Fast two-photon neuronal imaging and control using a spatial light modulator and ruthenium compounds

A new high-speed driver has been developed for the magneto-optic spatial light modulator (SLM). The driver allows the output of an image sensing device such as a CCD array to drive the SLM. Using digital circuitry, high frame rates are made possible. Furthermore, the digital nature of the interface allows real-time digital image processing to be performed on input imagery; the input image can be processed by a 3 X 3 kernel. For example, functions such as noise filtering, edge detection, or thresholding can be performed in real-time. Adaptive filters or multiple filter operations on the same data are also possible. Processed imagery can be displayed on the SLM at over 400 frames/second. In addition, the interface can be applied to other electrically-addressed SLMs. The potential for higher frame rates is possible with faster electronic components.

The digital micromirror device DMD is widely used in visible light projection, special-purpose spatial light modulation, and infrared scene simulation, due to its high resolution, uniformity and energy concentration. In some applications that require high frame rate scene image display, it is necessary to ensure that the DMD displays high gray level images at a high frame rate. However, the display frame rate of the pulse width modulation (PWM) method is limited by the minimum time required for DMD loading data, unable to achieve high frame rate display. Although the DMD binary display mode can meet the requirements of high frame rate display, it cannot meet the requirements of high gray level. The paper proposes an image display method that uses light source and DMD to synchronize modulation. Decompose the high-order gray image into bit planes according to the gray threshold, and the DMD displays each bit plane in binary mode under the trigger of an sync pulse. The intensity of the illumination laser source is modulated by an acousto-optic modulator to match the bit plane and the radiated laser power. This method makes use of the function of high frame rate display in DMD binary mode cooperate with light intensity modulation of illumination laser source, and realizes high frame rate and high dynamic range image display. With this method, the maximum frame rate of 8-bit gray level image with 1920 ×1080 resolution can reach 2KHz. The experimental system has realized 200Hz frame rate display of 8-bit gray level image with 1920 ×1080 resolution.

The purpose of this study was to assess whether or not high frame rate (HFR) videos recorded using high-speed digital imaging (HSDI) improve the visual recognition of the motions of the laryngopharyngeal structures during pharyngeal swallow in fiberoptic endoscopic evaluation of swallowing (FEES). Five healthy subjects were asked to swallow 0.5ml water under fiberoptic nasolaryngoscopy. The endoscope was connected to a high-speed camera, which recorded the laryngopharyngeal view throughout the swallowing process at 4000 frames/s (fps). Each HFR video was then copied and downsampled into a standard frame rate (SFR) video version (30 fps). Fifteen otorhinolaryngologists observed all of the HFR/SFR videos in random order and rated the four-point ordinal scale reflecting the degree of visual recognition of the rapid laryngopharyngeal structure motions just before the 'white-out' phenomenon. Significantly higher scores, reflecting better visibility, were seen for the HFR videos compared with the SFR videos for the following laryngopharyngeal structures: the posterior pharyngeal wall (p=0.001), left pharyngeal wall (p=0.015), right lateral pharyngeal wall (p=0.035), tongue base (p=0.005), and epiglottis tilting (p=0.005). However, when visualized with HFR and SFR, 'certainly clear observation' of the laryngeal structures was achieved in <50% of cases, because all the motions were not necessarily captured in each video. These results demonstrate the use of HSDI in FEES makes the motion perception of the laryngopharyngeal structures during pharyngeal swallow easier in comparison to SFR videos with equivalent image quality due to the ability of HSDI to depict the laryngopharyngeal motions in a continuous manner.

Charge coupled device(CCD) is one kind of photoelectric solid-state imaging device with excellent performance. It has the features of large array and good image quality. Working under very complex driving timing, it usually has low frame frequency and can not meet the demand of high imaging frame rate. The method of equivalent high frame rate imaging technique is introduced based on normal CCD in this paper. Some CCDs can be drived via electrodes separately. To meet the imaging demands of high frame rate, high resolution and high quality of two frame imaging technique for pulse light images, the right kind of CCDs should be adopted. The most important is that the CCD electrodes must be controlled directly and respectively. The charge transfer period is a key point while designing CCD driving timing for separate pulse light integration, charge package transfer and readout for two pulse light images. The validation experiments for the principle of equivalent high frame rate exposure of two pulse light images has been accomplished. It is shown that two pulse light images with interval of about 2 μs can be distinguished while all CCD’s inherent excellent performance are retained. A kind of two framing camera system with simple structure can be developed based on this principle.

In this paper, we report recent progress that has been made in the development of a high frame rate duplex HF ultrasound system with both B-scan imaging and Doppler flow measurements. A 32-channel HF analog beamformer module with transmitting focusing and dynamic focusing on reception was implemented. High-speed timing circuits were used to achieve high imaging frame rate by reducing the acquisition overhead. Therefore, the frame rate of the system relies only on the field of view. The system also included a 64-channel analog front-end pulser/receiver, a HF pulsed-wave (PW) Doppler module, a PC with a 200MS/s 14-bit PCI A/D card and real-time Labview software for data acquisition and image display. A wire phantom used to evaluate the resolution of the system. High frame rate B-scan images of mouse hearts have been obtained, as well as the PW Doppler blood flow velocity profiles at the specified location. The system is able to acquire real-time B-mode images at a rate greater than 400 frames per second in a 4.8 × 13 mm field of view. In vivo mouse experiment results show a promising future of this system in small animal research. The system will be expanded to support future arrays with more elements.

The use of flat panel detectors in computed tomography (CT) systems can improve resolution, reduce system cost, and add operational flexibility by combining fluoroscopy and radiography applications within CT systems. However, some prior studies have suggested that flat panel detectors would not perform well in CT applications due to their lack of high dynamic range, lag artifacts, and inadequate frame rate. The purpose of this study was to perform a physical evaluation of a prototype flat panel detector capable of high frame rates and extended dynamic range. The flat panel detector used had a pixel size of 194 microns and a matrix size of 2048x1536. The detector could be configured for several combinations of frame rate and matrix size up to 750 frames per second for a 512x16 matrix size with 4x4 binning. The evaluation was performed in terms of the MTF and DQE as a function of frame rate and exposure at the IEC RQA5 (~75 kVp, 21 mm Al) beam quality. The image lag was evaluated in terms of temporal-frequency dependent transfer function. Offset shift were also evaluated. Preliminary results indicate 0.1 MTF at 0.92 cycles/mm and DQE(0) of approximately 0.8, 0.6, 0.4, and 0.22 at 0.144, 0.065, 0.035, and 0.008 mR per frame exposures. The temporal MTF exhibited a low-frequency drop and a value of 0.5 at the Nyquist frequency. Offset shift was negligible. Considering high frame rate capabilities of the new detector, the results suggest that the detector has potential for use in real-time CT applications including CT angiography.

Current proposals for Advanced Television for the United States are based upon the premise that temporal and resolution layering are inefficient. These proposals therefore only provide a menu of individual formats from which to select, but each format only encodes and decodes a single resolution and frame rate. In addition, it is being suggested by some people that interlace is required, due to their claimed need to have one thousand lines at high frame rates, but based upon the notion that such images cannot be compressed within the available 18mbits/second. — This paper discusses an approach to image compression which demonstrably achieves thousand line image compression at high frame rates with high quality. It also achieves both temporal and spatial scalability at this resolution at high frame rates within the available 18mbits/second. This technique efficiently encodes 2 MegaPixel images at 72 frames per second, achieving over twice the compression ratio being proposed by ACATS for advanced television. Further, this proposed technique is more robust than the current unlayered ACATS format proposal for advanced television, since all of the bits may be allocated to the lower resolution base layer when stressful image material is encountered. — Thus, a number of key technical attributes are provided by this proposal, allowing substantial improvement over the ACATS proposal. These improvements include: the replacement of numerous resolutions and frame rates with a single layered resolution and frame rate; no need for interlace in order to achieve a thousand lines of two million pixels at high frame rates: and compatibility with computer displays through the use of 72 frames per second.

This paper presents our implementation of a multi-view autostereoscopic 3D display system by using time-multiplexing approach, digital micro-mirror devices (DMD), and the optical Wedgereg. The whole system consists of three major parts: high frame rate DMD projector, an active shutter, and an optical Wedgereg. This research investigates and develops the approaches to interface and control DMDs at very high bit rates and ultra-high frame rates to drive a novel flicker-free 3D flat panel device, with a wide viewing area and without need of special viewing glasses or head-tracking system. It needs to design a digital interface circuit capable of receiving video image data in a conventional format and translating it into a form appropriate for display on a DMD light modulator. This approach differs from existing ones in that it facilitates the modulation of the DMD to achieve much high frame rates, though with a trade-off in greyscale resolution. The outcomes of this research will have the great potential for commercialising the autostereoscopic display systems

Structured light illumination has been used for several decades to extract three-dimensional information from surface topology. Most of the research and development has been in the light structuring methodology and the electronic processing while a unified theoretical description has been lacking. With the advent of programmable spatial light modulators having high frame rates, structured light illumination methods using spatial and temporal patterns are practical. We present structured light systems using spatial light modulation as communication systems and use communications theory in their description. This theory is applied to the specific method of successive binary light striping and the tradeoffs between surface encoding quality and processing speeds are discussed. Shannon's theorem of channel capacity provides an objective measure to evaluate some of these tradeoffs and compare a variety of different approaches to structured light illumination. Another result of our analysis is the unification of structured light projection with pattern recognition. Methods of image recognition using Fourier expansion via orthogonal pattern projection are presented. The results of this analysis establish some physical limitations which guide us to effectively utilize both the methodology and the technology applicable to both 3-D data acquisition as well as pattern recognition. Both numerical and experimental results are presented to demonstrate concepts.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The digital revolution changed film production and its aesthetics in many ways. Although motion is a defining feature of moving images, it is also one of their most problematic aspects because of blurred images or other signal processing artifacts. An artistic research project was conducted to test the effects of high frame rates (HFR) on visual perception. Typical camera movements were recorded in different frame rates (24 / 48 / 96 fps) to generate test sequences for a cinema experiment. 69 participants were measured with an SMI eye tracking device and a questionnaire in a within subjects design. The results show that the participants valued the higher image quality of HFR, but rated the standard frame rate as more realistic and indicated more presence. Moreover, HFR produced a higher number of fixations than the standard frame rate. Open questions for future research projects on HFR will be discussed.

Spatial light modulator (SLMs) based on liquid crystal displays as phase only modulators can be used as programmable, diffractive optics. The field of applications ranges from adaptive optics, beam shapers to beam splitters. The quality of the beam shapers, measured on basis of diffraction efficiency and beam uniformity are the main deficiencies of such optics.Over the years many improvement in the generation of the holographic phase mask could be accomplished, but in the application, deviations in the SLMs lead to a degradation of the optical quality. In this paper we present two methods, to measure and compensate for the inhomogeneity of the maximum phase range and the distortion of the wave front by distortions of the surface layer of the SLM. The presented method allows the calibration of the SLM inside the optical setup.We use an iterative algorithm to address sub-regions of the SLM and measure the diffraction efficiency depending of the phase difference in a binary grating. From this data we can create a spatial map for the phase calibration curve, thus improving the overall efficiency of the SLM.Spatial light modulator (SLMs) based on liquid crystal displays as phase only modulators can be used as programmable, diffractive optics. The field of applications ranges from adaptive optics, beam shapers to beam splitters. The quality of the beam shapers, measured on basis of diffraction efficiency and beam uniformity are the main deficiencies of such optics.Over the years many improvement in the generation of the holographic phase mask could be accomplished, but in the application, deviations in the SLMs lead to a degradation of the optical quality. In this paper we present two methods, to measure and compensate for the inhomogeneity of the maximum phase range and the distortion of the wave front by distortions of the surface layer of the SLM. The presented method allows the calibration of the SLM inside the optical setup.We use an iterative algorithm to address sub-regions of the SLM and measure the diffraction efficiency depending of the phase difference in a binary grating. From this data we can cre...

We demonstrate a binocular holographic display with an amplitude‐only spatial light modulator (SLM), which enables us to display a 3D scene with much higher frame rate than the case of a conventional stereoscopic 3D. Instead of dividing either frames or pixels for assigning the left and right images, we divide the space near pupils by modulating the phase of a computer generated hologram.

In accordance with advances in camera technology, the requirement of high-quality video has greatly increased. Among the factors required for high-quality video are a high-resolution and a high frame rate. However, the limitation of the pixel transfer rate restricts compatibility of a high-resolution and a high frame rate in commercial camera. We propose a dual-sensor camera that consists of two cameras: one with a high-resolution and a low frame rate and the other with a low-resolution and a high frame rate. The system is capable of capturing two different image sequences: high-resolution images and high-frame-rate images. A sensor calibration for the dual-sensor camera is also proposed.

Fast color Doppler imaging (CDI) based on plane wave excitation and angle compounding is useful for evaluating vascular diseases with high frame rates. Due to limited spatial resolution from plane wave excitation, the image quality of CDI is substantially degraded. To enhance the spatial resolution, angle compounding, in which several tiled plane waves are excited and coherently summed together during receive beamforming, can be used. However, the effect of angle compounding on fast CDI has not been extensively analyzed. In this paper, the analysis of angle compounding on fast CDI with phantom studies is presented. To evaluate the effect of the angle compounding, in this paper, a new color Doppler imaging technique based on sliding angle compounding (CDI-SAC) is adopted. In CDI-SAC, the angle compounding is updated as each new angle compounding is acquired so that there is no reduction in both Doppler pulse-repetition frequency (PRF) and frame rate. For that reason, the CDI-SAC method is used for the analysis of angle compounding on fast CDI. The PRF of 2 kHz and four different sets of compounding angles (i.e., 3, 6, 8 and 12) were used for generating a color Doppler image. The results of each angle compounding from CDI-SAC shows improved hemodynamic representation as the number of combined angle increases. The measured root mean square errors (RMSEs) for three angle sets (3, 6, and 8) by assuming the 12 angle set as the reference are 0.0124, 0.0107 and 0.0082, respectively. These results indicate that the proper selection of the number of angles in fast color Doppler imaging is important for improving spatial resolution while reducing the blocky artifacts.

Two-photon microscopy is often performed at slow frame rates due to the need to serially scan all points in a field of view with a single laser beam. To overcome this problem, we have developed two optical methods that split and multiplex a laser beam across the sample. In the first method a diffractive optical element (DOE) generates a fixed number of beamlets that are scanned in parallel resulting in a corresponding increase in speed or in signal-to-noise ratio in time-lapse measurements. The second method uses a computer-controlled spatial light modulator (SLM) to generate any arbitrary spatio-temporal light pattern. With an SLM one can image or photostimulate any predefined region of the image such as neurons or dendritic spines. In addition, SLMs can be used to mimic a large number of optical transfer functions including light path corrections as adaptive optics.