrid kinematic-gimbal designs, and three-adjuster mounts with software-coordinated virtual pivot points, offer intermediate solutions [6].

4.1Thread Pitch and Angular Resolution

The angular resolution of a kinematic mount is determined by two parameters: the thread pitch of the adjustment screw and the lever arm distance from the screw to the pivot point. When the adjuster knob is turned one full revolution, the screw advances by one pitch length, tilting the front plate by an angle equal to the linear advance divided by the lever arm distance.

Where: TPI = threads per inch of the adjuster screw, L = lever arm distance from screw axis to pivot (mm or inches — units must be consistent), θ_rev = angular travel per revolution (radians).

For manual adjustment, the smallest reliable knob rotation is approximately 1° (some sources cite 0.25 mm of linear knob travel). The sensitivity per 1° of knob rotation is:

Higher TPI values yield finer resolution. Standard laboratory mounts use 80 TPI (e.g., Thorlabs KM100) or 100 TPI (e.g., Thorlabs KS1) adjusters. High-performance mounts use 170 TPI or 254 TPI adjusters (e.g., Newport Suprema series). Differential screw mechanisms achieve effective pitches far beyond what a single thread can provide — for example, the Thorlabs KS1 differential adjuster produces only 25 µm of linear travel per revolution by nesting two threads of nearly equal pitch (M3 × 0.40 and M3 × 0.375), with the net advance equal to the difference [6, 8].

4.2Actuator Types

Manual adjustment screws come in several forms. Thumbscrew knobs (the most common) allow quick, tool-free adjustment and are ideal for prototyping and frequent realignment. Knobs are typically removable — pulling them off exposes the hex socket for Allen key access, which reduces the mount footprint and discourages accidental tampering. Hex-key-only adjusters (no knob) are used in set-and-forget applications, particularly in OEM instruments where post-assembly adjustment is rare. Micrometer-head adjusters provide a graduated thimble for calibrated positioning, useful when absolute angular settings must be recorded and reproduced [6, 8].

Beyond manual adjusters, motorized and piezoelectric actuators enable remote and automated alignment. Stepper-motor-driven adjusters replace the manual knob with a motor that turns the same lead screw, offering computer-controlled positioning with resolution limited by the thread pitch and motor step size. Piezoelectric actuators bypass the screw entirely, using the expansion of a piezoelectric element to push the front plate directly. Piezo adjusters achieve sub-microradian resolution (0.05–0.3 µrad per step) over limited travel ranges (typically ±15 mrad), and are essential for laser cavity stabilization, fiber alignment, and active beam pointing control [8]. For multi-axis alignment systems combining motorized coarse positioning with piezo fine correction, see the Hybridized Positioning guide.

4.3Locking Mechanisms

Once a mount is aligned, the adjustment must remain stable. Locking mechanisms prevent the adjuster screws from drifting under vibration or thermal cycling. The most common approach is a lock nut — a bronze or brass nut threaded onto the adjuster shaft that is tightened against the back plate after alignment. Pretension screws (found on three-adjuster mounts) push the front plate away from the back plate, loading the adjusters in compression and reducing backlash. Some mounts use a setscrew that bears against the adjuster shaft at 90°, pinching it in place by friction [8].

5.1Thermal Drift and Thermal Hysteresis

Stability is the central performance metric for an optic mount. Two related but distinct quantities define thermal stability: drift and shift (also called hysteresis). Drift is the angular change in pointing direction as the mount temperature changes — it represents the instantaneous effect of thermal expansion. Shift is the angular difference between the original position and the position after a full thermal cycle (heat and return to original temperature) — it represents irreversible displacement caused by internal stress relaxation, friction at contacts, and plastic deformation [6].

A mount with low drift but high shift will track well during slow temperature changes but will not return to its original alignment after a thermal excursion. A mount with low shift but moderate drift will eventually return to alignment once the temperature stabilizes. For long-term stability in laboratory environments (where HVAC systems cycle the room temperature by 1–5 °C over hours), both metrics matter [6].

5.2Material Selection and CTE

The coefficient of thermal expansion (CTE) of the mount material is the primary driver of thermal drift. When different parts of the mount expand at different rates — for example, an aluminum front plate against a steel adjustment screw — the resulting differential expansion tilts the optic.

Where: α = CTE (ppm/°C or 10⁻⁶/°C), L = characteristic length (mm), ΔT = temperature change (°C), ΔL = dimensional change (mm).

Aluminum is the default material for general-purpose mounts because it is lightweight, inexpensive, and easy to machine. Its high CTE is the primary drawback. Stainless steel mounts — particularly those made from 400-series alloys — offer significantly lower drift at higher cost and weight. Invar, a nickel-iron alloy with near-zero CTE, is reserved for applications where sub-microradian stability is essential, such as interferometers and space-qualified instruments [1, 3, 6].

An important nuance is that aluminum's high thermal conductivity is actually advantageous in some scenarios. Because aluminum dissipates heat quickly, it reaches thermal equilibrium faster than stainless steel, reducing the duration of thermal transients. A stainless steel mount has lower CTE but conducts heat poorly, so thermal gradients within the mount persist longer and can cause larger instantaneous distortions during transients. The optimal material depends on whether the application is sensitive to steady-state drift or to transient behavior [6].

5.3Vibrational Stability and Resonant Frequency

A mounted optic is a spring-mass system. The springs between the front and back plates, combined with the mass of the front plate and optic, define a resonant frequency. Below this frequency, the mount effectively tracks the table vibrations with minimal relative motion. Near resonance, vibration is amplified. Above resonance, the mount attenuates vibration. For stability, the resonant frequency of the mount should be as high as possible — well above the dominant vibration frequencies in the laboratory (typically below 200 Hz) [1, 3].

Where: k = effective stiffness of the mount (N/m), m = mass of the front plate and optic (kg), f_n = natural frequency (Hz). Light materials and stiff springs increase f_n. This is why mount bodies are made from aluminum (low density) rather than steel when vibrational stability dominates over thermal concerns, and why stiffer springs are used in precision mounts [1, 3].

5.4Pointing Stability Specifications

Mount manufacturers specify pointing stability in several ways. Thermal drift is reported as µrad/°C — the angular change per degree of temperature change. Thermal shift (hysteresis) is reported as µrad after a defined thermal cycle. Vibrational stability may be reported as the mount's lowest resonant frequency or as a compliance spectrum. When comparing mounts across vendors, it is essential to verify that the test conditions (temperature range, cycle rate, measurement method) are comparable [6, 8].

6.1Mechanical Retention

The most common retention method in kinematic mounts is the nylon-tipped setscrew bearing against a double-bored hole. The double bore creates two tangent lines that cradle the round optic at two points, while the setscrew provides the third contact point — a three-point kinematic retention system within the mount itself. The nylon tip prevents scratching the optic edge. This method is simple, inexpensive, and provides adequate holding force for most laboratory applications [8].

For stress-sensitive applications, SM-threaded retaining rings replace the setscrew. The optic is placed into an internally threaded bore and secured by threading a retaining ring against it. Retaining rings distribute the clamping force around the full circumference, reducing point loading. Stress-free retaining rings (made from compliant materials or designed with flexure features) further reduce the axial clamping force to minimize wavefront distortion [8].

6.2Adhesive Bonding

Adhesive bonding permanently fixes the optic to the mount. UV-curing adhesives (such as Norland NOA 61) are the most common choice for precision applications. The adhesive is applied to the back surface of the optic (never the optical face), confined to a single plane. Relief cuts machined into the mount's bonding surface allow excess adhesive to flow away from the optic rather than onto its edges, preventing stress concentrations. The adhesive layer must be thin and uniform — thick or non-uniform bond lines create differential thermal stress as the adhesive expands at a different rate than the glass and metal [8].

Epoxy adhesives offer higher shear strength than UV-cure adhesives but are less forgiving of thermal mismatch. RTV silicone (room-temperature vulcanizing) is the most compliant option — its low modulus of elasticity absorbs CTE mismatch between the optic and mount, making it the preferred choice for large optics or systems that experience wide temperature swings. However, RTV has lower holding strength and can creep under sustained shear load [1, 7].

The single most important rule for adhesive bonding is to confine the adhesive to a single plane. If adhesive contacts both the back surface and the edge of the optic, the bond constrains the optic in more than the intended degrees of freedom, and thermal expansion of the adhesive will distort the optic surface [8].

6.3Magnetic Retention

Some kinematic mounts use magnets instead of springs to preload the front plate against the kinematic contacts. Magnetic retention allows the front plate (with the optic) to be removed and replaced in the same position with high repeatability — the magnets self-align the plate to the kinematic contacts every time. This is useful when optics must be swapped frequently (e.g., changing filters or mirrors between experiments) without losing alignment [1].

7.1Surface Deformation in Mirrors

Every optic mount applies force to the optic it holds — through setscrew pressure, retaining ring clamping, or adhesive shrinkage. In reflective optics, this force deforms the mirror surface, introducing wavefront error into the reflected beam. The effect is direct: a 5 µm edge deformation of a flat mirror shifts the focus, broadens the point spread function, and can reduce peak intensity by 50% or more in a focused beam [5].

The setscrew presents the worst case. A nylon-tipped setscrew applies a point load to the edge of the mirror, creating a cantilever-like bending deformation that propagates across the surface. The deflection depends on the mirror thickness, diameter, material stiffness, and the applied force. Thicker mirrors resist deformation more effectively — as a general rule, a mirror-to-thickness ratio of 6:1 or better provides adequate stiffness for setscrew retention without significant wavefront degradation [1, 5].

7.2Stress Birefringence in Transmissive Optics

When a transmissive optic (lens, window, waveplate) is clamped in a mount, the mechanical stress induces birefringence — a difference in refractive index between the two principal stress directions. Light polarized along the maximum stress direction travels at a different speed than light polarized along the minimum stress direction, creating an optical path difference (retardance) between the two polarization components.

Where: W_p = retardance (nm), K = stress-optic coefficient of the glass (Pa⁻¹), σ₁, σ₂ = maximum and minimum principal stresses in the glass (Pa), t = thickness of the stressed region (m). The stress-optic coefficient K is a material property, typically in the range of −2 to 4 × 10⁻¹² Pa⁻¹ for common optical glasses. BK7 has K ≈ 2.77 × 10⁻¹² Pa⁻¹. Fused silica has K ≈ 3.5 × 10⁻¹² Pa⁻¹. Calcium fluoride, commonly used in UV and IR optics, has a significantly higher stress-optic coefficient and is particularly sensitive to mounting stress [5, 7].

7.3Permissible Distortion Limits by Application

The acceptable level of mounting-induced distortion depends entirely on the application. Polarimetric and interferometric instruments, where wavefront phase must be preserved to a fraction of a wave, tolerate the least distortion. General-purpose imaging systems are more forgiving.

These limits are guidelines, not absolute thresholds. Each application should be evaluated individually based on its wavefront error budget, which allocates allowable distortion across all sources (mounting, surface figure, material homogeneity, thermal effects) [2, 5].

7.4Mitigation Strategies

Minimizing mounting-induced distortion begins with the retention method. Three-point contact (the kinematic principle applied within the optic bore) distributes the holding force without over-constraining the optic. Stress-free retaining rings with flexure features reduce axial clamping force. Adhesive bonding confined to a single plane on the back surface avoids edge stress. For the highest performance, heat-treated mount bodies (which relieve internal residual stresses from machining) reduce thermally induced hysteresis. And whenever possible, use the minimum retention force necessary to hold the optic securely — over-torquing a retaining ring or setscrew is the single most common cause of mounting-induced wavefront degradation in the laboratory [1, 5, 8].

8.1Posts and Post Holders

The post is the mechanical link between the optic mount and the optical table. Standard posts are Ø12.7 mm (½″) cylindrical rods, available in heights from 1″ to 12″, typically made from stainless steel or hardened alloy. The post sits inside a post holder — a hollow cylinder clamped to the table via a base or fork — and is secured by a thumbscrew that locks the post at the desired height and rotational orientation [8].

Post stiffness scales strongly with diameter and inversely with the cube of length (cantilever stiffness k = 3EI/L³). Doubling the post diameter increases stiffness by a factor of 16 (since I ∝ d⁴). Doubling the post length decreases stiffness by a factor of 8. For critical mirror mounts, use the shortest post possible and consider Ø1″ pedestal posts, which eliminate the post holder entirely — the pedestal bolts directly to the table through a slotted base, providing the stiffest possible mounting [8].

8.2Pedestal Posts

Pedestal posts are monolithic fixed-height posts with a large base footprint that bolts directly to the optical table. The elimination of the post-holder joint and the increased base contact area provide significantly higher stiffness and lower compliance than standard post-and-holder assemblies. Pedestal posts are the recommended mounting for mirrors and other alignment-critical optics. The tradeoff is the loss of height adjustability — the pedestal height is fixed at the time of purchase [8].

8.3Cage Systems

Cage systems use four (or six) rigid steel rods to mount optical components along a common optical axis, creating a self-contained optomechanical assembly independent of the table surface. Three standard rod spacings accommodate different optic sizes: 16 mm center-to-center for ؽ″ optics, 30 mm for Ø1″ optics, and 60 mm for Ø2″ optics. Cage plates with SM-threaded bores hold lenses, filters, and other components; specialized cage-compatible mounts hold mirrors and beam splitters at 45° within the cage structure [8].

Cage systems offer inherent alignment — all components share the axis defined by the rods — and are particularly useful for building compact, portable optical subsystems such as beam expanders, spatial filters, and relay systems.

8.4Lens Tube Integration

Lens tubes are internally and externally SM-threaded cylinders that stack together to form enclosed optical paths. Optics are held inside the tube between retaining rings. The SM threading standard defines the interface: SM05 (0.535″-40 thread) for ؽ″ optics, SM1 (1.035″-40) for Ø1″ optics, and SM2 (2.035″-40) for Ø2″ optics. Lens tubes interface with cage systems via cage plates and with free-space setups via lens tube clamps and slip rings mounted on posts [8].

9.1Mirror Mounting and the 2× Angular Sensitivity Rule

Mirrors are the most alignment-sensitive optic in any system. By the law of reflection, the angle of incidence equals the angle of reflection — and both are measured from the surface normal. When a mirror tilts by an angle Δθ, the reflected beam deflects by 2Δθ.

This 2× amplification means that every source of angular error — mount drift, post vibration, thermal expansion — has double the effect on beam pointing compared to a transmissive optic at the same position. Consequently, mirrors should always be mounted on the stiffest available infrastructure: pedestal posts, high-stability kinematic mounts (stainless steel or Invar), and the shortest feasible post heights [2, 4, 6].

9.2Lens and Filter Mounting

Lenses and filters are transmissive optics and are significantly less sensitive to mount tilt than mirrors. A small angular error in a lens shifts the transmitted beam laterally but does not steer it at the 2× amplification of a reflective surface. For this reason, lenses are commonly held in fixed mounts — SM-threaded lens housings with retaining rings — unless fine centration or tilt adjustment is required for coma correction or beam alignment. Filters in collimated beams can be mounted in simple fixed holders or filter wheels without kinematic adjustment [2].

9.3Polarizer and Waveplate Mounting

Polarizers and waveplates require precise rotation about the optical axis (Z-rotation). The mount of choice is the rotation mount, which provides 360° continuous rotation with a graduated angular scale and fine-adjustment capability. The optic is held in an SM-threaded bore with retaining rings. Critically, the mount must not induce stress birefringence in the optic — for waveplates, any mounting stress adds an uncontrolled retardance that degrades polarization performance. Stress-free retaining rings and minimal axial preload are essential [8].

9.4Prism and Beam Splitter Mounting

Prisms and cube beam splitters have flat, non-circular faces that do not fit standard bore-type mounts. Prism holders use a V-cut clamping arm (often made from Delrin or similar non-marring polymer) that grips the prism against a reference flat. Platform-style mounts accept the prism on a flat surface with lateral clamps. For cube beam splitters, dedicated cube mounts or platform mounts with threaded retention provide secure, stress-free holding. When angular adjustment is required, prism holders are mounted on rotation stages or kinematic platforms [8].

9.5Vacuum and Harsh Environment Mounting

Vacuum-compatible mounts require materials and lubricants with low outgassing rates to avoid contaminating the vacuum and depositing films on optical surfaces. Standard mount greases, nylon setscrew tips, and some adhesives are not suitable for high vacuum. Vacuum-rated mounts use dry-film lubricants (MoS₂ or PTFE), vented screws (to prevent trapped gas volumes), and are chemically cleaned and baked out before installation. For cryogenic applications, CTE matching between the mount and optic becomes critical — the large temperature excursions amplify any CTE mismatch, and adhesive joints may fail if the adhesive becomes brittle at low temperature [1, 8].

Selecting an optic mount is a six-step process:

Step 1 — Identify the optic. Determine the optic type (mirror, lens, filter, polarizer, prism), its shape (round, rectangular), diameter, and thickness. This narrows the mount category and size immediately.

Step 2 — Determine adjustment needs. Does the optic need tip/tilt adjustment (kinematic), Z-rotation (rotation mount), or no adjustment at all (fixed mount)? Mirrors and beam splitters almost always require kinematic adjustment. Lenses and filters in collimated beams usually do not.

Step 3 — Evaluate stability requirements. Assess the application class from the permissible OPD table: interferometric, precision, photographic, or visual. This determines the acceptable drift, shift, and distortion levels, which in turn constrain the mount material (aluminum vs. stainless vs. Invar) and retention method.

Step 4 — Choose a retention method. Setscrew retention is adequate for mirrors and thick optics in non-critical applications. Retaining rings are preferred for thin optics and stress-sensitive applications. Adhesive bonding is reserved for permanent assemblies requiring maximum stability and minimum distortion.

Step 5 — Select mounting infrastructure. Choose the post type (standard, slotted-base, or pedestal) based on the required stiffness — mirrors on pedestal posts, lenses on standard posts. Select the cage system compatibility if the optic is part of a caged assembly. Verify SM threading compatibility between the mount and any lens tube or cage components.

Step 6 — Verify environmental compatibility. Confirm that the mount material, lubricants, and adhesives are compatible with the operating environment: ambient laboratory, cleanroom, vacuum, cryogenic, or high-temperature.