Features

• 360° of Continuous Coarse Rotation
• Micrometer and Vernier Scale Provide ±5° Fine Adjustment
• Perimeter is Laser Engraved at 1° Increments
• Tapped Holes for Standard Optomechanics, Clamping Arms, or Rods for 30 mm Cage Systems
• Center Hole is SM1 Threaded (1.035"-40)
• Mounting Adapters Available for Optics, Translation Stages, Goniometers, and Rotating Cage Systems
• 25 lbs (11.4 kg) Load Capacity

Thorlabs' PR01(/M) High-Precision Rotation Stage provides precise, fine rotation for large optics and optomechanical assemblies. As shown in the animation to the right, if the steel locking thumbscrew is unlocked, the stage can be smoothly and continuously rotated by hand through a full 360°, measured by the 1° graduation marks on the side of the stage. When the thumbscrew is locked, the micrometer provides ±5° of fine adjustment, measured with 5 arcmin resolution by the vernier scale.

As shown to the right, the rotation stage features an array of 1/4"-20 (M6), 6-32 (M4), and 4-40 tapped holes, designed for standard optomechanics, our clamping arms (sold below), or our 30 mm cage systems. It attaches to an optical table or breadboard using the four 1/4" (M6) counterbored clearance slots.

Solid Adapter Plate
For applications that benefit from having a rotation platform without a hole, we offer the PR01A(/M) Adapter Plate. It attaches to the top of the PR01(/M) rotation stage and provides a tapped hole array designed for compatibility with our 1- and 2-axis goniometers and our miniature translation stages. As shown in the image at the top of the page, it is also well suited for holding optics in combination with a clamping arm.

Rotation Adapter for 30 mm Cage Systems
This adapter is designed to hold two 30 mm cage rods in a plane perpendicular to the axis of rotation. In combination with the PR01(/M) rotation stage , it allows a 30 mm cage segment to be rotated through a full 360° and precisely aligned using the stage's micrometer.

Reading a Vernier Scale on a Linear Main Scale

Vernier scales are typically used to add precision to standard, evenly divided scales (such as the scales on Thorlabs' rotation, goniometric, or translation mounts). A vernier scale has found common use in many precision measurement instruments, the most common being calipers and micrometers. The vernier scale uses two scales side-by-side: the main scale and the vernier scale. The direct vernier scale has a slightly smaller spacing between its tick marks owing to the vernier scale having N ticks for every N - 1 ticks on the main scale. Hence, the lines on the main scale will not line up with all the lines on the vernier scale. Only one line from the vernier scale will match well with one line of the main scale, and that is the trick to reading a vernier scale.

Figures 1 through 3 show a linear vernier scale system for three different situations. In each case, the scale on the left is the main scale, while the small scale on the right is the vernier scale. When reading a vernier scale, the main scale is used for the gross number, and the vernier scale gives the precision value. In this manner, a standard ruler or micrometer can become a precision instrument.

The 0 on the vernier scale is the "pointer" (marked by a red arrow in Figures 1 - 5) and will indicate the main scale reading. In Figure 1 we see the pointer is lined up directly with the 75.6 line. Notice that the only other vernier scale tick mark that lines up well with the main scale is 10. Since the pointer lines up with the main scale’s 75.6, the reading from Figure 1 is 75.60 (in whatever units the instrument measures).

That is essentially all there is to reading a vernier scale. It's a very straightforward way of increasing the precision of a measurement instrument. To expound, let’s look at Figure 2. Here we see that the pointer is no longer aligned with a line on the main scale, but instead it is slightly above 75.6 and below 75.7; thus, the gross measurement is 75.6. The first vernier line that coincides with a main scale line is the 5, shown with a blue arrow. The vernier scale gives the final digit of precision; since the 5 is aligned to the main scale, the precision measurement for Figure 2 is 75.65.

Since this vernier scale is 10% smaller than the main scale, moving the vernier scale by 1/10 of the main scale will align the next vernier marking. This asks the obvious question: what if the measurement is within the 1/10 precision of the vernier scale? Figure 3 shows just this. Again, the pointer line is in between 75.6 and 75.7, yielding the gross measurement of 75.6. If we look closely, we see that the vernier scale 7 (marked with a blue arrow) is very closely aligned to the main scale, giving a precision measurement of 75.67. However, the vernier scale 7 is very slightly above the main scale mark, and we can see that the vernier scale 8 (directly above 7) is slightly below its corresponding main scale mark. Hence, the scale on Figure 3 could be read as 75.673 ± 0.002. A reading error of about 0.002 would be appropriate for
this instrument.

Click to Enlarge
Figure 1: An example of how to read a vernier scale. The red arrow indicates what is known as the pointer. Since the tick mark labeled 10 on the vernier scale aligns with one of the tick marks on the main scale, this vernier scale is reading 75.60 (in whatever units the instrument measures).

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Figure 2: The red arrow indicates the pointer and the blue arrow indicates the vernier line that matches the main scale. This scale reads 75.65.

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Figure 3: The red arrow indicates the pointer, and the blue arrow indicates the vernier line that matches the main scale. This scale reads 75.67 but can be accurately read as
75.673 ± 0.002.

Reading a Vernier Scale on a Rotating Main Scale

The vernier scale may also be used on rotating scales where the main scale and vernier scale do not share units. Figures 4 and 5 show a vernier scale system for two different situations where the main scale is given in degrees and the vernier scale has ticks every 5 arcmin (60 arcmin = 1°). In each case, the scale on the top is the main scale, while the small scale on the bottom is the vernier scale.

In Figure 4 we see the pointer is lined up directly with the 341° line. Notice that the only other vernier scale tick marks that line up well with the main scale are ±60 arcmin. Since the pointer lines up with the main scale at 341°, the reading from Figure 4 is 341.00°.

There are two ways to determine the reading if the zero on the vernier scale line is between two lines of the main scale. For the first method, take the line on the left side of the pointer on the vernier scale and subtract that value (in arcmin) from the value on the main scale that is to the right on the main scale. As an example, in Figure 5 the vernier pointer is between 342° and 343°; using the left blue arrow of the vernier scale results in 343° - 15 arcmin = 342.75°. The second method is to take the reading from the blue arrow on the right side of the vernier pointer and add that value to the lower value from the main scale; reading the right blue arrow in Figure 5 results in 342° + 45 arcmin = 342.75°.

As we've seen here, vernier scales add precision to a standard scale measurement. While it takes a bit of getting used to, with a little practice, reading these scales is fairly straightforward. Vernier scales, whether they are direct or retrograde*, are read in the same fashion.

*A retrograde vernier scale has a larger spacing between its tick marks with N ticks for every N + 1 ticks on the main scale.

Click to Enlarge
Figure 4: An example of a vernier scale where the main scale and the vernier scale are in different units (degrees and arcmins, respectively). The red arrow indicates the pointer. This scale reads 341.00°.

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Figure 5: The red arrow indicates the pointer and the blue arrows give the precision value from the vernier scale.
This scale reads 342.75°.

Rotation Mount and Stage Selection Guide

Thorlabs offers a wide variety of manual and motorized rotation mounts and stages. Rotation mounts are designed with an inner bore to mount a Ø1/2", Ø1", or Ø2" optic, while rotation stages are designed with mounting taps to attach a variety of components or systems. Motorized options are powered by a DC Servo motor, 2 phase stepper motor, piezo inertia motor, or an Elliptec™ resonant piezo motor. Each offers 360° of continuous rotation.

Manual Rotation Mounts

Rotation Mounts for Ø1/2" Optics
Item #	MRM05(/M)	RSP05(/M)	CRM05	PRM05(/M)a	SRM05	KS05RS	CT104
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Features	Mini Series	Standard	External SM1 (1.035"-40) Threads	Micrometer	16 mm Cage-Compatible	±4° Kinematic Tip/Tilt Adjustment Plus Rotation	Compatible with 30 mm Cage Translation Stages and 1/4" Translation Stagesb
Additional Details

• This mount is available in the PRM05GL5 bundle, which includes the PRM05 rotation mount with the SM05PM5 polarizing prism mount.
• The CT104 is complatible with the 1/4" translation stages using our MS103(/M) adapter plate.
• The CT104 is compatible with the CT1A(/M) cage translation stage, which is designed for use with 30 mm cage systems.

Rotation Mounts for Ø1" Optics
Item #	RSP1(/M)	LRM1	RSP1D(/M)	DLM1(/M)	CLR1(/M)	RSP1X15(/M)	RSP1X225(/M)	PRM1(/M)a
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Features	Standard	External SM1 (1.035"-40) Threads	Adjustable Zero	Two Independently Rotating Carriages	Rotates Optic Within Fixed Lens Tube System	Continuous 360° Rotation or 15° Increments	Continuous 360° Rotation or 22.5° Increments	Micrometer
Additional Details

• This mount is available in the PRM1GL10 bundle, which includes the PRM1 rotation mount with the SM1PM10 polarizing prism mount.

Rotation Mounts for Ø1" Optics
Item #	LM1-A & LM1-B(/M)	CRM1T(/M)	CRM1LT(/M)	CRM1PT(/M)	KS1RS	K6XS
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Features	Optic Carriage Rotates Within Mounting Ring	30 mm Cage-Compatiblea	30 mm Cage-Compatible for Thick Opticsa	30 mm Cage-Compatible with Micrometera	±4° Kinematic Tip/Tilt Adjustment Plus Rotation	Six-Axis Kinematic Mounta
Additional Details

• This mount also features four 4-40 (M3) holes on the rotation dial for use with the K6A1(/M) prism platform.

Rotation Mounts for Ø2" Optics
Item #	RSP2(/M)	RSP2D(/M)	PRM2(/M)	LM2-A & LM2-B(/M)	LCRM2A(/M)	KS2RS	K6X2
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Features	Standard	Adjustable Zero	Micrometer	Optic Carriage Rotates Within Mounting Ring	60 mm Cage-Compatible	±4° Kinematic Tip/Tilt Adjustment Plus Rotation	Six-Axis Kinematic Mount
Additional Details

Manual Rotation Stages

Manual Rotation Stages
Item #	RP005(/M)	PR005(/M)	MSRP01(/M)	RP01(/M)	RP03(/M)	QRP02(/M)
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Features	Standard					Two Hard Stops
Additional Details

Manual Rotation Stages
Item #	XRNR1(/M)	XRR1(/M)	PR01(/M)	CR1(/M)	XYR1(/M)	OCT-XYR1(/M)
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Features	Fine Rotation Adjuster and 2" Wide Dovetail Quick Connect	Fine Rotation Adjuster and 3" Wide Dovetail Quick Connect	Fine Rotation Adjuster and SM1-Threaded Central Aperture	Fine Pitch Worm Gear	Rotation and 1/2" Linear XY Translation
Additional Details

• The stage profile is higher when it is mounted using the screw slots rather than stacked on another stage or accessory with mating dovetails.
• The OCT-XYR1(/M) stage includes the XYR1A solid sample plate. This plate can be detached from the stage to reveal the same mounting features present on the XYR1(/M) stage.

Motorized Rotation Mounts and Stages

Motorized Rotation Mounts and Stages with Central Clear Apertures
Item #	DDR25(/M)	PDR1C(/M)	PDR1(/M)	PDR1V(/M)	PDXR1(/M)
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Features	Compatible with SM05 Lens Tubes, 16 mm Cage System, & 30 mm Cage System	Compatible with 16 mm Cage System	Compatible with SM05 Lens Tubes & 30 mm Cage System	Vacuum-Compatible; Also Compatible with SM05 Lens Tubes & 30 mm Cage System	Compatible with SM05 Lens Tubes & 30 mm Cage System
Additional Details

Motorized Rotation Mounts and Stages with Central Clear Apertures
Item #	K10CR1(/M)	PRM1Z8(/M)a	DDR100(/M)	ELL14	HDR50(/M)
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Features	Compatible with SM1 Lens Tubes & 30 mm Cage System		Compatible with SM1 Lens Tubes, 16 mm Cage System, 30 mm Cage System	Compatible with SM1 Lens Tubes, Open Frame Design for OEM Applications	Compatible with SM2 Lens Tubes
Additional Details

• This stage is available in the KPRMTE(/M), which includes the PRMTZ8(/M) Motorized Rotation Stage with the KDC101 K-Cube DC Servo Motor Controller.

Motorized Rotation Mounts and Stages with Tapped Platforms
Item #	PRMTZ8(/M)a	ELL18(/M)b
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Features	Tapped Mounting Platform for Mounting Prisms or Other Optics	Tapped Mounting Platform, Open Frame Design for OEM Applications
Additional Details

• This stage is available in the KPRM1E(/M), which includes the PRMT1Z8(/M) Motorized Rotation Stage with the KDC101 K-Cube DC Servo Motor Controller.
• This stage is available in the ELL18K(/M), which includes an interface board, mounting brackets, and connectors for PC control.