Precision Optical Path Switching for Multimodal Raman-Fluorescence Microscopy

The Challenge:
A customer needed to perform single-cell metabolomics by identifying specific bacterial cells via widefield fluorescence imaging and subsequently analyzing those same cells using Raman spectroscopy. Because typical bacterial cells are only 1–10 μm in size, any mechanical deviation during the switch between fluorescence imaging and Raman spectroscopy would cause the Raman laser to miss the target identified in the fluorescence view. This customization allows the researcher to identify a target cell in fluorescence mode and trigger a Raman acquisition with a single software command. The automated switch occurs in under 350 ms, with the high precision of the kinematic mount ensuring the cell remains perfectly centered. This eliminates the need for manual recalibration between modes, allowing for much higher throughput.

The Solution:
Zaber’s Custom Engineering Team modified a Nucleus™ MKR microscope core by integrating an additional optical path to couple the Raman laser. We mounted a kinematic mirror mount and a notch dichroic onto a single motorized linear axis to switch the optical path between the Raman laser and detector, and the fluorescence illuminator and camera.

The Engineering Approach:

The system uses a Zaber X-LSM Linear Stage. as the switching mechanism within the Nucleus™ modular platform.

• Precision & Speed: The X-LSM's low pitch, roll, and yaw specifications were key to ensuring the mirror which couples the Raman laser always returns to the same angular orientation every time. This in turn ensures the consistent centering of the laser spot. The higher speed of a coarse-pitch lead screw LSM delivered a rapid < 350 ms switching time.
• Integrated Control The X-LSM’s integrated controller joined the same power and data daisy-chain as the other microscope modules. This simplified the setup and control of the hardware.
• Broad Compatibility: The modular design maintains compatibility with industry-standard objectives from Mitutoyo, Zeiss, Nikon, and Evident.

Our product customization team is able to complete most customizations within a two-week period. Contact us with your requests.