Display Refresh Research Articles

Model-based navigation of transcranial focused ultrasound neuromodulation in humans: Application to targeting the amygdala and thalamus

BackgroundTranscranial focused ultrasound (tFUS) neuromodulation has shown promise in animals but is challenging to translate to humans because of the thicker skull that heavily scatters ultrasound waves. ObjectiveWe develop and disseminate a model-based navigation (MBN) tool for acoustic dose delivery in the presence of skull aberrations that is easy to use by non-specialists. MethodsWe pre-compute acoustic beams for thousands of virtual transducer locations on the scalp of the subject under study. We use the hybrid angular spectrum solver mSOUND, which runs in ∼4 s per solve per CPU yielding pre-computation times under 1 h for scalp meshes with up to 4000 faces and a parallelization factor of 5. We combine this pre-computed set of beam solutions with optical tracking, thus allowing real-time display of the tFUS beam as the operator freely navigates the transducer around the subject’ scalp. We assess the impact of MBN versus line-of-sight targeting (LOST) positioning in simulations of 13 subjects. ResultsOur navigation tool has a display refresh rate of ∼10 Hz. In our simulations, MBN increased the acoustic dose in the thalamus and amygdala by 8–67 % compared to LOST and avoided complete target misses that affected 10–20 % of LOST cases. MBN also yielded a lower variability of the deposited dose across subjects than LOST. ConclusionsMBN may yield greater and more consistent (less variable) ultrasound dose deposition than transducer placement with line-of-sight targeting, and thus could become a helpful tool to improve the efficacy of tFUS neuromodulation.

58‐4: Late‐News Paper: Dynamic MTF Measurements of Gaming Monitors

Recent gaming monitors claim high refresh rates of ≥240 Hz with response times ≤1 ms. However, these temporal metrics do not clearly reveal their true spatiotemporal resolution, which depends on the velocity at which the images are displayed. This is the first study to demonstrate the line‐based dynamic modulation transfer function (MTF) measurement method for comparing the performances of different gaming monitors. A single line was scrolled on the monitors, and a small region of the screen was captured with a high‐speed camera during one display refresh period. The dynamic MTF results elucidate the dependence of spatiotemporal resolution characteristics on the scroll speed, refresh rate, and response time of the monitors.

Spatiotemporal image quality of virtual reality head mounted displays

Virtual reality (VR) head mounted displays (HMDs) require both high spatial resolution and fast temporal response. However, methods to quantify the VR image quality in the spatiotemporal domain when motion exists are not yet standardized. In this study, we characterize the spatiotemporal capabilities of three VR devices: the HTC VIVE, VIVE Pro, and VIVE Pro 2 during smooth pursuit. A spatiotemporal model for VR HMDs is presented using measured spatial and temporal characteristics. Among the three evaluated headsets, the VIVE Pro 2 improves the display temporal performance using a fast 120 Hz refresh rate and pulsed emission with a small duty cycle of 5%. In combination with a high pixel resolution beyond 2 k times 2 k per eye, the VIVE Pro 2 achieves an improved spatiotemporal performance compared to the VIVE and VIVE Pro in the high spatial frequency range above 8 cycles per degree during smooth pursuit. The result demonstrates that reducing the display emission duty cycle to less than 20% is beneficial to mitigate motion blur in VR HMDs. Frame rate reduction (e.g., to below 60 Hz) of the input signal compared to the display refresh rate of 120 Hz yields replicated shadow images that can affect the image quality under motion. This work supports the regulatory science research efforts in development of testing methods to characterize the spatiotemporal performance of VR devices for medical use.

헤드 마운티드 디스플레이를 위한 시간 제약 렌더링을 이용한 적응적 포비티드 광선 추적법

Ray tracing-based rendering creates by far more realistic images than the traditional rasterization-based rendering. However, it is still burdensome when implemented for a Head-Mounted Display (HMD) system that demands a wide field of view and a high display refresh rate. Furthermore, for presenting high-quality images on the HMD screen, a sufficient number of ray sampling should be carried out per pixel to alleviate visually annoying spatial and temporal aliases. In this paper, we extend the recent selective foveated ray tracing technique by Kim et al. [<xref ref-type="bibr" rid="B1">1</xref>], and propose an improved real-time rendering technique that realizes the rendering effect of the classic Whitted-style ray tracing on the HMD system. In particular, by combining the ray tracing hardware-based acceleration technique and time-constrained rendering scheme, we show that fast HMD ray tracing is possible that is well suited to human visual systems.

Asynchronous control and driver for high‐speed LED display with local scanning approach

This study presents an extendable full-colour light emitting diode (LED) display based on field-programmable gate array implementation. The LED display panel system includes memory management, image format conversion, serial parallel interface (SPI) interface, local scan techniques, LED driver and pulse width modulation (PWM) data control. To reduce I/O ports, data transmission system uses SPI interface to send the PWM data to the LED panels. A novel local scan technique, which could use a lower frequency for data transmission and achieve higher frame rate for LED display, is proposed. Each display module contains local memories for data self-scanning to LED. The display continues even if there is no new data input. The advantages are that the display rate does not care about the speed of data transmission. Only motion area, rather than complete frame, required sending data to display, which can greatly improve data bandwidth. This is very useful for high-resolution display system since even low data rate can achieve the fast display refresh. This approach is a module-based design, which can easily be extended to any size with auto re-configuration without using embedded processor.

The Effects of Adaptive Synchronization on Performance and Experience in Gameplay

Adaptive synchronization (Async) is a recent display technology that lowers frame time mean and variation by altering communication between display and GPU. While conventional graphics systems introduce delay to match irregular GPU frame rates to regular display refresh rates, Async systems instead match display refresh rates to to irregular frame rates. Both NVIDIA and AMD claim that Async displays improve experience for enthusiast gamers. In a first, controlled examination of these claims with non-professionals playing a popular first-person shooter, we find that Async improves gaming performance, can improve experience, and has intriguing relationships to game familiarity and years of gameplay.

Static Structures in Leaky Mode Waveguides

In this work, we suggest a new method of expanding the field of view in bottom-exit, leaky mode devices for transparent, monolithic, holographic, near-eye display. In this approach, we propose the use of static, laser-induced, grating structures within the device substrate to break the leaky mode light into diffracted orders. We then propose to use carefully timed illumination pulses to select which diffracted order is visible to the eye at every display refresh interval (up to 100 kHz). Each of these orders becomes a view for a different image point. To describe this new method, we use K-vector analysis. We give the relevant equations and a list of parameters which lead to a near-eye geometry with little or no overlap in higher-order view zones. We conclude that it should be possible to increase the field of view of our bottom-exit, leaky mode devices by as much as one order of magnitude by simply adding a laser-induced grating structure to the substrate and by carefully timing the device illumination. If successful, this method would make possible a transparent, holographic, near-eye display that is simple to fabricate, relative to pixelated approaches, and which has a wide field-of-view relative to our current bottom-exit displays.

A Quality-Centered Analysis of Eye Tracking Data in Foveated Rendering.

This work presents the analysis of data recorded by an eye tracking device in the course of evaluating a foveated rendering approach for head-mounted displays (HMDs). Foveated rendering methods adapt the image synthesis process to the user’s gaze and exploiting the human visual system’s limitations to increase rendering performance. Especially, foveated rendering has great potential when certain requirements have to be fulfilled, like low-latency rendering to cope with high display refresh rates. This is crucial for virtual reality (VR), as a high level of immersion, which can only be achieved with high rendering performance and also helps to reduce nausea, is an important factor in this field. We put things in context by first providing basic information about our rendering system, followed by a description of the user study and the collected data. This data stems from fixation tasks that subjects had to perform while being shown fly-through sequences of virtual scenes on an HMD. These fixation tasks consisted of a combination of various scenes and fixation modes. Besides static fixation targets, moving targets on randomized paths as well as a free focus mode were tested. Using this data, we estimate the precision of the utilized eye tracker and analyze the participants’ accuracy in focusing the displayed fixation targets. Here, we also take a look at eccentricity-dependent quality ratings. Comparing this information with the users’ quality ratings given for the displayed sequences then reveals an interesting connection between fixation modes, fixation accuracy and quality ratings.

Psychophysical Assessment of Perceptual Performance With Varying Display Frame Rates

This study assesses the impact of display refresh rate on the perception of dynamic visual stimuli in humans. A projection platform was developed in that context, allowing control of the frame rate on a trial-by-trial basis. Using this display, we introduce a series of psychophysical experiments aimed to quantitatively assess objective perceptual performance at different frame rates. Tasks that are often implicitly performed when watching movies on a television set, or when wearing a head mounted display, were chosen: speed discrimination, spatial discrimination, and reading abilities, with stimuli undergoing horizontal motion in a wide range of speeds ( $16-38\;\text{deg/s}$ ). The results show that whatever the stimuli or the task, performance is significantly better at high frame rate (HFR) compared to 60 Hz, providing clear-cut evidence that low refresh rates limit the ability to reliably analyze moving stimuli. These results extend those of previous psychophysical experiments performed at low refresh rates, further characterize genuine visual performance in humans and provide an objective benchmarking methodology allowing to assess visual performance with a variety of displays. Results indicate that for low resolution displays, where increasing spatial resolution is not an option, increasing frame rate could benefit motion perception. We discuss these results and their implications with regards to current and emerging categories of visual displays, such as head mounted displays.

Electrothermal Annealing (ETA) Method to Enhance the Electrical Performance of Amorphous-Oxide-Semiconductor (AOS) Thin-Film Transistors (TFTs).

An electro-thermal annealing (ETA) method, which uses an electrical pulse of less than 100 ns, was developed to improve the electrical performance of array-level amorphous-oxide-semiconductor (AOS) thin-film transistors (TFTs). The practicality of the ETA method was experimentally demonstrated with transparent amorphous In-Ga-Zn-O (a-IGZO) TFTs. The overall electrical performance metrics were boosted by the proposed method: up to 205% for the trans-conductance (gm), 158% for the linear current (Ilinear), and 206% for the subthreshold swing (SS). The performance enhancement were interpreted by X-ray photoelectron microscopy (XPS), showing a reduction of oxygen vacancies in a-IGZO after the ETA. Furthermore, by virtue of the extremely short operation time (80 ns) of ETA, which neither provokes a delay of the mandatory TFTs operation such as addressing operation for the display refresh nor demands extra physical treatment, the semipermanent use of displays can be realized.

Testing the accuracy of timing reports in visual timing tasks with a consumer-grade digital camera.

This study tested the accuracy of a visual timing task using a readily available and relatively inexpensive consumer grade digital camera. A visual inspection time task was recorded using short high-speed video clips and the timing as reported by the task's program was compared to the timing as recorded in the video clips. Discrepancies in these two timing reports were investigated further and based on display refresh rate, a decision was made whether the discrepancy was large enough to affect the results as reported by the task. In this particular study, the errors in timing were not large enough to impact the results of the study. The procedure presented in this article offers an alternative method for performing a timing test, which uses readily available hardware and can be used to test the timing in any software program on any operating system and display.

빠른 갱신속도의 변화가 상호작용 정확도에 미치는 영향에 관한 연구

본 논문에서는 시각적 피드백을 중심으로 하는 상호작용 시스템에서 화면 갱신속도와 상호작용 정확도의 상관관계를 다룬다. 일반적으로 인간의 시각인지 한계점은 초당 60프레임으로 생각되고 있으나, 본 연구에서는 이보다 높은 갱신속도가 사용자의 상호작용 정확도에 미치는 영향에 대해 알아보고자 한다. 실험을 통해 초당 60프레임 이상의 갱신속도에서도 상호작용 정확도는 증가함을 알 수 있었다. 이러한 결과에 영향을 준 원인을 이미지 렌더링 갱신속도와 사용자 입력 갱신속도 두 가지로 추정하여 이를 확인하기 위한 추가실험을 진행하였다. 비록 모니터의 화면 재생률이 초당 60프레임으로 되어있었지만 vertical sync를 사용하지 않음으로써 그 이상의 갱신속도와의 차이를 느낄 수 있었다. 실험결과를 통해 사용자 입력 갱신속도보다 이미지 렌더링 갱신속도가 상호작용 정확도에 더 큰 영향을 줌을 확인하였다. 본 연구는 상호작용 정확도를 높이기 위해 더욱 높은 갱신속도의 필요성을 제기하며, 인간의 시각인지 한계점은 초당 60프레임 이상이 될 수 있음을 보인다.

Using a High-Speed Movie Camera to Evaluate Slice Dropping in Clinical Image Interpretation with Stack Mode Viewers

The purpose of this study is to verify objectively the rate of slice omission during paging on picture archiving and communication system (PACS) viewers by recording the images shown on the computer displays of these viewers with a high-speed movie camera. This study was approved by the institutional review board. A sequential number from 1 to 250 was superimposed on each slice of a series of clinical Digital Imaging and Communication in Medicine (DICOM) data. The slices were displayed using several DICOM viewers, including in-house developed freeware and clinical PACS viewers. The freeware viewer and one of the clinical PACS viewers included functions to prevent slice dropping. The series was displayed in stack mode and paged in both automatic and manual paging modes. The display was recorded with a high-speed movie camera and played back at a slow speed to check whether slices were dropped. The paging speeds were also measured. With a paging speed faster than half the refresh rate of the display, some viewers dropped up to 52.4% of the slices, while other well-designed viewers did not, if used with the correct settings. Slice dropping during paging was objectively confirmed using a high-speed movie camera. To prevent slice dropping, the viewer must be specially designed for the purpose and must be used with the correct settings, or the paging speed must be slower than half of the display refresh rate.

13.3: Monochromator‐Based Transient Spectroradiometric Measurements of a Display's Refresh Cycle

AbstractThis paper describes an accurate and economical method of measuring the transient spectroradiometric properties of a display refresh cycle. Spectral data is collected from narrow bandwidths and synchronised using an independent optical input channel. This time resolved spectral data will facilitate research into visual perception of pulsed displays.

A Shared-Aperture Tracking Display for Augmented Reality

The operation and performance of a six degree-of-freedom (DOF) shared-aperture tracking system with image overlay is described. This unique tracking technology shares the same aperture or scanned optical beam with the visual display, virtual retinal display (VRD). This display technology provides high brightness in an AR helmet-mounted display, especially in the extreme environment of a military cockpit. The VRD generates an image by optically scanning visible light directly to the viewer's eye. By scanning both visible and infrared light, the head-worn display can be directly coupled to a head-tracking system. As a result, the proposed tracking system requires minimal calibration between the user's viewpoint and the tracker's viewpoint. This paper demonstrates that the proposed shared-aperture tracking system produces high accuracy and computational efficiency. The current proof-of-concept system has a precision of +/− 0.05 and +/− 0.01 deg. in the horizontal and vertical axes, respectively. The static registration error was measured to be 0.08 +/− 0.04 and 0.03 +/− 0.02 deg. for the horizontal and vertical axes, respectively. The dynamic registration error or the system latency was measured to be within 16.67 ms, equivalent to our display refresh rate of 60 Hz. In all testing, the VRD was fixed and the calibrated motion of a robot arm was tracked. By moving the robot arm within a restricted volume, this real-time shared-aperture method of tracking was extended to six-DOF measurements. Future AR applications of our shared-aperture tracking and display system will be highly accurate head tracking when the VRD is helmet mounted and worn within an enclosed space, such as an aircraft cockpit.

Aircraft vibration and the readability of an electronic flight instrument display

An advanced turboprop aircraft encountered icing conditions in flight and developed severe airframe vibration during which the pilot observed image break-up on the Electronic Flight Instrument System (EFIS) display. This effect was investigated using whole body, hand transmitted and direct head vibration. When vibration was applied directly to the head, the reported pattern of EFIS image break-up was observed if the vibration frequency was close to the display refresh frequency. It was concluded that vibration had caused retinal image motion, and that the observed effect occurred because spatially adjacent components of the display were written at separate times within the refresh cycle.

A reliable low-cost graphic system

The MERELIN display is a two-card system on the S100 bus. The display memory is provided from the normal memory on a separate S100 card. Therefore the memory is direct available to the CPU (display refresh is done by DMA). The MERELIN display allows several modes for different resolutions, the maximum resolution being 320 points × 200 points. This means an extern refresh memory of 8 K bytes. The MERELIN will be replaced by a Vektor Graphic Display with an internal refresh memory (the CPU makes DMA) and a resolution of 256 × 240, or 128 × 120 with a grey scale.

New Concepts in Display Technology

As the number of processing applications and users increases, so does the need for a low-cost processing system. This paper describes an approach to the implementation of a solid-state display which provides the nucleus for such a system. Combining a powerful display with modern random access memory refresh technology, the system features a unique image array processor in which entire images, instead of single pixels, may be manipulated and displayed arithmetically at video frame rates. Built on a modest budget around an LSI-11 microprocessor (see Figure 1), this system can nevertheless provide complete processing capabilities, using the display's refresh memories for temporary storage (in lieu of magnetic disk devices).

An introduction to computer graphic terminals

The purpose of this paper is to introduce the reader to some of the fundamental hardware and software aspects of typical CRT display consoles. Techniques for accomplishing display refresh are explained. The evolution of the CRT controller, from a device which simply includes a pair of digital-to-analog converters to a system which is a rather sophisticated, special-purpose hybrid processor (including analog function generators and digital control logic), is developed. Means by which a user generates display processor interrupts, particularly those associated with graphic input devices, are described. The use of electronic "pens" for user interaction with a display is then explained. Finally, the software structure for a typical graphic processor is discussed from a functional point of view. The linkage between a high-level symbolic picture description and the CRT "machine language" display file, via a set of generation subroutines, is described. The calling of picture modification programs by an interrupt analysis routine is also explained. Reasons for the need of a linked-list data structure are presented.