• Acta Photonica Sinica
  • Vol. 51, Issue 5, 0551313 (2022)
Shiyao TANG, Junshuai YAN, Jiajun XIE, Binglin SHEN, Wenhui YU, Yanping LI, Rui HU, Junle QU, and Liwei LIU*
Author Affiliations
  • College of Physics and Optoelectronic Engineering,Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education/Guangdong Province,Shenzhen University,Shenzhen,Guangdong 518060,China
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    DOI: 10.3788/gzxb20225105.0551313 Cite this Article
    Shiyao TANG, Junshuai YAN, Jiajun XIE, Binglin SHEN, Wenhui YU, Yanping LI, Rui HU, Junle QU, Liwei LIU. High Spatiotemporal Resolution System for Selective Optical Stimulation Based on DMD[J]. Acta Photonica Sinica, 2022, 51(5): 0551313 Copy Citation Text show less

    Abstract

    The optical stimulation system provides an important tool for light regulation, which modulates stably the optical waves to stimulate the target under investigation. In order to regulate vital movement precisely on cellular scale, scientists have developed various high-resolution optical stimulation systems. Traditional light stimulation methods include full-field light illumination, optical fiber illumination and galvanometer scanning illumination,etc. These methods can not accurately stimulate a single neuron in a specific area due to the lack of flexibility in spatial selection. Using Digital Micromirror Device (DMD) to project the target pattern on the sample plane greatly improves the spatial selectivity of the light stimulation system, but it has the disadvantage of low light energy utilization. Holographic light scanning allows not only complex selective light stimulation, but also achieves high spatial resolution and efficient light utilization.In this article, we embarked from computational holography and Dammann grating generation, and proposed a method of selective point-by-point stimulation with high spatiotemporal resolution based on a DMD. First, the structure transformed Dammann gratings generated by computational holography were loaded on the DMD. Then, the light modulated by the Dammann gratings stimulated the 2D target area point-by-point. The wide spectrum light from a halogen source was filtered by a 650/40 nm bandpass filter. An annular iris was placed in front of a condenser to realize dark field microscopy. We used LabView to complete the synchronization control and user interface display. The control algorithm first performs threshold to the dark-field images acquired by the sCMOS. Dammann grating phase diagrams was then calculated from stores the pixel coordinates with value of 1.Due to the working characteristics of DMD, the collimated 473 nm laser needs to be incident on the chip surface at 24°. DMD located on the front focal plane of the Fourier transform lens (f=200 mm) can produce a diffraction spot on the rear focal plane of the lens, and then a square diaphragm with adjustable aperture placed on the Fourier plane retains only one first-order diffraction spot as the scanning point. The tube lens (f=200 mm) and the objective lens (M=20×?) form a 4f system to make the scanning point conjugated to the sample surface for scanning light stimulation.We use Rhodamine A indicator to image the scanning path. The maximum scanning field is 400 μm×400 μm, the minimum scanning step is 0.204 μm, and the minimum half-height width of a single point peak is 1.5 μm. We proved that the system can not only scan the full field of view point by point in different scanning mode (such as square lattice, circle, spiral, etc.), but can also scan point by point through a custom path in Region of Interest (ROI). The maximum scanning speed is 10 kHz. We also proved that the system can clearly scan complex patterns on homogeneously-stained cancer cells in a transcellular manner under 10× objective.In this article, we present a selective light stimulation system, which used DMD to deliver light to specified targets with high spatiotemporal resolution. We also completed the experimental verification of the system functions: 1) it can perform optical stimulation on the imaging plane with arbitrary scanning mode; 2) it can perform point-by-point light stimulation on the ROI; 3) it can scan complex patterns on homogeneously-stained cells. The system is suitable for biomedical scientific research that requires optical stimulation on samples with high spatial resolution or real-time stimulation on ROI. For example, in optogenetics, the study of the contribution of single neuron in the entire neural circuit. On the basis of this system, adding a motorized stage can realize the real-time optogenetic research in freely moving organism. In terms of holographic projection, feedback algorithms such as G-S iteration can be applied to the system to realize the integration stimulation of regional light mode and selective point-by-point mode. In addition, combined with calcium imaging, two-photon microscopic imaging and other technologies, it can also obtain more microscopic neuronal activity information in real time, and analyze organism behaviors more effectively.
    Shiyao TANG, Junshuai YAN, Jiajun XIE, Binglin SHEN, Wenhui YU, Yanping LI, Rui HU, Junle QU, Liwei LIU. High Spatiotemporal Resolution System for Selective Optical Stimulation Based on DMD[J]. Acta Photonica Sinica, 2022, 51(5): 0551313
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