Compact Spatial Filter

The compact spatial filter is designed for devices in which space is limited and in which the once adjusted focusing position and pinhole alignment must remain stable even when there is vibration. Because of its small diameter of only 25 mm, it can readily be inserted into a number of standard holders and systems.

Because of the small dimensions of the compact spatial filter, some compromises had to be made in how and howfar it can be adjusted, in ease of use and particularly in accessability to the adjustable elements; however, all adjustments can be controlled visually while they are carried out, no matter how the spatial filter is mounted.

A key feature which has been incorporated from the larger version is the complete separation of focusing and pinhole alignment to ensure that the focus position remains constant even when different objectives are interchanged or when there is a change in wavelength.

Ordering information

To ensure that the compact spatial filter can be used flexibly for a maximum number of applications without requiring modification, it is assembled as a modular system.

To build a complete device (1) a focus and pinhole head, (2) a micro objective, (3) a pinhole, (4) a collimator focusing tube, (5) a collimator objective and in some cases (6) a distance tube are needed:

1. Focus and pinhole head

This part is the actual core of the system. It provides the facility for focusing the microscope objective and adjusting the pinhole. Outer diameter 25 mm (diameter tolerance f7, i.e. -20 to -41 µm). With standard microscope objective thread (W0.8" * 1/36") on the entrance side and M23 * 0.5 (removable through groove and three holding screws) for attachment of item 4 or 6 on the exit side. All adjustments can be locked into position to protect against vibration.

• Objective and pinhole not included → MRF 25.1

2. Micro objectives

With mounting thread and proper back focal length for item 1. See objectives.

• Individual micro objectives → on request

3. Pinholes

Mounted for item 1.
Refer to Laser Pinholes.

4. Collimator focusing tubes

Outer diameter 25 mm (diameter tolerance f7). Objective not included. With objective thread M23 * 0.5 on the entrance side and interface for thread adapter (MRA 25.2.0) on the exit side. With focusing thread for item 5 and locking ring to protect against vibration. For objectives with clear diameters up to approx. 18 mm.

• With locking ring, without objective. → MRF 25.2.1
• focusing and locking tool → on request
• Larger apertures → on request

5. Collimator objective

In mount M23 x 0.5 to fit item 4.Achromatic for the visible spectral range (488 and 633 nm). Broadband antireflection coating. Wavefront quality λ/10 for plane exiting waves up to an aperture ratio of f:5. See table for ordering codes.

• Other focal lengths and wavelengths → on request

6. Distance tubes

M23 x 0.5 inner and outer threads. Used to connect item 4 to item 1; length designed to compensate for the different back focal lengths.

• Collimator lenses, focusing and distance tubes for larger clear apertures → on request

Accessories

MRA 25.1.1 

1. Thread adapter

With W1" • 1/32" outer thread for mounting to a conventional laser head and W0.8" • 1/36" inner thread for mounting of compact spatial filter. Total diameter 50 mm; total thickness 12 mm. The adapter consists of two parts: the optical axes on both sides can be laterally adjusted by approx. 1 mm after loosening three screws. 
→ MRA 25.1.1

2. Thread attachment

With holding groove to fit the collimator focusing tube (item 4) and with W1" • 1/32" inner thread. For attachment of equipment with laser thread on the exit side of the compact spatial filter. Supplied as single part, not adjustable. → MRA 25.2.0

3. Thread attachment

With holding groove to fit the focus and pinhole head (item 1) and with W1" • 1/32" inner thread. For attachment of devices with laser thread in the diverging path of rays of the spatial filter. → MRA 25.3.0

We have available drawings of these adapters.

Available on special order

Because the compact spatial filter can be optically for mechanically adapted to suit a variety of different applications, we suggest that you contact us with your requirements. We would be happy to work out a solution for your particular application.