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Spatial uniformity of displayed luminance can vary widely between different makes and models of LCD, the major determinant of uniformity being the backlight scheme [34] (some older LCDs allowed VGA input and relied on built-in analog-to-digital conversion, also a potential source of noise). Two commonplace schemes are, first, direct backlighting, wherein a spatial array of light-emitting diodes (LEDs) and a diffuser screen sit behind the liquid crystal panel, and, second, edge illumination, wherein light emitted by a linear array of diodes at one of the display’s edges is spatially distributed via lightguide. We quantified the spatial uniformity of the CG247X by presenting low-, medium-, and high-luminance static test patches at nine display positions (Fig 2, inset) and using the LS-110 spot meter to measure the luminance of each patch. At each luminance tested, we calculated the grand average over all display positions, and divisively normalized measurements by that average. As illustrated in Fig 2, at medium- and high-luminance, the CG247X showed greater spatial uniformity than our consumer-grade LCD (Dell U2415b): for the CG247X, spatial variation was 5.1% at medium and 3.5% at high luminance, whereas for the U2415b, variation was 8.1% at medium and 8.5% at high luminance. The uniformity of the two displays was comparable at low luminance (CG247X, 27% versus U2415b, 17%). Prior to normalization, there were, as expected, marked differences between low-, medium-, and high-luminance measurements. For example, at display position 5 (Fig 2, inset) on the CG247X, low-luminance measurements ranged from 0.07 to 0.10 cd/m2, medium-luminance measurements ranged from 57.70 to 57.93 cd/m2, and high-luminance measurements ranged from 113.9 to 114.2 cd/m2 (Table 1). We also quantified spatial surround effects; using a tripod at 1 m, we measured displayed luminance at position 5 comparing large (1920-by-1200 pixels) and small (384-by-384 pixels) 100%-luminance patches. For CG247X, the mean of 10 large-patch measurements was 0.56 cd/m2 greater than that of 10 small-patch measurements (two-sample t-test, p < 0.01), i.e., an increase of 0.50%. For the U2415b, the increase was 0.71 cd/m2, i.e., 0.67% (two-sample t-test, p < 0.01).
In-plane switching (IPS) LCDs, like our CG247X and U2415b, enable larger viewing angles than older LCD technology (e.g., twisted-nematic displays) [23]. To do so, IPS displays interdigitate electrodes (see 23]. For the displays we tested, vendor-issued specifications state a viewing angle of 178 deg, however, in the absence of further details, that derived measure is difficult to assimilate. We measured displayed luminance as a function of viewing angle over a range of azimuth and elevation (±60 deg). We fit a circular von Mises function (Fig 3, the CG247X and U2415b performed comparably in this regard. For the CG247X, the FW90M was 28.6 deg (fitted parameters: α = 1.45, κ = 3.37) and 32.6 deg (α = 1.65, κ = 2.62) for azimuth and elevation, respectively. For the U2415b, the FW90M was 31.2 deg (α = 1.60, κ = 2.85) and 31.0 deg (α = 1.55, κ = 2.90) for azimuth and elevation, respectively. At high-luminance we made a reduced set of measurements, assuming rotational symmetry, varying azimuth or elevation from 0 to 60 deg. These additional measurements yielded similar FW90M estimates. This descriptive model can be used to select a viewing distance with tolerable attenuation due to viewing angle. For example, if the CG247X is viewed from 1 m, a stimulus presented at the top of the display’s vertical meridian (i.e., elevation = 9.2 deg) would, due to viewing angle, undergo luminance attenuation by a factor of 0.97.
We presented a large, static test patch, measuring luminance with the LS-110 spot meter near the display’s center. We used a turntable to rotate the display (
A common misconception among vision researchers and clinicians is that LCDs do not flicker (i.e., that LCDs are temporally uniform). In fact, there are two major sources of flicker that can affect a LCD: first, backlight flicker which usually occurs at temporal frequencies (e.g., 1000 Hz) well beyond the critical flicker fusion frequency (e.g., Elze & Tanner [24], and Ghodrati, Morris, & Price [35]), and, second, the so-called frame response which occurs at the refresh rate of the display (here, 60 Hz) [23, 36]. Frame responses are largely attributable to an LCD’s inversion scheme: a feature of modern displays wherein the polarity of the video signal voltage applied to the liquid crystal material is inverted from one video frame to the next. This inversion minimises long-term degradation, or aging, of the display by minimizing the DC voltage across the liquid crystal elements. Frame inversion schemes typically have fine spatial structure, on the scale of individual pixels, making them mostly imperceptible (e.g., dot inversion schemes [36]). We quantified the temporal uniformity of the CG247X by presenting (nominally) static test patches at display position 5 (Fig 2, inset) and using the linearized photodiode device to measure displayed luminance over time. At each of 11 luminances (0, 10, 20 … 100%) we made 10 one-second recordings, averaging the Fourier amplitude spectra of those 10 recordings. Fig 4 shows the average spectrum at each luminance. The spectra of the CG247X revealed a frame response comprising a 60 Hz component as well as harmonic components at integer multiples of 60 Hz. The response at 60 Hz varied non-monotonically in amplitude with the luminance of the static test patch, peaking at a luminance of 50%. However, the CG247X appeared free of backlight modulations. This absence of backlight modulations freed us of the consequences of said modulations (often desynchronized with the frame refresh signal) on increment/decrement transitions between luminances (see Fig 5 in [24]). The spectra of our consumer-grade LCD also revealed a frame response, as well as 1.2 kHz flicker, likely associated with the back light. This latter temporal nonuniformity increased linearly with the luminance of the static test patch.
We presented nominally static test patches at display position 5 (Fig 2, inset), measuring luminance with a linearized photodiode device. At each luminance (0, 10, 20 … 100%) we made ten 1-second recordings, deriving the Fourier amplitude spectrum for each. Each spectrum illustrated is the average of 10 spectra. For each display, we normalized spectra such that 1000 corresponds to the DC component at 50% luminance; therefore, a value of 5.0 corresponds to approximately 0.15 cd/m2. The spectra of the CG247X (upper) revealed a frame response, comprising a 60 Hz component and harmonic components at integer multiples of 60 Hz. This frame response varied non-monotonically in amplitude with the luminance of the static test patch, peaking between 40 and 50% luminance. The spectra of the U2415b (lower) also revealed a frame response, as well as 1.2 kHz flicker, the amplitude of which increased linearly with the luminance of the static test patch (amplitudes above 5.0 are not shown, arrowheads). For the U2415b, mains noise (50 Hz) was apparent at high-luminance. lum., luminance.
For each display, we verified that the frame response was optical and not related to any radiated electromagnetic noise: We used the oscilloscope to visualize the Fourier amplitude spectrum online. We then interposed opaque cardboard between the photodiode and display which caused the disappearance of the frame response. For the U2415b, we similarly verified that the 1.2 kHz response was optical.
In general, LCD response times—the duration of the rise or fall of a step from one luminance level to another—vary as a function of both step source and destination luminance. This nonlinear behaviour is owing largely to mechanisms of response time compensation (RTC) (e.g., the work of McCartney [25]), a feature of many modern LCDs designed to enhance video. RTC mechanisms speed luminance transitions by transiently altering the voltage applied to the liquid crystal associated with individual pixels (e.g., Fig 1 in [27]; Fig 5 in [24]). We measured the CG247X’s response times by presenting luminance steps—both increments and decrements—to the linearized photodiode device. Step source and destination took values 0, 25, 50, 75, or 100%. As illustrated in Fig 5, response times varied as a function of both luminance step source and destination. For example, stepping from 0% luminance to 25% luminance took 24.5 ms, stepping from 75% to 100% took 12.9 ms, and stepping from 25% to 0% took 8.1 ms. All of these steps are the same height, but response times differ markedly. Overall, the response times of our consumer-grade LCD were less than the CG247X response times. However, as we will illustrate below, faster is not better; although RTC mechanisms reduced the response times of our consumer-grade LCD, they contaminated displayed luminance with overshoot and undershoot artifacts which are problematic for many applications in clinical and experimental vision research, including the presentation of mean-modulated flicker. RTC mechanisms lower “black-white-black” and “grey-to-grey” response times, which are used to promote displays to the gaming community and other consumer markets.
(A) CG247X response times. The leftmost gray box (labelled “0%”) encompasses four points showing mean response times for transitions from source luminance = 0% to destination luminances = 25, 50, 75, and 100% (x axis). These rise times (upward triangles) decreased with increasing destination luminance. The gray box labelled “25%” shows mean response times of transitions from source luminance = 25% to destination luminances = 0, 50, 75, and 100%. The fall time (downward triangle), from 25% to 0% luminance, was less than the rise times. Overall, response times varied as a function of both source and destination luminance, as is generally expected of LCDs. We made 10 measurements at each source/destination luminance pair; error bars, where not obscured by symbols, mark the full range (from minimum to maximum) of these 10 measurements. (B) U2415b response times. Graphical conventions are as in A. Overall, U2415b response times were less than CG247X response times.
At the outset of this study, we made preliminary measurements similar to those illustrated in Fig 5. We noticed that rise and fall times straddling 50% luminance were approximately equal (e.g., rise time from 25% to 75% = 16.3 ms; fall time from 75% to 25% = 17.1 ms) which led us to wonder whether the CG247X could be used to display achromatic, mean-modulated flicker without the introduction of unworkable artifacts. To better determine the CG247X’s potential suitability for presenting mean-modulated flicker, and its susceptibility, or otherwise, to overshoot and undershoot artifacts typical of LCDs implementing RTC mechanisms, we presented mean-modulated flicker on both the CG247X and our consumer-grade display, using the linearized photodiode device to measure luminance over time. We used a flicker period of 20 frames (333.3 ms), and contrast ranging from 20 to 100%. As illustrated in Fig 6, the consumer-grade display’s luminance traces revealed overshoot and undershoot artifacts symptomatic of RTC. The CG247X’s luminance traces, however, appeared free of RTC artifacts. We used these traces to estimate response times specific to mean-modulated flicker, illustrated in Fig 7. Overall, CG247X rise and fall times were greater than those of our consumer-grade LCD. However, with the exception of 100% contrast, CG247X rise and fall times were approximately equal, indicating its potential suitability for presenting mean-modulated flicker.
Flicker period = 20 frames (333.3 ms), and contrast = 20 to 100% in increments of 20 as marked. At 40% contrast, the arrowheads show examples of luminance step source and destination as used in the computation of response times (Fig 7). For each display, we normalized traces to the luminance step destination at 100% contrast. For the U2415b, over- and undershoot are readily apparent at low and moderate contrast. The CG247X, however, shows exponential rise and fall, regardless of contrast.
To further determine whether the CG247X could be used to display achromatic, mean-modulated flicker without the introduction of unworkable artifacts, we presented flicker at frequencies ranging from 0.94 to 30 Hz and contrasts ranging from 20 to 100%. We used recorded traces (similar to those in Fig 6) to derive cycle-averaged luminance. In Fig 8, we illustrate how cycle-averaged luminance was approximately constant for all flicker frequencies, and for contrasts up to 80%. At 100% contrast, cycle-averaged luminance decreased with flicker frequency, indicating that, at full contrast, the monitor is not suitable for presenting mean-modulated flicker. Cycle-averaged luminance recorded from our consumer-grade LCD (Dell U2415b) varied as a function of flicker frequency at all contrasts tested; this variation is problematic for presenting achromatic, mean-modulated flicker. We also used CG247X traces to derive cycle-averaged r.m.s. luminance. In Fig 8, we illustrate how cycle-averaged r.m.s. luminance decreased with flicker frequency, indicative of loss of contrast. The consumer-grade LCD was affected by both changes in cycle-averaged luminance and loss of contrast.
We presented mean-modulated flicker at a range of flicker frequencies (0.94 to 30 Hz) and contrasts (20 to 100%). We used waveforms (e.g., Fig 6) recorded from the CG247X (A) to derive cycle-averaged luminance; we divisively normalized that derived measure using the cycle-averaged luminance of a “reference” waveform, that is, the response to contrast = 20% and flicker frequency = 0.94 Hz. This relatively low-contrast, low-frequency waveform was chosen as reference because it should be easily realized by both displays. For clarity, cycle-averaged responses for contrast = 40, 60, 80, and 100% are offset by -0.1, -0.2, -0.3, and -0.4 log units, respectively (arrowheads). As shown, cycle-averaged luminance was approximately constant for contrast = 20 to 80% at all flicker frequencies tested (0.94 to 30 Hz). At contrast = 100%, cycle-averaged luminance decreased with flicker frequency. Cycle-averaged luminance recorded from the consumer-grade U2415b (B) increased with flicker frequency at all contrasts tested. Graphical conventions are as in A. We used waveforms recorded from the CG247X (C) to derive cycle-averaged r.m.s. luminance; we divisively normalized that derived measure using cycle-averaged r.m.s. luminance of the reference waveform (20%, 0.94 Hz). As shown, at all contrasts tested (20 to 100%), cycle-averaged r.m.s. luminance decreased with flicker frequency, indicative of a loss of effective contrast. Cycle-averaged r.m.s. luminance recorded from the U2415b (D) revealed both increases and decreases to effective contrast with flicker frequency. Each symbol is the average of 10 measurements. (None of the data in panels C and D is offset.) We modeled cycle-average luminance and r.m.s. luminance on the CG247X as a causal exponential decay (Methods). This model comprised one free parameter, τ. For the illustrated fit (blue), τ = 6.6 ms. The red symbols in panel C (slightly offset rightward for clarity) show the result of a validation experiment (see
Taken together, Fig 8, and the traces used to derive the measures plotted there, indicated a simple relationship between nominal and displayed luminance on the CG247X, namely, that the latter was, simply, a low-pass-filtered version of the former. To test this hypothesis, we modeled the function transferring nominal luminance to displayed luminance as a causal, exponential decay (Methods). We optimized the single free parameter in this model, the time constant of the exponential decay (τ), by minimizing the sum of the squared error between the model-derived cycle-averaged mean luminance and cycle-averaged r.m.s. luminance, and those derived from the photodiode traces. For the CG247X, the fit is illustrated in Fig 8 (blue). There, the fitted parameter, τ, was 6.6 ms. To assess the fit to cycle-averaged luminance, we computed the root-mean-square error (RMSE) separately at each flicker contrast. For the CG247X, the RMSE was negligibly small for contrasts from 20 to 80% (ranging from 6.0e-4 to 6.3e-3 normalized units). At 100% contrast, RMSE was highest at 0.093. This simple model was a poor fit to the U2415b, not illustrated in Fig 8. For the U2415b, RMSEs were high, ranging from 0.04 at 20% contrast to 0.15 at 60% contrast. To assess the fit to cycle-averaged r.m.s. luminance, we calculated the square of Pearson’s correlation coefficient, R2, separately at each flicker contrast. For the CG247X, R2 was high, ranging from 0.9965 to 0.9999. As expected, the same calculation for the U2415b was consistent with a poor fit; at its worst, R2 = 0.03.
To quantify the nonlinearities associated with high-contrast, mean-modulated flicker, and to quantify temporal dependence between frames, we used a paired-pulse paradigm [37, 38]. We presented paired biphasic luminance pulses at position 5 (Fig 2, inset), systematically varying the inter-pulse interval, T (Methods). We used the measured responses to individual pulses to predict paired-pulse responses, and to model the display’s nonlinearities we subtracted each paired-pulse response from its prediction. Fig 9 shows the nonlinear behaviour of the CG247X and, for comparison, that of our consumer-grade LCD. In our CG247X, a nonlinear mechanism appeared to speed the transition between white and black (100% and 0% luminance, respectively; leftmost upper panel in Fig 9B). When paired pulses were separated by 16.67 ms or more (the three rightmost upper panels in Fig 9B where predicted and displayed luminance are approximately equal), the CG247X behaved linearly, that is, we saw no evidence of temporal dependence between frames. In our consumer-grade LCD, a nonlinear mechanism appeared to attenuate the transition to white (100% luminance; leftmost lower panel in Fig 9B). This attenuation reconciles with Fig 6 (lower), which shows marked overshoot at moderate contrast (e.g., 60% contrast, middlemost panel of Fig 6), but a near absence of overshoot at high-contrast (rightmost panel of Fig 6). Compared to the CG247X, the U2415b’s nonlinearities were large in magnitude and long-lasting. Paired pulses separated by as much as 33.33 ms (the third lower panel in Fig 9B, where predicted and displayed luminance are unequal) evoked nonlinear behaviour in the U2415b, that is, we saw clear evidence of temporal dependence between frames.
(A) Illustration of the paired-pulse paradigm. We presented a single biphasic luminance pulse (e.g., left panel), parametrically varying its latency relative to a trigger (cf. left and middle panels). We then presented a pair of biphasic luminance pulses (right panel), parametrically varying the offset between pulses comprising the pair, T = 0, 1, 2, and 3 times the frame period (frame period = 16.67 ms). Single-pulse responses can be used to predict the paired-pulse response; differences between this prediction and the displayed luminance model the display’s nonlinearities. (B) Nonlinear behaviour of the CG247X (upper). The four panels show responses to paired pulses with various offsets, T; we normalized responses (0, 0.5 and 1 corresponded to 0, 50 and 100% luminance, respectively) and then subtracted the baseline. For each offset, the predicted displayed luminance derived from single-pulse responses is shown in blue, and the measured displayed luminance in response to paired pulses is shown in black. The measured responses are an average of 16 recordings. The difference, that is, the nonlinearity, is shown in red. For the CG247X, superposition (T = 0 ms) of pulses evoked a nonlinearity which accelerated the transition from 100% luminance to 0% luminance. There was negligible nonlinearity of displayed lumiance for T > = 16.67 ms. Compared to the CG247X’s nonlinearity, the U2415b’s nonlinearity (lower panels) was large in magnitude and long-lasting, affecting subsequent frames (to T = 33.33 ms). Graphical conventions are as in B.
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At General Digital, we produce the finest rugged military displays available on the market for the U.S. Armed Forces and her allies. Every rugged monitor that we produce is uniquely equipped with highly specialized capabilities for use within tanks, armored personnel carriers, Humvees, submarines, aircraft carriers, helicopters, fighter jets and all types of land, marine, air, space and autonomous vehicle systems.
As innovators in the rugged display industry, we stay on top of the military"s ever-evolving mobile warfare approach to expertly answer the call for new, highly-advanced display technology, which includes:
These rugged LCD innovations continue to prove indispensable as the military continues its development of on-the-move intelligence systems, threat detection, surveillance and suppression operations. Therefore, every General Digital military-grade LCD monitor and ruggedized peripheral can be customized to meet the rigorous demands presented in the modern warfare theater.
General Digital"s reputation for going above and beyond military standards means we utilize in-house equipment for engineering, design, testing and validation of all of our rugged LCD displays.
General Digital designs and builds in the United States of America, so you know you’re getting robust and dependable flat panel military LCD monitors and accessories. Our monitors will last for years, long after the others have succumbed to the elements. Below is a list of our heavy-duty product line, which will suit just about any requirement you have. And if it doesn’t, we’ll build it for you.
TheTactical TwoViewand Tactical ThreeView are two of the first militarized workstations to supportvideo over USB-C, allowing power, video, and data to be handled over a singlecable—minimizing potential vulnerabilities and reducing maintenance time.General Digital developed a custom video controller to support this application,the first of its kind. It’s been futureproofed to allow for additional backlightingupgrades for sunlight/night readability and other enhancements.
This smart device features an integrated computer system designed to connectto a server through a gigabit Ethernet connection. As configured, the customizable computer allows two independent video feeds on the displays, and allowsthe keyboard and trackball to provide inputs to the host server.
The Saber series consists of standard rack mount, panel mount and standalone/VESA mount military-grade and COTS (Commercial Off-The-Shelf) LCD monitors. Options include sunlight readable displays, LED backlights, NVIS goggle compatibility, touch screens, multiple video inputs and more. The
The TwoView Micro (dual display), SlimLine Micro and Rack Mount Hinge series consist of 1U and 2U high rack mount, flip-up and flip-down military-grade LCD monitors in a rack mount drawer. Options include sunlight readable displays, LED backlights, NVIS goggle compatibility, touch screens, multiple video inputs and more. They have been used in military applications such as:
Integrated for use within Humvees and ECS transit cases for the CONDOR (Command and Control On-the-Move Network, Digital Over the Horizon Relay) program (high bright displays)
The TwoView (dual display), SlimLine 1U and SlimLine Lite II series consist of 1U and 2U high rack mount, flip-up military-grade LCD monitors with integral keyboards and trackballs in a rack mount drawer. Options include sunlight readable displays, LED backlights, NVIS goggle compatibility, touch screens, multiple video inputs, keyboards and more. They have been used in military applications such as:
Integrated for use within Humvees and ECS transit cases for the CONDOR (Command and Control On-the-Move Network, Digital Over the Horizon Relay) program (high bright displays)
The Barracuda series consists of NEMA 4/6 and IP67 environmentally sealed rack mount, panel mount and standalone/VESA mount military-grade and COTS (Commercial Off-The-Shelf) LCD monitors. Options include sunlight readable displays, LED backlights, NVIS goggle compatibility, touch screens, multiple video inputs and more. The marine-grade
The Impact series consists of an open frame military-grade LCD monitor kit, ready for mounting where you need it. Options include sunlight readable displays, LED backlights, NVIS goggle compatibility, touch screens, multiple video inputs and more. They have been used in military applications such as:
We appreciate all the hardships that our young fighting men and women must endure. They deserve the best America has to offer to keep them safe and sound, and General Digital is proud to supply them with ruggedized tactical display equipment upon which they and their battalion can depend.
With so many available rugged military display options available for the armed forces, we are happy to help you, the military professional, develop an individualized rugged monitor display system that matches your unique battlefield needs.
Data Vision is a manufacturer of LCD (Liquid Crystal Display) modules, established in 1990. Currently, we have manufacturing strongholds in Taiwan and China.
We are recognized as one of most progressive companies in our industry. Data Vision offers broad range of LCD modules, including mono LCM, Intelligent and Integrated LCM and TFT. In which, we provide extensive and complete solutions based on customer needs. Hence, Turnkey service is merely a part of our offerings. To make our competence qualified, we have certification of ISO9001:2008.
Our customers vary in size and industry as well as in the services they require. Today, Data Vision offers an array of services to help our customers improve their bottom lines and time to achieve objectives.
Spatial uniformity of displayed luminance can vary widely between different makes and models of LCD, the major determinant of uniformity being the backlight scheme [34] (some older LCDs allowed VGA input and relied on built-in analog-to-digital conversion, also a potential source of noise). Two commonplace schemes are, first, direct backlighting, wherein a spatial array of light-emitting diodes (LEDs) and a diffuser screen sit behind the liquid crystal panel, and, second, edge illumination, wherein light emitted by a linear array of diodes at one of the display’s edges is spatially distributed via lightguide. We quantified the spatial uniformity of the CG247X by presenting low-, medium-, and high-luminance static test patches at nine display positions (Fig 2, inset) and using the LS-110 spot meter to measure the luminance of each patch. At each luminance tested, we calculated the grand average over all display positions, and divisively normalized measurements by that average. As illustrated in Fig 2, at medium- and high-luminance, the CG247X showed greater spatial uniformity than our consumer-grade LCD (Dell U2415b): for the CG247X, spatial variation was 5.1% at medium and 3.5% at high luminance, whereas for the U2415b, variation was 8.1% at medium and 8.5% at high luminance. The uniformity of the two displays was comparable at low luminance (CG247X, 27% versus U2415b, 17%). Prior to normalization, there were, as expected, marked differences between low-, medium-, and high-luminance measurements. For example, at display position 5 (Fig 2, inset) on the CG247X, low-luminance measurements ranged from 0.07 to 0.10 cd/m2, medium-luminance measurements ranged from 57.70 to 57.93 cd/m2, and high-luminance measurements ranged from 113.9 to 114.2 cd/m2 (Table 1). We also quantified spatial surround effects; using a tripod at 1 m, we measured displayed luminance at position 5 comparing large (1920-by-1200 pixels) and small (384-by-384 pixels) 100%-luminance patches. For CG247X, the mean of 10 large-patch measurements was 0.56 cd/m2 greater than that of 10 small-patch measurements (two-sample t-test, p < 0.01), i.e., an increase of 0.50%. For the U2415b, the increase was 0.71 cd/m2, i.e., 0.67% (two-sample t-test, p < 0.01).
In-plane switching (IPS) LCDs, like our CG247X and U2415b, enable larger viewing angles than older LCD technology (e.g., twisted-nematic displays) [23]. To do so, IPS displays interdigitate electrodes (see 23]. For the displays we tested, vendor-issued specifications state a viewing angle of 178 deg, however, in the absence of further details, that derived measure is difficult to assimilate. We measured displayed luminance as a function of viewing angle over a range of azimuth and elevation (±60 deg). We fit a circular von Mises function (Fig 3, the CG247X and U2415b performed comparably in this regard. For the CG247X, the FW90M was 28.6 deg (fitted parameters: α = 1.45, κ = 3.37) and 32.6 deg (α = 1.65, κ = 2.62) for azimuth and elevation, respectively. For the U2415b, the FW90M was 31.2 deg (α = 1.60, κ = 2.85) and 31.0 deg (α = 1.55, κ = 2.90) for azimuth and elevation, respectively. At high-luminance we made a reduced set of measurements, assuming rotational symmetry, varying azimuth or elevation from 0 to 60 deg. These additional measurements yielded similar FW90M estimates. This descriptive model can be used to select a viewing distance with tolerable attenuation due to viewing angle. For example, if the CG247X is viewed from 1 m, a stimulus presented at the top of the display’s vertical meridian (i.e., elevation = 9.2 deg) would, due to viewing angle, undergo luminance attenuation by a factor of 0.97.
We presented a large, static test patch, measuring luminance with the LS-110 spot meter near the display’s center. We used a turntable to rotate the display (
A common misconception among vision researchers and clinicians is that LCDs do not flicker (i.e., that LCDs are temporally uniform). In fact, there are two major sources of flicker that can affect a LCD: first, backlight flicker which usually occurs at temporal frequencies (e.g., 1000 Hz) well beyond the critical flicker fusion frequency (e.g., Elze & Tanner [24], and Ghodrati, Morris, & Price [35]), and, second, the so-called frame response which occurs at the refresh rate of the display (here, 60 Hz) [23, 36]. Frame responses are largely attributable to an LCD’s inversion scheme: a feature of modern displays wherein the polarity of the video signal voltage applied to the liquid crystal material is inverted from one video frame to the next. This inversion minimises long-term degradation, or aging, of the display by minimizing the DC voltage across the liquid crystal elements. Frame inversion schemes typically have fine spatial structure, on the scale of individual pixels, making them mostly imperceptible (e.g., dot inversion schemes [36]). We quantified the temporal uniformity of the CG247X by presenting (nominally) static test patches at display position 5 (Fig 2, inset) and using the linearized photodiode device to measure displayed luminance over time. At each of 11 luminances (0, 10, 20 … 100%) we made 10 one-second recordings, averaging the Fourier amplitude spectra of those 10 recordings. Fig 4 shows the average spectrum at each luminance. The spectra of the CG247X revealed a frame response comprising a 60 Hz component as well as harmonic components at integer multiples of 60 Hz. The response at 60 Hz varied non-monotonically in amplitude with the luminance of the static test patch, peaking at a luminance of 50%. However, the CG247X appeared free of backlight modulations. This absence of backlight modulations freed us of the consequences of said modulations (often desynchronized with the frame refresh signal) on increment/decrement transitions between luminances (see Fig 5 in [24]). The spectra of our consumer-grade LCD also revealed a frame response, as well as 1.2 kHz flicker, likely associated with the back light. This latter temporal nonuniformity increased linearly with the luminance of the static test patch.
We presented nominally static test patches at display position 5 (Fig 2, inset), measuring luminance with a linearized photodiode device. At each luminance (0, 10, 20 … 100%) we made ten 1-second recordings, deriving the Fourier amplitude spectrum for each. Each spectrum illustrated is the average of 10 spectra. For each display, we normalized spectra such that 1000 corresponds to the DC component at 50% luminance; therefore, a value of 5.0 corresponds to approximately 0.15 cd/m2. The spectra of the CG247X (upper) revealed a frame response, comprising a 60 Hz component and harmonic components at integer multiples of 60 Hz. This frame response varied non-monotonically in amplitude with the luminance of the static test patch, peaking between 40 and 50% luminance. The spectra of the U2415b (lower) also revealed a frame response, as well as 1.2 kHz flicker, the amplitude of which increased linearly with the luminance of the static test patch (amplitudes above 5.0 are not shown, arrowheads). For the U2415b, mains noise (50 Hz) was apparent at high-luminance. lum., luminance.
For each display, we verified that the frame response was optical and not related to any radiated electromagnetic noise: We used the oscilloscope to visualize the Fourier amplitude spectrum online. We then interposed opaque cardboard between the photodiode and display which caused the disappearance of the frame response. For the U2415b, we similarly verified that the 1.2 kHz response was optical.
In general, LCD response times—the duration of the rise or fall of a step from one luminance level to another—vary as a function of both step source and destination luminance. This nonlinear behaviour is owing largely to mechanisms of response time compensation (RTC) (e.g., the work of McCartney [25]), a feature of many modern LCDs designed to enhance video. RTC mechanisms speed luminance transitions by transiently altering the voltage applied to the liquid crystal associated with individual pixels (e.g., Fig 1 in [27]; Fig 5 in [24]). We measured the CG247X’s response times by presenting luminance steps—both increments and decrements—to the linearized photodiode device. Step source and destination took values 0, 25, 50, 75, or 100%. As illustrated in Fig 5, response times varied as a function of both luminance step source and destination. For example, stepping from 0% luminance to 25% luminance took 24.5 ms, stepping from 75% to 100% took 12.9 ms, and stepping from 25% to 0% took 8.1 ms. All of these steps are the same height, but response times differ markedly. Overall, the response times of our consumer-grade LCD were less than the CG247X response times. However, as we will illustrate below, faster is not better; although RTC mechanisms reduced the response times of our consumer-grade LCD, they contaminated displayed luminance with overshoot and undershoot artifacts which are problematic for many applications in clinical and experimental vision research, including the presentation of mean-modulated flicker. RTC mechanisms lower “black-white-black” and “grey-to-grey” response times, which are used to promote displays to the gaming community and other consumer markets.
(A) CG247X response times. The leftmost gray box (labelled “0%”) encompasses four points showing mean response times for transitions from source luminance = 0% to destination luminances = 25, 50, 75, and 100% (x axis). These rise times (upward triangles) decreased with increasing destination luminance. The gray box labelled “25%” shows mean response times of transitions from source luminance = 25% to destination luminances = 0, 50, 75, and 100%. The fall time (downward triangle), from 25% to 0% luminance, was less than the rise times. Overall, response times varied as a function of both source and destination luminance, as is generally expected of LCDs. We made 10 measurements at each source/destination luminance pair; error bars, where not obscured by symbols, mark the full range (from minimum to maximum) of these 10 measurements. (B) U2415b response times. Graphical conventions are as in A. Overall, U2415b response times were less than CG247X response times.
At the outset of this study, we made preliminary measurements similar to those illustrated in Fig 5. We noticed that rise and fall times straddling 50% luminance were approximately equal (e.g., rise time from 25% to 75% = 16.3 ms; fall time from 75% to 25% = 17.1 ms) which led us to wonder whether the CG247X could be used to display achromatic, mean-modulated flicker without the introduction of unworkable artifacts. To better determine the CG247X’s potential suitability for presenting mean-modulated flicker, and its susceptibility, or otherwise, to overshoot and undershoot artifacts typical of LCDs implementing RTC mechanisms, we presented mean-modulated flicker on both the CG247X and our consumer-grade display, using the linearized photodiode device to measure luminance over time. We used a flicker period of 20 frames (333.3 ms), and contrast ranging from 20 to 100%. As illustrated in Fig 6, the consumer-grade display’s luminance traces revealed overshoot and undershoot artifacts symptomatic of RTC. The CG247X’s luminance traces, however, appeared free of RTC artifacts. We used these traces to estimate response times specific to mean-modulated flicker, illustrated in Fig 7. Overall, CG247X rise and fall times were greater than those of our consumer-grade LCD. However, with the exception of 100% contrast, CG247X rise and fall times were approximately equal, indicating its potential suitability for presenting mean-modulated flicker.
Flicker period = 20 frames (333.3 ms), and contrast = 20 to 100% in increments of 20 as marked. At 40% contrast, the arrowheads show examples of luminance step source and destination as used in the computation of response times (Fig 7). For each display, we normalized traces to the luminance step destination at 100% contrast. For the U2415b, over- and undershoot are readily apparent at low and moderate contrast. The CG247X, however, shows exponential rise and fall, regardless of contrast.
To further determine whether the CG247X could be used to display achromatic, mean-modulated flicker without the introduction of unworkable artifacts, we presented flicker at frequencies ranging from 0.94 to 30 Hz and contrasts ranging from 20 to 100%. We used recorded traces (similar to those in Fig 6) to derive cycle-averaged luminance. In Fig 8, we illustrate how cycle-averaged luminance was approximately constant for all flicker frequencies, and for contrasts up to 80%. At 100% contrast, cycle-averaged luminance decreased with flicker frequency, indicating that, at full contrast, the monitor is not suitable for presenting mean-modulated flicker. Cycle-averaged luminance recorded from our consumer-grade LCD (Dell U2415b) varied as a function of flicker frequency at all contrasts tested; this variation is problematic for presenting achromatic, mean-modulated flicker. We also used CG247X traces to derive cycle-averaged r.m.s. luminance. In Fig 8, we illustrate how cycle-averaged r.m.s. luminance decreased with flicker frequency, indicative of loss of contrast. The consumer-grade LCD was affected by both changes in cycle-averaged luminance and loss of contrast.
We presented mean-modulated flicker at a range of flicker frequencies (0.94 to 30 Hz) and contrasts (20 to 100%). We used waveforms (e.g., Fig 6) recorded from the CG247X (A) to derive cycle-averaged luminance; we divisively normalized that derived measure using the cycle-averaged luminance of a “reference” waveform, that is, the response to contrast = 20% and flicker frequency = 0.94 Hz. This relatively low-contrast, low-frequency waveform was chosen as reference because it should be easily realized by both displays. For clarity, cycle-averaged responses for contrast = 40, 60, 80, and 100% are offset by -0.1, -0.2, -0.3, and -0.4 log units, respectively (arrowheads). As shown, cycle-averaged luminance was approximately constant for contrast = 20 to 80% at all flicker frequencies tested (0.94 to 30 Hz). At contrast = 100%, cycle-averaged luminance decreased with flicker frequency. Cycle-averaged luminance recorded from the consumer-grade U2415b (B) increased with flicker frequency at all contrasts tested. Graphical conventions are as in A. We used waveforms recorded from the CG247X (C) to derive cycle-averaged r.m.s. luminance; we divisively normalized that derived measure using cycle-averaged r.m.s. luminance of the reference waveform (20%, 0.94 Hz). As shown, at all contrasts tested (20 to 100%), cycle-averaged r.m.s. luminance decreased with flicker frequency, indicative of a loss of effective contrast. Cycle-averaged r.m.s. luminance recorded from the U2415b (D) revealed both increases and decreases to effective contrast with flicker frequency. Each symbol is the average of 10 measurements. (None of the data in panels C and D is offset.) We modeled cycle-average luminance and r.m.s. luminance on the CG247X as a causal exponential decay (Methods). This model comprised one free parameter, τ. For the illustrated fit (blue), τ = 6.6 ms. The red symbols in panel C (slightly offset rightward for clarity) show the result of a validation experiment (see
Taken together, Fig 8, and the traces used to derive the measures plotted there, indicated a simple relationship between nominal and displayed luminance on the CG247X, namely, that the latter was, simply, a low-pass-filtered version of the former. To test this hypothesis, we modeled the function transferring nominal luminance to displayed luminance as a causal, exponential decay (Methods). We optimized the single free parameter in this model, the time constant of the exponential decay (τ), by minimizing the sum of the squared error between the model-derived cycle-averaged mean luminance and cycle-averaged r.m.s. luminance, and those derived from the photodiode traces. For the CG247X, the fit is illustrated in Fig 8 (blue). There, the fitted parameter, τ, was 6.6 ms. To assess the fit to cycle-averaged luminance, we computed the root-mean-square error (RMSE) separately at each flicker contrast. For the CG247X, the RMSE was negligibly small for contrasts from 20 to 80% (ranging from 6.0e-4 to 6.3e-3 normalized units). At 100% contrast, RMSE was highest at 0.093. This simple model was a poor fit to the U2415b, not illustrated in Fig 8. For the U2415b, RMSEs were high, ranging from 0.04 at 20% contrast to 0.15 at 60% contrast. To assess the fit to cycle-averaged r.m.s. luminance, we calculated the square of Pearson’s correlation coefficient, R2, separately at each flicker contrast. For the CG247X, R2 was high, ranging from 0.9965 to 0.9999. As expected, the same calculation for the U2415b was consistent with a poor fit; at its worst, R2 = 0.03.
To quantify the nonlinearities associated with high-contrast, mean-modulated flicker, and to quantify temporal dependence between frames, we used a paired-pulse paradigm [37, 38]. We presented paired biphasic luminance pulses at position 5 (Fig 2, inset), systematically varying the inter-pulse interval, T (Methods). We used the measured responses to individual pulses to predict paired-pulse responses, and to model the display’s nonlinearities we subtracted each paired-pulse response from its prediction. Fig 9 shows the nonlinear behaviour of the CG247X and, for comparison, that of our consumer-grade LCD. In our CG247X, a nonlinear mechanism appeared to speed the transition between white and black (100% and 0% luminance, respectively; leftmost upper panel in Fig 9B). When paired pulses were separated by 16.67 ms or more (the three rightmost upper panels in Fig 9B where predicted and displayed luminance are approximately equal), the CG247X behaved linearly, that is, we saw no evidence of temporal dependence between frames. In our consumer-grade LCD, a nonlinear mechanism appeared to attenuate the transition to white (100% luminance; leftmost lower panel in Fig 9B). This attenuation reconciles with Fig 6 (lower), which shows marked overshoot at moderate contrast (e.g., 60% contrast, middlemost panel of Fig 6), but a near absence of overshoot at high-contrast (rightmost panel of Fig 6). Compared to the CG247X, the U2415b’s nonlinearities were large in magnitude and long-lasting. Paired pulses separated by as much as 33.33 ms (the third lower panel in Fig 9B, where predicted and displayed luminance are unequal) evoked nonlinear behaviour in the U2415b, that is, we saw clear evidence of temporal dependence between frames.
(A) Illustration of the paired-pulse paradigm. We presented a single biphasic luminance pulse (e.g., left panel), parametrically varying its latency relative to a trigger (cf. left and middle panels). We then presented a pair of biphasic luminance pulses (right panel), parametrically varying the offset between pulses comprising the pair, T = 0, 1, 2, and 3 times the frame period (frame period = 16.67 ms). Single-pulse responses can be used to predict the paired-pulse response; differences between this prediction and the displayed luminance model the display’s nonlinearities. (B) Nonlinear behaviour of the CG247X (upper). The four panels show responses to paired pulses with various offsets, T; we normalized responses (0, 0.5 and 1 corresponded to 0, 50 and 100% luminance, respectively) and then subtracted the baseline. For each offset, the predicted displayed luminance derived from single-pulse responses is shown in blue, and the measured displayed luminance in response to paired pulses is shown in black. The measured responses are an average of 16 recordings. The difference, that is, the nonlinearity, is shown in red. For the CG247X, superposition (T = 0 ms) of pulses evoked a nonlinearity which accelerated the transition from 100% luminance to 0% luminance. There was negligible nonlinearity of displayed lumiance for T > = 16.67 ms. Compared to the CG247X’s nonlinearity, the U2415b’s nonlinearity (lower panels) was large in magnitude and long-lasting, affecting subsequent frames (to T = 33.33 ms). Graphical conventions are as in B.
H30 is a robust field housing in aluminum or stainless steel designed for tough environments. The field housing is available both with and without digital LCD indicator for installation directly in a 4-20 mA loop without need for external power. The LCD indicator is equipped with high-contrast, easy-to-read LCD digits with backlight. The scale is easily programmable, without reference signal, by two push buttons for any values between – 1999 and 9999.
At Rise Display, we make LED ticker displays easy. From getting a quote, to installation, to support after the sale, our turnkey ticker solution is seamless and painless. Whether you want a basic ticker display for a finance lab, a scrolling news ticker, or a multi-ticker integrated display that wows passersby, our custom ticker solutions can be built to fit your space and your budget. Our Rise Ticker App iscompletely integrated with our quality hardware and designed to run for years with no complications.And with our 5-year, on-site guarantee, you can rest easy knowing you’ve purchased a high-quality, reliable ticker display that will be easy to set up, program, and maintain.
While most ticker displays are straight and wall-mounted, we also support ceiling mounts, vertical mounts, flexible curved cabinets, wrap corners, and even outdoor weatherproofed units. For curved units, we can flex to a minimum of a two-foot radius.
Tickers are very lightweight and come with wall-mount hardware. LED tickers less than 8 feet in length come in a single section while longer versions are built in sections that are designed to be easily snapped together with quick-connect cables to carry data and power from section to section.View ticker quick install guide.
While the majority of our installs are in North America, we can ship displays anywhere and work remotely with your local installer. The hardware is universal and we have variable power supplies to adapt to different electrical standards. Understanding the data source and compatibility is key to ensuring success.
We have our own Rise Ticker App and licenses with financial and sports providers for the live content. Once a ticker is connected to your network (wired or wireless), your firewall must allow outbound TCP/IP access to cms.risedisplay.com via port 9090 to receive the live updates. No dedicated computer equipment is required. All of the “smarts” are built into the ticker display.More network setup info.
Yes, we do have to pay to license the data from the exchanges and sports providers. We offer a range of different packages to fit different data needs and budgets ranging from $20 to $50 per month, per ticker. We do offer discounts for multi-year prepays.More details on the content available.
The 24” display of the BOLDscreen provides maximum field of view for a 60cm bore. It is designed to be placed in close proximity to the viewer right at the exit of the bore of the scanner. This keeps the viewing distance is as short as possible - about 1m. Since viewing distance dramatically affects the field of view, BOLDscreen can achieve a larger field of view than bigger monitors with longer viewing distance. If you have a 70cm bore, consider the larger BOLDscreen 32 design.
The BOLDscreen"s high resolution display provides a pixel density of 94 pixels per inch. This is enough to make the each pixel indistinguishable - even at the closest possible viewing distance of 1m. (Where it translates into an angular resolution of 65 pixels per degree or more than one per arc minute.) More resolution is pointless as it"s beyond the limit of typical visual acuity.
Some manufacturers quote high contrast figures which compare white versus black with the screen switched off. We don"t think that"s a useful measurement, as the screen is not switched off when you"re presenting stimuli! We measure the contrast between the emitted light though the panel with the pixels set to white versus set to black with the same backlight intensity – what you see in actual use. Measured in this way, BOLDscreen has a typical contrast ratio of 1000:1, similar to most high quality IPS LCD displays.
The output of an LCD display varies greatly over time – typically luminance will change by up to 20% in the first hour and a half after turning the screen on. BOLDscreen offers real time luminance calibration ensuring a stable, calibrated display immediately from switch-on, and maintaining the same level of output even when BOLDscreen has been running for hours.
Yes! To achieve the image quality required for scientific visual stimulation, we illuminate the panel with our own unique, super bright, LED matrix backlight. This produces highly saturated chromatic displays at up to 800cd.m-2: many times brighter than any normal display.
The backlight has excellent spatial uniformity, typically 2% over central 75% of display area. Commercial backlights are not usually designed with uniformity in mind, meaning luminance can vary greatly from one area of the screen to another.
We selected this technology to deliver the best possible response time, viewing angle and colour reproduction. If you"d like to see the full specification of the LCD we chose for BOLDscreen, we can provide you with a copy of the manufacturer"s data sheet.
The mirror mode feature allows you to automatically left/right flip your image when your subject is viewing the display via a single mirror, without the requirement to manually adjust your stimuli.
We provide a 20m single link DVI fibre optic cable with each BOLDscreen display. This is passed through the waveguide into the control room and connected to your host computer DVI output.
We are the only manufacturer and vendor that provides a MR Safe LCD monitor that you can site anywhere inside the MRI room, even directly at the exit of the rear of the magnet bore so that you can maximise the visual field of view.
BOLDscreen has no observed effect on functional and structural MRI scans at 3T, even when located at directly at the exit of scanner bore, and no effect on displayed image whilst scanning. See our test data.
BOLDscreen is constructed mostly from aluminium, 316 stainless steel, glass and plastic. These materials are non-magnetic. There is a very small amount of ferro-magnetic content due mainly to nickel plating on some miniature electronic components, and some tiny ferrite components. This content is of the order of a few grammes in a total monitor mass of about 16.5kg. The BOLDscreen electronics have been designed to work in the high magnetic field (it is not just a normal LCD monitor in a screened box). There is therefore no electrical hazard from operating BOLDscreen in the magnetic field of any field strength. The display is MR Safe, and the power supply and cables are MR Conditional, as defined by ASTM F2503-08.