Slide 1 Slide 2 Slide 3 Slide 4 Slide 4 Slide 4 Slide 4

New Results by Dr. Meng Cui at HHMI Using Segmented 492-DM

Posted by Angelica Perrone on Fri, Oct 17, 2014 @ 11:00 AM

Tags: deformable mirror, adaptive optics, boston micromachines, resolution, biological imaging, deep tissue microscopy, Howard Hughes Medical Institute, Janelia Farm Research Campus, SLM, spatial light modulator, BMC, imaging systems, two photon, fluorescence, segmented, microscopy

Segmented 492-DMDr. Meng Cui at the Howard Hughes Medical Center has recently pioneered Super Penetration Multi-Photon Microscopy (S-MPM) at the Cui Lab. He has successfully reported on focusing light through static and dynamic strongly scattering media using our segmented 492-DM (See more on the application here). By using the iterative multi-photon adaptive compensation technique (IMPACT), he since reported new results on in vivo fluorescence microscopy, providing a unique solution to noninvasive brain imaging. I HIGHLY encourage everyone to read his paper for in depth details of his technique here.

As of today, IMPACT has been the only technique used for in vivo microscopy. Due to the complicated wavefront distortion encountered in highly scattering biological tissue, IMPACT has the highest success rate in enabling neuron imaging through intact skulls of adult mice. Through Dr. Cui's testing, he has proven that even with the unpredictable motion of awake mice, IMPACT using the segmented 492-DM were able to perform wavefront measurements and improve the image quality.

Dr. Cui used the BMC segmented 492-DM as both the wavefront modulation and correction device. The IMPACT measurement works by splitting the DM’s pixels and running parallel phase modulation with each actuator at a unique frequency. Modulating only a portion of the pixels while keeping the rest stationary, a linear phase shift is then used as a function of time over the entire 2π phase range. The unique modulation frequency then becomes the unique phase slope value.  At the end of the modulation, a Fourier transform is used in IMPACT to determine the correction phase values. Dr. Cui then goes on to explain in detail how to determine what fraction of the pixels should be modulated, how to split the pixels into two evenly distributed groups and how the Nyquist-Shannon sampling theorem is integrated.

The imaging starts by setting the laser beam at the point of interest. The parallel phase modulation begins at one half at a time. As the measurement progresses, the laser focus becomes stronger, and laser power is gradually reduced to preserve the fluorescence signal from the sample. At the conclusion of the measurement, the compensated wavefront is displayed on the DM, and laser scanning in a conventional scope is begun. Figure 1 below shows the test setup for the experiment.

Meng Cui multiphoton microscopy test bed

Figure 1. Setup of the multiphoton microscope integrated with IMPACT. 

Dr. Cui used IMPACT for imaging the dendrites and spines of layer 5 pyramidal cells, in vivo at 650-670um under the dura in the mouse S1 cortex. In Media 1 below, you can see they are hardly resolvable with system correction only. In Media 2, you can see the dendrites and spines are clearly determined when full compensation has been applied.

 

Meng Video media 2Meng Video media 3Media 1. Hardly resovable dendrites and spines        Media 2. Resolved dendrites and spines

 

For the first time, IMPACT enabled in vivo two-photon fluorescence imaging through the intact skull of adult mice.  The technique also improved the fluorescence signal by a factor of ~20, along with overall resolution and contrast, this has proven to be a much greater adaptive optics imaging method than any other before. Dr. Cui also concluded that through these experiments, he found it worked well for awake, head-restrained animal imaging, providing a new and innovative solution for noninvasive studies of the mouse brain.

For more information on research going on at the Cui Lab, click here.

If you are interested in finding out more information on how the segmented 492-DM can help you achieve fluorescent imaging, please contact us here!

Improved Two Photon-Imaging Through Laser Pulse Compression with the Linear Array DM

Posted by Michael Feinberg on Fri, Dec 07, 2012 @ 09:05 AM

Tags: boston micromachines, Howard Hughes Medical Institute, Janelia Farm Research Campus, BMC, two photon, fluorescence, microscopy, laser pulse compression

In our last blog post (Fast and Precise Laser Pulse Compression with the Linear Array DM) we discussed research being done in the Cui Lab at HHMI’s Janelia Farm Research Campus that used our Linear Array DM for laser pulse compression.  In part two we examine a two photon fluorescence microscopy project led by associate Reto Fiolka at Janelia Farm that illustrates the use of the Linear Array’s potential as a pulse compressor for imaging applications using the phase resolved interferometric spectral modulation (PRISM) optimization technique.

The Linear Array pulse compressor setup was used to restore the laser pulse to its transform limited state, thus improving the ability to excite fluorescence by two photon absorption. A sample consisting of 10 micron diameter fluorescence beads (emission: 465 nm) was prepared and spread on a cover-slip. The laser beam first propagated through the pulse compressor and was subsequently focused on the sample using a 20X NA 0.5 Nikon objective. A 2D image was obtained by translating a motorized sample stage. Without spectral pulse shaping, only a weak fluorescence signal could be obtained (See figures a and c). Since the objective adds significant additional dispersion to the laser pulse, the spectral phase correction that had been determined previously using the photodiode could not be used. Therefore PRISM optimization was repeated using the fluorescence signal coming from the beads itself as a feedback signal.

Janelia Farm’s results show a dramatic increase in fluorescence signal for the optimized spectral phase (see figures b and d). The signal strength was increased by a factor of ~6.5

twophoton microscopy resized 600

 

According to Fiolka, “The tested device represents a promising alternative to liquid crystal displays, since the MEMS technology enables high filling factor, high efficiency and operation speed, exceptional phase stability and accuracy and can be used over a very broad wavelength spectrum.”

We're very excited about these results and we are currently working with other groups interested in reproducing these results on tissue samples.  Thanks again to Dr. Fiolka and the Janelia Farm group for their efforts in improving two photon imaging techniques!!

More details can be found in our Linear Array white paper which includes an application overview of this exciting project.  You can also link to the research directly using the links to the Cui Lab and the scientific publication above.

Fast and Precise Laser Pulse Compression with the Linear Array DM

Posted by Michael Feinberg on Wed, Nov 07, 2012 @ 10:33 AM

Tags: deformable mirror, adaptive optics, boston micromachines, laser science, Janelia Farm Research Campus, microscopy, laser pulse shaping, ultrafast lasers

Linear ArrayUltrafast lasers have been extensively used in ground breaking  research including two Nobel Prizes.  Applications within spectroscopy, photochemistry, laser processing and microscopy are widespread.  However, to capitalize on such short laser pulses, a pulse compressor is required to compensate for the dispersion induced by optical elements. Liquid crystal based spatial light modulators are most commonly used in laser pulse compressors.  Although a proven technology in display applications, liquid crystals have drawbacks including phase jitter and a limited fill factor.  Researchers at the Cui Lab at HHMI’s Janelia Farm Research Campus looked to Boston Micromachines Corporation’s prototype Linear Array Deformable Mirror (DM) to address these challenges.

To evaluate the performance of the pulse compressor, the laser pulses were analyzed with frequency resolved optical gating (FROG) using a commercial instrument (Grenouille, Swamp Optics, Atlanta, GA). In Figure a and b, the temporal and spectral profile of the pulse is shown when a flat wavefront is displayed on the DM. Evidently, the pulse is distorted and the spectral phase is not flat at all (a flat spectral phase is required for a transform limited pulse). Next, the beam returning from the pulse compressor was focused with a concave mirror onto a GaAsP photodiode and the resulting nonlinear signal was used as a feedback for the correction algorithm. After optimization using a technique called Phase resolved interferometric spectral modulation (PRISM), the temporal profile (Figure c) shows a dramatically shorter, Gaussian shaped pulse. The spectral phase is perfectly flat (Figure d) with less than 0.01 radians phase error and is stable in time. These results suggest that the precision and stability of the Linear Array DM allows close to perfect restoration of transform limited laser pulses.  For more information on the optimization technique, you can access a scientific publication here.

 

 pulse compression, FROG, pulse shaper

 

In our next blog post, we will discuss the results of the use of the Linear Array DM in an interesting two-photon microscopy experiment.

More details can be found in our Linear Array white paper which includes a more detailed description of this application.

Dr. Meng Cui of HHMI Discusses Deep Tissue Microscopy Technique

Posted by Michael Feinberg on Wed, Aug 01, 2012 @ 02:39 PM

Tags: deformable mirror, adaptive optics, biological imaging, deep tissue microscopy, Howard Hughes Medical Institute, Janelia Farm Research Campus

hhmi logo

Our customers are constantly making exciting scientific discoveries and we’re proud of the part our deformable mirrors play in their research. Dr. Meng Cui, Lab Head at Howard Hughes Medical Institute, Janelia Farm Research Campus recently presented the Iterative MultiphotonAdvanced in Biological Photnics Adaptive Compensation Technique (IMPACT) that his team has developed for deep tissue microscopy at a webinar on “Advances in Biomedical Photonics”.  In Dr. Cui’s presentation he discussed IMPACT which utilizes iterative feedback and the nonlinearity of two-photon signals to measure and compensate wavefront distortion introduced in tissue.  He gave details on the imaging results on a variety of biological tissue including brain tissue through mouse skull and labeled  T cells inside lymph nodes and compared his team's technique with conventional adaptive optics methods.   For more details on Dr. Cui’s research you can view the entire webinar which was presented by Photonics Media at http://www.photonics.com/Webinar.aspx?WebinarID=21.  Details of the research can be downloaded from the following site: http://www.pnas.org/content/early/2012/05/09/1119590109.full.pdf