Speckle Limited, Multiwavelength, Laser Imaging Probe

Narrow band laser excitation of fluorescence markers via de-speckled collinear 638nm/520nm beams within a temperature controlled ultra-small form factor.

The Challenge

Design a highly stable, multiwavelength, speckle reduced, laser probe for biomedical fluorescence imaging. Laser-induced fluorescence imaging requires high spot homogeneity, wavelength stability, and accurate coalignment of multiple beams. Highly homogenized illumination at the imaging plane (minimum signal variation across pixels) necessitates active speckle reduction.

• Wavelength drift < ±0.25nm, < 0.5% power stability.
• Camera pixel noise due to laser speckle < 0.4%, illumination field intensity variation < 20%.
• 5µm coalignment of two beams at imaging plane, pointing stability drift at imaging plane <1µm.
• Ultra-small form factor

Our Solution

In collaboration with our end customer, DLC designed an innovative Speckle Limited, Multiwavelength, Laser Imaging Probe, meeting the demanding optical characteristics within a small form factor.

• Embedded active speckle reduction via spatial decoherence using vibrating diffuser.
• Computer simulated optical ray tracing yielding a short path length beam combining/shaping. method of the red (638nm) and green (520nm) diode emissions.
• TEC thermal management of the laser package for wavelength, pointing, and power stability.
• Custom packaging and mounting mechanics for seamless integration into customer’s end-system.

How It Works

All necessary optical, thermal, and electrical components are housed within a compact rectangular volume, with the only significant protrusion being the heat sink for the internal TEC.

• 60mW, 638nm and 520nm single mode diodes.
• Embedded vibrating diffuser yields < 0.4% camera pixel speckle.
• < 0.1°C laser diode temperature stability via imbedded TEC maintains wavelengths within ±0.25nm.
• A dichroic filter and cylindrical lenses combined and shape the diode emissions.
• DLCs’ advanced optical alignment techniques ensures high collinearity and pointing accuracy.
• Custom designed PCBA’s for logic control of internal electro-optic components.
• Very compact finished package, 35mm x 46mm x 46mm.

 

Applications

Unique electro-optic performance residing within this small package makes it well suited for both scientific and commercial applications.

• Biomedical Instrumentation
• Laser Speckle Contrast Imaging (LSCI)
• Fluorescence Spectroscopy