Pingyu Tang

H-PDLC based waveform controllable optical choppers for FDMF microscopy

An electrically waveform controllable optical chopper based on holographic polymer dispersed liquid crystal grating (H-PDLC) is presented in this paper. The theoretical analyses and experimental results show that the proposed optical chopper has following merits: (1) controllable waveform, (2) no mechanical motion induced vibrational noise, and 
(3) multiple-channel integration capability. The application of this unique electrically controllable optical chopper to frequency division multiplexed fluorescent microscopy is also addressed in this paper, which has the potential to increase the channel capacity, the stability and the reliability. This will be beneficial to the parallel detection, especially for dynamic studies of living biological samples.

Experiments and quantitative analysis of frequency division multiplexing confocal fluorescence microscopy with UV excitation

In this paper, we experimentally demonstrated a two‐channel frequency division multiplexing confocal fluorescence microscopy system using a UV laser as the excitation source. In our two‐channel frequency division multiplexing confocal fluorescence system, the incoming laser beam was divided into two beams and each beam was modulated with an individual carrier frequency. These two laser beams were then spatially combined with a small angle and focused into two diffraction‐limited spots on the targeted cell (rat neural cell) surface to generate fluorescent signal. As a result, the fluorescent signals from two spots of the rat neural cell surface can be demodulated and distinguished during data processing. Furthermore, a quantitative analysis on the cross‐talk among different frequencies was provided as well. The experimental results confirm that the two‐channel frequency division multiplexing confocal fluorescence technology can not only maintain the high spatial resolution, but also realize the multiple points detection simultaneously with high temporal resolution (within millisecond level range), which benefits the dynamic studies of living biological cells.

A four-channel frequency division multiplexed fluorescent microscope modulated by holographic polymer dispersed liquid crystal grating array

A four-channel frequency division multiplexed fluorescent microscope (FDMFM) modulated by holographic polymer dispersed liquid crystal (H-PDLC) grating array is presented in this paper. The four-channel H-PDLC grating array is developed and employed to generate frequency modulation. Fluorescent signals at four different locations on a rat neural cell have been successfully modulated with four different frequencies, collected by a single high-sensitivity photodetector, such as photomultiplier tubes, and distinguished by taking the Fourier transform of the detected sum signal. The experimental and simulation results agree well. The new system offers the advantages of (1) multiple channel modulation capability, (2) no mechanical noise and (3) flexible and controllable modulation profile (e.g. square wave, triangular wave, etc.). Thus this four-channel FDMFM system can be very helpful for studying fast-changing transient events in biological samples.

High-frequency H-PDLC optical chopper for frequency division multiplexing fluorescence confocal microscope system

The optical chopper array based on Holographic Polymer Dispersed Liquid Crystal (H-PDLC) working at high frequencies, for example 1KHz, 2KHz, and its application in an improved Frequency Division Multiplexed Fluorescence Confocal Microscope (FDMFCM) system are reported in this article. The system is a combination of the confocal microscopy and the frequency division multiplexing technique. Taking advantages of the optical chopper array based on H-PDLC that avoids mechanical movements, the FDMFCM system is able to obtain better Signal-Noise Ratio (SNR), smaller volume, more independent channels and more efficient scanning. Whats more, the FDMCFM maintained the high special resolution ability and realized faster temporal resolution than pervious system. Using the proposed device, the FDMFCM system conducts successful parallel detection of rat neural cells. Fluorescence intensity signals from two different points on the specimen, which represent concentration of certain kind of proteins in the sample cells, are achieved. The experimental results show that the proposed H-PDLC optical chopper array has feasibility in FDMFCM system, which owes to its unique characteristics such as fast response, simple fabrication and lower consumption etc. With the development of H-PDLC based devices, there will be prospective in upgrading FDMFCM systems performance in the biomedical area.